Kea Administrator Reference Manual

Kea is an open source implementation of the Dynamic Host Configuration Protocol (DHCP) servers, developed and maintained by Internet Systems Consortium (ISC).

This is the reference guide for Kea version 2.1.6. Links to the most up-to-date version of this document (in PDF, HTML, and plain text formats) can be found on Read the Docs. Other useful Kea information can be found in our Knowledgebase.

Introduction

Kea is the next generation of DHCP software, developed by Internet Systems Consortium (ISC). It supports both the DHCPv4 and DHCPv6 protocols along with their extensions, e.g. prefix delegation and dynamic updates to DNS.

This guide covers Kea version 2.1.6.

For information about supported platforms see Supported Platforms.

Supported Platforms

In general, this version of Kea builds and runs on any POSIX-compliant system with a C++ compiler (with C++11 support), the Botan cryptographic library, the log4cplus logging library and the Boost system library.

The Kea build has been checked with GCC g++ 4.8.5 and some later versions, and Clang 800.0.38 and some later versions.

ISC regularly tests Kea on many operating systems and architectures, but lacks the resources to test all of them. Consequently, ISC is only able to offer support on a “best-effort” basis for some.

Regularly Tested Platforms

Kea is officially supported on Alpine, CentOS, Fedora, Ubuntu, Debian, and FreeBSD systems. Kea-2.1.6 builds have been tested on:

• Alpine - 3.12, 3.13

• CentOS — 7

• Debian — 9, 10, 11

• Fedora — 34

• FreeBSD — 12, 13

• RHEL - 8

• Ubuntu — 18.04, 20.04

There are currently no plans to port Kea to Windows systems.

Best-Effort

The following are platforms on which Kea is known to build and run. ISC makes every effort to fix bugs on these platforms, but may be unable to do so quickly due to lack of hardware, less familiarity on the part of engineering staff, and other constraints.

• Alpine — 3.11

• FreeBSD - 11

• macOS — 10.13, 10.14

Community-Maintained

These systems may not all have the required dependencies for building Kea easily available, although it is possible in many cases to compile those directly from source. The community and interested parties may wish to help with maintenance, and we welcome patch contributions, although we cannot guarantee that we will accept them. All contributions are assessed against the risk of adverse effect on officially supported platforms.

These include platforms past their respective EOL dates, such as:

• Alpine — 3.10 (1 May 2021)

• CentOS — 6 (30 November 2020), 8 (31 December 2021)

• Fedora — 31, 32, 33

• Ubuntu — 14.04, 18.10, 19.04, 19.10, 21.04

• Debian — 8 (30 June 2020)

• FreeBSD — 10 (31 October 2018)

Unsupported Platforms

These are platforms on which versions of Kea since 1.7 are known not to build or run:

• Windows (all versions)

• Windows Server (all versions)

• Any platform with OpenSSL 1.0.1 or earlier, which does not also have Botan as an alternative

• Any platform with log4cplus version 1.0.2 or earlier.

Required Software at Runtime

Kea uses various extra software packages which may not be provided in the default installation of some operating systems, nor in the standard package collections. This required software may need to be installed separately. (For the build requirements, also see Build Requirements.)

• Kea supports two cryptographic libraries: Botan and OpenSSL. Only one of them is required to be installed during compilation. Kea uses the Botan library for C++ (https://botan.randombit.net/), version 2.0 or later; support for Botan versions earlier than 2.0 was removed as of Kea 1.7.0. As an alternative to Botan, Kea can use the OpenSSL cryptographic library (https://www.openssl.org/), version 1.0.2 or later.

• Kea uses the log4cplus C++ logging library (https://sourceforge.net/p/log4cplus/wiki/Home/). It requires log4cplus version 1.0.3 or later.

• Kea requires the Boost system library (https://www.boost.org/). Building with the header-only version of Boost is no longer recommended.

Some optional features of Kea have additional dependencies.

• To store lease information in a MySQL database, Kea requires MySQL headers and libraries. This is an optional dependency; Kea can be built without MySQL support.

• To store lease information in a PostgreSQL database, Kea requires PostgreSQL headers and libraries. This is an optional dependency; Kea can be built without PostgreSQL support.

• Integration with RADIUS is provided in Kea via the hook library available to ISC’s paid support customers. Use of this library requires the FreeRADIUS-client library to be present on the system where Kea is running. This is an optional dependency; Kea can be built without RADIUS support.

• Kea provides a NETCONF interface with the kea-netconf agent. This Kea module requires Sysrepo software when used. Building Kea with NETCONF support requires many dependencies to be installed, which are described in more detail in Installing NETCONF. This is an optional dependency; Kea can be built without NETCONF support.

• To sign and verify DNS updates the Kea DDNS server may use GSS-TSIG, which requires MIT Kerberos 5 or Heimdal libraries. The dependencies required to be installed are described in more detail in GSS-TSIG Compilation. This is an optional dependency; Kea can be built without GSS-TSIG support.

Kea Software

Kea is a modular DHCP server solution. This modularity is accomplished using multiple cooperating processes which, together, provide the server functionality. The following software is included with Kea:

• keactrl — This tool starts, stops, reconfigures, and reports the status of the Kea servers.

• kea-dhcp4 — The DHCPv4 server process. This process responds to DHCPv4 queries from clients.

• kea-dhcp6 — The DHCPv6 server process. This process responds to DHCPv6 queries from clients.

• kea-dhcp-ddns — The DHCP Dynamic DNS process. This process acts as an intermediary between the DHCP servers and external DNS servers. It receives name update requests from the DHCP servers and sends DNS update messages to the DNS servers.

• kea-admin — This is a useful tool for database backend maintenance (creating a new database, checking versions, upgrading, etc.).

• kea-lfc — This process removes redundant information from the files used to provide persistent storage for the memfile database backend. While it can be run standalone, it is normally run as and when required by the Kea DHCP servers.

• kea-ctrl-agent — The Kea Control Agent (CA) is a daemon that exposes a RESTful control interface for managing Kea servers.

• kea-netconf - kea-netconf is an agent that provides a YANG/NETCONF interface for configuring Kea.

• kea-shell — This simple text client uses the REST interface to connect to the Kea Control Agent.

• perfdhcp — This is a DHCP benchmarking tool which simulates multiple clients to test both DHCPv4 and DHCPv6 server performance.

The tools and modules are covered in full detail in this guide. In addition, manual pages are also provided in the default installation.

Kea also provides C++ libraries and programmer interfaces for DHCP. These include detailed developer documentation and code examples.

Quick Start

This section describes the basic steps needed to get Kea up and running. For further details, full customizations, and troubleshooting, see the respective chapters elsewhere in this Kea Administrator Reference Manual (ARM).

Quick Start Guide Using tarball

1. Install required runtime and build dependencies. See Build Requirements for details.

2. Download the Kea source tarball from the ISC.org downloads page or the ISC downloads site.

3. Extract the tarball. For example:

   $ tar -xvzf kea-2.1.6.tar.gz

4. Go into the source directory and run the configure script:

   $ cd kea-2.1.6
   $ ./configure [your extra parameters]

5. Build it:

   $ make
   

6. Install it (by default it will be placed in /usr/local/, so root privileges are likely required for this step):

   $ make install
   

Quick Start Guide Using Native Packages

ISC provides native Alpine, deb, and RPM packages, which make Kea installation much easier. Unless specific compilation options are desired, it is usually easier to install Kea using native packages.

1. Go to Kea on cloudsmith.io, choose the Kea version, and enter the repository.

2. Use Set Me Up and follow instructions to add the repository to the local system.

3. Update system repositories. For example:

   $ apt-get update
   

4. Kea is split into various packages. The entire list is available on cloudsmith.io or using apt/yum/dnf. For example:

   $ apt-cache search isc-kea
   

5. Install specific packages:

   $ sudo apt-get install isc-kea-dhcp6-server
   

   or all packages:

   $ sudo apt-get install isc-kea*
   

   or all packages with a specified version number:

   $ sudo apt-get install isc-kea*=1.8.1-isc0000920201106154401
   

6. All installed packages should be now available directly; for example:

   # kea-dhcp6 -c /path/to/your/kea6/config/file.json
   

   or using systemd:

   # systemctl restart isc-kea-dhcp6-server
   

   keactrl is not available in packages as similar functionality is provided by the native systemctl scripts.

Quick Start Guide for DHCPv4 and DHCPv6 Services

1. Edit the Kea configuration files, which by default are installed in the [kea-install-dir]/etc/kea/ directory. These are: kea-dhcp4.conf, kea-dhcp6.conf, kea-dhcp-ddns.conf and kea-ctrl-agent.conf, keactrl.conf for DHCPv4 server, DHCPv6 server, D2, Control Agent, and the keactrl script, respectively.

2. To start the DHCPv4 server in the background, run the following command (as root):

   # keactrl start -s dhcp4
   

   Or run the following command to start the DHCPv6 server:

   # keactrl start -s dhcp6
   

   Note that it is also possible to start all servers simultaneously:

   # keactrl start
   

3. Verify that the Kea server(s) is/are running:

   # keactrl status
   

   A server status of “inactive” may indicate a configuration error. Please check the log file (by default named [kea-install-dir]/var/log/kea-dhcp4.log, [kea-install-dir]/var/log/kea-dhcp6.log, [kea-install-dir]/var/log/kea-ddns.log, or [kea-install-dir]/var/log/kea-ctrl-agent.log) for the details of any errors.

4. If the server has started successfully, test that it is responding to DHCP queries and that the client receives a configuration from the server; for example, use the ISC DHCP client.

5. To stop running the server(s):

   # keactrl stop
   

For system-specific instructions, please read the system-specific notes, available in the Kea section of ISC’s Knowledgebase.

The details of keactrl script usage can be found in Managing Kea with keactrl.

Once Kea services are up and running, consider deploying a dashboard solution to monitor running services. For more details, see Monitoring Kea With Stork.

Running the Kea Servers Directly

The Kea servers can be started directly, without the need to use keactrl or systemctl. To start the DHCPv4 server run the following command:

# kea-dhcp4 -c /path/to/your/kea4/config/file.json

Similarly, to start the DHCPv6 server, run the following command:

# kea-dhcp6 -c /path/to/your/kea6/config/file.json

Installation

Packages

ISC publishes native RPM, deb, and APK packages, along with the tarballs with the source code. The packages are available on Cloudsmith at https://cloudsmith.io/~isc/repos. The native packages can be downloaded and installed using the system available in a specific distribution (such as dpkg or rpm). The Kea repository can also be added to the system, making it easier to install updates. For details, please go to https://cloudsmith.io/~isc/repos, choose the repository of interest, and then click the Set Me Up button for detailed instructions.

Installation Hierarchy

The following is the directory layout of the complete Kea installation. (All directory paths are relative to the installation directory.)

• etc/kea/ — configuration files.

• include/ — C++ development header files.

• lib/ — libraries.

• lib/kea/hooks — additional hooks libraries.

• sbin/ — server software and commands used by the system administrator.

• share/doc/kea/ — this guide, other supplementary documentation, and examples.

• share/kea/ — API command examples and database schema scripts.

• share/man/ — manual pages (online documentation).

• var/lib/kea/ — server identification and lease database files.

• var/log/ - log files.

• var/run/kea - PID file and logger lock file.

Build Requirements

In addition to the runtime requirements (listed in Required Software at Runtime), building Kea from source code requires various development include headers and program development tools.

Note

Some operating systems have split their distribution packages into a runtime and a development package. The development package versions, which include header files and libraries, must be installed to build Kea from the source code.

Building from source code requires the following software installed on the system:

• Boost C++ libraries (https://www.boost.org/). The oldest Boost version used for testing is 1.57 (although Kea may also work with older versions). The Boost system library must also be installed. Installing a header-only version of Boost is not recommended.

• OpenSSL (at least version 1.0.2) or Botan (at least version 2). OpenSSL version 1.1.1 or later is strongly recommended.

• log4cplus (at least version 1.0.3) development include headers.

• A C++ compiler (with C++11 support) and standard development headers. The Kea build has been checked with GCC g++ 4.8.5 and some later versions, and Clang 800.0.38 and some later versions.

• The development tools automake, libtool, and pkg-config.

• The MySQL client and the client development libraries, when using the --with-mysql configuration flag to build the Kea MySQL database backend. In this case, an instance of the MySQL server running locally or on a machine reachable over a network is required. Note that running the unit tests requires a local MySQL server.

• The PostgreSQL client and the client development libraries, when using the --with-pgsql configuration flag to build the Kea PostgreSQL database backend. In this case an instance of the PostgreSQL server running locally or on a machine reachable over a network is required. Note that running the unit tests requires a local PostgreSQL server.

• The FreeRADIUS client library is required to connect to a RADIUS server. This is specified using the --with-freeradius configuration switch.

• Sysrepo v1.4.140 and libyang v1.0.240 are needed to connect to a Sysrepo datastore. Earlier versions are no longer supported. When compiling from sources, the configure switches that can be used are --with-libyang and --with-sysrepo without any parameters. If these dependencies were installed in custom paths, point the switches to them.

• The MIT Kerberos 5 or Heimdal libraries are needed by Kea DDNS server to sign and verify DNS updates using GSS-TSIG. The configuration switch which enables this functionality is --with-gssapi without any parameters. If these dependencies were installed in custom paths, point the switch to them.

• googletest (version 1.8 or later) is required when using the --with-gtest configuration option to build the unit tests.

• The documentation generation tools Sphinx, texlive with its extensions, and Doxygen, if using the --enable-generate-docs configuration option to create the documentation. Specifically, with Fedora, python3-sphinx, texlive, and texlive-collection-latexextra are necessary; with Ubuntu, python3-sphinx, python3-sphinx-rtd-theme, and texlive-binaries are needed. If LaTeX packages are missing, Kea skips PDF generation and produces only HTML documents.

Visit ISC’s Knowledgebase at https://kb.isc.org/docs/installing-kea for system-specific installation tips.

Installation From Source

Although Kea may be available in pre-compiled, ready-to-use packages from operating system vendors, it is open source software written in C++. As such, it is freely available in source code form from ISC as a downloadable tar file. The source code can also be obtained from the Kea GitLab repository at https://gitlab.isc.org/isc-projects/kea. This section describes how to build Kea from the source code.

Download Tar File

The Kea release tarballs may be downloaded from: https://downloads.isc.org/isc/kea/.

Retrieve From Git

The latest development code is available on GitLab (see https://gitlab.isc.org/isc-projects/kea). The Kea source is public and development is done in the “master” branch.

Downloading this “bleeding edge” code is recommended only for developers or advanced users. Using development code in a production environment is not recommended.

Note

When building from source code retrieved via git, additional software is required: automake (v1.11 or later), libtoolize, and autoconf (v2.69 or later). These may need to be installed.

The code can be checked out from https://gitlab.isc.org/isc-projects/kea.git:

$ git clone https://gitlab.isc.org/isc-projects/kea.git

The code checked out from the git repository does not include the generated configure script or the Makefile.in files, nor their related build files. They can be created by running autoreconf with the --install switch. This will run autoconf, aclocal, libtoolize, autoheader, automake, and related commands.

Write access to the Kea repository is only granted to ISC staff. Developers planning to contribute to Kea should check our Contributor’s Guide. The Kea Developer’s Guide contains more information about the process, and describes the requirements for contributed code to be accepted by ISC.

Configure Before the Build

Kea uses the GNU Build System to discover build environment details. To generate the makefiles using the defaults, simply run:

$ ./configure

Run ./configure with the --help switch to view the different options. Some commonly used options are:

• --prefix Define the installation location (the default is /usr/local).

• --with-mysql Build Kea with code to allow it to store leases and host reservations in a MySQL database.

• --with-pgsql Build Kea with code to allow it to store leases and host reservations in a PostgreSQL database.

• --with-log4cplus Define the path to find the Log4cplus headers and libraries. Normally this is not necessary.

• --with-boost-include Define the path to find the Boost headers. Normally this is not necessary.

• --with-botan-config Specify the path to the botan-config script to build with Botan for cryptographic functions. It is preferable to use OpenSSL (see below).

• --with-openssl Use the OpenSSL cryptographic library instead of Botan. By default configure searches for a valid Botan installation; if one is not found, Kea searches for OpenSSL. Normally this is not necessary.

• --enable-shell Build the optional kea-shell tool (more in The Kea Shell). The default is to not build it.

• --with-site-packages Only useful when kea-shell is enabled, this switch causes the kea-shell Python packages to be installed in the specified directory. This is mostly useful for Debian-related distributions. While most systems store Python packages in ${prefix}/usr/lib/pythonX/site-packages, Debian introduced a separate directory for packages installed from DEB. Such Python packages are expected to be installed in /usr/lib/python3/dist-packages.

• --enable-perfdhcp Build the optional perfdhcp DHCP benchmarking tool. The default is to not build it.

• --with-freeradius Build the optional RADIUS hook. This option specifies the path to the patched version of the FreeRADIUS client. This feature is available in the subscriber-only version of Kea, and requires the subscription-only RADIUS hook.

• --with-freeradius-dictionary Specify a non-standard location for a FreeRADIUS dictionary file, which contains a list of supported RADIUS attributes. This feature is available in the subscriber-only version of Kea, and requires the subscription-only RADIUS hook.

If the RADIUS options are not available, ensure that the RADIUS hook sources are in the premium directory and rerun autoreconf -i.

Note

For instructions concerning the installation and configuration of database backends for Kea, see DHCP Database Installation and Configuration.

There are many options that are typically not necessary for regular users. However, they may be useful for package maintainers, developers, or people who want to extend Kea code or send patches:

• --with-gtest, --with-gtest-source Enable the building of C++ unit tests using the Google Test framework. This option specifies the path to the gtest source. (If the framework is not installed on the system, it can be downloaded from https://github.com/google/googletest.)

• --enable-generate-docs Enable the rebuilding of Kea documentation. ISC publishes Kea documentation for each release; however, in some cases it may be desirable to rebuild it: for example, to change something in the docs, or to generate new ones from git sources that are not yet released.

• --enable-generate-parser Enable the generation of parsers using flex or bison. Kea sources include .cc and .h parser files, pre-generated for users’ convenience. By default Kea does not use flex or bison, to avoid requiring installation of unnecessary dependencies for users. However, if anything in the parsers is changed (such as adding a new parameter), flex and bison are required to regenerate parsers. This option permits that.

• --enable-generate-messages Enable the regeneration of messages files from their messages source files, e.g. regenerate xxx_messages.h and xxx_messages.cc from xxx_messages.mes using the Kea message compiler. By default Kea is built using these .h and .cc files from the distribution. However, if anything in a .mes file is changed (such as adding a new message), the Kea message compiler needs to be built and used. This option permits that.

As an example, the following command configures Kea to find the Boost headers in /usr/pkg/include, specifies that PostgreSQL support should be enabled, and sets the installation location to /opt/kea:

$ ./configure \
      --with-boost-include=/usr/pkg/include \
      --with-pgsql=/usr/local/bin/pg_config \
      --prefix=/opt/kea

Users who have any problems with building Kea using the header-only Boost code, or who would like to use the Boost system library (assumed for the sake of this example to be located in /usr/pkg/lib), should issue these commands:

$ ./configure \
      --with-boost-libs=-lboost_system \
      --with-boost-lib-dir=/usr/pkg/lib

If configure fails, it may be due to missing or old dependencies.

When configure succeeds, it displays a report with the parameters used to build the code. This report is saved into the file config.report and is also embedded into the executable binaries, e.g., kea-dhcp4.

Build

After the configure step is complete, build the executables from the C++ code and prepare the Python scripts by running the command:

$ make

Install

To install the Kea executables, support files, and documentation, issue the command:

$ make install

Do not use any form of parallel or job server options (such as GNU make’s -j option) when performing this step; doing so may cause errors.

Note

The install step may require superuser privileges.

If required, run ldconfig as root with /usr/local/lib (or with prefix/lib if configured with --prefix) in /etc/ld.so.conf (or the relevant linker cache configuration file for the OS):

$ ldconfig

Note

If ldconfig is not run where required, users may see errors like the following:

program: error while loading shared libraries: libkea-something.so.1:
cannot open shared object file: No such file or directory

Cross-Building

It is possible to cross-build Kea, i.e. to create binaries in a separate system (the build system) from the one where Kea runs (the host system).

It is outside of the scope of common administrator operations and requires some developer skills, but the Developer Guide explains how to do that using an x86_64 Linux system to build Kea for a Raspberry Pi box running Raspbian: Kea Cross-Compiling Example.

DHCP Database Installation and Configuration

Kea stores its leases in a lease database. The software has been written in a way that makes it possible to choose which database product should be used to store the lease information. Kea supports four database backends: MySQL, PostgreSQL and memfile. To limit external dependencies, MySQL and PostgreSQL support are disabled by default and only memfile is available. Support for the optional external database backend must be explicitly included when Kea is built. This section covers the building of Kea with one of the optional backends and the creation of the lease database.

Note

When unit tests are built with Kea (i.e. the --with-gtest configuration option is specified), the databases must be manually pre-configured for the unit tests to run. The details of this configuration can be found in the Kea Developer’s Guide.

Building with MySQL Support

Install MySQL according to the instructions for the system. The client development libraries must be installed.

Build and install Kea as described in Installation, with the following modification. To enable the MySQL database code, at the “configure” step (see Configure Before the Build), the --with-mysql switch should be specified:

$ ./configure [other-options] --with-mysql

If MySQL was not installed in the default location, the location of the MySQL configuration program “mysql_config” should be included with the switch:

$ ./configure [other-options] --with-mysql=path-to-mysql_config

See First-Time Creation of the MySQL Database for details regarding MySQL database configuration.

Building with PostgreSQL support

Install PostgreSQL according to the instructions for the system. The client development libraries must be installed. Client development libraries are often packaged as “libpq”.

Build and install Kea as described in Installation, with the following modification. To enable the PostgreSQL database code, at the “configure” step (see Configure Before the Build), the --with-pgsql switch should be specified:

$ ./configure [other-options] --with-pgsql

If PostgreSQL was not installed in the default location, the location of the PostgreSQL configuration program “pg_config” should be included with the switch:

$ ./configure [other-options] --with-pgsql=path-to-pg_config

See First-Time Creation of the PostgreSQL Database for details regarding PostgreSQL database configuration.

Hammer Building Tool

Hammer is a Python 3 script that lets users automate tasks related to building Kea, such as setting up virtual machines, installing Kea dependencies, compiling Kea with various options, running unit-tests and more. This tool was created primarily for internal QA purposes at ISC and it is not included in the Kea distribution; however, it is available in the Kea git repository. This tool was developed primarily for internal purposes and ISC cannot guarantee its proper operation. Administrators who decide to use it should do so with care.

Note

Use of this tool is completely optional. Everything it does can be done manually.

The first-time user is strongly encouraged to look at Hammer’s built-in help:

$ ./hammer.py --help

It will list available parameters.

Hammer is able to set up various operating systems running either in LXC or in VirtualBox. For a list of supported systems, use the supported-systems command:

$ ./hammer.py supported-systems
fedora:
  - 27: lxc, virtualbox
  - 28: lxc, virtualbox
  - 29: lxc, virtualbox
centos:
  - 7: lxc, virtualbox
rhel:
  - 8: virtualbox
ubuntu:
  - 16.04: lxc, virtualbox
  - 18.04: lxc, virtualbox
  - 18.10: lxc, virtualbox
debian:
  - 8: lxc, virtualbox
  - 9: lxc, virtualbox
freebsd:
  - 11.2: virtualbox
  - 12.0: virtualbox

It is also possible to run the build locally, in the current system (if the OS is supported).

First, the Hammer dependencies must be installed: Vagrant and either VirtualBox or LXC. Hammer can install Vagrant and the required Vagrant plugins using the command:

$ ./hammer.py ensure-hammer-deps

VirtualBox and LXC must be installed manually.

The basic functions provided by Hammer are to prepare the build environment and perform the actual build, and to run the unit tests locally in the current system. This can be achieved by running the command:

$ ./hammer.py build -p local

The scope of the process can be defined using the --with (-w) and --without (-x) options. By default, the build command builds Kea with documentation, installs it locally, and runs unit tests.

To exclude the installation and generation of docs, type:

$ ./hammer.py build -p local -x install docs

The basic scope can be extended by mysql, pgsql, native-pkg, radius, shell, and forge.

Note

If building Kea locally, Hammer dependencies like Vagrant are not needed.

Hammer can be told to set up a new virtual machine with a specified operating system, without the build:

$ ./hammer.py prepare-system -p virtualbox -s freebsd -r 12.0

This way, a system can be prepared for our own use. To get to such a system using SSH, invoke:

$ ./hammer.py ssh -p virtualbox -s freebsd -r 12.0

It is possible to speed up subsequent Hammer builds via ccache. During compilation, ccache stores objects in a shared folder. In subsequent runs, instead of doing an actual compilation, ccache returns the stored earlier objects. The cache with these objects for reuse must be stored outside of VM or LXC. To indicate the folder, the --ccache-dir parameter for Hammer must be included. In the indicated folder, there are separate stored objects for each target operating system.

$ ./hammer.py build -p lxc -s ubuntu -r 18.04 --ccache-dir ~/kea-ccache

Note

ccache is currently only supported for LXC in Hammer; support for VirtualBox may be added later.

For more information check:

$ ./hammer.py --help

Running Kea From a Non-root Account on Linux

Both Kea DHCPv4 and DHCPv6 servers perform operations that in general require root access privileges. In particular, DHCPv4 opens raw sockets and both DHCPv4 and DHCPv6 open UDP sockets on privileged ports. However, with some extra system configuration, it is possible to run Kea from non-root accounts.

First, a regular user account must be created:

useradd admin

Then, change the binaries’ ownership and group to the new user. Note that the specific path may be different. Please refer to the --prefix parameter passed to the configure script:

chown -R admin /opt/kea
chgrp -R admin /opt/kea
chown -R admin /var/log/kea-dhcp4.log
chgrp -R admin /var/log/kea-dhcp4.log
chown -R admin /var/log/kea-dhcp6.log
chgrp -R admin /var/log/kea-dhcp6.log

If using systemd, modify its service file (e.g. /etc/systemd/system/kea-dhcp6.service):

User=admin
Group=admin

The most important step is to set the capabilities of the binaries. Refer to man capabilities to get more information.

setcap 'cap_net_bind_service,cap_net_raw=+ep' /opt/kea/sbin/kea-dhcp4
setcap 'cap_net_bind_service=+ep' /opt/kea/sbin/kea-dhcp6

If using systemd, also add this to the service file (e.g. /etc/systemd/system/kea-dhcp6.service):

ExecStartPre=setcap 'cap_net_bind_service=+ep' /opt/kea/sbin/kea-dhcp6

After this step is complete, the admin user should be able to run Kea. Note that the DHCPv4 server by default opens raw sockets. If the network is only using relayed traffic, Kea can be instructed to use regular UDP sockets (refer to dhcp-socket-type parameter in the Interface Configuration section) and the cap_net_raw capability can be skipped.

Note

It is possible to avoid running Kea with root privileges by instructing Kea to use non-privileged (greater than 1024) ports and redirecting traffic. This, however, only works for relayed traffic. This approach in general is considered experimental and has not been tested for deployment in production environments. Use with caution!

To use this approach, configure the server to listen on other non-privileged ports (e.g. 1547 and 1548) by running the process with the -p option in /etc/systemd/system/kea-dhcp4.service:

ExecStart=/opt/kea/sbin/kea-dhcp4 -d -c /etc/kea/kea-dhcp4.conf -p 2067

and /etc/systemd/system/kea-dhcp4.service:

ExecStart=/opt/kea/sbin/kea-dhcp6 -d -c /etc/kea/kea-dhcp6.conf -p 1547

Then configure port redirection with iptables and ip6tables for new ports (e.g. 1547 and 1548). Be sure to replace ens4 with the specific interface name.

iptables -t nat -A PREROUTING -i ens4 -p udp --dport 67 -j REDIRECT --to-port 2067
iptables -t nat -A PREROUTING -i ens4 -p udp --dport 2068 -j REDIRECT --to-port 68
ip6tables -t nat -A PREROUTING -i ens4 -p udp --dport 547 -j REDIRECT --to-port 1547
ip6tables -t nat -A PREROUTING -i ens4 -p udp --dport 1548 -j REDIRECT --to-port 548

Deprecated Features

This section lists significant features that have been or will be removed. We try to deprecate features before removing them to signal to current users to plan a migration. New users should not rely on deprecated features.

Sysrepo 0.x

Kea versions 1.9.9 and earlier required Sysrepo 0.7.x to run, when optional support for NETCONF was enabled. Kea versions 1.9.10 and later now require Sysrepo 1.4.x and the related libyang 1.x library to run. The earlier Sysrepo versions are no longer supported. The latest Sysrepo 2.x version does not provide C++ bindings, and as such, is not usable for Kea.

Kea Database Administration

Databases and Schema Versions

Kea may be configured to use a database as storage for leases or as a source of servers’ configurations and host reservations (i.e. static assignments of addresses, prefixes, options, etc.). As Kea is updated, new database schemas are introduced to facilitate new features and correct discovered issues with the existing schemas.

Each version of Kea expects a particular schema structure and checks for this by examining the version of the database it is using. Separate version numbers are maintained for the schemas, independent of the version of Kea itself. It is possible that the schema version will stay the same through several Kea revisions; similarly, it is possible that the version of the schema may go up several revisions during a single Kea version upgrade. Versions for each backend type are also independent, so an increment in the MySQL backend version does not imply an increment in that of PostgreSQL.

Schema versions are specified in a major.minor format. For the most recent versions, the minor version is always zero and only the major version is incremented.

Historically, the minor version used to be incremented when backward-compatible changes were introduced to the schema: for example - when a new index is added. This was opposed to incrementing the major version which implied an incompatible schema change: for example - changing the type of an existing column. If Kea attempts to run on a schema that is too old, as indicated by a mismatched schema version, it will fail; administrative action is required to upgrade the schema.

The kea-admin Tool

To manage the databases, Kea provides the kea-admin tool. It can initialize a new backend, check its version number, perform a backend upgrade, and dump lease data to a text file.

kea-admin takes two mandatory parameters: command and backend. Additional, non-mandatory options may be specified. The currently supported commands are:

• db-init — initializes a new database schema. This is useful during a new Kea installation. The database is initialized to the latest version supported by the version of the software being installed.

• db-version — reports the database backend version number. This is not necessarily equal to the Kea version number, as each backend has its own versioning scheme.

• db-upgrade — conducts a database schema upgrade. This is useful when upgrading Kea.

• lease-dump — dumps the contents of the lease database (for MySQL or PostgreSQL backends) to a CSV (comma-separated values) text file.

  The first line of the file contains the column names. This can be used as a way to switch from a database backend to a memfile backend. Alternatively, it can be used as a diagnostic tool, so it provides a portable form of the lease data.

• lease-upload — uploads leases from a CSV (comma-separated values) text file to a MySQL or a PostgreSQL lease database. The CSV file needs to be in memfile format.

backend specifies the type of backend database. The currently supported types are:

• memfile — lease information is stored on disk in a text file.

• mysql — information is stored in a MySQL relational database.

• pgsql — information is stored in a PostgreSQL relational database.

Additional parameters may be needed, depending on the setup and specific operation: username, password, and database name or the directory where specific files are located. See the appropriate manual page for details (man 8 kea-admin).

Supported Backends

The following table presents the capabilities of available backends. Please refer to the specific sections dedicated to each backend to better understand their capabilities and limitations. Choosing the right backend is essential for the success of the deployment.

List of available backends

Feature	Memfile	MySQL	PostgreSQL
Status	Stable	Stable	Stable
Data format	CSV file	SQL RMDB	SQL RMDB
Leases	yes	yes	yes
Host reservations	no	yes	yes
Options defined on per host basis	no	yes	yes
Configuration backend	no	yes	yes

Memfile

The memfile backend is able to store lease information, but cannot store host reservation details; these must be stored in the configuration file. (There are no plans to add a host reservations storage capability to this backend.)

No special initialization steps are necessary for the memfile backend. During the first run, both kea-dhcp4 and kea-dhcp6 create an empty lease file if one is not present. Necessary disk-write permission is required.

Upgrading Memfile Lease Files From an Earlier Version of Kea

There are no special steps required to upgrade memfile lease files between versions of Kea. During startup, the servers check the schema version of the lease files against their own. If there is a mismatch, the servers automatically launch the LFC process to convert the files to the server’s schema version. While this mechanism is primarily meant to ease the process of upgrading to newer versions of Kea, it can also be used for downgrading should the need arise. When upgrading, any values not present in the original lease files are assigned appropriate default values. When downgrading, any data present in the files but not in the server’s schema are dropped. To convert the files manually prior to starting the servers, run the lease file cleanup (LFC) process. See The LFC Process for more information.

MySQL

MySQL is able to store leases, host reservations, options defined on a per-host basis, and a subset of the server configuration parameters (serving as a configuration backend).

First-Time Creation of the MySQL Database

Before preparing any Kea-specific database and tables, the MySQL database must be configured to use the system timezone. It is recommended to use UTC as the timezone for both the system and the MySQL database.

To check the system timezone:

date +%Z

To check the MySQL timezone:

mysql> SELECT @@system_time_zone;
mysql> SELECT @@global.time_zone;
mysql> SELECT @@session.time_zone;

To configure the MySQL timezone for a specific server, please refer to the installed version documentation.

Usually the setting is configured in the [mysqld] section in /etc/mysql/my.cnf, /etc/mysql/mysql.cnf, /etc/mysql/mysqld.cnf, or /etc/mysql/mysql.conf.d/mysqld.cnf.

[mysqld]
# using default-time-zone
default-time-zone='+00:00'

# or using timezone
timezone='UTC'

When setting up the MySQL database for the first time, the database area must be created within MySQL, and the MySQL user ID under which Kea will access the database must be set up. This needs to be done manually, rather than via kea-admin.

To create the database:

1. Log into MySQL as “root”:

   $ mysql -u root -p
   Enter password:
   mysql>
   

2. Create the MySQL database:

   mysql> CREATE DATABASE database_name;
   

   (database_name is the name chosen for the database.)

3. Create the user under which Kea will access the database (and give it a password), then grant it access to the database tables:

   mysql> CREATE USER 'user-name'@'localhost' IDENTIFIED BY 'password';
   mysql> GRANT ALL ON database-name.* TO 'user-name'@'localhost';
   

   (user-name and password are the user ID and password used to allow Kea access to the MySQL instance. All apostrophes in the command lines above are required.)

4. Create the database.

   Exit the MySQL client

   mysql> quit
   Bye
   

   Then use the kea-admin tool to create the database.

   $ kea-admin db-init mysql -u database-user -p database-password -n database-name
   

   While it is possible to create the database from within the MySQL client, we recommend using the kea-admin tool as it performs some necessary validations to ensure Kea can access the database at runtime. Among those checks is verification that the schema does not contain any pre-existing tables; any pre-existing tables must be removed manually. An additional check examines the user’s ability to create functions and triggers. The following error indicates that the user does not have the necessary permissions to create functions or triggers:

   ERROR 1419 (HY000) at line 1: You do not have the SUPER privilege and binary logging is
   enabled (you *might* want to use the less safe log_bin_trust_function_creators variable)
   ERROR/kea-admin: mysql_can_create cannot trigger, check user permissions, mysql status = 1
   mysql: [Warning] Using a password on the command line interface can be insecure.
   ERROR/kea-admin: Create failed, the user, keatest, has insufficient privileges.
   

   The simplest way around this is to set the global MySQL variable, log_bin_trust_function_creators, to 1 via the MySQL client. Note this must be done as a user with SUPER privileges:

   mysql> set @@global.log_bin_trust_function_creators = 1;
   Query OK, 0 rows affected (0.00 sec)
   

   To create the database with MySQL directly, follow these steps:

   mysql> CONNECT database-name;
   mysql> SOURCE path-to-kea/share/kea/scripts/mysql/dhcpdb_create.mysql
   

   (where path-to-kea is the location where Kea is installed.)

   The database may also be dropped manually as follows:

   mysql> CONNECT database-name;
   mysql> SOURCE path-to-kea/share/kea/scripts/mysql/dhcpdb_drop.mysql
   

   (where path-to-kea is the location where Kea is installed.)

Warning

Dropping the database results in the unrecoverable loss of any data it contains.

5. Exit MySQL:

   mysql> quit
   Bye
   

If the tables were not created in Step 4, run the kea-admin tool to create them now:

$ kea-admin db-init mysql -u database-user -p database-password -n database-name

Do not do this if the tables were created in Step 4. kea-admin implements rudimentary checks; it will refuse to initialize a database that contains any existing tables. To start from scratch, all data must be removed manually. (This process is a manual operation on purpose, to avoid accidentally irretrievable mistakes by kea-admin.)

Upgrading a MySQL Database From an Earlier Version of Kea

Sometimes a new Kea version uses a newer database schema, so the existing database needs to be upgraded. This can be done using the kea-admin db-upgrade command.

To check the current version of the database, use the following command:

$ kea-admin db-version mysql -u database-user -p database-password -n database-name

(See Databases and Schema Versions for a discussion about versioning.) If the version does not match the minimum required for the new version of Kea (as described in the release notes), the database needs to be upgraded.

Before upgrading, please make sure that the database is backed up. The upgrade process does not discard any data, but depending on the nature of the changes, it may be impossible to subsequently downgrade to an earlier version.

To perform an upgrade, issue the following command:

$ kea-admin db-upgrade mysql -u database-user -p database-password -n database-name

Note

To search host reservations by hostname, it is critical that the collation of the hostname column in the host table be case-insensitive. Fortunately, that is the default in MySQL, but it can be verified via this command:

mysql> SELECT COLLATION('');
+-----------------+
| COLLATION('')   |
+-----------------+
| utf8_general_ci |
+-----------------+

According to mysql’s naming convention, when the name ends in _ci, the collation is case-insensitive.

Improved Performance With MySQL

Changing the MySQL internal value innodb_flush_log_at_trx_commit from the default value of 1 to 2 can result in a huge gain in Kea performance. In some deployments, the gain was over 1000% (10 times faster when set to 2, compared to the default value of 1). It can be set per-session for testing:

mysql> SET GLOBAL innodb_flush_log_at_trx_commit=2;
mysql> SHOW SESSION VARIABLES LIKE 'innodb_flush_log%';

or permanently in /etc/mysql/my.cnf:

[mysqld]
innodb_flush_log_at_trx_commit=2

Be aware that changing this value can cause problems during data recovery after a crash, so we recommend checking the MySQL documentation. With the default value of 1, MySQL writes changes to disk after every INSERT or UPDATE query (in Kea terms, every time a client gets a new lease or renews an existing lease). When innodb_flush_log_at_trx_commit is set to 2, MySQL writes the changes at intervals no longer than 1 second. Batching writes gives a substantial performance boost. The trade-off, however, is that in the worst-case scenario, all changes in the last second before crash could be lost. Given the fact that Kea is stable software and crashes very rarely, most deployments find it a beneficial trade-off.

PostgreSQL

PostgreSQL can store leases, host reservations, and options defined on a per-host basis.

First-Time Creation of the PostgreSQL Database

Before preparing any Kea-specific database and tables, the PostgreSQL database must be configured to use the system timezone. It is recommended to use UTC as the timezone for both the system and the PostgreSQL database.

To check the system timezone:

date +%Z

To check the PostgreSQL timezone:

postgres=# show timezone;
postgres=# SELECT * FROM pg_timezone_names WHERE name = current_setting('TIMEZONE');

To configure the PostgreSQL timezone for a specific server, please refer to the installed version documentation.

Usually the setting is configured in the postgresql.conf with the varying version path /etc/postgresql/<version>/main/postgresql.conf, but on some systems the files may be located in /var/lib/pgsql/data.

timezone = 'UTC'

The first task is to create both the database and the user under which the servers will access it. A number of steps are required:

1. Log into PostgreSQL as “root”:

   $ sudo -u postgres psql postgres
   Enter password:
   postgres=#
   

2. Create the database:

   postgres=# CREATE DATABASE database-name;
   CREATE DATABASE
   postgres=#
   

   (database-name is the name chosen for the database.)

3. Create the user under which Kea will access the database (and give it a password), then grant it access to the database:

   postgres=# CREATE USER user-name WITH PASSWORD 'password';
   CREATE ROLE
   postgres=# GRANT ALL PRIVILEGES ON DATABASE database-name TO user-name;
   GRANT
   postgres=#
   

4. Exit PostgreSQL:

   postgres=# \q
   Bye
   $
   

5. At this point, create the database tables either using the kea-admin tool, as explained in the next section (recommended), or manually. To create the tables manually, enter the following command. PostgreSQL will prompt the administrator to enter the new user’s password that was specified in Step 3. When the command completes, Kea will return to the shell prompt. The output should be similar to the following:

   $ psql -d database-name -U user-name -f path-to-kea/share/kea/scripts/pgsql/dhcpdb_create.pgsql
   Password for user user-name:
   CREATE TABLE
   CREATE INDEX
   CREATE INDEX
   CREATE TABLE
   CREATE INDEX
   CREATE TABLE
   START TRANSACTION
   INSERT 0 1
   INSERT 0 1
   INSERT 0 1
   COMMIT
   CREATE TABLE
   START TRANSACTION
   INSERT 0 1
   COMMIT
   $
   

   (path-to-kea is the location where Kea is installed.)

   If instead an error is encountered, such as:

   psql: FATAL:  no pg_hba.conf entry for host "[local]", user "user-name", database "database-name", SSL off
   

   … the PostgreSQL configuration will need to be altered. Kea uses password authentication when connecting to the database and must have the appropriate entries added to PostgreSQL’s pg_hba.conf file. This file is normally located in the primary data directory for the PostgreSQL server. The precise path may vary depending on the operating system and version, but the default location for PostgreSQL is /etc/postgresql/*/main/postgresql.conf. However, on some systems (notably CentOS 8), the file may reside in /var/lib/pgsql/data.

   Assuming Kea is running on the same host as PostgreSQL, adding lines similar to the following should be sufficient to provide password-authenticated access to Kea’s database:

   local   database-name    user-name                                 password
   host    database-name    user-name          127.0.0.1/32           password
   host    database-name    user-name          ::1/128                password
   

   These edits are primarily intended as a starting point, and are not a definitive reference on PostgreSQL administration or database security. Please consult the PostgreSQL user manual before making these changes, as they may expose other databases that are running. It may be necessary to restart PostgreSQL for the changes to take effect.

Initialize the PostgreSQL Database Using kea-admin

If the tables were not created manually, do so now by running the kea-admin tool:

$ kea-admin db-init pgsql -u database-user -p database-password -n database-name

Do not do this if the tables were already created manually. kea-admin implements rudimentary checks; it will refuse to initialize a database that contains any existing tables. To start from scratch, all data must be removed manually. (This process is a manual operation on purpose, to avoid accidentally irretrievable mistakes by kea-admin.)

Upgrading a PostgreSQL Database From an Earlier Version of Kea

The PostgreSQL database schema can be upgraded using the same tool and commands as described in Upgrading a MySQL Database From an Earlier Version of Kea, with the exception that the “pgsql” database backend type must be used in the commands.

Use the following command to check the current schema version:

$ kea-admin db-version pgsql -u database-user -p database-password -n database-name

Use the following command to perform an upgrade:

$ kea-admin db-upgrade pgsql -u database-user -p database-password -n database-name

PostgreSQL without OpenSSL support

Usually the PostgreSQL database client library is built with the OpenSSL support but Kea can be configured to handle the case where it is not supported:

$ ./configure [other-options] --disable-pgsql-ssl

Using Read-Only Databases With Host Reservations

If a read-only database is used for storing host reservations, Kea must be explicitly configured to operate on the database in read-only mode. Sections Using Read-Only Databases for Host Reservations With DHCPv4 and Using Read-Only Databases for Host Reservations with DHCPv6 describe when such a configuration may be required, and how to configure Kea to operate in this way for both DHCPv4 and DHCPv6.

Limitations Related to the Use of SQL Databases

Year 2038 Issue

The lease expiration time in Kea is stored in the SQL database for each lease as a timestamp value. Kea developers have observed that the MySQL database does not accept timestamps beyond 2147483647 seconds (the maximum signed 32-bit number) from the beginning of the UNIX epoch (00:00:00 on 1 January 1970). Some versions of PostgreSQL do accept greater values, but the value is altered when it is read back. For this reason, the lease database backends put a restriction on the maximum timestamp to be stored in the database, which is equal to the maximum signed 32-bit number. This effectively means that the current Kea version cannot store leases whose expiration time is later than 2147483647 seconds since the beginning of the epoch (around the year 2038). This will be fixed when database support for longer timestamps is available.

Kea Configuration

Kea uses JSON structures to represent server configurations. The following sections describe how the configuration structures are organized.

JSON Configuration

JSON is the notation used throughout the Kea project. The most obvious usage is for the configuration file, but JSON is also used for sending commands over the Management API (see Management API) and for communicating between DHCP servers and the DDNS update daemon.

Typical usage assumes that the servers are started from the command line, either directly or using a script, e.g. keactrl. The configuration file is specified upon startup using the -c parameter.

JSON Syntax

Configuration files for the DHCPv4, DHCPv6, DDNS, Control Agent, and NETCONF modules are defined in an extended JSON format. Basic JSON is defined in RFC 7159 and ECMA 404. In particular, the only boolean values allowed are true or false (all lowercase). The capitalized versions (True or False) are not accepted.

Even though the JSON standard (ECMA 404) does not require JSON objects (i.e. name/value maps) to have unique entries, Kea implements them using a C++ STL map with unique entries. Therefore, if there are multiple values for the same name in an object/map, the last value overwrites previous values. Since Kea 1.9.0, configuration file parsers raise a syntax error in such cases.

Kea components use extended JSON with additional features allowed:

• Shell comments: any text after the hash (#) character is ignored.

• C comments: any text after the double slashes (//) character is ignored.

• Multiline comments: any text between /* and */ is ignored. This comment can span multiple lines.

• File inclusion: JSON files can include other JSON files by using a statement of the form <?include “file.json”?>.

• Extra commas: to remove the inconvenience of errors caused by leftover commas after making changes to configuration. While parsing, a warning is printed with the location of the comma to give the user the ability to correct a potential mistake.

Warning

These features are meant to be used in a JSON configuration file. Their usage in any other way may result in errors.

The configuration file consists of a single object (often colloquially called a map) started with a curly bracket. It comprises only one of the “Dhcp4”, “Dhcp6”, “DhcpDdns”, “Control-agent”, or “Netconf” objects. It is possible to define additional elements but they will be ignored.

A very simple configuration for DHCPv4 could look like this:

# The whole configuration starts here.
{
    # DHCPv4 specific configuration starts here.
    "Dhcp4": {
        "interfaces-config": {
            "interfaces": [ "eth0" ],
            "dhcp-socket-type": "raw"
        },
        "valid-lifetime": 4000,
        "renew-timer": 1000,
        "rebind-timer": 2000,
        "subnet4": [{
           "pools": [ { "pool": "192.0.2.1-192.0.2.200" } ],
           "subnet": "192.0.2.0/24"
        }],

       # Now loggers are inside the DHCPv4 object.
       "loggers": [{
            "name": "*",
            "severity": "DEBUG"
        }]
    }

# The whole configuration structure ends here.
}

More examples are available in the installed share/doc/kea/examples directory.

To avoid repetition of mostly similar structures, examples in the rest of this guide will showcase only the subset of parameters appropriate for a given context. For example, when discussing the IPv6 subnets configuration in DHCPv6, only subnet6 parameters will be mentioned. It is implied that the remaining elements (the global map that holds Dhcp6) are present, but they are omitted for clarity. Usually, locations where extra parameters may appear are denoted by an ellipsis (…).

Comments and User Context

Shell, C, or C++ style comments are all permitted in the JSON configuration file if the file is used locally. This is convenient and works in simple cases where the configuration is kept statically using a local file. However, since comments are not part of JSON syntax, most JSON tools detect them as errors. Another problem with them is that once Kea loads its configuration, the shell, C, and C++ style comments are ignored. If commands such as config-get or config-write are used, those comments are lost. An example of such comments was presented in the previous section.

Historically, to address the problem, Kea code allowed the use of comment strings as valid JSON entities. This had the benefit of being retained through various operations (such as config-get), or allowing processing by JSON tools. An example JSON comment looks like this:

"Dhcp4": {
    "subnet4": [{
        "subnet": "192.0.2.0/24",
        "pools": [{ "pool": "192.0.2.10 - 192.0.2.20" }],
        "comment": "second floor"
    }]
}

However, the facts that the comment could only be a single line, and that it was not possible to add any other information in a more structured form, were frustrating. One specific example was a request to add floor levels and building numbers to subnets. This was one of the reasons why the concept of user context was introduced. It allows adding an arbitrary JSON structure to most Kea configuration structures.

This has a number of benefits compared to earlier approaches. First, it is fully compatible with JSON tools and Kea commands. Second, it allows storing simple comment strings, but it can also store much more complex data, such as multiple lines (as a string array), extra typed data (such as floor numbers being actual numbers), and more. Third, the data is exposed to hooks, so it is possible to develop third-party hooks that take advantage of that extra information. An example user context looks like this:

"Dhcp4": {
    "subnet4": [{
        "subnet": "192.0.2.0/24",
        "pools": [{ "pool": "192.0.2.10 - 192.0.2.20" }],
        "user-context": {
            "comment": "second floor",
            "floor": 2
        }
    }]
}

User contexts can store an arbitrary data file as long as it has valid JSON syntax and its top-level element is a map (i.e. the data must be enclosed in curly brackets). However, some hook libraries may expect specific formatting; please consult the specific hook library documentation for details.

In a sense the user-context mechanism has superseded the JSON comment capabilities; ISC encourages administrators to use user-context instead of the older mechanisms. To promote this way of storing comments, Kea compared converts JSON comments to user-context on the fly.

However, if the configuration uses the old JSON comment, the config-get command returns a slightly modified configuration. It is not uncommon for a call for config-set followed by a config-get to receive a slightly different structure. The best way to avoid this problem is simply to abandon JSON comments and use user-context.

For a discussion about user-context used in hooks, see User Contexts in Hooks.

Simplified Notation

It is sometimes convenient to refer to a specific element in the configuration hierarchy. Each hierarchy level is separated by a slash. If there is an array, a specific instance within that array is referenced by a number in square brackets (with numbering starting at zero). For example, in the above configuration the valid-lifetime in the Dhcp4 component can be referred to as Dhcp4/valid-lifetime, and the pool in the first subnet defined in the DHCPv4 configuration as Dhcp4/subnet4[0]/pool.

Kea Configuration Backend

Applicability

Kea Configuration Backend (CB or config backend) gives Kea servers the ability to manage and fetch their configuration from one or more databases. In this documentation, the term “Configuration Backend” may also refer to the particular Kea module providing support to manage and fetch the configuration information from the particular database type. For example, the MySQL Configuration Backend is the logic implemented within the mysql_cb hook library, which provides a complete set of functions to manage and fetch the configuration information from the MySQL database. The PostgreSQL Configuration Backend is the logic implemented within the pgsql_cb hook library, which provides a complete set of functions to manage and fetch the configuration information from the PostgreSQL database. From herein, the term “database” is used to refer to either a MySQL or PostgreSQL database.

In small deployments, e.g. those comprising a single DHCP server instance with limited and infrequently changing number of subnets, it may be impractical to use the CB as a configuration repository because it requires additional third-party software to be installed and configured - in particular the database server, client and libraries. Once the number of DHCP servers and/or the number of managed subnets in the network grows, the usefulness of the CB becomes obvious.

One use case for the CB is a pair of Kea DHCP servers that are configured to support High Availability as described in ha: High Availability. The configurations of both servers (including the value of the server-tag parameter) are almost exactly the same: they may differ by the server identifier and designation of the server as a primary or standby (or secondary), and/or by their interfaces’ configuration. Typically, the subnets, shared networks, option definitions, and global parameters are the same for both servers and can be sourced from a single database instance to both Kea servers.

Using the database as a single source of configuration for subnets and/or other configuration information supported by the CB has the advantage that any modifications to the configuration in the database are automatically applied to both servers.

Another case when the centralized configuration repository is useful is in deployments including a large number of DHCP servers, possibly using a common lease database to provide redundancy. New servers can be added to the pool frequently to fulfill growing scalability requirements. Adding a new server does not require replicating the entire configuration to the new server when a common database is used.

Using the database as a configuration repository for Kea servers also brings other benefits, such as:

• the ability to use database specific tools to access the configuration information;

• the ability to create customized statistics based on the information stored in the database; and

• the ability to backup the configuration information using the database’s built-in replication mechanisms.

CB Capabilities and Limitations

Currently, the Kea CB has the following limitations:

• It is only supported for MySQL and PostgreSQL databases.

• It is only supported for the DHCPv4 and DHCPv6 daemons; the Control Agent, D2 daemon, and the NETCONF daemon cannot be configured from the database,

• Only certain DHCP configuration parameters can be set in the database: global parameters, option definitions, global options, client classes, shared networks, and subnets. Other configuration parameters must be sourced from a JSON configuration file.

Kea CB stores data in a schema that is public. It is possible to insert configuration data into the tables manually or automatically using SQL scripts, but this requires SQL and schema knowledge. The supported method for managing the data is through the cb-cmds hook library, which provides management commands for config backends. It simplifies many typical operations, such as listing, adding, retrieving, and deleting global parameters, shared networks, subnets, pools, options, option definitions, and client classes. In addition, it provides essential business logic that ensures the logical integrity of the data. See commands starting with remote- in Appendix A of this manual for a complete list.

Note

The cb_cmds hook library is available only to ISC support subscribers. For more information on subscription options, please complete the form at https://www.isc.org/contact.

The schema creation scripts can be found at dhcpdb_create.mysql and ; dhcpdb_create.pgsql and ; other related design documents are stored in our GitLab: CB Design and Client Classes in CB Design.

We strongly recommend against duplication of configuration information in both the file and the database. For example, when specifying subnets for the DHCP server, please store them in either the configuration backend or in the configuration file, not both. Storing some subnets in the database and others in the file may put users at risk of potential configuration conflicts. Note that the configuration instructions from the database take precedence over instructions from the file, so parts of the configuration specified in the file may be overridden if contradicted by information in the database.

Although it is not recommended, it is possible to specify certain parameter types both in a configuration file and the database. For example, a subnet can be specified in the configuration file and another subnet in the database; in this case, the server will use both subnets. DHCP client classes, however, must not be specified in both the configuration file and the database, even if they do not overlap. If any client classes are specified in the database for a particular DHCP server, this server will use these classes and ignore all classes present in its configuration file. This behavior was introduced to ensure that the server receives a consistent set of client classes specified in an expected order with all inter-class dependencies fulfilled. It is impossible to guarantee consistency when client classes are specified in two independent configuration sources.

Note

It is recommended that the subnet_cmds hook library not be used to manage subnets when the configuration backend is used as a source of information about the subnets. The subnet_cmds hook library modifies the local subnets configuration in the server’s memory, not in the database. Use the cb_cmds hook library to manage the subnets information in the database instead.

Note

Using custom option formats requires creating definitions for these options. Suppose a user wishes to set option data in the configuration backend. In that case, we recommend specifying the definition for that option in the configuration backend as well. It is essential when multiple servers are managed via the configuration backend, and may differ in their configurations. The option data parser can search for an option definition appropriate for the server for which the option data is specified.

In a single-server deployment, or when all servers share the same configuration file information, it is possible to specify option definitions in the configuration files and option data in the configuration backend. The server receiving a command to set option data must have a valid definition in its configuration file, even when it sets option data for another server.

It is not supported to specify option definitions in the configuration backend and the corresponding option data in the server configuration files.

CB Components

To use a MySQL configuration backend you must compile the mysql_cb open source hook library and configure the DHCP servers to load it. It is compiled when the --with-mysql configuration switch is used during the Kea build. The MySQL C client libraries must be installed, as explained in DHCP Database Installation and Configuration.

To use a PostgreSQL configuration backend you must compile the pgsql_cb open source hook library and configure the DHCP servers to load it. It is compiled when the --with-pgsql configuration switch is used during the Kea build. The PostgreSQL C client libraries must be installed, as explained in DHCP Database Installation and Configuration.

Note

An existing database schema must be upgraded to the latest schema required by the particular Kea version using the kea-admin tool, as described in The kea-admin Tool.

The cb_cmds premium hook library, which is available to ISC’s paid support customers, provides a complete set of commands to manage the servers’ configuration information within the database. This library can be attached to both DHCPv4 and DHCPv6 server instances. While it is possible to manage the configuration information without the cb_cmds hook library with commonly available tools, such as MySQL Workbench or the command-line MySQL client, or by directly working with the database; these avenues are neither recommended nor supported.

Refer to cb_cmds: Configuration Backend Commands for the details regarding the cb_cmds hook library.

The DHCPv4 and DHCPv6 server-specific configurations of the CB, as well as the list of supported configuration parameters, can be found in Configuration Backend in DHCPv4 and Configuration Backend in DHCPv6, respectively.

Configuration Sharing and Server Tags

The configuration database is designed to store configuration information for multiple Kea servers. Depending on the use case, the entire configuration may be shared by all servers; parts of the configuration may be shared by multiple servers and the rest of the configuration may be different for these servers; or each server may have its own non-shared configuration.

The configuration elements in the database are associated with the servers by “server tags.” The server tag is an arbitrary string holding the name of the Kea server instance. The tags of the DHCPv4 and DHCPv6 servers are independent in the database, i.e. the same server tag can be created for both the DHCPv4 and the DHCPv6 server. The value is configured using the server-tag parameter in the Dhcp4 or Dhcp6 scope. The current server tag can be checked with the server-tag-get command.

The server definition, which consists of the server tag and the server description, must be stored in the configuration database prior to creating the dedicated configuration for that server. In cases when all servers use the same configuration, e.g. a pair of servers running as High Availability peers, there is no need to configure the server tags for these servers in the database.

Commands which contain the logical server all are applied to all servers connecting to the database. The all server cannot be deleted or modified, and it is not returned among other servers as a result of the remote-server[46]-get-all command.

In most cases, there are no server tags defined in the configuration database; all connecting servers get the same configuration regardless of the server tag they use. The server tag that a particular Kea instance presents to the database to fetch its configuration is specified in the Kea configuration file, using the config-control map (please refer to the Enabling the Configuration Backend and Enabling the Configuration Backend for details). All Kea instances presenting the same server tag to the configuration database are given the same configuration.

It is the administrator’s choice whether multiple Kea instances use the same server tag or each Kea instance uses a different server tag. There is no requirement that the instances running on the same physical or virtual machine use the same server tag. It is even possible to configure the Kea server without assigning it a server tag. In such a case the server will be given the configuration specified for all servers.

To differentiate between different Kea server configurations, a list of the server tags used by the servers must be stored in the database. For the DHCPv4 and DHCPv6 servers, it can be done using the commands described in remote-server4-set, remote-server6-set commands and remote-server4-set, remote-server6-set commands. The server tags can then be used to associate the configuration information with the servers. However, it is important to note that some DHCP configuration elements may be associated with multiple server tags (known as “shareable” elements), while other configuration elements may be associated with only one server tag (“non-shareable” elements). The Configuration Backend in DHCPv4 and Configuration Backend in DHCPv6 sections list the DHCP-specific shareable and non-shareable configuration elements; however, in this section we briefly explain the differences between them.

A shareable configuration element is one which has some unique property identifying it, and which may appear only once in the database. An example of a shareable DHCP element is a subnet instance: the subnet is a part of the network topology and we assume that any particular subnet may have only one definition within this network. Each subnet has two unique identifiers: the subnet identifier and the subnet prefix. The subnet identifier is used in Kea to uniquely identify the subnet within the network and to connect it with other configuration elements, e.g. in host reservations. Some commands provided by the cb_cmds hook library allow the subnet information to be accessed by either subnet identifier or prefix, and explicitly prohibit using the server tag to access the subnet. This is because, in general, the subnet definition is associated with multiple servers rather than a single server. In fact, it may even be associated with no servers (unassigned). Still, the unassigned subnet has an identifier and prefix which can be used to access the subnet.

A shareable configuration element may be associated with multiple servers, one server, or no servers. Deletion of the server which is associated with the shareable element does not cause the deletion of the shareable element. It merely deletes the association of the deleted server with the element.

Unlike a shareable element, a non-shareable element must not be explicitly associated with more than one server and must not exist after the server is deleted (must not remain unassigned). A non-shareable element only exists within the context of the server. An example of a non-shareable element in DHCP is a global parameter, e.g. renew-timer. The renew timer is the value to be used by a particular server and only this server. Other servers may have their respective renew timers set to the same or different values. The renew timer parameter has no unique identifier by which it could be accessed, modified, or otherwise used. Global parameters like the renew timer can be accessed by the parameter name and the tag of the server for which they are configured. For example: the commands described in The remote-global-parameter4-get, remote-global-parameter6-get Commands allow the value of the global parameter to be fetched by the parameter name and the server name. Getting the global parameter only by its name (without specifying the server tag) is not possible, because there may be many global parameters with a given name in the database.

When the server associated with a non-shareable configuration element is deleted, the configuration element is automatically deleted from the database along with the server because the non-shareable element must be always assigned to a server (or the logical server all).

The terms “shareable” and “non-shareable” only apply to associations with user-defined servers; all configuration elements associated with the logical server all are by definition shareable. For example: the renew-timer associated with all servers is used by all servers connecting to the database which do not have their specific renew timers defined. In a special case, when none of the configuration elements are associated with user-defined servers, the entire configuration in the database is shareable because all its pieces belong to all servers.

Note

Be very careful when associating configuration elements with different server tags. The configuration backend does not protect against some possible misconfigurations that may arise from the wrong server tags’ assignments. For example: if a shared network is assigned to one server and the subnets belonging to this shared network to another server, the servers will fail upon trying to fetch and use this configuration. The server fetching the subnets will be aware that the subnets are associated with the shared network, but the shared network will not be found by this server since it doesn’t belong to it. In such a case, both the shared network and the subnets should be assigned to the same set of servers.

Configuration Files Inclusion

The parser provides the ability to include files. The syntax was chosen to look similar to how Apache includes PHP scripts in HTML code. This particular syntax was chosen to emphasize that the include directive is an additional feature and not a part of JSON syntax.

The inclusion is implemented as a stack of files. You can use the include directive in nested includes. Up to ten nesting levels are supported. This arbitrarily chosen limit is protection against recursive inclusions.

The include directive has the form:

<?include "[PATH]"?>

The [PATH] pattern should be replaced with an absolute path or a path relative to the current working directory at the time the Kea process was launched.

To include one file from another, use the following syntax:

{
   "Dhcp6": {
      "interfaces-config": {
         "interfaces": [ "*" ]},
      "preferred-lifetime": 3000,
      "rebind-timer": 2000,
      "renew-timer": 1000,
      <?include "subnets.json"?>
      "valid-lifetime": 4000
   }
}

where the content of “subnets.json” may be:

"subnet4": [
   {
      "id": 123,
      "subnet": "192.0.2.0/24"
   },
   {
      "id": 234,
      "subnet": "192.0.3.0/24"
   },
   {
      "id": 345,
      "subnet": "10.0.0.0/8"
   }
],

Managing Kea with keactrl

Overview

keactrl is a shell script which controls the startup, shutdown, and reconfiguration of the Kea servers (kea-dhcp4, kea-dhcp6, kea-dhcp-ddns, kea-ctrl-agent, and kea-netconf). It also provides the means for checking the current status of the servers and determining the configuration files in use.

keactrl is available only when Kea is built from sources. When installing Kea using native packages, the native systemd scripts are provided. See Native Packages and systemd Section for details.

Command Line Options

keactrl is run as follows:

# keactrl <command> [-c keactrl-config-file] [-s server[,server,...]]

<command> is one of the commands described in Commands.

The optional -c keactrl-config-file switch allows specification of an alternate keactrl configuration file. (--ctrl-config is a synonym for -c.) In the absence of -c, keactrl uses the default configuration file [kea-install-dir]/etc/kea/keactrl.conf.

The optional -s server[,server,...] switch selects the servers to which the command is issued. (--server is a synonym for -s.) If absent, the command is sent to all servers enabled in the keactrl configuration file. If multiple servers are specified, they should be separated by commas with no intervening spaces.

The keactrl Configuration File

Depending on the administrator’s requirements, it may not be necessary to run all of the available servers. The keactrl configuration file sets which servers are enabled and which are disabled. The default configuration file is [kea-install-dir]/etc/kea/keactrl.conf, but this can be overridden on a per-command basis using the -c switch.

The contents of keactrl.conf are:

# This is a configuration file for keactrl script which controls
# the startup, shutdown, reconfiguration and gathering the status
# of the Kea processes.

# prefix holds the location where the Kea is installed.
prefix=@prefix@

# Location of Kea configuration file.
kea_dhcp4_config_file=@sysconfdir@/@PACKAGE@/kea-dhcp4.conf
kea_dhcp6_config_file=@sysconfdir@/@PACKAGE@/kea-dhcp6.conf
kea_dhcp_ddns_config_file=@sysconfdir@/@PACKAGE@/kea-dhcp-ddns.conf
kea_ctrl_agent_config_file=@sysconfdir@/@PACKAGE@/kea-ctrl-agent.conf
kea_netconf_config_file=@sysconfdir@/@PACKAGE@/kea-netconf.conf

# Location of Kea binaries.
exec_prefix=@exec_prefix@
dhcp4_srv=@sbindir@/kea-dhcp4
dhcp6_srv=@sbindir@/kea-dhcp6
dhcp_ddns_srv=@sbindir@/kea-dhcp-ddns
ctrl_agent_srv=@sbindir@/kea-ctrl-agent
netconf_srv=@sbindir@/kea-netconf

# Start DHCPv4 server?
dhcp4=yes

# Start DHCPv6 server?
dhcp6=yes

# Start DHCP DDNS server?
dhcp_ddns=no

# Start Control Agent?
ctrl_agent=yes

# Start Netconf?
netconf=no

# Be verbose?
kea_verbose=no

Note

In the example above, strings of the form @something@ are replaced by the appropriate values when Kea is installed.

Setting the dhcp4, dhcp6, dhcp_ddns, ctrl_agent, and netconf parameters set to “yes” configures keactrl to manage (start, reconfigure) all servers, i.e. kea-dhcp4, kea-dhcp6, kea-dhcp-ddns, kea-ctrl-agent, and kea-netconf. When any of these parameters is set to “no”, keactrl ignores the corresponding server when starting or reconfiguring Kea. Some daemons (dhcp_ddns and netconf) are disabled by default.

By default, Kea servers managed by keactrl are located in [kea-install-dir]/sbin. This should work for most installations. If the default location needs to be altered, the paths specified with the dhcp4_srv, dhcp6_srv, dhcp_ddns_srv, ctrl_agent_srv, and netconf_srv parameters should be modified.

The kea_verbose parameter specifies the verbosity of the servers being started. When kea_verbose is set to “yes,” the logging level of the server is set to DEBUG. Modification of the logging severity in a configuration file, as described in Logging, will have no effect as long as kea_verbose is set to “yes.” Setting it to “no” causes the server to use the logging levels specified in the Kea configuration file. If no logging configuration is specified, the default settings are used.

Note

The verbosity for the server is set when it is started. Once started, the verbosity can only be changed by stopping the server and starting it again with the new value of the kea_verbose parameter.

Commands

The following commands are supported by keactrl:

• start - starts the selected servers.

• stop - stops all running servers.

• reload - triggers reconfiguration of the selected servers by sending the SIGHUP signal to them.

• status - returns the status of the servers (active or inactive) and the names of the configuration files in use.

• version - prints out the version of the keactrl tool itself, together with the versions of the Kea daemons.

Typical output from keactrl when starting the servers looks similar to the following:

$ keactrl start
INFO/keactrl: Starting kea-dhcp4 -c /usr/local/etc/kea/kea-dhcp4.conf -d
INFO/keactrl: Starting kea-dhcp6 -c /usr/local/etc/kea/kea-dhcp6.conf -d
INFO/keactrl: Starting kea-dhcp-ddns -c /usr/local/etc/kea/kea-dhcp-ddns.conf -d
INFO/keactrl: Starting kea-ctrl-agent -c /usr/local/etc/kea/kea-ctrl-agent.conf -d
INFO/keactrl: Starting kea-netconf -c /usr/local/etc/kea/kea-netconf.conf -d

Kea’s servers create PID files upon startup. These files are used by keactrl to determine whether a given server is running. If one or more servers are running when the start command is issued, the output looks similar to the following:

$ keactrl start
INFO/keactrl: kea-dhcp4 appears to be running, see: PID 10918, PID file: /usr/local/var/run/kea/kea.kea-dhcp4.pid.
INFO/keactrl: kea-dhcp6 appears to be running, see: PID 10924, PID file: /usr/local/var/run/kea/kea.kea-dhcp6.pid.
INFO/keactrl: kea-dhcp-ddns appears to be running, see: PID 10930, PID file: /usr/local/var/run/kea/kea.kea-dhcp-ddns.pid.
INFO/keactrl: kea-ctrl-agent appears to be running, see: PID 10931, PID file: /usr/local/var/run/kea/kea.kea-ctrl-agent.pid.
INFO/keactrl: kea-netconf appears to be running, see: PID 10123, PID file: /usr/local/var/run/kea/kea.kea-netconf.pid.

During normal shutdowns, these PID files are deleted; they may, however, be left over as remnants following a system crash. It is possible, though highly unlikely, that upon system restart the PIDs they contain may actually refer to processes unrelated to Kea. This condition will cause keactrl to decide that the servers are running, when in fact they are not. In such a case the PID files listed in the keactrl output must be manually deleted.

The following command stops all servers:

$ keactrl stop
INFO/keactrl: Stopping kea-dhcp4...
INFO/keactrl: Stopping kea-dhcp6...
INFO/keactrl: Stopping kea-dhcp-ddns...
INFO/keactrl: Stopping kea-ctrl-agent...
INFO/keactrl: Stopping kea-netconf...

Note that the stop command attempts to stop all servers regardless of whether they are “enabled” in keactrl.conf. If any of the servers are not running, an informational message is displayed as in the stop command output below.

$ keactrl stop
INFO/keactrl: kea-dhcp4 isn't running.
INFO/keactrl: kea-dhcp6 isn't running.
INFO/keactrl: kea-dhcp-ddns isn't running.
INFO/keactrl: kea-ctrl-agent isn't running.
INFO/keactrl: kea-netconf isn't running.

As already mentioned, the reconfiguration of each Kea server is triggered by the SIGHUP signal. The reload command sends the SIGHUP signal to any servers that are enabled in the keactrl configuration file and that are currently running. When a server receives the SIGHUP signal it rereads its configuration file and, if the new configuration is valid, uses the new configuration. A reload is executed as follows:

$ keactrl reload
INFO/keactrl: Reloading kea-dhcp4...
INFO/keactrl: Reloading kea-dhcp6...
INFO/keactrl: Reloading kea-dhcp-ddns...
INFO/keactrl: Reloading kea-ctrl-agent...

If any of the servers are not running, an informational message is displayed as in the reload command output below. kea-netconf does not support the SIGHUP signal. If its configuration has changed, please stop and restart it for the change to take effect.

$ keactrl stop
INFO/keactrl: kea-dhcp4 isn't running.
INFO/keactrl: kea-dhcp6 isn't running.
INFO/keactrl: kea-dhcp-ddns isn't running.
INFO/keactrl: kea-ctrl-agent isn't running.
INFO/keactrl: kea-netconf isn't running.

Note

NETCONF is an optional feature that is disabled by default and can be enabled during compilation. If Kea was compiled without NETCONF support, keactrl does not provide information about it. The NETCONF entries are still present in the keactrl.conf file, but NETCONF status is not shown and other commands ignore it.

Note

Currently keactrl does not report configuration failures when the server is started or reconfigured. To check if the server’s configuration succeeded, the Kea log must be examined for errors. By default, the log is written to the syslog file.

Sometimes it is useful to check which servers are running. The status command reports this, with typical output that looks like:

$ keactrl status
DHCPv4 server: active
DHCPv6 server: inactive
DHCP DDNS: active
Control Agent: active
Netconf agent: inactive
Kea configuration file: /usr/local/etc/kea/kea.conf
Kea DHCPv4 configuration file: /usr/local/etc/kea/kea-dhcp4.conf
Kea DHCPv6 configuration file: /usr/local/etc/kea/kea-dhcp6.conf
Kea DHCP DDNS configuration file: /usr/local/etc/kea/kea-dhcp-ddns.conf
Kea Control Agent configuration file: /usr/local/etc/kea/kea-ctrl-agent.conf
Kea Netconf configuration file: /usr/local/etc/kea/kea-netconf.conf
keactrl configuration file: /usr/local/etc/kea/keactrl.conf

keactrl status offers basic reporting capabilities. For more extensive insight into Kea’s health and status, consider deploying Stork. For details, see Monitoring Kea With Stork.

Overriding the Server Selection

The optional -s switch allows the selection of the server(s) to which the keactrl command is issued. For example, the following instructs keactrl to stop the kea-dhcp4 and kea-dhcp6 servers and leave the kea-dhcp-ddns and kea-ctrl-agent running:

$ keactrl stop -s dhcp4,dhcp6

Similarly, the following starts only the kea-dhcp4 and kea-dhcp-ddns servers, but not kea-dhcp6 or kea-ctrl-agent.

$ keactrl start -s dhcp4,dhcp_ddns

Note that the behavior of the -s switch with the start and reload commands is different from its behavior with the stop command. On start and reload, keactrl checks whether the servers given as parameters to the -s switch are enabled in the keactrl configuration file; if not, the server is ignored. For stop, however, this check is not made; the command is applied to all listed servers, regardless of whether they have been enabled in the file.

The following keywords can be used with the -s command-line option:

• dhcp4 for kea-dhcp4.

• dhcp6 for kea-dhcp6.

• dhcp_ddns for kea-dhcp-ddns.

• ctrl_agent for kea-ctrl-agent.

• netconf for kea-netconf.

• all for all servers (default).

Native Packages and systemd

keactrl is a script that was developed to assist in managing Kea processes. However, all modern operating systems have their own process-management scripts, such as systemd. In general, these native scripts should be used, as they have several advantages. systemd scripts handle processes in a uniform way, so Kea is handled in a similar fashion to HTTP or a mail server. Second and more importantly, systemd allows dependencies to be defined between services. For example, it is easy to specify that the Kea server should not start until the network interfaces are operational. Using native scripts also has other benefits, such as the ability to enable or disable services using commands, and the ability to temporarily start a disabled service.

Thus, it is recommended to use systemctl commands if they are available. Native Kea packages do not provide keactrl; systemctl service definitions are provided instead. Consult the system documentation for details.

Briefly, here are example commands to check status, start, stop, and restart various Kea daemons:

# systemctl status isc-kea-ctrl-agent
# systemctl start isc-kea-dhcp4-server
# systemctl stop isc-kea-dhcp6-server
# systemctl restart isc-kea-dhcp-ddns-server

Note that the service names may be slightly different between Linux distributions; in general, we have followed the naming conventions in third-party packages. In particular, some systems may not have the isc- prefix.

The Kea Control Agent

Overview of the Kea Control Agent

The Kea Control Agent (CA) is a daemon which exposes a RESTful control interface for managing Kea servers. The daemon can receive control commands over HTTP and either forward these commands to the respective Kea servers or handle these commands on its own. The determination whether the command should be handled by the CA or forwarded is made by checking the value of the service parameter, which may be included in the command from the controlling client. The details of the supported commands, as well as their structures, are provided in Management API.

The CA can use hook libraries to provide support for additional commands or to program custom behavior of existing commands. Such hook libraries must implement callouts for the control_command_receive hook point. Details about creating new hook libraries and supported hook points can be found in the Kea Developer’s Guide.

The CA processes received commands according to the following algorithm:

• Pass command into any installed hooks (regardless of service value(s)). If the command is handled by a hook, return the response.

• If the service specifies one or more services, forward the command to the specified services and return the accumulated responses.

• If the service is not specified or is an empty list, handle the command if the CA supports it.

Configuration

The following example demonstrates the basic CA configuration.

{
    "Control-agent": {
        "http-host": "10.20.30.40",
        "http-port": 8000,
        "trust-anchor": "/path/to/the/ca-cert.pem",
        "cert-file": "/path/to/the/agent-cert.pem",
        "key-file": "/path/to/the/agent-key.pem",
        "cert-required": true,
        "authentication": {
            "type": "basic",
            "realm": "kea-control-agent",
            "clients": [
            {
                "user": "admin",
                "password": "1234"
            } ]
        },

        "control-sockets": {
            "dhcp4": {
                "comment": "main server",
                "socket-type": "unix",
                "socket-name": "/path/to/the/unix/socket-v4"
            },
            "dhcp6": {
                "socket-type": "unix",
                "socket-name": "/path/to/the/unix/socket-v6",
                "user-context": { "version": 3 }
            },
            "d2": {
                "socket-type": "unix",
                "socket-name": "/path/to/the/unix/socket-d2"
            },
        },

        "hooks-libraries": [
        {
            "library": "/opt/local/control-agent-commands.so",
            "parameters": {
                "param1": "foo"
            }
        } ],

        "loggers": [ {
            "name": "kea-ctrl-agent",
            "severity": "INFO"
        } ]
    }
}

The http-host and http-port parameters specify an IP address and port to which HTTP service will be bound. In the example configuration provided above, the RESTful service will be available at the URL https://10.20.30.40:8000/. If these parameters are not specified, the default URL is http://127.0.0.1:8000/.

When using Kea’s HA hook library with multi-threading, make sure that the address:port combination used for CA is different from the HA peer URLs, which are strictly for internal HA traffic between the peers. User commands should still be sent via CA.

The trust-anchor, cert-file, key-file, and cert-required parameters specify the TLS setup for HTTP, i.e. HTTPS. If these parameters are not specified, HTTP is used. The TLS/HTTPS support in Kea is described in TLS/HTTPS Support.

As mentioned in Overview of the Kea Control Agent, the CA can forward received commands to the Kea servers for processing. For example, config-get is sent to retrieve the configuration of one of the Kea services. When the CA receives this command, including a service parameter indicating that the client wishes to retrieve the configuration of the DHCPv4 server, the CA forwards the command to that server and passes the received response back to the client. More about the service parameter and the general structure of commands can be found in Management API.

The CA uses UNIX domain sockets to forward control commands and receive responses from other Kea services. The dhcp4, dhcp6, and d2 maps specify the files to which UNIX domain sockets are bound. In the configuration above, the CA connects to the DHCPv4 server via /path/to/the/unix/socket-v4 to forward the commands to it. Obviously, the DHCPv4 server must be configured to listen to connections via this same socket. In other words, the command-socket configuration for the DHCPv4 server and the CA (for that server) must match. Consult Management API for the DHCPv4 Server, Management API for the DHCPv6 Server, and Management API for the D2 Server to learn how the socket configuration is specified for the DHCPv4, DHCPv6, and D2 services.

User contexts can store arbitrary data as long as they are in valid JSON syntax and their top-level element is a map (i.e. the data must be enclosed in curly brackets). Some hook libraries may expect specific formatting; please consult the relevant hook library documentation for details.

User contexts can be specified on either global scope, control socket, basic authentication, or loggers. One other useful feature is the ability to store comments or descriptions; the parser translates a “comment” entry into a user context with the entry, which allows a comment to be attached within the configuration itself.

Basic HTTP authentication was added in Kea 1.9.0; it protects against unauthorized uses of the control agent by local users. For protection against remote attackers, HTTPS and reverse proxy of Secure Connections (in Versions Prior to Kea 1.9.6) provide stronger security.

The authentication is described in the authentication block with the mandatory type parameter, which selects the authentication. Currently only the basic HTTP authentication (type basic) is supported.

The realm authentication parameter is used for error messages when the basic HTTP authentication is required but the client is not authorized.

When the clients authentication list is configured and not empty, basic HTTP authentication is required. Each element of the list specifies a user ID and a password. The user ID is mandatory, must be not empty, and must not contain the colon (:) character. The password is optional; when it is not specified an empty password is used.

Note

The basic HTTP authentication user ID and password are encoded in UTF-8, but the current Kea JSON syntax only supports the Latin-1 (i.e. 0x00..0xff) Unicode subset.

To avoid to expose the password or both the user ID and the associated password these values can be read from files. The syntax was extended by:

• The directory authentication parameter which handles the common part of file paths. By default the value is the empty string.

• The``password-file`` client parameter which with the directory parameter specifies the path of a file where the password or when no user ID is given the whole basic HTTP authentication secret before encoding can be read.

• The user-file client parameter which with the directory parameter specifies the path of a file where the user ID can be read.

When files are used they are read when the configuration is loaded in order to detect configuration errors as soon as possible.

Hook libraries can be loaded by the Control Agent in the same way as they are loaded by the DHCPv4 and DHCPv6 servers. The CA currently supports one hook point - control_command_receive - which makes it possible to delegate processing of some commands to the hook library. The hooks-libraries list contains the list of hook libraries that should be loaded by the CA, along with their configuration information specified with parameters.

Please consult Logging for the details on how to configure logging. The CA’s root logger’s name is kea-ctrl-agent, as given in the example above.

Secure Connections (in Versions Prior to Kea 1.9.6)

The Control Agent does not natively support secure HTTP connections, like SSL or TLS, before Kea 1.9.6.

To set up a secure connection, please use one of the available third-party HTTP servers and configure it to run as a reverse proxy to the Control Agent. Kea has been tested with two major HTTP server implementations working as a reverse proxy: Apache2 and nginx. Example configurations, including extensive comments, are provided in the doc/examples/https/ directory.

The reverse proxy forwards HTTP requests received over a secure connection to the Control Agent using unsecured HTTP. Typically, the reverse proxy and the Control Agent are running on the same machine, but it is possible to configure them to run on separate machines as well. In this case, security depends on the protection of the communications between the reverse proxy and the Control Agent.

Apart from providing the encryption layer for the control channel, a reverse proxy server is also often used for authentication of the controlling clients. In this case, the client must present a valid certificate when it connects via reverse proxy. The proxy server authenticates the client by checking whether the presented certificate is signed by the certificate authority used by the server.

To illustrate this, the following is a sample configuration for the nginx server running as a reverse proxy to the Kea Control Agent. The server enables authentication of the clients using certificates.

#   The server certificate and key can be generated as follows:
#
#   openssl genrsa -des3 -out kea-proxy.key 4096
#   openssl req -new -x509 -days 365 -key kea-proxy.key -out kea-proxy.crt
#
#   The CA certificate and key can be generated as follows:
#
#   openssl genrsa -des3 -out ca.key 4096
#   openssl req -new -x509 -days 365 -key ca.key -out ca.crt
#
#
#   The client certificate needs to be generated and signed:
#
#   openssl genrsa -des3 -out kea-client.key 4096
#   openssl req -new -key kea-client.key -out kea-client.csr
#   openssl x509 -req -days 365 -in kea-client.csr -CA ca.crt \
#           -CAkey ca.key -set_serial 01 -out kea-client.crt
#
#   Note that the "common name" value used when generating the client
#   and the server certificates must differ from the value used
#   for the CA certificate.
#
#   The client certificate must be deployed on the client system.
#   In order to test the proxy configuration with "curl", run a
#   command similar to the following:
#
#   curl -k --key kea-client.key --cert kea-client.crt -X POST \
#        -H Content-Type:application/json -d '{ "command": "list-commands" }' \
#         https://kea.example.org/kea
#
#   curl syntax for basic authentication is -u user:password
#
#
#   nginx configuration starts here.

events {
}

http {
        #   HTTPS server
    server {
        #     Use default HTTPS port.
        listen 443 ssl;
        #     Set server name.
        server_name kea.example.org;

        #   Server certificate and key.
        ssl_certificate /path/to/kea-proxy.crt;
        ssl_certificate_key /path/to/kea-proxy.key;

        #   Certificate Authority. Client certificates must be signed by the CA.
        ssl_client_certificate /path/to/ca.crt;

        # Enable verification of the client certificate.
        ssl_verify_client on;

        # For URLs such as https://kea.example.org/kea, forward the
        # requests to http://127.0.0.1:8000.
        location /kea {
            proxy_pass http://127.0.0.1:8000;
        }
    }
}

Note

The configuration snippet provided above is for testing purposes only. It should be modified according to the security policies and best practices of the administrator’s organization.

When using an HTTP client without TLS support, such as kea-shell, it is possible to use an HTTP/HTTPS translator such as stunnel in client mode. A sample configuration is provided in the doc/examples/https/shell/ directory.

Secure Connections (in Kea 1.9.6 and Newer)

Since Kea 1.9.6, the Control Agent natively supports secure HTTP connections using TLS. This allows protection against users from the node where the agent runs, something that a reverse proxy cannot provide. More about TLS/HTTPS support in Kea can be found in TLS/HTTPS Support.

TLS is configured using three string parameters, giving file names and a boolean parameter:

• The trust-anchor specifies the Certification Authority file name or directory path.

• The cert-file specifies the server certificate file name.

• The key-file specifies the private key file name. The file must not be encrypted.

• The cert-required specifies whether client certificates are required or optional. The default is to require them and to perform mutual authentication.

The file format is PEM. Either all the string parameters are specified and HTTP over TLS (HTTPS) is used, or none is specified and plain HTTP is used. Configuring only one or two string parameters results in an error.

Note

When client certificates are not required, only the server side is authenticated, i.e. the communication is encrypted with an unknown client. This protects only against passive attacks; active attacks, such as “man-in-the-middle,” are still possible.

Note

No standard HTTP authentication scheme cryptographically binds its end entity with TLS. This means that the TLS client and server can be mutually authenticated, but there is no proof they are the same as for the HTTP authentication.

Since Kea 1.9.6, the kea-shell tool supports TLS.

Starting the Control Agent

The CA is started by running its binary and specifying the configuration file it should use. For example:

$ ./kea-ctrl-agent -c /usr/local/etc/kea/kea-ctrl-agent.conf

It can be started by keactrl as well (see Managing Kea with keactrl).

Connecting to the Control Agent

For an example of a tool that can take advantage of the RESTful API, see The Kea Shell.

The DHCPv4 Server

Starting and Stopping the DHCPv4 Server

It is recommended that the Kea DHCPv4 server be started and stopped using keactrl (described in Managing Kea with keactrl); however, it is also possible to run the server directly via the kea-dhcp4 command, which accepts the following command-line switches:

• -c file - specifies the configuration file. This is the only mandatory switch.

• -d - specifies whether the server logging should be switched to debug/verbose mode. In verbose mode, the logging severity and debuglevel specified in the configuration file are ignored; “debug” severity and the maximum debuglevel (99) are assumed. The flag is convenient for temporarily switching the server into maximum verbosity, e.g. when debugging.

• -p server-port - specifies the local UDP port on which the server listens. This is only useful during testing, as a DHCPv4 server listening on ports other than the standard ones is not able to handle regular DHCPv4 queries.

• -P client-port - specifies the remote UDP port to which the server sends all responses. This is only useful during testing, as a DHCPv4 server sending responses to ports other than the standard ones is not able to handle regular DHCPv4 queries.

• -t file - specifies a configuration file to be tested. kea-dhcp4 loads it, checks it, and exits. During the test, log messages are printed to standard output and error messages to standard error. The result of the test is reported through the exit code (0 = configuration looks OK, 1 = error encountered). The check is not comprehensive; certain checks are possible only when running the server.

• -v - displays the Kea version and exits.

• -V - displays the Kea extended version with additional parameters and exits. The listing includes the versions of the libraries dynamically linked to Kea.

• -W - displays the Kea configuration report and exits. The report is a copy of the config.report file produced by ./configure; it is embedded in the executable binary.

On startup, the server detects available network interfaces and attempts to open UDP sockets on all interfaces listed in the configuration file. Since the DHCPv4 server opens privileged ports, it requires root access; this daemon must be run as root.

During startup, the server attempts to create a PID file of the form: [runstatedir]/kea/[conf name].kea-dhcp4.pid, where:

• runstatedir: The value as passed into the build configure script; it defaults to /usr/local/var/run. Note that this value may be overridden at runtime by setting the environment variable KEA_PIDFILE_DIR, although this is intended primarily for testing purposes.

• conf name: The configuration file name used to start the server, minus all preceding paths and the file extension. For example, given a pathname of /usr/local/etc/kea/myconf.txt, the portion used would be myconf.

If the file already exists and contains the PID of a live process, the server issues a DHCP4_ALREADY_RUNNING log message and exits. It is possible, though unlikely, that the file is a remnant of a system crash and the process to which the PID belongs is unrelated to Kea. In such a case, it would be necessary to manually delete the PID file.

The server can be stopped using the kill command. When running in a console, the server can also be shut down by pressing Ctrl-c. Kea detects the key combination and shuts down gracefully.

DHCPv4 Server Configuration

Introduction

This section explains how to configure the Kea DHCPv4 server using a configuration file.

Before DHCPv4 is started, its configuration file must be created. The basic configuration is as follows:

{
# DHCPv4 configuration starts on the next line
"Dhcp4": {

# First we set up global values
    "valid-lifetime": 4000,
    "renew-timer": 1000,
    "rebind-timer": 2000,

# Next we set up the interfaces to be used by the server.
    "interfaces-config": {
        "interfaces": [ "eth0" ]
    },

# And we specify the type of lease database
    "lease-database": {
        "type": "memfile",
        "persist": true,
        "name": "/var/lib/kea/dhcp4.leases"
    },

# Finally, we list the subnets from which we will be leasing addresses.
    "subnet4": [
        {
            "subnet": "192.0.2.0/24",
            "pools": [
                {
                    "pool": "192.0.2.1 - 192.0.2.200"
                }
            ]
        }
    ]
# DHCPv4 configuration ends with the next line
}

}

The following paragraphs provide a brief overview of the parameters in the above example, along with their format. Subsequent sections of this chapter go into much greater detail for these and other parameters.

The lines starting with a hash (#) are comments and are ignored by the server; they do not impact its operation in any way.

The configuration starts in the first line with the initial opening curly bracket (or brace). Each configuration must contain an object specifying the configuration of the Kea module using it. In the example above, this object is called Dhcp4.

The Dhcp4 configuration starts with the "Dhcp4": { line and ends with the corresponding closing brace (in the above example, the brace after the last comment). Everything defined between those lines is considered to be the Dhcp4 configuration.

In general, the order in which those parameters appear does not matter, but there are two caveats. The first one is that the configuration file must be well-formed JSON, meaning that the parameters for any given scope must be separated by a comma, and there must not be a comma after the last parameter. When reordering a configuration file, moving a parameter to or from the last position in a given scope may also require moving the comma. The second caveat is that it is uncommon — although legal JSON — to repeat the same parameter multiple times. If that happens, the last occurrence of a given parameter in a given scope is used, while all previous instances are ignored. This is unlikely to cause any confusion as there are no real-life reasons to keep multiple copies of the same parameter in the configuration file.

The first few DHCPv4 configuration elements define some global parameters. valid-lifetime defines how long the addresses (leases) given out by the server are valid; the default is for a client to be allowed to use a given address for 4000 seconds. (Note that integer numbers are specified as is, without any quotes around them.) renew-timer and rebind-timer are values (also in seconds) that define the T1 and T2 timers that govern when the client begins the renewal and rebind processes.

Note

The lease valid lifetime is expressed as a triplet with minimum, default, and maximum values using configuration entries min-valid-lifetime, valid-lifetime, and max-valid-lifetime. Since Kea 1.9.5, these values may be specified in client classes. The procedure the server uses to select which lifetime value to use is as follows:

If the client query is a BOOTP query, the server always uses the infinite lease time (e.g. 0xffffffff). Otherwise, the server must determine which configured triplet to use by first searching all classes assigned to the query, and then the subnet selected for the query.

Classes are searched in the order they were assigned to the query; the server uses the triplet from the first class that specifies it. If no classes specify the triplet, the server uses the triplet specified by the subnet selected for the client. If the subnet does not explicitly specify it, the server next looks at the subnet’s shared-network (if one exists), then for a global specification, and finally the global default.

If the client requested a lifetime value via DHCP option 51, then the lifetime value used is the requested value bounded by the configured triplet. In other words, if the requested lifetime is less than the configured minimum, the configured minimum is used; if it is more than the configured maximum, the configured maximum is used. If the client did not provide a requested value, the lifetime value used is the triplet default value.

Note

Both renew-timer and rebind-timer are optional. The server only sends rebind-timer to the client, via DHCPv4 option code 59, if it is less than valid-lifetime; and it only sends renew-timer, via DHCPv4 option code 58, if it is less than rebind-timer (or valid-lifetime if rebind-timer was not specified). In their absence, the client should select values for T1 and T2 timers according to RFC 2131. See section Sending T1 (Option 58) and T2 (Option 59) for more details on generating T1 and T2.

The interfaces-config map specifies the network interfaces on which the server should listen to DHCP messages. The interfaces parameter specifies a list of network interfaces on which the server should listen. Lists are opened and closed with square brackets, with elements separated by commas. To listen on two interfaces, the interfaces-config element should look like this:

"interfaces-config": {
    "interfaces": [ "eth0", "eth1" ]
},

The next lines define the lease database, the place where the server stores its lease information. This particular example tells the server to use memfile, which is the simplest and fastest database backend. It uses an in-memory database and stores leases on disk in a CSV (comma-separated values) file. This is a very simple configuration example; usually the lease database configuration is more extensive and contains additional parameters. Note that lease-database is an object and opens up a new scope, using an opening brace. Its parameters (just one in this example: type) follow. If there were more than one, they would be separated by commas. This scope is closed with a closing brace. As more parameters for the Dhcp4 definition follow, a trailing comma is present.

Finally, we need to define a list of IPv4 subnets. This is the most important DHCPv4 configuration structure, as the server uses that information to process clients’ requests. It defines all subnets from which the server is expected to receive DHCP requests. The subnets are specified with the subnet4 parameter. It is a list, so it starts and ends with square brackets. Each subnet definition in the list has several attributes associated with it, so it is a structure and is opened and closed with braces. At a minimum, a subnet definition must have at least two parameters: subnet, which defines the whole subnet; and pools, which is a list of dynamically allocated pools that are governed by the DHCP server.

The example contains a single subnet. If more than one were defined, additional elements in the subnet4 parameter would be specified and separated by commas. For example, to define three subnets, the following syntax would be used:

"subnet4": [
    {
        "pools": [ { "pool":  "192.0.2.1 - 192.0.2.200" } ],
        "subnet": "192.0.2.0/24"
    },
    {
        "pools": [ { "pool": "192.0.3.100 - 192.0.3.200" } ],
        "subnet": "192.0.3.0/24"
    },
    {
        "pools": [ { "pool": "192.0.4.1 - 192.0.4.254" } ],
        "subnet": "192.0.4.0/24"
    }
]

Note that indentation is optional and is used for aesthetic purposes only. In some cases it may be preferable to use more compact notation.

After all the parameters have been specified, there are two contexts open: global and Dhcp4; thus, two closing curly brackets must be used to close them.

Lease Storage

All leases issued by the server are stored in the lease database. There are four database backends available: memfile (the default), MySQL, PostgreSQL.

Memfile - Basic Storage for Leases

The server is able to store lease data in different repositories. Larger deployments may elect to store leases in a database; Lease Database Configuration describes this option. In typical smaller deployments, though, the server stores lease information in a CSV file rather than a database. As well as requiring less administration, an advantage of using a file for storage is that it eliminates a dependency on third-party database software.

The configuration of the memfile backend is controlled through the Dhcp4/lease-database parameters. The type parameter is mandatory and specifies which storage for leases the server should use, through the "memfile" value. The following list gives additional optional parameters that can be used to configure the memfile backend.

• persist: controls whether the new leases and updates to existing leases are written to the file. It is strongly recommended that the value of this parameter be set to true at all times during the server’s normal operation. Not writing leases to disk means that if a server is restarted (e.g. after a power failure), it will not know which addresses have been assigned. As a result, it may assign new clients addresses that are already in use. The value of false is mostly useful for performance-testing purposes. The default value of the persist parameter is true, which enables writing lease updates to the lease file.

• name: specifies an absolute location of the lease file in which new leases and lease updates are recorded. The default value for this parameter is "[kea-install-dir]/var/lib/kea/kea-leases4.csv".

• lfc-interval: specifies the interval, in seconds, at which the server will perform a lease file cleanup (LFC). This removes redundant (historical) information from the lease file and effectively reduces the lease file size. The cleanup process is described in more detail later in this section. The default value of the lfc-interval is 3600. A value of 0 disables the LFC.

• max-row-errors: specifies the number of row errors before the server stops attempting to load a lease file. When the server loads a lease file, it is processed row by row, each row containing a single lease. If a row is flawed and cannot be processed correctly the server logs it, discards the row, and goes on to the next row. This parameter can be used to set a limit on the number of such discards that can occur, after which the server abandons the effort and exits. The default value of 0 disables the limit and allows the server to process the entire file, regardless of how many rows are discarded.

An example configuration of the memfile backend is presented below:

"Dhcp4": {
    "lease-database": {
        "type": "memfile",
        "persist": true,
        "name": "/tmp/kea-leases4.csv",
        "lfc-interval": 1800,
        "max-row-errors": 100
    }
}

This configuration selects /tmp/kea-leases4.csv as the storage for lease information and enables persistence (writing lease updates to this file). It also configures the backend to perform a periodic cleanup of the lease file every 1800 seconds (30 minutes) and sets the maximum number of row errors to 100.

Why Is Lease File Cleanup Necessary?

It is important to know how the lease file contents are organized to understand why the periodic lease file cleanup is needed. Every time the server updates a lease or creates a new lease for a client, the new lease information must be recorded in the lease file. For performance reasons, the server does not update the existing client’s lease in the file, as this would potentially require rewriting the entire file. Instead, it simply appends the new lease information to the end of the file; the previous lease entries for the client are not removed. When the server loads leases from the lease file, e.g. at server startup, it assumes that the latest lease entry for the client is the valid one. Previous entries are discarded, meaning that the server can reconstruct accurate information about the leases even though there may be many lease entries for each client. However, storing many entries for each client results in a bloated lease file and impairs the performance of the server’s startup and reconfiguration, as it needs to process a larger number of lease entries.

Lease file cleanup (LFC) removes all previous entries for each client and leaves only the latest ones. The interval at which the cleanup is performed is configurable, and it should be selected according to the frequency of lease renewals initiated by the clients. The more frequent the renewals, the smaller the value of lfc-interval should be. Note, however, that the LFC takes time and thus it is possible (although unlikely) that, if the lfc-interval is too short, a new cleanup may be started while the previous one is still running. The server would recover from this by skipping the new cleanup when it detected that the previous cleanup was still in progress, but it implies that the actual cleanups will be triggered more rarely than the configured interval. Moreover, triggering a new cleanup adds overhead to the server, which is not able to respond to new requests for a short period of time when the new cleanup process is spawned. Therefore, it is recommended that the lfc-interval value be selected in a way that allows the LFC to complete the cleanup before a new cleanup is triggered.

Lease file cleanup is performed by a separate process (in the background) to avoid a performance impact on the server process. To avoid conflicts between two processes using the same lease files, the LFC process starts with Kea opening a new lease file; the actual LFC process operates on the lease file that is no longer used by the server. There are also other files created as a side effect of the lease file cleanup. The detailed description of the LFC process is located later in this Kea Administrator’s Reference Manual: The LFC Process.

Lease Database Configuration

Note

Lease database access information must be configured for the DHCPv4 server, even if it has already been configured for the DHCPv6 server. The servers store their information independently, so each server can use a separate database or both servers can use the same database.

Note

Kea requires the database timezone to match the system timezone. For more details, see First-Time Creation of the MySQL Database and First-Time Creation of the PostgreSQL Database.

Lease database configuration is controlled through the Dhcp4/lease-database parameters. The database type must be set to memfile, mysql or postgresql, e.g.:

"Dhcp4": { "lease-database": { "type": "mysql", ... }, ... }

Next, the name of the database to hold the leases must be set; this is the name used when the database was created (see First-Time Creation of the MySQL Database or First-Time Creation of the PostgreSQL Database).

For MySQL or PostgreSQL:

"Dhcp4": { "lease-database": { "name": "database-name" , ... }, ... }

If the database is located on a different system from the DHCPv4 server, the database host name must also be specified:

"Dhcp4": { "lease-database": { "host": "remote-host-name", ... }, ... }

Normally, the database is on the same machine as the DHCPv4 server. In this case, set the value to the empty string:

"Dhcp4": { "lease-database": { "host" : "", ... }, ... }

Should the database use a port other than the default, it may be specified as well:

"Dhcp4": { "lease-database": { "port" : 12345, ... }, ... }

Should the database be located on a different system, the administrator may need to specify a longer interval for the connection timeout:

"Dhcp4": { "lease-database": { "connect-timeout" : timeout-in-seconds, ... }, ... }

The default value of five seconds should be more than adequate for local connections. If a timeout is given, though, it should be an integer greater than zero.

The maximum number of times the server automatically attempts to reconnect to the lease database after connectivity has been lost may be specified:

"Dhcp4": { "lease-database": { "max-reconnect-tries" : number-of-tries, ... }, ... }

If the server is unable to reconnect to the database after making the maximum number of attempts, the server will exit. A value of 0 (the default) disables automatic recovery and the server will exit immediately upon detecting a loss of connectivity (MySQL and PostgreSQL only).

The number of milliseconds the server waits between attempts to reconnect to the lease database after connectivity has been lost may also be specified:

"Dhcp4": { "lease-database": { "reconnect-wait-time" : number-of-milliseconds, ... }, ... }

The default value for MySQL and PostgreSQL is 0, which disables automatic recovery and causes the server to exit immediately upon detecting the loss of connectivity.

"Dhcp4": { "lease-database": { "on-fail" : "stop-retry-exit", ... }, ... }

The possible values are:

• stop-retry-exit - disables the DHCP service while trying to automatically recover lost connections. Shuts down the server on failure after exhausting max-reconnect-tries. This is the default value for MySQL and PostgreSQL.

• serve-retry-exit - continues the DHCP service while trying to automatically recover lost connections. Shuts down the server on failure after exhausting max-reconnect-tries.

• serve-retry-continue - continues the DHCP service and does not shut down the server even if the recovery fails.

Note

Automatic reconnection to database backends is configured individually per backend; this allows users to tailor the recovery parameters to each backend they use. We suggest that users enable it either for all backends or none, so behavior is consistent.

Losing connectivity to a backend for which reconnection is disabled results (if configured) in the server shutting itself down. This includes cases when the lease database backend and the hosts database backend are connected to the same database instance.

It is highly recommended not to change the stop-retry-exit default setting for the lease manager, as it is critical for the connection to be active while processing DHCP traffic. Change this only if the server is used exclusively as a configuration tool.

The host parameter is used by the MySQL and PostgreSQL backends.

Finally, the credentials of the account under which the server will access the database should be set:

"Dhcp4": { "lease-database": { "user": "user-name",
                               "password": "password",
                              ... },
           ... }

If there is no password to the account, set the password to the empty string "". (This is the default.)

Hosts Storage

Kea is also able to store information about host reservations in the database. The hosts database configuration uses the same syntax as the lease database. In fact, the Kea server opens independent connections for each purpose, be it lease or hosts information, which gives the most flexibility. Kea can keep leases and host reservations separately, but can also point to the same database. Currently the supported hosts database types are MySQL and PostgreSQL.

The following configuration can be used to configure a connection to MySQL:

"Dhcp4": {
    "hosts-database": {
        "type": "mysql",
        "name": "kea",
        "user": "kea",
        "password": "secret123",
        "host": "localhost",
        "port": 3306
    }
}

Depending on the database configuration, many of the parameters may be optional.

Please note that usage of hosts storage is optional. A user can define all host reservations in the configuration file, and that is the recommended way if the number of reservations is small. However, when the number of reservations grows, it is more convenient to use host storage. Please note that both storage methods (the configuration file and one of the supported databases) can be used together. If hosts are defined in both places, the definitions from the configuration file are checked first and external storage is checked later, if necessary.

Host information can be placed in multiple stores. Operations are performed on the stores in the order they are defined in the configuration file, although this leads to a restriction in ordering in the case of a host reservation addition; read-only stores must be configured after a (required) read-write store, or the addition will fail.

Note

Kea requires the database timezone to match the system timezone. For more details, see First-Time Creation of the MySQL Database and First-Time Creation of the PostgreSQL Database.

DHCPv4 Hosts Database Configuration

Hosts database configuration is controlled through the Dhcp4/hosts-database parameters. If enabled, the type of database must be set to mysql or postgresql.

"Dhcp4": { "hosts-database": { "type": "mysql", ... }, ... }

Next, the name of the database to hold the reservations must be set; this is the name used when the lease database was created (see Supported Backends for instructions on how to set up the desired database type):

"Dhcp4": { "hosts-database": { "name": "database-name" , ... }, ... }

If the database is located on a different system than the DHCPv4 server, the database host name must also be specified:

"Dhcp4": { "hosts-database": { "host": remote-host-name, ... }, ... }

Normally, the database is on the same machine as the DHCPv4 server. In this case, set the value to the empty string:

"Dhcp4": { "hosts-database": { "host" : "", ... }, ... }

Should the database use a port different than the default, it may be specified as well:

"Dhcp4": { "hosts-database": { "port" : 12345, ... }, ... }

The maximum number of times the server automatically attempts to reconnect to the host database after connectivity has been lost may be specified:

"Dhcp4": { "hosts-database": { "max-reconnect-tries" : number-of-tries, ... }, ... }

If the server is unable to reconnect to the database after making the maximum number of attempts, the server will exit. A value of 0 (the default) disables automatic recovery and the server will exit immediately upon detecting a loss of connectivity (MySQL and PostgreSQL only).

The number of milliseconds the server waits between attempts to reconnect to the host database after connectivity has been lost may also be specified:

"Dhcp4": { "hosts-database": { "reconnect-wait-time" : number-of-milliseconds, ... }, ... }

The default value for MySQL and PostgreSQL is 0, which disables automatic recovery and causes the server to exit immediately upon detecting the loss of connectivity.

"Dhcp4": { "hosts-database": { "on-fail" : "stop-retry-exit", ... }, ... }

The possible values are:

• stop-retry-exit - disables the DHCP service while trying to automatically recover lost connections. Shuts down the server on failure after exhausting max-reconnect-tries. This is the default value for MySQL and PostgreSQL.

• serve-retry-exit - continues the DHCP service while trying to automatically recover lost connections. Shuts down the server on failure after exhausting max-reconnect-tries.

• serve-retry-continue - continues the DHCP service and does not shut down the server even if the recovery fails.

Note

Automatic reconnection to database backends is configured individually per backend. This allows users to tailor the recovery parameters to each backend they use. We suggest that users enable it either for all backends or none, so behavior is consistent.

Losing connectivity to a backend for which reconnection is disabled results (if configured) in the server shutting itself down. This includes cases when the lease database backend and the hosts database backend are connected to the same database instance.

Finally, the credentials of the account under which the server will access the database should be set:

"Dhcp4": { "hosts-database": { "user": "user-name",
                               "password": "password",
                              ... },
           ... }

If there is no password to the account, set the password to the empty string "". (This is the default.)

The multiple-storage extension uses a similar syntax; a configuration is placed into a hosts-databases list instead of into a hosts-database entry, as in:

"Dhcp4": { "hosts-databases": [ { "type": "mysql", ... }, ... ], ... }

If the same host is configured both in-file and in-database, Kea does not issue a warning, as it would if both were specified in the same data source. Instead, the host configured in-file has priority over the one configured in-database.

Using Read-Only Databases for Host Reservations With DHCPv4

In some deployments, the user whose name is specified in the database backend configuration may not have write privileges to the database. This is often required by the policy within a given network to secure the data from being unintentionally modified. In many cases administrators have deployed inventory databases, which contain substantially more information about the hosts than just the static reservations assigned to them. The inventory database can be used to create a view of a Kea hosts database and such a view is often read-only.

Kea host-database backends operate with an implicit configuration to both read from and write to the database. If the user does not have write access to the host database, the backend will fail to start and the server will refuse to start (or reconfigure). However, if access to a read-only host database is required for retrieving reservations for clients and/or assigning specific addresses and options, it is possible to explicitly configure Kea to start in “read-only” mode. This is controlled by the readonly boolean parameter as follows:

"Dhcp4": { "hosts-database": { "readonly": true, ... }, ... }

Setting this parameter to false configures the database backend to operate in “read-write” mode, which is also the default configuration if the parameter is not specified.

Note

The readonly parameter is only supported for MySQL and PostgreSQL databases.

Interface Configuration

The DHCPv4 server must be configured to listen on specific network interfaces. The simplest network interface configuration tells the server to listen on all available interfaces:

"Dhcp4": {
    "interfaces-config": {
        "interfaces": [ "*" ]
    }
    ...
},

The asterisk plays the role of a wildcard and means “listen on all interfaces.” However, it is usually a good idea to explicitly specify interface names:

"Dhcp4": {
    "interfaces-config": {
        "interfaces": [ "eth1", "eth3" ]
    },
    ...
}

It is possible to use an interface wildcard (*) concurrently with explicit interface names:

"Dhcp4": {
    "interfaces-config": {
        "interfaces": [ "eth1", "eth3", "*" ]
    },
    ...
}

This format should only be used when it is desired to temporarily override a list of interface names and listen on all interfaces.

Some deployments of DHCP servers require that the servers listen on interfaces with multiple IPv4 addresses configured. In these situations, the address to use can be selected by appending an IPv4 address to the interface name in the following manner:

"Dhcp4": {
    "interfaces-config": {
        "interfaces": [ "eth1/10.0.0.1", "eth3/192.0.2.3" ]
    },
    ...
}

Should the server be required to listen on multiple IPv4 addresses assigned to the same interface, multiple addresses can be specified for an interface as in the example below:

"Dhcp4": {
    "interfaces-config": {
        "interfaces": [ "eth1/10.0.0.1", "eth1/10.0.0.2" ]
    },
    ...
}

Alternatively, if the server should listen on all addresses for the particular interface, an interface name without any address should be specified.

Kea supports responding to directly connected clients which do not have an address configured. This requires the server to inject the hardware address of the destination into the data-link layer of the packet being sent to the client. The DHCPv4 server uses raw sockets to achieve this, and builds the entire IP/UDP stack for the outgoing packets. The downside of raw socket use, however, is that incoming and outgoing packets bypass the firewalls (e.g. iptables).

Handling traffic on multiple IPv4 addresses assigned to the same interface can be a challenge, as raw sockets are bound to the interface. When the DHCP server is configured to use the raw socket on an interface to receive DHCP traffic, advanced packet filtering techniques (e.g. the BPF) must be used to receive unicast traffic on the desired addresses assigned to the interface. Whether clients use the raw socket or the UDP socket depends on whether they are directly connected (raw socket) or relayed (either raw or UDP socket).

Therefore, in deployments where the server does not need to provision the directly connected clients and only receives the unicast packets from the relay agents, the Kea server should be configured to use UDP sockets instead of raw sockets. The following configuration demonstrates how this can be achieved:

"Dhcp4": {
    "interfaces-config": {
        "interfaces": [ "eth1", "eth3" ],
        "dhcp-socket-type": "udp"
    },
    ...
}

The dhcp-socket-type parameter specifies that the IP/UDP sockets will be opened on all interfaces on which the server listens, i.e. “eth1” and “eth3” in this example. If dhcp-socket-type is set to raw, it configures the server to use raw sockets instead. If the dhcp-socket-type value is not specified, the default value raw is used.

Using UDP sockets automatically disables the reception of broadcast packets from directly connected clients. This effectively means that UDP sockets can be used for relayed traffic only. When using raw sockets, both the traffic from the directly connected clients and the relayed traffic are handled.

Caution should be taken when configuring the server to open multiple raw sockets on the interface with several IPv4 addresses assigned. If the directly connected client sends the message to the broadcast address, all sockets on this link will receive this message and multiple responses will be sent to the client. Therefore, the configuration with multiple IPv4 addresses assigned to the interface should not be used when the directly connected clients are operating on that link. To use a single address on such an interface, the “interface-name/address” notation should be used.

Note

Specifying the value raw as the socket type does not guarantee that raw sockets will be used! The use of raw sockets to handle traffic from the directly connected clients is currently supported on Linux and BSD systems only. If raw sockets are not supported on the particular OS in use, the server issues a warning and fall back to using IP/UDP sockets.

In a typical environment, the DHCP server is expected to send back a response on the same network interface on which the query was received. This is the default behavior. However, in some deployments it is desired that the outbound (response) packets be sent as regular traffic and the outbound interface be determined by the routing tables. This kind of asymmetric traffic is uncommon, but valid. Kea supports a parameter called outbound-interface that controls this behavior. It supports two values: the first one, same-as-inbound, tells Kea to send back the response on the same interface where the query packet was received. This is the default behavior. The second parameter, use-routing, tells Kea to send regular UDP packets and let the kernel’s routing table determine the most appropriate interface. This only works when dhcp-socket-type is set to udp. An example configuration looks as follows:

"Dhcp4": {
    "interfaces-config": {
        "interfaces": [ "eth1", "eth3" ],
        "dhcp-socket-type": "udp",
        "outbound-interface": "use-routing"
    },
    ...
}

Interfaces are re-detected at each reconfiguration. This behavior can be disabled by setting the re-detect value to false, for instance:

"Dhcp4": {
    "interfaces-config": {
        "interfaces": [ "eth1", "eth3" ],
        "re-detect": false
    },
    ...
}

Note that interfaces are not re-detected during config-test.

Usually loopback interfaces (e.g. the lo or lo0 interface) are not configured, but if a loopback interface is explicitly configured and IP/UDP sockets are specified, the loopback interface is accepted.

For example, this setup can be used to run Kea in a FreeBSD jail having only a loopback interface, to service a relayed DHCP request:

"Dhcp4": {
    "interfaces-config": {
        "interfaces": [ "lo0" ],
        "dhcp-socket-type": "udp"
    },
    ...
}

Kea binds the service sockets for each interface on startup. If another process is already using a port, then Kea logs the message and suppresses an error. DHCP service runs, but it is unavailable on some interfaces.

The “service-sockets-require-all” option makes Kea require all sockets to be successfully bound. If any opening fails, Kea interrupts the initialization and exits with a non-zero status. (Default is false).

"Dhcp4": {
    "interfaces-config": {
        "interfaces": [ "eth1", "eth3" ],
        "service-sockets-require-all": true
    },
    ...
}

Sometimes, immediate interruption isn’t a good choice. The port can be unavailable only temporary. In this case, retrying the opening may resolve the problem. Kea provides two options to specify the retrying: service-sockets-max-retries and service-sockets-retry-wait-time.

The first defines a maximal number of retries that Kea makes to open a socket. The zero value (default) means that the Kea doesn’t retry the process.

The second defines a wait time (in milliseconds) between attempts. The default value is 5000 (5 seconds).

"Dhcp4": {
    "interfaces-config": {
        "interfaces": [ "eth1", "eth3" ],
        "service-sockets-max-retries": 5,
        "service-sockets-retry-wait-time": 5000
    },
    ...
}

If “service-sockets-max-retries” is non-zero and “service-sockets-require-all” is false, then Kea retries the opening (if needed) but does not fail if any socket is still not opened.

Issues With Unicast Responses to DHCPINFORM

The use of UDP sockets has certain benefits in deployments where the server receives only relayed traffic; these benefits are mentioned in Interface Configuration. From the administrator’s perspective it is often desirable to configure the system’s firewall to filter out unwanted traffic, and the use of UDP sockets facilitates this. However, the administrator must also be aware of the implications related to filtering certain types of traffic, as it may impair the DHCP server’s operation.

In this section we focus on the case when the server receives the DHCPINFORM message from the client via a relay. According to RFC 2131, the server should unicast the DHCPACK response to the address carried in the ciaddr field. When the UDP socket is in use, the DHCP server relies on the low-level functions of an operating system to build the data link, IP, and UDP layers of the outgoing message. Typically, the OS first uses ARP to obtain the client’s link-layer address to be inserted into the frame’s header, if the address is not cached from a previous transaction that the client had with the server. When the ARP exchange is successful, the DHCP message can be unicast to the client, using the obtained address.

Some system administrators block ARP messages in their network, which causes issues for the server when it responds to the DHCPINFORM messages because the server is unable to send the DHCPACK if the preceding ARP communication fails. Since the OS is entirely responsible for the ARP communication and then sending the DHCP packet over the wire, the DHCP server has no means to determine that the ARP exchange failed and the DHCP response message was dropped. Thus, the server does not log any error messages when the outgoing DHCP response is dropped. At the same time, all hooks pertaining to the packet-sending operation will be called, even though the message never reaches its destination.

Note that the issue described in this section is not observed when raw sockets are in use, because, in this case, the DHCP server builds all the layers of the outgoing message on its own and does not use ARP. Instead, it inserts the value carried in the chaddr field of the DHCPINFORM message into the link layer.

Server administrators willing to support DHCPINFORM messages via relays should not block ARP traffic in their networks, or should use raw sockets instead of UDP sockets.

IPv4 Subnet Identifier

The subnet identifier (subnet ID) is a unique number associated with a particular subnet. In principle, it is used to associate clients’ leases with their respective subnets. When a subnet identifier is not specified for a subnet being configured, it is automatically assigned by the configuration mechanism. The identifiers are assigned starting at 1 and are monotonically increased for each subsequent subnet: 1, 2, 3, ….

If there are multiple subnets configured with auto-generated identifiers and one of them is removed, the subnet identifiers may be renumbered. For example: if there are four subnets and the third is removed, the last subnet will be assigned the identifier that the third subnet had before removal. As a result, the leases stored in the lease database for subnet 3 are now associated with subnet 4, something that may have unexpected consequences. The only remedy for this issue at present is to manually specify a unique identifier for each subnet.

Note

Subnet IDs must be greater than zero and less than 4294967295.

The following configuration assigns the specified subnet identifier to a newly configured subnet:

"Dhcp4": {
    "subnet4": [
        {
            "subnet": "192.0.2.0/24",
            "id": 1024,
            ...
        }
    ]
}

This identifier will not change for this subnet unless the id parameter is removed or set to 0. The value of 0 forces auto-generation of the subnet identifier.

IPv4 Subnet Prefix

The subnet prefix is the second way to identify a subnet. Kea can accept non-canonical subnet addresses; for instance, this configuration is accepted:

"Dhcp4": {
    "subnet4": [
        {
           "subnet": "192.0.2.1/24",
            ...
        }
    ]
}

This works even if there is another subnet with the “192.0.2.0/24” prefix; only the textual form of subnets are compared to avoid duplicates.

Note

Abuse of this feature can lead to incorrect subnet selection (see How the DHCPv4 Server Selects a Subnet for the Client).

Configuration of IPv4 Address Pools

The main role of a DHCPv4 server is address assignment. For this, the server must be configured with at least one subnet and one pool of dynamic addresses to be managed. For example, assume that the server is connected to a network segment that uses the 192.0.2.0/24 prefix. The administrator of that network decides that addresses from the range 192.0.2.10 to 192.0.2.20 are going to be managed by the DHCPv4 server. Such a configuration can be achieved in the following way:

"Dhcp4": {
    "subnet4": [
        {
            "subnet": "192.0.2.0/24",
            "pools": [
                { "pool": "192.0.2.10 - 192.0.2.20" }
            ],
            ...
        }
    ]
}

Note that subnet is defined as a simple string, but the pools parameter is actually a list of pools; for this reason, the pool definition is enclosed in square brackets, even though only one range of addresses is specified.

Each pool is a structure that contains the parameters that describe a single pool. Currently there is only one parameter, pool, which gives the range of addresses in the pool.

It is possible to define more than one pool in a subnet; continuing the previous example, further assume that 192.0.2.64/26 should also be managed by the server. It could be written as 192.0.2.64 to 192.0.2.127, or it can be expressed more simply as 192.0.2.64/26. Both formats are supported by Dhcp4 and can be mixed in the pool list. For example, the following pools could be defined:

"Dhcp4": {
    "subnet4": [
        {
            "subnet": "192.0.2.0/24",
            "pools": [
                { "pool": "192.0.2.10-192.0.2.20" },
                { "pool": "192.0.2.64/26" }
            ],
            ...
        }
    ],
    ...
}

White space in pool definitions is ignored, so spaces before and after the hyphen are optional. They can be used to improve readability.

The number of pools is not limited, but for performance reasons it is recommended to use as few as possible.

The server may be configured to serve more than one subnet. To add a second subnet, use a command similar to the following:

"Dhcp4": {
    "subnet4": [
        {
            "subnet": "192.0.2.0/24",
            "pools": [ { "pool": "192.0.2.1 - 192.0.2.200" } ],
            ...
        },
        {
            "subnet": "192.0.3.0/24",
            "pools": [ { "pool": "192.0.3.100 - 192.0.3.200" } ],
            ...
        },
        {
            "subnet": "192.0.4.0/24",
            "pools": [ { "pool": "192.0.4.1 - 192.0.4.254" } ],
            ...
        }
    ]
}

When configuring a DHCPv4 server using prefix/length notation, please pay attention to the boundary values. When specifying that the server can use a given pool, it is also able to allocate the first (typically a network address) and the last (typically a broadcast address) address from that pool. In the aforementioned example of pool 192.0.3.0/24, both the 192.0.3.0 and 192.0.3.255 addresses may be assigned as well. This may be invalid in some network configurations. To avoid this, use the min-max notation.

Note

Here are some liberties and limits to the values that subnets and pools can take in Kea configurations that are out of the ordinary:

Kea configuration case	Allowed	Comment
Overlapping subnets	Yes	Administrator should consider how clients are matched to these subnets.
Overlapping pools in one subnet	No	Startup error: DHCP4_PARSER_FAIL
Overlapping address pools in different subnets	Yes	Specifying the same address pool in different subnets can be used as an equivalent of the global address pool. In that case, the server can assign addresses from the same range regardless of the client’s subnet. If an address from such a pool is assigned to a client in one subnet, the same address will be renewed for this client if it moves to another subnet. Another client in a different subnet will not be assigned an address already assigned to the client in any of the subnets.
Pools not matching the subnet prefix	No	Startup error: DHCP4_PARSER_FAIL

Sending T1 (Option 58) and T2 (Option 59)

According to RFC 2131, servers should send values for T1 and T2 that are 50% and 87.5% of the lease lifetime, respectively. By default, kea-dhcp4 does not send either value; it can be configured to send values that are either specified explicitly or that are calculated as percentages of the lease time. The server’s behavior is governed by a combination of configuration parameters, two of which have already been mentioned. To send specific, fixed values use the following two parameters:

• renew-timer - specifies the value of T1 in seconds.

• rebind-timer - specifies the value of T2 in seconds.

The server only sends T2 if it is less than the valid lease time. T1 is only sent if T2 is being sent and T1 is less than T2; or T2 is not being sent and T1 is less than the valid lease time.

Calculating the values is controlled by the following three parameters.

• calculate-tee-times - when true, T1 and T2 are calculated as percentages of the valid lease time. It defaults to false.

• t1-percent - the percentage of the valid lease time to use for T1. It is expressed as a real number between 0.0 and 1.0 and must be less than t2-percent. The default value is 0.50, per RFC 2131.

• t2-percent - the percentage of the valid lease time to use for T2. It is expressed as a real number between 0.0 and 1.0 and must be greater than t1-percent. The default value is .875, per RFC 2131.

Note

In the event that both explicit values are specified and calculate-tee-times is true, the server will use the explicit values. Administrators with a setup where some subnets or shared-networks use explicit values and some use calculated values must not define the explicit values at any level higher than where they will be used. Inheriting them from too high a scope, such as global, will cause them to have explicit values at every level underneath (shared-networks and subnets), effectively disabling calculated values.

Standard DHCPv4 Options

One of the major features of the DHCPv4 server is the ability to provide configuration options to clients. Most of the options are sent by the server only if the client explicitly requests them using the Parameter Request List option. Those that do not require inclusion in the Parameter Request List option are commonly used options, e.g. “Domain Server”, and options which require special behavior, e.g. “Client FQDN”, which is returned to the client if the client has included this option in its message to the server.

List of standard DHCPv4 options configurable by an administrator comprises the list of the standard DHCPv4 options whose values can be configured using the configuration structures described in this section. This table excludes the options which require special processing and thus cannot be configured with fixed values. The last column of the table indicates which options can be sent by the server even when they are not requested in the Parameter Request List option, and those which are sent only when explicitly requested.

The following example shows how to configure the addresses of DNS servers, which is one of the most frequently used options. Options specified in this way are considered global and apply to all configured subnets.

"Dhcp4": {
    "option-data": [
        {
           "name": "domain-name-servers",
           "code": 6,
           "space": "dhcp4",
           "csv-format": true,
           "data": "192.0.2.1, 192.0.2.2"
        },
        ...
    ]
}

Note that either name or code is required; there is no need to specify both. space has a default value of dhcp4, so this can be skipped as well if a regular (not encapsulated) DHCPv4 option is defined. Finally, csv-format defaults to true, so it too can be skipped, unless the option value is specified as a hexadecimal string. Therefore, the above example can be simplified to:

"Dhcp4": {
    "option-data": [
        {
           "name": "domain-name-servers",
           "data": "192.0.2.1, 192.0.2.2"
        },
        ...
    ]
}

Defined options are added to the response when the client requests them, with a few exceptions which are always added. To enforce the addition of a particular option, set the always-send flag to true as in:

"Dhcp4": {
    "option-data": [
        {
           "name": "domain-name-servers",
           "data": "192.0.2.1, 192.0.2.2",
           "always-send": true
        },
        ...
    ]
}

The effect is the same as if the client added the option code in the Parameter Request List option (or its equivalent for vendor options):

"Dhcp4": {
    "option-data": [
        {
           "name": "domain-name-servers",
           "data": "192.0.2.1, 192.0.2.2",
           "always-send": true
        },
        ...
    ],
    "subnet4": [
        {
           "subnet": "192.0.3.0/24",
           "option-data": [
               {
                   "name": "domain-name-servers",
                   "data": "192.0.3.1, 192.0.3.2"
               },
               ...
           ],
           ...
        },
        ...
    ],
    ...
}

The domain-name-servers option is always added to responses (the always-send is “sticky”), but the value is the subnet one when the client is localized in the subnet.

The name parameter specifies the option name. For a list of currently supported names, see List of standard DHCPv4 options configurable by an administrator below. The code parameter specifies the option code, which must match one of the values from that list. The next line specifies the option space, which must always be set to dhcp4 as these are standard DHCPv4 options. For other option spaces, including custom option spaces, see Nested DHCPv4 Options (Custom Option Spaces). The next line specifies the format in which the data will be entered; use of CSV (comma-separated values) is recommended. The sixth line gives the actual value to be sent to clients. The data parameter is specified as normal text, with values separated by commas if more than one value is allowed.

Options can also be configured as hexadecimal values. If csv-format is set to false, option data must be specified as a hexadecimal string. The following commands configure the domain-name-servers option for all subnets with the following addresses: 192.0.3.1 and 192.0.3.2. Note that csv-format is set to false.

"Dhcp4": {
    "option-data": [
        {
            "name": "domain-name-servers",
            "code": 6,
            "space": "dhcp4",
            "csv-format": false,
            "data": "C0 00 03 01 C0 00 03 02"
        },
        ...
    ],
    ...
}

Kea supports the following formats when specifying hexadecimal data:

• Delimited octets - one or more octets separated by either colons or spaces (“:” or ” “). While each octet may contain one or two digits, we strongly recommend always using two digits. Valid examples are “ab:cd:ef” and “ab cd ef”.

• String of digits - a continuous string of hexadecimal digits with or without a “0x” prefix. Valid examples are “0xabcdef” and “abcdef”.

Care should be taken to use proper encoding when using hexadecimal format; Kea’s ability to validate data correctness in hexadecimal is limited.

It is also possible to specify data for binary options as a single-quoted text string within double quotes as shown (note that csv-format must be set to false):

"Dhcp4": {
    "option-data": [
        {
            "name": "user-class",
            "code": 77,
            "space": "dhcp4",
            "csv-format": false,
            "data": "'convert this text to binary'"
        },
        ...
    ],
    ...
}

Most of the parameters in the option-data structure are optional and can be omitted in some circumstances, as discussed in Unspecified Parameters for DHCPv4 Option Configuration.

It is possible to specify or override options on a per-subnet basis. If clients connected to most subnets are expected to get the same values of a given option, administrators should use global options. On the other hand, if different values are used in each subnet, it does not make sense to specify global option values; rather, only subnet-specific ones should be set.

The following commands override the global DNS servers option for a particular subnet, setting a single DNS server with address 192.0.2.3:

"Dhcp4": {
    "subnet4": [
        {
            "option-data": [
                {
                    "name": "domain-name-servers",
                    "code": 6,
                    "space": "dhcp4",
                    "csv-format": true,
                    "data": "192.0.2.3"
                },
                ...
            ],
            ...
        },
        ...
    ],
    ...
}

In some cases it is useful to associate some options with an address pool from which a client is assigned a lease. Pool-specific option values override subnet-specific and global option values; it is not possible to prioritize assignment of pool-specific options via the order of pool declarations in the server configuration.

The following configuration snippet demonstrates how to specify the DNS servers option, which is assigned to a client only if the client obtains an address from the given pool:

"Dhcp4": {
    "subnet4": [
        {
            "pools": [
                {
                    "pool": "192.0.2.1 - 192.0.2.200",
                    "option-data": [
                        {
                            "name": "domain-name-servers",
                            "data": "192.0.2.3"
                         },
                         ...
                    ],
                    ...
                },
                ...
            ],
            ...
        },
        ...
    ],
    ...
}

Options can also be specified in class or host-reservation scope. The current Kea options precedence order is (from most important to least): host reservation, pool, subnet, shared network, class, global.

When a data field is a string and that string contains the comma (,; U+002C) character, the comma must be escaped with two backslashes (\\,; U+005C). This double escape is required because both the routine splitting of CSV data into fields and JSON use the same escape character; a single escape (\,) would make the JSON invalid. For example, the string “foo,bar” must be represented as:

"Dhcp4": {
    "subnet4": [
        {
            "pools": [
                {
                    "option-data": [
                        {
                            "name": "boot-file-name",
                            "data": "foo\\,bar"
                        }
                    ]
                },
                ...
            ],
            ...
        },
        ...
    ],
    ...
}

Some options are designated as arrays, which means that more than one value is allowed. For example, the option time-servers allows the specification of more than one IPv4 address, enabling clients to obtain the addresses of multiple NTP servers.

Custom DHCPv4 Options describes the configuration syntax to create custom option definitions (formats). Creation of custom definitions for standard options is generally not permitted, even if the definition being created matches the actual option format defined in the RFCs. There is an exception to this rule for standard options for which Kea currently does not provide a definition. To use such options, a server administrator must create a definition as described in Custom DHCPv4 Options in the dhcp4 option space. This definition should match the option format described in the relevant RFC, but the configuration mechanism will allow any option format as it currently has no means to validate it.

The currently supported standard DHCPv4 options are listed in the table below. “Name” and “Code” are the values that should be used as a name/code in the option-data structures. “Type” designates the format of the data; the meanings of the various types are given in List of standard DHCP option types.

List of standard DHCPv4 options configurable by an administrator

Name	Code	Type	Array?	Returned if not requested?
time-offset	2	int32	false	false
routers	3	ipv4-address	true	true
time-servers	4	ipv4-address	true	false
name-servers	5	ipv4-address	true	false
domain-name-servers	6	ipv4-address	true	true
log-servers	7	ipv4-address	true	false
cookie-servers	8	ipv4-address	true	false
lpr-servers	9	ipv4-address	true	false
impress-servers	10	ipv4-address	true	false
resource-location-servers	11	ipv4-address	true	false
boot-size	13	uint16	false	false
merit-dump	14	string	false	false
domain-name	15	fqdn	false	true
swap-server	16	ipv4-address	false	false
root-path	17	string	false	false
extensions-path	18	string	false	false
ip-forwarding	19	boolean	false	false
non-local-source-routing	20	boolean	false	false
policy-filter	21	ipv4-address	true	false
max-dgram-reassembly	22	uint16	false	false
default-ip-ttl	23	uint8	false	false
path-mtu-aging-timeout	24	uint32	false	false
path-mtu-plateau-table	25	uint16	true	false
interface-mtu	26	uint16	false	false
all-subnets-local	27	boolean	false	false
broadcast-address	28	ipv4-address	false	false
perform-mask-discovery	29	boolean	false	false
mask-supplier	30	boolean	false	false
router-discovery	31	boolean	false	false
router-solicitation-address	32	ipv4-address	false	false
static-routes	33	ipv4-address	true	false
trailer-encapsulation	34	boolean	false	false
arp-cache-timeout	35	uint32	false	false
ieee802-3-encapsulation	36	boolean	false	false
default-tcp-ttl	37	uint8	false	false
tcp-keepalive-interval	38	uint32	false	false
tcp-keepalive-garbage	39	boolean	false	false
nis-domain	40	string	false	false
nis-servers	41	ipv4-address	true	false
ntp-servers	42	ipv4-address	true	false
vendor-encapsulated-options	43	empty	false	false
netbios-name-servers	44	ipv4-address	true	false
netbios-dd-server	45	ipv4-address	true	false
netbios-node-type	46	uint8	false	false
netbios-scope	47	string	false	false
font-servers	48	ipv4-address	true	false
x-display-manager	49	ipv4-address	true	false
dhcp-option-overload	52	uint8	false	false
dhcp-server-identifier	54	ipv4-address	false	true
dhcp-message	56	string	false	false
dhcp-max-message-size	57	uint16	false	false
vendor-class-identifier	60	string	false	false
nwip-domain-name	62	string	false	false
nwip-suboptions	63	binary	false	false
nisplus-domain-name	64	string	false	false
nisplus-servers	65	ipv4-address	true	false
tftp-server-name	66	string	false	false
boot-file-name	67	string	false	false
mobile-ip-home-agent	68	ipv4-address	true	false
smtp-server	69	ipv4-address	true	false
pop-server	70	ipv4-address	true	false
nntp-server	71	ipv4-address	true	false
www-server	72	ipv4-address	true	false
finger-server	73	ipv4-address	true	false
irc-server	74	ipv4-address	true	false
streettalk-server	75	ipv4-address	true	false
streettalk-directory-assistance-server	76	ipv4-address	true	false
user-class	77	binary	false	false
slp-directory-agent	78	record (boolean, ipv4-address)	true	false
slp-service-scope	79	record (boolean, string)	false	false
nds-server	85	ipv4-address	true	false
nds-tree-name	86	string	false	false
nds-context	87	string	false	false
bcms-controller-names	88	fqdn	true	false
bcms-controller-address	89	ipv4-address	true	false
client-system	93	uint16	true	false
client-ndi	94	record (uint8, uint8, uint8)	false	false
uuid-guid	97	record (uint8, binary)	false	false
uap-servers	98	string	false	false
geoconf-civic	99	binary	false	false
pcode	100	string	false	false
tcode	101	string	false	false
v6-only-preferred	108	uint32	false	false
netinfo-server-address	112	ipv4-address	true	false
netinfo-server-tag	113	string	false	false
v4-captive-portal	114	string	false	false
auto-config	116	uint8	false	false
name-service-search	117	uint16	true	false
domain-search	119	fqdn	true	false
vivco-suboptions	124	record (uint32, binary)	false	false
vivso-suboptions	125	uint32	false	false
pana-agent	136	ipv4-address	true	false
v4-lost	137	fqdn	false	false
capwap-ac-v4	138	ipv4-address	true	false
sip-ua-cs-domains	141	fqdn	true	false
rdnss-selection	146	record (uint8, ipv4-address, ipv4-address, fqdn)	true	false
v4-portparams	159	record (uint8, psid)	false	false
option-6rd	212	record (uint8, uint8, ipv6-address, ipv4-address)	true	false
v4-access-domain	213	fqdn	false	false

Note

The default-url option was replaced with v4-captive-portal in Kea 2.1.2, as introduced by RFC 8910. The new option has exactly the same format as the old one. The general perception is that default-url was seldom used. If you used it and migrating, please replace default-url with v4-captive-portal and your configuration will continue to work as before.

Kea also supports other options than those listed above; the following options are returned by the Kea engine itself and in general should not be configured manually.

List of standard DHCPv4 options managed by Kea on its own and not directly configurable by an administrator

Name	Code	Type	Description
subnet-mask	1	ipv4-address	calculated automatically, based on subnet definition.
host-name	12	string	sent by client, generally governed by the DNS configuration.
dhcp-requested-address	50	ipv6-address	may be sent by the client and the server should not set it.
dhcp-lease-time	51	uint32	set automatically based on the valid-lifetime parameter.
dhcp-message-type	53	string	sent by clients and servers. Set by the Kea engine depending on the situation and should never be configured explicitly.
dhcp-parameter-request-list	55	uint8 array	sent by clients and should never be sent by the server.
dhcp-renewal-time	58	uint32	governed by renew-timer parameter.
dhcp-rebinding-time	59	uint32	governed by rebind-timer parameter.
dhcp-client-identifier	61	binary	sent by client, echoed back with the value sent by the client.
fqdn	81	record (uint8, uint8, uint8, fqdn)	part of the DDNS and D2 configuration.
dhcp-agent-options	82	empty	sent by the relay agent. This is an empty container option; see RAI option detail later in this section.
authenticate	90	binary	sent by client, Kea does not yet validate it.
client-last-transaction-time	91	uint32	sent by client, server does not set it.
associated-ip	92	ipv4-address array	sent by client, server responds with list of addresses.
subnet-selection	118	ipv4-address	if present in client’s messages, will be used in the subnet selection process.

The following table lists all option types used in the previous two tables with a description of what values are accepted for them.

List of standard DHCP option types

Name	Meaning
binary	An arbitrary string of bytes, specified as a set of hexadecimal digits.
boolean	A boolean value with allowed values true or false.
empty	No value; data is carried in sub-options.
fqdn	Fully qualified domain name (e.g. www.example.com).
ipv4-address	IPv4 address in the usual dotted-decimal notation (e.g. 192.0.2.1).
ipv6-address	IPv6 address in the usual colon notation (e.g. 2001:db8::1).
ipv6-prefix	IPv6 prefix and prefix length specified using CIDR notation, e.g. 2001:db8:1::/64. This data type is used to represent an 8-bit field conveying a prefix length and the variable length prefix value.
psid	PSID and PSID length separated by a slash, e.g. 3/4 specifies PSID=3 and PSID length=4. In the wire format it is represented by an 8-bit field carrying PSID length (in this case equal to 4) and the 16-bits-long PSID value field (in this case equal to “0011000000000000b” using binary notation). Allowed values for a PSID length are 0 to 16. See RFC 7597 for details about the PSID wire representation.
record	Structured data that may be comprised of any types (except “record” and “empty”). The array flag applies to the last field only.
string	Any text. Please note that Kea silently discards any terminating/trailing nulls from the end of “string” options when unpacking received packets. This is in keeping with RFC 2132, Section 2.
tuple	A length encoded as an 8-bit (16-bit for DHCPv6) unsigned integer followed by a string of this length.
uint8	An 8-bit unsigned integer with allowed values 0 to 255.
uint16	A 16-bit unsigned integer with allowed values 0 to 65535.
uint32	A 32-bit unsigned integer with allowed values 0 to 4294967295.
int8	An 8-bit signed integer with allowed values -128 to 127.
int16	A 16-bit signed integer with allowed values -32768 to 32767.
int32	A 32-bit signed integer with allowed values -2147483648 to 2147483647.

Kea also supports the Relay Agent Information (RAI) option, sometimes referred to as the relay option, agent option, or simply option 82. The option itself is just a container and does not convey any information on its own. The following table contains a list of RAI sub-options that Kea can understand. The RAI and its sub-options are inserted by the relay agent and received by Kea; there is no need for Kea to be configured with those options.

List of RAI sub-options that Kea can understand

Name	Code	Comment
circuit-id	1	Used when host-reservation-identifiers is set to circuit-id.
remote-id	2	Can be used with flex-id to identify hosts.
link selection	5	If present, is used to select the appropriate subnet.
subscriber-id	6	Can be used with flex-id to identify hosts.
server-id-override	11	If sent by the relay, Kea accepts it as the server-id.
relay-source-port	19	If sent by the relay, Kea sends back its responses to this port.

All other RAI sub-options can be used in client classification to classify incoming packets to specific classes and/or by flex-id to construct a unique device identifier.

Custom DHCPv4 Options

Kea supports custom (non-standard) DHCPv4 options. Let’s say that we want to define a new DHCPv4 option called foo, which will have code 222 and will convey a single, unsigned, 32-bit integer value. Such an option can be defined by putting the following entry in the configuration file:

"Dhcp4": {
    "option-def": [
        {
            "name": "foo",
            "code": 222,
            "type": "uint32",
            "array": false,
            "record-types": "",
            "space": "dhcp4",
            "encapsulate": ""
        }, ...
    ],
    ...
}

The false value of the array parameter determines that the option does NOT comprise an array of uint32 values but is, instead, a single value. Two other parameters have been left blank: record-types and encapsulate. The former specifies the comma-separated list of option data fields, if the option comprises a record of data fields. The record-types value should be non-empty if type is set to “record”; otherwise it must be left blank. The latter parameter specifies the name of the option space being encapsulated by the particular option. If the particular option does not encapsulate any option space, the parameter should be left blank. Note that the option-def configuration statement only defines the format of an option and does not set its value(s).

The name, code, and type parameters are required; all others are optional. The array default value is false. The record-types and encapsulate default values are blank (""). The default space is dhcp4.

Once the new option format is defined, its value is set in the same way as for a standard option. For example, the following commands set a global value that applies to all subnets.

"Dhcp4": {
    "option-data": [
        {
            "name": "foo",
            "code": 222,
            "space": "dhcp4",
            "csv-format": true,
            "data": "12345"
        }, ...
    ],
    ...
}

New options can take more complex forms than the simple use of primitives (uint8, string, ipv4-address, etc.); it is possible to define an option comprising a number of existing primitives.

For example, say we want to define a new option that will consist of an IPv4 address, followed by an unsigned 16-bit integer, followed by a boolean value, followed by a text string. Such an option could be defined in the following way:

"Dhcp4": {
    "option-def": [
        {
            "name": "bar",
            "code": 223,
            "space": "dhcp4",
            "type": "record",
            "array": false,
            "record-types": "ipv4-address, uint16, boolean, string",
            "encapsulate": ""
        }, ...
    ],
    ...
}

The type is set to "record" to indicate that the option contains multiple values of different types. These types are given as a comma-separated list in the record-types field and should be ones from those listed in List of standard DHCP option types.

The option’s values are set in an option-data statement as follows:

"Dhcp4": {
    "option-data": [
        {
            "name": "bar",
            "space": "dhcp4",
            "code": 223,
            "csv-format": true,
            "data": "192.0.2.100, 123, true, Hello World"
        }
    ],
    ...
}

csv-format is set to "true" to indicate that the data field comprises a comma-separated list of values. The values in data must correspond to the types set in the record-types field of the option definition.

When array is set to "true" and type is set to "record", the last field is an array, i.e. it can contain more than one value, as in:

"Dhcp4": {
    "option-def": [
        {
            "name": "bar",
            "code": 223,
            "space": "dhcp4",
            "type": "record",
            "array": true,
            "record-types": "ipv4-address, uint16",
            "encapsulate": ""
        }, ...
    ],
    ...
}

The new option content is one IPv4 address followed by one or more 16-bit unsigned integers.

Note

In general, boolean values are specified as true or false, without quotes. Some specific boolean parameters may also accept "true", "false", 0, 1, "0", and "1".

Note

Numbers can be specified in decimal or hexadecimal format. The hexadecimal format can be either plain (e.g. abcd) or prefixed with 0x (e.g. 0xabcd).

DHCPv4 Private Options

Options with a code between 224 and 254 are reserved for private use. They can be defined at the global scope or at the client-class local scope; this allows option definitions to be used depending on context, and option data to be set accordingly. For instance, to configure an old PXEClient vendor:

"Dhcp4": {
    "client-classes": [
        {
            "name": "pxeclient",
            "test": "option[vendor-class-identifier].text == 'PXEClient'",
            "option-def": [
                {
                    "name": "configfile",
                    "code": 209,
                    "type": "string"
                }
            ],
            ...
        }, ...
    ],
    ...
}

As the Vendor-Specific Information (VSI) option (code 43) has a vendor-specific format, i.e. can carry either raw binary value or sub-options, this mechanism is also available for this option.

In the following example taken from a real configuration, two vendor classes use option 43 for different and incompatible purposes:

"Dhcp4": {
    "option-def": [
        {
            "name": "cookie",
            "code": 1,
            "type": "string",
            "space": "APC"
        },
        {
            "name": "mtftp-ip",
            "code": 1,
            "type": "ipv4-address",
            "space": "PXE"
        },
        ...
    ],
    "client-classes": [
        {
            "name": "APC",
            "test": "option[vendor-class-identifier].text == 'APC'",
            "option-def": [
                {
                    "name": "vendor-encapsulated-options",
                    "type": "empty",
                    "encapsulate": "APC"
                }
            ],
            "option-data": [
                {
                    "name": "cookie",
                    "space": "APC",
                    "data": "1APC"
                },
                {
                    "name": "vendor-encapsulated-options"
                },
                ...
            ],
            ...
        },
        {
            "name": "PXE",
            "test": "option[vendor-class-identifier].text == 'PXE'",
            "option-def": [
                {
                    "name": "vendor-encapsulated-options",
                    "type": "empty",
                    "encapsulate": "PXE"
                }
            ],
            "option-data": [
                {
                    "name": "mtftp-ip",
                    "space": "PXE",
                    "data": "0.0.0.0"
                },
                {
                    "name": "vendor-encapsulated-options"
                },
                ...
            ],
            ...
        },
        ...
    ],
    ...
}

The definition used to decode a VSI option is:

1. The local definition of a client class the incoming packet belongs to;

2. If none, the global definition;

3. If none, the last-resort definition described in the next section, DHCPv4 Vendor-Specific Options (backward-compatible with previous Kea versions).

Note

This last-resort definition for the Vendor-Specific Information option (code 43) is not compatible with a raw binary value. When there are known cases where a raw binary value will be used, a client class must be defined with both a classification expression matching these cases and an option definition for the VSI option with a binary type and no encapsulation.

Note

By default, in the Vendor-Specific Information option (code 43), sub-option code 0 and 255 mean PAD and END respectively, according to RFC 2132. In other words, the sub-option code values of 0 and 255 are reserved. Kea does, however, allow users to define sub-option codes from 0 to 255. If sub-options with codes 0 and/or 255 are defined, bytes with that value are no longer treated as a PAD or an END, but as the sub-option code when parsing a VSI option in an incoming query.

Option 43 input processing (also called unpacking) is deferred so that it happens after classification. This means clients cannot be classified using option 43 sub-options. The definition used to unpack option 43 is determined as follows:

• If defined at the global scope, this definition is used.

• If defined at client class scope and the packet belongs to this class, the client class definition is used.

• If not defined at global scope nor in a client class to which the packet belongs, the built-in last resort definition is used. This definition only says the sub-option space is "vendor-encapsulated-options-space".

The output definition selection is a bit simpler:

• If the packet belongs to a client class which defines the option 43, use this definition.

• If defined at the global scope, use this definition.

• Otherwise, use the built-in last-resort definition.

Since they use a specific/per vendor option space, sub-options are defined at the global scope.

Note

Option definitions in client classes are allowed only for this limited option set (codes 43 and from 224 to 254), and only for DHCPv4.

DHCPv4 Vendor-Specific Options

Currently there are two option spaces defined for the DHCPv4 daemon: dhcp4 (for the top-level DHCPv4 options) and "vendor-encapsulated-options-space", which is empty by default but in which options can be defined. Those options are carried in the Vendor-Specific Information option (code 43). The following examples show how to define an option foo with code 1 that comprises an IPv4 address, an unsigned 16-bit integer, and a string. The foo option is conveyed in a Vendor-Specific Information option.

The first step is to define the format of the option:

"Dhcp4": {
    "option-def": [
        {
            "name": "foo",
            "code": 1,
            "space": "vendor-encapsulated-options-space",
            "type": "record",
            "array": false,
            "record-types": "ipv4-address, uint16, string",
            "encapsulate": ""
        }
    ],
    ...
}

(Note that the option space is set to "vendor-encapsulated-options-space".) Once the option format is defined, the next step is to define actual values for that option:

"Dhcp4": {
    "option-data": [
        {
            "name": "foo",
            "space": "vendor-encapsulated-options-space",
            "code": 1,
            "csv-format": true,
            "data": "192.0.2.3, 123, Hello World"
        }
    ],
    ...
}

In this example, we also include the Vendor-Specific Information option, which conveys our sub-option foo. This is required; otherwise, the option will not be included in messages sent to the client.

"Dhcp4": {
    "option-data": [
        {
            "name": "vendor-encapsulated-options"
        }
    ],
    ...
}

Alternatively, the option can be specified using its code.

"Dhcp4": {
    "option-data": [
        {
            "code": 43
        }
    ],
    ...
}

Another popular option that is often somewhat imprecisely called the “vendor option” is option 125. Its proper name is the “vendor-independent vendor-specific information option” or “vivso”. The idea behind vivso options is that each vendor has its own unique set of options with their own custom formats. The vendor is identified by a 32-bit unsigned integer called enterprise-number or vendor-id.

The standard spaces defined in Kea and their options are:

• vendor-4491: Cable Television Laboratories, Inc. for DOCSIS3 options:

option code	option name	option description
1	oro	ORO (or Option Request Option) is used by clients to request a list of options they are interested in.
2	tftp-servers	a list of IPv4 addresses of TFTP servers to be used by the cable modem

In Kea each vendor is represented by its own vendor space. Since there are hundreds of vendors and sometimes they use different option definitions for different hardware, it is impossible for Kea to support them all natively. Fortunately, it’s easy to define support for new vendor options. Let’s take an example of the Genexis home gateway. This device requires sending the vivso 125 option with a sub-option 2 that contains a string with the TFTP server URL. To support such a device, three steps are needed: first, we need to define option definitions that will explain how the option is supposed to be formed. Second, we need to define option values. Third, we need to tell Kea when to send those specific options, which we can do via client classification.

An example snippet of a configuration could look similar to the following:

{
    // First, we need to define that the suboption 2 in vivso option for
    // vendor-id 25167 has a specific format (it's a plain string in this example).
    // After this definition, we can specify values for option tftp.
    "option-def": [
    {
        // We define a short name, so the option can be referenced by name.
        // The option has code 2 and resides within vendor space 25167.
        // Its data is a plain string.
        "name": "tftp",
        "code": 2,
        "space": "vendor-25167",
        "type": "string"
    } ],

    "client-classes": [
    {
        // We now need to tell Kea how to recognize when to use vendor space 25167.
        // Usually we can use a simple expression, such as checking if the device
        // sent a vivso option with specific vendor-id, e.g. "vendor[4491].exists".
        // Unfortunately, Genexis is a bit unusual in this aspect, because it
        // doesn't send vivso. In this case we need to look into the vendor class
        // (option code 60) and see if there's a specific string that identifies
        // the device.
        "name": "cpe_genexis",
        "test": "substring(option[60].hex,0,7) == 'HMC1000'",

        // Once the device is recognized, we want to send two options:
        // the vivso option with vendor-id set to 25167, and a suboption 2.
        "option-data": [
            {
                "name": "vivso-suboptions",
                "data": "25167"
            },

            // The suboption 2 value is defined as any other option. However,
            // we want to send this suboption 2, even when the client didn't
            // explicitly request it (often there is no way to do that for
            // vendor options). Therefore we use always-send to force Kea
            // to always send this option when 25167 vendor space is involved.
            {
                "name": "tftp",
                "space": "vendor-25167",
                "data": "tftp://192.0.2.1/genexis/HMC1000.v1.3.0-R.img",
                "always-send": true
            }
        ]
    } ]
}

By default, Kea sends back only those options that are requested by a client, unless there are protocol rules that tell the DHCP server to always send an option. This approach works nicely in most cases and avoids problems with clients refusing responses with options they do not understand. However, the situation with vendor options is more complex, as they are not requested the same way as other options, are not well-documented in official RFCs, or vary by vendor.

Some vendors (such as DOCSIS, identified by vendor option 4491) have a mechanism to request specific vendor options and Kea is able to honor those. Unfortunately, for many other vendors, such as Genexis (25167, discussed above), Kea does not have such a mechanism, so it cannot send any sub-options on its own. To solve this issue, we devised the concept of persistent options. Kea can be told to always send options, even if the client did not request them. This can be achieved by adding "always-send": true to the option definition. Note that in this particular case an option is defined in vendor space 25167. With always-send enabled, the option is sent every time there is a need to deal with vendor space 25167.

Another possibility is to redefine the option; see DHCPv4 Private Options.

Kea comes with several example configuration files. Some of them showcase how to configure options 60 and 43. See doc/examples/kea4/vendor-specific.json and doc/examples/kea6/vivso.json in the Kea sources.

Note

Currently only one vendor is supported for the vivco-suboptions (code 124) and vivso-suboptions (code 125) options. Specifying multiple enterprise numbers within a single option instance or multiple options with different enterprise numbers is not supported.

Nested DHCPv4 Options (Custom Option Spaces)

It is sometimes useful to define a completely new option space, such as when a user creates a new option in the standard option space (dhcp4) and wants this option to convey sub-options. Since they are in a separate space, sub-option codes have a separate numbering scheme and may overlap with the codes of standard options.

Note that the creation of a new option space is not required when defining sub-options for a standard option, because one is created by default if the standard option is meant to convey any sub-options (see DHCPv4 Vendor-Specific Options).

If we want a DHCPv4 option called container with code 222, that conveys two sub-options with codes 1 and 2, we first need to define the new sub-options:

"Dhcp4": {
    "option-def": [
        {
            "name": "subopt1",
            "code": 1,
            "space": "isc",
            "type": "ipv4-address",
            "record-types": "",
            "array": false,
            "encapsulate": ""
        },
        {
            "name": "subopt2",
            "code": 2,
            "space": "isc",
            "type": "string",
            "record-types": "",
            "array": false,
            "encapsulate": ""
        }
    ],
    ...
}

Note that we have defined the options to belong to a new option space (in this case, "isc").

The next step is to define a regular DHCPv4 option with the desired code and specify that it should include options from the new option space:

"Dhcp4": {
    "option-def": [
        ...,
        {
            "name": "container",
            "code": 222,
            "space": "dhcp4",
            "type": "empty",
            "array": false,
            "record-types": "",
            "encapsulate": "isc"
        }
    ],
    ...
}

The name of the option space in which the sub-options are defined is set in the encapsulate field. The type field is set to "empty", to indicate that this option does not carry any data other than sub-options.

Finally, we can set values for the new options:

"Dhcp4": {
    "option-data": [
        {
            "name": "subopt1",
            "code": 1,
            "space": "isc",
            "data": "192.0.2.3"
        },
        }
            "name": "subopt2",
            "code": 2,
            "space": "isc",
            "data": "Hello world"
        },
        {
            "name": "container",
            "code": 222,
            "space": "dhcp4"
        }
    ],
    ...
}

It is possible to create an option which carries some data in addition to the sub-options defined in the encapsulated option space. For example, if the container option from the previous example were required to carry a uint16 value as well as the sub-options, the type value would have to be set to "uint16" in the option definition. (Such an option would then have the following data structure: DHCP header, uint16 value, sub-options.) The value specified with the data parameter — which should be a valid integer enclosed in quotes, e.g. "123" — would then be assigned to the uint16 field in the container option.

Unspecified Parameters for DHCPv4 Option Configuration

In many cases it is not required to specify all parameters for an option configuration, and the default values can be used. However, it is important to understand the implications of not specifying some of them, as it may result in configuration errors. The list below explains the behavior of the server when a particular parameter is not explicitly specified:

• name - the server requires either an option name or an option code to identify an option. If this parameter is unspecified, the option code must be specified.

• code - the server requires either an option name or an option code to identify an option; this parameter may be left unspecified if the name parameter is specified. However, this also requires that the particular option have a definition (either as a standard option or an administrator-created definition for the option using an option-def structure), as the option definition associates an option with a particular name. It is possible to configure an option for which there is no definition (unspecified option format). Configuration of such options requires the use of the option code.

• space - if the option space is unspecified it defaults to dhcp4, which is an option space holding standard DHCPv4 options.

• data - if the option data is unspecified it defaults to an empty value. The empty value is mostly used for the options which have no payload (boolean options), but it is legal to specify empty values for some options which carry variable-length data and for which the specification allows a length of 0. For such options, the data parameter may be omitted in the configuration.

• csv-format - if this value is not specified, the server assumes that the option data is specified as a list of comma-separated values to be assigned to individual fields of the DHCP option.

Support for Long Options

The kea-dhcp4 server partially supports long options (RFC3396). Since Kea 2.1.6, the server accepts configuring long options and suboptions (longer than 255 bytes). The options and suboptions are stored internally in their unwrapped form and they can be processed as usual using the parser language. On send, the server splits long options and suboptions into multiple options and suboptions, using the respective option code.

"option-def": [
    {
        "array": false,
        "code\": 240,
        "encapsulate": "",
        "name": "my-option",
        "space": "dhcp4",
        "type": "string"
    }
],
"subnet4": [
    {
        "subnet": "192.0.2.0/24",
        "reservations": [
            {
                "hw-address": "aa:bb:cc:dd:ee:ff",
                "option-data": [
                    {
                        "always-send": false,
                        "code": 240,
                        "name": "my-option",
                        "csv-format": true,
                        "data": "data
                                 -00010203040506070809-00010203040506070809-00010203040506070809-00010203040506070809
                                 -00010203040506070809-00010203040506070809-00010203040506070809-00010203040506070809
                                 -00010203040506070809-00010203040506070809-00010203040506070809-00010203040506070809
                                 -data",
                        "space": "dhcp4"
                    }
                ]
            }
        ]
    }
]

Note

For this example, the data has been split on several lines, but Kea does not support this in the configuration file.

This example illustrates configuring a custom long option in a reservation. The server, when sending a response, will split this option into several options with the same code (11 options with option code 240).

Note

Currently the server does not support storing long options in the databases, either host reservations or configuration backend.

The server is also able to receive packets with split options (options using the same option code) and to fuse the data chunks into one option. This is also supported for suboptions if each suboption data chunk also contains the suboption code and suboption length.

Stateless Configuration of DHCPv4 Clients

The DHCPv4 server supports stateless client configuration, whereby the client has an IP address configured (e.g. using manual configuration) and only contacts the server to obtain other configuration parameters, such as addresses of DNS servers. To obtain the stateless configuration parameters, the client sends the DHCPINFORM message to the server with the ciaddr set to the address that the client is currently using. The server unicasts the DHCPACK message to the client that includes the stateless configuration (“yiaddr” not set).

The server responds to the DHCPINFORM when the client is associated with a subnet defined in the server’s configuration. An example subnet configuration looks like this:

"Dhcp4": {
    "subnet4": [
        {
            "subnet": "192.0.2.0/24"
            "option-data": [ {
                "name": "domain-name-servers",
                "code": 6,
                "data": "192.0.2.200,192.0.2.201",
                "csv-format": true,
                "space": "dhcp4"
            } ]
        }
    ]
}

This subnet specifies the single option which will be included in the DHCPACK message to the client in response to DHCPINFORM. The subnet definition does not require the address pool configuration if it will be used solely for stateless configuration.

This server will associate the subnet with the client if one of the following conditions is met:

• The DHCPINFORM is relayed and the giaddr matches the configured subnet.

• The DHCPINFORM is unicast from the client and the ciaddr matches the configured subnet.

• The DHCPINFORM is unicast from the client and the ciaddr is not set, but the source address of the IP packet matches the configured subnet.

• The DHCPINFORM is not relayed and the IP address on the interface on which the message is received matches the configured subnet.

Client Classification in DHCPv4

The DHCPv4 server includes support for client classification. For a deeper discussion of the classification process, see Client Classification.

In certain cases it is useful to configure the server to differentiate between DHCP client types and treat them accordingly. Client classification can be used to modify the behavior of almost any part of DHCP message processing. Kea currently offers client classification via private options and option 43 deferred unpacking; subnet selection; pool selection; assignment of different options; and, for cable modems, specific options for use with the TFTP server address and the boot file field.

Kea can be instructed to limit access to given subnets based on class information. This is particularly useful for cases where two types of devices share the same link and are expected to be served from two different subnets. The primary use case for such a scenario is cable networks, where there are two classes of devices: the cable modem itself, which should be handed a lease from subnet A; and all other devices behind the modem, which should get leases from subnet B. That segregation is essential to prevent overly curious end-users from playing with their cable modems. For details on how to set up class restrictions on subnets, see Configuring Subnets With Class Information.

When subnets belong to a shared network, the classification applies to subnet selection but not to pools; that is, a pool in a subnet limited to a particular class can still be used by clients which do not belong to the class, if the pool they are expected to use is exhausted. The limit on access based on class information is also available at the pool level within a subnet: see Configuring Pools With Class Information. This is useful when segregating clients belonging to the same subnet into different address ranges.

In a similar way, a pool can be constrained to serve only known clients, i.e. clients which have a reservation, using the built-in KNOWN or UNKNOWN classes. Addresses can be assigned to registered clients without giving a different address per reservation: for instance, when there are not enough available addresses. The determination whether there is a reservation for a given client is made after a subnet is selected, so it is not possible to use KNOWN/UNKNOWN classes to select a shared network or a subnet.

The process of classification is conducted in five steps. The first step is to assess an incoming packet and assign it to zero or more classes. The second step is to choose a subnet, possibly based on the class information. When the incoming packet is in the special class DROP, it is dropped and a debug message logged. The next step is to evaluate class expressions depending on the built-in KNOWN/UNKNOWN classes after host reservation lookup, using them for pool selection and assigning classes from host reservations. The list of required classes is then built and each class of the list has its expression evaluated; when it returns true, the packet is added as a member of the class. The last step is to assign options, again possibly based on the class information. More complete and detailed information is available in Client Classification.

There are two main methods of classification. The first is automatic and relies on examining the values in the vendor class options or the existence of a host reservation. Information from these options is extracted, and a class name is constructed from it and added to the class list for the packet. The second method specifies an expression that is evaluated for each packet. If the result is true, the packet is a member of the class.

Note

The new early-global-reservations-lookup global parameter flag enables a lookup for global reservations before the subnet selection phase. This lookup is similar to the general lookup described above with two differences:

• the lookup is limited to global host reservations

• the UNKNOWN class is never set

Note

Care should be taken with client classification, as it is easy for clients that do not meet class criteria to be denied all service.

Setting Fixed Fields in Classification

It is possible to specify that clients belonging to a particular class should receive packets with specific values in certain fixed fields. In particular, three fixed fields are supported: next-server (conveys an IPv4 address, which is set in the siaddr field), server-hostname (conveys a server hostname, can be up to 64 bytes long, and is sent in the sname field) and boot-file-name (conveys the configuration file, can be up to 128 bytes long, and is sent using the file field).

Obviously, there are many ways to assign clients to specific classes, but for PXE clients the client architecture type option (code 93) seems to be particularly suited to make the distinction. The following example checks whether the client identifies itself as a PXE device with architecture EFI x86-64, and sets several fields if it does. See Section 2.1 of RFC 4578) or the client documentation for specific values.

"Dhcp4": {
    "client-classes": [
        {
            "name": "ipxe_efi_x64",
            "test": "option[93].hex == 0x0009",
            "next-server": "192.0.2.254",
            "server-hostname": "hal9000",
            "boot-file-name": "/dev/null"
        },
        ...
    ],
    ...
          }

If an incoming packet is matched to multiple classes, then the value used for each field will come from the first class that specifies the field, in the order the classes are assigned to the packet.

Note

The classes are ordered as specified in the configuration.

Using Vendor Class Information in Classification

The server checks whether an incoming packet includes the vendor class identifier option (60). If it does, the content of that option is prepended with VENDOR_CLASS_, and it is interpreted as a class. For example, modern cable modems send this option with value docsis3.0, so the packet belongs to the class VENDOR_CLASS_docsis3.0.

Note

Certain special actions for clients in VENDOR_CLASS_docsis3.0 can be achieved by defining VENDOR_CLASS_docsis3.0 and setting its next-server and boot-file-name values appropriately.

This example shows a configuration using an automatically generated VENDOR_CLASS_ class. The administrator of the network has decided that addresses from the range 192.0.2.10 to 192.0.2.20 are going to be managed by the Dhcp4 server and only clients belonging to the DOCSIS 3.0 client class are allowed to use that pool.

"Dhcp4": {
    "subnet4": [
        {
            "subnet": "192.0.2.0/24",
            "pools": [ { "pool": "192.0.2.10 - 192.0.2.20" } ],
            "client-class": "VENDOR_CLASS_docsis3.0"
        }
    ],
    ...
}

Defining and Using Custom Classes

The following example shows how to configure a class using an expression and a subnet using that class. This configuration defines the class named Client_foo. It is comprised of all clients whose client IDs (option 61) start with the string foo. Members of this class will be given addresses from 192.0.2.10 to 192.0.2.20 and the addresses of their DNS servers set to 192.0.2.1 and 192.0.2.2.

"Dhcp4": {
    "client-classes": [
        {
            "name": "Client_foo",
            "test": "substring(option[61].hex,0,3) == 'foo'",
            "option-data": [
                {
                    "name": "domain-name-servers",
                    "code": 6,
                    "space": "dhcp4",
                    "csv-format": true,
                    "data": "192.0.2.1, 192.0.2.2"
                }
            ]
        },
        ...
    ],
    "subnet4": [
        {
            "subnet": "192.0.2.0/24",
            "pools": [ { "pool": "192.0.2.10 - 192.0.2.20" } ],
            "client-class": "Client_foo"
        },
        ...
    ],
    ...
}

Required Classification

In some cases it is useful to limit the scope of a class to a shared network, subnet, or pool. There are two parameters which are used to limit the scope of the class by instructing the server to evaluate test expressions when required.

The first one is the per-class only-if-required flag, which is false by default. When it is set to true, the test expression of the class is not evaluated at the reception of the incoming packet but later, and only if the class evaluation is required.

The second is require-client-classes, which takes a list of class names and is valid in shared-network, subnet, and pool scope. Classes in these lists are marked as required and evaluated after selection of this specific shared network/subnet/pool and before output-option processing.

In this example, a class is assigned to the incoming packet when the specified subnet is used:

"Dhcp4": {
    "client-classes": [
       {
           "name": "Client_foo",
           "test": "member('ALL')",
           "only-if-required": true
       },
       ...
    ],
    "subnet4": [
        {
            "subnet": "192.0.2.0/24",
            "pools": [ { "pool": "192.0.2.10 - 192.0.2.20" } ],
            "require-client-classes": [ "Client_foo" ],
            ...
        },
        ...
    ],
    ...
}

Required evaluation can be used to express complex dependencies like subnet membership. It can also be used to reverse the precedence; if option-data is set in a subnet, it takes precedence over option-data in a class. If option-data is moved to a required class and required in the subnet, a class evaluated earlier may take precedence.

Required evaluation is also available at the shared-network and pool levels. The order in which required classes are considered is: shared-network, subnet, and pool, i.e. in the reverse order from the way in which option-data is processed.

DDNS for DHCPv4

As mentioned earlier, kea-dhcp4 can be configured to generate requests to the DHCP-DDNS server, kea-dhcp-ddns, (referred to herein as “D2”) to update DNS entries. These requests are known as NameChangeRequests or NCRs. Each NCR contains the following information:

1. Whether it is a request to add (update) or remove DNS entries.

2. Whether the change requests forward DNS updates (A records), reverse DNS updates (PTR records), or both.

3. The Fully Qualified Domain Name (FQDN), lease address, and DHCID (information identifying the client associated with the FQDN).

DDNS-related parameters are split into two groups:

1. Connectivity Parameters

   These are parameters which specify where and how kea-dhcp4 connects to and communicates with D2. These parameters can only be specified within the top-level dhcp-ddns section in the kea-dhcp4 configuration. The connectivity parameters are listed below:

   • enable-updates

   • server-ip

   • server-port

   • sender-ip

   • sender-port

   • max-queue-size

   • ncr-protocol

   • ncr-format"

2. Behavioral Parameters

   These parameters influence behavior such as how client host names and FQDN options are handled. They have been moved out of the dhcp-ddns section so that they may be specified at the global, shared-network, and/or subnet levels. Furthermore, they are inherited downward from global to shared-network to subnet. In other words, if a parameter is not specified at a given level, the value for that level comes from the level above it. The behavioral parameters are as follows:

   • ddns-send-updates

   • ddns-override-no-update

   • ddns-override-client-update

   • ddns-replace-client-name"

   • ddns-generated-prefix

   • ddns-qualifying-suffix

   • ddns-update-on-renew

   • ddns-use-conflict-resolution

   • hostname-char-set

   • hostname-char-replacement

Note

For backward compatibility, configuration parsing still recognizes the original behavioral parameters specified in dhcp-ddns, by translating the parameter into its global equivalent. If a parameter is specified both globally and in dhcp-ddns, the latter value is ignored. In either case, a log is emitted explaining what has occurred. Specifying these values within dhcp-ddns is deprecated and support for it will be removed.

The default configuration and values would appear as follows:

"Dhcp4": {
     "dhcp-ddns": {
        // Connectivity parameters
        "enable-updates": false,
         "server-ip": "127.0.0.1",
         "server-port":53001,
         "sender-ip":"",
         "sender-port":0,
         "max-queue-size":1024,
         "ncr-protocol":"UDP",
         "ncr-format":"JSON"
     },

     // Behavioral parameters (global)
     "ddns-send-updates": true,
     "ddns-override-no-update": false,
     "ddns-override-client-update": false,
     "ddns-replace-client-name": "never",
     "ddns-generated-prefix": "myhost",
     "ddns-qualifying-suffix": "",
     "ddns-update-on-renew": false,
     "ddns-use-conflict-resolution": true,
     "hostname-char-set": "",
     "hostname-char-replacement": ""
     ...
}

There are two parameters which determine if kea-dhcp4 can generate DDNS requests to D2: the existing dhcp-ddns:enable-updates parameter, which now only controls whether kea-dhcp4 connects to D2; and the new behavioral parameter, ddns-send-updates, which determines whether DDNS updates are enabled at a given level (i.e. global, shared-network, or subnet). The following table shows how the two parameters function together:

Enabling and disabling DDNS updates

dhcp-ddns: enable-updates	Global ddns-send-updates	Outcome
false (default)	false	no updates at any scope
false	true (default)	no updates at any scope
true	false	updates only at scopes with a local value of true for ddns-enable-updates
true	true	updates at all scopes except those with a local value of false for ddns-enable-updates

Kea 1.9.1 added two new parameters; the first is ddns-update-on-renew. Normally, when leases are renewed, the server only updates DNS if the DNS information for the lease (e.g. FQDN, DNS update direction flags) has changed. Setting ddns-update-on-renew to true instructs the server to always update the DNS information when a lease is renewed, even if its DNS information has not changed. This allows Kea to “self-heal” if it was previously unable to add DNS entries or they were somehow lost by the DNS server.

Note

Setting ddns-update-on-renew to true may impact performance, especially for servers with numerous clients that renew often.

The second parameter added in Kea 1.9.1 is ddns-use-conflict-resolution. The value of this parameter is passed by kea-dhcp4 to D2 with each DNS update request. When true (the default value), D2 employs conflict resolution, as described in RFC 4703, when attempting to fulfill the update request. When false, D2 simply attempts to update the DNS entries per the request, regardless of whether they conflict with existing entries owned by other DHCPv4 clients.

Note

Setting ddns-use-conflict-resolution to false disables the overwrite safeguards that the rules of conflict resolution (from RFC 4703) are intended to prevent. This means that existing entries for an FQDN or an IP address made for Client-A can be deleted or replaced by entries for Client-B. Furthermore, there are two scenarios by which entries for multiple clients for the same key (e.g. FQDN or IP) can be created.

1. Client-B uses the same FQDN as Client-A but a different IP address. In this case, the forward DNS entries (A and DHCID RRs) for Client-A will be deleted as they match the FQDN and new entries for Client-B will be added. The reverse DNS entries (PTR and DHCID RRs) for Client-A, however, will not be deleted as they belong to a different IP address, while new entries for Client-B will still be added.

2. Client-B uses the same IP address as Client-A but a different FQDN. In this case the reverse DNS entries (PTR and DHCID RRs) for Client-A will be deleted as they match the IP address, and new entries for Client-B will be added. The forward DNS entries (A and DHCID RRs) for Client-A, however, will not be deleted, as they belong to a different FQDN, while new entries for Client-B will still be added.

Disabling conflict resolution should be done only after careful review of specific use cases. The best way to avoid unwanted DNS entries is to always ensure lease changes are processed through Kea, whether they are released, expire, or are deleted via the lease-del4 command, prior to reassigning either FQDNs or IP addresses. Doing so causes kea-dhcp4 to generate DNS removal requests to D2.

Note

The DNS entries Kea creates contain a value for TTL (time to live). Since Kea 1.9.3, kea-dhcp4 calculates that value based on RFC 4702, Section 5, which suggests that the TTL value be 1/3 of the lease’s lifetime, with a minimum value of 10 minutes. In earlier versions, the server set the TTL value equal to the lease’s valid lifetime.

DHCP-DDNS Server Connectivity

For NCRs to reach the D2 server, kea-dhcp4 must be able to communicate with it. kea-dhcp4 uses the following configuration parameters to control this communication:

• enable-updates - Enables connectivity to kea-dhcp-ddns such that DDNS updates can be constructed and sent. It must be true for NCRs to be generated and sent to D2. It defaults to false.

• server-ip - This is the IP address on which D2 listens for requests. The default is the local loopback interface at address 127.0.0.1. Either an IPv4 or IPv6 address may be specified.

• server-port - This is the port on which D2 listens for requests. The default value is 53001.

• sender-ip - This is the IP address which kea-dhcp4 uses to send requests to D2. The default value is blank, which instructs kea-dhcp4 to select a suitable address.

• sender-port - This is the port which kea-dhcp4 uses to send requests to D2. The default value of 0 instructs kea-dhcp4 to select a suitable port.

• max-queue-size - This is the maximum number of requests allowed to queue while waiting to be sent to D2. This value guards against requests accumulating uncontrollably if they are being generated faster than they can be delivered. If the number of requests queued for transmission reaches this value, DDNS updating is turned off until the queue backlog has been sufficiently reduced. The intent is to allow the kea-dhcp4 server to continue lease operations without running the risk that its memory usage grows without limit. The default value is 1024.

• ncr-protocol - This specifies the socket protocol to use when sending requests to D2. Currently only UDP is supported.

• ncr-format - This specifies the packet format to use when sending requests to D2. Currently only JSON format is supported.

By default, kea-dhcp-ddns is assumed to be running on the same machine as kea-dhcp4, and all of the default values mentioned above should be sufficient. If, however, D2 has been configured to listen on a different address or port, these values must be altered accordingly. For example, if D2 has been configured to listen on 192.168.1.10 port 900, the following configuration is required:

"Dhcp4": {
    "dhcp-ddns": {
        "server-ip": "192.168.1.10",
        "server-port": 900,
        ...
    },
    ...
}

When Does the kea-dhcp4 Server Generate a DDNS Request?

kea-dhcp4 follows the behavior prescribed for DHCP servers in RFC 4702. It is important to keep in mind that kea-dhcp4 makes the initial decision of when and what to update and forwards that information to D2 in the form of NCRs. Carrying out the actual DNS updates and dealing with such things as conflict resolution are within the purview of D2 itself (see The DHCP-DDNS Server). This section describes when kea-dhcp4 generates NCRs and the configuration parameters that can be used to influence this decision. It assumes that both the connectivity parameter enable-updates and the behavioral parameter ddns-send-updates, are true.

In general, kea-dhcp4 generates DDNS update requests when:

1. A new lease is granted in response to a DHCPREQUEST;

2. An existing lease is renewed but the FQDN associated with it has changed; or

3. An existing lease is released in response to a DHCPRELEASE.

In the second case, lease renewal, two DDNS requests are issued: one request to remove entries for the previous FQDN, and a second request to add entries for the new FQDN. In the third case, a lease release - a single DDNS request - to remove its entries will be made.

As for the first case, the decisions involved when granting a new lease are more complex. When a new lease is granted, kea-dhcp4 generates a DDNS update request if the DHCPREQUEST contains either the FQDN option (code 81) or the Host Name option (code 12). If both are present, the server uses the FQDN option. By default, kea-dhcp4 respects the FQDN N and S flags specified by the client as shown in the following table:

Default FQDN flag behavior

Client Flags:N-S	Client Intent	Server Response	Server Flags:N-S-O
0-0	Client wants to do forward updates, server should do reverse updates	Server generates reverse-only request	1-0-0
0-1	Server should do both forward and reverse updates	Server generates request to update both directions	0-1-0
1-0	Client wants no updates done	Server does not generate a request	1-0-0

The first row in the table above represents “client delegation.” Here the DHCP client states that it intends to do the forward DNS updates and the server should do the reverse updates. By default, kea-dhcp4 honors the client’s wishes and generates a DDNS request to the D2 server to update only reverse DNS data. The parameter ddns-override-client-update can be used to instruct the server to override client delegation requests. When this parameter is true, kea-dhcp4 disregards requests for client delegation and generates a DDNS request to update both forward and reverse DNS data. In this case, the N-S-O flags in the server’s response to the client will be 0-1-1 respectively.

(Note that the flag combination N=1, S=1 is prohibited according to RFC 4702. If such a combination is received from the client, the packet will be dropped by kea-dhcp4.)

To override client delegation, set the following values in the configuration file:

"Dhcp4": {
    ...
    "ddns-override-client-update": true,
    ...
}

The third row in the table above describes the case in which the client requests that no DNS updates be done. The parameter ddns-override-no-update can be used to instruct the server to disregard the client’s wishes. When this parameter is true, kea-dhcp4 generates DDNS update requests to kea-dhcp-ddns even if the client requests that no updates be done. The N-S-O flags in the server’s response to the client will be 0-1-1.

To override client delegation, issue the following commands:

"Dhcp4": {
    ...
    "ddns-override-no-update": true,
    ...
}

kea-dhcp4 always generates DDNS update requests if the client request only contains the Host Name option. In addition, it includes an FQDN option in the response to the client with the FQDN N-S-O flags set to 0-1-0, respectively. The domain name portion of the FQDN option is the name submitted to D2 in the DDNS update request.

kea-dhcp4 Name Generation for DDNS Update Requests

Each NameChangeRequest must of course include the fully qualified domain name whose DNS entries are to be affected. kea-dhcp4 can be configured to supply a portion or all of that name, based on what it receives from the client in the DHCPREQUEST.

The default rules for constructing the FQDN that will be used for DNS entries are:

1. If the DHCPREQUEST contains the client FQDN option, take the candidate name from there; otherwise, take it from the Host Name option.

2. If the candidate name is a partial (i.e. unqualified) name, then add a configurable suffix to the name and use the result as the FQDN.

3. If the candidate name provided is empty, generate an FQDN using a configurable prefix and suffix.

4. If the client provides neither option, then take no DNS action.

These rules can be amended by setting the ddns-replace-client-name parameter, which provides the following modes of behavior:

• never - use the name the client sent. If the client sent no name, do not generate one. This is the default mode.

• always - replace the name the client sent. If the client sent no name, generate one for the client.

• when-present - replace the name the client sent. If the client sent no name, do not generate one.

• when-not-present - use the name the client sent. If the client sent no name, generate one for the client.

Note

In early versions of Kea, this parameter was a boolean and permitted only values of true and false. Boolean values have been deprecated and are no longer accepted. Administrators currently using booleans must replace them with the desired mode name. A value of true maps to when-present, while false maps to never.

For example, to instruct kea-dhcp4 to always generate the FQDN for a client, set the parameter ddns-replace-client-name to always as follows:

"Dhcp4": {
    ...
    "ddns-replace-client-name": "always",
    ...
}

The prefix used in the generation of an FQDN is specified by the ddns-generated-prefix parameter. The default value is “myhost”. To alter its value, simply set it to the desired string:

"Dhcp4": {
    ...
    "ddns-generated-prefix": "another.host",
    ...
}

The suffix used when generating an FQDN, or when qualifying a partial name, is specified by the ddns-qualifying-suffix parameter. It is strongly recommended that the user supply a value for the qualifying prefix when DDNS updates are enabled. For obvious reasons, we cannot supply a meaningful default.

"Dhcp4": {
    ...
    "ddns-qualifying-suffix": "foo.example.org",
    ...
}

When generating a name, kea-dhcp4 constructs the name in the format:

[ddns-generated-prefix]-[address-text].[ddns-qualifying-suffix].

where address-text is simply the lease IP address converted to a hyphenated string. For example, if the lease address is 172.16.1.10, the qualifying suffix is “example.com”, and the default value is used for ddns-generated-prefix, the generated FQDN is:

myhost-172-16-1-10.example.com.

Sanitizing Client Host Name and FQDN Names

Some DHCP clients may provide values in the Host Name option (option code 12) or FQDN option (option code 81) that contain undesirable characters. It is possible to configure kea-dhcp4 to sanitize these values. The most typical use case is ensuring that only characters that are permitted by RFC 1035 be included: A-Z, a-z, 0-9, and “-”. This may be accomplished with the following two parameters:

• hostname-char-set - a regular expression describing the invalid character set. This can be any valid, regular expression using POSIX extended expression syntax. Embedded nulls (0x00) are always considered an invalid character to be replaced (or omitted). The default is "[^A-Za-z0-9.-]". This matches any character that is not a letter, digit, dot, hyphen, or null.

• hostname-char-replacement - a string of zero or more characters with which to replace each invalid character in the host name. An empty string causes invalid characters to be OMITTED rather than replaced. The default is "".

The following configuration replaces anything other than a letter, digit, dot, or hyphen with the letter “x”:

"Dhcp4": {
    ...
    "hostname-char-set": "[^A-Za-z0-9.-]",
    "hostname-char-replacement": "x",
    ...
}

Thus, a client-supplied value of “myhost-$[123.org” would become “myhost-xx123.org”. Sanitizing is performed only on the portion of the name supplied by the client, and it is performed before applying a qualifying suffix (if one is defined and needed).

Note

Name sanitizing is meant to catch the more common cases of invalid characters through a relatively simple character-replacement scheme. It is difficult to devise a scheme that works well in all cases, for both Host Name and FQDN options. Administrators who find they have clients with odd corner cases of character combinations that cannot be readily handled with this mechanism should consider writing a hook that can carry out sufficiently complex logic to address their needs.

If clients include domain names in the Host Name option and the administrator wants these preserved, they need to make sure that the dot, “.”, is considered a valid character by the hostname-char-set expression, such as this: "[^A-Za-z0-9.-]". This does not affect dots in FQDN Option values. When scrubbing FQDNs, dots are treated as delimiters and used to separate the option value into individual domain labels that are scrubbed and then re-assembled.

If clients are sending values that differ only by characters considered as invalid by the hostname-char-set, be aware that scrubbing them will yield identical values. In such cases, DDNS conflict rules will permit only one of them to register the name.

Finally, given the latitude clients have in the values they send, it is virtually impossible to guarantee that a combination of these two parameters will always yield a name that is valid for use in DNS. For example, using an empty value for hostname-char-replacement could yield an empty domain label within a name, if that label consists only of invalid characters.

Note

It is possible to specify hostname-char-set and/or hostname-char-replacement at the global scope. This allows host names to be sanitized without requiring a dhcp-ddns entry. When a hostname-char parameter is defined at both the global scope and in a dhcp-ddns entry, the second (local) value is used.

Next Server (siaddr)

In some cases, clients want to obtain configuration from a TFTP server. Although there is a dedicated option for it, some devices may use the siaddr field in the DHCPv4 packet for that purpose. That specific field can be configured using the next-server directive. It is possible to define it in the global scope or for a given subnet only. If both are defined, the subnet value takes precedence. The value in the subnet can be set to “0.0.0.0”, which means that next-server should not be sent. It can also be set to an empty string, which is equivalent to it not being defined at all; that is, it uses the global value.

The server-hostname (which conveys a server hostname, can be up to 64 bytes long, and is in the sname field) and boot-file-name (which conveys the configuration file, can be up to 128 bytes long, and is sent using the file field) directives are handled the same way as next-server.

"Dhcp4": {
    "next-server": "192.0.2.123",
    "boot-file-name": "/dev/null",
    ...,
    "subnet4": [
        {
            "next-server": "192.0.2.234",
            "server-hostname": "some-name.example.org",
            "boot-file-name": "bootfile.efi",
            ...
        }
    ]
}

Echoing Client-ID (RFC 6842)

The original DHCPv4 specification (RFC 2131) states that the DHCPv4 server must not send back client-id options when responding to clients. However, in some cases that results in confused clients that do not have a MAC address or client-id; see RFC 6842 for details. That behavior changed with the publication of RFC 6842, which updated RFC 2131. That update states that the server must send the client-id if the client sent it, and that is Kea’s default behavior. However, in some cases older devices that do not support RFC 6842 may refuse to accept responses that include the client-id option. To enable backward compatibility, an optional configuration parameter has been introduced. To configure it, use the following configuration statement:

"Dhcp4": {
    "echo-client-id": false,
    ...
}

Using Client Identifier and Hardware Address

The DHCP server must be able to identify the client from which it receives the message and distinguish it from other clients. There are many reasons why this identification is required; the most important ones are:

• When the client contacts the server to allocate a new lease, the server must store the client identification information in the lease database as a search key.

• When the client tries to renew or release the existing lease, the server must be able to find the existing lease entry in the database for this client, using the client identification information as a search key.

• Some configurations use static reservations for the IP addresses and other configuration information. The server’s administrator uses client identification information to create these static assignments.

• In dual-stack networks there is often a need to correlate the lease information stored in DHCPv4 and DHCPv6 servers for a particular host. Using common identification information by the DHCPv4 and DHCPv6 clients allows the network administrator to achieve this correlation and better administer the network. Beginning with release 2.1.2, Kea supports DHCPv6 DUIDs embedded within DHCPv4 Client Identifier options as described in RFC 4361.

DHCPv4 uses two distinct identifiers which are placed by the client in the queries sent to the server and copied by the server to its responses to the client: chaddr and client-identifier. The former was introduced as a part of the BOOTP specification and it is also used by DHCP to carry the hardware address of the interface used to send the query to the server (MAC address for the Ethernet). The latter is carried in the client-identifier option, introduced in RFC 2132.

RFC 2131 indicates that the server may use both of these identifiers to identify the client but the client identifier, if present, takes precedence over chaddr. One of the reasons for this is that the client identifier is independent from the hardware used by the client to communicate with the server. For example, if the client obtained the lease using one network card and then the network card is moved to another host, the server will wrongly identify this host as the one which obtained the lease. Moreover, RFC 4361 gives the recommendation to use a DUID (see RFC 8415, the DHCPv6 specification) carried as a client identifier when dual-stack networks are in use to provide consistent identification information for the client, regardless of the type of protocol it is using. Kea adheres to these specifications, and the client identifier by default takes precedence over the value carried in the chaddr field when the server searches, creates, updates, or removes the client’s lease.

When the server receives a DHCPDISCOVER or DHCPREQUEST message from the client, it tries to find out if the client already has a lease in the database; if it does, the server hands out that lease rather than allocates a new one. Each lease in the lease database is associated with the client identifier and/or chaddr. The server first uses the client identifier (if present) to search for the lease; if one is found, the server treats this lease as belonging to the client, even if the current chaddr and the chaddr associated with the lease do not match. This facilitates the scenario when the network card on the client system has been replaced and thus the new MAC address appears in the messages sent by the DHCP client. If the server fails to find the lease using the client identifier, it performs another lookup using the chaddr. If this lookup returns no result, the client is considered to not have a lease and a new lease is created.

A common problem reported by network operators is that poor client implementations do not use stable client identifiers, instead generating a new client identifier each time the client connects to the network. Another well-known case is when the client changes its client identifier during the multi-stage boot process (PXE). In such cases, the MAC address of the client’s interface remains stable, and using the chaddr field to identify the client guarantees that the particular system is considered to be the same client, even though its client identifier changes.

To address this problem, Kea includes a configuration option which enables client identification using chaddr only. This instructs the server to ignore the client identifier during lease lookups and allocations for a particular subnet. Consider the following simplified server configuration:

"Dhcp4": {
    ...
    "match-client-id": true,
    ...
    "subnet4": [
    {
        "subnet": "192.0.10.0/24",
        "pools": [ { "pool": "192.0.2.23-192.0.2.87" } ],
        "match-client-id": false
    },
    {
        "subnet": "10.0.0.0/8",
        "pools": [ { "pool": "10.0.0.23-10.0.2.99" } ],
    }
    ]
}

The match-client-id is a boolean value which controls this behavior. The default value of true indicates that the server will use the client identifier for lease lookups and chaddr if the first lookup returns no results. false means that the server will only use the chaddr to search for the client’s lease. Whether the DHCID for DNS updates is generated from the client identifier or chaddr is controlled through the same parameter.

The match-client-id parameter may appear both in the global configuration scope and/or under any subnet declaration. In the example shown above, the effective value of the match-client-id will be false for the subnet 192.0.10.0/24, because the subnet-specific setting of the parameter overrides the global value of the parameter. The effective value of the match-client-id for the subnet 10.0.0.0/8 will be set to true, because the subnet declaration lacks this parameter and the global setting is by default used for this subnet. In fact, the global entry for this parameter could be omitted in this case, because true is the default value.

It is important to understand what happens when the client obtains its lease for one setting of the match-client-id and then renews it when the setting has been changed. First, consider the case when the client obtains the lease and the match-client-id is set to true. The server stores the lease information, including the client identifier (if supplied) and chaddr, in the lease database. When the setting is changed and the client renews the lease, the server will determine that it should use the chaddr to search for the existing lease. If the client has not changed its MAC address, the server should successfully find the existing lease. The client identifier associated with the returned lease will be ignored and the client will be allowed to use this lease. When the lease is renewed only the chaddr will be recorded for this lease, according to the new server setting.

In the second case, the client has the lease with only a chaddr value recorded. When the match-client-id setting is changed to true, the server will first try to use the client identifier to find the existing client’s lease. This will return no results because the client identifier was not recorded for this lease. The server will then use the chaddr and the lease will be found. If the lease appears to have no client identifier recorded, the server will assume that this lease belongs to the client and that it was created with the previous setting of the match-client-id. However, if the lease contains a client identifier which is different from the client identifier used by the client, the lease will be assumed to belong to another client and a new lease will be allocated.

Authoritative DHCPv4 Server Behavior

The original DHCPv4 specification (RFC 2131) states that if a client requests an address in the INIT-REBOOT state of which the server has no knowledge, the server must remain silent, except if the server knows that the client has requested an IP address from the wrong network. By default, Kea follows the behavior of the ISC dhcpd daemon instead of the specification and also remains silent if the client requests an IP address from the wrong network, because configuration information about a given network segment is not known to be correct. Kea only rejects a client’s DHCPREQUEST with a DHCPNAK message if it already has a lease for the client with a different IP address. Administrators can override this behavior through the boolean authoritative (false by default) setting.

In authoritative mode, authoritative set to true, Kea always rejects INIT-REBOOT requests from unknown clients with DHCPNAK messages. The authoritative setting can be specified in global, shared-network, and subnet configuration scope and is automatically inherited from the parent scope, if not specified. All subnets in a shared-network must have the same authoritative setting.

DHCPv4-over-DHCPv6: DHCPv4 Side

The support of DHCPv4-over-DHCPv6 transport is described in RFC 7341 and is implemented using cooperating DHCPv4 and DHCPv6 servers. This section is about the configuration of the DHCPv4 side (the DHCPv6 side is described in DHCPv4-over-DHCPv6: DHCPv6 Side).

Note

DHCPv4-over-DHCPv6 support is experimental and the details of the inter-process communication may change; for instance, the support of port relay (RFC 8357) introduced an incompatible change. Both the DHCPv4 and DHCPv6 sides should be running the same version of Kea.

The dhcp4o6-port global parameter specifies the first of the two consecutive ports of the UDP sockets used for the communication between the DHCPv6 and DHCPv4 servers. The DHCPv4 server is bound to ::1 on port + 1 and connected to ::1 on port.

With DHCPv4-over-DHCPv6, the DHCPv4 server does not have access to several of the identifiers it would normally use to select a subnet. To address this issue, three new configuration entries are available; the presence of any of these allows the subnet to be used with DHCPv4-over-DHCPv6. These entries are:

• 4o6-subnet: takes a prefix (i.e., an IPv6 address followed by a slash and a prefix length) which is matched against the source address.

• 4o6-interface-id: takes a relay interface ID option value.

• 4o6-interface: takes an interface name which is matched against the incoming interface name.

ISC tested the following configuration:

{

# DHCPv4 conf
"Dhcp4": {

    "interfaces-config": {
        "interfaces": [ "eno33554984" ]
    },

    "lease-database": {
        "type": "memfile",
        "name": "leases4"
    },

    "valid-lifetime": 4000,

    "subnet4": [ {
        "subnet": "10.10.10.0/24",
        "4o6-interface": "eno33554984",
        "4o6-subnet": "2001:db8:1:1::/64",
        "pools": [ { "pool": "10.10.10.100 - 10.10.10.199" } ]
    } ],

    "dhcp4o6-port": 6767,

    "loggers": [ {
        "name": "kea-dhcp4",
        "output_options": [ {
            "output": "/tmp/kea-dhcp4.log"
        } ],
        "severity": "DEBUG",
        "debuglevel": 0
    } ]
}

}

Sanity Checks in DHCPv4

An important aspect of a well-running DHCP system is an assurance that the data remains consistent; however, in some cases it may be convenient to tolerate certain inconsistent data. For example, a network administrator who temporarily removes a subnet from a configuration would not want all the leases associated with it to disappear from the lease database. Kea has a mechanism to implement sanity checks for situations like this.

Kea supports a configuration scope called sanity-checks. It currently allows only a single parameter, called lease-checks, which governs the verification carried out when a new lease is loaded from a lease file. This mechanism permits Kea to attempt to correct inconsistent data.

Every subnet has a subnet-id value; this is how Kea internally identifies subnets. Each lease has a subnet-id parameter as well, which identifies the subnet it belongs to. However, if the configuration has changed, it is possible that a lease could exist with a subnet-id but without any subnet that matches it. Also, it is possible that the subnet’s configuration has changed and the subnet-id now belongs to a subnet that does not match the lease.

Kea’s corrective algorithm first checks to see if there is a subnet with the subnet-id specified by the lease. If there is, it verifies whether the lease belongs to that subnet. If not, depending on the lease-checks setting, the lease is discarded, a warning is displayed, or a new subnet is selected for the lease that matches it topologically.

There are five levels which are supported:

• none - do no special checks; accept the lease as is.

• warn - if problems are detected display a warning, but accept the lease data anyway. This is the default value.

• fix - if a data inconsistency is discovered, try to correct it. If the correction is not successful, insert the incorrect data anyway.

• fix-del - if a data inconsistency is discovered, try to correct it. If the correction is not successful, reject the lease. This setting ensures the data’s correctness, but some incorrect data may be lost. Use with care.

• del - if any inconsistency is detected, reject the lease. This is the strictest mode; use with care.

This feature is currently implemented for the memfile backend. The sanity check applies to the lease database in memory, not to the lease file, i.e. inconsistent leases will stay in the lease file.

An example configuration that sets this parameter looks as follows:

"Dhcp4": {
    "sanity-checks": {
        "lease-checks": "fix-del"
    },
    ...
}

Storing Extended Lease Information

To support such features as DHCP Leasequery (RFC 4388), additional information must be stored with each lease. Because the amount of information for each lease has ramifications in terms of performance and system resource consumption, storage of this additional information is configurable through the store-extended-info parameter. It defaults to false and may be set at the global, shared-network, and subnet levels.

"Dhcp4": {
    "store-extended-info": true,
    ...
}

When set to true, information relevant to the DHCPREQUEST asking for the lease is added into the lease’s user-context as a map element labeled “ISC”. Currently, the map contains a single value, the relay-agent-info option (DHCP Option 82), when the DHCPREQUEST received contains it. Since DHCPREQUESTs sent as renewals will likely not contain this information, the values taken from the last DHCPREQUEST that did contain it are retained on the lease. The lease’s user-context looks something like this:

{ "ISC": { "relay-agent-info": "0x52050104AABBCCDD" } }

Note

It is possible that other hook libraries are already using user-context. Enabling store-extended-info should not interfere with any other user-context content, as long as it does not also use an element labeled “ISC”. In other words, user-context is intended to be a flexible container serving multiple purposes. As long as no other purpose also writes an “ISC” element to user-context there should not be a conflict.

Multi-Threading Settings

The Kea server can be configured to process packets in parallel using multiple threads. These settings can be found under the multi-threading structure and are represented by:

• enable-multi-threading - use multiple threads to process packets in parallel. The default is false.

• thread-pool-size - specify the number of threads to process packets in parallel. It may be set to 0 (auto-detect), or any positive number explicitly sets the thread count. The default is 0.

• packet-queue-size - specify the size of the queue used by the thread pool to process packets. It may be set to 0 (unlimited), or any positive number explicitly sets the queue size. The default is 64.

An example configuration that sets these parameters looks as follows:

"Dhcp4": {
    "multi-threading": {
       "enable-multi-threading": true,
       "thread-pool-size": 4,
       "packet-queue-size": 16
    }
    ...
}

Multi-Threading Settings With Different Database Backends

Both kea-dhcp4 and kea-dhcp6 are tested by ISC to determine which settings give the best performance. Although this section describes our results, they are merely recommendations and are very dependent on the particular hardware used for testing. We strongly advise that administrators run their own performance tests.

A full report of performance results for the latest stable Kea version can be found here. This includes hardware and test scenario descriptions, as well as current results.

After enabling multi-threading, the number of threads is set by the thread-pool-size parameter. Results from our tests show that the best settings for kea-dhcp4 are:

• thread-pool-size: 4 when using memfile for storing leases.

• thread-pool-size: 12 or more when using mysql for storing leases.

• thread-pool-size: 8 when using postgresql.

Another very important parameter is packet-queue-size; in our tests we used it as a multiplier of thread-pool-size. The actual setting strongly depends on thread-pool-size.

We saw the best results in our tests with the following settings:

• packet-queue-size: 7 * thread-pool-size when using memfile for storing leases; in our case it was 7 * 4 = 28. This means that at any given time, up to 28 packets could be queued.

• packet-queue-size: 66 * thread-pool-size when using mysql for storing leases; in our case it was 66 * 12 = 792. This means that up to 792 packets could be queued.

• packet-queue-size: 11 * thread-pool-size when using postgresql for storing leases; in our case it was 11 * 8 = 88.

IPv6-Only Preferred Networks

RFC8925, recently published by the IETF, specifies a DHCPv4 option to indicate that a host supports an IPv6-only mode and is willing to forgo obtaining an IPv4 address if the network provides IPv6 connectivity. The general idea is that a network administrator can enable this option to signal to compatible dual-stack devices that IPv6 connectivity is available and they can shut down their IPv4 stack. The new option v6-only-preferred content is a 32-bit unsigned integer and specifies for how long the device should disable its stack. The value is expressed in seconds.

The RFC mentions the V6ONLY_WAIT timer. This is implemented in Kea by setting the value of the v6-only-preferred option. This follows the usual practice of setting options; the option value can be specified on the pool, subnet, shared network, or global levels, or even via host reservations.

There is no special processing involved; it follows the standard Kea option processing regime. The option is not sent back unless the client explicitly requests it. For example, to enable the option for the whole subnet, the following configuration can be used:

"subnet4": [
    {
        "pools": [ { "pool":  "192.0.2.1 - 192.0.2.200" } ],
        "subnet": "192.0.2.0/24",
        "option-data": [
            {
                // This will make the v6-only capable devices to disable their
                // v4 stack for half an hour and then try again
                "name": "v6-only-preferred",
                "data": "1800"
            }
        ]
    }
],

Lease Caching

Clients that attempt multiple renewals in a short period can cause the server to update and write to the database frequently, resulting in a performance impact on the server. The cache parameters instruct the DHCP server to avoid updating leases too frequently, thus avoiding this behavior. Instead, the server assigns the same lease (i.e. reuses it) with no modifications except for CLTT (Client Last Transmission Time), which does not require disk operations.

The two parameters are the cache-threshold double and the cache-max-age integer; they have no default setting, i.e. the lease caching feature must be explicitly enabled. These parameters can be configured at the global, shared-network, and subnet levels. The subnet level has precedence over the shared-network level, while the global level is used as a last resort. For example:

"subnet4": [
    {
        "pools": [ { "pool":  "192.0.2.1 - 192.0.2.200" } ],
        "subnet": "192.0.2.0/24",
        "cache-threshold": .25,
        "cache-max-age": 600,
        "valid-lifetime": 2000,
        ...
    }
],

When an already-assigned lease can fulfill a client query:

• any important change, e.g. for DDNS parameter, hostname, or valid lifetime reduction, makes the lease not reusable.

• lease age, i.e. the difference between the creation or last modification time and the current time, is computed (elapsed duration).

• if cache-max-age is explicitly configured, it is compared with the lease age; leases that are too old are not reusable. This means that the value 0 for cache-max-age disables the lease cache feature.

• if cache-threshold is explicitly configured and is between 0.0 and 1.0, it expresses the percentage of the lease valid lifetime which is allowed for the lease age. Values below and including 0.0 and values greater than 1.0 disable the lease cache feature.

In our example, a lease with a valid lifetime of 2000 seconds can be reused if it was committed less than 500 seconds ago. With a lifetime of 3000 seconds, a maximum age of 600 seconds applies.

In outbound client responses (e.g. DHCPACK messages), the dhcp-lease-time option is set to the reusable valid lifetime, i.e. the expiration date does not change. Other options based on the valid lifetime e.g. dhcp-renewal-time and dhcp-rebinding-time, also depend on the reusable lifetime.

Host Reservations in DHCPv4

There are many cases where it is useful to provide a configuration on a per-host basis. The most obvious one is to reserve a specific, static address for exclusive use by a given client (host); the returning client receives the same address from the server every time, and other clients generally do not receive that address. Host reservations are also convenient when a host has specific requirements, e.g. a printer that needs additional DHCP options. Yet another possible use case is to define unique names for hosts.

There may be cases when a new reservation has been made for a client for an address currently in use by another client. We call this situation a “conflict.” These conflicts get resolved automatically over time, as described in subsequent sections. Once a conflict is resolved, the correct client will receive the reserved configuration when it renews.

Host reservations are defined as parameters for each subnet. Each host must have its own unique identifier, such as the hardware/MAC address. There is an optional reservations array in the subnet4 structure; each element in that array is a structure that holds information about reservations for a single host. In particular, the structure has an identifier that uniquely identifies a host. In the DHCPv4 context, the identifier is usually a hardware or MAC address. In most cases an IP address will be specified. It is also possible to specify a hostname, host-specific options, or fields carried within the DHCPv4 message such as siaddr, sname, or file.

Note

The reserved address must be within the subnet.

The following example shows how to reserve addresses for specific hosts in a subnet:

"subnet4": [
    {
        "pools": [ { "pool":  "192.0.2.1 - 192.0.2.200" } ],
        "subnet": "192.0.2.0/24",
        "interface": "eth0",
        "reservations": [
            {
                "hw-address": "1a:1b:1c:1d:1e:1f",
                "ip-address": "192.0.2.202"
            },
            {
                "duid": "0a:0b:0c:0d:0e:0f",
                "ip-address": "192.0.2.100",
                "hostname": "alice-laptop"
            },
            {
                "circuit-id": "'charter950'",
                "ip-address": "192.0.2.203"
            },
            {
                "client-id": "01:11:22:33:44:55:66",
                "ip-address": "192.0.2.204"
            }
        ]
    }
]

The first entry reserves the 192.0.2.202 address for the client that uses a MAC address of 1a:1b:1c:1d:1e:1f. The second entry reserves the address 192.0.2.100 and the hostname of “alice-laptop” for the client using a DUID 0a:0b:0c:0d:0e:0f. (If DNS updates are planned, it is strongly recommended that the hostnames be unique.) The third example reserves address 192.0.3.203 for a client whose request would be relayed by a relay agent that inserts a circuit-id option with the value “charter950”. The fourth entry reserves address 192.0.2.204 for a client that uses a client identifier with value 01:11:22:33:44:55:66.

The above example is used for illustrational purposes only; in actual deployments it is recommended to use as few types as possible (preferably just one). See Fine-Tuning DHCPv4 Host Reservation for a detailed discussion of this point.

Making a reservation for a mobile host that may visit multiple subnets requires a separate host definition in each subnet that host is expected to visit. It is not possible to define multiple host definitions with the same hardware address in a single subnet. Multiple host definitions with the same hardware address are valid if each is in a different subnet.

Adding host reservations incurs a performance penalty. In principle, when a server that does not support host reservation responds to a query, it needs to check whether there is a lease for a given address being considered for allocation or renewal. The server that does support host reservation has to perform additional checks: not only whether the address is currently used (i.e., if there is a lease for it), but also whether the address could be used by someone else (i.e., if there is a reservation for it). That additional check incurs extra overhead.

Address Reservation Types

In a typical Kea scenario there is an IPv4 subnet defined, e.g. 192.0.2.0/24, with a certain part of it dedicated for dynamic allocation by the DHCPv4 server. That dynamic part is referred to as a dynamic pool or simply a pool. In principle, a host reservation can reserve any address that belongs to the subnet. The reservations that specify addresses that belong to configured pools are called “in-pool reservations.” In contrast, those that do not belong to dynamic pools are called “out-of-pool reservations.” There is no formal difference in the reservation syntax and both reservation types are handled uniformly.

Kea supports global host reservations. These are reservations that are specified at the global level within the configuration and that do not belong to any specific subnet. Kea still matches inbound client packets to a subnet as before, but when the subnet’s reservation mode is set to “global”, Kea looks for host reservations only among the global reservations defined. Typically, such reservations would be used to reserve hostnames for clients which may move from one subnet to another.

Note

Global reservations, while useful in certain circumstances, have aspects that must be given due consideration when using them. Please see Conflicts in DHCPv4 Reservations for more details.

Note

Since Kea 1.9.1, reservation mode has been replaced by three boolean flags, reservations-global, reservations-in-subnet, and reservations-out-of-pool, which allow the configuration of host reservations both globally and in a subnet. In such cases a subnet host reservation has preference over a global reservation when both exist for the same client.

Conflicts in DHCPv4 Reservations

As reservations and lease information are stored separately, conflicts may arise. Consider the following series of events: the server has configured the dynamic pool of addresses from the range of 192.0.2.10 to 192.0.2.20. Host A requests an address and gets 192.0.2.10. Now the system administrator decides to reserve address 192.0.2.10 for Host B. In general, reserving an address that is currently assigned to someone else is not recommended, but there are valid use cases where such an operation is warranted.

The server now has a conflict to resolve. If Host B boots up and requests an address, the server cannot immediately assign the reserved address 192.0.2.10. A naive approach would to be immediately remove the existing lease for Host A and create a new one for Host B. That would not solve the problem, though, because as soon as Host B gets the address, it will detect that the address is already in use (by Host A) and will send a DHCPDECLINE message. Therefore, in this situation, the server has to temporarily assign a different address from the dynamic pool (not matching what has been reserved) to Host B.

When Host A renews its address, the server will discover that the address being renewed is now reserved for another host - Host B. The server will inform Host A that it is no longer allowed to use it by sending a DHCPNAK message. The server will not remove the lease, though, as there’s a small chance that the DHCPNAK will not be delivered if the network is lossy. If that happens, the client will not receive any responses, so it will retransmit its DHCPREQUEST packet. Once the DHCPNAK is received by Host A, it will revert to server discovery and will eventually get a different address. Besides allocating a new lease, the server will also remove the old one. As a result, address 192.0.2.10 will become free.

When Host B tries to renew its temporarily assigned address, the server will detect that it has a valid lease, but will note that there is a reservation for a different address. The server will send DHCPNAK to inform Host B that its address is no longer usable, but will keep its lease (again, the DHCPNAK may be lost, so the server will keep it until the client returns for a new address). Host B will revert to the server discovery phase and will eventually send a DHCPREQUEST message. This time the server will find that there is a reservation for that host and that the reserved address 192.0.2.10 is not used, so it will be granted. It will also remove the lease for the temporarily assigned address that Host B previously obtained.

This recovery will succeed, even if other hosts attempt to get the reserved address. If Host C requests the address 192.0.2.10 after the reservation is made, the server will either offer a different address (when responding to DHCPDISCOVER) or send DHCPNAK (when responding to DHCPREQUEST).

This mechanism allows the server to fully recover from a case where reservations conflict with existing leases; however, this procedure takes roughly as long as the value set for renew-timer. The best way to avoid such a recovery is not to define new reservations that conflict with existing leases. Another recommendation is to use out-of-pool reservations; if the reserved address does not belong to a pool, there is no way that other clients can get it.

Note

The conflict-resolution mechanism does not work for global reservations. Although the global address reservations feature may be useful in certain settings, it is generally recommended not to use global reservations for addresses. Administrators who do choose to use global reservations must manually ensure that the reserved addresses are not in dynamic pools.

Reserving a Hostname

When the reservation for a client includes the hostname, the server returns this hostname to the client in the Client FQDN or Hostname option. The server responds with the Client FQDN option only if the client has included the Client FQDN option in its message to the server. The server responds with the Hostname option if the client included the Hostname option in its message to the server, or if the client requested the Hostname option using the Parameter Request List option. The server returns the Hostname option even if it is not configured to perform DNS updates. The reserved hostname always takes precedence over the hostname supplied by the client or the autogenerated (from the IPv4 address) hostname.

The server qualifies the reserved hostname with the value of the ddns-qualifying-suffix parameter. For example, the following subnet configuration:

{
    "subnet4": [ {
        "subnet": "10.0.0.0/24",
        "pools": [ { "pool": "10.0.0.10-10.0.0.100" } ],
        "ddns-qualifying-suffix": "example.isc.org.",
        "reservations": [
           {
             "hw-address": "aa:bb:cc:dd:ee:ff",
             "hostname": "alice-laptop"
           }
        ]
     }],
    "dhcp-ddns": {
        "enable-updates": true,
    }
}

will result in the “alice-laptop.example.isc.org.” hostname being assigned to the client using the MAC address “aa:bb:cc:dd:ee:ff”. If the ddns-qualifying-suffix is not specified, the default (empty) value will be used, and in this case the value specified as a hostname will be treated as a fully qualified name. Thus, by leaving the ddns-qualifying-suffix empty it is possible to qualify hostnames for different clients with different domain names:

{
    "subnet4": [ {
        "subnet": "10.0.0.0/24",
        "pools": [ { "pool": "10.0.0.10-10.0.0.100" } ],
        "reservations": [
           {
             "hw-address": "aa:bb:cc:dd:ee:ff",
             "hostname": "alice-laptop.isc.org."
           },
           {
             "hw-address": "12:34:56:78:99:AA",
             "hostname": "mark-desktop.example.org."
           }

        ]
     }],
    "dhcp-ddns": {
        "enable-updates": true,
    }
}

The above example results in the assignment of the “alice-laptop.isc.org.” hostname to the client using the MAC address “aa:bb:cc:dd:ee:ff”, and the hostname “mark-desktop.example.org.” to the client using the MAC address “12:34:56:78:99:AA”.

