void dns_server_mark_all(DnsServer *first) {
        if (!first)
                return;

        first->marked = true;
        dns_server_mark_all(first->servers_next);
}
void dns_server_mark_all(DnsServer *first) {
        if (!first)
                return;

        first->marked = true;
        dns_server_mark_all(first->servers_next);
}