client.go

   1 package torrent
   2
   3 import (
   4         "bufio"
   5         "bytes"
   6         "crypto/rand"
   7         "encoding/hex"
   8         "errors"
   9         "fmt"
  10         "io"
  11         "log"
  12         mathRand "math/rand"
  13         "net"
  14         "net/url"
  15         "strconv"
  16         "strings"
  17         "time"
  18
  19         "github.com/anacrolix/missinggo"
  20         "github.com/anacrolix/missinggo/pproffd"
  21         "github.com/anacrolix/missinggo/pubsub"
  22         "github.com/anacrolix/missinggo/slices"
  23         "github.com/anacrolix/sync"
  24         "github.com/anacrolix/utp"
  25         "github.com/dustin/go-humanize"
  26
  27         "github.com/anacrolix/torrent/bencode"
  28         "github.com/anacrolix/torrent/dht"
  29         "github.com/anacrolix/torrent/dht/krpc"
  30         "github.com/anacrolix/torrent/iplist"
  31         "github.com/anacrolix/torrent/metainfo"
  32         "github.com/anacrolix/torrent/mse"
  33         pp "github.com/anacrolix/torrent/peer_protocol"
  34         "github.com/anacrolix/torrent/storage"
  35 )
  36
  37 // Currently doesn't really queue, but should in the future.
  38 func (cl *Client) queuePieceCheck(t *Torrent, pieceIndex int) {
  39         piece := &t.pieces[pieceIndex]
  40         if piece.QueuedForHash {
  41                 return
  42         }
  43         piece.QueuedForHash = true
  44         t.publishPieceChange(pieceIndex)
  45         go cl.verifyPiece(t, pieceIndex)
  46 }
  47
  48 // Queue a piece check if one isn't already queued, and the piece has never
  49 // been checked before.
  50 func (cl *Client) queueFirstHash(t *Torrent, piece int) {
  51         p := &t.pieces[piece]
  52         if p.EverHashed || p.Hashing || p.QueuedForHash || t.pieceComplete(piece) {
  53                 return
  54         }
  55         cl.queuePieceCheck(t, piece)
  56 }
  57
  58 // Clients contain zero or more Torrents. A Client manages a blocklist, the
  59 // TCP/UDP protocol ports, and DHT as desired.
  60 type Client struct {
  61         halfOpenLimit int
  62         peerID        [20]byte
  63         // The net.Addr.String part that should be common to all active listeners.
  64         listenAddr     string
  65         tcpListener    net.Listener
  66         utpSock        *utp.Socket
  67         dHT            *dht.Server
  68         ipBlockList    iplist.Ranger
  69         config         Config
  70         extensionBytes peerExtensionBytes
  71         // Set of addresses that have our client ID. This intentionally will
  72         // include ourselves if we end up trying to connect to our own address
  73         // through legitimate channels.
  74         dopplegangerAddrs map[string]struct{}
  75         badPeerIPs        map[string]struct{}
  76
  77         defaultStorage *storage.Client
  78
  79         mu     sync.RWMutex
  80         event  sync.Cond
  81         closed missinggo.Event
  82
  83         torrents map[metainfo.Hash]*Torrent
  84 }
  85
  86 func (cl *Client) BadPeerIPs() []string {
  87         cl.mu.RLock()
  88         defer cl.mu.RUnlock()
  89         return slices.FromMapKeys(cl.badPeerIPs).([]string)
  90 }
  91
  92 func (cl *Client) IPBlockList() iplist.Ranger {
  93         cl.mu.Lock()
  94         defer cl.mu.Unlock()
  95         return cl.ipBlockList
  96 }
  97
  98 func (cl *Client) SetIPBlockList(list iplist.Ranger) {
  99         cl.mu.Lock()
 100         defer cl.mu.Unlock()
 101         cl.ipBlockList = list
 102         if cl.dHT != nil {
 103                 cl.dHT.SetIPBlockList(list)
 104         }
 105 }
 106
 107 func (cl *Client) PeerID() string {
 108         return string(cl.peerID[:])
 109 }
 110
 111 type torrentAddr string
 112
 113 func (me torrentAddr) Network() string { return "" }
 114
 115 func (me torrentAddr) String() string { return string(me) }
 116
 117 func (cl *Client) ListenAddr() net.Addr {
 118         if cl.listenAddr == "" {
 119                 return nil
 120         }
 121         return torrentAddr(cl.listenAddr)
 122 }
 123
 124 func (cl *Client) sortedTorrents() (ret []*Torrent) {
 125         return slices.Sort(slices.FromMapElems(cl.torrents), func(l, r metainfo.Hash) bool {
 126                 return l.AsString() < r.AsString()
 127         }).([]*Torrent)
 128 }
 129
 130 // Writes out a human readable status of the client, such as for writing to a
 131 // HTTP status page.
 132 func (cl *Client) WriteStatus(_w io.Writer) {
 133         w := bufio.NewWriter(_w)
 134         defer w.Flush()
 135         if addr := cl.ListenAddr(); addr != nil {
 136                 fmt.Fprintf(w, "Listening on %s\n", addr)
 137         } else {
 138                 fmt.Fprintln(w, "Not listening!")
 139         }
 140         fmt.Fprintf(w, "Peer ID: %+q\n", cl.PeerID())
 141         fmt.Fprintf(w, "Banned IPs: %d\n", len(cl.BadPeerIPs()))
 142         if dht := cl.DHT(); dht != nil {
 143                 dhtStats := dht.Stats()
 144                 fmt.Fprintf(w, "DHT nodes: %d (%d good, %d banned)\n", dhtStats.Nodes, dhtStats.GoodNodes, dhtStats.BadNodes)
 145                 fmt.Fprintf(w, "DHT Server ID: %x\n", dht.ID())
 146                 fmt.Fprintf(w, "DHT port: %d\n", missinggo.AddrPort(dht.Addr()))
 147                 fmt.Fprintf(w, "DHT announces: %d\n", dhtStats.ConfirmedAnnounces)
 148                 fmt.Fprintf(w, "Outstanding transactions: %d\n", dhtStats.OutstandingTransactions)
 149         }
 150         fmt.Fprintf(w, "# Torrents: %d\n", len(cl.Torrents()))
 151         fmt.Fprintln(w)
 152         for _, t := range slices.Sort(append([]*Torrent(nil), cl.Torrents()...), func(l, r *Torrent) bool {
 153                 return l.InfoHash().AsString() < r.InfoHash().AsString()
 154         }).([]*Torrent) {
 155                 if t.Name() == "" {
 156                         fmt.Fprint(w, "<unknown name>")
 157                 } else {
 158                         fmt.Fprint(w, t.Name())
 159                 }
 160                 fmt.Fprint(w, "\n")
 161                 if t.Info() != nil {
 162                         fmt.Fprintf(w, "%f%% of %d bytes (%s)", 100*(1-float64(t.BytesMissing())/float64(t.Info().TotalLength())), t.length, humanize.Bytes(uint64(t.Info().TotalLength())))
 163                 } else {
 164                         w.WriteString("<missing metainfo>")
 165                 }
 166                 fmt.Fprint(w, "\n")
 167                 t.writeStatus(w)
 168                 fmt.Fprintln(w)
 169         }
 170 }
 171
 172 func listenUTP(networkSuffix, addr string) (*utp.Socket, error) {
 173         return utp.NewSocket("udp"+networkSuffix, addr)
 174 }
 175
 176 func listenTCP(networkSuffix, addr string) (net.Listener, error) {
 177         return net.Listen("tcp"+networkSuffix, addr)
 178 }
 179
 180 func listenBothSameDynamicPort(networkSuffix, host string) (tcpL net.Listener, utpSock *utp.Socket, listenedAddr string, err error) {
 181         for {
 182                 tcpL, err = listenTCP(networkSuffix, net.JoinHostPort(host, "0"))
 183                 if err != nil {
 184                         return
 185                 }
 186                 listenedAddr = tcpL.Addr().String()
 187                 utpSock, err = listenUTP(networkSuffix, listenedAddr)
 188                 if err == nil {
 189                         return
 190                 }
 191                 tcpL.Close()
 192                 if !strings.Contains(err.Error(), "address already in use") {
 193                         return
 194                 }
 195         }
 196 }
 197
 198 // Listen to enabled protocols, ensuring ports match.
