[dns] Tests for resolver, related changes and refactorings

Author: igorw

BadServerException.php

@@ -0,0 +1,7 @@
+<?php
+
+namespace React\Dns;
+
+class BadServerException extends \Exception
+{
+}

Model/Record.php

@@ -9,4 +9,13 @@ class Record
     public $class;
     public $ttl;
     public $data;
+
+    public function __construct($name, $type, $class, $ttl = 0, $data = null)
+    {
+        $this->name     = $name;
+        $this->type     = $type;
+        $this->class    = $class;
+        $this->ttl      = $ttl;
+        $this->data     = $data;
+    }
 }

Parser.php

@@ -174,12 +174,9 @@ private function parseAnswer(Message $message)
 
         $message->data = substr($message->data, $consumed) ?: '';
 
-        $record = new Record();
-        $record->name = implode('.', $labels);
-        $record->type = $type;
-        $record->class = $class;
-        $record->ttl = $this->signedLongToUnsignedLong($ttl);
-        $record->data = $rdata;
+        $name = implode('.', $labels);
+        $ttl = $this->signedLongToUnsignedLong($ttl);
+        $record = new Record($name, $type, $class, $ttl, $rdata);
 
         $message->answers[] = $record;
 

RecordNotFoundException.php

@@ -0,0 +1,7 @@
+<?php
+
+namespace React\Dns;
+
+class RecordNotFoundException extends \Exception
+{
+}

Resolver.php

@@ -10,65 +10,119 @@ class Resolver
 {
     private $nameserver;
     private $loop;
+    private $parser;
+    private $dumper;
 
-    public function __construct($nameserver, LoopInterface $loop)
+    public function __construct($nameserver, LoopInterface $loop, Parser $parser = null, BinaryDumper $dumper = null)
     {
         $this->nameserver = $this->addPortToServerIfMissing($nameserver);
         $this->loop = $loop;
+        $this->parser = $parser ?: new Parser();
+        $this->dumper = $dumper ?: new BinaryDumper();
     }
 
-    public function resolve($domain, $callback)
+    public function resolve($domain, $callback, $errback = null)
     {
+        $that = $this;
+
         $query = new Query($domain, Message::TYPE_A, Message::CLASS_IN);
 
-        $this->query($this->nameserver, $query, function (Message $response) use ($callback) {
-            $answer = $response->answers[array_rand($response->answers)];
-            $address = $answer->data;
-            $callback($address);
+        $this->query($this->nameserver, $query, function (Message $response) use ($that, $callback, $errback) {
+            try {
+                $answer = $that->pickRandomAnswerOfType($response, Message::TYPE_A);
+                $address = $answer->data;
+                $callback($address);
+            } catch (RecordNotFoundException $e) {
+                if (!$errback) {
+                    throw $e;
+                }
+
+                $errback($e);
+            }
         });
     }
 
     public function query($nameserver, Query $query, $callback)
     {
-        $dumper = new BinaryDumper();
-        $parser = new Parser();
+        $request = $this->prepareRequest($query);
+
+        $queryData = $this->dumper->toBinary($request);
+        $transport = strlen($queryData) > 512 ? 'tcp' : 'udp';
+
+        $this->doQuery($nameserver, $transport, $queryData, $callback);
+    }
 
+    public function pickRandomAnswerOfType(Message $response, $type)
+    {
+        $filteredAnswers = array_filter($response->answers, function ($answer) use ($type) {
+            return $type === $answer->type;
+        });
+
+        if (0 === count($filteredAnswers)) {
+            $message = sprintf('DNS Request did not return valid answer. Received answers: %s', json_encode($response->answers));
+            throw new RecordNotFoundException($message);
+        }
+
+        $answer = $filteredAnswers[array_rand($filteredAnswers)];
+
+        return $answer;
+    }
+
+    public function prepareRequest(Query $query)
+    {
         $request = new Message();
         $request->header->set('id', rand());
         $request->header->set('rd', 1);
         $request->questions[] = (array) $query;
         $request->prepare();
 
-        $queryData = $dumper->toBinary($request);
-        $transport = strlen($queryData) > 512 ? 'tcp' : 'udp';
-
-        $this->doQuery($nameserver, $transport, $queryData, $parser, $callback);
+        return $request;
     }
 
-    public function doQuery($nameserver, $transport, $queryData, Parser $parser, $callback)
+    public function doQuery($nameserver, $transport, $queryData, $callback)
     {
         $that = $this;
+        $parser = $this->parser;
 
         $response = new Message();
 
-        $fd = stream_socket_client("$transport://$nameserver");
-        $conn = new Connection($fd, $this->loop);
-        $conn->on('data', function ($data) use ($that, $conn, $parser, $response, $callback) {
+        $retryWithTcp = function () use ($that, $nameserver, $queryData, $callback) {
+            $that->doQuery($nameserver, 'tcp', $queryData, $callback);
+        };
+
+        $conn = $this->createConnection($nameserver, $transport);
+        $conn->on('data', function ($data) use ($that, $retryWithTcp, $conn, $parser, $response, $transport, $callback) {
             $responseReady = $parser->parseChunk($data, $response);
-            if ($responseReady) {
-                if ($response->header->isTruncated()) {
-                    $conn->end();
-                    $that->doQuery($nameserver, 'tcp', $queryData, $parser, $callback);
-                    return;
+
+            if (!$responseReady) {
+                return;
+            }
+
+            if ($response->header->isTruncated()) {
+                if ('tcp' === $transport) {
+                    throw new BadServerException('The server set the truncated bit although we issued a TCP request');
                 }
+
                 $conn->end();
-                $callback($response);
+                $retryWithTcp();
+                return;
             }
+
+            $conn->end();
+            $callback($response);
         });
         $conn->write($queryData);
     }
 
-    private function addPortToServerIfMissing($nameserver)
+    protected function createConnection($nameserver, $transport)
+    {
+        $fd = stream_socket_client("$transport://$nameserver");
+        $conn = new Connection($fd, $this->loop);
+
+        return $conn;
+    }
+
+    protected function addPortToServerIfMissing($nameserver)
     {
         return false === strpos($nameserver, ':') ? "$nameserver:53" : $nameserver;
     }