syncthing/lib/beacon/broadcast.go
Jakob Borg 2f08f8021f lib/beacon: Don't exit after a single write failure (fixes #4414)
With VPNs and stuff we can get a single failure on an interface that
supposedly supports broadcasts without it being fatal.

GitHub-Pull-Request: https://github.com/syncthing/syncthing/pull/4415
2017-10-12 07:13:44 +00:00

243 lines
4.5 KiB
Go

// 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 https://mozilla.org/MPL/2.0/.
package beacon
import (
"fmt"
"net"
"time"
"github.com/syncthing/syncthing/lib/sync"
"github.com/thejerf/suture"
)
type Broadcast struct {
*suture.Supervisor
port int
inbox chan []byte
outbox chan recv
br *broadcastReader
bw *broadcastWriter
}
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) {
l.Debugln(line)
},
}),
port: port,
inbox: make(chan []byte),
outbox: make(chan recv, 16),
}
b.br = &broadcastReader{
port: port,
outbox: b.outbox,
connMut: sync.NewMutex(),
}
b.Add(b.br)
b.bw = &broadcastWriter{
port: port,
inbox: b.inbox,
connMut: sync.NewMutex(),
}
b.Add(b.bw)
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
}
func (b *Broadcast) Error() error {
if err := b.br.Error(); err != nil {
return err
}
return b.bw.Error()
}
type broadcastWriter struct {
port int
inbox chan []byte
conn *net.UDPConn
connMut sync.Mutex
errorHolder
}
func (w *broadcastWriter) Serve() {
l.Debugln(w, "starting")
defer l.Debugln(w, "stopping")
conn, err := net.ListenUDP("udp4", nil)
if err != nil {
l.Debugln(err)
w.setError(err)
return
}
defer conn.Close()
w.connMut.Lock()
w.conn = conn
w.connMut.Unlock()
for bs := range w.inbox {
addrs, err := net.InterfaceAddrs()
if err != nil {
l.Debugln(err)
w.setError(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})
}
l.Debugln("addresses:", dsts)
success := 0
for _, ip := range dsts {
dst := &net.UDPAddr{IP: ip, Port: w.port}
conn.SetWriteDeadline(time.Now().Add(time.Second))
_, err := conn.WriteTo(bs, dst)
conn.SetWriteDeadline(time.Time{})
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.Debugln(err)
w.setError(err)
return
}
if err != nil {
// Some other error that we don't expect. Debug and continue.
l.Debugln(err)
w.setError(err)
continue
}
l.Debugf("sent %d bytes to %s", len(bs), dst)
success++
}
if success > 0 {
w.setError(nil)
}
}
}
func (w *broadcastWriter) Stop() {
w.connMut.Lock()
if w.conn != nil {
w.conn.Close()
}
w.connMut.Unlock()
}
func (w *broadcastWriter) String() string {
return fmt.Sprintf("broadcastWriter@%p", w)
}
type broadcastReader struct {
port int
outbox chan recv
conn *net.UDPConn
connMut sync.Mutex
errorHolder
}
func (r *broadcastReader) Serve() {
l.Debugln(r, "starting")
defer l.Debugln(r, "stopping")
conn, err := net.ListenUDP("udp4", &net.UDPAddr{Port: r.port})
if err != nil {
l.Debugln(err)
r.setError(err)
return
}
defer conn.Close()
r.connMut.Lock()
r.conn = conn
r.connMut.Unlock()
bs := make([]byte, 65536)
for {
n, addr, err := conn.ReadFrom(bs)
if err != nil {
l.Debugln(err)
r.setError(err)
return
}
r.setError(nil)
l.Debugf("recv %d bytes from %s", n, addr)
c := make([]byte, n)
copy(c, bs)
select {
case r.outbox <- recv{c, addr}:
default:
l.Debugln("dropping message")
}
}
}
func (r *broadcastReader) Stop() {
r.connMut.Lock()
if r.conn != nil {
r.conn.Close()
}
r.connMut.Unlock()
}
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
}