add shadowsocks2022 udp client support

proxy/shadowsocks2022/client.go

@@ -4,13 +4,19 @@ import (
 	"context"
 	"github.com/v2fly/v2ray-core/v5/common"
 	"github.com/v2fly/v2ray-core/v5/common/buf"
+	"github.com/v2fly/v2ray-core/v5/common/environment"
+	"github.com/v2fly/v2ray-core/v5/common/environment/envctx"
 	"github.com/v2fly/v2ray-core/v5/common/net"
+	"github.com/v2fly/v2ray-core/v5/common/net/packetaddr"
 	"github.com/v2fly/v2ray-core/v5/common/retry"
 	"github.com/v2fly/v2ray-core/v5/common/session"
 	"github.com/v2fly/v2ray-core/v5/common/signal"
 	"github.com/v2fly/v2ray-core/v5/common/task"
 	"github.com/v2fly/v2ray-core/v5/transport"
 	"github.com/v2fly/v2ray-core/v5/transport/internet"
+	"github.com/v2fly/v2ray-core/v5/transport/internet/udp"
+	gonet "net"
+	"sync"
 	"time"
 )
 
@@ -19,6 +25,33 @@ type Client struct {
 	ctx    context.Context
 }
 
+const UDPConnectionState = "UDPConnectionState"
+
+type ClientUDPConnState struct {
+	session  *ClientUDPSession
+	initOnce *sync.Once
+}
+
+func (c *ClientUDPConnState) GetOrCreateSession(create func() (*ClientUDPSession, error)) (*ClientUDPSession, error) {
+	var err error
+	c.initOnce.Do(func() {
+		sessionState, err := create()
+		if err != nil {
+			err = newError("failed to create UDP session").Base(err)
+			return
+		}
+		c.session = sessionState
+	})
+	if err != nil {
+		return nil, newError("failed to initialize UDP State").Base(err)
+	}
+	return c.session, nil
+}
+
+func NewClientUDPConnState() (*ClientUDPConnState, error) {
+	return &ClientUDPConnState{initOnce: &sync.Once{}}, nil
+}
+
 func (c *Client) Process(ctx context.Context, link *transport.Link, dialer internet.Dialer) error {
 	outbound := session.OutboundFromContext(ctx)
 	if outbound == nil || !outbound.Target.IsValid() {
@@ -27,25 +60,6 @@ func (c *Client) Process(ctx context.Context, link *transport.Link, dialer inter
 	destination := outbound.Target
 	network := destination.Network
 
-	var conn internet.Connection
-
-	err := retry.ExponentialBackoff(5, 100).On(func() error {
-		dest := net.TCPDestination(c.config.Address.AsAddress(), net.Port(c.config.Port))
-		dest.Network = network
-		rawConn, err := dialer.Dial(ctx, dest)
-		if err != nil {
-			return err
-		}
-		conn = rawConn
-
-		return nil
-	})
-	if err != nil {
-		return newError("failed to find an available destination").AtWarning().Base(err)
-	}
-	newError("tunneling request to ", destination, " via ", network, ":", c.config.Address).WriteToLog(session.ExportIDToError(ctx))
-	defer conn.Close()
-
 	var keyDerivation = newBLAKE3KeyDerivation()
 	var method Method
 	switch c.config.Method {
@@ -62,7 +76,44 @@ func (c *Client) Process(ctx context.Context, link *transport.Link, dialer inter
 	ctx, cancel := context.WithCancel(ctx)
 	timer := signal.CancelAfterInactivity(ctx, cancel, time.Minute)
 
