chore: remove depend on lunixbochs/struc

go.mod

@@ -13,7 +13,6 @@ require (
 	github.com/gofrs/uuid/v5 v5.3.2
 	github.com/insomniacslk/dhcp v0.0.0-20250109001534-8abf58130905
 	github.com/klauspost/compress v1.17.9 // lastest version compatible with golang1.20
-	github.com/lunixbochs/struc v0.0.0-20200707160740-784aaebc1d40
 	github.com/mdlayher/netlink v1.7.2
 	github.com/metacubex/amneziawg-go v0.0.0-20240922133038-fdf3a4d5a4ab
 	github.com/metacubex/bart v0.20.5

go.sum

@@ -84,8 +84,6 @@ github.com/kr/text v0.2.0 h1:5Nx0Ya0ZqY2ygV366QzturHI13Jq95ApcVaJBhpS+AY=
 github.com/kr/text v0.2.0/go.mod h1:eLer722TekiGuMkidMxC/pM04lWEeraHUUmBw8l2grE=
 github.com/lufia/plan9stats v0.0.0-20211012122336-39d0f177ccd0 h1:6E+4a0GO5zZEnZ81pIr0yLvtUWk2if982qA3F3QD6H4=
 github.com/lufia/plan9stats v0.0.0-20211012122336-39d0f177ccd0/go.mod h1:zJYVVT2jmtg6P3p1VtQj7WsuWi/y4VnjVBn7F8KPB3I=
-github.com/lunixbochs/struc v0.0.0-20200707160740-784aaebc1d40 h1:EnfXoSqDfSNJv0VBNqY/88RNnhSGYkrHaO0mmFGbVsc=
-github.com/lunixbochs/struc v0.0.0-20200707160740-784aaebc1d40/go.mod h1:vy1vK6wD6j7xX6O6hXe621WabdtNkou2h7uRtTfRMyg=
 github.com/mailru/easyjson v0.7.7 h1:UGYAvKxe3sBsEDzO8ZeWOSlIQfWFlxbzLZe7hwFURr0=
 github.com/mailru/easyjson v0.7.7/go.mod h1:xzfreul335JAWq5oZzymOObrkdz5UnU4kGfJJLY9Nlc=
 github.com/mdlayher/netlink v1.7.2 h1:/UtM3ofJap7Vl4QWCPDGXY8d3GIY2UGSDbK+QWmY8/g=

transport/hysteria/core/client.go

@@ -1,7 +1,6 @@
 package core
 
 import (
-	"bytes"
 	"context"
 	"errors"
 	"fmt"
@@ -16,7 +15,6 @@ import (
 	"github.com/metacubex/mihomo/transport/hysteria/transport"
 	"github.com/metacubex/mihomo/transport/hysteria/utils"
 
-	"github.com/lunixbochs/struc"
 	"github.com/metacubex/quic-go"
 	"github.com/metacubex/quic-go/congestion"
 	"github.com/metacubex/randv2"
@@ -104,31 +102,23 @@ func (c *Client) connectToServer(dialer utils.PacketDialer) error {
 }
 
