connection.go

   1 package torrent
   2
   3 import (
   4         "bufio"
   5         "bytes"
   6         "fmt"
   7         "io"
   8         "math/rand"
   9         "net"
  10         "strconv"
  11         "strings"
  12         "sync"
  13         "time"
  14
  15         "github.com/anacrolix/log"
  16         "github.com/anacrolix/missinggo"
  17         "github.com/anacrolix/missinggo/iter"
  18         "github.com/anacrolix/missinggo/v2/bitmap"
  19         "github.com/anacrolix/missinggo/v2/prioritybitmap"
  20         "github.com/anacrolix/multiless"
  21         "github.com/pkg/errors"
  22
  23         "github.com/anacrolix/torrent/bencode"
  24         "github.com/anacrolix/torrent/mse"
  25         pp "github.com/anacrolix/torrent/peer_protocol"
  26 )
  27
  28 type peerSource string
  29
  30 const (
  31         peerSourceTracker         = "Tr"
  32         peerSourceIncoming        = "I"
  33         peerSourceDhtGetPeers     = "Hg" // Peers we found by searching a DHT.
  34         peerSourceDhtAnnouncePeer = "Ha" // Peers that were announced to us by a DHT.
  35         peerSourcePex             = "X"
  36 )
  37
  38 // Maintains the state of a connection with a peer.
  39 type connection struct {
  40         // First to ensure 64-bit alignment for atomics. See #262.
  41         _stats ConnStats
  42
  43         t *Torrent
  44         // The actual Conn, used for closing, and setting socket options.
  45         conn       net.Conn
  46         outgoing   bool
  47         network    string
  48         remoteAddr net.Addr
  49         // The Reader and Writer for this Conn, with hooks installed for stats,
  50         // limiting, deadlines etc.
  51         w io.Writer
  52         r io.Reader
  53         // True if the connection is operating over MSE obfuscation.
  54         headerEncrypted bool
  55         cryptoMethod    mse.CryptoMethod
  56         Discovery       peerSource
  57         trusted         bool
  58         closed          missinggo.Event
  59         // Set true after we've added our ConnStats generated during handshake to
  60         // other ConnStat instances as determined when the *Torrent became known.
  61         reconciledHandshakeStats bool
  62
  63         lastMessageReceived     time.Time
  64         completedHandshake      time.Time
  65         lastUsefulChunkReceived time.Time
  66         lastChunkSent           time.Time
  67
  68         // Stuff controlled by the local peer.
  69         Interested           bool
  70         lastBecameInterested time.Time
  71         priorInterest        time.Duration
  72
  73         lastStartedExpectingToReceiveChunks time.Time
  74         cumulativeExpectedToReceiveChunks   time.Duration
  75         _chunksReceivedWhileExpecting       int64
  76
  77         Choked           bool
  78         requests         map[request]struct{}
  79         requestsLowWater int
  80         // Chunks that we might reasonably expect to receive from the peer. Due to
  81         // latency, buffering, and implementation differences, we may receive
  82         // chunks that are no longer in the set of requests actually want.
  83         validReceiveChunks map[request]struct{}
  84         // Indexed by metadata piece, set to true if posted and pending a
  85         // response.
  86         metadataRequests []bool
  87         sentHaves        bitmap.Bitmap
  88
  89         // Stuff controlled by the remote peer.
  90         PeerID             PeerID
  91         PeerInterested     bool
  92         PeerChoked         bool
  93         PeerRequests       map[request]struct{}
  94         PeerExtensionBytes pp.PeerExtensionBits
  95         // The pieces the peer has claimed to have.
  96         _peerPieces bitmap.Bitmap
  97         // The peer has everything. This can occur due to a special message, when
  98         // we may not even know the number of pieces in the torrent yet.
  99         peerSentHaveAll bool
 100         // The highest possible number of pieces the torrent could have based on
 101         // communication with the peer. Generally only useful until we have the
 102         // torrent info.
 103         peerMinPieces pieceIndex
 104         // Pieces we've accepted chunks for from the peer.
 105         peerTouchedPieces map[pieceIndex]struct{}
 106         peerAllowedFast   bitmap.Bitmap
 107
 108         PeerMaxRequests  int // Maximum pending requests the peer allows.
 109         PeerExtensionIDs map[pp.ExtensionName]pp.ExtensionNumber
 110         PeerClientName   string
 111
 112         pieceInclination   []int
 113         _pieceRequestOrder prioritybitmap.PriorityBitmap
 114
 115         writeBuffer *bytes.Buffer
 116         uploadTimer *time.Timer
 117         writerCond  sync.Cond
 118
 119         logger log.Logger
 120 }
 121
 122 func (cn *connection) updateExpectingChunks() {
 123         if cn.expectingChunks() {
 124                 if cn.lastStartedExpectingToReceiveChunks.IsZero() {
 125                         cn.lastStartedExpectingToReceiveChunks = time.Now()
 126                 }
 127         } else {
 128                 if !cn.lastStartedExpectingToReceiveChunks.IsZero() {
 129                         cn.cumulativeExpectedToReceiveChunks += time.Since(cn.lastStartedExpectingToReceiveChunks)
 130                         cn.lastStartedExpectingToReceiveChunks = time.Time{}
 131                 }
 132         }
 133 }
 134
 135 func (cn *connection) expectingChunks() bool {
 136         return cn.Interested && !cn.PeerChoked
 137 }
 138
 139 // Returns true if the connection is over IPv6.
 140 func (cn *connection) ipv6() bool {
 141         ip := addrIpOrNil(cn.remoteAddr)
 142         if ip.To4() != nil {
 143                 return false
 144         }
 145         return len(ip) == net.IPv6len
 146 }
 147
 148 // Returns true the if the dialer/initiator has the lower client peer ID. TODO: Find the
 149 // specification for this.
 150 func (cn *connection) isPreferredDirection() bool {
 151         return bytes.Compare(cn.t.cl.peerID[:], cn.PeerID[:]) < 0 == cn.outgoing
 152 }
 153
 154 // Returns whether the left connection should be preferred over the right one,
 155 // considering only their networking properties. If ok is false, we can't
 156 // decide.
 157 func (l *connection) hasPreferredNetworkOver(r *connection) (left, ok bool) {
 158         var ml multiLess
 159         ml.NextBool(l.isPreferredDirection(), r.isPreferredDirection())
 160         ml.NextBool(!l.utp(), !r.utp())
 161         ml.NextBool(l.ipv6(), r.ipv6())
 162         return ml.FinalOk()
 163 }
 164
 165 func (cn *connection) cumInterest() time.Duration {
 166         ret := cn.priorInterest
 167         if cn.Interested {
 168                 ret += time.Since(cn.lastBecameInterested)
 169         }
 170         return ret
 171 }
 172
 173 func (cn *connection) peerHasAllPieces() (all bool, known bool) {
 174         if cn.peerSentHaveAll {
 175                 return true, true
 176         }
 177         if !cn.t.haveInfo() {
 178                 return false, false
 179         }
 180         return bitmap.Flip(cn._peerPieces, 0, bitmap.BitIndex(cn.t.numPieces())).IsEmpty(), true
 181 }
 182
 183 func (cn *connection) mu() sync.Locker {
 184         return cn.t.cl.locker()
 185 }
 186
 187 func (cn *connection) localAddr() net.Addr {
 188         return cn.conn.LocalAddr()
 189 }
 190
 191 func (cn *connection) supportsExtension(ext pp.ExtensionName) bool {
 192         _, ok := cn.PeerExtensionIDs[ext]
 193         return ok
 194 }
 195
 196 // The best guess at number of pieces in the torrent for this peer.
