17 utHolepunch "github.com/anacrolix/torrent/peer_protocol/ut-holepunch"
19 "github.com/RoaringBitmap/roaring"
20 . "github.com/anacrolix/generics"
21 "github.com/anacrolix/log"
22 "github.com/anacrolix/missinggo/v2/bitmap"
23 "github.com/anacrolix/multiless"
24 "golang.org/x/time/rate"
26 "github.com/anacrolix/torrent/bencode"
27 "github.com/anacrolix/torrent/internal/alloclim"
28 "github.com/anacrolix/torrent/metainfo"
29 "github.com/anacrolix/torrent/mse"
30 pp "github.com/anacrolix/torrent/peer_protocol"
33 // Maintains the state of a BitTorrent-protocol based connection with a peer.
34 type PeerConn struct {
37 // A string that should identify the PeerConn's net.Conn endpoints. The net.Conn could
38 // be wrapping WebRTC, uTP, or TCP etc. Used in writing the conn status for peers.
43 PeerExtensionBytes pp.PeerExtensionBits
45 // The actual Conn, used for closing, and setting socket options. Do not use methods on this
46 // while holding any mutexes.
48 // The Reader and Writer for this Conn, with hooks installed for stats,
49 // limiting, deadlines etc.
53 messageWriter peerConnMsgWriter
55 uploadTimer *time.Timer
58 // The pieces the peer has claimed to have.
59 _peerPieces roaring.Bitmap
60 // The peer has everything. This can occur due to a special message, when
61 // we may not even know the number of pieces in the torrent yet.
64 peerRequestDataAllocLimiter alloclim.Limiter
66 outstandingHolepunchingRendezvous map[netip.AddrPort]struct{}
69 func (cn *PeerConn) peerImplStatusLines() []string {
70 lines := make([]string, 0, 2)
73 fmt.Sprintf("%+-55q %v %s", cn.PeerID, cn.PeerExtensionBytes, cn.connString))
74 if cn.supportsExtension(pp.ExtensionNamePex) {
78 "pex: %v conns, %v unsent events",
79 cn.pex.remoteLiveConns,
85 // Returns true if the connection is over IPv6.
86 func (cn *PeerConn) ipv6() bool {
91 return len(ip) == net.IPv6len
94 // Returns true the if the dialer/initiator has the lower client peer ID. TODO: Find the
95 // specification for this.
96 func (cn *PeerConn) isPreferredDirection() bool {
97 return bytes.Compare(cn.t.cl.peerID[:], cn.PeerID[:]) < 0 == cn.outgoing
100 // Returns whether the left connection should be preferred over the right one,
101 // considering only their networking properties. If ok is false, we can't
103 func (l *PeerConn) hasPreferredNetworkOver(r *PeerConn) bool {
104 var ml multiless.Computation
105 ml = ml.Bool(r.isPreferredDirection(), l.isPreferredDirection())
106 ml = ml.Bool(l.utp(), r.utp())
107 ml = ml.Bool(r.ipv6(), l.ipv6())
111 func (cn *PeerConn) peerHasAllPieces() (all, known bool) {
112 if cn.peerSentHaveAll {
115 if !cn.t.haveInfo() {
118 return cn._peerPieces.GetCardinality() == uint64(cn.t.numPieces()), true
121 func (cn *PeerConn) onGotInfo(info *metainfo.Info) {
122 cn.setNumPieces(info.NumPieces())
125 // Correct the PeerPieces slice length. Return false if the existing slice is invalid, such as by
126 // receiving badly sized BITFIELD, or invalid HAVE messages.
