Linux Ethernet Bridging - Nov 2016 - [Bridge] Force IGMP membership

Hello,

I'm trying to add a bridge port to a multicast group manually to work around
the situation where VMs that are live migrated lose their IGMP membership. We
have IGMP snooping enabled on the bridge, and during this example there were
other VMs on the same bridge/vlan which are part of this multicast group address
sending/receiving traffic. These systems are running Ubuntu 14.04 (kernel 3.13).

Prior to live migration, I see the IGMP group membership on the kvm hypervisor:
$ bridge -d mdb | grep vnet8
dev br.128 port vnet8 grp 239.236.15.150 temp

After the live migration, multicast traffic to 239.236.15.150 stops as expected.
If I try to manually add the multicast group membership:
# bridge mdb add dev br.128 port vnet3 grp 239.236.15.150 temp     
# bridge mdb list | grep vnet3
dev onebr.128 port vnet3 grp 239.236.15.150 temp

The multicast traffic does not resume until the VM sends a IGMP membership
report after receiving an IGMP query from the switch, which takes too long most
of the time (over a minute).

I haven't been able to find anyone online in this situation, so any help
would be greatly appreciated.

Thank you,
Corey Melanson

On Fri, Nov 04, 2016 at 08:44:48PM +0000, Corey Melanson
wrote:
> After the live migration, multicast traffic to 239.236.15.150 stops as
expected. If I try to manually add the multicast group membership:
> # bridge mdb add dev br.128 port vnet3 grp 239.236.15.150 temp     
> # bridge mdb list | grep vnet3
> dev onebr.128 port vnet3 grp 239.236.15.150 temp
> 
> The multicast traffic does not resume until the VM sends a IGMP membership
report after receiving an IGMP query from the switch, which takes too long most
of the time (over a minute).
Hm, sounds weird. Have you verified with tcpdump that
on <brport-multicast-in> you see the according frame and on vnet3
it is missing then?

Does it make a difference when instead of adding a group
explicitly to mark the whole port as a router port?

($ echo 2 > /sys/class/net/vnet3/brport/multicast_router
- not a solution proposal but just to narrow things down)

Regards, Linus