2014-07-12 22:45:33 +00:00
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// Copyright (C) 2014 Jakob Borg and Contributors (see the CONTRIBUTORS file).
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// All rights reserved. Use of this source code is governed by an MIT-style
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// license that can be found in the LICENSE file.
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2014-06-01 20:50:14 +00:00
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2014-05-15 03:29:18 +00:00
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package beacon
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2014-03-28 10:04:48 +00:00
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2014-05-14 18:26:05 +00:00
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import "net"
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2014-03-28 10:04:48 +00:00
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type recv struct {
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data []byte
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src net.Addr
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}
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2014-05-11 21:20:14 +00:00
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type dst struct {
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intf string
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conn *net.UDPConn
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}
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type Beacon struct {
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conn *net.UDPConn
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port int
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conns []dst
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inbox chan []byte
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outbox chan recv
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}
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2014-05-15 03:29:18 +00:00
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func New(port int) (*Beacon, 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 := &Beacon{
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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 b.reader()
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go b.writer()
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return b, nil
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}
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func (b *Beacon) Send(data []byte) {
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b.inbox <- data
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}
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func (b *Beacon) 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 *Beacon) reader() {
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2014-06-18 21:57:22 +00:00
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bs := make([]byte, 65536)
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for {
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n, addr, err := b.conn.ReadFrom(bs)
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if err != nil {
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l.Warnln("Beacon read:", err)
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return
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}
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if debug {
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l.Debugf("recv %d bytes from %s", n, addr)
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}
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2014-06-18 21:57:22 +00:00
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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 b.outbox <- recv{c, addr}:
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default:
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if debug {
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l.Debugln("dropping message")
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}
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}
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2014-04-30 13:13:54 +00:00
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}
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}
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func (b *Beacon) 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("Beacon: 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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2014-06-14 09:14:37 +00:00
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if iaddr, ok := addr.(*net.IPNet); ok && 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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2014-05-15 00:08:56 +00:00
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if debug {
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l.Debugln("addresses:", dsts)
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}
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2014-05-14 18:26:05 +00:00
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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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2014-05-28 05:03:47 +00:00
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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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2014-04-30 13:13:54 +00:00
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}
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2014-03-28 10:04:48 +00:00
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}
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}
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2014-05-14 18:26:05 +00:00
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}
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2014-03-28 10:04:48 +00:00
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2014-05-14 18:26:05 +00:00
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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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2014-07-31 11:39:49 +00:00
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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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