Fix: refactor tun implement

core/src/main/cpp/main.c

@@ -96,15 +96,17 @@ Java_com_github_kr328_clash_core_bridge_Bridge_nativeNotifyInstalledAppChanged(J
 }
 
 JNIEXPORT void JNICALL
-Java_com_github_kr328_clash_core_bridge_Bridge_nativeStartTun(JNIEnv *env, jobject thiz, jint fd,
+Java_com_github_kr328_clash_core_bridge_Bridge_nativeStartTun(JNIEnv *env, jobject thiz,
-                                                              jint mtu, jstring dns,
+                                                              jint fd, jint mtu,
+                                                              jstring gateway, jstring dns,
                                                               jobject cb) {
     TRACE_METHOD();
 
+    scoped_string _gateway = get_string(gateway);
     scoped_string _dns = get_string(dns);
     jobject _interface = new_global(cb);
 
-    startTun(fd, mtu, _dns, _interface);
+    startTun(fd, mtu, _gateway, _dns, _interface);
 }
 
 JNIEXPORT void JNICALL

core/src/main/golang/tun.go

@@ -11,8 +11,6 @@ import (
 	"cfa/tun"
 
 	"golang.org/x/sync/semaphore"
-
-	"github.com/Dreamacro/clash/log"
 )
 
 type remoteTun struct {
@@ -23,7 +21,7 @@ type remoteTun struct {
 }
 
 func (t *remoteTun) markSocket(fd int) {
-	_ = t.limit.Acquire(context.Background(), 1)
+	_ = t.limit.Acquire(context.TODO(), 1)
 	defer t.limit.Release(1)
 
 	if t.closed {
@@ -34,7 +32,7 @@ func (t *remoteTun) markSocket(fd int) {
 }
 
 func (t *remoteTun) querySocketUid(protocol int, source, target string) int {
-	_ = t.limit.Acquire(context.Background(), 1)
+	_ = t.limit.Acquire(context.TODO(), 1)
 	defer t.limit.Release(1)
 
 	if t.closed {
@@ -50,26 +48,27 @@ func (t *remoteTun) stop() {
 
 	t.closed = true
 
-	C.release_object(t.callback)
+	app.ApplyTunContext(nil, nil)
 
-	log.Infoln("Android tun device destroyed")
+	C.release_object(t.callback)
 }
 
 //export startTun
-func startTun(fd, mtu C.int, dns C.c_string, callback unsafe.Pointer) C.int {
+func startTun(fd, mtu C.int, gateway, dns C.c_string, callback unsafe.Pointer) C.int {
 	f := int(fd)
 	m := int(mtu)
+	g := C.GoString(gateway)
 	d := C.GoString(dns)
 
 	remote := &remoteTun{callback: callback, closed: false, limit: semaphore.NewWeighted(4)}
 
-	if tun.Start(f, m, d) != nil {
-		return 1
-	}
-
 	app.ApplyTunContext(remote.markSocket, remote.querySocketUid)
 
-	log.Infoln("Android tun device created")
+	if tun.Start(f, m, g, d, remote.stop) != nil {
+		app.ApplyTunContext(nil, nil)
+
+		return 1
+	}
 
 	return 0
 }

core/src/main/golang/tun/dns.go

@@ -1,19 +1,12 @@
 package tun
 
 import (
-	"encoding/binary"
-	"io"
 	"net"
-	"time"
 
 	"github.com/Dreamacro/clash/component/resolver"
-	"github.com/kr328/tun2socket"
-
 	D "github.com/miekg/dns"
 )
 
-const defaultDnsReadTimeout = time.Second * 30
-
 func shouldHijackDns(dns net.IP, target net.IP, targetPort int) bool {
 	if targetPort != 53 {
 		return false
@@ -22,58 +15,7 @@ func shouldHijackDns(dns net.IP, target net.IP, targetPort int) bool {
 	return net.IPv4zero.Equal(dns) || target.Equal(dns)
 }
 
