syncthing/internal/beacon/multicast.go

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// 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
// License, v. 2.0. If a copy of the MPL was not distributed with this file,
// You can obtain one at http://mozilla.org/MPL/2.0/.
package beacon
import "net"
type Multicast struct {
conn *net.UDPConn
addr *net.UDPAddr
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 {
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if debug {
l.Debugln("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())
}
}
}
}
}