LFG

internal/nat/nat.go

@@ -0,0 +1,231 @@
+package nat
+
+import (
+	"context"
+	"fmt"
+	"net"
+	"sync"
+	"time"
+
+	"github.com/iwasforcedtobehere/goRZ/internal/config"
+	"github.com/iwasforcedtobehere/goRZ/internal/logger"
+	"github.com/pion/stun"
+	"github.com/pion/turn/v2"
+)
+
+// NATTraversal handles NAT traversal for the proxy server
+type NATTraversal struct {
+	config      *config.Config
+	logger      *logger.Logger
+	conn        net.PacketConn
+	externalIP  net.IP
+	externalPort int
+	mu          sync.RWMutex
+	running     bool
+}
+
+// NewNATTraversal creates a new NAT traversal instance
+func NewNATTraversal(cfg *config.Config, logger *logger.Logger) *NATTraversal {
+	return &NATTraversal{
+		config: cfg,
+		logger: logger,
+	}
+}
+
+// Start starts the NAT traversal process
+func (n *NATTraversal) Start() error {
+	if !n.config.NAT.Enabled {
+		n.logger.Info("NAT traversal is disabled")
+		return nil
+	}
+
+	n.mu.Lock()
+	defer n.mu.Unlock()
+
+	if n.running {
+		return fmt.Errorf("NAT traversal is already running")
+	}
+
+	// Create a UDP listener
+	conn, err := net.ListenPacket("udp4", "0.0.0.0:0")
+	if err != nil {
+		return fmt.Errorf("failed to create UDP listener: %w", err)
+	}
+	n.conn = conn
+
+	// Get external IP and port using STUN
+	if err := n.discoverExternalAddress(); err != nil {
+		conn.Close()
+		return fmt.Errorf("failed to discover external address: %w", err)
+	}
+
+	// Start TURN client if configured
+	if n.config.NAT.TURNServer != "" {
+		if err := n.startTURNClient(); err != nil {
+			conn.Close()
+			return fmt.Errorf("failed to start TURN client: %w", err)
+		}
+	}
+
+	n.running = true
+	n.logger.Info("NAT traversal started", 
+		logger.String("external_ip", n.externalIP.String()),
+		logger.Int("external_port", n.externalPort))
+
+	return nil
+}
+
+// Stop stops the NAT traversal process
+func (n *NATTraversal) Stop() {
+	n.mu.Lock()
+	defer n.mu.Unlock()
+
+	if !n.running {
+		return
+	}
+
+	if n.conn != nil {
+		n.conn.Close()
+		n.conn = nil
+	}
+
+	n.running = false
+	n.logger.Info("NAT traversal stopped")
+}
+
+// discoverExternalAddress discovers the external IP and port using STUN
+func (n *NATTraversal) discoverExternalAddress() error {
+	// Parse STUN server URL
+	stunURL, err := stun.ParseURI(n.config.NAT.STUNServer)
+	if err != nil {
+		return fmt.Errorf("failed to parse STUN server URL: %w", err)
+	}
+
+	// Create STUN client
+	client, err := stun.NewClient("udp4", n.conn)
+	if err != nil {
+		return fmt.Errorf("failed to create STUN client: %w", err)
+	}
+	defer client.Close()
+
+	// Send binding request
+	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+	defer cancel()
+
+	mappedAddr, err := client.Request(ctx, stunURL, stun.BindingRequest)
+	if err != nil {
+		return fmt.Errorf("STUN binding request failed: %w", err)
+	}
+
+	n.externalIP = mappedAddr.IP
+	n.externalPort = mappedAddr.Port
+
+	return nil
+}
+
+// startTURNClient starts a TURN client for relay connections
+func (n *NATTraversal) startTURNClient() error {
+	// Parse TURN server URL
+	turnURL, err := turn.ParseURI(n.config.NAT.TURNServer)
+	if err != nil {
+		return fmt.Errorf("failed to parse TURN server URL: %w", err)
+	}
+
+	// Create TURN client config
+	cfg := &turn.ClientConfig{
+		STUNServerAddr: n.config.NAT.STUNServer,
+		TURNServerAddr: n.config.NAT.TURNServer,
+		Username:       n.config.NAT.TURNUsername,
+		Credential:     n.config.NAT.TURNPassword,
+		LoggerFactory:  nil, // We'll use our own logger
+	}
+
+	// Create TURN client
+	client, err := turn.NewClient(cfg)
+	if err != nil {
+		return fmt.Errorf("failed to create TURN client: %w", err)
+	}
+	defer client.Close()
+
+	// Listen on provided conn
+	n.logger.Info("TURN client started", logger.String("server", n.config.NAT.TURNServer))
+
+	return nil
+}
+
+// GetExternalAddress returns the external IP and port
+func (n *NATTraversal) GetExternalAddress() (net.IP, int) {
+	n.mu.RLock()
+	defer n.mu.RUnlock()
+
+	return n.externalIP, n.externalPort
+}
+
+// IsRunning returns whether NAT traversal is running
+func (n *NATTraversal) IsRunning() bool {
+	n.mu.RLock()
+	defer n.mu.RUnlock()
+
+	return n.running
+}
+
+// CreateHolePunch attempts to create a hole in the NAT for direct peer-to-peer connections
+func (n *NATTraversal) CreateHolePunch(peerAddr string) (net.Conn, error) {
+	if !n.running {
+		return nil, fmt.Errorf("NAT traversal is not running")
+	}
+
+	// Parse peer address
+	udpAddr, err := net.ResolveUDPAddr("udp4", peerAddr)
+	if err != nil {
+		return nil, fmt.Errorf("failed to resolve peer address: %w", err)
+	}
+
+	// Create UDP connection
+	conn, err := net.DialUDP("udp4", nil, udpAddr)
+	if err != nil {
+		return nil, fmt.Errorf("failed to create UDP connection: %w", err)
+	}
+
+	// Send a small packet to punch a hole in the NAT
+	_, err = conn.Write([]byte("punch"))
+	if err != nil {
+		conn.Close()
+		return nil, fmt.Errorf("failed to punch hole: %w", err)
+	}
+
+	n.logger.Debug("Hole punch attempted", logger.String("peer", peerAddr))
+
+	return conn, nil
+}
+
+// GetNATType attempts to determine the type of NAT
+func (n *NATTraversal) GetNATType() (string, error) {
+	if !n.running {
+		return "", fmt.Errorf("NAT traversal is not running")
+	}
+
+	// This is a simplified NAT type detection
+	// In a real implementation, you would use more sophisticated methods
+	// like the one described in RFC 3489 and RFC 5780
+
+	// For now, we'll return a generic response
+	return "Unknown", nil
+}
+
+// CreateRelayConnection creates a relay connection through TURN
+func (n *NATTraversal) CreateRelayConnection(peerAddr string) (net.Conn, error) {
+	if !n.running {
+		return nil, fmt.Errorf("NAT traversal is not running")
+	}
+
+	if n.config.NAT.TURNServer == "" {
+		return nil, fmt.Errorf("TURN server not configured")
+	}
+
+	// This is a placeholder for TURN relay connection creation
+	// In a real implementation, you would use the TURN client to allocate
+	// a relay and create a connection to the peer
+
+	return nil, fmt.Errorf("not implemented")
+}