Including Specific DHCPv4 Options in Reservations

Kea offers the ability to specify options on a per-host basis. These options follow the same rules as any other options. These can be standard options (see Standard DHCPv4 Options), custom options (see Custom DHCPv4 Options), or vendor-specific options (see DHCPv4 Vendor-Specific Options). The following example demonstrates how standard options can be defined:

{
    "subnet4": [ {
        "reservations": [
        {
            "hw-address": "aa:bb:cc:dd:ee:ff",
            "ip-address": "192.0.2.1",
            "option-data": [
            {
                "name": "cookie-servers",
                "data": "10.1.1.202,10.1.1.203"
            },
            {
                "name": "log-servers",
                "data": "10.1.1.200,10.1.1.201"
            } ]
        } ]
    } ]
}

Vendor-specific options can be reserved in a similar manner:

{
    "subnet4": [ {
        "reservations": [
        {
            "hw-address": "aa:bb:cc:dd:ee:ff",
            "ip-address": "10.0.0.7",
            "option-data": [
            {
                "name": "vivso-suboptions",
                "data": "4491"
            },
            {
                "name": "tftp-servers",
                "space": "vendor-4491",
                "data": "10.1.1.202,10.1.1.203"
            } ]
        } ]
    } ]
}

Options defined at the host level have the highest priority. In other words, if there are options defined with the same type on the global, subnet, class, and host levels, the host-specific values are used.

Reserving Next Server, Server Hostname, and Boot File Name

BOOTP/DHCPv4 messages include “siaddr”, “sname”, and “file” fields. Even though DHCPv4 includes corresponding options, such as option 66 and option 67, some clients may not support these options. For this reason, server administrators often use the “siaddr”, “sname”, and “file” fields instead.

With Kea, it is possible to make static reservations for these DHCPv4 message fields:

{
    "subnet4": [ {
        "reservations": [
        {
            "hw-address": "aa:bb:cc:dd:ee:ff",
            "next-server": "10.1.1.2",
            "server-hostname": "server-hostname.example.org",
            "boot-file-name": "/tmp/bootfile.efi"
        } ]
    } ]
}

Note that those parameters can be specified in combination with other parameters for a reservation, such as a reserved IPv4 address. These parameters are optional; a subset of them can be specified, or all of them can be omitted.

Reserving Client Classes in DHCPv4

Using Expressions in Classification explains how to configure the server to assign classes to a client, based on the content of the options that this client sends to the server. Host reservation mechanisms also allow for the static assignment of classes to clients. The definitions of these classes are placed in the Kea configuration file or a database. The following configuration snippet shows how to specify that a client belongs to the classes reserved-class1 and reserved-class2. Those classes are associated with specific options sent to the clients which belong to them.

{
    "client-classes": [
    {
       "name": "reserved-class1",
       "option-data": [
       {
           "name": "routers",
           "data": "10.0.0.200"
       }
       ]
    },
    {
       "name": "reserved-class2",
       "option-data": [
       {
           "name": "domain-name-servers",
           "data": "10.0.0.201"
       }
       ]
    }
    ],
    "subnet4": [ {
        "subnet": "10.0.0.0/24",
        "pools": [ { "pool": "10.0.0.10-10.0.0.100" } ],
        "reservations": [
        {
            "hw-address": "aa:bb:cc:dd:ee:ff",

            "client-classes": [ "reserved-class1", "reserved-class2" ]

        }
        ]
    } ]
 }

In some cases the host reservations can be used in conjunction with client classes specified within the Kea configuration. In particular, when a host reservation exists for a client within a given subnet, the “KNOWN” built-in class is assigned to the client. Conversely, when there is no static assignment for the client, the “UNKNOWN” class is assigned to the client. Class expressions within the Kea configuration file can refer to “KNOWN” or “UNKNOWN” classes using the “member” operator. For example:

{
    "client-classes": [
        {
            "name": "dependent-class",
            "test": "member('KNOWN')",
            "only-if-required": true
        }
    ]
}

The only-if-required parameter is needed here to force evaluation of the class after the lease has been allocated and thus the reserved class has been also assigned.

Note

The classes specified in non-global host reservations are assigned to the processed packet after all classes with the only-if-required parameter set to false have been evaluated. This means that these classes must not depend on the statically assigned classes from the host reservations. If such a dependency is needed, the only-if-required parameter must be set to true for the dependent classes. Such classes are evaluated after the static classes have been assigned to the packet. This, however, imposes additional configuration overhead, because all classes marked as only-if-required must be listed in the require-client-classes list for every subnet where they are used.

Note

Client classes specified within the Kea configuration file may depend on the classes specified within the global host reservations. In such a case the only-if-required parameter is not needed. Refer to Pool Selection with Client Class Reservations and Subnet Selection with Client Class Reservations for specific use cases.

Storing Host Reservations in MySQL or PostgreSQL

Kea can store host reservations in MySQL or PostgreSQL. See Hosts Storage for information on how to configure Kea to use reservations stored in MySQL or PostgreSQL. Kea provides a dedicated hook for managing reservations in a database; section host_cmds: Host Commands provides detailed information. The Kea wiki provides some examples of how to conduct common host reservation operations.

Note

In Kea, the maximum length of an option specified per-host-reservation is arbitrarily set to 4096 bytes.

Fine-Tuning DHCPv4 Host Reservation

The host reservation capability introduces additional restrictions for the allocation engine (the component of Kea that selects an address for a client) during lease selection and renewal. In particular, three major checks are necessary. First, when selecting a new lease, it is not sufficient for a candidate lease to simply not be in use by another DHCP client; it also must not be reserved for another client. Similarly, when renewing a lease, an additional check must be performed to see whether the address being renewed is reserved for another client. Finally, when a host renews an address, the server must check whether there is a reservation for this host, which would mean the existing (dynamically allocated) address should be revoked and the reserved one be used instead.

Some of those checks may be unnecessary in certain deployments, and not performing them may improve performance. The Kea server provides the reservation-mode configuration parameter to select the types of reservations allowed for a particular subnet. Each reservation type has different constraints for the checks to be performed by the server when allocating or renewing a lease for the client. Although reservation-mode was deprecated in Kea 1.9.1, it is still available; the allowed values are:

• all - enables both in-pool and out-of-pool host reservation types. This setting is the default value, and is the safest and most flexible. However, as all checks are conducted, it is also the slowest. It does not check against global reservations.

• out-of-pool - allows only out-of-pool host reservations. With this setting in place, the server assumes that all host reservations are for addresses that do not belong to the dynamic pool. Therefore, it can skip the reservation checks when dealing with in-pool addresses, thus improving performance. Do not use this mode if any reservations use in-pool addresses. Caution is advised when using this setting; Kea does not sanity-check the reservations against reservation-mode and misconfiguration may cause problems.

• global - allows only global host reservations. With this setting in place, the server searches for reservations for a client only among the defined global reservations. If an address is specified, the server skips the reservation checks carried out in other modes, thus improving performance. Caution is advised when using this setting; Kea does not sanity-check reservations when global is set, and misconfiguration may cause problems.

• disabled - host reservation support is disabled. As there are no reservations, the server skips all checks. Any reservations defined are completely ignored. As checks are skipped, the server may operate faster in this mode.

Since Kea 1.9.1, the reservation-mode parameter is replaced by the reservations-global, reservations-in-subnet, and reservations-out-of-pool flags. The flags can be activated independently and can produce various combinations, some of which were not supported by the deprecated reservation-mode.

The reservation-mode parameter can be specified at:

• global level: .Dhcp4["reservation-mode"] (lowest priority: gets overridden by all others)

• subnet level: .Dhcp4.subnet4[]["reservation-mode"] (low priority)

• shared-network level: .Dhcp4["shared-networks"][]["reservation-mode"] (high priority)

• shared-network subnet-level: .Dhcp4["shared-networks"][].subnet4[]["reservation-mode"] (highest priority: overrides all others)

To decide which reservation-mode to choose, the following decision diagram may be useful:

                              O
                              |
                              v
+-----------------------------+------------------------------+
|         Is per-host configuration needed, such as          |
|                reserving specific addresses,               |
|               assigning specific options or                |
| assigning packets to specific classes on per-device basis? |
+-+-----------------+----------------------------------------+
  |                 |
no|              yes|
  |                 |   +--------------------------------------+
  |                 |   |         For all given hosts,         |
  +--> "disabled"   +-->+      can the reserved resources      |
                        |  be used in all configured subnets?  |
                        +--------+---------------------------+-+
                                 |                           |
+----------------------------+   |no                         |yes
|             Is             |   |                           |
|  at least one reservation  +<--+               "global" <--+
| used to reserve addresses? |
+-+------------------------+-+
  |                        |
no|                     yes|   +---------------------------+
  |                        |   | Is high leases-per-second |
  +--> "out-of-pool"       +-->+ performance or efficient  |
        ^                      |      resource usage       |
        |                      |  (CPU ticks, RAM usage,   |
        |                      |   database roundtrips)    |
        |                      | important to your setup?  |
        |                      +-+----------------+--------+
        |                        |                |
        |                     yes|              no|
        |                        |                |
        |          +-------------+                |
        |          |                              |
        |          |   +----------------------+   |
        |          |   | Can it be guaranteed |   |
        |          +-->+  that the reserved   |   |
        |              |      addresses       |   |
        |              |  aren't part of the  |   |
        |              |   pools configured   |   |
        |              |  in the respective   |   |
        |              |       subnet?        |   |
        |              +-+------------------+-+   |
        |                |                  |     |
        |             yes|                no|     |
        |                |                  |     V
        +----------------+                  +--> "all"

An example configuration that disables reservations looks as follows:

{
  "Dhcp4": {
    "subnet4": [
      {
        "pools": [
          {
            "pool": "192.0.2.10-192.0.2.100"
          }
        ],
        "reservation-mode": "disabled",
        "subnet": "192.0.2.0/24"
      }
    ]
  }
}

An example configuration using global reservations is shown below:

{
  "Dhcp4": {
    "reservation-mode": "global",
    "reservations": [
      {
        "hostname": "host-one",
        "hw-address": "01:bb:cc:dd:ee:ff"
      },
      {
        "hostname": "host-two",
        "hw-address": "02:bb:cc:dd:ee:ff"
      }
    ],
    "subnet4": [
      {
        "pools": [
          {
            "pool": "192.0.2.10-192.0.2.100"
          }
        ],
        "subnet": "192.0.2.0/24"
      }
    ]
  }
}

The meaning of the reservation flags are:

• reservations-global: fetch global reservations.

• reservations-in-subnet: fetch subnet reservations. For a shared network this includes all subnet members of the shared network.

• reservations-out-of-pool: this makes sense only when the reservations-in-subnet flag is true. When reservations-out-of-pool is true, the server assumes that all host reservations are for addresses that do not belong to the dynamic pool. Therefore, it can skip the reservation checks when dealing with in-pool addresses, thus improving performance. The server will not assign reserved addresses that are inside the dynamic pools to the respective clients. This also means that the addresses matching the respective reservations from inside the dynamic pools (if any) can be dynamically assigned to any client.

The disabled value from the deprecated reservation-mode corresponds to:

{
  "Dhcp4": {
    "reservations-global": false,
    "reservations-in-subnet": false
  }
}

The global value from the deprecated reservation-mode corresponds to:

{
  "Dhcp4": {
    "reservations-global": true,
    "reservations-in-subnet": false
  }
}

The out-of-pool value from the deprecated reservation-mode corresponds to:

{
  "Dhcp4": {
    "reservations-global": false,
    "reservations-in-subnet": true,
    "reservations-out-of-pool": true
  }
}

And the all value from the deprecated reservation-mode corresponds to:

{
  "Dhcp4": {
    "reservations-global": false,
    "reservations-in-subnet": true,
    "reservations-out-of-pool": false
  }
}

To activate both global and all, the following combination can be used:

{
  "Dhcp4": {
    "reservations-global": true,
    "reservations-in-subnet": true,
    "reservations-out-of-pool": false
  }
}

To activate both global and out-of-pool, the following combination can be used:

{
  "Dhcp4": {
    "reservations-global": true,
    "reservations-in-subnet": true,
    "reservations-out-of-pool": true
  }
}

Enabling out-of-pool and disabling in-subnet at the same time is not recommended because out-of-pool applies to host reservations in a subnet, which are fetched only when the in-subnet flag is true.

The parameter can be specified at the global, subnet, and shared-network levels.

An example configuration that disables reservations looks as follows:

{
  "Dhcp4": {
    "subnet4": [
      {
        "reservations-global": false,
        "reservations-in-subnet": false,
        "subnet": "192.0.2.0/24"
      }
    ]
  }
}

An example configuration using global reservations is shown below:

{
  "Dhcp4": {
    "reservations": [
      {
        "hostname": "host-one",
        "hw-address": "01:bb:cc:dd:ee:ff"
      },
      {
        "hostname": "host-two",
        "hw-address": "02:bb:cc:dd:ee:ff"
      }
    ],
    "reservations-global": true,
    "reservations-in-subnet": false,
    "subnet4": [
      {
        "pools": [
          {
            "pool": "192.0.2.10-192.0.2.100"
          }
        ],
        "subnet": "192.0.2.0/24"
      }
    ]
  }
}

For more details regarding global reservations, see Global Reservations in DHCPv4.

Another aspect of host reservations is the different types of identifiers. Kea currently supports four types of identifiers: hw-address, duid, client-id, and circuit-id. This is beneficial from a usability perspective; however, there is one drawback. For each incoming packet, Kea has to extract each identifier type and then query the database to see if there is a reservation by this particular identifier. If nothing is found, the next identifier is extracted and the next query is issued. This process continues until either a reservation is found or all identifier types have been checked. Over time, with an increasing number of supported identifier types, Kea would become slower and slower.

To address this problem, a parameter called host-reservation-identifiers is available. It takes a list of identifier types as a parameter. Kea checks only those identifier types enumerated in host-reservation-identifiers. From a performance perspective, the number of identifier types should be kept to a minimum, ideally one. If the deployment uses several reservation types, please enumerate them from most- to least-frequently used, as this increases the chances of Kea finding the reservation using the fewest queries. An example of a host-reservation-identifiers configuration looks as follows:

"host-reservation-identifiers": [ "circuit-id", "hw-address", "duid", "client-id" ],
"subnet4": [
    {
        "subnet": "192.0.2.0/24",
        ...
    }
]

If not specified, the default value is:

"host-reservation-identifiers": [ "hw-address", "duid", "circuit-id", "client-id" ]

Global Reservations in DHCPv4

In some deployments, such as mobile, clients can roam within the network and certain parameters must be specified regardless of the client’s current location. To meet such a need, Kea offers a global reservation mechanism. The idea behind it is that regular host reservations are tied to specific subnets, by using a specific subnet ID. Kea can specify a global reservation that can be used in every subnet that has global reservations enabled.

This feature can be used to assign certain parameters, such as hostname or other dedicated, host-specific options. It can also be used to assign addresses. However, global reservations that assign addresses bypass the whole topology determination provided by the DHCP logic implemented in Kea. It is very easy to misuse this feature and get a configuration that is inconsistent. To give a specific example, imagine a global reservation for the address 192.0.2.100 and two subnets 192.0.2.0/24 and 192.0.5.0/24. If global reservations are used in both subnets and a device matching global host reservations visits part of the network that is serviced by 192.0.5.0/24, it will get an IP address 192.0.2.100, a subnet 192.0.5.0, and a default router 192.0.5.1. Obviously, such a configuration is unusable, as the client will not be able to reach its default gateway.

To use global host reservations, a configuration similar to the following can be used:

"Dhcp4:" {
    # This specifies global reservations.
    # They will apply to all subnets that
    # have global reservations enabled.

    "reservations": [
    {
       "hw-address": "aa:bb:cc:dd:ee:ff",
       "hostname": "hw-host-dynamic"
    },
    {
       "hw-address": "01:02:03:04:05:06",
       "hostname": "hw-host-fixed",

       # Use of IP addresses in global reservations is risky.
       # If used outside of a matching subnet, such as 192.0.1.0/24,
       # it will result in a broken configuration being handed
       # to the client.
       "ip-address": "192.0.1.77"
    },
    {
       "duid": "01:02:03:04:05",
       "hostname": "duid-host"
    },
    {
       "circuit-id": "'charter950'",
       "hostname": "circuit-id-host"
    },
    {
       "client-id": "01:11:22:33:44:55:66",
       "hostname": "client-id-host"
    }
    ],
    "valid-lifetime": 600,
    "subnet4": [ {
        "subnet": "10.0.0.0/24",
        # It is replaced by the "reservations-global"
        # "reservations-in-subnet" and "reservations-out-of-pool"
        # parameters.
        # "reservation-mode": "global",
        # Specify if the server should lookup global reservations.
        "reservations-global": true,
        # Specify if the server should lookup in-subnet reservations.
        "reservations-in-subnet": false,
        # Specify if the server can assume that all reserved addresses
        # are out-of-pool. It can be ignored because "reservations-in-subnet"
        # is false.
        # "reservations-out-of-pool": false,
        "pools": [ { "pool": "10.0.0.10-10.0.0.100" } ]
    } ]
}

When using database backends, the global host reservations are distinguished from regular reservations by using a subnet-id value of 0.

Pool Selection with Client Class Reservations

Client classes can be specified in the Kea configuration file and/or via host reservations. The classes specified in the Kea configuration file are evaluated immediately after receiving the DHCP packet and therefore can be used to influence subnet selection using the client-class parameter specified in the subnet scope. The classes specified within the host reservations are fetched and assigned to the packet after the server has already selected a subnet for the client. This means that the client class specified within a host reservation cannot be used to influence subnet assignment for this client, unless the subnet belongs to a shared network. If the subnet belongs to a shared network, the server may dynamically change the subnet assignment while trying to allocate a lease. If the subnet does not belong to a shared network, the subnet is not changed once selected.

If the subnet does not belong to a shared network, it is possible to use host reservation-based client classification to select an address pool within the subnet as follows:

"Dhcp4": {
    "client-classes": [
        {
            "name": "reserved_class"
        },
        {
            "name": "unreserved_class",
            "test": "not member('reserved_class')"
        }
    ],
    "subnet4": [
        {
            "subnet": "192.0.2.0/24",
            "reservations": [{"
                "hw-address": "aa:bb:cc:dd:ee:fe",
                "client-classes": [ "reserved_class" ]
             }],
            "pools": [
                {
                    "pool": "192.0.2.10-192.0.2.20",
                    "client-class": "reserved_class"
                },
                {
                    "pool": "192.0.2.30-192.0.2.40",
                    "client-class": "unreserved_class"
                }
            ]
        }
    ]
}

The reserved_class is declared without the test parameter because it may only be assigned to the client via the host reservation mechanism. The second class, unreserved_class, is assigned to clients which do not belong to the reserved_class. The first pool within the subnet is only used for clients having a reservation for the reserved_class. The second pool is used for clients not having such a reservation. The configuration snippet includes one host reservation which causes the client with the MAC address aa:bb:cc:dd:ee:fe to be assigned to the reserved_class. Thus, this client will be given an IP address from the first address pool.

Subnet Selection with Client Class Reservations

There is one specific use case when subnet selection may be influenced by client classes specified within host reservations: when the client belongs to a shared network. In such a case it is possible to use classification to select a subnet within this shared network. Consider the following example:

"Dhcp4": {
    "client-classes": [
        {
            "name": "reserved_class"
        },
        {
            "name: "unreserved_class",
            "test": "not member('reserved_class')"
        }
    ],
    "reservations": [{"
        "hw-address": "aa:bb:cc:dd:ee:fe",
        "client-classes": [ "reserved_class" ]
    }],
    # It is replaced by the "reservations-global"
    # "reservations-in-subnet" and "reservations-out-of-pool" parameters.
    # Specify if the server should lookup global reservations.
    "reservations-global": true,
    # Specify if the server should lookup in-subnet reservations.
    "reservations-in-subnet": false,
    # Specify if the server can assume that all reserved addresses
    # are out-of-pool. It can be ignored because "reservations-in-subnet"
    # is false, but if specified, it is inherited by "shared-networks"
    # and "subnet4" levels.
    # "reservations-out-of-pool": false,
    "shared-networks": [{
        "subnet4": [
            {
                "subnet": "192.0.2.0/24",
                "pools": [
                    {
                        "pool": "192.0.2.10-192.0.2.20",
                        "client-class": "reserved_class"
                    }
                ]
            },
            {
                "subnet": "192.0.3.0/24",
                "pools": [
                    {
                        "pool": "192.0.3.10-192.0.3.20",
                        "client-class": "unreserved_class"
                    }
                ]
            }
        ]
    }]
}

This is similar to the example described in Pool Selection with Client Class Reservations. This time, however, there are two subnets, each of which has a pool associated with a different class. The clients that do not have a reservation for the reserved_class are assigned an address from the subnet 192.0.3.0/24. Clients with a reservation for the reserved_class are assigned an address from the subnet 192.0.2.0/24. The subnets must belong to the same shared network. In addition, the reservation for the client class must be specified at the global scope (global reservation) and reservations-global must be set to true.

In the example above, the client-class could also be specified at the subnet level rather than the pool level, and would yield the same effect.

Multiple Reservations for the Same IP

Host reservations were designed to preclude the creation of multiple reservations for the same IP address within a particular subnet, to avoid having two different clients compete for the same address. When using the default settings, the server returns a configuration error when it finds two or more reservations for the same IP address within a subnet in the Kea configuration file. The host_cmds: Host Commands hook library returns an error in response to the reservation-add command when it detects that the reservation exists in the database for the IP address for which the new reservation is being added.

In some deployments a single host can select one of several network interfaces to communicate with the DHCP server, and the server must assign the same IP address to the host regardless of the interface used. Since each interface is assigned a different MAC address, it implies that several host reservations must be created to associate all of the MAC addresses present on this host with IP addresses. Using different IP addresses for each interface is impractical and is considered a waste of the IPv4 address space, especially since the host typically uses only one interface for communication with the server, hence only one IP address is in use.

This causes a need to create multiple host reservations for a single IP address within a subnet; this is supported since the Kea 1.9.1 release as an optional mode of operation, enabled with the ip-reservations-unique global parameter.

The ip-reservations-unique is a boolean parameter that defaults to true, which forbids the specification of more than one reservation for the same IP address within a given subnet. Setting this parameter to false allows such reservations to be created both in the Kea configuration file and in the host database backend, via the host-cmds hook library.

This setting is currently supported by the most popular host database backends, i.e. MySQL and PostgreSQL. Host Cache (see host_cache: Caching Host Reservations), or the RADIUS backend (see radius: RADIUS Server Support). An attempt to set ip-reservations-unique to false when any of these three backends is in use yields a configuration error.

Note

When ip-reservations-unique is set to true (the default value), the server ensures that IP reservations are unique for a subnet within a single host backend and/or Kea configuration file. It does not guarantee that the reservations are unique across multiple backends.

The following is an example configuration with two reservations for the same IP address but different MAC addresses:

"Dhcp4": {
    "ip-reservations-unique": false,
    "subnet4": [
        {
            "subnet": "192.0.2.0/24",
            "reservations": [
                {
                    "hw-address": "1a:1b:1c:1d:1e:1f",
                    "ip-address": "192.0.2.11"
                },
                {
                    "hw-address": "2a:2b:2c:2d:2e:2f",
                    "ip-address": "192.0.2.11"
                }
            ]
        }
    ]
}

It is possible to control the ip-reservations-unique parameter via the Configuration Backend in DHCPv4. If the new setting of this parameter conflicts with the currently used backends (i.e. backends do not support the new setting), the new setting is ignored and a warning log message is generated. The backends continue to use the default setting, expecting that IP reservations are unique within each subnet. To allow the creation of non-unique IP reservations, the administrator must remove the backends which lack support for them from the configuration file.

Administrators must be careful when they have been using multiple reservations for the same IP address and later decide to return to the default mode in which this is no longer allowed. They must make sure that at most one reservation for a given IP address exists within a subnet, prior to switching back to the default mode. If such duplicates are left in the configuration file, the server reports a configuration error. Leaving such reservations in the host databases does not cause configuration errors but may lead to lease allocation errors during the server’s operation, when it unexpectedly finds multiple reservations for the same IP address.

Note

Currently the Kea server does not verify whether multiple reservations for the same IP address exist in MySQL and/or PostgreSQL host databases when ip-reservations-unique is updated from true to false. This may cause issues with lease allocations. The administrator must ensure that there is at most one reservation for each IP address within each subnet, prior to the configuration update.

The reservations-lookup-first is a boolean parameter which controls whether host reservations lookup should be performed before lease lookup. This parameter has effect only when multi-threading is disabled. When multi-threading is enabled, host reservations lookup is always performed first to avoid lease lookup resource locking. The reservations-lookup-first defaults to false when multi-threading is disabled.

Shared Networks in DHCPv4

DHCP servers use subnet information in two ways. It is used to both determine the point of attachment, i.e. where the client is connected to the network, and to group information pertaining to a specific location in the network. Sometimes it is useful to have more than one logical IP subnet deployed on the same physical link. Understanding that two or more subnets are used on the same link requires additional logic in the DHCP server. This capability is called “shared networks” in Kea, and sometimes also “shared subnets”; in Microsoft’s nomenclature it is called “multinet.”

There are many cases where the shared networks feature is useful; here we explain just a handful of the most common ones. The first and by far most common use case is an existing IPv4 network that has grown and is running out of available address space. Rather than migrating all devices to a new, larger subnet, it is easier to simply configure additional subnets on top of the existing one. Sometimes, due to address space fragmentation (e.g. only many disjointed /24s are available), this is the only choice. Also, configuring additional subnets has the advantage of not disrupting the operation of existing devices.

Another very frequent use case comes from cable networks. There are two types of devices in cable networks: cable modems and the end-user devices behind them. It is a common practice to use different subnets for cable modems to prevent users from tinkering with them. In this case, the distinction is based on the type of device, rather than on address-space exhaustion.

A client connected to a shared network may be assigned an address from any of the pools defined within the subnets belonging to the shared network. Internally, the server selects one of the subnets belonging to a shared network and tries to allocate an address from this subnet. If the server is unable to allocate an address from the selected subnet (e.g., due to address-pool exhaustion), it uses another subnet from the same shared network and tries to allocate an address from this subnet. The server typically allocates all addresses available in a given subnet before it starts allocating addresses from other subnets belonging to the same shared network. However, in certain situations the client can be allocated an address from another subnet before the address pools in the first subnet get exhausted; this sometimes occurs when the client provides a hint that belongs to another subnet, or the client has reservations in a subnet other than the default.

Note

Deployments should not assume that Kea waits until it has allocated all the addresses from the first subnet in a shared network before allocating addresses from other subnets.

To define a shared network, an additional configuration scope is introduced:

{
"Dhcp4": {
    "shared-networks": [
        {
            # Name of the shared network. It may be an arbitrary string
            # and it must be unique among all shared networks.
            "name": "my-secret-lair-level-1",

            # The subnet selector can be specified at the shared network level.
            # Subnets from this shared network will be selected for directly
            # connected clients sending requests to the server's "eth0" interface.
            "interface": "eth0",

            # This starts a list of subnets in this shared network.
            # There are two subnets in this example.
            "subnet4": [
                {
                    "subnet": "10.0.0.0/8",
                    "pools": [ { "pool":  "10.0.0.1 - 10.0.0.99" } ],
                },
                {
                    "subnet": "192.0.2.0/24",
                    "pools": [ { "pool":  "192.0.2.100 - 192.0.2.199" } ]
                }
            ],
        } ], # end of shared-networks

    # It is likely that in the network there will be a mix of regular,
    # "plain" subnets and shared networks. It is perfectly valid to mix
    # them in the same configuration file.
    #
    # This is a regular subnet. It is not part of any shared network.
    "subnet4": [
        {
            "subnet": "192.0.3.0/24",
            "pools": [ { "pool":  "192.0.3.1 - 192.0.3.200" } ],
            "interface": "eth1"
        }
    ]

} # end of Dhcp4
}

As demonstrated in the example, it is possible to mix shared and regular (“plain”) subnets. Each shared network must have a unique name. This is similar to the ID for subnets, but gives administrators more flexibility. It is used for logging, but also internally for identifying shared networks.

In principle it makes sense to define only shared networks that consist of two or more subnets. However, for testing purposes, an empty subnet or a network with just a single subnet is allowed. This is not a recommended practice in production networks, as the shared network logic requires additional processing and thus lowers the server’s performance. To avoid unnecessary performance degradation, shared subnets should only be defined when required by the deployment.

Shared networks provide the ability to specify many parameters in the shared network scope that apply to all subnets within it. If necessary, it is possible to specify a parameter in the shared-network scope and then override its value in the subnet scope. For example:

"shared-networks": [
    {
        "name": "lab-network3",

        "interface": "eth0",

        # This applies to all subnets in this shared network, unless
        # values are overridden on subnet scope.
        "valid-lifetime": 600,

        # This option is made available to all subnets in this shared
        # network.
        "option-data": [ {
            "name": "log-servers",
            "data": "1.2.3.4"
        } ],

        "subnet4": [
            {
                "subnet": "10.0.0.0/8",
                "pools": [ { "pool":  "10.0.0.1 - 10.0.0.99" } ],

                # This particular subnet uses different values.
                "valid-lifetime": 1200,
                "option-data": [
                {
                    "name": "log-servers",
                    "data": "10.0.0.254"
                },
                {
                    "name": "routers",
                    "data": "10.0.0.254"
                } ]
            },
            {
                 "subnet": "192.0.2.0/24",
                 "pools": [ { "pool":  "192.0.2.100 - 192.0.2.199" } ],

                 # This subnet does not specify its own valid-lifetime value,
                 # so it is inherited from shared network scope.
                 "option-data": [
                 {
                     "name": "routers",
                     "data": "192.0.2.1"
                 } ]
            }
        ]
    } ]

In this example, there is a log-servers option defined that is available to clients in both subnets in this shared network. Also, the valid lifetime is set to 10 minutes (600s). However, the first subnet overrides some of the values (the valid lifetime is 20 minutes, there is a different IP address for log-servers), but also adds its own option (the router address). Assuming a client asking for router and log-servers options is assigned a lease from this subnet, it will get a lease for 20 minutes and a log-servers and routers value of 10.0.0.254. If the same client is assigned to the second subnet, it will get a 10-minute lease, a log-servers value of 1.2.3.4, and routers set to 192.0.2.1.

Local and Relayed Traffic in Shared Networks

It is possible to specify an interface name at the shared network level, to tell the server that this specific shared network is reachable directly (not via relays) using the local network interface. As all subnets in a shared network are expected to be used on the same physical link, it is a configuration error to attempt to define a shared network using subnets that are reachable over different interfaces. In other words, all subnets within the shared network must have the same value for the interface parameter. The following configuration is an example of what NOT to do:

"shared-networks": [
    {
        "name": "office-floor-2",
        "subnet4": [
            {
                "subnet": "10.0.0.0/8",
                "pools": [ { "pool":  "10.0.0.1 - 10.0.0.99" } ],
                "interface": "eth0"
            },
            {
                 "subnet": "192.0.2.0/24",
                 "pools": [ { "pool":  "192.0.2.100 - 192.0.2.199" } ],

                 # Specifying the different interface name is a configuration
                 # error. This value should rather be "eth0" or the interface
                 # name in the other subnet should be "eth1".
                 "interface": "eth1"
            }
        ]
    } ]

To minimize the chance of configuration errors, it is often more convenient to simply specify the interface name once, at the shared-network level, as shown in the example below.

"shared-networks": [
    {
        "name": "office-floor-2",

        # This tells Kea that the whole shared network is reachable over a
        # local interface. This applies to all subnets in this network.
        "interface": "eth0",

        "subnet4": [
            {
                "subnet": "10.0.0.0/8",
                "pools": [ { "pool":  "10.0.0.1 - 10.0.0.99" } ],
            },
            {
                 "subnet": "192.0.2.0/24",
                 "pools": [ { "pool":  "192.0.2.100 - 192.0.2.199" } ]
            }
        ]
    } ]

With relayed traffic, subnets are typically selected using the relay agents’ addresses. If the subnets are used independently (not grouped within a shared network), a different relay address can be specified for each of these subnets. When multiple subnets belong to a shared network they must be selected via the same relay address and, similarly to the case of the local traffic described above, it is a configuration error to specify different relay addresses for the respective subnets in the shared network. The following configuration is another example of what NOT to do:

"shared-networks": [
    {
        "name": "kakapo",
        "subnet4": [
            {
                "subnet": "192.0.2.0/26",
                "relay": {
                    "ip-addresses": [ "192.1.1.1" ]
                },
                "pools": [ { "pool": "192.0.2.63 - 192.0.2.63" } ]
            },
            {
                "subnet": "10.0.0.0/24",
                "relay": {
                    # Specifying a different relay address for this
                    # subnet is a configuration error. In this case
                    # it should be 192.1.1.1 or the relay address
                    # in the previous subnet should be 192.2.2.2.
                    "ip-addresses": [ "192.2.2.2" ]
                },
                "pools": [ { "pool": "10.0.0.16 - 10.0.0.16" } ]
            }
        ]
    }
]

Again, it is better to specify the relay address at the shared-network level; this value will be inherited by all subnets belonging to the shared network.

"shared-networks": [
    {
        "name": "kakapo",
        "relay": {
            # This relay address is inherited by both subnets.
            "ip-addresses": [ "192.1.1.1" ]
        },
        "subnet4": [
            {
                "subnet": "192.0.2.0/26",
                "pools": [ { "pool": "192.0.2.63 - 192.0.2.63" } ]
            },
            {
                "subnet": "10.0.0.0/24",
                "pools": [ { "pool": "10.0.0.16 - 10.0.0.16" } ]
            }
        ]
    }
]

Even though it is technically possible to configure two (or more) subnets within the shared network to use different relay addresses, this will almost always lead to a different behavior than what the user expects. In this case, the Kea server will initially select one of the subnets by matching the relay address in the client’s packet with the subnet’s configuration. However, it MAY end up using the other subnet (even though it does not match the relay address) if the client already has a lease in this subnet or has a host reservation in this subnet, or simply if the initially selected subnet has no more addresses available. Therefore, it is strongly recommended to always specify subnet selectors (interface or relay address) at the shared-network level if the subnets belong to a shared network, as it is rarely useful to specify them at the subnet level and may lead to the configuration errors described above.

Client Classification in Shared Networks

Sometimes it is desirable to segregate clients into specific subnets based on certain properties. This mechanism is called client classification and is described in Client Classification. Client classification can be applied to subnets belonging to shared networks in the same way as it is used for subnets specified outside of shared networks. It is important to understand how the server selects subnets for clients when client classification is in use, to ensure that the appropriate subnet is selected for a given client type.

If a subnet is associated with a class, only the clients belonging to this class can use this subnet. If there are no classes specified for a subnet, any client connected to a given shared network can use this subnet. A common mistake is to assume that a subnet that includes a client class is preferred over subnets without client classes. Consider the following example:

{
    "client-classes": [
        {
            "name": "b-devices",
            "test": "option[93].hex == 0x0002"
        }
    ],
    "shared-networks": [
        {
            "name": "galah",
            "interface": "eth0",
            "subnet4": [
                {
                    "subnet": "192.0.2.0/26",
                    "pools": [ { "pool": "192.0.2.1 - 192.0.2.63" } ],
                },
                {
                    "subnet": "10.0.0.0/24",
                    "pools": [ { "pool": "10.0.0.2 - 10.0.0.250" } ],
                    "client-class": "b-devices"
                }
            ]
        }
    ]
}

If the client belongs to the “b-devices” class (because it includes option 93 with a value of 0x0002), that does not guarantee that the subnet 10.0.0.0/24 will be used (or preferred) for this client. The server can use either of the two subnets, because the subnet 192.0.2.0/26 is also allowed for this client. The client classification used in this case should be perceived as a way to restrict access to certain subnets, rather than as a way to express subnet preference. For example, if the client does not belong to the “b-devices” class, it may only use the subnet 192.0.2.0/26 and will never use the subnet 10.0.0.0/24.

A typical use case for client classification is in a cable network, where cable modems should use one subnet and other devices should use another subnet within the same shared network. In this case it is necessary to apply classification on all subnets. The following example defines two classes of devices, and the subnet selection is made based on option 93 values.

{
    "client-classes": [
        {

            "name": "a-devices",
            "test": "option[93].hex == 0x0001"
        },
        {
            "name": "b-devices",
            "test": "option[93].hex == 0x0002"
        }
    ],
    "shared-networks": [
        {
            "name": "galah",
            "interface": "eth0",
            "subnet4": [
                {
                    "subnet": "192.0.2.0/26",
                    "pools": [ { "pool": "192.0.2.1 - 192.0.2.63" } ],
                    "client-class": "a-devices"
                },
                {
                    "subnet": "10.0.0.0/24",
                    "pools": [ { "pool": "10.0.0.2 - 10.0.0.250" } ],
                    "client-class": "b-devices"
                }
            ]
        }
    ]
}

In this example each class has its own restriction. Only clients that belong to class “a-devices” are able to use subnet 192.0.2.0/26 and only clients belonging to “b-devices” are able to use subnet 10.0.0.0/24. Care should be taken not to define too-restrictive classification rules, as clients that are unable to use any subnets will be refused service. However, this may be a desired outcome if one wishes to provide service only to clients with known properties (e.g. only VoIP phones allowed on a given link).

It is possible to achieve an effect similar to the one presented in this section without the use of shared networks. If the subnets are placed in the global subnets scope, rather than in the shared network, the server will still use classification rules to pick the right subnet for a given class of devices. The major benefit of placing subnets within the shared network is that common parameters for the logically grouped subnets can be specified once in the shared-network scope, e.g. the interface or relay parameter. All subnets belonging to this shared network will inherit those parameters.

Host Reservations in Shared Networks

Subnets that are part of a shared network allow host reservations, similar to regular subnets:

{
    "shared-networks": [
    {
        "name": "frog",
        "interface": "eth0",
        "subnet4": [
            {
                "subnet": "192.0.2.0/26",
                "id": 100,
                "pools": [ { "pool": "192.0.2.1 - 192.0.2.63" } ],
                "reservations": [
                    {
                        "hw-address": "aa:bb:cc:dd:ee:ff",
                        "ip-address": "192.0.2.28"
                    }
                ]
            },
            {
                "subnet": "10.0.0.0/24",
                "id": 101,
                "pools": [ { "pool": "10.0.0.1 - 10.0.0.254" } ],
                "reservations": [
                    {
                        "hw-address": "11:22:33:44:55:66",
                        "ip-address": "10.0.0.29"
                    }
                ]
            }
        ]
    }
    ]
}

It is worth noting that Kea conducts additional checks when processing a packet if shared networks are defined. First, instead of simply checking whether there is a reservation for a given client in its initially selected subnet, Kea looks through all subnets in a shared network for a reservation. This is one of the reasons why defining a shared network may impact performance. If there is a reservation for a client in any subnet, that particular subnet is selected for the client. Although it is technically not an error, it is considered bad practice to define reservations for the same host in multiple subnets belonging to the same shared network.

While not strictly mandatory, it is strongly recommended to use explicit “id” values for subnets if database storage will be used for host reservations. If an ID is not specified, the values for it are auto-generated, i.e. Kea assigns increasing integer values starting from 1. Thus, the auto-generated IDs are not stable across configuration changes.

Server Identifier in DHCPv4

The DHCPv4 protocol uses a “server identifier” to allow clients to discriminate between several servers present on the same link; this value is an IPv4 address of the server. The server chooses the IPv4 address of the interface on which the message from the client (or relay) has been received. A single server instance uses multiple server identifiers if it is receiving queries on multiple interfaces.

It is possible to override the default server identifier values by specifying the dhcp-server-identifier option. This option configuration is only supported at the subnet, shared network, client class, and global levels. It must not be specified at the host-reservation level. When configuring the dhcp-server-identifier option at client-class level, the class must not set the only-if-required flag, because this class would not be evaluated before the server determines if the received DHCP message should be accepted for processing. Such classes are evaluated after subnet selection. See Required Classification for details.

The following example demonstrates how to override the server identifier for a subnet:

"subnet4": [
    {
        "subnet": "192.0.2.0/24",
        "option-data": [
            {
                "name": "dhcp-server-identifier",
                "data": "10.2.5.76"
            }
        ],
        ...
    }
]

How the DHCPv4 Server Selects a Subnet for the Client

The DHCPv4 server differentiates among directly connected clients, clients trying to renew leases, and clients sending their messages through relays. For directly connected clients, the server checks the configuration for the interface on which the message has been received and, if the server configuration does not match any configured subnet, the message is discarded.

Assuming that the server’s interface is configured with the IPv4 address 192.0.2.3, the server only processes messages received through this interface from a directly connected client if there is a subnet configured to which this IPv4 address belongs, such as 192.0.2.0/24. The server uses this subnet to assign an IPv4 address for the client.

The rule above does not apply when the client unicasts its message, i.e. is trying to renew its lease; such a message is accepted through any interface. The renewing client sets ciaddr to the currently used IPv4 address, and the server uses this address to select the subnet for the client (in particular, to extend the lease using this address).

If the message is relayed it is accepted through any interface. The giaddr set by the relay agent is used to select the subnet for the client.

It is also possible to specify a relay IPv4 address for a given subnet. It can be used to match incoming packets into a subnet in uncommon configurations, e.g. shared networks. See Using a Specific Relay Agent for a Subnet for details.

Note

The subnet selection mechanism described in this section is based on the assumption that client classification is not used. The classification mechanism alters the way in which a subnet is selected for the client, depending on the classes to which the client belongs.

Note

When the selected subnet is a member of a shared network, the whole shared network is selected.

Using a Specific Relay Agent for a Subnet

A relay must have an interface connected to the link on which the clients are being configured. Typically the relay has an IPv4 address configured on that interface, which belongs to the subnet from which the server assigns addresses. Normally, the server is able to use the IPv4 address inserted by the relay (in the giaddr field of the DHCPv4 packet) to select the appropriate subnet.

However, that is not always the case. In certain uncommon — but valid — deployments, the relay address may not match the subnet. This usually means that there is more than one subnet allocated for a given link. The two most common examples of this are long-lasting network renumbering (where both old and new address spaces are still being used) and a cable network. In a cable network, both cable modems and the devices behind them are physically connected to the same link, yet they use distinct addressing. In such a case, the DHCPv4 server needs additional information (the IPv4 address of the relay) to properly select an appropriate subnet.

The following example assumes that there is a subnet 192.0.2.0/24 that is accessible via a relay that uses 10.0.0.1 as its IPv4 address. The server is able to select this subnet for any incoming packets that come from a relay that has an address in the 192.0.2.0/24 subnet. It also selects that subnet for a relay with address 10.0.0.1.

"Dhcp4": {
    "subnet4": [
        {
            "subnet": "192.0.2.0/24",
            "pools": [ { "pool": "192.0.2.10 - 192.0.2.20" } ],
            "relay": {
                "ip-addresses": [ "10.0.0.1" ]
            },
        }
    ],
}

If relay is specified, the ip-addresses parameter within it is mandatory. The ip-addresses parameter supports specifying a list of addresses.

Segregating IPv4 Clients in a Cable Network

In certain cases, it is useful to mix relay address information (introduced in Using a Specific Relay Agent for a Subnet) with client classification (explained in Client Classification). One specific example is in a cable network, where modems typically get addresses from a different subnet than all the devices connected behind them.

Let us assume that there is one Cable Modem Termination System (CMTS) with one CM MAC (a physical link that modems are connected to). We want the modems to get addresses from the 10.1.1.0/24 subnet, while everything connected behind the modems should get addresses from the 192.0.2.0/24 subnet. The CMTS that acts as a relay uses address 10.1.1.1. The following configuration can serve that situation:

"Dhcp4": {
    "subnet4": [
        {
            "subnet": "10.1.1.0/24",
            "pools":  [ { "pool": "10.1.1.2 - 10.1.1.20" } ],
            "client-class" "docsis3.0",
            "relay": {
                "ip-addresses": [ "10.1.1.1 ]"
            }
        },
        {
            "subnet": "192.0.2.0/24",
            "pools": [ { "pool": "192.0.2.10 - 192.0.2.20" } ],
            "relay": {
                "ip-addresses": [ "10.1.1.1" ]
            }
        }
    ],
    ...
}

Duplicate Addresses (DHCPDECLINE Support)

The DHCPv4 server is configured with a certain pool of addresses that it is expected to hand out to DHCPv4 clients. It is assumed that the server is authoritative and has complete jurisdiction over those addresses. However, for various reasons such as misconfiguration or a faulty client implementation that retains its address beyond the valid lifetime, there may be devices connected that use those addresses without the server’s approval or knowledge.

Such an unwelcome event can be detected by legitimate clients (using ARP or ICMP Echo Request mechanisms) and reported to the DHCPv4 server using a DHCPDECLINE message. The server does a sanity check (to see whether the client declining an address really was supposed to use it) and then conducts a clean-up operation. Any DNS entries related to that address are removed, the event is logged, and hooks are triggered. After that is complete, the address is marked as declined (which indicates that it is used by an unknown entity and thus not available for assignment) and a probation time is set on it. Unless otherwise configured, the probation period lasts 24 hours; after that time, the server will recover the lease (i.e. put it back into the available state) and the address will be available for assignment again. It should be noted that if the underlying issue of a misconfigured device is not resolved, the duplicate-address scenario will repeat. If reconfigured correctly, this mechanism provides an opportunity to recover from such an event automatically, without any system administrator intervention.

To configure the decline probation period to a value other than the default, the following syntax can be used:

  "Dhcp4": {
    "decline-probation-period": 3600,
    "subnet4": [ ... ],
    ...
}

The parameter is expressed in seconds, so the example above instructs the server to recycle declined leases after one hour.

There are several statistics and hook points associated with the decline handling procedure. The lease4_decline hook is triggered after the incoming DHCPDECLINE message has been sanitized and the server is about to decline the lease. The declined-addresses statistic is increased after the hook returns (both the global and subnet-specific variants). (See Statistics in the DHCPv4 Server and Hook Libraries for more details on DHCPv4 statistics and Kea hook points.)

Once the probation time elapses, the declined lease is recovered using the standard expired-lease reclamation procedure, with several additional steps. In particular, both declined-addresses statistics (global and subnet-specific) are decreased. At the same time, reclaimed-declined-addresses statistics (again in two variants, global and subnet-specific) are increased.

A note about statistics: The Kea server does not decrease the assigned-addresses statistics when a DHCPDECLINE is received and processed successfully. While technically a declined address is no longer assigned, the primary usage of the assigned-addresses statistic is to monitor pool utilization. Most people would forget to include declined-addresses in the calculation, and would simply use assigned-addresses/total-addresses. This would cause a bias towards under-representing pool utilization. As this has a potential to cause serious confusion, ISC decided not to decrease assigned-addresses immediately after receiving DHCPDECLINE, but to do it later when Kea recovers the address back to the available pool.

Statistics in the DHCPv4 Server

The DHCPv4 server supports the following statistics:

DHCPv4 statistics

Statistic	Data Type	Description
pkt4-received	integer	Number of DHCPv4 packets received. This includes all packets: valid, bogus, corrupted, rejected, etc. This statistic is expected to grow rapidly.
pkt4-discover-received	integer	Number of DHCPDISCOVER packets received. This statistic is expected to grow; its increase means that clients that just booted started their configuration process and their initial packets reached the Kea server.
pkt4-offer-received	integer	Number of DHCPOFFER packets received. This statistic is expected to remain zero at all times, as DHCPOFFER packets are sent by the server and the server is never expected to receive them. A non-zero value indicates an error. One likely cause would be a misbehaving relay agent that incorrectly forwards DHCPOFFER messages towards the server, rather than back to the clients.
pkt4-request-received	integer	Number of DHCPREQUEST packets received. This statistic is expected to grow. Its increase means that clients that just booted received the server’s response (DHCPOFFER) and accepted it, and are now requesting an address (DHCPREQUEST).
pkt4-ack-received	integer	Number of DHCPACK packets received. This statistic is expected to remain zero at all times, as DHCPACK packets are sent by the server and the server is never expected to receive them. A non-zero value indicates an error. One likely cause would be a misbehaving relay agent that incorrectly forwards DHCPACK messages towards the server, rather than back to the clients.
pkt4-nak-received	integer	Number of DHCPNAK packets received. This statistic is expected to remain zero at all times, as DHCPNAK packets are sent by the server and the server is never expected to receive them. A non-zero value indicates an error. One likely cause would be a misbehaving relay agent that incorrectly forwards DHCPNAK messages towards the server, rather than back to the clients.
pkt4-release-received	integer	Number of DHCPRELEASE packets received. This statistic is expected to grow. Its increase means that clients that had an address are shutting down or ceasing to use their addresses.
pkt4-decline-received	integer	Number of DHCPDECLINE packets received. This statistic is expected to remain close to zero. Its increase means that a client leased an address, but discovered that the address is currently used by an unknown device elsewhere in the network.
pkt4-inform-received	integer	Number of DHCPINFORM packets received. This statistic is expected to grow. Its increase means that there are clients that either do not need an address or already have an address and are interested only in getting additional configuration parameters.
pkt4-unknown-received	integer	Number of packets received of an unknown type. A non-zero value of this statistic indicates that the server received a packet that it was not able to recognize, either with an unsupported type or possibly malformed (without a message-type option).
pkt4-sent	integer	Number of DHCPv4 packets sent. This statistic is expected to grow every time the server transmits a packet. In general, it should roughly match pkt4-received, as most incoming packets cause the server to respond. There are exceptions (e.g. DHCPRELEASE), so do not worry if it is less than pkt4-received.
pkt4-offer-sent	integer	Number of DHCPOFFER packets sent. This statistic is expected to grow in most cases after a DHCPDISCOVER is processed. There are certain uncommon, but valid, cases where incoming DHCPDISCOVER packets are dropped, but in general this statistic is expected to be close to pkt4-discover-received.
pkt4-ack-sent	integer	Number of DHCPACK packets sent. This statistic is expected to grow in most cases after a DHCPREQUEST is processed. There are certain cases where DHCPNAK is sent instead. In general, the sum of pkt4-ack-sent and pkt4-nak-sent should be close to pkt4-request-received.
pkt4-nak-sent	integer	Number of DHCPNAK packets sent. This statistic is expected to grow when the server chooses not to honor the address requested by a client. In general, the sum of pkt4-ack-sent and pkt4-nak-sent should be close to pkt4-request-received.
pkt4-parse-failed	integer	Number of incoming packets that could not be parsed. A non-zero value of this statistic indicates that the server received a malformed or truncated packet. This may indicate problems in the network, faulty clients, or a bug in the server.
pkt4-receive-drop	integer	Number of incoming packets that were dropped. The exact reason for dropping packets is logged, but the most common reasons may be: an unacceptable packet type was received, direct responses are forbidden, or the server-id sent by the client does not match the server’s server-id.
subnet[id].total-addresses	integer	Total number of addresses available for DHCPv4 management; in other words, this is the sum of all addresses in all configured pools. This statistic changes only during configuration updates. It does not take into account any addresses that may be reserved due to host reservation. The id is the subnet-id of a given subnet. This statistic is exposed for each subnet separately, and is reset during a reconfiguration event.
cumulative-assigned-addresses	integer	Cumulative number of addresses that have been assigned since server startup. It is incremented each time an address is assigned and is not reset when the server is reconfigured.
subnet[id].cumulative-assigned-addresses	integer	Cumulative number of assigned addresses in a given subnet. It increases every time a new lease is allocated (as a result of receiving a DHCPREQUEST message) and never decreases. The id is the subnet-id of the subnet. This statistic is exposed for each subnet separately, and is reset during a reconfiguration event.
subnet[id].assigned-addresses	integer	Number of assigned addresses in a given subnet. It increases every time a new lease is allocated (as a result of receiving a DHCPREQUEST message) and decreases every time a lease is released (a DHCPRELEASE message is received) or expires. The id is the subnet-id of the subnet. This statistic is exposed for each subnet separately, and is reset during a reconfiguration event.
reclaimed-leases	integer	Number of expired leases that have been reclaimed since server startup. It is incremented each time an expired lease is reclaimed and never decreases. It can be used as a long-term indicator of how many actual leases have been reclaimed. This is a global statistic that covers all subnets.
subnet[id].reclaimed-leases	integer	Number of expired leases associated with a given subnet (id is the subnet-id) that have been reclaimed since server startup. It is incremented each time an expired lease is reclaimed. The id is the subnet-id of a given subnet. This statistic is exposed for each subnet separately.
declined-addresses	integer	Number of IPv4 addresses that are currently declined; a count of the number of leases currently unavailable. Once a lease is recovered, this statistic is decreased; ideally, this statistic should be zero. If this statistic is non-zero or increasing, a network administrator should investigate whether there is a misbehaving device in the network. This is a global statistic that covers all subnets.
subnet[id].declined-addresses	integer	Number of IPv4 addresses that are currently declined in a given subnet; a count of the number of leases currently unavailable. Once a lease is recovered, this statistic is decreased; ideally, this statistic should be zero. If this statistic is non-zero or increasing, a network administrator should investigate whether there is a misbehaving device in the network. The id is the subnet-id of a given subnet. This statistic is exposed for each subnet separately.
reclaimed-declined-addresses	integer	Number of IPv4 addresses that were declined, but have now been recovered. Unlike declined-addresses, this statistic never decreases. It can be used as a long-term indicator of how many actual valid declines were processed and recovered from. This is a global statistic that covers all subnets.
subnet[id].reclaimed-declined-addresses	integer	Number of IPv4 addresses that were declined, but have now been recovered. Unlike declined-addresses, this statistic never decreases. It can be used as a long-term indicator of how many actual valid declines were processed and recovered from. The id is the subnet-id of a given subnet. This statistic is exposed for each subnet separately.
pkt4-lease-query-received	integer	Number of IPv4 DHCPLEASEQUERY packets received. (Only exists if Leasequery hook library is loaded.)
pkt4-lease-query-response-unknown-sent	integer	Number of IPv4 DHCPLEASEUNKNOWN responses sent. (Only exists if Leasequery hook library is loaded.)
pkt4-lease-query-response-unassigned-sent	integer	Number of IPv4 DHCPLEASEUNASSIGNED responses sent. (Only exists if Leasequery hook library is loaded.)
pkt4-lease-query-response-active-sent	integer	Number of IPv4 DHCPLEASEACTIVE responses sent. (Only exists if Leasequery hook library is loaded.)
v4-allocation-fail	integer	Number of total address allocation failures for a particular client. This consists in the number of lease allocation attempts that the server made before giving up and was unable to use any of the address pools. This is a global statistic that covers all subnets.
subnet[id].v4-allocation-fail	integer	Number of total address allocation failures for a particular client. This consists in the number of lease allocation attempts that the server made before giving up and was unable to use any of the address pools. The id is the subnet-id of a given subnet. This statistic is exposed for each subnet separately.
v4-allocation-fail-shared-network	integer	Number of address allocation failures for a particular client connected to a shared network. This is a global statistic that covers all subnets.
subnet[id].v4-allocation-fail-shared-network	integer	Number of address allocation failures for a particular client connected to a shared network. The id is the subnet-id of a given subnet. This statistic is exposed for each subnet separately.
v4-allocation-fail-subnet	integer	Number of address allocation failures for a particular client connected to a subnet that does not belong to a shared network. This is a global statistic that covers all subnets.
subnet[id].v4-allocation-fail-subnet	integer	Number of address allocation failures for a particular client connected to a subnet that does not belong to a shared network. The id is the subnet-id of a given subnet. This statistic is exposed for each subnet separately.
v4-allocation-fail-no-pools	integer	Number of address allocation failures because the server could not use any configured pools for a particular client. It is also possible that all of the subnets from which the server attempted to assign an address lack address pools. In this case, it should be considered misconfiguration if an operator expects that some clients should be assigned dynamic addresses. This is a global statistic that covers all subnets.
subnet[id].v4-allocation-fail-no-pools	integer	Number of address allocation failures because the server could not use any configured pools for a particular client. It is also possible that all of the subnets from which the server attempted to assign an address lack address pools. In this case, it should be considered misconfiguration if an operator expects that some clients should be assigned dynamic addresses. The id is the subnet-id of a given subnet. This statistic is exposed for each subnet separately.
v4-allocation-fail-classes	integer	Number of address allocation failures when the client’s packet belongs to one or more classes. There may be several reasons why a lease was not assigned. One of them may be a case when all pools require packet to belong to certain classes and the incoming packet didn’t belong to any of them. Another case where this information may be useful is to point out that the pool reserved to a given class has ran out of addresses. This is a global statistic that covers all subnets.
subnet[id].v4-allocation-fail-classes	integer	Number of address allocation failures when the client’s packet belongs to one or more classes. There may be several reasons why a lease was not assigned. One of them may be a case when all pools require packet to belong to certain classes and the incoming packet didn’t belong to any of them. Another case where this information may be useful is to point out that the pool reserved to a given class has ran out of addresses. The id is the subnet-id of a given subnet. This statistic is exposed for each subnet separately.

Note

This section describes DHCPv4-specific statistics. For a general overview and usage of statistics, see Statistics.

The DHCPv4 server provides two global parameters to control the default sample limits of statistics:

• statistic-default-sample-count - determines the default maximum number of samples which are kept. The special value of 0 indicates that a default maximum age should be used.

• statistic-default-sample-age - determines the default maximum age in seconds of samples which are kept.

For instance, to reduce the statistic-keeping overhead, set the default maximum sample count to 1 so only one sample is kept:

  "Dhcp4": {
    "statistic-default-sample-count": 1,
    "subnet4": [ ... ],
    ...
}

Statistics can be retrieved periodically to gain more insight into Kea operations. One tool that leverages that capability is ISC Stork. See Monitoring Kea With Stork for details.

Management API for the DHCPv4 Server

The management API allows the issuing of specific management commands, such as statistics retrieval, reconfiguration, or shutdown. For more details, see Management API. Currently, the only supported communication channel type is the UNIX stream socket. By default there are no sockets open; to instruct Kea to open a socket, the following entry in the configuration file can be used:

"Dhcp4": {
    "control-socket": {
        "socket-type": "unix",
        "socket-name": "/path/to/the/unix/socket"
    },

    "subnet4": [
        ...
    ],
    ...
}

The length of the path specified by the socket-name parameter is restricted by the maximum length for the UNIX socket name on the administrator’s operating system, i.e. the size of the sun_path field in the sockaddr_un structure, decreased by 1. This value varies on different operating systems, between 91 and 107 characters. Typical values are 107 on Linux and 103 on FreeBSD.

Communication over the control channel is conducted using JSON structures. See the Control Channel section in the Kea Developer’s Guide for more details.

The DHCPv4 server supports the following operational commands:

• build-report

• config-get

• config-reload

• config-set

• config-test

• config-write

• dhcp-disable

• dhcp-enable

• leases-reclaim

• list-commands

• shutdown

• status-get

• version-get

as described in Commands Supported by Both the DHCPv4 and DHCPv6 Servers. In addition, it supports the following statistics-related commands:

• statistic-get

• statistic-reset

• statistic-remove

• statistic-get-all

• statistic-reset-all

• statistic-remove-all

• statistic-sample-age-set

• statistic-sample-age-set-all

• statistic-sample-count-set

• statistic-sample-count-set-all

as described in Commands for Manipulating Statistics.

User Contexts in IPv4

Kea allows the loading of hook libraries that can sometimes benefit from additional parameters. If such a parameter is specific to the whole library, it is typically defined as a parameter for the hook library. However, sometimes there is a need to specify parameters that are different for each pool.

See Comments and User Context for additional background regarding the user-context idea. See User Contexts in Hooks for a discussion from the hooks perspective.

User contexts can be specified at global scope; at the shared-network, subnet, pool, client-class, option-data, or definition level; and via host reservation. One other useful feature is the ability to store comments or descriptions.

Let’s consider an imaginary case of devices that have colored LED lights. Depending on their location, they should glow red, blue, or green. It would be easy to write a hook library that would send specific values, maybe as a vendor option. However, the server has to have some way to specify that value for each pool. This need is addressed by user contexts. In essence, any user data can be specified in the user context as long as it is a valid JSON map. For example, the aforementioned case of LED devices could be configured in the following way:

"Dhcp4": {
    "subnet4": [{
        "subnet": "192.0.2.0/24",
        "pools": [{
            "pool": "192.0.2.10 - 192.0.2.20",
            # This is pool specific user context
            "user-context": { "color": "red" }
        } ],

        # This is a subnet-specific user context. Any type
        # of information can be entered here as long as it is valid JSON.
        "user-context": {
            "comment": "network on the second floor",
            "last-modified": "2017-09-04 13:32",
            "description": "you can put anything you like here",
            "phones": [ "x1234", "x2345" ],
            "devices-registered": 42,
            "billing": false
        }
    } ]
}

Kea does not interpret or use the user-context information; it simply stores it and makes it available to the hook libraries. It is up to each hook library to extract that information and use it. The parser translates a comment entry into a user context with the entry, which allows a comment to be attached inside the configuration itself.

Supported DHCP Standards

The following standards are currently supported in Kea:

• BOOTP Vendor Information Extensions, RFC 1497: This requires the open source BOOTP hook to be loaded. See BOOTP Support for details.

• Dynamic Host Configuration Protocol, RFC 2131: Supported messages are DHCPDISCOVER (1), DHCPOFFER (2), DHCPREQUEST (3), DHCPRELEASE (7), DHCPINFORM (8), DHCPACK (5), and DHCPNAK(6).

• DHCP Options and BOOTP Vendor Extensions, RFC 2132: Supported options are PAD (0), END(255), Message Type(53), DHCP Server Identifier (54), Domain Name (15), DNS Servers (6), IP Address Lease Time (51), Subnet Mask (1), and Routers (3).

• The IPv4 Subnet Selection Option for DHCP, RFC 3011: The subnet-selection option is supported; if received in a packet, it is used in the subnet-selection process.

• DHCP Relay Agent Information Option, RFC 3046: Relay Agent Information, Circuit ID, and Remote ID options are supported.

• Link Selection sub-option for the Relay Agent Option, RFC 3527: The link selection sub-option is supported.

• Vendor-Identifying Vendor Options for Dynamic Host Configuration Protocol version 4, RFC 3925: The Vendor-Identifying Vendor Class and Vendor-Identifying Vendor-Specific Information options are supported.

• Subscriber-ID Suboption for the DHCP Relay Agent Option, RFC 3993: The Subscriber-ID option is supported.

• The Dynamic Host Configuration Protocol (DHCP) Client Fully Qualified Domain Name (FQDN) Option, RFC 4702: The Kea server is able to handle the Client FQDN option. Also, it is able to use the kea-dhcp-ddns component to initiate appropriate DNS Update operations.

• Resolution of Fully Qualified Domain Name (FQDN) Conflicts among Dynamic Host Configuration Protocol (DHCP) Clients, RFC 4703: The DHCPv6 server uses a DHCP-DDNS server to resolve conflicts.

• Client Identifier Option in DHCP Server Replies, RFC 6842: The server by default sends back the client-id option. That capability can be disabled. See Echoing Client-ID (RFC 6842) for details.

• Generalized UDP Source Port for the DHCP Relay Agent Option, RFC 8357: The Kea server handles the Relay Agent Information Source Port sub-option in a received message, remembers the UDP port, and sends back a reply to the same relay agent using this UDP port.

• Captive-Portal Identification in DHCP and Router Advertisements (RAs), RFC 8910: The Kea server can configure both v4 and v6 versions of the captive portal options.

• IPv6-Only Preferred Option for DHCPv4, RFC 8925: The Kea server is able to designate its pools and subnets as IPv6-Only Preferred and send back the v6-only-preferred option to clients that requested it.

• Server Identifier Override sub-option for the Relay Agent Option, RFC 5107: The server identifier override sub-option is supported. The implementation is not complete according to the RFC, because the server does not store the RAI, but the functionality handles expected use cases.

Known RFC Violations

In principle, Kea aspires to be a reference implementation and aims to implement 100% of the RFC standards. However, in some cases there are practical aspects that prevent Kea from completely adhering to the text of the RFC documents.

• RFC 2131, page 30, says that if the incoming DHCPREQUEST packet has no “requested IP address” option and ciaddr is not set, the server is supposed to respond with NAK. However, broken clients exist that will always send a DHCPREQUEST without those options indicated. In that event, Kea accepts the DHCPREQUEST, assigns an address, and responds with an ACK.

• RFC 2131, table 5, says that messages of type DHCPDECLINE or DHCPRELEASE must have the server identifier set and should be dropped if that option is missing. However, ISC DHCP does not enforce this, presumably as a compatibility effort for broken clients, and the Kea team decided to follow suit.

DHCPv4 Server Limitations

These are the current known limitations of the Kea DHCPv4 server software. Most of them are reflections of the current stage of development and should be treated as “not implemented yet,” rather than as actual limitations. However, some of them are implications of the design choices made. Those are clearly marked as such.

• On the Linux and BSD system families, DHCP messages are sent and received over raw sockets (using LPF and BPF) and all packet headers (including data link layer, IP, and UDP headers) are created and parsed by Kea, rather than by the system kernel. Currently, Kea can only parse the data-link layer headers with a format adhering to the IEEE 802.3 standard, and assumes this data-link-layer header format for all interfaces. Thus, Kea does not work on interfaces which use different data-link-layer header formats (e.g. Infiniband).

• The DHCPv4 server does not verify that an assigned address is unused. According to RFC 2131, the allocating server should verify that an address is not used by sending an ICMP echo request.

Kea DHCPv4 Server Examples

A collection of simple-to-use examples for the DHCPv4 component of Kea is available with the source files, located in the doc/examples/kea4 directory.

Configuration Backend in DHCPv4

In the Kea Configuration Backend section we have described the Configuration Backend (CB) feature, its applicability, and its limitations. This section focuses on the usage of the CB with the Kea DHCPv4 server. It lists the supported parameters, describes limitations, and gives examples of DHCPv4 server configurations to take advantage of the CB. Please also refer to the corresponding section Configuration Backend in DHCPv6 for DHCPv6-specific usage of the CB.

Supported Parameters

The ultimate goal for the CB is to serve as a central configuration repository for one or multiple Kea servers connected to a database. In currently supported Kea versions, only a subset of the DHCPv4 server parameters can be configured in the database. All other parameters must be specified in the JSON configuration file, if required.

All supported parameters can be configured via the cb_cmds hook library described in the cb_cmds: Configuration Backend Commands section. The general rule is that scalar global parameters are set using remote-global-parameter4-set; shared-network-specific parameters are set using remote-network4-set; and subnet- and pool-level parameters are set using remote-subnet4-set. Whenever there is an exception to this general rule, it is highlighted in the table. Non-scalar global parameters have dedicated commands; for example, the global DHCPv4 options (option-data) are modified using remote-option4-global-set. Client classes, together with class-specific option definitions and DHCPv4 options, are configured using the remote-class4-set command.

The Configuration Sharing and Server Tags section explains the concept of shareable and non-shareable configuration elements and the limitations for sharing them between multiple servers. In the DHCP configuration (both DHCPv4 and DHCPv6), the shareable configuration elements are subnets and shared networks. Thus, they can be explicitly associated with multiple server tags. The global parameters, option definitions, and global options are non-shareable and can be associated with only one server tag. This rule does not apply to the configuration elements associated with all servers. Any configuration element associated with all servers (using the all keyword as a server tag) is used by all servers connecting to the configuration database.

The following table lists DHCPv4-specific parameters supported by the Configuration Backend, with an indication of the level of the hierarchy at which it is currently supported.

List of DHCPv4 parameters supported by the Configuration Backend

Parameter	Global	Client Class	Shared Network	Subnet	Pool
4o6-interface	n/a	n/a	n/a	yes	n/a
4o6-interface-id	n/a	n/a	n/a	yes	n/a
4o6-subnet	n/a	n/a	n/a	yes	n/a
boot-file-name	yes	yes	yes	yes	n/a
cache-max-age	yes	n/a	no	no	n/a
cache-threshold	yes	n/a	no	no	n/a
calculate-tee-times	yes	n/a	yes	yes	n/a
client-class	n/a	n/a	yes	yes	yes
ddns-send-update	yes	n/a	yes	yes	n/a
ddns-override-no-update	yes	n/a	yes	yes	n/a
ddns-override-client-update	yes	n/a	yes	yes	n/a
ddns-replace-client-name	yes	n/a	yes	yes	n/a
ddns-generated-prefix	yes	n/a	yes	yes	n/a
ddns-qualifying-suffix	yes	n/a	yes	yes	n/a
decline-probation-period	yes	n/a	n/a	n/a	n/a
dhcp4o6-port	yes	n/a	n/a	n/a	n/a
echo-client-id	yes	n/a	n/a	n/a	n/a
hostname-char-set	no	n/a	no	no	n/a
hostname-char-replacement	no	n/a	no	no	n/a
interface	n/a	n/a	yes	yes	n/a
match-client-id	yes	n/a	yes	yes	n/a
min-valid-lifetime	yes	yes	yes	yes	n/a
max-valid-lifetime	yes	yes	yes	yes	n/a
next-server	yes	yes	yes	yes	n/a
option-data	yes (via remote-option4-global-set)	yes	yes	yes	yes
option-def	yes (via remote-option-def4-set)	yes	n/a	n/a	n/a
rebind-timer	yes	n/a	yes	yes	n/a
renew-timer	yes	n/a	yes	yes	n/a
server-hostname	yes	yes	yes	yes	n/a
valid-lifetime	yes	yes	yes	yes	n/a
relay	n/a	n/a	yes	yes	n/a
require-client-classes	no	n/a	yes	yes	yes
reservation-mode	yes	n/a	yes	yes	n/a
reservations-global	yes	n/a	yes	yes	n/a
reservations-in-subnet	yes	n/a	yes	yes	n/a
reservations-out-of-pool	yes	n/a	yes	yes	n/a
t1-percent	yes	n/a	yes	yes	n/a
t2-percent	yes	n/a	yes	yes	n/a

• yes - indicates that the parameter is supported at the given level of the hierarchy and can be configured via the Configuration Backend.

• no - indicates that a parameter is supported at the given level of the hierarchy but cannot be configured via the Configuration Backend.

• n/a - indicates that a given parameter is not applicable at the particular level of the hierarchy or that the server does not support the parameter at that level.

Enabling the Configuration Backend

Consider the following configuration snippet, which uses a MySQL configuration database:

"Dhcp4": {
    "server-tag": "my DHCPv4 server",
    "config-control": {
        "config-databases": [{
            "type": "mysql",
            "name": "kea",
            "user": "kea",
            "password": "kea",
            "host": "192.0.2.1",
            "port": 3302
        }],
        "config-fetch-wait-time": 20
    },
    "hooks-libraries": [{
        "library": "/usr/local/lib/kea/hooks/libdhcp_mysql_cb.so"
    }, {
        "library": "/usr/local/lib/kea/hooks/libdhcp_cb_cmds.so"
    }],
}

The config-control command contains two parameters. config-databases is a list that contains one element, which includes the database type, its location, and the credentials to be used to connect to this database. (Note that the parameters specified here correspond to the database specification for the lease database backend and hosts database backend.) Currently only one database connection can be specified on the config-databases list. The server connects to this database during startup or reconfiguration, and fetches the configuration available for this server from the database. This configuration is merged into the configuration read from the configuration file.

The following snippet illustrates the use of a PostgreSQL database:

"Dhcp4": {
    "server-tag": "my DHCPv4 server",
    "config-control": {
        "config-databases": [{
            "type": "postgresql",
            "name": "kea",
            "user": "kea",
            "password": "kea",
            "host": "192.0.2.1",
            "port": 5432
        }],
        "config-fetch-wait-time": 20
    },
    "hooks-libraries": [{
        "library": "/usr/local/lib/kea/hooks/libdhcp_pgsql_cb.so"
    }, {
        "library": "/usr/local/lib/kea/hooks/libdhcp_cb_cmds.so"
    }],
}

Note

Whenever there is a conflict between the parameters specified in the configuration file and the database, the parameters from the database take precedence. We strongly recommend avoiding the duplication of parameters in the file and the database, but this recommendation is not enforced by the Kea servers. In particular, if the subnets’ configuration is sourced from the database, we recommend that all subnets be specified in the database and that no subnets be specified in the configuration file. It is possible to specify the subnets in both places, but the subnets in the configuration file with overlapping IDs and/or prefixes with the subnets from the database will be superseded by those from the database.

Once the Kea server is configured, it starts periodically polling the database for configuration changes. The polling frequency is controlled by the config-fetch-wait-time parameter, expressed in seconds; it is the period between the time when the server completed its last poll (and possibly the local configuration update) and the time when it will begin polling again. In the example above, this period is set to 20 seconds. This means that after adding a new configuration into the database (e.g. adding a new subnet), it will take up to 20 seconds (plus the time needed to fetch and apply the new configuration) before the server starts using this subnet. The lower the config-fetch-wait-time value, the shorter the time for the server to react to incremental configuration updates in the database. On the other hand, polling the database too frequently may impact the DHCP server’s performance, because the server needs to make at least one query to the database to discover any pending configuration updates. The default value of config-fetch-wait-time is 30 seconds.

The config-backend-pull command can be used to force the server to immediately poll any configuration changes from the database and avoid waiting for the next fetch cycle.

In the configuration examples above, two hook libraries are loaded. The first is a library which implements the Configuration Backend for a specific database type: libdhcp_mysql_cb.so provides support for MySQL and libdhcp_pgsql_cb.so provides support for PostgreSQL. The library loaded must match the database type specified within the config-control parameter or an will error be logged when the server attempts to load its configuration and the load will fail.

The second hook library, libdhcp_cb_cmds.so, is optional. It should be loaded when the Kea server instance is to be used to manage the configuration in the database. See the cb_cmds: Configuration Backend Commands section for details. This hook library is only available to ISC customers with a paid support contract.

Kea DHCPv4 Compatibility Configuration Parameters

ISC’s intention is for Kea to follow the RFC documents to promote better standards compliance. However, many buggy DHCP implementations already exist that cannot be easily fixed or upgraded. Therefore, Kea provides an easy-to-use compatibility mode for broken or non-compliant clients. For that purpose, the compatibility option must be enabled to permit uncommon practices:

{
  "Dhcp4": {
    "compatibility": {
    }
  }
}

Lenient Option Parsing

By default, tuple fields defined in custom options are parsed as a set of length-value pairs.

With "lenient-option-parsing": true, if a length ever exceeds the rest of the option’s buffer, previous versions of Kea returned a log message unable to parse the opaque data tuple, the buffer length is x, but the tuple length is y with x < y; this no longer occurs. Instead, the value is considered to be the rest of the buffer, or in terms of the log message above, the tuple length y becomes x.

{
  "Dhcp4": {
    "compatibility": {
      "lenient-option-parsing": true
    }
  }
}

The DHCPv6 Server

Starting and Stopping the DHCPv6 Server

It is recommended that the Kea DHCPv6 server be started and stopped using keactrl (described in Managing Kea with keactrl); however, it is also possible to run the server directly via the kea-dhcp6 command, which accepts the following command-line switches:

• -c file - specifies the configuration file. This is the only mandatory switch.

• -d - specifies whether the server logging should be switched to debug/verbose mode. In verbose mode, the logging severity and debuglevel specified in the configuration file are ignored; “debug” severity and the maximum debuglevel (99) are assumed. The flag is convenient for temporarily switching the server into maximum verbosity, e.g. when debugging.

• -p server-port - specifies the local UDP port on which the server listens. This is only useful during testing, as a DHCPv6 server listening on ports other than the standard ones is not able to handle regular DHCPv6 queries.

• -P client-port - specifies the remote UDP port to which the server sends all responses. This is only useful during testing, as a DHCPv6 server sending responses to ports other than the standard ones is not able to handle regular DHCPv6 queries.

• -t file - specifies a configuration file to be tested. kea-dhcp6 loads it, checks it, and exits. During the test, log messages are printed to standard output and error messages to standard error. The result of the test is reported through the exit code (0 = configuration looks OK, 1 = error encountered). The check is not comprehensive; certain checks are possible only when running the server.

• -v - displays the Kea version and exits.

• -V - displays the Kea extended version with additional parameters and exits. The listing includes the versions of the libraries dynamically linked to Kea.

• -W - displays the Kea configuration report and exits. The report is a copy of the config.report file produced by ./configure; it is embedded in the executable binary.

On startup, the server detects available network interfaces and attempts to open UDP sockets on all interfaces listed in the configuration file. Since the DHCPv6 server opens privileged ports, it requires root access; this daemon must be run as root.

During startup, the server attempts to create a PID file of the form: [runstatedir]/kea/[conf name].kea-dhcp6.pid, where:

• runstatedir: The value as passed into the build configure script; it defaults to /usr/local/var/run. Note that this value may be overridden at runtime by setting the environment variable KEA_PIDFILE_DIR, although this is intended primarily for testing purposes.

• conf name: The configuration file name used to start the server, minus all preceding paths and the file extension. For example, given a pathname of /usr/local/etc/kea/myconf.txt, the portion used would be myconf.

If the file already exists and contains the PID of a live process, the server issues a DHCP6_ALREADY_RUNNING log message and exits. It is possible, though unlikely, that the file is a remnant of a system crash and the process to which the PID belongs is unrelated to Kea. In such a case, it would be necessary to manually delete the PID file.

The server can be stopped using the kill command. When running in a console, the server can also be shut down by pressing Ctrl-c. Kea detects the key combination and shuts down gracefully.

DHCPv6 Server Configuration

Introduction

This section explains how to configure the Kea DHCPv6 server using a configuration file.

Before DHCPv6 is started, its configuration file must be created. The basic configuration is as follows:

{
# DHCPv6 configuration starts on the next line
"Dhcp6": {

# First we set up global values
    "valid-lifetime": 4000,
    "renew-timer": 1000,
    "rebind-timer": 2000,
    "preferred-lifetime": 3000,

# Next we set up the interfaces to be used by the server.
    "interfaces-config": {
        "interfaces": [ "eth0" ]
    },

# And we specify the type of lease database
    "lease-database": {
        "type": "memfile",
        "persist": true,
        "name": "/var/lib/kea/dhcp6.leases"
    },

# Finally, we list the subnets from which we will be leasing addresses.
    "subnet6": [
        {
            "subnet": "2001:db8:1::/64",
            "pools": [
                {
                    "pool": "2001:db8:1::1-2001:db8:1::ffff"
                }
             ]
        }
    ]
# DHCPv6 configuration ends with the next line
}

}

The following paragraphs provide a brief overview of the parameters in the above example, along with their format. Subsequent sections of this chapter go into much greater detail for these and other parameters.

The lines starting with a hash (#) are comments and are ignored by the server; they do not impact its operation in any way.

The configuration starts in the first line with the initial opening curly bracket (or brace). Each configuration must contain an object specifying the configuration of the Kea module using it. In the example above, this object is called Dhcp6.

The Dhcp6 configuration starts with the "Dhcp6": { line and ends with the corresponding closing brace (in the above example, the brace after the last comment). Everything defined between those lines is considered to be the Dhcp6 configuration.

In general, the order in which those parameters appear does not matter, but there are two caveats. The first one is that the configuration file must be well-formed JSON, meaning that the parameters for any given scope must be separated by a comma, and there must not be a comma after the last parameter. When reordering a configuration file, moving a parameter to or from the last position in a given scope may also require moving the comma. The second caveat is that it is uncommon — although legal JSON — to repeat the same parameter multiple times. If that happens, the last occurrence of a given parameter in a given scope is used, while all previous instances are ignored. This is unlikely to cause any confusion as there are no real-life reasons to keep multiple copies of the same parameter in the configuration file.

The first few DHCPv6 configuration elements define some global parameters. valid-lifetime defines how long the addresses (leases) given out by the server are valid; the default is for a client to be allowed to use a given address for 4000 seconds. (Note that integer numbers are specified as is, without any quotes around them.) The address will become deprecated in 3000 seconds, i.e. clients are allowed to keep old connections, but cannot use this address to create new connections. renew-timer and rebind-timer are values (also in seconds) that define T1 and T2 timers, which govern when the client begins the renewal and rebind procedures.

The interfaces-config map specifies the network interfaces on which the server should listen to DHCP messages. The interfaces parameter specifies a list of network interfaces on which the server should listen. Lists are opened and closed with square brackets, with elements separated by commas. To listen on two interfaces, the interfaces-config element should look like this:

"interfaces-config": {
    "interfaces": [ "eth0", "eth1" ]
},

The next lines define the lease database, the place where the server stores its lease information. This particular example tells the server to use memfile, which is the simplest and fastest database backend. It uses an in-memory database and stores leases on disk in a CSV (comma-separated values) file. This is a very simple configuration example; usually the lease database configuration is more extensive and contains additional parameters. Note that lease-database is an object and opens up a new scope, using an opening brace. Its parameters (just one in this example: type) follow. If there were more than one, they would be separated by commas. This scope is closed with a closing brace. As more parameters for the Dhcp6 definition follow, a trailing comma is present.

Finally, we need to define a list of IPv6 subnets. This is the most important DHCPv6 configuration structure, as the server uses that information to process clients’ requests. It defines all subnets from which the server is expected to receive DHCP requests. The subnets are specified with the subnet6 parameter. It is a list, so it starts and ends with square brackets. Each subnet definition in the list has several attributes associated with it, so it is a structure and is opened and closed with braces. At a minimum, a subnet definition must have at least two parameters: subnet, which defines the whole subnet; and pools, which is a list of dynamically allocated pools that are governed by the DHCP server.

The example contains a single subnet. If more than one were defined, additional elements in the subnet6 parameter would be specified and separated by commas. For example, to define two subnets, the following syntax would be used:

"subnet6": [
    {
        "pools": [ { "pool": "2001:db8:1::/112" } ],
        "subnet": "2001:db8:1::/64"
    },
    {
        "pools": [ { "pool": "2001:db8:2::1-2001:db8:2::ffff" } ],
        "subnet": "2001:db8:2::/64"
    }
]

Note that indentation is optional and is used for aesthetic purposes only. In some cases it may be preferable to use more compact notation.

After all the parameters have been specified, there are two contexts open: global and Dhcp6; thus, two closing curly brackets must be used to close them.

Lease Storage

All leases issued by the server are stored in the lease database. There are four database backends available: memfile (the default), MySQL, PostgreSQL.

Memfile - Basic Storage for Leases

The server is able to store lease data in different repositories. Larger deployments may elect to store leases in a database; Lease Database Configuration describes this option. In typical smaller deployments, though, the server stores lease information in a CSV file rather than a database. As well as requiring less administration, an advantage of using a file for storage is that it eliminates a dependency on third-party database software.

The configuration of the memfile backend is controlled through the Dhcp6/lease-database parameters. The type parameter is mandatory and specifies which storage for leases the server should use, through the "memfile" value. The following list gives additional optional parameters that can be used to configure the memfile backend.

• persist: controls whether the new leases and updates to existing leases are written to the file. It is strongly recommended that the value of this parameter be set to true at all times during the server’s normal operation. Not writing leases to disk means that if a server is restarted (e.g. after a power failure), it will not know which addresses have been assigned. As a result, it may assign new clients addresses that are already in use. The value of false is mostly useful for performance-testing purposes. The default value of the persist parameter is true, which enables writing lease updates to the lease file.

• name: specifies an absolute location of the lease file in which new leases and lease updates are recorded. The default value for this parameter is "[kea-install-dir]/var/lib/kea/kea-leases6.csv".

• lfc-interval: specifies the interval, in seconds, at which the server will perform a lease file cleanup (LFC). This removes redundant (historical) information from the lease file and effectively reduces the lease file size. The cleanup process is described in more detail later in this section. The default value of the lfc-interval is 3600. A value of 0 disables the LFC.

• max-row-errors: specifies the number of row errors before the server stops attempting to load a lease file. When the server loads a lease file, it is processed row by row, each row containing a single lease. If a row is flawed and cannot be processed correctly the server logs it, discards the row, and goes on to the next row. This parameter can be used to set a limit on the number of such discards that can occur, after which the server abandons the effort and exits. The default value of 0 disables the limit and allows the server to process the entire file, regardless of how many rows are discarded.

An example configuration of the memfile backend is presented below:

"Dhcp6": {
    "lease-database": {
        "type": "memfile",
        "persist": true,
        "name": "/tmp/kea-leases6.csv",
        "lfc-interval": 1800,
        "max-row-errors": 100
    }
}

This configuration selects /tmp/kea-leases6.csv as the storage file for lease information and enables persistence (writing lease updates to this file). It also configures the backend to perform a periodic cleanup of the lease file every 1800 seconds (30 minutes) and sets the maximum number of row errors to 100.

Why Is Lease File Cleanup Necessary?

It is important to know how the lease file contents are organized to understand why the periodic lease file cleanup is needed. Every time the server updates a lease or creates a new lease for a client, the new lease information must be recorded in the lease file. For performance reasons, the server does not update the existing client’s lease in the file, as this would potentially require rewriting the entire file. Instead, it simply appends the new lease information to the end of the file; the previous lease entries for the client are not removed. When the server loads leases from the lease file, e.g. at server startup, it assumes that the latest lease entry for the client is the valid one. Previous entries are discarded, meaning that the server can reconstruct accurate information about the leases even though there may be many lease entries for each client. However, storing many entries for each client results in a bloated lease file and impairs the performance of the server’s startup and reconfiguration, as it needs to process a larger number of lease entries.

Lease file cleanup (LFC) removes all previous entries for each client and leaves only the latest ones. The interval at which the cleanup is performed is configurable, and it should be selected according to the frequency of lease renewals initiated by the clients. The more frequent the renewals, the smaller the value of lfc-interval should be. Note, however, that the LFC takes time and thus it is possible (although unlikely) that, if the lfc-interval is too short, a new cleanup may be started while the previous one is still running. The server would recover from this by skipping the new cleanup when it detected that the previous cleanup was still in progress, but it implies that the actual cleanups will be triggered more rarely than the configured interval. Moreover, triggering a new cleanup adds overhead to the server, which is not able to respond to new requests for a short period of time when the new cleanup process is spawned. Therefore, it is recommended that the lfc-interval value be selected in a way that allows the LFC to complete the cleanup before a new cleanup is triggered.

Lease file cleanup is performed by a separate process (in the background) to avoid a performance impact on the server process. To avoid conflicts between two processes using the same lease files, the LFC process starts with Kea opening a new lease file; the actual LFC process operates on the lease file that is no longer used by the server. There are also other files created as a side effect of the lease file cleanup. The detailed description of the LFC process is located later in this Kea Administrator’s Reference Manual: The LFC Process.

Lease Database Configuration

Note

Lease database access information must be configured for the DHCPv6 server, even if it has already been configured for the DHCPv4 server. The servers store their information independently, so each server can use a separate database or both servers can use the same database.

Note

Kea requires the database timezone to match the system timezone. For more details, see First-Time Creation of the MySQL Database and First-Time Creation of the PostgreSQL Database.

Lease database configuration is controlled through the Dhcp6/lease-database parameters. The database type must be set to memfile, mysql or postgresql, e.g.:

"Dhcp6": { "lease-database": { "type": "mysql", ... }, ... }

Next, the name of the database to hold the leases must be set; this is the name used when the database was created (see First-Time Creation of the MySQL Database or First-Time Creation of the PostgreSQL Database).

For MySQL or PostgreSQL:

"Dhcp6": { "lease-database": { "name": "database-name" , ... }, ... }

If the database is located on a different system from the DHCPv6 server, the database host name must also be specified:

"Dhcp6": { "lease-database": { "host": "remote-host-name", ... }, ... }

Normally, the database is on the same machine as the DHCPv6 server. In this case, set the value to the empty string:

"Dhcp6": { "lease-database": { "host" : "", ... }, ... }

Should the database use a port other than the default, it may be specified as well:

"Dhcp6": { "lease-database": { "port" : 12345, ... }, ... }

Should the database be located on a different system, the administrator may need to specify a longer interval for the connection timeout:

"Dhcp6": { "lease-database": { "connect-timeout" : timeout-in-seconds, ... }, ... }

The default value of five seconds should be more than adequate for local connections. If a timeout is given, though, it should be an integer greater than zero.

The maximum number of times the server automatically attempts to reconnect to the lease database after connectivity has been lost may be specified:

"Dhcp6": { "lease-database": { "max-reconnect-tries" : number-of-tries, ... }, ... }

If the server is unable to reconnect to the database after making the maximum number of attempts, the server will exit. A value of 0 (the default) disables automatic recovery and the server will exit immediately upon detecting a loss of connectivity (MySQL and PostgreSQL only).

The number of milliseconds the server waits between attempts to reconnect to the lease database after connectivity has been lost may also be specified:

"Dhcp6": { "lease-database": { "reconnect-wait-time" : number-of-milliseconds, ... }, ... }

The default value for MySQL and PostgreSQL is 0, which disables automatic recovery and causes the server to exit immediately upon detecting the loss of connectivity.

"Dhcp6": { "lease-database": { "on-fail" : "stop-retry-exit", ... }, ... }

The possible values are:

• stop-retry-exit - disables the DHCP service while trying to automatically recover lost connections. Shuts down the server on failure after exhausting max-reconnect-tries. This is the default value for MySQL and PostgreSQL.

• serve-retry-exit - continues the DHCP service while trying to automatically recover lost connections. Shuts down the server on failure after exhausting max-reconnect-tries.

• serve-retry-continue - continues the DHCP service and does not shut down the server even if the recovery fails.

Note

Automatic reconnection to database backends is configured individually per backend; this allows users to tailor the recovery parameters to each backend they use. We suggest that users enable it either for all backends or none, so behavior is consistent.

Losing connectivity to a backend for which reconnection is disabled results (if configured) in the server shutting itself down. This includes cases when the lease database backend and the hosts database backend are connected to the same database instance.

It is highly recommended not to change the stop-retry-exit default setting for the lease manager, as it is critical for the connection to be active while processing DHCP traffic. Change this only if the server is used exclusively as a configuration tool.

The host parameter is used by the MySQL and PostgreSQL backends.

Finally, the credentials of the account under which the server will access the database should be set:

"Dhcp6": { "lease-database": { "user": "user-name",
                               "password": "password",
                              ... },
           ... }

If there is no password to the account, set the password to the empty string "". (This is the default.)

Hosts Storage

Kea is also able to store information about host reservations in the database. The hosts database configuration uses the same syntax as the lease database. In fact, the Kea server opens independent connections for each purpose, be it lease or hosts information, which gives the most flexibility. Kea can keep leases and host reservations separately, but can also point to the same database. Currently the supported hosts database types are MySQL and PostgreSQL.

The following configuration can be used to configure a connection to MySQL:

"Dhcp6": {
    "hosts-database": {
        "type": "mysql",
        "name": "kea",
        "user": "kea",
        "password": "secret123",
        "host": "localhost",
        "port": 3306
    }
}

Depending on the database configuration, many of the parameters may be optional.

Please note that usage of hosts storage is optional. A user can define all host reservations in the configuration file, and that is the recommended way if the number of reservations is small. However, when the number of reservations grows, it is more convenient to use host storage. Please note that both storage methods (the configuration file and one of the supported databases) can be used together. If hosts are defined in both places, the definitions from the configuration file are checked first and external storage is checked later, if necessary.

Host information can be placed in multiple stores. Operations are performed on the stores in the order they are defined in the configuration file, although this leads to a restriction in ordering in the case of a host reservation addition; read-only stores must be configured after a (required) read-write store, or the addition will fail.

Note

Kea requires the database timezone to match the system timezone. For more details, see First-Time Creation of the MySQL Database and First-Time Creation of the PostgreSQL Database.

DHCPv6 Hosts Database Configuration

Hosts database configuration is controlled through the Dhcp6/hosts-database parameters. If enabled, the type of database must be set to mysql or postgresql.

"Dhcp6": { "hosts-database": { "type": "mysql", ... }, ... }

Next, the name of the database to hold the reservations must be set; this is the name used when the lease database was created (see Supported Backends for instructions on how to set up the desired database type):

"Dhcp6": { "hosts-database": { "name": "database-name" , ... }, ... }

If the database is located on a different system than the DHCPv6 server, the database host name must also be specified:

"Dhcp6": { "hosts-database": { "host": remote-host-name, ... }, ... }

Normally, the database is on the same machine as the DHCPv6 server. In this case, set the value to the empty string:

"Dhcp6": { "hosts-database": { "host" : "", ... }, ... }

Should the database use a port different than the default, it may be specified as well:

"Dhcp6": { "hosts-database": { "port" : 12345, ... }, ... }

The maximum number of times the server automatically attempts to reconnect to the host database after connectivity has been lost may be specified:

"Dhcp6": { "hosts-database": { "max-reconnect-tries" : number-of-tries, ... }, ... }

If the server is unable to reconnect to the database after making the maximum number of attempts, the server will exit. A value of 0 (the default) disables automatic recovery and the server will exit immediately upon detecting a loss of connectivity (MySQL and PostgreSQL only).

The number of milliseconds the server waits between attempts to reconnect to the host database after connectivity has been lost may also be specified:

"Dhcp6": { "hosts-database": { "reconnect-wait-time" : number-of-milliseconds, ... }, ... }

The default value for MySQL and PostgreSQL is 0, which disables automatic recovery and causes the server to exit immediately upon detecting the loss of connectivity.

"Dhcp6": { "hosts-database": { "on-fail" : "stop-retry-exit", ... }, ... }

The possible values are:

• stop-retry-exit - disables the DHCP service while trying to automatically recover lost connections. Shuts down the server on failure after exhausting max-reconnect-tries. This is the default value for MySQL and PostgreSQL.

• serve-retry-exit - continues the DHCP service while trying to automatically recover lost connections. Shuts down the server on failure after exhausting max-reconnect-tries.

• serve-retry-continue - continues the DHCP service and does not shut down the server even if the recovery fails.

Note

Automatic reconnection to database backends is configured individually per backend. This allows users to tailor the recovery parameters to each backend they use. We suggest that users enable it either for all backends or none, so behavior is consistent.

Losing connectivity to a backend for which reconnection is disabled results (if configured) in the server shutting itself down. This includes cases when the lease database backend and the hosts database backend are connected to the same database instance.

Finally, the credentials of the account under which the server will access the database should be set:

"Dhcp6": { "hosts-database": { "user": "user-name",
                               "password": "password",
                              ... },
           ... }

If there is no password to the account, set the password to the empty string "". (This is the default.)

The multiple-storage extension uses a similar syntax; a configuration is placed into a hosts-databases list instead of into a hosts-database entry, as in:

"Dhcp6": { "hosts-databases": [ { "type": "mysql", ... }, ... ], ... }

If the same host is configured both in-file and in-database, Kea does not issue a warning, as it would if both were specified in the same data source. Instead, the host configured in-file has priority over the one configured in-database.

Using Read-Only Databases for Host Reservations with DHCPv6

In some deployments, the user whose name is specified in the database backend configuration may not have write privileges to the database. This is often required by the policy within a given network to secure the data from being unintentionally modified. In many cases administrators have deployed inventory databases, which contain substantially more information about the hosts than just the static reservations assigned to them. The inventory database can be used to create a view of a Kea hosts database and such a view is often read-only.

Kea host-database backends operate with an implicit configuration to both read from and write to the database. If the user does not have write access to the host database, the backend will fail to start and the server will refuse to start (or reconfigure). However, if access to a read-only host database is required for retrieving reservations for clients and/or assigning specific addresses and options, it is possible to explicitly configure Kea to start in “read-only” mode. This is controlled by the readonly boolean parameter as follows:

"Dhcp6": { "hosts-database": { "readonly": true, ... }, ... }

Setting this parameter to false configures the database backend to operate in “read-write” mode, which is also the default configuration if the parameter is not specified.

Note

The readonly parameter is only supported for MySQL and PostgreSQL databases.

Interface Configuration

The DHCPv6 server must be configured to listen on specific network interfaces. The simplest network interface configuration tells the server to listen on all available interfaces:

"Dhcp6": {
    "interfaces-config": {
        "interfaces": [ "*" ]
    }
    ...
}

The asterisk plays the role of a wildcard and means “listen on all interfaces.” However, it is usually a good idea to explicitly specify interface names:

"Dhcp6": {
    "interfaces-config": {
        "interfaces": [ "eth1", "eth3" ]
    },
    ...
}

It is possible to use an interface wildcard (*) concurrently with explicit interface names:

"Dhcp6": {
    "interfaces-config": {
        "interfaces": [ "eth1", "eth3", "*" ]
    },
    ...
}

This format should only be used when it is desired to temporarily override a list of interface names and listen on all interfaces.

As with the DHCPv4 server, binding to specific addresses and disabling re-detection of interfaces are supported. But dhcp-socket-type is not supported, because DHCPv6 uses only UDP/IPv6 sockets. The following example shows how to disable interface detection:

"Dhcp6": {
    "interfaces-config": {
        "interfaces": [ "eth1", "eth3" ],
        "re-detect": false
    },
    ...
}

The loopback interfaces (i.e. the lo or lo0 interface) are not configured by default, unless explicitly mentioned in the configuration. Note that Kea requires a link-local address (which does not exist on all systems) or a specified unicast address, as in:

"Dhcp6": {
    "interfaces-config": {
        "interfaces": [ "enp0s2/2001:db8::1234:abcd" ]
    },
    ...
}

Kea binds the service sockets for each interface on startup. If another process is already using a port, then Kea logs the message and suppresses an error. DHCP service runs, but it is unavailable on some interfaces.

The “service-sockets-require-all” option makes Kea require all sockets to be successfully bound. If any opening fails, Kea interrupts the initialization and exits with a non-zero status. (Default is false).

"Dhcp6": {
    "interfaces-config": {
        "interfaces": [ "eth1", "eth3" ],
        "service-sockets-require-all": true
    },
    ...
}

Sometimes, immediate interruption isn’t a good choice. The port can be unavailable only temporary. In this case, retrying the opening may resolve the problem. Kea provides two options to specify the retrying: service-sockets-max-retries and service-sockets-retry-wait-time.

The first defines a maximal number of retries that Kea makes to open a socket. The zero value (default) means that the Kea doesn’t retry the process.

The second defines a wait time (in milliseconds) between attempts. The default value is 5000 (5 seconds).

"Dhcp6": {
    "interfaces-config": {
        "interfaces": [ "eth1", "eth3" ],
        "service-sockets-max-retries": 5,
        "service-sockets-retry-wait-time": 5000
    },
    ...
}

If “service-sockets-max-retries” is non-zero and “service-sockets-require-all” is false, then Kea retries the opening (if needed) but does not fail if any socket is still not opened.

IPv6 Subnet Identifier

The subnet identifier (subnet ID) is a unique number associated with a particular subnet. In principle, it is used to associate clients’ leases with their respective subnets. When a subnet identifier is not specified for a subnet being configured, it is automatically assigned by the configuration mechanism. The identifiers are assigned starting at 1 and are monotonically increased for each subsequent subnet: 1, 2, 3, ….

If there are multiple subnets configured with auto-generated identifiers and one of them is removed, the subnet identifiers may be renumbered. For example: if there are four subnets and the third is removed, the last subnet will be assigned the identifier that the third subnet had before removal. As a result, the leases stored in the lease database for subnet 3 are now associated with subnet 4, something that may have unexpected consequences. The only remedy for this issue at present is to manually specify a unique identifier for each subnet.

Note

Subnet IDs must be greater than zero and less than 4294967295.

The following configuration assigns the specified subnet identifier to a newly configured subnet:

"Dhcp6": {
    "subnet6": [
        {
            "subnet": "2001:db8:1::/64",
            "id": 1024,
            ...
        }
    ]
}

This identifier will not change for this subnet unless the id parameter is removed or set to 0. The value of 0 forces auto-generation of the subnet identifier.

IPv6 Subnet Prefix

The subnet prefix is the second way to identify a subnet. Kea can accept non-canonical subnet addresses; for instance, this configuration is accepted:

"Dhcp6": {
   "subnet6": [
       {
            "subnet": "2001:db8:1::1/64",
            ...
       }
    ]
}

This works even if there is another subnet with the “2001:db8:1::/64” prefix; only the textual form of subnets are compared to avoid duplicates.

Note

Abuse of this feature can lead to incorrect subnet selection (see IPv6 Subnet Selection).

Unicast Traffic Support

When the DHCPv6 server starts, by default it listens to the DHCP traffic sent to multicast address ff02::1:2 on each interface that it is configured to listen on (see Interface Configuration). In some cases it is useful to configure a server to handle incoming traffic sent to global unicast addresses as well; the most common reason for this is to have relays send their traffic to the server directly. To configure the server to listen on a specific unicast address, add a slash (/) after the interface name, followed by the global unicast address on which the server should listen. The server will listen to this address in addition to normal link-local binding and listening on the ff02::1:2 address. The sample configuration below shows how to listen on 2001:db8::1 (a global address) configured on the eth1 interface.

"Dhcp6": {
    "interfaces-config": {
        "interfaces": [ "eth1/2001:db8::1" ]
    },
    ...
    "option-data": [
        {
            "name": "unicast",
            "data": "2001:db8::1"
        } ],
    ...
}

This configuration will cause the server to listen on eth1 on the link-local address, the multicast group (ff02::1:2), and 2001:db8::1.

Usually, unicast support is associated with a server unicast option which allows clients to send unicast messages to the server. The example above includes a server unicast option specification which causes the client to send messages to the specified unicast address.

It is possible to mix interface names, wildcards, and interface names/addresses in the list of interfaces. It is not possible, however, to specify more than one unicast address on a given interface.

Care should be taken to specify proper unicast addresses, as the server will attempt to bind to the addresses specified without any additional checks. This approach was selected intentionally, to allow the software to communicate over uncommon addresses if so desired.

Configuration of IPv6 Address Pools

The main role of a DHCPv6 server is address assignment. For this, the server must be configured with at least one subnet and one pool of dynamic addresses to be managed. For example, assume that the server is connected to a network segment that uses the 2001:db8:1::/64 prefix. The administrator of that network decides that addresses from the range 2001:db8:1::1 to 2001:db8:1::ffff are going to be managed by the DHCPv6 server. Such a configuration can be achieved in the following way:

"Dhcp6": {
    "subnet6": [
       {
           "subnet": "2001:db8:1::/64",
           "pools": [
               {
                   "pool": "2001:db8:1::1-2001:db8:1::ffff"
               }
           ],
           ...
       }
    ]
}

Note that subnet is defined as a simple string, but the pools parameter is actually a list of pools; for this reason, the pool definition is enclosed in square brackets, even though only one range of addresses is specified.

Each pool is a structure that contains the parameters that describe a single pool. Currently there is only one parameter, pool, which gives the range of addresses in the pool.

It is possible to define more than one pool in a subnet; continuing the previous example, further assume that 2001:db8:1:0:5::/80 should also be managed by the server. It could be written as 2001:db8:1:0:5:: to 2001:db8:1::5:ffff:ffff:ffff, but typing so many f``s is cumbersome. It can be expressed more simply as 2001:db8:1:0:5::/80. Both formats are supported by ``Dhcp6 and can be mixed in the pool list. For example, the following pools could be defined:

"Dhcp6": {
    "subnet6": [
    {
        "subnet": "2001:db8:1::/64",
        "pools": [
            { "pool": "2001:db8:1::1-2001:db8:1::ffff" },
            { "pool": "2001:db8:1:05::/80" }
        ],
        ...
    }
    ]
}

White space in pool definitions is ignored, so spaces before and after the hyphen are optional. They can be used to improve readability.

The number of pools is not limited, but for performance reasons it is recommended to use as few as possible.

The server may be configured to serve more than one subnet. To add a second subnet, use a command similar to the following:

"Dhcp6": {
    "subnet6": [
    {
        "subnet": "2001:db8:1::/64",
        "pools": [
            { "pool": "2001:db8:1::1-2001:db8:1::ffff" }
        ]
    },
    {
        "subnet": "2001:db8:2::/64",
        "pools": [
            { "pool": "2001:db8:2::/64" }
        ]
    },

        ...
    ]
}

In this example, we allow the server to dynamically assign all addresses available in the whole subnet. Although rather wasteful, it is certainly a valid configuration to dedicate the whole /64 subnet for that purpose. Note that the Kea server does not preallocate the leases, so there is no danger in using gigantic address pools.

When configuring a DHCPv6 server using prefix/length notation, please pay attention to the boundary values. When specifying that the server can use a given pool, it is also able to allocate the first (typically a network address) address from that pool. For example, for pool 2001:db8:2::/64, the 2001:db8:2:: address may be assigned as well. To avoid this, use the min-max notation.

Subnet and Prefix Delegation Pools

Subnets may also be configured to delegate prefixes, as defined in RFC 8415, section 6.3. A subnet may have one or more prefix delegation pools. Each pool has a prefixed address, which is specified as a prefix (prefix) and a prefix length (prefix-len), as well as a delegated prefix length (delegated-len). The delegated length must not be shorter than (i.e. it must be numerically greater than or equal to) the prefix length. If both the delegated and prefix lengths are equal, the server will be able to delegate only one prefix. The delegated prefix does not have to match the subnet prefix.

Below is a sample subnet configuration which enables prefix delegation for the subnet:

"Dhcp6": {
    "subnet6": [
        {
            "subnet": "2001:d8b:1::/64",
            "pd-pools": [
                {
                    "prefix": "3000:1::",
                    "prefix-len": 64,
                    "delegated-len": 96
                }
            ]
        }
    ],
    ...
}

Prefix Exclude Option

For each delegated prefix, the delegating router may choose to exclude a single prefix out of the delegated prefix as specified in RFC 6603. The requesting router must not assign the excluded prefix to any of its downstream interfaces. The excluded prefix is intended to be used on a link through which the delegating router exchanges DHCPv6 messages with the requesting router. The configuration example below demonstrates how to specify an excluded prefix within a prefix pool definition. The excluded prefix 2001:db8:1:8000:cafe:80::/72 will be sent to a requesting router which includes the Prefix Exclude option in the Option Request option (ORO), and which is delegated a prefix from this pool.

"Dhcp6": {
    "subnet6": [
        {
            "subnet": "2001:db8:1::/48",
            "pd-pools": [
                {
                    "prefix": "2001:db8:1:8000::",
                    "prefix-len": 48,
                    "delegated-len": 64,
                    "excluded-prefix": "2001:db8:1:8000:cafe:80::",
                    "excluded-prefix-len": 72
                }
            ]
        }
    ]
}

Note

Here are some liberties and limits to the values that subnets and pools can take in Kea configurations that are out of the ordinary:

Kea configuration case	Allowed	Comment
Overlapping subnets	Yes	Administrator consideration needs to be given to how clients are matched to these subnets.
Overlapping address pools in one subnet	No	Startup error: DHCP6_PARSER_FAIL
Overlapping address pools in different subnets	Yes	Specifying the same address pool in different subnets can be used as an equivalent of the global address pool. In that case, the server can assign addresses from the same range regardless of the client’s subnet. If an address from such a pool is assigned to a client in one subnet, the same address will be renewed for this client if it moves to another subnet. Another client in a different subnet will not be assigned an address already assigned to the client in any of the subnets.
Address pools that are outside the subnet they are configured under	No	Startup error: DHCP6_PARSER_FAIL
Overlapping prefix delegation pools in one subnet	No	Startup error: DHCP6_PARSER_FAIL
Overlapping prefix delegation pools in different subnets	Yes	Specifying the same prefix delegation pool in different subnets can be used as an equivalent of the global pool. In that case, the server can delegate the same prefixes regardless of the client’s subnet. If a prefix from such a pool is delegated to a client in one subnet, the same prefix will be renewed for this client if it moves to another subnet. Another client in a different subnet will not be delegated a prefix already delegated to the client in any of the subnets.
Prefix delegation pools not matching the subnet prefix	Yes	It is common in many deployments to configure the prefix delegation pools not matching the subnet prefix, e.g. a prefix pool of 3000::/96 within the 2001:db8:1::/64 subnet. Such use cases are supported by Kea DHCPv6 server.

Standard DHCPv6 Options

One of the major features of the DHCPv6 server is the ability to provide configuration options to clients. Although there are several options that require special behavior, most options are sent by the server only if the client explicitly requests them. The following example shows how to configure the addresses of DNS servers, one of the most frequently used options. Options specified in this way are considered global and apply to all configured subnets.

"Dhcp6": {
    "option-data": [
        {
           "name": "dns-servers",
           "code": 23,
           "space": "dhcp6",
           "csv-format": true,
           "data": "2001:db8::cafe, 2001:db8::babe"
        },
        ...
    ]
}

The option-data line creates a new entry in the option-data table. This table contains information on all global options that the server is supposed to configure in all subnets. The name line specifies the option name. (For a complete list of currently supported names, see List of standard DHCPv6 options configurable by an administrator.) The next line specifies the option code, which must match one of the values from that list. The line beginning with space specifies the option space, which must always be set to dhcp6 as these are standard DHCPv6 options. For other name spaces, including custom option spaces, see Nested DHCPv6 Options (Custom Option Spaces). The following line specifies the format in which the data will be entered; use of CSV (comma-separated values) is recommended. Finally, the data line gives the actual value to be sent to clients. The data parameter is specified as normal text, with values separated by commas if more than one value is allowed.

Options can also be configured as hexadecimal values. If csv-format is set to false, the option data must be specified as a hexadecimal string. The following commands configure the dns-servers option for all subnets with the addresses 2001:db8:1::cafe and 2001:db8:1::babe.

"Dhcp6": {
    "option-data": [
        {
           "name": "dns-servers",
           "code": 23,
           "space": "dhcp6",
           "csv-format": false,
           "data": "20 01 0D B8 00 01 00 00 00 00 00 00 00 00 CA FE
                    20 01 0D B8 00 01 00 00 00 00 00 00 00 00 BA BE"
        },
        ...
    ]
}

Note

The value for the setting of the data element is split across two lines in this example for clarity; when entering the command, the whole string should be entered on the same line.

Kea supports the following formats when specifying hexadecimal data:

• Delimited octets - one or more octets separated by either colons or spaces (“:” or ” “). While each octet may contain one or two digits, we strongly recommend always using two digits. Valid examples are “ab:cd:ef” and “ab cd ef”.

• String of digits - a continuous string of hexadecimal digits with or without a “0x” prefix. Valid examples are “0xabcdef” and “abcdef”.

Care should be taken to use proper encoding when using hexadecimal format; Kea’s ability to validate data correctness in hexadecimal is limited.

It is also possible to specify data for binary options as a single-quoted text string within double quotes, as shown (note that csv-format must be set to false):

"Dhcp6": {
    "option-data": [
        {
            "name": "subscriber-id",
            "code": 38,
            "space": "dhcp6",
            "csv-format": false,
            "data": "'convert this text to binary'"
        },
        ...
    ],
    ...
}

Most of the parameters in the option-data structure are optional and can be omitted in some circumstances, as discussed in Unspecified Parameters for DHCPv6 Option Configuration. Only one of name or code is required; it is not necessary to specify both. Space has a default value of dhcp6, so this can be skipped as well if a regular (not encapsulated) DHCPv6 option is defined. Finally, csv-format defaults to true, so it too can be skipped, unless the option value is specified as hexstring. Therefore, the above example can be simplified to:

"Dhcp6": {
    "option-data": [
        {
           "name": "dns-servers",
           "data": "2001:db8::cafe, 2001:db8::babe"
        },
        ...
    ]
}

Defined options are added to the response when the client requests them, as well as any options required by a protocol. An administrator can also specify that an option is always sent, even if a client did not specifically request it. To enforce the addition of a particular option, set the always-send flag to true, as in:

"Dhcp6": {
    "option-data": [
        {
           "name": "dns-servers",
           "data": "2001:db8::cafe, 2001:db8::babe",
           "always-send": true
        },
        ...
    ]
}

The effect is the same as if the client added the option code in the Option Request Option (or its equivalent for vendor options), as in:

"Dhcp6": {
    "option-data": [
        {
           "name": "dns-servers",
           "data": "2001:db8::cafe, 2001:db8::babe",
           "always-send": true
        },
        ...
    ],
    "subnet6": [
        {
           "subnet": "2001:db8:1::/64",
           "option-data": [
               {
                   "name": "dns-servers",
                   "data": "2001:db8:1::cafe, 2001:db8:1::babe"
               },
               ...
           ],
           ...
        },
        ...
    ],
    ...
}

The dns-servers option is always added to responses (the always-send is “sticky”), but the value is the subnet one when the client is localized in the subnet.

It is possible to override options on a per-subnet basis. If clients connected to most subnets are expected to get the same values of a given option, administrators should use global options; it is possible to override specific values for a small number of subnets. On the other hand, if different values are used in each subnet, it does not make sense to specify global option values; rather, only subnet-specific ones should be set.

The following commands override the global dns-servers option for a particular subnet, setting a single DNS server with address 2001:db8:1::3.

"Dhcp6": {
    "subnet6": [
        {
            "option-data": [
                {
                    "name": "dns-servers",
                    "code": 23,
                    "space": "dhcp6",
                    "csv-format": true,
                    "data": "2001:db8:1::3"
                },
                ...
            ],
            ...
        },
        ...
    ],
    ...
}

In some cases it is useful to associate some options with an address or prefix pool from which a client is assigned a lease. Pool-specific option values override subnet-specific and global option values. If the client is assigned multiple leases from different pools, the server assigns options from all pools from which the leases have been obtained. However, if the particular option is specified in multiple pools from which the client obtains the leases, only one instance of this option is handed out to the client. The server’s administrator must not try to prioritize assignment of pool-specific options by trying to order pool declarations in the server configuration.

The following configuration snippet demonstrates how to specify the dns-servers option, which will be assigned to a client only if the client obtains an address from the given pool:

"Dhcp6": {
    "subnet6": [
        {
            "pools": [
                {
                    "pool": "2001:db8:1::100-2001:db8:1::300",
                    "option-data": [
                        {
                            "name": "dns-servers",
                            "data": "2001:db8:1::10"
                        }
                    ]
                }
            ]
        },
        ...
    ],
    ...
}

Options can also be specified in class or host-reservation scope. The current Kea options precedence order is (from most important): host reservation, pool, subnet, shared network, class, global.

When a data field is a string and that string contains the comma (,; U+002C) character, the comma must be escaped with two backslashes (\\,; U+005C). This double escape is required because both the routine splitting CSV data into fields and JSON use the same escape character; a single escape (\,) would make the JSON invalid. For example, the string “EST5EDT4,M3.2.0/02:00,M11.1.0/02:00” must be represented as:

"Dhcp6": {
    "subnet6": [
        {
            "pools": [
                {
                    "option-data": [
                        {
                            "name": "new-posix-timezone",
                            "data": "EST5EDT4\\,M3.2.0/02:00\\,M11.1.0/02:00"
                        }
                    ]
                },
                ...
            ],
            ...
        },
        ...
    ],
    ...
}

Some options are designated as arrays, which means that more than one value is allowed. For example, the option dns-servers allows the specification of more than one IPv6 address, enabling clients to obtain the addresses of multiple DNS servers.

Custom DHCPv6 Options describes the configuration syntax to create custom option definitions (formats). Creation of custom definitions for standard options is generally not permitted, even if the definition being created matches the actual option format defined in the RFCs. However, there is an exception to this rule for standard options for which Kea currently does not provide a definition. To use such options, a server administrator must create a definition as described in Custom DHCPv6 Options in the dhcp6 option space. This definition should match the option format described in the relevant RFC, but the configuration mechanism allows any option format as there is currently no way to validate it.

The currently supported standard DHCPv6 options are listed in the table below. “Name” and “Code” are the values that should be used as a name/code in the option-data structures. “Type” designates the format of the data; the meanings of the various types are given in List of standard DHCP option types.

List of standard DHCPv6 options configurable by an administrator

Name	Code	Type	Array?
preference	7	uint8	false
unicast	12	ipv6-address	false
sip-server-dns	21	fqdn	true
sip-server-addr	22	ipv6-address	true
dns-servers	23	ipv6-address	true
domain-search	24	fqdn	true
nis-servers	27	ipv6-address	true
nisp-servers	28	ipv6-address	true
nis-domain-name	29	fqdn	true
nisp-domain-name	30	fqdn	true
sntp-servers	31	ipv6-address	true
information-refresh-time	32	uint32	false
bcmcs-server-dns	33	fqdn	true
bcmcs-server-addr	34	ipv6-address	true
geoconf-civic	36	record (uint8, uint16, binary)	false
remote-id	37	record (uint32, binary)	false
subscriber-id	38	binary	false
client-fqdn	39	record (uint8, fqdn)	false
pana-agent	40	ipv6-address	true
new-posix-timezone	41	string	false
new-tzdb-timezone	42	string	false
ero	43	uint16	true
lq-query (1)	44	record (uint8, ipv6-address)	false
client-data (1)	45	empty	false
clt-time (1)	46	uint32	false
lq-relay-data (1)	47	record (ipv6-address, binary)	false
lq-client-link (1)	48	ipv6-address	true
v6-lost	51	fqdn	false
capwap-ac-v6	52	ipv6-address	true
relay-id	53	binary	false
v6-access-domain	57	fqdn	false
sip-ua-cs-list	58	fqdn	true
bootfile-url	59	string	false
bootfile-param	60	tuple	true
client-arch-type	61	uint16	true
nii	62	record (uint8, uint8, uint8)	false
aftr-name	64	fqdn	false
erp-local-domain-name	65	fqdn	false
rsoo	66	empty	false
pd-exclude	67	binary	false
rdnss-selection	74	record (ipv6-address, uint8, fqdn)	true
client-linklayer-addr	79	binary	false
link-address	80	ipv6-address	false
solmax-rt	82	uint32	false
inf-max-rt	83	uint32	false
dhcp4o6-server-addr	88	ipv6-address	true
s46-rule	89	record (uint8, uint8, uint8, ipv4-address, ipv6-prefix)	false
s46-br	90	ipv6-address	false
s46-dmr	91	ipv6-prefix	false
s46-v4v6bind	92	record (ipv4-address, ipv6-prefix)	false
s46-portparams	93	record(uint8, psid)	false
s46-cont-mape	94	empty	false
s46-cont-mapt	95	empty	false
s46-cont-lw	96	empty	false
v6-captive-portal	103	string	false
ipv6-address-andsf	143	ipv6-address	true

Options marked with (1) have option definitions, but the logic behind them is not implemented. That means that, technically, Kea knows how to parse them in incoming messages or how to send them if configured to do so, but not what to do with them. Since the related RFCs require certain processing, the support for those options is non-functional. However, it may be useful in some limited lab testing; hence the definition formats are listed here.

Kea supports more options than those listed above. The following list is mostly useful for readers who want to understand whether Kea is able to support certain options. The following options are returned by the Kea engine itself and in general should not be configured manually.

List of standard DHCPv6 options managed by Kea on its own and not directly configurable by an administrator

Name	Code	Description
client-id	1	Sent by the client; Kea uses it to distinguish between clients.
server-id	2	Sent by clients to request action from a specific server and by the server to identify itself. See Server Identifier in DHCPv6 for details.
ia-na	3	A container option that conveys IPv6 addresses (iaddr options). Kea receives and sends those options using its allocation engine.
ia-ta	4	Conveys temporary addresses. Deprecated feature, not supported.
iaaddr	5	Conveys addresses with lifetimes in ia-na and ia-ta options.
oro	6	ORO (or Option Request Option) is used by clients to request a list of options they are interested in. Kea supports it and sends the requested options back if configured with required options.
elapsed-time	8	Sent by clients to identify how long they have been trying to obtain a configuration. Kea uses high values sent by clients as an indicator that something is wrong; this is one of the aspects used in HA to determine if the partner is healthy or not.
relay-msg	9	Used by relays to encapsulate the original client message. Kea uses it when sending back relayed responses to the relay agent.
auth	11	Used to pass authentication information between clients and server. The support for this option is very limited.
status-code	13	An option that the server can attach in case of various failures, such as running out of addresses or not being configured to assign prefixes.
rapid-commit	14	Used to signal the client’s willingness to support rapid-commit and the server’s acceptance for this configuration. See Rapid Commit for details.
user-class	15	Sent by the client to self-identify the device type. Kea can use this for client classification.
vendor-class	16	Similar to user-class, but vendor-specific.
vendor-opts	17	A vendor-specific container that is used by both the client and the server to exchange vendor-specific options. The logic behind those options varies between vendors. Vendor options are explained in DHCPv6 Vendor-Specific Options.
interface-id	18	May be inserted by the relay agent to identify the interface that the original client message was received on. Kea may be told to use this information to select specific subnets. Also, if specified, Kea echoes this option back, so the relay will know which interface to use to reach the client.
ia-pd	25	A container for conveying Prefix Delegations (PDs)) that are being delegated to clients. See Subnet and Prefix Delegation Pools for details.
iaprefix	26	Conveys the IPv6 prefix in the ia-pd option. See Subnet and Prefix Delegation Pools for details.

Common Softwire46 Options

Softwire46 options are involved in IPv4-over-IPv6 provisioning by means of tunneling or translation, as specified in RFC 7598. The following sections provide configuration examples of these options.

Softwire46 Container Options

Softwire46 (S46) container options group rules and optional port parameters for a specified domain. There are three container options specified in the “dhcp6” (top-level) option space: the MAP-E Container option, the MAP-T Container option, and the S46 Lightweight 4over6 Container option. These options only contain the encapsulated options specified below; they do not include any data fields.

To configure the server to send a specific container option along with all encapsulated options, the container option must be included in the server configuration as shown below:

"Dhcp6": {
    ...
    "option-data": [
        {
            "name": "s46-cont-mape"
        } ],
    ...
}

This configuration will cause the server to include the MAP-E Container option to the client. Use s46-cont-mapt or s46-cont-lw for the MAP-T Container and S46 Lightweight 4over6 Container options, respectively.

All remaining Softwire46 options described below are included in one of the container options. Thus, they must be included in appropriate option spaces by selecting a space name, which specifies the option where they are supposed to be included.

S46 Rule Option

The S46 Rule option is used to convey the Basic Mapping Rule (BMR) and Forwarding Mapping Rule (FMR).

{
    "space": "s46-cont-mape-options",
    "name": "s46-rule",
    "data": "128, 0, 24, 192.0.2.0, 2001:db8:1::/64"
}

Another possible space value is s46-cont-mapt-options.

The S46 Rule option conveys a number of parameters:

• flags - an unsigned 8-bit integer, with currently only the most-significant bit specified. It denotes whether the rule can be used for forwarding (128) or not (0).

• ea-len - an 8-bit-long Embedded Address length. Allowed values range from 0 to 48.

• IPv4 prefix length - an 8-bit-long expression of the prefix length of the Rule IPv4 prefix specified in the ipv4-prefix field. Allowed values range from 0 to 32.

• IPv4 prefix - a fixed-length 32-bit field that specifies the IPv4 prefix for the S46 rule. The bits in the prefix after a specific number of bits (defined in prefix4-len) are reserved, and MUST be initialized to zero by the sender and ignored by the receiver.

• IPv6 prefix - a field in prefix/length notation that specifies the IPv6 domain prefix for the S46 rule. The field is padded on the right with zero bits up to the nearest octet boundary, when prefix6-len is not evenly divisible by 8.

S46 BR Option

The S46 BR option is used to convey the IPv6 address of the Border Relay. This option is mandatory in the MAP-E Container option and is not permitted in the MAP-T and S46 Lightweight 4over6 Container options.

{
    "space": "s46-cont-mape-options",
    "name": "s46-br",
    "data": "2001:db8:cafe::1",
}

Another possible space value is s46-cont-lw-options.

S46 DMR Option

The S46 DMR option is used to convey values for the Default Mapping Rule (DMR). This option is mandatory in the MAP-T container option and is not permitted in the MAP-E and S46 Lightweight 4over6 Container options.

{
    "space": "s46-cont-mapt-options",
    "name": "s46-dmr",
    "data": "2001:db8:cafe::/64",
}

This option must not be included in other containers.

S46 IPv4/IPv6 Address Binding Option

The S46 IPv4/IPv6 Address Binding option may be used to specify the full or shared IPv4 address of the Customer Edge (CE). The IPv6 prefix field is used by the CE to identify the correct prefix to use for the tunnel source.

{
    "space": "s46-cont-lw",
    "name": "s46-v4v6bind",
    "data": "192.0.2.3, 2001:db8:1:cafe::/64"
}

This option must not be included in other containers.

S46 Port Parameters

The S46 Port Parameters option specifies optional port-set information that may be provided to CEs.

{
    "space": "s46-rule-options",
    "name": "s46-portparams",
    "data": "2, 3/4",
}

Another possible space value is s46-v4v6bind, to include this option in the S46 IPv4/IPv6 Address Binding option.

Note that the second value in the example above specifies the PSID and PSID-length fields in the format of PSID/PSID length. This is equivalent to the values of PSID-len=4 and PSID=12288 conveyed in the S46 Port Parameters option.

Custom DHCPv6 Options

Kea supports custom (non-standard) DHCPv6 options. Let’s say that we want to define a new DHCPv6 option called foo, which will have code 100 and will convey a single, unsigned, 32-bit integer value. Such an option can be defined by putting the following entry in the configuration file:

"Dhcp6": {
    "option-def": [
        {
            "name": "foo",
            "code": 100,
            "type": "uint32",
            "array": false,
            "record-types": "",
            "space": "dhcp6",
            "encapsulate": ""
        }, ...
    ],
    ...
}

The false value of the array parameter determines that the option does NOT comprise an array of uint32 values but is, instead, a single value. Two other parameters have been left blank: record-types and encapsulate. The former specifies the comma-separated list of option data fields, if the option comprises a record of data fields. The record-types value should be non-empty if type is set to record; otherwise it must be left blank. The latter parameter specifies the name of the option space being encapsulated by the particular option. If the particular option does not encapsulate any option space, the parameter should be left blank. Note that the option-def configuration statement only defines the format of an option and does not set its value(s).

The name, code, and type parameters are required; all others are optional. The array default value is false. The record-types and encapsulate default values are blank (""). The default space is dhcp6.

Once the new option format is defined, its value is set in the same way as for a standard option. For example, the following commands set a global value that applies to all subnets.

"Dhcp6": {
    "option-data": [
        {
            "name": "foo",
            "code": 100,
            "space": "dhcp6",
            "csv-format": true,
            "data": "12345"
        }, ...
    ],
    ...
}

New options can take more complex forms than the simple use of primitives (uint8, string, ipv6-address, etc.); it is possible to define an option comprising a number of existing primitives.

For example, say we want to define a new option that will consist of an IPv6 address, followed by an unsigned 16-bit integer, followed by a boolean value, followed by a text string. Such an option could be defined in the following way:

"Dhcp6": {
    "option-def": [
        {
            "name": "bar",
            "code": 101,
            "space": "dhcp6",
            "type": "record",
            "array": false,
            "record-types": "ipv6-address, uint16, boolean, string",
            "encapsulate": ""
        }, ...
    ],
    ...
}

The type is set to record to indicate that the option contains multiple values of different types. These types are given as a comma-separated list in the record-types field and should be ones from those listed in List of standard DHCP option types.

The values of the options are set in an option-data statement as follows:

"Dhcp6": {
    "option-data": [
        {
            "name": "bar",
            "space": "dhcp6",
            "code": 101,
            "csv-format": true,
            "data": "2001:db8:1::10, 123, false, Hello World"
        }
    ],
    ...
}

csv-format is set to true to indicate that the data field comprises a comma-separated list of values. The values in data must correspond to the types set in the record-types field of the option definition.

When array is set to "true" and type is set to "record", the last field is an array, i.e. it can contain more than one value, as in:

"Dhcp6": {
    "option-def": [
        {
            "name": "bar",
            "code": 101,
            "space": "dhcp6",
            "type": "record",
            "array": true,
            "record-types": "ipv6-address, uint16",
            "encapsulate": ""
        }, ...
    ],
    ...
}

The new option content is one IPv6 address followed by one or more 16-bit unsigned integers.

Note

In general, boolean values are specified as true or false, without quotes. Some specific boolean parameters may also accept "true", "false", 0, 1, "0", and "1".

DHCPv6 Vendor-Specific Options

Vendor options in DHCPv6 are carried in the Vendor-Specific Information option (code 17). The idea behind option 17 is that each vendor has its own unique set of options with their own custom formats. The vendor is identified by a 32-bit unsigned integer called enterprise-number or vendor-id.

The standard spaces defined in Kea and their options are:

• vendor-2495: Internet Systems Consortium, Inc. for 4o6 options:

option code	option name	option description
60000	4o6-interface	the name of the 4o6 server’s client-facing interface
60001	4o6-source-address	the address that the 4o6 server uses to send packets to the client
60002	4o6-source-port	the port that the 4o6 server opens to send packets to the client

• vendor-4491: Cable Television Laboratories, Inc. for DOCSIS3 options:

option code	option name	option description
1	oro	ORO (or Option Request Option) is used by clients to request a list of options they are interested in.
2	tftp-servers	a list of IPv4 addresses of TFTP servers to be used by the cable modem

The following examples show how to define an option "foo" with code 1 that consists of an IPv6 address, an unsigned 16-bit integer, and a string. The "foo" option is conveyed in a Vendor-Specific Information option, which comprises a single uint32 value that is set to 12345. The sub-option "foo" follows the data field holding this value.

The first step is to define the format of the option:

"Dhcp6": {
    "option-def": [
        {
            "name": "foo",
            "code": 1,
            "space": "vendor-12345",
            "type": "record",
            "array": false,
            "record-types": "ipv6-address, uint16, string",
            "encapsulate": ""
        }
    ],
    ...
}

(Note that the option space is set to "vendor-12345".) Once the option format is defined, the next step is to define actual values for that option:

"Dhcp6": {
    "option-data": [
        {
            "name": "foo",
            "space": "vendor-12345",
            "data": "2001:db8:1::10, 123, Hello World"
        },
        ...
    ],
    ...
}

We should also define a value ("enterprise-number") for the Vendor-Specific Information option, to convey the option foo.

"Dhcp6": {
    "option-data": [
        ...,
        {
            "name": "vendor-opts",
            "data": "12345"
        }
    ],
    ...
}

Alternatively, the option can be specified using its code.

"Dhcp6": {
    "option-data": [
        ...,
        {
            "code": 17,
            "data": "12345"
        }
    ],
    ...
}

A common configuration is to set the always-send flag to true, so the vendor option is sent even when the client did not specify it in the query.

Note

Only a single instance of the vendor-class (code 16) and a single instance of the vendor-opts (code 17) options can be specified. Specifying multiple options with different enterprise numbers is currently not supported by Kea.

Nested DHCPv6 Options (Custom Option Spaces)

It is sometimes useful to define a completely new option space, such as when a user creates a new option to convey sub-options that use a separate numbering scheme, such as sub-options with codes 1 and 2. Those option codes conflict with standard DHCPv6 options, so a separate option space must be defined.

Note that the creation of a new option space is not required when defining sub-options for a standard option, because one is created by default if the standard option is meant to convey any sub-options (see DHCPv6 Vendor-Specific Options).

If we want a DHCPv6 option called container with code 102, that conveys two sub-options with codes 1 and 2, we first need to define the new sub-options:

"Dhcp6": {
    "option-def": [
        {
            "name": "subopt1",
            "code": 1,
            "space": "isc",
            "type": "ipv6-address",
            "record-types": "",
            "array": false,
            "encapsulate": ""
        },
        {
            "name": "subopt2",
            "code": 2,
            "space": "isc",
            "type": "string",
            "record-types": "",
            "array": false
            "encapsulate": ""
        }
    ],
    ...
}

Note that we have defined the options to belong to a new option space (in this case, "isc").

The next step is to define a regular DHCPv6 option with the desired code and specify that it should include options from the new option space:

"Dhcp6": {
    "option-def": [
        ...,
        {
            "name": "container",
            "code": 102,
            "space": "dhcp6",
            "type": "empty",
            "array": false,
            "record-types": "",
            "encapsulate": "isc"
        }
    ],
    ...
}

The name of the option space in which the sub-options are defined is set in the encapsulate field. The type field is set to "empty", to indicate that this option does not carry any data other than sub-options.

Finally, we can set values for the new options:

"Dhcp6": {
    "option-data": [
        {
            "name": "subopt1",
            "code": 1,
            "space": "isc",
            "data": "2001:db8::abcd"
        },
        }
            "name": "subopt2",
            "code": 2,
            "space": "isc",
            "data": "Hello world"
        },
        {
            "name": "container",
            "code": 102,
            "space": "dhcp6"
        }
    ],
    ...
}

It is possible to create an option which carries some data in addition to the sub-options defined in the encapsulated option space. For example, if the container option from the previous example were required to carry a uint16 value as well as the sub-options, the type value would have to be set to "uint16" in the option definition. (Such an option would then have the following data structure: DHCP header, uint16 value, sub-options.) The value specified with the data parameter — which should be a valid integer enclosed in quotes, e.g. "123" — would then be assigned to the uint16 field in the container option.

Unspecified Parameters for DHCPv6 Option Configuration

In many cases it is not required to specify all parameters for an option configuration, and the default values can be used. However, it is important to understand the implications of not specifying some of them, as it may result in configuration errors. The list below explains the behavior of the server when a particular parameter is not explicitly specified:

• name - the server requires either an option name or an option code to identify an option. If this parameter is unspecified, the option code must be specified.

• code - the server requires either an option name or an option code to identify an option; this parameter may be left unspecified if the name parameter is specified. However, this also requires that the particular option have a definition (either as a standard option or an administrator-created definition for the option using an option-def structure), as the option definition associates an option with a particular name. It is possible to configure an option for which there is no definition (unspecified option format). Configuration of such options requires the use of the option code.

• space - if the option space is unspecified it defaults to dhcp6, which is an option space holding standard DHCPv6 options.

• data - if the option data is unspecified it defaults to an empty value. The empty value is mostly used for the options which have no payload (boolean options), but it is legal to specify empty values for some options which carry variable-length data and for which the specification allows a length of 0. For such options, the data parameter may be omitted in the configuration.

• csv-format - if this value is not specified, the server assumes that the option data is specified as a list of comma-separated values to be assigned to individual fields of the DHCP option.

Controlling the Values Sent for T1 and T2 Times

According to RFC 8415, section 21.4, the recommended T1 and T2 values are 50% and 80% of the preferred lease time, respectively. Kea can be configured to send values that are specified explicitly or that are calculated as percentages of the preferred lease time. The server’s behavior is determined by a combination of configuration parameters, of which T1 and T2 are only two.

The lease’s preferred and valid lifetimes are expressed as triplets with minimum, default, and maximum values using configuration entries:

• min-preferred-lifetime - specifies the minimum preferred lifetime (optional).

• preferred-lifetime - specifies the default preferred lifetime.

• max-preferred-lifetime - specifies the maximum preferred lifetime (optional).

• min-valid-lifetime - specifies the minimum valid lifetime (optional).

• valid-lifetime - specifies the default valid lifetime.

• max-valid-lifetime - specifies the maximum valid lifetime (optional).

Since Kea 1.9.11, these values may be specified within client classes.

When the client does not specify lifetimes, the default is used. A specified lifetime - using the IAADDR or IAPREFIX sub-option with non-zero values - uses these values when they are between the configured minimum and maximum bounds. Values outside the bounds are rounded up or down as needed.

To send specific fixed values, use the following two parameters:

• renew-timer - specifies the value of T1 in seconds.

• rebind-timer - specifies the value of T2 in seconds.

Any value greater than or equal to zero may be specified for T2. T1, if specified, must be less than T2. This flexibility allows a use case where administrators want to suppress client renewals and rebinds by deferring them beyond the lifespan of the lease. This should cause the lease to expire, rather than get renewed by clients. If T1 is specified as larger than T2, T1 is silently set to zero in the outbound IA.

In the great majority of cases, the values should follow this rule: T1 < T2 < preferred lifetime < valid lifetime. Alternatively, both T1 and T2 values can be configured to 0, which is a signal to DHCPv6 clients that they may renew at their own discretion. However, there are known broken client implementations in use that will start renewing immediately. Administrators who plan to use T1=T2=0 values should test first and make sure their clients behave rationally.

In some rare cases there may be a need to disable a client’s ability to renew addresses. This is undesired from a protocol perspective and should be avoided if possible. However, if necessary, administrators can configure the T1 and T2 values to be equal or greater to the valid lifetime. Be advised that this will cause clients to occasionally lose their addresses, which is generally perceived as poor service. However, there may be some rare business cases when this is desired (e.g. when it is desirable to intentionally break long-lasting connections).

Calculation of the values is controlled by the following three parameters:

• calculate-tee-times - when true, T1 and T2 are calculated as percentages of the valid lease time. It defaults to true.

• t1-percent - the percentage of the valid lease time to use for T1. It is expressed as a real number between 0.0 and 1.0 and must be less than t2-percent. The default value is 0.5, per RFC 8415.

• t2-percent - the percentage of the valid lease time to use for T2. It is expressed as a real number between 0.0 and 1.0 and must be greater than t1-percent. The default value is 0.8 per RFC 8415.

Note

If both explicit values are specified and calculate-tee-times is true, the server will use the explicit values. Administrators with a setup where some subnets or shared-networks use explicit values and some use calculated values must not define the explicit values at any level higher than where they will be used. Inheriting them from too high a scope, such as global, will cause them to have values at every level underneath (both shared-networks and subnets), effectively disabling calculated values.

IPv6 Subnet Selection

The DHCPv6 server may receive requests from local (connected to the same subnet as the server) and remote (connected via relays) clients. As the server may have many subnet configurations defined, it must select an appropriate subnet for a given request.

In IPv4, the server can determine which of the configured subnets are local, as there is a reasonable expectation that the server will have a (global) IPv4 address configured on the interface. That assumption is not true in IPv6; the DHCPv6 server must be able to operate while only using link-local addresses. Therefore, an optional interface parameter is available within a subnet definition to designate that a given subnet is local, i.e. reachable directly over the specified interface. For example, a server that is intended to serve a local subnet over eth0 may be configured as follows:

"Dhcp6": {
    "subnet6": [
        {
            "subnet": "2001:db8:beef::/48",
            "pools": [
                 {
                     "pool": "2001:db8:beef::/48"
                 }
             ],
            "interface": "eth0"
        }
    ],
    ...
}

Rapid Commit

The Rapid Commit option, described in RFC 8415, is supported by the Kea DHCPv6 server. However, support is disabled by default. It can be enabled on a per-subnet basis using the rapid-commit parameter as shown below:

"Dhcp6": {
    "subnet6": [
        {
            "subnet": "2001:db8:beef::/48",
            "rapid-commit": true,
            "pools": [
                 {
                     "pool": "2001:db8:beef::1-2001:db8:beef::10"
                 }
             ],
        }
    ],
    ...
}

This setting only affects the subnet for which rapid-commit is set to true. For clients connected to other subnets, the server ignores the Rapid Commit option sent by the client and follows the 4-way exchange procedure, i.e. responds with an Advertise for a Solicit containing a Rapid Commit option.

DHCPv6 Relays

A DHCPv6 server with multiple subnets defined must select the appropriate subnet when it receives a request from a client. For clients connected via relays, two mechanisms are used:

The first uses the linkaddr field in the RELAY_FORW message. The name of this field is somewhat misleading in that it does not contain a link-layer address; instead, it holds an address (typically a global address) that is used to identify a link. The DHCPv6 server checks to see whether the address belongs to a defined subnet and, if it does, that subnet is selected for the client’s request.

The second mechanism is based on interface-id options. While forwarding a client’s message, relays may insert an interface-id option into the message that identifies the interface on the relay that received the message. (Some relays allow configuration of that parameter, but it is sometimes hard-coded and may range from the very simple [e.g. “vlan100”] to the very cryptic; one example seen on real hardware was “ISAM144|299|ipv6|nt:vp:1:110”.) The server can use this information to select the appropriate subnet. The information is also returned to the relay, which then knows the interface to use to transmit the response to the client. For this to work successfully, the relay interface IDs must be unique within the network and the server configuration must match those values.

When configuring the DHCPv6 server, two similarly named parameters can be configured for a subnet:

• interface - defines which local network interface can be used to access a given subnet.

• interface-id - specifies the content of the interface-id option used by relays to identify the interface on the relay to which the response packet is sent.

The two are mutually exclusive; a subnet cannot be reachable both locally (direct traffic) and via relays (remote traffic). Specifying both is a configuration error and the DHCPv6 server will refuse such a configuration.

The following example configuration shows how to specify an interface-id with a value of “vlan123”:

"Dhcp6": {
    "subnet6": [
        {
            "subnet": "2001:db8:beef::/48",
            "pools": [
                 {
                     "pool": "2001:db8:beef::/48"
                 }
             ],
            "interface-id": "vlan123"
        }
    ],
    ...
}

Relay-Supplied Options

RFC 6422 defines a mechanism called Relay-Supplied DHCP Options. In certain cases relay agents are the only entities that may have specific information, and they can insert options when relaying messages from the client to the server. The server then does certain checks and copies those options to the response sent to the client.

There are certain conditions that must be met for the option to be included. First, the server must not provide the option itself; in other words, if both relay and server provide an option, the server always takes precedence. Second, the option must be RSOO-enabled. (RSOO is the “Relay Supplied Options option.”) IANA maintains a list of RSOO-enabled options here. However, there may be cases when system administrators want to echo other options. Kea can be instructed to treat other options as RSOO-enabled; for example, to mark options 110, 120, and 130 as RSOO-enabled, the following syntax should be used:

"Dhcp6": {
    "relay-supplied-options": [ "110", "120", "130" ],
    ...
}

At this time, only option 65 is RSOO-enabled by IANA. This option will always be treated as RSOO-enabled, so there is no need to explicitly mark it. When enabling standard options, it is also possible to use their names rather than their option code, e.g. use dns-servers instead of 23. See ref:dhcp6-std-options-list for the names. In certain cases this may also work for custom options, but due to the nature of the parser code this may be unreliable and should be avoided.

Client Classification in DHCPv6

The DHCPv6 server includes support for client classification. For a deeper discussion of the classification process, see Client Classification.

In certain cases it is useful to configure the server to differentiate between DHCP client types and treat them accordingly. Client classification can be used to modify the behavior of almost any part of DHCP message processing. Kea currently offers three mechanisms that take advantage of client classification in DHCPv6: subnet selection, address pool selection, and DHCP options assignment.

Kea can be instructed to limit access to given subnets based on class information. This is particularly useful for cases where two types of devices share the same link and are expected to be served from two different subnets. The primary use case for such a scenario is cable networks, where there are two classes of devices: the cable modem itself, which should be handed a lease from subnet A; and all other devices behind the modem, which should get leases from subnet B. That segregation is essential to prevent overly curious end-users from playing with their cable modems. For details on how to set up class restrictions on subnets, see Configuring Subnets With Class Information.

When subnets belong to a shared network, the classification applies to subnet selection but not to pools; that is, a pool in a subnet limited to a particular class can still be used by clients which do not belong to the class, if the pool they are expected to use is exhausted. The limit on access based on class information is also available at the address/prefix pool level within a subnet: see Configuring Pools With Class Information. This is useful when segregating clients belonging to the same subnet into different address ranges.

In a similar way, a pool can be constrained to serve only known clients, i.e. clients which have a reservation, using the built-in KNOWN or UNKNOWN classes. Addresses can be assigned to registered clients without giving a different address per reservation: for instance, when there are not enough available addresses. The determination whether there is a reservation for a given client is made after a subnet is selected, so it is not possible to use KNOWN/UNKNOWN classes to select a shared network or a subnet.

The process of classification is conducted in five steps. The first step is to assess an incoming packet and assign it to zero or more classes. The second step is to choose a subnet, possibly based on the class information. When the incoming packet is in the special class DROP, it is dropped and a debug message logged. The next step is to evaluate class expressions depending on the built-in KNOWN/UNKNOWN classes after host reservation lookup, using them for pool/pd-pool selection and assigning classes from host reservations. The list of required classes is then built and each class of the list has its expression evaluated; when it returns true, the packet is added as a member of the class. The last step is to assign options, again possibly based on the class information. More complete and detailed information is available in Client Classification.

There are two main methods of classification. The first is automatic and relies on examining the values in the vendor class options or the existence of a host reservation. Information from these options is extracted, and a class name is constructed from it and added to the class list for the packet. The second method specifies an expression that is evaluated for each packet. If the result is true, the packet is a member of the class.

Note

The new early-global-reservations-lookup global parameter flag enables a lookup for global reservations before the subnet selection phase. This lookup is similar to the general lookup described above with two differences:

• the lookup is limited to global host reservations

• the UNKNOWN class is never set

Note

Care should be taken with client classification, as it is easy for clients that do not meet class criteria to be denied all service.

Defining and Using Custom Classes

The following example shows how to configure a class using an expression and a subnet using that class. This configuration defines the class named Client_enterprise. It is comprised of all clients whose client identifiers start with the given hex string (which would indicate a DUID based on an enterprise id of 0xAABBCCDD). Members of this class will be given an address from 2001:db8:1::0 to 2001:db8:1::FFFF and the addresses of their DNS servers set to 2001:db8:0::1 and 2001:db8:2::1.

"Dhcp6": {
    "client-classes": [
        {
            "name": "Client_enterprise",
            "test": "substring(option[1].hex,0,6) == 0x0002AABBCCDD",
            "option-data": [
                {
                    "name": "dns-servers",
                    "code": 23,
                    "space": "dhcp6",
                    "csv-format": true,
                    "data": "2001:db8:0::1, 2001:db8:2::1"
                }
            ]
        },
        ...
    ],
    "subnet6": [
        {
            "subnet": "2001:db8:1::/64",
            "pools": [ { "pool": "2001:db8:1::-2001:db8:1::ffff" } ],
            "client-class": "Client_enterprise"
        }
    ],
    ...
}

This example shows a configuration using an automatically generated VENDOR_CLASS_ class. The administrator of the network has decided that addresses in the range 2001:db8:1::1 to 2001:db8:1::ffff are to be managed by the DHCP6 server and that only clients belonging to the eRouter1.0 client class are allowed to use that pool.

"Dhcp6": {
    "subnet6": [
        {
            "subnet": "2001:db8:1::/64",
            "pools": [
                 {
                     "pool": "2001:db8:1::-2001:db8:1::ffff"
                 }
             ],
            "client-class": "VENDOR_CLASS_eRouter1.0"
        }
    ],
    ...
}

Required Classification

In some cases it is useful to limit the scope of a class to a shared network, subnet, or pool. There are two parameters which are used to limit the scope of the class by instructing the server to evaluate test expressions when required.

The first one is the per-class only-if-required flag, which is false by default. When it is set to true, the test expression of the class is not evaluated at the reception of the incoming packet but later, and only if the class evaluation is required.

The second is require-client-classes, which takes a list of class names and is valid in shared-network, subnet, and pool scope. Classes in these lists are marked as required and evaluated after selection of this specific shared network/subnet/pool and before output-option processing.

In this example, a class is assigned to the incoming packet when the specified subnet is used:

"Dhcp6": {
    "client-classes": [
       {
           "name": "Client_foo",
           "test": "member('ALL')",
           "only-if-required": true
       },
       ...
    ],
    "subnet6": [
        {
            "subnet": "2001:db8:1::/64"
            "pools": [
                 {
                     "pool": "2001:db8:1::-2001:db8:1::ffff"
                 }
             ],
            "require-client-classes": [ "Client_foo" ],
            ...
        },
        ...
    ],
    ...
}

Required evaluation can be used to express complex dependencies like subnet membership. It can also be used to reverse the precedence; if option-data is set in a subnet, it takes precedence over option-data in a class. If option-data is moved to a required class and required in the subnet, a class evaluated earlier may take precedence.

Required evaluation is also available at shared-network and pool/pd-pool levels. The order in which required classes are considered is: shared-network, subnet, and (pd-)pool, i.e. in the reverse order from the way in which option-data is processed.

DDNS for DHCPv6

As mentioned earlier, kea-dhcp6 can be configured to generate requests to the DHCP-DDNS server (referred to here as “D2”) to update DNS entries. These requests are known as NameChangeRequests or NCRs. Each NCR contains the following information:

1. Whether it is a request to add (update) or remove DNS entries.

2. Whether the change requests forward DNS updates (AAAA records), reverse DNS updates (PTR records), or both.

3. The Fully Qualified Domain Name (FQDN), lease address, and DHCID (information identifying the client associated with the FQDN).

DDNS-related parameters are split into two groups:

1. Connectivity Parameters

   These are parameters which specify where and how kea-dhcp6 connects to and communicates with D2. These parameters can only be specified within the top-level dhcp-ddns section in the kea-dhcp6 configuration. The connectivity parameters are listed below:

   • enable-updates

   • server-ip

   • server-port

   • sender-ip

   • sender-port

   • max-queue-size

   • ncr-protocol

   • ncr-format"

2. Behavioral Parameters

   These parameters influence behavior such as how client host names and FQDN options are handled. They have been moved out of the dhcp-ddns section so that they may be specified at the global, shared-network, and/or subnet levels. Furthermore, they are inherited downward from global to shared-network to subnet. In other words, if a parameter is not specified at a given level, the value for that level comes from the level above it. The behavioral parameters are as follows:

   • ddns-send-updates

   • ddns-override-no-update

   • ddns-override-client-update

   • ddns-replace-client-name"

   • ddns-generated-prefix

   • ddns-qualifying-suffix

   • ddns-update-on-renew

   • ddns-use-conflict-resolution

   • hostname-char-set

   • hostname-char-replacement

Note

For backward compatibility, configuration parsing still recognizes the original behavioral parameters specified in dhcp-ddns, by translating the parameter into its global equivalent. If a parameter is specified both globally and in dhcp-ddns, the latter value is ignored. In either case, a log is emitted explaining what has occurred. Specifying these values within dhcp-ddns is deprecated and support for it will be removed.

The default configuration and values would appear as follows:

"Dhcp6": {
     "dhcp-ddns": {
        // Connectivity parameters
        "enable-updates": false,
         "server-ip": "127.0.0.1",
         "server-port":53001,
         "sender-ip":"",
         "sender-port":0,
         "max-queue-size":1024,
         "ncr-protocol":"UDP",
         "ncr-format":"JSON"
     },

     // Behavioral parameters (global)
     "ddns-send-updates": true,
     "ddns-override-no-update": false,
     "ddns-override-client-update": false,
     "ddns-replace-client-name": "never",
     "ddns-generated-prefix": "myhost",
     "ddns-qualifying-suffix": "",
     "ddns-update-on-renew": false,
     "ddns-use-conflict-resolution": true,
     "hostname-char-set": "",
     "hostname-char-replacement": ""
     ...
}

There are two parameters which determine if kea-dhcp6 can generate DDNS requests to D2: the existing dhcp-ddns:enable-updates parameter, which now only controls whether kea-dhcp6 connects to D2; and the new behavioral parameter, ddns-send-updates, which determines whether DDNS updates are enabled at a given level (i.e. global, shared-network, or subnet). The following table shows how the two parameters function together:

Enabling and disabling DDNS updates

dhcp-ddns: enable-updates	Global ddns-send-updates	Outcome
false (default)	false	no updates at any scope
false	true (default)	no updates at any scope
true	false	updates only at scopes with a local value of true for ddns-enable-updates
true	true	updates at all scopes except those with a local value of false for ddns-enable-updates

Kea 1.9.1 added two new parameters; the first is ddns-update-on-renew. Normally, when leases are renewed, the server only updates DNS if the DNS information for the lease (e.g. FQDN, DNS update direction flags) has changed. Setting ddns-update-on-renew to true instructs the server to always update the DNS information when a lease is renewed, even if its DNS information has not changed. This allows Kea to “self-heal” if it was previously unable to add DNS entries or they were somehow lost by the DNS server.

Note

Setting ddns-update-on-renew to true may impact performance, especially for servers with numerous clients that renew often.

The second parameter added in Kea 1.9.1 is ddns-use-conflict-resolution. The value of this parameter is passed by kea-dhcp6 to D2 with each DNS update request. When true (the default value), D2 employs conflict resolution, as described in RFC 4703, when attempting to fulfill the update request. When false, D2 simply attempts to update the DNS entries per the request, regardless of whether they conflict with existing entries owned by other DHCPv6 clients.

Note

Setting ddns-use-conflict-resolution to false disables the overwrite safeguards that the rules of conflict resolution (from RFC 4703) are intended to prevent. This means that existing entries for an FQDN or an IP address made for Client-A can be deleted or replaced by entries for Client-B. Furthermore, there are two scenarios by which entries for multiple clients for the same key (e.g. FQDN or IP) can be created.

1. Client-B uses the same FQDN as Client-A but a different IP address. In this case, the forward DNS entries (AAAA and DHCID RRs) for Client-A will be deleted as they match the FQDN and new entries for Client-B will be added. The reverse DNS entries (PTR and DHCID RRs) for Client-A, however, will not be deleted as they belong to a different IP address, while new entries for Client-B will still be added.

2. Client-B uses the same IP address as Client-A but a different FQDN. In this case the reverse DNS entries (PTR and DHCID RRs) for Client-A will be deleted as they match the IP address, and new entries for Client-B will be added. The forward DNS entries (AAAA and DHCID RRs) for Client-A, however, will not be deleted, as they belong to a different FQDN, while new entries for Client-B will still be added.

Disabling conflict resolution should be done only after careful review of specific use cases. The best way to avoid unwanted DNS entries is to always ensure lease changes are processed through Kea, whether they are released, expire, or are deleted via the lease-del6 command, prior to reassigning either FQDNs or IP addresses. Doing so causes kea-dhcp6 to generate DNS removal requests to D2.

Note

The DNS entries Kea creates contain a value for TTL (time to live). Since Kea 1.9.3, kea-dhcp6 calculates that value based on RFC 4702, Section 5, which suggests that the TTL value be 1/3 of the lease’s lifetime, with a minimum value of 10 minutes. In earlier versions, the server set the TTL value equal to the lease’s valid lifetime.

DHCP-DDNS Server Connectivity

For NCRs to reach the D2 server, kea-dhcp6 must be able to communicate with it. kea-dhcp6 uses the following configuration parameters to control this communication:

• enable-updates - Enables connectivity to kea-dhcp-ddns such that DDNS updates can be constructed and sent. It must be true for NCRs to be generated and sent to D2. It defaults to false.

• server-ip - This is the IP address on which D2 listens for requests. The default is the local loopback interface at address 127.0.0.1. Either an IPv4 or IPv6 address may be specified.

• server-port - This is the port on which D2 listens for requests. The default value is 53001.

• sender-ip - This is the IP address which kea-dhcp6 uses to send requests to D2. The default value is blank, which instructs kea-dhcp6 to select a suitable address.

• sender-port - This is the port which kea-dhcp6 uses to send requests to D2. The default value of 0 instructs kea-dhcp6 to select a suitable port.

• max-queue-size - This is the maximum number of requests allowed to queue while waiting to be sent to D2. This value guards against requests accumulating uncontrollably if they are being generated faster than they can be delivered. If the number of requests queued for transmission reaches this value, DDNS updating is turned off until the queue backlog has been sufficiently reduced. The intent is to allow the kea-dhcp6 server to continue lease operations without running the risk that its memory usage grows without limit. The default value is 1024.

• ncr-protocol - This specifies the socket protocol to use when sending requests to D2. Currently only UDP is supported.

• ncr-format - This specifies the packet format to use when sending requests to D2. Currently only JSON format is supported.

By default, kea-dhcp-ddns is assumed to be running on the same machine as kea-dhcp6, and all of the default values mentioned above should be sufficient. If, however, D2 has been configured to listen on a different address or port, these values must be altered accordingly. For example, if D2 has been configured to listen on 2001:db8::5 port 900, the following configuration is required:

"Dhcp6": {
    "dhcp-ddns": {
        "server-ip": "2001:db8::5",
        "server-port": 900,
        ...
    },
    ...
}

When Does the kea-dhcp6 Server Generate a DDNS Request?

kea-dhcp6 follows the behavior prescribed for DHCP servers in RFC 4704. It is important to keep in mind that kea-dhcp6 makes the initial decision of when and what to update and forwards that information to D2 in the form of NCRs. Carrying out the actual DNS updates and dealing with such things as conflict resolution are within the purview of D2 itself (see The DHCP-DDNS Server). This section describes when kea-dhcp6 generates NCRs and the configuration parameters that can be used to influence this decision. It assumes that the enable-updates parameter is true.

Note

Currently the interface between kea-dhcp6 and D2 only supports requests which update DNS entries for a single IP address. If a lease grants more than one address, kea-dhcp6 creates the DDNS update request for only the first of these addresses.

In general, kea-dhcp6 generates DDNS update requests when:

1. A new lease is granted in response to a DHCPREQUEST;

2. An existing lease is renewed but the FQDN associated with it has changed; or

3. An existing lease is released in response to a DHCPRELEASE.

In the second case, lease renewal, two DDNS requests are issued: one request to remove entries for the previous FQDN, and a second request to add entries for the new FQDN. In the third case, a lease release - a single DDNS request - to remove its entries will be made.

As for the first case, the decisions involved when granting a new lease are more complex. When a new lease is granted, kea-dhcp6 generates a DDNS update request only if the DHCPREQUEST contains the FQDN option (code 39). By default, kea-dhcp6 respects the FQDN N and S flags specified by the client as shown in the following table:

Default FQDN flag behavior

Client Flags:N-S	Client Intent	Server Response	Server Flags:N-S-O
0-0	Client wants to do forward updates, server should do reverse updates	Server generates reverse-only request	1-0-0
0-1	Server should do both forward and reverse updates	Server generates request to update both directions	0-1-0
1-0	Client wants no updates done	Server does not generate a request	1-0-0

The first row in the table above represents “client delegation.” Here the DHCP client states that it intends to do the forward DNS updates and the server should do the reverse updates. By default, kea-dhcp6 honors the client’s wishes and generates a DDNS request to D2 to update only reverse DNS data. The parameter ddns-override-client-update can be used to instruct the server to override client delegation requests. When this parameter is true, kea-dhcp6 disregards requests for client delegation and generates a DDNS request to update both forward and reverse DNS data. In this case, the N-S-O flags in the server’s response to the client will be 0-1-1 respectively.

(Note that the flag combination N=1, S=1 is prohibited according to RFC 4702. If such a combination is received from the client, the packet will be dropped by kea-dhcp6.)

To override client delegation, set the following values in the configuration file:

"Dhcp6": {
    ...
    "ddns-override-client-update": true,
    ...
}

The third row in the table above describes the case in which the client requests that no DNS updates be done. The parameter ddns-override-no-update can be used to instruct the server to disregard the client’s wishes. When this parameter is true, kea-dhcp6 generates DDNS update requests to kea-dhcp-ddns even if the client requests that no updates be done. The N-S-O flags in the server’s response to the client will be 0-1-1.

To override client delegation, issue the following commands:

"Dhcp6": {
    ...
    "ddns-override-no-update": true,
    ...
}

kea-dhcp6 Name Generation for DDNS Update Requests

Each NameChangeRequest must of course include the fully qualified domain name whose DNS entries are to be affected. kea-dhcp6 can be configured to supply a portion or all of that name, based upon what it receives from the client in the DHCPREQUEST.

The default rules for constructing the FQDN that will be used for DNS entries are:

1. If the DHCPREQUEST contains the client FQDN option, take the candidate name from there.

2. If the candidate name is a partial (i.e. unqualified) name, then add a configurable suffix to the name and use the result as the FQDN.

3. If the candidate name provided is empty, generate an FQDN using a configurable prefix and suffix.

4. If the client provides neither option, then take no DNS action.

These rules can be amended by setting the ddns-replace-client-name parameter, which provides the following modes of behavior:

• never - use the name the client sent. If the client sent no name, do not generate one. This is the default mode.

• always - replace the name the client sent. If the client sent no name, generate one for the client.

• when-present - replace the name the client sent. If the client sent no name, do not generate one.

• when-not-present - use the name the client sent. If the client sent no name, generate one for the client.

Note

In early versions of Kea, this parameter was a boolean and permitted only values of true and false. Boolean values have been deprecated and are no longer accepted. Administrators currently using booleans must replace them with the desired mode name. A value of true maps to when-present, while false maps to never.

For example, to instruct kea-dhcp6 to always generate the FQDN for a client, set the parameter ddns-replace-client-name to always as follows:

"Dhcp6": {
    ...
    "ddns-replace-client-name": "always",
    ...
}

The prefix used in the generation of an FQDN is specified by the ddns-generated-prefix parameter. The default value is “myhost”. To alter its value, simply set it to the desired string:

"Dhcp6": {
    ...
    "ddns-generated-prefix": "another.host",
    ...
}

The suffix used when generating an FQDN, or when qualifying a partial name, is specified by the ddns-qualifying-suffix parameter. This parameter has no default value; thus, it is mandatory when DDNS updates are enabled. To set its value simply set it to the desired string:

"Dhcp6": {
    ...
    "ddns-qualifying-suffix": "foo.example.org",
    ...
}

When qualifying a partial name, kea-dhcp6 constructs the name in the format:

[candidate-name].[ddns-qualifying-suffix].

where candidate-name is the partial name supplied in the DHCPREQUEST. For example, if the FQDN domain name value is “some-computer” and the ddns-qualifying-suffix is “example.com”, the generated FQDN is:

some-computer.example.com.

When generating the entire name, kea-dhcp6 constructs the name in the format:

[ddns-generated-prefix]-[address-text].[ddns-qualifying-suffix].

where address-text is simply the lease IP address converted to a hyphenated string. For example, if the lease address is 3001:1::70E, the qualifying suffix is “example.com”, and the default value is used for ddns-generated-prefix, the generated FQDN is:

myhost-3001-1--70E.example.com.

Sanitizing Client FQDN Names

Some DHCP clients may provide values in the name component of the FQDN option (option code 39) that contain undesirable characters. It is possible to configure kea-dhcp6 to sanitize these values. The most typical use case is ensuring that only characters that are permitted by RFC 1035 be included: A-Z, a-z, 0-9, and “-”. This may be accomplished with the following two parameters:

• hostname-char-set - a regular expression describing the invalid character set. This can be any valid, regular expression using POSIX extended expression syntax. Embedded nulls (0x00) are always considered an invalid character to be replaced (or omitted). The default is "[^A-Za-z0-9.-]". This matches any character that is not a letter, digit, dot, hyphen, or null.

• hostname-char-replacement - a string of zero or more characters with which to replace each invalid character in the host name. An empty string causes invalid characters to be OMITTED rather than replaced. The default is "".

The following configuration replaces anything other than a letter, digit, dot, or hyphen with the letter “x”:

"Dhcp6": {
    ...
    "hostname-char-set": "[^A-Za-z0-9.-]",
    "hostname-char-replacement": "x",
    ...
}

Thus, a client-supplied value of “myhost-$[123.org” would become “myhost-xx123.org”. Sanitizing is performed only on the portion of the name supplied by the client, and it is performed before applying a qualifying suffix (if one is defined and needed).

Note

Name sanitizing is meant to catch the more common cases of invalid characters through a relatively simple character-replacement scheme. It is difficult to devise a scheme that works well in all cases. Administrators who find they have clients with odd corner cases of character combinations that cannot be readily handled with this mechanism should consider writing a hook that can carry out sufficiently complex logic to address their needs.

Do not include dots in the hostname-char-set expression. When scrubbing FQDNs, dots are treated as delimiters and used to separate the option value into individual domain labels that are scrubbed and then re-assembled.

If clients are sending values that differ only by characters considered as invalid by the hostname-char-set, be aware that scrubbing them will yield identical values. In such cases, DDNS conflict rules will permit only one of them to register the name.

Finally, given the latitude clients have in the values they send, it is virtually impossible to guarantee that a combination of these two parameters will always yield a name that is valid for use in DNS. For example, using an empty value for hostname-char-replacement could yield an empty domain label within a name, if that label consists only of invalid characters.

Note

It is possible to specify hostname-char-set and/or hostname-char-replacement at the global scope. This allows host names to be sanitized without requiring a dhcp-ddns entry. When a hostname-char parameter is defined at both the global scope and in a dhcp-ddns entry, the second (local) value is used.

DHCPv4-over-DHCPv6: DHCPv6 Side

The support of DHCPv4-over-DHCPv6 transport is described in RFC 7341 and is implemented using cooperating DHCPv4 and DHCPv6 servers. This section is about the configuration of the DHCPv6 side (the DHCPv4 side is described in DHCPv4-over-DHCPv6: DHCPv4 Side).

Note

DHCPv4-over-DHCPv6 support is experimental and the details of the inter-process communication may change; for instance, the support of port relay (RFC 8357) introduced an incompatible change. Both the DHCPv4 and DHCPv6 sides should be running the same version of Kea.

There is only one specific parameter for the DHCPv6 side: dhcp4o6-port, which specifies the first of the two consecutive ports of the UDP sockets used for the communication between the DHCPv6 and DHCPv4 servers. The DHCPv6 server is bound to ::1 on port and connected to ::1 on port + 1.

Two other configuration entries are generally required: unicast traffic support (see Unicast Traffic Support) and the DHCP 4o6 server address option (name “dhcp4o6-server-addr”, code 88).

ISC tested the following configuration:

{

# DHCPv6 conf
"Dhcp6": {

    "interfaces-config": {
        "interfaces": [ "eno33554984/2001:db8:1:1::1" ]
    },

    "lease-database": {
        "type": "memfile",
        "name": "leases6"
    },

    "preferred-lifetime": 3000,
    "valid-lifetime": 4000,
    "renew-timer": 1000,
    "rebind-timer": 2000,

    "subnet6": [ {
        "subnet": "2001:db8:1:1::/64",
        "interface": "eno33554984",
        "pools": [ { "pool": "2001:db8:1:1::1:0/112" } ]
    } ],

    "dhcp4o6-port": 6767,

    "option-data": [ {
        "name": "dhcp4o6-server-addr",
        "code": 88,
        "space": "dhcp6",
        "csv-format": true,
        "data": "2001:db8:1:1::1"
    } ],


    "loggers": [ {
        "name": "kea-dhcp6",
        "output_options": [ {
            "output": "/tmp/kea-dhcp6.log"
        } ],
        "severity": "DEBUG",
        "debuglevel": 0
    } ]
}

}

Note

Relayed DHCPv4-QUERY DHCPv6 messages are not supported.

Sanity Checks in DHCPv6

An important aspect of a well-running DHCP system is an assurance that the data remains consistent; however, in some cases it may be convenient to tolerate certain inconsistent data. For example, a network administrator who temporarily removes a subnet from a configuration would not want all the leases associated with it to disappear from the lease database. Kea has a mechanism to implement sanity checks for situations like this.

Kea supports a configuration scope called sanity-checks. It currently allows only a single parameter, called lease-checks, which governs the verification carried out when a new lease is loaded from a lease file. This mechanism permits Kea to attempt to correct inconsistent data.

Every subnet has a subnet-id value; this is how Kea internally identifies subnets. Each lease has a subnet-id parameter as well, which identifies the subnet it belongs to. However, if the configuration has changed, it is possible that a lease could exist with a subnet-id but without any subnet that matches it. Also, it is possible that the subnet’s configuration has changed and the subnet-id now belongs to a subnet that does not match the lease.

Kea’s corrective algorithm first checks to see if there is a subnet with the subnet-id specified by the lease. If there is, it verifies whether the lease belongs to that subnet. If not, depending on the lease-checks setting, the lease is discarded, a warning is displayed, or a new subnet is selected for the lease that matches it topologically.

Since delegated prefixes do not have to belong to a subnet in which they are offered, there is no way to implement such a mechanism for IPv6 prefixes. As such, the mechanism works for IPv6 addresses only.

There are five levels which are supported:

• none - do no special checks; accept the lease as is.

• warn - if problems are detected display a warning, but accept the lease data anyway. This is the default value.

• fix - if a data inconsistency is discovered, try to correct it. If the correction is not successful, insert the incorrect data anyway.

• fix-del - if a data inconsistency is discovered, try to correct it. If the correction is not successful, reject the lease. This setting ensures the data’s correctness, but some incorrect data may be lost. Use with care.

• del - if any inconsistency is detected, reject the lease. This is the strictest mode; use with care.

This feature is currently implemented for the memfile backend. The sanity check applies to the lease database in memory, not to the lease file, i.e. inconsistent leases will stay in the lease file.

An example configuration that sets this parameter looks as follows:

"Dhcp6": {
    "sanity-checks": {
        "lease-checks": "fix-del"
    },
    ...
}

Storing Extended Lease Information

To support such features as DHCPv6 Reconfigure (RFC 3315) and Leasequery (RFC 5007), additional information must be stored with each lease. Because the amount of information stored for each lease has ramifications in terms of performance and system resource consumption, storage of this additional information is configurable through the store-extended-info parameter. It defaults to false and may be set at the global, shared-network, and subnet levels.

"Dhcp6": {
    "store-extended-info": true,
    ...
}

When set to true, information relevant to the DHCPv6 query (e.g. REQUEST, RENEW, or REBIND) asking for the lease is added into the lease’s user-context as a map element labeled “ISC”. Currently, the information contained in the map is a list of relays, one for each relay message layer that encloses the client query. The lease’s user-context for a two-hop query might look something like this (shown pretty-printed for clarity):

{
    "ISC": {
        "relays": [
        {
            "hop": 2,
            "link": "2001:db8::1",
            "peer": "2001:db8::2"
        },
        {
            "hop": 1,
            "link": "2001:db8::3",
            "options": "0x00C800080102030405060708",
            "peer": "2001:db8::4"
        }]
    }
}

Note

It is possible that other hook libraries are already using user-context. Enabling store-extended-info should not interfere with any other user-context content, as long as it does not also use an element labeled “ISC”. In other words, user-context is intended to be a flexible container serving multiple purposes. As long as no other purpose also writes an “ISC” element to user-context there should not be a conflict.

Multi-Threading Settings

The Kea server can be configured to process packets in parallel using multiple threads. These settings can be found under the multi-threading structure and are represented by:

• enable-multi-threading - use multiple threads to process packets in parallel. The default is false.

• thread-pool-size - specify the number of threads to process packets in parallel. It may be set to 0 (auto-detect), or any positive number explicitly sets the thread count. The default is 0.

• packet-queue-size - specify the size of the queue used by the thread pool to process packets. It may be set to 0 (unlimited), or any positive number explicitly sets the queue size. The default is 64.

An example configuration that sets these parameters looks as follows:

"Dhcp6": {
    "multi-threading": {
       "enable-multi-threading": true,
       "thread-pool-size": 4,
       "packet-queue-size": 16
    }
    ...
}

Multi-Threading Settings With Different Database Backends

Both kea-dhcp4 and kea-dhcp6 are tested by ISC to determine which settings give the best performance. Although this section describes our results, they are merely recommendations and are very dependent on the particular hardware used for testing. We strongly advise that administrators run their own performance tests.

A full report of performance results for the latest stable Kea version can be found here. This includes hardware and test scenario descriptions, as well as current results.

After enabling multi-threading, the number of threads is set by the thread-pool-size parameter. Results from our tests show that best configurations for kea-dhcp6 are:

• thread-pool-size: 4 when using memfile for storing leases.

• thread-pool-size: 12 or more when using mysql for storing leases.

• thread-pool-size: 6 when using postgresql.

Another very important parameter is packet-queue-size; in our tests we used it as a multiplier of thread-pool-size. The actual setting strongly depends on thread-pool-size.

We saw the best results in our tests with the following settings:

• packet-queue-size: 150 * thread-pool-size when using memfile for storing leases; in our case it was 150 * 4 = 600. This means that at any given time, up to 600 packets could be queued.

• packet-queue-size: 200 * thread-pool-size when using mysql for storing leases; in our case it was 200 * 12 = 2400. This means that up to 2400 packets could be queued.

• packet-queue-size: 11 * thread-pool-size when using postgresql for storing leases; in our case it was 11 * 6 = 66.

Lease Caching

Clients that attempt multiple renewals in a short period can cause the server to update and write to the database frequently, resulting in a performance impact on the server. The cache parameters instruct the DHCP server to avoid updating leases too frequently, thus avoiding this behavior. Instead, the server assigns the same lease (i.e. reuses it) with no modifications except for CLTT (Client Last Transmission Time), which does not require disk operations.

The two parameters are the cache-threshold double and the cache-max-age integer; they have no default setting, i.e. the lease caching feature must be explicitly enabled. These parameters can be configured at the global, shared-network and subnet levels. The subnet level has the precedence over the shared-network level, while the global level is used as a last resort. For example:

"subnet6": [
    {
        "subnet": "2001:db8:1:1::/64",
        "pools": [ { "pool": "2001:db8:1:1::1:0/112" } ],
        "cache-threshold": .25,
        "cache-max-age": 600,
        "valid-lifetime": 2000,
        ...
    }
],

When an already-assigned lease can fulfill a client query:

• any important change, e.g. for DDNS parameter, hostname, or preferred or valid lifetime reduction, makes the lease not reusable.

• lease age, i.e. the difference between the creation or last modification time and the current time, is computed (elapsed duration).

• if cache-max-age is explicitly configured, it is compared with the lease age; leases that are too old are not reusable. This means that the value 0 for cache-max-age disables the lease cache feature.

• if cache-threshold is explicitly configured and is between 0.0 and 1.0, it expresses the percentage of the lease valid lifetime which is allowed for the lease age. Values below and including 0.0 and values greater than 1.0 disable the lease cache feature.

In our example, a lease with a valid lifetime of 2000 seconds can be reused if it was committed less than 500 seconds ago. With a lifetime of 3000 seconds, a maximum age of 600 seconds applies.

In outbound client responses (e.g. DHCPV6_REPLY messages), the used preferred and valid lifetimes are the reusable values, i.e. the expiration dates do not change.

Host Reservations in DHCPv6

There are many cases where it is useful to provide a configuration on a per-host basis. The most obvious one is to reserve a specific, static IPv6 address or/and prefix for exclusive use by a given client (host); the returning client receives the same address and/or prefix every time, and other clients will never get that address. Host reservations are also convenient when a host has specific requirements, e.g. a printer that needs additional DHCP options or a cable modem that needs specific parameters. Yet another possible use case is to define unique names for hosts.

There may be cases when a new reservation has been made for a client for an address or prefix currently in use by another client. We call this situation a “conflict.” These conflicts get resolved automatically over time, as described in subsequent sections. Once a conflict is resolved, the correct client will receive the reserved configuration when it renews.

Host reservations are defined as parameters for each subnet. Each host must be identified by either DUID or its hardware/MAC address; see MAC/Hardware Addresses in DHCPv6 for details. There is an optional reservations array in the subnet6 structure; each element in that array is a structure that holds information about reservations for a single host. In particular, the structure has an identifier that uniquely identifies a host. In the DHCPv6 context, the identifier is usually a DUID, but it can also be a hardware or MAC address. One or more addresses or prefixes may also be specified, and it is possible to specify a hostname and DHCPv6 options for a given host.

Note

The reserved address must be within the subnet. This does not apply to reserved prefixes.

The following example shows how to reserve addresses and prefixes for specific hosts:

"subnet6": [
    {
        "subnet": "2001:db8:1::/48",
        "pools": [ { "pool": "2001:db8:1::/80" } ],
        "pd-pools": [
            {
                "prefix": "2001:db8:1:8000::",
                "prefix-len": 48,
                "delegated-len": 64
            }
        ],
        "reservations": [
            {
                "duid": "01:02:03:04:05:0A:0B:0C:0D:0E",
                "ip-addresses": [ "2001:db8:1::100" ]
            },
            {
                "hw-address": "00:01:02:03:04:05",
                "ip-addresses": [ "2001:db8:1::101", "2001:db8:1::102" ]
            },
            {
                "duid": "01:02:03:04:05:06:07:08:09:0A",
                "ip-addresses": [ "2001:db8:1::103" ],
                "prefixes": [ "2001:db8:2:abcd::/64" ],
                "hostname": "foo.example.com"
            }
        ]
    }
]

This example includes reservations for three different clients. The first reservation is for the address 2001:db8:1::100, for a client using DUID 01:02:03:04:05:0A:0B:0C:0D:0E. The second reservation is for two addresses, 2001:db8:1::101 and 2001:db8:1::102, for a client using MAC address 00:01:02:03:04:05. Lastly, address 2001:db8:1::103 and prefix 2001:db8:2:abcd::/64 are reserved for a client using DUID 01:02:03:04:05:06:07:08:09:0A. The last reservation also assigns a hostname to this client.

DHCPv6 allows a single client to lease multiple addresses and multiple prefixes at the same time. Therefore ip-addresses and prefixes are plural and are actually arrays. When the client sends multiple IA options (IA_NA or IA_PD), each reserved address or prefix is assigned to an individual IA of the appropriate type. If the number of IAs of a specific type is lower than the number of reservations of that type, the number of reserved addresses or prefixes assigned to the client is equal to the number of IA_NAs or IA_PDs sent by the client; that is, some reserved addresses or prefixes are not assigned. However, they still remain reserved for this client and the server will not assign them to any other client. If the number of IAs of a specific type sent by the client is greater than the number of reserved addresses or prefixes, the server will try to assign all reserved addresses or prefixes to the individual IAs and dynamically allocate addresses or prefixes to the remaining IAs. If the server cannot assign a reserved address or prefix because it is in use, the server will select the next reserved address or prefix and try to assign it to the client. If the server subsequently finds that there are no more reservations that can be assigned to the client at that moment, the server will try to assign leases dynamically.

Making a reservation for a mobile host that may visit multiple subnets requires a separate host definition in each subnet that host is expected to visit. It is not possible to define multiple host definitions with the same hardware address in a single subnet. Multiple host definitions with the same hardware address are valid if each is in a different subnet. The reservation for a given host should include only one identifier, either DUID or hardware address; defining both for the same host is considered a configuration error.

Adding host reservations incurs a performance penalty. In principle, when a server that does not support host reservation responds to a query, it needs to check whether there is a lease for a given address being considered for allocation or renewal. The server that does support host reservation has to perform additional checks: not only whether the address is currently used (i.e., if there is a lease for it), but also whether the address could be used by someone else (i.e., if there is a reservation for it). That additional check incurs extra overhead.

Address/Prefix Reservation Types

In a typical Kea scenario there is an IPv6 subnet defined, with a certain part of it dedicated for dynamic address allocation by the DHCPv6 server. There may be an additional address space defined for prefix delegation. Those dynamic parts are referred to as dynamic pools, address and prefix pools, or simply pools. In principle, a host reservation can reserve any address or prefix that belongs to the subnet. The reservations that specify addresses that belong to configured pools are called “in-pool reservations.” In contrast, those that do not belong to dynamic pools are called “out-of-pool reservations.” There is no formal difference in the reservation syntax and both reservation types are handled uniformly.

Kea supports global host reservations. These are reservations that are specified at the global level within the configuration and that do not belong to any specific subnet. Kea still matches inbound client packets to a subnet as before, but when the subnet’s reservation mode is set to “global”, Kea looks for host reservations only among the global reservations defined. Typically, such reservations would be used to reserve hostnames for clients which may move from one subnet to another.

Note

Global reservations, while useful in certain circumstances, have aspects that must be given due consideration when using them. Please see Conflicts in DHCPv6 Reservations for more details.

Note

Since Kea 1.9.1, reservation mode has been replaced by three boolean flags, reservations-global, reservations-in-subnet and reservations-out-of-pool, which allow the configuration of host reservations both globally and in a subnet. In such cases a subnet host reservation has preference over a global reservation when both exist for the same client.

Conflicts in DHCPv6 Reservations

As reservations and lease information are stored separately, conflicts may arise. Consider the following series of events: the server has configured the dynamic pool of addresses from the range of 2001:db8::10 to 2001:db8::20. Host A requests an address and gets 2001:db8::10. Now the system administrator decides to reserve address 2001:db8::10 for Host B. In general, reserving an address that is currently assigned to someone else is not recommended, but there are valid use cases where such an operation is warranted.

The server now has a conflict to resolve. If Host B boots up and requests an address, the server cannot immediately assign the reserved address 2001:db8::10. A naive approach would to be immediately remove the lease for Host A and create a new one for Host B. That would not solve the problem, though, because as soon as Host B gets the address, it will detect that the address is already in use (by Host A) and will send a DHCPDECLINE message. Therefore, in this situation, the server has to temporarily assign a different address from the dynamic pool (not matching what has been reserved) to Host B.

When Host A renews its address, the server will discover that the address being renewed is now reserved for someone else - Host B. The server will remove the lease for 2001:db8::10, select a new address, and create a new lease for it. It will send two addresses in its response: the old address, with the lifetime set to 0 to explicitly indicate that it is no longer valid; and the new address, with a non-zero lifetime. When Host B tries to renew its temporarily assigned address, the server will detect that the existing lease does not match the reservation, so it will release the current address Host B has and will create a new lease matching the reservation. As before, the server will send two addresses: the temporarily assigned one with a zero lifetime, and the new one that matches the reservation with the proper lifetime set.

This recovery will succeed, even if other hosts attempt to get the reserved address. If Host C requests the address 2001:db8::10 after the reservation is made, the server will propose a different address.

This recovery mechanism allows the server to fully recover from a case where reservations conflict with existing leases; however, this procedure takes roughly as long as the value set for renew-timer. The best way to avoid such a recovery is not to define new reservations that conflict with existing leases. Another recommendation is to use out-of-pool reservations; if the reserved address does not belong to a pool, there is no way that other clients can get it.

Note

The conflict-resolution mechanism does not work for global reservations. Although the global address reservations feature may be useful in certain settings, it is generally recommended not to use global reservations for addresses. Administrators who do choose to use global reservations must manually ensure that the reserved addresses are not in dynamic pools.

Reserving a Hostname

When the reservation for a client includes the hostname, the server assigns this hostname to the client and sends it back in the Client FQDN option, if the client included the Client FQDN option in its message to the server. The reserved hostname always takes precedence over the hostname supplied by the client (via the FQDN option) or the autogenerated (from the IPv6 address) hostname.

The server qualifies the reserved hostname with the value of the ddns-qualifying-suffix parameter. For example, the following subnet configuration:

"subnet6": [
    {
        "subnet": "2001:db8:1::/48",
        "pools": [ { "pool": "2001:db8:1::/80" } ],
        "ddns-qualifying-suffix": "example.isc.org.",
        "reservations": [
            {
                "duid": "01:02:03:04:05:0A:0B:0C:0D:0E",
                "ip-addresses": [ "2001:db8:1::100" ]
                "hostname": "alice-laptop"
            }
        ]
    }
],
"dhcp-ddns": {
    "enable-updates": true
}

will result the “alice-laptop.example.isc.org.” hostname being assigned to the client using the DUID “01:02:03:04:05:0A:0B:0C:0D:0E”. If the ddns-qualifying-suffix is not specified, the default (empty) value will be used, and in this case the value specified as a hostname will be treated as a fully qualified name. Thus, by leaving the ddns-qualifying-suffix empty it is possible to qualify hostnames for different clients with different domain names:

"subnet6": [
    {
        "subnet": "2001:db8:1::/48",
        "pools": [ { "pool": "2001:db8:1::/80" } ],
        "reservations": [
            {
                "duid": "01:02:03:04:05:0A:0B:0C:0D:0E",
                "ip-addresses": [ "2001:db8:1::100" ]
                "hostname": "mark-desktop.example.org."
            }
        ]
    }
],
"dhcp-ddns": {
    "enable-updates": true,
}

The above example results in the assignment of the “mark-desktop.example.org.” hostname to the client using the DUID “01:02:03:04:05:0A:0B:0C:0D:0E”.

Including Specific DHCPv6 Options in Reservations

Kea offers the ability to specify options on a per-host basis. These options follow the same rules as any other options. These can be standard options (see Standard DHCPv6 Options), custom options (see Custom DHCPv6 Options), or vendor-specific options (see DHCPv6 Vendor-Specific Options). The following example demonstrates how standard options can be defined.

"reservations": [
{
   "duid": "01:02:03:05:06:07:08",
   "ip-addresses": [ "2001:db8:1::2" ],
    "option-data": [
    {
        "option-data": [ {
            "name": "dns-servers",
            "data": "3000:1::234"
        },
        {
            "name": "nis-servers",
            "data": "3000:1::234"
        }
    } ]
} ]

Vendor-specific options can be reserved in a similar manner:

"reservations": [
{
    "duid": "aa:bb:cc:dd:ee:ff",
    "ip-addresses": [ "2001:db8::1" ],
    "option-data": [
    {
        "name": "vendor-opts",
        "data": 4491
    },
    {
        "name": "tftp-servers",
        "space": "vendor-4491",
        "data": "3000:1::234"
    } ]
} ]

Options defined at the host level have the highest priority. In other words, if there are options defined with the same type on global, subnet, class, and host levels, the host-specific values are used.

Reserving Client Classes in DHCPv6

Using Expressions in Classification explains how to configure the server to assign classes to a client, based on the content of the options that this client sends to the server. Host reservation mechanisms also allow for the static assignment of classes to clients. The definitions of these classes are placed in the Kea configuration file or a database. The following configuration snippet shows how to specify that a client belongs to the classes reserved-class1 and reserved-class2. Those classes are associated with specific options sent to the clients which belong to them.

{
    "client-classes": [
    {
       "name": "reserved-class1",
       "option-data": [
       {
           "name": "dns-servers",
           "data": "2001:db8:1::50"
       }
       ]
    },
    {
       "name": "reserved-class2",
       "option-data": [
       {
           "name": "nis-servers",
           "data": "2001:db8:1::100"
       }
       ]
    }
    ],
    "subnet6": [
    {   "pools": [ { "pool": "2001:db8:1::/64" } ],
        "subnet": "2001:db8:1::/48",
        "reservations": [
        {
            "duid": "01:02:03:04:05:06:07:08",

            "client-classes": [ "reserved-class1", "reserved-class2" ]

        }
        ]
    } ]
 }

In some cases the host reservations can be used in conjunction with client classes specified within the Kea configuration. In particular, when a host reservation exists for a client within a given subnet, the “KNOWN” built-in class is assigned to the client. Conversely, when there is no static assignment for the client, the “UNKNOWN” class is assigned to the client. Class expressions within the Kea configuration file can refer to “KNOWN” or “UNKNOWN” classes using the “member” operator. For example:

{
    "client-classes": [
        {
            "name": "dependent-class",
            "test": "member('KNOWN')",
            "only-if-required": true
        }
    ]
}

The only-if-required parameter is needed here to force evaluation of the class after the lease has been allocated and thus the reserved class has been also assigned.

Note

The classes specified in non-global host reservations are assigned to the processed packet after all classes with the only-if-required parameter set to false have been evaluated. This means that these classes must not depend on the statically assigned classes from the host reservations. If such a dependency is needed, the only-if-required must be set to true for the dependent classes. Such classes are evaluated after the static classes have been assigned to the packet. This, however, imposes additional configuration overhead, because all classes marked as only-if-required must be listed in the require-client-classes list for every subnet where they are used.

Note

Client classes specified within the Kea configuration file may depend on the classes specified within the global host reservations. In such a case the only-if-required parameter is not needed. Refer to the Pool Selection with Client Class Reservations and Subnet Selection with Client Class Reservations for specific use cases.

Storing Host Reservations in MySQL or PostgreSQL

Kea can store host reservations in MySQL or PostgreSQL. See Hosts Storage for information on how to configure Kea to use reservations stored in MySQL or PostgreSQL. Kea provides a dedicated hook for managing reservations in a database; section host_cmds: Host Commands provides detailed information. The Kea wiki provides some examples of how to conduct common host reservation operations.

Note

In Kea, the maximum length of an option specified per-host is arbitrarily set to 4096 bytes.

Fine-Tuning DHCPv6 Host Reservation

The host reservation capability introduces additional restrictions for the allocation engine (the component of Kea that selects an address for a client) during lease selection and renewal. In particular, three major checks are necessary. First, when selecting a new lease, it is not sufficient for a candidate lease to simply not be in use by another DHCP client; it also must not be reserved for another client. Similarly, when renewing a lease, an additional check must be performed to see whether the address being renewed is reserved for another client. Finally, when a host renews an address or a prefix, the server must check whether there is a reservation for this host, which would mean the existing (dynamically allocated) address should be revoked and the reserved one be used instead.

Some of those checks may be unnecessary in certain deployments, and not performing them may improve performance. The Kea server provides the reservation-mode configuration parameter to select the types of reservations allowed for a particular subnet. Each reservation type has different constraints for the checks to be performed by the server when allocating or renewing a lease for the client. Allowed values are:

• all - enables both in-pool and out-of-pool host reservation types. This setting is the default value, and is the safest and most flexible. However, as all checks are conducted, it is also the slowest. It does not check against global reservations.

• out-of-pool - allows only out-of-pool host reservations. With this setting in place, the server assumes that all host reservations are for addresses that do not belong to the dynamic pool. Therefore, it can skip the reservation checks when dealing with in-pool addresses, thus improving performance. Do not use this mode if any reservations use in-pool addresses. Caution is advised when using this setting; Kea does not sanity-check the reservations against reservation-mode and misconfiguration may cause problems.

• global - allows only global host reservations. With this setting in place, the server searches for reservations for a client only among the defined global reservations. If an address is specified, the server skips the reservation checks carried out in other modes, thus improving performance. Caution is advised when using this setting; Kea does not sanity-check the reservations when global is set, and misconfiguration may cause problems.

• disabled - host reservation support is disabled. As there are no reservations, the server skips all checks. Any reservations defined are completely ignored. As checks are skipped, the server may operate faster in this mode.

Since Kea 1.9.1, the reservation-mode parameter is replaced by the reservations-global, reservations-in-subnet and reservations-out-of-pool flags. The flags can be activated independently and can produce various combinations, some of them being unsupported by the deprecated reservation-mode.

The reservation-mode parameter can be specified at:

• global level: .Dhcp6["reservation-mode"] (lowest priority: gets overridden by all others)

• subnet level: .Dhcp6.subnet6[]["reservation-mode"] (low priority)

• shared-network level: .Dhcp6["shared-networks"][]["reservation-mode"] (high priority)

• shared-network subnet-level: .Dhcp6["shared-networks"][].subnet6[]["reservation-mode"] (highest priority: overrides all others)

To decide which "reservation-mode" to choose, the following decision diagram may be useful:

                              O
                              |
                              v
+-----------------------------+------------------------------+
|         Is per-host configuration needed, such as          |
|                reserving specific addresses,               |
|               assigning specific options or                |
| assigning packets to specific classes on per-device basis? |
+-+-----------------+----------------------------------------+
  |                 |
no|              yes|
  |                 |   +--------------------------------------+
  |                 |   |         For all given hosts,         |
  +--> "disabled"   +-->+      can the reserved resources      |
                        |  be used in all configured subnets?  |
                        +--------+---------------------------+-+
                                 |                           |
+----------------------------+   |no                         |yes
|             Is             |   |                           |
|  at least one reservation  +<--+               "global" <--+
| used to reserve addresses  |
|        or prefixes?        |
+-+------------------------+-+
  |                        |
no|                     yes|   +---------------------------+
  |                        |   | Is high leases-per-second |
  +--> "out-of-pool"       +-->+ performance or efficient  |
        ^                      |      resource usage       |
        |                      |  (CPU ticks, RAM usage,   |
        |                      |   database roundtrips)    |
        |                      | important to your setup?  |
        |                      +-+----------------+--------+
        |                        |                |
        |                     yes|              no|
        |                        |                |
        |          +-------------+                |
        |          |                              |
        |          |   +----------------------+   |
        |          |   | Can it be guaranteed |   |
        |          +-->+  that the reserved   |   |
        |              |  addresses/prefixes  |   |
        |              |  aren't part of the  |   |
        |              |   pools configured   |   |
        |              |  in the respective   |   |
        |              |       subnet?        |   |
        |              +-+------------------+-+   |
        |                |                  |     |
        |             yes|                no|     |
        |                |                  |     V
        +----------------+                  +--> "all"

An example configuration that disables reservations looks as follows:

{
  "Dhcp6": {
    "subnet6": [
      {
        "pools": [
          {
            "pool": "2001:db8:1::-2001:db8:1::100"
          }
        ],
        "reservation-mode": "disabled",
        "subnet": "2001:db8:1::/64"
      }
    ]
  }
}

An example configuration using global reservations is shown below:

{
  "Dhcp6": {
    "reservation-mode": "global",
    "reservations": [
      {
        "duid": "00:03:00:01:11:22:33:44:55:66",
        "hostname": "host-one"
      },
      {
        "duid": "00:03:00:01:99:88:77:66:55:44",
        "hostname": "host-two"
      }
    ],
    "subnet6": [
      {
        "pools": [
          {
            "pool": "2001:db8:1::-2001:db8:1::100"
          }
        ],
        "subnet": "2001:db8:1::/64"
      }
    ]
  }
}

The meaning of the reservation flags are:

• reservations-global: fetch global reservations.

• reservations-in-subnet: fetch subnet reservations. For a shared network this includes all subnet members of the shared network.

• reservations-out-of-pool: this makes sense only when the reservations-in-subnet flag is true. When reservations-out-of-pool is true, the server assumes that all host reservations are for addresses that do not belong to the dynamic pool. Therefore, it can skip the reservation checks when dealing with in-pool addresses, thus improving performance. The server will not assign reserved addresses that are inside the dynamic pools to the respective clients. This also means that the addresses matching the respective reservations from inside the dynamic pools (if any) can be dynamically assigned to any client.

The disabled value from the deprecated reservation-mode corresponds to:

{
  "Dhcp6": {
    "reservations-global": false,
    "reservations-in-subnet": false
  }
}

The global value from the deprecated reservation-mode corresponds to:

{
  "Dhcp6": {
    "reservations-global": true,
    "reservations-in-subnet": false
  }
}

The out-of-pool value from the deprecated reservation-mode corresponds to:

{
  "Dhcp6": {
    "reservations-global": false,
    "reservations-in-subnet": true,
    "reservations-out-of-pool": true
  }
}

And the all value from the deprecated reservation-mode corresponds to:

{
  "Dhcp6": {
    "reservations-global": false,
    "reservations-in-subnet": true,
    "reservations-out-of-pool": false
  }
}

To activate both global and all, the following combination can be used:

{
  "Dhcp6": {
    "reservations-global": true,
    "reservations-in-subnet": true,
    "reservations-out-of-pool": false
  }
}

To activate both global and out-of-pool, the following combination can be used:

{
  "Dhcp6": {
    "reservations-global": true,
    "reservations-in-subnet": true,
    "reservations-out-of-pool": true
  }
}

Enabling out-of-pool and disabling in-subnet at the same time is not recommended because out-of-pool applies to host reservations in a subnet, which are fetched only when the in-subnet flag is true.

The parameter can be specified at the global, subnet, and shared-network levels.

An example configuration that disables reservations looks as follows:

{
  "Dhcp6": {
    "subnet6": [
      {
        "reservations-global": false,
        "reservations-in-subnet": false,
        "subnet": "2001:db8:1::/64"
      }
    ]
  }
}

An example configuration using global reservations is shown below:

{
  "Dhcp6": {
    "reservations": [
      {
        "duid": "00:03:00:01:11:22:33:44:55:66",
        "hostname": "host-one"
      },
      {
        "duid": "00:03:00:01:99:88:77:66:55:44",
        "hostname": "host-two"
      }
    ],
    "reservations-global": true,
    "reservations-in-subnet": false,
    "subnet6": [
      {
        "pools": [
          {
            "pool": "2001:db8:1::-2001:db8:1::100"
          }
        ],
        "subnet": "2001:db8:1::/64"
      }
    ]
  }
}

For more details regarding global reservations, see Global Reservations in DHCPv6.

Another aspect of host reservations is the different types of identifiers. Kea currently supports two types of identifiers in DHCPv6: hardware address and DUID. This is beneficial from a usability perspective; however, there is one drawback. For each incoming packet Kea has to extract each identifier type and then query the database to see if there is a reservation by this particular identifier. If nothing is found, the next identifier is extracted and the next query is issued. This process continues until either a reservation is found or all identifier types have been checked. Over time, with an increasing number of supported identifier types, Kea would become slower and slower.

To address this problem, a parameter called host-reservation-identifiers is available. It takes a list of identifier types as a parameter. Kea checks only those identifier types enumerated in host-reservation-identifiers. From a performance perspective, the number of identifier types should be kept to a minimum, ideally one. If the deployment uses several reservation types, please enumerate them from most- to least-frequently used, as this increases the chances of Kea finding the reservation using the fewest queries. An example of a host-reservation-identifiers configuration looks as follows:

"host-reservation-identifiers": [ "duid", "hw-address" ],
"subnet6": [
    {
        "subnet": "2001:db8:1::/64",
        ...
    }
]

If not specified, the default value is:

"host-reservation-identifiers": [ "hw-address", "duid" ]

Global Reservations in DHCPv6

In some deployments, such as mobile, clients can roam within the network and certain parameters must be specified regardless of the client’s current location. To meet such a need, Kea offers a global reservation mechanism. The idea behind it is that regular host reservations are tied to specific subnets, by using a specific subnet ID. Kea can specify a global reservation that can be used in every subnet that has global reservations enabled.

This feature can be used to assign certain parameters, such as hostname or other dedicated, host-specific options. It can also be used to assign addresses or prefixes. However, global reservations that assign either of these bypass the whole topology determination provided by the DHCP logic implemented in Kea. It is very easy to misuse this feature and get a configuration that is inconsistent. To give a specific example, imagine a global reservation for the address 2001:db8:1111::1 and two subnets 2001:db8:1111::/48 and 2001:db8:ffff::/48. If global reservations are used in both subnets and a device matching global host reservations visits part of the network that is covered by 2001:db8:ffff::/48, it will get the IP address 2001:db8:ffff::1, which is outside of the prefix announced by its local router using router advertisements. Such a configuration is unusable or, at the very least, riddled with issues, such as downlink traffic not reaching the device.

To use global host reservations, a configuration similar to the following can be used:

"Dhcp6:" {
    # This specifies global reservations.
    # They will apply to all subnets that
    # have global reservations enabled.

    "reservations": [
    {
       "hw-address": "aa:bb:cc:dd:ee:ff",
       "hostname": "hw-host-dynamic"
    },
    {
       "hw-address": "01:02:03:04:05:06",
       "hostname": "hw-host-fixed",

       # Use of IP addresses in global reservations is risky.
       # If used outside of matching subnet, such as 3001::/64,
       # it will result in a broken configuration being handed
       # to the client.
       "ip-address": "2001:db8:ff::77"
    },
    {
       "duid": "01:02:03:04:05",
       "hostname": "duid-host"
    }
    ],
    "valid-lifetime": 600,
    "subnet4": [ {
        "subnet": "2001:db8:1::/64",
        # It is replaced by the "reservations-global"
        # "reservations-in-subnet" and "reservations-out-of-pool"
        # parameters.
        # "reservation-mode": "global",
        # Specify if the server should lookup global reservations.
        "reservations-global": true,
        # Specify if the server should lookup in-subnet reservations.
        "reservations-in-subnet": false,
        # Specify if the server can assume that all reserved addresses
        # are out-of-pool. It can be ignored because "reservations-in-subnet"
        # is false.
        # "reservations-out-of-pool": false,
        "pools": [ { "pool": "2001:db8:1::-2001:db8:1::100" } ]
    } ]
}

When using database backends, the global host reservations are distinguished from regular reservations by using a subnet-id value of 0.

Pool Selection with Client Class Reservations

Client classes can be specified both in the Kea configuration file and/or via host reservations. The classes specified in the Kea configuration file are evaluated immediately after receiving the DHCP packet and therefore can be used to influence subnet selection using the client-class parameter specified in the subnet scope. The classes specified within the host reservations are fetched and assigned to the packet after the server has already selected a subnet for the client. This means that the client class specified within a host reservation cannot be used to influence subnet assignment for this client, unless the subnet belongs to a shared network. If the subnet belongs to a shared network, the server may dynamically change the subnet assignment while trying to allocate a lease. If the subnet does not belong to a shared network, once selected, the subnet is not changed once selected.

If the subnet does not belong to a shared network, it is possible to use host reservation-based client classification to select an address pool within the subnet as follows:

"Dhcp6": {
    "client-classes": [
        {
            "name": "reserved_class"
        },
        {
            "name": "unreserved_class",
            "test": "not member('reserved_class')"
        }
    ],
    "subnet6": [
        {
            "subnet": "2001:db8:1::/64",
            "reservations": [{"
                "hw-address": "aa:bb:cc:dd:ee:fe",
                "client-classes": [ "reserved_class" ]
             }],
            "pools": [
                {
                    "pool": "2001:db8:1::10-2001:db8:1::20",
                    "client-class": "reserved_class"
                },
                {
                    "pool": "2001:db8:1::30-2001:db8:1::40",
                    "client-class": "unreserved_class"
                }
            ]
        }
    ]
}

The reserved_class is declared without the test parameter because it may be only assigned to the client via host reservation mechanism. The second class, unreserved_class, is assigned to clients which do not belong to the reserved_class. The first pool within the subnet is only used for clients having a reservation for the reserved_class. The second pool is used for clients not having such a reservation. The configuration snippet includes one host reservation which causes the client with the MAC address aa:bb:cc:dd:ee:fe to be assigned to the reserved_class. Thus, this client will be given an IP address from the first address pool.

Subnet Selection with Client Class Reservations

There is one specific use case when subnet selection may be influenced by client classes specified within host reservations: when the client belongs to a shared network. In such a case it is possible to use classification to select a subnet within this shared network. Consider the following example:

"Dhcp6": {
    "client-classes": [
        {
            "name": "reserved_class"
        },
        {
            "name: "unreserved_class",
            "test": "not member('reserved_class')"
        }
    ],
    "reservations": [{"
        "hw-address": "aa:bb:cc:dd:ee:fe",
        "client-classes": [ "reserved_class" ]
    }],
    # It is replaced by the "reservations-global"
    # "reservations-in-subnet" and "reservations-out-of-pool" parameters.
    # Specify if the server should lookup global reservations.
    "reservations-global": true,
    # Specify if the server should lookup in-subnet reservations.
    "reservations-in-subnet": false,
    # Specify if the server can assume that all reserved addresses
    # are out-of-pool. It can be ignored because "reservations-in-subnet"
    # is false, but if specified, it is inherited by "shared-networks"
    # and "subnet6" levels.
    # "reservations-out-of-pool": false,
    "shared-networks": [{
        "subnet6": [
            {
                "subnet": "2001:db8:1::/64",
                "pools": [
                    {
                        "pool": "2001:db8:1::10-2001:db8:1::20",
                        "client-class": "reserved_class"
                    }
                ]
            },
            {
                "subnet": "2001:db8:2::/64",
                "pools": [
                    {
                        "pool": "2001:db8:2::10-2001:db8:2::20",
                        "client-class": "unreserved_class"
                    }
                ]
            }
        ]
    }]
}

This is similar to the example described in the Pool Selection with Client Class Reservations. This time, however, there are two subnets, each of which has a pool associated with a different class. The clients that do not have a reservation for the reserved_class are assigned an address from the subnet 2001:db8:2::/64. Clients with a reservation for the reserved_class are assigned an address from the subnet 2001:db8:1::/64. The subnets must belong to the same shared network. In addition, the reservation for the client class must be specified at the global scope (global reservation) and reservations-global must be set to true.

In the example above, the client-class could also be specified at the subnet level rather than the pool level, and would yield the same effect.

Multiple Reservations for the Same IP

Host reservations were designed to preclude the creation of multiple reservations for the same IP address or delegated prefix within a particular subnet, to avoid having two different clients compete for the same lease. When using the default settings, the server returns a configuration error when it finds two or more reservations for the same lease within a subnet in the Kea configuration file. The host_cmds: Host Commands hook library returns an error in response to the reservation-add command when it detects that the reservation exists in the database for the lease for which the new reservation is being added.

Similar to DHCPv4 (see Multiple Reservations for the Same IP), the DHCPv6 server can also be configured to allow the creation of multiple reservations for the same IPv6 address and/or delegated prefix in a given subnet. This is supported since Kea release 1.9.1 as an optional mode of operation enabled with the ip-reservations-unique global parameter.

The ip-reservations-unique is a boolean parameter that defaults to true, which forbids the specification of more than one reservation for the same lease in a given subnet. Setting this parameter to false allows such reservations to be created both in the Kea configuration file and in the host database backend, via the host-cmds hook library.

This setting is currently supported by the most popular host database backends, i.e. MySQL and PostgreSQL. Host Cache (see host_cache: Caching Host Reservations), or the RADIUS backend (see radius: RADIUS Server Support). An attempt to set ip-reservations-unique to false when any of these three backends is in use yields a configuration error.

Note

When ip-reservations-unique is set to true (the default value), the server ensures that IP reservations are unique for a subnet within a single host backend and/or Kea configuration file. It does not guarantee that the reservations are unique across multiple backends.

The following is an example configuration with two reservations for the same IPv6 address but different MAC addresses:

"Dhcp6": {
    "ip-reservations-unique": false,
    "subnet6": [
        {
            "subnet": "2001:db8:1::/64",
            "reservations": [
                {
                    "hw-address": "1a:1b:1c:1d:1e:1f",
                    "ip-address": "2001:db8:1::11"
                },
                {
                    "hw-address": "2a:2b:2c:2d:2e:2f",
                    "ip-address": "2001:db8:1::11"
                }
            ]
        }
    ]
}

It is possible to control the ip-reservations-unique parameter via the Configuration Backend in DHCPv6. If the new setting of this parameter conflicts with the currently used backends (i.e. backends do not support the new setting), the new setting is ignored and a warning log message is generated. The backends continue to use the default setting, expecting that IP reservations are unique within each subnet. To allow the creation of non-unique IP reservations, the administrator must remove the backends which lack support for them from the configuration file.

Administrators must be careful when they have been using multiple reservations for the same IP address and/or delegated prefix and later decide to return to the default mode in which this is no longer allowed. They must make sure that at most one reservation for a given IP address or delegated prefix exists within a subnet, prior to switching back to the default mode. If such duplicates are left in the configuration file, the server reports a configuration error. Leaving such reservations in the host databases does not cause configuration errors but may lead to lease allocation errors during the server’s operation, when it unexpectedly finds multiple reservations for the same IP address or delegated prefix.

Note

Currently the Kea server does not verify whether multiple reservations for the same IP address and/or delegated prefix exist in MySQL and/or PostgreSQL) host databases when ip-reservations-unique is updated from true to false. This may cause issues with lease allocations. The administrator must ensure that there is at most one reservation for each IP address and/or delegated prefix within each subnet, prior to the configuration update.

The reservations-lookup-first is a boolean parameter which controls whether host reservations lookup should be performed before lease lookup. This parameter has effect only when multi-threading is disabled. When multi-threading is enabled, host reservations lookup is always performed first to avoid lease lookup resource locking. The reservations-lookup-first defaults to false when multi-threading is disabled.

Shared Networks in DHCPv6

DHCP servers use subnet information in two ways. It is used to both determine the point of attachment, i.e. where the client is connected to the network, and to group information pertaining to a specific location in the network. Sometimes it is useful to have more than one logical IP subnet being deployed on the same physical link. Understanding that two or more subnets are used on the same link requires additional logic in the DHCP server. This capability is called “shared networks” in Kea, and sometimes also “shared subnets”; in Microsoft’s nomenclature it is called “multinet.”

There are many cases where the shared networks feature is useful; here we explain just a handful of the most common ones. The first and by far most common use case is an existing IPv4 network that has grown and is running out of available address space. This is less common in IPv6, but shared networks are still useful: for example, with the exhaustion of IPv6- delegated prefixes within a subnet, or the desire to experiment with an addressing scheme. With the advent of IPv6 deployment and a vast address space, many organizations split the address space into subnets, deploy it, and then after a while discover that they want to split it differently. In the transition period, they want both the old and new addressing to be available: thus the need for more than one subnet on the same physical link.

Finally, the case of cable networks is directly applicable in IPv6. There are two types of devices in cable networks: cable modems and the end-user devices behind them. It is a common practice to use different subnets for cable modems to prevent users from tinkering with them. In this case, the distinction is based on the type of device, rather than on address-space exhaustion.

A client connected to a shared network may be assigned a lease (address or prefix) from any of the pools defined within the subnets belonging to the shared network. Internally, the server selects one of the subnets belonging to a shared network and tries to allocate a lease from this subnet. If the server is unable to allocate a lease from the selected subnet (e.g., due to pool exhaustion), it uses another subnet from the same shared network and tries to allocate a lease from this subnet. The server typically allocates all leases available in a given subnet before it starts allocating leases from other subnets belonging to the same shared network. However, in certain situations the client can be allocated a lease from another subnet before the pools in the first subnet get exhausted; this sometimes occurs when the client provides a hint that belongs to another subnet, or the client has reservations in a subnet other than the default.

Note

Deployments should not assume that Kea waits until it has allocated all the addresses from the first subnet in a shared network before allocating addresses from other subnets.

To define a shared network, an additional configuration scope is introduced:

"Dhcp6": {
    "shared-networks": [{
        # Name of the shared network. It may be an arbitrary string
        # and it must be unique among all shared networks.
        "name": "ipv6-lab-1",

        # The subnet selector can be specified on the shared network
        # level. Subnets from this shared network will be selected
        # for clients communicating via relay agent having
        # the specified IP address.
        "relay": {
            "ip-addresses": [ "2001:db8:2:34::1" ]
        },

        # This starts a list of subnets in this shared network.
        # There are two subnets in this example.
        "subnet6": [{
            "subnet": "2001:db8::/48",
            "pools": [{ "pool":  "2001:db8::1 - 2001:db8::ffff" }]
        }, {
            "subnet": "3ffe:ffe::/64",
            "pools": [{ "pool":  "3ffe:ffe::/64" }]
        }]
    }], # end of shared-networks

    # It is likely that in the network there will be a mix of regular,
    # "plain" subnets and shared networks. It is perfectly valid
    # to mix them in the same configuration file.
    #
    # This is a regular subnet. It is not part of any shared-network.
    "subnet6": [{
        "subnet": "2001:db9::/48",
        "pools": [{ "pool":  "2001:db9::/64" }],
        "relay": {
            "ip-addresses": [ "2001:db8:1:2::1" ]
        }
    }]
} # end of Dhcp6

As demonstrated in the example, it is possible to mix shared and regular (“plain”) subnets. Each shared network must have a unique name. This is similar to the ID for subnets, but gives administrators more flexibility. It is used for logging, but also internally for identifying shared networks.

In principle it makes sense to define only shared networks that consist of two or more subnets. However, for testing purposes, an empty subnet or a network with just a single subnet is allowed. This is not a recommended practice in production networks, as the shared network logic requires additional processing and thus lowers the server’s performance. To avoid unnecessary performance degradation, shared subnets should only be defined when required by the deployment.

Shared networks provide an ability to specify many parameters in the shared network scope that apply to all subnets within it. If necessary, it is possible to specify a parameter in the shared-network scope and then override its value in the subnet scope. For example:

"shared-networks": [
    {
        "name": "lab-network3",
        "relay": {
             "ip-addresses": [ "2001:db8:2:34::1" ]
        },

        # This applies to all subnets in this shared network, unless
        # values are overridden on subnet scope.
        "valid-lifetime": 600,

        # This option is made available to all subnets in this shared
        # network.
        "option-data": [ {
            "name": "dns-servers",
            "data": "2001:db8::8888"
        } ],

        "subnet6": [
            {
                "subnet": "2001:db8:1::/48",
                "pools": [ { "pool":  "2001:db8:1::1 - 2001:db8:1::ffff" } ],

                # This particular subnet uses different values.
                "valid-lifetime": 1200,
                "option-data": [
                {
                    "name": "dns-servers",
                    "data": "2001:db8::1:2"
                },
                {
                    "name": "unicast",
                    "data": "2001:abcd::1"
                } ]
            },
            {
                 "subnet": "2001:db8:2::/48",
                 "pools": [ { "pool":  "2001:db8:2::1 - 2001:db8:2::ffff" } ],

                 # This subnet does not specify its own valid-lifetime value,
                 # so it is inherited from shared network scope.
                 "option-data": [
                 {
                     "name": "dns-servers",
                     "data": "2001:db8:cafe::1"
                 } ]
            }
        ],
    } ]

In this example, there is a dns-servers option defined that is available to clients in both subnets in this shared network. Also, the valid lifetime is set to 10 minutes (600s). However, the first subnet overrides some of the values (the valid lifetime is 20 minutes, there is a different IP address for dns-servers), but also adds its own option (the unicast address). Assuming a client asking for server unicast and dns-servers options is assigned a lease from this subnet, it will get a lease for 20 minutes and dns-servers, and be allowed to use server unicast at address 2001:abcd::1. If the same client is assigned to the second subnet, it will get a 10-minute lease, a dns-servers value of 2001:db8:cafe::1, and no server unicast.

