[SCTP] Fix SCTP_INITMSG set socket option so that a parameter with 0

       value will not change its current value.

net/sctp/socket.c

@@ -1683,10 +1683,23 @@ static int sctp_setsockopt_peer_addr_params(struct sock *sk,
  */
 static int sctp_setsockopt_initmsg(struct sock *sk, char *optval, int optlen)
 {
+	struct sctp_initmsg sinit;
+	struct sctp_opt *sp = sctp_sk(sk);
+
 	if (optlen != sizeof(struct sctp_initmsg))
 		return -EINVAL;
-	if (copy_from_user(&sctp_sk(sk)->initmsg, optval, optlen))
+	if (copy_from_user(&sinit, optval, optlen))
 		return -EFAULT;
+
+	if (sinit.sinit_num_ostreams)
+		sp->initmsg.sinit_num_ostreams = sinit.sinit_num_ostreams;	
+	if (sinit.sinit_max_instreams)
+		sp->initmsg.sinit_max_instreams = sinit.sinit_max_instreams;	
+	if (sinit.sinit_max_attempts)
+		sp->initmsg.sinit_max_attempts = sinit.sinit_max_attempts;	
+	if (sinit.sinit_max_init_timeo)
+		sp->initmsg.sinit_max_init_timeo = sinit.sinit_max_init_timeo;	
+
 	return 0;
 }