+	if packetConn, err := packetaddr.ToPacketAddrConn(link, destination); err == nil {
+		udpSession, err := c.getUDPSession(c.ctx, network, dialer, method, keyDerivation)
+		if err != nil {
+			return newError("failed to get UDP udpSession").Base(err)
+		}
+		requestDone := func() error {
+			return udp.CopyPacketConn(udpSession, packetConn, udp.UpdateActivity(timer))
+		}
+		responseDone := func() error {
+			return udp.CopyPacketConn(packetConn, udpSession, udp.UpdateActivity(timer))
+		}
+		responseDoneAndCloseWriter := task.OnSuccess(responseDone, task.Close(link.Writer))
+		if err := task.Run(ctx, requestDone, responseDoneAndCloseWriter); err != nil {
+			return newError("connection ends").Base(err)
+		}
+		return nil
+	}
+
 	if network == net.Network_TCP {
+		var conn internet.Connection
+		err := retry.ExponentialBackoff(5, 100).On(func() error {
+			dest := net.TCPDestination(c.config.Address.AsAddress(), net.Port(c.config.Port))
+			dest.Network = network
+			rawConn, err := dialer.Dial(ctx, dest)
+			if err != nil {
+				return err
+			}
+			conn = rawConn
+
+			return nil
+		})
+
+		if err != nil {
+			return newError("failed to find an available destination").AtWarning().Base(err)
+		}
+		newError("tunneling request to ", destination, " via ", network, ":", c.config.Address).WriteToLog(session.ExportIDToError(ctx))
+		defer conn.Close()
+
 		request := &TCPRequest{
 			keyDerivation: keyDerivation,
 			method:        method,
@@ -107,11 +158,79 @@ func (c *Client) Process(ctx context.Context, link *transport.Link, dialer inter
 		}
 		return nil
 	} else {
-		return newError("not implemented")
+		udpSession, err := c.getUDPSession(c.ctx, network, dialer, method, keyDerivation)
+		if err != nil {
+			return newError("failed to get UDP udpSession").Base(err)
+		}
+		monoDestUDPConn := udp.NewMonoDestUDPConn(udpSession, &gonet.UDPAddr{IP: destination.Address.IP(), Port: int(destination.Port)})
+		requestDone := func() error {
+			return buf.Copy(link.Reader, monoDestUDPConn, buf.UpdateActivity(timer))
+		}
+		responseDone := func() error {
+			return buf.Copy(monoDestUDPConn, link.Writer, buf.UpdateActivity(timer))
+		}
+		responseDoneAndCloseWriter := task.OnSuccess(responseDone, task.Close(link.Writer))
+		if err := task.Run(ctx, requestDone, responseDoneAndCloseWriter); err != nil {
+			return newError("connection ends").Base(err)
+		}
+		return nil
 	}
 }
 
+func (c *Client) getUDPSession(ctx context.Context, network net.Network, dialer internet.Dialer, method Method, keyDerivation *BLAKE3KeyDerivation) (internet.AbstractPacketConn, error) {
+	storage := envctx.EnvironmentFromContext(ctx).(environment.ProxyEnvironment).TransientStorage()
+	clientUDPStateIfce, err := storage.Get(ctx, UDPConnectionState)
+	if err != nil {
+		return nil, newError("failed to get UDP connection state").Base(err)
+	}
+	clientUDPState, ok := clientUDPStateIfce.(*ClientUDPConnState)
+	if !ok {
+		return nil, newError("failed to cast UDP connection state")
+	}
+
+	sessionState, err := clientUDPState.GetOrCreateSession(func() (*ClientUDPSession, error) {
+		var conn internet.Connection
+		err := retry.ExponentialBackoff(5, 100).On(func() error {
+			dest := net.TCPDestination(c.config.Address.AsAddress(), net.Port(c.config.Port))
+			dest.Network = network
+			rawConn, err := dialer.Dial(ctx, dest)
+			if err != nil {
+				return err
+			}
+			conn = rawConn
+
+			return nil
+		})
+		if err != nil {
+			return nil, newError("failed to find an available destination").AtWarning().Base(err)
+		}
+		newError("creating udp session to ", network, ":", c.config.Address).WriteToLog(session.ExportIDToError(ctx))
+		packetProcessor, err := method.GetUDPClientProcessor(c.config.Ipsk, c.config.Psk, keyDerivation)
+		if err != nil {
+			return nil, newError("failed to create UDP client packet processor").Base(err)
+		}
+		return NewClientUDPSession(ctx, conn, packetProcessor), nil
+	})
+	if err != nil {
+		return nil, newError("failed to create UDP session").Base(err)
+	}
+	sessionConn, err := sessionState.NewSessionConn()
+	if err != nil {
+		return nil, newError("failed to create UDP session connection").Base(err)
+	}
+	return sessionConn, nil
+}
+
 func NewClient(ctx context.Context, config *ClientConfig) (*Client, error) {
+
+	storage := envctx.EnvironmentFromContext(ctx).(environment.ProxyEnvironment).TransientStorage()
+
+	udpState, err := NewClientUDPConnState()
+	if err != nil {
+		return nil, newError("failed to create UDP connection state").Base(err)
+	}
+	storage.Put(ctx, UDPConnectionState, udpState)
+
 	return &Client{
 		config: config,
 		ctx:    ctx,