Some parameters must be the same in all subnets in the same shared network. This restriction applies to the interface and rapid-commit settings. The most convenient way is to define them on the shared-network scope, but they can be specified for each subnet. However, each subnet must have the same value.

Note

There is an inherent ambiguity when using clients that send multiple IA options in a single request, and shared-networks whose subnets have different values for options and configuration parameters. The server sequentially processes IA options in the order that they occur in the client’s query; if the leases requested in the IA options end up being fulfilled from different subnets, which parameters and options should apply? Currently, the code uses the values from the last subnet of the last IA option fulfilled.

We view this largely as a site configuration issue. A shared network generally means the same physical link, so services configured by options from subnet A should be as easily reachable from subnet B and vice versa. There are a number of ways to avoid this situation:

• Use the same values for options and parameters for subnets within the shared network.

• Use subnet selectors or client class guards that ensure that for a single client’s query, the same subnet is used for all IA options in that query.

• Avoid using shared networks with clients that send multiple IA options per query.

Local and Relayed Traffic in Shared Networks

It is possible to specify an interface name at the shared network level, to tell the server that this specific shared network is reachable directly (not via relays) using the local network interface. As all subnets in a shared network are expected to be used on the same physical link, it is a configuration error to attempt to define a shared network using subnets that are reachable over different interfaces. In other words, all subnets within the shared network must have the same value for the interface parameter. The following configuration is an example of what NOT to do:

"shared-networks": [
    {
        "name": "office-floor-2",
        "subnet6": [
            {
                "subnet": "2001:db8::/64",
                "pools": [ { "pool":  "2001:db8::1 - 2001:db8::ffff" } ],
                "interface": "eth0"
            },
            {
                 "subnet": "3ffe:abcd::/64",
                 "pools": [ { "pool":  "3ffe:abcd::1 - 3ffe:abcd::ffff" } ],

                 # Specifying the different interface name is a configuration
                 # error. This value should rather be "eth0" or the interface
                 # name in the other subnet should be "eth1".
                 # "interface": "eth1"
            }
        ],
    } ]

To minimize the chance of configuration errors, it is often more convenient to simply specify the interface name once, at the shared-network level, as shown in the example below.

"shared-networks": [
    {
        "name": "office-floor-2",

        # This tells Kea that the whole shared network is reachable over a
        # local interface. This applies to all subnets in this network.
        "interface": "eth0",

        "subnet6": [
            {
                "subnet": "2001:db8::/64",
                "pools": [ { "pool":  "2001:db8::1 - 2001:db8::ffff" } ],
            },
            {
                 "subnet": "3ffe:abcd::/64",
                 "pools": [ { "pool":  "3ffe:abcd::1 - 3ffe:abcd::ffff" } ]
            }
        ],
    } ]

With relayed traffic, subnets are typically selected using the relay agents’ addresses. If the subnets are used independently (not grouped within a shared network), a different relay address can be specified for each of these subnets. When multiple subnets belong to a shared network they must be selected via the same relay address and, similarly to the case of the local traffic described above, it is a configuration error to specify different relay addresses for the respective subnets in the shared network. The following configuration is another example of what NOT to do:

"shared-networks": [
    {
        "name": "kakapo",
        "subnet6": [
            {
                "subnet": "2001:db8::/64",
                "relay": {
                    "ip-addresses": [ "2001:db8::1234" ]
                },
                "pools": [ { "pool":  "2001:db8::1 - 2001:db8::ffff" } ]
            },
            {
                "subnet": "3ffe:abcd::/64",
                "pools": [ { "pool":  "3ffe:abcd::1 - 3ffe:abcd::ffff" } ],
                "relay": {
                    # Specifying a different relay address for this
                    # subnet is a configuration error. In this case
                    # it should be 2001:db8::1234 or the relay address
                    # in the previous subnet should be 3ffe:abcd::cafe.
                    "ip-addresses": [ "3ffe:abcd::cafe" ]
                }
            }
        ]
    }
]

Again, it is better to specify the relay address at the shared-network level; this value will be inherited by all subnets belonging to the shared network.

"shared-networks": [
    {
        "name": "kakapo",
        "relay": {
            # This relay address is inherited by both subnets.
            "ip-addresses": [ "2001:db8::1234" ]
        },
        "subnet6": [
            {
                "subnet": "2001:db8::/64",
                "pools": [ { "pool":  "2001:db8::1 - 2001:db8::ffff" } ]
            },
            {
                 "subnet": "3ffe:abcd::/64",
                 "pools": [ { "pool":  "3ffe:abcd::1 - 3ffe:abcd::ffff" } ]
            }
        ]
    }
]

Even though it is technically possible to configure two (or more) subnets within the shared network to use different relay addresses, this will almost always lead to a different behavior than what the user would expect. In this case, the Kea server will initially select one of the subnets by matching the relay address in the client’s packet with the subnet’s configuration. However, it MAY end up using the other subnet (even though it does not match the relay address) if the client already has a lease in this subnet or has a host reservation in this subnet, or simply if the initially selected subnet has no more addresses available. Therefore, it is strongly recommended to always specify subnet selectors (interface or relay address) at the shared-network level if the subnets belong to a shared network, as it is rarely useful to specify them at the subnet level and may lead to the configuration errors described above.

Client Classification in Shared Networks

Sometimes it is desirable to segregate clients into specific subnets based on certain properties. This mechanism is called client classification and is described in Client Classification. Client classification can be applied to subnets belonging to shared networks in the same way as it is used for subnets specified outside of shared networks. It is important to understand how the server selects subnets for clients when client classification is in use, to ensure that the appropriate subnet is selected for a given client type.

If a subnet is associated with a class, only the clients belonging to this class can use this subnet. If there are no classes specified for a subnet, any client connected to a given shared network can use this subnet. A common mistake is to assume that the subnet that includes a client class is preferred over subnets without client classes. Consider the following example:

{
    "client-classes": [
        {
            "name": "b-devices",
            "test": "option[1234].hex == 0x0002"
        }
    ],
    "shared-networks": [
        {
            "name": "galah",
            "relay": {
                "ip-address": [ "2001:db8:2:34::1" ]
            },
            "subnet6": [
                {
                    "subnet": "2001:db8:1::/64",
                    "pools": [ { "pool": "2001:db8:1::20 - 2001:db8:1::ff" } ],
                },
                {
                    "subnet": "2001:db8:3::/64",
                    "pools": [ { "pool": "2001:db8:3::20 - 2001:db8:3::ff" } ],
                    "client-class": "b-devices"
                }
            ]
        }
    ]
}

If the client belongs to the “b-devices” class (because it includes option 1234 with a value of 0x0002), that does not guarantee that the subnet 2001:db8:3::/64 will be used (or preferred) for this client. The server can use either of the two subnets, because the subnet 2001:db8:1::/64 is also allowed for this client. The client classification used in this case should be perceived as a way to restrict access to certain subnets, rather than as a way to express subnet preference. For example, if the client does not belong to the “b-devices” class, it may only use the subnet 2001:db8:1::/64 and will never use the subnet 2001:db8:3::/64.

A typical use case for client classification is in a cable network, where cable modems should use one subnet and other devices should use another subnet within the same shared network. In this case it is necessary to apply classification on all subnets. The following example defines two classes of devices, and the subnet selection is made based on option 1234 values.

{
    "client-classes": [
        {

            "name": "a-devices",
            "test": "option[1234].hex == 0x0001"
        },
        {
            "name": "b-devices",
            "test": "option[1234].hex == 0x0002"
        }
    ],
    "shared-networks": [
        {
            "name": "galah",
            "relay": {
                "ip-addresses":  [ "2001:db8:2:34::1" ]
            },
            "subnet6": [
                {
                    "subnet": "2001:db8:1::/64",
                    "pools": [ { "pool": "2001:db8:1::20 - 2001:db8:1::ff" } ],
                    "client-class": "a-devices"
                },
                {
                    "subnet": "2001:db8:3::/64",
                    "pools": [ { "pool": "2001:db8:3::20 - 2001:db8:3::ff" } ],
                    "client-class": "b-devices"
                }
            ]
        }
    ]
}

In this example each class has its own restriction. Only clients that belong to class “a-devices” are able to use subnet 2001:db8:1::/64 and only clients belonging to “b-devices” are able to use subnet 2001:db8:3::/64. Care should be taken not to define too-restrictive classification rules, as clients that are unable to use any subnets will be refused service. However, this may be a desired outcome if one wishes to provide service only to clients with known properties (e.g. only VoIP phones allowed on a given link).

It is possible to achieve an effect similar to the one presented in this section without the use of shared networks. If the subnets are placed in the global subnets scope, rather than in the shared network, the server will still use classification rules to pick the right subnet for a given class of devices. The major benefit of placing subnets within the shared network is that common parameters for the logically grouped subnets can be specified once, in the shared network scope, e.g. the interface or relay parameter. All subnets belonging to this shared network will inherit those parameters.

Host Reservations in Shared Networks

Subnets that are part of a shared network allow host reservations, similar to regular subnets:

{
    "shared-networks": [
    {
        "name": "frog",
        "relay": {
            "ip-addresses": [ "2001:db8:2:34::1" ]
        },
        "subnet6": [
            {
                "subnet": "2001:db8:1::/64",
                "id": 100,
                "pools": [ { "2001:db8:1::1 - 2001:db8:1::64" } ],
                "reservations": [
                {
                    "duid": "00:03:00:01:11:22:33:44:55:66",
                    "ip-addresses": [ "2001:db8:1::28" ]
                }
                ]
            },
            {
                "subnet": "2001:db8:3::/64",
                "id": 101,
                "pools": [ { "pool": "2001:db8:3::1 - 2001:db8:3::64" } ],
                "reservations": [
                    {
                        "duid": "00:03:00:01:aa:bb:cc:dd:ee:ff",
                        "ip-addresses": [ "2001:db8:2::28" ]
                    }
                ]
            }
        ]
    }
    ]
}

It is worth noting that Kea conducts additional checks when processing a packet if shared networks are defined. First, instead of simply checking whether there is a reservation for a given client in its initially selected subnet, Kea looks through all subnets in a shared network for a reservation. This is one of the reasons why defining a shared network may impact performance. If there is a reservation for a client in any subnet, that particular subnet is picked for the client. Although it is technically not an error, it is considered bad practice to define reservations for the same host in multiple subnets belonging to the same shared network.

While not strictly mandatory, it is strongly recommended to use explicit “id” values for subnets if database storage will be used for host reservations. If an ID is not specified, the values for it are auto generated, i.e. Kea assigns increasing integer values starting from 1. Thus, the auto-generated IDs are not stable across configuration changes.

Server Identifier in DHCPv6

The DHCPv6 protocol uses a “server identifier” (also known as a DUID) to allow clients to discriminate between several servers present on the same link. RFC 8415 currently defines four DUID types: DUID-LLT, DUID-EN, DUID-LL, and DUID-UUID.

The Kea DHCPv6 server generates a server identifier once, upon the first startup, and stores it in a file. This identifier is not modified across restarts of the server and so is a stable identifier.

Kea follows the recommendation from RFC 8415 to use DUID-LLT as the default server identifier. However, ISC has received reports that some deployments require different DUID types, and that there is a need to administratively select both the DUID type and/or its contents.

The server identifier can be configured using parameters within the server-id map element in the global scope of the Kea configuration file. The following example demonstrates how to select DUID-EN as a server identifier:

"Dhcp6": {
    "server-id": {
        "type": "EN"
    },
    ...
}

Currently supported values for the type parameter are: “LLT”, “EN”, and “LL”, for DUID-LLT, DUID-EN, and DUID-LL respectively.

When a new DUID type is selected, the server generates its value and replaces any existing DUID in the file. The server then uses the new server identifier in all future interactions with clients.

Note

If the new server identifier is created after some clients have obtained their leases, the clients using the old identifier are not able to renew their leases; the server will ignore messages containing the old server identifier. Clients will continue sending RENEW until they transition to the rebinding state. In this state, they will start sending REBIND messages to the multicast address without a server identifier. The server will respond to the REBIND messages with a new server identifier, and the clients will associate the new server identifier with their leases. Although the clients will be able to keep their leases and will eventually learn the new server identifier, this will be at the cost of an increased number of renewals and multicast traffic due to a need to rebind. Therefore, it is recommended that modification of the server-identifier type and value be avoided if the server has already assigned leases and these leases are still valid.

There are cases when an administrator needs to explicitly specify a DUID value rather than allow the server to generate it. The following example demonstrates how to explicitly set all components of a DUID-LLT.

"Dhcp6": {
    "server-id": {
        "type": "LLT",
        "htype": 8,
        "identifier": "A65DC7410F05",
        "time": 2518920166
    },
    ...
}

where:

• htype is a 16-bit unsigned value specifying hardware type,

• identifier is a link-layer address, specified as a string of hexadecimal digits, and

• time is a 32-bit unsigned time value.

The hexadecimal representation of the DUID generated as a result of the configuration specified above is:

 00:01:00:08:96:23:AB:E6:A6:5D:C7:41:0F:05
|type |htype|   time    |   identifier    |

A special value of “0” for htype and time is allowed, which indicates that the server should use ANY value for these components. If the server already uses a DUID-LLT, it will use the values from this DUID; if the server uses a DUID of a different type or does not yet use any DUID, it will generate these values. Similarly, if the identifier is assigned an empty string, the value of the identifier will be generated. Omitting any of these parameters is equivalent to setting them to those special values.

For example, the following configuration:

"Dhcp6": {
    "server-id": {
        "type": "LLT",
        "htype": 0,
        "identifier": "",
        "time": 2518920166
    },
    ...
}

indicates that the server should use ANY link-layer address and hardware type. If the server is already using DUID-LLT, it will use the link-layer address and hardware type from the existing DUID. If the server is not yet using any DUID, it will use the link-layer address and hardware type from one of the available network interfaces. The server will use an explicit value of time; if it is different than a time value present in the currently used DUID, that value will be replaced, effectively modifying the current server identifier.

The following example demonstrates an explicit configuration of a DUID-EN:

"Dhcp6": {
    "server-id": {
        "type": "EN",
        "enterprise-id": 2495,
        "identifier": "87ABEF7A5BB545"
    },
    ...
}

where:

• enterprise-id is a 32-bit unsigned value holding an enterprise number, and

• identifier is a variable- length identifier within DUID-EN.

The hexadecimal representation of the DUID-EN created according to the configuration above is:

 00:02:00:00:09:BF:87:AB:EF:7A:5B:B5:45
|type |  ent-id   |     identifier     |

As in the case of the DUID-LLT, special values can be used for the configuration of the DUID-EN. If the enterprise-id is “0”, the server will use a value from the existing DUID-EN. If the server is not using any DUID or the existing DUID has a different type, the ISC enterprise ID will be used. When an empty string is entered for identifier, the identifier from the existing DUID-EN will be used. If the server is not using any DUID-EN, a new 6-byte-long identifier will be generated.

DUID-LL is configured in the same way as DUID-LLT except that the time parameter has no effect for DUID-LL, because this DUID type only comprises a hardware type and link-layer address. The following example demonstrates how to configure DUID-LL:

"Dhcp6": {
    "server-id": {
        "type": "LL",
        "htype": 8,
        "identifier": "A65DC7410F05"
    },
    ...
}

which will result in the following server identifier:

 00:03:00:08:A6:5D:C7:41:0F:05
|type |htype|   identifier    |

The server stores the generated server identifier in the following location: [kea-install-dir]/var/lib/kea/kea-dhcp6-serverid.

In some uncommon deployments where no stable storage is available, the server should be configured not to try to store the server identifier. This choice is controlled by the value of the persist boolean parameter:

"Dhcp6": {
    "server-id": {
        "type": "EN",
        "enterprise-id": 2495,
        "identifier": "87ABEF7A5BB545",
        "persist": false
    },
    ...
}

The default value of the persist parameter is true, which configures the server to store the server identifier on a disk.

In the example above, the server is configured not to store the generated server identifier on a disk. But if the server identifier is not modified in the configuration, the same value is used after server restart, because the entire server identifier is explicitly specified in the configuration.

DHCPv6 Data Directory

The Kea DHCPv6 server puts the server identifier file and the default memory lease file into its data directory. By default this directory is prefix/var/lib/kea but this location can be changed using the data-directory global parameter, as in:

"Dhcp6": {
    "data-directory": "/var/tmp/kea-server6",
    ...
}

Stateless DHCPv6 (INFORMATION-REQUEST Message)

Typically DHCPv6 is used to assign both addresses and options. These assignments (leases) have a state that changes over time, hence their description as “stateful.” DHCPv6 also supports a “stateless” mode, where clients request only configuration options. This mode is considered lightweight from the server perspective, as it does not require any state tracking.

The Kea server supports stateless mode. When clients send INFORMATION-REQUEST messages, the server sends back answers with the requested options, if they are available in the server configuration. The server attempts to use per-subnet options first; if that fails, it then tries to provide options defined in the global scope.

Stateless and stateful mode can be used together. No special configuration directives are required to handle this; simply use the configuration for stateful clients and the stateless clients will get only the options they requested.

It is possible to run a server that provides only options and no addresses or prefixes. If the options have the same value in each subnet, the configuration can define the required options in the global scope and skip subnet definitions altogether. Here’s a simple example of such a configuration:

"Dhcp6": {
    "interfaces-config": {
        "interfaces": [ "ethX" ]
    },
    "option-data": [ {
        "name": "dns-servers",
        "data": "2001:db8::1, 2001:db8::2"
    } ],
    "lease-database": {
        "type": "memfile"
    }
 }

This very simple configuration provides DNS server information to all clients in the network, regardless of their location. The memfile lease database must be specified, as Kea requires a lease database to be specified even if it is not used.

Support for RFC 7550 (now part of RFC 8415)

RFC 7550 introduced some changes to the previous DHCPv6 specifications, RFC 3315 and RFC 3633, to resolve issues with the coexistence of multiple stateful options in the messages sent between clients and servers. Those changes were later included in the most recent DHCPv6 protocol specification, RFC 8415, which obsoleted RFC 7550. Kea supports RFC 8415 along with these protocol changes, which are briefly described below.

When a client, such as a requesting router, requests an allocation of both addresses and prefixes during the 4-way (SARR) exchange with the server, and the server is not configured to allocate any prefixes but can allocate some addresses, it will respond with the IA_NA(s) containing allocated addresses and the IA_PD(s) containing the NoPrefixAvail status code. According to the updated specifications, if the client can operate without prefixes it should accept allocated addresses and transition to the “bound” state. When the client subsequently sends RENEW/REBIND messages to the server to extend the lifetimes of the allocated addresses, according to the T1 and T2 times, and if the client is still interested in obtaining prefixes from the server, it may also include an IA_PD in the RENEW/REBIND to request allocation of the prefixes. If the server still cannot allocate the prefixes, it will respond with the IA_PD(s) containing the NoPrefixAvail status code. However, if the server can allocate the prefixes, it allocates and sends them in the IA_PD(s) to the client. A similar situation occurs when the server is unable to allocate addresses for the client but can delegate prefixes: the client may request allocation of the addresses while renewing the delegated prefixes. Allocating leases for other IA types while renewing existing leases is by default supported by the Kea DHCPv6 server, and the server provides no configuration mechanisms to disable this behavior.

The following are the other behaviors first introduced in RFC 7550 (now part of RFC 8415) and supported by the Kea DHCPv6 server:

• Set T1/T2 timers to the same value for all stateful (IA_NA and IA_PD) options to facilitate renewal of all of a client’s leases at the same time (in a single message exchange).

• Place NoAddrsAvail and NoPrefixAvail status codes in the IA_NA and IA_PD options in the ADVERTISE message, rather than as the top-level options.

Using a Specific Relay Agent for a Subnet

The DHCPv6 server follows the same principles as the DHCPv4 server to select a subnet for the client, with noticeable differences mainly for relays.

Note

When the selected subnet is a member of a shared network, the whole shared network is selected.

A relay must have an interface connected to the link on which the clients are being configured. Typically the relay has a global IPv6 address configured on that interface, which belongs to the subnet from which the server assigns addresses. Normally, the server is able to use the IPv6 address inserted by the relay (in the link-addr field in the RELAY-FORW message) to select the appropriate subnet.

However, that is not always the case; the relay address may not match the subnet in certain deployments. This usually means that there is more than one subnet allocated for a given link. The two most common examples of this are long-lasting network renumbering (where both the old and new address spaces are still being used) and a cable network. In a cable network, both cable modems and the devices behind them are physically connected to the same link, yet they use distinct addressing. In such a case, the DHCPv6 server needs additional information (the value of the interface-id option or the IPv6 address inserted in the link-addr field in the RELAY-FORW message) to properly select an appropriate subnet.

The following example assumes that there is a subnet 2001:db8:1::/64 that is accessible via a relay that uses 3000::1 as its IPv6 address. The server is able to select this subnet for any incoming packets that come from a relay that has an address in the 2001:db8:1::/64 subnet. It also selects that subnet for a relay with address 3000::1.

"Dhcp6": {
    "subnet6": [
        {
            "subnet": "2001:db8:1::/64",
            "pools": [
                 {
                     "pool": "2001:db8:1::1-2001:db8:1::ffff"
                 }
            ],
            "relay": {
                "ip-addresses": [ "3000::1" ]
            }
        }
    ]
}

If relay is specified, the ip-addresses parameter within it is mandatory. The ip-addresses parameter supports specifying a list of addresses.

Segregating IPv6 Clients in a Cable Network

In certain cases, it is useful to mix relay address information (introduced in Using a Specific Relay Agent for a Subnet) with client classification (explained in Client Classification). One specific example is in a cable network, where modems typically get addresses from a different subnet than all the devices connected behind them.

Let us assume that there is one Cable Modem Termination System (CMTS) with one CM MAC (a physical link that modems are connected to). We want the modems to get addresses from the 3000::/64 subnet, while everything connected behind the modems should get addresses from the 2001:db8:1::/64 subnet. The CMTS that acts as a relay uses address 3000::1. The following configuration can serve that situation:

"Dhcp6": {
    "subnet6": [
        {
            "subnet": "3000::/64",
            "pools": [
                { "pool": "3000::2 - 3000::ffff" }
            ],
            "client-class": "VENDOR_CLASS_docsis3.0",
            "relay": {
                "ip-addresses": [ "3000::1" ]
            }
        },
        {
            "subnet": "2001:db8:1::/64",
            "pools": [
                 {
                     "pool": "2001:db8:1::1-2001:db8:1::ffff"
                 }
            ],
            "relay": {
                "ip-addresses": [ "3000::1" ]
            }
        }
    ]
}

MAC/Hardware Addresses in DHCPv6

MAC/hardware addresses are available in DHCPv4 messages from clients, and administrators frequently use that information to perform certain tasks like per-host configuration and address reservation for specific MAC addresses. Unfortunately, the DHCPv6 protocol does not provide any completely reliable way to retrieve that information. To mitigate that issue, a number of mechanisms have been implemented in Kea. Each of these mechanisms works in certain cases, but may not in others. Whether the mechanism works in a particular deployment is somewhat dependent on the network topology and the technologies used.

Kea allows specification of which of the supported methods should be used and in what order, via the mac-sources parameter. This configuration may be considered a fine tuning of the DHCP deployment.

Here is an example:

"Dhcp6": {
    "mac-sources": [ "method1", "method2", "method3", ... ],

    "subnet6": [ ... ],

    ...
}

When not specified, a value of “any” is used, which instructs the server to attempt to try all the methods in sequence and use the value returned by the first one that succeeds. In a typical deployment the default value of “any” is sufficient and there is no need to select specific methods. Changing the value of this parameter is most useful in cases when an administrator wants to disable certain methods; for example, if the administrator trusts the network infrastructure more than the information provided by the clients themselves, they may prefer information provided by the relays over that provided by clients.

If specified, mac-sources must have at least one value.

Supported methods are:

• any - this is not an actual method, just a keyword that instructs Kea to try all other methods and use the first one that succeeds. This is the default operation if no mac-sources are defined.

• raw - in principle, a DHCPv6 server could use raw sockets to receive incoming traffic and extract MAC/hardware address information. This is currently not implemented for DHCPv6 and this value has no effect.

• duid - DHCPv6 uses DUID identifiers instead of MAC addresses. There are currently four DUID types defined, and two of them (DUID-LLT, which is the default, and DUID-LL) convey MAC address information. Although RFC 8415 forbids it, it is possible to parse those DUIDs and extract necessary information from them. This method is not completely reliable, as clients may use other DUID types, namely DUID-EN or DUID-UUID.

• ipv6-link-local - another possible acquisition method comes from the source IPv6 address. In typical usage, clients are sending their packets from IPv6 link-local addresses. There is a good chance that those addresses are based on EUI-64, which contains a MAC address. This method is not completely reliable, as clients may use other link-local address types. In particular, privacy extensions, defined in RFC 4941, do not use MAC addresses. Also note that successful extraction requires that the address’s u-bit must be set to “1” and its g-bit set to “0”, indicating that it is an interface identifier as per RFC 2373, section 2.5.1.

• client-link-addr-option - one extension defined to alleviate missing MAC issues is the client link-layer address option, defined in RFC 6939. This is an option that is inserted by a relay and contains information about a client’s MAC address. This method requires a relay agent that supports the option and is configured to insert it. This method is useless for directly connected clients. The value rfc6939 is an alias for client-link-addr-option.

• remote-id - RFC 4649 defines a remote-id option that is inserted by a relay agent. Depending on the relay agent configuration, the inserted option may convey the client’s MAC address information. The value rfc4649 is an alias for remote-id.

• subscriber-id - Defined in RFC 4580, subscriber-id is somewhat similar to remote-id; it is also inserted by a relay agent. The value rfc4580 is an alias for subscriber-id. This method is currently not implemented.

• docsis-cmts - Yet another possible source of MAC address information are the DOCSIS options inserted by a CMTS that acts as a DHCPv6 relay agent in cable networks. This method attempts to extract MAC address information from sub-option 1026 (cm mac) of the vendor-specific option with vendor-id=4491. This vendor option is extracted from the Relay-forward message, not the original client’s message.

• docsis-modem - The final possible source of MAC address information are the DOCSIS options inserted by the cable modem itself. This method attempts to extract MAC address information from sub-option 36 (device-id) of the vendor-specific option with vendor-id=4491. This vendor option is extracted from the original client’s message, not from any relay options.

An empty mac-sources parameter is not allowed. Administrators who do not want to specify it should either simply omit the mac-sources definition or specify it with the “any” value, which is the default.

Duplicate Addresses (DHCPDECLINE Support)

The DHCPv6 server is configured with a certain pool of addresses that it is expected to hand out to DHCPv6 clients. It is assumed that the server is authoritative and has complete jurisdiction over those addresses. However, for various reasons such as misconfiguration or a faulty client implementation that retains its address beyond the valid lifetime, there may be devices connected that use those addresses without the server’s approval or knowledge.

Such an unwelcome event can be detected by legitimate clients (using Duplicate Address Detection) and reported to the DHCPv6 server using a DHCPDECLINE message. The server does a sanity check (to see whether the client declining an address really was supposed to use it), then conducts a clean-up operation, and confirms the DHCPDECLINE by sending back a REPLY message. Any DNS entries related to that address are removed, the event is logged, and hooks are triggered. After that is complete, the address is marked as declined (which indicates that it is used by an unknown entity and thus not available for assignment) and a probation time is set on it. Unless otherwise configured, the probation period lasts 24 hours; after that time, the server will recover the lease (i.e. put it back into the available state) and the address will be available for assignment again. It should be noted that if the underlying issue of a misconfigured device is not resolved, the duplicate-address scenario will repeat. If reconfigured correctly, this mechanism provides an opportunity to recover from such an event automatically, without any system administrator intervention.

To configure the decline probation period to a value other than the default, the following syntax can be used:

  "Dhcp6": {
    "decline-probation-period": 3600,
    "subnet6": [ ... ],
    ...
}

The parameter is expressed in seconds, so the example above instructs the server to recycle declined leases after one hour.

There are several statistics and hook points associated with the decline handling procedure. The lease6_decline hook is triggered after the incoming DHCPDECLINE message has been sanitized and the server is about to decline the lease. The declined-addresses statistic is increased after the hook returns (both the global and subnet-specific variants). (See Statistics in the DHCPv6 Server and Hook Libraries for more details on DHCPv6 statistics and Kea hook points.)

Once the probation time elapses, the declined lease is recovered using the standard expired-lease reclamation procedure, with several additional steps. In particular, both declined-addresses statistics (global and subnet-specific) are decreased. At the same time, reclaimed-declined-addresses statistics (again in two variants, global and subnet-specific) are increased.

A note about statistics: The Kea server does not decrease the assigned-nas statistics when a DHCPDECLINE message is received and processed successfully. While technically a declined address is no longer assigned, the primary usage of the assigned-nas statistic is to monitor pool utilization. Most people would forget to include declined-addresses in the calculation, and would simply use assigned-nas/total-nas. This would cause a bias towards under-representing pool utilization. As this has a potential to cause serious confusion, ISC decided not to decrease assigned-nas immediately after receiving DHCPDECLINE, but to do it later when Kea recovers the address back to the available pool.

Statistics in the DHCPv6 Server

The DHCPv6 server supports the following statistics:

DHCPv6 statistics

Statistic	Data Type	Description
pkt6-received	integer	Number of DHCPv6 packets received. This includes all packets: valid, bogus, corrupted, rejected, etc. This statistic is expected to grow rapidly.
pkt6-receive-drop	integer	Number of incoming packets that were dropped. The exact reason for dropping packets is logged, but the most common reasons may be: an unacceptable or not supported packet type is received, direct responses are forbidden, the server-id sent by the client does not match the server’s server-id, or the packet is malformed.
pkt6-parse-failed	integer	Number of incoming packets that could not be parsed. A non-zero value of this statistic indicates that the server received a malformed or truncated packet. This may indicate problems in the network, faulty clients, faulty relay agents, or a bug in the server.
pkt6-solicit-received	integer	Number of SOLICIT packets received. This statistic is expected to grow; its increase means that clients that just booted started their configuration process and their initial packets reached the Kea server.
pkt6-advertise-received	integer	Number of ADVERTISE packets received. ADVERTISE packets are sent by the server and the server is never expected to receive them. A non-zero value of this statistic indicates an error occurring in the network. One likely cause would be a misbehaving relay agent that incorrectly forwards ADVERTISE messages towards the server, rather than back to the clients.
pkt6-request-received	integer	Number of DHCPREQUEST packets received. This statistic is expected to grow. Its increase means that clients that just booted received the server’s response (DHCPADVERTISE) and accepted it, and are now requesting an address (DHCPREQUEST).
pkt6-reply-received	integer	Number of REPLY packets received. This statistic is expected to remain zero at all times, as REPLY packets are sent by the server and the server is never expected to receive them. A non-zero value indicates an error. One likely cause would be a misbehaving relay agent that incorrectly forwards REPLY messages towards the server, rather than back to the clients.
pkt6-renew-received	integer	Number of RENEW packets received. This statistic is expected to grow; its increase means that clients received their addresses and prefixes and are trying to renew them.
pkt6-rebind-received	integer	Number of REBIND packets received. A non-zero value indicates that clients did not receive responses to their RENEW messages (through the regular lease-renewal mechanism) and are attempting to find any server that is able to take over their leases. It may mean that some servers’ REPLY messages never reached the clients.
pkt6-release-received	integer	Number of RELEASE packets received. This statistic is expected to grow when a device is being shut down in the network; it indicates that the address or prefix assigned is reported as no longer needed. Note that many devices, especially wireless, do not send RELEASE packets either because of design choice or due to the client moving out of range.
pkt6-decline-received	integer	Number of DECLINE packets received. This statistic is expected to remain close to zero. Its increase means that a client leased an address, but discovered that the address is currently used by an unknown device in the network. If this statistic is growing, it may indicate a misconfigured server or devices that have statically assigned conflicting addresses.
pkt6-infrequest-received	integer	Number of INFORMATION-REQUEST packets received. This statistic is expected to grow if there are devices that are using stateless DHCPv6. INFORMATION-REQUEST messages are used by clients that request stateless configuration, i.e. options and parameters other than addresses or prefixes.
pkt6-dhcpv4-query-received	integer	Number of DHCPv4-QUERY packets received. This statistic is expected to grow if there are devices that are using DHCPv4-over-DHCPv6. DHCPv4-QUERY messages are used by DHCPv4 clients on an IPv6-only line which encapsulates the requests over DHCPv6.
pkt6-dhcpv4-response-received	integer	Number of DHCPv4-RESPONSE packets received. This statistic is expected to remain zero at all times, as DHCPv4-RESPONSE packets are sent by the server and the server is never expected to receive them. A non-zero value indicates an error. One likely cause would be a misbehaving relay agent that incorrectly forwards DHCPv4-RESPONSE message towards the server rather than back to the clients.
pkt6-unknown-received	integer	Number of packets received of an unknown type. A non-zero value of this statistic indicates that the server received a packet that it was unable to recognize; either it had an unsupported type or was possibly malformed.
pkt6-sent	integer	Number of DHCPv6 packets sent. This statistic is expected to grow every time the server transmits a packet. In general, it should roughly match pkt6-received, as most incoming packets cause the server to respond. There are exceptions (e.g. server receiving a REQUEST with server-id matching another server), so do not worry if it is less than pkt6-received.
pkt6-advertise-sent	integer	Number of ADVERTISE packets sent. This statistic is expected to grow in most cases after a SOLICIT is processed. There are certain uncommon, but valid, cases where incoming SOLICIT packets are dropped, but in general this statistic is expected to be close to pkt6-solicit-received.
pkt6-reply-sent	integer	Number of REPLY packets sent. This statistic is expected to grow in most cases after a SOLICIT (with rapid-commit), REQUEST, RENEW, REBIND, RELEASE, DECLINE, or INFORMATION-REQUEST is processed. There are certain cases where there is no response.
pkt6-dhcpv4-response-sent	integer	Number of DHCPv4-RESPONSE packets sent. This statistic is expected to grow in most cases after a DHCPv4-QUERY is processed. There are certain cases where there is no response.
subnet[id].total-nas	integer	Total number of NA addresses available for DHCPv6 management for a given subnet; in other words, this is the sum of all addresses in all configured pools. This statistic changes only during configuration changes. Note that it does not take into account any addresses that may be reserved due to host reservation. The id is the subnet-id of a given subnet. This statistic is exposed for each subnet separately, and is reset during a reconfiguration event.
cumulative-assigned-nas	integer	Cumulative number of NA addresses that have been assigned since server startup. It is incremented each time a NA address is assigned and is not reset when the server is reconfigured.
subnet[id].cumulative-assigned-nas	integer	Cumulative number of NA addresses in a given subnet that were assigned. It increases every time a new lease is allocated (as a result of receiving a REQUEST message) and is never decreased. The id is the subnet-id of a given subnet. This statistic is exposed for each subnet separately, and is reset during a reconfiguration event.
subnet[id].assigned-nas	integer	Number of NA addresses in a given subnet that are assigned. It increases every time a new lease is allocated (as a result of receiving a REQUEST message) and is decreased every time a lease is released (a RELEASE message is received) or expires. The id is the subnet-id of a given subnet. This statistic is exposed for each subnet separately, and is reset during a reconfiguration event.
subnet[id].total-pds	integer	Total number of PD prefixes available for DHCPv6 management for a given subnet; in other words, this is the sum of all prefixes in all configured pools. This statistic changes only during configuration changes. Note it does not take into account any prefixes that may be reserved due to host reservation. The id is the subnet-id of a given subnet. This statistic is exposed for each subnet separately, and is reset during a reconfiguration event.
cumulative-assigned-pds	integer	Cumulative number of PD prefixes that have been assigned since server startup. It is incremented each time a PD prefix is assigned and is not reset when the server is reconfigured.
subnet[id].cumulative-assigned-pds	integer	Cumulative number of PD prefixes in a given subnet that were assigned. It increases every time a new lease is allocated (as a result of receiving a REQUEST message) and is never decreased. The id is the subnet-id of a given subnet. This statistic is exposed for each subnet separately, and is reset during a reconfiguration event.
subnet[id].assigned-pds	integer	Number of PD prefixes in a given subnet that are assigned. It increases every time a new lease is allocated (as a result of receiving a REQUEST message) and is decreased every time a lease is released (a RELEASE message is received) or expires. The id is the subnet-id of a given subnet. This statistic is exposed for each subnet separately, and is reset during a reconfiguration event.
reclaimed-leases	integer	Number of expired leases that have been reclaimed since server startup. It is incremented each time an expired lease is reclaimed (counting both NA and PD reclamations). This statistic never decreases. It can be used as a long-term indicator of how many actual leases have been reclaimed. This is a global statistic that covers all subnets.
subnet[id].reclaimed-leases	integer	Number of expired leases associated with a given subnet that have been reclaimed since server startup. It is incremented each time an expired lease is reclaimed (counting both NA and PD reclamations). The id is the subnet-id of a given subnet. This statistic is exposed for each subnet separately.
declined-addresses	integer	Number of IPv6 addresses that are currently declined; a count of the number of leases currently unavailable. Once a lease is recovered, this statistic will be decreased; ideally, this statistic should be zero. If this statistic is non-zero or increasing, a network administrator should investigate whether there is a misbehaving device in the network. This is a global statistic that covers all subnets.
subnet[id].declined-addresses	integer	Number of IPv6 addresses that are currently declined in a given subnet; a count of the number of leases currently unavailable. Once a lease is recovered, this statistic will be decreased; ideally, this statistic should be zero. If this statistic is non-zero or increasing, a network administrator should investigate whether there is a misbehaving device in the network. The id is the subnet-id of a given subnet. This statistic is exposed for each subnet separately.
reclaimed-declined-addresses	integer	Number of IPv6 addresses that were declined, but have now been recovered. Unlike declined-addresses, this statistic never decreases. It can be used as a long-term indicator of how many actual valid declines were processed and recovered from. This is a global statistic that covers all subnets.
subnet[id].reclaimed-declined-addresses	integer	Number of IPv6 addresses that were declined, but have now been recovered. Unlike declined-addresses, this statistic never decreases. It can be used as a long-term indicator of how many actual valid declines were processed and recovered from. The id is the subnet-id of a given subnet. This statistic is exposed for each subnet separately.
v6-allocation-fail	integer	Number of total address allocation failures for a particular client. This consists in the number of lease allocation attempts that the server made before giving up and was unable to use any of the address pools. This is a global statistic that covers all subnets.
subnet[id].v6-allocation-fail	integer	Number of total address allocation failures for a particular client. This consists in the number of lease allocation attempts that the server made before giving up and was unable to use any of the address pools. The id is the subnet-id of a given subnet. This statistic is exposed for each subnet separately.
v6-allocation-fail-shared-network	integer	Number of address allocation failures for a particular client connected to a shared network. This is a global statistic that covers all subnets.
subnet[id].v6-allocation-fail-shared-network	integer	Number of address allocation failures for a particular client connected to a shared network. The id is the subnet-id of a given subnet. This statistic is exposed for each subnet separately.
v6-allocation-fail-subnet	integer	Number of address allocation failures for a particular client connected to a subnet that does not belong to a shared network. This is a global statistic that covers all subnets.
subnet[id].v6-allocation-fail-subnet	integer	Number of address allocation failures for a particular client connected to a subnet that does not belong to a shared network. The id is the subnet-id of a given subnet. This statistic is exposed for each subnet separately.
v6-allocation-fail-no-pools	integer	Number of address allocation failures because the server could not use any configured pools for a particular client. It is also possible that all of the subnets from which the server attempted to assign an address lack address pools. In this case, it should be considered misconfiguration if an operator expects that some clients should be assigned dynamic addresses. This is a global statistic that covers all subnets.
subnet[id].v6-allocation-fail-no-pools	integer	Number of address allocation failures because the server could not use any configured pools for a particular client. It is also possible that all of the subnets from which the server attempted to assign an address lack address pools. In this case, it should be considered misconfiguration if an operator expects that some clients should be assigned dynamic addresses. The id is the subnet-id of a given subnet. This statistic is exposed for each subnet separately.
v6-allocation-fail-classes	integer	Number of address allocation failures when the client’s packet belongs to one or more classes. There may be several reasons why a lease was not assigned. One of them may be a case when all pools require packet to belong to certain classes and the incoming packet didn’t belong to any of them. Another case where this information may be useful is to point out that the pool reserved to a given class has ran out of addresses. This is a global statistic that covers all subnets.
subnet[id].v6-allocation-fail-classes	integer	Number of address allocation failures when the client’s packet belongs to one or more classes. There may be several reasons why a lease was not assigned. One of them may be a case when all pools require packet to belong to certain classes and the incoming packet didn’t belong to any of them. Another case where this information may be useful is to point out that the pool reserved to a given class has ran out of addresses. The id is the subnet-id of a given subnet. This statistic is exposed for each subnet separately.

Note

This section describes DHCPv6-specific statistics. For a general overview and usage of statistics, see Statistics.

The DHCPv6 server provides two global parameters to control the default sample limits of statistics:

• statistic-default-sample-count - determines the default maximum number of samples which are kept. The special value of 0 indicates that a default maximum age should be used.

• statistic-default-sample-age - determines the default maximum age in seconds of samples which are kept.

For instance, to reduce the statistic-keeping overhead, set the default maximum sample count to 1 so only one sample is kept:

  "Dhcp6": {
    "statistic-default-sample-count": 1,
    "subnet6": [ ... ],
    ...
}

Statistics can be retrieved periodically to gain more insight into Kea operations. One tool that leverages that capability is ISC Stork. See Monitoring Kea With Stork for details.

Management API for the DHCPv6 Server

The management API allows the issuing of specific management commands, such as statistics retrieval, reconfiguration, or shutdown. For more details, see Management API. Currently, the only supported communication channel type is the UNIX stream socket. By default there are no sockets open; to instruct Kea to open a socket, the following entry in the configuration file can be used:

"Dhcp6": {
    "control-socket": {
        "socket-type": "unix",
        "socket-name": "/path/to/the/unix/socket"
    },

    "subnet6": [
        ...
    ],
    ...
}

The length of the path specified by the socket-name parameter is restricted by the maximum length for the UNIX socket name on the administrator’s operating system, i.e. the size of the sun_path field in the sockaddr_un structure, decreased by 1. This value varies on different operating systems, between 91 and 107 characters. Typical values are 107 on Linux and 103 on FreeBSD.

Communication over the control channel is conducted using JSON structures. See the Control Channel section in the Kea Developer’s Guide for more details.

The DHCPv6 server supports the following operational commands:

• build-report

• config-get

• config-reload

• config-set

• config-test

• config-write

• dhcp-disable

• dhcp-enable

• leases-reclaim

• list-commands

• shutdown

• status-get

• version-get

as described in Commands Supported by Both the DHCPv4 and DHCPv6 Servers. In addition, it supports the following statistics-related commands:

• statistic-get

• statistic-reset

• statistic-remove

• statistic-get-all

• statistic-reset-all

• statistic-remove-all

• statistic-sample-age-set

• statistic-sample-age-set-all

• statistic-sample-count-set

• statistic-sample-count-set-all

as described in Commands for Manipulating Statistics.

User Contexts in IPv6

Kea allows the loading of hook libraries that can sometimes benefit from additional parameters. If such a parameter is specific to the whole library, it is typically defined as a parameter for the hook library. However, sometimes there is a need to specify parameters that are different for each pool.

See Comments and User Context for additional background regarding the user-context idea. See User Contexts in Hooks for a discussion from the hooks perspective.

User contexts can be specified at global scope; at the shared-network, subnet, pool, client-class, option-data, or definition level; and via host reservation. One other useful feature is the ability to store comments or descriptions.

Let’s consider an example deployment of lightweight 4over6, an IPv6 transition technology that allows mapping IPv6 prefixes into full or partial IPv4 addresses. In the DHCP context, these are specific parameters that are supposed to be delivered to clients in the form of additional options. Values of these options are correlated to delegated prefixes, so it is reasonable to keep these parameters together with the prefix delegation (PD) pool. On the other hand, lightweight 4over6 is not a commonly used feature, so it is not a part of the base Kea code. The solution to this problem is to specify a user context. For each PD pool that is expected to be used for lightweight 4over6, a user context with extra parameters is defined. Those extra parameters will be used by a hook library and loaded only when dynamic calculation of the lightweight 4over6 option is actually needed. An example configuration looks as follows:

"Dhcp6": {
    "subnet6": [ {
        "pd-pools": [
        {
            "prefix":  "2001:db8::",
            "prefix-len": 56,
            "delegated-len": 64,

            # This is a pool specific context.
            "user-context": {
                "threshold-percent": 85,
                "v4-network": "192.168.0.0/16",
                "v4-overflow": "10.0.0.0/16",
                "lw4over6-sharing-ratio": 64,
                "lw4over6-v4-pool": "192.0.2.0/24",
                "lw4over6-sysports-exclude": true,
                "lw4over6-bind-prefix-len": 56
            }
        } ],
        "subnet": "2001:db8::/32",

        # This is a subnet-specific context. Any type of
        # information can be entered here as long as it is valid JSON.
        "user-context": {
            "comment": "Those v4-v6 migration technologies are tricky.",
            "experimental": true,
            "billing-department": 42,
            "contacts": [ "Alice", "Bob" ]
        }
    } ]
}

Kea does not interpret or use the user-context information; it simply stores it and makes it available to the hook libraries. It is up to each hook library to extract that information and use it. The parser translates a comment entry into a user context with the entry, which allows a comment to be attached inside the configuration itself.

Supported DHCPv6 Standards

The following standards are currently supported in Kea:

• Dynamic Host Configuration Protocol for IPv6, RFC 3315: Supported messages are SOLICIT, ADVERTISE, REQUEST, RELEASE, RENEW, REBIND, INFORMATION-REQUEST, CONFIRM, DECLINE and REPLY. The only unsupported message is RECONFIGURE.

• Dynamic Host Configuration Protocol (DHCPv6) Options for Session Initiation Protocol (SIP) Servers, RFC 3319: All defined options are supported.

• IPv6 Prefix Options for Dynamic Host Configuration Protocol (DHCP) version 6, RFC 3633: Supported options are IA_PD and IA_PREFIX. Also supported is the status code NoPrefixAvail.

• DNS Configuration options for Dynamic Host Configuration Protocol for IPv6 (DHCPv6), RFC 3646: All defined options are supported.

• Stateless Dynamic Host Configuration Protocol (DHCP) Service for IPv6, RFC 3736: Server operation in stateless mode is supported. Kea is currently server-only, so the client side is not implemented.

• Information Refresh Time Option for Dynamic Host Configuration Protocol for IPv6 (DHCPv6), RFC 4242: The sole defined option (information-refresh-time) is supported.

• The Dynamic Host Configuration Protocol for IPv6 (DHCPv6) Relay Agent Remote-ID Option, RFC 4649: The REMOTE-ID option is supported.

• Resolution of Fully Qualified Domain Name (FQDN) Conflicts among Dynamic Host Configuration Protocol (DHCP) Clients, RFC 4703: The DHCPv6 server uses the DHCP-DDNS server to resolve conflicts.

• The Dynamic Host Configuration Protocol for IPv6 (DHCPv6) Client Fully Qualified Domain Name (FQDN) Option, RFC 4704: The supported option is CLIENT_FQDN.

• Dynamic Host Configuration Protocol for IPv6 (DHCPv6) Option for Dual-Stack Lite, RFC 6334: The AFTR-Name DHCPv6 Option is supported.

• Relay-Supplied DHCP Options, RFC 6422: The full functionality is supported: OPTION_RSOO; the ability of the server to echo back the options; verification of whether an option is RSOO-enabled; the ability to mark additional options as RSOO-enabled.

• Prefix Exclude Option for DHCPv6-based Prefix Delegation, RFC 6603: The Prefix Exclude option is supported.

• Client Link-Layer Address Option in DHCPv6, RFC 6939: The supported option is the client link-layer address option.

• Issues and Recommendations with Multiple Stateful DHCPv6 Options, RFC 7550: All recommendations related to the DHCPv6 server operation are supported.

• DHCPv6 Options for Configuration of Softwire Address and Port-Mapped Clients, RFC 7598: All options indicated in this specification are supported by the DHCPv6 server.

• Generalized UDP Source Port for DHCP Relay, RFC 8357: The Kea server is able to handle Relay Source Port option in a received Relay-forward message, remembers the UDP port and sends back Relay-reply with a copy of the option to the relay agent using this UDP port.

• Dynamic Host Configuration Protocol for IPv6 (DHCPv6), RFC 8415: This new DHCPv6 protocol specification obsoletes RFC 3315, RFC 3633, RFC 3736, RFC 4242, RFC 7083, RFC 7283, and RFC 7550. All features, with the exception of the RECONFIGURE mechanism and the now-deprecated temporary addresses (IA_TA) mechanism, are supported.

• Captive-Portal Identification in DHCP and Router Advertisements (RAs), RFC 8910: The Kea server can configure both v4 and v6 versions of the captive portal options.

DHCPv6 Server Limitations

These are the current limitations of the DHCPv6 server software. Most of them are reflections of the current stage of development and should be treated as “not implemented yet”, rather than actual limitations.

• The server will allocate, renew, or rebind a maximum of one lease for a particular IA option (IA_NA or IA_PD) sent by a client. RFC 8415 allows for multiple addresses or prefixes to be allocated for a single IA.

• Temporary addresses are not supported. There is no intention to ever implement this feature, as it is deprecated in RFC 8415.

• Client reconfiguration (RECONFIGURE) is not yet supported.

Kea DHCPv6 Server Examples

A collection of simple-to-use examples for the DHCPv6 component of Kea is available with the source files, located in the doc/examples/kea6 directory.

Configuration Backend in DHCPv6

In the Kea Configuration Backend section we have described the Configuration Backend (CB) feature, its applicability, and its limitations. This section focuses on the usage of the CB with the DHCPv6 server. It lists the supported parameters, describes limitations, and gives examples of DHCPv6 server configurations to take advantage of the CB. Please also refer to the corresponding section Configuration Backend in DHCPv4 for DHCPv4-specific usage of the CB.

Supported Parameters

The ultimate goal for the CB is to serve as a central configuration repository for one or multiple Kea servers connected to a database. In currently supported Kea versions, only a subset of the DHCPv6 server parameters can be stored in the database. All other parameters must be specified in the JSON configuration file, if required.

All supported parameters can be configured via cb_cmds hook library described in the cb_cmds: Configuration Backend Commands section. The general rule is that scalar global parameters are set using remote-global-parameter6-set; shared-network-specific parameters are set using remote-network6-set; and subnet- and pool-level parameters are set using remote-subnet6-set. Whenever there is an exception to this general rule, it is highlighted in the table. Non-scalar global parameters have dedicated commands; for example, the global DHCPv6 options (option-data) are modified using remote-option6-global-set. Client classes, together with class-specific option definitions and DHCPv6 options, are configured using the remote-class6-set command.

The Configuration Sharing and Server Tags section explains the concept of shareable and non-shareable configuration elements and the limitations for sharing them between multiple servers. In the DHCP configuration (both DHCPv4 and DHCPv6), the shareable configuration elements are subnets and shared networks. Thus, they can be explicitly associated with multiple server tags. The global parameters, option definitions, and global options are non-shareable and can be associated with only one server tag. This rule does not apply to the configuration elements associated with all servers. Any configuration element associated with all servers (using the all keyword as a server tag) is used by all servers connecting to the configuration database.

The following table lists DHCPv6-specific parameters supported by the Configuration Backend, with an indication of the level of the hierarchy at which it is currently supported.

List of DHCPv6 parameters supported by the Configuration Backend

Parameter	Global	Client Class	Shared Network	Subnet	Pool	Prefix Delegation Pool
cache-max-age	yes	n/a	no	no	n/a	n/a
cache-threshold	yes	n/a	no	no	n/a	n/a
calculate-tee-times	yes	n/a	yes	yes	n/a	n/a
client-class	n/a	n/a	yes	yes	yes	yes
ddns-send-update	yes	n/a	yes	yes	n/a	n/a
ddns-override-no-update	yes	n/a	yes	yes	n/a	n/a
ddns-override-client-update	yes	n/a	yes	yes	n/a	n/a
ddns-replace-client-name	yes	n/a	yes	yes	n/a	n/a
ddns-generated-prefix	yes	n/a	yes	yes	n/a	n/a
ddns-qualifying-suffix	yes	n/a	yes	yes	n/a	n/a
decline-probation-period	yes	n/a	n/a	n/a	n/a	n/a
delegated-len	n/a	n/a	n/a	n/a	n/a	yes
dhcp4o6-port	yes	n/a	n/a	n/a	n/a	n/a
excluded-prefix	n/a	n/a	n/a	n/a	n/a	yes
excluded-prefix-len	n/a	n/a	n/a	n/a	n/a	yes
hostname-char-set	no	n/a	no	no	n/a	n/a
hostname-char-replacement	no	n/a	no	no	n/a	n/a
interface	n/a	n/a	yes	yes	n/a	n/a
interface-id	n/a	n/a	yes	yes	n/a	n/a
max-preferred-lifetime	yes	yes	yes	yes	n/a	n/a
max-valid-lifetime	yes	yes	yes	yes	n/a	n/a
min-preferred-lifetime	yes	yes	yes	yes	n/a	n/a
min-valid-lifetime	yes	yes	yes	yes	n/a	n/a
option-data	yes (via remote-option6-global-set)	yes	yes	yes	yes	yes
option-def	yes (via remote-option-def6-set)	yes	n/a	n/a	n/a	n/a
preferred-lifetime	yes	yes	yes	yes	n/a	n/a
prefix	n/a	n/a	n/a	n/a	n/a	yes
prefix-len	n/a	n/a	n/a	n/a	n/a	yes
rapid-commit	yes	n/a	yes	yes	n/a	n/a
rebind-timer	yes	n/a	yes	yes	n/a	n/a
relay	n/a	n/a	yes	yes	n/a	n/a
renew-timer	yes	n/a	yes	yes	n/a	n/a
require-client-classes	n/a	n/a	yes	yes	yes	yes
reservation-mode	yes	n/a	yes	yes	n/a	n/a
reservations-global	yes	n/a	yes	yes	n/a	n/a
reservations-in-subnet	yes	n/a	yes	yes	n/a	n/a
reservations-out-of-pool	yes	n/a	yes	yes	n/a	n/a
t1-percent	yes	n/a	yes	yes	n/a	n/a
t2-percent	yes	n/a	yes	yes	n/a	n/a
valid-lifetime	yes	yes	yes	yes	n/a	n/a

• yes - indicates that the parameter is supported at the given level of the hierarchy and can be configured via the Configuration Backend.

• no - indicates that a parameter is supported at the given level of the hierarchy but cannot be configured via the Configuration Backend.

• n/a - indicates that a given parameter is not applicable at the particular level of the hierarchy or that the server does not support the parameter at that level.

Enabling the Configuration Backend

The following configuration snippet demonstrates how to enable the MySQL Configuration Backend for the DHCPv6 server:

{
    "Dhcp6": {
    "server-tag": "my DHCPv6 server",
        "config-control": {
            "config-databases": [
                {
                    "type": "mysql",
                    "name": "kea",
                    "user": "kea",
                    "password": "kea",
                    "host": "2001:db8:1::1",
                    "port": 3302
                }
            ],
            "config-fetch-wait-time": 20
        },
        "hooks-libraries": [
            {
                "library": "/usr/local/lib/kea/hooks/libdhcp_mysql_cb.so"
            },
            {
                "library": "/usr/local/lib/kea/hooks/libdhcp_cb_cmds.so"
            }
        ],
        ...
    }
}

The configuration structure is almost identical to that of the DHCPv4 server (see Enabling the Configuration Backend for the detailed description).

Kea DHCPv6 Compatibility Configuration Parameters

ISC’s intention is for Kea to follow the RFC documents to promote better standards compliance. However, many buggy DHCP implementations already exist that cannot be easily fixed or upgraded. Therefore, Kea provides an easy-to-use compatibility mode for broken or non-compliant clients. For that purpose, the compatibility option must be enabled to permit uncommon practices:

{
  "Dhcp6": {
    "compatibility": {
    }
  }
}

Lenient Option Parsing

By default, DHCPv6 option 16’s vendor-class-data field is parsed as a set of length-value pairs. Same for tuple fields defined in custom options.

With "lenient-option-parsing": true, if a length ever exceeds the rest of the option’s buffer, previous versions of Kea returned a log message unable to parse the opaque data tuple, the buffer length is x, but the tuple length is y with x < y; this no longer occurs. Instead, the value is considered to be the rest of the buffer, or in terms of the log message above, the tuple length y becomes x.

Enabling this flag is expected to improve compatibility with devices such as RAD MiNID.

{
  "Dhcp6": {
    "compatibility": {
      "lenient-option-parsing": true
    }
  }
}

Database Connectivity

The Kea servers (kea-dhcp4 and kea-dhcp6) can be configured to use a variety of database backends for leases, hosts, and configuration. They can be configured to support automatic recovery when connectivity is lost, via the on-fail parameter. (The reconnect-wait-time and max-reconnect-tries parameters are described in Lease Database Configuration and Lease Database Configuration.)

It is important to understand how and when automatic recovery comes into play. Automatic recovery, when configured, only operates after a successful startup or reconfiguration during which connectivity to all backends has been successfully established.

During server startup, the inability to connect to any of the configured backends is always considered fatal. A fatal error is logged and the server exits, based on the idea that the configuration should be valid at startup. Exiting to the operating system allows nanny scripts to detect the problem.

During dynamic reconfiguration, all backends are disconnected and then reconnected using the new configuration. If connectivity to any of the backends cannot be established, the server logs a fatal error but remains up. It is able to process commands but does not serve clients. This allows the configuration to be corrected via the config-set or remote-* commands, if required.

During normal operations, if connectivity to any of the backends is lost and automatic recovery for that backend is enabled, the server disconnects from the respective backend and then attempts to reconnect. During the recovery process, the server ceases to serve clients according to the on-fail configured option but continues to respond to commands.

The on-fail parameter configures the actions the server should take when a connection is lost. It can have one of the following values:

• stop-retry-exit - indicates that the server should stop the service while it tries to recover the connection, and exit if recovery is not successful after max-reconnect-tries.

• serve-retry-exit - indicates that the server should not stop the service while it tries to recover the connection, and exit if recovery is not successful after max-reconnect-tries.

• serve-retry-continue - indicates that the server should not stop the service while it tries to recover the connection, and not exit if recovery is not successful after max-reconnect-tries.

If connectivity to all backends is restored, the server returns to normal operations. If the connection cannot be restored and the server is configured to exit, it issues a fatal error before shutdown.

The connection to the database server can optionally be protected by TLS. Corresponding database configuration parameters for Kea servers are:

• The trust-anchor specifies the Certification Authority file name or directory path.

• The cert-file specifies the client certificate file name.

• The key-file specifies the private key file name.

• The cipher-list specifies the list of TLS ciphers (the syntax of the content of this parameter is described in the OpenSSL ciphers manual).

These parameters are similar to the parameters of the secure connections with the agent but are interpreted by different backends using database configurations too.

Currently the support for each database is:

• MySQL supports the whole set, additional configuration must be done in the MySQL local setup, for instance certificate revocation list, choice of a specific TLS version, mutual authentication, etc. When a TLS connection was required but the actual connection is in clear text an error log is emitted.

• PostgreSQL only uses the configuration to enable the SSL/TLS support in the client library (libpq). Anything else must be done in the PostgreSQL local configuration.

Lease Expiration

The primary role of the DHCP server is to assign addresses and/or delegate prefixes to DHCP clients. These addresses and prefixes are often referred to as “leases.” Leases are typically assigned to clients for a finite amount of time, known as the “valid lifetime.” DHCP clients who wish to continue using their assigned leases periodically renew them by sending the appropriate message to the DHCP server. The DHCP server records the time when these leases are renewed and calculates new expiration times for them.

If the client does not renew a lease before its valid lifetime elapses, the lease is considered expired. There are many situations when the client may cease lease renewals; common scenarios include when the machine running the client shuts down for an extended period of time, or when a mobile device leaves the vicinity of a network.

The process through which the DHCP server makes expired leases available for reassignment is referred to as “lease reclamation,” and expired leases returned to availability through this process are referred to as “reclaimed.” The DHCP server attempts to reclaim an expired lease as soon as it detects that it has expired. The server has several possible ways to detect expiration: it may attempt to allocate a lease to a client but find this lease already present in the database and expired; or it can periodically query the lease database for expired leases. Regardless of how an expired lease is detected, it must be reclaimed before it can be assigned to a client.

This chapter explains how to configure the server to periodically query for the expired leases, and how to minimize the impact of the periodic lease-reclamation process on the server’s responsiveness. Finally, it explains “lease affinity,” which provides the means to assign the same lease to a returning client after its lease has expired.

Although all configuration examples in this section are provided for the DHCPv4 server, the same parameters may be used for DHCPv6 server configuration.

Lease Reclamation

Lease reclamation is the process through which an expired lease becomes available for assignment to the same or a different client. This process involves the following steps for each reclaimed lease:

• Invoke callouts for the lease4_expire or lease6_expire hook points, if hook libraries supporting those callouts are currently loaded.

• Update the DNS, i.e. remove any DNS entries associated with the expired lease.

• Update lease information in the lease database to indicate that the lease is now available for reassignment.

• Update counters on the server, a process that includes increasing the number of reclaimed leases and decreasing the number of assigned addresses or delegated prefixes.

Please refer to The DHCP-DDNS Server to see how to configure DNS updates in Kea, and to Hook Libraries for information about using hooks libraries.

Lease Reclamation Configuration Parameters

The following list presents all the configuration parameters pertaining to processing expired leases, with their default values:

• reclaim-timer-wait-time - this parameter governs intervals between the completion of the previous reclamation cycle and the start of the next one. Specified in seconds; the default value is 10.

• flush-reclaimed-timer-wait-time - this parameter controls how often the server initiates the lease reclamation procedure. Expressed in seconds; the default value is 25.

• hold-reclaimed-time - this parameter governs how long the lease should be kept after it is reclaimed. This enables lease affinity when set to a non-zero value. Expressed in seconds; the default value is 3600.

• max-reclaim-leases - this parameter specifies the maximum number of reclaimed leases that can be processed at one time. Zero means unlimited (i.e. process all reclaimed leases). The default value is 100.

• max-reclaim-time - this parameter specifies an upper limit to the length of time a lease reclamation procedure can take. Zero means no time limit. Expressed in milliseconds; the default value is 250.

• unwarned-reclaim-cycles - if lease reclamation limits are specified (max-reclaim-leases and/or max-reclaim-time), then under certain circumstances the server may not be able to deal with the leases to be reclaimed fast enough. This parameter specifies how many consecutive clean-up cycles must end with remaining leases to be processed before a warning is printed. The default is 5 cycles.

The parameters are explained in more detail in the rest of this chapter.

The default value for any parameter is used when the parameter is not explicitly specified in the configuration. If the expired-leases-processing map is omitted entirely in the configuration, the default values are used for all parameters listed above.

Configuring Lease Reclamation

Kea can be configured to periodically detect and reclaim expired leases. During this process the lease entries in the database are modified or removed. While this is happening the server does not process incoming DHCP messages, to avoid issues with concurrent access to database information. As a result, the server is unresponsive while lease reclamation is performed and DHCP queries will accumulate; responses will be sent once the lease-reclamation cycle is complete.

In deployments where response time is critical, administrators may wish to minimize the interruptions in service caused by lease reclamation. To this end, Kea provides configuration parameters to control the frequency of lease reclamation cycles, the maximum number of leases processed in a single reclamation cycle, and the maximum amount of time a single reclamation cycle is allowed to run before being interrupted. The following examples demonstrate how these parameters can be used:

"Dhcp4": {
    ...

    "expired-leases-processing": {
        "reclaim-timer-wait-time": 5,
        "max-reclaim-leases": 0,
        "max-reclaim-time": 0,
    },

    ...
}

The first parameter is expressed in seconds and specifies an interval between the two consecutive lease reclamation cycles. This is explained by the following diagram:

|  c1  |            | c2 |            |c3|            | c4 |
|<---->|<---------->|<-->|<---------->|<>|<---------->|<-->|<--
------------------------------------------------------------------>
|      |     5s     |    |     5s     |  |     5s     |    | time

This diagram shows four lease-reclamation cycles (c1 through c4) of variable duration. The duration of the reclamation cycle depends on the number of expired leases detected and processed in a particular cycle. This duration is usually significantly shorter than the interval between the cycles.

According to the reclaim-timer-wait-time, the server keeps fixed intervals of five seconds between the end of one cycle and the start of the next cycle. This guarantees the presence of 5-second-long periods during which the server remains responsive to DHCP queries and does not perform lease reclamation. The max-reclaim-leases and max-reclaim-time are set to 0, which sets no restriction on the maximum number of leases reclaimed in the particular cycle, or on the maximum duration of each cycle.

In deployments with high lease-pool utilization, relatively short valid lifetimes, and frequently disconnecting clients which allow leases to expire, the number of expired leases requiring reclamation at any given time may rise significantly. In this case, it is often desirable to apply restrictions to the maximum duration of a reclamation cycle or the maximum number of leases reclaimed in a cycle. The following configuration demonstrates how this can be done:

"Dhcp4": {
    ...

    "expired-leases-processing": {
        "reclaim-timer-wait-time": 3,
        "max-reclaim-leases": 100,
        "max-reclaim-time": 50,
        "unwarned-reclaim-cycles": 10,
    },

    ...
}

In this example, the max-reclaim-leases parameter limits the number of leases reclaimed in a single cycle to 100, and the max-reclaim-time limits the maximum duration of each cycle to 50ms. The lease-reclamation cycle will be interrupted if either of these limitations is reached. The reclamation of any unreclaimed leases will be attempted in subsequent cycles.

The following diagram illustrates the behavior of the system in the presence of many expired leases, when the limits are applied for the reclamation cycles:

| c1 |                | c2 |                | c3 |                | c4 |
|<-->|<-------------->|<-->|<-------------->|<-->|<-------------->|<-->|<--
------------------------------------------------------------------------------>
|50ms|       3s       |50ms|       3s       |50ms|       3s       |50ms|  time

In this case, if any reclamation cycle takes more than 50ms, it is interrupted according to the value of the max-reclaim-time. This results in equal durations of all reclamation cycles over time. In this example, the limitation of the maximum 100 leases is not reached. This may be the case when database transactions or callouts in the hook libraries attached to the server are slow. Regardless, the chosen values for either the maximum number of leases or a maximum cycle time strongly depend on the particular deployment, the lease database backend being used, any hook libraries, etc. Administrators may need to experiment to tune the system to suit the dynamics of their deployment.

It is important to realize that with the use of these limits, there is a risk that expired leases will accumulate faster than the server can reclaim them. This should not be a problem if the server is dealing with a temporary burst of expirations, because it should be able to eventually deal with them over time. However, if leases expire at a high rate for a long period of time, the unreclaimed leases will pile up in the database. To notify the administrator that the current configuration does not satisfy the needs for reclamation of expired leases, the server issues a warning message in the log if it is unable to reclaim all leases within several reclamation cycles. The number of cycles after which such a warning is issued is specified with the unwarned-reclaim-cycles configuration parameter.

Setting the reclaim-timer-wait-time to 0 disables periodic reclamation of the expired leases.

Configuring Lease Affinity

Suppose that a laptop goes into sleep mode after a period of user inactivity. While the laptop is in sleep mode, its DHCP client does not renew leases obtained from the server and these leases will eventually expire. When the laptop wakes up, it is often desirable for it to continue using its previous assigned IP addresses. To facilitate this, the server needs to correlate returning clients with their expired leases. When the client returns, the server first checks for those leases and reassigns them if they have not been assigned to another client. The ability of the server to reassign the same lease to a returning client is referred to as “lease affinity.”

When lease affinity is enabled (i.e. when hold-reclaimed-time is configured to a value greater than zero), the server still reclaims leases according to the parameters described in Configuring Lease Reclamation, but the reclaimed leases are held in the database for a specified amount of time rather than removed. When the client returns, the server first verifies whether there are any reclaimed leases associated with this client and then reassigns them if possible. However, it is important to note that any reclaimed lease may be assigned to another client if that client specifically asks for it. Therefore, lease affinity does not guarantee that the reclaimed lease will be available for the client who used it before; it merely increases the chances of the client being assigned the same lease. If the lease pool is small - namely, in DHCPv4, for which address space is limited - there is an increased likelihood that the expired lease will be assigned to another client.

Consider the following configuration:

"Dhcp4": {
    ...

    "expired-leases-processing": {
        "reclaim-timer-wait-time": 3,
        "hold-reclaimed-time": 1800,
        "flush-reclaimed-timer-wait-time": 5
    },

    ...
}

The hold-reclaim-time specifies how many seconds after an expiration a reclaimed lease should be held in the database for reassignment to the same client. In the example given above, reclaimed leases are held for 30 minutes (1800 seconds) after their expiration. During this time, the server will likely be able to reassign the same lease to the returning client, unless another client specifically requests this lease and the server assigns it.

The server must periodically remove reclaimed leases for which the time indicated by hold-reclaim-time has elapsed. The flush-reclaimed-timer-wait-time parameter controls how often the server removes such leases. In the example provided above, the server initiates removal of such leases five seconds after the previous removal attempt was completed. Setting this value to 0 disables lease affinity, meaning leases are removed from the lease database when they are reclaimed. If lease affinity is enabled, it is recommended that the hold-reclaim-time be set to a value significantly higher than the reclaim-timer-wait-time, as timely removal of expired-reclaimed leases is less critical than the removal process, which may impact server responsiveness.

There is no guarantee that lease affinity will work every time; if a server is running out of addresses, it will reassign expired addresses to new clients. Also, clients can request specific addresses and the server tries to honor such requests if possible. Administrators who want to ensure a client keeps its address, even after periods of inactivity, should consider using host reservations or leases with very long lifetimes.

Reclaiming Expired Leases via Command

The leases-reclaim command can be used to trigger lease reclamation at any time. Please consult the The leases-reclaim Command section for details about using this command.

Congestion Handling

What is Congestion?

Congestion occurs when servers are subjected to client queries faster than those queries can be processed. As a result, the servers begin accumulating a backlog of pending queries. The longer the high rate of traffic continues, the farther behind the servers fall. Depending on the client implementations, those that fail to get leases either give up or simply continue to retry forever. In the former case, the server may eventually recover, but the latter case is a vicious cycle from which the server is unable to escape.

Congestion typically occurs when there is a network event that causes overly large numbers of clients to simultaneously need leases, such as recovery after a network outage. In a well-planned deployment, the number and capacity of servers is matched to the maximum expected client load. If the load is routinely too heavy, then the deployment needs to be re-evaluated.

The goal of congestion handling is to help servers mitigate the peak in traffic by fulfilling as many of the most relevant requests as possible until the congestion subsides.

Configuring Congestion Handling

Congestion handling offers the ability to configure the server to use a separate thread to read packets from the interface socket buffers. As the thread reads packets from the buffers, they are added to an internal packet queue, and the server’s main application thread processes packets from this queue rather than from the socket buffers. By structuring it this way, a configurable layer has been introduced which can make decisions on which packets to process, how to store them, and the order in which they are processed by the server.

The default packet queue implementation for both kea-dhcp4 and kea-dhcp6 is a simple ring buffer. Once it reaches capacity, new packets get added to the back of the queue by discarding packets from the front of the queue. Rather than always discarding the newest packets, Kea now always discards the oldest packets. The capacity of the buffer, i.e. the maximum number of packets the buffer can contain, is configurable. A reasonable starting point is to match the capacity to the number of leases per second a specific installation of Kea can handle. This figure varies widely depending on the specifics of an individual deployment.

As there is no one algorithm that can best handle the dynamics of all sites, and because over time new approaches will evolve, the packet queue is implemented as a plug-in, which can be replaced by a custom queue implementation via a hook library. This should make it straightforward for interested parties to experiment with their own solutions. (Developers can refer to isc::dhcp::PacketQueue and isc::dhcp::PacketQueueMgr, described in the Kea Developer’s Guide.)

Packet queue behavior is configured in both kea-dhcp4 and kea-dhcp6 servers through an optional, top-level, configuration element, dhcp-queue-control. Omitting this element disables packet queueing:

"dhcp-queue-control": {
    "enable-queue": true|false,
    "queue-type": "queue type",
    "capacity" : n
}

where:

• enable-queue - enables or disables packet queueing. When true, the server processes packets from the packet queue, which is filled by a separate thread. When false, the server processes packets directly from the socket buffers in the main thread. It is disabled (false) by default.

• queue-type - the name of the queue implementation to use. This value exists so that custom implementations can be registered (via a hook library) and then selected. There is a default packet queue implementation that is pre-registered during server start up: “kea-ring4” for kea-dhcp4 and “kea-ring6” for kea-dhcp6.

• capacity - this is the maximum number of packets the queue can hold before packets are discarded. The optimal value for this is extremely site-dependent. The default value is 64 for both “kea-ring4” and “kea-ring6”.

The following example enables the default packet queue for kea-dhcp4, with a queue capacity of 250 packets:

"Dhcp4":
{
    ...
   "dhcp-queue-control": {
       "enable-queue": true,
       "queue-type": "kea-ring4",
       "capacity" : 250
    },
    ...
}

The following example enables the default packet queue for kea-dhcp6, with a queue capacity of 300 packets:

"Dhcp6":
{
    ...
   "dhcp-queue-control": {
       "enable-queue": true,
       "queue-type": "kea-ring6",
       "capacity" : 300
    },
    ...
}

The DHCP-DDNS Server

Overview

The DHCP-DDNS Server (kea-dhcp-ddns, known informally as D2) conducts the client side of the Dynamic DNS protocol (DDNS, defined in RFC 2136) on behalf of the DHCPv4 and DHCPv6 servers (kea-dhcp4 and kea-dhcp6 respectively). The DHCP servers construct DDNS update requests, known as NameChangeRequests (NCRs), based on DHCP lease change events and then post them to D2. D2 attempts to match each request to the appropriate DNS server(s) and carries out the necessary conversation with those servers to update the DNS data.

DNS Server Selection

To match a request to the appropriate DNS servers, D2 must have a catalog of servers from which to select. In fact, D2 has two such catalogs, one for forward DNS and one for reverse DNS; these catalogs are referred to as “DDNS domain lists.” Each list consists of one or more named DDNS domains. Further, each DDNS domain has a list of one or more DNS servers that publish the DNS data for that domain.

When conducting forward-domain matching, D2 compares the fully qualified domain name (FQDN) in the request against the name of each forward DDNS domain in its catalog. The domain whose name matches the longest portion of the FQDN is considered the best match. For example, if the FQDN is “myhost.sample.example.com.”, and there are two forward domains in the catalog, “sample.example.com.” and “example.com.”, the former is regarded as the best match. In some cases, it may not be possible to find a suitable match. Given the same two forward domains there would be no match for the FQDN “bogus.net”, so the request would be rejected. Finally, if there are no forward DDNS domains defined, D2 simply disregards the forward-update portion of requests.

When conducting reverse-domain matching, D2 constructs a reverse FQDN from the lease address in the request and compares that against the name of each reverse DDNS domain. Again, the domain whose name matches the longest portion of the FQDN is considered the best match. For instance, if the lease address is “172.16.1.40” and there are two reverse domains in the catalog, “1.16.172.in-addr.arpa.” and “16.172.in-addr.arpa”, the former is the best match. As with forward matching, D2 may not find a suitable match. Given the same two domains, there would be no match for the lease address, “192.168.1.50”, and the request would be rejected. As with forward-domain matching, if there are no reverse DDNS domains defined, D2 simply disregards the reverse-update portion of requests.

Conflict Resolution

D2 implements the conflict resolution strategy prescribed by RFC 4703. Conflict resolution is intended to prevent different clients from mapping to the same FQDN at the same time. To make this possible, the RFC requires that forward DNS entries for a given FQDN must be accompanied by a DHCID resource record (RR). This record contains a client identifier that uniquely identifies the client to whom the name belongs. Furthermore, any DNS updater that wishes to update or remove existing forward entries for an FQDN may only do so if their client matches that of the DHCID RR.

In other words, the DHCID RR maps an FQDN to the client to whom it belongs, and thereafter changes to that mapping can only be done by or at the behest of that client.

Conflict resolution can be indirectly enabled or disabled via the configuration parameter ddns-use-conflict-resolution, supported by both kea-dhcp4 and kea-dhcp6. These servers use this parameter to set a flag within each NameChangeRequest they send that tells D2 whether conflict resolution should be employed for that request. By default, conflict resolution is enabled. For more details, please refer to discussions of ddns-use-conflict-resolution in DDNS for DHCPv4 and DDNS for DHCPv6.

When conflict resolution is disabled, D2 still adds DHCID RRs but does not use them to enforce client ownership of DNS entries. Disabling it should only be used after careful consideration.

Dual-Stack Environments

RFC 4703, section 5.2, describes issues that may arise with dual-stack clients. These are clients that wish to have both IPv4 and IPv6 mappings for the same FQDN. To work properly, clients must embed their IPv6 DUID within their IPv4 client identifier option, as described in RFC 4361. In this way, DNS updates for both IPv4 and IPv6 can be managed under the same DHCID RR. This feature is supported by Kea beginning with release 2.1.2.

Starting and Stopping the DHCP-DDNS Server

kea-dhcp-ddns is the Kea DHCP-DDNS server and, due to the nature of DDNS, it runs alongside either the DHCPv4 or DHCPv6 component (or both). Like other parts of Kea, it is a separate binary that can be run on its own or through keactrl (see Managing Kea with keactrl). In normal operation, controlling kea-dhcp-ddns with keactrl is recommended; however, it is also possible to run the DHCP-DDNS server directly. It accepts the following command-line switches:

• -c file - specifies the configuration file. This is the only mandatory switch.

• -d - specifies whether server logging should be switched to debug/verbose mode. In verbose mode, the logging severity and debuglevel specified in the configuration file are ignored and “debug” severity and the maximum debuglevel (99) are assumed. The flag is convenient for temporarily switching the server into maximum verbosity, e.g. when debugging.

• -v - displays the Kea version and exits.

• -W - displays the Kea configuration report and exits. The report is a copy of the config.report file produced by ./configure; it is embedded in the executable binary.

• -t file - specifies the configuration file to be tested. kea-dhcp-ddns attempts to load it and conducts sanity checks. Certain checks are possible only while running the actual server. The actual status is reported with an exit code (0 = configuration looks okay, 1 = error encountered). Kea prints out log messages to standard output and errors to standard error when testing the configuration.

The config.report file may also be accessed directly, via the following command. The binary path may be found in the install directory or in the .libs subdirectory in the source tree. For example: kea/src/bin/d2/.libs/kea-dhcp-ddns.

strings path/kea-dhcp-ddns | sed -n 's/;;;; //p'

Upon startup, the module loads its configuration and begins listening for NCRs based on that configuration.

During startup, the server attempts to create a PID file of the form: [runstatedir]/[conf name].kea-dhcp-ddns.pid where:

• runstatedir - is the value as passed into the build configure script; it defaults to “/usr/local/var/run”. Note that this value may be overridden at runtime by setting the environment variable KEA_PIDFILE_DIR. This is intended primarily for testing purposes.

• conf name - is the configuration file name used to start the server, minus all preceding paths and the file extension. For example, given a pathname of “/usr/local/etc/kea/myconf.txt”, the portion used would be “myconf”.

If the file already exists and contains the PID of a live process, the server issues a DHCP_DDNS_ALREADY_RUNNING log message and exits. It is possible, though unlikely, that the file is a remnant of a system crash and the process to which the PID belongs is unrelated to Kea. In such a case it is necessary to manually delete the PID file.

Configuring the DHCP-DDNS Server

Before starting the kea-dhcp-ddns module for the first time, a configuration file must be created. The following default configuration is a template that can be customized to individual requirements.

"DhcpDdns": {
    "ip-address": "127.0.0.1",
    "port": 53001,
    "dns-server-timeout": 100,
    "ncr-protocol": "UDP",
    "ncr-format": "JSON",
    "tsig-keys": [ ],
    "forward-ddns": {
        "ddns-domains": [ ]
    },
    "reverse-ddns": {
        "ddns-domains": [ ]
    }
}

The configuration can be divided into the following sections, each of which is described below:

• Global Server Parameters - define values which control connectivity and global server behavior.

• Control Socket - defines the Control Socket type and name.

• TSIG Key Info - defines the TSIG keys used for secure traffic with DNS servers.

• Forward DDNS - defines the catalog of forward DDNS domains.

• Reverse DDNS - defines the catalog of reverse DDNS domains.

Global Server Parameters

• ip-address - the IP address on which D2 listens for requests. The default is the local loopback interface at address 127.0.0.1. Either an IPv4 or IPv6 address may be specified.

• port - the port on which D2 listens for requests. The default value is 53001.

• dns-server-timeout - the maximum amount of time, in milliseconds, that D2 will wait for a response from a DNS server to a single DNS update message.

• ncr-protocol - the socket protocol to use when sending requests to D2. Currently only UDP is supported.

• ncr-format - the packet format to use when sending requests to D2. Currently only JSON format is supported.

D2 must listen for change requests on a known address and port. By default it listens at 127.0.0.1 on port 53001. The following example illustrates how to change D2’s global parameters so it will listen at 192.168.1.10 port 900:

"DhcpDdns": {
    "ip-address": "192.168.1.10",
    "port": 900,
    ...
    }
}

Warning

It is possible for a malicious attacker to send bogus NameChangeRequests to the DHCP-DDNS server. Addresses other than the IPv4 or IPv6 loopback addresses (127.0.0.1 or ::1) should only be used for testing purposes; note that local users may still communicate with the DHCP-DDNS server.

Note

If the ip-address and port are changed, the corresponding values in the DHCP servers’ dhcp-ddns configuration section must be changed.

Management API for the D2 Server

The management API allows the issuing of specific management commands, such as configuration retrieval or shutdown. For more details, see Management API. Currently, the only supported communication channel type is the UNIX stream socket. By default there are no sockets open; to instruct Kea to open a socket, the following entry in the configuration file can be used:

"DhcpDdns": {
    "control-socket": {
        "socket-type": "unix",
        "socket-name": "/path/to/the/unix/socket"
    },
    ...
}

The length of the path specified by the socket-name parameter is restricted by the maximum length for the UNIX socket name on the operating system, i.e. the size of the sun_path field in the sockaddr_un structure, decreased by 1. This value varies on different operating systems, between 91 and 107 characters. Typical values are 107 on Linux and 103 on FreeBSD.

Communication over the control channel is conducted using JSON structures. See the Control Channel section in the Kea Developer’s Guide for more details.

The D2 server supports the following operational commands:

• build-report

• config-get

• config-reload

• config-set

• config-test

• config-write

• list-commands

• shutdown

• status-get

• version-get

Since Kea version 2.0.0, the D2 server also supports the following operational commands for statistics:

• statistic-get

• statistic-get-all

• statistic-reset

• statistic-reset-all

The shutdown command supports the extra type argument, which controls the way the D2 server cleans up on exit. The supported shutdown types are:

• normal - stops the queue manager and finishes all current transactions before exiting. This is the default.

• drain_first - stops the queue manager but continues processing requests from the queue until it is empty.

• now - exits immediately.

An example command may look like this:

{
    "command": "shutdown"
    "arguments": {
        "exit-value": 3,
        "type": "drain_first"
    }
}

TSIG Key List

A DDNS protocol exchange can be conducted with or without a transaction signature, or TSIG (defined in RFC 2845). This configuration section allows the administrator to define the set of TSIG keys that may be used in such exchanges.

To use TSIG when updating entries in a DNS domain, a key must be defined in the TSIG key list and referenced by name in that domain’s configuration entry. When D2 matches a change request to a domain, it checks whether the domain has a TSIG key associated with it. If so, D2 uses that key to sign DNS update messages sent to and verify responses received from the domain’s DNS server(s). For each TSIG key required by the DNS servers that D2 is working with, there must be a corresponding TSIG key in the TSIG key list.

As one might gather from the name, the tsig-key section of the D2 configuration lists the TSIG keys. Each entry describes a TSIG key used by one or more DNS servers to authenticate requests and sign responses. Every entry in the list has three parameters:

• name - is a unique text label used to identify this key within the list. This value is used to specify which key (if any) should be used when updating a specific domain. As long as the name is unique its content is arbitrary, although for clarity and ease of maintenance it is recommended that it match the name used on the DNS server(s). This field cannot be blank.

• algorithm - specifies which hashing algorithm should be used with this key. This value must specify the same algorithm used for the key on the DNS server(s). The supported algorithms are listed below:

  • HMAC-MD5

  • HMAC-SHA1

  • HMAC-SHA224

  • HMAC-SHA256

  • HMAC-SHA384

  • HMAC-SHA512

  This value is not case-sensitive.

• digest-bits - is used to specify the minimum truncated length in bits. The default value 0 means truncation is forbidden; non-zero values must be an integral number of octets, and be greater than both 80 and half of the full length. (Note that in BIND 9 this parameter is appended to the algorithm name, after a dash.)

• secret - is used to specify the shared secret key code for this key. This value is case-sensitive and must exactly match the value specified on the DNS server(s). It is a base64-encoded text value.

As an example, suppose that a domain D2 will be updating is maintained by a BIND 9 DNS server, which requires dynamic updates to be secured with TSIG. Suppose further that the entry for the TSIG key in BIND 9’s named.conf file looks like this:

:
key "key.four.example.com." {
    algorithm hmac-sha224;
    secret "bZEG7Ow8OgAUPfLWV3aAUQ==";
};
:

By default, the TSIG key list is empty:

"DhcpDdns": {
   "tsig-keys": [ ],
   ...
}

A new key must be added to the list:

"DhcpDdns": {
    "tsig-keys": [
        {
            "name": "key.four.example.com.",
            "algorithm": "HMAC-SHA224",
            "secret": "bZEG7Ow8OgAUPfLWV3aAUQ=="
        }
    ],
    ...
}

These steps must be repeated for each TSIG key needed, although the same TSIG key can be used with more than one domain.

Forward DDNS

The forward DDNS section is used to configure D2’s forward-update behavior. Currently it contains a single parameter, the catalog of forward DDNS domains, which is a list of structures.

"DhcpDdns": {
    "forward-ddns": {
        "ddns-domains": [ ]
    },
    ...
}

By default, this list is empty, which causes the server to ignore the forward-update portions of requests.

Adding Forward DDNS Domains

A forward DDNS domain maps a forward DNS zone to a set of DNS servers which maintain the forward DNS data (i.e. name-to-address mapping) for that zone. Each zone served needs one forward DDNS domain. Some or all of the zones may be maintained by the same servers, but one DDNS domain is still needed for each zone. Remember that matching a request to the appropriate server(s) is done by zone and a DDNS domain only defines a single zone.

This section describes how to add forward DDNS domains; repeat these steps for each forward DDNS domain desired. Each forward DDNS domain has the following parameters:

• name - this is the fully qualified domain name (or zone) that this DDNS domain can update. This value is compared against the request FQDN during forward matching. It must be unique within the catalog.

• key-name - if TSIG is used with this domain’s servers, this value should be the name of the key from the TSIG key list. If the value is blank (the default), TSIG will not be used in DDNS conversations with this domain’s servers.

• dns-servers - this is a list of one or more DNS servers which can conduct the server side of the DDNS protocol for this domain. The servers are used in a first-to-last preference; in other words, when D2 begins to process a request for this domain, it will pick the first server in this list and attempt to communicate with it. If that attempt fails, D2 will move to the next one in the list and so on, until either it is successful or the list is exhausted.

To create a new forward DDNS domain, add a new domain element and set its parameters:

"DhcpDdns": {
    "forward-ddns": {
        "ddns-domains": [
            {
                "name": "other.example.com.",
                "key-name": "",
                "dns-servers": [
                ]
            }
        ]
    }
}

It is possible to add a domain without any servers; however, if that domain matches a request, the request will fail. To make the domain useful, at least one DNS server must be added to it.

Adding Forward DNS Servers

This section describes how to add DNS servers to a forward DDNS domain. Repeat these instructions as needed for all the servers in each domain.

Forward DNS server entries represent actual DNS servers which support the server side of the DDNS protocol. Each forward DNS server has the following parameters:

• hostname - the resolvable host name of the DNS server; this parameter is not yet implemented.

• ip-address - the IP address at which the server listens for DDNS requests. This may be either an IPv4 or an IPv6 address.

• port - the port on which the server listens for DDNS requests. It defaults to the standard DNS service port of 53.

To create a new forward DNS server, a new server element must be added to the domain and its parameters filled in. If, for example, the service is running at “172.88.99.10”, set the forward DNS server as follows:

"DhcpDdns": {
    "forward-ddns": {
        "ddns-domains": [
            {
                "name": "other.example.com.",
                "key-name": "",
                "dns-servers": [
                    {
                        "ip-address": "172.88.99.10",
                        "port": 53
                    }
                ]
            }
        ]
    }
}

Note

Since hostname is not yet supported, the parameter ip-address must be set to the address of the DNS server.

Reverse DDNS

The reverse DDNS section is used to configure D2’s reverse update behavior, and the concepts are the same as for the forward DDNS section. Currently it contains a single parameter, the catalog of reverse DDNS domains, which is a list of structures.

"DhcpDdns": {
    "reverse-ddns": {
        "ddns-domains": [ ]
    }
    ...
}

By default, this list is empty, which causes the server to ignore the reverse-update portions of requests.

Adding Reverse DDNS Domains

A reverse DDNS domain maps a reverse DNS zone to a set of DNS servers which maintain the reverse DNS data (address-to-name mapping) for that zone. Each zone served needs one reverse DDNS domain. Some or all of the zones may be maintained by the same servers, but one DDNS domain entry is needed for each zone. Remember that matching a request to the appropriate server(s) is done by zone and a DDNS domain only defines a single zone.

This section describes how to add reverse DDNS domains; repeat these steps for each reverse DDNS domain desired. Each reverse DDNS domain has the following parameters:

• name - this is the fully qualified reverse zone that this DDNS domain can update. This is the value used during reverse matching, which compares it with a reversed version of the request’s lease address. The zone name should follow the appropriate standards; for example, to support the IPv4 subnet 172.16.1, the name should be “1.16.172.in-addr.arpa.”. Similarly, to support an IPv6 subnet of 2001:db8:1, the name should be “1.0.0.0.8.B.D.0.1.0.0.2.ip6.arpa.” The name must be unique within the catalog.

• key-name - if TSIG is used with this domain’s servers, this value should be the name of the key from the TSIG key list. If the value is blank (the default), TSIG will not be used in DDNS conversations with this domain’s servers.

• dns-servers - this is a list of one or more DNS servers which can conduct the server side of the DDNS protocol for this domain. Currently, the servers are used in a first-to-last preference; in other words, when D2 begins to process a request for this domain, it will pick the first server in this list and attempt to communicate with it. If that attempt fails, D2 will move to the next one in the list and so on, until either it is successful or the list is exhausted.

To create a new reverse DDNS domain, a new domain element must be added and its parameters set. For example, to support subnet 2001:db8:1::, the following configuration could be used:

"DhcpDdns": {
    "reverse-ddns": {
        "ddns-domains": [
            {
                "name": "1.0.0.0.8.B.D.0.1.0.0.2.ip6.arpa.",
                "key-name": "",
                "dns-servers": [
                ]
            }
        ]
    }
}

It is possible to add a domain without any servers; however, if that domain matches a request, the request will fail. To make the domain useful, at least one DNS server must be added to it.

Adding Reverse DNS Servers

This section describes how to add DNS servers to a reverse DDNS domain. Repeat these instructions as needed for all the servers in each domain.

Reverse DNS server entries represent actual DNS servers which support the server side of the DDNS protocol. Each reverse DNS server has the following parameters:

• hostname - the resolvable host name of the DNS server; this value is currently ignored.

• ip-address - the IP address at which the server listens for DDNS requests.

• port - the port on which the server listens for DDNS requests. It defaults to the standard DNS service port of 53.

To create a new reverse DNS server, a new server element must be added to the domain and its parameters specified. If, for example, the service is running at “172.88.99.10”, then set it as follows:

"DhcpDdns": {
    "reverse-ddns": {
        "ddns-domains": [
            {
                "name": "1.0.0.0.8.B.D.0.1.0.0.2.ip6.arpa.",
                "key-name": "",
                "dns-servers": [
                    {
                        "ip-address": "172.88.99.10",
                        "port": 53
                    }
                ]
            }
        ]
    }
}

Note

Since hostname is not yet supported, the parameter ip-address must be set to the address of the DNS server.

Per-DNS-Server TSIG Keys

Since Kea version 2.0.0, a TSIG key can be specified in a DNS server configuration. The priority rule is:

• if a not-empty key name is specified in a DNS server entry, this TSIG key protects DNS updates sent to this server.

• if the DNS server entry is empty, but a not-empty key name is specified in the parent’s domain entry, the parent domain’s TSIG key protects DNS updates sent to this server.

• if the DNS server entry is empty, and no key name is specified in its parent domain entry, no TSIG protects DNS updates sent to this server.

For instance, in this configuration:

"DhcpDdns": {
    "forward-ddns": {
        "ddns-domains": [
            {
                "name": "other.example.com.",
                "key-name": "foo",
                "dns-servers": [
                    {
                        "ip-address": "172.88.99.10",
                        "port": 53
                    },
                    {
                        "ip-address": "172.88.99.11",
                        "port": 53,
                        "key-name": "bar"
                    }
                ]
            }
        ]
    },
    "reverse-ddns": {
        "ddns-domains": [
            {
                "name": "1.0.0.0.8.B.D.0.1.0.0.2.ip6.arpa.",
                "dns-servers": [
                    {
                        "ip-address": "172.88.99.12",
                        "port": 53
                    },
                    {
                        "ip-address": "172.88.99.13",
                        "port": 53,
                        "key-name": "bar"
                    }
                ]
            }
        ]
    },
    "tsig-keys": [
        {
            "name": "foo",
            "algorithm": "HMAC-MD5",
            "secret": "LSWXnfkKZjdPJI5QxlpnfQ=="
        },
        {
            "name": "bar",
            "algorithm": "HMAC-SHA224",
            "secret": "bZEG7Ow8OgAUPfLWV3aAUQ=="
        }
    ]
}

The 172.88.99.10 server will use the “foo” TSIG key, the 172.88.99.11 and 172.88.99.13 servers will use the “bar” key. and 172.88.99.12 will not use TSIG.

User Contexts in DDNS

See Comments and User Context for additional background regarding the user context idea.

User contexts can be specified on a global scope, a DDNS domain, a DNS server, a TSIG key, and loggers. One other useful usage is the ability to store comments or descriptions; the parser translates a “comment” entry into a user context with the entry, which allows a comment to be attached inside the configuration itself.

Example DHCP-DDNS Server Configuration

This section provides a sample DHCP-DDNS server configuration, based on a small example network. Let’s suppose our example network has three domains, each with their own subnet.

Our example network

Domain	Subnet	Forward DNS Servers	Reverse DNS Servers
four.example.com	192.0.2.0/24	172.16.1.5, 172.16.2.5	172.16.1.5, 172.16.2.5
six.example.com	2001:db8:1::/64	3001:1::50	3001:1::51
example.com	192.0.0.0/16	172.16.2.5	172.16.2.5

We need to construct three forward DDNS domains:

Forward DDNS domains needed

#	DDNS Domain Name	DNS Servers
	four.example.com.	172.16.1.5, 172.16.2.5
	six.example.com.	3001:1::50
	example.com.	172.16.2.5

As discussed earlier, FQDN-to-domain matching is based on the longest match. The FQDN “myhost.four.example.com.” matches the first domain (“four.example.com”), while “admin.example.com.” matches the third domain (“example.com”). The FQDN “other.example.net.” fails to match any domain and is rejected.

The following example configuration specifies the forward DDNS domains.

"DhcpDdns": {
    "comment": "example configuration: forward part",
    "forward-ddns": {
        "ddns-domains": [
            {
                "name": "four.example.com.",
                "key-name": "",
                "dns-servers": [
                    { "ip-address": "172.16.1.5" },
                    { "ip-address": "172.16.2.5" }
                ]
            },
            {
                "name": "six.example.com.",
                "key-name": "",
                "dns-servers": [
                    { "ip-address": "2001:db8::1" }
                ]
            },
            {
                "name": "example.com.",
                "key-name": "",
                "dns-servers": [
                    { "ip-address": "172.16.2.5" }
                ],
                "user-context": { "backup": false }
            },

        ]
    }
}

Similarly, we need to construct the three reverse DDNS domains:

Reverse DDNS domains needed

#	DDNS Domain Name	DNS Servers
	2.0.192.in-addr.arpa.	172.16.1.5, 172.16.2.5
	1.0.0.0.8.d.b.0.1.0.0.2.ip6.arpa.	3001:1::50
	0.182.in-addr.arpa.	172.16.2.5

An address of “192.0.2.150” matches the first domain, “2001:db8:1::10” matches the second domain, and “192.0.50.77” matches the third domain.

These reverse DDNS domains are specified as follows:

"DhcpDdns": {
    "comment": "example configuration: reverse part",
    "reverse-ddns": {
        "ddns-domains": [
            {
                "name": "2.0.192.in-addr.arpa.",
                "key-name": "",
                "dns-servers": [
                    { "ip-address": "172.16.1.5" },
                    { "ip-address": "172.16.2.5" }
                ]
            }
            {
                "name": "1.0.0.0.8.B.D.0.1.0.0.2.ip6.arpa.",
                "key-name": "",
                "dns-servers": [
                    { "ip-address": "2001:db8::1" }
                ]
            }
            {
                "name": "0.192.in-addr.arpa.",
                "key-name": "",
                "dns-servers": [
                    { "ip-address": "172.16.2.5" }
                ]
            }
        ]
    }
}

DHCP-DDNS Server Statistics

Kea version 2.0.0 introduced statistics support for DHCP-DDNS.

Statistics are divided into three groups: NameChangeRequests, DNS updates, and per-TSIG-key DNS updates. While the statistics of the first two groups are cumulative, i.e. not affected by configuration change or reload, per-key statistics are reset to 0 when the underlying object is (re)created.

Currently Kea’s statistics management has the following limitations:

• only integer samples (i.e. a counter and a timestamp) are used;

• the maximum sample count is 1;

• there is no API to remove one or all statistics;

• there is no API to set the maximum sample count or age.

Note

Hook libraries, such as the the ISC subscriber-only GSS-TSIG library, make new statistics available in Kea.

More information about Kea statistics can be found at Statistics.

NCR Statistics

The NameChangeRequest statistics are:

• ncr-received - the number of received valid NCRs

• ncr-invalid - the number of received invalid NCRs

• ncr-error - the number of errors in NCR receptions other than an I/O cancel on shutdown

DNS Update Statistics

The global DNS update statistics are:

• update-sent - the number of DNS updates sent

• update-signed - the number of DNS updates sent and protected by TSIG

• update-unsigned - the number of DNS updates sent and not protected by TSIG

• update-success - the number of DNS updates which successfully completed

• update-timeout - the number of DNS updates which completed on timeout

• update-error - the number of DNS updates which completed with an error other than timeout

Per-TSIG-Key DNS Update Statistics

The per TSIG key DNS update statistics are:

• update-sent - the number of DNS updates sent

• update-success - the number of DNS updates which successfully completed

• update-timeout - the number of DNS updates which completed on timeout

• update-error - the number of DNS updates which completed with an error other than timeout

The name format for per-key statistics is key[<key-DNS-name>].<stat-name>: for instance, the name of the update-sent statistics for the key.example.com. TSIG key is key[key.example.com.].update-sent.

DHCP-DDNS Server Limitations

The following are the current limitations of the DHCP-DDNS server.

• Requests received from the DHCP servers are placed in a queue until they are processed. Currently, all queued requests are lost if the server shuts down.

Supported Standards

The following RFCs are supported by the DHCP-DDNS server:

• Secret Key Transaction Authentication for DNS (TSIG), RFC 2845: All DNS update packets sent and received by the DHCP-DDNS server can be protected by TSIG signatures.

• Dynamic Updates in the Domain Name System (DNS UPDATE), RFC 2136: The complete DNS update mechanism is supported.

• Resolution of Fully Qualified Domain Name (FQDN) Conflicts among Dynamic Host Configuration Protocol (DHCP) Clients, RFC 4703: DHCP-DDNS takes care of conflict resolution, for both DHCPv4 and DHCPv6 servers.

• A DNS Resource Record (RR) for Encoding Dynamic Host Configuration Protocol (DHCP) Information (DHCID RR), RFC 4701: The DHCP-DDNS server uses DHCID records.

The LFC Process

Overview

kea-lfc is a service process that removes redundant information from the files used to provide persistent storage for the memfile database backend. This service is written to run as a standalone process.

While kea-lfc can be started externally, there is usually no need to do so. kea-lfc is run on a periodic basis by the Kea DHCP servers.

The process operates on a set of files, using them to receive input and output of the lease entries and to indicate what stage the process is in, in the event of an interruption. Currently the caller must supply names for all of the files.

Command-Line Options

kea-lfc is run as follows:

kea-lfc [-4 | -6] -c config-file -p pid-file -x previous-file -i copy-file -o output-file -f finish-file

The argument -4 or -6 selects the protocol version of the lease files.

The -c argument specifies the configuration file. This is required, but is not currently used by the process.

The -p argument specifies the PID file. When the kea-lfc process starts, it attempts to determine whether another instance of the process is already running by examining the PID file. If one is already running, the new process is terminated; if one is not running, Kea writes its PID into the PID file.

The other filenames specify where the kea-lfc process should look for input, write its output, and perform its bookkeeping:

• previous — when kea-lfc starts, this is the result of any previous run of kea-lfc. When kea-lfc finishes, it is the result of this run. If kea-lfc is interrupted before completing, this file may not exist.

• input — before the DHCP server invokes kea-lfc, it moves the current lease file here and then calls kea-lfc with this file.

• output — this is the temporary file where kea-lfc writes the leases. Once the file has finished writing, it is moved to the finish file (see below).

• finish — this is another temporary file kea-lfc uses for bookkeeping. When kea-lfc completes writing the output file, it moves the contents to the file of this name. After kea-lfc finishes deleting the other files (previous and input), it moves this file to the previous lease file. By moving the files in this fashion, kea-lfc and the DHCP server processes can determine the correct file to use even if one of the processes is interrupted before completing its task.

There are several additional arguments, mostly for debugging purposes. -d sets the logging level to debug. -v and -V print out version stamps, with -V providing a longer form. -h prints out the usage string.

Client Classification

Client Classification Overview

In certain cases it is useful to differentiate among different types of clients and treat them accordingly. Common reasons include:

• The clients represent different pieces of topology, e.g. a cable modem is not the same as the clients behind that modem.

• The clients have different behavior, e.g. a smartphone behaves differently from a laptop.

• The clients require different values for some options, e.g. a docsis3.0 cable modem requires different settings from a docsis2.0 cable modem.

To make management easier, different clients can be grouped into a client class to receive common options.

An incoming packet can be associated with a client class in several ways:

• Implicitly, using a vendor class option or another built-in condition.

• Using an expression which evaluates to true.

• Using static host reservations, a shared network, a subnet, etc.

• Using a hook.

Client classification can be used to change the behavior of almost any part of the DHCP message processing. There are currently six mechanisms that take advantage of client classification: dropping queries, subnet selection, pool selection, definition of DHCPv4 private (codes 224-254) and code 43 options, assignment of different options, and, for DHCPv4 cable modems, the setting of specific options for use with the TFTP server address and the boot file field.

The classification process is conducted in several steps:

1. The ALL class is associated with the incoming packet.

2. Vendor class options are processed.

3. Classes with matching expressions and not marked for later evaluation (“on request” or depending on the KNOWN/UNKNOWN built-in classes) are processed in the order they are defined in the configuration; the boolean expression is evaluated and, if it returns true (a match), the incoming packet is associated with the class.

4. If a private or code 43 DHCPv4 option is received, it is decoded following its client-class or global (or, for option 43, last-resort) definition.

5. When the incoming packet belongs to the special class DROP, it is dropped and an informational message is logged with the packet information.

6. When the early-global-reservations-lookup global parameter is configured to true global reservations are looked for and the 8, 9 and 10 steps are partially performed: the lookup is limited to global reservations, if one is found the KNOWN class is set but if none is found the UNKNOWN class is not set.

7. A subnet is chosen, possibly based on the class information when some subnets are reserved. More precisely: when choosing a subnet, the server iterates over all of the subnets that are feasible given the information found in the packet (client address, relay address, etc.). It uses the first subnet it finds that either has no class associated with it, or has a class which matches one of the packet’s classes.

8. The server looks for host reservations. If an identifier from the incoming packet matches a host reservation in the subnet or shared network, the packet is associated with the KNOWN class and all classes of the host reservation. If a reservation is not found, the packet is assigned to the UNKNOWN class.

9. Classes with matching expressions - directly, or indirectly using the KNOWN/UNKNOWN built-in classes and not marked for later evaluation (“on request”) - are processed in the order they are defined in the configuration; the boolean expression is evaluated and, if it returns true (a match), the incoming packet is associated with the class. After a subnet is selected, the server determines whether there is a reservation for a given client. Therefore, it is not possible to use the UNKNOWN class to select a shared network or a subnet. For the KNOWN class only global reservations only global reservations are used and the early-global-reservations-lookup parameter must be configured to true

10. When the incoming packet belongs to the special class DROP, it is dropped and an informational message is logged with the packet information. Since Kea version 1.9.8, it is permissible to make the DROP class dependent on the KNOWN/UNKNOWN classes.

11. If needed, addresses and prefixes from pools are assigned, possibly based on the class information when some pools are reserved for class members.

12. Classes marked as “required” are evaluated in the order in which they are listed: first the shared network, then the subnet, and finally the pools that assigned resources belong to.

13. Options are assigned, again possibly based on the class information in the order that classes were associated with the incoming packet. For DHCPv4 private and code 43 options, this includes option definitions specified within classes.

Note

Client classes in Kea follow the order in which they are specified in the configuration (vs. alphabetical order). Required classes follow the order in which they are required.

When determining which options to include in the response, the server examines the union of options from all of the assigned classes. If two or more classes include the same option, the value from the first class examined is used; classes are examined in the order they were associated, so ALL is always the first class and matching required classes are last.

As an example, imagine that an incoming packet matches two classes. Class foo defines values for an NTP server (option 42 in DHCPv4) and an SMTP server (option 69 in DHCPv4), while class bar defines values for an NTP server and a POP3 server (option 70 in DHCPv4). The server examines the three options - NTP, SMTP, and POP3 - and returns any that the client requested. As the NTP server was defined twice, the server chooses only one of the values for the reply; the class from which the value is obtained is determined as explained in the previous paragraph.

Note

Care should be taken with client classification, as it is easy for clients that do not meet any class criteria to be denied service altogether.

Built-in Client Classes

Some classes are built-in, so they do not need to be defined. Vendor class information is the primary example: the server checks whether an incoming DHCPv4 packet includes the vendor class identifier option (60) or an incoming DHCPv6 packet includes the vendor class option (16). If it does, the content of that option is prepended with VENDOR_CLASS_ and the result is interpreted as a class. For example, modern cable modems send this option with value docsis3.0, so the packet belongs to class VENDOR_CLASS_docsis3.0.

The HA_ prefix is used by the High Availability hook library to designate certain servers to process DHCP packets as a result of load balancing. The class name is constructed by prepending the HA_ prefix to the name of the server which should process the DHCP packet. This server uses an appropriate pool or subnet to allocate IP addresses (and/or prefixes), based on the assigned client classes. The details can be found in ha: High Availability.

The BOOTP class is used by the BOOTP hook library to classify and respond to inbound BOOTP queries.

The SKIP_DDNS class is used by the DDNS-tuning hook library to suppress DDNS updates on a per client basis.

Other examples are the ALL class, to which all incoming packets belong, and the KNOWN class, assigned when host reservations exist for a particular client. By convention, the names of built-in classes begin with all capital letters.

Currently recognized built-in class names are ALL, KNOWN and UNKNOWN, and the prefixes VENDOR_CLASS_, HA_, AFTER_, EXTERNAL_, SKIP_DDNS. Although the AFTER_ prefix is a provision for an as-yet-unwritten hook, the EXTERNAL_ prefix can be freely used; built-in classes are implicitly defined so they never raise warnings if they do not appear in the configuration.

Using Expressions in Classification

The expression portion of a classification definition contains operators and values. All values are currently strings; operators take a string or strings and return another string. When all the operations have completed, the result should be a value of true or false. The packet belongs to the class (and the class name is added to the list of classes) if the result is true. Expressions are written in standard format and can be nested.

Expressions are pre-processed during the parsing of the configuration file and converted to an internal representation. This allows certain types of errors to be caught and logged during parsing. Examples of these errors include an incorrect number or type of argument to an operator. The evaluation code also checks for this class of error and generally throws an exception, though this should not occur in a normally functioning system.

Other issues, such as the starting position of a substring being outside of the substring or an option not existing in the packet, result in the operator returning an empty string.

Dependencies between classes are also checked. For instance, forward dependencies are rejected when the configuration is parsed; an expression can only depend on already-defined classes (including built-in classes) which are evaluated in a previous or the same evaluation phase. This does not apply to the KNOWN or UNKNOWN classes.

List of classification values

Name	Example expression	Example value
String literal	‘example’	‘example’
Hexadecimal string literal	0x5a7d	‘Z}’
IP address literal	10.0.0.1	0x0a000001
Integer literal	123	‘123’
Binary content of the option	option[123].hex	‘(content of the option)’
Option existence	option[123].exists	‘true’
Binary content of the sub-option	option[12].option[34].hex	‘(content of the sub-option)’
Sub-Option existence	option[12].option[34].exists	‘true’
Client class membership	member(‘foobar’)	‘true’
Known client	known	member(‘KNOWN’)
Unknown client	unknown	not member(‘KNOWN’)
DHCPv4 relay agent sub-option	relay4[123].hex	‘(content of the RAI sub-option)’
DHCPv6 Relay Options	relay6[nest].option[code].hex	(value of the option)
DHCPv6 Relay Peer Address	relay6[nest].peeraddr	2001:DB8::1
DHCPv6 Relay Link Address	relay6[nest].linkaddr	2001:DB8::1
Interface name of packet	pkt.iface	eth0
Source address of packet	pkt.src	10.1.2.3
Destination address of packet	pkt.dst	10.1.2.3
Length of packet	pkt.len	513
Hardware address in DHCPv4 packet	pkt4.mac	0x010203040506
Hardware length in DHCPv4 packet	pkt4.hlen	6
Hardware type in DHCPv4 packet	pkt4.htype	6
ciaddr field in DHCPv4 packet	pkt4.ciaddr	192.0.2.1
giaddr field in DHCPv4 packet	pkt4.giaddr	192.0.2.1
yiaddr field in DHCPv4 packet	pkt4.yiaddr	192.0.2.1
siaddr field in DHCPv4 packet	pkt4.siaddr	192.0.2.1
Message type in DHCPv4 packet	pkt4.msgtype	1
Transaction ID (xid) in DHCPv4 packet	pkt4.transid	12345
Message type in DHCPv6 packet	pkt6.msgtype	1
Transaction ID in DHCPv6 packet	pkt6.transid	12345
Vendor option existence (any vendor)	vendor[*].exists	true
Vendor option existence (specific vendor)	vendor[4491].exists	true
Enterprise-id from vendor option	vendor.enterprise	4491
Vendor sub-option existence	vendor[4491].option[1].exists	true
Vendor sub-option content	vendor[4491].option[1].hex	docsis3.0
Vendor class option existence (any vendor)	vendor-class[*].exist s	true
Vendor class option existence (specific vendor)	vendor-class[4491].exists	true
Enterprise-id from vendor class option	vendor-class.enterprise	4491
First data chunk from vendor class option	vendor-class[4491].data	docsis3.0
Specific data chunk from vendor class option	vendor-class[4491].data[3]	docsis3.0

Notes:

• Hexadecimal strings are converted into a string as expected. The starting “0X” or “0x” is removed, and if the string is an odd number of characters a “0” is prepended to it.

• IP addresses are converted into strings of length 4 or 16. IPv4, IPv6, and IPv4-embedded IPv6 (e.g. IPv4-mapped IPv6) addresses are supported.

• Integers in an expression are converted to 32-bit unsigned integers and are represented as four-byte strings; for example, 123 is represented as 0x0000007b. All expressions that return numeric values use 32-bit unsigned integers, even if the field in the packet is smaller. In general, it is easier to use decimal notation to represent integers, but it is also possible to use hexadecimal notation. When writing an integer in hexadecimal, care should be taken to make sure the value is represented as 32 bits, e.g. use 0x00000001 instead of 0x1 or 0x01. Also, make sure the value is specified in network order, e.g. 1 is represented as 0x00000001.

• option[code].hex extracts the value of the option with the code code from the incoming packet. If the packet does not contain the option, it returns an empty string. The string is presented as a byte string of the option payload, without the type code or length fields.

• option[code].exists checks whether an option with the code code is present in the incoming packet. It can be used with empty options.

• member('foobar') checks whether the packet belongs to the client class foobar. To avoid dependency loops, the configuration file parser verifies whether client classes were already defined or are built-in, i.e., beginning with VENDOR_CLASS_, AFTER_ (for the to-come “after” hook) and EXTERNAL_ or equal to ALL, KNOWN, UNKNOWN, etc.

  known and unknown are shorthand for member('KNOWN') and not member('KNOWN'). Note that the evaluation of any expression using the KNOWN class (directly or indirectly) is deferred after the host reservation lookup (i.e. when the KNOWN or UNKNOWN partition is determined).

• relay4[code].hex attempts to extract the value of the sub-option code from the option inserted as the DHCPv4 Relay Agent Information (82) option. If the packet does not contain a RAI option, or the RAI option does not contain the requested sub-option, the expression returns an empty string. The string is presented as a byte string of the option payload without the type code or length fields. This expression is allowed in DHCPv4 only.

• relay4 shares the same representation types as option; for instance, relay4[code].exists is supported.

• relay6[nest] allows access to the encapsulations used by any DHCPv6 relays that forwarded the packet. The nest level specifies the relay from which to extract the information, with a value of 0 indicating the relay closest to the DHCPv6 server. Negative values allow relays to be specified counting from the DHCPv6 client, with -1 indicating the relay closest to the client. If the requested encapsulation does not exist, an empty string "" is returned. This expression is allowed in DHCPv6 only.

• relay6[nest].option[code] shares the same representation types as option; for instance, relay6[nest].option[code].exists is supported.

• Expressions starting with pkt4 can be used only in DHCPv4. They allow access to DHCPv4 message fields.

• pkt6 refers to information from the client request. To access any information from an intermediate relay, use relay6. pkt6.msgtype and pkt6.transid output a 4-byte binary string for the message type or transaction ID. For example, the message type SOLICIT is 0x00000001 or simply 1, as in pkt6.msgtype == 1.

• “Vendor option” means the Vendor-Identifying Vendor-Specific Information option in DHCPv4 (code 125; see Section 4 of RFC 3925) and the Vendor-Specific Information Option in DHCPv6 (code 17, defined in Section 21.17 of RFC 8415). “Vendor class option” means the Vendor-Identifying Vendor Class Option in DHCPv4 (code 124; see Section 3 of RFC 3925) in DHCPv4 and the Class Option in DHCPv6 (code 16; see Section 21.16 of RFC 8415). Vendor options may have sub-options that are referenced by their codes. Vendor class options do not have sub-options, but rather data chunks, which are referenced by index value. Index 0 means the first data chunk, index 1 is for the second data chunk (if present), etc.

• In the vendor and vendor-class constructs an asterisk (*) or 0 can be used to specify a wildcard enterprise-id value, i.e. it will match any enterprise-id value.

• Vendor Class Identifier (option 60 in DHCPv4) can be accessed using the option[60] expression.

• RFC 3925 and RFC 8415 allow for multiple instances of vendor options to appear in a single message. The client classification code currently examines the first instance if more than one appear. For the vendor.enterprise and vendor-class.enterprise expressions, the value from the first instance is returned. Please submit a feature request on the Kea GitLab site to request support for multiple instances.

List of classification expressions

Name	Example	Description
Equal	‘foo’ == ‘bar’	Compare the two values and return true or false
Not	not (‘foo’ == ‘bar’)	Logical negation
And	(‘foo’ == ‘bar’) and (‘bar’ == ‘foo’)	Logical and
Or	(‘foo’ == ‘bar’) or (‘bar’ == ‘foo’)	Logical or
Substring	substring(‘foobar’,0,3)	Return the requested substring
Concat	concat(‘foo’,’bar’)	Return the concatenation of the strings
Concat (operator +)	‘foo’ + ‘bar’	Return the concatenation of the strings
Ifelse	ifelse(‘foo’ == ‘bar’,’us’,’them’)	Return the branch value according to the condition
Hexstring	hexstring(‘foo’, ‘-‘)	Converts the value to a hexadecimal string, e.g. 0a:1b:2c:3e
Split	split(‘foo.bar’, ‘.’, 2)	Return the second field, splitting on dots.

List of conversion-to-text expressions

Name	Example	Description
AddressToText	addrtotext (192.10.0.1) addrtotext (2003:db8::)	Represent the 4 bytes of an IPv4 address or the 16 bytes of an IPv6 address in human readable format
Int8ToText	int8totext (-1)	Represents the 8-bit signed integer in text format
Int16ToText	int16totext (-1)	Represents the 16-bit signed integer in text format
Int32ToText	int32totext (-1)	Represents the 32-bit signed integer in text format
UInt8ToText	uint8totext (255)	Represents the 8-bit unsigned integer in text format
UInt16ToText	uint16totext (65535)	Represents the 16-bit unsigned integer in text format
UInt32ToText	uint32totext (4294967295)	Represents the 32-bit unsigned integer in text format

Notes:

The conversion operators can be used to transform data from binary to the text representation. The only requirement is that the input data type length matches an expected value.

The AddressToText token expects 4 bytes for IPv4 addresses or 16 bytes for IPv6 addresses. The Int8ToText and UInt8ToText tokens expect 1 byte, the Int16ToText and UInt16ToText tokens expect 2 bytes, and Int32ToText and UInt32ToText expect 4 bytes. For all conversion tokens, if the data length is 0, the result string is empty.

Logical Operators

The Not, And, and Or logical operators are the common operators. Not has the highest precedence and Or the lowest. And and Or are (left) associative. Parentheses around a logical expression can be used to enforce a specific grouping; for instance, in “A and (B or C)”. Without parentheses, “A and B or C” means “(A and B) or C”.

Substring

The substring operator substring(value, start, length) accepts both positive and negative values for the starting position and the length. For start, a value of 0 is the first byte in the string while -1 is the last byte. If the starting point is outside of the original string an empty string is returned. length is the number of bytes to extract. A negative number means to count towards the beginning of the string but does not include the byte pointed to by start. The special value all means to return all bytes from start to the end of the string. If the length is longer than the remaining portion of the string, then the entire remaining portion is returned. Some examples may be helpful:

substring('foobar', 0, 6) == 'foobar'
substring('foobar', 3, 3) == 'bar'
substring('foobar', 3, all) == 'bar'
substring('foobar', 1, 4) == 'ooba'
substring('foobar', -5, 4) == 'ooba'
substring('foobar', -1, -3) == 'oba'
substring('foobar', 4, -2) == 'ob'
substring('foobar', 10, 2) == ''

Concat

The concat function concat(string1, string2) returns the concatenation of its two arguments. For instance:

concat('foo', 'bar') == 'foobar'

For user convenience, Kea version 1.9.8 added an associative operator version of the concat function. For instance:

'abc' + 'def' + 'ghi' + 'jkl' + '...'

is the same as:

concat(concat(concat(concat('abc', 'def'), 'ghi'), 'jkl'), '...')

or:

concat('abc', concat('def', concat('ghi', concat('jkl', '...'))))

or:

'abcdefghijkl...'

Split

The Split operator split(value, delimiters, field-number) accepts a list of characters to use as delimiters and a positive field number of the desired field when the value is split into fields separated by the delimiters. Adjacent delimiters are not compressed out, rather they result in an empty string for that field number. If value is an empty string, the result will be an empty string. If the delimiters list is empty, the result will be the original value. If the field-number is less than one or larger than the number of fields, the result will be an empty string. Some examples follow:

split ('one.two..four', '.', 1) == 'one'
split ('one.two..four', '.', 2) == 'two'
split ('one.two..four', '.', 3) == ''
split ('one.two..four', '.', 4) == 'four'
split ('one.two..four', '.', 5) == ''

Ifelse

The ifelse function ifelse(cond, iftrue, ifelse) returns the iftrue or ifelse branch value following the boolean condition cond. For instance:

ifelse(option[230].exists, option[230].hex, 'none')

Hexstring

The hexstring function hexstring(binary, separator) returns the binary value as its hexadecimal string representation: pairs of hexadecimal digits separated by the separator, e.g ':', '-', '' (empty separator).

hexstring(pkt4.mac, ':')

Note

The expression for each class is executed on each packet received. If the expressions are overly complex, the time taken to execute them may impact the performance of the server. Administrators who need complex or time-consuming expressions should consider writing a hook to perform the necessary work.

Configuring Classes

A class contains five items: a name, a test expression, option data, an option definition, and an only-if-required flag. The name must exist and must be unique among all classes. The test expression, option data and definition, and only-if-required flag are optional.

The test expression is a string containing the logical expression used to determine membership in the class. The entire expression is in double quotes (“).

The option data is a list which defines any options that should be assigned to members of this class.

The option definition is for DHCPv4 option 43 (DHCPv4 Vendor-Specific Options) and DHCPv4 private options (DHCPv4 Private Options).

Usually the test expression is evaluated before subnet selection, but in some cases it is useful to evaluate it later when the subnet, shared network, or pools are known but output-option processing has not yet been done. The only-if-required flag, which is false by default, allows the evaluation of the test expression only when it is required, i.e. in a require-client-classes list of the selected subnet, shared network, or pool.

The require-client-classes list, which is valid for shared-network, subnet, and pool scope, specifies the classes which are evaluated in the second pass before output-option processing. The list is built in the reversed precedence order of option data, i.e. an option data item in a subnet takes precedence over one in a shared network, but required class in a subnet is added after one in a shared network. The mechanism is related to the only-if-required flag but it is not mandatory that the flag be set to true.

In the following example, the class named “Client_foo” is defined. It is comprised of all clients whose client IDs (option 61) start with the string “foo”. Members of this class will be given 192.0.2.1 and 192.0.2.2 as their domain name servers.

"Dhcp4": {
    "client-classes": [
        {
            "name": "Client_foo",
            "test": "substring(option[61].hex,0,3) == 'foo'",
            "option-data": [
                {
                    "name": "domain-name-servers",
                    "code": 6,
                    "space": "dhcp4",
                    "csv-format": true,
                    "data": "192.0.2.1, 192.0.2.2"
                }
            ]
        },
        ...
    ],
    ...
}

The next example shows a client class being defined for use by the DHCPv6 server. In it the class named “Client_enterprise” is defined. It is comprised of all clients whose client identifiers start with the given hex string (which would indicate a DUID based on an enterprise ID of 0xAABBCCDD). Members of this class will be given 2001:db8:0::1 and 2001:db8:2::1 as their domain name servers.

"Dhcp6": {
    "client-classes": [
        {
            "name": "Client_enterprise",
            "test": "substring(option[1].hex,0,6) == 0x0002AABBCCDD",
            "option-data": [
                {
                    "name": "dns-servers",
                    "code": 23,
                    "space": "dhcp6",
                    "csv-format": true,
                    "data": "2001:db8:0::1, 2001:db8:2::1"
                }
            ]
        },
        ...
    ],
    ...
}

Using Static Host Reservations in Classification

Classes can be statically assigned to the clients using techniques described in Reserving Client Classes in DHCPv4 and Reserving Client Classes in DHCPv6.

Subnet host reservations are searched after subnet selection. Global host reservations are searched at the same time by default but the early-global-reservations-lookup allows to change this behavior into searching them before the subnet selection.

Pool selection is performed after all host reservations lookups.

Configuring Subnets With Class Information

In certain cases it is beneficial to restrict access to certain subnets only to clients that belong to a given class, using the client-class keyword when defining the subnet.

Let’s assume that the server is connected to a network segment that uses the 192.0.2.0/24 prefix. The administrator of that network has decided that addresses from the range 192.0.2.10 to 192.0.2.20 will be managed by the DHCP4 server. Only clients belonging to client class “Client_foo” are allowed to use this subnet. Such a configuration can be achieved in the following way:

"Dhcp4": {
    "client-classes": [
        {
            "name": "Client_foo",
            "test": "substring(option[61].hex,0,3) == 'foo'",
            "option-data": [
                {
                    "name": "domain-name-servers",
                    "code": 6,
                    "space": "dhcp4",
                    "csv-format": true,
                    "data": "192.0.2.1, 192.0.2.2"
                }
            ]
        },
        ...
    ],
    "subnet4": [
        {
            "subnet": "192.0.2.0/24",
            "pools": [ { "pool": "192.0.2.10 - 192.0.2.20" } ],
            "client-class": "Client_foo"
        },
        ...
    ],,
    ...
}

The following example shows how to restrict access to a DHCPv6 subnet. This configuration restricts use of the addresses in the range 2001:db8:1::1 to 2001:db8:1::FFFF to members of the “Client_enterprise” class.

"Dhcp6": {
    "client-classes": [
        {
            "name": "Client_enterprise",
            "test": "substring(option[1].hex,0,6) == 0x0002AABBCCDD",
            "option-data": [
                {
                    "name": "dns-servers",
                    "code": 23,
                    "space": "dhcp6",
                    "csv-format": true,
                    "data": "2001:db8:0::1, 2001:db8:2::1"
                }
            ]
        },
        ...
    ],
    "subnet6": [
        {
            "subnet": "2001:db8:1::/64",
            "pools": [ { "pool": "2001:db8:1::-2001:db8:1::ffff" } ],
            "client-class": "Client_enterprise"
        }
    ],
    ...
}

Configuring Pools With Class Information

Similar to subnets, in certain cases access to certain address or prefix pools must be restricted to only clients that belong to a given class, using the client-class when defining the pool.

Let’s assume that the server is connected to a network segment that uses the 192.0.2.0/24 prefix. The administrator of that network has decided that addresses from the range 192.0.2.10 to 192.0.2.20 are going to be managed by the DHCP4 server. Only clients belonging to client class “Client_foo” are allowed to use this pool. Such a configuration can be achieved in the following way:

"Dhcp4": {
    "client-classes": [
        {
            "name": "Client_foo",
            "test": "substring(option[61].hex,0,3) == 'foo'",
            "option-data": [
                {
                    "name": "domain-name-servers",
                    "code": 6,
                    "space": "dhcp4",
                    "csv-format": true,
                    "data": "192.0.2.1, 192.0.2.2"
                }
            ]
        },
        ...
    ],
    "subnet4": [
        {
            "subnet": "192.0.2.0/24",
            "pools": [
                {
                    "pool": "192.0.2.10 - 192.0.2.20",
                    "client-class": "Client_foo"
                }
            ]
        },
        ...
    ],,

}

The following example shows how to restrict access to an address pool. This configuration restricts use of the addresses in the range 2001:db8:1::1 to 2001:db8:1::FFFF to members of the “Client_enterprise” class.

"Dhcp6": {
    "client-classes": [
        {
            "name": "Client_enterprise_",
            "test": "substring(option[1].hex,0,6) == 0x0002AABBCCDD",
            "option-data": [
                {
                    "name": "dns-servers",
                    "code": 23,
                    "space": "dhcp6",
                    "csv-format": true,
                    "data": "2001:db8:0::1, 2001:db8:2::1"
                }
            ]
        },
        ...
    ],
    "subnet6": [
        {
            "subnet": "2001:db8:1::/64",

            "pools": [
                {
                    "pool": "2001:db8:1::-2001:db8:1::ffff",
                    "client-class": "Client_foo"
                }
            ]
        },
        ...
    ],
    ...
}

Using Classes

Currently classes can be used for two functions: they can supply options to members of the class, and they can be used to choose a subnet from which an address will be assigned to a class member.

When options are defined as part of the class definition they override any global options that may be defined, and in turn will be overridden by any options defined for an individual subnet.

Classes and Hooks

Hooks may be used to classify packets. This may be useful if the expression would be complex or time-consuming to write, and could be better or more easily written as code. Once the hook has added the proper class name to the packet, the rest of the classification system will work as expected in choosing a subnet and selecting options. For a description of hooks, see Hook Libraries; for information on configuring classes, see Configuring Classes and Configuring Subnets With Class Information.

Debugging Expressions

While constructing classification expressions, administrators may find it useful to enable logging; see Logging for a more complete description of the logging facility.

To enable the debug statements in the classification system, the severity must be set to DEBUG and the debug level to at least 55. The specific loggers are kea-dhcp4.eval and kea-dhcp6.eval.

To understand the logging statements, it is essential to understand a bit about how expressions are evaluated; for a more complete description, refer to the design document at https://gitlab.isc.org/isc-projects/kea/wikis/designs/Design-documents. In brief, there are two structures used during the evaluation of an expression: a list of tokens which represent the expressions, and a value stack which represents the values being manipulated.

The list of tokens is created when the configuration file is processed, with most expressions and values being converted to a token. The list is organized in reverse Polish notation. During execution, the list is traversed in order; as each token is executed, it is able to pop values from the top of the stack and eventually push its result on the top of the stack. Imagine the following expression:

"test": "substring(option[61].hex,0,3) == 'foo'",

This will result in the following tokens:

option, number (0), number (3), substring, text ('foo'), equals

In this example, the first three tokens will simply push values onto the stack. The substring token will then remove those three values and compute a result that it places on the stack. The text option also places a value on the stack, and finally the equals token removes the two tokens on the stack and places its result on the stack.

When debug logging is enabled, each time a token is evaluated it emits a log message indicating the values of any objects that were popped off of the value stack, and any objects that were pushed onto the value stack.

The values are displayed as either text, if the command is known to use text values, or hexadecimal, if the command either uses binary values or can manipulate either text or binary values. For expressions that pop multiple values off the stack, the values are displayed in the order they were popped. For most expressions this will not matter, but for the concat expression the values are displayed in reverse order from their written order in the expression.

Let us assume that the following test has been entered into the configuration. This example skips most of the configuration to concentrate on the test.

"test": "substring(option[61].hex,0,3) == 'foo'",

The logging might then resemble this:

2016-05-19 13:35:04.163 DEBUG [kea.eval/44478] EVAL_DEBUG_OPTION Pushing option 61 with value 0x666F6F626172
2016-05-19 13:35:04.164 DEBUG [kea.eval/44478] EVAL_DEBUG_STRING Pushing text string '0'
2016-05-19 13:35:04.165 DEBUG [kea.eval/44478] EVAL_DEBUG_STRING Pushing text string '3'
2016-05-19 13:35:04.166 DEBUG [kea.eval/44478] EVAL_DEBUG_SUBSTRING Popping length 3, start 0, string 0x666F6F626172 pushing result 0x666F6F
2016-05-19 13:35:04.167 DEBUG [kea.eval/44478] EVAL_DEBUG_STRING Pushing text string 'foo'
2016-05-19 13:35:04.168 DEBUG [kea.eval/44478] EVAL_DEBUG_EQUAL Popping 0x666F6F and 0x666F6F pushing result 'true'

Note

The debug logging may be quite verbose if there are multiple expressions to evaluate; it is intended as an aid in helping create and debug expressions. Administrators should plan to disable debug logging when expressions are working correctly. Users may also wish to include only one set of expressions at a time in the configuration file while debugging them, to limit the log statements. For example, when adding a new set of expressions, an administrator might find it more convenient to create a configuration file that only includes the new expressions until they are working correctly, and then add the new set to the main configuration file.

Hook Libraries

Introduction

Kea is both flexible and customizable, via the use of “hooks.” This feature lets Kea load one or more dynamically linked libraries (known as “hook libraries”) and, at various points in its processing (“hook points”), call functions in them. Those functions perform whatever custom processing is required.

The hooks concept allows the core Kea code to remain reasonably small by moving features to external libraries that some, but not all, users find useful. Those with no need for specific functions can simply choose not to load the libraries.

Hook libraries are loaded by individual Kea processes, not by Kea as a whole. This means, among other things, that it is possible to associate one set of libraries with the DHCP4 server and a different set with the DHCP6 server.

It is also possible for a process to load multiple libraries. When processing reaches a hook point, Kea calls the hook library functions attached to it. If multiple libraries have attached a function to a given hook point, Kea calls all of them, in the order in which the libraries are specified in the configuration file. The order may be important; consult the documentation of the libraries for specifics.

When a Kea process unloads a library, it expects the dlclose function to remove all library symbols, as well as the library code, from address space. Although most OSes implement the dlclose function, this behavior is not required by the POSIX standard and not all systems support it; for example, the musl library, used by default by Alpine Linux, implements the dlclose function as a no operation. On such systems a library actually remains loaded for the lifetime of the process, which means that it must be restarted to update libraries with newer versions; it is not sufficient to simply reconfigure or reload the Kea process.

The next section describes how to configure hook libraries. Users who are interested in writing their own hook library can find information in the Hooks Developer’s Guide section of the Kea Developer’s Guide.

Note that some libraries are available under different licenses.

Please also note that some libraries may require additional dependencies and/or compilation switches to be enabled, e.g. the RADIUS library requires the FreeRadius-client library to be present. If the --with-freeradius option is not specified, the RADIUS library is not built.

Installing Hook Packages

Note

For more details about installing the Kea Premium Hooks package, please read this Knowledge Base article.

Some hook packages are included in the base Kea sources. There is no need to do anything special to compile or install them, as they are covered by the usual building and installation procedures. Please refer to Installation for a general overview of the installation process.

ISC provides several additional premium hooks in the form of packages, which follow a similar installation procedure but with several additional steps. For our users’ convenience, the premium hooks installation procedure is described in this section.

1. Download the package; detailed instructions are provided in the KB article above. The package will be a file with a name similar to kea-premium-|release|.tar.gz. (The name may vary depending on the package purchased.)

2. Administrators who have the sources for the corresponding version of the open-source Kea package on their system from the initial Kea installation should skip this step. Otherwise, extract the Kea source from the original tarball that was downloaded. For example, with a download of Kea 2.1.6., there should be a tarball called kea-|release|.tar.gz on the system. Unpack this tarball:

$ tar -zxvf kea-2.1.6.tar.gz

This will unpack the tarball into the kea-|release| subdirectory of the current working directory.

3. Unpack the Kea premium hooks tarball into the same directory where the original Kea source is located. Once Kea 2.1.6 has been unpacked into a kea-|release| subdirectory and the Kea premium tarball is in the current directory, the following steps will unpack the premium tarball into the correct location:

$ cd kea-2.1.6
$ tar -xvf ../kea-premium-2.1.6.tar.gz

Note that unpacking the Kea premium package puts the files into a directory named premium. Regardless of the name of the package, the directory will always be called premium, although its contents will vary depending on the hooks package.

4. Run the autoreconf tools. This step is necessary to update Kea’s build script to include the additional directory. If this tool is not already available on the system, install the automake and autoconf tools. To generate the configure script, please use:

$ autoreconf -i

5. Rerun configure, using the same configuration options that were used when originally building Kea. It is possible to verify that configure has detected the premium package by inspecting the summary printed when it exits. The first section of the output should look something like this:

Package:
  Name:             kea
  Version:          2.1.6
  Extended version: 2.1.6 (tarball)
  OS Family:        Linux
  Using GNU sed:    yes
  Premium package:  yes
  Included Hooks:   forensic_log flex_id host_cmds

The last line indicates which specific hooks were detected. Note that some hooks may require their own dedicated switches, e.g. the RADIUS hook requires extra switches for FreeRADIUS. Please consult later sections of this chapter for details.

6. Rebuild Kea.

$ make

If the machine has multiple CPU cores, an interesting option to consider here is using the argument -j X, where X is the number of available cores.

7. Install Kea sources along with the hooks:

$ sudo make install

Note that as part of the installation procedure, the install script places additional hook libraries and associated files into the premium/ directory.

The installation location of the hook libraries depends on whether the --prefix parameter was specified in the configure script. If not, the default location is /usr/local/lib/kea/hooks. The proper installation of the libraries can be verified with this command:

$ ls -l /usr/local/lib/kea/hooks/*.so
/usr/local/lib/kea/hooks/libca_rbac.so
/usr/local/lib/kea/hooks/libdhcp_class_cmds.so
/usr/local/lib/kea/hooks/libdhcp_flex_id.so
/usr/local/lib/kea/hooks/libdhcp_flex_option.so
/usr/local/lib/kea/hooks/libdhcp_host_cmds.so
/usr/local/lib/kea/hooks/libdhcp_lease_cmds.so
/usr/local/lib/kea/hooks/libdhcp_legal_log.so
/usr/local/lib/kea/hooks/libdhcp_subnet_cmds.so

The exact list returned depends on the packages installed. If the directory was specified via --prefix, the hook libraries will be located in {prefix directory}/lib/kea/hooks.

Configuring Hook Libraries

The hook libraries for a given process are configured using the hooks-libraries keyword in the configuration for that process. (Note that the word “hooks” is plural.) The value of the keyword is an array of map structures, with each structure corresponding to a hook library. For example, to set up two hook libraries for the DHCPv4 server, the configuration would be:

"Dhcp4": {
    :
    "hooks-libraries": [
        {
            "library": "/opt/charging.so"
        },
        {
            "library": "/opt/local/notification.so",
            "parameters": {
                "mail": "spam@example.com",
                "floor": 13,
                "debug": false,
                "users": [ "alice", "bob", "charlie" ],
                "languages": {
                    "french": "bonjour",
                    "klingon": "yl'el"
                }
            }
        }
    ]
    :
}

Note

Libraries are reloaded even if their lists have not changed, because the parameters specified for the library (or the files those parameters point to) may have changed.

Libraries may have additional parameters that are not mandatory, in the sense that there may be libraries that do not require them. However, for any given library there is often a requirement to specify a certain set of parameters. Please consult the documentation for each individual library for details. In the example above, the first library (/opt/charging.so) has no parameters. The second library (/opt/local/notification.so) has five parameters: specifying mail (string parameter), floor (integer parameter), debug (boolean parameter), lists (list of strings), and maps (containing strings). Nested parameters can be used if the library supports it. This topic is explained in detail in the Hooks Developer’s Guide section of the Kea Developer’s Guide.

Notes:

• The full path to each library should be given.

• As noted above, the order in which the hooks are called may be important; consult the documentation for each library for specifics.

• An empty list has the same effect as omitting the hooks-libraries configuration element altogether.

  Note

  There is one case where this is not true: if Kea is running with a configuration that contains a hooks-libraries item, and that item is removed and the configuration reloaded, the removal will be ignored and the libraries remain loaded. As a workaround, instead of removing the hooks-libraries item, change it to an empty list.

At the moment, only the kea-dhcp4 and kea-dhcp6 processes support hook libraries.

Available Hook Libraries

As described above, the hook functionality provides a way to customize a Kea server without modifying the core code. ISC has chosen to take advantage of this feature to provide functions that may only be useful to a subset of Kea users. To this end, ISC has created some hook libraries, discussed in the following sections.

Note

Some of these libraries are available with the base code, while others are shared with organizations who contribute to Kea’s development through paid ISC support contracts. Paid support includes professional engineering assistance, advance security notifications, input into ISC’s roadmap planning, and many other benefits, while helping keep Kea sustainable in the long term.

The following table provides a list of hook libraries currently available from ISC. It is important to pay attention to which libraries may be loaded by which Kea processes. It is a common mistake to configure the kea-ctrl-agent process to load libraries that should, in fact, be loaded by the kea-dhcp4 or kea-dhcp6 processes. If a library from ISC does not work as expected, please make sure that it has been loaded by the correct process per the table below.

Warning

While the Kea Control Agent includes the “hooks” functionality, (i.e. hook libraries can be loaded by this process), none of ISC’s current hook libraries should be loaded by the Control Agent.

List of available hook libraries

Name	Availability	Description
User Check	Kea open source	Reads known users list from a file. Unknown users will be assigned a lease from the last subnet defined in the configuration file, e.g. to redirect them to a captive portal. This demonstrates how an external source of information can be used to influence the Kea allocation engine. This hook is part of the Kea source code and is available in the src/hooks/dhcp/user_chk directory.
Forensic Logging	ISC support customers	This library provides hooks that record a detailed log of lease assignments and renewals into a set of log files. In many legal jurisdictions, companies - especially ISPs - must record information about the addresses they have leased to DHCP clients. This library is designed to help with that requirement. If the information that it records is sufficient, it may be used directly. If a jurisdiction requires a different set of information to be saved, it can be used as a template or example to create custom logging hooks. In Kea 1.9.8, additional parameters were added to give users more flexibility regarding what information should be logged.
Flexible Identifier	ISC support customers	Kea software provides a way to handle host reservations that include addresses, prefixes, options, client classes and other features. The reservation can be based on hardware address, DUID, circuit-id or client-id in DHCPv4 and using hardware address or DUID in DHCPv6. However, there are sometimes scenarios where the reservation is more complex, e.g. uses other options than mentioned above, uses parts of specific options, or perhaps uses a combination of several options and fields to uniquely identify a client. Those scenarios are addressed by the Flexible Identifier hook application. It allows defining an expression, similar to the one used in client classification, e.g. substring(relay6[0].option[37],0,6). Each incoming packet is evaluated against that expression and its value is then searched in the reservations database.
Flexible Option	Kea open source	This library provides hooks that compute option values instead of static configured values. An expression is evaluated on the query packet. Defined add, supersede, and remove actions are applied on the response packet before it is sent using the evaluation result.
Host Commands	ISC support customers	Kea provides a way to store host reservations in a database. In many larger deployments it is useful to be able to manage that information while the server is running. This library provides management commands for adding, querying, and deleting host reservations in a safe way without restarting the server. In particular, it validates the parameters, so an attempt to insert incorrect data, e.g. add a host with conflicting identifier in the same subnet, is rejected. Those commands are exposed via the command channel (JSON over UNIX sockets) and the Control Agent (JSON over RESTful interface).
Subnet Commands	ISC support customers	In deployments in which subnet configuration needs to be frequently updated, it is a hard requirement that such updates be performed without the need for a full DHCP server reconfiguration or restart. This hook library allows for incremental changes to the subnet configuration such as adding or removing a subnet. It also allows for listing all available subnets and fetching detailed information about a selected subnet. The commands exposed by this library do not affect other subnets or configuration parameters currently used by the server.
Lease Commands	Kea open source	This hook library offers a number of commands used to manage leases. Kea can store lease information in various backends: memfile, MySQL, PostgreSQL. This library provides a unified interface to manipulate leases in an unified, safe way. In particular, it allows manipulation of memfile leases while Kea is running, sanity check changes, lease existence checks, and removal of all leases belonging to a specific subnet. It can also catch obscure errors, like the addition of a lease with subnet-id that does not exist in the configuration, or configuration of a lease to use an address that is outside of the subnet to which it is supposed to belong. This library allows easy management of user contexts associated with leases.
High Availability	Kea open source	The risk of DHCP service unavailability can be minimized by setting up a pair of DHCP servers in a network. Two modes of operation are supported. The first one is called load-balancing, and is sometimes referred to as “active-active.” Each server can handle selected groups of clients in this network, or all clients if it detects that its partner has become unavailable. It is also possible to designate one server to serve all DHCP clients, and leave another server as standby. This mode is called “hot standby” and is sometimes referred to as “active-passive.” This server activates its DHCP function only when it detects that its partner is not available. Such cooperation between the DHCP servers requires that these servers constantly communicate with each other to send updates about allocated leases, and to periodically test whether their partners are still operational. The hook library also provides an ability to send lease updates to external backup servers, making it much easier to have a replacement that is up-to-date.
Statistics Commands	Kea open source	This library provides additional commands for retrieving accurate DHCP lease statistics, for Kea DHCP servers that share the same lease database. This setup is common in deployments where DHCP service redundancy is required and a shared lease database is used to avoid lease-data replication between the DHCP servers. This hook library returns lease statistics for each subnet.
RADIUS	ISC support customers	The RADIUS hook library allows Kea to interact with RADIUS servers using access and accounting mechanisms. The access mechanism may be used for access control, assigning specific IPv4 or IPv6 addresses reserved by RADIUS, dynamically assigning addresses from designated pools chosen by RADIUS, or rejecting the client’s messages altogether. The accounting mechanism allows a RADIUS server to keep track of device activity over time.
Host Cache	ISC support customers	Some database backends, such as RADIUS, may take a long time to respond. Since Kea in general is synchronous, backend performance directly affects DHCP performance. To minimize performance impact, this library provides a way to cache responses from other hosts. This includes negative caching, i.e. the ability to remember that there is no client information in the database.
Class Commands	ISC support customers	This hook library allows configured DHCP client classes to be added, updated, deleted, and fetched without needing to restart the DHCP server.
MySQL Configuration Backend	Kea open source	This hook library is an implementation of the Kea Configuration Backend for MySQL. It uses a MySQL database as a repository for the Kea configuration information. Kea servers use this library to fetch their configurations.
PostgreSQL Configuration Backend	Kea open source	This hook library is an implementation of the Kea Configuration Backend for PostgreSQL. It uses a PostgreSQL database as a repository for the Kea configuration information. Kea servers use this library to fetch their configurations.
Configuration Backend Commands	ISC support customers	This hook library implements a collection of commands to manage Kea configuration information in a database. This library may only be used in conjunction with one of the supported Configuration Backend implementations.
BOOTP	Kea open source	This hook library adds BOOTP support, as defined in RFC 1497. It recognizes received BOOTP requests: they are translated into DHCPREQUEST packets, put into the BOOTP client class, and receive infinite lifetime leases.
Leasequery	ISC support customers	This library adds support for DHCPv4 Leasequery as described in RFC 4388; and for DHCPv6 Leasequery as described in RFC 5007.
Run Script	Kea open source	This hook library adds support to run external scripts for specific packet-processing hook points. There are several exported environment variables available for the script.
GSS-TSIG	ISC support customers	This hook library adds support to the Kea D2 server (kea-dhcp-ddns) for using GSS-TSIG to sign DNS updates.
RBAC	ISC support customers	This hook library adds support to the Kea Control Agent (kea-ctrl-agent) for Role Based Access Control filtering of commands.
DDNS-Tuning	ISC support customers	This hook library adds support for fine tuning various DDNS update aspects such as generating hostnames via expressions and skipping DDNS updates for select clients.

ISC hopes to see more hook libraries become available as time progresses, developed both internally and externally. Since this list may evolve dynamically, it is maintained on a wiki page, available at this link: https://gitlab.isc.org/isc-projects/kea/wikis/Hooks-available. Developers or others who are aware of any hook libraries not listed there are asked to please send a note to the kea-users or kea-dev mailing lists for updating. (Information on all of ISC’s public mailing lists can be found at https://www.isc.org/mailinglists/.)

The libraries developed by ISC are described in detail in the following sections.

user_chk: Checking User Access

The user_chk library serves several purposes:

• To assign “new” or “unregistered” users to a restricted subnet, while “known” or “registered” users are assigned to unrestricted subnets.

• To allow DHCP response options or vendor option values to be customized based on user identity.

• To provide a real-time record of user registration activity, which can be sampled by an external consumer.

• To serve as a demonstration of various capabilities possible using the hooks interface.

Once loaded, the library allows the separation of incoming requests into known and unknown clients. For known clients, packets are processed as usual, although it is possible to override the sending of certain options on a per-host basis. Clients that are not on the known hosts list are treated as unknown and are assigned to the last subnet defined in the configuration file.

As an example of a use case, this behavior may be implemented to put unknown users into a separate subnet that leads to a “walled garden,” where they can only access a registration portal. Once they fill in necessary data, their details are added to the known clients file and they get a proper address after their device is restarted.

Note

This library was developed several years before the host reservation mechanism became available. Host reservation is much more powerful and flexible, but the ability of user_chk to consult an external source of information about clients and alter Kea’s behavior remains useful and of educational value.

The library reads the /tmp/user_chk_registry.txt file while being loaded and each time an incoming packet is processed. Each line of the file is expected to contain a self-contained JSON snippet which must have the following two entries:

• type - whose value is "HW_ADDR" for IPv4 users or "DUID" for IPv6 users.

• id - whose value is either the hardware address or the DUID from the request formatted as a string of hex digits, with or without “:” delimiters.

and may have zero or more of the following entries:

• bootfile - whose value is the pathname of the desired file.

• tftp_server - whose value is the hostname or IP address of the desired server.

A sample user registry file is shown below:

{ "type" : "HW_ADDR", "id" : "0c:0e:0a:01:ff:04", "bootfile" : "/tmp/v4bootfile" }
{ "type" : "HW_ADDR", "id" : "0c:0e:0a:01:ff:06", "tftp_server" : "tftp.v4.example.com" }
{ "type" : "DUID", "id" : "00:01:00:01:19:ef:e6:3b:00:0c:01:02:03:04", "bootfile" : "/tmp/v6bootfile" }
{ "type" : "DUID", "id" : "00:01:00:01:19:ef:e6:3b:00:0c:01:02:03:06", "tftp_server" : "tftp.v6.example.com" }

As with any other hook libraries provided by ISC, internals of the user_chk code are well-documented. Users may refer to the user_chk library section of the Kea Developer’s Guide for information on how the code works internally. That, together with the Hooks Framework section of the Kea Developer’s Guide should give users some pointers on how to extend this library and perhaps even write one from scratch.

legal_log: Forensic Logging Hooks

This section describes the forensic log hook library. This library provides hooks that record a detailed log of assignments, renewals, releases, and other lease events into a set of log files.

Currently this library is only available to ISC customers with a paid support contract.

Note

This library may only be loaded by the kea-dhcp4 or kea-dhcp6 process.

In many legal jurisdictions, companies - especially ISPs - must record information about the addresses they have leased to DHCP clients. This library is designed to help with that requirement. If the information that it records is sufficient, it may be used directly.

If a jurisdiction requires that different information be saved, users may use the custom formatting capability to extract information from the inbound request packet, or from the outbound response packet. Administrators are advised to use this feature with caution, as it may affect server performance. The custom format cannot be used for control channel commands.

Alternatively, this library may be used as a template or an example for the user’s own custom logging hook. The logging is done as a set of hooks to allow it to be customized to any particular need; modifying a hook library is easier and safer than updating the core code. In addition, by using the hooks features, users who do not need to log this information can leave it out and avoid any performance penalties.

Log File Naming

The names of the log files follow a set pattern.

If using day, month, or year as the time unit, the file name follows the format:

path/base-name.CCYYMMDD.txt

where CC represents the century, YY represents the year, MM represents the month, and DD represents the day.

If using second as the time unit the file name follows the format:

path/base-name.TXXXXXXXXXXXXXXXXXXXX.txt

where XXXXXXXXXXXXXXXXXXXX represents the time in seconds since the beginning of the UNIX epoch.

When using second as the time unit, the file is rotated when the count number of seconds pass. In contrast, when using day, month, or year as the time unit, the file is rotated whenever the count of day, month, or year starts, as applicable.

The "path" and "base-name" are supplied in the configuration as described below; see Configuring the Forensic Log Hooks.

Note

When running Kea servers for both DHCPv4 and DHCPv6, the log names must be distinct. See the examples in Configuring the Forensic Log Hooks.

Configuring the Forensic Log Hooks

To use this functionality, the hook library must be included in the configuration of the desired DHCP server modules. The legal_log library can save logs to a text file or to a database (created using kea-admin; see First-Time Creation of the MySQL Database and First-Time Creation of the PostgreSQL Database). The library is installed alongside the Kea libraries in [kea-install-dir]/var/lib/kea, where kea-install-dir is determined by the --prefix option of the configure script; it defaults to /usr/local. Assuming the default value, kea-dhcp4 can be configured to load the legal_log library like this:

{
    "Dhcp4": {
        "hooks-libraries": [
            {
                "library": "/usr/local/lib/kea/hooks/libdhcp_legal_log.so",
                "parameters": {
                    "path": "/var/lib/kea/log",
                    "base-name": "kea-forensic4"
                }
            }
        ]
    }
}

For kea-dhcp6, the configuration is:

{
    "Dhcp6": {
        "hooks-libraries": [
            {
                "library": "/usr/local/lib/kea/hooks/libdhcp_legal_log.so",
                "parameters": {
                    "path": "/var/lib/kea/log",
                    "base-name": "kea-forensic6"
                }
            }
        ]
    }
}

The hook library parameters for the text file configuration are:

• path - the directory in which the forensic file(s) will be written. The default value is [prefix]/var/lib/kea. The directory must exist.

• base-name - an arbitrary value which is used in conjunction with the current system date to form the current forensic file name. It defaults to kea-legal.

• time-unit - configures the time unit used to rotate the log file. Valid values are second, day, month, or year. It defaults to day.

• count - configures the number of time units that need to pass until the log file is rotated. It can be any positive number, or 0, which disables log rotation. It defaults to 1.

If log rotation is disabled, a new file is created when the library is loaded; the new file name is different from any previous file name.

Additional actions can be performed just before closing the old file and after opening the new file. These actions must point to an external executable or script and are configured with the following settings:

• prerotate - an external executable or script called with the name of the file that will be closed. Kea does not wait for the process to finish.

• postrotate - an external executable or script called with the name of the file that was opened. Kea does not wait for the process to finish.

Custom formatting can be enabled for logging information that can be extracted either from the client’s request packet or from the server’s response packet. Use with caution as this might affect server performance. The custom format cannot be used for control channel commands. Two parameters can be used towards this goal, either together or separately:

• request-parser-format - an evaluated parsed expression used to extract and log data from the incoming packet.

• response-parser-format - an evaluated parsed expression used to extract and log data from the server response packet.

See Using Expressions in Classification for a list of expressions. If either request-parser-format or response-parser-format is configured, the default logging format is not used. If both of them are configured, the resulting log message is constructed by concatenating the data extracted from the request and the data extracted from the response.

The custom formatting permits logging on multiple lines using the hexstring 0x0a (ASCII code for new line). In the log file, each line is prepended with the log timestamp. For the database backend, the data is stored (including the newline character) in the same entry.

Examples:

{
    "Dhcp6": {
        "hooks-libraries": [
            {
                "library": "/usr/local/lib/kea/hooks/libdhcp_legal_log.so",
                "parameters": {
                    "path": "/var/lib/kea/log",
                    "base-name": "kea-forensic6",
                    "request-parser-format": "'first line' + 0x0a + 'second line'",
                    "response-parser-format": "'also second line' + 0x0a + 'third line'"
                }
            }
        ]
    }
}

Some data might be available in the request or only in the response; the data in the request packet might differ from that in the response packet.

The lease-client context can only be printed using the default format, as this information is not directly stored in the request packet or in the response packet.

The timestamp-format parameter can be used to change the timestamp logged at the beginning of each line. Permissible formatting is the one supported by strftime plus the ‘%Q’ extra format which adds the microseconds subunits. The default is: “%Y-%m-%d %H:%M:%S %Z”. This parameter has no effect for the database backends, where the timestamp is defined at the schema level.

Examples:

{
    "Dhcp6": {
        "hooks-libraries": [
            {
                "library": "/usr/local/lib/kea/hooks/libdhcp_legal_log.so",
                "parameters": {
                    "path": "/var/lib/kea/log",
                    "base-name": "kea-forensic6",
                    "timestamp-format": "%H%t%w %F%%"
                }
            }
        ]
    }
}

Additional parameters for the database connection can be specified, e.g:

{
  "Dhcp6": {
    "hooks-libraries": [
      {
        "library": "/usr/local/lib/kea/hooks/libdhcp_legal_log.so",
        "parameters": {
          "name": "database-name",
          "password": "passwd",
          "type": "mysql",
          "user": "user-name"
        }
      }
    ]
  }
}

For more specific information about database-related parameters, please refer to Lease Database Configuration and Lease Database Configuration.

If it is desired to restrict forensic logging to certain subnets, the "legal-logging" boolean parameter can be specified within a user context of these subnets. For example:

{
    "Dhcp4": {
        "subnet4": [
            {
                "subnet": "192.0.2.0/24",
                "pools": [
                    {
                        "pool": "192.0.2.1 - 192.0.2.200"
                    }
                ],
                "user-context": {
                    "legal-logging": false
                }
            }
        ]
    }
}

This configuration disables legal logging for the subnet “192.0.2.0/24”. If the "legal-logging" parameter is not specified, it defaults to true, which enables legal logging for the subnet.

The following example demonstrates how to selectively disable legal logging for an IPv6 subnet:

{
    "Dhcp6": {
        "subnet6": [
            {
                "subnet": "2001:db8:1::/64",
                "pools": [
                    {
                        "pool": "2001:db8:1::1-2001:db8:1::ffff"
                    }
                ],
                "user-context": {
                    "legal-logging": false
                }
            }
        ]
    }
}

See User Contexts in IPv4 and User Contexts in IPv6 to learn more about user contexts in Kea configuration.

DHCPv4 Log Entries

For DHCPv4, the library creates entries based on DHCPREQUEST, DHCPDECLINE, and DHCPRELEASE messages, et al., and their responses. The resulting packets and leases are taken into account, intercepted through the following hook points:

• pkt4_receive

• leases4_committed

• pkt4_send

• lease4_release

• lease4_decline

An entry is a single string with no embedded end-of-line markers and a prepended timestamp, and has the following sections:

timestamp address duration device-id {client-info} {relay-info} {user-context}

Where:

• timestamp - the date and time the log entry was written, in “%Y-%m-%d %H:%M:%S %Z” strftime format (“%Z” is the time zone name).

• address - the leased IPv4 address given out, and whether it was assigned, renewed, or released.

• duration - the lease lifetime expressed in days (if present), hours, minutes, and seconds. A lease lifetime of 0xFFFFFFFF will be denoted with the text “infinite duration.” This information is not given when the lease is released.

• device-id - the client’s hardware address shown as a numerical type and hex-digit string.

• client-info - the DHCP client id option (61) if present, shown as a hex string. When its content is printable it is displayed.

• relay-info - for relayed packets, the giaddr and the RAI circuit-id, remote-id, and subscriber-id options (option 82 sub options: 1, 2 and 6), if present. The circuit-id and remote-id are presented as hex strings. When their content is printable it is displayed.

• user-context - the optional user context associated with the lease.

For instance (line breaks are added here for readability; they are not present in the log file):

2018-01-06 01:02:03 CET Address: 192.2.1.100 has been renewed for 1 hrs 52 min 15 secs to a device with hardware address:
hwtype=1 08:00:2b:02:3f:4e, client-id: 17:34:e2:ff:09:92:54 connected via relay at address: 192.2.16.33,
identified by circuit-id: 68:6f:77:64:79 (howdy) and remote-id: 87:f6:79:77:ef

or for a release:

2018-01-06 01:02:03 CET Address: 192.2.1.100 has been released from a device with hardware address:
hwtype=1 08:00:2b:02:3f:4e, client-id: 17:34:e2:ff:09:92:54 connected via relay at address: 192.2.16.33,
identified by circuit-id: 68:6f:77:64:79 (howdy) and remote-id: 87:f6:79:77:ef

In addition to logging lease activity driven by DHCPv4 client traffic, the hook library also logs entries for the following lease management control channel commands: lease4-add, lease4-update, and lease4-del. These cannot have custom formatting. Each entry is a single string with no embedded end-of-line markers, and it will typically have the following form:

lease4-add:

*timestamp* Administrator added a lease of address: *address* to a device with hardware address: *device-id*

Depending on the arguments of the add command, it may also include the client-id and duration.

Example:

2018-01-06 01:02:03 CET Administrator added a lease of address: 192.0.2.202 to a device with hardware address:
1a:1b:1c:1d:1e:1f for 1 days 0 hrs 0 mins 0 secs

lease4-update:

*timestamp* Administrator updated information on the lease of address: *address* to a device with hardware address: *device-id*

Depending on the arguments of the update command, it may also include the client-id and lease duration.

Example:

2018-01-06 01:02:03 CET Administrator updated information on the lease of address: 192.0.2.202 to a device
with hardware address: 1a:1b:1c:1d:1e:1f, client-id: 1234567890

lease4-del: deletes have two forms, one by address and one by identifier and identifier type:

*timestamp* Administrator deleted the lease for address: *address*

or

*timestamp* Administrator deleted a lease for a device identified by: *identifier-type* of *identifier*

Currently only a type of @b hw-address (hardware address) is supported.

Examples:

2018-01-06 01:02:03 CET Administrator deleted the lease for address: 192.0.2.202

2018-01-06 01:02:12 CET Administrator deleted a lease for a device identified by: hw-address of 1a:1b:1c:1d:1e:1f

The request-parser-format and response-parser-format options can be used to extract and log data from the incoming packet and server response packet, respectively. The configured value is an evaluated parsed expression returning a string. A list of tokens is described in the server classification process. Use with caution as this might affect server performance. If either of them is configured, the default logging format is not used. If both of them are configured, the resulting log message is constructed by concatenating the logged data extracted from the request and the logged data extracted from the response.

The custom formatting permits logging on multiple lines using the hexstring 0x0a (ASCII code for new line). In the case of the log file, each line is prepended with the log timestamp. For the database backend, the data is stored (including the newline character) in the same entry.

Examples:

{
  "Dhcp4": {
    "hooks-libraries": [
      {
        "library": "/usr/local/lib/kea/hooks/libdhcp_legal_log.so",
        "parameters": {
          "name": "database-name",
          "password": "passwd",
          "type": "mysql",
          "user": "user-name",
          "request-parser-format": "'log entry' + 0x0a + 'same log entry'",
          "response-parser-format": "'also same log entry' + 0x0a + 'again same log entry'"
        }
      }
    ]
  }
}

Some data might be available in the request or in the response only, and some data might differ in the incoming packet from the one in the response packet.

Examples:

{
    "request-parser-format": "ifelse(pkt4.msgtype == 4 or pkt4.msgtype == 7, 'Address: ' + ifelse(option[50].exists, addrtotext(option[50].hex), addrtotext(pkt4.ciaddr)) + ' has been released from a device with hardware address: hwtype=' + substring(hexstring(pkt4.htype, ''), 7, 1) + ' ' + hexstring(pkt4.mac, ':') + ifelse(option[61].exists, ', client-id: ' + hexstring(option[61].hex, ':'), '') + ifelse(pkt4.giaddr == 0.0.0.0, '', ' connected via relay at address: ' + addrtotext(pkt4.giaddr) + ifelse(option[82].option[1].exists, ', circuit-id: ' + hexstring(option[82].option[1].hex, ':'), '') + ifelse(option[82].option[2].exists, ', remote-id: ' + hexstring(option[82].option[2].hex, ':'), '') + ifelse(option[82].option[6].exists, ', subscriber-id: ' + hexstring(option[82].option[6].hex, ':'), '')), '')",
    "response-parser-format": "ifelse(pkt4.msgtype == 5, 'Address: ' + addrtotext(pkt4.yiaddr) + ' has been assigned for ' + uint32totext(option[51].hex) + ' seconds to a device with hardware address: hwtype=' + substring(hexstring(pkt4.htype, ''), 7, 1) + ' ' + hexstring(pkt4.mac, ':') + ifelse(option[61].exists, ', client-id: ' + hexstring(option[61].hex, ':'), '') + ifelse(pkt4.giaddr == 0.0.0.0, '', ' connected via relay at address: ' + addrtotext(pkt4.giaddr) + ifelse(option[82].option[1].exists, ', circuit-id: ' + hexstring(option[82].option[1].hex, ':'), '') + ifelse(option[82].option[2].exists, ', remote-id: ' + hexstring(option[82].option[2].hex, ':'), '') + ifelse(option[82].option[6].exists, ', subscriber-id: ' + hexstring(option[82].option[6].hex, ':'), '')), '')"
}

Expand here!

{
    "request-parser-format":
        "ifelse(pkt4.msgtype == 4 or pkt4.msgtype == 7,
            'Address: ' +
            ifelse(option[50].exists,
                addrtotext(option[50].hex),
                addrtotext(pkt4.ciaddr)) +
            ' has been released from a device with hardware address: hwtype=' + substring(hexstring(pkt4.htype, ''), 7, 1) + ' ' + hexstring(pkt4.mac, ':') +
            ifelse(option[61].exists,
                ', client-id: ' + hexstring(option[61].hex, ':'),
                '') +
            ifelse(pkt4.giaddr == 0.0.0.0,
                '',
                ' connected via relay at address: ' + addrtotext(pkt4.giaddr) +
                ifelse(option[82].option[1].exists,
                    ', circuit-id: ' + hexstring(option[82].option[1].hex, ':'),
                    '') +
                ifelse(option[82].option[2].exists,
                    ', remote-id: ' + hexstring(option[82].option[2].hex, ':'),
                    '') +
                ifelse(option[82].option[6].exists,
                    ', subscriber-id: ' + hexstring(option[82].option[6].hex, ':'),
                    '')),
            '')",
    "response-parser-format":
        "ifelse(pkt4.msgtype == 5,
            'Address: ' + addrtotext(pkt4.yiaddr) + ' has been assigned for ' + uint32totext(option[51].hex) + ' seconds to a device with hardware address: hwtype=' + substring(hexstring(pkt4.htype, ''), 7, 1) + ' ' + hexstring(pkt4.mac, ':') +
            ifelse(option[61].exists,
                ', client-id: ' + hexstring(option[61].hex, ':'),
                '') +
            ifelse(pkt4.giaddr == 0.0.0.0,
                '',
                ' connected via relay at address: ' + addrtotext(pkt4.giaddr) +
                ifelse(option[82].option[1].exists,
                    ', circuit-id: ' + hexstring(option[82].option[1].hex, ':'),
                    '') +
                ifelse(option[82].option[2].exists,
                    ', remote-id: ' + hexstring(option[82].option[2].hex, ':'),
                    '') +
                ifelse(option[82].option[6].exists,
                    ', subscriber-id: ' + hexstring(option[82].option[6].hex, ':'),
                    '')),
            '')"
}

This will log the following data on request and renew:

Address: 192.2.1.100 has been assigned for 6735 seconds to a device with hardware address: hwtype=1 08:00:2b:02:3f:4e, client-id: 17:34:e2:ff:09:92:54 connected via relay at address: 192.2.16.33, circuit-id: 68:6f:77:64:79, remote-id: 87:f6:79:77:ef, subscriber-id: 1a:2b:3c:4d:5e:6f

This will log the following data on release and decline:

Address: 192.2.1.100 has been released from a device with hardware address: hwtype=1 08:00:2b:02:3f:4e, client-id: 17:34:e2:ff:09:92:54 connected via relay at address: 192.2.16.33, circuit-id: 68:6f:77:64:79, remote-id: 87:f6:79:77:ef, subscriber-id: 1a:2b:3c:4d:5e:6f

A similar result can be obtained by configuring only request-parser-format.

Examples:

{
    "request-parser-format": "ifelse(pkt4.msgtype == 3, 'Address: ' + ifelse(option[50].exists, addrtotext(option[50].hex), addrtotext(pkt4.ciaddr)) + ' has been assigned' + ifelse(option[51].exists, ' for ' + uint32totext(option[51].hex) + ' seconds', '') + ' to a device with hardware address: hwtype=' + substring(hexstring(pkt4.htype, ''), 7, 1) + ' ' + hexstring(pkt4.mac, ':') + ifelse(option[61].exists, ', client-id: ' + hexstring(option[61].hex, ':'), '') + ifelse(pkt4.giaddr == 0.0.0.0, '', ' connected via relay at address: ' + addrtotext(pkt4.giaddr) + ifelse(option[82].option[1].exists, ', circuit-id: ' + hexstring(option[82].option[1].hex, ':'), '') + ifelse(option[82].option[2].exists, ', remote-id: ' + hexstring(option[82].option[2].hex, ':'), '') + ifelse(option[82].option[6].exists, ', subscriber-id: ' + hexstring(option[82].option[6].hex, ':'), '')), ifelse(pkt4.msgtype == 4 or pkt4.msgtype == 7, 'Address: ' + ifelse(option[50].exists, addrtotext(option[50].hex), addrtotext(pkt4.ciaddr)) + ' has been released from a device with hardware address: hwtype=' + substring(hexstring(pkt4.htype, ''), 7, 1) + ' ' + hexstring(pkt4.mac, ':') + ifelse(option[61].exists, ', client-id: ' + hexstring(option[61].hex, ':'), '') + ifelse(pkt4.giaddr == 0.0.0.0, '', ' connected via relay at address: ' + addrtotext(pkt4.giaddr) + ifelse(option[82].option[1].exists, ', circuit-id: ' + hexstring(option[82].option[1].hex, ':'), '') + ifelse(option[82].option[2].exists, ', remote-id: ' + hexstring(option[82].option[2].hex, ':'), '') + ifelse(option[82].option[6].exists, ', subscriber-id: ' + hexstring(option[82].option[6].hex, ':'), '')), ''))"
}

Expand here!

{
    "request-parser-format":
        "ifelse(pkt4.msgtype == 3,
            'Address: ' +
            ifelse(option[50].exists,
                addrtotext(option[50].hex),
                addrtotext(pkt4.ciaddr)) +
            ' has been assigned' +
            ifelse(option[51].exists,
                ' for ' + uint32totext(option[51].hex) + ' seconds',
                '') +
            ' to a device with hardware address: hwtype=' + substring(hexstring(pkt4.htype, ''), 7, 1) + ' ' + hexstring(pkt4.mac, ':') +
            ifelse(option[61].exists,
                ', client-id: ' + hexstring(option[61].hex, ':'),
                '') +
            ifelse(pkt4.giaddr == 0.0.0.0,
                '',
                ' connected via relay at address: ' + addrtotext(pkt4.giaddr) +
                ifelse(option[82].option[1].exists,
                    ', circuit-id: ' + hexstring(option[82].option[1].hex, ':'),
                    '') +
                ifelse(option[82].option[2].exists,
                    ', remote-id: ' + hexstring(option[82].option[2].hex, ':'),
                    '') +
                ifelse(option[82].option[6].exists,
                    ', subscriber-id: ' + hexstring(option[82].option[6].hex, ':'),
                    '')),
            ifelse(pkt4.msgtype == 4 or pkt4.msgtype == 7,
                'Address: ' +
                ifelse(option[50].exists,
                    addrtotext(option[50].hex),
                    addrtotext(pkt4.ciaddr)) +
                ' has been released from a device with hardware address: hwtype=' + substring(hexstring(pkt4.htype, ''), 7, 1) + ' ' + hexstring(pkt4.mac, ':') +
                ifelse(option[61].exists,
                    ', client-id: ' + hexstring(option[61].hex, ':'),
                    '') +
                ifelse(pkt4.giaddr == 0.0.0.0,
                    '',
                    ' connected via relay at address: ' + addrtotext(pkt4.giaddr) +
                    ifelse(option[82].option[1].exists,
                        ', circuit-id: ' + hexstring(option[82].option[1].hex, ':'),
                        '') +
                    ifelse(option[82].option[2].exists,
                        ', remote-id: ' + hexstring(option[82].option[2].hex, ':'),
                        '') +
                    ifelse(option[82].option[6].exists,
                        ', subscriber-id: ' + hexstring(option[82].option[6].hex, ':'),
                        '')),
                ''))"
}

DHCPv6 Log Entries

For DHCPv6, the library creates entries based on REQUEST, RENEW, RELEASE, and DECLINE messages, et al. and their responses. The resulting packets and leases are taken into account, intercepted through the following hook points:

• pkt6_receive

• leases6_committed

• pkt6_send

• lease6_release

• lease6_decline

An entry is a single string with no embedded end-of-line markers and a prepended timestamp, and has the following sections:

timestamp address duration device-id {relay-info}* {user-context}

Where:

• timestamp - the date and time the log entry was written, in “%Y-%m-%d %H:%M:%S %Z” strftime format (“%Z” is the time zone name).

• address - the leased IPv6 address or prefix given out, and whether it was assigned, renewed, or released.

• duration - the lease lifetime expressed in days (if present), hours, minutes, and seconds. A lease lifetime of 0xFFFFFFFF will be denoted with the text “infinite duration.” This information is not given when the lease is released.

• device-id - the client’s DUID and hardware address (if present).

• relay-info - for relayed packets the content of relay agent messages, and the remote-id (code 37), subscriber-id (code 38), and interface-id (code 18) options, if present. Note that the interface-id option, if present, identifies the whole interface on which the relay agent received the message. This typically translates to a single link in the network, but it depends on the specific network topology. Nevertheless, this is useful information to better pinpoint the location of the device, so it is recorded, if present.

• user-context - the optional user context associated with the lease.

For instance (line breaks are added here for readability; they are not present in the log file):

2018-01-06 01:02:03 PST Address:2001:db8:1:: has been assigned for 0 hrs 11 mins 53 secs
to a device with DUID: 17:34:e2:ff:09:92:54 and hardware address: hwtype=1 08:00:2b:02:3f:4e
(from Raw Socket) connected via relay at address: fe80::abcd for client on link address: 3001::1,
hop count: 1, identified by remote-id: 01:02:03:04:0a:0b:0c:0d:0e:0f and subscriber-id: 1a:2b:3c:4d:5e:6f

or for a release:

2018-01-06 01:02:03 PST Address:2001:db8:1:: has been released
from a device with DUID: 17:34:e2:ff:09:92:54 and hardware address: hwtype=1 08:00:2b:02:3f:4e
(from Raw Socket) connected via relay at address: fe80::abcd for client on link address: 3001::1,
hop count: 1, identified by remote-id: 01:02:03:04:0a:0b:0c:0d:0e:0f and subscriber-id: 1a:2b:3c:4d:5e:6f

In addition to logging lease activity driven by DHCPv6 client traffic, the hook library also logs entries for the following lease management control channel commands: lease6-add, lease6-update, and lease6-del. Each entry is a single string with no embedded end-of-line markers, and it will typically have the following form:

lease6-add:

*timestamp* Administrator added a lease of address: *address* to a device with DUID: *DUID*

Depending on the arguments of the add command, it may also include the hardware address and duration.

Example:

2018-01-06 01:02:03 PST Administrator added a lease of address: 2001:db8::3 to a device with DUID:
1a:1b:1c:1d:1e:1f:20:21:22:23:24 for 1 days 0 hrs 0 mins 0 secs

lease6-update:

*timestamp* Administrator updated information on the lease of address: *address* to a device with DUID: *DUID*

Depending on the arguments of the update command, it may also include the hardware address and lease duration.

Example:

2018-01-06 01:02:03 PST Administrator updated information on the lease of address: 2001:db8::3 to a device with
DUID: 1a:1b:1c:1d:1e:1f:20:21:22:23:24, hardware address: 1a:1b:1c:1d:1e:1f

lease6-del: deletes have two forms, one by address and one by identifier and identifier type:

*timestamp* Administrator deleted the lease for address: *address*

or

*timestamp* Administrator deleted a lease for a device identified by: *identifier-type* of *identifier*

Currently only a type of DUID is supported.

Examples:

2018-01-06 01:02:03 PST Administrator deleted the lease for address: 2001:db8::3

2018-01-06 01:02:11 PST Administrator deleted a lease for a device identified by: duid of 1a:1b:1c:1d:1e:1f:20:21:22:23:24

The request-parser-format and response-parser-format options can be used to extract and log data from the incoming packet and server response packet, respectively. The configured value is an evaluated parsed expression returning a string. A list of tokens is described in the server classification process. Use with caution as this might affect server performance. If either of them is configured, the default logging format is not used. If both of them are configured, the resulting log message is constructed by concatenating the logged data extracted from the request and the logged data extracted from the response.

The custom formatting permits logging on multiple lines using the hexstring 0x0a (ASCII code for new line). In the case of the log file, each line is prepended with the log timestamp. For the database backend, the data is stored (including the newline character) in the same entry.

Examples:

{
  "Dhcp6": {
    "hooks-libraries": [
      {
        "library": "/usr/local/lib/kea/hooks/libdhcp_legal_log.so",
        "parameters": {
          "name": "database-name",
          "password": "passwd",
          "type": "mysql",
          "user": "user-name",
          "request-parser-format": "'log entry' + 0x0a + 'same log entry'",
          "response-parser-format": "'also same log entry' + 0x0a + 'again same log entry'"
        }
      }
    ]
  }
}

Some data might be available in the request or in the response only, and some data might differ in the incoming packet from the one in the response packet.

Notes:

In the case of IPv6, the packets can contain multiple IA_NA (3) or IA_PD (25) options, each containing multiple options, including OPTION_IAADDR (5) or OPTION_IAPREFIX (25) suboptions. To be able to print the current lease associated with the log entry, the forensic log hook library internally isolates the corresponding IA_NA or IA_PD option and respective suboption matching the current lease. The hook library will iterate over all new allocated addresses and all deleted addresses, making each address available for logging as the current lease for the respective logged entry.

They are accessible using the following parser expressions:

Current lease associated with OPTION_IAADDR:

addrtotext(substring(option[3].option[5].hex, 0, 16))

Current lease associated with OPTION_IAPREFIX:

addrtotext(substring(option[25].option[26].hex, 9, 16))

All other parameters of the options are available at their respective offsets in the option. Please read RFC8415 for more details.

Examples:

{
    "request-parser-format": "ifelse(pkt6.msgtype == 8 or pkt6.msgtype == 9, ifelse(option[3].option[5].exists, 'Address: ' + addrtotext(substring(option[3].option[5].hex, 0, 16)) + ' has been released from a device with DUID: ' + hexstring(option[1].hex, ':') + ifelse(relay6[0].peeraddr == '', '', ' connected via relay at address: ' + addrtotext(relay6[0].peeraddr) + ' for client on link address: ' + addrtotext(relay6[0].linkaddr) + ifelse(relay6[0].option[37].exists, ', remote-id: ' + hexstring(relay6[0].option[37].hex, ':'), '') + ifelse(relay6[0].option[38].exists, ', subscriber-id: ' + hexstring(relay6[0].option[38].hex, ':'), '') + ifelse(relay6[0].option[18].exists, ', connected at location interface-id: ' + hexstring(relay6[0].option[18].hex, ':'), '')), '') + ifelse(option[25].option[26].exists, 'Prefix: ' + addrtotext(substring(option[25].option[26].hex, 9, 16)) + '/' + uint8totext(substring(option[25].option[26].hex, 8, 1)) + ' has been released from a device with DUID: ' + hexstring(option[1].hex, ':') + ifelse(relay6[0].peeraddr == '', '', ' connected via relay at address: ' + addrtotext(relay6[0].peeraddr) + ' for client on link address: ' + addrtotext(relay6[0].linkaddr) + ifelse(relay6[0].option[37].exists, ', remote-id: ' + hexstring(relay6[0].option[37].hex, ':'), '') + ifelse(relay6[0].option[38].exists, ', subscriber-id: ' + hexstring(relay6[0].option[38].hex, ':'), '') + ifelse(relay6[0].option[18].exists, ', connected at location interface-id: ' + hexstring(relay6[0].option[18].hex, ':'), '')), ''), '')",
    "response-parser-format": "ifelse(pkt6.msgtype == 7, ifelse(option[3].option[5].exists and not (substring(option[3].option[5].hex, 20, 4) == 0), 'Address: ' + addrtotext(substring(option[3].option[5].hex, 0, 16)) + ' has been assigned for ' + uint32totext(substring(option[3].option[5].hex, 20, 4)) + ' seconds to a device with DUID: ' + hexstring(option[1].hex, ':') + ifelse(relay6[0].peeraddr == '', '', ' connected via relay at address: ' + addrtotext(relay6[0].peeraddr) + ' for client on link address: ' + addrtotext(relay6[0].linkaddr) + ifelse(relay6[0].option[37].exists, ', remote-id: ' + hexstring(relay6[0].option[37].hex, ':'), '') + ifelse(relay6[0].option[38].exists, ', subscriber-id: ' + hexstring(relay6[0].option[38].hex, ':'), '') + ifelse(relay6[0].option[18].exists, ', connected at location interface-id: ' + hexstring(relay6[0].option[18].hex, ':'), '')), '') + ifelse(option[25].option[26].exists and not (substring(option[25].option[26].hex, 4, 4) == 0), 'Prefix: ' + addrtotext(substring(option[25].option[26].hex, 9, 16)) + '/' + uint8totext(substring(option[25].option[26].hex, 8, 1)) + ' has been assigned for ' + uint32totext(substring(option[25].option[26].hex, 4, 4)) + ' seconds to a device with DUID: ' + hexstring(option[1].hex, ':') + ifelse(relay6[0].peeraddr == '', '', ' connected via relay at address: ' + addrtotext(relay6[0].peeraddr) + ' for client on link address: ' + addrtotext(relay6[0].linkaddr) + ifelse(relay6[0].option[37].exists, ', remote-id: ' + hexstring(relay6[0].option[37].hex, ':'), '') + ifelse(relay6[0].option[38].exists, ', subscriber-id: ' + hexstring(relay6[0].option[38].hex, ':'), '') + ifelse(relay6[0].option[18].exists, ', connected at location interface-id: ' + hexstring(relay6[0].option[18].hex, ':'), '')), ''), '')"
}

Expand here!

{
    "request-parser-format":
        "ifelse(pkt6.msgtype == 8 or pkt6.msgtype == 9,
            ifelse(option[3].option[5].exists,
                'Address: ' + addrtotext(substring(option[3].option[5].hex, 0, 16)) + ' has been released from a device with DUID: ' + hexstring(option[1].hex, ':') +
                ifelse(relay6[0].peeraddr == '',
                    '',
                    ' connected via relay at address: ' + addrtotext(relay6[0].peeraddr) + ' for client on link address: ' + addrtotext(relay6[0].linkaddr) +
                    ifelse(relay6[0].option[37].exists,
                        ', remote-id: ' + hexstring(relay6[0].option[37].hex, ':'),
                        '') +
                    ifelse(relay6[0].option[38].exists,
                        ', subscriber-id: ' + hexstring(relay6[0].option[38].hex, ':'),
                        '') +
                    ifelse(relay6[0].option[18].exists,
                        ', connected at location interface-id: ' + hexstring(relay6[0].option[18].hex, ':'),
                        '')),
                '') +
            ifelse(option[25].option[26].exists,
                'Prefix: ' + addrtotext(substring(option[25].option[26].hex, 9, 16)) + '/' + uint8totext(substring(option[25].option[26].hex, 8, 1)) + ' has been released from a device with DUID: ' + hexstring(option[1].hex, ':') +
                ifelse(relay6[0].peeraddr == '',
                    '',
                    ' connected via relay at address: ' + addrtotext(relay6[0].peeraddr) + ' for client on link address: ' + addrtotext(relay6[0].linkaddr) +
                    ifelse(relay6[0].option[37].exists,
                        ', remote-id: ' + hexstring(relay6[0].option[37].hex, ':'),
                        '') +
                    ifelse(relay6[0].option[38].exists,
                        ', subscriber-id: ' + hexstring(relay6[0].option[38].hex, ':'),
                        '') +
                    ifelse(relay6[0].option[18].exists,
                        ', connected at location interface-id: ' + hexstring(relay6[0].option[18].hex, ':'),
                        '')),
                ''),
            '')",
    "response-parser-format":
        "ifelse(pkt6.msgtype == 7,
            ifelse(option[3].option[5].exists and not (substring(option[3].option[5].hex, 20, 4) == 0),
                'Address: ' + addrtotext(substring(option[3].option[5].hex, 0, 16)) + ' has been assigned for ' + uint32totext(substring(option[3].option[5].hex, 20, 4)) + ' seconds to a device with DUID: ' + hexstring(option[1].hex, ':') +
                ifelse(relay6[0].peeraddr == '',
                    '',
                    ' connected via relay at address: ' + addrtotext(relay6[0].peeraddr) + ' for client on link address: ' + addrtotext(relay6[0].linkaddr) +
                    ifelse(relay6[0].option[37].exists,
                        ', remote-id: ' + hexstring(relay6[0].option[37].hex, ':'),
                        '') +
                    ifelse(relay6[0].option[38].exists,
                        ', subscriber-id: ' + hexstring(relay6[0].option[38].hex, ':'),
                        '') +
                    ifelse(relay6[0].option[18].exists,
                        ', connected at location interface-id: ' + hexstring(relay6[0].option[18].hex, ':'),
                        '')),
                '') +
            ifelse(option[25].option[26].exists and not (substring(option[25].option[26].hex, 4, 4) == 0),
                'Prefix: ' + addrtotext(substring(option[25].option[26].hex, 9, 16)) + '/' + uint8totext(substring(option[25].option[26].hex, 8, 1)) + ' has been assigned for ' + uint32totext(substring(option[25].option[26].hex, 4, 4)) + ' seconds to a device with DUID: ' + hexstring(option[1].hex, ':') +
                ifelse(relay6[0].peeraddr == '',
                    '',
                    ' connected via relay at address: ' + addrtotext(relay6[0].peeraddr) + ' for client on link address: ' + addrtotext(relay6[0].linkaddr) +
                    ifelse(relay6[0].option[37].exists,
                        ', remote-id: ' + hexstring(relay6[0].option[37].hex, ':'),
                        '') +
                    ifelse(relay6[0].option[38].exists,
                        ', subscriber-id: ' + hexstring(relay6[0].option[38].hex, ':'),
                        '') +
                    ifelse(relay6[0].option[18].exists,
                        ', connected at location interface-id: ' + hexstring(relay6[0].option[18].hex, ':'),
                        '')),
                ''),
            '')"
}

This will log the following data on request, renew, and rebind for NA:

Address: 2001:db8:1:: has been assigned for 713 seconds to a device with DUID: 17:34:e2:ff:09:92:54 connected via relay at address: fe80::abcd for client on link address: 3001::1, remote-id: 01:02:03:04:0a:0b:0c:0d:0e:0f, subscriber-id: 1a:2b:3c:4d:5e:6f, connected at location interface-id: 72:65:6c:61:79:31:3a:65:74:68:30

This will log the following data on request, renew and rebind for PD:

Prefix: 2001:db8:1::/64 has been assigned for 713 seconds to a device with DUID: 17:34:e2:ff:09:92:54 connected via relay at address: fe80::abcd for client on link address: 3001::1, remote-id: 01:02:03:04:0a:0b:0c:0d:0e:0f, subscriber-id: 1a:2b:3c:4d:5e:6f, connected at location interface-id: 72:65:6c:61:79:31:3a:65:74:68:30

This will log the following data on release and decline for NA:

Address: 2001:db8:1:: has been released from a device with DUID: 17:34:e2:ff:09:92:54 connected via relay at address: fe80::abcd for client on link address: 3001::1, remote-id: 01:02:03:04:0a:0b:0c:0d:0e:0f, subscriber-id: 1a:2b:3c:4d:5e:6f, connected at location interface-id: 72:65:6c:61:79:31:3a:65:74:68:30

This will log the following data on release and decline for PD:

Prefix: 2001:db8:1::/64 has been released from a device with DUID: 17:34:e2:ff:09:92:54 connected via relay at address: fe80::abcd for client on link address: 3001::1, remote-id: 01:02:03:04:0a:0b:0c:0d:0e:0f, subscriber-id: 1a:2b:3c:4d:5e:6f, connected at location interface-id: 72:65:6c:61:79:31:3a:65:74:68:30

A similar result can be obtained by configuring only request-parser-format.

Examples:

{
    "request-parser-format": "ifelse(pkt6.msgtype == 3 or pkt6.msgtype == 5 or pkt6.msgtype == 6, ifelse(option[3].option[5].exists, 'Address: ' + addrtotext(substring(option[3].option[5].hex, 0, 16)) + ' has been assigned for ' + uint32totext(substring(option[3].option[5].hex, 20, 4)) + ' seconds to a device with DUID: ' + hexstring(option[1].hex, ':') + ifelse(relay6[0].peeraddr == '', '', ' connected via relay at address: ' + addrtotext(relay6[0].peeraddr) + ' for client on link address: ' + addrtotext(relay6[0].linkaddr) + ifelse(relay6[0].option[37].exists, ', remote-id: ' + hexstring(relay6[0].option[37].hex, ':'), '') + ifelse(relay6[0].option[38].exists, ', subscriber-id: ' + hexstring(relay6[0].option[38].hex, ':'), '') + ifelse(relay6[0].option[18].exists, ', connected at location interface-id: ' + hexstring(relay6[0].option[18].hex, ':'), '')), '') + ifelse(option[25].option[26].exists, 'Prefix: ' + addrtotext(substring(option[25].option[26].hex, 9, 16)) + '/' + uint8totext(substring(option[25].option[26].hex, 8, 1)) + ' has been assigned for ' + uint32totext(substring(option[25].option[26].hex, 4, 4)) + ' seconds to a device with DUID: ' + hexstring(option[1].hex, ':') + ifelse(relay6[0].peeraddr == '', '', ' connected via relay at address: ' + addrtotext(relay6[0].peeraddr) + ' for client on link address: ' + addrtotext(relay6[0].linkaddr) + ifelse(relay6[0].option[37].exists, ', remote-id: ' + hexstring(relay6[0].option[37].hex, ':'), '') + ifelse(relay6[0].option[38].exists, ', subscriber-id: ' + hexstring(relay6[0].option[38].hex, ':'), '') + ifelse(relay6[0].option[18].exists, ', connected at location interface-id: ' + hexstring(relay6[0].option[18].hex, ':'), '')), ''), ifelse(pkt6.msgtype == 8 or pkt6.msgtype == 9, ifelse(option[3].option[5].exists, 'Address: ' + addrtotext(substring(option[3].option[5].hex, 0, 16)) + ' has been released from a device with DUID: ' + hexstring(option[1].hex, ':') + ifelse(relay6[0].peeraddr == '', '', ' connected via relay at address: ' + addrtotext(relay6[0].peeraddr) + ' for client on link address: ' + addrtotext(relay6[0].linkaddr) + ifelse(relay6[0].option[37].exists, ', remote-id: ' + hexstring(relay6[0].option[37].hex, ':'), '') + ifelse(relay6[0].option[38].exists, ', subscriber-id: ' + hexstring(relay6[0].option[38].hex, ':'), '') + ifelse(relay6[0].option[18].exists, ', connected at location interface-id: ' + hexstring(relay6[0].option[18].hex, ':'), '')), '') + ifelse(option[25].option[26].exists, 'Prefix: ' + addrtotext(substring(option[25].option[26].hex, 9, 16)) + '/' + uint8totext(substring(option[25].option[26].hex, 8, 1)) + ' has been released from a device with DUID: ' + hexstring(option[1].hex, ':') + ifelse(relay6[0].peeraddr == '', '', ' connected via relay at address: ' + addrtotext(relay6[0].peeraddr) + ' for client on link address: ' + addrtotext(relay6[0].linkaddr) + ifelse(relay6[0].option[37].exists, ', remote-id: ' + hexstring(relay6[0].option[37].hex, ':'), '') + ifelse(relay6[0].option[38].exists, ', subscriber-id: ' + hexstring(relay6[0].option[38].hex, ':'), '') + ifelse(relay6[0].option[18].exists, ', connected at location interface-id: ' + hexstring(relay6[0].option[18].hex, ':'), '')), ''), ''))"
}

Expand here!

{
    "request-parser-format":
        "ifelse(pkt6.msgtype == 3 or pkt6.msgtype == 5 or pkt6.msgtype == 6,
            ifelse(option[3].option[5].exists,
                'Address: ' + addrtotext(substring(option[3].option[5].hex, 0, 16)) + ' has been assigned for ' + uint32totext(substring(option[3].option[5].hex, 20, 4)) + ' seconds to a device with DUID: ' + hexstring(option[1].hex, ':') +
                ifelse(relay6[0].peeraddr == '',
                    '',
                    ' connected via relay at address: ' + addrtotext(relay6[0].peeraddr) + ' for client on link address: ' + addrtotext(relay6[0].linkaddr) +
                    ifelse(relay6[0].option[37].exists,
                        ', remote-id: ' + hexstring(relay6[0].option[37].hex, ':'),
                        '') +
                    ifelse(relay6[0].option[38].exists,
                        ', subscriber-id: ' + hexstring(relay6[0].option[38].hex, ':'),
                        '') +
                    ifelse(relay6[0].option[18].exists,
                        ', connected at location interface-id: ' + hexstring(relay6[0].option[18].hex, ':'),
                        '')),
                '') +
            ifelse(option[25].option[26].exists,
                'Prefix: ' + addrtotext(substring(option[25].option[26].hex, 9, 16)) + '/' + uint8totext(substring(option[25].option[26].hex, 8, 1)) + ' has been assigned for ' + uint32totext(substring(option[25].option[26].hex, 4, 4)) + ' seconds to a device with DUID: ' + hexstring(option[1].hex, ':') +
                ifelse(relay6[0].peeraddr == '',
                    '',
                    ' connected via relay at address: ' + addrtotext(relay6[0].peeraddr) + ' for client on link address: ' + addrtotext(relay6[0].linkaddr) +
                    ifelse(relay6[0].option[37].exists,
                        ', remote-id: ' + hexstring(relay6[0].option[37].hex, ':'),
                        '') +
                    ifelse(relay6[0].option[38].exists,
                        ', subscriber-id: ' + hexstring(relay6[0].option[38].hex, ':'),
                        '') +
                    ifelse(relay6[0].option[18].exists,
                        ', connected at location interface-id: ' + hexstring(relay6[0].option[18].hex, ':'),
                        '')),
                ''),
            ifelse(pkt6.msgtype == 8 or pkt6.msgtype == 9,
                ifelse(option[3].option[5].exists,
                    'Address: ' + addrtotext(substring(option[3].option[5].hex, 0, 16)) + ' has been released from a device with DUID: ' + hexstring(option[1].hex, ':') +
                    ifelse(relay6[0].peeraddr == '',
                        '',
                        ' connected via relay at address: ' + addrtotext(relay6[0].peeraddr) + ' for client on link address: ' + addrtotext(relay6[0].linkaddr) +
                        ifelse(relay6[0].option[37].exists,
                            ', remote-id: ' + hexstring(relay6[0].option[37].hex, ':'),
                            '') +
                        ifelse(relay6[0].option[38].exists,
                            ', subscriber-id: ' + hexstring(relay6[0].option[38].hex, ':'),
                            '') +
                        ifelse(relay6[0].option[18].exists,
                            ', connected at location interface-id: ' + hexstring(relay6[0].option[18].hex, ':'),
                            '')),
                    '') +
                ifelse(option[25].option[26].exists,
                    'Prefix: ' + addrtotext(substring(option[25].option[26].hex, 9, 16)) + '/' + uint8totext(substring(option[25].option[26].hex, 8, 1)) + ' has been released from a device with DUID: ' + hexstring(option[1].hex, ':') +
                    ifelse(relay6[0].peeraddr == '',
                        '',
                        ' connected via relay at address: ' + addrtotext(relay6[0].peeraddr) + ' for client on link address: ' + addrtotext(relay6[0].linkaddr) +
                        ifelse(relay6[0].option[37].exists,
                            ', remote-id: ' + hexstring(relay6[0].option[37].hex, ':'),
                            '') +
                        ifelse(relay6[0].option[38].exists,
                            ', subscriber-id: ' + hexstring(relay6[0].option[38].hex, ':'),
                            '') +
                        ifelse(relay6[0].option[18].exists,
                            ', connected at location interface-id: ' + hexstring(relay6[0].option[18].hex, ':'),
                            '')),
                    ''),
                ''))"
}

Database Backend

Log entries can be inserted into a database when Kea is configured with database backend support. Kea uses a table named logs, that includes a timestamp generated by the database software, and a text log with the same format as files without the timestamp.

Please refer to MySQL for information on using a MySQL database; or to PostgreSQL for PostgreSQL database information. The logs table is part of the Kea database schemas.

Configuration parameters are extended by standard lease database parameters as defined in Lease Database Configuration. The type parameter should be mysql, postgresql or logfile; when it is absent or set to logfile, files are used.

This database feature is experimental. No specific tools are provided to operate the database, but standard tools may be used, for example, to dump the logs table from a MYSQL database:

$ mysql --user keatest --password keatest -e "select * from logs;"
+---------------------+--------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------+----+
| timestamp           | address      | log                                                                                                                                                             | id |
+---------------------+--------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------+----+
| 2022-03-30 17:38:41 | 192.168.50.1 | Address: 192.168.50.1 has been assigned for 0 hrs 10 mins 0 secs to a device with hardware address: hwtype=1 ff:01:02:03:ff:04, client-id: 00:01:02:03:04:05:06 | 31 |
| 2022-03-30 17:38:43 | 192.168.50.1 | Address: 192.168.50.1 has been assigned for 0 hrs 10 mins 0 secs to a device with hardware address: hwtype=1 ff:01:02:03:ff:04, client-id: 00:01:02:03:04:05:06 | 32 |
| 2022-03-30 17:38:45 | 192.168.50.1 | Address: 192.168.50.1 has been assigned for 0 hrs 10 mins 0 secs to a device with hardware address: hwtype=1 ff:01:02:03:ff:04, client-id: 00:01:02:03:04:05:06 | 33 |
+---------------------+--------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------+----+

Like all the other database-centric features, forensic logging supports database connection recovery, which can be enabled by setting the on-fail parameter. If not specified, the on-fail parameter in forensic logging defaults to serve-retry-continue; this is a change from its behavior in the Lease Commands, Host Commands, and Configuration Backend hook libraries, where on-fail defaults to stop-retry-exit. In this case, the server continues serving clients and does not shut down even if the recovery mechanism fails. If on-fail is set to serve-retry-exit, the server will shut down if the connection to the database backend is not restored according to the max-reconnect-tries and reconnect-wait-time parameters, but it continues serving clients while this mechanism is activated.

flex_id: Flexible Identifiers for Host Reservations

The Kea software provides a way to handle host reservations that include addresses, prefixes, options, client classes, and other features. The reservation can be based on hardware address, DUID, circuit-id, or client-id in DHCPv4 and on hardware address or DUID in DHCPv6. However, there are sometimes scenarios where the reservation is more complex; it may use options other than those mentioned above, use parts of specific options, or perhaps even use a combination of several options and fields to uniquely identify a client. Those scenarios are addressed by the Flexible Identifiers hook application.

Currently this library is only available to ISC customers with a paid support contract.

Note

This library may only be loaded by the kea-dhcp4 or kea-dhcp6 process.

The library allows the definition of an expression, using notation initially used only for client classification. (See Using Expressions in Classification for a detailed description of the syntax available.) One notable difference is that for client classification, the expression currently has to evaluate to either true or false, while the flexible identifier expression is expected to evaluate to a string that will be used as an identifier. It is a valid case for the expression to evaluate to an empty string (e.g. in cases where a client does not send specific options). This expression is then evaluated for each incoming packet, and this evaluation generates an identifier that is used to identify the client. In particular, there may be host reservations that are tied to specific values of the flexible identifier.

The library can be loaded similarly to other hook libraries. It takes a mandatory parameter identifier-expression and an optional boolean parameter replace-client-id:

"Dhcp6": {
    "hooks-libraries": [
        {
            "library": "/path/libdhcp_flex_id.so",
            "parameters": {
                "identifier-expression": "expression",
                "replace-client-id": false
            }
        },
        ...
    ]
}

The flexible identifier library supports both DHCPv4 and DHCPv6.

Let’s consider a case of an IPv6 network that has an independent interface for each of its connected customers. Customers are able to plug in whatever device they want, so any type of identifier (e.g. a client-id) is unreliable. Therefore, the operator may decide to use an option inserted by a relay agent to differentiate between clients. In this particular deployment, the operator has verified that the interface-id is unique for each customer-facing interface, so it is suitable for usage as a reservation. However, only the first six bytes of the interface-id are interesting, because the remaining bytes are either randomly changed or not unique between devices. Therefore, the customer decides to use the first six bytes of the interface-id option inserted by the relay agent. After adding flex-id, the host-reservation-identifiers goal can be achieved by using the following configuration:

"Dhcp6": {
    "subnet6": [{ ..., # subnet definition starts here
    "reservations": [
        "flex-id": "'port1234'", # value of the first 8 bytes of the interface-id
        "ip-addresses": [ "2001:db8::1" ]
    ],
    }], # end of subnet definitions
    "host-reservation-identifiers": ["duid", "flex-id"], # add "flex-id" to reservation identifiers
    "hooks-libraries": [
        {
            "library": "/path/libdhcp_flex_id.so",
            "parameters": {
                "identifier-expression": "substring(relay6[0].option[18].hex,0,8)"
            }
        },
        ...
    ]
}

Note

Care should be taken when adjusting the expression. If the expression changes, then all the flex-id values may change, possibly rendering all reservations based on flex-id unusable until they are manually updated. It is strongly recommended that administrators start with the expression and a handful of reservations, and then adjust the expression as needed. Once the desired result is obtained with the expression, host reservations can be deployed on a broader scale.

flex-id values in host reservations can be specified in two ways. First, they can be expressed as a hex string, e.g. the string “bar” can be represented as 626174. Alternatively, it can be expressed as a quoted value (using double and single quotes), e.g. “‘bar’”. The former is more convenient for printable characters, while hex string values are more convenient for non-printable characters and do not require the use of the hexstring operator.

"Dhcp6": {
    "subnet6": [{ ..., # subnet definition starts here
    "reservations": [
        "flex-id": "01:02:03:04:05:06", # value of the first 8 bytes of the interface-id
        "ip-addresses": [ "2001:db8::1" ]
    ],
    }], # end of subnet definitions
    "host-reservation-identifiers": ["duid", "flex-id"], # add "flex-id" to reservation identifiers
    "hooks-libraries": [
        {
            "library": "/path/libdhcp_flex_id.so",
            "parameters": {
                "identifier-expression": "vendor[4491].option[1026].hex"
            }
        },
        ...
    ]
}

When replace-client-id is set to false (which is the default setting), the flex-id hook library uses the evaluated flexible identifier solely for identifying host reservations, i.e. searching for reservations within a database. This is the functional equivalent of other identifiers, similar to hardware address or circuit-id. However, this mode of operation implies that if a client device is replaced, it may cause a conflict between an existing lease (allocated to the old device) and the new lease being allocated to the new device. The conflict arises because the same flexible identifier is computed for the replaced device, so the server will try to allocate the same lease. The mismatch between client identifiers sent by the new device and the old device causes the server to refuse this new allocation until the old lease expires. A manifestation of this problem is dependent on the specific expression used as the flexible identifier, and is likely to appear if only options and other parameters are used that identify where the device is connected (e.g. circuit-id), rather than the device identification itself (e.g. MAC address).

The flex-id library offers a way to overcome the problem with lease conflicts by dynamically replacing the client identifier (or DUID in DHCPv6) with a value derived from the flexible identifier. The server processes the client’s query as if the flexible identifier were sent in the client identifier (or DUID) option. This guarantees that a returning client (for which the same flexible identifier is evaluated) will be assigned the same lease, despite the client identifier and/or MAC address change.

The following is a stub configuration that enables this behavior:

"Dhcp4": {
    "hooks-libraries": [
        {
            "library": "/path/libdhcp_flex_id.so",
            "parameters": {
                "identifier-expression": "expression",
                "replace-client-id": true
            }
        },
        ...
    ]
}

In the DHCPv4 case, the value derived from the flexible identifier is formed by prepending one byte with a value of zero to the flexible identifier. In the DHCPv6 case, it is formed by prepending two zero bytes before the flexible identifier.

Note that for this mechanism to take effect, the DHCPv4 server must be configured to respect the client identifier option value during lease allocation, i.e. match-client-id must be set to true. See Using Client Identifier and Hardware Address for details. No additional settings are required for DHCPv6.

If the replace-client-id option is set to true, the value of the echo-client-id parameter (which governs whether to send back a client-id option) is ignored.

The lease_cmds: Lease Commands section describes commands used to retrieve, update, and delete leases using various identifiers, such as hw-address and client-id. The lease_cmds library does not natively support querying for leases by flexible identifier. However, when replace-client-id is set to true, it makes it possible to query for leases using a value derived from the flexible identifier. In DHCPv4, the query looks similar to this:

{
    "command": "lease4-get",
    "arguments": {
        "identifier-type": "client-id",
        "identifier": "00:54:64:45:66",
        "subnet-id": 44
    }
}

where the hexadecimal value of “54:64:45:66” is a flexible identifier computed for the client.

In DHCPv6, the corresponding query looks something like this:

{
    "command": "lease6-get",
    "arguments": {
        "identifier-type": "duid",
        "identifier": "00:00:54:64:45:66",
        "subnet-id": 10
    }
}

flex_option Flexible Option for Option Value Settings

This library allows administrators to define an action to take, for a given option, based upon on the result of an expression. These actions are carried out during the final stages of constructing a query response packet, just before it is sent to the client. The three actions currently supported are add, supersede, and remove.

The syntax used for the action expressions is the same syntax used for client classification and the Flexible Identifier hook library; see either Using Expressions in Classification or flex_id: Flexible Identifiers for Host Reservations for a detailed description of the syntax.

The add and supersede actions use an expression returning a string, and do nothing if the string is empty. The remove application uses an expression returning true or false, and does nothing on false. When it is necessary to set an option to the empty value this mechanism does not work, but a client class can be used instead.

The add action adds an option only when the option does not already exist and the expression does not evaluate to the empty string. The supersede action does the same but it overwrites the option value if it already exists. The remove action removes the option from the response packet if it already exists and the expression evaluates to true.

The option to which an action applies may be specified by either its numeric code or its name; either the code or the name must be specified. The option space is DHCPv4 or DHCPv6, depending on the server where the hook library is loaded.

Similar to other hook libraries, the flex_option library can be loaded by either the kea-dhcp4 or kea-dhcp6` process. It takes a mandatory options parameter with a list of per-option parameter maps, with code, name, add, supersede, and remove actions. Action entries take a string value representing an expression.

  "Dhcp4": {
      "hooks-libraries": [
          {   "library": "/usr/local/lib/libdhcp_flex_option.so",
              "parameters": {
                  "options": [
                          {
                          "code": 67,
                          "add":
"ifelse(option[host-name].exists,concat(option[host-name].text,'.boot'),'')"
                      }
                  ]
              }
          },
          ...
      ]
  }

If (and only if) the query includes a host-name option (code 12), a boot-file-name option (code 67) is added to the response with the host name followed by .boot for content.

The flexible option library supports both DHCPv4 and DHCPv6.

Since Kea 1.9.0, the add and supersede actions take an optional `csv-format` boolean parameter. If not specified or set to false, the option data is set using the raw value of the evaluated expression. When it is configured to true, this value is parsed using the option definition from the option data specified in the configuration file. This eases option setting for options using complex record formats or fully qualified domain names.

For instance, if the expression evaluation returns “example.com” and the option is defined with the fqdn type, the domain name will be encoded into DNS binary format.

Since Kea 2.1.4, the client-class parameter specifies a class guard. It takes a client class name. If not empty, the client’s packet needs to belong to specified class for this entry to be used.

Since Kea 2.1.4, it is allowed to have multiple entries for the same option, but each entry must have exactly one action. If the option is not defined in the dhcp4 for DHCPv4 or dhcp6 for DHCPv6 you can specify the space where to find the option definition using its name with the new space parameter.

Since Kea 2.1.4, sub-options are supported with a new entry sub-options which replaces the action in the configuration of the container option, i.e. the option where sub-options are located.

The sub-options entry takes a list of sub-option configuration similar to the option one with:

• code - specifies the sub-option code, either the code or name must be specified. When both are given they must match or the configuration is rejected at load time.

• name - specifies the sub-option name, either the code or name must be specified. When both are given they must match or the configuration is rejected at load time.

• space - specifies the space where the sub-option can be defined. This parameter is optional because it can be found in the container option definition. The configuration is rejected if no valid space name is available at load time. Note that vendor spaces are supported for the DHCPv4 vivso-suboptions and for the DHCPv6 vendor-opts, both pre-defined (e.g. DoCSIS vendor id 4491) or custom.

• add - (action) adds a sub-option only if it does not already exist and the expression does not evaluate to the empty string.

• supersede - (action) adds or overwrites a sub-option if the expression does not evaluate to the empty string.

• remove - (action) removes a sub-option if it already exists and the expression evaluates to true.

• container-add - boolean value which specifies if the container option should be created if it does not exit in the add and supersede action. When not specified, it defaults to true.

• container-remove - boolean value which specifies if the container option should be deleted if it remains empty after the removal of a sub-option by the remove action. When not specified, it defaults to true.

• csv-format - boolean value which specifies if the raw value of the evaluated expression is used (false, default) or parsed using the sub-option definition (true).

• client-class - specifies if the sub-option entry must be skipped when the query does not belong to the specified client class. Note the similar parameter in the container option entry applies to the whole sub-options list.

For instance this configuration adds a string sub-option in the DHCPv4 vendor-encapsulated-options (code 43) option. Note this option in last resort encapsulates the vendor-encapsulated-options space.

"Dhcp4": {
    "hooks-libraries": [
        {   "library": "/usr/local/lib/libdhcp_flex_option.so",
            "parameters": {
                "options": [
                        {
                        "code": 43,
                        "sub-options": [
                            {
                               "code": 1,
                               "add": "'foobar'"
                            }
                        ]
                    }
                ]
            }
        },
        ...
    ]
}

host_cmds: Host Commands

Kea can store host reservations in a database; in many larger deployments, it is useful to be able to manage that information while the server is running. This library provides management commands for adding, querying, and deleting host reservations in a safe way without restarting the server. In particular, it validates the parameters, so an attempt to insert incorrect data - such as adding a host with a conflicting identifier in the same subnet - is rejected. Those commands are exposed via the command channel (JSON over UNIX sockets) and the Control Agent (JSON over a RESTful interface).

Currently this library is only available to ISC customers with a paid support contract.

Note

This library can only be loaded by the kea-dhcp4 or kea-dhcp6 process.

Currently, the following commands are supported:

• reservation-add, which adds a new host reservation.

• reservation-get, which returns an existing reservation if specified criteria are matched.

• reservation-get-all, which returns all reservations in a specified subnet.

• reservation-get-page, a variant of reservation-get-all that returns reservations by pages, either all or in a specified subnet.

• reservation-get-by-hostname, which returns all reservations with a specified hostname and optionally in a subnet.

• reservation-get-by-id, which returns all reservations with a specified identifier (since Kea version 1.9.0).

• reservation-del, which attempts to delete a reservation matching specified criteria.

To use the commands that change reservation information (i.e. reservation-add and reservation-del), the hosts database must be specified and it must not operate in read-only mode (for details, see the hosts-databases descriptions in DHCPv4 Hosts Database Configuration and DHCPv6 Hosts Database Configuration). If the hosts-databases are not specified or are running in read-only mode, the host_cmds library will load, but any attempts to use reservation-add or reservation-del will fail.

For a description of proposed future commands, see the Control API Requirements document.

All host commands use JSON syntax. They can be issued either using the control channel (see Management API) or via the Control Agent (see The Kea Control Agent).

The library can be loaded similarly to other hook libraries. It does not take any parameters, and it supports both the DHCPv4 and DHCPv6 servers.

"Dhcp6": {
    "hooks-libraries": [
        {
            "library": "/path/libdhcp_host_cmds.so"
        }
        ...
    ]
}

The subnet-id Parameter

Before examining the individual commands, it is worth discussing the parameter subnet-id. Currently this parameter is mandatory for all of the commands supplied by this library, with the exception of reservation-get-by-hostname, where it is optional. Since Kea 1.9.0, subnet-id is also optional in reservation-get-page, and it is forbidden in reservation-get-by-id.

