webseed-peer.go

   1 package torrent
   2
   3 import (
   4         "context"
   5         "errors"
   6         "fmt"
   7         "net/http"
   8         "strings"
   9         "sync"
  10
  11         "github.com/anacrolix/log"
  12         "github.com/anacrolix/torrent/common"
  13         "github.com/anacrolix/torrent/metainfo"
  14         pp "github.com/anacrolix/torrent/peer_protocol"
  15         "github.com/anacrolix/torrent/segments"
  16         "github.com/anacrolix/torrent/webseed"
  17 )
  18
  19 type webseedPeer struct {
  20         client         webseed.Client
  21         activeRequests map[Request]webseed.Request
  22         requesterCond  sync.Cond
  23         peer           Peer
  24         // Number of requester routines.
  25         maxRequests int
  26 }
  27
  28 var _ peerImpl = (*webseedPeer)(nil)
  29
  30 func (me *webseedPeer) connStatusString() string {
  31         return me.client.Url
  32 }
  33
  34 func (ws *webseedPeer) String() string {
  35         return fmt.Sprintf("webseed peer for %q", ws.client.Url)
  36 }
  37
  38 func (ws *webseedPeer) onGotInfo(info *metainfo.Info) {
  39         ws.client.FileIndex = segments.NewIndex(common.LengthIterFromUpvertedFiles(info.UpvertedFiles()))
  40         ws.client.Info = info
  41 }
  42
  43 func (ws *webseedPeer) writeInterested(interested bool) bool {
  44         return true
  45 }
  46
  47 func (ws *webseedPeer) _cancel(r RequestIndex) bool {
  48         active, ok := ws.activeRequests[ws.peer.t.requestIndexToRequest(r)]
  49         if ok {
  50                 active.Cancel()
  51                 if !ws.peer.deleteRequest(r) {
  52                         panic("cancelled webseed request should exist")
  53                 }
  54                 if ws.peer.isLowOnRequests() {
  55                         ws.peer.updateRequests("webseedPeer._cancel")
  56                 }
  57         }
  58         return true
  59 }
  60
  61 func (ws *webseedPeer) intoSpec(r Request) webseed.RequestSpec {
  62         return webseed.RequestSpec{ws.peer.t.requestOffset(r), int64(r.Length)}
  63 }
  64
  65 func (ws *webseedPeer) _request(r Request) bool {
  66         ws.requesterCond.Signal()
  67         return true
  68 }
  69
  70 func (ws *webseedPeer) doRequest(r Request) {
  71         webseedRequest := ws.client.NewRequest(ws.intoSpec(r))
  72         ws.activeRequests[r] = webseedRequest
  73         func() {
  74                 ws.requesterCond.L.Unlock()
  75                 defer ws.requesterCond.L.Lock()
  76                 ws.requestResultHandler(r, webseedRequest)
  77         }()
  78         delete(ws.activeRequests, r)
  79 }
  80
  81 func (ws *webseedPeer) requester() {
  82         ws.requesterCond.L.Lock()
  83         defer ws.requesterCond.L.Unlock()
  84 start:
  85         for !ws.peer.closed.IsSet() {
  86                 restart := false
  87                 ws.peer.actualRequestState.Requests.Iterate(func(x uint32) bool {
  88                         r := ws.peer.t.requestIndexToRequest(x)
  89                         if _, ok := ws.activeRequests[r]; ok {
  90                                 return true
  91                         }
  92                         ws.doRequest(r)
  93                         restart = true
  94                         return false
  95                 })
  96                 if restart {
  97                         goto start
  98                 }
  99                 ws.requesterCond.Wait()
 100         }
 101 }
 102
 103 func (ws *webseedPeer) connectionFlags() string {
 104         return "WS"
 105 }
 106
 107 // TODO: This is called when banning peers. Perhaps we want to be able to ban webseeds too. We could
 108 // return bool if this is even possible, and if it isn't, skip to the next drop candidate.
 109 func (ws *webseedPeer) drop() {}
 110
 111 func (ws *webseedPeer) handleUpdateRequests() {
 112         ws.peer.maybeUpdateActualRequestState()
 113 }
 114
 115 func (ws *webseedPeer) onClose() {
 116         ws.peer.logger.WithLevel(log.Debug).Print("closing")
 117         for _, r := range ws.activeRequests {
 118                 r.Cancel()
 119         }
 120         ws.requesterCond.Broadcast()
 121 }
 122
 123 func (ws *webseedPeer) requestResultHandler(r Request, webseedRequest webseed.Request) {
 124         result := <-webseedRequest.Result
 125         // We do this here rather than inside receiveChunk, since we want to count errors too. I'm not
 126         // sure if we can divine which errors indicate cancellation on our end without hitting the
 127         // network though.
 128         ws.peer.doChunkReadStats(int64(len(result.Bytes)))
 129         ws.peer.readBytes(int64(len(result.Bytes)))
 130         ws.peer.t.cl.lock()
 131         defer ws.peer.t.cl.unlock()
 132         if result.Err != nil {
 133                 if !errors.Is(result.Err, context.Canceled) {
 134                         ws.peer.logger.Printf("Request %v rejected: %v", r, result.Err)
 135                 }
 136                 // We need to filter out temporary errors, but this is a nightmare in Go. Currently a bad
 137                 // webseed URL can starve out the good ones due to the chunk selection algorithm.
 138                 const closeOnAllErrors = false
 139                 if closeOnAllErrors ||
 140                         strings.Contains(result.Err.Error(), "unsupported protocol scheme") ||
 141                         func() bool {
 142                                 var err webseed.ErrBadResponse
 143                                 if !errors.As(result.Err, &err) {
 144                                         return false
 145                                 }
 146                                 return err.Response.StatusCode == http.StatusNotFound
 147                         }() {
 148                         ws.peer.close()
 149                 } else {
 150                         ws.peer.remoteRejectedRequest(ws.peer.t.requestIndexFromRequest(r))
 151                 }
 152         } else {
 153                 err := ws.peer.receiveChunk(&pp.Message{
 154                         Type:  pp.Piece,
 155                         Index: r.Index,
 156                         Begin: r.Begin,
 157                         Piece: result.Bytes,
 158                 })
 159                 if err != nil {
 160                         panic(err)
 161                 }
 162         }
 163 }
 164
 165 func (me *webseedPeer) isLowOnRequests() bool {
 166         return me.peer.actualRequestState.Requests.GetCardinality() < uint64(me.maxRequests)
 167 }