tproxy: added udp6_lib_lookup function

Just like with IPv4, we need access to the UDP hash table to look up local
sockets, but instead of exporting the global udp_table, export a lookup
function.

Signed-off-by: Balazs Scheidler <bazsi@balabit.hu>
Signed-off-by: KOVACS Krisztian <hidden@balabit.hu>
Signed-off-by: Patrick McHardy <kaber@trash.net>
diff --git a/include/net/udp.h b/include/net/udp.h
index a184d34..200b828 100644
--- a/include/net/udp.h
+++ b/include/net/udp.h
@@ -183,6 +183,9 @@
 extern struct sock *udp4_lib_lookup(struct net *net, __be32 saddr, __be16 sport,
 				    __be32 daddr, __be16 dport,
 				    int dif);
+extern struct sock *udp6_lib_lookup(struct net *net, const struct in6_addr *saddr, __be16 sport,
+				    const struct in6_addr *daddr, __be16 dport,
+				    int dif);
 
 /*
  * 	SNMP statistics for UDP and UDP-Lite