syncthing/discover/discover.go
2014-03-28 11:04:48 +01:00

289 lines
6.4 KiB
Go

package discover
import (
"encoding/hex"
"errors"
"fmt"
"log"
"net"
"strings"
"sync"
"time"
"github.com/calmh/syncthing/buffers"
"github.com/calmh/syncthing/mc"
)
const (
AnnouncementPort = 21025
)
type Discoverer struct {
MyID string
ListenAddresses []string
BroadcastIntv time.Duration
ExtBroadcastIntv time.Duration
beacon *mc.Beacon
registry map[string][]string
registryLock sync.RWMutex
extServer string
localBroadcastTick <-chan time.Time
forcedBroadcastTick chan time.Time
}
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, extServer string) (*Discoverer, error) {
disc := &Discoverer{
MyID: id,
ListenAddresses: addresses,
BroadcastIntv: 30 * time.Second,
ExtBroadcastIntv: 1800 * time.Second,
beacon: mc.NewBeacon("239.21.0.25", 21025),
registry: make(map[string][]string),
extServer: extServer,
}
// Receive announcements sent to the local multicast group.
go disc.recvAnnouncements()
// If we got a list of addresses that we listen on, announce those
// locally.
if len(disc.ListenAddresses) > 0 {
disc.localBroadcastTick = time.Tick(disc.BroadcastIntv)
disc.forcedBroadcastTick = make(chan time.Time)
go disc.sendLocalAnnouncements()
// If we have an external server address, also announce to that
// server.
if len(disc.extServer) > 0 {
go disc.sendExternalAnnouncements()
}
}
return disc, nil
}
func (d *Discoverer) announcementPkt() []byte {
var addrs []Address
for _, astr := range d.ListenAddresses {
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.localBroadcastTick:
case <-d.forcedBroadcastTick:
}
}
}
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 = d.announcementPkt()
var errCounter = 0
for errCounter < maxErrors {
if debug {
dlog.Println("send announcement -> ", remote)
}
_, err = conn.WriteTo(buf, remote)
if err != nil {
log.Println("discover/write: warning:", err)
errCounter++
} else {
errCounter = 0
}
time.Sleep(d.ExtBroadcastIntv)
}
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", ipStr(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.forcedBroadcastTick <- 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 {
var nodeAddr string
if len(a.IP) > 0 {
nodeAddr = fmt.Sprintf("%s:%d", ipStr(a.IP), a.Port)
}
addrs = append(addrs, nodeAddr)
}
return addrs
}
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 ipStr(ip []byte) string {
var f = "%d"
var s = "."
if len(ip) > 4 {
f = "%x"
s = ":"
}
var ss = make([]string, len(ip))
for i := range ip {
ss[i] = fmt.Sprintf(f, ip[i])
}
return strings.Join(ss, s)
}