content: /*
   * Copyright (C) 2010 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;
  
  import android.app.AlarmManager;
  import android.app.PendingIntent;
  import android.content.BroadcastReceiver;
  import android.content.ContentResolver;
  import android.content.Context;
  import android.content.Intent;
  import android.content.IntentFilter;
  import android.database.ContentObserver;
  import android.net.ConnectivityManager;
  import android.net.ConnectivityManager.NetworkCallback;
  import android.net.Network;
  import android.os.Binder;
  import android.os.Handler;
  import android.os.HandlerThread;
  import android.os.Looper;
  import android.os.Message;
  import android.os.PowerManager;
  import android.os.SystemClock;
  import android.provider.Settings;
  import android.util.Log;
  import android.util.NtpTrustedTime;
  import android.util.TimeUtils;
  
  import com.android.internal.telephony.TelephonyIntents;
  import com.android.internal.util.DumpUtils;
  
  import java.io.FileDescriptor;
  import java.io.PrintWriter;
  
  /**
   * Monitors the network time and updates the system time if it is out of sync
   * and there hasn't been any NITZ update from the carrier recently.
   * If looking up the network time fails for some reason, it tries a few times with a short
   * interval and then resets to checking on longer intervals.
   * <p>
   * If the user enables AUTO_TIME, it will check immediately for the network time, if NITZ wasn't
   * available.
   * </p>
   */
  public class NewNetworkTimeUpdateService extends Binder implements NetworkTimeUpdateService {
  
      private static final String TAG = "NetworkTimeUpdateService";
      private static final boolean DBG = false;
  
      private static final int EVENT_AUTO_TIME_CHANGED = 1;
      private static final int EVENT_POLL_NETWORK_TIME = 2;
      private static final int EVENT_NETWORK_CHANGED = 3;
  
      private static final String ACTION_POLL =
              "com.android.server.NetworkTimeUpdateService.action.POLL";
  
      private static final int POLL_REQUEST = 0;
  
      private static final long NOT_SET = -1;
      private long mNitzTimeSetTime = NOT_SET;
      private Network mDefaultNetwork = null;
  
      private final Context mContext;
      private final NtpTrustedTime mTime;
      private final AlarmManager mAlarmManager;
      private final ConnectivityManager mCM;
      private final PendingIntent mPendingPollIntent;
      private final PowerManager.WakeLock mWakeLock;
  
      // NTP lookup is done on this thread and handler
      private Handler mHandler;
      private SettingsObserver mSettingsObserver;
      private NetworkTimeUpdateCallback mNetworkTimeUpdateCallback;
  
      // Normal polling frequency
      private final long mPollingIntervalMs;
      // Try-again polling interval, in case the network request failed
      private final long mPollingIntervalShorterMs;
      // Number of times to try again
      private final int mTryAgainTimesMax;
      // If the time difference is greater than this threshold, then update the time.
      private final int mTimeErrorThresholdMs;
      // Keeps track of how many quick attempts were made to fetch NTP time.
      // During bootup, the network may not have been up yet, or it's taking time for the
      // connection to happen.
      private int mTryAgainCounter;
  
      public NewNetworkTimeUpdateService(Context context) {
          mContext = context;
          mTime = NtpTrustedTime.getInstance(context);
          mAlarmManager = mContext.getSystemService(AlarmManager.class);
          mCM = mContext.getSystemService(ConnectivityManager.class);
  
          Intent pollIntent = new Intent(ACTION_POLL, null);
          mPendingPollIntent = PendingIntent.getBroadcast(mContext, POLL_REQUEST, pollIntent, 0);
  
          mPollingIntervalMs = mContext.getResources().getInteger(
                  com.android.internal.R.integer.config_ntpPollingInterval);
          mPollingIntervalShorterMs = mContext.getResources().getInteger(
                  com.android.internal.R.integer.config_ntpPollingIntervalShorter);
          mTryAgainTimesMax = mContext.getResources().getInteger(
                  com.android.internal.R.integer.config_ntpRetry);
          mTimeErrorThresholdMs = mContext.getResources().getInteger(
                  com.android.internal.R.integer.config_ntpThreshold);
  
          mWakeLock = context.getSystemService(PowerManager.class).newWakeLock(
                  PowerManager.PARTIAL_WAKE_LOCK, TAG);
      }
  
