syncthing/discover/discover.go
2014-05-02 08:53:19 +02:00

306 lines
6.7 KiB
Go

package discover
import (
"encoding/hex"
"errors"
"fmt"
"log"
"net"
"sync"
"time"
"github.com/calmh/syncthing/buffers"
"github.com/calmh/syncthing/mc"
)
const (
AnnouncementPort = 21025
)
type Discoverer struct {
myID string
listenAddrs []string
localBcastIntv time.Duration
globalBcastIntv time.Duration
beacon *mc.Beacon
registry map[string][]string
registryLock sync.RWMutex
extServer string
extPort uint16
localBcastTick <-chan time.Time
forcedBcastTick chan time.Time
extAnnounceOK bool
extAnnounceOKmut sync.Mutex
}
var (
ErrIncorrectMagic = errors.New("incorrect magic number")
)
// We tolerate a certain amount of errors because we might be running on
// 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 string, addresses []string) (*Discoverer, error) {
disc := &Discoverer{
myID: id,
listenAddrs: addresses,
localBcastIntv: 30 * time.Second,
globalBcastIntv: 1800 * time.Second,
beacon: mc.NewBeacon("239.21.0.25", 21025),
registry: make(map[string][]string),
}
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()
}
func (d *Discoverer) StartGlobal(server string, extPort uint16) {
d.extServer = server
d.extPort = extPort
go d.sendExternalAnnouncements()
}
func (d *Discoverer) ExtAnnounceOK() bool {
d.extAnnounceOKmut.Lock()
defer d.extAnnounceOKmut.Unlock()
return d.extAnnounceOK
}
func (d *Discoverer) Lookup(node string) []string {
d.registryLock.Lock()
addr, ok := d.registry[node]
d.registryLock.Unlock()
if ok {
return addr
} else if len(d.extServer) != 0 {
// We might want to cache this, but not permanently so it needs some intelligence
return d.externalLookup(node)
}
return nil
}
func (d *Discoverer) announcementPkt() []byte {
var addrs []Address
for _, astr := range d.listenAddrs {
addr, err := net.ResolveTCPAddr("tcp", astr)
if err != nil {
log.Printf("discover/announcement: %v: not announcing %s", err, astr)
continue
} else if debug {
dlog.Printf("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 = AnnounceV2{
Magic: AnnouncementMagicV2,
NodeID: d.myID,
Addresses: addrs,
}
return pkt.MarshalXDR()
}
func (d *Discoverer) sendLocalAnnouncements() {
var buf = d.announcementPkt()
for {
d.beacon.Send(buf)
select {
case <-d.localBcastTick:
case <-d.forcedBcastTick:
}
}
}
func (d *Discoverer) sendExternalAnnouncements() {
remote, err := net.ResolveUDPAddr("udp", d.extServer)
if err != nil {
log.Printf("discover/external: %v; no external announcements", err)
return
}
conn, err := net.ListenUDP("udp", nil)
if err != nil {
log.Printf("discover/external: %v; no external announcements", err)
return
}
var buf []byte
if d.extPort != 0 {
var pkt = AnnounceV2{
Magic: AnnouncementMagicV2,
NodeID: d.myID,
Addresses: []Address{{Port: d.extPort}},
}
buf = pkt.MarshalXDR()
} else {
buf = d.announcementPkt()
}
var errCounter = 0
for errCounter < maxErrors {
var ok bool
if debug {
dlog.Printf("send announcement -> %v\n%s", remote, hex.Dump(buf))
}
_, err = conn.WriteTo(buf, remote)
if err != nil {
log.Println("discover/write: warning:", err)
errCounter++
ok = false
} else {
errCounter = 0
// Verify that the announce server responds positively for our node ID
time.Sleep(1 * time.Second)
res := d.externalLookup(d.myID)
if debug {
dlog.Println("external lookup check:", res)
}
ok = len(res) > 0
}
d.extAnnounceOKmut.Lock()
d.extAnnounceOK = ok
d.extAnnounceOKmut.Unlock()
if ok {
time.Sleep(d.globalBcastIntv)
} else {
time.Sleep(60 * time.Second)
}
}
log.Printf("discover/write: %v: stopping due to too many errors: %v", remote, err)
}
func (d *Discoverer) recvAnnouncements() {
for {
buf, addr := d.beacon.Recv()
if debug {
dlog.Printf("read announcement:\n%s", hex.Dump(buf))
}
var pkt AnnounceV2
err := pkt.UnmarshalXDR(buf)
if err != nil {
continue
}
if debug {
dlog.Printf("parsed announcement: %#v", pkt)
}
if pkt.NodeID != d.myID {
var addrs []string
for _, a := range pkt.Addresses {
var nodeAddr string
if len(a.IP) > 0 {
nodeAddr = fmt.Sprintf("%s:%d", net.IP(a.IP), a.Port)
} else {
ua := addr.(*net.UDPAddr)
ua.Port = int(a.Port)
nodeAddr = ua.String()
}
addrs = append(addrs, nodeAddr)
}
if debug {
dlog.Printf("register: %#v", addrs)
}
d.registryLock.Lock()
_, seen := d.registry[pkt.NodeID]
if !seen {
select {
case d.forcedBcastTick <- time.Now():
}
}
d.registry[pkt.NodeID] = addrs
d.registryLock.Unlock()
}
}
}
func (d *Discoverer) externalLookup(node string) []string {
extIP, err := net.ResolveUDPAddr("udp", d.extServer)
if err != nil {
log.Printf("discover/external: %v; no external lookup", err)
return nil
}
conn, err := net.DialUDP("udp", nil, extIP)
if err != nil {
log.Printf("discover/external: %v; no external lookup", err)
return nil
}
defer conn.Close()
err = conn.SetDeadline(time.Now().Add(5 * time.Second))
if err != nil {
log.Printf("discover/external: %v; no external lookup", err)
return nil
}
buf := QueryV2{QueryMagicV2, node}.MarshalXDR()
_, err = conn.Write(buf)
if err != nil {
log.Printf("discover/external: %v; no external lookup", err)
return nil
}
buffers.Put(buf)
buf = buffers.Get(256)
defer buffers.Put(buf)
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 node ID
return nil
}
log.Printf("discover/external/read: %v; no external lookup", err)
return nil
}
if debug {
dlog.Printf("read external:\n%s", hex.Dump(buf[:n]))
}
var pkt AnnounceV2
err = pkt.UnmarshalXDR(buf[:n])
if err != nil {
log.Println("discover/external/decode:", err)
return nil
}
if debug {
dlog.Printf("parsed external: %#v", pkt)
}
var addrs []string
for _, a := range pkt.Addresses {
nodeAddr := fmt.Sprintf("%s:%d", net.IP(a.IP), a.Port)
addrs = append(addrs, nodeAddr)
}
return addrs
}