package kcp
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import (
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"encoding/binary"
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"github.com/v2fly/v2ray-core/v5/common/buf"
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)
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// Command is a KCP command that indicate the purpose of a Segment.
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type Command byte
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const (
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// CommandACK indicates an AckSegment.
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CommandACK Command = 0
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// CommandData indicates a DataSegment.
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CommandData Command = 1
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// CommandTerminate indicates that peer terminates the connection.
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CommandTerminate Command = 2
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// CommandPing indicates a ping.
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CommandPing Command = 3
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)
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type SegmentOption byte
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const (
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SegmentOptionClose SegmentOption = 1
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)
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type Segment interface {
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Release()
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Conversation() uint16
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Command() Command
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ByteSize() int32
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Serialize([]byte)
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parse(conv uint16, cmd Command, opt SegmentOption, buf []byte) (bool, []byte)
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}
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const (
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DataSegmentOverhead = 18
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)
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type DataSegment struct {
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Conv uint16
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Option SegmentOption
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Timestamp uint32
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Number uint32
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SendingNext uint32
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payload *buf.Buffer
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timeout uint32
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transmit uint32
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}
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func NewDataSegment() *DataSegment {
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return new(DataSegment)
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}
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func (s *DataSegment) parse(conv uint16, cmd Command, opt SegmentOption, buf []byte) (bool, []byte) {
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s.Conv = conv
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s.Option = opt
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if len(buf) < 15 {
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return false, nil
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}
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s.Timestamp = binary.BigEndian.Uint32(buf)
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buf = buf[4:]
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s.Number = binary.BigEndian.Uint32(buf)
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buf = buf[4:]
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s.SendingNext = binary.BigEndian.Uint32(buf)
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buf = buf[4:]
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dataLen := int(binary.BigEndian.Uint16(buf))
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buf = buf[2:]
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if len(buf) < dataLen {
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return false, nil
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}
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s.Data().Clear()
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s.Data().Write(buf[:dataLen])
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buf = buf[dataLen:]
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return true, buf
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}
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func (s *DataSegment) Conversation() uint16 {
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return s.Conv
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}
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func (*DataSegment) Command() Command {
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return CommandData
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}
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func (s *DataSegment) Detach() *buf.Buffer {
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r := s.payload
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s.payload = nil
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return r
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}
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func (s *DataSegment) Data() *buf.Buffer {
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if s.payload == nil {
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s.payload = buf.New()
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}
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return s.payload
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}
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func (s *DataSegment) Serialize(b []byte) {
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binary.BigEndian.PutUint16(b, s.Conv)
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b[2] = byte(CommandData)
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b[3] = byte(s.Option)
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binary.BigEndian.PutUint32(b[4:], s.Timestamp)
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binary.BigEndian.PutUint32(b[8:], s.Number)
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binary.BigEndian.PutUint32(b[12:], s.SendingNext)
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binary.BigEndian.PutUint16(b[16:], uint16(s.payload.Len()))
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copy(b[18:], s.payload.Bytes())
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}
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func (s *DataSegment) ByteSize() int32 {
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return 2 + 1 + 1 + 4 + 4 + 4 + 2 + s.payload.Len()
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}
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func (s *DataSegment) Release() {
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s.payload.Release()
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s.payload = nil
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}
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type AckSegment struct {
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Conv uint16
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Option SegmentOption
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ReceivingWindow uint32
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ReceivingNext uint32
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Timestamp uint32
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NumberList []uint32
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}
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const ackNumberLimit = 128
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func NewAckSegment() *AckSegment {
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return new(AckSegment)
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}
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func (s *AckSegment) parse(conv uint16, cmd Command, opt SegmentOption, buf []byte) (bool, []byte) {
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s.Conv = conv
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s.Option = opt
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if len(buf) < 13 {
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return false, nil
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}
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s.ReceivingWindow = binary.BigEndian.Uint32(buf)
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buf = buf[4:]
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s.ReceivingNext = binary.BigEndian.Uint32(buf)