proxy/shadowsocks2022/client_session.go

@@ -0,0 +1,162 @@
+package shadowsocks2022
+
+import (
+	"context"
+	"crypto/rand"
+	"github.com/v2fly/v2ray-core/v5/common/buf"
+	"github.com/v2fly/v2ray-core/v5/common/net"
+	"github.com/v2fly/v2ray-core/v5/transport/internet"
+	"io"
+	gonet "net"
+	"sync"
+	"time"
+)
+
+func NewClientUDPSession(ctx context.Context, conn io.ReadWriteCloser, packetProcessor UDPClientPacketProcessor) *ClientUDPSession {
+	session := &ClientUDPSession{
+		locker:          &sync.Mutex{},
+		conn:            conn,
+		packetProcessor: packetProcessor,
+		sessionMap:      make(map[string]*ClientUDPSessionConn),
+	}
+	session.ctx, session.finish = context.WithCancel(ctx)
+
+	go session.KeepReading()
+	return session
+}
+
+type ClientUDPSession struct {
+	locker *sync.Mutex
+
+	conn            io.ReadWriteCloser
+	packetProcessor UDPClientPacketProcessor
+	sessionMap      map[string]*ClientUDPSessionConn
+
+	ctx    context.Context
+	finish func()
+}
+
+func (c *ClientUDPSession) Close() error {
+	c.finish()
+	return c.conn.Close()
+}
+
+func (c *ClientUDPSession) WriteUDPRequest(request *UDPRequest) error {
+	buffer := buf.New()
+	defer buffer.Release()
+	err := c.packetProcessor.EncodeUDPRequest(request, buffer)
+	if request.Payload != nil {
+		request.Payload.Release()
+	}
+	if err != nil {
+		return newError("unable to encode udp request").Base(err)
+	}
+	_, err = c.conn.Write(buffer.Bytes())
+	if err != nil {
+		return newError("unable to write to conn").Base(err)
+	}
+	return nil
+}
+
+func (c *ClientUDPSession) KeepReading() {
+	for c.ctx.Err() == nil {
+		udpResp := &UDPResponse{}
+		buffer := make([]byte, 1600)
+		n, err := c.conn.Read(buffer)
+		if err != nil {
+			newError("unable to read from conn").Base(err).WriteToLog()
+			return
+		}
+		if n != 0 {
+			err := c.packetProcessor.DecodeUDPResp(buffer[:n], udpResp)
+			if err != nil {
+				newError("unable to decode udp response").Base(err).WriteToLog()
+				continue
+			}
+			c.locker.Lock()
+			session, ok := c.sessionMap[string(udpResp.ClientSessionID[:])]
+			if ok {
+				select {
+				case session.readChan <- udpResp:
+				default:
+				}
+			} else {
+				newError("misbehaving server: unknown client session ID").Base(err).WriteToLog()
+			}
+			c.locker.Unlock()
+		}
+	}
+}
+
+func (c *ClientUDPSession) NewSessionConn() (internet.AbstractPacketConn, error) {
+	sessionID := make([]byte, 8)
+	_, err := rand.Read(sessionID)
+	if err != nil {
+		return nil, newError("unable to generate session id").Base(err)
+	}
+
+	connctx, connfinish := context.WithCancel(c.ctx)
+
+	sessionConn := &ClientUDPSessionConn{
+		sessionID:         string(sessionID),
+		readChan:          make(chan *UDPResponse, 16),
+		parent:            c,
+		ctx:               connctx,
+		finish:            connfinish,
+		nextWritePacketID: 0,
+	}
+	c.locker.Lock()
+	c.sessionMap[sessionConn.sessionID] = sessionConn
+	c.locker.Unlock()
+	return sessionConn, nil
+}
+
+type ClientUDPSessionConn struct {
+	sessionID string
+	readChan  chan *UDPResponse
+	parent    *ClientUDPSession
+
+	nextWritePacketID uint64
+
+	ctx    context.Context
+	finish func()
+}
+
+func (c *ClientUDPSessionConn) Close() error {
+	delete(c.parent.sessionMap, c.sessionID)
+	c.finish()
+	return nil
+}
+
+func (c *ClientUDPSessionConn) WriteTo(p []byte, addr gonet.Addr) (n int, err error) {
+	thisPacketID := c.nextWritePacketID
+	c.nextWritePacketID += 1
+	req := &UDPRequest{
+		SessionID: [8]byte{},
+		PacketID:  thisPacketID,
+		TimeStamp: uint64(time.Now().Unix()),
+		Address:   net.IPAddress(addr.(*gonet.UDPAddr).IP),
+		Port:      addr.(*net.UDPAddr).Port,
+		Payload:   nil,
+	}
+	copy(req.SessionID[:], c.sessionID)
+	req.Payload = buf.New()
+	req.Payload.Write(p)
+	err = c.parent.WriteUDPRequest(req)
+	if err != nil {
+		return 0, newError("unable to write to parent session").Base(err)
+	}
+	return len(p), nil
+}
+
+func (c *ClientUDPSessionConn) ReadFrom(p []byte) (n int, addr net.Addr, err error) {
+	select {
+	case <-c.ctx.Done():
+		return 0, nil, io.EOF
+	case resp := <-c.readChan:
+		n = copy(p, resp.Payload.Bytes())
+		resp.Payload.Release()
+		addr = &net.UDPAddr{IP: resp.Address.IP(), Port: int(resp.Port)}
+	}
+	return
+}

