socketReadTimeoutMillis = socketReadTimeoutMillis,
              pingIntervalMillis = pingIntervalMillis,
              retryOnConnectionFailure = retryOnConnectionFailure,
              fastFallback = fastFallback,
              address = address,
              routeDatabase = routeDatabase,
              connectionUser = user,
            ),
          ),
          taskRunner,
        )
      },
    ),
  )

      socketReadTimeoutMillis = chain.readTimeoutMillis,
      pingIntervalMillis = client.pingIntervalMillis,
      retryOnConnectionFailure = client.retryOnConnectionFailure,
      fastFallback = client.fastFallback,
      address = address,
      routeDatabase = client.routeDatabase,
      connectionUser =
        CallConnectionUser(
          call,
          client.connectionPool.delegate.connectionListener,

  private fun newRouteSelector(
    address: Address,
    routeDatabase: RouteDatabase = this.routeDatabase,
    fastFallback: Boolean = false,
    call: RealCall = this.call,
  ): RouteSelector {
    return RouteSelector(
      address = address,
      routeDatabase = routeDatabase,
      fastFallback = fastFallback,
      connectionUser = CallConnectionUser(call, ConnectionListener.NONE, newChain(call)),
    )
  }

    dns[server1.hostName] = listOf(ipv6, ipv4)
    socketFactory[ipv6] = server1.inetSocketAddress
    socketFactory[ipv4] = server2.inetSocketAddress

    client =
      client.newBuilder()
        .fastFallback(false)
        .apply {
          retryOnConnectionFailure = false
        }
        .build()

    executeSynchronously(request)
      .assertFailureMatches("stream was reset: REFUSED_STREAM")

  private val listener = RecordingConnectionListener()
  private val handshakeCertificates = localhost()

  open val fastFallback: Boolean get() = true

  private var client: OkHttpClient =
    clientTestRule.newClientBuilder()
      .connectionPool(ConnectionPool(connectionListener = listener))
      .fastFallback(fastFallback)
      .build()

  @BeforeEach
  fun setUp(server: MockWebServer?) {
    this.server = server

          fastFallback = client.fastFallback,
          address = client.address(request.url),
          connectionUser = CallConnectionUser(this, connectionPool.connectionListener, chain),
          routeDatabase = client.routeDatabase,
        )
      this.exchangeFinder =
        when {
          client.fastFallback -> FastFallbackExchangeFinder(routePlanner, client.taskRunner)

     * wasted resources.
     *
     * Defaults to enabled, call with [fastFallback] = false to revert to 4.x behaviour.
     *
     * [rfc_6555]: https://datatracker.ietf.org/doc/html/rfc6555
     */
    fun fastFallback(fastFallback: Boolean) =
      apply {
        this.fastFallback = fastFallback
      }

    /**

OkHttp Android
==============

Enhanced APIs for using OkHttp on Android.

At the moment, this will mostly likely only be useful for fastFallback.

Download
--------

```kotlin
implementation("com.squareup.okhttp3:okhttp-android:4.12.0")

      newRouteSelector =
        RouteSelector(
          address = address,
          routeDatabase = routeDatabase,
          connectionUser = connectionUser,
          fastFallback = fastFallback,
        )
      routeSelector = newRouteSelector
    }

    // List available IP addresses for the current proxy. This may block in Dns.lookup().

 */
class RouteSelector(
  private val address: Address,
  private val routeDatabase: RouteDatabase,
  private val connectionUser: ConnectionUser,
  private val fastFallback: Boolean,
) {
  // State for negotiating the next proxy to use.
  private var proxies = emptyList<Proxy>()
  private var nextProxyIndex: Int = 0

  // State for negotiating the next socket address to use.