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

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Message-ID: <1314093424.2219.3.camel@edumazet-HP-Compaq-6005-Pro-SFF-PC>
Date:	Tue, 23 Aug 2011 11:57:03 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Ang Way Chuang <wcang@....wide.ad.jp>
Cc:	netdev@...r.kernel.org,
	Linus Lüssing <linus.luessing@....de>,
	Herbert Xu <herbert@...dor.apana.org.au>
Subject: 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) {


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