Reservations can be specified globally, and are not necessarily specific to any subnet. When reservations are supplied via the configuration file, the ID of the containing subnet (or lack thereof) is implicit in the configuration structure. However, when managing reservations using host commands, it is necessary to explicitly identify the scope to which the reservation belongs. This is done via the subnet-id parameter. For global reservations, use a value of zero (0). For reservations scoped to a specific subnet, use that subnet’s ID.

On the other hand, when the subnet-id is not specified in the command parameters, it is added to each host in responses. If the subnet-id has the unused special value, this means the host entry belongs only to the other IP version (i.e. IPv6 in DHCPv4 server or IPv4 in DHCPv6 server) and this entry is ignored.

The reservation-add Command

reservation-add allows for the insertion of a new host. It takes a set of arguments that vary depending on the nature of the host reservation. Any parameters allowed in the configuration file that pertain to host reservation are permitted here. For details regarding IPv4 reservations, see Host Reservations in DHCPv4; for IPv6 reservations, see Host Reservations in DHCPv6. The subnet-id is mandatory. Use a value of zero (0) to add a global reservation, or the ID of the subnet to which the reservation should be added. An example command can be as simple as:

{
    "command": "reservation-add",
    "arguments": {
        "reservation": {
            "subnet-id": 1,
            "hw-address": "1a:1b:1c:1d:1e:1f",
            "ip-address": "192.0.2.202"
        }
    }
}

but it can also take many more parameters, for example:

{
    "command": "reservation-add",
    "arguments": {
        "reservation": {
            "subnet-id": 1,
            "client-id": "01:0a:0b:0c:0d:0e:0f",
            "ip-address": "192.0.2.205",
            "next-server": "192.0.2.1",
            "server-hostname": "hal9000",
            "boot-file-name": "/dev/null",
            "option-data": [
                {
                    "name": "domain-name-servers",
                    "data": "10.1.1.202,10.1.1.203"
                }
            ],
            "client-classes": [ "special_snowflake", "office" ]
        }
    }
}

Here is an example of a complex IPv6 reservation:

{
    "command": "reservation-add",
    "arguments": {
        "reservation": {
            "subnet-id": 1,
            "duid": "01:02:03:04:05:06:07:08:09:0A",
            "ip-addresses": [ "2001:db8:1:cafe::1" ],
            "prefixes": [ "2001:db8:2:abcd::/64" ],
            "hostname": "foo.example.com",
            "option-data": [
                {
                    "name": "vendor-opts",
                    "data": "4491"
                },
                {
                    "name": "tftp-servers",
                    "space": "vendor-4491",
                    "data": "3000:1::234"
                }
            ]
        }
    }
}

The command returns a status that indicates either success (result 0) or failure (result 1). A failed command always includes a text parameter that explains the cause of the failure. Here’s an example of a successful addition:

{ "result": 0, "text": "Host added." }

And here’s an example of a failure:

{ "result": 1, "text": "Mandatory 'subnet-id' parameter missing." }

As reservation-add is expected to store the host, the hosts-databases parameter must be specified in the configuration, and databases must not run in read-only mode.

The reservation-get Command

reservation-get can be used to query the host database and retrieve existing reservations. This command supports two types of parameters: (subnet-id, address) or (subnet-id, identifier-type, identifier). The first type of query is used when the address (either IPv4 or IPv6) is known, but the details of the reservation are not. One common use for this type of query is to find out whether a given address is reserved. The second query uses identifiers. For maximum flexibility, Kea stores the host identifying information as a pair of values: the type and the actual identifier. Currently supported identifiers are "hw-address", "duid", "circuit-id", "client-id", and "flex-id". The subnet-id is mandatory. Use a value of zero (0) to fetch a global reservation, or the ID of the subnet to which the reservation belongs.

An example command for getting a host reservation by a (subnet-id, address) pair looks as follows:

{
    "command": "reservation-get",
    "arguments": {
        "subnet-id": 1,
        "ip-address": "192.0.2.202"
    }
}

An example query by (subnet-id, identifier-type, identifier) looks as follows:

{
    "command": "reservation-get",
    "arguments": {
        "subnet-id": 4,
        "identifier-type": "hw-address",
        "identifier": "01:02:03:04:05:06"
    }
}

reservation-get typically returns the result 0 when a query was conducted properly. In particular, 0 is returned when the host was not found. If the query was successful, the host parameters are returned. An example of a query that did not find the host looks as follows:

{ "result": 0, "text": "Host not found." }

Here’s an example of a result returned when the host was found successfully:

{
  "arguments": {
    "boot-file-name": "bootfile.efi",
    "client-classes": [

    ],
    "hostname": "somehost.example.org",
    "hw-address": "01:02:03:04:05:06",
    "ip-address": "192.0.2.100",
    "next-server": "192.0.0.2",
    "option-data": [

    ],
    "server-hostname": "server-hostname.example.org"
  },
  "result": 0,
  "text": "Host found."
}

An example result returned when the query was malformed might look like this:

{ "result": 1, "text": "No 'ip-address' provided and 'identifier-type'
                        is either missing or not a string." }

The reservation-get-all Command

reservation-get-all can be used to query the host database and retrieve all reservations in a specified subnet. This command uses parameters providing the mandatory subnet-id. Global host reservations can be retrieved by using a subnet-id value of zero (0).

For instance, retrieving host reservations for the subnet 1:

{
    "command": "reservation-get-all",
    "arguments": {
        "subnet-id": 1
     }
}

returns some IPv4 hosts:

{
    "arguments": {
        "hosts": [
            {
                "boot-file-name": "bootfile.efi",
                "client-classes": [ ],
                "hostname": "somehost.example.org",
                "hw-address": "01:02:03:04:05:06",
                "ip-address": "192.0.2.100",
                "next-server": "192.0.0.2",
                "option-data": [ ],
                "server-hostname": "server-hostname.example.org"
            },
            ...
            {
                "boot-file-name": "bootfile.efi",
                "client-classes": [ ],
                "hostname": "otherhost.example.org",
                "hw-address": "01:02:03:04:05:ff",
                "ip-address": "192.0.2.200",
                "next-server": "192.0.0.2",
                "option-data": [ ],
                "server-hostname": "server-hostname.example.org"
            }
        ]
    },
    "result": 0,
    "text": "72 IPv4 host(s) found."
}

The response returned by reservation-get-all can be very long. The DHCP server does not handle DHCP traffic while preparing a response to reservation-get-all, so if there are many reservations in a subnet, this may be disruptive; use with caution. For larger deployments, please consider using reservation-get-page instead (see The reservation-get-page command).

For more information, see The reservation-get-all Command.

The reservation-get-page command

reservation-get-page can be used to query the host database and retrieve all reservations in a specified subnet, by pages. This command uses parameters providing the mandatory subnet-id. Use a value of zero (0) to fetch global reservations. The second mandatory parameter is the page size limit. The optional source-index and from-host-id parameters, both of which default to 0, are used to chain page queries. Since Kea version 1.9.0, the subnet-id parameter is optional.

The usage of the from and source-index parameters requires additional explanation. For the first call, those parameters should not be specified (or should be specified as zeros). For any follow-up calls, they should be set to the values returned in previous calls, in a next map holding from and source-index values. Subsequent calls should be issued until all reservations are returned. The end is reached once the returned list is empty, the count is 0, no next map is present, and result status 3 (empty) is returned.

Note

The from and source-index parameters reflect the internal state of the search. There is no need to understand what they represent; it is simply a value that should be copied from one response to the next query. However, for those who are curious, the from field represents a 64-bit representation of the host identifier used by a host backend. The source-index is an internal representation of multiple host backends: 0 is used to represent hosts defined in a configuration file, and 1 represents the first database backend. In some uncommon cases there may be more than one database backend configured, so potentially there may be a 2. In any case, Kea iterates over all backends configured.

For instance, retrieving host reservations for the subnet 1 and requesting the first page can be done by:

{
    "command": "reservation-get-page",
    "arguments": {
        "subnet-id": 1,
        "limit": 10
     }
}

Since this is the first call, source-index and from should not be specified. They are set to their zero default values.

Some hosts are returned with information to get the next page:

{
    "arguments": {
        "count": 72,
        "hosts": [
            {
                "boot-file-name": "bootfile.efi",
                "client-classes": [ ],
                "hostname": "somehost.example.org",
                "hw-address": "01:02:03:04:05:06",
                "ip-address": "192.0.2.100",
                "next-server": "192.0.0.2",
                "option-data": [ ],
                "server-hostname": "server-hostname.example.org"
            },
            ...
            {
                "boot-file-name": "bootfile.efi",
                "client-classes": [ ],
                "hostname": "otherhost.example.org",
                "hw-address": "01:02:03:04:05:ff",
                "ip-address": "192.0.2.200",
                "next-server": "192.0.0.2",
                "option-data": [ ],
                "server-hostname": "server-hostname.example.org"
            }
        ],
        "next": {
            "from": 1234567,
            "source-index": 1
        }
    },
    "result": 0,
    "text": "72 IPv4 host(s) found."
}

Note that the from and source-index fields were specified in the response in the next map. Those two must be copied to the next command, so Kea continues from the place where the last command finished. To get the next page the following command can be sent:

{
    "command": "reservation-get-page",
    "arguments": {
        "subnet-id": 1,
        "source-index": 1,
        "from": 1234567,
        "limit": 10
     }
}

The response will contain a list of hosts with updated source-index and from fields. Continue calling the command until the last page is received. Its response will look like this:

{
    "arguments": {
        "count": 0,
        "hosts": [ ],
    },
    "result": 3,
    "0 IPv4 host(s) found."
}

This command is more complex than reservation-get-all, but lets users retrieve larger host reservations lists in smaller chunks. For small deployments with few reservations, it is easier to use reservation-get-all (see The reservation-get-all Command).

The reservation-get-by-hostname Command

reservation-get-by-hostname can be used to query the host database and retrieve all reservations with a specified hostname or in a specified subnet. This command uses parameters providing the mandatory hostname and the optional subnet-id. Global host reservations can be retrieved by using a subnet-id value of zero (0). Hostname matching is case-insensitive.

For instance, retrieving host reservations for “foobar” in the subnet 1:

{
    "command": "reservation-get-by-hostname",
    "arguments": {
        "hostname": "foobar.example.org",
        "subnet-id": 1
     }
}

returns some IPv4 hosts:

{
    "arguments": {
        "hosts": [
            {
                "boot-file-name": "bootfile.efi",
                "client-classes": [ ],
                "hostname": "foobar.example.org",
                "hw-address": "01:02:03:04:05:06",
                "ip-address": "192.0.2.100",
                "next-server": "192.0.0.2",
                "option-data": [ ],
                "server-hostname": "server-hostname.example.org"
            },
            ...
            {
                "boot-file-name": "bootfile.efi",
                "client-classes": [ ],
                "hostname": "foobar.example.org",
                "hw-address": "01:02:03:04:05:ff",
                "ip-address": "192.0.2.200",
                "next-server": "192.0.0.2",
                "option-data": [ ],
                "server-hostname": "server-hostname.example.org"
            }
        ]
    },
    "result": 0,
    "text": "5 IPv4 host(s) found."
}

The response returned by reservation-get-by-hostname can be long, particularly when responses are not limited to a subnet.

For more information, see The reservation-get-by-hostname Command.

Note

When using MySQL as the host backend, this command relies on the fact that the hostname column in the hosts table uses a case-insensitive collation, as explained in the MySQL section of Kea Database Administration.

The reservation-get-by-id Command

reservation-get-by-id can be used to query the host database and retrieve all reservations with a specified identifier (identifier-type and identifier parameters), independently of subnets. The syntax for parameters is the same as for ref:command-reservation-get. The subnet-id parameter cannot be used, to avoid confusion. This command is available since Kea version 1.9.0.

For instance, retrieving host reservations for the 01:02:03:04:05:06 MAC address:

{
    "command": "reservation-get-by-id",
    "arguments": {
        "identifier-type": "hw-address",
        "identifier": "01:02:03:04:05:06"
     }
 }

returns some IPv4 hosts:

{
    "arguments": {
        "hosts": [
            {
                "boot-file-name": "bootfile.efi",
                "client-classes": [ ],
                "hostname": "foo.example.org",
                "hw-address": "01:02:03:04:05:06",
                "ip-address": "192.0.2.100",
                "next-server": "192.0.0.2",
                "option-data": [ ],
                "server-hostname": "server-hostname.example.org",
                "subnet-id": 123
            },
            ...
            {
                "boot-file-name": "bootfile.efi",
                "client-classes": [ ],
                "hostname": "bar.example.org",
                "hw-address": "01:02:03:04:05:06",
                "ip-address": "192.0.2.200",
                "next-server": "192.0.0.2",
                "option-data": [ ],
                "server-hostname": "server-hostname.example.org",
                "subnet-id": 345
            }
        ]
    },
    "result": 0,
    "text": "5 IPv4 host(s) found."
}

The response returned by reservation-get-by-id can be long, particularly when responses are not limited to a subnet.

For more information, see The reservation-get-by-id Command.

The reservation-del Command

reservation-del can be used to delete a reservation from the host database. This command supports two types of parameters: (subnet-id, address) or (subnet-id, identifier-type, identifier). The first type of query is used when the address (either IPv4 or IPv6) is known, but the details of the reservation are not. One common use for this type of query is to remove a reservation (e.g. a specific address should no longer be reserved). The second query uses identifiers. For maximum flexibility, Kea stores the host identifying information as a pair of values: the type and the actual identifier. Currently supported identifiers are "hw-address", "duid", "circuit-id", "client-id", and "flex-id". The subnet-id is mandatory. Use a value of zero (0) to delete a global reservation, or the ID of the subnet from which the reservation should be deleted.

An example command for deleting a host reservation by (subnet-id, address) pair looks as follows:

{
    "command": "reservation-del",
    "arguments": {
        "subnet-id": 1,
        "ip-address": "192.0.2.202"
    }
}

An example deletion by (subnet-id, identifier-type, identifier) looks as follows:

{
    "command": "reservation-del",
    "arguments":
        "subnet-id": 4,
        "identifier-type": "hw-address",
        "identifier": "01:02:03:04:05:06"
    }
}

reservation-del returns a result of 0 when the host deletion was successful, or 1 if it failed. Descriptive text is provided in the event of an error. Here are some examples of possible results:

{
    "result": 1,
    "text": "Host not deleted (not found)."
}

{
    "result": 0,
    "text": "Host deleted."
}

{
    "result": 1,
    "text": "Unable to delete a host because there is no hosts-database
             configured."
}

lease_cmds: Lease Commands

Kea allows users to store lease information in several backends (memfile, MySQL and PostgreSQL), and this library provides an interface that can manipulate leases in a unified, safe way. In particular, it allows things that were previously impossible: lease manipulation in memfile while Kea is running, sanity check changes, lease existence checks, and removal of all leases belonging to a specific subnet. The hook library can also catch more obscure errors, like an attempt to add a lease with a subnet-id that does not exist in the configuration, or configuring a lease to use an address that is outside of the subnet to which it is supposed to belong. The library also provides a non-programmatic way to manage user contexts associated with leases.

The lease commands library is part of the open source code and is available to every Kea user.

Note

This library may only be loaded by the kea-dhcp4 or the kea-dhcp6 process.

There are many situations where an administrative command may be useful; for example, during migration between servers or different vendors, when a certain network is being retired, or when a device has been disconnected and the system administrator knows that it will not be coming back. The get queries may be useful for automating certain management and monitoring tasks, and they can also act as preparatory steps for lease updates and removals.

This library provides the following commands:

• lease4-add - adds a new IPv4 lease.

• lease6-add - adds a new IPv6 lease.

• lease6-bulk-apply - creates, updates, and/or deletes multiple IPv6 leases in a single transaction.

• lease4-get - checks whether an IPv4 lease with the specified parameters exists and returns it if it does.

• lease6-get - checks whether an IPv6 lease with the specified parameters exists and returns it if it does.

• lease4-get-all - returns all IPv4 leases or all IPv4 leases for the specified subnets.

• lease6-get-all - returns all IPv6 leases or all IPv6 leases for the specified subnets.

• lease4-get-page - returns a set (“page”) of leases from the list of all IPv4 leases in the database. By iterating through the pages it is possible to retrieve all the leases.

• lease6-get-page - returns a set (“page”) of leases from the list of all IPv6 leases in the database. By iterating through the pages it is possible to retrieve all the leases.

• lease4-get-by-hw-address - returns all IPv4 leases with the specified hardware address.

• lease4-get-by-client-id - returns all IPv4 leases with the specified client-id.

• lease6-get-by-duid - returns all IPv6 leases with the specified DUID.

• lease4-get-by-hostname - returns all IPv4 leases with the specified hostname.

• lease6-get-by-hostname - returns all IPv6 leases with the specified hostname.

• lease4-del - deletes an IPv4 lease with the specified parameters.

• lease6-del - deletes an IPv6 lease with the specified parameters.

• lease4-update - updates an IPv4 lease.

• lease6-update - updates an IPv6 lease.

• lease4-wipe - removes all leases from a specific IPv4 subnet or from all subnets.

• lease6-wipe - removes all leases from a specific IPv6 subnet or from all subnets.

• lease4-resend-ddns - resends a request to update DNS entries for an existing lease.

• lease6-resend-ddns - resends a request to update DNS entries for an existing lease.

All commands use JSON syntax and can be issued either using the control channel (see Management API) or Control Agent (see The Kea Control Agent).

The library can be loaded in the same way as other hook libraries, and it does not take any parameters. It supports both the DHCPv4 and DHCPv6 servers.

"Dhcp6": {
    "hooks-libraries": [
        {
            "library": "/path/libdhcp_lease_cmds.so"
        }
        ...
    ]
}

The lease4-add, lease6-add Commands

The lease4-add and lease6-add commands allow a new lease to be created. Typically Kea creates a lease when it first sees a new device; however, sometimes it may be convenient to create the lease manually. The lease4-add command requires at least two parameters: an IPv4 address and an identifier, i.e. hardware (MAC) address. A third parameter, subnet-id, is optional. If the subnet-id is not specified or the specified value is 0, Kea tries to determine the value by running a subnet-selection procedure. If specified, however, its value must match the existing subnet. The simplest successful call might look as follows:

{
    "command": "lease4-add",
    "arguments": {
        "ip-address": "192.0.2.202",
        "hw-address": "1a:1b:1c:1d:1e:1f"
    }
}

The lease6-add command requires three parameters: an IPv6 address, an IAID value (identity association identifier, a value sent by clients), and a DUID. As with lease4-add, the subnet-id parameter is optional. If the subnet-id is not specified or the provided value is 0, Kea tries to determine the value by running a subnet-selection procedure. If specified, however, its value must match the existing subnet. For example:

{
    "command": "lease6-add",
    "arguments": {
        "subnet-id": 66,
        "ip-address": "2001:db8::3",
        "duid": "1a:1b:1c:1d:1e:1f:20:21:22:23:24",
        "iaid": 1234
    }
}

lease6-add can also be used to add leases for IPv6 prefixes. In this case there are three additional parameters that must be specified: subnet-id, type (set to “IA_PD”), and prefix length. The actual prefix is set using the ip-address field. Note that Kea cannot guess subnet-id values for prefixes; they must be specified explicitly. For example, to configure a lease for prefix 2001:db8:abcd::/48, the following command can be used:

{
    "command": "lease6-add",
    "arguments": {
        "subnet-id": 66,
        "type": "IA_PD",
        "ip-address": "2001:db8:abcd::",
        "prefix-len": 48,
        "duid": "1a:1b:1c:1d:1e:1f:20:21:22:23:24",
        "iaid": 1234
    }
}

The commands can take several additional optional parameters:

• valid-lft - specifies the lifetime of the lease, expressed in seconds. If not specified, the value configured in the subnet related to the specified subnet-id is used.

• expire - creates a timestamp of the lease expiration time, expressed in UNIX format (seconds since 1 Jan 1970). If not specified, the default value is the current time plus the lease lifetime (the value of valid-lft).

• fqdn-fwd - specifies whether the lease should be marked as if a forward DNS update were conducted. This only affects the data stored in the lease database, and no DNS update will be performed. If configured, a DNS update to remove the A or AAAA records will be conducted when the lease is removed due to expiration or being released by a client. If not specified, the default value is false. The hostname parameter must be specified if fqdn-fwd is set to true.

• fqdn-rev - specifies whether the lease should be marked as if reverse DNS update were conducted. This only affects the data stored in the lease database, and no DNS update will be performed.. If configured, a DNS update to remove the PTR record will be conducted when the lease is removed due to expiration or being released by a client. If not specified, the default value is false. The hostname parameter must be specified if fqdn-fwd is set to true.

• hostname - specifies the hostname to be associated with this lease. Its value must be non-empty if either fqdn-fwd or fqdn-rev are set to true. If not specified, the default value is an empty string.

• hw-address - optionally specifies a hardware (MAC) address for an IPv6 lease. It is a mandatory parameter for an IPv4 lease.

• client-id - optionally specifies a client identifier for an IPv4 lease.

• preferred-lft - optionally specifies a preferred lifetime for IPv6 leases. If not specified, the value configured for the subnet corresponding to the specified subnet-id is used. This parameter is not used when adding an IPv4 lease.

• state - specifies the state of an added lease, which can be 0 for default, 1 for declined, and 2 for the expired-reclaimed state. Any other value causes an error. Using 1 for a "IA_PD" lease type is illegal and will be rejected.

• user-context - specifies the user context to be associated with this lease. It must be a JSON map.

Here is an example of a fairly complex lease addition:

{
    "command": "lease6-add",
    "arguments": {
        "subnet-id": 66,
        "ip-address": "2001:db8::3",
        "duid": "01:02:03:04:05:06:07:08",
        "iaid": 1234,
        "hw-address": "1a:1b:1c:1d:1e:1f",
        "preferred-lft": 500,
        "valid-lft": 1000,
        "expire": 12345678,
        "fqdn-fwd": true,
        "fqdn-rev": true,
        "state": 0,
        "hostname": "urania.example.org",
        "user-context": { "version": 1 }
    }
}

The command returns a status that indicates either success (result 0) or failure (result 1). A failed command always includes a text parameter that explains the cause of failure. For example:

{ "result": 0, "text": "Lease added." }

Example failure:

{ "result": 1, "text": "missing parameter 'ip-address' (<string>:3:19)" }

The lease6-bulk-apply Command

The lease6-bulk-apply was implemented to address the performance penalty in High-Availability mode when a single DHCPv6 transaction resulted in multiple lease updates sent to the partner, if multiple address and/or prefix leases were allocated. Consider the case when a DHCPv6 client requests the assignment of two IPv6 addresses and two IPv6 prefixes: it may result in the allocation of four leases. In addition, DHCPv6 may assign a different address than the one requested by the client during the renew or rebind stage, and delete the leases previously used by this client. There are six lease changes sent between the HA partners in this case. Sending these updates as individual commands, e.g. via lease6-update, is highly inefficient and produces unnecessary delays in communication, both between the HA partners and in sending the response to the DHCPv6 client.

The lease6-bulk-apply command deals with this problem by aggregating all lease changes - both deleted leases and new or updated leases - in a single command. The receiving server iterates over the deleted leases and deletes them from its lease database. Next, it iterates over the new/updated leases and adds them to the database or updates them if they already exist.

Even though High Availability is the major application for this command, it can be freely used in all cases when it is desirable to send multiple lease changes in a single command.

In the following example, we delete two leases and add or update two other leases in the database:

 {
   "command": "lease6-bulk-apply",
   "arguments": {
       "deleted-leases": [
           {
               "ip-address": "2001:db8:abcd::",
               "type": "IA_PD",
               ...
           },
           {
               "ip-address": "2001:db8:abcd::234",
               "type": "IA_NA",
               ...
           }
       ],
       "leases": [
           {
               "subnet-id": 66,
               "ip-address": "2001:db8:cafe::",
               "type": "IA_PD",
                ...
           },
           {
               "subnet-id": 66,
               "ip-address": "2001:db8:abcd::333",
               "type": "IA_NA",
               ...
           }
       ]
    }
}

If any of the leases are malformed, no lease changes are applied to the lease database. If the leases are well-formed but there is a failure to apply any of the lease changes to the database, the command continues to be processed for other leases. All the leases for which the command was unable to apply the changes in the database are listed in the response. For example:

{
    "result": 0,
    "text": "Bulk apply of 2 IPv6 leases completed".
    "arguments": {
        "failed-deleted-leases": [
            {
                "ip-address": "2001:db8:abcd::",
                "type": "IA_PD",
                "result": 3,
                "error-message": "no lease found"
            }
        ],
        "failed-leases": [
            {
                "ip-address": "2001:db8:cafe::",
                "type": "IA_PD",
                "result": 1,
                "error-message": "unable to communicate with the lease database"
            }
        ]
    }
}

The response above indicates that the hook library was unable to delete the lease for prefix “2001:db8:abcd::” and add or update the lease for prefix “2001:db8:cafe::”. However, there are two other lease changes which have been applied as indicated by the text message. The result is the status constant that indicates the type of the error experienced for the particular lease. The meanings of the returned codes are the same as the results returned for the commands. In particular, the result of 1 indicates an error while processing the lease, e.g. a communication error with the database. The result of 3 indicates that an attempt to delete the lease was unsuccessful because such a lease doesn’t exist (an empty result).

The lease4-get, lease6-get Commands

lease4-get and lease6-get can be used to query the lease database and retrieve existing leases. There are two types of parameters the lease4-get command supports: (address) or (subnet-id, identifier-type, identifier). There are also two types for lease6-get: (address, type) or (subnet-id, identifier-type, identifier, IAID, type). The first type of query is used when the address (either IPv4 or IPv6) is known, but the details of the lease are not; one common use case of this type of query is to find out whether a given address is being used. The second query uses identifiers; currently supported identifiers for leases are: "hw-address" (IPv4 only), "client-id" (IPv4 only), and "duid" (IPv6 only).

An example lease4-get command for getting a lease using an IPv4 address is:

{
    "command": "lease4-get",
    "arguments": {
        "ip-address": "192.0.2.1"
    }
}

An example of the lease6-get query is:

{
  "command": "lease6-get",
  "arguments": {
    "ip-address": "2001:db8:1234:ab::",
    "type": "IA_PD"
  }
}

An example query by "hw-address" for an IPv4 lease looks as follows:

{
    "command": "lease4-get",
    "arguments": {
        "identifier-type": "hw-address",
        "identifier": "08:08:08:08:08:08",
        "subnet-id": 44
    }
}

An example query by "client-id" for an IPv4 lease looks as follows:

{
    "command": "lease4-get",
    "arguments": {
        "identifier-type": "client-id",
        "identifier": "01:01:02:03:04:05:06",
        "subnet-id": 44
    }
}

An example query by (subnet-id, identifier-type, identifier, iaid, type) for an IPv6 lease is:

{
    "command": "lease4-get",
    "arguments": {
        "identifier-type": "duid",
        "identifier": "08:08:08:08:08:08",
        "iaid": 1234567,
        "type": "IA_NA",
        "subnet-id": 44
    }
}

The type is an optional parameter. Supported values are: IA_NA (non-temporary address) and IA_PD (IPv6 prefix). If not specified, IA_NA is assumed.

lease4-get and lease6-get return an indication of the result of the operation and lease details, if found. The result has one of the following values: 0 (success), 1 (error), or 3 (empty). An empty result means that a query has been completed properly, but the object (a lease in this case) has not been found. The lease parameters, if found, are returned as arguments.

An example result returned when the host was found:

{
  "arguments": {
    "client-id": "42:42:42:42:42:42:42:42",
    "cltt": 12345678,
    "fqdn-fwd": false,
    "fqdn-rev": true,
    "hostname": "myhost.example.com.",
    "hw-address": "08:08:08:08:08:08",
    "ip-address": "192.0.2.1",
    "state": 0,
    "subnet-id": 44,
    "valid-lft": 3600
  },
  "result": 0,
  "text": "IPv4 lease found."
}

Note

The client last transaction time (cltt field) is bound to the valid lifetime (valid-lft) and to the expire date (not reported here but stored in databases) by the equation \(cltt + valid\_lft = expire\)

at the exception of the infinite valid lifetime coded by the 0xfffffff (4294967295) special value which makes the expire value to overflow on MySQL and old PostgreSQL backends where timestamps are 32 bit long. So in these lease databases the expire date is the same as the cltt i.e. \(cltt = expire\) when \(valid\_lft = 4294967295\) and the lease backend is MySQL or PostgreSQL.

The lease4-get-all, lease6-get-all Commands

lease4-get-all and lease6-get-all are used to retrieve all IPv4 or IPv6 leases, or all leases for the specified set of subnets. All leases are returned when there are no arguments specified with the command, as in the following example:

{
    "command": "lease4-get-all"
}

If arguments are provided, it is expected that they contain the "subnets" parameter, which is a list of subnet identifiers for which leases should be returned. For example, to retrieve all IPv6 leases belonging to the subnets with identifiers 1, 2, 3, and 4:

{
    "command": "lease6-get-all",
    "arguments": {
        "subnets": [ 1, 2, 3, 4 ]
    }
}

The returned response contains a detailed list of leases in the following format:

{
    "arguments": {
        "leases": [
            {
                "cltt": 12345678,
                "duid": "42:42:42:42:42:42:42:42",
                "fqdn-fwd": false,
                "fqdn-rev": true,
                "hostname": "myhost.example.com.",
                "hw-address": "08:08:08:08:08:08",
                "iaid": 1,
                "ip-address": "2001:db8:2::1",
                "preferred-lft": 500,
                "state": 0,
                "subnet-id": 44,
                "type": "IA_NA",
                "valid-lft": 3600
            },
            {
                "cltt": 12345678,
                "duid": "21:21:21:21:21:21:21:21",
                "fqdn-fwd": false,
                "fqdn-rev": true,
                "hostname": "",
                "iaid": 1,
                "ip-address": "2001:db8:0:0:2::",
                "preferred-lft": 500,
                "prefix-len": 80,
                "state": 0,
                "subnet-id": 44,
                "type": "IA_PD",
                "valid-lft": 3600
            }
        ]
    },
    "result": 0,
    "text": "2 IPv6 lease(s) found."
}

Warning

The lease4-get-all and lease6-get-all commands may result in very large responses. This may have a negative impact on the DHCP server’s responsiveness while the response is generated and transmitted over the control channel, as the server imposes no restriction on the number of leases returned as a result of this command.

The lease4-get-page, lease6-get-page Commands

The lease4-get-all and lease6-get-all commands may result in very large responses; generating such a response may consume CPU bandwidth as well as memory. It may even cause the server to become unresponsive. In the case of large lease databases it is usually better to retrieve leases in chunks, using the paging mechanism. lease4-get-page and lease6-get-page implement a paging mechanism for DHCPv4 and DHCPv6 servers, respectively. The following command retrieves the first 1024 IPv4 leases:

{
    "command": "lease4-get-page",
    "arguments": {
        "from": "start",
        "limit": 1024
    }
}

The keyword start denotes that the first page of leases should be retrieved. Alternatively, an IPv4 zero address can be specified to retrieve the first page:

{
    "command": "lease4-get-page",
    "arguments": {
        "from": "0.0.0.0",
        "limit": 1024
    }
}

Similarly, the IPv6 zero address can be specified in the lease6-get-page command:

{
    "command": "lease6-get-page",
    "arguments": {
        "from": "::",
        "limit": 6
    }
}

The response has the following structure:

{
    "arguments": {
        "leases": [
            {
                "ip-address": "2001:db8:2::1",
                ...
            },
            {
                "ip-address": "2001:db8:2::9",
                ...
            },
            {
                "ip-address": "2001:db8:3::1",
                ...
            },
            {
                "ip-address": "2001:db8:5::3",
                ...
            }
            {
                "ip-address": "2001:db8:4::1",
                ...
            },
            {
                "ip-address": "2001:db8:2::7",
                ...
            }

        ],
        "count": 6
    },
    "result": 0,
    "text": "6 IPv6 lease(s) found."
}

Note that the leases’ details were excluded from the response above for brevity.

Generally, the returned list is not sorted in any particular order. Some lease database backends may sort leases in ascending order of addresses, but the controlling client must not rely on this behavior.

The count parameter contains the number of returned leases on the page.

To fetch the next page, the client must use the last address of the current page as an input to the next lease4-get-page or lease6-get-page command call. In this example it is:

{
    "command": "lease6-get-page",
    "arguments": {
        "from": "2001:db8:2::7",
        "count": 6
    }
}

because 2001:db8:2::7 is the last address on the current page.

The client may assume that it has reached the last page when the count value is lower than that specified in the command; this includes the case when the count is equal to 0, meaning that no leases were found.

The lease4-get-by-*, lease6-get-by-* Commands

lease4-get-by-* and lease6-get-by-* can be used to query the lease database and retrieve all existing leases matching a given feature (denoted by the *). These can include a specified hardware address (IPv4 only), client-id IPv4 only), duid (IPv6 only) identifiers, or hostname.

An example lease4-get-by-hw-address command for getting IPv4 leases with a given hardware address is:

{
    "command": "lease4-get-by-hw-address",
    "arguments": {
        "hw-address": "08:08:08:08:08:08"
    }
}

An example of the lease6-get-by-hostname is:

{
    "command": "lease6-get-by-hostname",
    "arguments": {
        "hostname": "myhost.example.org"
    }
}

The by key is the only parameter. The returned response contains a detailed list of leases in the same format as lease4-get-all or lease6-get-all. This list can be empty and is usually not large.

The lease4-del, lease6-del Commands

lease4-del and lease6-del can be used to delete a lease from the lease database. There are two types of parameters these commands support, similar to the lease4-get``and ``lease6-get commands: (address) for both v4 and v6, (subnet-id, identifier-type, identifier) for v4, and (subnet-id, identifier-type, identifier, type, IAID) for v6. The first type of query is used when the address (either IPv4 or IPv6) is known, but the details of the lease are not. One common use case is where an administrator wants a specified address to no longer be used. The second form of the command uses identifiers. For maximum flexibility, this interface uses identifiers as a pair of values: the type and the actual identifier. The currently supported identifiers are "hw-address" (IPv4 only), "client-id" (IPv4 only), and "duid" (IPv6 only).

An example command for deleting a lease by address is:

{
    "command": "lease4-del",
    "arguments": {
        "ip-address": "192.0.2.202"
    }
}

An example IPv4 lease deletion by "hw-address" is:

{
  "command": "lease4-del",
  "arguments": {
    "identifier": "08:08:08:08:08:08",
    "identifier-type": "hw-address",
    "subnet-id": 44
  }
}

Another parameter called update-ddns, when true, instructs the server to queue a request to kea-dhcp-ddns to remove DNS entries after the lease is successfully deleted if:

• DDNS updating is enabled (i.e. "dhcp-ddns":{ "enable-updates": true }).

• The lease’s hostname is not empty.

• At least one of the lease’s DNS direction flags (fqdn_fwd or fqdn_rev) is true.

This parameter defaults to false. An example of its use is shown below:

{
    "command": "lease4-del",
    "arguments": {
        "ip-address": "192.0.2.202",
        "update-ddns": true
    }
}

lease4-del and lease6-del return a result that indicates the outcome of the operation. It has one of the following values: 0 (success), 1 (error), or 3 (empty). The empty result means that a query has been completed properly, but the object (a lease, in this case) has not been found.

The lease4-update, lease6-update Commands

The lease4-update and lease6-update commands can be used to update existing leases. Since all lease database backends are indexed by IP addresses, it is not possible to update an address, but all other fields may be altered. If an address needs to be changed, please use lease4-del/lease6-del followed by lease4-add/lease6-add.

The subnet-id parameter is optional. If not specified, or if the specified value is 0, Kea tries to determine its value by running a subnet-selection procedure. If specified, however, its value must match the existing subnet.

The optional boolean parameter "force-create" specifies whether the lease should be created if it does not exist in the database. It defaults to false, which indicates that the lease is not created if it does not exist. In such a case, an error is returned when trying to update a non-existing lease. If the "force-create" parameter is set to true and the updated lease does not exist, the new lease is created as a result of receiving the lease4-update/lease6-update command.

An example of a command to update an IPv4 lease is:

{
  "command": "lease4-update",
  "arguments": {
    "ip-address": "192.0.2.1",
    "hostname": "newhostname.example.org",
    "hw-address": "1a:1b:1c:1d:1e:1f",
    "subnet-id": 44,
    "force-create": true
  }
}

An example of a command to update an IPv6 lease is:

{
  "command": "lease6-update",
  "arguments": {
    "ip-address": "2001:db8::1",
    "duid": "88:88:88:88:88:88:88:88",
    "iaid": 7654321,
    "hostname": "newhostname.example.org",
    "subnet-id": 66,
    "force-create": false
  }
}

The lease4-wipe, lease6-wipe Commands

lease4-wipe and lease6-wipe are designed to remove all leases associated with a given subnet. This administrative task is expected to be used when an existing subnet is being retired. The leases are not properly expired; no DNS updates are carried out, no log messages are created, and hooks are not called for the leases being removed.

An example of lease4-wipe is:

{
  "command": "lease4-wipe",
  "arguments": {
    "subnet-id": 44
  }
}

An example of lease6-wipe is:

{
  "command": "lease6-wipe",
  "arguments": {
    "subnet-id": 66
  }
}

The commands return a text description of the number of leases removed, plus the status code 0 (success) if any leases were removed or 3 (empty) if there were no leases. Status code 1 (error) may be returned if the parameters are incorrect or some other exception is encountered.

subnet-id 0 has a special meaning; it tells Kea to delete leases from all configured subnets. Also, the subnet-id parameter may be omitted. If not specified, leases from all subnets are wiped.

Note: currently only memfile lease storage supports this command.

The lease4-resend-ddns, lease6-resend-ddns Commands

lease4-resend-ddns and lease6-resend-ddns can be used to generate a request to kea-dhcp-ddns to update the DNS entries for an existing lease. The desired lease is selected by a single parameter, "ip-address". For an update request to be generated, DDNS updating must be enabled and DNS entries must have already been made (or attempted) for the lease. In other words, all of the following must be true:

• DDNS updating must be enabled (i.e. "dhcp-ddns":{ "enable-updates": true"}).

• The lease’s hostname must not be empty.

• At least one of the lease’s DNS direction flags (fqdn_fwd or fqdn_rev) must be true.

An example lease4-resend-ddns command for getting a lease using an IPv4 address is:

{
    "command": "lease4-resend-ddns",
    "arguments": {
        "ip-address": "192.0.2.1"
    }
}

An example of the lease6-resend-ddns query is:

{
  "command": "lease6-resend-ddns",
  "arguments": {
    "ip-address": "2001:db8:1::1"
  }
}

lease4-resend-ddns and lease6-resend-ddns return an indication of the result of the operation. It has one of the following values: 0 (success), 1 (error), or 3 (empty). An empty result means that a query has been completed properly, but the object (a lease in this case) has not been found.

A successful result does not mean that DNS has been successfully updated; it indicates that a request to update DNS has been successfully created and queued for transmission to kea-dhcp-ddns.

Here’s an example of a result returned when the lease was found:

{
  "result": 0,
  "text": "NCR generated for: 2001:db8:1::1, hostname: example.com."
}

subnet_cmds: Subnet Commands

This application offers commands used to query and manipulate subnet and shared network configurations in Kea. These can be very useful in deployments with a large number of subnets being managed by the DHCP servers, when those subnets are frequently updated. The commands offer a lightweight approach for manipulating subnets without needing to fully reconfigure the server, and without affecting existing servers’ configurations. An ability to manage shared networks (listing, retrieving details, adding new ones, removing existing ones, and adding subnets to and removing them from shared networks) is also provided.

Currently this library is only available to ISC customers with a paid support contract.

Note

This library may only be loaded by the kea-dhcp4 or kea-dhcp6 process.

The following commands are currently supported:

• subnet4-list/subnet6-list - lists all configured subnets.

• subnet4-get/subnet6-get - retrieves detailed information about a specified subnet.

• subnet4-add/subnet6-add - adds a new subnet into the server’s configuration.

• subnet4-update/subnet6-update - updates (replaces) a single subnet in the server’s configuration.

• subnet4-del/subnet6-del - removes a subnet from the server’s configuration.

• network4-list/network6-list - lists all configured shared networks.

• network4-get/network6-get - retrieves detailed information about a specified shared network.

• network4-add/network6-add - adds a new shared network to the server’s configuration.

• network4-del/network6-del - removes a shared network from the server’s configuration.

• network4-subnet-add/network6-subnet-add - adds an existing subnet to an existing shared network.

• network4-subnet-del/network6-subnet-del - removes a subnet from an existing shared network and demotes it to a plain subnet.

The subnet4-list Command

This command is used to list all currently configured subnets. Each subnet is returned with a subnet identifier and subnet prefix. To retrieve detailed information about the subnet, use the subnet4-get command.

This command has a simple structure:

{
    "command": "subnet4-list"
}

The list of subnets is returned in the following format:

{
    "result": 0,
    "text": "2 IPv4 subnets found",
    "arguments": {
    "subnets": [
        {
            "id": 10,
            "subnet": "10.0.0.0/8"
        },
        {
            "id": 100,
            "subnet": "192.0.2.0/24"
        }
    ]
}

If no IPv4 subnets are found, an error code is returned along with the error description.

The subnet6-list Command

This command is used to list all currently configured subnets. Each subnet is returned with a subnet identifier and subnet prefix. To retrieve detailed information about the subnet, use the subnet6-get command.

This command has a simple structure:

{
    "command": "subnet6-list"
}

The list of subnets is returned in the following format:

{
    "result": 0,
    "text": "2 IPv6 subnets found",
    "arguments": {
    "subnets": [
        {
            "id": 11,
            "subnet": "2001:db8:1::/64"
        },
        {
            "id": 233,
            "subnet": "3000::/16"
        }
    ]
}

If no IPv6 subnets are found, an error code is returned along with the error description.

The subnet4-get Command

This command is used to retrieve detailed information about the specified subnet. This command usually follows subnet4-list, which is used to discover available subnets with their respective subnet identifiers and prefixes. Any of those parameters can then be used in subnet4-get to fetch subnet information:

{
    "command": "subnet4-get",
    "arguments": {
        "id": 10
    }
}

or

{
    "command": "subnet4-get",
    "arguments": {
        "subnet": "10.0.0.0/8"
    }
}

If the subnet exists, the response will be similar to this:

{
    "result": 0,
    "text": "Info about IPv4 subnet 10.0.0.0/8 (id 10) returned",
    "arguments": {
        "subnets": [
            {
                "subnet": "10.0.0.0/8",
                "id": 1,
                "option-data": [
                    ....
                ]
                ...
            }
        ]
    }
}

The subnet6-get Command

This command is used to retrieve detailed information about the specified subnet. This command usually follows subnet6-list, which is used to discover available subnets with their respective subnet identifiers and prefixes. Any of those parameters can be then used in subnet6-get to fetch subnet information:

{
    "command": "subnet6-get",
    "arguments": {
        "id": 11
    }
}

or

{
    "command": "subnet6-get",
    "arguments": {
        "subnet": "2001:db8:1::/64"
    }
}

If the subnet exists, the response will be similar to this:

{
    "result": 0,
    "text": "Info about IPv6 subnet 2001:db8:1::/64 (id 11) returned",
    "arguments": {
        "subnets": [
            {
                "subnet": "2001:db8:1::/64",
                "id": 1,
                "option-data": [
                    ...
                ]
                ....
            }
        ]
    }
}

The subnet4-add Command

This command is used to create and add a new subnet to the existing server configuration. This operation has no impact on other subnets. The subnet identifier must be specified and must be unique among all subnets. If the identifier or a subnet prefix is not unique, an error is reported and the subnet is not added.

The subnet information within this command has the same structure as the subnet information in the server configuration file, with the exception that static host reservations cannot be specified within subnet4-add. The commands described in host_cmds: Host Commands should be used to add, remove, and modify static reservations.

{
    "command": "subnet4-add",
    "arguments": {
        "subnet4": [ {
            "id": 123,
            "subnet": "10.20.30.0/24",
            ...
        } ]
    }
}

The response to this command has the following structure:

{
    "result": 0,
    "text": "IPv4 subnet added",
    "arguments": {
        "subnet4": [
            {
                "id": 123,
                "subnet": "10.20.30.0/24"
            }
        ]
    }
}

The subnet6-add Command

This command is used to create and add a new subnet to the existing server configuration. This operation has no impact on other subnets. The subnet identifier must be specified and must be unique among all subnets. If the identifier or a subnet prefix is not unique, an error is reported and the subnet is not added.

The subnet information within this command has the same structure as the subnet information in the server configuration file, with the exception that static host reservations cannot be specified within subnet6-add. The commands described in host_cmds: Host Commands should be used to add, remove, and modify static reservations.

{
    "command": "subnet6-add",
    "arguments": {
        "subnet6": [ {
            "id": 234,
            "subnet": "2001:db8:1::/64",
            ...
        } ]
    }
}

The response to this command has the following structure:

{
    "result": 0,
    "text": "IPv6 subnet added",
    "arguments": {
        "subnet6": [
            {
                "id": 234,
                "subnet": "2001:db8:1::/64"
            }
        ]
    }
}

It is recommended, but not mandatory, to specify the subnet ID. If not specified, Kea will try to assign the next subnet-id value. This automatic ID value generator is simple; it returns the previous automatically assigned value, increased by 1. This works well, unless a subnet is manually created with a larger value than one previously used. For example, if subnet4-add is called five times, each without an ID, Kea will assign IDs 1, 2, 3, 4, and 5 and it will work just fine. However, if subnet4-add is called five times, with the first subnet having the subnet-id of value 3 and the remaining ones having no subnet-id, the operation will fail. The first command (with the explicit value) will use subnet-id 3; the second command will create a subnet with and ID of 1; the third will use a value of 2; and finally the fourth will have its subnet-id value auto-generated as 3. However, since there is already a subnet with that ID, the process will fail.

The general recommendation is either never to use explicit values, so that auto-generated values will always work; or always use explicit values, so that auto-generation is never used. The two approaches can be mixed only if the administrator understands how internal automatic subnet-id generation works in Kea.

Note

Subnet IDs must be greater than zero and less than 4294967295.

The subnet4-update Command

This command is used to update (overwrite) a single subnet in the existing server configuration. This operation has no impact on other subnets. The subnet identifier is used to identify the subnet to replace; it must be specified and must be unique among all subnets. The subnet prefix should not be updated.

The subnet information within this command has the same structure as the subnet information in the server configuration file, with the exception that static host reservations cannot be specified within subnet4-update. The commands described in host_cmds: Host Commands should be used to update, remove, and modify static reservations.

{
    "command": "subnet4-update",
    "arguments": {
        "subnet4": [ {
            "id": 123,
            "subnet": "10.20.30.0/24",
            ...
        } ]
    }
}

The response to this command has the following structure:

{
    "result": 0,
    "text": "IPv4 subnet updated",
    "arguments": {
        "subnet4": [
            {
                "id": 123,
                "subnet": "10.20.30.0/24"
            }
        ]
    }
}

The subnet6-update Command

This command is used to update (overwrite) a single subnet in the existing server configuration. This operation has no impact on other subnets. The subnet identifier is used to identify the subnet to replace; it must be specified and must be unique among all subnets. The subnet prefix should not be updated.

The subnet information within this command has the same structure as the subnet information in the server configuration file, with the exception that static host reservations cannot be specified within subnet6-update. The commands described in host_cmds: Host Commands should be used to update, remove, and modify static reservations.

{
    "command": "subnet6-update",
    "arguments": {
        "subnet6": [ {
            "id": 234,
            "subnet": "2001:db8:1::/64",
            ...
        } ]
    }
}

The response to this command has the following structure:

{
    "result": 0,
    "text": "IPv6 subnet updated",
    "arguments": {
        "subnet6": [
            {
                "id": 234,
                "subnet": "2001:db8:1::/64"
            }
        ]
    }
}

The subnet4-del Command

This command is used to remove a subnet from the server’s configuration. This command has no effect on other configured subnets, but removing a subnet does have certain implications.

In most cases the server has assigned some leases to the clients belonging to the subnet. The server may also be configured with static host reservations which are associated with this subnet. The current implementation of the subnet4-del command removes neither the leases nor the host reservations associated with a subnet. This is the safest approach because the server does not lose track of leases assigned to the clients from this subnet. However, removal of the subnet may still cause configuration errors and conflicts. For example: after removal of the subnet, the server administrator may update a new subnet with the ID used previously for the removed subnet. This means that the existing leases and static reservations will be in conflict with this new subnet. Thus, we recommend that this command be used with extreme caution.

This command can also be used to completely delete an IPv4 subnet that is part of a shared network. To simply remove the subnet from a shared network and keep the subnet configuration, use the network4-subnet-del command instead.

The command has the following structure:

{
    "command": "subnet4-del",
    "arguments": {
        "id": 123
    }
}

A successful response may look like this:

{
    "result": 0,
    "text": "IPv4 subnet 192.0.2.0/24 (id 123) deleted",
    "arguments": {
        "subnets": [
            {
                "id": 123,
                "subnet": "192.0.2.0/24"
            }
        ]
    }
}

The subnet6-del Command

This command is used to remove a subnet from the server’s configuration. This command has no effect on other configured subnets, but removing a subnet does have certain implications.

In most cases the server has assigned some leases to the clients belonging to the subnet. The server may also be configured with static host reservations which are associated with this subnet. The current implementation of the subnet6-del command removes neither the leases nor the host reservations associated with a subnet. This is the safest approach because the server does not lose track of leases assigned to the clients from this subnet. However, removal of the subnet may still cause configuration errors and conflicts. For example: after removal of the subnet, the server administrator may add a new subnet with the ID used previously for the removed subnet. This means that the existing leases and static reservations will be in conflict with this new subnet. Thus, we recommend that this command be used with extreme caution.

This command can also be used to completely delete an IPv6 subnet that is part of a shared network. To simply remove the subnet from a shared network and keep the subnet configuration, use the network6-subnet-del command instead.

The command has the following structure:

{
    "command": "subnet6-del",
    "arguments": {
        "id": 234
    }
}

A successful response may look like this:

{
    "result": 0,
    "text": "IPv6 subnet 2001:db8:1::/64 (id 234) deleted",
    "subnets": [
        {
            "id": 234,
            "subnet": "2001:db8:1::/64"
        }
    ]
}

The network4-list, network6-list Commands

These commands are used to retrieve the full list of currently configured shared networks. The list contains only very basic information about each shared network. If more details are needed, please use network4-get or network6-get to retrieve all information available. This command does not require any parameters and its invocation is very simple:

{
    "command": "network4-list"
}

An example response for network4-list looks as follows:

{
    "arguments": {
        "shared-networks": [
            { "name": "floor1" },
            { "name": "office" }
        ]
    },
    "result": 0,
    "text": "2 IPv4 network(s) found"
}

network6-list follows exactly the same syntax for both the query and the response.

The network4-get, network6-get Commands

These commands are used to retrieve detailed information about shared networks, including subnets that are currently part of a given network. Both commands take one mandatory parameter, name, which specifies the name of the shared network. An example command to retrieve details about an IPv4 shared network with the name “floor13” looks as follows:

{
    "command": "network4-get",
    "arguments": {
        "name": "floor13"
    }
}

An example response could look as follows:

{
    "result": 0,
    "text": "Info about IPv4 shared network 'floor13' returned",
    "arguments": {
        "shared-networks": [
        {
            "match-client-id": true,
            "name": "floor13",
            "option-data": [ ],
            "rebind-timer": 90,
            "relay": {
                "ip-address": "0.0.0.0"
            },
            "renew-timer": 60,
            # "reservation-mode": "all",
            # It is replaced by the "reservations-global"
            # "reservations-in-subnet" and "reservations-out-of-pool"
            # parameters.
            # Specify if the server should lookup global reservations.
            "reservations-global": false,
            # Specify if the server should lookup in-subnet reservations.
            "reservations-in-subnet": true,
            # Specify if the server can assume that all reserved addresses
            # are out-of-pool.
            "reservations-out-of-pool": false,
            "subnet4": [
                {
                    "subnet": "192.0.2.0/24",
                    "id": 5,
                    # many other subnet-specific details here
                },
                {
                    "id": 6,
                    "subnet": "192.0.3.0/31",
                    # many other subnet-specific details here
                }
            ],
            "valid-lifetime": 120
        }
        ]
    }
}

The actual response contains many additional fields that are omitted here for clarity. The response format is exactly the same as used in config-get, just limited to returning the shared network’s information.

The network4-add, network6-add Commands

These commands are used to add a new shared network, which must have a unique name. This command requires one parameter, shared-networks, which is a list and should contain exactly one entry that defines the network. The only mandatory element for a network is its name. Although it does not make operational sense, it is possible to add an empty shared network that does not have any subnets in it. That is allowed for testing purposes, but having empty networks (or networks with only one subnet) is discouraged in production environments. For details regarding syntax, see Shared Networks in DHCPv4 and Shared Networks in DHCPv6.

Note

As opposed to parameter inheritance during the processing of a full new configuration, this command does not fully handle parameter inheritance. Any missing parameters will be filled with default values, rather than inherited from the global scope.

An example that showcases how to add a new IPv4 shared network looks as follows:

{
    "command": "network4-add",
    "arguments": {
        "shared-networks": [ {
            "name": "floor13",
            "subnet4": [
            {
                "id": 100,
                "pools": [ { "pool": "192.0.2.2-192.0.2.99" } ],
                "subnet": "192.0.2.0/24",
                "option-data": [
                    {
                        "name": "routers",
                        "data": "192.0.2.1"
                    }
                ]
            },
            {
                "id": 101,
                "pools": [ { "pool": "192.0.3.2-192.0.3.99" } ],
                "subnet": "192.0.3.0/24",
                "option-data": [
                    {
                        "name": "routers",
                        "data": "192.0.3.1"
                    }
                ]
            } ]
        } ]
    }
}

Assuming there was no shared network with a name “floor13” and no subnets with IDs 100 and 101 previously configured, the command will be successful and will return the following response:

{
    "arguments": {
        "shared-networks": [ { "name": "floor13" } ]
    },
    "result": 0,
    "text": "A new IPv4 shared network 'floor13' added"
}

The network6-add command uses the same syntax for both the query and the response. However, there are some parameters that are IPv4-only (e.g. match-client-id) and some that are IPv6-only (e.g. interface-id). The same applies to subnets within the network.

The network4-del, network6-del Commands

These commands are used to delete existing shared networks. Both commands take exactly one parameter, name, that specifies the name of the network to be removed. An example invocation of the network4-del command looks as follows:

{
    "command": "network4-del",
    "arguments": {
        "name": "floor13"
    }
}

Assuming there was such a network configured, the response will look similar to the following:

{
    "arguments": {
        "shared-networks": [
            {
                "name": "floor13"
            }
        ]
    },
    "result": 0,
    "text": "IPv4 shared network 'floor13' deleted"
}

The network6-del command uses exactly the same syntax for both the command and the response.

If there are any subnets belonging to the shared network being deleted, they will be demoted to a plain subnet. There is an optional parameter called subnets-action that, if specified, takes one of two possible values: keep (which is the default) and delete. It controls whether the subnets are demoted to plain subnets or removed. An example usage in the network6-del command that deletes the shared network and all subnets in it could look as follows:

{
    "command": "network4-del",
    "arguments": {
        "name": "floor13",
        "subnets-action": "delete"
    }
}

Alternatively, to completely remove the subnets, it is possible to use the subnet4-del or subnet6-del commands.

The network4-subnet-add, network6-subnet-add Commands

These commands are used to add existing subnets to existing shared networks. There are several ways to add a new shared network. The system administrator can add the whole shared network at once, either by editing a configuration file or by calling the network4-add or network6-add command with the desired subnets in it. This approach works well for completely new shared subnets. However, there may be cases when an existing subnet is running out of addresses and needs to be extended with additional address space; in other words, another subnet needs to be added on top of it. For this scenario, a system administrator can use network4-add or network6-add, and then add an existing subnet to this newly created shared network using network4-subnet-add or network6-subnet-add.

The network4-subnet-add and network6-subnet-add commands take two parameters: id, which is an integer and specifies the ID of an existing subnet to be added to a shared network; and name, which specifies the name of the shared network to which the subnet will be added. The subnet must not belong to any existing network; to reassign a subnet from one shared network to another, use the network4-subnet-del or network6-subnet-del commands first.

An example invocation of the network4-subnet-add command looks as follows:

{
    "command": "network4-subnet-add",
    "arguments": {
        "name": "floor13",
        "id": 5
    }
}

Assuming there is a network named “floor13”, and there is a subnet with subnet-id 5 that is not a part of the existing network, the command will return a response similar to the following:

{
    "result": 0,
    "text": "IPv4 subnet 10.0.0.0/8 (id 5) is now part of shared network 'floor13'"
}

The network6-subnet-add command uses exactly the same syntax for both the command and the response.

Note

As opposed to parameter inheritance during the processing of a full new configuration or when adding a new shared network with new subnets, this command does not fully handle parameter inheritance. Any missing parameters will be filled with default values, rather than inherited from the global scope or from the shared network.

The network4-subnet-del, network6-subnet-del Commands

These commands are used to remove a subnet that is part of an existing shared network and demote it to a plain, stand-alone subnet. To remove a subnet completely, use the subnet4-del or subnet6-del commands instead. The network4-subnet-del and network6-subnet-del commands take two parameters: id, which is an integer and specifies the ID of an existing subnet to be removed from a shared network; and name, which specifies the name of the shared network from which the subnet will be removed.

An example invocation of the network4-subnet-del command looks as follows:

{
   "command": "network4-subnet-del",
   "arguments": {
       "name": "floor13",
       "id": 5
   }
}

Assuming there was a subnet with subnet-id 5, that was part of a shared network named “floor13”, the response would look similar to the following:

{
    "result": 0,
    "text": "IPv4 subnet 10.0.0.0/8 (id 5) is now removed from shared network 'floor13'"
}

The network6-subnet-del command uses exactly the same syntax for both the command and the response.

BOOTP Support

This hook library adds support for BOOTP with vendor-information extensions (RFC 1497). Received BOOTP requests are recognized, translated into DHCPREQUEST packets by adding a dhcp-message-type option, and put into the “BOOTP” client class. Members of this class get infinite lifetime leases but the class can also be used to guard a pool of addresses.

The DHCP-specific options, such as dhcp-message-type, are removed from the server’s responses; responses shorter than the BOOTP minimum size of 300 octets are padded to this size.

This open source library is loaded similarly to other hook libraries by the kea-dhcp4 process, and it takes no parameters.

"Dhcp4": {
    "hooks-libraries": [
        {   "library": "/usr/local/lib/libdhcp_bootp.so" },
        ...
    ]
}

Note

This library can only be loaded by the kea-dhcp4 process, as there is no BOOTP protocol for IPv6.

Note

A host reservation for a BOOTP client should use the hardware address as the identifier (the client-id option is a DHCP-specific option).

Incoming BOOTP packets are added to the BOOTP class, allowing administrators to segregate BOOTP clients into separate pools. For example:

"Dhcp4": {
    "client-classes": [
        {
            // The DHCP class is the complement of the BOOTP class
            "name": "DHCP",
            "test": "not member('BOOTP')"
        }
    ],
    "subnet4": [
        {
            "subnet": "192.0.2.0/24",
            "pools": [
            {
                // BOOTP clients will be handled here
                "pool": "192.0.2.200 - 192.0.2.254",
                "client-class": "BOOTP"
            },
            {
                // Regular DHCP clients will be handled here
                "pool": "192.0.2.1 - 192.0.2.199",
                "client-class": "DHCP"
            }],
            ...
        },
        ...
    ],
    ...
}

BOOTP Hooks Limitations

Currently the BOOTP library has the following limitation:

• Basic BOOTP, as defined in RFC 951, is not supported. Kea only supports BOOTP with vendor-information extensions.

class_cmds: Class Commands

This section describes the Class Commands hooks library, which exposes several control commands for manipulating client classes (part of the Kea DHCP servers’ configurations) without the need to restart those servers. Using these commands it is possible to add, update, delete, and list the client classes configured for a given server.

Note

This library may only be loaded by the kea-dhcp4 or kea-dhcp6 process.

The Class Commands hooks library is currently available only to ISC customers with a paid support contract.

The class-add Command

The class-add command adds a new client class to the DHCP server configuration. This class is appended at the end of the list of classes used by the server and may depend on any of the already-configured client classes.

The following example demonstrates how to add a new client class to the DHCPv4 server configuration:

{
    "command": "class-add",
    "arguments": {
        "client-classes": [
            {
                "name": "ipxe_efi_x64",
                "test": "option[93].hex == 0x0009",
                "next-server": "192.0.2.254",
                "server-hostname": "hal9000",
                "boot-file-name": "/dev/null"
            }
        ]
    }
}

Note that the client-classes parameter is a JSON list, but it allows only a single client class to be present.

Here is the response to the class-add command in our example:

{
    "result": 0,
    "text": "Class 'ipxe_efi_x64' added."
}

The class-update Command

The class-update command updates an existing client class in the DHCP server configuration. If the client class with the given name does not exist, the server returns the result code of 3, which means that the server configuration is not modified and the client class does not exist. The class-add command must be used instead to create the new client class.

The class-update command has the same argument structure as the class-add command:

{
    "command": "class-update",
    "arguments": {
        "client-classes": [
            {
                "name": "ipxe_efi_x64",
                "test": "option[93].hex == 0x0017",
                "next-server": "0.0.0.0",
                "server-hostname": "xfce",
                "boot-file-name": "/dev/null"
            }
        ]
    }
}

Here is the response for our example:

{
    "result": 0,
    "text": "Class 'ipxe_efi_x64' updated."
}

Any parameter of the client class can be modified with this command, except name. There is currently no way to rename the class, because the class name is used as a key for searching the class to be updated. To achieve a similar effect to renaming the class, an existing class can be removed with the class-del command and then added again with a different name using class-add. Note, however, that the class with the new name will be added at the end of the list of configured classes.

The class-del Command

The class-del command is used to remove a particular class from the server configuration. The class to be removed is identified by name. The class is not removed if there are other classes depending on it; to remove such a class, the dependent classes must be removed first.

The following is a sample command removing the ipxe_efi_x64 class:

{
    "command": "class-del",
    "arguments": {
        {
            "name": "ipxe_efi_x64"
        }
    }
}

Here is the response to the class-del command in our example, when the specified client class has been found:

{
    "result": 0,
    "text": "Class 'ipxe_efi_x64' deleted."
}

If the class does not exist, the result of 3 is returned.

The class-list Command

class-list is used to retrieve a list of all client classes. This command includes no arguments:

{
    "command": "class-list"
}

Here is the response of the server in our example, including the list of client classes:

{
    "result": 0,
    "text": "2 classes found",
    "arguments": {
        "client-classes": [
            {
                "name": "ipxe_efi_x64"
            },
            {
                "name": "pxeclient"
            }
        ]
    }
}

Note that the returned list does not contain full class definitions, but merely class names. To retrieve full class information, the class-get command should be used.

The class-get Command

class-get is used to retrieve detailed information about a specified class. The command structure is very simple:

{
    "command": "class-get",
    "arguments": {
        "name": "pxeclient"
    }
}

If the class with the specified name does not exist, the status code of 3 is returned. If the specified client class exists, the class details are returned in the following format:

{
    "result": 0,
    "text": "Class 'pxeclient' definition returned",
    "arguments": {
        "client-classes": [
            {
                "name": "pxeclient",
                "only-if-required": true,
                "test": "option[vendor-class-identifier].text == 'PXEClient'",
                "option-def": [
                    {
                        "name": "configfile",
                        "code": 209,
                        "type": "string"
                    }
                ],
                "option-data": [ ],
                "next-server": "0.0.0.0",
                "server-hostname": "xfce",
                "boot-file-name": "/dev/null"
            }
        ]
    }
}

Note that the example above is DHCPv4-specific; the last three parameters are only returned by the DHCPv4 server and are never returned by the DHCPv6 server. Also, some of the parameters provided in this example may not be returned if they are not specified for the class. Specifically, only-if-required, test, and option-def are not returned if they are not specified for the class.

cb_cmds: Configuration Backend Commands

This section describes the cb_cmds hooks library, used to manage Kea servers’ configurations in the Configuration Backends. This library must be used in conjunction with the available CB hooks libraries implementing the common APIs to create, read, update, and delete (CRUD) the configuration information in the respective databases. For example: the mysql_cb hooks library implements this API for MySQL while the pgsql_cg hooks library implements this API for PostgreSQL. To manage the configuration information in a MySQL database, both the mysql_cb and cb_cmds libraries must be loaded by the server used for the configuration management. To manage the configuration information in a PostgreSQL database, both the pgsql_cb and cb_cmds libraries must be loaded by the server used for the configuration management.

The cb_cmds library is only available to ISC customers with a paid support contract.

Note

This library may only be loaded by the kea-dhcp4 or kea-dhcp6 process.

Note

Please read about CB Capabilities and Limitations before using the commands described in this section.

Commands Structure

There are 5 types of commands supported by this library:

• del - delete the selected object from the database, e.g. remote-global-parameter4-del.

• get - fetch the selected object from the database, e.g. remote-subnet4-get.

• get-all - fetch all objects of the particular type from the database, e.g. remote-option-def4-get-all.

• list - list all objects of the particular type in the database, e.g. remote-network4-list; this class of commands returns brief information about each object compared to the output of get-all.

• set - creates or replaces an object of the given type in the database, e.g. remote-option4-global-set.

All types of commands accept an optional remote map which selects the database instance to which the command refers. For example:

{
    "command": "remote-subnet4-list",
    "arguments": {
        "remote": {
            "type": "mysql",
            "host": "192.0.2.33",
            "port": 3302
        }
    }
}

The cb_cmds library is only available to ISC customers with a paid support contract.

Note

This library may only be loaded by the kea-dhcp4 or kea-dhcp6 process.

Note

Please read about CB Capabilities and Limitations before using the commands described in this section.

Commands Structure

There are 5 types of commands supported by this library:

• del - delete the selected object from the database, e.g. remote-global-parameter4-del.

• get - fetch the selected object from the database, e.g. remote-subnet4-get.

• get-all - fetch all objects of the particular type from the database, e.g. remote-option-def4-get-all.

• list - list all objects of the particular type in the database, e.g. remote-network4-list; this class of commands returns brief information about each object compared to the output of get-all.

• set - creates or replaces an object of the given type in the database, e.g. remote-option4-global-set.

All types of commands accept an optional remote map which selects the database instance to which the command refers. For example:

{
    "command": "remote-subnet4-list",
    "arguments": {
        "remote": {
            "type": "mysql",
            "host": "192.0.2.33",
            "port": 3302
        }
    }
}

selects the MySQL database, running on host 192.0.2.33 and port 3302, to fetch the list of subnets from. All parameters in the remote argument are optional. The port parameter can be only specified in conjunction with the host. If no options in the remote parameter are to be specified, the parameter should be omitted. In this case, the server will use the first backend listed in the config-control map within the configuration of the server receiving the command.

Note

In the present Kea release, it is possible to configure the Kea server to use only one configuration backend. Strictly speaking, it is possible to point the Kea server to at most one database (either MySQL or PostgreSQL) using the config-control parameter. That’s why the remote parameter may be omitted in the commands and the cb_cmds hooks library will use the sole backend by default. The example command below most often show a value of “mysql” for the type parameter. It should be assumed that a value would be “postgresql” for installations using a PostgreSQL database.

Control Commands for DHCP Servers

This section describes and gives some examples of the control commands implemented by the cb_cmds hooks library, to manage the configuration information of the DHCPv4 and DHCPv6 servers. Many of the commands are almost identical between DHCPv4 and DHCPv6; they only differ by the command name. Other commands differ slightly by the structure of the inserted data; for example, the structure of the IPv4 subnet information is different than that of the IPv6 subnet. Nevertheless, they still share the structure of their command arguments and thus it makes sense to describe them together.

In the following sections, various commands are described and some usage examples are provided. In the sections jointly describing the DHCPv4 and DHCPv6 variants of the particular command, we sometimes use the following notation: the remote-subnet[46]-set is the wildcard name for the two commands: remote-subnet4-set and remote-subnet6-set.

In addition, whenever the text in the subsequent sections refers to a DHCP command or DHCP parameter, it refers to both DHCPv4 and DHCPv6 variants. The text specific to the particular server type refers to them as: DHCPv4 command, DHCPv4 parameter, DHCPv6 command, DHCPv6 parameter, etc.

Metadata

The typical response to the get or list command includes a list of returned objects (e.g. subnets), and each such object contains the metadata map with some database-specific information describing this object. In other words, the metadata contains any information about the fetched object which may be useful for an administrator but which is not part of the object specification from the DHCP server standpoint. In the present Kea release, the metadata is limited to the server-tag. It describes the association of the object with a particular server or all servers.

The following is the example response to the remote-network4-list command, which includes the metadata:

{
    "result": 0,
    "text": "1 IPv4 shared network(s) found.",
    "arguments": {
        "shared-networks": [
            {
                "name": "level3",
                "metadata": {
                    "server-tags": [ "all" ]
                }
            }
        ],
        "count": 1
    }
}

Client implementations must not assume that the metadata contains only the server-tags parameter. In future releases, this map will be extended with additional information, e.g. object modification time, log message created during the last modification, etc.

remote-server4-del, remote-server6-del commands

This command is used to delete the information about a selected DHCP server from the configuration database. The server is identified by a unique case insensitive server tag. For example:

{
    "command": "remote-server4-del",
    "arguments": {
        "servers": [
            {
                "server-tag": "server1"
            }
        ],
        "remote": {
            "type": "postgresql"
        }
    }
}

As a result of this command, the user defined server called server1 is removed from the database. All associations of the configuration information with this server are automatically removed from the database. The non-shareable configuration information, such as: global parameters, option definitions and global options associated with the server are removed from the database. The shareable configuration information, i.e. the configuration elements which may be associated with more than one server, is preserved. In particular, the subnets and shared networks associated with the deleted servers are preserved. If any of the shareable configuration elements was associated only with the deleted server, this object becomes unassigned (orphaned). For example: if a subnet has been created and associated with the server1 using the remote-subnet4-set command and the server1 is subsequently deleted, the subnet remains in the database but none of the servers can use this subnet. The subnet can be updated using the remote-subnet4-set and associated with some other server or with all servers using the special server tag “all”. Such subnet can be also deleted from the database using the remote-subnet4-del-by-id or remote-subnet4-del-by-prefix, if it is no longer needed.

The following is the successful response to the remote-server4-del command:

{
    "result": 0,
    "text": "1 DHCPv4 server(s) deleted."
    "arguments": {
        "count": 1
    }
}

Note

The remote-server4-del and remote-server6-del commands must be used with care, because an accidental deletion of the server causes some parts of the existing configurations to be lost permanently from the database. This operation is not reversible. Re-creation of the accidentally deleted server does not revert the lost configuration for that server and such configuration must be re-created manually by the user.

remote-server4-get, remote-server6-get commands

This command is used to fetch the information about the selected DHCP server from the configuration database. For example:

{
    "command": "remote-server6-get"
    "arguments": {
        "servers": [
            {
                "server-tag": "server1"
            }
        ],
        "remote": {
            "type": "mysql"
        }
    }
}

This command fetches the information about the DHCPv6 server identified by the server tag server1. The server tag is case insensitive. A successful response returns basic information about the server, such as server tag and the user’s description of the server:

{
    "result": 0,
    "text": "DHCP server server1 found.",
    "arguments": {
        "servers": [
            {
                "server-tag": "server1",
                "description": "A DHCPv6 server located on the first floor."
            }
        ],
        "count": 1
    }
}

remote-server4-get-all, remote-server6-get-all commands

This command is used to fetch all user defined DHCPv4 or DHCPv6 servers from the database. The command structure is very simple:

{
    "command": "remote-server4-get-all"
    "arguments": {
        "remote": {
            "type": "mysql"
        }
    }
}

The response includes basic information about each server, such as its server tag and description:

{
    "result": 0,
    "text": "DHCPv4 servers found.",
    "arguments": {
        "servers": [
            {
                "server-tag": "server1",
                "description": "A DHCP server located on the first floor."
            },
            {
                "server-tag": "server2",
                "description": "An old DHCP server to be soon replaced."
            }
        ],
       "count": 2
    }
}

remote-server4-set, remote-server6-set commands

This command is used to create or replace an information about a DHCP server in the database. The information about the server must be created when there is a need to differentiate the configurations used by various Kea instances connecting to the same database. Various configuration elements, e.g. global parameters, subnets etc. may be explicitly associated with the selected servers (using server tags as identifiers), allowing only these servers to use the respective configuration elements. Using the particular server tag to make such associations is only possible when the server information has been stored in the database via the remote-server4-set or remote-server6-set commands. The following command creates a new (or updates an existing) DHCPv6 server in the database:

{
    "command": "remote-server6-set"
    "arguments": {
        "servers": [
            {
                "server-tag": "server1",
                "description": "A DHCP server on the ground floor."
            }
        ],
        "remote": {
            "type": "mysql"
        }
    }
}

The server tag must be unique across all servers in the database. When the server information under the given server tag already exists, it is replaced with the new information. The specified server tag is case-insensitive, and the maximum length of the server tag is 256 characters. The following keywords are reserved and must not be used as server tags: “all” and “any”.

The following is the example response to the above command:

{
    "result": 0,
    "text": "DHCPv6 server successfully set.",
    "arguments": {
        "servers": [
            {
                "server-tag": "server1",
                "description": "A DHCP server on the ground floor."
            }
        ]
    }
}

The remote-global-parameter4-del, remote-global-parameter6-del Commands

These commands are used to delete a global DHCP parameter from the configuration database. When the parameter is deleted from the database, the server will use the value specified in the configuration file for this parameter, or a default value if the parameter is not specified in the configuration file.

The following command attempts to delete the DHCPv4 renew-timer parameter common for all servers from the database:

{
    "command": "remote-global-parameter4-del",
    "arguments": {
        "parameters": [ "renew-timer" ],
        "remote": {
            "type": "mysql"
         },
        "server-tags": [ "all" ]
    }
}

If the server specific parameter is to be deleted, the server-tags list must contain the tag of the appropriate server. There must be exactly one server tag specified in this list.

The remote-global-parameter4-get, remote-global-parameter6-get Commands

These commands are used to fetch a scalar global DHCP parameter from the configuration database.

The following command attempts to fetch the boot-file-name parameter for the “server1”:

{
    "command": "remote-global-parameter4-get",
    "arguments": {
        "parameters": [ "boot-file-name" ],
         "remote": {
             "type": "mysql"
         },
         "server-tags": [ "server1" ]
    }
}

The returned value has one of the four scalar types: string, integer, real, or boolean. Non-scalar global configuration parameters, such as map or list, are not returned by this command.

In the case of the example above, the string value is returned, e.g.:

{
    "result": 0,
    "text": "1 DHCPv4 global parameter found.",
    "arguments": {
        "parameters": {
            "boot-file-name": "/dev/null",
            "metadata": {
                "server-tags": [ "all" ]
            }
        },
        "count": 1
    }
}

Note that the response above indicates that the returned parameter is associated with “all” servers rather than “server1” used in the command. This indicates that there is no server1 specific value in the database. Therefore, the value shared by all servers is returned. If there was the server1 specific value in the database this value would be returned instead.

The example response for the integer value is:

{
    "result": 0,
    "text": "1 DHCPv4 global parameter found.",
    "arguments": {
        "parameters": {
            "renew-timer": 2000,
            "metadata": {
                "server-tags": [ "server1" ]
            }
        },
        "count": 1
    }
}

The real value:

{
    "result": 0,
    "text": "1 DHCPv4 global parameter found.",
    "arguments": {
        "parameters": {
            "t1-percent": 0.85,
            "metadata": {
                "server-tags": [ "all" ]
            }
        },
        "count": 1
    }
}

Finally, the boolean value:

{
    "result": 0,
    "text": "1 DHCPv4 global parameter found.",
    "arguments": {
        "parameters": {
            "match-client-id": true,
            "metadata": {
                "server-tags": [ "server2" ]
            }
        },
        "count": 1
    }
}

The remote-global-parameter4-get-all, remote-global-parameter6-get-all Commands

These commands are used to fetch all global DHCP parameters from the database for the specified server. The following example demonstrates how to fetch all global parameters to be used by the server “server1”:

{
    "command": "remote-global-parameter4-get-all",
    "arguments": {
        "remote": {
            "type": "mysql"
        },
        "server-tags": [ "server1" ]
    }
}

The example response may look as follows:

{
    "result": 0,
    "text": "DHCPv4 global parameters found.",
    "arguments": {
        "parameters": [
            {
                "boot-file-name": "/dev/null",
                "metadata": {
                    "server-tags": [ "server1" ]
                }
            },
            {
                "match-client-id": true,
                "metadata": {
                    "server-tags": [ "all" ]
                }
            }
        ],
        "count": 2
    }
}

The example response contains two parameters, one string parameter and one boolean parameter. The metadata returned for each parameter indicates if this parameter is specific to the “server1” or all servers. Since the match-client-id value is associated with “all” servers it indicates that there is no server1 specific setting for this parameter. Each parameter always has exactly one server tag associated with it, because the global parameters are non-shareable configuration elements.

Note

If the server tag is set to “all” in the command, the response will contain only the global parameters associated with the logical server “all”. When the server tag points to the specific server (as in the example above), the returned list combines parameters associated with this server and all servers, but the former take precedence.

The remote-global-parameter4-set, remote-global-parameter6-set Commands

This command is used to create scalar global DHCP parameters in the database. If any of the parameters already exists, its value is replaced as a result of this command. It is possible to set multiple parameters within a single command, each having one of the four types: string, integer, real, or boolean. For example:

{
    "command": "remote-global-parameter4-set"
    "arguments": {
        "parameters": {
            "boot-file-name": "/dev/null",
            "renew-timer": 2000,
            "t1-percent": 0.85,
            "match-client-id": true
        },
        "remote": {
            "type": "mysql"
        },
        "server-tags": [ "server1" ]
    }
}

An error is returned if any of the parameters is not supported by the DHCP server or its type does not match. Care should be taken when multiple parameters are specified in a single command, because it is possible that only some of the parameters are stored successfully and some fail. If an error occurs when processing this command, it is recommended to use remote-global-parameter[46]-get-all to check which of the parameters have been stored/updated successfully and which have failed.

The server-tags list is mandatory and it must contain a single server tag or the keyword “all”. In the example above, all specified parameters are associated with the “server1” server.

The remote-network4-del, remote-network6-del Commands

These commands are used to delete an IPv4 or IPv6 shared network from the database. The optional parameter subnets-action determines whether the subnets belonging to the deleted shared network should also be deleted or preserved. The subnets-action parameter defaults to keep, which preserves the subnets. If it is set to delete, the subnets are deleted along with the shared network.

The following command:

{
    "command": "remote-network6-del",
    "arguments": {
        "shared-networks": [
            {
                "name": "level3"
            }
        ],
        "subnets-action": "keep",
        "remote": {
            "type": "mysql"
        }
    }
}

deletes the “level3” IPv6 shared network. The subnets are preserved, but they are disassociated from the deleted shared network and become global. This behavior corresponds to the behavior of the network[46]-del commands with respect to the subnets-action parameter.

Note that the server-tags parameter must not be used for this command.

The remote-network4-get, remote-network6-get Commands

These commands are used to retrieve information about an IPv4 or IPv6 shared network. The optional parameter subnets-include denotes whether the subnets belonging to the shared network should also be returned. This parameter defaults to no, in which case the subnets are not returned. If this parameter is set to full, the subnets are returned together with the shared network.

The following command fetches the “level3” IPv6 shared network along with the full information about the subnets belonging to it:

{
    "command": "remote-network6-get",
    "arguments": {
        "shared-networks": [
            {
                "name": "level3"
            }
        ],
        "subnets-include": "full",
        "remote": {
            "type": "mysql"
        }
    }
}

Note that the server-tags parameter must not be used for this command.

The remote-network4-list, remote-network6-list Commands

These commands are used to list all IPv4 or IPv6 shared networks for a server.

The following command retrieves all shared networks to be used by the “server1” and “server2”:

{
    "command": "remote-network4-list"
    "arguments": {
        "remote": {
            "type": "mysql"
        },
        "server-tags": [ "server1", "server2" ]
    }
}

The server-tags parameter is mandatory and it contains one or more server tags. It may contain the keyword “all” to fetch the shared networks associated with all servers. When the server-tags list contains the null value the returned response contains a list of unassigned shared networks, i.e. the networks which are associated with no servers. For example:

{
    "command": "remote-network4-list"
    "arguments": {
        "remote": {
            "type": "mysql"
        },
        "server-tags": [ null ]
    }
}

The example response to this command when non-null server tags are specified looks similar to this:

{
    "result": 0,
    "text": "3 IPv4 shared network(s) found.",
    "arguments": {
        "shared-networks": [
            {
                "name": "ground floor",
                "metadata": {
                    "server-tags": [ "all" ]
                }
            },
            {
                "name": "floor2",
                "metadata": {
                    "server-tags": [ "server1" ]
                }
            },
            {
                "name": "floor3",
                "metadata": {
                    "server-tags": [ "server2" ]
                }
            }
        ],
        "count": 3
    }
}

The returned information about each shared network merely contains the shared network name and the metadata. In order to fetch the detailed information about the selected shared network, use the remote-network[46]-get command.

The example response above contains three shared networks. One of the shared networks is associated with all servers, so it is included in the list of shared networks to be used by “server1” and “server2”. The remaining two shared networks are returned because one of them is associated with the “server1” and another one is associated with the “server2”.

When listing unassigned shared networks, the response will look similar to this:

{
    "result": 0,
    "text": "1 IPv4 shared network(s) found.",
    "arguments": {
        "shared-networks": [
            {
                "name": "fancy",
                "metadata": {
                    "server-tags": [ null ]
                }
            }
        ],
        "count": 1
    }
}

The null value in the metadata indicates that the returned shared network is unassigned.

The remote-network4-set, remote-network6-set Commands

These commands create a new or replace an existing IPv4 or IPv6 shared network in the database. The structure of the shared network information is the same as in the Kea configuration file (see Shared Networks in DHCPv4 and Shared Networks in DHCPv6 for details), except that specifying subnets along with the shared network information is not allowed. Including the subnet4 or subnet6 parameter within the shared network information will result in an error.

These commands are intended to be used for managing the shared network-specific information and DHCP options. In order to associate and disassociate the subnets with the shared networks, the remote-subnet[46]-set commands should be used.

The following command adds the IPv6 shared network “level3” to the database:

{
    "command": "remote-network6-set",
    "arguments": {
        "shared-networks": [
            {
                "name": "level3",
                "interface": "eth0",
                "option-data": [ {
                    "name": "sntp-servers",
                    "data": "2001:db8:1::1"
                } ],
            }
        ],
        "remote": {
            "type": "mysql"
        },
        "server-tags": [ "all" ]
    }
}

This command includes the interface parameter, which sets the shared network-level interface name. Any remaining shared network-level parameters, which are not specified with the command, will be marked as “unspecified” in the database. The DHCP server will use the global values for unspecified parameters or, if the global values are not specified, the default values will be used.

The server-tags list is mandatory for this command and it must include one or more server tags. As a result the shared network is associated with all listed servers. The shared network may be associated with all servers connecting to the database when the keyword “all” is included.

Note

As with other “set” commands, this command replaces all the information about the given shared network in the database, if the shared network already exists. Therefore, when sending this command, make sure to always include all parameters that must be specified for the updated shared-network instance. Any unspecified parameter will be marked unspecified in the database, even if its value was present prior to sending the command.

The remote-option-def4-del, remote-option-def6-del Commands

These commands are used to delete a DHCP option definition from the database. The option definition is identified by an option code and option space. For example:

{
    "command": "remote-option-def6-del",
    "arguments": {
        "option-defs": [
            {
                "code": 1,
                "space": "isc"
            }
        ],
        "remote": {
            "type": "mysql"
        },
        "server-tags": [ "server1" ]
    }
}

deletes the definition of the option associated with the “server1”, having the code of 1 and belonging to the option space “isc”. The default option spaces are “dhcp4” and “dhcp6” for the DHCPv4 and DHCPv6 top level options respectively. If there is no such option explicitly associated with the server1, no option is deleted. In order to delete an option belonging to “all” servers, the keyword “all” must be used as the server tag. The server-tags list must contain exactly one tag. It must not include the null value.

The remote-option-def4-get, remote-option-def6-get Commands

These commands are used to fetch a specified DHCP option definition from the database. The option definition is identified by the option code and option space. The default option spaces are “dhcp4” and “dhcp6” for the DHCPv4 and DHCPv6 top-level options, respectively.

The following command retrieves a DHCPv4 option definition associated with all servers, having the code of 1 and belonging to the option space “isc”:

{
    "command": "remote-option-def4-get"
    "arguments": {
        "option-defs": [
            {
                "code": 1,
                "space": "isc"
            }
        ],
        "remote": {
            "type": "mysql"
        },
        "server-tags": [ "all" ]
    }
}

The server-tags list must include exactly one server tag or the keyword “all”. It must not contain the null value.

The remote-option-def4-get-all, remote-option-def6-get-all Commands

These commands are used to fetch all DHCP option definitions from the database for the particular server or all servers. For example:

{
    "command": "remote-option-def6-get-all"
    "arguments": {
        "remote": {
            "type": "mysql"
        },
        "server-tags": [ "all" ]
    }
}

This command attempts to fetch all DHCPv6 option definitions associated with “all” servers. The server-tags list is mandatory for this command and it must include exactly one server tag or the keyword “all”. It must not include the null value.</para>

The following is the example response to this command:

{
    "result": 0,
    "text": "1 DHCPv6 option definition(s) found.",
    "arguments": {
        "option-defs": [
            {
                "name": "bar",
                "code": 1012,
                "space": "dhcp6",
                "type": "record",
                "array": true,
                "record-types": "ipv6-address, uint16",
                "encapsulate": "",
                "metadata": {
                    "server-tags": [ "all" ]
                }
            }
        ],
        "count": 1
    }
}

The response contains an option definition associated with all servers as indicated by the metadata.

The remote-option-def4-set, remote-option-def6-set Commands

These commands create a new DHCP option definition or replace an existing option definition in the database. The structure of the option definition information is the same as in the Kea configuration file (see Custom DHCPv4 Options and Custom DHCPv6 Options). The following command creates the DHCPv4 option definition at the top-level “dhcp4” option space and associates it with the “server1”:

{
    "command": "remote-option-def4-set",
    "arguments": {
        "option-defs": [
            {
                "name": "foo",
                "code": 222,
                "type": "uint32",
                "array": false,
                "record-types": "",
                "space": "dhcp4",
                "encapsulate": ""
            }
        ],
        "remote": {
            "type": "mysql"
        },
        "server-tags": [ "server1" ]
    }
}

The server-tags list must include exactly one server tag or the keyword “all”. It must not contain the null value.

The remote-option4-global-del, remote-option6-global-del Commands

These commands are used to delete a global DHCP option from the database. The option is identified by an option code and option space. For example:

{
    "command": "remote-option4-global-del",
    "arguments": {
        "options": [
            {
                "code": 5
                "space": "dhcp4"
            }
        ],
        "remote": {
            "type": "mysql"
        },
        "server-tags": [ "server1" ]
    }
}

The “dhcp4” is the top-level option space where the standard DHCPv4 options belong. The server-tags is mandatory and it must include a single option tag or the keyword “all”. If the explicit server tag is specified then this command attempts to delete a global option associated with this server. If there is no such option associated with the given server, no option is deleted. In order to delete the option associated with all servers, the keyword “all” must be specified.

The remote-option4-global-get, remote-option6-global-get Commands

These commands are used to fetch a global DHCP option from the database. The option is identified by the code and option space. The top-level option spaces where DHCP standard options belong are called “dhcp4” and “dhcp6” for the DHCPv4 and DHCPv6 servers, respectively.

The following command retrieves the IPv6 “DNS Servers” (code 23) option associated with all servers:

{
    "command": "remote-option6-global-get",
    "arguments": {
        "options": [
            {
                "code": 23,
                "space": "dhcp6"
            }
        ],
        "remote": {
            "type": "mysql"
        },
        "server-tags": [ "all" ]
    }
}

The server-tags is mandatory and it must include exactly one server tag or the keyword “all”. It must not contain the null value.

The remote-option4-global-get-all, remote-option6-global-get-all Commands

These commands are used to fetch all global DHCP options from the configuration database for the particular server or for all servers. The following command fetches all global DHCPv4 options for the “server1”:

{
    "command": "remote-option6-global-get-all",
    "arguments": {
        "remote": {
            "type": "mysql"
        },
        "server-tags": [ "server1" ]
    }
}

The server-tags list is mandatory for this command and it must contain exactly one server tag or a keyword “all”. It must not contain the null value. The following is the example response to this command with a single option being associated with the “server1” returned:

{
    "result": 0,
    "text": "DHCPv4 options found.",
    "arguments": {
        "options": [
            {
                "name": "domain-name-servers",
                "code": 6,
                "space": "dhcp4",
                "csv-format": false,
                "data": "192.0.2.3",
                "metadata": {
                    "server-tags": [ "server1" ]
                }
            }
        ],
        "count": 1
    }
}

The remote-option4-global-set, remote-option6-global-set Commands

These commands create a new global DHCP option or replace an existing option in the database. The structure of the option information is the same as in the Kea configuration file (see Standard DHCPv4 Options and Standard DHCPv6 Options). For example:

{
    "command": "remote-option6-global-set",
    "arguments": {
        "options": [
            {
                "name": "dns-servers",
                "data": "2001:db8:1::1"
            }
        ],
        "remote": {
            "type": "mysql"
        },
        "server-tags": [ "server1" ]
    }
}

The server-tags list is mandatory for this command and it must include exactly one server tag or the keyword “all”. It must not include the null value. The command above associates the option with the “server1” server.

Note that specifying an option name instead of the option code only works reliably for the standard DHCP options. When specifying a value for the user-defined DHCP option, the option code should be specified instead of the name. For example:

{
    "command": "remote-option6-global-set",
    "arguments": {
        "options": [
            {
                "code": 1,
                "space": "isc",
                "data": "2001:db8:1::1"
            }
        ],
        "server-tags": [ "server1" ]
    }
}

The remote-option4-network-del, remote-option6-network-del Commands

These commands are used to delete a shared network specific DHCP option from the database. The option is identified by an option code and option space and these two parameters are passed within the options list. Another list, shared-networks, contains a map with the name of the shared network from which the option is to be deleted. If the option is not explicitly specified for this shared network, no option is deleted. In particular, the given option may be present for a subnet belonging to the shared network. Such an option instance is not affected by this command as this command merely deletes the shared network level option. In order to delete a subnet level option the remote-option[46]-subnet-del command must be used instead.

The following command attempts to delete an option having the option code 5 in the top-level option space from the shared network “fancy”.

{
    "command": "remote-option4-network-del",
    "arguments": {
        "shared-networks": [
            {
                "name": "fancy"
            }
        ],
        "options": [
            {
                "code": 5,
                "space": "dhcp4"
            }
        ],
        "remote": {
            "type": "mysql"
        }
    }
}

The “dhcp4” is the top-level option space where the standard DHCPv4 options belong. The server-tags parameter must not be specified for this command.

The remote-option4-network-set, remote-option6-network-set Commands

These commands create a new shared network specific DHCP option or replace an existing option in the database. The structure of the option information is the same as in the Kea configuration file (see Standard DHCPv4 Options and Standard DHCPv6 Options). The option information is carried in the options list. Another list, shared-networks, contains a map with the name of the shared network for which the option is to be set. If such an option already exists for the shared network, it is replaced with the new instance.

{
    "command": "remote-option6-network-set",
    "arguments": {
        "shared-networks": [
            {
                "name": "fancy"
            }
        ],
        "options": [
            {
                "name": "dns-servers",
                "data": "2001:db8:1::1"
            }
        ],
        "remote": {
            "type": "mysql"
        }
    }
}

The sever-tags parameter must not be specified for this command.

Specifying an option name instead of the option code only works reliably for the standard DHCP options. When specifying a value for the user-defined DHCP option, the option code should be specified instead of the name.

The remote-option6-pd-pool-del Command

This command is used to delete a prefix delegation pool specific DHCPv6 option from the database. The option is identified by an option code and option space and these two parameters are passed within the options list. Another list, pd-pools, contains a map with the prefix delegation pool prefix and length identifying the pool. If the option is not explicitly specified for this pool, no option is deleted. In particular, the given option may exist for a subnet containing the specified pool. Such an option instance is not affected by this command as this command merely deletes a prefix delegation pool level option. In order to delete a subnet level option the remote-option6-subnet-del command must be used instead.

{
    "command": "remote-option6-pd-pool-del",
    "arguments": {
        "pd-pools": [
            {
                "prefix": "3000::",
                "prefix-len": 64
            }
        ],
        "options": [
            {
                "code": 23,
                "space": "dhcp6"
            }
        ],
        "remote": {
            "type": "mysql"
        }
    }
}

The “dhcp6” is the top-level option space where the standard DHCPv6 options belong. The server-tags parameter must not be specified for this command.

The remote-option6-pd-pool-set Command

This command creates a new prefix delegation pool-specific DHCPv6 option or replaces an existing option in the database. The structure of the option information is the same as in the Kea configuration file (see Standard DHCPv4 Options and Standard DHCPv6 Options). The option information is carried in the options list. Another list, pd-pools, contains a map with the prefix delegation pool prefix and the prefix length identifying the pool. If such an option already exists for the prefix delegation pool, it is replaced with the new instance.

For example:

{
    "command": "remote-option6-pd-pool-set",
    "arguments": {
        "pd-pools": [
            {
                "prefix": "3001:1::",
                "length": 64
            }
        ],
        "options": [
            {
                "name": "dns-servers",
                "data": "2001:db8:1::1"
            }
        ],
        "remote": {
            "type": "mysql"
        }
    }
}

The sever-tags parameter must not be specified for this command.

Specifying an option name instead of the option code only works reliably for the standard DHCP options. When specifying a value for the user-defined DHCP option, the option code should be specified instead of the name.

The remote-option4-pool-del, remote-option6-pool-del Commands

These commands are used to delete an address pool specific DHCP option from the database. The option is identified by an option code and option space and these two parameters are passed within the options list. Another list, pools, contains a map with the IP address range or prefix identifying the pool. If the option is not explicitly specified for this pool, no option is deleted. In particular, the given option may exist for a subnet containing the specified pool. Such option instance is not affected by this command as this command merely deletes a pool level option. In order to delete subnet level option the remote-option[46]-subnet-del command must be used instead.

The following command attempts to delete an option having the option code 5 in the top-level option space from an IPv4 address pool:

{
    "command": "remote-option4-pool-del",
    "arguments": {
        "pools": [
            {
                "pool": "192.0.2.10 - 192.0.2.100"
            }
        ],
        "options": [
            {
                "code": 5,
                "space": "dhcp4"
            }
        ],
        "remote": {
            "type": "mysql"
        }
    }
}

The “dhcp4” is the top-level option space where the standard DHCPv4 options belong. The server-tags parameter must not be specified for this command.

The remote-option4-pool-set, remote-option6-pool-set Commands

These commands create a new address pool specific DHCP option or replace an existing option in the database. The structure of the option information is the same as in the Kea configuration file (see Standard DHCPv4 Options and Standard DHCPv6 Options). The option information is carried in the options list. Another list, pools, contains a map with the IP address range or prefix identifying the pool. If such an option already exists for the pool, it is replaced with the new instance.

For example:

{
    "command": "remote-option4-pool-set",
    "arguments": {
        "pools": [
            {
                "pool": "192.0.2.10 - 192.0.2.100"
            }
        ],
        "options": [
            {
                "name": "domain-name-servers",
                "data": "10.0.0.1"
            }
        ],
        "remote": {
            "type": "mysql"
        }
    }
}

The sever-tags parameter must not be specified for this command.

Specifying an option name instead of the option code only works reliably for the standard DHCP options. When specifying a value for the user-defined DHCP option, the option code should be specified instead of the name.

The remote-option4-subnet-del, remote-option6-subnet-del Commands

These commands are used to delete a subnet specific DHCP option from the database. The option is identified by an option code and option space and these two parameters are passed within the options list. Another list, subnets, contains a map with the identifier of the subnet from which the option is to be deleted. If the option is not explicitly specified for this subnet, no option is deleted.

The following command attempts to delete an option having the option code 5 in the top-level option space from the subnet having an identifier of 123.

{
    "command": "remote-option4-subnet-del",
    "arguments": {
        "subnets": [
            {
                "id": 123
            }
        ],
        "options": [
            {
                "code": 5,
                "space": "dhcp4"
            }
        ],
        "remote": {
            "type": "mysql"
        }
    }
}

The “dhcp4” is the top-level option space where the standard DHCPv4 options belong. The server-tags parameter must not be specified for this command.

The remote-option4-subnet-set, remote-option6-subnet-set Commands

These commands create a new subnet specific DHCP option or replace an existing option in the database. The structure of the option information is the same as in the Kea configuration file (see Standard DHCPv4 Options and Standard DHCPv6 Options). The option information is carried in the options list. Another list, subnets, contains a map with the identifier of the subnet for which the option is to be set. If such an option already exists for the subnet, it is replaced with the new instance.

{
    "command": "remote-option6-subnet-set",
    "arguments": {
        "subnets": [
            {
                "id": 123
            }
        ],
        "options": [
            {
                "name": "dns-servers",
                "data": "2001:db8:1::1"
            }
        ],
        "remote": {
            "type": "mysql"
        }
    }
}

The sever-tags parameter must not be specified for this command.

Specifying an option name instead of the option code only works reliably for the standard DHCP options. When specifying a value for the user-defined DHCP option, the option code should be specified instead of the name.

The remote-subnet4-del-by-id, remote-subnet6-del-by-id Commands

This is the first variant of the commands used to delete an IPv4 or IPv6 subnet from the database. It uses the subnet ID to identify the subnet. For example, to delete the IPv4 subnet with an ID of 5:

{
    "command": "remote-subnet4-del-by-id",
    "arguments": {
        "subnets": [
            {
                "id": 5
            }
        ],
        "remote": {
            "type": "mysql"
        }
    }
}

The server-tags parameter must not be used with this command.

The remote-subnet4-del-by-prefix, remote-subnet6-del-by-prefix Commands

This is the second variant of the commands used to delete an IPv4 or IPv6 subnet from the database. It uses the subnet prefix to identify the subnet. For example:

{
    "command": "remote-subnet6-del-by-prefix",
    "arguments": {
        "subnets": [
            {
                "subnet": "2001:db8:1::/64"
            }
        ],
        "remote": {
            "type": "mysql"
        }
    }
}

The server-tags parameter must not be used with this command.

The remote-subnet4-get-by-id, remote-subnet6-get-by-id Commands

This is the first variant of the commands used to fetch an IPv4 or IPv6 subnet from the database. It uses a subnet ID to identify the subnet. For example:

{
    "command": "remote-subnet4-get-by-id",
    "arguments": {
        "subnets": [
            {
                "id": 5
            }
        ],
        "remote": {
            "type": "mysql"
        }
    }
}

The server-tags parameter must not be used with this command.

The remote-subnet4-get-by-prefix, remote-subnet6-get-by-prefix Commands

This is the second variant of the commands used to fetch an IPv4 or IPv6 subnet from the database. It uses a subnet prefix to identify the subnet. For example:

{
    "command": "remote-subnet6-get-by-prefix",
    "arguments": {
        "subnets": [
            {
                "subnet": "2001:db8:1::/64"
            }
        ],
        "remote": {
            "type": "mysql"
        }
    }
}

The server-tags parameter must not be used with this command.

The remote-subnet4-list, remote-subnet6-list Commands

These commands are used to list all IPv4 or IPv6 subnets from the database for selected servers or all servers. The following command retrieves all servers to be used by the “server1” and “server2”:

{
    "command": "remote-subnet4-list"
    "arguments": {
        "remote": {
            "type": "mysql"
        },
        "server-tags": [ "server1", "server2" ]
    }
}

The server-tags parameter is mandatory and contains one or more server tags. It may contain the keyword “all”, to fetch the subnets associated with all servers. When the server-tags list contains the null value, the returned response contains a list of unassigned subnets, i.e. the subnets which are associated with no servers. For example:

{
    "command": "remote-subnet4-list"
    "arguments": {
        "remote": {
            "type": "mysql"
        },
        "server-tags": [ null ]
    }
}

The example response to this command when non-null server tags are specified looks similar to this:

{
    "result": 0,
    "text": "2 IPv4 subnet(s) found.",
    "arguments": {
        "subnets": [
            {
                "id": 1,
                "subnet": "192.0.2.0/24",
                "shared-network-name": null,
                "metadata": {
                    "server-tags": [ "server1", "server2" ]
                }
            },
            {
                "id": 2,
                "subnet": "192.0.3.0/24",
                "shared-network-name": null,
                "metadata": {
                    "server-tags": [ "all" ]
                }
            }
        ],
        "count": 2
    }
}

The returned information about each subnet is limited to subnet identifier, prefix and associated shared network name. In order to retrieve full information about the selected subnet use the remote-subnet[46]-get-by-id or remote-subnet[46]-get-by-prefix.

The example response above contains two subnets. One of the subnets is associated with both servers: “server1” and “server2”. The second subnet is associated with all servers, thus it is also present in the configuration for the “server1” and “server2”.

When listing unassigned subnets, the response will look similar to this:

{
    "result": 0,
    "text": "1 IPv4 subnet(s) found.",
    "arguments": {
        "subnets": [
            {
                "id": 3,
                "subnet": "192.0.4.0/24",
                "shared-network-name": null,
                "metadata": {
                    "server-tags": [ null ]
                }
            }
        ],
        "count": 1
    }
}

The null value in the metadata indicates that the returned subnet is unassigned.

The remote-subnet4-set, remote-subnet6-set Commands

These commands are used to create a new IPv4 or IPv6 subnet or replace an existing subnet in the database. Setting the subnet also associates or disassociates the subnet with a shared network.

The structure of the subnet information is similar to the structure used in the configuration file (see DHCPv4 Server Configuration and DHCPv6 Server Configuration). The subnet information conveyed in the remote-subnet[46]-set command must include the additional parameter shared-network-name, which denotes whether the subnet belongs to a shared network.

Consider the following example:

{
    "command": "remote-subnet4-set",
    "arguments": {
        "subnets": [
            {
                "id": 5,
                "subnet": "192.0.2.0/24",
                "shared-network-name": "level3",
                "pools": [ { "pool": "192.0.2.100-192.0.2.200" } ],
                "option-data": [ {
                    "name": "routers",
                    "data": "192.0.2.1"
                } ]
            }
        ],
        "remote": {
            "type": "mysql"
        },
        "server-tags": [ "all" ]
    }
}

It creates the subnet and associates it with the “level3” shared network. The “level3” shared network must be created with the remote-network4-set command prior to creating the subnet.

If the created subnet must be global - that is, not associated with any shared network - the shared-network-name must be explicitly set to null:

{
    "command": "remote-subnet4-set",
    "arguments": {
        "subnets": [
            {
                "id": 5,
                "subnet": "192.0.2.0/24",
                "shared-network-name": null,
                "pools": [ { "pool": "192.0.2.100-192.0.2.200" } ],
                "option-data": [ {
                    "name": "routers",
                    "data": "192.0.2.1"
                } ]
           }
        ],
        "server-tags": [ "all" ]
    }
}

The subnet created in the previous example is replaced with the new subnet having the same parameters, but it becomes global.

The shared-network-name parameter is mandatory for the remote-subnet4-set command. The server-tags list is mandatory and it must include one or more server tags. As a result, the subnet is associated with all of the listed servers. It may also be associated with “all” servers connecting to the database when the keyword “all” is used as the server tag.</para>

Note

As with other “set” commands, this command replaces all the information about the particular subnet in the database, if the subnet information is already present. Therefore, when sending this command, make sure to always include all parameters that must be specified for the updated subnet instance. Any unspecified parameter will be marked as unspecified in the database, even if its value was present prior to sending the command.

The remote-class4-del, remote-class6-del Commands

These commands delete a DHCPv4 or DHCPv6 client class by name. If any client classes in the database depend on the deleted class, an error is returned in response to this command. In this case, to successfully delete the class, the dependent client classes must be deleted first. Use the remote-class4-get-all command to fetch all client classes and find the dependent ones.

{
    "command": "remote-class4-del",
    "arguments": {
        "client-classes": [
            {
                "name": "foo"
            }
        ],
        "remote": {
            "type": "mysql"
        }
    }
}

The server-tags parameter must not be used for this command because client classes are uniquely identified by name.

The remote-class4-get, remote-class6-get Commands

These commands retrieve DHCPv4 or DHCPv6 client class information by a client class name.

{
    "command": "remote-class4-get",
    "arguments": {
        "client-classes": [
            {
                "name": "foo"
            }
        ],
        "remote": {
            "type": "mysql"
        }
    }
}

The server-tags parameter must not be used for this command because client classes are uniquely identified by name.

A response to the command looks similar to this:

{
    "result": 0,
    "text": "DHCPv4 client class 'foo' found.",
    "arguments": {
        "client-classes": [
            {
                "name": "foo",
                "metadata": {
                    "server-tags": [ "all" ]
                }
            }
        ],
        "count": 1
    }
}

The remote-class4-get-all, remote-class6-get-all Commands

These commands retrieve all DHCPv4 or DHCPv6 client classes for a particular server, multiple explicitly listed servers, or all servers. For example, the following command retrieves all client classes defined for a server having the server tag of server1 and all servers. In other words, it returns all client classes used by that server.

{
    "command": "remote-class4-get-all",
    "arguments": {
        "remote": {
            "type": "mysql"
        },
        "server-tags": [ "server1" ]
    }
}

The server-tags parameter is mandatory and it contains one or more server tags. It may contain the keyword “all” to fetch the client classes associated with all servers. When the server-tags list contains the null value the returned response contains a list of unassigned client classes, i.e. the networks which are associated with no servers.

A response to the command looks similar to this:

{
    "result": 0,
    "text": "2 DHCPv4 client class(es) found.",
    "arguments": {
        "client-classes": [
            {
                "name": "foo",
                "metadata": {
                    "server-tags": [ "all" ]
                }
            },
            {
                "name": "bar",
                "test": "member('foo')",
                "metadata": {
                    "server-tags": [ "all" ]
                }
            }
        ],
        "count": 2
    }
}

The remote-class4-set, remote-class6-set Commands

These commands insert a new or replace an existing DHCPv4 or DHCPv6 client class in the database. The client class information structure is the same as in the Kea configuration file (see Client Classification in DHCPv4 and Client Classification in DHCPv6 for details).

{
    "command": "remote-class4-set",
    "arguments": {
        "client-classes": [
            {
                "name": "foo",
                "test": "member('KNOWN') or member('bar')",
                "option-def": [
                    {
                        "name": "configfile",
                        "code": 224,
                        "type": "string"
                    }
                ],
                "option-data": [
                    {
                        "name": "configfile",
                        "data": "1APC"
                    }
                ]
            }
        ],
        "remote": {
            "type": "mysql"
        },
        "server-tags": [ "all" ]
    }
}

Client class ordering rules described in Using Expressions in Classification apply to the classes inserted into the database. It implies that the class bar referenced in the test expression must exist in the database when issuing the above command.

By default, a new client class is inserted at the end of the class hierarchy in the database and can reference any class associated with the same server tag or with the special server tag all. If an existing class is updated, it remains at its current position within the class hierarchy.

However, the class commands allow for specifying a position of the inserted or updated client class. The optional follow-class-name parameter can be included in the command to specify the name of the existing class after which the managed class should be placed. Suppose there are two DHCPv6 classes in the database: first-class and second-class. To add a new class, third-class, between these two, use the command similar to the following:

{
    "command": "remote-class6-set",
    "arguments": {
        "client-classes": [
            {
                "name": "third-class",
                "test": "member('first-class')"
            }
        ],
        "follow-class-name": "first-class",
        "remote": {
            "type": "mysql"
        },
        "server-tags": [ "all" ]
    }
}

Note that the third-class can depend on the first-class because it is placed after the first-class. The third-class must not depend on the second-class because it is placed before it. However, the second-class could now be updated to depend on the third-class.

The follow-class-name parameter can be explicitly set to null, e.g.:

{
    "command": "remote-class6-set",
    "arguments": {
        "client-classes": [
            {
                "name": "third-class",
                "test": "member('first-class')"
            }
        ],
        "follow-class-name": null,
        "remote": {
            "type": "mysql"
        },
        "server-tags": [ "all" ]
    }
}

It yields the same behavior as if the follow-class-name parameter is not included, i.e. the new class is appended at the end of the class hierarchy, and the updated class remains at the current position.

ha: High Availability

The High Availability hook library can be loaded on a pair of DHCPv4 or DHCPv6 servers, to increase the reliability of the DHCP service in the event of an outage of one of the servers. This library was previously only available to ISC’s paid subscribers, but is now part of the open source Kea, available to all users.

Note

This library may only be loaded by the kea-dhcp4 or kea-dhcp6 process.

High Availability (HA) of the DHCP service is provided by running multiple cooperating server instances. If any of these instances becomes unavailable for any reason (DHCP software crash, Control Agent software crash, power outage, hardware failure), a surviving server instance can continue providing reliable service to clients. Many DHCP server implementations include the “DHCP Failover” protocol, whose most significant features are communication between the servers, partner failure detection, and lease synchronization between the servers. However, the DHCPv4 failover standardization process was never completed by the IETF. The DHCPv6 failover standard (RFC 8156) was published, but it is complex, difficult to use, has significant operational constraints, and is different than its v4 counterpart. Although it may be useful for some users to use a “standard” failover protocol, it seems that most Kea users are simply interested in a working solution which guarantees high availability of the DHCP service. Therefore, the Kea HA hook library derives major concepts from the DHCP failover protocol but uses its own solutions for communication and configuration. It offers its own state machine, which greatly simplifies its implementation and generally fits better into Kea, and it provides the same features in both DHCPv4 and DHCPv6. This document intentionally uses the term “high availability” rather than “failover” to emphasize that it is not the failover protocol implementation.

The following sections describe the configuration and operation of the Kea HA hook library.

Supported Configurations

The Kea HA hook library supports three configurations, also known as HA modes: load-balancing, hot-standby, and passive-backup. In the load-balancing mode, two servers respond to DHCP requests. The load-balancing function is implemented as described in RFC 3074, with each server responding to half the received DHCP queries. When one of the servers allocates a lease for a client, it notifies the partner server over the control channel (via the RESTful API), so the partner can save the lease information in its own database. If the communication with the partner is unsuccessful, the DHCP query is dropped and the response is not returned to the DHCP client. If the lease update is successful, the response is returned to the DHCP client by the server which has allocated the lease. By exchanging lease updates, both servers get a copy of all leases allocated by the entire HA setup, and either server can be switched to handle the entire DHCP traffic if its partner becomes unavailable.

In the load-balancing configuration, one of the servers must be designated as primary and the other as secondary. Functionally, there is no difference between the two during normal operation. However, this distinction is required when the two servers are started at (nearly) the same time and have to synchronize their lease databases. The primary server synchronizes the database first. The secondary server waits for the primary server to complete the lease database synchronization before it starts the synchronization.

In the hot-standby configuration, one of the servers is designated as “primary” and the other as “standby.” However, during normal operation, the primary server is the only one that responds to DHCP requests. The standby server receives lease updates from the primary over the control channel; however, it does not respond to any DHCP queries as long as the primary is running or, more accurately, until the standby considers the primary to be offline. If the standby server detects the failure of the primary, it starts responding to all DHCP queries.

Note

Operators often wonder whether to use load-balancing or hot-standby mode. The load-balancing has the benefit of splitting the DHCP load between two instances, reducing the traffic processed by each of them. However, it is not always clear to the operators that using the load-balancing mode requires manually splitting the address pools between two Kea instances using client classification, to preclude both servers from allocating the same address to different clients. Such a split is not needed in the hot-standby mode. Thus, the benefit of using the hot-standby over the load-balancing mode is that the former has a simpler configuration. Conversely, load-balancing has higher performance potential at the cost of more complex configuration. See Load-Balancing Configuration for details on how to split the pools using client classification.

In the configurations described above, both the primary and secondary/standby are referred to as "active" servers, because they receive lease updates and can automatically react to the partner’s failures by responding to the DHCP queries which would normally be handled by the partner. The HA hook library supports another server type/role: backup. The use of a backup server is optional, and can be implemented in both load-balancing and hot-standby setup, in addition to the active servers. There is no limit on the number of backup servers in the HA setup; however, the presence of backup servers may increase the latency of DHCP responses, because not only do active servers send lease updates to each other, but also to the backup servers. The active servers do not expect acknowledgments from the backup servers before responding to the DHCP clients, so the overhead of sending lease updates to the backup servers is minimized.

In the last supported configuration, passive-backup, there is only one active server and typically one or more backup servers. A passive-backup configuration with no backup servers is also accepted, but it is no different than running a single server with no HA function at all.

The passive-backup configuration is used in situations when an administrator wants to take advantage of the backup servers as an additional storage for leases without a need for running the full-blown failover setup. In this case, if the primary server fails, the DHCP service is lost; it requires the administrator to manually start the primary to resume DHCP service. The administrator may also configure one of the backup servers to provide DHCP service to the clients, as these servers should have accurate or nearly accurate information about the allocated leases. The major advantage of the passive-backup mode is that it provides some redundancy of the lease information but with better performance of the primary server responding to the DHCP queries. The primary server does not have to wait for acknowledgments to the lease updates from the backup servers before it sends a response to the DHCP client. This reduces the response time compared to the load-balancing and hot-standby cases, in which the server responding to the DHCP query has to wait for the acknowledgment from the other active server before it can respond to the client.

Note

An interesting use case for a single active server running in the passive-backup mode is a notification service, in which software pretending to be a backup server receives live notifications about allocated and deleted leases from the primary server and can display them on a monitoring screen, trigger alerts, etc.

Clocks on Active Servers

Synchronized clocks are essential for the HA setup to operate reliably. The servers share lease information - via lease updates and during synchronization of the databases - including the time when the lease was allocated and when it expires. Some clock skew between the servers participating in the HA setup usually exists; this is acceptable as long as the clock skew is relatively low, compared to the lease lifetimes. However, if the clock skew becomes too high, the different lease expiration times on different servers may cause the HA system to malfunction. For example, one server may consider a lease to be expired when it is actually still valid. The lease reclamation process may remove a name associated with this lease from the DNS, causing problems when the client later attempts to renew the lease.

Each active server monitors the clock skew by comparing its current time with the time returned by its partner in response to the heartbeat command. This gives a good approximation of the clock skew, although it does not take into account the time between the partner sending the response and the receipt of this response by the server which sent the heartbeat command. If the clock skew exceeds 30 seconds, a warning log message is issued. The administrator may correct this problem by synchronizing the clocks (e.g. using NTP); the servers should notice the clock skew correction and stop issuing the warning.

If the clock skew is not corrected and exceeds 60 seconds, the HA service on each of the servers is terminated, i.e. the state machine enters the terminated state. The servers will continue to respond to DHCP clients (as in the load-balancing or hot-standby mode), but will exchange neither lease updates nor heartbeats and their lease databases will diverge. In this case, the administrator should synchronize the clocks and restart the servers.

Note

It is possible to restart the servers one at a time, in no particular order. The clocks must be in sync before restarting the servers.

Note

The clock skew is only assessed between two active servers, and only the active servers enter the terminated state if the skew is too high. The clock skew between active and backup servers is not assessed, because active servers do not exchange heartbeat messages with backup servers.

HTTPS Support

Since Kea 1.9.7, the High Availability hook library supports HTTPS via TLS, as described in TLS/HTTPS Support.

The HTTPS configuration parameters are:

• trust-anchor - specifies the name of a file or directory where the certification authority certificate of a Control Agent can be found.

• cert-file - specifies the name of the file containing the end-entity certificate to use.

• key-file - specifies the private key of the end-entity certificate to use.

These parameters can be configured at the global and peer levels. When configured at both levels the peer value is used, allowing common values to be shared.

The three parameters must be either all not specified (HTTPS disabled) or all specified (HTTPS enabled). Specification of the empty string is considered not specified; this can be used, for instance, to disable HTTPS for a particular peer when it is enabled at the global level.

As the High Availability hook library is an HTTPS client, there is no cert-required parameter in this hook configuration. This parameter can be set in Control Agent to require and verify client certificate in Client-Server communication. It does not affect communication between HA peers.

Currently using HTTPS in HA setup requires use of Control Agent on all peers. (See TLS/HTTPS Support for Control Agent TLS configuration).

Following is an example of HA server pair and Control Agent configuration for Hot-Standby with TLS.

Server 1:

"Dhcp4": {
    "hooks-libraries": [{
        "library": "/usr/lib/kea/hooks/libdhcp_lease_cmds.so",
        "parameters": { }
    }, {
        "library": "/usr/lib/kea/hooks/libdhcp_ha.so",
        "parameters": {
            "high-availability": [{
                "this-server-name": "server1",
                "trust-anchor": /usr/lib/kea/CA.pem,
                "cert-file": /usr/lib/kea/server1_cert.pem,
                "key-file": /usr/lib/kea/server1_key.pem
                "mode": "hot-standby",
                "heartbeat-delay": 10000,
                "max-response-delay": 60000,
                "max-ack-delay": 5000,
                "max-unacked-clients": 5,
                "peers": [{
                    "name": "server1",
                    "url": "http://192.168.56.33:8000/",
                    "role": "primary",
                    "auto-failover": true
                }, {
                    "name": "server2",
                    "url": "http://192.168.56.66:8000/",
                    "role": "standby",
                    "auto-failover": true
                }]
            }]
        }
    }],

    "subnet4": [{
        "subnet": "192.0.3.0/24",
        "pools": [{
            "pool": "192.0.3.100 - 192.0.3.250",
            }]
    }]
}

Server 2:

"Dhcp4": {
    "hooks-libraries": [{
        "library": "/usr/lib/kea/hooks/libdhcp_lease_cmds.so",
        "parameters": { }
    }, {
        "library": "/usr/lib/kea/hooks/libdhcp_ha.so",
        "parameters": {
            "high-availability": [{
                "this-server-name": "server2",
                "trust-anchor": /usr/lib/kea/CA.pem,
                "cert-file": /usr/lib/kea/server2_cert.pem,
                "key-file": /usr/lib/kea/server2_key.pem
                "mode": "hot-standby",
                "heartbeat-delay": 10000,
                "max-response-delay": 60000,
                "max-ack-delay": 5000,
                "max-unacked-clients": 5,
                "peers": [{
                    "name": "server1",
                    "url": "http://192.168.56.33:8000/",
                    "role": "primary",
                    "auto-failover": true
                }, {
                    "name": "server2",
                    "url": "http://192.168.56.66:8000/",
                    "role": "standby",
                    "auto-failover": true
                }]
            }]
        }
    }],

    "subnet4": [{
        "subnet": "192.0.3.0/24",
        "pools": [{
            "pool": "192.0.3.100 - 192.0.3.250",
            }]
    }]
}

Control Agent on Server 1:

{
    "Control-agent": {
        "http-host": "192.168.56.33",
        "http-port": 8000,
        "control-sockets": {
            "dhcp4": {
                "socket-type": "unix",
                "socket-name": "/var/run/kea/control_socket"
            }
        },
        "trust-anchor": "/var/lib/kea/CA.pem",
        "cert-file": "/var/lib/kea/server1_cert.pem",
        "key-file": "/var/lib/kea/server1_key.pem",
        "cert-required": true
    }
}

Control Agent on Server 2:

{
    "Control-agent": {
        "http-host": "192.168.56.66",
        "http-port": 8000,
        "control-sockets": {
            "dhcp4": {
                "socket-type": "unix",
                "socket-name": "/var/run/kea/control_socket"
            }
        },
        "trust-anchor": "/var/lib/kea/CA.pem",
        "cert-file": "/var/lib/kea/server2_cert.pem",
        "key-file": "/var/lib/kea/server2_key.pem",
        "cert-required": true
    }
}

Server States

A DHCP server operating within an HA setup runs a state machine, and the state of the server can be retrieved by its peers using the ha-heartbeat command sent over the RESTful API. If the partner server does not respond to the ha-heartbeat command within the specified amount of time, the communication is considered interrupted and the server may, depending on the configuration, use additional measures (described later in this document) to verify that the partner is still operating. If it finds that the partner is not operating, the server transitions to the partner-down state to handle all the DHCP traffic directed to the system.

In this case, the surviving server continues to send the ha-heartbeat command to detect when the partner wakes up. At that time, the partner synchronizes the lease database. When it is again ready to operate, the surviving server returns to normal operation, i.e. the load-balancing or hot-standby state.

The following is the list of all possible server states:

• backup - normal operation of the backup server. In this state it receives lease updates from the active server(s).

• communication-recovery - an active server running in load-balancing mode may transition to this state when it experiences communication issues with a partner server over the control channel. This is an intermediate state between the load-balancing and partner-down states. In this state the server continues to respond to DHCP queries but does not send lease updates to the partner; lease updates are queued and are sent when normal communication is resumed. If communication does not resume within the time specified, the primary server then transitions to the partner-down state. The communication-recovery state was introduced to ensure reliable DHCP service when both active servers remain operational but the communication between them is interrupted for a prolonged period of time. Either server can be configured to never enter this state by setting the delayed-updates-limit to 0. (Please refer to Load-Balancing Configuration, later in this chapter, for details on this parameter.) Disabling entry into the communication-recovery state causes the server to begin testing for the partner-down state as soon as the server is unable to communicate with its partner.

Note

In Kea 1.9.4, with the introduction of delayed-updates-limit, the default server’s behavior in load-balancing mode changed. When a server experiences communication issues with its partner, it now enters the communication-recovery state and queues lease updates until communication is resumed. Prior to Kea 1.9.4, a server that could not communicate with its partner in load-balancing mode would immediately begin the transition to the partner-down state.

• hot-standby - normal operation of the active server running in the hot-standby mode; both the primary and the standby server are in this state during their normal operation. The primary server responds to DHCP queries and sends lease updates to the standby server and to any backup servers that are present.

• load-balancing - normal operation of the active server running in the load-balancing mode; both the primary and the secondary server are in this state during their normal operation. Both servers respond to DHCP queries and send lease updates to each other and to any backup servers that are present.

• in-maintenance - an active server transitions to this state as a result of being notified by its partner that the administrator requested maintenance of the HA setup. The administrator requests the maintenance by sending the ha-maintenance-start command to the server which is supposed to take over the responsibility for responding to the DHCP clients while the other server is taken offline for maintenance. If the server is in the in-maintenance state it can be safely shut down. The partner is in the partner-in-maintenance state, from which it transitions to the partner-down state immediately after it discovers that the server in maintenance has been shut down.

• partner-down - an active server transitions to this state after detecting that its partner (another active server) is offline. The server does not transition to this state if only a backup server is unavailable. In the partner-down state the active server responds to all DHCP queries, including those queries which are normally handled by the server that is now unavailable.

• partner-in-maintenance - an active server transitions to this state after receiving a ha-maintenance-start command from the administrator. The server in this state becomes responsible for responding to all DHCP requests. The server sends a ha-maintenance-notify command to the partner, which should enter the in-maintenance state. The server remaining in the partner-in-maintenance state keeps sending lease updates to the partner until it finds that the partner has stopped responding to those lease updates, heartbeats, or any other commands. In this case, the server in the partner-in-maintenance state transitions to the partner-down state and keeps responding to the queries, but no longer sends lease updates.

• passive-backup - a primary server running in the passive-backup HA mode transitions to this state immediately after it boots up. The primary server in this state responds to all DHCP traffic and sends lease updates to the backup servers it is connected to. By default, the primary server does not wait for acknowledgments from the backup servers and responds to a DHCP query right after sending lease updates to all backup servers. If any of the lease updates fail, a backup server misses the lease update but the DHCP client is still provisioned. This default configuration can be changed by setting the wait-backup-ack configuration parameter to true, in which case the primary server always waits for the acknowledgements and drops the DHCP query if sending any of the corresponding lease updates fails. This improves lease database consistency between the primary and the secondary. However, if a communication failure between the active server and any of the backups occurs, it effectively causes the failure of the DHCP service from the DHCP clients’ perspective.

• ready - an active server transitions to this state after synchronizing its lease database with an active partner. This state indicates to the partner - which may be in the partner-down state - that it should return to normal operation. If and when it does, the server in the ready state also starts normal operation.

• syncing - an active server transitions to this state to fetch leases from the active partner and update the local lease database. When in this state, the server issues the dhcp-disable command to disable the DHCP service of the partner from which the leases are fetched. The DHCP service is disabled for a maximum time of 60 seconds, after which it is automatically re-enabled, in case the syncing partner was unable to re-enable the service. If the synchronization completes successfully, the synchronizing server issues the ha-sync-complete-notify command to notify the partner. In most states, the partner re-enables its DHCP service to continue responding to the DHCP queries. In the partner-down state, the partner first ensures that communication between the servers is re-established before enabling the DHCP service. The syncing operation is synchronous; the server waits for an answer from the partner and does nothing else while the lease synchronization takes place. A server that is configured not to synchronize the lease database with its partner, i.e. when the sync-leases configuration parameter is set to false, will never transition to this state. Instead, it transitions directly from the waiting state to the ready state.

• terminated - an active server transitions to this state when the High Availability hook library is unable to further provide reliable service and a manual intervention of the administrator is required to correct the problem. Various issues with the HA setup may cause the server to transition to this state. While in this state, the server continues responding to DHCP clients based on the HA mode selected (load-balancing or hot-standby), but lease updates are not exchanged and heartbeats are not sent. Once a server has entered the terminated state, it remains in this state until it is restarted. The administrator must correct the issue which caused this situation prior to restarting the server (e.g. synchronize the clocks); otherwise, the server will return to the “terminated” state once it finds that the issue persists.

• waiting - each started server instance enters this state. A backup server transitions directly from this state to the backup state. An active server sends a heartbeat to its partner to check its state; if the partner appears to be unavailable, the server transitions to the partner-down state. If the partner is available, the server transitions to the syncing or ready state, depending on the setting of the sync-leases configuration parameter. If both servers appear to be in the waiting state (concurrent startup), the primary server transitions to the next state first. The secondary or standby server remains in the waiting state until the primary transitions to the ready state.

Note

Currently, restarting the HA service from the terminated state requires restarting the DHCP server or reloading its configuration.

Whether the server responds to DHCP queries and which queries it responds to is a matter of the server’s state, if no administrative action is performed to configure the server otherwise. The following table provides the default behavior for various states.

The DHCP Service Scopes denote which group of received DHCP queries the server responds to in the given state. The HA configuration must specify a unique name for each server within the HA setup. This document uses the following convention within the provided examples: “server1” for a primary server, “server2” for the secondary or standby server, and “server3” for the backup server. In real life any names can be used as long as they remain unique.

An in-depth explanation of the scopes can be found below.

Default behavior of the server in various HA states

State	Server Type	DHCP Service	DHCP Service Scopes
backup	backup server	disabled	none
communication-recovery	primary or secondary (load-balancing mode only)	enabled	“HA_server1” or “HA_server2”
hot-standby	primary or standby (hot-standby mode)	enabled	“HA_server1” if primary, none otherwise
load-balancing	primary or secondary (load-balancing mode)	enabled	“HA_server1” or “HA_server2”
in-maintenance	active server	disabled	none
partner-down	active server	enabled	all scopes
partner-in-maintenance	active server	enabled	all scopes
passive-backup	active server	enabled	all scopes
ready	active server	disabled	none
syncing	active server	disabled	none
terminated	active server	enabled	same as in the load-balancing or hot-standby state
waiting	any server	disabled	none

In the load-balancing mode there are two scopes specified for the active servers: “HA_server1” and “HA_server2”. The DHCP queries load-balanced to server1 belong to the “HA_server1” scope and the queries load-balanced to server2 belong to the “HA_server2” scope. If either server is in the partner-down state, the active partner is responsible for serving both scopes.

In the hot-standby mode, there is only one scope - “HA_server1” - because only server1 is responding to DHCP queries. If that server becomes unavailable, server2 becomes responsible for this scope.

The backup servers do not have their own scopes. In some cases they can be used to respond to queries belonging to the scopes of the active servers. Also, a backup server which is neither in the partner-down state nor in normal operation serves no scopes.

The scope names can be used to associate pools, subnets, and networks with certain servers, so that only these servers can allocate addresses or prefixes from those pools, subnets, or networks. This is done via the client classification mechanism (see Load Balancing with Advanced Classification for more details).

Scope Transition in a Partner-Down Case

When one of the servers finds that its partner is unavailable, it starts serving clients from both its own scope and the scope of the unavailable partner. This is straightforward for new clients, i.e. those sending DHCPDISCOVER (DHCPv4) or Solicit (DHCPv6), because those requests are not sent to any particular server. The available server responds to all such queries when it is in the partner-down state.

When a client renews a lease, it sends its DHCPREQUEST (DHCPv4) or Renew (DHCPv6) message directly to the server which has allocated the lease being renewed. If this server is no longer available, the client will get no response. In that case, the client continues to use its lease and attempts to renew until the rebind timer (T2) elapses. The client then enters the rebinding phase, in which it sends a DHCPREQUEST (DHCPv4) or Rebind (DHCPv6) message to any available server. The surviving server receives the rebinding request and typically extends the lifetime of the lease. The client then continues to contact that new server to renew its lease as appropriate.

If and when the other server once again becomes available, both active servers will eventually transition to the load-balancing or hot-standby state, in which they will again be responsible for their own scopes. Some clients belonging to the scope of the restarted server will try to renew their leases via the surviving server, but this server will no longer respond to them; the client will eventually transition back to the correct server via the rebinding mechanism.

Load-Balancing Configuration

The following is the configuration snippet to enable high availability on the primary server within the load-balancing configuration. The same configuration should be applied on the secondary and backup servers, with the only difference that this-server-name should be set to “server2” and “server3” on those servers, respectively.

Note

Remember that load-balancing mode requires the address pools and delegated prefix pools to be split between the active servers. During normal operation, the servers use non-overlapping pools to avoid allocating the same lease to different clients by both instances. A server will only use the pool fragments owned by the partner when the partner is not running. See the notes in Supported Configurations highlighting differences between the load-balancing and hot-standby modes. The semantics of pool partitioning is explained further in this section. The Load Balancing with Advanced Classification section provides advanced pool-partitioning examples.

"Dhcp4": {
    "hooks-libraries": [{
        "library": "/usr/lib/kea/hooks/libdhcp_lease_cmds.so",
        "parameters": { }
    }, {
        "library": "/usr/lib/kea/hooks/libdhcp_ha.so",
        "parameters": {
            "high-availability": [{
                "this-server-name": "server1",
                "mode": "load-balancing",
                "heartbeat-delay": 10000,
                "max-response-delay": 60000,
                "max-ack-delay": 5000,
                "max-unacked-clients": 5,
                "delayed-updates-limit": 100,
                "peers": [{
                    "name": "server1",
                    "url": "http://192.168.56.33:8000/",
                    "role": "primary",
                    "auto-failover": true
                }, {
                    "name": "server2",
                    "url": "http://192.168.56.66:8000/",
                    "role": "secondary",
                    "auto-failover": true
                }, {
                    "name": "server3",
                    "url": "http://192.168.56.99:8000/",
                    "role": "backup",
                    "basic-auth-user": "foo",
                    "basic-auth-password": "bar",
                    "auto-failover": false
                }]
            }]
        }
    }],

    "subnet4": [{
        "subnet": "192.0.3.0/24",
        "pools": [{
            "pool": "192.0.3.100 - 192.0.3.150",
            "client-class": "HA_server1"
         }, {
            "pool": "192.0.3.200 - 192.0.3.250",
            "client-class": "HA_server2"
         }],

         "option-data": [{
            "name": "routers",
            "data": "192.0.3.1"
         }],

         "relay": { "ip-address": "10.1.2.3" }
    }]
}

Two hook libraries must be loaded to enable HA: libdhcp_lease_cmds.so and libdhcp_ha.so. The latter implements the HA feature, while the former enables control commands required by HA to fetch and manipulate leases on the remote servers. In the example provided above, it is assumed that Kea libraries are installed in the /usr/lib directory. If Kea is not installed in the /usr directory, the hook libraries locations must be updated accordingly.

The HA configuration is specified within the scope of libdhcp_ha.so. Note that while the top-level parameter high-availability is a list, only a single entry is currently supported.

The following are the global parameters which control the server’s behavior with respect to HA:

• this-server-name - is a unique identifier of the server within this HA setup. It must match with one of the servers specified within the peers list.

• mode - specifies an HA mode of operation. The currently supported modes are load-balancing and hot-standby.

• heartbeat-delay - specifies a duration in milliseconds between sending the last heartbeat (or other command sent to the partner) and the next heartbeat. Heartbeats are sent periodically to gather the status of the partner and to verify whether the partner is still operating. The default value of this parameter is 10000 ms.

• max-response-delay - specifies a duration in milliseconds since the last successful communication with the partner, after which the server assumes that communication with the partner is interrupted. This duration should be greater than the heartbeat-delay; typically it should be a multiple of heartbeat-delay. When the server detects that communication is interrupted, it may transition to the partner-down state (when max-unacked-clients is 0) or trigger the failure-detection procedure using the values of the two parameters below. The default value of this parameter is 60000 ms.

• max-ack-delay - is one of the parameters controlling partner failure-detection. When communication with the partner is interrupted, the server examines the values of the secs field (DHCPv4) or Elapsed Time option (DHCPv6), which denote how long the DHCP client has been trying to communicate with the DHCP server. This parameter specifies the maximum time in milliseconds for the client to try to communicate with the DHCP server, after which this server assumes that the client failed to communicate with the DHCP server (is unacknowledged or “unacked”). The default value of this parameter is 10000.

• max-unacked-clients - specifies how many “unacked” clients are allowed (see max-ack-delay) before this server assumes that the partner is offline and transitions to the partner-down state. The special value of 0 is allowed for this parameter, which disables the failure-detection mechanism. In this case, a server that cannot communicate with its partner over the control channel assumes that the partner server is down and transitions to the partner-down state immediately. The default value of this parameter is 10.

• delayed-updates-limit - specifies the maximum number of lease updates which can be queued while the server is in the communication-recovery state. This parameter was introduced in Kea 1.9.4. The special value of 0 configures the server to never transition to the communication-recovery state and the server behaves as in earlier Kea versions, i.e. if the server cannot reach its partner, it goes straight into the partner-down state. The default value of this parameter is 100.

The values of max-ack-delay and max-unacked-clients must be selected carefully, taking into account the specifics of the network in which the DHCP servers are operating. The server in question may not respond to some DHCP clients following administrative policy, or the server may drop malformed queries from clients. Therefore, selecting too low a value for the max-unacked-clients parameter may result in a transition to the partner-down state even though the partner is still operating. On the other hand, selecting too high a value may result in never transitioning to the partner-down state if the DHCP traffic in the network is very low (e.g. at night), because the number of distinct clients trying to communicate with the server could be lower than the max-unacked-clients setting.

In some cases it may be useful to disable the failure-detection mechanism altogether, if the servers are located very close to each other and network partitioning is unlikely, i.e. failure to respond to heartbeats is only possible when the partner is offline. In such cases, set max-unacked-clients to 0.

The delayed-updates-limit parameter is used to enable or disable the communication-recovery procedure, and controls the server’s behavior in the communication-recovery state. This parameter can only be used in the load-balancing mode.

If a server in the load-balancing state experiences communication issues with its partner (a heartbeat or lease update fail), the server transitions to the communication-recovery state. In this state, the server keeps responding to DHCP queries but does not send lease updates to the partner. The lease updates are queued until communication is re-established, to ensure that DHCP service remains available even in the event of the communication loss between the partners. There may appear to be communication loss when either one of the servers has terminated, or when both servers remain available but cannot communicate with each other. In the former case, the surviving server will follow the normal procedure and should eventually transition to the partner-down state. In the latter case, both servers should transition to the communication-recovery state and should never transition to the partner-down state (if max-unacked-clients is set to a non-zero value), because all DHCP queries are answered and neither server would see any unacked DHCP queries.

Introduction of the communication-recovery procedure was motivated by issues which may appear when two servers remain online but the communication between them remains interrupted for a period of time. In earlier Kea versions, the servers having communication issues used to drop DHCP packets before transitioning to the partner-down state. In some cases they both transitioned to the partner-down state, which could potentially result in allocations of the same IP addresses or delegated prefixes to different clients by the respective servers. By entering the intermediate communication-recovery state, these problems are avoided.

If a server in the communication-recovery state re-establishes communication with its partner, it tries to send the partner all of the outstanding lease updates it has queued. This is done synchronously and may take a considerable amount of time before the server transitions to the load-balancing state and resumes normal operation. The maximum number of lease updates which can be queued in the communication-recovery state is controlled by delayed-updates-limit. If the limit is exceeded, the server stops queuing lease updates and performs a full database synchronization after re-establishing the connection with the partner, instead of sending outstanding lease updates before transitioning to the load-balancing state. Even if the limit is exceeded, the server in the communication-recovery state remains responsive to DHCP clients.

It may be preferable to set higher values of delayed-updates-limit when there is a risk of prolonged communication interruption between the servers and when the lease database is large, to avoid costly lease-database synchronization. On the other hand, if the lease database is small, the time required to send outstanding lease updates may be longer than the lease-database synchronization. In such cases it may be better to use a lower value, e.g. 10. The default value of 100 is a reasonable compromise and should work well in most deployments with moderate traffic.

Note

This parameter is new and values for it that work well in some environments may not work well in others. Feedback from users will help us build a better working set of recommendations.

The peers parameter contains a list of servers within this HA setup. This configuration must contain at least one primary and one secondary server. It may also contain an unlimited number of backup servers. In this example, there is one backup server which receives lease updates from the active servers.

Since Kea version 1.9.0, basic HTTP authentication is available to protect the Kea control agent against local attackers.

These are the parameters specified for each of the peers within this list:

• name - specifies a unique name for the server.

• url - specifies the URL to be used to contact this server over the control channel. Other servers use this URL to send control commands to that server.

• basic-auth-user - specifies the user ID for basic HTTP authentication. If not specified or specified as an empty string, no authentication header will be added to HTTP transactions. It must not contain the colon (:) character.

• basic-auth-password - specifies the password for basic HTTP authentication. This parameter is ignored when the user ID is not specified or is empty. The password is optional; if not specified, an empty password is used.

• basic-auth-password-file - is an alternative to basic-auth-password: instead of presenting the password in the configuration file it is specified in the file indicated by this parameter.

• role - denotes the role of the server in the HA setup. The following roles are supported in the load-balancing configuration: primary, secondary, and backup. There must be exactly one primary and one secondary server in the load-balancing setup.

• auto-failover - a boolean value which denotes whether a server detecting a partner’s failure should automatically start serving the partner’s clients. The default value of this parameter is true.

In our example configuration above, both active servers can allocate leases from the subnet “192.0.3.0/24”. This subnet contains two address pools: “192.0.3.100 - 192.0.3.150” and “192.0.3.200 - 192.0.3.250”, which are associated with HA server scopes using client classification. When server1 processes a DHCP query, it uses the first pool for lease allocation. Conversely, when server2 processes a DHCP query it uses the second pool. If either of the servers is in the partner-down state, the other can serve leases from both pools; it selects the pool which is appropriate for the received query. In other words, if the query would normally be processed by server2 but this server is not available, server1 allocates the lease from the pool of “192.0.3.200 - 192.0.3.250”. The Kea control agent in front of server3 requires basic HTTP authentication, and authorizes the user ID “foo” with the password “bar”.

Note

The url schema can be http or https, but since Kea version 1.9.6 the https schema requires a TLS setup. The hostname part must be an IPv4 address or an IPv6 address between square brackets, e.g. http://[2001:db8::1]:8080/. Names are not accepted.

Load Balancing with Advanced Classification

In the previous section, we provided an example of a load-balancing configuration with client classification limited to the “HA_server1” and “HA_server2” classes, which are dynamically assigned to the received DHCP queries. In many cases, HA is needed in deployments which already use some other client classification.

Suppose there is a system which classifies devices into two groups: phones and laptops, based on some classification criteria specified in the Kea configuration file. Both types of devices are allocated leases from different address pools. Introducing HA in load-balancing mode results in a further split of each of those pools, as each server allocates leases for some phones and some laptops. This requires each of the existing pools to be split between “HA_server1” and “HA_server2”, so we end up with the following classes:

• “phones_server1”

• “laptops_server1”

• “phones_server2”

• “laptops_server2”

The corresponding server configuration, using advanced classification (and the member expression), is provided below. For brevity’s sake, the HA hook library configuration has been removed from this example.

"Dhcp4": {
    "client-classes": [{
        "name": "phones",
        "test": "substring(option[60].hex,0,6) == 'Aastra'",
    }, {
        "name": "laptops",
        "test": "not member('phones')"
    }, {
        "name": "phones_server1",
        "test": "member('phones') and member('HA_server1')"
    }, {
        "name": "phones_server2",
        "test": "member('phones') and member('HA_server2')"
    }, {
        "name": "laptops_server1",
        "test": "member('laptops') and member('HA_server1')"
    }, {
        "name": "laptops_server2",
        "test": "member('laptops') and member('HA_server2')"
    }],

    "hooks-libraries": [{
        "library": "/usr/lib/kea/hooks/libdhcp_lease_cmds.so",
        "parameters": { }
    }, {
        "library": "/usr/lib/kea/hooks/libdhcp_ha.so",
        "parameters": {
            "high-availability": [{
               ...
            }]
        }
    }],

    "subnet4": [{
        "subnet": "192.0.3.0/24",
        "pools": [{
            "pool": "192.0.3.100 - 192.0.3.125",
            "client-class": "phones_server1"
        }, {
            "pool": "192.0.3.126 - 192.0.3.150",
            "client-class": "laptops_server1"
        }, {
            "pool": "192.0.3.200 - 192.0.3.225",
            "client-class": "phones_server2"
        }, {
            "pool": "192.0.3.226 - 192.0.3.250",
            "client-class": "laptops_server2"
        }],

        "option-data": [{
            "name": "routers",
            "data": "192.0.3.1"
        }],

        "relay": { "ip-address": "10.1.2.3" }
    }],
}

The configuration provided above splits the address range into four pools: two pools dedicated to “HA_server1” and two to “HA_server2”. Each server can assign leases to both phones and laptops. Both groups of devices are assigned addresses from different pools. The “HA_server1” and “HA_server2” classes are built-in (see Built-in Client Classes) and do not need to be declared. They are assigned dynamically by the HA hook library as a result of the load-balancing algorithm. “phones_*” and “laptop_*” evaluate to true when the query belongs to a given combination of other classes, e.g. “HA_server1” and “phones”. The pool is selected accordingly as a result of such an evaluation.

Consult Client Classification for details on how to use the member expression and class dependencies.

Hot-Standby Configuration

The following is an example configuration of the primary server in a hot-standby configuration:

"Dhcp4": {
    "hooks-libraries": [{
        "library": "/usr/lib/kea/hooks/libdhcp_lease_cmds.so",
        "parameters": { }
    }, {
        "library": "/usr/lib/kea/hooks/libdhcp_ha.so",
        "parameters": {
            "high-availability": [{
                "this-server-name": "server1",
                "mode": "hot-standby",
                "heartbeat-delay": 10000,
                "max-response-delay": 60000,
                "max-ack-delay": 5000,
                "max-unacked-clients": 5,
                "peers": [{
                    "name": "server1",
                    "url": "http://192.168.56.33:8000/",
                    "role": "primary",
                    "auto-failover": true
                }, {
                    "name": "server2",
                    "url": "http://192.168.56.66:8000/",
                    "role": "standby",
                    "auto-failover": true
                }, {
                    "name": "server3",
                    "url": "http://192.168.56.99:8000/",
                    "basic-auth-user": "foo",
                    "basic-auth-password": "bar",
                    "role": "backup",
                    "auto-failover": false
                }]
            }]
        }
    }],

    "subnet4": [{
        "subnet": "192.0.3.0/24",
        "pools": [{
            "pool": "192.0.3.100 - 192.0.3.250",
            "client-class": "HA_server1"
        }],

        "option-data": [{
            "name": "routers",
            "data": "192.0.3.1"
        }],

        "relay": { "ip-address": "10.1.2.3" }
    }]
}

This configuration is very similar to the load-balancing configuration described in Load-Balancing Configuration, with a few notable differences.

The mode is now set to hot-standby, in which only one server responds to DHCP clients. If the primary server is online, it responds to all DHCP queries. The standby server takes over all DHCP traffic only if it discovers that the primary is unavailable.

In this mode, the non-primary active server is called standby and that is its role.

Finally, because there is always only one server responding to DHCP queries, there is only one scope - “HA_server1” - in use within pool definitions. In fact, the client-class parameter could be removed from this configuration without harm, because there can be no conflicts in lease allocations by different servers as they do not allocate leases concurrently. The client-class remains in this example mostly for demonstration purposes, to highlight the differences between the hot-standby and load-balancing modes of operation.

Passive-Backup Configuration

The following is an example configuration file for the primary server in a passive-backup configuration:

"Dhcp4": {
    "hooks-libraries": [{
        "library": "/usr/lib/kea/hooks/libdhcp_lease_cmds.so",
        "parameters": { }
    }, {
        "library": "/usr/lib/kea/hooks/libdhcp_ha.so",
        "parameters": {
            "high-availability": [{
                "this-server-name": "server1",
                "mode": "passive-backup",
                "wait-backup-ack": false,
                "peers": [{
                    "name": "server1",
                    "url": "http://192.168.56.33:8000/",
                    "role": "primary"
                }, {
                    "name": "server2",
                    "url": "http://192.168.56.66:8000/",
                    "role": "backup"
                }, {
                    "name": "server3",
                    "url": "http://192.168.56.99:8000/",
                    "basic-auth-user": "foo",
                    "basic-auth-password": "bar",
                    "role": "backup"
                }]
            }]
        }
    }],

    "subnet4": [{
        "subnet": "192.0.3.0/24",
        "pools": [{
            "pool": "192.0.3.100 - 192.0.3.250",
        }],

        "option-data": [{
            "name": "routers",
            "data": "192.0.3.1"
        }],

        "relay": { "ip-address": "10.1.2.3" }
    }]
}

The configurations of three peers are included: one for the primary and two for the backup servers.

Many of the parameters present in the load-balancing and hot-standby configuration examples are not relevant in the passive-backup mode, thus they are not specified here. For example: heartbeat-delay, max-unacked-clients, and others related to the automatic failover mechanism should not be specified in the passive-backup mode.

wait-backup-ack is a boolean parameter not present in previous examples. It defaults to false and must not be modified in the load-balancing and hot-standby modes. In the passive-backup mode this parameter can be set to true, which causes the primary server to expect acknowledgments to the lease updates from the backup servers prior to responding to the DHCP client. It ensures that the lease has propagated to all servers before the client is given the lease, but it poses a risk of losing a DHCP service if there is a communication problem with one of the backup servers. This setting also increases the latency of the DHCP response, because of the time that the primary spends waiting for the acknowledgements. We recommend that the wait-backup-ack setting be left at its default value (false) if the DHCP service reliability is more important than consistency of the lease information between the primary and the backups, and in all cases when the DHCP service latency should be minimal.

Note

Currently, active servers place lease updates to be sent to peers onto internal queues (one queue per peer/URL). In passive-backup mode, active servers do not wait for lease updates to be acknowledged; thus during times of heavy client traffic it is possible for the number of lease updates queued for transmission to accumulate faster than they can be delivered. As client traffic lessens the queues begin to empty. Since Kea 2.0.0, active servers monitor the size of these queues and emit periodic warnings (see HTTP_CILENT_QUEUE_SIZE_GROWING in Kea Messages Manual) if they perceive a queue as growing too quickly. The warnings cease once the queue size begins to shrink. These messages are intended as a bellwether and seeing them sporadically during times of heavy traffic load does not necessarily indicate a problem. If, however, they occur continually during times of routine traffic load, they likely indicate potential mismatches in server capabilities and/or configuration; this should be investigated, as the size of the queues may eventually impair an active server’s ability to respond to clients in a timely manner.

Lease Information Sharing

An HA-enabled server informs its active partner about allocated or renewed leases by sending appropriate control commands, and the partner updates the lease information in its own database. When the server starts up for the first time or recovers after a failure, it synchronizes its lease database with its partner. These two mechanisms guarantee consistency of the lease information between the servers and allow the designation of one of the servers to handle the entire DHCP traffic load if the other server becomes unavailable.

In some cases, though, it is desirable to disable lease updates and/or database synchronization between the active servers, if the exchange of information about the allocated leases is performed using some other mechanism. Kea supports various database types that can be used to store leases, including MySQL and PostgreSQL. Those databases include built-in solutions for data replication which are often used by Kea administrators to provide redundancy.

The HA hook library supports such scenarios by disabling lease updates over the control channel and/or lease-database synchronization, leaving the server to rely on the database replication mechanism. This is controlled by the two boolean parameters send-lease-updates and sync-leases, whose values default to true:

{
"Dhcp4": {

    ...

    "hooks-libraries": [
        {
            "library": "/usr/lib/kea/hooks/libdhcp_lease_cmds.so",
            "parameters": { }
        },
        {
            "library": "/usr/lib/kea/hooks/libdhcp_ha.so",
            "parameters": {
                "high-availability": [ {
                    "this-server-name": "server1",
                    "mode": "load-balancing",
                    "send-lease-updates": false,
                    "sync-leases": false,
                    "peers": [
                        {
                            "name": "server1",
                            "url": "http://192.168.56.33:8000/",
                            "role": "primary"
                        },
                        {
                            "name": "server2",
                            "url": "http://192.168.56.66:8000/",
                            "role": "secondary"
                        }
                    ]
                } ]
            }
        }
    ],

    ...

}

In the most typical use case, both parameters are set to the same value, i.e. both are false if database replication is in use, or both are true otherwise. Introducing two separate parameters to control lease updates and lease-database synchronization is aimed at possible special use cases; for example, when synchronization is performed by copying a lease file (therefore sync-leases is set to false), but lease updates should be conducted as usual (send-lease-updates is set to true). It should be noted that Kea does not natively support such use cases, but users may develop their own scripts and tools around Kea to provide such mechanisms. The HA hook library configuration is designed to maximize flexibility of administration.

Controlling Lease-Page Size Limit

An HA-enabled server initiates synchronization of the lease database after downtime or upon receiving the ha-sync command. The server uses commands described in The lease4-get-page, lease6-get-page Commands and The lease4-get-page, lease6-get-page Commands to fetch leases from its partner server (lease queries). The size of the results page (the maximum number of leases to be returned in a single response to one of these commands) can be controlled via configuration of the HA hook library. Increasing the page size decreases the number of lease queries sent to the partner server, but it causes the partner server to generate larger responses, which lengthens transmission time as well as increases memory and CPU utilization on both servers. Decreasing the page size helps to decrease resource utilization, but requires more lease queries to be issued to fetch the entire lease database.

The default value of the sync-page-limit command controlling the page size is 10000. This means that the entire lease database can be fetched with a single command if the size of the database is equal to or less than 10000 lines.

Timeouts

In deployments with a large number of clients connected to the network, lease-database synchronization after a server failure may be a time-consuming operation. The synchronizing server must gather all leases from its partner, which yields a large response over the RESTful interface. The server receives leases using the paging mechanism described in Controlling Lease-Page Size Limit. Before the page of leases is fetched, the synchronizing server sends a dhcp-disable command to disable the DHCP service on the partner server. If the service is already disabled, this command resets the timeout for the DHCP service being disabled, which by default is set to 60 seconds. If fetching a single page of leases takes longer than the specified time, the partner server assumes that the synchronizing server has died and resumes its DHCP service. The connection of the synchronizing server with its partner is also protected by the timeout. If the synchronization of a single page of leases takes longer than the specified time, the synchronizing server terminates the connection and the synchronization fails. Both timeout values are controlled by a single configuration parameter, sync-timeout. The following configuration snippet demonstrates how to modify the timeout for automatic re-enabling of the DHCP service on the partner server and how to increase the timeout for fetching a single page of leases from 60 seconds to 90 seconds:

{
"Dhcp4": {

    ...

    "hooks-libraries": [
        {
            "library": "/usr/lib/kea/hooks/libdhcp_lease_cmds.so",
            "parameters": { }
        },
        {
            "library": "/usr/lib/kea/hooks/libdhcp_ha.so",
            "parameters": {
                "high-availability": [ {
                    "this-server-name": "server1",
                    "mode": "load-balancing",
                    "sync-timeout": 90000,
                    "peers": [
                        {
                            "name": "server1",
                            "url": "http://192.168.56.33:8000/",
                            "role": "primary"
                        },
                        {
                            "name": "server2",
                            "url": "http://192.168.56.66:8000/",
                            "role": "secondary"
                        }
                    ]
                } ]
            }
        }
    ],

    ...

}

It is important to note that extending this sync-timeout value may sometimes be insufficient to prevent issues with timeouts during lease-database synchronization. The control commands travel via the Control Agent, which also monitors incoming (with a synchronizing server) and outgoing (with a DHCP server) connections for timeouts. The DHCP server also monitors the connection from the Control Agent for timeouts. Those timeouts cannot currently be modified via configuration; extending these timeouts is only possible by modifying them in the Kea code and recompiling the server. The relevant constants are located in the Kea source at: src/lib/config/timeouts.h.

Pausing the HA State Machine

The high-availability state machine includes many different states described in detail in Server States. The server enters each state when certain conditions are met, most often taking into account the partner server’s state. In some states the server performs specific actions, e.g. synchronization of the lease database in the syncing state, or responding to DHCP queries according to the configured mode of operation in the load-balancing and hot-standby states.

By default, transitions between the states are performed automatically and the server administrator has no direct control over when the transitions take place; in most cases, the administrator does not need such control. In some situations, however, the administrator may want to “pause” the HA state machine in a selected state to perform some additional administrative actions before the server transitions to the next state.

Consider a server failure which results in the loss of the entire lease database. Typically, the server rebuilds its lease database when it enters the syncing state by querying the partner server for leases, but it is possible that the partner was also experiencing a failure and lacks lease information. In this case, it may be required to reconstruct lease databases on both servers from some external source, e.g. a backup server. If the lease database is to be reconstructed via the RESTful API, the servers should be started in the initial, i.e. waiting, state and remain in this state while leases are being added. In particular, the servers should not attempt to synchronize their lease databases nor start serving DHCP clients.

The HA hook library provides configuration parameters and a command to control pausing and resuming the HA state machine. The following configuration causes the HA state machine to pause in the waiting state after server startup.

"Dhcp4": {

    ...

    "hooks-libraries": [
        {
            "library": "/usr/lib/kea/hooks/libdhcp_lease_cmds.so",
            "parameters": { }
        },
        {
            "library": "/usr/lib/kea/hooks/libdhcp_ha.so",
            "parameters": {
                "high-availability": [ {
                    "this-server-name": "server1",
                    "mode": "load-balancing",
                    "peers": [
                        {
                            "name": "server1",
                            "url": "http://192.168.56.33:8000/",
                            "role": "primary"
                        },
                        {
                            "name": "server2",
                            "url": "http://192.168.56.66:8000/",
                            "role": "secondary"
                        }
                    ],
                    "state-machine": {
                        "states":  [
                            {
                                "state": "waiting",
                                "pause": "once"
                            }
                        ]
                    }
                } ]
            }
        }
    ],

    ...

}

The pause parameter value once denotes that the state machine should be paused upon the first transition to the waiting state; later transitions to this state will not cause the state machine to pause. Two other supported values of the pause parameter are always and never. The latter is the default value for each state, which instructs the server never to pause the state machine.

In order to “unpause” the state machine, the ha-continue command must be sent to the paused server. This command does not take any arguments. See Control Commands for High Availability for details about commands specific to the HA hook library.

It is possible to configure the state machine to pause in more than one state. Consider the following configuration:

"Dhcp4": {

    ...

    "hooks-libraries": [
        {
            "library": "/usr/lib/kea/hooks/libdhcp_lease_cmds.so",
            "parameters": { }
        },
        {
            "library": "/usr/lib/kea/hooks/libdhcp_ha.so",
            "parameters": {
                "high-availability": [ {
                    "this-server-name": "server1",
                    "mode": "load-balancing",
                    "peers": [
                        {
                            "name": "server1",
                            "url": "http://192.168.56.33:8000/",
                            "role": "primary"
                        },
                        {
                            "name": "server2",
                            "url": "http://192.168.56.66:8000/",
                            "role": "secondary"
                        }
                    ],
                    "state-machine": {
                        "states": [
                            {
                                "state": "ready",
                                "pause": "always"
                            },
                            {
                                "state": "partner-down",
                                "pause": "once"
                            }
                        ]
                    }
                } ]
            }
        }
    ],

    ...

}

This configuration instructs the server to pause the state machine every time it transitions to the ready state and upon the first transition to the partner-down state.

Refer to Server States for a complete list of server states. The state machine can be paused in any of the supported states; however, it is not practical to pause in the backup or terminated states because the server never transitions out of these states anyway.

Note

In the syncing state the server is paused before it makes an attempt to synchronize the lease database with a partner. To pause the state machine after lease-database synchronization, use the ready state instead.

Note

The state of the HA state machine depends on the state of the cooperating server. Therefore, pausing the state machine of one server may affect the operation of the partner server. For example: if the primary server is paused in the waiting state, the partner server will also remain in the waiting state until the state machine of the primary server is resumed and that server transitions to the ready state.

Control Agent Configuration

The Kea Control Agent describes in detail the Kea daemon, which provides a RESTful interface to control the Kea servers. The same functionality is used by the High Availability hook library to establish communication between the HA peers. Therefore, the HA library requires that the Control Agent (CA) be started for each DHCP instance within the HA setup. If the Control Agent is not started, the peers cannot communicate with a particular DHCP server (even if the DHCP server itself is online) and may eventually consider this server to be offline.

The following is an example configuration for the CA running on the same machine as the primary server. This configuration is valid for both the load-balancing and the hot-standby cases presented in previous sections.

{
"Control-agent": {
    "http-host": "192.168.56.33",

     // If enabling HA and multi-threading, the 8000 port is used by the HA
     // hook library http listener. When using HA hook library with
     // multi-threading to function, make sure the port used by dedicated
     // listener is different (e.g. 8001) than the one used by CA. Note
     // the commands should still be sent via CA. The dedicated listener
     // is specifically for HA updates only.
    "http-port": 8000,

    "control-sockets": {
        "dhcp4": {
            "socket-type": "unix",
            "socket-name": "/tmp/kea-dhcp4-ctrl.sock"
        },
        "dhcp6": {
            "socket-type": "unix",
            "socket-name": "/tmp/kea-dhcp6-ctrl.sock"
        }
    }
}
}

Since Kea 1.9.0, basic HTTP authentication is supported.

Multi-Threaded Configuration (HA+MT)

HA peer communication consists of specialized API commands sent between HA peers. Prior to Kea 1.9.7, each peer had to be paired with a local instance of kea-ctrl-agent in order to exchange commands. The agent received HA commands via HTTP, communicated via Linux socket with the local peer to carry out the command, and then sent the response back to the requesting peer via HTTP. To send HA commands, each peer opened its own HTTP client connection to the URL of each of its peers.

In Kea 1.9.7 and newer, it is possible to configure HA to use direct multi- threaded communication between peers. We refer to this mode as HA+MT. With HA+MT enabled, each peer runs its own dedicated, internal HTTP listener (i.e. server) which receives and responds to commands directly, thus eliminating the need for an agent to carry out HA protocol between peers. In addition, both the listener and client components use multi- threading to support multiple, concurrent connections between peers. By eliminating the agent and executing multiple command exchanges in parallel, HA throughput between peers should improve considerably in most situations.

The following parameters have been added to the HA configuration, to support HA+MT operation:

• enable-multi-threading - enables or disables multi-threading HA peer communication (HA+MT). Kea core multi-threading must be enabled for HA+MT to operate. When false (the default), the server operates as in earlier versions, relying on kea-ctrl-agent and using single-threaded HTTP client processing.

• http-dedicated-listener - enables or disables the creation of a dedicated, internal HTTP listener through which the server receives HA messages from its peers. The internal listener replaces the role of kea-ctrl-agent traffic, allowing peers to send their HA commands directly to each other. The listener listens on the peer’s url. When false (the default), the server relies on kea-ctrl-agent. This parameter has been provided largely for flexibility and testing; running HA+MT without dedicated listeners enabled will substantially limit HA throughput.

• http-listener-threads - indicates the maximum number of threads the dedicated listener should use. A value of 0 instructs the server to use the same number of threads that the Kea core is using for DHCP multi-threading. The default is 0.

• http-client-threads - indicates the maximum number of threads that should be used to send HA messages to its peers. A value of 0 instructs the server to use the same number of threads that the Kea core is using for DHCP multi-threading. The default is 0.

These parameters are grouped together under a map element, multi-threading, as illustrated below:

"Dhcp4": {

    ...
    "hooks-libraries": [
        {
            "library": "/usr/lib/kea/hooks/libdhcp_lease_cmds.so",
            "parameters": { }
        },
        {
            "library": "/usr/lib/kea/hooks/libdhcp_ha.so",
            "parameters": {
                "high-availability": [ {
                    "this-server-name": "server1",
                    ...
                    "multi-threading": {
                        "enable-multi-threading": true,
                        "http-dedicated-listener": true,
                        "http-listener-threads": 4,
                        "http-client-threads": 4
                    },
                    ...
                    "peers": [
                      // This is the configuration of this server instance.
                      {
                          "name": "server1",
                          // This specifies the URL of our server instance. Since the
                          // HA+MT uses direct connection, the DHCPv4 server open its own
                          // socket. Note it must be different than the one used by the
                          // CA (typically 8000). In this example, 8001 is used.
                          "url": "http://192.0.2.1:8001/",
                          // This server is primary. The other one must be secondary.
                          "role": "primary"
                      },
                      // This is the configuration of our HA peer.
                      {
                          "name": "server2",
                          // This specifies the URL of our server instance. Since the
                          // HA+MT uses direct connection, the DHCPv4 server open its own
                          // socket. Note it must be different than the one used by the
                          // CA (typically 8000). In this example, 8001 is used.
                          "url": "http://192.0.2.2:8001/",
                          // The partner is a secondary. Our is primary.
                          "role": "secondary"
                      }
                    ...

In the example above, HA+MT is enabled with four threads for the listener and four threads for the client.

Note

It is essential to configure the ports correctly. One common mistake is to configure CA to listen on port 8000 and also configure dedicated listeners on port 8000. In such a configuration, the communication will still work over CA, but it will be slow and the DHCP server will fail to bind sockets. Administrators should ensure that dedicated listeners use a different port (8001 is a suggested alternative); if ports are misconfigured or the ports dedicated to CA are used, the performance bottlenecks caused by the single-threaded nature of CA and the sequential nature of the UNIX socket that connects CA to DHCP servers will nullify any performance gains offered by HA+MT.

Parked-Packet Limit

Kea servers contain a mechanism by which the response to a client packet may be held, pending completion of hook library work. We refer to this as “parking” the packet. The HA hook library makes use of this mechanism. When an HA server needs to send a lease update to its peer(s) to notify it of the change to the lease, it will “park” the client response until the peer acknowledges the lease update. At that point, the server will “unpark” the response and send it to the client. This applies to client queries which cause lease changes, such as DHCPREQUEST for DHCPv4 and Request, Renew, and Rebind for DHCPv6. It does not apply to DHPCDISCOVERs (v4) or Solicits (v6).

There is a global parameter, parked-packet-limit, that may be used to limit the number of responses that may be parked at any given time. This acts as a form of congestion handling and protects the server from being swamped when the volume of client queries is outpacing the server’s ability to respond. Once the limit is reached, the server emits a log and drops any new responses until parking spaces are available.

In general, smaller values for the parking lot limit are likely to cause more drops but with shorter response times. Larger values are likely to result in fewer drops but with longer response times. Currently, the default value for parked-packet-limit is 256.

Warning

Using too small a value may result in an unnecessarily high drop rate, while using too large a value may lead to response times that are simply too long to be useful. A value of 0, while allowed, disables the limit altogether, but this is highly discouraged as it may lead to Kea servers becoming unresponsive to clients. Choosing the best value is very site-specific; we recommend users initially leave it at the default value of 256 and observe how the system behaves over time with varying load conditions.

"Dhcp6": {

    ...
    // Limit the number of concurrently parked packets to 128.
    "parked-packet-limit": 128,
    "hooks-libraries": [
        {
            "library": "/usr/lib/kea/hooks/libdhcp_lease_cmds.so",
            "parameters": { }
        },
        {
            "library": "/usr/lib/kea/hooks/libdhcp_ha.so",
            "parameters": {
                "high-availability": [ {
                    "this-server-name": "server1",
                    ...

Note

While parked-packet-limit is not specifically tied to HA, currently HA is the only ISC hook that employs packet parking.

Controlled Shutdown and Maintenance of DHCP servers

Having a pair of servers providing High Availability allows for controlled shutdown and maintenance of those servers without disrupting the DHCP service. For example, an administrator can perform an upgrade of one of the servers while the other one continues to respond to DHCP queries. When the first server is upgraded and back online, the upgrade can be performed for the second server.

A typical problem reported with early versions of the High Availability hook library was that the administrator did not have direct control over the state of the DHCP server. Shutting down one of the servers for maintenance did not necessarily cause the other server to start responding to all DHCP queries, because the failure-detection algorithm described in Scope Transition in a Partner-Down Case requires that the partner not respond for a configured period of time and, depending on the configuration, may also require that a number of DHCP requests not be responded to for a specified period of time. The maintenance procedure, however, requires that the administrator be able to instruct one of the servers to instantly start serving all DHCP clients, and the other server to instantly stop serving any DHCP clients, so it can be safely shut down.

The maintenance feature of the High Availability hook library addresses this situation. The ha-maintenance-start command was introduced to allow the administrator to put the pair of the active servers in states in which one of them is responding to all DHCP queries and the other one is awaiting shutdown.

Suppose that the HA setup includes two active servers, server1 and server2, and the latter needs to be shut down for maintenance. The administrator can send the ha-maintenance-start command to server1, as this is the server which is going to handle the DHCP traffic while the other one is offline. server1 responds with an error if its state or the partner’s state does not allow for a maintenance shutdown: for example, if maintenance is not supported for the backup server or if the server is in the terminated state. Also, an error is returned if the ha-maintenance-start request was already sent to the other server.

Upon receiving the ha-maintenance-start command, server1 sends the ha-maintenance-notify command to server2 to put it in the in-maintenance state. If server2 confirms, server1 transitions to the partner-in-maintenance state. This is similar to the partner-down state, except that in the partner-in-maintenance state server1 continues to send lease updates to server2 until the administrator shuts down server2. server1 now responds to all DHCP queries.

The administrator can now safely shut down server2 in the in-maintenance state and perform any necessary maintenance actions. While server2 is offline, server1 will obviously not be able to communicate with its partner, so it will immediately transition to the partner-down state; it will continue to respond to all DHCP queries but will no longer send lease updates to server2. Restarting server2 after the maintenance will trigger normal state negotiation, lease-database synchronization, and, ultimately, a transition to the normal load-balancing or hot-standby state. Maintenance can then be performed on server1, after sending the ha-maintenance-start command to server2.

If the ha-maintenance-start command was sent to the server and the server has transitioned to the partner-in-maintenance state, it is possible to transition both it and its partner back to their previous states to resume the normal operation of the HA pair. This is achieved by sending the ha-maintenance-cancel command to the server that is in the partner-in-maintenance state. However, if the server has already transitioned to the partner-down state as a result of detecting that the partner is offline, canceling the maintenance is no longer possible. In that case, it is necessary to restart the other server and allowing it to complete its normal state negotiation process.

Upgrading from Older HA Versions

To upgrade from an older HA hook library to the current version, the administrator must shut down one of the servers and rely on the failover mechanism to force the online server to transition to the partner-down state and start serving all DHCP clients. Once the hook library on the first server is upgraded to a current version, the ha-maintenance-start command can be used to upgrade the second server.

In such a case, shut down the server running the old version. Next, send the ha-maintenance-start command to the server that has been upgraded. This server should immediately transition to the partner-down state as it cannot communicate with its offline partner. In the partner-down state the first (upgraded) server will respond to all DHCP requests, allowing the administrator to perform the upgrade on the second server.

Note

Do not send the ha-maintenance-start command while the server running the old hook library is still online. The server receiving this command will return an error.

Control Commands for High Availability

Even though the HA hook library is designed to automatically resolve issues with DHCP service interruptions by redirecting the DHCP traffic to a surviving server and synchronizing the lease database as needed, it may be useful for the administrator to have more control over both servers’ behavior. In particular, it may be useful to be able to trigger lease-database synchronization on demand, or to manually set the HA scopes that are being served.

The backup server can sometimes be used to handle DHCP traffic if both active servers are down. The backup server does not perform the failover function automatically; thus, in order to use the backup server to respond to DHCP queries, the server administrator must enable this function manually.

The following sections describe commands supported by the HA hook library which are available for the administrator.

The ha-sync Command

The ha-sync command instructs the server to synchronize its local lease database with the selected peer. The server fetches all leases from the peer and updates any locally stored leases which are older than those fetched. It also creates new leases when any of those fetched do not exist in the local database. All leases that are not returned by the peer but are in the local database are preserved. The database synchronization is unidirectional; only the database on the server to which the command has been sent is updated. To synchronize the peer’s database, a separate ha-sync command must be issued to that peer.

Database synchronization may be triggered for both active and backup server types. The ha-sync command has the following structure (in a DHCPv4 example):

{
    "command": "ha-sync",
    "service": [ "dhcp4 "],
    "arguments": {
        "server-name": "server2",
        "max-period": 60
    }
}

When the server receives this command it first disables the DHCP service of the server from which it will be fetching leases, by sending the dhcp-disable command to that server. The max-period parameter specifies the maximum duration (in seconds) for which the DHCP service should be disabled. If the DHCP service is successfully disabled, the synchronizing server fetches leases from the remote server by issuing one or more lease4-get-page commands. When the lease-database synchronization is complete, the synchronizing server sends the dhcp-enable command to the peer to re-enable its DHCP service.

The max-period value should be sufficiently long to guarantee that it does not elapse before the synchronization is completed. Otherwise, the DHCP server will automatically enable its DHCP function while the synchronization is still in progress. If the DHCP server subsequently allocates any leases during the synchronization, those new (or updated) leases will not be fetched by the synchronizing server, leading to database inconsistencies.

The ha-scopes Command

This command allows an administrator to modify the HA scopes being served. Consult Load-Balancing Configuration and Hot-Standby Configuration to learn which scopes are available for the different HA modes of operation. The ha-scopes command has the following structure (in a DHCPv4 example):

{
    "command": "ha-scopes",
    "service": [ "dhcp4" ],
    "arguments": {
        "scopes": [ "HA_server1", "HA_server2" ]
    }
}

This command configures the server to handle traffic from both the “HA_server1” and “HA_server2” scopes. To disable all scopes specify an empty list:

{
    "command": "ha-scopes",
    "service": [ "dhcp4 "],
    "arguments": {
        "scopes": [ ]
    }
}

The ha-continue Command

This command is used to resume the operation of the paused HA state machine, as described in Pausing the HA State Machine. It takes no arguments, so the command structure is simply:

{
    "command": "ha-continue",
    "service": [ "dhcp4" ]
}

The ha-heartbeat Command

The Server States section describes how the ha-heartbeat command is used by a pair of active HA servers to detect one partner’s failure. This command, however, can also be sent by the system administrator to one or both servers to check their HA state. This allows a monitoring system to be deployed on the HA enabled servers to periodically check whether they are operational or whether any manual intervention is required. The ha-heartbeat command takes no arguments:

{
    "command": "ha-heartbeat",
    "service": [ "dhcp4" ]
}

Upon successful communication with the server, a response similar to this should be returned:

{
   "result": 0,
   "text": "HA peer status returned.",
   "arguments":
       {
           "state": "partner-down",
           "date-time": "Thu, 07 Nov 2019 08:49:37 GMT",
           "scopes": [ "server1" ],
           "unsent-update-count": 123
       }
}

The returned state value should be one of the values listed in Server States. In the example above, the partner-down state is returned, which indicates that the server which responded to the command believes that its partner is offline; thus, it is serving all DHCP requests sent to the servers. To ensure that the partner is indeed offline, the administrator should send the ha-heartbeat command to the second server. If sending the command fails, e.g. due to an inability to establish a TCP connection to the Control Agent, or if the Control Agent reports issues with communication with the DHCP server, it is very likely that the server is not running.

The date-time parameter conveys the server’s notion of time.

The unsent-update-count value is a cumulative count of all unsent lease updates since the server was booted; its value is set to 0 when the server is started. It is never reset to 0 during the server’s operation, even after the partner synchronizes the database. It is incremented by the partner sending the heartbeat response when it cannot send the lease update. For example, suppose the failure is a result of a temporary communication interruption. In that case, the partner receiving the partner-down heartbeat response tracks the value changes and can determine, once communication is reestablished, whether there are any new lease updates that it did not receive. If the values on both servers do not match, it is an indication that the partner should synchronize its lease database. A non-zero value itself is not an indication of any present issues with lease updates, but a constantly incrementing value is.

The typical response returned by one server when both are operational is:

{
   "result": 0,
   "text": "HA peer status returned.",
   "arguments":
       {
           "state": "load-balancing",
           "date-time": "Thu, 07 Nov 2019 08:49:37 GMT",
           "scopes": [ "server1" ],
           "unsent-update-count": 0
       }
}

In most cases, the ha-heartbeat command should be sent to both HA-enabled servers to verify the state of the entire HA setup. In particular, if one of the servers indicates that it is in the load-balancing state, it means that this server is operating as if its partner is functional. When a partner goes down, it takes some time for the surviving server to realize it. The Scope Transition in a Partner-Down Case section describes the algorithm which the surviving server follows before it transitions to the partner-down state. If the ha-heartbeat command is sent during the time window between the failure of one of the servers and the transition of the surviving server to the partner-down state, the response from the surviving server does not reflect the failure. Resending the command detects the failure once the surviving server has entered the partner-down state.

The status-get Command

status-get is a general-purpose command supported by several Kea daemons, not only the DHCP servers. However, when sent to a DHCP server with HA enabled, it can be used to get insight into the details of the HA-specific server status. Not only does the response contain the status information of the server receiving this command, but also the information about its partner if it is available.

The following is an example response to the status-get command, including the HA status of two load-balancing servers:

{
    "result": 0,
    "text": "",
    "arguments": {
        "pid": 1234,
        "uptime": 3024,
        "reload": 1111,
        "high-availability": [
            {
                "ha-mode": "load-balancing",
                "ha-servers": {
                    "local": {
                        "role": "primary",
                        "scopes": [ "server1" ],
                        "state": "load-balancing"
                    },
                    "remote": {
                        "age": 10,
                        "in-touch": true,
                        "role": "secondary",
                        "last-scopes": [ "server2" ],
                        "last-state": "load-balancing",
                        "communication-interrupted": true,
                        "connecting-clients": 2,
                        "unacked-clients": 1,
                        "unacked-clients-left": 2,
                        "analyzed-packets": 8
                    }
                }
            }
        ],
        "multi-threading-enabled": true,
        "thread-pool-size": 4,
        "packet-queue-size": 64,
        "packet-queue-statistics": [ 0.2, 0.1, 0.1 ]
    }
}

The high-availability argument is a list which currently comprises only one element.

The ha-servers map contains two structures: local and remote. The former contains the status information of the server which received the command, while the latter contains the status information known to the local server about the partner. The role of the partner server is gathered from the local configuration file, and thus should always be available. The remaining status information, such as last-scopes and last-state, is not available until the local server communicates with the remote by successfully sending the ha-heartbeat command. If at least one such communication has taken place, the returned value of the in-touch parameter is set to true. By examining this value, the command’s sender can determine whether the information about the remote server is reliable.

The last-scopes and last-state parameters contain information about the HA scopes served by the partner and its state. This information is gathered during the heartbeat command exchange, so it may not be accurate if a communication problem occurs between the partners and this status information is not refreshed. In such a case, it may be useful to send the status-get command to the partner server directly to check its current state. The age parameter specifies the age of the information from the partner, in seconds.

The communication-interrupted boolean value indicates whether the server receiving the status-get command (the local server) has been unable to communicate with the partner longer than the duration specified as max-response-delay. In such a situation, the active servers are considered to be in the communication-interrupted state. At this point, the local server may start monitoring the DHCP traffic directed to the partner to see if the partner is responding to this traffic. More about the failover procedure can be found in Load-Balancing Configuration.

The connecting-clients, unacked-clients, unacked-clients-left, and analyzed-packets parameters were introduced along with the communication-interrupted parameter and they convey useful information about the state of the DHCP traffic monitoring in the communication-interrupted state. Once the server leaves the communication-interrupted state, these parameters are all reset to 0.

These parameters have the following meaning in the communication-interrupted state:

• connecting-clients - this is the number of different clients which have attempted to get a lease from the remote server. These clients are differentiated by their MAC address and client identifier (in DHCPv4) or DUID (in DHCPv6). This number includes “unacked” clients (for which the “secs” field or “elapsed time” value exceeded the max-response-delay).

• unacked-clients - this is the number of different clients which have been considered “unacked”, i.e. the clients which have been trying to get the lease longer than the value of the “secs” field, or for which the “elapsed time” exceeded the max-response-delay setting.

• unacked-clients-left - this indicates the number of additional clients which have to be considered “unacked” before the server enters the partner-down state. This value decreases when the unacked-clients value increases. The local server enters the partner-down state when this value decreases to 0.

• analyzed-packets - this is the total number of packets directed to the partner server and analyzed by the local server since entering the communication interrupted state. It includes retransmissions from the same clients.

Monitoring these values helps to predict when the local server will enter the partner-down state or to understand why the server has not yet entered this state.

The ha-mode parameter returns the HA mode of operation selected using the mode parameter in the configuration file. It can hold one of the following values: load-balancing, hot-standby, or passive-backup.

The status-get response has the format described above only in the load-balancing and hot-standby modes. In the passive-backup mode the remote map is not included in the response because in this mode there is only one active server (local). The response includes no information about the status of the backup servers.

The ha-maintenance-start Command

This command is used to initiate transition of the server’s partner into the in-maintenance state and the transition of the server receiving the command into the partner-in-maintenance state. See the Controlled Shutdown and Maintenance of DHCP servers section for details.

{
    "command": "ha-maintenance-start",
    "service": [ "dhcp4" ]
}

The ha-maintenance-cancel Command

This command is used to cancel the maintenance previously initiated using the ha-maintenance-start command. The server receiving this command will first send ha-maintenance-notify, with the cancel flag set to true, to its partner. Next, the server reverts from the partner-in-maintenance state to its previous state. See the Controlled Shutdown and Maintenance of DHCP servers section for details.

{
    "command": "ha-maintenance-cancel",
    "service": [ "dhcp4" ]
}

The ha-maintenance-notify Command

This command is sent by the server receiving the ha-maintenance-start or the ha-maintenance-cancel command to its partner, to cause the partner to transition to the in-maintenance state or to revert from this state to a previous state. See the Controlled Shutdown and Maintenance of DHCP servers section for details.

{
    "command": "ha-maintenance-notify",
    "service": [ "dhcp4" ],
    "arguments": {
        "cancel": false
    }
}

Warning

The ha-maintenance-notify command is not meant to be used by system administrators. It is used for internal communication between a pair of HA-enabled DHCP servers. Direct use of this command is not supported and may produce unintended consequences.

The ha-reset Command

This command causes the server to reset its High Availability state machine by transitioning it to the waiting state. A partner in the communication-recovery state may send this command to cause the server to synchronize its lease database. Database synchronization is required when the partner has failed to send all lease database updates after re-establishing connection after a temporary connection failure. It is also required when the delayed-updates-limit is exceeded, when the server is in the communication-recovery state.

A server administrator may send the command to reset a misbehaving state machine.

This command includes no arguments:

{
    "command": "ha-reset",
    "service": [ "dhcp4" ]
}

And elicits the response:

{
    "result": 0,
    "text": "HA state machine reset."
}

If the server receiving this command is already in the waiting state, the command has no effect.

The ha-sync-complete-notify Command

A server sends this command to its partner to signal that it has completed lease-database synchronization. The partner may enable its DHCP service if it can allocate new leases in its current state. The partner does not enable the DHCP service in the partner-down state until it sends a successful heartbeat test to its partner server. If the connection is still unavailable, the server in the partner-down state enables its own DHCP service to continue responding to clients.

This command includes no arguments:

{
    "command": "ha-sync-complete-notify",
    "service": [ "dhcp4" ]
}

And elicits the response:

{
    "result": 0,
    "text": "Server successfully notified about the synchronization completion."
}

Warning

The ha-sync-complete-notify command is not meant to be used by system administrators. It is used for internal communication between a pair of HA-enabled DHCP servers. Direct use of this command is not supported and may produce unintended consequences.

stat_cmds: Supplemental Statistics Commands

This library provides additional commands for retrieving lease statistics from Kea DHCP servers. These commands were added to address an issue with obtaining accurate lease statistics in deployments running multiple Kea servers that use a shared lease backend. The in-memory statistics kept by individual servers only track lease changes made by that server; thus, in a deployment with multiple servers (e.g. two kea-dhcp6 servers using the same PostgreSQL database for lease storage), these statistics are incomplete. The MySQL and PostgreSQL backends in Kea track lease allocation changes as they occur via database triggers. Additionally, all the lease backends were extended to support retrieving lease statistics for a single subnet, a range of subnets, or all subnets. Finally, this library provides commands for retrieving these statistics.

Note

This library may only be loaded by the kea-dhcp4 or kea-dhcp6 process.

The commands currently provided by this library are:

• stat-lease4-get - fetches DHCPv4 lease statistics.

• stat-lease6-get - fetches DHCPv6 lease statistics.

The statistics commands library is part of the open source code and is available to every Kea user.

All commands use JSON syntax and can be issued directly to the servers via either the control channel (see Management API) or the Control Agent (see The Kea Control Agent).

This library may be loaded by both the kea-dhcp4 and kea-dhcp6 servers. It is loaded in the same way as other libraries and currently has no parameters:

"Dhcp6": {
    "hooks-libraries": [
        {
            "library": "/path/libdhcp_stat_cmds.so"
        }
        ...
    ]
}

In a deployment with multiple Kea DHCP servers sharing a common lease storage, this hook library may be loaded by any or all of the servers. However, a server’s response to a stat-lease[46]-get command will only contain data for subnets known to that server. In other words, if a subnet does not appear in a server’s configuration, Kea will not retrieve statistics for it.

The stat-lease4-get, stat-lease6-get Commands

The stat-lease4-get and stat-lease6-get commands fetch lease statistics for a range of known subnets. The range of subnets is determined through the use of optional command input parameters:

• subnet-id - the ID of the subnet for which lease statistics should be fetched; used to get statistics for a single subnet. If the subnet does not exist, the command result code is 3 (i.e. CONTROL_RESULT_EMPTY).

• subnet-range - a pair of subnet IDs which describe an inclusive range of subnets for which statistics should be retrieved. The range may include one or more IDs that correspond to no subnet; in this case, the command only outputs lease statistics for those that exist. However, if the range does not include any known subnets, the command result code is 3 (i.e. CONTROL_RESULT_EMPTY).

  • first-subnet-id - the ID of the first subnet in the range.

  • last-subnet-id - the ID of the last subnet in the range.

The use of subnet-id and subnet-range are mutually exclusive. If no parameters are given, the result will contain data for all known subnets. Note that in configurations with many subnets, this can result in a large response.

The following command fetches lease statistics for all known subnets from a kea-dhcp4 server:

{
  "command": "stat-lease4-get"
}

The following command fetches lease statistics for subnet ID 10 from a kea-dhcp6 server:

{
  "command": "stat-lease6-get",
  "arguments": {
    "subnet-id" : 10
  }
}

The following command fetches lease statistics for all subnets with IDs in the range 10 through 50 from a kea-dhcp4 server:

{
  "command": "stat-lease4-get",
  "arguments": {
    "subnet-range" {
      "first-subnet-id": 10,
      "last-subnet-id": 50,
    }
  }
}

The response to either command will contain three elements:

• result - a numeric value indicating the outcome of the command where:

  • 0 - the command was successful;

  • 1 - an error occurred, and an explanation is the “text” element; or

  • 2 - the fetch found no matching data.

• text - an explanation of the command outcome. When the command succeeds, it contains the command name along with the number of rows returned.

• arguments - a map containing the data returned by the command as the element “result-set”, which is patterned after SQL statement responses:

  • columns - a list of text column labels. The columns returned for DHCPv4 are:

    • subnet-id - the ID of the subnet.

    • total-addresses - the total number of addresses available for DHCPv4 management in the subnet. In other words, this is the sum of all addresses in all the configured pools in the subnet.

    • cumulative-assigned-addresses - the cumulative number of addresses in the subnet that have been assigned to a client by the server since it started.

    • assigned-addresses - the number of addresses in the subnet that are currently assigned to a client.

    • declined-addresses - the number of addresses in the subnet that are currently declined and are thus unavailable for assignment.

  • The columns returned for DHCPv6 are:

    • subnet-id - the ID of the subnet.

    • total-nas - the number of NA addresses available for DHCPv6 management in the subnet. In other words, this is the sum of all the NA addresses in all the configured NA pools in the subnet.

    • cumulative-assigned-nas - the cumulative number of NA addresses in the subnet that have been assigned to a client by the server since it started.

    • assigned-nas - the number of NA addresses in the subnet that are currently assigned to a client.

    • declined-nas - the number of NA addresses that are currently declined and are thus unavailable for assignment.

    • total-pds - the total number of PD prefixes available of DHCPv6 management in the subnet. In other words, this is the sum of all prefixes in all the configured prefix pools in the subnet.

    • cumulative-assigned-pds - the cumulative number of PD prefixes in the subnet that have been assigned to a client by the server since it started.

    • assigned-pds - the number of PD prefixes in the subnet that are currently assigned to a client.

  • rows - a list of rows, one per subnet ID. Each row contains a data value corresponding to and in the same order as each column listed in “columns” for a given subnet.

  • timestamp - the textual date and time the data were fetched, expressed as GMT.

The response to a DHCPv4 command might look as follows:

{
  "result": 0,
  "text": "stat-lease4-get: 2 rows found",
  "arguments": {
    "result-set": {
      "columns": [ "subnet-id", "total-addresses", "cumulative-assigned-addresses", "assigned-addresses", "declined-addresses" ]
      "rows": [
        [ 10, 256, 300, 111, 0 ],
        [ 20, 4098, 2034, 2034, 4 ]
      ],
    "timestamp": "2018-05-04 15:03:37.000000"
    }
  }
}

The response to a DHCPv6 command might look as follows, assuming subnet 10 has no prefix pools, subnet 20 has no NA pools, and subnet 30 has both NA and PD pools:

{
  "result": 0,
  "text": "stat-lease6-get: 2 rows found",
  "arguments": {
    "result-set": {
      "columns": [ "subnet-id", "total-nas", "cumulative-assigned-nas", "assigned-nas", "declined-nas", "total-pds", "cumulative-assigned-pds", "assigned-pds" ]
      "rows": [
        [ 10, 4096, 5000, 2400, 3, 0, 0, 0],
        [ 20, 0, 0, 0, 0, 1048, 300, 233 ]
        [ 30, 256, 60, 60, 0, 1048, 15, 15 ]
      ],
    "timestamp": "2018-05-04 15:03:37.000000"
    }
  }
}

radius: RADIUS Server Support

The RADIUS hook library allows Kea to interact with two types of RADIUS servers: access and accounting. Although the most common DHCP and RADIUS integration is done on the DHCP relay-agent level (DHCP clients send DHCP packets to DHCP relays; those relays contact the RADIUS server and depending on the response either send the packet to the DHCP server or drop it), it does require DHCP relay hardware to support RADIUS communication. Also, even if the relay has the necessary support, it is often not flexible enough to send and receive additional RADIUS attributes. As such, the alternative looks more appealing: to extend the DHCP server to talk to RADIUS directly. That is the goal of this library.

Note

This library can only be loaded by the kea-dhcp4 or the kea-dhcp6 process.

The major feature of this hook library is the ability to use RADIUS authorization. When a DHCP packet is received, the Kea server sends an Access-Request to the RADIUS server and waits for a response. The server then sends back either an Access-Accept with specific client attributes, or an Access-Reject. There are two cases supported here: first, the Access-Accept includes a Framed-IP-Address attribute (for DHCPv4) or a Framed-IPv6-Address attribute (for DHCPv6), which are interpreted by Kea as instructions to assign the specified IPv4 or IPv6 address. This effectively means RADIUS can act as an address-reservation database.

The second supported case is the ability to assign clients to specific pools based on a RADIUS response. In this case, the RADIUS server sends back an Access-Accept with a Framed-Pool attribute. For both DHCPv4 and DHCPv6, Kea interprets this attribute as a client class. With the addition of the ability to limit access to pools to specific classes (see Configuring Pools With Class Information), RADIUS can be used to force the client to be assigned a dynamic address from a specific pool. Furthermore, the same mechanism can be used to control what kind of options the client gets if there are DHCP options specified for a particular class.

Compilation and Installation of the RADIUS Hook

The following section describes how to compile and install the software on CentOS 7.0. Other systems may differ slightly.

Note

ISC provides Kea software and hooks in convenient-to-use native Alpine, deb, and RPM packages. This includes the RADIUS hook and the required patched version of the FreeRADIUS client library. The software compilation for RADIUS is complicated; unless there are specific reasons to compile it, administrators should seriously consider using native packages.

STEP 1: Install dependencies

Several tools are needed to build the dependencies and Kea itself. The following commands should install them:

$ sudo rpm -Uvh https://dl.fedoraproject.org/pub/epel/epel-release-latest-7.noarch.rpm
$ sudo yum install gcc-g++ openssl-devel log4cplus-devel wget git

STEP 2: Install FreeRADIUS

The Kea RADIUS hook library uses the FreeRADIUS client library to conduct RADIUS communication. Unfortunately, the standard 1.1.7 release available from the project website https://freeradius.org/sub_projects/ has several serious deficiencies; ISC engineers observed a segmentation fault during testing. Also, the base version of the library does not offer asynchronous transmissions, which are essential for effective accounting implementation. Both of these issues were addressed by ISC engineers, and the changes have been reported to the FreeRADIUS client project. Acceptance of those changes is outside of ISC’s control, so until those are processed, it is strongly recommended to use the FreeRADIUS client with ISC’s patches. To download and compile this version, please use the following steps:

$ git clone https://github.com/fxdupont/freeradius-client.git
$ cd freeradius-client/
$ git checkout iscdev
$ ./configure
$ make
$ sudo make install

Additional parameters may be passed to the configure script, if needed. The FreeRADIUS client will be installed in /usr/local, which is the default path where Kea will look for it. It can be installed in a different directory; if so, make sure to add that path to the configure script when compiling Kea.

STEP 3: Install a recent Boost version

Kea requires a reasonably recent Boost version. Unfortunately, the version available in CentOS 7 is too old, so a newer Boost version is necessary. Furthermore, CentOS 7 has an old version of the g++ compiler that does not handle the latest Boost versions. Fortunately, Boost 1.65 meets both requirements; it is both recent enough for Kea and can be compiled using the g++ 4.8 version in CentOS.

To download and compile Boost 1.65, please use the following commands:

$ wget -nd https://boostorg.jfrog.io/artifactory/main/release/1.65.1/source/boost_1_65_1.tar.gz
$ tar -zxvf boost_1_65_1.tar.gz
$ cd boost_1_65_1/
$ ./bootstrap.sh
$ ./b2 --without-python
$ sudo ./b2 install

Note that the b2 script may optionally take extra parameters; one of them specifies the destination path where the sources are to be compiled.

Alternatively, some systems provide newer Boost packages. For example, CentOS 7 provides boost169-devel. If it is installed with yum install boost169-devel, Kea must be pointed to it with:

$ ./configure --with-boost-include=/usr/include/boost169 --with-boost-lib-dir=/usr/lib64/boost169

STEP 4: Compile and install Kea

Obtain the Kea sources either by downloading them from the git repository or extracting the tarball. Use one of these commands to obtain the Kea sources.

Choice 1: Retrieve from GitHub

$ git clone https://github.com/isc-projects/kea.git

Choice 2: Retrieve a tarball and extract it

$ tar -zxvf kea-2.1.6.tar.gz

The next step is to extract the premium Kea package that contains the RADIUS repository into the Kea sources. After the tarball is extracted, the Kea sources should have a premium/ subdirectory.

$ cd kea
$ tar -zxvf ../kea-premium-radius-2.1.6.tar.gz

Once this is done, verify that the Kea sources look similar to this:

$ ls -l
total 952
-rw-r--r--   1 thomson  staff    6192 Apr 25 17:38 AUTHORS
-rw-r--r--   1 thomson  staff   29227 Apr 25 17:38 COPYING
-rw-r--r--   1 thomson  staff  360298 Apr 25 20:00 ChangeLog
-rw-r--r--   1 thomson  staff     645 Apr 25 17:38 INSTALL
-rw-r--r--   1 thomson  staff    5015 Apr 25 17:38 Makefile.am
-rw-r--r--   1 thomson  staff     587 Apr 25 17:38 README
-rw-r--r--   1 thomson  staff   62323 Apr 25 17:38 configure.ac
drwxr-xr-x  12 thomson  staff     408 Apr 26 19:04 doc
drwxr-xr-x   7 thomson  staff     238 Apr 25 17:38 examples
drwxr-xr-x   5 thomson  staff     170 Apr 26 19:04 ext
drwxr-xr-x   8 thomson  staff     272 Apr 26 19:04 m4macros
drwxr-xr-x  20 thomson  staff     680 Apr 26 11:22 premium
drwxr-xr-x  10 thomson  staff     340 Apr 26 19:04 src
drwxr-xr-x  14 thomson  staff     476 Apr 26 19:04 tools

The makefiles must be regenerated using autoreconf.

The next step is to configure Kea, and there are several essential steps necessary here. Running autoreconf -if is necessary to compile the premium package that contains RADIUS. Also, the --with-freeradius option is necessary to tell Kea where the FreeRADIUS client sources can be found. Also, since the non-standard Boost is used, the path to it must be specified.

$ autoreconf -i
$ ./configure --with-freeradius=/path/to/freeradius --with-boost-include=/path/to/boost --with-boost-lib-dir=/path/to/boost/state/lib

For example, assuming the FreeRADIUS client was installed in the default directory (/usr/local) and the Boost 1.65 sources were compiled in /home/thomson/devel/boost1_65_1, the configure path should look as follows:

$ ./configure --with-freeradius=/usr/local \
      --with-boost-include=/home/thomson/devel/boost_1_65_1 \
      --with-boost-lib-dir=/home/thomson/devel/boost_1_65_1/stage/lib

After some checks, the configure script should print a report similar to the following:

       Kea source configure results:
    -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

Package:
  Name:              kea
  Version:           2.1.6
  Extended version:  2.1.6 (tarball)
  OS Family:         Linux

  Hooks directory:   /usr/local/lib/kea/hooks
  Premium hooks:     yes
  Included Hooks:    forensic_log flex_id host_cmds subnet_cmds radius host_cache

C++ Compiler:
  CXX:             g++ --std=c++11
  CXX_VERSION:     g++ (GCC) 4.8.5 20150623 (Red Hat 4.8.5-16)
  CXX_STANDARD:    201103
  DEFS:            -DHAVE_CONFIG_H
  CPPFLAGS:         -DOS_LINUX  -DBOOST_ASIO_HEADER_ONLY
  CXXFLAGS:        -g -O2
  LDFLAGS:          -lpthread
  KEA_CXXFLAGS:     -Wall -Wextra -Wnon-virtual-dtor -Wwrite-strings -Woverloaded-virtual -Wno-sign-compare -pthread -Wno-missing-field-initializers -fPIC

Python:
  PYTHON_VERSION:  not needed (because kea-shell is disabled)

Boost:
  BOOST_VERSION:   1.65.1
  BOOST_INCLUDES:  -I/home/thomson/devel/boost_1_65_1
  BOOST_LIBS:      -L/home/thomson/devel/boost_1_65_1/stage/lib  -lboost_system

OpenSSL:
  CRYPTO_VERSION:  OpenSSL 1.0.2k  26 Jan 2017
  CRYPTO_CFLAGS:
  CRYPTO_INCLUDES:
  CRYPTO_LDFLAGS:
  CRYPTO_LIBS:     -lcrypto

Botan: no

Log4cplus:
  LOG4CPLUS_VERSION:  1.1.3
  LOG4CPLUS_INCLUDES: -I/usr/include
  LOG4CPLUS_LIBS:     -L/usr/lib -L/usr/lib64 -llog4cplus

Flex/bison:
  FLEX:  flex
  BISON: bison -y

MySQL:
  no

PostgreSQL:
  no

Google Test:
  no

FreeRADIUS client:
  FREERADIUS_INCLUDE:    -I/usr/local/include
  FREERADIUS_LIB:        -L/usr/local/lib -lfreeradius-client
  FREERADIUS_DICTIONARY: /usr/local/etc/radiusclient/dictionary

Developer:
  Enable Debugging:       no
  Google Tests:           no
  Valgrind:               not found
  C++ Code Coverage:      no
  Logger checks:          no
  Generate Documentation: no
  Parser Generation:      no
  Kea-shell:              no
  Perfdhcp:               no

Please make sure that the compilation includes the following:

• RADIUS listed in Included Hooks;

• FreeRADIUS client directories printed and pointing to the right directories;

• Boost version at least 1.65.1. The versions available in CentOS 7 (1.48 and 1.53) are too old.

Once the configuration is complete, compile Kea using make. If the system has more than one core, using the -jN option is recommended to speed up the build.

$ make -j5
$ sudo make install

RADIUS Hook Configuration

The RADIUS hook is a library that must be loaded by either DHCPv4 or DHCPv6 Kea servers. Unlike some other available hook libraries, this one takes many parameters. For example, this configuration could be used:

"Dhcp4": {

# Your regular DHCPv4 configuration parameters here.

"hooks-libraries": [
{
    # Note that RADIUS requires host-cache for proper operation,
    # so that library is loaded as well.
    "library": "/usr/local/lib/kea/hooks/libdhcp_host_cache.so"
},
{
    "library": "/usr/local/lib/kea/hooks/libdhc_radius.so",
    "parameters": {

        # Specify where FreeRADIUS dictionary could be located
        "dictionary": "/usr/local/etc/freeradius/dictionary",

        # Specify which address to use to communicate with RADIUS servers
        "bindaddr": "*",

        # more RADIUS parameters here
    }
} ]

RADIUS is a complicated environment. As such, it is not feasible to provide a default configuration that works for everyone. However, we do have an example that showcases some of the more common features. Please see doc/examples/kea4/hooks-radius.json in the Kea sources.

The RADIUS hook library supports the following global configuration flags, which correspond to FreeRADIUS client library options:

• bindaddr (default *) - specifies the address to be used by the hook library in communication with RADIUS servers. The * special value tells the kernel to choose the address.

• canonical-mac-address (default false) - specifies whether MAC addresses in attributes follow the canonical RADIUS format (lowercase pairs of hexadecimal digits separated by -).

• client-id-pop0 (default false) - used with flex-id, removes the leading zero (or pair of zeroes in DHCPv6) type in client-id (duid in DHCPv6). Implied by client-id-printable.

• client-id-printable (default false) - checks whether the client-id/duid content is printable and uses it as is instead of in hexadecimal. Implies client-id-pop0 and extract-duid as 0 and 255 are not printable.

• deadtime (default 0) - is a mechanism to try unresponsive servers after responsive servers. Its value specifies the number of seconds after which a server is considered not to have answered, so 0 disables the mechanism. As the asynchronous communication does not use locks or atomics, it is recommended not to use this feature when running in this mode.

• dictionary (default set by configure at build time) - is the attribute and value dictionary. Note that it is a critical parameter. Dictionary examples can be found in the FreeRADIUS repository under the etc/ directory.

• extract-duid (default true) - extracts the embedded duid from an RFC 4361-compliant DHCPv4 client-id. Implied by client-id-printable.

• identifier-type4 (default client-id) - specifies the identifier type to build the User-Name attribute. It should be the same as the host identifier, and when the flex-id hook library is used the replace-client-id must be set to true; client-id is used with client-id-pop0.

• identifier-type6 (default duid) - specifies the identifier type to build the User-Name attribute. It should be the same as the host identifier, and when the flex-id hook library is used the replace-client-id must be set to true; duid is used with client-id-pop0.

• realm (default "") - is the default realm.

• reselect-subnet-address (default false) - uses the Kea reserved address/RADIUS Framed-IP-Address or Framed-IPv6-Address to reselect subnets where the address is not in the subnet range.

• reselect-subnet-pool (default false) - uses the Kea client-class/RADIUS Frame-Pool to reselect subnets where no available pool can be found.

• retries (default 3) - is the number of retries before trying the next server. Note that it is not supported for asynchronous communication.

• session-history (default "") - is the name of the file providing persistent storage for accounting session history.

• timeout (default 10) - is the number of seconds during which a response is awaited.

When reselect-subnet-pool or reselect-subnet-address is set to true at the reception of RADIUS Access-Accept, the selected subnet is checked against the client-class name or the reserved address; if it does not match, another subnet is selected among matching subnets.

Two services are supported:

• access - the authentication service.

• accounting - the accounting service.

Configuration of services is divided into two parts:

• Servers that define RADIUS servers that the library is expected to contact. Each server may have the following items specified:

  • name - specifies the IP address of the server (it is possible to use a name which will be resolved, but it is not recommended).

  • port (default RADIUS authentication or accounting service) - specifies the UDP port of the server. Note that the FreeRADIUS client library by default uses ports 1812 (authorization) and 1813 (accounting). Some server implementations use 1645 (authorization) and 1646 (accounting). The port parameter may be used to adjust as needed.

  • secret - authenticates messages.

  There may be up to eight servers. Note that when no server is specified, the service is disabled.

• Attributes which define additional information that the Kea server sends to a RADIUS server. The parameter must be identified either by a name or type. Its value can be specified in one of three possible ways: data (which defines a plain text value), raw (which defines the value in hex), or expr (which defines an expression that is evaluated for each incoming packet independently).

  • name - the name of the attribute.

  • type - the type of the attribute. Either the type or the name must be provided, and the attribute must be defined in the dictionary.

  • data - the first of three ways to specify the attribute content. The data entry is parsed by the FreeRADIUS library, so values defined in the dictionary of the attribute may be used.

  • raw - the second of three ways to specify the attribute content; it specifies the content in hexadecimal. Note that it does not work with integer-content attributes (date, integer, and IPv4 address); a string-content attribute (string, IPv6 address, and IPv6 prefix) is required.

  • expr - the last way to specify the attribute content. It specifies an evaluation expression which must return a not-empty string when evaluated with the DHCP query packet. Currently this is restricted to the access service.

For example, to specify a single access server available on localhost that uses “xyz123” as a secret, and tell Kea to send three additional attributes (Password, Connect-Info, and Configuration-Token), the following snippet could be used:

"parameters": {

    # Other RADIUS parameters here

    "access": {

        # This starts the list of access servers
        "servers": [
        {
            # These are parameters for the first (and only) access server
            "name": "127.0.0.1",
            "port": 1812,
            "secret": "xyz123"
        }
        # Additional access servers could be specified here
        ],

        # This defines a list of additional attributes Kea will send to each
        # access server in Access-Request.
        "attributes": [
        {
            # This attribute is identified by name (must be present in the
            # dictionary) and has static value (i.e. the same value will be
            # sent to every server for every packet)
            "name": "Password",
            "data": "mysecretpassword"
        },
        {
            # It is also possible to specify an attribute using its type,
            # rather than a name. 77 is Connect-Info. The value is specified
            # using hex. Again, this is a static value. It will be sent the
            # same for every packet and to every server.
            "type": 77,
            "raw": "65666a6a71"
        },
        {
            # This example shows how an expression can be used to send dynamic
            # value. The expression (see Section 13) may take any value from
            # the incoming packet or even its metadata (e.g. the interface
            # it was received over from)
            "name": "Configuration-Token",
            "expr": "hexstring(pkt4.mac,':')"
        }
        ] # End of attributes
    }, # End of access

    # Accounting parameters.
    "accounting": {
        # This starts the list of accounting servers
        "servers": [
        {
            # These are parameters for the first (and only) accounting server
            "name": "127.0.0.1",
            "port": 1813,
            "secret": "sekret"
        }
        # Additional accounting servers could be specified here
        ]
    }

}

Customization is sometimes required for certain attributes by devices belonging to various vendors. This is a great way to leverage the expression evaluation mechanism. For example, MAC addresses which might be used as a convenience value for the User-Name attribute are most likely to appear in colon-hexadecimal notation (de:ad:be:ef:ca:fe), but they might need to be expressed in hyphen-hexadecimal notation (de-ad-be-ef-ca-fe). Here’s how to specify that:

{
   "parameters": {
      "access": {
         "attributes": [
            {
               "name": "User-Name",
               "expr": "hexstring(pkt4.mac, '-')"
            }
         ]
      }
   }
}

And here’s how to specify period-separated hexadecimal notation (dead.beef.cafe), preferred by Cisco devices:

{
   "parameters": {
      "access": {
         "attributes": [
            {
               "name": "User-Name",
               "expr": "concat(concat(concat(substring(hexstring(pkt4.mac, ''), 0, 4), '.'), concat(substring(hexstring(pkt4.mac, ''), 4, 4), '.'), concat(substring(hexstring(pkt4.mac, ''), 8, 4), '.'))"
            }
         ]
      }
   }
}

For the RADIUS hook library to operate properly in DHCPv4, the Host Cache hook library must also be loaded. The reason for this is somewhat complex. In a typical deployment, the DHCP clients send their packets via DHCP relay, which inserts certain Relay Agent Information options, such as circuit-id or remote-id. The values of those options are then used by the Kea DHCP server to formulate the necessary attributes in the Access-Request message sent to the RADIUS server. However, once the DHCP client gets its address, it then renews by sending packets directly to the DHCP server. As a result, the relays are not able to insert their RAI options, and the DHCP server cannot send the Access-Request queries to the RADIUS server by using just the information from incoming packets. Kea needs to keep the information received during the initial Discover/Offer exchanges and use it again later when sending accounting messages.

This mechanism is implemented based on user context in host reservations. (See Comments and User Context and User Contexts in Hooks for details.) The host-cache mechanism allows the information retrieved by RADIUS to be stored and later used for sending accounting and access queries to the RADIUS server. In other words, the host-cache mechanism is mandatory, unless administrators do not want RADIUS communication for messages other than Discover and the first Request from each client.

Note

Currently the RADIUS hook library is incompatible with the early-global-reservations-lookup global parameter i.e. setting the parameter to true raises an error when the hook library is loaded.

host_cache: Caching Host Reservations

Some database backends, such as RADIUS, are slow and may take a long time to respond. Since Kea in general is synchronous, backend performance directly affects DHCP performance. To minimize the impact and improve performance, the Host Cache library provides a way to cache information from the database locally. This includes negative caching, i.e. the ability to remember that there is no client information in the database.

Note

This library can only be loaded by the kea-dhcp4 or kea-dhcp6 process.

In principle, this hook library can be used with any backend that may introduce performance degradation (MySQL, PostgreSQL or RADIUS). Host Cache must be loaded for the RADIUS accounting mechanism to work.

The Host Cache hook library is very simple. It takes only one optional parameter (maximum), which defines the maximum number of hosts to be cached. If not specified, the default value of 0 is used, which means there is no limit. This hook library can be loaded the same way as any other hook library; for example, this configuration could be used:

"Dhcp4": {

# Your regular DHCPv4 configuration parameters here.

"hooks-libraries": [
{
    "library": "/usr/local/lib/kea/hooks/libdhc_host_cache.so",
    "parameters": {

        # Tells Kea to never cache more than 1000 hosts.
        "maximum": 1000

    }
} ]

Once loaded, the Host Cache hook library provides a number of new commands which can be used either over the control channel (see Using the Control Channel) or the RESTful API (see Overview of the Kea Control Agent). An example RESTful API client is described in Overview of the Kea Shell. The following sections describe the commands available.

The cache-flush Command

This command allows removal of a specified number of cached host entries. It takes one parameter, which defines the number of hosts to be removed. An example usage looks as follows:

{
    "command": "cache-flush",
    "arguments": 1000
}

This command removes 1000 hosts; to delete all cached hosts, use cache-clear instead. The hosts are stored in FIFO (first-in, first-out) order, so the oldest entries are always removed.

The cache-clear Command

This command allows removal of all cached host entries. An example usage looks as follows:

{
    "command": "cache-clear"
}

This command removes all hosts. To delete only a certain number of cached hosts, please use cache-flush instead.

The cache-size Command

This command returns the number of host entries. An example usage looks as follows:

{
    "command": "cache-size"
}

The cache-write Command

In general, the cache content is considered a runtime state and the server can be shut down or restarted as usual; the cache is then repopulated after restart. However, there are some cases when it is useful to store the contents of the cache. One such case is RADIUS, where the cached hosts also retain additional cached RADIUS attributes; there is no easy way to obtain this information again, because renewing clients send their packet to the DHCP server directly. Another use case is when an administrator wants to restart the server and, for performance reasons, wants it to start with a hot (populated) cache.

This command allows writing the contents of the in-memory cache to a file on disk. It takes one parameter, which defines the filename. An example usage looks as follows:

{
    "command": "cache-write",
    "arguments": "/tmp/kea-host-cache.json"
}

This causes the contents to be stored in the /tmp/kea-host-cache.json file. That file can then be loaded with the cache-load command or processed by any other tool that is able to understand JSON format.

The cache-load Command

See the previous section for a discussion of use cases where it may be useful to write and load contents of the host cache to disk.

This command allows the contents of a file on disk to be loaded into an in-memory cache. It takes one parameter, which defines the filename. An example usage looks as follows:

{
    "command": "cache-load",
    "arguments": "/tmp/kea-host-cache.json"
}

This command stores the contents to the /tmp/kea-host-cache.json file. That file can then be loaded with the cache-load command or processed by any other tool that is able to understand JSON format.

The cache-get Command

This command is similar to cache-write, but instead of writing the cache contents to disk, it returns the contents to whoever sent the command.

This command allows the contents of a file on disk to be loaded into an in-memory cache. It takes one parameter, which defines the filename. An example usage looks as follows:

{
    "command": "cache-get"
}

This command returns all the cached hosts; the response may be large.

The cache-get-by-id Command

This command is similar to cache-get, but instead of returning the whole content it returns only the entries matching the given identifier.

It takes one parameter, which defines the identifier of wanted cached host reservations. An example usage looks as follows:

{
    "command": "cache-get-by-id",
    "arguments": {
        "hw-address": "01:02:03:04:05:06"
    }
}

This command returns all the cached hosts with the given hardware address.

The cache-insert Command

This command may be used to manually insert a host into the cache; there are very few use cases when this command might be useful. This command expects its arguments to follow the usual syntax for specifying host reservations (see Host Reservations in DHCPv4 or Host Reservations in DHCPv6), with one difference: the subnet-id value must be explicitly specified.

