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<?php
namespace Kelunik\LightD;
use Amp\Deferred;
use Amp\Delayed;
use Amp\Dns\DnsException;
use Amp\Dns\Record;
use Amp\Loop;
use Amp\Promise;
use LibDNS\Decoder\Decoder;
use LibDNS\Decoder\DecodingContextFactory;
use LibDNS\Encoder\Encoder;
use LibDNS\Encoder\EncodingContextFactory;
use LibDNS\Messages\MessageFactory;
use LibDNS\Messages\MessageTypes;
use LibDNS\Packets\PacketFactory;
use LibDNS\Records\QuestionFactory;
use LibDNS\Records\RDataBuilder;
use LibDNS\Records\RDataFactory;
use LibDNS\Records\ResourceBuilder;
use LibDNS\Records\ResourceFactory;
use LibDNS\Records\TypeDefinitions\FieldDefinitionFactory;
use LibDNS\Records\TypeDefinitions\TypeDefinitionFactory;
use LibDNS\Records\TypeDefinitions\TypeDefinitionManager;
use LibDNS\Records\Types\TypeBuilder;
use LibDNS\Records\Types\TypeFactory;
use function Amp\call;
final class MulticastDns
{
public function query(string $name): Promise
{
return call(static function () use ($name) {
for ($attempt = 1; $attempt < 3; $attempt++) {
$context = \stream_context_create([
'socket' => [
'so_reuseport' => true,
'so_reuseaddr' => true,
'bindto' => '0.0.0.0:5353',
],
]);
$stream = \stream_socket_server('udp://0.0.0.0:5353', $errno, $error, \STREAM_SERVER_BIND, $context);
$socket = \socket_import_stream($stream);
if (!$socket) {
throw new \RuntimeException('Failed to access socket');
}
if (!\socket_set_option($socket, \IPPROTO_IP, \MCAST_JOIN_GROUP,
['group' => '224.0.0.251', 'interface' => 0])) {
throw new \RuntimeException('Failed to join multicast group');
}
if (!\socket_set_option($socket, \IPPROTO_IP, \IP_MULTICAST_TTL, 255)) {
throw new \RuntimeException('Failed to set multicast TTL');
}
if (!\socket_set_option($socket, \IPPROTO_IP, \IP_MULTICAST_LOOP, 1)) {
throw new \RuntimeException('Failed to set multicast loop');
}
$question = (new QuestionFactory)->create(Record::PTR);
$question->setName($name);
$request = (new MessageFactory)->create(MessageTypes::QUERY);
$request->getQuestionRecords()->add($question);
$request->isRecursionDesired(false);
$request->setID(0);
$data = (new Encoder(new PacketFactory, new EncodingContextFactory))->encode($request);
\stream_socket_sendto($stream, $data, null, '224.0.0.251:5353');
$timeout = new Delayed(3000, false);
$timeout->unreference();
$devices = [];
read:
$deferred = new Deferred;
$watcher = Loop::onReadable($stream, static function ($watcher) use ($deferred) {
Loop::cancel($watcher);
$deferred->resolve(true);
});
if (!yield Promise\first([$deferred->promise(), $timeout])) {
Loop::cancel($watcher);
if ($devices) {
return $devices;
}
continue;
}
$data = \stream_socket_recvfrom($stream, 8192, null, $addr);
if ($data === null || $data === false) {
continue;
}
$typeBuilder = new TypeBuilder(new TypeFactory);
$resourceBuilder = new ResourceBuilder(
new ResourceFactory,
new RDataBuilder(new RDataFactory, $typeBuilder),
new TypeDefinitionManager(new TypeDefinitionFactory, new FieldDefinitionFactory)
);
$response = (new Decoder(
new PacketFactory(),
new MessageFactory(),
new QuestionFactory(),
$resourceBuilder,
$typeBuilder,
new DecodingContextFactory
))->decode($data);
if ($response->getType() !== MessageTypes::RESPONSE) {
goto read; // loop back or a question
}
$answers = $response->getAnswerRecords();
$pointers = $answers->getRecordsByName($name);
if (!$pointers) {
goto read; // response to another query
}
$records = [];
foreach ($answers as $answer) {
$records[] = $answer;
}
foreach ($response->getAdditionalRecords() as $answer) {
$records[] = $answer;
}
$hosts = [];
foreach ($records as $answer) {
\assert($answer instanceof \LibDNS\Records\Resource);
if ($answer->getType() === Record::A) {
$hosts[] = $answer->getData()->getFieldByName('address')->getValue();
}
if ($answer->getType() === Record::AAAA) {
$hosts[] = '[' . $answer->getData()->getFieldByName('address')->getValue() . ']';
}
}
if (empty($hosts)) {
throw new DnsException('Failed to find A or AAAA record for ' . $name);
}
// automatically prefers IPv4, because IPv6 starts with '[' and IPv4 starts with digits
\sort($hosts);
$devices[] = $hosts;
goto read;
}
throw new DnsException('Query for ' . $name . ' timed out');
});
}
}
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