 199 func listen(tcp, utp bool, networkSuffix, addr string) (tcpL net.Listener, utpSock *utp.Socket, listenedAddr string, err error) {
 200         if addr == "" {
 201                 addr = ":50007"
 202         }
 203         if tcp && utp {
 204                 var host string
 205                 var port int
 206                 host, port, err = missinggo.ParseHostPort(addr)
 207                 if err != nil {
 208                         return
 209                 }
 210                 if port == 0 {
 211                         // If both protocols are active, they need to have the same port.
 212                         return listenBothSameDynamicPort(networkSuffix, host)
 213                 }
 214         }
 215         defer func() {
 216                 if err != nil {
 217                         listenedAddr = ""
 218                 }
 219         }()
 220         if tcp {
 221                 tcpL, err = listenTCP(networkSuffix, addr)
 222                 if err != nil {
 223                         return
 224                 }
 225                 defer func() {
 226                         if err != nil {
 227                                 tcpL.Close()
 228                         }
 229                 }()
 230                 listenedAddr = tcpL.Addr().String()
 231         }
 232         if utp {
 233                 utpSock, err = listenUTP(networkSuffix, addr)
 234                 if err != nil {
 235                         return
 236                 }
 237                 listenedAddr = utpSock.Addr().String()
 238         }
 239         return
 240 }
 241
 242 // Creates a new client.
 243 func NewClient(cfg *Config) (cl *Client, err error) {
 244         if cfg == nil {
 245                 cfg = &Config{}
 246         }
 247
 248         defer func() {
 249                 if err != nil {
 250                         cl = nil
 251                 }
 252         }()
 253         cl = &Client{
 254                 halfOpenLimit:     defaultHalfOpenConnsPerTorrent,
 255                 config:            *cfg,
 256                 dopplegangerAddrs: make(map[string]struct{}),
 257                 torrents:          make(map[metainfo.Hash]*Torrent),
 258         }
 259         missinggo.CopyExact(&cl.extensionBytes, defaultExtensionBytes)
 260         cl.event.L = &cl.mu
 261         storageImpl := cfg.DefaultStorage
 262         if storageImpl == nil {
 263                 storageImpl = storage.NewFile(cfg.DataDir)
 264         }
 265         cl.defaultStorage = storage.NewClient(storageImpl)
 266         if cfg.IPBlocklist != nil {
 267                 cl.ipBlockList = cfg.IPBlocklist
 268         }
 269
 270         if cfg.PeerID != "" {
 271                 missinggo.CopyExact(&cl.peerID, cfg.PeerID)
 272         } else {
 273                 o := copy(cl.peerID[:], bep20)
 274                 _, err = rand.Read(cl.peerID[o:])
 275                 if err != nil {
 276                         panic("error generating peer id")
 277                 }
 278         }
 279
 280         cl.tcpListener, cl.utpSock, cl.listenAddr, err = listen(
 281                 !cl.config.DisableTCP,
 282                 !cl.config.DisableUTP,
 283                 func() string {
 284                         if cl.config.DisableIPv6 {
 285                                 return "4"
 286                         } else {
 287                                 return ""
 288                         }
 289                 }(),
 290                 cl.config.ListenAddr)
 291         if err != nil {
 292                 return
 293         }
 294         if cl.tcpListener != nil {
 295                 go cl.acceptConnections(cl.tcpListener, false)
 296         }
 297         if cl.utpSock != nil {
 298                 go cl.acceptConnections(cl.utpSock, true)
 299         }
 300         if !cfg.NoDHT {
 301                 dhtCfg := cfg.DHTConfig
 302                 if dhtCfg.IPBlocklist == nil {
 303                         dhtCfg.IPBlocklist = cl.ipBlockList
 304                 }
 305                 dhtCfg.Addr = firstNonEmptyString(dhtCfg.Addr, cl.listenAddr, cl.config.ListenAddr)
 306                 if dhtCfg.Conn == nil && cl.utpSock != nil {
 307                         dhtCfg.Conn = cl.utpSock
 308                 }
 309                 cl.dHT, err = dht.NewServer(&dhtCfg)
 310                 if err != nil {
 311                         return
 312                 }
 313         }
 314
 315         return
 316 }
 317
 318 func firstNonEmptyString(ss ...string) string {
 319         for _, s := range ss {
 320                 if s != "" {
 321                         return s
 322                 }
 323         }
 324         return ""
 325 }
 326
 327 // Stops the client. All connections to peers are closed and all activity will
 328 // come to a halt.
 329 func (cl *Client) Close() {
 330         cl.mu.Lock()
 331         defer cl.mu.Unlock()
 332         cl.closed.Set()
 333         if cl.dHT != nil {
 334                 cl.dHT.Close()
 335         }
 336         if cl.utpSock != nil {
 337                 cl.utpSock.CloseNow()
 338         }
 339         if cl.tcpListener != nil {
 340                 cl.tcpListener.Close()
 341         }
 342         for _, t := range cl.torrents {
 343                 t.close()
 344         }
 345         cl.event.Broadcast()
 346 }
 347
 348 var ipv6BlockRange = iplist.Range{Description: "non-IPv4 address"}
 349
 350 func (cl *Client) ipBlockRange(ip net.IP) (r iplist.Range, blocked bool) {
 351         if cl.ipBlockList == nil {
 352                 return
 353         }
 354         ip4 := ip.To4()
 355         // If blocklists are enabled, then block non-IPv4 addresses, because
 356         // blocklists do not yet support IPv6.
 357         if ip4 == nil {
 358                 if missinggo.CryHeard() {
 359                         log.Printf("blocking non-IPv4 address: %s", ip)
 360                 }
 361                 r = ipv6BlockRange
 362                 blocked = true
 363                 return
 364         }
 365         return cl.ipBlockList.Lookup(ip4)
 366 }
 367
 368 func (cl *Client) waitAccept() {
 369         for {
 370                 for _, t := range cl.torrents {
 371                         if t.wantConns() {
 372                                 return
 373                         }
 374                 }
 375                 if cl.closed.IsSet() {
 376                         return
 377                 }
 378                 cl.event.Wait()
 379         }
 380 }
 381
 382 func (cl *Client) acceptConnections(l net.Listener, utp bool) {
 383         cl.mu.Lock()
 384         defer cl.mu.Unlock()
 385         for {
 386                 cl.waitAccept()
 387                 cl.mu.Unlock()
 388                 conn, err := l.Accept()
 389                 conn = pproffd.WrapNetConn(conn)
 390                 cl.mu.Lock()
 391                 if cl.closed.IsSet() {
 392                         if conn != nil {
 393                                 conn.Close()
 394                         }
 395                         return
 396                 }
 397                 if err != nil {
 398                         log.Print(err)
 399                         // I think something harsher should happen here? Our accept
 400                         // routine just fucked off.
 401                         return
 402                 }
 403                 if utp {
 404                         acceptUTP.Add(1)
 405                 } else {
 406                         acceptTCP.Add(1)
 407                 }
 408                 reject := cl.badPeerIPPort(
 409                         missinggo.AddrIP(conn.RemoteAddr()),
 410                         missinggo.AddrPort(conn.RemoteAddr()))
 411                 if reject {
 412                         acceptReject.Add(1)
 413                         conn.Close()
 414                         continue
 415                 }
 416                 go cl.incomingConnection(conn, utp)
 417         }
 418 }
 419
 420 func (cl *Client) incomingConnection(nc net.Conn, utp bool) {
 421         defer nc.Close()
 422         if tc, ok := nc.(*net.TCPConn); ok {
 423                 tc.SetLinger(0)
 424         }
 425         c := newConnection(nc, &cl.mu)
 426         c.Discovery = peerSourceIncoming
 427         c.uTP = utp
 428         cl.runReceivedConn(c)
 429 }
 430
 431 // Returns a handle to the given torrent, if it's present in the client.
