feat: add headless mode support for SSH -N connections

- use s.lifecycle.GetConnection().Wait() to block until SSH connection closes
- Prevent premature session closure in headless mode

In headless mode (ssh -N), there's no channel interaction to block on,
so the session would immediately return and close. Now blocking on
conn.Wait() keeps the session alive until the client disconnects.

server/server.go

@@ -90,7 +90,6 @@ func (s *Server) handleConnection(conn net.Conn) {
 		user = u
 		cancel()
 	}
-
 	log.Println("SSH connection established:", sshConn.User())
 	sshSession := session.New(sshConn, forwardingReqs, chans, s.sessionRegistry, user)
 	err = sshSession.Start()

session/handler.go

@@ -165,7 +165,6 @@ func (s *SSHSession) HandleTCPIPForward(req *ssh.Request) {
 func (s *SSHSession) HandleHTTPForward(req *ssh.Request, portToBind uint16) {
 	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)
 		err := req.Reply(false, nil)
@@ -203,7 +202,6 @@ func (s *SSHSession) HandleHTTPForward(req *ssh.Request, portToBind uint16) {
 	s.forwarder.SetForwardedPort(portToBind)
 	s.slugManager.Set(slug)
 	s.lifecycle.SetStatus(types.RUNNING)
-	s.interaction.Start()
 }
 
 func (s *SSHSession) HandleTCPForward(req *ssh.Request, addr string, portToBind uint16) {
@@ -282,7 +280,6 @@ func (s *SSHSession) HandleTCPForward(req *ssh.Request, addr string, portToBind
 	s.slugManager.Set(key.Id)
 	s.lifecycle.SetStatus(types.RUNNING)
 	go s.forwarder.AcceptTCPConnections()
-	s.interaction.Start()
 }
 
 func readSSHString(reader *bytes.Reader) (string, error) {

session/interaction/interaction.go

@@ -37,6 +37,9 @@ type Controller interface {
 	SetWH(w, h int)
 	Redraw()
 	SetSessionRegistry(registry SessionRegistry)
+	SetMode(m types.Mode)
+	GetMode() types.Mode
+	Send(message string) error
 }
 
 type Forwarder interface {
@@ -54,8 +57,24 @@ type Interaction struct {
 	program         *tea.Program
 	ctx             context.Context
 	cancel          context.CancelFunc
+	mode            types.Mode
 }
 
+func (i *Interaction) SetMode(m types.Mode) {
+	i.mode = m
+}
+
+func (i *Interaction) GetMode() types.Mode {
+	return i.mode
+}
+
+func (i *Interaction) Send(message string) error {
+	if i.channel != nil {
+		_, err := i.channel.Write([]byte(message))
+		return err
+	}
+	return nil
+}
 func (i *Interaction) SetWH(w, h int) {
 	if i.program != nil {
 		i.program.Send(tea.WindowSizeMsg{
@@ -749,6 +768,9 @@ func (m *model) View() string {
 }
 
 func (i *Interaction) Start() {
+	if i.mode == types.HEADLESS {
+		return
+	}
 	lipgloss.SetColorProfile(termenv.TrueColor)
 
 	domain := config.Getenv("DOMAIN", "localhost")

session/session.go

@@ -9,6 +9,7 @@ import (
 	"tunnel_pls/session/interaction"
 	"tunnel_pls/session/lifecycle"
 	"tunnel_pls/session/slug"
+	"tunnel_pls/types"
 
 	"golang.org/x/crypto/ssh"
 )
@@ -87,31 +88,56 @@ func (s *SSHSession) Detail() Detail {
 }
 
 func (s *SSHSession) Start() error {
-	channel := <-s.sshReqChannel
-	ch, reqs, err := channel.Accept()
-	if err != nil {
-		log.Printf("failed to accept channel: %v", err)
-		return err
+	var channel ssh.NewChannel
+	var ok bool
+	select {
+	case channel, ok = <-s.sshReqChannel:
+		if !ok {
+			log.Println("Forwarding request channel closed")
+			return nil
+		}
+		ch, reqs, err := channel.Accept()
+		if err != nil {
+			log.Printf("failed to accept channel: %v", err)
+			return err
+		}
+		go s.HandleGlobalRequest(reqs)
+
+		s.lifecycle.SetChannel(ch)
+		s.interaction.SetChannel(ch)
+		s.interaction.SetMode(types.INTERACTIVE)
+	case <-time.After(500 * time.Millisecond):
+		s.interaction.SetMode(types.HEADLESS)
 	}
-	go s.HandleGlobalRequest(reqs)
 
 	tcpipReq := s.waitForTCPIPForward()
 	if tcpipReq == nil {
-		_, err := ch.Write([]byte(fmt.Sprintf("Port forwarding request not received. Ensure you ran the correct command with -R flag. Example: ssh %s -p %s -R 80:localhost:3000", config.Getenv("DOMAIN", "localhost"), config.Getenv("PORT", "2200"))))
+		err := s.interaction.Send(fmt.Sprintf("Port forwarding request not received. Ensure you ran the correct command with -R flag. Example: ssh %s -p %s -R 80:localhost:3000", config.Getenv("DOMAIN", "localhost"), config.Getenv("PORT", "2200")))
 		if err != nil {
 			return err
 		}
-		if err := s.lifecycle.Close(); err != nil {
+		if err = s.lifecycle.Close(); err != nil {
 			log.Printf("failed to close session: %v", err)
 		}
 		return fmt.Errorf("no forwarding Request")
 	}
 
-	s.lifecycle.SetChannel(ch)
-	s.interaction.SetChannel(ch)
+	if (s.interaction.GetMode() == types.HEADLESS && config.Getenv("MODE", "standalone") == "standalone") || s.lifecycle.GetUser() == "UNAUTHORIZED" {
+		if err := tcpipReq.Reply(false, nil); err != nil {
+			log.Printf("cannot reply to tcpip req: %s\n", err)
+			return err
+		}
+		if err := s.lifecycle.Close(); err != nil {
+			log.Printf("failed to close session: %v", err)
+			return err
+		}
+		return nil
+	}
 
 	s.HandleTCPIPForward(tcpipReq)
+	s.interaction.Start()
 
+	s.lifecycle.GetConnection().Wait()
 	if err := s.lifecycle.Close(); err != nil {
 		log.Printf("failed to close session: %v", err)
 		return err

types/types.go

@@ -8,6 +8,13 @@ const (
 	SETUP        Status = "SETUP"
 )
 
+type Mode string
+
+const (
+	INTERACTIVE Mode = "INTERACTIVE"
+	HEADLESS    Mode = "HEADLESS"
+)
+
 type TunnelType string
 
 const (