package torrent import ( "bufio" "bytes" "context" "errors" "fmt" "io" "math/rand" "net" "strconv" "strings" "time" "github.com/RoaringBitmap/roaring" . "github.com/anacrolix/generics" "github.com/anacrolix/log" "github.com/anacrolix/missinggo/v2/bitmap" "github.com/anacrolix/multiless" "golang.org/x/time/rate" "github.com/anacrolix/torrent/bencode" "github.com/anacrolix/torrent/internal/alloclim" "github.com/anacrolix/torrent/metainfo" "github.com/anacrolix/torrent/mse" pp "github.com/anacrolix/torrent/peer_protocol" ) // Maintains the state of a BitTorrent-protocol based connection with a peer. type PeerConn struct { Peer // A string that should identify the PeerConn's net.Conn endpoints. The net.Conn could // be wrapping WebRTC, uTP, or TCP etc. Used in writing the conn status for peers. connString string // See BEP 3 etc. PeerID PeerID PeerExtensionBytes pp.PeerExtensionBits // The actual Conn, used for closing, and setting socket options. Do not use methods on this // while holding any mutexes. conn net.Conn // The Reader and Writer for this Conn, with hooks installed for stats, // limiting, deadlines etc. w io.Writer r io.Reader messageWriter peerConnMsgWriter uploadTimer *time.Timer pex pexConnState // The pieces the peer has claimed to have. _peerPieces roaring.Bitmap // The peer has everything. This can occur due to a special message, when // we may not even know the number of pieces in the torrent yet. peerSentHaveAll bool peerRequestDataAllocLimiter alloclim.Limiter } func (cn *PeerConn) peerImplStatusLines() []string { return []string{fmt.Sprintf("%+-55q %s %s", cn.PeerID, cn.PeerExtensionBytes, cn.connString)} } // Returns true if the connection is over IPv6. func (cn *PeerConn) ipv6() bool { ip := cn.remoteIp() if ip.To4() != nil { return false } return len(ip) == net.IPv6len } // Returns true the if the dialer/initiator has the lower client peer ID. TODO: Find the // specification for this. func (cn *PeerConn) isPreferredDirection() bool { return bytes.Compare(cn.t.cl.peerID[:], cn.PeerID[:]) < 0 == cn.outgoing } // Returns whether the left connection should be preferred over the right one, // considering only their networking properties. If ok is false, we can't // decide. func (l *PeerConn) hasPreferredNetworkOver(r *PeerConn) bool { var ml multiless.Computation ml = ml.Bool(r.isPreferredDirection(), l.isPreferredDirection()) ml = ml.Bool(l.utp(), r.utp()) ml = ml.Bool(r.ipv6(), l.ipv6()) return ml.Less() } func (cn *PeerConn) peerHasAllPieces() (all, known bool) { if cn.peerSentHaveAll { return true, true } if !cn.t.haveInfo() { return false, false } return cn._peerPieces.GetCardinality() == uint64(cn.t.numPieces()), true } func (cn *PeerConn) onGotInfo(info *metainfo.Info) { cn.setNumPieces(info.NumPieces()) } // Correct the PeerPieces slice length. Return false if the existing slice is invalid, such as by // receiving badly sized BITFIELD, or invalid HAVE messages. func (cn *PeerConn) setNumPieces(num pieceIndex) { cn._peerPieces.RemoveRange(bitmap.BitRange(num), bitmap.ToEnd) cn.peerPiecesChanged() } func (cn *PeerConn) peerPieces() *roaring.Bitmap { return &cn._peerPieces } func (cn *PeerConn) connectionFlags() (ret string) { c := func(b byte) { ret += string([]byte{b}) } if cn.cryptoMethod == mse.CryptoMethodRC4 { c('E') } else if cn.headerEncrypted { c('e') } ret += string(cn.Discovery) if cn.utp() { c('U') } return } func (cn *PeerConn) utp() bool { return parseNetworkString(cn.Network).Udp } func (cn *PeerConn) onClose() { if