 432 func (cl *Client) Torrent(ih metainfo.Hash) (t *Torrent, ok bool) {
 433         cl.mu.Lock()
 434         defer cl.mu.Unlock()
 435         t, ok = cl.torrents[ih]
 436         return
 437 }
 438
 439 func (cl *Client) torrent(ih metainfo.Hash) *Torrent {
 440         return cl.torrents[ih]
 441 }
 442
 443 type dialResult struct {
 444         Conn net.Conn
 445         UTP  bool
 446 }
 447
 448 func doDial(dial func(addr string, t *Torrent) (net.Conn, error), ch chan dialResult, utp bool, addr string, t *Torrent) {
 449         conn, err := dial(addr, t)
 450         if err != nil {
 451                 if conn != nil {
 452                         conn.Close()
 453                 }
 454                 conn = nil // Pedantic
 455         }
 456         ch <- dialResult{conn, utp}
 457         if err == nil {
 458                 successfulDials.Add(1)
 459                 return
 460         }
 461         unsuccessfulDials.Add(1)
 462 }
 463
 464 func reducedDialTimeout(max time.Duration, halfOpenLimit int, pendingPeers int) (ret time.Duration) {
 465         ret = max / time.Duration((pendingPeers+halfOpenLimit)/halfOpenLimit)
 466         if ret < minDialTimeout {
 467                 ret = minDialTimeout
 468         }
 469         return
 470 }
 471
 472 // Returns whether an address is known to connect to a client with our own ID.
 473 func (cl *Client) dopplegangerAddr(addr string) bool {
 474         _, ok := cl.dopplegangerAddrs[addr]
 475         return ok
 476 }
 477
 478 // Start the process of connecting to the given peer for the given torrent if
 479 // appropriate.
 480 func (cl *Client) initiateConn(peer Peer, t *Torrent) {
 481         if peer.Id == cl.peerID {
 482                 return
 483         }
 484         if cl.badPeerIPPort(peer.IP, peer.Port) {
 485                 return
 486         }
 487         addr := net.JoinHostPort(peer.IP.String(), fmt.Sprintf("%d", peer.Port))
 488         if t.addrActive(addr) {
 489                 return
 490         }
 491         t.halfOpen[addr] = struct{}{}
 492         go cl.outgoingConnection(t, addr, peer.Source)
 493 }
 494
 495 func (cl *Client) dialTimeout(t *Torrent) time.Duration {
 496         cl.mu.Lock()
 497         pendingPeers := len(t.peers)
 498         cl.mu.Unlock()
 499         return reducedDialTimeout(nominalDialTimeout, cl.halfOpenLimit, pendingPeers)
 500 }
 501
 502 func (cl *Client) dialTCP(addr string, t *Torrent) (c net.Conn, err error) {
 503         c, err = net.DialTimeout("tcp", addr, cl.dialTimeout(t))
 504         if err == nil {
 505                 c.(*net.TCPConn).SetLinger(0)
 506         }
 507         c = pproffd.WrapNetConn(c)
 508         return
 509 }
 510
 511 func (cl *Client) dialUTP(addr string, t *Torrent) (c net.Conn, err error) {
 512         return cl.utpSock.DialTimeout(addr, cl.dialTimeout(t))
 513 }
 514
 515 // Returns a connection over UTP or TCP, whichever is first to connect.
 516 func (cl *Client) dialFirst(addr string, t *Torrent) (conn net.Conn, utp bool) {
 517         // Initiate connections via TCP and UTP simultaneously. Use the first one
 518         // that succeeds.
 519         left := 0
 520         if !cl.config.DisableUTP {
 521                 left++
 522         }
 523         if !cl.config.DisableTCP {
 524                 left++
 525         }
 526         resCh := make(chan dialResult, left)
 527         if !cl.config.DisableUTP {
 528                 go doDial(cl.dialUTP, resCh, true, addr, t)
 529         }
 530         if !cl.config.DisableTCP {
 531                 go doDial(cl.dialTCP, resCh, false, addr, t)
 532         }
 533         var res dialResult
 534         // Wait for a successful connection.
 535         for ; left > 0 && res.Conn == nil; left-- {
 536                 res = <-resCh
 537         }
 538         if left > 0 {
 539                 // There are still incompleted dials.
 540                 go func() {
 541                         for ; left > 0; left-- {
 542                                 conn := (<-resCh).Conn
 543                                 if conn != nil {
 544                                         conn.Close()
 545                                 }
 546                         }
 547                 }()
 548         }
 549         conn = res.Conn
 550         utp = res.UTP
 551         return
 552 }
 553
 554 func (cl *Client) noLongerHalfOpen(t *Torrent, addr string) {
 555         if _, ok := t.halfOpen[addr]; !ok {
 556                 panic("invariant broken")
 557         }
 558         delete(t.halfOpen, addr)
 559         cl.openNewConns(t)
 560 }
 561
 562 // Performs initiator handshakes and returns a connection. Returns nil
 563 // *connection if no connection for valid reasons.
 564 func (cl *Client) handshakesConnection(nc net.Conn, t *Torrent, encrypted, utp bool) (c *connection, err error) {
 565         c = newConnection(nc, &cl.mu)
 566         c.encrypted = encrypted
 567         c.uTP = utp
 568         err = nc.SetDeadline(time.Now().Add(handshakesTimeout))
 569         if err != nil {
 570                 return
 571         }
 572         ok, err := cl.initiateHandshakes(c, t)
 573         if !ok {
 574                 c = nil
 575         }
 576         return
 577 }
 578
 579 // Returns nil connection and nil error if no connection could be established
 580 // for valid reasons.
 581 func (cl *Client) establishOutgoingConn(t *Torrent, addr string) (c *connection, err error) {
 582         nc, utp := cl.dialFirst(addr, t)
 583         if nc == nil {
 584                 return
 585         }
 586         c, err = cl.handshakesConnection(nc, t, !cl.config.DisableEncryption, utp)
 587         if err != nil {
 588                 nc.Close()
 589                 return
 590         } else if c != nil {
 591                 return
 592         }
 593         nc.Close()
 594         if cl.config.DisableEncryption {
 595                 // We already tried without encryption.
 596                 return
 597         }
 598         // Try again without encryption, using whichever protocol type worked last
 599         // time.
 600         if utp {
 601                 nc, err = cl.dialUTP(addr, t)
 602         } else {
 603                 nc, err = cl.dialTCP(addr, t)
 604         }
 605         if err != nil {
 606                 err = fmt.Errorf("error dialing for unencrypted connection: %s", err)
 607                 return
 608         }
 609         c, err = cl.handshakesConnection(nc, t, false, utp)
 610         if err != nil || c == nil {
 611                 nc.Close()
 612         }
 613         return
 614 }
 615
 616 // Called to dial out and run a connection. The addr we're given is already
 617 // considered half-open.
 618 func (cl *Client) outgoingConnection(t *Torrent, addr string, ps peerSource) {
 619         c, err := cl.establishOutgoingConn(t, addr)
 620         cl.mu.Lock()
 621         defer cl.mu.Unlock()
 622         // Don't release lock between here and addConnection, unless it's for
 623         // failure.
 624         cl.noLongerHalfOpen(t, addr)
 625         if err != nil {
 626                 if cl.config.Debug {
 627                         log.Printf("error establishing outgoing connection: %s", err)
 628                 }
 629                 return
 630         }
 631         if c == nil {
 632                 return
 633         }
 634         defer c.Close()
 635         c.Discovery = ps
 636         cl.runInitiatedHandshookConn(c, t)
 637 }
 638
 639 // The port number for incoming peer connections. 0 if the client isn't
 640 // listening.
 641 func (cl *Client) incomingPeerPort() int {
 642         if cl.listenAddr == "" {
 643                 return 0
 644         }
 645         _, port, err := missinggo.ParseHostPort(cl.listenAddr)
 646         if err != nil {
 647                 panic(err)
 648         }
 649         return port
 650 }
 651
 652 // Convert a net.Addr to its compact IP representation. Either 4 or 16 bytes
 653 // per "yourip" field of http://www.bittorrent.org/beps/bep_0010.html.
