Add checksum offload stub

go.mod

@@ -7,7 +7,7 @@ require (
 	github.com/go-ole/go-ole v1.3.0
 	github.com/sagernet/gvisor v0.0.0-20231209105102-8d27a30e436e
 	github.com/sagernet/netlink v0.0.0-20220905062125-8043b4a9aa97
-	github.com/sagernet/sing v0.2.20-0.20231211084415-35e7014b0898
+	github.com/sagernet/sing v0.3.0-beta.3
 	github.com/scjalliance/comshim v0.0.0-20230315213746-5e51f40bd3b9
 	go4.org/netipx v0.0.0-20231129151722-fdeea329fbba
 	golang.org/x/net v0.19.0

go.sum

@@ -1,17 +1,20 @@
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/fsnotify/fsnotify v1.7.0 h1:8JEhPFa5W2WU7YfeZzPNqzMP6Lwt7L2715Ggo0nosvA=
 github.com/fsnotify/fsnotify v1.7.0/go.mod h1:40Bi/Hjc2AVfZrqy+aj+yEI+/bRxZnMJyTJwOpGvigM=
 github.com/go-ole/go-ole v1.3.0 h1:Dt6ye7+vXGIKZ7Xtk4s6/xVdGDQynvom7xCFEdWr6uE=
 github.com/go-ole/go-ole v1.3.0/go.mod h1:5LS6F96DhAwUc7C+1HLexzMXY1xGRSryjyPPKW6zv78=
 github.com/google/btree v1.1.2 h1:xf4v41cLI2Z6FxbKm+8Bu+m8ifhj15JuZ9sa0jZCMUU=
 github.com/google/btree v1.1.2/go.mod h1:qOPhT0dTNdNzV6Z/lhRX0YXUafgPLFUh+gZMl761Gm4=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/sagernet/gvisor v0.0.0-20231209105102-8d27a30e436e h1:DOkjByVeAR56dkszjnMZke4wr7yM/1xHaJF3G9olkEE=
 github.com/sagernet/gvisor v0.0.0-20231209105102-8d27a30e436e/go.mod h1:fLxq/gtp0qzkaEwywlRRiGmjOK5ES/xUzyIKIFP2Asw=
 github.com/sagernet/netlink v0.0.0-20220905062125-8043b4a9aa97 h1:iL5gZI3uFp0X6EslacyapiRz7LLSJyr4RajF/BhMVyE=
 github.com/sagernet/netlink v0.0.0-20220905062125-8043b4a9aa97/go.mod h1:xLnfdiJbSp8rNqYEdIW/6eDO4mVoogml14Bh2hSiFpM=
-github.com/sagernet/sing v0.2.20-0.20231211084415-35e7014b0898 h1:ZR0wpw4/0NCICOX10SIUW8jpPVV7+D98nGA6p4zWICo=
-github.com/sagernet/sing v0.2.20-0.20231211084415-35e7014b0898/go.mod h1:Ce5LNojQOgOiWhiD8pPD6E9H7e2KgtOe3Zxx4Ou5u80=
+github.com/sagernet/sing v0.3.0-beta.3 h1:E2xBoJUducK/FE6EwMk95Rt2bkXeht9l1BTYRui+DXs=
+github.com/sagernet/sing v0.3.0-beta.3/go.mod h1:9pfuAH6mZfgnz/YjP6xu5sxx882rfyjpcrTdUpd6w3g=
 github.com/scjalliance/comshim v0.0.0-20230315213746-5e51f40bd3b9 h1:rc/CcqLH3lh8n+csdOuDfP+NuykE0U6AeYSJJHKDgSg=
 github.com/scjalliance/comshim v0.0.0-20230315213746-5e51f40bd3b9/go.mod h1:a/83NAfUXvEuLpmxDssAXxgUgrEy12MId3Wd7OTs76s=
+github.com/stretchr/testify v1.8.4 h1:CcVxjf3Q8PM0mHUKJCdn+eZZtm5yQwehR5yeSVQQcUk=
 github.com/vishvananda/netns v0.0.0-20211101163701-50045581ed74 h1:gga7acRE695APm9hlsSMoOoE65U4/TcqNj90mc69Rlg=
 github.com/vishvananda/netns v0.0.0-20211101163701-50045581ed74/go.mod h1:DD4vA1DwXk04H54A1oHXtwZmA0grkVMdPxx/VGLCah0=
 go4.org/netipx v0.0.0-20231129151722-fdeea329fbba h1:0b9z3AuHCjxk0x/opv64kcgZLBseWJUpBw5I82+2U4M=
@@ -24,3 +27,4 @@ golang.org/x/sys v0.15.0 h1:h48lPFYpsTvQJZF4EKyI4aLHaev3CxivZmv7yZig9pc=
 golang.org/x/sys v0.15.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
 golang.org/x/time v0.5.0 h1:o7cqy6amK/52YcAKIPlM3a+Fpj35zvRj2TP+e1xFSfk=
 golang.org/x/time v0.5.0/go.mod h1:3BpzKBy/shNhVucY/MWOyx10tF3SFh9QdLuxbVysPQM=
+gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=