 func (c *Client) handleControlStream(qs *quic.Conn, stream *quic.Stream) (bool, string, error) {
-	// Send protocol version
-	_, err := stream.Write([]byte{protocolVersion})
-	if err != nil {
-		return false, "", err
-	}
 	// Send client hello
-	err = struc.Pack(stream, &clientHello{
+	err := WriteClientHello(stream, ClientHello{
-		Rate: transmissionRate{
+		SendBPS: c.sendBPS,
-			SendBPS: c.sendBPS,
+		RecvBPS: c.recvBPS,
-			RecvBPS: c.recvBPS,
+		Auth:    c.auth,
-		},
-		Auth: c.auth,
 	})
 	if err != nil {
 		return false, "", err
 	}
 	// Receive server hello
-	var sh serverHello
+	sh, err := ReadServerHello(stream)
-	err = struc.Unpack(stream, &sh)
 	if err != nil {
 		return false, "", err
 	}
 	// Set the congestion accordingly
 	if sh.OK && c.congestionFactory != nil {
-		qs.SetCongestionControl(c.congestionFactory(sh.Rate.RecvBPS))
+		qs.SetCongestionControl(c.congestionFactory(sh.RecvBPS))
 	}
 	return sh.OK, sh.Message, nil
 }
@@ -140,7 +130,7 @@ func (c *Client) handleMessage(qs *quic.Conn) {
 			break
 		}
 		var udpMsg udpMessage
-		err = struc.Unpack(bytes.NewBuffer(msg), &udpMsg)
+		err = udpMsg.Unpack(msg)
 		if err != nil {
 			continue
 		}
@@ -200,7 +190,7 @@ func (c *Client) DialTCP(host string, port uint16, dialer utils.PacketDialer) (n
 		return nil, err
 	}
 	// Send request
-	err = struc.Pack(stream, &clientRequest{
+	err = WriteClientRequest(stream, ClientRequest{
 		UDP:  false,
 		Host: host,
 		Port: port,
@@ -213,8 +203,8 @@ func (c *Client) DialTCP(host string, port uint16, dialer utils.PacketDialer) (n
 	// and defer the response handling to the first Read() call
 	if !c.fastOpen {
 		// Read response
-		var sr serverResponse
+		var sr *ServerResponse
-		err = struc.Unpack(stream, &sr)
+		sr, err = ReadServerResponse(stream)
 		if err != nil {
 			_ = stream.Close()
 			return nil, err
@@ -239,16 +229,16 @@ func (c *Client) DialUDP(dialer utils.PacketDialer) (UDPConn, error) {
 		return nil, err
 	}
 	// Send request
-	err = struc.Pack(stream, &clientRequest{
+	err = WriteClientRequest(stream, ClientRequest{
-		UDP: true,
+		UDP: false,
 	})
 	if err != nil {
 		_ = stream.Close()
 		return nil, err
 	}
 	// Read response
-	var sr serverResponse
+	var sr *ServerResponse
-	err = struc.Unpack(stream, &sr)
+	sr, err = ReadServerResponse(stream)
 	if err != nil {
 		_ = stream.Close()
 		return nil, err
@@ -306,8 +296,8 @@ type quicConn struct {
 
 func (w *quicConn) Read(b []byte) (n int, err error) {
 	if !w.Established {
-		var sr serverResponse
+		var sr *ServerResponse
-		err := struc.Unpack(w.Orig, &sr)
+		sr, err = ReadServerResponse(w.Orig)
 		if err != nil {
 			_ = w.Close()
 			return 0, err
@@ -401,9 +391,7 @@ func (c *quicPktConn) WriteTo(p []byte, addr string) error {
 		Data:      p,
 	}
 	// try no frag first
-	var msgBuf bytes.Buffer
+	err = c.Session.SendDatagram(msg.Pack())
-	_ = struc.Pack(&msgBuf, &msg)
-	err = c.Session.SendDatagram(msgBuf.Bytes())
 	if err != nil {
 		var errSize *quic.DatagramTooLargeError
 		if errors.As(err, &errSize) {
@@ -411,9 +399,7 @@ func (c *quicPktConn) WriteTo(p []byte, addr string) error {
 			msg.MsgID = uint16(randv2.IntN(0xFFFF)) + 1 // msgID must be > 0 when fragCount > 1
 			fragMsgs := fragUDPMessage(msg, int(errSize.MaxDatagramPayloadSize))
 			for _, fragMsg := range fragMsgs {
-				msgBuf.Reset()
+				err = c.Session.SendDatagram(fragMsg.Pack())
-				_ = struc.Pack(&msgBuf, &fragMsg)
-				err = c.Session.SendDatagram(msgBuf.Bytes())
 				if err != nil {
 					return err
 				}

