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<chapter id="hooks-libraries">
<title>Hooks Libraries</title>
<section id="hooks-libraries-introduction">
<title>Introduction</title>
<para>
Although Kea offers a lot of flexibility, there may be cases where
its behavior needs customization. To accommodate this possibility,
Kea includes the idea of "Hooks". This feature lets Kea load one
or more dynamically-linked libraries (known as "hooks libraries")
and, at various points in its processing ("hook points"), call
functions in them. Those functions perform whatever custom
processing is required.
</para>
<para>
Hooks libraries are attached to individual Kea processes, not to
Kea as a whole. This means (for example) that it is possible
to associate one set of libraries with the DHCP4 server and a
different set to the DHCP6 server.
</para>
<para>
Another point to note is that it is possible for a process to
load multiple libraries. When processing reaches a hook point,
Kea calls the hooks 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 to see if this is the case.
</para>
<para>
The next section describes how to configure hooks libraries. If you
are interested in writing your own hooks library, information can be
found in the <ulink url="https://jenkins.isc.org/job/Fedora20_32_doxygen_doc/doxygen/">Kea
Developer's Guide</ulink>.
</para>
</section> <!-- end Introduction -->
<section>
<title>Configuring Hooks Libraries</title>
<para>
The hooks libraries for a given process are configured using the
<command>hooks-libraries</command> 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, each structure corresponding to a hooks
library. For example, to set up two hooks libraries for the DHCPv4
server, the configuration would be:
<screen>
<userinput>"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"
}
}
}
]
:
}</userinput>
</screen>
</para>
<note><para>
This is a change to the syntax used in Kea 0.9.2 and earlier, where
hooks-libraries was a list of strings, each string being the name of
a library. The change was made in Kea 1.0 to facilitate the
specification of library-specific parameters, a capability
available in Kea 1.1.0 onwards.
</para></note>
<note>
<para>
The library reloading behavior has changed in Kea 1.1. Libraries are
reloaded, even if their list hasn't changed. Kea does that, because
the parameters specified for the library (or the files those
parameters point to) may have changed.
</para>
</note>
<para>
Libraries may have additional parameters. Those are not mandatory in the
sense that there may be libraries that don't require them. However, for
specific library there is often specific requirement for specify certain
set of parameters. Please consult the documentation for your library
for details. In the example above, the first library has no parameters.
The second library has five parameters, specifying mail (string
parameter), floor (integer parameter), debug (boolean parameter) and
even lists (list of strings) and maps (containing strings). Nested
parameters could be used if the library supports it. This topic is
explained in detail in the Hooks Developer's Guide in the "Configuring
Hooks Libraries" section.
</para>
<para>
Notes:
<itemizedlist mark='bullet'>
<listitem><para>
The full path to each library should be given.
</para></listitem>
<listitem><para>
As noted above, order may be important - consult the documentation for
each library.
</para></listitem>
<listitem><para>
An empty list has the same effect as omitting the
<command>hooks-libraries</command> configuration element all together.
</para>
<note><para>
There is one case where this is not true: if Kea
is running with a configuration that contains a
<command>hooks-libraries</command> 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 <command>hooks-libraries</command>
item, change it to an empty list. This will be fixed in a
future version of Kea.
</para></note>
</listitem>
</itemizedlist>
</para>
<para>
At the present time, only the kea-dhcp4 and kea-dhcp6 processes support
hooks libraries.
</para>
</section>
<section>
<title>Available Hooks Libraries</title>
<para>
As described above, the hooks 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 hooks
libraries; these discussed in the following sections.
</para>
<note><para>
Some of these libraries will be available with the base code while others
will be shared with organizations supporting development of Kea
, possibly as a 'benefit' or 'thank you' for helping to sustain
the larger Kea project. If you would like to get access to those
libraries, please consider taking out a support contract: this includes
professional support, advance security notifications, input into our
roadmap planning, and many other benefits, while helping
making Kea sustainable in the long term.
</para></note>
<para>Currently the following libraries are available or planned from ISC:
<table frame="all" id="hook-libs">
<title>List of available hooks libraries</title>
<tgroup cols='3'>
<colspec colname='name' />
<colspec colname='avail' />
<colspec colname='description' />
<thead>
<row>
<entry>Name</entry>
<entry>Availability</entry>
<entry>Since</entry>
<entry>Description</entry>
</row>
</thead>
<tbody>
<row>
<entry>user_chk</entry>
<entry>Kea sources</entry>
<entry>Kea 0.8</entry>
<entry>Reads known users list from a file. Unknown users
will be assigned a
lease from the last subnet defined in the configuration file,
e.g. to redirect them 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.</entry>
</row>
<row>
<entry>Forensic Logging</entry>
<entry>Support customers</entry>
<entry>Kea 1.1.0</entry>
<entry>This library provides hooks that record a detailed log of
lease assignments and renewals into a set of log files. In many
legal jurisdictions companies, especially ISPs, must record
information about the addresses they have leased to DHCP
clients. This library is designed to help with that
requirement. If the information that it records is sufficient it
may be used directly. If your jurisdiction requires that you save
a different set of information, you may use it as a template or
example and create your own custom logging hooks.</entry>
</row>
<row>
<entry>Flexible Identifier</entry>
<entry>Support customers</entry>
<entry>Kea 1.2.0</entry>
<entry>Kea software provides a way to handle host reservations
that include addresses, prefixes, options, client classes and
other features. The reservation can be based on hardware address,
DUID, circuit-id or client-id in DHCPv4 and using hardware address
or DUID in DHCPv6. However, there are sometimes scenarios where the
reservation is more complex, e.g. uses other options that
mentioned above, uses part of specific options or perhaps even a
combination of several options and fields to uniquely identify a
client. Those scenarios are addressed by the Flexible Identifiers
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.
</entry>
</row>
<row>
<entry>Host Commands</entry>
<entry>Support customers</entry>
<entry>Kea 1.2.0</entry>
<entry>Kea provides a way to store host reservations in a
database. In many larger deployments it is useful to be able to
manage that information while the server is running. This library
provides management commands for adding, querying and deleting
host reservations in a safe way without restarting the server.
In particular, it validates the parameters, so an attempt to
insert incorrect data, e.g. add a host with conflicting identifier
in the same subnet will be rejected. Those commands are
exposed via command channel (JSON over unix sockets) and Control
Agent (JSON over RESTful interface). Additional commands and
capabilities related to host reservations will be added in the
future.</entry>
</row>
<row>
<entry>Subnet Commands</entry>
<entry>Support customers</entry>
<entry>Kea 1.3.0</entry>
<entry>In deployments in which subnet configuration needs to
be frequently updated, it is a hard requirement that such updates be
performed without the need for a full DHCP server reconfiguration
or restart. This hooks library allows for incremental changes
to the subnet configuration such as: adding a subnet, 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.
