netdev - Re: [PATCH 2/2] IGMP snooping: set mrouters_only flag for IPv6 traffic properly

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Date:	Thu, 16 Jun 2011 23:14:53 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	fernando@....ntt.co.jp
Cc:	herbert@...dor.hengli.com.au, shemminger@...tta.com,
	netdev@...r.kernel.org, yoshfuji@...ux-ipv6.org
Subject: Re: [PATCH 2/2] IGMP snooping: set mrouters_only flag for IPv6
 traffic properly

From: Fernando Luis Vázquez Cao <fernando@....ntt.co.jp>
Date: Tue, 14 Jun 2011 10:06:58 +0900

> Upon reception of a MGM report packet the kernel sets the mrouters_only flag
> in a skb that is a clone of the original skb, which means that the bridge
> loses track of MGM packets (cb buffers are tied to a specific skb and not
> shared) and it ends up forwading join requests to the bridge interface.
> 
> This can cause unexpected membership timeouts and intermitent/permanent loss
> of connectivity as described in RFC 4541 [2.1.1. IGMP Forwarding Rules]:
> 
>     A snooping switch should forward IGMP Membership Reports only to
>     those ports where multicast routers are attached.
>     [...]
>     Sending membership reports to other hosts can result, for IGMPv1
>     and IGMPv2, in unintentionally preventing a host from joining a
>     specific multicast group.
> 
> 
> Signed-off-by: Fernando Luis Vazquez Cao <fernando@....ntt.co.jp>

Applied.
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