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/in6.h b/include/linux/in6.h
index 097a34b..5c83d9e 100644
--- a/include/linux/in6.h
+++ b/include/linux/in6.h
@@ -271,6 +271,7 @@
 #define IPV6_ORIGDSTADDR        74
 #define IPV6_RECVORIGDSTADDR    IPV6_ORIGDSTADDR
 #define IPV6_TRANSPARENT        75
+#define IPV6_UNICAST_IF         76
 
 /*
  * Multicast Routing: