.. ischooklib:: libdhcp_lease_query.so
.. _hooks-lease-query:

``libdhcp_lease_query.so``: Leasequery Support
==============================================

This library provides support for DHCPv4 Leasequery as described in
`RFC 4388 <https://tools.ietf.org/html/rfc4388>`__; and for DHCPv6
Leasequery as described in (`RFC 5007 <https://tools.ietf.org/html/rfc5007>`__).

.. note::

    :ischooklib:`libdhcp_lease_query.so` is part of the open source code and is
    available to every Kea user.
    It was previously available only to ISC customers with a paid support contract.

.. note::

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

Kea version 2.3.4 added support for DHCPv6 Bulk Leasequery
(`RFC 5460  <https://tools.ietf.org/html/rfc5460>`__);
Kea version 2.3.5 added support for DHCPv4 Bulk Leasequery
(`RFC 6926  <https://tools.ietf.org/html/rfc6926>`__) using
the memfile lease backend.

.. _lease-query-dhcpv4:

DHCPv4 Leasequery
~~~~~~~~~~~~~~~~~

DHCPv4 simple Leasequery provides a requester the ability to query for
active lease information for either a single IP address or a single client.
RFC 4388 calls for three such queries:

- Query by IP address

    The IP address of interest is contained within the ``ciaddr`` field of
    the query.
- Query by hardware address

    The hardware address of interest is contained with the ``chaddr`` field
    of the query.
- Query by client identifier

    The client identifier of interest is sent in the ``dhcp-client-identifier``
    option (61) of the query.

The inbound DHCPLEASEQUERY packet must supply only one of the three values
above. Queries which supply more than one of these values are dropped.

In addition, the query must contain the IP address of the requester in
``giaddr``. This value is used not only as the destination for the
query response but also to validate the requester against a known
list of IP addresses which are permitted to query. This list of valid
requester addresses is specified as part of the Leasequery hook library's
configuration (see the section on configuration below).

In response to a valid query, the server returns one of three message
types:

- DHCPLEASEUNKNOWN

    Returned when the IP address of interest is not one the server knows
    about (query by IP address); or there are no active leases for the
    client of interest (query by hardware address or client ID).

- DHCPLEASEUNASSIGNED

    Returned when the IP address is one the server knows of but for which
    there are no active leases (applies only to query by IP address).

- DHCPLEASEACTIVE

    Returned when there is at least one active lease found matching the
    criteria.

For both DHCPLEASEUNKNOWN and DHCPLEASEUNASSIGNED responses, the only
information sent back to the requester in response is the query parameter
itself (i.e. one of: IP address, hardware address, or client identifier).

For DHCPLEASEACTIVE the server provides the following information
for the newest active lease that matches the criteria, in the response:

- ``ciaddr`` - set to the lease's IP address
- ``chaddr`` - set to the lease's hardware address

In addition, one or more of the following options are included:

.. tabularcolumns:: |p{0.2\linewidth}|p{0.1\linewidth}|p{0.7\linewidth}|

.. table:: DHCPLEASEACTIVE options
   :class: longtable
   :widths: 30 10 70

   +------------------------------+-------+-----------------------------------------------+
   | Option                       | Code  | Content                                       |
   +==============================+=======+===============================================+
   | dhcp-client-identifier       |  61   | copied from the lease (if appropriate)        |
   +------------------------------+-------+-----------------------------------------------+
   | client-last-transaction-time |  91   | the amount of time that has elapsed since the |
   |                              |       | lease's client-last-transaction-time (CLTT).  |
   |                              |       | This value is also used by the server to      |
   |                              |       | adjust lifetime and timer values.             |
   +------------------------------+-------+-----------------------------------------------+
   | dhcp-lease-time              |  51   | lease's lifetime reduced by CLTT              |
   +------------------------------+-------+-----------------------------------------------+
   | dhcp-renewal-time            |  58   | as controlled by kea-dhcp4 configuration and  |
   |                              |       | then reduced by CLTT                          |
   +------------------------------+-------+-----------------------------------------------+
   | dhcp-rebind-time             |  59   | as dictated by kea-dhcp4 configuration and    |
   |                              |       | then reduced by CLTT                          |
   +------------------------------+-------+-----------------------------------------------+
   | dhcp-agent-options           |  82   | if stored on the lease. (See                  |
   |                              |       | :ref:`dhcp4-store-extended-info`)             |
   +------------------------------+-------+-----------------------------------------------+
   | associated-ip                |  92   | a list of all other IP addresses for which    |
   |                              |       | the client has active leases. (Does not apply |
   |                              |       | to query by IP address)                       |
   +------------------------------+-------+-----------------------------------------------+

The ``dhcp-server-identifier`` option (54) is returned in all responses in keeping with
RFC 2131, section 4.3.1.

RFC 4388 allows requesters to ask for specific options via the
``dhcp-parameter-request-list`` (PRL, option 55). This is not currently supported in Kea.

.. _lease-query-dhcpv4-config:

DHCPv4 Leasequery Configuration
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Configuring the Leasequery hook library for use is straightforward. It
supports a single parameter, ``requesters``, which is a list of IP addresses from
which DHCPLEASEQUERY packets are accepted. In other words, it is a list of
known requesters. The following code shows an example configuration with two requester
addresses:

::

   {
    "hooks-libraries": [
        {
            "library": "libdhcp_lease_query.so",
            "parameters": {
                "requesters": [ "192.0.1.1", "10.0.0.2" ]
            }
        }
    ],
    ...
   }

.. note::

    For security purposes, there is no way to specify wildcards. Each requester address
    must be explicitly listed.

.. _lease-query-dhcpv6:

DHCPv6 Leasequery
~~~~~~~~~~~~~~~~~

