client.go

   1 package torrent
   2
   3 import (
   4         "bufio"
   5         "bytes"
   6         "container/heap"
   7         "crypto/rand"
   8         "crypto/sha1"
   9         "encoding/hex"
  10         "errors"
  11         "expvar"
  12         "fmt"
  13         "io"
  14         "log"
  15         "math/big"
  16         mathRand "math/rand"
  17         "net"
  18         "net/url"
  19         "os"
  20         "path/filepath"
  21         "sort"
  22         "strconv"
  23         "strings"
  24         "syscall"
  25         "time"
  26
  27         "github.com/anacrolix/sync"
  28         "github.com/anacrolix/utp"
  29         "github.com/bradfitz/iter"
  30
  31         "github.com/anacrolix/torrent/bencode"
  32         "github.com/anacrolix/torrent/data"
  33         filePkg "github.com/anacrolix/torrent/data/file"
  34         "github.com/anacrolix/torrent/dht"
  35         "github.com/anacrolix/torrent/internal/pieceordering"
  36         "github.com/anacrolix/torrent/iplist"
  37         "github.com/anacrolix/torrent/logonce"
  38         "github.com/anacrolix/torrent/metainfo"
  39         "github.com/anacrolix/torrent/mse"
  40         pp "github.com/anacrolix/torrent/peer_protocol"
  41         "github.com/anacrolix/torrent/tracker"
  42         . "github.com/anacrolix/torrent/util"
  43 )
  44
  45 var (
  46         unusedDownloadedChunksCount = expvar.NewInt("unusedDownloadedChunksCount")
  47         chunksDownloadedCount       = expvar.NewInt("chunksDownloadedCount")
  48         peersFoundByDHT             = expvar.NewInt("peersFoundByDHT")
  49         peersFoundByPEX             = expvar.NewInt("peersFoundByPEX")
  50         peersFoundByTracker         = expvar.NewInt("peersFoundByTracker")
  51         uploadChunksPosted          = expvar.NewInt("uploadChunksPosted")
  52         unexpectedCancels           = expvar.NewInt("unexpectedCancels")
  53         postedCancels               = expvar.NewInt("postedCancels")
  54         duplicateConnsAvoided       = expvar.NewInt("duplicateConnsAvoided")
  55         failedPieceHashes           = expvar.NewInt("failedPieceHashes")
  56         unsuccessfulDials           = expvar.NewInt("unsuccessfulDials")
  57         successfulDials             = expvar.NewInt("successfulDials")
  58         acceptedConns               = expvar.NewInt("acceptedConns")
  59         inboundConnsBlocked         = expvar.NewInt("inboundConnsBlocked")
  60         peerExtensions              = expvar.NewMap("peerExtensions")
  61         // Count of connections to peer with same client ID.
  62         connsToSelf = expvar.NewInt("connsToSelf")
  63         // Number of completed connections to a client we're already connected with.
  64         duplicateClientConns       = expvar.NewInt("duplicateClientConns")
  65         receivedMessageTypes       = expvar.NewMap("receivedMessageTypes")
  66         supportedExtensionMessages = expvar.NewMap("supportedExtensionMessages")
  67 )
  68
  69 const (
  70         // Justification for set bits follows.
  71         //
  72         // Extension protocol: http://www.bittorrent.org/beps/bep_0010.html ([5]|=0x10)
  73         // DHT: http://www.bittorrent.org/beps/bep_0005.html ([7]|=1)
  74         // Fast Extension:
  75         //       http://bittorrent.org/beps/bep_0006.html ([7]|=4)
  76         //   Disabled until AllowedFast is implemented
  77         defaultExtensionBytes = "\x00\x00\x00\x00\x00\x10\x00\x01"
  78
  79         socketsPerTorrent     = 40
  80         torrentPeersHighWater = 200
  81         torrentPeersLowWater  = 50
  82
  83         // Limit how long handshake can take. This is to reduce the lingering
  84         // impact of a few bad apples. 4s loses 1% of successful handshakes that
  85         // are obtained with 60s timeout, and 5% of unsuccessful handshakes.
  86         btHandshakeTimeout = 4 * time.Second
  87         handshakesTimeout  = 20 * time.Second
  88
  89         pruneInterval = 10 * time.Second
  90
  91         metadataExtendedId = iota + 1 // 0 is reserved for deleting keys
  92         pexExtendedId
  93
  94         extendedHandshakeClientVersion = "go.torrent dev 20140825"
  95 )
  96
  97 // Currently doesn't really queue, but should in the future.
  98 func (cl *Client) queuePieceCheck(t *torrent, pieceIndex pp.Integer) {
  99         piece := t.Pieces[pieceIndex]
 100         if piece.QueuedForHash {
 101                 return
 102         }
 103         piece.QueuedForHash = true
 104         go cl.verifyPiece(t, pieceIndex)
 105 }
 106
 107 // Queue a piece check if one isn't already queued, and the piece has never
 108 // been checked before.
 109 func (cl *Client) queueFirstHash(t *torrent, piece int) {
 110         p := t.Pieces[piece]
 111         if p.EverHashed || p.Hashing || p.QueuedForHash || t.pieceComplete(piece) {
 112                 return
 113         }
 114         cl.queuePieceCheck(t, pp.Integer(piece))
 115 }
 116
 117 type Client struct {
 118         halfOpenLimit  int
 119         peerID         [20]byte
 120         listeners      []net.Listener
 121         utpSock        *utp.Socket
 122         dHT            *dht.Server
 123         ipBlockList    *iplist.IPList
 124         bannedTorrents map[InfoHash]struct{}
 125         config         Config
 126         pruneTimer     *time.Timer
 127         extensionBytes peerExtensionBytes
 128         // Set of addresses that have our client ID. This intentionally will
 129         // include ourselves if we end up trying to connect to our own address
 130         // through legitimate channels.
 131         dopplegangerAddrs map[string]struct{}
 132
 133         torrentDataOpener TorrentDataOpener
 134
 135         mu    sync.RWMutex
 136         event sync.Cond
 137         quit  chan struct{}
 138
 139         torrents map[InfoHash]*torrent
 140 }
 141
 142 func (me *Client) IPBlockList() *iplist.IPList {
 143         me.mu.Lock()
 144         defer me.mu.Unlock()
 145         return me.ipBlockList
 146 }
 147
 148 func (me *Client) SetIPBlockList(list *iplist.IPList) {
 149         me.mu.Lock()
 150         defer me.mu.Unlock()
 151         me.ipBlockList = list
 152         if me.dHT != nil {
 153                 me.dHT.SetIPBlockList(list)
 154         }
 155 }
 156
 157 func (me *Client) PeerID() string {
 158         return string(me.peerID[:])
 159 }
 160
 161 func (me *Client) ListenAddr() (addr net.Addr) {
 162         for _, l := range me.listeners {
 163                 if addr != nil && l.Addr().String() != addr.String() {
 164                         panic("listeners exist on different addresses")
 165                 }
 166                 addr = l.Addr()
 167         }
 168         return
 169 }
 170
 171 type hashSorter struct {
 172         Hashes []InfoHash
 173 }
 174
 175 func (me hashSorter) Len() int {
 176         return len(me.Hashes)
 177 }
 178
 179 func (me hashSorter) Less(a, b int) bool {
 180         return (&big.Int{}).SetBytes(me.Hashes[a][:]).Cmp((&big.Int{}).SetBytes(me.Hashes[b][:])) < 0
 181 }
 182
 183 func (me hashSorter) Swap(a, b int) {
 184         me.Hashes[a], me.Hashes[b] = me.Hashes[b], me.Hashes[a]
 185 }
 186
 187 func (cl *Client) sortedTorrents() (ret []*torrent) {
 188         var hs hashSorter
 189         for ih := range cl.torrents {
 190                 hs.Hashes = append(hs.Hashes, ih)
 191         }
 192         sort.Sort(hs)
 193         for _, ih := range hs.Hashes {
 194                 ret = append(ret, cl.torrent(ih))
 195         }
 196         return
 197 }
 198
 199 // Writes out a human readable status of the client, such as for writing to a
 200 // HTTP status page.
 201 func (cl *Client) WriteStatus(_w io.Writer) {
 202         cl.mu.RLock()
 203         defer cl.mu.RUnlock()
 204         w := bufio.NewWriter(_w)
 205         defer w.Flush()
 206         if addr := cl.ListenAddr(); addr != nil {
 207                 fmt.Fprintf(w, "Listening on %s\n", cl.ListenAddr())
 208         } else {
 209                 fmt.Fprintln(w, "Not listening!")
 210         }
 211         fmt.Fprintf(w, "Peer ID: %q\n", cl.peerID)
 212         if cl.dHT != nil {
 213                 dhtStats := cl.dHT.Stats()
 214                 fmt.Fprintf(w, "DHT nodes: %d (%d good)\n", dhtStats.Nodes, dhtStats.GoodNodes)
 215                 fmt.Fprintf(w, "DHT Server ID: %x\n", cl.dHT.ID())
 216                 fmt.Fprintf(w, "DHT port: %d\n", addrPort(cl.dHT.Addr()))
 217                 fmt.Fprintf(w, "DHT announces: %d\n", dhtStats.ConfirmedAnnounces)
 218                 fmt.Fprintf(w, "Outstanding transactions: %d\n", dhtStats.OutstandingTransactions)
 219         }
 220         fmt.Fprintf(w, "# Torrents: %d\n", len(cl.torrents))
 221         fmt.Fprintln(w)
 222         for _, t := range cl.sortedTorrents() {
 223                 if t.Name() == "" {
 224                         fmt.Fprint(w, "<unknown name>")
 225                 } else {
 226                         fmt.Fprint(w, t.Name())
 227                 }
 228                 fmt.Fprint(w, "\n")
 229                 if t.haveInfo() {
 230                         fmt.Fprintf(w, "%f%% of %d bytes", 100*(1-float32(t.bytesLeft())/float32(t.Length())), t.Length())
 231                 } else {
 232                         w.WriteString("<missing metainfo>")
 233                 }
 234                 fmt.Fprint(w, "\n")
 235                 t.writeStatus(w)
 236                 fmt.Fprintln(w)
 237         }
 238 }
 239
 240 // A Data that implements this has a streaming interface that should be
 241 // preferred over ReadAt. For example, the data is stored in blocks on the
 242 // network and have a fixed cost to open.
 243 type SectionOpener interface {
 244         // Open a ReadCloser at the given offset into torrent data. n is how many
 245         // bytes we intend to read.
 246         OpenSection(off, n int64) (io.ReadCloser, error)
 247 }
 248
 249 func dataReadAt(d data.Data, b []byte, off int64) (n int, err error) {
 250         // defer func() {
 251         //      if err == io.ErrUnexpectedEOF && n != 0 {
 252         //              err = nil
 253         //      }
 254         // }()
 255         // log.Println("data read at", len(b), off)
 256 again:
 257         if ra, ok := d.(io.ReaderAt); ok {
 258                 return ra.ReadAt(b, off)
 259         }
 260         if so, ok := d.(SectionOpener); ok {
 261                 var rc io.ReadCloser
 262                 rc, err = so.OpenSection(off, int64(len(b)))
 263                 if err != nil {
 264                         return
 265                 }
 266                 defer rc.Close()
 267                 return io.ReadFull(rc, b)
 268         }
 269         if dp, ok := super(d); ok {
 270                 d = dp.(data.Data)
 271                 goto again
 272         }
 273         panic(fmt.Sprintf("can't read from %T", d))
 274 }
 275
 276 // Calculates the number of pieces to set to Readahead priority, after the
 277 // Now, and Next pieces.
