syncthing/lib/beacon/multicast.go
2017-02-09 08:04:16 +01:00

228 lines
4.1 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 (
"errors"
"fmt"
"net"
"time"
"github.com/thejerf/suture"
"golang.org/x/net/ipv6"
)
type Multicast struct {
*suture.Supervisor
inbox chan []byte
outbox chan recv
mr *multicastReader
mw *multicastWriter
}
func NewMulticast(addr string) *Multicast {
m := &Multicast{
Supervisor: suture.New("multicastBeacon", 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)
},
}),
inbox: make(chan []byte),
outbox: make(chan recv, 16),
}
m.mr = &multicastReader{
addr: addr,
outbox: m.outbox,
stop: make(chan struct{}),
}
m.Add(m.mr)
m.mw = &multicastWriter{
addr: addr,
inbox: m.inbox,
stop: make(chan struct{}),
}
m.Add(m.mw)
return m
}
func (m *Multicast) Send(data []byte) {
m.inbox <- data
}
func (m *Multicast) Recv() ([]byte, net.Addr) {
recv := <-m.outbox
return recv.data, recv.src
}
func (m *Multicast) Error() error {
if err := m.mr.Error(); err != nil {
return err
}
return m.mw.Error()
}
type multicastWriter struct {
addr string
inbox <-chan []byte
errorHolder
stop chan struct{}
}
func (w *multicastWriter) Serve() {
l.Debugln(w, "starting")
defer l.Debugln(w, "stopping")
gaddr, err := net.ResolveUDPAddr("udp6", w.addr)
if err != nil {
l.Debugln(err)
w.setError(err)
return
}
conn, err := net.ListenPacket("udp6", ":0")
if err != nil {
l.Debugln(err)
w.setError(err)
return
}
pconn := ipv6.NewPacketConn(conn)
wcm := &ipv6.ControlMessage{
HopLimit: 1,
}
for bs := range w.inbox {
intfs, err := net.Interfaces()
if err != nil {
l.Debugln(err)
w.setError(err)
return
}
success := 0
for _, intf := range intfs {
wcm.IfIndex = intf.Index
pconn.SetWriteDeadline(time.Now().Add(time.Second))
_, err = pconn.WriteTo(bs, wcm, gaddr)
pconn.SetWriteDeadline(time.Time{})
if err != nil {
l.Debugln(err, "on write to", gaddr, intf.Name)
w.setError(err)
continue
}
l.Debugf("sent %d bytes to %v on %s", len(bs), gaddr, intf.Name)
success++
}
if success > 0 {
w.setError(nil)
} else {
l.Debugln(err)
w.setError(err)
}
}
}
func (w *multicastWriter) Stop() {
close(w.stop)
}
func (w *multicastWriter) String() string {
return fmt.Sprintf("multicastWriter@%p", w)
}
type multicastReader struct {
addr string
outbox chan<- recv
errorHolder
stop chan struct{}
}
func (r *multicastReader) Serve() {
l.Debugln(r, "starting")
defer l.Debugln(r, "stopping")
gaddr, err := net.ResolveUDPAddr("udp6", r.addr)
if err != nil {
l.Debugln(err)
r.setError(err)
return
}
conn, err := net.ListenPacket("udp6", r.addr)
if err != nil {
l.Debugln(err)
r.setError(err)
return
}
intfs, err := net.Interfaces()
if err != nil {
l.Debugln(err)
r.setError(err)
return
}
pconn := ipv6.NewPacketConn(conn)
joined := 0
for _, intf := range intfs {
err := pconn.JoinGroup(&intf, &net.UDPAddr{IP: gaddr.IP})
if err != nil {
l.Debugln("IPv6 join", intf.Name, "failed:", err)
} else {
l.Debugln("IPv6 join", intf.Name, "success")
}
joined++
}
if joined == 0 {
l.Debugln("no multicast interfaces available")
r.setError(errors.New("no multicast interfaces available"))
return
}
bs := make([]byte, 65536)
for {
n, _, addr, err := pconn.ReadFrom(bs)
if err != nil {
l.Debugln(err)
r.setError(err)
continue
}
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 *multicastReader) Stop() {
close(r.stop)
}
func (r *multicastReader) String() string {
return fmt.Sprintf("multicastReader@%p", r)
}