syncthing/discover/discover.go

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// Copyright (C) 2014 Jakob Borg and Contributors (see the CONTRIBUTORS file).
// All rights reserved. Use of this source code is governed by an MIT-style
// license that can be found in the LICENSE file.
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package discover
import (
"bytes"
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"encoding/hex"
"errors"
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"fmt"
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"io"
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"net"
"sync"
"time"
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"github.com/syncthing/syncthing/beacon"
"github.com/syncthing/syncthing/events"
"github.com/syncthing/syncthing/protocol"
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)
type Discoverer struct {
myID protocol.NodeID
listenAddrs []string
localBcastIntv time.Duration
globalBcastIntv time.Duration
errorRetryIntv time.Duration
cacheLifetime time.Duration
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beacon *beacon.Beacon
registry map[protocol.NodeID][]cacheEntry
registryLock sync.RWMutex
extServer string
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extPort uint16
localBcastTick <-chan time.Time
stopGlobal chan struct{}
globalWG sync.WaitGroup
forcedBcastTick chan time.Time
extAnnounceOK bool
extAnnounceOKmut sync.Mutex
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globalBcastStop chan bool
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}
type cacheEntry struct {
addr string
seen time.Time
}
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var (
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ErrIncorrectMagic = errors.New("incorrect magic number")
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)
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// We tolerate a certain amount of errors because we might be running on
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// laptops that sleep and wake, have intermittent network connectivity, etc.
// When we hit this many errors in succession, we stop.
const maxErrors = 30
func NewDiscoverer(id protocol.NodeID, addresses []string, localPort int) (*Discoverer, error) {
b, err := beacon.New(localPort)
if err != nil {
return nil, err
}
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disc := &Discoverer{
myID: id,
listenAddrs: addresses,
localBcastIntv: 30 * time.Second,
globalBcastIntv: 1800 * time.Second,
errorRetryIntv: 60 * time.Second,
cacheLifetime: 5 * time.Minute,
beacon: b,
registry: make(map[protocol.NodeID][]cacheEntry),
}
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go disc.recvAnnouncements()
return disc, nil
}
func (d *Discoverer) StartLocal() {
d.localBcastTick = time.Tick(d.localBcastIntv)
d.forcedBcastTick = make(chan time.Time)
go d.sendLocalAnnouncements()
}
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func (d *Discoverer) StartGlobal(server string, extPort uint16) {
// Wait for any previous announcer to stop before starting a new one.
d.globalWG.Wait()
d.extServer = server
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d.extPort = extPort
d.stopGlobal = make(chan struct{})
d.globalWG.Add(1)
go d.sendExternalAnnouncements()
}
func (d *Discoverer) StopGlobal() {
close(d.stopGlobal)
d.globalWG.Wait()
}
func (d *Discoverer) ExtAnnounceOK() bool {
d.extAnnounceOKmut.Lock()
defer d.extAnnounceOKmut.Unlock()
return d.extAnnounceOK
}
func (d *Discoverer) Lookup(node protocol.NodeID) []string {
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d.registryLock.Lock()
cached := d.filterCached(d.registry[node])
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d.registryLock.Unlock()
if len(cached) > 0 {
addrs := make([]string, len(cached))
for i := range cached {
addrs[i] = cached[i].addr
}
return addrs
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} else if len(d.extServer) != 0 {
addrs := d.externalLookup(node)
cached = make([]cacheEntry, len(addrs))
for i := range addrs {
cached[i] = cacheEntry{
addr: addrs[i],
seen: time.Now(),
}
}
d.registryLock.Lock()
d.registry[node] = cached
d.registryLock.Unlock()
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}
return nil
}
func (d *Discoverer) Hint(node string, addrs []string) {
resAddrs := resolveAddrs(addrs)
var id protocol.NodeID
id.UnmarshalText([]byte(node))
d.registerNode(nil, Node{
Addresses: resAddrs,
ID: id[:],
})
}
func (d *Discoverer) All() map[protocol.NodeID][]cacheEntry {
d.registryLock.RLock()
nodes := make(map[protocol.NodeID][]cacheEntry, len(d.registry))
for node, addrs := range d.registry {
addrsCopy := make([]cacheEntry, len(addrs))
copy(addrsCopy, addrs)
nodes[node] = addrsCopy
}
d.registryLock.RUnlock()
return nodes
}
func (d *Discoverer) announcementPkt() []byte {
var addrs []Address
for _, astr := range d.listenAddrs {
addr, err := net.ResolveTCPAddr("tcp", astr)
if err != nil {
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l.Warnln("%v: not announcing %s", err, astr)
continue
} else if debug {
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l.Debugf("discover: announcing %s: %#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)})
}
}
var pkt = Announce{
Magic: AnnouncementMagic,
This: Node{d.myID[:], addrs},
}
return pkt.MarshalXDR()
}
func (d *Discoverer) sendLocalAnnouncements() {
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var addrs = resolveAddrs(d.listenAddrs)
var pkt = Announce{
Magic: AnnouncementMagic,
This: Node{d.myID[:], addrs},
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}
msg := pkt.MarshalXDR()
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for {
d.beacon.Send(msg)
select {
case <-d.localBcastTick:
case <-d.forcedBcastTick:
}
}
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}
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func (d *Discoverer) sendExternalAnnouncements() {
defer d.globalWG.Done()
remote, err := net.ResolveUDPAddr("udp", d.extServer)
for err != nil {
l.Warnf("Global discovery: %v; trying again in %v", err, d.errorRetryIntv)
time.Sleep(d.errorRetryIntv)
remote, err = net.ResolveUDPAddr("udp", d.extServer)
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}
conn, err := net.ListenUDP("udp", nil)
for err != nil {
l.Warnf("Global discovery: %v; trying again in %v", err, d.errorRetryIntv)
time.Sleep(d.errorRetryIntv)
conn, err = net.ListenUDP("udp", nil)
}
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var buf []byte
if d.extPort != 0 {
var pkt = Announce{
Magic: AnnouncementMagic,
This: Node{d.myID[:], []Address{{Port: d.extPort}}},
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}
buf = pkt.MarshalXDR()
} else {
buf = d.announcementPkt()
}
var bcastTick = time.Tick(d.globalBcastIntv)
var errTick <-chan time.Time
sendOneAnnouncement := func() {
var ok bool
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if debug {
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l.Debugf("discover: send announcement -> %v\n%s", remote, hex.Dump(buf))
}
_, err := conn.WriteTo(buf, remote)
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if err != nil {
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if debug {
l.Debugln("discover: warning:", err)
}
ok = false
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} else {
// Verify that the announce server responds positively for our node ID
