RealRoutePlanner.kt

/*
 * Copyright (C) 2015 Square, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package okhttp3.internal.connection

import java.io.IOException
import java.net.HttpURLConnection
import java.net.Socket
import java.net.UnknownServiceException
import okhttp3.Address
import okhttp3.ConnectionListener
import okhttp3.ConnectionSpec
import okhttp3.HttpUrl
import okhttp3.OkHttpClient
import okhttp3.Protocol
import okhttp3.Request
import okhttp3.Response
import okhttp3.Route
import okhttp3.internal.canReuseConnectionFor
import okhttp3.internal.closeQuietly
import okhttp3.internal.connection.RoutePlanner.Plan
import okhttp3.internal.http.RealInterceptorChain
import okhttp3.internal.platform.Platform
import okhttp3.internal.toHostHeader
import okhttp3.internal.userAgent

class RealRoutePlanner(
  private val client: OkHttpClient,
  override val address: Address,
  private val call: RealCall,
  private val chain: RealInterceptorChain,
  private val connectionListener: ConnectionListener
) : RoutePlanner {
  private val doExtensiveHealthChecks = chain.request.method != "GET"

  private var routeSelection: RouteSelector.Selection? = null
  private var routeSelector: RouteSelector? = null
  private var nextRouteToTry: Route? = null

  override val deferredPlans = ArrayDeque<Plan>()

  override fun isCanceled(): Boolean = call.isCanceled()

  @Throws(IOException::class)
  override fun plan(): Plan {
    val reuseCallConnection = planReuseCallConnection()
    if (reuseCallConnection != null) return reuseCallConnection

    // Attempt to get a connection from the pool.
    val pooled1 = planReusePooledConnection()
    if (pooled1 != null) return pooled1

    // Attempt a deferred plan before new routes.
    if (deferredPlans.isNotEmpty()) return deferredPlans.removeFirst()

    // Do blocking calls to plan a route for a new connection.
    val connect = planConnect()

    // Now that we have a set of IP addresses, make another attempt at getting a connection from
    // the pool. We have a better chance of matching thanks to connection coalescing.
    val pooled2 = planReusePooledConnection(connect, connect.routes)
    if (pooled2 != null) return pooled2

    return connect
  }

  /**
   * Returns the connection already attached to the call if it's eligible for a new exchange.
   *
   * If the call's connection exists and is eligible for another exchange, it is returned. If it
   * exists but cannot be used for another exchange, it is closed and this returns null.
   */
  private fun planReuseCallConnection(): ReusePlan? {
    // This may be mutated by releaseConnectionNoEvents()!
    val candidate = call.connection ?: return null

    // Make sure this connection is healthy & eligible for new exchanges. If it's no longer needed
    // then we're on the hook to close it.
    val healthy = candidate.isHealthy(doExtensiveHealthChecks)
    var noNewExchangesEvent = false
    val toClose: Socket? = synchronized(candidate) {
      when {
        !healthy -> {
          noNewExchangesEvent = !candidate.noNewExchanges
          candidate.noNewExchanges = true
          call.releaseConnectionNoEvents()
        }
        candidate.noNewExchanges || !sameHostAndPort(candidate.route().address.url) -> {
          call.releaseConnectionNoEvents()
        }
        else -> null
      }
    }

    // If the call's connection wasn't released, reuse it. We don't call connectionAcquired() here
    // because we already acquired it.
    if (call.connection != null) {
      check(toClose == null)
      return ReusePlan(candidate)
    }

    // The call's connection was released.
    toClose?.closeQuietly()
    call.eventListener.connectionReleased(call, candidate)
    candidate.connectionListener.connectionReleased(candidate, call)
    if (toClose != null) {
      candidate.connectionListener.connectionClosed(candidate)
    } else if (noNewExchangesEvent) {
      candidate.connectionListener.noNewExchanges(candidate)
    }
    return null
  }

  /** Plans to make a new connection by deciding which route to try next. */
  @Throws(IOException::class)
  private fun planConnect(): ConnectPlan {
    // Use a route from a preceding coalesced connection.
    val localNextRouteToTry = nextRouteToTry
    if (localNextRouteToTry != null) {
      nextRouteToTry = null
      return planConnectToRoute(localNextRouteToTry)
    }

    // Use a route from an existing route selection.
    val existingRouteSelection = routeSelection
    if (existingRouteSelection != null && existingRouteSelection.hasNext()) {
      return planConnectToRoute(existingRouteSelection.next())
    }

    // Decide which proxy to use, if any. This may block in ProxySelector.select().
    var newRouteSelector = routeSelector
    if (newRouteSelector == null) {
      newRouteSelector = RouteSelector(
        address = address,
        routeDatabase = call.client.routeDatabase,
        call = call,
        fastFallback = client.fastFallback,
        eventListener = call.eventListener
      )
      routeSelector = newRouteSelector
    }

    // List available IP addresses for the current proxy. This may block in Dns.lookup().
    if (!newRouteSelector.hasNext()) throw IOException("exhausted all routes")
    val newRouteSelection = newRouteSelector.next()
    routeSelection = newRouteSelection

    if (call.isCanceled()) throw IOException("Canceled")

    return planConnectToRoute(newRouteSelection.next(), newRouteSelection.routes)
  }

