229 lines
4.2 KiB
Go
229 lines
4.2 KiB
Go
// Copyright (C) 2014 The Syncthing Authors.
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//
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// This Source Code Form is subject to the terms of the Mozilla Public
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// License, v. 2.0. If a copy of the MPL was not distributed with this file,
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// You can obtain one at https://mozilla.org/MPL/2.0/.
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package beacon
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import (
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"errors"
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"fmt"
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"net"
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"time"
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"github.com/thejerf/suture"
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"golang.org/x/net/ipv6"
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)
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type Multicast struct {
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*suture.Supervisor
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inbox chan []byte
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outbox chan recv
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mr *multicastReader
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mw *multicastWriter
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}
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func NewMulticast(addr string) *Multicast {
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m := &Multicast{
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Supervisor: suture.New("multicastBeacon", suture.Spec{
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// Don't retry too frenetically: an error to open a socket or
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// whatever is usually something that is either permanent or takes
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// a while to get solved...
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FailureThreshold: 2,
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FailureBackoff: 60 * time.Second,
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// Only log restarts in debug mode.
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Log: func(line string) {
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l.Debugln(line)
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},
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PassThroughPanics: true,
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}),
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inbox: make(chan []byte),
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outbox: make(chan recv, 16),
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}
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m.mr = &multicastReader{
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addr: addr,
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outbox: m.outbox,
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stop: make(chan struct{}),
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}
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m.Add(m.mr)
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m.mw = &multicastWriter{
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addr: addr,
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inbox: m.inbox,
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stop: make(chan struct{}),
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}
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m.Add(m.mw)
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return m
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}
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func (m *Multicast) Send(data []byte) {
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m.inbox <- data
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}
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func (m *Multicast) Recv() ([]byte, net.Addr) {
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recv := <-m.outbox
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return recv.data, recv.src
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}
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func (m *Multicast) Error() error {
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if err := m.mr.Error(); err != nil {
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return err
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}
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return m.mw.Error()
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}
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type multicastWriter struct {
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addr string
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inbox <-chan []byte
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errorHolder
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stop chan struct{}
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}
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func (w *multicastWriter) Serve() {
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l.Debugln(w, "starting")
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defer l.Debugln(w, "stopping")
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gaddr, err := net.ResolveUDPAddr("udp6", w.addr)
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if err != nil {
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l.Debugln(err)
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w.setError(err)
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return
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}
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conn, err := net.ListenPacket("udp6", ":0")
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if err != nil {
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l.Debugln(err)
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w.setError(err)
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return
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}
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pconn := ipv6.NewPacketConn(conn)
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wcm := &ipv6.ControlMessage{
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HopLimit: 1,
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}
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for bs := range w.inbox {
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intfs, err := net.Interfaces()
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if err != nil {
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l.Debugln(err)
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w.setError(err)
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return
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}
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success := 0
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for _, intf := range intfs {
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wcm.IfIndex = intf.Index
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_ = pconn.SetWriteDeadline(time.Now().Add(time.Second))
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_, err = pconn.WriteTo(bs, wcm, gaddr)
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_ = pconn.SetWriteDeadline(time.Time{})
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if err != nil {
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l.Debugln(err, "on write to", gaddr, intf.Name)
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w.setError(err)
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continue
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}
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l.Debugf("sent %d bytes to %v on %s", len(bs), gaddr, intf.Name)
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success++
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}
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if success > 0 {
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w.setError(nil)
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} else {
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l.Debugln(err)
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w.setError(err)
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}
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}
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}
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func (w *multicastWriter) Stop() {
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close(w.stop)
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}
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func (w *multicastWriter) String() string {
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return fmt.Sprintf("multicastWriter@%p", w)
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}
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type multicastReader struct {
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addr string
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outbox chan<- recv
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errorHolder
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stop chan struct{}
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}
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func (r *multicastReader) Serve() {
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l.Debugln(r, "starting")
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defer l.Debugln(r, "stopping")
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gaddr, err := net.ResolveUDPAddr("udp6", r.addr)
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if err != nil {
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l.Debugln(err)
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r.setError(err)
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return
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}
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conn, err := net.ListenPacket("udp6", r.addr)
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if err != nil {
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l.Debugln(err)
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r.setError(err)
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return
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}
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intfs, err := net.Interfaces()
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if err != nil {
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l.Debugln(err)
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r.setError(err)
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return
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}
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pconn := ipv6.NewPacketConn(conn)
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joined := 0
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for _, intf := range intfs {
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err := pconn.JoinGroup(&intf, &net.UDPAddr{IP: gaddr.IP})
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if err != nil {
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l.Debugln("IPv6 join", intf.Name, "failed:", err)
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} else {
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l.Debugln("IPv6 join", intf.Name, "success")
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}
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joined++
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}
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if joined == 0 {
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l.Debugln("no multicast interfaces available")
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r.setError(errors.New("no multicast interfaces available"))
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return
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}
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bs := make([]byte, 65536)
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for {
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n, _, addr, err := pconn.ReadFrom(bs)
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if err != nil {
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l.Debugln(err)
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r.setError(err)
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continue
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}
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l.Debugf("recv %d bytes from %s", n, addr)
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c := make([]byte, n)
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copy(c, bs)
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select {
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case r.outbox <- recv{c, addr}:
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default:
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l.Debugln("dropping message")
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}
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}
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}
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func (r *multicastReader) Stop() {
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close(r.stop)
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}
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func (r *multicastReader) String() string {
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return fmt.Sprintf("multicastReader@%p", r)
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}
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