netns xfrm: per-netns xfrm_state_bydst hash

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/netns/xfrm.h b/include/net/netns/xfrm.h
index 6ae234a..02487b3 100644
--- a/include/net/netns/xfrm.h
+++ b/include/net/netns/xfrm.h
@@ -5,6 +5,15 @@
 
 struct netns_xfrm {
 	struct list_head	state_all;
+	/*
+	 * Hash table to find appropriate SA towards given target (endpoint of
+	 * tunnel or destination of transport mode) allowed by selector.
+	 *
+	 * Main use is finding SA after policy selected tunnel or transport
+	 * mode. Also, it can be used by ah/esp icmp error handler to find
+	 * offending SA.
+	 */
+	struct hlist_head	*state_bydst;
 };
 
 #endif