Merge "Change NetworkTimeUpdateServiceImpl behavior"

core/java/android/app/timedetector/ITimeDetectorService.aidl

@@ -17,6 +17,7 @@
 package android.app.timedetector;
 
 import android.app.timedetector.ManualTimeSuggestion;
+import android.app.timedetector.NetworkTimeSuggestion;
 import android.app.timedetector.PhoneTimeSuggestion;
 
 /**
@@ -35,4 +36,5 @@ import android.app.timedetector.PhoneTimeSuggestion;
 interface ITimeDetectorService {
   void suggestPhoneTime(in PhoneTimeSuggestion timeSuggestion);
   void suggestManualTime(in ManualTimeSuggestion timeSuggestion);
+  void suggestNetworkTime(in NetworkTimeSuggestion timeSuggestion);
 }

core/java/android/app/timedetector/NetworkTimeSuggestion.aidl

@@ -0,0 +1,19 @@
+/*
+ * Copyright (C) 2019 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 android.app.timedetector;
+
+parcelable NetworkTimeSuggestion;

core/java/android/app/timedetector/NetworkTimeSuggestion.java

@@ -0,0 +1,129 @@
+/*
+ * Copyright (C) 2019 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 android.app.timedetector;
+
+import android.annotation.NonNull;
+import android.annotation.Nullable;
+import android.os.Parcel;
+import android.os.Parcelable;
+import android.util.TimestampedValue;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.List;
+import java.util.Objects;
+
+/**
+ * A time signal from a network time source like NTP. The value consists of the number of
+ * milliseconds elapsed since 1/1/1970 00:00:00 UTC and the time according to the elapsed realtime
+ * clock when that number was established. The elapsed realtime clock is considered accurate but
+ * volatile, so time signals must not be persisted across device resets.
+ *
+ * @hide
+ */
+public final class NetworkTimeSuggestion implements Parcelable {
+
+    public static final @NonNull Creator<NetworkTimeSuggestion> CREATOR =
+            new Creator<NetworkTimeSuggestion>() {
+                public NetworkTimeSuggestion createFromParcel(Parcel in) {
+                    return NetworkTimeSuggestion.createFromParcel(in);
+                }
+
+                public NetworkTimeSuggestion[] newArray(int size) {
+                    return new NetworkTimeSuggestion[size];
+                }
+            };
+
+    @NonNull
+    private final TimestampedValue<Long> mUtcTime;
+    @Nullable
+    private ArrayList<String> mDebugInfo;
+
+    public NetworkTimeSuggestion(@NonNull TimestampedValue<Long> utcTime) {
+        mUtcTime = Objects.requireNonNull(utcTime);
+        Objects.requireNonNull(utcTime.getValue());
+    }
+
+    private static NetworkTimeSuggestion createFromParcel(Parcel in) {
+        TimestampedValue<Long> utcTime = in.readParcelable(null /* classLoader */);
+        NetworkTimeSuggestion suggestion = new NetworkTimeSuggestion(utcTime);
+        @SuppressWarnings("unchecked")
+        ArrayList<String> debugInfo = (ArrayList<String>) in.readArrayList(null /* classLoader */);
+        suggestion.mDebugInfo = debugInfo;
+        return suggestion;
+    }
+
+    @Override
+    public int describeContents() {
+        return 0;
+    }
+
+    @Override
+    public void writeToParcel(@NonNull Parcel dest, int flags) {
+        dest.writeParcelable(mUtcTime, 0);
+        dest.writeList(mDebugInfo);
+    }
+
+    @NonNull
+    public TimestampedValue<Long> getUtcTime() {
+        return mUtcTime;
+    }
+
+    @NonNull
+    public List<String> getDebugInfo() {
+        return mDebugInfo == null
+                ? Collections.emptyList() : Collections.unmodifiableList(mDebugInfo);
+    }
+
+    /**
+     * Associates information with the instance that can be useful for debugging / logging. The
+     * information is present in {@link #toString()} but is not considered for
+     * {@link #equals(Object)} and {@link #hashCode()}.
+     */
+    public void addDebugInfo(String... debugInfos) {
+        if (mDebugInfo == null) {
+            mDebugInfo = new ArrayList<>();
+        }
+        mDebugInfo.addAll(Arrays.asList(debugInfos));
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) {
+            return true;
+        }
+        if (o == null || getClass() != o.getClass()) {
+            return false;
+        }
+        NetworkTimeSuggestion that = (NetworkTimeSuggestion) o;
+        return Objects.equals(mUtcTime, that.mUtcTime);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(mUtcTime);
+    }
+
+    @Override
+    public String toString() {
+        return "NetworkTimeSuggestion{"
+                + "mUtcTime=" + mUtcTime
+                + ", mDebugInfo=" + mDebugInfo
+                + '}';
+    }
+}

core/java/android/app/timedetector/TimeDetector.java

@@ -85,4 +85,19 @@ public class TimeDetector {
         manualTimeSuggestion.addDebugInfo(why);
         return manualTimeSuggestion;
     }
+
+    /**
+     * Suggests the time according to a network time source like NTP.
+     */
+    @RequiresPermission(android.Manifest.permission.SET_TIME)
+    public void suggestNetworkTime(NetworkTimeSuggestion timeSuggestion) {
+        if (DEBUG) {
+            Log.d(TAG, "suggestNetworkTime called: " + timeSuggestion);
+        }
+        try {
+            mITimeDetectorService.suggestNetworkTime(timeSuggestion);
+        } catch (RemoteException e) {
+            throw e.rethrowFromSystemServer();
+        }
+    }
 }

core/java/android/util/NtpTrustedTime.java

@@ -175,4 +175,22 @@ public class NtpTrustedTime implements TrustedTime {
     public long getCachedNtpTimeReference() {
         return mCachedNtpElapsedRealtime;
     }
+
+    /**
+     * Returns the combination of {@link #getCachedNtpTime()} and {@link
+     * #getCachedNtpTimeReference()} as a {@link TimestampedValue}. This method is useful when
+     * passing the time to another component that will adjust for elapsed time.
+     *
+     * @throws IllegalStateException if there is no cached value
+     */
+    @UnsupportedAppUsage
+    public TimestampedValue<Long> getCachedNtpTimeSignal() {
+        if (!mHasCache) {
+            throw new IllegalStateException("Missing authoritative time source");
+        }
+        if (LOGD) Log.d(TAG, "currentTimeMillis() cache hit");
+
+        return new TimestampedValue<>(mCachedNtpElapsedRealtime, mCachedNtpTime);
+    }
+
 }

core/res/res/values/config.xml

@@ -2266,9 +2266,6 @@
     <!-- Number of times to try again with the shorter interval, before backing
          off until the normal polling interval. A value < 0 indicates infinite. -->
     <integer name="config_ntpRetry">3</integer>
-    <!-- If the time difference is greater than this threshold in milliseconds,
-         then update the time. -->
-    <integer name="config_ntpThreshold">5000</integer>
     <!-- Timeout to wait for NTP server response in milliseconds. -->
     <integer name="config_ntpTimeout">5000</integer>
 

core/res/res/values/symbols.xml

@@ -489,7 +489,6 @@
   <java-symbol type="integer" name="config_ntpPollingInterval" />
   <java-symbol type="integer" name="config_ntpPollingIntervalShorter" />
   <java-symbol type="integer" name="config_ntpRetry" />
-  <java-symbol type="integer" name="config_ntpThreshold" />
   <java-symbol type="integer" name="config_ntpTimeout" />
   <java-symbol type="integer" name="config_shortPressOnPowerBehavior" />
   <java-symbol type="integer" name="config_toastDefaultGravity" />