 197 func (cn *connection) bestPeerNumPieces() pieceIndex {
 198         if cn.t.haveInfo() {
 199                 return cn.t.numPieces()
 200         }
 201         return cn.peerMinPieces
 202 }
 203
 204 func (cn *connection) completedString() string {
 205         have := pieceIndex(cn._peerPieces.Len())
 206         if cn.peerSentHaveAll {
 207                 have = cn.bestPeerNumPieces()
 208         }
 209         return fmt.Sprintf("%d/%d", have, cn.bestPeerNumPieces())
 210 }
 211
 212 // Correct the PeerPieces slice length. Return false if the existing slice is
 213 // invalid, such as by receiving badly sized BITFIELD, or invalid HAVE
 214 // messages.
 215 func (cn *connection) setNumPieces(num pieceIndex) error {
 216         cn._peerPieces.RemoveRange(bitmap.BitIndex(num), bitmap.ToEnd)
 217         cn.peerPiecesChanged()
 218         return nil
 219 }
 220
 221 func eventAgeString(t time.Time) string {
 222         if t.IsZero() {
 223                 return "never"
 224         }
 225         return fmt.Sprintf("%.2fs ago", time.Since(t).Seconds())
 226 }
 227
 228 func (cn *connection) connectionFlags() (ret string) {
 229         c := func(b byte) {
 230                 ret += string([]byte{b})
 231         }
 232         if cn.cryptoMethod == mse.CryptoMethodRC4 {
 233                 c('E')
 234         } else if cn.headerEncrypted {
 235                 c('e')
 236         }
 237         ret += string(cn.Discovery)
 238         if cn.utp() {
 239                 c('U')
 240         }
 241         return
 242 }
 243
 244 func (cn *connection) utp() bool {
 245         return parseNetworkString(cn.network).Udp
 246 }
 247
 248 // Inspired by https://github.com/transmission/transmission/wiki/Peer-Status-Text.
 249 func (cn *connection) statusFlags() (ret string) {
 250         c := func(b byte) {
 251                 ret += string([]byte{b})
 252         }
 253         if cn.Interested {
 254                 c('i')
 255         }
 256         if cn.Choked {
 257                 c('c')
 258         }
 259         c('-')
 260         ret += cn.connectionFlags()
 261         c('-')
 262         if cn.PeerInterested {
 263                 c('i')
 264         }
 265         if cn.PeerChoked {
 266                 c('c')
 267         }
 268         return
 269 }
 270
 271 // func (cn *connection) String() string {
 272 //      var buf bytes.Buffer
 273 //      cn.WriteStatus(&buf, nil)
 274 //      return buf.String()
 275 // }
 276
 277 func (cn *connection) downloadRate() float64 {
 278         return float64(cn._stats.BytesReadUsefulData.Int64()) / cn.cumInterest().Seconds()
 279 }
 280
 281 func (cn *connection) WriteStatus(w io.Writer, t *Torrent) {
 282         // \t isn't preserved in <pre> blocks?
 283         fmt.Fprintf(w, "%+-55q %s %s-%s\n", cn.PeerID, cn.PeerExtensionBytes, cn.localAddr(), cn.remoteAddr)
 284         fmt.Fprintf(w, "    last msg: %s, connected: %s, last helpful: %s, itime: %s, etime: %s\n",
 285                 eventAgeString(cn.lastMessageReceived),
 286                 eventAgeString(cn.completedHandshake),
 287                 eventAgeString(cn.lastHelpful()),
 288                 cn.cumInterest(),
 289                 cn.totalExpectingTime(),
 290         )
 291         fmt.Fprintf(w,
 292                 "    %s completed, %d pieces touched, good chunks: %v/%v-%v reqq: (%d,%d,%d]-%d, flags: %s, dr: %.1f KiB/s\n",
 293                 cn.completedString(),
 294                 len(cn.peerTouchedPieces),
 295                 &cn._stats.ChunksReadUseful,
 296                 &cn._stats.ChunksRead,
 297                 &cn._stats.ChunksWritten,
 298                 cn.requestsLowWater,
 299                 cn.numLocalRequests(),
 300                 cn.nominalMaxRequests(),
 301                 len(cn.PeerRequests),
 302                 cn.statusFlags(),
 303                 cn.downloadRate()/(1<<10),
 304         )
 305         fmt.Fprintf(w, "    next pieces: %v%s\n",
 306                 iter.ToSlice(iter.Head(10, cn.iterPendingPiecesUntyped)),
 307                 func() string {
 308                         if cn == t.fastestConn {
 309                                 return " (fastest)"
 310                         } else {
 311                                 return ""
 312                         }
 313                 }(),
 314         )
 315 }
 316
 317 func (cn *connection) Close() {
 318         if !cn.closed.Set() {
 319                 return
 320         }
 321         cn.tickleWriter()
 322         cn.discardPieceInclination()
 323         cn._pieceRequestOrder.Clear()
 324         if cn.conn != nil {
 325                 go cn.conn.Close()
 326         }
 327 }
 328
 329 func (cn *connection) PeerHasPiece(piece pieceIndex) bool {
 330         return cn.peerSentHaveAll || cn._peerPieces.Contains(bitmap.BitIndex(piece))
 331 }
 332
 333 // Writes a message into the write buffer.
 334 func (cn *connection) Post(msg pp.Message) {
 335         torrent.Add(fmt.Sprintf("messages posted of type %s", msg.Type.String()), 1)
 336         // We don't need to track bytes here because a connection.w Writer wrapper
 337         // takes care of that (although there's some delay between us recording
 338         // the message, and the connection writer flushing it out.).
 339         cn.writeBuffer.Write(msg.MustMarshalBinary())
 340         // Last I checked only Piece messages affect stats, and we don't post
 341         // those.
 342         cn.wroteMsg(&msg)
 343         cn.tickleWriter()
 344 }
 345
 346 func (cn *connection) requestMetadataPiece(index int) {
 347         eID := cn.PeerExtensionIDs[pp.ExtensionNameMetadata]
 348         if eID == 0 {
 349                 return
 350         }
 351         if index < len(cn.metadataRequests) && cn.metadataRequests[index] {
 352                 return
 353         }
 354         cn.logger.Printf("requesting metadata piece %d", index)
 355         cn.Post(pp.Message{
 356                 Type:       pp.Extended,
 357                 ExtendedID: eID,
 358                 ExtendedPayload: func() []byte {
 359                         b, err := bencode.Marshal(map[string]int{
 360                                 "msg_type": pp.RequestMetadataExtensionMsgType,
 361                                 "piece":    index,
 362                         })
 363                         if err != nil {
 364                                 panic(err)
 365                         }
 366                         return b
 367                 }(),
 368         })
 369         for index >= len(cn.metadataRequests) {
 370                 cn.metadataRequests = append(cn.metadataRequests, false)
 371         }
 372         cn.metadataRequests[index] = true
 373 }
 374
 375 func (cn *connection) requestedMetadataPiece(index int) bool {
 376         return index < len(cn.metadataRequests) && cn.metadataRequests[index]
 377 }
 378
 379 // The actual value to use as the maximum outbound requests.
