dht: Improve Server.GetPeers so new nodes are fed directly back into the current discovery

dht/dht.go

@@ -148,6 +148,14 @@ func (m Msg) T() (t string) {
 	return
 }
 
+func (m Msg) Nodes() []NodeInfo {
+	var r findNodeResponse
+	if err := r.UnmarshalKRPCMsg(m); err != nil {
+		return nil
+	}
+	return r.Nodes
+}
+
 type KRPCError struct {
 	Code int
 	Msg  string
@@ -159,12 +167,21 @@ func (me KRPCError) Error() string {
 
 var _ error = KRPCError{}
 
-func (m Msg) Error() *KRPCError {
+func (m Msg) Error() (ret *KRPCError) {
 	if m["y"] != "e" {
-		return nil
+		return
 	}
-	l := m["e"].([]interface{})
-	return &KRPCError{int(l[0].(int64)), l[1].(string)}
+	ret = &KRPCError{}
+	switch e := m["e"].(type) {
+	case []interface{}:
+		ret.Code = int(e[0].(int64))
+		ret.Msg = e[1].(string)
+	case string:
+		ret.Msg = e
+	default:
+		logonce.Stderr.Printf(`KRPC error "e" value has unexpected type: %T`, e)
+	}
+	return
 }
 
 // Returns the token given in response to a get_peers request for future
@@ -175,6 +192,7 @@ func (m Msg) AnnounceToken() string {
 }
 
 type transaction struct {
+	mu         sync.Mutex
 	remoteAddr dHTAddr
 	t          string
 	Response   chan Msg
@@ -183,12 +201,36 @@ type transaction struct {
 }
 
 func (t *transaction) timeout() {
+	t.Close()
+}
+
+func (t *transaction) closing() bool {
+	select {
+	case <-t.done:
+		return true
+	default:
+		return false
+	}
+}
+
+func (t *transaction) Close() {
+	t.mu.Lock()
+	defer t.mu.Unlock()
+	if t.closing() {
+		return
+	}
 	close(t.Response)
 	close(t.done)
 }
 
 func (t *transaction) handleResponse(m Msg) {
+	t.mu.Lock()
+	if t.closing() {
+		t.mu.Unlock()
+		return
+	}
 	close(t.done)
+	t.mu.Unlock()
 	if t.onResponse != nil {
 		t.onResponse(m)
 	}
@@ -272,6 +314,8 @@ func (s *Server) serve() error {
 }
 
 func (s *Server) AddNode(ni NodeInfo) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
 	if s.nodes == nil {
 		s.nodes = make(map[string]*Node)
 	}
@@ -697,27 +741,6 @@ func (s *Server) findNode(addr dHTAddr, targetID string) (t *transaction, err er
 	return
 }
 
-type peerStreamValue struct {
-	Peers    []util.CompactPeer // Peers given in get_peers response.
-	NodeInfo                    // The node that gave the response.
-}
-
-type peerStream struct {
-	mu     sync.Mutex
-	Values chan peerStreamValue
-	stop   chan struct{}
-}
-
-func (ps *peerStream) Close() {
-	ps.mu.Lock()
-	select {
-	case <-ps.stop:
-	default:
-		close(ps.stop)
-	}
-	ps.mu.Unlock()
-}
-
 func extractValues(m Msg) (vs []util.CompactPeer) {
 	r, ok := m["r"]
 	if !ok {
@@ -752,63 +775,6 @@ func extractValues(m Msg) (vs []util.CompactPeer) {
 	return
 }
 
-func (s *Server) GetPeers(infoHash string) (ps *peerStream, err error) {
-	ps = &peerStream{
-		Values: make(chan peerStreamValue),
-		stop:   make(chan struct{}),
-	}
-	done := make(chan struct{})
-	pending := 0
-	s.mu.Lock()
-	for _, n := range s.closestGoodNodes(160, infoHash) {
-		var t *transaction
-		t, err = s.getPeers(n.addr, infoHash)
-		if err != nil {
-			ps.Close()
-			break
-		}
-		go func() {
-			select {
-			case m := <-t.Response:
-				vs := extractValues(m)
-				if vs != nil {
-					nodeInfo := NodeInfo{
-						Addr: t.remoteAddr,
-					}
-					id := func() string {
-						defer func() {
-							recover()
-						}()
-						return m["r"].(map[string]interface{})["id"].(string)
-					}()
-					copy(nodeInfo.ID[:], id)
-					select {
-					case ps.Values <- peerStreamValue{
-						Peers:    vs,
-						NodeInfo: nodeInfo,
-					}:
-					case <-ps.stop:
-					}
-				}
-			case <-ps.stop:
-			}
-			done <- struct{}{}
-		}()
-		pending++
-	}
-	s.mu.Unlock()
-	go func() {
-		for ; pending > 0; pending-- {
-			select {
-			case <-done:
-			case <-s.closed:
-			}
-		}
-		close(ps.Values)
-	}()
-	return
-}
-
 func (s *Server) getPeers(addr dHTAddr, infoHash string) (t *transaction, err error) {
 	if len(infoHash) != 20 {
 		err = fmt.Errorf("infohash has bad length")
@@ -825,6 +791,10 @@ func (s *Server) getPeers(addr dHTAddr, infoHash string) (t *transaction, err er
 	return
 }
 
