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kea/doc/guide/hooks-lease-cmds.xml
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<section xml: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.
It provides a non programmatic way to manage user contexts
associated to leases.
<note>
<para>This library may only be loaded by <command>kea-dhcp4</command>
or <command>kea-dhcp6</command> process.
</para>
</note>
</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-get-all</command> - returns all IPv4 leases
or IPv4 leases for specified subnets;</para>
</listitem>
<listitem>
<para><command>lease6-get-all</command> - returns all IPv6 leases
or IPv6 leases for specified subnets;</para>
</listitem>
<listitem>
<para><command>lease4-get-page</command> - returns a page of all
IPv4 leases; by iterating over pages it is possible to retrieve
all leases in chunks;</para>
</listitem>
<listitem>
<para><command>lease6-get-page</command> - returns a page of all
IPv6 leases; by iterating over pages it is possible to retrieve
all leases in chunks;</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 or all subnets;</para>
</listitem>
<listitem>
<para><command>lease6-wipe</command> - removes all leases from a
specific IPv6 subnet or all subnets;</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 id="command-lease4-add">
<title>lease4-add, lease6-add commands</title>
<para id="command-lease6-add">
<command>lease4-add</command> and <command>lease6-add</command>
commands allow for the 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 two parameters: an IPv4 address, and an identifier: hardware
(MAC) address. A third parameter, subnet-id, was mandatory in
Kea 1.4.0, but is optional beginning with Kea 1.5.0.. If not
specified or specified value is 0, Kea will try to determine the
value by running a subnet selection procedure. If specified, however,
its value must match the existing subnet. The simplest successful
call might look as follows:
<screen>
{
"command": "lease4-add",
"arguments": {
"ip-address": "192.0.2.202",
"hw-address": "1a:1b:1c:1d:1e:1f"
}
}
</screen>
</para>
<para><command>lease6-add</command> command requires four parameters: an
IPv6 address, and IAID value (identity association identifier, a value
sent by clients) and a DUID. The same principle for subnet-id as in
lease4-add applies. If not specified or specified value is 0, Kea will
try to determine the value own by running a subnet selection procedure.
If specified, however, its value must match the existing subnet. For
example:
<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 three additional parameters that must be
specified: subnet-id, type (set to value of "IA_PD") and a prefix
length. The actual prefix is set using ip-address field. Note that Kea is not
able to guess subnet-id values for prefixes, so it must be specified explicitly.
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 specified, 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
specified, 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>
<listitem>
<para><command>user-context</command> - specifies the user
context to be associated with this lease. It must be a
JSON map.</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",
"user-context": { "version": 1 }
}
}
</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' (&lt;string&gt;:3:19)" }</screen>
</para>
<section id="command-lease4-get">
<title>lease4-get, lease6-get commands</title>
<para id="command-lease6-get">
<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. Currently supported identifiers for leases are:
"hw-address" (IPv4 only), "client-id" (IPv4 only) and "duid" (IPv6 only).
</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 "hw-address" 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 "client-id" for IPv4 lease looks
as follows:
<screen>
{
"command": "lease4-get",
"arguments": {
"identifier-type": "client-id",
"identifier": "01:01:02:03:04:05:06",
"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 id="command-lease4-get-all">
<title>lease4-get-all, lease6-get-all commands</title>
<para id="command-lease6-get-all"><command>lease4-get-all</command> and
<command>lease6-get-all</command> are used to retrieve all
IPv4 or IPv6 leases or all leases for the specified set of
subnets. All leases are returned when there are no arguments
specified with the command as in the following example:
<screen>
{
"command": "lease4-get-all"
}
</screen>
</para>
<para>If the arguments are provided, it is expected that they contain
"subnets" parameter, being a list of subnet identifiers for which the
leases should be returned. For example, in order to retrieve all IPv6
leases belonging to the subnets with identifiers 1, 2, 3 and 4:
<screen>
{
"command": "lease6-get-all",
"arguments": {
"subnets": [ 1, 2, 3, 4 ]
}
}
</screen>
</para>
<para>
The returned response contains a detailed list of leases in the
following format:
<screen>{
"arguments": {
"leases": [
{
"cltt": 12345678,
"duid": "42:42:42:42:42:42:42:42",
"fqdn-fwd": false,
"fqdn-rev": true,
"hostname": "myhost.example.com.",
"hw-address": "08:08:08:08:08:08",
"iaid": 1,
"ip-address": "2001:db8:2::1",
"preferred-lft": 500,
"state": 0,
"subnet-id": 44,
"type": "IA_NA",
"valid-lft": 3600
},
{
"cltt": 12345678,
"duid": "21:21:21:21:21:21:21:21",
"fqdn-fwd": false,
"fqdn-rev": true,
"hostname": "",
"iaid": 1,
"ip-address": "2001:db8:0:0:2::",
"preferred-lft": 500,
"prefix-len": 80,
"state": 0,
"subnet-id": 44,
"type": "IA_PD",
"valid-lft": 3600
}
]
},
"result": 0,
"text": "2 IPv6 lease(s) found."
