netdev - Re: [PATCH 1/2] IGMP snooping: set mrouters_only flag for IPv4 traffic properly

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Date:	Thu, 16 Jun 2011 23:14:47 -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, kakuta.hayato@....ntt.co.jp
Subject: Re: [PATCH 1/2] IGMP snooping: set mrouters_only flag for IPv4
 traffic properly

From: Fernando Luis Vázquez Cao <fernando@....ntt.co.jp>
Date: Tue, 14 Jun 2011 10:04:43 +0900

> Upon reception of a IGMP/IGMPv2 membership report the kernel sets the
> mrouters_only flag in a skb that may be a clone of the original skb, which
> means that sometimes the bridge loses track of membership report 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>
> Tested-by: Hayato Kakuta <kakuta.hayato@....ntt.co.jp>

Applied.
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