ips := make([]netip.Addr, 0)
	for i := 0; i < 64; i++ {
		ips = append(ips, netip.MustParseAddr(fmt.Sprintf("240.0.0.%d", i)))
	}
	return a("aaaaaaaaaaaa.aaaaaa.", ips)
}()

func makeUpstream(t test.Failer, responses map[string]string) string {
	mux := dns.NewServeMux()
	mux.HandleFunc(".", func(resp dns.ResponseWriter, msg *dns.Msg) {
		answer := new(dns.Msg)
		answer.SetReply(msg)