[dns] Use mt_rand to generate id, limit to id field size (16 bits)

Author: igorw

Query/Executor.php

@@ -36,7 +36,7 @@ public function query($nameserver, Query $query, $callback)
     public function prepareRequest(Query $query)
     {
         $request = new Message();
-        $request->header->set('id', rand());
+        $request->header->set('id', $this->generateId());
         $request->header->set('rd', 1);
         $request->questions[] = (array) $query;
         $request->prepare();
@@ -79,6 +79,11 @@ public function doQuery($nameserver, $transport, $queryData, $callback)
         $conn->write($queryData);
     }
 
+    protected function generateId()
+    {
+        return mt_rand(0, 0xffff);
+    }
+
     protected function createConnection($nameserver, $transport)
     {
         $fd = stream_socket_client("$transport://$nameserver");