From 037a53accba0b2a7d2f3af2f40be7042859b1e0b Mon Sep 17 00:00:00 2001
From: Astro <astro@spaceboyz.net>
Date: Mon, 8 Dec 2014 23:42:05 +0100
Subject: [PATCH 01/16] server: split out parseHttpRequest()

---
 server.js | 155 +++++++++++++++++++++++++++++++++++-------------------
 1 file changed, 101 insertions(+), 54 deletions(-)

diff --git a/server.js b/server.js
index 3370b56..26b12e0 100644
--- a/server.js
+++ b/server.js
@@ -1,4 +1,5 @@
 module.exports = Server
+module.exports.parseHttpRequest = parseHttpRequest
 
 var bencode = require('bencode')
 var bufferEqual = require('buffer-equal')
@@ -138,48 +139,43 @@ Server.prototype._getSwarm = function (binaryInfoHash) {
 
 Server.prototype._onHttpRequest = function (req, res) {
   var self = this
-  var s = req.url.split('?')
-  var params = common.querystringParse(s[1])
+
+  var params
+  try {
+    params = parseHttpRequest(req, {
+      trustProxy: self._trustProxy
+    })
+  } catch (err) {
+    debug('sent error %s', err.message)
+    res.end(bencode.encode({
+      'failure reason': err.message
+    }))
+
+    // even though it's an error for the client, it's just a warning for the server.
+    // don't crash the server because a client sent bad data :)
+    self.emit('warning', err)
+    
+    return
+  }
+  
   var response
-  if (s[0] === '/announce') {
-    var infoHash = typeof params.info_hash === 'string' && params.info_hash
-    var peerId = typeof params.peer_id === 'string' && common.binaryToUtf8(params.peer_id)
-    var port = Number(params.port)
-
-    if (!infoHash) return error('invalid info_hash')
-    if (infoHash.length !== 20) return error('invalid info_hash')
-    if (!peerId) return error('invalid peer_id')
-    if (peerId.length !== 20) return error('invalid peer_id')
-    if (!port) return error('invalid port')
-
-    var left = Number(params.left)
-    var compact = Number(params.compact)
-
-    var ip = self._trustProxy
-      ? req.headers['x-forwarded-for'] || req.connection.remoteAddress
-      : req.connection.remoteAddress.replace(REMOVE_IPV6_RE, '') // force ipv4
-    var addr = ip + ':' + port
-    var swarm = self._getSwarm(infoHash)
-    var peer = swarm.peers[addr]
-
-    var numWant = Math.min(
-      Number(params.numwant) || NUM_ANNOUNCE_PEERS,
-      MAX_ANNOUNCE_PEERS
-    )
+  if (params && params.request === 'announce') {
+    var swarm = self._getSwarm(params.info_hash)
+    var peer = swarm.peers[params.addr]
 
     var start = function () {
       if (peer) {
         debug('unexpected `started` event from peer that is already in swarm')
         return update() // treat as an update
       }
-      if (left === 0) swarm.complete += 1
+      if (params.left === 0) swarm.complete += 1
       else swarm.incomplete += 1
-      peer = swarm.peers[addr] = {
-        ip: ip,
-        port: port,
-        peerId: peerId
+      peer = swarm.peers[params.addr] = {
+        ip: params.ip,
+        port: params.port,
+        peerId: params.peer_id
       }
-      self.emit('start', addr)
+      self.emit('start', params.addr)
     }
 
     var stop = function () {
@@ -189,8 +185,8 @@ Server.prototype._onHttpRequest = function (req, res) {
       }
       if (peer.complete) swarm.complete -= 1
       else swarm.incomplete -= 1
-      swarm.peers[addr] = null
-      self.emit('stop', addr)
+      swarm.peers[params.addr] = null
+      self.emit('stop', params.addr)
     }
 
     var complete = function () {
@@ -205,7 +201,7 @@ Server.prototype._onHttpRequest = function (req, res) {
       swarm.complete += 1
       swarm.incomplete -= 1
       peer.complete = true
-      self.emit('complete', addr)
+      self.emit('complete', params.addr)
     }
 
     var update = function () {
@@ -213,7 +209,7 @@ Server.prototype._onHttpRequest = function (req, res) {
         debug('unexpected `update` event from peer that is not in swarm')
         return start() // treat as a start
       }
-      self.emit('update', addr)
+      self.emit('update', params.addr)
     }
 
     switch (params.event) {
@@ -233,12 +229,12 @@ Server.prototype._onHttpRequest = function (req, res) {
         return error('invalid event') // early return
     }
 
-    if (left === 0 && peer) peer.complete = true
+    if (params.left === 0 && peer) peer.complete = true
 
     // send peers
-    var peers = compact === 1
-      ? self._getPeersCompact(swarm, numWant)
-      : self._getPeers(swarm, numWant)
+    var peers = params.compact === 1
+      ? self._getPeersCompact(swarm, params.numwant)
+      : self._getPeers(swarm, params.numwant)
 
     response = {
       complete: swarm.complete,
@@ -250,11 +246,12 @@ Server.prototype._onHttpRequest = function (req, res) {
     res.end(bencode.encode(response))
     debug('sent response %s', response)
 
-  } else if (s[0] === '/scrape') { // unofficial scrape message
+  } else if (params.request === 'scrape') { // unofficial scrape message
     if (typeof params.info_hash === 'string') {
       params.info_hash = [ params.info_hash ]
     } else if (params.info_hash == null) {
       // if info_hash param is omitted, stats for all torrents are returned
+      // TODO: make this configurable!
       params.info_hash = Object.keys(self.torrents)
     }
 
@@ -268,11 +265,6 @@ Server.prototype._onHttpRequest = function (req, res) {
     }
 
     params.info_hash.some(function (infoHash) {
-      if (infoHash.length !== 20) {
-        error('invalid info_hash')
-        return true // early return
-      }
-
       var swarm = self._getSwarm(infoHash)
 
       response.files[infoHash] = {
@@ -338,7 +330,7 @@ Server.prototype._onUdpRequest = function (msg, rinfo) {
     var event = msg.readUInt32BE(80)
     var ip = msg.readUInt32BE(84) // optional
     var key = msg.readUInt32BE(88) // TODO: what is this for?
-    var numWant = msg.readUInt32BE(92) // optional
+    var numwant = msg.readUInt32BE(92) // optional
     var port = msg.readUInt16BE(96) // optional
 
     if (ip) {
@@ -358,7 +350,7 @@ Server.prototype._onUdpRequest = function (msg, rinfo) {
 
     // never send more than MAX_ANNOUNCE_PEERS or else the UDP packet will get bigger than
     // 512 bytes which is not safe
-    numWant = Math.min(numWant || NUM_ANNOUNCE_PEERS, MAX_ANNOUNCE_PEERS)
+    numwant = Math.min(numwant || NUM_ANNOUNCE_PEERS, MAX_ANNOUNCE_PEERS)
 
     var start = function () {
       if (peer) {
@@ -429,7 +421,7 @@ Server.prototype._onUdpRequest = function (msg, rinfo) {
     if (left === 0 && peer) peer.complete = true
 
     // send peers
-    var peers = self._getPeersCompact(swarm, numWant)
+    var peers = self._getPeersCompact(swarm, numwant)
 
     send(Buffer.concat([
       common.toUInt32(common.ACTIONS.ANNOUNCE),
@@ -479,10 +471,10 @@ Server.prototype._onUdpRequest = function (msg, rinfo) {
   }
 }
 
-Server.prototype._getPeers = function (swarm, numWant) {
+Server.prototype._getPeers = function (swarm, numwant) {
   var peers = []
   for (var peerId in swarm.peers) {
-    if (peers.length >= numWant) break
+    if (peers.length >= numwant) break
     var peer = swarm.peers[peerId]
     if (!peer) continue // ignore null values
     peers.push({
@@ -494,11 +486,11 @@ Server.prototype._getPeers = function (swarm, numWant) {
   return peers
 }
 
-Server.prototype._getPeersCompact = function (swarm, numWant) {
+Server.prototype._getPeersCompact = function (swarm, numwant) {
   var peers = []
 
   for (var peerId in swarm.peers) {
-    if (peers.length >= numWant) break
+    if (peers.length >= numwant) break
     var peer = swarm.peers[peerId]
     if (!peer) continue // ignore null values
     peers.push(peer.ip + ':' + peer.port)
@@ -507,6 +499,61 @@ Server.prototype._getPeersCompact = function (swarm, numWant) {
   return string2compact(peers)
 }
 
+
+function parseHttpRequest (req, options) {
+  var s = req.url.split('?')
+  var params = common.querystringParse(s[1])
+
+  if (s[0] === '/announce') {
+    params.request = 'announce'
+    
+    params.peer_id = typeof params.peer_id === 'string' && common.binaryToUtf8(params.peer_id)
+    params.port = Number(params.port)
+
+    if (typeof params.info_hash !== 'string') throw new Error('invalid info_hash')
+    if (params.info_hash.length !== 20) throw new Error('invalid info_hash length')
+    if (typeof params.peer_id !== 'string') throw new Error('invalid peer_id')
+    if (params.peer_id.length !== 20) throw new Error('invalid peer_id length')
+    if (!params.port) throw new Error('invalid port')
+
+    params.left = Number(params.left)
+    params.compact = Number(params.compact)
+
+    params.ip = options.trustProxy
+      ? req.headers['x-forwarded-for'] || req.connection.remoteAddress
+      : req.connection.remoteAddress.replace(REMOVE_IPV6_RE, '') // force ipv4
+    params.addr = params.ip + ':' + params.port // TODO: ipv6 brackets?
+
+    params.numwant = Math.min(
+      Number(params.numwant) || NUM_ANNOUNCE_PEERS,
+      MAX_ANNOUNCE_PEERS
+    )
+
+    return params
+  } else if (s[0] === '/scrape') { // unofficial scrape message
+    params.request = 'scrape'
+
+    if (typeof params.info_hash === 'string') {
+      params.info_hash = [ params.info_hash ]
+    }
+
+    if (params.info_hash) {
+        if (!Array.isArray(params.info_hash)) throw new Error('invalid info_hash')
+
+      params.info_hash.some(function (infoHash) {
+        if (infoHash.length !== 20) {
+          throw new Error('invalid info_hash')
+        }
+      })
+    }
+
+    return params
+  } else {
+    return null
+  }
+}
+
+
 // HELPER FUNCTIONS
 
 var TWO_PWR_32 = (1 << 16) * 2

From 0bc88bcf22a81436faa7ba9277ea319ffcb3e349 Mon Sep 17 00:00:00 2001
From: Astro <astro@spaceboyz.net>
Date: Tue, 9 Dec 2014 00:22:36 +0100
Subject: [PATCH 02/16] server: split out parseUdpRequest()

