.. ischooklib:: libdhcp_cb_cmds.so
.. _hooks-cb-cmds:

``libdhcp_cb_cmds.so``: Configuration Backend Commands
======================================================

This hook library is used to manage Kea servers' configurations in a
configuration backend database. This library must be used in conjunction with
the available CB hook libraries implementing the common APIs to create, read,
update, and delete (CRUD) the configuration information in the respective
databases. For example: :ischooklib:`libdhcp_mysql.so` implements this API for
MySQL while :ischooklib:`libdhcp_pgsql.so` implements this API for PostgreSQL.
To manage the configuration information in a MySQL database, both
:ischooklib:`libdhcp_mysql.so` and :ischooklib:`libdhcp_cb_cmds.so` must be
loaded by the server used for configuration management.
To manage the configuration information in a PostgreSQL database, both
:ischooklib:`libdhcp_pgsql.so` and :ischooklib:`libdhcp_cb_cmds.so` must be
loaded by the server used for configuration management.

More information on how to configure the Configuration Backend hook library for
use with a MySQL or PostgreSQL database can be found in the :ref:`dhcp4-cb`
and :ref:`dhcp6-cb` sections.

.. note::

    :ischooklib:`libdhcp_cb_cmds.so` is available only to ISC customers with
    a paid support contract. For more information on subscription options,
    please complete the form at https://www.isc.org/contact.

.. note::

   This library can only be loaded by the :iscman:`kea-dhcp4` or
   :iscman:`kea-dhcp6` process.

.. note::

   Please read about :ref:`cb-limitations` before using the commands
   described in this section.

Command Structure
~~~~~~~~~~~~~~~~~

There are 5 types of commands supported by this library:

-  ``del`` - delete the selected object from the database, e.g.
   :isccmd:`remote-global-parameter4-del`.

-  ``get`` - fetch the selected object from the database, e.g.
   :isccmd:`remote-subnet4-get-by-id`.

-  ``get-all`` - fetch all objects of the particular type from the
   database, e.g. :isccmd:`remote-option-def4-get-all`.

-  ``list`` - list all objects of the particular type in the database,
   e.g. :isccmd:`remote-network4-list`; this class of commands returns brief
   information about each object compared to the output of ``get-all``.

-  ``set`` - creates or replaces an object of the given type in the
   database, e.g. :isccmd:`remote-option4-global-set`.

All types of commands accept an optional ``remote`` map which selects the
database instance to which the command refers. For example:

.. code-block:: json

   {
       "command": "remote-subnet4-list",
       "arguments": {
           "remote": {
               "type": "mysql",
               "host": "192.0.2.33",
               "port": 3302
           }
       }
   }

selects the MySQL database, running on host 192.0.2.33 and port 3302, to
fetch the list of subnets from. All parameters in the ``remote`` argument are
optional. The ``port`` parameter can be only specified in conjunction
with the ``host``. If no options in the ``remote`` parameter are to
be specified, the parameter should be omitted. In this case, the server
will use the first backend listed in the ``config-control`` map within
the configuration of the server receiving the command.

.. note::

   In the current Kea release, it is only possible to configure the Kea server
   to use a single configuration backend. Strictly speaking, it is
   possible to point the Kea server to at most one database (either MySQL or
   PostgreSQL) using the ``config-control`` parameter. Therefore, the ``remote``
   parameter may be omitted in the commands and :ischooklib:`libdhcp_cb_cmds.so`
   uses the sole backend by default.  The example commands below most often show a
   value of "mysql" for the ``type`` parameter; it should be assumed that the
   value is "postgresql" for installations using a PostgreSQL database.

.. _cb-cmds-dhcp:

Control Commands for DHCP Servers
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

This section describes and gives some examples of the control commands
implemented by :ischooklib:`libdhcp_cb_cmds.so`, to manage the
configuration information of the DHCPv4 and DHCPv6 servers. Many of the
commands are almost identical between DHCPv4 and DHCPv6; they only
differ by the command name. Other commands differ slightly by the
structure of the inserted data; for example, the structure of the IPv4 subnet
information is different than that of the IPv6 subnet.
Nevertheless, they still share the structure of their command arguments
and thus it makes sense to describe them together.

In addition, whenever the text in the subsequent sections refers to a
DHCP command or DHCP parameter, it refers to both DHCPv4 and DHCPv6
variants. The text specific to the particular server type refers to them
as: DHCPv4 command, DHCPv4 parameter, DHCPv6 command, DHCPv6 parameter,
etc.

.. _cb-cmds-metadata:

Metadata
~~~~~~~~

The typical response to the ``get`` or ``list`` command includes a list
of returned objects (e.g. subnets), and each such object contains the
``metadata`` map with some database-specific information describing this
object. In other words, the metadata contains any information about the
fetched object which may be useful for an administrator but which is not
part of the object specification from the DHCP server standpoint. In the
present Kea release, the metadata is limited to the ``server-tag``. It
describes the association of the object with a particular server or
all servers.

The following is the example response to the :isccmd:`remote-network4-list`
command, which includes the metadata:

.. code-block:: json

   {
       "result": 0,
       "text": "1 IPv4 shared network(s) found.",
       "arguments": {
           "shared-networks": [
               {
                   "name": "level3",
                   "metadata": {
                       "server-tags": [ "all" ]
                   }
               }
           ],
           "count": 1
       }
   }


Client implementations must not assume that the metadata contains only
the ``server-tags`` parameter. In future releases, it is expected that this
map will be extended with additional information, e.g. object modification
time, log message created during the last modification, etc.

.. _cb-cmds-option-class-tags-as-keys:

Option Class-tags as Keys
~~~~~~~~~~~~~~~~~~~~~~~~~

:ref:`option-class-tagging` added a list of client classes, ``client-classes``,
to option specifications. Thus in any list of option specifications (e.g.
`option-data`), there may be more than one specification for the same ``code``
and ``space``' but with different ``client-classes`` lists and different
data content.

In order to support this construct, Kea uses the option's ``client-classes``
list in addition to code and space to uniquely identifiy each option. This
is important to keep in mind when using the Management API to alter your
configuration. As of Kea 3.1.1 commands which get, set, or delete an
individual option now accept an optional ``client-classes`` parameter in
addition to ``code`` and ``space`` parameters.

If the ``client-classes`` parameter is omitted:

1.  Get - Fetches one of n that matches code and space. Which option is returned
    is indeterminate when more than one match exists.

2.  Set - Updates only the option that matches code and space and has an empty
    client-classes list. If no match is found then the option is created.

3.  Delete - Deletes all options that match the code and space, if they exist.

If the ``client-classes`` parameter is specified:

1.  Get - Fetches the option that matches code, space and client-classes if
    one exists.

2.  Set - Updates only the option that matches code, space and client-classes.
    If no match is found then the option is created.

3.  Delete - Deletes only the option that matches code, space and client-classes,
    if one exists.

An empty ``client-classes`` list is specified as '[  ]' with or without white spaces
between the brackets. When managing lists of options that do not employ client class-
tagging, the ``client-classes`` parameter may simply be omitted.

.. isccmd:: remote-server4-del
.. _command-remote-server4-del:
.. isccmd:: remote-server6-del
.. _command-remote-server6-del:

The ``remote-server4-del``, ``remote-server6-del`` Commands
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

This command is used to delete the information about a selected DHCP server from
the configuration database. The server is identified by a unique case
insensitive server tag. For example:

.. code-block:: json

    {
        "command": "remote-server4-del",
        "arguments": {
            "servers": [
                {
                    "server-tag": "server1"
                }
            ],
            "remote": {
                "type": "postgresql"
            }
        }
    }

As a result of this command, all associations of the configuration for the
user-defined server called "server1" are removed from the database, including
non-shareable configuration information, such as global parameters, option
definitions, and global options. Any shareable configuration information,
i.e. the configuration elements which may
be associated with more than one server, is preserved. In particular, the
subnets and shared networks associated with the deleted servers are
preserved. If any of the shareable configuration elements was associated only
with the deleted server, this object becomes unassigned (orphaned). For
example: if a subnet has been created and associated with "server1" using
the :isccmd:`remote-subnet4-set` command and "server1" is subsequently deleted, the
subnet remains in the database but no servers can use this subnet. The
subnet can be updated using the :isccmd:`remote-subnet4-set` command, and can be
associated with either another server or with all servers, using the special
server tag "all". Such a subnet can be also deleted from the database
using the :isccmd:`remote-subnet4-del-by-id` or
:isccmd:`remote-subnet4-del-by-prefix` command, if it is no longer needed.

The following is the successful response to the :isccmd:`remote-server4-del` command:

.. code-block:: json

    {
        "result": 0,
        "text": "1 DHCPv4 server(s) deleted.",
        "arguments": {
            "count": 1
        }
    }


.. warning::

   The :isccmd:`remote-server4-del` and
   :isccmd:`remote-server6-del` commands must be used with
   care, because an accidental deletion of the server can cause some parts of the
   existing configurations to be lost permanently from the database. This
   operation is not reversible. Re-creation of the accidentally deleted server
   does not revert the lost configuration for that server and such configuration
   must be re-created manually by the user.

.. isccmd:: remote-server4-get
.. _command-remote-server4-get:
.. isccmd:: remote-server6-get
.. _command-remote-server6-get:

The ``remote-server4-get``, ``remote-server6-get`` Commands
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

This command is used to fetch the information about the selected DHCP server
from the configuration database. For example:

.. code-block:: json

    {
        "command": "remote-server6-get",
        "arguments": {
            "servers": [
                {
                    "server-tag": "server1"
                }
            ],
            "remote": {
                "type": "mysql"
            }
        }
    }


This command fetches the information about the DHCPv6 server identified by the
server tag "server1". The server tag is case-insensitive. A successful response
returns basic information about the server, such as the server tag and the user's
description of the server:

.. code-block:: json

    {
        "result": 0,
        "text": "DHCP server server1 found.",
        "arguments": {
            "servers": [
                {
                    "server-tag": "server1",
                    "description": "A DHCPv6 server located on the first floor."
                }
            ],
            "count": 1
        }
    }

.. isccmd:: remote-server4-get-all
.. _command-remote-server4-get-all:
.. isccmd:: remote-server6-get-all
.. _command-remote-server6-get-all:

The ``remote-server4-get-all``, ``remote-server6-get-all`` Commands
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

This command is used to fetch all user-defined DHCPv4 or DHCPv6 servers from the
database. The command structure is very simple:

.. code-block:: json

    {
        "command": "remote-server4-get-all",
        "arguments": {
            "remote": {
                "type": "mysql"
            }
        }
    }

The response includes basic information about each server, such as its server
tag and description:

.. code-block:: json

    {
        "result": 0,
        "text": "DHCPv4 servers found.",
        "arguments": {
            "servers": [
                {
                    "server-tag": "server1",
                    "description": "A DHCP server located on the first floor."
                },
                {
                    "server-tag": "server2",
                    "description": "An old DHCP server to be soon replaced."
                }
            ],
           "count": 2
        }
    }

.. isccmd:: remote-server4-set
.. _command-remote-server4-set:
.. isccmd:: remote-server6-set
.. _command-remote-server6-set:

The ``remote-server4-set``, ``remote-server6-set`` Commands
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

This command is used to create or replace an information about a DHCP server in
the database. The information about the server must be created when there is a
need to differentiate the configurations used by various Kea instances
connecting to the same database. Various configuration elements, e.g. global
parameters, subnets, etc. may be explicitly associated with the selected servers
(using server tags as identifiers), allowing only these servers to use the
respective configuration elements. Using the particular server tag to make such
associations is only possible when the server information has been stored in the
database via the :isccmd:`remote-server4-set` or
:isccmd:`remote-server6-set` commands. The
following command creates a new (or updates an existing) DHCPv6 server in the
database:

.. code-block:: json

    {
        "command": "remote-server6-set",
        "arguments": {
            "servers": [
                {
                    "server-tag": "server1",
                    "description": "A DHCP server on the ground floor."
                }
            ],
            "remote": {
                "type": "mysql"
            }
        }
    }

The server tag must be unique across all servers in the database. When the
server information under the given server tag already exists, it is replaced
with the new information. The specified server tag is case-insensitive, and the
maximum length of the server tag is 256 characters. The following keywords are
reserved and cannot be used as server tags: "all" and "any".

The following is the example response to the above command:

.. code-block:: json

    {
        "result": 0,
        "text": "DHCPv6 server successfully set.",
        "arguments": {
            "servers": [
                {
                    "server-tag": "server1",
                    "description": "A DHCP server on the ground floor."
                }
            ]
        }
    }


.. isccmd:: remote-global-parameter4-del
.. _command-remote-global-parameter4-del:

.. isccmd:: remote-global-parameter6-del
.. _command-remote-global-parameter6-del:

The ``remote-global-parameter4-del``, ``remote-global-parameter6-del`` Commands
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

These commands are used to delete a global DHCP parameter from the
configuration database. When the parameter is deleted from the database,
the server uses the value specified in the configuration file for
this parameter, or a default value if the parameter is not specified in
the configuration file.

The following command attempts to delete the DHCPv4 ``renew-timer``
parameter common for all servers from the database:

.. code-block:: json

   {
       "command": "remote-global-parameter4-del",