transport/hysteria/core/frag.go

@@ -18,7 +18,6 @@ func fragUDPMessage(m udpMessage, maxSize int) []udpMessage {
 		frag := m
 		frag.FragID = fragID
 		frag.FragCount = fragCount
-		frag.DataLen = uint16(payloadSize)
 		frag.Data = fullPayload[off : off+payloadSize]
 		frags = append(frags, frag)
 		off += payloadSize
@@ -56,7 +55,6 @@ func (d *defragger) Feed(m udpMessage) *udpMessage {
 			for _, frag := range d.frags {
 				data = append(data, frag.Data...)
 			}
-			m.DataLen = uint16(len(data))
 			m.Data = data
 			m.FragID = 0
 			m.FragCount = 1

transport/hysteria/core/frag_test.go

@@ -20,13 +20,11 @@ func Test_fragUDPMessage(t *testing.T) {
 			args{
 				udpMessage{
 					SessionID: 123,
-					HostLen:   4,
 					Host:      "test",
 					Port:      123,
 					MsgID:     123,
 					FragID:    0,
 					FragCount: 1,
-					DataLen:   5,
 					Data:      []byte("hello"),
 				},
 				100,
@@ -34,13 +32,11 @@ func Test_fragUDPMessage(t *testing.T) {
 			[]udpMessage{
 				udpMessage{
 					SessionID: 123,
-					HostLen:   4,
 					Host:      "test",
 					Port:      123,
 					MsgID:     123,
 					FragID:    0,
 					FragCount: 1,
-					DataLen:   5,
 					Data:      []byte("hello"),
 				},
 			},
@@ -50,13 +46,11 @@ func Test_fragUDPMessage(t *testing.T) {
 			args{
 				udpMessage{
 					SessionID: 123,
-					HostLen:   4,
 					Host:      "test",
 					Port:      123,
 					MsgID:     123,
 					FragID:    0,
 					FragCount: 1,
-					DataLen:   5,
 					Data:      []byte("hello"),
 				},
 				22,
@@ -64,24 +58,20 @@ func Test_fragUDPMessage(t *testing.T) {
 			[]udpMessage{
 				udpMessage{
 					SessionID: 123,
-					HostLen:   4,
 					Host:      "test",
 					Port:      123,
 					MsgID:     123,
 					FragID:    0,
 					FragCount: 2,
-					DataLen:   4,
 					Data:      []byte("hell"),
 				},
 				udpMessage{
 					SessionID: 123,
-					HostLen:   4,
 					Host:      "test",
 					Port:      123,
 					MsgID:     123,
 					FragID:    1,
 					FragCount: 2,
-					DataLen:   1,
 					Data:      []byte("o"),
 				},
 			},
@@ -91,13 +81,11 @@ func Test_fragUDPMessage(t *testing.T) {
 			args{
 				udpMessage{
 					SessionID: 123,
-					HostLen:   4,
 					Host:      "test",
 					Port:      123,
 					MsgID:     123,
 					FragID:    0,
 					FragCount: 1,
-					DataLen:   20,
 					Data:      []byte("wow wow wow lol lmao"),
 				},
 				23,
@@ -105,46 +93,38 @@ func Test_fragUDPMessage(t *testing.T) {
 			[]udpMessage{
 				udpMessage{
 					SessionID: 123,
-					HostLen:   4,
 					Host:      "test",
 					Port:      123,
 					MsgID:     123,
 					FragID:    0,
 					FragCount: 4,
-					DataLen:   5,
 					Data:      []byte("wow w"),
 				},
 				udpMessage{
 					SessionID: 123,
-					HostLen:   4,
 					Host:      "test",
 					Port:      123,
 					MsgID:     123,
 					FragID:    1,
 					FragCount: 4,
-					DataLen:   5,
 					Data:      []byte("ow wo"),
 				},
 				udpMessage{
 					SessionID: 123,
-					HostLen:   4,
 					Host:      "test",
 					Port:      123,
 					MsgID:     123,
 					FragID:    2,
 					FragCount: 4,
-					DataLen:   5,
 					Data:      []byte("w lol"),
 				},
 				udpMessage{
 					SessionID: 123,
-					HostLen:   4,
 					Host:      "test",
 					Port:      123,
 					MsgID:     123,
