-
Notifications
You must be signed in to change notification settings - Fork 0
/
arpv4_pdu.go
136 lines (112 loc) · 2.73 KB
/
arpv4_pdu.go
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
package edurouter
import (
"bytes"
"encoding/binary"
"github.com/mdlayher/ethernet"
"io"
"net"
)
type ARPOperation uint16
const (
ARPOperationRequest ARPOperation = 1
ARPOperationResponse ARPOperation = 2
HTYPEEthernet = 1
)
var EmptyHardwareAddr = []byte{
0x0, 0x0, 0x0,
0x0, 0x0, 0x0,
}
type ARPv4Pdu struct {
HTYPE uint16
PTYPE ethernet.EtherType
HLEN uint8
PLEN uint8
Operation ARPOperation
SrcHardwareAddr []byte
SrcProtoAddr []byte
DstHardwareAddr []byte
DstProtoAddr []byte
}
func (a *ARPv4Pdu) IsEthernetAndIPv4() bool {
if a.HTYPE != HTYPEEthernet {
// not ethernet
return false
}
if a.PTYPE != ethernet.EtherTypeARP && a.PTYPE != ethernet.EtherTypeIPv4 {
// not IPv4
return false
}
if a.HLEN != HardwareAddrLen {
// MAC's are 6 bytes
return false
}
if a.PLEN != net.IPv4len {
// IP's are 4 bytes
return false
}
return true
}
func (a *ARPv4Pdu) IsArpRequestForConfig(config *InterfaceConfig) bool {
if a.Operation != ARPOperationRequest {
// not request
return false
}
if !bytes.Equal(a.DstHardwareAddr, EmptyHardwareAddr) {
// something went wrong, should be empty
return false
}
if !bytes.Equal(a.DstProtoAddr, config.Addr.IP) {
// targetAddr should be the same
return false
}
return true
}
func (a *ARPv4Pdu) IsArpResponse() bool {
return a.Operation == ARPOperationResponse
}
func (a *ARPv4Pdu) BuildARPResponseWithConfig(config *InterfaceConfig) *ARPv4Pdu {
return &ARPv4Pdu{
HTYPE: a.HTYPE,
PTYPE: a.PTYPE,
HLEN: a.HLEN,
PLEN: a.PLEN,
Operation: ARPOperationResponse,
// provide configured mac as src
SrcHardwareAddr: *config.HardwareAddr,
SrcProtoAddr: config.Addr.IP,
// flip original sender to target
DstHardwareAddr: a.SrcHardwareAddr,
DstProtoAddr: a.SrcProtoAddr,
}
}
func (a *ARPv4Pdu) MarshalBinary() ([]byte, error) {
b := make([]byte, 28)
b[0] = byte(a.HTYPE >> 8)
b[1] = byte(a.HTYPE)
b[2] = byte(a.PTYPE >> 8)
b[3] = byte(a.PTYPE)
b[4] = a.HLEN
b[5] = a.PLEN
b[6] = byte(a.Operation >> 8)
b[7] = byte(a.Operation)
copy(b[8:], a.SrcHardwareAddr)
copy(b[14:], a.SrcProtoAddr)
copy(b[18:], a.DstHardwareAddr)
copy(b[24:], a.DstProtoAddr)
return b, nil
}
func (a *ARPv4Pdu) UnmarshalBinary(payload []byte) error {
if len(payload) < 27 {
return io.ErrUnexpectedEOF
}
a.HTYPE = binary.BigEndian.Uint16(payload[0:2])
a.PTYPE = ethernet.EtherType(binary.BigEndian.Uint16(payload[2:4]))
a.HLEN = payload[4]
a.PLEN = payload[5]
a.Operation = ARPOperation(binary.BigEndian.Uint16(payload[6:8]))
a.SrcHardwareAddr = payload[8:14]
a.SrcProtoAddr = payload[14:18]
a.DstHardwareAddr = payload[18:24]
a.DstProtoAddr = payload[24:28]
return nil
}