net/ipv4: fix IPv4 multicast over network namespaces

When using multicast over a local bridge feeding a number of LXC guests using veth, the LXC guests are unable to get a response from other guests when pinging 224.0.0.1. Multicast packets did not appear to be getting delivered to the network namespaces of the guest hosts, and further inspection showed that the incoming route was pointing to the loopback device of the host, not the guest. This lead to the wrong network namespace being picked up by sockets (like ICMP). Fix this by using the correct network namespace when creating the inbound route entry.

---
 net/ipv4/route.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

index 12ccf88..3b110a4 100644
@@ -2042,7 +2042,7 @@ static int ip_route_input_mc(struct sk_buff *skb, __be32 daddr, __be32 saddr,
 		if (err < 0)
 			goto e_err;
 	}
-	rth = rt_dst_alloc(init_net.loopback_dev,
+	rth = rt_dst_alloc(dev_net(dev)->loopback_dev,
 			   IN_DEV_CONF_GET(in_dev, NOPOLICY), false);
 	if (!rth)
 		goto e_nobufs;

1.7.4.1


-- 
"Thought is the essence of where you are now."

From: Benjamin LaHaise <[email protected]>
Date: Tue, 27 Mar 2012 21:55:32 -0400

Applied.