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>

include/linux/in6.h

@@ -271,6 +271,7 @@ struct in6_flowlabel_req {
 #define IPV6_ORIGDSTADDR        74
 #define IPV6_RECVORIGDSTADDR    IPV6_ORIGDSTADDR
 #define IPV6_TRANSPARENT        75
+#define IPV6_UNICAST_IF         76
 
 /*
  * Multicast Routing:

include/linux/ipv6.h

@@ -324,6 +324,7 @@ struct ipv6_pinfo {
 				__unused_2:6;
 	__s16			mcast_hops:9;
 #endif
+	int			ucast_oif;
 	int			mcast_oif;
 
 	/* pktoption flags */

net/ipv6/icmp.c

@@ -468,6 +468,8 @@ void icmpv6_send(struct sk_buff *skb, u8 type, u8 code, __u32 info)
 
 	if (!fl6.flowi6_oif && ipv6_addr_is_multicast(&fl6.daddr))
 		fl6.flowi6_oif = np->mcast_oif;
+	else if (!fl6.flowi6_oif)
+		fl6.flowi6_oif = np->ucast_oif;
 
 	dst = icmpv6_route_lookup(net, skb, sk, &fl6);
 	if (IS_ERR(dst))
@@ -553,6 +555,8 @@ static void icmpv6_echo_reply(struct sk_buff *skb)
 
 	if (!fl6.flowi6_oif && ipv6_addr_is_multicast(&fl6.daddr))
 		fl6.flowi6_oif = np->mcast_oif;
+	else if (!fl6.flowi6_oif)
+		fl6.flowi6_oif = np->ucast_oif;
 
 	err = ip6_dst_lookup(sk, &dst, &fl6);
 	if (err)

net/ipv6/ipv6_sockglue.c

@@ -516,6 +516,36 @@ static int do_ipv6_setsockopt(struct sock *sk, int level, int optname,
 		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 @@ static int do_ipv6_getsockopt(struct sock *sk, int level, int optname,
 		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;

net/ipv6/raw.c

@@ -856,6 +856,8 @@ static int rawv6_sendmsg(struct kiocb *iocb, struct sock *sk,
 
 	if (!fl6.flowi6_oif && ipv6_addr_is_multicast(&fl6.daddr))
 		fl6.flowi6_oif = np->mcast_oif;
+	else if (!fl6.flowi6_oif)
+		fl6.flowi6_oif = np->ucast_oif;
 	security_sk_classify_flow(sk, flowi6_to_flowi(&fl6));
 
 	dst = ip6_dst_lookup_flow(sk, &fl6, final_p, true);

net/ipv6/udp.c

@@ -1130,7 +1130,8 @@ int udpv6_sendmsg(struct kiocb *iocb, struct sock *sk,
 	if (!fl6.flowi6_oif && ipv6_addr_is_multicast(&fl6.daddr)) {
 		fl6.flowi6_oif = np->mcast_oif;
 		connected = 0;
-	}
+	} else if (!fl6.flowi6_oif)
+		fl6.flowi6_oif = np->ucast_oif;
 
 	security_sk_classify_flow(sk, flowi6_to_flowi(&fl6));