18 "github.com/RoaringBitmap/roaring"
19 "github.com/anacrolix/generics"
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/exp/maps"
25 "golang.org/x/time/rate"
27 "github.com/anacrolix/torrent/bencode"
28 "github.com/anacrolix/torrent/internal/alloclim"
29 "github.com/anacrolix/torrent/metainfo"
30 "github.com/anacrolix/torrent/mse"
31 pp "github.com/anacrolix/torrent/peer_protocol"
32 utHolepunch "github.com/anacrolix/torrent/peer_protocol/ut-holepunch"
35 // Maintains the state of a BitTorrent-protocol based connection with a peer.
36 type PeerConn struct {
39 // A string that should identify the PeerConn's net.Conn endpoints. The net.Conn could
40 // be wrapping WebRTC, uTP, or TCP etc. Used in writing the conn status for peers.
45 PeerExtensionBytes pp.PeerExtensionBits
48 // The actual Conn, used for closing, and setting socket options. Do not use methods on this
49 // while holding any mutexes.
51 // The Reader and Writer for this Conn, with hooks installed for stats,
52 // limiting, deadlines etc.
56 messageWriter peerConnMsgWriter
58 PeerExtensionIDs map[pp.ExtensionName]pp.ExtensionNumber
59 PeerClientName atomic.Value
60 uploadTimer *time.Timer
63 // The pieces the peer has claimed to have.
64 _peerPieces roaring.Bitmap
65 // The peer has everything. This can occur due to a special message, when
66 // we may not even know the number of pieces in the torrent yet.
69 peerRequestDataAllocLimiter alloclim.Limiter
71 outstandingHolepunchingRendezvous map[netip.AddrPort]struct{}
74 func (cn *PeerConn) pexStatus() string {
75 if !cn.bitExtensionEnabled(pp.ExtensionBitLtep) {
76 return "extended protocol disabled"
78 if cn.PeerExtensionIDs == nil {
79 return "pending extended handshake"
81 if !cn.supportsExtension(pp.ExtensionNamePex) {
86 "%v conns, %v unsent events",
87 len(cn.pex.remoteLiveConns),
91 // This alternative branch prints out the remote live conn addresses.
93 "%v conns, %v unsent events",
94 strings.Join(generics.SliceMap(
95 maps.Keys(cn.pex.remoteLiveConns),
96 func(from netip.AddrPort) string {
104 func (cn *PeerConn) peerImplStatusLines() []string {
107 fmt.Sprintf("peer id: %+q", cn.PeerID),
108 fmt.Sprintf("extensions: %v", cn.PeerExtensionBytes),
109 fmt.Sprintf("ltep extensions: %v", cn.PeerExtensionIDs),
110 fmt.Sprintf("pex: %s", cn.pexStatus()),
114 // Returns true if the connection is over IPv6.
115 func (cn *PeerConn) ipv6() bool {
120 return len(ip) == net.IPv6len
123 // Returns true the if the dialer/initiator has the higher client peer ID. See
124 // https://github.com/arvidn/libtorrent/blame/272828e1cc37b042dfbbafa539222d8533e99755/src/bt_peer_connection.cpp#L3536-L3557.
125 // As far as I can tell, Transmission just keeps the oldest connection.
126 func (cn *PeerConn) isPreferredDirection() bool {
127 // True if our client peer ID is higher than the remote's peer ID.
128 return bytes.Compare(cn.PeerID[:], cn.t.cl.peerID[:]) < 0 == cn.outgoing
131 // Returns whether the left connection should be preferred over the right one,
132 // considering only their networking properties. If ok is false, we can't
134 func (l *PeerConn) hasPreferredNetworkOver(r *PeerConn) bool {
135 var ml multiless.Computation
136 ml = ml.Bool(r.isPreferredDirection(), l.isPreferredDirection())
137 ml = ml.Bool(l.utp(), r.utp())
138 ml = ml.Bool(r.ipv6(), l.ipv6())
142 func (cn *PeerConn) peerHasAllPieces() (all, known bool) {
143 if cn.peerSentHaveAll {
146 if !cn.t.haveInfo() {
149 return cn._peerPieces.GetCardinality() == uint64(cn.t.numPieces()), true
152 func (cn *PeerConn) onGotInfo(info *metainfo.Info) {
153 cn.setNumPieces(info.NumPieces())
156 // Correct the PeerPieces slice length. Return false if the existing slice is invalid, such as by
157 // receiving badly sized BITFIELD, or invalid HAVE messages.
158 func (cn *PeerConn) setNumPieces(num pieceIndex) {
159 cn._peerPieces.RemoveRange(bitmap.BitRange(num), bitmap.ToEnd)
160 cn.peerPiecesChanged()
163 func (cn *PeerConn) peerPieces() *roaring.Bitmap {
164 return &cn._peerPieces
167 func (cn *PeerConn) connectionFlags() (ret string) {
169 ret += string([]byte{b})
171 if cn.cryptoMethod == mse.CryptoMethodRC4 {
173 } else if cn.headerEncrypted {
176 ret += string(cn.Discovery)
183 func (cn *PeerConn) utp() bool {
184 return parseNetworkString(cn.Network).Udp
187 func (cn *PeerConn) onClose() {
188 if cn.pex.IsEnabled() {
195 if cb := cn.callbacks.PeerConnClosed; cb != nil {
200 // Writes a message into the write buffer. Returns whether it's okay to keep writing. Writing is
201 // done asynchronously, so it may be that we're not able to honour backpressure from this method.
202 func (cn *PeerConn) write(msg pp.Message) bool {
203 torrent.Add(fmt.Sprintf("messages written of type %s", msg.Type.String()), 1)
204 // We don't need to track bytes here because the connection's Writer has that behaviour injected
205 // (although there's some delay between us buffering the message, and the connection writer
206 // flushing it out.).
207 notFull := cn.messageWriter.write(msg)
208 // Last I checked only Piece messages affect stats, and we don't write those.
214 func (cn *PeerConn) requestMetadataPiece(index int) {
215 eID := cn.PeerExtensionIDs[pp.ExtensionNameMetadata]
216 if eID == pp.ExtensionDeleteNumber {
219 if index < len(cn.metadataRequests) && cn.metadataRequests[index] {
222 cn.logger.WithDefaultLevel(log.Debug).Printf("requesting metadata piece %d", index)
223 cn.write(pp.MetadataExtensionRequestMsg(eID, index))
224 for index >= len(cn.metadataRequests) {
225 cn.metadataRequests = append(cn.metadataRequests, false)
227 cn.metadataRequests[index] = true
230 func (cn *PeerConn) requestedMetadataPiece(index int) bool {
231 return index < len(cn.metadataRequests) && cn.metadataRequests[index]
234 func (cn *PeerConn) onPeerSentCancel(r Request) {
235 if _, ok := cn.peerRequests[r]; !ok {
236 torrent.Add("unexpected cancels received", 1)
239 if cn.fastEnabled() {
242 delete(cn.peerRequests, r)
246 func (cn *PeerConn) choke(msg messageWriter) (more bool) {
251 more = msg(pp.Message{
254 if !cn.fastEnabled() {
255 cn.deleteAllPeerRequests()
260 func (cn *PeerConn) deleteAllPeerRequests() {
261 for _, state := range cn.peerRequests {
262 state.allocReservation.Drop()
264 cn.peerRequests = nil
267 func (cn *PeerConn) unchoke(msg func(pp.Message) bool) bool {
272 return msg(pp.Message{
277 func (pc *PeerConn) writeInterested(interested bool) bool {
278 return pc.write(pp.Message{
279 Type: func() pp.MessageType {
283 return pp.NotInterested
289 func (me *PeerConn) _request(r Request) bool {
290 return me.write(pp.Message{
298 func (me *PeerConn) _cancel(r RequestIndex) bool {
299 me.write(makeCancelMessage(me.t.requestIndexToRequest(r)))
300 // Transmission does not send rejects for received cancels. See
301 // https://github.com/transmission/transmission/pull/2275.
302 return me.fastEnabled() && !me.remoteIsTransmission()
305 func (cn *PeerConn) fillWriteBuffer() {
306 if cn.messageWriter.writeBuffer.Len() > writeBufferLowWaterLen {
307 // Fully committing to our max requests requires sufficient space (see
308 // maxLocalToRemoteRequests). Flush what we have instead. We also prefer always to make
309 // requests than to do PEX or upload, so we short-circuit before handling those. Any update
310 // request reason will not be cleared, so we'll come right back here when there's space. We
311 // can't do this in maybeUpdateActualRequestState because it's a method on Peer and has no
312 // knowledge of write buffers.
314 cn.maybeUpdateActualRequestState()
315 if cn.pex.IsEnabled() {
316 if flow := cn.pex.Share(cn.write); !flow {
323 func (cn *PeerConn) have(piece pieceIndex) {
324 if cn.sentHaves.Get(bitmap.BitIndex(piece)) {
329 Index: pp.Integer(piece),
331 cn.sentHaves.Add(bitmap.BitIndex(piece))
334 func (cn *PeerConn) postBitfield() {
335 if cn.sentHaves.Len() != 0 {
336 panic("bitfield must be first have-related message sent")
338 if !cn.t.haveAnyPieces() {
343 Bitfield: cn.t.bitfield(),
345 cn.sentHaves = bitmap.Bitmap{cn.t._completedPieces.Clone()}
348 func (cn *PeerConn) handleUpdateRequests() {
349 // The writer determines the request state as needed when it can write.
353 func (cn *PeerConn) raisePeerMinPieces(newMin pieceIndex) {
354 if newMin > cn.peerMinPieces {
355 cn.peerMinPieces = newMin
359 func (cn *PeerConn) peerSentHave(piece pieceIndex) error {
360 if cn.t.haveInfo() && piece >= cn.t.numPieces() || piece < 0 {
361 return errors.New("invalid piece")
363 if cn.peerHasPiece(piece) {
366 cn.raisePeerMinPieces(piece + 1)
367 if !cn.peerHasPiece(piece) {
368 cn.t.incPieceAvailability(piece)
370 cn._peerPieces.Add(uint32(piece))
371 if cn.t.wantPieceIndex(piece) {
372 cn.updateRequests("have")
374 cn.peerPiecesChanged()
378 func (cn *PeerConn) peerSentBitfield(bf []bool) error {
380 panic("expected bitfield length divisible by 8")
382 // We know that the last byte means that at most the last 7 bits are wasted.
383 cn.raisePeerMinPieces(pieceIndex(len(bf) - 7))
384 if cn.t.haveInfo() && len(bf) > int(cn.t.numPieces()) {
385 // Ignore known excess pieces.
386 bf = bf[:cn.t.numPieces()]
388 bm := boolSliceToBitmap(bf)
389 if cn.t.haveInfo() && pieceIndex(bm.GetCardinality()) == cn.t.numPieces() {
390 cn.onPeerHasAllPieces()
394 cn.raisePeerMinPieces(pieceIndex(bm.Maximum()) + 1)
396 shouldUpdateRequests := false
397 if cn.peerSentHaveAll {
398 if !cn.t.deleteConnWithAllPieces(&cn.Peer) {
401 cn.peerSentHaveAll = false
402 if !cn._peerPieces.IsEmpty() {
403 panic("if peer has all, we expect no individual peer pieces to be set")
406 bm.Xor(&cn._peerPieces)
408 cn.peerSentHaveAll = false
409 // bm is now 'on' for pieces that are changing
410 bm.Iterate(func(x uint32) bool {
412 if cn._peerPieces.Contains(x) {
413 // Then we must be losing this piece
414 cn.t.decPieceAvailability(pi)
416 if !shouldUpdateRequests && cn.t.wantPieceIndex(pieceIndex(x)) {
417 shouldUpdateRequests = true
419 // We must be gaining this piece
420 cn.t.incPieceAvailability(pieceIndex(x))
424 // Apply the changes. If we had everything previously, this should be empty, so xor is the same
426 cn._peerPieces.Xor(&bm)
427 if shouldUpdateRequests {
428 cn.updateRequests("bitfield")
430 // We didn't guard this before, I see no reason to do it now.
431 cn.peerPiecesChanged()
435 func (cn *PeerConn) onPeerHasAllPieces() {
438 cn._peerPieces.Iterate(func(x uint32) bool {
439 t.decPieceAvailability(pieceIndex(x))
443 t.addConnWithAllPieces(&cn.Peer)
444 cn.peerSentHaveAll = true
445 cn._peerPieces.Clear()
446 if !cn.t._pendingPieces.IsEmpty() {
447 cn.updateRequests("Peer.onPeerHasAllPieces")
449 cn.peerPiecesChanged()
452 func (cn *PeerConn) onPeerSentHaveAll() error {
453 cn.onPeerHasAllPieces()
457 func (cn *PeerConn) peerSentHaveNone() error {
458 if !cn.peerSentHaveAll {
459 cn.t.decPeerPieceAvailability(&cn.Peer)
461 cn._peerPieces.Clear()
462 cn.peerSentHaveAll = false
463 cn.peerPiecesChanged()
467 func (c *PeerConn) requestPendingMetadata() {
471 if c.PeerExtensionIDs[pp.ExtensionNameMetadata] == 0 {
472 // Peer doesn't support this.
475 // Request metadata pieces that we don't have in a random order.
477 for index := 0; index < c.t.metadataPieceCount(); index++ {
478 if !c.t.haveMetadataPiece(index) && !c.requestedMetadataPiece(index) {
479 pending = append(pending, index)
482 rand.Shuffle(len(pending), func(i, j int) { pending[i], pending[j] = pending[j], pending[i] })
483 for _, i := range pending {
484 c.requestMetadataPiece(i)
488 func (cn *PeerConn) wroteMsg(msg *pp.Message) {
489 torrent.Add(fmt.Sprintf("messages written of type %s", msg.Type.String()), 1)
490 if msg.Type == pp.Extended {
491 for name, id := range cn.PeerExtensionIDs {
492 if id != msg.ExtendedID {
495 torrent.Add(fmt.Sprintf("Extended messages written for protocol %q", name), 1)
498 cn.allStats(func(cs *ConnStats) { cs.wroteMsg(msg) })
501 func (cn *PeerConn) wroteBytes(n int64) {
502 cn.allStats(add(n, func(cs *ConnStats) *Count { return &cs.BytesWritten }))
505 func (c *PeerConn) fastEnabled() bool {
506 return c.PeerExtensionBytes.SupportsFast() && c.t.cl.config.Extensions.SupportsFast()
509 func (c *PeerConn) reject(r Request) {
510 if !c.fastEnabled() {
511 panic("fast not enabled")
513 c.write(r.ToMsg(pp.Reject))
514 // It is possible to reject a request before it is added to peer requests due to being invalid.
515 if state, ok := c.peerRequests[r]; ok {
516 state.allocReservation.Drop()
517 delete(c.peerRequests, r)
521 func (c *PeerConn) maximumPeerRequestChunkLength() (_ Option[int]) {
522 uploadRateLimiter := c.t.cl.config.UploadRateLimiter
523 if uploadRateLimiter.Limit() == rate.Inf {
526 return Some(uploadRateLimiter.Burst())
529 // startFetch is for testing purposes currently.
530 func (c *PeerConn) onReadRequest(r Request, startFetch bool) error {
531 requestedChunkLengths.Add(strconv.FormatUint(r.Length.Uint64(), 10), 1)
532 if _, ok := c.peerRequests[r]; ok {
533 torrent.Add("duplicate requests received", 1)
535 return errors.New("received duplicate request with fast enabled")
540 torrent.Add("requests received while choking", 1)
542 torrent.Add("requests rejected while choking", 1)
547 // TODO: What if they've already requested this?
548 if len(c.peerRequests) >= localClientReqq {
549 torrent.Add("requests received while queue full", 1)
553 // BEP 6 says we may close here if we choose.
556 if opt := c.maximumPeerRequestChunkLength(); opt.Ok && int(r.Length) > opt.Value {
557 err := fmt.Errorf("peer requested chunk too long (%v)", r.Length)
558 c.logger.Levelf(log.Warning, err.Error())
566 if !c.t.havePiece(pieceIndex(r.Index)) {
567 // TODO: Tell the peer we don't have the piece, and reject this request.
568 requestsReceivedForMissingPieces.Add(1)
569 return fmt.Errorf("peer requested piece we don't have: %v", r.Index.Int())
571 pieceLength := c.t.pieceLength(pieceIndex(r.Index))
572 // Check this after we know we have the piece, so that the piece length will be known.
573 if chunkOverflowsPiece(r.ChunkSpec, pieceLength) {
574 torrent.Add("bad requests received", 1)
575 return errors.New("chunk overflows piece")
577 if c.peerRequests == nil {
578 c.peerRequests = make(map[Request]*peerRequestState, localClientReqq)
580 value := &peerRequestState{
581 allocReservation: c.peerRequestDataAllocLimiter.Reserve(int64(r.Length)),
583 c.peerRequests[r] = value
585 // TODO: Limit peer request data read concurrency.
586 go c.peerRequestDataReader(r, value)
591 func (c *PeerConn) peerRequestDataReader(r Request, prs *peerRequestState) {
592 // Should we depend on Torrent closure here? I think it's okay to get cancelled from elsewhere,
593 // or fail to read and then cleanup. Also, we used to hang here if the reservation was never
594 // dropped, that was fixed.
595 ctx := context.Background()
596 err := prs.allocReservation.Wait(ctx)
598 c.logger.WithDefaultLevel(log.Debug).Levelf(log.ErrorLevel(err), "waiting for alloc limit reservation: %v", err)
601 b, err := c.readPeerRequestData(r)
603 defer c.locker().Unlock()
605 c.peerRequestDataReadFailed(err, r)
608 panic("data must be non-nil to trigger send")
610 torrent.Add("peer request data read successes", 1)
612 // This might be required for the error case too (#752 and #753).
617 // If this is maintained correctly, we might be able to support optional synchronous reading for
618 // chunk sending, the way it used to work.
619 func (c *PeerConn) peerRequestDataReadFailed(err error, r Request) {
620 torrent.Add("peer request data read failures", 1)
621 logLevel := log.Warning
622 if c.t.hasStorageCap() {
623 // It's expected that pieces might drop. See
624 // https://github.com/anacrolix/torrent/issues/702#issuecomment-1000953313.
627 c.logger.Levelf(logLevel, "error reading chunk for peer Request %v: %v", r, err)
628 if c.t.closed.IsSet() {
631 i := pieceIndex(r.Index)
632 if c.t.pieceComplete(i) {
633 // There used to be more code here that just duplicated the following break. Piece
634 // completions are currently cached, so I'm not sure how helpful this update is, except to
635 // pull any completion changes pushed to the storage backend in failed reads that got us
637 c.t.updatePieceCompletion(i)
639 // We've probably dropped a piece from storage, but there's no way to communicate this to the
640 // peer. If they ask for it again, we kick them allowing us to send them updated piece states if
641 // we reconnect. TODO: Instead, we could just try to update them with Bitfield or HaveNone and
642 // if they kick us for breaking protocol, on reconnect we will be compliant again (at least
648 // If fast isn't enabled, I think we would have wiped all peer requests when we last
649 // choked, and requests while we're choking would be ignored. It could be possible that
650 // a peer request data read completed concurrently to it being deleted elsewhere.
651 c.logger.WithDefaultLevel(log.Warning).Printf("already choking peer, requests might not be rejected correctly")
653 // Choking a non-fast peer should cause them to flush all their requests.
658 func (c *PeerConn) readPeerRequestData(r Request) ([]byte, error) {
659 b := make([]byte, r.Length)
660 p := c.t.info.Piece(int(r.Index))
661 n, err := c.t.readAt(b, p.Offset()+int64(r.Begin))
668 panic("expected error")
674 func (c *PeerConn) logProtocolBehaviour(level log.Level, format string, arg ...interface{}) {
675 c.logger.WithContextText(fmt.Sprintf(
676 "peer id %q, ext v %q", c.PeerID, c.PeerClientName.Load(),
677 )).SkipCallers(1).Levelf(level, format, arg...)
680 // Processes incoming BitTorrent wire-protocol messages. The client lock is held upon entry and
681 // exit. Returning will end the connection.
682 func (c *PeerConn) mainReadLoop() (err error) {
685 torrent.Add("connection.mainReadLoop returned with error", 1)
687 torrent.Add("connection.mainReadLoop returned with no error", 1)
693 decoder := pp.Decoder{
694 R: bufio.NewReaderSize(c.r, 1<<17),
695 MaxLength: 4 * pp.Integer(max(int64(t.chunkSize), defaultChunkSize)),
703 err = decoder.Decode(&msg)
705 if cb := c.callbacks.ReadMessage; cb != nil && err == nil {
708 if t.closed.IsSet() || c.closed.IsSet() {
714 c.lastMessageReceived = time.Now()
716 receivedKeepalives.Add(1)
719 messageTypesReceived.Add(msg.Type.String(), 1)
720 if msg.Type.FastExtension() && !c.fastEnabled() {
721 runSafeExtraneous(func() { torrent.Add("fast messages received when extension is disabled", 1) })
722 return fmt.Errorf("received fast extension message (type=%v) but extension is disabled", msg.Type)
729 if !c.fastEnabled() {
730 c.deleteAllRequests("choked by non-fast PeerConn")
732 // We don't decrement pending requests here, let's wait for the peer to either
733 // reject or satisfy the outstanding requests. Additionally, some peers may unchoke
734 // us and resume where they left off, we don't want to have piled on to those chunks
735 // in the meanwhile. I think a peer's ability to abuse this should be limited: they
736 // could let us request a lot of stuff, then choke us and never reject, but they're
737 // only a single peer, our chunk balancing should smooth over this abuse.
740 c.updateExpectingChunks()
743 // Some clients do this for some reason. Transmission doesn't error on this, so we
744 // won't for consistency.
745 c.logProtocolBehaviour(log.Debug, "received unchoke when already unchoked")
748 c.peerChoking = false
750 c.requestState.Requests.Iterate(func(x RequestIndex) bool {
751 if !c.peerAllowedFast.Contains(c.t.pieceIndexOfRequestIndex(x)) {
756 if preservedCount != 0 {
757 // TODO: Yes this is a debug log but I'm not happy with the state of the logging lib
759 c.logger.Levelf(log.Debug,
760 "%v requests were preserved while being choked (fast=%v)",
764 torrent.Add("requestsPreservedThroughChoking", int64(preservedCount))
766 if !c.t._pendingPieces.IsEmpty() {
767 c.updateRequests("unchoked")
769 c.updateExpectingChunks()
771 c.peerInterested = true
773 case pp.NotInterested:
774 c.peerInterested = false
775 // We don't clear their requests since it isn't clear in the spec.
776 // We'll probably choke them for this, which will clear them if
777 // appropriate, and is clearly specified.
779 err = c.peerSentHave(pieceIndex(msg.Index))
781 err = c.peerSentBitfield(msg.Bitfield)
783 r := newRequestFromMessage(&msg)
784 err = c.onReadRequest(r, true)
786 err = fmt.Errorf("on reading request %v: %w", r, err)
789 c.doChunkReadStats(int64(len(msg.Piece)))
790 err = c.receiveChunk(&msg)
791 if len(msg.Piece) == int(t.chunkSize) {
792 t.chunkPool.Put(&msg.Piece)
795 err = fmt.Errorf("receiving chunk: %w", err)
798 req := newRequestFromMessage(&msg)
799 c.onPeerSentCancel(req)
801 ipa, ok := tryIpPortFromNetAddr(c.RemoteAddr)
805 pingAddr := net.UDPAddr{
810 pingAddr.Port = int(msg.Port)
812 cl.eachDhtServer(func(s DhtServer) {
816 torrent.Add("suggests received", 1)
817 log.Fmsg("peer suggested piece %d", msg.Index).AddValues(c, msg.Index).LogLevel(log.Debug, c.t.logger)
818 c.updateRequests("suggested")
820 err = c.onPeerSentHaveAll()
822 err = c.peerSentHaveNone()
824 req := newRequestFromMessage(&msg)
825 if !c.remoteRejectedRequest(c.t.requestIndexFromRequest(req)) {
826 c.logger.Printf("received invalid reject [request=%v, peer=%v]", req, c)
827 err = fmt.Errorf("received invalid reject [request=%v]", req)
830 torrent.Add("allowed fasts received", 1)
831 log.Fmsg("peer allowed fast: %d", msg.Index).AddValues(c).LogLevel(log.Debug, c.t.logger)
832 c.updateRequests("PeerConn.mainReadLoop allowed fast")
834 err = c.onReadExtendedMsg(msg.ExtendedID, msg.ExtendedPayload)
836 err = fmt.Errorf("received unknown message type: %#v", msg.Type)
844 func (c *PeerConn) onReadExtendedMsg(id pp.ExtensionNumber, payload []byte) (err error) {
846 // TODO: Should we still do this?
848 // These clients use their own extension IDs for outgoing message
849 // types, which is incorrect.
850 if bytes.HasPrefix(c.PeerID[:], []byte("-SD0100-")) || strings.HasPrefix(string(c.PeerID[:]), "-XL0012-") {
858 case pp.HandshakeExtendedID:
859 var d pp.ExtendedHandshakeMessage
860 if err := bencode.Unmarshal(payload, &d); err != nil {
861 c.logger.Printf("error parsing extended handshake message %q: %s", payload, err)
862 return fmt.Errorf("unmarshalling extended handshake payload: %w", err)
864 if cb := c.callbacks.ReadExtendedHandshake; cb != nil {
867 // c.logger.WithDefaultLevel(log.Debug).Printf("received extended handshake message:\n%s", spew.Sdump(d))
869 c.PeerMaxRequests = d.Reqq
871 c.PeerClientName.Store(d.V)
872 if c.PeerExtensionIDs == nil {
873 c.PeerExtensionIDs = make(map[pp.ExtensionName]pp.ExtensionNumber, len(d.M))
875 c.PeerListenPort = d.Port
876 c.PeerPrefersEncryption = d.Encryption
877 for name, id := range d.M {
878 if _, ok := c.PeerExtensionIDs[name]; !ok {
879 peersSupportingExtension.Add(
880 // expvar.Var.String must produce valid JSON. "ut_payme\xeet_address" was being
881 // entered here which caused problems later when unmarshalling.
882 strconv.Quote(string(name)),
885 c.PeerExtensionIDs[name] = id
887 if d.MetadataSize != 0 {
888 if err = t.setMetadataSize(d.MetadataSize); err != nil {
889 return fmt.Errorf("setting metadata size to %d: %w", d.MetadataSize, err)
892 c.requestPendingMetadata()
893 if !t.cl.config.DisablePEX {
894 t.pex.Add(c) // we learnt enough now
895 // This checks the extension is supported internally.
899 case metadataExtendedId:
900 err := cl.gotMetadataExtensionMsg(payload, t, c)
902 return fmt.Errorf("handling metadata extension message: %w", err)
906 if !c.pex.IsEnabled() {
907 return nil // or hang-up maybe?
909 err = c.pex.Recv(payload)
911 err = fmt.Errorf("receiving pex message: %w", err)
914 case utHolepunchExtendedId:
915 var msg utHolepunch.Msg
916 err = msg.UnmarshalBinary(payload)
918 err = fmt.Errorf("unmarshalling ut_holepunch message: %w", err)
921 err = c.t.handleReceivedUtHolepunchMsg(msg, c)
924 return fmt.Errorf("unexpected extended message ID: %v", id)
928 // Set both the Reader and Writer for the connection from a single ReadWriter.
929 func (cn *PeerConn) setRW(rw io.ReadWriter) {
934 // Returns the Reader and Writer as a combined ReadWriter.
935 func (cn *PeerConn) rw() io.ReadWriter {
942 func (c *PeerConn) uploadAllowed() bool {
943 if c.t.cl.config.NoUpload {
946 if c.t.dataUploadDisallowed {
952 if !c.peerHasWantedPieces() {
955 // Don't upload more than 100 KiB more than we download.
956 if c._stats.BytesWrittenData.Int64() >= c._stats.BytesReadData.Int64()+100<<10 {
962 func (c *PeerConn) setRetryUploadTimer(delay time.Duration) {
963 if c.uploadTimer == nil {
964 c.uploadTimer = time.AfterFunc(delay, c.tickleWriter)
966 c.uploadTimer.Reset(delay)
970 // Also handles choking and unchoking of the remote peer.
971 func (c *PeerConn) upload(msg func(pp.Message) bool) bool {
972 // Breaking or completing this loop means we don't want to upload to the
973 // peer anymore, and we choke them.
975 for c.uploadAllowed() {
976 // We want to upload to the peer.
980 for r, state := range c.peerRequests {
981 if state.data == nil {
984 res := c.t.cl.config.UploadRateLimiter.ReserveN(time.Now(), int(r.Length))
986 panic(fmt.Sprintf("upload rate limiter burst size < %d", r.Length))
991 c.setRetryUploadTimer(delay)
992 // Hard to say what to return here.
995 more := c.sendChunk(r, msg, state)
996 delete(c.peerRequests, r)
1007 func (cn *PeerConn) drop() {
1008 cn.t.dropConnection(cn)
1011 func (cn *PeerConn) ban() {
1012 cn.t.cl.banPeerIP(cn.remoteIp())
1015 // This is called when something has changed that should wake the writer, such as putting stuff into
1016 // the writeBuffer, or changing some state that the writer can act on.
1017 func (c *PeerConn) tickleWriter() {
1018 c.messageWriter.writeCond.Broadcast()
1021 func (c *PeerConn) sendChunk(r Request, msg func(pp.Message) bool, state *peerRequestState) (more bool) {
1022 c.lastChunkSent = time.Now()
1023 state.allocReservation.Release()
1024 return msg(pp.Message{
1032 func (c *PeerConn) setTorrent(t *Torrent) {
1034 panic("connection already associated with a torrent")
1037 c.logger.WithDefaultLevel(log.Debug).Printf("set torrent=%v", t)
1038 t.reconcileHandshakeStats(c)
1041 func (c *PeerConn) pexPeerFlags() pp.PexPeerFlags {
1042 f := pp.PexPeerFlags(0)
1043 if c.PeerPrefersEncryption {
1044 f |= pp.PexPrefersEncryption
1047 f |= pp.PexOutgoingConn
1050 f |= pp.PexSupportsUtp
1055 // This returns the address to use if we want to dial the peer again. It incorporates the peer's
1056 // advertised listen port.
1057 func (c *PeerConn) dialAddr() PeerRemoteAddr {
1058 if c.outgoing || c.PeerListenPort == 0 {
1061 addrPort, err := addrPortFromPeerRemoteAddr(c.RemoteAddr)
1065 "error parsing %q for alternate dial port: %v",
1071 return netip.AddrPortFrom(addrPort.Addr(), uint16(c.PeerListenPort))
1074 func (c *PeerConn) pexEvent(t pexEventType) (_ pexEvent, err error) {
1075 f := c.pexPeerFlags()
1076 dialAddr := c.dialAddr()
1077 addr, err := addrPortFromPeerRemoteAddr(dialAddr)
1078 if err != nil || !addr.IsValid() {
1079 err = fmt.Errorf("parsing dial addr %q: %w", dialAddr, err)
1082 return pexEvent{t, addr, f, nil}, nil
1085 func (c *PeerConn) String() string {
1086 return fmt.Sprintf("%T %p [id=%+q, exts=%v, v=%q]", c, c, c.PeerID, c.PeerExtensionBytes, c.PeerClientName.Load())
1089 // Returns the pieces the peer could have based on their claims. If we don't know how many pieces
1090 // are in the torrent, it could be a very large range the peer has sent HaveAll.
1091 func (cn *PeerConn) PeerPieces() *roaring.Bitmap {
1093 defer cn.locker().RUnlock()
1094 return cn.newPeerPieces()
1097 func (pc *PeerConn) remoteIsTransmission() bool {
1098 return bytes.HasPrefix(pc.PeerID[:], []byte("-TR")) && pc.PeerID[7] == '-'
1101 func (pc *PeerConn) remoteDialAddrPort() (netip.AddrPort, error) {
1102 dialAddr := pc.dialAddr()
1103 return addrPortFromPeerRemoteAddr(dialAddr)
1106 func (pc *PeerConn) bitExtensionEnabled(bit pp.ExtensionBit) bool {
1107 return pc.t.cl.config.Extensions.GetBit(bit) && pc.PeerExtensionBytes.GetBit(bit)
1110 func (cn *PeerConn) peerPiecesChanged() {
1111 cn.t.maybeDropMutuallyCompletePeer(cn)
1114 // Returns whether the connection could be useful to us. We're seeding and
1115 // they want data, we don't have metainfo and they can provide it, etc.
1116 func (c *PeerConn) useful() bool {
1118 if c.closed.IsSet() {
1122 return c.supportsExtension("ut_metadata")
1124 if t.seeding() && c.peerInterested {
1127 if c.peerHasWantedPieces() {