proxy/shadowsocks2022/eih_aes.go

@@ -1,6 +1,7 @@
 package shadowsocks2022
 
 import (
+	"crypto/subtle"
 	"github.com/lunixbochs/struc"
 	"github.com/v2fly/v2ray-core/v5/common/buf"
 	"io"
@@ -78,18 +79,33 @@ func newAESEIHGeneratorContainer(size int, effectivePsk []byte, ipsk [][]byte) *
 }
 
 func (a *aesEIHGenerator) GenerateEIH(derivation KeyDerivation, method Method, salt []byte) (ExtensibleIdentityHeaders, error) {
+	return a.generateEIHWithMask(derivation, method, salt, nil)
+}
+
+func (a *aesEIHGenerator) GenerateEIHUDP(derivation KeyDerivation, method Method, mask []byte) (ExtensibleIdentityHeaders, error) {
+	return a.generateEIHWithMask(derivation, method, nil, mask)
+}
+
+func (a *aesEIHGenerator) generateEIHWithMask(derivation KeyDerivation, method Method, salt, mask []byte) (ExtensibleIdentityHeaders, error) {
 	eih := make([][16]byte, a.length)
 	current := a.length - 1
 	currentPskHash := a.pskHash
 	for {
 		identityKeyBuf := buf.New()
 		identityKey := identityKeyBuf.Extend(int32(method.GetSessionSubKeyAndSaltLength()))
-		err := derivation.GetIdentitySubKey(a.ipsk[current], salt, identityKey)
-		if err != nil {
-			return nil, newError("failed to get identity sub key").Base(err)
+		if mask == nil {
+			err := derivation.GetIdentitySubKey(a.ipsk[current], salt, identityKey)
+			if err != nil {
+				return nil, newError("failed to get identity sub key").Base(err)
+			}
+		} else {
+			copy(identityKey, a.ipsk[current])
 		}
 		eih[current] = [16]byte{}
-		err = method.GenerateEIH(identityKey, currentPskHash[:], eih[current][:])
+		if mask != nil {
+			subtle.XORBytes(currentPskHash[:], mask, currentPskHash[:])
+		}
+		err := method.GenerateEIH(identityKey, currentPskHash[:], eih[current][:])
 		if err != nil {
 			return nil, newError("failed to generate EIH").Base(err)
 		}

proxy/shadowsocks2022/method_aes128gcm.go

@@ -36,3 +36,37 @@ func (A AES128GCMMethod) GenerateEIH(CurrentIdentitySubKey []byte, nextPskHash [
 	aesCipher.Encrypt(out, nextPskHash)
 	return nil
 }
+
+func (A AES128GCMMethod) GetUDPClientProcessor(ipsk [][]byte, psk []byte, derivation KeyDerivation) (UDPClientPacketProcessor, error) {
+	reqSeparateHeaderPsk := psk
+	if ipsk != nil {
+		reqSeparateHeaderPsk = ipsk[0]
+	}
+	reqSeparateHeaderCipher, err := aes.NewCipher(reqSeparateHeaderPsk)
+	if err != nil {
+		return nil, newError("failed to create AES cipher").Base(err)
+	}
+	respSeparateHeaderCipher, err := aes.NewCipher(psk)
+	if err != nil {
+		return nil, newError("failed to create AES cipher").Base(err)
+	}
+	getPacketAEAD := func(sessionID []byte) cipher.AEAD {
+		sessionKey := make([]byte, A.GetSessionSubKeyAndSaltLength())
+		derivation.GetSessionSubKey(psk, sessionID, sessionKey)
+		block, err := aes.NewCipher(sessionKey)
+		aead, err := cipher.NewGCM(block)
+		if err != nil {
+			panic(err)
+		}
+		return aead
+	}
+	eihGenerator := newAESEIHGeneratorContainer(len(ipsk), psk, ipsk)
+	getEIH := func(mask []byte) ExtensibleIdentityHeaders {
+		eih, err := eihGenerator.GenerateEIHUDP(derivation, A, mask)
+		if err != nil {
+			newError("failed to generate EIH").Base(err).WriteToLog()
+		}
+		return eih
+	}
+	return NewAESUDPClientPacketProcessor(reqSeparateHeaderCipher, respSeparateHeaderCipher, getPacketAEAD, getEIH), nil
+}

