TUN-6666: Define packet package

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

vendor/github.com/google/gopacket/decode.go

@@ -0,0 +1,157 @@
+// 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 gopacket
+
+import (
+	"errors"
+)
+
+// DecodeFeedback is used by DecodingLayer layers to provide decoding metadata.
+type DecodeFeedback interface {
+	// SetTruncated should be called if during decoding you notice that a packet
+	// is shorter than internal layer variables (HeaderLength, or the like) say it
+	// should be.  It sets packet.Metadata().Truncated.
+	SetTruncated()
+}
+
+type nilDecodeFeedback struct{}
+
+func (nilDecodeFeedback) SetTruncated() {}
+
+// NilDecodeFeedback implements DecodeFeedback by doing nothing.
+var NilDecodeFeedback DecodeFeedback = nilDecodeFeedback{}
+
+// PacketBuilder is used by layer decoders to store the layers they've decoded,
+// and to defer future decoding via NextDecoder.
+// Typically, the pattern for use is:
+//  func (m *myDecoder) Decode(data []byte, p PacketBuilder) error {
+//    if myLayer, err := myDecodingLogic(data); err != nil {
+//      return err
+//    } else {
+//      p.AddLayer(myLayer)
+//    }
+//    // maybe do this, if myLayer is a LinkLayer
+//    p.SetLinkLayer(myLayer)
+//    return p.NextDecoder(nextDecoder)
+//  }
+type PacketBuilder interface {
+	DecodeFeedback
+	// AddLayer should be called by a decoder immediately upon successful
+	// decoding of a layer.
+	AddLayer(l Layer)
+	// The following functions set the various specific layers in the final
+	// packet.  Note that if many layers call SetX, the first call is kept and all
+	// other calls are ignored.
+	SetLinkLayer(LinkLayer)
+	SetNetworkLayer(NetworkLayer)
+	SetTransportLayer(TransportLayer)
+	SetApplicationLayer(ApplicationLayer)
+	SetErrorLayer(ErrorLayer)
+	// NextDecoder should be called by a decoder when they're done decoding a
+	// packet layer but not done with decoding the entire packet.  The next
+	// decoder will be called to decode the last AddLayer's LayerPayload.
+	// Because of this, NextDecoder must only be called once all other
+	// PacketBuilder calls have been made.  Set*Layer and AddLayer calls after
+	// NextDecoder calls will behave incorrectly.
+	NextDecoder(next Decoder) error
+	// DumpPacketData is used solely for decoding.  If you come across an error
+	// you need to diagnose while processing a packet, call this and your packet's
+	// data will be dumped to stderr so you can create a test.  This should never
+	// be called from a production decoder.
+	DumpPacketData()
+	// DecodeOptions returns the decode options
+	DecodeOptions() *DecodeOptions
+}
+
+// Decoder is an interface for logic to decode a packet layer.  Users may
+// implement a Decoder to handle their own strange packet types, or may use one
+// of the many decoders available in the 'layers' subpackage to decode things
+// for them.
+type Decoder interface {
+	// Decode decodes the bytes of a packet, sending decoded values and other
+	// information to PacketBuilder, and returning an error if unsuccessful.  See
+	// the PacketBuilder documentation for more details.
+	Decode([]byte, PacketBuilder) error
+}
+
+// DecodeFunc wraps a function to make it a Decoder.
+type DecodeFunc func([]byte, PacketBuilder) error
+
+// Decode implements Decoder by calling itself.
+func (d DecodeFunc) Decode(data []byte, p PacketBuilder) error {
+	// function, call thyself.
+	return d(data, p)
+}
+
+// DecodePayload is a Decoder that returns a Payload layer containing all
+// remaining bytes.
+var DecodePayload Decoder = DecodeFunc(decodePayload)
+
+// DecodeUnknown is a Decoder that returns an Unknown layer containing all
+// remaining bytes, useful if you run up against a layer that you're unable to
+// decode yet.  This layer is considered an ErrorLayer.
+var DecodeUnknown Decoder = DecodeFunc(decodeUnknown)
+
+// DecodeFragment is a Decoder that returns a Fragment layer containing all
+// remaining bytes.
+var DecodeFragment Decoder = DecodeFunc(decodeFragment)
+
+// LayerTypeZero is an invalid layer type, but can be used to determine whether
+// layer type has actually been set correctly.
+var LayerTypeZero = RegisterLayerType(0, LayerTypeMetadata{Name: "Unknown", Decoder: DecodeUnknown})
+
+// LayerTypeDecodeFailure is the layer type for the default error layer.
+var LayerTypeDecodeFailure = RegisterLayerType(1, LayerTypeMetadata{Name: "DecodeFailure", Decoder: DecodeUnknown})
+
+// LayerTypePayload is the layer type for a payload that we don't try to decode
+// but treat as a success, IE: an application-level payload.
+var LayerTypePayload = RegisterLayerType(2, LayerTypeMetadata{Name: "Payload", Decoder: DecodePayload})
+
+// LayerTypeFragment is the layer type for a fragment of a layer transported
+// by an underlying layer that supports fragmentation.
+var LayerTypeFragment = RegisterLayerType(3, LayerTypeMetadata{Name: "Fragment", Decoder: DecodeFragment})
+
+// DecodeFailure is a packet layer created if decoding of the packet data failed
+// for some reason.  It implements ErrorLayer.  LayerContents will be the entire
+// set of bytes that failed to parse, and Error will return the reason parsing
+// failed.
+type DecodeFailure struct {
+	data  []byte
+	err   error
+	stack []byte
+}
+
+// Error returns the error encountered during decoding.
+func (d *DecodeFailure) Error() error { return d.err }
+
+// LayerContents implements Layer.
+func (d *DecodeFailure) LayerContents() []byte { return d.data }
+
+// LayerPayload implements Layer.
+func (d *DecodeFailure) LayerPayload() []byte { return nil }
+
+// String implements fmt.Stringer.
+func (d *DecodeFailure) String() string {
+	return "Packet decoding error: " + d.Error().Error()
+}
+
+// Dump implements Dumper.
+func (d *DecodeFailure) Dump() (s string) {
+	if d.stack != nil {
+		s = string(d.stack)
+	}
+	return
+}
+
+// LayerType returns LayerTypeDecodeFailure
+func (d *DecodeFailure) LayerType() LayerType { return LayerTypeDecodeFailure }
+
+// decodeUnknown "decodes" unsupported data types by returning an error.
+// This decoder will thus always return a DecodeFailure layer.
+func decodeUnknown(data []byte, p PacketBuilder) error {
+	return errors.New("Layer type not currently supported")
+}