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- // 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
- }
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