 380 func (cn *connection) nominalMaxRequests() (ret int) {
 381         return int(clamp(
 382                 1,
 383                 int64(cn.PeerMaxRequests),
 384                 int64(cn.t.requestStrategy.nominalMaxRequests(cn.requestStrategyConnection())),
 385         ))
 386 }
 387
 388 func (cn *connection) totalExpectingTime() (ret time.Duration) {
 389         ret = cn.cumulativeExpectedToReceiveChunks
 390         if !cn.lastStartedExpectingToReceiveChunks.IsZero() {
 391                 ret += time.Since(cn.lastStartedExpectingToReceiveChunks)
 392         }
 393         return
 394
 395 }
 396
 397 func (cn *connection) onPeerSentCancel(r request) {
 398         if _, ok := cn.PeerRequests[r]; !ok {
 399                 torrent.Add("unexpected cancels received", 1)
 400                 return
 401         }
 402         if cn.fastEnabled() {
 403                 cn.reject(r)
 404         } else {
 405                 delete(cn.PeerRequests, r)
 406         }
 407 }
 408
 409 func (cn *connection) Choke(msg messageWriter) (more bool) {
 410         if cn.Choked {
 411                 return true
 412         }
 413         cn.Choked = true
 414         more = msg(pp.Message{
 415                 Type: pp.Choke,
 416         })
 417         if cn.fastEnabled() {
 418                 for r := range cn.PeerRequests {
 419                         // TODO: Don't reject pieces in allowed fast set.
 420                         cn.reject(r)
 421                 }
 422         } else {
 423                 cn.PeerRequests = nil
 424         }
 425         return
 426 }
 427
 428 func (cn *connection) Unchoke(msg func(pp.Message) bool) bool {
 429         if !cn.Choked {
 430                 return true
 431         }
 432         cn.Choked = false
 433         return msg(pp.Message{
 434                 Type: pp.Unchoke,
 435         })
 436 }
 437
 438 func (cn *connection) SetInterested(interested bool, msg func(pp.Message) bool) bool {
 439         if cn.Interested == interested {
 440                 return true
 441         }
 442         cn.Interested = interested
 443         if interested {
 444                 cn.lastBecameInterested = time.Now()
 445         } else if !cn.lastBecameInterested.IsZero() {
 446                 cn.priorInterest += time.Since(cn.lastBecameInterested)
 447         }
 448         cn.updateExpectingChunks()
 449         // log.Printf("%p: setting interest: %v", cn, interested)
 450         return msg(pp.Message{
 451                 Type: func() pp.MessageType {
 452                         if interested {
 453                                 return pp.Interested
 454                         } else {
 455                                 return pp.NotInterested
 456                         }
 457                 }(),
 458         })
 459 }
 460
 461 // The function takes a message to be sent, and returns true if more messages
 462 // are okay.
 463 type messageWriter func(pp.Message) bool
 464
 465 // Proxies the messageWriter's response.
 466 func (cn *connection) request(r request, mw messageWriter) bool {
 467         if _, ok := cn.requests[r]; ok {
 468                 panic("chunk already requested")
 469         }
 470         if !cn.PeerHasPiece(pieceIndex(r.Index)) {
 471                 panic("requesting piece peer doesn't have")
 472         }
 473         if _, ok := cn.t.conns[cn]; !ok {
 474                 panic("requesting but not in active conns")
 475         }
 476         if cn.closed.IsSet() {
 477                 panic("requesting when connection is closed")
 478         }
 479         if cn.PeerChoked {
 480                 if cn.peerAllowedFast.Get(int(r.Index)) {
 481                         torrent.Add("allowed fast requests sent", 1)
 482                 } else {
 483                         panic("requesting while choked and not allowed fast")
 484                 }
 485         }
 486         if cn.t.hashingPiece(pieceIndex(r.Index)) {
 487                 panic("piece is being hashed")
 488         }
 489         if cn.t.pieceQueuedForHash(pieceIndex(r.Index)) {
 490                 panic("piece is queued for hash")
 491         }
 492         if cn.requests == nil {
 493                 cn.requests = make(map[request]struct{})
 494         }
 495         cn.requests[r] = struct{}{}
 496         if cn.validReceiveChunks == nil {
 497                 cn.validReceiveChunks = make(map[request]struct{})
 498         }
 499         cn.validReceiveChunks[r] = struct{}{}
 500         cn.t.pendingRequests[r]++
 501         cn.t.requestStrategy.hooks().sentRequest(r)
 502         cn.updateExpectingChunks()
 503         return mw(pp.Message{
 504                 Type:   pp.Request,
 505                 Index:  r.Index,
 506                 Begin:  r.Begin,
 507                 Length: r.Length,
 508         })
 509 }
 510
 511 func (cn *connection) fillWriteBuffer(msg func(pp.Message) bool) {
 512         if !cn.t.networkingEnabled {
 513                 if !cn.SetInterested(false, msg) {
 514                         return
 515                 }
 516                 if len(cn.requests) != 0 {
 517                         for r := range cn.requests {
 518                                 cn.deleteRequest(r)
 519                                 // log.Printf("%p: cancelling request: %v", cn, r)
 520                                 if !msg(makeCancelMessage(r)) {
 521                                         return
 522                                 }
 523                         }
 524                 }
 525         }
 526         if len(cn.requests) <= cn.requestsLowWater {
 527                 filledBuffer := false
 528                 cn.iterPendingPieces(func(pieceIndex pieceIndex) bool {
 529                         cn.iterPendingRequests(pieceIndex, func(r request) bool {
 530                                 if !cn.SetInterested(true, msg) {
 531                                         filledBuffer = true
 532                                         return false
 533                                 }
 534                                 if len(cn.requests) >= cn.nominalMaxRequests() {
 535                                         return false
 536                                 }
 537                                 // Choking is looked at here because our interest is dependent
 538                                 // on whether we'd make requests in its absence.
 539                                 if cn.PeerChoked {
 540                                         if !cn.peerAllowedFast.Get(bitmap.BitIndex(r.Index)) {
 541                                                 return false
 542                                         }
 543                                 }
 544                                 if _, ok := cn.requests[r]; ok {
 545                                         return true
 546                                 }
 547                                 filledBuffer = !cn.request(r, msg)
 548                                 return !filledBuffer
 549                         })
 550                         return !filledBuffer
 551                 })
 552                 if filledBuffer {
 553                         // If we didn't completely top up the requests, we shouldn't mark
 554                         // the low water, since we'll want to top up the requests as soon
 555                         // as we have more write buffer space.
 556                         return
 557                 }
 558                 cn.requestsLowWater = len(cn.requests) / 2
 559         }
 560
 561         cn.upload(msg)
 562 }
 563
 564 // Routine that writes to the peer. Some of what to write is buffered by
 565 // activity elsewhere in the Client, and some is determined locally when the
 566 // connection is writable.