internal/clashtcpip/tcp.go

@@ -50,6 +50,10 @@ func (p TCPPacket) SetChecksum(sum [2]byte) {
 	p[17] = sum[1]
 }
 
+func (p TCPPacket) OffloadChecksum() {
+	p.SetChecksum(zeroChecksum)
+}
+
 func (p TCPPacket) ResetChecksum(psum uint32) {
 	p.SetChecksum(zeroChecksum)
 	p.SetChecksum(Checksum(psum, p))

internal/clashtcpip/udp.go

@@ -45,6 +45,10 @@ func (p UDPPacket) SetChecksum(sum [2]byte) {
 	p[7] = sum[1]
 }
 
+func (p UDPPacket) OffloadChecksum() {
+	p.SetChecksum(zeroChecksum)
+}
+
 func (p UDPPacket) ResetChecksum(psum uint32) {
 	p.SetChecksum(zeroChecksum)
 	p.SetChecksum(Checksum(psum, p))

stack_mixed.go

@@ -91,17 +91,18 @@ func (m *Mixed) tunLoop() {
 		m.wintunLoop(winTun)
 		return
 	}
-	if batchTUN, isBatchTUN := m.tun.(BatchTUN); isBatchTUN {
-		batchSize := batchTUN.BatchSize()
+	if linuxTUN, isLinuxTUN := m.tun.(LinuxTUN); isLinuxTUN {
+		m.frontHeadroom = linuxTUN.FrontHeadroom()
+		m.txChecksumOffload = linuxTUN.TXChecksumOffload()
+		batchSize := linuxTUN.BatchSize()
 		if batchSize > 1 {
-			m.batchLoop(batchTUN, batchSize)
+			m.batchLoop(linuxTUN, batchSize)
 			return
 		}
 	}
-	frontHeadroom := m.tun.FrontHeadroom()
-	packetBuffer := make([]byte, m.mtu+frontHeadroom+PacketOffset)
+	packetBuffer := make([]byte, m.mtu+PacketOffset)
 	for {
-		n, err := m.tun.Read(packetBuffer[frontHeadroom:])
+		n, err := m.tun.Read(packetBuffer)
 		if err != nil {
 			if E.IsClosed(err) {
 				return
@@ -111,8 +112,8 @@ func (m *Mixed) tunLoop() {
 		if n < clashtcpip.IPv4PacketMinLength {
 			continue
 		}
-		rawPacket := packetBuffer[:frontHeadroom+n]
-		packet := packetBuffer[frontHeadroom+PacketOffset : frontHeadroom+n]
+		rawPacket := packetBuffer[:n]
+		packet := packetBuffer[PacketOffset:n]
 		if m.processPacket(packet) {
 			_, err = m.tun.Write(rawPacket)
 			if err != nil {
@@ -142,16 +143,15 @@ func (m *Mixed) wintunLoop(winTun WinTun) {
 	}
 }
 