       "arguments": {
           "parameters": [ "renew-timer" ],
           "remote": {
               "type": "mysql"
            },
           "server-tags": [ "all" ]
       }
   }

If a server-specific parameter is to be deleted, the
``server-tags`` list must contain the tag of the appropriate
server. There must be exactly one server tag specified in this list.

.. isccmd:: remote-global-parameter4-get
.. _command-remote-global-parameter4-get:

.. isccmd:: remote-global-parameter6-get
.. _command-remote-global-parameter6-get:

The ``remote-global-parameter4-get``, ``remote-global-parameter6-get`` Commands
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

These commands are used to fetch a scalar global DHCP parameter from the
configuration database.

The following command attempts to fetch the ``boot-file-name``
parameter for "server1":

.. code-block:: json

   {
       "command": "remote-global-parameter4-get",
       "arguments": {
           "parameters": [ "boot-file-name" ],
            "remote": {
                "type": "mysql"
            },
            "server-tags": [ "server1" ]
       }
   }


The returned value has one of the four scalar types: string, integer,
real, or boolean. Non-scalar global configuration parameters, such as map
or list, are not returned by this command.

In the case of the example above, the string value is returned, e.g.:

.. code-block:: json

   {
       "result": 0,
       "text": "1 DHCPv4 global parameter found.",
       "arguments": {
           "parameters": {
               "boot-file-name": "/dev/null",
               "metadata": {
                   "server-tags": [ "all" ]
               }
           },
           "count": 1
       }
   }


Note that the response above indicates that the returned parameter is associated
with "all" servers rather than "server1", used in the command. This indicates
that there is no "server1"-specific value in the database and therefore, the value
shared by all servers is returned. If there were a "server1"-specific value
in the database, that value would be returned instead.

The example response for the integer value is:

.. code-block:: json

   {
       "result": 0,
       "text": "1 DHCPv4 global parameter found.",
       "arguments": {
           "parameters": {
               "renew-timer": 2000,
               "metadata": {
                   "server-tags": [ "server1" ]
               }
           },
           "count": 1
       }
   }


The real value:

.. code-block:: json

   {
       "result": 0,
       "text": "1 DHCPv4 global parameter found.",
       "arguments": {
           "parameters": {
               "t1-percent": 0.85,
               "metadata": {
                   "server-tags": [ "all" ]
               }
           },
           "count": 1
       }
   }


Finally, the boolean value:

.. code-block:: json

   {
       "result": 0,
       "text": "1 DHCPv4 global parameter found.",
       "arguments": {
           "parameters": {
               "match-client-id": true,
               "metadata": {
                   "server-tags": [ "server2" ]
               }
           },
           "count": 1
       }
   }


.. isccmd:: remote-global-parameter4-get-all
.. _command-remote-global-parameter4-get-all:

.. isccmd:: remote-global-parameter6-get-all
.. _command-remote-global-parameter6-get-all:

The ``remote-global-parameter4-get-all``, ``remote-global-parameter6-get-all`` Commands
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

These commands are used to fetch all global DHCP parameters from the database
for the specified server. The following example demonstrates how to fetch all
global parameters to be used by the server "server1":

.. code-block:: json

    {
        "command": "remote-global-parameter4-get-all",
        "arguments": {
            "remote": {
                "type": "mysql"
            },
            "server-tags": [ "server1" ]
        }
    }

The example response may look as follows:

.. code-block:: json

    {
        "result": 0,
        "text": "DHCPv4 global parameters found.",
        "arguments": {
            "parameters": [
                {
                    "boot-file-name": "/dev/null",
                    "metadata": {
                        "server-tags": [ "server1" ]
                    }
                },
                {
                    "match-client-id": true,
                    "metadata": {
                        "server-tags": [ "all" ]
                    }
                }
            ],
            "count": 2
        }
    }


The example response contains two parameters: one string parameter and one
boolean parameter. The metadata returned for each parameter indicates
whether this parameter is specific to "server1" or applies to all servers. Since the
``match-client-id`` value is associated with "all" servers,
it indicates that there is no "server1"-specific setting for this parameter.
Each parameter always has exactly one server tag associated with it, because
global parameters are non-shareable configuration elements.

.. note::

   If the server tag is set to "all" in the command, the response will
   contain only the global parameters associated with the logical server
   "all". When the server tag points to the specific server (as in the
   example above), the returned list combines parameters associated with
   this server and all servers, but the former take precedence.

.. isccmd:: remote-global-parameter4-set
.. _command-remote-global-parameter4-set:

.. isccmd:: remote-global-parameter6-set
.. _command-remote-global-parameter6-set:

The ``remote-global-parameter4-set``, ``remote-global-parameter6-set`` Commands
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

This command is used to create scalar global DHCP parameters in the
database. If any of the parameters already exists, its value is replaced
as a result of this command. It is possible to set multiple parameters
within a single command, each having one of the four types: string,
integer, real, or boolean. For example:

.. code-block:: json

   {
       "command": "remote-global-parameter4-set",
       "arguments": {
           "parameters": {
               "boot-file-name": "/dev/null",
               "renew-timer": 2000,
               "t1-percent": 0.85,
               "match-client-id": true
           },
           "remote": {
               "type": "mysql"
           },
           "server-tags": [ "server1" ]
       }
   }

An error is returned if any of the parameters is not supported by the DHCP
server or its type does not match. Care should be taken when multiple parameters
are specified in a single command, because it is possible that only some of the
parameters will be stored successfully and some will fail. If an error occurs when
processing this command, it is recommended to use
:isccmd:`remote-global-parameter4-get-all` or
:isccmd:`remote-global-parameter6-get-all`
to check which of the parameters have
been stored/updated successfully and which have failed.

The ``server-tags`` list is mandatory and must contain a single server tag or
the keyword "all". In the example above, all specified parameters are associated
with the "server1" server.

.. isccmd:: remote-network4-del
.. _command-remote-network4-del:

.. isccmd:: remote-network6-del
.. _command-remote-network6-del:

The ``remote-network4-del``, ``remote-network6-del`` Commands
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

These commands are used to delete an IPv4 or IPv6 shared network from
the database. The optional parameter ``subnets-action`` determines
whether the subnets belonging to the deleted shared network should also
be deleted or preserved. The ``subnets-action`` parameter defaults to ``keep``,
which preserves the subnets. If it is set to ``delete``, the subnets are
deleted along with the shared network.

The following command:

.. code-block:: json

   {
       "command": "remote-network6-del",
       "arguments": {
           "shared-networks": [
               {
                   "name": "level3"
               }
           ],
           "subnets-action": "keep",
           "remote": {
               "type": "mysql"
           }
       }
   }


deletes the "level3" IPv6 shared network. The subnets are preserved, but
they are disassociated from the deleted shared network and become
global. This behavior corresponds to the behavior of the
:isccmd:`network4-del`, :isccmd:`network6-del` commands with respect to the
``subnets-action`` parameter.

Note that the ``server-tags`` parameter cannot be used for this command.

.. isccmd:: remote-network4-get
.. _command-remote-network4-get:

.. isccmd:: remote-network6-get
.. _command-remote-network6-get:

The ``remote-network4-get``, ``remote-network6-get`` Commands
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

These commands are used to retrieve information about an IPv4 or
IPv6 shared network. The optional parameter ``subnets-include`` denotes
whether the subnets belonging to the shared network should also be
returned. This parameter defaults to ``no``, in which case the subnets
are not returned. If this parameter is set to ``full``, the subnets are
returned together with the shared network.

The following command fetches the "level3" IPv6 shared network along
with the full information about the subnets belonging to it:

.. code-block:: json

   {
       "command": "remote-network6-get",
       "arguments": {
           "shared-networks": [
               {
                   "name": "level3"
               }
           ],
           "subnets-include": "full",
           "remote": {
               "type": "mysql"
           }
       }
   }

Note that the ``server-tags`` parameter cannot be used for this command.

.. isccmd:: remote-network4-list
.. _command-remote-network4-list:

.. isccmd:: remote-network6-list
.. _command-remote-network6-list:

The ``remote-network4-list``, ``remote-network6-list`` Commands
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

These commands are used to list all IPv4 or IPv6 shared networks for a server.

The following command retrieves all shared networks to be used by
"server1" and "server2":

.. code-block:: json

    {
        "command": "remote-network4-list",
        "arguments": {
            "remote": {
                "type": "mysql"
            },
            "server-tags": [ "server1", "server2" ]
        }
    }

The ``server-tags`` parameter is mandatory and contains one or more server
tags. It may contain the keyword "all" to fetch the shared networks associated
with all servers. When the ``server-tags`` list contains the
``null`` value, the returned response contains a list of unassigned shared
networks, i.e. the networks which are associated with no servers. For example:

.. code-block:: json

    {
        "command": "remote-network4-list",
        "arguments": {
            "remote": {
                "type": "mysql"
            },
            "server-tags": [ null ]
        }
    }

The example response to this command when non-null server tags are specified
looks similar to this:

.. code-block:: json

    {
        "result": 0,
        "text": "3 IPv4 shared network(s) found.",
        "arguments": {
            "shared-networks": [
                {
                    "name": "ground floor",
                    "metadata": {
                        "server-tags": [ "all" ]
                    }
                },
                {
                    "name": "floor2",
                    "metadata": {
                        "server-tags": [ "server1" ]
                    }
                },
                {
                    "name": "floor3",
                    "metadata": {
                        "server-tags": [ "server2" ]
                    }
                }
            ],
            "count": 3
        }
    }

The returned information about each shared network merely contains the shared
network name and the metadata. To fetch detailed information about
the selected shared network, use the :isccmd:`remote-network4-get` or
:isccmd:`remote-network6-get` command.

The example response above contains three shared networks. One of the
shared networks is associated with all servers, so it is included in
the list of shared networks to be used by "server1" and "server2".
The remaining two shared networks are returned because one of them
is associated with "server1" and another one is associated with
"server2".

When listing unassigned shared networks, the response looks similar
to this:

.. code-block:: json

    {
        "result": 0,
        "text": "1 IPv4 shared network(s) found.",
        "arguments": {
            "shared-networks": [
                {
                    "name": "fancy",
                    "metadata": {
                        "server-tags": [ null ]
                    }
                }
            ],
            "count": 1
        }
    }

The ``null`` value in the metadata indicates that the
returned shared network is unassigned.

.. isccmd:: remote-network4-set
.. _command-remote-network4-set:

.. isccmd:: remote-network6-set
.. _command-remote-network6-set:

The ``remote-network4-set``, ``remote-network6-set`` Commands
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

These commands create a new or replace an existing IPv4 or IPv6 shared
network in the database. The structure of the shared network information
is the same as in the Kea configuration file (see
:ref:`shared-network4` and :ref:`shared-network6` for details),
except that specifying subnets along with the shared
network information is not allowed. Including the ``subnet4`` or ``subnet6`` parameter
within the shared network information results in an error.

These commands are intended to be used for managing the shared
network-specific information and DHCP options. To associate and
disassociate the subnets with the shared networks, the
:isccmd:`remote-subnet4-set`, :isccmd:`remote-subnet6-set`
commands should be used.

The following command adds the IPv6 shared network "level3" to the
database:

.. code-block:: json

   {
       "command": "remote-network6-set",
       "arguments": {
           "shared-networks": [
               {
                   "name": "level3",
                   "interface": "eth0",
                   "option-data": [ {
                       "name": "sntp-servers",
                       "data": "2001:db8:1::1"
                   } ]
               }
           ],
           "remote": {
               "type": "mysql"
           },
           "server-tags": [ "all" ]
       }
   }


This command includes the ``interface`` parameter, which sets the shared
network-level interface name. Any remaining shared-network-level parameters,
which are not specified with the command, will be marked as
"unspecified" in the database. The DHCP server uses the global
values for unspecified parameters or, if the global values are not
specified, the default values are used.

The ``server-tags`` list is mandatory for this command and must include one or
more server tags. As a result, the shared network is associated with all listed
servers. The shared network may be associated with all servers connecting to the
database when the keyword "all" is included.

.. note::

   As with other "set" commands, this command replaces all the
   information about the given shared network in the database, if the
   shared network already exists. Therefore, when sending this command,
   make sure to always include all parameters that must be specified for
   the updated shared-network instance. Any unspecified parameter will
   be marked unspecified in the database, even if its value was present
   prior to sending the command.

.. isccmd:: remote-option-def4-del
.. _command-remote-option-def4-del:

.. isccmd:: remote-option-def6-del
.. _command-remote-option-def6-del:

The ``remote-option-def4-del``, ``remote-option-def6-del`` Commands
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

These commands are used to delete a DHCP option definition from the
database. The option definition is identified by an option code and
option space. For example:

.. code-block:: json

   {
       "command": "remote-option-def6-del",
       "arguments": {
           "option-defs": [
               {
                   "code": 1,
                   "space": "isc"
               }
           ],
           "remote": {
               "type": "mysql"
           },
           "server-tags": [ "server1" ]
       }
   }


deletes the definition of the option associated with "server1", having the
code of 1 and belonging to the option space "isc". The default option spaces are
"dhcp4" and "dhcp6" for the DHCPv4 and DHCPv6 top-level options, respectively. If
there is no such option definition explicitly associated with "server1", no option
definition is deleted. To delete an option definition belonging to "all" servers,
the keyword "all" must be used as the server tag. The ``server-tags`` list must
contain exactly one tag and cannot include the ``null`` value.

As of Kea 3.1.2, before deleting an option definition, the server will first
check if there are any options specified that depend upon that definition. If
so the delete command will be rejected with an error message explaining why.
This default behavior may be overridden by setting the optional ``force``
parameter to true as shown below:

.. code-block:: json

   {
       "command": "remote-option-def6-del",
       "arguments": {
           "option-defs": [
               {
                   "code": 1,
                   "space": "isc",
                   "force": true
               }
           ],
           "remote": {
               "type": "mysql"
           },
           "server-tags": [ "server1" ]
       }
   }

.. note::

    The ``force`` parameter should only be used after careful consideration.
    Removing an option definition while a dependent option specification exists
    will cause that option to be excluded from the running configuration.
    This parameter is provided to handle use cases where a definition may
    need to be corrected while leaving the option in place.

.. isccmd:: remote-option-def4-get
.. _command-remote-option-def4-get:

.. isccmd:: remote-option-def6-get
.. _command-remote-option-def6-get:

The ``remote-option-def4-get``, ``remote-option-def6-get`` Commands
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

These commands are used to fetch a specified DHCP option definition from
the database. The option definition is identified by the option code and
option space. The default option spaces are "dhcp4" and "dhcp6" for the
DHCPv4 and DHCPv6 top-level options, respectively.

The following command retrieves a DHCPv4 option definition associated with all
servers, having the code of 1 and belonging to the option space "isc":

.. code-block:: json

   {
       "command": "remote-option-def4-get",
       "arguments": {
           "option-defs": [
               {
                   "code": 1,
                   "space": "isc"
               }
           ],
           "remote": {
               "type": "mysql"
           },
           "server-tags": [ "all" ]
       }
   }

The ``server-tags`` list must include exactly one server tag or the keyword
"all", and cannot contain the `null` value.

.. isccmd:: remote-option-def4-get-all
.. _command-remote-option-def4-get-all:

.. isccmd:: remote-option-def6-get-all
.. _command-remote-option-def6-get-all:

The ``remote-option-def4-get-all``, ``remote-option-def6-get-all`` Commands
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

These commands are used to fetch all DHCP option definitions from the database
for the given server or all servers. For example:

.. code-block:: json

    {
        "command": "remote-option-def6-get-all",
        "arguments": {