</entry>
</row>
</tbody>
</tgroup>
</table>
</para>
<para>
ISC hopes to see more hooks libraries become available as time
progresses, both developed internally and externally. Since
this list may evolve dynamically, we decided to keep it on a
wiki page, available at this link: <ulink
url="http://kea.isc.org/wiki/Hooks">http://kea.isc.org/wiki/Hooks</ulink>.
If you are a developer or are aware of any hooks libraries not
listed there, please send a note to the kea-users or kea-dev
mailing lists and someone will update it.
</para>
<section>
<title>user_chk: Checking User Access</title>
<para>
The user_chk library is the first hooks library published by ISC. It
attempts to serve several purposes:
<itemizedlist>
<listitem>
<para>To assign "new" or "unregistered" users to a
restricted subnet, while "known" or "registered" users are assigned
to unrestricted subnets.</para>
</listitem>
<listitem>
<para>To allow DHCP response options or vendor option
values to be customized based upon user identity. </para>
</listitem>
<listitem>
<para>To provide a real time record of the user registration
activity which can be sampled by an external consumer.</para>
</listitem>
<listitem>
<para> To serve as a demonstration of various capabilities
possible using the hooks interface.</para>
</listitem>
</itemizedlist>
</para>
<para>
Once loaded, the library allows segregating incoming requests into
known and unknown clients. For known clients, the packets are
processed mostly as usual, except it is possible to override certain
options being sent. That can be done on a per host basis. Clients
that are not on the known hosts list will be treated as unknown and
will be assigned to the last subnet defined in the configuration file.
</para>
<para>
As an example of use, this behavior may be used 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.
</para>
<note><para>This library was developed several years before the host
reservation mechanism has become available. Currently host reservation is
much more
powerful and flexible, but nevertheless the user_chk capability to consult
and external source of information about clients and alter Kea's
behavior is useful and remains of educational value.
</para></note>
<para>
The library reads the /tmp/user_chk_registry.txt file while being
loaded and each time an incoming packet is processed. The file is expected
to have each line contain a self-contained JSON snippet which must
have the following two entries:
<itemizedlist>
<listitem><para><command>type</command>, whose value
is "HW_ADDR" for IPv4 users or "DUID" for IPv6
users</para></listitem>
<listitem><para><command>id</command>, whose value is
either the hardware address or the DUID from the request
formatted as a string of hex digits, with or without
":" delimiters.</para></listitem>
</itemizedlist>
and may have the zero or more of the following entries:
<itemizedlist>
<listitem><para><command>bootfile</command> whose value
is the pathname of the desired file</para></listitem>
<listitem><para><command>tftp_server</command> whose
value is the hostname or IP address of the desired
server</para></listitem>
</itemizedlist>
A sample user registry file is shown below:
<screen>{ "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" }</screen>
</para>
<para>As with any other hooks libraries provided by ISC, internals of the
user_chk code are well documented. You can take a look at the <ulink
url="https://jenkins.isc.org/job/Fedora20_32_doxygen_doc/doxygen/d8/db2/libdhcp_user_chk.html">Kea Developer's Guide section dedicated to the user_chk library</ulink>
that discusses how the code works internally. That, together with
our general entries in <ulink
url="https://jenkins.isc.org/job/Fedora20_32_doxygen_doc/doxygen/">Hooks
Framework section</ulink> should give you some pointers how to extend
this library and perhaps even write your own from scratch.</para>
</section>
<section>
<title>legal_log: Forensic Logging Hooks</title>
<para>
This section describes the forensic log hooks library. This library
provides hooks that record a detailed log of lease assignments
and renewals into a set of log files. Currently this library
is only available to ISC customers with a support contract.
</para>
<para>
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 your jurisdiction requires that you save a different set of
information you may use it as a template or example and create your
own custom logging hooks.
</para>
<para>
This logging is done as a set of hooks to allow it to be customized
to any particular need. Modifying a hooks library is easier and
safer than updating the core code. In addition by using the hooks
features those users who don't need to log this information can
leave it out and avoid any performance penalties.
</para>
<section>
<title>Log File Naming</title>
<para>
The names for the log files have the following form:
</para>
<screen>
path/base-name.CCYYMMDD.txt
</screen>
<para>
The "path" and "base-name" are supplied in the
configuration as described below see
<xref linkend="forensic-log-configuration"/>. The next part of the name is
the date the log file was started, with four digits for year, two digits
for month and two digits for day. The file is rotated on a daily basis.
</para>
<note><para>
When running Kea servers for both DHCPv4 and DHCPv6 the log names must
be distinct. See the examples in <xref linkend="forensic-log-configuration"/>.
</para></note>
</section>
<section>
<title>DHCPv4 Log Entries</title>
<para>
For DHCPv4 the library creates entries based on DHCPREQUEST messages
and corresponding DHCPv4 leases intercepted by lease4_select
(for new leases) and lease4_renew (for renewed leases) hooks.
</para>
<para>
An entry is a single string with no embedded end-of-line markers
and has the following sections:
<screen>
address duration device-id {client-info} {relay-info}
</screen>
</para>
<para>
Where:
<itemizedlist>
<listitem><para>
address - the leased IPv4 address given out and whether it was
assigned or renewed.
</para></listitem>
<listitem><para>
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".
</para></listitem>
<listitem><para>
device-id - the client's hardware address shown as numerical type
and hex digit string.
</para></listitem>
<listitem><para>
client-info - the DHCP client id option (61) if present, shown as
a hex string.
</para></listitem>
<listitem><para>
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
</para></listitem>
</itemizedlist>
</para>
<para>
For instance (line breaks added for readability, they would not
be present in the log file).
<screen>
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 and remote-id: 87:f6:79:77:ef
</screen>
</para>
<para>
In addition to logging lease activity driven by DHCPv4 client traffic, it also
logs entries for the following lease management control channel commands:
lease4-add, lease4-update, and lease4-del. Each entry is a single string
with no embedded end-of-line markers and they will typically have the following
forms:
</para>
<para>
<command>lease4-add:</command>
<screen>
Administrator added a lease of address: *address* to a device with hardware address: *device-id*
</screen>
Dependent on the arguments of the add command, it may also include the
client-id and duration.