-func (m *Mixed) batchLoop(linuxTUN BatchTUN, batchSize int) {
-	frontHeadroom := m.tun.FrontHeadroom()
+func (m *Mixed) batchLoop(linuxTUN LinuxTUN, batchSize int) {
 	packetBuffers := make([][]byte, batchSize)
 	writeBuffers := make([][]byte, batchSize)
 	packetSizes := make([]int, batchSize)
 	for i := range packetBuffers {
-		packetBuffers[i] = make([]byte, m.mtu+frontHeadroom)
+		packetBuffers[i] = make([]byte, m.mtu+m.frontHeadroom)
 	}
 	for {
-		n, err := linuxTUN.BatchRead(packetBuffers, frontHeadroom, packetSizes)
+		n, err := linuxTUN.BatchRead(packetBuffers, m.frontHeadroom, packetSizes)
 		if err != nil {
 			if E.IsClosed(err) {
 				return
@@ -167,13 +167,13 @@ func (m *Mixed) batchLoop(linuxTUN BatchTUN, batchSize int) {
 				continue
 			}
 			packetBuffer := packetBuffers[i]
-			packet := packetBuffer[frontHeadroom : frontHeadroom+packetSize]
+			packet := packetBuffer[m.frontHeadroom : m.frontHeadroom+packetSize]
 			if m.processPacket(packet) {
-				writeBuffers = append(writeBuffers, packetBuffer[:frontHeadroom+packetSize])
+				writeBuffers = append(writeBuffers, packetBuffer[:m.frontHeadroom+packetSize])
 			}
 		}
 		if len(writeBuffers) > 0 {
-			err = linuxTUN.BatchWrite(writeBuffers, frontHeadroom)
+			err = linuxTUN.BatchWrite(writeBuffers, m.frontHeadroom)
 			if err != nil {
 				m.logger.Trace(E.Cause(err, "batch write packet"))
 			}

stack_system.go

@@ -41,6 +41,8 @@ type System struct {
 	udpNat             *udpnat.Service[netip.AddrPort]
 	bindInterface      bool
 	interfaceFinder    control.InterfaceFinder
+	frontHeadroom      int
+	txChecksumOffload  bool
 }
 
 type Session struct {
@@ -144,17 +146,18 @@ func (s *System) tunLoop() {
 		s.wintunLoop(winTun)
 		return
 	}
-	if batchTUN, isBatchTUN := s.tun.(BatchTUN); isBatchTUN {
-		batchSize := batchTUN.BatchSize()
+	if linuxTUN, isLinuxTUN := s.tun.(LinuxTUN); isLinuxTUN {
+		s.frontHeadroom = linuxTUN.FrontHeadroom()
+		s.txChecksumOffload = linuxTUN.TXChecksumOffload()
+		batchSize := linuxTUN.BatchSize()
 		if batchSize > 1 {
-			s.batchLoop(batchTUN, batchSize)
+			s.batchLoop(linuxTUN, batchSize)
 			return
 		}
 	}
-	frontHeadroom := s.tun.FrontHeadroom()
-	packetBuffer := make([]byte, s.mtu+frontHeadroom+PacketOffset)
+	packetBuffer := make([]byte, s.mtu+PacketOffset)
 	for {
-		n, err := s.tun.Read(packetBuffer[frontHeadroom:])
+		n, err := s.tun.Read(packetBuffer)
 		if err != nil {
 			if E.IsClosed(err) {
 				return
@@ -164,8 +167,8 @@ func (s *System) tunLoop() {
 		if n < clashtcpip.IPv4PacketMinLength {
 			continue
 		}
-		rawPacket := packetBuffer[:frontHeadroom+n]
-		packet := packetBuffer[frontHeadroom+PacketOffset : frontHeadroom+n]
+		rawPacket := packetBuffer[:n]
+		packet := packetBuffer[PacketOffset:n]
 		if s.processPacket(packet) {
 			_, err = s.tun.Write(rawPacket)
 			if err != nil {
@@ -195,16 +198,15 @@ func (s *System) wintunLoop(winTun WinTun) {
 	}
 }
 