            "remote": {
                "type": "mysql"
            },
            "server-tags": [ "all" ]
        }
    }

This command attempts to fetch all DHCPv6 option definitions associated
with "all" servers. The ``server-tags`` list is mandatory for
this command and must include exactly one server tag or the keyword "all".
It cannot include the ``null`` value.

The following is the example response to this command:

.. code-block:: json

    {
        "result": 0,
        "text": "1 DHCPv6 option definition(s) found.",
        "arguments": {
            "option-defs": [
                {
                    "name": "bar",
                    "code": 1012,
                    "space": "dhcp6",
                    "type": "record",
                    "array": true,
                    "record-types": "ipv6-address, uint16",
                    "encapsulate": "",
                    "metadata": {
                        "server-tags": [ "all" ]
                    }
                }
            ],
            "count": 1
        }
    }

The response contains an option definition associated with all servers, as
indicated by the metadata.

.. isccmd:: remote-option-def4-set
.. _command-remote-option-def4-set:

.. isccmd:: remote-option-def6-set
.. _command-remote-option-def6-set:

The ``remote-option-def4-set``, ``remote-option-def6-set`` Commands
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

These commands create a new DHCP option definition or replace an
existing option definition in the database. The structure of the option
definition information is the same as in the Kea configuration file (see
:ref:`dhcp4-custom-options` and :ref:`dhcp6-custom-options`).
The following command creates the DHCPv4 option definition at the
top-level "dhcp4" option space and associates it with "server1":

.. code-block:: json

   {
       "command": "remote-option-def4-set",
       "arguments": {
           "option-defs": [
               {
                   "name": "foo",
                   "code": 222,
                   "type": "uint32",
                   "array": false,
                   "record-types": "",
                   "space": "dhcp4",
                   "encapsulate": ""
               }
           ],
           "remote": {
               "type": "mysql"
           },
           "server-tags": [ "server1" ]
       }
   }

The ``server-tags`` list must include exactly one
server tag or the keyword "all", and cannot contain the
``null`` value.

.. isccmd:: remote-option4-global-del
.. _command-remote-option4-global-del:

.. isccmd:: remote-option6-global-del
.. _command-remote-option6-global-del:

The ``remote-option4-global-del``, ``remote-option6-global-del`` Commands
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

These commands are used to delete a global DHCP option from the
database. The option is identified by an option code and option space.
As of Kea 3.1.1 an optional ``client-classes`` parameter may also be
specified (see :ref:`cb-cmds-option-class-tags-as-keys`).

For example:

.. code-block:: json

   {
       "command": "remote-option4-global-del",
       "arguments": {
           "options": [
               {
                   "code": 5,
                   "space": "dhcp4",
                   "client-classes": [ "class-one" ]
               }
           ],
           "remote": {
               "type": "mysql"
           },
           "server-tags": [ "server1" ]
       }
   }

The "dhcp4" value represents the top-level option space where the standard DHCPv4
options belong. The ``server-tags`` parameter is mandatory and must include a
single option tag or the keyword "all". If the explicit server tag is specified,
this command attempts to delete a global option associated with this
server. If there is no such option associated with the given server, no option
is deleted. To delete an option associated with all servers, the
keyword "all" must be specified.


.. isccmd:: remote-option4-global-get
.. _command-remote-option4-global-get:

.. isccmd:: remote-option6-global-get
.. _command-remote-option6-global-get:

The ``remote-option4-global-get``, ``remote-option6-global-get`` Commands
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

These commands are used to fetch a global DHCP option from the database.
The option is identified by the code and option space. The top-level
option spaces where DHCP standard options belong are called "dhcp4" and
"dhcp6" for the DHCPv4 and DHCPv6 servers, respectively.
As of Kea 3.1.1, an optional ``client-classes`` parameter may also be
specified (see :ref:`cb-cmds-option-class-tags-as-keys`).

The following command retrieves the IPv6 "DNS Servers" (code 23) option
associated with all servers:

.. code-block:: json

   {
       "command": "remote-option6-global-get",
       "arguments": {
           "options": [
               {
                   "code": 23,
                   "space": "dhcp6",
                   "client-classes": [ "class-one" ]
               }
           ],
           "remote": {
               "type": "mysql"
           },
           "server-tags": [ "all" ]
       }
   }

The ``server-tags`` parameter is mandatory and must include exactly one
server tag or the keyword "all". It cannot contain the ``null``
value.

.. isccmd:: remote-option4-global-get-all
.. _command-remote-option4-global-get-all:

.. isccmd:: remote-option6-global-get-all
.. _command-remote-option6-global-get-all:

The ``remote-option4-global-get-all``, ``remote-option6-global-get-all`` Commands
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

These commands are used to fetch all global DHCP options from the configuration
database for the given server or for all servers. The following command
fetches all global DHCPv4 options for "server1":

.. code-block:: json

    {
        "command": "remote-option6-global-get-all",
        "arguments": {
            "remote": {
                "type": "mysql"
            },
            "server-tags": [ "server1" ]
        }
    }

The ``server-tags`` list is mandatory for this command and
must contain exactly one server tag or a keyword "all"; it cannot contain
the ``null`` value.

The following is a example response to this
command with a single option being associated with "server1" returned:

.. code-block:: json

    {
        "result": 0,
        "text": "DHCPv4 options found.",
        "arguments": {
            "options": [
                {
                    "name": "domain-name-servers",
                    "code": 6,
                    "space": "dhcp4",
                    "csv-format": false,
                    "data": "192.0.2.3",
                    "metadata": {
                        "server-tags": [ "server1" ]
                    }
                }
            ],
            "count": 1
        }
    }

.. isccmd:: remote-option4-global-set
.. _command-remote-option4-global-set:

.. isccmd:: remote-option6-global-set
.. _command-remote-option6-global-set:

The ``remote-option4-global-set``, ``remote-option6-global-set`` Commands
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

These commands create a new global DHCP option or replace an existing
option in the database. The structure of the option information is the
same as in the Kea configuration file (see :ref:`dhcp4-std-options`
and :ref:`dhcp6-std-options`). For example:

.. code-block:: json

   {
       "command": "remote-option6-global-set",
       "arguments": {
           "options": [
               {
                   "name": "dns-servers",
                   "data": "2001:db8:1::1"
               }
           ],
           "remote": {
               "type": "mysql"
           },
           "server-tags": [ "server1" ]
       }
   }

The ``server-tags`` list is mandatory for this command
and must include exactly one server tag or the keyword "all"; it cannot
include the ``null`` value. The command above associates
the option with the "server1" server.

Note that specifying an option name instead of the option code only
works reliably for standard DHCP options. When specifying a value
for a user-defined DHCP option, the option code should be indicated
instead of the name. For example:

.. code-block:: json

   {
       "command": "remote-option6-global-set",
       "arguments": {
           "options": [
               {
                   "code": 1,
                   "space": "isc",
                   "data": "2001:db8:1::1"
               }
           ],
           "server-tags": [ "server1" ]
       }
   }

.. isccmd:: remote-option4-network-del
.. _command-remote-option4-network-del:

.. isccmd:: remote-option6-network-del
.. _command-remote-option6-network-del:

The ``remote-option4-network-del``, ``remote-option6-network-del`` Commands
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

These commands are used to delete a shared-network-specific DHCP
option from the database. The option is identified by an option code
and option space, and as of Kea 3.1.1, an optional ``client-classes``
parameter may also be specified (see :ref:`cb-cmds-option-class-tags-as-keys`).
These parameters are passed within the ``options`` list.
Another list, ``shared-networks``, contains a map
with the name of the shared network from which the option is to
be deleted. If the option is not explicitly specified for this
shared network, no option is deleted. In particular, the given
option may be present for a subnet belonging to the shared network.
Such an option instance is not affected by this command as this
command merely deletes the shared-network-level option. To
delete a subnet-level option, the :isccmd:`remote-option4-subnet-del`,
:isccmd:`remote-option6-subnet-del` commands must be used instead.

The following command attempts to delete an option having the
option code 5 in the top-level option space and an empty client-classes
list from the shared network "fancy".

.. code-block:: json

