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discover.go
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discover.go
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// Copyright (C) 2014 The Syncthing Authors.
//
// 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 discover
import (
"bytes"
"encoding/hex"
"errors"
"io"
"net"
"strconv"
"time"
"github.com/syncthing/protocol"
"github.com/syncthing/syncthing/lib/beacon"
"github.com/syncthing/syncthing/lib/events"
"github.com/syncthing/syncthing/lib/sync"
)
type Discoverer struct {
myID protocol.DeviceID
listenAddrs []string
localBcastIntv time.Duration
localBcastStart time.Time
cacheLifetime time.Duration
negCacheCutoff time.Duration
beacons []beacon.Interface
extPort uint16
localBcastTick <-chan time.Time
forcedBcastTick chan time.Time
registryLock sync.RWMutex
registry map[protocol.DeviceID][]CacheEntry
lastLookup map[protocol.DeviceID]time.Time
clients []Client
mut sync.RWMutex
}
type CacheEntry struct {
Address string
Seen time.Time
}
var (
ErrIncorrectMagic = errors.New("incorrect magic number")
)
func NewDiscoverer(id protocol.DeviceID, addresses []string) *Discoverer {
return &Discoverer{
myID: id,
listenAddrs: addresses,
localBcastIntv: 30 * time.Second,
cacheLifetime: 5 * time.Minute,
negCacheCutoff: 3 * time.Minute,
registry: make(map[protocol.DeviceID][]CacheEntry),
lastLookup: make(map[protocol.DeviceID]time.Time),
registryLock: sync.NewRWMutex(),
mut: sync.NewRWMutex(),
}
}
func (d *Discoverer) StartLocal(localPort int, localMCAddr string) {
if localPort > 0 {
d.startLocalIPv4Broadcasts(localPort)
}
if len(localMCAddr) > 0 {
d.startLocalIPv6Multicasts(localMCAddr)
}
if len(d.beacons) == 0 {
l.Warnln("Local discovery unavailable")
return
}
d.localBcastTick = time.Tick(d.localBcastIntv)
d.forcedBcastTick = make(chan time.Time)
d.localBcastStart = time.Now()
go d.sendLocalAnnouncements()
}
func (d *Discoverer) startLocalIPv4Broadcasts(localPort int) {
bb := beacon.NewBroadcast(localPort)
d.beacons = append(d.beacons, bb)
go d.recvAnnouncements(bb)
bb.ServeBackground()
}
func (d *Discoverer) startLocalIPv6Multicasts(localMCAddr string) {
mb, err := beacon.NewMulticast(localMCAddr)
if err != nil {
if debug {
l.Debugln("beacon.NewMulticast:", err)
}
l.Infoln("Local discovery over IPv6 unavailable")
return
}
d.beacons = append(d.beacons, mb)
go d.recvAnnouncements(mb)
}
func (d *Discoverer) StartGlobal(servers []string, extPort uint16) {
d.mut.Lock()
defer d.mut.Unlock()
if len(d.clients) > 0 {
d.stopGlobal()
}
d.extPort = extPort
pkt := d.announcementPkt()
wg := sync.NewWaitGroup()
clients := make(chan Client, len(servers))
for _, address := range servers {
wg.Add(1)
go func(addr string) {
defer wg.Done()
client, err := New(addr, pkt)
if err != nil {
l.Infoln("Error creating discovery client", addr, err)
return
}
clients <- client
}(address)
}
wg.Wait()
close(clients)
for client := range clients {
d.clients = append(d.clients, client)
}
}
func (d *Discoverer) StopGlobal() {
d.mut.Lock()
defer d.mut.Unlock()
d.stopGlobal()
}
func (d *Discoverer) stopGlobal() {
for _, client := range d.clients {
client.Stop()
}
d.clients = []Client{}
}
func (d *Discoverer) ExtAnnounceOK() map[string]bool {
d.mut.RLock()
defer d.mut.RUnlock()
ret := make(map[string]bool)
for _, client := range d.clients {
ret[client.Address()] = client.StatusOK()
}
return ret
}
func (d *Discoverer) Lookup(device protocol.DeviceID) []string {
d.registryLock.RLock()
cached := d.filterCached(d.registry[device])
lastLookup := d.lastLookup[device]
d.registryLock.RUnlock()
d.mut.RLock()
defer d.mut.RUnlock()
if len(cached) > 0 {
// There are cached address entries.
addrs := make([]string, len(cached))
for i := range cached {
addrs[i] = cached[i].Address
}
return addrs
}
if time.Since(lastLookup) < d.negCacheCutoff {
// We have recently tried to lookup this address and failed. Lets
// chill for a while.
return nil
}
if len(d.clients) != 0 && time.Since(d.localBcastStart) > d.localBcastIntv {
// Only perform external lookups if we have at least one external
// server client and one local announcement interval has passed. This is
// to avoid finding local peers on their remote address at startup.
