/
server.go
903 lines (843 loc) · 21.1 KB
/
server.go
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package dht
import (
"context"
"crypto/rand"
"encoding/binary"
"fmt"
"io"
"log"
"net"
"sync"
"text/tabwriter"
"time"
"github.com/pkg/errors"
"github.com/anacrolix/dht/v2/krpc"
"github.com/anacrolix/missinggo"
"github.com/anacrolix/missinggo/conntrack"
"github.com/anacrolix/torrent/bencode"
"github.com/anacrolix/torrent/iplist"
"github.com/anacrolix/torrent/logonce"
"github.com/anacrolix/torrent/metainfo"
)
// A Server defines parameters for a DHT node server that is able to send
// queries, and respond to the ones from the network. Each node has a globally
// unique identifier known as the "node ID." Node IDs are chosen at random
// from the same 160-bit space as BitTorrent infohashes and define the
// behaviour of the node. Zero valued Server does not have a valid ID and thus
// is unable to function properly. Use `NewServer(nil)` to initialize a
// default node.
type Server struct {
id int160
socket net.PacketConn
mu sync.RWMutex
transactions map[transactionKey]*Transaction
nextT uint64 // unique "t" field for outbound queries
table table
closed missinggo.Event
ipBlockList iplist.Ranger
tokenServer tokenServer // Manages tokens we issue to our queriers.
config ServerConfig
stats ServerStats
}
func (s *Server) numGoodNodes() (num int) {
s.table.forNodes(func(n *node) bool {
if n.IsGood() {
num++
}
return true
})
return
}
func prettySince(t time.Time) string {
if t.IsZero() {
return "never"
}
d := time.Since(t)
d /= time.Second
d *= time.Second
return fmt.Sprintf("%s ago", d)
}
func (s *Server) WriteStatus(w io.Writer) {
fmt.Fprintf(w, "Listening on %s\n", s.Addr())
s.mu.Lock()
defer s.mu.Unlock()
fmt.Fprintf(w, "Nodes in table: %d good, %d total\n", s.numGoodNodes(), s.numNodes())
fmt.Fprintf(w, "Ongoing transactions: %d\n", len(s.transactions))
fmt.Fprintf(w, "Server node ID: %x\n", s.id.Bytes())
fmt.Fprintln(w)
tw := tabwriter.NewWriter(w, 0, 0, 1, ' ', 0)
fmt.Fprintf(tw, "b#\tnode id\taddr\tanntok\tlast query\tlast response\tcf\n")
for i, b := range s.table.buckets {
b.EachNode(func(n *node) bool {
fmt.Fprintf(tw, "%d\t%x\t%s\t%v\t%s\t%s\t%d\n",
i,
n.id.Bytes(),
n.addr,
func() int {
if n.announceToken == nil {
return -1
}
return len(*n.announceToken)
}(),
prettySince(n.lastGotQuery),
prettySince(n.lastGotResponse),
n.consecutiveFailures,
)
return true
})
}
tw.Flush()
fmt.Fprintln(w)
}
func (s *Server) numNodes() (num int) {
s.table.forNodes(func(n *node) bool {
num++
return true
})
return
}
// Stats returns statistics for the server.
func (s *Server) Stats() ServerStats {
s.mu.Lock()
defer s.mu.Unlock()
ss := s.stats
ss.GoodNodes = s.numGoodNodes()
ss.Nodes = s.numNodes()
ss.OutstandingTransactions = len(s.transactions)
return ss
}
// Addr returns the listen address for the server. Packets arriving to this address
// are processed by the server (unless aliens are involved).
func (s *Server) Addr() net.Addr {
return s.socket.LocalAddr()
}
// NewServer initializes a new DHT node server.