proxy/shadowsocks2022/method_aes256gcm.go

@@ -36,3 +36,37 @@ func (A AES256GCMMethod) GenerateEIH(CurrentIdentitySubKey []byte, nextPskHash [
 	aesCipher.Encrypt(out, nextPskHash)
 	return nil
 }
+
+func (A AES256GCMMethod) GetUDPClientProcessor(ipsk [][]byte, psk []byte, derivation KeyDerivation) (UDPClientPacketProcessor, error) {
+	reqSeparateHeaderPsk := psk
+	if ipsk != nil {
+		reqSeparateHeaderPsk = ipsk[0]
+	}
+	reqSeparateHeaderCipher, err := aes.NewCipher(reqSeparateHeaderPsk)
+	if err != nil {
+		return nil, newError("failed to create AES cipher").Base(err)
+	}
+	respSeparateHeaderCipher, err := aes.NewCipher(psk)
+	if err != nil {
+		return nil, newError("failed to create AES cipher").Base(err)
+	}
+	getPacketAEAD := func(sessionID []byte) cipher.AEAD {
+		sessionKey := make([]byte, A.GetSessionSubKeyAndSaltLength())
+		derivation.GetSessionSubKey(psk, sessionID, sessionKey)
+		block, err := aes.NewCipher(sessionKey)
+		aead, err := cipher.NewGCM(block)
+		if err != nil {
+			panic(err)
+		}
+		return aead
+	}
+	eihGenerator := newAESEIHGeneratorContainer(len(ipsk), psk, ipsk)
+	getEIH := func(mask []byte) ExtensibleIdentityHeaders {
+		eih, err := eihGenerator.GenerateEIHUDP(derivation, A, mask)
+		if err != nil {
+			newError("failed to generate EIH").Base(err).WriteToLog()
+		}
+		return eih
+	}
+	return NewAESUDPClientPacketProcessor(reqSeparateHeaderCipher, respSeparateHeaderCipher, getPacketAEAD, getEIH), nil
+}

proxy/shadowsocks2022/ss2022.go

@@ -3,6 +3,7 @@ package shadowsocks2022
 import (
 	"crypto/cipher"
 	"github.com/lunixbochs/struc"
+	"github.com/v2fly/v2ray-core/v5/common/buf"
 	"github.com/v2fly/v2ray-core/v5/common/net"
 	"github.com/v2fly/v2ray-core/v5/common/protocol"
 	"io"
@@ -19,6 +20,7 @@ type Method interface {
 	GetSessionSubKeyAndSaltLength() int
 	GetStreamAEAD(SessionSubKey []byte) (cipher.AEAD, error)
 	GenerateEIH(CurrentIdentitySubKey []byte, nextPskHash []byte, out []byte) error
+	GetUDPClientProcessor(ipsk [][]byte, psk []byte, derivation KeyDerivation) (UDPClientPacketProcessor, error)
 }
 
 type ExtensibleIdentityHeaders interface {
@@ -86,3 +88,27 @@ var addrParser = protocol.NewAddressParser(
 	protocol.AddressFamilyByte(0x04, net.AddressFamilyIPv6),
 	protocol.AddressFamilyByte(0x03, net.AddressFamilyDomain),
 )
+
+type UDPRequest struct {
+	SessionID [8]byte
+	PacketID  uint64
+	TimeStamp uint64
+	Address   DestinationAddress
+	Port      int
+	Payload   *buf.Buffer
+}
+
+type UDPResponse struct {
+	UDPRequest
+	ClientSessionID [8]byte
+}
+
+const UDPHeaderTypeClientToServerStream = byte(0x00)
+const UDPHeaderTypeServerToClientStream = byte(0x01)
+
+// UDPClientPacketProcessor
+// Caller retain and receive all ownership of the buffer
+type UDPClientPacketProcessor interface {
+	EncodeUDPRequest(request *UDPRequest, out *buf.Buffer) error
+	DecodeUDPResp(input []byte, resp *UDPResponse) error
+}