 278 func readaheadPieces(readahead, pieceLength int64) int {
 279         return int((readahead+pieceLength-1)/pieceLength - 1)
 280 }
 281
 282 func (cl *Client) readRaisePiecePriorities(t *torrent, off, readaheadBytes int64) {
 283         index := int(off / int64(t.usualPieceSize()))
 284         cl.raisePiecePriority(t, index, piecePriorityNow)
 285         index++
 286         if index >= t.numPieces() {
 287                 return
 288         }
 289         cl.raisePiecePriority(t, index, piecePriorityNext)
 290         for range iter.N(readaheadPieces(readaheadBytes, t.Info.PieceLength)) {
 291                 index++
 292                 if index >= t.numPieces() {
 293                         break
 294                 }
 295                 cl.raisePiecePriority(t, index, piecePriorityReadahead)
 296         }
 297 }
 298
 299 func (cl *Client) addUrgentRequests(t *torrent, off int64, n int) {
 300         for n > 0 {
 301                 req, ok := t.offsetRequest(off)
 302                 if !ok {
 303                         break
 304                 }
 305                 if _, ok := t.urgent[req]; !ok && !t.haveChunk(req) {
 306                         if t.urgent == nil {
 307                                 t.urgent = make(map[request]struct{}, (n+chunkSize-1)/chunkSize)
 308                         }
 309                         t.urgent[req] = struct{}{}
 310                         cl.event.Broadcast() // Why?
 311                         index := int(req.Index)
 312                         cl.queueFirstHash(t, index)
 313                         cl.pieceChanged(t, index)
 314                 }
 315                 reqOff := t.requestOffset(req)
 316                 n1 := req.Length - pp.Integer(off-reqOff)
 317                 off += int64(n1)
 318                 n -= int(n1)
 319         }
 320         // log.Print(t.urgent)
 321 }
 322
 323 func (cl *Client) configDir() string {
 324         if cl.config.ConfigDir == "" {
 325                 return filepath.Join(os.Getenv("HOME"), ".config/torrent")
 326         }
 327         return cl.config.ConfigDir
 328 }
 329
 330 func (cl *Client) ConfigDir() string {
 331         return cl.configDir()
 332 }
 333
 334 func (t *torrent) connPendPiece(c *connection, piece int) {
 335         c.pendPiece(piece, t.Pieces[piece].Priority)
 336 }
 337
 338 func (cl *Client) raisePiecePriority(t *torrent, piece int, priority piecePriority) {
 339         if t.Pieces[piece].Priority < priority {
 340                 cl.event.Broadcast()
 341                 cl.prioritizePiece(t, piece, priority)
 342         }
 343 }
 344
 345 func (cl *Client) prioritizePiece(t *torrent, piece int, priority piecePriority) {
 346         if t.havePiece(piece) {
 347                 return
 348         }
 349         cl.queueFirstHash(t, piece)
 350         t.Pieces[piece].Priority = priority
 351         cl.pieceChanged(t, piece)
 352 }
 353
 354 func (cl *Client) setEnvBlocklist() (err error) {
 355         filename := os.Getenv("TORRENT_BLOCKLIST_FILE")
 356         defaultBlocklist := filename == ""
 357         if defaultBlocklist {
 358                 filename = filepath.Join(cl.configDir(), "blocklist")
 359         }
 360         f, err := os.Open(filename)
 361         if err != nil {
 362                 if defaultBlocklist {
 363                         err = nil
 364                 }
 365                 return
 366         }
 367         defer f.Close()
 368         var ranges []iplist.Range
 369         uniqStrs := make(map[string]string)
 370         scanner := bufio.NewScanner(f)
 371         lineNum := 1
 372         for scanner.Scan() {
 373                 r, ok, lineErr := iplist.ParseBlocklistP2PLine(scanner.Bytes())
 374                 if lineErr != nil {
 375                         err = fmt.Errorf("error reading torrent blocklist line %d: %s", lineNum, lineErr)
 376                         return
 377                 }
 378                 lineNum++
 379                 if !ok {
 380                         continue
 381                 }
 382                 if s, ok := uniqStrs[r.Description]; ok {
 383                         r.Description = s
 384                 } else {
 385                         uniqStrs[r.Description] = r.Description
 386                 }
 387                 ranges = append(ranges, r)
 388         }
 389         err = scanner.Err()
 390         if err != nil {
 391                 err = fmt.Errorf("error reading torrent blocklist: %s", err)
 392                 return
 393         }
 394         cl.ipBlockList = iplist.New(ranges)
 395         return
 396 }
 397
 398 func (cl *Client) initBannedTorrents() error {
 399         f, err := os.Open(filepath.Join(cl.configDir(), "banned_infohashes"))
 400         if err != nil {
 401                 if os.IsNotExist(err) {
 402                         return nil
 403                 }
 404                 return fmt.Errorf("error opening banned infohashes file: %s", err)
 405         }
 406         defer f.Close()
 407         scanner := bufio.NewScanner(f)
 408         cl.bannedTorrents = make(map[InfoHash]struct{})
 409         for scanner.Scan() {
 410                 if strings.HasPrefix(strings.TrimSpace(scanner.Text()), "#") {
 411                         continue
 412                 }
 413                 var ihs string
 414                 n, err := fmt.Sscanf(scanner.Text(), "%x", &ihs)
 415                 if err != nil {
 416                         return fmt.Errorf("error reading infohash: %s", err)
 417                 }
 418                 if n != 1 {
 419                         continue
 420                 }
 421                 if len(ihs) != 20 {
 422                         return errors.New("bad infohash")
 423                 }
 424                 var ih InfoHash
 425                 CopyExact(&ih, ihs)
 426                 cl.bannedTorrents[ih] = struct{}{}
 427         }
 428         if err := scanner.Err(); err != nil {
 429                 return fmt.Errorf("error scanning file: %s", err)
 430         }
 431         return nil
 432 }
 433
 434 // Creates a new client. Clients contain zero or more Torrents.
 435 func NewClient(cfg *Config) (cl *Client, err error) {
 436         if cfg == nil {
 437                 cfg = &Config{}
 438         }
 439
 440         defer func() {
 441                 if err != nil {
 442                         cl = nil
 443                 }
 444         }()
 445         cl = &Client{
 446                 halfOpenLimit: socketsPerTorrent,
 447                 config:        *cfg,
 448                 torrentDataOpener: func(md *metainfo.Info) data.Data {
 449                         return filePkg.TorrentData(md, cfg.DataDir)
 450                 },
 451                 dopplegangerAddrs: make(map[string]struct{}),
 452
 453                 quit:     make(chan struct{}),
 454                 torrents: make(map[InfoHash]*torrent),
 455         }
 456         CopyExact(&cl.extensionBytes, defaultExtensionBytes)
 457         cl.event.L = &cl.mu
 458         if cfg.TorrentDataOpener != nil {
 459                 cl.torrentDataOpener = cfg.TorrentDataOpener
 460         }
 461
 462         if !cfg.NoDefaultBlocklist {
 463                 err = cl.setEnvBlocklist()
 464                 if err != nil {
 465                         return
 466                 }
 467         }
 468
 469         if err = cl.initBannedTorrents(); err != nil {
 470                 err = fmt.Errorf("error initing banned torrents: %s", err)
 471                 return
 472         }
 473
 474         if cfg.PeerID != "" {
 475                 CopyExact(&cl.peerID, cfg.PeerID)
 476         } else {
 477                 o := copy(cl.peerID[:], bep20)
 478                 _, err = rand.Read(cl.peerID[o:])
 479                 if err != nil {
 480                         panic("error generating peer id")
 481                 }
 482         }
 483
 484         // Returns the laddr string to listen on for the next Listen call.
 485         listenAddr := func() string {
 486                 if addr := cl.ListenAddr(); addr != nil {
 487                         return addr.String()
 488                 }
 489                 if cfg.ListenAddr == "" {
 490                         // IPv6 isn't well supported with blocklists, or with trackers and
 491                         // DHT.
 492                         return "0.0.0.0:50007"
 493                 }
 494                 return cfg.ListenAddr
 495         }
 496         if !cl.config.DisableTCP {
 497                 var l net.Listener
 498                 l, err = net.Listen("tcp", listenAddr())
 499                 if err != nil {
 500                         return
 501                 }
 502                 cl.listeners = append(cl.listeners, l)
 503                 go cl.acceptConnections(l, false)
 504         }
 505         if !cl.config.DisableUTP {
 506                 cl.utpSock, err = utp.NewSocket(listenAddr())
 507                 if err != nil {
 508                         return
 509                 }
 510                 cl.listeners = append(cl.listeners, cl.utpSock)
 511                 go cl.acceptConnections(cl.utpSock, true)
 512         }
 513         if !cfg.NoDHT {
 514                 dhtCfg := cfg.DHTConfig
 515                 if dhtCfg == nil {
 516                         dhtCfg = &dht.ServerConfig{}
 517                 }
 518                 if dhtCfg.Addr == "" {
 519                         dhtCfg.Addr = listenAddr()
 520                 }
 521                 if dhtCfg.Conn == nil && cl.utpSock != nil {
 522                         dhtCfg.Conn = cl.utpSock.PacketConn()
 523                 }
 524                 cl.dHT, err = dht.NewServer(dhtCfg)
 525                 if err != nil {
 526                         return
 527                 }
 528                 if cl.ipBlockList != nil {
 529                         cl.dHT.SetIPBlockList(cl.ipBlockList)
 530                 }
 531         }
 532
 533         return
 534 }
 535
 536 func (cl *Client) stopped() bool {
 537         select {
 538         case <-cl.quit:
 539                 return true
 540         default:
 541                 return false
 542         }
 543 }
 544
 545 // Stops the client. All connections to peers are closed and all activity will
 546 // come to a halt.
 547 func (me *Client) Close() {
 548         me.mu.Lock()
 549         defer me.mu.Unlock()
 550         close(me.quit)
 551         for _, l := range me.listeners {
 552                 l.Close()
 553         }
 554         me.event.Broadcast()
 555         for _, t := range me.torrents {
 556                 t.close()
 557         }
 558 }
 559
 560 var ipv6BlockRange = iplist.Range{Description: "non-IPv4 address"}
 561
 562 func (cl *Client) ipBlockRange(ip net.IP) (r *iplist.Range) {
 563         if cl.ipBlockList == nil {
 564                 return
 565         }
 566         ip4 := ip.To4()
 567         if ip4 == nil {
 568                 log.Printf("blocking non-IPv4 address: %s", ip)
 569                 r = &ipv6BlockRange
 570                 return
 571         }
 572         r = cl.ipBlockList.Lookup(ip4)
 573         return
 574 }
 575
 576 func (cl *Client) waitAccept() {
 577         cl.mu.Lock()
 578         defer cl.mu.Unlock()
 579         for {
 580                 for _, t := range cl.torrents {
 581                         if cl.wantConns(t) {
 582                                 return
 583                         }
 584                 }
 585                 cl.event.Wait()
 586         }
 587 }
 588
 589 func (cl *Client) acceptConnections(l net.Listener, utp bool) {
 590         for {
 591                 cl.waitAccept()
 592                 // We accept all connections immediately, because we don't know what
 593                 // torrent they're for.
 594                 conn, err := l.Accept()
 595                 select {
 596                 case <-cl.quit:
 597                         if conn != nil {
 598                                 conn.Close()
 599                         }
 600                         return
 601                 default:
 602                 }
 603                 if err != nil {
 604                         log.Print(err)
 605                         return
 606                 }
 607                 acceptedConns.Add(1)
 608                 cl.mu.RLock()
 609                 doppleganger := cl.dopplegangerAddr(conn.RemoteAddr().String())
 610                 blockRange := cl.ipBlockRange(AddrIP(conn.RemoteAddr()))
 611                 cl.mu.RUnlock()
 612                 if blockRange != nil || doppleganger {
 613                         inboundConnsBlocked.Add(1)
 614                         // log.Printf("inbound connection from %s blocked by %s", conn.RemoteAddr(), blockRange)
 615                         conn.Close()
 616                         continue
 617                 }
 618                 go cl.incomingConnection(conn, utp)
 619         }
 620 }
 621
 622 func (cl *Client) incomingConnection(nc net.Conn, utp bool) {
 623         defer nc.Close()
 624         if tc, ok := nc.(*net.TCPConn); ok {
 625                 tc.SetLinger(0)
 626         }
 627         c := newConnection()
 628         c.conn = nc
 629         c.rw = nc
 630         c.Discovery = peerSourceIncoming
 631         c.uTP = utp
 632         err := cl.runReceivedConn(c)
 633         if err != nil {
 634                 // log.Print(err)
 635         }
 636 }
 637
 638 // Returns a handle to the given torrent, if it's present in the client.