DHCPv6 simple Leasequery gives a requester the ability to query for
active lease information for either a single IP address or a single client
DUID. The query type and parameters are conveyed in an ``lq-query`` option (44)
attached to a ``DHCPV6_LEASEQUERY`` message:

- ``query-type``

    This is either ``query-by-address`` (1) or ``query-by-clientid`` (2)

- ``link-address``

    The global link address, when not empty, instructs the query to be
    limited to leases within that "link." Kea uses this value to
    select only leases that belong to subnets whose prefix matches
    this value. Active leases for prefix delegations for
    a matched subnet are included in the query reply, even if the
    delegated prefix itself falls outside the subnet prefix.

- ``query-options``

    A single ``iaaddr`` option (12) must be supplied when querying by address.
    When querying by client ID, a single ``clientid`` option (1) must be
    supplied. RFC 5007 also calls for an optional, ``oro`` option (6), to
    request specific options be returned for matched leases. This is
    not currently implemented.

.. note::

    `RFC 5007, Section 3.3 <https://tools.ietf.org/html/rfc5007#section-3.3>`__
    states that querying by IP address should return either a lease (e.g.
    binding) for the address itself or a lease for a delegated prefix that
    contains the address.

``DHCPV6_LEASEQUERY`` queries are only honored if the source address of
the query matches an entry in a list of known IP addresses which are
permitted to query. This list of valid requester addresses is specified
as part of the Leasequery hook library’s configuration (see the section
on configuration below). Queries received from unknown requesters are
logged and dropped.

In response to a valid query, the server carries out the requisite
activities and returns a ``DHCPV6_LEASEQUERY_REPLY``. All replies contain
at least a ``status-code`` option (13) that indicates the outcome of the query
as detailed in the following table:

.. tabularcolumns:: |p{0.5\linewidth}|p{0.3\linewidth}|p{0.1\linewidth}|p{0.3\linewidth}|

.. table:: DHCPV6_LEASEQUERY_REPLY status option values per query outcome
   :class: longtable
   :widths: 50 30 10 30

