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.. _hooks-libraries:
***************
Hook Libraries
***************
.. _hooks-libraries-introduction:
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 <https://reports.kea.isc.org/dev_guide/df/d46/hooksdgDevelopersGuide.html>`__.
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 introduced in
Kea 1.4 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 <https://kb.isc.org/docs/aa-01587>`__.
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 :ref:`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 |release|.,
there should be a tarball called ``kea-|release|.tar.gz`` on the system.
Unpack this tarball:
.. parsed-literal::
$ tar -zxvf kea-|release|.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 |release| 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:
.. parsed-literal::
$ cd kea-|release|
$ tar -xvf ../kea-premium-|release|.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:
.. parsed-literal::
Package:
Name: kea
Version: |release|
Extended version: |release| (tarball)
OS Family: Linux
Using GNU sed: yes
Premium package: yes
Included Hooks: forensic_log flex_id host_cmds subnet_cmds radius host_cache class_cmds cb_cmds lease_query
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/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::
This syntax is effective as of Kea 1.1.0, to facilitate the
specification of library-specific parameters. Libraries should allow a
parameter entry for comments, as is the case with many configuration
scopes.
.. note::
In all versions of Kea since 1.1.0, 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
<https://reports.kea.isc.org/dev_guide/df/d46/hooksdgDevelopersGuide.html>`__.
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.
.. tabularcolumns:: |p{0.1\linewidth}|p{0.1\linewidth}|p{0.8\linewidth}|
.. table:: List of available hook libraries
:class: longtable
:widths: 10 10 80
+-----------------+---------------+------------------------------------------------------------+
| Name | Availability | Description |
+=================+===============+============================================================+
| User Check | Kea open |Reads known users list from a file. Unknown users will be |
| | source |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 | ISC support |This library provides hooks that record a detailed log of |
| Logging | customers |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 | ISC support |Kea software provides a way to handle host reservations that|
| Identifier | customers |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 | Kea open |This library provides hooks that compute option values |
| Option | source |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 |Kea provides a way to store host reservations in a |
| | customers |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 |In deployments in which subnet configuration needs to be |
| | customers |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 |This hook library offers a number of |
| | source |commands used to manage leases. Kea can store |
| | |lease information in various backends: memfile, MySQL, |
| | |PostgreSQL, and Cassandra. 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 | Kea open |The risk of DHCP service unavailability can be minimized |
| Availability | source |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 | Kea open |This library provides additional |
| Commands | source |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 |The RADIUS hook library allows Kea to interact with |
| | customers |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 |Some database backends, such as RADIUS, |
| | customers |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 |This hook library allows configured DHCP client classes to |
| | customers |be added, updated, deleted, and fetched without |
| | |needing to restart the DHCP server. |
+-----------------+---------------+------------------------------------------------------------+
| MySQL | Kea open |This hook library is an implementation of the Kea |
| Configuration | source |Configuration Backend for MySQL. It uses a MySQL database as|
| Backend | |a repository for the Kea configuration information. Kea |
| | |servers use this library to fetch their configurations. |
+-----------------+---------------+------------------------------------------------------------+
| Configuration | ISC support |This hook |
| Backend | customers |library implements a collection of commands to manage |
| Commands | |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 |This hook library adds BOOTP support, as defined in |
| | source |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 |This library adds support for DHCPv4 |
| | customers |Leasequery as described in RFC 4388; and for DHCPv6 |
| | |Leasequery as described in RFC 5007. |
+-----------------+---------------+------------------------------------------------------------+
| Run Script | Kea open |This hook library adds support to run external |
| | source |scripts for specific packet-processing hook points. There |
| | |are several exported environment variables available for |
| | |the script. |
+-----------------+---------------+------------------------------------------------------------+
| GSS-TSIG | ISC support |This hook library adds support to the Kea D2 server |
| | customers |(kea-dhcp-ddns) for using GSS-TSIG to sign DNS updates. |
+-----------------+---------------+------------------------------------------------------------+
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
<https://reports.kea.isc.org/dev_guide/d8/db2/libdhcp_user_chk.html>`__
for information on how the code works internally. That, together with the
`Hooks Framework section of the Kea Developer's Guide
<https://reports.kea.isc.org/dev_guide/index.html#hooksFramework>`__ 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 :ref:`forensic-log-configuration`.
.. note::
When running Kea servers for both DHCPv4 and DHCPv6, the log names
must be distinct. See the examples in :ref:`forensic-log-configuration`.
.. _forensic-log-configuration:
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 :ref:`mysql-database-create` and :ref:`pgsql-database-create`).
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:
.. code-block:: json
{
"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:
.. code-block:: json
{
"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 :ref:`classification-using-expressions` 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:
.. code-block:: json
{
"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.
Additional parameters for the database connection can be specified, e.g:
.. code-block:: json
{
"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
:ref:`database-configuration4` and :ref:`database-configuration6`.
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:
.. code-block:: json
{
"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:
.. code-block:: json
{
"Dhcp6": {
"subnet6": [
{
"subnet": "2001:db8:1::/64",
"pools": [
{
"pool": "2001:db8:1::1-2001:db8:1::ffff"
}
],
"user-context": {
"legal-logging": false
}
}
]
}
}
See :ref:`dhcp4-user-contexts` and :ref:`dhcp6-user-contexts` 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:
.. code-block:: json
{
"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:
.. code-block:: json
{
"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, ':'), '')), '')"
}
.. raw:: html
<details><summary>Expand here!</summary>
<pre>{
"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, ':'),
'')),
'')"
}</pre>
</details><br>
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:
.. code-block:: json
{
"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, ':'), '')), ''))"
}
.. raw:: html
<details><summary>Expand here!</summary>
<pre>{
"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, ':'),
'')),
''))"
}</pre>
</details><br>
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:
.. code-block:: json
{
"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.
