package kcp import ( "v2ray.com/core/common" "v2ray.com/core/common/alloc" "v2ray.com/core/common/serial" ) // Command is a KCP command that indicate the purpose of a Segment. type Command byte const ( // CommandACK indicates a AckSegment. CommandACK Command = 0 // CommandData indicates a DataSegment. CommandData Command = 1 // CommandTerminate indicates that peer terminates the connection. CommandTerminate Command = 2 // CommandPing indicates a ping. CommandPing Command = 3 ) type SegmentOption byte const ( SegmentOptionClose SegmentOption = 1 ) type Segment interface { common.Releasable Conversation() uint16 Command() Command ByteSize() int Bytes() alloc.BytesWriter } const ( DataSegmentOverhead = 18 ) type DataSegment struct { Conv uint16 Option SegmentOption Timestamp uint32 Number uint32 SendingNext uint32 Data *alloc.Buffer timeout uint32 transmit uint32 } func NewDataSegment() *DataSegment { return new(DataSegment) } func (v *DataSegment) Conversation() uint16 { return v.Conv } func (v *DataSegment) Command() Command { return CommandData } func (v *DataSegment) SetData(b []byte) { if v.Data == nil { v.Data = alloc.NewSmallBuffer() } v.Data.Clear() v.Data.Append(b) } func (v *DataSegment) Bytes() alloc.BytesWriter { return func(b []byte) int { b = serial.Uint16ToBytes(v.Conv, b[:0]) b = append(b, byte(CommandData), byte(v.Option)) b = serial.Uint32ToBytes(v.Timestamp, b) b = serial.Uint32ToBytes(v.Number, b) b = serial.Uint32ToBytes(v.SendingNext, b) b = serial.Uint16ToBytes(uint16(v.Data.Len()), b) b = append(b, v.Data.Bytes()...) return v.ByteSize() } } func (v *DataSegment) ByteSize() int { return 2 + 1 + 1 + 4 + 4 + 4 + 2 + v.Data.Len() } func (v *DataSegment) Release() { v.Data.Release() v.Data = nil } type AckSegment struct { Conv uint16 Option SegmentOption ReceivingWindow uint32 ReceivingNext uint32 Timestamp uint32 Count byte NumberList []uint32 } const ackNumberLimit = 128 func NewAckSegment() *AckSegment { return &AckSegment{ NumberList: make([]uint32, 0, ackNumberLimit), } } func (v *AckSegment) Conversation() uint16 { return v.Conv } func (v *AckSegment) Command() Command { return CommandACK } func (v *AckSegment) PutTimestamp(timestamp uint32) { if timestamp-v.Timestamp < 0x7FFFFFFF { v.Timestamp = timestamp } } func (v *AckSegment) PutNumber(number uint32) { v.Count++ v.NumberList = append(v.NumberList, number) } func (v *AckSegment) IsFull() bool { return v.Count == ackNumberLimit } func (v *AckSegment) ByteSize() int { return 2 + 1 + 1 + 4 + 4 + 4 + 1 + int(v.Count)*4 } func (v *AckSegment) Bytes() alloc.BytesWriter { return func(b []byte) int { b = serial.Uint16ToBytes(v.Conv, b[:0]) b = append(b, byte(CommandACK), byte(v.Option)) b = serial.Uint32ToBytes(v.ReceivingWindow, b) b = serial.Uint32ToBytes(v.ReceivingNext, b) b = serial.Uint32ToBytes(v.Timestamp, b) b = append(b, v.Count) for i := byte(0); i < v.Count; i++ { b = serial.Uint32ToBytes(v.NumberList[i], b) } return v.ByteSize() } } func (v *AckSegment) Release() { v.NumberList = nil } type CmdOnlySegment struct { Conv uint16 Cmd Command Option SegmentOption SendingNext uint32 ReceivinNext uint32 PeerRTO uint32 } func NewCmdOnlySegment() *CmdOnlySegment { return new(CmdOnlySegment) } func (v *CmdOnlySegment) Conversation() uint16 { return v.Conv } func (v *CmdOnlySegment) Command() Command { return v.Cmd } func (v *CmdOnlySegment) ByteSize() int { return 2 + 1 + 1 + 4 + 4 + 4 } func (v *CmdOnlySegment) Bytes() alloc.BytesWriter { return func(b []byte) int { b = serial.Uint16ToBytes(v.Conv, b[:0]) b = append(b, byte(v.Cmd), byte(v.Option)) b = serial.Uint32ToBytes(v.SendingNext, b) b = serial.Uint32ToBytes(v.ReceivinNext, b) b = serial.Uint32ToBytes(v.PeerRTO, b) return v.ByteSize() } } func (v *CmdOnlySegment) Release() { } func ReadSegment(buf []byte) (Segment, []byte) { if len(buf) < 4 { return nil, nil } conv := serial.BytesToUint16(buf) buf = buf[2:] cmd := Command(buf[0]) opt := SegmentOption(buf[1]) buf = buf[2:] if cmd == CommandData { seg := NewDataSegment() seg.Conv = conv seg.Option = opt if len(buf) < 16 { return nil, nil } seg.Timestamp = serial.BytesToUint32(buf) buf = buf[4:] seg.Number = serial.BytesToUint32(buf) buf = buf[4:] seg.SendingNext = serial.BytesToUint32(buf) buf = buf[4:] dataLen := int(serial.BytesToUint16(buf)) buf = buf[2:] if len(buf) < dataLen { return nil, nil } seg.SetData(buf[:dataLen]) buf = buf[dataLen:] return seg, buf } if cmd == CommandACK { seg := NewAckSegment() seg.Conv = conv seg.Option = opt if len(buf) < 13 { return nil, nil } seg.ReceivingWindow = serial.BytesToUint32(buf) buf = buf[4:] seg.ReceivingNext = serial.BytesToUint32(buf) buf = buf[4:] seg.Timestamp = serial.BytesToUint32(buf) buf = buf[4:] count := int(buf[0]) buf = buf[1:] if len(buf) < count*4 { return nil, nil } for i := 0; i < count; i++ { seg.PutNumber(serial.BytesToUint32(buf)) buf = buf[4:] } return seg, buf } seg := NewCmdOnlySegment() seg.Conv = conv seg.Cmd = cmd seg.Option = opt if len(buf) < 12 { return nil, nil } seg.SendingNext = serial.BytesToUint32(buf) buf = buf[4:] seg.ReceivinNext = serial.BytesToUint32(buf) buf = buf[4:] seg.PeerRTO = serial.BytesToUint32(buf) buf = buf[4:] return seg, buf }