 567 func (cn *connection) writer(keepAliveTimeout time.Duration) {
 568         var (
 569                 lastWrite      time.Time = time.Now()
 570                 keepAliveTimer *time.Timer
 571         )
 572         keepAliveTimer = time.AfterFunc(keepAliveTimeout, func() {
 573                 cn.mu().Lock()
 574                 defer cn.mu().Unlock()
 575                 if time.Since(lastWrite) >= keepAliveTimeout {
 576                         cn.tickleWriter()
 577                 }
 578                 keepAliveTimer.Reset(keepAliveTimeout)
 579         })
 580         cn.mu().Lock()
 581         defer cn.mu().Unlock()
 582         defer cn.Close()
 583         defer keepAliveTimer.Stop()
 584         frontBuf := new(bytes.Buffer)
 585         for {
 586                 if cn.closed.IsSet() {
 587                         return
 588                 }
 589                 if cn.writeBuffer.Len() == 0 {
 590                         cn.fillWriteBuffer(func(msg pp.Message) bool {
 591                                 cn.wroteMsg(&msg)
 592                                 cn.writeBuffer.Write(msg.MustMarshalBinary())
 593                                 torrent.Add(fmt.Sprintf("messages filled of type %s", msg.Type.String()), 1)
 594                                 return cn.writeBuffer.Len() < 1<<16 // 64KiB
 595                         })
 596                 }
 597                 if cn.writeBuffer.Len() == 0 && time.Since(lastWrite) >= keepAliveTimeout {
 598                         cn.writeBuffer.Write(pp.Message{Keepalive: true}.MustMarshalBinary())
 599                         postedKeepalives.Add(1)
 600                 }
 601                 if cn.writeBuffer.Len() == 0 {
 602                         // TODO: Minimize wakeups....
 603                         cn.writerCond.Wait()
 604                         continue
 605                 }
 606                 // Flip the buffers.
 607                 frontBuf, cn.writeBuffer = cn.writeBuffer, frontBuf
 608                 cn.mu().Unlock()
 609                 n, err := cn.w.Write(frontBuf.Bytes())
 610                 cn.mu().Lock()
 611                 if n != 0 {
 612                         lastWrite = time.Now()
 613                         keepAliveTimer.Reset(keepAliveTimeout)
 614                 }
 615                 if err != nil {
 616                         return
 617                 }
 618                 if n != frontBuf.Len() {
 619                         panic("short write")
 620                 }
 621                 frontBuf.Reset()
 622         }
 623 }
 624
 625 func (cn *connection) Have(piece pieceIndex) {
 626         if cn.sentHaves.Get(bitmap.BitIndex(piece)) {
 627                 return
 628         }
 629         cn.Post(pp.Message{
 630                 Type:  pp.Have,
 631                 Index: pp.Integer(piece),
 632         })
 633         cn.sentHaves.Add(bitmap.BitIndex(piece))
 634 }
 635
 636 func (cn *connection) PostBitfield() {
 637         if cn.sentHaves.Len() != 0 {
 638                 panic("bitfield must be first have-related message sent")
 639         }
 640         if !cn.t.haveAnyPieces() {
 641                 return
 642         }
 643         cn.Post(pp.Message{
 644                 Type:     pp.Bitfield,
 645                 Bitfield: cn.t.bitfield(),
 646         })
 647         cn.sentHaves = cn.t._completedPieces.Copy()
 648 }
 649
 650 func (cn *connection) updateRequests() {
 651         // log.Print("update requests")
 652         cn.tickleWriter()
 653 }
 654
 655 // Emits the indices in the Bitmaps bms in order, never repeating any index.
 656 // skip is mutated during execution, and its initial values will never be
 657 // emitted.
 658 func iterBitmapsDistinct(skip *bitmap.Bitmap, bms ...bitmap.Bitmap) iter.Func {
 659         return func(cb iter.Callback) {
 660                 for _, bm := range bms {
 661                         if !iter.All(
 662                                 func(i interface{}) bool {
 663                                         skip.Add(i.(int))
 664                                         return cb(i)
 665                                 },
 666                                 bitmap.Sub(bm, *skip).Iter,
 667                         ) {
 668                                 return
 669                         }
 670                 }
 671         }
 672 }
 673
 674 func iterUnbiasedPieceRequestOrder(cn requestStrategyConnection, f func(piece pieceIndex) bool) bool {
 675         now, readahead := cn.torrent().readerPiecePriorities()
 676         skip := bitmap.Flip(cn.peerPieces(), 0, cn.torrent().numPieces())
 677         skip.Union(cn.torrent().ignorePieces())
 678         // Return an iterator over the different priority classes, minus the skip pieces.
 679         return iter.All(
 680                 func(_piece interface{}) bool {
 681                         return f(pieceIndex(_piece.(bitmap.BitIndex)))
 682                 },
 683                 iterBitmapsDistinct(&skip, now, readahead),
 684                 // We have to iterate _pendingPieces separately because it isn't a Bitmap.
 685                 func(cb iter.Callback) {
 686                         cn.torrent().pendingPieces().IterTyped(func(piece int) bool {
 687                                 if skip.Contains(piece) {
 688                                         return true
 689                                 }
 690                                 more := cb(piece)
 691                                 skip.Add(piece)
 692                                 return more
 693                         })
 694                 },
 695         )
 696 }
 697
 698 // The connection should download highest priority pieces first, without any inclination toward
 699 // avoiding wastage. Generally we might do this if there's a single connection, or this is the
 700 // fastest connection, and we have active readers that signal an ordering preference. It's
 701 // conceivable that the best connection should do this, since it's least likely to waste our time if
 702 // assigned to the highest priority pieces, and assigning more than one this role would cause
 703 // significant wasted bandwidth.
 704 func (cn *connection) shouldRequestWithoutBias() bool {
 705         return cn.t.requestStrategy.shouldRequestWithoutBias(cn.requestStrategyConnection())
 706 }
 707
 708 func (cn *connection) iterPendingPieces(f func(pieceIndex) bool) bool {
 709         if !cn.t.haveInfo() {
 710                 return false
 711         }
 712         return cn.t.requestStrategy.iterPendingPieces(cn, f)
 713 }
 714 func (cn *connection) iterPendingPiecesUntyped(f iter.Callback) {
 715         cn.iterPendingPieces(func(i pieceIndex) bool { return f(i) })
 716 }
 717
 718 func (cn *connection) iterPendingRequests(piece pieceIndex, f func(request) bool) bool {
 719         return cn.t.requestStrategy.iterUndirtiedChunks(
 720                 cn.t.piece(piece).requestStrategyPiece(),
 721                 func(cs chunkSpec) bool {
 722                         return f(request{pp.Integer(piece), cs})
 723                 },
 724         )
 725 }
 726
 727 // check callers updaterequests
 728 func (cn *connection) stopRequestingPiece(piece pieceIndex) bool {
 729         return cn._pieceRequestOrder.Remove(bitmap.BitIndex(piece))
 730 }
 731
 732 // This is distinct from Torrent piece priority, which is the user's
 733 // preference. Connection piece priority is specific to a connection and is
 734 // used to pseudorandomly avoid connections always requesting the same pieces
 735 // and thus wasting effort.