 639 func (cl *Client) Torrent(ih InfoHash) (T Torrent, ok bool) {
 640         cl.mu.Lock()
 641         defer cl.mu.Unlock()
 642         t, ok := cl.torrents[ih]
 643         if !ok {
 644                 return
 645         }
 646         T = Torrent{cl, t, t.gotMetainfo}
 647         return
 648 }
 649
 650 func (me *Client) torrent(ih InfoHash) *torrent {
 651         return me.torrents[ih]
 652 }
 653
 654 type dialResult struct {
 655         Conn net.Conn
 656         UTP  bool
 657 }
 658
 659 func doDial(dial func(addr string, t *torrent) (net.Conn, error), ch chan dialResult, utp bool, addr string, t *torrent) {
 660         conn, err := dial(addr, t)
 661         if err != nil {
 662                 if conn != nil {
 663                         conn.Close()
 664                 }
 665                 conn = nil // Pedantic
 666         }
 667         ch <- dialResult{conn, utp}
 668         if err == nil {
 669                 successfulDials.Add(1)
 670                 return
 671         }
 672         unsuccessfulDials.Add(1)
 673         if netErr, ok := err.(net.Error); ok && netErr.Timeout() {
 674                 return
 675         }
 676         if netOpErr, ok := err.(*net.OpError); ok {
 677                 switch netOpErr.Err {
 678                 case syscall.ECONNREFUSED, syscall.EHOSTUNREACH:
 679                         return
 680                 }
 681         }
 682         if err != nil {
 683                 log.Printf("error dialing %s: %s", addr, err)
 684                 return
 685         }
 686 }
 687
 688 func reducedDialTimeout(max time.Duration, halfOpenLimit int, pendingPeers int) (ret time.Duration) {
 689         ret = max / time.Duration((pendingPeers+halfOpenLimit)/halfOpenLimit)
 690         if ret < minDialTimeout {
 691                 ret = minDialTimeout
 692         }
 693         return
 694 }
 695
 696 func (me *Client) dopplegangerAddr(addr string) bool {
 697         _, ok := me.dopplegangerAddrs[addr]
 698         return ok
 699 }
 700
 701 // Start the process of connecting to the given peer for the given torrent if
 702 // appropriate.
 703 func (me *Client) initiateConn(peer Peer, t *torrent) {
 704         if peer.Id == me.peerID {
 705                 return
 706         }
 707         addr := net.JoinHostPort(peer.IP.String(), fmt.Sprintf("%d", peer.Port))
 708         if me.dopplegangerAddr(addr) || t.addrActive(addr) {
 709                 duplicateConnsAvoided.Add(1)
 710                 return
 711         }
 712         if r := me.ipBlockRange(peer.IP); r != nil {
 713                 log.Printf("outbound connect to %s blocked by IP blocklist rule %s", peer.IP, r)
 714                 return
 715         }
 716         t.HalfOpen[addr] = struct{}{}
 717         go me.outgoingConnection(t, addr, peer.Source)
 718 }
 719
 720 func (me *Client) dialTimeout(t *torrent) time.Duration {
 721         me.mu.Lock()
 722         pendingPeers := len(t.Peers)
 723         me.mu.Unlock()
 724         return reducedDialTimeout(nominalDialTimeout, me.halfOpenLimit, pendingPeers)
 725 }
 726
 727 func (me *Client) dialTCP(addr string, t *torrent) (c net.Conn, err error) {
 728         c, err = net.DialTimeout("tcp", addr, me.dialTimeout(t))
 729         if err == nil {
 730                 c.(*net.TCPConn).SetLinger(0)
 731         }
 732         return
 733 }
 734
 735 func (me *Client) dialUTP(addr string, t *torrent) (c net.Conn, err error) {
 736         return me.utpSock.DialTimeout(addr, me.dialTimeout(t))
 737 }
 738
 739 // Returns a connection over UTP or TCP.
 740 func (me *Client) dial(addr string, t *torrent) (conn net.Conn, utp bool) {
 741         // Initiate connections via TCP and UTP simultaneously. Use the first one
 742         // that succeeds.
 743         left := 0
 744         if !me.config.DisableUTP {
 745                 left++
 746         }
 747         if !me.config.DisableTCP {
 748                 left++
 749         }
 750         resCh := make(chan dialResult, left)
 751         if !me.config.DisableUTP {
 752                 go doDial(me.dialUTP, resCh, true, addr, t)
 753         }
 754         if !me.config.DisableTCP {
 755                 go doDial(me.dialTCP, resCh, false, addr, t)
 756         }
 757         var res dialResult
 758         // Wait for a successful connection.
 759         for ; left > 0 && res.Conn == nil; left-- {
 760                 res = <-resCh
 761         }
 762         if left > 0 {
 763                 // There are still incompleted dials.
 764                 go func() {
 765                         for ; left > 0; left-- {
 766                                 conn := (<-resCh).Conn
 767                                 if conn != nil {
 768                                         conn.Close()
 769                                 }
 770                         }
 771                 }()
 772         }
 773         conn = res.Conn
 774         utp = res.UTP
 775         return
 776 }
 777
 778 func (me *Client) noLongerHalfOpen(t *torrent, addr string) {
 779         if _, ok := t.HalfOpen[addr]; !ok {
 780                 panic("invariant broken")
 781         }
 782         delete(t.HalfOpen, addr)
 783         me.openNewConns(t)
 784 }
 785
 786 // Returns nil connection and nil error if no connection could be established
 787 // for valid reasons.
 788 func (me *Client) establishOutgoingConn(t *torrent, addr string) (c *connection, err error) {
 789         handshakesConnection := func(nc net.Conn, encrypted, utp bool) (c *connection, err error) {
 790                 c = newConnection()
 791                 c.conn = nc
 792                 c.rw = nc
 793                 c.encrypted = encrypted
 794                 c.uTP = utp
 795                 err = nc.SetDeadline(time.Now().Add(handshakesTimeout))
 796                 if err != nil {
 797                         return
 798                 }
 799                 ok, err := me.initiateHandshakes(c, t)
 800                 if !ok {
 801                         c = nil
 802                 }
 803                 return
 804         }
 805         nc, utp := me.dial(addr, t)
 806         if nc == nil {
 807                 return
 808         }
 809         c, err = handshakesConnection(nc, !me.config.DisableEncryption, utp)
 810         if err != nil {
 811                 nc.Close()
 812                 return
 813         } else if c != nil {
 814                 return
 815         }
 816         nc.Close()
 817         if utp {
 818                 nc, err = me.dialUTP(addr, t)
 819         } else {
 820                 nc, err = me.dialTCP(addr, t)
 821         }
 822         if err != nil {
 823                 err = fmt.Errorf("error dialing for unencrypted connection: %s", err)
 824                 return
 825         }
 826         c, err = handshakesConnection(nc, false, utp)
 827         if err != nil {
 828                 nc.Close()
 829         }
 830         return
 831 }
 832
 833 // Called to dial out and run a connection. The addr we're given is already
 834 // considered half-open.
 835 func (me *Client) outgoingConnection(t *torrent, addr string, ps peerSource) {
 836         c, err := me.establishOutgoingConn(t, addr)
 837         me.mu.Lock()
 838         defer me.mu.Unlock()
 839         // Don't release lock between here and addConnection, unless it's for
 840         // failure.
 841         me.noLongerHalfOpen(t, addr)
 842         if err != nil {
 843                 return
 844         }
 845         if c == nil {
 846                 return
 847         }
 848         defer c.Close()
 849         c.Discovery = ps
 850         err = me.runInitiatedHandshookConn(c, t)
 851         if err != nil {
 852                 // log.Print(err)
 853         }
 854 }
 855
 856 // The port number for incoming peer connections. 0 if the client isn't
 857 // listening.
 858 func (cl *Client) incomingPeerPort() int {
 859         listenAddr := cl.ListenAddr()
 860         if listenAddr == nil {
 861                 return 0
 862         }
 863         return addrPort(listenAddr)
 864 }
 865
 866 // Convert a net.Addr to its compact IP representation. Either 4 or 16 bytes
 867 // per "yourip" field of http://www.bittorrent.org/beps/bep_0010.html.
 868 func addrCompactIP(addr net.Addr) (string, error) {
 869         host, _, err := net.SplitHostPort(addr.String())
 870         if err != nil {
 871                 return "", err
 872         }
 873         ip := net.ParseIP(host)
 874         if v4 := ip.To4(); v4 != nil {
 875                 if len(v4) != 4 {
 876                         panic(v4)
 877                 }
 878                 return string(v4), nil
 879         }
 880         return string(ip.To16()), nil
 881 }
 882
 883 func handshakeWriter(w io.Writer, bb <-chan []byte, done chan<- error) {
 884         var err error
 885         for b := range bb {
 886                 _, err = w.Write(b)
 887                 if err != nil {
 888                         break
 889                 }
 890         }
 891         done <- err
 892 }
 893
 894 type (
 895         peerExtensionBytes [8]byte
 896         peerID             [20]byte
 897 )
 898
 899 func (me *peerExtensionBytes) SupportsExtended() bool {
 900         return me[5]&0x10 != 0
 901 }
 902
 903 func (me *peerExtensionBytes) SupportsDHT() bool {
 904         return me[7]&0x01 != 0
 905 }
 906
 907 func (me *peerExtensionBytes) SupportsFast() bool {
 908         return me[7]&0x04 != 0
 909 }
 910
 911 type handshakeResult struct {
 912         peerExtensionBytes
 913         peerID
 914         InfoHash
 915 }
 916
 917 // ih is nil if we expect the peer to declare the InfoHash, such as when the
 918 // peer initiated the connection. Returns ok if the handshake was successful,
 919 // and err if there was an unexpected condition other than the peer simply
 920 // abandoning the handshake.
 921 func handshake(sock io.ReadWriter, ih *InfoHash, peerID [20]byte, extensions peerExtensionBytes) (res handshakeResult, ok bool, err error) {
 922         // Bytes to be sent to the peer. Should never block the sender.
 923         postCh := make(chan []byte, 4)
 924         // A single error value sent when the writer completes.
 925         writeDone := make(chan error, 1)
 926         // Performs writes to the socket and ensures posts don't block.
 927         go handshakeWriter(sock, postCh, writeDone)
 928
 929         defer func() {
 930                 close(postCh) // Done writing.
 931                 if !ok {
 932                         return
 933                 }
 934                 if err != nil {
 935                         panic(err)
 936                 }
 937                 // Wait until writes complete before returning from handshake.
 938                 err = <-writeDone
 939                 if err != nil {
 940                         err = fmt.Errorf("error writing: %s", err)
 941                 }
 942         }()
 943
 944         post := func(bb []byte) {
 945                 select {
 946                 case postCh <- bb:
 947                 default:
 948                         panic("mustn't block while posting")
 949                 }
 950         }
 951
 952         post([]byte(pp.Protocol))
 953         post(extensions[:])
 954         if ih != nil { // We already know what we want.
 955                 post(ih[:])
 956                 post(peerID[:])
 957         }
 958         var b [68]byte
 959         _, err = io.ReadFull(sock, b[:68])
 960         if err != nil {
 961                 err = nil
 962                 return
 963         }
 964         if string(b[:20]) != pp.Protocol {
 965                 return
 966         }
 967         CopyExact(&res.peerExtensionBytes, b[20:28])
 968         CopyExact(&res.InfoHash, b[28:48])
 969         CopyExact(&res.peerID, b[48:68])
 970         peerExtensions.Add(hex.EncodeToString(res.peerExtensionBytes[:]), 1)
 971
 972         // TODO: Maybe we can just drop peers here if we're not interested. This
 973         // could prevent them trying to reconnect, falsely believing there was
 974         // just a problem.
 975         if ih == nil { // We were waiting for the peer to tell us what they wanted.
 976                 post(res.InfoHash[:])
 977                 post(peerID[:])
 978         }
 979
 980         ok = true
 981         return
 982 }
 983
 984 // Wraps a raw connection and provides the interface we want for using the
 985 // connection in the message loop.
