-
-
Notifications
You must be signed in to change notification settings - Fork 4.1k
/
broadcast.go
229 lines (196 loc) · 4.57 KB
/
broadcast.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
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
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
// Copyright (C) 2014 The Syncthing Authors.
//
// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this file,
// You can obtain one at http://mozilla.org/MPL/2.0/.
package beacon
import (
"fmt"
"net"
"time"
"github.com/thejerf/suture"
)
type Broadcast struct {
*suture.Supervisor
port int
inbox chan []byte
outbox chan recv
}
func NewBroadcast(port int) *Broadcast {
b := &Broadcast{
Supervisor: suture.New("broadcastBeacon", suture.Spec{
// Don't retry too frenetically: an error to open a socket or
// whatever is usually something that is either permanent or takes
// a while to get solved...
FailureThreshold: 2,
FailureBackoff: 60 * time.Second,
// Only log restarts in debug mode.
Log: func(line string) {
if debug {
l.Debugln(line)
}
},
}),
port: port,
inbox: make(chan []byte),
outbox: make(chan recv, 16),
}
b.Add(&broadcastReader{
port: port,
outbox: b.outbox,
})
b.Add(&broadcastWriter{
port: port,
inbox: b.inbox,
})
return b
}
func (b *Broadcast) Send(data []byte) {
b.inbox <- data
}
func (b *Broadcast) Recv() ([]byte, net.Addr) {
recv := <-b.outbox
return recv.data, recv.src
}
type broadcastWriter struct {
port int
inbox chan []byte
conn *net.UDPConn
failed bool // Have we already logged a failure reason?
}
func (w *broadcastWriter) Serve() {
if debug {
l.Debugln(w, "starting")
defer l.Debugln(w, "stopping")
}
var err error
w.conn, err = net.ListenUDP("udp4", nil)
if err != nil {
if !w.failed {
l.Warnln("Local discovery over IPv4 unavailable:", err)
w.failed = true
}
return
}
defer w.conn.Close()
w.failed = false
for bs := range w.inbox {
addrs, err := net.InterfaceAddrs()
if err != nil {
if debug {
l.Debugln("Local discovery (broadcast writer):", err)
}
continue
}
var dsts []net.IP
for _, addr := range addrs {
if iaddr, ok := addr.(*net.IPNet); ok && len(iaddr.IP) >= 4 && iaddr.IP.IsGlobalUnicast() && iaddr.IP.To4() != nil {
baddr := bcast(iaddr)
dsts = append(dsts, baddr.IP)
}
}
if len(dsts) == 0 {
// Fall back to the general IPv4 broadcast address
dsts = append(dsts, net.IP{0xff, 0xff, 0xff, 0xff})
}
if debug {
l.Debugln("addresses:", dsts)
}
for _, ip := range dsts {
dst := &net.UDPAddr{IP: ip, Port: w.port}
w.conn.SetWriteDeadline(time.Now().Add(10 * time.Second))
_, err := w.conn.WriteTo(bs, dst)
if err, ok := err.(net.Error); ok && err.Timeout() {
// Write timeouts should not happen. We treat it as a fatal
// error on the socket.
l.Infoln("Local discovery (broadcast writer):", err)
w.failed = true
return
} else if err, ok := err.(net.Error); ok && err.Temporary() {
// A transient error. Lets hope for better luck in the future.
if debug {
l.Debugln(err)
}
continue
} else if err != nil {
// Some other error that we don't expect. Bail and retry.
l.Infoln("Local discovery (broadcast writer):", err)
w.failed = true
return
} else if debug {
l.Debugf("sent %d bytes to %s", len(bs), dst)
}
}
}
}
func (w *broadcastWriter) Stop() {
w.conn.Close()
}
func (w *broadcastWriter) String() string {
return fmt.Sprintf("broadcastWriter@%p", w)
}
type broadcastReader struct {
port int
outbox chan recv
conn *net.UDPConn
failed bool
}
func (r *broadcastReader) Serve() {
if debug {
l.Debugln(r, "starting")
defer l.Debugln(r, "stopping")
}
var err error
r.conn, err = net.ListenUDP("udp4", &net.UDPAddr{Port: r.port})
if err != nil {
if !r.failed {
l.Warnln("Local discovery over IPv4 unavailable:", err)
r.failed = true
}
return
}
defer r.conn.Close()
bs := make([]byte, 65536)
for {
n, addr, err := r.conn.ReadFrom(bs)
if err != nil {
if !r.failed {
l.Infoln("Local discovery (broadcast reader):", err)
r.failed = true
}
return
}
r.failed = false
if debug {
l.Debugf("recv %d bytes from %s", n, addr)
}
c := make([]byte, n)
copy(c, bs)
select {
case r.outbox <- recv{c, addr}:
default:
if debug {
l.Debugln("dropping message")
}
}
}
}
func (r *broadcastReader) Stop() {
r.conn.Close()
}
func (r *broadcastReader) String() string {
return fmt.Sprintf("broadcastReader@%p", r)
}
func bcast(ip *net.IPNet) *net.IPNet {
var bc = &net.IPNet{}
bc.IP = make([]byte, len(ip.IP))
copy(bc.IP, ip.IP)
bc.Mask = ip.Mask
offset := len(bc.IP) - len(bc.Mask)
for i := range bc.IP {
if i-offset >= 0 {
bc.IP[i] = ip.IP[i] | ^ip.Mask[i-offset]
}
}
return bc
}