127 func (cn *PeerConn) setNumPieces(num pieceIndex) {
128 cn._peerPieces.RemoveRange(bitmap.BitRange(num), bitmap.ToEnd)
129 cn.peerPiecesChanged()
132 func (cn *PeerConn) peerPieces() *roaring.Bitmap {
133 return &cn._peerPieces
136 func (cn *PeerConn) connectionFlags() (ret string) {
138 ret += string([]byte{b})
140 if cn.cryptoMethod == mse.CryptoMethodRC4 {
142 } else if cn.headerEncrypted {
145 ret += string(cn.Discovery)
152 func (cn *PeerConn) utp() bool {
153 return parseNetworkString(cn.Network).Udp
156 func (cn *PeerConn) onClose() {
157 if cn.pex.IsEnabled() {
164 if cb := cn.callbacks.PeerConnClosed; cb != nil {
169 // Writes a message into the write buffer. Returns whether it's okay to keep writing. Writing is
170 // done asynchronously, so it may be that we're not able to honour backpressure from this method.
171 func (cn *PeerConn) write(msg pp.Message) bool {
172 torrent.Add(fmt.Sprintf("messages written of type %s", msg.Type.String()), 1)
173 // We don't need to track bytes here because the connection's Writer has that behaviour injected
174 // (although there's some delay between us buffering the message, and the connection writer
175 // flushing it out.).
176 notFull := cn.messageWriter.write(msg)
177 // Last I checked only Piece messages affect stats, and we don't write those.
183 func (cn *PeerConn) requestMetadataPiece(index int) {
184 eID := cn.PeerExtensionIDs[pp.ExtensionNameMetadata]
185 if eID == pp.ExtensionDeleteNumber {
188 if index < len(cn.metadataRequests) && cn.metadataRequests[index] {
191 cn.logger.WithDefaultLevel(log.Debug).Printf("requesting metadata piece %d", index)
192 cn.write(pp.MetadataExtensionRequestMsg(eID, index))
193 for index >= len(cn.metadataRequests) {
194 cn.metadataRequests = append(cn.metadataRequests, false)
196 cn.metadataRequests[index] = true
199 func (cn *PeerConn) requestedMetadataPiece(index int) bool {
200 return index < len(cn.metadataRequests) && cn.metadataRequests[index]
203 func (cn *PeerConn) onPeerSentCancel(r Request) {
204 if _, ok := cn.peerRequests[r]; !ok {
205 torrent.Add("unexpected cancels received", 1)
208 if cn.fastEnabled() {
211 delete(cn.peerRequests, r)
215 func (cn *PeerConn) choke(msg messageWriter) (more bool) {
220 more = msg(pp.Message{
223 if !cn.fastEnabled() {
224 cn.deleteAllPeerRequests()
229 func (cn *PeerConn) deleteAllPeerRequests() {
230 for _, state := range cn.peerRequests {
231 state.allocReservation.Drop()
233 cn.peerRequests = nil
236 func (cn *PeerConn) unchoke(msg func(pp.Message) bool) bool {
241 return msg(pp.Message{
246 func (pc *PeerConn) writeInterested(interested bool) bool {
247 return pc.write(pp.Message{
248 Type: func() pp.MessageType {
252 return pp.NotInterested
258 func (me *PeerConn) _request(r Request) bool {
259 return me.write(pp.Message{
267 func (me *PeerConn) _cancel(r RequestIndex) bool {
268 me.write(makeCancelMessage(me.t.requestIndexToRequest(r)))
269 // Transmission does not send rejects for received cancels. See
270 // https://github.com/transmission/transmission/pull/2275.
271 return me.fastEnabled() && !me.remoteIsTransmission()
274 func (cn *PeerConn) fillWriteBuffer() {
275 if cn.messageWriter.writeBuffer.Len() > writeBufferLowWaterLen {
276 // Fully committing to our max requests requires sufficient space (see
277 // maxLocalToRemoteRequests). Flush what we have instead. We also prefer always to make
278 // requests than to do PEX or upload, so we short-circuit before handling those. Any update
279 // request reason will not be cleared, so we'll come right back here when there's space. We
280 // can't do this in maybeUpdateActualRequestState because it's a method on Peer and has no
281 // knowledge of write buffers.
283 cn.maybeUpdateActualRequestState()
284 if cn.pex.IsEnabled() {
285 if flow := cn.pex.Share(cn.write); !flow {
292 func (cn *PeerConn) have(piece pieceIndex) {
293 if cn.sentHaves.Get(bitmap.BitIndex(piece)) {
298 Index: pp.Integer(piece),
300 cn.sentHaves.Add(bitmap.BitIndex(piece))
303 func (cn *PeerConn) postBitfield() {
304 if cn.sentHaves.Len() != 0 {
305 panic("bitfield must be first have-related message sent")
307 if !cn.t.haveAnyPieces() {
312 Bitfield: cn.t.bitfield(),
314 cn.sentHaves = bitmap.Bitmap{cn.t._completedPieces.Clone()}
317 func (cn *PeerConn) handleUpdateRequests() {
318 // The writer determines the request state as needed when it can write.
322 func (cn *PeerConn) raisePeerMinPieces(newMin pieceIndex) {
323 if newMin > cn.peerMinPieces {
324 cn.peerMinPieces = newMin
328 func (cn *PeerConn) peerSentHave(piece pieceIndex) error {
329 if cn.t.haveInfo() && piece >= cn.t.numPieces() || piece < 0 {
330 return errors.New("invalid piece")
332 if cn.peerHasPiece(piece) {
335 cn.raisePeerMinPieces(piece + 1)
336 if !cn.peerHasPiece(piece) {
337 cn.t.incPieceAvailability(piece)
339 cn._peerPieces.Add(uint32(piece))
340 if cn.t.wantPieceIndex(piece) {
341 cn.updateRequests("have")
343 cn.peerPiecesChanged()
347 func (cn *PeerConn) peerSentBitfield(bf []bool) error {
349 panic("expected bitfield length divisible by 8")
351 // We know that the last byte means that at most the last 7 bits are wasted.
352 cn.raisePeerMinPieces(pieceIndex(len(bf) - 7))
353 if cn.t.haveInfo() && len(bf) > int(cn.t.numPieces()) {
354 // Ignore known excess pieces.
355 bf = bf[:cn.t.numPieces()]
357 bm := boolSliceToBitmap(bf)
358 if cn.t.haveInfo() && pieceIndex(bm.GetCardinality()) == cn.t.numPieces() {
359 cn.onPeerHasAllPieces()
363 cn.raisePeerMinPieces(pieceIndex(bm.Maximum()) + 1)
365 shouldUpdateRequests := false
366 if cn.peerSentHaveAll {
367 if !cn.t.deleteConnWithAllPieces(&cn.Peer) {
370 cn.peerSentHaveAll = false
371 if !cn._peerPieces.IsEmpty() {
372 panic("if peer has all, we expect no individual peer pieces to be set")
375 bm.Xor(&cn._peerPieces)
377 cn.peerSentHaveAll = false
378 // bm is now 'on' for pieces that are changing
379 bm.Iterate(func(x uint32) bool {
381 if cn._peerPieces.Contains(x) {
382 // Then we must be losing this piece
383 cn.t.decPieceAvailability(pi)
385 if !shouldUpdateRequests && cn.t.wantPieceIndex(pieceIndex(x)) {
386 shouldUpdateRequests = true
388 // We must be gaining this piece
389 cn.t.incPieceAvailability(pieceIndex(x))
393 // Apply the changes. If we had everything previously, this should be empty, so xor is the same
395 cn._peerPieces.Xor(&bm)
396 if shouldUpdateRequests {
397 cn.updateRequests("bitfield")
399 // We didn't guard this before, I see no reason to do it now.
400 cn.peerPiecesChanged()
404 func (cn *PeerConn) onPeerHasAllPieces() {
407 cn._peerPieces.Iterate(func(x uint32) bool {
408 t.decPieceAvailability(pieceIndex(x))
412 t.addConnWithAllPieces(&cn.Peer)
413 cn.peerSentHaveAll = true
414 cn._peerPieces.Clear()
415 if !cn.t._pendingPieces.IsEmpty() {
416 cn.updateRequests("Peer.onPeerHasAllPieces")
418 cn.peerPiecesChanged()
421 func (cn *PeerConn) onPeerSentHaveAll() error {
422 cn.onPeerHasAllPieces()
426 func (cn *PeerConn) peerSentHaveNone() error {
427 if !cn.peerSentHaveAll {
428 cn.t.decPeerPieceAvailability(&cn.Peer)
430 cn._peerPieces.Clear()
431 cn.peerSentHaveAll = false
432 cn.peerPiecesChanged()
436 func (c *PeerConn) requestPendingMetadata() {
440 if c.PeerExtensionIDs[pp.ExtensionNameMetadata] == 0 {
441 // Peer doesn't support this.
444 // Request metadata pieces that we don't have in a random order.
446 for index := 0; index < c.t.metadataPieceCount(); index++ {
447 if !c.t.haveMetadataPiece(index) && !c.requestedMetadataPiece(index) {
448 pending = append(pending, index)
451 rand.Shuffle(len(pending), func(i, j int) { pending[i], pending[j] = pending[j], pending[i] })
452 for _, i := range pending {
453 c.requestMetadataPiece(i)
457 func (cn *PeerConn) wroteMsg(msg *pp.Message) {
458 torrent.Add(fmt.Sprintf("messages written of type %s", msg.Type.String()), 1)
459 if msg.Type == pp.Extended {
460 for name, id := range cn.PeerExtensionIDs {
461 if id != msg.ExtendedID {
464 torrent.Add(fmt.Sprintf("Extended messages written for protocol %q", name), 1)
467 cn.allStats(func(cs *ConnStats) { cs.wroteMsg(msg) })
470 func (cn *PeerConn) wroteBytes(n int64) {
471 cn.allStats(add(n, func(cs *ConnStats) *Count { return &cs.BytesWritten }))
474 func (c *PeerConn) fastEnabled() bool {
475 return c.PeerExtensionBytes.SupportsFast() && c.t.cl.config.Extensions.SupportsFast()
478 func (c *PeerConn) reject(r Request) {
479 if !c.fastEnabled() {
480 panic("fast not enabled")
482 c.write(r.ToMsg(pp.Reject))
483 // It is possible to reject a request before it is added to peer requests due to being invalid.
484 if state, ok := c.peerRequests[r]; ok {
485 state.allocReservation.Drop()
486 delete(c.peerRequests, r)
490 func (c *PeerConn) maximumPeerRequestChunkLength() (_ Option[int]) {
491 uploadRateLimiter := c.t.cl.config.UploadRateLimiter
492 if uploadRateLimiter.Limit() == rate.Inf {
495 return Some(uploadRateLimiter.Burst())
498 // startFetch is for testing purposes currently.
499 func (c *PeerConn) onReadRequest(r Request, startFetch bool) error {
500 requestedChunkLengths.Add(strconv.FormatUint(r.Length.Uint64(), 10), 1)
501 if _, ok := c.peerRequests[r]; ok {
502 torrent.Add("duplicate requests received", 1)
504 return errors.New("received duplicate request with fast enabled")
509 torrent.Add("requests received while choking", 1)
511 torrent.Add("requests rejected while choking", 1)
516 // TODO: What if they've already requested this?
517 if len(c.peerRequests) >= localClientReqq {
518 torrent.Add("requests received while queue full", 1)
522 // BEP 6 says we may close here if we choose.
525 if opt := c.maximumPeerRequestChunkLength(); opt.Ok && int(r.Length) > opt.Value {
526 err := fmt.Errorf("peer requested chunk too long (%v)", r.Length)
527 c.logger.Levelf(log.Warning, err.Error())
535 if !c.t.havePiece(pieceIndex(r.Index)) {
536 // TODO: Tell the peer we don't have the piece, and reject this request.
537 requestsReceivedForMissingPieces.Add(1)
538 return fmt.Errorf("peer requested piece we don't have: %v", r.Index.Int())
540 pieceLength := c.t.pieceLength(pieceIndex(r.Index))
541 // Check this after we know we have the piece, so that the piece length will be known.