  /**
   * Returns a plan to reuse a pooled connection, or null if the pool doesn't have a connection for
   * this address.
   *
   * If [planToReplace] is non-null, this will swap it for a pooled connection if that pooled
   * connection uses HTTP/2. That results in fewer sockets overall and thus fewer TCP slow starts.
   */
  internal fun planReusePooledConnection(
    planToReplace: ConnectPlan? = null,
    routes: List<Route>? = null,
  ): ReusePlan? {
    val result = client.connectionPool.delegate.callAcquirePooledConnection(
      doExtensiveHealthChecks = doExtensiveHealthChecks,
      address = address,
      call = call,
      routes = routes,
      requireMultiplexed = planToReplace != null && planToReplace.isReady
    ) ?: return null

    // If we coalesced our connection, remember the replaced connection's route. That way if the
    // coalesced connection later fails we don't waste a valid route.
    if (planToReplace != null) {
      nextRouteToTry = planToReplace.route
      planToReplace.closeQuietly()
    }

    call.eventListener.connectionAcquired(call, result)
    result.connectionListener.connectionAcquired(result, call)
    return ReusePlan(result)
  }

  /** Returns a plan for the first attempt at [route]. This throws if no plan is possible. */
  @Throws(IOException::class)
  internal fun planConnectToRoute(route: Route, routes: List<Route>? = null): ConnectPlan {
    if (route.address.sslSocketFactory == null) {
      if (ConnectionSpec.CLEARTEXT !in route.address.connectionSpecs) {
        throw UnknownServiceException("CLEARTEXT communication not enabled for client")
      }

      val host = route.address.url.host
      if (!Platform.get().isCleartextTrafficPermitted(host)) {
        throw UnknownServiceException(
          "CLEARTEXT communication to $host not permitted by network security policy"
        )
      }
    } else {
      if (Protocol.H2_PRIOR_KNOWLEDGE in route.address.protocols) {
        throw UnknownServiceException("H2_PRIOR_KNOWLEDGE cannot be used with HTTPS")
      }
    }

    val tunnelRequest = when {
      route.requiresTunnel() -> createTunnelRequest(route)
      else -> null
    }

    return ConnectPlan(
      client = client,
      call = call,
      chain = chain,
      routePlanner = this,
      route = route,
      routes = routes,
      attempt = 0,
      tunnelRequest = tunnelRequest,
      connectionSpecIndex = -1,
      isTlsFallback = false,
      connectionListener = connectionListener
    )
  }

  /**
   * Returns a request that creates a TLS tunnel via an HTTP proxy. Everything in the tunnel request
   * is sent unencrypted to the proxy server, so tunnels include only the minimum set of headers.
   * This avoids sending potentially sensitive data like HTTP cookies to the proxy unencrypted.
   *
   * In order to support preemptive authentication we pass a fake "Auth Failed" response to the
   * authenticator. This gives the authenticator the option to customize the CONNECT request. It can
   * decline to do so by returning null, in which case OkHttp will use it as-is.
   */
  @Throws(IOException::class)
  private fun createTunnelRequest(route: Route): Request {
    val proxyConnectRequest = Request.Builder()
      .url(route.address.url)
      .method("CONNECT", null)
      .header("Host", route.address.url.toHostHeader(includeDefaultPort = true))
      .header("Proxy-Connection", "Keep-Alive") // For HTTP/1.0 proxies like Squid.
      .header("User-Agent", userAgent)
      .build()

    val fakeAuthChallengeResponse = Response.Builder()
      .request(proxyConnectRequest)
      .protocol(Protocol.HTTP_1_1)
      .code(HttpURLConnection.HTTP_PROXY_AUTH)
      .message("Preemptive Authenticate")
      .sentRequestAtMillis(-1L)
      .receivedResponseAtMillis(-1L)
      .header("Proxy-Authenticate", "OkHttp-Preemptive")
      .build()

    val authenticatedRequest = route.address.proxyAuthenticator
      .authenticate(route, fakeAuthChallengeResponse)

    return authenticatedRequest ?: proxyConnectRequest
  }

  override fun hasNext(failedConnection: RealConnection?): Boolean {
    if (deferredPlans.isNotEmpty()) {
      return true
    }

    if (nextRouteToTry != null) {
      return true
    }

    if (failedConnection != null) {
      val retryRoute = retryRoute(failedConnection)
      if (retryRoute != null) {
        // Lock in the route because retryRoute() is racy and we don't want to call it twice.
        nextRouteToTry = retryRoute
        return true
      }
    }

    // If we have a routes left, use 'em.
    if (routeSelection?.hasNext() == true) return true

    // If we haven't initialized the route selector yet, assume it'll have at least one route.
    val localRouteSelector = routeSelector ?: return true

    // If we do have a route selector, use its routes.
    return localRouteSelector.hasNext()
  }

  /**
   * Return the route from [connection] if it should be retried, even if the connection itself is
   * unhealthy. The biggest gotcha here is that we shouldn't reuse routes from coalesced
   * connections.
   */
  private fun retryRoute(connection: RealConnection): Route? {
    return synchronized(connection) {
      if (connection.routeFailureCount != 0) null
      else if (!connection.noNewExchanges) null // This route is still in use.
      else if (!connection.route().address.url.canReuseConnectionFor(address.url)) null
      else connection.route()
    }
  }

  override fun sameHostAndPort(url: HttpUrl): Boolean {
    val routeUrl = address.url
    return url.port == routeUrl.port && url.host == routeUrl.host
  }
}