 					FragID:    3,
 					FragCount: 4,
-					DataLen:   5,
 					Data:      []byte(" lmao"),
 				},
 			},
@@ -174,25 +154,21 @@ func Test_defragger_Feed(t *testing.T) {
 			args{
 				udpMessage{
 					SessionID: 123,
-					HostLen:   4,
 					Host:      "test",
 					Port:      123,
 					MsgID:     123,
 					FragID:    0,
 					FragCount: 1,
-					DataLen:   5,
 					Data:      []byte("hello"),
 				},
 			},
 			&udpMessage{
 				SessionID: 123,
-				HostLen:   4,
 				Host:      "test",
 				Port:      123,
 				MsgID:     123,
 				FragID:    0,
 				FragCount: 1,
-				DataLen:   5,
 				Data:      []byte("hello"),
 			},
 		},
@@ -201,13 +177,11 @@ func Test_defragger_Feed(t *testing.T) {
 			args{
 				udpMessage{
 					SessionID: 123,
-					HostLen:   4,
 					Host:      "test",
 					Port:      123,
 					MsgID:     666,
 					FragID:    0,
 					FragCount: 3,
-					DataLen:   5,
 					Data:      []byte("hello"),
 				},
 			},
@@ -218,13 +192,11 @@ func Test_defragger_Feed(t *testing.T) {
 			args{
 				udpMessage{
 					SessionID: 123,
-					HostLen:   4,
 					Host:      "test",
 					Port:      123,
 					MsgID:     666,
 					FragID:    1,
 					FragCount: 3,
-					DataLen:   8,
 					Data:      []byte(" shitty "),
 				},
 			},
@@ -235,25 +207,21 @@ func Test_defragger_Feed(t *testing.T) {
 			args{
 				udpMessage{
 					SessionID: 123,
-					HostLen:   4,
 					Host:      "test",
 					Port:      123,
 					MsgID:     666,
 					FragID:    2,
 					FragCount: 3,
-					DataLen:   7,
 					Data:      []byte("world!!"),
 				},
 			},
 			&udpMessage{
 				SessionID: 123,
-				HostLen:   4,
 				Host:      "test",
 				Port:      123,
 				MsgID:     666,
 				FragID:    0,
 				FragCount: 1,
-				DataLen:   20,
 				Data:      []byte("hello shitty world!!"),
 			},
 		},
@@ -262,13 +230,11 @@ func Test_defragger_Feed(t *testing.T) {
 			args{
 				udpMessage{
 					SessionID: 123,
-					HostLen:   4,
 					Host:      "test",
 					Port:      123,
 					MsgID:     777,
 					FragID:    0,
 					FragCount: 2,
-					DataLen:   5,
 					Data:      []byte("hello"),
 				},
 			},
@@ -279,13 +245,11 @@ func Test_defragger_Feed(t *testing.T) {
 			args{
 				udpMessage{
 					SessionID: 123,
-					HostLen:   4,
 					Host:      "test",
 					Port:      123,
 					MsgID:     778,
 					FragID:    1,
 					FragCount: 2,
-					DataLen:   5,
 					Data:      []byte(" moto"),
 				},
 			},
@@ -296,13 +260,11 @@ func Test_defragger_Feed(t *testing.T) {
 			args{
 				udpMessage{
 					SessionID: 123,
-					HostLen:   4,
 					Host:      "test",
 					Port:      123,
 					MsgID:     777,
 					FragID:    1,
 					FragCount: 2,
-					DataLen:   5,
 					Data:      []byte(" moto"),
 				},
 			},
@@ -313,25 +275,21 @@ func Test_defragger_Feed(t *testing.T) {
 			args{
 				udpMessage{
 					SessionID: 123,
-					HostLen:   4,
 					Host:      "test",
 					Port:      123,
 					MsgID:     777,
 					FragID:    0,
 					FragCount: 2,
-					DataLen:   5,
 					Data:      []byte("hello"),
 				},
 			},
 			&udpMessage{
 				SessionID: 123,
-				HostLen:   4,
 				Host:      "test",
 				Port:      123,
 				MsgID:     777,
 				FragID:    0,
 				FragCount: 1,
-				DataLen:   10,
 				Data:      []byte("hello moto"),
 			},
 		},