Examples:
.. code-block:: json
{
"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, '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, ':'), '')), ''), '')"
}
.. raw:: html
<details><summary>Expand here!</summary>
<pre>{
"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,
'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, ':'),
'')),
''),
'')"
}</pre>
</details><br>
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:
.. code-block:: json
{
"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, ':'), '')), ''), ''))"
}
.. raw:: html
<details><summary>Expand here!</summary>
<pre>{
"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, ':'),
'')),
''),
''))"
}</pre>
</details><br>
.. _forensic-log-database:
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
(timeuuid for Cassandra) generated by the database software, and a
text log with the same format as files without the timestamp.
Please refer to :ref:`mysql-database` for information on using a MySQL database;
to :ref:`pgsql-database` for PostgreSQL database information; or to
:ref:`cql-database` for information on using a Cassandra (CQL) database. The
``logs`` table is part of the Kea database schemas.
Configuration parameters are extended by standard lease database
parameters as defined in :ref:`database-configuration4`. The ``type``
parameter should be ``mysql``, ``postgresql``, ``cql``, 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 CQL database:
::
$ echo 'SELECT dateOf(timeuuid), log FROM logs;' | cqlsh -k database-name
system.dateof(timeuuid) | log
---------------------------------+---------------------------------------
2018-01-06 01:02:03.227000+0000 | Address: 192.2.1.100 has been renewed ...
...
(12 rows)
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:
``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
:ref:`classification-using-expressions` 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
:ref:`dhcp4-match-client-id` 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 :ref:`lease-cmds` 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:
``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 :ref:`classification-using-expressions` or :ref:`flex-id`
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.
.. _host-cmds:
``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, six 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 all reservations in a specified
subnet by pages (and, since Kea version 1.9.0, all reservations);
``reservation-get-by-hostname``, which returns all reservations
with a specified hostname and optionally in a subnet; since Kea version
1.7.1, ``reservation-get-by-id``, which returns all reservations with a
specified identifier since Kea version 1.9.0;
and ``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 :ref:`hosts-databases-configuration4`
and :ref:`hosts-databases-configuration6`). 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 <https://gitlab.isc.org/isc-projects/kea/wikis/designs/commands>`__
document.
All host commands use JSON syntax. They can be issued either using the
control channel (see :ref:`ctrl-channel`) or via the Control Agent (see
:ref:`kea-ctrl-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.
.. _command-reservation-add:
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 :ref:`host-reservation-v4`; for IPv6 reservations, see
:ref:`host-reservation-v6`. 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:
.. code-block:: json
{
"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:
.. code-block:: json
{
"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:
.. code-block:: json
{
"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.
.. _command-reservation-get:
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." }
.. _command-reservation-get-all:
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
:ref:`command-reservation-get-page`).
For more information, see :ref:`command-reservation-get-all`.
.. _command-reservation-get-page:
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 :ref:`command-reservation-get-all`).
.. note::
``reservation-get-page`` is not supported by the Cassandra
host backend.
.. _command-reservation-get-by-hostname:
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. This command is available since
Kea version 1.7.1.
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 :ref:`command-reservation-get-by-hostname`.
.. 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 :ref:`mysql-database` section of
:ref:`admin`.
.. _command-reservation-get-by-id:
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 :ref:`command-reservation-get-by-id`.
.. _command-reservation-del:
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."
}
.. include:: hooks-lease-cmds.rst
.. _subnet-cmds:
``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 a 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.
.. _command-subnet4-list:
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.
.. _command-subnet6-list:
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.
.. _command-subnet4-get:
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": [
....
]
...
}
]
}
}
.. _command-subnet6-get:
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": [
...
]
....
}
]
}
}
.. _command-subnet4-add:
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 :ref:`host-cmds` 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"
}
]
}
}
.. _command-subnet6-add:
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 :ref:`host-cmds` 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.
.. _command-subnet4-update:
The ``subnet4-update`` Command
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
This command is used to update a 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 :ref:`host-cmds` 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"
}
]
}
}
.. _command-subnet6-update:
The ``subnet6-update`` Command
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
This command is used to update a 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 :ref:`host-cmds` 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"
}
]
}
}
.. _command-subnet4-del:
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"
}
]
}
}
.. _command-subnet6-del:
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"
}
]
}
.. _command-network4-list:
.. _command-network6-list:
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.
.. _command-network4-get:
.. _command-network6-get:
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.
.. _command-network4-add:
.. _command-network6-add:
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 :ref:`shared-network4` and
:ref:`shared-network6`.
.. 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.
.. _command-network4-del:
.. _command-network6-del:
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.
.. _command-network4-subnet-add:
.. _command-network6-subnet-add:
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.
.. _command-network4-subnet-del:
.. _command-network6-subnet-del:
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.
.. include:: hooks-bootp.rst
.. include:: hooks-class-cmds.rst
.. include:: hooks-cb-cmds.rst
.. include:: hooks-ha.rst
.. include:: hooks-stat-cmds.rst
.. include:: hooks-radius.rst
.. include:: hooks-host-cache.rst
.. include:: hooks-lease-query.rst
.. include:: hooks-run-script.rst
.. _user-context-hooks:
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. The pretty
print of a configuration did the opposite operation and put "comment"
entries at the beginning of maps, but this was withdrawn in 1.7.9.
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.
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