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https://github.com/danog/dns.git
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357 lines
12 KiB
PHP
357 lines
12 KiB
PHP
<?php
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namespace Amp\Dns;
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use Amp\Cache\ArrayCache;
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use Amp\Cache\Cache;
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use Amp\Loop;
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use Amp\MultiReasonException;
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use Amp\Promise;
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use Amp\Success;
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use LibDNS\Messages\Message;
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use LibDNS\Messages\MessageTypes;
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use LibDNS\Records\Question;
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use LibDNS\Records\QuestionFactory;
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use function Amp\call;
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class BasicResolver implements Resolver {
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const CACHE_PREFIX = "amphp.dns.";
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/** @var \Amp\Dns\ConfigLoader */
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private $configLoader;
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/** @var \LibDNS\Records\QuestionFactory */
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private $questionFactory;
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/** @var \Amp\Dns\Config|null */
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private $config;
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/** @var Cache */
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private $cache;
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/** @var Server[] */
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private $servers = [];
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/** @var Promise[] */
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private $pendingServers = [];
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/** @var Promise[] */
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private $pendingQueries = [];
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/** @var string */
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private $gcWatcher;
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public function __construct(Cache $cache = null, ConfigLoader $configLoader = null) {
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$this->cache = $cache ?? new ArrayCache;
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$this->configLoader = $configLoader ?? \stripos(PHP_OS, "win") === 0
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? new WindowsConfigLoader
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: new UnixConfigLoader;
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$this->questionFactory = new QuestionFactory;
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$this->gcWatcher = Loop::repeat(5000, function () {
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$now = \time();
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foreach ($this->servers as $server) {
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if ($server->getLastActivity() < $now - 60) {
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unset($this->servers);
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}
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}
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});
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Loop::unreference($this->gcWatcher);
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}
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public function __destruct() {
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Loop::cancel($this->gcWatcher);
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}
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/** @inheritdoc */
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public function resolve(string $name, int $typeRestriction = null): Promise {
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if ($typeRestriction !== null && $typeRestriction !== Record::A && $typeRestriction !== Record::AAAA) {
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throw new \Error("Invalid value for parameter 2: null|Record::A|Record::AAAA expected");
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}
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return call(function () use ($name, $typeRestriction) {
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if (!$this->config) {
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$this->config = yield $this->configLoader->loadConfig();
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}
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$inAddr = @\inet_pton($name);
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if ($inAddr !== false) {
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// It's already a valid IP, don't query, immediately return
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if ($typeRestriction) {
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if ($typeRestriction === Record::A && isset($inAddr[4])) {
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throw new ResolutionException("Got an IPv6 address, but type is restricted to IPv4");
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}
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if ($typeRestriction === Record::AAAA && !isset($inAddr[4])) {
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throw new ResolutionException("Got an IPv4 address, but type is restricted to IPv6");
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}
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}
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return [
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new Record($name, isset($inAddr[4]) ? Record::AAAA : Record::A, null),
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];
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}
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$name = normalizeDnsName($name);
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if ($records = $this->queryHosts($name, $typeRestriction)) {
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return $records;
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}
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for ($redirects = 0; $redirects < 5; $redirects++) {
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try {
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if ($typeRestriction) {
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$records = yield $this->query($name, $typeRestriction);
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} else {
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try {
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list(, $records) = yield Promise\some([
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$this->query($name, Record::A),
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$this->query($name, Record::AAAA),
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]);
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$records = \array_merge(...$records);
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} catch (MultiReasonException $e) {
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foreach ($e->getReasons() as $reason) {
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if ($reason instanceof NoRecordException) {
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throw $reason;
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}
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}
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throw new ResolutionException("All query attempts failed", 0, $e);
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}
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}
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} catch (NoRecordException $e) {
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try {
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/** @var Record[] $cnameRecords */
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$cnameRecords = yield $this->query($name, Record::CNAME);
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$name = $cnameRecords[0]->getValue();
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continue;
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} catch (NoRecordException $e) {
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/** @var Record[] $dnameRecords */
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$dnameRecords = yield $this->query($name, Record::DNAME);
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$name = $dnameRecords[0]->getValue();
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continue;
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}
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}
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}
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return $records;
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});
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}
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private function queryHosts(string $name, int $typeRestriction = null): array {
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$hosts = $this->config->getKnownHosts();
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$records = [];
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$returnIPv4 = $typeRestriction === null || $typeRestriction === Record::A;
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$returnIPv6 = $typeRestriction === null || $typeRestriction === Record::AAAA;
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if ($returnIPv4 && isset($hosts[Record::A][$name])) {
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$records[] = new Record($hosts[Record::A][$name], Record::A, null);
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}
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if ($returnIPv6 && isset($hosts[Record::AAAA][$name])) {
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$records[] = new Record($hosts[Record::AAAA][$name], Record::AAAA, null);
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}
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return $records;
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}
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/** @inheritdoc */
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public function query(string $name, int $type): Promise {
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if (isset($this->pendingQueries[$type . " " . $name])) {
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return $this->pendingQueries[$type . " " . $name];
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}
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$promise = call(function () use ($name, $type) {
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if (!$this->config) {
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$this->config = yield $this->configLoader->loadConfig();
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}
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$name = $this->normalizeName($name, $type);
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$question = $this->createQuestion($name, $type);
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if (null !== $cachedValue = yield $this->cache->get($this->getCacheKey($name, $type))) {
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return $this->decodeCachedResult($name, $type, $cachedValue);
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}
