sctp: check ipv6 addr with sk_bound_dev if set

When binding to an ipv6 address, it calls ipv6_chk_addr() to check if
this address is on any dev. If a socket binds to a l3mdev but no dev
is passed to do this check, all l3mdev and slaves will be skipped and
the check will fail.

This patch is to pass the bound_dev to make sure the devices under the
same l3mdev can be returned in ipv6_chk_addr(). When the bound_dev is
not a l3mdev or l3slave, l3mdev_master_dev_rcu() will return NULL in
__ipv6_chk_addr_and_flags(), it will keep compitable with before when
NULL dev was passed.
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sctp/ipv6.c

@@ -680,9 +680,11 @@ static int sctp_v6_is_any(const union sctp_addr *addr)
 /* Should this be available for binding?   */
 static int sctp_v6_available(union sctp_addr *addr, struct sctp_sock *sp)
 {
-	int type;
-	struct net *net = sock_net(&sp->inet.sk);
 	const struct in6_addr *in6 = (const struct in6_addr *)&addr->v6.sin6_addr;
+	struct sock *sk = &sp->inet.sk;
+	struct net *net = sock_net(sk);
+	struct net_device *dev = NULL;
+	int type;
 
 	type = ipv6_addr_type(in6);
 	if (IPV6_ADDR_ANY == type)
@@ -696,8 +698,14 @@ static int sctp_v6_available(union sctp_addr *addr, struct sctp_sock *sp)
 	if (!(type & IPV6_ADDR_UNICAST))
 		return 0;
 
+	if (sk->sk_bound_dev_if) {
+		dev = dev_get_by_index_rcu(net, sk->sk_bound_dev_if);
+		if (!dev)
+			return 0;
+	}
+
 	return ipv6_can_nonlocal_bind(net, &sp->inet) ||
-	       ipv6_chk_addr(net, in6, NULL, 0);
+	       ipv6_chk_addr(net, in6, dev, 0);
 }
 
 /* This function checks if the address is a valid address to be used for