Change to URL based announce server addresses (fixes #943)

internal/discover/client_udp.go

@@ -0,0 +1,250 @@
+// Copyright (C) 2014 The Syncthing Authors.
+//
+// This program is free software: you can redistribute it and/or modify it
+// under the terms of the GNU General Public License as published by the Free
+// Software Foundation, either version 3 of the License, or (at your option)
+// any later version.
+//
+// This program is distributed in the hope that it will be useful, but WITHOUT
+// ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+// FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+// more details.
+//
+// You should have received a copy of the GNU General Public License along
+// with this program. If not, see <http://www.gnu.org/licenses/>.
+
+package discover
+
+import (
+	"encoding/hex"
+	"io"
+	"net"
+	"net/url"
+	"strconv"
+	"sync"
+	"time"
+
+	"github.com/syncthing/syncthing/internal/protocol"
+)
+
+func init() {
+	for _, proto := range []string{"udp", "udp4", "udp6"} {
+		Register(proto, func(uri *url.URL, pkt *Announce) (Client, error) {
+			c := &UDPClient{}
+			err := c.Start(uri, pkt)
+			if err != nil {
+				return nil, err
+			}
+			return c, nil
+		})
+	}
+}
+
+type UDPClient struct {
+	url *url.URL
+
+	id protocol.DeviceID
+
+	stop          chan struct{}
+	wg            sync.WaitGroup
+	listenAddress *net.UDPAddr
+
+	globalBroadcastInterval time.Duration
+	errorRetryInterval      time.Duration
+
+	status bool
+	mut    sync.RWMutex
+}
+
+func (d *UDPClient) Start(uri *url.URL, pkt *Announce) error {
+	d.url = uri
+	d.id = protocol.DeviceIDFromBytes(pkt.This.ID)
+	d.stop = make(chan struct{})
+
+	params := uri.Query()
+	// The address must not have a port, as otherwise both announce and lookup
+	// sockets would try to bind to the same port.
+	addr, err := net.ResolveUDPAddr(d.url.Scheme, params.Get("listenaddress")+":0")
+	if err != nil {
+		return err
+	}
+	d.listenAddress = addr
+
+	broadcastSeconds, err := strconv.ParseUint(params.Get("broadcast"), 0, 0)
+	if err != nil {
+		d.globalBroadcastInterval = DefaultGlobalBroadcastInterval
+	} else {
+		d.globalBroadcastInterval = time.Duration(broadcastSeconds) * time.Second
+	}
+
+	retrySeconds, err := strconv.ParseUint(params.Get("retry"), 0, 0)
+	if err != nil {
+		d.errorRetryInterval = DefaultErrorRetryInternval
+	} else {
+		d.errorRetryInterval = time.Duration(retrySeconds) * time.Second
+	}
+
+	d.wg.Add(1)
+	go d.broadcast(pkt.MustMarshalXDR())
+	return nil
+}
+
+func (d *UDPClient) broadcast(pkt []byte) {
+	defer d.wg.Done()
+	timer := time.NewTimer(0)
+
+	conn, err := net.ListenUDP(d.url.Scheme, d.listenAddress)
+	for err != nil {
+		timer.Reset(d.errorRetryInterval)
+		l.Warnf("Global UDP discovery (%s): %v; trying again in %v", d.url, err, d.errorRetryInterval)
+		select {
+		case <-d.stop:
+			return
+		case <-timer.C:
+		}
+		conn, err = net.ListenUDP(d.url.Scheme, d.listenAddress)
+	}
+	defer conn.Close()
+
+	remote, err := net.ResolveUDPAddr(d.url.Scheme, d.url.Host)
+	for err != nil {
+		timer.Reset(d.errorRetryInterval)
+		l.Warnf("Global UDP discovery (%s): %v; trying again in %v", d.url, err, d.errorRetryInterval)
+		select {
+		case <-d.stop:
+			return
+		case <-timer.C:
+		}
+		remote, err = net.ResolveUDPAddr(d.url.Scheme, d.url.Host)
+	}
+
+	timer.Reset(0)
+
+	for {
+		select {
+		case <-d.stop:
+			return
+
+		case <-timer.C:
+			var ok bool
+
+			if debug {
+				l.Debugf("Global UDP discovery (%s): send announcement -> %v\n%s", d.url, remote, hex.Dump(pkt))
+			}
+
+			_, err := conn.WriteTo(pkt, remote)
+			if err != nil {
+				if debug {
+					l.Debugf("discover %s: warning: %s", d.url, err)
+				}
+				ok = false
+			} else {
+				// Verify that the announce server responds positively for our device ID
+
+				time.Sleep(1 * time.Second)
+
+				res := d.Lookup(d.id)
+				if debug {
+					l.Debugf("discover %s: external lookup check: %v", d.url, res)
+				}
+				ok = len(res) > 0
+			}
+
+			d.mut.Lock()
+			d.status = ok
+			d.mut.Unlock()
+
+			if ok {
+				timer.Reset(d.globalBroadcastInterval)
+			} else {
+				timer.Reset(d.errorRetryInterval)
+			}
+		}
+	}
+}
+
+func (d *UDPClient) Lookup(device protocol.DeviceID) []string {
+	extIP, err := net.ResolveUDPAddr(d.url.Scheme, d.url.Host)
+	if err != nil {
+		if debug {
+			l.Debugf("discover %s: %v; no external lookup", d.url, err)
+		}
+		return nil
+	}
+
+	conn, err := net.DialUDP(d.url.Scheme, d.listenAddress, extIP)
+	if err != nil {
+		if debug {
+			l.Debugf("discover %s: %v; no external lookup", d.url, err)
+		}
+		return nil
+	}
+	defer conn.Close()
+
+	err = conn.SetDeadline(time.Now().Add(5 * time.Second))
+	if err != nil {
+		if debug {
+			l.Debugf("discover %s: %v; no external lookup", d.url, err)
+		}
+		return nil
+	}
+
+	buf := Query{QueryMagic, device[:]}.MustMarshalXDR()
+	_, err = conn.Write(buf)
+	if err != nil {
+		if debug {
+			l.Debugf("discover %s: %v; no external lookup", d.url, err)
+		}
+		return nil
+	}
+
+	buf = make([]byte, 2048)
+	n, err := conn.Read(buf)
+	if err != nil {
+		if err, ok := err.(net.Error); ok && err.Timeout() {
+			// Expected if the server doesn't know about requested device ID
+			return nil
+		}
+		if debug {
+			l.Debugf("discover %s: %v; no external lookup", d.url, err)
+		}
+		return nil
+	}
+
+	if debug {
+		l.Debugf("discover %s: read external:\n%s", d.url, hex.Dump(buf[:n]))
+	}
+
+	var pkt Announce
+	err = pkt.UnmarshalXDR(buf[:n])
+	if err != nil && err != io.EOF {
+		if debug {
+			l.Debugln("discover %s:", d.url, err)
+		}
+		return nil
+	}
+
+	var addrs []string
+	for _, a := range pkt.This.Addresses {
+		deviceAddr := net.JoinHostPort(net.IP(a.IP).String(), strconv.Itoa(int(a.Port)))
+		addrs = append(addrs, deviceAddr)
+	}
+	return addrs
+}
+
+func (d *UDPClient) Stop() {
+	if d.stop != nil {
+		close(d.stop)
+		d.wg.Wait()
+	}
+}
+
+func (d *UDPClient) StatusOK() bool {
+	d.mut.RLock()
+	defer d.mut.RUnlock()
+	return d.status
+}
+
+func (d *UDPClient) Address() string {
+	return d.url.String()
+}