sctp: Allow bindx_del to accept 0 port

We allow 0 port when adding new addresses.  It only
makes sence to allow 0 port when removing addresses.
When removing the currently bound port will be used
when the port in the address is set to 0.

Signed-off-by: Vlad Yasevich <vladislav.yasevich@hp.com>
Signed-off-by: Wei Yongjun <yjwei@cn.fujitsu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sctp/socket.c

diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index 5c9980a..431b890 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -658,11 +658,15 @@
 			goto err_bindx_rem;
 		}
 
-		if (sa_addr->v4.sin_port != htons(bp->port)) {
+		if (sa_addr->v4.sin_port &&
+		    sa_addr->v4.sin_port != htons(bp->port)) {
 			retval = -EINVAL;
 			goto err_bindx_rem;
 		}
 
+		if (!sa_addr->v4.sin_port)
+			sa_addr->v4.sin_port = htons(bp->port);
+
 		/* FIXME - There is probably a need to check if sk->sk_saddr and
 		 * sk->sk_rcv_addr are currently set to one of the addresses to
 		 * be removed. This is something which needs to be looked into