 986 type deadlineReader struct {
 987         nc net.Conn
 988         r  io.Reader
 989 }
 990
 991 func (me deadlineReader) Read(b []byte) (n int, err error) {
 992         // Keep-alives should be received every 2 mins. Give a bit of gracetime.
 993         err = me.nc.SetReadDeadline(time.Now().Add(150 * time.Second))
 994         if err != nil {
 995                 err = fmt.Errorf("error setting read deadline: %s", err)
 996         }
 997         n, err = me.r.Read(b)
 998         // Convert common errors into io.EOF.
 999         // if err != nil {
1000         //      if opError, ok := err.(*net.OpError); ok && opError.Op == "read" && opError.Err == syscall.ECONNRESET {
1001         //              err = io.EOF
1002         //      } else if netErr, ok := err.(net.Error); ok && netErr.Timeout() {
1003         //              if n != 0 {
1004         //                      panic(n)
1005         //              }
1006         //              err = io.EOF
1007         //      }
1008         // }
1009         return
1010 }
1011
1012 type readWriter struct {
1013         io.Reader
1014         io.Writer
1015 }
1016
1017 func maybeReceiveEncryptedHandshake(rw io.ReadWriter, skeys [][]byte) (ret io.ReadWriter, encrypted bool, err error) {
1018         var protocol [len(pp.Protocol)]byte
1019         _, err = io.ReadFull(rw, protocol[:])
1020         if err != nil {
1021                 return
1022         }
1023         ret = readWriter{
1024                 io.MultiReader(bytes.NewReader(protocol[:]), rw),
1025                 rw,
1026         }
1027         if string(protocol[:]) == pp.Protocol {
1028                 return
1029         }
1030         encrypted = true
1031         ret, err = mse.ReceiveHandshake(ret, skeys)
1032         return
1033 }
1034
1035 func (cl *Client) receiveSkeys() (ret [][]byte) {
1036         for ih := range cl.torrents {
1037                 ret = append(ret, ih[:])
1038         }
1039         return
1040 }
1041
1042 func (me *Client) initiateHandshakes(c *connection, t *torrent) (ok bool, err error) {
1043         if c.encrypted {
1044                 c.rw, err = mse.InitiateHandshake(c.rw, t.InfoHash[:], nil)
1045                 if err != nil {
1046                         return
1047                 }
1048         }
1049         ih, ok, err := me.connBTHandshake(c, &t.InfoHash)
1050         if ih != t.InfoHash {
1051                 ok = false
1052         }
1053         return
1054 }
1055
1056 // Do encryption and bittorrent handshakes as receiver.
1057 func (cl *Client) receiveHandshakes(c *connection) (t *torrent, err error) {
1058         cl.mu.Lock()
1059         skeys := cl.receiveSkeys()
1060         cl.mu.Unlock()
1061         if !cl.config.DisableEncryption {
1062                 c.rw, c.encrypted, err = maybeReceiveEncryptedHandshake(c.rw, skeys)
1063                 if err != nil {
1064                         if err == mse.ErrNoSecretKeyMatch {
1065                                 err = nil
1066                         }
1067                         return
1068                 }
1069         }
1070         ih, ok, err := cl.connBTHandshake(c, nil)
1071         if err != nil {
1072                 fmt.Errorf("error during bt handshake: %s", err)
1073                 return
1074         }
1075         if !ok {
1076                 return
1077         }
1078         cl.mu.Lock()
1079         t = cl.torrents[ih]
1080         cl.mu.Unlock()
1081         return
1082 }
1083
1084 // Returns !ok if handshake failed for valid reasons.
1085 func (cl *Client) connBTHandshake(c *connection, ih *InfoHash) (ret InfoHash, ok bool, err error) {
1086         res, ok, err := handshake(c.rw, ih, cl.peerID, cl.extensionBytes)
1087         if err != nil || !ok {
1088                 return
1089         }
1090         ret = res.InfoHash
1091         c.PeerExtensionBytes = res.peerExtensionBytes
1092         c.PeerID = res.peerID
1093         c.completedHandshake = time.Now()
1094         return
1095 }
1096
1097 func (cl *Client) runInitiatedHandshookConn(c *connection, t *torrent) (err error) {
1098         if c.PeerID == cl.peerID {
1099                 // Only if we initiated the connection is the remote address a
1100                 // listen addr for a doppleganger.
1101                 connsToSelf.Add(1)
1102                 addr := c.conn.RemoteAddr().String()
1103                 cl.dopplegangerAddrs[addr] = struct{}{}
1104                 return
1105         }
1106         return cl.runHandshookConn(c, t)
1107 }
1108
1109 func (cl *Client) runReceivedConn(c *connection) (err error) {
1110         err = c.conn.SetDeadline(time.Now().Add(handshakesTimeout))
1111         if err != nil {
1112                 return
1113         }
1114         t, err := cl.receiveHandshakes(c)
1115         if err != nil {
1116                 err = fmt.Errorf("error receiving handshakes: %s", err)
1117                 return
1118         }
1119         if t == nil {
1120                 return
1121         }
1122         cl.mu.Lock()
1123         defer cl.mu.Unlock()
1124         if c.PeerID == cl.peerID {
1125                 return
1126         }
1127         return cl.runHandshookConn(c, t)
1128 }
1129
1130 func (cl *Client) runHandshookConn(c *connection, t *torrent) (err error) {
1131         c.conn.SetWriteDeadline(time.Time{})
1132         c.rw = readWriter{
1133                 deadlineReader{c.conn, c.rw},
1134                 c.rw,
1135         }
1136         if !cl.addConnection(t, c) {
1137                 return
1138         }
1139         defer cl.dropConnection(t, c)
1140         go c.writer()
1141         go c.writeOptimizer(time.Minute)
1142         cl.sendInitialMessages(c, t)
1143         if t.haveInfo() {
1144                 t.initRequestOrdering(c)
1145         }
1146         err = cl.connectionLoop(t, c)
1147         if err != nil {
1148                 err = fmt.Errorf("error during connection loop: %s", err)
1149         }
1150         return
1151 }
1152
1153 func (me *Client) sendInitialMessages(conn *connection, torrent *torrent) {
1154         if conn.PeerExtensionBytes.SupportsExtended() && me.extensionBytes.SupportsExtended() {
1155                 conn.Post(pp.Message{
1156                         Type:       pp.Extended,
1157                         ExtendedID: pp.HandshakeExtendedID,
1158                         ExtendedPayload: func() []byte {
1159                                 d := map[string]interface{}{
1160                                         "m": func() (ret map[string]int) {
1161                                                 ret = make(map[string]int, 2)
1162                                                 ret["ut_metadata"] = metadataExtendedId
1163                                                 if !me.config.DisablePEX {
1164                                                         ret["ut_pex"] = pexExtendedId
1165                                                 }
1166                                                 return
1167                                         }(),
1168                                         "v": extendedHandshakeClientVersion,
1169                                         // No upload queue is implemented yet.
1170                                         "reqq": func() int {
1171                                                 if me.config.NoUpload {
1172                                                         // No need to look strange if it costs us nothing.
1173                                                         return 250
1174                                                 } else {
1175                                                         return 1
1176                                                 }
1177                                         }(),
1178                                 }
1179                                 if !me.config.DisableEncryption {
1180                                         d["e"] = 1
1181                                 }
1182                                 if torrent.metadataSizeKnown() {
1183                                         d["metadata_size"] = torrent.metadataSize()
1184                                 }
1185                                 if p := me.incomingPeerPort(); p != 0 {
1186                                         d["p"] = p
1187                                 }
1188                                 yourip, err := addrCompactIP(conn.remoteAddr())
1189                                 if err != nil {
1190                                         log.Printf("error calculating yourip field value in extension handshake: %s", err)
1191                                 } else {
1192                                         d["yourip"] = yourip
1193                                 }
1194                                 // log.Printf("sending %v", d)
1195                                 b, err := bencode.Marshal(d)
1196                                 if err != nil {
1197                                         panic(err)
1198                                 }
1199                                 return b
1200                         }(),
1201                 })
1202         }
1203         if torrent.haveAnyPieces() {
1204                 conn.Post(pp.Message{
1205                         Type:     pp.Bitfield,
1206                         Bitfield: torrent.bitfield(),
1207                 })
1208         } else if me.extensionBytes.SupportsFast() && conn.PeerExtensionBytes.SupportsFast() {
1209                 conn.Post(pp.Message{
1210                         Type: pp.HaveNone,
1211                 })
1212         }
1213         if conn.PeerExtensionBytes.SupportsDHT() && me.extensionBytes.SupportsDHT() && me.dHT != nil {
1214                 conn.Post(pp.Message{
1215                         Type: pp.Port,
1216                         Port: uint16(AddrPort(me.dHT.Addr())),
1217                 })
1218         }
1219 }
1220
1221 // Randomizes the piece order for this connection. Every connection will be
1222 // given a different ordering. Having it stored per connection saves having to
1223 // randomize during request filling, and constantly recalculate the ordering
1224 // based on piece priorities.
1225 func (t *torrent) initRequestOrdering(c *connection) {
1226         if c.pieceRequestOrder != nil || c.piecePriorities != nil {
1227                 panic("double init of request ordering")
1228         }
1229         c.piecePriorities = mathRand.Perm(t.numPieces())
1230         c.pieceRequestOrder = pieceordering.New()
1231         for i := range iter.N(t.Info.NumPieces()) {
1232                 if !c.PeerHasPiece(i) {
1233                         continue
1234                 }
1235                 if !t.wantPiece(i) {
1236                         continue
1237                 }
1238                 t.connPendPiece(c, i)
1239         }
1240 }
1241
1242 func (me *Client) peerGotPiece(t *torrent, c *connection, piece int) {
1243         if !c.peerHasAll {
1244                 if t.haveInfo() {
1245                         if c.PeerPieces == nil {
1246                                 c.PeerPieces = make([]bool, t.numPieces())
1247                         }
1248                 } else {
1249                         for piece >= len(c.PeerPieces) {
1250                                 c.PeerPieces = append(c.PeerPieces, false)
1251                         }
1252                 }
1253                 c.PeerPieces[piece] = true
1254         }
1255         if t.wantPiece(piece) {
1256                 t.connPendPiece(c, piece)
1257                 me.replenishConnRequests(t, c)
1258         }
1259 }
1260
1261 func (me *Client) peerUnchoked(torrent *torrent, conn *connection) {
1262         me.replenishConnRequests(torrent, conn)
1263 }
1264
1265 func (cl *Client) connCancel(t *torrent, cn *connection, r request) (ok bool) {
1266         ok = cn.Cancel(r)
1267         if ok {
1268                 postedCancels.Add(1)
1269         }
1270         return
1271 }
1272
1273 func (cl *Client) connDeleteRequest(t *torrent, cn *connection, r request) {
1274         if !cn.RequestPending(r) {
1275                 return
1276         }
1277         delete(cn.Requests, r)
1278 }
1279
1280 func (cl *Client) requestPendingMetadata(t *torrent, c *connection) {
1281         if t.haveInfo() {
1282                 return
1283         }
1284         if c.PeerExtensionIDs["ut_metadata"] == 0 {
1285                 // Peer doesn't support this.
1286                 return
1287         }
1288         // Request metadata pieces that we don't have in a random order.
1289         var pending []int
1290         for index := 0; index < t.metadataPieceCount(); index++ {
1291                 if !t.haveMetadataPiece(index) && !c.requestedMetadataPiece(index) {
1292                         pending = append(pending, index)
1293                 }
1294         }
1295         for _, i := range mathRand.Perm(len(pending)) {
1296                 c.requestMetadataPiece(pending[i])
1297         }
1298 }
1299
1300 func (cl *Client) completedMetadata(t *torrent) {
1301         h := sha1.New()
1302         h.Write(t.MetaData)
1303         var ih InfoHash
1304         CopyExact(&ih, h.Sum(nil))
1305         if ih != t.InfoHash {
1306                 log.Print("bad metadata")
1307                 t.invalidateMetadata()
1308                 return
1309         }
1310         var info metainfo.Info
1311         err := bencode.Unmarshal(t.MetaData, &info)
1312         if err != nil {
1313                 log.Printf("error unmarshalling metadata: %s", err)
1314                 t.invalidateMetadata()
1315                 return
1316         }
1317         // TODO(anacrolix): If this fails, I think something harsher should be
1318         // done.
