/*
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* Copyright (C) 2017 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.android.server.wifi;
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import android.util.Log;
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import java.util.Iterator;
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import java.util.LinkedList;
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/**
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* This class is used to recover the wifi stack from a fatal failure. The recovery mechanism
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* involves triggering a stack restart (essentially simulating an airplane mode toggle) using
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* {@link WifiController}.
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* The current triggers for:
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* 1. Last resort watchdog bite.
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* 2. HAL/wificond crashes during normal operation.
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* 3. TBD: supplicant crashes during normal operation.
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*/
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public class SelfRecovery {
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private static final String TAG = "WifiSelfRecovery";
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/**
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* Reason codes for the various recovery triggers.
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*/
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public static final int REASON_LAST_RESORT_WATCHDOG = 0;
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public static final int REASON_WIFINATIVE_FAILURE = 1;
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public static final int REASON_STA_IFACE_DOWN = 2;
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public static final long MAX_RESTARTS_IN_TIME_WINDOW = 2; // 2 restarts per hour
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public static final long MAX_RESTARTS_TIME_WINDOW_MILLIS = 60 * 60 * 1000; // 1 hour
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protected static final String[] REASON_STRINGS = {
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"Last Resort Watchdog", // REASON_LAST_RESORT_WATCHDOG
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"WifiNative Failure", // REASON_WIFINATIVE_FAILURE
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"Sta Interface Down" // REASON_STA_IFACE_DOWN
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};
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private final WifiController mWifiController;
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private final Clock mClock;
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// Time since boot (in millis) that restart occurred
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private final LinkedList<Long> mPastRestartTimes;
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public SelfRecovery(WifiController wifiController, Clock clock) {
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mWifiController = wifiController;
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mClock = clock;
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mPastRestartTimes = new LinkedList<Long>();
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}
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/**
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* Trigger recovery.
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*
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* This method does the following:
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* 1. Checks reason code used to trigger recovery
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* 2. Checks for sta iface down triggers and disables wifi by sending {@link
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* WifiController#CMD_RECOVERY_DISABLE_WIFI} to {@link WifiController} to disable wifi.
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* 3. Throttles restart calls for underlying native failures
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* 4. Sends {@link WifiController#CMD_RECOVERY_RESTART_WIFI} to {@link WifiController} to
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* initiate the stack restart.
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* @param reason One of the above |REASON_*| codes.
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*/
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public void trigger(int reason) {
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if (!(reason == REASON_LAST_RESORT_WATCHDOG || reason == REASON_WIFINATIVE_FAILURE
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|| reason == REASON_STA_IFACE_DOWN)) {
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Log.e(TAG, "Invalid trigger reason. Ignoring...");
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return;
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}
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if (reason == REASON_STA_IFACE_DOWN) {
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Log.e(TAG, "STA interface down, disable wifi");
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mWifiController.sendMessage(WifiController.CMD_RECOVERY_DISABLE_WIFI);
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return;
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}
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Log.e(TAG, "Triggering recovery for reason: " + REASON_STRINGS[reason]);
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if (reason == REASON_WIFINATIVE_FAILURE) {
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trimPastRestartTimes();
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// Ensure there haven't been too many restarts within MAX_RESTARTS_TIME_WINDOW
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if (mPastRestartTimes.size() >= MAX_RESTARTS_IN_TIME_WINDOW) {
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Log.e(TAG, "Already restarted wifi (" + MAX_RESTARTS_IN_TIME_WINDOW + ") times in"
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+ " last (" + MAX_RESTARTS_TIME_WINDOW_MILLIS + "ms ). Disabling wifi");
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mWifiController.sendMessage(WifiController.CMD_RECOVERY_DISABLE_WIFI);
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return;
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}
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mPastRestartTimes.add(mClock.getElapsedSinceBootMillis());
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}
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mWifiController.sendMessage(WifiController.CMD_RECOVERY_RESTART_WIFI, reason);
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}
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/**
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* Process the mPastRestartTimes list, removing elements outside the max restarts time window
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*/
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private void trimPastRestartTimes() {
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Iterator<Long> iter = mPastRestartTimes.iterator();
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long now = mClock.getElapsedSinceBootMillis();
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while (iter.hasNext()) {
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Long restartTimeMillis = iter.next();
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if (now - restartTimeMillis > MAX_RESTARTS_TIME_WINDOW_MILLIS) {
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iter.remove();
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} else {
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break;
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}
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}
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}
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}
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