proxy/shadowsocks2022/udp_aes.go

@@ -0,0 +1,157 @@
+package shadowsocks2022
+
+import (
+	"bytes"
+	"crypto/cipher"
+	"github.com/lunixbochs/struc"
+	"github.com/v2fly/v2ray-core/v5/common/buf"
+	"github.com/v2fly/v2ray-core/v5/common/net"
+	"io"
+)
+
+type AESUDPClientPacketProcessor struct {
+	requestSeparateHeaderBlockCipher  cipher.Block
+	responseSeparateHeaderBlockCipher cipher.Block
+	mainPacketAEAD                    func([]byte) cipher.AEAD
+	EIHGenerator                      func([]byte) ExtensibleIdentityHeaders
+}
+
+func NewAESUDPClientPacketProcessor(requestSeparateHeaderBlockCipher, responseSeparateHeaderBlockCipher cipher.Block, mainPacketAEAD func([]byte) cipher.AEAD, eih func([]byte) ExtensibleIdentityHeaders) *AESUDPClientPacketProcessor {
+	return &AESUDPClientPacketProcessor{
+		requestSeparateHeaderBlockCipher:  requestSeparateHeaderBlockCipher,
+		responseSeparateHeaderBlockCipher: responseSeparateHeaderBlockCipher,
+		mainPacketAEAD:                    mainPacketAEAD,
+		EIHGenerator:                      eih,
+	}
+}
+
+type separateHeader struct {
+	SessionID [8]byte
+	PacketID  uint64
+}
+
+type header struct {
+	Type          byte
+	TimeStamp     uint64
+	PaddingLength uint16 `struc:"sizeof=Padding"`
+	Padding       []byte
+}
+
+type respHeader struct {
+	Type            byte
+	TimeStamp       uint64
+	ClientSessionID [8]byte
+	PaddingLength   uint16 `struc:"sizeof=Padding"`
+	Padding         []byte
+}
+
+func (p *AESUDPClientPacketProcessor) EncodeUDPRequest(request *UDPRequest, out *buf.Buffer) error {
+	separateHeaderStruct := separateHeader{PacketID: request.PacketID, SessionID: request.SessionID}
+	separateHeaderBuffer := buf.New()
+	defer separateHeaderBuffer.Release()
+	{
+		err := struc.Pack(separateHeaderBuffer, &separateHeaderStruct)
+		if err != nil {
+			return newError("failed to pack separateHeader").Base(err)
+		}
+	}
+	separateHeaderBufferBytes := separateHeaderBuffer.Bytes()
+	{
+		encryptedDest := out.Extend(16)
+		p.requestSeparateHeaderBlockCipher.Encrypt(encryptedDest, separateHeaderBufferBytes)
+	}
+
+	if p.EIHGenerator != nil {
+		eih := p.EIHGenerator(separateHeaderBufferBytes[0:16])
+		eihHeader := struct {
+			EIH ExtensibleIdentityHeaders
+		}{
+			EIH: eih,
+		}
+		err := struc.Pack(out, &eihHeader)
+		if err != nil {
+			return newError("failed to pack eih").Base(err)
+		}
+	}
+
+	headerStruct := header{
+		Type:          UDPHeaderTypeClientToServerStream,
+		TimeStamp:     request.TimeStamp,
+		PaddingLength: 0,
+		Padding:       nil,
+	}
+	requestBodyBuffer := buf.New()
+	{
+		err := struc.Pack(requestBodyBuffer, &headerStruct)
+		if err != nil {
