1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
|
const { default: BitField } = require('bitfield')
const debugFactory = require('debug')
const get = require('simple-get')
const ltDontHave = require('lt_donthave')
const sha1 = require('simple-sha1')
const Wire = require('bittorrent-protocol')
const debug = debugFactory('webtorrent:webconn')
const VERSION = require('../package.json').version
const SOCKET_TIMEOUT = 60000
const RETRY_DELAY = 10000
/**
* Converts requests for torrent blocks into http range requests.
* @param {string} url web seed url
* @param {Object} torrent
*/
class WebConn extends Wire {
constructor (url, torrent) {
super()
this.url = url
this.connId = url // Unique id to deduplicate web seeds
this.webPeerId = sha1.sync(url) // Used as the peerId for this fake remote peer
this._torrent = torrent
this._init()
}
_init () {
this.setKeepAlive(true)
this.use(ltDontHave())
this.once('handshake', (infoHash, peerId) => {
if (this.destroyed) return
this.handshake(infoHash, this.webPeerId)
const numPieces = this._torrent.pieces.length
const bitfield = new BitField(numPieces)
for (let i = 0; i <= numPieces; i++) {
bitfield.set(i, true)
}
this.bitfield(bitfield)
})
this.once('interested', () => {
debug('interested')
this.unchoke()
})
this.on('uninterested', () => { debug('uninterested') })
this.on('choke', () => { debug('choke') })
this.on('unchoke', () => { debug('unchoke') })
this.on('bitfield', () => { debug('bitfield') })
this.lt_donthave.on('donthave', () => { debug('donthave') })
this.on('request', (pieceIndex, offset, length, callback) => {
debug('request pieceIndex=%d offset=%d length=%d', pieceIndex, offset, length)
this.httpRequest(pieceIndex, offset, length, (err, data) => {
if (err) {
// Cancel all in progress requests for this piece
this.lt_donthave.donthave(pieceIndex)
// Wait a little while before saying the webseed has the failed piece again
const retryTimeout = setTimeout(() => {
if (this.destroyed) return
this.have(pieceIndex)
}, RETRY_DELAY)
if (retryTimeout.unref) retryTimeout.unref()
}
callback(err, data)
})
})
}
httpRequest (pieceIndex, offset, length, cb) {
const pieceOffset = pieceIndex * this._torrent.pieceLength
const rangeStart = pieceOffset + offset /* offset within whole torrent */
const rangeEnd = rangeStart + length - 1
// Web seed URL format:
// For single-file torrents, make HTTP range requests directly to the web seed URL
// For multi-file torrents, add the torrent folder and file name to the URL
const files = this._torrent.files
let requests
if (files.length <= 1) {
requests = [{
url: this.url,
start: rangeStart,
end: rangeEnd
}]
} else {
const requestedFiles = files.filter(file => file.offset <= rangeEnd && (file.offset + file.length) > rangeStart)
if (requestedFiles.length < 1) {
return cb(new Error('Could not find file corresponding to web seed range request'))
}
requests = requestedFiles.map(requestedFile => {
const fileEnd = requestedFile.offset + requestedFile.length - 1
const url = this.url +
(this.url[this.url.length - 1] === '/' ? '' : '/') +
requestedFile.path.replace(this._torrent.path, '')
return {
url,
fileOffsetInRange: Math.max(requestedFile.offset - rangeStart, 0),
start: Math.max(rangeStart - requestedFile.offset, 0),
end: Math.min(fileEnd, rangeEnd - requestedFile.offset)
}
})
}
// Now make all the HTTP requests we need in order to load this piece
// Usually that's one requests, but sometimes it will be multiple
// Send requests in parallel and wait for them all to come back
let numRequestsSucceeded = 0
let hasError = false
let ret
if (requests.length > 1) {
ret = Buffer.alloc(length)
}
requests.forEach(request => {
const url = request.url
const start = request.start
const end = request.end
debug(
'Requesting url=%s pieceIndex=%d offset=%d length=%d start=%d end=%d',
url, pieceIndex, offset, length, start, end
)
const opts = {
url,
method: 'GET',
headers: {
'user-agent': `WebTorrent/${VERSION} (https://webtorrent.io)`,
range: `bytes=${start}-${end}`
},
timeout: SOCKET_TIMEOUT
}
function onResponse (res, data) {
if (res.statusCode < 200 || res.statusCode >= 300) {
if (hasError) return
hasError = true
return cb(new Error(`Unexpected HTTP status code ${res.statusCode}`))
}
debug('Got data of length %d', data.length)
if (requests.length === 1) {
// Common case: fetch piece in a single HTTP request, return directly
cb(null, data)
} else {
// Rare case: reconstruct multiple HTTP requests across 2+ files into one
// piece buffer
data.copy(ret, request.fileOffsetInRange)
if (++numRequestsSucceeded === requests.length) {
cb(null, ret)
}
}
}
get.concat(opts, (err, res, data) => {
if (hasError) return
if (err) {
// Browsers allow HTTP redirects for simple cross-origin
// requests but not for requests that require preflight.
// Use a simple request to unravel any redirects and get the
// final URL. Retry the original request with the new URL if
// it's different.
//
// This test is imperfect but it's simple and good for common
// cases. It catches all cross-origin cases but matches a few
// same-origin cases too.
if (typeof window === 'undefined' || url.startsWith(`${window.location.origin}/`)) {
hasError = true
return cb(err)
}
return get.head(url, (errHead, res) => {
if (hasError) return
if (errHead) {
hasError = true
return cb(errHead)
}
if (res.statusCode < 200 || res.statusCode >= 300) {
hasError = true
return cb(new Error(`Unexpected HTTP status code ${res.statusCode}`))
}
if (res.url === url) {
hasError = true
return cb(err)
}
opts.url = res.url
get.concat(opts, (err, res, data) => {
if (hasError) return
if (err) {
hasError = true
return cb(err)
}
onResponse(res, data)
})
})
}
onResponse(res, data)
})
})
}
destroy () {
super.destroy()
this._torrent = null
}
}
module.exports = WebConn
|
