Linux bridge not forward multicast traffic

As it turns out, it's a bug in the igmp snooping code in the kernel that's
the problem with multicast traffic not being forwarded.

This seems to affect recent versions. To check if it's turned on, run
cat /sys/devices/virtual/net//bridge/multicast_snooping

If it's 1, it's highly this is the culprit causing the non-propagation of
the multicast traffic. The solution is to turn it off by setting it 0.

In my case:

echo 0 > /sys/devices/virtual/net/br0/bridge/multicast_snooping

Source