TUN-6666: Define packet package

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

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

@@ -0,0 +1,123 @@
+// Copyright 2016 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"
+)
+
+//  VXLAN is specifed in RFC 7348 https://tools.ietf.org/html/rfc7348
+//  G, D, A, Group Policy ID from https://tools.ietf.org/html/draft-smith-vxlan-group-policy-00
+//  0                   1                   2                   3
+//  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+//  0             8               16              24              32
+// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+// |G|R|R|R|I|R|R|R|R|D|R|R|A|R|R|R|       Group Policy ID         |
+// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+// |     24 bit VXLAN Network Identifier           |   Reserved    |
+// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+
+// VXLAN is a VXLAN packet header
+type VXLAN struct {
+	BaseLayer
+	ValidIDFlag      bool   // 'I' bit per RFC 7348
+	VNI              uint32 // 'VXLAN Network Identifier' 24 bits per RFC 7348
+	GBPExtension     bool   // 'G' bit per Group Policy https://tools.ietf.org/html/draft-smith-vxlan-group-policy-00
+	GBPDontLearn     bool   // 'D' bit per Group Policy
+	GBPApplied       bool   // 'A' bit per Group Policy
+	GBPGroupPolicyID uint16 // 'Group Policy ID' 16 bits per Group Policy
+}
+
+// LayerType returns LayerTypeVXLAN
+func (vx *VXLAN) LayerType() gopacket.LayerType { return LayerTypeVXLAN }
+
+// CanDecode returns the layer type this DecodingLayer can decode
+func (vx *VXLAN) CanDecode() gopacket.LayerClass {
+	return LayerTypeVXLAN
+}
+
+// NextLayerType retuns the next layer we should see after vxlan
+func (vx *VXLAN) NextLayerType() gopacket.LayerType {
+	return LayerTypeEthernet
+}
+
+// DecodeFromBytes takes a byte buffer and decodes
+func (vx *VXLAN) DecodeFromBytes(data []byte, df gopacket.DecodeFeedback) error {
+	if len(data) < 8 {
+		return errors.New("vxlan packet too small")
+	}
+	// VNI is a 24bit number, Uint32 requires 32 bits
+	var buf [4]byte
+	copy(buf[1:], data[4:7])
+
+	// RFC 7348 https://tools.ietf.org/html/rfc7348
+	vx.ValidIDFlag = data[0]&0x08 > 0        // 'I' bit per RFC7348
+	vx.VNI = binary.BigEndian.Uint32(buf[:]) // VXLAN Network Identifier per RFC7348
+
+	// Group Based Policy https://tools.ietf.org/html/draft-smith-vxlan-group-policy-00
+	vx.GBPExtension = data[0]&0x80 > 0                       // 'G' bit per the group policy draft
+	vx.GBPDontLearn = data[1]&0x40 > 0                       // 'D' bit - the egress VTEP MUST NOT learn the source address of the encapsulated frame.
+	vx.GBPApplied = data[1]&0x80 > 0                         // 'A' bit - indicates that the group policy has already been applied to this packet.
+	vx.GBPGroupPolicyID = binary.BigEndian.Uint16(data[2:4]) // Policy ID as per the group policy draft
+
+	// Layer information
+	const vxlanLength = 8
+	vx.Contents = data[:vxlanLength]
+	vx.Payload = data[vxlanLength:]
+
+	return nil
+
+}
+
+func decodeVXLAN(data []byte, p gopacket.PacketBuilder) error {
+	vx := &VXLAN{}
+	err := vx.DecodeFromBytes(data, p)
+	if err != nil {
+		return err
+	}
+
+	p.AddLayer(vx)
+	return p.NextDecoder(LinkTypeEthernet)
+}
+
+// SerializeTo writes the serialized form of this layer into the
+// SerializationBuffer, implementing gopacket.SerializableLayer.
+// See the docs for gopacket.SerializableLayer for more info.
+func (vx *VXLAN) SerializeTo(b gopacket.SerializeBuffer, opts gopacket.SerializeOptions) error {
+	bytes, err := b.PrependBytes(8)
+	if err != nil {
+		return err
+	}
+
+	// PrependBytes does not guarantee that bytes are zeroed.  Setting flags via OR requires that they start off at zero
+	bytes[0] = 0
+	bytes[1] = 0
+
+	if vx.ValidIDFlag {
+		bytes[0] |= 0x08
+	}
+	if vx.GBPExtension {
+		bytes[0] |= 0x80
+	}
+	if vx.GBPDontLearn {
+		bytes[1] |= 0x40
+	}
+	if vx.GBPApplied {
+		bytes[1] |= 0x80
+	}
+
+	binary.BigEndian.PutUint16(bytes[2:4], vx.GBPGroupPolicyID)
+	if vx.VNI >= 1<<24 {
+		return fmt.Errorf("Virtual Network Identifier = %x exceeds max for 24-bit uint", vx.VNI)
+	}
+	binary.BigEndian.PutUint32(bytes[4:8], vx.VNI<<8)
+	return nil
+}