dns/lib/UnixConfigLoader.php

<?php

namespace Amp\Dns;

use Amp\File;
use Amp\File\FilesystemException;
use Amp\Promise;
use function Amp\call;

final class UnixConfigLoader implements ConfigLoader {
    private $path;
    private $hostLoader;

    public function __construct(string $path = "/etc/resolv.conf", HostLoader $hostLoader = null) {
        $this->path = $path;
        $this->hostLoader = $hostLoader ?? new HostLoader;
    }

    public function loadConfig(): Promise {
        return call(function () {
            $path = $this->path;
            $nameservers = [];
            $timeout = 3000;
            $attempts = 2;

            try {
                $fileContent = yield File\get($path);
                $lines = \explode("\n", $fileContent);

                foreach ($lines as $line) {
                    $line = \preg_split('#\s+#', $line, 2);

                    if (\count($line) !== 2) {
                        continue;
                    }

                    list($type, $value) = $line;

                    if ($type === "nameserver") {
                        $value = \trim($value);
                        $ip = @\inet_pton($value);

                        if ($ip === false) {
                            continue;
                        }

                        if (isset($ip[15])) { // IPv6
                            $nameservers[] = "[" . $value . "]:53";
                        } else { // IPv4
                            $nameservers[] = $value . ":53";
                        }
                    } elseif ($type === "options") {
                        $optline = \preg_split('#\s+#', $value, 2);

                        if (\count($optline) !== 2) {
                            continue;
                        }

                        list($option, $value) = $optline;

                        switch ($option) {
                            case "timeout":
                                $timeout = (int) $value;
                                break;

                            case "attempts":
                                $attempts = (int) $value;
                        }
                    }
                }
            } catch (FilesystemException $e) {
                throw new ConfigException("Could not read configuration file ({$path})", $e);
            }

            $hosts = yield $this->hostLoader->loadHosts();

            return new Config($nameservers, $hosts, $timeout, $attempts);
        });
    }
}