[UDP]: Make use of inet_iif() when doing socket lookups.

UDP currently uses skb->dev->ifindex which may provide the wrong
information when the socket bound to a specific interface.
This patch makes inet_iif() accessible to UDP and makes UDP use it.

The scenario we are trying to fix is when a client is running on
the same system and the server and both client and server bind to
a non-loopback device.
Signed-off-by: Vlad Yasevich <vladislav.yasevich@hp.com>
Acked-by: David L Stevens <dlstevens@us.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/inet_hashtables.h

@@ -26,7 +26,6 @@
 
 #include <net/inet_connection_sock.h>
 #include <net/inet_sock.h>
-#include <net/route.h>
 #include <net/sock.h>
 #include <net/tcp_states.h>
 
@@ -266,11 +265,6 @@ static inline void inet_unhash(struct inet_hashinfo *hashinfo, struct sock *sk)
 		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(struct inet_hashinfo *hashinfo,
 					   const __be32 daddr,
 					   const unsigned short hnum,

include/net/inet_sock.h

@@ -24,6 +24,7 @@
 #include <net/flow.h>
 #include <net/sock.h>
 #include <net/request_sock.h>
+#include <net/route.h>
 
 /** struct ip_options - IP Options
  *
@@ -190,4 +191,10 @@ static inline int inet_sk_ehashfn(const struct sock *sk)
 	return inet_ehashfn(laddr, lport, faddr, fport);
 }
 
+
+static inline int inet_iif(const struct sk_buff *skb)
+{
+	return ((struct rtable *)skb->dst)->rt_iif;
+}
+
 #endif	/* _INET_SOCK_H */

net/ipv4/udp.c

@@ -1152,7 +1152,7 @@ int __udp4_lib_rcv(struct sk_buff *skb, struct hlist_head udptable[],
 		return __udp4_lib_mcast_deliver(skb, uh, saddr, daddr, udptable);
 
 	sk = __udp4_lib_lookup(saddr, uh->source, daddr, uh->dest,
-			       skb->dev->ifindex, udptable        );
+			       inet_iif(skb), udptable);
 
 	if (sk != NULL) {
 		int ret = udp_queue_rcv_skb(sk, skb);