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<?php
namespace RectorPrefix202410\React\Dns\Query;
use RectorPrefix202410\React\Dns\Model\Message;
use RectorPrefix202410\React\Dns\Protocol\BinaryDumper;
use RectorPrefix202410\React\Dns\Protocol\Parser;
use RectorPrefix202410\React\EventLoop\Loop;
use RectorPrefix202410\React\EventLoop\LoopInterface;
use RectorPrefix202410\React\Promise\Deferred;
/**
* Send DNS queries over a UDP transport.
*
* This is the main class that sends a DNS query to your DNS server and is used
* internally by the `Resolver` for the actual message transport.
*
* For more advanced usages one can utilize this class directly.
* The following example looks up the `IPv6` address for `igor.io`.
*
* ```php
* $executor = new UdpTransportExecutor('8.8.8.8:53');
*
* $executor->query(
* new Query($name, Message::TYPE_AAAA, Message::CLASS_IN)
* )->then(function (Message $message) {
* foreach ($message->answers as $answer) {
* echo 'IPv6: ' . $answer->data . PHP_EOL;
* }
* }, 'printf');
* ```
*
* See also the [fourth example](examples).
*
* Note that this executor does not implement a timeout, so you will very likely
* want to use this in combination with a `TimeoutExecutor` like this:
*
* ```php
* $executor = new TimeoutExecutor(
* new UdpTransportExecutor($nameserver),
* 3.0
* );
* ```
*
* Also note that this executor uses an unreliable UDP transport and that it
* does not implement any retry logic, so you will likely want to use this in
* combination with a `RetryExecutor` like this:
*
* ```php
* $executor = new RetryExecutor(
* new TimeoutExecutor(
* new UdpTransportExecutor($nameserver),
* 3.0
* )
* );
* ```
*
* Note that this executor is entirely async and as such allows you to execute
* any number of queries concurrently. You should probably limit the number of
* concurrent queries in your application or you're very likely going to face
* rate limitations and bans on the resolver end. For many common applications,
* you may want to avoid sending the same query multiple times when the first
* one is still pending, so you will likely want to use this in combination with
* a `CoopExecutor` like this:
*
* ```php
* $executor = new CoopExecutor(
* new RetryExecutor(
* new TimeoutExecutor(
* new UdpTransportExecutor($nameserver),
* 3.0
* )
* )
* );
* ```
*
* > Internally, this class uses PHP's UDP sockets and does not take advantage
* of [react/datagram](https://github.com/reactphp/datagram) purely for
* organizational reasons to avoid a cyclic dependency between the two
* packages. Higher-level components should take advantage of the Datagram
* component instead of reimplementing this socket logic from scratch.
*/
final class UdpTransportExecutor implements ExecutorInterface
{
private $nameserver;
private $loop;
private $parser;
private $dumper;
/**
* maximum UDP packet size to send and receive
*
* @var int
*/
private $maxPacketSize = 512;
/**
* @param string $nameserver
* @param ?LoopInterface $loop
*/
public function __construct($nameserver, $loop = null)
{
if (\strpos($nameserver, '[') === \false && \substr_count($nameserver, ':') >= 2 && \strpos($nameserver, '://') === \false) {
// several colons, but not enclosed in square brackets => enclose IPv6 address in square brackets
$nameserver = '[' . $nameserver . ']';
}
$parts = \parse_url((\strpos($nameserver, '://') === \false ? 'udp://' : '') . $nameserver);
if (!isset($parts['scheme'], $parts['host']) || $parts['scheme'] !== 'udp' || @\inet_pton(\trim($parts['host'], '[]')) === \false) {
throw new \InvalidArgumentException('Invalid nameserver address given');
}
if ($loop !== null && !$loop instanceof LoopInterface) {
// manual type check to support legacy PHP < 7.1
throw new \InvalidArgumentException('Argument #2 ($loop) expected null|React\\EventLoop\\LoopInterface');
}
$this->nameserver = 'udp://' . $parts['host'] . ':' . (isset($parts['port']) ? $parts['port'] : 53);
$this->loop = $loop ?: Loop::get();
$this->parser = new Parser();
$this->dumper = new BinaryDumper();
}
public function query(Query $query)
{
$request = Message::createRequestForQuery($query);
$queryData = $this->dumper->toBinary($request);
if (isset($queryData[$this->maxPacketSize])) {
return \RectorPrefix202410\React\Promise\reject(new \RuntimeException('DNS query for ' . $query->describe() . ' failed: Query too large for UDP transport', \defined('SOCKET_EMSGSIZE') ? \SOCKET_EMSGSIZE : 90));
}
// UDP connections are instant, so try connection without a loop or timeout
$errno = 0;
$errstr = '';
$socket = @\stream_socket_client($this->nameserver, $errno, $errstr, 0);
if ($socket === \false) {
return \RectorPrefix202410\React\Promise\reject(new \RuntimeException('DNS query for ' . $query->describe() . ' failed: Unable to connect to DNS server ' . $this->nameserver . ' (' . $errstr . ')', $errno));
}
// set socket to non-blocking and immediately try to send (fill write buffer)
\stream_set_blocking($socket, \false);
\set_error_handler(function ($_, $error) use(&$errno, &$errstr) {
// 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.
// 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
\preg_match('/errno=(\\d+) (.+)/', $error, $m);
$errno = isset($m[1]) ? (int) $m[1] : 0;
$errstr = isset($m[2]) ? $m[2] : $error;
});
$written = \fwrite($socket, $queryData);
\restore_error_handler();
if ($written !== \strlen($queryData)) {
return \RectorPrefix202410\React\Promise\reject(new \RuntimeException('DNS query for ' . $query->describe() . ' failed: Unable to send query to DNS server ' . $this->nameserver . ' (' . $errstr . ')', $errno));
}
$loop = $this->loop;
$deferred = new Deferred(function () use($loop, $socket, $query) {
// cancellation should remove socket from loop and close socket
$loop->removeReadStream($socket);
\fclose($socket);
throw new CancellationException('DNS query for ' . $query->describe() . ' has been cancelled');
});
$max = $this->maxPacketSize;
$parser = $this->parser;
$nameserver = $this->nameserver;
$loop->addReadStream($socket, function ($socket) use($loop, $deferred, $query, $parser, $request, $max, $nameserver) {
// 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, $max);
if ($data === \false) {
return;
}
try {
$response = $parser->parseMessage($data);
} catch (\Exception $e) {
// ignore and await next if we received an invalid message from remote server
// this may as well be a fake response from an attacker (possible DOS)
return;
}
// ignore and await next if we received an unexpected response ID
// this may as well be a fake response from an attacker (possible cache poisoning)
if ($response->id !== $request->id) {
return;
}
// we only react to the first valid message, so remove socket from loop and close
$loop->removeReadStream($socket);
\fclose($socket);
if ($response->tc) {
$deferred->reject(new \RuntimeException('DNS query for ' . $query->describe() . ' failed: The DNS server ' . $nameserver . ' returned a truncated result for a UDP query', \defined('SOCKET_EMSGSIZE') ? \SOCKET_EMSGSIZE : 90));
return;
}
$deferred->resolve($response);
});
return $deferred->promise();
}
}