/**
* Query DNS server for A / AAAA records in batches of 2.
*
* @param string $host Host name to be resolved.
* @return array Resolved address and expiration time.
*
* @throws MultiReasonException When no IP address could be resolved.
*/
protected function resolveHost(string $host) : \Generator
{
$errors = [];
foreach (\array_chunk($this->servers, 2) as $servers) {
$ipv4 = [];
$ipv6 = [];
foreach ($servers as $server) {
if (Socket::isIPv6Supported()) {
$ipv6[] = new Coroutine($this->lookupAddress($server, $errors, $host, Request::TYPE_AAAA));
}
$ipv4[] = new Coroutine($this->lookupAddress($server, $errors, $host, Request::TYPE_A));
}
list($ipv4, $ipv6) = (yield new AwaitAll([$this->awaitFirstResult($ipv6, $errors), $this->awaitFirstResult($ipv4, $errors)]));
if (empty($ipv4) && empty($ipv6)) {
continue;
}
$ttl = min($ipv4['ttl'] ?? PHP_INT_MAX, $ipv6['ttl'] ?? PHP_INT_MAX);
$ttl = max(1, min(300, $ttl));
$address = null;
foreach (\array_merge((array) $ipv4['ips'], (array) $ipv6['ips']) as $ip) {
try {
$address = $address ? $address->mergeWith(new Address($ip)) : new Address($ip);
} catch (\Throwable $e) {
$errors[] = $e;
}
}
if ($address && \count($address)) {
return ['address' => $address, 'expires' => \time() + $ttl];
}
}
$error = '';
foreach ($errors as $e) {
$error .= \sprintf("\n+ [%s] %s", \get_class($e), $e->getMessage());
}
if (!empty($errors)) {
$error .= "\n";
}
throw new MultiReasonException($errors, \sprintf('Unable to resolve host "%s" into an IP address%s', $host, $error));
}
