private var nextAddress = 0xff000064L // 255.0.0.100 in IPv4; ::ff00:64 in IPv6.

  /** Sets the results for `hostname`.  */
  operator fun set(
    hostname: String,
    addresses: List<InetAddress>,
  ): FakeDns {
    hostAddresses[hostname] = addresses
    return this
  }

  /** Clears the results for `hostname`.  */
  fun clear(hostname: String): FakeDns {
    hostAddresses.remove(hostname)
    return this
  }

    InetAddress addressV6_66_ff = InetAddress.getByName("2001:db8::66ff");
    InetAddress addressV6_67_0 = InetAddress.getByName("2001:db8::6700");

    InetAddress address = addressV6_66_0;
    for (int i = 0; i < 255; i++) {
      address = InetAddresses.increment(address);
    }
    assertEquals(addressV6_66_ff, address);

    address = InetAddresses.increment(address);
    assertEquals(addressV6_67_0, address);

    InetAddress addressV6_66_ff = InetAddress.getByName("2001:db8::66ff");
    InetAddress addressV6_67_0 = InetAddress.getByName("2001:db8::6700");

    InetAddress address = addressV6_66_0;
    for (int i = 0; i < 255; i++) {
      address = InetAddresses.increment(address);
    }
    assertEquals(addressV6_66_ff, address);

    address = InetAddresses.increment(address);
    assertEquals(addressV6_67_0, address);

  // addressType specifies the type of address carried by this EndpointSlice.
  // All addresses in this slice must be the same type. This field is
  // immutable after creation. The following address types are currently
  // supported:
  // * IPv4: Represents an IPv4 Address.
  // * IPv6: Represents an IPv6 Address.
  // * FQDN: Represents a Fully Qualified Domain Name.

    val latch = CountDownLatch(1)

    // assumes an IPv4 address
    AndroidAsyncDns.IPv4.query(
      hostname,
      object : AsyncDns.Callback {
        override fun onResponse(
          hostname: String,
          addresses: List<InetAddress>,
        ) {
          allAddresses.addAll(addresses)
          latch.countDown()
        }

        override fun onFailure(

    dnsResults =
      listOf(
        localhostIpv4,
        localhostIpv6,
        TestUtil.UNREACHABLE_ADDRESS_IPV4.address,
      )
    serverIpv4.protocols = listOf(Protocol.H2_PRIOR_KNOWLEDGE)
    serverIpv6.protocols = listOf(Protocol.H2_PRIOR_KNOWLEDGE)

    // Yield the first IP address so the second IP address completes first.
    val firstConnectLatch = CountDownLatch(1)
    val socketFactory =

  // addressType specifies the type of address carried by this EndpointSlice.
  // All addresses in this slice must be the same type. This field is
  // immutable after creation. The following address types are currently
  // supported:
  // * IPv4: Represents an IPv4 Address.
  // * IPv6: Represents an IPv6 Address.
  // * FQDN: Represents a Fully Qualified Domain Name.

  # outbound connections.
  # If "REDIRECT", use iptables REDIRECT to NAT and redirect to Envoy.
  # The "REDIRECT" mode loses source addresses during redirection.
  # If "TPROXY", use iptables TPROXY to redirect to Envoy.
  # The "TPROXY" mode preserves both the source and destination IP
  # addresses and ports, so that they can be used for advanced filtering
  # and manipulation.
  # The "TPROXY" mode also configures the sidecar to run with the

  companion object {
    /**
     * A network that resolves only one IP address per host. Use this when testing route selection
     * fallbacks to prevent the host machine's various IP addresses from interfering.
     */
    private val SINGLE_INET_ADDRESS_DNS =
      Dns { hostname ->
        val addresses = Dns.SYSTEM.lookup(hostname)
        listOf(addresses[0])
      }

		// Only grab the first (client) address. Note that '192.168.0.1,
		// 10.1.1.1' is a valid key for X-Forwarded-For where addresses after
		// the first may represent forwarding proxies earlier in the chain.
		s := strings.Index(fwd, ", ")
		if s == -1 {
			s = len(fwd)
		}
		addr = fwd[:s]
	} else if fwd := r.Header.Get(xRealIP); fwd != "" {
		// X-Real-IP should only contain one IP address (the client making the
		// request).