      @Override
      public void systemRunning() {
          registerForTelephonyIntents();
          registerForAlarms();
  
          HandlerThread thread = new HandlerThread(TAG);
          thread.start();
          mHandler = new MyHandler(thread.getLooper());
          mNetworkTimeUpdateCallback = new NetworkTimeUpdateCallback();
          mCM.registerDefaultNetworkCallback(mNetworkTimeUpdateCallback, mHandler);
  
          mSettingsObserver = new SettingsObserver(mHandler, EVENT_AUTO_TIME_CHANGED);
          mSettingsObserver.observe(mContext);
      }
  
      private void registerForTelephonyIntents() {
          IntentFilter intentFilter = new IntentFilter();
          intentFilter.addAction(TelephonyIntents.ACTION_NETWORK_SET_TIME);
          mContext.registerReceiver(mNitzReceiver, intentFilter);
      }
  
      private void registerForAlarms() {
          mContext.registerReceiver(
              new BroadcastReceiver() {
                  @Override
                  public void onReceive(Context context, Intent intent) {
                      mHandler.obtainMessage(EVENT_POLL_NETWORK_TIME).sendToTarget();
                  }
              }, new IntentFilter(ACTION_POLL));
      }
  
      private void onPollNetworkTime(int event) {
          // If Automatic time is not set, don't bother. Similarly, if we don't
          // have any default network, don't bother.
          if (mDefaultNetwork == null) return;
          mWakeLock.acquire();
          try {
              onPollNetworkTimeUnderWakeLock(event);
          } finally {
              mWakeLock.release();
          }
      }
  
      private void onPollNetworkTimeUnderWakeLock(int event) {
          // Force an NTP fix when outdated
          if (mTime.getCacheAge() >= mPollingIntervalMs) {
              if (DBG) Log.d(TAG, "Stale NTP fix; forcing refresh");
              mTime.forceRefresh();
          }
  
          if (mTime.getCacheAge() < mPollingIntervalMs) {
              // Obtained fresh fix; schedule next normal update
              resetAlarm(mPollingIntervalMs);
              if (isAutomaticTimeRequested()) {
                  updateSystemClock(event);
              }
  
          } else {
              // No fresh fix; schedule retry
              mTryAgainCounter++;
              if (mTryAgainTimesMax < 0 || mTryAgainCounter <= mTryAgainTimesMax) {
                  resetAlarm(mPollingIntervalShorterMs);
              } else {
                  // Try much later
                  mTryAgainCounter = 0;
                  resetAlarm(mPollingIntervalMs);
              }
          }
      }
  
      private long getNitzAge() {
          if (mNitzTimeSetTime == NOT_SET) {
              return Long.MAX_VALUE;
          } else {
              return SystemClock.elapsedRealtime() - mNitzTimeSetTime;
          }
      }
  
      /**
       * Consider updating system clock based on current NTP fix, if requested by
       * user, significant enough delta, and we don't have a recent NITZ.
       */
      private void updateSystemClock(int event) {
          final boolean forceUpdate = (event == EVENT_AUTO_TIME_CHANGED);
          if (!forceUpdate) {
              if (getNitzAge() < mPollingIntervalMs) {
                  if (DBG) Log.d(TAG, "Ignoring NTP update due to recent NITZ");
                  return;
              }
  
              final long skew = Math.abs(mTime.currentTimeMillis() - System.currentTimeMillis());
              if (skew < mTimeErrorThresholdMs) {
                  if (DBG) Log.d(TAG, "Ignoring NTP update due to low skew");
                  return;
              }
          }
  