+			return newError("failed to header").Base(err)
+		}
+	}
+	{
+		err := addrParser.WriteAddressPort(requestBodyBuffer, request.Address, net.Port(request.Port))
+		if err != nil {
+			return newError("failed to write address port").Base(err)
+		}
+	}
+	{
+		_, err := io.Copy(requestBodyBuffer, bytes.NewReader(request.Payload.Bytes()))
+		if err != nil {
+			return newError("failed to copy payload").Base(err)
+		}
+	}
+	{
+		mainPacketAEADMaterialized := p.mainPacketAEAD(separateHeaderBufferBytes[0:8])
+		encryptedDest := out.Extend(int32(mainPacketAEADMaterialized.Overhead()) + requestBodyBuffer.Len())
+		mainPacketAEADMaterialized.Seal(encryptedDest[:0], separateHeaderBuffer.Bytes()[4:16], requestBodyBuffer.Bytes(), nil)
+	}
+	return nil
+}
+
+func (p *AESUDPClientPacketProcessor) DecodeUDPResp(input []byte, resp *UDPResponse) error {
+	separateHeaderBuffer := buf.New()
+	defer separateHeaderBuffer.Release()
+	{
+		encryptedDest := separateHeaderBuffer.Extend(16)
+		p.responseSeparateHeaderBlockCipher.Decrypt(encryptedDest, input)
+	}
+	separateHeaderStruct := separateHeader{}
+	{
+		err := struc.Unpack(separateHeaderBuffer, &separateHeaderStruct)
+		if err != nil {
+			return newError("failed to unpack separateHeader").Base(err)
+		}
+	}
+	resp.PacketID = separateHeaderStruct.PacketID
+	resp.SessionID = separateHeaderStruct.SessionID
+	{
+		mainPacketAEADMaterialized := p.mainPacketAEAD(separateHeaderBuffer.Bytes()[0:8])
+		decryptedDestBuffer := buf.New()
+		decryptedDest := decryptedDestBuffer.Extend(int32(len(input)) - 16 - int32(mainPacketAEADMaterialized.Overhead()))
+		_, err := mainPacketAEADMaterialized.Open(decryptedDest[:0], separateHeaderBuffer.Bytes()[4:16], input[16:], nil)
+		if err != nil {
+			return newError("failed to open main packet").Base(err)
+		}
+		decryptedDestReader := bytes.NewReader(decryptedDest)
+		headerStruct := respHeader{}
+		{
+			err := struc.Unpack(decryptedDestReader, &headerStruct)
+			if err != nil {
+				return newError("failed to unpack header").Base(err)
+			}
+		}
+		resp.TimeStamp = headerStruct.TimeStamp
+		var addressReaderBuf = buf.New()
+		defer addressReaderBuf.Release()
+		var port net.Port
+		resp.Address, port, err = addrParser.ReadAddressPort(addressReaderBuf, decryptedDestReader)
+		if err != nil {
+			return newError("failed to read address port").Base(err)
+		}
+		resp.Port = int(port)
+		readedLength := decryptedDestReader.Size() - int64(decryptedDestReader.Len())
+		decryptedDestBuffer.Advance(int32(readedLength))
+		resp.Payload = decryptedDestBuffer
+		resp.ClientSessionID = headerStruct.ClientSessionID
+		return nil
+	}
+}