---
 lib/common.js |   6 ++
 server.js     | 173 +++++++++++++++++++++++++++-----------------------
 2 files changed, 101 insertions(+), 78 deletions(-)

diff --git a/lib/common.js b/lib/common.js
index ccf1bd4..cb83d5b 100644
--- a/lib/common.js
+++ b/lib/common.js
@@ -7,6 +7,12 @@ var querystring = require('querystring')
 exports.CONNECTION_ID = Buffer.concat([ toUInt32(0x417), toUInt32(0x27101980) ])
 exports.ACTIONS = { CONNECT: 0, ANNOUNCE: 1, SCRAPE: 2, ERROR: 3 }
 exports.EVENTS = { update: 0, completed: 1, started: 2, stopped: 3 }
+exports.EVENT_IDS = {
+  0: 'update',
+  1: 'completed',
+  2: 'started',
+  3: 'stopped'
+};
 
 function toUInt32 (n) {
   var buf = new Buffer(4)
diff --git a/server.js b/server.js
index 26b12e0..ec8790c 100644
--- a/server.js
+++ b/server.js
@@ -296,75 +296,40 @@ Server.prototype._onHttpRequest = function (req, res) {
 Server.prototype._onUdpRequest = function (msg, rinfo) {
   var self = this
 
-  if (msg.length < 16) {
-    return error('received packet is too short')
+  var params
+  try {
+    params = parseUdpRequest(msg, rinfo)
+  } catch (err) {
+    console.error(err.stack)
+    return error(err.message)
   }
-
-  if (rinfo.family !== 'IPv4') {
-    return error('udp tracker does not support IPv6')
-  }
-
-  var connectionId = msg.slice(0, 8) // 64-bit
-  var action = msg.readUInt32BE(8)
-  var transactionId = msg.readUInt32BE(12)
-
-  if (!bufferEqual(connectionId, common.CONNECTION_ID)) {
-    return error('received packet with invalid connection id')
-  }
-
+  
   var socket = dgram.createSocket('udp4')
 
-  var infoHash, swarm
-  if (action === common.ACTIONS.CONNECT) {
+  var swarm
+  if (params && params.request === 'connect') {
     send(Buffer.concat([
       common.toUInt32(common.ACTIONS.CONNECT),
-      common.toUInt32(transactionId),
-      connectionId
+      common.toUInt32(params.transactionId),
+      params.connectionId
     ]))
-  } else if (action === common.ACTIONS.ANNOUNCE) {
-    infoHash = msg.slice(16, 36).toString('binary') // 20 bytes
-    var peerId = msg.slice(36, 56).toString('utf8') // 20 bytes
-    var downloaded = fromUInt64(msg.slice(56, 64)) // TODO: track this?
-    var left = fromUInt64(msg.slice(64, 72))
-    var uploaded = fromUInt64(msg.slice(72, 80)) // TODO: track this?
-    var event = msg.readUInt32BE(80)
-    var ip = msg.readUInt32BE(84) // optional
-    var key = msg.readUInt32BE(88) // TODO: what is this for?
-    var numwant = msg.readUInt32BE(92) // optional
-    var port = msg.readUInt16BE(96) // optional
-
-    if (ip) {
-      ip = ipLib.toString(ip)
-    } else {
-      ip = rinfo.address
-    }
-
-    if (!port) {
-      port = rinfo.port
-    }
-
-    var addr = ip + ':' + port
-
-    swarm = self._getSwarm(infoHash)
-    var peer = swarm.peers[addr]
-
-    // never send more than MAX_ANNOUNCE_PEERS or else the UDP packet will get bigger than
-    // 512 bytes which is not safe
-    numwant = Math.min(numwant || NUM_ANNOUNCE_PEERS, MAX_ANNOUNCE_PEERS)
+  } else if (params && params.request === 'announce') {
+    swarm = self._getSwarm(params.info_hash)
+    var peer = swarm.peers[params.addr]
 
     var start = function () {
       if (peer) {
         debug('unexpected `started` event from peer that is already in swarm')
         return update() // treat as an update
       }
-      if (left === 0) swarm.complete += 1
+      if (params.left === 0) swarm.complete += 1
       else swarm.incomplete += 1
-      peer = swarm.peers[addr] = {
-        ip: ip,
-        port: port,
-        peerId: peerId
+      peer = swarm.peers[params.addr] = {
+        ip: params.ip,
+        port: params.port,
+        peerId: params.peer_id
       }
-      self.emit('start', addr)
+      self.emit('start', params.addr)
     }
 
     var stop = function () {
@@ -374,8 +339,8 @@ Server.prototype._onUdpRequest = function (msg, rinfo) {
       }
       if (peer.complete) swarm.complete -= 1
       else swarm.incomplete -= 1
-      swarm.peers[addr] = null
-      self.emit('stop', addr)
+      swarm.peers[params.addr] = null
+      self.emit('stop', params.addr)
     }
 
     var complete = function () {
@@ -390,7 +355,7 @@ Server.prototype._onUdpRequest = function (msg, rinfo) {
       swarm.complete += 1
       swarm.incomplete -= 1
       peer.complete = true
-      self.emit('complete', addr)
+      self.emit('complete', params.addr)
     }
 
     var update = function () {
@@ -398,53 +363,46 @@ Server.prototype._onUdpRequest = function (msg, rinfo) {
         debug('unexpected `update` event from peer that is not in swarm')
         return start() // treat as a start
       }
-      self.emit('update', addr)
+      self.emit('update', params.addr)
     }
 
-    switch (event) {
-      case common.EVENTS.started:
+    switch (params.event) {
+      case 'started':
         start()
         break
-      case common.EVENTS.stopped:
+      case 'stopped':
         stop()
         break
-      case common.EVENTS.completed:
+      case 'completed':
         complete()
         break
-      case common.EVENTS.update: // update
+      case 'update':
         update()
         break
       default:
         return error('invalid event') // early return
     }
 
-    if (left === 0 && peer) peer.complete = true
+    if (params.left === 0 && peer) peer.complete = true
 
     // send peers
-    var peers = self._getPeersCompact(swarm, numwant)
+    var peers = self._getPeersCompact(swarm, params.numwant)
 
     send(Buffer.concat([
       common.toUInt32(common.ACTIONS.ANNOUNCE),
-      common.toUInt32(transactionId),
+      common.toUInt32(params.transactionId),
       common.toUInt32(self._intervalMs),
       common.toUInt32(swarm.incomplete),
       common.toUInt32(swarm.complete),
       peers
     ]))
 
-  } else if (action === common.ACTIONS.SCRAPE) { // scrape message
-    infoHash = msg.slice(16, 36).toString('binary') // 20 bytes
-
-    // TODO: support multiple info_hash scrape
-    if (msg.length > 36) {
-      error('multiple info_hash scrape not supported')
-    }
-
-    swarm = self._getSwarm(infoHash)
+  } else if (params && params.request === 'scrape') { // scrape message
+    swarm = self._getSwarm(params.info_hash)
 
     send(Buffer.concat([
       common.toUInt32(common.ACTIONS.SCRAPE),
-      common.toUInt32(transactionId),
+      common.toUInt32(params.transactionId),
       common.toUInt32(swarm.complete),
       common.toUInt32(swarm.complete), // TODO: this only provides a lower-bound
       common.toUInt32(swarm.incomplete)
@@ -464,7 +422,7 @@ Server.prototype._onUdpRequest = function (msg, rinfo) {
     debug('sent error %s', message)
     send(Buffer.concat([
       common.toUInt32(common.ACTIONS.ERROR),
-      common.toUInt32(transactionId || 0),
+      common.toUInt32(params.transactionId || 0),
       new Buffer(message, 'utf8')
     ]))
     self.emit('warning', new Error(message))
@@ -553,6 +511,65 @@ function parseHttpRequest (req, options) {
   }
 }
 
+function parseUdpRequest (msg, rinfo) {
+  if (msg.length < 16) {
+    throw new Error('received packet is too short')
+  }
+
+  if (rinfo.family !== 'IPv4') {
+    throw new Error('udp tracker does not support IPv6')
+  }
+
+  var params = {
+    connectionId: msg.slice(0, 8), // 64-bit
+    action: msg.readUInt32BE(8),
+    transactionId: msg.readUInt32BE(12)
+  }
+
+  // TODO: randomize:
+  if (!bufferEqual(params.connectionId, common.CONNECTION_ID)) {
+    throw new Error('received packet with invalid connection id')
+  }
+
+  if (params.action === common.ACTIONS.CONNECT) {
+    params.request = 'connect'
+  } else if (params.action === common.ACTIONS.ANNOUNCE) {
+    params.request = 'announce'
+    params.info_hash = msg.slice(16, 36).toString('binary') // 20 bytes
+    params.peer_id = msg.slice(36, 56).toString('utf8') // 20 bytes
+    params.downloaded = fromUInt64(msg.slice(56, 64)) // TODO: track this?
+    params.left = fromUInt64(msg.slice(64, 72))
+    params.uploaded = fromUInt64(msg.slice(72, 80)) // TODO: track this?
+    params.event = msg.readUInt32BE(80)
+    params.event = common.EVENT_IDS[params.event]
+    if (!params.event) throw new Error('invalid event') // early return
+    params.ip = msg.readUInt32BE(84) // optional
+    params.ip = params.ip ?
+      ipLib.toString(params.ip) :
+      params.ip = rinfo.address
+    params.key = msg.readUInt32BE(88) // TODO: what is this for?
+    params.numwant = msg.readUInt32BE(92) // optional
+    // never send more than MAX_ANNOUNCE_PEERS or else the UDP packet will get bigger than
+    // 512 bytes which is not safe
+    params.numwant = Math.min(params.numwant || NUM_ANNOUNCE_PEERS, MAX_ANNOUNCE_PEERS)
+    params.port = msg.readUInt16BE(96) || rinfo.port // optional
+    params.addr = params.ip + ':' + params.port // TODO: ipv6 brackets
+
+  } else if (params.action === common.ACTIONS.SCRAPE) { // scrape message
+    params.request = 'scrape'
+    params.info_hash = msg.slice(16, 36).toString('binary') // 20 bytes
+
+    // TODO: support multiple info_hash scrape
+    if (msg.length > 36) {
+      throw new Error('multiple info_hash scrape not supported')
+    }
+  } else {
+    return null
+  }
+
+  return params
+}
+
 
