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Add TcpTransportExecutor to send DNS queries over TCP/IP connection
This changeset implements a fully functional TCP/IP transport for DNS queries. In its current form, it requires manual setup (see examples) and only the UDP transport is used by default. A follow-up PR will implement proper transport selection based on query type and whether a UDP query resulted in a truncated response.
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‎README.md‎

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@@ -18,6 +18,7 @@ easily be used to create a DNS server.
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* [resolveAll()](#resolveall)
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* [Advanced usage](#advanced-usage)
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* [UdpTransportExecutor](#udptransportexecutor)
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* [TcpTransportExecutor](#tcptransportexecutor)
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* [HostsFileExecutor](#hostsfileexecutor)
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* [Install](#install)
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* [Tests](#tests)
@@ -276,6 +277,71 @@ $executor = new CoopExecutor(
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packages. Higher-level components should take advantage of the Datagram
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component instead of reimplementing this socket logic from scratch.
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### TcpTransportExecutor
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The `TcpTransportExecutor` class can be used to
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send DNS queries over a TCP/IP stream transport.
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This is one of the main classes that send a DNS query to your DNS server.
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For more advanced usages one can utilize this class directly.
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The following example looks up the `IPv6` address for `reactphp.org`.
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```php
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$loop = Factory::create();
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$executor = new TcpTransportExecutor('8.8.8.8:53', $loop);
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$executor->query(
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new Query($name, Message::TYPE_AAAA, Message::CLASS_IN)
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)->then(function (Message $message) {
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foreach ($message->answers as $answer) {
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echo 'IPv6: ' . $answer->data . PHP_EOL;
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}
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}, 'printf');
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$loop->run();
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```
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See also [example #92](examples).
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Note that this executor does not implement a timeout, so you will very likely
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want to use this in combination with a `TimeoutExecutor` like this:
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```php
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$executor = new TimeoutExecutor(
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new TcpTransportExecutor($nameserver, $loop),
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3.0,
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$loop
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);
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```
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Unlike the `UdpTransportExecutor`, this class uses a reliable TCP/IP
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transport, so you do not necessarily have to implement any retry logic.
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Note that this executor is entirely async and as such allows you to execute
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any number of queries concurrently. You should probably limit the number of
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concurrent queries in your application or you're very likely going to face
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rate limitations and bans on the resolver end. For many common applications,
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you may want to avoid sending the same query multiple times when the first
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one is still pending, so you will likely want to use this in combination with
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a `CoopExecutor` like this:
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```php
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$executor = new CoopExecutor(
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new TimeoutExecutor(
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new TcpTransportExecutor($nameserver, $loop),
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3.0,
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$loop
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)
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);
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```
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> Internally, this class uses PHP's TCP/IP sockets and does not take advantage
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of [react/socket](https://github.com/reactphp/socket) purely for
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organizational reasons to avoid a cyclic dependency between the two
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packages. Higher-level components should take advantage of the Socket
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component instead of reimplementing this socket logic from scratch.
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### HostsFileExecutor
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Note that the above `UdpTransportExecutor` class always performs an actual DNS query.

‎examples/92-query-any.php‎

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<?php
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// $ php examples/92-query-any.php mailbox.org
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// $ php examples/92-query-any.php _carddav._tcp.mailbox.org
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use React\Dns\Model\Message;
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use React\Dns\Model\Record;
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use React\Dns\Query\Query;
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use React\Dns\Query\UdpTransportExecutor;
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use React\Dns\Query\TcpTransportExecutor;
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use React\EventLoop\Factory;
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require __DIR__ . '/../vendor/autoload.php';
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$loop = Factory::create();
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$executor = new UdpTransportExecutor('8.8.8.8:53', $loop);
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$executor = new TcpTransportExecutor('8.8.8.8:53', $loop);
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$name = isset($argv[1]) ? $argv[1] : 'google.com';
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‎src/Query/TcpTransportExecutor.php‎