-func hijackUDPDns(pkt []byte, lAddr, rAddr net.Addr, udp tun2socket.UDP) {
+func relayDns(payload []byte) ([]byte, error) {
-	go func() {
-		answer, err := relayDnsPacket(pkt)
-
-		if err != nil {
-			return
-		}
-
-		_, _ = udp.WriteTo(answer, lAddr, rAddr)
-
-		recycleUDP(pkt)
-	}()
-}
-
-func hijackTCPDns(conn net.Conn) {
-	go func() {
-		defer conn.Close()
-
-		for {
-			if err := conn.SetReadDeadline(time.Now().Add(defaultDnsReadTimeout)); err != nil {
-				return
-			}
-
-			var length uint16
-			if binary.Read(conn, binary.BigEndian, &length) != nil {
-				return
-			}
-
-			data := make([]byte, length)
-
-			_, err := io.ReadFull(conn, data)
-			if err != nil {
-				return
-			}
-
-			rb, err := relayDnsPacket(data)
-			if err != nil {
-				continue
-			}
-
-			if binary.Write(conn, binary.BigEndian, uint16(len(rb))) != nil {
-				return
-			}
-
-			if _, err := conn.Write(rb); err != nil {
-				return
-			}
-		}
-	}()
-}
-
-func relayDnsPacket(payload []byte) ([]byte, error) {
 	msg := &D.Msg{}
 	if err := msg.Unpack(payload); err != nil {
 		return nil, err
@@ -84,14 +26,6 @@ func relayDnsPacket(payload []byte) ([]byte, error) {
 		return nil, err
 	}
 
-	for _, ans := range r.Answer {
-		header := ans.Header()
-
-		if header.Class == D.ClassINET && (header.Rrtype == D.TypeA || header.Rrtype == D.TypeAAAA) {
-			header.Ttl = 1
-		}
-	}
-
 	r.SetRcode(msg, r.Rcode)
 
 	return r.Pack()

core/src/main/golang/tun/link.go

@@ -0,0 +1,39 @@
+package tun
+
+import "github.com/Dreamacro/clash/log"
+
+func (a *adapter) rx() {
+	log.Infoln("[ATUN] Device rx started")
+	defer log.Infoln("[ATUN] Device rx exited")
+	defer a.once.Do(a.stop)
+	defer a.close()
+
+	buf := make([]byte, a.mtu)
+
+	for {
+		n, err := a.device.Read(buf)
+		if err != nil {
+			return
+		}
+
+		_, _ = a.stack.Link().Write(buf[:n])
+	}
+}
+
+func (a *adapter) tx() {
+	log.Infoln("[ATUN] Device tx started")
+	defer log.Infoln("[ATUN] Device tx exited")
+	defer a.once.Do(a.stop)
+	defer a.close()
+
+	buf := make([]byte, a.mtu)
+
+	for {
+		n, err := a.stack.Link().Read(buf)
+		if err != nil {
+			return
+		}
+
+		_, _ = a.device.Write(buf[:n])
+	}
+}

core/src/main/golang/tun/tcp.go

@@ -1,27 +1,100 @@
 package tun
 
 import (
+	"encoding/binary"
+	"io"
 	"net"
 	"strconv"
+	"time"
 
 	C "github.com/Dreamacro/clash/constant"
-	CTX "github.com/Dreamacro/clash/context"
+	"github.com/Dreamacro/clash/context"
+	"github.com/Dreamacro/clash/log"
 	"github.com/Dreamacro/clash/tunnel"
 )
 
-func handleTCP(conn net.Conn, source *net.TCPAddr, target *net.TCPAddr) {
+const defaultDnsReadTimeout = time.Second * 30
+
+func (a *adapter) tcp() {
+	log.Infoln("[ATUN] TCP listener started")
+	defer log.Infoln("[ATUN] TCP listener exited")
+	defer a.stack.Close()
+
+	for {
+		conn, err := a.stack.TCP().Accept()
+		if err != nil {
+			return
+		}
+
+		sAddr := conn.LocalAddr().(*net.TCPAddr)
+		tAddr := conn.RemoteAddr().(*net.TCPAddr)
+
+		// handle dns messages
+		if a.hijackTCPDNS(conn, tAddr) {
+			continue
+		}
+
+		// drop all connections connect to gateway
+		if a.gateway.Contains(tAddr.IP) {
+			continue
+		}
+
 		metadata := &C.Metadata{
 			NetWork:    C.TCP,
 			Type:       C.SOCKS,
-		SrcIP:      source.IP,
+			SrcIP:      sAddr.IP,
-		DstIP:      target.IP,
+			DstIP:      tAddr.IP,
-		SrcPort:    strconv.Itoa(source.Port),
+			SrcPort:    strconv.Itoa(sAddr.Port),
-		DstPort:    strconv.Itoa(target.Port),
+			DstPort:    strconv.Itoa(tAddr.Port),
 			AddrType:   C.AtypIPv4,
 			Host:       "",
-		RawSrcAddr: source,
+			RawSrcAddr: sAddr,
-		RawDstAddr: target,
+			RawDstAddr: tAddr,
 		}
 