 // HELPER FUNCTIONS
 

From 85be917d5177f871190c9a77cae6c41864d89008 Mon Sep 17 00:00:00 2001
From: Astro <astro@spaceboyz.net>
Date: Tue, 9 Dec 2014 00:25:29 +0100
Subject: [PATCH 03/16] server: replace request string by action number

---
 server.js | 18 ++++++++----------
 1 file changed, 8 insertions(+), 10 deletions(-)

diff --git a/server.js b/server.js
index ec8790c..dc041ba 100644
--- a/server.js
+++ b/server.js
@@ -159,7 +159,7 @@ Server.prototype._onHttpRequest = function (req, res) {
   }
   
   var response
-  if (params && params.request === 'announce') {
+  if (params && params.action === common.ACTIONS.ANNOUNCE) {
     var swarm = self._getSwarm(params.info_hash)
     var peer = swarm.peers[params.addr]
 
@@ -246,7 +246,7 @@ Server.prototype._onHttpRequest = function (req, res) {
     res.end(bencode.encode(response))
     debug('sent response %s', response)
 
-  } else if (params.request === 'scrape') { // unofficial scrape message
+  } else if (params.action === common.ACTIONS.SCRAPE) { // unofficial scrape message
     if (typeof params.info_hash === 'string') {
       params.info_hash = [ params.info_hash ]
     } else if (params.info_hash == null) {
@@ -307,13 +307,13 @@ Server.prototype._onUdpRequest = function (msg, rinfo) {
   var socket = dgram.createSocket('udp4')
 
   var swarm
-  if (params && params.request === 'connect') {
+  if (params && params.action === common.ACTIONS.CONNECT) {
     send(Buffer.concat([
       common.toUInt32(common.ACTIONS.CONNECT),
       common.toUInt32(params.transactionId),
       params.connectionId
     ]))
-  } else if (params && params.request === 'announce') {
+  } else if (params && params.action === common.ACTIONS.ANNOUNCE) {
     swarm = self._getSwarm(params.info_hash)
     var peer = swarm.peers[params.addr]
 
@@ -397,7 +397,7 @@ Server.prototype._onUdpRequest = function (msg, rinfo) {
       peers
     ]))
 
-  } else if (params && params.request === 'scrape') { // scrape message
+  } else if (params && params.action === common.ACTIONS.SCRAPE) { // scrape message
     swarm = self._getSwarm(params.info_hash)
 
     send(Buffer.concat([
@@ -463,7 +463,7 @@ function parseHttpRequest (req, options) {
   var params = common.querystringParse(s[1])
 
   if (s[0] === '/announce') {
-    params.request = 'announce'
+    params.action = common.ACTIONS.ANNOUNCE
     
     params.peer_id = typeof params.peer_id === 'string' && common.binaryToUtf8(params.peer_id)
     params.port = Number(params.port)
@@ -489,7 +489,7 @@ function parseHttpRequest (req, options) {
 
     return params
   } else if (s[0] === '/scrape') { // unofficial scrape message
-    params.request = 'scrape'
+    params.action = common.ACTIONS.SCRAPE
 
     if (typeof params.info_hash === 'string') {
       params.info_hash = [ params.info_hash ]
@@ -532,9 +532,8 @@ function parseUdpRequest (msg, rinfo) {
   }
 
   if (params.action === common.ACTIONS.CONNECT) {
-    params.request = 'connect'
+    // No further params
   } else if (params.action === common.ACTIONS.ANNOUNCE) {
-    params.request = 'announce'
     params.info_hash = msg.slice(16, 36).toString('binary') // 20 bytes
     params.peer_id = msg.slice(36, 56).toString('utf8') // 20 bytes
     params.downloaded = fromUInt64(msg.slice(56, 64)) // TODO: track this?
@@ -556,7 +555,6 @@ function parseUdpRequest (msg, rinfo) {
     params.addr = params.ip + ':' + params.port // TODO: ipv6 brackets
 
   } else if (params.action === common.ACTIONS.SCRAPE) { // scrape message
-    params.request = 'scrape'
     params.info_hash = msg.slice(16, 36).toString('binary') // 20 bytes
 
     // TODO: support multiple info_hash scrape

From 366b49bf068b17c4adbb72efa696a991650d4d39 Mon Sep 17 00:00:00 2001
From: Astro <astro@spaceboyz.net>
Date: Tue, 9 Dec 2014 02:35:05 +0100
Subject: [PATCH 04/16] server: split out _onRequest() et al

---
 server.js | 452 +++++++++++++++++++++++++-----------------------------
 1 file changed, 206 insertions(+), 246 deletions(-)

diff --git a/server.js b/server.js
index dc041ba..10f8bcb 100644
--- a/server.js
+++ b/server.js
@@ -157,140 +157,18 @@ Server.prototype._onHttpRequest = function (req, res) {
     
     return
   }
-  
-  var response
-  if (params && params.action === common.ACTIONS.ANNOUNCE) {
-    var swarm = self._getSwarm(params.info_hash)
-    var peer = swarm.peers[params.addr]
 
-    var start = function () {
-      if (peer) {
-        debug('unexpected `started` event from peer that is already in swarm')
-        return update() // treat as an update
+  this._onRequest(params, function (err, response) {
+    if (err) {
+      self.emit('warning', new Error(err.message))
+      response = {
+        action: common.ACTIONS.ERRROR,
+        'failure reason': err.message
       }
-      if (params.left === 0) swarm.complete += 1
-      else swarm.incomplete += 1
-      peer = swarm.peers[params.addr] = {
-        ip: params.ip,
-        port: params.port,
-        peerId: params.peer_id
-      }
-      self.emit('start', params.addr)
-    }
-
-    var stop = function () {
-      if (!peer) {
-        debug('unexpected `stopped` event from peer that is not in swarm')
-        return // do nothing
-      }
-      if (peer.complete) swarm.complete -= 1
-      else swarm.incomplete -= 1
-      swarm.peers[params.addr] = null
-      self.emit('stop', params.addr)
-    }
-
-    var complete = function () {
-      if (!peer) {
-        debug('unexpected `completed` event from peer that is not in swarm')
-        return start() // treat as a start
-      }
-      if (peer.complete) {
-        debug('unexpected `completed` event from peer that is already marked as completed')
-        return // do nothing
-      }
-      swarm.complete += 1
-      swarm.incomplete -= 1
-      peer.complete = true
-      self.emit('complete', params.addr)
-    }
-
-    var update = function () {
-      if (!peer) {
-        debug('unexpected `update` event from peer that is not in swarm')
-        return start() // treat as a start
-      }
-      self.emit('update', params.addr)
-    }
-
-    switch (params.event) {
-      case 'started':
-        start()
-        break
-      case 'stopped':
-        stop()
-        break
-      case 'completed':
-        complete()
-        break
-      case '': case undefined: // update
-        update()
-        break
-      default:
-        return error('invalid event') // early return
-    }
-
-    if (params.left === 0 && peer) peer.complete = true
-
-    // send peers
-    var peers = params.compact === 1
-      ? self._getPeersCompact(swarm, params.numwant)
-      : self._getPeers(swarm, params.numwant)
-
-    response = {
-      complete: swarm.complete,
-      incomplete: swarm.incomplete,
-      peers: peers,
-      interval: self._intervalMs
     }
 
     res.end(bencode.encode(response))
-    debug('sent response %s', response)
-
-  } else if (params.action === common.ACTIONS.SCRAPE) { // unofficial scrape message
-    if (typeof params.info_hash === 'string') {
-      params.info_hash = [ params.info_hash ]
-    } else if (params.info_hash == null) {
-      // if info_hash param is omitted, stats for all torrents are returned
-      // TODO: make this configurable!
-      params.info_hash = Object.keys(self.torrents)
-    }
-
-    if (!Array.isArray(params.info_hash)) return error('invalid info_hash')
-
-    response = {
-      files: {},
-      flags: {
-        min_request_interval: self._intervalMs
-      }
-    }
-
-    params.info_hash.some(function (infoHash) {
-      var swarm = self._getSwarm(infoHash)
-
-      response.files[infoHash] = {
-        complete: swarm.complete,
-        incomplete: swarm.incomplete,
-        downloaded: swarm.complete // TODO: this only provides a lower-bound
-      }
-    })
-
-    res.end(bencode.encode(response))
-    debug('sent response %s', response)
-
-  } else {
-    error('only /announce and /scrape are valid endpoints')
-  }
-
-  function error (message) {
-    debug('sent error %s', message)
-    res.end(bencode.encode({
-      'failure reason': message
-    }))
-
-    // even though it's an error for the client, it's just a warning for the server.
-    // don't crash the server because a client sent bad data :)
-    self.emit('warning', new Error(message))
-  }
+  })
 }
 