1319         err = cl.setMetaData(t, &info, t.MetaData)
1320         if err != nil {
1321                 log.Printf("error setting metadata: %s", err)
1322                 t.invalidateMetadata()
1323                 return
1324         }
1325         log.Printf("%s: got metadata from peers", t)
1326 }
1327
1328 // Process incoming ut_metadata message.
1329 func (cl *Client) gotMetadataExtensionMsg(payload []byte, t *torrent, c *connection) (err error) {
1330         var d map[string]int
1331         err = bencode.Unmarshal(payload, &d)
1332         if err != nil {
1333                 err = fmt.Errorf("error unmarshalling payload: %s: %q", err, payload)
1334                 return
1335         }
1336         msgType, ok := d["msg_type"]
1337         if !ok {
1338                 err = errors.New("missing msg_type field")
1339                 return
1340         }
1341         piece := d["piece"]
1342         switch msgType {
1343         case pp.DataMetadataExtensionMsgType:
1344                 if t.haveInfo() {
1345                         break
1346                 }
1347                 begin := len(payload) - metadataPieceSize(d["total_size"], piece)
1348                 if begin < 0 || begin >= len(payload) {
1349                         log.Printf("got bad metadata piece")
1350                         break
1351                 }
1352                 if !c.requestedMetadataPiece(piece) {
1353                         log.Printf("got unexpected metadata piece %d", piece)
1354                         break
1355                 }
1356                 c.metadataRequests[piece] = false
1357                 t.saveMetadataPiece(piece, payload[begin:])
1358                 c.UsefulChunksReceived++
1359                 c.lastUsefulChunkReceived = time.Now()
1360                 if !t.haveAllMetadataPieces() {
1361                         break
1362                 }
1363                 cl.completedMetadata(t)
1364         case pp.RequestMetadataExtensionMsgType:
1365                 if !t.haveMetadataPiece(piece) {
1366                         c.Post(t.newMetadataExtensionMessage(c, pp.RejectMetadataExtensionMsgType, d["piece"], nil))
1367                         break
1368                 }
1369                 start := (1 << 14) * piece
1370                 c.Post(t.newMetadataExtensionMessage(c, pp.DataMetadataExtensionMsgType, piece, t.MetaData[start:start+t.metadataPieceSize(piece)]))
1371         case pp.RejectMetadataExtensionMsgType:
1372         default:
1373                 err = errors.New("unknown msg_type value")
1374         }
1375         return
1376 }
1377
1378 type peerExchangeMessage struct {
1379         Added      CompactPeers `bencode:"added"`
1380         AddedFlags []byte       `bencode:"added.f"`
1381         Dropped    CompactPeers `bencode:"dropped"`
1382 }
1383
1384 // Extracts the port as an integer from an address string.
1385 func addrPort(addr net.Addr) int {
1386         return AddrPort(addr)
1387 }
1388
1389 func (cl *Client) peerHasAll(t *torrent, cn *connection) {
1390         cn.peerHasAll = true
1391         cn.PeerPieces = nil
1392         if t.haveInfo() {
1393                 for i := 0; i < t.numPieces(); i++ {
1394                         cl.peerGotPiece(t, cn, i)
1395                 }
1396         }
1397 }
1398
1399 // Processes incoming bittorrent messages. The client lock is held upon entry
1400 // and exit.
1401 func (me *Client) connectionLoop(t *torrent, c *connection) error {
1402         decoder := pp.Decoder{
1403                 R:         bufio.NewReader(c.rw),
1404                 MaxLength: 256 * 1024,
1405         }
1406         for {
1407                 me.mu.Unlock()
1408                 var msg pp.Message
1409                 err := decoder.Decode(&msg)
1410                 receivedMessageTypes.Add(strconv.FormatInt(int64(msg.Type), 10), 1)
1411                 me.mu.Lock()
1412                 c.lastMessageReceived = time.Now()
1413                 select {
1414                 case <-c.closing:
1415                         return nil
1416                 default:
1417                 }
1418                 if err != nil {
1419                         if me.stopped() || err == io.EOF {
1420                                 return nil
1421                         }
1422                         return err
1423                 }
1424                 if msg.Keepalive {
1425                         continue
1426                 }
1427                 switch msg.Type {
1428                 case pp.Choke:
1429                         c.PeerChoked = true
1430                         for r := range c.Requests {
1431                                 me.connDeleteRequest(t, c, r)
1432                         }
1433                         // We can then reset our interest.
1434                         me.replenishConnRequests(t, c)
1435                 case pp.Reject:
1436                         me.connDeleteRequest(t, c, newRequest(msg.Index, msg.Begin, msg.Length))
1437                         me.replenishConnRequests(t, c)
1438                 case pp.Unchoke:
1439                         c.PeerChoked = false
1440                         me.peerUnchoked(t, c)
1441                 case pp.Interested:
1442                         c.PeerInterested = true
1443                         // TODO: This should be done from a dedicated unchoking routine.
1444                         if me.config.NoUpload {
1445                                 break
1446                         }
1447                         c.Unchoke()
1448                 case pp.NotInterested:
1449                         c.PeerInterested = false
1450                         c.Choke()
1451                 case pp.Have:
1452                         me.peerGotPiece(t, c, int(msg.Index))
1453                 case pp.Request:
1454                         if me.config.NoUpload {
1455                                 break
1456                         }
1457                         if c.PeerRequests == nil {
1458                                 c.PeerRequests = make(map[request]struct{}, maxRequests)
1459                         }
1460                         request := newRequest(msg.Index, msg.Begin, msg.Length)
1461                         // TODO: Requests should be satisfied from a dedicated upload
1462                         // routine.
1463                         // c.PeerRequests[request] = struct{}{}
1464                         p := make([]byte, msg.Length)
1465                         n, err := dataReadAt(t.data, p, int64(t.pieceLength(0))*int64(msg.Index)+int64(msg.Begin))
1466                         if err != nil {
1467                                 return fmt.Errorf("reading t data to serve request %q: %s", request, err)
1468                         }
1469                         if n != int(msg.Length) {
1470                                 return fmt.Errorf("bad request: %v", msg)
1471                         }
1472                         c.Post(pp.Message{
1473                                 Type:  pp.Piece,
1474                                 Index: msg.Index,
1475                                 Begin: msg.Begin,
1476                                 Piece: p,
1477                         })
1478                         uploadChunksPosted.Add(1)
1479                 case pp.Cancel:
1480                         req := newRequest(msg.Index, msg.Begin, msg.Length)
1481                         if !c.PeerCancel(req) {
1482                                 unexpectedCancels.Add(1)
1483                         }
1484                 case pp.Bitfield:
1485                         if c.PeerPieces != nil || c.peerHasAll {
1486                                 err = errors.New("received unexpected bitfield")
1487                                 break
1488                         }
1489                         if t.haveInfo() {
1490                                 if len(msg.Bitfield) < t.numPieces() {
1491                                         err = errors.New("received invalid bitfield")
1492                                         break
1493                                 }
1494                                 msg.Bitfield = msg.Bitfield[:t.numPieces()]
1495                         }
1496                         c.PeerPieces = msg.Bitfield
1497                         for index, has := range c.PeerPieces {
1498                                 if has {
1499                                         me.peerGotPiece(t, c, index)
1500                                 }
1501                         }
1502                 case pp.HaveAll:
1503                         if c.PeerPieces != nil || c.peerHasAll {
1504                                 err = errors.New("unexpected have-all")
1505                                 break
1506                         }
1507                         me.peerHasAll(t, c)
1508                 case pp.HaveNone:
1509                         if c.peerHasAll || c.PeerPieces != nil {
1510                                 err = errors.New("unexpected have-none")
1511                                 break
1512                         }
1513                         c.PeerPieces = make([]bool, func() int {
1514                                 if t.haveInfo() {
1515                                         return t.numPieces()
1516                                 } else {
1517                                         return 0
1518                                 }
1519                         }())
1520                 case pp.Piece:
1521                         err = me.downloadedChunk(t, c, &msg)
1522                 case pp.Extended:
1523                         switch msg.ExtendedID {
1524                         case pp.HandshakeExtendedID:
1525                                 // TODO: Create a bencode struct for this.
1526                                 var d map[string]interface{}
1527                                 err = bencode.Unmarshal(msg.ExtendedPayload, &d)
1528                                 if err != nil {
1529                                         err = fmt.Errorf("error decoding extended message payload: %s", err)
1530                                         break
1531                                 }
1532                                 // log.Printf("got handshake from %q: %#v", c.Socket.RemoteAddr().String(), d)
1533                                 if reqq, ok := d["reqq"]; ok {
1534                                         if i, ok := reqq.(int64); ok {
1535                                                 c.PeerMaxRequests = int(i)
1536                                         }
1537                                 }
1538                                 if v, ok := d["v"]; ok {
1539                                         c.PeerClientName = v.(string)
1540                                 }
1541                                 m, ok := d["m"]
1542                                 if !ok {
1543                                         err = errors.New("handshake missing m item")
1544                                         break
1545                                 }
1546                                 mTyped, ok := m.(map[string]interface{})
1547                                 if !ok {
1548                                         err = errors.New("handshake m value is not dict")
1549                                         break
1550                                 }
1551                                 if c.PeerExtensionIDs == nil {
1552                                         c.PeerExtensionIDs = make(map[string]byte, len(mTyped))
1553                                 }
1554                                 for name, v := range mTyped {
1555                                         id, ok := v.(int64)
1556                                         if !ok {
1557                                                 log.Printf("bad handshake m item extension ID type: %T", v)
1558                                                 continue
1559                                         }
1560                                         if id == 0 {
1561                                                 delete(c.PeerExtensionIDs, name)
1562                                         } else {
1563                                                 if c.PeerExtensionIDs[name] == 0 {
1564                                                         supportedExtensionMessages.Add(name, 1)
1565                                                 }
1566                                                 c.PeerExtensionIDs[name] = byte(id)
1567                                         }
1568                                 }
1569                                 metadata_sizeUntyped, ok := d["metadata_size"]
1570                                 if ok {
1571                                         metadata_size, ok := metadata_sizeUntyped.(int64)
1572                                         if !ok {
1573                                                 log.Printf("bad metadata_size type: %T", metadata_sizeUntyped)
1574                                         } else {
1575                                                 t.setMetadataSize(metadata_size, me)
1576                                         }
1577                                 }
1578                                 if _, ok := c.PeerExtensionIDs["ut_metadata"]; ok {
1579                                         me.requestPendingMetadata(t, c)
1580                                 }
1581                         case metadataExtendedId:
1582                                 err = me.gotMetadataExtensionMsg(msg.ExtendedPayload, t, c)
1583                                 if err != nil {
1584                                         err = fmt.Errorf("error handling metadata extension message: %s", err)
1585                                 }
1586                         case pexExtendedId:
1587                                 if me.config.DisablePEX {
1588                                         break
1589                                 }
1590                                 var pexMsg peerExchangeMessage
1591                                 err := bencode.Unmarshal(msg.ExtendedPayload, &pexMsg)
1592                                 if err != nil {
1593                                         err = fmt.Errorf("error unmarshalling PEX message: %s", err)
1594                                         break
1595                                 }
1596                                 go func() {
1597                                         me.mu.Lock()
1598                                         me.addPeers(t, func() (ret []Peer) {
1599                                                 for i, cp := range pexMsg.Added {
1600                                                         p := Peer{
1601                                                                 IP:     make([]byte, 4),
1602                                                                 Port:   int(cp.Port),
1603                                                                 Source: peerSourcePEX,
1604                                                         }
1605                                                         if i < len(pexMsg.AddedFlags) && pexMsg.AddedFlags[i]&0x01 != 0 {
1606                                                                 p.SupportsEncryption = true
1607                                                         }
1608                                                         CopyExact(p.IP, cp.IP[:])
1609                                                         ret = append(ret, p)
1610                                                 }
1611                                                 return
1612                                         }())
1613                                         me.mu.Unlock()
1614                                         peersFoundByPEX.Add(int64(len(pexMsg.Added)))
1615                                 }()
1616                         default:
1617                                 err = fmt.Errorf("unexpected extended message ID: %v", msg.ExtendedID)
1618                         }
1619                         if err != nil {
1620                                 // That client uses its own extension IDs for outgoing message
1621                                 // types, which is incorrect.
