Andrea Campanella | 7167ebb | 2020-02-24 09:56:38 +0100 | [diff] [blame^] | 1 | // Copyright 2012 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 | package gopacket |
| 8 | |
| 9 | import ( |
| 10 | "fmt" |
| 11 | ) |
| 12 | |
| 13 | // Layer represents a single decoded packet layer (using either the |
| 14 | // OSI or TCP/IP definition of a layer). When decoding, a packet's data is |
| 15 | // broken up into a number of layers. The caller may call LayerType() to |
| 16 | // figure out which type of layer they've received from the packet. Optionally, |
| 17 | // they may then use a type assertion to get the actual layer type for deep |
| 18 | // inspection of the data. |
| 19 | type Layer interface { |
| 20 | // LayerType is the gopacket type for this layer. |
| 21 | LayerType() LayerType |
| 22 | // LayerContents returns the set of bytes that make up this layer. |
| 23 | LayerContents() []byte |
| 24 | // LayerPayload returns the set of bytes contained within this layer, not |
| 25 | // including the layer itself. |
| 26 | LayerPayload() []byte |
| 27 | } |
| 28 | |
| 29 | // Payload is a Layer containing the payload of a packet. The definition of |
| 30 | // what constitutes the payload of a packet depends on previous layers; for |
| 31 | // TCP and UDP, we stop decoding above layer 4 and return the remaining |
| 32 | // bytes as a Payload. Payload is an ApplicationLayer. |
| 33 | type Payload []byte |
| 34 | |
| 35 | // LayerType returns LayerTypePayload |
| 36 | func (p Payload) LayerType() LayerType { return LayerTypePayload } |
| 37 | |
| 38 | // LayerContents returns the bytes making up this layer. |
| 39 | func (p Payload) LayerContents() []byte { return []byte(p) } |
| 40 | |
| 41 | // LayerPayload returns the payload within this layer. |
| 42 | func (p Payload) LayerPayload() []byte { return nil } |
| 43 | |
| 44 | // Payload returns this layer as bytes. |
| 45 | func (p Payload) Payload() []byte { return []byte(p) } |
| 46 | |
| 47 | // String implements fmt.Stringer. |
| 48 | func (p Payload) String() string { return fmt.Sprintf("%d byte(s)", len(p)) } |
| 49 | |
| 50 | // GoString implements fmt.GoStringer. |
| 51 | func (p Payload) GoString() string { return LongBytesGoString([]byte(p)) } |
| 52 | |
| 53 | // CanDecode implements DecodingLayer. |
| 54 | func (p Payload) CanDecode() LayerClass { return LayerTypePayload } |
| 55 | |
| 56 | // NextLayerType implements DecodingLayer. |
| 57 | func (p Payload) NextLayerType() LayerType { return LayerTypeZero } |
| 58 | |
| 59 | // DecodeFromBytes implements DecodingLayer. |
| 60 | func (p *Payload) DecodeFromBytes(data []byte, df DecodeFeedback) error { |
| 61 | *p = Payload(data) |
| 62 | return nil |
| 63 | } |
| 64 | |
| 65 | // SerializeTo writes the serialized form of this layer into the |
| 66 | // SerializationBuffer, implementing gopacket.SerializableLayer. |
| 67 | // See the docs for gopacket.SerializableLayer for more info. |
| 68 | func (p Payload) SerializeTo(b SerializeBuffer, opts SerializeOptions) error { |
| 69 | bytes, err := b.PrependBytes(len(p)) |
| 70 | if err != nil { |
| 71 | return err |
| 72 | } |
| 73 | copy(bytes, p) |
| 74 | return nil |
| 75 | } |
| 76 | |
| 77 | // decodePayload decodes data by returning it all in a Payload layer. |
| 78 | func decodePayload(data []byte, p PacketBuilder) error { |
| 79 | payload := &Payload{} |
| 80 | if err := payload.DecodeFromBytes(data, p); err != nil { |
| 81 | return nil |
| 82 | } |
| 83 | p.AddLayer(payload) |
| 84 | p.SetApplicationLayer(payload) |
| 85 | return nil |
| 86 | } |
| 87 | |