 Server.prototype._onUdpRequest = function (msg, rinfo) {
@@ -300,133 +178,173 @@ Server.prototype._onUdpRequest = function (msg, rinfo) {
   try {
     params = parseUdpRequest(msg, rinfo)
   } catch (err) {
-    console.error(err.stack)
-    return error(err.message)
-  }
-  
-  var socket = dgram.createSocket('udp4')
-
-  var swarm
-  if (params && params.action === common.ACTIONS.CONNECT) {
-    send(Buffer.concat([
-      common.toUInt32(common.ACTIONS.CONNECT),
-      common.toUInt32(params.transactionId),
-      params.connectionId
-    ]))
-  } else if (params && params.action === common.ACTIONS.ANNOUNCE) {
-    swarm = self._getSwarm(params.info_hash)
-    var peer = swarm.peers[params.addr]
-
-    var start = function () {
-      if (peer) {
-        debug('unexpected `started` event from peer that is already in swarm')
-        return update() // treat as an update
-      }
-      if (params.left === 0) swarm.complete += 1
-      else swarm.incomplete += 1
-      peer = swarm.peers[params.addr] = {
-        ip: params.ip,
-        port: params.port,
-        peerId: params.peer_id
-      }
-      self.emit('start', params.addr)
-    }
-
-    var stop = function () {
-      if (!peer) {
-        debug('unexpected `stopped` event from peer that is not in swarm')
-        return // do nothing
-      }
-      if (peer.complete) swarm.complete -= 1
-      else swarm.incomplete -= 1
-      swarm.peers[params.addr] = null
-      self.emit('stop', params.addr)
-    }
-
-    var complete = function () {
-      if (!peer) {
-        debug('unexpected `completed` event from peer that is not in swarm')
-        return start() // treat as a start
-      }
-      if (peer.complete) {
-        debug('unexpected `completed` event from peer that is already marked as completed')
-        return // do nothing
-      }
-      swarm.complete += 1
-      swarm.incomplete -= 1
-      peer.complete = true
-      self.emit('complete', params.addr)
-    }
-
-    var update = function () {
-      if (!peer) {
-        debug('unexpected `update` event from peer that is not in swarm')
-        return start() // treat as a start
-      }
-      self.emit('update', params.addr)
-    }
-
-    switch (params.event) {
-      case 'started':
-        start()
-        break
-      case 'stopped':
-        stop()
-        break
-      case 'completed':
-        complete()
-        break
-      case 'update':
-        update()
-        break
-      default:
-        return error('invalid event') // early return
-    }
-
-    if (params.left === 0 && peer) peer.complete = true
-
-    // send peers
-    var peers = self._getPeersCompact(swarm, params.numwant)
-
-    send(Buffer.concat([
-      common.toUInt32(common.ACTIONS.ANNOUNCE),
-      common.toUInt32(params.transactionId),
-      common.toUInt32(self._intervalMs),
-      common.toUInt32(swarm.incomplete),
-      common.toUInt32(swarm.complete),
-      peers
-    ]))
-
-  } else if (params && params.action === common.ACTIONS.SCRAPE) { // scrape message
-    swarm = self._getSwarm(params.info_hash)
-
-    send(Buffer.concat([
-      common.toUInt32(common.ACTIONS.SCRAPE),
-      common.toUInt32(params.transactionId),
-      common.toUInt32(swarm.complete),
-      common.toUInt32(swarm.complete), // TODO: this only provides a lower-bound
-      common.toUInt32(swarm.incomplete)
-    ]))
+    self.emit('warning', err)
+    // Do not reply for parsing errors
+    return
   }
 
-  function send (buf) {
-    debug('sent response %s', buf.toString('hex'))
+  // Do nothing with invalid request
+  if (!params) return
+
+  // Handle
+  this._onRequest(params, function (err, response) {
+    if (err) {
+      self.emit('warning', new Error(err.message))
+      response = {
+        action: common.ACTIONS.ERRROR,
+        'failure reason': err.message
+      }
+    }
+    
+    var socket = dgram.createSocket('udp4')
+    response.transactionId = params.transactionId
+    response.connectionId = params.connectionId
+    var buf = makeUdpPacket(response)
     socket.send(buf, 0, buf.length, rinfo.port, rinfo.address, function () {
       try {
         socket.close()
       } catch (err) {}
     })
+  })
+}
+
+Server.prototype._onRequest = function (params, cb) {
+  var response
+  if (params && params.action === common.ACTIONS.CONNECT) {
+    cb(null, { action: common.ACTIONS.CONNECT })
+  } else if (params && params.action === common.ACTIONS.ANNOUNCE) {
+    this._onAnnounce(params, cb)
+  } else if (params && params.action === common.ACTIONS.SCRAPE) {
+    this._onScrape(params, cb)
+  } else {
+    cb(new Error('Invalid action'))
+  }
+}
+
+Server.prototype._onAnnounce = function (params, cb) {
+  var self = this
+
+  var swarm = self._getSwarm(params.info_hash)
+  var peer = swarm.peers[params.addr]
+
+  var start = function () {
+    if (peer) {
+      debug('unexpected `started` event from peer that is already in swarm')
+      return update() // treat as an update
+    }
+    if (params.left === 0) swarm.complete += 1
+    else swarm.incomplete += 1
+    peer = swarm.peers[params.addr] = {
+      ip: params.ip,
+      port: params.port,
+      peerId: params.peer_id
+    }
+    self.emit('start', params.addr)
   }
 
-  function error (message) {
-    debug('sent error %s', message)
-    send(Buffer.concat([
-      common.toUInt32(common.ACTIONS.ERROR),
-      common.toUInt32(params.transactionId || 0),
-      new Buffer(message, 'utf8')
-    ]))
-    self.emit('warning', new Error(message))
+  var stop = function () {
+    if (!peer) {
+      debug('unexpected `stopped` event from peer that is not in swarm')
+      return // do nothing
+    }
+    if (peer.complete) swarm.complete -= 1
+    else swarm.incomplete -= 1
+    swarm.peers[params.addr] = null
+    self.emit('stop', params.addr)
   }
+
+  var complete = function () {
+    if (!peer) {
+      debug('unexpected `completed` event from peer that is not in swarm')
+      return start() // treat as a start
+    }
+    if (peer.complete) {
+      debug('unexpected `completed` event from peer that is already marked as completed')
+      return // do nothing
+    }
+    swarm.complete += 1
+    swarm.incomplete -= 1
+    peer.complete = true
+    self.emit('complete', params.addr)
+  }
+
+  var update = function () {
+    if (!peer) {
+      debug('unexpected `update` event from peer that is not in swarm')
+      return start() // treat as a start
+    }
+    self.emit('update', params.addr)
+  }
+
+  switch (params.event) {
+  case 'started':
+    start()
+    break
+  case 'stopped':
+    stop()
+    break
+  case 'completed':
+    complete()
+    break
+  case '': case undefined: case 'empty': case 'update': // update
+    update()
+    break
+  default:
+    return cb(new Error('invalid event')) // early return
+  }
+
+  if (params.left === 0 && peer) peer.complete = true
+
+  // send peers
+  var peers = params.compact === 1
+        ? self._getPeersCompact(swarm, params.numwant)
+        : self._getPeers(swarm, params.numwant)
+
+  cb(null, {
+    action: common.ACTIONS.ANNOUNCE,
+    complete: swarm.complete,
+    incomplete: swarm.incomplete,
+    peers: peers,
+    intervalMs: self._intervalMs
+  })
+}
+
+Server.prototype._onScrape = function (params, cb) {
+  var self = this
+  
+  if (typeof params.info_hash === 'string') {
+    params.info_hash = [ params.info_hash ]
+  } else if (params.info_hash == null) {
+    // if info_hash param is omitted, stats for all torrents are returned
+    // TODO: make this configurable!
+    params.info_hash = Object.keys(self.torrents)
+  }
+  
+  if (!Array.isArray(params.info_hash)) {
+    var err = new Error('invalid info_hash')
+    self.emit('warning', err)
+    return cb(err)
+  }
+  
+  var response = {
+    action: common.ACTIONS.SCRAPE,
+    files: {},
+    flags: {
+      min_request_interval: self._intervalMs
+    }
+  }
+  
+  params.info_hash.some(function (infoHash) {
+    var swarm = self._getSwarm(infoHash)
+    
+    response.files[infoHash] = {
+      complete: swarm.complete,
+      incomplete: swarm.incomplete,
+      downloaded: swarm.complete // TODO: this only provides a lower-bound
+    }
+  })
+
+  cb(null, response)
 }
 
 Server.prototype._getPeers = function (swarm, numwant) {
@@ -553,6 +471,7 @@ function parseUdpRequest (msg, rinfo) {
     params.numwant = Math.min(params.numwant || NUM_ANNOUNCE_PEERS, MAX_ANNOUNCE_PEERS)
     params.port = msg.readUInt16BE(96) || rinfo.port // optional
     params.addr = params.ip + ':' + params.port // TODO: ipv6 brackets
+    params.compact = 1 // udp is always compact
 
   } else if (params.action === common.ACTIONS.SCRAPE) { // scrape message
     params.info_hash = msg.slice(16, 36).toString('binary') // 20 bytes
@@ -568,6 +487,47 @@ function parseUdpRequest (msg, rinfo) {
   return params
 }
 
+function makeUdpPacket (params) {
+  switch (params.action) {
+    case common.ACTIONS.CONNECT:
+      return Buffer.concat([
+        common.toUInt32(common.ACTIONS.CONNECT),
+        common.toUInt32(params.transactionId),
+        params.connectionId
+      ])
+    case common.ACTIONS.ANNOUNCE:
+      return Buffer.concat([
+        common.toUInt32(common.ACTIONS.ANNOUNCE),
+        common.toUInt32(params.transactionId),
+        common.toUInt32(params.intervalMs),
+        common.toUInt32(params.incomplete),
+        common.toUInt32(params.complete),
+        params.peers
+      ])
+    case common.ACTIONS.SCRAPE:
+      var firstInfoHash = Object.keys(params.files)[0]
+      var scrapeInfo = firstInfoHash ? {
+        complete: params.files[firstInfoHash].complete,
+        incomplete: params.files[firstInfoHash].incomplete,
+        completed: params.files[firstInfoHash].complete // TODO: this only provides a lower-bound
+      } : {}
+      return Buffer.concat([
+        common.toUInt32(common.ACTIONS.SCRAPE),
+        common.toUInt32(params.transactionId),
+        common.toUInt32(scrapeInfo.complete),
+        common.toUInt32(scrapeInfo.completed),
+        common.toUInt32(scrapeInfo.incomplete)
+      ])
+    case common.ACTIONS.ERROR:
+      return Buffer.concat([
+        common.toUInt32(common.ACTIONS.ERROR),
+        common.toUInt32(params.transactionId || 0),
+        new Buffer(params.message, 'utf8')
+      ])
+  default:
+    throw new Error('Action not implemented: ' + params.action)
+  }
+}
 
 // HELPER FUNCTIONS
 

From fee289b0740aa8070a8b3fd7024ac35c85189666 Mon Sep 17 00:00:00 2001
From: Astro <astro@spaceboyz.net>
Date: Tue, 9 Dec 2014 23:18:20 +0100
Subject: [PATCH 05/16] server: rm superfluous action fields

---
 server.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/server.js b/server.js
index 10f8bcb..7e18dfc 100644
--- a/server.js
+++ b/server.js
@@ -162,11 +162,11 @@ Server.prototype._onHttpRequest = function (req, res) {
     if (err) {
       self.emit('warning', new Error(err.message))
       response = {
-        action: common.ACTIONS.ERRROR,
         'failure reason': err.message
       }
     }
 
