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

   1 // Copyright 2015 Google, Inc. All rights reserved.
   2 //
   3 // Use of this source code is governed by a BSD-style license
   4 // that can be found in the LICENSE file in the root of the source
   5 // tree.
   6
   7 // http://www.tcpdump.org/linktypes/LINKTYPE_IEEE802_11_PRISM.html
   8
   9 package layers
  10
  11 import (
  12         "encoding/binary"
  13         "errors"
  14
  15         "github.com/google/gopacket"
  16 )
  17
  18 func decodePrismValue(data []byte, pv *PrismValue) {
  19         pv.DID = PrismDID(binary.LittleEndian.Uint32(data[0:4]))
  20         pv.Status = binary.LittleEndian.Uint16(data[4:6])
  21         pv.Length = binary.LittleEndian.Uint16(data[6:8])
  22         pv.Data = data[8 : 8+pv.Length]
  23 }
  24
  25 type PrismDID uint32
  26
  27 const (
  28         PrismDIDType1HostTime                  PrismDID = 0x10044
  29         PrismDIDType2HostTime                  PrismDID = 0x01041
  30         PrismDIDType1MACTime                   PrismDID = 0x20044
  31         PrismDIDType2MACTime                   PrismDID = 0x02041
  32         PrismDIDType1Channel                   PrismDID = 0x30044
  33         PrismDIDType2Channel                   PrismDID = 0x03041
  34         PrismDIDType1RSSI                      PrismDID = 0x40044
  35         PrismDIDType2RSSI                      PrismDID = 0x04041
  36         PrismDIDType1SignalQuality             PrismDID = 0x50044
  37         PrismDIDType2SignalQuality             PrismDID = 0x05041
  38         PrismDIDType1Signal                    PrismDID = 0x60044
  39         PrismDIDType2Signal                    PrismDID = 0x06041
  40         PrismDIDType1Noise                     PrismDID = 0x70044
  41         PrismDIDType2Noise                     PrismDID = 0x07041
  42         PrismDIDType1Rate                      PrismDID = 0x80044
  43         PrismDIDType2Rate                      PrismDID = 0x08041
  44         PrismDIDType1TransmittedFrameIndicator PrismDID = 0x90044
  45         PrismDIDType2TransmittedFrameIndicator PrismDID = 0x09041
  46         PrismDIDType1FrameLength               PrismDID = 0xA0044
  47         PrismDIDType2FrameLength               PrismDID = 0x0A041
  48 )
  49
  50 const (
  51         PrismType1MessageCode uint16 = 0x00000044
  52         PrismType2MessageCode uint16 = 0x00000041
  53 )
  54
  55 func (p PrismDID) String() string {
  56         dids := map[PrismDID]string{
  57                 PrismDIDType1HostTime:                  "Host Time",
  58                 PrismDIDType2HostTime:                  "Host Time",
  59                 PrismDIDType1MACTime:                   "MAC Time",
  60                 PrismDIDType2MACTime:                   "MAC Time",
  61                 PrismDIDType1Channel:                   "Channel",
  62                 PrismDIDType2Channel:                   "Channel",
  63                 PrismDIDType1RSSI:                      "RSSI",
  64                 PrismDIDType2RSSI:                      "RSSI",
  65                 PrismDIDType1SignalQuality:             "Signal Quality",
  66                 PrismDIDType2SignalQuality:             "Signal Quality",
  67                 PrismDIDType1Signal:                    "Signal",
  68                 PrismDIDType2Signal:                    "Signal",
  69                 PrismDIDType1Noise:                     "Noise",
  70                 PrismDIDType2Noise:                     "Noise",
  71                 PrismDIDType1Rate:                      "Rate",
  72                 PrismDIDType2Rate:                      "Rate",
  73                 PrismDIDType1TransmittedFrameIndicator: "Transmitted Frame Indicator",
  74                 PrismDIDType2TransmittedFrameIndicator: "Transmitted Frame Indicator",
  75                 PrismDIDType1FrameLength:               "Frame Length",
  76                 PrismDIDType2FrameLength:               "Frame Length",
  77         }
  78
  79         if str, ok := dids[p]; ok {
  80                 return str
  81         }
  82
  83         return "Unknown DID"
  84 }
  85
  86 type PrismValue struct {
  87         DID    PrismDID
  88         Status uint16
  89         Length uint16
  90         Data   []byte
  91 }
  92
  93 func (pv *PrismValue) IsSupplied() bool {
  94         return pv.Status == 1
  95 }
  96
  97 var ErrPrismExpectedMoreData = errors.New("Expected more data.")
  98 var ErrPrismInvalidCode = errors.New("Invalid header code.")
  99
 100 func decodePrismHeader(data []byte, p gopacket.PacketBuilder) error {
 101         d := &PrismHeader{}
 102         return decodingLayerDecoder(d, data, p)
 103 }
 104
 105 type PrismHeader struct {
 106         BaseLayer
 107         Code       uint16
 108         Length     uint16
 109         DeviceName string
 110         Values     []PrismValue
 111 }
 112
 113 func (m *PrismHeader) LayerType() gopacket.LayerType { return LayerTypePrismHeader }
 114
 115 func (m *PrismHeader) DecodeFromBytes(data []byte, df gopacket.DecodeFeedback) error {
 116         m.Code = binary.LittleEndian.Uint16(data[0:4])
 117         m.Length = binary.LittleEndian.Uint16(data[4:8])
 118         m.DeviceName = string(data[8:24])
 119         m.BaseLayer = BaseLayer{Contents: data[:m.Length], Payload: data[m.Length:len(data)]}
 120
 121         switch m.Code {
 122         case PrismType1MessageCode:
 123                 fallthrough
 124         case PrismType2MessageCode:
 125                 // valid message code
 126         default:
 127                 return ErrPrismInvalidCode
 128         }
 129
 130         offset := uint16(24)
 131
 132         m.Values = make([]PrismValue, (m.Length-offset)/12)
 133         for i := 0; i < len(m.Values); i++ {
 134                 decodePrismValue(data[offset:offset+12], &m.Values[i])
 135                 offset += 12
 136         }
 137
 138         if offset != m.Length {
 139                 return ErrPrismExpectedMoreData
 140         }
 141
 142         return nil
 143 }
 144
 145 func (m *PrismHeader) CanDecode() gopacket.LayerClass    { return LayerTypePrismHeader }
 146 func (m *PrismHeader) NextLayerType() gopacket.LayerType { return LayerTypeDot11 }