   {
       "command": "remote-option4-network-del",
       "arguments": {
           "shared-networks": [
               {
                   "name": "fancy"
               }
           ],
           "options": [
               {
                   "code": 5,
                   "space": "dhcp4",
                   "client-classes" : [ ]
               }
           ],
           "remote": {
               "type": "mysql"
           }
       }
   }

The "dhcp4" value represents the top-level option space where the standard DHCPv4
options belong. The ``server-tags`` parameter cannot be specified for this command.

.. isccmd:: remote-option4-network-set
.. _command-remote-option4-network-set:

.. isccmd:: remote-option6-network-set
.. _command-remote-option6-network-set:

The ``remote-option4-network-set``, ``remote-option6-network-set`` Commands
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

These commands create a new shared-network-specific DHCP option or replace
an existing option in the database. The structure of the option information
is the same as in the Kea configuration file (see :ref:`dhcp4-std-options`
and :ref:`dhcp6-std-options`). The option information is carried in the
``options`` list.  Another list, ``shared-networks``, contains a map with the
name of the shared network for which the option is to be set. If such an option
already exists for the shared network, it is replaced with the new instance.

.. code-block:: json

   {
       "command": "remote-option6-network-set",
       "arguments": {
           "shared-networks": [
               {
                   "name": "fancy"
               }
           ],
           "options": [
               {
                   "name": "dns-servers",
                   "data": "2001:db8:1::1"
               }
           ],
           "remote": {
               "type": "mysql"
           }
       }
   }

The ``server-tags`` parameter cannot be specified for this command.

Specifying an option name instead of the option code only works reliably
for standard DHCP options. When specifying a value for a user-defined
DHCP option, the option code should be indicated instead of the name.

.. isccmd:: remote-option6-pd-pool-del
.. _command-remote-option6-pd-pool-del:

The ``remote-option6-pd-pool-del`` Command
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

This command is used to delete a prefix delegation pool-specific DHCPv6
option from the database. The option is identified by an option code and
option space, and as of Kea 3.1.1, an optional ``client-classes`` parameter
may also be specified (see :ref:`cb-cmds-option-class-tags-as-keys`).
These parameters are passed within the ``options`` list.
Another list, ``pd-pools``, contains a map with the
prefix-delegation-pool prefix and length identifying the pool. If the
option is not explicitly specified for this pool, no option is deleted.
In particular, the given option may exist for a subnet containing
the specified pool. Such an option instance is not affected by this
command, as this command merely deletes a prefix delegation pool-level
option. To delete a subnet-level option, the
:isccmd:`remote-option6-subnet-del` command must be used instead.

.. code-block:: json

   {
       "command": "remote-option6-pd-pool-del",
       "arguments": {
           "pd-pools": [
               {
                   "prefix": "3000::",
                   "prefix-len": 64
               }
           ],
           "options": [
               {
                   "code": 23,
                   "space": "dhcp6"
               }
           ],
           "remote": {
               "type": "mysql"
           }
       }
   }

The "dhcp6" value represents the top-level option space where the standard DHCPv6
options belong. The ``server-tags`` parameter cannot be specified for this command.

.. isccmd:: remote-option6-pd-pool-set
.. _command-remote-option6-pd-pool-set:

The ``remote-option6-pd-pool-set`` Command
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

This command creates a new prefix delegation pool-specific DHCPv6 option or
replaces an existing option in the database. The structure of the option
information is the same as in the Kea configuration file (see :ref:`dhcp4-std-options`
and :ref:`dhcp6-std-options`). The option information is carried in the
``options`` list. Another list, ``pd-pools``, contains a map with the
prefix-delegation-pool prefix and the prefix length identifying the pool. If such an
option already exists for the prefix delegation pool, it is replaced with
the new instance.

For example:

.. code-block:: json

   {
       "command": "remote-option6-pd-pool-set",
       "arguments": {
           "pd-pools": [
               {
                   "prefix": "3001:1::",
                   "length": 64
               }
           ],
           "options": [
               {
                   "name": "dns-servers",
                   "data": "2001:db8:1::1"
               }
           ],
           "remote": {
               "type": "mysql"
           }
       }
   }

The ``server-tags`` parameter cannot be specified for this command.

Specifying an option name instead of the option code only works reliably
for standard DHCP options. When specifying a value for a user-defined
DHCP option, the option code should be indicated instead of the name.

.. isccmd:: remote-option4-pool-del
.. _command-remote-option4-pool-del:

.. isccmd:: remote-option6-pool-del
.. _command-remote-option6-pool-del:

The ``remote-option4-pool-del``, ``remote-option6-pool-del`` Commands
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

These commands are used to delete an address-pool-specific DHCP
option from the database. The option is identified by an option code
and option space, and as of Kea 3.1.1, an optional ``client-classes`` parameter
may also be specified (see :ref:`cb-cmds-option-class-tags-as-keys`).
These parameters are passed within the ``options`` list.
Another list, ``pools``, contains a map with the
IP address range or prefix identifying the pool. If the option
is not explicitly specified for this pool, no option is deleted.
In particular, the given option may exist for a subnet containing
the specified pool. Such an option instance is not affected by this
command, as this command merely deletes a pool-level option. To
delete a subnet-level option, the :isccmd:`remote-option4-subnet-del`
or :isccmd:`remote-option6-subnet-del` command must be used instead.

The following command attempts to delete an option having the
option code 5 in the top-level option space from an IPv4 address
pool:

.. code-block:: json

   {
       "command": "remote-option4-pool-del",
       "arguments": {
           "pools": [
               {
                   "pool": "192.0.2.10 - 192.0.2.100"
               }
           ],
           "options": [
               {
                   "code": 5,
                   "space": "dhcp4"
               }
           ],
           "remote": {
               "type": "mysql"
           }
       }
   }

The "dhcp4" value represents the top-level option space where the standard DHCPv4
options belong. The ``server-tags`` parameter cannot be specified for this command.

.. isccmd:: remote-option4-pool-set
.. _command-remote-option4-pool-set:

.. isccmd:: remote-option6-pool-set
.. _command-remote-option6-pool-set:

The ``remote-option4-pool-set``, ``remote-option6-pool-set`` Commands
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

These commands create a new address-pool-specific DHCP option or replace
an existing option in the database. The structure of the option information
is the same as in the Kea configuration file (see :ref:`dhcp4-std-options`
and :ref:`dhcp6-std-options`). The option information is carried in the
``options`` list. Another list, ``pools``, contains a map with the IP address
range or prefix identifying the pool. If such an option already exists for
the pool, it is replaced with the new instance.

For example:

.. code-block:: json

   {
       "command": "remote-option4-pool-set",
       "arguments": {
           "pools": [
               {
                   "pool": "192.0.2.10 - 192.0.2.100"
               }
           ],
           "options": [
               {
                   "name": "domain-name-servers",
                   "data": "10.0.0.1"
               }
           ],
           "remote": {
               "type": "mysql"
           }
       }
   }

The ``server-tags`` parameter cannot be specified for this command.

Specifying an option name instead of the option code only works reliably
for standard DHCP options. When specifying a value for a user-defined
DHCP option, the option code should be indicated instead of the name.

.. isccmd:: remote-option4-subnet-del
.. _command-remote-option4-subnet-del:

.. isccmd:: remote-option6-subnet-del
.. _command-remote-option6-subnet-del:

The ``remote-option4-subnet-del``, ``remote-option6-subnet-del`` Commands
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

These commands are used to delete a subnet-specific DHCP option
from the database. The option is identified by an option code
and option space, and, as of Kea 3.1.1, an optional ``client-classes``
parameter (see :ref:`cb-cmds-option-class-tags-as-keys`).
These parameters are passed within the ``options`` list.
Another list, ``subnets``, contains a map with the
identifier of the subnet from which the option is to be deleted.
If the option is not explicitly specified for this subnet, no
option is deleted.

The following command attempts to delete an option having the
option code 5 in the top-level option space from the subnet
having an identifier of 123.

.. code-block:: json

   {
       "command": "remote-option4-subnet-del",
       "arguments": {
           "subnets": [
               {
                   "id": 123
               }
           ],
           "options": [
               {
