function checkdns() {
    global $_G;
    if (empty($_G['siteurl'])) {
        return true;
    }
    $xmlf = importfile();
    $xmlt = @implode('', file($xmlf));
    require_once libfile('class/xml');
    $xmld = xml2array($xmlt);
    $deve = preg_match('(' . $_G['siteurl'] . ')', $xmld['From']);
    if ($deve) {
        return false;
    }
    $matc = parse_url($_G['siteurl']);
    $host = !empty($matc['host']) ? $matc['host'] : $_G['clientip'];
    $clip = gethostbyname($host);
    if ($clip == $host) {
        return true;
    } else {
        return preg_match('#^(10|127|172\.16|192\.168)\.#', $clip);
    }
}