[docs] Add OVS/OVN min requirement table

In PTGs we talked about that we could have a table of OVS/OVN version
requirements. After some grepping in the zuul directory for variables
OVS_BRANCH and OVN_BRANCH I came up with the table in this commit. I
simplified the results quite a lot, because in 2024.1 and earlier
different zuul jobs may have used different OVS/OVN versions, but in
the hope that we keep this uniform in the future I only included the
versions used in base. Also add an item to the release checklist so we
keep this table up to date.

Change-Id: I65143e6a6d1273f7b50aafcfe69844b7e7658d04
Signed-off-by: Bence Romsics <bence.romsics@gmail.com>

doc/source/contributor/policies/release-checklist.rst

@@ -31,6 +31,8 @@ Prior to major release,
    deprecations.txt file in those log directories); also, check whether any
    Launchpad bugs with the 'deprecation' tag need a clean-up or a follow-up in
    the context of the release being planned;
+#. update the ovs-ovn minimum requirement table in
+   ``doc/source/install/ovs-ovn-requirements.rst``;
 #. check that release notes and sample configuration files render correctly,
    arrange clean-up if needed;
 #. ensure all doc links are valid by running ``tox -e linkcheck`` and

doc/source/install/index.rst

@@ -13,6 +13,7 @@ Networking service Installation Guide
    install-rdo.rst
    install-ubuntu.rst
    ovn/index.rst
+   ovs-ovn-requirements.rst
 
 This chapter explains how to install and configure the Networking
 service (neutron) using the :ref:`provider networks <network1>` or

doc/source/install/ovs-ovn-requirements.rst

@@ -0,0 +1,69 @@
+=======================================
+Open vSwitch (OVS) and OVN requirements
+=======================================
+
+Neutron uses Open vSwitch with the ML2/openswitch and ML2/ovn mechanism
+drivers. The latter also uses OVN. These are binary dependencies of a
+Neutron deployment with some version constraints. In the table below we
+hope to document the known minimum versions of OVS and OVN per Neutron
+release. Or at least the minimum versions we know we used in our CI system
+while developing.
+
+We also have CI jobs to test with the main branch of OVS and OVN
+therefore we feel no need to document the known maximum versions -
+the newest OVS/OVN release should work.
+
+.. warning::
+
+   In releases 2024.1 and earlier it happened that different groups
+   of CI jobs (or rather Zuul job templates: base, grenade, rally) used
+   different OVS and OVN versions. Here we document only the base version,
+   that is the version used in single and multinode tempest jobs. Stadium
+   projects like ovn-bgp-agent may also have different requirements.
+
+.. list-table:: OpenStack Neutron OVS/OVN Minimum Requirement Matrix
+
+    * - OpenStack Release
+      - Neutron Release
+      - ``OVS_BRANCH``
+      - ``OVN_BRANCH``
+    * - 2025.2 (flamingo)
+      - 27.0
+      - branch-3.3
+      - branch-24.03
+    * - 2025.1 (epoxy)
+      - 26.0
+      - branch-3.3
+      - branch-24.03
+    * - 2024.2 (dalmatian)
+      - 25.0
+      - branch-3.3
+      - branch-24.03
+    * - 2024.1 (caracal)
+      - 24.0
+      - a4b04276ab5934d087669ff2d191a23931335c87
+      - v21.06.0
+    * - 2023.1 (antelope)
+      - 22.0
+      - a4b04276ab5934d087669ff2d191a23931335c87
+      - v21.06.0
+    * - zed
+      - 21.0
+      - a4b04276ab5934d087669ff2d191a23931335c87
+      - v21.06.0
+    * - yoga
+      - 20.0
+      - v2.16.0
+      - v21.06.0
+    * - xena
+      - 19.0
+      - v2.16.0
+      - v21.06.0
+    * - wallaby
+      - 18.0
+      - 0047ca3a0290f1ef954f2c76b31477cf4b9755f5
+      - v20.06.1
+    * - victoria
+      - 17.0
+      - 51e9479da62edb04a5be47a7655de75c299b9fa1
+      - v20.06.1