-func (s *System) batchLoop(linuxTUN BatchTUN, batchSize int) {
-	frontHeadroom := s.tun.FrontHeadroom()
+func (s *System) batchLoop(linuxTUN LinuxTUN, batchSize int) {
 	packetBuffers := make([][]byte, batchSize)
 	writeBuffers := make([][]byte, batchSize)
 	packetSizes := make([]int, batchSize)
 	for i := range packetBuffers {
-		packetBuffers[i] = make([]byte, s.mtu+frontHeadroom)
+		packetBuffers[i] = make([]byte, s.mtu+s.frontHeadroom)
 	}
 	for {
-		n, err := linuxTUN.BatchRead(packetBuffers, frontHeadroom, packetSizes)
+		n, err := linuxTUN.BatchRead(packetBuffers, s.frontHeadroom, packetSizes)
 		if err != nil {
 			if E.IsClosed(err) {
 				return
@@ -220,13 +222,13 @@ func (s *System) batchLoop(linuxTUN BatchTUN, batchSize int) {
 				continue
 			}
 			packetBuffer := packetBuffers[i]
-			packet := packetBuffer[frontHeadroom : frontHeadroom+packetSize]
+			packet := packetBuffer[s.frontHeadroom : s.frontHeadroom+packetSize]
 			if s.processPacket(packet) {
-				writeBuffers = append(writeBuffers, packetBuffer[:frontHeadroom+packetSize])
+				writeBuffers = append(writeBuffers, packetBuffer[:s.frontHeadroom+packetSize])
 			}
 		}
 		if len(writeBuffers) > 0 {
-			err = linuxTUN.BatchWrite(writeBuffers, frontHeadroom)
+			err = linuxTUN.BatchWrite(writeBuffers, s.frontHeadroom)
 			if err != nil {
 				s.logger.Trace(E.Cause(err, "batch write packet"))
 			}
@@ -352,8 +354,13 @@ func (s *System) processIPv4TCP(packet clashtcpip.IPv4Packet, header clashtcpip.
 		packet.SetDestinationIP(s.inet4ServerAddress)
 		header.SetDestinationPort(s.tcpPort)
 	}
-	header.ResetChecksum(packet.PseudoSum())
-	packet.ResetChecksum()
+	if !s.txChecksumOffload {
+		header.ResetChecksum(packet.PseudoSum())
+		packet.ResetChecksum()
+	} else {
+		header.OffloadChecksum()
+		packet.ResetChecksum()
+	}
 	return nil
 }
 
@@ -378,8 +385,11 @@ func (s *System) processIPv6TCP(packet clashtcpip.IPv6Packet, header clashtcpip.
 		packet.SetDestinationIP(s.inet6ServerAddress)
 		header.SetDestinationPort(s.tcpPort6)
 	}
-	header.ResetChecksum(packet.PseudoSum())
-	packet.ResetChecksum()
+	if !s.txChecksumOffload {
+		header.ResetChecksum(packet.PseudoSum())
+	} else {
+		header.OffloadChecksum()
+	}
 	return nil
 }
 
@@ -410,7 +420,13 @@ func (s *System) processIPv4UDP(packet clashtcpip.IPv4Packet, header clashtcpip.
 		headerLen := packet.HeaderLen() + clashtcpip.UDPHeaderSize
 		headerCopy := make([]byte, headerLen)
 		copy(headerCopy, packet[:headerLen])
-		return &systemUDPPacketWriter4{s.tun, s.tun.FrontHeadroom() + PacketOffset, headerCopy, source}
+		return &systemUDPPacketWriter4{
+			s.tun,
+			s.frontHeadroom + PacketOffset,
+			headerCopy,
+			source,
+			s.txChecksumOffload,
+		}
 	})
 	return nil
 }
@@ -436,7 +452,13 @@ func (s *System) processIPv6UDP(packet clashtcpip.IPv6Packet, header clashtcpip.
 		headerLen := len(packet) - int(header.Length()) + clashtcpip.UDPHeaderSize
 		headerCopy := make([]byte, headerLen)
 		copy(headerCopy, packet[:headerLen])
-		return &systemUDPPacketWriter6{s.tun, s.tun.FrontHeadroom() + PacketOffset, headerCopy, source}
+		return &systemUDPPacketWriter6{
+			s.tun,
+			s.frontHeadroom + PacketOffset,
+			headerCopy,
+			source,
+			s.txChecksumOffload,
+		}
 	})
 	return nil
 }
@@ -468,10 +490,11 @@ func (s *System) processIPv6ICMP(packet clashtcpip.IPv6Packet, header clashtcpip
 }
 
