1 /* 2 * Copyright (C) 2020 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.location.gnss; 18 19 import android.content.Context; 20 import android.net.ConnectivityManager; 21 import android.net.NetworkInfo; 22 import android.os.Handler; 23 import android.os.Looper; 24 import android.os.PowerManager; 25 import android.os.PowerManager.WakeLock; 26 import android.util.Log; 27 import android.util.NtpTrustedTime; 28 29 import com.android.internal.annotations.GuardedBy; 30 import com.android.internal.annotations.VisibleForTesting; 31 32 import java.util.Date; 33 34 /** 35 * Handles inject NTP time to GNSS. 36 * 37 * <p>The client is responsible to call {@link #onNetworkAvailable()} when network is available 38 * for retrieving NTP Time. 39 */ 40 class NtpTimeHelper { 41 42 private static final String TAG = "NtpTimeHelper"; 43 private static final boolean DEBUG = Log.isLoggable(TAG, Log.DEBUG); 44 45 // states for injecting ntp 46 private static final int STATE_PENDING_NETWORK = 0; 47 private static final int STATE_RETRIEVING_AND_INJECTING = 1; 48 private static final int STATE_IDLE = 2; 49 50 // how often to request NTP time, in milliseconds 51 // current setting 24 hours 52 @VisibleForTesting 53 static final long NTP_INTERVAL = 24 * 60 * 60 * 1000; 54 55 // how long to wait if we have a network error in NTP 56 // the initial value of the exponential backoff 57 // current setting - 5 minutes 58 @VisibleForTesting 59 static final long RETRY_INTERVAL = 5 * 60 * 1000; 60 // how long to wait if we have a network error in NTP 61 // the max value of the exponential backoff 62 // current setting - 4 hours 63 private static final long MAX_RETRY_INTERVAL = 4 * 60 * 60 * 1000; 64 65 private static final long WAKELOCK_TIMEOUT_MILLIS = 60 * 1000; 66 private static final String WAKELOCK_KEY = "NtpTimeHelper"; 67 68 private final ExponentialBackOff mNtpBackOff = new ExponentialBackOff(RETRY_INTERVAL, 69 MAX_RETRY_INTERVAL); 70 71 private final ConnectivityManager mConnMgr; 72 private final NtpTrustedTime mNtpTime; 73 private final WakeLock mWakeLock; 74 private final Handler mHandler; 75 76 @GuardedBy("this") 77 private final InjectNtpTimeCallback mCallback; 78 79 // flags to trigger NTP when network becomes available 80 // initialized to STATE_PENDING_NETWORK so we do NTP when the network comes up after booting 81 @GuardedBy("this") 82 private int mInjectNtpTimeState = STATE_PENDING_NETWORK; 83 84 // set to true if the GPS engine requested on-demand NTP time requests 85 @GuardedBy("this") 86 private boolean mOnDemandTimeInjection; 87 88 interface InjectNtpTimeCallback { injectTime(long time, long timeReference, int uncertainty)89 void injectTime(long time, long timeReference, int uncertainty); 90 } 91 92 @VisibleForTesting NtpTimeHelper(Context context, Looper looper, InjectNtpTimeCallback callback, NtpTrustedTime ntpTime)93 NtpTimeHelper(Context context, Looper looper, InjectNtpTimeCallback callback, 94 NtpTrustedTime ntpTime) { 95 mConnMgr = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE); 96 mCallback = callback; 97 mNtpTime = ntpTime; 98 mHandler = new Handler(looper); 99 PowerManager powerManager = (PowerManager) context.getSystemService(Context.POWER_SERVICE); 100 mWakeLock = powerManager.