Merge pull request #917 from apernet/fix-reconnect

fix: incorrect reconnect logic that causes blocking when dialing connections

core/client/reconnect.go

@@ -56,53 +56,56 @@ func (rc *reconnectableClientImpl) reconnect() error {
 	}
 }
 
-func (rc *reconnectableClientImpl) TCP(addr string) (net.Conn, error) {
+// clientDo calls f with the current client.
+// If the client is nil, it will first reconnect.
+// It will also detect if the client is closed, and if so,
+// set it to nil for reconnect next time.
+func (rc *reconnectableClientImpl) clientDo(f func(Client) (interface{}, error)) (interface{}, error) {
 	rc.m.Lock()
-	defer rc.m.Unlock()
 	if rc.closed {
+		rc.m.Unlock()
 		return nil, coreErrs.ClosedError{}
 	}
 	if rc.client == nil {
 		// No active connection, connect first
 		if err := rc.reconnect(); err != nil {
+			rc.m.Unlock()
 			return nil, err
 		}
 	}
-	conn, err := rc.client.TCP(addr)
+	client := rc.client
+	rc.m.Unlock()
+
+	ret, err := f(client)
 	if _, ok := err.(coreErrs.ClosedError); ok {
-		// Connection closed, reconnect
-		if err := rc.reconnect(); err != nil {
-			return nil, err
+		// Connection closed, set client to nil for reconnect next time
+		rc.m.Lock()
+		if rc.client == client {
+			// This check is in case the client is already changed by another goroutine
+			rc.client = nil
 		}
-		return rc.client.TCP(addr)
+		rc.m.Unlock()
+	}
+	return ret, err
+}
+
+func (rc *reconnectableClientImpl) TCP(addr string) (net.Conn, error) {
+	if c, err := rc.clientDo(func(client Client) (interface{}, error) {
+		return client.TCP(addr)
+	}); err != nil {
+		return nil, err
 	} else {
-		// OK or some other temporary error
-		return conn, err
+		return c.(net.Conn), nil
 	}
 }
 
 func (rc *reconnectableClientImpl) UDP() (HyUDPConn, error) {
-	rc.m.Lock()
-	defer rc.m.Unlock()
-	if rc.closed {
-		return nil, coreErrs.ClosedError{}
-	}
-	if rc.client == nil {
-		// No active connection, connect first
-		if err := rc.reconnect(); err != nil {
-			return nil, err
-		}
-	}
-	conn, err := rc.client.UDP()
-	if _, ok := err.(coreErrs.ClosedError); ok {
-		// Connection closed, reconnect
-		if err := rc.reconnect(); err != nil {
-			return nil, err
-		}
-		return rc.client.UDP()
+	if c, err := rc.clientDo(func(client Client) (interface{}, error) {
+		return client.UDP()
+	}); err != nil {
+		return nil, err
 	} else {
-		// OK or some other temporary error
-		return conn, err
+		return c.(HyUDPConn), nil
 	}
 }