TUN-6666: Define packet package

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

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

@@ -0,0 +1,193 @@
+// 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"
+)
+
+// LLC is the layer used for 802.2 Logical Link Control headers.
+// See http://standards.ieee.org/getieee802/download/802.2-1998.pdf
+type LLC struct {
+	BaseLayer
+	DSAP    uint8
+	IG      bool // true means group, false means individual
+	SSAP    uint8
+	CR      bool // true means response, false means command
+	Control uint16
+}
+
+// LayerType returns gopacket.LayerTypeLLC.
+func (l *LLC) LayerType() gopacket.LayerType { return LayerTypeLLC }
+
+// DecodeFromBytes decodes the given bytes into this layer.
+func (l *LLC) DecodeFromBytes(data []byte, df gopacket.DecodeFeedback) error {
+	if len(data) < 3 {
+		return errors.New("LLC header too small")
+	}
+	l.DSAP = data[0] & 0xFE
+	l.IG = data[0]&0x1 != 0
+	l.SSAP = data[1] & 0xFE
+	l.CR = data[1]&0x1 != 0
+	l.Control = uint16(data[2])
+
+	if l.Control&0x1 == 0 || l.Control&0x3 == 0x1 {
+		if len(data) < 4 {
+			return errors.New("LLC header too small")
+		}
+		l.Control = l.Control<<8 | uint16(data[3])
+		l.Contents = data[:4]
+		l.Payload = data[4:]
+	} else {
+		l.Contents = data[:3]
+		l.Payload = data[3:]
+	}
+	return nil
+}
+
+// CanDecode returns the set of layer types that this DecodingLayer can decode.
+func (l *LLC) CanDecode() gopacket.LayerClass {
+	return LayerTypeLLC
+}
+
+// NextLayerType returns the layer type contained by this DecodingLayer.
+func (l *LLC) NextLayerType() gopacket.LayerType {
+	switch {
+	case l.DSAP == 0xAA && l.SSAP == 0xAA:
+		return LayerTypeSNAP
+	case l.DSAP == 0x42 && l.SSAP == 0x42:
+		return LayerTypeSTP
+	}
+	return gopacket.LayerTypeZero // Not implemented
+}
+
+// SNAP is used inside LLC.  See
+// http://standards.ieee.org/getieee802/download/802-2001.pdf.
+// From http://en.wikipedia.org/wiki/Subnetwork_Access_Protocol:
+//  "[T]he Subnetwork Access Protocol (SNAP) is a mechanism for multiplexing,
+//  on networks using IEEE 802.2 LLC, more protocols than can be distinguished
+//  by the 8-bit 802.2 Service Access Point (SAP) fields."
+type SNAP struct {
+	BaseLayer
+	OrganizationalCode []byte
+	Type               EthernetType
+}
+
+// LayerType returns gopacket.LayerTypeSNAP.
+func (s *SNAP) LayerType() gopacket.LayerType { return LayerTypeSNAP }
+
+// DecodeFromBytes decodes the given bytes into this layer.
+func (s *SNAP) DecodeFromBytes(data []byte, df gopacket.DecodeFeedback) error {
+	if len(data) < 5 {
+		return errors.New("SNAP header too small")
+	}
+	s.OrganizationalCode = data[:3]
+	s.Type = EthernetType(binary.BigEndian.Uint16(data[3:5]))
+	s.BaseLayer = BaseLayer{data[:5], data[5:]}
+	return nil
+}
+
+// CanDecode returns the set of layer types that this DecodingLayer can decode.
+func (s *SNAP) CanDecode() gopacket.LayerClass {
+	return LayerTypeSNAP
+}
+
+// NextLayerType returns the layer type contained by this DecodingLayer.
+func (s *SNAP) NextLayerType() gopacket.LayerType {
+	// See BUG(gconnel) in decodeSNAP
+	return s.Type.LayerType()
+}
+
+func decodeLLC(data []byte, p gopacket.PacketBuilder) error {
+	l := &LLC{}
+	err := l.DecodeFromBytes(data, p)
+	if err != nil {
+		return err
+	}
+	p.AddLayer(l)
+	return p.NextDecoder(l.NextLayerType())
+}
+
+func decodeSNAP(data []byte, p gopacket.PacketBuilder) error {
+	s := &SNAP{}
+	err := s.DecodeFromBytes(data, p)
+	if err != nil {
+		return err
+	}
+	p.AddLayer(s)
+	// BUG(gconnell):  When decoding SNAP, we treat the SNAP type as an Ethernet
+	// type.  This may not actually be an ethernet type in all cases,
+	// depending on the organizational code.  Right now, we don't check.
+	return p.NextDecoder(s.Type)
+}
+
+// SerializeTo writes the serialized form of this layer into the
+// SerializationBuffer, implementing gopacket.SerializableLayer.
+// See the docs for gopacket.SerializableLayer for more info.
+func (l *LLC) SerializeTo(b gopacket.SerializeBuffer, opts gopacket.SerializeOptions) error {
+	var igFlag, crFlag byte
+	var length int
+
+	if l.Control&0xFF00 != 0 {
+		length = 4
+	} else {
+		length = 3
+	}
+
+	if l.DSAP&0x1 != 0 {
+		return errors.New("DSAP value invalid, should not include IG flag bit")
+	}
+
+	if l.SSAP&0x1 != 0 {
+		return errors.New("SSAP value invalid, should not include CR flag bit")
+	}
+
+	if buf, err := b.PrependBytes(length); err != nil {
+		return err
+	} else {
+		igFlag = 0
+		if l.IG {
+			igFlag = 0x1
+		}
+
+		crFlag = 0
+		if l.CR {
+			crFlag = 0x1
+		}
+
+		buf[0] = l.DSAP + igFlag
+		buf[1] = l.SSAP + crFlag
+
+		if length == 4 {
+			buf[2] = uint8(l.Control >> 8)
+			buf[3] = uint8(l.Control)
+		} else {
+			buf[2] = uint8(l.Control)
+		}
+	}
+
+	return nil
+}
+
+// SerializeTo writes the serialized form of this layer into the
+// SerializationBuffer, implementing gopacket.SerializableLayer.
+// See the docs for gopacket.SerializableLayer for more info.
+func (s *SNAP) SerializeTo(b gopacket.SerializeBuffer, opts gopacket.SerializeOptions) error {
+	if buf, err := b.PrependBytes(5); err != nil {
+		return err
+	} else {
+		buf[0] = s.OrganizationalCode[0]
+		buf[1] = s.OrganizationalCode[1]
+		buf[2] = s.OrganizationalCode[2]
+		binary.BigEndian.PutUint16(buf[3:5], uint16(s.Type))
+	}
+
+	return nil
+}