results := make(chan []string, len(d.clients))
wg := sync.NewWaitGroup()
for _, client := range d.clients {
wg.Add(1)
go func(c Client) {
defer wg.Done()
results <- c.Lookup(device)
}(client)
}
wg.Wait()
close(results)
cached := []CacheEntry{}
seen := make(map[string]struct{})
now := time.Now()
var addrs []string
for result := range results {
for _, addr := range result {
_, ok := seen[addr]
if !ok {
cached = append(cached, CacheEntry{
Address: addr,
Seen: now,
})
seen[addr] = struct{}{}
addrs = append(addrs, addr)
}
}
}
d.registryLock.Lock()
d.registry[device] = cached
d.lastLookup[device] = time.Now()
d.registryLock.Unlock()
return addrs
}
return nil
}
func (d *Discoverer) Hint(device string, addrs []string) {
resAddrs := resolveAddrs(addrs)
var id protocol.DeviceID
id.UnmarshalText([]byte(device))
d.registerDevice(nil, Device{
Addresses: resAddrs,
ID: id[:],
})
}
func (d *Discoverer) All() map[protocol.DeviceID][]CacheEntry {
d.registryLock.RLock()
devices := make(map[protocol.DeviceID][]CacheEntry, len(d.registry))
for device, addrs := range d.registry {
addrsCopy := make([]CacheEntry, len(addrs))
copy(addrsCopy, addrs)
devices[device] = addrsCopy
}
d.registryLock.RUnlock()
return devices
}
func (d *Discoverer) announcementPkt() *Announce {
var addrs []Address
if d.extPort != 0 {
addrs = []Address{{Port: d.extPort}}
} else {
for _, astr := range d.listenAddrs {
addr, err := net.ResolveTCPAddr("tcp", astr)
if err != nil {
l.Warnln("discover: %v: not announcing %s", err, astr)
continue
} else if debug {
l.Debugf("discover: resolved %s as %#v", astr, addr)
}
if len(addr.IP) == 0 || addr.IP.IsUnspecified() {
addrs = append(addrs, Address{Port: uint16(addr.Port)})
} else if bs := addr.IP.To4(); bs != nil {
addrs = append(addrs, Address{IP: bs, Port: uint16(addr.Port)})
} else if bs := addr.IP.To16(); bs != nil {
addrs = append(addrs, Address{IP: bs, Port: uint16(addr.Port)})
}
}
}
return &Announce{
Magic: AnnouncementMagic,
This: Device{d.myID[:], addrs},
}
}
func (d *Discoverer) sendLocalAnnouncements() {
var addrs = resolveAddrs(d.listenAddrs)
var pkt = Announce{
Magic: AnnouncementMagic,
This: Device{d.myID[:], addrs},
}
msg := pkt.MustMarshalXDR()
for {
for _, b := range d.beacons {
b.Send(msg)
}
select {
case <-d.localBcastTick:
case <-d.forcedBcastTick:
}
}
}
func (d *Discoverer) recvAnnouncements(b beacon.Interface) {
for {
buf, addr := b.Recv()
var pkt Announce
err := pkt.UnmarshalXDR(buf)
if err != nil && err != io.EOF {
if debug {
l.Debugf("discover: Failed to unmarshal local announcement from %s:\n%s", addr, hex.Dump(buf))
}
continue
}
if debug {
l.Debugf("discover: Received local announcement from %s for %s", addr, protocol.DeviceIDFromBytes(pkt.This.ID))
}
var newDevice bool
if bytes.Compare(pkt.This.ID, d.myID[:]) != 0 {
newDevice = d.registerDevice(addr, pkt.This)
}
if newDevice {
select {
case d.forcedBcastTick <- time.Now():
}
}
}
}
func (d *Discoverer) registerDevice(addr net.Addr, device Device) bool {
var id protocol.DeviceID
copy(id[:], device.ID)
d.registryLock.Lock()
defer d.registryLock.Unlock()
current := d.filterCached(d.registry[id])
orig := current
for _, a := range device.Addresses {
var deviceAddr string
if len(a.IP) > 0 {
deviceAddr = net.JoinHostPort(net.IP(a.IP).String(), strconv.Itoa(int(a.Port)))
} else if addr != nil {
ua := addr.(*net.UDPAddr)
ua.Port = int(a.Port)
deviceAddr = ua.String()
}
for i := range current {
if current[i].Address == deviceAddr {
current[i].Seen = time.Now()
goto done
}
}
current = append(current, CacheEntry{
Address: deviceAddr,
Seen: time.Now(),
})
done:
}
if debug {
l.Debugf("discover: Caching %s addresses: %v", id, current)
}
d.registry[id] = current
if len(current) > len(orig) {
addrs := make([]string, len(current))
for i := range current {
addrs[i] = current[i].Address
}
events.Default.Log(events.DeviceDiscovered, map[string]interface{}{
"device": id.String(),
"addrs": addrs,
})
}
return len(current) > len(orig)
}
func (d *Discoverer) filterCached(c []CacheEntry) []CacheEntry {
for i := 0; i < len(c); {
if ago := time.Since(c[i].Seen); ago > d.cacheLifetime {
if debug {
l.Debugf("discover: Removing cached address %s - seen %v ago", c[i].Address, ago)
}
c[i] = c[len(c)-1]
c = c[:len(c)-1]
} else {
i++
}
}
return c
}
func addrToAddr(addr *net.TCPAddr) Address {
if len(addr.IP) == 0 || addr.IP.IsUnspecified() {
return Address{Port: uint16(addr.Port)}
} else if bs := addr.IP.To4(); bs != nil {
return Address{IP: bs, Port: uint16(addr.Port)}
} else if bs := addr.IP.To16(); bs != nil {
return Address{IP: bs, Port: uint16(addr.Port)}
}
return Address{}
}
func resolveAddrs(addrs []string) []Address {
var raddrs []Address
for _, addrStr := range addrs {
addrRes, err := net.ResolveTCPAddr("tcp", addrStr)
if err != nil {
continue
}
addr := addrToAddr(addrRes)
if len(addr.IP) > 0 {
raddrs = append(raddrs, addr)
} else {
raddrs = append(raddrs, Address{Port: addr.Port})
}
}
return raddrs
}