transport/hysteria/core/protocol.go

@@ -1,60 +1,241 @@
 package core
 
 import (
+	"bytes"
+	"encoding/binary"
+	"errors"
+	"io"
 	"time"
 )
 
 const (
-	protocolVersion   = uint8(3)
+	protocolVersion = uint8(3)
-	protocolVersionV2 = uint8(2)
+	protocolTimeout = 10 * time.Second
-	protocolTimeout   = 10 * time.Second
 
 	closeErrorCodeGeneric  = 0
 	closeErrorCodeProtocol = 1
 	closeErrorCodeAuth     = 2
 )
 
-type transmissionRate struct {
+type ClientHello struct {
 	SendBPS uint64
 	RecvBPS uint64
-}
-
-type clientHello struct {
-	Rate    transmissionRate
-	AuthLen uint16 `struc:"sizeof=Auth"`
 	Auth    []byte
 }
 
-type serverHello struct {
+func WriteClientHello(stream io.Writer, hello ClientHello) error {
-	OK         bool
+	var requestLen int
-	Rate       transmissionRate
+	requestLen += 1 // version
-	MessageLen uint16 `struc:"sizeof=Message"`
+	requestLen += 8 // sendBPS
-	Message    string
+	requestLen += 8 // recvBPS
+	requestLen += 2 // auth len
+	requestLen += len(hello.Auth)
+	request := make([]byte, requestLen)
+	request[0] = protocolVersion
+	binary.BigEndian.PutUint64(request[1:9], hello.SendBPS)
+	binary.BigEndian.PutUint64(request[9:17], hello.RecvBPS)
+	binary.BigEndian.PutUint16(request[17:19], uint16(len(hello.Auth)))
+	copy(request[19:], hello.Auth)
+	_, err := stream.Write(request)
+	return err
 }
 
-type clientRequest struct {
+func ReadClientHello(stream io.Reader) (*ClientHello, error) {
-	UDP     bool
+	var responseLen int
-	HostLen uint16 `struc:"sizeof=Host"`
+	responseLen += 1 // ok
-	Host    string
+	responseLen += 8 // sendBPS
-	Port    uint16
+	responseLen += 8 // recvBPS
+	responseLen += 2 // auth len
+	response := make([]byte, responseLen)
+	_, err := io.ReadFull(stream, response)
+	if err != nil {
+		return nil, err
+	}
+
+	if response[0] != protocolVersion {
+		return nil, errors.New("unsupported client version")
+	}
+	var clientHello ClientHello
+	clientHello.SendBPS = binary.BigEndian.Uint64(response[1:9])
+	clientHello.RecvBPS = binary.BigEndian.Uint64(response[9:17])
+	authLen := binary.BigEndian.Uint16(response[17:19])
+
+	if clientHello.SendBPS == 0 || clientHello.RecvBPS == 0 {
+		return nil, errors.New("invalid rate from client")
+	}
+
+	authBytes := make([]byte, authLen)
+	_, err = io.ReadFull(stream, authBytes)
+	if err != nil {
+		return nil, err
+	}
+	clientHello.Auth = authBytes
+	return &clientHello, nil
 }
 