-	tunnel.Add(CTX.NewConnContext(conn, metadata))
+		tunnel.Add(context.NewConnContext(conn, metadata))
+	}
+}
+
+func (a *adapter) hijackTCPDNS(conn net.Conn, tAddr *net.TCPAddr) bool {
+	if !shouldHijackDns(a.dns, tAddr.IP, tAddr.Port) {
+		return false
+	}
+
+	go func() {
+		defer conn.Close()
+
+		for {
+			if err := conn.SetReadDeadline(time.Now().Add(defaultDnsReadTimeout)); err != nil {
+				return
+			}
+
+			var length uint16
+			if binary.Read(conn, binary.BigEndian, &length) != nil {
+				return
+			}
+
+			data := make([]byte, length)
+
+			_, err := io.ReadFull(conn, data)
+			if err != nil {
+				return
+			}
+
+			rb, err := relayDns(data)
+			if err != nil {
+				continue
+			}
+
+			if binary.Write(conn, binary.BigEndian, uint16(len(rb))) != nil {
+				return
+			}
+
+			if _, err := conn.Write(rb); err != nil {
+				return
+			}
+		}
+	}()
+
+	return true
 }

core/src/main/golang/tun/tun.go

@@ -4,33 +4,40 @@ import (
 	"net"
 	"os"
 	"sync"
+	"syscall"
 
 	"github.com/kr328/tun2socket"
 )
 
-type context struct {
+type adapter struct {
 	device  *os.File
 	stack   tun2socket.Stack
+	gateway *net.IPNet
+	dns     net.IP
+	mtu     int
+	once    sync.Once
+	stop    func()
 }
 
 var lock sync.Mutex
-var tun *context
+var instance *adapter
 
-func (ctx *context) close() {
+func (a *adapter) close() {
-	_ = ctx.stack.Close()
+	_ = a.stack.Close()
-	_ = ctx.device.Close()
+	_ = a.device.Close()
 }
 
-func Start(fd, mtu int, dns string) error {
+func Start(fd, mtu int, gateway, dns string, stop func()) error {
 	lock.Lock()
 	defer lock.Unlock()
 
-	stopLocked()
+	if instance != nil {
+		instance.close()
+	}
 
-	dnsIP := net.ParseIP(dns)
+	_ = syscall.SetNonblock(fd, true)
 
 	device := os.NewFile(uintptr(fd), "/dev/tun")
-
 	stack, err := tun2socket.NewStack(mtu)
 	if err != nil {
 		_ = device.Close()
@@ -38,100 +45,23 @@ func Start(fd, mtu int, dns string) error {
 		return err
 	}
 
-	ctx := &context{
+	dn := net.ParseIP(dns)
+	_, gw, _ := net.ParseCIDR(gateway)
+
+	instance = &adapter{
 		device:  device,
 		stack:   stack,
+		gateway: gw,
+		dns:     dn,
+		mtu:     mtu,
+		once:    sync.Once{},
+		stop:    stop,
 	}
 
