1 /*
2  * Copyright (C) 2017 The Android Open Source Project
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  *      http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 
17 package com.android.server.wifi;
18 
19 import android.util.Log;
20 
21 import java.util.Iterator;
22 import java.util.LinkedList;
23 
24 /**
25  * This class is used to recover the wifi stack from a fatal failure. The recovery mechanism
26  * involves triggering a stack restart (essentially simulating an airplane mode toggle) using
27  * {@link WifiController}.
28  * The current triggers for:
29  * 1. Last resort watchdog bite.
30  * 2. HAL/wificond crashes during normal operation.
31  * 3. TBD: supplicant crashes during normal operation.
32  */
33 public class SelfRecovery {
34     private static final String TAG = "WifiSelfRecovery";
35 
36     /**
37      * Reason codes for the various recovery triggers.
38      */
39     public static final int REASON_LAST_RESORT_WATCHDOG = 0;
40     public static final int REASON_WIFINATIVE_FAILURE = 1;
41     public static final int REASON_STA_IFACE_DOWN = 2;
42     public static final long MAX_RESTARTS_IN_TIME_WINDOW = 2; // 2 restarts per hour
43     public static final long MAX_RESTARTS_TIME_WINDOW_MILLIS = 60 * 60 * 1000; // 1 hour
44     protected static final String[] REASON_STRINGS = {
45             "Last Resort Watchdog",  // REASON_LAST_RESORT_WATCHDOG
46             "WifiNative Failure",    // REASON_WIFINATIVE_FAILURE
47             "Sta Interface Down"     // REASON_STA_IFACE_DOWN
48     };
49 
50     private final WifiController mWifiController;
51     private final Clock mClock;
52     // Time since boot (in millis) that restart occurred
53     private final LinkedList<Long> mPastRestartTimes;
SelfRecovery(WifiController wifiController, Clock clock)54     public SelfRecovery(WifiController wifiController, Clock clock) {
55         mWifiController = wifiController;
56         mClock = clock;
57         mPastRestartTimes = new LinkedList<Long>();
58     }
59 
60     /**
61      * Trigger recovery.
62      *
63      * This method does the following:
64      * 1. Checks reason code used to trigger recovery
65      * 2. Checks for sta iface down triggers and disables wifi by sending {@link
66      * WifiController#CMD_RECOVERY_DISABLE_WIFI} to {@link WifiController} to disable wifi.
67      * 3. Throttles restart calls for underlying native failures
68      * 4. Sends {@link WifiController#CMD_RECOVERY_RESTART_WIFI} to {@link WifiController} to
69      * initiate the stack restart.
70      * @param reason One of the above |REASON_*| codes.
71      */
trigger(int reason)72     public void trigger(int reason) {
73         if (!(reason == REASON_LAST_RESORT_WATCHDOG || reason == REASON_WIFINATIVE_FAILURE
74                   || reason == REASON_STA_IFACE_DOWN)) {
75             Log.e(TAG, "Invalid trigger reason. Ignoring...");
76             return;
77         }
78         if (reason == REASON_STA_IFACE_DOWN) {
79             Log.e(TAG, "STA interface down, disable wifi");
80             mWifiController.sendMessage(WifiController.CMD_RECOVERY_DISABLE_WIFI);
81             return;
82         }
83 
84         Log.e(TAG, "Triggering recovery for reason: " + REASON_STRINGS[reason]);
85         if (reason == REASON_WIFINATIVE_FAILURE) {
86             trimPastRestartTimes();
87             // Ensure there haven't been too many restarts within MAX_RESTARTS_TIME_WINDOW
88             if (mPastRestartTimes.size() >= MAX_RESTARTS_IN_TIME_WINDOW) {
89                 Log.e(TAG, "Already restarted wifi (" + MAX_RESTARTS_IN_TIME_WINDOW + ") times in"
90                         + " last (" + MAX_RESTARTS_TIME_WINDOW_MILLIS + "ms ). Disabling wifi");
91                 mWifiController.sendMessage(WifiController.CMD_RECOVERY_DISABLE_WIFI);
92                 return;
93             }
94             mPastRestartTimes.add(mClock.getElapsedSinceBootMillis());
95         }
96         mWifiController.sendMessage(WifiController.CMD_RECOVERY_RESTART_WIFI, reason);
97     }
98 
99     /**
100      * Process the mPastRestartTimes list, removing elements outside the max restarts time window
101      */
trimPastRestartTimes()102     private void trimPastRestartTimes() {
103         Iterator<Long> iter = mPastRestartTimes.iterator();
104         long now = mClock.getElapsedSinceBootMillis();
105         while (iter.hasNext()) {
106             Long restartTimeMillis = iter.next();
107             if (now - restartTimeMillis > MAX_RESTARTS_TIME_WINDOW_MILLIS) {
108                 iter.remove();
109             } else {
110                 break;
111             }
112         }
113     }
114 }
115