cn.pex.IsEnabled() { cn.pex.Close() } cn.tickleWriter() if cn.conn != nil { go cn.conn.Close() } if cb := cn.callbacks.PeerConnClosed; cb != nil { cb(cn) } } // Writes a message into the write buffer. Returns whether it's okay to keep writing. Writing is // done asynchronously, so it may be that we're not able to honour backpressure from this method. func (cn *PeerConn) write(msg pp.Message) bool { torrent.Add(fmt.Sprintf("messages written of type %s", msg.Type.String()), 1) // We don't need to track bytes here because the connection's Writer has that behaviour injected // (although there's some delay between us buffering the message, and the connection writer // flushing it out.). notFull := cn.messageWriter.write(msg) // Last I checked only Piece messages affect stats, and we don't write those. cn.wroteMsg(&msg) cn.tickleWriter() return notFull } func (cn *PeerConn) requestMetadataPiece(index int) { eID := cn.PeerExtensionIDs[pp.ExtensionNameMetadata] if eID == pp.ExtensionDeleteNumber { return } if index < len(cn.metadataRequests) && cn.metadataRequests[index] { return } cn.logger.WithDefaultLevel(log.Debug).Printf("requesting metadata piece %d", index) cn.write(pp.MetadataExtensionRequestMsg(eID, index)) for index >= len(cn.metadataRequests) { cn.metadataRequests = append(cn.metadataRequests, false) } cn.metadataRequests[index] = true } func (cn *PeerConn) requestedMetadataPiece(index int) bool { return index < len(cn.metadataRequests) && cn.metadataRequests[index] } func (cn *PeerConn) onPeerSentCancel(r Request) { if _, ok := cn.peerRequests[r]; !ok { torrent.Add("unexpected cancels received", 1) return } if cn.fastEnabled() { cn.reject(r) } else { delete(cn.peerRequests, r) } } func (cn *PeerConn) choke(msg messageWriter) (more bool) { if cn.choking { return true } cn.choking = true more = msg(pp.Message{ Type: pp.Choke, }) if !cn.fastEnabled() { cn.deleteAllPeerRequests() } return } func (cn *PeerConn) deleteAllPeerRequests() { for _, state := range cn.peerRequests { state.allocReservation.Drop() } cn.peerRequests = nil } func (cn *PeerConn) unchoke(msg func(pp.Message) bool) bool { if !cn.choking { return true } cn.choking = false return msg(pp.Message{ Type: pp.Unchoke, }) } func (pc *PeerConn) writeInterested(interested bool) bool { return pc.write(pp.Message{ Type: func() pp.MessageType { if interested { return pp.Interested } else { return pp.NotInterested } }(), }) } func (me *PeerConn) _request(r Request) bool { return me.write(pp.Message{ Type: pp.Request, Index: r.Index, Begin: r.Begin, Length: r.Length, }) } func (me *PeerConn) _cancel(r RequestIndex) bool { me.write(makeCancelMessage(me.t.requestIndexToRequest(r))) // Transmission does not send rejects for received cancels. See // https://github.com/transmission/transmission/pull/2275. return me.fastEnabled() && !me.remoteIsTransmission() } func (cn *PeerConn) fillWriteBuffer() { if cn.messageWriter.writeBuffer.Len() > writeBufferLowWaterLen { // Fully committing to our max requests requires sufficient space (see // maxLocalToRemoteRequests). Flush what we have instead. We also prefer always to make // requests than to do PEX or upload, so we short-circuit before handling those. Any update // request reason will not be cleared, so we'll come right back here when there's space. We // can't do this in maybeUpdateActualRequestState because it's a method on Peer and has no // knowledge of write buffers. } cn.maybeUpdateActualRequestState() if cn.pex.IsEnabled() { if flow := cn.pex.Share(cn.write); !flow { return } } cn.upload(cn.write) } func (cn *PeerConn) have(piece pieceIndex) { if cn.sentHaves.Get(bitmap.BitIndex(piece)) { return } cn.write(pp.Message{ Type: pp.Have, Index: pp.Integer(piece), }) cn.sentHaves.Add(bitmap.BitIndex(piece)) } func (cn *PeerConn) postBitfield() { if cn.sentHaves.Len() != 0 { panic("bitfield must be first have-related message sent") } if !cn.t.haveAnyPieces() { return } cn.write(pp.Message{ Type: pp.Bitfield, Bitfield: cn.t.bitfield(), }) cn.sentHaves = bitmap.Bitmap{cn.t._completedPieces.Clone()} } func (cn *PeerConn) handleUpdateRequests() { // The writer determines the request state as needed when it can write. cn.tickleWriter() } func (cn *PeerConn) raisePeerMinPieces(newMin pieceIndex) { if newMin > cn.peerMinPieces { cn.peerMinPieces = newMin } } func (cn *PeerConn) peerSentHave(piece pieceIndex) error { if cn.t.haveInfo() && piece >= cn.t.numPieces() || piece < 0 { return errors.New("invalid piece") } if cn.peerHasPiece(piece) { return nil } cn.raisePeerMinPieces(piece + 1) if !cn.peerHasPiece(piece) { cn.t.incPieceAvailability(piece) } cn._peerPieces.Add(uint32(piece)) if cn.t.wantPieceIndex(piece) { cn.updateRequests("have") } cn.peerPiecesChanged() return nil } func (cn *PeerConn) peerSentBitfield(bf []bool) error { if len(bf)%8 != 0 { panic("expected bitfield length divisible by 8") } // We know that the last byte means that at most the last 7 bits are wasted. cn.raisePeerMinPieces(pieceIndex(len(bf) - 7)) if cn.t.haveInfo() && len(bf) > int(cn.t.numPieces()) { // Ignore known excess pieces. bf = bf[:cn.t.numPieces()] } bm := boolSliceToBitmap(bf) if cn.t.haveInfo() && pieceIndex(bm.GetCardinality()) == cn.t.numPieces() { cn.onPeerHasAllPieces() return nil } if !bm.IsEmpty() { cn.raisePeerMinPieces(pieceIndex(bm.Maximum()) + 1) } shouldUpdateRequests := false if cn.peerSentHaveAll { if !cn.t.deleteConnWithAllPieces(&cn.Peer) { panic(cn) } cn.peerSentHaveAll = false if !cn._peerPieces.IsEmpty() { panic("if peer has all, we expect no individual peer pieces to be set") } } else { bm.Xor(&cn._peerPieces) } cn.peerSentHaveAll = false // bm is now 'on' for pieces that are changing bm.Iterate(func(x uint32) bool { pi := pieceIndex(x) if cn._peerPieces.Contains(x) { // Then we must be losing this piece cn.t.decPieceAvailability(pi) } else { if !shouldUpdateRequests && cn.t.wantPieceIndex(pieceIndex(x)) { shouldUpdateRequests = true } // We must be gaining this piece cn.t.incPieceAvailability(pieceIndex(x)) } return true }) // Apply the changes. If we had everything previously, this should be empty, so xor is the same // as or. cn._peerPieces.Xor(&bm) if shouldUpdateRequests { cn.updateRequests("bitfield") } // We didn't guard this before, I see no reason to do it now. cn.peerPiecesChanged() return nil } func (cn *PeerConn) onPeerHasAllPieces() { t := cn.t if t.haveInfo() { cn._peerPieces.Iterate(func(x uint32) bool { t.decPieceAvailability(pieceIndex(x)) return true }) } t.addConnWithAllPieces(&cn.Peer) cn.peerSentHaveAll = true cn._peerPieces.Clear() if !cn.t._pendingPieces.IsEmpty() { cn.updateRequests("Peer.onPeerHasAllPieces") } cn.peerPiecesChanged() } func (cn *PeerConn) onPeerSentHaveAll() error { cn.onPeerHasAllPieces() return nil } func (cn *PeerConn) peerSentHaveNone() error { if !cn.peerSentHaveAll { cn.t.decPeerPieceAvailability(&cn.Peer) } cn._peerPieces.Clear() cn.peerSentHaveAll = false cn.peerPiecesChanged() return nil } func (c *PeerConn) requestPendingMetadata() { if