1/*
2 * Copyright (C) 2010 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
17package com.android.server;
18
19import android.app.AlarmManager;
20import android.app.PendingIntent;
21import android.content.BroadcastReceiver;
22import android.content.ContentResolver;
23import android.content.Context;
24import android.content.Intent;
25import android.content.IntentFilter;
26import android.database.ContentObserver;
27import android.net.ConnectivityManager;
28import android.net.NetworkInfo;
29import android.os.Handler;
30import android.os.HandlerThread;
31import android.os.Looper;
32import android.os.Message;
33import android.os.SystemClock;
34import android.provider.Settings;
35import android.util.Log;
36import android.util.NtpTrustedTime;
37import android.util.TrustedTime;
38
39import com.android.internal.telephony.TelephonyIntents;
40
41/**
42 * Monitors the network time and updates the system time if it is out of sync
43 * and there hasn't been any NITZ update from the carrier recently.
44 * If looking up the network time fails for some reason, it tries a few times with a short
45 * interval and then resets to checking on longer intervals.
46 * <p>
47 * If the user enables AUTO_TIME, it will check immediately for the network time, if NITZ wasn't
48 * available.
49 * </p>
50 */
51public class NetworkTimeUpdateService {
52
53    private static final String TAG = "NetworkTimeUpdateService";
54    private static final boolean DBG = false;
55
56    private static final int EVENT_AUTO_TIME_CHANGED = 1;
57    private static final int EVENT_POLL_NETWORK_TIME = 2;
58    private static final int EVENT_NETWORK_CHANGED = 3;
59
60    private static final String ACTION_POLL =
61            "com.android.server.NetworkTimeUpdateService.action.POLL";
62    private static int POLL_REQUEST = 0;
63
64    private static final long NOT_SET = -1;
65    private long mNitzTimeSetTime = NOT_SET;
66    // TODO: Have a way to look up the timezone we are in
67    private long mNitzZoneSetTime = NOT_SET;
68
69    private Context mContext;
70    private TrustedTime mTime;
71
72    // NTP lookup is done on this thread and handler
73    private Handler mHandler;
74    private AlarmManager mAlarmManager;
75    private PendingIntent mPendingPollIntent;
76    private SettingsObserver mSettingsObserver;
77    // The last time that we successfully fetched the NTP time.
78    private long mLastNtpFetchTime = NOT_SET;
79
80    // Normal polling frequency
81    private final long mPollingIntervalMs;
82    // Try-again polling interval, in case the network request failed
83    private final long mPollingIntervalShorterMs;
84    // Number of times to try again
85    private final int mTryAgainTimesMax;
86    // If the time difference is greater than this threshold, then update the time.
87    private final int mTimeErrorThresholdMs;
88    // Keeps track of how many quick attempts were made to fetch NTP time.
89    // During bootup, the network may not have been up yet, or it's taking time for the
90    // connection to happen.
