Resolv::DNS#fetch_resource

# File tmp/rubies/ruby-3.3.0/lib/resolv.rb, line 521
def fetch_resource(name, typeclass)
  lazy_initialize
  begin
    requester = make_udp_requester
  rescue Errno::EACCES
    # fall back to TCP
  end
  senders = {}
  begin
    @config.resolv(name) {|candidate, tout, nameserver, port|
      requester ||= make_tcp_requester(nameserver, port)
      msg = Message.new
      msg.rd = 1
      msg.add_question(candidate, typeclass)
      unless sender = senders[[candidate, nameserver, port]]
        sender = requester.sender(msg, candidate, nameserver, port)
        next if !sender
        senders[[candidate, nameserver, port]] = sender
      end
      reply, reply_name = requester.request(sender, tout)
      case reply.rcode
      when RCode::NoError
        if reply.tc == 1 and not Requester::TCP === requester
          requester.close
          # Retry via TCP:
          requester = make_tcp_requester(nameserver, port)
          senders = {}
          # This will use TCP for all remaining candidates (assuming the
          # current candidate does not already respond successfully via
          # TCP).  This makes sense because we already know the full
          # response will not fit in an untruncated UDP packet.
          redo
        else
          yield(reply, reply_name)
        end
        return
      when RCode::NXDomain
        raise Config::NXDomain.new(reply_name.to_s)
      else
        raise Config::OtherResolvError.new(reply_name.to_s)
      end
    }
  ensure
    requester&.close
  end
end