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/syncookies.c b/net/ipv6/syncookies.c
index 676c80b..711175e 100644
--- a/net/ipv6/syncookies.c
+++ b/net/ipv6/syncookies.c
@@ -259,7 +259,7 @@
 
 		if (final_p)
 			ipv6_addr_copy(&fl.fl6_dst, final_p);
-		if ((xfrm_lookup(&dst, &fl, sk, 0)) < 0)
+		if ((xfrm_lookup(sock_net(sk), &dst, &fl, sk, 0)) < 0)
 			goto out_free;
 	}