</para>
<para>
Example:
<screen>
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
</screen>
</para>
<para>
<command>lease4-update:</command>
<screen>
Administrator updated information on the lease of address: *address* to a device with hardware address: *device-id*
</screen>
Dependent on the arguments of the update command, it may also include the
client-id and lease duration.
</para>
<para>
Example:
<screen>
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
</screen>
</para>
<para>
<command>lease4-del:</command>
Deletes have two forms, one by address and one by identifier and identifier type:
<screen>
Administrator deleted the lease for address: *address*
</screen>
or
<screen>
Administrator deleted a lease for a device identified by: *identifier-type* of *identifier*
</screen>
Currently only a type of @b hw-address (hardware address) is supported.
</para>
<para>
Examples:
<screen>
Administrator deleted the lease for address: 192.0.2.202
Administrator deleted a lease for a device identified by: hw-address of 1a:1b:1c:1d:1e:1f
</screen>
</para>
</section>
<section>
<title>DHCPv6 Log Entries</title>
<para>
For DHCPv6 the library creates entries based on lease management
actions intercepted by the lease6_select (for new leases), lease6_renew
(for renewed leases) and lease6_rebind (for rebound leases).
</para>
<para>
An entry is a single string with no embedded end-of-line markers
and has the following sections:
<screen>
address duration device-id {relay-info}*
</screen>
</para>
<para>
Where:
<itemizedlist>
<listitem><para>
address - the leased IPv6 address or prefix given out and whether
it was assigned or renewed.
</para></listitem>
<listitem><para>
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".
</para></listitem>
<listitem><para>
device-id - the client's DUID and hardware address (if present).
</para></listitem>
<listitem><para>
relay-info - for relayed packets the content of relay agent
messages, remote-id (code 37), subscriber-id (code 38) and
interface-id (code 18) options if present. Note that
interface-id option, if present, identifies the whole interface the
relay agent received the message on. This typically translates to a
single link in your network, but it depends on your specific network
topology. Nevertheless, this is useful information to better scope
down the location of the device, so it is being recorded, if present.
</para></listitem>
</itemizedlist>
</para>
<para>
For instance (line breaks added for readability, they would not
be present in the log file).
<screen>
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
</screen>
</para>
<para>
In addition to logging lease activity driven by DHCPv6 client traffic, it 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 they will typically have the following
forms:
</para>
<para>
<command>lease6-add:</command>
<screen>
Administrator added a lease of address: *address* to a device with DUID: *DUID*
</screen>
Dependent on the arguments of the add command, it may also include the hardware address and duration.
</para>
<para>
Example:
<screen>
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
</screen>
</para>
<para>
<command>lease6-update:</command>
<screen>
Administrator updated information on the lease of address: *address* to a device with DUID: *DUID*
</screen>
Dependent on the arguments of the update command, it may also include the hardware address and lease duration.
</para>
<para>
Example:
<screen>
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
</screen>
</para>
<para>
<command>lease6-del:</command>
Deletes have two forms, one by address and one by identifier and identifier type:
<screen>
Administrator deleted the lease for address: *address*
</screen>
or
<screen>
Administrator deleted a lease for a device identified by: *identifier-type* of *identifier*
</screen>
Currently only a type of DUID is supported.
</para>
<para>
Examples:
<screen>
Administrator deleted the lease for address: 2001:db8::3
Administrator deleted a lease for a device identified by: duid of 1a:1b:1c:1d:1e:1f:20:21:22:23:24
</screen>
</para>
</section>
<section id="forensic-log-configuration">
<title>Configuring the Forensic Log Hooks</title>
<para>
To use this functionality the hook library must be included in the
configuration of the desired DHCP server modules. The legal_log
library is installed alongside the Kea libraries in
<filename>[kea-install-dir]/lib</filename> where
<filename>kea-install-dir</filename> is determined by the
"--prefix" option of the configure script. It defaults to
<filename>/usr/local</filename>. Assuming the
default value then, configuring kea-dhcp4 to load the legal_log
library could be done with the following Kea4 configuration:
<screen>
"Dhcp4": { <userinput>
"hooks-libraries": [
{
"library": "/usr/local/lib/libdhcp_legal_log.so",
"parameters": {
"path": "/var/kea/var",
"base-name": "kea-forensic4"
}
},
...
] </userinput>
}
</screen>
</para>
<para>
To configure it for kea-dhcp6, the commands are simply as shown below:
<screen>
"Dhcp6": { <userinput>
"hooks-libraries": [
{
"library": "/usr/local/lib/libdhcp_legal_log.so",
"parameters": {
"path": "/var/kea/var",
"base-name": "kea-forensic6"
}
},
...
] </userinput>
}
</screen>
</para>
<para>
Two Hook Library parameters are supported:
<itemizedlist>
<listitem><para>
path - the directory in which the forensic file(s) will be written. The
default value is
<filename>[prefix]/kea/var</filename>. The directory must exist.
</para></listitem>
<listitem><para>
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 <filename>kea-legal</filename>.
</para></listitem>
</itemizedlist>
</para>
</section>
</section>
<section id="flex-id">
<title>flex_id: Flexible Identifiers for Host Reservations</title>
<para>
This section describes a hook application dedicated to generate
flexible identifiers for host reservation. Kea software provides a way
to handle host reservations that include addresses, prefixes, options,
client classes and other features. The reservation can be based on
hardware address, DUID, circuit-id or client-id in DHCPv4 and using
hardware address or DUID in DHCPv6. However, there are sometimes
scenario where the reservation is more complex, e.g. uses other
options that mentioned above, uses part of specific options or perhaps
even a combination of several options and fields to uniquely identify
a client. Those scenarios are addressed by the Flexible Identifiers
hook application.</para>
<para>Currently this library is only available to ISC customers with a
support contract.</para>
<para>The library allows for defining an expression, using notation
initially used for client classification only. See <xref
linkend="classification-using-expressions" /> for 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 identifier. It is a valid case
for the expression to evaluate to empty string (e.g. in cases where a
client does not sent specific options). This expression is then
evaluated for each incoming packet. 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.</para>
<para>
The library can be loaded in similar way as other hook libraries. It
takes one mandatory parameter identifier-expression:
<screen>
"Dhcp6": { <userinput>
"hooks-libraries": [
{
"library": "/path/libdhcp_flex_id.so",
"parameters": {
"identifier-expression": "<userinput>expression</userinput>"
}
},
...
] </userinput>
}
</screen>
</para>
<para>
The flexible identifier library supports both DHCPv4 and DHCPv6.