func NewServer(c *ServerConfig) (s *Server, err error) {
if c == nil {
c = &ServerConfig{
Conn: mustListen(":0"),
NoSecurity: true,
StartingNodes: GlobalBootstrapAddrs,
ConnectionTracking: conntrack.NewInstance(),
}
}
if c.Conn == nil {
return nil, errors.New("non-nil Conn required")
}
if missinggo.IsZeroValue(c.NodeId) {
c.NodeId = RandomNodeID()
if !c.NoSecurity && c.PublicIP != nil {
SecureNodeId(&c.NodeId, c.PublicIP)
}
}
s = &Server{
config: *c,
ipBlockList: c.IPBlocklist,
tokenServer: tokenServer{
maxIntervalDelta: 2,
interval: 5 * time.Minute,
secret: make([]byte, 20),
},
transactions: make(map[transactionKey]*Transaction),
table: table{
k: 8,
},
}
if s.config.ConnectionTracking == nil {
s.config.ConnectionTracking = conntrack.NewInstance()
}
rand.Read(s.tokenServer.secret)
s.socket = c.Conn
s.id = int160FromByteArray(c.NodeId)
s.table.rootID = s.id
go s.serveUntilClosed()
return
}
func (s *Server) serveUntilClosed() {
err := s.serve()
s.mu.Lock()
defer s.mu.Unlock()
if s.closed.IsSet() {
return
}
if err != nil {
panic(err)
}
}
// Returns a description of the Server. Python repr-style.
func (s *Server) String() string {
return fmt.Sprintf("dht server on %s", s.socket.LocalAddr())
}
// Packets to and from any address matching a range in the list are dropped.
func (s *Server) SetIPBlockList(list iplist.Ranger) {
s.mu.Lock()
defer s.mu.Unlock()
s.ipBlockList = list
}
func (s *Server) IPBlocklist() iplist.Ranger {
return s.ipBlockList
}
func (s *Server) processPacket(b []byte, addr Addr) {
if len(b) < 2 || b[0] != 'd' {
// KRPC messages are bencoded dicts.
readNotKRPCDict.Add(1)
return
}
var d krpc.Msg
err := bencode.Unmarshal(b, &d)
if _, ok := err.(bencode.ErrUnusedTrailingBytes); ok {
// log.Printf("%s: received message packet with %d trailing bytes: %q", s, _err.NumUnusedBytes, b[len(b)-_err.NumUnusedBytes:])
expvars.Add("processed packets with trailing bytes", 1)
} else if err != nil {
readUnmarshalError.Add(1)
func() {
if se, ok := err.(*bencode.SyntaxError); ok {
// The message was truncated.
if int(se.Offset) == len(b) {
return
}
// Some messages seem to drop to nul chars abrubtly.
if int(se.Offset) < len(b) && b[se.Offset] == 0 {
return
}
// The message isn't bencode from the first.
if se.Offset == 0 {
return
}
}
// if missinggo.CryHeard() {
// log.Printf("%s: received bad krpc message from %s: %s: %+q", s, addr, err, b)
// }
}()
return
}
s.mu.Lock()
defer s.mu.Unlock()
if s.closed.IsSet() {
return
}
var n *node
if sid := d.SenderID(); sid != nil {
n, _ = s.getNode(addr, int160FromByteArray(*sid), !d.ReadOnly)
if n != nil && d.ReadOnly {
n.readOnly = true
}
}
if d.Y == "q" {
expvars.Add("received queries", 1)
s.handleQuery(addr, d)
return
}
t := s.findResponseTransaction(d.T, addr)
if t == nil {
return
}
go t.handleResponse(d)
if n != nil {
n.lastGotResponse = time.Now()
n.consecutiveFailures = 0
}
s.deleteTransaction(t)
}
func (s *Server) serve() error {
var b [0x10000]byte
for {
n, addr, err := s.socket.ReadFrom(b[:])
if err != nil {
return err
}
expvars.Add("packets read", 1)
if n == len(b) {
logonce.Stderr.Printf("received dht packet exceeds buffer size")
continue
}
if missinggo.AddrPort(addr) == 0 {
readZeroPort.Add(1)
continue
}
s.mu.Lock()
blocked := s.ipBlocked(missinggo.AddrIP(addr))
s.mu.Unlock()
if blocked {
readBlocked.Add(1)
continue
}
s.processPacket(b[:n], NewAddr(addr))
}
}
func (s *Server) ipBlocked(ip net.IP) (blocked bool) {
if s.ipBlockList == nil {
return
}
_, blocked = s.ipBlockList.Lookup(ip)
return
}
// Adds directly to the node table.