core/tests/coretests/src/android/app/timedetector/NetworkTimeSuggestionTest.java

@@ -0,0 +1,66 @@
+/*
+ * Copyright 2019 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 android.app.timedetector;
+
+import static android.app.timezonedetector.ParcelableTestSupport.assertRoundTripParcelable;
+import static android.app.timezonedetector.ParcelableTestSupport.roundTripParcelable;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotEquals;
+
+import android.util.TimestampedValue;
+
+import org.junit.Test;
+
+public class NetworkTimeSuggestionTest {
+
+    private static final TimestampedValue<Long> ARBITRARY_TIME =
+            new TimestampedValue<>(1111L, 2222L);
+
+    @Test
+    public void testEquals() {
+        NetworkTimeSuggestion one = new NetworkTimeSuggestion(ARBITRARY_TIME);
+        assertEquals(one, one);
+
+        NetworkTimeSuggestion two = new NetworkTimeSuggestion(ARBITRARY_TIME);
+        assertEquals(one, two);
+        assertEquals(two, one);
+
+        TimestampedValue<Long> differentTime = new TimestampedValue<>(
+                ARBITRARY_TIME.getReferenceTimeMillis() + 1,
+                ARBITRARY_TIME.getValue());
+        NetworkTimeSuggestion three = new NetworkTimeSuggestion(differentTime);
+        assertNotEquals(one, three);
+        assertNotEquals(three, one);
+
+        // DebugInfo must not be considered in equals().
+        one.addDebugInfo("Debug info 1");
+        two.addDebugInfo("Debug info 2");
+        assertEquals(one, two);
+    }
+
+    @Test
+    public void testParcelable() {
+        NetworkTimeSuggestion suggestion = new NetworkTimeSuggestion(ARBITRARY_TIME);
+        assertRoundTripParcelable(suggestion);
+
+        // DebugInfo should also be stored (but is not checked by equals()
+        suggestion.addDebugInfo("This is debug info");
+        NetworkTimeSuggestion rtSuggestion = roundTripParcelable(suggestion);
+        assertEquals(suggestion.getDebugInfo(), rtSuggestion.getDebugInfo());
+    }
+}

services/core/java/com/android/server/NetworkTimeUpdateServiceImpl.java

@@ -18,6 +18,8 @@ package com.android.server;
 
 import android.app.AlarmManager;
 import android.app.PendingIntent;
+import android.app.timedetector.NetworkTimeSuggestion;
+import android.app.timedetector.TimeDetector;
 import android.content.BroadcastReceiver;
 import android.content.ContentResolver;
 import android.content.Context;
@@ -35,10 +37,10 @@ import android.os.Message;
 import android.os.PowerManager;
 import android.os.SystemClock;
 import android.provider.Settings;
-import android.telephony.TelephonyManager;
 import android.util.Log;
 import android.util.NtpTrustedTime;
 import android.util.TimeUtils;
+import android.util.TimestampedValue;
 
 import com.android.internal.util.DumpUtils;
 
@@ -46,21 +48,19 @@ import java.io.FileDescriptor;
 import java.io.PrintWriter;
 
 /**
- * Monitors the network time and updates the system time if it is out of sync
+ * Monitors the network time. If looking up the network time fails for some reason, it tries a few
- * and there hasn't been any NITZ update from the carrier recently.
+ * times with a short interval and then resets to checking on longer intervals.
- * 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>When available, the time is always suggested to the {@link
- * <p>
+ * com.android.server.timedetector.TimeDetectorService} where it may be used to set the device
- * If the user enables AUTO_TIME, it will check immediately for the network time, if NITZ wasn't
+ * system clock, depending on user settings and what other signals are available.
- * available.
- * </p>
  */
 public class NetworkTimeUpdateServiceImpl 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_AUTO_TIME_ENABLED = 1;
     private static final int EVENT_POLL_NETWORK_TIME = 2;
     private static final int EVENT_NETWORK_CHANGED = 3;
 
@@ -69,20 +69,19 @@ public class NetworkTimeUpdateServiceImpl extends Binder implements NetworkTimeU
 
     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 TimeDetector mTimeDetector;
     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 AutoTimeSettingObserver mAutoTimeSettingObserver;
     private NetworkTimeUpdateCallback mNetworkTimeUpdateCallback;
 
     // Normal polling frequency
@@ -91,8 +90,6 @@ public class NetworkTimeUpdateServiceImpl extends Binder implements NetworkTimeU
     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.
@@ -102,6 +99,7 @@ public class NetworkTimeUpdateServiceImpl extends Binder implements NetworkTimeU
         mContext = context;
         mTime = NtpTrustedTime.getInstance(context);
         mAlarmManager = mContext.getSystemService(AlarmManager.class);
+        mTimeDetector = mContext.getSystemService(TimeDetector.class);
         mCM = mContext.getSystemService(ConnectivityManager.class);
 
         Intent pollIntent = new Intent(ACTION_POLL, null);
@@ -113,8 +111,6 @@ public class NetworkTimeUpdateServiceImpl extends Binder implements NetworkTimeU
                 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);
@@ -122,7 +118,6 @@ public class NetworkTimeUpdateServiceImpl extends Binder implements NetworkTimeU
 
     @Override
     public void systemRunning() {
-        registerForTelephonyIntents();
         registerForAlarms();
 
         HandlerThread thread = new HandlerThread(TAG);
@@ -131,14 +126,9 @@ public class NetworkTimeUpdateServiceImpl extends Binder implements NetworkTimeU
         mNetworkTimeUpdateCallback = new NetworkTimeUpdateCallback();
         mCM.registerDefaultNetworkCallback(mNetworkTimeUpdateCallback, mHandler);
 
-        mSettingsObserver = new SettingsObserver(mHandler, EVENT_AUTO_TIME_CHANGED);
+        mAutoTimeSettingObserver = new AutoTimeSettingObserver(mContext, mHandler,
-        mSettingsObserver.observe(mContext);
+                EVENT_AUTO_TIME_ENABLED);
-    }
+        mAutoTimeSettingObserver.observe();
-
-    private void registerForTelephonyIntents() {
-        IntentFilter intentFilter = new IntentFilter();
-        intentFilter.addAction(TelephonyManager.ACTION_NETWORK_SET_TIME);
-        mContext.registerReceiver(mNitzReceiver, intentFilter);
     }
 
     private void registerForAlarms() {
@@ -152,8 +142,7 @@ public class NetworkTimeUpdateServiceImpl extends Binder implements NetworkTimeU
     }
 
     private void onPollNetworkTime(int event) {
-        // If Automatic time is not set, don't bother. Similarly, if we don't
+        // If we don't have any default network, don't bother.
-        // have any default network, don't bother.
         if (mDefaultNetwork == null) return;
         mWakeLock.acquire();
         try {
@@ -173,10 +162,12 @@ public class NetworkTimeUpdateServiceImpl extends Binder implements NetworkTimeU
         if (mTime.getCacheAge() < mPollingIntervalMs) {
             // Obtained fresh fix; schedule next normal update
             resetAlarm(mPollingIntervalMs);
-            if (isAutomaticTimeRequested()) {
-                updateSystemClock(event);
-            }
 
+            // Suggest the time to the time detector. It may choose use it to set the system clock.
+            TimestampedValue<Long> timeSignal = mTime.getCachedNtpTimeSignal();
+            NetworkTimeSuggestion timeSuggestion = new NetworkTimeSuggestion(timeSignal);
+            timeSuggestion.addDebugInfo("Origin: NetworkTimeUpdateServiceImpl. event=" + event);
+            mTimeDetector.suggestNetworkTime(timeSuggestion);
         } else {
             // No fresh fix; schedule retry
             mTryAgainCounter++;
@@ -190,36 +181,6 @@ public class NetworkTimeUpdateServiceImpl extends Binder implements NetworkTimeU
         }
     }
 
-    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.
      *
@@ -232,27 +193,6 @@ public class NetworkTimeUpdateServiceImpl extends Binder implements NetworkTimeU
         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 (TelephonyManager.ACTION_NETWORK_SET_TIME.equals(action)) {
-                mNitzTimeSetTime = SystemClock.elapsedRealtime();
-            }
-        }
-    };
-
     /** Handler to do the network accesses on */
     private class MyHandler extends Handler {
 
@@ -263,7 +203,7 @@ public class NetworkTimeUpdateServiceImpl extends Binder implements NetworkTimeU
         @Override
         public void handleMessage(Message msg) {
             switch (msg.what) {
-                case EVENT_AUTO_TIME_CHANGED:
+                case EVENT_AUTO_TIME_ENABLED:
                 case EVENT_POLL_NETWORK_TIME:
                 case EVENT_NETWORK_CHANGED:
                     onPollNetworkTime(msg.what);
@@ -287,30 +227,45 @@ public class NetworkTimeUpdateServiceImpl extends Binder implements NetworkTimeU
         }
     }
 
-    /** Observer to watch for changes to the AUTO_TIME setting */
+    /**
-    private static class SettingsObserver extends ContentObserver {
+     * Observer to watch for changes to the AUTO_TIME setting. It only triggers when the setting
+     * is enabled.
+     */
+    private static class AutoTimeSettingObserver extends ContentObserver {
 
-        private int mMsg;
+        private final Context mContext;
-        private Handler mHandler;
+        private final int mMsg;
+        private final Handler mHandler;
 