1622                                 if bytes.HasPrefix(c.PeerID[:], []byte("-SD0100-")) ||
1623                                         strings.HasPrefix(string(c.PeerID[:]), "-XL0012-") {
1624                                         return nil
1625                                 }
1626                         }
1627                 case pp.Port:
1628                         if me.dHT == nil {
1629                                 break
1630                         }
1631                         pingAddr, err := net.ResolveUDPAddr("", c.remoteAddr().String())
1632                         if err != nil {
1633                                 panic(err)
1634                         }
1635                         if msg.Port != 0 {
1636                                 pingAddr.Port = int(msg.Port)
1637                         }
1638                         _, err = me.dHT.Ping(pingAddr)
1639                 default:
1640                         err = fmt.Errorf("received unknown message type: %#v", msg.Type)
1641                 }
1642                 if err != nil {
1643                         return err
1644                 }
1645         }
1646 }
1647
1648 func (me *Client) dropConnection(torrent *torrent, conn *connection) {
1649         me.event.Broadcast()
1650         for r := range conn.Requests {
1651                 me.connDeleteRequest(torrent, conn, r)
1652         }
1653         conn.Close()
1654         for i0, c := range torrent.Conns {
1655                 if c != conn {
1656                         continue
1657                 }
1658                 i1 := len(torrent.Conns) - 1
1659                 if i0 != i1 {
1660                         torrent.Conns[i0] = torrent.Conns[i1]
1661                 }
1662                 torrent.Conns = torrent.Conns[:i1]
1663                 me.openNewConns(torrent)
1664                 return
1665         }
1666         panic("connection not found")
1667 }
1668
1669 func (me *Client) addConnection(t *torrent, c *connection) bool {
1670         if me.stopped() {
1671                 return false
1672         }
1673         select {
1674         case <-t.ceasingNetworking:
1675                 return false
1676         default:
1677         }
1678         if !me.wantConns(t) {
1679                 return false
1680         }
1681         for _, c0 := range t.Conns {
1682                 if c.PeerID == c0.PeerID {
1683                         // Already connected to a client with that ID.
1684                         duplicateClientConns.Add(1)
1685                         return false
1686                 }
1687         }
1688         t.Conns = append(t.Conns, c)
1689         // TODO: This should probably be done by a routine that kills off bad
1690         // connections, and extra connections killed here instead.
1691         if len(t.Conns) > socketsPerTorrent {
1692                 wcs := t.worstConnsHeap()
1693                 heap.Pop(wcs).(*connection).Close()
1694         }
1695         return true
1696 }
1697
1698 func (t *torrent) needData() bool {
1699         if !t.haveInfo() {
1700                 return true
1701         }
1702         for i := range t.Pieces {
1703                 if t.wantPiece(i) {
1704                         return true
1705                 }
1706         }
1707         return false
1708 }
1709
1710 // TODO: I'm sure there's something here to do with seeding.
1711 func (t *torrent) badConn(c *connection) bool {
1712         // A 30 second grace for initial messages to go through.
1713         if time.Since(c.completedHandshake) < 30*time.Second {
1714                 return false
1715         }
1716         if !t.haveInfo() {
1717                 if !c.supportsExtension("ut_metadata") {
1718                         return true
1719                 }
1720                 if time.Since(c.completedHandshake) > 2*time.Minute {
1721                         return true
1722                 }
1723         }
1724         return !t.connHasWantedPieces(c)
1725 }
1726
1727 func (t *torrent) numGoodConns() (num int) {
1728         for _, c := range t.Conns {
1729                 if !t.badConn(c) {
1730                         num++
1731                 }
1732         }
1733         return
1734 }
1735
1736 func (me *Client) wantConns(t *torrent) bool {
1737         if me.config.NoUpload && !t.needData() {
1738                 return false
1739         }
1740         if t.numGoodConns() >= socketsPerTorrent {
1741                 return false
1742         }
1743         return true
1744 }
1745
1746 func (me *Client) openNewConns(t *torrent) {
1747         select {
1748         case <-t.ceasingNetworking:
1749                 return
1750         default:
1751         }
1752         for len(t.Peers) != 0 {
1753                 if !me.wantConns(t) {
1754                         return
1755                 }
1756                 if len(t.HalfOpen) >= me.halfOpenLimit {
1757                         return
1758                 }
1759                 var (
1760                         k peersKey
1761                         p Peer
1762                 )
1763                 for k, p = range t.Peers {
1764                         break
1765                 }
1766                 delete(t.Peers, k)
1767                 me.initiateConn(p, t)
1768         }
1769         t.wantPeers.Broadcast()
1770 }
1771
1772 func (me *Client) addPeers(t *torrent, peers []Peer) {
1773         for _, p := range peers {
1774                 if me.dopplegangerAddr(net.JoinHostPort(p.IP.String(), strconv.FormatInt(int64(p.Port), 10))) {
1775                         continue
1776                 }
1777                 if me.ipBlockRange(p.IP) != nil {
1778                         continue
1779                 }
1780                 t.addPeer(p)
1781         }
1782         me.openNewConns(t)
1783 }
1784
1785 func (cl *Client) cachedMetaInfoFilename(ih InfoHash) string {
1786         return filepath.Join(cl.configDir(), "torrents", ih.HexString()+".torrent")
1787 }
1788
1789 func (cl *Client) saveTorrentFile(t *torrent) error {
1790         path := cl.cachedMetaInfoFilename(t.InfoHash)
1791         os.MkdirAll(filepath.Dir(path), 0777)
1792         f, err := os.OpenFile(path, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0666)
1793         if err != nil {
1794                 return fmt.Errorf("error opening file: %s", err)
1795         }
1796         defer f.Close()
1797         e := bencode.NewEncoder(f)
1798         err = e.Encode(t.MetaInfo())
1799         if err != nil {
1800                 return fmt.Errorf("error marshalling metainfo: %s", err)
1801         }
1802         mi, err := cl.torrentCacheMetaInfo(t.InfoHash)
1803         if err != nil {
1804                 // For example, a script kiddy makes us load too many files, and we're
1805                 // able to save the torrent, but not load it again to check it.
1806                 return nil
1807         }
1808         if !bytes.Equal(mi.Info.Hash, t.InfoHash[:]) {
1809                 log.Fatalf("%x != %x", mi.Info.Hash, t.InfoHash[:])
1810         }
1811         return nil
1812 }
1813
1814 func (cl *Client) startTorrent(t *torrent) {
1815         if t.Info == nil || t.data == nil {
1816                 panic("nope")
1817         }
1818         // If the client intends to upload, it needs to know what state pieces are
1819         // in.
1820         if !cl.config.NoUpload {
1821                 // Queue all pieces for hashing. This is done sequentially to avoid
1822                 // spamming goroutines.
1823                 for _, p := range t.Pieces {
1824                         p.QueuedForHash = true
1825                 }
1826                 go func() {
1827                         for i := range t.Pieces {
1828                                 cl.verifyPiece(t, pp.Integer(i))
1829                         }
1830                 }()
1831         }
1832 }
1833
1834 // Storage cannot be changed once it's set.
1835 func (cl *Client) setStorage(t *torrent, td data.Data) (err error) {
1836         err = t.setStorage(td)
1837         cl.event.Broadcast()
1838         if err != nil {
1839                 return
1840         }
1841         for index := range iter.N(t.numPieces()) {
1842                 cl.pieceChanged(t, index)
1843         }
1844         cl.startTorrent(t)
1845         return
1846 }
1847
1848 type TorrentDataOpener func(*metainfo.Info) data.Data
1849
1850 func (cl *Client) setMetaData(t *torrent, md *metainfo.Info, bytes []byte) (err error) {
1851         err = t.setMetadata(md, bytes, &cl.mu)
1852         if err != nil {
1853                 return
1854         }
1855         if !cl.config.DisableMetainfoCache {
1856                 if err := cl.saveTorrentFile(t); err != nil {
1857                         log.Printf("error saving torrent file for %s: %s", t, err)
1858                 }
1859         }
1860         cl.event.Broadcast()
1861         close(t.gotMetainfo)
1862         td := cl.torrentDataOpener(md)
1863         err = cl.setStorage(t, td)
1864         return
1865 }
1866
1867 // Prepare a Torrent without any attachment to a Client. That means we can
1868 // initialize fields all fields that don't require the Client without locking
1869 // it.
1870 func newTorrent(ih InfoHash) (t *torrent, err error) {
1871         t = &torrent{
1872                 InfoHash: ih,
1873                 Peers:    make(map[peersKey]Peer),
1874
1875                 closing:           make(chan struct{}),
1876                 ceasingNetworking: make(chan struct{}),
1877
1878                 gotMetainfo: make(chan struct{}),
1879
1880                 HalfOpen: make(map[string]struct{}),
1881         }
1882         t.wantPeers.L = &t.stateMu
1883         return
1884 }
1885
1886 func init() {
1887         // For shuffling the tracker tiers.
1888         mathRand.Seed(time.Now().Unix())
1889 }
1890
1891 // The trackers within each tier must be shuffled before use.
1892 // http://stackoverflow.com/a/12267471/149482
1893 // http://www.bittorrent.org/beps/bep_0012.html#order-of-processing
1894 func shuffleTier(tier []tracker.Client) {
1895         for i := range tier {
1896                 j := mathRand.Intn(i + 1)
1897                 tier[i], tier[j] = tier[j], tier[i]
1898         }
1899 }
1900
1901 func copyTrackers(base [][]tracker.Client) (copy [][]tracker.Client) {
1902         for _, tier := range base {
1903                 copy = append(copy, append([]tracker.Client{}, tier...))
1904         }
1905         return
1906 }
1907
1908 func mergeTier(tier []tracker.Client, newURLs []string) []tracker.Client {
1909 nextURL:
1910         for _, url := range newURLs {
1911                 for _, tr := range tier {
1912                         if tr.URL() == url {
1913                                 continue nextURL
1914                         }
1915                 }
1916                 tr, err := tracker.New(url)
1917                 if err != nil {
1918                         log.Printf("error creating tracker client for %q: %s", url, err)
1919                         continue
1920                 }
1921                 tier = append(tier, tr)
1922         }
1923         return tier
1924 }
1925
1926 func (t *torrent) addTrackers(announceList [][]string) {
1927         newTrackers := copyTrackers(t.Trackers)
1928         for tierIndex, tier := range announceList {
1929                 if tierIndex < len(newTrackers) {
1930                         newTrackers[tierIndex] = mergeTier(newTrackers[tierIndex], tier)
1931                 } else {
1932                         newTrackers = append(newTrackers, mergeTier(nil, tier))
1933                 }
1934                 shuffleTier(newTrackers[tierIndex])
1935         }
1936         t.Trackers = newTrackers
1937 }
1938
1939 // Don't call this before the info is available.
1940 func (t *torrent) BytesCompleted() int64 {
1941         if !t.haveInfo() {
1942                 return 0
1943         }
1944         return t.Info.TotalLength() - t.bytesLeft()
1945 }
1946
1947 func (t Torrent) NumPieces() int {
1948         return t.numPieces()
1949 }
1950
1951 func (t Torrent) Drop() {
1952         t.cl.mu.Lock()
1953         t.cl.dropTorrent(t.InfoHash)
1954         t.cl.mu.Unlock()
1955 }
1956
1957 // A file-like handle to some torrent data resource.
1958 type Handle interface {
1959         io.Reader
1960         io.Seeker
1961         io.Closer
1962         io.ReaderAt
1963 }
1964
1965 // Returns handles to the files in the torrent. This requires the metainfo is
1966 // available first.