An example command to insert an IPv4 host into the host cache looks as follows:

{
    "command": "cache-insert",
    "arguments": {
        "hw-address": "01:02:03:04:05:06",
        "subnet-id4": 4,
        "subnet-id6": 0,
        "ip-address": "192.0.2.100",
        "hostname": "somehost.example.org",
        "client-classes4": [ ],
        "client-classes6": [ ],
        "option-data4": [ ],
        "option-data6": [ ],
        "next-server": "192.0.0.2",
        "server-hostname": "server-hostname.example.org",
        "boot-file-name": "bootfile.efi",
        "host-id": 0
    }
}

An example command to insert an IPv6 host into the host cache looks as follows:

{
    "command": "cache-insert",
    "arguments": {
        "hw-address": "01:02:03:04:05:06",
        "subnet-id4": 0,
        "subnet-id6": 6,
        "ip-addresses": [ "2001:db8::cafe:babe" ],
        "prefixes": [ "2001:db8:dead:beef::/64" ],
        "hostname": "",
        "client-classes4": [ ],
        "client-classes6": [ ],
        "option-data4": [ ],
        "option-data6": [ ],
        "next-server": "0.0.0.0",
        "server-hostname": "",
        "boot-file-name": "",
        "host-id": 0
    }
}

The cache-remove Command

Sometimes it is useful to remove a single entry from the host cache: for example, consider a situation where the device is active, Kea has already provided configuration, and the host entry is in cache. As a result of administrative action (e.g. the customer hasn’t paid their bills or has been upgraded to better service), the information in the backend database (e.g. MySQL or RADIUS) is being updated. However, since the cache is in use, Kea does not notice the change as the cached values are used. The cache-remove command can solve this problem by removing a cached entry after administrative changes.

The cache-remove command works similarly to the reservation-get command. It allows querying by two parameters: either subnet-id4 or subnet-id6; or ip-address (may be an IPv4 or IPv6 address), hw-address (specifies a hardware/MAC address), duid, circuit-id, client-id, or flex-id.

An example command to remove an IPv4 host with reserved address 192.0.2.1 from a subnet with a subnet-id 123 looks as follows:

{
    "command": "cache-remove",
    "arguments": {
        "ip-address": "192.0.2.1",
        "subnet-id": 123
    }
}

Another example that removes an IPv6 host identifier by DUID and specific subnet-id is:

{
    "command": "cache-remove",
    "arguments": {
        "duid": "00:01:ab:cd:f0:a1:c2:d3:e4",
        "subnet-id": 123
    }
}

lease_query: Leasequery

This library provides support for DHCPv4 Leasequery as described in RFC 4388; and for DHCPv6 Leasequery (RFC 5007).

Note

This library can only be loaded by the kea-dhcp4 or kea-dhcp6 process.

The Leasequery library is only available to ISC customers with a paid support contract.

DHCPv4 Leasequery

DHCPv4 simple Leasequery provides a requester the ability to query for active lease information for either a single IP address or a single client. RFC 4388 calls for three such queries:

• Query by IP address

  The IP address of interest is contained within the ciaddr field of the query.

• Query by hardware address

  The hardware address of interest is contained with the chaddr field of the query.

• Query by client identifier

  The client identifier of interest is sent in the dhcp-client-identifier option (61) of the query.

The inbound DHCPLEASEQUERY packet must supply only one of the three values above. Queries which supply more than one of these values are dropped.

In addition, the query must contain the IP address of the requester in giaddr. This value is used not only as the destination for the query response but also to validate the requester against a known list of IP addresses which are permitted to query. This list of valid requester addresses is specified as part of the Leasequery hook library’s configuration (see the section on configuration below).

In response to a valid query, the server returns one of three message types:

• DHCPLEASEUNKNOWN

  Returned when the IP address of interest is not one the server knows about (query by IP address); or there are no active leases for the client of interest (query by hardware address or client ID).

• DHCPLEASEUNASSIGNED

  Returned when the IP address is one the server knows of but for which there are no active leases (applies only to query by IP address).

• DHCPLEASEACTIVE

  Returned when there is at least one active lease found matching the criteria.

For both DHCPLEASEUNKNOWN and DHCPLEASEUNASSIGNED responses, the only information sent back to the requester in response is the query parameter itself (i.e. one of: IP address, hardware address, or client identifier).

For DHCPLEASEACTIVE the server provides the following information for the newest active lease that matches the criteria, in the response:

• ciaddr - set to the lease’s IP address

• chaddr - set to the lease’s hardware address

In addition, one or more of the following options are included:

DHCPLEASEACTIVE options

Option	Code	Content
dhcp-client-identifier	61	copied from the lease (if appropriate)
client-last-transaction-time	91	the amount of time that has elapsed since the lease’s client-last-transaction-time (CLTT). This value is also used by the server to adjust lifetime and timer values.
dhcp-lease-time	51	lease’s lifetime reduced by CLTT
dhcp-renewal-time	58	as controlled by kea-dhcp4 configuration and then reduced by CLTT
dhcp-rebind-time	59	as dictated by kea-dhcp4 configuration and then reduced by CLTT
dhcp-agent-options	82	if stored on the lease. (See Storing Extended Lease Information)
associated-ip	92	a list of all other IP addresses for which the client has active leases. (Does not apply to query by IP address)

The dhcp-server-identifier option (54) is returned in all responses in keeping with RFC 2131, section 4.3.1.

RFC 4388 allows requesters to ask for specific options via the dhcp-parameter-request-list (PRL, option 55). This is not currently supported in Kea.

DHCPv4 Leasequery Configuration

Configuring the Leasequery hook library for use is straightforward. It supports a single parameter, requesters, which is a list of IP addresses from which DHCPLEASEQUERY packets are accepted. In other words, it is a list of known requesters. The following code shows an example configuration with two requester addresses:

:
   "hooks-libraries": [
       {
           "library": "lib/kea/hooks/libdhcp_lease_query.so",
           "parameters": {
               "requesters": [ "192.0.1.1", "10.0.0.2" ]
           }
       }
   ],
:

Note

For security purposes, there is no way to specify wildcards. Each requester address must be explicitly listed.

DHCPv6 Leasequery

DHCPv6 simple Leasequery gives a requester the ability to query for active lease information for either a single IP address or a single client DUID. The query type and parameters are conveyed in an lq-query option (44) attached to a DHCPV6_LEASEQUERY message:

• query-type

  This is either query-by-address (1) or query-by-clientid (2)

• link-address

  The global link address, when not empty, instructs the query to be limited to leases within that “link.” Kea uses this value to select only leases that belong to subnets whose prefix matches this value. Active leases for prefix delegations for a matched subnet are included in the query reply, even if the delegated prefix itself falls outside the subnet prefix.

• query-options

  A single iaaddr option (12) must be supplied when querying by address. When querying by client ID, a single clientid option (1) must be supplied. RFC 5007 also calls for an optional, oro option (6), to request specific options be returned for matched leases. This is not currently implemented.

Note

RFC 5007, Section 3.3 states that querying by IP address should return either a lease (e.g. binding) for the address itself or a lease for a delegated prefix that contains the address. The latter is not currently implemented. Leases for delegated prefixes may only be returned when querying by client ID. See GitLab issue #1275

DHCPV6_LEASEQUERY queries are only honored if the source address of the query matches an entry in a list of known IP addresses which are permitted to query. This list of valid requester addresses is specified as part of the Leasequery hook library’s configuration (see the section on configuration below). Queries received from unknown requesters are logged and dropped.

In response to a valid query, the server carries out the requisite activities and returns a DHCPV6_LEASEQUERY_REPLY. All replies contain at least a status-code option (13) that indicates the outcome of the query as detailed in the following table:

DHCPV6_LEASEQUERY_REPLY status option values per query outcome

Query Outcome	Status Label	Status Code	Status Text
Invalid query type field	STATUS_UnknownQueryType	7	“unknown query-type”
Query by IP address that does not contain an address option	STATUS_Malformed	10	“missing D6O_IAADDR”
Query by IP address for an address that does fall within any configured pools	STATUS_NotConfigured	9	“address not in a configured pool”
Query by IP address which found only an inactive lease (e.g. expired, declined, reclaimed-expired)	STATUS_Success	0	“inactive lease exists”
Query by IP address that found no leases (active or otherwise)	STATUS_Success	0	“no active lease”
Query by IP address that found an active lease for the address	STATUS_Success	0	“active lease found”
Query by Client ID that does not contain a client ID option	STATUS_Malformed	10	“missing D6O_CLIENTID”
Query by Client ID with a link address that does not match any configured subnets	STATUS_NotConfigured	9	“not a configured link”
Query by client ID which found no matching leases	STATUS_Success	0	“no active leases”
Query by client ID which found one or more active leases	STATUS_Success	0	“active lease(s) found”

For those scenarios where the query was either invalid or for which no matching active leases were found, the DHCPV6_LEASEQUERY_REPLY only contains the status-code option (12) per the above table.

When a query finds active leases in more than one subnet and the query’s link-address is empty, then, in addition to the status-code, the DHCPV6_LEASEQUERY_REPLY contains an lq-client-link option (48). The lq-client-link contains a list of IPv6 addresses, one for each subnet in which a lease was found (see RFC 5007, Section 4.1.2.5) If, however, the query’s link-address is not empty, the list of queries is pruned to contain only leases that belong to that subnet.

When the query results in one or more active leases which all belong to a single subnet, in addition to the status-code, the DHCPV6_LEASEQUERY_REPLY contains a client-data option (45) (see RFC 5007, Section 4.1.2.2). The client-data option encapsulates the following options:

OPTION_CLIENT_DATA returned when active lease(s) are found

Option	Code	Content
clientid	1	copied from the lease (if one exists)
clt-time	46	amount of time that has elapsed since the lease’s client-last-transaction-time (CLTT). This value will also be used by the server to adjust lifetime and timer values.
iaaddr	5	One option per matched address. Fields in each option: - lease address - valid lifetime reduced by CLTT - preferred lifetime reduced by CLTT
iaprefix	26	One option per matched prefix. Fields in each option: - prefix - prefix length - valid lifetime reduced by CLTT - preferred lifetime reduced by CLTT

If the lease with the most recent client-last-transaction-time (CLTT) value has relay information in its user-context (see Storing Extended Lease Information), then an OPTION_LQ_RELAY_DATA option is added to the reply (see RFC 5007, Section 4.1.2.4).

The relay information on the lease is a list with an entry for each relay layer the client packet (e.g. DHCPV6_REQUEST) traversed, with the first entry in the list being the outermost layer (closest to the server). The peer-address field of the lq-rely-option is set to the peer address of this relay. The list of relays is then used to construct a DHCPV6_RELAY_FORW message equivalent to that which contained the client packet, minus the client packet. This message is stored in the DHCP-relay-message field of the lq-relay-data option.

DHCPv6 Leasequery Configuration

Configuring the Leasequery hook library for use is straightforward. It supports a single parameter, requesters, which is a list of IP addresses from which DHCPV6_LEASEQUERY packets are accepted. In other words, it is a list of known requesters. The following code shows an example configuration with two requester addresses:

:
   "hooks-libraries": [
       {
           "library": "lib/kea/hooks/libdhcp_lease_query.so",
           "parameters": {
               "requesters": [ "2001:db8:1::1", "2001:db8:2::1" ]
           }
       }
   ],
:

Note

For security purposes, there is no way to specify wildcards. Each requester address must be explicitly listed.

Run Script Support

This hook library adds support for calling an external script for specific packet-processing hook points.

The library, which was added in Kea 1.9.5, can be loaded in a similar way to other hook libraries by the kea-dhcp4 and kea-dhcp6 processes.

{
    "hooks-libraries": [
        {
            "library": "/usr/local/lib/libdhcp_run_script.so",
            "parameters": {
                "name": "/full_path_to/script_name.sh",
                "sync": false
            }
        }
    ]
}

The parameters contain the name, which indicates the full path to the external script to be called on each hook point, and also the sync option, to be able to wait synchronously for the script to finish execution. If the sync parameter is false, then the script will launch and Kea will not wait for the execution to finish, causing all the OUT parameters of the script (including the next step) to be ignored.

Note

The script inherits all privileges from the server which calls it.

Note

Currently, enabling synchronous calls to external scripts is not supported.

This library has several hook-point functions implemented, which are called at the specific packet-processing stage.

The dhcpv4 hook points:

lease4_renew
lease4_expire
lease4_recover
leases4_committed
lease4_release
lease4_decline

The dhcpv6 hook points:

lease6_renew
lease6_rebind
lease6_expire
lease6_recover
leases6_committed
lease6_release
lease6_decline

Each hook point extracts the Kea internal data and exports it as string environment variables. These parameters are shared with the target script using the child process environment. The only parameter passed to the call of the target script is the name of the hook point.

An example of a script implementing all hook points is presented below:

#!/bin/bash

unknown_handle() {
    echo "Unhandled function call ${*}"
    exit 123
}


lease4_renew () {
    ...
}

lease4_expire () {
    ...
}

lease4_recover () {
    ...
}

leases4_committed () {
    ...
}

lease4_release () {
    ...
}

lease4_decline () {
    ...
}

lease6_renew () {
    ...
}

lease6_rebind () {
    ...
}

lease6_expire () {
    ...
}

lease6_recover () {
    ...
}

leases6_committed () {
    ...
}

lease6_release () {
    ...
}

lease6_decline () {
    ...
}

case "$1" in
    "lease4_renew")
        lease4_renew
        ;;
    "lease4_expire")
        lease4_expire
        ;;
    "lease4_recover")
        lease4_recover
        ;;
    "leases4_committed")
        leases4_committed
        ;;
    "lease4_release")
        lease4_release
        ;;
    "lease4_decline")
        lease4_decline
        ;;
    "lease6_renew")
        lease6_renew
        ;;
    "lease6_rebind")
        lease6_rebind
        ;;
    "lease6_expire")
        lease6_expire
        ;;
    "lease6_recover")
        lease6_recover
        ;;
    "leases6_committed")
        leases6_committed
        ;;
    "lease6_release")
        lease6_release
        ;;
    "lease6_decline")
        lease6_decline
        ;;
    *)
        unknown_handle "${@}"
        ;;
esac

Available parameters for each hook point are presented below.

DHCPv4:

lease4_renew

QUERY4_TYPE
QUERY4_TXID
QUERY4_LOCAL_ADDR
QUERY4_LOCAL_PORT
QUERY4_REMOTE_ADDR
QUERY4_REMOTE_PORT
QUERY4_IFACE_INDEX
QUERY4_IFACE_NAME
QUERY4_HOPS
QUERY4_SECS
QUERY4_FLAGS
QUERY4_CIADDR
QUERY4_SIADDR
QUERY4_YIADDR
QUERY4_GIADDR
QUERY4_RELAYED
QUERY4_HWADDR
QUERY4_HWADDR_TYPE
QUERY4_LOCAL_HWADDR
QUERY4_LOCAL_HWADDR_TYPE
QUERY4_REMOTE_HWADDR
QUERY4_REMOTE_HWADDR_TYPE
QUERY4_OPTION_82
QUERY4_OPTION_82_SUB_OPTION_1
QUERY4_OPTION_82_SUB_OPTION_2
SUBNET4_ID
SUBNET4_NAME
SUBNET4_PREFIX
SUBNET4_PREFIX_LEN
PKT4_CLIENT_ID
PKT4_HWADDR
PKT4_HWADDR_TYPE
LEASE4_ADDRESS
LEASE4_CLTT
LEASE4_HOSTNAME
LEASE4_HWADDR
LEASE4_HWADDR_TYPE
LEASE4_STATE
LEASE4_SUBNET_ID
LEASE4_VALID_LIFETIME
LEASE4_CLIENT_ID

lease4_expire

LEASE4_ADDRESS
LEASE4_CLTT
LEASE4_HOSTNAME
LEASE4_HWADDR
LEASE4_HWADDR_TYPE
LEASE4_STATE
LEASE4_SUBNET_ID
LEASE4_VALID_LIFETIME
LEASE4_CLIENT_ID
REMOVE_LEASE

lease4_recover

LEASE4_ADDRESS
LEASE4_CLTT
LEASE4_HOSTNAME
LEASE4_HWADDR
LEASE4_HWADDR_TYPE
LEASE4_STATE
LEASE4_SUBNET_ID
LEASE4_VALID_LIFETIME
LEASE4_CLIENT_ID

leases4_committed

QUERY4_TYPE
QUERY4_TXID
QUERY4_LOCAL_ADDR
QUERY4_LOCAL_PORT
QUERY4_REMOTE_ADDR
QUERY4_REMOTE_PORT
QUERY4_IFACE_INDEX
QUERY4_IFACE_NAME
QUERY4_HOPS
QUERY4_SECS
QUERY4_FLAGS
QUERY4_CIADDR
QUERY4_SIADDR
QUERY4_YIADDR
QUERY4_GIADDR
QUERY4_RELAYED
QUERY4_HWADDR
QUERY4_HWADDR_TYPE
QUERY4_LOCAL_HWADDR
QUERY4_LOCAL_HWADDR_TYPE
QUERY4_REMOTE_HWADDR
QUERY4_REMOTE_HWADDR_TYPE
QUERY4_OPTION_82
QUERY4_OPTION_82_SUB_OPTION_1
QUERY4_OPTION_82_SUB_OPTION_2
LEASES4_SIZE
DELETED_LEASES4_SIZE

If LEASES4_SIZE or DELETED_LEASES4_SIZE is non-zero, then each lease has its own unique identifier, as shown below. The first index starts at 0.

LEASES4_AT0_ADDRESS
LEASES4_AT0_CLTT
LEASES4_AT0_HOSTNAME
LEASES4_AT0_HWADDR
LEASES4_AT0_HWADDR_TYPE
LEASES4_AT0_STATE
LEASES4_AT0_SUBNET_ID
LEASES4_AT0_VALID_LIFETIME
LEASES4_AT0_CLIENT_ID
DELETED_LEASES4_AT0_ADDRESS
DELETED_LEASES4_AT0_CLTT
DELETED_LEASES4_AT0_HOSTNAME
DELETED_LEASES4_AT0_HWADDR
DELETED_LEASES4_AT0_HWADDR_TYPE
DELETED_LEASES4_AT0_STATE
DELETED_LEASES4_AT0_SUBNET_ID
DELETED_LEASES4_AT0_VALID_LIFETIME
DELETED_LEASES4_AT0_CLIENT_ID

lease4_release

QUERY4_TYPE
QUERY4_TXID
QUERY4_LOCAL_ADDR
QUERY4_LOCAL_PORT
QUERY4_REMOTE_ADDR
QUERY4_REMOTE_PORT
QUERY4_IFACE_INDEX
QUERY4_IFACE_NAME
QUERY4_HOPS
QUERY4_SECS
QUERY4_FLAGS
QUERY4_CIADDR
QUERY4_SIADDR
QUERY4_YIADDR
QUERY4_GIADDR
QUERY4_RELAYED
QUERY4_HWADDR
QUERY4_HWADDR_TYPE
QUERY4_LOCAL_HWADDR
QUERY4_LOCAL_HWADDR_TYPE
QUERY4_REMOTE_HWADDR
QUERY4_REMOTE_HWADDR_TYPE
QUERY4_OPTION_82
QUERY4_OPTION_82_SUB_OPTION_1
QUERY4_OPTION_82_SUB_OPTION_2
LEASE4_ADDRESS
LEASE4_CLTT
LEASE4_HOSTNAME
LEASE4_HWADDR
LEASE4_HWADDR_TYPE
LEASE4_STATE
LEASE4_SUBNET_ID
LEASE4_VALID_LIFETIME
LEASE4_CLIENT_ID

lease4_decline

QUERY4_TYPE
QUERY4_TXID
QUERY4_LOCAL_ADDR
QUERY4_LOCAL_PORT
QUERY4_REMOTE_ADDR
QUERY4_REMOTE_PORT
QUERY4_IFACE_INDEX
QUERY4_IFACE_NAME
QUERY4_HOPS
QUERY4_SECS
QUERY4_FLAGS
QUERY4_CIADDR
QUERY4_SIADDR
QUERY4_YIADDR
QUERY4_GIADDR
QUERY4_RELAYED
QUERY4_HWADDR
QUERY4_HWADDR_TYPE
QUERY4_LOCAL_HWADDR
QUERY4_LOCAL_HWADDR_TYPE
QUERY4_REMOTE_HWADDR
QUERY4_REMOTE_HWADDR_TYPE
QUERY4_OPTION_82
QUERY4_OPTION_82_SUB_OPTION_1
QUERY4_OPTION_82_SUB_OPTION_2
LEASE4_ADDRESS
LEASE4_CLTT
LEASE4_HOSTNAME
LEASE4_HWADDR
LEASE4_HWADDR_TYPE
LEASE4_STATE
LEASE4_SUBNET_ID
LEASE4_VALID_LIFETIME
LEASE4_CLIENT_ID

DHCPv6:

lease6_renew

QUERY6_TYPE
QUERY6_TXID
QUERY6_LOCAL_ADDR
QUERY6_LOCAL_PORT
QUERY6_REMOTE_ADDR
QUERY6_REMOTE_PORT
QUERY6_IFACE_INDEX
QUERY6_IFACE_NAME
QUERY6_REMOTE_HWADDR
QUERY6_REMOTE_HWADDR_TYPE
QUERY6_PROTO
QUERY6_CLIENT_ID
LEASE6_ADDRESS
LEASE6_CLTT
LEASE6_HOSTNAME
LEASE6_HWADDR
LEASE6_HWADDR_TYPE
LEASE6_STATE
LEASE6_SUBNET_ID
LEASE6_VALID_LIFETIME
LEASE6_DUID
LEASE6_IAID
LEASE6_PREFERRED_LIFETIME
LEASE6_PREFIX_LEN
LEASE6_TYPE
PKT6_IA_IAID
PKT6_IA_IA_TYPE
PKT6_IA_IA_T1
PKT6_IA_IA_T2

lease6_rebind

QUERY6_TYPE
QUERY6_TXID
QUERY6_LOCAL_ADDR
QUERY6_LOCAL_PORT
QUERY6_REMOTE_ADDR
QUERY6_REMOTE_PORT
QUERY6_IFACE_INDEX
QUERY6_IFACE_NAME
QUERY6_REMOTE_HWADDR
QUERY6_REMOTE_HWADDR_TYPE
QUERY6_PROTO
QUERY6_CLIENT_ID
LEASE6_ADDRESS
LEASE6_CLTT
LEASE6_HOSTNAME
LEASE6_HWADDR
LEASE6_HWADDR_TYPE
LEASE6_STATE
LEASE6_SUBNET_ID
LEASE6_VALID_LIFETIME
LEASE6_DUID
LEASE6_IAID
LEASE6_PREFERRED_LIFETIME
LEASE6_PREFIX_LEN
LEASE6_TYPE
PKT6_IA_IAID
PKT6_IA_IA_TYPE
PKT6_IA_IA_T1
PKT6_IA_IA_T2

lease6_expire

LEASE6_ADDRESS
LEASE6_CLTT
LEASE6_HOSTNAME
LEASE6_HWADDR
LEASE6_HWADDR_TYPE
LEASE6_STATE
LEASE6_SUBNET_ID
LEASE6_VALID_LIFETIME
LEASE6_DUID
LEASE6_IAID
LEASE6_PREFERRED_LIFETIME
LEASE6_PREFIX_LEN
LEASE6_TYPE
REMOVE_LEASE

lease6_recover

LEASE6_ADDRESS
LEASE6_CLTT
LEASE6_HOSTNAME
LEASE6_HWADDR
LEASE6_HWADDR_TYPE
LEASE6_STATE
LEASE6_SUBNET_ID
LEASE6_VALID_LIFETIME
LEASE6_DUID
LEASE6_IAID
LEASE6_PREFERRED_LIFETIME
LEASE6_PREFIX_LEN
LEASE6_TYPE

leases6_committed

QUERY6_TYPE
QUERY6_TXID
QUERY6_LOCAL_ADDR
QUERY6_LOCAL_PORT
QUERY6_REMOTE_ADDR
QUERY6_REMOTE_PORT
QUERY6_IFACE_INDEX
QUERY6_IFACE_NAME
QUERY6_REMOTE_HWADDR
QUERY6_REMOTE_HWADDR_TYPE
QUERY6_PROTO
QUERY6_CLIENT_ID
LEASES6_SIZE
DELETED_LEASES6_SIZE

If LEASES6_SIZE or DELETED_LEASES6_SIZE is non-zero, then each lease has its own unique identifier, as shown below. The first index starts at 0.

LEASES6_AT0_ADDRESS
LEASES6_AT0_CLTT
LEASES6_AT0_HOSTNAME
LEASES6_AT0_HWADDR
LEASES6_AT0_HWADDR_TYPE
LEASES6_AT0_STATE
LEASES6_AT0_SUBNET_ID
LEASES6_AT0_VALID_LIFETIME
LEASES6_AT0_DUID
LEASES6_AT0_IAID
LEASES6_AT0_PREFERRED_LIFETIME
LEASES6_AT0_PREFIX_LEN
LEASES6_AT0_TYPE
DELETED_LEASES6_AT0_ADDRESS
DELETED_LEASES6_AT0_CLTT
DELETED_LEASES6_AT0_HOSTNAME
DELETED_LEASES6_AT0_HWADDR
DELETED_LEASES6_AT0_HWADDR_TYPE
DELETED_LEASES6_AT0_STATE
DELETED_LEASES6_AT0_SUBNET_ID
DELETED_LEASES6_AT0_VALID_LIFETIME
DELETED_LEASES6_AT0_DUID
DELETED_LEASES6_AT0_IAID
DELETED_LEASES6_AT0_PREFERRED_LIFETIME
DELETED_LEASES6_AT0_PREFIX_LEN
DELETED_LEASES6_AT0_TYPE

lease6_release

QUERY6_TYPE
QUERY6_TXID
QUERY6_LOCAL_ADDR
QUERY6_LOCAL_PORT
QUERY6_REMOTE_ADDR
QUERY6_REMOTE_PORT
QUERY6_IFACE_INDEX
QUERY6_IFACE_NAME
QUERY6_REMOTE_HWADDR
QUERY6_REMOTE_HWADDR_TYPE
QUERY6_PROTO
QUERY6_CLIENT_ID
LEASE6_ADDRESS
LEASE6_CLTT
LEASE6_HOSTNAME
LEASE6_HWADDR
LEASE6_HWADDR_TYPE
LEASE6_STATE
LEASE6_SUBNET_ID
LEASE6_VALID_LIFETIME
LEASE6_DUID
LEASE6_IAID
LEASE6_PREFERRED_LIFETIME
LEASE6_PREFIX_LEN
LEASE6_TYPE

lease6_decline

QUERY6_TYPE
QUERY6_TXID
QUERY6_LOCAL_ADDR
QUERY6_LOCAL_PORT
QUERY6_REMOTE_ADDR
QUERY6_REMOTE_PORT
QUERY6_IFACE_INDEX
QUERY6_IFACE_NAME
QUERY6_REMOTE_HWADDR
QUERY6_REMOTE_HWADDR_TYPE
QUERY6_PROTO
QUERY6_CLIENT_ID
LEASE6_ADDRESS
LEASE6_CLTT
LEASE6_HOSTNAME
LEASE6_HWADDR
LEASE6_HWADDR_TYPE
LEASE6_STATE
LEASE6_SUBNET_ID
LEASE6_VALID_LIFETIME
LEASE6_DUID
LEASE6_IAID
LEASE6_PREFERRED_LIFETIME
LEASE6_PREFIX_LEN
LEASE6_TYPE

ddns_tuning: Tuning DDNS updates

This hook library adds support for fine tuning various DNS update aspects. Currently it supports procedural host name generation and the ability to skip performing DDNS updates for select clients. The DDNS Tuning hook is a premium feature.

The library, which was added in Kea 2.1.5, can be loaded by the kea-dhcp4 and kea-dhcp6 daemons by adding it to hooks-libraries element of the server’s configuration:

{
    "hooks-libraries": [
        :
        ,
        {
            "library": "/usr/local/lib/libdhcp_ddns_tuning.so",
            "parameters": {
                :
            }
        },
        :
    ]
}

Procedural Host name generation

This hook library provides the ability to generate host names, procedurally, based on an expression. The expression can be defined globally in the hook parameters, using hostname-expr. If defined globally, it will apply to all hosts in all subnets. The expressions can use all tokens defined in Client Classification. An example of a global expression is shown below:

{
    "hooks-libraries": [
        :
        ,
        {
            "library": "/usr/local/lib/libdhcp_ddns_tuning.so",
            "parameters": {
                :
                "hostname-expr": "'host-'+hexstring(pkt4.mac,'-')"
            }
        },
        :
    ]
}

It is also possible to define this parameter in a subnet, using user-context mechanism. If defined at the subnet level, the expression applies to specific subnet only. If the subnet expression is defined as empty, “”, it suppresses (or disables) the use of a global expression for that subnet. An example subnet expression is shown below:

"subnet4": [{
    "subnet": "192.0.2.0/24",
    "pools": [{
        "pool": "192.0.2.10 - 192.0.2.20",
    } ],

    // This is a subnet-specific user context.
    "user-context": {
        "ddns-tuning:" {
            "hostname-expr": "'guest-'+Int8ToText(substring(pkt4.yiaddr, 0,1))+'-' \
                                     +Int8ToText(substring(pkt4.yiaddr, 1,2))+'-' \
                                     +Int8ToText(substring(pkt4.yiaddr, 2,3))+'-' \
                                     +Int8ToText(substring(pkt4.yiaddr, 3,4))",
        },
        "last-modified": "2017-09-04 13:32",
        "description": "you can put anything you like here",
        "phones": [ "x1234", "x2345" ],
        "devices-registered": 42,
        "billing": false
    }
}]

Note

The expression value above uses a slash, ‘', to show line continuation. This is for clarity only and is not valid JSON supported by Kea parsing. The actual value has to be expressed in a single line.

Note

Privacy should be taken into consideration when generating a host name. The host name is usually inserted into the DNS, which is a public system. Exposing identifiers that can be used to track devices, such as MAC address, are usually a very bad idea. The global expression example used MAC address for simplicity.

DHCPv4 host name generation

With this library installed the behavior for kea-dhcp4 when forming host names in response to a client query (e.g. DISCOVER, REQUEST) is as follows:

1. If a host name is supplied via a host reservation use it along with the DDNS behavioral parameters to form the final host name. Goto step 4.

2. If the client supplied an FQDN option (option 81) use the domain name value specified within it along with the DDNS behavioral parameters to form the final host name. Goto step 4.

3. If the client supplied a host name option (option 12) use the host name specified within it along with the DDNS behavioral parameters to form the final host name.

4. If there is an ddns-tuning in-scope host name expression (either global or subnet), calculate the host name using the expression. If the calculated value is not a fully qualified name and there is an in-scope ddns-qualifying-suffix, append the suffix.

5. If the value calculated by the hook is not an empty string and is different than the host name formed in the prior steps (1 or 2), the calculated value becomes the final host name.

DHCPv6 host name generation

With this library installed the behavior for kea-dhcp6 when forming host names in response to a client query (e.g. SOLICIT, REQUEST, RENEW, REBIND) is as follows:

1. If the client supplied an FQDN option (option 39) use the domain name value specified within it along with the DDNS behavioral parameters to form the final host name. Goto step 4.

2. If the client did not supply an FQDN but ddns-replace-client-name is either always or when-not-present, then calculate the final form of the host name and use it to create an outbound FQDN. Goto step 4.

3. If there is no outbound FQDN at this point, client name processing for this packet stops. Without an outbound FQDN there is no way to communicate a host name to the client.

4. If a host name is supplied via a host reservation use it along with the DDNS behavioral parameters to form the final host name, and supersedes the FQDN value calculated in steps 1 or 2.

5. If there is a ddns-tuning in-scope host name expression (either global or subnet), calculate the host name using the expression. If the calculated value is not a fully qualified name and there is an in-scope ddns-qualifying-suffix, append the suffix.

6. If the value calculated by the hook is not an empty string and is different than the host name formed in the prior steps (1 or 2), the calculated value becomes the final host name.

Skipping DDNS Updates

The ddns-tuning library also provides the ability to skip DDNS updates on a per client basis. The library recognizes a special client class, “SKIP_DDNS”. When a client is matched to this class, kea servers (kea-dhcp4 and kea-dhcp6) will not send DDNS update requests (NCRs) to kea-dhcp-ddns. A common use-case would be to skip DDNS updates for fixed-address host reservations. This is done easily by simply assigning the class to the host reservation as shown below:

{
    "reservations": [
    {
        "hw-address": "01:02:03:04:05:06",
        "ip-address": "192.0.2.1",
        "client-classes": [ "SKIP_DDNS", "foo", "bar" ]
    }]
}

The ddns-tuning library will spot the presence of the “SKIP_DDNS” class in the client’s class list each time the client requests, renews, or releases its lease, and instruct kea-dhcp4 to bypass sending DDNS updates. A similar work flow is supported for kea-dhcp6:

{
    "reservations": [
    {
        "duid": "01:02:03:04:05:06",
        "ip-address": "2001:db8::1",
        "client-classes": [ "SKIP_DDNS", "foo", "bar" ]
    }]
}

Although, “SKIP_DDNS” is a special class, it can be defined with a test expression. Defining it as shown below, would omit DDNS updates for all KNOWN clients:

{
    "client-classes":[
    {
        "name": "SKIP_DDNS",
        "test": "member('KNOWN')"
    }]
}

Note

In order for the SKIP_DDNS class to have an effect, the DDNS-tuning hook library must be loaded.

limits: Rate Limiting

This hook library enables limiting the rate at which packets are being processed. The limits hook library is part of the subscription package.

Configuration

The library can be loaded by both kea-dhcp4 and kea-dhcp6 servers by adding its path in the "hooks-libraries" element of the server’s configuration.

The rate limit can be specified in the format "<p> packets per <time-unit>". <p> is any number that can be represented by an unsigned integer on 32 bits i.e. between 0 and 4,294,967,295. <time-unit> can be any of second, minute, hour, day, week, month, year. month is considered to be 30 days for simplicity. Similarly, year is 365 days for all intents and purposes of limiting. This syntax covers a high range of rates from one lease per year to four billion leases per second.

The configured value of 0 packets is a convenient way of disabling packet processing for certain clients entirely. As such, it means its literal value and is not a special value for disabling limiting altogether as it might be imagined. Disabling limiting altogether is achieved by removing the “rate-limit” leaf configuration entry, the “limits” map around it or the user context around it or the hook library configuration.

There are two ways to configure which packets get limited. One is through the client classes that are initially assigned to the packet. In this case, the limit is configured in the user context in the client class definition. Class rate limits are checked early in packet processing cycle and is thus limited to those classes which are assigned to the packet via test expression and that do not depend on host reservations, the special “BOOTP” or “KNOWN” classes, and is not marked with “only-if-required”.

Note

It can be tempting to think that assigning a rate limit of n packets per time unit results in n DORA or n SARR exchanges. By default, all inbound packets are counted. That means that a full message exchange accounts for 2 packets. To achieve the desired effect of counting an exchange only once, you may use client class rate limiting with a test expression that binds pkt4.msgtype to DHCPDISCOVER messages or pkt6.msgtype to SOLICIT messages.

The other way is through the subnet that the Kea selects for the packet. To achieve this, the limit is added to the user context of the subnet definition.

Note

Subnet rate limits are enforced only on the initially selected subnet for a given packet. If the selected subnet is subsequently changed, as may be the case for subnets in a shared-network or when reselection is enabled in libraries such as the RADIUS hook, rate limits on the newly selected subnet will be ignored. In other words, packets are gated only by the rate limit on the original subnet.

The following is an example that adds one rate limit on a client class and another one in a subnet in kea-dhcp6. A valid configuration for kea-dhcp4 can be easily extrapolated.

{
  "Dhcp6": {
    "client-classes": [
      {
        "name": "gold",
        "user-context": {
          "limits": {
            "rate-limit": "1000 packets per second"
          }
        }
      }
    ],
    "hooks-libraries": [
      {
        "library": "/usr/local/lib/libdhcp_limits.so"
      }
    ],
    "subnet6": [
      {
        "id": 1,
        "pools": [
          {
            "pool": "2001:db8::/64"
          }
        ],
        "subnet": "2001:db8::/64",
        "user-context": {
          "limits": {
            "rate-limit": "10 packets per minute"
          }
        }
      }
    ]
  }

Role Based Access Control

Role Based Access Control Overview

Before the processing of commands in received HTTP requests, the hook takes some parameters e.g. the common name part of the client certificate subject name to assign a role to the request. The configuration associated to this role is used to accept or reject the command. After the processing the response can be rewritten e.g. removing parts.

Summary of the request processing:

• the HTTP library records some information to be used later, e.g. the remote address.

• when TLS is required but the request was not protected by TLS, reject the request by sending an unauthorized response.

• extract the command from the request.

• assign a role using recorded information in the request.

• use the role to accept (i.e. pass through) or reject (i.e. send a forbidden response) the command.

Summary of response processing:

• retrieve some information attached to the request during the request processing (when the request was accepted).

• applies request filters to the response.

Role Based Access Control Configuration

Role Assignment

The role assignment is governed by the configured role assignment method.

Role assignment methods

Name	Description
remote-address	remote/client IP address
cert-subject	common name part of the client certificate subject name
cert-issuer	common name part of the client certificate issuer name
basic-authentication	user ID of basic HTTP authentication
custom-value	for extension

Role Configuration

If the role assignment returns the empty role the configuration of the default role is used: by default the request is rejected. If the role assignment returns a not empty role without a configuration, the configuration of the unknown role is used.

Role configuration parameters

Name	Description
name	the role name (at the exception of the default and unknown roles)
accept-commands	the accept access list
reject-commands	the reject access list
other-commands	specifies what to do for commands not matching accept and reject lists (default reject)
list-match-first	specifies what to do for commands matching both accept and reject list by giving the list to check and apply first (default accept)
response-filters	filters to apply to responses

API Commands

All commands of the REST API are described in files in a directory which can be found in sources in src/share/api or in installed Kea in .../share/kea/api. The hook reads these files to take the name, access right (i.e. read or write) and the hook name.

Extra commands definition parameters

Name	Description
name	(mandatory) the command name
access	(mandatory) the access right i.e. read or write
hook	(optional) the hook name (empty or not present for commands of servers or agents)

Note

These command description files are security sensitive e.g. with too permissive access rights a local attacker may modify them and defeat the RBAC goal.

Access Control Lists

Access control lists can be specified using a name (string) or a single entry map.

Predefined named access list

Name	Description
ALL	matches everything
NONE	matches nothing
READ	matches commands with the read access right
WRITE	matches commands with the write access right

Map access list specifications use a kind in the name of the single entry and parameter in the value.

Access list kinds

Name	Description	Parameter
not	logical not	access list
and	logical and	list of access lists
or	logical or	list of access lists
command	explicit list	list of command names
access	by access right	access right (read or write)
hook	by hook	hook name (can be empty)

Response Filters

Predefined response filters

Name	Description
list-commands	Removes not allowed commands from the list-commands response

Global Parameters

Global parameters are:

• assign-role-method: (mandatory) the name of the method which is used for role assignment.

• api-files: (mandatory) the path of the directory where the API files describing commands can be found.

• require-tls: specifies if received requests on HTTP vs HTTPS are rejected. Default to false when the role assignment method is not based on certificates.

• commands: the list of extra command configurations.

• access-control-lists: named access control list definitions (each definition is a single entry map: the name of the entry is the name of the access list, the value is the specification).

• roles: role configurations.

• default-role: the configuration of the default role (used when “” is assigned).

• unknown-role: takes the configuration of the unknown role (used when the not empty assigned role has no configuration).

Sample Configuration

A sample configuration is available in doc/examples/agent/rbac.json in the Kea source and is copied below.

{
"Control-agent": {
    // We need to specify where the agent should listen to incoming HTTP
    // queries.
    "http-host": "127.0.0.1",

    // If enabling HA and multi-threading, the 8000 port is used by the HA
    // hook library http listener. When using HA hook library with
    // multi-threading to function, make sure the port used by dedicated
    // listener is different (e.g. 8001) than the one used by CA. Note
    // the commands should still be sent via CA. The dedicated listener
    // is specifically for HA updates only.
    "http-port": 8000,

    // TLS trust anchor (Certificate Authority). This is a file name or
    // (for OpenSSL only) a directory path.
    "trust-anchor": "my-ca",

    // TLS server certificate file name.
    "cert-file": "my-cert",

    // TLS server private key file name.
    "key-file": "my-key",

    // TLS require client certificates flag. Default is true and means
    // require client certificates. False means they are optional.
    "cert-required": true,

    // Add hooks here.
    "hooks-libraries": [
    {
        "library": "/opt/lib/libca_rbac.so",
        "parameters": {
            // This section configures the RBAC hook library.
            // Mandatory parameters.
            "assign-role-method": "cert-subject",
            "api-files": "/opt/share/kea/api",
            // Optional parameters.
            "require-tls": true,
            "commands": [
            {
                "name": "my-command",
                "access": "read",
                "hook": "my-hook"
            } ],
            "access-control-lists": [
            {
                "my-none": { "not": "ALL" }
            },{
                "another-none": { "and": [ "ALL", "NONE" ] }
            },{
                "my-read": { "access": "read" }
            } ],
            "roles": [
            {
                "name": "kea-client",
                "accept-commands":
                {
                    "commands": [ "list-commands", "status-get" ]
                },
                "reject-commands": "NONE",
                "other-commands": "reject",
                "list-match-first": "accept",
                "response-filters": [ "list-commands" ]
            },{
                "name": "admin",
                "accept-commands": "ALL",
                "reject-commands":
                {
                    "hook": "cb_cmds"
                },
                "list-match-first": "reject"
            } ],
            "default-role":
            {
                "accept-commands": "NONE",
                "reject-commands": "ALL"
            },
            "unknown-role":
            {
                "accept-commands": "READ",
                "reject-commands": "WRITE"
            }
        }
    } ]

    // Additional parameters, such as logging and others
    // omitted for clarity.

}
}

Accept/Reject Algorithm

Here is the pseudo-code of the accept/reject decision algorithm which returns true i.e. accept or false i.e. reject.

bool match(command) {
    if (list-match-first == accept) {
        if (accept_list && accept_list->match(command)) {
            return (true);
        }
        if (reject_list && reject_list->match(command)) {
            return (false);
        }
    } else {
        if (reject_list && reject_list->match(command)) {
            return (false);
        }
        if (accept_list && accept_list->match(command)) {
            return (true);
        }
    }
    if (others == reject) {
       return (false);
    } else {
       return (true);
    }
}

Extensive Example

Here is an extensive example for a role accepting all read commands at the exception of “config-get”, e.g. for hiding passwords or this access list to a remote user (if the user is local “config-write” should be rejected too.

The first option is to put the allowed commands in the “accept-commands” list and to reject anything else:

...
"roles": [
{
    "name": "user1",
    "accept-commands":
    {
        "and": [
            "READ",
            { "not":
                { "commands": [ "config-get" ] }
            }
        ]
    },
    "reject-commands": "ALL",
    // This is the default but as the config relies on it
    // it is explicitly set.
    "list-match-first": "accept"
 },
 ...
 ],
 ...

A common alternative is to not set the “reject-commands” list i.e. leaving it empty and to rely on the “other-commands” to reject anything else.

...
"roles": [
{
    "name": "user2",
    "accept-commands":
    {
        "and": [
            "READ",
            { "not":
                { "commands": [ "config-get" ] }
            }
        ]
    },
    // This is the default but as the config relies on it
    // it is explicitly set.
    "other-commands": "reject"
 },
 ...
 ],
 ...

One can do the opposite i.e. setting only the “reject-commands” list.

...
"roles": [
{
    "name": "user3",
    "reject-commands":
    {
        "or": [
            "WRITE",
            { "commands": [ "config-get" ] }
        ]
    },
    "other-commands": "accept"
 },
 ...
 ],
 ...

Or use both lists with the exception in the “reject-commands” list which must be checked first as “config-get” has the read access right.

...
"roles": [
{
    "name": "user4",
    "accept-commands": "READ",
    "reject-commands": { "commands": [ "config-get" ] },
    "list-match-first": "reject"
 },
 ...
 ],
 ...

To check any configuration it is a good idea to use the “list-commands” response filter which shows errors i.e. missing (rejected) commands and extra (accepted) commands.

User Contexts in Hooks

Hook libraries can have their own configuration parameters, which is convenient if the parameter applies to the whole library. However, sometimes it is useful to extend certain configuration entities with additional configuration data. This is where the concept of user contexts comes in. A system administrator can define an arbitrary set of data and attach it to Kea structures, as long as the data is specified as a JSON map. In particular, it is possible to define fields that are integers, strings, boolean, lists, or maps. It is possible to define nested structures of arbitrary complexity. Kea does not use that data on its own; it simply stores it and makes it available for the hook libraries.

Another use case for user contexts may be storing comments and other information that will be retained by Kea. Regular comments are discarded when the configuration is loaded, but user contexts are retained. This is useful if administrators want their comments to survive config-set or config-get operations, for example.

If user context is supported in a given context, the parser translates “comment” entries into user context with a “comment” entry.

Kea supports user contexts at the following levels: global scope, interfaces configuration, shared networks, subnets, client classes, option data and definitions, host reservations, control socket, DHCP-DDNS, loggers, and server ID. These are supported in both DHCPv4 and DHCPv6, with the exception of server ID, which is DHCPv6 only.

Statistics

Statistics Overview

Both Kea DHCP servers support statistics gathering. A working DHCP server encounters various events that can cause certain statistics to be collected. For example, a DHCPv4 server may receive a packet (the pkt4-received statistic increases by one) that after parsing is identified as a DHCPDISCOVER (pkt4-discover-received). The server processes it and decides to send a DHCPOFFER representing its answer (the pkt4-offer-sent and pkt4-sent statistics increase by one). Such events happen frequently, so it is not uncommon for the statistics to have values in the high thousands. They can serve as an easy and powerful tool for observing a server’s and a network’s health. For example, if the pkt4-received statistic stops growing, it means that the clients’ packets are not reaching the server.

There are four types of statistics:

• integer - this is the most common type. It is implemented as a 64-bit integer (int64_t in C++), so it can hold any value between -2^63 to 2^63-1.

• floating point - this type is intended to store floating-point precision. It is implemented as a C++ double type.

• duration - this type is intended for recording time periods. It uses the `boost::posix_time::time_duration type, which stores hours, minutes, seconds, and microseconds.

• string - this type is intended for recording statistics in text form. It uses the C++ std::string type.

During normal operation, the DHCPv4 and DHCPv6 servers gather statistics. For a list of DHCPv4 and DHCPv6 statistics, see Statistics in the DHCPv4 Server and Statistics in the DHCPv6 Server, respectively.

To extract data from the statistics module, the control channel can be used. See Management API for details. It is possible to retrieve a single statistic or all statistics, reset the statistics (i.e. set them to a neutral value, typically zero), or even completely remove a single statistic or all statistics. See the section Commands for Manipulating Statistics for a list of statistics-oriented commands.

Statistics can be used by external tools to monitor Kea. One example of such a tool is Stork. See Monitoring Kea With Stork for details on how to use it and other data sources to retrieve statistics periodically to get better insight into Kea’s health and operational status.

Statistics Lifecycle

All of the statistics supported by Kea’s servers are initialized upon the servers’ startup and are returned in response to the commands such as statistic-get-all. The runtime statistics concerning DHCP packets processed are initially set to 0 and are reset upon the server restart.

Per-subnet statistics are recalculated when reconfiguration takes place.

In general, once a statistic is initialized it is held in the manager until explicitly removed, via statistic-remove or statistic-remove-all, or when the server is shut down.

Removing a statistic that is updated frequently makes little sense, as it will be re-added when the server code next records that statistic. The statistic-remove and statistic-remove-all commands are intended to remove statistics that are not expected to be observed in the near future. For example, a misconfigured device in a network may cause clients to report duplicate addresses, so the server will report increasing values of pkt4-decline-received. Once the problem is found and the device is removed, the system administrator may want to remove the pkt4-decline-received statistic so that it is no longer reported, until and unless a duplicate address is again detected.

Commands for Manipulating Statistics

There are several commands defined that can be used for accessing (-get), resetting to zero or a neutral value (-reset), or removing a statistic completely (-remove). The statistics time-based limit (-sample-age-set) and size-based limit (-sample-count-set), which control how long or how many samples of a given statistic are retained, can also be changed.

The difference between -reset and -remove is somewhat subtle. The -reset command sets the value of the statistic to zero or a neutral value, so that after this operation, the statistic has a value of 0 (integer), 0.0 (float), 0h0m0s0us (duration), or “” (string). When requested, a statistic with the values mentioned is returned. -remove removes a statistic completely, so the statistic is no longer reported. However, the server code may add it back if there is a reason to record it.

Note

The following sections describe commands that can be sent to the server; the examples are not fragments of a configuration file. For more information on sending commands to Kea, see Management API.

The statistic-get Command

The statistic-get command retrieves a single statistic. It takes a single-string parameter called name, which specifies the statistic name. An example command may look like this:

{
    "command": "statistic-get",
    "arguments": {
        "name": "pkt4-received"
    }
}

The server returns details of the requested statistic, with a result of 0 indicating success and the specified statistic as the value of the arguments parameter. If the requested statistic is not found, the response contains an empty map, i.e. only { } as an argument, but the status code still indicates success (0).

Here is an example response:

{
    "command": "statistic-get",
    "arguments": {
        "pkt4-received": [ [ 125, "2019-07-30 10:11:19.498739" ], [ 100, "2019-07-30 10:11:19.498662" ] ]
    },
    "result": 0
}

The statistic-reset Command

The statistic-reset command sets the specified statistic to its neutral value: 0 for integer, 0.0 for float, 0h0m0s0us for time duration, and “” for string type. It takes a single-string parameter called name, which specifies the statistic name. An example command may look like this:

{
    "command": "statistic-reset",
    "arguments": {
        "name": "pkt4-received"
    }
}

If the specific statistic is found and the reset is successful, the server responds with a status of 0, indicating success, and an empty parameters field. If an error is encountered (e.g. the requested statistic was not found), the server returns a status code of 1 (error) and the text field contains the error description.

The statistic-remove Command

The statistic-remove command deletes a single statistic. It takes a single-string parameter called name, which specifies the statistic name. An example command may look like this:

{
    "command": "statistic-remove",
    "arguments": {
        "name": "pkt4-received"
    }
}

If the specific statistic is found and its removal is successful, the server responds with a status of 0, indicating success, and an empty parameters field. If an error is encountered (e.g. the requested statistic was not found), the server returns a status code of 1 (error) and the text field contains the error description.

The statistic-get-all Command

The statistic-get-all command retrieves all statistics recorded. An example command may look like this:

{
    "command": "statistic-get-all",
    "arguments": { }
}

The server responds with details of all recorded statistics, with a result set to 0 to indicate that it iterated over all statistics (even when the total number of statistics is zero).

Here is an example response returning all collected statistics:

{
    "command": "statistic-get-all",
    "arguments": {
        "cumulative-assigned-addresses": [
            [
                0,
                "2022-02-11 17:54:17.487569"
            ]
        ],
        "declined-addresses": [
            [
                0,
                "2022-02-11 17:54:17.487555"
            ]
        ],
        "pkt4-ack-received": [
            [
                0,
                "2022-02-11 17:54:17.455233"
            ]
        ],
        "pkt4-ack-sent": [
            [
                0,
                "2022-02-11 17:54:17.455256"
            ]
        ],
        "pkt4-decline-received": [
            [
                0,
                "2022-02-11 17:54:17.455259"
            ]
        ],
        "pkt4-discover-received": [
            [
                0,
                "2022-02-11 17:54:17.455263"
            ]
        ],
        "pkt4-inform-received": [
            [
                0,
                "2022-02-11 17:54:17.455265"
            ]
        ],
        "pkt4-nak-received": [
            [
                0,
                "2022-02-11 17:54:17.455269"
            ]
        ],
        "pkt4-nak-sent": [
            [
                0,
                "2022-02-11 17:54:17.455271"
            ]
        ],
        "pkt4-offer-received": [
            [
                0,
                "2022-02-11 17:54:17.455274"
            ]
        ],
        "pkt4-offer-sent": [
            [
                0,
                "2022-02-11 17:54:17.455277"
            ]
        ],
        "pkt4-parse-failed": [
            [
                0,
                "2022-02-11 17:54:17.455280"
            ]
        ],
        "pkt4-receive-drop": [
            [
                0,
                "2022-02-11 17:54:17.455284"
            ]
        ],
        "pkt4-received": [
            [
                0,
                "2022-02-11 17:54:17.455287"
            ]
        ],
        "pkt4-release-received": [
            [
                0,
                "2022-02-11 17:54:17.455290"
            ]
        ],
        "pkt4-request-received": [
            [
                0,
                "2022-02-11 17:54:17.455293"
            ]
        ],
        "pkt4-sent": [
            [
                0,
                "2022-02-11 17:54:17.455296"
            ]
        ],
        "pkt4-unknown-received": [
            [
                0,
                "2022-02-11 17:54:17.455299"
            ]
        ],
        "reclaimed-declined-addresses": [
            [
                0,
                "2022-02-11 17:54:17.487559"
            ]
        ],
        "reclaimed-leases": [
            [
                0,
                "2022-02-11 17:54:17.487564"
            ]
        ],
        "subnet[1].assigned-addresses": [
            [
                0,
                "2022-02-11 17:54:17.487579"
            ]
        ],
        "subnet[1].cumulative-assigned-addresses": [
            [
                0,
                "2022-02-11 17:54:17.487528"
            ]
        ],
        "subnet[1].declined-addresses": [
            [
                0,
                "2022-02-11 17:54:17.487585"
            ]
        ],
        "subnet[1].reclaimed-declined-addresses": [
            [
                0,
                "2022-02-11 17:54:17.487595"
            ]
        ],
        "subnet[1].reclaimed-leases": [
            [
                0,
                "2022-02-11 17:54:17.487604"
            ]
        ],
        "subnet[1].total-addresses": [
            [
                200,
                "2022-02-11 17:54:17.487512"
            ]
        ],
        "v4-allocation-fail": [
            [
                0,
                "2022-02-11 17:54:17.455302"
            ]
        ],
        "v4-allocation-fail-classes": [
            [
                0,
                "2022-02-11 17:54:17.455306"
            ]
        ],
        "v4-allocation-fail-no-pools": [
            [
                0,
                "2022-02-11 17:54:17.455310"
            ]
        ],
        "v4-allocation-fail-shared-network": [
            [
                0,
                "2022-02-11 17:54:17.455319"
            ]
        ],
        "v4-allocation-fail-subnet": [
            [
                0,
                "2022-02-11 17:54:17.455323"
            ]
        ]
    },
    "result": 0
}

The statistic-reset-all Command

The statistic-reset command sets all statistics to their neutral values: 0 for integer, 0.0 for float, 0h0m0s0us for time duration, and “” for string type. An example command may look like this:

{
    "command": "statistic-reset-all",
    "arguments": { }
}

If the operation is successful, the server responds with a status of 0, indicating success, and an empty parameters field. If an error is encountered, the server returns a status code of 1 (error) and the text field contains the error description.

The statistic-remove-all Command

The statistic-remove-all command attempts to delete all statistics. An example command may look like this:

{
    "command": "statistic-remove-all",
    "arguments": { }
}

If the removal of all statistics is successful, the server responds with a status of 0, indicating success, and an empty parameters field. If an error is encountered, the server returns a status code of 1 (error) and the text field contains the error description.

The statistic-sample-age-set Command

The statistic-sample-age-set command sets a time-based limit on samples for a given statistic. It takes two parameters: a string called name, which specifies the statistic name, and an integer value called duration, which specifies the time limit for the given statistic in seconds. An example command may look like this:

{
    "command": "statistic-sample-age-set",
    "arguments": {
        "name": "pkt4-received",
        "duration": 1245
    }

}

If the command is successful, the server responds with a status of 0, indicating success, and an empty parameters field. If an error is encountered (e.g. the requested statistic was not found), the server returns a status code of 1 (error) and the text field contains the error description.

The statistic-sample-age-set-all Command

The statistic-sample-age-set-all command sets time-based limits on samples for all statistics. It takes a single-integer parameter called duration, which specifies the time limit for the statistic in seconds. An example command may look like this:

{
    "command": "statistic-sample-age-set-all",
    "arguments": {
        "duration": 1245
    }

}

If the command is successful, the server responds with a status of 0, indicating success, and an empty parameters field. If an error is encountered, the server returns a status code of 1 (error) and the text field contains the error description.

The statistic-sample-count-set Command

The statistic-sample-count-set command sets a size-based limit on samples for a given statistic. An example command may look like this:

{
    "command": "statistic-sample-count-set",
    "arguments": {
        "name": "pkt4-received",
        "max-samples": 100
    }

}

If the command is successful, the server responds with a status of 0, indicating success, and an empty parameters field. If an error is encountered (e.g. the requested statistic was not found), the server returns a status code of 1 (error) and the text field contains the error description.

The statistic-sample-count-set-all Command

The statistic-sample-count-set-all command sets size-based limits on samples for all statistics. An example command may look like this:

{
    "command": "statistic-sample-count-set-all",
    "arguments": {
        "max-samples": 100
    }

}

If the command is successful, the server responds with a status of 0, indicating success, and an empty parameters field. If an error is encountered, the server returns a status code of 1 (error) and the text field contains the error description.

Time Series

With certain statistics, a single isolated data point may be useful. However, some statistics, such as received packet size, packet processing time, or number of database queries needed to process a packet, are not cumulative and it is useful to keep many data points, perhaps to do some statistical analysis afterwards.

Each Kea statistic holds 20 data points; setting such a limit prevents unlimited memory growth. There are two ways to define the limits: time-based (e.g. keep samples from the last 5 minutes) and size-based. The size-based limit can be changed using one of two commands: statistic-sample-count-set, to set a size limit for a single statistic, and statistic-sample-count-set-all, to set size-based limits for all statistics. To set time-based limits for a single statistic, use statistic-sample-age-set; use statistic-sample-age-set-all to set time-based limits for all statistics. For a given statistic only one type of limit can be active; storage is limited by either time or size, not both.

Management API

A classic approach to daemon configuration assumes that the server’s configuration is stored in configuration files and, when the configuration is changed, the daemon is restarted. This approach has the significant disadvantage of introducing periods of downtime when client traffic is not handled. Another risk is that if the new configuration is invalid for any reason, the server may refuse to start, which will further extend the downtime period until the issue is resolved.

To avoid such problems, the DHCPv4, DHCPv6, and D2 servers in Kea include support for a mechanism that allows online reconfiguration without requiring server shutdown. Both servers can be instructed to open control sockets, which is a communications channel. The server is able to receive commands on that channel, act on them, and report back status.

The DHCPv4, DHCPv6, and D2 servers receive commands over the UNIX domain sockets. For details on how to configure these sockets, see Management API for the DHCPv4 Server and Management API for the DHCPv6 Server. While it is possible to control the servers directly using UNIX domain sockets, that requires that the controlling client be running on the same machine as the server. SSH is usually used to connect remotely to the controlled machine.

Network administrators usually prefer using some form of a RESTful API to control the servers, rather than using UNIX domain sockets directly. Therefore, Kea includes a component called the Control Agent (CA), which exposes a RESTful API to the controlling clients and can forward commands to the respective Kea services over the UNIX domain sockets. The CA configuration is described in Configuration.

The HTTP requests received by the CA contain the control commands encapsulated within HTTP requests. Simply speaking, the CA is responsible for stripping the HTTP layer from the received commands and forwarding the commands in a JSON format over the UNIX domain sockets to the respective services. Because the CA receives commands for all services, it requires additional “forwarding” information to be included in the client’s messages. This forwarding information is carried within the service parameter of the received command. If the service parameter is not included, or if the parameter is a blank list, the CA assumes that the control command is targeted at the CA itself and attempts to respond.

Control connections over both HTTP and UNIX domain sockets are guarded with timeouts. The timeout value is set to 10 seconds and is not configurable.

This API can be used by external tools to manage and monitor Kea operation. An example of such a monitoring tool is ISC’s Stork. For details, see Monitoring Kea With Stork.

Data Syntax

Communication over the control channel is conducted using JSON structures. If configured, Kea opens a socket and listens for incoming connections. A process connecting to this socket is expected to send JSON commands structured as follows:

{
    "command": "foo",
    "service": [ "dhcp4" ]
    "arguments": {
        "param1": "value1",
        "param2": "value2",
        ...
    }
}

The same command sent over the RESTful interface to the CA has the following structure:

POST / HTTP/1.1\r\n
Content-Type: application/json\r\n
Content-Length: 147\r\n\r\n
{
    "command": "foo",
    "service": [ "dhcp4" ]
    "arguments": {
        "param1": "value1",
        "param2": "value2",
        ...
    }
}

command is the name of the command to execute and is mandatory. arguments is a map of the parameters required to carry out the given command. The exact content and format of the map are command-specific.

service is a list of the servers at which the control command is targeted. In the example above, the control command is targeted at the DHCPv4 server. In most cases, the CA simply forwards this command to the DHCPv4 server for processing via a UNIX domain socket. Sometimes, the command including a service value may also be processed by the CA, if the CA is running a hook library which handles such a command for the given server. As an example, the hook library loaded by the CA may perform some operations on the database, such as adding host reservations, modifying leases, etc. An advantage of performing DHCPv4-specific administrative operations in the CA, rather than forwarding it to the DHCPv4 server, is the ability to perform these operations without disrupting the DHCPv4 service, since the DHCPv4 server does not have to stop processing DHCP messages to apply changes to the database. Nevertheless, these situations are rather rare; in most cases, when the service parameter contains a name of the service, the commands are simply forwarded by the CA. The forwarded command includes the service parameter, but this parameter is ignored by the receiving server. This parameter is only meaningful to the CA.

If the command received by the CA does not include a service parameter or this list is empty, the CA simply processes this message on its own. For example, a config-get command which includes no service parameter returns the Control Agent’s own configuration. The config-get command with a service value “dhcp4” is forwarded to the DHCPv4 server and returns the DHCPv4 server’s configuration.

The following list shows the mapping of the values carried within the service parameter to the servers to which the commands are forwarded:

• dhcp4 - the command is forwarded to the kea-dhcp4 server.

• dhcp6 - the command is forwarded to the kea-dhcp6 server.

• d2 - the command is forwarded to the kea-dhcp-ddns server.

The server processing the incoming command sends a response of the form:

{
    "result": 0|1|2|3,
    "text": "textual description",
    "arguments": {
        "argument1": "value1",
        "argument2": "value2",
        ...
    }
}

result indicates the outcome of the command. A value of 0 means success, while any non-zero value designates an error or a failure to complete the requested action. Currently 1 indicates a generic error, 2 means that a command is not supported, and 3 means that the requested operation was completed, but the requested object was not found. For example, a well-formed command that requests a subnet that exists in a server’s configuration returns the result 0. If the server encounters an error condition, it returns 1. If the command asks for the IPv6 subnet, but was sent to a DHCPv4 server, it returns 2. If the query asks for a subnet-id and there is no subnet with such an ID, the result is 3.

The text field typically appears when the result is non-zero and contains a description of the error encountered, but it often also appears for successful outcomes. The exact text is command-specific, but in general uses plain English to describe the outcome of the command. arguments is a map of additional data values returned by the server which are specific to the command issued. The map may be present, but that depends on the specific command.

Note

When sending commands via the Control Agent, it is possible to specify multiple services at which the command is targeted. CA forwards this command to each service individually. Thus, the CA response to the controlling client contains an array of individual responses.

Note

Since Kea 1.9.7, it is possible to put comments in commands as in the configuration file. For instance:

{
    "command": "foo",
    // service is a list
    "service": [ "dhcp4" ]
    # command arguments are here.
    "arguments": {
        "param1": "value1"/*,
        "param2": "value2",
        ...*/
    }
}

Using the Control Channel

The easiest way to start interacting with the control API is to use common UNIX/Linux tools such as socat and curl.

In order to control the given Kea service via a UNIX domain socket, use socat in interactive mode as follows:

$ socat UNIX:/path/to/the/kea/socket -

or in batch mode, include the “ignoreeof” option as shown below to ensure socat waits long enough for the server to respond:

$ echo "{ some command...}" | socat UNIX:/path/to/the/kea/socket -,ignoreeof

where /path/to/the/kea/socket is the path specified in the Dhcp4/control-socket/socket-name parameter in the Kea configuration file. Text passed to socat is sent to Kea and the responses received from Kea are printed to standard output. This approach communicates with the specific server directly and bypasses the Control Agent.

It is also easy to open a UNIX socket programmatically. An example of a simple client written in C is available in the Kea Developer’s Guide, in the Control Channel Overview chapter, in the Using Control Channel section.

To use Kea’s RESTful API with curl, use the following:

$ curl -X POST -H "Content-Type: application/json" -d '{ "command": "config-get", "service": [ "dhcp4" ] }' http://ca.example.org:8000/

This assumes that the Control Agent is running on host ca.example.org and is running the RESTful service on port 8000.

Commands Supported by Both the DHCPv4 and DHCPv6 Servers

The build-report Command

The build-report command returns on the control channel what the command line -W argument displays, i.e. the embedded content of the config.report file. This command does not take any parameters.

{
    "command": "build-report"
}

The config-get Command

The config-get command retrieves the current configuration used by the server. This command does not take any parameters. The configuration returned is roughly equal to the configuration that was loaded using the -c command-line option during server start-up, or was later set using the config-set command. However, there may be certain differences, as comments are not retained. If the original configuration used file inclusion, the returned configuration will include all parameters from all included files.

Warning

The returned configuration is not redacted, i.e. it contains database passwords in plain text, if those were specified in the original configuration. Care should be taken not to expose the command channel to unprivileged users.

An example command invocation looks like this:

{
    "command": "config-get"
}

The config-reload Command

The config-reload command instructs Kea to load again the configuration file that was used previously. This operation is useful if the configuration file has been changed by some external source; for example, a system administrator can tweak the configuration file and use this command to force Kea pick up the changes.

Caution should be taken when mixing this with config-set commands. Kea remembers the location of the configuration file it was started with, and this configuration can be significantly changed using the config-set command. When config-reload is issued after config-set, Kea attempts to reload its original configuration from the file, possibly losing all changes introduced using config-set or other commands.

config-reload does not take any parameters. An example command invocation looks like this:

{
    "command": "config-reload"
}

If the configuration file is incorrect, reloading it can raise an error which leaves the server in an unusable state. See The config-set Command to learn how to recover from a non-working server.

The config-test Command

The config-test command instructs the server to check whether the new configuration supplied in the command’s arguments can be loaded. The supplied configuration is expected to be the full configuration for the target server, along with an optional logger configuration. The configuration is sanity-checked to the extent possible without the server actually attempting to load it; it is possible for a configuration which successfully passes this command to still fail in the config-set command or at launch time. The structure of the command is as follows:

{
    "command": "config-test",
    "arguments":  {
        "<server>": {
        }
     }
}

where <server> is the configuration element name for a given server, such as “Dhcp4” or “Dhcp6”. For example:

{
    "command": "config-test",
    "arguments":  {
        "Dhcp6": {
            :
        }
     }
}

The server’s response contains a numeric code, result (0 for success, non-zero on failure), and a string, text, describing the outcome:

{"result": 0, "text": "Configuration seems sane..." }

or

{"result": 1, "text": "unsupported parameter: BOGUS (<string>:16:26)" }

The config-write Command

The config-write command instructs the Kea server to write its current configuration to a file on disk. It takes one optional argument, called “filename”, that specifies the name of the file to write the configuration to. If not specified, the name used when starting Kea (passed as a -c argument) is used. If a relative path is specified, Kea writes its files only in the directory where it is running.

An example command invocation looks like this:

{
    "command": "config-write",
    "arguments": {
        "filename": "config-modified-2017-03-15.json"
    }
}

The leases-reclaim Command

The leases-reclaim command instructs the server to reclaim all expired leases immediately. The command has the following JSON syntax:

{
    "command": "leases-reclaim",
    "arguments": {
        "remove": true
    }
}

The remove boolean parameter is mandatory and indicates whether the reclaimed leases should be removed from the lease database (if true), or left in the expired-reclaimed state (if false). The latter facilitates lease affinity, i.e. the ability to re-assign an expired lease to a returning client that previously used that lease. See Configuring Lease Affinity for details. Also, see Lease Reclamation for general information about the processing of expired leases (lease reclamation).

The libreload Command

The libreload command first unloads and then loads all currently loaded hook libraries. This is primarily intended to allow one or more hook libraries to be replaced with newer versions, without requiring Kea servers to be reconfigured or restarted. The hook libraries are passed the same parameter values (if any) that were passed when they originally loaded.

{
    "command": "libreload",
    "arguments": { }
}

The server responds with a result of either 0, indicating success, or 1, indicating failure.

The list-commands Command

The list-commands command retrieves a list of all commands supported by the server. It does not take any arguments. An example command may look like this:

{
    "command": "list-commands",
    "arguments": { }
}

The server responds with a list of all supported commands. The arguments element is a list of strings, each of which conveys one supported command.

The config-set Command

The config-set command instructs the server to replace its current configuration with the new configuration supplied in the command’s arguments. The supplied configuration is expected to be the full configuration for the target server, along with an optional logger configuration. While optional, the logger configuration is highly recommended, as without it the server reverts to its default logging configuration. The structure of the command is as follows:

{
    "command": "config-set",
    "arguments":  {
        "<server>": {
        }
     }
}

where <server> is the configuration element name for a given server, such as “Dhcp4” or “Dhcp6”. For example:

{
    "command": "config-set",
    "arguments":  {
        "Dhcp6": {
            :
        }
     }
}

If the new configuration proves to be invalid, the server retains its current configuration; however, in some cases a fatal error message is logged indicating that the server no longer provides any service: a working configuration must be loaded as soon as possible. If the control channel is dead, the configuration file can still be reloaded using the SIGHUP signal. If that is unsuccessful, restart the server.

Please note that the new configuration is retained in memory only; if the server is restarted or a configuration reload is triggered via a signal, the server uses the configuration stored in its configuration file. The server’s response contains a numeric code, result (0 for success, non-zero on failure), and a string, text, describing the outcome:

{"result": 0, "text": "Configuration successful." }

or

{"result": 1, "text": "unsupported parameter: BOGUS (<string>:16:26)" }

The shutdown Command

The shutdown command instructs the server to initiate its shutdown procedure. It is the equivalent of sending a SIGTERM signal to the process. This command does not take any arguments. An example command may look like this:

{
    "command": "shutdown"
    "arguments": {
        "exit-value": 3
    }
}

The server responds with a confirmation that the shutdown procedure has been initiated. The optional parameter, exit-value, specifies the numeric value with which the server process exits to the system. The default value is zero.

The DDNS daemon supports an extra parameter, type, which controls the way the process cleans up on exit. The supported shutdown types are:

• “normal” - stops the queue manager and finishes all current transactions before exiting. This is the default.

• “drain_first” - stops the queue manager but continues processing requests from the queue until it is empty.

• “now” - exits immediately.

An example command may look like this:

{
    "command": "shutdown"
    "arguments": {
        "exit-value": 3,
        "type": "drain_first"
    }
}

The dhcp-disable Command

The dhcp-disable command globally disables the DHCP service. The server continues to operate, but it drops all received DHCP messages. This command is useful when the server’s maintenance requires that the server temporarily stop allocating new leases and renew existing leases. It is also useful in failover-like configurations during a synchronization of the lease databases at startup, or recovery after a failure. The optional parameter max-period specifies the time in seconds after which the DHCP service should be automatically re-enabled, if the dhcp-enable command is not sent before this time elapses.

Since Kea 1.9.4, there is an additional origin parameter that specifies the command source. A server administrator should typically omit this parameter because the default value “user” indicates that the administrator sent the command. This command can also be sent by the partner server running HA hooks library. In that case, the partner server sets the parameter to “ha-partner”. This value is reserved for the communication between HA partners and should not be specified in the administrator’s commands, as it may interfere with HA operation. The administrator should either omit this parameter or set it to “user”.

{
    "command": "dhcp-disable",
    "arguments": {
        "max-period": 20,
        "origin": "user"
    }
}

The dhcp-enable Command

The dhcp-enable command globally enables the DHCP service.

Since Kea 1.9.4, there is an additional origin parameter that specifies the command source. A server administrator should typically omit this parameter because the default value “user” indicates that the administrator sent the command. This command can also be sent by the partner server running the HA hook library. In that case, the partner server sets the parameter to “ha-partner”. This value is reserved for the communication between HA partners and should not be specified in the administrator’s commands, as it may interfere with HA operation. The administrator should either omit this parameter or set it to “user”.

{
    "command": "dhcp-enable",
    "arguments": {
        "origin": "user"
    }
}

The status-get Command

The status-get command returns the server’s runtime information:

• pid: the process ID.

• uptime: the number of seconds since the start of the server.

• reload: the number of seconds since the last configuration (re)load.

• high-availability: HA-specific status information about the DHCP servers configured to use the HA hook library:

  • local: the state, the role (primary, secondary, …), and the scopes (i.e. what the server is actually processing) of the local server.

  • remote: the remote server’s last known state, its served HA scopes, and the role of the remote server in the HA relationship.

• multi-threading-enabled: a flag indicating whether multi-threading is enabled.

• thread-pool-size: the number of DHCP service threads.

• packet-queue-size: the maximum size of the packet queue. There is one queue, regardless of the number of running threads.

• packet-queue-statistics: the average queue size for the last 10, 100, and 1000 packets, using an approach similar to the UNIX top command. The average queue size for the last 10 packets can be considered an instantaneous value, while the average for the last 1000 packets shows a longer-term trend.

The high-availability information is returned only when the command is sent to the DHCP servers in an HA setup. This parameter is never returned when the status-get command is sent to the Control Agent or DDNS daemon.

The thread-pool-size, packet-queue-size and packet-queue-statistics parameters are returned only when the command is sent to DHCP servers with multi-threading enabled. These three parameters and multi-threading-enabled are never returned when the status-get command is sent to the Control Agent or DDNS daemon.

To learn more about the HA status information returned by the status-get command, please refer to the The status-get Command section.

The server-tag-get Command:

The server-tag-get command returns the configured server tag of the DHCPv4 or DHCPv6 server (Configuration Sharing and Server Tags explains the server tag concept).

The config-backend-pull Command:

The config-backend-pull command triggers the polling of configuration backends (which must be configured for this command to have an effect), explained in Enabling the Configuration Backend.

The version-get Command

The version-get command returns extended information about the Kea version. It is the same information available via the -V command-line argument. This command does not take any parameters.

{
    "command": "version-get"
}

Commands Supported by the D2 Server

The D2 server supports only a subset of the DHCPv4/DHCPv6 server commands:

• build-report

• config-get

• config-reload

• config-set

• config-test

• config-write

• list-commands

• shutdown

• status-get

• version-get

Commands Supported by the Control Agent

The following commands, listed in Commands Supported by Both the DHCPv4 and DHCPv6 Servers, are also supported by the Control Agent; when the service parameter is blank, the commands are handled by the CA and they relate to the CA process itself:

• build-report

• config-get

• config-reload

• config-set

• config-test

• config-write

• list-commands

• shutdown

• status-get

• version-get

Logging

Logging Configuration

During its operation Kea may produce many log messages. They differ in severity (some are more important than others) and source (different components, like hooks, produce different messages). It is useful to understand which log messages are critical and which are not, and to configure logging appropriately. For example, debug-level messages can be safely ignored in a typical deployment. They are, however, very useful when debugging a problem.

The logging system in Kea is configured through the loggers entry in the server section of the configuration file.

Loggers

Within Kea, a message is logged through an entity called a “logger.” Different components log messages through different loggers, and each logger can be configured independently of the others. Some components, in particular the DHCP server processes, may use multiple loggers to log messages pertaining to different logical functions of the component. For example, the DHCPv4 server uses one logger for messages about packet reception and transmission, another logger for messages related to lease allocation, and so on. Some of the libraries used by the Kea server, such as libdhcpsrv, use their own loggers.

Users implementing hook libraries (code attached to the server at runtime) are responsible for creating the loggers used by those libraries. Such loggers should have unique names, different from the logger names used by Kea. That way, the messages produced by the hook library can be distinguished from messages issued by the core Kea code. Unique names also allow the hook loggers to be configured independently of loggers used by Kea. Whenever it makes sense, a hook library can use multiple loggers to log messages pertaining to different logical parts of the library.

In the server section of a configuration file, the configuration for zero or more loggers (including loggers used by the proprietary hook libraries) can be specified. If there are no loggers specified, the code uses default values; these cause Kea to log messages of INFO severity or greater to standard output. There is a small time window after Kea has been started but before it has read its configuration; logging in this short period can be controlled using environment variables. For details, see Logging During Kea Startup.

The three main elements of a logger configuration are: name (the component that is generating the messages), severity (what to log), and output_commands (where to log). There is also a debuglevel element, which is only relevant if debug-level logging has been selected.

The name (string) Logger

Each logger in the system has a name: that of the component binary file using it to log messages. For instance, to configure logging for the DHCPv4 server, add an entry for a logger named “kea-dhcp4”. This configuration will then be used by the loggers in the DHCPv4 server and all the libraries used by it, unless a library defines its own logger and there is a specific logger configuration that applies to that logger.

When tracking down an issue with the server’s operation, use of DEBUG logging is required to obtain the verbose output needed for problem diagnosis. However, the high verbosity is likely to overwhelm the logging system in cases where the server is processing high-volume traffic. To mitigate this problem, Kea can use multiple loggers, for different functional parts of the server, that can each be configured independently. If the user is reasonably confident that a problem originates in a specific function of the server, or that the problem is related to a specific type of operation, they may enable high verbosity only for the relevant logger, thereby limiting the DEBUG messages to the required minimum.

The loggers are associated with a particular library or binary of Kea. However, each library or binary may (and usually does) include multiple loggers. For example, the DHCPv4 server binary contains separate loggers for packet parsing, dropped packets, callouts, etc.

The loggers form a hierarchy. For each program in Kea, there is a “root” logger, named after the program (e.g. the root logger for kea-dhcp4, the DHCPv4 server, is named kea-dhcp4). All other loggers are children of this logger and are named accordingly, e.g. the allocation engine in the DHCPv4 server logs messages using a logger called kea-dhcp4.alloc-engine.

This relationship is important, as each child logger derives its default configuration from its parent root logger. In the typical case, the root logger configuration is the only logging configuration specified in the configuration file and so applies to all loggers. If an entry is made for a given logger, any attributes specified override those of the root logger, whereas any not specified are inherited from it.

To illustrate this, suppose we are using the DHCPv4 server with the root logger kea-dhcp4 logging at the INFO level. In order to enable DEBUG verbosity for DHCPv4 packet drops, we must create a configuration entry for the logger called “kea-dhcp4.bad-packets” and specify severity DEBUG for this logger. All other configuration parameters may be omitted for this logger if the logger should use the default values specified in the root logger’s configuration.

If there are multiple logger specifications in the configuration that might match a particular logger, the specification with the more specific logger name takes precedence. For example, if there are entries for both kea-dhcp4 and kea-dhcp4.dhcpsrv, the main DHCPv4 server program — and all libraries it uses other than the dhcpsrv library (libdhcpsrv) — logs messages according to the configuration in the first entry (kea-dhcp4). Messages generated by the dhcpsrv library are logged according to the configuration set by the second entry.

Currently defined loggers are listed in the following table. The “Software Package” column of this table specifies whether the particular loggers belong to the core Kea code (open source Kea binaries and libraries), or hook libraries (open source or premium).

List of loggers supported by Kea servers and hook libraries shipped with Kea/premium packages

Logger Name	Software Package	Description
kea-ctrl-agent	core	The root logger for the Control Agent exposing the RESTful control API. All components used by the Control Agent inherit the settings from this logger.
kea-ctrl-agent.auth	core	A logger which covers access control details, such as a result of the basic HTTP authentication.
kea-ctrl-agent.http	core	A logger which outputs log messages related to receiving, parsing, and sending HTTP messages.
kea-dhcp4	core	The root logger for the DHCPv4 server. All components used by the DHCPv4 server inherit the settings from this logger.
kea-dhcp6	core	The root logger for the DHCPv6 server. All components used by the DHCPv6 server inherit the settings from this logger.
kea-dhcp4.alloc-engine, kea-dhcp6.alloc-engine	core	Used by the lease allocation engine, which is responsible for managing leases in the lease database, i.e. creating, modifying, and removing DHCP leases as a result of processing messages from clients.
kea-dhcp4.bad-packets, kea-dhcp6.bad-packets	core	Used by the DHCP servers for logging inbound client packets that were dropped or to which the server responded with a DHCPNAK. It allows administrators to configure a separate log output that contains only packet drop and reject entries.
kea-dhcp4.bootp-hooks	libdhcp_bootp hook library	This logger is used to log messages related to the operation of the BOOTP hook library.
kea-dhcp4.callouts, kea-dhcp6.callouts	core	Used to log messages pertaining to the callouts registration and execution for the particular hook point.
kea-dhcp4.commands, kea-dhcp6.commands	core	Used to log messages relating to the handling of commands received by the DHCP server over the command channel.
kea-dhcp4.database, kea-dhcp6.database	core	Used to log messages relating to general operations on the relational databases.
kea-dhcp4.ddns, kea-dhcp6.ddns	core	Used by the DHCP server to log messages related to Client FQDN and Hostname option processing. It also includes log messages related to the relevant DNS updates.
kea-dhcp4.dhcp4	core	Used by the DHCPv4 server daemon to log basic operations.
kea-dhcp4.dhcpsrv, kea-dhcp6.dhcpsrv	core	The base loggers for the libkea-dhcpsrv library.
kea-dhcp4.eval, kea-dhcp6.eval	core	Used to log messages relating to the client classification expression evaluation code.
kea-dhcp4.host-cache-hooks, kea-dhcp6.host-cache-hooks	libdhcp_host_cache premium hook library	Used to log messages related to the operation of the Host Cache hook library.
kea-dhcp4.flex-id-hooks, kea-dhcp6.flex-id-hooks	libdhcp_flex_id premium hook library	Used to log messages related to the operation of the Flexible Identifier hook library.
kea-dhcp4.ha-hooks, kea-dhcp6.ha-hooks	libdhcp_ha hook library	Used to log messages related to the operation of the High Availability hook library.
kea-dhcp4.hooks, kea-dhcp6.hooks	core	Used to log messages related to the management of hook libraries, e.g. registration and deregistration of the libraries, and to the initialization of the callouts execution for various hook points within the DHCP server.
kea-dhcp4.host-cmds-hooks, kea-dhcp6.host-cmds-hooks	libdhcp_host_cmds premium hook library	Used to log messages related to the operation of the Host Commands hook library. In general, these pertain to the loading and unloading of the library and the execution of commands by the library.
kea-dhcp4.hosts, kea-dhcp6.hosts	core	Used within libdhcpsrv, it logs messages related to the management of DHCP host reservations, i.e. retrieving reservations and adding new reservations.
kea-dhcp4.lease-cmds-hooks, kea-dhcp6.lease-cmds-hooks	libdhcp_lease_cmds hook library	Used to log messages related to the operation of the Lease Commands hook library. In general, these pertain to the loading and unloading of the library and the execution of commands by the library.
kea-dhcp4.leases, kea-dhcp6.leases	core	Used by the DHCP server to log messages related to lease allocation. The messages include detailed information about the allocated or offered leases, errors during the lease allocation, etc.
kea-dhcp4.legal-log-hooks, kea-dhcp6.legal-log-hooks	libdhcp_legal_log premium hook library	Used to log messages related to the operation of the Forensic Logging hook library.
kea-dhcp4.options, kea-dhcp6.options	core	Used by the DHCP server to log messages related to the processing of options in the DHCP messages, i.e. parsing options, encoding options into on-wire format, and packet classification using options contained in the received packets.
kea-dhcp4.packets, kea-dhcp6.packets	core	Mostly used to log messages related to transmission of the DHCP packets, i.e. packet reception and the sending of a response. Such messages include information about the source and destination IP addresses and interfaces used to transmit packets. The logger is also used to log messages related to subnet selection, as this selection is usually based on the IP addresses, relay addresses, and/or interface names, which can be retrieved from the received packet even before the DHCP message carried in the packet is parsed.
kea-dhcp4.radius-hooks, kea-dhcp6.radius-hooks	libdhcp_radius premium hook library	Used to log messages related to the operation of the RADIUS hook library.
kea-dhcp4.stat-cmds-hooks, kea-dhcp6.stat-cmds-hooks	libdhcp_stat_cmds hook library	Used to log messages related to the operation of the Statistics Commands hook library. In general, these pertain to loading and unloading the library and the execution of commands by the library.
kea-dhcp4.subnet-cmds-hooks, kea-dhcp6.subnet-cmds-hooks	libdhcp_subnet_cmds hook library	Used to log messages related to the operation of the Subnet Commands hook library. In general, these pertain to loading and unloading the library and the execution of commands by the library.
kea-dhcp4.mysql-cb-hooks, kea-dhcp6.mysql-cb-hooks	libdhcp_mysql_cb_hooks hook library	Used to log messages related to the operation of the MySQL Configuration Backend hook library.
kea-dhcp-ddns	core	The root logger for the kea-dhcp-ddns daemon. All components used by this daemon inherit the settings from this logger unless there are configurations for more specialized loggers.
kea-dhcp-ddns.dctl	core	Used by the kea-dhcp-ddns daemon to log basic information about the process, received signals, and triggered reconfigurations.
kea-dhcp-ddns.dhcpddns	core	Used by the kea-dhcp-ddns daemon to log events related to DDNS operations.
kea-dhcp-ddns.dhcp-to-d2	core	Used by the kea-dhcp-ddns daemon to log information about events dealing with receiving messages from the DHCP servers and adding them to the queue for processing.
kea-dhcp-ddns.d2-to-dns	core	Used by the kea-dhcp-ddns daemon to log information about events dealing with sending and receiving messages to and from the DNS servers.
kea-netconf	core	The root logger for the NETCONF agent. All components used by NETCONF inherit the settings from this logger if there is no specialized logger provided.
kea-dhcp4.lease-query-hooks, kea-dhcp6.lease-query-hooks	libdhcp_lease_query hook library	Used to log messages related to the operation of the Leasequery hook library.

Note that user-defined hook libraries should not use any of the loggers mentioned above, but should instead define new loggers with names that correspond to the libraries using them. Suppose that a user created a library called “libdhcp-packet-capture” to dump packets received and transmitted by the server to a file. An appropriate name for the logger could be kea-dhcp4.packet-capture-hooks. (Note that the hook library implementer only specifies the second part of this name, i.e. “packet-capture”. The first part is a root-logger name and is prepended by the Kea logging system.) It is also important to note that since this new logger is a child of a root logger, it inherits the configuration from the root logger, something that can be overridden by an entry in the configuration file.

The easiest way to find a logger name is to configure all logging to go to a single destination and look there for specific logger names. See Logging Message Format for details.

The severity (string) Logger

This specifies the category of messages logged. Each message is logged with an associated severity, which may be one of the following (in descending order of severity):

• FATAL - associated with messages generated by a condition that is so serious that the server cannot continue executing.

• ERROR - associated with messages generated by an error condition. The server continues executing, but the results may not be as expected.

• WARN - indicates an out-of-the-ordinary condition. However, the server continues executing normally.

• INFO - an informational message marking some event.

• DEBUG - messages produced for debugging purposes.

When the severity of a logger is set to one of these values, it only logs messages of that severity and above (e.g. setting the logging severity to INFO logs INFO, WARN, ERROR, and FATAL messages). The severity may also be set to NONE, in which case all messages from that logger are inhibited.

Note

The keactrl tool, described in Managing Kea with keactrl, can be configured to start the servers in verbose mode. If this is the case, the settings of the logging severity in the configuration file have no effect; the servers use a logging severity of DEBUG regardless of the logging settings specified in the configuration file. To control severity via the configuration file, please make sure that the kea_verbose value is set to “no” within the keactrl configuration.

The debuglevel (integer) Logger

When a logger’s severity is set to DEBUG, this value specifies the level of debug messages to be printed. It ranges from 0 (least verbose) to 99 (most verbose). If severity for the logger is not DEBUG, this value is ignored.

The output_options (list) Logger

Each logger can have zero or more output_options. These specify where log messages are sent and are explained in detail below.

The output (string) Option

This value determines the type of output. There are several special values allowed here: stdout (messages are printed on standard output), stderr (messages are printed on stderr), syslog (messages are logged to syslog using the default name), syslog:name (messages are logged to syslog using a specified name). Any other value is interpreted as a filename to which messages should be written.

The flush (boolean) Option

This flushes the buffers after each log message. Doing this reduces performance but ensures that if the program terminates abnormally, all messages up to the point of termination are output. The default is true.

The maxsize (integer) Option

This option is only relevant when the destination is a file; this is the maximum size in bytes that a log file may reach. When the maximum size is reached, the file is renamed and a new file created. Initially, a “.1” is appended to the name; if a “.1” file exists, it is renamed “.2”, etc. This is referred to as rotation.

The default value is 10240000 (10MB). The smallest value that can be specified without disabling rotation is 204800. Any value less than this, including 0, disables rotation. The greatest possible value is INT_MAX MB, which is approximately 2PB.

Note

Due to a limitation of the underlying logging library (log4cplus), rolling over the log files (from “.1” to “.2”, etc.) may show odd results; there can be multiple small files at the timing of rollover. This can happen when multiple processes try to roll over the files simultaneously. Version 1.1.0 of log4cplus solved this problem, so if this version or later of log4cplus is used to build Kea, the issue should not occur. Even with older versions, it is normally expected to happen rarely unless the log messages are produced very frequently by multiple different processes.

The maxver (integer) Option

This option is only relevant when the destination is a file and rotation is enabled (i.e. maxsize is large enough). This is the maximum number of rotated versions that will be kept. Once that number of files has been reached, the oldest file, “log-name.maxver”, is discarded each time the log rotates. In other words, at most there will be the active log file plus maxver rotated files. The minimum and default value is 1.

The pattern (string) Option

This option can be used to specify the layout pattern of messages for a logger. Kea logging is implemented using the log4cplus library and its output formatting is based, conceptually, on the printf formatting from C; this is discussed in detail in the next section, Logging Message Format.

Each output type (stdout, file, or syslog) has a default pattern which describes the content of its log messages. This parameter can be used to specify a desired pattern. The pattern for each logger is governed individually, so each configured logger can have its own pattern. Omitting the pattern parameter or setting it to an empty string, “”, causes Kea to use the default pattern for that logger’s output type.

In addition to the log text itself, the default patterns used for stdout and files contain information such as date and time, logger level, and process information. The default pattern for syslog is limited primarily to log level, source, and the log text. This avoids duplicating information which is usually supplied by syslog.

Warning

Users are strongly encouraged to test their pattern(s) on a local, non-production instance of Kea, running in the foreground and logging to stdout.

Logging Message Format

As mentioned above, Kea log message content is controlled via a scheme similar to the C language’s printf formatting. The “pattern” used for each message is described by a string containing one or more format components as part of a text string. In addition to the components, the string may contain any other useful text for the administrator.

The behavior of Kea’s format strings is determined by log4cplus. The following format options are possible:

List of supported format string components by Kea’s logger

Component	Value
%a	Abbreviated weekday name
%A	Full weekday name
%b	Abbreviated month name
%B	Full month name
%c	Standard date and time string
%d	Day of month as a decimal(1-31)
%H	Hour(0-23)
%I	Hour(1-12)
%j	Day of year as a decimal(1-366)
%m	Month as decimal(1-12)
%M	Minute as decimal(0-59)
%p	Locale’s equivalent of AM or PM
%q	milliseconds as decimal(0-999)
%Q	microseconds as decimal(0-999.999)
%S	Second as decimal(0-59)
%U	Week of year, Sunday being first day(0-53)
%w	Weekday as a decimal(0-6, Sunday being 0)
%W	Week of year, Monday being first day(0-53)
%x	Standard date string
%X	Standard time string
%y	Year in decimal without century(0-99)
%Y	Year including century as decimal
%Z	Time zone name
%%	The percent sign

Refer to the documentation for the strftime() function found in the <ctime> header or the strftime(3) UNIX manual page for more information.

It is probably easiest to understand this by examining the default pattern for stdout and files; currently they are the same. That pattern is shown below:

"%D{%Y-%m-%d %H:%M:%S.%q} %-5p [%c/%i.%t] %m\n";

and a typical log produced by this pattern looks something like this:

2019-08-05 14:27:45.871 DEBUG [kea-dhcp4.dhcpsrv/8475.12345] DHCPSRV_TIMERMGR_START_TIMER starting timer: reclaim-expired-leases

That breaks down to:

• %D{%Y-%m-%d %H:%M:%S.%q} “%D” is the local date and time when the log message is generated, while everything between the curly braces, “{}”, are date and time components. From the example log above this produces: 2019-08-05 14:27:45.871

• %-5p The severity of the message, output as a minimum of five characters, using right-padding with spaces. In our example log: DEBUG

• %c The log source. This includes two elements: the Kea process generating the message, in this case, kea-dhcp4; and the component within the program from which the message originated, dhcpsrv (e.g. the name of the library used by DHCP server implementations).

• %i The process ID. From the example log: 8475.

• %t The thread ID. From the example log: 12345. The format of the thread ID is OS-dependent: e.g. on some systems it is an address, so it is displayed in hexadecimal.

• %m The log message itself. Kea log messages all begin with a message identifier followed by arbitrary log text. Every message in Kea has a unique identifier, which can be used as an index to the Kea Messages Manual, where more information can be obtained. In our example log above, the identifier is DHCPSRV_TIMERMGR_START_TIMER. The log text is typically a brief description detailing the condition that caused the message to be logged. In our example, the information logged, starting timer: reclaim-expired-leases, explains that the timer for the expired lease reclamation cycle has been started.

Warning

Omitting %m omits the log message text from the output, making it rather useless. %m should be considered mandatory.

Finally, note that spacing between components, the square brackets around the log source and PID, and the final carriage return \n are all literal text specified as part of the pattern.

Warning

To ensure that each log entry is a separate line, patterns must end with an \n. There may be use cases where it is not desired so we do not enforce its inclusion. If it is omitted from the pattern, the log entries will run together in one long “line”.

The default pattern for syslog output is:

"%-5p [%c.%t] %m\n";

It omits the date and time as well as the process ID, as this information is typically output by syslog. Note that Kea uses the pattern to construct the text it sends to syslog (or any other destination). It has no influence on the content syslog may add or formatting it may do.

Consult the OS documentation for syslog behavior, as there are multiple implementations.

Example Logger Configurations

In this example, we want to set the server logging to write to the console using standard output.

"Server": {
    "loggers": [
        {
            "name": "kea-dhcp4",
            "output_options": [
                {
                    "output": "stdout"
                }
            ],
            "severity": "WARN"
        }
    ]
}

As a second example, we want to store DEBUG log messages in a file that is at most 2MB and keep up to eight copies of old log files. Once the logfile grows to 2MB, it should be renamed and a new file should be created.

"Server": {
    "loggers": [
        {
            "name": "kea-dhcp6",
            "output_options": [
                {
                    "output": "/var/log/kea-debug.log",
                    "maxver": 8,
                    "maxsize": 204800,
                    "flush": true
                    "pattern": "%d{%j %H:%M:%S.%q} %c %m\n"
                }
            ],
            "severity": "DEBUG",
            "debuglevel": 99
        }
   ]
}

Notice that the above configuration uses a custom pattern which produces output like this:

220 13:50:31.783 kea-dhcp4.dhcp4 DHCP4_STARTED Kea DHCPv4 server version 1.6.0-beta2-git started

Logging During Kea Startup

The logging configuration is specified in the configuration file. However, when Kea starts, the configuration file is not read until partway into the initialization process. Prior to that, the logging settings are set to default values, although it is possible to modify some aspects of the settings by means of environment variables. In the absence of any logging configuration in the configuration file, the settings of the (possibly modified) default configuration will persist while the program is running.

The following environment variables can be used to control the behavior of logging during startup:

KEA_LOCKFILE_DIR

Specifies a directory where the logging system should create its lock file. If not specified, it is prefix/var/run/kea, where “prefix” defaults to /usr/local. This variable must not end with a slash. There is one special value: “none”, which instructs Kea not to create a lock file at all. This may cause issues if several processes log to the same file.

KEA_LOGGER_DESTINATION

Specifies logging output. There are several special values:

stdout Log to standard output.

stderr Log to standard error.

syslog[:fac] Log via syslog. The optional “fac” (which is separated from the word “syslog” by a colon) specifies the facility to be used for the log messages. Unless specified, messages are logged using the facility “local0”.

Any other value is treated as a name of the output file. If not otherwise specified, Kea logs to standard output.

Logging Levels

All Kea servers follow the overall intention to let the user know what is going on while not overloading the logging system with too much information, as that could easily be used as a denial-of-service attack.

Unlike the FATAL, ERROR, WARN and INFO levels, DEBUG has additional parameters. The following list details the basic information that is logged on each level. Sometimes the circumstances determine whether a piece of information is logged on a higher or lower level. For example, if a packet is being dropped due to configured classification, that is an execution of the configured policy and would be logged on debuglevel 15. However, if the packet is dropped due to an exception being thrown, it is much more important, as it may indicate a software bug, serious problems with memory, or database connectivity problems. As such it may be logged on much higher levels, such as WARN or even ERROR.

• 0 - singular messages printed during startup or shutdown of the server.

• 10 - log information about received API commands.

• 15 - information about reasons why a packet was dropped.

• 40 - tracing information, including processing decisions, results of expression evaluations, and more.

• 45 - similar to level 40, but with more details, e.g. the subnet being selected for an incoming packet.

• 50 - evaluations of expressions, status received from hook points, lease processing, packet processing details, including unpacking, packing, sending, etc.

• 55 - includes all details available, including full packet contents with all options printed.

The debug levels apply only to messages logged on DEBUG, and are configured using the debuglevel option. See the The debuglevel (integer) Logger section for details.

The Kea Shell

Overview of the Kea Shell

The Kea Control Agent (CA, see The Kea Control Agent) provides a RESTful control interface over HTTP. That API is typically expected to be used by various IPAMs and similar management systems. Nevertheless, there may be cases when an administrator wants to send a command to the CA directly, and the Kea shell provides a way to do this. It is a simple command-line, scripting-friendly, text client that is able to connect to the CA, send it commands with parameters, retrieve the responses, and display them.

As the primary purpose of the Kea shell is as a tool in a scripting environment, it is not interactive. However, by following simple guidelines it can be run manually.

Kea 1.9.0 introduced basic HTTP authentication support.

Shell Usage

kea-shell is run as follows:

$ kea-shell [--host hostname] [--port number] [--path path] [--auth-user] [--auth-password] [--timeout seconds] [--service service-name] [command]

where:

• --host hostname specifies the hostname of the CA. If not specified, “localhost” is used.

• --port number specifies the TCP port on which the CA listens. If not specified, 8000 is used.

• --path path specifies the path in the URL to connect to. If not specified, an empty path is used. As the CA listens at the empty path, this parameter is useful only with a reverse proxy.

• --auth-user specifies the user ID for basic HTTP authentication. If not specified or specified as the empty string, authentication is not used.

• --auth-password specifies the password for basic HTTP authentication. If not specified but the user ID is specified, an empty password is used.

• --timeout seconds specifies the timeout (in seconds) for the connection. If not given, 10 seconds is used.

• --service service-name specifies the target of a command. If not given, the CA is used as the target. This may be used more than once to specify multiple targets.

• command specifies the command to be sent. If not specified, the list-commands command is used.

Other switches are:

• -h - prints a help message.

• -v - prints the software version.

See TLS Support for new command-line arguments associated with TLS/HTTPS support.

Once started, the shell reads the parameters for the command from standard input, which are expected to be in JSON format. When all have been read, the shell establishes a connection with the CA using HTTP, sends the command, and awaits a response. Once that is received, it is displayed on standard output.

For a list of available commands, see Management API; additional commands may be provided by hook libraries. For a list of all supported commands from the CA, use the list-commands command.

The following shows a simple example of usage:

$ kea-shell --host 192.0.2.1 --port 8001 --service dhcp4 list-commands
^D

After the command line is entered, the program waits for command parameters to be entered. Since list-commands does not take any arguments, Ctrl-D (represented in the above example by “^D”) indicates end-of-file and terminates the parameter input. The shell then contacts the CA and prints out the list of available commands returned for the service named dhcp4.

The Kea shell will likely be most frequently used in scripts; the next example shows a simple scripted execution. It sends the command config-write to the CA (the --service parameter has not been used), along with the parameters specified in param.json. The result will be stored in result.json.

$ cat param.json
"filename": "my-config-file.json"
$ cat param.json | kea-shell --host 192.0.2.1 config-write > result.json

When a reverse proxy is used to de-multiplex requests to different servers, the default empty path in the URL is not enough, so the --path parameter should be used. For instance, if requests to the “/kea” path are forwarded to the CA this can be used:

$ kea-shell --host 192.0.2.1 --port 8001 --path kea ...

The Kea shell requires Python to be installed on the system. It has been tested with Python 2.7 and various versions of Python 3, up to 3.5. Since not every Kea deployment uses this feature and there are deployments that do not have Python, the Kea shell is not enabled by default. To use it, specify --enable-shell when running configure during the installation of Kea. When building on Debian systems, --with-site-packages=... may also be useful.

The Kea shell is intended to serve more as a demonstration of the RESTful interface’s capabilities (and, perhaps, an illustration for people interested in integrating their management environments with Kea) than as a serious management client. It is not likely to be significantly expanded in the future; it is, and will remain, a simple tool.

Note

When using this tool with basic HTTP authentication, please keep in mind that command-line arguments are not hidden from local users.

TLS Support

Since Kea 1.9.6, kea-shell supports HTTPS connections. The TLS/HTTPS support requires Python 3. The additional command-line arguments are:

• --ca specifies the file or directory name of the Certification Authority. If not specified, HTTPS is not used.

• --cert specifies the file name of the user end-entity public key certificate. If specified, the file name of the user key must also be specified.

• --key specifies the file name of the user key file. If specified, the file name of the user certificate must also be specified. Encrypted key files are not supported.

For example, a basic HTTPS request to get a list of commands could look like this:

$ kea-shell --host 127.0.0.1 --port 8000 --ca ./kea-ca.crt list-commands

Integration With External Systems

Kea provides optional support for a variety of external systems, such as RADIUS, NETCONF, YANG, and GSS-TSIG. The following sections describe how to compile Kea with those additional capabilities and how to configure them.

YANG/NETCONF

Overview

The Network Configuration Protocol, or NETCONF, is a network management protocol defined in RFC 4741. It uses YANG modeling language, defined in RFC 6020, to provide a uniform way of handling the configuration syntax of varied networking devices. Kea provides optional support for a YANG/NETCONF interface with the kea-netconf agent.

Installing NETCONF

To get its NETCONF capabilities, Kea uses libyang v1.0.240 and Sysrepo v1.4.140. Use packages if they are provided by the system. If not, users can build from sources, which should work on all popular OSes:

Installing libyang From Sources

$ git clone https://github.com/CESNET/libyang.git
$ cd libyang
$ git checkout v1.0.240
$ mkdir build
$ cd build
$ cmake .. -DGEN_CPP_BINDINGS=ON -DGEN_LANGUAGE_BINDINGS=ON -DGEN_PYTHON_BINDINGS=OFF
$ make
$ make install  # without sudo if you're doing development and want to run unit tests

Installing Sysrepo From Sources

$ git clone https://github.com/sysrepo/sysrepo.git
$ cd sysrepo
$ git checkout v1.4.140
$ mkdir build
$ cd build
$ cmake .. -DGEN_CPP_BINDINGS=ON -DGEN_LANGUAGE_BINDINGS=ON -DGEN_PYTHON_BINDINGS=OFF
$ make
$ make install  # without sudo if you're doing development and want to run unit tests

Quick Sysrepo Overview

This section offers a brief overview of a subset of available functions in Sysrepo. For more complete information, see the Sysrepo homepage.

In YANG, configurations and state data are described in the YANG syntax in module files named: "module-name"``[@”revision”]``.yang

The revision part is optional and has YYYY-MM-DD format. An alternate XML syntax YIN is defined but less user-friendly. Top-level modules are named in Kea models (a short version of schema models).

There are two major modules that Kea is able to support: kea-dhcp4-server and kea-dhcp6-server. While there is an active effort in the DHC working group at IETF to develop a DHCPv6 YANG model, a similar initiative in the past for DHCPv4 failed. Therefore, Kea uses its own dedicated models for DHCPv4 and DHCPv6 but partially supports the IETF model for DHCPv6.

All of the models have extra modules as dependencies. The dependency modules are also provided in src/share/yang/modules in sources and in share/kea/yang/modules in the installation directory.

To install modules from sources, do the following to install all modules:

$ ./src/share/yang/modules/utils/reinstall.sh

If Sysrepo is installed in a custom path, use:

$ ./src/share/yang/modules/utils/reinstall.sh -s /path/to/sysrepo

To individually install all modules:

$ cd ./src/share/yang/modules
$ sysrepoctl -i ./ietf-dhcpv6-server*.yang
$ sysrepoctl -i ./kea-dhcp4-server*.yang
$ sysrepoctl -i ./kea-dhcp6-server*.yang
...

The installation should look similar to the following:

$ ./src/share/yang/modules/utils/reinstall.sh
[INF]: Libyang internal module "yang" was installed.
[INF]: File "ietf-datastores@2018-02-14.yang" was installed.
[INF]: Sysrepo internal dependency module "ietf-datastores" was installed.
[INF]: File "ietf-yang-library@2019-01-04.yang" was installed.
[INF]: Sysrepo internal module "ietf-yang-library" was installed.
[INF]: File "sysrepo-monitoring@2021-01-15.yang" was installed.
[INF]: Sysrepo internal module "sysrepo-monitoring" was installed.
[INF]: File "sysrepo-plugind@2020-12-10.yang" was installed.
[INF]: Sysrepo internal module "sysrepo-plugind" was installed.
[INF]: File "ietf-netconf@2011-06-01.yang" was installed.
[INF]: Sysrepo internal dependency module "ietf-netconf" was installed.
[INF]: File "ietf-netconf-with-defaults@2011-06-01.yang" was installed.
[INF]: Sysrepo internal module "ietf-netconf-with-defaults" was installed.
[INF]: File "ietf-netconf-notifications@2012-02-06.yang" was installed.
[INF]: Sysrepo internal module "ietf-netconf-notifications" was installed.
[INF]: File "ietf-origin@2018-02-14.yang" was installed.
[INF]: Sysrepo internal module "ietf-origin" was installed.
[INF]: Connection 20 created.
[INF]: Module "keatest-module" scheduled for installation.
[INF]: Applying scheduled changes.
[INF]: File "keatest-module@2018-11-20.yang" was installed.
[INF]: Module "keatest-module" was installed.
[INF]: Scheduled changes applied.
[INF]: Connection 21 created.
[INF]: Module "ietf-interfaces" scheduled for installation.
[INF]: Applying scheduled changes.
[INF]: File "ietf-interfaces@2018-02-20.yang" was installed.
[INF]: Module "ietf-interfaces" was installed.
[INF]: Scheduled changes applied.
[INF]: Connection 22 created.
[INF]: Module "ietf-dhcpv6-client" scheduled for installation.
[INF]: File "ietf-dhcpv6-options@2018-09-04.yang" was installed.
[INF]: File "ietf-dhcpv6-types@2018-09-04.yang" was installed.
[INF]: Applying scheduled changes.
[INF]: File "ietf-dhcpv6-client@2018-09-04.yang" was installed.
[INF]: Module "ietf-dhcpv6-client" was installed.
[INF]: Scheduled changes applied.
[INF]: Connection 23 created.
[INF]: Module "ietf-dhcpv6-relay" scheduled for installation.
[INF]: Applying scheduled changes.
[INF]: File "ietf-dhcpv6-relay@2018-09-04.yang" was installed.
[INF]: Module "ietf-dhcpv6-relay" was installed.
[INF]: Scheduled changes applied.
[INF]: Connection 24 created.
[INF]: Module "ietf-dhcpv6-server" scheduled for installation.
[INF]: Applying scheduled changes.
[INF]: File "ietf-dhcpv6-server@2018-09-04.yang" was installed.
[INF]: Module "ietf-dhcpv6-server" was installed.
[INF]: Scheduled changes applied.
[INF]: Connection 25 created.
[INF]: Module "ietf-yang-types" scheduled for installation.
[INF]: Applying scheduled changes.
[INF]: Module "ietf-yang-types" was installed.
[INF]: Scheduled changes applied.
[INF]: Connection 26 created.
[INF]: Module "ietf-dhcpv6-options" scheduled for installation.
[INF]: Applying scheduled changes.
[INF]: Module "ietf-dhcpv6-options" was installed.
[INF]: Scheduled changes applied.
[INF]: Connection 27 created.
[INF]: Module "ietf-dhcpv6-types" scheduled for installation.
[INF]: Applying scheduled changes.
[INF]: Module "ietf-dhcpv6-types" was installed.
[INF]: Scheduled changes applied.
[INF]: Connection 28 created.
[INF]: Module "ietf-inet-types" scheduled for installation.
[INF]: Applying scheduled changes.
[INF]: Module "ietf-inet-types" was installed.
[INF]: Scheduled changes applied.
[INF]: Connection 29 created.
[INF]: Module "kea-types" scheduled for installation.
[INF]: Applying scheduled changes.
[INF]: File "kea-types@2019-08-12.yang" was installed.
[INF]: Module "kea-types" was installed.
[INF]: Scheduled changes applied.
[INF]: Connection 30 created.
[INF]: Module "kea-dhcp-types" scheduled for installation.
[INF]: Applying scheduled changes.
[INF]: File "kea-dhcp-types@2019-08-12.yang" was installed.
[INF]: Module "kea-dhcp-types" was installed.
[INF]: Scheduled changes applied.
[INF]: Connection 31 created.
[INF]: Module "kea-dhcp-ddns" scheduled for installation.
[INF]: Applying scheduled changes.
[INF]: File "kea-dhcp-ddns@2019-08-12.yang" was installed.
[INF]: Module "kea-dhcp-ddns" was installed.
[INF]: Scheduled changes applied.
[INF]: Connection 32 created.
[INF]: Module "kea-ctrl-agent" scheduled for installation.
[INF]: Applying scheduled changes.
[INF]: File "kea-ctrl-agent@2019-08-12.yang" was installed.
[INF]: Module "kea-ctrl-agent" was installed.
[INF]: Scheduled changes applied.
[INF]: Connection 33 created.
[INF]: Module "kea-dhcp4-server" scheduled for installation.
[INF]: Applying scheduled changes.
[INF]: File "kea-dhcp4-server@2019-08-12.yang" was installed.
[INF]: Module "kea-dhcp4-server" was installed.
[INF]: Scheduled changes applied.
[INF]: Connection 34 created.
[INF]: Module "kea-dhcp6-server" scheduled for installation.

It is possible to confirm whether the models are imported correctly. To list the currently installed YANG modules:

$ sysrepoctl -l

After installation the result should be similar to this:

Sysrepo repository: /etc/sysrepo

Module Name                | Revision   | Flags | Owner         | Permissions | Submodules | Features
-----------------------------------------------------------------------------------------------------
ietf-datastores            | 2018-02-14 | I     | user:user     | 664         |            |
ietf-dhcpv6-client         | 2018-09-04 | I     | user:user     | 600         |            |
ietf-dhcpv6-options        | 2018-09-04 | I     | user:user     | 600         |            |
ietf-dhcpv6-relay          | 2018-09-04 | I     | user:user     | 600         |            |
ietf-dhcpv6-server         | 2018-09-04 | I     | user:user     | 600         |            |
ietf-dhcpv6-types          | 2018-09-04 | I     | user:user     | 600         |            |
ietf-inet-types            | 2013-07-15 | I     | user:user     | 664         |            |
ietf-interfaces            | 2018-02-20 | I     | user:user     | 600         |            |
ietf-netconf               | 2011-06-01 | I     | user:user     | 664         |            |
ietf-netconf-notifications | 2012-02-06 | I     | user:user     | 664         |            |
ietf-netconf-with-defaults | 2011-06-01 | I     | user:user     | 664         |            |
ietf-origin                | 2018-02-14 | I     | user:user     | 664         |            |
ietf-yang-library          | 2019-01-04 | I     | user:user     | 664         |            |
ietf-yang-metadata         | 2016-08-05 | i     |               |             |            |
ietf-yang-types            | 2013-07-15 | I     | user:user     | 664         |            |
kea-ctrl-agent             | 2019-08-12 | I     | user:user     | 600         |            |
kea-dhcp-ddns              | 2019-08-12 | I     | user:user     | 600         |            |
kea-dhcp-types             | 2019-08-12 | I     | user:user     | 600         |            |
kea-dhcp4-server           | 2019-08-12 | I     | user:user     | 600         |            |
kea-dhcp6-server           | 2019-08-12 | I     | user:user     | 600         |            |
kea-types                  | 2019-08-12 | I     | user:user     | 600         |            |
keatest-module             | 2018-11-20 | I     | user:user     | 600         |            |
sysrepo-monitoring         | 2021-01-15 | I     | user:user     | 600         |            |
sysrepo-plugind            | 2020-12-10 | I     | user:user     | 664         |            |
yang                       | 2017-02-20 | I     | user:user     | 664         |            |

Flags meaning: I - Installed/i - Imported; R - Replay support; N - New/X - Removed/U - Updated; F - Feature changes
Features: ! - Means that the feature is effectively disabled because of its false if-feature(s)

To reinstall a module, if the revision YANG entry was bumped, simply installing it will update it automatically. Otherwise, it must first be uninstalled:

$ sysrepoctl -u kea-dhcp4-server

If the module is used (i.e. imported) by other modules, it can be uninstalled only after the dependent modules have first been uninstalled. Installation and uninstallation must be done in dependency order and reverse-dependency order accordingly.

Supported YANG Models

The only currently supported models are kea-dhcp4-server and kea-dhcp6-server. There is partial support for ietf-dhcpv6-server, but the primary focus of testing has been on Kea DHCP servers. Other models (kea-dhcp-ddns and kea-ctrl-agent) are currently not supported.

Using the NETCONF Agent

The NETCONF agent follows this algorithm:

• For each managed server, get the initial configuration from the server through the control socket.

• Open a connection with the Sysrepo environment and establish two sessions with the startup and running datastores.

• Check that the used (not-essential) and required (essential) modules are installed in the Sysrepo repository at the right revision. If an essential module - that is, a module where the configuration schema for a managed server is defined - is not installed, raise a fatal error.

• For each managed server, get the YANG configuration from the startup datastore, translate it to JSON, and load it onto the server being configured.

• For each managed server, subscribe a module change callback using its model name.

• When a running configuration is changed, try to validate or load the updated configuration via the callback to the managed server.

Configuration

The behavior described in Using the NETCONF Agent is controlled by several configuration flags, which can be set in the global scope or in a specific managed-server scope. If the latter, the value defined in the managed-server scope takes precedence. These flags are:

• boot-update - controls the initial configuration phase; when true (the default), the initial configuration retrieved from the classic Kea server JSON configuration file is loaded first, and then the startup YANG model is loaded. This setting lets administrators define a control socket in the local JSON file and then download the configuration from YANG. When set to false, this phase is skipped.

• subscribe-changes - controls the module change subscription; when true (the default), a module change callback is subscribed, but when false the phase is skipped and running configuration updates are disabled. When set to true, the running datastore is used to subscribe for changes.

• validate-changes - controls how Kea monitors changes in the Sysrepo configuration. Sysrepo offers two stages where Kea can interact: validation and application. At the validation (or SR_EV_CHANGE event, in the Sysrepo naming convention) stage, Kea retrieves the newly committed configuration and verifies it. If the configuration is incorrect for any reason, the Kea servers reject it and the error is propagated back to the Sysrepo, which then returns an error. This step only takes place if validate-changes is set to true. In the application (or SR_EV_UPDATE event in the Sysrepo naming convention) stage, the actual configuration is applied. At this stage Kea can receive the configuration, but it is too late to signal back any errors as the configuration has already been committed.

The idea behind the initial configuration phase is to boot Kea servers with a minimal configuration which includes only a control socket, making them manageable. For instance, for the DHCPv4 server:

{
    "Dhcp4": {
        "control-socket": {
           "socket-name": "/tmp/kea-dhcp4-ctrl.sock",
           "socket-type": "unix"
        }
    }
}

With module change subscriptions enabled, the kea-netconf daemon monitors any configuration changes as they appear in the Sysrepo. Such changes can be done using the sysrepocfg tool or remotely using any NETCONF client. For details, please see the Sysrepo documentation or A Step-by-Step NETCONF Agent Operation Example. Those tools can be used to modify YANG configurations in the running datastore. Note that committed configurations are only updated in the running datastore; to keep them between server reboots they must be copied to the startup datastore.

When module changes are tracked (using subscribe-changes set to true) and the running configuration has changed (e.g. using sysrepocfg or any NETCONF client), the callback validates the modified configuration (if validate-changes was not set to false) and runs a second time to apply the new configuration. If the validation fails, the callback is still called again but with an SR_EV_ABORT (vs. SR_EV_DONE) event with rollback changes.

The returned code of the callback on an SR_EV_DONE event is ignored, as it is too late to refuse a bad configuration.

There are four ways in which a modified YANG configuration might be incorrect:

1. It could be non-compliant with the schema, e.g. an unknown entry, missing a mandatory entry, a value with a bad type, or not matching a constraint.

2. It could fail to be translated from YANG to JSON, e.g. an invalid user context.

3. It could fail Kea server sanity checks, e.g. an out-of-subnet-pool range or an unsupported database type.

4. The syntax may be correct and pass server sanity checks but the configuration could fail to run, e.g. the configuration specifies database credentials but the database refuses the connection.

The first case is handled by Sysrepo. The second and third cases are handled by kea-netconf in the validation phase (if not disabled by setting validate-changes to true). The last case causes the application phase to fail without a sensible report to Sysrepo.

The managed Kea servers and agents are described in the managed-servers section. Each sub-section begins with the service name: dhcp4, dhcp6, d2 (the DHCP-DDNS server does not support the control-channel feature yet), and ca (the control agent).

Each managed server entry may contain:

• control flags - boot-update, subscribe-changes, and/or validate-changes.

• model - specifies the YANG model/module name. For each service, the default is the corresponding Kea YANG model, e.g. for "dhcp4" it is "kea-dhcp4-server".

• control-socket - specifies the control socket for managing the service configuration.

A control socket is specified by:

• socket-type - the socket type is either stdout, unix, or http. stdout is the default; it is not really a socket, but it allows kea-netconf to run in debugging mode where everything is printed on stdout, and it can also be used to redirect commands easily. unix is the standard direct server control channel, which uses UNIX sockets; http uses a control agent, which accepts HTTP connections.

• socket-name - the local socket name for the unix socket type (default empty string).

• socket-url - the HTTP URL for the http socket type (default http://127.0.0.1:8000/).

User contexts can store arbitrary data as long as they are in valid JSON syntax and their top-level element is a map (i.e. the data must be enclosed in curly brackets). They are accepted at the NETCONF entry, i.e. below the top-level, managed-service entry, and control-socket entry scopes.

Hook libraries can be loaded by the NETCONF agent just as with other servers or agents; however, currently no hook points are defined. The hooks-libraries list contains the list of hook libraries that should be loaded by kea-netconf, along with their configuration information specified with parameters.

Please consult Logging for details on how to configure logging. The name of the NETCONF agent’s main logger is kea-netconf, as given in the example above.

A kea-netconf Configuration Example

The following example demonstrates the basic NETCONF configuration. More examples are available in the doc/examples/netconf directory in the Kea sources.

// This is a simple example of a configuration for the NETCONF agent.
// This server provides a YANG interface for all Kea servers and the agent.
{
    "Netconf":
    {
        // Control flags can be defined in the global scope or
        // in a managed server scope. Precedences are:
        // - use the default value (true)
        // - use the global value
        // - use the local value.
        // So this overwrites the default value:
        "boot-update": false,

        // This map specifies how each server is managed. For each server there
        // is a name of the YANG model to be used and the control channel.
        //
        // Currently three control channel types are supported:
        // "stdout" which outputs the configuration on the standard output,
        // "unix" which uses the local control channel supported by the
        // "dhcp4" and "dhcp6" servers ("d2" support is not yet available),
        // and "http" which uses the Control Agent "ca" to manage itself or
        // to forward commands to "dhcp4" or "dhcp6".
        "managed-servers":
        {
            // This is how kea-netconf can communicate with the DHCPv4 server.
            "dhcp4":
            {
                "comment": "DHCP4 server",
                "model": "kea-dhcp4-server",
                "control-socket":
                {
                    "socket-type": "unix",
                    "socket-name": "/tmp/kea4-ctrl-socket"
                }
            },

            // DHCPv6 parameters.
            "dhcp6":
            {
                "model": "kea-dhcp6-server",
                "control-socket":
                {
                    "socket-type": "unix",
                    "socket-name": "/tmp/kea6-ctrl-socket"
                }
            },

            // Currently the DHCP-DDNS (nicknamed D2) server does not support
            // a command channel.
            "d2":
            {
                "model": "kea-dhcp-ddns",
                "control-socket":
                {
                    "socket-type": "stdout",
                    "user-context": { "in-use": false }
                }
            },

            // Of course the Control Agent (CA) supports HTTP.
            "ca":
            {
                "model": "kea-ctrl-agent",
                "control-socket":
                {
                    "socket-type": "http",
                    "socket-url": "http://127.0.0.1:8000/"
                }
            }
        },

        // kea-netconf is able to load hook libraries that augment its operation.
        // Currently there are no hook points defined in kea-netconf
        // processing.
        "hooks-libraries": [
            // The hooks libraries list may contain more than one library.
            {
                // The only necessary parameter is the library filename.
                "library": "/opt/local/netconf-commands.so",

                // Some libraries may support parameters. Make sure you
                // type this section carefully, as kea-netconf does not
                // validate it (because the format is library-specific).
                "parameters": {
                    "param1": "foo"
                }
            }
        ],

        // Similar to other Kea components, NETCONF also uses logging.
        "loggers": [
            {
                "name": "kea-netconf",
                "output_options": [
                    {
                        "output": "/var/log/kea-netconf.log",
                        // Several additional parameters are possible in
                        // addition to the typical output.
                        // Flush determines whether logger flushes output
                        //  to a file.
                        // Maxsize determines maximum filesize before
                        // the file is being rotated.
                        // Maxver specifies the maximum number of
                        //  rotated files being kept.
                        "flush": true,
                        "maxsize": 204800,
                        "maxver": 4
                    }
                ],
                "severity": "INFO",
                "debuglevel": 0
            }
        ]
    }
}

Starting and Stopping the NETCONF Agent

kea-netconf accepts the following command-line switches:

• -c file - specifies the configuration file.

• -d - specifies whether the agent logging should be switched to debug/verbose mode. In verbose mode, the logging severity and debuglevel specified in the configuration file are ignored and “debug” severity and the maximum debuglevel (99) are assumed. The flag is convenient for temporarily switching the server into maximum verbosity, e.g. when debugging.

• -t file - specifies the configuration file to be tested. kea-netconf attempts to load it and conducts sanity checks; certain checks are possible only while running the actual server. The actual status is reported with exit code (0 = configuration appears valid, 1 = error encountered). Kea prints out log messages to standard output and error to standard error when testing the configuration.

• -v - displays the version of kea-netconf and exits.

• -V - displays the extended version information for kea-netconf and exits. The listing includes the versions of the libraries dynamically linked to Kea.

• -W - displays the Kea configuration report and exits. The report is a copy of the config.report file produced by ./configure; it is embedded in the executable binary.

A Step-by-Step NETCONF Agent Operation Example

Note

Copies of example configurations presented within this section can be found in the Kea source code, under doc/examples/netconf/kea-dhcp6-operations.

Setup of NETCONF Agent Operation Example

The test box has an Ethernet interface named eth1. On some systems it is possible to rename interfaces; for instance, on Linux with an ens38 interface:

# ip link set down dev ens38
# ip link set name eth1 dev ens38
# ip link set up dev eth1

The interface must have an address in the test prefix:

# ip -6 addr add 2001:db8::1/64 dev eth1

The Kea DHCPv6 server must be launched with the configuration specifying a control socket used to receive control commands. The kea-netconf process uses this socket to communicate with the DHCPv6 server, i.e. it pushes translated configurations to that server using control commands. The following is an example control socket specification for the Kea DHCPv6 server:

{
    "Dhcp6": {
        "control-socket": {
           "socket-name": "/tmp/kea-dhcp6-ctrl.sock",
           "socket-type": "unix"
        }
    }
}

In order to launch the Kea DHCPv6 server using the configuration contained within the boot.json file, run:

# kea-dhcp6 -d -c boot.json

The current configuration of the server can be fetched via a control socket by running:

# echo '{ "command": "config-get" }' | socat UNIX:/tmp/kea-dhcp6-ctrl.sock '-,ignoreeof'

The following is the example netconf.json configuration for kea-netconf, to manage the Kea DHCPv6 server:

{
  "Netconf": {
    "loggers": [
      {
        "debuglevel": 99,
        "name": "kea-netconf",
        "output_options": [
          {
            "output": "stderr"
          }
        ],
        "severity": "DEBUG"
      }
    ],
    "managed-servers": {
      "dhcp6": {
        "control-socket": {
          "socket-name": "/tmp/kea-dhcp6-ctrl.sock",
          "socket-type": "unix"
        }
      }
    }
  }
}

Note that in production there should not be a need to log at the DEBUG level.

The Kea NETCONF agent is launched by:

# kea-netconf -d -c netconf.json

Now that both kea-netconf and kea-dhcp6 are running, it is possible to populate updates to the configuration to the DHCPv6 server. The following is the configuration extracted from startup.xml:

<config xmlns="urn:ietf:params:xml:ns:yang:kea-dhcp6-server">
  <subnet6>
    <id>1</id>
    <pool>
      <start-address>2001:db8::1:0</start-address>
      <end-address>2001:db8::1:ffff</end-address>
      <prefix>2001:db8::1:0/112</prefix>
    </pool>
    <subnet>2001:db8::/64</subnet>
  </subnet6>
  <interfaces-config>
    <interfaces>eth1</interfaces>
  </interfaces-config>
  <control-socket>
    <socket-name>/tmp/kea-dhcp6-ctrl.sock</socket-name>
    <socket-type>unix</socket-type>
  </control-socket>
</config>

To populate this new configuration:

$ sysrepocfg -d startup -f xml -m kea-dhcp6-server --edit=startup.xml

kea-netconf pushes the configuration found in the Sysrepo startup datastore to all Kea servers during its initialization phase, after it subscribes to module changes in the Sysrepo running datastore. This action copies the configuration from the startup datastore to the running datastore and enables the running datastore, making it available.

Changes to the running datastore are applied after validation to the Kea servers. Note that they are not by default copied back to the startup datastore, i.e. changes are not permanent.

Error Handling in NETCONF Operation Example

There are four classes of issues with configurations applied via NETCONF:

1. The configuration does not comply with the YANG schema.

2. The configuration cannot be translated from YANG to the Kea JSON.

3. The configuration is rejected by the Kea server.

4. The configuration was validated by the Kea server but cannot be applied.

In the first case, consider the following BAD-schema.xml configuration file:

<config xmlns="urn:ietf:params:xml:ns:yang:kea-dhcp6-server">
  <subnet4>
    <id>1</id>
    <pool>
      <start-address>2001:db8::1:0</start-address>
      <end-address>2001:db8::1:ffff</end-address>
      <prefix>2001:db8::1:0/112</prefix>
    </pool>
    <subnet>2001:db8::/64</subnet>
  </subnet6>
  <interfaces-config>
    <interfaces>eth1</interfaces>
  </interfaces-config>
  <control-socket>
    <socket-name>/tmp/kea-dhcp6-ctrl.sock</socket-name>
    <socket-type>unix</socket-type>
  </control-socket>
</config>

It is directly rejected by sysrepocfg:

$ sysrepocfg -d running -f xml -m kea-dhcp6-server --edit=BAD-schema.xml

In the second case, the configuration is rejected by kea-netconf. For example, consider this BAD-translator.xml file:

<config xmlns="urn:ietf:params:xml:ns:yang:kea-dhcp6-server">
  <subnet6>
    <id>1</id>
    <pool>
      <start-address>2001:db8::1:0</start-address>
      <end-address>2001:db8::1:ffff</end-address>
      <prefix>2001:db8::1:0/112</prefix>
    </pool>
    <subnet>2001:db8::/64</subnet>
  </subnet6>
  <interfaces-config>
    <interfaces>eth1</interfaces>
  </interfaces-config>
  <control-socket>
    <socket-name>/tmp/kea-dhcp6-ctrl.sock</socket-name>
    <socket-type>unix</socket-type>
  </control-socket>
  <user-context>bad</user-context>
</config>

In the third case, the configuration is presented to the Kea DHCPv6 server and fails to validate, as in this BAD-config.xml file:

<config xmlns="urn:ietf:params:xml:ns:yang:kea-dhcp6-server">
  <subnet6>
    <id>1</id>
    <pool>
      <start-address>2001:db8:1::0</start-address>
      <end-address>2001:db8:1::ffff</end-address>
      <prefix>2001:db8:1::0/112</prefix>
    </pool>
    <subnet>2001:db8::/64</subnet>
  </subnet6>
  <interfaces-config>
    <interfaces>eth1</interfaces>
  </interfaces-config>
  <control-socket>
    <socket-name>/tmp/kea-dhcp6-ctrl.sock</socket-name>
    <socket-type>unix</socket-type>
  </control-socket>
</config>

In the last case, the misconfiguration is detected too late and the change must be reverted in Sysrepo, e.g. using the startup datastore as a backup.

NETCONF Operation Example with Two Pools

This example adds a second pool to the initial (i.e. startup) configuration in the twopools.xml file:

<config xmlns="urn:ietf:params:xml:ns:yang:kea-dhcp6-server">
  <subnet6>
    <id>1</id>
    <pool>
      <start-address>2001:db8::1:0</start-address>
      <end-address>2001:db8::1:ffff</end-address>
      <prefix>2001:db8::1:0/112</prefix>
    </pool>
    <pool>
      <start-address>2001:db8::2:0</start-address>
      <end-address>2001:db8::2:ffff</end-address>
      <prefix>2001:db8::2:0/112</prefix>
    </pool>
    <subnet>2001:db8::/64</subnet>
  </subnet6>
  <interfaces-config>
    <interfaces>eth1</interfaces>
  </interfaces-config>
  <control-socket>
    <socket-name>/tmp/kea-dhcp6-ctrl.sock</socket-name>
    <socket-type>unix</socket-type>
  </control-socket>
</config>

This configuration is installed by:

$ sysrepocfg -d running -f xml -m kea-dhcp6-server --edit=twopools.xml

NETCONF Operation Example with Two Subnets

This example specifies two subnets in the twosubnets.xml file:

<config xmlns="urn:ietf:params:xml:ns:yang:kea-dhcp6-server">
  <subnet6>
    <id>1</id>
    <pool>
      <start-address>2001:db8:1::</start-address>
      <end-address>2001:db8:1::ffff</end-address>
      <prefix>2001:db8:1::/112</prefix>
    </pool>
    <subnet>2001:db8:1::/64</subnet>
  </subnet6>
  <subnet6>
    <id>2</id>
    <pool>
      <start-address>2001:db8:2::</start-address>
      <end-address>2001:db8:2::ffff</end-address>
      <prefix>2001:db8:2::/112</prefix>
    </pool>
    <subnet>2001:db8:2::/64</subnet>
  </subnet6>
  <interfaces-config>
    <interfaces>eth1</interfaces>
  </interfaces-config>
  <control-socket>
    <socket-name>/tmp/kea-dhcp6-ctrl.sock</socket-name>
    <socket-type>unix</socket-type>
  </control-socket>
</config>

This configuration is installed by:

$ sysrepocfg -d running -f xml -m kea-dhcp6-server --edit=twosubnets.xml

NETCONF Operation Example with Logging

This example adds a logger entry to the initial (i.e. startup) configuration in the logging.xml file:

<config xmlns="urn:ietf:params:xml:ns:yang:kea-dhcp6-server">
  <interfaces-config>
    <interfaces>eth1</interfaces>
  </interfaces-config>
  <subnet6>
    <id>1</id>
    <pool>
      <start-address>2001:db8::1:0</start-address>
      <end-address>2001:db8::1:ffff</end-address>
      <prefix>2001:db8::1:0/112</prefix>
    </pool>
    <subnet>2001:db8::/64</subnet>
  </subnet6>
  <control-socket>
    <socket-name>/tmp/kea-dhcp6-ctrl.sock</socket-name>
    <socket-type>unix</socket-type>
  </control-socket>
  <logger>
    <name>kea-dhcp6</name>
    <output-option>
      <output>stderr</output>
    </output-option>
    <debuglevel>99</debuglevel>
    <severity>DEBUG</severity>
  </logger>
</config>

The corresponding Kea configuration in JSON is:

{
  "Dhcp6": {
    "control-socket": {
      "socket-name": "/tmp/kea-dhcp6-ctrl.sock",
      "socket-type": "unix"
    },
    "interfaces-config": {
      "interfaces": [ "eth1" ]
    },
    "subnet6": [
      {
        "id": 1,
        "pools": [
          {
            "pool": "2001:db8::1:0/112"
          }
        ],
        "subnet": "2001:db8::/64"
      }
    ],
    "loggers": [
      {
        "name": "kea-dhcp6",
        "output_options": [
          {
            "output": "stderr"
          }
        ],
        "severity": "DEBUG",
        "debuglevel": 99
      }
   ]
 }
}

Finally, any of the previous examples can be replayed by using sysrepocfg in edit mode as follows:

$ sysrepocfg -d running -f xml -m kea-dhcp6-server --edit

or by using a NETCONF client like netopeer2-cli from the Netopeer2 NETCONF Toolset.

Migrating YANG Data from Sysrepo v0.x to v1.x

Start the migration after turning off kea-netconf to make sure that backups for both datastores are done at the same configuration state and no change happens between exporting them.

Unfortunately, Sysrepo v0.x does not support import/export of all YANG modules. This was added in Sysrepo v1.x, so users of earlier versions will need to do per-module backup. This has the added benefit of isolating potential failures and preventing them from affecting all modules.

With Sysrepo v0.x:

$ sysrepocfg --datastore running --export=save.xml --format=xml kea-dhcp6-server
$ sysrepocfg --datastore startup --export=save.xml --format=xml kea-dhcp6-server

Install Sysrepo v1.x and then:

$ sysrepocfg --datastore running --edit=save.xml
$ sysrepocfg --datastore startup --edit=save.xml

Module name and format are optional for v1.x; they are detected automatically. If necessary, they can be provided with the --format xml and --module kea-dhcp6-server flags.

If upgrading from a very old version of Sysrepo, there may also be changes to the YANG modules themselves. In that case, the backups will need some minor massaging, as would be required with normal periodic maintenance.

GSS-TSIG

GSS-TSIG Overview

Kea provides support for DNS updates, which can be protected using Transaction Signatures (or TSIG). This protection is often adequate. However, some systems, in particular Active Directory (AD) on Microsoft Windows servers, have chosen to adopt a more complex GSS-TSIG approach that offers additional capabilities, such as using negotiated dynamic keys.

Kea supports GSS-TSIG to protect DNS updates sent by the Kea DHCP-DDNS (D2) server in a premium hook, called gss_tsig.

GSS-TSIG is defined in RFC 3645. The GSS-TSIG protocol itself is an implementation of generic GSS-API v2 services, defined in RFC 2743.

Many protocols are involved in this mechanism:

• Kerberos 5 - RFC 4120, which provides the security framework;

• GSS-API (Generic Security Services Application Program Interface) - RFC 2743 for the API, RFC 2744 for the C bindings, and RFC 4121 for the application to Kerberos 5;

• SPNEGO (Simple and Protected GSS-API Negotiation Mechanism) - RFC 4178 for the negotiation;

• DNS update RFC 2136;

• TSIG (Secret Key Transaction Authentication for DNS) - RFC 8945, which protects DNS exchanges;

• Secure Domain Name System (DNS) Dynamic Update - RFC 3007, which is the application of TSIG to DNS update protection;

• TKEY (Secret Key Establishment for DNS) - RFC 2930, which establishes secret keys for TSIG by transmitting crypto payloads between DNS parties; and

• GSS-TSIG - RFC 3645, which is the application of GSS-API to TSIG.

To summarize, GSS-API for Kerberos 5 with SPNEGO and TKEY are used to negotiate a security context between the Kea D2 server and a DNS server:

The security context is then used by GSS-TSIG to protect updates:

The Kea implementation of GSS-TSIG uses a GSS-API for Kerberos 5 with the SPNEGO library. Two implementations meet this criteria: MIT Kerberos 5 and Heimdal.

GSS-TSIG Compilation

The following procedure was tested on Ubuntu 20.10 and 21.04. A similar approach can be applied to other systems.

1. Obtain the Kea sources and premium packages, extract the Kea sources, and then extract the premium packages into the premium/ directory within the Kea source tree.

2. Run autoreconf:

autoreconf -i

3. Make sure ./configure --help shows the --with-gssapi option.

4. Install either the MIT (libkrb5-dev) or the Heimdal (heimdal-dev) library, for instance:

sudo apt install libkrb5-dev

5. Run configure with the --with-gssapi option:

./configure --with-gssapi

The --with-gssapi parameter requires the krb5-config tool to be present. This tool is provided by both MIT Kerberos 5 and Heimdal; however, on some systems where both Kerberos 5 and Heimdal are installed, it is a symbolic link to one of them. If the tool is not in the standard location, it can be specified with --with-gssapi=/path/to/krb5-config. It is strongly recommended to use the default installation locations provided by the packages.

The ./configure script should complete with a successful GSS-API detection, similar to this:

GSS-API support:
  GSSAPI_CFLAGS:         -isystem /usr/include/mit-krb5
  GSSAPI_LIBS:           -L/usr/lib/x86_64-linux-gnu/mit-krb5 -Wl,-Bsymbolic-functions -Wl,-z,relro -lgssapi_krb5 -lkrb5 -lk5crypto -lcom_err

6. Compile make -jX, where X is the number of CPU cores available.

7. After compilation, the gss_tsig hook is available in the premium/src/hooks/d2/gss_tsig directory. It can be loaded by the Kea DHCP-DDNS (D2) daemon.

The gss_tsig hook library was developed using the MIT Kerberos 5 implementation, but Heimdal is also supported. Note that Heimdal is picky about security-sensitive file permissions and is known to emit an unclear error message. It is a good idea to keep these files plain, with one link and no access for the group or other users.

The krb5-config script should provide an --all option which identifies the implementation.

GSS-TSIG Deployment

Before using GSS-TSIG, a GSS-TSIG capable DNS server, such as BIND 9 or Microsoft Active Directory (AD), must be deployed. Other GSS-TSIG capable implementations may work, but have not been tested.

Kerberos 5 Setup

There are two kinds of key tables (keytab files): the system one used by servers, and client tables used by clients. For Kerberos 5, Kea is a client.

Install the Kerberos 5 client library and kadmin tool:

sudo apt install krb5-kdc krb5-admin-server

The following examples use the EXAMPLE.ORG realm to demonstrate required configuration steps and settings.

The Kerberos 5 client library must be configured to accept incoming requests for the realm EXAMPLE.ORG by updating the krb5.conf file (e.g. on Linux: /etc/krb5.conf):

[libdefaults]
    default_realm = EXAMPLE.ORG
    kdc_timesync = 1
    ccache_type = 4
    forwardable = true
    proxiable = true

[realms]
    EXAMPLE.ORG = {
            kdc = kdc.example.org
            admin_server = kdc.example.org
    }

In addition to the krb5.conf file, the kdc.conf file can be used (e.g. on Linux: /etc/krb5kdc/kdc.conf):

[kdcdefaults]
    kdc_ports = 750,88

[realms]
    EXAMPLE.ORG = {
        database_name = /var/lib/krb5kdc/principal
        admin_keytab = FILE:/etc/krb5kdc/kadm5.keytab
        acl_file = /etc/krb5kdc/kadm5.acl
        key_stash_file = /etc/krb5kdc/stash
        kdc_ports = 750,88
        max_life = 10h 0m 0s
        max_renewable_life = 7d 0h 0m 0s
        master_key_type = des3-hmac-sha1
        #supported_enctypes = aes256-cts:normal aes128-cts:normal
        default_principal_flags = +preauth
    }

The kadmind daemon Access Control List (ACL) must be configured to give permissions to the DNS client principal to access the Kerberos 5 database (e.g. on Linux: /etc/krb5kdc/kadm5.acl):

DHCP/admin.example.org@EXAMPLE.ORG       *

The administrator password for the default realm must be set:

krb5_newrealm

After the following message is displayed, enter the password for the default realm:

This script should be run on the master KDC/admin server to initialize
a Kerberos realm.  It will ask you to type in a master key password.
This password will be used to generate a key that is stored in
/etc/krb5kdc/stash.  You should try to remember this password, but it
is much more important that it be a strong password than that it be
remembered.  However, if you lose the password and /etc/krb5kdc/stash,
you cannot decrypt your Kerberos database.
Loading random data
Initializing database '/var/lib/krb5kdc/principal' for realm 'EXAMPLE.ORG',
master key name 'K/M@EXAMPLE.ORG'
You will be prompted for the database Master Password.
It is important that you NOT FORGET this password.
Enter KDC database master key:

Then retype the password:

Re-enter KDC database master key to verify:

If successfully applied, the following message is displayed:

Now that your realm is set up you may wish to create an administrative
principal using the addprinc subcommand of the kadmin.local program.
Then, this principal can be added to /etc/krb5kdc/kadm5.acl so that
you can use the kadmin program on other computers.  Kerberos admin
principals usually belong to a single user and end in /admin.  For
example, if jruser is a Kerberos administrator, then in addition to
the normal jruser principal, a jruser/admin principal should be
created.

Don't forget to set up DNS information so your clients can find your
KDC and admin servers.  Doing so is documented in the administration
guide.

The next step is to create the principals for the BIND 9 DNS server (the service protected by the GSS-TSIG TKEY) and for the DNS client (the Kea DHCP-DDNS server).

The BIND 9 DNS server principal (used for authentication) is created the following way:

kadmin.local -q "addprinc -randkey DNS/server.example.org"

If successfully created, the following message is displayed:

No policy specified for DNS/server.example.org@EXAMPLE.ORG; defaulting to no policy
Authenticating as principal root/admin@EXAMPLE.ORG with password.
Principal "DNS/server.example.org@EXAMPLE.ORG" created.

The DNS server principal must be exported so that it can be used by the BIND 9 DNS server. Only this principal is required, and it is exported to the keytab file with the name dns.keytab.

kadmin.local -q "ktadd -k /tmp/dns.keytab DNS/server.example.org"

If successfully exported, the following message is displayed:

Authenticating as principal root/admin@EXAMPLE.ORG with password.
Entry for principal DNS/server.example.org with kvno 2, encryption type aes256-cts-hmac-sha1-96 added to keytab WRFILE:/tmp/dns.keytab.
Entry for principal DNS/server.example.org with kvno 2, encryption type aes128-cts-hmac-sha1-96 added to keytab WRFILE:/tmp/dns.keytab.

The DHCP client principal (used by the Kea DHCP-DDNS server) is created the following way:

kadmin.local -q "addprinc -randkey DHCP/admin.example.org"

If successfully created, the following message is displayed:

No policy specified for DHCP/admin.example.org@EXAMPLE.ORG; defaulting to no policy
Authenticating as principal root/admin@EXAMPLE.ORG with password.
Principal "DHCP/admin.example.org@EXAMPLE.ORG" created.

The DHCP client principal must be exported so that it can be used by the Kea DHCP-DDNS server and the GSS-TSIG hook library. It is exported to the client keytab file with the name dhcp.keytab.

kadmin.local -q "ktadd -k /tmp/dhcp.keytab DHCP/admin.example.org"

Finally, the krb5-admin-server must be restarted:

systemctl restart krb5-admin-server.service

BIND 9 with GSS-TSIG Configuration

The BIND 9 DNS server must be configured to use GSS-TSIG, and to use the previously exported DNS server principal from the keytab file dns.keytab. Updating the named.conf file is required:

options {
    ...
    directory "/var/cache/bind";
    dnssec-validation auto;
    listen-on-v6 { any; };
    tkey-gssapi-keytab "/etc/bind/dns.keytab";
};
zone "example.org" {
    type master;
    file "/var/lib/bind/db.example.org";
    update-policy {
        grant "DHCP/admin.example.org@EXAMPLE.ORG" zonesub any;
    };
};
zone "84.102.10.in-addr.arpa" {
    type master;
    file "/etc/bind/db.10";
};

The zone files should have an entry for the server principal FQDN server.example.org.

The /etc/bind/db.10 file needs to be created or updated:

;
; BIND reverse data file for local loopback interface
;
$TTL    604800                      ; 1 week
@       IN      SOA      server.example.org. root.example.org. (
                         2          ; Serial
                         604800     ; Refresh
                         86400      ; Retry
                         2419200    ; Expire
                         604800     ; Negative Cache TTL
                         )
;
@       IN      NS      ns.
40      IN      PTR     ns.example.org.

The /var/lib/bind/db.example.org file needs to be created or updated:

$ORIGIN .
$TTL                604800             ; 1 week
example.org         IN SOA  server.example.org. root.example.org. (
                            8          ; serial
                            604800     ; refresh (1 week)
                            86400      ; retry (1 day)
                            2419200    ; expire (4 weeks)
                            604800     ; minimum (1 week)
                            )
                    NS      example.org.
                    A       ${BIND9_IP_ADDR}
                    AAAA    ::1
$ORIGIN example.org.
kdc                 A       ${KDC_IP_ADDR}
server              A       ${BIND9_IP_ADDR}

After any configuration change the server must be reloaded or restarted:

systemctl restart named.service

It is possible to get the status or restart the logs:

systemctl status named.service
journalctl -u named | tail -n 30

Windows Active Directory Configuration

This sub-section is based on an Amazon AWS provided Microsoft Windows Server 2016 with Active Directory pre-installed, so it describes only the steps used for GSS-TSIG deployment. (For the complete configuration process, please refer to Microsoft’s documentation or other external resources. We found this tutorial very useful during configuration of our internal QA testing systems.)

Two Active Directory (AD) user accounts are needed:

• the first account is used to download AD information, such as the client key table of Kea

• the second account is mapped to the Kea DHCP client principal

Kea needs to know:

• the server IP address

• the domain/realm name: the domain is in lower case, the realm in upper case, both without a final dot

• the server name

The second account (named kea below) is used to create a Service Principal Name (SPN):

setspn -S DHCP/kea.<domain> kea

After a shared secret key is generated and put in a key table file:

ktpass -princ DHCP/kea.<domain>@<REALM> -mapuser kea +rndpass -mapop set -ptype KRB5_NT_PRINCIPAL -out dhcp.keytab

The dhcp.keytab takes the same usage as for UNIX Kerberos.

GSS-TSIG Troubleshooting

While testing GSS-TSIG integration with Active Directory we came across one very cryptic error:

INFO  [kea-dhcp-ddns.gss-tsig-hooks/4678.139690935890624] GSS_TSIG_VERIFY_FAILED GSS-TSIG verify failed: gss_verify_mic failed with GSSAPI error:
Major = 'A token had an invalid Message Integrity Check (MIC)' (393216), Minor = 'Packet was replayed in wrong direction' (100002).

In our case, the problem was that the Kea D2 server was trying to perform an update of a reverse DNS zone while it was not configured. An easy solution is to add a reverse DNS zone similar to the one configured in Kea. To do that, open the “DNS Manager” and choose “DNS” from the list; from the dropdown list, choose “Reverse Lookup Zones”; then click “Action” and “New Zone”; finally, follow the New Zone Wizard to add a new zone.

Using GSS-TSIG

There are a number of steps required to enable the GSS-TSIG mechanism:

1. The gss_tsig hook library must be loaded by the D2 server.

2. The GSS-TSIG-capable DNS servers must be specified with their parameters.

An excerpt from a D2 server configuration is provided below; more examples are available in the doc/examples/ddns directory in the Kea sources.

{
"DhcpDdns": {
    // The following parameters are used to receive NCRs (NameChangeRequests)
    // from the local Kea DHCP server. Make sure your kea-dhcp4 and kea-dhcp6
    // matches this.
    "ip-address": "127.0.0.1",
    "port": 53001,
    "dns-server-timeout" : 1000,

    // Forward zone: secure.example.org. It uses GSS-TSIG. It is served
    // by two DNS servers, which listen for DDNS requests at 192.0.2.1
    // and 192.0.2.2.
    "forward-ddns":
    {
        "ddns-domains":
        [
            // DdnsDomain for zone "secure.example.org."
            {
                "name": "secure.example.org.",
                "comment": "DdnsDomain example",
                "dns-servers":
                [
                    { // This server has an entry in gss/servers and
                      // thus will use GSS-TSIG.
                        "ip-address": "192.0.2.1"
                    },
                    { // This server also has an entry there, so will
                      // use GSS-TSIG, too.
                        "ip-address": "192.0.2.2",
                        "port": 5300
                    }
                ]
            }
        ]
    },

    // Reverse zone: we want to update the reverse zone "2.0.192.in-addr.arpa".
    "reverse-ddns":
    {
        "ddns-domains":
        [
            {
                "name": "2.0.192.in-addr.arpa.",
                "dns-servers":
                [
                    {
                        // There is a GSS-TSIG definition for this server (see
                        // DhcpDdns/gss-tsig/servers), so it will use
                        // Krb/GSS-TSIG.
                        "ip-address": "192.0.2.1"
                    }
                ]
            }
        ]
    },

    // Need to add gss-tsig hook here
    "hooks-libraries": [
    {
        "library": "/opt/lib/libddns_gss_tsig.so",
        "parameters": {
            // This section governs the GSS-TSIG integration. Each server
            // mentioned in forward-ddns and/or reverse-ddns needs to have
            // an entry here to be able to use GSS-TSIG defaults (optional,
            // if specified they apply to all the GSS-TSIG servers, unless
            // overwritten on specific server level).

            "server-principal": "DNS/server.example.org@EXAMPLE.ORG",
            "client-principal": "DHCP/admin.example.org@EXAMPLE.ORG",
            "client-keytab": "FILE:/etc/dhcp.keytab", // toplevel only
            "credentials-cache": "FILE:/etc/ccache", // toplevel only
            "tkey-lifetime": 3600, // 1 hour
            "rekey-interval": 2700, // 45 minutes
            "retry-interval": 120, // 2 minutes
            "tkey-protocol": "TCP",
            "fallback": false,

            // The list of GSS-TSIG capable servers
            "servers": [
                {
                    // First server (identification is required)
                    "id": "server1",
                    "domain-names": [ ], // if not specified or empty, will
                                         // match all domains that want to
                                         // use this IP+port pair
                    "ip-address": "192.0.2.1",
                    "port": 53,
                    "server-principal": "DNS/server1.example.org@EXAMPLE.ORG",
                    "client-principal": "DHCP/admin1.example.org@EXAMPLE.ORG",
                    "tkey-lifetime": 7200, // 2 hours
                    "rekey-interval": 5400, // 90 minutes
                    "retry-interval": 240, // 4 minutes
                    "tkey-protocol": "TCP",
                    "fallback": true // if no key is available fallback to the
                                     // standard behavior (vs skip this server)
                },
                {
                    // The second server (it has most of the parameters missing
                    // as those are using the defaults specified above)
                    "id": "server2",
                    "ip-address": "192.0.2.2",
                    "port": 5300
                }
            ]
        }
    }
    ]

    // Additional parameters, such as logging, control socket and
    // others omitted for clarity.
}

}

This configuration file contains a number of extra elements.

First, a list of forward and/or reverse domains with related DNS servers identified by their IP+port pairs is defined. If the port is not specified, the default of 53 is assumed. This is similar to basic mode, with no authentication done using TSIG keys, with the exception that static TSIG keys are not referenced by name.

Second, the libddns_gss_tsig.so library must be specified on the hooks-libraries list. This hook takes many parameters. The most important one is servers, which is a list of GSS-TSIG-capable servers. If there are several servers and they share some characteristics, the values can be specified in the parameters scope as defaults. In the example above, the defaults that apply to all servers, unless otherwise specified on a per-server scope, are defined in lines 63 through 68. The defaults can be skipped if there is only one server defined, or if all servers have different values.

List of available parameters

Name	Scope	Type	Default value	Description
client-keytab	global / server	string	empty	the Kerberos client key table
credentials-cache	global / server	string	empty	the Kerberos credentials cache
server-principal	global / server	string	empty	the Kerberos principal name of the DNS server that will receive updates
client-principal	global / server	string	empty	the Kerberos principal name of the Kea D2 service
tkey-protocol	global / server	string “TCP” / “UDP”	“TCP”	the protocol used to establish the security context with the DNS servers
tkey-lifetime	global / server	uint32	3600 seconds ( 1 hour )	the lifetime of GSS-TSIG keys
rekey-interval	global / server	uint32	2700 seconds ( 45 minutes )	the time interval the keys are checked for rekeying
retry-interval	global / server	uint32	120 seconds ( 2 minutes )	the time interval to retry to create a key if any error occurred previously
fallback	global / server	true / false	false	the behavior to fallback to non-GSS-TSIG when GSS-TSIG should be used but no GSS-TSIG key is available.
exchange-timeout	global / server	uint32	3000 milliseconds ( 3 seconds )	the time used to wait for the GSS-TSIG TKEY exchange to finish before it timeouts
user-context	global / server	string	empty	the user-provided data in JSON format (not used by the GSS-TSIG hook)
comment	global / server	string	empty	ignored
id	server	string	empty	identifier to a DNS server (required)
domain-names	server	list of strings	empty	the many-to-one relationship between D2 DNS servers and GSS-TSIG DNS servers
ip-address	server	IPv4 / IPv6 address	empty	the IP address at which the GSS-TSIG DNS server listens for DDNS and TKEY requests (required)
port	server	uint16	53	the DNS transport port at which the GSS-TSIG DNS server listens for DDNS and TKEY requests

The global parameters are described below:

• client-keytab specifies the Kerberos client key table. For instance, FILE:<filename> can be used to point to a specific file. This parameter can be specified only once, in the parameters scope, and is the equivalent of setting the KRB5_CLIENT_KTNAME environment variable. An empty value is silently ignored.

• credentials-cache specifies the Kerberos credentials cache. For instance, FILE:<filename> can be used to point to a file or, if using a directory which supports more than one principal, DIR:<directory-path>. This parameter can be specified only once, in the parameters scope, and is the equivalent of setting the KRB5CCNAME environment variable. An empty value is silently ignored.

• server-principal is the Kerberos principal name of the DNS server that receives updates. In other words, this is the DNS server’s name in the Kerberos system. This parameter is mandatory, and uses the typical Kerberos notation: <SERVICE-NAME>/<server-domain-name>@<REALM>.

• client-principal is the Kerberos principal name of the Kea D2 service. It is optional, and uses the typical Kerberos notation: <SERVICE-NAME>/<server-domain-name>@<REALM>.

• tkey-protocol determines which protocol is used to establish the security context with the DNS servers. Currently, the only supported values are TCP (the default) and UDP.

• tkey-lifetime determines the lifetime of GSS-TSIG keys in the TKEY protocol. The value must be greater than the rekey-interval value. It is expressed in seconds and defaults to 3600 (one hour).

• rekey-interval governs the time interval at which the keys for each configured server are checked for rekeying, i.e. when a new key is created to replace the current usable one if its age is greater than the rekey-interval value. The value must be smaller than the tkey-lifetime value (it is recommended to be set between 50% and 80% of the tkey-lifetime value). It is expressed in seconds and defaults to 2700 (45 minutes, or 75% of one hour).

• retry-interval governs the time interval at which to retry to create a key if any error occurred previously for any configured server. The value must be smaller than the rekey-interval value, and should be at most 1/3 of the difference between tkey-lifetime and rekey-interval. It is expressed in seconds and defaults to 120 (2 minutes).

• fallback governs the behavior when GSS-TSIG should be used (a matching DNS server is configured) but no GSS-TSIG key is available. If set to false (the default), this server is skipped; if set to true, the DNS server is ignored and the DNS update is sent with the configured DHCP-DDNS protection (e.g. TSIG key), or without any protection when none was configured.

• exchange-timeout governs the amount of time to wait for the GSS-TSIG TKEY exchange to finish before the process times out. It is expressed in milliseconds and defaults to 3000 (3 seconds).

• user-context is an optional parameter (see Comments and User Context for a general description of user contexts in Kea).

• comment is allowed but currently ignored.

• servers specifies the list of DNS servers where GSS-TSIG is enabled.

The server map parameters are described below:

• id assigns an identifier to a DNS server. It is used for statistics and commands. It is required, and must be both not empty and unique.

• domain-names governs the many-to-one relationship between D2 DNS servers and GSS-TSIG DNS servers: for each domain name on this list, Kea looks for a D2 DNS server for this domain with the specified IP address and port. An empty list (the default) means that all domains match.

• ip-address specifies the IP address at which the GSS-TSIG DNS server listens for DDNS and TKEY requests. It is a mandatory parameter.

• port specifies the DNS transport port on which the GSS-TSIG DNS server listens for DDNS and TKEY requests. It defaults to 53.

• server-principal is the Kerberos principal name of the DNS server that receives updates. The server-principal parameter set at the per-server level takes precedence over one set at the global level. It is a mandatory parameter which must be specified at either the global or the server level.

• client-principal is the Kerberos principal name of the Kea D2 service for this DNS server. The client-principal parameter set at the per-server level takes precedence over one set at the global level. It is an optional parameter.

• tkey-protocol determines which protocol is used to establish the security context with the DNS server. The tkey-protocol parameter set at the per-server level takes precedence over one set at the global level. The default and supported values for the per-server level parameter are the same as for the global-level parameter.

• tkey-lifetime determines the lifetime of GSS-TSIG keys in the TKEY protocol for the DNS server. The tkey-lifetime parameter set at the per-server level takes precedence over one set at the global level. The default and supported values for the per-server level parameter are the same as for the global-level parameter.

• rekey-interval governs the time interval at which the keys for this particular server are checked for rekeying, i.e. when a new key is created to replace the current usable one if its age is greater than the rekey-interval value. The value must be smaller than the tkey-lifetime value (it is recommended to be set between 50% and 80% of the tkey-lifetime value). The rekey-interval parameter set at the per-server level takes precedence over one set at the global level. The default and supported values for the per-server level parameter are the same as for the global-level parameter.

• retry-interval governs the time interval at which to retry to create a key if any error occurred previously for this particular server. The value must be smaller than the rekey-interval value, and should be at most 1/3 of the difference between tkey-lifetime and rekey-interval. The retry-interval parameter set at the per-server level takes precedence over one set at the global level. The default and supported values for the per-server level parameter are the same as for the global-level parameter.

• fallback governs the behavior when GSS-TSIG should be used (a matching DNS server is configured) but no GSS-TSIG key is available. The fallback parameter set at the per-server level takes precedence over one set at the global level. The default and supported values for the per-server level parameter are the same as for the global-level parameter..

• exchange-timeout governs the amount of time to wait for the GSS-TSIG TKEY exchange to finish before the process times out. The exchange-timeout parameter set at the per-server level takes precedence over one set at the global level. The default and supported values for the per-server level parameter are the same as for the global-level parameter.

• user-context is an optional parameter (see Comments and User Context for a general description of user contexts in Kea).

• comment is allowed but currently ignored.

GSS-TSIG Automatic Key Removal

The server periodically deletes keys after they have been expired more than three times the length of the maximum key lifetime (the tkey-lifetime parameter). The user has the option to purge keys on demand by using the gss-tsig-purge-all command (see The gss-tsig-purge-all Command) or the gss-tsig-purge command (see The gss-tsig-purge Command).

GSS-TSIG Configuration for Deployment

When using Kerberos 5 and BIND 9 as described in GSS-TSIG Deployment, the local resolver must point to the BIND 9 named server address. The local Kerberos must also be configured by putting the following text into the krb5.conf file:

[libdefaults]
    default_realm = EXAMPLE.ORG
    kdc_timesync = 1
    ccache_type = 4
    forwardable = true
    proxiable = true
[realms]
    EXAMPLE.ORG = {
            kdc = kdc.example.org
            admin_server = kdc.example.org
    }

With Windows AD, the DNS service is provided by AD, which also provides the Kerberos service. The required text in the krb5.conf file becomes:

[libdefaults]
    default_realm = <REALM>
    kdc_timesync = 1
    ccache_type = 4
    forwardable = true
    proxiable = true
[realms]
    ${REALM} = {
            kdc = <AD_IP_ADDR>
            admin_server = <AD_IP_ADDR>
    }

Even when the GSS-API library can use the secret from the client key table, it is far better for performance to get and cache credentials.

This can be done manually via the command:

kinit -k -t /tmp/dhcp.keytab DHCP/admin.example.org

or, when using AD:

kinit -k -t /tmp/dhcp.keytab DHCP/kea.<domain>

The credential cache can be displayed using klist.

In production, it is better to rely on a Kerberos Credential Manager as the System Security Services Daemon (sssd).

When using BIND 9, the server principal is in the form “DNS/server.example.org@EXAMPLE.ORG¨; with AD, the format is “DNS/<server>.<domain>@<REALM>”.

GSS-TSIG Statistics

The GSS-TSIG hook library introduces new statistics at global and per-DNS-server levels:

• gss-tsig-key-created - the number of created GSS-TSIG keys

• tkey-sent - the number of sent TKEY exchange initial requests

• tkey-success - the number of TKEY exchanges which completed with a success

• tkey-timeout - the number of TKEY exchanges which completed on timeout

• tkey-error - the number of TKEY exchanges which completed with an error other than a timeout

The relationship between keys and DNS servers is very different between the D2 code and static TSIG keys, and GSS-TSIG keys and DNS servers:

• a static TSIG key can be shared between many DNS servers;

• a GSS-TSIG key is only used by one DNS server inside a dedicated set of keys.

GSS-TSIG Commands

The GSS-TSIG hook library supports some commands, which are described below.

The gss-tsig-get-all Command

This command lists all the GSS-TSIG servers and keys.

An example command invocation looks like this:

{
    "command": "gss-tsig-get-all"
}

Here is an example of a response returning one GSS-TSIG server and one key:

{
    "result": 0,
    "text": "1 GSS-TSIG servers and 1 keys",
    "arguments": {
        "gss-tsig-servers": [
            {
                "id": "foo",
                "ip-address": "192.1.2.3",
                "port": 53,
                "server-principal": "DNS/foo.com@FOO.COM",
                "key-name-suffix": "foo.com.",
                "tkey-lifetime": 3600,
                "tkey-protocol": "TCP",
                "keys": [
                    {
                        "name": "1234.sig-foo.com.",
                        "inception-date": "2021-09-05 12:23:36.281176",
                        "server-id": "foo",
                        "expire-date": "2021-09-05 13:23:36.281176",
                        "status": "not yet ready",
                        "tkey-exchange": true
                    }
                ]
            },
            {
                "id": "bar",
                "ip-address": "192.1.2.4",
                "port": 53,
                "server-principal": "DNS/bar.com@FOO.COM",
                "key-name-suffix": "bar.com.",
                "tkey-lifetime": 7200,
                "tkey-protocol": "UDP",
                "keys": [ ]
            }
        ]
    }
}

The gss-tsig-get Command

This command retrieves information about the specified GSS-TSIG server.

An example command invocation looks like this:

{
    "command": "gss-tsig-get",
    "arguments": {
        "server-id": "foo"
    }
}

Here is an example of a response returning information about the server “foo”:

{
    "result": 0,
    "text": "GSS-TSIG server[foo] found",
    "arguments": {
        "id": "foo",
        "ip-address": "192.1.2.3",
        "port": 53,
        "server-principal": "DNS/foo.com@FOO.COM",
        "key-name-suffix": "foo.com.",
        "tkey-lifetime": 3600,
        "tkey-protocol": "TCP",
        "keys": [
            {
                "name": "1234.sig-foo.com.",
                "server-id": "foo",
                "inception-date": "2021-09-05 12:23:36.281176",
                "expire-date": "2021-09-05 13:23:36.281176",
                "status": "not yet ready",
                "tkey-exchange": true
            }
        ]
    }
}

The gss-tsig-list Command

This command generates a list of GSS-TSIG server IDs and key names.

An example command invocation looks like this:

{
    "command": "gss-tsig-list"
}

Here is an example of a response returning two GSS-TSIG servers and three keys:

{
    "result": 0,
    "text": "2 GSS-TSIG servers and 3 keys",
    "arguments": {
        "gss-tsig-servers": [
            "foo",
            "bar"
        ],
        "gss-tsig-keys": [
            "1234.example.com.",
            "5678.example.com.",
            "43888.example.org."
        ]
    }
}

The gss-tsig-key-get Command

This command retrieves information about the specified GSS-TSIG key.

An example command invocation looks like this:

{
    "command": "gss-tsig-key-get",
    "arguments": {
        "key-name": "1234.sig-foo.com."
    }
}

Here is an example of a response returning information about GSS-TSIG key “1234.sig-foo.com.”:

{
    "result": 0,
    "text": "GSS-TSIG key '1234.sig-foo.com.' found",
    "arguments": {
        "name": "1234.sig-foo.com.",
        "server-id": "foo",
        "inception-date": "2021-09-05 12:23:36.281176",
        "expire-date": "2021-09-05 13:23:36.281176",
        "status": "not yet ready",
        "tkey-exchange": true
    }
}

The gss-tsig-key-expire Command

This command expires the specified GSS-TSIG key.

An example command invocation looks like this:

{
    "command": "gss-tsig-key-expire",
    "arguments": {
        "key-name": "1234.sig-foo.com."
    }
}

Here is an example of a response indicating that GSS-TSIG key “1234.sig-foo.com.” has been expired:

{
    "result": 0,
    "text": "GSS-TSIG key '1234.sig-foo.com.' expired"
}

The gss-tsig-key-del Command

This command deletes the specified GSS-TSIG key.

An example command invocation looks like this:

{
    "command": "gss-tsig-key-del",
    "arguments": {
        "key-name": "1234.sig-foo.com."
    }
}

Here is an example of a response indicating that GSS-TSIG key “1234.sig-foo.com.” has been deleted:

{
    "result": 0,
    "text": "GSS-TSIG key '1234.sig-foo.com.' deleted"
}

The gss-tsig-purge-all Command

This command removes all unusable GSS-TSIG keys.

An example command invocation looks like this:

{
    "command": "gss-tsig-purge-all"
}

Here is an example of a response indicating that two GSS-TSIG keys have been purged:

{
    "result": 0,
    "text": "2 purged GSS-TSIG keys"
}

The gss-tsig-purge Command

This command removes unusable GSS-TSIG keys for the specified server.

An example command invocation looks like this:

{
    "command": "gss-tsig-purge",
    "arguments": {
        "server-id": "foo"
    }
}

Here is an example of a response indicating that two GSS-TSIG keys for server “foo” have been purged:

{
    "result": 0,
    "text": "2 purged keys for GSS-TSIG server[foo]"
}

The gss-tsig-rekey-all Command

This command unconditionally creates new GSS-TSIG keys (rekeys) for all DNS servers.

An example command invocation looks like this:

{
    "command": "gss-tsig-rekey-all"
}

Here is an example of a response indicating that a rekey was performed:

{
    "result": 0,
    "text": "rekeyed"
}

This command is useful when, for instance, the DHCP-DDNS server is reconnected to the network.

The gss-tsig-rekey Command

This command unconditionally creates new GSS-TSIG keys (rekeys) for a specified DNS server.

An example command invocation looks like this:

{
    "command": "gss-tsig-rekey",
    "arguments": {
        "server-id": "foo"
    }
}

Here is an example of a response indicating that a rekey was performed:

{
    "result": 0,
    "text": "GSS-TSIG server[foo] rekeyed"
}

This command is typically used when a DNS server has been rebooted, so that existing GSS-TSIG keys shared with this server can no longer be used.

Monitoring Kea With Stork

Most administrators want to be able to monitor any Kea services that are running. Kea offers so many pieces of information - configuration files, API, statistics, logs, open database content, and more - that it may sometimes be overwhelming to keep up. ISC’s Stork project is intended to address this problem for both Kea and BIND 9. Stork is useful in a variety of ways:

• Stork can be used as a dashboard. It provides insight into what exactly is happening on the servers. In particular, it allows users to: see up-to-date details regarding pool utilization in subnets and shared networks; monitor the state of the HA pair (and provide extra insight in case of failover and recovery events); list, filter, and search for specific host reservations; and more. Only a single Stork server needs to be deployed, and one Stork agent on each machine to be monitored.

• The Stork agent can integrate Kea with Prometheus and Grafana. Once the Stork agent is active on the server, it serves as a Prometheus exporter. Users who have deployed Prometheus in their networks can visualize statistics as time series using Grafana.

• Stork can act as both a dashboard and an integrator for Prometheus/Grafana. Once Stork is linked to where Grafana is deployed on the network, users can inspect the current status and visit a customized link to Grafana to see how a given property behaves over time.

Stork is available as source code, but also as native deb and RPM packages, which makes it easy to install on most popular systems. For more details, please see the Stork ARM or the Stork project page. The ARM has a nice collection of screenshots that is frequently updated, to give users an idea of what is currently available. Stork is in the midst of full development with monthly releases, so please check back frequently.

Kea Statistics in Grafana

The ISC Stork project provides an agent that can be deployed alongside Kea. It exposes Kea statistics in a format that is accepted by Prometheus. One of the major benefits of Prometheus is that it turns repeated one-time observations into time series, which lets users monitor how certain behaviors change over time. It is easy to use other tools to visualize data available in Prometheus; the most common approach is to use Grafana to provide visual dashboards. The Stork project provides dashboard definitions for Kea that can be imported into Grafana very easily.

Learn more about Prometheus and Grafana on their websites: Prometheus <https://prometheus.io/> and Grafana <https://grafana.com/>.

Kea Security

Kea was originally designed to be installed in a protected environment, in a network datacenter; it did not offer hardened security features. However, due to customer demand and evolving network requirements, support for basic HTTP authentication and Transport Layer Security (TLS) have been added to Kea.

TLS/HTTPS Support

Since Kea 1.9.6, TLS can be used to secure HTTP communication. There are three levels of protection possible:

• No TLS. The connection is plain-text, unencrypted HTTP. (This is the only option available in versions prior to Kea 1.9.6.)

• Encryption, which protects against passive attacks and eavesdropping. In this case, the server is authenticated but the client is not. This is the typical mode when securing a website, where clients and servers are not under the control of a common entity.

• Mutual authentication between the client and the server. This is the strictest security mode and is the default when TLS is enabled.

Note

TLS mutual authentication is for TLS entities only. When TLS and an HTTP authentication scheme are used together, there is no binding between the two security mechanisms, and therefore no proof that the TLS client and server are the same as the HTTP authentication client and server.

Building Kea with TLS/HTTPS Support

TLS/HTTPS support is available with either the OpenSSL or the Botan cryptographic library. There are some constraints on the Boost library that must be used:

• OpenSSL versions older than 1.0.2 are obsolete and should not be used. Kea TLS support has not been tested with and is not supported on these versions.

• OpenSSL version 1.0.2 has extended support, but only for OpenSSL premium customers. Kea TLS support has been tested but is not supported on this version.

• OpenSSL versions 1.1.x and later have been tested and are supported. Many recent operating system versions include TLS 1.3 support.

• OpenSSL 3.x is not yet released; it is unknown whether Kea will build with it.

• LibreSSL 3.2.4 has been tested. LibreSSL shares the OpenSSL 1.0.2 API, so it should work, but is not supported.

• Botan 1.x versions are obsolete and should not be used. Kea TLS support has not been tested and is not supported with these versions.

• Botan versions 2.14.0 and later have been tested and are supported. Kea TLS support requires the four Asio header files which are included in Botan packages and which are installed only if Botan is configured with the --with-boost option.

  Many packages provided by operating systems, such as Ubuntu 20.10, do not build Botan with Boost support, making those packages unusable for Kea with TLS.

  It is still possible to take these files from the corresponding Botan distribution and install them manually in the Botan include directory, but this should be a last-resort procedure.

  Without these header files, or with a Botan version prior to 2.14.0, Kea can still build, but the TLS/HTTPS support is disabled; any attempt to use it will fail with a fatal error.

• Very old Boost versions provide SSL support (based on OpenSSL) without offering a choice of the TLS version; Kea can still use them, but they are not recommended.

• Boost versions prior to 1.64 provide SSL support with a fixed choice of the TLS version; Kea enforces the use of TLS 1.2 with them.

• Boost versions 1.64 or newer provide SSL support with a generic TLS version; the best (highest) version available on both peers is selected.

TLS/HTTPS Configuration

The TLS configuration parameters are:

• trust-anchor - this string parameter specifies the name of a file or directory where the certification authority (CA) certificate of the other peer can be found. With OpenSSL, the directory must include hash symbolic links. With Botan, the directory is recursively searched for certificates.

• cert-file - this string parameter specifies the name of the file containing the end-entity certificate of the Kea instance being configured.

• key-file - this string parameter specifies the private key of the end-entity certificate of the Kea instance being configured. The file must not be encrypted; it is highly recommended to restrict its access.

The three string parameters must be either all unspecified (TLS disabled) or all specified (TLS enabled).

TLS is asymmetric: the authentication of the server by the client is mandatory but the authentication of the client by the server is optional. In TLS terms, this means the server may require the client certificate, or may not; there is a server-specific TLS parameter.

• cert-required - this boolean parameter allows a server to not require the client certificate. Its default value is true, which means the client certificate is required and the client must be authenticated. This flag has no meaning on the client side; the server always provides a certificate which is validated by the client.

Objects in files must be in the PEM format. Files can contain more than one certificate, but this has not been tested and is not supported.

Botan requires CA certificates to have the standard CA certificate attributes, verifies that end-entity certificates are version 3 certificates (as required by the TLS standard), and supports only PKCS 8 files for the private key.

Note

Some cryptographic libraries (e.g. Botan and recent OpenSSL) enforce minimal strength (i.e. key length), e.g. at least 2048 for RSA.

A sample set of certificates and associated objects is available at src/lib/asiolink/testutils/ca in the Kea sources, with a doc.txt file explaining how they were generated using the openssl command. These files are for testing purposes only. Do not use them in production.

TLS handshake, the phase where the cryptographic parameters are exchanged and authentication is verified, can fail in multiple ways. Error messages often do not help to pinpoint the source of the problem. Both OpenSSL and Botan provide a command-line tool with a verify command which can be used to understand and fix handshake issues.

Securing a Kea Deployment

Below is a list of considerations for administrators wishing to improve Kea’s security. In many cases, there are trade-offs between convenience and security.

Component-Based Design

The Kea architecture is modular, with separate daemons for separate tasks. A Kea deployment may include DHCPv4, DHCPv6, and Dynamic DNS daemons; a Control Agent daemon run on each application server; the kea-lfc utility for doing periodic lease file cleanup; MySQL and or PostgreSQL databases, run either locally on the application servers or accessed over the internal network; and a Stork monitoring system. This modular architecture allows the administrator to minimize the attack surface by minimizing the code that is loaded and running. For example, kea-dhcp-ddns should not be run unless DNS updates are required. Similarly, kea-lfc is never triggered (and can be safely removed or never installed) if memfile is not used. Potential Kea security issues can be minimized by running only those processes required in the local environment.

Limiting Application Permissions

The DHCPv4 and DHCPv6 protocols assume the server opens privileged UDP port 67 (DHCPv4) or 547 (DHCPv6), which requires root access under normal circumstances. However, via the capabilities mechanism on Linux systems, Kea can run from an unprivileged account. See Running Kea From a Non-root Account on Linux for details on how to run Kea without root access.

The Control Agent (CA) can accept incoming HTTP or HTTPS connections. The default port is 8000, which does not require privileged access.

Securing Kea Administrative Access

The three primary Kea daemons (kea-dhcp4, kea-dhcp6 and kea-dhcp-ddns) all support a control channel, which is implemented as a UNIX socket. The control channel, which opens a UNIX socket, is disabled by default; however, many configuration examples have it enabled, as it is a very popular feature. To read from or write to this socket, root access is generally required, although if Kea is configured to run as non-root, the owner of the process can write to it. Access can be controlled using normal file-access control on POSIX systems (owner, group, others, read/write).

Kea configuration is controlled by a JSON file on the Kea server. This file can be viewed or edited by anyone with file permissions (which are controlled by the operating system). Note that passwords are stored in clear text in the configuration file, so anyone with access to read the configuration file can find this information. As a practical matter, anyone with permission to edit the configuration file has control over Kea. Limiting user permission to read or write the Kea configuration file is an important security step.

Securing Database Connections

Kea can use an external MySQL or PostgreSQL database to store configuration, host reservations, or/and leases, or/and for forensic logging. The use of databases is a popular feature, but it is optional; it is also possible to store data in a flat file on disk.

When using a database, Kea stores and uses the following credentials to authenticate with the database: username, password, host, port, and database name. These are stored in clear text in the configuration file.

Depending on the database configuration, it is also possible to verify whether the system user matches the database username. Consult the MySQL or PostgreSQL manual for details.

Information Leakage Through Logging

It is possible for Kea to log an entire configuration file, including passwords and secrets. Since Kea 1.9.7, this issue has been resolved by replacing the value of all entries ending in password or secret with asterisks, as was already done for database logs.

Logs are sent to stdout, stderr, files, or syslog; system file permissions system apply to stdout/stderr and files. Syslog may export the logs over the network, exposing them further to possible snooping.

Cryptography Components

Kea supports the use of either of two cryptographic libraries: Botan or OpenSSL. The choice is made at compile time, and creates both compile and runtime dependencies between the Kea and the selected library. While OpenSSL is the most popular choice for deployments, Botan remains a fully supported alternative.

The primary use cases for the cryptographic libraries are:

• TLS support for the Control Agent (CA), introduced in Kea 1.9.6.

• TSIG signatures when sending DNS updates.

• calculating DHCID records when sending DNS updates.

• random number generation (but not for usage requiring a crypto grade generator).

For OpenSSL and Botan, only the low-level crypto interface is used (e.g. libcrypto). Kea does not link with libssl. Some dependent software systems, such as database client libraries, can also depend on a crypto library.

One way to limit exposure for potential OpenSSL or Botan vulnerabilities is not to use DDNS. The libraries would still be needed to build and run Kea, but the code would never be used, so any potential bugs in the libraries would not be exploitable.

TSIG Signatures

Kea supports the following algorithms when signing DNS updates with TSIG signatures:

• HMAC-MD5

• HMAC-SHA1

• HMAC-SHA224

• HMAC-SHA256

• HMAC-SHA384

• HMAC-SHA512

See TSIG Key List for an up-to-date list.

Kea uses SHA256 to calculate DHCID records. This is irrelevant from the cryptography perspective, as the DHCID record is only used to generate unique identifiers for two devices that may have been assigned the same IP address at different times.

Raw Socket Support

In principle, Kea DHCPv4 uses raw sockets to receive traffic from clients. The difficulty is with receiving packets from devices that do not yet have an IPv4 address. When dealing with direct traffic (where both client and server are connected to the same link, not separated by relays), the kernel normally drops the packet as the source IP address is 0.0.0.0. Therefore, Kea needs to open raw sockets to be able to receive this traffic.

However, this is not necessary if all the traffic is coming via relays, which is often the case in many networks. In that case normal UDP sockets can be used instead. There is a dhcp-socket-type parameter that controls this behavior.

The default is to permit raw socket usage, as it is more versatile.

When using raw sockets, Kea is able to receive raw layer 2 packets, bypassing most firewalls (including iptables). This effectively means that when raw sockets are used, the iptables cannot be used to block DHCP traffic. This is a design choice of the Linux kernel.

Kea can be switched to use UDP sockets. This is an option when all traffic is relayed. However, it does not work for directly connected devices. If Kea is limited to UDP sockets, iptables should work properly.

If raw sockets are not required, disabling this access can improve security.

Remote Administrative Access

Kea’s Control Agent (CA) exposes a RESTful API over HTTP or HTTPS (HTTP over TLS). The CA is an optional feature that is disabled by default, but it is very popular. When enabled, it listens on the loopback address (127.0.0.1 or ::1) by default, unless configured otherwise. See TLS/HTTPS Support for information about protecting the TLS traffic. Limiting the incoming connections with a firewall, such as iptables, is generally a good idea.

Note that in High Availability (HA) deployments, DHCP partners connect to each other using a CA connection.

Authentication for Kea’s RESTful API

Kea 1.9.0 added support for basic HTTP authentication (RFC 7617), to control access for incoming REST commands over HTTP. The credentials (username, password) are stored in a local Kea configuration file on disk. The username is logged with the API command, so it is possible to determine which authenticated user performed each command. The access control details are logged using a dedicated auth logger. Basic HTTP authentication is weak on its own as there are known dictionary attacks, but those attacks require a “man in the middle” to get access to the HTTP traffic. That can be eliminated by using basic HTTP authentication exclusively over TLS. In fact, if possible, using client certificates for TLS is better than using basic HTTP authentication.

Kea 1.9.2 introduced a new auth hook point. With this new hook point, it is possible to develop an external hook library to extend the access controls, integrate with another authentication authority, or add role-based access control to the Control Agent.

Kea Security Processes

The following sections discuss how the Kea DHCP development team ensures code quality and handles vulnerabilities.

Vulnerability Handling

ISC is an experienced and active participant in the industry-standard vulnerability disclosure process and maintains accurate documentation on our process and vulnerabilities in ISC software. See https://kb.isc.org/docs/aa-00861 for ISC’s Software Defect and Security Vulnerability Disclosure Policy.

In case of a security vulnerability in Kea, ISC notifies support customers ahead of any public disclosure, and provides a patch and/or updated installer package to remediate the vulnerability.

When a security update is published, both the source tarballs and the ISC-maintained packages are published on the same day. This enables users of the native Linux update mechanisms (such as Debian’s and Ubuntu’s apt or RedHat’s dnf) to update their systems promptly.

Code Quality and Testing

Kea undergoes extensive tests during its development. The following are some of the processes that are used to ensure adequate code quality:

• Each line of code goes through a formal review before it is accepted. The review process is documented and available publicly.

• Roughly 50% of the source code is dedicated to unit tests. As of December 2020, there were over 6000 unit tests and the number is increasing with time. Unit tests are required to commit any new feature.

• There are around 1500 system tests for Kea. These simulate both correct and invalid situations, covering network packets (mostly DHCP, but also DNS, HTTP, HTTPS and others), command-line usage, API calls, database interactions, scripts, and more.

• There are performance tests with over 80 scenarios that test Kea overall performance and resiliency to various levels of traffic, and measuring various metrics (latency, leases per seconds, packets per seconds, CPU usage, memory utilization, and others).

• Kea uses Continuous Integration (CI). This means that the great majority of tests (all unit and system tests, and in some cases also performance tests) are run for every commit. Many “lighter” tests are run on branches, before the code is even accepted.

• Many unit and system tests check for negative scenarios, such as incomplete, broken, or truncated packets, API commands, and configuration files, as well as incorrect sequences (such as sending packets in an invalid order) and more.

• The Kea development team uses many tools that perform automatic code quality checks, such as danger, as well as internally developed sanity checkers.

• The Kea team uses the following static code analyzers: Coverity Scan, shellcheck, and danger.

• The Kea team uses the following dynamic code analyzers: Valgrind and Thread Sanitizer (TSAN).

Fuzz Testing

The Kea team has a process for running fuzz testing, using AFL. There are two modes which are run: the first mode fuzzes incoming packets, effectively throwing millions of mostly broken packets at Kea per day, while the second mode fuzzes configuration structures and forces Kea to attempt to load them. Kea has been fuzzed since around 2018 in both modes. The input seeds (the data being used to generate or “fuzz” other input) are changed periodically.

Release Integrity

All ISC software releases are signed with PGP and distributed via the ISC website, which is itself DNSSEC-signed, so users can be confident the software has not been tampered with.

Bus Factor

According to the Core Infrastructure project, a “bus factor” or “truck factor” is the minimum number of project members that have to suddenly disappear from a project (“be hit by a bus”) before the project stalls due to lack of knowledgeable or competent personnel. It is hard to estimate precisely, but the bus factor for Kea is somewhere around five. As of 2021, there are six core developers and two quality assurance engineers, with many additional casual contributors (product manager, support team, IT, etc.). The team is geographically dispersed.

API Reference

Kea currently supports 186 commands in kea-ctrl-agent, kea-dhcp-ddns, kea-dhcp4, kea-dhcp6 daemons and cb_cmds, class_cmds, gss_tsig, high_availability, host_cache, host_cmds, lease_cmds, stat_cmds, subnet_cmds hook libraries.

Commands supported by kea-ctrl-agent daemon: build-report, config-get, config-reload, config-set, config-test, config-write, list-commands, shutdown, status-get, version-get.

Commands supported by kea-dhcp-ddns daemon: build-report, config-get, config-reload, config-set, config-test, config-write, gss-tsig-get, gss-tsig-get-all, gss-tsig-key-del, gss-tsig-key-expire, gss-tsig-key-get, gss-tsig-list, gss-tsig-purge, gss-tsig-purge-all, gss-tsig-rekey, gss-tsig-rekey-all, list-commands, shutdown, statistic-get, statistic-get-all, statistic-reset, statistic-reset-all, status-get, version-get.

Commands supported by kea-dhcp4 daemon: build-report, cache-clear, cache-flush, cache-get, cache-get-by-id, cache-insert, cache-load, cache-remove, cache-size, cache-write, class-add, class-del, class-get, class-list, class-update, config-backend-pull, config-get, config-reload, config-set, config-test, config-write, dhcp-disable, dhcp-enable, ha-continue, ha-heartbeat, ha-maintenance-cancel, ha-maintenance-notify, ha-maintenance-start, ha-reset, ha-scopes, ha-sync, ha-sync-complete-notify, lease4-add, lease4-del, lease4-get, lease4-get-all, lease4-get-by-client-id, lease4-get-by-hostname, lease4-get-by-hw-address, lease4-get-page, lease4-resend-ddns, lease4-update, lease4-wipe, leases-reclaim, libreload, list-commands, network4-add, network4-del, network4-get, network4-list, network4-subnet-add, network4-subnet-del, remote-class4-del, remote-class4-get, remote-class4-get-all, remote-class4-set, remote-global-parameter4-del, remote-global-parameter4-get, remote-global-parameter4-get-all, remote-global-parameter4-set, remote-network4-del, remote-network4-get, remote-network4-list, remote-network4-set, remote-option-def4-del, remote-option-def4-get, remote-option-def4-get-all, remote-option-def4-set, remote-option4-global-del, remote-option4-global-get, remote-option4-global-get-all, remote-option4-global-set, remote-option4-network-del, remote-option4-network-set, remote-option4-pool-del, remote-option4-pool-set, remote-option4-subnet-del, remote-option4-subnet-set, remote-server4-del, remote-server4-get, remote-server4-get-all, remote-server4-set, remote-subnet4-del-by-id, remote-subnet4-del-by-prefix, remote-subnet4-get-by-id, remote-subnet4-get-by-prefix, remote-subnet4-list, remote-subnet4-set, reservation-add, reservation-del, reservation-get, reservation-get-all, reservation-get-by-hostname, reservation-get-by-id, reservation-get-page, server-tag-get, shutdown, stat-lease4-get, statistic-get, statistic-get-all, statistic-remove, statistic-remove-all, statistic-reset, statistic-reset-all, statistic-sample-age-set, statistic-sample-age-set-all, statistic-sample-count-set, statistic-sample-count-set-all, status-get, subnet4-add, subnet4-del, subnet4-get, subnet4-list, subnet4-update, version-get.

Commands supported by kea-dhcp6 daemon: build-report, cache-clear, cache-flush, cache-get, cache-get-by-id, cache-insert, cache-load, cache-remove, cache-size, cache-write, class-add, class-del, class-get, class-list, class-update, config-backend-pull, config-get, config-reload, config-set, config-test, config-write, dhcp-disable, dhcp-enable, ha-continue, ha-heartbeat, ha-maintenance-cancel, ha-maintenance-notify, ha-maintenance-start, ha-reset, ha-scopes, ha-sync, ha-sync-complete-notify, lease6-add, lease6-bulk-apply, lease6-del, lease6-get, lease6-get-all, lease6-get-by-duid, lease6-get-by-hostname, lease6-get-page, lease6-resend-ddns, lease6-update, lease6-wipe, leases-reclaim, libreload, list-commands, network6-add, network6-del, network6-get, network6-list, network6-subnet-add, network6-subnet-del, remote-class6-del, remote-class6-get, remote-class6-get-all, remote-class6-set, remote-global-parameter6-del, remote-global-parameter6-get, remote-global-parameter6-get-all, remote-global-parameter6-set, remote-network6-del, remote-network6-get, remote-network6-list, remote-network6-set, remote-option-def6-del, remote-option-def6-get, remote-option-def6-get-all, remote-option-def6-set, remote-option6-global-del, remote-option6-global-get, remote-option6-global-get-all, remote-option6-global-set, remote-option6-network-del, remote-option6-network-set, remote-option6-pd-pool-del, remote-option6-pd-pool-set, remote-option6-pool-del, remote-option6-pool-set, remote-option6-subnet-del, remote-option6-subnet-set, remote-server6-del, remote-server6-get, remote-server6-get-all, remote-server6-set, remote-subnet6-del-by-id, remote-subnet6-del-by-prefix, remote-subnet6-get-by-id, remote-subnet6-get-by-prefix, remote-subnet6-list, remote-subnet6-set, reservation-add, reservation-del, reservation-get, reservation-get-all, reservation-get-by-hostname, reservation-get-by-id, reservation-get-page, server-tag-get, shutdown, stat-lease6-get, statistic-get, statistic-get-all, statistic-remove, statistic-remove-all, statistic-reset, statistic-reset-all, statistic-sample-age-set, statistic-sample-age-set-all, statistic-sample-count-set, statistic-sample-count-set-all, status-get, subnet6-add, subnet6-del, subnet6-get, subnet6-list, subnet6-update, version-get.

Commands supported by cb_cmds hook library: remote-class4-del, remote-class4-get, remote-class4-get-all, remote-class4-set, remote-class6-del, remote-class6-get, remote-class6-get-all, remote-class6-set, remote-global-parameter4-del, remote-global-parameter4-get, remote-global-parameter4-get-all, remote-global-parameter4-set, remote-global-parameter6-del, remote-global-parameter6-get, remote-global-parameter6-get-all, remote-global-parameter6-set, remote-network4-del, remote-network4-get, remote-network4-list, remote-network4-set, remote-network6-del, remote-network6-get, remote-network6-list, remote-network6-set, remote-option-def4-del, remote-option-def4-get, remote-option-def4-get-all, remote-option-def4-set, remote-option-def6-del, remote-option-def6-get, remote-option-def6-get-all, remote-option-def6-set, remote-option4-global-del, remote-option4-global-get, remote-option4-global-get-all, remote-option4-global-set, remote-option4-network-del, remote-option4-network-set, remote-option4-pool-del, remote-option4-pool-set, remote-option4-subnet-del, remote-option4-subnet-set, remote-option6-global-del, remote-option6-global-get, remote-option6-global-get-all, remote-option6-global-set, remote-option6-network-del, remote-option6-network-set, remote-option6-pd-pool-del, remote-option6-pd-pool-set, remote-option6-pool-del, remote-option6-pool-set, remote-option6-subnet-del, remote-option6-subnet-set, remote-server4-del, remote-server4-get, remote-server4-get-all, remote-server4-set, remote-server6-del, remote-server6-get, remote-server6-get-all, remote-server6-set, remote-subnet4-del-by-id, remote-subnet4-del-by-prefix, remote-subnet4-get-by-id, remote-subnet4-get-by-prefix, remote-subnet4-list, remote-subnet4-set, remote-subnet6-del-by-id, remote-subnet6-del-by-prefix, remote-subnet6-get-by-id, remote-subnet6-get-by-prefix, remote-subnet6-list, remote-subnet6-set.

Commands supported by class_cmds hook library: class-add, class-del, class-get, class-list, class-update.

Commands supported by gss_tsig hook library: gss-tsig-get, gss-tsig-get-all, gss-tsig-key-del, gss-tsig-key-expire, gss-tsig-key-get, gss-tsig-list, gss-tsig-purge, gss-tsig-purge-all, gss-tsig-rekey, gss-tsig-rekey-all.

Commands supported by high_availability hook library: ha-continue, ha-heartbeat, ha-maintenance-cancel, ha-maintenance-notify, ha-maintenance-start, ha-reset, ha-scopes, ha-sync, ha-sync-complete-notify.

Commands supported by host_cache hook library: cache-clear, cache-flush, cache-get, cache-get-by-id, cache-insert, cache-load, cache-remove, cache-size, cache-write.

Commands supported by host_cmds hook library: reservation-add, reservation-del, reservation-get, reservation-get-all, reservation-get-by-hostname, reservation-get-by-id, reservation-get-page.

Commands supported by lease_cmds hook library: lease4-add, lease4-del, lease4-get, lease4-get-all, lease4-get-by-client-id, lease4-get-by-hostname, lease4-get-by-hw-address, lease4-get-page, lease4-resend-ddns, lease4-update, lease4-wipe, lease6-add, lease6-bulk-apply, lease6-del, lease6-get, lease6-get-all, lease6-get-by-duid, lease6-get-by-hostname, lease6-get-page, lease6-resend-ddns, lease6-update, lease6-wipe.

Commands supported by stat_cmds hook library: stat-lease4-get, stat-lease6-get.

Commands supported by subnet_cmds hook library: network4-add, network4-del, network4-get, network4-list, network4-subnet-add, network4-subnet-del, network6-add, network6-del, network6-get, network6-list, network6-subnet-add, network6-subnet-del, subnet4-add, subnet4-del, subnet4-get, subnet4-list, subnet4-update, subnet6-add, subnet6-del, subnet6-get, subnet6-list, subnet6-update.

build-report

This command returns the list of compilation options that this particular binary was built with.

Supported by: kea-ctrl-agent, kea-dhcp-ddns, kea-dhcp4, kea-dhcp6

Availability: 1.2.0 (built-in)

Access: read (parameter ignored in this Kea version)

Description and examples: see build-report command

Command syntax:

{
    "command": "build-report"
}

Response syntax:

{
    "result": 0,
    "text": <string with build details>
}

cache-clear

This command removes all cached host reservations.

Supported by: kea-dhcp4, kea-dhcp6

Availability: 1.4.0 (host_cache hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see cache-clear command

Command syntax:

{
    "command": "cache-clear"
}

Response syntax:

{
    "result": <integer>,
    "text": "<string>"
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

cache-flush

This command removes up to the given number or all cached host reservations.

Supported by: kea-dhcp4, kea-dhcp6

Availability: 1.4.0 (host_cache hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see cache-flush command

Command syntax:

{
    "command": "cache-flush",
    "arguments": 5
}

Response syntax:

{
    "result": <integer>,
    "text": "<string>"
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

cache-get

This command returns the full content of the host cache.

Supported by: kea-dhcp4, kea-dhcp6

Availability: 1.4.0 (host_cache hook library)

Access: read (parameter ignored in this Kea version)

Description and examples: see cache-get command

Command syntax:

{
    "command": "cache-get"
}

Response syntax:

{
    "result": 0,
    "text": "123 entries returned.",
    "arguments": <list of host reservations>
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

cache-get-by-id

This command returns entries matching the given identifier from the host cache.

Supported by: kea-dhcp4, kea-dhcp6

Availability: 1.6.0 (host_cache hook library)

Access: read (parameter ignored in this Kea version)

Description and examples: see cache-get-by-id command

Command syntax:

{
    "command": "cache-get-by-id",
    "arguments": {
        "hw-address": "01:02:03:04:05:06"
    }
}

Response syntax:

{
    "result": 0,
    "text": "2 entries returned.",
    "arguments": <list of host reservations>
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

cache-insert

This command inserts a host into the cache.

Supported by: kea-dhcp4, kea-dhcp6

Availability: 1.4.0 (host_cache hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see cache-insert command

Command syntax:

{
    "command": "cache-insert",
    "arguments": {
        "hw-address": "01:02:03:04:05:06",
        "subnet-id4": 4,
        "subnet-id6": 0,
        "ip-address": "192.0.2.100",
        "hostname": "somehost.example.org",
        "client-classes4": [ ],
        "client-classes6": [ ],
        "option-data4": [ ],
        "option-data6": [ ],
        "next-server": "192.0.0.2",
        "server-hostname": "server-hostname.example.org",
        "boot-file-name": "bootfile.efi",
        "host-id": 0
    }
},
{
    "command": "cache-insert",
    "arguments": {
        "hw-address": "01:02:03:04:05:06",
        "subnet-id4": 0,
        "subnet-id6": 6,
        "ip-addresses": [ "2001:db8::cafe:babe" ],
        "prefixes": [ "2001:db8:dead:beef::/64" ],
        "hostname": "",
        "client-classes4": [ ],
        "client-classes6": [ ],
        "option-data4": [ ],
        "option-data6": [ ],
        "next-server": "0.0.0.0",
        "server-hostname": "",
        "boot-file-name": "",
        "host-id": 0
    }
}

Response syntax:

{
    "result": <integer>,
    "text": "<string>"
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

cache-load

This command allows the contents of a file on disk to be loaded into an in-memory cache.

Supported by: kea-dhcp4, kea-dhcp6

Availability: 1.4.0 (host_cache hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see cache-load command

Command syntax:

{
    "command": "cache-load",
    "arguments": "/tmp/kea-host-cache.json"
}

Response syntax:

{
    "result": <integer>,
    "text": "<string>"
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

cache-remove

This command removes entries from the host cache. It takes parameters similar to the reservation-get command.

Supported by: kea-dhcp4, kea-dhcp6

Availability: 1.4.0 (host_cache hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see cache-remove command

Command syntax:

{
    "command": "cache-remove",
    "arguments": {
        "ip-address": "192.0.2.1",
        "subnet-id": 123
    }
}

Another example that removes the IPv6 host identifier by DUID and specific subnet-id is:
{
    "command": "cache-remove",
    "arguments": {
        "duid": "00:01:ab:cd:f0:a1:c2:d3:e4",
        "subnet-id": 123
    }
}

Response syntax:

{
    "result": <integer>,
    "text": "<string>"
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

cache-size

This command returns the number of entries in the host cache.

Supported by: kea-dhcp4, kea-dhcp6

Availability: 1.6.0 (host_cache hook library)

Access: read (parameter ignored in this Kea version)

Description and examples: see cache-size command

Command syntax:

{
    "command": "cache-size"
}

Response syntax:

{
    "result": 0,
    "text": "123 entries.",
    "arguments": { "size": 123 }
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

cache-write

This command instructs Kea to write its host cache content to disk.

Supported by: kea-dhcp4, kea-dhcp6

Availability: 1.4.0 (host_cache hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see cache-write command

Command syntax:

{
    "command": "cache-write",
    "arguments": "/path/to/the/file.json"
}

The command takes one mandatory argument that specifies the filename path of a file to be written.

Response syntax:

{
    "result": <integer>,
    "text": "<string>"
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

class-add

This command adds a new class to the existing server configuration.

Supported by: kea-dhcp4, kea-dhcp6

Availability: 1.5.0 (class_cmds hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see class-add command

Command syntax:

{
    "command": "class-add",
    "arguments": {
        "client-classes": [ {
           "name": <name of the class>,
           "test": <test expression to be evaluated on incoming packets>,
           "option-data": [ <option values here> ],
           "option-def": [ <option definitions here> ],
           "next-server": <ipv4 address>,
           "server-hostname": <string>,
           "boot-file-name": <name of the boot file>
        } ]
    }
}

The next-server, server-hostname, and boot-file-name are DHCPv4-specific. Only one client class can be added with a single command.

Response syntax:

{
    "result": 0,
    "text": "Class '<class-name>' added."
}

The command is successful (result 0), unless the class name is a duplicate or another error occurs (result 1).

class-del

This command removes a client class from the server configuration.

Supported by: kea-dhcp4, kea-dhcp6

Availability: 1.5.0 (class_cmds hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see class-del command

Command syntax:

{
    "command": "class-del",
    "arguments": {
        "name": <name of the class>
    }
}

Response syntax:

{
    "result": 0,
    "text": "Class '<class-name>' deleted."
}

The command returns a result of 3 (empty) if the client class does not exist. If the client class exists, the returned result is 0 if the deletion was successful; the result is 1 if the deletion is unsuccessful.

class-get

This command returns detailed information about an existing client class.

Supported by: kea-dhcp4, kea-dhcp6

Availability: 1.5.0 (class_cmds hook library)

Access: read (parameter ignored in this Kea version)

Description and examples: see class-get command

Command syntax:

{
    "command": "class-get",
    "arguments": {
        "name": <name of the class>
    }
}

Response syntax:

{
    "result": 0,
    "text": "Class '<class-name>' definition returned",
    "arguments": {
        "client-classes": [
            {
                "name": <name of the class>,
                "only-if-required": <only if required boolean value>,
                "test": <test expression to be evaluated on incoming packets>,
                "option-data": [ <option values here> ],
                "option-def": [ <option definitions here> ],
                "next-server": <ipv4 address>,
                "server-hostname": <string>,
                "boot-file-name": <name of the boot file>
            }
        ]
    }
}

The returned information depends on the DHCP server type, i.e. some parameters are specific to the DHCPv4 server. Also, some parameters may not be returned if they are not set for the client class. If a class with the specified name does not exist, a result of 3 (empty) is returned. If the client class is found, the result of 0 is returned. If there is an error while processing the command, the result of 1 is returned.

class-list

This command retrieves a list of all client classes from the server configuration.

Supported by: kea-dhcp4, kea-dhcp6

Availability: 1.5.0 (class_cmds hook library)

Access: read (parameter ignored in this Kea version)

Description and examples: see class-list command

Command syntax:

{
    "command": "class-list"
}

This command includes no arguments.

Response syntax:

{
    "result": 0,
    "text": "'<number of>' classes found",
    "arguments": {
        "client-classes": [
            {
                "name": <first class name>
            },
            {
                "name": <second class name>
            }
        ]
    }
}

The returned list of classes merely contains their names. In order to retrieve full information about one of these classes, use The class-get Command. The returned result is 3 (empty) if no classes are found. If the command is processed successfully and the list of client classes is not empty, the result of 0 is returned. If there is an error while processing the command, the result of 1 is returned.

class-update

This command updates an existing client class in the server configuration.

Supported by: kea-dhcp4, kea-dhcp6

Availability: 1.5.0 (class_cmds hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see class-update command

Command syntax:

{
    "command": "class-update",
    "arguments": {
        "client-classes": [ {
           "name": <name of the class>,
           "test": <test expression to be evaluated on incoming packets>,
           "option-data": [ <option values here> ],
           "option-def": [ <option definitions here> ],
           "next-server": <ipv4 address>,
           "server-hostname": <string>,
           "boot-file-name": <name of the boot file>
        } ]
    }
}

The next-server, server-hostname, and boot-file-name are DHCPv4-specific. Only one client class can be updated with a single command.

Response syntax:

{
    "result": 0,
    "text": "Class '<class-name>' updated."
}

The command returns the result of 3 (empty) if the client class does not exist. If the client class exists, the returned result is 0 if the update was successful, or 1 if the update is unsuccessful.

config-backend-pull

This command forces an immediate update of the server using Config Backends. This command does not take any parameters.

Supported by: kea-dhcp4, kea-dhcp6

Availability: 1.7.1 (built-in)

Access: write (parameter ignored in this Kea version)

Description and examples: see config-backend-pull command

Command syntax:

{
    "command": "config-backend-pull"
}

Response syntax:

{
    "result": 0,
    "text": "On demand configuration update successful."
}

When no Config Backends are configured this command returns empty (3); If an error occurs error (1) is returned with the error details; otherwise success (0) is returned.

config-get

This command retrieves the current configuration used by the server. The configuration is essentially the same as the contents of the configuration file, but includes additional changes made by other commands and due to parameters’ inheritance.

Supported by: kea-ctrl-agent, kea-dhcp-ddns, kea-dhcp4, kea-dhcp6

Availability: 1.2.0 (built-in)

Access: read (parameter ignored in this Kea version)

Description and examples: see config-get command

Command syntax:

{
    "command": "config-get"
}

This command takes no parameters.

Response syntax:

{
    "result": <integer>,
    "arguments": {
        <Dhcp4, Dhcp6, or Control-agent object>: <JSON configuration here>
    }
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

config-reload

This command instructs Kea to reload the configuration file that was used previously.

Supported by: kea-ctrl-agent, kea-dhcp-ddns, kea-dhcp4, kea-dhcp6

Availability: 1.2.0 (built-in)

Access: write (parameter ignored in this Kea version)

Description and examples: see config-reload command

Command syntax:

{
    "command": "config-reload"
}

Response syntax:

{
    "result": <integer>,
    "text": "<string>"
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

config-set

This command instructs the server to replace its current configuration with the new configuration supplied in the command’s arguments.

Supported by: kea-ctrl-agent, kea-dhcp-ddns, kea-dhcp4, kea-dhcp6

Availability: 1.2.0 (built-in)

Access: write (parameter ignored in this Kea version)

Description and examples: see config-set command

Command syntax:

{
    "command": "config-set",
    "arguments":  {
        "'<server>'": {
        }
     }
}

In the example below, ‘<server>’ is the configuration element name for a given server such as “Dhcp4” or “Dhcp6”.

Response syntax:

{"result": 0, "text": "Configuration successful." }

or

{"result": 1, "text": "unsupported parameter: BOGUS (<string>:16:26)" }

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

config-test

This command instructs the server to check whether the new configuration supplied in the command’s arguments can be loaded.

Supported by: kea-ctrl-agent, kea-dhcp-ddns, kea-dhcp4, kea-dhcp6

Availability: 1.2.0 (built-in)

Access: write (parameter ignored in this Kea version)

Description and examples: see config-test command

Command syntax:

{
    "command": "config-test",
    "arguments":  {
        "'<server>'": {
        }
     }
}

In the example below, <server> is the configuration element name for a given server such as “Dhcp4” or “Dhcp6”.

Response syntax:

{ "result": 0, "text": "Configuration seems sane..." }

or

{ "result": 1, "text": "unsupported parameter: BOGUS (<string>:16:26)" }

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

config-write

This command instructs the Kea server to write its current configuration to a file on disk.

Supported by: kea-ctrl-agent, kea-dhcp-ddns, kea-dhcp4, kea-dhcp6

Availability: 1.2.0 (built-in)

Access: write (parameter ignored in this Kea version)

Description and examples: see config-write command

Command syntax:

{
    "command": "config-write",
    "arguments": {
        "filename": "config-modified-2017-03-15.json"
    }
}

Response syntax:

{
    "result": <integer>,
    "text": "<string>"
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

dhcp-disable

This command globally disables the DHCP service.

Supported by: kea-dhcp4, kea-dhcp6

Availability: 1.4.0 (built-in)

Access: write (parameter ignored in this Kea version)

Description and examples: see dhcp-disable command

Command syntax:

{
    "command": "dhcp-disable",
    "arguments": {
        "max-period": 20,
        "origin": "user"
    }
}

Response syntax:

{
    "result": <integer>,
    "text": "<string>"
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

dhcp-enable

This command globally enables the DHCP service.

Supported by: kea-dhcp4, kea-dhcp6

Availability: 1.4.0 (built-in)

Access: write (parameter ignored in this Kea version)

Description and examples: see dhcp-enable command

Command syntax:

{
    "command": "dhcp-enable",
    "arguments": {
        "origin": "user"
    }
}

Response syntax:

{
    "result": <integer>,
    "text": "<string>"
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

gss-tsig-get

This command retrieves information about the specified GSS-TSIG server.

Supported by: kea-dhcp-ddns

Availability: 2.0.0 (gss_tsig hook library)

Access: read (parameter ignored in this Kea version)

Description and examples: see gss-tsig-get command

Command syntax:

{
    "command": "gss-tsig-get",
    "arguments": {
        "server-id": "foo"
    }
}

Response syntax:

{
    "result": 0,
    "text": "GSS-TSIG server[foo] found",
    "arguments": {
        "id": "foo",
        "ip-address": "192.1.2.3",
        "port": 53,
        "server-principal": "DNS/foo.com@FOO.COM",
        "key-name-suffix": "foo.com.",
        "tkey-lifetime": 3600,
        "tkey-protocol": "TCP",
        "keys": [
            "{
                "name": "1234.sig-foo.com.",
                "server-id": "foo",
                "inception-date": "2021-09-05 12:23:36.281176",
                "expire-date": "2021-09-05 13:23:36.281176",
                "status": "not yet ready",
                "tkey-exchange": true
            }
        ]
    }
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

gss-tsig-get-all

This command lists GSS-TSIG servers and keys.

Supported by: kea-dhcp-ddns

Availability: 2.0.0 (gss_tsig hook library)

Access: read (parameter ignored in this Kea version)

Description and examples: see gss-tsig-get-all command

Command syntax:

{
    "command": "gss-tsig-get-all"
}

Response syntax:

{
    "result": 0,
    "text": "1 GSS-TSIG servers and 1 keys",
    "arguments": {
        "gss-tsig-servers": [
            {
                "id": "foo",
                "ip-address": "192.1.2.3",
                "port": 53,
                "server-principal": "DNS/foo.com@FOO.COM",
                "key-name-suffix": "foo.com.",
                "tkey-lifetime": 3600,
                "tkey-protocol": "TCP",
                "keys": [
                    "{
                        "name": "1234.sig-foo.com.",
                        "inception-date": "2021-09-05 12:23:36.281176",
                        "server-id": "foo",
                        "expire-date": "2021-09-05 13:23:36.281176",
                        "status": "not yet ready",
                        "tkey-exchange": true
                    }
                ]
            },
            {
                "id": "bar",
                "ip-address": "192.1.2.4",
                "port": 53,
                "server-principal": "DNS/bar.com@FOO.COM",
                "key-name-suffix": "bar.com.",
                "tkey-lifetime": 7200,
                "tkey-protocol": "UDP",
                "keys": [ ]
            }
        ]
    }
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

gss-tsig-key-del

This command deletes the specified GSS-TSIG key.

Supported by: kea-dhcp-ddns

Availability: 2.0.0 (gss_tsig hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see gss-tsig-key-del command

Command syntax:

{
    "command": "gss-tsig-key-del",
    "arguments": {
        "key-name": "1234.sig-foo.com."
    }
}

Response syntax:

{
    "result": 0,
    "text": "GSS-TSIG key '1234.sig-foo.com.' deleted"
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

gss-tsig-key-expire

This command expires the specified GSS-TSIG key.

Supported by: kea-dhcp-ddns

Availability: 2.0.0 (gss_tsig hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see gss-tsig-key-expire command

Command syntax:

{
    "command": "gss-tsig-key-expire",
    "arguments": {
        "key-name": "1234.sig-foo.com."
    }
}

Response syntax:

{
    "result": 0,
    "text": "GSS-TSIG key '1234.sig-foo.com.' expired"
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

gss-tsig-key-get

This command retrieves information about the specified GSS-TSIG key.

Supported by: kea-dhcp-ddns

Availability: 2.0.0 (gss_tsig hook library)

Access: read (parameter ignored in this Kea version)

Description and examples: see gss-tsig-key-get command

Command syntax:

{
    "command": "gss-tsig-key-get",
    "arguments": {
        "key-name": "1234.sig-foo.com."
    }
}

Response syntax:

{
    "result": 0,
    "text": "GSS-TSIG key '1234.sig-foo.com.' found",
    "arguments": {
        "name": "1234.sig-foo.com.",
        "server-id": "foo",
        "inception-date": "2021-09-05 12:23:36.281176",
        "expire-date": "2021-09-05 13:23:36.281176",
        "status": "not yet ready",
        "tkey-exchange": true
    }
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

gss-tsig-list

This command lists GSS-TSIG server IDs and key names.