 654 func addrCompactIP(addr net.Addr) (string, error) {
 655         host, _, err := net.SplitHostPort(addr.String())
 656         if err != nil {
 657                 return "", err
 658         }
 659         ip := net.ParseIP(host)
 660         if v4 := ip.To4(); v4 != nil {
 661                 if len(v4) != 4 {
 662                         panic(v4)
 663                 }
 664                 return string(v4), nil
 665         }
 666         return string(ip.To16()), nil
 667 }
 668
 669 func handshakeWriter(w io.Writer, bb <-chan []byte, done chan<- error) {
 670         var err error
 671         for b := range bb {
 672                 _, err = w.Write(b)
 673                 if err != nil {
 674                         break
 675                 }
 676         }
 677         done <- err
 678 }
 679
 680 type (
 681         peerExtensionBytes [8]byte
 682         peerID             [20]byte
 683 )
 684
 685 func (pex *peerExtensionBytes) SupportsExtended() bool {
 686         return pex[5]&0x10 != 0
 687 }
 688
 689 func (pex *peerExtensionBytes) SupportsDHT() bool {
 690         return pex[7]&0x01 != 0
 691 }
 692
 693 func (pex *peerExtensionBytes) SupportsFast() bool {
 694         return pex[7]&0x04 != 0
 695 }
 696
 697 type handshakeResult struct {
 698         peerExtensionBytes
 699         peerID
 700         metainfo.Hash
 701 }
 702
 703 // ih is nil if we expect the peer to declare the InfoHash, such as when the
 704 // peer initiated the connection. Returns ok if the handshake was successful,
 705 // and err if there was an unexpected condition other than the peer simply
 706 // abandoning the handshake.
 707 func handshake(sock io.ReadWriter, ih *metainfo.Hash, peerID [20]byte, extensions peerExtensionBytes) (res handshakeResult, ok bool, err error) {
 708         // Bytes to be sent to the peer. Should never block the sender.
 709         postCh := make(chan []byte, 4)
 710         // A single error value sent when the writer completes.
 711         writeDone := make(chan error, 1)
 712         // Performs writes to the socket and ensures posts don't block.
 713         go handshakeWriter(sock, postCh, writeDone)
 714
 715         defer func() {
 716                 close(postCh) // Done writing.
 717                 if !ok {
 718                         return
 719                 }
 720                 if err != nil {
 721                         panic(err)
 722                 }
 723                 // Wait until writes complete before returning from handshake.
 724                 err = <-writeDone
 725                 if err != nil {
 726                         err = fmt.Errorf("error writing: %s", err)
 727                 }
 728         }()
 729
 730         post := func(bb []byte) {
 731                 select {
 732                 case postCh <- bb:
 733                 default:
 734                         panic("mustn't block while posting")
 735                 }
 736         }
 737
 738         post([]byte(pp.Protocol))
 739         post(extensions[:])
 740         if ih != nil { // We already know what we want.
 741                 post(ih[:])
 742                 post(peerID[:])
 743         }
 744         var b [68]byte
 745         _, err = io.ReadFull(sock, b[:68])
 746         if err != nil {
 747                 err = nil
 748                 return
 749         }
 750         if string(b[:20]) != pp.Protocol {
 751                 return
 752         }
 753         missinggo.CopyExact(&res.peerExtensionBytes, b[20:28])
 754         missinggo.CopyExact(&res.Hash, b[28:48])
 755         missinggo.CopyExact(&res.peerID, b[48:68])
 756         peerExtensions.Add(hex.EncodeToString(res.peerExtensionBytes[:]), 1)
 757
 758         // TODO: Maybe we can just drop peers here if we're not interested. This
 759         // could prevent them trying to reconnect, falsely believing there was
 760         // just a problem.
 761         if ih == nil { // We were waiting for the peer to tell us what they wanted.
 762                 post(res.Hash[:])
 763                 post(peerID[:])
 764         }
 765
 766         ok = true
 767         return
 768 }
 769
 770 // Wraps a raw connection and provides the interface we want for using the
 771 // connection in the message loop.
 772 type deadlineReader struct {
 773         nc net.Conn
 774         r  io.Reader
 775 }
 776
 777 func (r deadlineReader) Read(b []byte) (n int, err error) {
 778         // Keep-alives should be received every 2 mins. Give a bit of gracetime.
 779         err = r.nc.SetReadDeadline(time.Now().Add(150 * time.Second))
 780         if err != nil {
 781                 err = fmt.Errorf("error setting read deadline: %s", err)
 782         }
 783         n, err = r.r.Read(b)
 784         // Convert common errors into io.EOF.
 785         // if err != nil {
 786         //      if opError, ok := err.(*net.OpError); ok && opError.Op == "read" && opError.Err == syscall.ECONNRESET {
 787         //              err = io.EOF
 788         //      } else if netErr, ok := err.(net.Error); ok && netErr.Timeout() {
 789         //              if n != 0 {
 790         //                      panic(n)
 791         //              }
 792         //              err = io.EOF
 793         //      }
 794         // }
 795         return
 796 }
 797
 798 type readWriter struct {
 799         io.Reader
 800         io.Writer
 801 }
 802
 803 func maybeReceiveEncryptedHandshake(rw io.ReadWriter, skeys [][]byte) (ret io.ReadWriter, encrypted bool, err error) {
 804         var protocol [len(pp.Protocol)]byte
 805         _, err = io.ReadFull(rw, protocol[:])
 806         if err != nil {
 807                 return
 808         }
 809         ret = readWriter{
 810                 io.MultiReader(bytes.NewReader(protocol[:]), rw),
 811                 rw,
 812         }
 813         if string(protocol[:]) == pp.Protocol {
 814                 return
 815         }
 816         encrypted = true
 817         ret, err = mse.ReceiveHandshake(ret, skeys)
 818         return
 819 }
 820
 821 func (cl *Client) receiveSkeys() (ret [][]byte) {
 822         for ih := range cl.torrents {
 823                 ret = append(ret, ih[:])
 824         }
 825         return
 826 }
 827
 828 func (cl *Client) initiateHandshakes(c *connection, t *Torrent) (ok bool, err error) {
 829         if c.encrypted {
 830                 c.rw, err = mse.InitiateHandshake(c.rw, t.infoHash[:], nil)
 831                 if err != nil {
 832                         return
 833                 }
 834         }
 835         ih, ok, err := cl.connBTHandshake(c, &t.infoHash)
 836         if ih != t.infoHash {
 837                 ok = false
 838         }
 839         return
 840 }
 841
 842 // Do encryption and bittorrent handshakes as receiver.
 843 func (cl *Client) receiveHandshakes(c *connection) (t *Torrent, err error) {
 844         cl.mu.Lock()
 845         skeys := cl.receiveSkeys()
 846         cl.mu.Unlock()
 847         if !cl.config.DisableEncryption {
 848                 c.rw, c.encrypted, err = maybeReceiveEncryptedHandshake(c.rw, skeys)
 849                 if err != nil {
 850                         if err == mse.ErrNoSecretKeyMatch {
 851                                 err = nil
 852                         }
 853                         return
 854                 }
 855         }
 856         ih, ok, err := cl.connBTHandshake(c, nil)
 857         if err != nil {
 858                 err = fmt.Errorf("error during bt handshake: %s", err)
 859                 return
 860         }
 861         if !ok {
 862                 return
 863         }
 864         cl.mu.Lock()
 865         t = cl.torrents[ih]
 866         cl.mu.Unlock()
 867         return
 868 }
 869
 870 // Returns !ok if handshake failed for valid reasons.
 871 func (cl *Client) connBTHandshake(c *connection, ih *metainfo.Hash) (ret metainfo.Hash, ok bool, err error) {
 872         res, ok, err := handshake(c.rw, ih, cl.peerID, cl.extensionBytes)
 873         if err != nil || !ok {
 874                 return
 875         }
 876         ret = res.Hash
 877         c.PeerExtensionBytes = res.peerExtensionBytes
 878         c.PeerID = res.peerID
 879         c.completedHandshake = time.Now()
 880         return
 881 }
 882
 883 func (cl *Client) runInitiatedHandshookConn(c *connection, t *Torrent) {
 884         if c.PeerID == cl.peerID {
 885                 connsToSelf.Add(1)
 886                 addr := c.conn.RemoteAddr().String()
 887                 cl.dopplegangerAddrs[addr] = struct{}{}
 888                 return
 889         }
 890         cl.runHandshookConn(c, t)
 891 }
 892
 893 func (cl *Client) runReceivedConn(c *connection) {
 894         err := c.conn.SetDeadline(time.Now().Add(handshakesTimeout))
 895         if err != nil {
 896                 panic(err)
 897         }
 898         t, err := cl.receiveHandshakes(c)
 899         if err != nil {
 900                 if cl.config.Debug {
 901                         log.Printf("error receiving handshakes: %s", err)
 902                 }
 903                 return
 904         }
 905         if t == nil {
 906                 return
 907         }
 908         cl.mu.Lock()
 909         defer cl.mu.Unlock()
 910         if c.PeerID == cl.peerID {
 911                 // Because the remote address is not necessarily the same as its
 912                 // client's torrent listen address, we won't record the remote address
 913                 // as a doppleganger. Instead, the initiator can record *us* as the
 914                 // doppleganger.