-        SettingsObserver(Handler handler, int msg) {
+        AutoTimeSettingObserver(Context context, Handler handler, int msg) {
             super(handler);
+            mContext = context;
             mHandler = handler;
             mMsg = msg;
         }
 
-        void observe(Context context) {
+        void observe() {
-            ContentResolver resolver = context.getContentResolver();
+            ContentResolver resolver = mContext.getContentResolver();
             resolver.registerContentObserver(Settings.Global.getUriFor(Settings.Global.AUTO_TIME),
                     false, this);
         }
 
         @Override
         public void onChange(boolean selfChange) {
+            if (isAutomaticTimeEnabled()) {
                 mHandler.obtainMessage(mMsg).sendToTarget();
             }
         }
 
+        /**
+         * Checks if the user prefers to automatically set the time.
+         */
+        private boolean isAutomaticTimeEnabled() {
+            ContentResolver resolver = mContext.getContentResolver();
+            return Settings.Global.getInt(resolver, Settings.Global.AUTO_TIME, 0) != 0;
+        }
+    }
+
     @Override
     protected void dump(FileDescriptor fd, PrintWriter pw, String[] args) {
         if (!DumpUtils.checkDumpPermission(mContext, TAG, pw)) return;
@@ -319,8 +274,6 @@ public class NetworkTimeUpdateServiceImpl extends Binder implements NetworkTimeU
         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());

services/core/java/com/android/server/timedetector/TimeDetectorService.java

@@ -20,6 +20,7 @@ import android.annotation.NonNull;
 import android.annotation.Nullable;
 import android.app.timedetector.ITimeDetectorService;
 import android.app.timedetector.ManualTimeSuggestion;
+import android.app.timedetector.NetworkTimeSuggestion;
 import android.app.timedetector.PhoneTimeSuggestion;
 import android.content.ContentResolver;
 import android.content.Context;
@@ -105,6 +106,14 @@ public final class TimeDetectorService extends ITimeDetectorService.Stub {
         mHandler.post(() -> mTimeDetectorStrategy.suggestManualTime(timeSignal));
     }
 
+    @Override
+    public void suggestNetworkTime(@NonNull NetworkTimeSuggestion timeSignal) {
+        enforceSuggestNetworkTimePermission();
+        Objects.requireNonNull(timeSignal);
+
+        mHandler.post(() -> mTimeDetectorStrategy.suggestNetworkTime(timeSignal));
+    }
+
     @VisibleForTesting
     public void handleAutoTimeDetectionToggle() {
         mHandler.post(mTimeDetectorStrategy::handleAutoTimeDetectionChanged);
@@ -129,4 +138,10 @@ public final class TimeDetectorService extends ITimeDetectorService.Stub {
                 android.Manifest.permission.SUGGEST_MANUAL_TIME_AND_ZONE,
                 "suggest manual time and time zone");
     }
+
+    private void enforceSuggestNetworkTimePermission() {
+        mContext.enforceCallingOrSelfPermission(
+                android.Manifest.permission.SET_TIME,
+                "set time");
+    }
 }

services/core/java/com/android/server/timedetector/TimeDetectorStrategy.java

@@ -19,6 +19,7 @@ package com.android.server.timedetector;
 import android.annotation.NonNull;
 import android.annotation.Nullable;
 import android.app.timedetector.ManualTimeSuggestion;
+import android.app.timedetector.NetworkTimeSuggestion;
 import android.app.timedetector.PhoneTimeSuggestion;
 import android.content.Intent;
 import android.util.TimestampedValue;
@@ -86,6 +87,9 @@ public interface TimeDetectorStrategy {
     /** Process the suggested manually entered time. */
     void suggestManualTime(@NonNull ManualTimeSuggestion timeSuggestion);
 
+    /** Process the suggested time from network sources. */
+    void suggestNetworkTime(@NonNull NetworkTimeSuggestion timeSuggestion);
+
     /** Handle the auto-time setting being toggled on or off. */
     void handleAutoTimeDetectionChanged();
 

services/core/java/com/android/server/timedetector/TimeDetectorStrategyImpl.java

@@ -21,6 +21,7 @@ import android.annotation.NonNull;
 import android.annotation.Nullable;
 import android.app.AlarmManager;
 import android.app.timedetector.ManualTimeSuggestion;
+import android.app.timedetector.NetworkTimeSuggestion;
 import android.app.timedetector.PhoneTimeSuggestion;
 import android.content.Intent;
 import android.telephony.TelephonyManager;
@@ -32,6 +33,7 @@ import com.android.internal.annotations.GuardedBy;
 import com.android.internal.annotations.VisibleForTesting;
 import com.android.internal.util.IndentingPrintWriter;
 import com.android.server.timezonedetector.ArrayMapWithHistory;
+import com.android.server.timezonedetector.ReferenceWithHistory;
 
 import java.io.PrintWriter;
 import java.lang.annotation.Retention;
@@ -56,11 +58,11 @@ public final class TimeDetectorStrategyImpl implements TimeDetectorStrategy {
     /** Each bucket is this size. All buckets are equally sized. */
     @VisibleForTesting
     static final int PHONE_BUCKET_SIZE_MILLIS = 60 * 60 * 1000;
-    /** Phone suggestions older than this value are considered too old. */
+    /** Phone and network suggestions older than this value are considered too old to be used. */
     @VisibleForTesting
-    static final long PHONE_MAX_AGE_MILLIS = PHONE_BUCKET_COUNT * PHONE_BUCKET_SIZE_MILLIS;
+    static final long MAX_UTC_TIME_AGE_MILLIS = PHONE_BUCKET_COUNT * PHONE_BUCKET_SIZE_MILLIS;
 
-    @IntDef({ ORIGIN_PHONE, ORIGIN_MANUAL })
+    @IntDef({ ORIGIN_PHONE, ORIGIN_MANUAL, ORIGIN_NETWORK })
     @Retention(RetentionPolicy.SOURCE)
     public @interface Origin {}
 
@@ -72,6 +74,10 @@ public final class TimeDetectorStrategyImpl implements TimeDetectorStrategy {
     @Origin
     private static final int ORIGIN_MANUAL = 2;
 
+    /** Used when a time value originated from a network signal. */
+    @Origin
+    private static final int ORIGIN_NETWORK = 3;
+
     /**
      * CLOCK_PARANOIA: The maximum difference allowed between the expected system clock time and the
      * actual system clock time before a warning is logged. Used to help identify situations where
@@ -101,9 +107,13 @@ public final class TimeDetectorStrategyImpl implements TimeDetectorStrategy {
      * will have a small number of telephony devices and phoneIds are assumed to be stable.
      */
     @GuardedBy("this")
-    private ArrayMapWithHistory<Integer, PhoneTimeSuggestion> mSuggestionByPhoneId =
+    private final ArrayMapWithHistory<Integer, PhoneTimeSuggestion> mSuggestionByPhoneId =
             new ArrayMapWithHistory<>(KEEP_SUGGESTION_HISTORY_SIZE);
 
+    @GuardedBy("this")
+    private final ReferenceWithHistory<NetworkTimeSuggestion> mLastNetworkSuggestion =
+            new ReferenceWithHistory<>(KEEP_SUGGESTION_HISTORY_SIZE);
+
     @Override
     public void initialize(@NonNull Callback callback) {
         mCallback = callback;
@@ -121,6 +131,19 @@ public final class TimeDetectorStrategyImpl implements TimeDetectorStrategy {
         setSystemClockIfRequired(ORIGIN_MANUAL, newUtcTime, cause);
     }
 
+    @Override
+    public synchronized void suggestNetworkTime(@NonNull NetworkTimeSuggestion timeSuggestion) {
+        if (!validateSuggestionTime(timeSuggestion.getUtcTime(), timeSuggestion)) {
+            return;
+        }
+        mLastNetworkSuggestion.set(timeSuggestion);
+
+        // Now perform auto time detection. The new suggestion may be used to modify the system
+        // clock.
+        String reason = "New network time suggested. timeSuggestion=" + timeSuggestion;
+        doAutoTimeDetection(reason);
+    }
+
     @Override
     public synchronized void suggestPhoneTime(@NonNull PhoneTimeSuggestion timeSuggestion) {
         // Empty time suggestion means that telephony network connectivity has been lost.
@@ -184,6 +207,11 @@ public final class TimeDetectorStrategyImpl implements TimeDetectorStrategy {
         mSuggestionByPhoneId.dump(ipw);
         ipw.decreaseIndent(); // level 2
 
