327 lines
7.0 KiB
Go
327 lines
7.0 KiB
Go
package discover
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import (
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"encoding/hex"
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"errors"
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"fmt"
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"log"
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"net"
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"strings"
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"sync"
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"time"
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"github.com/calmh/syncthing/buffers"
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)
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const (
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AnnouncementPort = 21025
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Debug = false
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)
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type Discoverer struct {
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MyID string
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ListenPort int
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BroadcastIntv time.Duration
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ExtBroadcastIntv time.Duration
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conn *net.UDPConn
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registry map[string][]string
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registryLock sync.RWMutex
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extServer string
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localBroadcastTick <-chan time.Time
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forcedBroadcastTick chan time.Time
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}
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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.
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// When we hit this many errors in succession, we stop.
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const maxErrors = 30
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func NewDiscoverer(id string, port int, extServer string) (*Discoverer, error) {
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local := &net.UDPAddr{IP: nil, Port: AnnouncementPort}
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conn, err := net.ListenUDP("udp", local)
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if err != nil {
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return nil, err
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}
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disc := &Discoverer{
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MyID: id,
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ListenPort: port,
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BroadcastIntv: 30 * time.Second,
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ExtBroadcastIntv: 1800 * time.Second,
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conn: conn,
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registry: make(map[string][]string),
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extServer: extServer,
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}
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go disc.recvAnnouncements()
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if disc.ListenPort > 0 {
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disc.localBroadcastTick = time.Tick(disc.BroadcastIntv)
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disc.forcedBroadcastTick = make(chan time.Time)
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go disc.sendAnnouncements()
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}
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if len(disc.extServer) > 0 {
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go disc.sendExtAnnouncements()
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}
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return disc, nil
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}
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func (d *Discoverer) sendAnnouncements() {
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var pkt = AnnounceV2{AnnouncementMagicV2, d.MyID, []Address{{nil, 22000}}}
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var buf = pkt.MarshalXDR()
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var errCounter = 0
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var err error
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for errCounter < maxErrors {
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for _, ipStr := range allBroadcasts() {
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var addrStr = ipStr + ":21025"
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remote, err := net.ResolveUDPAddr("udp4", addrStr)
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if err != nil {
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log.Printf("discover/external: %v; no external announcements", err)
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return
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}
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if Debug {
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log.Println("send announcement -> ", remote)
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}
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_, _, err = d.conn.WriteMsgUDP(buf, nil, remote)
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if err != nil {
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log.Println("discover/write: warning:", err)
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errCounter++
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} else {
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errCounter = 0
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}
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}
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select {
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case <-d.localBroadcastTick:
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case <-d.forcedBroadcastTick:
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}
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}
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log.Println("discover/write: local: stopping due to too many errors:", err)
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}
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func (d *Discoverer) sendExtAnnouncements() {
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remote, err := net.ResolveUDPAddr("udp", d.extServer)
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if err != nil {
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log.Printf("discover/external: %v; no external announcements", err)
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return
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}
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var pkt = AnnounceV2{AnnouncementMagicV2, d.MyID, []Address{{nil, 22000}}}
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var buf = pkt.MarshalXDR()
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var errCounter = 0
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for errCounter < maxErrors {
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if Debug {
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log.Println("send announcement -> ", remote)
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}
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_, _, err = d.conn.WriteMsgUDP(buf, nil, remote)
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if err != nil {
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log.Println("discover/write: warning:", err)
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errCounter++
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} else {
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errCounter = 0
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}
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time.Sleep(d.ExtBroadcastIntv)
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}
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log.Printf("discover/write: %v: stopping due to too many errors: %v", remote, err)
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}
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func (d *Discoverer) recvAnnouncements() {
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var buf = make([]byte, 1024)
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var errCounter = 0
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var err error
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for errCounter < maxErrors {
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n, addr, err := d.conn.ReadFromUDP(buf)
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if err != nil {
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errCounter++
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time.Sleep(time.Second)
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continue
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}
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if Debug {
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log.Printf("read announcement:\n%s", hex.Dump(buf[:n]))
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}
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var pkt AnnounceV2
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err = pkt.UnmarshalXDR(buf[:n])
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if err != nil {
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errCounter++
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time.Sleep(time.Second)
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continue
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}
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if Debug {