func (s *Server) AddNode(ni krpc.NodeInfo) error {
id := int160FromByteArray(ni.ID)
if id.IsZero() {
return s.Ping(ni.Addr.UDP(), nil)
}
_, err := s.getNode(NewAddr(ni.Addr.UDP()), int160FromByteArray(ni.ID), true)
return err
}
func wantsContain(ws []krpc.Want, w krpc.Want) bool {
for _, _w := range ws {
if _w == w {
return true
}
}
return false
}
func shouldReturnNodes(queryWants []krpc.Want, querySource net.IP) bool {
if len(queryWants) != 0 {
return wantsContain(queryWants, krpc.WantNodes)
}
return querySource.To4() != nil
}
func shouldReturnNodes6(queryWants []krpc.Want, querySource net.IP) bool {
if len(queryWants) != 0 {
return wantsContain(queryWants, krpc.WantNodes6)
}
return querySource.To4() == nil
}
func (s *Server) makeReturnNodes(target int160, filter func(krpc.NodeAddr) bool) []krpc.NodeInfo {
return s.closestGoodNodeInfos(8, target, filter)
}
var krpcErrMissingArguments = krpc.Error{
Code: krpc.ErrorCodeProtocolError,
Msg: "missing arguments dict",
}
func (s *Server) setReturnNodes(r *krpc.Return, queryMsg krpc.Msg, querySource Addr) *krpc.Error {
if queryMsg.A == nil {
return &krpcErrMissingArguments
}
target := int160FromByteArray(queryMsg.A.InfoHash)
if shouldReturnNodes(queryMsg.A.Want, querySource.IP()) {
r.Nodes = s.makeReturnNodes(target, func(na krpc.NodeAddr) bool { return na.IP.To4() != nil })
}
if shouldReturnNodes6(queryMsg.A.Want, querySource.IP()) {
r.Nodes6 = s.makeReturnNodes(target, func(krpc.NodeAddr) bool { return true })
}
return nil
}
// TODO: Probably should write error messages back to senders if something is
// wrong.
func (s *Server) handleQuery(source Addr, m krpc.Msg) {
go func() {
expvars.Add(fmt.Sprintf("received query %s", m.Q), 1)
if a := m.A; a != nil {
if a.NoSeed != 0 {
expvars.Add("received argument noseed", 1)
}
if a.Scrape != 0 {
expvars.Add("received argument scrape", 1)
}
}
}()
if m.SenderID() != nil {
if n, _ := s.getNode(source, int160FromByteArray(*m.SenderID()), !m.ReadOnly); n != nil {
n.lastGotQuery = time.Now()
}
}
if s.config.OnQuery != nil {
propagate := s.config.OnQuery(&m, source.Raw())
if !propagate {
return
}
}
// Don't respond.
if s.config.Passive {
return
}
// TODO: Should we disallow replying to ourself?
args := m.A
switch m.Q {
case "ping":
s.reply(source, m.T, krpc.Return{})
case "get_peers":
var r krpc.Return
// TODO: Return values.
if err := s.setReturnNodes(&r, m, source); err != nil {
s.sendError(source, m.T, *err)
break
}
r.Token = func() *string {
t := s.createToken(source)
return &t
}()
s.reply(source, m.T, r)
case "find_node":
var r krpc.Return
if err := s.setReturnNodes(&r, m, source); err != nil {
s.sendError(source, m.T, *err)
break
}
s.reply(source, m.T, r)
case "announce_peer":
readAnnouncePeer.Add(1)
if !s.validToken(args.Token, source) {
expvars.Add("received announce_peer with invalid token", 1)
return
}
expvars.Add("received announce_peer with valid token", 1)
if h := s.config.OnAnnouncePeer; h != nil {
p := Peer{
IP: source.IP(),
Port: args.Port,
}
if args.ImpliedPort {
p.Port = source.Port()
}
go h(metainfo.Hash(args.InfoHash), p)
}
s.reply(source, m.T, krpc.Return{})
default:
s.sendError(source, m.T, krpc.ErrorMethodUnknown)
}
}
func (s *Server) sendError(addr Addr, t string, e krpc.Error) {
m := krpc.Msg{
T: t,
Y: "e",
E: &e,
}
b, err := bencode.Marshal(m)
if err != nil {
panic(err)
}
_, err = s.writeToNode(b, addr)
if err != nil {
log.Printf("error replying to %s: %s", addr, err)
}
}
func (s *Server) reply(addr Addr, t string, r krpc.Return) {
expvars.Add("replied to peer", 1)
r.ID = s.id.AsByteArray()
m := krpc.Msg{
T: t,
Y: "r",
R: &r,
IP: addr.KRPC(),
}
b, err := bencode.Marshal(m)
if err != nil {
panic(err)
}
_, err = s.writeToNode(b, addr)
if err != nil {
log.Printf("error replying to %s: %s", addr, err)
}
}
// Returns the node if it's in the routing table, adding it if appropriate.