+    delete response.action  // only needed for UDP encoding
     res.end(bencode.encode(response))
   })
 }

From aea3c44c0841b6df64e74bd1fcd5695a32d5076f Mon Sep 17 00:00:00 2001
From: Astro <astro@spaceboyz.net>
Date: Tue, 9 Dec 2014 23:18:47 +0100
Subject: [PATCH 06/16] server: expose getSwarm()

drops capability to pass a *hex* infoHash
---
 server.js      | 21 ++++++++-------------
 test/server.js |  2 +-
 2 files changed, 9 insertions(+), 14 deletions(-)

diff --git a/server.js b/server.js
index 7e18dfc..93df5af 100644
--- a/server.js
+++ b/server.js
@@ -116,16 +116,9 @@ Server.prototype.close = function (cb) {
   }
 }
 
-Server.prototype.getSwarm = function (infoHash) {
-  var self = this
-  var binaryInfoHash = Buffer.isBuffer(infoHash)
-    ? infoHash.toString('binary')
-    : new Buffer(infoHash, 'hex').toString('binary')
-  return self._getSwarm(binaryInfoHash)
-}
-
-Server.prototype._getSwarm = function (binaryInfoHash) {
+Server.prototype.getSwarm = function (binaryInfoHash) {
   var self = this
+  if (Buffer.isBuffer(binaryInfoHash)) binaryInfoHash = binaryInfoHash.toString('binary')
   var swarm = self.torrents[binaryInfoHash]
   if (!swarm) {
     swarm = self.torrents[binaryInfoHash] = {
@@ -224,7 +217,7 @@ Server.prototype._onRequest = function (params, cb) {
 Server.prototype._onAnnounce = function (params, cb) {
   var self = this
 
-  var swarm = self._getSwarm(params.info_hash)
+  var swarm = self.getSwarm(params.info_hash)
   var peer = swarm.peers[params.addr]
 
   var start = function () {
@@ -335,7 +328,7 @@ Server.prototype._onScrape = function (params, cb) {
   }
   
   params.info_hash.some(function (infoHash) {
-    var swarm = self._getSwarm(infoHash)
+    var swarm = self.getSwarm(infoHash)
     
     response.files[infoHash] = {
       complete: swarm.complete,
@@ -414,12 +407,14 @@ function parseHttpRequest (req, options) {
     }
 
     if (params.info_hash) {
-        if (!Array.isArray(params.info_hash)) throw new Error('invalid info_hash')
+      if (!Array.isArray(params.info_hash)) throw new Error('invalid info_hash array')
 
-      params.info_hash.some(function (infoHash) {
+      params.info_hash = params.info_hash.map(function (infoHash) {
         if (infoHash.length !== 20) {
           throw new Error('invalid info_hash')
         }
+
+        return infoHash
       })
     }
 
diff --git a/test/server.js b/test/server.js
index c27b4f5..f6ddd8d 100644
--- a/test/server.js
+++ b/test/server.js
@@ -2,7 +2,7 @@ var Client = require('../')
 var Server = require('../').Server
 var test = require('tape')
 
-var infoHash = '4cb67059ed6bd08362da625b3ae77f6f4a075705'
+var infoHash = new Buffer('4cb67059ed6bd08362da625b3ae77f6f4a075705', 'hex')
 var peerId = '01234567890123456789'
 var peerId2 = '12345678901234567890'
 var torrentLength = 50000

From 1c754a2f49cad23512336c7112372743a6b20c01 Mon Sep 17 00:00:00 2001
From: Astro <astro@spaceboyz.net>
Date: Wed, 10 Dec 2014 00:44:45 +0100
Subject: [PATCH 07/16] move parseHttpRequest(), parseUdpRequest() to
 lib/parse_{http,udp}.js

---
 lib/common.js     |   3 +
 lib/parse_http.js |  60 ++++++++++++++++++++
 lib/parse_udp.js  |  79 ++++++++++++++++++++++++++
 server.js         | 137 +---------------------------------------------
 4 files changed, 145 insertions(+), 134 deletions(-)
 create mode 100644 lib/parse_http.js
 create mode 100644 lib/parse_udp.js

diff --git a/lib/common.js b/lib/common.js
index cb83d5b..727e239 100644
--- a/lib/common.js
+++ b/lib/common.js
@@ -4,6 +4,9 @@
 
 var querystring = require('querystring')
 
+exports.NUM_ANNOUNCE_PEERS = 50
+exports.MAX_ANNOUNCE_PEERS = 82
+
 exports.CONNECTION_ID = Buffer.concat([ toUInt32(0x417), toUInt32(0x27101980) ])
 exports.ACTIONS = { CONNECT: 0, ANNOUNCE: 1, SCRAPE: 2, ERROR: 3 }
 exports.EVENTS = { update: 0, completed: 1, started: 2, stopped: 3 }
diff --git a/lib/parse_http.js b/lib/parse_http.js
new file mode 100644
index 0000000..0f7a775
--- /dev/null
+++ b/lib/parse_http.js
@@ -0,0 +1,60 @@
+var common = require('./common')
+
+var REMOVE_IPV6_RE = /^::ffff:/
+
+module.exports = parseHttpRequest
+
+function parseHttpRequest (req, options) {
+  var s = req.url.split('?')
+  var params = common.querystringParse(s[1])
+
+  if (s[0] === '/announce') {
+    params.action = common.ACTIONS.ANNOUNCE
+    
+    params.peer_id = typeof params.peer_id === 'string' && common.binaryToUtf8(params.peer_id)
+    params.port = Number(params.port)
+
+    if (typeof params.info_hash !== 'string') throw new Error('invalid info_hash')
+    if (params.info_hash.length !== 20) throw new Error('invalid info_hash length')
+    if (typeof params.peer_id !== 'string') throw new Error('invalid peer_id')
+    if (params.peer_id.length !== 20) throw new Error('invalid peer_id length')
+    if (!params.port) throw new Error('invalid port')
+
+    params.left = Number(params.left)
+    params.compact = Number(params.compact)
+
+    params.ip = options.trustProxy
+      ? req.headers['x-forwarded-for'] || req.connection.remoteAddress
+      : req.connection.remoteAddress.replace(REMOVE_IPV6_RE, '') // force ipv4
+    params.addr = params.ip + ':' + params.port // TODO: ipv6 brackets?
+
+    params.numwant = Math.min(
+      Number(params.numwant) || common.NUM_ANNOUNCE_PEERS,
+      common.MAX_ANNOUNCE_PEERS
+    )
+
+    return params
+  } else if (s[0] === '/scrape') { // unofficial scrape message
+    params.action = common.ACTIONS.SCRAPE
+
+    if (typeof params.info_hash === 'string') {
+      params.info_hash = [ params.info_hash ]
+    }
+
+    if (params.info_hash) {
+      if (!Array.isArray(params.info_hash)) throw new Error('invalid info_hash array')
+
+      params.info_hash = params.info_hash.map(function (infoHash) {
+        if (infoHash.length !== 20) {
+          throw new Error('invalid info_hash')
+        }
+
+        return infoHash
+      })
+    }
+
+    return params
+  } else {
+    return null
+  }
+}
diff --git a/lib/parse_udp.js b/lib/parse_udp.js
new file mode 100644
index 0000000..411d5b2
--- /dev/null
+++ b/lib/parse_udp.js
@@ -0,0 +1,79 @@
+var bufferEqual = require('buffer-equal')
+var common = require('./common')
+
+
+module.exports = parseUdpRequest
+
+function parseUdpRequest (msg, rinfo) {
+  if (msg.length < 16) {
+    throw new Error('received packet is too short')
+  }
+
+  if (rinfo.family !== 'IPv4') {
+    throw new Error('udp tracker does not support IPv6')
+  }
+
+  var params = {
+    connectionId: msg.slice(0, 8), // 64-bit
+    action: msg.readUInt32BE(8),
+    transactionId: msg.readUInt32BE(12)
+  }
+
+  // TODO: randomize:
+  if (!bufferEqual(params.connectionId, common.CONNECTION_ID)) {
+    throw new Error('received packet with invalid connection id')
+  }
+
+  if (params.action === common.ACTIONS.CONNECT) {
+    // No further params
+  } else if (params.action === common.ACTIONS.ANNOUNCE) {
+    params.info_hash = msg.slice(16, 36).toString('binary') // 20 bytes
+    params.peer_id = msg.slice(36, 56).toString('utf8') // 20 bytes
+    params.downloaded = fromUInt64(msg.slice(56, 64)) // TODO: track this?
+    params.left = fromUInt64(msg.slice(64, 72))
+    params.uploaded = fromUInt64(msg.slice(72, 80)) // TODO: track this?
+    params.event = msg.readUInt32BE(80)
+    params.event = common.EVENT_IDS[params.event]
+    if (!params.event) throw new Error('invalid event') // early return
+    params.ip = msg.readUInt32BE(84) // optional
+    params.ip = params.ip ?
+      ipLib.toString(params.ip) :
+      params.ip = rinfo.address
+    params.key = msg.readUInt32BE(88) // TODO: what is this for?
+    params.numwant = msg.readUInt32BE(92) // optional
+    // never send more than MAX_ANNOUNCE_PEERS or else the UDP packet will get bigger than
+    // 512 bytes which is not safe
+    params.numwant = Math.min(params.numwant || common.NUM_ANNOUNCE_PEERS, common.MAX_ANNOUNCE_PEERS)
+    params.port = msg.readUInt16BE(96) || rinfo.port // optional
+    params.addr = params.ip + ':' + params.port // TODO: ipv6 brackets
+    params.compact = 1 // udp is always compact
+
+  } else if (params.action === common.ACTIONS.SCRAPE) { // scrape message
+    params.info_hash = msg.slice(16, 36).toString('binary') // 20 bytes
+
+    // TODO: support multiple info_hash scrape
+    if (msg.length > 36) {
+      throw new Error('multiple info_hash scrape not supported')
+    }
+  } else {
+    return null
+  }
+
+  return params
+}
+
+// HELPER FUNCTIONS
+
+var TWO_PWR_32 = (1 << 16) * 2
+
+/**
+ * Return the closest floating-point representation to the buffer value. Precision will be
+ * lost for big numbers.
+ */
+function fromUInt64 (buf) {
+  var high = buf.readUInt32BE(0) | 0 // force
+  var low = buf.readUInt32BE(4) | 0
+  var lowUnsigned = (low >= 0) ? low : TWO_PWR_32 + low
+
+  return high * TWO_PWR_32 + lowUnsigned
+}
diff --git a/server.js b/server.js
index 93df5af..d84de01 100644
--- a/server.js
+++ b/server.js
@@ -1,8 +1,6 @@
 module.exports = Server
-module.exports.parseHttpRequest = parseHttpRequest
 
 var bencode = require('bencode')
-var bufferEqual = require('buffer-equal')
 var common = require('./lib/common')
 var debug = require('debug')('bittorrent-tracker')
 var dgram = require('dgram')
@@ -13,12 +11,12 @@ var ipLib = require('ip')
 var portfinder = require('portfinder')
 var string2compact = require('string2compact')
 
