ipv6: Implement IPV6_UNICAST_IF socket option.

The IPV6_UNICAST_IF feature is the IPv6 compliment to IP_UNICAST_IF.

Signed-off-by: Erich E. Hoover <ehoover@mines.edu>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/ipv6.h b/include/linux/ipv6.h
index 6318268..743a16a 100644
--- a/include/linux/ipv6.h
+++ b/include/linux/ipv6.h
@@ -324,6 +324,7 @@
 				__unused_2:6;
 	__s16			mcast_hops:9;
 #endif
+	int			ucast_oif;
 	int			mcast_oif;
 
 	/* pktoption flags */