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Matteo Scandoloa6a3aee2019-11-26 13:30:14 -07001// Copyright 2012 Google, Inc. All rights reserved.
2// Copyright 2009-2011 Andreas Krennmair. All rights reserved.
3//
4// Use of this source code is governed by a BSD-style license
5// that can be found in the LICENSE file in the root of the source
6// tree.
7
8package layers
9
10import (
11 "encoding/binary"
12 "errors"
13
14 "github.com/google/gopacket"
15)
16
17// Potential values for ARP.Operation.
18const (
19 ARPRequest = 1
20 ARPReply = 2
21)
22
23// ARP is a ARP packet header.
24type ARP struct {
25 BaseLayer
26 AddrType LinkType
27 Protocol EthernetType
28 HwAddressSize uint8
29 ProtAddressSize uint8
30 Operation uint16
31 SourceHwAddress []byte
32 SourceProtAddress []byte
33 DstHwAddress []byte
34 DstProtAddress []byte
35}
36
37// LayerType returns LayerTypeARP
38func (arp *ARP) LayerType() gopacket.LayerType { return LayerTypeARP }
39
40// DecodeFromBytes decodes the given bytes into this layer.
41func (arp *ARP) DecodeFromBytes(data []byte, df gopacket.DecodeFeedback) error {
42 arp.AddrType = LinkType(binary.BigEndian.Uint16(data[0:2]))
43 arp.Protocol = EthernetType(binary.BigEndian.Uint16(data[2:4]))
44 arp.HwAddressSize = data[4]
45 arp.ProtAddressSize = data[5]
46 arp.Operation = binary.BigEndian.Uint16(data[6:8])
47 arp.SourceHwAddress = data[8 : 8+arp.HwAddressSize]
48 arp.SourceProtAddress = data[8+arp.HwAddressSize : 8+arp.HwAddressSize+arp.ProtAddressSize]
49 arp.DstHwAddress = data[8+arp.HwAddressSize+arp.ProtAddressSize : 8+2*arp.HwAddressSize+arp.ProtAddressSize]
50 arp.DstProtAddress = data[8+2*arp.HwAddressSize+arp.ProtAddressSize : 8+2*arp.HwAddressSize+2*arp.ProtAddressSize]
51
52 arpLength := 8 + 2*arp.HwAddressSize + 2*arp.ProtAddressSize
53 arp.Contents = data[:arpLength]
54 arp.Payload = data[arpLength:]
55 return nil
56}
57
58// SerializeTo writes the serialized form of this layer into the
59// SerializationBuffer, implementing gopacket.SerializableLayer.
60// See the docs for gopacket.SerializableLayer for more info.
61func (arp *ARP) SerializeTo(b gopacket.SerializeBuffer, opts gopacket.SerializeOptions) error {
62 size := 8 + len(arp.SourceHwAddress) + len(arp.SourceProtAddress) + len(arp.DstHwAddress) + len(arp.DstProtAddress)
63 bytes, err := b.PrependBytes(size)
64 if err != nil {
65 return err
66 }
67 if opts.FixLengths {
68 if len(arp.SourceHwAddress) != len(arp.DstHwAddress) {
69 return errors.New("mismatched hardware address sizes")
70 }
71 arp.HwAddressSize = uint8(len(arp.SourceHwAddress))
72 if len(arp.SourceProtAddress) != len(arp.DstProtAddress) {
73 return errors.New("mismatched prot address sizes")
74 }
75 arp.ProtAddressSize = uint8(len(arp.SourceProtAddress))
76 }
77 binary.BigEndian.PutUint16(bytes, uint16(arp.AddrType))
78 binary.BigEndian.PutUint16(bytes[2:], uint16(arp.Protocol))
79 bytes[4] = arp.HwAddressSize
80 bytes[5] = arp.ProtAddressSize
81 binary.BigEndian.PutUint16(bytes[6:], arp.Operation)
82 start := 8
83 for _, addr := range [][]byte{
84 arp.SourceHwAddress,
85 arp.SourceProtAddress,
86 arp.DstHwAddress,
87 arp.DstProtAddress,
88 } {
89 copy(bytes[start:], addr)
90 start += len(addr)
91 }
92 return nil
93}
94
95// CanDecode returns the set of layer types that this DecodingLayer can decode.
96func (arp *ARP) CanDecode() gopacket.LayerClass {
97 return LayerTypeARP
98}
99
100// NextLayerType returns the layer type contained by this DecodingLayer.
101func (arp *ARP) NextLayerType() gopacket.LayerType {
102 return gopacket.LayerTypePayload
103}
104
105func decodeARP(data []byte, p gopacket.PacketBuilder) error {
106
107 arp := &ARP{}
108 return decodingLayerDecoder(arp, data, p)
109}