+func bootstrapAddr() (net.Addr, error) {
+	return net.ResolveUDPAddr("udp4", "router.bittorrent.com:6881")
+}
+
 func (s *Server) addRootNode() error {
 	addr, err := net.ResolveUDPAddr("udp4", "router.bittorrent.com:6881")
 	if err != nil {

dht/getpeers.go

@@ -0,0 +1,170 @@
+package dht
+
+import (
+	"log"
+	"net"
+	"sync"
+
+	"bitbucket.org/anacrolix/go.torrent/util"
+)
+
+type peerDiscovery struct {
+	*peerStream
+	triedAddrs        map[string]struct{}
+	contactAddrs      chan net.Addr
+	pending           int
+	transactionClosed chan struct{}
+	server            *Server
+	infoHash          string
+}
+
+func (me *peerDiscovery) Close() {
+	me.peerStream.Close()
+	close(me.contactAddrs)
+}
+
+func (s *Server) GetPeers(infoHash string) (*peerStream, error) {
+	disc := &peerDiscovery{
+		peerStream: &peerStream{
+			Values: make(chan peerStreamValue),
+			stop:   make(chan struct{}),
+		},
+		triedAddrs:        make(map[string]struct{}, 500),
+		contactAddrs:      make(chan net.Addr),
+		transactionClosed: make(chan struct{}),
+		server:            s,
+		infoHash:          infoHash,
+	}
+	go disc.loop()
+	s.mu.Lock()
+	startAddrs := func() (ret []net.Addr) {
+		for _, n := range s.closestGoodNodes(160, infoHash) {
+			ret = append(ret, n.addr)
+		}
+		return
+	}()
+	s.mu.Unlock()
+	for _, addr := range startAddrs {
+		disc.contact(addr)
+	}
+	if len(startAddrs) == 0 {
+		addr, err := bootstrapAddr()
+		if err != nil {
+			disc.Close()
+			return nil, err
+		}
+		disc.contact(addr)
+	}
+	return disc.peerStream, nil
+}
+
+func (me *peerDiscovery) contact(addr net.Addr) {
+	select {
+	case me.contactAddrs <- addr:
+	case <-me.closingCh():
+	}
+}
+
+func (me *peerDiscovery) responseNode(node NodeInfo) {
+	me.contact(node.Addr)
+}
+
+func (me *peerDiscovery) loop() {
+	for {
+		select {
+		case addr := <-me.contactAddrs:
+			if me.pending >= 160 {
+				break
+			}
+			if _, ok := me.triedAddrs[addr.String()]; ok {
+				break
+			}
+			me.triedAddrs[addr.String()] = struct{}{}
+			if err := me.getPeers(addr); err != nil {
+				log.Printf("error sending get_peers request to %s: %s", addr, err)
+				break
+			}
+			// log.Printf("contacting %s", addr)
+			me.pending++
+		case <-me.transactionClosed:
+			me.pending--
+			// log.Printf("pending: %d", me.pending)
+			if me.pending == 0 {
+				me.Close()
+				return
+			}
+		}
+	}
+}
+
+func (me *peerDiscovery) closingCh() chan struct{} {
+	return me.peerStream.stop
+}
+
+func (me *peerDiscovery) getPeers(addr net.Addr) error {
+	me.server.mu.Lock()
+	defer me.server.mu.Unlock()
+	t, err := me.server.getPeers(addr, me.infoHash)
+	if err != nil {
+		return err
+	}
+	go func() {
+		select {
+		case m := <-t.Response:
+			if nodes := m.Nodes(); len(nodes) != 0 {
+				for _, n := range nodes {
+					me.responseNode(n)
+				}
+			}
+			if vs := extractValues(m); vs != nil {
+				nodeInfo := NodeInfo{
+					Addr: t.remoteAddr,
+				}
+				id := func() string {
+					defer func() {
+						recover()
+					}()
+					return m["r"].(map[string]interface{})["id"].(string)
+				}()
+				copy(nodeInfo.ID[:], id)
+				select {
+				case me.peerStream.Values <- peerStreamValue{
+					Peers:    vs,
+					NodeInfo: nodeInfo,
+				}:
+				case <-me.peerStream.stop:
+				}
+			}
+		case <-me.closingCh():
+		}
+		t.Close()
+		me.transactionClosed <- struct{}{}
+	}()
+	return nil
+}
+
+func (me *peerDiscovery) streamValue(psv peerStreamValue) {
+	me.peerStream.Values <- psv
+}
+
+type peerStreamValue struct {
+	Peers    []util.CompactPeer // Peers given in get_peers response.
+	NodeInfo                    // The node that gave the response.
+}
+
+type peerStream struct {
+	mu     sync.Mutex
+	Values chan peerStreamValue
+	stop   chan struct{}
+}
+
+func (ps *peerStream) Close() {
+	ps.mu.Lock()
+	select {
+	case <-ps.stop:
+	default:
+		close(ps.stop)
+		close(ps.Values)
+	}
+	ps.mu.Unlock()
+}