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())
+				}
+			}
+		}
+	}
+}