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log.Printf("read announcement: %#v", pkt)
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}
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errCounter = 0
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if pkt.NodeID != d.MyID {
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var addrs []string
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for _, a := range pkt.Addresses {
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var nodeAddr string
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if len(a.IP) > 0 {
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nodeAddr = fmt.Sprintf("%s:%d", ipStr(a.IP), a.Port)
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} else {
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nodeAddr = fmt.Sprintf("%s:%d", addr.IP.String(), a.Port)
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}
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addrs = append(addrs, nodeAddr)
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}
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if Debug {
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log.Printf("register: %#v", addrs)
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}
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d.registryLock.Lock()
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_, seen := d.registry[pkt.NodeID]
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if !seen {
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select {
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case d.forcedBroadcastTick <- time.Now():
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}
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}
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d.registry[pkt.NodeID] = addrs
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d.registryLock.Unlock()
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}
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}
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log.Println("discover/read: stopping due to too many errors:", err)
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}
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func (d *Discoverer) externalLookup(node string) []string {
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extIP, err := net.ResolveUDPAddr("udp", d.extServer)
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if err != nil {
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log.Printf("discover/external: %v; no external lookup", err)
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return nil
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}
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conn, err := net.DialUDP("udp", nil, extIP)
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if err != nil {
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log.Printf("discover/external: %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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log.Printf("discover/external: %v; no external lookup", err)
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return nil
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}
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buf := QueryV2{QueryMagicV2, node}.MarshalXDR()
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_, err = conn.Write(buf)
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if err != nil {
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log.Printf("discover/external: %v; no external lookup", err)
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return nil
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}
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buffers.Put(buf)
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buf = buffers.Get(256)
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defer buffers.Put(buf)
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n, err := conn.Read(buf)
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if err != nil {
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if err, ok := err.(net.Error); ok && err.Timeout() {
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// 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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log.Printf("discover/external/read: %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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log.Printf("read external:\n%s", hex.Dump(buf[:n]))
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}
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var pkt AnnounceV2
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err = pkt.UnmarshalXDR(buf[:n])
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if err != nil {
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log.Println("discover/external/decode:", err)
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return nil
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}
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if Debug {
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log.Printf("read external: %#v", pkt)
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}
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var addrs []string
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for _, a := range pkt.Addresses {
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var nodeAddr string
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if len(a.IP) > 0 {
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nodeAddr = fmt.Sprintf("%s:%d", ipStr(a.IP), a.Port)
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}
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addrs = append(addrs, nodeAddr)
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}
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return addrs
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}
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func (d *Discoverer) Lookup(node string) []string {
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d.registryLock.Lock()
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addr, ok := d.registry[node]
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d.registryLock.Unlock()
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if ok {
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return addr
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} else if len(d.extServer) != 0 {
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// We might want to cache this, but not permanently so it needs some intelligence
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return d.externalLookup(node)
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}
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return nil
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}
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func ipStr(ip []byte) string {
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var f = "%d"
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var s = "."
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if len(ip) > 4 {
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f = "%x"
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s = ":"
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}
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var ss = make([]string, len(ip))
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for i := range ip {
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ss[i] = fmt.Sprintf(f, ip[i])
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}
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return strings.Join(ss, s)
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}
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func allBroadcasts() []string {
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var bcasts = make(map[string]bool)
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addrs, err := net.InterfaceAddrs()
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if err != nil {
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return nil
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}
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for _, addr := range addrs {
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switch {
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case strings.HasPrefix(addr.String(), "127."):
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// Ignore v4 localhost
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case strings.Contains(addr.String(), ":"):
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// Ignore all v6, because we need link local multicast there which I haven't implemented
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default:
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if in, ok := addr.(*net.IPNet); ok {
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il := len(in.IP) - 1
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ml := len(in.Mask) - 1
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for i := range in.Mask {
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in.IP[il-i] = in.IP[il-i] | ^in.Mask[ml-i]
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}
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parts := strings.Split(in.String(), "/")
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bcasts[parts[0]] = true
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}
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}
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}
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var l []string
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for ip := range bcasts {
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l = append(l, ip)
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}
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return l
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}
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