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
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
|
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]
}
func delOption(options []Option, code OptionCode) []Option {
newOpts := make([]Option, 0, len(options))
for _, opt := range options {
if opt.Code() != code {
newOpts = append(newOpts, opt)
}
}
return newOpts
}
// 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
}
// DecapsulateRelayIndex extracts the content of a relay message. It takes an
// integer as index (e.g. if 0 return the outermost relay, 1 returns the
// second, etc, and -1 returns the last). Returns the original packet if
// it is not not a relay message.
func DecapsulateRelayIndex(l DHCPv6, index int) (DHCPv6, error) {
if !l.IsRelay() {
return l, nil
}
if index < -1 {
return nil, fmt.Errorf("Invalid index: %d", index)
} else if index == -1 {
for {
d, err := DecapsulateRelay(l)
if err != nil {
return nil, err
}
if !d.IsRelay() {
return l, nil
}
l = d
}
}
for i := 0; i <= index; i++ {
d, err := DecapsulateRelay(l)
if err != nil {
return nil, err
}
l = d
}
return l, 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
}
|