1967 func (t Torrent) Files() (ret []File) {
1968         t.cl.mu.Lock()
1969         info := t.Info()
1970         t.cl.mu.Unlock()
1971         if info == nil {
1972                 return
1973         }
1974         var offset int64
1975         for _, fi := range info.UpvertedFiles() {
1976                 ret = append(ret, File{
1977                         t,
1978                         strings.Join(append([]string{info.Name}, fi.Path...), "/"),
1979                         offset,
1980                         fi.Length,
1981                         fi,
1982                 })
1983                 offset += fi.Length
1984         }
1985         return
1986 }
1987
1988 func (t Torrent) SetRegionPriority(off, len int64) {
1989         t.cl.mu.Lock()
1990         defer t.cl.mu.Unlock()
1991         pieceSize := int64(t.usualPieceSize())
1992         for i := off / pieceSize; i*pieceSize < off+len; i++ {
1993                 t.cl.prioritizePiece(t.torrent, int(i), piecePriorityNormal)
1994         }
1995 }
1996
1997 func (t Torrent) AddPeers(pp []Peer) error {
1998         cl := t.cl
1999         cl.mu.Lock()
2000         defer cl.mu.Unlock()
2001         cl.addPeers(t.torrent, pp)
2002         return nil
2003 }
2004
2005 // Marks the entire torrent for download. Requires the info first, see
2006 // GotInfo.
2007 func (t Torrent) DownloadAll() {
2008         t.cl.mu.Lock()
2009         defer t.cl.mu.Unlock()
2010         for i := range iter.N(t.numPieces()) {
2011                 t.cl.raisePiecePriority(t.torrent, i, piecePriorityNormal)
2012         }
2013         // Nice to have the first and last pieces sooner for various interactive
2014         // purposes.
2015         t.cl.raisePiecePriority(t.torrent, 0, piecePriorityReadahead)
2016         t.cl.raisePiecePriority(t.torrent, t.numPieces()-1, piecePriorityReadahead)
2017 }
2018
2019 // Returns nil metainfo if it isn't in the cache. Checks that the retrieved
2020 // metainfo has the correct infohash.
2021 func (cl *Client) torrentCacheMetaInfo(ih InfoHash) (mi *metainfo.MetaInfo, err error) {
2022         if cl.config.DisableMetainfoCache {
2023                 return
2024         }
2025         f, err := os.Open(cl.cachedMetaInfoFilename(ih))
2026         if err != nil {
2027                 if os.IsNotExist(err) {
2028                         err = nil
2029                 }
2030                 return
2031         }
2032         defer f.Close()
2033         dec := bencode.NewDecoder(f)
2034         err = dec.Decode(&mi)
2035         if err != nil {
2036                 return
2037         }
2038         if !bytes.Equal(mi.Info.Hash, ih[:]) {
2039                 err = fmt.Errorf("cached torrent has wrong infohash: %x != %x", mi.Info.Hash, ih[:])
2040                 return
2041         }
2042         return
2043 }
2044
2045 // Specifies a new torrent for adding to a client. There are helpers for
2046 // magnet URIs and torrent metainfo files.
2047 type TorrentSpec struct {
2048         Trackers    [][]string
2049         InfoHash    InfoHash
2050         Info        *metainfo.InfoEx
2051         DisplayName string
2052 }
2053
2054 func TorrentSpecFromMagnetURI(uri string) (spec *TorrentSpec, err error) {
2055         m, err := ParseMagnetURI(uri)
2056         if err != nil {
2057                 return
2058         }
2059         spec = &TorrentSpec{
2060                 Trackers:    [][]string{m.Trackers},
2061                 DisplayName: m.DisplayName,
2062                 InfoHash:    m.InfoHash,
2063         }
2064         return
2065 }
2066
2067 func TorrentSpecFromMetaInfo(mi *metainfo.MetaInfo) (spec *TorrentSpec) {
2068         spec = &TorrentSpec{
2069                 Trackers:    mi.AnnounceList,
2070                 Info:        &mi.Info,
2071                 DisplayName: mi.Info.Name,
2072         }
2073         CopyExact(&spec.InfoHash, &mi.Info.Hash)
2074         return
2075 }
2076
2077 // Add or merge a torrent spec. If the torrent is already present, the
2078 // trackers will be merged with the existing ones. If the Info isn't yet
2079 // known, it will be set. The display name is replaced if the new spec
2080 // provides one. Returns new if the torrent wasn't already in the client.
2081 func (cl *Client) AddTorrentSpec(spec *TorrentSpec) (T Torrent, new bool, err error) {
2082         T.cl = cl
2083         cl.mu.Lock()
2084         defer cl.mu.Unlock()
2085
2086         t, ok := cl.torrents[spec.InfoHash]
2087         if !ok {
2088                 new = true
2089
2090                 if _, ok := cl.bannedTorrents[spec.InfoHash]; ok {
2091                         err = errors.New("banned torrent")
2092                         return
2093                 }
2094
2095                 t, err = newTorrent(spec.InfoHash)
2096                 if err != nil {
2097                         return
2098                 }
2099         }
2100         if spec.DisplayName != "" {
2101                 t.DisplayName = spec.DisplayName
2102         }
2103         // Try to merge in info we have on the torrent. Any err left will
2104         // terminate the function.
2105         if t.Info == nil {
2106                 if spec.Info != nil {
2107                         err = cl.setMetaData(t, &spec.Info.Info, spec.Info.Bytes)
2108                 } else {
2109                         var mi *metainfo.MetaInfo
2110                         mi, err = cl.torrentCacheMetaInfo(spec.InfoHash)
2111                         if err != nil {
2112                                 log.Printf("error getting cached metainfo: %s", err)
2113                                 err = nil
2114                         } else if mi != nil {
2115                                 t.addTrackers(mi.AnnounceList)
2116                                 err = cl.setMetaData(t, &mi.Info.Info, mi.Info.Bytes)
2117                         }
2118                 }
2119         }
2120         if err != nil {
2121                 return
2122         }
2123         t.addTrackers(spec.Trackers)
2124
2125         cl.torrents[spec.InfoHash] = t
2126         T.torrent = t
2127
2128         // From this point onwards, we can consider the torrent a part of the
2129         // client.
2130         if new {
2131                 t.pruneTimer = time.AfterFunc(0, func() {
2132                         cl.pruneConnectionsUnlocked(T.torrent)
2133                 })
2134                 if !cl.config.DisableTrackers {
2135                         go cl.announceTorrentTrackers(T.torrent)
2136                 }
2137                 if cl.dHT != nil {
2138                         go cl.announceTorrentDHT(T.torrent, true)
2139                 }
2140         }
2141         return
2142 }
2143
2144 // Prunes unused connections. This is required to make space to dial for
2145 // replacements.
2146 func (cl *Client) pruneConnectionsUnlocked(t *torrent) {
2147         select {
2148         case <-t.ceasingNetworking:
2149                 return
2150         case <-t.closing:
2151                 return
2152         default:
2153         }
2154         cl.mu.Lock()
2155         license := len(t.Conns) - (socketsPerTorrent+1)/2
2156         for _, c := range t.Conns {
2157                 if license <= 0 {
2158                         break
2159                 }
2160                 if time.Now().Sub(c.lastUsefulChunkReceived) < time.Minute {
2161                         continue
2162                 }
2163                 if time.Now().Sub(c.completedHandshake) < time.Minute {
2164                         continue
2165                 }
2166                 c.Close()
2167                 license--
2168         }
2169         cl.mu.Unlock()
2170         t.pruneTimer.Reset(pruneInterval)
2171 }
2172
2173 func (me *Client) dropTorrent(infoHash InfoHash) (err error) {
2174         t, ok := me.torrents[infoHash]
2175         if !ok {
2176                 err = fmt.Errorf("no such torrent")
2177                 return
2178         }
2179         err = t.close()
2180         if err != nil {
2181                 panic(err)
2182         }
2183         delete(me.torrents, infoHash)
2184         return
2185 }
2186
2187 // Returns true when peers are required, or false if the torrent is closing.
2188 func (cl *Client) waitWantPeers(t *torrent) bool {
2189         cl.mu.Lock()
2190         defer cl.mu.Unlock()
2191         t.stateMu.Lock()
2192         defer t.stateMu.Unlock()
2193         for {
2194                 select {
2195                 case <-t.ceasingNetworking:
2196                         return false
2197                 default:
2198                 }
2199                 if len(t.Peers) < torrentPeersLowWater && t.needData() {
2200                         return true
2201                 }
2202                 cl.mu.Unlock()
2203                 t.wantPeers.Wait()
2204                 t.stateMu.Unlock()
2205                 cl.mu.Lock()
2206                 t.stateMu.Lock()
2207         }
2208 }
2209
2210 func (cl *Client) announceTorrentDHT(t *torrent, impliedPort bool) {
2211         for cl.waitWantPeers(t) {
2212                 log.Printf("getting peers for %q from DHT", t)
2213                 ps, err := cl.dHT.Announce(string(t.InfoHash[:]), cl.incomingPeerPort(), impliedPort)
2214                 if err != nil {
2215                         log.Printf("error getting peers from dht: %s", err)
2216                         return
2217                 }
2218                 allAddrs := make(map[string]struct{})
2219         getPeers:
2220                 for {
2221                         select {
2222                         case v, ok := <-ps.Peers:
2223                                 if !ok {
2224                                         break getPeers
2225                                 }
2226                                 peersFoundByDHT.Add(int64(len(v.Peers)))
2227                                 for _, p := range v.Peers {
2228                                         allAddrs[(&net.UDPAddr{
2229                                                 IP:   p.IP[:],
2230                                                 Port: int(p.Port),
2231                                         }).String()] = struct{}{}
2232                                 }
2233                                 // log.Printf("%s: %d new peers from DHT", t, len(v.Peers))
2234                                 cl.mu.Lock()
2235                                 cl.addPeers(t, func() (ret []Peer) {
2236                                         for _, cp := range v.Peers {
2237                                                 ret = append(ret, Peer{
2238                                                         IP:     cp.IP[:],
2239                                                         Port:   int(cp.Port),
2240                                                         Source: peerSourceDHT,
2241                                                 })
2242                                         }
2243                                         return
2244                                 }())
2245                                 numPeers := len(t.Peers)
2246                                 cl.mu.Unlock()
2247                                 if numPeers >= torrentPeersHighWater {
2248                                         break getPeers
2249                                 }
2250                         case <-t.ceasingNetworking:
2251                                 ps.Close()
2252                                 return
2253                         }
2254                 }
2255                 ps.Close()
2256                 log.Printf("finished DHT peer scrape for %s: %d peers", t, len(allAddrs))
2257         }
2258 }
2259
2260 func (cl *Client) trackerBlockedUnlocked(tr tracker.Client) (blocked bool, err error) {
2261         url_, err := url.Parse(tr.URL())
2262         if err != nil {
2263                 return
2264         }
2265         host, _, err := net.SplitHostPort(url_.Host)
2266         if err != nil {
2267                 host = url_.Host
2268         }
2269         addr, err := net.ResolveIPAddr("ip", host)
2270         if err != nil {
2271                 return
2272         }
2273         cl.mu.Lock()
2274         if cl.ipBlockList != nil {
2275                 if cl.ipBlockRange(addr.IP) != nil {
2276                         blocked = true
2277                 }
2278         }
2279         cl.mu.Unlock()
2280         return
2281 }
2282
2283 func (cl *Client) announceTorrentSingleTracker(tr tracker.Client, req *tracker.AnnounceRequest, t *torrent) error {
2284         blocked, err := cl.trackerBlockedUnlocked(tr)
2285         if err != nil {
2286                 return fmt.Errorf("error determining if tracker blocked: %s", err)
2287         }
2288         if blocked {
2289                 return fmt.Errorf("tracker blocked: %s", tr)
2290         }
2291         if err := tr.Connect(); err != nil {
2292                 return fmt.Errorf("error connecting: %s", err)
2293         }
2294         resp, err := tr.Announce(req)
2295         if err != nil {
2296                 return fmt.Errorf("error announcing: %s", err)
2297         }
2298         var peers []Peer
2299         for _, peer := range resp.Peers {
2300                 peers = append(peers, Peer{
2301                         IP:   peer.IP,
2302                         Port: peer.Port,
2303                 })
2304         }
2305         cl.mu.Lock()
2306         cl.addPeers(t, peers)
2307         cl.mu.Unlock()
2308
2309         log.Printf("%s: %d new peers from %s", t, len(peers), tr)
2310         peersFoundByTracker.Add(int64(len(peers)))
2311
2312         time.Sleep(time.Second * time.Duration(resp.Interval))
2313         return nil
2314 }
2315
2316 func (cl *Client) announceTorrentTrackersFastStart(req *tracker.AnnounceRequest, trackers [][]tracker.Client, t *torrent) (atLeastOne bool) {
2317         oks := make(chan bool)
2318         outstanding := 0
2319         for _, tier := range trackers {
2320                 for _, tr := range tier {
2321                         outstanding++
2322                         go func(tr tracker.Client) {
2323                                 err := cl.announceTorrentSingleTracker(tr, req, t)
2324                                 oks <- err == nil
2325                         }(tr)
2326                 }
2327         }
2328         for outstanding > 0 {
2329                 ok := <-oks
2330                 outstanding--
2331                 if ok {
2332                         atLeastOne = true
2333                 }
2334         }
2335         return
2336 }
2337
2338 // Announce torrent to its trackers.
