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[Bug 1218959] Re: KVM virbr# no longer forwards multicast traffic by default (U12.04)


I had thought that we'd need a udev rule to work around this, but
looking over the fedora bug in more detail it looks like cherrypicking
the two patches mentioned in comment 31 (
https://bugzilla.redhat.com/show_bug.cgi?id=880035#c31 ) should do it.

Can those who are suffering from this bug please tell us precisely which
kernel they are using?  If I understand right, this should be fixed in
3.11, so I would expect anyone using the saucy backport kernel to not be

** Bug watch added: Red Hat Bugzilla #880035

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  KVM virbr# no longer forwards multicast traffic by default (U12.04)

Status in “libvirt” package in Ubuntu:
  Fix Released
Status in “linux” package in Ubuntu:
Status in “libvirt” source package in Precise:
Status in “linux” source package in Precise:

Bug description:
  A recent kernel update (Apr 2013) has made it's way to U12.04.2 LTS
  (approx June-Aug 2013) and has stopped the (default) behaviour of
  automatically forwarding multicast traffic over virbr#.  Some updates
  the bridge subsystem now, by default, disable multicast traffic
  without IGMP Querier being enabled on that bridge.

  The corresponding Fedora/RHEL bug tracks the progress/updates of this specific change in relation to Fedora.  

  (I have yet to find a similar bug report in Ubuntu so I have created
  this bug to help the Ubuntu community identify multicast issues that
  may arise since April 2013 in U12.04 LTS and presumably other Ubuntu
  releases as backports are made and break regression testing.)

  Using the latest patches in U12.04.2 LTS this following addition, with some modifications, can be made to the udev rules will enable multicast on virbr# bridge:

  While this is an improvement/correction to KVM bridge networking it
  has broken existing functionality in U12.04.2 LTS and broke regressed
  functionality that once worked.

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