+        ipw.println("Network suggestion history:");
+        ipw.increaseIndent(); // level 2
+        mLastNetworkSuggestion.dump(ipw);
+        ipw.decreaseIndent(); // level 2
+
         ipw.decreaseIndent(); // level 1
         ipw.flush();
     }
@@ -253,23 +281,34 @@ public final class TimeDetectorStrategyImpl implements TimeDetectorStrategy {
             return;
         }
 
+        // Android devices currently prioritize any telephony over network signals. There are
+        // carrier compliance tests that would need to be changed before we could ignore NITZ or
+        // prefer NTP generally. This check is cheap on devices without phone hardware.
         PhoneTimeSuggestion bestPhoneSuggestion = findBestPhoneSuggestion();
-
+        if (bestPhoneSuggestion != null) {
-        // Work out what to do with the best suggestion.
-        if (bestPhoneSuggestion == null) {
-            // There is no good phone suggestion.
-            if (DBG) {
-                Slog.d(LOG_TAG, "Could not determine time: No best phone suggestion."
-                        + " detectionReason=" + detectionReason);
-            }
-            return;
-        }
-
             final TimestampedValue<Long> newUtcTime = bestPhoneSuggestion.getUtcTime();
-        String cause = "Found good suggestion."
+            String cause = "Found good phone suggestion."
                     + ", bestPhoneSuggestion=" + bestPhoneSuggestion
                     + ", detectionReason=" + detectionReason;
             setSystemClockIfRequired(ORIGIN_PHONE, newUtcTime, cause);
+            return;
+        }
+
+        // There is no good phone suggestion, try network.
+        NetworkTimeSuggestion networkSuggestion = findLatestValidNetworkSuggestion();
+        if (networkSuggestion != null) {
+            final TimestampedValue<Long> newUtcTime = networkSuggestion.getUtcTime();
+            String cause = "Found good network suggestion."
+                    + ", networkSuggestion=" + networkSuggestion
+                    + ", detectionReason=" + detectionReason;
+            setSystemClockIfRequired(ORIGIN_NETWORK, newUtcTime, cause);
+            return;
+        }
+
+        if (DBG) {
+            Slog.d(LOG_TAG, "Could not determine time: No best phone or network suggestion."
+                    + " detectionReason=" + detectionReason);
+        }
     }
 
     @GuardedBy("this")
@@ -348,37 +387,50 @@ public final class TimeDetectorStrategyImpl implements TimeDetectorStrategy {
 
     private static int scorePhoneSuggestion(
             long elapsedRealtimeMillis, @NonNull PhoneTimeSuggestion timeSuggestion) {
-        // The score is based on the age since receipt. Suggestions are bucketed so two
+
-        // suggestions in the same bucket from different phoneIds are scored the same.
+        // Validate first.
         TimestampedValue<Long> utcTime = timeSuggestion.getUtcTime();
-        long referenceTimeMillis = utcTime.getReferenceTimeMillis();
+        if (!validateSuggestionUtcTime(elapsedRealtimeMillis, utcTime)) {
-        if (referenceTimeMillis > elapsedRealtimeMillis) {
+            Slog.w(LOG_TAG, "Existing suggestion found to be invalid "
-            // Future times are ignored. They imply the reference time was wrong, or the elapsed
-            // realtime clock has gone backwards, neither of which are supportable situations.
-            Slog.w(LOG_TAG, "Existing suggestion found to be in the future. "
                     + " elapsedRealtimeMillis=" + elapsedRealtimeMillis
                     + ", timeSuggestion=" + timeSuggestion);
             return PHONE_INVALID_SCORE;
         }
 
-        long ageMillis = elapsedRealtimeMillis - referenceTimeMillis;
+        // The score is based on the age since receipt. Suggestions are bucketed so two
+        // suggestions in the same bucket from different phoneIds are scored the same.
+        long ageMillis = elapsedRealtimeMillis - utcTime.getReferenceTimeMillis();
 
-        // Any suggestion > MAX_AGE_MILLIS is treated as too old. Although time is relentless and
+        // Turn the age into a discrete value: 0 <= bucketIndex < PHONE_BUCKET_COUNT.
-        // predictable, the accuracy of the reference time clock may be poor over long periods which
+        int bucketIndex = (int) (ageMillis / PHONE_BUCKET_SIZE_MILLIS);
-        // would lead to errors creeping in. Also, in edge cases where a bad suggestion has been
+        if (bucketIndex >= PHONE_BUCKET_COUNT) {
-        // made and never replaced, it could also mean that the time detection code remains
-        // opinionated using a bad invalid suggestion. This caps that edge case at MAX_AGE_MILLIS.
-        if (ageMillis > PHONE_MAX_AGE_MILLIS) {
             return PHONE_INVALID_SCORE;
         }
 
-        // Turn the age into a discrete value: 0 <= bucketIndex < MAX_AGE_HOURS.
-        int bucketIndex = (int) (ageMillis / PHONE_BUCKET_SIZE_MILLIS);
-
         // We want the lowest bucket index to have the highest score. 0 > score >= BUCKET_COUNT.
         return PHONE_BUCKET_COUNT - bucketIndex;
     }
 
+    /** Returns the latest, valid, network suggestion. Returns {@code null} if there isn't one. */
+    @GuardedBy("this")
+    @Nullable
+    private NetworkTimeSuggestion findLatestValidNetworkSuggestion() {
+        NetworkTimeSuggestion networkSuggestion = mLastNetworkSuggestion.get();
+        if (networkSuggestion == null) {
+            // No network suggestions received. This is normal if there's no connectivity.
+            return null;
+        }
+
+        TimestampedValue<Long> utcTime = networkSuggestion.getUtcTime();
+        long elapsedRealTimeMillis = mCallback.elapsedRealtimeMillis();
+        if (!validateSuggestionUtcTime(elapsedRealTimeMillis, utcTime)) {
+            // The latest suggestion is not valid, usually due to its age.
+            return null;
+        }
+
+        return networkSuggestion;
+    }
+
     @GuardedBy("this")
     private void setSystemClockIfRequired(
             @Origin int origin, @NonNull TimestampedValue<Long> time, @NonNull String cause) {
@@ -415,7 +467,7 @@ public final class TimeDetectorStrategyImpl implements TimeDetectorStrategy {
     }
 
     private static boolean isOriginAutomatic(@Origin int origin) {
-        return origin == ORIGIN_PHONE;
+        return origin != ORIGIN_MANUAL;
     }
 
     @GuardedBy("this")
@@ -506,6 +558,16 @@ public final class TimeDetectorStrategyImpl implements TimeDetectorStrategy {
         return findBestPhoneSuggestion();
     }
 
+    /**
+     * Returns the latest valid network suggestion. Not intended for general use: it is used during
+     * tests to check strategy behavior.
+     */
+    @VisibleForTesting
+    @Nullable
+    public NetworkTimeSuggestion findLatestValidNetworkSuggestionForTests() {
+        return findLatestValidNetworkSuggestion();
+    }
+
     /**
      * A method used to inspect state during tests. Not intended for general use.
      */
@@ -514,4 +576,32 @@ public final class TimeDetectorStrategyImpl implements TimeDetectorStrategy {
     public synchronized PhoneTimeSuggestion getLatestPhoneSuggestion(int phoneId) {
         return mSuggestionByPhoneId.get(phoneId);
     }
+
+    /**
+     * A method used to inspect state during tests. Not intended for general use.
+     */
+    @VisibleForTesting
+    @Nullable
+    public NetworkTimeSuggestion getLatestNetworkSuggestion() {
+        return mLastNetworkSuggestion.get();
+    }
+
+    private static boolean validateSuggestionUtcTime(
+            long elapsedRealtimeMillis, TimestampedValue<Long> utcTime) {
+        long referenceTimeMillis = utcTime.getReferenceTimeMillis();
+        if (referenceTimeMillis > elapsedRealtimeMillis) {
+            // Future reference times are ignored. They imply the reference time was wrong, or the
+            // elapsed realtime clock used to derive it has gone backwards, neither of which are
+            // supportable situations.
+            return false;
+        }
+
+        // Any suggestion > MAX_AGE_MILLIS is treated as too old. Although time is relentless and
+        // predictable, the accuracy of the reference time clock may be poor over long periods which
+        // would lead to errors creeping in. Also, in edge cases where a bad suggestion has been
+        // made and never replaced, it could also mean that the time detection code remains
+        // opinionated using a bad invalid suggestion. This caps that edge case at MAX_AGE_MILLIS.
+        long ageMillis = elapsedRealtimeMillis - referenceTimeMillis;
+        return ageMillis <= MAX_UTC_TIME_AGE_MILLIS;
+    }
 }

services/tests/servicestests/src/com/android/server/timedetector/TimeDetectorServiceTest.java