542 if chunkOverflowsPiece(r.ChunkSpec, pieceLength) {
543 torrent.Add("bad requests received", 1)
544 return errors.New("chunk overflows piece")
546 if c.peerRequests == nil {
547 c.peerRequests = make(map[Request]*peerRequestState, localClientReqq)
549 value := &peerRequestState{
550 allocReservation: c.peerRequestDataAllocLimiter.Reserve(int64(r.Length)),
552 c.peerRequests[r] = value
554 // TODO: Limit peer request data read concurrency.
555 go c.peerRequestDataReader(r, value)
560 func (c *PeerConn) peerRequestDataReader(r Request, prs *peerRequestState) {
561 b, err := c.readPeerRequestData(r, prs)
563 defer c.locker().Unlock()
565 c.peerRequestDataReadFailed(err, r)
568 panic("data must be non-nil to trigger send")
570 torrent.Add("peer request data read successes", 1)
572 // This might be required for the error case too (#752 and #753).
577 // If this is maintained correctly, we might be able to support optional synchronous reading for
578 // chunk sending, the way it used to work.
579 func (c *PeerConn) peerRequestDataReadFailed(err error, r Request) {
580 torrent.Add("peer request data read failures", 1)
581 logLevel := log.Warning
582 if c.t.hasStorageCap() {
583 // It's expected that pieces might drop. See
584 // https://github.com/anacrolix/torrent/issues/702#issuecomment-1000953313.
587 c.logger.WithDefaultLevel(logLevel).Printf("error reading chunk for peer Request %v: %v", r, err)
588 if c.t.closed.IsSet() {
591 i := pieceIndex(r.Index)
592 if c.t.pieceComplete(i) {
593 // There used to be more code here that just duplicated the following break. Piece
594 // completions are currently cached, so I'm not sure how helpful this update is, except to
595 // pull any completion changes pushed to the storage backend in failed reads that got us
597 c.t.updatePieceCompletion(i)
599 // We've probably dropped a piece from storage, but there's no way to communicate this to the
600 // peer. If they ask for it again, we kick them allowing us to send them updated piece states if
601 // we reconnect. TODO: Instead, we could just try to update them with Bitfield or HaveNone and
602 // if they kick us for breaking protocol, on reconnect we will be compliant again (at least
608 // If fast isn't enabled, I think we would have wiped all peer requests when we last
609 // choked, and requests while we're choking would be ignored. It could be possible that
610 // a peer request data read completed concurrently to it being deleted elsewhere.
611 c.logger.WithDefaultLevel(log.Warning).Printf("already choking peer, requests might not be rejected correctly")
613 // Choking a non-fast peer should cause them to flush all their requests.
618 func (c *PeerConn) readPeerRequestData(r Request, prs *peerRequestState) ([]byte, error) {
619 // Should we depend on Torrent closure here? I think it's okay to get cancelled from elsewhere,
620 // or fail to read and then cleanup.
621 ctx := context.Background()
622 err := prs.allocReservation.Wait(ctx)
624 if ctx.Err() == nil {
625 // The error is from the reservation itself. Something is very broken, or we're not
626 // guarding against excessively large requests.
627 err = log.WithLevel(log.Critical, err)
629 err = fmt.Errorf("waiting for alloc limit reservation: %w", err)
632 b := make([]byte, r.Length)
633 p := c.t.info.Piece(int(r.Index))
634 n, err := c.t.readAt(b, p.Offset()+int64(r.Begin))
641 panic("expected error")
647 func (c *PeerConn) logProtocolBehaviour(level log.Level, format string, arg ...interface{}) {
648 c.logger.WithContextText(fmt.Sprintf(
649 "peer id %q, ext v %q", c.PeerID, c.PeerClientName.Load(),
650 )).SkipCallers(1).Levelf(level, format, arg...)
653 // Processes incoming BitTorrent wire-protocol messages. The client lock is held upon entry and
654 // exit. Returning will end the connection.
