mirror of
https://github.com/webtorrent/bittorrent-tracker.git
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77 lines
2.6 KiB
JavaScript
77 lines
2.6 KiB
JavaScript
module.exports = parseUdpRequest
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var bufferEqual = require('buffer-equal')
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var ipLib = require('ip')
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var common = require('./common')
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function parseUdpRequest (msg, rinfo) {
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if (msg.length < 16) throw new Error('received packet is too short')
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var params = {
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connectionId: msg.slice(0, 8), // 64-bit
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action: msg.readUInt32BE(8),
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transactionId: msg.readUInt32BE(12)
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}
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// TODO: randomize
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if (!bufferEqual(params.connectionId, common.CONNECTION_ID)) {
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throw new Error('received packet with invalid connection id')
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}
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if (params.action === common.ACTIONS.CONNECT) {
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// No further params
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} else if (params.action === common.ACTIONS.ANNOUNCE) {
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params.info_hash = msg.slice(16, 36).toString('hex') // 20 bytes
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params.peer_id = msg.slice(36, 56).toString('hex') // 20 bytes
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params.downloaded = fromUInt64(msg.slice(56, 64)) // TODO: track this?
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params.left = fromUInt64(msg.slice(64, 72))
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params.uploaded = fromUInt64(msg.slice(72, 80)) // TODO: track this?
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params.event = common.EVENT_IDS[msg.readUInt32BE(80)]
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if (!params.event) throw new Error('invalid event') // early return
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var ip = msg.readUInt32BE(84) // optional
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params.ip = ip
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? ipLib.toString(ip)
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: rinfo.address
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params.key = msg.readUInt32BE(88) // Optional: unique random key from client
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// never send more than MAX_ANNOUNCE_PEERS or else the UDP packet will get bigger than
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// 512 bytes which is not safe
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params.numwant = Math.min(
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msg.readUInt32BE(92) || common.DEFAULT_ANNOUNCE_PEERS, // optional
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common.MAX_ANNOUNCE_PEERS
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)
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params.port = msg.readUInt16BE(96) || rinfo.port // optional
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params.addr = params.ip + ':' + params.port // TODO: ipv6 brackets
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params.compact = 1 // udp is always compact
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} else if (params.action === common.ACTIONS.SCRAPE) { // scrape message
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if ((msg.length - 16) % 20 !== 0) throw new Error('invalid scrape message')
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params.info_hash = []
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for (var i = 0, len = (msg.length - 16) / 20; i < len; i += 1) {
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var infoHash = msg.slice(16 + (i * 20), 36 + (i * 20)).toString('hex') // 20 bytes
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params.info_hash.push(infoHash)
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}
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} else {
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throw new Error('Invalid action in UDP packet: ' + params.action)
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}
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return params
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}
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var TWO_PWR_32 = (1 << 16) * 2
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/**
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* Return the closest floating-point representation to the buffer value. Precision will be
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* lost for big numbers.
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*/
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function fromUInt64 (buf) {
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var high = buf.readUInt32BE(0) | 0 // force
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var low = buf.readUInt32BE(4) | 0
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var lowUnsigned = (low >= 0) ? low : TWO_PWR_32 + low
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return high * TWO_PWR_32 + lowUnsigned
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}
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