@@ -29,6 +29,7 @@ import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.when;
 
 import android.app.timedetector.ManualTimeSuggestion;
+import android.app.timedetector.NetworkTimeSuggestion;
 import android.app.timedetector.PhoneTimeSuggestion;
 import android.content.Context;
 import android.content.pm.PackageManager;
@@ -143,6 +144,36 @@ public class TimeDetectorServiceTest {
         mStubbedTimeDetectorStrategy.verifySuggestManualTimeCalled(manualTimeSuggestion);
     }
 
+    @Test(expected = SecurityException.class)
+    public void testSuggestNetworkTime_withoutPermission() {
+        doThrow(new SecurityException("Mock"))
+                .when(mMockContext).enforceCallingOrSelfPermission(anyString(), any());
+        NetworkTimeSuggestion NetworkTimeSuggestion = createNetworkTimeSuggestion();
+
+        try {
+            mTimeDetectorService.suggestNetworkTime(NetworkTimeSuggestion);
+            fail();
+        } finally {
+            verify(mMockContext).enforceCallingOrSelfPermission(
+                    eq(android.Manifest.permission.SET_TIME), anyString());
+        }
+    }
+
+    @Test
+    public void testSuggestNetworkTime() throws Exception {
+        doNothing().when(mMockContext).enforceCallingOrSelfPermission(anyString(), any());
+
+        NetworkTimeSuggestion NetworkTimeSuggestion = createNetworkTimeSuggestion();
+        mTimeDetectorService.suggestNetworkTime(NetworkTimeSuggestion);
+        mTestHandler.assertTotalMessagesEnqueued(1);
+
+        verify(mMockContext).enforceCallingOrSelfPermission(
+                eq(android.Manifest.permission.SET_TIME), anyString());
+
+        mTestHandler.waitForEmptyQueue();
+        mStubbedTimeDetectorStrategy.verifySuggestNetworkTimeCalled(NetworkTimeSuggestion);
+    }
+
     @Test
     public void testDump() {
         when(mMockContext.checkCallingOrSelfPermission(android.Manifest.permission.DUMP))
@@ -180,11 +211,17 @@ public class TimeDetectorServiceTest {
         return new ManualTimeSuggestion(timeValue);
     }
 
+    private static NetworkTimeSuggestion createNetworkTimeSuggestion() {
+        TimestampedValue<Long> timeValue = new TimestampedValue<>(100L, 1_000_000L);
+        return new NetworkTimeSuggestion(timeValue);
+    }
+
     private static class StubbedTimeDetectorStrategy implements TimeDetectorStrategy {
 
         // Call tracking.
         private PhoneTimeSuggestion mLastPhoneSuggestion;
         private ManualTimeSuggestion mLastManualSuggestion;
+        private NetworkTimeSuggestion mLastNetworkSuggestion;
         private boolean mLastAutoTimeDetectionToggleCalled;
         private boolean mDumpCalled;
 
@@ -204,6 +241,12 @@ public class TimeDetectorServiceTest {
             mLastManualSuggestion = timeSuggestion;
         }
 
+        @Override
+        public void suggestNetworkTime(NetworkTimeSuggestion timeSuggestion) {
+            resetCallTracking();
+            mLastNetworkSuggestion = timeSuggestion;
+        }
+
         @Override
         public void handleAutoTimeDetectionChanged() {
             resetCallTracking();
@@ -219,6 +262,7 @@ public class TimeDetectorServiceTest {
         void resetCallTracking() {
             mLastPhoneSuggestion = null;
             mLastManualSuggestion = null;
+            mLastNetworkSuggestion = null;
             mLastAutoTimeDetectionToggleCalled = false;
             mDumpCalled = false;
         }
@@ -231,6 +275,10 @@ public class TimeDetectorServiceTest {
             assertEquals(expectedSuggestion, mLastManualSuggestion);
         }
 
+        public void verifySuggestNetworkTimeCalled(NetworkTimeSuggestion expectedSuggestion) {
+            assertEquals(expectedSuggestion, mLastNetworkSuggestion);
+        }
+
         void verifyHandleAutoTimeDetectionToggleCalled() {
             assertTrue(mLastAutoTimeDetectionToggleCalled);
         }

services/tests/servicestests/src/com/android/server/timedetector/TimeDetectorStrategyImplTest.java

@@ -24,6 +24,7 @@ import static org.junit.Assert.assertTrue;
 import static org.junit.Assert.fail;
 
 import android.app.timedetector.ManualTimeSuggestion;
+import android.app.timedetector.NetworkTimeSuggestion;
 import android.app.timedetector.PhoneTimeSuggestion;
 import android.content.Intent;
 import android.icu.util.Calendar;
@@ -45,14 +46,16 @@ public class TimeDetectorStrategyImplTest {
     private static final TimestampedValue<Long> ARBITRARY_CLOCK_INITIALIZATION_INFO =
             new TimestampedValue<>(
                     123456789L /* realtimeClockMillis */,
-                    createUtcTime(1977, 1, 1, 12, 0, 0));
+                    createUtcTime(2008, 5, 23, 12, 0, 0));
 
+    /**
+     * An arbitrary time, very different from the {@link #ARBITRARY_CLOCK_INITIALIZATION_INFO}
+     * time. Can be used as the basis for time suggestions.
+     */
     private static final long ARBITRARY_TEST_TIME_MILLIS = createUtcTime(2018, 1, 1, 12, 0, 0);
 
     private static final int ARBITRARY_PHONE_ID = 123456;
 
-    private static final long ONE_DAY_MILLIS = Duration.ofDays(1).toMillis();
-
     private Script mScript;
 
     @Before
@@ -67,14 +70,15 @@ public class TimeDetectorStrategyImplTest {
 
         int phoneId = ARBITRARY_PHONE_ID;
         long testTimeMillis = ARBITRARY_TEST_TIME_MILLIS;
+
         PhoneTimeSuggestion timeSuggestion =
                 mScript.generatePhoneTimeSuggestion(phoneId, testTimeMillis);
-        int clockIncrement = 1000;
+        mScript.simulateTimePassing()
-        long expectedSystemClockMillis = testTimeMillis + clockIncrement;
+                .simulatePhoneTimeSuggestion(timeSuggestion);
 
-        mScript.simulateTimePassing(clockIncrement)
+        long expectedSystemClockMillis =
-                .simulatePhoneTimeSuggestion(timeSuggestion)
+                mScript.calculateTimeInMillisForNow(timeSuggestion.getUtcTime());
-                .verifySystemClockWasSetAndResetCallTracking(
+        mScript.verifySystemClockWasSetAndResetCallTracking(
                 expectedSystemClockMillis, true /* expectNetworkBroadcast */)
                 .assertLatestPhoneSuggestion(phoneId, timeSuggestion);
     }
@@ -94,26 +98,24 @@ public class TimeDetectorStrategyImplTest {
 
     @Test
     public void testSuggestPhoneTime_systemClockThreshold() {
-        int systemClockUpdateThresholdMillis = 1000;
+        final int systemClockUpdateThresholdMillis = 1000;
+        final int clockIncrementMillis = 100;
         mScript.pokeFakeClocks(ARBITRARY_CLOCK_INITIALIZATION_INFO)
                 .pokeThresholds(systemClockUpdateThresholdMillis)
                 .pokeAutoTimeDetectionEnabled(true);
 
-        final int clockIncrement = 100;
         int phoneId = ARBITRARY_PHONE_ID;
 
         // Send the first time signal. It should be used.
         {
-            long testTimeMillis = ARBITRARY_TEST_TIME_MILLIS;
             PhoneTimeSuggestion timeSuggestion1 =
-                    mScript.generatePhoneTimeSuggestion(phoneId, testTimeMillis);
+                    mScript.generatePhoneTimeSuggestion(phoneId, ARBITRARY_TEST_TIME_MILLIS);
-            TimestampedValue<Long> utcTime1 = timeSuggestion1.getUtcTime();
 
