[Bug 2148509] Re: [SRU] Neutron stable point releases

Brian Haley 2148509 at bugs.launchpad.net
Wed Oct 7 22:24:07 UTC 2026 

I've been able to verify the neutron Epoxy update. Further testing
information below.

Version tested:
neutron-server 2:26.0.5-0ubuntu0.24.04.1

Ran charmed-openstack-tester, results will be attached (accidentally
deleted). No failures due to neutron update, all in unrelated tests.

Did individual verification of the following bugs, as I knew their fixes
were addressed.

1) https://bugs.launchpad.net/neutron/+bug/2069442

Issue was traceback seen intermittently when deleting VMs

Verified changed code was present and neutron traceback didn't happen over multiple
attempts creating/deleting instances in a loop, for example:

while true; do
  openstack server create...
  openstack server delete...
done

2) https://bugs.launchpad.net/neutron/+bug/2116087

Verified changed code was present and neutron port binding operates as
expected.

3) https://bugs.launchpad.net/neutron/+bug/2032817

Issue was that mixed network MTU values would lead to traffic being
dropped transiting the router/gateway node.

First verified "need to frag" was set to true on neutron-api unit:

plugins/ml2/ml2_conf.ini:ovn_emit_need_to_frag = True

Then created some test resources from the undercloud:

$ openstack network create foo
$ openstack subnet create --network foo --subnet-range 10.2.0.0/24 foo
$ openstack network create --mtu 1400 bar
$ openstack subnet create --network bar --subnet-range 10.3.0.0/24 bar
$ openstack router create foobar
$ openstack router add subnet foobar foo
$ openstack router add subnet foobar bar
$ openstack router set --external-gateway ext_net foobar
  (on newer clouds: openstack router add gateway foobar ext_net)

Verified on ovn-central node that the logical router port had the lower
of the two mtus:

$ sudo ovn-nbctl list Logical_Router_Port 9bf41218-10ad-4635-99cf-2e594992656b
_uuid               : 9bf41218-10ad-4635-99cf-2e594992656b
dhcp_relay          : []
enabled             : []
external_ids        : {"neutron:is_ext_gw"=True, "neutron:network_name"=neutron-9e8e0666-42aa-431c-a287-5d2e0906f80b, "neutron:revision_number"="5", "neutron:router_name"="5739d37e-d240-4ffc-b81e-6b96335f2dce", "neutron:subnet_ids"="1415a905-7d5b-42bf-938d-e311330c0fbf"}
gateway_chassis     : [11f17ada-e082-4952-934f-21e0ec425e85, 212cdd51-763a-4d5c-92db-679d6ac44baf, 72c9c344-bf65-47f3-a91e-ac5b8e6eb537]
ha_chassis_group    : []
ipv6_prefix         : []
ipv6_ra_configs     : {}
mac                 : "fa:16:3e:b1:bf:ac"
name                : lrp-ab8c6a58-f182-4801-abcc-0b9148f37486
networks            : ["10.159.5.219/25"]
options             : {gateway_mtu="1400", reside-on-redirect-chassis="true"}
peer                : []
status              : {hosting-chassis=juju-716782-zaza-659c195dee9d-29}

"1400" here is correct, would have been 1442 without the fix.

Launched two instances, one on each network, so one will have a larger
mtu than the other.

$ ./tools/instance_launch.sh 1 --image jammy --name foovm --network foo
$ ./tools/instance_launch.sh 1 --image jammy --name barvm --network bar
$ ./tools/float_all.sh

Logged-into the VM with the larger mtu (foovm).

Verified mtu settings:

$ ip a s dev ens2

2: ens2: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1442 qdisc fq_codel state
UP group default qlen 1000

Then pinged the floating IP of the other VM, which has a smaller mtu:

$ ping -s 1400 10.159.5.213
PING 10.159.5.213 (10.159.5.213) 1400(1428) bytes of data.
>From 10.159.5.219 icmp_seq=1 Frag needed and DF set (mtu = 1400)
1408 bytes from 10.159.5.213: icmp_seq=3 ttl=62 time=11.5 ms
1408 bytes from 10.159.5.213: icmp_seq=4 ttl=62 time=0.852 ms

Frag needed message indicates fix worked correctly. Ping also
succeeded.