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK, WAKELOCK_KEY); 101 } 102 NtpTimeHelper(Context context, Looper looper, InjectNtpTimeCallback callback)103 NtpTimeHelper(Context context, Looper looper, InjectNtpTimeCallback callback) { 104 this(context, looper, callback, NtpTrustedTime.getInstance(context)); 105 } 106 enablePeriodicTimeInjection()107 synchronized void enablePeriodicTimeInjection() { 108 mOnDemandTimeInjection = true; 109 } 110 onNetworkAvailable()111 synchronized void onNetworkAvailable() { 112 if (mInjectNtpTimeState == STATE_PENDING_NETWORK) { 113 retrieveAndInjectNtpTime(); 114 } 115 } 116 117 /** 118 * @return {@code true} if there is a network available for outgoing connections, 119 * {@code false} otherwise. 120 */ isNetworkConnected()121 private boolean isNetworkConnected() { 122 NetworkInfo activeNetworkInfo = mConnMgr.getActiveNetworkInfo(); 123 return activeNetworkInfo != null && activeNetworkInfo.isConnected(); 124 } 125 retrieveAndInjectNtpTime()126 synchronized void retrieveAndInjectNtpTime() { 127 if (mInjectNtpTimeState == STATE_RETRIEVING_AND_INJECTING) { 128 // already downloading data 129 return; 130 } 131 if (!isNetworkConnected()) { 132 // try again when network is up 133 mInjectNtpTimeState = STATE_PENDING_NETWORK; 134 return; 135 } 136 mInjectNtpTimeState = STATE_RETRIEVING_AND_INJECTING; 137 138 // hold wake lock while task runs 139 mWakeLock.acquire(WAKELOCK_TIMEOUT_MILLIS); 140 new Thread(this::blockingGetNtpTimeAndInject).start(); 141 } 142 143 /** {@link NtpTrustedTime#forceRefresh} is a blocking network operation. */ blockingGetNtpTimeAndInject()144 private void blockingGetNtpTimeAndInject() { 145 long delay; 146 147 // force refresh NTP cache when outdated 148 boolean refreshSuccess = true; 149 NtpTrustedTime.TimeResult ntpResult = mNtpTime.getCachedTimeResult(); 150 if (ntpResult == null || ntpResult.getAgeMillis() >= NTP_INTERVAL) { 151 // Blocking network operation. 152 refreshSuccess = mNtpTime.forceRefresh(); 153 } 154 155 synchronized (this) { 156 mInjectNtpTimeState = STATE_IDLE; 157 158 // only update when NTP time is fresh 159 // If refreshSuccess is false, cacheAge does not drop down. 160 ntpResult = mNtpTime.getCachedTimeResult(); 161 if (ntpResult != null && ntpResult.getAgeMillis() < NTP_INTERVAL) { 162 long time = ntpResult.getTimeMillis(); 163 long timeReference = ntpResult.getElapsedRealtimeMillis(); 164 long certainty = ntpResult.getCertaintyMillis(); 165 166 if (DEBUG) { 167 long now = System.currentTimeMillis(); 168 Log.d(TAG, "NTP server returned: " 169 + time + " (" + new Date(time) + ")" 170 + " ntpResult: " + ntpResult 171 + " system time offset: " + (time - now)); 172 } 173 174 // Ok to cast to int, as can't rollover in practice 175 mHandler.post(() -> mCallback.injectTime(time, timeReference, (int) certainty)); 176 177 delay = NTP_INTERVAL; 178 mNtpBackOff.reset(); 179 } else { 180 Log.e(TAG, "requestTime failed"); 181 delay = mNtpBackOff.nextBackoffMillis(); 182 } 183 184 if (DEBUG) { 185 Log.d(TAG, String.format( 186 "onDemandTimeInjection=%s, refreshSuccess=%s, delay=%s", 187 mOnDemandTimeInjection, 188 refreshSuccess, 189 delay)); 190 } 191 // TODO(b/73893222): reconcile Capabilities bit 'on demand' name vs. de facto periodic 192 // injection. 193 if (mOnDemandTimeInjection || !refreshSuccess) { 194 /* Schedule next NTP injection. 195 * Since this is delayed, the wake lock is released right away, and will be held 196 * again when the delayed task runs. 197 */ 198 mHandler.postDelayed(this::retrieveAndInjectNtpTime, delay); 199 } 200 } 201 // release wake lock held by task 202 mWakeLock.release(); 203 } 204 } 205