func (s *Server) getNode(addr Addr, id int160, tryAdd bool) (*node, error) {
if n := s.table.getNode(addr, id); n != nil {
return n, nil
}
n := &node{nodeKey: nodeKey{
id: id,
addr: addr,
}}
// Check that the node would be good to begin with. (It might have a bad
// ID or banned address, or we fucked up the initial node field
// invariant.)
if err := s.nodeErr(n); err != nil {
return nil, err
}
if !tryAdd {
return nil, errors.New("node not present and add flag false")
}
b := s.table.bucketForID(id)
if b.Len() >= s.table.k {
if b.EachNode(func(n *node) bool {
if s.nodeIsBad(n) {
s.table.dropNode(n)
}
return b.Len() >= s.table.k
}) {
return nil, errors.New("no room in bucket")
}
}
if err := s.table.addNode(n); err != nil {
panic(fmt.Sprintf("expected to add node: %s", err))
}
return n, nil
}
func (s *Server) nodeIsBad(n *node) bool {
return s.nodeErr(n) != nil
}
func (s *Server) nodeErr(n *node) error {
if n.id == s.id {
return errors.New("is self")
}
if n.id.IsZero() {
return errors.New("has zero id")
}
if !s.config.NoSecurity && !n.IsSecure() {
return errors.New("not secure")
}
if n.IsGood() {
return nil
}
if n.consecutiveFailures >= 3 {
return fmt.Errorf("has %d consecutive failures", n.consecutiveFailures)
}
return nil
}
func (s *Server) writeToNode(b []byte, node Addr) (wrote bool, err error) {
if list := s.ipBlockList; list != nil {
if r, ok := list.Lookup(node.IP()); ok {
err = fmt.Errorf("write to %s blocked: %s", node, r.Description)
return
}
}
// log.Printf("writing to %s: %q", node.UDPAddr(), b)
n, err := s.socket.WriteTo(b, node.Raw())
writes.Add(1)
if err != nil {
writeErrors.Add(1)
err = fmt.Errorf("error writing %d bytes to %s: %s", len(b), node, err)
return
}
wrote = true
if n != len(b) {
err = io.ErrShortWrite
return
}
return
}
func (s *Server) findResponseTransaction(transactionID string, sourceNode Addr) *Transaction {
return s.transactions[transactionKey{
sourceNode.String(),
transactionID}]
}
func (s *Server) nextTransactionID() string {
var b [binary.MaxVarintLen64]byte
n := binary.PutUvarint(b[:], s.nextT)
s.nextT++
return string(b[:n])
}
func (s *Server) deleteTransaction(t *Transaction) {
delete(s.transactions, t.key())
}
func (s *Server) deleteTransactionUnlocked(t *Transaction) {
s.mu.Lock()
defer s.mu.Unlock()
s.deleteTransaction(t)
}
func (s *Server) addTransaction(t *Transaction) {
if _, ok := s.transactions[t.key()]; ok {
panic("transaction not unique")
}
s.transactions[t.key()] = t
}
// ID returns the 20-byte server ID. This is the ID used to communicate with the
// DHT network.
func (s *Server) ID() [20]byte {
return s.id.AsByteArray()
}
func (s *Server) createToken(addr Addr) string {
return s.tokenServer.CreateToken(addr)
}
func (s *Server) validToken(token string, addr Addr) bool {
return s.tokenServer.ValidToken(token, addr)
}
func (s *Server) connTrackEntryForAddr(a Addr) conntrack.Entry {
return conntrack.Entry{
s.socket.LocalAddr().Network(),
s.socket.LocalAddr().String(),
a.String(),
}
}
func (s *Server) query(addr Addr, q string, a *krpc.MsgArgs, callback func(krpc.Msg, error)) error {
if callback == nil {
callback = func(krpc.Msg, error) {}
}
go func() {
callback(s.queryContext(context.Background(), addr, q, a))
}()
return nil
}
func (s *Server) queryContext(ctx context.Context, addr Addr, q string, a *krpc.MsgArgs) (reply krpc.Msg, err error) {
s.mu.Lock()
defer s.mu.Unlock()
tid := s.nextTransactionID()
if a == nil {
a = &krpc.MsgArgs{}
}
a.ID = s.ID()
m := krpc.Msg{
T: tid,
Y: "q",
Q: q,
A: a,
}
// BEP 43. Outgoing queries from passive nodes should contain "ro":1 in
// the top level dictionary.
