Golang gopacket.DecodeFunc函數代碼示例

func init() {
	layers.MPLSPayloadDecoder = gopacket.DecodeFunc(decodeMPLS)
	layers.EthernetTypeMetadata[ethernetTypeDot1QSTag] = layers.EthernetTypeMetadata[layers.EthernetTypeDot1Q]
	layers.EthernetTypeMetadata[ethernetTypeDot1QITag] = layers.EnumMetadata{
		DecodeWith: gopacket.DecodeFunc(decodePBB),
		Name:       "PBB",
		LayerType:  LayerTypePBB,
	}
	layers.EthernetTypeMetadata[ethernetTypeLwapp] = layers.EnumMetadata{
		DecodeWith: gopacket.DecodeFunc(decodeLwapp),
		Name:       "Lwapp",
		LayerType:  LayerTypeLwapp,
	}
}

func decodeSCTPEmptyLayer(data []byte, p gopacket.PacketBuilder) error {
	sc := &SCTPEmptyLayer{
		SCTPChunk: decodeSCTPChunk(data),
	}
	p.AddLayer(sc)
	return p.NextDecoder(gopacket.DecodeFunc(decodeWithSCTPChunkTypePrefix))
}

func decodeSCTPChunkTypeUnknown(data []byte, p gopacket.PacketBuilder) error {
	sc := &SCTPUnknownChunkType{SCTPChunk: decodeSCTPChunk(data)}
	sc.bytes = data[:sc.ActualLength]
	p.AddLayer(sc)
	p.SetErrorLayer(sc)
	return p.NextDecoder(gopacket.DecodeFunc(decodeWithSCTPChunkTypePrefix))
}

func decodeSCTPShutdown(data []byte, p gopacket.PacketBuilder) error {
	sc := &SCTPShutdown{
		SCTPChunk:        decodeSCTPChunk(data),
		CumulativeTSNAck: binary.BigEndian.Uint32(data[4:8]),
	}
	p.AddLayer(sc)
	return p.NextDecoder(gopacket.DecodeFunc(decodeWithSCTPChunkTypePrefix))
}

func decodeSCTPCookieEcho(data []byte, p gopacket.PacketBuilder) error {
	sc := &SCTPCookieEcho{
		SCTPChunk: decodeSCTPChunk(data),
	}
	sc.Cookie = data[4:sc.Length]
	p.AddLayer(sc)
	return p.NextDecoder(gopacket.DecodeFunc(decodeWithSCTPChunkTypePrefix))
}

func decodeSCTPEmptyLayer(data []byte, p gopacket.PacketBuilder) error {
	chunk, err := decodeSCTPChunk(data)
	if err != nil {
		return err
	}
	sc := &SCTPEmptyLayer{
		SCTPChunk: chunk,
	}
	p.AddLayer(sc)
	return p.NextDecoder(gopacket.DecodeFunc(decodeWithSCTPChunkTypePrefix))
}

func decodeEthernetCTP(data []byte, p gopacket.PacketBuilder) error {
	c := &EthernetCTP{
		SkipCount: binary.LittleEndian.Uint16(data[:2]),
		BaseLayer: BaseLayer{data[:2], data[2:]},
	}
	if c.SkipCount%2 != 0 {
		return fmt.Errorf("EthernetCTP skip count is odd: %d", c.SkipCount)
	}
	p.AddLayer(c)
	return p.NextDecoder(gopacket.DecodeFunc(decodeEthernetCTPFromFunctionType))
}

func decodeSCTPHeartbeat(data []byte, p gopacket.PacketBuilder) error {
	sc := &SCTPHeartbeat{
		SCTPChunk: decodeSCTPChunk(data),
	}
	paramData := data[4:sc.Length]
	for len(paramData) > 0 {
		p := SCTPHeartbeatParameter(decodeSCTPParameter(paramData))
		paramData = paramData[p.ActualLength:]
		sc.Parameters = append(sc.Parameters, p)
	}
	p.AddLayer(sc)
	return p.NextDecoder(gopacket.DecodeFunc(decodeWithSCTPChunkTypePrefix))
}