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time.Sleep(1 * time.Second)
res := d.externalLookup(d.myID)
if debug {
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l.Debugln("discover: external lookup check:", res)
}
ok = len(res) > 0
}
d.extAnnounceOKmut.Lock()
d.extAnnounceOK = ok
d.extAnnounceOKmut.Unlock()
if ok {
errTick = nil
} else if errTick != nil {
errTick = time.Tick(d.errorRetryIntv)
}
}
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// Announce once, immediately
sendOneAnnouncement()
loop:
for {
select {
case <-d.stopGlobal:
break loop
case <-errTick:
sendOneAnnouncement()
case <-bcastTick:
sendOneAnnouncement()
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}
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}
if debug {
l.Debugln("discover: stopping global")
}
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}
func (d *Discoverer) recvAnnouncements() {
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for {
buf, addr := d.beacon.Recv()
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if debug {
l.Debugf("discover: read announcement from %s:\n%s", addr, hex.Dump(buf))
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}
var pkt Announce
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err := pkt.UnmarshalXDR(buf)
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if err != nil && err != io.EOF {
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continue
}
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var newNode bool
if bytes.Compare(pkt.This.ID, d.myID[:]) != 0 {
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newNode = d.registerNode(addr, pkt.This)
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}
if newNode {
select {
case d.forcedBcastTick <- time.Now():
}
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}
}
}
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func (d *Discoverer) registerNode(addr net.Addr, node Node) bool {
var id protocol.NodeID
copy(id[:], node.ID)
d.registryLock.RLock()
current := d.filterCached(d.registry[id])
d.registryLock.RUnlock()
orig := current
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for _, a := range node.Addresses {
var nodeAddr string
if len(a.IP) > 0 {
nodeAddr = fmt.Sprintf("%s:%d", net.IP(a.IP), a.Port)
} else if addr != nil {
ua := addr.(*net.UDPAddr)
ua.Port = int(a.Port)
nodeAddr = ua.String()
}
for i := range current {
if current[i].addr == nodeAddr {
current[i].seen = time.Now()
goto done
}
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}
current = append(current, cacheEntry{
addr: nodeAddr,
seen: time.Now(),
})
done:
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}
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if debug {
l.Debugf("discover: register: %v -> %v", id, current)
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}
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d.registryLock.Lock()
d.registry[id] = current
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d.registryLock.Unlock()
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if len(current) > len(orig) {
addrs := make([]string, len(current))
for i := range current {
addrs[i] = current[i].addr
}
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events.Default.Log(events.NodeDiscovered, map[string]interface{}{
"node": id.String(),
"addrs": addrs,
})
}
return len(current) > len(orig)
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}
func (d *Discoverer) externalLookup(node protocol.NodeID) []string {
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extIP, err := net.ResolveUDPAddr("udp", d.extServer)
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if err != nil {
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if debug {
l.Debugf("discover: %v; no external lookup", err)
}
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return nil
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}
conn, err := net.DialUDP("udp", nil, extIP)
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if err != nil {
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if debug {
l.Debugf("discover: %v; no external lookup", err)
}
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return nil
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}
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defer conn.Close()
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err = conn.SetDeadline(time.Now().Add(5 * time.Second))
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if err != nil {
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if debug {
l.Debugf("discover: %v; no external lookup", err)
}
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return nil
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}
buf := Query{QueryMagic, node[:]}.MarshalXDR()
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_, err = conn.Write(buf)
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if err != nil {
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if debug {
l.Debugf("discover: %v; no external lookup", err)
}
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return nil
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}
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buf = make([]byte, 2048)
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n, err := conn.Read(buf)
if err != nil {
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if err, ok := err.(net.Error); ok && err.Timeout() {
// Expected if the server doesn't know about requested node ID
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return nil
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}
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if debug {
l.Debugf("discover: %v; no external lookup", err)
}
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return nil
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}
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if debug {
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l.Debugf("discover: read external:\n%s", hex.Dump(buf[:n]))
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}
var pkt Announce
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err = pkt.UnmarshalXDR(buf[:n])
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if err != nil && err != io.EOF {
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if debug {
l.Debugln("discover:", err)
}
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return nil
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}
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var addrs []string
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for _, a := range pkt.This.Addresses {
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nodeAddr := fmt.Sprintf("%s:%d", net.IP(a.IP), a.Port)
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addrs = append(addrs, nodeAddr)
}
return addrs
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}
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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("removing cached address %s: seen %v ago", c[i].addr, ago)
}
c[i] = c[len(c)-1]
c = c[:len(c)-1]
} else {
i++
}
}
return c
}
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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)
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} else {
raddrs = append(raddrs, Address{Port: addr.Port})
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}
}
return raddrs
}