</para>
<para>
EXAMPLE: Let's consider a case of an IPv6 network that has an
independent interface for each of the 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 verified
that the interface-id is unique for each customer facing
interface. Therefore it is suitable for usage as reservation. However,
only the first 6 bytes of the interface-id are interesting, because
remaining bytes are either randomly changed or not unique between
devices. Therefore the customer decided to use first 6 bytes of the
interface-id option inserted by the relay agent. After adding "flex-id"
host-reservation-identifiers goal can be achieved by using the
following configuration:
<screen>
"Dhcp6": {
"subnet6": [{ ..., // subnet definition starts here
"reservations": [
<userinput>"flex-id": "'port1234'"</userinput>, // 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": "<userinput>substring(relay6[0].option[18].hex,0,8)</userinput>"
}
},
...
]
}
</screen>
</para>
<para>
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're
manually updated. Therefore it is strongly recommended to start with
the expression and a handful reservations, adjust the expression as
needed and only after it was confirmed the expression does exactly
what is expected out of it go forward with host reservations on any
broader scale.
</para>
<para>
flex-id values in host reservations can be specified in two
ways. First, they can be expressed as hex string, e.g. bar string
can be represented as 626174. Alternatively, it can be expressed
as 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.
</para>
<screen>
"Dhcp6": {
"subnet6": [{ ..., // subnet definition starts here
"reservations": [
<userinput>"flex-id": "01:02:03:04:05:06"</userinput>, // 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": "<userinput>vendor[4491].option[1026].hex</userinput>"
}
},
...
]
}
</screen>
</section>
<section id="host-cmds">
<title>host_cmds: Host Commands</title>
<para>
This section describes a hook application that offers a number of new
commands used to query and manipulate host reservations. Kea provides
a way to store host reservations in a database. In many larger
deployments it is useful to be able to manage that information while
the server is running. This library provides management commands for
adding, querying and deleting host reservations in a safe way without
restarting the server. In particular, it validates the parameters, so
an attempt to insert incorrect data e.g. add a host with conflicting
identifier in the same subnet will be rejected. Those commands are
exposed via command channel (JSON over unix sockets) and Control Agent
(JSON over RESTful interface). Additional commands and capabilities
related to host reservations will be added in the future.
</para>
<para>Currently this library is only available to ISC customers with a
support contract.</para>
<para>
Currently three commands are supported: reservation-add (which adds
new host reservation), reservation-get (which returns existing
reservation if specified criteria are matched) and reservation-del
(which attempts to delete a reservation matching specified
criteria). To use commands that change the reservation information
(currently these are reservation-add and reservation-del, but this
rule applies to other commands that may be implemented in the future),
hosts database must be specified (see hosts-database description in
<xref linkend="hosts-database-configuration4"/> and <xref
linkend="hosts-database-configuration6"/>) and it must not operate in
read-only mode. If the hosts-database is not specified or is running
in read-only mode, the host_cmds library will load, but any attempts
to use reservation-add or reservation-del will fail.
</para>
<para>
Additional host reservation commands are planned in the future. For
a description of envisaged commands, see
<ulink url="http://kea.isc.org/wiki/ControlAPIRequirements">Control API
Requirements </ulink> document.</para>
<para>
All commands are using JSON syntax. They can be issued either using
control channel (see <xref linkend="ctrl-channel"/>) or via Control
Agent (see <xref linkend="kea-ctrl-agent"/>).
</para>
<para>
The library can be loaded in similar way as other hook libraries. It
does not take any parameters. It supports both DHCPv4 and DHCPv6
servers.
<screen>
"Dhcp6": { <userinput>
"hooks-libraries": [
{
"library": "/path/libdhcp_host_cmds.so"
}
...
] </userinput>
}
</screen>
</para>
<section>
<title>reservation-add command</title>
<para>
<command>reservation-add</command> allows 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 <xref linkend="host-reservation-v4"/> and <xref
linkend="host-reservation-v6"/>. There is one notable addition. A
<command>subnet-id</command> must be specified. This parameter is
mandatory, because reservations specified in the configuration file
are always defined within a subnet, so the subnet they belong to is
clear. This is not the case with reservation-add, therefore the
subnet-id must be specified explicitly. An example command can be as
simple as:
<screen>{
"command": "reservation-add",
"arguments": {
<userinput>"reservation": {
"subnet-id": 1,
"hw-address": "1a:1b:1c:1d:1e:1f",
"ip-address": "192.0.2.202"
}</userinput>
}
}</screen> but can also take many more parameters, for example:
<screen>
{
"command": "reservation-add",
"arguments": {
<userinput>"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" ]
}</userinput>
}
}</screen>
Here is an example of complex IPv6 reservation:
<screen>
{
"command": "reservation-add",
"arguments": {
<userinput>"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"
}
]
}</userinput>
}
}</screen>
</para>
<para>
The command returns a status that indicates either a success (result
0) or a failure (result 1). Failed command always includes text
parameter that explains the cause of failure. Example results:
<screen>{ "result": 0, "text": "Host added." }</screen> Example failure:
<screen>{ "result": 1, "text": "Mandatory 'subnet-id' parameter missing." }</screen>
</para>
<para>
As <command>reservation-add</command> is expected to store the host,
hosts-database parameter must be specified in your configuration and
the database must not run in read-only mode. In the future versions
it will be possible to modify the reservations read from a
configuration file. Please contact ISC if you are interested in this
functionality.
</para>
</section>
<section>
<title>reservation-get command</title>
<para><command>reservation-get</command> can be used to query the host
database and retrieve existing reservations. There are two types of
parameters this command supports: (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 aren't. One common use case of this type of query is to
find out whether a given address is reserved or not. The second query
uses identifiers. For maximum flexibility, Kea stores the host
identifying information as a pair of values: type and the actual
identifier. Currently supported identifiers are "hw-address", "duid",
"circuit-id", "client-id" and "flex-id", but additional types may be
added in the future. If any new identifier types are defined in the
future, reservation-get command will support them
automatically.</para>
<para>
An example command for getting a host reservation by (subnet-id,
address) pair looks as follows:
<screen>
{
"command": "reservation-get",
"arguments": {
"subnet-id": 1,
"ip-address": "192.0.2.202"
}
}</screen>
An example query by (subnet-id, identifier-type, identifier) looks as follows:
<screen>
{
"command": "reservation-get",
"arguments":
"subnet-id": 4,
"identifier-type": "hw-address",
"identifier": "01:02:03:04:05:06"
}
}</screen>
</para>
<para><command>reservation-get</command> typically returns result 0
when the query was conducted properly. In particular, 0 is returned
when the host was not found. If the query was successful a number
of host parameters will be returned. An example of a query that
did not find the host looks as follows:
<screen>{ "result": 0, "text": "Host not found." }</screen>
An example result returned when the host was found:
<screen>{
"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."