Supported by: kea-dhcp-ddns

Availability: 2.0.0 (gss_tsig hook library)

Access: read (parameter ignored in this Kea version)

Description and examples: see gss-tsig-list command

Command syntax:

{
    "command": "gss-tsig-list"
}

Response syntax:

{
    "result": 0,
    "text": "2 GSS-TSIG servers and 3 keys",
    "arguments": {
        "gss-tsig-servers": [
            "foo",
            "bar"
        ],
        "gss-tsig-keys": [
            "1234.example.com.",
            "5678.example.com.",
            "43888.example.org."
        ]
    }
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

gss-tsig-purge

This command removes not usable GSS-TSIG keys for the specified server.

Supported by: kea-dhcp-ddns

Availability: 2.0.0 (gss_tsig hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see gss-tsig-purge command

Command syntax:

{
    "command": "gss-tsig-purge",
    "arguments": {
        "server-id": "foo"
    }
}

Response syntax:

{
    "result": 0,
    "text": "2 purged keys for GSS-TSIG server[foo]"
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

gss-tsig-purge-all

This command removes not usable GSS-TSIG keys.

Supported by: kea-dhcp-ddns

Availability: 2.0.0 (gss_tsig hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see gss-tsig-purge-all command

Command syntax:

{
    "command": "gss-tsig-purge-all"
}

Response syntax:

{
    "result": 0,
    "text": "2 purged GSS-TSIG keys"
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

gss-tsig-rekey

The command unconditionally creates new GSS-TSIG keys for (rekeys) a specified DNS server.

Supported by: kea-dhcp-ddns

Availability: 2.0.0 (gss_tsig hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see gss-tsig-rekey command

Command syntax:

{
    "command": "gss-tsig-rekey",
    "arguments": {
        "server-id": "foo"
    }
}

Response syntax:

{
    "result": 0,
    "text": "GSS-TSIG server[foo] rekeyed"
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

gss-tsig-rekey-all

This command unconditionally creates new GSS-TSIG keys (rekeys) for all DNS servers.

Supported by: kea-dhcp-ddns

Availability: 2.0.0 (gss_tsig hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see gss-tsig-rekey-all command

Command syntax:

{
    "command": "gss-tsig-rekey-all"
}

Response syntax:

{
    "result": 0,
    "text": "rekeyed"
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

ha-continue

This command resumes the operation of a paused HA state machine.

Supported by: kea-dhcp4, kea-dhcp6

Availability: 1.4.0 (high_availability hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see ha-continue command

Command syntax:

{
    "command": "ha-continue"
}

Response syntax:

{
    "result": <integer>,
    "text": "<string>"
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

ha-heartbeat

This command is sent internally by a Kea partner when operating in High Availability (HA) mode or by the system administrator to verify the state of the servers with regards to the High Availability. It retrieves the server’s HA state and clock value.

Supported by: kea-dhcp4, kea-dhcp6

Availability: 1.4.0 (high_availability hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see ha-heartbeat command

Command syntax:

{
    "command": "ha-heartbeat"
}

Response syntax:

{
    "result": 0,
    "text": "HA peer status returned.",
    "arguments": {
        "state": <server state>,
        "date-time": <server notion of time>,
        "scopes": [ <first scope>, <second scope>, ... ],
        "unsent-update-count": <total number of lease allocations in partner-down state>
    }
}

The response includes a server state (see Server States), current clock value, served scopes and the counter indicating how many leases the server has allocated without sending lease updates to its partner. The partner uses this counter to determine if it should synchronize its lease database.

ha-maintenance-cancel

This command is sent to instruct a server in the partner-in-maintenance state to transition back to the previous state, effectively canceling the maintenance.

Supported by: kea-dhcp4, kea-dhcp6

Availability: 1.7.4 (high_availability hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see ha-maintenance-cancel command

Command syntax:

{
    "command": "ha-maintenance-cancel"
}

This command takes no arguments.

Response syntax:

{
    "result": <integer>,
    "text": "<string>"
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

ha-maintenance-notify

This command is sent by the server receiving the ha-maintenance-start to its partner to cause the partner to transition to the in-maintenance state or to revert it from the in-maintenance state as a result of receiving the ha-maintenance-cancel command.

Supported by: kea-dhcp4, kea-dhcp6

Availability: 1.7.4 (high_availability hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see ha-maintenance-notify command

Command syntax:

{
    "command": "ha-maintenance-notify",
    "arguments": {
        "cancel": <boolean>
    }
}

This command includes a boolean argument which, if false, indicates that the server should transition to the in-maintenance state. If the argument is set to true it instructs the server to revert from the in-maintenance state to its previous state. This command is not meant to be used by the administrator. It is merely used for internal communication between the HA partners.

Response syntax:

{
    "result": <integer>,
    "text": "<string>"
}

The response may include a special error code of 1001 to indicate that the partner refused to enter the maintenance state.

ha-maintenance-start

This command is sent to instruct one of the servers to transition to the partner-in-maintenance state in which it will be responding to all DHCP queries. The server receiving this command sends the ha-maintenance-notify to its partner to cause the partner to transition to the in-maintenance state.

Supported by: kea-dhcp4, kea-dhcp6

Availability: 1.7.4 (high_availability hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see ha-maintenance-start command

Command syntax:

{
    "command": "ha-maintenance-start"
}

This command takes no arguments.

Response syntax:

{
    "result": <integer>,
    "text": "<string>"
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

ha-reset

This command resets the HA state machine of the server by transitioning it to the waiting state.

Supported by: kea-dhcp4, kea-dhcp6

Availability: 1.9.4 (high_availability hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see ha-reset command

Command syntax:

{
    "command": "ha-reset"
}

Response syntax:

{
    "result": <integer>,
    "text": "<string>"
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

ha-scopes

This command modifies the scope that the server is responsible for serving when operating in High Availability (HA) mode.

Supported by: kea-dhcp4, kea-dhcp6

Availability: 1.4.0 (high_availability hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see ha-scopes command

Command syntax:

{
    "command": "ha-scopes",
    "service": [ <service, typically 'dhcp4' or 'dhcp6'> ],
    "arguments": {
        "scopes": [ "HA_server1", "HA_server2" ]
    }
}

In the example below, the arguments configure the server to handle traffic from both the HA_server1 and HA_server2 scopes.

Response syntax:

{
    "result": <integer>,
    "text": "<string>"
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

ha-sync

This command instructs the server running in HA mode to synchronize its local lease database with the selected peer.

Supported by: kea-dhcp4, kea-dhcp6

Availability: 1.4.0 (high_availability hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see ha-sync command

Command syntax:

{
    "command": "ha-sync",
    "service": [ <service affected: 'dhcp4' or 'dhcp6'> ],
    "arguments": {
        "server-name": <name of the partner server>,
        "max-period": <integer, in seconds>
    }
}

Response syntax:

{
    "result": <integer>,
    "text": "<string>"
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

ha-sync-complete-notify

A server notifies its partner with this command that it has finished the lease database synchronization. If the partner is in the partner-down state it temporarily stops allocating new leases until it transitions to a normal operation state (e.g. load-balancing). If the partner observes a failing heartbeat it can resume allocating new leases in the partner-down state.

Supported by: kea-dhcp4, kea-dhcp6

Availability: 1.9.11 (high_availability hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see ha-sync-complete-notify command

Command syntax:

{
    "command": "ha-sync-complete-notify"
}

This command takes no arguments.

Response syntax:

{
    "result": <integer>,
    "text": "<string>"
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

lease4-add

This command administratively adds a new IPv4 lease.

Supported by: kea-dhcp4

Availability: 1.3.0 (lease_cmds hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see lease4-add command

Command syntax:

{
    "command": "lease4-add",
    "arguments": {
        "ip-address": "192.0.2.202",
        "hw-address": "1a:1b:1c:1d:1e:1f"
    }
}

Note that Kea 1.4 requires an additional argument, subnet-ID, which is optional as of Kea 1.5. A number of other, more-detailed, optional arguments are also supported.

Response syntax:

{
    "result": <integer>,
    "text": "<string>"
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

lease4-del

This command deletes a lease from the lease database.

Supported by: kea-dhcp4

Availability: 1.3.0 (lease_cmds hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see lease4-del command

Command syntax:

{
    "command": "lease4-del",
    "arguments": {
        "ip-address": "192.0.2.202"
    }
}

The lease to be deleted can be specified either by IP address or by identifier-type and identifier value. The currently supported identifiers are “hw-address” and “client-id”.

Response syntax:

{
    "result": <integer>,
    "text": "<string>"
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

lease4-get

This command queries the lease database and retrieves existing leases.

Supported by: kea-dhcp4

Availability: 1.3.0 (lease_cmds hook library)

Access: read (parameter ignored in this Kea version)

Description and examples: see lease4-get command

Command syntax:

{
    "command": "lease4-get",
    "arguments": {
        "ip-address": "192.0.2.1"
    }
}

Response syntax:

{
  "arguments": {
    "client-id": "42:42:42:42:42:42:42:42",
    "cltt": 12345678,
    "fqdn-fwd": false,
    "fqdn-rev": true,
    "hostname": "myhost.example.com.",
    "hw-address": "08:08:08:08:08:08",
    "ip-address": "192.0.2.1",
    "state": 0,
    "subnet-id": 44,
    "valid-lft": 3600
  },
  "result": 0,
  "text": "IPv4 lease found."
}

lease4-get returns a result that indicates the outcome of the operation and lease details, if found. It has one of the following values: 0 (success), 1 (error), or 3 (empty). Result 3 is returned if no leases are found with specified IP address.

lease4-get-all

This command retrieves all IPv4 leases or all leases for the specified set of subnets.

Supported by: kea-dhcp4

Availability: 1.4.0 (lease_cmds hook library)

Access: read (parameter ignored in this Kea version)

Description and examples: see lease4-get-all command

Command syntax:

{
    "command": "lease4-get-all",
    "arguments": {
        "subnets": [ 1, 2, 3, ... ]
    }
}

The lease4-get-all command may result in very large responses. Please consider using lease4-get-page to get them in chunks. The subnets parameter is optional. If not specified, leases from all subnets are returned.

Response syntax:

[
  {
    "arguments": {
      "leases": [
        {
          "client-id": "01:00:0c:01:02:03:04",
          "cltt": 1600432232,
          "fqdn-fwd": false,
          "fqdn-rev": false,
          "hostname": "",
          "hw-address": "00:0c:01:02:03:04",
          "ip-address": "192.168.1.150",
          "state": 0,
          "subnet-id": 1,
          "valid-lft": 4000
        },
        {
          "client-id": "01:00:0c:01:02:03:05",
          "cltt": 1600432234,
          "fqdn-fwd": false,
          "fqdn-rev": false,
          "hostname": "",
          "hw-address": "00:0c:01:02:03:05",
          "ip-address": "192.168.1.151",
          "state": 0,
          "subnet-id": 1,
          "valid-lft": 4000
        }
      ]
    },
    "result": 0,
    "text": "2 IPv4 lease(s) found."
  }
]

Result 0 is returned when at least one lease is found, 1 when parameters are malformed or missing, 3 is returned if no leases are found with specified parameter.

lease4-get-by-client-id

This command retrieves all IPv4 leases with the specified client id.

Supported by: kea-dhcp4

Availability: 1.7.1 (lease_cmds hook library)

Access: read (parameter ignored in this Kea version)

Description and examples: see lease4-get-by-client-id command

Command syntax:

{
    "command": "lease4-get-by-client-id",
    "arguments": {
        "client-id": "01:00:0c:01:02:03:04"
    }
}

Response syntax:

[
  {
    "arguments": {
      "leases": [
        {
          "client-id": "01:00:0c:01:02:03:04",
          "cltt": 1600432232,
          "fqdn-fwd": false,
          "fqdn-rev": false,
          "hostname": "",
          "hw-address": "00:0c:01:02:03:04",
          "ip-address": "192.168.1.150",
          "state": 0,
          "subnet-id": 1,
          "valid-lft": 4000
        },
      ]
    },
    "result": 0,
    "text": "1 IPv4 lease(s) found."
  }
]

Result 0 is returned when at least one lease is found, 1 when parameters are malformed or missing, 3 is returned if no leases are found.

lease4-get-by-hostname

This command retrieves all IPv4 leases with the specified hostname.

Supported by: kea-dhcp4

Availability: 1.7.1 (lease_cmds hook library)

Access: read (parameter ignored in this Kea version)

Description and examples: see lease4-get-by-hostname command

Command syntax:

{
    "command": "lease4-get-by-hostname",
    "arguments": {
        "hostname": "myhost.example.com."
    }
}

Response syntax:

[
  {
    "arguments": {
      "leases": [
        {
          "client-id": "01:00:0c:01:02:03:04",
          "cltt": 1600432232,
          "fqdn-fwd": false,
          "fqdn-rev": false,
          "hostname": "myhost.example.com.",
          "hw-address": "00:0c:01:02:03:04",
          "ip-address": "192.168.1.150",
          "state": 0,
          "subnet-id": 1,
          "valid-lft": 4000
        },
      ]
    },
    "result": 0,
    "text": "1 IPv4 lease(s) found."
  }
]

Result 0 is returned when at least one lease is found, 1 when parameters are malformed or missing, 3 is returned if no leases are found.

lease4-get-by-hw-address

This command retrieves all IPv4 leases with the specified hardware address.

Supported by: kea-dhcp4

Availability: 1.7.1 (lease_cmds hook library)

Access: read (parameter ignored in this Kea version)

Description and examples: see lease4-get-by-hw-address command

Command syntax:

{
    "command": "lease4-get-by-hw-address",
    "arguments": {
        "hw-address": "00:0c:01:02:03:04"
    }
}

Response syntax:

[
  {
    "arguments": {
      "leases": [
        {
          "client-id": "01:00:0c:01:02:03:04",
          "cltt": 1600432232,
          "fqdn-fwd": false,
          "fqdn-rev": false,
          "hostname": "myhost.example.com.",
          "hw-address": "00:0c:01:02:03:04",
          "ip-address": "192.168.1.150",
          "state": 0,
          "subnet-id": 1,
          "valid-lft": 4000
        },
      ]
    },
    "result": 0,
    "text": "1 IPv4 lease(s) found."
  }
]

Result 0 is returned when at least one lease is found, 1 when parameters are malformed or missing, 3 is returned if no leases are found.

lease4-get-page

This command retrieves all IPv4 leases by page.

Supported by: kea-dhcp4

Availability: 1.5.0 (lease_cmds hook library)

Access: read (parameter ignored in this Kea version)

Description and examples: see lease4-get-page command

Command syntax:

{
    "command": "lease4-get-page",
    "arguments": {
        "limit": <integer>,
        "from": <IPv4 address or "start">
    }
}

The from address and the page size limit are mandatory.

Response syntax:

[
  {
    "arguments": {
      "leases": [
        {
          "client-id": "01:00:0c:01:02:03:04",
          "cltt": 1600432232,
          "fqdn-fwd": false,
          "fqdn-rev": false,
          "hostname": "",
          "hw-address": "00:0c:01:02:03:04",
          "ip-address": "192.168.1.150",
          "state": 0,
          "subnet-id": 1,
          "valid-lft": 4000
        },
        {
          "client-id": "01:00:0c:01:02:03:05",
          "cltt": 1600432234,
          "fqdn-fwd": false,
          "fqdn-rev": false,
          "hostname": "",
          "hw-address": "00:0c:01:02:03:05",
          "ip-address": "192.168.1.151",
          "state": 0,
          "subnet-id": 1,
          "valid-lft": 4000
        }
      ]
    },
    "result": 0,
    "text": "2 IPv4 lease(s) found."
  }
]

Result 0 is returned when at least one lease is found, 1 when parameters are malformed or missing, 3 is returned if no leases are found with specified parameters.

lease4-resend-ddns

This command resends a request to kea-dhcp-ddns to update DNS for an existing lease.

Supported by: kea-dhcp4

Availability: 1.7.6 (lease_cmds hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see lease4-resend-ddns command

Command syntax:

{
    "command": "lease4-resend-ddns",
    "arguments": {
        "ip-address": "192.0.2.1"
    }
}

Response syntax:

{
  "arguments": {
  },
  "result": 0,
  "text": "NCR generated for: 192.0.2.1, hostname: example.com."
}

lease4-resend-ddns returns a result that indicates the outcome of the operation and lease details, if found. It has one of the following values: 0 (success), 1 (error), or 3 (empty).

lease4-update

This command updates existing leases.

Supported by: kea-dhcp4

Availability: 1.3.0 (lease_cmds hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see lease4-update command

Command syntax:

{
  "command": "lease4-update",
  "arguments": {
    "ip-address": "192.0.2.1",
    "hostname": "newhostname.example.org",
    "hw-address": "1a:1b:1c:1d:1e:1f",
    "subnet-id": 44,
    "force-create": true
  }
}

Response syntax:

{
    "result": <integer>,
    "text": "<string>"
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

lease4-wipe

This command removes all leases associated with a given subnet.

Supported by: kea-dhcp4

Availability: 1.3.0 (lease_cmds hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see lease4-wipe command

Command syntax:

{
    "command": "lease4-wipe",
    "arguments": {
        "subnet-id": 44
    }
}

Response syntax:

{
    "result": <integer>,
    "text": "<string>"
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

lease6-add

This command administratively creates a new lease.

Supported by: kea-dhcp6

Availability: 1.3.0 (lease_cmds hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see lease6-add command

Command syntax:

{
    "command": "lease6-add",
    "arguments": {
        "subnet-id": 66,
        "ip-address": "2001:db8::3",
        "duid": "1a:1b:1c:1d:1e:1f:20:21:22:23:24",
        "iaid": 1234
    }
}

lease6-add can be also used to add leases for IPv6 prefixes.

Response syntax:

{ "result": 0, "text": "Lease added." }
or
{ "result": 1, "text": "missing parameter 'ip-address' (<string>:3:19)" }

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

lease6-bulk-apply

This command creates, updates, or deletes multiple IPv6 leases in a single transaction. It communicates lease changes between HA peers, but may be used in all cases where it is desirable to apply multiple lease updates in a single transaction.

Supported by: kea-dhcp6

Availability: 1.6.0 (lease_cmds hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see lease6-bulk-apply command

Command syntax:

{
    "command": "lease6-bulk-apply",
    "arguments": {
        "deleted-leases": [
            {
                "ip-address": "2001:db8:abcd::",
                "type": "IA_PD",
                ...
            },
            {
                "ip-address": "2001:db8:abcd::234",
                "type": "IA_NA",
                ...
            }
        ],
        "leases": [
            {
                "subnet-id": 66,
                "ip-address": "2001:db8:cafe::",
                "type": "IA_PD",
                ...
            },
            {
                "subnet-id": 66,
                "ip-address": "2001:db8:abcd::333",
                "type": "IA_NA",
                ...
            }
        ]
    }
}

If any of the leases is malformed, all changes are rolled back. If the leases are well-formed but the operation fails for one or more leases, these leases are listed in the response; however, the changes are preserved for all leases for which the operation was successful. The “deleted-leases” and “leases” are optional parameters, but one of them must be specified.

Response syntax:

{
    "result": 0,
    "text": "IPv6 leases bulk apply completed.",
    "arguments": {
        "failed-deleted-leases": [
            {
                "ip-address": "2001:db8:abcd::",
                "type": "IA_PD",
                "result": <control result>,
                "error-message": <error message>
            }
        ],
        "failed-leases": [
            {
                "ip-address": "2001:db8:cafe::",
                "type": "IA_PD",
                "result": <control result>,
                "error-message": <error message>
            }
        ]
    }
}

The “failed-deleted-leases” holds the list of leases which failed to delete; this includes leases which were not found in the database. The “failed-leases” includes the list of leases which failed to create or update. For each lease for which there was an error during processing, insertion into the database, etc., the result is set to 1. For each lease which was not deleted because the server did not find it in the database, the result of 3 is returned.

lease6-del

This command deletes a lease from the lease database.

Supported by: kea-dhcp6

Availability: 1.3.0 (lease_cmds hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see lease6-del command

Command syntax:

{
    "command": "lease6-del",
    "arguments": {
        "ip-address": "192.0.2.202"
    }
}

lease6-del returns a result that indicates the outcome of the operation. It has one of the following values: 0 (success), 1 (error), or 3 (empty).

Response syntax:

{
    "result": <integer>,
    "text": "<string>"
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

lease6-get

This command queries the lease database and retrieves existing leases.

Supported by: kea-dhcp6

Availability: 1.3.0 (lease_cmds hook library)

Access: read (parameter ignored in this Kea version)

Description and examples: see lease6-get command

Command syntax:

{
  "command": "lease6-get",
  "arguments": {
    "ip-address": "2001:db8:1234:ab::",
    "type": "IA_PD"
  }
}

lease6-get returns a result that indicates the outcome of the operation and lease details, if found.

Response syntax:

[
  {
    "arguments": {
      "leases": [
        {
          "cltt": 1600439560,
          "duid": "00:01:00:01:26:f7:81:88:00:0c:01:02:03:04",
          "fqdn-fwd": false,
          "fqdn-rev": false,
          "hostname": "foobar.example.org",
          "hw-address": "00:0c:01:02:03:04",
          "iaid": 1,
          "ip-address": "2001:db8:1::",
          "preferred-lft": 3000,
          "state": 0,
          "subnet-id": 1,
          "type": "IA_NA",
          "valid-lft": 4000
        }
      ]
    },
    "result": 0,
    "text": "1 IPv6 lease(s) found."
  }
]

Result 0 is returned when at least one lease is found, 1 when parameters are malformed or missing, 3 is returned if no leases are found with specified parameter.

lease6-get-all

This command retrieves all IPv6 leases or all leases for the specified set of subnets.

Supported by: kea-dhcp6

Availability: 1.3.0 (lease_cmds hook library)

Access: read (parameter ignored in this Kea version)

Description and examples: see lease6-get-all command

Command syntax:

{
    "command": "lease6-get-all",
    "arguments": {
        "subnets": [ 1, 2, 3, 4 ]
    }
}

The lease6-get-all command may result in very large responses. Please consider using lease6-get-page to get them in chunks. the subnets parameter is optional. If not specified, leases from all subnets are returned.

Response syntax:

{
    "arguments": {
        "leases": [
            {
                "cltt": 12345678,
                "duid": "42:42:42:42:42:42:42:42",
                "fqdn-fwd": false,
                "fqdn-rev": true,
                "hostname": "myhost.example.com.",
                "hw-address": "08:08:08:08:08:08",
                "iaid": 1,
                "ip-address": "2001:db8:2::1",
                "preferred-lft": 500,
                "state": 0,
                "subnet-id": 44,
                "type": "IA_NA",
                "valid-lft": 3600
            },
            {
                "cltt": 12345678,
                "duid": "21:21:21:21:21:21:21:21",
                "fqdn-fwd": false,
                "fqdn-rev": true,
                "hostname": "",
                "iaid": 1,
                "ip-address": "2001:db8:0:0:2::",
                "preferred-lft": 500,
                "prefix-len": 80,
                "state": 0,
                "subnet-id": 44,
                "type": "IA_PD",
                "valid-lft": 3600
            }
        ]
    },
    "result": 0,
    "text": "2 IPv6 lease(s) found."
}

Result 0 is returned when at least one lease is found, 1 when parameters are malformed or missing, 3 is returned if no leases are found with specified parameter.

lease6-get-by-duid

This command retrieves all IPv6 leases with the specified hardware address.

Supported by: kea-dhcp6

Availability: 1.7.1 (lease_cmds hook library)

Access: read (parameter ignored in this Kea version)

Description and examples: see lease6-get-by-duid command

Command syntax:

{
    "command": "lease6-get-by-duid",
    "arguments": {
        "duid": "1a:1b:1c:1d:1e:1f:20:21:22:23:24"
    }
}

Response syntax:

[
  {
    "arguments": {
      "leases": [
        {
          "cltt": 1600439560,
          "duid": "00:01:00:01:26:f7:81:88:00:0c:01:02:03:04",
          "fqdn-fwd": false,
          "fqdn-rev": false,
          "hostname": "foobar.example.org",
          "hw-address": "00:0c:01:02:03:04",
          "iaid": 1,
          "ip-address": "2001:db8:1::",
          "preferred-lft": 3000,
          "state": 0,
          "subnet-id": 1,
          "type": "IA_NA",
          "valid-lft": 4000
        }
      ]
    },
    "result": 0,
    "text": "1 IPv6 lease(s) found."
  }
]

Result 0 is returned when at least one lease is found, 1 when parameters are malformed or missing, 3 is returned if no leases are found with specified parameter.

lease6-get-by-hostname

This command retrieves all IPv6 leases with the specified hostname.

Supported by: kea-dhcp6

Availability: 1.7.1 (lease_cmds hook library)

Access: read (parameter ignored in this Kea version)

Description and examples: see lease6-get-by-hostname command

Command syntax:

{
    "command": "lease6-get-by-hostname",
    "arguments": {
        "hostname": "myhost.example.com."
    }
}

Response syntax:

[
  {
    "arguments": {
      "leases": [
        {
          "cltt": 1600439560,
          "duid": "00:01:00:01:26:f7:81:88:00:0c:01:02:03:04",
          "fqdn-fwd": false,
          "fqdn-rev": false,
          "hostname": "foobar.example.org",
          "hw-address": "00:0c:01:02:03:04",
          "iaid": 1,
          "ip-address": "2001:db8:1::",
          "preferred-lft": 3000,
          "state": 0,
          "subnet-id": 1,
          "type": "IA_NA",
          "valid-lft": 4000
        }
      ]
    },
    "result": 0,
    "text": "1 IPv6 lease(s) found."
  }
]

Result 0 is returned when at least one lease is found, 1 when parameters are malformed or missing, 3 is returned if no leases are found with specified parameter.

lease6-get-page

This command retrieves all IPv6 leases by page.

Supported by: kea-dhcp6

Availability: 1.5.0 (lease_cmds hook library)

Access: read (parameter ignored in this Kea version)

Description and examples: see lease6-get-page command

Command syntax:

{
    "command": "lease6-get-page",
    "arguments": {
        "limit": <integer>,
        "from": <IPv6 address or "start">
    }
}

The from address and the page size limit are mandatory.

Response syntax:

[
  {
    "arguments": {
      "leases": [
        {
          "cltt": 1600439560,
          "duid": "00:01:00:01:26:f7:81:88:00:0c:01:02:03:04",
          "fqdn-fwd": false,
          "fqdn-rev": false,
          "hostname": "foo.example.org",
          "hw-address": "00:0c:01:02:03:04",
          "iaid": 1,
          "ip-address": "2001:db8:1::1",
          "preferred-lft": 3000,
          "state": 0,
          "subnet-id": 1,
          "type": "IA_NA",
          "valid-lft": 4000
        }
        {
          "cltt": 1600439570,
          "duid": "00:01:00:01:26:f7:81:88:00:0c:01:02:03:05",
          "fqdn-fwd": false,
          "fqdn-rev": false,
          "hostname": "bar.example.org",
          "hw-address": "00:0c:01:02:03:05",
          "iaid": 1,
          "ip-address": "2001:db8:1::2",
          "preferred-lft": 3000,
          "state": 0,
          "subnet-id": 1,
          "type": "IA_NA",
          "valid-lft": 4000
        }
      ]
    },
    "result": 0,
    "text": "1 IPv6 lease(s) found."
}
]

Result 0 is returned when at least one lease is found, 1 when parameters are malformed or missing, 3 is returned if no leases are found.

lease6-resend-ddns

This command resends a request to kea-dhcp-ddns to update DNS for an existing lease.

Supported by: kea-dhcp6

Availability: 1.7.6 (lease_cmds hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see lease6-resend-ddns command

Command syntax:

{
    "command": "lease6-resend-ddns",
    "arguments": {
        "ip-address": "2001:db8::1"
    }
}

Response syntax:

{
  "arguments": {
  },
  "result": 0,
  "text": "NCR generated for: 2001:db8::1, hostname: example.com."
}

lease6-resend-ddns returns a result that indicates the outcome of the operation and lease details, if found. It has one of the following values: 0 (success), 1 (error), or 3 (empty).

lease6-update

This command updates existing leases.

Supported by: kea-dhcp6

Availability: 1.3.0 (lease_cmds hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see lease6-update command

Command syntax:

{
  "command": "lease6-update",
  "arguments": {
    "ip-address": "2001:db8::1",
    "duid": "88:88:88:88:88:88:88:88",
    "iaid": 7654321,
    "hostname": "newhostname.example.org",
    "subnet-id": 66,
    "force-create": false
  }
}

Response syntax:

{
    "result": <integer>,
    "text": "<string>"
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

lease6-wipe

This command removes all leases associated with a given subnet.

Supported by: kea-dhcp6

Availability: 1.3.0 (lease_cmds hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see lease6-wipe command

Command syntax:

{
  "command": "lease6-wipe",
  "arguments": {
    "subnet-id": 66
  }
}

Note: not all backends support this command.

Response syntax:

{
    "result": <integer>,
    "text": "<string>"
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

leases-reclaim

This command instructs the server to reclaim all expired leases immediately.

Supported by: kea-dhcp4, kea-dhcp6

Availability: 1.0.0 (built-in)

Access: write (parameter ignored in this Kea version)

Description and examples: see leases-reclaim command

Command syntax:

{
    "command": "leases-reclaim",
    "arguments": {
        "remove": true
    }
}

Response syntax:

{
    "result": <integer>,
    "text": "<string>"
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

libreload

This command first unloads and then reloads all currently loaded hooks libraries.

Supported by: kea-dhcp4, kea-dhcp6

Availability: 1.2.0 (built-in)

Access: write (parameter ignored in this Kea version)

Description and examples: see libreload command

Command syntax:

{
    "command": "libreload",
    "arguments": { }
}

The server responds with 0, indicating success, or 1, indicating a failure.

Response syntax:

{
    "result": <integer>,
    "text": "<string>"
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

list-commands

This command retrieves a list of all commands supported by the server.

Supported by: kea-ctrl-agent, kea-dhcp-ddns, kea-dhcp4, kea-dhcp6

Availability: 1.0.0 (built-in)

Access: read (parameter ignored in this Kea version)

Description and examples: see list-commands command

Command syntax:

{
    "command": "list-commands",
    "arguments": { }
}

The server responds with a list of all supported commands.

Response syntax:

{
    "result": <integer>,
    "text": "<string>"
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

network4-add

This command adds a new shared network.

Supported by: kea-dhcp4

Availability: 1.3.0 (subnet_cmds hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see network4-add command

Command syntax:

{
    "command": "network4-add",
    "arguments": {
        "shared-networks": [ {
            "name": "floor13",
            "subnet4": [
            {
                "id": 100,
                "pools": [ { "pool": "192.0.2.2-192.0.2.99" } ],
                "subnet": "192.0.2.0/24",
                "option-data": [
                    {
                        "name": "routers",
                        "data": "192.0.2.1"
                    }
                ]
            },
            {
                "id": 101,
                "pools": [ { "pool": "192.0.3.2-192.0.3.99" } ],
                "subnet": "192.0.3.0/24",
                "option-data": [
                    {
                        "name": "routers",
                        "data": "192.0.3.1"
                    }
                ]
            } ]
        } ]
    }
}

Response syntax:

{
    "arguments": {
        "shared-networks": [ { "name": "floor13" } ]
    },
    "result": 0,
    "text": "A new IPv4 shared network 'floor13' added"
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

network4-del

This command deletes existing shared networks.

Supported by: kea-dhcp4

Availability: 1.3.0 (subnet_cmds hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see network4-del command

Command syntax:

{
    "command": "network4-del",
    "arguments": {
        "name": "floor13"
    }
}

Response syntax:

{
    "arguments": {
        "shared-networks": [
            {
                "name": "floor13"
            }
        ]
    },
    "result": 0,
    "text": "IPv4 shared network 'floor13' deleted"
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

network4-get

This command retrieves detailed information about shared networks, including subnets that are currently part of a given network.

Supported by: kea-dhcp4

Availability: 1.3.0 (subnet_cmds hook library)

Access: read (parameter ignored in this Kea version)

Description and examples: see network4-get command

Command syntax:

{
    "command": "network4-get",
    "arguments": {
        "name": "floor13"
    }
}

Response syntax:

{
    "result": 0,
    "text": "Info about IPv4 shared network 'floor13' returned",
    "arguments": {
        "shared-networks": [
        {
            "match-client-id": true,
            "name": "floor13",
            "option-data": [ ],
            "rebind-timer": 90,
            "relay": {
                "ip-address": "0.0.0.0"
            },
            "renew-timer": 60,
            "subnet4": [
                {
                    "subnet": "192.0.2.0/24",
                    "id": 5,
                    // many other subnet-specific details here
                },
                {
                    "subnet": "192.0.3.0/31",
                    "id": 6,
                    // many other subnet-specific details here
                }
            ],
            "valid-lifetime": 120
        }
        ]
    }
}

Note that the actual response contains many additional fields that are omitted here for clarity.

network4-list

This command retrieves the full list of currently configured shared networks.

Supported by: kea-dhcp4

Availability: 1.3.0 (subnet_cmds hook library)

Access: read (parameter ignored in this Kea version)

Description and examples: see network4-list command

Command syntax:

{
    "command": "network4-list"
}

Response syntax:

{
    "arguments": {
        "shared-networks": [
            { "name": "floor1" },
            { "name": "office" }
        ]
    },
    "result": 0,
    "text": "2 IPv4 network(s) found"
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

network4-subnet-add

This command adds existing subnets to existing shared networks.

Supported by: kea-dhcp4

Availability: 1.3.0 (subnet_cmds hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see network4-subnet-add command

Command syntax:

{
    "command": "network4-subnet-add",
    "arguments": {
        "name": "floor13",
        "id": 5
    }
}

Response syntax:

{
    "result": 0,
    "text": "IPv4 subnet 10.0.0.0/8 (id 5) is now part of shared network 'floor1'"
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

network4-subnet-del

This command removes a subnet that is part of an existing shared network and demotes it to a plain, stand-alone subnet.

Supported by: kea-dhcp4

Availability: 1.3.0 (subnet_cmds hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see network4-subnet-del command

Command syntax:

{
    "command": "network4-subnet-del",
    "arguments": {
        "name": "floor13",
        "id": 5
    }
 }

Response syntax:

{
    "result": 0,
    "text": "IPv4 subnet 10.0.0.0/8 (id 5) is now removed from shared network 'floor13'"
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

network6-add

This command adds a new shared network.

Supported by: kea-dhcp6

Availability: 1.3.0 (subnet_cmds hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see network6-add command

Command syntax:

{
    "command": "network4-add",
    "arguments": {
        "shared-networks": [ {
            "name": "floor13",
            "subnet4": [
            {
                "id": 100,
                "pools": [ { "pool": "192.0.2.2-192.0.2.99" } ],
                "subnet": "192.0.2.0/24",
                "option-data": [
                    {
                        "name": "routers",
                        "data": "192.0.2.1"
                    }
                ]
            },
            {
                "id": 101,
                "pools": [ { "pool": "192.0.3.2-192.0.3.99" } ],
                "subnet": "192.0.3.0/24",
                "option-data": [
                    {
                        "name": "routers",
                        "data": "192.0.3.1"
                    }
                ]
            } ]
        } ]
    }
}

The network6-add command uses the same syntax as network4-add for both the query and the response. However, there are some parameters that are IPv4-only (e.g. match-client-id) and some that are IPv6-only (e.g. interface-id).

Response syntax:

{
    "arguments": {
        "shared-networks": [ { "name": "floor13" } ]
    },
    "result": 0,
    "text": "A new IPv4 shared network 'floor13' added"
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

network6-del

This command deletes existing shared networks.

Supported by: kea-dhcp6

Availability: 1.3.0 (subnet_cmds hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see network6-del command

Command syntax:

{
    "command": "network4-del",
    "arguments": {
        "name": "floor13"
    }
}

The network6-del command uses exactly the same syntax as network4-del for both the query and the response.

Response syntax:

{
    "command": "network4-del",
    "arguments": {
        "name": "floor13",
        "subnets-action": "delete"
    }
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

network6-get

The network6-get command retrieves detailed information about shared networks, including subnets that are currently part of a given network.

Supported by: kea-dhcp6

Availability: 1.3.0 (subnet_cmds hook library)

Access: read (parameter ignored in this Kea version)

Description and examples: see network6-get command

Command syntax:

{
    "command": "network4-get",
    "arguments": {
        "name": "floor13"
    }
}

Response syntax:

{
    "result": 0,
    "text": "Info about IPv4 shared network 'floor13' returned",
    "arguments": {
        "shared-networks": [
        {
            "match-client-id": true,
            "name": "floor13",
            "option-data": [ ],
            "rebind-timer": 90,
            "relay": {
                "ip-address": "0.0.0.0"
            },
            "renew-timer": 60,
            "subnet4": [
                {
                    "subnet": "192.0.2.0/24",
                    "id": 5,
                    // many other subnet specific details here
                },
                {
                    "subnet": "192.0.3.0/31",
                    "id": 6,
                    // many other subnet specific details here
                }
            ],
            "valid-lifetime": 120
        }
        ]
    }
}

Note that the actual response contains many additional fields that are omitted here for clarity.

network6-list

This command retrieves the full list of currently configured shared networks.

Supported by: kea-dhcp6

Availability: 1.3.0 (subnet_cmds hook library)

Access: read (parameter ignored in this Kea version)

Description and examples: see network6-list command

Command syntax:

{
    "command": "network4-list"
}

The network6-list command uses exactly the same syntax as network4-list for both the query and the response.

Response syntax:

{
    "arguments": {
        "shared-networks": [
            { "name": "floor1" },
            { "name": "office" }
        ]
    },
    "result": 0,
    "text": "2 IPv4 network(s) found"
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

network6-subnet-add

This command adds existing subnets to existing shared networks.

Supported by: kea-dhcp6

Availability: 1.3.0 (subnet_cmds hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see network6-subnet-add command

Command syntax:

{
    "command": "network4-subnet-add",
    "arguments": {
        "name": "floor13",
        "id": 5
    }
}

The network6-subnet-add command uses exactly the same syntax as network4-subnet-add for both the query and the response.

Response syntax:

{
    "result": 0,
    "text": "IPv4 subnet 10.0.0.0/8 (id 5) is now part of shared network 'floor1'"
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

network6-subnet-del

This command removes a subnet that is part of an existing shared network and demotes it to a plain, stand-alone subnet.

Supported by: kea-dhcp6

Availability: 1.3.0 (subnet_cmds hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see network6-subnet-del command

Command syntax:

{
    "command": "network4-subnet-del",
    "arguments": {
        "name": "floor13",
        "id": 5
    }
 }

The network6-subnet-del command uses exactly the same syntax as network4-subnet-del for both the query and the response.

Response syntax:

{
    "result": 0,
    "text": "IPv4 subnet 10.0.0.0/8 (id 5) is now removed from shared network 'floor13'"
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

remote-class4-del

This command deletes a DHCPv4 client class from the configuration database.

Supported by: kea-dhcp4

Availability: 1.9.10 (cb_cmds hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see remote-class4-del command

Command syntax:

{
    "command": "remote-class4-del",
    "arguments": {
        "client-classes": [
            {
                "name": <client class name>
            }
        ],
        "remote": {
            <specification of the database to connect to>
        }
    }
}

This command includes a list with exactly one name of the client class to be deleted. The server-tags parameter must not be specified for this command.

Response syntax:

{
    "result": 0,
    "text": "1 DHCPv4 client class(es) deleted.",
    "arguments": {
        "count": 1
    }
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

remote-class4-get

This command fetches a selected DHCPv4 client class by name from the specified database.

Supported by: kea-dhcp4

Availability: 1.9.10 (cb_cmds hook library)

Access: read (parameter ignored in this Kea version)

Description and examples: see remote-class4-get command

Command syntax:

{
    "command": "remote-class4-get",
    "arguments": {
        "client-classes": [
            {
                "name": <client class name>
            }
        ],
        "remote": {
            <specification of the database to connect to>
        }
    }
}

This command includes a list with exactly one name of the client class to be returned. The server-tags parameter must not be specified for this command.

Response syntax:

{
    "result": 0,
    "text": "DHCPv4 client class found.",
    "arguments": {
        "client-classes": [
            {
                "name": <client class name>,
                "metadata": {
                    "server-tags": [ <first server tag>, <second server tag>, ... ]
                },
                <the rest of the client class information>
            }
        ],
        "count": 1
    }
}

The metadata is included in the returned shared network definition and provides the database-specific information associated with the returned object.

remote-class4-get-all

This command fetches all DHCPv4 client classes for specified servers from the configuration database.

Supported by: kea-dhcp4

Availability: 1.9.10 (cb_cmds hook library)

Access: read (parameter ignored in this Kea version)

Description and examples: see remote-class4-get-all command

Command syntax:

{
    "command": "remote-class4-get-all",
    "arguments": {
        "remote": {
            <specification of the database to connect to>
        },
        "server-tags": [ <first server tag>, <second server tag>, ... ]
    }
}

The server-tags list is required for this command, and must not be empty.

Response syntax:

{
    "result": 0,
    "text": "2 DHCPv4 client class(es) found.",
    "arguments": {
        "client-classes": [
            {
                <first client class specification>,
                "metadata": {
                    "server-tags": [ <first server tag>, <second server tag>, ... ]
                }
            },
            {
                <second client class specification>,
                "metadata": {
                    "server-tags": [ <first server tag>, ... ]
                }
            }
        ],
        "count": 2
    }
}

The returned response contains a list of maps. Each map contains a client class name and the metadata, which provides database-specific information associated with the client class.

remote-class4-set

This command creates or replaces a DHCPv4 client class in the configuration database.

Supported by: kea-dhcp4

Availability: 1.9.10 (cb_cmds hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see remote-class4-set command

Command syntax:

{
    "command": "remote-class4-set",
    "arguments": {
        "client-class": [
            {
                <client class specification>
                "follow-class-name": <existing class name>
            }
        ],
        "remote": {
            <specification of the database to connect to>
        },
        "server-tags": [ <first server tag>, <second server tag>, ... ]
    }
}

The provided list must contain exactly one client class specification. It may contain an optional parameter “follow-class-name” which can specify an existing class name to indicate that the class from the command is placed right after this existing class in the hierarchy. This parameter can be omitted or set to “null” to indicate that the new client class should be appended at the end of the hierarchy or an updated class should remain at the current position. The server-tags list is mandatory and must contain one or more server tags as strings to explicitly associate the client class with one or more user-defined servers. It may include the special server tag “all” to associate the class with all servers.

Response syntax:

{
    "result": 0,
    "text": "DHCPv4 shared network successfully set."
    "arguments": {
        "client-classes": [
            {
                "name": <set client class name>
            }
    ]
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

remote-class6-del

This command deletes a DHCPv6 client class from the configuration database.

Supported by: kea-dhcp6

Availability: 1.9.10 (cb_cmds hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see remote-class6-del command

Command syntax:

{
    "command": "remote-class6-del",
    "arguments": {
        "client-classes": [
            {
                "name": <client class name>
            }
        ],
        "remote": {
            <specification of the database to connect to>
        }
    }
}

This command includes a list with exactly one name of the client class to be deleted. The server-tags parameter must not be specified for this command.

Response syntax:

{
    "result": 0,
    "text": "1 DHCPv6 client class(es) deleted.",
    "arguments": {
        "count": 1
    }
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

remote-class6-get

This command fetches a selected DHCPv6 client class by name from the specified database.

Supported by: kea-dhcp6

Availability: 1.9.10 (cb_cmds hook library)

Access: read (parameter ignored in this Kea version)

Description and examples: see remote-class6-get command

Command syntax:

{
    "command": "remote-class6-get",
    "arguments": {
        "client-classes": [
            {
                "name": <client class name>
            }
        ],
        "remote": {
            <specification of the database to connect to>
        }
    }
}

This command includes a list with exactly one name of the client class to be returned. The server-tags parameter must not be specified for this command.

Response syntax:

{
    "result": 0,
    "text": "DHCPv6 client class found.",
    "arguments": {
        "client-classes": [
            {
                "name": <client class name>,
                "metadata": {
                    "server-tags": [ <first server tag>, <second server tag>, ... ]
                },
                <the rest of the client class information>
            }
        ],
        "count": 1
    }
}

The metadata is included in the returned shared network definition and provides the database-specific information associated with the returned object.

remote-class6-get-all

This command fetches all DHCPv6 client classes for specified servers from the configuration database.

Supported by: kea-dhcp6

Availability: 1.9.10 (cb_cmds hook library)

Access: read (parameter ignored in this Kea version)

Description and examples: see remote-class6-get-all command

Command syntax:

{
    "command": "remote-class6-get-all",
    "arguments": {
        "remote": {
            <specification of the database to connect to>
        },
        "server-tags": [ <first server tag>, <second server tag>, ... ]
    }
}

The server-tags list is required for this command, and must not be empty.

Response syntax:

{
    "result": 0,
    "text": "2 DHCPv6 client class(es) found.",
    "arguments": {
        "client-classes": [
            {
                <first client class specification>,
                "metadata": {
                    "server-tags": [ <first server tag>, <second server tag>, ... ]
                }
            },
            {
                <second client class specification>,
                "metadata": {
                    "server-tags": [ <first server tag>, ... ]
                }
            }
        ],
        "count": 2
    }
}

The returned response contains a list of maps. Each map contains a client class name and the metadata, which provides database-specific information associated with the client class.

remote-class6-set

This command creates or replaces a DHCPv6 client class in the configuration database.

Supported by: kea-dhcp6

Availability: 1.9.10 (cb_cmds hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see remote-class6-set command

Command syntax:

{
    "command": "remote-class6-set",
    "arguments": {
        "client-class": [
            {
                <client class specification>
                "follow-class-name": <existing class name>
            }
        ],
        "remote": {
            <specification of the database to connect to>
        },
        "server-tags": [ <first server tag>, <second server tag>, ... ]
    }
}

The provided list must contain exactly one client class specification. It may contain an optional parameter “follow-class-name” which can specify an existing class name to indicate that the class from the command is placed right after this existing class in the hierarchy. This parameter can be omitted or set to “null” to indicate that the new client class should be appended at the end of the hierarchy or an updated class should remain at the current position. The server-tags list is mandatory and must contain one or more server tags as strings to explicitly associate the client class with one or more user-defined servers. It may include the special server tag “all” to associate the class with all servers.

Response syntax:

{
    "result": 0,
    "text": "DHCPv6 shared network successfully set."
    "arguments": {
        "client-classes": [
            {
                "name": <set client class name>
            }
    ]
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

remote-global-parameter4-del

This command deletes a global DHCPv4 parameter from the configuration database. The server uses the value specified in the configuration file, or a default value if the parameter is not specified, after deleting the parameter from the database.

Supported by: kea-dhcp4

Availability: 1.6.0 (cb_cmds hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see remote-global-parameter4-del command

Command syntax:

{
    "command": "remote-global-parameter4-del",
    "arguments": {
        "parameters": [ <parameter name as string> ],
        "remote": {
            <specification of the database to connect to>
        },
        "server-tags": [ <single server tag as string> ]
    }
}

This command carries the list including exactly one name of the parameter to be deleted. The server-tags list is mandatory and it must contain exactly one server tag. Specifying an empty list, a value of null, or multiple server tags will result in an error.

Response syntax:

{
    "result": 0,
    "text": "DHCPv4 global parameter(s) deleted.",
    "arguments": {
        "count": 1
    }
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

remote-global-parameter4-get

This command fetches the selected global parameter for the server from the specified database.

Supported by: kea-dhcp4

Availability: 1.6.0 (cb_cmds hook library)

Access: read (parameter ignored in this Kea version)

Description and examples: see remote-global-parameter4-get command

Command syntax:

{
    "command": "remote-global-parameter4-get",
    "arguments": {
        "parameters": [ <parameter name as string> ],
        "remote": {
            <specification of the database to connect to>
        },
        "server-tags": [ <single server tag as string> ]
    }
}

This command carries a list including exactly one name of the parameter to be fetched. The server-tags list is mandatory and must contain exactly one server tag. Specifying an empty list, a value of null, or multiple server tags will result in an error. The server tag “all” is allowed; it fetches the global parameter value shared by all servers.

Response syntax:

{
    "result": 0,
    "text": "DHCPv4 global parameter found.",
    "arguments": {
        "parameters": {
            <parameter name>: <parameter value>,
            "metadata": {
                "server-tags": [ <server tag> ]
            }
        },
        "count": 1
    }
}

The returned response contains a map with a global parameter name/value pair. The value may be a JSON string, integer, real, or boolean. The metadata is included and provides database-specific information associated with the returned object. If the “all” server tag is specified, the command attempts to fetch the global parameter value associated with all servers. If the explicit server tag is specified, the command fetches the value associated with the given server. If the server-specific value does not exist, the remote-global-parameter4-get command fetches the value associated with all servers.

remote-global-parameter4-get-all

This command fetches all global parameters for the server from the specified database.

Supported by: kea-dhcp4

Availability: 1.6.0 (cb_cmds hook library)

Access: read (parameter ignored in this Kea version)

Description and examples: see remote-global-parameter4-get-all command

Command syntax:

{
    "command": "remote-global-parameter4-get-all",
    "arguments": {
        "remote": {
            <specification of the database to connect to>
        },
        "server-tags": [ <single server tag as string> ]
    }
}

The server-tags list is mandatory and must contain exactly one server tag. Specifying an empty list, a value of null, or multiple server tags will result in an error. The special server tag “all” is allowed; it fetches the global parameters shared by all servers.

Response syntax:

{
    "result": 0,
    "text": "DHCPv4 global parameters found.",
    "arguments": {
        "parameters": [
            {
                <first parameter name>: <first parameter value>,
                "metadata": {
                    "server-tags": [ <server tag> ]
                }
            },
            {
                <second parameter name>: <second parameter value>,
                "metadata": {
                    "server-tags": [ <server tag> ]
                }
            }
        ],
        "count": 2
    }
}

The returned response contains a list of maps. Each map contains a global parameter name/value pair. The value may be a JSON string, integer, real, or boolean. The metadata is appended to each parameter and provides database-specific information associated with the returned objects. If the server tag “all” is included in the command, the response contains the global parameters shared among all servers. It excludes server-specific global parameters. If an explicit server tag is included in the command, the response contains all global parameters directly associated with the given server, and the global parameters associated with all servers when server-specific values are not present.

remote-global-parameter4-set

This command creates or updates one or more global parameters in the configuration database.

Supported by: kea-dhcp4

Availability: 1.6.0 (cb_cmds hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see remote-global-parameter4-set command

Command syntax:

{
    "command": "remote-global-parameter4-set",
    "arguments": {
        "parameters": {
            <first parameter name>: <first parameter value>,
            <second parameter name>: <second parameter value>
        },
        "remote": {
            <specification of the database to connect to>
        },
        "server-tags": [ <single server tag as string> ]
    }
}

This command carries multiple global parameters with their values. Care should be taken when specifying more than one parameter; in some cases, only a subset of the parameters may be successfully stored in the database and other parameters may fail to be stored. In such cases the remote-global-parameter4-get-all command may be useful to verify the contents of the database after the update. The server-tags list is mandatory and must contain exactly one server tag. Specifying an empty list, a value of null, or multiple server tags will result in an error. The server tag “all” is allowed; it associates the specified parameters with all servers.

Response syntax:

{
    "result": 0,
    "text": "DHCPv4 global parameter(s) successfully set.",
    "arguments": {
        "parameters": {
            <first parameter name>: <first parameter value>,
            <second parameter name>: <second parameter value>
        },
        "count": 2
    }
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

remote-global-parameter6-del

This command deletes a global DHCPv6 parameter from the configuration database. The server uses the value specified in the configuration file, or a default value if the parameter is not specified in the configuration file, after deleting the parameter from the database.

Supported by: kea-dhcp6

Availability: 1.6.0 (cb_cmds hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see remote-global-parameter6-del command

Command syntax:

{
    "command": "remote-global-parameter6-del",
    "arguments": {
        "parameters": [ <parameter name as string> ],
        "remote": {
            <specification of the database to connect to>
        },
        "server-tags": [ <single server tag as string> ]
    }
}

This command carries the list including exactly one name of the parameter to be deleted. The server-tags list is mandatory and must contain exactly one server tag. Specifying an empty list, a value of null, or multiple server tags will result in an error.

Response syntax:

{
    "result": 0,
    "text": "DHCPv6 global parameter(s) deleted.",
    "arguments": {
        "count": 1
    }
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

remote-global-parameter6-get

This command fetches the selected global parameter for the server from the specified database.

Supported by: kea-dhcp6

Availability: 1.6.0 (cb_cmds hook library)

Access: read (parameter ignored in this Kea version)

Description and examples: see remote-global-parameter6-get command

Command syntax:

{
    "command": "remote-global-parameter6-get",
    "arguments": {
        "parameters": [ <parameter name as string> ],
        "remote": {
            <specification of the database to connect to>
        },
        "server-tags": [ <single server tag as string> ]
    }
}

This command carries a list including exactly one name of the parameter to be fetched. The server-tags list is mandatory and must contain exactly one server tag. Specifying an empty list, a value of null, or multiple server tags will result in an error. The server tag “all” is allowed; it fetches the global parameter value shared by all servers.

Response syntax:

{
    "result": 0,
    "text": "DHCPv6 global parameter found.",
    "arguments": {
        "parameters": {
            <parameter name>: <parameter value>,
            "metadata": {
                "server-tags": [ <server tag> ]
            }
        },
        "count": 1
    }
}

The returned response contains a map with a global parameter name/value pair. The value may be a JSON string, integer, real, or boolean. The metadata is included and provides database-specific information associated with the returned object. If the “all” server tag is specified, the command attempts to fetch the global parameter value associated with all servers. If the explicit server tag is specified, the command fetches the value associated with the given server. If the server-specific value does not exist, the remote-global-parameter6-get fetches the value associated with all servers.

remote-global-parameter6-get-all

This command fetches all global parameters for the server from the specified database.

Supported by: kea-dhcp6

Availability: 1.6.0 (cb_cmds hook library)

Access: read (parameter ignored in this Kea version)

Description and examples: see remote-global-parameter6-get-all command

Command syntax:

{
    "command": "remote-global-parameter6-get-all",
    "arguments": {
        "remote": {
            <specification of the database to connect to>
        },
        "server-tags": [ <single server tag as string> ]
    }
}

The server-tags list is mandatory and must contain exactly one server tag. Specifying an empty list, a value of null, or multiple server tags will result in an error. The special server tag “all” is allowed; it fetches the global parameters shared by all servers.

Response syntax:

{
    "result": 0,
    "text": "DHCPv6 global parameters found.",
    "arguments": {
        "parameters": [
            {
                <first parameter name>: <first parameter value>,
                "metadata": {
                    "server-tags": [ <server tag> ]
                }
            },
            {
                <second parameter name>: <second parameter value>,
                "metadata": {
                    "server-tags": [ <server tag> ]
                }
            }
        ],
        "count": 2
    }
}

The returned response contains a list of maps. Each map contains a global parameter name/value pair. The value may be a JSON string, integer, real, or boolean. The metadata is appended to each parameter and provides database-specific information associated with the returned objects. If the server tag “all” is included in the command, the response contains the global parameters shared among all servers. It excludes server-specific global parameters. If an explicit server tag is included in the command, the response contains all global parameters directly associated with the given server, and the global parameters associated with all servers when server-specific values are not present.

remote-global-parameter6-set

This command creates or updates one or more global parameters in the configuration database.

Supported by: kea-dhcp6

Availability: 1.6.0 (cb_cmds hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see remote-global-parameter6-set command

Command syntax:

{
    "command": "remote-global-parameter6-set",
    "arguments": {
        "parameters": {
            <first parameter name>: <first parameter value>,
            <second parameter name>: <second parameter value>
        },
        "remote": {
            <specification of the database to connect to>
        },
        "server-tags": [ <single server tag as string> ]
    }
}

This command carries multiple global parameters with their values. Care should be taken when specifying more than one parameter; in some cases, only a subset of the parameters may be successfully stored in the database and other parameters may fail to be stored. In such cases the remote-global-parameter6-get-all command may be useful to verify the contents of the database after the update. The server-tags list is mandatory and must contain exactly one server tag. Specifying an empty list, a value of null, or multiple server tags will result in an error. The server tag “all” is allowed; it associates the specified parameters with all servers.

Response syntax:

{
    "result": 0,
    "text": "DHCPv6 global parameter(s) successfully set.",
    "arguments": {
        "parameters": {
            <first parameter name>: <first parameter value>,
            <second parameter name>: <second parameter value>
        },
        "count": 2
    }
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

remote-network4-del

This command deletes an IPv4 shared network from the configuration database.

Supported by: kea-dhcp4

Availability: 1.6.0 (cb_cmds hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see remote-network4-del command

Command syntax:

{
    "command": "remote-network4-del",
    "arguments": {
        "shared-networks": [
            {
                "name": <shared network name>
            }
        ],
        "subnets-action": <'keep' | 'delete'>,
        "remote": {
            <specification of the database to connect to>
        }
    }
}

This command includes a list with exactly one name of the shared network to be deleted. The subnets-action parameter denotes whether the subnets in this shared network should be deleted. The server-tags parameter must not be specified for this command.

Response syntax:

{
    "result": 0,
    "text": "1 IPv4 shared network(s) deleted.",
    "arguments": {
        "count": 1
    }
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

remote-network4-get

This command fetches the selected IPv4 shared network for the server from the specified database.

Supported by: kea-dhcp4

Availability: 1.6.0 (cb_cmds hook library)

Access: read (parameter ignored in this Kea version)

Description and examples: see remote-network4-get command

Command syntax:

{
    "command": "remote-network4-get",
    "arguments": {
        "shared-networks": [
            {
                "name": <shared network name>
            }
        ],
        "subnets-include": <'full' | 'no'>,
        "remote": {
            <specification of the database to connect to>
        }
    }
}

This command includes a list with exactly one name of the shared network to be returned. The subnets-include optional parameter allows for specifying whether the subnets belonging to the shared network should also be returned. The server-tags parameter must not be specified for this command.

Response syntax:

{
    "result": 0,
    "text": "IPv4 shared network found.",
    "arguments": {
        "shared-networks": [
            {
                "name": <shared network name>,
                "metadata": {
                    "server-tags": [ <first server tag>, <second server tag>, ... ]
                },
                <the rest of the shared network information, potentially including subnets>
            }
        ],
        "count": 1
    }
}

If the subnets are returned with the shared network, they are carried in the subnet4 list within the shared network definition. The metadata is included in the returned shared network definition and provides the database-specific information associated with the returned object.

remote-network4-list

This command fetches a list of all IPv4 shared networks from the configuration database.

Supported by: kea-dhcp4

Availability: 1.6.0 (cb_cmds hook library)

Access: read (parameter ignored in this Kea version)

Description and examples: see remote-network4-list command

Command syntax:

{
    "command": "remote-network4-list",
    "arguments": {
        "remote": {
            <specification of the database to connect to>
        },
        "server-tags": [ <first server tag>, <second server tag>, ... ]
    }
}

The server-tags list is required for this command, and must not be empty. It may either contain one or multiple server tags as strings, or a single null value.

Response syntax:

{
    "result": 0,
    "text": "2 IPv4 shared network(s) found.",
    "arguments": {
        "shared-networks": [
            {
                "name": <first shared network name>,
                "metadata": {
                    "server-tags": [ <first server tag>, <second server tag>, ... ]
                }
            },
            {
                "name": <second shared network name>,
                "metadata": {
                    "server-tags": [ <first server tag>, ... ]
                }
            }
        ],
        "count": 2
    }
}

The returned response contains the list of maps. Each map contains the shared network name and the metadata, which provides database-specific information associated with the shared network. The returned list does not contain full definitions of the shared networks; use remote-network4-get to fetch the full information about the selected shared networks. If the command includes explicit server tags as strings (including the special server tag “all”), the list contains all shared networks which are associated with any of the specified tags. A network is returned even if it is associated with multiple servers and only one of the specified tags matches. If the command includes the null value in the server-tags list, the response contains all shared networks which are assigned to no servers (unassigned).

remote-network4-set

This command creates or replaces an IPv4 shared network in the configuration database.

Supported by: kea-dhcp4

Availability: 1.6.0 (cb_cmds hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see remote-network4-set command

Command syntax:

{
    "command": "remote-network4-set",
    "arguments": {
        "shared-networks": [
            {
                <shared network specification excluding subnets list>
            }
        ],
        "remote": {
            <specification of the database to connect to>
        },
        "server-tags": [ <first server tag>, <second server tag>, ... ]
    }
}

The provided list must contain exactly one shared network specification, and must not contain subnets (the “subnet4” parameter). The subnets are added to the shared network using the remote-subnet4-set command. The server-tags list is mandatory and must contain one or more server tags as strings to explicitly associate the shared network with one or more user-defined servers. It may include the special server tag “all” to associate the network with all servers.

Response syntax:

{
    "result": 0,
    "text": "IPv4 shared network successfully set."
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

remote-network6-del

This command deletes an IPv6 shared network from the configuration database.

Supported by: kea-dhcp6

Availability: 1.6.0 (cb_cmds hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see remote-network6-del command

Command syntax:

{
    "command": "remote-network6-del",
    "arguments": {
        "shared-networks": [
            {
                "name": <shared network name>
            }
        ],
        "subnets-action": <'keep' | 'delete'>,
        "remote": {
            <specification of the database to connect to>
        }
    }
}

This command includes a list with exactly one name of the shared network to be deleted. The subnets-action parameter indicates whether the subnets in this shared network should be deleted. The server-tags parameter must not be specified for this command.

Response syntax:

{
    "result": 0,
    "text": "1 IPv6 shared network(s) deleted.",
    "arguments": {
        "count": 1
    }
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

remote-network6-get

This command fetches the selected IPv6 shared network for the server from the specified database.

Supported by: kea-dhcp6

Availability: 1.6.0 (cb_cmds hook library)

Access: read (parameter ignored in this Kea version)

Description and examples: see remote-network6-get command

Command syntax:

{
    "command": "remote-network6-get",
    "arguments": {
        "shared-networks": [
            {
                "name": <shared network name>
            }
        ],
        "subnets-include": <'full' | 'no'>,
        "remote": {
            <specification of the database to connect to>
        }
    }
}

This command includes a list with exactly one name of the shared network to be returned. The subnets-include optional parameter allows for specifying whether the subnets belonging to the shared network should also be returned. The server-tags parameter must not be specified for this command.

Response syntax:

{
    "result": 0,
    "text": "IPv6 shared network found.",
    "arguments": {
        "shared-networks": [
            {
                "name": <shared network name>,
                "metadata": {
                    "server-tags": [ <first server tag>, <second server tag>, ... ]
                },
                <the rest of the shared network information, potentially including subnets>
            }
        ],
        "count": 1
    }
}

If the subnets are returned with the shared network, they are carried in the subnet6 list within the shared network definition. The metadata is included in the returned shared network definition and provides the database-specific information associated with the returned object.

remote-network6-list

This command fetches a list of all IPv6 shared networks from the configuration database.

Supported by: kea-dhcp6

Availability: 1.6.0 (cb_cmds hook library)

Access: read (parameter ignored in this Kea version)

Description and examples: see remote-network6-list command

Command syntax:

{
    "command": "remote-network6-list",
    "arguments": {
        "remote": {
            <specification of the database to connect to>
        },
        "server-tags": [ <first server tag>, <second server tag>, ... ]
    }
}

The server-tags list is required for this command, and must not be empty. It may either contain one or multiple server tags as strings, or a single null value.

Response syntax:

{
    "result": 0,
    "text": "2 IPv6 shared network(s) found.",
    "arguments": {
        "shared-networks": [
            {
                "name": <first shared network name>,
                "metadata": {
                    "server-tags": [ <first server tag>, <second server tag>, ... ]
                }
            },
            {
                "name": <second shared network name>,
                "metadata": {
                    "server-tags": [ <first server tag>, ... ]
                }
            }
        ],
        "count": 2
    }
}

The returned response contains the list of maps. Each map contains the shared network name and the metadata, which provides database-specific information associated with the shared network. The returned list does not contain full definitions of the shared networks; use remote-network6-get to fetch the full information about the selected shared networks. If the command includes explicit server tags as strings (including the special server tag “all”), the list contains all shared networks which are associated with any of the specified tags. A network is returned even if it is associated with multiple servers and only one of the specified tags matches. If the command includes the null value in the server-tags list, the response contains all shared networks which are assigned to no servers (unassigned).

remote-network6-set

This command creates or replaces an IPv6 shared network in the configuration database.

Supported by: kea-dhcp6

Availability: 1.6.0 (cb_cmds hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see remote-network6-set command

Command syntax:

{
    "command": "remote-network6-set",
    "arguments": {
        "shared-networks": [
            {
                <shared network specification excluding subnets list>
            }
        ],
        "remote": {
            <specification of the database to connect to>
        },
        "server-tags": [ <first server tag>, <second server tag>, ... ]
    }
}

The provided list must contain exactly one shared network specification, and must not contain subnets (the “subnet6” parameter). The subnets are added to the shared network using the remote-subnet6-set command. The server-tags list is mandatory and must contain one or more server tags as strings to explicitly associate the shared network with one or more user-defined servers. It may include the special server tag “all” to associate the network with all servers.

Response syntax:

{
    "result": 0,
    "text": "IPv6 shared network successfully set."
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

remote-option-def4-del

This command deletes a DHCPv4 option definition from the configuration database.

Supported by: kea-dhcp4

Availability: 1.6.0 (cb_cmds hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see remote-option-def4-del command

Command syntax:

{
    "command": "remote-option-def4-del",
    "arguments": {
        "option-defs": [ {
            "code": <option code>,
            "space": <option space>
        } ],
        "remote": {
            <specification of the database to connect to>
        },
        "server-tags": [ <single server tag as string> ]
    }
}

This command includes a list with exactly one option definition specification, comprising an option name and code. The server-tags list is mandatory and must contain exactly one server tag. Specifying an empty list, a value of null, or multiple server tags will result in an error.

Response syntax:

{
    "result": 0,
    "text": "1 DHCPv4 option definition(s) deleted.",
    "arguments": {
        "count": 1
    }
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

remote-option-def4-get

This command fetches a DHCPv4 option definition from the configuration database.

Supported by: kea-dhcp4

Availability: 1.6.0 (cb_cmds hook library)

Access: read (parameter ignored in this Kea version)

Description and examples: see remote-option-def4-get command

Command syntax:

{
    "command": "remote-option-def4-get",
    "arguments": {
        "option-defs": [
            {
                "code": <option code>,
                "space": <option space>
            }
        ],
        "remote": {
            <specification of the database to connect to>
        },
        "server-tags": [ <single server tag as string> ]
    }
}

The desired option definition is identified by the pair of option code/space values. The server-tags list is mandatory and must contain exactly one server tag. Specifying an empty list, a value of null, or multiple server tags will result in an error. The server tag “all” is allowed, to fetch the option definition instance shared by all servers.

Response syntax:

{
    "result": 0,
    "text": "DHCPv4 option definition found.",
    "arguments": {
        "option-defs": [
            {
                <option definition>,
                "metadata": {
                    "server-tags": [ <server tag> ]
                }
            }
        ],
        "count": 1
    }
}

The metadata is included and provides database-specific information associated with the returned object. If the “all” server tag is specified, the command attempts to fetch the option definition associated with all servers. If the explicit server tag is specified, the command fetches the option definition associated with the given server. If the server-specific option definition does not exist, the remote-option-def4-get command fetches the option definition associated with all servers.

remote-option-def4-get-all

This command fetches all DHCPv4 option definitions from the configuration database.

Supported by: kea-dhcp4

Availability: 1.6.0 (cb_cmds hook library)

Access: read (parameter ignored in this Kea version)

Description and examples: see remote-option-def4-get-all command

Command syntax:

{
    "command": "remote-option-def4-get-all",
    "arguments": {
        "remote": {
            <specification of the database to connect to>
        },
        "server-tags": [ <single server tag as string> ]
    }
}

The server-tags list is mandatory and must contain exactly one server tag. Specifying an empty list, a value of null, or multiple server tags will result in an error. The special server tag “all” is allowed, to fetch the option definitions shared by all servers.

Response syntax:

{
    "result": 0,
    "text": "2 DHCPv4 option definition(s) found.",
    "arguments": {
        "option-defs": [
            {
                <first option definition>,
                "metadata": {
                    "server-tags": [ <server tag> ]
                }
            },
            {
                <second option definition>,
                "metadata": {
                    "server-tags": [ <server tag> ]
                }
            }
        ],
        "count": 2
    }
}

The returned response contains a list of maps. Each map contains an option definition specification and the metadata, including database-specific information associated with the returned objects. If the server tag “all” is included in the command, the response contains the option definitions shared among all servers. It excludes server-specific option definitions. If an explicit server tag is included in the command, the response contains all option definitions directly associated with the given server, and the option definitions associated with all servers when server-specific option definitions are not present.

remote-option-def4-set

This command creates or replaces a DHCPv4 option definition in the configuration database.

Supported by: kea-dhcp4

Availability: 1.6.0 (cb_cmds hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see remote-option-def4-set command

Command syntax:

{
    "command": "remote-option-def4-set",
    "arguments": {
        "option-defs": [
            {
                <option definition specification>
            }
        ],
        "remote": {
            <specification of the database to connect to>
        },
        "server-tags": [ <single server tag as string> ]
    }
}

The provided list must contain exactly one option definition specification. The server-tags list is mandatory and must contain exactly one server tag. Specifying an empty list, a value of null, or multiple server tags will result in an error. The server tag “all” is allowed; it associates the specified option definition with all servers.

Response syntax:

{
    "result": 0,
    "text": "DHCPv4 option definition set."
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

remote-option-def6-del

This command deletes a DHCPv6 option definition from the configuration database.

Supported by: kea-dhcp6

Availability: 1.6.0 (cb_cmds hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see remote-option-def6-del command

Command syntax:

{
    "command": "remote-option-def6-del",
    "arguments": {
        "option-defs": [ {
            "code": <option code>,
            "space": <option space>
        } ],
        "remote": {
            <specification of the database to connect to>
        },
        "server-tags": [ <single server tag as string> ]
    }
}

This command includes a list with exactly one option definition specification, comprising an option name and code. The server-tags list is mandatory and must contain exactly one server tag. Specifying an empty list, a value of null, or multiple server tags will result in an error.

Response syntax:

{
    "result": 0,
    "text": "1 DHCPv6 option definition(s) deleted.",
    "arguments": {
        "count": 1
    }
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

remote-option-def6-get

This command fetches a DHCPv6 option definition from the configuration database.

Supported by: kea-dhcp6

Availability: 1.6.0 (cb_cmds hook library)

Access: read (parameter ignored in this Kea version)

Description and examples: see remote-option-def6-get command

Command syntax:

{
    "command": "remote-option-def6-get",
    "arguments": {
        "option-defs": [
            {
                "code": <option code>,
                "space": <option space>
            }
        ],
        "remote": {
            <specification of the database to connect to>
        },
        "server-tags": [ <single server tag as string> ]
    }
}

The desired option definition is identified by the pair of option code/space values. The server-tags list is mandatory and must contain exactly one server tag. Specifying an empty list, a value of null, or multiple server tags will result in an error. The server tag “all” is allowed, to fetch the option definition instance shared by all servers.

Response syntax:

{
    "result": 0,
    "text": "DHCPv6 option definition found.",
    "arguments": {
        "option-defs": [
            {
                <option definition>,
                "metadata": {
                    "server-tags": [ <server tag> ]
                }
            }
        ],
        "count": 1
    }
}

The metadata is included and provides database-specific information associated with the returned object. If the “all” server tag is specified, the command fetches the option definition associated with all servers. If the explicit server tag is specified, the command fetches the option definition associated with the given server. If the server-specific option definition does not exist, the remote-option-def6-get command fetches the option definition associated with all servers.

remote-option-def6-get-all

This command fetches all DHCPv6 option definitions from the configuration database.

Supported by: kea-dhcp6

Availability: 1.6.0 (cb_cmds hook library)

Access: read (parameter ignored in this Kea version)

Description and examples: see remote-option-def6-get-all command

Command syntax:

{
    "command": "remote-option-def6-get-all",
    "arguments": {
        "remote": {
            <specification of the database to connect to>
        },
        "server-tags": [ <single server tag as string> ]
    }
}

The server-tags list is mandatory and must contain exactly one server tag. Specifying an empty list, a value of null, or multiple server tags will result in an error. The special server tag “all” is allowed, to fetch the option definitions shared by all servers.

Response syntax:

{
    "result": 0,
    "text": "2 DHCPv6 option definition(s) found.",
    "arguments": {
        "option-defs": [
            {
                <first option definition>,
                "metadata": {
                    "server-tags": [ <server tag> ]
                }
            },
            {
                <second option definition>,
                "metadata": {
                    "server-tags": [ <server tag> ]
                }
            }
        ],
        "count": 2
    }
}

The returned response contains a list of maps. Each map contains an option definition specification and the metadata, including database-specific information associated with the returned objects. If the server tag “all” is included in the command, the response contains the option definitions shared among all servers. It excludes server-specific option definitions. If an explicit server tag is included in the command, the response contains all option definitions directly associated with the given server, and the option definitions associated with all servers when server-specific option definitions are not present.

remote-option-def6-set

This command creates or replaces a DHCPv6 option definition in the configuration database.

Supported by: kea-dhcp6

Availability: 1.6.0 (cb_cmds hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see remote-option-def6-set command

Command syntax:

{
    "command": "remote-option-def6-set",
    "arguments": {
        "option-defs": [
            {
                <option definition specification>
            }
        ],
        "remote": {
            <specification of the database to connect to>
        },
        "server-tags": [ <single server tag as string> ]
    }
}

The provided list must contain exactly one option definition specification. The server-tags list is mandatory and must contain exactly one server tag. Specifying an empty list, a value of null, or multiple server tags will result in an error. The server tag “all” is allowed; it associates the specified option definition with all servers.

Response syntax:

{
    "result": 0,
    "text": "DHCPv6 option definition set."
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

remote-option4-global-del

This command deletes a DHCPv4 global option from the configuration database.

Supported by: kea-dhcp4

Availability: 1.6.0 (cb_cmds hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see remote-option4-global-del command

Command syntax:

{
    "command": "remote-option4-global-del",
    "arguments": {
        "options": [
            {
                "code": <option code>,
                "space": <option space>
            }
        ],
        "remote": {
            <specification of the database to connect to>
        },
        "server-tags": [ <single server tag as string> ]
    }
}

This command includes a list with exactly one option specification, comprising an option name and code. Specifying an empty list, a value of null, or multiple server tags will result in an error.

Response syntax:

{
    "result": 0,
    "text": "1 DHCPv4 option(s) deleted.",
    "arguments": {
        "count": 1
    }
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

remote-option4-global-get

This command fetches a global DHCPv4 option for the server from the specified database.

Supported by: kea-dhcp4

Availability: 1.6.0 (cb_cmds hook library)

Access: read (parameter ignored in this Kea version)

Description and examples: see remote-option4-global-get command

Command syntax:

{
    "command": "remote-option4-global-get",
    "arguments": {
        "options": [
            {
                "code": <option code>,
                "space": <option space>
            }
        ],
        "remote": {
            <specification of the database to connect to>
        },
        "server-tags": [ <single server tag as string> ]
    }
}

The option is identified by the pair of option code/space values. The server-tags list is mandatory and must contain exactly one server tag. Specifying an empty list, a value of null, or multiple server tags will result in an error. The server tag “all” is allowed, to fetch the global option instance shared by all servers.

Response syntax:

{
    "result": 0,
    "text": "DHCPv4 option is found.",
    "arguments": {
        "options": [
            {
                <option information>,
                "metadata": {
                    "server-tags": [ <server tag> ]
                }
            }
        ]
    }
}

The metadata is included and provides database specific information associated with the returned object. If the “all” server tag is specified, the command fetches the global option associated with all servers. If the explicit server tag is specified, the command fetches the global option associated with the given server. If the server specific option does not exist, it fetches the option associated with all servers.

remote-option4-global-get-all

This command fetches all DHCPv4 global options for the server from the configuration database.

Supported by: kea-dhcp4

Availability: 1.6.0 (cb_cmds hook library)

Access: read (parameter ignored in this Kea version)

Description and examples: see remote-option4-global-get-all command

Command syntax:

{
    "command": "remote-option4-global-get-all",
    "arguments": {
        "remote": {
            <specification of the database to connect to>
        },
        "server-tags": [ <single server tag as string> ]
    }
}

The server-tags list is mandatory and must contain exactly one server tag. Specifying an empty list, a value of null, or multiple server tags will result in an error. The special server tag “all” is allowed, to fetch the global options shared by all servers.

Response syntax:

{
    "result": 0,
    "text": "2 DHCPv4 option(s) found.",
    "arguments": {
        "options": [
            {
                <first option specification>,
                "metadata": {
                    "server-tags": [ <server tag> ]
                }
            },
            {
                <second option specification>,
                "metadata": {
                    "server-tags": [ <server tag> ]
                }
            }
        ],
        "count": 2
    }
}

The returned response contains a list of maps. Each map contains a global option specification and the metadata, including database-specific information associated with the returned object. If the server tag “all” is included in the command, the response contains the global options shared among all servers. It excludes server-specific global options. If an explicit server tag is included in the command, the response contains all global options directly associated with the given server, and the options associated with all servers when server-specific options are not present.

remote-option4-global-set

This command creates or replaces a DHCPv4 global option in the configuration database.

Supported by: kea-dhcp4

Availability: 1.6.0 (cb_cmds hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see remote-option4-global-set command

Command syntax:

{
    "command": "remote-option4-global-set",
    "arguments": {
        "options": [
            {
                <global option specification>
            }
        ],
        "remote": {
            <specification of the database to connect to>
        },
        "server-tags": [ <single server tag as string> ]
    }
}

The provided list must contain exactly one option specification. The server-tags list is mandatory and must contain exactly one server tag. Specifying an empty list, a value of null, or multiple server tags will result in an error. The server tag “all” is allowed; it associates the specified option with all servers.

Response syntax:

{
    "result": 0,
    "text": "DHCPv4 option set.",
    "arguments": {
        "options": [
            {
                "code": <option code>,
                "space": <option space>
            }
        ]
    }
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

remote-option4-network-del

This command deletes a DHCPv4 option from a shared network from the configuration database.

Supported by: kea-dhcp4

Availability: 1.6.0 (cb_cmds hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see remote-option4-network-del command

Command syntax:

{
    "command": "remote-option4-network-del",
    "arguments": {
        "shared-networks": [
            {
                "name": <shared network name>
            }
        ],
        "options": [
            {
                "code": <option code>,
                "space": <option space>
            }
        ],
        "remote": {
            <specification of the database to connect to>
        }
    }
}

This command includes two lists with exactly one name of the shared network and exactly one option specification, comprising an option name and code. Specifying an empty list, a value of null, or a server tag will result in an error.

Response syntax:

{
    "result": 0,
    "text": "1 DHCPv4 option(s) deleted.",
    "arguments": {
        "count": 1
    }
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

remote-option4-network-set

This command creates or replaces a DHCPv4 option in a shared network in the configuration database.

Supported by: kea-dhcp4

Availability: 1.6.0 (cb_cmds hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see remote-option4-network-set command

Command syntax:

{
    "command": "remote-option4-network-set",
    "arguments": {
        "shared-networks": [
            {
                "name": <shared network name>
            }
        ],
        "options": [
            {
                <shared network option specification>
            }
        ],
        "remote": {
            <specification of the database to connect to>
        }
    }
}

The provided lists must contain exactly one name of the shared network and one option specification. Specifying an empty list, a value of null, or a server tag will result in an error.

Response syntax:

{
    "result": 0,
    "text": "DHCPv4 option successfully set.",
    "arguments": {
        "options": [
            {
                "code": <option code>,
                "space": <option space>
            }
        ]
    }
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

remote-option4-pool-del

This command deletes a DHCPv4 option from an address pool from the configuration database.

Supported by: kea-dhcp4

Availability: 1.6.0 (cb_cmds hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see remote-option4-pool-del command

Command syntax:

{
    "command": "remote-option4-pool-del",
    "arguments": {
        "pools": [
            {
                "pool": <pool range or prefix>
            }
        ],
        "options": [
            {
                "code": <option code>,
                "space": <option space>
            }
        ],
        "remote": {
            <specification of the database to connect to>
        }
    }
}

This command includes two lists with exactly one address pool specification and exactly one option specification comprising an option space name and code. Specifying an empty list, a value of null, or a server tag will result in an error.

Response syntax:

{
    "result": 0,
    "text": "1 DHCPv4 option(s) deleted.",
    "arguments": {
        "count": 1
    }
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

remote-option4-pool-set

This command creates or replaces a DHCPv4 option in an address pool in the configuration database.

Supported by: kea-dhcp4

Availability: 1.6.0 (cb_cmds hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see remote-option4-pool-set command

Command syntax:

{
    "command": "remote-option4-pool-set",
    "arguments": {
        "pools": [
            {
                "pool": <pool range or prefix>
            }
        ],
        "options": [
            {
                <address pool option specification>
            }
        ],
        "remote": {
            <specification of the database to connect to>
        }
    }
}

This command includes two lists with exactly address pool specification and exactly one option specification. Specifying an empty list, a value of null, or a server tag will result in an error.

Response syntax:

{
    "result": 0,
    "text": "DHCPv4 option successfully set.",
    "arguments": {
        "options": [
            {
                "code": <option code>,
                "space": <option space>
            }
        ]
    }
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

remote-option4-subnet-del

This command deletes a DHCPv4 option from a subnet from the configuration database.

Supported by: kea-dhcp4

Availability: 1.6.0 (cb_cmds hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see remote-option4-subnet-del command

Command syntax:

{
    "command": "remote-option4-subnet-del",
    "arguments": {
        "subnets": [
            {
                "id": <subnet identifier>
            }
        ],
        "options": [
            {
                "code": <option code>,
                "space": <option space>
            }
        ],
        "remote": {
            <specification of the database to connect to>
        }
    }
}

This command includes two lists with exactly one ID of the subnet and exactly one option specification, comprising an option name and code. Specifying an empty list, a value of null, or a server tag will result in an error.

Response syntax:

{
    "result": 0,
    "text": "1 DHCPv4 option(s) deleted.",
    "arguments": {
        "count": 1
    }
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

remote-option4-subnet-set

This command creates or replaces a DHCPv4 option in a subnet in the configuration database.

Supported by: kea-dhcp4

Availability: 1.6.0 (cb_cmds hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see remote-option4-subnet-set command

Command syntax:

{
    "command": "remote-option4-subnet-set",
    "arguments": {
        "subnets": [
            {
                "id": <subnet identifier>
            }
        ],
        "options": [
            {
                <subnet option specification>
            }
        ],
        "remote": {
            <specification of the database to connect to>
        }
    }
}

The provided lists must contain exactly one ID of the subnet and one option specification. Specifying an empty list, a value of null, or a server tag will result in an error.

Response syntax:

{
    "result": 0,
    "text": "DHCPv4 option successfully set.",
    "arguments": {
        "options": [
            {
                "code": <option code>,
                "space": <option space>
            }
        ]
    }
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

remote-option6-global-del

This command deletes a DHCPv6 global option from the configuration database.

Supported by: kea-dhcp6

Availability: 1.6.0 (cb_cmds hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see remote-option6-global-del command

Command syntax:

{
    "command": "remote-option6-global-del",
    "arguments": {
        "options": [
            {
                "code": <option code>,
                "space": <option space>
            }
        ],
        "remote": {
            <specification of the database to connect to>
        },
        "server-tags": [ <single server tag as string> ]
    }
}

This command includes a list with exactly one option specification, comprising an option name and code. Specifying an empty list, a value of null, or multiple server tags will result in an error.

Response syntax:

{
    "result": 0,
    "text": "1 DHCPv6 option(s) deleted.",
    "arguments": {
        "count": 1
    }
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

remote-option6-global-get

This command fetches a global DHCPv6 option for the server from the specified database.

Supported by: kea-dhcp6

Availability: 1.6.0 (cb_cmds hook library)

Access: read (parameter ignored in this Kea version)

Description and examples: see remote-option6-global-get command

Command syntax:

{
    "command": "remote-option6-global-get",
    "arguments": {
        "options": [
            {
                "code": <option code>,
                "space": <option space>
            }
        ],
        "remote": {
            <specification of the database to connect to>
        },
        "server-tags": [ <single server tag as string> ]
    }
}

The option is identified by the pair of option code/space values. The server-tags list is mandatory and must contain exactly one server tag. Specifying an empty list, a value of null, or multiple server tags will result in an error. The server tag “all” is allowed, to fetch the global option instance shared by all servers.

Response syntax:

{
    "result": 0,
    "text": "DHCPv6 option is found.",
    "arguments": {
        "options": [
            {
                <option information>,
                "metadata": {
                    "server-tags": [ <server tag> ]
                }
            }
        ]
    }
}

The metadata is included and provides database-specific information associated with the returned object. If the “all” server tag is specified, the command attempts to fetch the global option associated with all servers. If the explicit server tag is specified, the command will fetch the global option associated with the given server. If the server-specific option does not exist, it fetches the option associated with all servers.

remote-option6-global-get-all

This command fetches all DHCPv6 global options for the server from the configuration database.

Supported by: kea-dhcp6

Availability: 1.6.0 (cb_cmds hook library)

Access: read (parameter ignored in this Kea version)

Description and examples: see remote-option6-global-get-all command

Command syntax:

{
    "command": "remote-option6-global-get-all",
    "arguments": {
        "remote": {
            <specification of the database to connect to>
        },
        "server-tags": [ <single server tag as string> ]
    }
}

The server-tags list is mandatory and must contain exactly one server tag. Specifying an empty list, a value of null, or multiple server tags will result in an error. The special server tag “all” is allowed, to fetch the global options shared by all servers.

Response syntax:

{
    "result": 0,
    "text": "2 DHCPv6 option(s) found.",
    "arguments": {
        "options": [
            {
                <first option specification>,
                "metadata": {
                    "server-tags": [ <server tag> ]
                }
            },
            {
                <second option specification>,
                "metadata": {
                    "server-tags": [ <server tag> ]
                }
            }
        ],
        "count": 2
    }
}

The returned response contains a list of maps. Each map contains a global option specification and the metadata, including database-specific information associated with the returned object. If the server tag “all” is included in the command, the response contains the global options shared between all servers. It excludes server-specific global options. If an explicit server tag is included in the command, the response contains all global options directly associated with the given server, and the options associated with all servers when server-specific options are not present.

remote-option6-global-set

This command creates or replaces a DHCPv6 global option in the configuration database.

Supported by: kea-dhcp6

Availability: 1.6.0 (cb_cmds hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see remote-option6-global-set command

Command syntax:

{
    "command": "remote-option6-global-set",
    "arguments": {
        "options": [
            {
                <global option specification>
            }
        ],
        "remote": {
            <specification of the database to connect to>
        },
        "server-tags": [ <single server tag as string> ]
    }
}

The provided list must contain exactly one option specification. The server-tags list is mandatory and must contain exactly one server tag. Specifying an empty list, a value of null, or multiple server tags will result in an error. The server tag “all” is allowed; it associates the specified option with all servers.

Response syntax:

{
    "result": 0,
    "text": "DHCPv6 option set.",
    "arguments": {
        "options": [
            {
                "code": <option code>,
                "space": <option space>
            }
        ]
    }
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

remote-option6-network-del

This command deletes a DHCPv6 option from a shared network from the configuration database.

Supported by: kea-dhcp6

Availability: 1.6.0 (cb_cmds hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see remote-option6-network-del command

Command syntax:

{
    "command": "remote-option6-network-del",
    "arguments": {
        "shared-networks": [
            {
                "name": <shared network name>
            }
        ],
        "options": [
            {
                "code": <option code>,
                "space": <option space>
            }
        ],
        "remote": {
            <specification of the database to connect to>
        }
    }
}

This command includes two lists with exactly one name of the shared network and exactly one option specification, comprising an option name and code. Specifying an empty list, a value of null, or a server tag will result in an error.

Response syntax:

{
    "result": 0,
    "text": "1 DHCPv6 option(s) deleted.",
    "arguments": {
        "count": 1
    }
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

remote-option6-network-set

This command creates or replaces a DHCPv6 option in a shared network in the configuration database.

Supported by: kea-dhcp6

Availability: 1.6.0 (cb_cmds hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see remote-option6-network-set command

Command syntax:

{
    "command": "remote-option6-network-set",
    "arguments": {
        "shared-networks": [
            {
                "name": <shared network name>
            }
        ],
        "options": [
            {
                <shared network option specification>
            }
        ],
        "remote": {
            <specification of the database to connect to>
        }
    }
}

The provided lists must contain exactly one name of the shared network and one option specification. Specifying an empty list, a value of null, or a server tag will result in an error.

Response syntax:

{
    "result": 0,
    "text": "DHCPv6 option successfully set.",
    "arguments": {
        "options": [
            {
                "code": <option code>,
                "space": <option space>
            }
        ]
    }
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

remote-option6-pd-pool-del

This command deletes a DHCPv6 option from a prefix delegation pool from the configuration database.

Supported by: kea-dhcp6

Availability: 1.6.0 (cb_cmds hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see remote-option6-pd-pool-del command

Command syntax:

{
    "command": "remote-option6-pd-pool-del",
    "arguments": {
        "pd-pools": [
            {
                "prefix": <pool prefix (address part)>
                "prefix-len": <pool prefix (length part)>
            }
        ],
        "options": [
            {
                "code": <option code>,
                "space": <option space>
            }
        ],
        "remote": {
            <specification of the database to connect to>
        }
    }
}

This command includes two lists with exactly one prefix delegation pool specification and exactly one option specification, comprising an option name and code. Specifying an empty list, a value of null, or a server tag will result in an error.

Response syntax:

{
    "result": 0,
    "text": "1 DHCPv6 option(s) deleted.",
    "arguments": {
        "count": 1
    }
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

remote-option6-pd-pool-set

This command creates or replaces a DHCPv6 option in a prefix delegation pool in the configuration database.

Supported by: kea-dhcp6

Availability: 1.6.0 (cb_cmds hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see remote-option6-pd-pool-set command

Command syntax:

{
    "command": "remote-option6-pd-pool-set",
    "arguments": {
        "pd-pools": [
            {
                "prefix": <pool prefix (address part)>
                "prefix-len": <pool prefix (length part)>
            }
        ],
        "options": [
            {
                <prefix delegation pool option specification>
            }
        ],
        "remote": {
            <specification of the database to connect to>
        }
    }
}

This command includes two lists with exactly one prefix delegation pool specification and exactly one option specification. Specifying an empty list, a value of null, or a server tag will result in an error.

Response syntax:

{
    "result": 0,
    "text": "DHCPv6 option successfully set.",
    "arguments": {
        "options": [
            {
                "code": <option code>,
                "space": <option space>
            }
        ]
    }
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

remote-option6-pool-del

This command deletes a DHCPv6 option from an address pool from the configuration database.

Supported by: kea-dhcp6

Availability: 1.6.0 (cb_cmds hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see remote-option6-pool-del command

Command syntax:

{
    "command": "remote-option6-pool-del",
    "arguments": {
        "pools": [
            {
                "pool": <pool range or prefix>
            }
        ],
        "options": [
            {
                "code": <option code>,
                "space": <option space>
            }
        ],
        "remote": {
            <specification of the database to connect to>
        }
    }
}

This command includes two lists with exactly one address pool specification and exactly one option specification, comprising an option name and code. Specifying an empty list, a value of null, or a server tag will result in an error.

Response syntax:

{
    "result": 0,
    "text": "1 DHCPv6 option(s) deleted.",
    "arguments": {
        "count": 1
    }
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

remote-option6-pool-set

This command creates or replaces a DHCPv6 option in an address pool in the configuration database.

Supported by: kea-dhcp6

Availability: 1.6.0 (cb_cmds hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see remote-option6-pool-set command

Command syntax:

{
    "command": "remote-option6-pool-set",
    "arguments": {
        "pools": [
            {
                "pool": <pool range or prefix>
            }
        ],
        "options": [
            {
                <address pool option specification>
            }
        ],
        "remote": {
            <specification of the database to connect to>
        }
    }
}

This command includes two lists with exactly address pool specification and exactly one option specification. Specifying an empty list, a value of null, or a server tag will result in an error.

Response syntax:

{
    "result": 0,
    "text": "DHCPv6 option successfully set.",
    "arguments": {
        "options": [
            {
                "code": <option code>,
                "space": <option space>
            }
        ]
    }
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

remote-option6-subnet-del

This command deletes a DHCPv6 option from a subnet from the configuration database.

Supported by: kea-dhcp6

Availability: 1.6.0 (cb_cmds hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see remote-option6-subnet-del command

Command syntax:

{
    "command": "remote-option6-subnet-del",
    "arguments": {
        "subnets": [
            {
                "id": <subnet identifier>
            }
        ],
        "options": [
            {
                "code": <option code>,
                "space": <option space>
            }
        ],
        "remote": {
            <specification of the database to connect to>
        }
    }
}

This command includes two lists with exactly one ID of the subnet and exactly one option specification, comprising an option name and code. Specifying an empty list, a value of null, or a server tag will result in an error.

Response syntax:

{
    "result": 0,
    "text": "1 DHCPv6 option(s) deleted.",
    "arguments": {
        "count": 1
    }
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

remote-option6-subnet-set

This command creates or replaces a DHCPv6 option in a subnet in the configuration database.

Supported by: kea-dhcp6

Availability: 1.6.0 (cb_cmds hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see remote-option6-subnet-set command

Command syntax:

{
    "command": "remote-option6-subnet-set",
    "arguments": {
        "subnets": [
            {
                "id": <subnet identifier>
            }
        ],
        "options": [
            {
                <subnet option specification>
            }
        ],
        "remote": {
            <specification of the database to connect to>
        }
    }
}

The provided lists must contain exactly one ID of the subnet and one option specification. Specifying an empty list, a value of null, or a server tag will result in an error.

Response syntax:

{
    "result": 0,
    "text": "DHCPv6 option successfully set.",
    "arguments": {
        "options": [
            {
                "code": <option code>,
                "space": <option space>
            }
        ]
    }
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

remote-server4-del

This command deletes information about a DHCPv4 server from the configuration database. Any configuration explicitly associated with the deleted server is automatically disassociated. In addition, configuration elements not shareable with other servers (e.g. global DHCP parameters) are deleted. Shareable configuration elements (e.g. subnets, shared networks) are not deleted as they may be used by other servers.

Supported by: kea-dhcp4

Availability: 1.6.0 (cb_cmds hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see remote-server4-del command

Command syntax:

{
    "command": "remote-server4-del",
    "arguments": {
        "servers": [
            {
                "server-tag": <server name>
            }
        ],
        "remote": {
            <specification of the database to connect to>
        }
    }
}

This command carries the list including exactly one map with the tag of the server to be deleted.

Response syntax:

{
    "result": 0,
    "text": "1 DHCPv4 server(s) deleted.",
    "arguments": {
        "count": 1
    }
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

remote-server4-get

This command fetches information about the DHCPv4 server, such as the server tag and description.

Supported by: kea-dhcp4

Availability: 1.6.0 (cb_cmds hook library)

Access: read (parameter ignored in this Kea version)

Description and examples: see remote-server4-get command

Command syntax:

{
    "command": "remote-server4-get",
    "arguments": {
        "servers": [
            {
                "server-tag": <server tag>
            }
        ],
        "remote": {
            <specification of the database to connect to>
        }
    }
}

This command carries the list including exactly one map with the tag of the server to be fetched.

Response syntax:

{
    "result": 0,
    "text": "DHCP server 'server tag' found.",
    "arguments": {
        "servers": [
            {
                "server-tag": <server tag>,
                "description": <server description>
            }
        ],
        "count": 1
    }
}

The server tag is the unique identifier of the server, used to associate the configuration elements in the database with the particular server instance. The returned server description is specified by the user when setting the server information.

remote-server4-get-all

This command fetches information about all DHCPv4 servers specified by the user.

Supported by: kea-dhcp4

Availability: 1.6.0 (cb_cmds hook library)

Access: read (parameter ignored in this Kea version)

Description and examples: see remote-server4-get-all command

Command syntax:

{
    "command": "remote-server4-get-all",
    "arguments": {
        "remote": {
            <specification of the database to connect to>
        }
    }
}

This command contains no arguments besides the optional remote.

Response syntax:

{
    "result": 0,
    "text": "DHCPv4 servers found.",
    "arguments": {
        "servers": [
            {
                "server-tag": <first server tag>,
                "description": <first server description>
            },
            {
                "server-tag": <second server tag>,
                "description": <second server description>
            }
        ],
        "count": 2
    }
}

The returned response contain a list of maps. Each map contains a server tag uniquely identifying a server, and the user-defined description of the server. The Kea Configuration Backend uses the keyword all to associate parts of the configuration with all servers. Internally, it creates the logical server all for this purpose. However, this logical server is not returned as a result of the remote-server4-get-all command; only the user-defined servers are returned.

remote-server4-set

This command creates or replaces information about the DHCPv4 server in the database.

Supported by: kea-dhcp4

Availability: 1.6.0 (cb_cmds hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see remote-server4-set command

Command syntax:

{
    "command": "remote-server4-set",
    "arguments": {
        "servers": [
            {
                "server-tag": <server tag>,
                "description": <server description>
            }
        ],
        "remote": {
            <specification of the database to connect to>
        }
    }
}

The provided list must contain exactly one server specification. The server-tag must be unique across all servers within the configuration database. The description is the arbitrary text describing the server, its location within the network, etc.

Response syntax:

{
    "result": 0,
    "text": "DHCPv4 server successfully set.",
    "arguments": {
        "servers": [
            {
                "server-tag": <server tag>,
                "description": <server description>
            }
        ]
    }
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

remote-server6-del

This command deletes information about a DHCPv6 server from the configuration database. Any configuration explicitly associated with the deleted server is automatically disassociated. In addition, configuration elements not shareable with other servers (e.g. global DHCP parameters) are deleted. Shareable configuration elements (e.g. subnets, shared networks) are not deleted as they may be used by other servers.

Supported by: kea-dhcp6

Availability: 1.6.0 (cb_cmds hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see remote-server6-del command

Command syntax:

{
    "command": "remote-server6-del",
    "arguments": {
        "servers": [
            {
                "server-tag": <server name>
            }
        ],
        "remote": {
            <specification of the database to connect to>
        }
    }
}

This command carries the list including exactly one map with the tag of the server to be deleted.

Response syntax:

{
    "result": 0,
    "text": "1 DHCPv6 server(s) deleted.",
    "arguments": {
        "count": 1
    }
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

remote-server6-get

This command fetches information about the DHCPv6 server, such as the server tag and description.

Supported by: kea-dhcp6

Availability: 1.6.0 (cb_cmds hook library)

Access: read (parameter ignored in this Kea version)

Description and examples: see remote-server6-get command

Command syntax:

{
    "command": "remote-server6-get",
    "arguments": {
        "servers": [
            {
                "server-tag": <server tag>
            }
        ],
        "remote": {
            <specification of the database to connect to>
        }
    }
}

This command carries the list including exactly one map with the tag of the server to be fetched.

Response syntax:

{
    "result": 0,
    "text": "DHCP server 'server tag' found.",
    "arguments": {
        "servers": [
            {
                "server-tag": <server tag>,
                "description": <server description>
            }
        ],
        "count": 1
    }
}

The server tag is the unique identifier of the server, used to associate the configuration elements in the database with the particular server instance. The returned server description is specified by the user when setting the server information.

remote-server6-get-all

This command fetches information about all DHCPv6 servers specified by the user.

Supported by: kea-dhcp6

Availability: 1.6.0 (cb_cmds hook library)

Access: read (parameter ignored in this Kea version)

Description and examples: see remote-server6-get-all command

Command syntax:

{
    "command": "remote-server6-get-all",
    "arguments": {
        "remote": {
            <specification of the database to connect to>
        }
    }
}

This command contains no arguments besides the optional remote.

Response syntax:

{
    "result": 0,
    "text": "DHCPv6 servers found.",
    "arguments": {
        "servers": [
            {
                "server-tag": <first server tag>,
                "description": <first server description>
            },
            {
                "server-tag": <second server tag>,
                "description": <second server description>
            }
        ],
        "count": 2
    }
}

The returned response contain a list of maps. Each map contains a server tag uniquely identifying a server, and the user-defined description of the server. The Kea Configuration Backend uses the keyword all to associate parts of the configuration with all servers. Internally, it creates the logical server all for this purpose. However, this logical server is not returned as a result of the remote-server6-get-all command; only the user-defined servers are returned.

remote-server6-set

This command creates or replaces information about the DHCPv6 server in the database.

Supported by: kea-dhcp6

Availability: 1.6.0 (cb_cmds hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see remote-server6-set command

Command syntax:

{
    "command": "remote-server6-set",
    "arguments": {
        "servers": [
            {
                "server-tag": <server tag>,
                "description": <server description>
            }
        ],
        "remote": {
            <specification of the database to connect to>
        }
    }
}

The provided list must contain exactly one server specification. The server-tag must be unique across all servers within the configuration database. The description is the arbitrary text describing the server, its location within the network, etc.

Response syntax:

{
    "result": 0,
    "text": "DHCPv6 server successfully set.",
    "arguments": {
        "servers": [
            {
                "server-tag": <server tag>,
                "description": <server description>
            }
        ]
    }
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

remote-subnet4-del-by-id

This command deletes an IPv4 subnet by ID from the configuration database.

Supported by: kea-dhcp4

Availability: 1.6.0 (cb_cmds hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see remote-subnet4-del-by-id command

Command syntax:

{
    "command": "remote-subnet4-del-by-id",
    "arguments": {
        "subnets": [
            {
                "id": <subnet identifier>
            }
        ],
        "remote": {
            <specification of the database to connect to>
        }
    }
}

This command includes a list with exactly one ID of the subnet to be deleted. The server-tags parameter must not be specified for this command.

Response syntax:

{
    "result": 0,
    "text": "1 IPv4 subnet(s) deleted.",
    "arguments": {
        "count": 1
    }
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

remote-subnet4-del-by-prefix

This command deletes an IPv4 subnet by prefix from the configuration database.

Supported by: kea-dhcp4

Availability: 1.6.0 (cb_cmds hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see remote-subnet4-del-by-prefix command

Command syntax:

{
    "command": "remote-subnet4-del-by-prefix",
    "arguments": {
        "subnets": [
            {
                "subnet": <subnet prefix>
            }
        ],
        "remote": {
            <specification of the database to connect to>
        }
    }
}

This command includes a list with exactly one prefix of the subnet to be deleted. The server-tags parameter must not be specified for this command.

Response syntax:

{
    "result": 0,
    "text": "1 IPv4 subnet(s) deleted.",
    "arguments": {
        "count": 1
    }
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

remote-subnet4-get-by-id

This command fetches the selected IPv4 subnet by ID from the configuration database.

Supported by: kea-dhcp4

Availability: 1.6.0 (cb_cmds hook library)

Access: read (parameter ignored in this Kea version)

Description and examples: see remote-subnet4-get-by-id command

Command syntax:

{
    "command": "remote-subnet4-get-by-id",
    "arguments": {
        "subnets": [ {
            "id": <subnet identifier>
        } ],
        "remote": {
            <specification of the database to connect to>
        }
    }
}

This command includes a list with exactly one ID of the subnet to be returned. The server-tags parameter must not be specified for this command.

Response syntax:

{
    "result": 0,
    "text": "IPv4 subnet found.",
    "arguments": {
        "subnets": [ {
            "id": <subnet identifier>,
            "subnet": <subnet prefix>,
            "shared-network-name": <shared network name> | null,
            "metadata": {
                "server-tags": [ <first server tag>, <second server tag>, ... ]
            },
            <the rest of the subnet specification here>
        } ],
        "count": 1
    }
}

If the shared network name is null, it means that the returned subnet does not belong to any shared network (a global subnet). The metadata is included in the returned subnet definition and provides database-specific information associated with the returned object.

remote-subnet4-get-by-prefix

This command fetches the selected IPv4 subnet by prefix from the configuration database.

Supported by: kea-dhcp4

Availability: 1.6.0 (cb_cmds hook library)

Access: read (parameter ignored in this Kea version)

Description and examples: see remote-subnet4-get-by-prefix command

Command syntax:

{
    "command": "remote-subnet4-get-by-prefix",
    "arguments": {
        "subnets": [ {
            "subnet": <subnet prefix>
        } ],
        "remote": {
            <specification of the database to connect to>
        }
    }
}

This command includes a list with exactly one prefix of the subnet to be returned. The server-tags parameter must not be specified for this command.

Response syntax:

{
    "result": 0,
    "text": "IPv4 subnet found.",
    "arguments": {
        "subnets": [
            {
                "id": <subnet identifier>,
                "subnet": <subnet prefix>,
                "shared-network-name": <shared network name> | null,
                "metadata": {
                    "server-tags": [ <first server tag>, <second server tag>, ... ]
                },
                <the rest of the subnet specification here>
            }
        ],
        "count": 1
    }
}

If the shared network name is null, it means that the returned subnet does not belong to any shared network (global subnet). The metadata is included in the returned subnet definition and provides database-specific information associated with the returned object.

remote-subnet4-list

This command fetches a list of all IPv4 subnets from the configuration database.

Supported by: kea-dhcp4

Availability: 1.6.0 (cb_cmds hook library)

Access: read (parameter ignored in this Kea version)

Description and examples: see remote-subnet4-list command

Command syntax:

{
    "command": "remote-subnet4-list",
    "arguments": {
        "remote": {
            <specification of the database to connect to>
        },
        "server-tags": [ <first server tag>, <second server tag>, ... ]
    }
}

The server-tags list is required for this command, and must not be empty. It may either contain one or multiple server tags as strings, or a single null value.

Response syntax:

{
    "result": 0,
    "text": "2 IPv4 subnets found.",
    "arguments": {
        "subnets": [
            {
                "id": <first subnet identifier>,
                "subnet": <first subnet prefix>,
                "shared-network-name": <shared network name> | null,
                "metadata": {
                    "server-tags": [ <first server tag>, <second server tag>, ... ]
                }
            },
            {
                "id": <second subnet identifier>,
                "subnet": <second subnet prefix>,
                "shared-network-name": <shared network name> | null,
                "metadata": {
                    "server-tags": [ <first server tag>, ... ]
                }
            }
        ],
        "count": 2
    }
}

The returned response contains a list of maps. Each map contains a subnet identifier, prefix, and shared network name to which the subnet belongs. If the subnet does not belong to a shared network, the name is null. The metadata includes database-specific information associated with the subnets. The returned list does not contain full subnet definitions; use remote-subnet4-get to fetch the full information about the selected subnets. If the command includes explicit server tags as strings (including the special server tag “all”), the list contains all subnets which are associated with any of the specified tags. A subnet is returned even if it is associated with multiple servers and only one of the specified tags matches. If the command includes the null value in the server-tags list, the response contains all subnets which are assigned to no servers (unassigned).

remote-subnet4-set

This command creates or replaces an IPv4 subnet in the configuration database.

Supported by: kea-dhcp4

Availability: 1.6.0 (cb_cmds hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see remote-subnet4-set command

Command syntax:

{
    "command": "remote-subnet4-set",
    "arguments": {
        "subnets": [
            {
                "id": <subnet identifier>,
                "subnet": <subnet prefix>,
                "shared-network-name": <shared network name> | null,
                <the rest of the subnet specification here>
            }
        ],
        "remote": {
            <specification of the database to connect to>
        },
        "server-tags": [ <first server tag>, <second server tag>, ... ]
    }
}

The provided list must contain exactly one subnet specification. The shared-network-name parameter is required for these commands; it associates the subnet with the shared network by its name. If the subnet must not belong to any shared network (a global subnet), the null value must be specified for the shared network name. The server-tags list is mandatory and must contain one or more server tags as strings to explicitly associate the subnet with one or more user-defined servers. The remote-subnet4-set command may include the special server tag “all” to associate the subnet with all servers.

Response syntax:

{
    "result": 0,
    "text": "IPv4 subnet successfully set.",
    "arguments": {
        "id": <subnet identifier>,
        "subnet": <subnet prefix>
    }
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

remote-subnet6-del-by-id

This command deletes an IPv6 subnet by ID from the configuration database.

Supported by: kea-dhcp6

Availability: 1.6.0 (cb_cmds hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see remote-subnet6-del-by-id command

Command syntax:

{
    "command": "remote-subnet6-del-by-id",
    "arguments": {
        "subnets": [
            {
                "id": <subnet identifier>
            }
        ],
        "remote": {
            <specification of the database to connect to>
        }
    }
}

This command includes a list with exactly one ID of the subnet to be deleted. The server-tags parameter must not be specified for this command.

Response syntax:

{
    "result": 0,
    "text": "1 IPv6 subnet(s) deleted.",
    "arguments": {
        "count": 1
    }
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

remote-subnet6-del-by-prefix

This command deletes an IPv6 subnet by prefix from the configuration database.

Supported by: kea-dhcp6

Availability: 1.6.0 (cb_cmds hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see remote-subnet6-del-by-prefix command

Command syntax:

{
    "command": "remote-subnet6-del-by-prefix",
    "arguments": {
        "subnets": [
            {
                "subnet": <subnet prefix>
            }
        ],
        "remote": {
            <specification of the database to connect to>
        }
    }
}

This command includes a list with exactly one prefix of the subnet to be deleted. The server-tags parameter must not be specified for this command.

Response syntax:

{
    "result": 0,
    "text": "1 IPv6 subnet(s) deleted.",
    "arguments": {
        "count": 1
    }
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

remote-subnet6-get-by-id

This command fetches the selected IPv6 subnet by ID from the configuration database.

Supported by: kea-dhcp6

Availability: 1.6.0 (cb_cmds hook library)

Access: read (parameter ignored in this Kea version)

Description and examples: see remote-subnet6-get-by-id command

Command syntax:

{
    "command": "remote-subnet6-get-by-id",
    "arguments": {
        "subnets": [
            {
                "id": <subnet identifier>
            }
        ],
        "remote": {
            <specification of the database to connect to>
        }
    }
}

This command includes a list with exactly one ID of the subnet to be returned. The server-tags parameter must not be specified for this command.

Response syntax:

{
    "result": 0,
    "text": "IPv6 subnet found.",
    "arguments": {
        "subnets": [
            {
                "id": <subnet identifier>,
                "subnet": <subnet prefix>,
                "shared-network-name": <shared network name> | null,
                "metadata": {
                    "server-tags": [ <first server tag>, <second server tag>, ... ]
                },
                <the rest of the subnet specification here>
            }
        ],
        "count": 1
    }
}

If the shared network name is null, it means that the returned subnet does not belong to any shared network (a global subnet). The metadata is included in the returned subnet definition and provides database-specific information associated with the returned object.

remote-subnet6-get-by-prefix

This command fetches the selected IPv6 subnet by prefix from the configuration database.

Supported by: kea-dhcp6

Availability: 1.6.0 (cb_cmds hook library)

Access: read (parameter ignored in this Kea version)

Description and examples: see remote-subnet6-get-by-prefix command

Command syntax:

{
    "command": "remote-subnet6-get-by-prefix",
    "arguments": {
        "subnets": [
            {
                "subnet": <subnet prefix>
            }
        ],
        "remote": {
            <specification of the database to connect to>
        }
    }
}

This command includes a list with exactly one prefix of the subnet to be returned. The server-tags parameter must not be specified for this command.

Response syntax:

{
    "result": 0,
    "text": "IPv6 subnet found.",
    "arguments": {
        "subnets": [ {
            "id": <subnet identifier>,
            "subnet": <subnet prefix>,
            "shared-network-name": <shared network name> | null,
            "metadata": {
                "server-tags": [ <first server tag>, <second server tag>, ... ]
            },
            <the rest of the subnet specification here>
        } ],
        "count": 1
    }
}

If the shared network name is null, it means that the returned subnet does not belong to any shared network (global subnet). The metadata is included in the returned subnet definition and provides database-specific information associated with the returned object.

remote-subnet6-list

This command fetches a list of all IPv6 subnets from the configuration database.

Supported by: kea-dhcp6

Availability: 1.6.0 (cb_cmds hook library)

Access: read (parameter ignored in this Kea version)

Description and examples: see remote-subnet6-list command

Command syntax:

{
    "command": "remote-subnet6-list",
    "arguments": {
        "remote": {
            <specification of the database to connect to>
        },
        "server-tags": [ <first server tag>, <second server tag>, ... ]
    }
}

The server-tags list is required for this command, and must not be empty. It may either contain one or multiple server tags as strings, or a single null value.

Response syntax:

{
    "result": 0,
    "text": "2 IPv6 subnets found.",
    "arguments": {
        "subnets": [
            {
                "id": <first subnet identifier>,
                "subnet": <first subnet prefix>,
                "shared-network-name": <shared network name> | null,
                "metadata": {
                    "server-tags": [ <first server tag>, <second server tag>, ... ]
                }
            },
            {
                "id": <second subnet identifier>,
                "subnet": <second subnet prefix>,
                "shared-network-name": <shared network name> | null,
                "metadata": {
                    "server-tags": [ <first server tag>, ... ]
                }
            }
        ],
        "count": 2
    }
}

The returned response contains a list of maps. Each map contains a subnet identifier, prefix, and shared network name to which the subnet belongs. If the subnet does not belong to a shared network, the name is null. The metadata includes database-specific information associated with the subnets. The returned list does not contain full subnet definitions; use remote-subnet6-get to fetch the full information about the selected subnets. If the command includes explicit server tags as strings (including the special server tag “all”), the list contains all subnets which are associated with any of the specified tags. A subnet is returned even if it is associated with multiple servers and only one of the specified tags matches. If the command includes the null value in the server-tags list, the response contains all subnets which are assigned to no servers (unassigned).

remote-subnet6-set

This command creates or replaces an IPv6 subnet in the configuration database.

Supported by: kea-dhcp6

Availability: 1.6.0 (cb_cmds hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see remote-subnet6-set command

Command syntax:

{
    "command": "remote-subnet6-set",
    "arguments": {
        "subnets": [
            {
                "id": <subnet identifier>,
                "subnet": <subnet prefix>,
                "shared-network-name": <shared network name> | null,
                <the rest of the subnet specification here>
            }
        ],
        "remote": {
            <specification of the database to connect to>
        },
        "server-tags": [ <first server tag>, <second server tag>, ... ]
    }
}

The provided list must contain exactly one subnet specification. The shared-network-name parameter is required for these commands; it associates the subnet with the shared network by its name. If the subnet must not belong to any shared network (a global subnet), the null value must be specified for the shared network name. The server-tags list is mandatory and must contain one or more server tags as strings to explicitly associate the subnet with one or more user-defined servers. The remote-subnet6-set command may include the special server tag “all” to associate the subnet with all servers.

Response syntax:

{
    "result": 0,
    "text": "IPv6 subnet successfully set.",
    "arguments": {
        "id": <subnet identifier>,
        "subnet": <subnet prefix>
    }
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

reservation-add

This command adds a new host reservation. The reservation may include IPv4 addresses, IPv6 addresses, IPv6 prefixes, various identifiers, a class the client will be assigned to, DHCPv4 and DHCPv6 options, and more.

Supported by: kea-dhcp4, kea-dhcp6

Availability: 1.2.0 (host_cmds hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see reservation-add command

Command syntax:

{
    "command": "reservation-add",
    "arguments": {
        "reservation": {
            "boot-file-name": <string>,
            "comment": <string>,
            "client-id": <string>,
            "circuit-id": <string>,
            "duid": <string>,
            "flex-id": <string>,
            "ip-address": <string (IPv4 address)>,
            "ip-addresses": [ <comma-separated strings> ],
            "hw-address": <string>,
            "hostname": <string>,
            "next-server": <string (IPv4 address)>,
            "option-data": [ <comma-separated structures defining options> ],
            "prefixes": [ <comma-separated IPv6 prefixes> ],
            "client-classes": [ <comma-separated strings> ],
            "server-hostname": <string>,
            "subnet-id": <integer>,
            "user-context": <any valid JSON>
        }
    }
}

Note that ip-address, client-id, next-server, server-hostname, and boot-file-name are IPv4-specific. duid, ip-addresses, and prefixes are IPv6-specific.

Response syntax:

{
    "result": <integer>,
    "text": <string>
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

reservation-del

This command deletes an existing host reservation.

Supported by: kea-dhcp4, kea-dhcp6

Availability: 1.2.0 (host_cmds hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see reservation-del command

Command syntax:

{
    "command": "reservation-del",
    "arguments": {
        "subnet-id": <integer>,
        "ip-address": <string>,
        "identifier-type": <one of 'hw-address', 'duid', 'circuit-id', 'client-id' and 'flex-id'>,
        "identifier": <string>
    }
}

The host reservation can be identified by either the (subnet-id, ip-address) pair or a triplet of (subnet-id, identifier-type, identifier).

Response syntax:

{
    "result": <integer>,
    "text": "<string>"
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

reservation-get

This command retrieves an existing host reservation.

Supported by: kea-dhcp4, kea-dhcp6

Availability: 1.2.0 (host_cmds hook library)

Access: read (parameter ignored in this Kea version)

Description and examples: see reservation-get command

Command syntax:

{
    "command": "reservation-get",
    "arguments": {
        "subnet-id": <integer>,
        "identifier-type": <one of 'hw-address', 'duid', 'circuit-id', 'client-id' and 'flex-id'>,
        "identifier": <string>
    }
}

The host reservation can be identified by either the (subnet-id, ip-address) pair or a triplet of (subnet-id, identifier-type, identifier).

Response syntax:

{
    "result": <integer>,
    "text": <string>,
    "arguments": {
        "boot-file-name": <string>,
        "comment": <string>,
        "client-id": <string>,
        "circuit-id": <string>,
        "duid": <string>,
        "flex-id": <string>,
        "ip-address": <string (IPv4 address)>,
        "ip-addresses": [ <comma-separated strings> ],
        "hw-address": <string>,
        "hostname": <string>,
        "next-server": <string (IPv4 address)>,
        "option-data": [ <comma-separated structures defining options> ],
        "prefixes": [ <comma-separated IPv6 prefixes> ],
        "client-classes": [ <comma-separated strings> ],
        "server-hostname": <string>,
        "subnet-id": <integer>,
        "user-context": <any valid JSON>
    }
}

The arguments object appears only if a host is found. Many fields in the arguments object appear only if a specific field is set.

reservation-get-all

This command retrieves all host reservations for a specified subnet.

Supported by: kea-dhcp4, kea-dhcp6

Availability: 1.6.0 (host_cmds hook library)

Access: read (parameter ignored in this Kea version)

Description and examples: see reservation-get-all command

Command syntax:

{
    "command": "reservation-get-all",
    "arguments": {
        "subnet-id": <integer>
    }
}

Response syntax:

{
    "result": <integer>,
    "text": "<string>"
}

The reservation-get-all command may result in very large responses.

reservation-get-by-hostname

This command retrieves all host reservations for a specified hostname and optionally a specified subnet.

Supported by: kea-dhcp4, kea-dhcp6

Availability: 1.7.1 (host_cmds hook library)

Access: read (parameter ignored in this Kea version)

Description and examples: see reservation-get-by-hostname command

Command syntax:

{
    "command": "reservation-get-by-hostname",
    "arguments": {
        "hostname": <hostname>,
        "subnet-id": <integer>
    }
}

Response syntax:

{
    "result": <integer>,
    "text": "<string>"
}

The reservation-get-by-hostname command may result in large responses.

reservation-get-by-id

This command retrieves all host reservations for a specified identifier (type and value).

Supported by: kea-dhcp4, kea-dhcp6

Availability: 1.9.0 (host_cmds hook library)

Access: read (parameter ignored in this Kea version)

Description and examples: see reservation-get-by-id command

Command syntax:

{
    "command": "reservation-get-by-id",
    "arguments": {
        "identifier-type": <one of 'hw-address', 'duid', 'circuit-id', 'client-id' and 'flex-id'>,
        "identifier": <string>
    }
}

Response syntax:

{
    "result": <integer>,
    "text": "<string>"
}

The reservation-get-by-id command may result in large responses.

reservation-get-page

This command retrieves all host reservations or host reservations for a specified subnet by page.

Supported by: kea-dhcp4, kea-dhcp6

Availability: 1.6.0 (host_cmds hook library)

Access: read (parameter ignored in this Kea version)

Description and examples: see reservation-get-page command

Command syntax:

{
    "command": "reservation-get-page",
    "arguments": {
        "subnet-id": <integer>,
        "limit": <integer>,
        "source-index": <integer>,
        "from": <integer>
    }
}

The page size limit is mandatory. The subnet-id is optional since version 1.9.0. The source-index and from host-id are optional and default to 0. Values to use to load the next page are returned in responses in a next map.

Response syntax:

{
    "result": <integer>,
    "text": "<string>"
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

server-tag-get

This command returns the server tag used by the server. Server tag is essential configuration parameter in the Config Backend configuration. This parameter is configured in the local config file. This command does not take any parameters.

Supported by: kea-dhcp4, kea-dhcp6

Availability: 1.6.0 (built-in)

Access: read (parameter ignored in this Kea version)

Description and examples: see server-tag-get command

Command syntax:

{
    "command": "server-tag-get"
}

Response syntax:

{
    "result": 0,
    "arguments": {
        "server-tag": "office1"
    }
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

shutdown

This command instructs the server to initiate its shutdown procedure.

Supported by: kea-ctrl-agent, kea-dhcp-ddns, kea-dhcp4, kea-dhcp6

Availability: 1.0.0 (built-in)

Access: write (parameter ignored in this Kea version)

Description and examples: see shutdown command

Command syntax:

{
    "command": "shutdown"
    "arguments": {
        "exit-value": 123
    }
}

The server responds with a confirmation that the shutdown procedure has been initiated.

Response syntax:

{
    "result": <integer>,
    "text": "<string>"
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

stat-lease4-get

This command fetches lease statistics for a range of known IPv4 subnets.

Supported by: kea-dhcp4

Availability: 1.4.0 (stat_cmds hook library)

Access: read (parameter ignored in this Kea version)

Description and examples: see stat-lease4-get command

Command syntax:

{
  "command": "stat-lease4-get"
}

Response syntax:

{
    "result": 0,
    "text": "stat-lease4-get: 2 rows found",
    "arguments": {
      "result-set": {
        "columns": [ "subnet-id",
                       "total-addresses",
                       "cumulative-assigned-addresses",
                       "assigned-addresses",
                       "declined-addresses" ],
        "rows": [
          [ 10, 256, 200, 111, 0 ],
          [ 20, 4098, 5000, 2034, 4 ]
        ],
      "timestamp": "2018-05-04 15:03:37.000000"
      }
    }
  }

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

stat-lease6-get

This command fetches lease statistics for a range of known IPv6 subnets.

Supported by: kea-dhcp6

Availability: 1.4.0 (stat_cmds hook library)

Access: read (parameter ignored in this Kea version)

Description and examples: see stat-lease6-get command

Command syntax:

{
  "command": "stat-lease6-get",
  "arguments": {
    "subnet-id" : 10
  }
}

Response syntax:

{
    "result": 0,
    "text": "stat-lease6-get: 2 rows found",
    "arguments": {
      "result-set": {
        "columns": [ "subnet-id", "total-nas", "cumulative-assigned-nas", "assigned-nas", "declined-nas", "total-pds",  "cumulative-assigned-pds", "assigned-pds" ],
        "rows": [
          [ 10, 4096, 3000, 2400, 3, 0, 0],
          [ 20, 0, 0, 0, 1048, 500, 233 ],
          [ 30, 256, 300, 60, 0, 1048, 15, 15 ]
        ],
      "timestamp": "2018-05-04 15:03:37.000000"
      }
    }
  }

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

statistic-get

This command retrieves a single statistic. It takes a single string parameter called name that specifies the statistic name.

Supported by: kea-dhcp-ddns, kea-dhcp4, kea-dhcp6

Availability: 1.0.0 (built-in)

Access: read (parameter ignored in this Kea version)

Description and examples: see statistic-get command

Command syntax:

{
    "command": "statistic-get",
    "arguments": {
        "name": "pkt4-received"
    }
}

The server responds with the details of the requested statistic, with a result of 0 indicating success, and the specified statistic as the value of the “arguments” parameter.

Response syntax:

{
   "result": 0,
   "arguments": {
       "pkt4-received": [ [ "first_value", "2019-07-30 10:11:19.498739" ], [ "second_value", "2019-07-30 10:11:19.498662" ] ]
       }
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

statistic-get-all

This command retrieves all recorded statistics.

Supported by: kea-dhcp-ddns, kea-dhcp4, kea-dhcp6

Availability: 1.0.0 (built-in)

Access: read (parameter ignored in this Kea version)

Description and examples: see statistic-get-all command

Command syntax:

{
    "command": "statistic-get-all",
    "arguments": { }
}

The server responds with the details of all recorded statistics, with a result of 0 indicating that it iterated over all statistics (even when the total number of statistics is zero).

Response syntax:

{
   "result": 0,
   "arguments": {
       "cumulative-assigned-addresses": [ [ 0, "2022-02-11 17:54:17.487569" ] ],
       "declined-addresses": [ [ 0, "2022-02-11 17:54:17.487555" ] ],
       "pkt4-ack-received": [ [ 0, "2022-02-11 17:54:17.455233" ] ],
       "pkt4-ack-sent": [ [ 0, "2022-02-11 17:54:17.455256" ] ],
       "pkt4-decline-received": [ [ 0, "2022-02-11 17:54:17.455259" ] ],
       "pkt4-discover-received": [ [ 0, "2022-02-11 17:54:17.455263" ] ],
       "pkt4-inform-received": [ [ 0, "2022-02-11 17:54:17.455265" ] ],
       "pkt4-nak-received": [ [ 0, "2022-02-11 17:54:17.455269" ] ],
       "pkt4-nak-sent": [ [ 0, "2022-02-11 17:54:17.455271" ] ],
       "pkt4-offer-received": [ [ 0, "2022-02-11 17:54:17.455274" ] ],
       "pkt4-offer-sent": [ [ 0, "2022-02-11 17:54:17.455277" ] ],
       "pkt4-parse-failed": [ [ 0, "2022-02-11 17:54:17.455280" ] ],
       "pkt4-receive-drop": [ [ 0, "2022-02-11 17:54:17.455284" ] ],
       "pkt4-received": [ [ 0, "2022-02-11 17:54:17.455287" ] ],
       "pkt4-release-received": [ [ 0, "2022-02-11 17:54:17.455290" ] ],
       "pkt4-request-received": [ [ 0, "2022-02-11 17:54:17.455293" ] ],
       "pkt4-sent": [ [ 0, "2022-02-11 17:54:17.455296" ] ],
       "pkt4-unknown-received": [ [ 0, "2022-02-11 17:54:17.455299" ] ],
       "reclaimed-declined-addresses": [ [ 0, "2022-02-11 17:54:17.487559" ] ],
       "reclaimed-leases": [ [ 0, "2022-02-11 17:54:17.487564" ] ],
       "subnet[1].assigned-addresses": [ [ 0, "2022-02-11 17:54:17.487579" ] ],
       "subnet[1].cumulative-assigned-addresses": [ [ 0, "2022-02-11 17:54:17.487528" ] ],
       "subnet[1].declined-addresses": [ [ 0, "2022-02-11 17:54:17.487585" ] ],
       "subnet[1].reclaimed-declined-addresses": [ [ 0, "2022-02-11 17:54:17.487595" ] ],
       "subnet[1].reclaimed-leases": [ [ 0, "2022-02-11 17:54:17.487604" ] ],
       "subnet[1].total-addresses": [ [ 200, "2022-02-11 17:54:17.487512" ] ],
       "v4-allocation-fail": [ [ 0, "2022-02-11 17:54:17.455302" ] ],
       "v4-allocation-fail-classes": [ [ 0, "2022-02-11 17:54:17.455306" ] ],
       "v4-allocation-fail-no-pools": [ [ 0, "2022-02-11 17:54:17.455310" ] ],
       "v4-allocation-fail-shared-network": [ [ 0, "2022-02-11 17:54:17.455319" ] ],
       "v4-allocation-fail-subnet": [ [ 0, "2022-02-11 17:54:17.455323" ] ]
   }
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

statistic-remove

This command deletes a single statistic. It takes a single string parameter called name that specifies the statistic name.

Supported by: kea-dhcp4, kea-dhcp6

Availability: 1.0.0 (built-in)

Access: write (parameter ignored in this Kea version)

Description and examples: see statistic-remove command

Command syntax:

{
    "command": "statistic-remove",
    "arguments": {
        "name": "pkt4-received"
    }
}

If the specific statistic is found and its removal is successful, the server responds with a status of 0, indicating success, and an empty parameters field. If an error is encountered (e.g. the requested statistic was not found), the server returns a status code of 1 (error) and the text field contains the error description.

Response syntax:

{
    "result": <integer>,
    "text": "<string>"
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

statistic-remove-all

(Deprecated) This command deletes all statistics.

Supported by: kea-dhcp4, kea-dhcp6

Availability: 1.0.0 (built-in)

Access: write (parameter ignored in this Kea version)

Description and examples: see statistic-remove-all command

Command syntax:

{
    "command": "statistic-remove-all",
    "arguments": { }
}

If the removal of all statistics is successful, the server responds with a status of 0, indicating success, and an empty parameters field. If an error is encountered, the server returns a status code of 1 (error) and the text field contains the error description.

Response syntax:

{
    "result": <integer>,
    "text": "<string>"
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

statistic-reset

This command sets the specified statistic to its neutral value: 0 for integer, 0.0 for float, 0h0m0s0us for time duration, and “” for string type. It takes a single string parameter called name that specifies the statistic name.

Supported by: kea-dhcp-ddns, kea-dhcp4, kea-dhcp6

Availability: 1.0.0 (built-in)

Access: write (parameter ignored in this Kea version)

Description and examples: see statistic-reset command

Command syntax:

{
    "command": "statistic-reset",
    "arguments": {
        "name": "pkt4-received"
    }
}

If the specific statistic is found and the reset is successful, the server responds with a status of 0, indicating success, and an empty parameters field. If an error is encountered (e.g. the requested statistic was not found), the server returns a status code of 1 (error) and the text field contains the error description.

Response syntax:

{
    "result": <integer>,
    "text": "<string>"
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

statistic-reset-all

This command sets all statistics to their neutral values: 0 for integer, 0.0 for float, 0h0m0s0us for time duration, and “” for string type.

Supported by: kea-dhcp-ddns, kea-dhcp4, kea-dhcp6

Availability: 1.0.0 (built-in)

Access: write (parameter ignored in this Kea version)

Description and examples: see statistic-reset-all command

Command syntax:

{
    "command": "statistic-reset-all",
    "arguments": { }
}

If the operation is successful, the server responds with a status of 0, indicating success, and an empty parameters field. If an error is encountered, the server returns a status code of 1 (error) and the text field contains the error description.

Response syntax:

{
    "result": <integer>,
    "text": "<string>"
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

statistic-sample-age-set

This command sets a time-based limit for a single statistic. It takes two parameters: a string called name and an integer value called duration.

Supported by: kea-dhcp4, kea-dhcp6

Availability: 1.6.0 (built-in)

Access: write (parameter ignored in this Kea version)

Description and examples: see statistic-sample-age-set command

Command syntax:

{
    "command": "statistic-sample-age-set",
    "arguments": {
        "name": "pkt4-received",
        "duration": 1245
    }
}

The server responds with a message about a successfully set limit for the given statistic, with a result of 0 indicating success, and an empty parameters field. If an error is encountered (e.g. the requested statistic was not found), the server returns a status code of 1 (error) and the text field contains the error description.

Response syntax:

{
    "result": <integer>,
    "text": "<string>"
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

statistic-sample-age-set-all

This command sets a time-based limit for all statistics. It takes a single integer parameter called duration.

Supported by: kea-dhcp4, kea-dhcp6

Availability: 1.6.0 (built-in)

Access: write (parameter ignored in this Kea version)

Description and examples: see statistic-sample-age-set-all command

Command syntax:

{
    "command": "statistic-sample-age-set-all",
    "arguments": {
        "duration": 1245
    }
}

The server responds with a message about successfully set limits for all statistics, with a result of 0 indicating success, and an empty parameters field. If an error is encountered, the server returns a status code of 1 (error) and the text field contains the error description.

Response syntax:

{
    "result": <integer>,
    "text": "<string>"
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

statistic-sample-count-set

This command sets a size-based limit for a single statistic. It takes two parameters: a string called name and an integer value called max-samples.

Supported by: kea-dhcp4, kea-dhcp6

Availability: 1.6.0 (built-in)

Access: write (parameter ignored in this Kea version)

Description and examples: see statistic-sample-count-set command

Command syntax:

{
    "command": "statistic-sample-count-set",
    "arguments": {
        "name": "pkt4-received",
        "max-samples": 100
    }
}

The server responds with a message about a successfully set limit for the given statistic, with a result of 0 indicating success, and an empty parameters field. If an error is encountered (e.g. the requested statistic was not found), the server returns a status code of 1 (error) and the text field contains the error description.

Response syntax:

{
    "result": <integer>,
    "text": "<string>"
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

statistic-sample-count-set-all

This command sets a size-based limit for all statistics. It takes a single integer parameter called max-samples.

Supported by: kea-dhcp4, kea-dhcp6

Availability: 1.6.0 (built-in)

Access: write (parameter ignored in this Kea version)

Description and examples: see statistic-sample-count-set-all command

Command syntax:

{
    "command": "statistic-sample-count-set-all",
    "arguments": {
        "max-samples": 100
    }
}

The server responds with a message about successfully set limits for all statistics, with a result of 0 indicating success, and an empty parameters field. If an error is encountered, the server returns a status code of 1 (error) and the text field contains the error description.

Response syntax:

{
    "result": <integer>,
    "text": "<string>"
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

status-get

This command returns server’s runtime information. It takes no arguments.

Supported by: kea-ctrl-agent, kea-dhcp-ddns, kea-dhcp4, kea-dhcp6

Availability: 1.7.3 (built-in)

Access: read (parameter ignored in this Kea version)

Description and examples: see status-get command

Command syntax:

{
    "command": "status-get"
}

Response syntax:

{
    "result": <integer>,
    "arguments": {
        "pid": <integer>,
        "uptime": <uptime in seconds>,
        "reload": <time since reload in seconds>,
        "high-availability": [
            {
                "ha-mode": <HA mode configured for this relationship>
                "ha-servers": {
                    "local": {
                        "role": <role of this server as in the configuration file>,
                        "scopes": <list of scope names served by this server>,
                        "state": <HA state name of the server receiving the command>,
                    },
                    "remote": {
                        "age": <the age of the remote status in seconds>,
                        "in-touch": <indicates if this server communicated with remote>,
                        "last-scopes": <list of scopes served by partner>,
                        "last-state": <HA state name of the partner>,
                        "role": <partner role>
                    }
                }
            }
        ],
        "multi-threading-enabled": true,
        "thread-pool-size": 4,
        "packet-queue-size": 64,
        "packet-queue-statistics": [ 1.2, 2.3, 3.4 ]
    }
}

If the libdhcp_ha (High Availability) hooks library is loaded by the DHCP server receiving this command the response also includes the HA specific status information of the server receiving the command and its partner’s status.

subnet4-add

This command creates and adds a new subnet to the existing server configuration. This operation has no impact on other subnets.

Supported by: kea-dhcp4

Availability: 1.3.0 (subnet_cmds hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see subnet4-add command

Command syntax:

{
    "command": "subnet4-add",
    "arguments": {
        "subnets": [ {
            "id": 123,
            "subnet": "10.20.30.0/24",
            ...
        } ]
    }
}

Response syntax:

{
    "result": 0,
    "text": "IPv4 subnet added",
    "arguments": {
        "subnets": [
            {
                "id": 123,
                "subnet": "10.20.30.0/24"
            }
        ]
    }
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

subnet4-del

This command removes a subnet from the server’s configuration. This command has no effect on other configured subnets, but removing a subnet has certain implications which the server’s administrator should be aware of.

Supported by: kea-dhcp4

Availability: 1.3.0 (subnet_cmds hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see subnet4-del command

Command syntax:

{
    "command": "subnet4-del",
    "arguments": {
        "id": 123
    }
}

Response syntax:

{
    "result": 0,
    "text": "IPv4 subnet 192.0.2.0/24 (id 123) deleted",
    "arguments": {
        "subnets": [
            {
                "id": 123,
                "subnet": "192.0.2.0/24"
            }
        ]
    }
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

subnet4-get

This command retrieves detailed information about the specified subnet. This command usually follows subnet4-list, which discovers available subnets with their respective subnet identifiers and prefixes.

Supported by: kea-dhcp4

Availability: 1.3.0 (subnet_cmds hook library)

Access: read (parameter ignored in this Kea version)

Description and examples: see subnet4-get command

Command syntax:

{
    "command": "subnet4-get",
    "arguments": {
        "id": 10
    }
}

Response syntax:

{
    "result": 0,
    "text": "Info about IPv4 subnet 10.0.0.0/8 (id 10) returned",
    "arguments": {
        "subnets": [
            {
                "subnet": "10.0.0.0/8",
                "id": 1,
                "option-data": [
                    ...
                ],
                ...
            }
        ]
    }
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

subnet4-list

This command lists all currently configured subnets. The subnets are returned in a brief format, i.e. a subnet identifier and subnet prefix are included for each subnet.

Supported by: kea-dhcp4

Availability: 1.3.0 (subnet_cmds hook library)

Access: read (parameter ignored in this Kea version)

Description and examples: see subnet4-list command

Command syntax:

{
    "command": "subnet4-list"
}

Response syntax:

{
    "result": 0,
    "text": "2 IPv4 subnets found",
    "arguments": {
        "subnets": [
            {
                "id": 10,
                "subnet": "10.0.0.0/8"
            },
            {
                "id": 100,
                "subnet": "192.0.2.0/24"
            }
        ]
    }
}

If no IPv4 subnets are found, an error code is returned along with the error description.

subnet4-update

This command updates (overwrites) a single subnet in the existing server configuration. This operation has no impact on other subnets.

Supported by: kea-dhcp4

Availability: 1.6.0 (subnet_cmds hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see subnet4-update command

Command syntax:

{
    "command": "subnet4-update",
    "arguments": {
        "subnets": [ {
            "id": 123,
            "subnet": "10.20.30.0/24",
            ...
        } ]
    }
}

Response syntax:

{
    "result": 0,
    "text": "IPv4 subnet updated",
    "arguments": {
        "subnets": [
            {
                "id": 123,
                "subnet": "10.20.30.0/24"
            }
        ]
    }
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

subnet6-add

This command creates and adds a new subnet to the existing server configuration. This operation has no impact on other subnets.

Supported by: kea-dhcp6

Availability: 1.3.0 (subnet_cmds hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see subnet6-add command

Command syntax:

{
    "command": "subnet6-add",
    "arguments": {
        "subnet6": [ {
            "id": 234,
            "subnet": "2001:db8:1::/64",
            ...
        } ]
    }
}

Response syntax:

{
    "result": 0,
    "text": "IPv6 subnet added",
    "arguments": {
        "subnet6": [
            {
                "id": 234,
                "subnet": "2001:db8:1::/64"
            }
        ]
    }
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

subnet6-del

This command removes a subnet from the server’s configuration. This command has no effect on other configured subnets, but removing a subnet has certain implications which the server’s administrator should be aware of.

Supported by: kea-dhcp6

Availability: 1.3.0 (subnet_cmds hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see subnet6-del command

Command syntax:

{
    "command": "subnet6-del",
    "arguments": {
        "id": 234
    }
}

Response syntax:

{
    "result": 0,
    "text": "IPv6 subnet 2001:db8:1::/64 (id 234) deleted",
    "subnets": [
        {
            "id": 234,
            "subnet": "2001:db8:1::/64"
        }
    ]
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

subnet6-get

This command retrieves detailed information about the specified subnet. This command usually follows subnet6-list, which discovers available subnets with their respective subnet identifiers and prefixes.

Supported by: kea-dhcp6

Availability: 1.3.0 (subnet_cmds hook library)

Access: read (parameter ignored in this Kea version)

Description and examples: see subnet6-get command

Command syntax:

{
    "command": "subnet6-get",
    "arguments": {
        "id": 11
    }
}

Response syntax:

{
    "result": 0,
    "text": "Info about IPv6 subnet 2001:db8:1::/64 (id 11) returned",
    "arguments": {
        "subnets": [
            {
                "subnet": "2001:db8:1::/64",
                "id": 1,
                "option-data": [
                    ...
                ],
                ...
            }
        ]
    }
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

subnet6-list

This command lists all currently configured subnets. The subnets are returned in a brief format, i.e. a subnet identifier and subnet prefix are included for each subnet.

Supported by: kea-dhcp6

Availability: 1.3.0 (subnet_cmds hook library)

Access: read (parameter ignored in this Kea version)

Description and examples: see subnet6-list command

Command syntax:

{
    "command": "subnet6-list"
}

Response syntax:

{
    "result": 0,
    "text": "2 IPv6 subnets found",
    "arguments": {
        "subnets": [
            {
                "id": 11,
                "subnet": "2001:db8:1::/64"
            },
            {
                "id": 233,
                "subnet": "3000::/16"
            }
        ]
    }
}

If no IPv6 subnets are found, an error code is returned along with the error description.

subnet6-update

This command updates (overwrites) a single subnet in the existing server configuration. This operation has no impact on other subnets.

Supported by: kea-dhcp6

Availability: 1.6.0 (subnet_cmds hook library)

Access: write (parameter ignored in this Kea version)

Description and examples: see subnet6-update command

Command syntax:

{
    "command": "subnet6-update",
    "arguments": {
        "subnet6": [ {
            "id": 234,
            "subnet": "2001:db8:1::/64",
            ...
        } ]
    }
}

Response syntax:

{
    "result": 0,
    "text": "IPv6 subnet updated",
    "arguments": {
        "subnet6": [
            {
                "id": 234,
                "subnet": "2001:db8:1::/64"
            }
        ]
    }
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

version-get

This command returns extended information about the Kea version that is running. The returned string is the same as if Kea were run with the -V command-line option.

Supported by: kea-ctrl-agent, kea-dhcp-ddns, kea-dhcp4, kea-dhcp6

Availability: 1.2.0 (built-in)

Access: read (parameter ignored in this Kea version)

Description and examples: see version-get command

Command syntax:

{
    "command": "version-get"
}

Response syntax:

{
    "result": <integer>,
    "text": "<string>"
}

Result is an integer representation of the status. Currently supported statuses are:

• 0 - success

• 1 - error

• 2 - unsupported

• 3 - empty (command was completed successfully, but no data was affected or returned)

Manual Pages

kea-dhcp4 - DHCPv4 server in Kea

Synopsis

kea-dhcp4 [-v] [-V] [-W] [-d] [-c config-file] [-t config-file] [-p server-port-number] [-P client-port-number]

Description

The kea-dhcp4 daemon provides the DHCPv4 server implementation.

Arguments

The arguments are as follows:

-v

Displays the version.

-V

Displays the extended version.

-W

Displays the configuration report.

-d

Enables the debug mode with extra verbosity.

-c config-file

Specifies the configuration file with the configuration for the DHCPv4 server. It may also contain configuration entries for other Kea services.

-t config-file

Checks the configuration file and reports the first error, if any. Note that not all parameters are completely checked; in particular, service and control channel sockets are not opened, and hook libraries are not loaded.

-p server-port-number

Specifies the server port number (1-65535) on which the server listens. This is useful for testing purposes only.

-P client-port-number

Specifies the client port number (1-65535) to which the server responds. This is useful for testing purposes only.

Documentation

Kea comes with an extensive Kea Administrator Reference Manual that covers all aspects of running the Kea software - compilation, installation, configuration, configuration examples, and much more. Kea also features a Kea Messages Manual, which lists all possible messages Kea can print with a brief description for each of them. Both documents are available in various formats (.txt, .html, .pdf) with the Kea distribution. The Kea documentation is available at https://kea.readthedocs.io.

Kea source code is documented in the Kea Developer’s Guide, available at https://reports.kea.isc.org/dev_guide/.

The Kea project website is available at https://kea.isc.org.

Mailing Lists and Support

There are two public mailing lists available for the Kea project. kea-users (kea-users at lists.isc.org) is intended for Kea users, while kea-dev (kea-dev at lists.isc.org) is intended for Kea developers, prospective contributors, and other advanced users. Both lists are available at https://lists.isc.org. The community provides best-effort support on both of those lists.

ISC provides professional support for Kea services. See https://www.isc.org/kea/ for details.

History

The b10-dhcp4 daemon was first coded in November 2011 by Tomek Mrugalski.

In mid-2014, Kea was decoupled from the BIND 10 framework and became a standalone DHCP server. The DHCPv4 server binary was renamed to kea-dhcp4. Kea 1.0.0 was released in December 2015.

See Also

kea-dhcp6(8), kea-dhcp-ddns(8), kea-ctrl-agent(8), kea-admin(8), keactrl(8), perfdhcp(8), kea-netconf(8), kea-lfc(8), Kea Administrator Reference Manual.

kea-dhcp6 - DHCPv6 server in Kea

Synopsis

kea-dhcp6 [-v] [-V] [-W] [-d] [-c config-file] [-t config-file] [-p server-port-number] [-P client-port-number]

Description

The kea-dhcp6 daemon provides the DHCPv6 server implementation.

Arguments

The arguments are as follows:

-v

Displays the version.

-V

Displays the extended version.

-W

Displays the configuration report.

-d

Enables the debug mode with extra verbosity.

-c config-file

Specifies the configuration file with the configuration for the DHCPv6 server. It may also contain configuration entries for other Kea services.

-t config-file

Checks the configuration file and reports the first error, if any. Note that not all parameters are completely checked; in particular, service and control channel sockets are not opened, and hook libraries are not loaded.

-p server-port-number

Specifies the server port number (1-65535) on which the server listens. This is useful for testing purposes only.

-P client-port-number

Specifies the client port number (1-65535) to which the server responds. This is useful for testing purposes only.

Documentation

Kea comes with an extensive Kea Administrator Reference Manual that covers all aspects of running the Kea software - compilation, installation, configuration, configuration examples, and much more. Kea also features a Kea Messages Manual, which lists all possible messages Kea can print with a brief description for each of them. Both documents are available in various formats (.txt, .html, .pdf) with the Kea distribution. The Kea documentation is available at https://kea.readthedocs.io.

Kea source code is documented in the Kea Developer’s Guide, available at https://reports.kea.isc.org/dev_guide/.

The Kea project website is available at https://kea.isc.org.

Mailing Lists and Support

There are two public mailing lists available for the Kea project. kea-users (kea-users at lists.isc.org) is intended for Kea users, while kea-dev (kea-dev at lists.isc.org) is intended for Kea developers, prospective contributors, and other advanced users. Both lists are available at https://lists.isc.org. The community provides best-effort support on both of those lists.

ISC provides professional support for Kea services. See https://www.isc.org/kea/ for details.

History

The b10-dhcp6 daemon was first coded in June 2011 by Tomek Mrugalski.

In mid-2014, Kea was decoupled from the BIND 10 framework and became a standalone DHCP server. The DHCPv6 server binary was renamed to kea-dhcp6. Kea 1.0.0 was released in December 2015.

See Also

kea-dhcp4(8), kea-dhcp-ddns(8), kea-ctrl-agent(8), kea-admin(8), keactrl(8), perfdhcp(8), kea-netconf(8), kea-lfc(8), Kea Administrator Reference Manual.

kea-ctrl-agent - Control Agent process in Kea

Synopsis

kea-ctrl-agent [-v] [-V] [-W] [-d] [-c config-file] [-t config-file]

Description

The kea-ctrl-agent provides a REST service for controlling Kea services. The received HTTP requests are decapsulated and forwarded to the respective Kea services in JSON format. Received JSON responses are encapsulated within HTTP responses and returned to the controlling entity. Some commands may be handled by the Control Agent directly, and not forwarded to any Kea service.

Arguments

The arguments are as follows:

-v

Displays the version.

-V

Displays the extended version.

-W

Displays the configuration report.

-d

Sets the logging level to debug with extra verbosity. This is primarily for development purposes in stand-alone mode.

-c config-file

Specifies the file with the configuration for the Control Agent server. It may also contain configuration entries for other Kea services.

-t config-file

Checks the syntax of the configuration file and reports the first error, if any. Note that not all parameters are completely checked; in particular, service and client sockets are not opened, and hook libraries are not loaded.

Documentation

Kea comes with an extensive Kea Administrator Reference Manual that covers all aspects of running the Kea software - compilation, installation, configuration, configuration examples, and much more. Kea also features a Kea Messages Manual, which lists all possible messages Kea can print with a brief description for each of them. Both documents are available in various formats (.txt, .html, .pdf) with the Kea distribution. The Kea documentation is available at https://kea.readthedocs.io.

Kea source code is documented in the Kea Developer’s Guide, available at https://reports.kea.isc.org/dev_guide/.

The Kea project website is available at https://kea.isc.org.

Mailing Lists and Support

There are two public mailing lists available for the Kea project. kea-users (kea-users at lists.isc.org) is intended for Kea users, while kea-dev (kea-dev at lists.isc.org) is intended for Kea developers, prospective contributors, and other advanced users. Both lists are available at https://lists.isc.org. The community provides best-effort support on both of those lists.

ISC provides professional support for Kea services. See https://www.isc.org/kea/ for details.

History

The kea-ctrl-agent was first coded in December 2016 by Marcin Siodelski.

See Also

kea-dhcp4(8), kea-dhcp6(8), kea-dhcp-ddns(8), kea-admin(8), keactrl(8), perfdhcp(8), kea-lfc(8), Kea Administrator Reference Manual.

keactrl - Shell script for managing Kea

Synopsis

keactrl [command] [-c keactrl-config-file] [-s server[,server,…]] [-v]

Description

keactrl is a shell script which controls the startup, shutdown, and reconfiguration of the Kea servers (kea-dhcp4, kea-dhcp6, kea-dhcp-ddns, kea-ctrl-agent, and kea-netconf). It also provides a way to check the current status of the servers and determine the configuration files in use.

Configuration File

Depending on the user’s requirements, not all of the available servers need be run. The keactrl configuration file specifies which servers are enabled and which are disabled. By default the configuration file is [kea-install-dir]/etc/kea/keactrl.conf.

See the Kea Administrator Reference Manual for documentation of the parameters in the keactrl configuration file.

Options

command

Specifies the command to be issued to the servers. It can be one of the following:

start

Starts the servers.

stop

Stops the servers.

reload

Instructs the servers to re-read the Kea configuration file. This command is not supported by the NETCONF agent.

status

Prints the status of the servers.

-c|--ctrl-config keactrl-config-file

Specifies the keactrl configuration file. Without this switch, keactrl uses the file [kea-install-dir]/etc/kea/keactrl.conf.

-s|--server server[,server,...]

Specifies a subset of the enabled servers to which the command should be issued. The list of servers should be separated by commas, with no intervening spaces. Acceptable values are:

dhcp4

DHCPv4 server (kea-dhcp4).

dhcp6

DHCPv6 server (kea-dhcp6).

dhcp_ddns

DHCP DDNS server (kea-dhcp-ddns).

ctrl_agent

Control Agent (kea-ctrl-agent).

netconf

NETCONF agent (kea-netconf).

all

All servers, including NETCONF if it was configured to be built. This is the default.

-v|--version

Prints the keactrl version and quits.

Documentation

Kea comes with an extensive Kea Administrator Reference Manual that covers all aspects of running the Kea software - compilation, installation, configuration, configuration examples, and much more. Kea also features a Kea Messages Manual, which lists all possible messages Kea can print with a brief description for each of them. Both documents are available in various formats (.txt, .html, .pdf) with the Kea distribution. The Kea documentation is available at https://kea.readthedocs.io.

Kea source code is documented in the Kea Developer’s Guide, available at https://reports.kea.isc.org/dev_guide/.

The Kea project website is available at https://kea.isc.org.

Mailing Lists and Support

There are two public mailing lists available for the Kea project. kea-users (kea-users at lists.isc.org) is intended for Kea users, while kea-dev (kea-dev at lists.isc.org) is intended for Kea developers, prospective contributors, and other advanced users. Both lists are available at https://lists.isc.org. The community provides best-effort support on both of those lists.

ISC provides professional support for Kea services. See https://www.isc.org/kea/ for details.

See Also

kea-dhcp4(8), kea-dhcp6(8), kea-dhcp-ddns(8), kea-ctrl-agent(8), kea-admin(8), kea-netconf(8), perfdhcp(8), kea-lfc(8), Kea Administrator Reference Manual.

kea-admin - Shell script for managing Kea databases

Synopsis

kea-admin [command] [backend] [-h database_host] [-P database_port] [-u database_username] [-p [database_password]] [-n database_name] [-d script_directory] [-v] [-4 | -6] [-o output_file] [-x extra_argument [-x extra_argument …]]

Description

kea-admin is a shell script that offers database maintenance. In particular, it features database initialization, database version checking, and database schema upgrading.

Arguments

command

Specifies the command to be issued to the servers. It can be one of the following:

db-init

Initializes a new database schema. This is useful during a new Kea installation. The database is initialized to the latest version supported by the version of the software being installed.

db-version

Reports the database backend version number. This is not necessarily equal to the Kea version number, as each backend has its own versioning scheme.

db-upgrade

Conducts a database schema upgrade. This is useful when upgrading Kea.

lease-dump

Dumps the contents of the lease database (for MySQL or PostgreSQL backends) to a CSV (comma-separated values) text file. (Support for the Cassandra backend has been deprecated.) The first line of the file contains the column names. This can be used as a way to switch from a database backend to a memfile backend. Alternatively, it can be used as a diagnostic tool, so it provides a portable form of the lease data.

lease-upload

Uploads leases from a CSV (comma-separated values) text file to a MySQL or a PostgreSQL lease database. The CSV file needs to be in memfile format.

stats-recount

Recounts lease statistics for a MySQL or PostgreSQL database.

backend

Specifies the backend type. Currently allowed backends are: memfile, mysql, and pgsql; cql has been deprecated.

-h|--host hostname

Specifies the hostname when connecting to a database. The default value is localhost.

-P|--port port

Specifies the port when connecting to a database. If not specified, the default value chosen by the database client is used.

-u|--user username

Specifies the username when connecting to a database. The default value is keatest.

-p|--password password

Specifies the password when connecting to a database. If only -p or --password is given, the user is prompted for a password. If not specified at all, the KEA_ADMIN_DB_PASSWORD environment variable is checked for a value and used if it exists. Otherwise the default value of keatest is used.

-n|--name database-name

Specifies the name of the database to connect to. The default value is keatest.

-d|--directory script-directory

Specifies the override scripts directory. That script is used during upgrades, database initialization, and possibly other operations. The default value is (prefix)/share/kea/scripts/.

-o|--output output_file

Specifies the file to which the lease data will be dumped. Required for lease-dump.

-v|--version

Prints the kea-admin version and quits.

-4

Directs kea-admin to lease-dump the DHCPv4 leases. Incompatible with the -6 option.

-6

Directs kea-admin to lease-dump the DHCPv6 leases. Incompatible with the -4 option.

-x|--extra

Specifies an extra argument to pass to the database command tool e.g. to invoke mysql with the --ssl argument. This can be repeated to pass more than one argument. Quotes are not preserved. Avoid commands containing spaces.

Documentation

Kea comes with an extensive Kea Administrator Reference Manual that covers all aspects of running the Kea software - compilation, installation, configuration, configuration examples, and much more. Kea also features a Kea Messages Manual, which lists all possible messages Kea can print with a brief description for each of them. Both documents are available in various formats (.txt, .html, .pdf) with the Kea distribution. The Kea documentation is available at https://kea.readthedocs.io.

Kea source code is documented in the Kea Developer’s Guide, available at https://reports.kea.isc.org/dev_guide/.

The Kea project website is available at https://kea.isc.org.

Mailing Lists and Support

There are two public mailing lists available for the Kea project. kea-users (kea-users at lists.isc.org) is intended for Kea users, while kea-dev (kea-dev at lists.isc.org) is intended for Kea developers, prospective contributors, and other advanced users. Both lists are available at https://lists.isc.org. The community provides best-effort support on both of those lists.

ISC provides professional support for Kea services. See https://www.isc.org/kea/ for details.

See Also

kea-dhcp4(8), kea-dhcp6(8), kea-dhcp-ddns(8), kea-ctrl-agent(8), keactrl(8), perfdhcp(8), kea-netconf(8), Kea Administrator Reference Manual.

kea-dhcp-ddns - DHCP-DDNS process in Kea

Synopsis

kea-dhcp-ddns [-v] [-V] [-W] [-d] [-c config-file] [-t config-file]

Description

The kea-dhcp-ddns service process requests an update of DNS mapping based on DHCP lease-change events. It runs as a separate process that expects to receive Name Change Requests from Kea DHCP servers.

Arguments

The arguments are as follows:

-v

Displays the version.

-V

Displays the extended version.

-W

Displays the configuration report.

-d

Sets the logging level to debug with extra verbosity. This is primarily for development purposes in stand-alone mode.

-c config-file

Specifies the configuration file with the configuration for the DHCP-DDNS server. It may also contain configuration entries for other Kea services.

-t config-file

Checks the syntax of the configuration file and reports the first error, if any. Note that not all parameters are completely checked; in particular, a service socket is not opened.

Documentation

Kea comes with an extensive Kea Administrator Reference Manual that covers all aspects of running the Kea software - compilation, installation, configuration, configuration examples, and much more. Kea also features a Kea Messages Manual, which lists all possible messages Kea can print with a brief description for each of them. Both documents are available in various formats (.txt, .html, .pdf) with the Kea distribution. The Kea documentation is available at https://kea.readthedocs.io.

Kea source code is documented in the Kea Developer’s Guide, available at https://reports.kea.isc.org/dev_guide/.

The Kea project website is available at https://kea.isc.org.

Mailing Lists and Support

There are two public mailing lists available for the Kea project. kea-users (kea-users at lists.isc.org) is intended for Kea users, while kea-dev (kea-dev at lists.isc.org) is intended for Kea developers, prospective contributors, and other advanced users. Both lists are available at https://lists.isc.org. The community provides best-effort support on both of those lists.

ISC provides professional support for Kea services. See https://www.isc.org/kea/ for details.

History

The b10-dhcp-ddns process was first coded in May 2013 by Thomas Markwalder.

Kea became a standalone server and the BIND 10 framework was removed. The DHCP-DDNS server binary was renamed to kea-dhcp-ddns in July 2014. Kea 1.0.0 was released in December 2015.

See Also

kea-dhcp4(8), kea-dhcp6(8), kea-ctrl-agent(8), kea-admin(8), keactrl(8), perfdhcp(8), kea-netconf(8), kea-lfc(8), Kea Administrator Reference Manual.

kea-lfc - Lease File Cleanup process in Kea

Synopsis

kea-lfc [-4**|-6**] [-c config-file] [-p pid-file] [-x previous-file] [-i copy-file] [-o output-file] [-f finish-file] [-v] [-V] [-W] [-d] [-h]

Description

The kea-lfc service process removes redundant information from the files used to provide persistent storage for the memfile database backend. The service is written to run as a stand-alone process. While it can be started externally, there is usually no need to do this. It is run periodically by the Kea DHCP servers.

Arguments

The arguments are as follows:

-4 | -6

Indicates the protocol version of the lease files; must be either 4 or 6.

-c config-file

Specifies the file with the configuration for the kea-lfc process. It may also contain configuration entries for other Kea services. Currently kea-lfc gets all of its arguments from the command line.

-p pid-file

Specifies the PID file. When the kea-lfc process starts, it attempts to determine if another instance of the process is already running, by examining the PID file. If one is already running, the new process is terminated. If one is not running, Kea writes its PID into the PID file.

-x previous-file

Specifies the previous or ex-lease file. When kea-lfc starts, this is the result of any previous run of kea-lfc; when kea-lfc finishes, it is the result of the current run. If kea-lfc is interrupted before completing, this file may not exist.

-i copy-file

Specifies the input or copy of lease file. Before the DHCP server invokes kea-lfc, it moves the current lease file here and then calls kea-lfc with this file.

-o output-file

Specifies the output lease file, which is the temporary file kea-lfc should use to write the leases. Once this file is finished writing, it is moved to the finish file (see below).

-f finish-file

Specifies the finish or completion file, another temporary file kea-lfc uses for bookkeeping. When kea-lfc finishes writing the output file, it moves it to this file name. After kea-lfc finishes deleting the other files (previous and input), it moves this file to the previous lease file. By moving the files in this fashion, the kea-lfc and the DHCP server processes can determine the correct file to use even if one of the processes was interrupted before completing its task.

-v

Causes the version stamp to be printed.

-V

Causes a longer form of the version stamp to be printed.

-W

Displays the configuration report.

-d

Sets the logging level to debug with extra verbosity. This is primarily for development purposes in stand-alone mode.

-h

Causes the usage string to be printed.

Documentation

Kea comes with an extensive Kea Administrator Reference Manual that covers all aspects of running the Kea software - compilation, installation, configuration, configuration examples, and much more. Kea also features a Kea Messages Manual, which lists all possible messages Kea can print with a brief description for each of them. Both documents are available in various formats (.txt, .html, .pdf) with the Kea distribution. The Kea documentation is available at https://kea.readthedocs.io.

Kea source code is documented in the Kea Developer’s Guide, available at https://reports.kea.isc.org/dev_guide/.

The Kea project website is available at https://kea.isc.org.

Mailing Lists and Support

There are two public mailing lists available for the Kea project. kea-users (kea-users at lists.isc.org) is intended for Kea users, while kea-dev (kea-dev at lists.isc.org) is intended for Kea developers, prospective contributors, and other advanced users. Both lists are available at https://lists.isc.org. The community provides best-effort support on both of those lists.

ISC provides professional support for Kea services. See https://www.isc.org/kea/ for details.

History

The kea-lfc process was first coded in January 2015 by the ISC Kea/DHCP team.

See Also

kea-dhcp4(8), kea-dhcp6(8), kea-dhcp-ddns(8), kea-ctrl-agent(8), kea-admin(8), keactrl(8), perfdhcp(8), kea-netconf(8), Kea Administrator Reference Manual.

kea-shell - Text client for Control Agent process

Synopsis

kea-shell [-h] [-v] [–host] [–port] [–path] [–ca] [–cert] [–key] [–auth-user] [–auth-password] [–timeout] [–service] [command]

Description

The kea-shell provides a REST client for the Kea Control Agent (CA). It takes commands as a command-line parameter that is sent to the CA with proper JSON encapsulation. Optional arguments may be specified on the standard input. The request is sent via HTTP and a response is retrieved, displayed on the standard output. Basic HTTP authentication and HTTPS, i.e. TLS transport, are supported.

Arguments

The arguments are as follows:

-h

Displays help regarding command-line parameters.

-v

Displays the version.

--host

Specifies the host to connect to. The Control Agent must be running at the specified host. If not specified, 127.0.0.1 is used.

--port

Specifies the TCP port to connect to. Control Agent must be listening at the specified port. If not specified, 8000 is used.

--path

Specifies the path in the URL to connect to. If not specified, an empty path is used. As Control Agent listens at the empty path, this parameter is useful only with a reverse proxy.

--ca

Specifies the file or directory name of the Certification Authority. If not specified, HTTPS is not used.

--cert

Specifies the file name of the user end-entity public key certificate. If specified, the file name of the user key must also be specified.

--key

Specifies the file name of the user key file. If specified, the file name of the user certificate must also be specified. Encrypted key files are not supported.

--auth-user

Specifies the user ID for basic HTTP authentication. If not specified, or specified as the empty string, authentication is not used.

--auth-password

Specifies the password for basic HTTP authentication. If not specified but the user ID is specified, an empty password is used.

--timeout

Specifies the connection timeout, in seconds. The default is 10.

--service

Specifies the service that is the target of a command. If not specified, the Control Agent itself is targeted. May be used more than once to specify multiple targets.

command

Specifies the command to be sent to the CA. If not specified, list-commands is used.

Documentation

Kea comes with an extensive Kea Administrator Reference Manual that covers all aspects of running the Kea software - compilation, installation, configuration, configuration examples, and much more. Kea also features a Kea Messages Manual, which lists all possible messages Kea can print with a brief description for each of them. Both documents are available in various formats (.txt, .html, .pdf) with the Kea distribution. The Kea documentation is available at https://kea.readthedocs.io.

Kea source code is documented in the Kea Developer’s Guide, available at https://reports.kea.isc.org/dev_guide/.

The Kea project website is available at https://kea.isc.org.

Mailing Lists and Support

There are two public mailing lists available for the Kea project. kea-users (kea-users at lists.isc.org) is intended for Kea users, while kea-dev (kea-dev at lists.isc.org) is intended for Kea developers, prospective contributors, and other advanced users. Both lists are available at https://lists.isc.org. The community provides best-effort support on both of those lists.

ISC provides professional support for Kea services. See https://www.isc.org/kea/ for details.

History

The kea-shell was first coded in March 2017 by Tomek Mrugalski.

See Also

kea-dhcp4(8), kea-dhcp6(8), kea-dhcp-ddns(8), kea-ctrl-agent(8), kea-admin(8), keactrl(8), perfdhcp(8), kea-lfc(8), Kea Administrator Reference Manual.

kea-netconf - NETCONF agent for configuring Kea

Synopsis

kea-netconf [-v] [-V] [-W] [-d] [-c config-file] [-t config-file]

Description

The kea-netconf agent provides a YANG/NETCONF interface for the Kea environment.

Arguments

The arguments are as follows:

-v

Displays the version.

-V

Displays the extended version.

-W

Displays the configuration report.

-d

Enables the debug mode with extra verbosity.

-c config-file

Specifies the file with the configuration for the NETCONF agent.

-t config-file

Checks the syntax of the configuration file and reports the first error, if any. Note that not all parameters are completely checked; in particular, service and client sockets are not opened, and hook libraries are not loaded.

Documentation

Kea comes with an extensive Kea Administrator Reference Manual that covers all aspects of running the Kea software - compilation, installation, configuration, configuration examples, and much more. Kea also features a Kea Messages Manual, which lists all possible messages Kea can print with a brief description for each of them. Both documents are available in various formats (.txt, .html, .pdf) with the Kea distribution. The Kea documentation is available at https://kea.readthedocs.io.

Kea source code is documented in the Kea Developer’s Guide, available at https://reports.kea.isc.org/dev_guide/.

The Kea project website is available at https://kea.isc.org.

Mailing Lists and Support

There are two public mailing lists available for the Kea project. kea-users (kea-users at lists.isc.org) is intended for Kea users, while kea-dev (kea-dev at lists.isc.org) is intended for Kea developers, prospective contributors, and other advanced users. Both lists are available at https://lists.isc.org. The community provides best-effort support on both of those lists.

ISC provides professional support for Kea services. See https://www.isc.org/kea/ for details.

History

Early prototypes of kea-netconf implementation were written during IETF Hackathons in Berlin, London, and Montreal. An actual production-ready implementation was started in August 2018 by Tomek Mrugalski and Francis Dupont.

See Also

kea-dhcp4(8), kea-dhcp6(8), kea-dhcp-ddns(8), kea-ctrl-agent(8), kea-admin(8), keactrl(8), perfdhcp(8), kea-lfc(8), Kea Administrator Reference Manual.

perfdhcp - DHCP benchmarking tool

Synopsis

perfdhcp [-1] [-4 | -6] [-A encapsulation-level] [-b base] [-B] [-c] [-C separator] [-d drop-time] [-D max-drop] [-e lease-type] [-E time-offset] [-f renew-rate] [-F release-rate] [-g thread-mode] [-h] [-i] [-I ip-offset] [-J remote-address-list-file] [-l local-address|interface] [-L local-port] [-M mac-list-file] [-n num-request] [-N remote-port] [-O random-offset] [-o code,hexstring] [-p test-period] [-P preload] [-r rate] [-R num-clients] [-s seed] [-S srvid-offset] [–scenario name] [-t report] [-T template-file] [-u] [-v] [-W exit-wait-time] [-w script_name] [-x diagnostic-selector] [-X xid-offset] [server]

Description

perfdhcp is a DHCP benchmarking tool. It provides a way to measure the performance of DHCP servers by generating large amounts of traffic from multiple simulated clients. It is able to test both IPv4 and IPv6 servers, and provides statistics concerning response times and the number of requests that are dropped.

The tool supports two different scenarios, which offer certain behaviors to be tested. By default (the basic scenario), tests are run using the full four-packet exchange sequence (DORA for DHCPv4, SARR for DHCPv6). An option is provided to run tests using the initial two-packet exchange (DO and SA) instead. It is also possible to configure perfdhcp to send DHCPv6 RENEW and RELEASE messages at a specified rate, in parallel with the DHCPv6 four-way exchanges. By default, if there is no response received with one second, a response is considered lost and perfdhcp continues with other transactions.

A second scenario, called avalanche, is selected via --scenario avalanche. It first sends the number of Discovery or Solicit messages specified by the -R option; then a retransmission (with an exponential back-off mechanism) is used for each simulated client, until all requests are answered. It generates a report when all clients receive their addresses, or when it is manually stopped. This scenario attempts to replicate a case where the server is not able to handle the traffic swiftly enough. Real clients will assume the packet or response was lost and will retransmit, further increasing DHCP traffic. This is sometimes called an avalanche effect, thus the scenario name. Option -p is ignored in the avalanche scenario.

When running a performance test, perfdhcp exchanges packets with the server under test as quickly as possible, unless the -r parameter is used to limit the request rate. The length of the test can be limited by setting a threshold on any or all of the number of requests made by perfdhcp, the elapsed time, or the number of requests dropped by the server.

Templates

To allow the contents of packets sent to the server to be customized, perfdhcp allows the specification of template files that determine the contents of the packets. For example, the customized packet may contain a DHCPv6 ORO to request a set of options to be returned by the server, or it may contain the Client FQDN option to request that the server perform DNS updates. This may be used to discover performance bottlenecks for different server configurations (e.g. DDNS enabled or disabled).

Up to two template files can be specified on the command line, with each file representing the contents of a particular type of packet, and the type being determined by the test being carried out. For example, if testing DHCPv6:

• With no template files specified on the command line, perfdhcp generates both Solicit and Request packets.

• With one template file specified, that file is used as the pattern for Solicit packets: perfdhcp generates the Request packets.

• With two template files given on the command line, the first is used as the pattern for Solicit packets, and the second as the pattern for Request packets.

(A similar determination applies to DHCPv4’s DHCPDISCOVER and DHCPREQUEST packets.)

The template file holds the DHCP packet, represented as a stream of ASCII hexadecimal digits; it excludes any IP/UDP stack headers. The template file must not contain any characters other than hexadecimal digits and spaces. Spaces are discarded when the template file is parsed; in the file, 12B4 is the same as 12 B4, which is the same as 1 2 B 4.

The template files should be used in conjunction with the command-line parameters which specify offsets of the data fields being modified in outbound packets. For example, the -E time-offset switch specifies the offset of the DHCPv6 Elapsed Time option in the packet template. If the offset is specified, perfdhcp injects the current elapsed-time value into this field before sending the packet to the server.

In many scenarios, perfdhcp needs to simulate multiple clients, each having a unique client identifier. Since packets for each client are generated from the same template file, it is necessary to randomize the client identifier (or HW address in DHCPv4) in the packet created from it. The -O random-offset option allows specification of the offset in the template where randomization should be performed. It is important to note that this offset points to the end (not the beginning) of the client identifier (or HW address field). The number of bytes being randomized depends on the number of simulated clients. If the number of simulated clients is between 1 and 255, only one byte (to which the randomization offset points) is randomized. If the number of simulated clients is between 256 and 65535, two bytes are randomized. Note that the last two bytes of the client identifier are randomized in this case: the byte which the randomization offset parameter points to, and the one which precedes it (random-offset - 1). If the number of simulated clients exceeds 65535, three bytes are randomized, and so on.

perfdhcp can simulate traffic from multiple subnets by enabling option -J and passing a path to a file that contains v4 or v6 addresses to be used as relays in generated messages. That enables testing of vast numbers of Kea shared networks. While testing DHCPv4, Kea should be started with the KEA_TEST_SEND_RESPONSES_TO_SOURCE environment variable, to force Kea to send generated messages to the source address of the incoming packet.

Templates may currently be used to generate packets being sent to the server in 4-way exchanges, i.e. Solicit, Request (DHCPv6) and DHCPDISCOVER, DHCPREQUEST (DHCPv4). They cannot be used when Renew or DHCPRELEASE packets are being sent.

Options

-1

Takes the server-id option from the first received message.

-4

Establishes DHCPv4 operation; this is the default. It is incompatible with the -6 option.

-6

Establishes DHCPv6 operation. It is incompatible with the -4 option.

-b basetype=value

Indicates the base MAC or DUID used to simulate different clients. The basetype may be “mac” or “duid”. (The keyword “ether” may alternatively used for MAC.) The -b option can be specified multiple times. The MAC address must consist of six octets separated by single (:) or double (::) colons; for example: mac=00:0c:01:02:03:04. The DUID value is a hexadecimal string; it must be at least six octets long and not longer than 64 bytes, and the length must be less than 128 hexadecimal digits. For example: duid=0101010101010101010110111F14.

-d drop-time

Specifies the time after which a request is treated as having been lost. The value is given in seconds and may contain a fractional component. The default is 1.

-e lease-type

Specifies the type of lease being requested from the server. It may be one of the following:

address-only

Only regular addresses (v4 or v6) are requested.

prefix-only

Only IPv6 prefixes are requested.

address-and-prefix

Both IPv6 addresses and prefixes are requested.

The -e prefix-only and -e address-and-prefix forms may not be used with the -4 option.

-F release-rate

Specifies the rate at which DHCPv4 DHCPRELEASE or DHCPv6 Release requests are sent to a server. This value is only valid when used in conjunction with the exchange rate (given by -r rate). Furthermore, the sum of this value and the renew-rate (given by -f rate) must be equal to or less than the exchange rate value.

-f renew-rate

Specifies the rate at which DHCPv4 DHCPREQUEST or DHCPv6 Renew requests are sent to a server. This value is only valid when used in conjunction with the exchange rate (given by -r rate). Furthermore, the sum of this value and the release-rate (given by -F rate) must be equal to or less than the exchange rate.

-g thread-mode

Allows selection of thread-mode, which can be either single or multi. In multi-thread mode, packets are received in a separate thread, which allows better utilisation of CPUs. In a single-CPU system it is better to run in one thread, to avoid threads blocking each other. If more than one CPU is present in the system, multi-thread mode is the default; otherwise single-thread is the default.

-h

Prints help and exits.

-i

Performs only the initial part of the exchange: DISCOVER-OFFER if -4 is selected, Solicit-Advertise if -6 is chosen.

-i is incompatible with the following options: -1, -d, -D, -E, -S, -I and -F. In addition, it cannot be used with multiple instances of -O, -T, and -X.

-J remote-address-list-file

Specifies a text file that includes multiple addresses, and is designed to test shared networks. If provided, perfdhcp randomly chooses one of the addresses for each exchange, to generate traffic from multiple subnets. When testing DHCPv4, it should be started with the KEA_TEST_SEND_RESPONSES_TO_SOURCE=ENABLE environment variable; otherwise, perfdhcp will not be able to receive responses.

-l local-addr|interface

For DHCPv4 operation, specifies the local hostname/address to use when communicating with the server. By default, the interface address through which traffic would normally be routed to the server is used. For DHCPv6 operation, specifies the name of the network interface through which exchanges are initiated.

-L local-port

Specifies the local port to use. This must be zero or a positive integer up to 65535. A value of 0 (the default) allows perfdhcp to choose its own port.

-M mac-list-file

Specifies a text file containing a list of MAC addresses, one per line. If provided, a MAC address is chosen randomly from this list for every new exchange. In DHCPv6, MAC addresses are used to generate DUID-LLs. This parameter must not be used in conjunction with the -b parameter.

-N remote-port

Specifies the remote port to use. This must be zero or a positive integer up to 65535. A value of 0 (the default) allows perfdhcp to choose the standard service port.

-o code,hexstring

Forces perfdhcp to insert the specified extra option (or options if used several times) into packets being transmitted. The code specifies the option code and the hexstring is a hexadecimal string that defines the content of the option. Care should be taken as perfdhcp does not offer any kind of logic behind those options; they are simply inserted into packets and sent as is. Be careful not to duplicate options that are already inserted. For example, to insert client class identifier (option code 60) with a string “docsis”, use “-o 60,646f63736973”. The -o may be used multiple times. It is necessary to specify the protocol family (either -4 or -6) before using -o.

-P preload

Initiates preload exchanges back-to-back at startup. Must be 0 (the default) or a positive integer.

-r rate

Initiates the rate of DORA/SARR (or if -i is given, DO/SA) exchanges per second. A periodic report is generated showing the number of exchanges which were not completed, as well as the average response latency. The program continues until interrupted, at which point a final report is generated.

-R num-clients

Specifies how many different clients are used. With a value of 1 (the default), all requests appear to come from the same client. Must be a positive number.

-s seed

Specifies the seed for randomization, making runs of perfdhcp repeatable. This must be 0 or a positive integer. The value 0 means that a seed is not used; this is the default.

--scenario name

Specifies the type of scenario, and can be basic (the default) or avalanche.

-T template-file

Specifies a file containing the template to use as a stream of hexadecimal digits. This may be specified up to two times and controls the contents of the packets sent (see the “Templates” section above).

-u

Enables checks for address uniqueness. The lease valid-lifetime should not be shorter than the test duration, and clients should not request an address more than once without releasing it.

-v

Prints the version of this program.

-W exit-wait-time

Specifies the exit-wait-time parameter, which causes perfdhcp to wait for a certain amount of time after an exit condition has been met, to receive all packets without sending any new packets. Expressed in microseconds. If not specified, 0 is used (i.e. exit immediately after exit conditions are met).

-w script_name

Specifies the name of the script to be run before/after perfdhcp. When called, the script is passed a single parameter, either “start” or “stop”, indicating whether it is being called before or after perfdhcp.

-x diagnostic-selector

Includes extended diagnostics in the output. This is a string of single keywords specifying the operations for which verbose output is desired. The selector key letters are:

a

Prints the decoded command-line arguments.

e

Prints the exit reason.

i

Prints the rate-processing details.

l

Prints the received leases.

s

Prints the first server ID.

t

When finished, prints timers of all successful exchanges.

T

When finished, prints templates.

-y seconds

Time in seconds after which perfdhcp starts simulating the client waiting longer for server responses. This increases the secs field in DHCPv4 and sends increased values in the Elapsed Time option in DHCPv6. Must be used with -Y.

-Y seconds

Time in seconds during which perfdhcp simulates the client waiting longer for server responses. This increases the secs field in DHCPv4 and sends increased values in the Elapsed Time option in DHCPv6. Must be used with -y.

DHCPv4-Only Options

The following options only apply for DHCPv4 (i.e. when -4 is given).

-B

Forces broadcast handling.

DHCPv6-Only Options

The following options only apply for DHCPv6 (i.e. when -6 is given).

-c

Adds a rapid-commit option (exchanges are Solicit-Advertise).

-A encapsulation-level

Specifies that relayed traffic must be generated. The argument specifies the level of encapsulation, i.e. how many relay agents are simulated. Currently the only supported encapsulation-level value is 1, which means that the generated traffic is equivalent to the amount of traffic passing through a single relay agent.

Template-Related Options

The following options may only be used in conjunction with -T and control how perfdhcp modifies the template. The options may be specified multiple times on the command line; each occurrence affects the corresponding template file (see “Templates” above).

-E time-offset

Specifies the offset of the secs field (DHCPv4) or Elapsed Time option (DHCPv6) in the second (i.e. Request) template; must be 0 or a positive integer. A value of 0 disables this.

-I ip-offset

Specifies the offset of the IP address (DHCPv4) in the requested-ip option or IA_NA option (DHCPv6) in the second (Request) template.

-O random-offset

Specifies the offset of the last octet to randomize in the template. This must be an integer greater than 3. The -T switch must be given to use this option.

-S srvid-offset

Specifies the offset of the server-id option in the second (Request) template. This must be a positive integer, and the switch can only be used when the template option (-T) is also given.

-X xid-offset

Specifies the offset of the transaction ID (xid) in the template. This must be a positive integer, and the switch can only be used when the template option (-T) is also given.

Options Controlling a Test

-D max-drop

Aborts the test immediately if “max-drop” requests have been dropped. Use -D 0 to abort if even a single request has been dropped. “max-drop” must be a positive integer. If “max-drop” includes the suffix %, it specifies the maximum percentage of requests that may be dropped before aborting. In this case, testing of the threshold begins after 10 requests are expected to have been received.

-n num-requests

Initiates “num-request” transactions. No report is generated until all transactions have been initiated/waited-for, after which a report is generated and the program terminates.

-p test-period

Sends requests for “test-period”, which is specified in the same manner as -d. This can be used as an alternative to -n, or both options can be given, in which case the testing is completed when either limit is reached.

-t interval

Sets the delay (in seconds) between two successive reports.

-C separator

Suppresses the preliminary output and causes the interim data to only contain the values delimited by separator. Used in conjunction with -t to produce easily parsable reports at -t intervals.

Arguments

server

Indicates the server to test, specified as an IP address. In the DHCPv6 case, the special name all can be used to refer to All_DHCP_Relay_Agents_and_Servers (the multicast address FF02::1:2), or the special name servers to refer to All_DHCP_Servers (the multicast address FF05::1:3). The server is mandatory except where the -l option is given to specify an interface, in which case it defaults to all.

Errors

perfdhcp can report the following errors in the packet exchange:

tooshort

A message was received that was too short.

orphans

A message was received which does not match one sent to the server (i.e. it is a duplicate message, a message that has arrived after an excessive delay, or one that is just not recognized).

locallimit

Local system limits have been reached when sending a message.

Exit Status

perfdhcp exits with one of the following status codes:

0

Success.

1

General error.

2

Error in command-line arguments.

3

No general failures in operation, but one or more exchanges were unsuccessful.

Usage Examples

Here is an example that simulates regular DHCPv4 traffic of 100 DHCPv4 devices (-R 100), 10 packets per second (-r 10), shows the query/response rate details (-xi), shows a report every 2 seconds (-t 2), and sends the packets to the IP 192.0.2.1:

sudo perfdhcp -xi -t 2 -r 10 -R 100 192.0.2.1

Here’s a similar case, but for DHCPv6. Note that the DHCPv6 protocol uses link-local addresses, so the interface (eth0 in this example) must be specified on which to send the traffic. all is a convenience alias for All_DHCP_Relay_Agents_and_Servers (the multicast address FF02::1:2). It is also possible to use the servers alias to refer to All_DHCP_Servers (the multicast address FF05::1:3). The default is all.

sudo perfdhcp -6 -xi -t 1 -r 1 -R 10 -l eth0 all

The following examples simulate normal DHCPv4 and DHCPv6 traffic that, after 3 seconds, starts pretending not to receive any responses from the server for 10 seconds. The DHCPv4 protocol signals this by an increased secs field, while DHCPv6 uses the Elapsed Time option. In real networks, this indicates that clients are not getting responses in a timely matter. This can be used to simulate some HA scenarios, as Kea uses the secs field and Elapsed Time option value as one of the indicators that the HA partner is not responding. When enabled with -y and -Y, the secs and Elapsed Time values increase steadily.

sudo perfdhcp -xi -t 1 -r 1 -y 10 -Y 3 192.0.2.1

sudo perfdhcp -6 -xi -t 1 -r 1 -y 10 -Y 3 2001:db8::1

Documentation

Kea comes with an extensive Kea Administrator Reference Manual that covers all aspects of running the Kea software - compilation, installation, configuration, configuration examples, and much more. Kea also features a Kea Messages Manual, which lists all possible messages Kea can print with a brief description for each of them. Both documents are available in various formats (.txt, .html, .pdf) with the Kea distribution. The Kea documentation is available at https://kea.readthedocs.io.

Kea source code is documented in the Kea Developer’s Guide, available at https://reports.kea.isc.org/dev_guide/.

The Kea project website is available at https://kea.isc.org.

Mailing Lists and Support

There are two public mailing lists available for the Kea project. kea-users (kea-users at lists.isc.org) is intended for Kea users, while kea-dev (kea-dev at lists.isc.org) is intended for Kea developers, prospective contributors, and other advanced users. Both lists are available at https://lists.isc.org. The community provides best-effort support on both of those lists.

ISC provides professional support for Kea services. See https://www.isc.org/kea/ for details.

History

The perfdhcp tool was initially coded in October 2011 by John DuBois, Francis Dupont, and Marcin Siodelski of ISC. Kea 1.0.0, which included perfdhcp, was released in December 2015.

See Also

kea-dhcp4(8), kea-dhcp6(8), kea-dhcp-ddns(8), kea-ctrl-agent(8), kea-admin(8), kea-netconf(8), keactrl(8), kea-lfc(8), Kea Administrator Reference Manual.

Kea Messages Manual

Kea is an open source implementation of the Dynamic Host Configuration Protocol (DHCP) servers, developed and maintained by Internet Systems Consortium (ISC).

This is the reference guide for Kea version 2.1.6. Links to the most up-to-date version of this document (in PDF, HTML, and plain text formats), along with other useful information about Kea, can be found in ISC’s Knowledgebase.

Please note that in the messages below, the percent sign (“%”) followed by a number is used to indicate a placeholder for data that is provided by the Kea code during its operation.

ALLOC

ALLOC_ENGINE_LEASE_RECLAIMED

successfully reclaimed lease %1

This debug message is logged when the allocation engine successfully reclaims a lease. The lease is now available for assignment.

ALLOC_ENGINE_REMOVAL_NCR_FAILED

sending removal name change request failed for lease %1: %2

This error message is logged when sending a removal NameChangeRequest to DHCP DDNS failed. This NameChangeRequest is usually generated when the lease reclamation routine acts upon expired leases. If a lease being reclaimed has a corresponding DNS entry it needs to be removed. This message indicates that removal of the DNS entry has failed. Nevertheless the lease will be reclaimed.

ALLOC_ENGINE_V4_ALLOC_ERROR

%1: error during attempt to allocate an IPv4 address: %2

An error occurred during an attempt to allocate an IPv4 address, the reason for the failure being contained in the message. The server will return a message to the client refusing a lease. The first argument includes the client identification information.

ALLOC_ENGINE_V4_ALLOC_FAIL

%1: failed to allocate an IPv4 address after %2 attempt(s)

This is an old warning message issued when the allocation engine fails to allocate a lease for a client. This message includes a number of lease allocation attempts that the engine made before giving up. If the number of attempts is 0 because the engine was unable to use any of the address pools for the particular client, this message is not logged. Even though, several more detailed logs precede this message, it was left for backward compatibility. This message may indicate that your address pool is too small for the number of clients you are trying to service and should be expanded. Alternatively, if the you know that the number of concurrently active clients is less than the addresses you have available, you may want to consider reducing the lease lifetime. This way, addresses allocated to clients that are no longer active on the network will become available sooner.

ALLOC_ENGINE_V4_ALLOC_FAIL_CLASSES

%1: Failed to allocate an IPv4 address for client with classes: %2

This warning message is printed when Kea failed to allocate an address and the client’s packet belongs to one or more classes. There may be several reasons why a lease was not assigned. One of them may be a case when all pools require packet to belong to certain classes and the incoming packet didn’t belong to any of them. Another case where this information may be useful is to point out that the pool reserved to a given class has ran out of addresses. When you see this message, you may consider checking your pool size and your classification definitions.

ALLOC_ENGINE_V4_ALLOC_FAIL_NO_POOLS

%1: no pools were available for the address allocation

This warning message is issued when the allocation engine fails to allocate a lease because it could not use any configured pools for the particular client. It is also possible that all of the subnets from which the allocation engine attempted to assign an address lack address pools. In this case, it should be considered misconfiguration if an operator expects that some clients should be assigned dynamic addresses. A subnet may lack any pools only when all clients should be assigned reserved IP addresses. Suppose the subnets connected to a shared network or a single subnet to which the client belongs have pools configured. In that case, this message is an indication that none of the pools could be used for the client because the client does not belong to appropriate client classes.

ALLOC_ENGINE_V4_ALLOC_FAIL_SHARED_NETWORK

%1: failed to allocate an IPv4 address in the shared network %2: %3 subnets have no available addresses, %4 subnets have no matching pools

This warning message is issued when the allocation engine fails to allocate a lease for a client connected to a shared network. The shared network should contain at least one subnet, but typically it aggregates multiple subnets. This log message indicates that the allocation engine could not find and allocate any suitable lease in any of the subnets within the shared network. The first argument includes the client identification information. The second argument specifies the shared network name. The remaining two arguments provide additional information useful for debugging why the allocation engine could not assign a lease. The allocation engine tries to allocate addresses from different subnets in the shared network, and it may fail for some subnets because there are no leases available in those subnets or the free leases are reserved to other clients. The number of such subnets is specified in the third argument. For other subnets the allocation may fail because their pools may not be available to the particular client. These pools are guarded by client classes that the client does not belong to. The fourth argument specifies the number of such subnets. By looking at the values in the third and fourth argument, an operator can identify the situations when there are no addresses left in some of the pools. He or she can also identify a client classification misconfigurations causing some clients to be refused the service.

ALLOC_ENGINE_V4_ALLOC_FAIL_SUBNET

%1: failed to allocate an IPv4 address in the subnet %2, subnet-id %3, shared network %4

This warning message is issued when the allocation engine fails to allocate a lease for a client connected to a subnet that does not belong to a shared network. The first argument includes the client identification information. The second and third arguments identify the subnet. The fourth argument specifies the shared network, if the subnet belongs to a shared network. There are many reasons for failing lease allocations. One of them may be the address pools exhaustion or existing reservations for the free leases. However, in some cases, the allocation engine may fail to find a suitable pool for the client when the pools are only available to certain client classes, but the requesting client does not belong to them. Further log messages provide more information to distinguish between these different cases.

ALLOC_ENGINE_V4_DECLINED_RECOVERED

IPv4 address %1 was recovered after %2 seconds of probation-period

This informational message indicates that the specified address was reported as duplicate (client sent DECLINE) and the server marked this address as unavailable for a period of time. This time now has elapsed and the address has been returned to the available pool. This step concludes the decline recovery process.

ALLOC_ENGINE_V4_DISCOVER_ADDRESS_CONFLICT

%1: conflicting reservation for address %2 with existing lease %3

This warning message is issued when the DHCP server finds that the address reserved for the client can’t be offered because this address is currently allocated to another client. The server will try to allocate a different address to the client to use until the conflict is resolved. The first argument includes the client identification information.

ALLOC_ENGINE_V4_DISCOVER_HR

client %1 sending DHCPDISCOVER has reservation for the address %2

This message is issued when the allocation engine determines that the client sending the DHCPDISCOVER has a reservation for the specified address. The allocation engine will try to offer this address to the client.

ALLOC_ENGINE_V4_LEASES_RECLAMATION_COMPLETE

reclaimed %1 leases in %2

This debug message is logged when the allocation engine completes reclamation of a set of expired leases. The maximum number of leases to be reclaimed in a single pass of the lease reclamation routine is configurable using ‘max-reclaim-leases’ parameter. However, the number of reclaimed leases may also be limited by the timeout value, configured with ‘max-reclaim-time’. The message includes the number of reclaimed leases and the total time.

ALLOC_ENGINE_V4_LEASES_RECLAMATION_SLOW

expired leases still exist after %1 reclamations

This warning message is issued when the server has been unable to reclaim all expired leases in a specified number of consecutive attempts. This indicates that the value of “reclaim-timer-wait-time” may be too high. However, if this is just a short burst of leases’ expirations the value does not have to be modified and the server should deal with this in subsequent reclamation attempts. If this is a result of a permanent increase of the server load, the value of “reclaim-timer-wait-time” should be decreased, or the values of “max-reclaim-leases” and “max-reclaim-time” should be increased to allow processing more leases in a single cycle. Alternatively, these values may be set to 0 to remove the limitations on the number of leases and duration. However, this may result in longer periods of server’s unresponsiveness to DHCP packets, while it processes the expired leases.

ALLOC_ENGINE_V4_LEASES_RECLAMATION_START

starting reclamation of expired leases (limit = %1 leases or %2 milliseconds)

This debug message is issued when the allocation engine starts the reclamation of the expired leases. The maximum number of leases to be reclaimed and the timeout is included in the message. If any of these values is 0, it means “unlimited”.

ALLOC_ENGINE_V4_LEASES_RECLAMATION_TIMEOUT

timeout of %1 ms reached while reclaiming IPv4 leases

This debug message is issued when the allocation engine hits the timeout for performing reclamation of the expired leases. The reclamation will now be interrupted and all leases which haven’t been reclaimed, because of the timeout, will be reclaimed when the next scheduled reclamation is started. The argument is the timeout value expressed in milliseconds.

ALLOC_ENGINE_V4_LEASE_RECLAIM

%1: reclaiming expired lease for address %2

This debug message is issued when the server begins reclamation of the expired DHCPv4 lease. The first argument specifies the client identification information. The second argument holds the leased IPv4 address.

ALLOC_ENGINE_V4_LEASE_RECLAMATION_FAILED

failed to reclaim the lease %1: %2

This error message is logged when the allocation engine fails to reclaim an expired lease. The reason for the failure is included in the message. The error may be triggered in the lease expiration hook or while performing the operation on the lease database.

ALLOC_ENGINE_V4_NO_MORE_EXPIRED_LEASES

all expired leases have been reclaimed

This debug message is issued when the server reclaims all expired DHCPv4 leases in the database.

ALLOC_ENGINE_V4_OFFER_EXISTING_LEASE

allocation engine will try to offer existing lease to the client %1

This message is issued when the allocation engine determines that the client has a lease in the lease database, it doesn’t have reservation for any other lease, and the leased address is not reserved for any other client. The allocation engine will try to offer the same lease to the client.

ALLOC_ENGINE_V4_OFFER_NEW_LEASE

allocation engine will try to offer new lease to the client %1

This message is issued when the allocation engine will try to offer a new lease to the client. This is the case when the client doesn’t have any existing lease, it has no reservation or the existing or reserved address is leased to another client. Also, the client didn’t specify a hint, or the address in the hint is in use.

ALLOC_ENGINE_V4_OFFER_REQUESTED_LEASE

allocation engine will try to offer requested lease %1 to the client %2

This message is issued when the allocation engine will try to offer the lease specified in the hint. This situation may occur when: (a) client doesn’t have any reservations, (b) client has reservation but the reserved address is leased to another client.

ALLOC_ENGINE_V4_RECLAIMED_LEASES_DELETE

begin deletion of reclaimed leases expired more than %1 seconds ago

This debug message is issued when the allocation engine begins deletion of the reclaimed leases which have expired more than a specified number of seconds ago. This operation is triggered periodically according to the “flush-reclaimed-timer-wait-time” parameter. The “hold-reclaimed-time” parameter defines a number of seconds for which the leases are stored before they are removed.

ALLOC_ENGINE_V4_RECLAIMED_LEASES_DELETE_COMPLETE

successfully deleted %1 expired-reclaimed leases

This debug message is issued when the server successfully deletes “expired-reclaimed” leases from the lease database. The number of deleted leases is included in the log message.

ALLOC_ENGINE_V4_RECLAIMED_LEASES_DELETE_FAILED

deletion of expired-reclaimed leases failed: %1

This error message is issued when the deletion of “expired-reclaimed” leases from the database failed. The error message is appended to the log message.

ALLOC_ENGINE_V4_REQUEST_ADDRESS_RESERVED

%1: requested address %2 is reserved

This message is issued when the allocation engine refused to allocate address requested by the client because this address is reserved for another client. The first argument includes the client identification information.

ALLOC_ENGINE_V4_REQUEST_ALLOC_REQUESTED

%1: trying to allocate requested address %2

This message is issued when the allocation engine is trying to allocate (or reuse an expired) address which has been requested by the client. The first argument includes the client identification information.

ALLOC_ENGINE_V4_REQUEST_EXTEND_LEASE

%1: extending lifetime of the lease for address %2

This message is issued when the allocation engine determines that the client already has a lease whose lifetime can be extended, and which can be returned to the client. The first argument includes the client identification information.

ALLOC_ENGINE_V4_REQUEST_INVALID

client %1 having a reservation for address %2 is requesting invalid address %3

This message is logged when the client, having a reservation for one address, is requesting a different address. The client is only allowed to do this when the reserved address is in use by another client. However, the allocation engine has determined that the reserved address is available and the client should request the reserved address.

ALLOC_ENGINE_V4_REQUEST_IN_USE

%1: requested address %2 is in use

This message is issued when the client is requesting or has a reservation for an address which is in use. The first argument includes the client identification information.

ALLOC_ENGINE_V4_REQUEST_OUT_OF_POOL

client %1, which doesn’t have a reservation, requested address %2 out of the dynamic pool

This message is issued when the client has requested allocation of the address which doesn’t belong to any address pool from which addresses are dynamically allocated. The client also doesn’t have reservation for this address. This address could only be allocated if the client had reservation for it.

ALLOC_ENGINE_V4_REQUEST_PICK_ADDRESS

client %1 hasn’t specified an address - picking available address from the pool

This message is logged when the client hasn’t specified any preferred address (the client should always do it, but Kea tries to be forgiving). The allocation engine will try to pick an available address from the dynamic pool and allocate it to the client.

ALLOC_ENGINE_V4_REQUEST_REMOVE_LEASE

%1: removing previous client’s lease %2

This message is logged when the allocation engine removes previous lease for the client because the client has been allocated new one.

ALLOC_ENGINE_V4_REQUEST_USE_HR

client %1 hasn’t requested specific address, using reserved address %2

This message is issued when the client is not requesting any specific address but the allocation engine has determined that there is a reservation for this client. The allocation engine will try to allocate the reserved address.

ALLOC_ENGINE_V4_REUSE_EXPIRED_LEASE_DATA

%1: reusing expired lease, updated lease information: %2

This message is logged when the allocation engine is reusing an existing lease. The details of the updated lease are printed. The first argument includes the client identification information.

ALLOC_ENGINE_V6_ALLOC_ERROR

%1: error during attempt to allocate an IPv6 address: %2

An error occurred during an attempt to allocate an IPv6 address, the reason for the failure being contained in the message. The server will return a message to the client refusing a lease. The first argument includes the client identification information.

ALLOC_ENGINE_V6_ALLOC_FAIL

%1: failed to allocate an IPv6 lease after %2 attempt(s)

This is an old warning message issued when the allocation engine fails to allocate a lease for a client. This message includes a number of lease allocation attempts that the engine made before giving up. If the number of attempts is 0 because the engine was unable to use any of the pools for the particular client, this message is not logged. Even though, several more detailed logs precede this message, it was left for backward compatibility. This message may indicate that your pool is too small for the number of clients you are trying to service and should be expanded. Alternatively, if the you know that the number of concurrently active clients is less than the leases you have available, you may want to consider reducing the lease lifetime. This way, leases allocated to clients that are no longer active on the network will become available sooner.

ALLOC_ENGINE_V6_ALLOC_FAIL_CLASSES

%1: Failed to allocate an IPv6 address for client with classes: %2

This warning message is printed when Kea failed to allocate an address and the client’s packet belongs to one or more classes. There may be several reasons why a lease was not assigned. One of them may be a case when all pools require packet to belong to certain classes and the incoming packet didn’t belong to any of them. Another case where this information may be useful is to point out that the pool reserved to a given class has ran out of addresses. When you see this message, you may consider checking your pool size and your classification definitions.

ALLOC_ENGINE_V6_ALLOC_FAIL_NO_POOLS

%1: no pools were available for the lease allocation

This warning message is issued when the allocation engine fails to allocate a lease because it could not use any configured pools for the particular client. It is also possible that all of the subnets from which the allocation engine attempted to assign an address lack address pools. In this case, it should be considered misconfiguration if an operator expects that some clients should be assigned dynamic addresses. A subnet may lack any pools only when all clients should be assigned reserved leases. Suppose the subnets connected to a shared network or a single subnet to which the client belongs have pools configured. In that case, this message is an indication that none of the pools could be used for the client because the client does not belong to appropriate client classes.

ALLOC_ENGINE_V6_ALLOC_FAIL_SHARED_NETWORK

%1: failed to allocate a lease in the shared network %2: %3 subnets have no available leases, %4 subnets have no matching pools

This warning message is issued when the allocation engine fails to allocate a lease for a client connected to a shared network. The shared network should contain at least one subnet, but typically it aggregates multiple subnets. This log message indicates that the allocation engine could not find and allocate any suitable lease in any of the subnets within the shared network. The first argument includes the client identification information. The second argument specifies the shared network name. The remaining two arguments provide additional information useful for debugging why the allocation engine could not assign a lease. The allocation engine tries to allocate leases from different subnets in the shared network, and it may fail for some subnets because there are no leases available in those subnets or the free leases are reserved to other clients. The number of such subnets is specified in the third argument. For other subnets the allocation may fail because their pools may not be available to the particular client. These pools are guarded by client classes that the client does not belong to. The fourth argument specifies the number of such subnets. By looking at the values in the third and fourth argument, an operator can identify the situations when there are no leases left in some of the pools. He or she can also identify client classification misconfigurations causing some clients to be refused the service.

ALLOC_ENGINE_V6_ALLOC_FAIL_SUBNET

%1: failed to allocate an IPv6 lease in the subnet with id %2

This warning message is issued when the allocation engine fails to allocate a lease for a client connected to a subnet that does not belong to a shared network. The first argument includes the client identification information. The second argument specifies the subnet identifier. There are many reasons for failing lease allocations. One of them may be the pools exhaustion or existing reservations for the free leases. However, in some cases, the allocation engine may fail to find a suitable pool for the client when the pools are only available to certain client classes, but the requesting client does not belong to them. Further log messages provide more information to distinguish between these different cases.

ALLOC_ENGINE_V6_ALLOC_HR_LEASE_EXISTS

%1: lease type %2 for reserved address/prefix %3 already exists

This debug message is issued when the allocation engine determines that the lease for the IPv6 address or prefix has already been allocated for the client and the client can continue using it. The first argument includes the client identification information.

ALLOC_ENGINE_V6_ALLOC_LEASES_HR

leases and static reservations found for client %1

This message is logged when the allocation engine is in the process of allocating leases for the client, it found existing leases and static reservations for the client. The allocation engine will verify if existing leases match reservations. Those leases that are reserved for other clients and those that are not reserved for the client will be removed. All leases matching the reservations will be renewed and returned.

ALLOC_ENGINE_V6_ALLOC_LEASES_NO_HR

no reservations found but leases exist for client %1

This message is logged when the allocation engine is in the process if allocating leases for the client, there are no static reservations, but lease(s) exist for the client. The allocation engine will remove leases which are reserved for other clients, and return all remaining leases to the client.

ALLOC_ENGINE_V6_ALLOC_NO_LEASES_HR

no leases found but reservations exist for client %1

This message is logged when the allocation engine is in the process of allocating leases for the client. It hasn’t found any existing leases for this client, but the client appears to have static reservations. The allocation engine will try to allocate the reserved resources for the client.

ALLOC_ENGINE_V6_ALLOC_NO_V6_HR

%1: unable to allocate reserved leases - no IPv6 reservations

This message is logged when the allocation engine determines that the client has no IPv6 reservations and thus the allocation engine will have to try to allocate allocating leases from the dynamic pool or stop the allocation process if none can be allocated. The first argument includes the client identification information.

ALLOC_ENGINE_V6_ALLOC_UNRESERVED

no static reservations available - trying to dynamically allocate leases for client %1

This debug message is issued when the allocation engine will attempt to allocate leases from the dynamic pools. This may be due to one of (a) there are no reservations for this client, (b) there are reservations for the client but they are not usable because the addresses are in use by another client or (c) we had a reserved lease but that has now been allocated to another client.

ALLOC_ENGINE_V6_DECLINED_RECOVERED

IPv6 address %1 was recovered after %2 seconds of probation-period

This informational message indicates that the specified address was reported as duplicate (client sent DECLINE) and the server marked this address as unavailable for a period of time. This time now has elapsed and the address has been returned to the available pool. This step concludes the decline recovery process.

ALLOC_ENGINE_V6_EXPIRED_HINT_RESERVED

%1: expired lease for the client’s hint %2 is reserved for another client

This message is logged when the allocation engine finds that the expired lease for the client’s hint can’t be reused because it is reserved for another client. The first argument includes the client identification information.

ALLOC_ENGINE_V6_EXTEND_ALLOC_UNRESERVED

allocate new (unreserved) leases for the renewing client %1

This debug message is issued when the allocation engine is trying to allocate new leases for the renewing client because it was unable to renew any of the existing client’s leases, e.g. because leases are reserved for another client or for any other reason.

ALLOC_ENGINE_V6_EXTEND_ERROR

%1: allocation engine experienced error with attempting to extend lease lifetime: %2

This error message indicates that an error was experienced during Renew or Rebind processing. Additional explanation is provided with this message. Depending on its nature, manual intervention may be required to continue processing messages from this particular client; other clients will be unaffected. The first argument includes the client identification information.

ALLOC_ENGINE_V6_EXTEND_LEASE

%1: extending lifetime of the lease type %2, address %3

This debug message is issued when the allocation engine is trying to extend lifetime of the lease. The first argument includes the client identification information.

ALLOC_ENGINE_V6_EXTEND_LEASE_DATA

%1: detailed information about the lease being extended: %2

This debug message prints detailed information about the lease which lifetime is being extended (renew or rebind). The first argument includes the client identification information.

ALLOC_ENGINE_V6_EXTEND_NEW_LEASE_DATA

%1: new lease information for the lease being extended: %2

This debug message prints updated information about the lease to be extended. If the lease update is successful, the information printed by this message will be stored in the database. The first argument includes the client identification information.

ALLOC_ENGINE_V6_HINT_RESERVED

%1: lease for the client’s hint %2 is reserved for another client

This message is logged when the allocation engine cannot allocate the lease using the client’s hint because the lease for this hint is reserved for another client. The first argument includes the client identification information.

ALLOC_ENGINE_V6_HR_ADDR_GRANTED

reserved address %1 was assigned to client %2

This informational message signals that the specified client was assigned the address reserved for it.

ALLOC_ENGINE_V6_HR_PREFIX_GRANTED

reserved prefix %1/%2 was assigned to client %3

This informational message signals that the specified client was assigned the prefix reserved for it.

ALLOC_ENGINE_V6_LEASES_RECLAMATION_COMPLETE

reclaimed %1 leases in %2

This debug message is logged when the allocation engine completes reclamation of a set of expired leases. The maximum number of leases to be reclaimed in a single pass of the lease reclamation routine is configurable using ‘max-reclaim-leases’ parameter. However, the number of reclaimed leases may also be limited by the timeout value, configured with ‘max-reclaim-time’. The message includes the number of reclaimed leases and the total time.

ALLOC_ENGINE_V6_LEASES_RECLAMATION_SLOW

expired leases still exist after %1 reclamations

This warning message is issued when the server has been unable to reclaim all expired leases in a specified number of consecutive attempts. This indicates that the value of “reclaim-timer-wait-time” may be too high. However, if this is just a short burst of leases’ expirations the value does not have to be modified and the server should deal with this in subsequent reclamation attempts. If this is a result of a permanent increase of the server load, the value of “reclaim-timer-wait-time” should be decreased, or the values of “max-reclaim-leases” and “max-reclaim-time” should be increased to allow processing more leases in a single cycle. Alternatively, these values may be set to 0 to remove the limitations on the number of leases and duration. However, this may result in longer periods of server’s unresponsiveness to DHCP packets, while it processes the expired leases.

ALLOC_ENGINE_V6_LEASES_RECLAMATION_START

starting reclamation of expired leases (limit = %1 leases or %2 milliseconds)

This debug message is issued when the allocation engine starts the reclamation of the expired leases. The maximum number of leases to be reclaimed and the timeout is included in the message. If any of these values is 0, it means “unlimited”.

ALLOC_ENGINE_V6_LEASES_RECLAMATION_TIMEOUT

timeout of %1 ms reached while reclaiming IPv6 leases

This debug message is issued when the allocation engine hits the timeout for performing reclamation of the expired leases. The reclamation will now be interrupted and all leases which haven’t been reclaimed, because of the timeout, will be reclaimed when the next scheduled reclamation is started. The argument is the timeout value expressed in milliseconds.

ALLOC_ENGINE_V6_LEASE_RECLAIM

%1: reclaiming expired lease for prefix %2/%3

This debug message is issued when the server begins reclamation of the expired DHCPv6 lease. The reclaimed lease may either be an address lease or delegated prefix. The first argument provides the client identification information. The other arguments specify the prefix and the prefix length for the lease. The prefix length for address lease is equal to 128.

ALLOC_ENGINE_V6_LEASE_RECLAMATION_FAILED

failed to reclaim the lease %1: %2

This error message is logged when the allocation engine fails to reclaim an expired lease. The reason for the failure is included in the message. The error may be triggered in the lease expiration hook or while performing the operation on the lease database.

ALLOC_ENGINE_V6_NO_MORE_EXPIRED_LEASES

all expired leases have been reclaimed

This debug message is issued when the server reclaims all expired DHCPv6 leases in the database.

ALLOC_ENGINE_V6_RECLAIMED_LEASES_DELETE

begin deletion of reclaimed leases expired more than %1 seconds ago

This debug message is issued when the allocation engine begins deletion of the reclaimed leases which have expired more than a specified number of seconds ago. This operation is triggered periodically according to the “flush-reclaimed-timer-wait-time” parameter. The “hold-reclaimed-time” parameter defines a number of seconds for which the leases are stored before they are removed.

ALLOC_ENGINE_V6_RECLAIMED_LEASES_DELETE_COMPLETE

successfully deleted %1 expired-reclaimed leases

This debug message is issued when the server successfully deletes “expired-reclaimed” leases from the lease database. The number of deleted leases is included in the log message.

ALLOC_ENGINE_V6_RECLAIMED_LEASES_DELETE_FAILED

deletion of expired-reclaimed leases failed: %1

This error message is issued when the deletion of “expired-reclaimed” leases from the database failed. The error message is appended to the log message.

ALLOC_ENGINE_V6_RENEW_HR

allocating leases reserved for the client %1 as a result of Renew

This debug message is issued when the allocation engine tries to allocate reserved leases for the client sending a Renew message. The server will also remove any leases that the client is trying to renew that are not reserved for the client.

ALLOC_ENGINE_V6_RENEW_REMOVE_RESERVED

%1: checking if existing client’s leases are reserved for another client

This message is logged when the allocation engine finds leases for the client and will check if these leases are reserved for another client. If they are, they will not be renewed for the client requesting their renewal. The first argument includes the client identification information.

ALLOC_ENGINE_V6_RENEW_REMOVE_UNRESERVED

dynamically allocating leases for the renewing client %1

This debug message is issued as the allocation engine is trying to dynamically allocate new leases for the renewing client. This is the case when the server couldn’t renew any of the existing client’s leases, e.g. because leased resources are reserved for another client.

ALLOC_ENGINE_V6_REUSE_EXPIRED_LEASE_DATA

%1: reusing expired lease, updated lease information: %2

This message is logged when the allocation engine is reusing an existing lease. The details of the updated lease are printed. The first argument includes the client identification information.

ALLOC_ENGINE_V6_REVOKED_ADDR_LEASE

address %1 was revoked from client %2 as it is reserved for client %3

This informational message is an indication that the specified IPv6 address was used by client A but it is now reserved for client B. Client A has been told to stop using it so that it can be leased to client B. This is a normal occurrence during conflict resolution, which can occur in cases such as the system administrator adding a reservation for an address that is currently in use by another client. The server will fully recover from this situation, but clients will change their addresses.