             // Increment the the device clocks to simulate the passage of time.
-            mScript.simulateTimePassing(clockIncrement);
+            mScript.simulateTimePassing(clockIncrementMillis);
 
             long expectedSystemClockMillis1 =
-                    TimeDetectorStrategy.getTimeAt(utcTime1, mScript.peekElapsedRealtimeMillis());
+                    mScript.calculateTimeInMillisForNow(timeSuggestion1.getUtcTime());
 
             mScript.simulatePhoneTimeSuggestion(timeSuggestion1)
                     .verifySystemClockWasSetAndResetCallTracking(
@@ -127,7 +129,7 @@ public class TimeDetectorStrategyImplTest {
             int underThresholdMillis = systemClockUpdateThresholdMillis - 1;
             PhoneTimeSuggestion timeSuggestion2 = mScript.generatePhoneTimeSuggestion(
                     phoneId, mScript.peekSystemClockMillis() + underThresholdMillis);
-            mScript.simulateTimePassing(clockIncrement)
+            mScript.simulateTimePassing(clockIncrementMillis)
                     .simulatePhoneTimeSuggestion(timeSuggestion2)
                     .verifySystemClockWasNotSetAndResetCallTracking()
                     .assertLatestPhoneSuggestion(phoneId, timeSuggestion2);
@@ -138,11 +140,10 @@ public class TimeDetectorStrategyImplTest {
             PhoneTimeSuggestion timeSuggestion3 = mScript.generatePhoneTimeSuggestion(
                     phoneId,
                     mScript.peekSystemClockMillis() + systemClockUpdateThresholdMillis);
-            mScript.simulateTimePassing(clockIncrement);
+            mScript.simulateTimePassing(clockIncrementMillis);
 
             long expectedSystemClockMillis3 =
-                    TimeDetectorStrategy.getTimeAt(timeSuggestion3.getUtcTime(),
+                    mScript.calculateTimeInMillisForNow(timeSuggestion3.getUtcTime());
-                            mScript.peekElapsedRealtimeMillis());
 
             mScript.simulatePhoneTimeSuggestion(timeSuggestion3)
                     .verifySystemClockWasSetAndResetCallTracking(
@@ -162,17 +163,16 @@ public class TimeDetectorStrategyImplTest {
         int phone1Id = ARBITRARY_PHONE_ID;
         int phone2Id = ARBITRARY_PHONE_ID + 1;
         long phone1TimeMillis = ARBITRARY_TEST_TIME_MILLIS;
-        long phone2TimeMillis = phone1TimeMillis + 60000;
+        long phone2TimeMillis = ARBITRARY_TEST_TIME_MILLIS + Duration.ofDays(1).toMillis();
-
-        final int clockIncrement = 999;
 
         // Make a suggestion with phone2Id.
         {
             PhoneTimeSuggestion phone2TimeSuggestion =
                     mScript.generatePhoneTimeSuggestion(phone2Id, phone2TimeMillis);
-            mScript.simulateTimePassing(clockIncrement);
+            mScript.simulateTimePassing();
 
-            long expectedSystemClockMillis = phone2TimeMillis + clockIncrement;
+            long expectedSystemClockMillis =
+                    mScript.calculateTimeInMillisForNow(phone2TimeSuggestion.getUtcTime());
 
             mScript.simulatePhoneTimeSuggestion(phone2TimeSuggestion)
                     .verifySystemClockWasSetAndResetCallTracking(
@@ -181,15 +181,16 @@ public class TimeDetectorStrategyImplTest {
                     .assertLatestPhoneSuggestion(phone2Id, phone2TimeSuggestion);
         }
 
-        mScript.simulateTimePassing(clockIncrement);
+        mScript.simulateTimePassing();
 
         // Now make a different suggestion with phone1Id.
         {
             PhoneTimeSuggestion phone1TimeSuggestion =
                     mScript.generatePhoneTimeSuggestion(phone1Id, phone1TimeMillis);
-            mScript.simulateTimePassing(clockIncrement);
+            mScript.simulateTimePassing();
 
-            long expectedSystemClockMillis = phone1TimeMillis + clockIncrement;
+            long expectedSystemClockMillis =
+                    mScript.calculateTimeInMillisForNow(phone1TimeSuggestion.getUtcTime());
 
             mScript.simulatePhoneTimeSuggestion(phone1TimeSuggestion)
                     .verifySystemClockWasSetAndResetCallTracking(
@@ -198,14 +199,14 @@ public class TimeDetectorStrategyImplTest {
 
         }
 
-        mScript.simulateTimePassing(clockIncrement);
+        mScript.simulateTimePassing();
 
         // Make another suggestion with phone2Id. It should be stored but not used because the
         // phone1Id suggestion will still "win".
         {
             PhoneTimeSuggestion phone2TimeSuggestion =
                     mScript.generatePhoneTimeSuggestion(phone2Id, phone2TimeMillis);
-            mScript.simulateTimePassing(clockIncrement);
+            mScript.simulateTimePassing();
 
             mScript.simulatePhoneTimeSuggestion(phone2TimeSuggestion)
                     .verifySystemClockWasNotSetAndResetCallTracking()
@@ -220,9 +221,10 @@ public class TimeDetectorStrategyImplTest {
         {
             PhoneTimeSuggestion phone2TimeSuggestion =
                     mScript.generatePhoneTimeSuggestion(phone2Id, phone2TimeMillis);
-            mScript.simulateTimePassing(clockIncrement);
+            mScript.simulateTimePassing();
 
-            long expectedSystemClockMillis = phone2TimeMillis + clockIncrement;
+            long expectedSystemClockMillis =
+                    mScript.calculateTimeInMillisForNow(phone2TimeSuggestion.getUtcTime());
 
             mScript.simulatePhoneTimeSuggestion(phone2TimeSuggestion)
                     .verifySystemClockWasSetAndResetCallTracking(
@@ -239,7 +241,7 @@ public class TimeDetectorStrategyImplTest {
         int phoneId = ARBITRARY_PHONE_ID;
         PhoneTimeSuggestion timeSuggestion =
                 mScript.generatePhoneTimeSuggestion(phoneId, ARBITRARY_TEST_TIME_MILLIS);
-        mScript.simulateTimePassing(1000)
+        mScript.simulateTimePassing()
                 .simulatePhoneTimeSuggestion(timeSuggestion)
                 .verifySystemClockWasNotSetAndResetCallTracking()
                 .assertLatestPhoneSuggestion(phoneId, timeSuggestion);
@@ -260,9 +262,8 @@ public class TimeDetectorStrategyImplTest {
         TimestampedValue<Long> utcTime1 = timeSuggestion1.getUtcTime();
 
         // Initialize the strategy / device with a time set from a phone suggestion.
-        mScript.simulateTimePassing(100);
+        mScript.simulateTimePassing();
-        long expectedSystemClockMillis1 =
+        long expectedSystemClockMillis1 = mScript.calculateTimeInMillisForNow(utcTime1);
-                TimeDetectorStrategy.getTimeAt(utcTime1, mScript.peekElapsedRealtimeMillis());
         mScript.simulatePhoneTimeSuggestion(timeSuggestion1)
                 .verifySystemClockWasSetAndResetCallTracking(
                         expectedSystemClockMillis1, true /* expectNetworkBroadcast */)
@@ -299,8 +300,7 @@ public class TimeDetectorStrategyImplTest {
         long validReferenceTimeMillis = utcTime1.getReferenceTimeMillis() + 100;
         TimestampedValue<Long> utcTime4 = new TimestampedValue<>(
                 validReferenceTimeMillis, validUtcTimeMillis);
-        long expectedSystemClockMillis4 =
+        long expectedSystemClockMillis4 = mScript.calculateTimeInMillisForNow(utcTime4);
-                TimeDetectorStrategy.getTimeAt(utcTime4, mScript.peekElapsedRealtimeMillis());
         PhoneTimeSuggestion timeSuggestion4 =
                 createPhoneTimeSuggestion(phoneId, utcTime4);
         mScript.simulatePhoneTimeSuggestion(timeSuggestion4)
@@ -335,8 +335,7 @@ public class TimeDetectorStrategyImplTest {
         // Simulate more time passing.
         mScript.simulateTimePassing(clockIncrementMillis);
 
-        long expectedSystemClockMillis1 =
+        long expectedSystemClockMillis1 = mScript.calculateTimeInMillisForNow(utcTime1);
-                TimeDetectorStrategy.getTimeAt(utcTime1, mScript.peekElapsedRealtimeMillis());
 
         // Turn on auto time detection.
         mScript.simulateAutoTimeDetectionToggle()
@@ -357,8 +356,8 @@ public class TimeDetectorStrategyImplTest {
         // Simulate more time passing.
         mScript.simulateTimePassing(clockIncrementMillis);
 
