Implement IPv6 multicast again (fixes #346)

beacon/beacon.go

@@ -0,0 +1,46 @@
+// Copyright (C) 2014 Jakob Borg and Contributors (see the CONTRIBUTORS file).
+// All rights reserved. Use of this source code is governed by an MIT-style
+// license that can be found in the LICENSE file.
+
+package beacon
+
+import "net"
+
+type recv struct {
+	data []byte
+	src  net.Addr
+}
+
+type dst struct {
+	intf string
+	conn *net.UDPConn
+}
+
+type Interface interface {
+	Send(data []byte)
+	Recv() ([]byte, net.Addr)
+}
+
+func genericReader(conn *net.UDPConn, outbox chan<- recv) {
+	bs := make([]byte, 65536)
+	for {
+		n, addr, err := conn.ReadFrom(bs)
+		if err != nil {
+			l.Warnln("multicast read:", err)
+			return
+		}
+		if debug {
+			l.Debugf("recv %d bytes from %s", n, addr)
+		}
+
+		c := make([]byte, n)
+		copy(c, bs)
+		select {
+		case outbox <- recv{c, addr}:
+		default:
+			if debug {
+				l.Debugln("dropping message")
+			}
+		}
+	}
+}

beacon/broadcast.go

@@ -6,16 +6,6 @@ package beacon
 
 import "net"
 
-type recv struct {
-	data []byte
-	src  net.Addr
-}
-
-type dst struct {
-	intf string
-	conn *net.UDPConn
-}
-
 type Broadcast struct {
 	conn   *net.UDPConn
 	port   int
@@ -36,7 +26,7 @@ func NewBroadcast(port int) (*Broadcast, error) {
 		outbox: make(chan recv, 16),
 	}
 
-	go b.reader()
+	go genericReader(b.conn, b.outbox)
 	go b.writer()
 
 	return b, nil
@@ -51,30 +41,6 @@ func (b *Broadcast) Recv() ([]byte, net.Addr) {
 	return recv.data, recv.src
 }
 
-func (b *Broadcast) reader() {
-	bs := make([]byte, 65536)
-	for {
-		n, addr, err := b.conn.ReadFrom(bs)
-		if err != nil {
-			l.Warnln("Broadcast read:", err)
-			return
-		}
-		if debug {
-			l.Debugf("recv %d bytes from %s", n, addr)
-		}
-
-		c := make([]byte, n)
-		copy(c, bs)
-		select {
-		case b.outbox <- recv{c, addr}:
-		default:
-			if debug {
-				l.Debugln("dropping message")
-			}
-		}
-	}
-}
-
 func (b *Broadcast) writer() {
 	for bs := range b.inbox {
 

beacon/multicast.go

@@ -0,0 +1,70 @@
+// Copyright (C) 2014 Jakob Borg and Contributors (see the CONTRIBUTORS file).
+// All rights reserved. Use of this source code is governed by an MIT-style
+// license that can be found in the LICENSE file.
+
+package beacon
+
+import "net"
+
+type Multicast struct {
+	conn   *net.UDPConn
+	addr   *net.UDPAddr
+	conns  []dst
+	inbox  chan []byte
+	outbox chan recv
+}
+
+func NewMulticast(addr string) (*Multicast, error) {
+	gaddr, err := net.ResolveUDPAddr("udp", addr)
+	if err != nil {
+		return nil, err
+	}
+	conn, err := net.ListenMulticastUDP("udp", nil, gaddr)
+	if err != nil {
+		return nil, err
+	}
+	b := &Multicast{
+		conn:   conn,
+		addr:   gaddr,
+		inbox:  make(chan []byte),
+		outbox: make(chan recv, 16),
+	}
+
+	go genericReader(b.conn, b.outbox)
+	go b.writer()
+
+	return b, nil
+}
+
+func (b *Multicast) Send(data []byte) {
+	b.inbox <- data
+}
+
+func (b *Multicast) Recv() ([]byte, net.Addr) {
+	recv := <-b.outbox
+	return recv.data, recv.src
+}
+
+func (b *Multicast) writer() {
+	for bs := range b.inbox {
+		intfs, err := net.Interfaces()
+		if err != nil {
+			l.Warnln("multicast interfaces:", err)
+			continue
+		}
+		for _, intf := range intfs {
+			if intf.Flags&net.FlagUp != 0 && intf.Flags&net.FlagMulticast != 0 {
+				addr := *b.addr
+				addr.Zone = intf.Name
+				_, err = b.conn.WriteTo(bs, &addr)
+				if err != nil {
+					if debug {
+						l.Debugln(err, "on write to", addr)
+					}
+				} else if debug {
+					l.Debugf("sent %d bytes to %s", len(bs), addr.String())
+				}
+			}
+		}
+	}
+}

cmd/syncthing/main.go

@@ -985,7 +985,7 @@ func setTCPOptions(conn *net.TCPConn) {
 }
 
 func discovery(extPort int) *discover.Discoverer {
-	disc, err := discover.NewDiscoverer(myID, cfg.Options.ListenAddress, cfg.Options.LocalAnnPort)
+	disc, err := discover.NewDiscoverer(myID, cfg.Options.ListenAddress, cfg.Options.LocalAnnPort, cfg.Options.LocalAnnMCAddr)
 	if err != nil {
 		l.Warnf("No discovery possible (%v)", err)
 		return nil

config/config.go

@@ -113,6 +113,7 @@ type OptionsConfiguration struct {
 	GlobalAnnEnabled   bool     `xml:"globalAnnounceEnabled" default:"true"`
 	LocalAnnEnabled    bool     `xml:"localAnnounceEnabled" default:"true"`
 	LocalAnnPort       int      `xml:"localAnnouncePort" default:"21025"`
+	LocalAnnMCAddr     string   `xml:"localAnnounceMCAddr" default:"[ff32::5222]:21026"`
 	ParallelRequests   int      `xml:"parallelRequests" default:"16"`
 	MaxSendKbps        int      `xml:"maxSendKbps"`
 	RescanIntervalS    int      `xml:"rescanIntervalS" default:"60"`

config/config_test.go

@@ -30,6 +30,7 @@ func TestDefaultValues(t *testing.T) {
 		GlobalAnnEnabled:   true,
 		LocalAnnEnabled:    true,
 		LocalAnnPort:       21025,
+		LocalAnnMCAddr:     "[ff32::5222]:21026",
 		ParallelRequests:   16,
 		MaxSendKbps:        0,
 		RescanIntervalS:    60,
@@ -200,6 +201,7 @@ func TestOverriddenValues(t *testing.T) {
         <globalAnnounceEnabled>false</globalAnnounceEnabled>
         <localAnnounceEnabled>false</localAnnounceEnabled>
         <localAnnouncePort>42123</localAnnouncePort>
+        <localAnnounceMCAddr>quux:3232</localAnnounceMCAddr>
         <parallelRequests>32</parallelRequests>
         <maxSendKbps>1234</maxSendKbps>
         <rescanIntervalS>600</rescanIntervalS>
@@ -218,6 +220,7 @@ func TestOverriddenValues(t *testing.T) {
 		GlobalAnnEnabled:   false,
 		LocalAnnEnabled:    false,
 		LocalAnnPort:       42123,
+		LocalAnnMCAddr:     "quux:3232",
 		ParallelRequests:   32,
 		MaxSendKbps:        1234,
 		RescanIntervalS:    600,

discover/discover.go

@@ -26,7 +26,8 @@ type Discoverer struct {
 	globalBcastIntv  time.Duration
 	errorRetryIntv   time.Duration
 	cacheLifetime    time.Duration
-	broadcastBeacon  *beacon.Broadcast
+	broadcastBeacon  beacon.Interface
+	multicastBeacon  beacon.Interface
 	registry         map[protocol.NodeID][]cacheEntry
 	registryLock     sync.RWMutex
 	extServer        string
@@ -54,11 +55,7 @@ var (
 // When we hit this many errors in succession, we stop.
 const maxErrors = 30
 
-func NewDiscoverer(id protocol.NodeID, addresses []string, localPort int) (*Discoverer, error) {
-	b, err := beacon.NewBroadcast(localPort)
-	if err != nil {
-		return nil, err
-	}
+func NewDiscoverer(id protocol.NodeID, addresses []string, localPort int, localMCAddr string) (*Discoverer, error) {
 	disc := &Discoverer{
 		myID:            id,
 		listenAddrs:     addresses,
@@ -66,11 +63,26 @@ func NewDiscoverer(id protocol.NodeID, addresses []string, localPort int) (*Disc
 		globalBcastIntv: 1800 * time.Second,
 		errorRetryIntv:  60 * time.Second,
 		cacheLifetime:   5 * time.Minute,
-		broadcastBeacon: b,
 		registry:        make(map[protocol.NodeID][]cacheEntry),
 	}
 
-	go disc.recvAnnouncements()
+	if localPort > 0 {
+		bb, err := beacon.NewBroadcast(localPort)
+		if err != nil {
+			return nil, err
+		}
+		disc.broadcastBeacon = bb
+		go disc.recvAnnouncements(bb)
+	}
+
+	if len(localMCAddr) > 0 {
+		mb, err := beacon.NewMulticast(localMCAddr)
+		if err != nil {
+			return nil, err
+		}
+		disc.multicastBeacon = mb
+		go disc.recvAnnouncements(mb)
+	}
 
 	return disc, nil
 }
@@ -187,7 +199,12 @@ func (d *Discoverer) sendLocalAnnouncements() {
 	msg := pkt.MarshalXDR()
 
 	for {
-		d.broadcastBeacon.Send(msg)
+		if d.multicastBeacon != nil {
+			d.multicastBeacon.Send(msg)
+		}
+		if d.broadcastBeacon != nil {
+			d.broadcastBeacon.Send(msg)
+		}
 
 		select {
 		case <-d.localBcastTick:
@@ -284,9 +301,9 @@ loop:
 	}
 }
 
-func (d *Discoverer) recvAnnouncements() {
+func (d *Discoverer) recvAnnouncements(b beacon.Interface) {
 	for {
-		buf, addr := d.broadcastBeacon.Recv()
+		buf, addr := b.Recv()
 
 		if debug {
 			l.Debugf("discover: read announcement from %s:\n%s", addr, hex.Dump(buf))

gui/index.html

@@ -614,10 +614,6 @@
                     </label>
                   </div>
                 </div>
-                <div class="form-group">
-                  <label translate for="LocalAnnPort">Local Discovery Port</label>
-                  <input ng-disabled="!tmpOptions.LocalAnnEnabled" id="LocalAnnPort" class="form-control" type="number" ng-model="tmpOptions.LocalAnnPort">
-                </div>
                 <div class="form-group">
                   <div class="checkbox">
                     <label>