-	go func() {
+	go instance.rx()
-		// device -> lwip
+	go instance.tx()
-
+	go instance.tcp()
-		defer ctx.close()
+	go instance.udp()
-
-		buf := make([]byte, mtu)
-
-		for {
-			n, err := device.Read(buf)
-			if err != nil {
-				return
-			}
-
-			_, _ = stack.Link().Write(buf[:n])
-		}
-	}()
-
-	go func() {
-		// lwip -> device
-
-		defer ctx.close()
-
-		buf := make([]byte, mtu)
-
-		for {
-			n, err := stack.Link().Read(buf)
-			if err != nil {
-				return
-			}
-
-			_, _ = device.Write(buf[:n])
-		}
-	}()
-
-	go func() {
-		// lwip tcp
-
-		defer ctx.close()
-
-		for {
-			conn, err := stack.TCP().Accept()
-			if err != nil {
-				return
-			}
-
-			source := conn.LocalAddr().(*net.TCPAddr)
-			target := conn.RemoteAddr().(*net.TCPAddr)
-
-			if shouldHijackDns(dnsIP, target.IP, target.Port) {
-				hijackTCPDns(conn)
-
-				continue
-			}
-
-			handleTCP(conn, source, target)
-		}
-	}()
-
-	go func() {
-		// lwip udp
-
-		defer ctx.close()
-
-		for {
-			buf := allocUDP(mtu)
-
-			n, lAddr, rAddr, err := stack.UDP().ReadFrom(buf)
-			if err != nil {
-				return
-			}
-
-			source := lAddr.(*net.UDPAddr)
-			target := rAddr.(*net.UDPAddr)
-
-			if n == 0 {
-				continue
-			}
-
-			if shouldHijackDns(dnsIP, target.IP, target.Port) {
-				hijackUDPDns(buf[:n], source, target, stack.UDP())
-
-				continue
-			}
-
-			handleUDP(buf[:n], source, target, stack.UDP())
-		}
-	}()
-
-	tun = ctx
 
 	return nil
 }
@@ -140,13 +70,9 @@ func Stop() {
 	lock.Lock()
 	defer lock.Unlock()
 
-	stopLocked()
+	if instance != nil {
-}
+		instance.close()
-
-func stopLocked() {
-	if tun != nil {
-		tun.close()
 	}
 
-	tun = nil
+	instance = nil
 }

core/src/main/golang/tun/udp.go

@@ -3,6 +3,7 @@ package tun
 import (
 	"net"
 
+	"github.com/Dreamacro/clash/log"
 	"github.com/Dreamacro/clash/transport/socks5"
 	"github.com/kr328/tun2socket"
 
@@ -12,48 +13,88 @@ import (
 	"github.com/Dreamacro/clash/tunnel"
 )
 
-type udpPacket struct {
+type packet struct {
-	source   *net.UDPAddr
+	stack tun2socket.Stack
+	local *net.UDPAddr
 	data  []byte
-	udp      tun2socket.UDP
 }
 
-func (u *udpPacket) Data() []byte {
+func (pkt *packet) Data() []byte {
-	return u.data
+	return pkt.data
 }
 
-func (u *udpPacket) WriteBack(b []byte, addr net.Addr) (n int, err error) {
+func (pkt *packet) WriteBack(b []byte, addr net.Addr) (n int, err error) {
-	return u.udp.WriteTo(b, u.source, addr)
+	return pkt.stack.UDP().WriteTo(b, pkt.local, addr)
 }
 
-func (u *udpPacket) Drop() {
+func (pkt *packet) Drop() {
-	recycleUDP(u.data)
+	pool.Put(pkt.data)
 }
 
-func (u *udpPacket) LocalAddr() net.Addr {
+func (pkt *packet) LocalAddr() net.Addr {
 	return &net.UDPAddr{
-		IP:   u.source.IP,
+		IP:   pkt.local.IP,
-		Port: u.source.Port,
+		Port: pkt.local.Port,
 		Zone: "",
 	}
 }
 
-func handleUDP(payload []byte, source *net.UDPAddr, target *net.UDPAddr, udp tun2socket.UDP) {
+func (a *adapter) udp() {
-	pkt := &udpPacket{
+	log.Infoln("[ATUN] UDP receiver started")
-		source:   source,
+	defer log.Infoln("[ATUN] UDP receiver exited")
-		data:     payload,
+	defer a.stack.Close()
-		udp:      udp,
+
+	for {
+		buf := pool.Get(a.mtu)
+
+		n, lAddr, rAddr, err := a.stack.UDP().ReadFrom(buf)
+		if err != nil {
+			return
 		}
 