ALLOC_ENGINE_V6_REVOKED_PREFIX_LEASE

prefix %1/%2 was revoked from client %3 as it is reserved for client %4

This informational message is an indication that the specified IPv6 prefix was used by client A but it is now reserved for client B. Client A has been told to stop using it so that it can be leased to client B. This is a normal occurrence during conflict resolution, which can occur in cases such as the system administrator adding a reservation for an address that is currently in use by another client. The server will fully recover from this situation, but clients will change their prefixes.

ALLOC_ENGINE_V6_REVOKED_SHARED_ADDR_LEASE

address %1 was revoked from client %2 as it is reserved for %3 other clients

This informational message is an indication that the specified IPv6 address was used by client A but it is now reserved for multiple other clients. Client A has been told to stop using it so that it can be leased to one of the clients having the reservation for it. This is a normal occurrence during conflict resolution, which can occur in cases such as the system administrator adding reservations for an address that is currently in use by another client. The server will fully recover from this situation, but clients will change their addresses.

ASIODNS

ASIODNS_FD_ADD_TCP

adding a new TCP server by opened fd %1

A debug message informing about installing a file descriptor as a server. The file descriptor number is noted.

ASIODNS_FD_ADD_UDP

adding a new UDP server by opened fd %1

A debug message informing about installing a file descriptor as a server. The file descriptor number is noted.

ASIODNS_FETCH_COMPLETED

upstream fetch to %1(%2) has now completed

A debug message, this records that the upstream fetch (a query made by the resolver on behalf of its client) to the specified address has completed.

ASIODNS_FETCH_STOPPED

upstream fetch to %1(%2) has been stopped

An external component has requested the halting of an upstream fetch. This is an allowed operation, and the message should only appear if debug is enabled.

ASIODNS_OPEN_SOCKET

error %1 opening %2 socket to %3(%4)

The asynchronous I/O code encountered an error when trying to open a socket of the specified protocol in order to send a message to the target address. The number of the system error that caused the problem is given in the message.

ASIODNS_READ_DATA

error %1 reading %2 data from %3(%4)

The asynchronous I/O code encountered an error when trying to read data from the specified address on the given protocol. The number of the system error that caused the problem is given in the message.

ASIODNS_READ_TIMEOUT

receive timeout while waiting for data from %1(%2)

An upstream fetch from the specified address timed out. This may happen for any number of reasons and is most probably a problem at the remote server or a problem on the network. The message will only appear if debug is enabled.

ASIODNS_SEND_DATA

error %1 sending data using %2 to %3(%4)

The asynchronous I/O code encountered an error when trying to send data to the specified address on the given protocol. The number of the system error that caused the problem is given in the message.

ASIODNS_SYNC_UDP_CLOSE_FAIL

failed to close a DNS/UDP socket: %1

This is the same to ASIODNS_UDP_CLOSE_FAIL but happens on the “synchronous UDP server”, mainly used for the authoritative DNS server daemon.

ASIODNS_TCP_ACCEPT_FAIL

failed to accept TCP DNS connection: %1

Accepting a TCP connection from a DNS client failed due to an error that could happen but should be rare. The reason for the error is included in the log message. The server still keeps accepting new connections, so unless it happens often it’s probably okay to ignore this error. If the shown error indicates something like “too many open files”, it’s probably because the run time environment is too restrictive on this limitation, so consider adjusting the limit using a tool such as ulimit. If you see other types of errors too often, there may be something overlooked; please file a bug report in that case.

ASIODNS_TCP_CLEANUP_CLOSE_FAIL

failed to close a DNS/TCP socket on port cleanup: %1

A TCP DNS server tried to close a TCP socket (one created on accepting a new connection or is already unused) as a step of cleaning up the corresponding listening port, but it failed to do that. This is generally an unexpected event and so is logged as an error. See also the description of ASIODNS_TCP_CLOSE_ACCEPTOR_FAIL.

ASIODNS_TCP_CLOSE_ACCEPTOR_FAIL

failed to close listening TCP socket: %1

A TCP DNS server tried to close a listening TCP socket (for accepting new connections) as a step of cleaning up the corresponding listening port (e.g., on server shutdown or updating port configuration), but it failed to do that. This is generally an unexpected event and so is logged as an error. See ASIODNS_TCP_CLOSE_FAIL on the implication of related system resources.

ASIODNS_TCP_CLOSE_FAIL

failed to close DNS/TCP socket with a client: %1

A TCP DNS server tried to close a TCP socket used to communicate with a client, but it failed to do that. While closing a socket should normally be an error-free operation, there have been known cases where this happened with a “connection reset by peer” error. This might be because of some odd client behavior, such as sending a TCP RST after establishing the connection and before the server closes the socket, but how exactly this could happen seems to be system dependent (i.e, it’s not part of the standard socket API), so it’s difficult to provide a general explanation. In any case, it is believed that an error on closing a socket doesn’t mean leaking system resources (the kernel should clean up any internal resource related to the socket, just reporting an error detected in the close call), but, again, it seems to be system dependent. This message is logged at a debug level as it’s known to happen and could be triggered by a remote node and it would be better to not be too verbose, but you might want to increase the log level and make sure there’s no resource leak or other system level troubles when it’s logged.

ASIODNS_TCP_CLOSE_NORESP_FAIL

failed to close DNS/TCP socket with a client: %1

A TCP DNS server tried to close a TCP socket used to communicate with a client without returning an answer (which normally happens for zone transfer requests), but it failed to do that. See ASIODNS_TCP_CLOSE_FAIL for more details.

ASIODNS_TCP_GETREMOTE_FAIL

failed to get remote address of a DNS TCP connection: %1

A TCP DNS server tried to get the address and port of a remote client on a connected socket but failed. It’s expected to be rare but can still happen. See also ASIODNS_TCP_READLEN_FAIL.

ASIODNS_TCP_READDATA_FAIL

failed to get DNS data on a TCP socket: %1

A TCP DNS server tried to read a DNS message (that follows a 2-byte length field) but failed. It’s expected to be rare but can still happen. See also ASIODNS_TCP_READLEN_FAIL.

ASIODNS_TCP_READLEN_FAIL

failed to get DNS data length on a TCP socket: %1

A TCP DNS server tried to get the length field of a DNS message (the first 2 bytes of a new chunk of data) but failed. This is generally expected to be rare but can still happen, e.g, due to an unexpected reset of the connection. A specific reason for the failure is included in the log message.

ASIODNS_TCP_WRITE_FAIL

failed to send DNS message over a TCP socket: %1

A TCP DNS server tried to send a DNS message to a remote client but failed. It’s expected to be rare but can still happen. See also ASIODNS_TCP_READLEN_FAIL.

ASIODNS_UDP_ASYNC_SEND_FAIL

Error sending UDP packet to %1: %2

The low-level ASIO library reported an error when trying to send a UDP packet in asynchronous UDP mode. This can be any error reported by send_to(), and can indicate problems such as too high a load on the network, or a problem in the underlying library or system. This packet is dropped and will not be sent, but service should resume normally. If you see a single occurrence of this message, it probably does not indicate any significant problem, but if it is logged often, it is probably a good idea to inspect your network traffic.

ASIODNS_UDP_CLOSE_FAIL

failed to close a DNS/UDP socket: %1

A UDP DNS server tried to close its UDP socket, but failed to do that. This is generally an unexpected event and so is logged as an error.

ASIODNS_UDP_RECEIVE_FAIL

failed to receive UDP DNS packet: %1

Receiving a UDP packet from a DNS client failed due to an error that could happen but should be very rare. The server still keeps receiving UDP packets on this socket. The reason for the error is included in the log message. This log message is basically not expected to appear at all in practice; if it does, there may be some system level failure and other system logs may have to be checked.

ASIODNS_UDP_SYNC_RECEIVE_FAIL

failed to receive UDP DNS packet: %1

This is the same to ASIODNS_UDP_RECEIVE_FAIL but happens on the “synchronous UDP server”, mainly used for the authoritative DNS server daemon.

ASIODNS_UDP_SYNC_SEND_FAIL

Error sending UDP packet to %1: %2

The low-level ASIO library reported an error when trying to send a UDP packet in synchronous UDP mode. See ASIODNS_UDP_ASYNC_SEND_FAIL for more information.

ASIODNS_UNKNOWN_ORIGIN

unknown origin for ASIO error code %1 (protocol: %2, address %3)

An internal consistency check on the origin of a message from the asynchronous I/O module failed. This may indicate an internal error; please submit a bug report.

BOOTP

BOOTP_BOOTP_QUERY

recognized a BOOTP query: %1

This debug message is printed when the BOOTP query was recognized. The BOOTP client class was added and the message type set to DHCPREQUEST. The query client and transaction identification are displayed.

BOOTP_LOAD

Bootp hooks library has been loaded

This info message indicates that the Bootp hooks library has been loaded.

BOOTP_PACKET_OPTIONS_SKIPPED

an error unpacking an option, caused subsequent options to be skipped: %1

A debug message issued when an option failed to unpack correctly, making it impossible to unpack the remaining options in the DHCPv4 query. The server will still attempt to service the packet. The sole argument provides a reason for unpacking error.

BOOTP_PACKET_PACK

%1: preparing on-wire format of the packet to be sent

This debug message is issued when the server starts preparing the on-wire format of the packet to be sent back to the client. The argument specifies the client and the transaction identification information.

BOOTP_PACKET_PACK_FAIL

%1: preparing on-wire-format of the packet to be sent failed %2

This error message is issued when preparing an on-wire format of the packet has failed. The first argument identifies the client and the BOOTP transaction. The second argument includes the error string.

BOOTP_PACKET_UNPACK_FAILED

failed to parse query from %1 to %2, received over interface %3, reason: %4

This debug message is issued when received DHCPv4 query is malformed and can’t be parsed by the buffer4_receive callout. The query will be dropped by the server. The first three arguments specify source IP address, destination IP address and the interface. The last argument provides a reason for failure.

COMMAND

COMMAND_ACCEPTOR_START

Starting to accept connections via unix domain socket bound to %1

This informational message is issued when the Kea server starts an acceptor via which it is going to accept new control connections. The acceptor is bound to the endpoint associated with the filename provided as an argument. If starting the acceptor fails, subsequent error messages will provide a reason for failure.

COMMAND_DEREGISTERED

Command %1 deregistered

This debug message indicates that the daemon stopped supporting specified command. This command can no longer be issued. If the command socket is open and this command is issued, the daemon will not be able to process it.

COMMAND_EXTENDED_REGISTERED

Command %1 registered

This debug message indicates that the daemon started supporting specified command. The handler for the registered command includes a parameter holding entire command to be processed.

COMMAND_HTTP_LISTENER_STARTED

Command HTTP listener started with %1 threads, listening on %2:%3

This debug messages is issued when an HTTP listener has been started to accept connections from Command API clients through which commands can be received and responses sent. Arguments detail the number of threads that the listener is using, and the address and port at which it is listening.

COMMAND_HTTP_LISTENER_STOPPED

Command HTTP listener for %1:%2 stopped.

This debug messages is issued when the Command HTTP listener, listening at the given address and port, has completed shutdown.

COMMAND_HTTP_LISTENER_STOPPING

Stopping Command HTTP listener for %1:%2

This debug messages is issued when the Command HTTP listener, listening at the given address and port, has begun to shutdown.

COMMAND_PROCESS_ERROR1

Error while processing command: %1

This warning message indicates that the server encountered an error while processing received command. Additional information will be provided, if available. Additional log messages may provide more details.

COMMAND_PROCESS_ERROR2

Error while processing command: %1

This warning message indicates that the server encountered an error while processing received command. The difference, compared to COMMAND_PROCESS_ERROR1 is that the initial command was well formed and the error occurred during logic processing, not the command parsing. Additional information will be provided, if available. Additional log messages may provide more details.

COMMAND_RECEIVED

Received command ‘%1’

This informational message indicates that a command was received over command socket. The nature of this command and its possible results will be logged with separate messages.

COMMAND_REGISTERED

Command %1 registered

This debug message indicates that the daemon started supporting specified command. If the command socket is open, this command can now be issued.

COMMAND_RESPONSE_ERROR

Server failed to generate response for command: %1

This error message indicates that the server failed to generate response for specified command. This likely indicates a server logic error, as the server is expected to generate valid responses for all commands, even malformed ones.

COMMAND_SOCKET_ACCEPT_FAIL

Failed to accept incoming connection on command socket %1: %2

This error indicates that the server detected incoming connection and executed accept system call on said socket, but this call returned an error. Additional information may be provided by the system as second parameter.

COMMAND_SOCKET_CLOSED_BY_FOREIGN_HOST

Closed command socket %1 by foreign host, %2

This is an information message indicating that the command connection has been closed by a command control client, and whether or not any partially read data was discarded.

COMMAND_SOCKET_CONNECTION_CANCEL_FAIL

Failed to cancel read operation on socket %1: %2

This error message is issued to indicate an error to cancel asynchronous read of the control command over the control socket. The cancel operation is performed when the timeout occurs during communication with a client. The error message includes details about the reason for failure.

COMMAND_SOCKET_CONNECTION_CLOSED

Closed socket %1 for existing command connection

This is a debug message indicating that the socket created for handling client’s connection is closed. This usually means that the client disconnected, but may also mean a timeout.

COMMAND_SOCKET_CONNECTION_CLOSE_FAIL

Failed to close command connection: %1

This error message is issued when an error occurred when closing a command connection and/or removing it from the connections pool. The detailed error is provided as an argument.

COMMAND_SOCKET_CONNECTION_OPENED

Opened socket %1 for incoming command connection

This is a debug message indicating that a new incoming command connection was detected and a dedicated socket was opened for that connection.

COMMAND_SOCKET_CONNECTION_SHUTDOWN_FAIL

Encountered error %1 while trying to gracefully shutdown socket

This message indicates an error while trying to gracefully shutdown command connection. The type of the error is included in the message.

COMMAND_SOCKET_CONNECTION_TIMEOUT

Timeout occurred for connection over socket %1

This is an informational message that indicates that the timeout has occurred for one of the command channel connections. The response sent by the server indicates a timeout and is then closed.

COMMAND_SOCKET_READ

Received %1 bytes over command socket %2

This debug message indicates that specified number of bytes was received over command socket identified by specified file descriptor.

COMMAND_SOCKET_READ_FAIL

Encountered error %1 while reading from command socket %2

This error message indicates that an error was encountered while reading from command socket.

COMMAND_SOCKET_WRITE

Sent response of %1 bytes (%2 bytes left to send) over command socket %3

This debug message indicates that the specified number of bytes was sent over command socket identifier by the specified file descriptor.

COMMAND_SOCKET_WRITE_FAIL

Error while writing to command socket %1 : %2

This error message indicates that an error was encountered while attempting to send a response to the command socket.

COMMAND_WATCH_SOCKET_CLEAR_ERROR

watch socket failed to clear: %1

This error message is issued when the command manager was unable to reset the ready status after completing a send. This is a programmatic error that should be reported. The command manager may or may not continue to operate correctly.

COMMAND_WATCH_SOCKET_CLOSE_ERROR

watch socket failed to close: %1

This error message is issued when command manager attempted to close the socket used for indicating the ready status for send operations. This should not have any negative impact on the operation of the command manager as it happens when the connection is being terminated.

CTRL

CTRL_AGENT_COMMAND_FORWARDED

command %1 successfully forwarded to the service %2 from remote address %3

This informational message is issued when the CA successfully forwards the control message to the specified Kea service and receives a response.

CTRL_AGENT_COMMAND_FORWARD_BEGIN

begin forwarding command %1 to service %2

This debug message is issued when the Control Agent starts forwarding a received command to one of the Kea servers.

CTRL_AGENT_COMMAND_FORWARD_FAILED

failed forwarding command %1: %2

This debug message is issued when the Control Agent failed forwarding a received command to one of the Kea servers. The second argument provides the details of the error.

CTRL_AGENT_COMMAND_RECEIVED

command %1 received from remote address %2

This informational message is issued when the CA receives a control message, whether it is destined to the control agent itself, or to be forwarded on.

CTRL_AGENT_CONFIG_CHECK_FAIL

Control Agent configuration check failed: %1

This error message indicates that the CA had failed configuration check. Details are provided. Additional details may be available in earlier log entries, possibly on lower levels.

CTRL_AGENT_CONFIG_FAIL

Control Agent configuration failed: %1

This error message indicates that the CA had failed configuration attempt. Details are provided. Additional details may be available in earlier log entries, possibly on lower levels.

CTRL_AGENT_CONFIG_SYNTAX_WARNING

Control Agent configuration syntax warning: %1

This warning message indicates that the CA configuration had a minor syntax error. The error was displayed and the configuration parsing resumed.

CTRL_AGENT_FAILED

application experienced a fatal error: %1

This is a fatal error message issued when the Control Agent application encounters an unrecoverable error from within the event loop.

CTRL_AGENT_HTTPS_SERVICE_STARTED

HTTPS service bound to address %1:%2

This informational message indicates that the server has started HTTPS service on the specified address and port. All control commands should be sent to this address and port over a TLS channel.

CTRL_AGENT_HTTP_SERVICE_STARTED

HTTP service bound to address %1:%2

This informational message indicates that the server has started HTTP service on the specified address and port. All control commands should be sent to this address and port.

CTRL_AGENT_RUN_EXIT

application is exiting the event loop

This is a debug message issued when the Control Agent exits its event loop.

DATABASE

DATABASE_INVALID_ACCESS

invalid database access string: %1

This is logged when an attempt has been made to parse a database access string and the attempt ended in error. The access string in question - which should be of the form ‘keyword=value keyword=value…’ is included in the message.

DATABASE_MYSQL_COMMIT

committing to MySQL database

The code has issued a commit call. All outstanding transactions will be committed to the database. Note that depending on the MySQL settings, the committal may not include a write to disk.

DATABASE_MYSQL_FATAL_ERROR

Unrecoverable MySQL error occurred: %1 for <%2>, reason: %3 (error code: %4).

An error message indicating that communication with the MySQL database server has been lost. If automatic recovery has been enabled, then the server will attempt to recover connectivity. If not, then the server will exit with a non-zero exit code. The cause of such an error is most likely a network issue or the MySQL server has gone down.

DATABASE_MYSQL_ROLLBACK

rolling back MySQL database

The code has issued a rollback call. All outstanding transaction will be rolled back and not committed to the database.

DATABASE_MYSQL_START_TRANSACTION

starting new MySQL transaction

A debug message issued when a new MySQL transaction is being started. This message is typically not issued when inserting data into a single table because the server doesn’t explicitly start transactions in this case. This message is issued when data is inserted into multiple tables with multiple INSERT statements and there may be a need to rollback the whole transaction if any of these INSERT statements fail.

DATABASE_PGSQL_COMMIT

committing to PostgreSQL database

The code has issued a commit call. All outstanding transactions will be committed to the database. Note that depending on the PostgreSQL settings, the committal may not include a write to disk.

DATABASE_PGSQL_CREATE_SAVEPOINT

creating a new PostgreSQL savepoint: %1

The code is issuing a call to create a savepoint within the current transaction. Database modifications made up to this point will be preserved should a subsequent call to rollback to this savepoint occurs prior to the transaction being committed.

DATABASE_PGSQL_DEALLOC_ERROR

An error occurred deallocating SQL statements while closing the PostgreSQL lease database: %1

This is an error message issued when a DHCP server (either V4 or V6) experienced and error freeing database SQL resources as part of closing its connection to the PostgreSQL database. The connection is closed as part of normal server shutdown. This error is most likely a programmatic issue that is highly unlikely to occur or negatively impact server operation.

DATABASE_PGSQL_FATAL_ERROR

Unrecoverable PostgreSQL error occurred: Statement: <%1>, reason: %2 (error code: %3).

An error message indicating that communication with the PostgreSQL database server has been lost. If automatic recovery has been enabled, then the server will attempt to recover the connectivity. If not, then the server will exit with a non-zero exit code. The cause of such an error is most likely a network issue or the PostgreSQL server has gone down.

DATABASE_PGSQL_ROLLBACK

rolling back PostgreSQL database

The code has issued a rollback call. All outstanding transaction will be rolled back and not committed to the database.

DATABASE_PGSQL_ROLLBACK_SAVEPOINT

rolling back PostgreSQL database to savepoint: $1

The code is issuing a call to rollback to the given savepoint. Any database modifications that were made after the savepoint was created will be rolled back and not committed to the database.

DATABASE_PGSQL_START_TRANSACTION

starting a new PostgreSQL transaction

A debug message issued when a new PostgreSQL transaction is being started. This message is typically not issued when inserting data into a single table because the server doesn’t explicitly start transactions in this case. This message is issued when data is inserted into multiple tables with multiple INSERT statements and there may be a need to rollback the whole transaction if any of these INSERT statements fail.

DCTL

DCTL_ALREADY_RUNNING

%1 already running? %2

This is an error message that occurs when a module encounters a pre-existing PID file which contains the PID of a running process. This most likely indicates an attempt to start a second instance of a module using the same configuration file. It is possible, though unlikely, that the PID file is a remnant left behind by a server crash or power failure and the PID it contains refers to a process other than Kea process. In such an event, it would be necessary to manually remove the PID file. The first argument is the process name, the second contains the PID and PID file.

DCTL_CCSESSION_ENDING

%1 ending control channel session

This debug message is issued just before the controller attempts to disconnect from its session with the Kea control channel.

DCTL_CFG_FILE_RELOAD_ERROR

configuration reload failed: %1, reverting to current configuration.

This is an error message indicating that the application attempted to reload its configuration from file and encountered an error. This is likely due to invalid content in the configuration file. The application should continue to operate under its current configuration.

DCTL_CFG_FILE_RELOAD_SIGNAL_RECVD

OS signal %1 received, reloading configuration from file: %2

This is an informational message indicating the application has received a signal instructing it to reload its configuration from file.

DCTL_COMMAND_RECEIVED

%1 received command: %2, arguments: %3

A debug message listing the command (and possible arguments) received from the Kea control system by the controller.

DCTL_CONFIG_CHECK_COMPLETE

server has completed configuration check: %1, result: %2

This is an informational message announcing the successful processing of a new configuration check is complete. The result of that check is printed. This informational message is printed when configuration check is requested.

DCTL_CONFIG_COMPLETE

server has completed configuration: %1

This is an informational message announcing the successful processing of a new configuration. It is output during server startup, and when an updated configuration is committed by the administrator. Additional information may be provided.

DCTL_CONFIG_DEPRECATED

server configuration includes a deprecated object: %1

This error message is issued when the configuration includes a deprecated object (i.e. a top level element) which will be ignored.

DCTL_CONFIG_FETCH

Fetching configuration data from config backends.

This is an informational message emitted when the Kea server is about to begin retrieving configuration data from one or more configuration backends.

DCTL_CONFIG_FILE_LOAD_FAIL

%1 reason: %2

This fatal error message indicates that the application attempted to load its initial configuration from file and has failed. The service will exit.

DCTL_CONFIG_LOAD_FAIL

%1 configuration failed to load: %2

This critical error message indicates that the initial application configuration has failed. The service will start, but will not process requests until the configuration has been corrected.

DCTL_CONFIG_START

parsing new configuration: %1

A debug message indicating that the application process has received an updated configuration and has passed it to its configuration manager for parsing.

DCTL_CONFIG_STUB

%1 configuration stub handler called

This debug message is issued when the dummy handler for configuration events is called. This only happens during initial startup.

DCTL_CONFIG_UPDATE

%1 updated configuration received: %2

A debug message indicating that the controller has received an updated configuration from the Kea configuration system.

DCTL_DEVELOPMENT_VERSION

This software is a development branch of Kea. It is not recommended for production use.

This warning message is displayed when the version is a development (vs stable) one: the second number of the version is odd.

DCTL_INIT_PROCESS

%1 initializing the application

This debug message is issued just before the controller attempts to create and initialize its application instance.

DCTL_INIT_PROCESS_FAIL

%1 application initialization failed: %2

This error message is issued if the controller could not initialize the application and will exit.

DCTL_NOT_RUNNING

%1 application instance is not running

A warning message is issued when an attempt is made to shut down the application when it is not running.

DCTL_OPEN_CONFIG_DB

Opening configuration database: %1

This message is printed when the Kea server is attempting to open a configuration database. The database access string with password redacted is logged.

DCTL_PARSER_FAIL

: %1

On receipt of a new configuration, the server failed to create a parser to decode the contents of the named configuration element, or the creation succeeded but the parsing actions and committal of changes failed. The reason for the failure is given in the message.

DCTL_PID_FILE_ERROR

%1 could not create a PID file: %2

This is an error message that occurs when the server is unable to create its PID file. The log message should contain details sufficient to determine the underlying cause. The most likely culprits are that some portion of the pathname does not exist or a permissions issue. The default path is determined by –localstatedir or –runstatedir configure parameters but may be overridden by setting environment variable, KEA_PIDFILE_DIR. The first argument is the process name.

DCTL_PROCESS_FAILED

%1 application execution failed: %2

The controller has encountered a fatal error while running the application and is terminating. The reason for the failure is included in the message.

DCTL_RUN_PROCESS

%1 starting application event loop

This debug message is issued just before the controller invokes the application run method.

DCTL_SESSION_FAIL

%1 controller failed to establish Kea session: %1

The controller has failed to establish communication with the rest of Kea and will exit.

DCTL_SHUTDOWN

%1 has shut down, pid: %2, version: %3

This is an informational message indicating that the service has shut down. The argument specifies a name of the service.

DCTL_SHUTDOWN_SIGNAL_RECVD

OS signal %1 received, starting shutdown

This is a debug message indicating the application has received a signal instructing it to shutdown.

DCTL_STANDALONE

%1 skipping message queue, running standalone

This is a debug message indicating that the controller is running in the application in standalone mode. This means it will not connected to the Kea message queue. Standalone mode is only useful during program development, and should not be used in a production environment.

DCTL_STARTING

%1 starting, pid: %2, version: %3 (%4)

This is an informational message issued when controller for the service first starts. Version is also reported.

DCTL_UNLOAD_LIBRARIES_ERROR

error unloading hooks libraries during shutdown: %1

This error message indicates that during shutdown, unloading hooks libraries failed to close them. If the list of libraries is empty it is a programmatic error in the server code. If it is not empty it could be a programmatic error in one of the hooks libraries which could lead to a crash during finalization.

DHCP4

DHCP4_ACTIVATE_INTERFACE

activating interface %1

This message is printed when DHCPv4 server enabled an interface to be used to receive DHCPv4 traffic. IPv4 socket on this interface will be opened once Interface Manager starts up procedure of opening sockets.

DHCP4_ALREADY_RUNNING

%1 already running? %2

This is an error message that occurs when the DHCPv4 server encounters a pre-existing PID file which contains the PID of a running process. This most likely indicates an attempt to start a second instance of the server using the same configuration file. It is possible, though unlikely that the PID file is a remnant left behind by a server crash or power failure and the PID it contains refers to a process other than the server. In such an event, it would be necessary to manually remove the PID file. The first argument is the DHCPv4 process name, the second contains the PID and PID file.

DHCP4_BUFFER_RECEIVED

received buffer from %1:%2 to %3:%4 over interface %5

This debug message is logged when the server has received a packet over the socket. When the message is logged the contents of the received packet hasn’t been parsed yet. The only available information is the interface and the source and destination IPv4 addresses/ports.

DHCP4_BUFFER_RECEIVE_FAIL

error on attempt to receive packet: %1

The DHCPv4 server tried to receive a packet but an error occurred during this attempt. The reason for the error is included in the message.

DHCP4_BUFFER_UNPACK

parsing buffer received from %1 to %2 over interface %3

This debug message is issued when the server starts parsing the received buffer holding the DHCPv4 message. The arguments specify the source and destination IPv4 addresses as well as the interface over which the buffer has been received.

DHCP4_BUFFER_WAIT_SIGNAL

signal received while waiting for next packet

This debug message is issued when the server was waiting for the packet, but the wait has been interrupted by the signal received by the process. The signal will be handled before the server starts waiting for next packets.

DHCP4_CB_ON_DEMAND_FETCH_UPDATES_FAIL

error on demand attempt to fetch configuration updates from the configuration backend(s): %1

This error message is issued when the server attempted to fetch configuration updates from the database and this on demand attempt failed. The sole argument which is returned to the config-backend-pull command caller too contains the reason for failure.

DHCP4_CB_PERIODIC_FETCH_UPDATES_FAIL

error on periodic attempt to fetch configuration updates from the configuration backend(s): %1

This error message is issued when the server attempted to fetch configuration updates from the database and this periodic attempt failed. The server will re-try according to the configured value of the config-fetch-wait-time parameter. The sole argument contains the reason for failure.

DHCP4_CB_PERIODIC_FETCH_UPDATES_RETRIES_EXHAUSTED

maximum number of configuration fetch attempts: 10, has been exhausted without success

This error indicates that the server has made a number of unsuccessful periodic attempts to fetch configuration updates from a configuration backend. The server will continue to operate but won’t make any further attempts to fetch configuration updates. The administrator must fix the configuration in the database and reload (or restart) the server.

DHCP4_CLASS_ASSIGNED

%1: client packet has been assigned to the following class(es): %2

This debug message informs that incoming packet has been assigned to specified class or classes. This is a normal behavior and indicates successful operation. The first argument specifies the client and transaction identification information. The second argument includes all classes to which the packet has been assigned.

DHCP4_CLASS_UNCONFIGURED

%1: client packet belongs to an unconfigured class: %2

This debug message informs that incoming packet belongs to a class which cannot be found in the configuration. Either a hook written before the classification was added to Kea is used, or class naming is inconsistent.

DHCP4_CLASS_UNDEFINED

required class %1 has no definition

This debug message informs that a class is listed for required evaluation but has no definition.

DHCP4_CLASS_UNTESTABLE

required class %1 has no test expression

This debug message informs that a class was listed for required evaluation but its definition does not include a test expression to evaluate.

DHCP4_CLIENTID_IGNORED_FOR_LEASES

%1: not using client identifier for lease allocation for subnet %2

This debug message is issued when the server is processing the DHCPv4 message for which client identifier will not be used when allocating new lease or renewing existing lease. The server is explicitly configured to not use client identifier to lookup existing leases for the client and will not record client identifier in the lease database. This mode of operation is useful when clients don’t use stable client identifiers, e.g. multi stage booting. The first argument includes the client and transaction identification information. The second argument specifies the identifier of the subnet where the client is connected and for which this mode of operation is configured on the server.

DHCP4_CLIENT_FQDN_DATA

%1: Client sent FQDN option: %2

This debug message includes the detailed information extracted from the Client FQDN option sent in the query. The first argument includes the client and transaction identification information. The second argument specifies the detailed information about the FQDN option received by the server.

DHCP4_CLIENT_FQDN_PROCESS

%1: processing Client FQDN option

This debug message is issued when the server starts processing the Client FQDN option sent in the client’s query. The argument includes the client and transaction identification information.

DHCP4_CLIENT_HOSTNAME_DATA

%1: client sent Hostname option: %2

This debug message includes the detailed information extracted from the Hostname option sent in the query. The first argument includes the client and transaction identification information. The second argument specifies the hostname carried in the Hostname option sent by the client.

DHCP4_CLIENT_HOSTNAME_MALFORMED

%1: client hostname option malformed: %2

This debug message is issued when the DHCP server was unable to process the the hostname option sent by the client because the content is malformed. The first argument includes the client and transaction identification information. The second argument contains a description of the data error.

DHCP4_CLIENT_HOSTNAME_PROCESS

%1: processing client’s Hostname option

This debug message is issued when the server starts processing the Hostname option sent in the client’s query. The argument includes the client and transaction identification information.

DHCP4_CLIENT_NAME_PROC_FAIL

%1: failed to process the fqdn or hostname sent by a client: %2

This debug message is issued when the DHCP server was unable to process the FQDN or Hostname option sent by a client. This is likely because the client’s name was malformed or due to internal server error. The first argument contains the client and transaction identification information. The second argument holds the detailed description of the error.

DHCP4_COMMAND_RECEIVED

received command %1, arguments: %2

A debug message listing the command (and possible arguments) received from the Kea control system by the DHCPv4 server.

DHCP4_CONFIG_COMPLETE

DHCPv4 server has completed configuration: %1

This is an informational message announcing the successful processing of a new configuration. It is output during server startup, and when an updated configuration is committed by the administrator. Additional information may be provided.

DHCP4_CONFIG_FETCH

Fetching configuration data from config backends.

This is an informational message emitted when the DHCPv4 server about to begin retrieving configuration data from one or more configuration backends.

DHCP4_CONFIG_LOAD_FAIL

configuration error using file: %1, reason: %2

This error message indicates that the DHCPv4 configuration has failed. If this is an initial configuration (during server’s startup) the server will fail to start. If this is a dynamic reconfiguration attempt the server will continue to use an old configuration.

DHCP4_CONFIG_NEW_SUBNET

a new subnet has been added to configuration: %1

This is an informational message reporting that the configuration has been extended to include the specified IPv4 subnet.

DHCP4_CONFIG_OPTION_DUPLICATE

multiple options with the code %1 added to the subnet %2

This warning message is issued on an attempt to configure multiple options with the same option code for a particular subnet. Adding multiple options is uncommon for DHCPv4, but is not prohibited.

DHCP4_CONFIG_PACKET_QUEUE

DHCPv4 packet queue info after configuration: %1

This informational message is emitted during DHCPv4 server configuration, immediately after configuring the DHCPv4 packet queue. The information shown depends upon the packet queue type selected.

DHCP4_CONFIG_RECEIVED

received configuration %1

A debug message listing the configuration received by the DHCPv4 server. The source of that configuration depends on used configuration backend.

DHCP4_CONFIG_START

DHCPv4 server is processing the following configuration: %1

This is a debug message that is issued every time the server receives a configuration. That happens at start up and also when a server configuration change is committed by the administrator.

DHCP4_CONFIG_SYNTAX_WARNING

configuration syntax warning: %1

This warning message indicates that the DHCPv4 configuration had a minor syntax error. The error was displayed and the configuration parsing resumed.

DHCP4_CONFIG_UNRECOVERABLE_ERROR

DHCPv4 server new configuration failed with an error which cannot be recovered

This fatal error message is issued when a new configuration raised an error which cannot be recovered. A correct configuration must be applied as soon as possible as the server is no longer working. The configuration can be fixed in several ways. If the control channel is open, config-set with a valid configuration can be used. Alternatively, the original config file on disk could be fixed and SIGHUP signal could be sent (or the config-reload command issued). Finally, the server could be restarted completely.

DHCP4_CONFIG_UNSUPPORTED_OBJECT

DHCPv4 server configuration includes an unsupported object: %1

This error message is issued when the configuration includes an unsupported object (i.e. a top level element).

DHCP4_CONFIG_UPDATE

updated configuration received: %1

A debug message indicating that the DHCPv4 server has received an updated configuration from the Kea configuration system.

DHCP4_DB_RECONNECT_DISABLED

database reconnect is disabled: max-reconnect-tries %1, reconnect-wait-time %2

This is an informational message indicating that connectivity to either the lease or host database or both and that automatic reconnect is not enabled.

DHCP4_DB_RECONNECT_FAILED

maximum number of database reconnect attempts: %1, has been exhausted without success

This error indicates that the server failed to reconnect to the lease and/or host database(s) after making the maximum configured number of reconnect attempts. This might cause the server to shut down as specified in the configuration. Loss of connectivity is typically a network or database server issue.

DHCP4_DB_RECONNECT_LOST_CONNECTION

database connection lost.

This info message indicates that the connection has been lost and the dhcp service might have been disabled, as specified in the configuration, in order to try to recover the connection.

DHCP4_DB_RECONNECT_NO_DB_CTL

unexpected error in database reconnect

This is an error message indicating a programmatic error that should not occur. It prohibits the server from attempting to reconnect to its databases if connectivity is lost, and the server exits. This error should be reported.

DHCP4_DB_RECONNECT_SUCCEEDED

database connection recovered.

This info message indicates that the connection has been recovered and the dhcp service has been restored.

DHCP4_DDNS_REQUEST_SEND_FAILED

failed sending a request to kea-dhcp-ddns, error: %1, ncr: %2

This error message indicates that DHCP4 server attempted to send a DDNS update request to the DHCP-DDNS server. This is most likely a configuration or networking error.

DHCP4_DEACTIVATE_INTERFACE

deactivate interface %1

This message is printed when DHCPv4 server disables an interface from being used to receive DHCPv4 traffic. Sockets on this interface will not be opened by the Interface Manager until interface is enabled.

DHCP4_DECLINE_FAIL

%1: error on decline lease for address %2: %3

This error message indicates that the software failed to decline a lease from the lease database due to an error during a database operation. The first argument includes the client and the transaction identification information. The second argument holds the IPv4 address which decline was attempted. The last one contains the reason for failure.

DHCP4_DECLINE_LEASE

Received DHCPDECLINE for addr %1 from client %2. The lease will be unavailable for %3 seconds.

This informational message is printed when a client received an address, but discovered that it is being used by some other device and notified the server by sending a DHCPDECLINE message. The server checked that this address really was leased to the client and marked this address as unusable for a certain amount of time. This message may indicate a misconfiguration in a network, as there is either a buggy client or more likely a device that is using an address that it is not supposed to. The server will fully recover from this situation, but if the underlying problem of a misconfigured or rogue device is not solved, this address may be declined again in the future.

DHCP4_DECLINE_LEASE_MISMATCH

Received DHCPDECLINE for addr %1 from client %2, but the data doesn’t match: received hwaddr: %3, lease hwaddr: %4, received client-id: %5, lease client-id: %6

This informational message means that a client attempted to report his address as declined (i.e. used by unknown entity). The server has information about a lease for that address, but the client’s hardware address or client identifier does not match the server’s stored information. The client’s request will be ignored.

DHCP4_DECLINE_LEASE_NOT_FOUND

Received DHCPDECLINE for addr %1 from client %2, but no such lease found.

This warning message indicates that a client reported that his address was detected as a duplicate (i.e. another device in the network is using this address). However, the server does not have a record for this address. This may indicate a client’s error or a server’s purged database.

DHCP4_DEFERRED_OPTION_MISSING

can find deferred option code %1 in the query

This debug message is printed when a deferred option cannot be found in the query.

DHCP4_DEFERRED_OPTION_UNPACK_FAIL

An error unpacking the deferred option %1: %2

A debug message issued when deferred unpacking of an option failed, making it to be left unpacked in the packet. The first argument is the option code, the second the error.

DHCP4_DEVELOPMENT_VERSION

This software is a development branch of Kea. It is not recommended for production use.

This warning message is displayed when the version is a development (vs stable) one: the second number of the version is odd.

DHCP4_DHCP4O6_BAD_PACKET

received malformed DHCPv4o6 packet: %1

A malformed DHCPv4o6 packet was received.

DHCP4_DHCP4O6_PACKET_RECEIVED

received DHCPv4o6 packet from DHCPv4 server (type %1) for %2 on interface %3

This debug message is printed when the server is receiving a DHCPv4o6 from the DHCPv4 server over inter-process communication.

DHCP4_DHCP4O6_PACKET_SEND

%1: trying to send packet %2 (type %3) to %4 port %5 on interface %6 encapsulating %7: %8 (type %9)

The arguments specify the client identification information (HW address and client identifier), DHCPv6 message name and type, source IPv6 address and port, and interface name, DHCPv4 client identification, message name and type.

DHCP4_DHCP4O6_PACKET_SEND_FAIL

%1: failed to send DHCPv4o6 packet: %2

This error is output if the IPv4 DHCP server fails to send an DHCPv4o6 message to the IPv6 DHCP server. The reason for the error is included in the message.

DHCP4_DHCP4O6_RECEIVE_FAIL

failed to receive DHCPv4o6: %1

This debug message indicates the inter-process communication with the DHCPv6 server failed. The reason for the error is included in the message.

DHCP4_DHCP4O6_RECEIVING

receiving DHCPv4o6 packet from DHCPv6 server

This debug message is printed when the server is receiving a DHCPv4o6 from the DHCPv6 server over inter-process communication socket.

DHCP4_DHCP4O6_RESPONSE_DATA

%1: responding with packet %2 (type %3), packet details: %4

A debug message including the detailed data about the packet being sent to the DHCPv6 server to be forwarded to the client. The first argument contains the client and the transaction identification information. The second and third argument contains the packet name and type respectively. The fourth argument contains detailed packet information.

DHCP4_DYNAMIC_RECONFIGURATION

initiate server reconfiguration using file: %1, after receiving SIGHUP signal or config-reload command

This is the info message logged when the DHCPv4 server starts reconfiguration as a result of receiving SIGHUP signal or config-reload command.

DHCP4_DYNAMIC_RECONFIGURATION_FAIL

dynamic server reconfiguration failed with file: %1

This is a fatal error message logged when the dynamic reconfiguration of the DHCP server failed.

DHCP4_DYNAMIC_RECONFIGURATION_SUCCESS

dynamic server reconfiguration succeeded with file: %1

This is info message logged when the dynamic reconfiguration of the DHCP server succeeded.

DHCP4_EMPTY_HOSTNAME

%1: received empty hostname from the client, skipping processing of this option

This debug message is issued when the server received an empty Hostname option from a client. Server does not process empty Hostname options and therefore option is skipped. The argument holds the client and transaction identification information.

DHCP4_FLEX_ID

flexible identifier generated for incoming packet: %1

This debug message is printed when host reservation type is set to flexible identifier and the expression specified in its configuration generated (was evaluated to) an identifier for incoming packet. This debug message is mainly intended as a debugging assistance for flexible identifier.

DHCP4_GENERATE_FQDN

%1: client did not send a FQDN or hostname; FQDN will be generated for the client

This debug message is issued when the server did not receive a Hostname option from the client and hostname generation is enabled. This provides a means to create DNS entries for unsophisticated clients.

DHCP4_HANDLE_SIGNAL_EXCEPTION

An exception was thrown while handing signal: %1

This error message is printed when an ISC or standard exception was raised during signal processing. This likely indicates a coding error and should be reported to ISC.

DHCP4_HOOKS_LIBS_RELOAD_FAIL

reload of hooks libraries failed

A “libreload” command was issued to reload the hooks libraries but for some reason the reload failed. Other error messages issued from the hooks framework will indicate the nature of the problem.

DHCP4_HOOK_BUFFER_RCVD_DROP

received buffer from %1 to %2 over interface %3 was dropped because a callout set the drop flag

This debug message is printed when a callout installed on buffer4_receive hook point set the drop flag. For this particular hook point, the setting of the flag by a callout instructs the server to drop the packet. The arguments specify the source and destination IPv4 address as well as the name of the interface over which the buffer has been received.

DHCP4_HOOK_BUFFER_RCVD_SKIP

received buffer from %1 to %2 over interface %3 is not parsed because a callout set the next step to SKIP.

This debug message is printed when a callout installed on buffer4_receive hook point set the next step to SKIP. For this particular hook point, this value set by a callout instructs the server to not parse the buffer because it was already parsed by the hook. The arguments specify the source and destination IPv4 address as well as the name of the interface over which the buffer has been received.

DHCP4_HOOK_BUFFER_SEND_SKIP

%1: prepared response is dropped because a callout set the next step to SKIP.

This debug message is printed when a callout installed on buffer4_send hook point set the next step to SKIP. For this particular hook point, the SKIP value set by a callout instructs the server to drop the packet. Server completed all the processing (e.g. may have assigned, updated or released leases), but the response will not be send to the client.

DHCP4_HOOK_DDNS_UPDATE

A hook has updated the DDNS parameters: hostname %1=>%2, forward update %3=>%4, reverse update %5=>%6

This message indicates that there was a hook called on ddns4_update hook point and that hook updated the DDNS update parameters: hostname, or whether to conduct forward (A record) or reverse (PTR record) DDNS updates.

DHCP4_HOOK_DECLINE_SKIP

Decline4 hook callouts set status to DROP, ignoring packet.

This message indicates that the server received DHCPDECLINE message, it was verified to be correct and matching server’s lease information. The server called hooks for decline4 hook point and one of the callouts set next step status to DROP. The server will now abort processing of the packet as if it was never received. The lease will continue to be assigned to this client.

DHCP4_HOOK_LEASE4_RELEASE_SKIP

%1: lease was not released because a callout set the next step to SKIP

This debug message is printed when a callout installed on lease4_release hook point set the next step status to SKIP. For this particular hook point, the value set by a callout instructs the server to not release a lease.

DHCP4_HOOK_LEASES4_COMMITTED_DROP

%1: packet is dropped, because a callout set the next step to DROP

This debug message is printed when a callout installed on the leases4_committed hook point sets the next step to DROP.

DHCP4_HOOK_LEASES4_COMMITTED_PARK

%1: packet is parked, because a callout set the next step to PARK

This debug message is printed when a callout installed on the leases4_committed hook point sets the next step to PARK.

DHCP4_HOOK_LEASES4_PARKING_LOT_FULL

The parked-packet-limit %1, has been reached, dropping query: %2

This debug message occurs when the parking lot used to hold client queries while hook library work for them completes has reached or exceeded the limit set by the parked-packet-limit global parameter. This can occur when kea-dhcp4 is using hook libraries (e.g. HA) that implement the “leases4-committed” callout and client queries are arriving faster than those callouts can fulfill them.

DHCP4_HOOK_PACKET_RCVD_SKIP

%1: packet is dropped, because a callout set the next step to SKIP

This debug message is printed when a callout installed on the pkt4_receive hook point sets the next step to SKIP. For this particular hook point, the value setting of the flag instructs the server to drop the packet.

DHCP4_HOOK_PACKET_SEND_DROP

%1: prepared DHCPv4 response was not sent because a callout set the next ste to DROP

This debug message is printed when a callout installed on the pkt4_send hook point set the next step to DROP. For this particular hook point, the setting of the value by a callout instructs the server to drop the packet. This effectively means that the client will not get any response, even though the server processed client’s request and acted on it (e.g. possibly allocated a lease). The argument specifies the client and transaction identification information.

DHCP4_HOOK_PACKET_SEND_SKIP

%1: prepared response is not sent, because a callout set the next stp to SKIP

This debug message is printed when a callout installed on the pkt4_send hook point sets the next step to SKIP. For this particular hook point, this setting instructs the server to drop the packet. This means that the client will not get any response, even though the server processed client’s request and acted on it (e.g. possibly allocated a lease).

DHCP4_HOOK_SUBNET4_SELECT_DROP

%1: packet was dropped, because a callout set the next step to ‘drop’

This debug message is printed when a callout installed on the subnet4_select hook point sets the next step to ‘drop’ value. For this particular hook point, the setting to that value instructs the server to drop the received packet. The argument specifies the client and transaction identification information.

DHCP4_HOOK_SUBNET4_SELECT_SKIP

%1: no subnet was selected, because a callout set the next skip flag

This debug message is printed when a callout installed on the subnet4_select hook point sets the next step to SKIP value. For this particular hook point, the setting of the flag instructs the server not to choose a subnet, an action that severely limits further processing; the server will be only able to offer global options - no addresses will be assigned. The argument specifies the client and transaction identification information.

DHCP4_INFORM_DIRECT_REPLY

%1: DHCPACK in reply to the DHCPINFORM will be sent directly to %2 over %3

This debug message is issued when the DHCPACK will be sent directly to the client, rather than via a relay. The first argument contains the client and transaction identification information. The second argument contains the client’s IPv4 address to which the response will be sent. The third argument contains the local interface name.

DHCP4_INIT_FAIL

failed to initialize Kea server: %1

The server has failed to initialize. This may be because the configuration was not successful, or it encountered any other critical error on startup. Attached error message provides more details about the issue.

DHCP4_INIT_REBOOT

%1: client is in INIT-REBOOT state and requests address %2

This informational message is issued when the client is in the INIT-REBOOT state and is requesting an IPv4 address it is using to be allocated for it. The first argument includes the client and transaction identification information. The second argument specifies the requested IPv4 address.

DHCP4_LEASE_ADVERT

%1: lease %2 will be advertised

This informational message indicates that the server has found the lease to be offered to the client. It is up to the client to choose one server out of those which offered leases and continue allocation with that server. The first argument specifies the client and the transaction identification information. The second argument specifies the IPv4 address to be offered.

DHCP4_LEASE_ALLOC

%1: lease %2 has been allocated for %3 seconds

This informational message indicates that the server successfully granted a lease in response to client’s DHCPREQUEST message. The lease information will be sent to the client in the DHCPACK message. The first argument contains the client and the transaction identification information. The second argument contains the allocated IPv4 address. The third argument is the validity lifetime.

DHCP4_LEASE_REUSE

%1: lease %2 has been reused for %3 seconds

This informational message indicates that the server successfully reused a lease in response to client’s message. The lease information will be sent to the client in the DHCPACK message. The first argument contains the client and the transaction identification information. The second argument contains the allocated IPv4 address. The third argument is the validity lifetime.

DHCP4_MULTI_THREADING_INFO

enabled: %1, number of threads: %2, queue size: %3

This is a message listing some information about the multi-threading parameters with which the server is running.

DHCP4_NCR_CREATION_FAILED

%1: failed to generate name change requests for DNS: %2

This message indicates that server was unable to generate NameChangeRequests which should be sent to the kea-dhcp_ddns module to create new DNS records for the lease being acquired or to update existing records for the renewed lease. The first argument contains the client and transaction identification information. The second argument includes the reason for the failure.

DHCP4_NOT_RUNNING

DHCPv4 server is not running

A warning message is issued when an attempt is made to shut down the DHCPv4 server but it is not running.

DHCP4_NO_LEASE_INIT_REBOOT

%1: no lease for address %2 requested by INIT-REBOOT client

This debug message is issued when the client being in the INIT-REBOOT state requested an IPv4 address but this client is unknown. The server will not respond. The first argument includes the client and the transaction id identification information. The second argument includes the IPv4 address requested by the client.

DHCP4_NO_SOCKETS_OPEN

no interface configured to listen to DHCP traffic

This warning message is issued when current server configuration specifies no interfaces that server should listen on, or specified interfaces are not configured to receive the traffic.

DHCP4_OPEN_CONFIG_DB

Opening configuration database: %1

This message is printed when the DHCPv4 server is attempting to open a configuration database. The database access string with password redacted is logged.

DHCP4_OPEN_SOCKET

opening service sockets on port %1

A debug message issued during startup, this indicates that the DHCPv4 server is about to open sockets on the specified port.

DHCP4_OPEN_SOCKETS_FAILED

maximum number of open service sockets attempts: %1, has been exhausted without success

This error indicates that the server failed to bind service sockets after making the maximum configured number of reconnect attempts. This might cause the server to shut down as specified in the configuration.

DHCP4_OPEN_SOCKETS_NO_RECONNECT_CTL

unexpected error in bind service sockets.

This is an error message indicating a programmatic error that should not occur. It prohibits the server from attempting to bind to its service sockets if they are unavailable, and the server exits. This error should be reported.

DHCP4_OPEN_SOCKET_FAIL

failed to open socket: %1

A warning message issued when IfaceMgr fails to open and bind a socket. The reason for the failure is appended as an argument of the log message.

DHCP4_PACKET_DROP_0001

failed to parse packet from %1 to %2, received over interface %3, reason: %4

The DHCPv4 server has received a packet that it is unable to interpret. The reason why the packet is invalid is included in the message.

DHCP4_PACKET_DROP_0002

%1, from interface %2: no suitable subnet configured for a direct client

This info message is logged when received a message from a directly connected client but there is no suitable subnet configured for the interface on which this message has been received. The IPv4 address assigned on this interface must belong to one of the configured subnets. Otherwise received message is dropped.

DHCP4_PACKET_DROP_0003

%1, from interface %2: it contains a foreign server identifier

This debug message is issued when received DHCPv4 message is dropped because it is addressed to a different server, i.e. a server identifier held by this message doesn’t match the identifier used by our server. The arguments of this message hold the name of the transaction id and interface on which the message has been received.

DHCP4_PACKET_DROP_0004

%1, from interface %2: missing msg-type option

This is a debug message informing that incoming DHCPv4 packet did not have mandatory DHCP message type option and thus was dropped. The arguments specify the client and transaction identification information, as well as the interface on which the message has been received.

DHCP4_PACKET_DROP_0005

%1: unrecognized type %2 in option 53

This debug message indicates that the message type carried in DHCPv4 option 53 is unrecognized by the server. The valid message types are listed on the IANA website: http://www.iana.org/assignments/bootp-dhcp-parameters/bootp-dhcp-parameters.xhtml#message-type-53. The message will not be processed by the server. The arguments specify the client and transaction identification information, as well as the received message type.

DHCP4_PACKET_DROP_0006

%1: unsupported DHCPv4 message type %2

This debug message indicates that the message type carried in DHCPv4 option 53 is valid but the message will not be processed by the server. This includes messages being normally sent by the server to the client, such as DHCPOFFER, DHCPACK, DHCPNAK etc. The first argument specifies the client and transaction identification information. The second argument specifies the message type.

DHCP4_PACKET_DROP_0007

%1: failed to process packet: %2

This is a general catch-all message indicating that the processing of a received packet failed. The reason is given in the message. The server will not send a response but will instead ignore the packet. The first argument contains the client and transaction identification information. The second argument includes the details of the error.

DHCP4_PACKET_DROP_0008

%1: DHCP service is globally disabled

This debug message is issued when a packet is dropped because the DHCP service has been temporarily disabled. This affects all received DHCP packets. The service may be enabled by the “dhcp-enable” control command or automatically after a specified amount of time since receiving “dhcp-disable” command.

DHCP4_PACKET_DROP_0009

%1: Option 53 missing (no DHCP message type), is this a BOOTP packet?

This debug message is issued when a packet is dropped because it did contain option 53 and thus has no DHCP message type. The most likely explanation is that it was BOOTP packet.

DHCP4_PACKET_DROP_0010

dropped as member of the special class ‘DROP’: %1

This debug message is emitted when an incoming packet was classified into the special class ‘DROP’ and dropped. The packet details are displayed.

DHCP4_PACKET_DROP_0011

dropped as sent by the same client than a packet being processed by another thread: dropped %1 by thread %2 as duplicate of %3 processed by %4

Currently multi-threading processing avoids races between packets sent by a client using the same client id option by dropping new packets until processing is finished. Packet details and thread identifiers are included for both packets in this warning message.

DHCP4_PACKET_DROP_0012

dropped as sent by the same client than a packet being processed by another thread: dropped %1 by thread %2 as duplicate of %3 processed by %4

Currently multi-threading processing avoids races between packets sent by a client using the same hardware address by dropping new packets until processing is finished. Packet details and thread identifiers are included for both packets in this warning message.

DHCP4_PACKET_DROP_0013

dropped as member of the special class ‘DROP’ after host reservation lookup: %1

This debug message is emitted when an incoming packet was classified after host reservation lookup into the special class ‘DROP’ and dropped. The packet details are displayed.

DHCP4_PACKET_DROP_0014

dropped as member of the special class ‘DROP’ after early global host reservations lookup: %1

This debug message is emitted when an incoming packet was classified after early global host reservations lookup into the special class ‘DROP’ and dropped. The packet details are displayed.

DHCP4_PACKET_NAK_0001

%1: failed to select a subnet for incoming packet, src %2, type %3

This error message is output when a packet was received from a subnet for which the DHCPv4 server has not been configured. The most probable cause is a misconfiguration of the server. The first argument contains the client and transaction identification information. The second argument contains the source IPv4 address of the packet. The third argument contains the name of the received packet.

DHCP4_PACKET_NAK_0002

%1: invalid address %2 requested by INIT-REBOOT

This debug message is issued when the client being in the INIT-REBOOT state requested an IPv4 address which is not assigned to him. The server will respond to this client with DHCPNAK. The first argument contains the client and the transaction identification information. The second arguments holds the IPv4 address requested by the client.

DHCP4_PACKET_NAK_0003

%1: failed to advertise a lease, client sent ciaddr %2, requested-ip-address %3

This message indicates that the server has failed to offer a lease to the specified client after receiving a DISCOVER message from it. There are many possible reasons for such a failure. The first argument contains the client and the transaction identification information. The second argument contains the IPv4 address in the ciaddr field. The third argument contains the IPv4 address in the requested-ip-address option (if present).

DHCP4_PACKET_NAK_0004

%1: failed to grant a lease, client sent ciaddr %2, requested-ip-address %3

This message indicates that the server failed to grant a lease to the specified client after receiving a REQUEST message from it. There are many possible reasons for such a failure. Additional messages will indicate the reason. The first argument contains the client and the transaction identification information. The second argument contains the IPv4 address in the ciaddr field. The third argument contains the IPv4 address in the requested-ip-address option (if present).

DHCP4_PACKET_OPTIONS_SKIPPED

An error unpacking an option, caused subsequent options to be skipped: %1

A debug message issued when an option failed to unpack correctly, making it impossible to unpack the remaining options in the packet. The server will server will still attempt to service the packet.

DHCP4_PACKET_OPTION_UNPACK_FAIL

An error unpacking the option %1: %2

A debug message issued when an option failed to unpack correctly, making it to be left unpacked in the packet. The first argument is the option code, the second the error.

DHCP4_PACKET_PACK

%1: preparing on-wire format of the packet to be sent

This debug message is issued when the server starts preparing the on-wire format of the packet to be sent back to the client. The argument specifies the client and the transaction identification information.

DHCP4_PACKET_PACK_FAIL

%1: preparing on-wire-format of the packet to be sent failed %2

This error message is issued when preparing an on-wire format of the packet has failed. The first argument identifies the client and the DHCP transaction. The second argument includes the error string.

DHCP4_PACKET_PROCESS_EXCEPTION

exception occurred during packet processing

This error message indicates that a non-standard exception was raised during packet processing that was not caught by other, more specific exception handlers. This packet will be dropped and the server will continue operation.

DHCP4_PACKET_PROCESS_STD_EXCEPTION

exception occurred during packet processing: %1

This error message indicates that a standard exception was raised during packet processing that was not caught by other, more specific exception handlers. This packet will be dropped and the server will continue operation.

DHCP4_PACKET_QUEUE_FULL

multi-threading packet queue is full

A debug message noting that the multi-threading packet queue is full so the oldest packet of the queue was dropped to make room for the received one.

DHCP4_PACKET_RECEIVED

%1: %2 (type %3) received from %4 to %5 on interface %6

A debug message noting that the server has received the specified type of packet on the specified interface. The first argument specifies the client and transaction identification information. The second and third argument specify the name of the DHCPv4 message and its numeric type respectively. The remaining arguments specify the source IPv4 address, destination IPv4 address and the name of the interface on which the message has been received.

DHCP4_PACKET_SEND

%1: trying to send packet %2 (type %3) from %4:%5 to %6:%7 on interface %8

The arguments specify the client identification information (HW address and client identifier), DHCP message name and type, source IPv4 address and port, destination IPv4 address and port and the interface name. This debug message is issued when the server is trying to send the response to the client. When the server is using an UDP socket to send the packet there are cases when this operation may be unsuccessful and no error message will be displayed. One such situation occurs when the server is unicasting the response to the ‘ciaddr’ of a DHCPINFORM message. This often requires broadcasting an ARP message to obtain the link layer address of the unicast destination. If broadcast ARP messages are blocked in the network, according to the firewall policy, the ARP message will not cause a response. Consequently, the response to the DHCPINFORM will not be sent. Since the ARP communication is under the OS control, Kea is not notified about the drop of the packet which it is trying to send and it has no means to display an error message.

DHCP4_PACKET_SEND_FAIL

%1: failed to send DHCPv4 packet: %2

This error is output if the DHCPv4 server fails to send an assembled DHCP message to a client. The first argument includes the client and the transaction identification information. The second argument includes the reason for failure.

DHCP4_PARSER_COMMIT_EXCEPTION

parser failed to commit changes

On receipt of message containing details to a change of the DHCPv4 server configuration, a set of parsers were successfully created, but one of them failed to commit its changes due to a low-level system exception being raised. Additional messages may be output indicating the reason.

DHCP4_PARSER_COMMIT_FAIL

parser failed to commit changes: %1

On receipt of message containing details to a change of the DHCPv4 server configuration, a set of parsers were successfully created, but one of them failed to commit its changes. The reason for the failure is given in the message.

DHCP4_PARSER_EXCEPTION

failed to create or run parser for configuration element %1

On receipt of message containing details to a change of its configuration, the DHCPv4 server failed to create a parser to decode the contents of the named configuration element, or the creation succeeded but the parsing actions and committal of changes failed. The message has been output in response to a non-Kea exception being raised. Additional messages may give further information.

DHCP4_PARSER_FAIL

failed to create or run parser for configuration element %1: %2

On receipt of message containing details to a change of its configuration, the DHCPv4 server failed to create a parser to decode the contents of the named configuration element, or the creation succeeded but the parsing actions and committal of changes failed. The reason for the failure is given in the message.

DHCP4_POST_ALLOCATION_NAME_UPDATE_FAIL

%1: failed to update hostname %2 in a lease after address allocation: %3

This message indicates the failure when trying to update the lease and/or options in the server’s response with the hostname generated by the server or reserved for the client belonging to a shared network. The latter is the case when the server dynamically switches to another subnet (than initially selected for allocation) from the same shared network.

DHCP4_QUERY_DATA

%1, packet details: %2

A debug message printing the details of the received packet. The first argument includes the client and the transaction identification information.

DHCP4_RECLAIM_EXPIRED_LEASES_FAIL

failed to reclaim expired leases: %1

This error message indicates that the reclaim expired leases operation failed and provides the cause of failure.

DHCP4_RELEASE

%1: address %2 was released properly.

This informational message indicates that an address was released properly. It is a normal operation during client shutdown. The first argument includes the client and transaction identification information. The second argument includes the released IPv4 address.

DHCP4_RELEASE_EXCEPTION

%1: while trying to release address %2 an exception occurred: %3

This message is output when an error was encountered during an attempt to process a DHCPRELEASE message. The error will not affect the client, which does not expect any response from the server for DHCPRELEASE messages. Depending on the nature of problem, it may affect future server operation. The first argument includes the client and the transaction identification information. The second argument includes the IPv4 address which release was attempted. The last argument includes the detailed error description.

DHCP4_RELEASE_FAIL

%1: failed to remove lease for address %2

This error message indicates that the software failed to remove a lease from the lease database. It is probably due to an error during a database operation: resolution will most likely require administrator intervention (e.g. check if DHCP process has sufficient privileges to update the database). It may also be triggered if a lease was manually removed from the database during RELEASE message processing. The first argument includes the client and the transaction identification information. The second argument holds the IPv4 address which release was attempted.

DHCP4_RELEASE_FAIL_NO_LEASE

%1: client is trying to release non-existing lease %2

This debug message is printed when client attempts to release a lease, but no such lease is known to the server. The first argument contains the client and transaction identification information. The second argument contains the IPv4 address which the client is trying to release.

DHCP4_RELEASE_FAIL_WRONG_CLIENT

%1: client is trying to release the lease %2 which belongs to a different client

This debug message is issued when a client is trying to release the lease for the address which is currently used by another client, i.e. the ‘client identifier’ or ‘chaddr’ doesn’t match between the client and the lease. The first argument includes the client and the transaction identification information. The second argument specifies the leased address.

DHCP4_RESERVATIONS_LOOKUP_FIRST_ENABLED

Multi-threading is enabled and host reservations lookup is always performed first.

This is a message informing that host reservations lookup is performed before lease lookup when multi-threading is enabled overwriting configured value.

DHCP4_RESERVED_HOSTNAME_ASSIGNED

%1: server assigned reserved hostname %2

This debug message is issued when the server found a hostname reservation for a client and uses this reservation in a hostname option sent back to this client. The reserved hostname is qualified with a value of ‘qualifying-suffix’ parameter, if this parameter is specified.

DHCP4_RESPONSE_DATA

%1: responding with packet %2 (type %3), packet details: %4

A debug message including the detailed data about the packet being sent to the client. The first argument contains the client and the transaction identification information. The second and third argument contains the packet name and type respectively. The fourth argument contains detailed packet information.

DHCP4_RESPONSE_FQDN_DATA

%1: including FQDN option in the server’s response: %2

This debug message is issued when the server is adding the Client FQDN option in its response to the client. The first argument includes the client and transaction identification information. The second argument includes the details of the FQDN option being included. Note that the name carried in the FQDN option may be modified by the server when the lease is acquired for the client.

DHCP4_RESPONSE_HOSTNAME_DATA

%1: including Hostname option in the server’s response: %2

This debug message is issued when the server is adding the Hostname option in its response to the client. The first argument includes the client and transaction identification information. The second argument includes the details of the FQDN option being included. Note that the name carried in the Hostname option may be modified by the server when the lease is acquired for the client.

DHCP4_RESPONSE_HOSTNAME_GENERATE

%1: server has generated hostname %2 for the client

This debug message includes the auto-generated hostname which will be used for the client which message is processed. Hostnames may need to be generated when required by the server’s configuration or when the client hasn’t supplied its hostname. The first argument includes the client and the transaction identification information. The second argument holds the generated hostname.

DHCP4_SERVER_FAILED

server failed: %1

The DHCPv4 server has encountered a fatal error and is terminating. The reason for the failure is included in the message.

DHCP4_SHUTDOWN

server shutdown

The DHCPv4 server has terminated normally.

DHCP4_SHUTDOWN_REQUEST

shutdown of server requested

This debug message indicates that a shutdown of the DHCPv4 server has been requested via a call to the ‘shutdown’ method of the core Dhcpv4Srv object.

DHCP4_SRV_CONSTRUCT_ERROR

error creating Dhcpv4Srv object, reason: %1

This error message indicates that during startup, the construction of a core component within the DHCPv4 server (the Dhcpv4 server object) has failed. As a result, the server will exit. The reason for the failure is given within the message.

DHCP4_SRV_D2STOP_ERROR

error stopping IO with DHCP_DDNS during shutdown: %1

This error message indicates that during shutdown, an error occurred while stopping IO between the DHCPv4 server and the DHCP_DDNS server. This is probably due to a programmatic error is not likely to impact either server upon restart. The reason for the failure is given within the message.

DHCP4_SRV_DHCP4O6_ERROR

error stopping IO with DHCPv4o6 during shutdown: %1

This error message indicates that during shutdown, an error occurred while stopping IO between the DHCPv4 server and the DHCPv6o6 server. This is probably due to a programmatic error is not likely to impact either server upon restart. The reason for the failure is given within the message.

DHCP4_SRV_UNLOAD_LIBRARIES_ERROR

error unloading hooks libraries during shutdown: %1

This error message indicates that during shutdown, unloading hooks libraries failed to close them. If the list of libraries is empty it is a programmatic error in the server code. If it is not empty it could be a programmatic error in one of the hooks libraries which could lead to a crash during finalization.

DHCP4_STARTED

Kea DHCPv4 server version %1 started

This informational message indicates that the DHCPv4 server has processed all configuration information and is ready to process DHCPv4 packets. The version is also printed.

DHCP4_STARTING

Kea DHCPv4 server version %1 (%2) starting

This informational message indicates that the DHCPv4 server has processed any command-line switches and is starting. The version is also printed.

DHCP4_START_INFO

pid: %1, server port: %2, client port: %3, verbose: %4

This is a debug message issued during the DHCPv4 server startup. It lists some information about the parameters with which the server is running.

DHCP4_SUBNET_DATA

%1: the selected subnet details: %2

This debug message includes the details of the subnet selected for the client. The first argument includes the client and the transaction identification information. The second arguments includes the subnet details.

DHCP4_SUBNET_DYNAMICALLY_CHANGED

%1: changed selected subnet %2 to subnet %3 from shared network %4 for client assignments

This debug message indicates that the server is using another subnet than initially selected for client assignments. This newly selected subnet belongs to the same shared network as the original subnet. Some reasons why the new subnet was selected include: address pool exhaustion in the original subnet or the fact that the new subnet includes some static reservations for this client.

DHCP4_SUBNET_SELECTED

%1: the subnet with ID %2 was selected for client assignments

This is a debug message noting the selection of a subnet to be used for address and option assignment. Subnet selection is one of the early steps in the processing of incoming client message. The first argument includes the client and the transaction identification information. The second argument holds the selected subnet id.

DHCP4_SUBNET_SELECTION_FAILED

%1: failed to select subnet for the client

This debug message indicates that the server failed to select the subnet for the client which has sent a message to the server. The server will not be able to offer any lease to the client and will drop its message if the received message was DHCPDISCOVER, and will send DHCPNAK if the received message was DHCPREQUEST. The argument includes the client and the transaction identification information.

DHCP4_TESTING_MODE_SEND_TO_SOURCE_ENABLED

All packets will be send to source address of an incoming packet - use only for testing

This message is printed then KEA_TEST_SEND_RESPONSES_TO_SOURCE environment variable is set. It’s causing Kea to send packets to source address of incoming packet. Usable just in testing environment to simulate multiple subnet traffic from single source.

DHCP4_UNKNOWN_ADDRESS_REQUESTED

%1: client requested an unknown address, client sent ciaddr %2, requested-ip-address %3

This message indicates that the client requested an address that does not belong to any dynamic pools managed by this server. The first argument contains the client and the transaction identification information. The second argument contains the IPv4 address in the ciaddr field. The third argument contains the IPv4 address in the requested-ip-address option (if present).

DHCP6

DHCP6_ACTIVATE_INTERFACE

activating interface %1

This message is printed when DHCPv6 server enabled an interface to be used to receive DHCPv6 traffic. IPv6 socket on this interface will be opened once Interface Manager starts up procedure of opening sockets.

DHCP6_ADD_GLOBAL_STATUS_CODE

%1: adding Status Code to DHCPv6 packet: %2

This message is logged when the server is adding the top-level Status Code option. The first argument includes the client and the transaction identification information. The second argument includes the details of the status code.

DHCP6_ADD_STATUS_CODE_FOR_IA

%1: adding Status Code to IA with iaid=%2: %3

This message is logged when the server is adding the Status Code option to an IA. The first argument includes the client and the transaction identification information. The second argument specifies the IAID. The third argument includes the details of the status code.

DHCP6_ALREADY_RUNNING

%1 already running? %2

This is an error message that occurs when the DHCPv6 server encounters a pre-existing PID file which contains the PID of a running process. This most likely indicates an attempt to start a second instance of the server using the same configuration file. It is possible, though unlikely that the PID file is a remnant left behind by a server crash or power failure and the PID it contains refers to a process other than the server. In such an event, it would be necessary to manually remove the PID file. The first argument is the DHCPv6 process name, the second contains the PID and PID file.

DHCP6_BUFFER_RECEIVED

received buffer from %1:%2 to %3:%4 over interface %5

This debug message is logged when the server has received a packet over the socket. When the message is logged the contents of the received packet hasn’t been parsed yet. The only available information is the interface and the source and destination addresses/ports.

DHCP6_BUFFER_UNPACK

parsing buffer received from %1 to %2 over interface %3

This debug message is issued when the server starts parsing the received buffer holding the DHCPv6 message. The arguments specify the source and destination addresses as well as the interface over which the buffer has been received.

DHCP6_BUFFER_WAIT_SIGNAL

signal received while waiting for next packet

This debug message is issued when the server was waiting for the packet, but the wait has been interrupted by the signal received by the process. The signal will be handled before the server starts waiting for next packets.

DHCP6_CB_ON_DEMAND_FETCH_UPDATES_FAIL

error on demand attempt to fetch configuration updates from the configuration backend(s): %1

This error message is issued when the server attempted to fetch configuration updates from the database and this on demand attempt failed. The sole argument which is returned to the config-backend-pull command caller too contains the reason for failure.

DHCP6_CB_PERIODIC_FETCH_UPDATES_FAIL

error on periodic attempt to fetch configuration updates from the configuration backend(s): %1

This error message is issued when the server attempted to fetch configuration updates from the database and this periodic attempt failed. The server will re-try according to the configured value of the config-fetch-wait-time parameter. The sole argument contains the reason for failure.

DHCP6_CB_PERIODIC_FETCH_UPDATES_RETRIES_EXHAUSTED

maximum number of configuration fetch attempts: 10, has been exhausted without success

This error indicates that the server has made a number of unsuccessful periodic attempts to fetch configuration updates from a configuration backend. The server will continue to operate but won’t make any further attempts to fetch configuration updates. The administrator must fix the configuration in the database and reload (or restart) the server.

DHCP6_CLASS_ASSIGNED

%1: client packet has been assigned to the following class(es): %2

This debug message informs that incoming packet has been assigned to specified class or classes. This is a normal behavior and indicates successful operation. The first argument specifies the client and transaction identification information. The second argument includes all classes to which the packet has been assigned.

DHCP6_CLASS_UNCONFIGURED

%1: client packet belongs to an unconfigured class: %2

This debug message informs that incoming packet belongs to a class which cannot be found in the configuration. Either a hook written before the classification was added to Kea is used, or class naming is inconsistent.

DHCP6_CLASS_UNDEFINED

required class %1 has no definition

This debug message informs that a class is listed for required evaluation but has no definition.

DHCP6_CLASS_UNTESTABLE

required class %1 has no test expression

This debug message informs that a class was listed for required evaluation but its definition does not include a test expression to evaluate.

DHCP6_COMMAND_RECEIVED

received command %1, arguments: %2

A debug message listing the command (and possible arguments) received from the Kea control system by the IPv6 DHCP server.

DHCP6_CONFIG_COMPLETE

DHCPv6 server has completed configuration: %1

This is an informational message announcing the successful processing of a new configuration. it is output during server startup, and when an updated configuration is committed by the administrator. Additional information may be provided.

DHCP6_CONFIG_LOAD_FAIL

configuration error using file: %1, reason: %2

This error message indicates that the DHCPv6 configuration has failed. If this is an initial configuration (during server’s startup) the server will fail to start. If this is a dynamic reconfiguration attempt the server will continue to use an old configuration.

DHCP6_CONFIG_PACKET_QUEUE

DHCPv6 packet queue info after configuration: %1

This informational message is emitted during DHCPv6 server configuration, immediately after configuring the DHCPv6 packet queue. The information shown depends upon the packet queue type selected.

DHCP6_CONFIG_RECEIVED

received configuration: %1

A debug message listing the configuration received by the DHCPv6 server. The source of that configuration depends on used configuration backend.

DHCP6_CONFIG_START

DHCPv6 server is processing the following configuration: %1

This is a debug message that is issued every time the server receives a configuration. That happens start up and also when a server configuration change is committed by the administrator.

DHCP6_CONFIG_SYNTAX_WARNING

configuration syntax warning: %1

This warning message indicates that the DHCPv6 configuration had a minor syntax error. The error was displayed and the configuration parsing resumed.

DHCP6_CONFIG_UNRECOVERABLE_ERROR

DHCPv6 server new configuration failed with an error which cannot be recovered

This fatal error message is issued when a new configuration raised an error which cannot be recovered. A correct configuration must be applied as soon as possible as the server is no longer working. The configuration can be fixed in several ways. If the control channel is open, config-set with a valid configuration can be used. Alternatively, the original config file on disk could be fixed and SIGHUP signal could be sent (or the config-reload command issued). Finally, the server could be restarted completely.

DHCP6_CONFIG_UNSUPPORTED_OBJECT

DHCPv6 server configuration includes an unsupported object: %1

This error message is issued when the configuration includes an unsupported object (i.e. a top level element).

DHCP6_CONFIG_UPDATE

updated configuration received: %1

A debug message indicating that the IPv6 DHCP server has received an updated configuration from the Kea configuration system.

DHCP6_DB_BACKEND_STARTED

lease database started (type: %1, name: %2)

This informational message is printed every time the IPv6 DHCP server is started. It indicates what database backend type is being to store lease and other information.

DHCP6_DB_RECONNECT_DISABLED

database reconnect is disabled: max-reconnect-tries %1, reconnect-wait-time %2

This is an informational message indicating that connectivity to either the lease or host database or both and that automatic reconnect is not enabled.

DHCP6_DB_RECONNECT_FAILED

maximum number of database reconnect attempts: %1, has been exhausted without success

This error indicates that the server failed to reconnect to the lease and/or host database(s) after making the maximum configured number of reconnect attempts. This might cause the server to shut down as specified in the configuration. Loss of connectivity is typically a network or database server issue.

DHCP6_DB_RECONNECT_LOST_CONNECTION

database connection lost.

This info message indicates that the connection has been lost and the dhcp service might have been disabled, as specified in the configuration, in order to try to recover the connection.

DHCP6_DB_RECONNECT_NO_DB_CTL

unexpected error in database reconnect

This is an error message indicating a programmatic error that should not occur. It prohibits the server from attempting to reconnect to its databases if connectivity is lost, and the server exits. This error should be reported.

DHCP6_DB_RECONNECT_SUCCEEDED

database connection recovered.

This info message indicates that the connection has been recovered and the dhcp service has been restored.

DHCP6_DDNS_CREATE_ADD_NAME_CHANGE_REQUEST

created name change request: %1

This debug message is logged when the new NameChangeRequest has been created to perform the DNS Update, which adds new RRs.

DHCP6_DDNS_FQDN_GENERATED

%1: generated FQDN for the client: %2

This debug message is logged when the server generated FQDN (name) for the client which message is processed. The names may be generated by the server when required by the server’s policy or when the client doesn’t provide any specific FQDN in its message to the server. The first argument includes the client and transaction identification information. The second argument includes the generated FQDN.

DHCP6_DDNS_GENERATED_FQDN_UPDATE_FAIL

%1: failed to update the lease using address %2, after generating FQDN for a client, reason: %3

This message indicates the failure when trying to update the lease and/or options in the server’s response with the hostname generated by the server from the acquired address. The first argument includes the client and the transaction identification information. The second argument is a leased address. The third argument includes the reason for the failure.

DHCP6_DDNS_GENERATE_FQDN

%1: client did not send a FQDN option; FQDN will be

generated for the client. This debug message is issued when the server did not receive a FQDN option from the client and client name replacement is enabled. This provides a means to create DNS entries for unsophisticated clients.

DHCP6_DDNS_RECEIVE_FQDN

%1: received DHCPv6 Client FQDN option: %2

This debug message is logged when server has found the DHCPv6 Client FQDN Option sent by a client and started processing it. The first argument includes the client and transaction identification information. The second argument includes the received FQDN.

DHCP6_DDNS_REMOVE_OLD_LEASE_FQDN

%1: FQDN for a lease: %2 has changed. New values: hostname = %3, reverse mapping = %4, forward mapping = %5

This debug message is logged during lease renewal when an old lease that is no longer being offered has a different FQDN than the renewing lease. Thus the old DNS entries need to be removed. The first argument includes the client and the transaction identification information. The second argument holds the details about the lease for which the FQDN information and/or mappings have changed. The remaining arguments hold the new FQDN information and flags for mappings.

DHCP6_DDNS_REQUEST_SEND_FAILED

failed sending a request to kea-dhcp-ddns, error: %1, ncr: %2

This error message indicates that IPv6 DHCP server failed to send a DDNS update request to the DHCP-DDNS server. This is most likely a configuration or networking error.

DHCP6_DDNS_RESPONSE_FQDN_DATA

%1: including FQDN option in the server’s response: %2

This debug message is issued when the server is adding the Client FQDN option in its response to the client. The first argument includes the client and transaction identification information. The second argument includes the details of the FQDN option being included. Note that the name carried in the FQDN option may be modified by the server when the lease is acquired for the client.

DHCP6_DDNS_SEND_FQDN

sending DHCPv6 Client FQDN Option to the client: %1

This debug message is logged when server includes an DHCPv6 Client FQDN Option in its response to the client.

DHCP6_DEACTIVATE_INTERFACE

deactivate interface %1

This message is printed when DHCPv6 server disables an interface from being used to receive DHCPv6 traffic. Sockets on this interface will not be opened by the Interface Manager until interface is enabled.

DHCP6_DECLINE_FAIL

%1: error on decline lease for address %2: %3

This error message indicates that the software failed to decline a lease from the lease database due to an error during a database operation. The first argument includes the client and the transaction identification information. The second argument holds the IPv6 address which decline was attempted. The last one contains the reason for failure.

DHCP6_DECLINE_FAIL_DUID_MISMATCH

Client %1 sent DECLINE for address %2, but it belongs to client with DUID %3

This informational message is printed when a client attempts to decline a lease, but that lease belongs to a different client. The decline request will be rejected.

DHCP6_DECLINE_FAIL_IAID_MISMATCH

Client %1 sent DECLINE for address %2, but used a wrong IAID (%3), instead of expected %4

This informational message is printed when a client attempts to decline a lease. The server has a lease for this address, it belongs to this client, but the recorded IAID does not match what client has sent. This means the server will reject this Decline.

DHCP6_DECLINE_FAIL_LEASE_WITHOUT_DUID

Client %1 sent DECLINE for address %2, but the associated lease has no DUID

This error condition likely indicates database corruption, as every IPv6 lease is supposed to have a DUID, even if it is an empty one.

DHCP6_DECLINE_FAIL_NO_LEASE

Client %1 sent DECLINE for address %2, but there’s no lease for it

This informational message is printed when a client tried to decline an address, but the server has no lease for said address. This means that the server’s and client’s perception of the leases are different. The likely causes of this could be: a confused (e.g. skewed clock) or broken client (e.g. client moved to a different location and didn’t notice) or possibly an attack (a rogue client is trying to decline random addresses). The server will inform the client that his decline request was rejected and client should be able to recover from that.

DHCP6_DECLINE_LEASE

Client %1 sent DECLINE for address %2 and the server marked it as declined. The lease will be recovered in %3 seconds.

This informational message indicates that the client leased an address, but discovered that it is being used by some other device and reported this to the server by sending a Decline message. The server marked the lease as declined. This likely indicates a misconfiguration in the network. Either the server is configured with an incorrect pool or there are devices that have statically assigned addresses that are supposed to be assigned by the DHCP server. Both client (will request a different address) and server (will recover the lease after decline-probation-time elapses) will recover automatically. However, if the underlying problem is not solved, the conditions leading to this message may reappear.

DHCP6_DECLINE_PROCESS_IA

Processing of IA (IAID: %1) from client %2 started.

This debug message is printed when the server starts processing an IA_NA option received in Decline message. It’s expected that the option will contain an address that is being declined. Specific information will be printed in a separate message.

DHCP6_DEVELOPMENT_VERSION

This software is a development branch of Kea. It is not recommended for production use.

This warning message is displayed when the version is a development (vs stable) one: the second number of the version is odd.

DHCP6_DHCP4O6_PACKET_RECEIVED

received DHCPv4o6 packet from DHCPv4 server (type %1) for %2 port %3 on interface %4

This debug message is printed when the server is receiving a DHCPv4o6 from the DHCPv4 server over inter-process communication.

DHCP6_DHCP4O6_RECEIVE_FAIL

failed to receive DHCPv4o6: %1

This debug message indicates the inter-process communication with the DHCPv4 server failed. The reason for the error is included in the message.

DHCP6_DHCP4O6_RECEIVING

receiving DHCPv4o6 packet from DHCPv4 server

This debug message is printed when the server is receiving a DHCPv4o6 from the DHCPv4 server over inter-process communication socket.

DHCP6_DHCP4O6_SEND_FAIL

failed to send DHCPv4o6 packet: %1

This error is output if the IPv6 DHCP server fails to send an assembled DHCPv4o6 message to a client. The reason for the error is included in the message.

DHCP6_DYNAMIC_RECONFIGURATION

initiate server reconfiguration using file: %1, after receiving SIGHUP signal or config-reload command

This is the info message logged when the DHCPv6 server starts reconfiguration as a result of receiving SIGHUP signal or config-reload command.

DHCP6_DYNAMIC_RECONFIGURATION_FAIL

dynamic server reconfiguration failed with file: %1

This is a fatal error message logged when the dynamic reconfiguration of the DHCP server failed.

DHCP6_DYNAMIC_RECONFIGURATION_SUCCESS

dynamic server reconfiguration succeeded with file: %1

This is info message logged when the dynamic reconfiguration of the DHCP server succeeded.

DHCP6_FLEX_ID

flexible identifier generated for incoming packet: %1

This debug message is printed when host reservation type is set to flexible identifier and the expression specified in its configuration generated (was evaluated to) an identifier for incoming packet. This debug message is mainly intended as a debugging assistance for flexible identifier.

DHCP6_HANDLE_SIGNAL_EXCEPTION

An exception was thrown while handing signal: %1

This error message is printed when an exception was raised during signal processing. This likely indicates a coding error and should be reported to ISC.

DHCP6_HOOKS_LIBS_RELOAD_FAIL

reload of hooks libraries failed

A “libreload” command was issued to reload the hooks libraries but for some reason the reload failed. Other error messages issued from the hooks framework will indicate the nature of the problem.

DHCP6_HOOK_BUFFER_RCVD_DROP

received buffer from %1 to %2 over interface %3 was dropped because a callout set the drop flag

This debug message is printed when a callout installed on buffer6_receive hook point set the drop flag. For this particular hook point, the setting of the flag by a callout instructs the server to drop the packet. The arguments specify the source and destination address as well as the name of the interface over which the buffer has been received.

DHCP6_HOOK_BUFFER_RCVD_SKIP

received buffer from %1 to %2 over interface %3 is not parsed because a callout set the next step to SKIP

This debug message is printed when a callout installed on buffer6_receive hook point set the next step status to skip. For this particular hook point, this value set by a callout instructs the server to not parse the buffer because it was already parsed by the hook. The arguments specify the source and destination address as well as the name of the interface over which the buffer has been received.

DHCP6_HOOK_BUFFER_SEND_SKIP

%1: prepared DHCPv6 response was dropped because a callout set the next step to SKIP

This debug message is printed when a callout installed on buffer6_send hook point set the next step to SKIP value. For this particular hook point, the SKIP setting a callout instructs the server to drop the packet. Server completed all the processing (e.g. may have assigned, updated or released leases), but the response will not be send to the client. The argument includes the client and transaction identification information.

DHCP6_HOOK_DDNS_UPDATE

A hook has updated the DDNS parameters: hostname %1=>%2, forward update %3=>%4, reverse update %5=>%6

This message indicates that there was a hook called on ddns6_update hook point and that hook updated the DDNS update parameters: hostname, or whether to conduct forward (A record) or reverse (PTR record) DDNS updates.

DHCP6_HOOK_DECLINE_DROP

During Decline processing (client=%1, interface=%2, addr=%3) hook callout set next step to DROP, dropping packet.

This message indicates that the server received DECLINE message, it was verified to be correct and matching server’s lease information. The server called hooks for the lease6_decline hook point and one of the callouts set next step status to DROP. The server will now abort processing of the packet as if it was never received. The lease will continue to be assigned to this client.

DHCP6_HOOK_DECLINE_SKIP

During Decline processing (client=%1, interface=%2, addr=%3) hook callout set status to SKIP, skipping decline.

This message indicates that the server received DECLINE message, it was verified to be correct and matching server’s lease information. The server called hooks for the lease6_decline hook point and one of the callouts set next step status to SKIP. The server will skip the operation of moving the lease to the declined state and will continue processing the packet. In particular, it will send a REPLY message as if the decline actually took place.

DHCP6_HOOK_LEASE6_RELEASE_NA_SKIP

%1: DHCPv6 address lease was not released because a callout set the next step to SKIP

This debug message is printed when a callout installed on the lease6_release hook point set the next step to SKIP. For this particular hook point, this setting by a callout instructs the server to not release a lease. If a client requested the release of multiples leases (by sending multiple IA options), the server will retain this particular lease and proceed with other releases as usual. The argument holds the client and transaction identification information.

DHCP6_HOOK_LEASE6_RELEASE_PD_SKIP

%1: prefix lease was not released because a callout set the next step to SKIP

This debug message is printed when a callout installed on lease6_release hook point set the next step to SKIP value. For this particular hook point, that setting by a callout instructs the server to not release a lease. If client requested release of multiples leases (by sending multiple IA options), the server will retains this particular lease and will proceed with other renewals as usual. The argument holds the client and transaction identification information.

DHCP6_HOOK_LEASES6_COMMITTED_DROP

%1: packet is dropped, because a callout set the next step to DROP

This debug message is printed when a callout installed on the leases6_committed hook point sets the next step to DROP.

DHCP6_HOOK_LEASES6_COMMITTED_PARK

%1: packet is parked, because a callout set the next step to PARK

This debug message is printed when a callout installed on the leases6_committed hook point sets the next step to PARK.

DHCP6_HOOK_LEASES6_PARKING_LOT_FULL

The parked-packet-limit %1, has been reached, dropping query: %2

This debug message occurs when the parking lot used to hold client queries while hook library work for them completes has reached or exceeded the limit set by the parked-packet-limit global parameter. This can occur when kea-dhcp6 is using hook libraries (e.g. HA) that implement the “leases6-committed” callout and client queries are arriving faster than those callouts can fulfill them.

DHCP6_HOOK_PACKET_RCVD_SKIP

%1: packet is dropped, because a callout set the next step to SKIP

This debug message is printed when a callout installed on the pkt6_receive hook point sets the next step to SKIP. For this particular hook point, the value setting instructs the server to drop the packet.

DHCP6_HOOK_PACKET_SEND_DROP

%1: prepared DHCPv6 response was not sent because a callout set the next ste to DROP

This debug message is printed when a callout installed on the pkt6_send hook point set the next step to DROP. For this particular hook point, the setting of the value by a callout instructs the server to drop the packet. This effectively means that the client will not get any response, even though the server processed client’s request and acted on it (e.g. possibly allocated a lease). The argument specifies the client and transaction identification information.

DHCP6_HOOK_PACKET_SEND_SKIP

%1: prepared DHCPv6 response is not built because a callout set the next step to SKIP

This debug message is printed when a callout installed on the pkt6_send hook point set the next step to SKIP. For this particular hook point, the setting of the value by a callout instructs the server to not build the wire data (pack) because it was already done by the book. The argument specifies the client and transaction identification information.

DHCP6_HOOK_SUBNET6_SELECT_DROP

%1: packet was dropped because a callout set the drop flag

This debug message is printed when a callout installed on the subnet6_select hook point set the drop flag. For this particular hook point, the setting of the flag instructs the server to drop the received packet. The argument holds the client and transaction identification information.

DHCP6_HOOK_SUBNET6_SELECT_SKIP

%1: no subnet was selected because a callout set the next step to SKIP

This debug message is printed when a callout installed on the subnet6_select hook point set the next step to SKIP value. For this particular hook point, the setting of this value instructs the server not to choose a subnet, an action that severely limits further processing; the server will be only able to offer global options - no addresses or prefixes will be assigned. The argument holds the client and transaction identification information.

DHCP6_INIT_FAIL

failed to initialize Kea server: %1

The server has failed to establish communication with the rest of Kea, failed to read JSON configuration file or encountered any other critical issue that prevents it from starting up properly. Attached error message provides more details about the issue.

DHCP6_LEASE_ADVERT

%1: lease for address %2 and iaid=%3 will be advertised

This informational message indicates that the server will advertise an address to the client in the ADVERTISE message. The client will request allocation of this address with the REQUEST message sent in the next message exchange. The first argument includes the client and transaction identification information. The remaining arguments hold the allocated address and IAID.

DHCP6_LEASE_ADVERT_FAIL

%1: failed to advertise an address lease for iaid=%2

This message indicates that in response to a received SOLICIT, the server failed to advertise a non-temporary lease for a given client. There may be many reasons for such failure. Each failure is logged in a separate log entry. The first argument holds the client and transaction identification information. The second argument holds the IAID.

DHCP6_LEASE_ALLOC

%1: lease for address %2 and iaid=%3 has been allocated for %4 seconds

This informational message indicates that in response to a client’s REQUEST message, the server successfully granted a non-temporary address lease. This is a normal behavior and indicates successful operation. The first argument includes the client and transaction identification information. The remaining arguments hold the allocated address, IAID and validity lifetime.

DHCP6_LEASE_ALLOC_FAIL

%1: failed to grant an address lease for iaid=%2

This message indicates that in response to a received REQUEST, the server failed to grant a non-temporary address lease for the client. There may be many reasons for such failure. Each failure is logged in a separate log entry. The first argument holds the client and transaction identification information. The second argument holds the IAID.

DHCP6_LEASE_DATA

%1: detailed lease information for iaid=%2: %3

This debug message is used to print the detailed information about the allocated lease or a lease which will be advertised to the client. The first argument holds the client and the transaction identification information. The second argument holds the IAID. The third argument holds the detailed lease information.

DHCP6_LEASE_NA_WITHOUT_DUID

%1: address lease for address %2 does not have a DUID

This error message indicates a database consistency problem. The lease database has an entry indicating that the given address is in use, but the lease does not contain any client identification. This is most likely due to a software error: please raise a bug report. As a temporary workaround, manually remove the lease entry from the database. The first argument includes the client and transaction identification information. The second argument holds the address to be released.

DHCP6_LEASE_PD_WITHOUT_DUID

%1: lease for prefix %2/%3 does not have a DUID

This error message indicates a database consistency failure. The lease database has an entry indicating that the given prefix is in use, but the lease does not contain any client identification. This is most likely due to a software error: please raise a bug report. As a temporary workaround, manually remove the lease entry from the database. The first argument includes client and transaction identification information. The second and third argument hold the prefix and the prefix length.

DHCP6_LEASE_RENEW

%1: lease for address %2 and iaid=%3 has been allocated

This informational message indicates that in response to a client’s REQUEST message, the server successfully renewed a non-temporary address lease. This is a normal behavior and indicates successful operation. The first argument includes the client and transaction identification information. The remaining arguments hold the allocated address and IAID.

DHCP6_LEASE_REUSE

%1: lease for address %2 and iaid=%3 has been reused for %4 seconds

This informational message indicates that in response to a client’s message, the server successfully reused a non-temporary address lease. This is a normal behavior and indicates successful operation. The first argument includes the client and transaction identification information. The remaining arguments hold the allocated address, IAID and validity lifetime.

DHCP6_MULTI_THREADING_INFO

enabled: %1, number of threads: %2, queue size: %3

This is a message listing some information about the multi-threading parameters with which the server is running.

DHCP6_NOT_RUNNING

IPv6 DHCP server is not running

A warning message is issued when an attempt is made to shut down the IPv6 DHCP server but it is not running.

DHCP6_NO_INTERFACES

failed to detect any network interfaces

During startup the IPv6 DHCP server failed to detect any network interfaces and is therefore shutting down.

DHCP6_NO_SOCKETS_OPEN

no interface configured to listen to DHCP traffic

This warning message is issued when current server configuration specifies no interfaces that server should listen on, or specified interfaces are not configured to receive the traffic.

DHCP6_OPEN_SOCKET

opening service sockets on port %1

A debug message issued during startup, this indicates that the IPv6 DHCP server is about to open sockets on the specified port.

DHCP6_OPEN_SOCKETS_FAILED

maximum number of open service sockets attempts: %1, has been exhausted without success

This error indicates that the server failed to bind service sockets after making the maximum configured number of reconnect attempts. This might cause the server to shut down as specified in the configuration.

DHCP6_OPEN_SOCKETS_NO_RECONNECT_CTL

unexpected error in bind service sockets.

This is an error message indicating a programmatic error that should not occur. It prohibits the server from attempting to bind to its service sockets if they are unavailable, and the server exits. This error should be reported.

DHCP6_OPEN_SOCKET_FAIL

failed to open socket: %1

A warning message issued when IfaceMgr fails to open and bind a socket. The reason for the failure is appended as an argument of the log message.

DHCP6_PACKET_DROP_DHCP_DISABLED

%1: DHCP service is globally disabled

This debug message is issued when a packet is dropped because the DHCP service has been temporarily disabled. This affects all received DHCP packets. The service may be enabled by the “dhcp-enable” control command or automatically after a specified amount of time since receiving “dhcp-disable” command.

DHCP6_PACKET_DROP_DROP_CLASS

dropped as member of the special class ‘DROP’: %1

This debug message is emitted when an incoming packet was classified into the special class ‘DROP’ and dropped. The packet details are displayed.

DHCP6_PACKET_DROP_DROP_CLASS2

dropped as member of the special class ‘DROP’ after host reservation lookup: %1

This debug message is emitted when an incoming packet was classified after host reservation lookup into the special class ‘DROP’ and dropped. The packet details are displayed.

DHCP6_PACKET_DROP_DROP_CLASS_EARLY

dropped as member of the special class ‘DROP’ after early global host reservations lookup: %1

This debug message is emitted when an incoming packet was classified after early global host reservations lookup into the special class ‘DROP’ and dropped. The packet details are displayed.

DHCP6_PACKET_DROP_DUPLICATE

dropped as sent by the same client than a packet being processed by another thread: dropped %1 by thread %2 as duplicate of %3 processed by %4

Currently multi-threading processing avoids races between packets sent by the same client by dropping new packets until processing is finished. Packet details and thread identifiers are included for both packets in this warning message.

DHCP6_PACKET_DROP_PARSE_FAIL

failed to parse packet from %1 to %2, received over interface %3, reason: %4

The DHCPv6 server has received a packet that it is unable to interpret. The reason why the packet is invalid is included in the message.

DHCP6_PACKET_DROP_SERVERID_MISMATCH

%1: dropping packet with server identifier: %2, server is using: %3

A debug message noting that server has received message with server identifier option that not matching server identifier that server is using.

DHCP6_PACKET_DROP_UNICAST

%1: dropping unicast %2 packet as this packet should be sent to multicast

This debug message is issued when the server drops the unicast packet, because packets of this type must be sent to multicast. The first argument specifies the client and transaction identification information, the second argument specifies packet type.

DHCP6_PACKET_OPTIONS_SKIPPED

An error unpacking an option, caused subsequent options to be skipped: %1

A debug message issued when an option failed to unpack correctly, making it impossible to unpack the remaining options in the packet. The server will server will still attempt to service the packet.

DHCP6_PACKET_PROCESS_EXCEPTION

exception occurred during packet processing

This error message indicates that a non-standard exception was raised during packet processing that was not caught by other, more specific exception handlers. This packet will be dropped and the server will continue operation.

DHCP6_PACKET_PROCESS_FAIL

processing of %1 message received from %2 failed: %3

This is a general catch-all message indicating that the processing of the specified packet type from the indicated address failed. The reason is given in the message. The server will not send a response but will instead ignore the packet.

DHCP6_PACKET_PROCESS_STD_EXCEPTION

exception occurred during packet processing: %1

This error message indicates that a standard exception was raised during packet processing that was not caught by other, more specific exception handlers. This packet will be dropped and the server will continue operation.

DHCP6_PACKET_QUEUE_FULL

multi-threading packet queue is full

A debug message noting that the multi-threading packet queue is full so the oldest packet of the queue was dropped to make room for the received one.

DHCP6_PACKET_RECEIVED

%1: %2 (type %3) received from %4 to %5 on interface %6

A debug message noting that the server has received the specified type of packet on the specified interface. The first argument specifies the client and transaction identification information. The second and third argument specify the name of the DHCPv6 message and its numeric type respectively. The remaining arguments specify the source address, destination IP address and the name of the interface on which the message has been received.

DHCP6_PACKET_RECEIVE_FAIL

error on attempt to receive packet: %1

The IPv6 DHCP server tried to receive a packet but an error occurred during this attempt. The reason for the error is included in the message.

DHCP6_PACKET_SEND

%1: trying to send packet %2 (type %3) from [%4]:%5 to [%6]:%7 on interface %8

The arguments specify the client identification information (HW address and client identifier), DHCP message name and type, source IPv6 address and port, destination IPv6 address and port and the interface name.

DHCP6_PACKET_SEND_FAIL

failed to send DHCPv6 packet: %1

This error is output if the IPv6 DHCP server fails to send an assembled DHCP message to a client. The reason for the error is included in the message.

DHCP6_PACK_FAIL

failed to assemble response correctly

This error is output if the server failed to assemble the data to be returned to the client into a valid packet. The reason is most likely to be to a programming error: please raise a bug report.

DHCP6_PARSER_COMMIT_EXCEPTION

parser failed to commit changes

On receipt of message containing details to a change of the IPv6 DHCP server configuration, a set of parsers were successfully created, but one of them failed to commit its changes due to a low-level system exception being raised. Additional messages may be output indicating the reason.

DHCP6_PARSER_COMMIT_FAIL

parser failed to commit changes: %1

On receipt of message containing details to a change of the IPv6 DHCP server configuration, a set of parsers were successfully created, but one of them failed to commit its changes. The reason for the failure is given in the message.

DHCP6_PARSER_EXCEPTION

failed to create or run parser for configuration element %1

On receipt of message containing details to a change of its configuration, the IPv6 DHCP server failed to create a parser to decode the contents of the named configuration element, or the creation succeeded but the parsing actions and committal of changes failed. The message has been output in response to a non-Kea exception being raised. Additional messages may give further information. The most likely cause of this is that the specification file for the server (which details the allowable contents of the configuration) is not correct for this version of Kea. This may be the result of an interrupted installation of an update to Kea.

DHCP6_PARSER_FAIL

failed to create or run parser for configuration element %1: %2

On receipt of message containing details to a change of its configuration, the IPv6 DHCP server failed to create a parser to decode the contents of the named configuration element, or the creation succeeded but the parsing actions and committal of changes failed. The reason for the failure is given in the message.

DHCP6_PD_LEASE_ADVERT

%1: lease for prefix %2/%3 and iaid=%4 will be advertised

This informational message indicates that the server will advertise a prefix to the client in the ADVERTISE message. The client will request allocation of this prefix with the REQUEST message sent in the next message exchange. The first argument includes the client and transaction identification information. The remaining arguments hold the allocated prefix, prefix length and IAID.

DHCP6_PD_LEASE_ADVERT_FAIL

%1: failed to advertise a prefix lease for iaid=%2

This message indicates that in response to a received SOLICIT, the server failed to advertise a prefix lease for a given client. There may be many reasons for such failure. Each failure is logged in a separate log entry. The first argument holds the client and transaction identification information. The second argument holds the IAID.

DHCP6_PD_LEASE_ALLOC

%1: lease for prefix %2/%3 and iaid=%4 has been allocated for %5 seconds

This informational message indicates that in response to a client’s REQUEST message, the server successfully granted a prefix lease. This is a normal behavior and indicates successful operation. The first argument includes the client and transaction identification information. The remaining arguments hold the allocated prefix, prefix length, IAID and validity lifetime.

DHCP6_PD_LEASE_ALLOC_FAIL

%1: failed to grant a prefix lease for iaid=%2

This message indicates that in response to a received REQUEST, the server failed to grant a prefix lease for the client. There may be many reasons for such failure. Each failure is logged in a separate log entry. The first argument holds the client and transaction identification information. The second argument holds the IAID.

DHCP6_PD_LEASE_RENEW

%1: lease for prefix %2/%3 and iaid=%4 has been allocated

This informational message indicates that in response to a client’s REQUEST message, the server successfully renewed a prefix lease. This is a normal behavior and indicates successful operation. The first argument includes the client and transaction identification information. The remaining arguments hold the allocated prefix, prefix length and IAID.

DHCP6_PD_LEASE_REUSE

%1: lease for prefix %2/%3 and iaid=%4 has been reused for %5 seconds

This informational message indicates that in response to a client’s message, the server successfully reused a prefix lease. This is a normal behavior and indicates successful operation. The first argument includes the client and transaction identification information. The remaining arguments hold the allocated prefix, prefix length, IAID and validity lifetime.

DHCP6_PROCESS_IA_NA_EXTEND

%1: extending lease lifetime for IA_NA option with iaid=%2

This message is logged when the server is starting to extend the lifetime of the address lease associated with the particular IAID. The first argument includes the client and transaction identification information. The second argument contains the IAID.

DHCP6_PROCESS_IA_NA_RELEASE

%1: releasing lease for IA_NA option with iaid=%2

This message is logged when the server is trying to release the client’s as a result of receiving the RELEASE message. The first argument includes the client and transaction identification information. The second argument contains the IAID.

DHCP6_PROCESS_IA_NA_REQUEST

%1: server is processing IA_NA option with iaid=%2 and hint=%3

This is a debug message that indicates the processing of a received IA_NA option. The first argument contains the client and the transaction identification information. The second argument holds the IAID of the IA_NA option. The third argument may hold the hint for the server about the address that the client would like to have allocated. If there is no hint, the argument should provide the text indicating that the hint hasn’t been sent.

DHCP6_PROCESS_IA_PD_EXTEND

%1: extending lease lifetime for IA_PD option with iaid=%2

This message is logged when the server is starting to extend the lifetime of the prefix lease associated with the particular IAID. The first argument includes the client and transaction identification information. The second argument contains the IAID.

DHCP6_PROCESS_IA_PD_REQUEST

%1: server is processing IA_PD option with iaid=%2 and hint=%3

This is a debug message that indicates a processing of received IA_PD option. The first argument contains the client and the transaction identification information. The second argument holds the IAID of the IA_PD option. The third argument may hold the hint for the server about the prefix that the client would like to have allocated. If there is no hint, the argument should provide the text indicating that the hint hasn’t been sent.

DHCP6_QUERY_DATA

%1, packet details: %2

A debug message printing the details of the received packet. The first argument includes the client and the transaction identification information.

DHCP6_RAPID_COMMIT

%1: Rapid Commit option received, following 2-way exchange

This debug message is issued when the server found a Rapid Commit option in the client’s message and 2-way exchanges are supported by the server for the subnet on which the client is connected. The argument specifies the client and transaction identification information.

DHCP6_RECLAIM_EXPIRED_LEASES_FAIL

failed to reclaim expired leases: %1

This error message indicates that the reclaim expired leases operation failed and provides the cause of failure.

DHCP6_RELEASE_NA

%1: binding for address %2 and iaid=%3 was released properly

This informational message indicates that an address was released properly. It is a normal operation during client shutdown.

DHCP6_RELEASE_NA_FAIL

%1: failed to remove address lease for address %2 and iaid=%3

This error message indicates that the software failed to remove an address lease from the lease database. It probably due to an error during a database operation: resolution will most likely require administrator intervention (e.g. check if DHCP process has sufficient privileges to update the database). It may also be triggered if a lease was manually removed from the database during RELEASE message processing. The first argument holds the client and transaction identification information. The second and third argument hold the released address and IAID respectively.

DHCP6_RELEASE_NA_FAIL_WRONG_DUID

%1: client tried to release address %2, but it belongs to another client using duid=%3

This warning message indicates that a client tried to release an address that belongs to a different client. This should not happen in normal circumstances and may indicate a misconfiguration of the client. However, since the client releasing the address will stop using it anyway, there is a good chance that the situation will correct itself.

DHCP6_RELEASE_NA_FAIL_WRONG_IAID

%1: client tried to release address %2, but it used wrong IAID (expected %3, but got %4)

This warning message indicates that client tried to release an address that does belong to it, but the address was expected to be in a different IA (identity association) container. This probably means that the client’s support for multiple addresses is flawed.

DHCP6_RELEASE_PD

%1: prefix %2/%3 for iaid=%4 was released properly

This informational message indicates that a prefix was released properly. It is a normal operation during client shutdown. The first argument holds the client and transaction identification information. The second and third argument define the prefix and its length. The fourth argument holds IAID.

DHCP6_RELEASE_PD_FAIL

%1: failed to release prefix %2/%3 for iaid=%4

This error message indicates that the software failed to remove a prefix lease from the lease database. It probably due to an error during a database operation: resolution will most likely require administrator intervention (e.g. check if DHCP process has sufficient privileges to update the database). It may also be triggered if a lease was manually removed from the database during RELEASE message processing. The first argument hold the client and transaction identification information. The second and third argument define the prefix and its length. The fourth argument holds the IAID.

DHCP6_RELEASE_PD_FAIL_WRONG_DUID

%1: client tried to release prefix %2/%3, but it belongs to another client (duid=%4)

This warning message indicates that client tried to release a prefix that belongs to a different client. This should not happen in normal circumstances and may indicate a misconfiguration of the client. However, since the client releasing the prefix will stop using it anyway, there is a good chance that the situation will correct itself. The first argument includes the client and the transaction identification information. The second and third argument include the prefix and prefix length. The last argument holds the DUID of the client holding the lease.

DHCP6_RELEASE_PD_FAIL_WRONG_IAID

%1: client tried to release prefix %2/%3, but it used wrong IAID (expected %4, but got %5)

This warning message indicates that client tried to release a prefix that does belong to it, but the address was expected to be in a different IA (identity association) container. This probably means that the client’s support for multiple prefixes is flawed. The first argument includes the client and transaction identification information. The second and third argument identify the prefix. The fourth and fifth argument hold the expected IAID and IAID found respectively.

DHCP6_REQUIRED_OPTIONS_CHECK_FAIL

%1 message received from %2 failed the following check: %3

This message indicates that received DHCPv6 packet is invalid. This may be due to a number of reasons, e.g. the mandatory client-id option is missing, the server-id forbidden in that particular type of message is present, there is more than one instance of client-id or server-id present, etc. The exact reason for rejecting the packet is included in the message.

DHCP6_RESERVATIONS_LOOKUP_FIRST_ENABLED

Multi-threading is enabled and host reservations lookup is always performed first.

This is a message informing that host reservations lookup is performed before lease lookup when multi-threading is enabled overwriting configured value.

DHCP6_RESPONSE_DATA

responding with packet type %1 data is %2

A debug message listing the data returned to the client.

DHCP6_SERVER_FAILED

server failed: %1

The IPv6 DHCP server has encountered a fatal error and is terminating. The reason for the failure is included in the message.

DHCP6_SHUTDOWN

server shutdown

The IPv6 DHCP server has terminated normally.

DHCP6_SHUTDOWN_REQUEST

shutdown of server requested

This debug message indicates that a shutdown of the IPv6 server has been requested via a call to the ‘shutdown’ method of the core Dhcpv6Srv object.

DHCP6_SOCKET_UNICAST

server is about to open socket on address %1 on interface %2

This is a debug message that inform that a unicast socket will be opened.

DHCP6_SRV_CONSTRUCT_ERROR

error creating Dhcpv6Srv object, reason: %1

This error message indicates that during startup, the construction of a core component within the IPv6 DHCP server (the Dhcpv6 server object) has failed. As a result, the server will exit. The reason for the failure is given within the message.

DHCP6_SRV_D2STOP_ERROR

error stopping IO with DHCP_DDNS during shutdown: %1

This error message indicates that during shutdown, an error occurred while stopping IO between the DHCPv6 server and the DHCP_DDNS server. This is probably due to a programmatic error is not likely to impact either server upon restart. The reason for the failure is given within the message.

DHCP6_SRV_UNLOAD_LIBRARIES_ERROR

error unloading hooks libraries during shutdown: %1

This error message indicates that during shutdown, unloading hooks libraries failed to close them. If the list of libraries is empty it is a programmatic error in the server code. If it is not empty it could be a programmatic error in one of the hooks libraries which could lead to a crash during finalization.

DHCP6_STANDALONE

skipping message queue, running standalone

This is a debug message indicating that the IPv6 server is running in standalone mode, not connected to the message queue. Standalone mode is only useful during program development, and should not be used in a production environment.

DHCP6_STARTED

Kea DHCPv6 server version %1 started

This informational message indicates that the IPv6 DHCP server has processed all configuration information and is ready to process DHCPv6 packets. The version is also printed.

DHCP6_STARTING

Kea DHCPv6 server version %1 (%2) starting

This informational message indicates that the IPv6 DHCP server has processed any command-line switches and is starting. The version is also printed.

DHCP6_START_INFO

pid: %1, server port: %2, client port: %3, verbose: %4

This is a debug message issued during the IPv6 DHCP server startup. It lists some information about the parameters with which the server is running.

DHCP6_SUBNET_DATA

%1: the selected subnet details: %2

This debug message includes the details of the subnet selected for the client. The first argument includes the client and the transaction identification information. The second argument includes the subnet details.

DHCP6_SUBNET_DYNAMICALLY_CHANGED

%1: changed selected subnet %2 to subnet %3 from shared network %4 for client assignments

This debug message indicates that the server is using another subnet than initially selected for client assignments. This newly selected subnet belongs to the same shared network as the original subnet. Some reasons why the new subnet was selected include: address pool exhaustion in the original subnet or the fact that the new subnet includes some static reservations for this client.

DHCP6_SUBNET_SELECTED

%1: the subnet with ID %2 was selected for client assignments

This is a debug message noting the selection of a subnet to be used for address and option assignment. Subnet selection is one of the early steps in the processing of incoming client message. The first argument includes the client and the transaction identification information. The second argument holds the selected subnet id.

DHCP6_SUBNET_SELECTION_FAILED

%1: failed to select subnet for the client

This debug message indicates that the server failed to select the subnet for the client which has sent a message to the server. The cause is likely due to a misconfiguration of the server. The packet processing will continue, but the response will only contain generic configuration and no addresses or prefixes. The argument includes the client and the transaction identification information.

DHCP6_UNKNOWN_MSG_RECEIVED

received unknown message (type %1) on interface %2

This debug message is printed when server receives a message of unknown type. That could either mean missing functionality or invalid or broken relay or client. The list of formally defined message types is available here: http://www.iana.org/assignments/dhcpv6-parameters.

DHCPSRV

DHCPSRV_CFGMGR_ADD_IFACE

listening on interface %1

An info message issued when a new interface is being added to the collection of interfaces on which the server listens to DHCP messages.

DHCPSRV_CFGMGR_ADD_SUBNET4

adding subnet %1

A debug message reported when the DHCP configuration manager is adding the specified IPv4 subnet to its database.

DHCPSRV_CFGMGR_ADD_SUBNET6

adding subnet %1

A debug message reported when the DHCP configuration manager is adding the specified IPv6 subnet to its database.

DHCPSRV_CFGMGR_ALL_IFACES_ACTIVE

enabling listening on all interfaces

A debug message issued when the server is being configured to listen on all interfaces.

DHCPSRV_CFGMGR_CFG_DHCP_DDNS

Setting DHCP-DDNS configuration to: %1

A debug message issued when the server’s DHCP-DDNS settings are changed.

DHCPSRV_CFGMGR_CLEAR_ACTIVE_IFACES

stop listening on all interfaces

A debug message issued when configuration manager clears the internal list of active interfaces. This doesn’t prevent the server from listening to the DHCP traffic through open sockets, but will rather be used by Interface Manager to select active interfaces when sockets are re-opened.

DHCPSRV_CFGMGR_CONFIG4_MERGED

Configuration backend data has been merged.

This is an informational message emitted when the DHCPv4 server has successfully merged configuration data retrieved from its configuration backends into the current configuration.

DHCPSRV_CFGMGR_CONFIG6_MERGED

Configuration backend data has been merged.

This is an informational message emitted when the DHCPv6 server has successfully merged configuration data retrieved from its configuration backends into the current configuration.

DHCPSRV_CFGMGR_CONFIGURE_SERVERID

server configuration includes specification of a server identifier

This warning message is issued when the server specified configuration of a server identifier. If this new configuration overrides an existing server identifier, this will affect existing bindings of the clients. Clients will use old server identifier when they renew their bindings. The server will not respond to those renews, and the clients will eventually transition to rebinding state. The server should reassign existing bindings and the clients will subsequently use new server identifier. It is recommended to not modify the server identifier, unless there is a good reason for it, to avoid increased number of renewals and a need for rebinding (increase of multicast traffic, which may be received by multiple servers).

DHCPSRV_CFGMGR_DDNS_PARAMETER_IGNORED

dhcp-ddns:%1 is deprecated, using existing global:%2

This is an informational message issued during configuration parsing when the server detects that a deprecated parameter has been specified in the “dhcp-ddns” element which conflicts with its corresponding global parameter. When this occurs the server simply ignores the value from dhcp-ddns. The log message shows be the deprecated and the supported parameter names. Note the configuration change only affects the in-memory configuration. Modify the configuration to comply with the supported parameters.

DHCPSRV_CFGMGR_DDNS_PARAMETER_MOVED

dhcp-ddns:%1 is deprecated, moving it to global:%2

This is an informational message issued during configuration parsing when the server detects that a deprecated parameter has been specified in the “dhcp-ddns” element for which no corresponding global value exists. When this occurs, the server removes the parameter from dhcp-ddns and inserts the parameter into the global scope. The log message shows the deprecated and the supported parameter names. Note the configuration change only affects the in-memory configuration. Modify the configuration to comply with the supported parameters.

DHCPSRV_CFGMGR_DEL_SUBNET4

IPv4 subnet %1 removed

This debug message is issued when a subnet is successfully removed from the server configuration. The argument identifies the removed subnet.

DHCPSRV_CFGMGR_DEL_SUBNET6

IPv6 subnet %1 removed

This debug message is issued when a subnet is successfully removed from the server configuration. The argument identifies the removed subnet.

DHCPSRV_CFGMGR_IPV4_RESERVATIONS_NON_UNIQUE_IGNORED

ignoring “ip-reservations-unique” setting because at least one of the host database backends does not support non-unique IP reservations in a subnet

This warning message is issued when the server failed to use the new setting of the ip-reservations-unique global parameter configured via the configuration backend. Some host database backends used apparently do not support specifying several reservations for the same IP address in a subnet. The administrator should either stop using the backend that does not support this setting or set the value of the ip-reservations-unique to true to resolve the configuration issue.

DHCPSRV_CFGMGR_IPV6_RESERVATIONS_NON_UNIQUE_IGNORED

ignoring “ip-reservations-unique” setting because at least one of the host database backends does not support non unique IP reservations in a subnet

This warning message is issued when the server failed to use the new setting of the ip-reservations-unique global parameter configured via the configuration backend. Some host database backends used apparently do not support specifying several reservations for the same IP address or delegated prefix in a subnet. The administrator should either stop using the backend that does not support this setting or set the value of the ip-reservations-unique to true to resolve the configuration issue.

DHCPSRV_CFGMGR_IP_RESERVATIONS_UNIQUE_DUPLICATES_POSSIBLE

setting “ip-reservations-unique” from false to true poses a risk that some host backends may still contain multiple reservations for the same IP address

This warning message is issued when the DHCP server is configured to not allow multiple reservations for the same IP address. However, the host database backends may still contain multiple reservations for the same IP addresses causing problems with lease allocation for certain addresses. Please ensure that all such duplicates are removed.

DHCPSRV_CFGMGR_NEW_SUBNET4

a new subnet has been added to configuration: %1

This is an informational message reporting that the configuration has been extended to include the specified IPv4 subnet.

DHCPSRV_CFGMGR_NEW_SUBNET6

a new subnet has been added to configuration: %1

This is an informational message reporting that the configuration has been extended to include the specified subnet.

DHCPSRV_CFGMGR_NO_SUBNET4

no suitable subnet is defined for address hint %1

This debug message is output when the DHCP configuration manager has received a request for an IPv4 subnet for the specified address, but no such subnet exists.

DHCPSRV_CFGMGR_NO_SUBNET6

no suitable subnet is defined for address hint %1

This debug message is output when the DHCP configuration manager has received a request for an IPv6 subnet for the specified address, but no such subnet exists.

DHCPSRV_CFGMGR_ONLY_SUBNET4

retrieved subnet %1 for address hint %2

This is a debug message reporting that the DHCP configuration manager has returned the specified IPv4 subnet when given the address hint specified because it is the only subnet defined.

DHCPSRV_CFGMGR_ONLY_SUBNET6

retrieved subnet %1 for address hint %2

This is a debug message reporting that the DHCP configuration manager has returned the specified IPv6 subnet when given the address hint specified because it is the only subnet defined.

DHCPSRV_CFGMGR_OPTION_DUPLICATE

multiple options with the code: %1 added to the subnet: %2

This warning message is issued on an attempt to configure multiple options with the same option code for the particular subnet. Adding multiple options is uncommon for DHCPv6, but it is not prohibited.

DHCPSRV_CFGMGR_RELAY_IP_ADDRESS_DEPRECATED

“relay” uses “ip-address”, which has been deprecated, please use “ip-addresses”: %1

This is debug message issued when the “relay” element being parse contains “ip-address” rather than its replacement, “ip-addresses”. The server will still honor the value but users are encouraged to move to the new list parameter.

DHCPSRV_CFGMGR_SOCKET_RAW_UNSUPPORTED

use of raw sockets is unsupported on this OS, UDP sockets will be used

This warning message is logged when the user specified that the DHCPv4 server should use the raw sockets to receive the DHCP messages and respond to the clients, but the use of raw sockets is not supported on the particular environment. The raw sockets are useful when the server must respond to the directly connected clients which don’t have an address yet. If the raw sockets are not supported by Kea on the particular platform, Kea will fall back to use of the IP/UDP sockets. The responses to the directly connected clients will be broadcast. The responses to relayed clients will be unicast as usual.

DHCPSRV_CFGMGR_SOCKET_TYPE_DEFAULT

“dhcp-socket-type” not specified , using default socket type %1

This informational message is logged when the administrator hasn’t specified the “dhcp-socket-type” parameter in configuration for interfaces. In such case, the default socket type will be used.

DHCPSRV_CFGMGR_SOCKET_TYPE_SELECT

using socket type %1

This informational message is logged when the DHCPv4 server selects the socket type to be used for all sockets that will be opened on the interfaces. Typically, the socket type is specified by the server administrator. If the socket type hasn’t been specified, the raw socket will be selected. If the raw socket has been selected but Kea doesn’t support the use of raw sockets on the particular OS, it will use an UDP socket instead.

DHCPSRV_CFGMGR_SUBNET4

retrieved subnet %1 for address hint %2

This is a debug message reporting that the DHCP configuration manager has returned the specified IPv4 subnet when given the address hint specified as the address is within the subnet.

DHCPSRV_CFGMGR_SUBNET4_ADDR

selected subnet %1 for packet received by matching address %2

This is a debug message reporting that the DHCP configuration manager has returned the specified IPv4 subnet for a received packet. This particular subnet was selected, because an IPv4 address was matched which belonged to that subnet.

DHCPSRV_CFGMGR_SUBNET4_IFACE

selected subnet %1 for packet received over interface %2

This is a debug message reporting that the DHCP configuration manager has returned the specified IPv4 subnet for a packet received over the given interface. This particular subnet was selected, because it was specified as being directly reachable over the given interface. (see ‘interface’ parameter in the subnet4 definition).

DHCPSRV_CFGMGR_SUBNET4_RELAY

selected subnet %1, because of matching relay addr %2

This is a debug message reporting that the DHCP configuration manager has returned the specified IPv4 subnet, because detected relay agent address matches value specified for this subnet.

DHCPSRV_CFGMGR_SUBNET6

retrieved subnet %1 for address hint %2

This is a debug message reporting that the DHCP configuration manager has returned the specified IPv6 subnet when given the address hint specified as the address is within the subnet.

DHCPSRV_CFGMGR_SUBNET6_IFACE

selected subnet %1 for packet received over interface %2

This is a debug message reporting that the DHCP configuration manager has returned the specified IPv6 subnet for a packet received over given interface. This particular subnet was selected, because it was specified as being directly reachable over given interface. (see ‘interface’ parameter in the subnet6 definition).

DHCPSRV_CFGMGR_SUBNET6_IFACE_ID

selected subnet %1 (interface-id match) for incoming packet

This is a debug message reporting that the DHCP configuration manager has returned the specified IPv6 subnet for a received packet. This particular subnet was selected, because value of interface-id option matched what was configured in the server’s interface-id option for that selected subnet6. (see ‘interface-id’ parameter in the subnet6 definition).

DHCPSRV_CFGMGR_SUBNET6_RELAY

selected subnet %1, because of matching relay addr %2

This is a debug message reporting that the DHCP configuration manager has returned the specified IPv6 subnet, because detected relay agent address matches value specified for this subnet.

DHCPSRV_CFGMGR_UNICAST_LINK_LOCAL

specified link local address %1 for unicast traffic on interface %2

This warning message is logged when user specified a link-local address to receive unicast traffic. The warning message is issued because it is an uncommon use.

DHCPSRV_CFGMGR_UPDATE_SUBNET4

updating subnet %1 (result %2)

A debug message reported when the DHCP configuration manager is updating the specified IPv4 subnet in its current configuration. Subnet ID and result (expected to be true) are displayed.

DHCPSRV_CFGMGR_UPDATE_SUBNET6

updating subnet %1 (result %2)

A debug message reported when the DHCP configuration manager is replacing the specified IPv6 subnet in its current configuration. Subnet ID and result (expected to be true) are displayed.

DHCPSRV_CFGMGR_USE_ADDRESS

listening on address %1, on interface %2

A message issued when the server is configured to listen on the explicitly specified IP address on the given interface.

DHCPSRV_CFGMGR_USE_UNICAST

listening on unicast address %1, on interface %2

An info message issued when configuring the DHCP server to listen on the unicast address on the specific interface.

DHCPSRV_CLOSE_DB

closing currently open %1 database

This is a debug message, issued when the DHCP server closes the currently open lease database. It is issued at program shutdown and whenever the database access parameters are changed: in the latter case, the server closes the currently open database, and opens a database using the new parameters.

DHCPSRV_DEPRECATED

This configuration is using a deprecated feature: %1

This warning is printed every time a deprecated feature (identified by the parameter) is used. A deprecated feature is functional now, but there will be a future Kea release where it will be completely removed. If you see this message it’s not a reason for panic, but you should consider your long term strategy to eventually stop using the deprecated feature.

DHCPSRV_DHCP4O6_RECEIVED_BAD_PACKET

received bad DHCPv4o6 packet: %1

A bad DHCPv4o6 packet was received.

DHCPSRV_DHCP_DDNS_ERROR_EXCEPTION

error handler for DHCP_DDNS IO generated an expected exception: %1

This is an error message that occurs when an attempt to send a request to kea-dhcp-ddns fails there registered error handler threw an uncaught exception. This is a programmatic error which should not occur. By convention, the error handler should not propagate exceptions. Please report this error.

DHCPSRV_DHCP_DDNS_HANDLER_NULL

error handler for DHCP_DDNS IO is not set.

This is an error message that occurs when an attempt to send a request to kea-dhcp-ddns fails and there is no registered error handler. This is a programmatic error which should never occur and should be reported.

DHCPSRV_DHCP_DDNS_NCR_REJECTED

NameChangeRequest rejected by the sender: %1, ncr: %2

This is an error message indicating that NameChangeSender used to deliver DDNS update requests to kea-dhcp-ddns rejected the request. This most likely cause is the sender’s queue has reached maximum capacity. This would imply that requests are being generated faster than they can be delivered.

DHCPSRV_DHCP_DDNS_NCR_SENT

NameChangeRequest sent to kea-dhcp-ddns: %1

A debug message issued when a NameChangeRequest has been successfully sent to kea-dhcp-ddns.

DHCPSRV_DHCP_DDNS_SENDER_STARTED

NameChangeRequest sender has been started: %1

An informational message issued when a communication with kea-dhcp-ddns has been successfully started.

DHCPSRV_DHCP_DDNS_SENDER_STOPPED

NameChangeRequest sender has been stopped.

An informational message issued when a communication with kea-dhcp-ddns has been stopped. This normally occurs during reconfiguration and as part of normal shutdown. It may occur if kea-dhcp-ddns communications break down.

DHCPSRV_DHCP_DDNS_SUSPEND_UPDATES

DHCP_DDNS updates are being suspended.

This is a warning message indicating the DHCP_DDNS updates have been turned off. This should only occur if IO errors communicating with kea-dhcp-ddns have been experienced. Any such errors should have preceding entries in the log with details. No further attempts to communicate with kea-dhcp-ddns will be made without intervention.

DHCPSRV_HOOK_LEASE4_RECOVER_SKIP

DHCPv4 lease %1 was not recovered from the declined state because a callout set the skip status.

This debug message is printed when a callout installed on lease4_recover hook point set the next step status to SKIP. For this particular hook point, this indicates that the server should not recover the lease from declined state. The server will leave the lease as it is, in the declined state. The server will attempt to recover it the next time decline recovery procedure takes place.

DHCPSRV_HOOK_LEASE4_RENEW_SKIP

DHCPv4 lease was not renewed because a callout set the skip flag.

This debug message is printed when a callout installed on lease4_renew hook point set the skip flag. For this particular hook point, the setting of the flag by a callout instructs the server to not renew a lease. The server will use existing lease as it is, without extending its lifetime.

DHCPSRV_HOOK_LEASE4_SELECT_SKIP

Lease4 creation was skipped, because of callout skip flag.

This debug message is printed when a callout installed on lease4_select hook point sets the skip flag. It means that the server was told that no lease4 should be assigned. The server will not put that lease in its database and the client will get a NAK packet.

DHCPSRV_HOOK_LEASE6_EXTEND_SKIP

DHCPv6 lease lifetime was not extended because a callout set the skip flag for message %1

This debug message is printed when a callout installed on lease6_renew or the lease6_rebind hook point set the skip flag. For this particular hook point, the setting of the flag by a callout instructs the server to not extend the lifetime for a lease. If the client requested renewal of multiple leases (by sending multiple IA options), the server will skip the renewal of the one in question and will proceed with other renewals as usual.

DHCPSRV_HOOK_LEASE6_RECOVER_SKIP

DHCPv6 lease %1 was not recovered from declined state because a callout set the skip status.

This debug message is printed when a callout installed on lease6_recover hook point set the next step status to SKIP. For this particular hook point, this indicates that the server should not recover the lease from declined state. The server will leave the lease as it is, in the declined state. The server will attempt to recover it the next time decline recovery procedure takes place.

DHCPSRV_HOOK_LEASE6_SELECT_SKIP

Lease6 (non-temporary) creation was skipped, because of callout skip flag.

This debug message is printed when a callout installed on lease6_select hook point sets the skip flag. It means that the server was told that no lease6 should be assigned. The server will not put that lease in its database and the client will get a NoAddrsAvail for that IA_NA option.

DHCPSRV_INVALID_ACCESS

invalid database access string: %1

This is logged when an attempt has been made to parse a database access string and the attempt ended in error. The access string in question - which should be of the form ‘keyword=value keyword=value…’ is included in the message.

DHCPSRV_LEASE_SANITY_FAIL

The lease %1 with subnet-id %2 failed subnet-id checks (%3).

This warning message is printed when the lease being loaded does not match the configuration. Due to lease-checks value, the lease will be loaded, but it will most likely be unused by Kea, as there is no subnet that matches the IP address associated with the lease.

DHCPSRV_LEASE_SANITY_FAIL_DISCARD

The lease %1 with subnet-id %2 failed subnet-id checks (%3) and was dropped.

This warning message is printed when a lease was loaded, but Kea was told (by setting lease-checks parameter) to discard leases with inconsistent data. The lease was discarded, because either there is no subnet configured with matching subnet-id or the address of the lease does not belong to the subnet.

DHCPSRV_LEASE_SANITY_FIXED

The lease %1 with subnet-id %2 failed subnet-id checks, but was corrected to subnet-id %3.

This informational message is printed when a lease was loaded, but had incorrect subnet-id value. The lease-checks parameter was set to a value that told Kea to try to correct the problem. There is a matching subnet, so Kea updated subnet-id and loaded the lease successfully.

DHCPSRV_MEMFILE_ADD_ADDR4

adding IPv4 lease with address %1

A debug message issued when the server is about to add an IPv4 lease with the specified address to the memory file backend database.

DHCPSRV_MEMFILE_ADD_ADDR6

adding IPv6 lease with address %1

A debug message issued when the server is about to add an IPv6 lease with the specified address to the memory file backend database.

DHCPSRV_MEMFILE_BEGIN_TRANSACTION

committing to memory file database

The code has issued a begin transaction call. For the memory file database, this is a no-op.

DHCPSRV_MEMFILE_COMMIT

committing to memory file database

The code has issued a commit call. For the memory file database, this is a no-op.

DHCPSRV_MEMFILE_CONVERTING_LEASE_FILES

running LFC now to convert lease files to the current schema: %1.%2

A warning message issued when the server has detected lease files that need to be either upgraded or downgraded to match the server’s schema, and that the server is automatically running the LFC process to perform the conversion. This should only occur the first time the server is launched following a Kea installation upgrade (or downgrade).

DHCPSRV_MEMFILE_DB

opening memory file lease database: %1

This informational message is logged when a DHCP server (either V4 or V6) is about to open a memory file lease database. The parameters of the connection including database name and username needed to access it (but not the password if any) are logged.

DHCPSRV_MEMFILE_DELETE_ADDR

deleting lease for address %1

A debug message issued when the server is attempting to delete a lease for the specified address from the memory file database for the specified address.

DHCPSRV_MEMFILE_DELETE_EXPIRED_RECLAIMED4

deleting reclaimed IPv4 leases that expired more than %1 seconds ago

A debug message issued when the server is removing reclaimed DHCPv4 leases which have expired longer than a specified period of time. The argument is the amount of time Kea waits after a reclaimed lease expires before considering its removal.

DHCPSRV_MEMFILE_DELETE_EXPIRED_RECLAIMED6

deleting reclaimed IPv6 leases that expired more than %1 seconds ago

A debug message issued when the server is removing reclaimed DHCPv6 leases which have expired longer than a specified period of time. The argument is the amount of time Kea waits after a reclaimed lease expires before considering its removal.

DHCPSRV_MEMFILE_DELETE_EXPIRED_RECLAIMED_START

starting deletion of %1 expired-reclaimed leases

A debug message issued when the server has found expired-reclaimed leases to be removed. The number of leases to be removed is logged in the message.

DHCPSRV_MEMFILE_GET4

obtaining all IPv4 leases

A debug message issued when the server is attempting to obtain all IPv4 leases from the memory file database.

DHCPSRV_MEMFILE_GET6

obtaining all IPv6 leases

A debug message issued when the server is attempting to obtain all IPv6 leases from the memory file database.

DHCPSRV_MEMFILE_GET6_DUID

obtaining IPv6 leases for DUID %1

A debug message issued when the server is attempting to obtain IPv6 leases from the memory file database for the DUID.

DHCPSRV_MEMFILE_GET_ADDR4

obtaining IPv4 lease for address %1

A debug message issued when the server is attempting to obtain an IPv4 lease from the memory file database for the specified address.

DHCPSRV_MEMFILE_GET_ADDR6

obtaining IPv6 lease for address %1 and lease type %2

A debug message issued when the server is attempting to obtain an IPv6 lease from the memory file database for the specified address.

DHCPSRV_MEMFILE_GET_CLIENTID

obtaining IPv4 leases for client ID %1

A debug message issued when the server is attempting to obtain a set of IPv4 leases from the memory file database for a client with the specified client identification.

DHCPSRV_MEMFILE_GET_EXPIRED4

obtaining maximum %1 of expired IPv4 leases

A debug message issued when the server is attempting to obtain expired IPv4 leases to reclaim them. The maximum number of leases to be retrieved is logged in the message.

DHCPSRV_MEMFILE_GET_EXPIRED6

obtaining maximum %1 of expired IPv6 leases

A debug message issued when the server is attempting to obtain expired IPv6 leases to reclaim them. The maximum number of leases to be retrieved is logged in the message.

DHCPSRV_MEMFILE_GET_HOSTNAME4

obtaining IPv4 leases for hostname %1

A debug message issued when the server is attempting to obtain a set of IPv4 leases from the memory file database for a client with the specified hostname.

DHCPSRV_MEMFILE_GET_HOSTNAME6

obtaining IPv6 leases for hostname %1

A debug message issued when the server is attempting to obtain a set of IPv6 leases from the memory file database for a client with the specified hostname.

DHCPSRV_MEMFILE_GET_HWADDR

obtaining IPv4 leases for hardware address %1

A debug message issued when the server is attempting to obtain a set of IPv4 leases from the memory file database for a client with the specified hardware address.

DHCPSRV_MEMFILE_GET_IAID_DUID

obtaining IPv6 leases for IAID %1 and DUID %2 and lease type %3

A debug message issued when the server is attempting to obtain a set of IPv6 leases from the memory file database for a client with the specified IAID (Identity Association ID) and DUID (DHCP Unique Identifier).

DHCPSRV_MEMFILE_GET_IAID_SUBID_DUID

obtaining IPv6 leases for IAID %1, Subnet ID %2, DUID %3 and lease type %4

A debug message issued when the server is attempting to obtain an IPv6 lease from the memory file database for a client with the specified IAID (Identity Association ID), Subnet ID and DUID (DHCP Unique Identifier).

DHCPSRV_MEMFILE_GET_PAGE4

obtaining at most %1 IPv4 leases starting from address %2

A debug message issued when the server is attempting to obtain a page of leases beginning with the specified address.

DHCPSRV_MEMFILE_GET_PAGE6

obtaining at most %1 IPv6 leases starting from address %2

A debug message issued when the server is attempting to obtain a page of leases beginning with the specified address.

DHCPSRV_MEMFILE_GET_SUBID4

obtaining IPv4 leases for subnet ID %1

A debug message issued when the server is attempting to obtain all IPv4 leases for a given subnet identifier from the memory file database.

DHCPSRV_MEMFILE_GET_SUBID6

obtaining IPv6 leases for subnet ID %1

A debug message issued when the server is attempting to obtain all IPv6 leases for a given subnet identifier from the memory file database.

DHCPSRV_MEMFILE_GET_SUBID_CLIENTID

obtaining IPv4 lease for subnet ID %1 and client ID %2

A debug message issued when the server is attempting to obtain an IPv4 lease from the memory file database for a client with the specified subnet ID and client ID.

DHCPSRV_MEMFILE_GET_SUBID_HWADDR

obtaining IPv4 lease for subnet ID %1 and hardware address %2

A debug message issued when the server is attempting to obtain an IPv4 lease from the memory file database for a client with the specified subnet ID and hardware address.

DHCPSRV_MEMFILE_GET_VERSION

obtaining schema version information

A debug message issued when the server is about to obtain schema version information from the memory file database.

DHCPSRV_MEMFILE_LEASE_FILE_LOAD

loading leases from file %1

An info message issued when the server is about to start reading DHCP leases from the lease file. All leases currently held in the memory will be replaced by those read from the file.

DHCPSRV_MEMFILE_LEASE_LOAD

loading lease %1

A debug message issued when DHCP lease is being loaded from the file to memory.

DHCPSRV_MEMFILE_LEASE_LOAD_ROW_ERROR

discarding row %1, error: %2

An error message issued if the DHCP lease being loaded from the given row of the lease file fails. The log message should contain the specific reason the row was discarded. The server continues loading the remaining data. This may indicate a corrupt lease file.

DHCPSRV_MEMFILE_LFC_EXECUTE

executing Lease File Cleanup using: %1

An informational message issued when the memfile lease database backend starts a new process to perform Lease File Cleanup.

DHCPSRV_MEMFILE_LFC_LEASE_FILE_RENAME_FAIL

failed to rename the current lease file %1 to %2, reason: %3

An error message logged when the memfile lease database backend fails to move the current lease file to a new file on which the cleanup should be performed. This effectively means that the lease file cleanup does not take place.

DHCPSRV_MEMFILE_LFC_LEASE_FILE_REOPEN_FAIL

failed to reopen lease file %1 after preparing input file for lease file cleanup, reason: %2, new leases will not persist!

An error message logged when the memfile lease database backend failed to re-open or re-create the lease file after renaming the lease file for lease file cleanup. The server continues to operate but leases do not persist to disk.

DHCPSRV_MEMFILE_LFC_SETUP

setting up the Lease File Cleanup interval to %1 sec

An informational message logged when the memfile lease database backend configures the LFC to be executed periodically. The argument holds the interval in seconds in which the LFC will be executed.

DHCPSRV_MEMFILE_LFC_SPAWN_FAIL

lease file cleanup failed to run because kea-lfc process couldn’t be spawned

This error message is logged when the Kea server fails to run kea-lfc, the program that cleans up the lease file. The server will try again the next time a lease file cleanup is scheduled. Although this message should not appear and the reason why it did investigated, the occasional failure to start the lease file cleanup will not impact operations. Should the failure persist however, the size of the lease file will increase without bound.

DHCPSRV_MEMFILE_LFC_START

starting Lease File Cleanup

An informational message issued when the Memfile lease database backend starts the periodic Lease File Cleanup.

DHCPSRV_MEMFILE_LFC_UNREGISTER_TIMER_FAILED

failed to unregister timer ‘memfile-lfc’: %1

This debug message is logged when Memfile backend fails to unregister timer used for lease file cleanup scheduling. There are several reasons why this could occur, although the most likely cause is that the system is being shut down and some other component has unregistered the timer. The message includes the reason for this error.

DHCPSRV_MEMFILE_NEEDS_DOWNGRADING

version of lease file: %1 schema is later than version %2

A warning message issued when the schema of the lease file loaded by the server is newer than the memfile schema of the server. The server converts the lease data from newer schemas to its schema as it is read, therefore the lease information in use by the server will be correct. Note though, that any data stored in newer schema fields will be dropped. What remains is for the file itself to be rewritten using the current schema.

DHCPSRV_MEMFILE_NEEDS_UPGRADING

version of lease file: %1 schema is earlier than version %2

A warning message issued when the schema of the lease file loaded by the server pre-dates the memfile schema of the server. Note that the server converts the lease data from older schemas to the current schema as it is read, therefore the lease information in use by the server will be correct. What remains is for the file itself to be rewritten using the current schema.

DHCPSRV_MEMFILE_NO_STORAGE

running in non-persistent mode, leases will be lost after restart

A warning message issued when writes of leases to disk have been disabled in the configuration. This mode is useful for some kinds of performance testing but should not be enabled in normal circumstances. Non-persistence mode is enabled when ‘persist4=no persist6=no’ parameters are specified in the database access string.

DHCPSRV_MEMFILE_READ_HWADDR_FAIL

failed to read hardware address from lease file: %1

A warning message issued when read attempt of the hardware address stored in a disk file failed. The parameter should provide the exact nature of the failure. The database read will continue, but that particular lease will no longer have hardware address associated with it.

DHCPSRV_MEMFILE_ROLLBACK

rolling back memory file database

The code has issued a rollback call. For the memory file database, this is a no-op.

DHCPSRV_MEMFILE_UPDATE_ADDR4

updating IPv4 lease for address %1

A debug message issued when the server is attempting to update IPv4 lease from the memory file database for the specified address.

DHCPSRV_MEMFILE_UPDATE_ADDR6

updating IPv6 lease for address %1

A debug message issued when the server is attempting to update IPv6 lease from the memory file database for the specified address.

DHCPSRV_MEMFILE_WIPE_LEASES4

removing all IPv4 leases from subnet %1

This informational message is printed when removal of all leases from specified IPv4 subnet is commencing. This is a result of receiving administrative command.

DHCPSRV_MEMFILE_WIPE_LEASES4_FINISHED

removing all IPv4 leases from subnet %1 finished, removed %2 leases

This informational message is printed when removal of all leases from a specified IPv4 subnet has finished. The number of removed leases is printed.

DHCPSRV_MEMFILE_WIPE_LEASES6

removing all IPv6 leases from subnet %1

This informational message is printed when removal of all leases from specified IPv6 subnet is commencing. This is a result of receiving administrative command.

DHCPSRV_MEMFILE_WIPE_LEASES6_FINISHED

removing all IPv6 leases from subnet %1 finished, removed %2 leases

This informational message is printed when removal of all leases from a specified IPv6 subnet has finished. The number of removed leases is printed.

DHCPSRV_MULTIPLE_RAW_SOCKETS_PER_IFACE

current configuration will result in opening multiple broadcast capable sockets on some interfaces and some DHCP messages may be duplicated

A warning message issued when the current configuration indicates that multiple sockets, capable of receiving broadcast traffic, will be opened on some of the interfaces. It must be noted that this may lead to receiving and processing the same DHCP message multiple times, as it will be received by each socket individually.

DHCPSRV_MYSQL_ADD_ADDR4

adding IPv4 lease with address %1

A debug message issued when the server is about to add an IPv4 lease with the specified address to the MySQL backend database.

DHCPSRV_MYSQL_ADD_ADDR6

adding IPv6 lease with address %1, lease type %2

A debug message issued when the server is about to add an IPv6 lease with the specified address to the MySQL backend database.

DHCPSRV_MYSQL_BEGIN_TRANSACTION

committing to MySQL database

The code has issued a begin transaction call.

DHCPSRV_MYSQL_COMMIT

committing to MySQL database

The code has issued a commit call. All outstanding transactions will be committed to the database. Note that depending on the MySQL settings, the commit may not include a write to disk.

DHCPSRV_MYSQL_DB

opening MySQL lease database: %1

This informational message is logged when a DHCP server (either V4 or V6) is about to open a MySQL lease database. The parameters of the connection including database name and username needed to access it (but not the password if any) are logged.

DHCPSRV_MYSQL_DELETED_EXPIRED_RECLAIMED

deleted %1 reclaimed leases from the database

A debug message issued when the server has removed a number of reclaimed leases from the database. The number of removed leases is included in the message.

DHCPSRV_MYSQL_DELETE_ADDR

deleting lease for address %1

A debug message issued when the server is attempting to delete a lease for the specified address from the MySQL database for the specified address.

DHCPSRV_MYSQL_DELETE_EXPIRED_RECLAIMED4

deleting reclaimed IPv4 leases that expired more than %1 seconds ago

A debug message issued when the server is removing reclaimed DHCPv4 leases which have expired longer than a specified period of time. The argument is the amount of time Kea waits after a reclaimed lease expires before considering its removal.

DHCPSRV_MYSQL_DELETE_EXPIRED_RECLAIMED6

deleting reclaimed IPv6 leases that expired more than %1 seconds ago

A debug message issued when the server is removing reclaimed DHCPv6 leases which have expired longer than a specified period of time. The argument is the amount of time Kea waits after a reclaimed lease expires before considering its removal.

DHCPSRV_MYSQL_FATAL_ERROR

Unrecoverable MySQL error occurred: %1 for <%2>, reason: %3 (error code: %4).

An error message indicating that communication with the MySQL database server has been lost. If automatic recovery has been enabled, then the server will attempt to recover the connectivity. If not the server will exit with a non-zero exit code. The cause of such an error is most likely a network issue or the MySQL server has gone down.

DHCPSRV_MYSQL_GET4

obtaining all IPv4 leases

A debug message issued when the server is attempting to obtain all IPv4 leases from the MySQL database.

DHCPSRV_MYSQL_GET6

obtaining all IPv6 leases

A debug message issued when the server is attempting to obtain all IPv6 leases from the MySQL database.

DHCPSRV_MYSQL_GET_ADDR4

obtaining IPv4 lease for address %1

A debug message issued when the server is attempting to obtain an IPv4 lease from the MySQL database for the specified address.

DHCPSRV_MYSQL_GET_ADDR6

obtaining IPv6 lease for address %1, lease type %2

A debug message issued when the server is attempting to obtain an IPv6 lease from the MySQL database for the specified address.

DHCPSRV_MYSQL_GET_CLIENTID

obtaining IPv4 leases for client ID %1

A debug message issued when the server is attempting to obtain a set of IPv4 leases from the MySQL database for a client with the specified client identification.

DHCPSRV_MYSQL_GET_DUID

obtaining IPv6 lease for duid %1,

A debug message issued when the server is attempting to obtain an IPv6 lease from the MySQL database for the specified duid.

DHCPSRV_MYSQL_GET_EXPIRED4

obtaining maximum %1 of expired IPv4 leases

A debug message issued when the server is attempting to obtain expired IPv4 leases to reclaim them. The maximum number of leases to be retrieved is logged in the message.

DHCPSRV_MYSQL_GET_EXPIRED6

obtaining maximum %1 of expired IPv6 leases

A debug message issued when the server is attempting to obtain expired IPv6 leases to reclaim them. The maximum number of leases to be retrieved is logged in the message.

DHCPSRV_MYSQL_GET_HOSTNAME4

obtaining IPv4 leases for hostname %1

A debug message issued when the server is attempting to obtain a set of IPv4 leases from the MySQL database for a client with the specified hostname.

DHCPSRV_MYSQL_GET_HOSTNAME6

obtaining IPv6 leases for hostname %1

A debug message issued when the server is attempting to obtain a set of IPv6 leases from the MySQL database for a client with the specified hostname.

DHCPSRV_MYSQL_GET_HWADDR

obtaining IPv4 leases for hardware address %1

A debug message issued when the server is attempting to obtain a set of IPv4 leases from the MySQL database for a client with the specified hardware address.

DHCPSRV_MYSQL_GET_IAID_DUID

obtaining IPv6 leases for IAID %1, DUID %2, lease type %3

A debug message issued when the server is attempting to obtain a set of IPv6 leases from the MySQL database for a client with the specified IAID (Identity Association ID) and DUID (DHCP Unique Identifier).

DHCPSRV_MYSQL_GET_IAID_SUBID_DUID

obtaining IPv6 leases for IAID %1, Subnet ID %2, DUID %3, lease type %4

A debug message issued when the server is attempting to obtain an IPv6 lease from the MySQL database for a client with the specified IAID (Identity Association ID), Subnet ID and DUID (DHCP Unique Identifier).

DHCPSRV_MYSQL_GET_PAGE4

obtaining at most %1 IPv4 leases starting from address %2

A debug message issued when the server is attempting to obtain a page of leases beginning with the specified address.

DHCPSRV_MYSQL_GET_PAGE6

obtaining at most %1 IPv6 leases starting from address %2

A debug message issued when the server is attempting to obtain a page of leases beginning with the specified address.

DHCPSRV_MYSQL_GET_SUBID4

obtaining IPv4 leases for subnet ID %1

A debug message issued when the server is attempting to obtain all IPv4 leases for a given subnet identifier from the MySQL database.

DHCPSRV_MYSQL_GET_SUBID6

obtaining IPv6 leases for subnet ID %1

A debug message issued when the server is attempting to obtain all IPv6 leases for a given subnet identifier from the MySQL database.

DHCPSRV_MYSQL_GET_SUBID_CLIENTID

obtaining IPv4 lease for subnet ID %1 and client ID %2

A debug message issued when the server is attempting to obtain an IPv4 lease from the MySQL database for a client with the specified subnet ID and client ID.

DHCPSRV_MYSQL_GET_SUBID_HWADDR

obtaining IPv4 lease for subnet ID %1 and hardware address %2

A debug message issued when the server is attempting to obtain an IPv4 lease from the MySQL database for a client with the specified subnet ID and hardware address.

DHCPSRV_MYSQL_GET_VERSION

obtaining schema version information

A debug message issued when the server is about to obtain schema version information from the MySQL database.

DHCPSRV_MYSQL_HOST_DB

opening MySQL hosts database: %1

This informational message is logged when a DHCP server (either V4 or V6) is about to open a MySQL hosts database. The parameters of the connection including database name and username needed to access it (but not the password if any) are logged.

DHCPSRV_MYSQL_HOST_DB_GET_VERSION

obtaining schema version information for the MySQL hosts database

A debug message issued when the server is about to obtain schema version information from the MySQL hosts database.

DHCPSRV_MYSQL_HOST_DB_READONLY

MySQL host database opened for read access only

This informational message is issued when the user has configured the MySQL database in read-only mode. Kea will not be able to insert or modify host reservations but will be able to retrieve existing ones and assign them to the clients communicating with the server.

DHCPSRV_MYSQL_HOST_DB_RECONNECT_ATTEMPT_FAILED

database reconnect failed: %1

An error message issued when an attempt to reconnect has failed.

DHCPSRV_MYSQL_HOST_DB_RECONNECT_ATTEMPT_SCHEDULE

scheduling attempt %1 of %2 in %3 milliseconds

An info message issued when the server is scheduling the next attempt to reconnect to the database. This occurs when the server has lost database connectivity and is attempting to reconnect automatically.

DHCPSRV_MYSQL_HOST_DB_RECONNECT_FAILED

maximum number of database reconnect attempts: %1, has been exhausted without success

An error message issued when the server failed to reconnect. Loss of connectivity is typically a network or database server issue.

DHCPSRV_MYSQL_LEASE_DB_RECONNECT_ATTEMPT_FAILED

database reconnect failed: %1

An error message issued when an attempt to reconnect has failed.

DHCPSRV_MYSQL_LEASE_DB_RECONNECT_ATTEMPT_SCHEDULE

scheduling attempt %1 of %2 in %3 milliseconds

An info message issued when the server is scheduling the next attempt to reconnect to the database. This occurs when the server has lost database connectivity and is attempting to reconnect automatically.

DHCPSRV_MYSQL_LEASE_DB_RECONNECT_FAILED

maximum number of database reconnect attempts: %1, has been exhausted without success

An error message issued when the server failed to reconnect. Loss of connectivity is typically a network or database server issue.

DHCPSRV_MYSQL_NEGATIVE_LEASES_STAT

recount of leases returned a negative value

This warning message is issued when the recount of leases using counters in the MySQL database returned a negative value. This shows a problem which can be fixed only by an offline direct recount on the database. This message is issued only once.

DHCPSRV_MYSQL_NO_TLS

TLS was required but is not used

This error message is issued when TLS for the connection was required but TLS is not used.

DHCPSRV_MYSQL_ROLLBACK

rolling back MySQL database

The code has issued a rollback call. All outstanding transaction will be rolled back and not committed to the database.

DHCPSRV_MYSQL_START_TRANSACTION

starting new MySQL transaction

A debug message issued when a new MySQL transaction is being started. This message is typically not issued when inserting data into a single table because the server doesn’t explicitly start transactions in this case. This message is issued when data is inserted into multiple tables with multiple INSERT statements and there may be a need to rollback the whole transaction if any of these INSERT statements fail.

DHCPSRV_MYSQL_TLS_CIPHER

TLS cipher: %1

A debug message issued when a new MySQL connected is created with TLS. The TLS cipher name is logged.

DHCPSRV_MYSQL_UPDATE_ADDR4

updating IPv4 lease for address %1

A debug message issued when the server is attempting to update IPv4 lease from the MySQL database for the specified address.

DHCPSRV_MYSQL_UPDATE_ADDR6

updating IPv6 lease for address %1, lease type %2

A debug message issued when the server is attempting to update IPv6 lease from the MySQL database for the specified address.

DHCPSRV_NOTYPE_DB

no ‘type’ keyword to determine database backend: %1

This is an error message, logged when an attempt has been made to access a database backend, but where no ‘type’ keyword has been included in the access string. The access string (less any passwords) is included in the message.

DHCPSRV_NO_SOCKETS_OPEN

no interface configured to listen to DHCP traffic

This warning message is issued when the current server configuration specifies no interfaces that the server should listen on, or when the specified interfaces are not configured to receive the traffic.

DHCPSRV_OPEN_SOCKET_FAIL

failed to open socket: %1

A warning message issued when IfaceMgr fails to open and bind a socket. The reason for the failure is appended as an argument of the log message.

DHCPSRV_PGSQL_ADD_ADDR4

adding IPv4 lease with address %1

A debug message issued when the server is about to add an IPv4 lease with the specified address to the PostgreSQL backend database.

DHCPSRV_PGSQL_ADD_ADDR6

adding IPv6 lease with address %1, lease type %2

A debug message issued when the server is about to add an IPv6 lease with the specified address to the PostgreSQL backend database.

DHCPSRV_PGSQL_BEGIN_TRANSACTION

committing to PostgreSQL database

The code has issued a begin transaction call.

DHCPSRV_PGSQL_COMMIT

committing to PostgreSQL database

The code has issued a commit call. All outstanding transactions will be committed to the database. Note that depending on the PostgreSQL settings, the commit may not include a write to disk.

DHCPSRV_PGSQL_DB

opening PostgreSQL lease database: %1

This informational message is logged when a DHCP server (either V4 or V6) is about to open a PostgreSQL lease database. The parameters of the connection including database name and username needed to access it (but not the password if any) are logged.

DHCPSRV_PGSQL_DEALLOC_ERROR

An error occurred deallocating SQL statements while closing the PostgreSQL lease database: %1

This is an error message issued when a DHCP server (either V4 or V6) experienced and error freeing database SQL resources as part of closing its connection to the PostgreSQL database. The connection is closed as part of normal server shutdown. This error is most likely a programmatic issue that is highly unlikely to occur or negatively impact server operation.

DHCPSRV_PGSQL_DELETE_ADDR

deleting lease for address %1

A debug message issued when the server is attempting to delete a lease for the specified address from the PostgreSQL database for the specified address.

DHCPSRV_PGSQL_DELETE_EXPIRED_RECLAIMED4

deleting reclaimed IPv4 leases that expired more than %1 seconds ago

A debug message issued when the server is removing reclaimed DHCPv4 leases which have expired longer than a specified period of time. The argument is the amount of time Kea waits after a reclaimed lease expires before considering its removal.

DHCPSRV_PGSQL_DELETE_EXPIRED_RECLAIMED6

deleting reclaimed IPv6 leases that expired more than %1 seconds ago

A debug message issued when the server is removing reclaimed DHCPv6 leases which have expired longer than a specified period of time. The argument is the amount of time Kea waits after a reclaimed lease expires before considering its removal.

DHCPSRV_PGSQL_FATAL_ERROR

Unrecoverable PostgreSQL error occurred: Statement: <%1>, reason: %2 (error code: %3).

An error message indicating that communication with the PostgreSQL database server has been lost. If automatic recovery has been enabled, then the server will attempt to recover the connectivity. If not the server will exit with a non-zero exit code. The cause of such an error is most likely a network issue or the PostgreSQL server has gone down.

DHCPSRV_PGSQL_GET4

obtaining all IPv4 leases

A debug message issued when the server is attempting to obtain all IPv4 leases from the PostgreSQL database.

DHCPSRV_PGSQL_GET6

obtaining all IPv6 leases

A debug message issued when the server is attempting to obtain all IPv6 leases from the PostgreSQL database.

DHCPSRV_PGSQL_GET_ADDR4

obtaining IPv4 lease for address %1

A debug message issued when the server is attempting to obtain an IPv4 lease from the PostgreSQL database for the specified address.

DHCPSRV_PGSQL_GET_ADDR6

obtaining IPv6 lease for address %1 (lease type %2)

A debug message issued when the server is attempting to obtain an IPv6 lease from the PostgreSQL database for the specified address.

DHCPSRV_PGSQL_GET_CLIENTID

obtaining IPv4 leases for client ID %1

A debug message issued when the server is attempting to obtain a set of IPv4 leases from the PostgreSQL database for a client with the specified client identification.

DHCPSRV_PGSQL_GET_DUID

obtaining IPv6 leases for DUID %1,

A debug message issued when the server is attempting to obtain a set of IPv6 leases from the PostgreSQL database for a client with the specified DUID (DHCP Unique Identifier).

DHCPSRV_PGSQL_GET_EXPIRED4

obtaining maximum %1 of expired IPv4 leases

A debug message issued when the server is attempting to obtain expired IPv4 leases to reclaim them. The maximum number of leases to be retrieved is logged in the message.

DHCPSRV_PGSQL_GET_EXPIRED6

obtaining maximum %1 of expired IPv6 leases

A debug message issued when the server is attempting to obtain expired IPv6 leases to reclaim them. The maximum number of leases to be retrieved is logged in the message.

DHCPSRV_PGSQL_GET_HOSTNAME4

obtaining IPv4 leases for hostname %1

A debug message issued when the server is attempting to obtain a set of IPv4 leases from the PostgreSQL database for a client with the specified hostname.

DHCPSRV_PGSQL_GET_HOSTNAME6

obtaining IPv6 leases for hostname %1

A debug message issued when the server is attempting to obtain a set of IPv6 leases from the PostgreSQL database for a client with the specified hostname.

DHCPSRV_PGSQL_GET_HWADDR

obtaining IPv4 leases for hardware address %1

A debug message issued when the server is attempting to obtain a set of IPv4 leases from the PostgreSQL database for a client with the specified hardware address.

DHCPSRV_PGSQL_GET_IAID_DUID

obtaining IPv4 leases for IAID %1 and DUID %2, lease type %3

A debug message issued when the server is attempting to obtain a set of IPv6 leases from the PostgreSQL database for a client with the specified IAID (Identity Association ID) and DUID (DHCP Unique Identifier).

DHCPSRV_PGSQL_GET_IAID_SUBID_DUID

obtaining IPv4 leases for IAID %1, Subnet ID %2, DUID %3, and lease type %4

A debug message issued when the server is attempting to obtain an IPv6 lease from the PostgreSQL database for a client with the specified IAID (Identity Association ID), Subnet ID and DUID (DHCP Unique Identifier).

DHCPSRV_PGSQL_GET_PAGE4

obtaining at most %1 IPv4 leases starting from address %2

A debug message issued when the server is attempting to obtain a page of leases beginning with the specified address.

DHCPSRV_PGSQL_GET_PAGE6

obtaining at most %1 IPv6 leases starting from address %2

A debug message issued when the server is attempting to obtain a page of leases beginning with the specified address.

DHCPSRV_PGSQL_GET_SUBID4

obtaining IPv4 leases for subnet ID %1

A debug message issued when the server is attempting to obtain all IPv4 leases for a given subnet identifier from the PostgreSQL database.

DHCPSRV_PGSQL_GET_SUBID6

obtaining IPv6 leases for subnet ID %1

A debug message issued when the server is attempting to obtain all IPv6 leases for a given subnet identifier from the PostgreSQL database.

DHCPSRV_PGSQL_GET_SUBID_CLIENTID

obtaining IPv4 lease for subnet ID %1 and client ID %2

A debug message issued when the server is attempting to obtain an IPv4 lease from the PostgreSQL database for a client with the specified subnet ID and client ID.

DHCPSRV_PGSQL_GET_SUBID_HWADDR

obtaining IPv4 lease for subnet ID %1 and hardware address %2

A debug message issued when the server is attempting to obtain an IPv4 lease from the PostgreSQL database for a client with the specified subnet ID and hardware address.

DHCPSRV_PGSQL_GET_VERSION

obtaining schema version information

A debug message issued when the server is about to obtain schema version information from the PostgreSQL database.

DHCPSRV_PGSQL_HOST_DB

opening PostgreSQL hosts database: %1

This informational message is logged when a DHCP server (either V4 or V6) is about to open a PostgreSQL hosts database. The parameters of the connection including database name and username needed to access it (but not the password if any) are logged.

DHCPSRV_PGSQL_HOST_DB_GET_VERSION

obtaining schema version information for the PostgreSQL hosts database

A debug message issued when the server is about to obtain schema version information from the PostgreSQL hosts database.

DHCPSRV_PGSQL_HOST_DB_READONLY

PostgreSQL host database opened for read access only

This informational message is issued when the user has configured the PostgreSQL database in read-only mode. Kea will not be able to insert or modify host reservations but will be able to retrieve existing ones and assign them to the clients communicating with the server.

DHCPSRV_PGSQL_HOST_DB_RECONNECT_ATTEMPT_FAILED

database reconnect failed: %1

An error message issued when an attempt to reconnect has failed.

DHCPSRV_PGSQL_HOST_DB_RECONNECT_ATTEMPT_SCHEDULE

scheduling attempt %1 of %2 in %3 milliseconds

An info message issued when the server is scheduling the next attempt to reconnect to the database. This occurs when the server has lost database connectivity and is attempting to reconnect automatically.

DHCPSRV_PGSQL_HOST_DB_RECONNECT_FAILED

maximum number of database reconnect attempts: %1, has been exhausted without success

An error message issued when the server failed to reconnect. Loss of connectivity is typically a network or database server issue.

DHCPSRV_PGSQL_LEASE_DB_RECONNECT_ATTEMPT_FAILED

database reconnect failed: %1

An error message issued when an attempt to reconnect has failed.

DHCPSRV_PGSQL_LEASE_DB_RECONNECT_ATTEMPT_SCHEDULE

scheduling attempt %1 of %2 in %3 milliseconds

An info message issued when the server is scheduling the next attempt to reconnect to the database. This occurs when the server has lost database connectivity and is attempting to reconnect automatically.

DHCPSRV_PGSQL_LEASE_DB_RECONNECT_FAILED

maximum number of database reconnect attempts: %1, has been exhausted without success

An error message issued when the server failed to reconnect. Loss of connectivity is typically a network or database server issue.

DHCPSRV_PGSQL_NEGATIVE_LEASES_STAT

recount of leases returned a negative value

This warning message is issued when the recount of leases using counters in the PostgreSQL database returned a negative value. This shows a problem which can be fixed only by an offline direct recount on the database. This message is issued only once.

DHCPSRV_PGSQL_NO_TLS_SUPPORT

Attempt to configure TLS (unsupported for PostgreSQL): %1

This error message is printed when TLS support was required in the Kea configuration: Kea was built with this feature disabled for PostgreSQL. The parameters of the connection are logged.

DHCPSRV_PGSQL_ROLLBACK

rolling back PostgreSQL database

The code has issued a rollback call. All outstanding transaction will be rolled back and not committed to the database.

DHCPSRV_PGSQL_START_TRANSACTION

starting a new PostgreSQL transaction

A debug message issued when a new PostgreSQL transaction is being started. This message is typically not issued when inserting data into a single table because the server doesn’t explicitly start transactions in this case. This message is issued when data is inserted into multiple tables with multiple INSERT statements and there may be a need to rollback the whole transaction if any of these INSERT statements fail.

DHCPSRV_PGSQL_TLS_SUPPORT

Attempt to configure TLS: %1

This informational message is printed when TLS support was required in the Kea configuration: The TLS support in PostgreSQL will be initialized but its configuration is fully managed outside the C API. The parameters of the connection are logged.

DHCPSRV_PGSQL_UPDATE_ADDR4

updating IPv4 lease for address %1

A debug message issued when the server is attempting to update IPv4 lease from the PostgreSQL database for the specified address.

DHCPSRV_PGSQL_UPDATE_ADDR6

updating IPv6 lease for address %1, lease type %2

A debug message issued when the server is attempting to update IPv6 lease from the PostgreSQL database for the specified address.

DHCPSRV_QUEUE_NCR

%1: Name change request to %2 DNS entry queued: %3

A debug message which is logged when the NameChangeRequest to add or remove a DNS entries for a particular lease has been queued. The first argument includes the client identification information. The second argument indicates whether the DNS entry is to be added or removed. The third argument carries the details of the NameChangeRequest.

DHCPSRV_QUEUE_NCR_FAILED

%1: queuing %2 name change request failed for lease %3: %4

This error message is logged when sending a NameChangeRequest to DHCP DDNS failed. The first argument includes the client identification information. The second argument indicates whether the DNS entry is to be added or removed. The third argument specifies the leased address. The last argument provides the reason for failure.

DHCPSRV_QUEUE_NCR_SKIP

%1: skip queuing name change request for lease: %2

This debug message is issued when the server decides to not queue the name change request because the lease doesn’t include the FQDN, the forward and reverse update is disabled for this lease or the DNS updates are disabled in the configuration. The first argument includes the client identification information. The second argument includes the leased address.

DHCPSRV_SUBNET4O6_SELECT_FAILED

Failed to select any subnet for the DHCPv4o6 packet

A debug message issued when the server was unable to select any subnet for the DHCPv4o6 packet.

DHCPSRV_SUBNET4_SELECT_BY_ADDRESS_FAILED

Failed to select any subnet using address: %1

A debug message issued when the server was unable to select any subnet using specified address.

DHCPSRV_SUBNET4_SELECT_BY_INTERFACE_FAILED

Failed to select any subnet using interface: %1

A debug message issued when the server was unable to select any subnet using specified interface name.

DHCPSRV_SUBNET4_SELECT_BY_RELAY_ADDRESS_FAILED

Failed to select any subnet using relay address: %1

A debug message issued when the server was unable to select any subnet using the specified relay address.

DHCPSRV_SUBNET4_SELECT_FAILED_NO_ADDRESS

Failed to select any subnet because no suitable address to use for subnet selection was found.

A debug message issued when the server was unable to select any subnet because no suitable address to use for subnet selection was found.

DHCPSRV_SUBNET4_SELECT_FAILED_NO_RAI_OPTIONS_ADDRESS

Failed to select any subnet because no suitable address to use for subnet selection was found in the relay supplied options.

A debug message issued when the server was unable to select any subnet because no suitable address to use for subnet selection was found in the relay supplied options.

DHCPSRV_SUBNET4_SELECT_FAILED_NO_RELAY_ADDRESS

Failed to select any subnet because no relay address to use for subnet selection was found.

A debug message issued when the server was unable to select any subnet because no relay address to use for subnet selection was found.

DHCPSRV_SUBNET6_SELECT_BY_ADDRESS_FAILED

Failed to select any subnet using address: %1

A debug message issued when the server was unable to select any subnet using specified address.

DHCPSRV_SUBNET6_SELECT_BY_INTERFACE_FAILED

Failed to select any subnet using interface: %1

A debug message issued when the server was unable to select any subnet using specified interface name.

DHCPSRV_SUBNET6_SELECT_BY_INTERFACE_ID_FAILED

Failed to select any subnet using interface-id: %1

A debug message issued when the server was unable to select any subnet using specified interface id.

DHCPSRV_TIMERMGR_CALLBACK_FAILED

running handler for timer %1 caused exception: %2

This error message is emitted when the timer elapsed and the operation associated with this timer has thrown an exception. The timer name and the reason for exception is logged.

DHCPSRV_TIMERMGR_REGISTER_TIMER

registering timer: %1, using interval: %2 ms

A debug message issued when the new interval timer is registered in the Timer Manager. This timer will have a callback function associated with it, and this function will be executed according to the interval specified. The unique name of the timer and the interval at which the callback function will be executed is included in the message.

DHCPSRV_TIMERMGR_RUN_TIMER_OPERATION

running operation for timer: %1

A debug message issued when the Timer Manager is about to run a periodic operation associated with the given timer. An example of such operation is a periodic cleanup of expired leases. The name of the timer is included in the message.

DHCPSRV_TIMERMGR_START_TIMER

starting timer: %1

A debug message issued when the registered interval timer is being started. If this operation is successful the timer will periodically execute the operation associated with it. The name of the started timer is included in the message.

DHCPSRV_TIMERMGR_STOP_TIMER

stopping timer: %1

A debug message issued when the registered interval timer is being stopped. The timer remains registered and can be restarted if necessary. The name of the timer is included in the message.

DHCPSRV_TIMERMGR_UNREGISTER_ALL_TIMERS

unregistering all timers

A debug message issued when all registered interval timers are being unregistered from the Timer Manager.

DHCPSRV_TIMERMGR_UNREGISTER_TIMER

unregistering timer: %1

A debug message issued when one of the registered interval timers is unregistered from the Timer Manager. The name of the timer is included in the message.

DHCPSRV_UNEXPECTED_NAME

database access parameters passed through ‘%1’, expected ‘lease-database’

The parameters for access the lease database were passed to the server through the named configuration parameter, but the code was expecting them to be passed via the parameter named “lease-database”. If the database opens successfully, there is no impact on server operation. However, as this does indicate an error in the source code, please submit a bug report.

DHCP

DHCP_DDNS_ADD_FAILED

DHCP_DDNS Request ID %1: Transaction outcome %2

This is an error message issued after DHCP_DDNS attempts to submit DNS mapping entry additions have failed. The precise reason for the failure should be documented in preceding log entries.

DHCP_DDNS_ADD_SUCCEEDED

DHCP_DDNS Request ID %1: successfully added the DNS mapping addition for this request: %2

This is an informational message issued after DHCP_DDNS has submitted DNS mapping additions which were received and accepted by an appropriate DNS server.

DHCP_DDNS_ALREADY_RUNNING

%1 already running? %2

This is an error message that occurs when DHCP_DDNS encounters a pre-existing PID file which contains the PID of a running process. This most likely indicates an attempt to start a second instance of DHCP_DDNS using the same configuration file. It is possible, though unlikely, that the PID file is a remnant left behind by a server crash or power failure and the PID it contains refers to a process other than DHCP_DDNS. In such an event, it would be necessary to manually remove the PID file. The first argument is the DHCP_DDNS process name, the second contains the PID and PID file.

DHCP_DDNS_AT_MAX_TRANSACTIONS

application has %1 queued requests but has reached maximum number of %2 concurrent transactions

This is a debug message that indicates that the application has DHCP_DDNS requests in the queue but is working as many concurrent requests as allowed.

DHCP_DDNS_CLEARED_FOR_SHUTDOWN

application has met shutdown criteria for shutdown type: %1

This is a debug message issued when the application has been instructed to shutdown and has met the required criteria to exit.

DHCP_DDNS_COMMAND

command directive received, command: %1 - args: %2

This is a debug message issued when the DHCP-DDNS application command method has been invoked.

DHCP_DDNS_CONFIGURE

configuration %1 received: %2

This is a debug message issued when the DHCP-DDNS application configure method has been invoked.

DHCP_DDNS_CONFIGURED_CALLOUT_DROP

configuration was rejected because a callout set the next step to ‘drop’: %1

This error message indicates that the DHCP-DDNS had failed configuration attempt because the next step of the configured callout was set to ‘drop’ by a hook library. The error message provided by the hook library is displayed.

DHCP_DDNS_CONFIG_CHECK_FAIL

DHCP-DDNS server configuration check failed: %1

This error message indicates that the DHCP-DDNS had failed configuration check. Details are provided. Additional details may be available in earlier log entries, possibly on lower levels.

DHCP_DDNS_CONFIG_FAIL

DHCP-DDNS server configuration failed: %1

This error message indicates that the DHCP-DDNS had failed configuration attempt. Details are provided. Additional details may be available in earlier log entries, possibly on lower levels.

DHCP_DDNS_CONFIG_SYNTAX_WARNING

DHCP-DDNS server configuration syntax warning: %1

This warning message indicates that the DHCP-DDNS configuration had a minor syntax error. The error was displayed and the configuration parsing resumed.

DHCP_DDNS_FAILED

application experienced a fatal error: %1

This is a debug message issued when the DHCP-DDNS application encounters an unrecoverable error from within the event loop.

DHCP_DDNS_FORWARD_ADD_BAD_DNSCLIENT_STATUS

DHCP_DDNS Request ID %1: received an unknown DNSClient status: %2, while adding a forward address mapping for FQDN %3 to DNS server %4

This is an error message issued when DNSClient returns an unrecognized status while DHCP_DDNS was adding a forward address mapping. The request will be aborted. This is most likely a programmatic issue and should be reported.

DHCP_DDNS_FORWARD_ADD_BUILD_FAILURE

DNS Request ID %1: update message to add a forward DNS entry could not be constructed for this request: %2, reason: %3

This is an error message issued when an error occurs attempting to construct the server bound packet requesting a forward address addition. This is due to invalid data contained in the NameChangeRequest. The request will be aborted. This is most likely a configuration issue.

DHCP_DDNS_FORWARD_ADD_IO_ERROR

DHCP_DDNS Request ID %1: encountered an IO error sending a forward mapping add for FQDN %2 to DNS server %3

This is an error message issued when a communication error occurs while DHCP_DDNS is carrying out a forward address update. The application will retry against the same server or others as appropriate.

DHCP_DDNS_FORWARD_ADD_REJECTED

DNS Request ID %1: Server, %2, rejected a DNS update request to add the address mapping for FQDN, %3, with an RCODE: %4

This is an error message issued when an update was rejected by the DNS server it was sent to for the reason given by the RCODE. The rcode values are defined in RFC 2136.

DHCP_DDNS_FORWARD_ADD_RESP_CORRUPT

DHCP_DDNS Request ID %1: received a corrupt response from the DNS server, %2, while adding forward address mapping for FQDN, %3

This is an error message issued when the response received by DHCP_DDNS, to a update request to add a forward address mapping, is mangled or malformed. The application will retry against the same server or others as appropriate.

DHCP_DDNS_FORWARD_REMOVE_ADDRS_BAD_DNSCLIENT_STATUS

DHCP_DDNS Request ID %1: received an unknown DNSClient status: %2, while removing a forward address mapping for FQDN %3 to DNS server %4

This is an error message issued when DNSClient returns an unrecognized status while DHCP_DDNS was removing a forward address mapping. The request will be aborted. This is most likely a programmatic issue and should be reported.

DHCP_DDNS_FORWARD_REMOVE_ADDRS_BUILD_FAILURE

DNS Request ID %1: update message to remove a forward DNS Address entry could not be constructed for this request: %2, reason: %3

This is an error message issued when an error occurs attempting to construct the server bound packet requesting a forward address (A or AAAA) removal. This is due to invalid data contained in the NameChangeRequest. The request will be aborted. This is most likely a configuration issue. /sar/

DHCP_DDNS_FORWARD_REMOVE_ADDRS_IO_ERROR

DHCP_DDNS Request ID %1: encountered an IO error sending a forward mapping address removal for FQDN %2 to DNS server %3

This is an error message issued when a communication error occurs while DHCP_DDNS is carrying out a forward address remove. The application will retry against the same server or others as appropriate.

DHCP_DDNS_FORWARD_REMOVE_ADDRS_REJECTED

DNS Request ID %1: Server, %2, rejected a DNS update request to remove the forward address mapping for FQDN, %3, with an RCODE: %4

This is an error message issued when an update was rejected by the DNS server it was sent to for the reason given by the RCODE. The rcode values are defined in RFC 2136.

DHCP_DDNS_FORWARD_REMOVE_ADDRS_RESP_CORRUPT

DHCP_DDNS Request ID %1: received a corrupt response from the DNS server, %2, while removing forward address mapping for FQDN, %3

This is an error message issued when the response received by DHCP_DDNS, to a update request to remove a forward address mapping, is mangled or malformed. The application will retry against the same server or others as appropriate.

DHCP_DDNS_FORWARD_REMOVE_RRS_BAD_DNSCLIENT_STATUS

DHCP_DDNS Request ID %1: received an unknown DNSClient status: %2, while removing forward RRs for FQDN %3 to DNS server %4

This is an error message issued when DNSClient returns an unrecognized status while DHCP_DDNS was removing forward RRs. The request will be aborted. This is most likely a programmatic issue and should be reported.

DHCP_DDNS_FORWARD_REMOVE_RRS_BUILD_FAILURE

DNS Request ID %1: update message to remove forward DNS RR entries could not be constructed for this request: %2, reason: %3

This is an error message issued when an error occurs attempting to construct the server bound packet requesting forward RR (DHCID RR) removal. This is due to invalid data contained in the NameChangeRequest. The request will be aborted. This is most likely a configuration issue.

DHCP_DDNS_FORWARD_REMOVE_RRS_IO_ERROR

DHCP_DDNS Request ID %1: encountered an IO error sending a forward RR removal for FQDN %2 to DNS server %3

This is an error message issued when a communication error occurs while DHCP_DDNS is carrying out a forward RR remove. The application will retry against the same server.

DHCP_DDNS_FORWARD_REMOVE_RRS_REJECTED

DNS Request ID %1: Server, %2, rejected a DNS update request to remove forward RR entries for FQDN, %3, with an RCODE: %4

This is an error message issued when an update was rejected by the DNS server it was sent to for the reason given by the RCODE. The rcode values are defined in RFC 2136.

DHCP_DDNS_FORWARD_REMOVE_RRS_RESP_CORRUPT

DHCP_DDNS Request ID %1: received a corrupt response from the DNS server, %2, while removing forward RRs for FQDN, %3

This is an error message issued when the response received by DHCP_DDNS, to a update request to remove forward RRs mapping, is mangled or malformed. The application will retry against the same server or others as appropriate. /sar/

DHCP_DDNS_FORWARD_REPLACE_BAD_DNSCLIENT_STATUS

DHCP_DDNS Request ID %1: received an unknown DNSClient status: %2, while replacing forward address mapping for FQDN %3 to DNS server %4

This is an error message issued when DNSClient returns an unrecognized status while DHCP_DDNS was replacing a forward address mapping. The request will be aborted. This is most likely a programmatic issue and should be reported.

DHCP_DDNS_FORWARD_REPLACE_BUILD_FAILURE

DNS Request ID %1: update message to replace a forward DNS entry could not be constructed from this request: %2, reason: %3

This is an error message issued when an error occurs attempting to construct the server bound packet requesting a forward address replacement. This is due to invalid data contained in the NameChangeRequest. The request will be aborted. This is most likely a configuration issue.

DHCP_DDNS_FORWARD_REPLACE_IO_ERROR

DHCP_DDNS Request ID %1: encountered an IO error sending a forward mapping replace for FQDN %2 to DNS server %3

This is an error message issued when a communication error occurs while DHCP_DDNS is carrying out a forward address update. The application will retry against the same server or others as appropriate.

DHCP_DDNS_FORWARD_REPLACE_REJECTED

DNS Request ID %1: Server, %2, rejected a DNS update request to replace the address mapping for FQDN, %3, with an RCODE: %4

This is an error message issued when an update was rejected by the DNS server it was sent to for the reason given by the RCODE. The rcode values are defined in RFC 2136.

DHCP_DDNS_FORWARD_REPLACE_RESP_CORRUPT

DHCP_DDNS Request ID %1: received a corrupt response from the DNS server, %2, while replacing forward address mapping for FQDN, %3

This is an error message issued when the response received by DHCP_DDNS, to a update request to replace a forward address mapping, is mangled or malformed. The application will retry against the same server or others as appropriate.

DHCP_DDNS_FWD_REQUEST_IGNORED

Request ID %1: Forward updates are disabled, the forward portion of request will be ignored: %2

This is a debug message issued when forward DNS updates are disabled and DHCP_DDNS receives an update request containing a forward DNS update. The forward update will not performed.

DHCP_DDNS_INVALID_NCR

application received an invalid DNS update request: %1

This is an error message that indicates that an invalid request to update a DNS entry was received by the application. Either the format or the content of the request is incorrect. The request will be ignored.

DHCP_DDNS_INVALID_RESPONSE

received response to DNS Update message is malformed: %1

This is a debug message issued when the DHCP-DDNS application encountered an error while decoding a response to DNS Update message. Typically, this error will be encountered when a response message is malformed.

DHCP_DDNS_NCR_FLUSH_IO_ERROR

DHCP-DDNS Last send before stopping did not complete successfully: %1

This is an error message that indicates the DHCP-DDNS client was unable to complete the last send prior to exiting send mode. This is a programmatic error, highly unlikely to occur, and should not impair the application’s ability to process requests.

DHCP_DDNS_NCR_LISTEN_CLOSE_ERROR

application encountered an error while closing the listener used to receive NameChangeRequests : %1

This is an error message that indicates the application was unable to close the listener connection used to receive NameChangeRequests. Closure may occur during the course of error recovery or during normal shutdown procedure. In either case the error is unlikely to impair the application’s ability to process requests but it should be reported for analysis.

DHCP_DDNS_NCR_RECV_NEXT_ERROR

application could not initiate the next read following a request receive.

This is an error message indicating that NameChangeRequest listener could not start another read after receiving a request. While possible, this is highly unlikely and is probably a programmatic error. The application should recover on its own.

DHCP_DDNS_NCR_SEND_CLOSE_ERROR

DHCP-DDNS client encountered an error while closing the sender connection used to send NameChangeRequests: %1

This is an error message that indicates the DHCP-DDNS client was unable to close the connection used to send NameChangeRequests. Closure may occur during the course of error recovery or during normal shutdown procedure. In either case the error is unlikely to impair the client’s ability to send requests but it should be reported for analysis.

DHCP_DDNS_NCR_SEND_NEXT_ERROR

DHCP-DDNS client could not initiate the next request send following send completion: %1

This is an error message indicating that NameChangeRequest sender could not start another send after completing the send of the previous request. While possible, this is highly unlikely and is probably a programmatic error. The application should recover on its own.

DHCP_DDNS_NCR_UDP_CLEAR_READY_ERROR

NCR UDP watch socket failed to clear: %1

This is an error message that indicates the application was unable to reset the UDP NCR sender ready status after completing a send. This is programmatic error that should be reported. The application may or may not continue to operate correctly.

DHCP_DDNS_NCR_UDP_RECV_CANCELED

UDP socket receive was canceled while listening for DNS Update requests

This is a debug message indicating that the listening on a UDP socket for DNS update requests has been canceled. This is a normal part of suspending listening operations.

DHCP_DDNS_NCR_UDP_RECV_ERROR

UDP socket receive error while listening for DNS Update requests: %1

This is an error message indicating that an I/O error occurred while listening over a UDP socket for DNS update requests. This could indicate a network connectivity or system resource issue.

DHCP_DDNS_NCR_UDP_SEND_CANCELED

UDP socket send was canceled while sending a DNS Update request to DHCP_DDNS: %1

This is an informational message indicating that sending requests via UDP socket to DHCP_DDNS has been interrupted. This is a normal part of suspending send operations.

DHCP_DDNS_NCR_UDP_SEND_ERROR

UDP socket send error while sending a DNS Update request: %1

This is an error message indicating that an IO error occurred while sending a DNS update request to DHCP_DDNS over a UDP socket. This could indicate a network connectivity or system resource issue.

DHCP_DDNS_NOT_ON_LOOPBACK

the DHCP-DDNS server has been configured to listen on %1 which is not the local loopback. This is an insecure configuration supported for testing purposes only

This is a warning message issued when the DHCP-DDNS server is configured to listen at an address other than the loopback address (127.0.0.1 or ::1). It is possible for a malicious attacker to send bogus NameChangeRequests to it and change entries in the DNS. For this reason, addresses other than the IPv4 or IPv6 loopback addresses should only be used for testing purposes. A future version of Kea will implement authentication to guard against such attacks.

DHCP_DDNS_NO_ELIGIBLE_JOBS

although there are queued requests, there are pending transactions for each, Queue count: %1 Transaction count: %2

This is a debug message issued when all of the queued requests represent clients for which there is an update already in progress. This may occur under normal operations but should be temporary situation.

DHCP_DDNS_NO_FWD_MATCH_ERROR

Request ID %1: the configured list of forward DDNS domains does not contain a match for: %2 The request has been discarded.

This is an error message that indicates that DHCP_DDNS received a request to update the forward DNS information for the given FQDN but for which there are no configured DDNS domains in the DHCP_DDNS configuration. Either the DHCP_DDNS configuration needs to be updated or the source of the FQDN itself should be investigated.

DHCP_DDNS_NO_MATCH

No DNS servers match FQDN %1

This is warning message issued when there are no domains in the configuration which match the cited fully qualified domain name (FQDN). The DNS Update request for the FQDN cannot be processed.

DHCP_DDNS_NO_REV_MATCH_ERROR

Request ID %1: the configured list of reverse DDNS domains does not contain a match for: %2 The request has been discarded.

This is an error message that indicates that DHCP_DDNS received a request to update the reverse DNS information for the given FQDN but for which there are no configured DDNS domains in the DHCP_DDNS configuration. Either the DHCP_DDNS configuration needs to be updated or the source of the FQDN itself should be investigated.

DHCP_DDNS_PROCESS_INIT

application init invoked

This is a debug message issued when the DHCP-DDNS application enters its initialization method.

DHCP_DDNS_QUEUE_MGR_QUEUE_FULL

application request queue has reached maximum number of entries %1

This an error message indicating that DHCP-DDNS is receiving DNS update requests faster than they can be processed. This may mean the maximum queue needs to be increased, the DHCP-DDNS clients are simply generating too many requests too quickly, or perhaps upstream DNS servers are experiencing load issues.

DHCP_DDNS_QUEUE_MGR_QUEUE_RECEIVE

Request ID %1: received and queued a request.

This is an informational message indicating that the NameChangeRequest listener used by DHCP-DDNS to receive a request has received a request and queued it for further processing.

DHCP_DDNS_QUEUE_MGR_RECONFIGURING

application is reconfiguring the queue manager

This is an informational message indicating that DHCP_DDNS is reconfiguring the queue manager as part of normal startup or in response to a new configuration.

DHCP_DDNS_QUEUE_MGR_RECOVERING

application is attempting to recover from a queue manager IO error

This is an informational message indicating that DHCP_DDNS is attempting to restart the queue manager after it suffered an IO error while receiving requests.

DHCP_DDNS_QUEUE_MGR_RECV_ERROR

application’s queue manager was notified of a request receive error by its listener.

This is an error message indicating that the NameChangeRequest listener used by DHCP-DDNS to receive requests encountered an IO error. There should be corresponding log messages from the listener layer with more details. This may indicate a network connectivity or system resource issue.

DHCP_DDNS_QUEUE_MGR_RESUME_ERROR

application could not restart the queue manager, reason: %1

This is an error message indicating that DHCP_DDNS’s Queue Manager could not be restarted after stopping due to a full receive queue. This means that the application cannot receive requests. This is most likely due to DHCP_DDNS configuration parameters referring to resources such as an IP address or port, that is no longer unavailable. DHCP_DDNS will attempt to restart the queue manager if given a new configuration.

DHCP_DDNS_QUEUE_MGR_RESUMING

application is resuming listening for requests now that the request queue size has reached %1 of a maximum %2 allowed

This is an informational message indicating that DHCP_DDNS, which had stopped accepting new requests, has processed enough entries from the receive queue to resume accepting requests.

DHCP_DDNS_QUEUE_MGR_STARTED

application’s queue manager has begun listening for requests.

This is a debug message indicating that DHCP_DDNS’s Queue Manager has successfully started and is now listening for NameChangeRequests.

DHCP_DDNS_QUEUE_MGR_START_ERROR

application could not start the queue manager, reason: %1

This is an error message indicating that DHCP_DDNS’s Queue Manager could not be started. This means that the application cannot receive requests. This is most likely due to DHCP_DDNS configuration parameters referring to resources such as an IP address or port, that are unavailable. DHCP_DDNS will attempt to restart the queue manager if given a new configuration.

DHCP_DDNS_QUEUE_MGR_STOPPED

application’s queue manager has stopped listening for requests.

This is a debug message indicating that DHCP_DDNS’s Queue Manager has stopped listening for NameChangeRequests. This may be because of normal event such as reconfiguration or as a result of an error. There should be log messages preceding this one to indicate why it has stopped.

DHCP_DDNS_QUEUE_MGR_STOPPING

application is stopping the queue manager for %1

This is an informational message indicating that DHCP_DDNS is stopping the queue manager either to reconfigure it or as part of application shutdown.

DHCP_DDNS_QUEUE_MGR_STOP_ERROR

application encountered an error stopping the queue manager: %1

This is an error message indicating that DHCP_DDNS encountered an error while trying to stop the queue manager. This error is unlikely to occur or to impair the application’s ability to function but it should be reported for analysis.

DHCP_DDNS_QUEUE_MGR_UNEXPECTED_HANDLER_ERROR

application’s queue manager request receive handler experienced an unexpected exception %1:

This is an error message indicating that an unexpected error occurred within the DHCP_DDNS’s Queue Manager request receive completion handler. This is most likely a programmatic issue that should be reported. The application may recover on its own.

DHCP_DDNS_QUEUE_MGR_UNEXPECTED_STOP

application’s queue manager receive was

aborted unexpectedly while queue manager state is: %1 This is an error message indicating that DHCP_DDNS’s Queue Manager request receive was unexpected interrupted. Normally, the read is receive is only interrupted as a normal part of stopping the queue manager. This is most likely a programmatic issue that should be reported.

DHCP_DDNS_REMOVE_FAILED

DHCP_DDNS Request ID %1: Transaction outcome: %2

This is an error message issued after DHCP_DDNS attempts to submit DNS mapping entry removals have failed. The precise reason for the failure should be documented in preceding log entries.

DHCP_DDNS_REMOVE_SUCCEEDED

DHCP_DDNS Request ID %1: successfully removed the DNS mapping addition for this request: %2

This is an informational message issued after DHCP_DDNS has submitted DNS mapping removals which were received and accepted by an appropriate DNS server.

DHCP_DDNS_REQUEST_DROPPED

Request ID %1: Request contains no enabled update requests and will be dropped: %2

This is a debug message issued when DHCP_DDNS receives a request which does not contain updates in a direction that is enabled. In other words, if only forward updates are enabled and request is received that asks only for reverse updates then the request is dropped.

DHCP_DDNS_REVERSE_REMOVE_BAD_DNSCLIENT_STATUS

DHCP_DDNS Request ID %1: received an unknown DNSClient status: %2, while removing reverse address mapping for FQDN %3 to DNS server %4

This is an error message issued when DNSClient returns an unrecognized status while DHCP_DDNS was removing a reverse address mapping. The request will be aborted. This is most likely a programmatic issue and should be reported.

DHCP_DDNS_REVERSE_REMOVE_BUILD_FAILURE

DNS Request ID %1: update message to remove a reverse DNS entry could not be constructed from this request: %2, reason: %3

This is an error message issued when an error occurs attempting to construct the server bound packet requesting a reverse PTR removal. This is due to invalid data contained in the NameChangeRequest. The request will be aborted. This is most likely a configuration issue.

DHCP_DDNS_REVERSE_REMOVE_IO_ERROR

DHCP_DDNS Request ID %1: encountered an IO error sending a reverse mapping remove for FQDN %2 to DNS server %3

This is an error message issued when a communication error occurs while DHCP_DDNS is carrying out a reverse address update. The application will retry against the same server or others as appropriate.

DHCP_DDNS_REVERSE_REMOVE_REJECTED

DNS Request ID %1: Server, %2, rejected a DNS update request to remove the reverse mapping for FQDN, %3, with an RCODE: %4

This is an error message issued when an update was rejected by the DNS server it was sent to for the reason given by the RCODE. The rcode values are defined in RFC 2136.

DHCP_DDNS_REVERSE_REMOVE_RESP_CORRUPT

DHCP_DDNS Request ID %1: received a corrupt response from the DNS server, %2, while removing reverse address mapping for FQDN, %3

This is an error message issued when the response received by DHCP_DDNS, to a update request to remove a reverse address, is mangled or malformed. The application will retry against the same server or others as appropriate.

DHCP_DDNS_REVERSE_REPLACE_BAD_DNSCLIENT_STATUS

DHCP_DDNS Request ID %1: received an unknown DNSClient status: %2, while replacing reverse address mapping for FQDN %3 to DNS server %4

This is an error message issued when DNSClient returns an unrecognized status while DHCP_DDNS was replacing a reverse address mapping. The request will be aborted. This is most likely a programmatic issue and should be reported.

DHCP_DDNS_REVERSE_REPLACE_BUILD_FAILURE

DNS Request ID %1: update message to replace a reverse DNS entry could not be constructed from this request: %2, reason: %3

This is an error message issued when an error occurs attempting to construct the server bound packet requesting a reverse PTR replacement. This is due to invalid data contained in the NameChangeRequest. The request will be aborted. This is most likely a configuration issue.

DHCP_DDNS_REVERSE_REPLACE_IO_ERROR

DHCP_DDNS Request ID %1: encountered an IO error sending a reverse mapping replacement for FQDN %2 to DNS server %3

This is an error message issued when a communication error occurs while DHCP_DDNS is carrying out a reverse address update. The application will retry against the same server or others as appropriate.

DHCP_DDNS_REVERSE_REPLACE_REJECTED

DNS Request ID %1: Server, %2, rejected a DNS update request to replace the reverse mapping for FQDN, %3, with an RCODE: %4

This is an error message issued when an update was rejected by the DNS server it was sent to for the reason given by the RCODE. The rcode values are defined in RFC 2136.

DHCP_DDNS_REVERSE_REPLACE_RESP_CORRUPT

DHCP_DDNS Request ID %1: received a corrupt response from the DNS server, %2, while replacing reverse address mapping for FQDN, %3

This is an error message issued when the response received by DHCP_DDNS, to a update request to replace a reverse address, is mangled or malformed. The application will retry against the same server or others as appropriate.

DHCP_DDNS_REV_REQUEST_IGNORED

Request ID %1: Reverse updates are disabled, the reverse portion of request will be ignored: %2

This is a debug message issued when reverse DNS updates are disabled and DHCP_DDNS receives an update request containing a reverse DNS update. The reverse update will not performed.

DHCP_DDNS_RUN_EXIT

application is exiting the event loop

This is a debug message issued when the DHCP-DDNS server exits its event lo

DHCP_DDNS_SHUTDOWN_COMMAND

application received shutdown command with args: %1

This is a debug message issued when the application has been instructed to shut down by the controller.

DHCP_DDNS_STARTED

Kea DHCP-DDNS server version %1 started

This informational message indicates that the DHCP-DDNS server has processed all configuration information and is ready to begin processing. The version is also printed.

DHCP_DDNS_STARTING_TRANSACTION

Request ID %1:

This is a debug message issued when DHCP-DDNS has begun a transaction for a given request.

DHCP_DDNS_STATE_MODEL_UNEXPECTED_ERROR

Request ID %1: application encountered an unexpected error while carrying out a NameChangeRequest: %2

This is error message issued when the application fails to process a NameChangeRequest correctly. Some or all of the DNS updates requested as part of this update did not succeed. This is a programmatic error and should be reported.

DHCP_DDNS_TRANS_SEND_ERROR

Request ID %1: application encountered an unexpected error while attempting to send a DNS update: %2

This is error message issued when the application is able to construct an update message but the attempt to send it suffered an unexpected error. This is most likely a programmatic error, rather than a communications issue. Some or all of the DNS updates requested as part of this request did not succeed.

DHCP_DDNS_UDP_SENDER_WATCH_SOCKET_CLOSE_ERROR

watch socket failed to close: %1

This is an error message that indicates the application was unable to close the inbound or outbound side of a NCR sender’s watch socket. While technically possible the error is highly unlikely to occur and should not impair the application’s ability to process requests.

DHCP_DDNS_UNCAUGHT_NCR_RECV_HANDLER_ERROR

unexpected exception thrown from the application receive completion handler: %1

This is an error message that indicates that an exception was thrown but not caught in the application’s request receive completion handler. This is a programmatic error that needs to be reported. Dependent upon the nature of the error the application may or may not continue operating normally.

DHCP_DDNS_UPDATE_REQUEST_SENT

Request ID %1: %2 to server: %3

This is a debug message issued when DHCP_DDNS sends a DNS request to a DNS server.

EVAL

EVAL_DEBUG_AND

Popping %1 and %2 pushing %3

This debug message indicates that two values are popped from the value stack. Then are then combined via logical and and the result is pushed onto the value stack.

EVAL_DEBUG_CONCAT

Popping %1 and %2 pushing %3

This debug message indicates that the two strings are being popped off of the stack. They are then concatenated and the resulting string is pushed onto the stack. The strings are displayed in hex.

EVAL_DEBUG_EQUAL

Popping %1 and %2 pushing result %3

This debug message indicates that the two strings are being popped off of the value stack and the result of comparing them is being pushed onto the value stack. The strings are displayed in hex.

EVAL_DEBUG_HEXSTRING

Pushing hex string %1

This debug message indicates that the given binary string is being pushed onto the value stack. The string is displayed in hex.

EVAL_DEBUG_IFELSE_FALSE

Popping %1 (false) and %2, leaving %3

This debug message indicates that the condition is false so the iftrue branch value is removed and the ifelse branch value is left on the value stack.

EVAL_DEBUG_IFELSE_TRUE

Popping %1 (true) and %2, leaving %3

This debug message indicates that the condition is true so the ifelse branch value is removed and the iftrue branch value is left on the value stack.

EVAL_DEBUG_INT16TOTEXT

Pushing Int16 %1

This debug message indicates that the given address string representation is being pushed onto the value stack. This represents a 16 bit integer.

EVAL_DEBUG_INT32TOTEXT

Pushing Int32 %1

This debug message indicates that the given address string representation is being pushed onto the value stack. This represents a 32 bit integer.

EVAL_DEBUG_INT8TOTEXT

Pushing Int8 %1

This debug message indicates that the given address string representation is being pushed onto the value stack. This represents an 8 bit integer.

EVAL_DEBUG_IPADDRESS

Pushing IPAddress %1

This debug message indicates that the given binary string is being pushed onto the value stack. This represents either an IPv4 or IPv6 address. The string is displayed in hex.

EVAL_DEBUG_IPADDRESSTOTEXT

Pushing IPAddress %1

This debug message indicates that the given address string representation is being pushed onto the value stack. This represents either an IPv4 or IPv6 address.

EVAL_DEBUG_MEMBER

Checking membership of ‘%1’, pushing result %2

This debug message indicates that the membership of the packet for the client class was checked.

EVAL_DEBUG_NOT

Popping %1 pushing %2

This debug message indicates that the first value is popped from the value stack, negated and then pushed onto the value stack. The string is displayed in text.

EVAL_DEBUG_OPTION

Pushing option %1 with value %2

This debug message indicates that the given string representing the value of the requested option is being pushed onto the value stack. The string may be the text or binary value of the string based on the representation type requested (.text or .hex) or “true” or “false” if the requested type is .exists. The option code may be for either an option or a sub-option as requested in the classification statement.

EVAL_DEBUG_OR

Popping %1 and %2 pushing %3

This debug message indicates that two values are popped from the value stack. Then are then combined via logical or and the result is pushed onto the value stack. The string is displayed in text.

EVAL_DEBUG_PKT

Pushing PKT meta data %1 with value %2

This debug message indicates that the given binary string representing the value of the requested meta data is being pushed onto the value stack. The string is displayed in hex at the exception of interface name.

EVAL_DEBUG_PKT4

Pushing PKT4 field %1 with value %2

This debug message indicates that the given binary string representing the value of the requested field is being pushed onto the value stack. The string is displayed in hex.

EVAL_DEBUG_PKT6

Pushing PKT6 field %1 with value %2

This debug message indicates that the given binary string representing the value of the requested field is being pushed onto the value stack. The string is displayed in hex.

EVAL_DEBUG_RELAY6

Pushing PKT6 relay field %1 nest %2 with value %3

This debug message indicates that the given binary string representing the value of the requested field is being pushed onto the value stack. The string is displayed in hex.

EVAL_DEBUG_RELAY6_RANGE

Pushing PKT6 relay field %1 nest %2 with value %3

This debug message is generated if the nest field is out of range. The empty string will always be the value pushed onto the stack.

EVAL_DEBUG_SPLIT

Popping field %1, delimiters %2, string %3, pushing result %4

This debug message indicates that three values are being popped from the stack and a result is being pushed onto the stack. The values being popped are the field, delimiter and string. The result is the extracted field which is pushed onto the stack. The strings are displayed in hex.

EVAL_DEBUG_SPLIT_DELIM_EMPTY

Popping field %1, delimiters %2, string %3, pushing result %4

This debug message indicates that the delimiter popped from the stack was empty and so the result will be the entire string. The field, delimiter and string are still popped from the stack and the result is still pushed.

EVAL_DEBUG_SPLIT_EMPTY

Popping field %1, delimiters %2, string %3, pushing result %4

This debug message indicates that the string popped from the stack was empty and so the result will also be empty. The field, delimiter and string are still popped from the stack and the result is still pushed.

EVAL_DEBUG_SPLIT_FIELD_OUT_OF_RANGE

Popping field %1, delimiters %2, string %3, pushing result %4

This debug message indicates that the field is either less than one or larger than the number of fields in the string popped from the stack. The result will be empty. The field, delimiter and string are still popped from the stack and the result is still pushed.

EVAL_DEBUG_STRING

Pushing text string %1

This debug message indicates that the given text string is being pushed onto the value stack. The string is displayed in text.

EVAL_DEBUG_SUBSTRING

Popping length %1, start %2, string %3 pushing result %4

This debug message indicates that three values are being popped from the value stack and a result is being pushed onto the value stack. The values being popped are the starting point and length of a substring to extract from the given string. The resulting string is pushed onto the stack. The strings are displayed in hex.

EVAL_DEBUG_SUBSTRING_EMPTY

Popping length %1, start %2, string %3 pushing result %4

This debug message indicates that the string popped from the stack was empty and so the result will also be empty. The start, length and string are still popped from the stack and the result is still pushed.

EVAL_DEBUG_SUBSTRING_RANGE

Popping length %1, start %2, string %3 pushing result %4

This debug message indicates that the value of start is outside of the string and an empty result will be pushed onto the stack. The start, length and string are still popped from the stack and the result is still pushed. The strings are displayed in hex.

EVAL_DEBUG_SUB_OPTION

Pushing option %1 sub-option %2 with value %3

This debug message indicates that the given string representing the value of the requested sub-option of the requested parent option is being pushed onto the value stack. The string may be the text or binary value of the string based on the representation type requested (.text or .hex) or “true” or “false” if the requested type is .exists. The codes are the parent option and the sub-option codes as requested in the classification statement.

EVAL_DEBUG_SUB_OPTION_NO_OPTION

Requested option %1 sub-option %2, but the parent option is not present, pushing result %3

This debug message indicates that the parent option was not found. The codes are the parent option and the sub-option codes as requested in the classification statement.

EVAL_DEBUG_TOHEXSTRING

Popping binary value %1 and separator %2, pushing result %3

This debug message indicates that two values are being popped from the value stack and a result is being pushed onto the value stack. The values being popped are the binary value to convert and the separator. The binary value is converted to its hexadecimal string representation and pushed onto the stack. The binary value is displayed in hex.

EVAL_DEBUG_UINT16TOTEXT

Pushing UInt16 %1

This debug message indicates that the given address string representation is being pushed onto the value stack. This represents a 16 bit unsigned integer.

EVAL_DEBUG_UINT32TOTEXT

Pushing UInt32 %1

This debug message indicates that the given address string representation is being pushed onto the value stack. This represents a 32 bit unsigned integer.

EVAL_DEBUG_UINT8TOTEXT

Pushing UInt8 %1

This debug message indicates that the given address string representation is being pushed onto the value stack. This represents an 8 bit unsigned integer.

EVAL_DEBUG_VENDOR_CLASS_DATA

Data %1 (out of %2 received) in vendor class found, pushing result ‘%3’

This debug message indicates that vendor class option was found and passed enterprise-id checks and has sufficient number of data chunks. The total number of chunks and value pushed are reported as debugging aid.

EVAL_DEBUG_VENDOR_CLASS_DATA_NOT_FOUND

Requested data index %1, but option with enterprise-id %2 has only %3 data tuple(s), pushing result ‘%4’

This debug message indicates that vendor class option was found and passed enterprise-id checks, but does not have sufficient number of data chunks. Note that the index starts at 0, so there has to be at least (index + 1) data chunks.

EVAL_DEBUG_VENDOR_CLASS_ENTERPRISE_ID

Pushing enterprise-id %1 as result 0x%2

This debug message indicates that the expression has been evaluated and vendor class option was found and its enterprise-id is being reported.

EVAL_DEBUG_VENDOR_CLASS_ENTERPRISE_ID_MISMATCH

Was looking for %1, option had %2, pushing result ‘%3’

This debug message indicates that the expression has been evaluated and vendor class option was found, but has different enterprise-id than specified in the expression.

EVAL_DEBUG_VENDOR_CLASS_EXISTS

Option with enterprise-id %1 found, pushing result ‘%2’

This debug message indicates that the expression has been evaluated and vendor class option was found.

EVAL_DEBUG_VENDOR_CLASS_NO_OPTION

Option with code %1 missing, pushing result ‘%2’

This debug message indicates that the expression has been evaluated and vendor class option was not found.

EVAL_DEBUG_VENDOR_ENTERPRISE_ID

Pushing enterprise-id %1 as result 0x%2

This debug message indicates that the expression has been evaluated and vendor option was found and its enterprise-id is being reported.

EVAL_DEBUG_VENDOR_ENTERPRISE_ID_MISMATCH

Was looking for %1, option had %2, pushing result ‘%3’

This debug message indicates that the expression has been evaluated and vendor option was found, but has different enterprise-id than specified in the expression.

EVAL_DEBUG_VENDOR_EXISTS

Option with enterprise-id %1 found, pushing result ‘%2’

This debug message indicates that the expression has been evaluated and vendor option was found.

EVAL_DEBUG_VENDOR_NO_OPTION

Option with code %1 missing, pushing result ‘%2’

This debug message indicates that the expression has been evaluated and vendor option was not found.

FLEX

FLEX_OPTION_LOAD_ERROR

loading Flex Option hooks library failed: %1

This error message indicates an error during loading the Flex Option hooks library. The details of the error are provided as argument of the log message.

FLEX_OPTION_PROCESS_ADD

Added the option code %1 with value %2

This debug message is printed when an option was added into the response packet. The option code and the value (between quotes if printable, in hexadecimal if not) are provided.

FLEX_OPTION_PROCESS_CLIENT_CLASS

Skip processing of the option code %1 for class ‘%2’

This debug message is printed when the processing for an option is skipped because the query does not belongs to the client class. The option code and the client class name are provided.

FLEX_OPTION_PROCESS_ERROR

An error occurred processing query %1: %2

This error message indicates an error during processing of a query by the Flex Option hooks library. The client identification information from the query and the details of the error are provided as arguments of the log message.

FLEX_OPTION_PROCESS_REMOVE

Removed option code %1

This debug message is printed when an option was removed from the response packet. The option code is provided.

FLEX_OPTION_PROCESS_SUB_ADD

Added the sub-option code %1 in option code %2 with value %3

This debug message is printed when an sub-option was added into the response packet. The sub-option and container option codes, and the value (between quotes if printable, in hexadecimal if not) are provided.

FLEX_OPTION_PROCESS_SUB_CLIENT_CLASS

Skip processing of the sub-option code %1 in option code %2 for class ‘%3’

This debug message is printed when the processing for a sub-option is skipped because the query does not belongs to the client class. The sub-option and container option codes, and the client class name are provided.

FLEX_OPTION_PROCESS_SUB_REMOVE

Removed sub-option code %1 in option code %2

This debug message is printed when a sub-option was removed from the response packet. The sub-option and container option codes are provided.

FLEX_OPTION_PROCESS_SUB_SUPERSEDE

Supersedes the sub-option code %1 in option code %2 with value %3

This debug message is printed when a sub-option was superseded into the response packet. The sub-option and container option codes, and the value (between quotes if printable, in hexadecimal if not) are provided.

FLEX_OPTION_PROCESS_SUPERSEDE

Supersedes the option code %1 with value %2

This debug message is printed when an option was superseded into the response packet. The option code and the value (between quotes if printable, in hexadecimal if not) are provided.

FLEX_OPTION_PROCESS_VENDOR_ID_MISMATCH

Skip processing of vendor option code %1 with vendor id %2 not matching wanted %3

This debug message is printed when a sub-option of a vendor option is processed but vendor ids do not match. The code of the vendor option and the two vendor ids are provided.

HA

HA_BUFFER4_RECEIVE_FAILED

buffer4_receive callout failed: %1

This error message is issued when the callout for the buffer4_receive hook point failed. This may occur as a result of an internal server error. The argument contains a reason for the error.

HA_BUFFER4_RECEIVE_NOT_FOR_US

%1: dropping query to be processed by another server

This debug message is issued when the received DHCPv4 query is dropped by this server because it should be served by another server. This is the case when the remote server was designated to process the packet as a result of load balancing or because it is a primary server in the hot standby configuration. The argument provides client identification information retrieved from the query.

HA_BUFFER4_RECEIVE_PACKET_OPTIONS_SKIPPED

an error unpacking an option, caused subsequent options to be skipped: %1

A debug message issued when an option failed to unpack correctly, making it impossible to unpack the remaining options in the DHCPv4 query. The server will still attempt to service the packet. The sole argument provides a reason for unpacking error.

HA_BUFFER4_RECEIVE_UNPACK_FAILED

failed to parse query from %1 to %2, received over interface %3, reason: %4

This debug message is issued when received DHCPv4 query is malformed and can’t be parsed by the buffer4_receive callout. The query will be dropped by the server. The first three arguments specify source IP address, destination IP address and the interface. The last argument provides a reason for failure.

HA_BUFFER6_RECEIVE_FAILED

buffer6_receive callout failed: %1

This error message is issued when the callout for the buffer6_receive hook point failed. This may occur as a result of an internal server error. The argument contains a reason for the error.

HA_BUFFER6_RECEIVE_NOT_FOR_US

%1: dropping query to be processed by another server

This debug message is issued when the received DHCPv6 query is dropped by this server because it should be served by another server. This is the case when the remote server was designated to process the packet as a result of load balancing or because it is a primary server in the hot standby configuration. The argument provides client identification information retrieved from the query.

HA_BUFFER6_RECEIVE_PACKET_OPTIONS_SKIPPED

an error unpacking an option, caused subsequent options to be skipped: %1

A debug message issued when an option failed to unpack correctly, making it impossible to unpack the remaining options in the DHCPv6 query. The server will still attempt to service the packet. The sole argument provides a reason for unpacking error.

