fun systemDns(systemDns: Dns) =
      apply {
        this.systemDns = systemDns
      }
  }

  companion object {
    val DNS_MESSAGE: MediaType = "application/dns-message".toMediaType()
    const val MAX_RESPONSE_SIZE = 64 * 1024

    private fun buildBootstrapClient(builder: Builder): Dns {
      val hosts = builder.bootstrapDnsHosts

      return if (hosts != null) {