   +--------------------------------------+-------------------------+--------+------------------------------+
   |                                      | Status                  | Status |  Status                      |
   | Query Outcome                        | Label                   | Code   |  Text                        |
   +======================================+=========================+========+==============================+
   | Invalid query type field             | STATUS_UnknownQueryType |   7    | "unknown query-type"         |
   +--------------------------------------+-------------------------+--------+------------------------------+
   | Query by IP address that does not    | STATUS_Malformed        |   10   | "missing D6O_IAADDR"         |
   | contain an address option            |                         |        |                              |
   +--------------------------------------+-------------------------+--------+------------------------------+
   | Query by IP address for an address   | STATUS_NotConfigured    |    9   | "address not in a configured |
   | that does fall within any configured |                         |        | pool"                        |
   | pools                                |                         |        |                              |
   +--------------------------------------+-------------------------+--------+------------------------------+
   | Query by IP address which found only | STATUS_Success          |    0   | "inactive lease exists"      |
   | an inactive lease (e.g. expired,     |                         |        |                              |
   | declined, reclaimed-expired)         |                         |        |                              |
   +--------------------------------------+-------------------------+--------+------------------------------+
   | Query by IP address that found no    | STATUS_Success          |    0   | "no active lease"            |
   | leases (active or otherwise)         |                         |        |                              |
   +--------------------------------------+-------------------------+--------+------------------------------+
   | Query by IP address that found an    | STATUS_Success          |    0   | "active lease found"         |
   | active lease for the address         |                         |        |                              |
   +--------------------------------------+-------------------------+--------+------------------------------+
   | Query by Client ID that does not     | STATUS_Malformed        |   10   | "missing D6O_CLIENTID"       |
   | contain a client ID option           |                         |        |                              |
   +--------------------------------------+-------------------------+--------+------------------------------+
   | Query by Client ID with a link       | STATUS_NotConfigured    |    9   | "not a configured link"      |
   | address that does not match any      |                         |        |                              |
   | configured subnets                   |                         |        |                              |
   +--------------------------------------+-------------------------+--------+------------------------------+
   | Query by client ID which found no    | STATUS_Success          |    0   | "no active leases"           |
   | matching leases                      |                         |        |                              |
   +--------------------------------------+-------------------------+--------+------------------------------+
   | Query by client ID which found one   | STATUS_Success          |    0   | "active lease(s) found"      |
   | or more active leases                |                         |        |                              |
   +--------------------------------------+-------------------------+--------+------------------------------+

For those scenarios where the query was either invalid or for which no matching active
leases were found, the ``DHCPV6_LEASEQUERY_REPLY`` only contains the ``status-code``
option (12) per the above table.

When a query finds active leases in more than one subnet and the query's ``link-address``
is empty, then, in addition to the status-code, the ``DHCPV6_LEASEQUERY_REPLY``
contains an ``lq-client-link`` option (48). The ``lq-client-link`` contains a list of
IPv6 addresses, one for each subnet in which a lease was found (see
`RFC 5007, Section 4.1.2.5 <https://tools.ietf.org/html/rfc5007#section-4.1.2.5>`__)
If, however, the query's ``link-address`` is not empty, the list of queries is
pruned to contain only leases that belong to that subnet.

When the query results in one or more active leases which all belong to a single
subnet, in addition to the ``status-code``, the ``DHCPV6_LEASEQUERY_REPLY`` contains a
``client-data`` option (45) (see
`RFC 5007, Section 4.1.2.2 <https://tools.ietf.org/html/rfc5007#section-4.1.2.2>`__).
The client-data option encapsulates the following options:

.. tabularcolumns:: |p{0.2\linewidth}|p{0.1\linewidth}|p{0.7\linewidth}|

.. table:: OPTION_CLIENT_DATA returned when active lease(s) are found
   :class: longtable
   :widths: 30 10 70

