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
|
/* SPDX-License-Identifier: MIT
*
* Copyright (C) 2017-2023 WireGuard LLC. All Rights Reserved.
*/
package tuntest
import (
"encoding/binary"
"io"
"net/netip"
"os"
"golang.zx2c4.com/wireguard/tun"
)
func Ping(dst, src netip.Addr) []byte {
localPort := uint16(1337)
seq := uint16(0)
payload := make([]byte, 4)
binary.BigEndian.PutUint16(payload[0:], localPort)
binary.BigEndian.PutUint16(payload[2:], seq)
return genICMPv4(payload, dst, src)
}
// Checksum is the "internet checksum" from https://tools.ietf.org/html/rfc1071.
func checksum(buf []byte, initial uint16) uint16 {
v := uint32(initial)
for i := 0; i < len(buf)-1; i += 2 {
v += uint32(binary.BigEndian.Uint16(buf[i:]))
}
if len(buf)%2 == 1 {
v += uint32(buf[len(buf)-1]) << 8
}
for v > 0xffff {
v = (v >> 16) + (v & 0xffff)
}
return ^uint16(v)
}
func genICMPv4(payload []byte, dst, src netip.Addr) []byte {
const (
icmpv4ProtocolNumber = 1
icmpv4Echo = 8
icmpv4ChecksumOffset = 2
icmpv4Size = 8
ipv4Size = 20
ipv4TotalLenOffset = 2
ipv4ChecksumOffset = 10
ttl = 65
headerSize = ipv4Size + icmpv4Size
)
pkt := make([]byte, headerSize+len(payload))
ip := pkt[0:ipv4Size]
icmpv4 := pkt[ipv4Size : ipv4Size+icmpv4Size]
// https://tools.ietf.org/html/rfc792
icmpv4[0] = icmpv4Echo // type
icmpv4[1] = 0 // code
chksum := ^checksum(icmpv4, checksum(payload, 0))
binary.BigEndian.PutUint16(icmpv4[icmpv4ChecksumOffset:], chksum)
// https://tools.ietf.org/html/rfc760 section 3.1
length := uint16(len(pkt))
ip[0] = (4 << 4) | (ipv4Size / 4)
binary.BigEndian.PutUint16(ip[ipv4TotalLenOffset:], length)
ip[8] = ttl
ip[9] = icmpv4ProtocolNumber
copy(ip[12:], src.AsSlice())
copy(ip[16:], dst.AsSlice())
chksum = ^checksum(ip[:], 0)
binary.BigEndian.PutUint16(ip[ipv4ChecksumOffset:], chksum)
copy(pkt[headerSize:], payload)
return pkt
}
type ChannelTUN struct {
Inbound chan []byte // incoming packets, closed on TUN close
Outbound chan []byte // outbound packets, blocks forever on TUN close
closed chan struct{}
events chan tun.Event
tun chTun
}
func NewChannelTUN() *ChannelTUN {
c := &ChannelTUN{
Inbound: make(chan []byte),
Outbound: make(chan []byte),
closed: make(chan struct{}),
events: make(chan tun.Event, 1),
}
c.tun.c = c
c.events <- tun.EventUp
return c
}
func (c *ChannelTUN) TUN() tun.Device {
return &c.tun
}
type chTun struct {
c *ChannelTUN
}
func (t *chTun) File() *os.File { return nil }
func (t *chTun) Read(packets [][]byte, sizes []int, offset int) (int, error) {
select {
case <-t.c.closed:
return 0, os.ErrClosed
case msg := <-t.c.Outbound:
n := copy(packets[0][offset:], msg)
sizes[0] = n
return 1, nil
}
}
// Write is called by the wireguard device to deliver a packet for routing.
func (t *chTun) Write(packets [][]byte, offset int) (int, error) {
if offset == -1 {
close(t.c.closed)
close(t.c.events)
return 0, io.EOF
}
for i, data := range packets {
msg := make([]byte, len(data)-offset)
copy(msg, data[offset:])
select {
case <-t.c.closed:
return i, os.ErrClosed
case t.c.Inbound <- msg:
}
}
return len(packets), nil
}
func (t *chTun) BatchSize() int {
return 1
}
const DefaultMTU = 1420
func (t *chTun) MTU() (int, error) { return DefaultMTU, nil }
func (t *chTun) Name() (string, error) { return "loopbackTun1", nil }
func (t *chTun) Events() <-chan tun.Event { return t.c.events }
func (t *chTun) Close() error {
t.Write(nil, -1)
return nil
}
|