91    private int mTryAgainCounter;
92
93    public NetworkTimeUpdateService(Context context) {
94        mContext = context;
95        mTime = NtpTrustedTime.getInstance(context);
96        mAlarmManager = (AlarmManager) mContext.getSystemService(Context.ALARM_SERVICE);
97        Intent pollIntent = new Intent(ACTION_POLL, null);
98        mPendingPollIntent = PendingIntent.getBroadcast(mContext, POLL_REQUEST, pollIntent, 0);
99
100        mPollingIntervalMs = mContext.getResources().getInteger(
101                com.android.internal.R.integer.config_ntpPollingInterval);
102        mPollingIntervalShorterMs = mContext.getResources().getInteger(
103                com.android.internal.R.integer.config_ntpPollingIntervalShorter);
104        mTryAgainTimesMax = mContext.getResources().getInteger(
105                com.android.internal.R.integer.config_ntpRetry);
106        mTimeErrorThresholdMs = mContext.getResources().getInteger(
107                com.android.internal.R.integer.config_ntpThreshold);
108    }
109
110    /** Initialize the receivers and initiate the first NTP request */
111    public void systemRunning() {
112        registerForTelephonyIntents();
113        registerForAlarms();
114        registerForConnectivityIntents();
115
116        HandlerThread thread = new HandlerThread(TAG);
117        thread.start();
118        mHandler = new MyHandler(thread.getLooper());
119        // Check the network time on the new thread
120        mHandler.obtainMessage(EVENT_POLL_NETWORK_TIME).sendToTarget();
121
122        mSettingsObserver = new SettingsObserver(mHandler, EVENT_AUTO_TIME_CHANGED);
123        mSettingsObserver.observe(mContext);
124    }
125
126    private void registerForTelephonyIntents() {
127        IntentFilter intentFilter = new IntentFilter();
128        intentFilter.addAction(TelephonyIntents.ACTION_NETWORK_SET_TIME);
129        intentFilter.addAction(TelephonyIntents.ACTION_NETWORK_SET_TIMEZONE);
130        mContext.registerReceiver(mNitzReceiver, intentFilter);
131    }
132
133    private void registerForAlarms() {
134        mContext.registerReceiver(
135            new BroadcastReceiver() {
136                @Override
137                public void onReceive(Context context, Intent intent) {
138                    mHandler.obtainMessage(EVENT_POLL_NETWORK_TIME).sendToTarget();
139                }
140            }, new IntentFilter(ACTION_POLL));
141    }
142
143    private void registerForConnectivityIntents() {
144        IntentFilter intentFilter = new IntentFilter();
145        intentFilter.addAction(ConnectivityManager.CONNECTIVITY_ACTION);
146        mContext.registerReceiver(mConnectivityReceiver, intentFilter);
147    }
148
149    private void onPollNetworkTime(int event) {
150        // If Automatic time is not set, don't bother.
151        if (!isAutomaticTimeRequested()) return;
152
153        final long refTime = SystemClock.elapsedRealtime();
154        // If NITZ time was received less than mPollingIntervalMs time ago,
155        // no need to sync to NTP.
156        if (mNitzTimeSetTime != NOT_SET && refTime - mNitzTimeSetTime < mPollingIntervalMs) {
157            resetAlarm(mPollingIntervalMs);
158            return;
159        }
160        final long currentTime = System.currentTimeMillis();
161        if (DBG) Log.d(TAG, "System time = " + currentTime);
162        // Get the NTP time
163        if (mLastNtpFetchTime == NOT_SET || refTime >= mLastNtpFetchTime + mPollingIntervalMs
164                || event == EVENT_AUTO_TIME_CHANGED) {
165            if (DBG) Log.d(TAG, "Before Ntp fetch");
166
167            // force refresh NTP cache when outdated
168            if (mTime.getCacheAge() >= mPollingIntervalMs) {
169                mTime.forceRefresh();
170            }
171
172            // only update when NTP time is fresh
173            if (mTime.getCacheAge() < mPollingIntervalMs) {
174                final long ntp = mTime.currentTimeMillis();
175                mTryAgainCounter = 0;
176                // If the clock is more than N seconds off or this is the first time it's been
177                // fetched since boot, set the current time.
