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[Launchpad Bug Tracker <1904399@xxxxxxxxxxxxxxxxxx>]

This bug was fixed in the package neutron - 2:17.0.0-0ubuntu3

---------------
neutron (2:17.0.0-0ubuntu3) groovy; urgency=medium

  * d/p/ovn-fix-inconsistent-igmp-configuration.patch: Cherry-picked from
    upstream stable/victoria to ensure flooding of unregistered multicast
    packets to all ports is disabled (LP: #1904399).

 -- Corey Bryant <corey.bryant@xxxxxxxxxxxxx>  Mon, 08 Feb 2021 12:25:46
-0500

** Changed in: neutron (Ubuntu Groovy)
       Status: Fix Committed => Fix Released

** Changed in: neutron (Ubuntu Focal)
       Status: Fix Committed => Fix Released

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https://bugs.launchpad.net/bugs/1904399

Title:
  [OVN] Inconsistent "flooding to unregistered" IGMP configuration

Status in Ubuntu Cloud Archive:
  Fix Committed
Status in Ubuntu Cloud Archive ussuri series:
  Fix Committed
Status in Ubuntu Cloud Archive victoria series:
  Fix Committed
Status in neutron:
  Fix Released
Status in neutron package in Ubuntu:
  Fix Released
Status in neutron source package in Focal:
  Fix Released
Status in neutron source package in Groovy:
  Fix Released
Status in neutron source package in Hirsute:
  Fix Released

Bug description:
  ML2/OVN reuses the same "[ovs]/igmp_snooping_enable" configuration
  option from ML2/OVS, which says [0]:

  "Setting this option to True will also enable Open vSwitch mcast-
  snooping-disable-flood-unregistered flag. This option will disable
  flooding of unregistered multicast packets to all ports."

  But, that's not true for ML2/OVN, in fact, this is the opposite
  because ML2/OVN does have the option to flood to unregistered VMs
  enabled by default.

  In order to keep the consistent between both drivers and this
  configuration option, ML2/OVN needs to disable the
  "mcast_flood_unregistered" configuration in the other_config column
  from the Logical Switch table when igmp_snooping_enable is True.

  [0]
  https://opendev.org/openstack/neutron/src/branch/master/neutron/conf/agent/ovs_conf.py#L36-L47

  [Impact]

  See above.

  [Test Case]

  Run the following and expect success:
  root@f1:~# sudo apt install python3-neutron
  root@f1:/usr/lib/python3/dist-packages# python3 -m unittest neutron.tests.unit.plugins.ml2.drivers.ovn.mech_driver.ovsdb.test_maintenance.TestDBInconsistenciesPeriodics.test_check_for_igmp_snoop_support

  I would also like to get test feedback from Canonical bootstack as
  they are hitting this issue.

  [Regression Potential]
  This is a very minimal and targeted change that always hard codes MCAST_FLOOD_UNREGISTERED to 'false'.

  In assessing regression potential for changes like this, one that
  comes to mind is potential of a type error when setting
  MCAST_FLOOD_UNREGISTERED. Upon visual inspection of this code fix, a
  type error would be impossible, as what was once set to a 'true' or
  'false' value is now set to 'false'.

  Another thought is whether MCAST_FLOOD_UNREGISTERED has any use if
  MCAST_SNOOP is set to false, but that is not the case according to
  upstream OVN documentation which states: mcast_flood_unregistered:
  optional string, either true or false Determines whether unregistered
  multicast traffic should be flooded or not. Only applicable if
  other_config:mcast_snoop is enabled.

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