Comment 13 for bug 1959702

Harry,

 I'm still working to reproduce this, without success. I have set
the .autoconf sysctl to 0 (which controls creation of local addresses in
response to received Router Advertisements), as well as setting
.addr_gen_mode to 1 (to disable SLAAC (fe80::) addresses).

 In any event, .autoconf=0 and .addr_gen_mode=1 still fails to
reproduce the issue on my test system.

 I find that if I disable mcast_flood on the relevant bridge ports
(i.e., bridge link set dev vnet1 mcast_flood off) I do see the behavior
you describe, but in that case no variant that I've tried (no vid, and all
vids in use) of "bridge mdb add ... grp ff02::1:ff00:2" appears to permit
ND traffic to pass to the VM destination.

 Can you provide more specifics of how exactly the bridge and ports
are configured? Ideally, both the method to set it up, as well as the
configuration details when failing (i.e., "ip -s -d link show" for the
bridge and relevant bridge ports, "bridge vlan show", "bridge mdb show",
"bridge fdb show br [bridgename]")

 Also, to answer a question from your original report, the default
setting in the kernel for multicast_snooping (enabled, i.e., 1) hasn't
changed recently (and quite possibly ever).