}</screen>
An example result returned when the query was malformed:<screen>
{ "result": 1, "text": "No 'ip-address' provided and 'identifier-type'
is either missing or not a string." }</screen>
</para>
</section>
<section>
<title>reservation-del command</title>
<para><command>reservation-del</command> can be used to delete a
reservation from the host database. There are two types of parameters
this command supports: (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 aren't. One common use case of this type of query is to
remove a reservation (e.g. you want a specific address to no longer be
reserved). The second query uses identifiers. For maximum flexibility,
Kea stores the host identifying information as a pair of values: type
and the actual identifier. Currently supported identifiers are
"hw-address", "duid", "circuit-id", "client-id" and "flex-id", but
additional types may be added in the future. If any new identifier
types are defined in the future, reservation-get command will support
them automatically.</para>
<para>
An example command for deleting a host reservation by (subnet-id,
address) pair looks as follows:
<screen>
{
"command": "reservation-del",
"arguments": {
"subnet-id": 1,
"ip-address": "192.0.2.202"
}
}</screen>
An example deletion by (subnet-id, identifier-type, identifier) looks as follows:
<screen>
{
"command": "reservation-del",
"arguments":
"subnet-id": 4,
"identifier-type": "hw-address",
"identifier": "01:02:03:04:05:06"
}
}</screen>
</para>
<para>
<command>reservation-del</command> returns result 0 when the host
deletion was successful or 1 if it was not. A descriptive text is
provided in case of error. Example results look as follows:
<screen>
{
"result": 1,
"text": "Host not deleted (not found)."
}</screen>
<screen>
{
"result": 0,
"text": "Host deleted."
}</screen>
<screen>
{
"result": 1,
"text": "Unable to delete a host because there is no hosts-database
configured."
}</screen>
</para>
</section>
</section>
<!-- ================================================================= -->
<!-- === lease_cmds ================================================== -->
<!-- ================================================================= -->
<section id="lease-cmds">
<title>lease_cmds: Lease Commands</title>
<para>
This section describes the hook library that offers a number of new
commands used to manage leases. Kea provides a way to store lease
information in several backends (memfile, MySQL, PostgreSQL and
Cassandra). This library provides a unified interface that can
manipulate leases in an unified, safe way. In particular, it allows
things previously impossible: manipulate leases in memfile while Kea
is running, sanity check changes, check lease existence and remove all
leases belonging to specific subnet. It can also catch more obscure
errors, like adding a lease with subnet-id that does not exist in the
configuration or configuring a lease to use an address that is outside
of the subnet to which it is supposed to belong.
</para>
<para>There are many use cases when an administrative command may be
useful: during migration between servers (possibly even between
different vendors), when a certain network is being retired, when a
device has been disconnected and the sysadmin knows for sure that it
will not be coming back. The "get" queries may be useful for automating
certain management and monitoring tasks. They can also act as
preparatory steps for lease updates and removals.</para>
<para>
This library provides the following commands:
<itemizedlist>
<listitem>
<para><command>lease4-add</command> - adds new IPv4 lease;</para>
</listitem>
<listitem>
<para><command>lease6-add</command> - adds new IPv6 lease;</para>
</listitem>
<listitem>
<para><command>lease4-get</command> - checks if an IPv4 lease with
the specified parameters exists and returns it if it does;</para>
</listitem>
<listitem>
<para><command>lease6-get</command> - checks if an IPv6 lease with
the specified parameters exists and returns it if it does;</para>
</listitem>
<listitem>
<para><command>lease4-del</command> - attempts to delete an IPv4
lease with the specified parameters;</para>
</listitem>
<listitem>
<para><command>lease6-del</command> - attempts to delete an IPv6
lease with the specified parameters;</para>
</listitem>
<listitem>
<para><command>lease4-update</command> - updates an IPv4 lease;</para>
</listitem>
<listitem>
<para><command>lease6-update</command> - updates an IPv6 lease;</para>
</listitem>
<listitem>
<para><command>lease4-wipe</command> - removes all leases from a
specific IPv4 subnet;</para>
</listitem>
<listitem>
<para><command>lease6-wipe</command> - removes all leases from a
specific IPv6 subnet;</para>
</listitem>
</itemizedlist>
</para>
<para>Lease commands library is part of the open source code and is
available to every Kea user.</para>
<para>
All commands are using JSON syntax. They can be issued either using
control channel (see <xref linkend="ctrl-channel"/>) or via Control
Agent (see <xref linkend="kea-ctrl-agent"/>).
</para>
<para>
The library can be loaded in the same way as other hook libraries. It
does not take any parameters. It supports both DHCPv4 and DHCPv6
servers.
<screen>
"Dhcp6": { <userinput>
"hooks-libraries": [
{
"library": "/path/libdhcp_lease_cmds.so"
}
...
