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
|
// Copyright 2016 The Netstack Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package header
import (
"encoding/binary"
"gvisor.googlesource.com/gvisor/pkg/tcpip"
)
const (
versTCFL = 0
payloadLen = 4
nextHdr = 6
hopLimit = 7
v6SrcAddr = 8
v6DstAddr = 24
)
// IPv6Fields contains the fields of an IPv6 packet. It is used to describe the
// fields of a packet that needs to be encoded.
type IPv6Fields struct {
// TrafficClass is the "traffic class" field of an IPv6 packet.
TrafficClass uint8
// FlowLabel is the "flow label" field of an IPv6 packet.
FlowLabel uint32
// PayloadLength is the "payload length" field of an IPv6 packet.
PayloadLength uint16
// NextHeader is the "next header" field of an IPv6 packet.
NextHeader uint8
// HopLimit is the "hop limit" field of an IPv6 packet.
HopLimit uint8
// SrcAddr is the "source ip address" of an IPv6 packet.
SrcAddr tcpip.Address
// DstAddr is the "destination ip address" of an IPv6 packet.
DstAddr tcpip.Address
}
// IPv6 represents an ipv6 header stored in a byte array.
// Most of the methods of IPv6 access to the underlying slice without
// checking the boundaries and could panic because of 'index out of range'.
// Always call IsValid() to validate an instance of IPv6 before using other methods.
type IPv6 []byte
const (
// IPv6MinimumSize is the minimum size of a valid IPv6 packet.
IPv6MinimumSize = 40
// IPv6AddressSize is the size, in bytes, of an IPv6 address.
IPv6AddressSize = 16
// IPv6ProtocolNumber is IPv6's network protocol number.
IPv6ProtocolNumber tcpip.NetworkProtocolNumber = 0x86dd
// IPv6Version is the version of the ipv6 protocol.
IPv6Version = 6
// IPv6MinimumMTU is the minimum MTU required by IPv6, per RFC 2460,
// section 5.
IPv6MinimumMTU = 1280
)
// PayloadLength returns the value of the "payload length" field of the ipv6
// header.
func (b IPv6) PayloadLength() uint16 {
return binary.BigEndian.Uint16(b[payloadLen:])
}
// HopLimit returns the value of the "hop limit" field of the ipv6 header.
func (b IPv6) HopLimit() uint8 {
return b[hopLimit]
}
// NextHeader returns the value of the "next header" field of the ipv6 header.
func (b IPv6) NextHeader() uint8 {
return b[nextHdr]
}
// TransportProtocol implements Network.TransportProtocol.
func (b IPv6) TransportProtocol() tcpip.TransportProtocolNumber {
return tcpip.TransportProtocolNumber(b.NextHeader())
}
// Payload implements Network.Payload.
func (b IPv6) Payload() []byte {
return b[IPv6MinimumSize:][:b.PayloadLength()]
}
// SourceAddress returns the "source address" field of the ipv6 header.
func (b IPv6) SourceAddress() tcpip.Address {
return tcpip.Address(b[v6SrcAddr : v6SrcAddr+IPv6AddressSize])
}
// DestinationAddress returns the "destination address" field of the ipv6
// header.
func (b IPv6) DestinationAddress() tcpip.Address {
return tcpip.Address(b[v6DstAddr : v6DstAddr+IPv6AddressSize])
}
// Checksum implements Network.Checksum. Given that IPv6 doesn't have a
// checksum, it just returns 0.
func (IPv6) Checksum() uint16 {
return 0
}
// TOS returns the "traffic class" and "flow label" fields of the ipv6 header.
func (b IPv6) TOS() (uint8, uint32) {
v := binary.BigEndian.Uint32(b[versTCFL:])
return uint8(v >> 20), v & 0xfffff
}
// SetTOS sets the "traffic class" and "flow label" fields of the ipv6 header.
func (b IPv6) SetTOS(t uint8, l uint32) {
vtf := (6 << 28) | (uint32(t) << 20) | (l & 0xfffff)
binary.BigEndian.PutUint32(b[versTCFL:], vtf)
}
// SetPayloadLength sets the "payload length" field of the ipv6 header.
func (b IPv6) SetPayloadLength(payloadLength uint16) {
binary.BigEndian.PutUint16(b[payloadLen:], payloadLength)
}
// SetSourceAddress sets the "source address" field of the ipv6 header.
func (b IPv6) SetSourceAddress(addr tcpip.Address) {
copy(b[v6SrcAddr:v6SrcAddr+IPv6AddressSize], addr)
}
// SetDestinationAddress sets the "destination address" field of the ipv6
// header.
func (b IPv6) SetDestinationAddress(addr tcpip.Address) {
copy(b[v6DstAddr:v6DstAddr+IPv6AddressSize], addr)
}
// SetNextHeader sets the value of the "next header" field of the ipv6 header.
func (b IPv6) SetNextHeader(v uint8) {
b[nextHdr] = v
}
// SetChecksum implements Network.SetChecksum. Given that IPv6 doesn't have a
// checksum, it is empty.
func (IPv6) SetChecksum(uint16) {
}
// Encode encodes all the fields of the ipv6 header.
func (b IPv6) Encode(i *IPv6Fields) {
b.SetTOS(i.TrafficClass, i.FlowLabel)
b.SetPayloadLength(i.PayloadLength)
b[nextHdr] = i.NextHeader
b[hopLimit] = i.HopLimit
copy(b[v6SrcAddr:v6SrcAddr+IPv6AddressSize], i.SrcAddr)
copy(b[v6DstAddr:v6DstAddr+IPv6AddressSize], i.DstAddr)
}
// IsValid performs basic validation on the packet.
func (b IPv6) IsValid(pktSize int) bool {
if len(b) < IPv6MinimumSize {
return false
}
dlen := int(b.PayloadLength())
if dlen > pktSize-IPv6MinimumSize {
return false
}
return true
}
// IsV4MappedAddress determines if the provided address is an IPv4 mapped
// address by checking if its prefix is 0:0:0:0:0:ffff::/96.
func IsV4MappedAddress(addr tcpip.Address) bool {
if len(addr) != IPv6AddressSize {
return false
}
const prefix = "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\xff\xff"
for i := 0; i < len(prefix); i++ {
if prefix[i] != addr[i] {
return false
}
}
return true
}
|