+var parseHttpRequest = require('./lib/parse_http')
+var parseUdpRequest = require('./lib/parse_udp')
+
 // Use random port above 1024
 portfinder.basePort = Math.floor(Math.random() * 60000) + 1025
 
-var NUM_ANNOUNCE_PEERS = 50
-var MAX_ANNOUNCE_PEERS = 82
-var REMOVE_IPV6_RE = /^::ffff:/
 
 inherits(Server, EventEmitter)
 
@@ -369,119 +367,6 @@ Server.prototype._getPeersCompact = function (swarm, numwant) {
 }
 
 
-function parseHttpRequest (req, options) {
-  var s = req.url.split('?')
-  var params = common.querystringParse(s[1])
-
-  if (s[0] === '/announce') {
-    params.action = common.ACTIONS.ANNOUNCE
-    
-    params.peer_id = typeof params.peer_id === 'string' && common.binaryToUtf8(params.peer_id)
-    params.port = Number(params.port)
-
-    if (typeof params.info_hash !== 'string') throw new Error('invalid info_hash')
-    if (params.info_hash.length !== 20) throw new Error('invalid info_hash length')
-    if (typeof params.peer_id !== 'string') throw new Error('invalid peer_id')
-    if (params.peer_id.length !== 20) throw new Error('invalid peer_id length')
-    if (!params.port) throw new Error('invalid port')
-
-    params.left = Number(params.left)
-    params.compact = Number(params.compact)
-
-    params.ip = options.trustProxy
-      ? req.headers['x-forwarded-for'] || req.connection.remoteAddress
-      : req.connection.remoteAddress.replace(REMOVE_IPV6_RE, '') // force ipv4
-    params.addr = params.ip + ':' + params.port // TODO: ipv6 brackets?
-
-    params.numwant = Math.min(
-      Number(params.numwant) || NUM_ANNOUNCE_PEERS,
-      MAX_ANNOUNCE_PEERS
-    )
-
-    return params
-  } else if (s[0] === '/scrape') { // unofficial scrape message
-    params.action = common.ACTIONS.SCRAPE
-
-    if (typeof params.info_hash === 'string') {
-      params.info_hash = [ params.info_hash ]
-    }
-
-    if (params.info_hash) {
-      if (!Array.isArray(params.info_hash)) throw new Error('invalid info_hash array')
-
-      params.info_hash = params.info_hash.map(function (infoHash) {
-        if (infoHash.length !== 20) {
-          throw new Error('invalid info_hash')
-        }
-
-        return infoHash
-      })
-    }
-
-    return params
-  } else {
-    return null
-  }
-}
-
-function parseUdpRequest (msg, rinfo) {
-  if (msg.length < 16) {
-    throw new Error('received packet is too short')
-  }
-
-  if (rinfo.family !== 'IPv4') {
-    throw new Error('udp tracker does not support IPv6')
-  }
-
-  var params = {
-    connectionId: msg.slice(0, 8), // 64-bit
-    action: msg.readUInt32BE(8),
-    transactionId: msg.readUInt32BE(12)
-  }
-
-  // TODO: randomize:
-  if (!bufferEqual(params.connectionId, common.CONNECTION_ID)) {
-    throw new Error('received packet with invalid connection id')
-  }
-
-  if (params.action === common.ACTIONS.CONNECT) {
-    // No further params
-  } else if (params.action === common.ACTIONS.ANNOUNCE) {
-    params.info_hash = msg.slice(16, 36).toString('binary') // 20 bytes
-    params.peer_id = msg.slice(36, 56).toString('utf8') // 20 bytes
-    params.downloaded = fromUInt64(msg.slice(56, 64)) // TODO: track this?
-    params.left = fromUInt64(msg.slice(64, 72))
-    params.uploaded = fromUInt64(msg.slice(72, 80)) // TODO: track this?
-    params.event = msg.readUInt32BE(80)
-    params.event = common.EVENT_IDS[params.event]
-    if (!params.event) throw new Error('invalid event') // early return
-    params.ip = msg.readUInt32BE(84) // optional
-    params.ip = params.ip ?
-      ipLib.toString(params.ip) :
-      params.ip = rinfo.address
-    params.key = msg.readUInt32BE(88) // TODO: what is this for?
-    params.numwant = msg.readUInt32BE(92) // optional
-    // never send more than MAX_ANNOUNCE_PEERS or else the UDP packet will get bigger than
-    // 512 bytes which is not safe
-    params.numwant = Math.min(params.numwant || NUM_ANNOUNCE_PEERS, MAX_ANNOUNCE_PEERS)
-    params.port = msg.readUInt16BE(96) || rinfo.port // optional
-    params.addr = params.ip + ':' + params.port // TODO: ipv6 brackets
-    params.compact = 1 // udp is always compact
-
-  } else if (params.action === common.ACTIONS.SCRAPE) { // scrape message
-    params.info_hash = msg.slice(16, 36).toString('binary') // 20 bytes
-
-    // TODO: support multiple info_hash scrape
-    if (msg.length > 36) {
-      throw new Error('multiple info_hash scrape not supported')
-    }
-  } else {
-    return null
-  }
-
-  return params
-}
-
 function makeUdpPacket (params) {
   switch (params.action) {
     case common.ACTIONS.CONNECT:
@@ -523,19 +408,3 @@ function makeUdpPacket (params) {
     throw new Error('Action not implemented: ' + params.action)
   }
 }
-
-// HELPER FUNCTIONS
-
-var TWO_PWR_32 = (1 << 16) * 2
-
-/**
- * Return the closest floating-point representation to the buffer value. Precision will be
- * lost for big numbers.
- */
-function fromUInt64 (buf) {
-  var high = buf.readUInt32BE(0) | 0 // force
-  var low = buf.readUInt32BE(4) | 0
-  var lowUnsigned = (low >= 0) ? low : TWO_PWR_32 + low
-
-  return high * TWO_PWR_32 + lowUnsigned
-}

From b72960dee3dc52869a298509da01d163c189dc1e Mon Sep 17 00:00:00 2001
From: Astro <astro@spaceboyz.net>
Date: Wed, 10 Dec 2014 16:47:41 +0100
Subject: [PATCH 08/16] server: split out Swarm

---
 lib/swarm.js | 133 ++++++++++++++++++++++++++++++++++++++++++++
 package.json |   1 +
 server.js    | 152 ++++++++++-----------------------------------------
 3 files changed, 163 insertions(+), 123 deletions(-)
 create mode 100644 lib/swarm.js

diff --git a/lib/swarm.js b/lib/swarm.js
new file mode 100644
index 0000000..2413139
--- /dev/null
+++ b/lib/swarm.js
@@ -0,0 +1,133 @@
+var debug = require('debug')('bittorrent-tracker')
+var string2compact = require('string2compact')
+
+module.exports = Swarm
+
+// Regard this as the default implementation of an interface that you
+// need to support when overriding Server.getSwarm()
+function Swarm (infoHash, server) {
+  this.peers = {}
+  this.complete = 0
+  this.incomplete = 0
+  this.emit = server.emit.bind(server)
+}
+
+Swarm.prototype.announce = function (params, cb) {
+  var self = this
+  var peer = self.peers[params.addr]
+
+  var start = function () {
+    if (peer) {
+      debug('unexpected `started` event from peer that is already in swarm')
+      return update() // treat as an update
+    }
+    if (params.left === 0) self.complete += 1
+    else self.incomplete += 1
+    peer = self.peers[params.addr] = {
+      ip: params.ip,
+      port: params.port,
+      peerId: params.peer_id
+    }
+    self.emit('start', params.addr)
+  }
+
+  var stop = function () {
+    if (!peer) {
+      debug('unexpected `stopped` event from peer that is not in swarm')
+      return // do nothing
+    }
+    if (peer.complete) self.complete -= 1
+    else self.incomplete -= 1
+    self.peers[params.addr] = null
+    self.emit('stop', params.addr)
+  }
+
+  var complete = function () {
+    if (!peer) {
+      debug('unexpected `completed` event from peer that is not in swarm')
+      return start() // treat as a start
+    }
+    if (peer.complete) {
+      debug('unexpected `completed` event from peer that is already marked as completed')
+      return // do nothing
+    }
+    self.complete += 1
+    self.incomplete -= 1
+    peer.complete = true
+    self.emit('complete', params.addr)
+  }
+
+  var update = function () {
+    if (!peer) {
+      debug('unexpected `update` event from peer that is not in swarm')
+      return start() // treat as a start
+    }
+    self.emit('update', params.addr)
+  }
+
+  switch (params.event) {
+  case 'started':
+    start()
+    break
+  case 'stopped':
+    stop()
+    break
+  case 'completed':
+    complete()
+    break
+  case '': case undefined: case 'empty': case 'update': // update
+    update()
+    break
+  default:
+    return cb(new Error('invalid event')) // early return
+  }
+
+  if (params.left === 0 && peer) peer.complete = true
+
+  // send peers
+  var peers = params.compact === 1
+        ? self._getPeersCompact(params.numwant)
+        : self._getPeers(params.numwant)
+
+  cb(null, {
+    complete: this.complete,
+    incomplete: this.incomplete,
+    peers: peers
+  })
+}
+
+Swarm.prototype._getPeers = function (numwant) {
+  var peers = []
+  for (var peerId in this.peers) {
+    if (peers.length >= numwant) break
+    var peer = this.peers[peerId]
+    if (!peer) continue // ignore null values
+    peers.push({
+      'peer id': peer.peerId,
+      ip: peer.ip,
+      port: peer.port
+    })
+  }
+  return peers
+}
+
+Swarm.prototype._getPeersCompact = function (numwant) {
+  var peers = []
+
+  for (var peerId in this.peers) {
+    if (peers.length >= numwant) break
+    var peer = this.peers[peerId]
+    if (!peer) continue // ignore null values
+    peers.push(peer.ip + ':' + peer.port)
+  }
+
+  return string2compact(peers)
+}
+
+
+Swarm.prototype.scrape = function (infoHash, params, cb) {
+  cb(null, {
+    complete: this.complete,
+    incomplete: this.incomplete
+  })
+}
diff --git a/package.json b/package.json
index a83fc5c..e002d8a 100644
--- a/package.json
+++ b/package.json
@@ -26,6 +26,7 @@
     "ip": "^0.3.0",
     "once": "^1.3.0",
     "portfinder": "^0.2.1",
+    "run-series": "^1.0.2",
     "string2compact": "^1.1.1"
   },
   "devDependencies": {
diff --git a/server.js b/server.js
index d84de01..241e12c 100644
--- a/server.js
+++ b/server.js
@@ -1,7 +1,6 @@
 module.exports = Server
 
 var bencode = require('bencode')
-var common = require('./lib/common')
 var debug = require('debug')('bittorrent-tracker')
 var dgram = require('dgram')
 var EventEmitter = require('events').EventEmitter
@@ -9,8 +8,10 @@ var http = require('http')
 var inherits = require('inherits')
 var ipLib = require('ip')
 var portfinder = require('portfinder')
-var string2compact = require('string2compact')
+var series = require('run-series')
 