c.t.haveInfo() { return } if c.PeerExtensionIDs[pp.ExtensionNameMetadata] == 0 { // Peer doesn't support this. return } // Request metadata pieces that we don't have in a random order. var pending []int for index := 0; index < c.t.metadataPieceCount(); index++ { if !c.t.haveMetadataPiece(index) && !c.requestedMetadataPiece(index) { pending = append(pending, index) } } rand.Shuffle(len(pending), func(i, j int) { pending[i], pending[j] = pending[j], pending[i] }) for _, i := range pending { c.requestMetadataPiece(i) } } func (cn *PeerConn) wroteMsg(msg *pp.Message) { torrent.Add(fmt.Sprintf("messages written of type %s", msg.Type.String()), 1) if msg.Type == pp.Extended { for name, id := range cn.PeerExtensionIDs { if id != msg.ExtendedID { continue } torrent.Add(fmt.Sprintf("Extended messages written for protocol %q", name), 1) } } cn.allStats(func(cs *ConnStats) { cs.wroteMsg(msg) }) } func (cn *PeerConn) wroteBytes(n int64) { cn.allStats(add(n, func(cs *ConnStats) *Count { return &cs.BytesWritten })) } func (c *PeerConn) fastEnabled() bool { return c.PeerExtensionBytes.SupportsFast() && c.t.cl.config.Extensions.SupportsFast() } func (c *PeerConn) reject(r Request) { if !c.fastEnabled() { panic("fast not enabled") } c.write(r.ToMsg(pp.Reject)) // It is possible to reject a request before it is added to peer requests due to being invalid. if state, ok := c.peerRequests[r]; ok { state.allocReservation.Drop() delete(c.peerRequests, r) } } func (c *PeerConn) maximumPeerRequestChunkLength() (_ Option[int]) { uploadRateLimiter := c.t.cl.config.UploadRateLimiter if uploadRateLimiter.Limit() == rate.Inf { return } return Some(uploadRateLimiter.Burst()) } // startFetch is for testing purposes currently. func (c *PeerConn) onReadRequest(r Request, startFetch bool) error { requestedChunkLengths.Add(strconv.FormatUint(r.Length.Uint64(), 10), 1) if _, ok := c.peerRequests[r]; ok { torrent.Add("duplicate requests received", 1) if c.fastEnabled() { return errors.New("received duplicate request with fast enabled") } return nil } if c.choking { torrent.Add("requests received while choking", 1) if c.fastEnabled() { torrent.Add("requests rejected while choking", 1) c.reject(r) } return nil } // TODO: What if they've already requested this? if len(c.peerRequests) >= localClientReqq { torrent.Add("requests received while queue full", 1) if c.fastEnabled() { c.reject(r) } // BEP 6 says we may close here if we choose. return nil } if opt := c.maximumPeerRequestChunkLength(); opt.Ok && int(r.Length) > opt.Value { err := fmt.Errorf("peer requested chunk too long (%v)", r.Length) c.logger.Levelf(log.Warning, err.Error()) if c.fastEnabled() { c.reject(r) return nil } else { return err } } if !c.t.havePiece(pieceIndex(r.Index)) { // TODO: Tell the peer we don't have the piece, and reject this request. requestsReceivedForMissingPieces.Add(1) return fmt.Errorf("peer requested piece we don't have: %v", r.Index.Int()) } pieceLength := c.t.pieceLength(pieceIndex(r.Index)) // Check this after we know we have the piece, so that the piece length will be known. if chunkOverflowsPiece(r.ChunkSpec, pieceLength) { torrent.Add("bad requests received", 1) return errors.New("chunk overflows piece") } if c.peerRequests == nil { c.peerRequests = make(map[Request]*peerRequestState, localClientReqq) } value := &peerRequestState{ allocReservation: c.peerRequestDataAllocLimiter.Reserve(int64(r.Length)), } c.peerRequests[r] = value if startFetch { // TODO: Limit peer request data read concurrency. go