companion object {
    /**
     * A DNS that uses [InetAddress.getAllByName] to ask the underlying operating system to
     * lookup IP addresses. Most custom [Dns] implementations should delegate to this instance.
     */
    @JvmField
    val SYSTEM: Dns = DnsSystem()

    private class DnsSystem : Dns {
      override fun lookup(hostname: String): List<InetAddress> {
        try {

    var routeSelector = newRouteSelector(address)
    dns[PROXY_A_HOST] = dns.allocate(1)
    dns[PROXY_B_HOST] = dns.allocate(1)

    // Mark the ProxyA route as failed.
    val selection = routeSelector.next()
    dns.assertRequests(PROXY_A_HOST)
    val route = selection.next()
    assertRoute(route, address, proxyA, dns.lookup(PROXY_A_HOST, 0), PROXY_A_PORT)
    routeDatabase.failed(route)

    .url("https://dns.google/dns-query".toHttpUrl())
    .bootstrapDnsHosts(InetAddress.getByName("8.8.4.4"), InetAddress.getByName("8.8.8.8"))
    .build()

  val client = bootstrapClient.newBuilder().dns(dns).build()
```

  private lateinit var dns: Dns
  private val cacheFs = FakeFileSystem()
  private val bootstrapClient =
    OkHttpClient.Builder()
      .protocols(listOf(Protocol.HTTP_2, Protocol.HTTP_1_1))
      .build()

  @BeforeEach
  fun setUp(server: MockWebServer) {
    this.server = server
    server.protocols = bootstrapClient.protocols
    dns = buildLocalhost(bootstrapClient, false)
  }

  @Test

    server.useHttps(handshakeCertificates.sslSocketFactory())

    val dns =
      Dns {
        Dns.SYSTEM.lookup(server.hostName)
      }

    val client =
      clientTestRule.newClientBuilder()
        .sslSocketFactory(
          handshakeCertificates.sslSocketFactory(),
          handshakeCertificates.trustManager,
        )
        .dns(dns)
        .build()

    server.enqueue(MockResponse())

        .dns {
          Dns.SYSTEM.lookup("sni.cloudflaressl.com")
        }
        .build()

    val request =
      Request.Builder()
        .url("https://cloudflare-dns.com/cdn-cgi/trace")
        .build()
    client.newCall(request).execute().use { response ->
      assertThat(response.code).isEqualTo(200)
      assertThat(response.protocol).isEqualTo(Protocol.HTTP_2)

/**
 * [DNS over HTTPS implementation][doh_spec].
 *
 * > A DNS API client encodes a single DNS query into an HTTP request
 * > using either the HTTP GET or POST method and the other requirements
 * > of this section.  The DNS API server defines the URI used by the
 * > request through the use of a URI Template.
 *
 * [doh_spec]: https://tools.ietf.org/html/draft-ietf-doh-dns-over-https-13
 */

        continue
      }

      val dns = route?.address?.dns ?: defaultDns
      val auth =
        if (proxyAuthorization) {
          val proxyAddress = proxy.address() as InetSocketAddress
          Authenticator.requestPasswordAuthentication(
            proxyAddress.hostName,
            proxy.connectToInetAddress(url, dns),
            proxyAddress.port,
            url.scheme,

        .addSubjectAlternativeName("differentdns.com")
        .build()
    serverIps = Dns.SYSTEM.lookup(server.hostName)
    dns[server.hostName] = serverIps
    dns["san.com"] = serverIps
    dns["nonsan.com"] = serverIps
    dns["www.wildcard.com"] = serverIps
    dns["differentdns.com"] = listOf()
    val handshakeCertificates =
      HandshakeCertificates.Builder()

 * configure the factory when sample values impact the correctness of the test.
 */
class TestValueFactory : Closeable {
  var taskFaker: TaskFaker = TaskFaker()
  var taskRunner: TaskRunner = taskFaker.taskRunner
  var dns: Dns = Dns.SYSTEM
  var proxy: Proxy = Proxy.NO_PROXY
  var proxySelector: ProxySelector = RecordingProxySelector()
  var proxyAuthenticator: Authenticator = RecordingOkAuthenticator("password", null)