mirror of
https://github.com/danog/dns.git
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530 lines
18 KiB
PHP
530 lines
18 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\Dns\Internal\Socket;
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use Amp\Dns\Internal\TcpSocket;
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use Amp\Dns\Internal\UdpSocket;
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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\Records\Question;
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use LibDNS\Records\QuestionFactory;
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use function Amp\call;
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final class Rfc1035StubResolver implements Resolver
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{
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const CACHE_PREFIX = "amphp.dns.";
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const CONFIG_NOT_LOADED = 0;
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const CONFIG_LOADED = 1;
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const CONFIG_FAILED = 2;
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/** @var ConfigLoader */
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private $configLoader;
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/** @var QuestionFactory */
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private $questionFactory;
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/** @var Config|null */
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private $config;
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/** @var int */
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private $configStatus = self::CONFIG_NOT_LOADED;
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/** @var Promise|null */
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private $pendingConfig;
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/** @var Cache */
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private $cache;
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/** @var Socket[] */
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private $sockets = [];
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/** @var Promise[] */
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private $pendingSockets = [];
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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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/** @var BlockingFallbackResolver */
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private $blockingFallbackResolver;
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/** @var int */
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private $nextNameserver = 0;
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public function __construct(Cache $cache = null, ConfigLoader $configLoader = null)
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{
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$this->cache = $cache ?? new ArrayCache(5000 /* default gc interval */, 256 /* size */);
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$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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$this->blockingFallbackResolver = new BlockingFallbackResolver;
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$sockets = &$this->sockets;
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$this->gcWatcher = Loop::repeat(5000, static function () use (&$sockets) {
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if (!$sockets) {
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return;
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}
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$now = \time();
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foreach ($sockets as $key => $server) {
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if ($server->getLastActivity() < $now - 60) {
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$server->close();
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unset($sockets[$key]);
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}
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}
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});
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Loop::unreference($this->gcWatcher);
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}
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public function __destruct()
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{
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Loop::cancel($this->gcWatcher);
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}
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/** @inheritdoc */
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public function resolve(string $name, int $typeRestriction = null): Promise
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{
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if ($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->configStatus === self::CONFIG_NOT_LOADED) {
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yield $this->reloadConfig();
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}
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if ($this->configStatus === self::CONFIG_FAILED) {
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return $this->blockingFallbackResolver->resolve($name, $typeRestriction);
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}
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switch ($typeRestriction) {
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case Record::A:
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if (\filter_var($name, FILTER_VALIDATE_IP, FILTER_FLAG_IPV4)) {
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return [new Record($name, Record::A, null)];
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}
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if (\filter_var($name, FILTER_VALIDATE_IP, FILTER_FLAG_IPV6)) {
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throw new DnsException("Got an IPv6 address, but type is restricted to IPv4");
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}
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break;
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case Record::AAAA:
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if (\filter_var($name, FILTER_VALIDATE_IP, FILTER_FLAG_IPV6)) {
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return [new Record($name, Record::AAAA, null)];
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}
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if (\filter_var($name, FILTER_VALIDATE_IP, FILTER_FLAG_IPV4)) {
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throw new DnsException("Got an IPv4 address, but type is restricted to IPv6");
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}
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break;
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default:
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if (\filter_var($name, FILTER_VALIDATE_IP, FILTER_FLAG_IPV4)) {
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return [new Record($name, Record::A, null)];
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}
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if (\filter_var($name, FILTER_VALIDATE_IP, FILTER_FLAG_IPV6)) {
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return [new Record($name, Record::AAAA, null)];
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}
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break;
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}
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$dots = \substr_count($name, ".");
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// Should be replaced with $name[-1] from 7.1
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$trailingDot = \substr($name, -1, 1) === ".";
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$name = normalizeName($name);
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if ($records = $this->queryHosts($name, $typeRestriction)) {
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return $records;
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}
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// Follow RFC 6761 and never send queries for localhost to the caching DNS server
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// Usually, these queries are already resolved via queryHosts()
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if ($name === 'localhost') {
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return $typeRestriction === Record::AAAA
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? [new Record('::1', Record::AAAA, null)]
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: [new Record('127.0.0.1', Record::A, null)];
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}
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$searchList = [null];
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if (!$trailingDot && $dots < $this->config->getNdots()) {
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$searchList = \array_merge($this->config->getSearchList(), $searchList);
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}
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foreach ($searchList as $search) {
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for ($redirects = 0; $redirects < 5; $redirects++) {
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$searchName = $name;
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if ($search !== null) {
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$searchName = $name . "." . $search;
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}
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try {
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if ($typeRestriction) {
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return yield $this->query($searchName, $typeRestriction);
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}
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try {
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list(, $records) = yield Promise\some([
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$this->query($searchName, Record::A),
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$this->query($searchName, Record::AAAA),
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]);
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return \array_merge(...$records);
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} catch (MultiReasonException $e) {
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$errors = [];
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foreach ($e->getReasons() as $reason) {
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if ($reason instanceof NoRecordException) {
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throw $reason;
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}
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$errors[] = $reason->getMessage();
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}
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throw new DnsException(
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"All query attempts failed for {$searchName}: " . \implode(", ", $errors),
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0,
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$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 $this->query($searchName, 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 $this->query($searchName, Record::DNAME);
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$name = $dnameRecords[0]->getValue();
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continue;
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}
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}
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}
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}
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throw new DnsException("Giving up resolution of '{$searchName}', too many redirects");
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});
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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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{
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if ($this->pendingConfig) {
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return $this->pendingConfig;
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}
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$promise = call(function () {
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try {
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$this->config = yield $this->configLoader->loadConfig();
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$this->configStatus = self::CONFIG_LOADED;
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} catch (ConfigException $e) {
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$this->configStatus = self::CONFIG_FAILED;
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try {
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\trigger_error(
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"Could not load the system's DNS configuration, using synchronous, blocking fallback",
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\E_USER_WARNING
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);
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} catch (\Throwable $triggerException) {
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\set_error_handler(null);
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\trigger_error(