178                if (Math.abs(ntp - currentTime) > mTimeErrorThresholdMs
179                        || mLastNtpFetchTime == NOT_SET) {
180                    // Set the system time
181                    if (DBG && mLastNtpFetchTime == NOT_SET
182                            && Math.abs(ntp - currentTime) <= mTimeErrorThresholdMs) {
183                        Log.d(TAG, "For initial setup, rtc = " + currentTime);
184                    }
185                    if (DBG) Log.d(TAG, "Ntp time to be set = " + ntp);
186                    // Make sure we don't overflow, since it's going to be converted to an int
187                    if (ntp / 1000 < Integer.MAX_VALUE) {
188                        SystemClock.setCurrentTimeMillis(ntp);
189                    }
190                } else {
191                    if (DBG) Log.d(TAG, "Ntp time is close enough = " + ntp);
192                }
193                mLastNtpFetchTime = SystemClock.elapsedRealtime();
194            } else {
195                // Try again shortly
196                mTryAgainCounter++;
197                if (mTryAgainTimesMax < 0 || mTryAgainCounter <= mTryAgainTimesMax) {
198                    resetAlarm(mPollingIntervalShorterMs);
199                } else {
200                    // Try much later
201                    mTryAgainCounter = 0;
202                    resetAlarm(mPollingIntervalMs);
203                }
204                return;
205            }
206        }
207        resetAlarm(mPollingIntervalMs);
208    }
209
210    /**
211     * Cancel old alarm and starts a new one for the specified interval.
212     *
213     * @param interval when to trigger the alarm, starting from now.
214     */
215    private void resetAlarm(long interval) {
216        mAlarmManager.cancel(mPendingPollIntent);
217        long now = SystemClock.elapsedRealtime();
218        long next = now + interval;
219        mAlarmManager.set(AlarmManager.ELAPSED_REALTIME, next, mPendingPollIntent);
220    }
221
222    /**
223     * Checks if the user prefers to automatically set the time.
224     */
225    private boolean isAutomaticTimeRequested() {
226        return Settings.Global.getInt(
227                mContext.getContentResolver(), Settings.Global.AUTO_TIME, 0) != 0;
228    }
229
230    /** Receiver for Nitz time events */
231    private BroadcastReceiver mNitzReceiver = new BroadcastReceiver() {
232
233        @Override
234        public void onReceive(Context context, Intent intent) {
235            String action = intent.getAction();
236            if (TelephonyIntents.ACTION_NETWORK_SET_TIME.equals(action)) {
237                mNitzTimeSetTime = SystemClock.elapsedRealtime();
238            } else if (TelephonyIntents.ACTION_NETWORK_SET_TIMEZONE.equals(action)) {
239                mNitzZoneSetTime = SystemClock.elapsedRealtime();
240            }
241        }
242    };
243
244    /** Receiver for ConnectivityManager events */
245    private BroadcastReceiver mConnectivityReceiver = new BroadcastReceiver() {
246
247        @Override
248        public void onReceive(Context context, Intent intent) {
249            String action = intent.getAction();
250            if (ConnectivityManager.CONNECTIVITY_ACTION.equals(action)) {
251                // Don't bother checking if we have connectivity, NtpTrustedTime does that for us.
252                mHandler.obtainMessage(EVENT_NETWORK_CHANGED).sendToTarget();
253            }
254        }
255    };
256
257    /** Handler to do the network accesses on */
258    private class MyHandler extends Handler {
259
260        public MyHandler(Looper l) {
261            super(l);
262        }
263
264        @Override
265        public void handleMessage(Message msg) {
266            switch (msg.what) {
267                case EVENT_AUTO_TIME_CHANGED:
268                case EVENT_POLL_NETWORK_TIME:
269                case EVENT_NETWORK_CHANGED:
270                    onPollNetworkTime(msg.what);
271                    break;
272            }
273        }
274    }
275
276    /** Observer to watch for changes to the AUTO_TIME setting */
277    private static class SettingsObserver extends ContentObserver {
278
279        private int mMsg;
280        private Handler mHandler;
281
282        SettingsObserver(Handler handler, int msg) {
283            super(handler);
284            mHandler = handler;
285            mMsg = msg;
286        }
287
288        void observe(Context context) {
289            ContentResolver resolver = context.getContentResolver();
290            resolver.registerContentObserver(Settings.Global.getUriFor(Settings.Global.AUTO_TIME),
291                    false, this);
292        }
293
294        @Override
295        public void onChange(boolean selfChange) {
296            mHandler.obtainMessage(mMsg).sendToTarget();
297        }
298    }
299}
300