support custom filter error messages

In addition to returning a boolean (`true` for allowed, `false` for
disallowed), you can return an `Error` object to disallow and provide a
custom reason.

Fixes #85

README.md

@@ -113,16 +113,18 @@ var server = new Server({
   http: true, // enable http server? [default=true]
   ws: true, // enable websocket server? [default=false]
   filter: function (infoHash, params, cb) {
-    // black/whitelist for disallowing/allowing torrents [default=allow all]
+    // Blacklist/whitelist function for allowing/disallowing torrents. If this option is
-    // this example only allows this one torrent
+    // omitted, all torrents are allowed. It is possible to interface with a database or
-    cb(infoHash === 'aaa67059ed6bd08362da625b3ae77f6f4a075aaa')
+    // external system before deciding to allow/deny, because this function is async.
 
-    // it's possible to interface with a database or external system before
+    // It is possible to block by peer id (whitelisting torrent clients) or by secret
-    // deciding, because this function is async
+    // key (private trackers). Full access to the original HTTP/UDP request parameters
+    // are available n `params`.
 
-    // it's possible to block by peer id (whitelisting torrent clients) or
+    // This example only allows one torrent.
-    // by secret key, as you get full access to the original http/udp
+
-    // request parameters in `params`
+    var allowed = (infoHash === 'aaa67059ed6bd08362da625b3ae77f6f4a075aaa')
+    cb(allowed)
   })
 })
 

server.js

@@ -385,11 +385,13 @@ Server.prototype._onAnnounce = function (params, cb) {
   function createSwarm () {
     if (self._filter) {
       self._filter(params.info_hash, params, function (allowed) {
-        if (allowed) {
+        if (allowed instanceof Error) {
+          cb(allowed)
+        } else if (!allowed) {
+          cb(new Error('disallowed info_hash'))
+        } else {
           swarm = self.createSwarm(params.info_hash)
           announce()
-        } else {
-          cb(new Error('disallowed info_hash'))
         }
       })
     } else {
@@ -432,7 +434,7 @@ Server.prototype._onAnnounce = function (params, cb) {
         })
       } // else, return full peer objects (used for websocket responses)
 
-      cb(err, response)
+      cb(null, response)
     })
   }
 

test/filter.js

@@ -13,7 +13,7 @@ var parsedLeaves = parseTorrent(leaves)
 var peerId = new Buffer('01234567890123456789')
 
 function testFilterOption (t, serverType) {
-  t.plan(6)
+  t.plan(8)
   var opts = serverType === 'http' ? { udp: false } : { http: false }
   opts.filter = function (infoHash, params, cb) {
     process.nextTick(function () {
@@ -44,7 +44,8 @@ function testFilterOption (t, serverType) {
     client.once('warning', function (err) {
       t.ok(/disallowed info_hash/.test(err.message), 'got client warning')
 
-      client.destroy()
+      client.destroy(function () {
+        t.pass('client destroyed')
         client = new Client(peerId, port, parsedLeaves)
 
         client.on('error', function (err) {
@@ -56,7 +57,9 @@ function testFilterOption (t, serverType) {
 
         client.on('update', function () {
           t.pass('got announce')
-        client.destroy()
+          client.destroy(function () {
+            t.pass('client destroyed')
+          })
           server.close(function () {
             t.pass('server closed')
           })
@@ -68,6 +71,7 @@ function testFilterOption (t, serverType) {
 
         client.start()
       })
+    })
 
     server.once('warning', function (err) {
       t.ok(/disallowed info_hash/.test(err.message), 'got server warning')
@@ -85,3 +89,82 @@ test('http: filter option blocks tracker from tracking torrent', function (t) {
 test('udp: filter option blocks tracker from tracking torrent', function (t) {
   testFilterOption(t, 'udp')
 })
+
+function testFilterCustomError (t, serverType) {
+  t.plan(8)
+  var opts = serverType === 'http' ? { udp: false } : { http: false }
+  opts.filter = function (infoHash, params, cb) {
+    process.nextTick(function () {
+      if (infoHash === parsedBitlove.infoHash) cb(new Error('bitlove blocked'))
+      else cb(true)
+    })
+  }
+  var server = new Server(opts)
+
+  server.on('error', function (err) {
+    t.error(err)
+  })
+
+  server.listen(0, function () {
+    var port = server[serverType].address().port
+    var announceUrl = serverType === 'http'
+      ? 'http://127.0.0.1:' + port + '/announce'
+      : 'udp://127.0.0.1:' + port
+
+    parsedBitlove.announce = [ announceUrl ]
+    parsedLeaves.announce = [ announceUrl ]
+
+    var client = new Client(peerId, port, parsedBitlove)
+
+    client.on('error', function (err) {
+      t.error(err)
+    })
+
+    client.once('warning', function (err) {
+      t.ok(/bitlove blocked/.test(err.message), 'got client warning')
+
+      client.destroy(function () {
+        t.pass('client destroyed')
+        client = new Client(peerId, port, parsedLeaves)
+
+        client.on('error', function (err) {
+          t.error(err)
+        })
+        client.on('warning', function (err) {
+          t.error(err)
+        })
+
+        client.on('update', function () {
+          t.pass('got announce')
+          client.destroy(function () {
+            t.pass('client destroyed')
+          })
+          server.close(function () {
+            t.pass('server closed')
+          })
+        })
+
+        server.on('start', function () {
+          t.equal(Object.keys(server.torrents).length, 1)
+        })
+
+        client.start()
+      })
+    })
+
+    server.once('warning', function (err) {
+      t.ok(/bitlove blocked/.test(err.message), 'got server warning')
+      t.equal(Object.keys(server.torrents).length, 0)
+    })
+
+    client.start()
+  })
+}
+
+test('http: filter option with custom error', function (t) {
+  testFilterCustomError(t, 'http')
+})
+
+test('udp: filter option filter option with custom error', function (t) {
+  testFilterCustomError(t, 'udp')
+})