[Bug 1965297] Re: l3ha don't set backup qg ports down

[Edward Hope-Morley]

jammy-proposed verified using [Test Plan] and had the following output:

# apt-cache policy neutron-common
neutron-common:
  Installed: 2:20.1.0-0ubuntu2
  Candidate: 2:20.1.0-0ubuntu2
  Version table:
 *** 2:20.1.0-0ubuntu2 500
        500 http://archive.ubuntu.com/ubuntu jammy-proposed/main amd64 Packages
        100 /var/lib/dpkg/status
     2:20.0.0-0ubuntu3 500
        500 http://nova.clouds.archive.ubuntu.com/ubuntu jammy/main amd64 Packages

$ juju run -a neutron-gateway -- ip netns exec qrouter-e6f9b06a-039f-48a1-b2b6-484aa61f9d8d ip link show| grep qg-6940823b-80
    3: qg-6940823b-80 at if12: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP mode DEFAULT group default qlen 1000
    3: qg-6940823b-80 at if13: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP mode DEFAULT group default qlen 1000
    3: qg-6940823b-80 at if13: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP mode DEFAULT group default qlen 1000


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

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https://bugs.launchpad.net/bugs/1965297

Title:
  l3ha don't set backup qg ports down

Status in Ubuntu Cloud Archive:
  Fix Released
Status in Ubuntu Cloud Archive ussuri series:
  Triaged
Status in Ubuntu Cloud Archive victoria series:
  Triaged
Status in Ubuntu Cloud Archive wallaby series:
  In Progress
Status in Ubuntu Cloud Archive xena series:
  Fix Committed
Status in Ubuntu Cloud Archive yoga series:
  Fix Committed
Status in Ubuntu Cloud Archive zed series:
  Fix Released
Status in neutron:
  Fix Released
Status in neutron package in Ubuntu:
  Fix Released
Status in neutron source package in Focal:
  Triaged
Status in neutron source package in Impish:
  Fix Committed
Status in neutron source package in Jammy:
  Fix Committed
Status in neutron source package in Kinetic:
  Fix Released

Bug description:
  The history to this request is as follows; bug 1916024 fixed an issue
  that subsequently had to be reverted due to a regression that it
  introduced (see bug 1927868) and the original issue can once again
  present itself in that keepalived is unable to send GARP on the qg
  port until the port is marked as UP by neutron which in loaded
  environments can sometimes take longer than keepalived will wait (e.g.
  when an l3-agent is restarted on a host that has hundreds of routers).
  The reason why qg- ports are marked as DOWN is because of the patch
  landed as part of bug 1859832 and as I understand it there is now
  consensus from upstream [1] to revert that patch as well and a better
  solution is needed to fix that particular issue. I have not found a
  bug open yet for the revert hence why I am opening this one.

  [1]
  https://meetings.opendev.org/meetings/neutron_drivers/2022/neutron_drivers.2022-03-04-14.03.log.txt

  ------------

  [Impact]
  Please see LP bug description for full details but in short, this patch is a revert of a patch that has show instability in the field for users of Neutron L3HA.

  [Test Plan]
    * Deploy Openstack with Neutron L3 HA enabled
    * Create a number of HA routers
    * Check all qrouter namespaces and ensure that the qg- port is UP in all

  [Regression Potential]
  Since the original patch was intended to address issues with MLDv2 it is possible that reverting it will re-introduce those issues and a new patch will need to be proposed to address that.

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