refactor: consolidate error handling with fail() function in session handlers

- Replace repetitive error handling code with fail() function in HandleGlobalRequest
- Standardize error response pattern across all handler methods
- Improve code maintainability and reduce duplication

internal/port/port.go

@@ -74,7 +74,6 @@ func (pm *manager) GetUnassignedPort() (uint16, bool) {
 
 	for _, port := range pm.sortedPorts {
 		if !pm.ports[port] {
-			pm.ports[port] = true
 			return port, true
 		}
 	}

session/handler.go

@@ -59,142 +59,79 @@ func (s *SSHSession) HandleGlobalRequest(GlobalRequest <-chan *ssh.Request) {
 func (s *SSHSession) HandleTCPIPForward(req *ssh.Request) {
 	log.Println("Port forwarding request detected")
 
+	fail := func(msg string) {
+		log.Println(msg)
+		if err := req.Reply(false, nil); err != nil {
+			log.Println("Failed to reply to request:", err)
+			return
+		}
+		if err := s.lifecycle.Close(); err != nil {
+			log.Printf("failed to close session: %v", err)
+		}
+	}
+
 	reader := bytes.NewReader(req.Payload)
 
 	addr, err := readSSHString(reader)
 	if err != nil {
-		log.Println("Failed to read address from payload:", err)
+		fail(fmt.Sprintf("Failed to read address from payload: %v", err))
-		err := req.Reply(false, nil)
-		if err != nil {
-			log.Println("Failed to reply to request:", err)
-			return
-		}
-		err = s.lifecycle.Close()
-		if err != nil {
-			log.Printf("failed to close session: %v", err)
-		}
 		return
 	}
 
 	var rawPortToBind uint32
-	if err := binary.Read(reader, binary.BigEndian, &rawPortToBind); err != nil {
+	if err = binary.Read(reader, binary.BigEndian, &rawPortToBind); err != nil {
-		log.Println("Failed to read port from payload:", err)
+		fail(fmt.Sprintf("Failed to read port from payload: %v", err))
-		err := req.Reply(false, nil)
-		if err != nil {
-			log.Println("Failed to reply to request:", err)
-			return
-		}
-		err = s.lifecycle.Close()
-		if err != nil {
-			log.Printf("failed to close session: %v", err)
-		}
 		return
 	}
 
 	if rawPortToBind > 65535 {
-		log.Printf("Port %d is larger than allowed port of 65535", rawPortToBind)
+		fail(fmt.Sprintf("Port %d is larger than allowed port of 65535", rawPortToBind))
-		err := req.Reply(false, nil)
-		if err != nil {
-			log.Println("Failed to reply to request:", err)
-			return
-		}
-		err = s.lifecycle.Close()
-		if err != nil {
-			log.Printf("failed to close session: %v", err)
-		}
 		return
 	}
 
 	portToBind := uint16(rawPortToBind)
 	if isBlockedPort(portToBind) {
-		log.Printf("Port %d is blocked or restricted", portToBind)
+		fail(fmt.Sprintf("Port %d is blocked or restricted", portToBind))
-		err := req.Reply(false, nil)
-		if err != nil {
-			log.Println("Failed to reply to request:", err)
-			return
-		}
-		err = s.lifecycle.Close()
-		if err != nil {
-			log.Printf("failed to close session: %v", err)
-		}
 		return
 	}
 
-	if portToBind == 80 || portToBind == 443 {
+	switch portToBind {
+	case 80, 443:
 		s.HandleHTTPForward(req, portToBind)
-		return
+	default:
+		s.HandleTCPForward(req, addr, portToBind)
 	}
-	if portToBind == 0 {
-		unassign, success := portUtil.Default.GetUnassignedPort()
-		portToBind = unassign
-		if !success {
-			log.Println("No available port")
-			err := req.Reply(false, nil)
-			if err != nil {
-				log.Println("Failed to reply to request:", err)
-				return
-			}
-			err = s.lifecycle.Close()
-			if err != nil {
-				log.Printf("failed to close session: %v", err)
-			}
-			return
-		}
-	} else if isUse, isExist := portUtil.Default.GetPortStatus(portToBind); isExist && isUse {
-		log.Printf("Port %d is already in use or restricted", portToBind)
-		err := req.Reply(false, nil)
-		if err != nil {
-			log.Println("Failed to reply to request:", err)
-			return
-		}
-		err = s.lifecycle.Close()
-		if err != nil {
-			log.Printf("failed to close session: %v", err)
-		}
-		return
-	}
-	err = portUtil.Default.SetPortStatus(portToBind, true)
-	if err != nil {
-		log.Println("Failed to set port status:", err)
-		return
-	}
-
-	s.HandleTCPForward(req, addr, portToBind)
 }
 
 func (s *SSHSession) HandleHTTPForward(req *ssh.Request, portToBind uint16) {
+	fail := func(msg string, key *types.SessionKey) {
+		log.Println(msg)
+		if key != nil {
+			s.registry.Remove(*key)
+		}
+		if err := req.Reply(false, nil); err != nil {
+			log.Println("Failed to reply to request:", err)
+		}
+	}
+
 	slug := random.GenerateRandomString(20)
 	key := types.SessionKey{Id: slug, Type: types.HTTP}
 	if !s.registry.Register(key, s) {
-		log.Printf("Failed to register client with slug: %s", slug)
+		fail(fmt.Sprintf("Failed to register client with slug: %s", slug), nil)
-		err := req.Reply(false, nil)
-		if err != nil {
-			log.Println("Failed to reply to request:", err)
-		}
 		return
 	}
 
 	buf := new(bytes.Buffer)
 	err := binary.Write(buf, binary.BigEndian, uint32(portToBind))
 	if err != nil {
-		log.Println("Failed to write port to buffer:", err)
+		fail(fmt.Sprintf("Failed to write port to buffer: %v", err), &key)
-		s.registry.Remove(key)
-		err = req.Reply(false, nil)
-		if err != nil {
-			log.Println("Failed to reply to request:", err)
-		}
 		return
 	}
 	log.Printf("HTTP forwarding approved on port: %d", portToBind)
 
 	err = req.Reply(true, buf.Bytes())
 	if err != nil {
-		log.Println("Failed to reply to request:", err)
+		fail(fmt.Sprintf("Failed to reply to request: %v", err), &key)
-		s.registry.Remove(key)
-		err = req.Reply(false, nil)
-		if err != nil {
-			log.Println("Failed to reply to request:", err)
-		}
 		return
 	}
 