-        long expectedSystemClockMillis2 = TimeDetectorStrategy.getTimeAt(
+        long expectedSystemClockMillis2 =
-                timeSuggestion2.getUtcTime(), mScript.peekElapsedRealtimeMillis());
+                mScript.calculateTimeInMillisForNow(timeSuggestion2.getUtcTime());
 
         // The new time, though valid, should not be set in the system clock because auto time is
         // disabled.
@@ -382,19 +381,21 @@ public class TimeDetectorStrategyImplTest {
         long testTimeMillis = ARBITRARY_TEST_TIME_MILLIS;
         PhoneTimeSuggestion phoneSuggestion =
                 mScript.generatePhoneTimeSuggestion(phoneId, testTimeMillis);
-        int clockIncrementMillis = 1000;
 
-        mScript.simulateTimePassing(clockIncrementMillis)
+        mScript.simulateTimePassing();
-                .simulatePhoneTimeSuggestion(phoneSuggestion)
+
+        long expectedSystemClockMillis =
+                mScript.calculateTimeInMillisForNow(phoneSuggestion.getUtcTime());
+        mScript.simulatePhoneTimeSuggestion(phoneSuggestion)
                 .verifySystemClockWasSetAndResetCallTracking(
-                        testTimeMillis + clockIncrementMillis, true /* expectedNetworkBroadcast */)
+                        expectedSystemClockMillis, true /* expectedNetworkBroadcast */)
                 .assertLatestPhoneSuggestion(phoneId, phoneSuggestion);
 
         // Look inside and check what the strategy considers the current best phone suggestion.
         assertEquals(phoneSuggestion, mScript.peekBestPhoneSuggestion());
 
         // Simulate time passing, long enough that phoneSuggestion is now too old.
-        mScript.simulateTimePassing(TimeDetectorStrategyImpl.PHONE_MAX_AGE_MILLIS);
+        mScript.simulateTimePassing(TimeDetectorStrategyImpl.MAX_UTC_TIME_AGE_MILLIS);
 
         // Look inside and check what the strategy considers the current best phone suggestion. It
         // should still be the, it's just no longer used.
@@ -407,13 +408,14 @@ public class TimeDetectorStrategyImplTest {
         mScript.pokeFakeClocks(ARBITRARY_CLOCK_INITIALIZATION_INFO)
                 .pokeAutoTimeDetectionEnabled(false);
 
-        long testTimeMillis = ARBITRARY_TEST_TIME_MILLIS;
+        ManualTimeSuggestion timeSuggestion =
-        ManualTimeSuggestion timeSuggestion = mScript.generateManualTimeSuggestion(testTimeMillis);
+                mScript.generateManualTimeSuggestion(ARBITRARY_TEST_TIME_MILLIS);
-        final int clockIncrement = 1000;
-        long expectedSystemClockMillis = testTimeMillis + clockIncrement;
 
-        mScript.simulateTimePassing(clockIncrement)
+        mScript.simulateTimePassing();
-                .simulateManualTimeSuggestion(timeSuggestion)
+
+        long expectedSystemClockMillis =
+                mScript.calculateTimeInMillisForNow(timeSuggestion.getUtcTime());
+        mScript.simulateManualTimeSuggestion(timeSuggestion)
                 .verifySystemClockWasSetAndResetCallTracking(
                         expectedSystemClockMillis, false /* expectNetworkBroadcast */);
     }
@@ -430,21 +432,19 @@ public class TimeDetectorStrategyImplTest {
         long testTimeMillis = ARBITRARY_TEST_TIME_MILLIS;
         PhoneTimeSuggestion phoneTimeSuggestion =
                 mScript.generatePhoneTimeSuggestion(phoneId, testTimeMillis);
-        long expectedAutoClockMillis = phoneTimeSuggestion.getUtcTime().getValue();
-        final int clockIncrement = 1000;
 
         // Simulate the passage of time.
-        mScript.simulateTimePassing(clockIncrement);
+        mScript.simulateTimePassing();
-        expectedAutoClockMillis += clockIncrement;
 
+        long expectedAutoClockMillis =
+                mScript.calculateTimeInMillisForNow(phoneTimeSuggestion.getUtcTime());
         mScript.simulatePhoneTimeSuggestion(phoneTimeSuggestion)
                 .verifySystemClockWasSetAndResetCallTracking(
                         expectedAutoClockMillis, true /* expectNetworkBroadcast */)
                 .assertLatestPhoneSuggestion(phoneId, phoneTimeSuggestion);
 
         // Simulate the passage of time.
-        mScript.simulateTimePassing(clockIncrement);
+        mScript.simulateTimePassing();
-        expectedAutoClockMillis += clockIncrement;
 
         // Switch to manual.
         mScript.simulateAutoTimeDetectionToggle()
@@ -452,26 +452,29 @@ public class TimeDetectorStrategyImplTest {
                 .assertLatestPhoneSuggestion(phoneId, phoneTimeSuggestion);
 
         // Simulate the passage of time.
-        mScript.simulateTimePassing(clockIncrement);
+        mScript.simulateTimePassing();
-        expectedAutoClockMillis += clockIncrement;
 
         // Simulate a manual suggestion 1 day different from the auto suggestion.
-        long manualTimeMillis = testTimeMillis + ONE_DAY_MILLIS;
+        long manualTimeMillis = testTimeMillis + Duration.ofDays(1).toMillis();
-        long expectedManualClockMillis = manualTimeMillis;
         ManualTimeSuggestion manualTimeSuggestion =
                 mScript.generateManualTimeSuggestion(manualTimeMillis);
+        mScript.simulateTimePassing();
+
+        long expectedManualClockMillis =
+                mScript.calculateTimeInMillisForNow(manualTimeSuggestion.getUtcTime());
         mScript.simulateManualTimeSuggestion(manualTimeSuggestion)
                 .verifySystemClockWasSetAndResetCallTracking(
                         expectedManualClockMillis, false /* expectNetworkBroadcast */)
                 .assertLatestPhoneSuggestion(phoneId, phoneTimeSuggestion);
 
         // Simulate the passage of time.
-        mScript.simulateTimePassing(clockIncrement);
+        mScript.simulateTimePassing();
-        expectedAutoClockMillis += clockIncrement;
 
         // Switch back to auto.
         mScript.simulateAutoTimeDetectionToggle();
 
+        expectedAutoClockMillis =
+                mScript.calculateTimeInMillisForNow(phoneTimeSuggestion.getUtcTime());
         mScript.verifySystemClockWasSetAndResetCallTracking(
                         expectedAutoClockMillis, true /* expectNetworkBroadcast */)
                 .assertLatestPhoneSuggestion(phoneId, phoneTimeSuggestion);
@@ -492,13 +495,143 @@ public class TimeDetectorStrategyImplTest {
 
         ManualTimeSuggestion timeSuggestion =
                 mScript.generateManualTimeSuggestion(ARBITRARY_TEST_TIME_MILLIS);
-        final int clockIncrement = 1000;
 
-        mScript.simulateTimePassing(clockIncrement)
+        mScript.simulateTimePassing()
                 .simulateManualTimeSuggestion(timeSuggestion)
                 .verifySystemClockWasNotSetAndResetCallTracking();
     }
 