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"Could not load the system's DNS configuration, using synchronous, blocking fallback",
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\E_USER_WARNING
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);
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\restore_error_handler();
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}
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}
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});
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$this->pendingConfig = $promise;
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$promise->onResolve(function () {
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$this->pendingConfig = null;
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});
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return $promise;
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}
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/** @inheritdoc */
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public function query(string $name, int $type): Promise
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{
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$pendingQueryKey = $type . " " . $name;
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if (isset($this->pendingQueries[$pendingQueryKey])) {
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return $this->pendingQueries[$pendingQueryKey];
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}
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$promise = call(function () use ($name, $type) {
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if ($this->configStatus === self::CONFIG_NOT_LOADED) {
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yield $this->reloadConfig();
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}
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if ($this->configStatus === self::CONFIG_FAILED) {
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return $this->blockingFallbackResolver->query($name, $type);
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}
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$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 = $this->selectNameservers();
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$nameserversCount = \count($nameservers);
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$attempts = $this->config->getAttempts();
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$protocol = "udp";
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$attempt = 0;
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/** @var Socket $socket */
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$uri = $protocol . "://" . $nameservers[0];
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$socket = yield $this->getSocket($uri);
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$attemptDescription = [];
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while ($attempt < $attempts) {
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try {
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if (!$socket->isAlive()) {
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unset($this->sockets[$uri]);
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$socket->close();
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$uri = $protocol . "://" . $nameservers[$attempt % $nameserversCount];
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$socket = yield $this->getSocket($uri);
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}
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$attemptDescription[] = $uri;
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/** @var Message $response */
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$response = yield $socket->ask($question, $this->config->getTimeout());
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$this->assertAcceptableResponse($response);
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// UDP sockets are never reused, they're not in the $this->sockets map
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if ($protocol === "udp") {
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// Defer call, because it interferes with the unreference() call in Internal\Socket otherwise
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Loop::defer(static function () use ($socket) {
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$socket->close();
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});
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}
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if ($response->isTruncated()) {
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if ($protocol !== "tcp") {
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// Retry with TCP, don't count attempt
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$protocol = "tcp";
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$uri = $protocol . "://" . $nameservers[$attempt % $nameserversCount];
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$socket = yield $this->getSocket($uri);
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continue;
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}
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throw new DnsException("Server returned a truncated response for '{$name}' (" . Record::getName($type) . ")");
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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) $record->getData();
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// Cache for max one day
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$ttls[$recordType] = \min($ttls[$recordType] ?? 86400, $record->getTTL());
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}
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foreach ($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(
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$this->getCacheKey($name, $recordType),
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\json_encode($records),
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$ttls[$recordType]
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);
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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}' (" . Record::getName($type) . ")");
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}
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return \array_map(static function ($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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} catch (TimeoutException $e) {
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// Defer call, because it might interfere with the unreference() call in Internal\Socket otherwise
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Loop::defer(function () use ($socket, $uri) {
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unset($this->sockets[$uri]);
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$socket->close();
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});
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$uri = $protocol . "://" . $nameservers[++$attempt % $nameserversCount];
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$socket = yield $this->getSocket($uri);
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continue;
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}
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}
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throw new TimeoutException(\sprintf(
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"No response for '%s' (%s) from any nameserver after %d attempts, tried %s",
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$name,
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Record::getName($type),
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$attempts,
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\implode(", ", $attemptDescription)
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));
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});
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$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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private function queryHosts(string $name, int $typeRestriction = null): array
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{
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$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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private function normalizeName(string $name, int $type)
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{
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if ($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], true)) {
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$name = normalizeName($name);
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}
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return $name;
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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 Question
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*/
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private function createQuestion(string $name, int $type): Question
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{
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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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{
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return self::CACHE_PREFIX . $name . "#" . $type;
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}
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private function decodeCachedResult(string $name, int $type, string $encoded): array
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{
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$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 $result;
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}
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private function getSocket($uri): Promise
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{
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// We use a new socket for each UDP request, as that increases the entropy and mitigates response forgery.
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if (\substr($uri, 0, 3) === "udp") {
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return UdpSocket::connect($uri);
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}
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// Over TCP we might reuse sockets if the server allows to keep them open. Sequence IDs in TCP are already
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// better than a random port. Additionally, a TCP connection is more expensive.
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if (isset($this->sockets[$uri])) {
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return new Success($this->sockets[$uri]);
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}
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if (isset($this->pendingSockets[$uri])) {
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return $this->pendingSockets[$uri];
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}
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$server = TcpSocket::connect($uri);
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$server->onResolve(function ($error, $server) use ($uri) {
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unset($this->pendingSockets[$uri]);
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if (!$error) {
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$this->sockets[$uri] = $server;
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}
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});
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return $server;
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}
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/**
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* @throws DnsException
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*/
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private function assertAcceptableResponse(Message $response)
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{
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if ($response->getResponseCode() !== 0) {
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throw new DnsException(\sprintf("Server returned error code: %d", $response->getResponseCode()));
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}
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}
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private function selectNameservers(): array
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{
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$nameservers = $this->config->getNameservers();
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if ($this->config->isRotationEnabled() && ($nameserversCount = \count($nameservers)) > 1) {
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$nameservers = \array_merge(
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\array_slice($nameservers, $this->nextNameserver),
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\array_slice($nameservers, 0, $this->nextNameserver)
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);
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$this->nextNameserver = ++$this->nextNameserver % $nameserversCount;
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}
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return $nameservers;
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}
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}
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