2339 func (cl *Client) announceTorrentTrackers(t *torrent) {
2340         req := tracker.AnnounceRequest{
2341                 Event:    tracker.Started,
2342                 NumWant:  -1,
2343                 Port:     uint16(cl.incomingPeerPort()),
2344                 PeerId:   cl.peerID,
2345                 InfoHash: t.InfoHash,
2346         }
2347         if !cl.waitWantPeers(t) {
2348                 return
2349         }
2350         cl.mu.RLock()
2351         req.Left = uint64(t.bytesLeft())
2352         trackers := t.Trackers
2353         cl.mu.RUnlock()
2354         if cl.announceTorrentTrackersFastStart(&req, trackers, t) {
2355                 req.Event = tracker.None
2356         }
2357 newAnnounce:
2358         for cl.waitWantPeers(t) {
2359                 cl.mu.RLock()
2360                 req.Left = uint64(t.bytesLeft())
2361                 trackers = t.Trackers
2362                 cl.mu.RUnlock()
2363                 numTrackersTried := 0
2364                 for _, tier := range trackers {
2365                         for trIndex, tr := range tier {
2366                                 numTrackersTried++
2367                                 err := cl.announceTorrentSingleTracker(tr, &req, t)
2368                                 if err != nil {
2369                                         logonce.Stderr.Printf("%s: error announcing to %s: %s", t, tr, err)
2370                                         continue
2371                                 }
2372                                 // Float the successful announce to the top of the tier. If
2373                                 // the trackers list has been changed, we'll be modifying an
2374                                 // old copy so it won't matter.
2375                                 cl.mu.Lock()
2376                                 tier[0], tier[trIndex] = tier[trIndex], tier[0]
2377                                 cl.mu.Unlock()
2378
2379                                 req.Event = tracker.None
2380                                 continue newAnnounce
2381                         }
2382                 }
2383                 if numTrackersTried != 0 {
2384                         log.Printf("%s: all trackers failed", t)
2385                 }
2386                 // TODO: Wait until trackers are added if there are none.
2387                 time.Sleep(10 * time.Second)
2388         }
2389 }
2390
2391 func (cl *Client) allTorrentsCompleted() bool {
2392         for _, t := range cl.torrents {
2393                 if !t.haveInfo() {
2394                         return false
2395                 }
2396                 if t.numPiecesCompleted() != t.numPieces() {
2397                         return false
2398                 }
2399         }
2400         return true
2401 }
2402
2403 // Returns true when all torrents are completely downloaded and false if the
2404 // client is stopped before that.
2405 func (me *Client) WaitAll() bool {
2406         me.mu.Lock()
2407         defer me.mu.Unlock()
2408         for !me.allTorrentsCompleted() {
2409                 if me.stopped() {
2410                         return false
2411                 }
2412                 me.event.Wait()
2413         }
2414         return true
2415 }
2416
2417 func (me *Client) fillRequests(t *torrent, c *connection) {
2418         if c.Interested {
2419                 if c.PeerChoked {
2420                         return
2421                 }
2422                 if len(c.Requests) > c.requestsLowWater {
2423                         return
2424                 }
2425         }
2426         addRequest := func(req request) (again bool) {
2427                 // TODO: Couldn't this check also be done *after* the request?
2428                 if len(c.Requests) >= 64 {
2429                         return false
2430                 }
2431                 return c.Request(req)
2432         }
2433         for req := range t.urgent {
2434                 if !addRequest(req) {
2435                         return
2436                 }
2437         }
2438         for e := c.pieceRequestOrder.First(); e != nil; e = e.Next() {
2439                 pieceIndex := e.Piece()
2440                 if !c.PeerHasPiece(pieceIndex) {
2441                         panic("piece in request order but peer doesn't have it")
2442                 }
2443                 if !t.wantPiece(pieceIndex) {
2444                         panic("unwanted piece in connection request order")
2445                 }
2446                 piece := t.Pieces[pieceIndex]
2447                 for _, cs := range piece.shuffledPendingChunkSpecs() {
2448                         r := request{pp.Integer(pieceIndex), cs}
2449                         if !addRequest(r) {
2450                                 return
2451                         }
2452                 }
2453         }
2454         return
2455 }
2456
2457 func (me *Client) replenishConnRequests(t *torrent, c *connection) {
2458         if !t.haveInfo() {
2459                 return
2460         }
2461         me.fillRequests(t, c)
2462         if len(c.Requests) == 0 && !c.PeerChoked {
2463                 // So we're not choked, but we don't want anything right now. We may
2464                 // have completed readahead, and the readahead window has not rolled
2465                 // over to the next piece. Better to stay interested in case we're
2466                 // going to want data in the near future.
2467                 c.SetInterested(!t.haveAllPieces())
2468         }
2469 }
2470
2471 // Handle a received chunk from a peer.
2472 func (me *Client) downloadedChunk(t *torrent, c *connection, msg *pp.Message) error {
2473         chunksDownloadedCount.Add(1)
2474
2475         req := newRequest(msg.Index, msg.Begin, pp.Integer(len(msg.Piece)))
2476
2477         // Request has been satisfied.
2478         me.connDeleteRequest(t, c, req)
2479
2480         defer me.replenishConnRequests(t, c)
2481
2482         piece := t.Pieces[req.Index]
2483
2484         // Do we actually want this chunk?
2485         if !t.wantChunk(req) {
2486                 unusedDownloadedChunksCount.Add(1)
2487                 c.UnwantedChunksReceived++
2488                 return nil
2489         }
2490
2491         c.UsefulChunksReceived++
2492         c.lastUsefulChunkReceived = time.Now()
2493
2494         // Write the chunk out.
2495         err := t.writeChunk(int(msg.Index), int64(msg.Begin), msg.Piece)
2496         if err != nil {
2497                 return fmt.Errorf("error writing chunk: %s", err)
2498         }
2499
2500         // log.Println("got chunk", req)
2501         piece.Event.Broadcast()
2502         // Record that we have the chunk.
2503         delete(piece.PendingChunkSpecs, req.chunkSpec)
2504         delete(t.urgent, req)
2505         if len(piece.PendingChunkSpecs) == 0 {
2506                 for _, c := range t.Conns {
2507                         c.pieceRequestOrder.DeletePiece(int(req.Index))
2508                 }
2509                 me.queuePieceCheck(t, req.Index)
2510         }
2511
2512         // Cancel pending requests for this chunk.
2513         for _, c := range t.Conns {
2514                 if me.connCancel(t, c, req) {
2515                         me.replenishConnRequests(t, c)
2516                 }
2517         }
2518
2519         return nil
2520 }
2521
2522 func (me *Client) pieceHashed(t *torrent, piece pp.Integer, correct bool) {
2523         p := t.Pieces[piece]
2524         if p.EverHashed && !correct {
2525                 log.Printf("%s: piece %d failed hash", t, piece)
2526                 failedPieceHashes.Add(1)
2527         }
2528         p.EverHashed = true
2529         if correct {
2530                 if sd, ok := t.data.(StatefulData); ok {
2531                         err := sd.PieceCompleted(int(piece))
2532                         if err != nil {
2533                                 log.Printf("error completing piece: %s", err)
2534                                 correct = false
2535                         }
2536                 }
2537         }
2538         me.pieceChanged(t, int(piece))
2539 }
2540
2541 // TODO: Check this isn't called more than once for each piece being correct.
2542 func (me *Client) pieceChanged(t *torrent, piece int) {
2543         correct := t.pieceComplete(piece)
2544         p := t.Pieces[piece]
2545         if correct {
2546                 p.Priority = piecePriorityNone
2547                 p.PendingChunkSpecs = nil
2548                 for req := range t.urgent {
2549                         if int(req.Index) == piece {
2550                                 delete(t.urgent, req)
2551                         }
2552                 }
2553                 p.Event.Broadcast()
2554         } else {
2555                 if len(p.PendingChunkSpecs) == 0 {
2556                         t.pendAllChunkSpecs(int(piece))
2557                 }
2558                 if t.wantPiece(piece) {
2559                         me.openNewConns(t)
2560                 }
2561         }
2562         for _, conn := range t.Conns {
2563                 if correct {
2564                         conn.Post(pp.Message{
2565                                 Type:  pp.Have,
2566                                 Index: pp.Integer(piece),
2567                         })
2568                         // TODO: Cancel requests for this piece.
2569                         for r := range conn.Requests {
2570                                 if int(r.Index) == piece {
2571                                         panic("wat")
2572                                 }
2573                         }
2574                         conn.pieceRequestOrder.DeletePiece(int(piece))
2575                 }
2576                 if t.wantPiece(piece) && conn.PeerHasPiece(piece) {
2577                         t.connPendPiece(conn, int(piece))
2578                         me.replenishConnRequests(t, conn)
2579                 }
2580         }
2581         if t.haveAllPieces() && me.config.NoUpload {
2582                 t.ceaseNetworking()
2583         }
2584         me.event.Broadcast()
2585 }
2586
2587 func (cl *Client) verifyPiece(t *torrent, index pp.Integer) {
2588         cl.mu.Lock()
2589         defer cl.mu.Unlock()
2590         p := t.Pieces[index]
2591         for p.Hashing || t.data == nil {
2592                 cl.event.Wait()
2593         }
2594         p.QueuedForHash = false
2595         if t.isClosed() || t.pieceComplete(int(index)) {
2596                 return
2597         }
2598         p.Hashing = true
2599         cl.mu.Unlock()
2600         sum := t.hashPiece(index)
2601         cl.mu.Lock()
2602         select {
2603         case <-t.closing:
2604                 return
2605         default:
2606         }
2607         p.Hashing = false
2608         cl.pieceHashed(t, index, sum == p.Hash)
2609 }
2610
2611 // Returns handles to all the torrents loaded in the Client.
2612 func (me *Client) Torrents() (ret []Torrent) {
2613         me.mu.Lock()
2614         for _, t := range me.torrents {
2615                 ret = append(ret, Torrent{me, t, t.gotMetainfo})
2616         }
2617         me.mu.Unlock()
2618         return
2619 }
2620
2621 func (me *Client) AddMagnet(uri string) (T Torrent, err error) {
2622         spec, err := TorrentSpecFromMagnetURI(uri)
2623         if err != nil {
2624                 return
2625         }
2626         T, _, err = me.AddTorrentSpec(spec)
2627         return
2628 }
2629
2630 func (me *Client) AddTorrent(mi *metainfo.MetaInfo) (T Torrent, err error) {
2631         T, _, err = me.AddTorrentSpec(TorrentSpecFromMetaInfo(mi))
2632         return
2633 }
2634
2635 func (me *Client) AddTorrentFromFile(filename string) (T Torrent, err error) {
2636         mi, err := metainfo.LoadFromFile(filename)
2637         if err != nil {
2638                 return
2639         }
2640         T, _, err = me.AddTorrentSpec(TorrentSpecFromMetaInfo(mi))
2641         return
2642 }