transport/internet/udp/monodest.go

@@ -0,0 +1,51 @@
+package udp
+
+import (
+	"github.com/v2fly/v2ray-core/v5/common/buf"
+	"github.com/v2fly/v2ray-core/v5/common/net"
+	"github.com/v2fly/v2ray-core/v5/transport/internet"
+)
+
+func NewMonoDestUDPConn(conn internet.AbstractPacketConn, addr net.Addr) *MonoDestUDPConn {
+	return &MonoDestUDPConn{
+		AbstractPacketConn: conn,
+		dest:               addr,
+	}
+}
+
+type MonoDestUDPConn struct {
+	internet.AbstractPacketConn
+	dest net.Addr
+}
+
+func (m *MonoDestUDPConn) ReadMultiBuffer() (buf.MultiBuffer, error) {
+	buffer := buf.New()
+	buffer.Extend(2048)
+	nBytes, _, err := m.AbstractPacketConn.ReadFrom(buffer.Bytes())
+	if err != nil {
+		buffer.Release()
+		return nil, err
+	}
+	buffer.Resize(0, int32(nBytes))
+	return buf.MultiBuffer{buffer}, nil
+}
+
+func (m *MonoDestUDPConn) WriteMultiBuffer(buffer buf.MultiBuffer) error {
+	for _, b := range buffer {
+		_, err := m.AbstractPacketConn.WriteTo(b.Bytes(), m.dest)
+		if err != nil {
+			return err
+		}
+	}
+	buf.ReleaseMulti(buffer)
+	return nil
+}
+
+func (m *MonoDestUDPConn) Read(p []byte) (n int, err error) {
+	n, _, err = m.AbstractPacketConn.ReadFrom(p)
+	return
+}
+
+func (m *MonoDestUDPConn) Write(p []byte) (n int, err error) {
+	return m.AbstractPacketConn.WriteTo(p, m.dest)
+}