func decodeMPLS(data []byte, p gopacket.PacketBuilder) error {
	decoded := binary.BigEndian.Uint32(data[:4])
	mpls := &MPLS{
		Label:        decoded >> 12,
		TrafficClass: uint8(decoded>>9) & 0x7,
		StackBottom:  decoded&0x100 != 0,
		TTL:          uint8(decoded),
		BaseLayer:    BaseLayer{data[:4], data[4:]},
	}
	p.AddLayer(mpls)
	if mpls.StackBottom {
		return p.NextDecoder(MPLSPayloadDecoder)
	}
	return p.NextDecoder(gopacket.DecodeFunc(decodeMPLS))
}

func decodeSCTPData(data []byte, p gopacket.PacketBuilder) error {
	sc := &SCTPData{
		SCTPChunk:       decodeSCTPChunk(data),
		Unordered:       data[1]&0x4 != 0,
		BeginFragment:   data[1]&0x2 != 0,
		EndFragment:     data[1]&0x1 != 0,
		TSN:             binary.BigEndian.Uint32(data[4:8]),
		StreamId:        binary.BigEndian.Uint16(data[8:10]),
		StreamSequence:  binary.BigEndian.Uint16(data[10:12]),
		PayloadProtocol: binary.BigEndian.Uint32(data[12:16]),
	}
	// Length is the length in bytes of the data, INCLUDING the 16-byte header.
	sc.PayloadData = data[16:sc.Length]
	p.AddLayer(sc)
	p.SetApplicationLayer(sc)
	return p.NextDecoder(gopacket.DecodeFunc(decodeWithSCTPChunkTypePrefix))
}

func decodeSCTPInit(data []byte, p gopacket.PacketBuilder) error {
	sc := &SCTPInit{
		SCTPChunk:                      decodeSCTPChunk(data),
		InitiateTag:                    binary.BigEndian.Uint32(data[4:8]),
		AdvertisedReceiverWindowCredit: binary.BigEndian.Uint32(data[8:12]),
		OutboundStreams:                binary.BigEndian.Uint16(data[12:14]),
		InboundStreams:                 binary.BigEndian.Uint16(data[14:16]),
		InitialTSN:                     binary.BigEndian.Uint32(data[16:20]),
	}
	paramData := data[20:sc.ActualLength]
	for len(paramData) > 0 {
		p := SCTPInitParameter(decodeSCTPParameter(paramData))
		paramData = paramData[p.ActualLength:]
		sc.Parameters = append(sc.Parameters, p)
	}
	p.AddLayer(sc)
	return p.NextDecoder(gopacket.DecodeFunc(decodeWithSCTPChunkTypePrefix))
}

func decodeSCTPError(data []byte, p gopacket.PacketBuilder) error {
	// remarkably similar to decodeSCTPHeartbeat ;)
	chunk, err := decodeSCTPChunk(data)
	if err != nil {
		return err
	}
	sc := &SCTPError{
		SCTPChunk: chunk,
	}
	paramData := data[4:sc.Length]
	for len(paramData) > 0 {
		p := SCTPErrorParameter(decodeSCTPParameter(paramData))
		paramData = paramData[p.ActualLength:]
		sc.Parameters = append(sc.Parameters, p)
	}
	p.AddLayer(sc)
	return p.NextDecoder(gopacket.DecodeFunc(decodeWithSCTPChunkTypePrefix))
}

