Re: IPv6 multicast snooping behaviour on 2.6.39-rc2 and later

Le mardi 23 août 2011 à 17:41 +0900, Ang Way Chuang a écrit :

Hi all,

    Sorry for cross-posting. I have a testbed setup on my VM
environment that needs to use MLDv2 report message. My PIM router
which is connected to a port on the bridge relies upon MLDv2 message
to work. However, the setup failed to work after 2.6.39-rc2 or later.
MLDv2 won't be forwarded to any slave ports bound to the bridge
interface. Specifically, I track the cause down to this commit id:

      ff9a57a62afbbe2d0f3a09af321f1fd7645f38a5

    However, as soon as I disable multicast snooping on sysfs, MLDv2
message can be forwarded again.

    I am not knowledgeable on the subject of multicast snooping, but
is this right behaviour for multicast snooping? IPv4 doesn't seem to
suffer the same fate though, IGMP can be forwarded even if
multicast_snooping is enabled. Thank you in advance.

Thanks very much for the report and your tracking.

Added some CC

I wonder if the  ff9a57a62afb commit doesnt uncover a prior bug, could
you try the following patch ?

Thanks !

diff --git a/net/bridge/br_multicast.c b/net/bridge/br_multicast.c
index 2d85ca7..51e3b2d 100644
--- a/net/bridge/br_multicast.c
+++ b/net/bridge/br_multicast.c

@@ -1520,6 +1520,7 @@ static int br_multicast_ipv6_rcv(struct net_bridge *br,
 		err = pskb_trim_rcsum(skb2, len);
 		if (err)
 			goto out;
+		icmp6h = icmp6_hdr(skb2);
 	}
 
 	switch (skb2->ip_summed) {