| 88 | // Fragment is a Layer containing a fragment of a larger frame, used by layers |
| 89 | // like IPv4 and IPv6 that allow for fragmentation of their payloads. |
| 90 | type Fragment []byte |
| 91 | |
| 92 | // LayerType returns LayerTypeFragment |
| 93 | func (p *Fragment) LayerType() LayerType { return LayerTypeFragment } |
| 94 | |
| 95 | // LayerContents implements Layer. |
| 96 | func (p *Fragment) LayerContents() []byte { return []byte(*p) } |
| 97 | |
| 98 | // LayerPayload implements Layer. |
| 99 | func (p *Fragment) LayerPayload() []byte { return nil } |
| 100 | |
| 101 | // Payload returns this layer as a byte slice. |
| 102 | func (p *Fragment) Payload() []byte { return []byte(*p) } |
| 103 | |
| 104 | // String implements fmt.Stringer. |
| 105 | func (p *Fragment) String() string { return fmt.Sprintf("%d byte(s)", len(*p)) } |
| 106 | |
| 107 | // CanDecode implements DecodingLayer. |
| 108 | func (p *Fragment) CanDecode() LayerClass { return LayerTypeFragment } |
| 109 | |
| 110 | // NextLayerType implements DecodingLayer. |
| 111 | func (p *Fragment) NextLayerType() LayerType { return LayerTypeZero } |
| 112 | |
| 113 | // DecodeFromBytes implements DecodingLayer. |
| 114 | func (p *Fragment) DecodeFromBytes(data []byte, df DecodeFeedback) error { |
| 115 | *p = Fragment(data) |
| 116 | return nil |
| 117 | } |
| 118 | |
| 119 | // SerializeTo writes the serialized form of this layer into the |
| 120 | // SerializationBuffer, implementing gopacket.SerializableLayer. |
| 121 | // See the docs for gopacket.SerializableLayer for more info. |
| 122 | func (p *Fragment) SerializeTo(b SerializeBuffer, opts SerializeOptions) error { |
| 123 | bytes, err := b.PrependBytes(len(*p)) |
| 124 | if err != nil { |
| 125 | return err |
| 126 | } |
| 127 | copy(bytes, *p) |
| 128 | return nil |
| 129 | } |
| 130 | |
| 131 | // decodeFragment decodes data by returning it all in a Fragment layer. |
| 132 | func decodeFragment(data []byte, p PacketBuilder) error { |
| 133 | payload := &Fragment{} |
| 134 | if err := payload.DecodeFromBytes(data, p); err != nil { |
| 135 | return nil |
| 136 | } |
| 137 | p.AddLayer(payload) |
| 138 | p.SetApplicationLayer(payload) |
| 139 | return nil |
| 140 | } |
| 141 | |
| 142 | // These layers correspond to Internet Protocol Suite (TCP/IP) layers, and their |
| 143 | // corresponding OSI layers, as best as possible. |
| 144 | |
| 145 | // LinkLayer is the packet layer corresponding to TCP/IP layer 1 (OSI layer 2) |
| 146 | type LinkLayer interface { |
| 147 | Layer |
| 148 | LinkFlow() Flow |
| 149 | } |
| 150 | |
| 151 | // NetworkLayer is the packet layer corresponding to TCP/IP layer 2 (OSI |
| 152 | // layer 3) |
| 153 | type NetworkLayer interface { |
| 154 | Layer |
| 155 | NetworkFlow() Flow |
| 156 | } |
| 157 | |
| 158 | // TransportLayer is the packet layer corresponding to the TCP/IP layer 3 (OSI |
| 159 | // layer 4) |
| 160 | type TransportLayer interface { |
| 161 | Layer |
| 162 | TransportFlow() Flow |
| 163 | } |
| 164 | |
| 165 | // ApplicationLayer is the packet layer corresponding to the TCP/IP layer 4 (OSI |
| 166 | // layer 7), also known as the packet payload. |
| 167 | type ApplicationLayer interface { |
| 168 | Layer |
| 169 | Payload() []byte |
| 170 | } |
| 171 | |
| 172 | // ErrorLayer is a packet layer created when decoding of the packet has failed. |
| 173 | // Its payload is all the bytes that we were unable to decode, and the returned |
| 174 | // error details why the decoding failed. |
| 175 | type ErrorLayer interface { |
| 176 | Layer |
| 177 | Error() error |
| 178 | } |