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>

include/net/udp.h

@@ -183,6 +183,9 @@ extern int udp_lib_setsockopt(struct sock *sk, int level, int optname,
 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

net/ipv6/udp.c

@@ -320,6 +320,14 @@ static struct sock *__udp6_lib_lookup_skb(struct sk_buff *skb,
 				 udptable);
 }
 
+struct sock *udp6_lib_lookup(struct net *net, const struct in6_addr *saddr, __be16 sport,
+			     const struct in6_addr *daddr, __be16 dport, int dif)
+{
+	return __udp6_lib_lookup(net, saddr, sport, daddr, dport, dif, &udp_table);
+}
+EXPORT_SYMBOL_GPL(udp6_lib_lookup);
+
+
 /*
  * 	This should be easy, if there is something there we
  * 	return it, otherwise we block.