// Compute the next set of routes to attempt.
    val routes = mutableListOf<Route>()
    while (hasNextProxy()) {
      // Postponed routes are always tried last. For example, if we have 2 proxies and all the
      // routes for proxy1 should be postponed, we'll move to proxy2. Only after we've exhausted
      // all the good routes will we attempt the postponed routes.
      val proxy = nextProxy()

 *     a race in fast follow-up.
 *
 *  4. If there's no existing connection, make a list of routes (which may require blocking DNS
 *     lookups) and attempt a new connection them. When failures occur, retries iterate the list of
 *     available routes.
 *
 * If the pool gains an eligible connection while DNS, TCP, or TLS work is in flight, this finder

    server.enqueue(MockResponse(socketPolicy = DisconnectAtStart))
    server.enqueue(MockResponse(socketPolicy = DisconnectAtStart))

    client =
      client.newBuilder()
        .dns(DoubleInetAddressDns()) // Two routes so we get two failures.
        .build()

    val request = Request(server.url("/"))
    assertFailsWith<IOException> {
      client.newCall(request).execute()
    }.also { expected ->

  val responses = mutableListOf<Response>()
  val routes = mutableListOf<Route>()

  fun onlyResponse() = responses.single()

  fun onlyRoute() = routes.single()

  @Throws(IOException::class)
  override fun authenticate(
    route: Route?,
    response: Response,
  ): Request? {
    if (route == null) throw NullPointerException("route == null")
    responses += response
    routes += route

package okhttp3.internal.connection

import okhttp3.Route

/**
 * A denylist of failed routes to avoid when creating a new connection to a target address. This is
 * used so that OkHttp can learn from its mistakes: if there was a failure attempting to connect to
 * a specific IP address or proxy server, that failure is remembered and alternate routes are
 * preferred.
 */
class RouteDatabase {
  private val _failedRoutes = mutableSetOf<Route>()

 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package okhttp3.internal.connection

import java.io.IOException

/** Attempt routes one at a time until one connects. */
internal class SequentialExchangeFinder(
  override val routePlanner: RoutePlanner,
) : ExchangeFinder {
  override fun find(): RealConnection {
    var firstException: IOException? = null

 *
 * Requires org.conscrypt:conscrypt-openjdk-uber >= 2.1.0 on the classpath.
 */
class ConscryptPlatform private constructor() : Platform() {
  private val provider: Provider = Conscrypt.newProvider()

  // See release notes https://groups.google.com/forum/#!forum/conscrypt
  // for version differences
  override fun newSSLContext(): SSLContext =
    // supports TLSv1.3 by default (version api is >= 1.4.0)
    SSLContext.getInstance("TLS", provider)