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

 

Hello Michael, or anyone else affected,

Accepted libvirt into precise-proposed. The package will build now and
be available at
http://launchpad.net/ubuntu/+source/libvirt/0.9.8-2ubuntu17.19 in a few
hours, and then in the -proposed repository.

Please help us by testing this new package.  See
https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to
enable and use -proposed.  Your feedback will aid us getting this update
out to other Ubuntu users.

If this package fixes the bug for you, please add a comment to this bug,
mentioning the version of the package you tested, and change the tag
from verification-needed to verification-done. If it does not fix the
bug for you, please add a comment stating that, and change the tag to
verification-failed.  In either case, details of your testing will help
us make a better decision.

Further information regarding the verification process can be found at
https://wiki.ubuntu.com/QATeam/PerformingSRUVerification .  Thank you in
advance!

** Changed in: libvirt (Ubuntu Precise)
       Status: Confirmed => Fix Committed

** Tags added: verification-needed

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https://bugs.launchpad.net/bugs/1218959

Title:
  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:
  Fix Released
Status in “libvirt” source package in Precise:
  Fix Committed
Status in “linux” source package in Precise:
  Won't Fix

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.  
  https://bugzilla.redhat.com/show_bug.cgi?id=880035

  (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:
  https://bugzilla.redhat.com/show_bug.cgi?id=880035#c38

  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.

  IMPACT: multicast is broken over libvirt bridges
  FIX: set a (new, introduced by a new kernel) toggle on the bridges
  TEST CASE: cat /sys/devices/virtual/net/virbr0/bridge/multicast_querier - if 0, then forwarding multicast will be broken.
  REGRESSION POTENTIAL: should be none. older kernels do not have the toggle, and failure to set it will be ignored

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