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/ndisc.c b/net/ipv6/ndisc.c
index af6705f..e4acc21 100644
--- a/net/ipv6/ndisc.c
+++ b/net/ipv6/ndisc.c
@@ -524,7 +524,7 @@
 		return;
 	}
 
-	err = xfrm_lookup(&dst, &fl, NULL, 0);
+	err = xfrm_lookup(net, &dst, &fl, NULL, 0);
 	if (err < 0) {
 		kfree_skb(skb);
 		return;
@@ -1524,7 +1524,7 @@
 	if (dst == NULL)
 		return;
 
-	err = xfrm_lookup(&dst, &fl, NULL, 0);
+	err = xfrm_lookup(net, &dst, &fl, NULL, 0);
 	if (err)
 		return;