          SystemClock.setCurrentTimeMillis(mTime.currentTimeMillis());
      }
  
      /**
       * Cancel old alarm and starts a new one for the specified interval.
       *
       * @param interval when to trigger the alarm, starting from now.
       */
      private void resetAlarm(long interval) {
          mAlarmManager.cancel(mPendingPollIntent);
          long now = SystemClock.elapsedRealtime();
          long next = now + interval;
          mAlarmManager.set(AlarmManager.ELAPSED_REALTIME, next, mPendingPollIntent);
      }
  
      /**
       * Checks if the user prefers to automatically set the time.
       */
      private boolean isAutomaticTimeRequested() {
          return Settings.Global.getInt(
                  mContext.getContentResolver(), Settings.Global.AUTO_TIME, 0) != 0;
      }
  
      /** Receiver for Nitz time events */
      private BroadcastReceiver mNitzReceiver = new BroadcastReceiver() {
  
          @Override
          public void onReceive(Context context, Intent intent) {
              String action = intent.getAction();
              if (DBG) Log.d(TAG, "Received " + action);
              if (TelephonyIntents.ACTION_NETWORK_SET_TIME.equals(action)) {
                  mNitzTimeSetTime = SystemClock.elapsedRealtime();
              }
          }
      };
  
      /** Handler to do the network accesses on */
      private class MyHandler extends Handler {
  
          public MyHandler(Looper l) {
              super(l);
          }
  
          @Override
          public void handleMessage(Message msg) {
              switch (msg.what) {
                  case EVENT_AUTO_TIME_CHANGED:
                  case EVENT_POLL_NETWORK_TIME:
                  case EVENT_NETWORK_CHANGED:
                      onPollNetworkTime(msg.what);
                      break;
              }
          }
      }
  
      private class NetworkTimeUpdateCallback extends NetworkCallback {
          @Override
          public void onAvailable(Network network) {
              Log.d(TAG, String.format("New default network %s; checking time.", network));
              mDefaultNetwork = network;
              // Running on mHandler so invoke directly.
              onPollNetworkTime(EVENT_NETWORK_CHANGED);
          }
  
          @Override
          public void onLost(Network network) {
              if (network.equals(mDefaultNetwork)) mDefaultNetwork = null;
          }
      }
  
      /** Observer to watch for changes to the AUTO_TIME setting */
      private static class SettingsObserver extends ContentObserver {
  
          private int mMsg;
          private Handler mHandler;
  
          SettingsObserver(Handler handler, int msg) {
              super(handler);
              mHandler = handler;
              mMsg = msg;
          }
  
          void observe(Context context) {
              ContentResolver resolver = context.getContentResolver();
              resolver.registerContentObserver(Settings.Global.getUriFor(Settings.Global.AUTO_TIME),
                      false, this);
          }
  
          @Override
          public void onChange(boolean selfChange) {
              mHandler.obtainMessage(mMsg).sendToTarget();
          }
      }
  
      @Override
      protected void dump(FileDescriptor fd, PrintWriter pw, String[] args) {
          if (!DumpUtils.checkDumpPermission(mContext, TAG, pw)) return;
          pw.print("PollingIntervalMs: ");
          TimeUtils.formatDuration(mPollingIntervalMs, pw);
          pw.print("\nPollingIntervalShorterMs: ");
          TimeUtils.formatDuration(mPollingIntervalShorterMs, pw);
          pw.println("\nTryAgainTimesMax: " + mTryAgainTimesMax);
          pw.print("TimeErrorThresholdMs: ");
          TimeUtils.formatDuration(mTimeErrorThresholdMs, pw);
          pw.println("\nTryAgainCounter: " + mTryAgainCounter);
          pw.println("NTP cache age: " + mTime.getCacheAge());
          pw.println("NTP cache certainty: " + mTime.getCacheCertainty());
          pw.println();
      }
  }
  