] </userinput>
}
</screen>
</para>
<section>
<title>lease4-add, lease6-add commands</title>
<para>
<command>lease4-add</command> and <command>lease6-add</command>
commands allow creation of a new lease. Typically Kea creates a lease
on its own, when it first sees a new device. However, sometimes it may
be convenient to create the lease administratively. The
<command>lease4-add</command> command requires at least three
parameters: an IPv4 address, a subnet-id and an identifier: hardware
(MAC) address. The simplest successful call might look as follows:
<screen>
{
"command": "lease4-add",
"arguments": {
"subnet-id": 44,
"ip-address": "192.0.2.202",
"hw-address": "1a:1b:1c:1d:1e:1f"
}
}
</screen>
</para>
<para><command>lease6-add</command> command requires four
paramaters: an IPv6 address, a subnet-id, and IAID value
(identity association identifier, a value sent by clients) and
a DUID:
<screen>
{
"command": "lease6-add",
"arguments": {
"subnet-id": 66,
"ip-address": "2001:db8::3",
"duid": "1a:1b:1c:1d:1e:1f:20:21:22:23:24",
"iaid": 1234
}
}</screen>
<command>lease6-add</command> can be also used to add leases for IPv6
prefixes. In this case there are two parameters that must be
specified: type (set to value of "IA_PD") and a prefix
length. The actual prefix is set using ip-address field. For example,
to configure a lease for prefix 2001:db8:abcd::/48, the following
command can be used:
<screen>
{
"command": "lease6-add",
"arguments": {
"subnet-id": 66,
"type": "IA_PD",
"ip-address": "2001:db8:abcd::",
"prefix-len": 48,
"duid": "1a:1b:1c:1d:1e:1f:20:21:22:23:24",
"iaid": 1234
}
}</screen>
The commands can take a number of additional optional parameters:
<itemizedlist>
<listitem>
<para><command>valid-lft</command> - specifies the lifetime of the
lease, expressed in seconds. If not specified, the value
configured in the subnet related to specified subnet-id is
used.</para>
</listitem>
<listitem>
<para><command>expire</command> - timestamp of the lease
expiration time, expressed in unix format (seconds since 1 Jan
1970). If not specified, the default value is now + valid
lifetime.</para>
</listitem>
<listitem>
<para><command>fqdn-fwd</command> - specifies whether the lease
should be marked as if forward DNS update was conducted. Note this
only affects the lease parameter and the actual DNS update will
not be conducted at the lease insertion time. If configured, a DNS
update to remove the A or AAAA records will be conducted when the
lease is removed due to expiration or being released by a
client. If not specifed, the default value is false. Hostname
parameter must be specified in fqdn-fwd is set to true.</para>
</listitem>
<listitem>
<para><command>fqdn-rev</command> - specifies whether the lease
should be marked as if reverse DNS update was conducted. Note this
only affects the lease parameter and the actual DNS update will
not be conducted at the lease insertion time. If configured, a DNS
update to remove the PTR record will be conducted when the lease
is removed due to expiration or being released by a client. If not
specifed, the default value is false. Hostname parameter must be
specified in fqdn-fwd is set to true.</para>
</listitem>
<listitem>
<para><command>hostname</command> - specifies the hostname to be
associated with this lease. Its value must be non-empty if either
fqdn-fwd or fwdn-rev are set to true. If not specified, the
default value is an empty string.</para>
</listitem>
<listitem>
<para><command>hw-address</command> - hardware (MAC) address can
be optionally specified for IPv6 lease. It is mandatory parameter
for IPv4 lease.</para>
</listitem>
<listitem>
<para><command>client-id</command> - client identifier is an
optional parameter that can be specified for IPv4 lease.</para>
</listitem>
<listitem>
<para><command>preferred-lft</command> - Preferred lifetime is an
optional parameter for IPv6 leases. If not specified, the value
configured for the subnet corresponding to the specified subnet-id
is used. This parameter is not used in IPv4.</para>
</listitem>
</itemizedlist>
</para>
<para>Here's an example of more complex lease addition:
<screen>
{
"command": "lease6-add",
"arguments": {
"subnet-id": 66,
"ip-address": "2001:db8::3",
"duid": "01:02:03:04:05:06:07:08",
"iaid": 1234,
"hw-address": "1a:1b:1c:1d:1e:1f",
"preferred-lft": 500,
"valid-lft": 1000,
"expire": 12345678,
"fqdn-fwd": true,
"fqdn-rev": true,
"hostname": "urania.example.org"
}
}
</screen>
</para>
<para>
The command returns a status that indicates either a success (result
0) or a failure (result 1). Failed command always includes text
parameter that explains the cause of failure. Example results:
<screen>{ "result": 0, "text": "Lease added." }</screen> Example failure:
<screen>{ "result": 1, "text": "missing parameter 'ip-address' (<string>:3:19)" }</screen>
</para>
<section>
<title>lease4-get, lease6-get commands</title>
<para><command>lease4-get</command> or <command>lease6-get</command>
can be used to query the lease database and retrieve existing
leases. There are two types of parameters the
<command>lease4-get</command> supports: (address) or (subnet-id,
identifier-type, identifier). There are two types for
<command>lease6-get</command>: (address,type) or (subnet-id,
identifier-type, identifier, IAID, type). The first type of query is
used when the address (either IPv4 or IPv6) is known, but the details
of the lease aren't. One common use case of this type of query is to
find out whether a given address is being used or not. The second
query uses identifiers. For maximum flexibility, Kea stores the host
identifying information as a pair of values: type and the actual
identifier. Currently supported identifiers are "hw-address", "duid",
"circuit-id", "client-id" and "flex-id", but additional types may be
added in the future. If any new identifier types are defined in the
future, reservation-get command will support them
automatically.</para>
<para>
An example <command>lease4-get</command> command for getting a lease
by an IPv4 address looks as follows:
<screen>
{
"command": "lease4-get",
"arguments": {
"ip-address": "192.0.2.1"
}
}
</screen>
</para>
<para>An example of the <command>lease6-get</command> query
looks as follows:
<screen>
{
"command": "lease6-get",
"arguments": {
"ip-address": "2001:db8:1234:ab::",
"type": "IA_PD"
}
}</screen>
</para>
<para>An example query by (subnet-id, identifier-type,
identifier) for IPv4 lease looks as follows:
<screen>
{
"command": "lease4-get",
"arguments": {
"identifier-type": "hw-address",
"identifier": "08:08:08:08:08:08",
"subnet-id": 44
}
}</screen>
</para>
<para>An example query by (subnet-id, identifier-type,
identifier, iaid, type) for IPv6 lease looks as follows:
<screen>
{
"command": "lease4-get",
"arguments": {
"identifier-type": "duid",
"identifier": "08:08:08:08:08:08",
"iaid": 1234567,
"type": "IA_NA",
"subnet-id": 44
}
}</screen>
The type is an optional parameter. Supported values are: IA_NA
(non-temporary address) and IA_PD (IPv6 prefix) are supported.
If not specified, IA_NA is assumed.
</para>
<para><command>leaseX-get</command> returns a result that indicates a
result of the operation and lease details, if found. It has one of the
following values: 0 (success), 1 (error) or 2 (empty). The empty
result means that a query has been completed properly, but the object
(a lease in this case) has not been found. The lease parameters, if
found, are returned as arguments.
</para>
<para>
An example result returned when the host was found:
<screen>{
"arguments": {
"client-id": "42:42:42:42:42:42:42:42",
"cltt": 12345678,
"fqdn-fwd": false,
"fqdn-rev": true,
"hostname": "myhost.example.com.",
"hw-address": "08:08:08:08:08:08",
"ip-address": "192.0.2.1",
"state": 0,
"subnet-id": 44,
"valid-lft": 3600
},
"result": 0,
"text": "IPv4 lease found."
