[ICSK]: Generalise tcp_listen_{start,stop}

This also moved inet_iif from tcp to inet_hashtables.h, as it is
needed by the inet_lookup callers, perhaps this needs a bit of
polishing, but for now seems fine.

Signed-off-by: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/inet_hashtables.h

@@ -26,6 +26,7 @@
 #include <linux/wait.h>
 
 #include <net/inet_connection_sock.h>
+#include <net/route.h>
 #include <net/sock.h>
 #include <net/tcp_states.h>
 
@@ -280,6 +281,11 @@ out:
 		wake_up(&hashinfo->lhash_wait);
 }
 
+static inline int inet_iif(const struct sk_buff *skb)
+{
+	return ((struct rtable *)skb->dst)->rt_iif;
+}
+
 extern struct sock *__inet_lookup_listener(const struct hlist_head *head,
 					   const u32 daddr,
 					   const unsigned short hnum,