-type serverResponse struct {
+type ServerHello struct {
+	OK      bool
+	SendBPS uint64
+	RecvBPS uint64
+	Message string
+}
+
+func ReadServerHello(stream io.Reader) (*ServerHello, error) {
+	var responseLen int
+	responseLen += 1 // ok
+	responseLen += 8 // sendBPS
+	responseLen += 8 // recvBPS
+	responseLen += 2 // message len
+	response := make([]byte, responseLen)
+	_, err := io.ReadFull(stream, response)
+	if err != nil {
+		return nil, err
+	}
+	var serverHello ServerHello
+	serverHello.OK = response[0] == 1
+	serverHello.SendBPS = binary.BigEndian.Uint64(response[1:9])
+	serverHello.RecvBPS = binary.BigEndian.Uint64(response[9:17])
+	messageLen := binary.BigEndian.Uint16(response[17:19])
+	if messageLen == 0 {
+		return &serverHello, nil
+	}
+	message := make([]byte, messageLen)
+	_, err = io.ReadFull(stream, message)
+	if err != nil {
+		return nil, err
+	}
+	serverHello.Message = string(message)
+	return &serverHello, nil
+}
+
+func WriteServerHello(stream io.Writer, hello ServerHello) error {
+	var responseLen int
+	responseLen += 1 // ok
+	responseLen += 8 // sendBPS
+	responseLen += 8 // recvBPS
+	responseLen += 2 // message len
+	responseLen += len(hello.Message)
+	response := make([]byte, responseLen)
+	if hello.OK {
+		response[0] = 1
+	} else {
+		response[0] = 0
+	}
+	binary.BigEndian.PutUint64(response[1:9], hello.SendBPS)
+	binary.BigEndian.PutUint64(response[9:17], hello.RecvBPS)
+	binary.BigEndian.PutUint16(response[17:19], uint16(len(hello.Message)))
+	copy(response[19:], hello.Message)
+	_, err := stream.Write(response)
+	return err
+}
+
+type ClientRequest struct {
+	UDP  bool
+	Host string
+	Port uint16
+}
+
+func ReadClientRequest(stream io.Reader) (*ClientRequest, error) {
+	var clientRequest ClientRequest
+	err := binary.Read(stream, binary.BigEndian, &clientRequest.UDP)
+	if err != nil {
+		return nil, err
+	}
+	var hostLen uint16
+	err = binary.Read(stream, binary.BigEndian, &hostLen)
+	if err != nil {
+		return nil, err
+	}
+	host := make([]byte, hostLen)
+	_, err = io.ReadFull(stream, host)
+	if err != nil {
+		return nil, err
+	}
+	clientRequest.Host = string(host)
+	err = binary.Read(stream, binary.BigEndian, &clientRequest.Port)
+	if err != nil {
+		return nil, err
+	}
+	return &clientRequest, nil
+}
+
+func WriteClientRequest(stream io.Writer, request ClientRequest) error {
+	var requestLen int
+	requestLen += 1 // udp
+	requestLen += 2 // host len
+	requestLen += len(request.Host)
+	requestLen += 2 // port
+	buffer := make([]byte, requestLen)
+	if request.UDP {
+		buffer[0] = 1
+	} else {
+		buffer[0] = 0
+	}
+	binary.BigEndian.PutUint16(buffer[1:3], uint16(len(request.Host)))
+	n := copy(buffer[3:], request.Host)
+	binary.BigEndian.PutUint16(buffer[3+n:3+n+2], request.Port)
+	_, err := stream.Write(buffer)
+	return err
+}
+
+type ServerResponse struct {
 	OK           bool
 	UDPSessionID uint32
-	MessageLen   uint16 `struc:"sizeof=Message"`
 	Message      string
 }
 