-	adapter := adapters.NewPacket(socks5.ParseAddrToSocksAddr(target), pkt, C.SOCKS)
+		sAddr := lAddr.(*net.UDPAddr)
+		tAddr := rAddr.(*net.UDPAddr)
+
+		// handle dns messages
+		if a.hijackUDPDNS(buf[:n], sAddr, tAddr) {
+			continue
+		}
+
+		// drop all packets send to gateway
+		if a.gateway.Contains(tAddr.IP) {
+			pool.Put(buf)
+
+			continue
+		}
+
+		pkt := &packet{
+			stack: a.stack,
+			local: sAddr,
+			data:  buf[:n],
+		}
+
+		adapter := adapters.NewPacket(socks5.ParseAddrToSocksAddr(tAddr), pkt, C.SOCKS)
 
 		tunnel.AddPacket(adapter)
+	}
 }
 
-func allocUDP(size int) []byte {
+func (a *adapter) hijackUDPDNS(pkt []byte, sAddr, tAddr *net.UDPAddr) bool {
-	return pool.Get(size)
+	if !shouldHijackDns(a.dns, tAddr.IP, tAddr.Port) {
-}
+		return false
+	}
 
-func recycleUDP(payload []byte) {
+	go func() {
-	_ = pool.Put(payload)
+		answer, err := relayDns(pkt)
+
+		if err != nil {
+			return
+		}
+
+		_, _ = a.stack.UDP().WriteTo(answer, sAddr, tAddr)
+
+		pool.Put(pkt)
+	}()
+
+	return true
 }

core/src/main/java/com/github/kr328/clash/core/Clash.kt

@@ -61,11 +61,12 @@ object Clash {
     fun startTun(
         fd: Int,
         mtu: Int,
+        gateway: String,
         dns: String,
         markSocket: (Int) -> Boolean,
         querySocketUid: (protocol: Int, source: InetSocketAddress, target: InetSocketAddress) -> Int
     ) {
-        Bridge.nativeStartTun(fd, mtu, dns, object : TunInterface {
+        Bridge.nativeStartTun(fd, mtu, gateway, dns, object : TunInterface {
             override fun markSocket(fd: Int) {
                 markSocket(fd)
             }

core/src/main/java/com/github/kr328/clash/core/bridge/Bridge.kt

@@ -17,7 +17,7 @@ object Bridge {
     external fun nativeQueryTrafficTotal(): Long
     external fun nativeNotifyDnsChanged(dnsList: String)
     external fun nativeNotifyInstalledAppChanged(uidList: String)
-    external fun nativeStartTun(fd: Int, mtu: Int, dns: String, cb: TunInterface)
+    external fun nativeStartTun(fd: Int, mtu: Int, gateway: String, dns: String, cb: TunInterface)
     external fun nativeStopTun()
     external fun nativeStartHttp(listenAt: String): String?
     external fun nativeStopHttp()

service/src/main/java/com/github/kr328/clash/service/TunService.kt

@@ -217,6 +217,7 @@ class TunService : VpnService(), CoroutineScope by CoroutineScope(Dispatchers.De
                 fd = establish()?.detachFd()
                     ?: throw NullPointerException("Establish VPN rejected by system"),
                 mtu = TUN_MTU,
+                gateway = "$TUN_GATEWAY/$TUN_SUBNET_PREFIX",
                 dns = if (store.dnsHijacking) NET_ANY else TUN_DNS,
             )
         }

service/src/main/java/com/github/kr328/clash/service/clash/module/TunModule.kt

@@ -16,7 +16,8 @@ class TunModule(private val vpn: VpnService) : Module<Unit>(vpn) {
     data class TunDevice(
         val fd: Int,
         val mtu: Int,
-        val dns: String
+        val gateway: String,
+        val dns: String,
     )
 
     private val connectivity = service.getSystemService<ConnectivityManager>()!!
@@ -56,6 +57,7 @@ class TunModule(private val vpn: VpnService) : Module<Unit>(vpn) {
         Clash.startTun(
             fd = device.fd,
             mtu = device.mtu,
+            gateway = device.gateway,
             dns = device.dns,
             markSocket = vpn::protect,
             querySocketUid = this::queryUid