+var common = require('./lib/common')
+var Swarm = require('./lib/swarm')
 var parseHttpRequest = require('./lib/parse_http')
 var parseUdpRequest = require('./lib/parse_udp')
 
@@ -119,11 +120,7 @@ Server.prototype.getSwarm = function (binaryInfoHash) {
   if (Buffer.isBuffer(binaryInfoHash)) binaryInfoHash = binaryInfoHash.toString('binary')
   var swarm = self.torrents[binaryInfoHash]
   if (!swarm) {
-    swarm = self.torrents[binaryInfoHash] = {
-      complete: 0,
-      incomplete: 0,
-      peers: {}
-    }
+    swarm = self.torrents[binaryInfoHash] = new Swarm(binaryInfoHash, this)
   }
   return swarm
 }
@@ -214,89 +211,13 @@ Server.prototype._onRequest = function (params, cb) {
 
 Server.prototype._onAnnounce = function (params, cb) {
   var self = this
-
   var swarm = self.getSwarm(params.info_hash)
-  var peer = swarm.peers[params.addr]
-
-  var start = function () {
-    if (peer) {
-      debug('unexpected `started` event from peer that is already in swarm')
-      return update() // treat as an update
+  swarm.announce(params, function (err, response) {
+    if (response) {
+      if (!response.action) response.action = common.ACTIONS.ANNOUNCE
+      if (!response.intervalMs) response.intervalMs = self._intervalMs
     }
-    if (params.left === 0) swarm.complete += 1
-    else swarm.incomplete += 1
-    peer = swarm.peers[params.addr] = {
-      ip: params.ip,
-      port: params.port,
-      peerId: params.peer_id
-    }
-    self.emit('start', params.addr)
-  }
-
-  var stop = function () {
-    if (!peer) {
-      debug('unexpected `stopped` event from peer that is not in swarm')
-      return // do nothing
-    }
-    if (peer.complete) swarm.complete -= 1
-    else swarm.incomplete -= 1
-    swarm.peers[params.addr] = null
-    self.emit('stop', params.addr)
-  }
-
-  var complete = function () {
-    if (!peer) {
-      debug('unexpected `completed` event from peer that is not in swarm')
-      return start() // treat as a start
-    }
-    if (peer.complete) {
-      debug('unexpected `completed` event from peer that is already marked as completed')
-      return // do nothing
-    }
-    swarm.complete += 1
-    swarm.incomplete -= 1
-    peer.complete = true
-    self.emit('complete', params.addr)
-  }
-
-  var update = function () {
-    if (!peer) {
-      debug('unexpected `update` event from peer that is not in swarm')
-      return start() // treat as a start
-    }
-    self.emit('update', params.addr)
-  }
-
-  switch (params.event) {
-  case 'started':
-    start()
-    break
-  case 'stopped':
-    stop()
-    break
-  case 'completed':
-    complete()
-    break
-  case '': case undefined: case 'empty': case 'update': // update
-    update()
-    break
-  default:
-    return cb(new Error('invalid event')) // early return
-  }
-
-  if (params.left === 0 && peer) peer.complete = true
-
-  // send peers
-  var peers = params.compact === 1
-        ? self._getPeersCompact(swarm, params.numwant)
-        : self._getPeers(swarm, params.numwant)
-
-  cb(null, {
-    action: common.ACTIONS.ANNOUNCE,
-    complete: swarm.complete,
-    incomplete: swarm.incomplete,
-    peers: peers,
-    intervalMs: self._intervalMs
+    cb(err, response)
   })
 }
 
@@ -324,46 +245,31 @@ Server.prototype._onScrape = function (params, cb) {
       min_request_interval: self._intervalMs
     }
   }
-  
-  params.info_hash.some(function (infoHash) {
+
+  series(params.info_hash.map(function (infoHash) {
     var swarm = self.getSwarm(infoHash)
-    
-    response.files[infoHash] = {
-      complete: swarm.complete,
-      incomplete: swarm.incomplete,
-      downloaded: swarm.complete // TODO: this only provides a lower-bound
+    return function (cb) {
+      swarm.scrape(infoHash, params, function (err, scrapeInfo) {
+        cb(err, scrapeInfo && {
+          infoHash: infoHash,
+          complete: scrapeInfo.complete || 0,
+          incomplete: scrapeInfo.incomplete || 0
+        })
+      })
     }
-  })
+  }), function (err, results) {
+    if (err) return cb(err)
 
-  cb(null, response)
-}
-
-Server.prototype._getPeers = function (swarm, numwant) {
-  var peers = []
-  for (var peerId in swarm.peers) {
-    if (peers.length >= numwant) break
-    var peer = swarm.peers[peerId]
-    if (!peer) continue // ignore null values
-    peers.push({
-      'peer id': peer.peerId,
-      ip: peer.ip,
-      port: peer.port
+    results.forEach(function (result) {
+      response.files[result.infoHash] = {
+        complete: result.complete,
+        incomplete: result.incomplete,
+        downloaded: result.complete // TODO: this only provides a lower-bound
+      }
     })
-  }
-  return peers
-}
 
-Server.prototype._getPeersCompact = function (swarm, numwant) {
-  var peers = []
-
-  for (var peerId in swarm.peers) {
-    if (peers.length >= numwant) break
-    var peer = swarm.peers[peerId]
-    if (!peer) continue // ignore null values
-    peers.push(peer.ip + ':' + peer.port)
-  }
-
-  return string2compact(peers)
+    cb(null, response)
+  })
 }
 
 

From 8439300df99943fc4993ef07f2aad60b13c461a4 Mon Sep 17 00:00:00 2001
From: Astro <astro@spaceboyz.net>
Date: Wed, 10 Dec 2014 16:51:35 +0100
Subject: [PATCH 09/16] server: unify compact serialization

---
 lib/swarm.js | 19 +------------------
 server.js    |  6 ++++++
 2 files changed, 7 insertions(+), 18 deletions(-)

diff --git a/lib/swarm.js b/lib/swarm.js
index 2413139..fbdc9df 100644
--- a/lib/swarm.js
+++ b/lib/swarm.js
@@ -1,5 +1,4 @@
 var debug = require('debug')('bittorrent-tracker')
-var string2compact = require('string2compact')
 
 module.exports = Swarm
 
@@ -85,9 +84,7 @@ Swarm.prototype.announce = function (params, cb) {
   if (params.left === 0 && peer) peer.complete = true
 
   // send peers
-  var peers = params.compact === 1
-        ? self._getPeersCompact(params.numwant)
-        : self._getPeers(params.numwant)
+  var peers = self._getPeers(params.numwant)
 
   cb(null, {
     complete: this.complete,
@@ -111,20 +108,6 @@ Swarm.prototype._getPeers = function (numwant) {
   return peers
 }
 
-Swarm.prototype._getPeersCompact = function (numwant) {
-  var peers = []
-
-  for (var peerId in this.peers) {
-    if (peers.length >= numwant) break
-    var peer = this.peers[peerId]
-    if (!peer) continue // ignore null values
-    peers.push(peer.ip + ':' + peer.port)
-  }
-
-  return string2compact(peers)
-}
-
-
 Swarm.prototype.scrape = function (infoHash, params, cb) {
   cb(null, {
     complete: this.complete,
diff --git a/server.js b/server.js
index 241e12c..e567835 100644
--- a/server.js
+++ b/server.js
@@ -9,6 +9,7 @@ var inherits = require('inherits')
 var ipLib = require('ip')
 var portfinder = require('portfinder')
 var series = require('run-series')
+var string2compact = require('string2compact')
 
 var common = require('./lib/common')
 var Swarm = require('./lib/swarm')
@@ -216,6 +217,11 @@ Server.prototype._onAnnounce = function (params, cb) {
     if (response) {
       if (!response.action) response.action = common.ACTIONS.ANNOUNCE
       if (!response.intervalMs) response.intervalMs = self._intervalMs
+      if (params.compact === 1) {
+        response.peers = string2compact(response.peers.map(function (peer) {
+          return peer.ip + ':' + peer.port // TODO: ipv6 brackets
+        }))
+      }
     }
     cb(err, response)
   })

From e234f14d56aa5dd0c008457422c7af8a14593b5c Mon Sep 17 00:00:00 2001
From: Astro <astro@spaceboyz.net>
Date: Wed, 10 Dec 2014 17:01:34 +0100
Subject: [PATCH 10/16] server swarm: split out announce events

---
 lib/swarm.js | 132 ++++++++++++++++++++++++++-------------------------
 1 file changed, 67 insertions(+), 65 deletions(-)

diff --git a/lib/swarm.js b/lib/swarm.js
index fbdc9df..40e4577 100644
--- a/lib/swarm.js
+++ b/lib/swarm.js
@@ -15,82 +15,84 @@ Swarm.prototype.announce = function (params, cb) {
   var self = this
   var peer = self.peers[params.addr]
 
