Feat: add option to disable UDP functionality

Author: SuzukiHonoka

engine/engine.go

@@ -133,6 +133,10 @@ func general(k *Key) error {
 		}
 		tunnel.T().SetUDPTimeout(k.UDPTimeout)
 	}
+
+	if k.UDPDisabled {
+		tunnel.T().SetUDPDisabled(true)
+	}
 	return nil
 }
 

engine/key.go

@@ -17,4 +17,5 @@ type Key struct {
 	TUNPreUp                 string        `yaml:"tun-pre-up"`
 	TUNPostUp                string        `yaml:"tun-post-up"`
 	UDPTimeout               time.Duration `yaml:"udp-timeout"`
+	UDPDisabled              bool          `yaml:"udp-disabled"`
 }

main.go

@@ -27,6 +27,7 @@ func init() {
 	flag.IntVar(&key.Mark, "fwmark", 0, "Set firewall MARK (Linux only)")
 	flag.IntVar(&key.MTU, "mtu", 0, "Set device maximum transmission unit (MTU)")
 	flag.DurationVar(&key.UDPTimeout, "udp-timeout", 0, "Set timeout for each UDP session")
+	flag.BoolVar(&key.UDPDisabled, "udp-disabled", false, "Disable UDP")
 	flag.StringVar(&configFile, "config", "", "YAML format configuration file")
 	flag.StringVar(&key.Device, "device", "", "Use this device [driver://]name")
 	flag.StringVar(&key.Interface, "interface", "", "Use network INTERFACE (Linux/MacOS only)")

tunnel/tunnel.go

@@ -31,6 +31,9 @@ type Tunnel struct {
 	// UDP session timeout.
 	udpTimeout *atomic.Duration
 
+	// UDP disabled flag.
+	udpDisabled *atomic.Bool
+
 	// Internal proxy.Dialer for Tunnel.
 	dialerMu sync.RWMutex
 	dialer   proxy.Dialer
@@ -44,12 +47,13 @@ type Tunnel struct {
 
 func New(dialer proxy.Dialer, manager *statistic.Manager) *Tunnel {
 	return &Tunnel{
-		tcpQueue:   make(chan adapter.TCPConn),
-		udpQueue:   make(chan adapter.UDPConn),
-		udpTimeout: atomic.NewDuration(udpSessionTimeout),
-		dialer:     dialer,
-		manager:    manager,
-		procCancel: func() { /* nop */ },
+		tcpQueue:    make(chan adapter.TCPConn),
+		udpQueue:    make(chan adapter.UDPConn),
+		udpTimeout:  atomic.NewDuration(udpSessionTimeout),
+		udpDisabled: atomic.NewBool(false),
+		dialer:      dialer,
+		manager:     manager,
+		procCancel:  func() { /* nop */ },
 	}
 }
 
@@ -114,3 +118,7 @@ func (t *Tunnel) SetDialer(dialer proxy.Dialer) {
 func (t *Tunnel) SetUDPTimeout(timeout time.Duration) {
 	t.udpTimeout.Store(timeout)
 }
+
+func (t *Tunnel) SetUDPDisabled(disabled bool) {
+	t.udpDisabled.Store(disabled)
+}

tunnel/udp.go

@@ -17,6 +17,11 @@ import (
 func (t *Tunnel) handleUDPConn(uc adapter.UDPConn) {
 	defer uc.Close()
 
+	if t.udpDisabled.Load() {
+		log.Warnf("[UDP] dial %s: blocked", uc.ID().RemoteAddress)
+		return
+	}
+
 	id := uc.ID()
 	metadata := &M.Metadata{
 		Network: M.UDP,