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/net/ipv6/ipv6_sockglue.c b/net/ipv6/ipv6_sockglue.c
index 18a2719..6d6b65f 100644
--- a/net/ipv6/ipv6_sockglue.c
+++ b/net/ipv6/ipv6_sockglue.c
@@ -516,6 +516,36 @@
 		retv = 0;
 		break;
 
+	case IPV6_UNICAST_IF:
+	{
+		struct net_device *dev = NULL;
+		int ifindex;
+
+		if (optlen != sizeof(int))
+			goto e_inval;
+
+		ifindex = (__force int)ntohl((__force __be32)val);
+		if (ifindex == 0) {
+			np->ucast_oif = 0;
+			retv = 0;
+			break;
+		}
+
+		dev = dev_get_by_index(net, ifindex);
+		retv = -EADDRNOTAVAIL;
+		if (!dev)
+			break;
+		dev_put(dev);
+
+		retv = -EINVAL;
+		if (sk->sk_bound_dev_if)
+			break;
+
+		np->ucast_oif = ifindex;
+		retv = 0;
+		break;
+	}
+
 	case IPV6_MULTICAST_IF:
 		if (sk->sk_type == SOCK_STREAM)
 			break;
@@ -1160,6 +1190,10 @@
 		val = np->mcast_oif;
 		break;
 
+	case IPV6_UNICAST_IF:
+		val = (__force int)htonl((__u32) np->ucast_oif);
+		break;
+
 	case IPV6_MTU_DISCOVER:
 		val = np->pmtudisc;
 		break;