c.peerRequestDataReader(r, value) } return nil } func (c *PeerConn) peerRequestDataReader(r Request, prs *peerRequestState) { b, err := c.readPeerRequestData(r, prs) c.locker().Lock() defer c.locker().Unlock() if err != nil { c.peerRequestDataReadFailed(err, r) } else { if b == nil { panic("data must be non-nil to trigger send") } torrent.Add("peer request data read successes", 1) prs.data = b // This might be required for the error case too (#752 and #753). c.tickleWriter() } } // If this is maintained correctly, we might be able to support optional synchronous reading for // chunk sending, the way it used to work. func (c *PeerConn) peerRequestDataReadFailed(err error, r Request) { torrent.Add("peer request data read failures", 1) logLevel := log.Warning if c.t.hasStorageCap() { // It's expected that pieces might drop. See // https://github.com/anacrolix/torrent/issues/702#issuecomment-1000953313. logLevel = log.Debug } c.logger.WithDefaultLevel(logLevel).Printf("error reading chunk for peer Request %v: %v", r, err) if c.t.closed.IsSet() { return } i := pieceIndex(r.Index) if c.t.pieceComplete(i) { // There used to be more code here that just duplicated the following break. Piece // completions are currently cached, so I'm not sure how helpful this update is, except to // pull any completion changes pushed to the storage backend in failed reads that got us // here. c.t.updatePieceCompletion(i) } // We've probably dropped a piece from storage, but there's no way to communicate this to the // peer. If they ask for it again, we kick them allowing us to send them updated piece states if // we reconnect. TODO: Instead, we could just try to update them with Bitfield or HaveNone and // if they kick us for breaking protocol, on reconnect we will be compliant again (at least // initially). if c.fastEnabled() { c.reject(r) } else { if c.choking { // If fast isn't enabled, I think we would have wiped all peer requests when we last // choked, and requests while we're choking would be ignored. It could be possible that // a peer request data read completed concurrently to it being deleted elsewhere. c.logger.WithDefaultLevel(log.Warning).Printf("already choking peer, requests might not be rejected correctly") } // Choking a non-fast peer should cause them to flush all their requests. c.choke(c.write) } } func (c *PeerConn) readPeerRequestData(r Request, prs *peerRequestState) ([]byte, error) { // Should we depend on Torrent closure here? I think it's okay to get cancelled from elsewhere, // or fail to read and then cleanup. ctx := context.Background() err := prs.allocReservation.Wait(ctx) if err != nil { if ctx.Err() == nil { // The error is from the reservation itself. Something is very broken, or we're not // guarding against excessively large requests. err = log.WithLevel(log.Critical, err) } err = fmt.Errorf("waiting for alloc limit reservation: %w", err) return nil, err } b := make([]byte, r.Length) p := c.t.info.Piece(int(r.Index)) n, err := c.t.readAt(b, p.Offset()+int64(r.Begin)) if n == len(b) { if err == io.EOF { err = nil } } else { if err == nil { panic("expected error") } } return b, err } func (c *PeerConn) logProtocolBehaviour(level log.Level, format string, arg ...interface{}) { c.logger.WithContextText(fmt.Sprintf( "peer id %q, ext v %q", c.PeerID, c.PeerClientName.Load(), )).SkipCallers(1).Levelf(level, format, arg...) } // Processes incoming BitTorrent wire-protocol messages. The client lock is held upon entry and // exit. Returning will end the