net: ipv4: dst for local input routes should use l3mdev if relevant

[ Upstream commit f5a0aab8 ]

IPv4 output routes already use l3mdev device instead of loopback for dst's
if it is applicable. Change local input routes to do the same.

This fixes icmp responses for unreachable UDP ports which are directed
to the wrong table after commit 9d1a6c4e because local_input
routes use the loopback device. Moving from ingress device to loopback
loses the L3 domain causing responses based on the dst to get to lost.

Fixes: 9d1a6c4e ("net: icmp_route_lookup should use rt dev to
		       determine L3 domain")
Signed-off-by: David Ahern <dsa@cumulusnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

net/ipv4/route.c

@@ -1902,7 +1902,8 @@ out:	return err;
 		}
 	}
 
-	rth = rt_dst_alloc(net->loopback_dev, flags | RTCF_LOCAL, res.type,
+	rth = rt_dst_alloc(l3mdev_master_dev_rcu(dev) ? : net->loopback_dev,
+			   flags | RTCF_LOCAL, res.type,
 			   IN_DEV_CONF_GET(in_dev, NOPOLICY), false, do_cache);
 	if (!rth)
 		goto e_nobufs;