** Description changed:
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
** Changed in: linux (Ubuntu)
Status: Incomplete => Fix Released
** Changed in: linux (Ubuntu Precise)
Status: Incomplete => Won't Fix
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https://bugs.launchpad.net/bugs/1218959
Title:
KVM virbr# no longer forwards multicast traffic by default (U12.04)
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