 736 func (cn *connection) updatePiecePriority(piece pieceIndex) bool {
 737         tpp := cn.t.piecePriority(piece)
 738         if !cn.PeerHasPiece(piece) {
 739                 tpp = PiecePriorityNone
 740         }
 741         if tpp == PiecePriorityNone {
 742                 return cn.stopRequestingPiece(piece)
 743         }
 744         prio := cn.getPieceInclination()[piece]
 745         prio = cn.t.requestStrategy.piecePriority(cn, piece, tpp, prio)
 746         return cn._pieceRequestOrder.Set(bitmap.BitIndex(piece), prio) || cn.shouldRequestWithoutBias()
 747 }
 748
 749 func (cn *connection) getPieceInclination() []int {
 750         if cn.pieceInclination == nil {
 751                 cn.pieceInclination = cn.t.getConnPieceInclination()
 752         }
 753         return cn.pieceInclination
 754 }
 755
 756 func (cn *connection) discardPieceInclination() {
 757         if cn.pieceInclination == nil {
 758                 return
 759         }
 760         cn.t.putPieceInclination(cn.pieceInclination)
 761         cn.pieceInclination = nil
 762 }
 763
 764 func (cn *connection) peerPiecesChanged() {
 765         if cn.t.haveInfo() {
 766                 prioritiesChanged := false
 767                 for i := pieceIndex(0); i < cn.t.numPieces(); i++ {
 768                         if cn.updatePiecePriority(i) {
 769                                 prioritiesChanged = true
 770                         }
 771                 }
 772                 if prioritiesChanged {
 773                         cn.updateRequests()
 774                 }
 775         }
 776 }
 777
 778 func (cn *connection) raisePeerMinPieces(newMin pieceIndex) {
 779         if newMin > cn.peerMinPieces {
 780                 cn.peerMinPieces = newMin
 781         }
 782 }
 783
 784 func (cn *connection) peerSentHave(piece pieceIndex) error {
 785         if cn.t.haveInfo() && piece >= cn.t.numPieces() || piece < 0 {
 786                 return errors.New("invalid piece")
 787         }
 788         if cn.PeerHasPiece(piece) {
 789                 return nil
 790         }
 791         cn.raisePeerMinPieces(piece + 1)
 792         cn._peerPieces.Set(bitmap.BitIndex(piece), true)
 793         if cn.updatePiecePriority(piece) {
 794                 cn.updateRequests()
 795         }
 796         return nil
 797 }
 798
 799 func (cn *connection) peerSentBitfield(bf []bool) error {
 800         cn.peerSentHaveAll = false
 801         if len(bf)%8 != 0 {
 802                 panic("expected bitfield length divisible by 8")
 803         }
 804         // We know that the last byte means that at most the last 7 bits are
 805         // wasted.
 806         cn.raisePeerMinPieces(pieceIndex(len(bf) - 7))
 807         if cn.t.haveInfo() && len(bf) > int(cn.t.numPieces()) {
 808                 // Ignore known excess pieces.
 809                 bf = bf[:cn.t.numPieces()]
 810         }
 811         for i, have := range bf {
 812                 if have {
 813                         cn.raisePeerMinPieces(pieceIndex(i) + 1)
 814                 }
 815                 cn._peerPieces.Set(i, have)
 816         }
 817         cn.peerPiecesChanged()
 818         return nil
 819 }
 820
 821 func (cn *connection) onPeerSentHaveAll() error {
 822         cn.peerSentHaveAll = true
 823         cn._peerPieces.Clear()
 824         cn.peerPiecesChanged()
 825         return nil
 826 }
 827
 828 func (cn *connection) peerSentHaveNone() error {
 829         cn._peerPieces.Clear()
 830         cn.peerSentHaveAll = false
 831         cn.peerPiecesChanged()
 832         return nil
 833 }
 834
 835 func (c *connection) requestPendingMetadata() {
 836         if c.t.haveInfo() {
 837                 return
 838         }
 839         if c.PeerExtensionIDs[pp.ExtensionNameMetadata] == 0 {
 840                 // Peer doesn't support this.
 841                 return
 842         }
 843         // Request metadata pieces that we don't have in a random order.
 844         var pending []int
 845         for index := 0; index < c.t.metadataPieceCount(); index++ {
 846                 if !c.t.haveMetadataPiece(index) && !c.requestedMetadataPiece(index) {
 847                         pending = append(pending, index)
 848                 }
 849         }
 850         rand.Shuffle(len(pending), func(i, j int) { pending[i], pending[j] = pending[j], pending[i] })
 851         for _, i := range pending {
 852                 c.requestMetadataPiece(i)
 853         }
 854 }
 855
 856 func (cn *connection) wroteMsg(msg *pp.Message) {
 857         torrent.Add(fmt.Sprintf("messages written of type %s", msg.Type.String()), 1)
 858         cn.allStats(func(cs *ConnStats) { cs.wroteMsg(msg) })
 859 }
 860
 861 func (cn *connection) readMsg(msg *pp.Message) {
 862         cn.allStats(func(cs *ConnStats) { cs.readMsg(msg) })
 863 }
 864
 865 // After handshake, we know what Torrent and Client stats to include for a
 866 // connection.
 867 func (cn *connection) postHandshakeStats(f func(*ConnStats)) {
 868         t := cn.t
 869         f(&t.stats)
 870         f(&t.cl.stats)
 871 }
 872
 873 // All ConnStats that include this connection. Some objects are not known
 874 // until the handshake is complete, after which it's expected to reconcile the
 875 // differences.
 876 func (cn *connection) allStats(f func(*ConnStats)) {
 877         f(&cn._stats)
 878         if cn.reconciledHandshakeStats {
 879                 cn.postHandshakeStats(f)
 880         }
 881 }
 882
 883 func (cn *connection) wroteBytes(n int64) {
 884         cn.allStats(add(n, func(cs *ConnStats) *Count { return &cs.BytesWritten }))
 885 }
 886
 887 func (cn *connection) readBytes(n int64) {
 888         cn.allStats(add(n, func(cs *ConnStats) *Count { return &cs.BytesRead }))
 889 }
 890
 891 // Returns whether the connection could be useful to us. We're seeding and
 892 // they want data, we don't have metainfo and they can provide it, etc.
 893 func (c *connection) useful() bool {
 894         t := c.t
 895         if c.closed.IsSet() {
 896                 return false
 897         }
 898         if !t.haveInfo() {
 899                 return c.supportsExtension("ut_metadata")
 900         }
 901         if t.seeding() && c.PeerInterested {
 902                 return true
 903         }
 904         if c.peerHasWantedPieces() {
 905                 return true
 906         }
 907         return false
 908 }
 909
 910 func (c *connection) lastHelpful() (ret time.Time) {
 911         ret = c.lastUsefulChunkReceived
 912         if c.t.seeding() && c.lastChunkSent.After(ret) {
 913                 ret = c.lastChunkSent
 914         }
 915         return
 916 }
 917
 918 func (c *connection) fastEnabled() bool {
 919         return c.PeerExtensionBytes.SupportsFast() && c.t.cl.extensionBytes.SupportsFast()
 920 }
 921
 922 func (c *connection) reject(r request) {
 923         if !c.fastEnabled() {
 924                 panic("fast not enabled")
 925         }
 926         c.Post(r.ToMsg(pp.Reject))
 927         delete(c.PeerRequests, r)
 928 }
 929
 930 func (c *connection) onReadRequest(r request) error {
 931         requestedChunkLengths.Add(strconv.FormatUint(r.Length.Uint64(), 10), 1)
 932         if _, ok := c.PeerRequests[r]; ok {
 933                 torrent.Add("duplicate requests received", 1)
 934                 return nil
 935         }
 936         if c.Choked {
 937                 torrent.Add("requests received while choking", 1)
 938                 if c.fastEnabled() {
 939                         torrent.Add("requests rejected while choking", 1)
 940                         c.reject(r)
 941                 }
 942                 return nil
 943         }
 944         if len(c.PeerRequests) >= maxRequests {
 945                 torrent.Add("requests received while queue full", 1)
 946                 if c.fastEnabled() {
 947                         c.reject(r)
 948                 }
 949                 // BEP 6 says we may close here if we choose.
 950                 return nil
 951         }
 952         if !c.t.havePiece(pieceIndex(r.Index)) {
 953                 // This isn't necessarily them screwing up. We can drop pieces
 954                 // from our storage, and can't communicate this to peers
 955                 // except by reconnecting.
