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
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
|
package dhcpv6
import (
"fmt"
"net"
)
type DHCPv6 interface {
Type() MessageType
ToBytes() []byte
Options() []Option
String() string
Summary() string
Length() int
IsRelay() bool
GetOption(code OptionCode) []Option
GetOneOption(code OptionCode) Option
SetOptions(options []Option)
AddOption(Option)
UpdateOption(Option)
}
// Modifier defines the signature for functions that can modify DHCPv6
// structures. This is used to simplify packet manipulation
type Modifier func(d DHCPv6) DHCPv6
func FromBytes(data []byte) (DHCPv6, error) {
var (
isRelay = false
headerSize int
messageType = MessageType(data[0])
)
if messageType == RELAY_FORW || messageType == RELAY_REPL {
isRelay = true
}
if isRelay {
headerSize = RelayHeaderSize
} else {
headerSize = MessageHeaderSize
}
if len(data) < headerSize {
return nil, fmt.Errorf("Invalid header size: shorter than %v bytes", headerSize)
}
if isRelay {
var (
linkAddr, peerAddr []byte
)
d := DHCPv6Relay{
messageType: messageType,
hopCount: uint8(data[1]),
}
linkAddr = append(linkAddr, data[2:18]...)
d.linkAddr = linkAddr
peerAddr = append(peerAddr, data[18:34]...)
d.peerAddr = peerAddr
options, err := OptionsFromBytes(data[34:])
if err != nil {
return nil, err
}
// TODO fail if no OptRelayMessage is present
d.options = options
return &d, nil
} else {
tid, err := BytesToTransactionID(data[1:4])
if err != nil {
return nil, err
}
d := DHCPv6Message{
messageType: messageType,
transactionID: *tid,
}
options, err := OptionsFromBytes(data[4:])
if err != nil {
return nil, err
}
d.options = options
return &d, nil
}
}
// NewMessage creates a new DHCPv6 message with default options
func NewMessage(modifiers ...Modifier) (DHCPv6, error) {
tid, err := GenerateTransactionID()
if err != nil {
return nil, err
}
msg := DHCPv6Message{
messageType: SOLICIT,
transactionID: *tid,
}
// apply modifiers
d := DHCPv6(&msg)
for _, mod := range modifiers {
d = mod(d)
}
return d, nil
}
func getOptions(options []Option, code OptionCode, onlyFirst bool) []Option {
var ret []Option
for _, opt := range options {
if opt.Code() == code {
ret = append(ret, opt)
if onlyFirst {
break
}
}
}
return ret
}
func getOption(options []Option, code OptionCode) Option {
opts := getOptions(options, code, true)
if opts == nil {
return nil
}
return opts[0]
}
// DecapsulateRelay extracts the content of a relay message. It does not recurse
// if there are nested relay messages. Returns the original packet if is not not
// a relay message
func DecapsulateRelay(l DHCPv6) (DHCPv6, error) {
if !l.IsRelay() {
return l, nil
}
opt := l.GetOneOption(OPTION_RELAY_MSG)
if opt == nil {
return nil, fmt.Errorf("No OptRelayMsg found")
}
relayOpt := opt.(*OptRelayMsg)
if relayOpt.RelayMessage() == nil {
return nil, fmt.Errorf("Relay message cannot be nil")
}
return relayOpt.RelayMessage(), nil
}
// EncapsulateRelay creates a DHCPv6Relay message containing the passed DHCPv6
// message as payload. The passed message type must be either RELAY_FORW or
// RELAY_REPL
func EncapsulateRelay(d DHCPv6, mType MessageType, linkAddr, peerAddr net.IP) (DHCPv6, error) {
if mType != RELAY_FORW && mType != RELAY_REPL {
return nil, fmt.Errorf("Message type must be either RELAY_FORW or RELAY_REPL")
}
outer := DHCPv6Relay{
messageType: mType,
linkAddr: linkAddr,
peerAddr: peerAddr,
}
if d.IsRelay() {
relay := d.(*DHCPv6Relay)
outer.hopCount = relay.hopCount + 1
} else {
outer.hopCount = 0
}
orm := OptRelayMsg{relayMessage: d}
outer.AddOption(&orm)
return &outer, nil
}
|