if s.config.Passive {
m.ReadOnly = true
}
b, err := bencode.Marshal(m)
if err != nil {
return
}
replyChan := make(chan krpc.Msg, 1)
errChan := make(chan error, 1)
t := &Transaction{
remoteAddr: addr,
t: tid,
querySender: func() error {
cteh := s.config.ConnectionTracking.Wait(ctx, s.connTrackEntryForAddr(addr), "send dht query", -1)
wrote, err := s.writeToNode(b, addr)
if wrote {
cteh.Done()
} else {
cteh.Forget()
}
return err
},
onResponse: func(m krpc.Msg) {
replyChan <- m
},
onTimeout: func() {
errChan <- errors.New("query timed out")
},
onSendError: func(err error) {
errChan <- fmt.Errorf("error sending query: %s", err)
},
queryResendDelay: func() time.Duration {
if s.config.QueryResendDelay != nil {
return s.config.QueryResendDelay()
}
return defaultQueryResendDelay()
},
}
s.stats.OutboundQueriesAttempted++
t.mu.Lock()
t.startResendTimer()
t.mu.Unlock()
s.addTransaction(t)
defer func() {
if err != nil {
for _, n := range s.table.addrNodes(addr) {
n.consecutiveFailures++
}
}
}()
defer s.deleteTransaction(t)
s.mu.Unlock()
go expvars.Add(fmt.Sprintf("outbound %s queries", q), 1)
defer s.mu.Lock()
select {
case reply = <-replyChan:
return
case <-ctx.Done():
err = ctx.Err()
return
case err = <-errChan:
return
}
}
// Sends a ping query to the address given.
func (s *Server) Ping(node *net.UDPAddr, callback func(krpc.Msg, error)) error {
s.mu.Lock()
defer s.mu.Unlock()
return s.ping(node, callback)
}
func (s *Server) ping(node *net.UDPAddr, callback func(krpc.Msg, error)) error {
return s.query(NewAddr(node), "ping", nil, callback)
}
func (s *Server) announcePeer(node Addr, infoHash int160, port int, token string, impliedPort bool, callback func(krpc.Msg, error)) error {
if port == 0 && !impliedPort {
return errors.New("nothing to announce")
}
return s.query(node, "announce_peer", &krpc.MsgArgs{
ImpliedPort: impliedPort,
InfoHash: infoHash.AsByteArray(),
Port: port,
Token: token,
}, func(m krpc.Msg, err error) {
if callback != nil {
go callback(m, err)
}
if err := m.Error(); err != nil {
announceErrors.Add(1)
return
}
s.mu.Lock()
defer s.mu.Unlock()
s.stats.SuccessfulOutboundAnnouncePeerQueries++
})
}
// Add response nodes to node table.
func (s *Server) addResponseNodes(d krpc.Msg) {
if d.R == nil {
return
}
d.R.ForAllNodes(func(ni krpc.NodeInfo) {
s.getNode(NewAddr(ni.Addr.UDP()), int160FromByteArray(ni.ID), true)
})
}
// Sends a find_node query to addr. targetID is the node we're looking for.
func (s *Server) findNode(addr Addr, targetID int160, callback func(krpc.Msg, error)) (err error) {
return s.query(addr, "find_node", &krpc.MsgArgs{
Target: targetID.AsByteArray(),
Want: []krpc.Want{krpc.WantNodes, krpc.WantNodes6},
}, func(m krpc.Msg, err error) {
// Scrape peers from the response to put in the server's table before
// handing the response back to the caller.
s.mu.Lock()
s.addResponseNodes(m)
s.mu.Unlock()
callback(m, err)
})
}
type TraversalStats struct {
NumAddrsTried int
NumResponses int
}
func (me TraversalStats) String() string {
return fmt.Sprintf("%#v", me)
}
// Populates the node table.