   +------------------------------+-------+-----------------------------------------------+
   | Option                       | Code  | Content                                       |
   +==============================+=======+===============================================+
   | clientid                     |   1   | copied from the lease (if one exists)         |
   +------------------------------+-------+-----------------------------------------------+
   | clt-time                     |  46   | amount of time that has elapsed since the     |
   |                              |       | lease's client-last-transaction-time (CLTT).  |
   |                              |       | This value will also be used by the server to |
   |                              |       | adjust lifetime and timer values.             |
   +------------------------------+-------+-----------------------------------------------+
   | iaaddr                       |   5   | One option per matched address. Fields in     |
   |                              |       | each option:                                  |
   |                              |       | - lease address                               |
   |                              |       | - valid lifetime reduced by CLTT              |
   |                              |       | - preferred lifetime reduced by CLTT          |
   +------------------------------+-------+-----------------------------------------------+
   | iaprefix                     |   26  | One option per matched prefix. Fields in      |
   |                              |       | each option:                                  |
   |                              |       | - prefix                                      |
   |                              |       | - prefix length                               |
   |                              |       | - valid lifetime reduced by CLTT              |
   |                              |       | - preferred lifetime reduced by CLTT          |
   +------------------------------+-------+-----------------------------------------------+

If the lease with the most recent client-last-transaction-time (CLTT)
value has relay information in its user context (see
:ref:`store-extended-info-v6`), then an ``OPTION_LQ_RELAY_DATA`` option is
added to the reply (see
`RFC 5007, Section 4.1.2.4 <https://tools.ietf.org/html/rfc5007#section-4.1.2.4>`__).

The relay information on the lease is a list with an entry for each
relay layer the client packet (e.g. ``DHCPV6_REQUEST``) traversed, with the
first entry in the list being the outermost layer (closest to the server). The
``peer-address`` field of the ``lq-rely-option`` is set to the peer address of this
relay. The list of relays is then used to construct a ``DHCPV6_RELAY_FORW`` message
equivalent to that which contained the client packet, minus the client packet.
This message is stored in the ``DHCP-relay-message`` field of the ``lq-relay-data`` option.

.. _lease-query-dhcpv6-config:

DHCPv6 Leasequery Configuration
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Configuring the Leasequery hook library for use is straightforward. It
supports a single parameter, ``requesters``, which is a list of IP addresses from
which DHCPV6_LEASEQUERY packets are accepted. In other words, it is a list of
known requesters. The following code shows an example configuration with two requester
addresses:

::

   {
    "hooks-libraries": [
        {
            "library": "libdhcp_lease_query.so",
            "parameters": {
                "requesters": [ "2001:db8:1::1", "2001:db8:2::1" ],
                "prefix-lengths": [ 72 ]
            }
        }
    ],
    ...
   }

.. note::

    For security purposes, there is no way to specify wildcards. Each requester address
    must be explicitly listed.

When a query by IP address does not match an existing address lease,
a search for a matching delegated prefix is conducted. This is carried
out by iterating over a list of prefix lengths in descending order,
extracting a prefix of that length from the query address, and searching
for a delegation matching the resulting prefix. This continues for each
length in the list until a match is found or the list is exhausted.

By default, the list of prefix lengths to use in the search is determined
dynamically after (re)configuration events. The resulting list
contains unique values of ``delegated-len``, gleaned from the currently
configured set of PD pools.

There is an optional parameter, ``prefix-lengths``, which
provides the ability to explicitly configure the list rather than having
it be determined dynamically. This provides tighter control over which
prefix lengths are searched. In the above example, the prefix-length
search is restricted to a single pass, using a length of 72, regardless
of whether there are pools using other values for ``delegated-len``.
Specifying an empty list, as shown below:

::

 :
                "prefix-lengths": [ ]
 :

disables the search for delegated prefixes for query by IP address.