655 func (c *PeerConn) mainReadLoop() (err error) {
658 torrent.Add("connection.mainReadLoop returned with error", 1)
660 torrent.Add("connection.mainReadLoop returned with no error", 1)
666 decoder := pp.Decoder{
667 R: bufio.NewReaderSize(c.r, 1<<17),
668 MaxLength: 4 * pp.Integer(max(int64(t.chunkSize), defaultChunkSize)),
676 err = decoder.Decode(&msg)
678 if cb := c.callbacks.ReadMessage; cb != nil && err == nil {
681 if t.closed.IsSet() || c.closed.IsSet() {
687 c.lastMessageReceived = time.Now()
689 receivedKeepalives.Add(1)
692 messageTypesReceived.Add(msg.Type.String(), 1)
693 if msg.Type.FastExtension() && !c.fastEnabled() {
694 runSafeExtraneous(func() { torrent.Add("fast messages received when extension is disabled", 1) })
695 return fmt.Errorf("received fast extension message (type=%v) but extension is disabled", msg.Type)
702 if !c.fastEnabled() {
703 c.deleteAllRequests("choked by non-fast PeerConn")
705 // We don't decrement pending requests here, let's wait for the peer to either
706 // reject or satisfy the outstanding requests. Additionally, some peers may unchoke
707 // us and resume where they left off, we don't want to have piled on to those chunks
708 // in the meanwhile. I think a peer's ability to abuse this should be limited: they
709 // could let us request a lot of stuff, then choke us and never reject, but they're
710 // only a single peer, our chunk balancing should smooth over this abuse.
713 c.updateExpectingChunks()
716 // Some clients do this for some reason. Transmission doesn't error on this, so we
717 // won't for consistency.
718 c.logProtocolBehaviour(log.Debug, "received unchoke when already unchoked")
721 c.peerChoking = false
723 c.requestState.Requests.Iterate(func(x RequestIndex) bool {
724 if !c.peerAllowedFast.Contains(c.t.pieceIndexOfRequestIndex(x)) {
729 if preservedCount != 0 {
730 // TODO: Yes this is a debug log but I'm not happy with the state of the logging lib
732 c.logger.Levelf(log.Debug,
733 "%v requests were preserved while being choked (fast=%v)",
737 torrent.Add("requestsPreservedThroughChoking", int64(preservedCount))
739 if !c.t._pendingPieces.IsEmpty() {
740 c.updateRequests("unchoked")
742 c.updateExpectingChunks()
744 c.peerInterested = true
746 case pp.NotInterested:
747 c.peerInterested = false
748 // We don't clear their requests since it isn't clear in the spec.
749 // We'll probably choke them for this, which will clear them if
750 // appropriate, and is clearly specified.
752 err = c.peerSentHave(pieceIndex(msg.Index))
754 err = c.peerSentBitfield(msg.Bitfield)
756 r := newRequestFromMessage(&msg)
757 err = c.onReadRequest(r, true)
759 err = fmt.Errorf("on reading request %v: %w", r, err)
762 c.doChunkReadStats(int64(len(msg.Piece)))
763 err = c.receiveChunk(&msg)
764 if len(msg.Piece) == int(t.chunkSize) {
765 t.chunkPool.Put(&msg.Piece)
768 err = fmt.Errorf("receiving chunk: %w", err)
771 req := newRequestFromMessage(&msg)
772 c.onPeerSentCancel(req)
774 ipa, ok := tryIpPortFromNetAddr(c.RemoteAddr)
778 pingAddr := net.UDPAddr{
783 pingAddr.Port = int(msg.Port)
785 cl.eachDhtServer(func(s DhtServer) {
789 torrent.Add("suggests received", 1)
790 log.Fmsg("peer suggested piece %d", msg.Index).AddValues(c, msg.Index).LogLevel(log.Debug, c.t.logger)
791 c.updateRequests("suggested")
793 err = c.onPeerSentHaveAll()
795 err = c.peerSentHaveNone()
797 req := newRequestFromMessage(&msg)
798 if !c.remoteRejectedRequest(c.t.requestIndexFromRequest(req)) {
799 c.logger.Printf("received invalid reject [request=%v, peer=%v]", req, c)
800 err = fmt.Errorf("received invalid reject [request=%v]", req)
803 torrent.Add("allowed fasts received", 1)
804 log.Fmsg("peer allowed fast: %d", msg.Index).AddValues(c).LogLevel(log.Debug, c.t.logger)
805 c.updateRequests("PeerConn.mainReadLoop allowed fast")
807 err = c.onReadExtendedMsg(msg.ExtendedID, msg.ExtendedPayload)
809 err = fmt.Errorf("received unknown message type: %#v", msg.Type)
817 func (c *PeerConn) onReadExtendedMsg(id pp.ExtensionNumber, payload []byte) (err error) {
819 // TODO: Should we still do this?