}</screen>
</para>
</section>
<section>
<title>lease4-del, lease6-del commands</title>
<para><command>leaseX-del</command> can be used to delete a lease from
the lease database. There are two types of parameters this command
supports, similar to leaseX-get commands: (address) for both v4 and
v6, (subnet-id, identifier-type, identifier) for v4 and (subnet-id,
identifier-type, identifier, type, IAID) for v6. The first type of
query is used when the address (either IPv4 or IPv6) is known, but the
details of the lease are not. One common use case of this type of query
is to remove a lease (e.g. you want a specific address to no longer be
used, no matter who may use it). The second query uses
identifiers. For maximum flexibility, this interface uses identifiers
as a pair of values: type and the actual identifier. Currently
supported identifiers are "hw-address" and "duid", but additional
types may be added in the future. </para>
<para>
An example command for deleting a host reservation by address looks
as follows:
<screen>
{
"command": "lease4-del",
"arguments": {
"ip-address": "192.0.2.202"
}
}</screen>
An example IPv4 lease deletion by (subnet-id, identifier-type, identifier) looks
as follows:
<screen>{
"command": "lease4-del",
"arguments": {
"identifier": "08:08:08:08:08:08",
"identifier-type": "hw-address",
"subnet-id": 44
}
}</screen>
</para>
<para><command>leaseX-get</command> returns a result that
indicates a outcome of the operation. It has one of the
following values: 0 (success), 1 (error) or 2 (empty). The
empty result means that a query has been completed properly,
but the object (a lease in this case) has not been found.
</para>
</section>
<section>
<title>lease4-update, lease6-update commands</title>
<para><command>lease4-update</command> and
<command>lease6-update</command> commands can be used to update
existing leases. Since all lease database backends are indexed by IP
addresses, it is not possible to update an address. All other fields
may be updated. If an address needs to be changed, please use
<command>leaseX-del</command> followed by
<command>leaseX-add</command> commands.</para>
<para>To use <command>leaseX-update</command> the lease must
be present in the lease database. If the lease is not there,
an error will be returned. Please use
<command>leaseX-add</command> to add new leases. You may
check if a lease is present using
<command>leaseX-get</command>, if needed.</para>
<para>
An example command updating IPv6 lease looks as follows:
<screen>{
"command": "lease4-update",
"arguments": {
"ip-address": "192.0.2.1",
"hostname": "newhostname.example.org",
"hw-address": "1a:1b:1c:1d:1e:1f",
"subnet-id": 44
}
}</screen>
</para>
<para>
An example command updating IPv6 lease looks as follows:
<screen>{
"command": "lease6-update",
"arguments": {
"ip-address": "2001:db8::1",
"duid": "88:88:88:88:88:88:88:88",
"iaid": 7654321,
"hostname": "newhostname.example.org",
"subnet-id": 66
}
}</screen>
</para>
</section>
<section>
<title>lease4-wipe, lease6-wipe commands</title>
<para><command>lease4-wipe</command> and
<command>lease6-wipe</command> are designed to remove all
leases associated with a given subnet. This administrative
task is expected to be used when existing subnet is being
retired. Note that the leases are not properly expired,
there are no DNS updates conducted, no log messages and
hooks are not called for leases being removed.</para>
<para>An example of <command>lease4-wipe</command> looks as follows:
<screen>{
"command": "lease4-wipe",
"arguments": {
"subnet-id": 44
}
}</screen>
</para>
<para>An example of <command>lease6-wipe</command> looks as follows:
<screen>{
"command": "lease6-wipe",
"arguments": {
"subnet-id": 66
}
}</screen>
</para>
<para>The commands return a textual description of the
number of leases removed and 0 (success) status code if any
leases were removed and 2 (empty) if there were no
leases. Status code 1 (error) may be returned in case the
parameeters are incorrect or some other exception is
encountered.</para>
<para>Note: not all backends support this command.</para>
</section>
</section>
</section>
<section id="subnet-cmds">
<title>subnet_cmds: Subnet Commands</title>
<para>
This section describes a hook application that offers a number of new
commands used to query and manipulate subnet configurations in Kea.
This application is very useful in deployments with a large number of
subnets being managed by the DHCP servers and when the subnets are
frequently updated. The commands offer lightweight approach for
manipulating subnets without a need to fully reconfigure the server
and without affecting existing servers' configurations.
</para>
<para>Currently this library is only available to ISC customers with a
support contract.</para>
<para>The following commands are currently supported:
<itemizedlist mark='bullet'>
<listitem>
<simpara><command>subnet4-list/subnet6-list</command>: lists all configured subnets
</simpara>
</listitem>
<listitem>
<simpara>
<command>subnet4-get/subnet6-get</command>: retrieves detailed information about a selected subnet
</simpara>
</listitem>
<listitem>
<simpara>
<command>subnet4-add/subnet6-add</command>: adds new subnet into server's configuration
</simpara>
</listitem>
<listitem>
<simpara>
<command>subnet4-del/subnet6-del</command>: removes a subnet from the server's configuration
</simpara>
</listitem>
</itemizedlist>
</para>
<section>
<title>subnet4-list command</title>
<para>
This command is used to list all currently configured subnets. The
subnets are returned in a brief form, i.e. a subnet identifier
and subnet prefix is included for each subnet. In order to retrieve
the detailed information about the subnet the
<command>subnet4-get</command> should be used.
</para>
<para>
This command has the simple structure:
<screen>
{
"command": "subnet4-list"
}
</screen>
</para>
<para>
The list of subnets returned as a result of this command is returned
in the following format:
<screen>
{
"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"
}
]
}
</screen>
</para>
<para>
If no IPv4 subnets are found, an error code is returned along with
the error description.
</para>
</section>
<section>
<title>subnet6-list command</title>
<para>
This command is used to list all currently configured subnets. The
subnets are returned in a brief form, i.e. a subnet identifier
and subnet prefix is included for each subnet. In order to retrieve
the detailed information about the subnet the
<command>subnet6-get</command> should be used.
</para>
<para>
This command has the simple structure:
<screen>
{
"command": "subnet6-list"
}
</screen>
</para>
<para>
The list of subnets returned as a result of this command is returned
in the following format:
<screen>
{
"result": 0,
"text": "2 IPv6 subnets found",
"arguments": {
"subnets": [
{
"id": 11,
"subnet": "2001:db8:1::/64"
},
{
"id": 233,
"subnet": "3000::/16"
}
]
}
</screen>
</para>
<para>
If no IPv6 subnets are found, an error code is returned along with
the error description.
