tipc: refactor function tipc_sk_filter_connect()

We refactor the function tipc_sk_filter_connect(), both to make it
more readable and as a preparation for the next commit.
Acked-by: Ying Xue <ying.xue@windriver.com>
Signed-off-by: Jon Maloy <jon.maloy@ericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/tipc/socket.c

@@ -1959,91 +1959,76 @@ static void tipc_sk_proto_rcv(struct sock *sk,
 }
 
 /**
- * tipc_filter_connect - Handle incoming message for a connection-based socket
+ * tipc_sk_filter_connect - check incoming message for a connection-based socket
  * @tsk: TIPC socket
- * @skb: pointer to message buffer. Set to NULL if buffer is consumed
- *
- * Returns true if everything ok, false otherwise
+ * @skb: pointer to message buffer.
+ * Returns true if message should be added to receive queue, false otherwise
  */
 static bool tipc_sk_filter_connect(struct tipc_sock *tsk, struct sk_buff *skb)
 {
 	struct sock *sk = &tsk->sk;
 	struct net *net = sock_net(sk);
 	struct tipc_msg *hdr = buf_msg(skb);
-	u32 pport = msg_origport(hdr);
-	u32 pnode = msg_orignode(hdr);
+	bool con_msg = msg_connected(hdr);
+	u32 pport = tsk_peer_port(tsk);
+	u32 pnode = tsk_peer_node(tsk);
+	u32 oport = msg_origport(hdr);
+	u32 onode = msg_orignode(hdr);
+	int err = msg_errcode(hdr);
 
 	if (unlikely(msg_mcast(hdr)))
 		return false;
 
 	switch (sk->sk_state) {
 	case TIPC_CONNECTING:
-		/* Accept only ACK or NACK message */
-		if (unlikely(!msg_connected(hdr))) {
-			if (pport != tsk_peer_port(tsk) ||
-			    pnode != tsk_peer_node(tsk))
-				return false;
-
-			tipc_set_sk_state(sk, TIPC_DISCONNECTING);
-			sk->sk_err = ECONNREFUSED;
-			sk->sk_state_change(sk);
-			return true;
-		}
-
-		if (unlikely(msg_errcode(hdr))) {
-			tipc_set_sk_state(sk, TIPC_DISCONNECTING);
-			sk->sk_err = ECONNREFUSED;
-			sk->sk_state_change(sk);
-			return true;
-		}
-
-		if (unlikely(!msg_isdata(hdr))) {
-			tipc_set_sk_state(sk, TIPC_DISCONNECTING);
-			sk->sk_err = EINVAL;
-			sk->sk_state_change(sk);
-			return true;
+		/* Setup ACK */
+		if (likely(con_msg)) {
+			if (err)
+				break;
+			tipc_sk_finish_conn(tsk, oport, onode);
+			msg_set_importance(&tsk->phdr, msg_importance(hdr));
+			/* ACK+ message with data is added to receive queue */
+			if (msg_data_sz(hdr))
+				return true;
+			/* Empty ACK-, - wake up sleeping connect() and drop */
+			sk->sk_data_ready(sk);
+			msg_set_dest_droppable(hdr, 1);
+			return false;
 		}
+		/* Ignore connectionless message if not from listening socket */
+		if (oport != pport || onode != pnode)
+			return false;
 
-		tipc_sk_finish_conn(tsk, msg_origport(hdr), msg_orignode(hdr));
-		msg_set_importance(&tsk->phdr, msg_importance(hdr));
-
-		/* If 'ACK+' message, add to socket receive queue */
-		if (msg_data_sz(hdr))
-			return true;
-
-		/* If empty 'ACK-' message, wake up sleeping connect() */
-		sk->sk_data_ready(sk);
-
-		/* 'ACK-' message is neither accepted nor rejected: */
-		msg_set_dest_droppable(hdr, 1);
-		return false;
-
+		/* Rejected SYN - abort */
+		break;
 	case TIPC_OPEN:
 	case TIPC_DISCONNECTING:
-		break;
+		return false;
 	case TIPC_LISTEN:
 		/* Accept only SYN message */
-		if (!msg_connected(hdr) && !(msg_errcode(hdr)))
+		if (!con_msg && !err)
 			return true;
-		break;
+		return false;
 	case TIPC_ESTABLISHED:
 		/* Accept only connection-based messages sent by peer */
-		if (unlikely(!tsk_peer_msg(tsk, hdr)))
+		if (likely(con_msg && !err && pport == oport && pnode == onode))
+			return true;
+		if (!tsk_peer_msg(tsk, hdr))
 			return false;
-
-		if (unlikely(msg_errcode(hdr))) {
-			tipc_set_sk_state(sk, TIPC_DISCONNECTING);
-			/* Let timer expire on it's own */
-			tipc_node_remove_conn(net, tsk_peer_node(tsk),
-					      tsk->portid);
-			sk->sk_state_change(sk);
-		}
+		if (!err)
+			return true;
+		tipc_set_sk_state(sk, TIPC_DISCONNECTING);
+		tipc_node_remove_conn(net, pnode, tsk->portid);
+		sk->sk_state_change(sk);
 		return true;
 	default:
 		pr_err("Unknown sk_state %u\n", sk->sk_state);
 	}
-
-	return false;
+	/* Abort connection setup attempt */
+	tipc_set_sk_state(sk, TIPC_DISCONNECTING);
+	sk->sk_err = ECONNREFUSED;
+	sk->sk_state_change(sk);
+	return true;
 }
 
 /**