.. _bulk-lease-query-dhcpv4:

DHCPv4 Bulk Leasequery
~~~~~~~~~~~~~~~~~~~~~~

DHCPv4 Bulk Leasequery gives a requester the ability to query for
active lease information over a TCP connection. This allows the server
to return all leases matching a given query.

Two of the query types identified by RFC 4388 - Query by MAC address and
Query by Client-identifier - are Bulk Leasequery types specified by RFC
6926. That RFC also defines these new Bulk Leasequery types:

- Query by Relay Identifier

    The query carries an RAI (dhcp-agent-options (82)) option with
    a relay-id (12) sub-option.

- Query by Remote ID

    The query carries an RAI (dhcp-agent-options (82) option) with
    a remote-id (2) sub-option.

- Query for All Configured IP Addresses

    This query type is selected when no other query type is specified.

RFC 6926 also defines new options for Bulk Leasequery:

- status-code (151)

    This reply option carries a status code such as MalformedQuery or
    NotAllowed, with an optional text message.

- base-time (152)

    This reply option carries the absolute current time that the response
    was created. All other time-based reply options are related to
    this value.

- start-time-of-state (153)

    This reply option carries the time of the lease's transition into its
    current state.

- query-start-time (154)

    This query option specifies a start-query time; replies will only
    contain leases that are older than this value.

- query-end-time (155)

    This query option specifies an end-query time; replies will only
    contain leases that are newer than this value.

- dhcp-state (156)

    This reply option carries the lease state.

- data-source (157)

    This reply option carries the source of the data as a remote flag.

RFC 6926 reuses and extends the Virtual Subnet Selection option (221)
defined in RFC 6607.

.. note::

   Kea does not yet support querying for all configured IP addresses,
   so the dhcp-state option cannot be used, as only active leases can be
   returned in replies. Kea does not keep the start time of the lease's state,
   nor the local/remote information, so it cannot emit the corresponding
   start-time-of-state and data-source options. Kea does not support VPNs
   so the presence of option 221 in the query is considered a
   (NotAllowed) error.

.. _bulk-lease-query-dhcpv6:

DHCPv6 Bulk Leasequery
~~~~~~~~~~~~~~~~~~~~~~

DHCPv6 Bulk Leasequery gives a requester the ability to query for
active lease information over a TCP connection. This allows the server
to return all active leases matching a query.

New query types are available: ``query-by-relay-id`` (3),
``query-by-link-address`` (4), and ``query-by-remote-id`` (5).

A new status code, ``STATUS_QueryTerminated`` (11), has been defined but it is
not yet used by the hook library.

.. note::

   Kea attempts to map link address parameters to the prefixes of configured
   subnets. If a given address falls outside all configured subnet prefixes,
   the query fails with a status code of ``STATUS_NotConfigured``. If
   the link address parameter for ``query-by-relay-id`` or ``query-by-remote-id``
   is not ``::`` (i.e. not empty), only delegated prefixes that lie within matching
   subnet prefixes are returned. Currently, ``query-by-address`` does not
   support finding delegated prefixes by specifying an address that lies within
   the prefix.

.. _bulk-lease-query-dhcpv6-config:

Bulk Leasequery Configuration
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Bulk Leasequery configuration is specified via a new map parameter, ``advanced``,
with these possible entries:

- ``bulk-query-enabled``

    When ``true``, Kea accepts connections from IP addresses in the requesters
    list and processes received bulk leasequeries. The default is ``false``.

- ``active-query-enabled``

    This is an anticipated parameter: if set, it must be ``false``.

- ``extended-info-tables-enabled``

    When ``true``, the lease backend manages DHCPv6 lease extended info
    (relay info) in tables to support the new DHCPv6 Bulk Leasequery
    by-relay-id and by-remote-id types. The default is to use the
    same value as ``bulk-query-enabled``.

- ``lease-query-ip``

    This is the IP address upon which to listen for connections. The address must be
    of the same family as the server, e.g. IPv6 for the DHCPv6 server.

- ``lease-query-port``

    This is the port upon which to listen. The default is 67 for IPv4 and 547 for IPv6,
    i.e. the same value as for the UDP DHCP service, but for TCP.

- ``max-bulk-query-threads``

    This indicates the maximum number of threads that bulk leasequery processing
    should use. A value of 0 instructs the server to use the same number of
    threads that the Kea core is using for DHCP multi-threading.
    The default is 0.

- ``max-requester-connections``

    This is the maximum number of concurrent requester connections. The default
    is 10; the value must be greater than 0.