</para>
</section>
<section>
<title>subnet4-get command</title>
<para>This command is used to retrieve detailed information about the
specified subnet. This command usually follows the
<command>subnet4-list</command>, which is used to discover available
subnets with their respective subnet identifiers and prefixes. Any of
those parameters can be then used in <command>subnet4-get</command>
to fetch subnet information:
<screen>
{
"command": "subnet4-get",
"arguments": {
"id": 10
}
}</screen>
or
<screen>
{
"command": "subnet4-get",
"arguments": {
"subnet": "10.0.0.0/8"
}
}
</screen>
</para>
<para>
If the subnet exists the response will be similar to this:
<screen>
{
"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": [
....
]
...
}
]
}
}
</screen>
</para>
</section>
<section>
<title>subnet6-get command</title>
<para>This command is used to retrieve detailed information about the
specified subnet. This command usually follows the
<command>subnet6-list</command>, which is used to discover available
subnets with their respective subnet identifiers and prefixes. Any of
those parameters can be then used in <command>subnet6-get</command>
to fetch subnet information:
<screen>
{
"command": "subnet6-get",
"arguments": {
"id": 11
}
}
</screen>
or
<screen>
{
"command": "subnet6-get",
"arguments": {
"subnet": "2001:db8:1::/64"
}
}</screen>
If the subnet exists the response will be similar to this:
<screen>
{
"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": [
...
]
....
}
]
}
}
</screen>
</para>
</section>
<section>
<title>subnet4-add</title>
<para>
This command is used to create and add 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.
</para>
<para>
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 must not be specified
within <command>subnet4-add</command>. The commands described in
<xref linkend="host-cmds"/> should be used to add, remove and
modify static reservations.
<screen>
{
"command": "subnet4-add",
"arguments": {
"subnets": [ {
"id": 123,
"subnet": "10.20.30.0/24",
...
} ]
}
}
</screen>
</para>
<para>
The response to this command has the following structure:
<screen>
{
"result": 0,
"text": "IPv4 subnet added",
"arguments": {
"subnets": [
{
"id": 123,
"subnet": "10.20.30.0/24"
}
]
}
}
</screen>
</para>
</section>
<section>
<title>subnet6-add</title>
<para>
This command is used to create and add 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.
</para>
<para>
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 must not be specified
within <command>subnet6-add</command>. The commands described in
<xref linkend="host-cmds"/> should be used to add, remove and
modify static reservations.
<screen>
{
"command": "subnet6-add",
"arguments": {
"subnet6": [ {
"id": 234,
"subnet": "2001:db8:1::/64",
...
} ]
}
}
</screen>
</para>
<para>
The response to this command has the following structure:
<screen>
{
"result": 0,
"text": "IPv6 subnet added",
"arguments": {
"subnet6": [
{
"id": 234,
"subnet": "2001:db8:1::/64"
}
]
}
}
</screen>
</para>
<para>
It is recommended, but not mandatory to specify subnet
id. If not specified, Kea will try to assign the next
subnet-id value. This automatic ID value generator is
simple. It returns a previously automatically assigned value
increased by 1. This works well, unless you manually create
a subnet with a value bigger than previously used. For
example, if you call subnet4-add five times, each without
id, Kea will assign IDs: 1,2,3,4 and 5 and it will work just
fine. However, if you try to call subnet4-add five times,
with the first subnet having subnet-id of value 3 and
remaining ones having no subnet-id, it will fail. The first
command (with explicit value) will use subnet-id 3, the
second command will create a subnet with id of 1, the third
will use value of 2 and finally the fourth will have the
subnet-id value auto-generated as 3. However, since there is
already a subnet with that id, it will fail.
</para>
<para>
The general recommendation is to either: never use explicit
values (so the auto-generated values will always work) or
always use explicit values (so the auto-generation is never
used). You can mix those two approaches only if you
understand how the internal automatic subnet-id generation works.
</para>
</section>
<section>
<title>subnet4-del command</title>
<para>
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 has certain implications which the server's administrator
should be aware of.
</para>
<para>
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 <command>subnet4-del</command>
removes neither the leases nor host reservations associated with
a subnet. This is the safest approach because the server doesn't
loose 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 is used with extreme
caution.
</para>
<para>The command has the following structure:
<screen>
{
"command": "subnet4-del",
"arguments": {
"id": 123
}
}
</screen>
</para>
<para>
The example successful response may look like this:
<screen>
{
"result": 0,
"text": "IPv4 subnet 192.0.2.0/24 (id 123) deleted",
"arguments": {
"subnets": [
{
"id": 123,
"subnet": "192.0.2.0/24"
}
]
}
}
</screen>
</para>
</section>
<section>
<title>subnet6-del command</title>
<para>
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 has certain implications which the server's administrator
should be aware of.
</para>
<para>
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 <command>subnet6-del</command>
removes neither the leases nor host reservations associated with
a subnet. This is the safest approach because the server doesn't
loose 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 is used with extreme
caution.
</para>
<para>The command has the following structure:
<screen>
{
"command": "subnet6-del",
"arguments": {
"id": 234
}
}
</screen>
</para>
<para>
The example successful response may look like this:
<screen>
{
"result": 0,
"text": "IPv6 subnet 2001:db8:1::/64 (id 234) deleted",
"subnets": [
{
"id": 234,
"subnet": "2001:db8:1::/64"
}
]
}
</screen>
</para>
</section>
</section>
</section> <!-- end of subnet commands -->
<section id="user-context">
<title>User contexts</title>
<para>Hook libraries can have their own configuration parameters. That is
convenient if the parameter applies to the whole library. However,
sometimes it is very useful if certain configuration entities are extended
with additional configuration data. This is where the concept of user
contexts comes in. A sysadmin can define an arbitrary set of data and
attach it to Kea structures, as long as the data is specified as JSON map.
In particular, it is possible to define fields that are integers, strings,
boolean, lists and maps. It is possible to define nested structures of
arbitrary complexity. Kea does not use that data on its own, simply stores
and makes it available for the hook libraries.
</para>
<para>
Another use case for user contexts may be storing comments and other
information that will be retained by Kea. Regular comments are discarded
when configuration is loaded, but user contexts are retained. This is
useful if you want your comments to survive config-set, config-get
operations for example.
</para>
<para>
As of Kea 1.3, the structures that allow user contexts are pools of all
types (addresses and prefixes) and subnets. These are supported in both
DHCPv4 and DHCPv6. It is expected that other structures will be extended
in the future to provide the user context capability.
</para>
</section>
</chapter> <!-- hooks-libraries -->