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| 1 | +<?php |
| 2 | + |
| 3 | +namespace React\Dns\Query; |
| 4 | + |
| 5 | +use React\Dns\Model\Message; |
| 6 | +use React\Dns\Protocol\BinaryDumper; |
| 7 | +use React\Dns\Protocol\Parser; |
| 8 | +use React\EventLoop\LoopInterface; |
| 9 | +use React\Promise\Deferred; |
| 10 | + |
| 11 | +/** |
| 12 | + * Send DNS queries over a datagram transport such as UDP. |
| 13 | + * |
| 14 | + * This is the main class that sends a DNS query to your DNS server and is used |
| 15 | + * internally by the `Resolver` for the actual message transport. |
| 16 | + * |
| 17 | + * For more advanced usages one can utilize this class directly. |
| 18 | + * The following example looks up the `IPv6` address for `igor.io`. |
| 19 | + * |
| 20 | + * ```php |
| 21 | + * $loop = Factory::create(); |
| 22 | + * $executor = new DatagramTransportExecutor($loop); |
| 23 | + * |
| 24 | + * $executor->query( |
| 25 | + * '8.8.8.8:53', |
| 26 | + * new Query($name, Message::TYPE_AAAA, Message::CLASS_IN, time()) |
| 27 | + * )->then(function (Message $message) { |
| 28 | + * foreach ($message->answers as $answer) { |
| 29 | + * echo 'IPv6: ' . $answer->data . PHP_EOL; |
| 30 | + * } |
| 31 | + * }, 'printf'); |
| 32 | + * |
| 33 | + * $loop->run(); |
| 34 | + * ``` |
| 35 | + * |
| 36 | + * See also the [fourth example](examples). |
| 37 | + * |
| 38 | + * Note that this executor does not implement a timeout, so you will very likely |
| 39 | + * want to use this in combination with a `TimeoutExecutor` like this: |
| 40 | + * |
| 41 | + * ```php |
| 42 | + * $executor = new TimeoutExecutor( |
| 43 | + * new DatagramTransportExecutor($loop), |
| 44 | + * 3.0, |
| 45 | + * $loop |
| 46 | + * ); |
| 47 | + * ``` |
| 48 | + * |
| 49 | + * Also note that this executor uses an unreliable UDP transport and that it |
| 50 | + * does not implement any retry logic, so you will likely want to use this in |
| 51 | + * combination with a `RetryExecutor` like this: |
| 52 | + * |
| 53 | + * ```php |
| 54 | + * $executor = new RetryExecutor( |
| 55 | + * new TimeoutExecutor( |
| 56 | + * new DatagramTransportExecutor($loop), |
| 57 | + * 3.0, |
| 58 | + * $loop |
| 59 | + * ) |
| 60 | + * ); |
| 61 | + * ``` |
| 62 | + * |
| 63 | + * > Internally, this class uses PHP's UDP sockets and does not take advantage |
| 64 | + * of [react/datagram](https://github.com/reactphp/datagram) purely for |
| 65 | + * organizational reasons to avoid a cyclic dependency between the two |
| 66 | + * packages. Higher-level components should take advantage of the Datagram |
| 67 | + * component instead of reimplementing this socket logic from scratch. |
| 68 | + */ |
| 69 | +class DatagramTransportExecutor implements ExecutorInterface |
| 70 | +{ |
| 71 | + private $loop; |
| 72 | + private $parser; |
| 73 | + private $dumper; |
| 74 | + |
| 75 | + /** |
| 76 | + * @param LoopInterface $loop |
| 77 | + * @param null|Parser $parser optional/advanced: DNS protocol parser to use |
| 78 | + * @param null|BinaryDumper $dumper optional/advanced: DNS protocol dumper to use |
| 79 | + */ |
| 80 | + public function __construct(LoopInterface $loop, Parser $parser = null, BinaryDumper $dumper = null) |
| 81 | + { |
| 82 | + if ($parser === null) { |
| 83 | + $parser = new Parser(); |
| 84 | + } |
| 85 | + if ($dumper === null) { |
| 86 | + $dumper = new BinaryDumper(); |
| 87 | + } |
| 88 | + |
| 89 | + $this->loop = $loop; |
| 90 | + $this->parser = $parser; |
| 91 | + $this->dumper = $dumper; |
| 92 | + } |
| 93 | + |
| 94 | + public function query($nameserver, Query $query) |
| 95 | + { |
| 96 | + $request = Message::createRequestForQuery($query); |
| 97 | + |
| 98 | + $queryData = $this->dumper->toBinary($request); |
| 99 | + if (isset($queryData[512])) { |
| 100 | + return \React\Promise\reject(new \RuntimeException( |
| 101 | + 'DNS query for ' . $query->name . ' failed: Query too large for UDP transport' |
| 102 | + )); |
| 103 | + } |
| 104 | + |
| 105 | + // UDP connections are instant, so try connection without a loop or timeout |
| 106 | + $socket = @\stream_socket_client("udp://$nameserver", $errno, $errstr, 0); |
| 107 | + if ($socket === false) { |
| 108 | + return \React\Promise\reject(new \RuntimeException( |
| 109 | + 'DNS query for ' . $query->name . ' failed: Unable to connect to DNS server (' . $errstr . ')', |
| 110 | + $errno |
| 111 | + )); |
| 112 | + } |
| 113 | + |
| 114 | + // set socket to non-blocking and immediately try to send (fill write buffer) |
| 115 | + \stream_set_blocking($socket, false); |
| 116 | + \fwrite($socket, $queryData); |
| 117 | + |
| 118 | + $loop = $this->loop; |
| 119 | + $deferred = new Deferred(function () use ($loop, $socket, $query) { |
| 120 | + // cancellation should remove socket from loop and close socket |
| 121 | + $loop->removeReadStream($socket); |
| 122 | + \fclose($socket); |
| 123 | + |
| 124 | + throw new CancellationException('DNS query for ' . $query->name . ' has been cancelled'); |
| 125 | + }); |
| 126 | + |
| 127 | + $parser = $this->parser; |
| 128 | + $loop->addReadStream($socket, function ($socket) use ($loop, $deferred, $query, $parser) { |
| 129 | + // try to read a single data packet from the DNS server |
| 130 | + // ignoring any errors, this is uses UDP packets and not a stream of data |
| 131 | + $data = @\fread($socket, 512); |
| 132 | + |
| 133 | + // we only react to the first message, so immediately remove socket from loop and close |
| 134 | + $loop->removeReadStream($socket); |
| 135 | + \fclose($socket); |
| 136 | + |
| 137 | + try { |
| 138 | + $response = $parser->parseMessage($data); |
| 139 | + } catch (\Exception $e) { |
| 140 | + // reject if we received an invalid message from remote server |
| 141 | + $deferred->reject($e); |
| 142 | + return; |
| 143 | + } |
| 144 | + |
| 145 | + if ($response->header->isTruncated()) { |
| 146 | + $deferred->reject(new \RuntimeException('DNS query for ' . $query->name . ' failed: The server returned a truncated result for a UDP query, but retrying via TCP is currently not supported')); |
| 147 | + return; |
| 148 | + } |
| 149 | + |
| 150 | + $deferred->resolve($response); |
| 151 | + }); |
| 152 | + |
| 153 | + return $deferred->promise(); |
| 154 | + } |
| 155 | +} |
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