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$nameservers = $this->config->getNameservers();
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$attempts = $this->config->getAttempts();
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$receivedTruncatedResponse = false;
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for ($attempt = 0; $attempt < $attempts; ++$attempt) {
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$i = $attempt % \count($nameservers);
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$protocol = $receivedTruncatedResponse ? "tcp" : "udp";
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/** @var \Amp\Dns\Server $server */
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$server = yield $this->getServer($protocol . "://" . $nameservers[$i]);
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if (!$server->isAlive()) {
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unset($this->servers[$protocol . "://" . $nameservers[$i]]);
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/** @var \Amp\Dns\Server $server */
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$server = yield $this->getServer($protocol . "://" . $nameservers[$i]);
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}
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/** @var Message $response */
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$response = yield $server->ask($question, $this->config->getTimeout());
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$this->assertAcceptableResponse($response);
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if ($response->isTruncated()) {
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if (!$receivedTruncatedResponse) {
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// Retry with TCP, don't count attempt
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$receivedTruncatedResponse = true;
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$attempt--;
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continue;
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}
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throw new ResolutionException("Server returned truncated response");
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}
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$answers = $response->getAnswerRecords();
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$result = [];
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$ttls = [];
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/** @var \LibDNS\Records\Resource $record */
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foreach ($answers as $record) {
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$recordType = $record->getType();
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$result[$recordType][] = (string) $record->getData();
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$ttls[$recordType] = \min($ttls[$recordType] ?? \PHP_INT_MAX, $record->getTTL());
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}
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foreach ($result as $recordType => $records) {
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// We don't care here whether storing in the cache fails
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$this->cache->set($this->getCacheKey($name, $recordType), \json_encode($records), $ttls[$recordType]);
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}
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if (!isset($result[$type])) {
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// "it MUST NOT cache it for longer than five (5) minutes" per RFC 2308 section 7.1
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$this->cache->set($this->getCacheKey($name, $type), \json_encode([]), 300);
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throw new NoRecordException("No records returned for {$name}");
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}
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return \array_map(function ($data) use ($type, $ttls) {
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return new Record($data, $type, $ttls[$type]);
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}, $result[$type]);
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}
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throw new ResolutionException("No response from any nameserver after {$attempts} attempts");
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});
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$this->pendingQueries[$type . " " . $name] = $promise;
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$promise->onResolve(function () use ($name, $type) {
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unset($this->pendingQueries[$type . " " . $name]);
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});
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return $promise;
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}
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/**
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* Reloads the configuration in the background.
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*
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* Once it's finished, the configuration will be used for new requests.
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*
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* @return Promise
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*/
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public function reloadConfig(): Promise {
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return call(function () {
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$this->config = yield $this->configLoader->loadConfig();
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});
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}
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/**
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* @param string $name
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* @param int $type
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*
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* @return \LibDNS\Records\Question
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*/
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private function createQuestion(string $name, int $type): Question {
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if (0 > $type || 0xffff < $type) {
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$message = \sprintf('%d does not correspond to a valid record type (must be between 0 and 65535).', $type);
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throw new \Error($message);
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}
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$question = $this->questionFactory->create($type);
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$question->setName($name);
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return $question;
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}
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private function getCacheKey(string $name, int $type): string {
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return self::CACHE_PREFIX . $name . "#" . $type;
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}
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private function decodeCachedResult(string $name, string $type, string $encoded) {
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$decoded = \json_decode($encoded, true);
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if (!$decoded) {
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throw new NoRecordException("No records returned for {$name} (cached result)");
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}
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$result = [];
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foreach ($decoded as $data) {
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$result[] = new Record($data, $type);
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}
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return $result;
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}
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private function normalizeName(string $name, int $type) {
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if ($type === Record::PTR) {
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if (($packedIp = @inet_pton($name)) !== false) {
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if (isset($packedIp[4])) { // IPv6
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$name = \wordwrap(\strrev(\bin2hex($packedIp)), 1, ".", true) . ".ip6.arpa";
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} else { // IPv4
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$name = \inet_ntop(\strrev($packedIp)) . ".in-addr.arpa";
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}
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}
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} elseif (\in_array($type, [Record::A, Record::AAAA])) {
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$name = normalizeDnsName($name);
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}
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return $name;
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}
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private function getServer($uri): Promise {
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if (isset($this->servers[$uri])) {
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return new Success($this->servers[$uri]);
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}
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if (isset($this->pendingServers[$uri])) {
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return $this->pendingServers[$uri];
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}
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if (\substr($uri, 0, 3) === "udp") {
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$server = UdpServer::connect($uri);
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} else {
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$server = TcpServer::connect($uri);
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}
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$server->onResolve(function ($error, $server) use ($uri) {
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if ($error) {
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unset($this->pendingServers[$uri]);
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} else {
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$this->servers[$uri] = $server;
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}
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});
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return $server;
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}
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private function assertAcceptableResponse(Message $response) {
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if ($response->getResponseCode() !== 0) {
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throw new ResolutionException(\sprintf("Server returned error code: %d", $response->getResponseCode()));
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}
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if ($response->getType() !== MessageTypes::RESPONSE) {
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throw new ResolutionException("Invalid server reply; expected RESPONSE but received QUERY");
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}
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}
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}
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