 956                 requestsReceivedForMissingPieces.Add(1)
 957                 return fmt.Errorf("peer requested piece we don't have: %v", r.Index.Int())
 958         }
 959         // Check this after we know we have the piece, so that the piece length will be known.
 960         if r.Begin+r.Length > c.t.pieceLength(pieceIndex(r.Index)) {
 961                 torrent.Add("bad requests received", 1)
 962                 return errors.New("bad request")
 963         }
 964         if c.PeerRequests == nil {
 965                 c.PeerRequests = make(map[request]struct{}, maxRequests)
 966         }
 967         c.PeerRequests[r] = struct{}{}
 968         c.tickleWriter()
 969         return nil
 970 }
 971
 972 // Processes incoming BitTorrent wire-protocol messages. The client lock is held upon entry and
 973 // exit. Returning will end the connection.
 974 func (c *connection) mainReadLoop() (err error) {
 975         defer func() {
 976                 if err != nil {
 977                         torrent.Add("connection.mainReadLoop returned with error", 1)
 978                 } else {
 979                         torrent.Add("connection.mainReadLoop returned with no error", 1)
 980                 }
 981         }()
 982         t := c.t
 983         cl := t.cl
 984
 985         decoder := pp.Decoder{
 986                 R:         bufio.NewReaderSize(c.r, 1<<17),
 987                 MaxLength: 256 * 1024,
 988                 Pool:      t.chunkPool,
 989         }
 990         for {
 991                 var msg pp.Message
 992                 func() {
 993                         cl.unlock()
 994                         defer cl.lock()
 995                         err = decoder.Decode(&msg)
 996                 }()
 997                 if t.closed.IsSet() || c.closed.IsSet() || err == io.EOF {
 998                         return nil
 999                 }
1000                 if err != nil {
1001                         return err
1002                 }
1003                 c.readMsg(&msg)
1004                 c.lastMessageReceived = time.Now()
1005                 if msg.Keepalive {
1006                         receivedKeepalives.Add(1)
1007                         continue
1008                 }
1009                 messageTypesReceived.Add(msg.Type.String(), 1)
1010                 if msg.Type.FastExtension() && !c.fastEnabled() {
1011                         return fmt.Errorf("received fast extension message (type=%v) but extension is disabled", msg.Type)
1012                 }
1013                 switch msg.Type {
1014                 case pp.Choke:
1015                         c.PeerChoked = true
1016                         c.deleteAllRequests()
1017                         // We can then reset our interest.
1018                         c.updateRequests()
1019                         c.updateExpectingChunks()
1020                 case pp.Unchoke:
1021                         c.PeerChoked = false
1022                         c.tickleWriter()
1023                         c.updateExpectingChunks()
1024                 case pp.Interested:
1025                         c.PeerInterested = true
1026                         c.tickleWriter()
1027                 case pp.NotInterested:
1028                         c.PeerInterested = false
1029                         // We don't clear their requests since it isn't clear in the spec.
1030                         // We'll probably choke them for this, which will clear them if
1031                         // appropriate, and is clearly specified.
1032                 case pp.Have:
1033                         err = c.peerSentHave(pieceIndex(msg.Index))
1034                 case pp.Bitfield:
1035                         err = c.peerSentBitfield(msg.Bitfield)
1036                 case pp.Request:
1037                         r := newRequestFromMessage(&msg)
1038                         err = c.onReadRequest(r)
1039                 case pp.Piece:
1040                         err = c.receiveChunk(&msg)
1041                         if len(msg.Piece) == int(t.chunkSize) {
1042                                 t.chunkPool.Put(&msg.Piece)
1043                         }
1044                         if err != nil {
1045                                 err = fmt.Errorf("receiving chunk: %s", err)
1046                         }
1047                 case pp.Cancel:
1048                         req := newRequestFromMessage(&msg)
1049                         c.onPeerSentCancel(req)
1050                 case pp.Port:
1051                         ipa, ok := tryIpPortFromNetAddr(c.remoteAddr)
1052                         if !ok {
1053                                 break
1054                         }
1055                         pingAddr := net.UDPAddr{
1056                                 IP:   ipa.IP,
1057                                 Port: ipa.Port,
1058                         }
1059                         if msg.Port != 0 {
1060                                 pingAddr.Port = int(msg.Port)
1061                         }
1062                         cl.eachDhtServer(func(s DhtServer) {
1063                                 go s.Ping(&pingAddr)
1064                         })
1065                 case pp.Suggest:
1066                         torrent.Add("suggests received", 1)
1067                         log.Fmsg("peer suggested piece %d", msg.Index).AddValues(c, msg.Index, debugLogValue).Log(c.t.logger)
1068                         c.updateRequests()
1069                 case pp.HaveAll:
1070                         err = c.onPeerSentHaveAll()
1071                 case pp.HaveNone:
1072                         err = c.peerSentHaveNone()
1073                 case pp.Reject:
1074                         c.deleteRequest(newRequestFromMessage(&msg))
1075                         delete(c.validReceiveChunks, newRequestFromMessage(&msg))
1076                 case pp.AllowedFast:
1077                         torrent.Add("allowed fasts received", 1)
1078                         log.Fmsg("peer allowed fast: %d", msg.Index).AddValues(c, debugLogValue).Log(c.t.logger)
1079                         c.peerAllowedFast.Add(int(msg.Index))
1080                         c.updateRequests()
1081                 case pp.Extended:
1082                         err = c.onReadExtendedMsg(msg.ExtendedID, msg.ExtendedPayload)
1083                 default:
1084                         err = fmt.Errorf("received unknown message type: %#v", msg.Type)
1085                 }
1086                 if err != nil {
1087                         return err
1088                 }
1089         }
1090 }
1091
1092 func (c *connection) onReadExtendedMsg(id pp.ExtensionNumber, payload []byte) (err error) {
1093         defer func() {
1094                 // TODO: Should we still do this?
1095                 if err != nil {
1096                         // These clients use their own extension IDs for outgoing message
1097                         // types, which is incorrect.
1098                         if bytes.HasPrefix(c.PeerID[:], []byte("-SD0100-")) || strings.HasPrefix(string(c.PeerID[:]), "-XL0012-") {
1099                                 err = nil
1100                         }
1101                 }
1102         }()
1103         t := c.t
1104         cl := t.cl
1105         switch id {
1106         case pp.HandshakeExtendedID:
1107                 var d pp.ExtendedHandshakeMessage
1108                 if err := bencode.Unmarshal(payload, &d); err != nil {
1109                         c.t.logger.Printf("error parsing extended handshake message %q: %s", payload, err)
1110                         return errors.Wrap(err, "unmarshalling extended handshake payload")
1111                 }
1112                 if d.Reqq != 0 {
1113                         c.PeerMaxRequests = d.Reqq
1114                 }
1115                 c.PeerClientName = d.V
1116                 if c.PeerExtensionIDs == nil {
1117                         c.PeerExtensionIDs = make(map[pp.ExtensionName]pp.ExtensionNumber, len(d.M))
1118                 }
1119                 for name, id := range d.M {
1120                         if _, ok := c.PeerExtensionIDs[name]; !ok {
1121                                 torrent.Add(fmt.Sprintf("peers supporting extension %q", name), 1)
1122                         }
1123                         c.PeerExtensionIDs[name] = id
1124                 }
1125                 if d.MetadataSize != 0 {
1126                         if err = t.setMetadataSize(d.MetadataSize); err != nil {
1127                                 return errors.Wrapf(err, "setting metadata size to %d", d.MetadataSize)
1128                         }
1129                 }
1130                 c.requestPendingMetadata()
1131                 return nil
1132         case metadataExtendedId:
1133                 err := cl.gotMetadataExtensionMsg(payload, t, c)
1134                 if err != nil {
1135                         return fmt.Errorf("handling metadata extension message: %w", err)
1136                 }
1137                 return nil
1138         case pexExtendedId:
1139                 if cl.config.DisablePEX {
1140                         // TODO: Maybe close the connection. Check that we're not
1141                         // advertising that we support PEX if it's disabled.