}</screen>
</para>
<warning>
<para>The <command>lease4-get-all</command> and
<command>lease6-get-all</command> commands may result in very
large responses. This may have negative impact on the DHCP server
responsiveness while the response is generated and transmitted
over the control channel, as the server imposes no restriction
on the number of leases returned as a result of this command.
</para>
</warning>
</section>
<section xml:id="lease-get-page-cmds">
<title>lease4-get-page, lease6-get-page commands</title>
<para>The <command>lease4-get-all</command> and
<command>lease6-get-all</command> commands may result in very
large responses. Generating such a response may consume CPU bandwith
as well as memory. It may even cause the server to become
unresponsive. In case of large lease databases it is usually better
to retrieve leases in chunks, using paging mechanism. The
<command>lease4-get-page</command> and <command>lease6-get-page</command>
implement paging mechanism for DHCPv4 and DHCPv6 servers respectively.
The following command retrieves first 1024 IPv4 leases:
<screen>
{
"command": "lease4-get-page",
"arguments": {
"from": "start",
"limit": 1024
}
}
</screen>
</para>
<para>The keyword <command>start</command> denotes that the first page
of leases should be retrieved. Alternatively, an IPv4 zero address
can be specified to retrieve the first page:
<screen>
{
"command": "lease4-get-page",
"arguments": {
"from": "0.0.0.0",
"limit": 1024
}
}
</screen>
</para>
<para>Similaraly, the IPv6 zero address can be specified in the
<command>lease6-get-page</command> command:
<screen>
{
"command": "lease6-get-page",
"arguments": {
"from": "::",
"limit": 6
}
}
</screen>
</para>
<para>The response has the following structure:
<screen>
{
"arguments": {
"leases": [
{
"ip-address": "2001:db8:2::1",
...
},
{
"ip-address": "2001:db8:2::9",
...
},
{
"ip-address": "2001:db8:3::1",
...
},
{
"ip-address": "2001:db8:5::3",
...
}
{
"ip-address": "2001:db8:4::1",
...
},
{
"ip-address": "2001:db8:2::7",
...
}
],
"count": 6
},
"result": 0,
"text": "6 IPv6 lease(s) found."
}
</screen>
</para>
<para>Note that the leases' details were excluded from the response above
for brevity.</para>
<para>Generally, the returned list isn't sorted in any particular order.
Some lease database backends may sort leases in ascending order of addresses,
but the controlling client must not rely on this behavior. In case of
highly distributed databases, such as Cassandra, ordering may be inefficient
or even impossible.</para>
<para>The <command>count</command> parameter contains a number of returned
leases on the page.
</para>
<para>In order to fetch next page the client must use the last address
of the current page as an input to the next
<command>lease4-get-page</command> or <command>lease6-get-page</command>
command call. In this example it is going to be:
<screen>
{
"command": "lease6-get-page",
"arguments": {
"from": "2001:db8:2::7",
"count": 6
}
}
</screen>
because the 2001:db8:2::7 is the last address on the current page.
</para>
<para>The client may assume that it has reached the last page when the
<command>count</command> value is lower than specified in the command,
including the case when the <command>count</command> is equal to 0,
which means that no leases were found.
</para>
</section>
<section id="command-lease4-del">
<title>lease4-del, lease6-del commands</title>
<para id="command-lease6-del">
<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" (IPv4 only), "client-id"
(IPv4 only) and "duid" (IPv6 only), 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 "hw-address" 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-del</command> returns a result that
indicates a outcome of the operation. It has one of the
following values: 0 (success), 1 (error) or 3 (empty). The
empty result means that a query has been completed properly,
but the object (a lease in this case) has not been found.
</para>
</section>
<section id="command-lease4-update">
<title>lease4-update, lease6-update commands</title>
<para id="command-lease6-update"><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>Subnet-id parameter, used to be mandatory in Kea 1.4.0, but it
is optional since 1.5.0. If not specified or specified value is 0, Kea
will try to determine its value by running a subnet selection
procedure. If specified, however, its value must match the existing
subnet.</para>
<para>The optional boolean parameter "force-create" specifies
if the lease should be created if it doesn't exist in the database.
It defaults to false, which indicates that the lease is not created
if it doesn't exist. In such case, an error is returned as a result
of trying to update a non-existing lease. If the "force-create" parameter
is set to true and the updated lease doesn't exist, the new lease is
created as a result of receiving the <command>leaseX-update</command>.
</para>
<para>
An example command updating IPv4 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,
"force-create": true
}
}</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,
"force-create": false
}
}</screen>
</para>
</section>
<section id="command-lease4-wipe">
<title>lease4-wipe, lease6-wipe commands</title>
<para id="command-lease6-wipe"><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
parameters are incorrect or some other exception is
encountered.</para>
<para>The subnet-id 0 has special meaning. It tells Kea to
delete leases from all configured subnets. Also, the
subnet-id parameter may be omitted. If not specified, leases
from all subnets are wiped.</para>
<para>Note: not all backends support this command.</para>
</section>
</section>
</section>