 915                 return
 916         }
 917         cl.runHandshookConn(c, t)
 918 }
 919
 920 func (cl *Client) runHandshookConn(c *connection, t *Torrent) {
 921         c.conn.SetWriteDeadline(time.Time{})
 922         c.rw = readWriter{
 923                 deadlineReader{c.conn, c.rw},
 924                 c.rw,
 925         }
 926         completedHandshakeConnectionFlags.Add(c.connectionFlags(), 1)
 927         if !t.addConnection(c) {
 928                 return
 929         }
 930         defer t.dropConnection(c)
 931         go c.writer(time.Minute)
 932         cl.sendInitialMessages(c, t)
 933         err := cl.connectionLoop(t, c)
 934         if err != nil && cl.config.Debug {
 935                 log.Printf("error during connection loop: %s", err)
 936         }
 937 }
 938
 939 func (cl *Client) sendInitialMessages(conn *connection, torrent *Torrent) {
 940         if conn.PeerExtensionBytes.SupportsExtended() && cl.extensionBytes.SupportsExtended() {
 941                 conn.Post(pp.Message{
 942                         Type:       pp.Extended,
 943                         ExtendedID: pp.HandshakeExtendedID,
 944                         ExtendedPayload: func() []byte {
 945                                 d := map[string]interface{}{
 946                                         "m": func() (ret map[string]int) {
 947                                                 ret = make(map[string]int, 2)
 948                                                 ret["ut_metadata"] = metadataExtendedId
 949                                                 if !cl.config.DisablePEX {
 950                                                         ret["ut_pex"] = pexExtendedId
 951                                                 }
 952                                                 return
 953                                         }(),
 954                                         "v": extendedHandshakeClientVersion,
 955                                         // No upload queue is implemented yet.
 956                                         "reqq": 64,
 957                                 }
 958                                 if !cl.config.DisableEncryption {
 959                                         d["e"] = 1
 960                                 }
 961                                 if torrent.metadataSizeKnown() {
 962                                         d["metadata_size"] = torrent.metadataSize()
 963                                 }
 964                                 if p := cl.incomingPeerPort(); p != 0 {
 965                                         d["p"] = p
 966                                 }
 967                                 yourip, err := addrCompactIP(conn.remoteAddr())
 968                                 if err != nil {
 969                                         log.Printf("error calculating yourip field value in extension handshake: %s", err)
 970                                 } else {
 971                                         d["yourip"] = yourip
 972                                 }
 973                                 // log.Printf("sending %v", d)
 974                                 b, err := bencode.Marshal(d)
 975                                 if err != nil {
 976                                         panic(err)
 977                                 }
 978                                 return b
 979                         }(),
 980                 })
 981         }
 982         if torrent.haveAnyPieces() {
 983                 conn.Bitfield(torrent.bitfield())
 984         } else if cl.extensionBytes.SupportsFast() && conn.PeerExtensionBytes.SupportsFast() {
 985                 conn.Post(pp.Message{
 986                         Type: pp.HaveNone,
 987                 })
 988         }
 989         if conn.PeerExtensionBytes.SupportsDHT() && cl.extensionBytes.SupportsDHT() && cl.dHT != nil {
 990                 conn.Post(pp.Message{
 991                         Type: pp.Port,
 992                         Port: uint16(missinggo.AddrPort(cl.dHT.Addr())),
 993                 })
 994         }
 995 }
 996
 997 func (cl *Client) peerUnchoked(torrent *Torrent, conn *connection) {
 998         conn.updateRequests()
 999 }
1000
1001 func (cl *Client) connCancel(t *Torrent, cn *connection, r request) (ok bool) {
1002         ok = cn.Cancel(r)
1003         if ok {
1004                 postedCancels.Add(1)
1005         }
1006         return
1007 }
1008
1009 func (cl *Client) connDeleteRequest(t *Torrent, cn *connection, r request) bool {
1010         if !cn.RequestPending(r) {
1011                 return false
1012         }
1013         delete(cn.Requests, r)
1014         return true
1015 }
1016
1017 // Process incoming ut_metadata message.
1018 func (cl *Client) gotMetadataExtensionMsg(payload []byte, t *Torrent, c *connection) error {
1019         var d map[string]int
1020         err := bencode.Unmarshal(payload, &d)
1021         if err != nil {
1022                 return fmt.Errorf("error unmarshalling payload: %s: %q", err, payload)
1023         }
1024         msgType, ok := d["msg_type"]
1025         if !ok {
1026                 return errors.New("missing msg_type field")
1027         }
1028         piece := d["piece"]
1029         switch msgType {
1030         case pp.DataMetadataExtensionMsgType:
1031                 if !c.requestedMetadataPiece(piece) {
1032                         return fmt.Errorf("got unexpected piece %d", piece)
1033                 }
1034                 c.metadataRequests[piece] = false
1035                 begin := len(payload) - metadataPieceSize(d["total_size"], piece)
1036                 if begin < 0 || begin >= len(payload) {
1037                         return fmt.Errorf("data has bad offset in payload: %d", begin)
1038                 }
1039                 t.saveMetadataPiece(piece, payload[begin:])
1040                 c.UsefulChunksReceived++
1041                 c.lastUsefulChunkReceived = time.Now()
1042                 return t.maybeCompleteMetadata()
1043         case pp.RequestMetadataExtensionMsgType:
1044                 if !t.haveMetadataPiece(piece) {
1045                         c.Post(t.newMetadataExtensionMessage(c, pp.RejectMetadataExtensionMsgType, d["piece"], nil))
1046                         return nil
1047                 }
1048                 start := (1 << 14) * piece
1049                 c.Post(t.newMetadataExtensionMessage(c, pp.DataMetadataExtensionMsgType, piece, t.metadataBytes[start:start+t.metadataPieceSize(piece)]))
1050                 return nil
1051         case pp.RejectMetadataExtensionMsgType:
1052                 return nil
1053         default:
1054                 return errors.New("unknown msg_type value")
1055         }
1056 }
1057
1058 func (cl *Client) upload(t *Torrent, c *connection) {
1059         if cl.config.NoUpload {
1060                 return
1061         }
1062         if !c.PeerInterested {
1063                 return
1064         }
1065         seeding := t.seeding()
1066         if !seeding && !t.connHasWantedPieces(c) {
1067                 return
1068         }
1069 another:
1070         for seeding || c.chunksSent < c.UsefulChunksReceived+6 {
1071                 c.Unchoke()
1072                 for r := range c.PeerRequests {
1073                         err := cl.sendChunk(t, c, r)
1074                         if err != nil {
1075                                 i := int(r.Index)
1076                                 if t.pieceComplete(i) {
1077                                         t.updatePieceCompletion(i)
1078                                         if !t.pieceComplete(i) {
1079                                                 // We had the piece, but not anymore.
1080                                                 break another
1081                                         }
1082                                 }
1083                                 log.Printf("error sending chunk %+v to peer: %s", r, err)
1084                                 // If we failed to send a chunk, choke the peer to ensure they
1085                                 // flush all their requests. We've probably dropped a piece,
1086                                 // but there's no way to communicate this to the peer. If they
1087                                 // ask for it again, we'll kick them to allow us to send them
1088                                 // an updated bitfield.
1089                                 break another
1090                         }
1091                         delete(c.PeerRequests, r)
1092                         goto another
1093                 }
1094                 return
1095         }
1096         c.Choke()
1097 }
1098
1099 func (cl *Client) sendChunk(t *Torrent, c *connection, r request) error {
1100         // Count the chunk being sent, even if it isn't.
