udp: Export UDP socket lookup function

The iptables tproxy code has to be able to do UDP socket hash lookups,
so we have to provide an exported lookup function for this purpose.
Signed-off-by: NKOVACS Krisztian <hidden@sch.bme.hu>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

include/net/udp.h

@@ -148,6 +148,10 @@ extern int 	udp_lib_setsockopt(struct sock *sk, int level, int optname,
 				   char __user *optval, int optlen,
 				   int (*push_pending_frames)(struct sock *));
 
+extern struct sock *udp4_lib_lookup(struct net *net, __be32 saddr, __be16 sport,
+				    __be32 daddr, __be16 dport,
+				    int dif);
+
 DECLARE_SNMP_STAT(struct udp_mib, udp_stats_in6);
 
 /* UDP-Lite does not have a standardized MIB yet, so we inherit from UDP */

net/ipv4/udp.c

@@ -302,6 +302,13 @@ static struct sock *__udp4_lib_lookup(struct net *net, __be32 saddr,
 	return result;
 }
 
+struct sock *udp4_lib_lookup(struct net *net, __be32 saddr, __be16 sport,
+			     __be32 daddr, __be16 dport, int dif)
+{
+	return __udp4_lib_lookup(net, saddr, sport, daddr, dport, dif, udp_hash);
+}
+EXPORT_SYMBOL_GPL(udp4_lib_lookup);
+
 static inline struct sock *udp_v4_mcast_next(struct sock *sk,
 					     __be16 loc_port, __be32 loc_addr,
 					     __be16 rmt_port, __be32 rmt_addr,