content: /*
   * Copyright (C) 2017 The Android Open Source Project
   *
   * 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 com.android.server.wifi;
  
  import android.util.Log;
  
  import java.util.Iterator;
  import java.util.LinkedList;
  
  /**
   * This class is used to recover the wifi stack from a fatal failure. The recovery mechanism
   * involves triggering a stack restart (essentially simulating an airplane mode toggle) using
   * {@link WifiController}.
   * The current triggers for:
   * 1. Last resort watchdog bite.
   * 2. HAL/wificond crashes during normal operation.
   * 3. TBD: supplicant crashes during normal operation.
   */
  public class SelfRecovery {
      private static final String TAG = "WifiSelfRecovery";
  
      /**
       * Reason codes for the various recovery triggers.
       */
      public static final int REASON_LAST_RESORT_WATCHDOG = 0;
      public static final int REASON_WIFINATIVE_FAILURE = 1;
      public static final int REASON_STA_IFACE_DOWN = 2;
      public static final long MAX_RESTARTS_IN_TIME_WINDOW = 2; // 2 restarts per hour
      public static final long MAX_RESTARTS_TIME_WINDOW_MILLIS = 60 * 60 * 1000; // 1 hour
      protected static final String[] REASON_STRINGS = {
              "Last Resort Watchdog",  // REASON_LAST_RESORT_WATCHDOG
              "WifiNative Failure",    // REASON_WIFINATIVE_FAILURE
              "Sta Interface Down"     // REASON_STA_IFACE_DOWN
      };
  
      private final WifiController mWifiController;
      private final Clock mClock;
      // Time since boot (in millis) that restart occurred
      private final LinkedList<Long> mPastRestartTimes;
      public SelfRecovery(WifiController wifiController, Clock clock) {
          mWifiController = wifiController;
          mClock = clock;
          mPastRestartTimes = new LinkedList<Long>();
      }
  
      /**
       * Trigger recovery.
       *
       * This method does the following:
       * 1. Checks reason code used to trigger recovery
       * 2. Checks for sta iface down triggers and disables wifi by sending {@link
       * WifiController#CMD_RECOVERY_DISABLE_WIFI} to {@link WifiController} to disable wifi.
       * 3. Throttles restart calls for underlying native failures
       * 4. Sends {@link WifiController#CMD_RECOVERY_RESTART_WIFI} to {@link WifiController} to
       * initiate the stack restart.
       * @param reason One of the above |REASON_*| codes.
       */
      public void trigger(int reason) {
          if (!(reason == REASON_LAST_RESORT_WATCHDOG || reason == REASON_WIFINATIVE_FAILURE
                    || reason == REASON_STA_IFACE_DOWN)) {
              Log.e(TAG, "Invalid trigger reason. Ignoring...");
              return;
          }
          if (reason == REASON_STA_IFACE_DOWN) {
              Log.e(TAG, "STA interface down, disable wifi");
              mWifiController.sendMessage(WifiController.CMD_RECOVERY_DISABLE_WIFI);
              return;
          }
  
          Log.e(TAG, "Triggering recovery for reason: " + REASON_STRINGS[reason]);
          if (reason == REASON_WIFINATIVE_FAILURE) {
              trimPastRestartTimes();
              // Ensure there haven't been too many restarts within MAX_RESTARTS_TIME_WINDOW
              if (mPastRestartTimes.size() >= MAX_RESTARTS_IN_TIME_WINDOW) {
                  Log.e(TAG, "Already restarted wifi (" + MAX_RESTARTS_IN_TIME_WINDOW + ") times in"
                          + " last (" + MAX_RESTARTS_TIME_WINDOW_MILLIS + "ms ). Disabling wifi");
                  mWifiController.sendMessage(WifiController.CMD_RECOVERY_DISABLE_WIFI);
                  return;
              }
              mPastRestartTimes.add(mClock.getElapsedSinceBootMillis());
          }
          mWifiController.sendMessage(WifiController.CMD_RECOVERY_RESTART_WIFI, reason);
      }
  
      /**
       * Process the mPastRestartTimes list, removing elements outside the max restarts time window
       */
      private void trimPastRestartTimes() {
          Iterator<Long> iter = mPastRestartTimes.iterator();
          long now = mClock.getElapsedSinceBootMillis();
          while (iter.hasNext()) {
              Long restartTimeMillis = iter.next();
              if (now - restartTimeMillis > MAX_RESTARTS_TIME_WINDOW_MILLIS) {
                  iter.remove();
              } else {
                  break;
              }
          }
      }
  }
  