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// 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/gopacket/gopacket"
)
// Geneve is specifed here https://tools.ietf.org/html/draft-ietf-nvo3-geneve-03
// Geneve Header:
//
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// |Ver| Opt Len |O|C| Rsvd. | Protocol Type |
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// | Virtual Network Identifier (VNI) | Reserved |
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// | Variable Length Options |
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
type Geneve struct {
BaseLayer
Version uint8 // 2 bits
OptionsLength uint8 // 6 bits
OAMPacket bool // 1 bits
CriticalOption bool // 1 bits
Protocol EthernetType // 16 bits
VNI uint32 // 24bits
Options []*GeneveOption
}
// Geneve Tunnel Options
//
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// | Option Class | Type |R|R|R| Length |
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// | Variable Option Data |
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
type GeneveOption struct {
Class uint16 // 16 bits
Type uint8 // 8 bits
Flags uint8 // 3 bits
Length uint8 // 5 bits
Data []byte
}
// LayerType returns LayerTypeGeneve
func (gn *Geneve) LayerType() gopacket.LayerType { return LayerTypeGeneve }
func decodeGeneveOption(data []byte, gn *Geneve, df gopacket.DecodeFeedback) (*GeneveOption, uint8, error) {
if len(data) < 3 {
df.SetTruncated()
return nil, 0, errors.New("geneve option too small")
}
opt := &GeneveOption{}
opt.Class = binary.BigEndian.Uint16(data[0:2])
opt.Type = data[2]
opt.Flags = data[3] >> 5
opt.Length = (data[3]&0x1f)*4 + 4
if len(data) < int(opt.Length) {
df.SetTruncated()
return nil, 0, errors.New("geneve option too small")
}
opt.Data = make([]byte, opt.Length-4)
copy(opt.Data, data[4:opt.Length])
return opt, opt.Length, nil
}
func (gn *Geneve) DecodeFromBytes(data []byte, df gopacket.DecodeFeedback) error {
if len(data) < 7 {
df.SetTruncated()
return errors.New("geneve packet too short")
}
gn.Version = data[0] >> 7
gn.OptionsLength = (data[0] & 0x3f) * 4
gn.OAMPacket = data[1]&0x80 > 0
gn.CriticalOption = data[1]&0x40 > 0
gn.Protocol = EthernetType(binary.BigEndian.Uint16(data[2:4]))
var buf [4]byte
copy(buf[1:], data[4:7])
gn.VNI = binary.BigEndian.Uint32(buf[:])
offset, length := uint8(8), int32(gn.OptionsLength)
if len(data) < int(length+7) {
df.SetTruncated()
return errors.New("geneve packet too short")
}
for length > 0 {
opt, len, err := decodeGeneveOption(data[offset:], gn, df)
if err != nil {
return err
}
gn.Options = append(gn.Options, opt)
length -= int32(len)
offset += len
}
gn.BaseLayer = BaseLayer{data[:offset], data[offset:]}
return nil
}
func (gn *Geneve) NextLayerType() gopacket.LayerType {
return gn.Protocol.LayerType()
}
func decodeGeneve(data []byte, p gopacket.PacketBuilder) error {
gn := &Geneve{}
return decodingLayerDecoder(gn, data, p)
}
// SerializeTo writes the serialized form of this layer into the
// SerializationBuffer, implementing gopacket.SerializableLayer.
// See the docs for gopacket.SerializableLayer for more info.
func (gn *Geneve) SerializeTo(b gopacket.SerializeBuffer, opts gopacket.SerializeOptions) error {
var optionsLength int
for _, o := range gn.Options {
dataLen := len(o.Data) & ^3
optionsLength += 4 + dataLen
}
if opts.FixLengths {
gn.OptionsLength = uint8(optionsLength)
}
plen := int(8 + optionsLength)
bytes, err := b.PrependBytes(plen)
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
// Construct Geneve
bytes[0] |= gn.Version << 6
bytes[0] |= ((gn.OptionsLength >> 2) & 0x3f)
if gn.OAMPacket {
bytes[1] |= 0x80
}
if gn.CriticalOption {
bytes[1] |= 0x40
}
binary.BigEndian.PutUint16(bytes[2:4], uint16(gn.Protocol))
if gn.VNI >= 1<<24 {
return fmt.Errorf("Virtual Network Identifier = %x exceeds max for 24-bit uint", gn.VNI)
}
binary.BigEndian.PutUint32(bytes[4:8], gn.VNI<<8)
// Construct Options
offset := 8
for _, o := range gn.Options {
dataLen := len(o.Data) & ^3
if opts.FixLengths {
o.Length = uint8(4 + dataLen)
}
binary.BigEndian.PutUint16(bytes[offset:(offset+2)], uint16(o.Class))
offset += 2
bytes[offset] = o.Type
offset += 1
bytes[offset] = o.Flags << 5
bytes[offset] |= ((o.Length - 4) >> 2) & 0x1f
offset += 1
copy(bytes[offset:(offset+dataLen)], o.Data)
offset += dataLen
}
return nil
}
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