1142                         return nil
1143                 }
1144                 var pexMsg pp.PexMsg
1145                 err := bencode.Unmarshal(payload, &pexMsg)
1146                 if err != nil {
1147                         return fmt.Errorf("error unmarshalling PEX message: %s", err)
1148                 }
1149                 torrent.Add("pex added6 peers received", int64(len(pexMsg.Added6)))
1150                 var peers Peers
1151                 peers.AppendFromPex(pexMsg.Added6, pexMsg.Added6Flags)
1152                 peers.AppendFromPex(pexMsg.Added, pexMsg.AddedFlags)
1153                 t.addPeers(peers)
1154                 return nil
1155         default:
1156                 return fmt.Errorf("unexpected extended message ID: %v", id)
1157         }
1158 }
1159
1160 // Set both the Reader and Writer for the connection from a single ReadWriter.
1161 func (cn *connection) setRW(rw io.ReadWriter) {
1162         cn.r = rw
1163         cn.w = rw
1164 }
1165
1166 // Returns the Reader and Writer as a combined ReadWriter.
1167 func (cn *connection) rw() io.ReadWriter {
1168         return struct {
1169                 io.Reader
1170                 io.Writer
1171         }{cn.r, cn.w}
1172 }
1173
1174 // Handle a received chunk from a peer.
1175 func (c *connection) receiveChunk(msg *pp.Message) error {
1176         t := c.t
1177         cl := t.cl
1178         torrent.Add("chunks received", 1)
1179
1180         req := newRequestFromMessage(msg)
1181
1182         if c.PeerChoked {
1183                 torrent.Add("chunks received while choked", 1)
1184         }
1185
1186         if _, ok := c.validReceiveChunks[req]; !ok {
1187                 torrent.Add("chunks received unexpected", 1)
1188                 return errors.New("received unexpected chunk")
1189         }
1190         delete(c.validReceiveChunks, req)
1191
1192         if c.PeerChoked && c.peerAllowedFast.Get(int(req.Index)) {
1193                 torrent.Add("chunks received due to allowed fast", 1)
1194         }
1195
1196         // Request has been satisfied.
1197         if c.deleteRequest(req) {
1198                 if c.expectingChunks() {
1199                         c._chunksReceivedWhileExpecting++
1200                 }
1201         } else {
1202                 torrent.Add("chunks received unwanted", 1)
1203         }
1204
1205         // Do we actually want this chunk?
1206         if t.haveChunk(req) {
1207                 torrent.Add("chunks received wasted", 1)
1208                 c.allStats(add(1, func(cs *ConnStats) *Count { return &cs.ChunksReadWasted }))
1209                 return nil
1210         }
1211
1212         piece := &t.pieces[req.Index]
1213
1214         c.allStats(add(1, func(cs *ConnStats) *Count { return &cs.ChunksReadUseful }))
1215         c.allStats(add(int64(len(msg.Piece)), func(cs *ConnStats) *Count { return &cs.BytesReadUsefulData }))
1216         c.lastUsefulChunkReceived = time.Now()
1217         // if t.fastestConn != c {
1218         // log.Printf("setting fastest connection %p", c)
1219         // }
1220         t.fastestConn = c
1221
1222         // Need to record that it hasn't been written yet, before we attempt to do
1223         // anything with it.
1224         piece.incrementPendingWrites()
1225         // Record that we have the chunk, so we aren't trying to download it while
1226         // waiting for it to be written to storage.
1227         piece.unpendChunkIndex(chunkIndex(req.chunkSpec, t.chunkSize))
1228
1229         // Cancel pending requests for this chunk.
1230         for c := range t.conns {
1231                 c.postCancel(req)
1232         }
1233
1234         err := func() error {
1235                 cl.unlock()
1236                 defer cl.lock()
1237                 concurrentChunkWrites.Add(1)
1238                 defer concurrentChunkWrites.Add(-1)
1239                 // Write the chunk out. Note that the upper bound on chunk writing
1240                 // concurrency will be the number of connections. We write inline with
1241                 // receiving the chunk (with this lock dance), because we want to
1242                 // handle errors synchronously and I haven't thought of a nice way to
1243                 // defer any concurrency to the storage and have that notify the
1244                 // client of errors. TODO: Do that instead.
1245                 return t.writeChunk(int(msg.Index), int64(msg.Begin), msg.Piece)
1246         }()
1247
1248         piece.decrementPendingWrites()
1249
1250         if err != nil {
1251                 panic(fmt.Sprintf("error writing chunk: %v", err))
1252                 t.pendRequest(req)
1253                 t.updatePieceCompletion(pieceIndex(msg.Index))
1254                 return nil
1255         }
1256
1257         c.onDirtiedPiece(pieceIndex(req.Index))
1258
1259         if t.pieceAllDirty(pieceIndex(req.Index)) {
1260                 t.queuePieceCheck(pieceIndex(req.Index))
1261                 // We don't pend all chunks here anymore because we don't want code dependent on the dirty
1262                 // chunk status (such as the haveChunk call above) to have to check all the various other
1263                 // piece states like queued for hash, hashing etc. This does mean that we need to be sure
1264                 // that chunk pieces are pended at an appropriate time later however.
1265         }
1266
1267         cl.event.Broadcast()
1268         // We do this because we've written a chunk, and may change PieceState.Partial.
1269         t.publishPieceChange(pieceIndex(req.Index))
1270
1271         return nil
1272 }
1273
1274 func (c *connection) onDirtiedPiece(piece pieceIndex) {
1275         if c.peerTouchedPieces == nil {
1276                 c.peerTouchedPieces = make(map[pieceIndex]struct{})
1277         }
1278         c.peerTouchedPieces[piece] = struct{}{}
1279         ds := &c.t.pieces[piece].dirtiers
1280         if *ds == nil {
1281                 *ds = make(map[*connection]struct{})
1282         }
1283         (*ds)[c] = struct{}{}
1284 }
1285
1286 func (c *connection) uploadAllowed() bool {
1287         if c.t.cl.config.NoUpload {
1288                 return false
1289         }
1290         if c.t.seeding() {
1291                 return true
1292         }
1293         if !c.peerHasWantedPieces() {
1294                 return false
1295         }
1296         // Don't upload more than 100 KiB more than we download.
1297         if c._stats.BytesWrittenData.Int64() >= c._stats.BytesReadData.Int64()+100<<10 {
1298                 return false
1299         }
1300         return true
1301 }
1302
1303 func (c *connection) setRetryUploadTimer(delay time.Duration) {
1304         if c.uploadTimer == nil {
1305                 c.uploadTimer = time.AfterFunc(delay, c.writerCond.Broadcast)
1306         } else {
1307                 c.uploadTimer.Reset(delay)
1308         }
1309 }
1310
1311 // Also handles choking and unchoking of the remote peer.
