89 lines
2.4 KiB
Go
89 lines
2.4 KiB
Go
// Copyright 2012 Google, Inc. All rights reserved.
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//
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// Use of this source code is governed by a BSD-style license
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// that can be found in the LICENSE file in the root of the source
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// tree.
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package layers
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import (
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"encoding/binary"
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"errors"
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"github.com/google/gopacket"
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)
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// PPP is the layer for PPP encapsulation headers.
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type PPP struct {
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BaseLayer
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PPPType PPPType
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HasPPTPHeader bool
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}
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// PPPEndpoint is a singleton endpoint for PPP. Since there is no actual
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// addressing for the two ends of a PPP connection, we use a singleton value
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// named 'point' for each endpoint.
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var PPPEndpoint = gopacket.NewEndpoint(EndpointPPP, nil)
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// PPPFlow is a singleton flow for PPP. Since there is no actual addressing for
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// the two ends of a PPP connection, we use a singleton value to represent the
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// flow for all PPP connections.
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var PPPFlow = gopacket.NewFlow(EndpointPPP, nil, nil)
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// LayerType returns LayerTypePPP
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func (p *PPP) LayerType() gopacket.LayerType { return LayerTypePPP }
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// LinkFlow returns PPPFlow.
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func (p *PPP) LinkFlow() gopacket.Flow { return PPPFlow }
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func decodePPP(data []byte, p gopacket.PacketBuilder) error {
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ppp := &PPP{}
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offset := 0
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if data[0] == 0xff && data[1] == 0x03 {
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offset = 2
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ppp.HasPPTPHeader = true
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}
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if data[offset]&0x1 == 0 {
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if data[offset+1]&0x1 == 0 {
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return errors.New("PPP has invalid type")
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}
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ppp.PPPType = PPPType(binary.BigEndian.Uint16(data[offset : offset+2]))
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ppp.Contents = data[offset : offset+2]
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ppp.Payload = data[offset+2:]
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} else {
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ppp.PPPType = PPPType(data[offset])
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ppp.Contents = data[offset : offset+1]
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ppp.Payload = data[offset+1:]
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}
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p.AddLayer(ppp)
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p.SetLinkLayer(ppp)
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return p.NextDecoder(ppp.PPPType)
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}
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// SerializeTo writes the serialized form of this layer into the
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// SerializationBuffer, implementing gopacket.SerializableLayer.
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// See the docs for gopacket.SerializableLayer for more info.
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func (p *PPP) SerializeTo(b gopacket.SerializeBuffer, opts gopacket.SerializeOptions) error {
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if p.PPPType&0x100 == 0 {
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bytes, err := b.PrependBytes(2)
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if err != nil {
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return err
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}
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binary.BigEndian.PutUint16(bytes, uint16(p.PPPType))
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} else {
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bytes, err := b.PrependBytes(1)
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if err != nil {
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return err
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}
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bytes[0] = uint8(p.PPPType)
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}
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if p.HasPPTPHeader {
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bytes, err := b.PrependBytes(2)
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if err != nil {
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return err
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}
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bytes[0] = 0xff
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bytes[1] = 0x03
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}
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return nil
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}
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