TUN-6666: Define packet package

This package defines IP and ICMP packet, decoders, encoder and flow

vendor/github.com/google/gopacket/layers/lcm.go

@@ -0,0 +1,218 @@
+// Copyright 2018 Google, Inc. All rights reserved.
+//
+// Use of this source code is governed by a BSD-style license
+// that can be found in the LICENSE file in the root of the source
+// tree.
+
+package layers
+
+import (
+	"encoding/binary"
+	"errors"
+	"fmt"
+
+	"github.com/google/gopacket"
+)
+
+const (
+	// LCMShortHeaderMagic is the LCM small message header magic number
+	LCMShortHeaderMagic uint32 = 0x4c433032
+	// LCMFragmentedHeaderMagic is the LCM fragmented message header magic number
+	LCMFragmentedHeaderMagic uint32 = 0x4c433033
+)
+
+// LCM (Lightweight Communications and Marshalling) is a set of libraries and
+// tools for message passing and data marshalling, targeted at real-time systems
+// where high-bandwidth and low latency are critical. It provides a
+// publish/subscribe message passing model and automatic
+// marshalling/unmarshalling code generation with bindings for applications in a
+// variety of programming languages.
+//
+// References
+//   https://lcm-proj.github.io/
+//   https://github.com/lcm-proj/lcm
+type LCM struct {
+	// Common (short & fragmented header) fields
+	Magic          uint32
+	SequenceNumber uint32
+	// Fragmented header only fields
+	PayloadSize    uint32
+	FragmentOffset uint32
+	FragmentNumber uint16
+	TotalFragments uint16
+	// Common field
+	ChannelName string
+	// Gopacket helper fields
+	Fragmented  bool
+	fingerprint LCMFingerprint
+	contents    []byte
+	payload     []byte
+}
+
+// LCMFingerprint is the type of a LCM fingerprint.
+type LCMFingerprint uint64
+
+var (
+	// lcmLayerTypes contains a map of all LCM fingerprints that we support and
+	// their LayerType
+	lcmLayerTypes  = map[LCMFingerprint]gopacket.LayerType{}
+	layerTypeIndex = 1001
+)
+
+// RegisterLCMLayerType allows users to register decoders for the underlying
+// LCM payload. This is done based on the fingerprint that every LCM message
+// contains and which identifies it uniquely. If num is not the zero value it
+// will be used when registering with RegisterLayerType towards gopacket,
+// otherwise an incremental value starting from 1001 will be used.
+func RegisterLCMLayerType(num int, name string, fingerprint LCMFingerprint,
+	decoder gopacket.Decoder) gopacket.LayerType {
+	metadata := gopacket.LayerTypeMetadata{Name: name, Decoder: decoder}
+
+	if num == 0 {
+		num = layerTypeIndex
+		layerTypeIndex++
+	}
+
+	lcmLayerTypes[fingerprint] = gopacket.RegisterLayerType(num, metadata)
+
+	return lcmLayerTypes[fingerprint]
+}
+
+// SupportedLCMFingerprints returns a slice of all LCM fingerprints that has
+// been registered so far.
+func SupportedLCMFingerprints() []LCMFingerprint {
+	fingerprints := make([]LCMFingerprint, 0, len(lcmLayerTypes))
+	for fp := range lcmLayerTypes {
+		fingerprints = append(fingerprints, fp)
+	}
+	return fingerprints
+}
+
+// GetLCMLayerType returns the underlying LCM message's LayerType.
+// This LayerType has to be registered by using RegisterLCMLayerType.
+func GetLCMLayerType(fingerprint LCMFingerprint) gopacket.LayerType {
