From: Andrew Lunn <andrew@lunn.ch>
Date: Fri, 1 May 2015 14:39:54 +0000 (+0200)
Subject: net: ipv4: route: Fix sending IGMP messages with link address
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=6a21165480a066a27c1f1dbd32aec581c612ba23;p=linux-beck.git

net: ipv4: route: Fix sending IGMP messages with link address

In setups with a global scope address on an interface, and a lesser
scope address on an interface sending IGMP reports, the reports can be
sent using the other interfaces global scope address rather than the
local interface address. RFC 2236 suggests:

     Ignore the Report if you cannot identify the source address of
     the packet as belonging to a subnet assigned to the interface on
     which the packet was received.

since such reports could be forged.

Look at the protocol when deciding if a RT_SCOPE_LINK address should
be used for the packet.

Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>
---

diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 7cad0bf1c71c..9e15f5ca4495 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -2091,7 +2091,8 @@ struct rtable *__ip_route_output_key(struct net *net, struct flowi4 *fl4)
 			goto out;
 		}
 		if (ipv4_is_local_multicast(fl4->daddr) ||
-		    ipv4_is_lbcast(fl4->daddr)) {
+		    ipv4_is_lbcast(fl4->daddr) ||
+		    fl4->flowi4_proto == IPPROTO_IGMP) {
 			if (!fl4->saddr)
 				fl4->saddr = inet_select_addr(dev_out, 0,
 							      RT_SCOPE_LINK);