                   "code": 5,
                   "space": "dhcp4"
               }
           ],
           "remote": {
               "type": "mysql"
           }
       }
   }

The "dhcp4" value represents the top-level option space where the standard DHCPv4
options belong. The ``server-tags`` parameter cannot be specified for this command.

.. isccmd:: remote-option4-subnet-set
.. _command-remote-option4-subnet-set:

.. isccmd:: remote-option6-subnet-set
.. _command-remote-option6-subnet-set:

The ``remote-option4-subnet-set``, ``remote-option6-subnet-set`` Commands
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

These commands create a new subnet-specific DHCP option or replace an existing
option in the database. The structure of the option information is the same as
in the Kea configuration file (see :ref:`dhcp4-std-options`
and :ref:`dhcp6-std-options`). The option information is carried in the
``options`` list. Another list, ``subnets``, contains a map with the identifier of
the subnet for which the option is to be set. If such an option already exists
for the subnet, it is replaced with the new instance.

.. code-block:: json

   {
       "command": "remote-option6-subnet-set",
       "arguments": {
           "subnets": [
               {
                   "id": 123
               }
           ],
           "options": [
               {
                   "name": "dns-servers",
                   "data": "2001:db8:1::1"
               }
           ],
           "remote": {
               "type": "mysql"
           }
       }
   }

The ``server-tags`` parameter cannot be specified for this command.

Specifying an option name instead of the option code only works reliably
for the standard DHCP options. When specifying a value for the user-defined
DHCP option, the option code should be indicated instead of the name.

.. isccmd:: remote-subnet4-del-by-id
.. _command-remote-subnet4-del-by-id:

.. isccmd:: remote-subnet6-del-by-id
.. _command-remote-subnet6-del-by-id:

The ``remote-subnet4-del-by-id``, ``remote-subnet6-del-by-id`` Commands
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

This is the first variant of the commands used to delete an IPv4 or IPv6
subnet from the database. It uses the subnet ID to identify the subnet. For
example, to delete the IPv4 subnet with an ID of 5:

.. code-block:: json

   {
       "command": "remote-subnet4-del-by-id",
       "arguments": {
           "subnets": [
               {
                   "id": 5
               }
           ],
           "remote": {
               "type": "mysql"
           }
       }
   }

The ``server-tags`` parameter cannot be used with this command.

.. isccmd:: remote-subnet4-del-by-prefix
.. _command-remote-subnet4-del-by-prefix:

.. isccmd:: remote-subnet6-del-by-prefix
.. _command-remote-subnet6-del-by-prefix:

The ``remote-subnet4-del-by-prefix``, ``remote-subnet6-del-by-prefix`` Commands
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

This is the second variant of the commands used to delete an IPv4 or
IPv6 subnet from the database. It uses the subnet prefix to identify the
subnet. For example:

.. code-block:: json

   {
       "command": "remote-subnet6-del-by-prefix",
       "arguments": {
           "subnets": [
               {
                   "subnet": "2001:db8:1::/64"
               }
           ],
           "remote": {
               "type": "mysql"
           }
       }
   }

The ``server-tags`` parameter cannot be used with this command.

.. isccmd:: remote-subnet4-get-by-id
.. _command-remote-subnet4-get-by-id:

.. isccmd:: remote-subnet6-get-by-id
.. _command-remote-subnet6-get-by-id:

The ``remote-subnet4-get-by-id``, ``remote-subnet6-get-by-id`` Commands
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

This is the first variant of the commands used to fetch an IPv4 or IPv6
subnet from the database. It uses a subnet ID to identify the subnet.
For example:

.. code-block:: json

   {
       "command": "remote-subnet4-get-by-id",
       "arguments": {
           "subnets": [
               {
                   "id": 5
               }
           ],
           "remote": {
               "type": "mysql"
           }
       }
   }

The ``server-tags`` parameter cannot be used with this command.

.. isccmd:: remote-subnet4-get-by-prefix
.. _command-remote-subnet4-get-by-prefix:

.. isccmd:: remote-subnet6-get-by-prefix
.. _command-remote-subnet6-get-by-prefix:

The ``remote-subnet4-get-by-prefix``, ``remote-subnet6-get-by-prefix`` Commands
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

This is the second variant of the commands used to fetch an IPv4 or IPv6
subnet from the database. It uses a subnet prefix to identify the
subnet. For example:

.. code-block:: json

   {
       "command": "remote-subnet6-get-by-prefix",
       "arguments": {
           "subnets": [
               {
                   "subnet": "2001:db8:1::/64"
               }
           ],
           "remote": {
               "type": "mysql"
           }
       }
   }

The ``server-tags`` parameter cannot be used with this command.

.. isccmd:: remote-subnet4-list
.. _command-remote-subnet4-list:

.. isccmd:: remote-subnet6-list
.. _command-remote-subnet6-list:

The ``remote-subnet4-list``, ``remote-subnet6-list`` Commands
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

These commands are used to list all IPv4 or IPv6 subnets from the database for
selected servers or all servers. The following command retrieves all servers to
be used by "server1" and "server2":

.. code-block:: json

    {
        "command": "remote-subnet4-list",
        "arguments": {
            "remote": {
                "type": "mysql"
            },
            "server-tags": [ "server1", "server2" ]
        }
    }

The ``server-tags`` parameter is mandatory and contains one or
more server tags. It may contain the keyword "all", to fetch the subnets
associated with all servers. When the ``server-tags`` list
contains the ``null`` value, the returned response contains a list
of unassigned subnets, i.e. the subnets which are associated with no servers.
For example:

.. code-block:: json

    {
        "command": "remote-subnet4-list",
        "arguments": {
            "remote": {
                "type": "mysql"
            },
            "server-tags": [ null ]
        }
    }

The example response to this command when non-null server tags are specified
looks similar to this:

.. code-block:: json

    {
        "result": 0,
        "text": "2 IPv4 subnet(s) found.",
        "arguments": {
            "subnets": [
                {
                    "id": 1,
                    "subnet": "192.0.2.0/24",
                    "shared-network-name": null,
                    "metadata": {
                        "server-tags": [ "server1", "server2" ]
                    }
                },
                {
                    "id": 2,
                    "subnet": "192.0.3.0/24",
                    "shared-network-name": null,
                    "metadata": {
                        "server-tags": [ "all" ]
                    }
                }
            ],
            "count": 2
        }
    }

The returned information about each subnet is limited to the subnet identifier,
prefix, and associated shared network name. To retrieve full
information about the selected subnet, use
the :isccmd:`remote-subnet4-get-by-id` / :isccmd:`remote-subnet6-get-by-id` command
or the :isccmd:`remote-subnet4-get-by-prefix` / :isccmd:`remote-subnet6-get-by-prefix` command.

The example response above contains two subnets. One of the subnets is
associated with both servers: "server1" and "server2". The second subnet is
associated with all servers, so it is also present in the configurations for
"server1" and "server2".

When listing unassigned subnets, the response will look similar to this:

.. code-block:: json

    {
        "result": 0,
        "text": "1 IPv4 subnet(s) found.",
        "arguments": {
            "subnets": [
                {
                    "id": 3,
                    "subnet": "192.0.4.0/24",
                    "shared-network-name": null,
                    "metadata": {
                        "server-tags": [ null ]
                    }
                }
            ],
            "count": 1
        }
    }

The ``null`` value in the metadata indicates that the
returned subnet is unassigned.

.. isccmd:: remote-subnet4-set
.. _command-remote-subnet4-set:

.. isccmd:: remote-subnet6-set
.. _command-remote-subnet6-set:

The ``remote-subnet4-set``, ``remote-subnet6-set`` Commands
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

These commands are used to create a new IPv4 or IPv6 subnet or replace
an existing subnet in the database. Setting the subnet also associates
or disassociates the subnet with a shared network.

The structure of the subnet information is similar to the structure used
in the configuration file (see :ref:`dhcp4-configuration` and
:ref:`dhcp6-configuration`). The subnet information conveyed in the
:isccmd:`remote-subnet4-set` or :isccmd:`remote-subnet6-set` command
must include the additional parameter
``shared-network-name``, which denotes whether the subnet belongs to a
shared network.

Consider the following example:

.. code-block:: json

   {
       "command": "remote-subnet4-set",
       "arguments": {
           "subnets": [
               {
                   "id": 5,
                   "subnet": "192.0.2.0/24",
                   "shared-network-name": "level3",
                   "pools": [ { "pool": "192.0.2.100-192.0.2.200" } ],
                   "option-data": [ {
                       "name": "routers",
                       "data": "192.0.2.1"
                   } ]
               }
           ],
           "remote": {
               "type": "mysql"
           },
           "server-tags": [ "all" ]
       }
   }