1101         b := make([]byte, r.Length)
1102         p := t.info.Piece(int(r.Index))
1103         n, err := t.readAt(b, p.Offset()+int64(r.Begin))
1104         if n != len(b) {
1105                 if err == nil {
1106                         panic("expected error")
1107                 }
1108                 return err
1109         }
1110         c.Post(pp.Message{
1111                 Type:  pp.Piece,
1112                 Index: r.Index,
1113                 Begin: r.Begin,
1114                 Piece: b,
1115         })
1116         c.chunksSent++
1117         uploadChunksPosted.Add(1)
1118         c.lastChunkSent = time.Now()
1119         return nil
1120 }
1121
1122 // Processes incoming bittorrent messages. The client lock is held upon entry
1123 // and exit. Returning will end the connection.
1124 func (cl *Client) connectionLoop(t *Torrent, c *connection) error {
1125         decoder := pp.Decoder{
1126                 R:         bufio.NewReader(c.rw),
1127                 MaxLength: 256 * 1024,
1128         }
1129         for {
1130                 cl.mu.Unlock()
1131                 var msg pp.Message
1132                 err := decoder.Decode(&msg)
1133                 cl.mu.Lock()
1134                 if cl.closed.IsSet() || c.closed.IsSet() || err == io.EOF {
1135                         return nil
1136                 }
1137                 if err != nil {
1138                         return err
1139                 }
1140                 c.readMsg(&msg)
1141                 c.lastMessageReceived = time.Now()
1142                 if msg.Keepalive {
1143                         receivedKeepalives.Add(1)
1144                         continue
1145                 }
1146                 receivedMessageTypes.Add(strconv.FormatInt(int64(msg.Type), 10), 1)
1147                 switch msg.Type {
1148                 case pp.Choke:
1149                         c.PeerChoked = true
1150                         c.Requests = nil
1151                         // We can then reset our interest.
1152                         c.updateRequests()
1153                 case pp.Reject:
1154                         cl.connDeleteRequest(t, c, newRequest(msg.Index, msg.Begin, msg.Length))
1155                         c.updateRequests()
1156                 case pp.Unchoke:
1157                         c.PeerChoked = false
1158                         cl.peerUnchoked(t, c)
1159                 case pp.Interested:
1160                         c.PeerInterested = true
1161                         cl.upload(t, c)
1162                 case pp.NotInterested:
1163                         c.PeerInterested = false
1164                         c.Choke()
1165                 case pp.Have:
1166                         err = c.peerSentHave(int(msg.Index))
1167                 case pp.Request:
1168                         if c.Choked {
1169                                 break
1170                         }
1171                         if !c.PeerInterested {
1172                                 err = errors.New("peer sent request but isn't interested")
1173                                 break
1174                         }
1175                         if !t.havePiece(msg.Index.Int()) {
1176                                 // This isn't necessarily them screwing up. We can drop pieces
1177                                 // from our storage, and can't communicate this to peers
1178                                 // except by reconnecting.
1179                                 requestsReceivedForMissingPieces.Add(1)
1180                                 err = errors.New("peer requested piece we don't have")
1181                                 break
1182                         }
1183                         if c.PeerRequests == nil {
1184                                 c.PeerRequests = make(map[request]struct{}, maxRequests)
1185                         }
1186                         c.PeerRequests[newRequest(msg.Index, msg.Begin, msg.Length)] = struct{}{}
1187                         cl.upload(t, c)
1188                 case pp.Cancel:
1189                         req := newRequest(msg.Index, msg.Begin, msg.Length)
1190                         if !c.PeerCancel(req) {
1191                                 unexpectedCancels.Add(1)
1192                         }
1193                 case pp.Bitfield:
1194                         err = c.peerSentBitfield(msg.Bitfield)
1195                 case pp.HaveAll:
1196                         err = c.peerSentHaveAll()
1197                 case pp.HaveNone:
1198                         err = c.peerSentHaveNone()
1199                 case pp.Piece:
1200                         cl.downloadedChunk(t, c, &msg)
1201                 case pp.Extended:
1202                         switch msg.ExtendedID {
1203                         case pp.HandshakeExtendedID:
1204                                 // TODO: Create a bencode struct for this.
1205                                 var d map[string]interface{}
1206                                 err = bencode.Unmarshal(msg.ExtendedPayload, &d)
1207                                 if err != nil {
1208                                         err = fmt.Errorf("error decoding extended message payload: %s", err)
1209                                         break
1210                                 }
1211                                 // log.Printf("got handshake from %q: %#v", c.Socket.RemoteAddr().String(), d)
1212                                 if reqq, ok := d["reqq"]; ok {
1213                                         if i, ok := reqq.(int64); ok {
1214                                                 c.PeerMaxRequests = int(i)
1215                                         }
1216                                 }
1217                                 if v, ok := d["v"]; ok {
1218                                         c.PeerClientName = v.(string)
1219                                 }
1220                                 m, ok := d["m"]
1221                                 if !ok {
1222                                         err = errors.New("handshake missing m item")
1223                                         break
1224                                 }
1225                                 mTyped, ok := m.(map[string]interface{})
1226                                 if !ok {
1227                                         err = errors.New("handshake m value is not dict")
1228                                         break
1229                                 }
1230                                 if c.PeerExtensionIDs == nil {
1231                                         c.PeerExtensionIDs = make(map[string]byte, len(mTyped))
1232                                 }
1233                                 for name, v := range mTyped {
1234                                         id, ok := v.(int64)
1235                                         if !ok {
1236                                                 log.Printf("bad handshake m item extension ID type: %T", v)
1237                                                 continue
1238                                         }
1239                                         if id == 0 {
1240                                                 delete(c.PeerExtensionIDs, name)
1241                                         } else {
1242                                                 if c.PeerExtensionIDs[name] == 0 {
1243                                                         supportedExtensionMessages.Add(name, 1)
1244                                                 }
1245                                                 c.PeerExtensionIDs[name] = byte(id)
1246                                         }
1247                                 }
1248                                 metadata_sizeUntyped, ok := d["metadata_size"]
1249                                 if ok {
1250                                         metadata_size, ok := metadata_sizeUntyped.(int64)
1251                                         if !ok {
1252                                                 log.Printf("bad metadata_size type: %T", metadata_sizeUntyped)
1253                                         } else {
1254                                                 err = t.setMetadataSize(metadata_size)
1255                                                 if err != nil {
1256                                                         err = fmt.Errorf("error setting metadata size to %d", metadata_size)
1257                                                         break
1258                                                 }
1259                                         }
1260                                 }
1261                                 if _, ok := c.PeerExtensionIDs["ut_metadata"]; ok {
1262                                         c.requestPendingMetadata()
1263                                 }
1264                         case metadataExtendedId:
1265                                 err = cl.gotMetadataExtensionMsg(msg.ExtendedPayload, t, c)
1266                                 if err != nil {
1267                                         err = fmt.Errorf("error handling metadata extension message: %s", err)
1268                                 }
1269                         case pexExtendedId:
1270                                 if cl.config.DisablePEX {
1271                                         break
1272                                 }
1273                                 var pexMsg peerExchangeMessage
1274                                 err = bencode.Unmarshal(msg.ExtendedPayload, &pexMsg)
1275                                 if err != nil {
1276                                         err = fmt.Errorf("error unmarshalling PEX message: %s", err)
1277                                         break
1278                                 }
1279                                 go func() {
1280                                         cl.mu.Lock()
1281                                         t.addPeers(func() (ret []Peer) {
1282                                                 for i, cp := range pexMsg.Added {
1283                                                         p := Peer{
1284                                                                 IP:     make([]byte, 4),
1285                                                                 Port:   cp.Port,
1286                                                                 Source: peerSourcePEX,
1287                                                         }
1288                                                         if i < len(pexMsg.AddedFlags) && pexMsg.AddedFlags[i]&0x01 != 0 {
1289                                                                 p.SupportsEncryption = true
1290                                                         }
1291                                                         missinggo.CopyExact(p.IP, cp.IP[:])
1292                                                         ret = append(ret, p)
1293                                                 }
1294                                                 return
1295                                         }())
1296                                         cl.mu.Unlock()
1297                                 }()
1298                         default:
1299                                 err = fmt.Errorf("unexpected extended message ID: %v", msg.ExtendedID)
1300                         }
1301                         if err != nil {
1302                                 // That client uses its own extension IDs for outgoing message
1303                                 // types, which is incorrect.
