[Kea-users] Kea 1.2.0 - not finding host reservation via flex-id & pgsql

Jason Lixfeld jason-kea at lixfeld.ca
Fri Sep 15 18:12:17 UTC 2017


Hello,

I was troubleshooting an issue with host reservations via flex-id and postgresql.

I tracked it down to a difference in how the database was storing identifier_value, vs. how the identifier_expression is configured in the kea config file.

The kea debug shows the generated flex-id:

2017-09-15 13:32:01.182 DEBUG [kea-dhcp4.packets/631] DHCP4_FLEX_ID flexible identifier generated for incoming packet: flex-id=010972677730312E6C616200040C370201

The kea config identifier_expression is like so:

                "hooks-libraries": [
                        {
                        "library": "/usr/local/lib/hooks/libdhcp_flex_id.so",
                        "parameters":
                                {
                                "identifier-expression": "concat(relay4[2].hex,relay4[1].hex)"
                                }
                        }
                ],

I set the identifier_value per the how-to (https://kea.isc.org/wiki/HostReservationsHowTo) to match what the kea debug generated for the flex-id:

…
…
kea=# \set identifier_value ‘010972677730312e6c616200040c370201'
…
…

When I noticed that the reservation was not working, I looked at the postgres query that Kea was making, and it appears as though $3 is prepended with \x :

2017-09-15 13:32:01.189 EDT [726] kea at kea LOG:  execute get_host_subid4_dhcpid: SELECT h.host_id, h.dhcp_identifier, h.dhcp_identifier_type,   h.dhcp4_subnet_id, h.dhcp6_subnet_id, h.ipv4_address, h.hostname,   h.dhcp4_client_classes, h.dhcp6_client_classes,   h.dhcp4_next_server, h.dhcp4_server_hostname, h.dhcp4_boot_file_name,   o.option_id, o.code, o.value, o.formatted_value, o.space, o.persistent FROM hosts AS h LEFT JOIN dhcp4_options AS o ON h.host_id = o.host_id WHERE h.dhcp4_subnet_id = $1 AND h.dhcp_identifier_type = $2    AND h.dhcp_identifier = $3 ORDER BY h.host_id, o.option_id
2017-09-15 13:32:01.189 EDT [726] kea at kea DETAIL:  parameters: $1 = '1', $2 = '4', $3 = '\x010972677730312e6c616200040c370201’

Making that query directly of course fails, which is where the issue lies:

SELECT h.host_id, h.dhcp_identifier, h.dhcp_identifier_type,   h.dhcp4_subnet_id, h.dhcp6_subnet_id, h.ipv4_address, h.hostname,   h.dhcp4_client_classes, h.dhcp6_client_classes,   h.dhcp4_next_server, h.dhcp4_server_hostname, h.dhcp4_boot_file_name,   o.option_id, o.code, o.value, o.formatted_value, o.space, o.persistent FROM hosts AS h LEFT JOIN dhcp4_options AS o ON h.host_id = o.host_id WHERE h.dhcp4_subnet_id = '1' AND h.dhcp_identifier_type = '4' AND h.dhcp_identifier = '\x010972677730312e6c616200040c370201' ORDER BY h.host_id, o.option_id;

 host_id | dhcp_identifier | dhcp_identifier_type | dhcp4_subnet_id | dhcp6_subnet_id | ipv4_address | hostname | dhcp4_client_classes | dhcp6_client_classes | dhcp4_next_server | dhcp4_server_hostname | dhcp4_boot_file_name | option_id | code | value | formatted_value | space | persistent
---------+-----------------+----------------------+-----------------+-----------------+--------------+----------+----------------------+----------------------+-------------------+-----------------------+----------------------+-----------+------+-------+-----------------+-------+------------
(0 rows)

If I remove the leading \x from the query, the expected results are presented:

SELECT h.host_id, h.dhcp_identifier, h.dhcp_identifier_type,   h.dhcp4_subnet_id, h.dhcp6_subnet_id, h.ipv4_address, h.hostname,   h.dhcp4_client_classes, h.dhcp6_client_classes,   h.dhcp4_next_server, h.dhcp4_server_hostname, h.dhcp4_boot_file_name,   o.option_id, o.code, o.value, o.formatted_value, o.space, o.persistent FROM hosts AS h LEFT JOIN dhcp4_options AS o ON h.host_id = o.host_id WHERE h.dhcp4_subnet_id = '1' AND h.dhcp_identifier_type = '4' AND h.dhcp_identifier = '010972677730312e6c616200040c370201' ORDER BY h.host_id, o.option_id;

 host_id |                            dhcp_identifier                             | dhcp_identifier_type | dhcp4_subnet_id | dhcp6_subnet_id | ipv4_address | hostname | dhcp4_client_classes | dhcp6_client_classes | dhcp4_next_server | dhcp4_server_hostname | dhcp4_boot_file_name | option_id | code | value | formatted_value | space | persistent
---------+------------------------------------------------------------------------+----------------------+-----------------+-----------------+--------------+----------+----------------------+----------------------+-------------------+-----------------------+----------------------+-----------+------+-------+-----------------+-------+------------
       6 | \x30313039373236373737333033313265366336313632303030343063333730323031 |                    4 |               1 |                 |    171966277 |          |                      |                      |                   |                       | bootfile.efi         |           |      |       |                 |       |
(1 row)

Manually decoding the dhcp_identifier shows the non-prepended value:

kea=# select convert_from('\x30313039373236373737333033313265366336313632303030343063333730323031', 'UTF-8');
            convert_from
------------------------------------
 010972677730312e6c616200040c370201
(1 row)
 
kea=#

So my question is did I misinterpret the instructions (either by cluelessness or oversight) when setting this up, or is this a bug?

Thanks!


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