+func ReadServerResponse(stream io.Reader) (*ServerResponse, error) {
+	var responseLen int
+	responseLen += 1 // ok
+	responseLen += 4 // udp session id
+	responseLen += 2 // message len
+	response := make([]byte, responseLen)
+	_, err := io.ReadFull(stream, response)
+	if err != nil {
+		return nil, err
+	}
+	var serverResponse ServerResponse
+	serverResponse.OK = response[0] == 1
+	serverResponse.UDPSessionID = binary.BigEndian.Uint32(response[1:5])
+	messageLen := binary.BigEndian.Uint16(response[5:7])
+	if messageLen == 0 {
+		return &serverResponse, nil
+	}
+	message := make([]byte, messageLen)
+	_, err = io.ReadFull(stream, message)
+	if err != nil {
+		return nil, err
+	}
+	serverResponse.Message = string(message)
+	return &serverResponse, nil
+}
+
+func WriteServerResponse(stream io.Writer, response ServerResponse) error {
+	var responseLen int
+	responseLen += 1 // ok
+	responseLen += 4 // udp session id
+	responseLen += 2 // message len
+	responseLen += len(response.Message)
+	buffer := make([]byte, responseLen)
+	if response.OK {
+		buffer[0] = 1
+	} else {
+		buffer[0] = 0
+	}
+	binary.BigEndian.PutUint32(buffer[1:5], response.UDPSessionID)
+	binary.BigEndian.PutUint16(buffer[5:7], uint16(len(response.Message)))
+	copy(buffer[7:], response.Message)
+	_, err := stream.Write(buffer)
+	return err
+}
+
 type udpMessage struct {
 	SessionID uint32
-	HostLen   uint16 `struc:"sizeof=Host"`
 	Host      string
 	Port      uint16
 	MsgID     uint16 // doesn't matter when not fragmented, but must not be 0 when fragmented
 	FragID    uint8  // doesn't matter when not fragmented, starts at 0 when fragmented
 	FragCount uint8  // must be 1 when not fragmented
-	DataLen   uint16 `struc:"sizeof=Data"`
 	Data      []byte
 }
 
@@ -66,11 +247,62 @@ func (m udpMessage) Size() int {
 	return m.HeaderSize() + len(m.Data)
 }
 
-type udpMessageV2 struct {
+func (m udpMessage) Pack() []byte {
-	SessionID uint32
+	data := make([]byte, m.Size())
-	HostLen   uint16 `struc:"sizeof=Host"`
+	buffer := bytes.NewBuffer(data)
-	Host      string
+	_ = binary.Write(buffer, binary.BigEndian, m.SessionID)
-	Port      uint16
+	_ = binary.Write(buffer, binary.BigEndian, uint16(len(m.Host)))
-	DataLen   uint16 `struc:"sizeof=Data"`
+	buffer.WriteString(m.Host)
-	Data      []byte
+	_ = binary.Write(buffer, binary.BigEndian, m.Port)
+	_ = binary.Write(buffer, binary.BigEndian, m.MsgID)
+	_ = binary.Write(buffer, binary.BigEndian, m.FragID)
+	_ = binary.Write(buffer, binary.BigEndian, m.FragCount)
+	_ = binary.Write(buffer, binary.BigEndian, uint16(len(m.Data)))
+	buffer.Write(m.Data)
+	return buffer.Bytes()
+}
+
+func (m *udpMessage) Unpack(data []byte) error {
+	reader := bytes.NewReader(data)
+	err := binary.Read(reader, binary.BigEndian, &m.SessionID)
+	if err != nil {
+		return err
+	}
+	var hostLen uint16
+	err = binary.Read(reader, binary.BigEndian, &hostLen)
+	if err != nil {
+		return err
+	}
+	hostBytes := make([]byte, hostLen)
+	_, err = io.ReadFull(reader, hostBytes)
+	if err != nil {
+		return err
+	}
+	m.Host = string(hostBytes)
+	err = binary.Read(reader, binary.BigEndian, &m.Port)
+	if err != nil {
+		return err
+	}
+	err = binary.Read(reader, binary.BigEndian, &m.MsgID)
+	if err != nil {
+		return err
+	}
+	err = binary.Read(reader, binary.BigEndian, &m.FragID)
+	if err != nil {
+		return err
+	}
+	err = binary.Read(reader, binary.BigEndian, &m.FragCount)
+	if err != nil {
+		return err
+	}
+	var dataLen uint16
+	err = binary.Read(reader, binary.BigEndian, &dataLen)
+	if err != nil {
+		return err
+	}
+	if reader.Len() != int(dataLen) {
+		return errors.New("invalid data length")
+	}
+	m.Data = data[len(data)-reader.Len():]
+	return nil
 }