1312 func (c *connection) upload(msg func(pp.Message) bool) bool {
1313         // Breaking or completing this loop means we don't want to upload to the
1314         // peer anymore, and we choke them.
1315 another:
1316         for c.uploadAllowed() {
1317                 // We want to upload to the peer.
1318                 if !c.Unchoke(msg) {
1319                         return false
1320                 }
1321                 for r := range c.PeerRequests {
1322                         res := c.t.cl.config.UploadRateLimiter.ReserveN(time.Now(), int(r.Length))
1323                         if !res.OK() {
1324                                 panic(fmt.Sprintf("upload rate limiter burst size < %d", r.Length))
1325                         }
1326                         delay := res.Delay()
1327                         if delay > 0 {
1328                                 res.Cancel()
1329                                 c.setRetryUploadTimer(delay)
1330                                 // Hard to say what to return here.
1331                                 return true
1332                         }
1333                         more, err := c.sendChunk(r, msg)
1334                         if err != nil {
1335                                 i := pieceIndex(r.Index)
1336                                 if c.t.pieceComplete(i) {
1337                                         c.t.updatePieceCompletion(i)
1338                                         if !c.t.pieceComplete(i) {
1339                                                 // We had the piece, but not anymore.
1340                                                 break another
1341                                         }
1342                                 }
1343                                 log.Str("error sending chunk to peer").AddValues(c, r, err).Log(c.t.logger)
1344                                 // If we failed to send a chunk, choke the peer to ensure they
1345                                 // flush all their requests. We've probably dropped a piece,
1346                                 // but there's no way to communicate this to the peer. If they
1347                                 // ask for it again, we'll kick them to allow us to send them
1348                                 // an updated bitfield.
1349                                 break another
1350                         }
1351                         delete(c.PeerRequests, r)
1352                         if !more {
1353                                 return false
1354                         }
1355                         goto another
1356                 }
1357                 return true
1358         }
1359         return c.Choke(msg)
1360 }
1361
1362 func (cn *connection) Drop() {
1363         cn.t.dropConnection(cn)
1364 }
1365
1366 func (cn *connection) netGoodPiecesDirtied() int64 {
1367         return cn._stats.PiecesDirtiedGood.Int64() - cn._stats.PiecesDirtiedBad.Int64()
1368 }
1369
1370 func (c *connection) peerHasWantedPieces() bool {
1371         return !c._pieceRequestOrder.IsEmpty()
1372 }
1373
1374 func (c *connection) numLocalRequests() int {
1375         return len(c.requests)
1376 }
1377
1378 func (c *connection) deleteRequest(r request) bool {
1379         if _, ok := c.requests[r]; !ok {
1380                 return false
1381         }
1382         delete(c.requests, r)
1383         c.updateExpectingChunks()
1384         c.t.requestStrategy.hooks().deletedRequest(r)
1385         pr := c.t.pendingRequests
1386         pr[r]--
1387         n := pr[r]
1388         if n == 0 {
1389                 delete(pr, r)
1390         }
1391         if n < 0 {
1392                 panic(n)
1393         }
1394         c.updateRequests()
1395         for _c := range c.t.conns {
1396                 if !_c.Interested && _c != c && c.PeerHasPiece(pieceIndex(r.Index)) {
1397                         _c.updateRequests()
1398                 }
1399         }
1400         return true
1401 }
1402
1403 func (c *connection) deleteAllRequests() {
1404         for r := range c.requests {
1405                 c.deleteRequest(r)
1406         }
1407         if len(c.requests) != 0 {
1408                 panic(len(c.requests))
1409         }
1410         // for c := range c.t.conns {
1411         //      c.tickleWriter()
1412         // }
1413 }
1414
1415 func (c *connection) tickleWriter() {
1416         c.writerCond.Broadcast()
1417 }
1418
1419 func (c *connection) postCancel(r request) bool {
1420         if !c.deleteRequest(r) {
1421                 return false
1422         }
1423         c.Post(makeCancelMessage(r))
1424         return true
1425 }
1426
1427 func (c *connection) sendChunk(r request, msg func(pp.Message) bool) (more bool, err error) {
1428         // Count the chunk being sent, even if it isn't.
1429         b := make([]byte, r.Length)
1430         p := c.t.info.Piece(int(r.Index))
1431         n, err := c.t.readAt(b, p.Offset()+int64(r.Begin))
1432         if n != len(b) {
1433                 if err == nil {
1434                         panic("expected error")
1435                 }
1436                 return
1437         } else if err == io.EOF {
1438                 err = nil
1439         }
1440         more = msg(pp.Message{
1441                 Type:  pp.Piece,
1442                 Index: r.Index,
1443                 Begin: r.Begin,
1444                 Piece: b,
1445         })
1446         c.lastChunkSent = time.Now()
1447         return
1448 }
1449
1450 func (c *connection) setTorrent(t *Torrent) {
1451         if c.t != nil {
1452                 panic("connection already associated with a torrent")
1453         }
1454         c.t = t
1455         c.logger.Printf("torrent=%v", t)
1456         t.reconcileHandshakeStats(c)
1457 }
1458
1459 func (c *connection) peerPriority() peerPriority {
1460         return bep40PriorityIgnoreError(c.remoteIpPort(), c.t.cl.publicAddr(c.remoteIp()))
1461 }
1462
1463 func (c *connection) remoteIp() net.IP {
1464         return addrIpOrNil(c.remoteAddr)
1465 }
1466
1467 func (c *connection) remoteIpPort() IpPort {
1468         ipa, _ := tryIpPortFromNetAddr(c.remoteAddr)
1469         return IpPort{ipa.IP, uint16(ipa.Port)}
1470 }
1471
1472 func (c *connection) String() string {
1473         return fmt.Sprintf("connection %p", c)
1474 }
1475
1476 func (c *connection) trust() connectionTrust {
1477         return connectionTrust{c.trusted, c.netGoodPiecesDirtied()}
1478 }
1479
1480 type connectionTrust struct {
1481         Implicit            bool
1482         NetGoodPiecesDirted int64
1483 }
1484
1485 func (l connectionTrust) Less(r connectionTrust) bool {
1486         return multiless.New().Bool(l.Implicit, r.Implicit).Int64(l.NetGoodPiecesDirted, r.NetGoodPiecesDirted).Less()
1487 }
1488
1489 func (cn *connection) requestStrategyConnection() requestStrategyConnection {
1490         return cn
1491 }
1492
1493 func (cn *connection) chunksReceivedWhileExpecting() int64 {
1494         return cn._chunksReceivedWhileExpecting
1495 }
1496
1497 func (cn *connection) fastest() bool {
1498         return cn == cn.t.fastestConn
1499 }
1500
1501 func (cn *connection) peerMaxRequests() int {
1502         return cn.PeerMaxRequests
1503 }
1504
1505 func (cn *connection) peerPieces() bitmap.Bitmap {
1506         ret := cn._peerPieces.Copy()
1507         if cn.peerSentHaveAll {
1508                 ret.AddRange(0, cn.t.numPieces())
1509         }
1510         return ret
1511 }
1512
1513 func (cn *connection) pieceRequestOrder() *prioritybitmap.PriorityBitmap {
1514         return &cn._pieceRequestOrder
1515 }
1516
1517 func (cn *connection) stats() *ConnStats {
1518         return &cn._stats
1519 }
1520
1521 func (cn *connection) torrent() requestStrategyTorrent {
1522         return cn.t.requestStrategyTorrent()
1523 }