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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>
This commit is contained in:
Andrew Lunn 2015-05-01 16:39:54 +02:00 committed by David S. Miller
parent 087c1a601a
commit 6a21165480
1 changed files with 2 additions and 1 deletions
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3
net/ipv4/route.c
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@ -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);