 type systemUDPPacketWriter4 struct {
-	tun           Tun
-	frontHeadroom int
-	header        []byte
-	source        netip.AddrPort
+	tun               Tun
+	frontHeadroom     int
+	header            []byte
+	source            netip.AddrPort
+	txChecksumOffload bool
 }
 
 func (w *systemUDPPacketWriter4) WritePacket(buffer *buf.Buffer, destination M.Socksaddr) error {
@@ -488,8 +511,13 @@ func (w *systemUDPPacketWriter4) WritePacket(buffer *buf.Buffer, destination M.S
 	udpHdr.SetDestinationPort(udpHdr.SourcePort())
 	udpHdr.SetSourcePort(destination.Port)
 	udpHdr.SetLength(uint16(buffer.Len() + clashtcpip.UDPHeaderSize))
-	udpHdr.ResetChecksum(ipHdr.PseudoSum())
-	ipHdr.ResetChecksum()
+	if !w.txChecksumOffload {
+		udpHdr.ResetChecksum(ipHdr.PseudoSum())
+		ipHdr.ResetChecksum()
+	} else {
+		udpHdr.OffloadChecksum()
+		ipHdr.ResetChecksum()
+	}
 	if PacketOffset > 0 {
 		newPacket.ExtendHeader(PacketOffset)[3] = syscall.AF_INET
 	} else {
@@ -499,10 +527,11 @@ func (w *systemUDPPacketWriter4) WritePacket(buffer *buf.Buffer, destination M.S
 }
 
 type systemUDPPacketWriter6 struct {
-	tun           Tun
-	frontHeadroom int
-	header        []byte
-	source        netip.AddrPort
+	tun               Tun
+	frontHeadroom     int
+	header            []byte
+	source            netip.AddrPort
+	txChecksumOffload bool
 }
 
 func (w *systemUDPPacketWriter6) WritePacket(buffer *buf.Buffer, destination M.Socksaddr) error {
@@ -520,7 +549,11 @@ func (w *systemUDPPacketWriter6) WritePacket(buffer *buf.Buffer, destination M.S
 	udpHdr.SetDestinationPort(udpHdr.SourcePort())
 	udpHdr.SetSourcePort(destination.Port)
 	udpHdr.SetLength(udpLen)
-	udpHdr.ResetChecksum(ipHdr.PseudoSum())
+	if !w.txChecksumOffload {
+		udpHdr.ResetChecksum(ipHdr.PseudoSum())
+	} else {
+		udpHdr.OffloadChecksum()
+	}
 	if PacketOffset > 0 {
 		newPacket.ExtendHeader(PacketOffset)[3] = syscall.AF_INET6
 	} else {

tun.go

@@ -24,7 +24,6 @@ type Handler interface {
 type Tun interface {
 	io.ReadWriter
 	N.VectorisedWriter
-	N.FrontHeadroom
 	Close() error
 }
 
@@ -33,11 +32,13 @@ type WinTun interface {
 	ReadPacket() ([]byte, func(), error)
 }
 
-type BatchTUN interface {
+type LinuxTUN interface {
 	Tun
+	N.FrontHeadroom
 	BatchSize() int
 	BatchRead(buffers [][]byte, offset int, readN []int) (n int, err error)
 	BatchWrite(buffers [][]byte, offset int) error
+	TXChecksumOffload() bool
 }
 
 type Options struct {
@@ -63,6 +64,9 @@ type Options struct {
 	TableIndex               int
 	FileDescriptor           int
 	Logger                   logger.Logger
+
+	// No work for TCP, do not use.
+	_TXChecksumOffload bool
 }
 
 func CalculateInterfaceName(name string) (tunName string) {

tun_darwin.go

@@ -5,7 +5,6 @@ import (
 	"net"
 	"net/netip"
 	"os"
-	"runtime"
 	"syscall"
 	"unsafe"
 
@@ -68,14 +67,9 @@ func New(options Options) (Tun, error) {
 	if !ok {
 		panic("create vectorised writer")
 	}
-	runtime.SetFinalizer(nativeTun.tunFile, nil)
 	return nativeTun, nil
 }
 
-func (t *NativeTun) FrontHeadroom() int {
-	return 0
-}
-
 func (t *NativeTun) Read(p []byte) (n int, err error) {
 	return t.tunFile.Read(p)
 }