conduit/cmd/link.go

package cmd

import (
	"fmt"
	"net"
	"net/url"
	"sync"

	"github.com/gorilla/websocket"
	log "github.com/sirupsen/logrus"
	"github.com/spf13/cobra"
	"reichard.io/conduit/types"
)

var serverAddr string

var linkCmd = &cobra.Command{
	Use:   "link <name> <host:port>",
	Short: "Create a tunnel link",
	Args:  cobra.ExactArgs(2),
	Run: func(cmd *cobra.Command, args []string) {
		tunnelName := args[0]
		tunnelTarget := args[1]

		// Create Tunnel
		tunnel, err := NewTunnel(tunnelName, tunnelTarget, serverAddr)
		if err != nil {
			log.Fatal("Failed to start tunnel:", err)
		}

		// Start Tunnel
		log.Infof("Creating TCP tunnel: %s -> %s\n", tunnelName, tunnelTarget)
		if err := tunnel.Start(); err != nil {
			log.Fatal("Failed to start tunnel:", err)
		}
	},
}

func init() {
	linkCmd.Flags().StringVarP(&serverAddr, "server", "s", "http://localhost:8080", "Conduit server address")
}

type TunnelConfig struct {
	// The conduit server address, e.g. https://conduit.example.com
	ServerAddress string `default:"http://localhost:8080"`
}

func NewTunnel(tunnelName, tunnelTarget, serverAddress string) (*Tunnel, error) {
	// Parse Server URL
	serverURL, err := url.Parse(serverAddress)
	if err != nil {
		return nil, err
	}

	// Parse Scheme
	var wsScheme string
	switch serverURL.Scheme {
	case "https":
		wsScheme = "wss"
	case "http":
		wsScheme = "ws"
	default:
		return nil, fmt.Errorf("unsupported scheme: %s", serverURL.Scheme)
	}

	// Connect Server WS
	wsURL := fmt.Sprintf("%s://%s/_conduit/tunnel?tunnelName=%s", wsScheme, serverURL.Host, tunnelName)
	serverConn, _, err := websocket.DefaultDialer.Dial(wsURL, nil)
	if err != nil {
		return nil, fmt.Errorf("failed to connect: %v", err)
	}

	return &Tunnel{
		name:       tunnelName,
		target:     tunnelTarget,
		serverConn: serverConn,
		localConns: make(map[string]net.Conn),
	}, nil

}

type Tunnel struct {
	name   string
	target string

	serverConn *websocket.Conn
	localConns map[string]net.Conn
	mu         sync.RWMutex
}

func (t *Tunnel) Start() error {
	log.Infof("TCP Tunnel active! %s.example.com -> %s\n", t.name, t.target)
	defer t.serverConn.Close()

	// Handle Messages
	for {
		// Read Message
		var msg types.Message
		err := t.serverConn.ReadJSON(&msg)
		if err != nil {
			log.Errorf("Error reading from tunnel: %v", err)
			break
		}

		switch msg.Type {
		case types.MessageTypeData:
			localConn, err := t.getLocalConn(msg.StreamID)
			if err != nil {
				log.Errorf("Failed to get local connection: %v", err)
				continue
			}

			// Write data to local connection
			if _, err := localConn.Write(msg.Data); err != nil {
				log.Errorf("Error writing to local connection: %v", err)
				localConn.Close()
				t.mu.Lock()
				delete(t.localConns, msg.StreamID)
				t.mu.Unlock()
			}

		case types.MessageTypeClose:
			t.mu.Lock()
			if localConn, exists := t.localConns[msg.StreamID]; exists {
				localConn.Close()
				delete(t.localConns, msg.StreamID)
			}
			t.mu.Unlock()
		}
	}

	return nil
}

func (t *Tunnel) getLocalConn(streamID string) (net.Conn, error) {
	// Get Cached Connection
	t.mu.RLock()
	localConn, exists := t.localConns[streamID]
	t.mu.RUnlock()
	if exists {
		return localConn, nil
	}

	// Initiate Connection & Cache
	localConn, err := net.Dial("tcp", t.target)
	if err != nil {
		log.Errorf("Failed to connect to %s: %v", t.target, err)
		return nil, err
	}
	t.mu.Lock()
	t.localConns[streamID] = localConn
	t.mu.Unlock()

	// Start Response Relay & Return Connection
	go t.startResponseRelay(streamID, localConn)
	return localConn, nil
}

func (t *Tunnel) startResponseRelay(streamID string, lConn net.Conn) {
	defer func() {
		t.mu.Lock()
		delete(t.localConns, streamID)
		t.mu.Unlock()
		lConn.Close()
	}()

	buffer := make([]byte, 4096)
	for {
		n, err := lConn.Read(buffer)
		if err != nil {
			break
		}

		response := types.Message{
			Type:     types.MessageTypeData,
			StreamID: streamID,
			Data:     buffer[:n],
		}

		if err := t.serverConn.WriteJSON(response); err != nil {
			break
		}
	}
}