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.annotation.IntDef;
20 import android.content.Context;
21 import android.util.Log;
22 
23 import com.android.wifi.resources.R;
24 
25 import java.lang.annotation.Retention;
26 import java.lang.annotation.RetentionPolicy;
27 import java.util.Iterator;
28 import java.util.LinkedList;
29 import java.util.concurrent.TimeUnit;
30 
31 /**
32  * This class is used to recover the wifi stack from a fatal failure. The recovery mechanism
33  * involves triggering a stack restart (essentially simulating an airplane mode toggle) using
34  * {@link ActiveModeWarden}.
35  * The current triggers for:
36  * 1. Last resort watchdog bite.
37  * 2. HAL/wificond crashes during normal operation.
38  * 3. TBD: supplicant crashes during normal operation.
39  */
40 public class SelfRecovery {
41     private static final String TAG = "WifiSelfRecovery";
42 
43     /**
44      * Reason codes for the various recovery triggers.
45      */
46     public static final int REASON_LAST_RESORT_WATCHDOG = 0;
47     public static final int REASON_WIFINATIVE_FAILURE = 1;
48     public static final int REASON_STA_IFACE_DOWN = 2;
49 
50     @Retention(RetentionPolicy.SOURCE)
51     @IntDef(prefix = {"REASON_"}, value = {
52             REASON_LAST_RESORT_WATCHDOG,
53             REASON_WIFINATIVE_FAILURE,
54             REASON_STA_IFACE_DOWN})
55     public @interface RecoveryReason {}
56 
57     protected static final String[] REASON_STRINGS = {
58             "Last Resort Watchdog",  // REASON_LAST_RESORT_WATCHDOG
59             "WifiNative Failure",    // REASON_WIFINATIVE_FAILURE
60             "Sta Interface Down"     // REASON_STA_IFACE_DOWN
61     };
62 
63     private final Context mContext;
64     private final ActiveModeWarden mActiveModeWarden;
65     private final Clock mClock;
66     // Time since boot (in millis) that restart occurred
67     private final LinkedList<Long> mPastRestartTimes;
SelfRecovery(Context context, ActiveModeWarden activeModeWarden, Clock clock)68     public SelfRecovery(Context context, ActiveModeWarden activeModeWarden, Clock clock) {
69         mContext = context;
70         mActiveModeWarden = activeModeWarden;
71         mClock = clock;
72         mPastRestartTimes = new LinkedList<>();
73     }
74 
75     /**
76      * Trigger recovery.
77      *
78      * This method does the following:
79      * 1. Checks reason code used to trigger recovery
80      * 2. Checks for sta iface down triggers and disables wifi by sending {@link
81      * ActiveModeWarden#recoveryDisableWifi()} to {@link ActiveModeWarden} to disable wifi.
82      * 3. Throttles restart calls for underlying native failures
83      * 4. Sends {@link ActiveModeWarden#recoveryRestartWifi(int)} to {@link ActiveModeWarden} to
84      * initiate the stack restart.
85      * @param reason One of the above |REASON_*| codes.
86      */
trigger(@ecoveryReason int reason)87     public void trigger(@RecoveryReason int reason) {
88         if (!(reason == REASON_LAST_RESORT_WATCHDOG || reason == REASON_WIFINATIVE_FAILURE
89                   || reason == REASON_STA_IFACE_DOWN)) {
90             Log.e(TAG, "Invalid trigger reason. Ignoring...");
91             return;
92         }
93         if (reason == REASON_STA_IFACE_DOWN) {
94             Log.e(TAG, "STA interface down, disable wifi");
95             mActiveModeWarden.recoveryDisableWifi();
96             return;
97         }
98 
99         Log.e(TAG, "Triggering recovery for reason: " + REASON_STRINGS[reason]);
100         if (reason == REASON_WIFINATIVE_FAILURE) {
101             int maxRecoveriesPerHour = mContext.getResources().getInteger(
102                     R.integer.config_wifiMaxNativeFailureSelfRecoveryPerHour);
103             if (maxRecoveriesPerHour == 0) {
104                 Log.e(TAG, "Recovery disabled. Disabling wifi");
105                 mActiveModeWarden.recoveryDisableWifi();
106                 return;
107             }
108             trimPastRestartTimes();
109             if (mPastRestartTimes.size() >= maxRecoveriesPerHour) {
110                 Log.e(TAG, "Already restarted wifi " + maxRecoveriesPerHour + " times in"
111                         + " last 1 hour. Disabling wifi");
112                 mActiveModeWarden.recoveryDisableWifi();
113                 return;
114             }
115             mPastRestartTimes.add(mClock.getElapsedSinceBootMillis());
116         }
117         mActiveModeWarden.recoveryRestartWifi(reason);
118     }
119 
120     /**
121      * Process the mPastRestartTimes list, removing elements outside the max restarts time window
122      */
trimPastRestartTimes()123     private void trimPastRestartTimes() {
124         Iterator<Long> iter = mPastRestartTimes.iterator();
125         long now = mClock.getElapsedSinceBootMillis();
126         while (iter.hasNext()) {
127             Long restartTimeMillis = iter.next();
128             if (now - restartTimeMillis > TimeUnit.HOURS.toMillis(1)) {
129                 iter.remove();
130             } else {
131                 break;
132             }
133         }
134     }
135 }
136