1304                                 if bytes.HasPrefix(c.PeerID[:], []byte("-SD0100-")) ||
1305                                         strings.HasPrefix(string(c.PeerID[:]), "-XL0012-") {
1306                                         return nil
1307                                 }
1308                         }
1309                 case pp.Port:
1310                         if cl.dHT == nil {
1311                                 break
1312                         }
1313                         pingAddr, err := net.ResolveUDPAddr("", c.remoteAddr().String())
1314                         if err != nil {
1315                                 panic(err)
1316                         }
1317                         if msg.Port != 0 {
1318                                 pingAddr.Port = int(msg.Port)
1319                         }
1320                         cl.dHT.Ping(pingAddr)
1321                 default:
1322                         err = fmt.Errorf("received unknown message type: %#v", msg.Type)
1323                 }
1324                 if err != nil {
1325                         return err
1326                 }
1327         }
1328 }
1329
1330 func (cl *Client) openNewConns(t *Torrent) {
1331         defer t.updateWantPeersEvent()
1332         for len(t.peers) != 0 {
1333                 if !t.wantConns() {
1334                         return
1335                 }
1336                 if len(t.halfOpen) >= cl.halfOpenLimit {
1337                         return
1338                 }
1339                 var (
1340                         k peersKey
1341                         p Peer
1342                 )
1343                 for k, p = range t.peers {
1344                         break
1345                 }
1346                 delete(t.peers, k)
1347                 cl.initiateConn(p, t)
1348         }
1349 }
1350
1351 func (cl *Client) badPeerIPPort(ip net.IP, port int) bool {
1352         if port == 0 {
1353                 return true
1354         }
1355         if cl.dopplegangerAddr(net.JoinHostPort(ip.String(), strconv.FormatInt(int64(port), 10))) {
1356                 return true
1357         }
1358         if _, ok := cl.ipBlockRange(ip); ok {
1359                 return true
1360         }
1361         if _, ok := cl.badPeerIPs[ip.String()]; ok {
1362                 return true
1363         }
1364         return false
1365 }
1366
1367 // Return a Torrent ready for insertion into a Client.
1368 func (cl *Client) newTorrent(ih metainfo.Hash) (t *Torrent) {
1369         t = &Torrent{
1370                 cl:        cl,
1371                 infoHash:  ih,
1372                 chunkSize: defaultChunkSize,
1373                 peers:     make(map[peersKey]Peer),
1374
1375                 halfOpen:          make(map[string]struct{}),
1376                 pieceStateChanges: pubsub.NewPubSub(),
1377
1378                 storageOpener:       cl.defaultStorage,
1379                 maxEstablishedConns: defaultEstablishedConnsPerTorrent,
1380         }
1381         return
1382 }
1383
1384 func init() {
1385         // For shuffling the tracker tiers.
1386         mathRand.Seed(time.Now().Unix())
1387 }
1388
1389 type trackerTier []string
1390
1391 // The trackers within each tier must be shuffled before use.
1392 // http://stackoverflow.com/a/12267471/149482
1393 // http://www.bittorrent.org/beps/bep_0012.html#order-of-processing
1394 func shuffleTier(tier trackerTier) {
1395         for i := range tier {
1396                 j := mathRand.Intn(i + 1)
1397                 tier[i], tier[j] = tier[j], tier[i]
1398         }
1399 }
1400
1401 // A file-like handle to some torrent data resource.
1402 type Handle interface {
1403         io.Reader
1404         io.Seeker
1405         io.Closer
1406         io.ReaderAt
1407 }
1408
1409 func (cl *Client) AddTorrentInfoHash(infoHash metainfo.Hash) (t *Torrent, new bool) {
1410         cl.mu.Lock()
1411         defer cl.mu.Unlock()
1412         t, ok := cl.torrents[infoHash]
1413         if ok {
1414                 return
1415         }
1416         new = true
1417         t = cl.newTorrent(infoHash)
1418         if cl.dHT != nil {
1419                 go t.dhtAnnouncer()
1420         }
1421         cl.torrents[infoHash] = t
1422         t.updateWantPeersEvent()
1423         // Tickle Client.waitAccept, new torrent may want conns.
1424         cl.event.Broadcast()
1425         return
1426 }
1427
1428 // Add or merge a torrent spec. If the torrent is already present, the
1429 // trackers will be merged with the existing ones. If the Info isn't yet
1430 // known, it will be set. The display name is replaced if the new spec
1431 // provides one. Returns new if the torrent wasn't already in the client.
1432 func (cl *Client) AddTorrentSpec(spec *TorrentSpec) (t *Torrent, new bool, err error) {
1433         t, new = cl.AddTorrentInfoHash(spec.InfoHash)
1434         if spec.DisplayName != "" {
1435                 t.SetDisplayName(spec.DisplayName)
1436         }
1437         if spec.InfoBytes != nil {
1438                 err = t.SetInfoBytes(spec.InfoBytes)
1439                 if err != nil {
1440                         return
1441                 }
1442         }
1443         cl.mu.Lock()
1444         defer cl.mu.Unlock()
1445         if spec.ChunkSize != 0 {
1446                 t.chunkSize = pp.Integer(spec.ChunkSize)
1447         }
1448         t.addTrackers(spec.Trackers)
1449         t.maybeNewConns()
1450         return
1451 }
1452
1453 func (cl *Client) dropTorrent(infoHash metainfo.Hash) (err error) {
1454         t, ok := cl.torrents[infoHash]
1455         if !ok {
1456                 err = fmt.Errorf("no such torrent")
1457                 return
1458         }
1459         err = t.close()
1460         if err != nil {
1461                 panic(err)
1462         }
1463         delete(cl.torrents, infoHash)
1464         return
1465 }
1466
1467 func (cl *Client) prepareTrackerAnnounceUnlocked(announceURL string) (blocked bool, urlToUse string, host string, err error) {
1468         _url, err := url.Parse(announceURL)
1469         if err != nil {
1470                 return
1471         }
1472         hmp := missinggo.SplitHostMaybePort(_url.Host)
1473         if hmp.Err != nil {
1474                 err = hmp.Err
1475                 return
1476         }
1477         addr, err := net.ResolveIPAddr("ip", hmp.Host)
1478         if err != nil {
1479                 return
1480         }
1481         cl.mu.RLock()
1482         _, blocked = cl.ipBlockRange(addr.IP)
1483         cl.mu.RUnlock()
1484         host = _url.Host
1485         hmp.Host = addr.String()
1486         _url.Host = hmp.String()
1487         urlToUse = _url.String()
1488         return
1489 }
1490
1491 func (cl *Client) allTorrentsCompleted() bool {
1492         for _, t := range cl.torrents {
1493                 if !t.haveInfo() {
1494                         return false
1495                 }
1496                 if t.numPiecesCompleted() != t.numPieces() {
1497                         return false
1498                 }
1499         }
1500         return true
1501 }
1502
1503 // Returns true when all torrents are completely downloaded and false if the
1504 // client is stopped before that.
1505 func (cl *Client) WaitAll() bool {
1506         cl.mu.Lock()
1507         defer cl.mu.Unlock()
1508         for !cl.allTorrentsCompleted() {
1509                 if cl.closed.IsSet() {
1510                         return false
1511                 }
1512                 cl.event.Wait()
1513         }
1514         return true
1515 }
1516
1517 // Handle a received chunk from a peer.
1518 func (cl *Client) downloadedChunk(t *Torrent, c *connection, msg *pp.Message) {
1519         chunksReceived.Add(1)
1520
1521         req := newRequest(msg.Index, msg.Begin, pp.Integer(len(msg.Piece)))
1522
1523         // Request has been satisfied.
1524         if cl.connDeleteRequest(t, c, req) {
1525                 defer c.updateRequests()
1526         } else {
1527                 unexpectedChunksReceived.Add(1)
1528         }
1529
1530         index := int(req.Index)
1531         piece := &t.pieces[index]
1532
1533         // Do we actually want this chunk?
1534         if !t.wantPiece(req) {
1535                 unwantedChunksReceived.Add(1)
1536                 c.UnwantedChunksReceived++
1537                 return
1538         }
1539
1540         c.UsefulChunksReceived++
1541         c.lastUsefulChunkReceived = time.Now()
1542
1543         cl.upload(t, c)
1544
1545         // Need to record that it hasn't been written yet, before we attempt to do
1546         // anything with it.