@@ -205,72 +142,82 @@ func (s *SSHSession) HandleHTTPForward(req *ssh.Request, portToBind uint16) {
 }
 
 func (s *SSHSession) HandleTCPForward(req *ssh.Request, addr string, portToBind uint16) {
-	log.Printf("Requested forwarding on %s:%d", addr, portToBind)
+	fail := func(msg string) {
-	listener, err := net.Listen("tcp", fmt.Sprintf("0.0.0.0:%d", portToBind))
+		log.Println(msg)
-	if err != nil {
+		if err := req.Reply(false, nil); err != nil {
-		log.Printf("Port %d is already in use or restricted", portToBind)
-		if setErr := portUtil.Default.SetPortStatus(portToBind, false); setErr != nil {
-			log.Printf("Failed to reset port status: %v", setErr)
-		}
-		err = req.Reply(false, nil)
-		if err != nil {
 			log.Println("Failed to reply to request:", err)
 			return
 		}
-		err = s.lifecycle.Close()
+		if err := s.lifecycle.Close(); err != nil {
-		if err != nil {
 			log.Printf("failed to close session: %v", err)
 		}
+	}
+
+	cleanup := func(msg string, port uint16, listener net.Listener, key *types.SessionKey) {
+		log.Println(msg)
+		if key != nil {
+			s.registry.Remove(*key)
+		}
+		if port != 0 {
+			if setErr := portUtil.Default.SetPortStatus(port, false); setErr != nil {
+				log.Printf("Failed to reset port status: %v", setErr)
+			}
+		}
+		if listener != nil {
+			if closeErr := listener.Close(); closeErr != nil {
+				log.Printf("Failed to close listener: %v", closeErr)
+			}
+		}
+		if err := req.Reply(false, nil); err != nil {
+			log.Println("Failed to reply to request:", err)
+		}
+		_ = s.lifecycle.Close()
+	}
+
+	if portToBind == 0 {
+		unassigned, ok := portUtil.Default.GetUnassignedPort()
+		if !ok {
+			fail("No available port")
+			return
+		}
+		portToBind = unassigned
+	}
+
+	if isUsed, exists := portUtil.Default.GetPortStatus(portToBind); exists && isUsed {
+		fail(fmt.Sprintf("Port %d is already in use or restricted", portToBind))
+		return
+	}
+
+	if err := portUtil.Default.SetPortStatus(portToBind, true); err != nil {
+		fail(fmt.Sprintf("Failed to set port status: %v", err))
+		return
+	}
+
+	log.Printf("Requested forwarding on %s:%d", addr, portToBind)
+	listener, err := net.Listen("tcp", fmt.Sprintf("0.0.0.0:%d", portToBind))
+	if err != nil {
+		cleanup(fmt.Sprintf("Port %d is already in use or restricted", portToBind), portToBind, nil, nil)
 		return
 	}
 
 	key := types.SessionKey{Id: fmt.Sprintf("%d", portToBind), Type: types.TCP}
 
 	if !s.registry.Register(key, s) {
-		log.Printf("Failed to register TCP client with id: %s", key.Id)
+		cleanup(fmt.Sprintf("Failed to register TCP client with id: %s", key.Id), portToBind, listener, nil)
-		if setErr := portUtil.Default.SetPortStatus(portToBind, false); setErr != nil {
-			log.Printf("Failed to reset port status: %v", setErr)
-		}
-		if closeErr := listener.Close(); closeErr != nil {
-			log.Printf("Failed to close listener: %s", closeErr)
-		}
-		err = req.Reply(false, nil)
-		if err != nil {
-			log.Println("Failed to reply to request:", err)
-		}
-		_ = s.lifecycle.Close()
 		return
 	}
 
 	buf := new(bytes.Buffer)
 	err = binary.Write(buf, binary.BigEndian, uint32(portToBind))
 	if err != nil {
-		log.Println("Failed to write port to buffer:", err)
+		cleanup(fmt.Sprintf("Failed to write port to buffer: %v", err), portToBind, listener, &key)
-		s.registry.Remove(key)
-		if setErr := portUtil.Default.SetPortStatus(portToBind, false); setErr != nil {
-			log.Printf("Failed to reset port status: %v", setErr)
-		}
-		err = listener.Close()
-		if err != nil {
-			log.Printf("Failed to close listener: %s", err)
-			return
-		}
 		return
 	}
 
 	log.Printf("TCP forwarding approved on port: %d", portToBind)
 	err = req.Reply(true, buf.Bytes())
 	if err != nil {
-		log.Println("Failed to reply to request:", err)
+		cleanup(fmt.Sprintf("Failed to reply to request: %v", err), portToBind, listener, &key)
-		s.registry.Remove(key)
-		if setErr := portUtil.Default.SetPortStatus(portToBind, false); setErr != nil {
-			log.Printf("Failed to reset port status: %v", setErr)
-		}
-		err = listener.Close()
-		if err != nil {
-			log.Printf("Failed to close listener: %s", err)
-			return
-		}
 		return
 	}