func decodeCiscoDiscovery(data []byte, p gopacket.PacketBuilder) error {
	c := &CiscoDiscovery{
		Version:  data[0],
		TTL:      data[1],
		Checksum: binary.BigEndian.Uint16(data[2:4]),
	}
	if c.Version != 1 && c.Version != 2 {
		return fmt.Errorf("Invalid CiscoDiscovery version number %d", c.Version)
	}
	var err error
	c.Values, err = decodeCiscoDiscoveryTLVs(data[4:])
	if err != nil {
		return err
	}
	c.Contents = data[0:4]
	c.Payload = data[4:]
	p.AddLayer(c)
	return p.NextDecoder(gopacket.DecodeFunc(decodeCiscoDiscoveryInfo))
}

func decodeSCTPSack(data []byte, p gopacket.PacketBuilder) error {
	chunk, err := decodeSCTPChunk(data)
	if err != nil {
		return err
	}
	sc := &SCTPSack{
		SCTPChunk:                      chunk,
		CumulativeTSNAck:               binary.BigEndian.Uint32(data[4:8]),
		AdvertisedReceiverWindowCredit: binary.BigEndian.Uint32(data[8:12]),
		NumGapACKs:                     binary.BigEndian.Uint16(data[12:14]),
		NumDuplicateTSNs:               binary.BigEndian.Uint16(data[14:16]),
	}
	// We maximize gapAcks and dupTSNs here so we're not allocating tons
	// of memory based on a user-controlable field.  Our maximums are not exact,
	// but should give us sane defaults... we'll still hit slice boundaries and
	// fail if the user-supplied values are too high (in the for loops below), but
	// the amount of memory we'll have allocated because of that should be small
	// (< sc.ActualLength)
	gapAcks := sc.SCTPChunk.ActualLength / 2
	dupTSNs := (sc.SCTPChunk.ActualLength - gapAcks*2) / 4
	if gapAcks > int(sc.NumGapACKs) {
		gapAcks = int(sc.NumGapACKs)
	}
	if dupTSNs > int(sc.NumDuplicateTSNs) {
		dupTSNs = int(sc.NumDuplicateTSNs)
	}
	sc.GapACKs = make([]uint16, 0, gapAcks)
	sc.DuplicateTSNs = make([]uint32, 0, dupTSNs)
	bytesRemaining := data[16:]
	for i := 0; i < int(sc.NumGapACKs); i++ {
		sc.GapACKs = append(sc.GapACKs, binary.BigEndian.Uint16(bytesRemaining[:2]))
		bytesRemaining = bytesRemaining[2:]
	}
	for i := 0; i < int(sc.NumDuplicateTSNs); i++ {
		sc.DuplicateTSNs = append(sc.DuplicateTSNs, binary.BigEndian.Uint32(bytesRemaining[:4]))
		bytesRemaining = bytesRemaining[4:]
	}
	p.AddLayer(sc)
	return p.NextDecoder(gopacket.DecodeFunc(decodeWithSCTPChunkTypePrefix))
}

// decodeEthernetCTPFromFunctionType reads in the first 2 bytes to determine the EthernetCTP
// layer type to decode next, then decodes based on that.
func decodeEthernetCTPFromFunctionType(data []byte, p gopacket.PacketBuilder) error {
	function := EthernetCTPFunction(binary.LittleEndian.Uint16(data[:2]))
	switch function {
	case EthernetCTPFunctionReply:
		reply := &EthernetCTPReply{
			Function:      function,
			ReceiptNumber: binary.LittleEndian.Uint16(data[2:4]),
			Data:          data[4:],
			BaseLayer:     BaseLayer{data, nil},
		}
		p.AddLayer(reply)
		p.SetApplicationLayer(reply)
		return nil
	case EthernetCTPFunctionForwardData:
		forward := &EthernetCTPForwardData{
			Function:       function,
			ForwardAddress: data[2:8],
			BaseLayer:      BaseLayer{data[:8], data[8:]},
		}
		p.AddLayer(forward)
		return p.NextDecoder(gopacket.DecodeFunc(decodeEthernetCTPFromFunctionType))
	}
	return fmt.Errorf("Unknown EthernetCTP function type %v", function)
}