netns xfrm: lookup in netns

Pass netns to xfrm_lookup()/__xfrm_lookup(). For that pass netns
to flow_cache_lookup() and resolver callback.

Take it from socket or netdevice. Stub DECnet to init_net.

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv6/mcast.c b/net/ipv6/mcast.c
index 870a1d6..0f38960 100644
--- a/net/ipv6/mcast.c
+++ b/net/ipv6/mcast.c
@@ -1466,7 +1466,7 @@
 			 &ipv6_hdr(skb)->saddr, &ipv6_hdr(skb)->daddr,
 			 skb->dev->ifindex);
 
-	err = xfrm_lookup(&skb->dst, &fl, NULL, 0);
+	err = xfrm_lookup(net, &skb->dst, &fl, NULL, 0);
 	if (err)
 		goto err_out;
 
@@ -1831,7 +1831,7 @@
 			 &ipv6_hdr(skb)->saddr, &ipv6_hdr(skb)->daddr,
 			 skb->dev->ifindex);
 
-	err = xfrm_lookup(&skb->dst, &fl, NULL, 0);
+	err = xfrm_lookup(net, &skb->dst, &fl, NULL, 0);
 	if (err)
 		goto err_out;