Minor refactoring to simplify testing UDP write errors

Author: clue

src/Query/UdpTransportExecutor.php

@@ -92,6 +92,13 @@ final class UdpTransportExecutor implements ExecutorInterface
     private $parser;
     private $dumper;
 
+    /**
+     * maximum UDP packet size to send and receive
+     *
+     * @var int
+     */
+    private $maxPacketSize = 512;
+
     /**
      * @param string        $nameserver
      * @param LoopInterface $loop
@@ -119,7 +126,7 @@ public function query(Query $query)
         $request = Message::createRequestForQuery($query);
 
         $queryData = $this->dumper->toBinary($request);
-        if (isset($queryData[512])) {
+        if (isset($queryData[$this->maxPacketSize])) {
             return \React\Promise\reject(new \RuntimeException(
                 'DNS query for ' . $query->name . ' failed: Query too large for UDP transport',
                 \defined('SOCKET_EMSGSIZE') ? \SOCKET_EMSGSIZE : 90
@@ -142,14 +149,14 @@ public function query(Query $query)
         if ($written !== \strlen($queryData)) {
             // Write may potentially fail, but most common errors are already caught by connection check above.
             // Among others, macOS is known to report here when trying to send to broadcast address.
-            // @codeCoverageIgnoreStart
+            // This can also be reproduced by writing data exceeding `stream_set_chunk_size()` to a server refusing UDP data.
+            // fwrite(): send of 8192 bytes failed with errno=111 Connection refused
             $error = \error_get_last();
             \preg_match('/errno=(\d+) (.+)/', $error['message'], $m);
             return \React\Promise\reject(new \RuntimeException(
                 'DNS query for ' . $query->name . ' failed: Unable to send query to DNS server ('  . (isset($m[2]) ? $m[2] : $error['message']) . ')',
                 isset($m[1]) ? (int) $m[1] : 0
             ));
-            // @codeCoverageIgnoreEnd
         }
 
         $loop = $this->loop;
@@ -161,11 +168,12 @@ public function query(Query $query)
             throw new CancellationException('DNS query for ' . $query->name . ' has been cancelled');
         });
 
+        $max = $this->maxPacketSize;
         $parser = $this->parser;
-        $loop->addReadStream($socket, function ($socket) use ($loop, $deferred, $query, $parser, $request) {
+        $loop->addReadStream($socket, function ($socket) use ($loop, $deferred, $query, $parser, $request, $max) {
             // try to read a single data packet from the DNS server
             // ignoring any errors, this is uses UDP packets and not a stream of data
-            $data = @\fread($socket, 512);
+            $data = @\fread($socket, $max);
 
             try {
                 $response = $parser->parseMessage($data);

tests/Query/UdpTransportExecutorTest.php

@@ -126,7 +126,8 @@ public function testQueryRejectsIfServerConnectionFails()
             $exception = $reason;
         });
 
-        $this->setExpectedException('RuntimeException', 'Unable to connect to DNS server (Failed to parse address "///")');
+        // PHP (Failed to parse address "///") differs from HHVM (Name or service not known)
+        $this->setExpectedException('RuntimeException', 'Unable to connect to DNS server');
         throw $exception;
     }
 
@@ -135,9 +136,14 @@ public function testQueryRejectsIfSendToServerFailsAfterConnection()
         $loop = $this->getMockBuilder('React\EventLoop\LoopInterface')->getMock();
         $loop->expects($this->never())->method('addReadStream');
 
-        $executor = new UdpTransportExecutor('255.255.255.255', $loop);
+        $executor = new UdpTransportExecutor('0.0.0.0', $loop);
 
-        $query = new Query('google.com', Message::TYPE_A, Message::CLASS_IN);
+        // increase hard-coded maximum packet size to allow sending excessive data
+        $ref = new \ReflectionProperty($executor, 'maxPacketSize');
+        $ref->setAccessible(true);
+        $ref->setValue($executor, PHP_INT_MAX);
+
+        $query = new Query(str_repeat('a.', 100000) . '.example', Message::TYPE_A, Message::CLASS_IN);
         $promise = $executor->query($query);
 
         $this->assertInstanceOf('React\Promise\PromiseInterface', $promise);
@@ -147,7 +153,8 @@ public function testQueryRejectsIfSendToServerFailsAfterConnection()
             $exception = $reason;
         });
 
-        $this->setExpectedException('RuntimeException', 'to DNS server (Permission denied)', SOCKET_EACCES);
+        // ECONNREFUSED( Connection refused) on Linux, EMSGSIZE (Message too long) on macOS
+        $this->setExpectedException('RuntimeException', 'Unable to send query to DNS server');
         throw $exception;
     }