- ``max-concurrent-queries``

    This is the maximum number of concurrent queries per connection. The value 0
    allows Kea to determine the number, and is the default.

- ``max-requester-idle-time``

    This is the amount of time that may elapse after receiving data from a requester
    before its connection is closed as idle, in seconds. The default
    is 300.

- ``max-leases-per-fetch``

    This is the maximum number of leases to return in a single fetch. The default is 100.

Once TLS is supported, we expect to implement common TLS parameters.

For instance, for DHCPv4:

::

   {
     "hooks-libraries": [
         {
             "library": "libdhcp_lease_query.so",
             "parameters": {
                 "requesters": [ "192.0.2.1", "192.0.2.2" ],
                 "advanced" : {
                      "bulk-query-enabled": true,
                      "active-query-enabled": false,

                      "lease-query-ip": "127.0.0.1",
                      "lease-query-tcp-port": 67,

                      "max-bulk-query-threads": 0,
                      "max-requester-connections": 10,
                      "max-concurrent-queries": 4,
                      "max-requester-idle-time": 300,
                      "max-leases-per-fetch": 100
                 }
             }
         }
     ],
     ...
   }

or for DHCPv6:

::

   {
     "hooks-libraries": [
         {
             "library": "libdhcp_lease_query.so",
             "parameters": {
                 "requesters": [ "2001:db8:1::1", "2001:db8:2::1" ],
                 "advanced" : {
                      "bulk-query-enabled": true,
                      "active-query-enabled": false,

                      "extended-info-tables-enabled": true,

                      "lease-query-ip": "::1",
                      "lease-query-tcp-port": 547,

                      "max-bulk-query-threads": 0,
                      "max-requester-connections": 10,
                      "max-concurrent-queries": 4,
                      "max-requester-idle-time": 300,
                      "max-leases-per-fetch": 100
                 }
             }
         }
     ],
     ...
   }

.. _updating-existing-leases:

Updating Existing Leases in SQL Lease Backends
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Bulk Leasequery requires additions to the lease data that is stored. With SQL lease
backends, leases created prior to the server being configured for bulk lease
query do not contain the new data required. In order to populate this data,
it is necessary to run these API commands:

.. note::

   Existing leases must have been created by Kea with ``store-extended-info``
   enabled, in order for the new data from extended info to be extracted
   and stored.

.. isccmd:: extended-info4-upgrade
.. _command-extended-info4-upgrade:

For DHCPv4 lease data, the command is:

::

    {
        "command": "extended-info4-upgrade"
    }

For DHCPv6 lease data, the command is:

.. isccmd:: extended-info6-upgrade
.. _command-extended-info6-upgrade:

For extended info used by relay ID and by remote ID, the command is:

::

    {
        "command": "extended-info6-upgrade"
    }


In all cases, the response indicates whether it succeeded or failed
and includes either the count of leases updated or the nature of the failure:

::

    {
        "result": 0,
        "text": "Upgraded 1000 leases"
    }


This ``extended-info6-upgrade`` command must be called when:

- the database schema was upgraded from 2.4.1 or older version.
  ``extended-info4-upgrade`` can be used when upgrading from 2.3.8 or older version.

- Bulk Leasequery was not enabled; tables are maintained only when v6 BLQ is
  enabled.

- data in tables does not seem to be consistent; tables are not maintained in
  an atomic way, so consistency is not guaranteed. For instance, when a database
  is shared between several servers, races can happen between updates.

The operation of the extended info command is governed by the ``extended-info-checks``
parameter, under the ``sanity-checks`` element. Please see :ref:`sanity-checks4`
or :ref:`sanity-checks6`.

For large numbers of leases, this command may take some time to complete.

.. note::

    Both the ``extended-info4-upgrade`` and ``extended-info6-upgrade`` commands
    are intended for one-time use after upgrading to a version of Kea that fully
    supports Bulk Leasequery in database backends. These commands are not meant
    for regular use and will be removed in future Kea versions.
