Bug 203137

Summary:	Bridge does not forward multicast if multicast_querier is enabled
Product:	Networking	Reporter:	liam.mcbirnie
Component:	Other	Assignee:	Stephen Hemminger (stephen)
Status:	NEW ---
Severity:	normal
Priority:	P1
Hardware:	All
OS:	Linux
Kernel Version:	5.0.3	Subsystem:
Regression:	Yes	Bisected commit-id:

Description liam.mcbirnie 2019-04-03 04:49:49 UTC

When multicast querier is enabled on a bridge, multicasts are not forwarded according to the multicast forwarding database.

"bridge mdb" shows the multicast forwarding entries but they are not forwarded to the ports.
Manually adding the port to the bridge multicast DB works.

Wireshark shows the packets arriving on the bridge but not being sent out the proper port.

The regression was introduced by commit 19e3a9c90c53479fecaa02307bf2db5ab8b3ffe3, "net: bridge: convert multicast to generic rhashtable" by Nikolay Aleksandrov <nikolay@cumulusnetworks.com>.

Steps to reproduce:

ip link add br0 type bridge mcast_querier 1
ip link set br0 up

ip link add v2 type veth peer name v3
ip link set v2 master br0
ip link set v2 up
ip link set v3 up
ip addr add 3.0.0.2/24 dev v3

ip netns add test
ip link add v1 type veth peer name v1 netns test
ip link set v1 master br0
ip link set v1 up
ip -n test link set v1 up
ip -n test addr add 3.0.0.1/24 dev v1

# Multicast receiver
ip netns exec test socat UDP4-RECVFROM:5588,ip-add-membership=224.224.224.224:3.0.0.1,fork -

# Multicast sender
echo hello | nc -u -s 3.0.0.2 224.224.224.224 5588

Observe that 'bridge mdb' has an entry for 224.224.224.224 on port v1.
Observe that the multicast packets are seen on v2, v3 and br0 but not v1.