** Tags removed: verification-epoxy-needed
** Tags added: verification-epoxy-done

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https://bugs.launchpad.net/bugs/2148509

Title:
  [SRU] Neutron stable point releases

Status in Ubuntu Cloud Archive:
  New
Status in Ubuntu Cloud Archive caracal series:
  New
Status in Ubuntu Cloud Archive dalmatian series:
  Won't Fix
Status in Ubuntu Cloud Archive epoxy series:
  Fix Committed
Status in Ubuntu Cloud Archive flamingo series:
  Fix Committed
Status in neutron package in Ubuntu:
  New
Status in neutron source package in Jammy:
  New
Status in neutron source package in Noble:
  New
Status in neutron source package in Questing:
  Won't Fix
Status in neutron source package in Resolute:
  Fix Released

Bug description:
  [Impact]
  This release contains mostly bug-fixes and we would like to make sure all of our users have access to these improvements.

  The update contains the following package updates:

  * neutron 27.0.2 (Questing/Flamingo)
  * neutron 26.0.3 (Epoxy)
  * neutron 25.2.3 (Dalmatian) - no longer applicable, release EOL
  * neutron 24.2.2 (Noble/Caracal)

  [Test Case]
  The following SRU process was followed:
  https://wiki.ubuntu.com/OpenStack/StableReleaseUpdates

  In order to avoid regression of existing consumers, the SEG team will
  run their continuous integration test against the packages that are in
  -proposed. A successful run of all available tests will be required
  before the proposed packages can be let into -updates.

  The SEG team will be in charge of attaching the output summary of the
  executed tests. The SEG team members will not mark ‘verification-done’
  until this has happened.

  [Regression Potential]
  In order to mitigate the regression potential, the results of the aforementioned tests are attached to this bug.

  [Extra Notes]
  As the current Neutron PTL, and a member of the upstream Neutron core and stable teams, I was one of the maintainers involved in back-porting changes to the stable branches, making sure they meet specific requirements and apply cleanly. I've added some links to commit messages for each release as an example of the changes that have been applied.

  This work also eases future SRU work, as any future patches will be
  based on these later versions, so will have less merge conflicts.

  Releases created using UCA scripts from
  https://git.launchpad.net/~ubuntu-cloud-archive/+git/pkg-scripts

  Caracal - There are at least 45 bug fixes and various CI fixes contained in this 24.2.2 point release. Links to the three most recent commits:
  - https://review.opendev.org/c/openstack/releases/+/951191/1//COMMIT_MSG
  - https://review.opendev.org/c/openstack/releases/+/954472/3//COMMIT_MSG
  - https://review.opendev.org/c/openstack/releases/+/964540/1//COMMIT_MSG

  In addition, for Caracal, I added a CVE fix for https://bugs.launchpad.net/neutron/+bug/2141589 which was not included in the
  point release. It's review is here:
  - https://review.opendev.org/c/openstack/neutron/+/977907

  Epoxy - There are at least 55 bug fixes and various CI fixes contained in this 26.0.3 point release, along with one CVE fix. Links to the three most recent commits:
  - https://review.opendev.org/c/openstack/releases/+/951195/4//COMMIT_MSG
  - https://review.opendev.org/c/openstack/releases/+/964098/1//COMMIT_MSG
  - https://review.opendev.org/c/openstack/releases/+/984897/2//COMMIT_MSG

  Flamingo - There are at least 8 bug fixes and various CI fixes contained in this 27.0.2 point release, along with one CVE fix. Links to the two most recent commits:
  - https://review.opendev.org/c/openstack/releases/+/964097/1//COMMIT_MSG
  - https://review.opendev.org/c/openstack/releases/+/984897/2//COMMIT_MSG

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