func (s *Server) Bootstrap() (ts TraversalStats, err error) {
initialAddrs, err := s.traversalStartingNodes()
if err != nil {
return
}
var outstanding sync.WaitGroup
triedAddrs := newBloomFilterForTraversal()
var onAddr func(addr Addr)
onAddr = func(addr Addr) {
if triedAddrs.Test([]byte(addr.String())) {
return
}
ts.NumAddrsTried++
outstanding.Add(1)
triedAddrs.AddString(addr.String())
s.findNode(addr, s.id, func(m krpc.Msg, err error) {
defer outstanding.Done()
s.mu.Lock()
defer s.mu.Unlock()
if err != nil {
return
}
ts.NumResponses++
if r := m.R; r != nil {
r.ForAllNodes(func(ni krpc.NodeInfo) {
onAddr(NewAddr(ni.Addr.UDP()))
})
}
})
}
s.mu.Lock()
for _, addr := range initialAddrs {
onAddr(NewAddr(addr.Addr.UDP()))
}
s.mu.Unlock()
outstanding.Wait()
return
}
// Returns how many nodes are in the node table.
func (s *Server) NumNodes() int {
s.mu.Lock()
defer s.mu.Unlock()
return s.numNodes()
}
// Exports the current node table.
func (s *Server) Nodes() (nis []krpc.NodeInfo) {
s.mu.Lock()
defer s.mu.Unlock()
s.table.forNodes(func(n *node) bool {
nis = append(nis, krpc.NodeInfo{
Addr: n.addr.KRPC(),
ID: n.id.AsByteArray(),
})
return true
})
return
}
// Stops the server network activity. This is all that's required to clean-up a Server.
func (s *Server) Close() {
s.mu.Lock()
defer s.mu.Unlock()
s.closed.Set()
s.socket.Close()
}
func (s *Server) getPeers(ctx context.Context, addr Addr, infoHash int160) (krpc.Msg, error) {
m, err := s.queryContext(ctx, addr, "get_peers", &krpc.MsgArgs{
InfoHash: infoHash.AsByteArray(),
Want: []krpc.Want{krpc.WantNodes, krpc.WantNodes6},
})
s.mu.Lock()
defer s.mu.Unlock()
s.addResponseNodes(m)
if m.R != nil {
if m.R.Token == nil {
expvars.Add("get_peers responses with no token", 1)
} else if len(*m.R.Token) == 0 {
expvars.Add("get_peers responses with empty token", 1)
} else {
expvars.Add("get_peers responses with token", 1)
}
if m.SenderID() != nil && m.R.Token != nil {
if n, _ := s.getNode(addr, int160FromByteArray(*m.SenderID()), false); n != nil {
n.announceToken = m.R.Token
}
}
}
return m, err
}
func (s *Server) closestGoodNodeInfos(
k int,
targetID int160,
filter func(krpc.NodeAddr) bool,
) (
ret []krpc.NodeInfo,
) {
for _, n := range s.closestNodes(k, targetID, func(n *node) bool {
return n.IsGood() && filter(n.NodeInfo().Addr)
}) {
ret = append(ret, n.NodeInfo())
}
return
}
func (s *Server) closestNodes(k int, target int160, filter func(*node) bool) []*node {
return s.table.closestNodes(k, target, filter)
}
func (s *Server) traversalStartingNodes() (nodes []addrMaybeId, err error) {
s.mu.RLock()
s.table.forNodes(func(n *node) bool {
nodes = append(nodes, addrMaybeId{n.addr.KRPC(), &n.id})
return true
})
s.mu.RUnlock()
if len(nodes) > 0 {
return
}
if s.config.StartingNodes != nil {
addrs, err := s.config.StartingNodes()
if err != nil {
return nil, errors.Wrap(err, "getting starting nodes")
}
for _, a := range addrs {
nodes = append(nodes, addrMaybeId{a.KRPC(), nil})
}
}
if len(nodes) == 0 {
err = errors.New("no initial nodes")
}
return
}
func (s *Server) AddNodesFromFile(fileName string) (added int, err error) {
ns, err := ReadNodesFromFile(fileName)
if err != nil {
return
}
for _, n := range ns {
if s.AddNode(n) == nil {
added++
}
}
return
}