linux-kernel - [STABLE] [PATCH] IGMP snooping: set mrouters

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Date:	Thu, 28 Jul 2011 10:53:30 +0900
From:	Fernando Luis Vazquez Cao <fernando@....ntt.co.jp>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	pablo@...filter.org, gregkh@...e.de, ak@...ux.intel.com,
	linux-kernel@...r.kernel.org, stable@...nel.org,
	tim.bird@...sony.com
Subject: [STABLE] [PATCH] IGMP snooping: set mrouters_only flag for IPv4
 traffic properly

From: Fernando Luis Vázquez Cao <fernando@....ntt.co.jp>

commit 62b2bcb49cca72f6d3f39f831127a6ab315a475d upstream.

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>
Signed-off-by: David S. Miller <davem@...an.davemloft.net>
---

diff -urNp linux-2.6.35.13-orig/net/bridge/br_multicast.c linux-2.6.35.13/net/bridge/br_multicast.c
--- linux-2.6.35.13-orig/net/bridge/br_multicast.c	2011-04-29 00:21:24.000000000 +0900
+++ linux-2.6.35.13/net/bridge/br_multicast.c	2011-07-28 10:28:08.505872639 +0900
@@ -1403,7 +1403,7 @@ static int br_multicast_ipv4_rcv(struct
 	switch (ih->type) {
 	case IGMP_HOST_MEMBERSHIP_REPORT:
 	case IGMPV2_HOST_MEMBERSHIP_REPORT:
-		BR_INPUT_SKB_CB(skb2)->mrouters_only = 1;
+		BR_INPUT_SKB_CB(skb)->mrouters_only = 1;
 		err = br_ip4_multicast_add_group(br, port, ih->group);
 		break;
 	case IGMPV3_HOST_MEMBERSHIP_REPORT:


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