fix(proxy): prevent deleting wrong tunnel in defer cleanup

Add pointer check before delete to handle race where UpdateLocalSNIs
removes our tunnel and a new one is created for the same hostname.

proxy/proxy.go

@@ -18,6 +18,7 @@ import (
 
 	"github.com/fosrl/gerbil/logger"
 	"github.com/patrickmn/go-cache"
+	"golang.org/x/sync/errgroup"
 )
 
 // RouteRecord represents a routing configuration
@@ -72,7 +73,9 @@ type SNIProxy struct {
 }
 
 type activeTunnel struct {
-	conns []net.Conn
+	ctx    context.Context
+	cancel context.CancelFunc
+	count  int // protected by activeTunnelsLock
 }
 
 // readOnlyConn is a wrapper for io.Reader that implements net.Conn
@@ -588,37 +591,32 @@ func (p *SNIProxy) handleConnection(clientConn net.Conn) {
 		}
 	}
 
-	// Track this tunnel by SNI
+	// Track this tunnel by SNI using context for cancellation
 	p.activeTunnelsLock.Lock()
 	tunnel, ok := p.activeTunnels[hostname]
 	if !ok {
-		tunnel = &activeTunnel{}
+		ctx, cancel := context.WithCancel(p.ctx)
+		tunnel = &activeTunnel{ctx: ctx, cancel: cancel}
 		p.activeTunnels[hostname] = tunnel
 	}
-	tunnel.conns = append(tunnel.conns, actualClientConn)
+	tunnel.count++
+	tunnelCtx := tunnel.ctx
 	p.activeTunnelsLock.Unlock()
 
 	defer func() {
-		// Remove this conn from active tunnels
 		p.activeTunnelsLock.Lock()
-		if tunnel, ok := p.activeTunnels[hostname]; ok {
-			newConns := make([]net.Conn, 0, len(tunnel.conns))
-			for _, c := range tunnel.conns {
-				if c != actualClientConn {
-					newConns = append(newConns, c)
-				}
-			}
-			if len(newConns) == 0 {
+		tunnel.count--
+		if tunnel.count == 0 {
+			tunnel.cancel()
+			if p.activeTunnels[hostname] == tunnel {
 				delete(p.activeTunnels, hostname)
-			} else {
-				tunnel.conns = newConns
 			}
 		}
 		p.activeTunnelsLock.Unlock()
 	}()
 
-	// Start bidirectional data transfer
-	p.pipe(actualClientConn, targetConn, clientReader)
+	// Start bidirectional data transfer with tunnel context
+	p.pipe(tunnelCtx, actualClientConn, targetConn, clientReader)
 }
 
 // getRoute retrieves routing information for a hostname
@@ -754,47 +752,36 @@ func (p *SNIProxy) selectStickyEndpoint(clientAddr string, endpoints []string) s
 }
 
 // pipe handles bidirectional data transfer between connections
-func (p *SNIProxy) pipe(clientConn, targetConn net.Conn, clientReader io.Reader) {
-	var wg sync.WaitGroup
-	wg.Add(2)
+func (p *SNIProxy) pipe(ctx context.Context, clientConn, targetConn net.Conn, clientReader io.Reader) {
+	g, gCtx := errgroup.WithContext(ctx)
 
-	// closeOnce ensures we only close connections once
-	var closeOnce sync.Once
-	closeConns := func() {
-		closeOnce.Do(func() {
-			// Close both connections to unblock any pending reads
-			clientConn.Close()
-			targetConn.Close()
-		})
-	}
+	// Close connections when context cancels to unblock io.Copy operations
+	context.AfterFunc(gCtx, func() {
+		clientConn.Close()
+		targetConn.Close()
+	})
 
-	// Copy data from client to target (using the buffered reader)
-	go func() {
-		defer wg.Done()
-		defer closeConns()
-
-		// Use a large buffer for better performance
+	// Copy data from client to target
+	g.Go(func() error {
 		buf := make([]byte, 32*1024)
 		_, err := io.CopyBuffer(targetConn, clientReader, buf)
 		if err != nil && err != io.EOF {
 			logger.Debug("Copy client->target error: %v", err)
 		}
-	}()
+		return err
+	})
 
