[L3] L3 agent extension should always inherit from "L3AgentExtension"

[Rodolfo Alonso]

All L3 agent extensions should inherit from "neutron_lib.agent.l3_extension.L3AgentExtension". The "L3AgentExtensionsManager" should check, just after the extension initialization, if the loaded extensions inherit from this API. If not, the extension will raise an exception and exit.

Once this check is done, all methods ("add_router", "update_router", "delete_router" and "ha_state_change") can directly call the extension function without checking the presence or not of the related function. That is ensured by making all extension inherit by the defined API (located in neutron-lib and available for any project).

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.opendev.org/c/openstack/neutron/+/818540

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/c/openstack/neutron/+/818540
Committed: https://opendev.org/openstack/neutron/commit/ebca47365c261b881d0c0e0135821ce03471a336
Submitter: "Zuul (22348)"
Branch: master

commit ebca47365c261b881d0c0e0135821ce03471a336
Author: Rodolfo Alonso Hernandez <email address hidden>
Date: Fri Nov 19 11:45:15 2021 +0000

    "L3AgentExtensionsManager" check loaded extensions

    Now "L3AgentExtensionsManager" lists loaded extension, checking if
    they inherit from "neutron_lib.agent.l3_extension.L3AgentExtension".
    If any extension does not, the L3 agent raises an exception and exits.

    Closes-Bug: #1951569
    Change-Id: I3ce4858cef9b3a3d7eab005dd1ad2bb3b5ef6ef3

[OpenStack Infra (hudson-openstack)]

Related fix proposed to branch: master
Review: https://review.opendev.org/c/openstack/neutron-lib/+/831002

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/c/openstack/neutron-lib/+/831002
Committed: https://opendev.org/openstack/neutron-lib/commit/f765e3c21c52f97c713697db4d84c526054078f3
Submitter: "Zuul (22348)"
Branch: master

commit f765e3c21c52f97c713697db4d84c526054078f3
Author: Rodolfo Alonso Hernandez <email address hidden>
Date: Fri Feb 25 15:59:31 2022 +0000

    Rehome exception ``L3ExtensionException``

    Change-Id: I460b3d1b6c219534e56a263bcb41790fce32dd5e
    Related-Bug: #1951569

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/neutron 20.0.0.0rc1 release candidate.