HA_BUFFER6_RECEIVE_UNPACK_FAILED

failed to parse query from %1 to %2, received over interface %3, reason: %4

This debug message is issued when received DHCPv6 query is malformed and can’t be parsed by the buffer6_receive callout. The query will be dropped by the server. The first three arguments specify source IP address, destination IP address and the interface. The last argument provides a reason for failure.

HA_COMMAND_PROCESSED_FAILED

command_processed callout failed: %1

This error message is issued when the callout for the command_processed hook point failed. The argument contains a reason for the error.

HA_COMMUNICATION_INTERRUPTED

communication with %1 is interrupted

This warning message is issued by the server which discovered that the communication to the active partner has been interrupted for a time period longer than the configured heartbeat-delay time. At this stage the server starts the failover procedure by monitoring the DHCP traffic sent to the partner and checking whether the partner server responds to this traffic. If the max-unacked-clients value is set to 0 such verification is disabled in which case the server will transition to the partner-down state.

HA_COMMUNICATION_INTERRUPTED_CLIENT4

%1: new client attempting to get a lease from the partner

This informational message is issued when the surviving server observes a DHCP packet sent to the partner with which the communication is interrupted. The client whose packet is observed is not yet considered “unacked” because the secs field value does not exceed the configured threshold specified with max-ack-delay.

HA_COMMUNICATION_INTERRUPTED_CLIENT4_UNACKED

%1: partner server failed to respond, %2 clients unacked so far, %3 clients left before transitioning to the partner-down state

This informational message is issued when the surviving server determines that its partner failed to respond to the DHCP query and that this client is considered to not be served by the partner. The surviving server counts such clients and if the number of such clients exceeds the max-unacked-clients threshold, the server will transition to the partner-down state. The first argument contains client identification information. The second argument specifies the number of clients to which the server has failed to respond. The third argument specifies the number of additional clients which, if not provisioned, will cause the server to transition to the partner-down state.

HA_COMMUNICATION_INTERRUPTED_CLIENT6

%1: new client attempting to get a lease from the partner

This informational message is issued when the surviving server observes a DHCP packet sent to the partner with which the communication is interrupted. The client whose packet is observed is not yet considered “unacked” because the elapsed time option value does not exceed the configured threshold specified with max-ack-delay. The sole argument specifies client identification information.

HA_COMMUNICATION_INTERRUPTED_CLIENT6_UNACKED

%1: partner server failed to respond, %2 clients unacked so far, %3 clients left before transitioning to the partner-down state

This informational message is issued when the surviving server determines that its partner failed to respond to the DHCP query and that this client is considered to not be served by the partner. The surviving server counts such clients and if the number of such clients exceeds the max-unacked-clients threshold, the server will transition to the partner-down state. The first argument contains client identification information. The second argument specifies the number of clients to which the server has failed to respond. The third argument specifies the number of additional clients which, if not provisioned, will cause the server to transition to the partner-down state.

HA_CONFIGURATION_FAILED

failed to configure High Availability hooks library: %1

This error message is issued when there is an error configuring the HA hooks library. The argument provides the detailed error message.

HA_CONFIGURATION_SUCCESSFUL

HA hook library has been successfully configured

This informational message is issued when the HA hook library configuration parser successfully parses and validates the new configuration.

HA_CONFIG_AUTO_FAILOVER_DISABLED

auto-failover disabled for %1

This warning message is issued to indicate that the ‘auto-failover’ parameter was administratively disabled for the specified server. The server will not automatically start serving partner’s scope when the partner failure is detected. The server administrator will need to enable this scope manually by sending appropriate ha-scopes command.

HA_CONFIG_DHCP_MT_DISABLED

HA multi-threading has been disabled, it cannot be enabled when Kea global multi-threading is disabled

This informational message is issued when HA configuration has enabled multi-threading while Kea global configuration has multi-threading disabled.

HA_CONFIG_LEASE_SYNCING_DISABLED

lease database synchronization between HA servers is disabled

This warning message is issued when the lease database synchronization is administratively disabled. This is valid configuration if the leases are replicated between lease databases via some other mechanism, e.g. SQL database replication.

HA_CONFIG_LEASE_SYNCING_DISABLED_REMINDER

bypassing SYNCING state because lease database synchronization is administratively disabled

This informational message is issued as a reminder that lease database synchronization is administratively disabled and therefore the server transitions directly from the “waiting” to “ready” state.

HA_CONFIG_LEASE_UPDATES_AND_SYNCING_DIFFER

unusual configuration where “send-lease-updates”: %1 and “sync-leases”: %2

This warning message is issued when the configuration values of the send-lease-updates and sync-leases parameters differ. This may be a valid configuration but is unusual. Normally, if the lease database with replication is in use, both values are set to false. If a lease database without replication is in use (e.g. memfile), both values are set to true. Providing different values for those parameters means that an administrator either wants the server to not synchronize leases upon startup but later send lease updates to the partner, or the lease database should be synchronized upon startup, but no lease updates are later sent as a result of leases allocation.

HA_CONFIG_LEASE_UPDATES_DISABLED

lease updates will not be generated

This warning message is issued when the lease updates are administratively disabled. This is valid configuration if the leases are replicated to the partner’s database via some other mechanism, e.g. SQL database replication.

HA_CONFIG_LEASE_UPDATES_DISABLED_REMINDER

lease updates are administratively disabled and will not be generated while in %1 state

This informational message is issued as a reminder that the lease updates are administratively disabled and will not be issued in the HA state to which the server has transitioned. The sole argument specifies the state into which the server has transitioned.

HA_CONFIG_SYSTEM_MT_UNSUPPORTED

HA multi-threading has been disabled, auto-detection of thread support reports 0

This informational message is issued when HA multi-threading configuration has specified auto-detection for the number of threads to use and the system reports the number of concurrent threads as 0. If you know your system can support multiple threads, then you may override this condition by specifying explicit values for http-listener-threads and http-client-threads.

HA_CONTINUE_HANDLER_FAILED

ha-continue command failed: %1

This error message is issued to indicate that the ha-continue command handler failed while processing the command. The argument provides the reason for failure.

HA_DEINIT_OK

unloading High Availability hooks library successful

This informational message indicates that the High Availability hooks library has been unloaded successfully.

HA_DHCP4_START_SERVICE_FAILED

failed to start DHCPv4 HA service in dhcp4_srv_configured callout: %1

This error message is issued when an attempt to start High Availability service for the DHCPv4 server failed in the dhcp4_srv_configured callout. This is internal server error and a bug report should be created.

HA_DHCP6_START_SERVICE_FAILED

failed to start DHCPv4 HA service in dhcp6_srv_configured callout: %1

This error message is issued when an attempt to start High Availability service for the DHCPv4 server failed in the dhcp4_srv_configured callout. This is internal server error and a bug report should be created.

HA_DHCP_DISABLE_COMMUNICATIONS_FAILED

failed to send request to disable DHCP service of %1: %2

This warning message indicates that there was a problem in communication with a HA peer while sending the dhcp-disable command. The first argument provides the remote server’s name. The second argument provides a reason for failure.

HA_DHCP_DISABLE_FAILED

failed to disable DHCP service of %1: %2

This warning message indicates that a peer returned an error status code in response to a dhcp-disable command. The first argument provides the remote server’s name. The second argument provides a reason for failure.

HA_DHCP_ENABLE_COMMUNICATIONS_FAILED

failed to send request to enable DHCP service of %1: %2

This warning message indicates that there was a problem in communication with a HA peer while sending the dhcp-enable command. The first argument provides the remote server’s name. The second argument provides a reason for failure.

HA_DHCP_ENABLE_FAILED

failed to enable DHCP service of %1: %2

This warning message indicates that a peer returned an error status code in response to a dhcp-enable command. The first argument provides the remote server’s name. The second argument provides a reason for failure.

HA_HEARTBEAT_COMMUNICATIONS_FAILED

failed to send heartbeat to %1: %2

This warning message indicates that there was a problem in communication with a HA peer while sending a heartbeat. This is a first sign that the peer may be down. The server will keep trying to send heartbeats until it considers that communication is interrupted.

HA_HEARTBEAT_FAILED

heartbeat to %1 failed: %2

This warning message indicates that a peer returned an error status code in response to a heartbeat. This is the sign that the peer may not function properly. The server will keep trying to send heartbeats until it considers that communication is interrupted.

HA_HEARTBEAT_HANDLER_FAILED

heartbeat command failed: %1

This error message is issued to indicate that the heartbeat command handler failed while processing the command. The argument provides the reason for failure.

HA_HIGH_CLOCK_SKEW

%1, please synchronize clocks!

This warning message is issued when the clock skew between the active servers exceeds 30 seconds. The HA service continues to operate but may not function properly, especially for low lease lifetimes. The administrator should should synchronize the clocks, e.g. using NTP. If the clock skew exceeds 60 seconds, the HA service will terminate.

HA_HIGH_CLOCK_SKEW_CAUSES_TERMINATION

%1, causing HA service to terminate

This warning message is issued when the clock skew between the active servers exceeds 60 seconds. The HA service stops. The servers will continue to respond to the DHCP queries but won’t exchange lease updates or send heartbeats. The administrator is required to synchronize the clocks and then restart the servers to resume the HA service.

HA_INIT_OK

loading High Availability hooks library successful

This informational message indicates that the High Availability hooks library has been loaded successfully.

HA_INVALID_PARTNER_STATE_COMMUNICATION_RECOVERY

partner is in the communication-recovery state unexpectedly

This warning message is issued when a partner is in the communication-recovery state, and this server is not running in the load balancing mode. The server may only transition to the communication-recovery state when it runs in the load balancing mode. The HA mode of both servers must be the same.

HA_INVALID_PARTNER_STATE_HOT_STANDBY

partner is in the hot-standby state unexpectedly

This warning message is issued when a partner is in the hot-standby state, and this server is not running in the hot standby mode. The server may only transition to the hot-standby state when it runs in the hot standby mode. The HA mode of both servers must be the same.

HA_INVALID_PARTNER_STATE_LOAD_BALANCING

partner is in the load-balancing state unexpectedly

This warning message is issued when a partner is in the load-balancing state, and this server is not running in the load balancing mode. The server may only transition to the load-balancing state when it runs in the load balancing mode. The HA mode of both servers must be the same.

HA_LEASES4_COMMITTED_FAILED

leases4_committed callout failed: %1

This error message is issued when the callout for the leases4_committed hook point failed. This includes unexpected errors like wrong arguments provided to the callout by the DHCP server (unlikely internal server error). The argument contains a reason for the error.

HA_LEASES4_COMMITTED_NOTHING_TO_UPDATE

%1: leases4_committed callout was invoked without any leases

This debug message is issued when the “leases4_committed” callout returns because there are neither new leases nor deleted leases for which updates should be sent. The sole argument specifies the details of the client which sent the packet.

HA_LEASES6_COMMITTED_FAILED

leases6_committed callout failed: %1

This error message is issued when the callout for the leases6_committed hook point failed. This includes unexpected errors like wrong arguments provided to the callout by the DHCP server (unlikely internal server error). The argument contains a reason for the error.

HA_LEASES6_COMMITTED_NOTHING_TO_UPDATE

%1: leases6_committed callout was invoked without any leases

This debug message is issued when the “leases6_committed” callout returns because there are neither new leases nor deleted leases for which updates should be sent. The sole argument specifies the details of the client which sent the packet.

HA_LEASES_BACKLOG_COMMUNICATIONS_FAILED

failed to communicate with %1 while sending lease updates backlog: %2

This error message is issued to indicate that there was a communication error with a partner server while sending outstanding lease updates after resuming connection. The second argument contains a reason for the error.

HA_LEASES_BACKLOG_FAILED

failed to send lease updates backlog to %1: %2

This error message is issued to indicate that sending lease updates backlog to a partner server failed. The lease updates backlog is sent to the partner after resuming temporarily broken communication with the partner. If this operation fails the server will transition to the waiting state to initiate full lease database synchronization.

HA_LEASES_BACKLOG_NOTHING_TO_SEND

no leases in backlog after communication recovery

This informational message is issued when there are no outstanding leases to be sent after communication recovery with a partner. This means that the communication interruption was short enough that no DHCP clients obtained any leases from the server while it was in the communication-recovery state. The server may now transition to the load-balancing state.

HA_LEASES_BACKLOG_START

starting to send %1 outstanding lease updates to %2

This informational message is issued when the server starts to send outstanding lease updates to the partner after resuming communications. The first argument specifies the number of lease updates to be sent. The name of the partner is specified with the second argument.

HA_LEASES_BACKLOG_SUCCESS

sending lease updates backlog to %1 successful in %2

This informational message is issued when server successfully completes sending lease updates backlog to the partner. The first argument specifies the name of the remote server. The second argument specifies the duration of this operation.

HA_LEASES_SYNC_COMMUNICATIONS_FAILED

failed to communicate with %1 while syncing leases: %2

This error message is issued to indicate that there was a communication error with a partner server while trying to fetch leases from its lease database. The argument contains a reason for the error.

HA_LEASES_SYNC_FAILED

failed to synchronize leases with %1: %2

This error message is issued to indicate that there was a problem while parsing a response from the server from which leases have been fetched for local database synchronization. The argument contains a reason for the error.

HA_LEASES_SYNC_LEASE_PAGE_RECEIVED

received %1 leases from %2

This informational message is issued during lease database synchronization to indicate that a bulk of leases have been received. The first argument holds the count of leases received. The second argument specifies the partner server name.

HA_LEASE_SYNC_FAILED

synchronization failed for lease: %1, reason: %2

This warning message is issued when creating or updating a lease in the local lease database fails. The lease information in the JSON format is provided as a first argument. The second argument provides a reason for the failure.

HA_LEASE_SYNC_STALE_LEASE4_SKIP

skipping stale lease %1 in subnet %2

This debug message is issued during lease database synchronization, when fetched IPv4 lease instance appears to be older than the instance in the local database. The newer instance is left in the database and the fetched lease is dropped. The remote server will still hold the older lease instance until it synchronizes its database with this server. The first argument specifies leased address. The second argument specifies a subnet to which the lease belongs.

HA_LEASE_SYNC_STALE_LEASE6_SKIP

skipping stale lease %1 in subnet %2

This debug message is issued during lease database synchronization, when fetched IPv6 lease instance appears to be older than the instance in the local database. The newer instance is left in the database and the fetched lease is dropped. The remote server will still hold the older lease instance until it synchronizes its database with this server. The first argument specifies leased address. The second argument specifies a subnet to which the lease belongs.

HA_LEASE_UPDATES_DISABLED

lease updates will not be sent to the partner while in %1 state

This informational message is issued to indicate that lease updates will not be sent to the partner while the server is in the current state. The argument specifies the server’s current state name. The lease updates are still sent to the backup servers if they are configured but any possible errors in communication with the backup servers are ignored.

HA_LEASE_UPDATES_ENABLED

lease updates will be sent to the partner while in %1 state

This informational message is issued to indicate that lease updates will be sent to the partner while the server is in the current state. The argument specifies the server’s current state name.

HA_LEASE_UPDATE_COMMUNICATIONS_FAILED

%1: failed to communicate with %2: %3

This warning message indicates that there was a problem in communication with a HA peer while processing a DHCP client query and sending lease update. The client’s DHCP message will be dropped.

HA_LEASE_UPDATE_CREATE_UPDATE_FAILED_ON_PEER

%1: failed to create or update the lease having type %2 for address %3, reason: %4

This informational message is issued when one of the leases failed to be created or updated on the HA peer while processing the lease updates sent from this server. This may indicate an issue with communication between the peer and its lease database.

HA_LEASE_UPDATE_DELETE_FAILED_ON_PEER

%1: failed to delete the lease having type %2 for address %3, reason: %4

This informational message is issued when one of the leases failed to delete on the HA peer while processing lease updates sent from this server. Typically, the lease fails to delete when it doesn’t exist in the peer’s database.

HA_LEASE_UPDATE_FAILED

%1: lease update to %2 failed: %3

This warning message indicates that a peer returned an error status code in response to a lease update. The client’s DHCP message will be dropped.

HA_LOAD_BALANCING_DUID_MISSING

load balancing failed for the DHCPv6 message (transaction id: %1) because DUID is missing

This debug message is issued when the HA hook library was unable to load balance an incoming DHCPv6 query because neither client identifier nor HW address was included in the query. The query will be dropped. The sole argument contains transaction id.

HA_LOAD_BALANCING_IDENTIFIER_MISSING

load balancing failed for the DHCPv4 message (transaction id: %1) because HW address and client identifier are missing

This debug message is issued when the HA hook library was unable to load balance an incoming DHCPv4 query because neither client identifier nor HW address was included in the query. The query will be dropped. The sole argument contains transaction id.

HA_LOCAL_DHCP_DISABLE

local DHCP service is disabled while the %1 is in the %2 state

This informational message is issued to indicate that the local DHCP service is disabled because the server remains in a state in which the server should not respond to DHCP clients, e.g. the server hasn’t synchronized its lease database. The first argument specifies server name. The second argument specifies server’s state.

HA_LOCAL_DHCP_ENABLE

local DHCP service is enabled while the %1 is in the %2 state

This informational message is issued to indicate that the local DHCP service is enabled because the server remains in a state in which it should respond to the DHCP clients. The first argument specifies server name. The second argument specifies server’s state.

HA_MAINTENANCE_CANCEL_HANDLER_FAILED

ha-maintenance-cancel command failed: %1

This error message is issued to indicate that the ha-maintenance-cancel command handler failed while processing the command. The argument provides the reason for failure.

HA_MAINTENANCE_NOTIFY_CANCEL_COMMUNICATIONS_FAILED

failed to send ha-maintenance-notify to %1 in attempt to cancel its maintenance: %2

This warning message indicates that there was a problem in communication with a HA peer while sending the ha-maintenance-notify command with the cancel flag set to true. The first argument provides the remote server’s name. The second argument provides a reason for failure.

HA_MAINTENANCE_NOTIFY_CANCEL_FAILED

error returned while processing ha-maintenance-notify by %1 in attempt to cancel its maintenance: %2

This warning message indicates that a peer returned an error status code in response to a ha-maintenance-notify command with the cancel flag set to true. The first argument provides the remote server’s name. The second argument provides a reason for failure.

HA_MAINTENANCE_NOTIFY_COMMUNICATIONS_FAILED

failed to send ha-maintenance-notify to %1: %2

This warning message indicates that there was a problem in communication with a HA peer while sending the ha-maintenance-notify command. The first argument provides the remote server’s name. The second argument provides a reason for failure.

HA_MAINTENANCE_NOTIFY_FAILED

error returned while processing ha-maintenance-notify by %1: %2

This warning message indicates that a peer returned an error status code in response to a ha-maintenance-notify command. The first argument provides the remote server’s name. The second argument provides a reason for failure.

HA_MAINTENANCE_NOTIFY_HANDLER_FAILED

ha-maintenance-notify command failed: %1

This error message is issued to indicate that the ha-maintenance-notify command handler failed while processing the command. The argument provides the reason for failure.

HA_MAINTENANCE_SHUTDOWN_SAFE

the server can now be shutdown for maintenance as the partner has taken over the DHCP traffic

This informational message is displayed after the server transitions to the in-maintenance state. This server no longer responds to any DHCP queries and its partner - in partner-in-maintenance state - has taken over the DHCP traffic. When the server in-maintenance state is shut down, the partner moves to the partner-down state immediately.

HA_MAINTENANCE_STARTED

the server is now in the partner-in-maintenance state and the partner is in-maintenance state

This informational message is displayed when the server receiving the ha-maintenance-start command transitions to the partner-in-maintenance state. The server does it after sending the ha-maintenance-notify to its partner to put the partner in the in-maintenance state. From now on, the server in the partner-in-maintenance state will be responding to all queries and the partner will respond to no queries. The partner may be safely shut down for maintenance in which case this server will automatically transition from the partner-in-maintenance state to the partner-down state.

HA_MAINTENANCE_STARTED_IN_PARTNER_DOWN

the server is now in the partner-down mode as a result of requested maintenance

This informational message is displayed when the server receiving the ha-maintenance-start command transitions to the partner-down state because it was unable to communicate with the partner while receiving the command. It is assumed that in such situation the partner is already offline for the maintenance. Note that in this case the normal failover procedure does not take place. The server does not wait for a heartbeat to fail several times, nor it monitors the DHCP traffic for not responded queries. In the maintenance case the server transitions to the partner-down state when it first encounters a communication problem with the partner.

HA_MAINTENANCE_START_HANDLER_FAILED

ha-maintenance-start command failed: %1

This error message is issued to indicate that the ha-maintenance-start command handler failed while processing the command. The argument provides the reason for failure.

HA_MISSING_CONFIGURATION

high-availability parameter not specified for High Availability hooks library

This error message is issued to indicate that the configuration for the High Availability hooks library hasn’t been specified. The ‘high-availability’ parameter must be specified for the hooks library to load properly.

HA_PAUSE_CLIENT_LISTENER_FAILED

Pausing multi-threaded HTTP processing failed: %1

This error message is emitted when attempting to pause HA’s HTTP client and listener threads. This error is highly unlikely and indicates a programmatic issue that should be reported as a defect.

HA_PAUSE_CLIENT_LISTENER_ILLEGAL

Pausing multi-threaded HTTP processing failed: %1

This error message is emitted when attempting to pause HA’s HTTP client or listener thread pools from a worker thread. This error indicates that a command run on the listener threads is trying to use a critical section which would result in a dead-lock.

HA_RESET_COMMUNICATIONS_FAILED

failed to send ha-reset command to %1: %2

This warning message indicates a problem with communication with a HA peer while sending the ha-reset command. The first argument specifies a remote server name. The second argument specifies a reason for failure.

HA_RESET_FAILED

failed to reset HA state machine of %1: %2

This warning message indicates that a peer returned an error status code in response to the ha-reset command. The first argument specifies a remote server name. The second argument specifies a reason for failure.

HA_RESET_HANDLER_FAILED

ha-reset command failed: %1

This error message is issued to indicate that the ha-reset command handler failed while processing the command. The argument provides the reason for failure.

HA_RESUME_CLIENT_LISTENER_FAILED

Resuming multi-threaded HTTP processing failed: %1

This error message is emitted when attempting to resume HA’s HTTP client and listener threads. This error is highly unlikely and indicates a programmatic issue that should be reported as a defect.

HA_SCOPES_HANDLER_FAILED

ha-scopes command failed: %1

This error message is issued to indicate that the ha-scopes command handler failed while processing the command. The argument provides reason for the failure.

HA_SERVICE_STARTED

started high availability service in %1 mode as %2 server

This informational message is issued when the HA service is started as a result of server startup or reconfiguration. The first argument provides the HA mode. The second argument specifies the role of this server instance in this configuration.

HA_STATE_MACHINE_CONTINUED

state machine is un-paused

This informational message is issued when the HA state machine is un-paused. This unlocks the server from the current state. It may transition to any other state if it needs to do so, e.g. ‘partner-down’ if its partner appears to be offline. The server may also remain in the current state if the HA setup state warrants such behavior.

HA_STATE_MACHINE_PAUSED

state machine paused in state %1

This informational message is issued when the HA state machine is paused. HA state machine may be paused in certain states specified in the HA hooks library configuration. When the state machine is paused, the server remains in the given state until it is explicitly unpaused (via the ha-continue command). If the state machine is paused, the server operates normally but cannot transition to any other state.

HA_STATE_TRANSITION

server transitions from %1 to %2 state, partner state is %3

This informational message is issued when the server transitions to a new state as a result of some interaction (or lack of thereof) with its partner. The arguments specify initial server state, new server state and the partner’s state.

HA_STATE_TRANSITION_PASSIVE_BACKUP

server transitions from %1 to %2 state

This informational message is issued when the server in passive-backup mode transitions to a new state. The arguments specify initial server state and a new server state.

HA_SYNC_COMPLETE_NOTIFY_COMMUNICATIONS_FAILED

failed to send ha-sync-complete-notify to %1: %2

This warning message indicates that there was a problem in communication with an HA peer while sending the ha-sync-complete-notify command. The first argument provides the remote server’s name. The second argument provides a reason for failure.

HA_SYNC_COMPLETE_NOTIFY_FAILED

error processing ha-sync-complete-notify command on %1: %2

This warning message indicates that a peer returned an error status code in response to the ha-sync-complete-notify command. The first argument provides the remote server’s name. The second argument provides a reason for failure.

HA_SYNC_COMPLETE_NOTIFY_HANDLER_FAILED

ha-sync-complete-notify command failed: %1

This error message is issued to indicate that the ha-sync-complete-notify command handler failed while processing the command. The argument provides the reason for failure.

HA_SYNC_FAILED

lease database synchronization with %1 failed: %2

This error message is issued to indicate that the lease database synchronization failed. The first argument provides the partner server’s name. The second argument provides a reason for the failure.

HA_SYNC_HANDLER_FAILED

ha-sync command failed: %1

This error message is issued to indicate that the ha-sync command handler failed while processing the command. The argument provides the reason for failure.

HA_SYNC_START

starting lease database synchronization with %1

This informational message is issued when the server starts lease database synchronization with a partner. The name of the partner is specified with the sole argument.

HA_SYNC_SUCCESSFUL

lease database synchronization with %1 completed successfully in %2

This informational message is issued when the server successfully completed lease database synchronization with the partner. The first argument specifies the name of the partner server. The second argument specifies the duration of the synchronization.

HA_TERMINATED

HA service terminated due to an unrecoverable condition. Check previous error message(s), address the problem and restart!

This error message is issued to indicate that the HA service has been stopped due to an unacceptable condition (e.g. too large of a clock skew). The exact cause should appear in a previous error message. Address the condition reported then restart the servers to resume service.

HOOKS

HOOKS_ALL_CALLOUTS_DEREGISTERED

hook library at index %1 removed all callouts on hook %2

A debug message issued when all callouts on the specified hook registered by the library with the given index were removed. This is similar to the HOOKS_CALLOUTS_REMOVED message (and the two are likely to be seen together), but is issued at a lower-level in the hook framework.

HOOKS_CALLOUTS_BEGIN

begin all callouts for hook %1

This debug message is issued when callout manager begins to invoke callouts for the hook. The argument specifies the hook name.

HOOKS_CALLOUTS_COMPLETE

completed callouts for hook %1 (total callouts duration: %2)

This debug message is issued when callout manager has completed execution of all callouts for the particular hook. The arguments specify the hook name and total execution time for all callouts in milliseconds.

HOOKS_CALLOUTS_REMOVED

callouts removed from hook %1 for library %2

This is a debug message issued during library unloading. It notes that one of more callouts registered by that library have been removed from the specified hook. This is similar to the HOOKS_DEREGISTER_ALL_CALLOUTS message (and the two are likely to be seen together), but is issued at a higher-level in the hook framework.

HOOKS_CALLOUT_CALLED

hooks library with index %1 has called a callout on hook %2 that has address %3 (callout duration: %4)

Only output at a high debugging level, this message indicates that a callout on the named hook registered by the library with the given index (in the list of loaded libraries) has been called and returned a success state. The address of the callout is given in the message. The message includes the callout execution time in milliseconds.

HOOKS_CALLOUT_DEREGISTERED

hook library at index %1 deregistered a callout on hook %2

A debug message issued when all instances of a particular callouts on the hook identified in the message that were registered by the library with the given index have been removed.

HOOKS_CALLOUT_ERROR

error returned by callout on hook %1 registered by library with index %2 (callout address %3) (callout duration %4)

If a callout returns an error status when called, this error message is issued. It identifies the hook to which the callout is attached, the index of the library (in the list of loaded libraries) that registered it and the address of the callout. The error is otherwise ignored. The error message includes the callout execution time in milliseconds.

HOOKS_CALLOUT_EXCEPTION

exception thrown by callout on hook %1 registered by library with index %2 (callout address %3): %4 (callout duration: %5)

If a callout throws an exception when called, this error message is issued. It identifies the hook to which the callout is attached, the index of the library (in the list of loaded libraries) that registered it and the address of the callout. The error is otherwise ignored. The error message includes the callout execution time in milliseconds.

HOOKS_CALLOUT_REGISTRATION

hooks library with index %1 registering callout for hook ‘%2’

This is a debug message, output when a library (whose index in the list of libraries (being) loaded is given) registers a callout.

HOOKS_CLOSE_ERROR

failed to close hook library %1: %2

Kea has failed to close the named hook library for the stated reason. Although this is an error, this should not affect the running system other than as a loss of resources. If this error persists, you should restart Kea.

HOOKS_HOOK_LIST_RESET

the list of hooks has been reset

This is a message indicating that the list of hooks has been reset. While this is usual when running the Kea test suite, it should not be seen when running Kea in a production environment. If this appears, please report a bug through the usual channels.

HOOKS_INCORRECT_VERSION

hook library %1 is at version %2, require version %3

Kea has detected that the named hook library has been built against a version of Kea that is incompatible with the version of Kea running on your system. It has not loaded the library. This is most likely due to the installation of a new version of Kea without rebuilding the hook library. A rebuild and re-install of the library should fix the problem in most cases.

HOOKS_LIBRARY_CLOSED

hooks library %1 successfully closed

This information message is issued when a user-supplied hooks library has been successfully closed.

HOOKS_LIBRARY_LOADED

hooks library %1 successfully loaded

This information message is issued when a user-supplied hooks library has been successfully loaded.

HOOKS_LIBRARY_LOADING

loading hooks library %1

This is a debug message output just before the specified library is loaded. If the action is successfully, it will be followed by the HOOKS_LIBRARY_LOADED informational message.

HOOKS_LIBRARY_MULTI_THREADING_COMPATIBLE

hooks library %1 reports its multi-threading compatibility as %2

A debug message issued when the “multi_threading_compatible” function was called. The returned value (0 means not compatible, others compatible) is displayed.

HOOKS_LIBRARY_MULTI_THREADING_NOT_COMPATIBLE

hooks library %1 is not compatible with multi-threading

When multi-threading is enabled and the library is not compatible (either because the “multi_threading_compatible” function returned 0 or was not implemented) this error message is issued. The library must be removed from the configuration or the multi-threading disabled.

HOOKS_LIBRARY_UNLOADED

hooks library %1 successfully unloaded

This information message is issued when a user-supplied hooks library has been successfully unloaded.

HOOKS_LIBRARY_UNLOADING

unloading library %1

This is a debug message called when the specified library is being unloaded. If all is successful, it will be followed by the HOOKS_LIBRARY_UNLOADED informational message.

HOOKS_LIBRARY_VERSION

hooks library %1 reports its version as %2

A debug message issued when the version check on the hooks library has succeeded.

HOOKS_LOAD_ERROR

‘load’ function in hook library %1 returned error %2

A “load” function was found in the library named in the message and was called. The function returned a non-zero status (also given in the message) which was interpreted as an error. The library has been unloaded and no callouts from it will be installed.

HOOKS_LOAD_EXCEPTION

‘load’ function in hook library %1 threw an exception

A “load” function was found in the library named in the message and was called. The function threw an exception (an error indication) during execution, which is an error condition. The library has been unloaded and no callouts from it will be installed.

HOOKS_LOAD_FRAMEWORK_EXCEPTION

‘load’ function in hook library %1 threw an exception: reason %2

A “load” function was found in the library named in the message and was called. Either the hooks framework or the function threw an exception (an error indication) during execution, which is an error condition; the cause of the exception is recorded in the message. The library has been unloaded and no callouts from it will be installed.

HOOKS_LOAD_SUCCESS

‘load’ function in hook library %1 returned success

This is a debug message issued when the “load” function has been found in a hook library and has been successfully called.

HOOKS_MULTI_THREADING_COMPATIBLE_EXCEPTION

‘multi_threading_compatible’ function in hook library %1 threw an exception

This error message is issued if the multi_threading_compatible() function in the specified hooks library was called and generated an exception. The library is considered unusable and will not be loaded.

HOOKS_NO_LOAD

no ‘load’ function found in hook library %1

This is a debug message saying that the specified library was loaded but no function called “load” was found in it. Providing the library contained some “standard” functions (i.e. functions with the names of the hooks for the given server), this is not an issue.

HOOKS_NO_UNLOAD

no ‘unload’ function found in hook library %1

This is a debug message issued when the library is being unloaded. It merely states that the library did not contain an “unload” function.

HOOKS_NO_VERSION

no ‘version’ function found in hook library %1

The shared library named in the message was found and successfully loaded, but Kea did not find a function named “version” in it. This function is required and should return the version of Kea against which the library was built. The value is used to check that the library was built against a compatible version of Kea. The library has not been loaded.

HOOKS_OPEN_ERROR

failed to open hook library %1: %2

Kea failed to open the specified hook library for the stated reason. The library has not been loaded. Kea will continue to function, but without the services offered by the library.

HOOKS_STD_CALLOUT_REGISTERED

hooks library %1 registered standard callout for hook %2 at address %3

This is a debug message, output when the library loading function has located a standard callout (a callout with the same name as a hook point) and registered it. The address of the callout is indicated.

HOOKS_UNLOAD_ERROR

‘unload’ function in hook library %1 returned error %2

During the unloading of a library, an “unload” function was found. It was called, but returned an error (non-zero) status, resulting in the issuing of this message. The unload process continued after this message and the library has been unloaded.

HOOKS_UNLOAD_EXCEPTION

‘unload’ function in hook library %1 threw an exception

During the unloading of a library, an “unload” function was found. It was called, but in the process generated an exception (an error indication). The unload process continued after this message and the library has been unloaded.

HOOKS_UNLOAD_FRAMEWORK_EXCEPTION

‘unload’ function in hook library %1 threw an exception, reason %2

During the unloading of a library, an “unload” function was found. It was called, but in the process either it or the hooks framework generated an exception (an error indication); the cause of the error is recorded in the message. The unload process continued after this message and the library has been unloaded.

HOOKS_UNLOAD_SUCCESS

‘unload’ function in hook library %1 returned success

This is a debug message issued when an “unload” function has been found in a hook library during the unload process, called, and returned success.

HOSTS

HOSTS_BACKENDS_REGISTERED

the following host backend types are available: %1

This informational message lists all possible host backends that could be used in hosts-database[s].

HOSTS_BACKEND_DEREGISTER

deregistered host backend type: %1

This debug message is issued when a backend factory was deregistered. It is no longer possible to use host backend of this type.

HOSTS_BACKEND_REGISTER

registered host backend type: %1

This debug message is issued when a backend factory was successfully registered. It is now possible to use host backend of this type.

HOSTS_CFG_ADD_HOST

add the host for reservations: %1

This debug message is issued when new host (with reservations) is added to the server’s configuration. The argument describes the host and its reservations in detail.

HOSTS_CFG_CACHE_HOST_DATA_SOURCE

get host cache data source: %1

This informational message is issued when a host cache data source is detected by the host manager.

HOSTS_CFG_CLOSE_HOST_DATA_SOURCE

Closing host data source: %1

This is a normal message being printed when the server closes host data source connection.

HOSTS_CFG_DEL_ALL_SUBNET4

deleted all %1 host(s) for subnet id %2

This debug message is issued when all IPv4 reservations are deleted for the specified subnet. The first argument specifies how many reservations have been deleted. The second argument is the subnet identifier.

HOSTS_CFG_DEL_ALL_SUBNET6

deleted all %1 host(s) having %2 IPv6 reservation(s) for subnet id %3

This debug message is issued when all IPv6 reservations are deleted for the specified subnet. The first argument specifies how many hosts have been deleted. The second argument specifies how many IPv6 (addresses and prefixes) have been deleted. The third argument is the subnet identifier.

HOSTS_CFG_GET_ALL

get all hosts with reservations

This debug message is issued when starting to retrieve all hosts.

HOSTS_CFG_GET_ALL_ADDRESS4

get all hosts with reservations for IPv4 address %1

This debug message is issued when starting to retrieve all hosts, holding the reservation for the specific IPv4 address, from the configuration. The argument specifies the IPv4 address used to search the hosts.

HOSTS_CFG_GET_ALL_ADDRESS4_COUNT

using address %1, found %2 host(s)

This debug message logs the number of hosts found using the specified IPv4 address. The arguments specify the IPv4 address used and the number of hosts found respectively.

HOSTS_CFG_GET_ALL_ADDRESS4_HOST

using address %1 found host: %2

This debug message is issued when found host with the reservation for the specified IPv4 address. The arguments specify the IPv4 address and the detailed description of the host found.

HOSTS_CFG_GET_ALL_ADDRESS6

get all hosts with reservations for IPv6 address %1

This debug message is issued when starting to retrieve all hosts, holding the reservation for the specific IPv6 address, from the configuration. The argument specifies the IPv6 address used to search the hosts.

HOSTS_CFG_GET_ALL_ADDRESS6_COUNT

using address %1, found %2 host(s)

This debug message logs the number of hosts found using the specified IPv6 address. The arguments specify the IPv6 address used and the number of hosts found respectively.

HOSTS_CFG_GET_ALL_ADDRESS6_HOST

using address %1 found host: %2

This debug message is issued when found host with the reservation for the specified IPv6 address. The arguments specify the IPv6 address and the detailed description of the host found.

HOSTS_CFG_GET_ALL_COUNT

found %1 host(s)

This debug message include the details of the host found. The argument specifies the number of hosts found.

HOSTS_CFG_GET_ALL_HOST

found host: %1

This debug message includes the details of the host found. The argument specifies found host details.

HOSTS_CFG_GET_ALL_HOSTNAME

get all hosts with reservations for hostname %1

This debug message is issued when starting to retrieve all hosts with the specific hostname. The argument specifies hostname.

HOSTS_CFG_GET_ALL_HOSTNAME_COUNT

using hostname %1, found %2 host(s)

This debug message include the details of the host found using the hostname. The arguments specify hostname and the number of hosts found respectively.

HOSTS_CFG_GET_ALL_HOSTNAME_HOST

using hostname %1, found host: %2

This debug message includes the details of the host found using the hostname. The arguments specify hostname and found host details respectively.

HOSTS_CFG_GET_ALL_HOSTNAME_SUBNET_ID4

get all hosts with reservations for hostname %1 and IPv4 subnet %2

This debug message is issued when starting to retrieve all hosts with the specific hostname connected to the specific DHCPv4 subnet. The argument specifies hostname and subnet id.

HOSTS_CFG_GET_ALL_HOSTNAME_SUBNET_ID4_COUNT

using hostname %1 and IPv4 subnet %2, found %3 host(s)

This debug message include the details of the host found using the hostname and the DHCPv4 subnet id. The arguments specify hostname, subnet id and the number of hosts found respectively.

HOSTS_CFG_GET_ALL_HOSTNAME_SUBNET_ID4_HOST

using hostname %1 and IPv4 subnet %2, found host: %3

This debug message includes the details of the host found using the hostname and the DHCPv4 subnet id. The arguments specify hostname, subnet id and found host details respectively.

HOSTS_CFG_GET_ALL_HOSTNAME_SUBNET_ID6

get all hosts with reservations for hostname %1 and IPv6 subnet %2

This debug message is issued when starting to retrieve all hosts with the specific hostname connected to the specific DHCPv6 subnet. The argument specifies hostname and subnet id.

HOSTS_CFG_GET_ALL_HOSTNAME_SUBNET_ID6_COUNT

using hostname %1 and IPv6 subnet %2, found %3 host(s)

This debug message include the details of the host found using the hostname and the DHCPv6 subnet id. The arguments specify hostname, subnet id and the number of hosts found respectively.

HOSTS_CFG_GET_ALL_HOSTNAME_SUBNET_ID6_HOST

using hostname %1 and IPv6 subnet %2, found host: %3

This debug message includes the details of the host found using the hostname and the DHCPv6 subnet id. The arguments specify hostname, subnet id and found host details respectively.

HOSTS_CFG_GET_ALL_IDENTIFIER

get all hosts with reservations using identifier: %1

This debug message is issued when starting to retrieve reservations for all hosts identified by HW address or DUID. The argument holds both the identifier type and the value.

HOSTS_CFG_GET_ALL_IDENTIFIER_COUNT

using identifier %1, found %2 host(s)

This debug message logs the number of hosts found using the specified identifier. The arguments specify the identifier used and the number of hosts found respectively.

HOSTS_CFG_GET_ALL_IDENTIFIER_HOST

using identifier: %1, found host: %2

This debug message is issued when found host identified by the specific identifier. The arguments specify the identifier and the detailed description of the host found.

HOSTS_CFG_GET_ALL_SUBNET_ID4

get all hosts with reservations for IPv4 subnet %1

This debug message is issued when starting to retrieve all hosts connected to the specific DHCPv4 subnet. The argument specifies subnet id.

HOSTS_CFG_GET_ALL_SUBNET_ID4_COUNT

using IPv4 subnet %1, found %2 host(s)

This debug message include the details of the host found using the DHCPv4 subnet id. The arguments specify subnet id and the number of hosts found respectively.

HOSTS_CFG_GET_ALL_SUBNET_ID4_HOST

using IPv4 subnet %1, found host: %2

This debug message includes the details of the host found using the DHCPv4 subnet id. The arguments specify subnet id and found host details respectively.

HOSTS_CFG_GET_ALL_SUBNET_ID6

get all hosts with reservations for IPv6 subnet %1

This debug message is issued when starting to retrieve all hosts connected to the specific DHCPv6 subnet. The argument specifies subnet id.

HOSTS_CFG_GET_ALL_SUBNET_ID6_COUNT

using IPv6 subnet %1, found %2 host(s)

This debug message include the details of the host found using the DHCPv6 subnet id. The arguments specify subnet id and the number of hosts found respectively.

HOSTS_CFG_GET_ALL_SUBNET_ID6_HOST

using IPv6 subnet %1, found host: %2

This debug message includes the details of the host found using the DHCPv6 subnet id. The arguments specify subnet id and found host details respectively.

HOSTS_CFG_GET_ALL_SUBNET_ID_ADDRESS4

get all hosts with reservations for subnet id %1 and IPv4 address %2

This debug message is issued when starting to retrieve all hosts having the reservation for the given IPv4 address within the given subnet. The first argument specifies subnet identifier. The second argument specifies the IPv4 address for which the reservation is to be returned.

HOSTS_CFG_GET_ALL_SUBNET_ID_ADDRESS4_COUNT

using IPv4 subnet %1 and IPv4 address %2, found %3 host(s)

This debug message logs the number of hosts found having the reservation for the specified IPv4 address within the specified subnet. The first argument specifies the subnet identifier. The second argument specifies the reserved IPv4 address. The third argument specifies the number of hosts found.

HOSTS_CFG_GET_ALL_SUBNET_ID_ADDRESS4_HOST

using IPv4 subnet %1 and IPv4 address %2, found host: %3

This debug message is issued when found host having the reservation for the specified IPv4 address in the specified subnet. The first argument specifies the subnet identifier. The second argument specifies the reserved IPv4 address. The third argument specifies host details.

HOSTS_CFG_GET_ALL_SUBNET_ID_ADDRESS6

get all hosts with reservations for subnet id %1 and IPv6 address %2

This debug message is issued when starting to retrieve all hosts connected to the specific subnet and having the specific IPv6 address reserved. The arguments specify subnet id and IPv6 address respectively.

HOSTS_CFG_GET_ALL_SUBNET_ID_ADDRESS6_COUNT

using subnet id %1 and address %2, found %3 host(s)

This debug message include the details of the host found using the subnet id and address. The arguments specify subnet id, address and the number of hosts found respectively.

HOSTS_CFG_GET_ALL_SUBNET_ID_ADDRESS6_HOST

using subnet id %1 and address %2, found host: %3

This debug message includes the details of the host found using the subnet id and address. The arguments specify subnet id, address and the number of hosts found respectively. found host details respectively.

HOSTS_CFG_GET_ONE_PREFIX

get one host with reservation for prefix %1/%2

This debug message is issued when starting to retrieve a host having a reservation for a specified prefix. The arguments specify a prefix and prefix length.

HOSTS_CFG_GET_ONE_PREFIX_HOST

using prefix %1/%2, found host: %3

This debug message includes the details of the host found using the specific prefix/prefix length. The arguments specify prefix, prefix length and host details respectively.

HOSTS_CFG_GET_ONE_PREFIX_NULL

host not found using prefix %1/%2

This debug message is issued when no host was found for a specified prefix and prefix length.

HOSTS_CFG_GET_ONE_SUBNET_ID_ADDRESS4

get one host with reservation for subnet id %1 and IPv4 address %2

This debug message is issued when starting to retrieve a host connected to the specific subnet and having the specific IPv4 address reserved. The arguments specify subnet id and IPv4 address respectively.

HOSTS_CFG_GET_ONE_SUBNET_ID_ADDRESS4_HOST

using subnet id %1 and address %2, found host: %3

This debug message logs the details of the host found using the subnet id and IPv4 address.

HOSTS_CFG_GET_ONE_SUBNET_ID_ADDRESS4_NULL

host not found using subnet id %1 and address %2

This debug message is issued when no host was found for the specified subnet id and IPv4 address.

HOSTS_CFG_GET_ONE_SUBNET_ID_ADDRESS6

get one host with reservation for subnet id %1 and having IPv6 address %2

This debug message is issued when starting to retrieve a host connected to the specific subnet and having the specific IPv6 address reserved. The arguments specify subnet id and IPv6 address respectively.

HOSTS_CFG_GET_ONE_SUBNET_ID_ADDRESS6_HOST

using subnet id %1 and address %2, found host: %3

This debug message logs the details of the host found using the subnet id and IPv6 address.

HOSTS_CFG_GET_ONE_SUBNET_ID_ADDRESS6_NULL

host not found using subnet id %1 and address %2

This debug message is issued when no host was found using the specified subnet if and IPv6 address.

HOSTS_CFG_GET_ONE_SUBNET_ID_IDENTIFIER

get one host with %1 reservation for subnet id %2, identified by %3

This debug message is issued when starting to retrieve a host holding IPv4 or IPv6 reservations, which is connected to a specific subnet and is identified by a specific unique identifier. The first argument identifies if the IPv4 or IPv6 reservation is desired.

HOSTS_CFG_GET_ONE_SUBNET_ID_IDENTIFIER_HOST

using subnet id %1 and identifier %2, found host: %3

This debug message includes the details of a host found using a subnet id and specific host identifier.

HOSTS_CFG_GET_ONE_SUBNET_ID_IDENTIFIER_NULL

host not found using subnet id %1 and identifier %2

This debug message is issued when no host was found using the specified subnet id and host identifier.

HOSTS_MGR_ALTERNATE_GET4_SUBNET_ID_ADDRESS4

trying alternate sources for host using subnet id %1 and address %2

This debug message is issued when the Host Manager doesn’t find the host connected to the specific subnet and having the reservation for the specific IPv4 address, and it is starting to search for this host in alternate host data sources.

HOSTS_MGR_ALTERNATE_GET4_SUBNET_ID_IDENTIFIER

get one host with IPv4 reservation for subnet id %1, identified by %2

This debug message is issued when starting to retrieve a host holding IPv4 reservation, which is connected to a specific subnet and is identified by a specific unique identifier.

HOSTS_MGR_ALTERNATE_GET4_SUBNET_ID_IDENTIFIER_HOST

using subnet id %1 and identifier %2, found in %3 host: %4

This debug message includes the details of a host returned by an alternate hosts data source using a subnet id and specific host identifier.

HOSTS_MGR_ALTERNATE_GET4_SUBNET_ID_IDENTIFIER_NULL

host not found using subnet id %1 and identifier %2

This debug message is issued when no host was found using the specified subnet id and host identifier.

HOSTS_MGR_ALTERNATE_GET6_PREFIX

trying alternate sources for host using prefix %1/%2

This debug message is issued when the Host Manager doesn’t find the host connected to the specific subnet and having the reservation for the specified prefix, and it is starting to search for this host in alternate host data sources.

HOSTS_MGR_ALTERNATE_GET6_SUBNET_ID_ADDRESS6

trying alternate sources for host using subnet id %1 and IPv6 address %2

This debug message is issued when the Host Manager doesn’t find the host connected to the specific subnet and having the reservation for the specified IPv6 address, and it is starting to search for this host in alternate host data sources.

HOSTS_MGR_ALTERNATE_GET6_SUBNET_ID_IDENTIFIER

get one host with IPv6 reservation for subnet id %1, identified by %2

This debug message is issued when starting to retrieve a host holding IPv4 reservation, which is connected to a specific subnet and is identified by a specific unique identifier.

HOSTS_MGR_ALTERNATE_GET6_SUBNET_ID_IDENTIFIER_HOST

using subnet id %1 and identifier %2, found in %3 host: %4

This debug message includes the details of a host returned by an alternate host data source using a subnet id and specific host identifier.

HOSTS_MGR_ALTERNATE_GET6_SUBNET_ID_IDENTIFIER_NULL

host not found using subnet id %1 and identifier %2

This debug message is issued when no host was found using the specified subnet id and host identifier.

HOSTS_MGR_ALTERNATE_GET_ALL_SUBNET_ID_ADDRESS4

trying alternate sources for hosts using subnet id %1 and address %2

This debug message is issued when the Host Manager is starting to search for hosts in alternate host data sources by subnet ID and IPv4 address.

HOSTS_MGR_ALTERNATE_GET_ALL_SUBNET_ID_ADDRESS6

trying alternate sources for hosts using subnet id %1 and address %2

This debug message is issued when the Host Manager is starting to search for hosts in alternate host data sources by subnet ID and IPv6 address.

HTTPS

HTTPS_REQUEST_RECEIVE_START

start receiving request from %1

This debug message is issued when the server starts receiving new request over the established connection. The argument specifies the address of the remote endpoint.

HTTP

HTTP_BAD_CLIENT_REQUEST_RECEIVED

bad request received from %1: %2

This debug message is issued when an HTTP client sends malformed request to the server. This includes HTTP requests using unexpected content types, including malformed JSON etc. The first argument specifies an address of the remote endpoint which sent the request. The second argument provides a detailed error message.

HTTP_BAD_CLIENT_REQUEST_RECEIVED_DETAILS

detailed information about bad request received from %1:n%2

This debug message is issued when an HTTP client sends malformed request to the server. It includes detailed information about the received request rejected by the server. The first argument specifies an address of the remote endpoint which sent the request. The second argument provides a request in the textual format. The request is truncated by the logger if it is too large to be printed.

HTTP_BAD_SERVER_RESPONSE_RECEIVED

bad response received when communicating with %1: %2

This debug message is issued when an HTTP client fails to receive a response from the server or when this response is malformed. The first argument specifies the server URL. The second argument provides a detailed error message.

HTTP_BAD_SERVER_RESPONSE_RECEIVED_DETAILS

detailed information about bad response received from %1:n%2

This debug message is issued when an HTTP client receives malformed response from the server. The first argument specifies an URL of the server. The second argument provides a response in the textual format. The request is truncated by the logger if it is too large to be printed.

HTTP_CLIENT_MT_STARTED

HttpClient has been started in multi-threaded mode running %1 threads

This debug message is issued when a multi-threaded HTTP client instance has been created. The argument specifies the maximum number of threads.

HTTP_CLIENT_QUEUE_SIZE_GROWING

queue for URL: %1, now has %2 entries and may be growing too quickly

This warning message is issued when the queue of pending requests for the given URL appears to be growing more quickly than the requests can be handled. It will be emitted periodically as long as the queue size continues to grow. This may occur with a surge of client traffic creating a momentary backlog which then subsides as the surge subsides. If it happens continually then it most likely indicates a deployment configuration that cannot sustain the client load.

HTTP_CLIENT_REQUEST_AUTHORIZED

received HTTP request authorized for ‘%1’

This information message is issued when the server receives with a matching authentication header. The argument provides the user id.

HTTP_CLIENT_REQUEST_BAD_AUTH_HEADER

received HTTP request with malformed authentication header: %1

This information message is issued when the server receives a request with a malformed authentication header. The argument explains the problem.

HTTP_CLIENT_REQUEST_NOT_AUTHORIZED

received HTTP request with not matching authentication header

This information message is issued when the server receives a request with authentication header carrying not recognized credential: the user provided incorrect user id and/or password.

HTTP_CLIENT_REQUEST_RECEIVED

received HTTP request from %1

This debug message is issued when the server finished receiving a HTTP request from the remote endpoint. The address of the remote endpoint is specified as an argument.

HTTP_CLIENT_REQUEST_RECEIVED_DETAILS

detailed information about well-formed request received from %1:n%2

This debug message is issued when the HTTP server receives a well-formed request. It includes detailed information about the received request. The first argument specifies an address of the remote endpoint which sent the request. The second argument provides the request in the textual format. The request is truncated by the logger if it is too large to be printed.

HTTP_CLIENT_REQUEST_SEND

sending HTTP request %1 to %2

This debug message is issued when the client is starting to send a HTTP request to a server. The first argument holds basic information about the request (HTTP version number and status code). The second argument specifies a URL of the server.

HTTP_CLIENT_REQUEST_SEND_DETAILS

detailed information about request sent to %1:n%2

This debug message is issued right before the client sends an HTTP request to the server. It includes detailed information about the request. The first argument specifies an URL of the server to which the request is being sent. The second argument provides the request in the textual form. The request is truncated by the logger if it is too large to be printed.

HTTP_CLIENT_REQUEST_TIMEOUT_OCCURRED

HTTP request timeout occurred when communicating with %1

This debug message is issued when the HTTP request timeout has occurred and the server is going to send a response with Http Request timeout status code.

HTTP_CONNECTION_CLOSE_CALLBACK_FAILED

Connection close callback threw an exception

This is an error message emitted when the close connection callback registered on the connection failed unexpectedly. This is a programmatic error that should be submitted as a bug.

HTTP_CONNECTION_HANDSHAKE_FAILED

TLS handshake with %1 failed with %2

This information message is issued when the TLS handshake failed at the server side. The client address and the error message are displayed.

HTTP_CONNECTION_HANDSHAKE_START

start TLS handshake with %1 with timeout %2

This debug message is issued when the server starts the TLS handshake with the remote endpoint. The first argument specifies the address of the remote endpoint. The second argument specifies request timeout in seconds.

HTTP_CONNECTION_SHUTDOWN

shutting down HTTP connection from %1

This debug message is issued when one of the HTTP connections is shut down. The connection can be stopped as a result of an error or after the successful message exchange with a client.

HTTP_CONNECTION_SHUTDOWN_FAILED

shutting down HTTP connection failed

This error message is issued when an error occurred during shutting down a HTTP connection with a client.

HTTP_CONNECTION_STOP

stopping HTTP connection from %1

This debug message is issued when one of the HTTP connections is stopped. The connection can be stopped as a result of an error or after the successful message exchange with a client.

HTTP_CONNECTION_STOP_FAILED

stopping HTTP connection failed

This error message is issued when an error occurred during closing a HTTP connection with a client.

HTTP_DATA_RECEIVED

received %1 bytes from %2

This debug message is issued when the server receives a chunk of data from the remote endpoint. This may include the whole request or only a part of the request. The first argument specifies the amount of received data. The second argument specifies an address of the remote endpoint which produced the data.

HTTP_IDLE_CONNECTION_TIMEOUT_OCCURRED

closing persistent connection with %1 as a result of a timeout

This debug message is issued when the persistent HTTP connection is being closed as a result of being idle.

HTTP_PREMATURE_CONNECTION_TIMEOUT_OCCURRED

premature connection timeout occurred: in transaction ? %1, transid: %2, current_transid: %3

This warning message is issued when unexpected timeout occurred during the transaction. This is proven to occur when the system clock is moved manually or as a result of synchronization with a time server. Any ongoing transactions will be interrupted. New transactions should be conducted normally.

HTTP_REQUEST_RECEIVE_START

start receiving request from %1 with timeout %2

This debug message is issued when the server starts receiving new request over the established connection. The first argument specifies the address of the remote endpoint. The second argument specifies request timeout in seconds.

HTTP_SERVER_RESPONSE_RECEIVED

received HTTP response from %1

This debug message is issued when the client finished receiving an HTTP response from the server. The URL of the server is specified as an argument.

HTTP_SERVER_RESPONSE_RECEIVED_DETAILS

detailed information about well-formed response received from %1:n%2

This debug message is issued when the HTTP client receives a well-formed response from the server. It includes detailed information about the received response. The first argument specifies a URL of the server which sent the response. The second argument provides the response in the textual format. The response is truncated by the logger if it is too large to be printed.

HTTP_SERVER_RESPONSE_SEND

sending HTTP response %1 to %2

This debug message is issued when the server is starting to send a HTTP response to a remote endpoint. The first argument holds basic information about the response (HTTP version number and status code). The second argument specifies an address of the remote endpoint.

LEASE

LEASE_CMDS_ADD4

lease4-add command successful (parameters: %1)

The lease4-add command has been successful. Parameters of the host added are logged.

LEASE_CMDS_ADD4_FAILED

lease4-add command failed (parameters: %1, reason: %2)

The lease4-add command has failed. Both the reason as well as the parameters passed are logged.

LEASE_CMDS_ADD6

lease6-add command successful (parameters: %1)

The lease6-add command has been successful. Parameters of the host added are logged.

LEASE_CMDS_ADD6_FAILED

Lease6-add command failed (parameters: %1, reason: %2)

The lease6-add command has failed. Both the reason as well as the parameters passed are logged.

LEASE_CMDS_DEINIT_FAILED

unloading Lease Commands hooks library failed: %1

This error message indicates an error during unloading the Lease Commands hooks library. The details of the error are provided as argument of the log message.

LEASE_CMDS_DEINIT_OK

unloading Lease Commands hooks library successful

This info message indicates that the Lease Commands hooks library has been removed successfully.

LEASE_CMDS_DEL4

lease4-del command successful (parameters: %1)

The attempt to delete an IPv4 lease (lease4-del command) has been successful. Parameters of the host removed are logged.

LEASE_CMDS_DEL4_FAILED

lease4-del command failed (parameters: %1, reason: %2)

The attempt to delete an IPv4 lease (lease4-del command) has failed. Both the reason as well as the parameters passed are logged.

LEASE_CMDS_DEL6

lease4-del command successful (parameters: %1)

The attempt to delete an IPv4 lease (lease4-del command) has been successful. Parameters of the host removed are logged.

LEASE_CMDS_DEL6_FAILED

lease6-del command failed (parameters: %1, reason: %2)

The attempt to delete an IPv6 lease (lease4-del command) has failed. Both the reason as well as the parameters passed are logged.

LEASE_CMDS_INIT_FAILED

loading Lease Commands hooks library failed: %1

This error message indicates an error during loading the Lease Commands hooks library. The details of the error are provided as argument of the log message.

LEASE_CMDS_INIT_OK

loading Lease Commands hooks library successful

This info message indicates that the Lease Commands hooks library has been loaded successfully. Enjoy!

LEASE_CMDS_RESEND_DDNS4

lease4-resend-ddns command successful: %1

A request to update DNS for the requested IPv4 lease has been successfully queued for transmission to kea-dhcp-ddns.

LEASE_CMDS_RESEND_DDNS4_FAILED

lease4-resend-ddns command failed: %1

A request to update DNS for the requested IPv4 lease has failed. The reason for the failure is logged.

LEASE_CMDS_RESEND_DDNS6

lease6-resend-ddns command successful: %1

A request to update DNS for the requested IPv6 lease has been successfully queued for transmission to kea-dhcp-ddns.

LFC

LFC_FAIL_PID_CREATE

: %1

This message is issued if LFC detected a failure when trying to create the PID file. It includes a more specific error string.

LFC_FAIL_PID_DEL

: %1

This message is issued if LFC detected a failure when trying to delete the PID file. It includes a more specific error string.

LFC_FAIL_PROCESS

: %1

This message is issued if LFC detected a failure when trying to process the files. It includes a more specific error string.

LFC_FAIL_ROTATE

: %1

This message is issued if LFC detected a failure when trying to rotate the files. It includes a more specific error string.

LFC_PROCESSING

Previous file: %1, copy file: %2

This message is issued just before LFC starts processing the lease files.

LFC_READ_STATS

Leases: %1, attempts: %2, errors: %3.

This message prints out the number of leases that were read, the number of attempts to read leases and the number of errors encountered while reading.

LFC_ROTATING

LFC rotating files

This message is issued just before LFC starts rotating the lease files - removing the old and replacing them with the new.

LFC_RUNNING

LFC instance already running

This message is issued if LFC detects that a previous copy of LFC may still be running via the PID check.

LFC_START

Starting lease file cleanup

This message is issued as the LFC process starts.

LFC_TERMINATE

LFC finished processing

This message is issued when the LFC process completes. It does not indicate that the process was successful only that it has finished.

LOGIMPL

LOGIMPL_ABOVE_MAX_DEBUG

debug level of %1 is too high and will be set to the maximum of %2

A message from the interface to the underlying logger implementation reporting that the debug level (as set by an internally-created string DEBUGn, where n is an integer, e.g. DEBUG22) is above the maximum allowed value and has been reduced to that value. The appearance of this message may indicate a programming error - please submit a bug report.

LOGIMPL_BAD_DEBUG_STRING

debug string ‘%1’ has invalid format

A message from the interface to the underlying logger implementation reporting that an internally-created string used to set the debug level is not of the correct format (it should be of the form DEBUGn, where n is an integer, e.g. DEBUG22). The appearance of this message indicates a programming error - please submit a bug report.

LOG

LOG_BAD_DESTINATION

unrecognized log destination: %1

A logger destination value was given that was not recognized. The destination should be one of “console”, “file”, or “syslog”.

LOG_BAD_SEVERITY

unrecognized log severity: %1

A logger severity value was given that was not recognized. The severity should be one of “DEBUG”, “INFO”, “WARN”, “ERROR”, “FATAL” or “NONE”.

LOG_BAD_STREAM

bad log console output stream: %1

Logging has been configured so that output is written to the terminal (console) but the stream on which it is to be written is not recognized. Allowed values are “stdout” and “stderr”.

LOG_DUPLICATE_MESSAGE_ID

duplicate message ID (%1) in compiled code

During start-up, Kea detected that the given message identification had been defined multiple times in the Kea code. This indicates a programming error; please submit a bug report.

LOG_DUPLICATE_NAMESPACE

line %1: duplicate $NAMESPACE directive found

When reading a message file, more than one $NAMESPACE directive was found. (This directive is used to set a C++ namespace when generating header files during software development.) Such a condition is regarded as an error and the read will be abandoned.

LOG_INPUT_OPEN_FAIL

unable to open message file %1 for input: %2

The program was not able to open the specified input message file for the reason given.

LOG_INVALID_MESSAGE_ID

line %1: invalid message identification ‘%2’

An invalid message identification (ID) has been found during the read of a message file. Message IDs should comprise only alphanumeric characters and the underscore, and should not start with a digit.

LOG_NAMESPACE_EXTRA_ARGS

line %1: $NAMESPACE directive has too many arguments

The $NAMESPACE directive in a message file takes a single argument, a namespace in which all the generated symbol names are placed. This error is generated when the compiler finds a $NAMESPACE directive with more than one argument.

LOG_NAMESPACE_INVALID_ARG

line %1: $NAMESPACE directive has an invalid argument (‘%2’)

The $NAMESPACE argument in a message file should be a valid C++ namespace. This message is output if the simple check on the syntax of the string carried out by the reader fails.

LOG_NAMESPACE_NO_ARGS

line %1: no arguments were given to the $NAMESPACE directive

The $NAMESPACE directive in a message file takes a single argument, a C++ namespace in which all the generated symbol names are placed. This error is generated when the compiler finds a $NAMESPACE directive with no arguments.

LOG_NO_MESSAGE_ID

line %1: message definition line found without a message ID

Within a message file, message are defined by lines starting with a “%”. The rest of the line should comprise the message ID and text describing the message. This error indicates the message compiler found a line in the message file comprising just the “%” and nothing else.

LOG_NO_MESSAGE_TEXT

line %1: line found containing a message ID (‘%2’) and no text

Within a message file, message are defined by lines starting with a “%”. The rest of the line should comprise the message ID and text describing the message. This error indicates the message compiler found a line in the message file comprising just the “%” and message identification, but no text.

LOG_NO_SUCH_MESSAGE

could not replace message text for ‘%1’: no such message

During start-up a local message file was read. A line with the listed message identification was found in the file, but the identification is not one contained in the compiled-in message dictionary. This message may appear a number of times in the file, once for every such unknown message identification. There are several reasons why this message may appear: - The message ID has been misspelled in the local message file. - The program outputting the message may not use that particular message (e.g. it originates in a module not used by the program). - The local file was written for an earlier version of the Kea software and the later version no longer generates that message. Whatever the reason, there is no impact on the operation of Kea.

LOG_OPEN_OUTPUT_FAIL

unable to open %1 for output: %2

Originating within the logging code, the program was not able to open the specified output file for the reason given.

LOG_PREFIX_EXTRA_ARGS

line %1: $PREFIX directive has too many arguments

Within a message file, the $PREFIX directive takes a single argument, a prefix to be added to the symbol names when a C++ file is created. This error is generated when the compiler finds a $PREFIX directive with more than one argument. Note: the $PREFIX directive is deprecated and will be removed in a future version of Kea.

LOG_PREFIX_INVALID_ARG

line %1: $PREFIX directive has an invalid argument (‘%2’)

Within a message file, the $PREFIX directive takes a single argument, a prefix to be added to the symbol names when a C++ file is created. As such, it must adhere to restrictions on C++ symbol names (e.g. may only contain alphanumeric characters or underscores, and may nor start with a digit). A $PREFIX directive was found with an argument (given in the message) that violates those restrictions. Note: the $PREFIX directive is deprecated and will be removed in a future version of Kea.

LOG_READING_LOCAL_FILE

reading local message file %1

This is an informational message output by Kea when it starts to read a local message file. (A local message file may replace the text of one or more messages; the ID of the message will not be changed though.)

LOG_READ_ERROR

error reading from message file %1: %2

The specified error was encountered reading from the named message file.

LOG_UNRECOGNIZED_DIRECTIVE

line %1: unrecognized directive ‘%2’

Within a message file, a line starting with a dollar symbol was found (indicating the presence of a directive) but the first word on the line (shown in the message) was not recognized.

MYSQL

MYSQL_CB_CREATE_UPDATE_BY_POOL_OPTION4

create or update option pool start: %1 pool end: %2

Debug message issued when triggered an action to create or update option by pool

MYSQL_CB_CREATE_UPDATE_BY_POOL_OPTION6

create or update option pool start: %1 pool end: %2

Debug message issued when triggered an action to create or update option by pool

MYSQL_CB_CREATE_UPDATE_BY_PREFIX_OPTION6

create or update option prefix: %1 prefix len: %2

Debug message issued when triggered an action to create or update option by prefix

MYSQL_CB_CREATE_UPDATE_BY_SUBNET_ID_OPTION4

create or update option by subnet id: %1

Debug message issued when triggered an action to create or update option by subnet id

MYSQL_CB_CREATE_UPDATE_BY_SUBNET_ID_OPTION6

create or update option by subnet id: %1

Debug message issued when triggered an action to create or update option by subnet id

MYSQL_CB_CREATE_UPDATE_CLIENT_CLASS4

create or update client class: %1

Debug message issued when triggered an action to create or update client class

MYSQL_CB_CREATE_UPDATE_CLIENT_CLASS6

create or update client class: %1

Debug message issued when triggered an action to create or update client class

MYSQL_CB_CREATE_UPDATE_GLOBAL_PARAMETER4

create or update global parameter: %1

Debug message issued when triggered an action to create or update global parameter

MYSQL_CB_CREATE_UPDATE_GLOBAL_PARAMETER6

create or update global parameter: %1

Debug message issued when triggered an action to create or update global parameter

MYSQL_CB_CREATE_UPDATE_OPTION4

create or update option

Debug message issued when triggered an action to create or update option

MYSQL_CB_CREATE_UPDATE_OPTION6

create or update option

Debug message issued when triggered an action to create or update option

MYSQL_CB_CREATE_UPDATE_OPTION_DEF4

create or update option definition: %1 code: %2

Debug message issued when triggered an action to create or update option definition

MYSQL_CB_CREATE_UPDATE_OPTION_DEF6

create or update option definition: %1 code: %2

Debug message issued when triggered an action to create or update option definition

MYSQL_CB_CREATE_UPDATE_SERVER4

create or update server: %1

Debug message issued when triggered an action to create or update a DHCPv4 server information.

MYSQL_CB_CREATE_UPDATE_SERVER6

create or update server: %1

Debug message issued when triggered an action to create or update a DHCPv6 server information.

MYSQL_CB_CREATE_UPDATE_SHARED_NETWORK4

create or update shared network: %1

Debug message issued when triggered an action to create or update shared network

MYSQL_CB_CREATE_UPDATE_SHARED_NETWORK6

create or update shared network: %1

Debug message issued when triggered an action to create or update shared network

MYSQL_CB_CREATE_UPDATE_SHARED_NETWORK_OPTION4

create or update shared network: %1 option

Debug message issued when triggered an action to create or update shared network option

MYSQL_CB_CREATE_UPDATE_SHARED_NETWORK_OPTION6

create or update shared network: %1 option

Debug message issued when triggered an action to create or update shared network option

MYSQL_CB_CREATE_UPDATE_SUBNET4

create or update subnet: %1

Debug message issued when triggered an action to create or update subnet

MYSQL_CB_CREATE_UPDATE_SUBNET6

create or update subnet: %1

Debug message issued when triggered an action to create or update subnet

MYSQL_CB_DEINIT_OK

unloading MYSQL CB hooks library successful

This informational message indicates that the MySQL Configuration Backend hooks library has been unloaded successfully.

MYSQL_CB_DELETE_ALL_CLIENT_CLASSES4

delete all client classes

Debug message issued when triggered an action to delete all client classes

MYSQL_CB_DELETE_ALL_CLIENT_CLASSES4_RESULT

deleted: %1 entries

Debug message indicating the result of an action to delete all client classes

MYSQL_CB_DELETE_ALL_CLIENT_CLASSES6

delete all client classes

Debug message issued when triggered an action to delete all client classes

MYSQL_CB_DELETE_ALL_CLIENT_CLASSES6_RESULT

deleted: %1 entries

Debug message indicating the result of an action to delete all client classes

MYSQL_CB_DELETE_ALL_GLOBAL_PARAMETERS4

delete all global parameters

Debug message issued when triggered an action to delete all global parameters

MYSQL_CB_DELETE_ALL_GLOBAL_PARAMETERS4_RESULT

deleted: %1 entries

Debug message indicating the result of an action to delete all global parameters

MYSQL_CB_DELETE_ALL_GLOBAL_PARAMETERS6

delete all global parameters

Debug message issued when triggered an action to delete all global parameters

MYSQL_CB_DELETE_ALL_GLOBAL_PARAMETERS6_RESULT

deleted: %1 entries

Debug message indicating the result of an action to delete all global parameters

MYSQL_CB_DELETE_ALL_OPTION_DEFS4

delete all option definitions

Debug message issued when triggered an action to delete all option definitions

MYSQL_CB_DELETE_ALL_OPTION_DEFS4_RESULT

deleted: %1 entries

Debug message indicating the result of an action to delete all option definitions

MYSQL_CB_DELETE_ALL_OPTION_DEFS6

delete all option definitions

Debug message issued when triggered an action to delete all option definitions

MYSQL_CB_DELETE_ALL_OPTION_DEFS6_RESULT

deleted: %1 entries

Debug message indicating the result of an action to delete all option definitions

MYSQL_CB_DELETE_ALL_SERVERS4

delete all DHCPv4 servers

Debug message issued when triggered an action to delete all servers.

MYSQL_CB_DELETE_ALL_SERVERS4_RESULT

deleted: %1 entries

Debug message indicating the result of an action to delete all servers.

MYSQL_CB_DELETE_ALL_SERVERS6

delete all DHCPv6 servers

Debug message issued when triggered an action to delete all servers.

MYSQL_CB_DELETE_ALL_SERVERS6_RESULT

deleted: %1 entries

Debug message indicating the result of an action to delete all servers.

MYSQL_CB_DELETE_ALL_SHARED_NETWORKS4

delete all shared networks

Debug message issued when triggered an action to delete all shared networks

MYSQL_CB_DELETE_ALL_SHARED_NETWORKS4_RESULT

deleted: %1 entries

Debug message indicating the result of an action to delete all shared networks

MYSQL_CB_DELETE_ALL_SHARED_NETWORKS6

delete all shared networks

Debug message issued when triggered an action to delete all shared networks

MYSQL_CB_DELETE_ALL_SHARED_NETWORKS6_RESULT

deleted: %1 entries

Debug message indicating the result of an action to delete all shared networks

MYSQL_CB_DELETE_ALL_SUBNETS4

delete all subnets

Debug message issued when triggered an action to delete all subnets

MYSQL_CB_DELETE_ALL_SUBNETS4_RESULT

deleted: %1 entries

Debug message indicating the result of an action to delete all subnets

MYSQL_CB_DELETE_ALL_SUBNETS6

delete all subnets

Debug message issued when triggered an action to delete all subnets

MYSQL_CB_DELETE_ALL_SUBNETS6_RESULT

deleted: %1 entries

Debug message indicating the result of an action to delete all subnets

MYSQL_CB_DELETE_BY_POOL_OPTION4

delete pool start: %1 pool end: %2 option code: %3 space: %4

Debug message issued when triggered an action to delete option by pool

MYSQL_CB_DELETE_BY_POOL_OPTION4_RESULT

deleted: %1 entries

Debug message indicating the result of an action to delete option by pool

MYSQL_CB_DELETE_BY_POOL_OPTION6

delete pool start: %1 pool end: %2 option code: %3 space: %4

Debug message issued when triggered an action to delete option by pool

MYSQL_CB_DELETE_BY_POOL_OPTION6_RESULT

deleted: %1 entries

Debug message indicating the result of an action to delete option by pool

MYSQL_CB_DELETE_BY_POOL_PREFIX_OPTION6

delete prefix: %1 prefix len: %2 option code: %3 space: %4

Debug message issued when triggered an action to delete option by prefix

MYSQL_CB_DELETE_BY_POOL_PREFIX_OPTION6_RESULT

deleted: %1 entries

Debug message indicating the result of an action to delete option by prefix

MYSQL_CB_DELETE_BY_PREFIX_SUBNET4

delete subnet by prefix: %1

Debug message issued when triggered an action to delete subnet by prefix

MYSQL_CB_DELETE_BY_PREFIX_SUBNET4_RESULT

deleted: %1 entries

Debug message indicating the result of an action to delete subnet by prefix

MYSQL_CB_DELETE_BY_PREFIX_SUBNET6

delete subnet by prefix: %1

Debug message issued when triggered an action to delete subnet by prefix

MYSQL_CB_DELETE_BY_PREFIX_SUBNET6_RESULT

deleted: %1 entries

Debug message indicating the result of an action to delete subnet by prefix

MYSQL_CB_DELETE_BY_SUBNET_ID_OPTION4

delete by subnet id: %1 option code: %2 space: %3

Debug message issued when triggered an action to delete option by subnet id

MYSQL_CB_DELETE_BY_SUBNET_ID_OPTION4_RESULT

deleted: %1 entries

Debug message indicating the result of an action to delete option by subnet id

MYSQL_CB_DELETE_BY_SUBNET_ID_OPTION6

delete by subnet id: %1 option code: %2 space: %3

Debug message issued when triggered an action to delete option by subnet id

MYSQL_CB_DELETE_BY_SUBNET_ID_OPTION6_RESULT

deleted: %1 entries

Debug message indicating the result of an action to delete option by subnet id

MYSQL_CB_DELETE_BY_SUBNET_ID_SUBNET4

delete subnet by subnet id: %1

Debug message issued when triggered an action to delete subnet by subnet id

MYSQL_CB_DELETE_BY_SUBNET_ID_SUBNET4_RESULT

deleted: %1 entries

Debug message indicating the result of an action to delete subnet by subnet id

MYSQL_CB_DELETE_BY_SUBNET_ID_SUBNET6

delete subnet by subnet id: %1

Debug message issued when triggered an action to delete subnet by subnet id

MYSQL_CB_DELETE_BY_SUBNET_ID_SUBNET6_RESULT

deleted: %1 entries

Debug message indicating the result of an action to delete subnet by subnet id

MYSQL_CB_DELETE_CLIENT_CLASS4

delete client class: %1

Debug message issued when triggered an action to delete client class

MYSQL_CB_DELETE_CLIENT_CLASS4_RESULT

deleted: %1 entries

Debug message indicating the result of an action to delete client class

MYSQL_CB_DELETE_CLIENT_CLASS6

delete client class: %1

Debug message issued when triggered an action to delete client class

MYSQL_CB_DELETE_CLIENT_CLASS6_RESULT

deleted: %1 entries

Debug message indicating the result of an action to delete client class

MYSQL_CB_DELETE_GLOBAL_PARAMETER4

delete global parameter: %1

Debug message issued when triggered an action to delete global parameter

MYSQL_CB_DELETE_GLOBAL_PARAMETER4_RESULT

deleted: %1 entries

Debug message indicating the result of an action to delete global parameter

MYSQL_CB_DELETE_GLOBAL_PARAMETER6

delete global parameter: %1

Debug message issued when triggered an action to delete global parameter

MYSQL_CB_DELETE_GLOBAL_PARAMETER6_RESULT

deleted: %1 entries

Debug message indicating the result of an action to delete global parameter

MYSQL_CB_DELETE_OPTION4

delete option code: %1 space: %2

Debug message issued when triggered an action to delete option

MYSQL_CB_DELETE_OPTION4_RESULT

deleted: %1 entries

Debug message indicating the result of an action to delete option

MYSQL_CB_DELETE_OPTION6

delete option code: %1 space: %2

Debug message issued when triggered an action to delete option

MYSQL_CB_DELETE_OPTION6_RESULT

deleted: %1 entries

Debug message indicating the result of an action to delete option

MYSQL_CB_DELETE_OPTION_DEF4

delete option definition code: %1 space: %2

Debug message issued when triggered an action to delete option definition

MYSQL_CB_DELETE_OPTION_DEF4_RESULT

deleted: %1 entries

Debug message indicating the result of an action to delete option definition

MYSQL_CB_DELETE_OPTION_DEF6

delete option definition code: %1 space: %2

Debug message issued when triggered an action to delete option definition

MYSQL_CB_DELETE_OPTION_DEF6_RESULT

deleted: %1 entries

Debug message indicating the result of an action to delete option definition

MYSQL_CB_DELETE_SERVER4

delete DHCPv4 server: %1

Debug message issued when triggered an action to delete a server.

MYSQL_CB_DELETE_SERVER4_RESULT

deleted: %1 entries

Debug message indicating the result of an action to delete a server.

MYSQL_CB_DELETE_SERVER6

delete DHCPv6 server: %1

Debug message issued when triggered an action to delete a server.

MYSQL_CB_DELETE_SERVER6_RESULT

deleted: %1 entries

Debug message indicating the result of an action to delete a server.

MYSQL_CB_DELETE_SHARED_NETWORK4

delete shared network: %1

Debug message issued when triggered an action to delete shared network

MYSQL_CB_DELETE_SHARED_NETWORK4_RESULT

deleted: %1 entries

Debug message indicating the result of an action to delete shared network

MYSQL_CB_DELETE_SHARED_NETWORK6

delete shared network: %1

Debug message issued when triggered an action to delete shared network

MYSQL_CB_DELETE_SHARED_NETWORK6_RESULT

deleted: %1 entries

Debug message indicating the result of an action to delete shared network

MYSQL_CB_DELETE_SHARED_NETWORK_OPTION4

delete shared network: %1 option code: %2 space: %3

Debug message issued when triggered an action to delete shared network option

MYSQL_CB_DELETE_SHARED_NETWORK_OPTION4_RESULT

deleted: %1 entries

Debug message indicating the result of an action to delete shared network option

MYSQL_CB_DELETE_SHARED_NETWORK_OPTION6

delete shared network: %1 option code: %2 space: %3

Debug message issued when triggered an action to delete shared network option

MYSQL_CB_DELETE_SHARED_NETWORK_OPTION6_RESULT

deleted: %1 entries

Debug message indicating the result of an action to delete shared network option

MYSQL_CB_DELETE_SHARED_NETWORK_SUBNETS4

delete shared network: %1 subnets

Debug message issued when triggered an action to delete shared network subnets

MYSQL_CB_DELETE_SHARED_NETWORK_SUBNETS4_RESULT

deleted: %1 entries

Debug message indicating the result of an action to delete shared network subnets

MYSQL_CB_DELETE_SHARED_NETWORK_SUBNETS6

delete shared network: %1 subnets

Debug message issued when triggered an action to delete shared network subnets

MYSQL_CB_DELETE_SHARED_NETWORK_SUBNETS6_RESULT

deleted: %1 entries

Debug message indicating the result of an action to delete shared network subnets

MYSQL_CB_GET_ALL_CLIENT_CLASSES4

retrieving all client classes

Debug message issued when triggered an action to retrieve all client classes

MYSQL_CB_GET_ALL_CLIENT_CLASSES4_RESULT

retrieving: %1 elements

Debug message indicating the result of an action to retrieve all client classes

MYSQL_CB_GET_ALL_CLIENT_CLASSES6

retrieving all client classes

Debug message issued when triggered an action to retrieve all client classes

MYSQL_CB_GET_ALL_CLIENT_CLASSES6_RESULT

retrieving: %1 elements

Debug message indicating the result of an action to retrieve all client classes

MYSQL_CB_GET_ALL_GLOBAL_PARAMETERS4

retrieving all global parameters

Debug message issued when triggered an action to retrieve all global parameters

MYSQL_CB_GET_ALL_GLOBAL_PARAMETERS4_RESULT

retrieving: %1 elements

Debug message indicating the result of an action to retrieve all global parameters

MYSQL_CB_GET_ALL_GLOBAL_PARAMETERS6

retrieving all global parameters

Debug message issued when triggered an action to retrieve all global parameters

MYSQL_CB_GET_ALL_GLOBAL_PARAMETERS6_RESULT

retrieving: %1 elements

Debug message indicating the result of an action to retrieve all global parameters

MYSQL_CB_GET_ALL_OPTIONS4

retrieving all options

Debug message issued when triggered an action to retrieve all options

MYSQL_CB_GET_ALL_OPTIONS4_RESULT

retrieving: %1 elements

Debug message indicating the result of an action to retrieve all options

MYSQL_CB_GET_ALL_OPTIONS6

retrieving all options

Debug message issued when triggered an action to retrieve all options

MYSQL_CB_GET_ALL_OPTIONS6_RESULT

retrieving: %1 elements

Debug message indicating the result of an action to retrieve all options

MYSQL_CB_GET_ALL_OPTION_DEFS4

retrieving all option definitions

Debug message issued when triggered an action to retrieve all option definitions

MYSQL_CB_GET_ALL_OPTION_DEFS4_RESULT

retrieving: %1 elements

Debug message indicating the result of an action to retrieve all option definitions

MYSQL_CB_GET_ALL_OPTION_DEFS6

retrieving all option definitions

Debug message issued when triggered an action to retrieve all option definitions

MYSQL_CB_GET_ALL_OPTION_DEFS6_RESULT

retrieving: %1 elements

Debug message indicating the result of an action to retrieve all option definitions

MYSQL_CB_GET_ALL_SERVERS4

retrieving all servers

Debug message issued when triggered an action to retrieve all DHCPv4 servers

MYSQL_CB_GET_ALL_SERVERS4_RESULT

retrieving: %1 elements

Debug message indicating the result of an action to retrieve all DHCPv4 servers

MYSQL_CB_GET_ALL_SERVERS6

retrieving all DHCPv6 servers

Debug message issued when triggered an action to retrieve all DHCPv6 servers

MYSQL_CB_GET_ALL_SERVERS6_RESULT

retrieving: %1 elements

Debug message indicating the result of an action to retrieve all DHCPv6 servers

MYSQL_CB_GET_ALL_SHARED_NETWORKS4

retrieving all shared networks

Debug message issued when triggered an action to retrieve all shared networks

MYSQL_CB_GET_ALL_SHARED_NETWORKS4_RESULT

retrieving: %1 elements

Debug message indicating the result of an action to retrieve all shared networks

MYSQL_CB_GET_ALL_SHARED_NETWORKS6

retrieving all shared networks

Debug message issued when triggered an action to retrieve all shared networks

MYSQL_CB_GET_ALL_SHARED_NETWORKS6_RESULT

retrieving: %1 elements

Debug message indicating the result of an action to retrieve all shared networks

MYSQL_CB_GET_ALL_SUBNETS4

retrieving all subnets

Debug message issued when triggered an action to retrieve all subnets

MYSQL_CB_GET_ALL_SUBNETS4_RESULT

retrieving: %1 elements

Debug message indicating the result of an action to retrieve all subnets

MYSQL_CB_GET_ALL_SUBNETS6

retrieving all subnets

Debug message issued when triggered an action to retrieve all subnets

MYSQL_CB_GET_ALL_SUBNETS6_RESULT

retrieving: %1 elements

Debug message indicating the result of an action to retrieve all subnets

MYSQL_CB_GET_CLIENT_CLASS4

retrieving client class: %1

Debug message issued when triggered an action to retrieve a client class

MYSQL_CB_GET_CLIENT_CLASS6

retrieving client class: %1

Debug message issued when triggered an action to retrieve a client class

MYSQL_CB_GET_GLOBAL_PARAMETER4

retrieving global parameter: %1

Debug message issued when triggered an action to retrieve global parameter

MYSQL_CB_GET_GLOBAL_PARAMETER6

retrieving global parameter: %1

Debug message issued when triggered an action to retrieve global parameter

MYSQL_CB_GET_HOST4

get host

Debug message issued when triggered an action to retrieve host

MYSQL_CB_GET_HOST6

get host

Debug message issued when triggered an action to retrieve host

MYSQL_CB_GET_MODIFIED_CLIENT_CLASSES4

retrieving modified client classes from: %1

Debug message issued when triggered an action to retrieve modified client classes from specified time

MYSQL_CB_GET_MODIFIED_CLIENT_CLASSES4_RESULT

retrieving: %1 elements

Debug message indicating the result of an action to retrieve modified client classes from specified time

MYSQL_CB_GET_MODIFIED_CLIENT_CLASSES6

retrieving modified client classes from: %1

Debug message issued when triggered an action to retrieve modified client classes from specified time

MYSQL_CB_GET_MODIFIED_CLIENT_CLASSES6_RESULT

retrieving: %1 elements

Debug message indicating the result of an action to retrieve modified client classes from specified time

MYSQL_CB_GET_MODIFIED_GLOBAL_PARAMETERS4

retrieving modified global parameters from: %1

Debug message issued when triggered an action to retrieve modified global parameters from specified time

MYSQL_CB_GET_MODIFIED_GLOBAL_PARAMETERS4_RESULT

retrieving: %1 elements

Debug message indicating the result of an action to retrieve modified global parameters from specified time

MYSQL_CB_GET_MODIFIED_GLOBAL_PARAMETERS6

retrieving modified global parameters from: %1

Debug message issued when triggered an action to retrieve modified global parameters from specified time

MYSQL_CB_GET_MODIFIED_GLOBAL_PARAMETERS6_RESULT

retrieving: %1 elements

Debug message indicating the result of an action to retrieve modified global parameters from specified time

MYSQL_CB_GET_MODIFIED_OPTIONS4

retrieving modified options from: %1

Debug message issued when triggered an action to retrieve modified options from specified time

MYSQL_CB_GET_MODIFIED_OPTIONS4_RESULT

retrieving: %1 elements

Debug message indicating the result of an action to retrieve modified options from specified time

MYSQL_CB_GET_MODIFIED_OPTIONS6

retrieving modified options from: %1

Debug message issued when triggered an action to retrieve modified options from specified time

MYSQL_CB_GET_MODIFIED_OPTIONS6_RESULT

retrieving: %1 elements

Debug message indicating the result of an action to retrieve modified options from specified time

MYSQL_CB_GET_MODIFIED_OPTION_DEFS4

retrieving modified option definitions from: %1

Debug message issued when triggered an action to retrieve modified option definitions from specified time

MYSQL_CB_GET_MODIFIED_OPTION_DEFS4_RESULT

retrieving: %1 elements

Debug message indicating the result of an action to retrieve modified option definitions from specified time

MYSQL_CB_GET_MODIFIED_OPTION_DEFS6

retrieving modified option definitions from: %1

Debug message issued when triggered an action to retrieve modified option definitions from specified time

MYSQL_CB_GET_MODIFIED_OPTION_DEFS6_RESULT

retrieving: %1 elements

Debug message indicating the result of an action to retrieve modified option definitions from specified time

MYSQL_CB_GET_MODIFIED_SHARED_NETWORKS4

retrieving modified shared networks from: %1

Debug message issued when triggered an action to retrieve modified shared networks from specified time

MYSQL_CB_GET_MODIFIED_SHARED_NETWORKS4_RESULT

retrieving: %1 elements

Debug message indicating the result of an action to retrieve modified shared networks from specified time

MYSQL_CB_GET_MODIFIED_SHARED_NETWORKS6

retrieving modified shared networks from: %1

Debug message issued when triggered an action to retrieve modified shared networks from specified time

MYSQL_CB_GET_MODIFIED_SHARED_NETWORKS6_RESULT

retrieving: %1 elements

Debug message indicating the result of an action to retrieve modified shared networks from specified time

MYSQL_CB_GET_MODIFIED_SUBNETS4

retrieving modified subnets from: %1

Debug message issued when triggered an action to retrieve modified subnets from specified time

MYSQL_CB_GET_MODIFIED_SUBNETS4_RESULT

retrieving: %1 elements

Debug message indicating the result of an action to retrieve modified subnets from specified time

MYSQL_CB_GET_MODIFIED_SUBNETS6

retrieving modified subnets from: %1

Debug message issued when triggered an action to retrieve modified subnets from specified time

MYSQL_CB_GET_MODIFIED_SUBNETS6_RESULT

retrieving: %1 elements

Debug message indicating the result of an action to retrieve modified subnets from specified time

MYSQL_CB_GET_OPTION4

retrieving option code: %1 space: %2

Debug message issued when triggered an action to retrieve option

MYSQL_CB_GET_OPTION6

retrieving option code: %1 space: %2

Debug message issued when triggered an action to retrieve option

MYSQL_CB_GET_OPTION_DEF4

retrieving option definition code: %1 space: %2

Debug message issued when triggered an action to retrieve option definition

MYSQL_CB_GET_OPTION_DEF6

retrieving option definition code: %1 space: %2

Debug message issued when triggered an action to retrieve option definition

MYSQL_CB_GET_PORT4

get port

Debug message issued when triggered an action to retrieve port

MYSQL_CB_GET_PORT6

get port

Debug message issued when triggered an action to retrieve port

MYSQL_CB_GET_RECENT_AUDIT_ENTRIES4

retrieving audit entries from: %1 %2

Debug message issued when triggered an action to retrieve audit entries from specified time and id.

MYSQL_CB_GET_RECENT_AUDIT_ENTRIES4_RESULT

retrieving: %1 elements

Debug message indicating the result of an action to retrieve audit entries from specified time

MYSQL_CB_GET_RECENT_AUDIT_ENTRIES6

retrieving audit entries from: %1 %2

Debug message issued when triggered an action to retrieve audit entries from specified time and id

MYSQL_CB_GET_RECENT_AUDIT_ENTRIES6_RESULT

retrieving: %1 elements

Debug message indicating the result of an action to retrieve audit entries from specified time

MYSQL_CB_GET_SERVER4

retrieving DHCPv4 server: %1

Debug message issued when triggered an action to retrieve a DHCPv4 server information.

MYSQL_CB_GET_SERVER6

retrieving DHCPv6 server: %1

Debug message issued when triggered an action to retrieve a DHCPv6 server information.

MYSQL_CB_GET_SHARED_NETWORK4

retrieving shared network: %1

Debug message issued when triggered an action to retrieve shared network

MYSQL_CB_GET_SHARED_NETWORK6

retrieving shared network: %1

Debug message issued when triggered an action to retrieve shared network

MYSQL_CB_GET_SHARED_NETWORK_SUBNETS4

retrieving shared network: %1 subnets

Debug message issued when triggered an action to retrieve shared network subnets

MYSQL_CB_GET_SHARED_NETWORK_SUBNETS4_RESULT

retrieving: %1 elements

Debug message indicating the result of an action to retrieve shared network subnets

MYSQL_CB_GET_SHARED_NETWORK_SUBNETS6

retrieving shared network: %1 subnets

Debug message issued when triggered an action to retrieve shared network subnets

MYSQL_CB_GET_SHARED_NETWORK_SUBNETS6_RESULT

retrieving: %1 elements

Debug message indicating the result of an action to retrieve shared network subnets

MYSQL_CB_GET_SUBNET4_BY_PREFIX

retrieving subnet by prefix: %1

Debug message issued when triggered an action to retrieve subnet by prefix

MYSQL_CB_GET_SUBNET4_BY_SUBNET_ID

retrieving subnet by subnet id: %1

Debug message issued when triggered an action to retrieve subnet by subnet id

MYSQL_CB_GET_SUBNET6_BY_PREFIX

retrieving subnet by prefix: %1

Debug message issued when triggered an action to retrieve subnet by prefix

MYSQL_CB_GET_SUBNET6_BY_SUBNET_ID

retrieving subnet by subnet id: %1

Debug message issued when triggered an action to retrieve subnet by subnet id

MYSQL_CB_GET_TYPE4

get type

Debug message issued when triggered an action to retrieve type

MYSQL_CB_GET_TYPE6

get type

Debug message issued when triggered an action to retrieve type

MYSQL_CB_INIT_OK

loading MYSQL CB hooks library successful

This informational message indicates that the MySQL Configuration Backend hooks library has been loaded successfully.

MYSQL_CB_NO_TLS

TLS was required but is not used

This error message is issued when TLS for the connection was required but TLS is not used.

MYSQL_CB_RECONNECT_ATTEMPT_FAILED4

database reconnect failed: %1

Error message issued when an attempt to reconnect has failed.

MYSQL_CB_RECONNECT_ATTEMPT_FAILED6

database reconnect failed: %1

Error message issued when an attempt to reconnect has failed.

MYSQL_CB_RECONNECT_ATTEMPT_SCHEDULE4

scheduling attempt %1 of %2 in %3 milliseconds

Info message issued when the server is scheduling the next attempt to reconnect to the database. This occurs when the server has lost database connectivity and is attempting to reconnect automatically.

MYSQL_CB_RECONNECT_ATTEMPT_SCHEDULE6

scheduling attempt %1 of %2 in %3 milliseconds

Info message issued when the server is scheduling the next attempt to reconnect to the database. This occurs when the server has lost database connectivity and is attempting to reconnect automatically.

MYSQL_CB_RECONNECT_FAILED4

maximum number of database reconnect attempts: %1, has been exhausted without success

Error message issued when the server failed to reconnect. Loss of connectivity is typically a network or database server issue.

MYSQL_CB_RECONNECT_FAILED6

maximum number of database reconnect attempts: %1, has been exhausted without success

Error message issued when the server failed to reconnect. Loss of connectivity is typically a network or database server issue.

MYSQL_CB_REGISTER_BACKEND_TYPE4

register backend

Debug message issued when triggered an action to register backend

MYSQL_CB_REGISTER_BACKEND_TYPE6

register backend

Debug message issued when triggered an action to register backend

MYSQL_CB_TLS_CIPHER

TLS cipher: %1

A debug message issued when a new MySQL connected is created with TLS. The TLS cipher name is logged.

MYSQL_CB_UNREGISTER_BACKEND_TYPE4

unregister backend

Debug message issued when triggered an action to unregister backend

NETCONF

NETCONF_BOOT_UPDATE_COMPLETED

Boot-update configuration completed for server %1

This informational message is issued when the initial configuration was retrieved from Netconf and successfully applied to Kea server.

NETCONF_CONFIG_CHANGED_DETAIL

YANG configuration changed: %1

This debug message indicates a YANG configuration change. The format is the change operation (created, modified, deleted or moved) followed by xpaths and values of old and new nodes.

NETCONF_CONFIG_CHANGE_EVENT

Received YANG configuration change %1 event

This informational message is issued when Netconf receives a YANG configuration change event. The type of event is printed.

NETCONF_CONFIG_CHECK_FAIL

Netconf configuration check failed: %1

This error message indicates that Netconf had failed configuration check. Details are provided. Additional details may be available in earlier log entries, possibly on lower levels.

NETCONF_CONFIG_FAIL

Netconf configuration failed: %1

This error message indicates that Netconf had failed configuration attempt. Details are provided. Additional details may be available in earlier log entries, possibly on lower levels.

NETCONF_CONFIG_SYNTAX_WARNING

Netconf configuration syntax warning: %1

This warning message indicates that the Netconf configuration had a minor syntax error. The error was displayed and the configuration parsing resumed.

NETCONF_FAILED

application experienced a fatal error: %1

This is a fatal error message issued when the Netconf application got an unrecoverable error from within the event loop.

NETCONF_GET_CONFIG

got configuration from %1 server: %2

This debug message indicates that Netconf got the configuration from a Kea server. The server name and the retrieved configuration are printed.

NETCONF_GET_CONFIG_FAILED

getting configuration from %1 server failed: %2

The error message indicates that Netconf got an error getting the configuration from a Kea server. Make sure that the server is up and running, has appropriate control socket defined and that the controls socket configuration on the server matches that of kea-netconf. The name of the server and the error are printed.

NETCONF_GET_CONFIG_STARTED

getting configuration from %1 server

This informational message indicates that Netconf is trying to get the configuration from a Kea server.

NETCONF_LOG_CHANGE_FAIL

Netconf configuration change logging failed: %1

The warning message indicates that the configuration change logging encountered an unexpected condition. Details of it will be logged.

NETCONF_MODULE_MISSING_ERR

Missing essential module %1 in sysrepo

This fatal error message indicates that a module required by Netconf configuration is not available in the sysrepo repository. The name of the module is printed.

NETCONF_MODULE_MISSING_WARN

Missing module %1 in sysrepo

This warning message indicates that a module used by Kea is not available in the sysrepo repository. The name of the module is printed.

NETCONF_MODULE_REVISION_ERR

Essential module %1 does NOT have the right revision: expected %2, got %3

This fatal error message indicates that a module required by Netconf configuration is not at the right revision in the sysrepo repository. The name, expected and available revisions of the module are printed.

NETCONF_MODULE_REVISION_WARN

Module %1 does NOT have the right revision: expected %2, got %3

This warning message indicates that a module used by Kea is not at the right revision in the sysrepo repository. The name, expected and available revisions of the module are printed.

NETCONF_NOTIFICATION_RECEIVED

Received notification of type %1 for module %1: %2

This informational message logs any YANG notification that has been signaled by the server, sent to kea-netconf which then was forwarded to subscribed clients. To achieve this, kea-netconf subscribes itself as a client to all notifications for the configured module.

NETCONF_RUN_EXIT

application is exiting the event loop

This is a debug message issued when the Netconf application exits its event loop. This is a normal step during kea-netconf shutdown.

NETCONF_SET_CONFIG

set configuration to %1 server: %2

This debug message indicates that Netconf set the configuration to a Kea server. The server name and the applied configuration are printed.

NETCONF_SET_CONFIG_FAILED

setting configuration to %1 server failed: %2

The error message indicates that Netconf got an error setting the configuration to a Kea server. Make sure that the server is up and running, has appropriate control socket defined and that the controls socket configuration on the server matches that of kea-netconf. The name of the server and the error are printed.

NETCONF_SET_CONFIG_STARTED

setting configuration to %1 server

This informational message indicates that Netconf is trying to set the configuration to a Kea server.

NETCONF_STARTED

Netconf (version %1) started

This informational message indicates that Netconf has processed all configuration information and is ready to begin processing. The version is also printed.

NETCONF_SUBSCRIBE_CONFIG

subscribing configuration changes for %1 server with %2 module

This information message indicates that Netconf is trying to subscribe configuration changes for a Kea server. The names of the server and the module are printed.

NETCONF_SUBSCRIBE_CONFIG_FAILED

subscribe configuration changes for %1 server with %2 module failed: %3

The error message indicates that Netconf got an error subscribing configuration changes for a Kea server. The names of the server and the module, and the error are printed.

NETCONF_SUBSCRIBE_NOTIFICATIONS

subscribing to notifications for %1 server with %2 module

This information message indicates that Netconf is trying to subscribe to notifications for a Kea server. The server name and module name are printed.

NETCONF_SUBSCRIBE_NOTIFICATIONS_FAILED

subscribing to notifications for %1 server with %2 module failed: %3

The error message indicates that Netconf got an error subscribing to notifications for a Kea server. The server name, module name and the error are printed.

NETCONF_UPDATE_CONFIG

updating configuration with %1 server: %2

This debug message indicates that Netconf update the configuration of a Kea server. The server name and the updated configuration are printed.

NETCONF_UPDATE_CONFIG_COMPLETED

completed updating configuration for %1 server

This informational message indicates that Netconf updated with success the configuration of a Kea server.

NETCONF_UPDATE_CONFIG_FAILED

updating configuration with %1 server: %2

The error message indicates that Netconf got an error updating the configuration of a Kea server. This includes a configuration rejected by a Kea server when it tried to apply it. The name of the server and the error are printed.

NETCONF_UPDATE_CONFIG_STARTED

started updating configuration for %1 server

This informational message indicates that Netconf is trying to update the configuration of a Kea server.

NETCONF_VALIDATE_CONFIG

validating configuration with %1 server: %2

This debug message indicates that Netconf is validating the configuration with a Kea server. The server name and the validated configuration are printed.

NETCONF_VALIDATE_CONFIG_COMPLETED

completed validating configuration for %1 server

This informational message indicates that Netconf validated with success the configuration with a Kea server.

NETCONF_VALIDATE_CONFIG_FAILED

validating configuration with %1 server got an error: %2

The error message indicates that Netconf got an error validating the configuration with a Kea server. This message is produced when exception is thrown during an attempt to validate received configuration. Additional explanation may be provided as a parameter. You may also take a look at earlier log messages. The name of the server and the error are printed.

NETCONF_VALIDATE_CONFIG_REJECTED

validating configuration with %1 server was rejected: %2

The warning message indicates that Netconf got an error validating the configuration with a Kea server. This message is printed when the configuration was rejected during normal processing. Additional explanation may be provided as a parameter. You may also take a look at earlier log messages. The name of the server and the error are printed.

STAT

STAT_CMDS_DEINIT_FAILED

unloading Stat Commands hooks library failed: %1

This error message indicates an error during unloading the Lease Commands hooks library. The details of the error are provided as argument of the log message.

STAT_CMDS_DEINIT_OK

unloading Stat Commands hooks library successful

This info message indicates that the Stat Commands hooks library has been removed successfully.

STAT_CMDS_INIT_FAILED

loading Stat Commands hooks library failed: %1

This error message indicates an error during loading the Lease Commands hooks library. The details of the error are provided as argument of the log message.

STAT_CMDS_INIT_OK

loading Stat Commands hooks library successful

This info message indicates that the Stat Commands hooks library has been loaded successfully. Enjoy!

STAT_CMDS_LEASE4_FAILED

stat-lease4-get command failed: reason: %1

The stat-lease4-get command has failed. The reason for failure is logged.

STAT_CMDS_LEASE4_GET

stat-lease4-get command successful, parameters: %1 rows found: %2

The stat-lease4-get command has been successful. The log will contain the parameters supplied and the number of rows found.

STAT_CMDS_LEASE4_GET_FAILED

stat-lease4-get command failed: parameters: %1, reason: %2

The stat-lease4-get command has failed. Both the parameters supplied and the reason for failure are logged.

STAT_CMDS_LEASE4_GET_INVALID

stat-lease4-get command is malformed or invalid, reason: %1

The stat-lease4-get command was either malformed or contained invalid parameters. A detailed explanation should be logged.

STAT_CMDS_LEASE4_GET_NO_SUBNETS

stat-lease4-get, parameters: %1, %2”

The parameters submitted with stat-lease4-get were valid but excluded all known subnets. The parameters supplied along with an explanation should be logged.

STAT_CMDS_LEASE4_ORPHANED_STATS

stat-lease4-get command omitted statistics for one or more non-existent subnets

During processing the stat-lease4-get found statistics for subnet IDs for non-existent subnets. These values were omitted from the command response returned to the user. This may occur when subnets have been removed from the configuration in a manner that did not also remove the statistics. While the existence of such statistics is not harmful, steps should be considered to remove them. For memfile lease storage, the problem should disappear upon configuration reload or server restart. For database lease storage the issue is more complicated and as of Kea 2.0.0 we do not yet have a clean solution.

STAT_CMDS_LEASE6_FAILED

stat-lease6-get command failed: reason: %1

The stat-lease6-get command has failed. The reason for failure is logged.

STAT_CMDS_LEASE6_GET

stat-lease6-get command successful, parameters: %1 rows found: %2

The stat-lease6-get command has been successful. The log will contain the parameters supplied and the number of rows found.

STAT_CMDS_LEASE6_GET_FAILED

stat-lease6-get command failed: parameters: %1, reason: %2

The stat-lease6-get command has failed. Both the parameters supplied and the reason for failure are logged.

STAT_CMDS_LEASE6_GET_INVALID

stat-lease6-get command is malformed or invalid, reason: %1

The stat-lease6-get command was either malformed or contained invalid parameters. A detailed explanation should be logged.

STAT_CMDS_LEASE6_GET_NO_SUBNETS

stat-lease6-get, parameters: %1, %2”

The parameters submitted with stat-lease6-get were valid but excluded all known subnets. The parameters supplied along with an explanation should be logged.

USER

USER_CHK_HOOK_LOAD_ERROR

DHCP UserCheckHook could not be loaded: %1

This is an error message issued when the DHCP UserCheckHook could not be loaded. The exact cause should be explained in the log message. User subnet selection will revert to default processing.

USER_CHK_HOOK_UNLOAD_ERROR

DHCP UserCheckHook an error occurred unloading the library: %1

This is an error message issued when an error occurs while unloading the UserCheckHook library. This is unlikely to occur and normal operations of the library will likely resume when it is next loaded.

USER_CHK_SUBNET4_SELECT_ERROR

DHCP UserCheckHook an unexpected error occurred in subnet4_select callout: %1

This is an error message issued when the DHCP UserCheckHook subnet4_select hook encounters an unexpected error. The message should contain a more detailed explanation.

USER_CHK_SUBNET4_SELECT_REGISTRY_NULL

DHCP UserCheckHook UserRegistry has not been created.

This is an error message issued when the DHCP UserCheckHook subnet4_select hook has been invoked but the UserRegistry has not been created. This is a programmatic error and should not occur.

USER_CHK_SUBNET6_SELECT_ERROR

DHCP UserCheckHook an unexpected error occurred in subnet6_select callout: %1

This is an error message issued when the DHCP UserCheckHook subnet6_select hook encounters an unexpected error. The message should contain a more detailed explanation.

Configuration Templates

The following sections include configuration templates for certain deployment types. The example configuration files are also available in the Kea sources, in the doc/examples directory.

Template: Home Network of a Power User

Below are some templates to assist in configuring the home network of a power user; they may also be appropriate for a small office. These templates make the following assumptions:

• the administrator wants to use a single /24 class of IPv4 addresses.

• High Availability is desired, so there are two DHCP servers.

• there are a handful of devices, and some of them (e.g. a printer or NAS) require static addresses or extra options.

• the administrator does not want to be bothered with database management.

• the setup is optimized for minimal-to-zero maintenance.

• performance is not an issue; hundreds of queries per second are not expected.

• IPv6 is not used.

• DNS updates will not be performed by Kea.

The logical setup consists of two hosts, each running a Kea DHCPv4 server and a Control Agent (CA). The server connects with the CA using UNIX sockets. Each DHCPv4+CA acts as one partner of the HA pair.

```
 +-host-1-+       +-host-2-+
 |        |       |        |
 |   CA <===\   /===> CA   |    ===== - HTTP connection
 |   #    |  \ /  |   #    |
 |   #    |   X   |   #    |    ##### - UNIX socket
 |   #    |  / \      #    |
 | DHCPv4 ==/   \== DHCPv4 |
 |        |       |        |
 +--------+       +--------+
```

The CA on host-1 and CA on host-2 both listen on port 8000. The DHCP servers communicate with each other via the CAs, which forward control commands to the DHCP servers over the UNIX domain sockets.

Deployment Considerations

The setup is not expected to be very performant; most modest hardware will do. There are successful deployments on Raspberry Pi platforms. If it is running on a VM, 2GB of RAM with one CPU core should be enough. Ubuntu LTS is a choice that is easy to set up and is low maintenance; however, any Linux or FreeBSD operating system is fine. Less popular systems, such as OpenBSD or NetBSD, should also work in principle, but they are not regularly tested.

The assumption is that there are two hosts that are running the Kea setup:

• 192.168.1.2 - primary HA server (active, handles all the traffic)

• 192.168.1.3 - secondary HA server (passive, ready to take over if the primary fails)

The network is 192.168.1.0/24. It is assumed that 192.168.1.1 is the default router.

The whole subnet is split into dynamic and static pools:

• 192.168.1.100 - 192.168.1.199 - this is the dynamic pool. When new devices appear in the network, they are assigned dynamic addresses from this pool.

• The reservations are done outside of this dynamic range (depending on the addressing preference, either 192.168.1.1-192.168.1.99 or 192.168.1.200-192.168.1.254).

To deploy this setup, conduct the following steps:

1. Install CA and DHCPv4 on host-1, and copy the configuration files to their typical locations. They are usually in /etc/kea on Linux and /usr/local/etc/kea on FreeBSD, and the files are typically called kea-ctrl-agent.conf and kea-dhcp4.conf. Please consult the start-up scripts for any specific system.

2. Alter the following to match the local setup:

   • the interface name that Kea should listen on (interfaces in interfaces-config).

   • the interface name that is used to access the subnet (interface in subnet4).

   • the addressing, if using something other than 192.168.1.0/24. Make sure the CA port configuration (http-host and http-port in kea-ca.conf) matches the DHCPv4 server configuration (url in hook-libraries/parameters/high-availability/peers in kea-dhcp4.conf).

   • the router option, to match the actual network.

   • the DNS option, to match the actual network.

   • the path to the hook libraries. This is a very OS-specific parameter; the library names are generally the same everywhere, but the path varies. See Introduction for details.

3. If using a firewall, make sure host-1 can reach host-2. An easy way to ensure that is to try to retrieve host-2’s config from host-1:

   curl -X POST -H "Content-Type: application/json" -d '{ "command": "config-get", "service": [ "dhcp4" ] }'  http://192.168.1.3:8000/

   The DHCPv4 running configuration should be returned, in JSON format.

4. Verify that communication between the hosts works in the opposite direction as well (host-2 can connect to host-1), by repeating step 3 from host-2 using host-1’s IP address and port.

5. Install the CA and DHCPv4 on host-2, as in steps 1 and 2. The config file for the standby server is very similar to the one on the primary server, other than the definition of the this-server-name field (and possibly the interface names).

Possible Extensions

The proposed configuration is somewhat basic, but functional. Once it is set up and running, administrators may wish to consider the following changes:

• if there is a local DNS server, DNS updates can be configured via Kea. This requires running a DHCP-DDNS update server (kea-dhcp-ddns). See Overview for details.

• to run Stateful DHCP for IPv6, a kea-dhcp6 server is necessary. Its configuration is very similar to kea-dhcp4, but there are some notable differences: the default gateway is not configured via the DHCPv6 protocol, but via router advertisements sent by the local router. Also, the DHCPv6 concept of prefix delegation does not exist in DHCPv4. See The DHCPv6 Server for details.

• to expand the local network, adding a MySQL or PostgreSQL database is a popular solution. Users can choose to store leases, host reservations, and even most of the configuration in a database. See Kea Database Administration and the lease-database, hosts-database, and config-control parameters in The DHCPv4 Server.

• to provide more insight into how the DHCP server operates, Kea’s RESTful API can query for many runtime statistics or even change the configuration during runtime. Users may also consider deploying Stork, which is a new but quickly developing dashboard for Kea. See Monitoring Kea With Stork for more information.

• all Kea users should read Kea Security: to learn about various trade-offs between convenience and security in Kea.

Some tweaking of these templates may be required to match specific system needs: at a minimum, the lines highlighted in yellow must be adjusted to match the actual deployment.

Server1’s Control Agent configuration file:

// This is an example of a configuration for Control-Agent (CA) listening
// for incoming HTTP traffic. This is necessary for handling API commands,
// in particular lease update commands needed for HA setup.
{
    "Control-agent":
    {
        // We need to specify where the agent should listen to incoming HTTP
        // queries.
        "http-host": "192.168.1.2",

        // This specifies the port CA will listen on.
        "http-port": 8000,

        "control-sockets":
        {
            // This is how the Agent can communicate with the DHCPv4 server.
            "dhcp4":
            {
                "comment": "socket to DHCP4 server",
                "socket-type": "unix",
                "socket-name": "/tmp/kea4-ctrl-socket"
            },

            // Location of the DHCPv6 command channel socket.
            "dhcp6":
            {
                "socket-type": "unix",
                "socket-name": "/tmp/kea6-ctrl-socket"
            },

            // Location of the D2 command channel socket.
            "d2":
            {
                "socket-type": "unix",
                "socket-name": "/tmp/kea-ddns-ctrl-socket",
                "user-context": { "in-use": false }
            }
        },


        // Similar to other Kea components, CA also uses logging.
        "loggers": [
            {
                "name": "kea-ctrl-agent",
                "output_options": [
                    {
                        "output": "/var/log/kea-ctrl-agent.log",

                        // Several additional parameters are possible in addition
                        // to the typical output. Flush determines whether logger
                        // flushes output to a file. Maxsize determines maximum
                        // filesize before the file is being rotated. maxver
                        // specifies the maximum number of rotated files being
                        // kept.
                        "flush": true,
                        "maxsize": 204800,
                        "maxver": 4,
                        // We use pattern to specify custom log message layout
                        "pattern": "%d{%y.%m.%d %H:%M:%S.%q} %-5p [%c/%i] %m\n"
                    }
                ],
                "severity": "INFO",
                "debuglevel": 0 // debug level only applies when severity is set to DEBUG.
            }
        ]
    }
}

Server1’s DHCPv4 configuration file:

// This is an example configuration of the Kea DHCPv4 server 1:
//
// - uses High Availability hooks library and Lease Commands hooks library
//   to enable High Availability function for the DHCP server. This config
//   file is for the primary (the active) server.
// - uses memfile, which stores lease data in a local CSV file
// - it assumes a single /24 addressing over a link that is directly reachable
//   (no DHCP relays)
// - there is a handful of IP reservations
//
// It is expected to run with a standby (the passive) server, which has a very similar
// configuration. The only difference is that "this-server-name" must be set to "server2" on the
// other server. Also, the interface configuration depends on the network settings of the
// particular machine.

{

"Dhcp4": {

    // Add names of your network interfaces to listen on.
    "interfaces-config": {
        // The DHCPv4 server listens on this interface. When changing this to
        // the actual name of your interface, make sure to also update the
        // interface parameter in the subnet definition below.
        "interfaces": [ "enp0s8" ]
    },

    // Control socket is required for communication between the Control
    // Agent and the DHCP server. High Availability requires Control Agent
    // to be running because lease updates are sent over the RESTful
    // API between the HA peers.
    "control-socket": {
        "socket-type": "unix",
        "socket-name": "/tmp/kea4-ctrl-socket"
    },

    // Use Memfile lease database backend to store leases in a CSV file.
    // Depending on how Kea was compiled, it may also support SQL databases
    // (MySQL and/or PostgreSQL). Those database backends require more
    // parameters, like name, host and possibly user and password.
    // There are dedicated examples for each backend. See Section 7.2.2 "Lease
    // Storage" for details.
    "lease-database": {
        // Memfile is the simplest and easiest backend to use. It's an in-memory
        // database with data being written to a CSV file. It is very similar to
        // what ISC DHCP does.
        "type": "memfile"
    },

    // Let's configure some global parameters. The home network is not very dynamic
    // and there's no shortage of addresses, so no need to recycle aggressively.
    "valid-lifetime": 43200, // leases will be valid for 12h
    "renew-timer": 21600, // clients should renew every 6h
    "rebind-timer": 32400, // clients should start looking for other servers after 9h

    // Kea will clean up its database of expired leases once per hour. However, it
    // will keep the leases in expired state for 2 days. This greatly increases the
    // chances for returning devices to get the same address again. To guarantee that,
    // use host reservation.
    "expired-leases-processing": {
        "reclaim-timer-wait-time": 3600,
        "hold-reclaimed-time": 172800,
        "max-reclaim-leases": 0,
        "max-reclaim-time": 0
    },

    // HA requires two hooks libraries to be loaded: libdhcp_lease_cmds.so and
    // libdhcp_ha.so. The former handles incoming lease updates from the HA peers.
    // The latter implements high availability feature for Kea. Note the library name
    // should be the same, but the path is OS specific.
    "hooks-libraries": [
        // The lease_cmds library must be loaded because HA makes use of it to
        // deliver lease updates to the server as well as synchronize the
        // lease database after failure.
        {
            "library": "/usr/lib/x86_64-linux-gnu/kea/hooks/libdhcp_lease_cmds.so"
        },

        {
            // The HA hooks library should be loaded.
            "library": "/usr/lib/x86_64-linux-gnu/kea/hooks/libdhcp_ha.so",
            "parameters": {
                // Each server should have the same HA configuration, except for the
                // "this-server-name" parameter.
                "high-availability": [ {
                    // This parameter points to this server instance. The respective
                    // HA peers must have this parameter set to their own names.
                    "this-server-name": "server1",
                    // The HA mode is set to hot-standby. In this mode, the active server handles
                    // all the traffic. The standby takes over if the primary becomes unavailable.
                    "mode": "hot-standby",
                    // Heartbeat is to be sent every 10 seconds if no other control
                    // commands are transmitted.
                    "heartbeat-delay": 10000,
                    // Maximum time for partner's response to a heartbeat, after which
                    // failure detection is started. This is specified in milliseconds.
                    // If we don't hear from the partner in 60 seconds, it's time to
                    // start worrying.
                    "max-response-delay": 60000,
                    // The following parameters control how the server detects the
                    // partner's failure. The ACK delay sets the threshold for the
                    // 'secs' field of the received discovers. This is specified in
                    // milliseconds.
                    "max-ack-delay": 5000,
                    // This specifies the number of clients which send messages to
                    // the partner but appear to not receive any response.
                    "max-unacked-clients": 5,
                    // This specifies the maximum timeout (in milliseconds) for the server
                    // to complete sync. If you have a large deployment (high tens or
                    // hundreds of thousands of clients), you may need to increase it
                    // further. The default value is 60000ms (60 seconds).
                    "sync-timeout": 60000,
                    "peers": [
                        // This is the configuration of this server instance.
                        {
                            "name": "server1",
                            // This specifies the URL of our server instance. The
                            // Control Agent must run along with our DHCPv4 server
                            // instance and the "http-host" and "http-port" must be
                            // set to the corresponding values.
                            "url": "http://192.168.1.2:8000/",
                            // This server is primary. The other one must be
                            // secondary.
                            "role": "primary"
                        },
                        // This is the configuration of our HA peer.
                        {
                            "name": "server2",
                            // Specifies the URL on which the partner's control
                            // channel can be reached. The Control Agent is required
                            // to run on the partner's machine with "http-host" and
                            // "http-port" values set to the corresponding values.
                            "url": "http://192.168.1.3:8000/",
                            // The partner is a secondary. Our is primary.
                            "role": "standby"
                        }
                    ]
                } ]
            }
        }
    ],

    // This example contains a single subnet declaration.
    "subnet4": [
        {
            // Subnet prefix.
            "subnet": "192.168.1.0/24",

            // There are no relays in this network, so we need to tell Kea that this subnet
            // is reachable directly via the specified interface.
            "interface": "enp0s8",

            // Specify a dynamic address pool.
            "pools": [
                {
                    "pool": "192.168.1.100-192.168.1.199"
                }
            ],

            // These are options that are subnet specific. In most cases, you need to define at
            // least routers option, as without this option your clients will not be able to reach
            // their default gateway and will not have Internet connectivity. If you have many
            // subnets and they share the same options (e.g. DNS servers typically is the same
            // everywhere), you may define options at the global scope, so you don't repeat them
            // for every network.
            "option-data": [
                {
                    // For each IPv4 subnet you typically need to specify at least one router.
                    "name": "routers",
                    "data": "192.168.1.1"
                },
                {
                    // Using cloudflare or Quad9 is a reasonable option. Change this
                    // to your own DNS servers is you have them. Another popular
                    // choice is 8.8.8.8, owned by Google. Using third party DNS
                    // service raises some privacy concerns.
                    "name": "domain-name-servers",
                    "data": "1.1.1.1,9.9.9.9"
                }
            ],

            // Some devices should get a static address. Since the .100 - .199 range is dynamic,
            // let's use the lower address space for this. There are many ways how reservation
            // can be defined, but using MAC address (hw-address) is by far the most popular one.
            // You can use client-id, duid and even custom defined flex-id that may use whatever
            // parts of the packet you want to use as identifiers. Also, there are many more things
            // you can specify in addition to just an IP address: extra options, next-server, hostname,
            // assign device to client classes etc. See the Kea ARM, Section 8.3 for details.
            // The reservations are subnet specific.
            "reservations": [
                {
                    "hw-address": "1a:1b:1c:1d:1e:1f",
                    "ip-address": "192.168.1.10"
                },
                {
                    "client-id": "01:11:22:33:44:55:66",
                    "ip-address": "192.168.1.11"
                }
            ]
        }
    ],

    // Logging configuration starts here.
    "loggers": [
    {
        // This section affects kea-dhcp4, which is the base logger for DHCPv4 component. It tells
        // DHCPv4 server to write all log messages (on severity INFO or higher) to a file. The file
        // will be rotated once it grows to 2MB and up to 4 files will be kept. The debuglevel
        // (range 0 to 99) is used only when logging on DEBUG level.
        "name": "kea-dhcp4",
        "output_options": [
            {
                "output": "/var/log/kea-dhcp4.log",
                "maxsize": 2048000,
                "maxver": 4
            }
        ],
        "severity": "INFO",
        "debuglevel": 0
    }
  ]
}
}

Server2’s Control Agent configuration file:

// This is an example of a configuration for Control-Agent (CA) listening
// for incoming HTTP traffic. This is necessary for handling API commands,
// in particular lease update commands needed for HA setup.
{
    "Control-agent":
    {
        // We need to specify where the agent should listen to incoming HTTP
        // queries.
        "http-host": "192.168.1.3",

        // This specifies the port CA will listen on.
        "http-port": 8000,

        "control-sockets":
        {
            // This is how the Agent can communicate with the DHCPv4 server.
            "dhcp4":
            {
                "comment": "socket to DHCP4 server",
                "socket-type": "unix",
                "socket-name": "/tmp/kea4-ctrl-socket"
            },

            // Location of the DHCPv6 command channel socket.
            "dhcp6":
            {
                "socket-type": "unix",
                "socket-name": "/tmp/kea6-ctrl-socket"
            },

            // Location of the D2 command channel socket.
            "d2":
            {
                "socket-type": "unix",
                "socket-name": "/tmp/kea-ddns-ctrl-socket",
                "user-context": { "in-use": false }
            }
        },


        // Similar to other Kea components, CA also uses logging.
        "loggers": [
            {
                "name": "kea-ctrl-agent",
                "output_options": [
                    {
                        "output": "/var/log/kea-ctrl-agent.log",

                        // Several additional parameters are possible in addition
                        // to the typical output. Flush determines whether logger
                        // flushes output to a file. Maxsize determines maximum
                        // filesize before the file is being rotated. maxver
                        // specifies the maximum number of rotated files being
                        // kept.
                        "flush": true,
                        "maxsize": 204800,
                        "maxver": 4,
                        // We use pattern to specify custom log message layout
                        "pattern": "%d{%y.%m.%d %H:%M:%S.%q} %-5p [%c/%i] %m\n"
                    }
                ],
                "severity": "INFO",
                "debuglevel": 0 // debug level only applies when severity is set to DEBUG.
            }
        ]
    }
}

Server2’s DHCPv4 configuration file:

// This is an example configuration of the Kea DHCPv4 server 2:
//
// - uses High Availability hooks library and Lease Commands hooks library
//   to enable High Availability function for the DHCP server. This config
//   file is for the primary (the active) server.
// - uses memfile, which stores lease data in a local CSV file
// - it assumes a single /24 addressing over a link that is directly reachable
//   (no DHCP relays)
// - there is a handful of IP reservations
//
// It is expected to run with a primary (the active) server, which has a very similar
// configuration. The only difference is that "this-server-name" must be set to "server2" on the
// other server. Also, the interface configuration depends on the network settings of the
// particular machine.

{

"Dhcp4": {

    // Add names of your network interfaces to listen on.
    "interfaces-config": {
        // The DHCPv4 server listens on this interface. When changing this to
        // the actual name of your interface, make sure to also update the
        // interface parameter in the subnet definition below.
        "interfaces": [ "enp0s8" ]
    },

    // Control socket is required for communication between the Control
    // Agent and the DHCP server. High Availability requires Control Agent
    // to be running because lease updates are sent over the RESTful
    // API between the HA peers.
    "control-socket": {
        "socket-type": "unix",
        "socket-name": "/tmp/kea4-ctrl-socket"
    },

    // Use Memfile lease database backend to store leases in a CSV file.
    // Depending on how Kea was compiled, it may also support SQL databases
    // (MySQL and/or PostgreSQL). Those database backends require more
    // parameters, like name, host and possibly user and password.
    // There are dedicated examples for each backend. See Section 7.2.2 "Lease
    // Storage" for details.
    "lease-database": {
        // Memfile is the simplest and easiest backend to use. It's an in-memory
        // database with data being written to a CSV file. It is very similar to
        // what ISC DHCP does.
        "type": "memfile"
    },

    // Let's configure some global parameters. The home network is not very dynamic
    // and there's no shortage of addresses, so no need to recycle aggressively.
    "valid-lifetime": 43200, // leases will be valid for 12h
    "renew-timer": 21600, // clients should renew every 6h
    "rebind-timer": 32400, // clients should start looking for other servers after 9h

    // Kea will clean up its database of expired leases once per hour. However, it
    // will keep the leases in expired state for 2 days. This greatly increases the
    // chances for returning devices to get the same address again. To guarantee that,
    // use host reservation.
    "expired-leases-processing": {
        "reclaim-timer-wait-time": 3600,
        "hold-reclaimed-time": 172800,
        "max-reclaim-leases": 0,
        "max-reclaim-time": 0
    },

    // HA requires two hooks libraries to be loaded: libdhcp_lease_cmds.so and
    // libdhcp_ha.so. The former handles incoming lease updates from the HA peers.
    // The latter implements high availability feature for Kea. Note the library name
    // should be the same, but the path is OS specific.
    "hooks-libraries": [
        // The lease_cmds library must be loaded because HA makes use of it to
        // deliver lease updates to the server as well as synchronize the
        // lease database after failure.
        {
            "library": "/usr/lib/x86_64-linux-gnu/kea/hooks/libdhcp_lease_cmds.so"
        },

        {
            // The HA hooks library should be loaded.
            "library": "/usr/lib/x86_64-linux-gnu/kea/hooks/libdhcp_ha.so",
            "parameters": {
                // Each server should have the same HA configuration, except for the
                // "this-server-name" parameter.
                "high-availability": [ {
                    // This parameter points to this server instance. The respective
                    // HA peers must have this parameter set to their own names.
                    "this-server-name": "server2",
                    // The HA mode is set to hot-standby. In this mode, the active server handles
                    // all the traffic. The standby takes over if the primary becomes unavailable.
                    "mode": "hot-standby",
                    // Heartbeat is to be sent every 10 seconds if no other control
                    // commands are transmitted.
                    "heartbeat-delay": 10000,
                    // Maximum time for partner's response to a heartbeat, after which
                    // failure detection is started. This is specified in milliseconds.
                    // If we don't hear from the partner in 60 seconds, it's time to
                    // start worrying.
                    "max-response-delay": 60000,
                    // The following parameters control how the server detects the
                    // partner's failure. The ACK delay sets the threshold for the
                    // 'secs' field of the received discovers. This is specified in
                    // milliseconds.
                    "max-ack-delay": 5000,
                    // This specifies the number of clients which send messages to
                    // the partner but appear to not receive any response.
                    "max-unacked-clients": 5,
                    // This specifies the maximum timeout (in milliseconds) for the server
                    // to complete sync. If you have a large deployment (high tens or
                    // hundreds of thousands of clients), you may need to increase it
                    // further. The default value is 60000ms (60 seconds).
                    "sync-timeout": 60000,
                    "peers": [
                        // This is the configuration of this server instance.
                        {
                            "name": "server1",
                            // This specifies the URL of the partner's server instance. The
                            // Control Agent must run along with partner DHCPv4 server
                            // instance and the "http-host" and "http-port" must be
                            // set to the corresponding values.
                            "url": "http://192.168.1.2:8000/",
                            // That server is primary. Our server must be
                            // standby.
                            "role": "primary"
                        },
                        // This is our (server2) configuration.
                        {
                            "name": "server2",
                            // Specifies the URL on which the control agent for this server
                            // can be reached. The Control Agent is required
                            // to run on this machine with "http-host" and
                            // "http-port" values set to the corresponding values.
                            "url": "http://192.168.1.3:8000/",
                            // Our server is standby. The other server is primary.
                            "role": "standby"
                        }
                    ]
                } ]
            }
        }
    ],

    // This example contains a single subnet declaration.
    "subnet4": [
        {
            // Subnet prefix.
            "subnet": "192.168.1.0/24",

            // There are no relays in this network, so we need to tell Kea that this subnet
            // is reachable directly via the ethX interface.
            "interface": "enp0s8",

            // Specify a dynamic address pool.
            "pools": [
                {
                    "pool": "192.168.1.100-192.168.1.199"
                }
            ],

            // These are options that are subnet specific. In most cases, you need to define at
            // least routers option, as without this option your clients will not be able to reach
            // their default gateway and will not have Internet connectivity. If you have many
            // subnets and they share the same options (e.g. DNS servers typically is the same
            // everywhere), you may define options at the global scope, so you don't repeat them
            // for every network.
            "option-data": [
                {
                    // For each IPv4 subnet you typically need to specify at least one router.
                    "name": "routers",
                    "data": "192.168.1.1"
                },
                {
                    // Using cloudflare or Quad9 is a reasonable option. Change this
                    // to your own DNS servers is you have them. Another popular
                    // choice is 8.8.8.8, owned by Google. Using third party DNS
                    // service raises some privacy concerns.
                    "name": "domain-name-servers",
                    "data": "1.1.1.1,9.9.9.9"
                }
            ],

            // Some devices should get a static address. Since the .100 - .199 range is dynamic,
            // let's use the lower address space for this. There are many ways how reservation
            // can be defined, but using MAC address (hw-address) is by far the most popular one.
            // You can use client-id, duid and even custom defined flex-id that may use whatever
            // parts of the packet you want to use as identifiers. Also, there are many more things
            // you can specify in addition to just an IP address: extra options, next-server, hostname,
            // assign device to client classes etc. See the Kea ARM, Section 8.3 for details.
            // The reservations are subnet specific.
            "reservations": [
                {
                    "hw-address": "1a:1b:1c:1d:1e:1f",
                    "ip-address": "192.168.1.10"
                },
                {
                    "client-id": "01:11:22:33:44:55:66",
                    "ip-address": "192.168.1.11"
                }
            ]
        }
    ],

    // Logging configuration starts here.
    "loggers": [
    {
        // This section affects kea-dhcp4, which is the base logger for DHCPv4 component. It tells
        // DHCPv4 server to write all log messages (on severity INFO or higher) to a file. The file
        // will be rotated once it grows to 2MB and up to 4 files will be kept. The debuglevel
        // (range 0 to 99) is used only when logging on DEBUG level.
        "name": "kea-dhcp4",
        "output_options": [
            {
                "output": "/var/log/kea-dhcp4.log",
                "maxsize": 2048000,
                "maxver": 4
            }
        ],
        "severity": "INFO",
        "debuglevel": 0
    }
  ]
}
}

Kea Flow Diagrams

These flow diagrams describe Kea’s DHCPv4 server implementation, and they may be useful for system administrators. To design a configuration that results in clients getting the intended addresses and options, it is important to understand the sequence of request-processing steps. For example, Kea iterates looking for a suitable address, and conditionally accepts the first available address, so the order in which addresses are evaluated matters.

It is also useful to understand Kea’s processing logic because there are configuration choices which can make the process far more efficient. Kea is very flexible, so it can be applied to very different use cases and in different environments. In an environment where throughput and efficiency are a priority, the administrator can choose to limit some of the processing steps. For example, it is possible to limit the number of different client identifiers Kea evaluates in looking for a host reservation, or even to skip the step of checking for host reservations.

These diagrams are focused on those aspects of Kea processing that will be most useful to operators. The diagrams illustrate DHCPv4 request processing, but most of the logic applies equally to DHCPv6. Following the title of each diagram is a Kea version number. Kea behavior has evolved over time, and the diagrams document the behavior as of the Kea version indicated. These diagrams are provided in the Kea source tree in UML (source), PNG, and SVG formats.

Main Loop

The main loop is common to both DHCPv4 and DHPCv6 servers.

The DHCP server main loop

DHCPv4 Packet Processing

DHCPv4 packet processing evaluates the type DHCP message: Discover, Request, Release, Decline, or Inform. This diagram shows the general, high-level flow for processing an inbound client DHCP packet from receipt to the server’s response.

DHCPv4 packet processing

DHCPREQUEST Processing

The following diagrams focus on DHCPREQUEST processing. This chart gives an overview of the process, from subnet selection to checking for host reservations to evaluating client classes. Finally, before acknowledging the lease, the options are evaluated and added to the message.

DHCPREQUEST processing

DHCPv4 Subnet Selection

Subnet selection is the process of choosing a subnet that is topologically appropriate for the client. When the selected subnet is a member of a shared network, the whole shared network is selected. During subnet selection the client class may be checked more than once while iterating through subnets, to determine whether it is permitted in the selected subnet.

DHCPv4 subnet selection

DHCPv4 Special Case of Double-Booting

After subnet selection and before lease allocation, the DHCPv4 server handles the special case of clients restarting with an image provided by PXE boot or bootp. The Lease Request box is expanded below.

DHCPv4 lease assignment

DHCPv4 Lease Allocation

The first diagram below illustrates the details of processing the client request, showing the renewal of an existing lease, the assignment of a reserved lease, and the allocation of an unreserved lease.

DHCPREQUEST lease allocation

The second diagram shows the algorithm used to validate a requested lease or select a new address to offer. The right-hand side of the diagram shows how a new address is selected, when a new lease is required and the client has neither a requested address nor a reservation. When a new lease is required and Kea iterates over pools and subnets, it starts with the subnet selected above in the subnet selection process.

The requestLease4 algorithm

Note

Declined addresses are included in the statistic for assigned addresses, so the \(assigned + free = total\) equation is true.

Lease States

This diagram illustrates the different lease states, including the free one, where no lease object exists.

Lease states

Checking for Host Reservations

The allocation engine checks for host reservations after selecting a subnet; this diagram shows the details of that operation. Subnet selection is based on network topology. Host reservations are primarily for assigning options, and options are evaluated after subnet selection. However, if client classes are added in the host reservation, those are also evaluated against the selected subnet in a further check (added in Kea 1.7.10). Kea includes several options to skip checking for host reservations, which can make this process much more efficient if reservations are not being used.

Note

To find a free lease, the allocation engine begins by evaluating the most recently used subnet. The current subnet depends on the history of prior queries.

Host reservation evaluation

Building the Options List

Before sending a response, options are added:

• evaluate required client classes

• build the configured option list

• append requested options

• append requested vendor options

• append basic options

The buildCfgOptionList (build configured option list) algorithm

The appendRequestedOptions (append requested options) algorithm

The appendRequestedVendorOptions (append vendor requested options) algorithm

Kea Configuration File Syntax (BNF)

Kea consists of several daemons, each with its own configuration syntax. The following sections provide a complete syntax of all possible parameters, written in Backus-Naur Form (BNF). See this Wikipedia article on BNF for more information.

BNF Grammar for DHCPv4

This grammar is generated from dhcp4_parser.yy. See The DHCPv4 Server for more details.

  Grammar

  $accept ::= start EOF

  start ::= TOPLEVEL_JSON sub_json

  start ::= TOPLEVEL_DHCP4 syntax_map

  start ::= SUB_DHCP4 sub_dhcp4

  start ::= SUB_INTERFACES4 sub_interfaces4

  start ::= SUB_SUBNET4 sub_subnet4

  start ::= SUB_POOL4 sub_pool4

  start ::= SUB_RESERVATION sub_reservation

  start ::= SUB_OPTION_DEFS sub_option_def_list

  start ::= SUB_OPTION_DEF sub_option_def

  start ::= SUB_OPTION_DATA sub_option_data

  start ::= SUB_HOOKS_LIBRARY sub_hooks_library

  start ::= SUB_DHCP_DDNS sub_dhcp_ddns

  start ::= SUB_CONFIG_CONTROL sub_config_control

  value ::= INTEGER
       | FLOAT
       | BOOLEAN
       | STRING
       | NULL
       | map2
       | list_generic

  sub_json ::= value

  map2 ::= "{" map_content "}"

  map_value ::= map2

  map_content ::=
             | not_empty_map

  not_empty_map ::= STRING ":" value
               | not_empty_map "," STRING ":" value
               | not_empty_map ","

  list_generic ::= "[" list_content "]"

  list_content ::=
              | not_empty_list

  not_empty_list ::= value
                | not_empty_list "," value
                | not_empty_list ","

  list_strings ::= "[" list_strings_content "]"

  list_strings_content ::=
                      | not_empty_list_strings

  not_empty_list_strings ::= STRING
                        | not_empty_list_strings "," STRING
                        | not_empty_list_strings ","

  unknown_map_entry ::= STRING ":"

  syntax_map ::= "{" global_object "}"

  global_object ::= "Dhcp4" ":" "{" global_params "}"
               | global_object_comma

  global_object_comma ::= global_object ","

  sub_dhcp4 ::= "{" global_params "}"

  global_params ::= global_param
               | global_params "," global_param
               | global_params ","

  global_param ::= valid_lifetime
              | min_valid_lifetime
              | max_valid_lifetime
              | renew_timer
              | rebind_timer
              | decline_probation_period
              | subnet4_list
              | shared_networks
              | interfaces_config
              | lease_database
              | hosts_database
              | hosts_databases
              | host_reservation_identifiers
              | client_classes
              | option_def_list
              | option_data_list
              | hooks_libraries
              | expired_leases_processing
              | dhcp4o6_port
              | control_socket
              | dhcp_queue_control
              | dhcp_ddns
              | echo_client_id
              | match_client_id
              | authoritative
              | next_server
              | server_hostname
              | boot_file_name
              | user_context
              | comment
              | sanity_checks
              | reservations
              | config_control
              | server_tag
              | reservation_mode
              | reservations_global
              | reservations_in_subnet
              | reservations_out_of_pool
              | calculate_tee_times
              | t1_percent
              | t2_percent
              | cache_threshold
              | cache_max_age
              | loggers
              | hostname_char_set
              | hostname_char_replacement
              | ddns_send_updates
              | ddns_override_no_update
              | ddns_override_client_update
              | ddns_replace_client_name
              | ddns_generated_prefix
              | ddns_qualifying_suffix
              | ddns_update_on_renew
              | ddns_use_conflict_resolution
              | store_extended_info
              | statistic_default_sample_count
              | statistic_default_sample_age
              | dhcp_multi_threading
              | early_global_reservations_lookup
              | ip_reservations_unique
              | reservations_lookup_first
              | compatibility
              | parked_packet_limit
              | unknown_map_entry

  valid_lifetime ::= "valid-lifetime" ":" INTEGER

  min_valid_lifetime ::= "min-valid-lifetime" ":" INTEGER

  max_valid_lifetime ::= "max-valid-lifetime" ":" INTEGER

  renew_timer ::= "renew-timer" ":" INTEGER

  rebind_timer ::= "rebind-timer" ":" INTEGER

  calculate_tee_times ::= "calculate-tee-times" ":" BOOLEAN

  t1_percent ::= "t1-percent" ":" FLOAT

  t2_percent ::= "t2-percent" ":" FLOAT

  cache_threshold ::= "cache-threshold" ":" FLOAT

  cache_max_age ::= "cache-max-age" ":" INTEGER

  decline_probation_period ::= "decline-probation-period" ":" INTEGER

  server_tag ::= "server-tag" ":" STRING

  parked_packet_limit ::= "parked-packet-limit" ":" INTEGER

  echo_client_id ::= "echo-client-id" ":" BOOLEAN

  match_client_id ::= "match-client-id" ":" BOOLEAN

  authoritative ::= "authoritative" ":" BOOLEAN

  ddns_send_updates ::= "ddns-send-updates" ":" BOOLEAN

  ddns_override_no_update ::= "ddns-override-no-update" ":" BOOLEAN

  ddns_override_client_update ::= "ddns-override-client-update" ":" BOOLEAN

  ddns_replace_client_name ::= "ddns-replace-client-name" ":" ddns_replace_client_name_value

  ddns_replace_client_name_value ::= "when-present"
                                | "never"
                                | "always"
                                | "when-not-present"
                                | BOOLEAN

  ddns_generated_prefix ::= "ddns-generated-prefix" ":" STRING

  ddns_qualifying_suffix ::= "ddns-qualifying-suffix" ":" STRING

  ddns_update_on_renew ::= "ddns-update-on-renew" ":" BOOLEAN

  ddns_use_conflict_resolution ::= "ddns-use-conflict-resolution" ":" BOOLEAN

  hostname_char_set ::= "hostname-char-set" ":" STRING

  hostname_char_replacement ::= "hostname-char-replacement" ":" STRING

  store_extended_info ::= "store-extended-info" ":" BOOLEAN

  statistic_default_sample_count ::= "statistic-default-sample-count" ":" INTEGER

  statistic_default_sample_age ::= "statistic-default-sample-age" ":" INTEGER

  early_global_reservations_lookup ::= "early-global-reservations-lookup" ":" BOOLEAN

  ip_reservations_unique ::= "ip-reservations-unique" ":" BOOLEAN

  reservations_lookup_first ::= "reservations-lookup-first" ":" BOOLEAN

  interfaces_config ::= "interfaces-config" ":" "{" interfaces_config_params "}"

  interfaces_config_params ::= interfaces_config_param
                          | interfaces_config_params "," interfaces_config_param
                          | interfaces_config_params ","

  interfaces_config_param ::= interfaces_list
                         | dhcp_socket_type
                         | outbound_interface
                         | re_detect
                         | service_sockets_require_all
                         | service_sockets_retry_wait_time
                         | service_sockets_max_retries
                         | user_context
                         | comment
                         | unknown_map_entry

  sub_interfaces4 ::= "{" interfaces_config_params "}"

  interfaces_list ::= "interfaces" ":" list_strings

  dhcp_socket_type ::= "dhcp-socket-type" ":" socket_type

  socket_type ::= "raw"
             | "udp"

  outbound_interface ::= "outbound-interface" ":" outbound_interface_value

  outbound_interface_value ::= "same-as-inbound"
                          | "use-routing"

  re_detect ::= "re-detect" ":" BOOLEAN

  service_sockets_require_all ::= "service-sockets-require-all" ":" BOOLEAN

  service_sockets_retry_wait_time ::= "service-sockets-retry-wait-time" ":" INTEGER

  service_sockets_max_retries ::= "service-sockets-max-retries" ":" INTEGER

  lease_database ::= "lease-database" ":" "{" database_map_params "}"

  sanity_checks ::= "sanity-checks" ":" "{" sanity_checks_params "}"

  sanity_checks_params ::= sanity_checks_param
                      | sanity_checks_params "," sanity_checks_param
                      | sanity_checks_params ","

  sanity_checks_param ::= lease_checks

  lease_checks ::= "lease-checks" ":" STRING

  hosts_database ::= "hosts-database" ":" "{" database_map_params "}"

  hosts_databases ::= "hosts-databases" ":" "[" database_list "]"

  database_list ::=
               | not_empty_database_list

  not_empty_database_list ::= database
                         | not_empty_database_list "," database
                         | not_empty_database_list ","

  database ::= "{" database_map_params "}"

  database_map_params ::= database_map_param
                     | database_map_params "," database_map_param
                     | database_map_params ","

  database_map_param ::= database_type
                    | user
                    | password
                    | host
                    | port
                    | name
                    | persist
                    | lfc_interval
                    | readonly
                    | connect_timeout
                    | max_reconnect_tries
                    | reconnect_wait_time
                    | on_fail
                    | max_row_errors
                    | trust_anchor
                    | cert_file
                    | key_file
                    | cipher_list
                    | unknown_map_entry

  database_type ::= "type" ":" db_type

  db_type ::= "memfile"
         | "mysql"
         | "postgresql"

  user ::= "user" ":" STRING

  password ::= "password" ":" STRING

  host ::= "host" ":" STRING

  port ::= "port" ":" INTEGER

  name ::= "name" ":" STRING

  persist ::= "persist" ":" BOOLEAN

  lfc_interval ::= "lfc-interval" ":" INTEGER

  readonly ::= "readonly" ":" BOOLEAN

  connect_timeout ::= "connect-timeout" ":" INTEGER

  max_reconnect_tries ::= "max-reconnect-tries" ":" INTEGER

  reconnect_wait_time ::= "reconnect-wait-time" ":" INTEGER

  on_fail ::= "on-fail" ":" on_fail_mode

  on_fail_mode ::= "stop-retry-exit"
              | "serve-retry-exit"
              | "serve-retry-continue"

  max_row_errors ::= "max-row-errors" ":" INTEGER

  trust_anchor ::= "trust-anchor" ":" STRING

  cert_file ::= "cert-file" ":" STRING

  key_file ::= "key-file" ":" STRING

  cipher_list ::= "cipher-list" ":" STRING

  host_reservation_identifiers ::= "host-reservation-identifiers" ":" "[" host_reservation_identifiers_list "]"

  host_reservation_identifiers_list ::= host_reservation_identifier
                                   | host_reservation_identifiers_list "," host_reservation_identifier
                                   | host_reservation_identifiers_list ","

  host_reservation_identifier ::= duid_id
                             | hw_address_id
                             | circuit_id
                             | client_id
                             | flex_id

  duid_id ::= "duid"

  hw_address_id ::= "hw-address"

  circuit_id ::= "circuit-id"

  client_id ::= "client-id"

  flex_id ::= "flex-id"

  dhcp_multi_threading ::= "multi-threading" ":" "{" multi_threading_params "}"

  multi_threading_params ::= multi_threading_param
                        | multi_threading_params "," multi_threading_param
                        | multi_threading_params ","

  multi_threading_param ::= enable_multi_threading
                       | thread_pool_size
                       | packet_queue_size
                       | user_context
                       | comment
                       | unknown_map_entry

  enable_multi_threading ::= "enable-multi-threading" ":" BOOLEAN

  thread_pool_size ::= "thread-pool-size" ":" INTEGER

  packet_queue_size ::= "packet-queue-size" ":" INTEGER

  hooks_libraries ::= "hooks-libraries" ":" "[" hooks_libraries_list "]"

  hooks_libraries_list ::=
                      | not_empty_hooks_libraries_list

  not_empty_hooks_libraries_list ::= hooks_library
                                | not_empty_hooks_libraries_list "," hooks_library
                                | not_empty_hooks_libraries_list ","

  hooks_library ::= "{" hooks_params "}"

  sub_hooks_library ::= "{" hooks_params "}"

  hooks_params ::= hooks_param
              | hooks_params "," hooks_param
              | hooks_params ","
              | unknown_map_entry

  hooks_param ::= library
             | parameters

  library ::= "library" ":" STRING

  parameters ::= "parameters" ":" map_value

  expired_leases_processing ::= "expired-leases-processing" ":" "{" expired_leases_params "}"

  expired_leases_params ::= expired_leases_param
                       | expired_leases_params "," expired_leases_param
                       | expired_leases_params ","

  expired_leases_param ::= reclaim_timer_wait_time
                      | flush_reclaimed_timer_wait_time
                      | hold_reclaimed_time
                      | max_reclaim_leases
                      | max_reclaim_time
                      | unwarned_reclaim_cycles

  reclaim_timer_wait_time ::= "reclaim-timer-wait-time" ":" INTEGER

  flush_reclaimed_timer_wait_time ::= "flush-reclaimed-timer-wait-time" ":" INTEGER

  hold_reclaimed_time ::= "hold-reclaimed-time" ":" INTEGER

  max_reclaim_leases ::= "max-reclaim-leases" ":" INTEGER

  max_reclaim_time ::= "max-reclaim-time" ":" INTEGER

  unwarned_reclaim_cycles ::= "unwarned-reclaim-cycles" ":" INTEGER

  subnet4_list ::= "subnet4" ":" "[" subnet4_list_content "]"

  subnet4_list_content ::=
                      | not_empty_subnet4_list

  not_empty_subnet4_list ::= subnet4
                        | not_empty_subnet4_list "," subnet4
                        | not_empty_subnet4_list ","

  subnet4 ::= "{" subnet4_params "}"

  sub_subnet4 ::= "{" subnet4_params "}"

  subnet4_params ::= subnet4_param
                | subnet4_params "," subnet4_param
                | subnet4_params ","

  subnet4_param ::= valid_lifetime
               | min_valid_lifetime
               | max_valid_lifetime
               | renew_timer
               | rebind_timer
               | option_data_list
               | pools_list
               | subnet
               | interface
               | id
               | client_class
               | require_client_classes
               | reservations
               | reservation_mode
               | reservations_global
               | reservations_in_subnet
               | reservations_out_of_pool
               | relay
               | match_client_id
               | authoritative
               | next_server
               | server_hostname
               | boot_file_name
               | subnet_4o6_interface
               | subnet_4o6_interface_id
               | subnet_4o6_subnet
               | user_context
               | comment
               | calculate_tee_times
               | t1_percent
               | t2_percent
               | cache_threshold
               | cache_max_age
               | ddns_send_updates
               | ddns_override_no_update
               | ddns_override_client_update
               | ddns_replace_client_name
               | ddns_generated_prefix
               | ddns_qualifying_suffix
               | ddns_update_on_renew
               | ddns_use_conflict_resolution
               | hostname_char_set
               | hostname_char_replacement
               | store_extended_info
               | unknown_map_entry

  subnet ::= "subnet" ":" STRING

  subnet_4o6_interface ::= "4o6-interface" ":" STRING

  subnet_4o6_interface_id ::= "4o6-interface-id" ":" STRING

  subnet_4o6_subnet ::= "4o6-subnet" ":" STRING

  interface ::= "interface" ":" STRING

  client_class ::= "client-class" ":" STRING

  require_client_classes ::= "require-client-classes" ":" list_strings

  reservations_global ::= "reservations-global" ":" BOOLEAN

  reservations_in_subnet ::= "reservations-in-subnet" ":" BOOLEAN

  reservations_out_of_pool ::= "reservations-out-of-pool" ":" BOOLEAN

  reservation_mode ::= "reservation-mode" ":" hr_mode

  hr_mode ::= "disabled"
         | "out-of-pool"
         | "global"
         | "all"

  id ::= "id" ":" INTEGER

  shared_networks ::= "shared-networks" ":" "[" shared_networks_content "]"

  shared_networks_content ::=
                         | shared_networks_list

  shared_networks_list ::= shared_network
                      | shared_networks_list "," shared_network
                      | shared_networks_list ","

  shared_network ::= "{" shared_network_params "}"

  shared_network_params ::= shared_network_param
                       | shared_network_params "," shared_network_param
                       | shared_network_params ","

  shared_network_param ::= name
                      | subnet4_list
                      | interface
                      | renew_timer
                      | rebind_timer
                      | option_data_list
                      | match_client_id
                      | authoritative
                      | next_server
                      | server_hostname
                      | boot_file_name
                      | relay
                      | reservation_mode
                      | reservations_global
                      | reservations_in_subnet
                      | reservations_out_of_pool
                      | client_class
                      | require_client_classes
                      | valid_lifetime
                      | min_valid_lifetime
                      | max_valid_lifetime
                      | user_context
                      | comment
                      | calculate_tee_times
                      | t1_percent
                      | t2_percent
                      | cache_threshold
                      | cache_max_age
                      | ddns_send_updates
                      | ddns_override_no_update
                      | ddns_override_client_update
                      | ddns_replace_client_name
                      | ddns_generated_prefix
                      | ddns_qualifying_suffix
                      | ddns_update_on_renew
                      | ddns_use_conflict_resolution
                      | hostname_char_set
                      | hostname_char_replacement
                      | store_extended_info
                      | unknown_map_entry

  option_def_list ::= "option-def" ":" "[" option_def_list_content "]"

  sub_option_def_list ::= "{" option_def_list "}"

  option_def_list_content ::=
                         | not_empty_option_def_list

  not_empty_option_def_list ::= option_def_entry
                           | not_empty_option_def_list "," option_def_entry
                           | not_empty_option_def_list ","

  option_def_entry ::= "{" option_def_params "}"

  sub_option_def ::= "{" option_def_params "}"

  option_def_params ::=
                   | not_empty_option_def_params

  not_empty_option_def_params ::= option_def_param
                             | not_empty_option_def_params "," option_def_param
                             | not_empty_option_def_params ","

  option_def_param ::= option_def_name
                  | option_def_code
                  | option_def_type
                  | option_def_record_types
                  | option_def_space
                  | option_def_encapsulate
                  | option_def_array
                  | user_context
                  | comment
                  | unknown_map_entry

  option_def_name ::= name

  code ::= "code" ":" INTEGER

  option_def_code ::= code

  option_def_type ::= "type" ":" STRING

  option_def_record_types ::= "record-types" ":" STRING

  space ::= "space" ":" STRING

  option_def_space ::= space

  option_def_encapsulate ::= "encapsulate" ":" STRING

  option_def_array ::= "array" ":" BOOLEAN

  option_data_list ::= "option-data" ":" "[" option_data_list_content "]"

  option_data_list_content ::=
                          | not_empty_option_data_list

  not_empty_option_data_list ::= option_data_entry
                            | not_empty_option_data_list "," option_data_entry
                            | not_empty_option_data_list ","

  option_data_entry ::= "{" option_data_params "}"

  sub_option_data ::= "{" option_data_params "}"

  option_data_params ::=
                    | not_empty_option_data_params

  not_empty_option_data_params ::= option_data_param
                              | not_empty_option_data_params "," option_data_param
                              | not_empty_option_data_params ","

  option_data_param ::= option_data_name
                   | option_data_data
                   | option_data_code
                   | option_data_space
                   | option_data_csv_format
                   | option_data_always_send
                   | user_context
                   | comment
                   | unknown_map_entry

  option_data_name ::= name

  option_data_data ::= "data" ":" STRING

  option_data_code ::= code

  option_data_space ::= space

  option_data_csv_format ::= "csv-format" ":" BOOLEAN

  option_data_always_send ::= "always-send" ":" BOOLEAN

  pools_list ::= "pools" ":" "[" pools_list_content "]"

  pools_list_content ::=
                    | not_empty_pools_list

  not_empty_pools_list ::= pool_list_entry
                      | not_empty_pools_list "," pool_list_entry
                      | not_empty_pools_list ","

  pool_list_entry ::= "{" pool_params "}"

  sub_pool4 ::= "{" pool_params "}"

  pool_params ::= pool_param
             | pool_params "," pool_param
             | pool_params ","

  pool_param ::= pool_entry
            | option_data_list
            | client_class
            | require_client_classes
            | user_context
            | comment
            | unknown_map_entry

  pool_entry ::= "pool" ":" STRING

  user_context ::= "user-context" ":" map_value

  comment ::= "comment" ":" STRING

  reservations ::= "reservations" ":" "[" reservations_list "]"

  reservations_list ::=
                   | not_empty_reservations_list

  not_empty_reservations_list ::= reservation
                             | not_empty_reservations_list "," reservation
                             | not_empty_reservations_list ","

  reservation ::= "{" reservation_params "}"

  sub_reservation ::= "{" reservation_params "}"

  reservation_params ::=
                    | not_empty_reservation_params

  not_empty_reservation_params ::= reservation_param
                              | not_empty_reservation_params "," reservation_param
                              | not_empty_reservation_params ","

  reservation_param ::= duid
                   | reservation_client_classes
                   | client_id_value
                   | circuit_id_value
                   | flex_id_value
                   | ip_address
                   | hw_address
                   | hostname
                   | option_data_list
                   | next_server
                   | server_hostname
                   | boot_file_name
                   | user_context
                   | comment
                   | unknown_map_entry

  next_server ::= "next-server" ":" STRING

  server_hostname ::= "server-hostname" ":" STRING

  boot_file_name ::= "boot-file-name" ":" STRING

  ip_address ::= "ip-address" ":" STRING

  ip_addresses ::= "ip-addresses" ":" list_strings

  duid ::= "duid" ":" STRING

  hw_address ::= "hw-address" ":" STRING

  client_id_value ::= "client-id" ":" STRING

  circuit_id_value ::= "circuit-id" ":" STRING

  flex_id_value ::= "flex-id" ":" STRING

  hostname ::= "hostname" ":" STRING

  reservation_client_classes ::= "client-classes" ":" list_strings

  relay ::= "relay" ":" "{" relay_map "}"

  relay_map ::= ip_address
           | ip_addresses

  client_classes ::= "client-classes" ":" "[" client_classes_list "]"

  client_classes_list ::= client_class_entry
                     | client_classes_list "," client_class_entry
                     | client_classes_list ","

  client_class_entry ::= "{" client_class_params "}"

  client_class_params ::=
                     | not_empty_client_class_params

  not_empty_client_class_params ::= client_class_param
                               | not_empty_client_class_params "," client_class_param
                               | not_empty_client_class_params ","

  client_class_param ::= client_class_name
                    | client_class_test
                    | only_if_required
                    | option_def_list
                    | option_data_list
                    | next_server
                    | server_hostname
                    | boot_file_name
                    | user_context
                    | comment
                    | unknown_map_entry
                    | valid_lifetime
                    | min_valid_lifetime
                    | max_valid_lifetime

  client_class_name ::= name

  client_class_test ::= "test" ":" STRING

  only_if_required ::= "only-if-required" ":" BOOLEAN

  dhcp4o6_port ::= "dhcp4o6-port" ":" INTEGER

  control_socket ::= "control-socket" ":" "{" control_socket_params "}"

  control_socket_params ::= control_socket_param
                       | control_socket_params "," control_socket_param
                       | control_socket_params ","

  control_socket_param ::= control_socket_type
                      | control_socket_name
                      | user_context
                      | comment
                      | unknown_map_entry

  control_socket_type ::= "socket-type" ":" STRING

  control_socket_name ::= "socket-name" ":" STRING

  dhcp_queue_control ::= "dhcp-queue-control" ":" "{" queue_control_params "}"

  queue_control_params ::= queue_control_param
                      | queue_control_params "," queue_control_param
                      | queue_control_params ","

  queue_control_param ::= enable_queue
                     | queue_type
                     | capacity
                     | user_context
                     | comment
                     | arbitrary_map_entry

  enable_queue ::= "enable-queue" ":" BOOLEAN

  queue_type ::= "queue-type" ":" STRING

  capacity ::= "capacity" ":" INTEGER

  arbitrary_map_entry ::= STRING ":" value

  dhcp_ddns ::= "dhcp-ddns" ":" "{" dhcp_ddns_params "}"

  sub_dhcp_ddns ::= "{" dhcp_ddns_params "}"

  dhcp_ddns_params ::= dhcp_ddns_param
                  | dhcp_ddns_params "," dhcp_ddns_param
                  | dhcp_ddns_params ","

  dhcp_ddns_param ::= enable_updates
                 | server_ip
                 | server_port
                 | sender_ip
                 | sender_port
                 | max_queue_size
                 | ncr_protocol
                 | ncr_format
                 | dep_override_no_update
                 | dep_override_client_update
                 | dep_replace_client_name
                 | dep_generated_prefix
                 | dep_qualifying_suffix
                 | dep_hostname_char_set
                 | dep_hostname_char_replacement
                 | user_context
                 | comment
                 | unknown_map_entry

  enable_updates ::= "enable-updates" ":" BOOLEAN

  server_ip ::= "server-ip" ":" STRING

  server_port ::= "server-port" ":" INTEGER

  sender_ip ::= "sender-ip" ":" STRING

  sender_port ::= "sender-port" ":" INTEGER

  max_queue_size ::= "max-queue-size" ":" INTEGER

  ncr_protocol ::= "ncr-protocol" ":" ncr_protocol_value

  ncr_protocol_value ::= "udp"
                    | "tcp"

  ncr_format ::= "ncr-format" ":" "JSON"

  dep_qualifying_suffix ::= "qualifying-suffix" ":" STRING

  dep_override_no_update ::= "override-no-update" ":" BOOLEAN

  dep_override_client_update ::= "override-client-update" ":" BOOLEAN

  dep_replace_client_name ::= "replace-client-name" ":" ddns_replace_client_name_value

  dep_generated_prefix ::= "generated-prefix" ":" STRING

  dep_hostname_char_set ::= "hostname-char-set" ":" STRING

  dep_hostname_char_replacement ::= "hostname-char-replacement" ":" STRING

  config_control ::= "config-control" ":" "{" config_control_params "}"

  sub_config_control ::= "{" config_control_params "}"

  config_control_params ::= config_control_param
                       | config_control_params "," config_control_param
                       | config_control_params ","

  config_control_param ::= config_databases
                      | config_fetch_wait_time

  config_databases ::= "config-databases" ":" "[" database_list "]"

  config_fetch_wait_time ::= "config-fetch-wait-time" ":" INTEGER

  loggers ::= "loggers" ":" "[" loggers_entries "]"

  loggers_entries ::= logger_entry
                 | loggers_entries "," logger_entry
                 | loggers_entries ","

  logger_entry ::= "{" logger_params "}"

  logger_params ::= logger_param
               | logger_params "," logger_param
               | logger_params ","

  logger_param ::= name
              | output_options_list
              | debuglevel
              | severity
              | user_context
              | comment
              | unknown_map_entry

  debuglevel ::= "debuglevel" ":" INTEGER

  severity ::= "severity" ":" STRING

  output_options_list ::= "output_options" ":" "[" output_options_list_content "]"

  output_options_list_content ::= output_entry
                             | output_options_list_content "," output_entry
                             | output_options_list_content ","

  output_entry ::= "{" output_params_list "}"

  output_params_list ::= output_params
                    | output_params_list "," output_params
                    | output_params_list ","

  output_params ::= output
               | flush
               | maxsize
               | maxver
               | pattern

  output ::= "output" ":" STRING

  flush ::= "flush" ":" BOOLEAN

  maxsize ::= "maxsize" ":" INTEGER

  maxver ::= "maxver" ":" INTEGER

  pattern ::= "pattern" ":" STRING

  compatibility ::= "compatibility" ":" "{" compatibility_params "}"

  compatibility_params ::= compatibility_param
                      | compatibility_params "," compatibility_param
                      | compatibility_params ","

  compatibility_param ::= lenient_option_parsing
                     | unknown_map_entry

  lenient_option_parsing ::= "lenient-option-parsing" ":" BOOLEAN

BNF Grammar for DHCPv6

This grammar is generated from dhcp6_parser.yy. See The DHCPv6 Server for more details.

  Grammar

  $accept ::= start EOF

  start ::= TOPLEVEL_JSON sub_json

  start ::= TOPLEVEL_DHCP6 syntax_map

  start ::= SUB_DHCP6 sub_dhcp6

  start ::= SUB_INTERFACES6 sub_interfaces6

  start ::= SUB_SUBNET6 sub_subnet6

  start ::= SUB_POOL6 sub_pool6

  start ::= SUB_PD_POOL sub_pd_pool

  start ::= SUB_RESERVATION sub_reservation

  start ::= SUB_OPTION_DEFS sub_option_def_list

  start ::= SUB_OPTION_DEF sub_option_def

  start ::= SUB_OPTION_DATA sub_option_data

  start ::= SUB_HOOKS_LIBRARY sub_hooks_library

  start ::= SUB_DHCP_DDNS sub_dhcp_ddns

  start ::= SUB_CONFIG_CONTROL sub_config_control

  value ::= INTEGER
       | FLOAT
       | BOOLEAN
       | STRING
       | NULL
       | map2
       | list_generic

  sub_json ::= value

  map2 ::= "{" map_content "}"

  map_value ::= map2

  map_content ::=
             | not_empty_map

  not_empty_map ::= STRING ":" value
               | not_empty_map "," STRING ":" value
               | not_empty_map ","

  list_generic ::= "[" list_content "]"

  list_content ::=
              | not_empty_list

  not_empty_list ::= value
                | not_empty_list "," value
                | not_empty_list ","

  list_strings ::= "[" list_strings_content "]"

  list_strings_content ::=
                      | not_empty_list_strings

  not_empty_list_strings ::= STRING
                        | not_empty_list_strings "," STRING
                        | not_empty_list_strings ","

  unknown_map_entry ::= STRING ":"

  syntax_map ::= "{" global_object "}"

  global_object ::= "Dhcp6" ":" "{" global_params "}"
               | global_object_comma

  global_object_comma ::= global_object ","

  sub_dhcp6 ::= "{" global_params "}"

  global_params ::= global_param
               | global_params "," global_param
               | global_params ","

  global_param ::= data_directory
              | preferred_lifetime
              | min_preferred_lifetime
              | max_preferred_lifetime
              | valid_lifetime
              | min_valid_lifetime
              | max_valid_lifetime
              | renew_timer
              | rebind_timer
              | decline_probation_period
              | subnet6_list
              | shared_networks
              | interfaces_config
              | lease_database
              | hosts_database
              | hosts_databases
              | mac_sources
              | relay_supplied_options
              | host_reservation_identifiers
              | client_classes
              | option_def_list
              | option_data_list
              | hooks_libraries
              | expired_leases_processing
              | server_id
              | dhcp4o6_port
              | control_socket
              | dhcp_queue_control
              | dhcp_ddns
              | user_context
              | comment
              | sanity_checks
              | reservations
              | config_control
              | server_tag
              | reservation_mode
              | reservations_global
              | reservations_in_subnet
              | reservations_out_of_pool
              | calculate_tee_times
              | t1_percent
              | t2_percent
              | cache_threshold
              | cache_max_age
              | loggers
              | hostname_char_set
              | hostname_char_replacement
              | ddns_send_updates
              | ddns_override_no_update
              | ddns_override_client_update
              | ddns_replace_client_name
              | ddns_generated_prefix
              | ddns_qualifying_suffix
              | ddns_update_on_renew
              | ddns_use_conflict_resolution
              | store_extended_info
              | statistic_default_sample_count
              | statistic_default_sample_age
              | dhcp_multi_threading
              | early_global_reservations_lookup
              | ip_reservations_unique
              | reservations_lookup_first
              | compatibility
              | parked_packet_limit
              | unknown_map_entry

  data_directory ::= "data-directory" ":" STRING

  preferred_lifetime ::= "preferred-lifetime" ":" INTEGER

  min_preferred_lifetime ::= "min-preferred-lifetime" ":" INTEGER

  max_preferred_lifetime ::= "max-preferred-lifetime" ":" INTEGER

  valid_lifetime ::= "valid-lifetime" ":" INTEGER

  min_valid_lifetime ::= "min-valid-lifetime" ":" INTEGER

  max_valid_lifetime ::= "max-valid-lifetime" ":" INTEGER

  renew_timer ::= "renew-timer" ":" INTEGER

  rebind_timer ::= "rebind-timer" ":" INTEGER

  calculate_tee_times ::= "calculate-tee-times" ":" BOOLEAN

  t1_percent ::= "t1-percent" ":" FLOAT

  t2_percent ::= "t2-percent" ":" FLOAT

  cache_threshold ::= "cache-threshold" ":" FLOAT

  cache_max_age ::= "cache-max-age" ":" INTEGER

  decline_probation_period ::= "decline-probation-period" ":" INTEGER

  ddns_send_updates ::= "ddns-send-updates" ":" BOOLEAN

  ddns_override_no_update ::= "ddns-override-no-update" ":" BOOLEAN

  ddns_override_client_update ::= "ddns-override-client-update" ":" BOOLEAN

  ddns_replace_client_name ::= "ddns-replace-client-name" ":" ddns_replace_client_name_value

  ddns_replace_client_name_value ::= "when-present"
                                | "never"
                                | "always"
                                | "when-not-present"
                                | BOOLEAN

  ddns_generated_prefix ::= "ddns-generated-prefix" ":" STRING

  ddns_qualifying_suffix ::= "ddns-qualifying-suffix" ":" STRING

  ddns_update_on_renew ::= "ddns-update-on-renew" ":" BOOLEAN

  ddns_use_conflict_resolution ::= "ddns-use-conflict-resolution" ":" BOOLEAN

  hostname_char_set ::= "hostname-char-set" ":" STRING

  hostname_char_replacement ::= "hostname-char-replacement" ":" STRING

  store_extended_info ::= "store-extended-info" ":" BOOLEAN

  statistic_default_sample_count ::= "statistic-default-sample-count" ":" INTEGER

  statistic_default_sample_age ::= "statistic-default-sample-age" ":" INTEGER

  server_tag ::= "server-tag" ":" STRING

  parked_packet_limit ::= "parked-packet-limit" ":" INTEGER

  early_global_reservations_lookup ::= "early-global-reservations-lookup" ":" BOOLEAN

  ip_reservations_unique ::= "ip-reservations-unique" ":" BOOLEAN

  reservations_lookup_first ::= "reservations-lookup-first" ":" BOOLEAN

  interfaces_config ::= "interfaces-config" ":" "{" interfaces_config_params "}"

  sub_interfaces6 ::= "{" interfaces_config_params "}"

  interfaces_config_params ::= interfaces_config_param
                          | interfaces_config_params "," interfaces_config_param
                          | interfaces_config_params ","

  interfaces_config_param ::= interfaces_list
                         | re_detect
                         | service_sockets_require_all
                         | service_sockets_retry_wait_time
                         | service_sockets_max_retries
                         | user_context
                         | comment
                         | unknown_map_entry

  interfaces_list ::= "interfaces" ":" list_strings

  re_detect ::= "re-detect" ":" BOOLEAN

  service_sockets_require_all ::= "service-sockets-require-all" ":" BOOLEAN

  service_sockets_retry_wait_time ::= "service-sockets-retry-wait-time" ":" INTEGER

  service_sockets_max_retries ::= "service-sockets-max-retries" ":" INTEGER

  lease_database ::= "lease-database" ":" "{" database_map_params "}"

  hosts_database ::= "hosts-database" ":" "{" database_map_params "}"

  hosts_databases ::= "hosts-databases" ":" "[" database_list "]"

  database_list ::=
               | not_empty_database_list

  not_empty_database_list ::= database
                         | not_empty_database_list "," database
                         | not_empty_database_list ","

  database ::= "{" database_map_params "}"

  database_map_params ::= database_map_param
                     | database_map_params "," database_map_param
                     | database_map_params ","

  database_map_param ::= database_type
                    | user
                    | password
                    | host
                    | port
                    | name
                    | persist
                    | lfc_interval
                    | readonly
                    | connect_timeout
                    | max_reconnect_tries
                    | reconnect_wait_time
                    | on_fail
                    | max_row_errors
                    | trust_anchor
                    | cert_file
                    | key_file
                    | cipher_list
                    | unknown_map_entry

  database_type ::= "type" ":" db_type

  db_type ::= "memfile"
         | "mysql"
         | "postgresql"

  user ::= "user" ":" STRING

  password ::= "password" ":" STRING

  host ::= "host" ":" STRING

  port ::= "port" ":" INTEGER

  name ::= "name" ":" STRING

  persist ::= "persist" ":" BOOLEAN

  lfc_interval ::= "lfc-interval" ":" INTEGER

  readonly ::= "readonly" ":" BOOLEAN

  connect_timeout ::= "connect-timeout" ":" INTEGER

  reconnect_wait_time ::= "reconnect-wait-time" ":" INTEGER

  on_fail ::= "on-fail" ":" on_fail_mode

  on_fail_mode ::= "stop-retry-exit"
              | "serve-retry-exit"
              | "serve-retry-continue"

  max_row_errors ::= "max-row-errors" ":" INTEGER

  max_reconnect_tries ::= "max-reconnect-tries" ":" INTEGER

  trust_anchor ::= "trust-anchor" ":" STRING

  cert_file ::= "cert-file" ":" STRING

  key_file ::= "key-file" ":" STRING

  cipher_list ::= "cipher-list" ":" STRING

  sanity_checks ::= "sanity-checks" ":" "{" sanity_checks_params "}"

  sanity_checks_params ::= sanity_checks_param
                      | sanity_checks_params "," sanity_checks_param
                      | sanity_checks_params ","

  sanity_checks_param ::= lease_checks

  lease_checks ::= "lease-checks" ":" STRING

  mac_sources ::= "mac-sources" ":" "[" mac_sources_list "]"

  mac_sources_list ::= mac_sources_value
                  | mac_sources_list "," mac_sources_value
                  | mac_sources_list ","

  mac_sources_value ::= duid_id
                   | string_id

  duid_id ::= "duid"

  string_id ::= STRING

  host_reservation_identifiers ::= "host-reservation-identifiers" ":" "[" host_reservation_identifiers_list "]"

  host_reservation_identifiers_list ::= host_reservation_identifier
                                   | host_reservation_identifiers_list "," host_reservation_identifier
                                   | host_reservation_identifiers_list ","

  host_reservation_identifier ::= duid_id
                             | hw_address_id
                             | flex_id

  hw_address_id ::= "hw-address"

  flex_id ::= "flex-id"

  relay_supplied_options ::= "relay-supplied-options" ":" "[" list_content "]"

  dhcp_multi_threading ::= "multi-threading" ":" "{" multi_threading_params "}"

  multi_threading_params ::= multi_threading_param
                        | multi_threading_params "," multi_threading_param
                        | multi_threading_params ","

  multi_threading_param ::= enable_multi_threading
                       | thread_pool_size
                       | packet_queue_size
                       | user_context
                       | comment
                       | unknown_map_entry

  enable_multi_threading ::= "enable-multi-threading" ":" BOOLEAN

  thread_pool_size ::= "thread-pool-size" ":" INTEGER

  packet_queue_size ::= "packet-queue-size" ":" INTEGER

  hooks_libraries ::= "hooks-libraries" ":" "[" hooks_libraries_list "]"

  hooks_libraries_list ::=
                      | not_empty_hooks_libraries_list

  not_empty_hooks_libraries_list ::= hooks_library
                                | not_empty_hooks_libraries_list "," hooks_library
                                | not_empty_hooks_libraries_list ","

  hooks_library ::= "{" hooks_params "}"

  sub_hooks_library ::= "{" hooks_params "}"

  hooks_params ::= hooks_param
              | hooks_params "," hooks_param
              | hooks_params ","
              | unknown_map_entry

  hooks_param ::= library
             | parameters

  library ::= "library" ":" STRING

  parameters ::= "parameters" ":" map_value

  expired_leases_processing ::= "expired-leases-processing" ":" "{" expired_leases_params "}"

  expired_leases_params ::= expired_leases_param
                       | expired_leases_params "," expired_leases_param
                       | expired_leases_params ","

  expired_leases_param ::= reclaim_timer_wait_time
                      | flush_reclaimed_timer_wait_time
                      | hold_reclaimed_time
                      | max_reclaim_leases
                      | max_reclaim_time
                      | unwarned_reclaim_cycles

  reclaim_timer_wait_time ::= "reclaim-timer-wait-time" ":" INTEGER

  flush_reclaimed_timer_wait_time ::= "flush-reclaimed-timer-wait-time" ":" INTEGER

  hold_reclaimed_time ::= "hold-reclaimed-time" ":" INTEGER

  max_reclaim_leases ::= "max-reclaim-leases" ":" INTEGER

  max_reclaim_time ::= "max-reclaim-time" ":" INTEGER

  unwarned_reclaim_cycles ::= "unwarned-reclaim-cycles" ":" INTEGER

  subnet6_list ::= "subnet6" ":" "[" subnet6_list_content "]"

  subnet6_list_content ::=
                      | not_empty_subnet6_list

  not_empty_subnet6_list ::= subnet6
                        | not_empty_subnet6_list "," subnet6
                        | not_empty_subnet6_list ","

  subnet6 ::= "{" subnet6_params "}"

  sub_subnet6 ::= "{" subnet6_params "}"

  subnet6_params ::= subnet6_param
                | subnet6_params "," subnet6_param
                | subnet6_params ","

  subnet6_param ::= preferred_lifetime
               | min_preferred_lifetime
               | max_preferred_lifetime
               | valid_lifetime
               | min_valid_lifetime
               | max_valid_lifetime
               | renew_timer
               | rebind_timer
               | option_data_list
               | pools_list
               | pd_pools_list
               | subnet
               | interface
               | interface_id
               | id
               | rapid_commit
               | client_class
               | require_client_classes
               | reservations
               | reservation_mode
               | reservations_global
               | reservations_in_subnet
               | reservations_out_of_pool
               | relay
               | user_context
               | comment
               | calculate_tee_times
               | t1_percent
               | t2_percent
               | cache_threshold
               | cache_max_age
               | hostname_char_set
               | hostname_char_replacement
               | ddns_send_updates
               | ddns_override_no_update
               | ddns_override_client_update
               | ddns_replace_client_name
               | ddns_generated_prefix
               | ddns_qualifying_suffix
               | ddns_update_on_renew
               | ddns_use_conflict_resolution
               | store_extended_info
               | unknown_map_entry

  subnet ::= "subnet" ":" STRING

  interface ::= "interface" ":" STRING

  interface_id ::= "interface-id" ":" STRING

  client_class ::= "client-class" ":" STRING

  require_client_classes ::= "require-client-classes" ":" list_strings

  reservations_global ::= "reservations-global" ":" BOOLEAN

  reservations_in_subnet ::= "reservations-in-subnet" ":" BOOLEAN

  reservations_out_of_pool ::= "reservations-out-of-pool" ":" BOOLEAN

  reservation_mode ::= "reservation-mode" ":" hr_mode

  hr_mode ::= "disabled"
         | "out-of-pool"
         | "global"
         | "all"

  id ::= "id" ":" INTEGER

  rapid_commit ::= "rapid-commit" ":" BOOLEAN

  shared_networks ::= "shared-networks" ":" "[" shared_networks_content "]"

  shared_networks_content ::=
                         | shared_networks_list

  shared_networks_list ::= shared_network
                      | shared_networks_list "," shared_network
                      | shared_networks_list ","

  shared_network ::= "{" shared_network_params "}"

  shared_network_params ::= shared_network_param
                       | shared_network_params "," shared_network_param
                       | shared_network_params ","

  shared_network_param ::= name
                      | subnet6_list
                      | interface
                      | interface_id
                      | renew_timer
                      | rebind_timer
                      | option_data_list
                      | relay
                      | reservation_mode
                      | reservations_global
                      | reservations_in_subnet
                      | reservations_out_of_pool
                      | client_class
                      | require_client_classes
                      | preferred_lifetime
                      | min_preferred_lifetime
                      | max_preferred_lifetime
                      | rapid_commit
                      | valid_lifetime
                      | min_valid_lifetime
                      | max_valid_lifetime
                      | user_context
                      | comment
                      | calculate_tee_times
                      | t1_percent
                      | t2_percent
                      | cache_threshold
                      | cache_max_age
                      | hostname_char_set
                      | hostname_char_replacement
                      | ddns_send_updates
                      | ddns_override_no_update
                      | ddns_override_client_update
                      | ddns_replace_client_name
                      | ddns_generated_prefix
                      | ddns_qualifying_suffix
                      | ddns_update_on_renew
                      | ddns_use_conflict_resolution
                      | store_extended_info
                      | unknown_map_entry

  option_def_list ::= "option-def" ":" "[" option_def_list_content "]"

  sub_option_def_list ::= "{" option_def_list "}"

  option_def_list_content ::=
                         | not_empty_option_def_list

  not_empty_option_def_list ::= option_def_entry
                           | not_empty_option_def_list "," option_def_entry
                           | not_empty_option_def_list ","

  option_def_entry ::= "{" option_def_params "}"

  sub_option_def ::= "{" option_def_params "}"

  option_def_params ::=
                   | not_empty_option_def_params

  not_empty_option_def_params ::= option_def_param
                             | not_empty_option_def_params "," option_def_param
                             | not_empty_option_def_params ","

  option_def_param ::= option_def_name
                  | option_def_code
                  | option_def_type
                  | option_def_record_types
                  | option_def_space
                  | option_def_encapsulate
                  | option_def_array
                  | user_context
                  | comment
                  | unknown_map_entry

  option_def_name ::= name

  code ::= "code" ":" INTEGER

  option_def_code ::= code

  option_def_type ::= "type" ":" STRING

  option_def_record_types ::= "record-types" ":" STRING

  space ::= "space" ":" STRING

  option_def_space ::= space

  option_def_encapsulate ::= "encapsulate" ":" STRING

  option_def_array ::= "array" ":" BOOLEAN

  option_data_list ::= "option-data" ":" "[" option_data_list_content "]"

  option_data_list_content ::=
                          | not_empty_option_data_list

  not_empty_option_data_list ::= option_data_entry
                            | not_empty_option_data_list "," option_data_entry
                            | not_empty_option_data_list ","

  option_data_entry ::= "{" option_data_params "}"

  sub_option_data ::= "{" option_data_params "}"

  option_data_params ::=
                    | not_empty_option_data_params

  not_empty_option_data_params ::= option_data_param
                              | not_empty_option_data_params "," option_data_param
                              | not_empty_option_data_params ","

  option_data_param ::= option_data_name
                   | option_data_data
                   | option_data_code
                   | option_data_space
                   | option_data_csv_format
                   | option_data_always_send
                   | user_context
                   | comment
                   | unknown_map_entry

  option_data_name ::= name

  option_data_data ::= "data" ":" STRING

  option_data_code ::= code

  option_data_space ::= space

  option_data_csv_format ::= "csv-format" ":" BOOLEAN

  option_data_always_send ::= "always-send" ":" BOOLEAN

  pools_list ::= "pools" ":" "[" pools_list_content "]"

  pools_list_content ::=
                    | not_empty_pools_list

  not_empty_pools_list ::= pool_list_entry
                      | not_empty_pools_list "," pool_list_entry
                      | not_empty_pools_list ","

  pool_list_entry ::= "{" pool_params "}"

  sub_pool6 ::= "{" pool_params "}"

  pool_params ::= pool_param
             | pool_params "," pool_param
             | pool_params ","

  pool_param ::= pool_entry
            | option_data_list
            | client_class
            | require_client_classes
            | user_context
            | comment
            | unknown_map_entry

  pool_entry ::= "pool" ":" STRING

  user_context ::= "user-context" ":" map_value

  comment ::= "comment" ":" STRING

  pd_pools_list ::= "pd-pools" ":" "[" pd_pools_list_content "]"

  pd_pools_list_content ::=
                       | not_empty_pd_pools_list

  not_empty_pd_pools_list ::= pd_pool_entry
                         | not_empty_pd_pools_list "," pd_pool_entry
                         | not_empty_pd_pools_list ","

  pd_pool_entry ::= "{" pd_pool_params "}"

  sub_pd_pool ::= "{" pd_pool_params "}"

  pd_pool_params ::= pd_pool_param
                | pd_pool_params "," pd_pool_param
                | pd_pool_params ","

  pd_pool_param ::= pd_prefix
               | pd_prefix_len
               | pd_delegated_len
               | option_data_list
               | client_class
               | require_client_classes
               | excluded_prefix
               | excluded_prefix_len
               | user_context
               | comment
               | unknown_map_entry

  pd_prefix ::= "prefix" ":" STRING

  pd_prefix_len ::= "prefix-len" ":" INTEGER

  excluded_prefix ::= "excluded-prefix" ":" STRING

  excluded_prefix_len ::= "excluded-prefix-len" ":" INTEGER

  pd_delegated_len ::= "delegated-len" ":" INTEGER

  reservations ::= "reservations" ":" "[" reservations_list "]"

  reservations_list ::=
                   | not_empty_reservations_list

  not_empty_reservations_list ::= reservation
                             | not_empty_reservations_list "," reservation
                             | not_empty_reservations_list ","

  reservation ::= "{" reservation_params "}"

  sub_reservation ::= "{" reservation_params "}"

  reservation_params ::=
                    | not_empty_reservation_params

  not_empty_reservation_params ::= reservation_param
                              | not_empty_reservation_params "," reservation_param
                              | not_empty_reservation_params ","

  reservation_param ::= duid
                   | reservation_client_classes
                   | ip_addresses
                   | prefixes
                   | hw_address
                   | hostname
                   | flex_id_value
                   | option_data_list
                   | user_context
                   | comment
                   | unknown_map_entry

  ip_addresses ::= "ip-addresses" ":" list_strings

  prefixes ::= "prefixes" ":" list_strings

  duid ::= "duid" ":" STRING

  hw_address ::= "hw-address" ":" STRING

  hostname ::= "hostname" ":" STRING

  flex_id_value ::= "flex-id" ":" STRING

  reservation_client_classes ::= "client-classes" ":" list_strings

  relay ::= "relay" ":" "{" relay_map "}"

  relay_map ::= ip_address
           | ip_addresses

  ip_address ::= "ip-address" ":" STRING

  client_classes ::= "client-classes" ":" "[" client_classes_list "]"

  client_classes_list ::= client_class_entry
                     | client_classes_list "," client_class_entry
                     | client_classes_list ","

  client_class_entry ::= "{" client_class_params "}"

  client_class_params ::=
                     | not_empty_client_class_params

  not_empty_client_class_params ::= client_class_param
                               | not_empty_client_class_params "," client_class_param
                               | not_empty_client_class_params ","

  client_class_param ::= client_class_name
                    | client_class_test
                    | only_if_required
                    | option_data_list
                    | user_context
                    | comment
                    | preferred_lifetime
                    | min_preferred_lifetime
                    | max_preferred_lifetime
                    | valid_lifetime
                    | min_valid_lifetime
                    | max_valid_lifetime
                    | unknown_map_entry

  client_class_name ::= name

  client_class_test ::= "test" ":" STRING

  only_if_required ::= "only-if-required" ":" BOOLEAN

  server_id ::= "server-id" ":" "{" server_id_params "}"

  server_id_params ::= server_id_param
                  | server_id_params "," server_id_param
                  | server_id_params ","

  server_id_param ::= server_id_type
                 | identifier
                 | time
                 | htype
                 | enterprise_id
                 | persist
                 | user_context
                 | comment
                 | unknown_map_entry

  server_id_type ::= "type" ":" duid_type

  duid_type ::= "LLT"
           | "EN"
           | "LL"

  htype ::= "htype" ":" INTEGER

  identifier ::= "identifier" ":" STRING

  time ::= "time" ":" INTEGER

  enterprise_id ::= "enterprise-id" ":" INTEGER

  dhcp4o6_port ::= "dhcp4o6-port" ":" INTEGER

  control_socket ::= "control-socket" ":" "{" control_socket_params "}"

  control_socket_params ::= control_socket_param
                       | control_socket_params "," control_socket_param
                       | control_socket_params ","

  control_socket_param ::= socket_type
                      | socket_name
                      | user_context
                      | comment
                      | unknown_map_entry

  socket_type ::= "socket-type" ":" STRING

  socket_name ::= "socket-name" ":" STRING

  dhcp_queue_control ::= "dhcp-queue-control" ":" "{" queue_control_params "}"

  queue_control_params ::= queue_control_param
                      | queue_control_params "," queue_control_param
                      | queue_control_params ","

  queue_control_param ::= enable_queue
                     | queue_type
                     | capacity
                     | user_context
                     | comment
                     | arbitrary_map_entry

  enable_queue ::= "enable-queue" ":" BOOLEAN

  queue_type ::= "queue-type" ":" STRING

  capacity ::= "capacity" ":" INTEGER

  arbitrary_map_entry ::= STRING ":" value

  dhcp_ddns ::= "dhcp-ddns" ":" "{" dhcp_ddns_params "}"

  sub_dhcp_ddns ::= "{" dhcp_ddns_params "}"

  dhcp_ddns_params ::= dhcp_ddns_param
                  | dhcp_ddns_params "," dhcp_ddns_param
                  | dhcp_ddns_params ","

  dhcp_ddns_param ::= enable_updates
                 | server_ip
                 | server_port
                 | sender_ip
                 | sender_port
                 | max_queue_size
                 | ncr_protocol
                 | ncr_format
                 | dep_override_no_update
                 | dep_override_client_update
                 | dep_replace_client_name
                 | dep_generated_prefix
                 | dep_qualifying_suffix
                 | dep_hostname_char_set
                 | dep_hostname_char_replacement
                 | user_context
                 | comment
                 | unknown_map_entry

  enable_updates ::= "enable-updates" ":" BOOLEAN

  dep_qualifying_suffix ::= "qualifying-suffix" ":" STRING

  server_ip ::= "server-ip" ":" STRING

  server_port ::= "server-port" ":" INTEGER

  sender_ip ::= "sender-ip" ":" STRING

  sender_port ::= "sender-port" ":" INTEGER

  max_queue_size ::= "max-queue-size" ":" INTEGER

  ncr_protocol ::= "ncr-protocol" ":" ncr_protocol_value

  ncr_protocol_value ::= "UDP"
                    | "TCP"

  ncr_format ::= "ncr-format" ":" "JSON"

  dep_override_no_update ::= "override-no-update" ":" BOOLEAN

  dep_override_client_update ::= "override-client-update" ":" BOOLEAN

  dep_replace_client_name ::= "replace-client-name" ":" ddns_replace_client_name_value

  dep_generated_prefix ::= "generated-prefix" ":" STRING

  dep_hostname_char_set ::= "hostname-char-set" ":" STRING

  dep_hostname_char_replacement ::= "hostname-char-replacement" ":" STRING

  config_control ::= "config-control" ":" "{" config_control_params "}"

  sub_config_control ::= "{" config_control_params "}"

  config_control_params ::= config_control_param
                       | config_control_params "," config_control_param
                       | config_control_params ","

  config_control_param ::= config_databases
                      | config_fetch_wait_time

  config_databases ::= "config-databases" ":" "[" database_list "]"

  config_fetch_wait_time ::= "config-fetch-wait-time" ":" INTEGER

  loggers ::= "loggers" ":" "[" loggers_entries "]"

  loggers_entries ::= logger_entry
                 | loggers_entries "," logger_entry
                 | loggers_entries ","

  logger_entry ::= "{" logger_params "}"

  logger_params ::= logger_param
               | logger_params "," logger_param
               | logger_params ","

  logger_param ::= name
              | output_options_list
              | debuglevel
              | severity
              | user_context
              | comment
              | unknown_map_entry

  debuglevel ::= "debuglevel" ":" INTEGER

  severity ::= "severity" ":" STRING

  output_options_list ::= "output_options" ":" "[" output_options_list_content "]"

  output_options_list_content ::= output_entry
                             | output_options_list_content "," output_entry
                             | output_options_list_content ","

  output_entry ::= "{" output_params_list "}"

  output_params_list ::= output_params
                    | output_params_list "," output_params
                    | output_params_list ","

  output_params ::= output
               | flush
               | maxsize
               | maxver
               | pattern

  output ::= "output" ":" STRING

  flush ::= "flush" ":" BOOLEAN

  maxsize ::= "maxsize" ":" INTEGER

  maxver ::= "maxver" ":" INTEGER

  pattern ::= "pattern" ":" STRING

  compatibility ::= "compatibility" ":" "{" compatibility_params "}"

  compatibility_params ::= compatibility_param
                      | compatibility_params "," compatibility_param
                      | compatibility_params ","

  compatibility_param ::= lenient_option_parsing
                     | unknown_map_entry

  lenient_option_parsing ::= "lenient-option-parsing" ":" BOOLEAN

BNF Grammar for Control Agent

This grammar is generated from agent_parser.yy. See The Kea Control Agent for more details.

  Grammar

  $accept ::= start EOF

  start ::= START_JSON json

  start ::= START_AGENT agent_syntax_map

  start ::= START_SUB_AGENT sub_agent

  sub_agent ::= "{" global_params "}"

  json ::= value

  value ::= INTEGER
       | FLOAT
       | BOOLEAN
       | STRING
       | NULL
       | map
       | list_generic

  map ::= "{" map_content "}"

  map_value ::= map

  map_content ::=
             | not_empty_map

  not_empty_map ::= STRING ":" value
               | not_empty_map "," STRING ":" value
               | not_empty_map ","

  list_generic ::= "[" list_content "]"

  list_content ::=
              | not_empty_list

  not_empty_list ::= value
                | not_empty_list "," value
                | not_empty_list ","

  unknown_map_entry ::= STRING ":"

  agent_syntax_map ::= "{" global_object "}"

  global_object ::= "Control-agent" ":" "{" global_params "}"
               | global_object_comma

  global_object_comma ::= global_object ","

  global_params ::= global_param
               | global_params "," global_param
               | global_params ","

  global_param ::= http_host
              | http_port
              | trust_anchor
              | cert_file
              | key_file
              | cert_required
              | authentication
              | control_sockets
              | hooks_libraries
              | loggers
              | user_context
              | comment
              | unknown_map_entry

  http_host ::= "http-host" ":" STRING

  http_port ::= "http-port" ":" INTEGER

  trust_anchor ::= "trust-anchor" ":" STRING

  cert_file ::= "cert-file" ":" STRING

  key_file ::= "key-file" ":" STRING

  cert_required ::= "cert-required" ":" BOOLEAN

  user_context ::= "user-context" ":" map_value

  comment ::= "comment" ":" STRING

  hooks_libraries ::= "hooks-libraries" ":" "[" hooks_libraries_list "]"

  hooks_libraries_list ::=
                      | not_empty_hooks_libraries_list

  not_empty_hooks_libraries_list ::= hooks_library
                                | not_empty_hooks_libraries_list "," hooks_library
                                | not_empty_hooks_libraries_list ","

  hooks_library ::= "{" hooks_params "}"

  hooks_params ::= hooks_param
              | hooks_params "," hooks_param
              | hooks_params ","
              | unknown_map_entry

  hooks_param ::= library
             | parameters

  library ::= "library" ":" STRING

  parameters ::= "parameters" ":" map_value

  control_sockets ::= "control-sockets" ":" "{" control_sockets_params "}"

  control_sockets_params ::= control_socket
                        | control_sockets_params "," control_socket
                        | control_sockets_params ","

  control_socket ::= dhcp4_server_socket
                | dhcp6_server_socket
                | d2_server_socket
                | unknown_map_entry

  dhcp4_server_socket ::= "dhcp4" ":" "{" control_socket_params "}"

  dhcp6_server_socket ::= "dhcp6" ":" "{" control_socket_params "}"

  d2_server_socket ::= "d2" ":" "{" control_socket_params "}"

  control_socket_params ::= control_socket_param
                       | control_socket_params "," control_socket_param
                       | control_socket_params ","

  control_socket_param ::= socket_name
                      | socket_type
                      | user_context
                      | comment
                      | unknown_map_entry

  socket_name ::= "socket-name" ":" STRING

  socket_type ::= "socket-type" ":" socket_type_value

  socket_type_value ::= "unix"

  authentication ::= "authentication" ":" "{" auth_params "}"

  auth_params ::= auth_param
             | auth_params "," auth_param
             | auth_params ","

  auth_param ::= auth_type
            | realm
            | directory
            | clients
            | comment
            | user_context
            | unknown_map_entry

  auth_type ::= "type" ":" auth_type_value

  auth_type_value ::= "basic"

  realm ::= "realm" ":" STRING

  directory ::= "directory" ":" STRING

  clients ::= "clients" ":" "[" clients_list "]"

  clients_list ::=
              | not_empty_clients_list

  not_empty_clients_list ::= basic_auth
                        | not_empty_clients_list "," basic_auth
                        | not_empty_clients_list ","

  basic_auth ::= "{" clients_params "}"

  clients_params ::= clients_param
                | clients_params "," clients_param
                | clients_params ","

  clients_param ::= user
               | user_file
               | password
               | password_file
               | user_context
               | comment
               | unknown_map_entry

  user ::= "user" ":" STRING

  user_file ::= "user-file" ":" STRING

  password ::= "password" ":" STRING

  password_file ::= "password-file" ":" STRING

  loggers ::= "loggers" ":" "[" loggers_entries "]"

  loggers_entries ::= logger_entry
                 | loggers_entries "," logger_entry
                 | loggers_entries ","

  logger_entry ::= "{" logger_params "}"

  logger_params ::= logger_param
               | logger_params "," logger_param
               | logger_params ","

  logger_param ::= name
              | output_options_list
              | debuglevel
              | severity
              | user_context
              | comment
              | unknown_map_entry

  name ::= "name" ":" STRING

  debuglevel ::= "debuglevel" ":" INTEGER

  severity ::= "severity" ":" STRING

  output_options_list ::= "output_options" ":" "[" output_options_list_content "]"

  output_options_list_content ::= output_entry
                             | output_options_list_content "," output_entry
                             | output_options_list_content ","

  output_entry ::= "{" output_params_list "}"

  output_params_list ::= output_params
                    | output_params_list "," output_params
                    | output_params_list ","

  output_params ::= output
               | flush
               | maxsize
               | maxver
               | pattern

  output ::= "output" ":" STRING

  flush ::= "flush" ":" BOOLEAN

  maxsize ::= "maxsize" ":" INTEGER

  maxver ::= "maxver" ":" INTEGER

  pattern ::= "pattern" ":" STRING

BNF Grammar for DHCP-DDNS

This grammar is generated from d2_parser.yy. See The DHCP-DDNS Server for more details.

  Grammar

  $accept ::= start EOF

  start ::= TOPLEVEL_JSON sub_json

  start ::= TOPLEVEL_DHCPDDNS syntax_map

  start ::= SUB_DHCPDDNS sub_dhcpddns

  start ::= SUB_TSIG_KEY sub_tsig_key

  start ::= SUB_TSIG_KEYS sub_tsig_keys

  start ::= SUB_DDNS_DOMAIN sub_ddns_domain

  start ::= SUB_DDNS_DOMAINS sub_ddns_domains

  start ::= SUB_DNS_SERVER sub_dns_server

  start ::= SUB_DNS_SERVERS sub_dns_servers

  start ::= SUB_HOOKS_LIBRARY sub_hooks_library

  value ::= INTEGER
       | FLOAT
       | BOOLEAN
       | STRING
       | NULL
       | map2
       | list_generic

  sub_json ::= value

  map2 ::= "{" map_content "}"

  map_value ::= map2

  map_content ::=
             | not_empty_map

  not_empty_map ::= STRING ":" value
               | not_empty_map "," STRING ":" value
               | not_empty_map ","

  list_generic ::= "[" list_content "]"

  list_content ::=
              | not_empty_list

  not_empty_list ::= value
                | not_empty_list "," value
                | not_empty_list ","

  unknown_map_entry ::= STRING ":"

  syntax_map ::= "{" global_object "}"

  global_object ::= "DhcpDdns" ":" "{" dhcpddns_params "}"
               | global_object_comma

  global_object_comma ::= global_object ","

  sub_dhcpddns ::= "{" dhcpddns_params "}"

  dhcpddns_params ::= dhcpddns_param
                 | dhcpddns_params "," dhcpddns_param
                 | dhcpddns_params ","

  dhcpddns_param ::= ip_address
                | port
                | dns_server_timeout
                | ncr_protocol
                | ncr_format
                | forward_ddns
                | reverse_ddns
                | tsig_keys
                | control_socket
                | hooks_libraries
                | loggers
                | user_context
                | comment
                | unknown_map_entry

  ip_address ::= "ip-address" ":" STRING

  port ::= "port" ":" INTEGER

  dns_server_timeout ::= "dns-server-timeout" ":" INTEGER

  ncr_protocol ::= "ncr-protocol" ":" ncr_protocol_value

  ncr_protocol_value ::= "UDP"
                    | "TCP"

  ncr_format ::= "ncr-format" ":" "JSON"

  user_context ::= "user-context" ":" map_value

  comment ::= "comment" ":" STRING

  forward_ddns ::= "forward-ddns" ":" "{" ddns_mgr_params "}"

  reverse_ddns ::= "reverse-ddns" ":" "{" ddns_mgr_params "}"

  ddns_mgr_params ::=
                 | not_empty_ddns_mgr_params

  not_empty_ddns_mgr_params ::= ddns_mgr_param
                           | ddns_mgr_params "," ddns_mgr_param
                           | ddns_mgr_params ","

  ddns_mgr_param ::= ddns_domains
                | unknown_map_entry

  ddns_domains ::= "ddns-domains" ":" "[" ddns_domain_list "]"

  sub_ddns_domains ::= "[" ddns_domain_list "]"

  ddns_domain_list ::=
                  | not_empty_ddns_domain_list

  not_empty_ddns_domain_list ::= ddns_domain
                            | not_empty_ddns_domain_list "," ddns_domain
                            | not_empty_ddns_domain_list ","

  ddns_domain ::= "{" ddns_domain_params "}"

  sub_ddns_domain ::= "{" ddns_domain_params "}"

  ddns_domain_params ::= ddns_domain_param
                    | ddns_domain_params "," ddns_domain_param
                    | ddns_domain_params ","

  ddns_domain_param ::= ddns_domain_name
                   | ddns_key_name
                   | dns_servers
                   | user_context
                   | comment
                   | unknown_map_entry

  ddns_domain_name ::= "name" ":" STRING

  ddns_key_name ::= "key-name" ":" STRING

  dns_servers ::= "dns-servers" ":" "[" dns_server_list "]"

  sub_dns_servers ::= "[" dns_server_list "]"

  dns_server_list ::= dns_server
                 | dns_server_list "," dns_server
                 | dns_server_list ","

  dns_server ::= "{" dns_server_params "}"

  sub_dns_server ::= "{" dns_server_params "}"

  dns_server_params ::= dns_server_param
                   | dns_server_params "," dns_server_param
                   | dns_server_params ","

  dns_server_param ::= dns_server_hostname
                  | dns_server_ip_address
                  | dns_server_port
                  | ddns_key_name
                  | user_context
                  | comment
                  | unknown_map_entry

  dns_server_hostname ::= "hostname" ":" STRING

  dns_server_ip_address ::= "ip-address" ":" STRING

  dns_server_port ::= "port" ":" INTEGER

  tsig_keys ::= "tsig-keys" ":" "[" tsig_keys_list "]"

  sub_tsig_keys ::= "[" tsig_keys_list "]"

  tsig_keys_list ::=
                | not_empty_tsig_keys_list

  not_empty_tsig_keys_list ::= tsig_key
                          | not_empty_tsig_keys_list "," tsig_key
                          | not_empty_tsig_keys_list ","

  tsig_key ::= "{" tsig_key_params "}"

  sub_tsig_key ::= "{" tsig_key_params "}"

  tsig_key_params ::= tsig_key_param
                 | tsig_key_params "," tsig_key_param
                 | tsig_key_params ","

  tsig_key_param ::= tsig_key_name
                | tsig_key_algorithm
                | tsig_key_digest_bits
                | tsig_key_secret
                | user_context
                | comment
                | unknown_map_entry

  tsig_key_name ::= "name" ":" STRING

  tsig_key_algorithm ::= "algorithm" ":" STRING

  tsig_key_digest_bits ::= "digest-bits" ":" INTEGER

  tsig_key_secret ::= "secret" ":" STRING

  control_socket ::= "control-socket" ":" "{" control_socket_params "}"

  control_socket_params ::= control_socket_param
                       | control_socket_params "," control_socket_param
                       | control_socket_params ","

  control_socket_param ::= control_socket_type
                      | control_socket_name
                      | user_context
                      | comment
                      | unknown_map_entry

  control_socket_type ::= "socket-type" ":" STRING

  control_socket_name ::= "socket-name" ":" STRING

  hooks_libraries ::= "hooks-libraries" ":" "[" hooks_libraries_list "]"

  hooks_libraries_list ::=
                      | not_empty_hooks_libraries_list

  not_empty_hooks_libraries_list ::= hooks_library
                                | not_empty_hooks_libraries_list "," hooks_library
                                | not_empty_hooks_libraries_list ","

  hooks_library ::= "{" hooks_params "}"

  sub_hooks_library ::= "{" hooks_params "}"

  hooks_params ::= hooks_param
              | hooks_params "," hooks_param
              | hooks_params ","
              | unknown_map_entry

  hooks_param ::= library
             | parameters

  library ::= "library" ":" STRING

  parameters ::= "parameters" ":" map_value

  loggers ::= "loggers" ":" "[" loggers_entries "]"

  loggers_entries ::= logger_entry
                 | loggers_entries "," logger_entry
                 | loggers_entries ","

  logger_entry ::= "{" logger_params "}"

  logger_params ::= logger_param
               | logger_params "," logger_param
               | logger_params ","

  logger_param ::= name
              | output_options_list
              | debuglevel
              | severity
              | user_context
              | comment
              | unknown_map_entry

  name ::= "name" ":" STRING

  debuglevel ::= "debuglevel" ":" INTEGER

  severity ::= "severity" ":" STRING

  output_options_list ::= "output_options" ":" "[" output_options_list_content "]"

  output_options_list_content ::= output_entry
                             | output_options_list_content "," output_entry
                             | output_options_list_content ","

  output_entry ::= "{" output_params_list "}"

  output_params_list ::= output_params
                    | output_params_list "," output_params
                    | output_params_list ","

  output_params ::= output
               | flush
               | maxsize
               | maxver
               | pattern

  output ::= "output" ":" STRING

  flush ::= "flush" ":" BOOLEAN

  maxsize ::= "maxsize" ":" INTEGER

  maxver ::= "maxver" ":" INTEGER

  pattern ::= "pattern" ":" STRING

BNF Grammar for the Kea NETCONF Agent

This grammar is generated from netconf_parser.yy. See YANG/NETCONF for more details.

  Grammar

  $accept ::= start EOF

  start ::= START_JSON json

  start ::= START_NETCONF netconf_syntax_map

  start ::= START_SUB_NETCONF sub_netconf

  sub_netconf ::= "{" global_params "}"

  json ::= value

  value ::= INTEGER
       | FLOAT
       | BOOLEAN
       | STRING
       | NULL
       | map
       | list_generic

  map ::= "{" map_content "}"

  map_value ::= map

  map_content ::=
             | not_empty_map

  not_empty_map ::= STRING ":" value
               | not_empty_map "," STRING ":" value
               | not_empty_map ","

  list_generic ::= "[" list_content "]"

  list_content ::=
              | not_empty_list

  not_empty_list ::= value
                | not_empty_list "," value
                | not_empty_list ","

  unknown_map_entry ::= STRING ":"

  netconf_syntax_map ::= "{" global_object "}"

  global_object ::= "Netconf" ":" "{" global_params "}"
               | global_object_comma

  global_object_comma ::= global_object ","

  global_params ::=
               | not_empty_global_params

  not_empty_global_params ::= global_param
                         | not_empty_global_params "," global_param
                         | not_empty_global_params ","

  global_param ::= boot_update
              | subscribe_changes
              | validate_changes
              | managed_servers
              | hooks_libraries
              | loggers
              | user_context
              | comment
              | unknown_map_entry

  boot_update ::= "boot-update" ":" BOOLEAN

  subscribe_changes ::= "subscribe-changes" ":" BOOLEAN

  validate_changes ::= "validate-changes" ":" BOOLEAN

  user_context ::= "user-context" ":" map_value

  comment ::= "comment" ":" STRING

  hooks_libraries ::= "hooks-libraries" ":" "[" hooks_libraries_list "]"

  hooks_libraries_list ::=
                      | not_empty_hooks_libraries_list

  not_empty_hooks_libraries_list ::= hooks_library
                                | not_empty_hooks_libraries_list "," hooks_library
                                | not_empty_hooks_libraries_list ","

  hooks_library ::= "{" hooks_params "}"

  hooks_params ::= hooks_param
              | hooks_params "," hooks_param
              | hooks_params ","
              | unknown_map_entry

  hooks_param ::= library
             | parameters

  library ::= "library" ":" STRING

  parameters ::= "parameters" ":" map_value

  managed_servers ::= "managed-servers" ":" "{" servers_entries "}"

  servers_entries ::=
                 | not_empty_servers_entries

  not_empty_servers_entries ::= server_entry
                           | not_empty_servers_entries "," server_entry
                           | not_empty_servers_entries ","

  server_entry ::= dhcp4_server
              | dhcp6_server
              | d2_server
              | ca_server
              | unknown_map_entry

  dhcp4_server ::= "dhcp4" ":" "{" managed_server_params "}"

  dhcp6_server ::= "dhcp6" ":" "{" managed_server_params "}"

  d2_server ::= "d2" ":" "{" managed_server_params "}"

  ca_server ::= "ca" ":" "{" managed_server_params "}"

  managed_server_params ::= managed_server_param
                       | managed_server_params "," managed_server_param
                       | managed_server_params ","

  managed_server_param ::= model
                      | boot_update
                      | subscribe_changes
                      | validate_changes
                      | control_socket
                      | user_context
                      | comment
                      | unknown_map_entry

  model ::= "model" ":" STRING

  control_socket ::= "control-socket" ":" "{" control_socket_params "}"

  control_socket_params ::= control_socket_param
                       | control_socket_params "," control_socket_param
                       | control_socket_params ","

  control_socket_param ::= socket_type
                      | socket_name
                      | socket_url
                      | user_context
                      | comment
                      | unknown_map_entry

  socket_type ::= "socket-type" ":" socket_type_value

  socket_type_value ::= "unix"
                   | "http"
                   | "stdout"

  socket_name ::= "socket-name" ":" STRING

  socket_url ::= "socket-url" ":" STRING

  loggers ::= "loggers" ":" "[" loggers_entries "]"

  loggers_entries ::= logger_entry
                 | loggers_entries "," logger_entry
                 | loggers_entries ","

  logger_entry ::= "{" logger_params "}"

  logger_params ::= logger_param
               | logger_params "," logger_param
               | logger_params ","

  logger_param ::= name
              | output_options_list
              | debuglevel
              | severity
              | user_context
              | comment
              | unknown_map_entry

  name ::= "name" ":" STRING

  debuglevel ::= "debuglevel" ":" INTEGER

  severity ::= "severity" ":" STRING

  output_options_list ::= "output_options" ":" "[" output_options_list_content "]"

  output_options_list_content ::= output_entry
                             | output_options_list_content "," output_entry
                             | output_options_list_content ","

  output_entry ::= "{" output_params_list "}"

  output_params_list ::= output_params
                    | output_params_list "," output_params
                    | output_params_list ","

  output_params ::= output
               | flush
               | maxsize
               | maxver
               | pattern

  output ::= "output" ":" STRING

  flush ::= "flush" ":" BOOLEAN

  maxsize ::= "maxsize" ":" INTEGER

  maxver ::= "maxver" ":" INTEGER

  pattern ::= "pattern" ":" STRING

Acknowledgments

Kea is an open source project designed, developed, and maintained by Internet Systems Consortium, Inc, a 501(c)3 non-profit organization. ISC is primarily funded by revenues from support subscriptions for our open source, and we encourage all professional users to consider this option. To learn more, see https://www.isc.org/support/.

We thank all the organizations and individuals who have helped to make Kea possible. Comcast and the Comcast Innovation Fund provided major support for the development of Kea’s DHCPv4, DHCPv6, and DDNS modules. Mozilla funded initial work on the RESTful API via a MOSS award.

Kea was initially implemented as a collection of applications within the BIND 10 framework. We thank the founding sponsors of the BIND 10 project: Afilias, IIS.SE, Nominet, SIDN, JPRS, and CIRA; and additional sponsors AFNIC, CNNIC, CZ.NIC, DENIC eG, Google, RIPE NCC, Registro.br, .nz Registry Services, and Technical Center of Internet.