-  var start = function () {
-    if (peer) {
-      debug('unexpected `started` event from peer that is already in swarm')
-      return update() // treat as an update
-    }
-    if (params.left === 0) self.complete += 1
-    else self.incomplete += 1
-    peer = self.peers[params.addr] = {
-      ip: params.ip,
-      port: params.port,
-      peerId: params.peer_id
-    }
-    self.emit('start', params.addr)
+  // Dispatch announce event
+  if (!params.event || params.event === 'empty') params.event = 'update'
+  var fn = '_onAnnounce_' + params.event
+  if (self[fn]) {
+    self[fn](params, peer, function (err) {
+      // event processed, prepare response:
+
+      if (params.left === 0 && peer) peer.complete = true
+
+      // send peers
+      var peers = self._getPeers(params.numwant)
+
+      cb(null, {
+        complete: self.complete,
+        incomplete: self.incomplete,
+        peers: peers
+      })
+    })
+  } else {
+    cb(new Error('invalid event'))
   }
+}
 
-  var stop = function () {
-    if (!peer) {
-      debug('unexpected `stopped` event from peer that is not in swarm')
-      return // do nothing
-    }
-    if (peer.complete) self.complete -= 1
-    else self.incomplete -= 1
-    self.peers[params.addr] = null
-    self.emit('stop', params.addr)
+Swarm.prototype._onAnnounce_started = function (params, peer, cb) {
+  if (peer) {
+    debug('unexpected `started` event from peer that is already in swarm')
+    return this._onAnnounce_update() // treat as an update
   }
-
-  var complete = function () {
-    if (!peer) {
-      debug('unexpected `completed` event from peer that is not in swarm')
-      return start() // treat as a start
-    }
-    if (peer.complete) {
-      debug('unexpected `completed` event from peer that is already marked as completed')
-      return // do nothing
-    }
-    self.complete += 1
-    self.incomplete -= 1
-    peer.complete = true
-    self.emit('complete', params.addr)
+  if (params.left === 0) this.complete += 1
+  else this.incomplete += 1
+  peer = this.peers[params.addr] = {
+    ip: params.ip,
+    port: params.port,
+    peerId: params.peer_id
   }
+  this.emit('start', params.addr)
 
-  var update = function () {
-    if (!peer) {
-      debug('unexpected `update` event from peer that is not in swarm')
-      return start() // treat as a start
-    }
-    self.emit('update', params.addr)
+  cb()
+}
+
+Swarm.prototype._onAnnounce_stopped = function (params, peer, cb) {
+  if (!peer) {
+    debug('unexpected `stopped` event from peer that is not in swarm')
+    return // do nothing
   }
+  if (peer.complete) this.complete -= 1
+  else this.incomplete -= 1
+  this.peers[params.addr] = null
+  this.emit('stop', params.addr)
 
-  switch (params.event) {
-  case 'started':
-    start()
-    break
-  case 'stopped':
-    stop()
-    break
-  case 'completed':
-    complete()
-    break
-  case '': case undefined: case 'empty': case 'update': // update
-    update()
-    break
-  default:
-    return cb(new Error('invalid event')) // early return
+  cb()
+}
+
+Swarm.prototype._onAnnounce_completed = function (params, peer, cb) {
+  if (!peer) {
+    debug('unexpected `completed` event from peer that is not in swarm')
+    return start() // treat as a start
   }
+  if (peer.complete) {
+    debug('unexpected `completed` event from peer that is already marked as completed')
+    return // do nothing
+  }
+  this.complete += 1
+  this.incomplete -= 1
+  peer.complete = true
+  this.emit('complete', params.addr)
 
-  if (params.left === 0 && peer) peer.complete = true
+  cb()
+}
 
-  // send peers
-  var peers = self._getPeers(params.numwant)
+Swarm.prototype._onAnnounce_update = function (params, peer, cb) {
+  if (!peer) {
+    debug('unexpected `update` event from peer that is not in swarm')
+    return start() // treat as a start
+  }
+  this.emit('update', params.addr)
 
-  cb(null, {
-    complete: this.complete,
-    incomplete: this.incomplete,
-    peers: peers
-  })
+  cb()
 }
 
 Swarm.prototype._getPeers = function (numwant) {

From 7a417a591d35a6d001fa82000dc97fc60b216d67 Mon Sep 17 00:00:00 2001
From: Astro <astro@spaceboyz.net>
Date: Thu, 11 Dec 2014 16:11:12 +0100
Subject: [PATCH 11/16] parseUdpRequest(): fix params.ip

---
 lib/parse_udp.js | 3 ++-
 server.js        | 1 -
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/lib/parse_udp.js b/lib/parse_udp.js
index 411d5b2..2c1ee8e 100644
--- a/lib/parse_udp.js
+++ b/lib/parse_udp.js
@@ -1,4 +1,5 @@
 var bufferEqual = require('buffer-equal')
+var ipLib = require('ip')
 var common = require('./common')
 
 
@@ -38,7 +39,7 @@ function parseUdpRequest (msg, rinfo) {
     params.ip = msg.readUInt32BE(84) // optional
     params.ip = params.ip ?
       ipLib.toString(params.ip) :
-      params.ip = rinfo.address
+      rinfo.address
     params.key = msg.readUInt32BE(88) // TODO: what is this for?
     params.numwant = msg.readUInt32BE(92) // optional
     // never send more than MAX_ANNOUNCE_PEERS or else the UDP packet will get bigger than
diff --git a/server.js b/server.js
index e567835..8fb4aaa 100644
--- a/server.js
+++ b/server.js
@@ -6,7 +6,6 @@ var dgram = require('dgram')
 var EventEmitter = require('events').EventEmitter
 var http = require('http')
 var inherits = require('inherits')
-var ipLib = require('ip')
 var portfinder = require('portfinder')
 var series = require('run-series')
 var string2compact = require('string2compact')

From e64fecc063b896ae3286420bcdced571ec9e572b Mon Sep 17 00:00:00 2001
From: Astro <astro@spaceboyz.net>
Date: Thu, 11 Dec 2014 16:19:08 +0100
Subject: [PATCH 12/16] parseUdpRequest(): throw on invalid packet

---
 lib/parse_udp.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/parse_udp.js b/lib/parse_udp.js
index 2c1ee8e..7e5ccdf 100644
--- a/lib/parse_udp.js
+++ b/lib/parse_udp.js
@@ -57,7 +57,7 @@ function parseUdpRequest (msg, rinfo) {
       throw new Error('multiple info_hash scrape not supported')
     }
   } else {
-    return null
+    throw new Error('Invalid action in UDP packet: ' + params.action)
   }
 
   return params

From 74d91390494becb06af12e1b353f21a81eb1bbfb Mon Sep 17 00:00:00 2001
From: Astro <astro@spaceboyz.net>
Date: Thu, 11 Dec 2014 16:22:17 +0100
Subject: [PATCH 13/16] server _onHttpRequest(): ensure non-empty params

---
 server.js | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/server.js b/server.js
index 8fb4aaa..b5a3cdb 100644
--- a/server.js
+++ b/server.js
@@ -127,21 +127,26 @@ Server.prototype.getSwarm = function (binaryInfoHash) {
 
 Server.prototype._onHttpRequest = function (req, res) {
   var self = this
-
+  var error
   var params
   try {
     params = parseHttpRequest(req, {
       trustProxy: self._trustProxy
     })
   } catch (err) {
-    debug('sent error %s', err.message)
+    error = err
+  }
+
+  if (!error && !params) error = new Error('Empty HTTP parameters')
+  if (error) {
+    debug('sent error %s', error.message)
     res.end(bencode.encode({
-      'failure reason': err.message
+      'failure reason': error.message
     }))
 
     // even though it's an error for the client, it's just a warning for the server.
     // don't crash the server because a client sent bad data :)
-    self.emit('warning', err)
+    self.emit('warning', error)
     
     return
   }

From 7a8f9a779fb026b70e90319f828c90a7ea68dcd8 Mon Sep 17 00:00:00 2001
From: Astro <astro@spaceboyz.net>
Date: Thu, 11 Dec 2014 16:24:33 +0100
Subject: [PATCH 14/16] server _onHttpRequest(): don't wrap errors in errors

---
 server.js | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/server.js b/server.js
index b5a3cdb..72c0ce8 100644
--- a/server.js
+++ b/server.js
@@ -153,7 +153,7 @@ Server.prototype._onHttpRequest = function (req, res) {
 
   this._onRequest(params, function (err, response) {
     if (err) {
-      self.emit('warning', new Error(err.message))
+      self.emit('warning', err)
       response = {
         'failure reason': err.message
       }
@@ -182,7 +182,7 @@ Server.prototype._onUdpRequest = function (msg, rinfo) {
   // Handle
   this._onRequest(params, function (err, response) {
     if (err) {
-      self.emit('warning', new Error(err.message))
+      self.emit('warning', err)
       response = {
         action: common.ACTIONS.ERRROR,
         'failure reason': err.message

From 217bcf7de5238892748ce05183809079fcc64270 Mon Sep 17 00:00:00 2001
From: Astro <astro@spaceboyz.net>
Date: Thu, 11 Dec 2014 16:39:10 +0100
Subject: [PATCH 15/16] server _onUdpRequest(): don't check empty params,
 errors will be thrown now

---
 server.js | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/server.js b/server.js
index 72c0ce8..ed1a229 100644
--- a/server.js
+++ b/server.js
@@ -176,9 +176,6 @@ Server.prototype._onUdpRequest = function (msg, rinfo) {
     return
   }
 
-  // Do nothing with invalid request
-  if (!params) return
-
   // Handle
   this._onRequest(params, function (err, response) {
     if (err) {

From c97e4236f4f6a97bded56482072b056a61d374cb Mon Sep 17 00:00:00 2001
From: Astro <astro@spaceboyz.net>
Date: Thu, 11 Dec 2014 17:07:37 +0100
Subject: [PATCH 16/16] server parseHttpRequest(): simplify info_hash checking

---
 lib/parse_http.js | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/lib/parse_http.js b/lib/parse_http.js
index 0f7a775..85e3519 100644
--- a/lib/parse_http.js
+++ b/lib/parse_http.js
@@ -44,12 +44,10 @@ function parseHttpRequest (req, options) {
     if (params.info_hash) {
       if (!Array.isArray(params.info_hash)) throw new Error('invalid info_hash array')
 
-      params.info_hash = params.info_hash.map(function (infoHash) {
+      params.info_hash.forEach(function (infoHash) {
         if (infoHash.length !== 20) {
           throw new Error('invalid info_hash')
         }
-
-        return infoHash
       })
     }