821 // These clients use their own extension IDs for outgoing message
822 // types, which is incorrect.
823 if bytes.HasPrefix(c.PeerID[:], []byte("-SD0100-")) || strings.HasPrefix(string(c.PeerID[:]), "-XL0012-") {
831 case pp.HandshakeExtendedID:
832 var d pp.ExtendedHandshakeMessage
833 if err := bencode.Unmarshal(payload, &d); err != nil {
834 c.logger.Printf("error parsing extended handshake message %q: %s", payload, err)
835 return fmt.Errorf("unmarshalling extended handshake payload: %w", err)
837 if cb := c.callbacks.ReadExtendedHandshake; cb != nil {
840 // c.logger.WithDefaultLevel(log.Debug).Printf("received extended handshake message:\n%s", spew.Sdump(d))
842 c.PeerMaxRequests = d.Reqq
844 c.PeerClientName.Store(d.V)
845 if c.PeerExtensionIDs == nil {
846 c.PeerExtensionIDs = make(map[pp.ExtensionName]pp.ExtensionNumber, len(d.M))
848 c.PeerListenPort = d.Port
849 c.PeerPrefersEncryption = d.Encryption
850 for name, id := range d.M {
851 if _, ok := c.PeerExtensionIDs[name]; !ok {
852 peersSupportingExtension.Add(
853 // expvar.Var.String must produce valid JSON. "ut_payme\xeet_address" was being
854 // entered here which caused problems later when unmarshalling.
855 strconv.Quote(string(name)),
858 c.PeerExtensionIDs[name] = id
860 if d.MetadataSize != 0 {
861 if err = t.setMetadataSize(d.MetadataSize); err != nil {
862 return fmt.Errorf("setting metadata size to %d: %w", d.MetadataSize, err)
865 c.requestPendingMetadata()
866 if !t.cl.config.DisablePEX {
867 t.pex.Add(c) // we learnt enough now
868 // This checks the extension is supported internally.
872 case metadataExtendedId:
873 err := cl.gotMetadataExtensionMsg(payload, t, c)
875 return fmt.Errorf("handling metadata extension message: %w", err)
879 if !c.pex.IsEnabled() {
880 return nil // or hang-up maybe?
882 err = c.pex.Recv(payload)
884 err = fmt.Errorf("receiving pex message: %w", err)
887 case utHolepunchExtendedId:
888 var msg utHolepunch.Msg
889 err = msg.UnmarshalBinary(payload)
891 err = fmt.Errorf("unmarshalling ut_holepunch message: %w", err)
895 return fmt.Errorf("unexpected extended message ID: %v", id)
899 // Set both the Reader and Writer for the connection from a single ReadWriter.
900 func (cn *PeerConn) setRW(rw io.ReadWriter) {
905 // Returns the Reader and Writer as a combined ReadWriter.
906 func (cn *PeerConn) rw() io.ReadWriter {
913 func (c *PeerConn) uploadAllowed() bool {
914 if c.t.cl.config.NoUpload {
917 if c.t.dataUploadDisallowed {
923 if !c.peerHasWantedPieces() {
926 // Don't upload more than 100 KiB more than we download.
