* href="https://iabtechlab.com/wp-content/uploads/2019/06/VAST_4.2_final_june26.pdf">{@code
   * X-Device-IP}</a> header field name. Header used for VAST requests to provide the IP address of
   * the device on whose behalf the request is being made.
   *
   * @since 31.0
   */
  public static final String X_DEVICE_IP = "X-Device-IP";

  /**
   * The HTTP <a

 * ## Modern TLS
 *
 * There are trade-offs when selecting which options to include when negotiating a secure connection
 * to a remote host. Newer TLS options are quite useful:
 *
 *  * Server Name Indication (SNI) enables one IP address to negotiate secure connections for
 *    multiple domain names.
 *
 *  * Application Layer Protocol Negotiation (ALPN) enables the HTTPS port (443) to be used to
 *    negotiate HTTP/2.
 *

     *   <li>OPTIONS - Returns the HTTP methods that the server supports.</li>
     *   <li>TRACE - Echoes back the received request, used for debugging.</li>
     *   <li>CONNECT - Converts the request connection to a transparent TCP/IP tunnel.</li>
     * </ul>
     */
    public enum Method {
        /**
         * HTTP GET method.
         */
        GET,
        /**
         * HTTP POST method.
         */
        POST,

 *
 * HTTP requests that share the same [Address] may also share the same [Connection].
 */
class Address(
  uriHost: String,
  uriPort: Int,
  /** Returns the service that will be used to resolve IP addresses for hostnames. */
  @get:JvmName("dns") val dns: Dns,
  /** Returns the socket factory for new connections. */
  @get:JvmName("socketFactory") val socketFactory: SocketFactory,

    // https://daniel.haxx.se/blog/2016/08/18/http2-connection-coalescing/

    // 1. This connection must be HTTP/2.
    if (http2Connection == null) return false

    // 2. The routes must share an IP address.
    if (routes == null || !routeMatchesAny(routes)) return false

    // 3. This connection's server certificates must cover the new host.
    if (address.hostnameVerifier !== OkHostnameVerifier) return false

import okhttp3.internal.connection.RoutePlanner.ConnectResult
import okhttp3.internal.connection.RoutePlanner.Plan
import okhttp3.internal.okHttpName

/**
 * Speculatively connects to each IP address of a target address, returning as soon as one of them
 * connects successfully. This kicks off new attempts every 250 ms until a connect succeeds.
 */
internal class FastFallbackExchangeFinder(

    proxySelector.proxies.add(proxyA)
    proxySelector.proxies.add(proxyB)
    val routeSelector = newRouteSelector(address)
    proxySelector.assertRequests(address.url.toUri())

    // First try the IP addresses of the first proxy, in sequence.
    assertThat(routeSelector.hasNext()).isTrue()
    dns[PROXY_A_HOST] = dns.allocate(2)
    val selection1 = routeSelector.next()

     *     represented as a combination of scheme, host and port. When empty, the origin is that of
     *     the `streamId`.
     * @param protocol an ALPN protocol, such as `h2`.
     * @param host an IP address or hostname.
     * @param port the IP port associated with the service.
     * @param maxAge time in seconds that this alternative is considered fresh.
     */
    fun alternateService(
      streamId: Int,
      origin: String,

    * 3. Maximum of two entries is allowed in `--service-cluster-ip-range` and they are validated to be dual stacked `i.e. --service-cluster-ip-range=<v4>,<v6> or --service-cluster-ip-range=<v6>,<v4>`
    * 4. Max 20 bit for range (min network bits `<v6>/108` or <v4>/12)

* Only use the first IP address got from instance metadata. This is because Azure CNI would set up a list of IP addresses in instance metadata, while only the first one is the Node's IP. ([#71736](https://github.com/kubernetes/kubernetes/pull/71736), [@feiskyer](https://github.com/feiskyer))