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buf = buf[4:]
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s.Timestamp = binary.BigEndian.Uint32(buf)
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buf = buf[4:]
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count := int(buf[0])
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buf = buf[1:]
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if len(buf) < count*4 {
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return false, nil
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}
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for i := 0; i < count; i++ {
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s.PutNumber(binary.BigEndian.Uint32(buf))
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buf = buf[4:]
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}
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return true, buf
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}
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func (s *AckSegment) Conversation() uint16 {
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return s.Conv
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}
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func (*AckSegment) Command() Command {
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return CommandACK
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}
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func (s *AckSegment) PutTimestamp(timestamp uint32) {
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if timestamp-s.Timestamp < 0x7FFFFFFF {
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s.Timestamp = timestamp
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}
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}
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func (s *AckSegment) PutNumber(number uint32) {
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s.NumberList = append(s.NumberList, number)
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}
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func (s *AckSegment) IsFull() bool {
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return len(s.NumberList) == ackNumberLimit
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}
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func (s *AckSegment) IsEmpty() bool {
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return len(s.NumberList) == 0
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}
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func (s *AckSegment) ByteSize() int32 {
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return 2 + 1 + 1 + 4 + 4 + 4 + 1 + int32(len(s.NumberList)*4)
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}
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func (s *AckSegment) Serialize(b []byte) {
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binary.BigEndian.PutUint16(b, s.Conv)
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b[2] = byte(CommandACK)
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b[3] = byte(s.Option)
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binary.BigEndian.PutUint32(b[4:], s.ReceivingWindow)
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binary.BigEndian.PutUint32(b[8:], s.ReceivingNext)
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binary.BigEndian.PutUint32(b[12:], s.Timestamp)
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b[16] = byte(len(s.NumberList))
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n := 17
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for _, number := range s.NumberList {
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binary.BigEndian.PutUint32(b[n:], number)
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n += 4
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}
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}
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func (s *AckSegment) Release() {}
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type CmdOnlySegment struct {
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Conv uint16
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Cmd Command
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Option SegmentOption
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SendingNext uint32
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ReceivingNext uint32
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PeerRTO uint32
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}
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func NewCmdOnlySegment() *CmdOnlySegment {
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return new(CmdOnlySegment)
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}
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func (s *CmdOnlySegment) parse(conv uint16, cmd Command, opt SegmentOption, buf []byte) (bool, []byte) {
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s.Conv = conv
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s.Cmd = cmd
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s.Option = opt
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if len(buf) < 12 {
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return false, nil
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}
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s.SendingNext = binary.BigEndian.Uint32(buf)
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buf = buf[4:]
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s.ReceivingNext = binary.BigEndian.Uint32(buf)
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buf = buf[4:]
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s.PeerRTO = binary.BigEndian.Uint32(buf)
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buf = buf[4:]
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return true, buf
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}
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func (s *CmdOnlySegment) Conversation() uint16 {
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return s.Conv
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}
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func (s *CmdOnlySegment) Command() Command {
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return s.Cmd
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}
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func (*CmdOnlySegment) ByteSize() int32 {
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return 2 + 1 + 1 + 4 + 4 + 4
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}
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func (s *CmdOnlySegment) Serialize(b []byte) {
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binary.BigEndian.PutUint16(b, s.Conv)
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b[2] = byte(s.Cmd)
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b[3] = byte(s.Option)
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binary.BigEndian.PutUint32(b[4:], s.SendingNext)
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binary.BigEndian.PutUint32(b[8:], s.ReceivingNext)
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binary.BigEndian.PutUint32(b[12:], s.PeerRTO)
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}
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func (*CmdOnlySegment) Release() {}
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func ReadSegment(buf []byte) (Segment, []byte) {
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if len(buf) < 4 {
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return nil, nil
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}
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conv := binary.BigEndian.Uint16(buf)
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buf = buf[2:]
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cmd := Command(buf[0])
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opt := SegmentOption(buf[1])
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buf = buf[2:]
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var seg Segment
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switch cmd {
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case CommandData:
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seg = NewDataSegment()
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case CommandACK:
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seg = NewAckSegment()
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default:
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seg = NewCmdOnlySegment()
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}
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valid, extra := seg.parse(conv, cmd, opt, buf)
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if !valid {
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return nil, nil
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}
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return seg, extra
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}
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