anchor.diff:                      Nodes = load_balancing:choose_ns_nodes_for_dns(LBAdvice),
                       {ok, TTL} = application:get_env(?APP_NAME, dns_ns_response_ttl),
                       {ok,
  -                        % TODO!!
  -                            [dns_server:answer_record(Domain, TTL, ns, inet_parse:ntoa(IP)) || IP <- Nodes] ++
  +                            [dns_server:answer_record(Domain, TTL, ?S_NS, inet_parse:ntoa(IP)) || IP <- Nodes] ++
                               [dns_server:authoritative_answer_flag(true)]
                       };
                   Other ->
  
positive.code:                     Nodes = load_balancing:choose_nodes_for_dns(LBAdvice),
                      {ok, TTL} = application:get_env(?APP_NAME, dns_a_response_ttl),
                      {ok,
                          % TODO!!!!! ?S_A
                              [dns_server:answer_record(Domain, TTL, a, IP) || IP <- Nodes] ++
                              [dns_server:authoritative_answer_flag(true)]
                      };
                  Other ->
  
negative.code: %%--------------------------------------------------------------------
  -spec check_dns_connectivity() -> ok | {error, server_not_responding}.
  check_dns_connectivity() ->
      {ok, HealthcheckTimeout} = application:get_env(?APP_NAME, nagios_healthcheck_timeout),
      {ok, DNSPort} = application:get_env(?APP_NAME, dns_port),
      Query = inet_dns:encode(
          #dns_rec{
              header = #dns_header{
                  id = crypto:rand_uniform(1, 16#FFFF),
                  opcode = 'query',
                  rd = true
              },
              qdlist = [#dns_query{
                  domain = "localhost",
                  type = soa,
                  class = in
              }],
              arlist = [{dns_rr_opt, ".", opt, 1280, 0, 0, 0, <<>>}]
          }),
      {ok, Socket} = gen_udp:open(0, [binary, {active, false}]),
      gen_udp:send(Socket, "127.0.0.1", DNSPort, Query),
      case gen_udp:recv(Socket, 65535, HealthcheckTimeout) of
          {ok, _} ->
              % DNS is working
              ok;
          _ ->
              % DNS is not working
              {error, server_not_responding}
      end.