 	// Copy data from target to client
-	go func() {
-		defer wg.Done()
-		defer closeConns()
-
-		// Use a large buffer for better performance
+	g.Go(func() error {
 		buf := make([]byte, 32*1024)
 		_, err := io.CopyBuffer(clientConn, targetConn, buf)
 		if err != nil && err != io.EOF {
 			logger.Debug("Copy target->client error: %v", err)
 		}
-	}()
+		return err
+	})
 
-	wg.Wait()
+	g.Wait()
 }
 
 // GetCacheStats returns cache statistics
@@ -830,16 +817,14 @@ func (p *SNIProxy) UpdateLocalSNIs(fullDomains []string) {
 
 	logger.Debug("Updated local SNIs, added %d, removed %d", len(newSNIs), len(removed))
 
-	// Terminate tunnels for removed SNIs
+	// Terminate tunnels for removed SNIs via context cancellation
 	if len(removed) > 0 {
 		p.activeTunnelsLock.Lock()
 		for _, sni := range removed {
-			if tunnels, ok := p.activeTunnels[sni]; ok {
-				for _, conn := range tunnels.conns {
-					conn.Close()
-				}
+			if tunnel, ok := p.activeTunnels[sni]; ok {
+				tunnel.cancel()
 				delete(p.activeTunnels, sni)
-				logger.Debug("Closed tunnels for SNI target change: %s", sni)
+				logger.Debug("Cancelled tunnel context for SNI target change: %s", sni)
 			}
 		}
 		p.activeTunnelsLock.Unlock()

relay/relay.go

@@ -9,7 +9,6 @@ import (
 	"io"
 	"net"
 	"net/http"
-	"runtime"
 	"sync"
 	"time"
 
@@ -119,13 +118,6 @@ type Packet struct {
 	n          int
 }
 
-// holePunchRateLimitEntry tracks hole punch message counts within a sliding 1-second window.
-type holePunchRateLimitEntry struct {
-	mu          sync.Mutex
-	count       int
-	windowStart time.Time
-}
-
 // WireGuard message types
 const (
 	WireGuardMessageTypeHandshakeInitiation = 1
@@ -161,11 +153,6 @@ type UDPProxyServer struct {
 	// Communication pattern tracking for rebuilding sessions
 	// Key format: "clientIP:clientPort-destIP:destPort"
 	commPatterns sync.Map
-	// Rate limiter for encrypted hole punch messages, keyed by "ip:port"
-	holePunchRateLimiter sync.Map
-	// Cache for resolved UDP addresses to avoid per-packet DNS lookups
-	// Key: "ip:port" string, Value: *net.UDPAddr
-	addrCache sync.Map
 	// ReachableAt is the URL where this server can be reached
 	ReachableAt string
 }
@@ -177,7 +164,7 @@ func NewUDPProxyServer(parentCtx context.Context, addr, serverURL string, privat
 		addr:        addr,
 		serverURL:   serverURL,
 		privateKey:  privateKey,
-		packetChan:  make(chan Packet, 50000), // Increased from 1000 to handle high throughput
+		packetChan:  make(chan Packet, 1000),
 		ReachableAt: reachableAt,
 		ctx:         ctx,
 		cancel:      cancel,
@@ -202,13 +189,8 @@ func (s *UDPProxyServer) Start() error {
 	s.conn = conn
 	logger.Info("UDP server listening on %s", s.addr)
 