1547         piece.incrementPendingWrites()
1548         // Record that we have the chunk.
1549         piece.unpendChunkIndex(chunkIndex(req.chunkSpec, t.chunkSize))
1550
1551         // Cancel pending requests for this chunk.
1552         for _, c := range t.conns {
1553                 if cl.connCancel(t, c, req) {
1554                         c.updateRequests()
1555                 }
1556         }
1557
1558         cl.mu.Unlock()
1559         // Write the chunk out. Note that the upper bound on chunk writing
1560         // concurrency will be the number of connections.
1561         err := t.writeChunk(int(msg.Index), int64(msg.Begin), msg.Piece)
1562         cl.mu.Lock()
1563
1564         piece.decrementPendingWrites()
1565
1566         if err != nil {
1567                 log.Printf("%s: error writing chunk %v: %s", t, req, err)
1568                 t.pendRequest(req)
1569                 t.updatePieceCompletion(int(msg.Index))
1570                 return
1571         }
1572
1573         // It's important that the piece is potentially queued before we check if
1574         // the piece is still wanted, because if it is queued, it won't be wanted.
1575         if t.pieceAllDirty(index) {
1576                 cl.queuePieceCheck(t, int(req.Index))
1577         }
1578
1579         if c.peerTouchedPieces == nil {
1580                 c.peerTouchedPieces = make(map[int]struct{})
1581         }
1582         c.peerTouchedPieces[index] = struct{}{}
1583
1584         cl.event.Broadcast()
1585         t.publishPieceChange(int(req.Index))
1586         return
1587 }
1588
1589 // Return the connections that touched a piece, and clear the entry while
1590 // doing it.
1591 func (cl *Client) reapPieceTouches(t *Torrent, piece int) (ret []*connection) {
1592         for _, c := range t.conns {
1593                 if _, ok := c.peerTouchedPieces[piece]; ok {
1594                         ret = append(ret, c)
1595                         delete(c.peerTouchedPieces, piece)
1596                 }
1597         }
1598         return
1599 }
1600
1601 func (cl *Client) pieceHashed(t *Torrent, piece int, correct bool) {
1602         if t.closed.IsSet() {
1603                 return
1604         }
1605         p := &t.pieces[piece]
1606         if p.EverHashed {
1607                 // Don't score the first time a piece is hashed, it could be an
1608                 // initial check.
1609                 if correct {
1610                         pieceHashedCorrect.Add(1)
1611                 } else {
1612                         log.Printf("%s: piece %d (%x) failed hash", t, piece, p.Hash)
1613                         pieceHashedNotCorrect.Add(1)
1614                 }
1615         }
1616         p.EverHashed = true
1617         touchers := cl.reapPieceTouches(t, piece)
1618         if correct {
1619                 for _, c := range touchers {
1620                         c.goodPiecesDirtied++
1621                 }
1622                 err := p.Storage().MarkComplete()
1623                 if err != nil {
1624                         log.Printf("%T: error completing piece %d: %s", t.storage, piece, err)
1625                 }
1626                 t.updatePieceCompletion(piece)
1627         } else if len(touchers) != 0 {
1628                 log.Printf("dropping and banning %d conns that touched piece", len(touchers))
1629                 for _, c := range touchers {
1630                         c.badPiecesDirtied++
1631                         t.cl.banPeerIP(missinggo.AddrIP(c.remoteAddr()))
1632                         t.dropConnection(c)
1633                 }
1634         }
1635         cl.pieceChanged(t, piece)
1636 }
1637
1638 func (cl *Client) onCompletedPiece(t *Torrent, piece int) {
1639         t.pendingPieces.Remove(piece)
1640         t.pendAllChunkSpecs(piece)
1641         for _, conn := range t.conns {
1642                 conn.Have(piece)
1643                 for r := range conn.Requests {
1644                         if int(r.Index) == piece {
1645                                 conn.Cancel(r)
1646                         }
1647                 }
1648                 // Could check here if peer doesn't have piece, but due to caching
1649                 // some peers may have said they have a piece but they don't.
1650                 cl.upload(t, conn)
1651         }
1652 }
1653
1654 func (cl *Client) onFailedPiece(t *Torrent, piece int) {
1655         if t.pieceAllDirty(piece) {
1656                 t.pendAllChunkSpecs(piece)
1657         }
1658         if !t.wantPieceIndex(piece) {
1659                 return
1660         }
1661         cl.openNewConns(t)
1662         for _, conn := range t.conns {
1663                 if conn.PeerHasPiece(piece) {
1664                         conn.updateRequests()
1665                 }
1666         }
1667 }
1668
1669 func (cl *Client) pieceChanged(t *Torrent, piece int) {
1670         correct := t.pieceComplete(piece)
1671         defer cl.event.Broadcast()
1672         if correct {
1673                 cl.onCompletedPiece(t, piece)
1674         } else {
1675                 cl.onFailedPiece(t, piece)
1676         }
1677         t.updatePiecePriority(piece)
1678 }
1679
1680 func (cl *Client) verifyPiece(t *Torrent, piece int) {
1681         cl.mu.Lock()
1682         defer cl.mu.Unlock()
1683         p := &t.pieces[piece]
1684         for p.Hashing || t.storage == nil {
1685                 cl.event.Wait()
1686         }
1687         p.QueuedForHash = false
1688         if t.closed.IsSet() || t.pieceComplete(piece) {
1689                 t.updatePiecePriority(piece)
1690                 return
1691         }
1692         p.Hashing = true
1693         t.publishPieceChange(piece)
1694         cl.mu.Unlock()
1695         sum := t.hashPiece(piece)
1696         cl.mu.Lock()
1697         p.Hashing = false
1698         cl.pieceHashed(t, piece, sum == p.Hash)
1699 }
1700
1701 // Returns handles to all the torrents loaded in the Client.
1702 func (cl *Client) Torrents() (ret []*Torrent) {
1703         cl.mu.Lock()
1704         for _, t := range cl.torrents {
1705                 ret = append(ret, t)
1706         }
1707         cl.mu.Unlock()
1708         return
1709 }
1710
1711 func (cl *Client) AddMagnet(uri string) (T *Torrent, err error) {
1712         spec, err := TorrentSpecFromMagnetURI(uri)
1713         if err != nil {
1714                 return
1715         }
1716         T, _, err = cl.AddTorrentSpec(spec)
1717         return
1718 }
1719
1720 func (cl *Client) AddTorrent(mi *metainfo.MetaInfo) (T *Torrent, err error) {
1721         T, _, err = cl.AddTorrentSpec(TorrentSpecFromMetaInfo(mi))
1722         var ss []string
1723         slices.MakeInto(&ss, mi.Nodes)
1724         cl.AddDHTNodes(ss)
1725         return
1726 }
1727
1728 func (cl *Client) AddTorrentFromFile(filename string) (T *Torrent, err error) {
1729         mi, err := metainfo.LoadFromFile(filename)
1730         if err != nil {
1731                 return
1732         }
1733         return cl.AddTorrent(mi)
1734 }
1735
1736 func (cl *Client) DHT() *dht.Server {
1737         return cl.dHT
1738 }
1739
1740 func (cl *Client) AddDHTNodes(nodes []string) {
1741         for _, n := range nodes {
1742                 hmp := missinggo.SplitHostMaybePort(n)
1743                 ip := net.ParseIP(hmp.Host)
1744                 if ip == nil {
1745                         log.Printf("won't add DHT node with bad IP: %q", hmp.Host)
1746                         continue
1747                 }
1748                 ni := krpc.NodeInfo{
1749                         Addr: &net.UDPAddr{
1750                                 IP:   ip,
1751                                 Port: hmp.Port,
1752                         },
1753                 }
1754                 cl.DHT().AddNode(ni)
1755         }
1756 }
1757
1758 func (cl *Client) banPeerIP(ip net.IP) {
1759         if cl.badPeerIPs == nil {
1760                 cl.badPeerIPs = make(map[string]struct{})
1761         }
1762         cl.badPeerIPs[ip.String()] = struct{}{}
1763 }