100 lines
2.0 KiB
Go
100 lines
2.0 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 http://mozilla.org/MPL/2.0/.
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package beacon
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import "net"
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type Broadcast struct {
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conn *net.UDPConn
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port int
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inbox chan []byte
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outbox chan recv
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}
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func NewBroadcast(port int) (*Broadcast, error) {
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conn, err := net.ListenUDP("udp", &net.UDPAddr{Port: port})
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if err != nil {
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return nil, err
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}
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b := &Broadcast{
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conn: conn,
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port: port,
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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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go genericReader(b.conn, b.outbox)
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go b.writer()
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return b, nil
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}
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func (b *Broadcast) Send(data []byte) {
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b.inbox <- data
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}
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func (b *Broadcast) Recv() ([]byte, net.Addr) {
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recv := <-b.outbox
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return recv.data, recv.src
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}
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func (b *Broadcast) writer() {
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for bs := range b.inbox {
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addrs, err := net.InterfaceAddrs()
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if err != nil {
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l.Warnln("Broadcast: interface addresses:", err)
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continue
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}
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var dsts []net.IP
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for _, addr := range addrs {
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if iaddr, ok := addr.(*net.IPNet); ok && len(iaddr.IP) >= 4 && iaddr.IP.IsGlobalUnicast() && iaddr.IP.To4() != nil {
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baddr := bcast(iaddr)
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dsts = append(dsts, baddr.IP)
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}
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}
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if len(dsts) == 0 {
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// Fall back to the general IPv4 broadcast address
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dsts = append(dsts, net.IP{0xff, 0xff, 0xff, 0xff})
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}
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if debug {
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l.Debugln("addresses:", dsts)
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}
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for _, ip := range dsts {
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dst := &net.UDPAddr{IP: ip, Port: b.port}
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_, err := b.conn.WriteTo(bs, dst)
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if err != nil {
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if debug {
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l.Debugln(err)
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}
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} else if debug {
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l.Debugf("sent %d bytes to %s", len(bs), dst)
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}
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}
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}
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}
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func bcast(ip *net.IPNet) *net.IPNet {
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var bc = &net.IPNet{}
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bc.IP = make([]byte, len(ip.IP))
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copy(bc.IP, ip.IP)
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bc.Mask = ip.Mask
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offset := len(bc.IP) - len(bc.Mask)
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for i := range bc.IP {
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if i-offset >= 0 {
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bc.IP[i] = ip.IP[i] | ^ip.Mask[i-offset]
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}
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}
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return bc
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}
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