*
 * Returns hardcoded results for the known host.
 */
internal class BootstrapDns(
  private val dnsHostname: String,
  private val dnsServers: List<InetAddress>,
) : Dns {
  @Throws(UnknownHostException::class)
  override fun lookup(hostname: String): List<InetAddress> {
    if (this.dnsHostname != hostname) {
      throw UnknownHostException(
        "BootstrapDns called for $hostname instead of $dnsHostname",
      )
    }

    const val MAX_RESPONSE_SIZE = 64 * 1024

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

      return if (hosts != null) {
        BootstrapDns(builder.url!!.host, hosts)
      } else {
        builder.systemDns
      }
    }

    internal fun isPrivateHost(host: String): Boolean {