+	layerType, ok := lcmLayerTypes[fingerprint]
+	if !ok {
+		return gopacket.LayerTypePayload
+	}
+
+	return layerType
+}
+
+func decodeLCM(data []byte, p gopacket.PacketBuilder) error {
+	lcm := &LCM{}
+
+	err := lcm.DecodeFromBytes(data, p)
+	if err != nil {
+		return err
+	}
+
+	p.AddLayer(lcm)
+	p.SetApplicationLayer(lcm)
+
+	return p.NextDecoder(lcm.NextLayerType())
+}
+
+// DecodeFromBytes decodes the given bytes into this layer.
+func (lcm *LCM) DecodeFromBytes(data []byte, df gopacket.DecodeFeedback) error {
+	if len(data) < 8 {
+		df.SetTruncated()
+		return errors.New("LCM < 8 bytes")
+	}
+	offset := 0
+
+	lcm.Magic = binary.BigEndian.Uint32(data[offset:4])
+	offset += 4
+
+	if lcm.Magic != LCMShortHeaderMagic && lcm.Magic != LCMFragmentedHeaderMagic {
+		return fmt.Errorf("Received LCM header magic %v does not match know "+
+			"LCM magic numbers. Dropping packet.", lcm.Magic)
+	}
+
+	lcm.SequenceNumber = binary.BigEndian.Uint32(data[offset:8])
+	offset += 4
+
+	if lcm.Magic == LCMFragmentedHeaderMagic {
+		lcm.Fragmented = true
+
+		lcm.PayloadSize = binary.BigEndian.Uint32(data[offset : offset+4])
+		offset += 4
+
+		lcm.FragmentOffset = binary.BigEndian.Uint32(data[offset : offset+4])
+		offset += 4
+
+		lcm.FragmentNumber = binary.BigEndian.Uint16(data[offset : offset+2])
+		offset += 2
+
+		lcm.TotalFragments = binary.BigEndian.Uint16(data[offset : offset+2])
+		offset += 2
+	} else {
+		lcm.Fragmented = false
+	}
+
+	if !lcm.Fragmented || (lcm.Fragmented && lcm.FragmentNumber == 0) {
+		buffer := make([]byte, 0)
+		for _, b := range data[offset:] {
+			offset++
+
+			if b == 0 {
+				break
+			}
+
+			buffer = append(buffer, b)
+		}
+
+		lcm.ChannelName = string(buffer)
+	}
+
+	lcm.fingerprint = LCMFingerprint(
+		binary.BigEndian.Uint64(data[offset : offset+8]))
+
+	lcm.contents = data[:offset]
+	lcm.payload = data[offset:]
+
+	return nil
+}
+
+// CanDecode returns a set of layers that LCM objects can decode.
+// As LCM objects can only decode the LCM layer, we just return that layer.
+func (lcm LCM) CanDecode() gopacket.LayerClass {
+	return LayerTypeLCM
+}
+
+// NextLayerType specifies the LCM payload layer type following this header.
+// As LCM packets are serialized structs with uniq fingerprints for each uniq
+// combination of data types, lookup of correct layer type is based on that
+// fingerprint.
+func (lcm LCM) NextLayerType() gopacket.LayerType {
+	if !lcm.Fragmented || (lcm.Fragmented && lcm.FragmentNumber == 0) {
+		return GetLCMLayerType(lcm.fingerprint)
+	}
+
+	return gopacket.LayerTypeFragment
+}
+
+// LayerType returns LayerTypeLCM
+func (lcm LCM) LayerType() gopacket.LayerType {
+	return LayerTypeLCM
+}
+
+// LayerContents returns the contents of the LCM header.
+func (lcm LCM) LayerContents() []byte {
+	return lcm.contents
+}
+
+// LayerPayload returns the payload following this LCM header.
+func (lcm LCM) LayerPayload() []byte {
+	return lcm.payload
+}
+
+// Payload returns the payload following this LCM header.
+func (lcm LCM) Payload() []byte {
+	return lcm.LayerPayload()
+}
+
+// Fingerprint returns the LCM fingerprint of the underlying message.
+func (lcm LCM) Fingerprint() LCMFingerprint {
+	return lcm.fingerprint
+}