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/*
* 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_HAL_CRASH = 1;
public static final int REASON_WIFICOND_CRASH = 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
private static final String[] REASON_STRINGS = {
"Last Resort Watchdog", // REASON_LAST_RESORT_WATCHDOG
"Hal Crash", // REASON_HAL_CRASH
"Wificond Crash" // REASON_WIFICOND_CRASH
};
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. Raises a wtf.
* 2. Sends {@link WifiController#CMD_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_HAL_CRASH
|| reason == REASON_WIFICOND_CRASH)) {
Log.e(TAG, "Invalid trigger reason. Ignoring...");
return;
}
Log.wtf(TAG, "Triggering recovery for reason: " + REASON_STRINGS[reason]);
if (reason == REASON_WIFICOND_CRASH || reason == REASON_HAL_CRASH) {
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 ). Ignoring...");
return;
}
mPastRestartTimes.add(mClock.getElapsedSinceBootMillis());
}
mWifiController.sendMessage(WifiController.CMD_RESTART_WIFI);
}
/**
* 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;
}
}
}
}
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