connection. func (c *PeerConn) mainReadLoop() (err error) { defer func() { if err != nil { torrent.Add("connection.mainReadLoop returned with error", 1) } else { torrent.Add("connection.mainReadLoop returned with no error", 1) } }() t := c.t cl := t.cl decoder := pp.Decoder{ R: bufio.NewReaderSize(c.r, 1<<17), MaxLength: 4 * pp.Integer(max(int64(t.chunkSize), defaultChunkSize)), Pool: &t.chunkPool, } for { var msg pp.Message func() { cl.unlock() defer cl.lock() err = decoder.Decode(&msg) }() if cb := c.callbacks.ReadMessage; cb != nil && err == nil { cb(c, &msg) } if t.closed.IsSet() || c.closed.IsSet() { return nil } if err != nil { return err } c.lastMessageReceived = time.Now() if msg.Keepalive { receivedKeepalives.Add(1) continue } messageTypesReceived.Add(msg.Type.String(), 1) if msg.Type.FastExtension() && !c.fastEnabled() { runSafeExtraneous(func() { torrent.Add("fast messages received when extension is disabled", 1) }) return fmt.Errorf("received fast extension message (type=%v) but extension is disabled", msg.Type) } switch msg.Type { case pp.Choke: if c.peerChoking { break } if !c.fastEnabled() { c.deleteAllRequests("choked by non-fast PeerConn") } else { // We don't decrement pending requests here, let's wait for the peer to either // reject or satisfy the outstanding requests. Additionally, some peers may unchoke // us and resume where they left off, we don't want to have piled on to those chunks // in the meanwhile. I think a peer's ability to abuse this should be limited: they // could let us request a lot of stuff, then choke us and never reject, but they're // only a single peer, our chunk balancing should smooth over this abuse. } c.peerChoking = true c.updateExpectingChunks() case pp.Unchoke: if !c.peerChoking { // Some clients do this for some reason. Transmission doesn't error on this, so we // won't for consistency. c.logProtocolBehaviour(log.Debug, "received unchoke when already unchoked") break } c.peerChoking = false preservedCount := 0 c.requestState.Requests.Iterate(func(x RequestIndex) bool { if !c.peerAllowedFast.Contains(c.t.pieceIndexOfRequestIndex(x)) { preservedCount++ } return true }) if preservedCount != 0 { // TODO: Yes this is a debug log but I'm not happy with the state of the logging lib // right now. c.logger.Levelf(log.Debug, "%v requests were preserved while being choked (fast=%v)", preservedCount, c.fastEnabled()) torrent.Add("requestsPreservedThroughChoking", int64(preservedCount)) } if !c.t._pendingPieces.IsEmpty() { c.updateRequests("unchoked") } c.updateExpectingChunks() case pp.Interested: c.peerInterested = true c.tickleWriter() case pp.NotInterested: c.peerInterested = false // We don't clear their requests since it isn't clear in the spec. // We'll probably choke them for this, which will clear them if // appropriate, and is clearly specified. case pp.Have: err = c.peerSentHave(pieceIndex(msg.Index)) case pp.Bitfield: err = c.peerSentBitfield(msg.Bitfield) case pp.Request: r := newRequestFromMessage(&msg) err = c.onReadRequest(r, true) if err != nil { err = fmt.Errorf("on reading request %v: %w", r, err) } case pp.Piece: c.doChunkReadStats(int64(len(msg.Piece))) err = c.receiveChunk(&msg) if len(msg.Piece) == int(t.chunkSize) { t.chunkPool.Put(&msg.Piece) } if err != nil { err = fmt.Errorf("receiving chunk: %w", err) } case pp.Cancel: req := newRequestFromMessage(&msg) c.onPeerSentCancel(req) case pp.Port: ipa, ok := tryIpPortFromNetAddr(c.RemoteAddr) if !ok { break } pingAddr := net.UDPAddr{ IP: ipa.IP, Port: ipa.Port, } if msg.Port != 0 { pingAddr.Port = int(msg.Port) } cl.eachDhtServer(func(s DhtServer) { go s.Ping(&pingAddr) }) case pp.Suggest: torrent.Add("suggests received", 1) log.Fmsg("peer suggested piece %d", msg.Index).AddValues(c, msg.Index).LogLevel(log.Debug, c.t.logger) c.updateRequests("suggested") case pp.HaveAll: err = c.onPeerSentHaveAll() case pp.HaveNone: err = c.peerSentHaveNone() case pp.Reject: req := newRequestFromMessage(&msg) if !c.remoteRejectedRequest(c.t.requestIndexFromRequest(req)) { c.logger.Printf("received invalid reject [request=%v, peer=%v]", req, c) err = fmt.Errorf("received invalid reject [request=%v]", req) } case pp.AllowedFast: torrent.Add("allowed fasts received", 1) log.Fmsg("peer allowed fast: %d", msg.Index).AddValues(c).LogLevel(log.Debug, c.t.logger) c.updateRequests("PeerConn.mainReadLoop allowed fast") case pp.Extended: err = c.onReadExtendedMsg(msg.ExtendedID, msg.ExtendedPayload) default: err = fmt.Errorf("received unknown message type: %#v", msg.Type) } if err != nil { return err } } } func (c *PeerConn) onReadExtendedMsg(id pp.ExtensionNumber, payload []byte) (err error) { defer func() { // TODO: Should we still do this? if err != nil { // These clients use their own extension IDs for outgoing message // types, which is incorrect. if bytes.HasPrefix(c.PeerID[:], []byte("-SD0100-")) || strings.HasPrefix(string(c.PeerID[:]), "-XL0012-") { err = nil } } }() t := c.t cl := t.cl switch id { case pp.HandshakeExtendedID: var d pp.ExtendedHandshakeMessage if err := bencode.Unmarshal(payload, &d); err != nil { c.logger.Printf("error parsing extended handshake message %q: %s", payload, err) return fmt.Errorf("unmarshalling extended handshake payload: %w", err) } if cb := c.callbacks.ReadExtendedHandshake; cb != nil { cb(c, &d) } // c.logger.WithDefaultLevel(log.Debug).Printf("received extended handshake message:\n%s", spew.Sdump(d)) if d.Reqq != 0 { c.PeerMaxRequests = d.Reqq } c.PeerClientName.Store(d.V) if c.PeerExtensionIDs == nil { c.PeerExtensionIDs = make(map[pp.ExtensionName]pp.ExtensionNumber, len(d.M)) } c.PeerListenPort = d.Port c.PeerPrefersEncryption = d.Encryption for name, id := range d.M { if _, ok := c.PeerExtensionIDs[name]; !ok { peersSupportingExtension.Add( // expvar.Var.String must produce valid JSON. "ut_payme\xeet_address" was being // entered here which caused problems later when unmarshalling. strconv.Quote(string(name)), 1) } c.PeerExtensionIDs[name] = id } if d.MetadataSize != 0 { if err = t.setMetadataSize(d.MetadataSize); err != nil { return fmt.Errorf("setting metadata size to %d: %w", d.MetadataSize, err) } } c.requestPendingMetadata() if !t.cl.config.DisablePEX { t.pex.Add(c) // we learnt enough now c.pex.Init(c) } return nil case metadataExtendedId: err := cl.gotMetadataExtensionMsg(payload, t, c) if err != nil { return fmt.Errorf("handling metadata extension message: %w", err) } return nil case pexExtendedId: if !c.pex.IsEnabled() { return nil // or hang-up maybe? } return c.pex.Recv(payload) default: return fmt.Errorf("unexpected extended message ID: %v", id) } } // Set both the Reader and Writer for the connection from a single ReadWriter. func (cn *PeerConn) setRW(rw io.ReadWriter) { cn.r = rw cn.w = rw } // Returns the Reader and Writer as a combined ReadWriter. func (cn *PeerConn) rw() io.ReadWriter { return struct { io.Reader io.Writer }{cn.r, cn.w} } func (c *PeerConn) uploadAllowed() bool { if c.t.cl.config.NoUpload { return false } if c.t.dataUploadDisallowed { return false } if c.t.seeding() { return true } if !c.peerHasWantedPieces() { return false } // Don't upload more than 100 KiB more than we download. if c._stats.BytesWrittenData.Int64() >= c._stats.BytesReadData.Int64()+100<<10 { return false } return true } func (c *PeerConn) setRetryUploadTimer(delay time.Duration) { if c.uploadTimer == nil { c.uploadTimer = time.AfterFunc(delay, c.tickleWriter) } else { c.uploadTimer.Reset(delay) } } // Also handles choking and unchoking of the remote peer. func (c *PeerConn) upload(msg func(pp.Message) bool) bool { // Breaking or completing this loop means we don't want to upload to the // peer anymore, and we choke them. another: for c.uploadAllowed() { // We want to upload to the peer. if !c.unchoke(msg) { return false } for r, state := range c.peerRequests { if state.data == nil { continue } res := c.t.cl.config.UploadRateLimiter.ReserveN(time.Now(), int(r.Length)) if !res.OK() { panic(fmt.Sprintf("upload rate limiter burst size < %d", r.Length)) } delay := res.Delay() if delay > 0 { res.Cancel() c.setRetryUploadTimer(delay) // Hard to say what to return here. return true } more := c.sendChunk(r, msg, state) delete(c.peerRequests, r) if !more { return false } goto another } return true } return c.choke(msg) } func (cn *PeerConn) drop() { cn.t.dropConnection(cn) } func (cn *PeerConn) ban() { cn.t.cl.banPeerIP(cn.remoteIp()) } // This is called when something has changed that should wake the writer, such as putting stuff into // the writeBuffer, or changing some state that the writer can act on. func (c *PeerConn) tickleWriter() { c.messageWriter.writeCond.Broadcast() } func (c *PeerConn) sendChunk(r Request, msg func(pp.Message) bool, state *peerRequestState) (more bool) { c.lastChunkSent = time.Now() state.allocReservation.Release() return msg(pp.Message{ Type: pp.Piece, Index: r.Index, Begin: r.Begin, Piece: state.data, }) } func (c *PeerConn) setTorrent(t *Torrent) { if c.t != nil { panic("connection already associated with a torrent") } c.t = t c.logger.WithDefaultLevel(log.Debug).Printf("set torrent=%v", t) t.reconcileHandshakeStats(c) } func (c *PeerConn) pexPeerFlags() pp.PexPeerFlags { f := pp.PexPeerFlags(0) if c.PeerPrefersEncryption { f |= pp.PexPrefersEncryption } if c.outgoing { f |= pp.PexOutgoingConn } if c.utp() { f |= pp.PexSupportsUtp } return f } // This returns the address to use if we want to dial the peer again. It incorporates the peer's // advertised listen port. func (c *PeerConn) dialAddr() PeerRemoteAddr { if !c.outgoing && c.PeerListenPort != 0 { switch addr := c.RemoteAddr.(type) { case *net.TCPAddr: dialAddr := *addr dialAddr.Port = c.PeerListenPort return &dialAddr case *net.UDPAddr: dialAddr := *addr dialAddr.Port = c.PeerListenPort return &dialAddr } } return c.RemoteAddr } func (c *PeerConn) pexEvent(t pexEventType) pexEvent { f := c.pexPeerFlags() addr := c.dialAddr() return pexEvent{t, addr, f, nil} } func (c *PeerConn) String() string { return fmt.Sprintf("%T %p [id=%q, exts=%v, v=%q]", c, c, c.PeerID, c.PeerExtensionBytes, c.PeerClientName.Load()) } // Returns the pieces the peer could have based on their claims. If we don't know how many pieces // are in the torrent, it could be a very large range the peer has sent HaveAll. func (cn *PeerConn) PeerPieces() *roaring.Bitmap { cn.locker().RLock() defer cn.locker().RUnlock() return cn.newPeerPieces() } func (pc *PeerConn) remoteIsTransmission() bool { return bytes.HasPrefix(pc.PeerID[:], []byte("-TR")) && pc.PeerID[7] == '-' }