It creates the subnet and associates it with the "level3" shared
network. The "level3" shared network must be created with the :isccmd:`remote-network4-set`
command prior to creating the subnet.

If the created subnet must be global - that is, not associated with any shared
network - the ``shared-network-name`` must be explicitly set to
``null``:

.. code-block:: json

   {
       "command": "remote-subnet4-set",
       "arguments": {
           "subnets": [
               {
                   "id": 5,
                   "subnet": "192.0.2.0/24",
                   "shared-network-name": null,
                   "pools": [ { "pool": "192.0.2.100-192.0.2.200" } ],
                   "option-data": [ {
                       "name": "routers",
                       "data": "192.0.2.1"
                   } ]
              }
           ],
           "server-tags": [ "all" ]
       }
   }

The subnet created in the previous example is replaced with the new
subnet having the same parameters, but it becomes global.

The ``shared-network-name`` parameter is mandatory for the
:isccmd:`remote-subnet4-set` command. The ``server-tags`` list is mandatory and must
include one or more server tags. As a result, the subnet is associated with all
of the listed servers. It may also be associated with all servers connecting
to the database when the keyword "all" is used as the server tag.

.. note::

   As with other "set" commands, this command replaces all the
   information about the particular subnet in the database, if the
   subnet information is already present. Therefore, when sending this
   command, make sure to always include all parameters that must be
   specified for the updated subnet instance. Any unspecified parameter
   will be marked as unspecified in the database, even if its value was
   present prior to sending the command.

.. isccmd:: remote-class4-del
.. _command-remote-class4-del:

.. isccmd:: remote-class6-del
.. _command-remote-class6-del:

The ``remote-class4-del``, ``remote-class6-del`` Commands
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

These commands delete a DHCPv4 or DHCPv6 client class by name. If any client
classes in the database depend on the deleted class, an error is returned in
response to this command. In this case, to successfully delete the class,
the dependent client classes must be deleted first. Use the
:isccmd:`remote-class4-get-all` command to fetch all client classes and find
the dependent ones.

.. code-block:: json

    {
        "command": "remote-class4-del",
        "arguments": {
            "client-classes": [
                {
                    "name": "foo"
                }
            ],
            "remote": {
                "type": "mysql"
            }
        }
    }

The ``server-tags`` parameter cannot be used for this command because client
classes are uniquely identified by name.

.. isccmd:: remote-class4-get
.. _command-remote-class4-get:

.. isccmd:: remote-class6-get
.. _command-remote-class6-get:

The ``remote-class4-get``, ``remote-class6-get`` Commands
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

These commands retrieve DHCPv4 or DHCPv6 client class information by a
client-class name.

.. code-block:: json

    {
        "command": "remote-class4-get",
        "arguments": {
            "client-classes": [
                {
                    "name": "foo"
                }
            ],
            "remote": {
                "type": "mysql"
            }
        }
    }

The ``server-tags`` parameter cannot be used for this command because client
classes are uniquely identified by name.

A response to the command looks similar to this:

.. code-block:: json

    {
        "result": 0,
        "text": "DHCPv4 client class 'foo' found.",
        "arguments": {
            "client-classes": [
                {
                    "name": "foo",
                    "metadata": {
                        "server-tags": [ "all" ]
                    }
                }
            ],
            "count": 1
        }
    }

.. isccmd:: remote-class4-get-all
.. _command-remote-class4-get-all:

.. isccmd:: remote-class6-get-all
.. _command-remote-class6-get-all:

The ``remote-class4-get-all``, ``remote-class6-get-all`` Commands
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

These commands retrieve all DHCPv4 or DHCPv6 client classes for a particular server,
multiple explicitly listed servers, and/or all servers. A given server has its own
server-specific tag and also has the "all" server tag; these commands retrieve
the classes for both an individual server and for "all" servers. For example, the
following command retrieves all client classes defined for "server1" as well as
the client classes defined for "all" servers:

.. code-block:: json

    {
        "command": "remote-class4-get-all",
        "arguments": {
            "remote": {
                "type": "mysql"
            },
            "server-tags": [ "server1" ]
        }
    }

The ``server-tags`` parameter is mandatory and contains one or more server
tags. If other server tags are specified, "all" does not need to be included
in ``server-tags``, as every server automatically also has the "all" server tag.
If ``server-tags`` contains only the keyword "all", only the client classes associated
with "all" servers are returned. When the ``server-tags`` list contains the
``null`` value, the returned response contains a list of unassigned client
classes, i.e. the networks which are associated with no servers.

A response to the command looks similar to this:

.. code-block:: json

    {
        "result": 0,
        "text": "2 DHCPv4 client class(es) found.",
        "arguments": {
            "client-classes": [
                {
                    "name": "foo",
                    "metadata": {
                        "server-tags": [ "all" ]
                    }
                },
                {
                    "name": "bar",
                    "test": "member('foo')",
                    "metadata": {
                        "server-tags": [ "all" ]
                    }
                }
            ],
            "count": 2
        }
    }

.. isccmd:: remote-class4-set
.. _command-remote-class4-set:

.. isccmd:: remote-class6-set
.. _command-remote-class6-set:

The ``remote-class4-set``, ``remote-class6-set`` Commands
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

These commands insert a new or replace an existing DHCPv4 or DHCPv6 client class in
the database. The client class information structure is the same as in the Kea
configuration file (see :ref:`dhcp4-client-classifier` and
:ref:`dhcp6-client-classifier` for details).

.. code-block:: json

    {
        "command": "remote-class4-set",
        "arguments": {
            "client-classes": [
                {
                    "name": "foo",
                    "test": "member('KNOWN') or member('bar')",
                    "option-def": [
                        {
                            "name": "configfile",
                            "code": 224,
                            "type": "string"
                        }
                    ],
                    "option-data": [
                        {
                            "name": "configfile",
                            "data": "1APC"
                        }
                    ]
                }
            ],
            "remote": {
                "type": "mysql"
            },
            "server-tags": [ "all" ]
        }
    }


Client-class ordering rules described in :ref:`classification-using-expressions`
apply to the classes inserted into the database. They imply that the class `bar`
referenced in the test expression must exist in the database when issuing the
above command.

By default, a new client class is inserted at the end of the class hierarchy in
the database and can reference any class associated with the same server tag or
with the special server tag "all". If an existing class is updated, it remains
at its current position within the class hierarchy.

However, the class commands allow the position of the inserted
or updated client class to be specified. The optional ``follow-class-name`` parameter can be
included in the command to indicate the name of the existing class after which
the managed class should be placed. Suppose there are two DHCPv6 classes in the
database: `first-class` and `second-class`. To add a new class, `third-class`,
between these two, use a command similar to the following:

.. code-block:: json

    {
        "command": "remote-class6-set",
        "arguments": {
            "client-classes": [
                {
                    "name": "third-class",
                    "test": "member('first-class')"
                }
            ],
            "follow-class-name": "first-class",
            "remote": {
                "type": "mysql"
            },
            "server-tags": [ "all" ]
        }
    }

Note that `third-class` can depend on `first-class` because it is placed
after `first-class`; `third-class` cannot depend on `second-class`
because it is placed before it. However, `second-class` could be updated to
depend on `third-class`.

The ``follow-class-name`` parameter can be explicitly set to ``null``, e.g.:

.. code-block:: json

    {
        "command": "remote-class6-set",
        "arguments": {
            "client-classes": [
                {
                    "name": "third-class",
                    "test": "member('first-class')"
                }
            ],
            "follow-class-name": null,
            "remote": {
                "type": "mysql"
            },
            "server-tags": [ "all" ]
        }
    }

It yields the same behavior as if the ``follow-class-name`` parameter were not included,
i.e. the new class is appended at the end of the class hierarchy, and the updated
class remains at the current position.
