TUN-6666: Define packet package

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

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

@@ -0,0 +1,87 @@
+// Copyright 2012 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"
+	"github.com/google/gopacket"
+)
+
+// MPLS is the MPLS packet header.
+type MPLS struct {
+	BaseLayer
+	Label        uint32
+	TrafficClass uint8
+	StackBottom  bool
+	TTL          uint8
+}
+
+// LayerType returns gopacket.LayerTypeMPLS.
+func (m *MPLS) LayerType() gopacket.LayerType { return LayerTypeMPLS }
+
+// ProtocolGuessingDecoder attempts to guess the protocol of the bytes it's
+// given, then decode the packet accordingly.  Its algorithm for guessing is:
+//  If the packet starts with byte 0x45-0x4F: IPv4
+//  If the packet starts with byte 0x60-0x6F: IPv6
+//  Otherwise:  Error
+// See draft-hsmit-isis-aal5mux-00.txt for more detail on this approach.
+type ProtocolGuessingDecoder struct{}
+
+func (ProtocolGuessingDecoder) Decode(data []byte, p gopacket.PacketBuilder) error {
+	switch data[0] {
+	// 0x40 | header_len, where header_len is at least 5.
+	case 0x45, 0x46, 0x47, 0x48, 0x49, 0x4a, 0x4b, 0x4c, 0x4d, 0x4e, 0x4f:
+		return decodeIPv4(data, p)
+		// IPv6 can start with any byte whose first 4 bits are 0x6.
+	case 0x60, 0x61, 0x62, 0x63, 0x64, 0x65, 0x66, 0x67, 0x68, 0x69, 0x6a, 0x6b, 0x6c, 0x6d, 0x6e, 0x6f:
+		return decodeIPv6(data, p)
+	}
+	return errors.New("Unable to guess protocol of packet data")
+}
+
+// MPLSPayloadDecoder is the decoder used to data encapsulated by each MPLS
+// layer.  MPLS contains no type information, so we have to explicitly decide
+// which decoder to use.  This is initially set to ProtocolGuessingDecoder, our
+// simple attempt at guessing protocols based on the first few bytes of data
+// available to us.  However, if you know that in your environment MPLS always
+// encapsulates a specific protocol, you may reset this.
+var MPLSPayloadDecoder gopacket.Decoder = ProtocolGuessingDecoder{}
+
+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))
+}
+
+// SerializeTo writes the serialized form of this layer into the
+// SerializationBuffer, implementing gopacket.SerializableLayer.
+// See the docs for gopacket.SerializableLayer for more info.
+func (m *MPLS) SerializeTo(b gopacket.SerializeBuffer, opts gopacket.SerializeOptions) error {
+	bytes, err := b.PrependBytes(4)
+	if err != nil {
+		return err
+	}
+	encoded := m.Label << 12
+	encoded |= uint32(m.TrafficClass) << 9
+	encoded |= uint32(m.TTL)
+	if m.StackBottom {
+		encoded |= 0x100
+	}
+	binary.BigEndian.PutUint32(bytes, encoded)
+	return nil
+}