223 lines
3.9 KiB
Go
223 lines
3.9 KiB
Go
package main
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import (
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"encoding/binary"
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"encoding/hex"
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"flag"
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"log"
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"net"
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"os"
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"sync"
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"time"
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"github.com/calmh/syncthing/discover"
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"github.com/golang/groupcache/lru"
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"github.com/juju/ratelimit"
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)
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type Node struct {
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Addresses []Address
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Updated time.Time
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}
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type Address struct {
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IP []byte
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Port uint16
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}
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var (
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nodes = make(map[string]Node)
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lock sync.Mutex
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queries = 0
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answered = 0
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limited = 0
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debug = false
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limiter = lru.New(1024)
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)
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func main() {
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var listen string
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var timestamp bool
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flag.StringVar(&listen, "listen", ":22025", "Listen address")
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flag.BoolVar(&debug, "debug", false, "Enable debug output")
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flag.BoolVar(×tamp, "timestamp", true, "Timestamp the log output")
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flag.Parse()
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log.SetOutput(os.Stdout)
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if !timestamp {
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log.SetFlags(0)
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}
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addr, _ := net.ResolveUDPAddr("udp", listen)
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conn, err := net.ListenUDP("udp", addr)
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if err != nil {
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log.Fatal(err)
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}
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go logStats()
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var buf = make([]byte, 1024)
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for {
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buf = buf[:cap(buf)]
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n, addr, err := conn.ReadFromUDP(buf)
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if limit(addr) {
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// Rate limit in effect for source
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continue
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}
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if err != nil {
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log.Fatal(err)
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}
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if n < 4 {
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log.Printf("Received short packet (%d bytes)", n)
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continue
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}
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buf = buf[:n]
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magic := binary.BigEndian.Uint32(buf)
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switch magic {
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case discover.AnnouncementMagicV2:
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handleAnnounceV2(addr, buf)
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case discover.QueryMagicV2:
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handleQueryV2(conn, addr, buf)
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}
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}
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}
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func limit(addr *net.UDPAddr) bool {
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key := addr.IP.String()
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lock.Lock()
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defer lock.Unlock()
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bkt, ok := limiter.Get(key)
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if ok {
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bkt := bkt.(*ratelimit.Bucket)
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if bkt.TakeAvailable(1) != 1 {
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// Rate limit exceeded; ignore packet
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if debug {
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log.Println("Rate limit exceeded for", key)
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}
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limited++
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return true
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}
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} else {
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if debug {
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log.Println("New limiter for", key)
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}
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// One packet per ten seconds average rate, burst ten packets
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limiter.Add(key, ratelimit.NewBucket(10*time.Second, 10))
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}
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return false
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}
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func handleAnnounceV2(addr *net.UDPAddr, buf []byte) {
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var pkt discover.AnnounceV2
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err := pkt.UnmarshalXDR(buf)
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if err != nil {
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log.Println("AnnounceV2 Unmarshal:", err)
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log.Println(hex.Dump(buf))
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return
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}
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if debug {
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log.Printf("<- %v %#v", addr, pkt)
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}
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ip := addr.IP.To4()
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if ip == nil {
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ip = addr.IP.To16()
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}
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var addrs []Address
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for _, addr := range pkt.Addresses {
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tip := addr.IP
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if len(tip) == 0 {
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tip = ip
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}
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addrs = append(addrs, Address{
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IP: tip,
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Port: addr.Port,
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})
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}
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node := Node{
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Addresses: addrs,
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Updated: time.Now(),
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}
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lock.Lock()
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nodes[pkt.NodeID] = node
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lock.Unlock()
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}
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func handleQueryV2(conn *net.UDPConn, addr *net.UDPAddr, buf []byte) {
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var pkt discover.QueryV2
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err := pkt.UnmarshalXDR(buf)
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if err != nil {
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log.Println("QueryV2 Unmarshal:", err)
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log.Println(hex.Dump(buf))
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return
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}
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if debug {
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log.Printf("<- %v %#v", addr, pkt)
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}
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lock.Lock()
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node, ok := nodes[pkt.NodeID]
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queries++
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lock.Unlock()
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if ok && len(node.Addresses) > 0 {
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pkt := discover.AnnounceV2{
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Magic: discover.AnnouncementMagicV2,
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NodeID: pkt.NodeID,
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}
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for _, addr := range node.Addresses {
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pkt.Addresses = append(pkt.Addresses, discover.Address{IP: addr.IP, Port: addr.Port})
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}
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if debug {
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log.Printf("-> %v %#v", addr, pkt)
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}
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tb := pkt.MarshalXDR()
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_, _, err = conn.WriteMsgUDP(tb, nil, addr)
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if err != nil {
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log.Println("QueryV2 response write:", err)
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}
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lock.Lock()
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answered++
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lock.Unlock()
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}
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}
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func logStats() {
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for {
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time.Sleep(600 * time.Second)
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lock.Lock()
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var deleted = 0
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for id, node := range nodes {
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if time.Since(node.Updated) > 60*time.Minute {
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delete(nodes, id)
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deleted++
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}
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}
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log.Printf("Expired %d nodes; %d nodes in registry; %d queries (%d answered)", deleted, len(nodes), queries, answered)
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log.Printf("Limited %d queries; %d entries in limiter cache", limited, limiter.Len())
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queries = 0
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answered = 0
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limited = 0
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lock.Unlock()
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}
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}
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