-	// Start worker goroutines based on CPU cores for better parallelism
-	// At high throughput (160+ Mbps), we need many workers to avoid bottlenecks
-	workerCount := runtime.NumCPU() * 10
-	if workerCount < 20 {
-		workerCount = 20 // Minimum 20 workers
-	}
-	logger.Info("Starting %d packet workers (CPUs: %d)", workerCount, runtime.NumCPU())
+	// Start a fixed number of worker goroutines.
+	workerCount := 10 // TODO: Make this configurable or pick it better!
 	for i := 0; i < workerCount; i++ {
 		go s.packetWorker()
 	}
@@ -228,9 +210,6 @@ func (s *UDPProxyServer) Start() error {
 	// Start the communication pattern cleanup routine
 	go s.cleanupIdleCommunicationPatterns()
 
-	// Start the hole punch rate limiter cleanup routine
-	go s.cleanupHolePunchRateLimiter()
-
 	return nil
 }
 
@@ -293,27 +272,6 @@ func (s *UDPProxyServer) packetWorker() {
 			// Process as a WireGuard packet.
 			s.handleWireGuardPacket(packet.data, packet.remoteAddr)
 		} else {
-			// Rate limit: allow at most 2 hole punch messages per IP:Port per second
-			rateLimitKey := packet.remoteAddr.String()
-			entryVal, _ := s.holePunchRateLimiter.LoadOrStore(rateLimitKey, &holePunchRateLimitEntry{
-				windowStart: time.Now(),
-			})
-			rlEntry := entryVal.(*holePunchRateLimitEntry)
-			rlEntry.mu.Lock()
-			now := time.Now()
-			if now.Sub(rlEntry.windowStart) >= time.Second {
-				rlEntry.count = 0
-				rlEntry.windowStart = now
-			}
-			rlEntry.count++
-			allowed := rlEntry.count <= 2
-			rlEntry.mu.Unlock()
-			if !allowed {
-				// logger.Debug("Rate limiting hole punch message from %s", rateLimitKey)
-				bufferPool.Put(packet.data[:1500])
-				continue
-			}
-
 			// Process as an encrypted hole punch message
 			var encMsg EncryptedHolePunchMessage
 			if err := json.Unmarshal(packet.data, &encMsg); err != nil {
@@ -333,7 +291,7 @@ func (s *UDPProxyServer) packetWorker() {
 			// This appears to be an encrypted message
 			decryptedData, err := s.decryptMessage(encMsg)
 			if err != nil {
-				// logger.Error("Failed to decrypt message: %v", err)
+				logger.Error("Failed to decrypt message: %v", err)
 				// Return the buffer to the pool for reuse and continue with next packet
 				bufferPool.Put(packet.data[:1500])
 				continue
@@ -458,43 +416,6 @@ func extractWireGuardIndices(packet []byte) (uint32, uint32, bool) {
 	return 0, 0, false
 }
 
-// cachedAddr holds a resolved UDP address with TTL
-type cachedAddr struct {
-	addr      *net.UDPAddr
-	expiresAt time.Time
-}
-
-// addrCacheTTL is how long resolved addresses are cached before re-resolving
-const addrCacheTTL = 5 * time.Minute
-
-// getCachedAddr returns a cached UDP address or resolves and caches it.
-// This avoids per-packet DNS lookups which are a major throughput bottleneck.
-func (s *UDPProxyServer) getCachedAddr(ip string, port int) (*net.UDPAddr, error) {
-	key := fmt.Sprintf("%s:%d", ip, port)
-
-	// Check cache first
-	if cached, ok := s.addrCache.Load(key); ok {
-		entry := cached.(*cachedAddr)
-		if time.Now().Before(entry.expiresAt) {
-			return entry.addr, nil
-		}
-		// Cache expired, delete and re-resolve
-		s.addrCache.Delete(key)
-	}
-
-	// Resolve and cache
-	addr, err := net.ResolveUDPAddr("udp", key)
-	if err != nil {
-		return nil, err
-	}
-
-	s.addrCache.Store(key, &cachedAddr{
-		addr:      addr,
-		expiresAt: time.Now().Add(addrCacheTTL),
-	})
-	return addr, nil
-}
-
 // Updated to handle multi-peer WireGuard communication
 func (s *UDPProxyServer) handleWireGuardPacket(packet []byte, remoteAddr *net.UDPAddr) {
 	if len(packet) == 0 {
@@ -529,7 +450,7 @@ func (s *UDPProxyServer) handleWireGuardPacket(packet []byte, remoteAddr *net.UD
 		logger.Debug("Forwarding handshake initiation from %s (sender index: %d) to peers %v", remoteAddr, senderIndex, proxyMapping.Destinations)
 
