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

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

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

    if (newRouteSelector == null) {
      newRouteSelector =
        RouteSelector(
          address = address,
          routeDatabase = routeDatabase,
          call = call,
          fastFallback = fastFallback,
        )
      routeSelector = newRouteSelector
    }

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

  private fun newRouteSelector(
    address: Address,
    routeDatabase: RouteDatabase = this.routeDatabase,
    fastFallback: Boolean = false,
    call: RealCall = this.call,
  ): RouteSelector =
    RouteSelector(
      address = address,
      routeDatabase = routeDatabase,
      fastFallback = fastFallback,
      call = call,
    )

  companion object {
    private const val PROXY_A_PORT = 1001

        .newClientBuilder()
        .eventListenerFactory(clientTestRule.wrap(eventRecorder))
        .connectTimeout(60, TimeUnit.SECONDS) // Deliberately exacerbate slow fallbacks.
        .dns { dnsResults }
        .fastFallback(true)
        .build()
    url =
      serverIpv4
        .url("/")
        .newBuilder()
        .host("localhost")
        .build()
  }

  @AfterEach
  internal fun tearDown() {

          retryOnConnectionFailure = chain.retryOnConnectionFailure,
          fastFallback = client.fastFallback,
          address = chain.address(request.url),
          routeDatabase = client.routeDatabase,
          call = this,
          request = request,
        )
      this.exchangeFinder =
        when {
          client.fastFallback -> FastFallbackExchangeFinder(routePlanner, client.taskRunner)

      HandshakeCertificates
        .Builder()
        .addTrustedCertificate(rootCa.certificate)
        .build()
    client =
      clientTestRule
        .newClientBuilder()
        .fastFallback(false) // Avoid data races.
        .dns(dns)
        .sslSocketFactory(
          handshakeCertificates.sslSocketFactory(),
          handshakeCertificates.trustManager,
        ).build()

## Version 5.0.0-alpha.11

_2022-12-24_

 *  New: Enable fast fallback by default. It's our implementation of Happy Eyeballs,
    [RFC 8305][rfc_8305]. Disable with `OkHttpClient.Builder.fastFallback(false)`.
 *  Fix: Don't log response bodies for server-sent events.
 *  Fix: Skip early hints (status code 103) responses.
 *  Fix: Don't log sensitive headers in `Request.toString()`.