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<?php
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namespace React\Dns\Query;
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use React\Dns\Model\Message;
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use React\Dns\Protocol\BinaryDumper;
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use React\Dns\Protocol\Parser;
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use React\EventLoop\LoopInterface;
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use React\Promise\Deferred;
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/**
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* Send DNS queries over a TCP/IP stream transport.
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*
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* This is one of the main classes that send a DNS query to your DNS server.
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*
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* For more advanced usages one can utilize this class directly.
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* The following example looks up the `IPv6` address for `reactphp.org`.
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*
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* ```php
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* $loop = Factory::create();
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* $executor = new TcpTransportExecutor('8.8.8.8:53', $loop);
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*
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* $executor->query(
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* new Query($name, Message::TYPE_AAAA, Message::CLASS_IN)
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* )->then(function (Message $message) {
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* foreach ($message->answers as $answer) {
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* echo 'IPv6: ' . $answer->data . PHP_EOL;
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* }
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* }, 'printf');
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*
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* $loop->run();
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* ```
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*
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* See also [example #92](examples).
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*
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* Note that this executor does not implement a timeout, so you will very likely
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* want to use this in combination with a `TimeoutExecutor` like this:
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*
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* ```php
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* $executor = new TimeoutExecutor(
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* new TcpTransportExecutor($nameserver, $loop),
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* 3.0,
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* $loop
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* );
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* ```
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*
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* Unlike the `UdpTransportExecutor`, this class uses a reliable TCP/IP
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* transport, so you do not necessarily have to implement any retry logic.
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*
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* Note that this executor is entirely async and as such allows you to execute
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* any number of queries concurrently. You should probably limit the number of
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* concurrent queries in your application or you're very likely going to face
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* rate limitations and bans on the resolver end. For many common applications,
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* you may want to avoid sending the same query multiple times when the first
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* one is still pending, so you will likely want to use this in combination with
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* a `CoopExecutor` like this:
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*
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* ```php
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* $executor = new CoopExecutor(
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* new TimeoutExecutor(
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* new TcpTransportExecutor($nameserver, $loop),
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* 3.0,
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* $loop
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* )
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* );
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* ```
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*
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* > Internally, this class uses PHP's TCP/IP sockets and does not take advantage
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* of [react/socket](https://github.com/reactphp/socket) purely for
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* organizational reasons to avoid a cyclic dependency between the two
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* packages. Higher-level components should take advantage of the Socket
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* component instead of reimplementing this socket logic from scratch.
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*/
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class TcpTransportExecutor implements ExecutorInterface
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{
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private $nameserver;
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private $loop;
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private $parser;
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private $dumper;
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/**
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* @param string $nameserver
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* @param LoopInterface $loop
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*/
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public function __construct($nameserver, LoopInterface $loop)
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{
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if (\strpos($nameserver, '[') === false && \substr_count($nameserver, ':') >= 2) {
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// several colons, but not enclosed in square brackets => enclose IPv6 address in square brackets
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$nameserver = '[' . $nameserver . ']';
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}
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$parts = \parse_url('tcp://' . $nameserver);
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if (!isset($parts['scheme'], $parts['host']) || !\filter_var(\trim($parts['host'], '[]'), \FILTER_VALIDATE_IP)) {
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throw new \InvalidArgumentException('Invalid nameserver address given');
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}
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$this->nameserver = $parts['host'] . ':' . (isset($parts['port']) ? $parts['port'] : 53);
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$this->loop = $loop;
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$this->parser = new Parser();
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$this->dumper = new BinaryDumper();
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}
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public function query(Query $query)
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{
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$request = Message::createRequestForQuery($query);
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$queryData = $this->dumper->toBinary($request);
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$length = \strlen($queryData);
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if ($length > 0xffff) {
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return \React\Promise\reject(new \RuntimeException(
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'DNS query for ' . $query->name . ' failed: Query too large for TCP transport'
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));
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}
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$queryData = \pack('n', $length) . $queryData;
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// create async TCP/IP connection (may take a while)
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$socket = @\stream_socket_client($this->nameserver, $errno, $errstr, 0, \STREAM_CLIENT_CONNECT | \STREAM_CLIENT_ASYNC_CONNECT);
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if ($socket === false) {
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return \React\Promise\reject(new \RuntimeException(
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'DNS query for ' . $query->name . ' failed: Unable to connect to DNS server (' . $errstr . ')',
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$errno
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));
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}
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$loop = $this->loop;
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$deferred = new Deferred(function () use ($loop, $socket, $query) {
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// cancellation should remove socket from loop and close socket
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$loop->removeReadStream($socket);
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$loop->removeWriteStream($socket);
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\fclose($socket);
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throw new CancellationException('DNS query for ' . $query->name . ' has been cancelled');
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});
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// set socket to non-blocking and wait for it to become writable (connection success/rejected)
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\stream_set_blocking($socket, false);
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$loop->addWriteStream($socket, function ($socket) use ($loop, $query, $queryData, $deferred) {
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$loop->removeWriteStream($socket);
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$name = @\stream_socket_get_name($socket, true);
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if ($name === false) {
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$loop->removeReadStream($socket);
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@\fclose($socket);
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$deferred->reject(new \RuntimeException(
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'DNS query for ' . $query->name . ' failed: Connection to DNS server rejected'
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));
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return;
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}
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$written = @\fwrite($socket, $queryData);
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if ($written !== \strlen($queryData)) {
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$loop->removeReadStream($socket);
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\fclose($socket);
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$deferred->reject(new \RuntimeException(
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'DNS query for ' . $query->name . ' failed: Unable to write DNS query message in one chunk'
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));
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}
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});
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$buffer = '';
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$parser = $this->parser;
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$loop->addReadStream($socket, function ($socket) use (&$buffer, $loop, $deferred, $query, $parser, $request) {
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// read one chunk of data from the DNS server
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// any error is fatal, this is a stream of TCP/IP data
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$chunk = @\fread($socket, 65536);
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if ($chunk === false || $chunk === '') {
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$loop->removeReadStream($socket);
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\fclose($socket);
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$deferred->reject(new \RuntimeException(
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'DNS query for ' . $query->name . ' failed: Connection to DNS server lost'
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));
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return;
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}
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// reassemble complete message by concatenating all chunks.
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// response message header contains at least 12 bytes
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$buffer .= $chunk;
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if (!isset($buffer[11])) {
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return;
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}
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// read response message length from first 2 bytes and ensure we have length + data in buffer
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list(, $length) = \unpack('n', $buffer);
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if (!isset($buffer[$length + 1])) {
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return;
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}
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// we only react to the first complete message, so remove socket from loop and close
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$loop->removeReadStream($socket);
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\fclose($socket);
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$data = \substr($buffer, 2, $length);
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$buffer = '';
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try {
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$response = $parser->parseMessage($data);
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} catch (\Exception $e) {
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// reject if we received an invalid message from remote server
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$deferred->reject(new \RuntimeException(
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'DNS query for ' . $query->name . ' failed: Invalid message received from DNS server',
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0,
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$e
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));
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return;
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}
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// reject if we received an unexpected response ID or truncated response
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if ($response->id !== $request->id || $response->tc) {
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$deferred->reject(new \RuntimeException(
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'DNS query for ' . $query->name . ' failed: Invalid response message received from DNS server'
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));
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return;
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}
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$deferred->resolve($response);
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});
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return $deferred->promise();
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}
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}

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