 		for _, dest := range proxyMapping.Destinations {
-			destAddr, err := s.getCachedAddr(dest.DestinationIP, dest.DestinationPort)
+			destAddr, err := net.ResolveUDPAddr("udp", fmt.Sprintf("%s:%d", dest.DestinationIP, dest.DestinationPort))
 			if err != nil {
 				logger.Error("Failed to resolve destination address: %v", err)
 				continue
@@ -565,7 +486,7 @@ func (s *UDPProxyServer) handleWireGuardPacket(packet []byte, remoteAddr *net.UD
 
 		// Forward the response to the original sender
 		for _, dest := range proxyMapping.Destinations {
-			destAddr, err := s.getCachedAddr(dest.DestinationIP, dest.DestinationPort)
+			destAddr, err := net.ResolveUDPAddr("udp", fmt.Sprintf("%s:%d", dest.DestinationIP, dest.DestinationPort))
 			if err != nil {
 				logger.Error("Failed to resolve destination address: %v", err)
 				continue
@@ -622,7 +543,7 @@ func (s *UDPProxyServer) handleWireGuardPacket(packet []byte, remoteAddr *net.UD
 			// No known session, fall back to forwarding to all peers
 			logger.Debug("No session found for receiver index %d, forwarding to all destinations", receiverIndex)
 			for _, dest := range proxyMapping.Destinations {
-				destAddr, err := s.getCachedAddr(dest.DestinationIP, dest.DestinationPort)
+				destAddr, err := net.ResolveUDPAddr("udp", fmt.Sprintf("%s:%d", dest.DestinationIP, dest.DestinationPort))
 				if err != nil {
 					logger.Error("Failed to resolve destination address: %v", err)
 					continue
@@ -650,7 +571,7 @@ func (s *UDPProxyServer) handleWireGuardPacket(packet []byte, remoteAddr *net.UD
 
 		// Forward to all peers
 		for _, dest := range proxyMapping.Destinations {
-			destAddr, err := s.getCachedAddr(dest.DestinationIP, dest.DestinationPort)
+			destAddr, err := net.ResolveUDPAddr("udp", fmt.Sprintf("%s:%d", dest.DestinationIP, dest.DestinationPort))
 			if err != nil {
 				logger.Error("Failed to resolve destination address: %v", err)
 				continue
@@ -1109,30 +1030,6 @@ func (s *UDPProxyServer) tryRebuildSession(pattern *CommunicationPattern) {
 }
 
 // cleanupIdleCommunicationPatterns periodically removes idle communication patterns
-// cleanupHolePunchRateLimiter periodically evicts stale rate limit entries to prevent unbounded growth.
-func (s *UDPProxyServer) cleanupHolePunchRateLimiter() {
-	ticker := time.NewTicker(30 * time.Second)
-	defer ticker.Stop()
-	for {
-		select {
-		case <-ticker.C:
-			now := time.Now()
-			s.holePunchRateLimiter.Range(func(key, value interface{}) bool {
-				rlEntry := value.(*holePunchRateLimitEntry)
-				rlEntry.mu.Lock()
-				stale := now.Sub(rlEntry.windowStart) > 10*time.Second
-				rlEntry.mu.Unlock()
-				if stale {
-					s.holePunchRateLimiter.Delete(key)
-				}
-				return true
-			})
-		case <-s.ctx.Done():
-			return
-		}
-	}
-}
-
 func (s *UDPProxyServer) cleanupIdleCommunicationPatterns() {
 	ticker := time.NewTicker(10 * time.Minute)
 	defer ticker.Stop()