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/af_inet6.c b/net/ipv6/af_inet6.c
index 01edac8..437b750 100644
--- a/net/ipv6/af_inet6.c
+++ b/net/ipv6/af_inet6.c
@@ -637,7 +637,7 @@
 		if (final_p)
 			ipv6_addr_copy(&fl.fl6_dst, final_p);
 
-		if ((err = xfrm_lookup(&dst, &fl, sk, 0)) < 0) {
+		if ((err = xfrm_lookup(sock_net(sk), &dst, &fl, sk, 0)) < 0) {
 			sk->sk_err_soft = -err;
 			return err;
 		}