927 if c._stats.BytesWrittenData.Int64() >= c._stats.BytesReadData.Int64()+100<<10 {
933 func (c *PeerConn) setRetryUploadTimer(delay time.Duration) {
934 if c.uploadTimer == nil {
935 c.uploadTimer = time.AfterFunc(delay, c.tickleWriter)
937 c.uploadTimer.Reset(delay)
941 // Also handles choking and unchoking of the remote peer.
942 func (c *PeerConn) upload(msg func(pp.Message) bool) bool {
943 // Breaking or completing this loop means we don't want to upload to the
944 // peer anymore, and we choke them.
946 for c.uploadAllowed() {
947 // We want to upload to the peer.
951 for r, state := range c.peerRequests {
952 if state.data == nil {
955 res := c.t.cl.config.UploadRateLimiter.ReserveN(time.Now(), int(r.Length))
957 panic(fmt.Sprintf("upload rate limiter burst size < %d", r.Length))
962 c.setRetryUploadTimer(delay)
963 // Hard to say what to return here.
966 more := c.sendChunk(r, msg, state)
967 delete(c.peerRequests, r)
978 func (cn *PeerConn) drop() {
979 cn.t.dropConnection(cn)
982 func (cn *PeerConn) ban() {
983 cn.t.cl.banPeerIP(cn.remoteIp())
986 // This is called when something has changed that should wake the writer, such as putting stuff into
987 // the writeBuffer, or changing some state that the writer can act on.
988 func (c *PeerConn) tickleWriter() {
989 c.messageWriter.writeCond.Broadcast()
992 func (c *PeerConn) sendChunk(r Request, msg func(pp.Message) bool, state *peerRequestState) (more bool) {
993 c.lastChunkSent = time.Now()
994 state.allocReservation.Release()
995 return msg(pp.Message{
1003 func (c *PeerConn) setTorrent(t *Torrent) {
1005 panic("connection already associated with a torrent")
1008 c.logger.WithDefaultLevel(log.Debug).Printf("set torrent=%v", t)
1009 t.reconcileHandshakeStats(c)
1012 func (c *PeerConn) pexPeerFlags() pp.PexPeerFlags {
1013 f := pp.PexPeerFlags(0)
1014 if c.PeerPrefersEncryption {
1015 f |= pp.PexPrefersEncryption
1018 f |= pp.PexOutgoingConn
1021 f |= pp.PexSupportsUtp
1026 // This returns the address to use if we want to dial the peer again. It incorporates the peer's
1027 // advertised listen port.
1028 func (c *PeerConn) dialAddr() PeerRemoteAddr {
1029 if !c.outgoing && c.PeerListenPort != 0 {
1030 switch addr := c.RemoteAddr.(type) {
1033 dialAddr.Port = c.PeerListenPort
1037 dialAddr.Port = c.PeerListenPort
1044 func (c *PeerConn) pexEvent(t pexEventType) pexEvent {
1045 f := c.pexPeerFlags()
1046 addr := c.dialAddr()
1047 return pexEvent{t, addr, f, nil}
1050 func (c *PeerConn) String() string {
1051 return fmt.Sprintf("%T %p [id=%q, exts=%v, v=%q]", c, c, c.PeerID, c.PeerExtensionBytes, c.PeerClientName.Load())
1054 // Returns the pieces the peer could have based on their claims. If we don't know how many pieces
1055 // are in the torrent, it could be a very large range the peer has sent HaveAll.
1056 func (cn *PeerConn) PeerPieces() *roaring.Bitmap {
1058 defer cn.locker().RUnlock()
1059 return cn.newPeerPieces()
1062 func (pc *PeerConn) remoteIsTransmission() bool {
1063 return bytes.HasPrefix(pc.PeerID[:], []byte("-TR")) && pc.PeerID[7] == '-'
1066 func (pc *PeerConn) remoteAddrPort() Option[netip.AddrPort] {
1067 return Some(pc.conn.RemoteAddr().(interface {
1068 AddrPort() netip.AddrPort