+    @Test
+    public void testSuggestNetworkTime_autoTimeEnabled() {
+        mScript.pokeFakeClocks(ARBITRARY_CLOCK_INITIALIZATION_INFO)
+                .pokeAutoTimeDetectionEnabled(true);
+
+        NetworkTimeSuggestion timeSuggestion =
+                mScript.generateNetworkTimeSuggestion(ARBITRARY_TEST_TIME_MILLIS);
+
+        mScript.simulateTimePassing();
+
+        long expectedSystemClockMillis =
+                mScript.calculateTimeInMillisForNow(timeSuggestion.getUtcTime());
+        mScript.simulateNetworkTimeSuggestion(timeSuggestion)
+                .verifySystemClockWasSetAndResetCallTracking(
+                        expectedSystemClockMillis, false /* expectNetworkBroadcast */);
+    }
+
+    @Test
+    public void testSuggestNetworkTime_autoTimeDisabled() {
+        mScript.pokeFakeClocks(ARBITRARY_CLOCK_INITIALIZATION_INFO)
+                .pokeAutoTimeDetectionEnabled(false);
+
+        NetworkTimeSuggestion timeSuggestion =
+                mScript.generateNetworkTimeSuggestion(ARBITRARY_TEST_TIME_MILLIS);
+
+        mScript.simulateTimePassing()
+                .simulateNetworkTimeSuggestion(timeSuggestion)
+                .verifySystemClockWasNotSetAndResetCallTracking();
+    }
+
+    @Test
+    public void testSuggestNetworkTime_phoneSuggestionsBeatNetworkSuggestions() {
+        mScript.pokeFakeClocks(ARBITRARY_CLOCK_INITIALIZATION_INFO)
+                .pokeAutoTimeDetectionEnabled(true);
+
+        // Three obviously different times that could not be mistaken for each other.
+        long networkTimeMillis1 = ARBITRARY_TEST_TIME_MILLIS;
+        long networkTimeMillis2 = ARBITRARY_TEST_TIME_MILLIS + Duration.ofDays(30).toMillis();
+        long phoneTimeMillis = ARBITRARY_TEST_TIME_MILLIS + Duration.ofDays(60).toMillis();
+        // A small increment used to simulate the passage of time, but not enough to interfere with
+        // macro-level time changes associated with suggestion age.
+        final long smallTimeIncrementMillis = 101;
+
+        // A network suggestion is made. It should be used because there is no phone suggestion.
+        NetworkTimeSuggestion networkTimeSuggestion1 =
+                mScript.generateNetworkTimeSuggestion(networkTimeMillis1);
+        mScript.simulateTimePassing(smallTimeIncrementMillis)
+                .simulateNetworkTimeSuggestion(networkTimeSuggestion1)
+                .verifySystemClockWasSetAndResetCallTracking(
+                        mScript.calculateTimeInMillisForNow(networkTimeSuggestion1.getUtcTime()),
+                        false /* expectNetworkBroadcast */);
+
+        // Check internal state.
+        mScript.assertLatestPhoneSuggestion(ARBITRARY_PHONE_ID, null)
+                .assertLatestNetworkSuggestion(networkTimeSuggestion1);
+        assertEquals(networkTimeSuggestion1, mScript.peekLatestValidNetworkSuggestion());
+        assertNull(mScript.peekBestPhoneSuggestion());
+
+        // Simulate a little time passing.
+        mScript.simulateTimePassing(smallTimeIncrementMillis)
+                .verifySystemClockWasNotSetAndResetCallTracking();
+
+        // Now a phone suggestion is made. Phone suggestions are prioritized over network
+        // suggestions so it should "win".
+        PhoneTimeSuggestion phoneTimeSuggestion =
+                mScript.generatePhoneTimeSuggestion(ARBITRARY_PHONE_ID, phoneTimeMillis);
+        mScript.simulateTimePassing(smallTimeIncrementMillis)
+                .simulatePhoneTimeSuggestion(phoneTimeSuggestion)
+                .verifySystemClockWasSetAndResetCallTracking(
+                        mScript.calculateTimeInMillisForNow(phoneTimeSuggestion.getUtcTime()),
+                        true /* expectNetworkBroadcast */);
+
+        // Check internal state.
+        mScript.assertLatestPhoneSuggestion(ARBITRARY_PHONE_ID, phoneTimeSuggestion)
+                .assertLatestNetworkSuggestion(networkTimeSuggestion1);
+        assertEquals(networkTimeSuggestion1, mScript.peekLatestValidNetworkSuggestion());
+        assertEquals(phoneTimeSuggestion, mScript.peekBestPhoneSuggestion());
+
+        // Simulate some significant time passing: half the time allowed before a time signal
+        // becomes "too old to use".
+        mScript.simulateTimePassing(TimeDetectorStrategyImpl.MAX_UTC_TIME_AGE_MILLIS / 2)
+                .verifySystemClockWasNotSetAndResetCallTracking();
+
+        // Now another network suggestion is made. Phone suggestions are prioritized over network
+        // suggestions so the latest phone suggestion should still "win".
+        NetworkTimeSuggestion networkTimeSuggestion2 =
+                mScript.generateNetworkTimeSuggestion(networkTimeMillis2);
+        mScript.simulateTimePassing(smallTimeIncrementMillis)
+                .simulateNetworkTimeSuggestion(networkTimeSuggestion2)
+                .verifySystemClockWasNotSetAndResetCallTracking();
+
+        // Check internal state.
+        mScript.assertLatestPhoneSuggestion(ARBITRARY_PHONE_ID, phoneTimeSuggestion)
+                .assertLatestNetworkSuggestion(networkTimeSuggestion2);
+        assertEquals(networkTimeSuggestion2, mScript.peekLatestValidNetworkSuggestion());
+        assertEquals(phoneTimeSuggestion, mScript.peekBestPhoneSuggestion());
+
+        // Simulate some significant time passing: half the time allowed before a time signal
+        // becomes "too old to use". This should mean that phoneTimeSuggestion is now too old to be
+        // used but networkTimeSuggestion2 is not.
+        mScript.simulateTimePassing(TimeDetectorStrategyImpl.MAX_UTC_TIME_AGE_MILLIS / 2);
+
+        // NOTE: The TimeDetectorStrategyImpl doesn't set an alarm for the point when the last
+        // suggestion it used becomes too old: it requires a new suggestion or an auto-time toggle
+        // to re-run the detection logic. This may change in future but until then we rely on a
+        // steady stream of suggestions to re-evaluate.
+        mScript.verifySystemClockWasNotSetAndResetCallTracking();
+
+        // Check internal state.
+        mScript.assertLatestPhoneSuggestion(ARBITRARY_PHONE_ID, phoneTimeSuggestion)
+                .assertLatestNetworkSuggestion(networkTimeSuggestion2);
+        assertEquals(networkTimeSuggestion2, mScript.peekLatestValidNetworkSuggestion());
+        assertNull(mScript.peekBestPhoneSuggestion());
+
+        // Toggle auto-time off and on to force the detection logic to run.
+        mScript.simulateAutoTimeDetectionToggle()
+                .simulateTimePassing(smallTimeIncrementMillis)
+                .simulateAutoTimeDetectionToggle();
+
+        // Verify the latest network time now wins.
+        mScript.verifySystemClockWasSetAndResetCallTracking(
+                mScript.calculateTimeInMillisForNow(networkTimeSuggestion2.getUtcTime()),
+                false /* expectNetworkTimeBroadcast */);
+
+        // Check internal state.
+        mScript.assertLatestPhoneSuggestion(ARBITRARY_PHONE_ID, phoneTimeSuggestion)
+                .assertLatestNetworkSuggestion(networkTimeSuggestion2);
+        assertEquals(networkTimeSuggestion2, mScript.peekLatestValidNetworkSuggestion());
+        assertNull(mScript.peekBestPhoneSuggestion());
+    }
+
     /**
      * A fake implementation of TimeDetectorStrategy.Callback. Besides tracking changes and behaving
      * like the real thing should, it also asserts preconditions.
@@ -674,6 +807,11 @@ public class TimeDetectorStrategyImplTest {
             return this;
         }
 
+        Script simulateNetworkTimeSuggestion(NetworkTimeSuggestion timeSuggestion) {
+            mTimeDetectorStrategy.suggestNetworkTime(timeSuggestion);
+            return this;
+        }
+
         Script simulateAutoTimeDetectionToggle() {
             mFakeCallback.simulateAutoTimeZoneDetectionToggle();
             mTimeDetectorStrategy.handleAutoTimeDetectionChanged();
@@ -685,6 +823,13 @@ public class TimeDetectorStrategyImplTest {
             return this;
         }
 
+        /**
+         * Simulates time passing by an arbitrary (but relatively small) amount.
+         */
+        Script simulateTimePassing() {
+            return simulateTimePassing(999);
+        }
+
         Script verifySystemClockWasNotSetAndResetCallTracking() {
             mFakeCallback.verifySystemClockNotSet();
             mFakeCallback.verifyIntentWasNotBroadcast();
@@ -710,14 +855,30 @@ public class TimeDetectorStrategyImplTest {
             return this;
         }
 
+        /**
+         * White box test info: Asserts the latest network suggestion is as expected.
+         */
+        Script assertLatestNetworkSuggestion(NetworkTimeSuggestion expected) {
+            assertEquals(expected, mTimeDetectorStrategy.getLatestNetworkSuggestion());
+            return this;
+        }
+
         /**
          * White box test info: Returns the phone suggestion that would be used, if any, given the
-         * current elapsed real time clock.
+         * current elapsed real time clock and regardless of origin prioritization.
          */
         PhoneTimeSuggestion peekBestPhoneSuggestion() {
             return mTimeDetectorStrategy.findBestPhoneSuggestionForTests();
         }
 
+        /**
+         * White box test info: Returns the network suggestion that would be used, if any, given the
+         * current elapsed real time clock and regardless of origin prioritization.
+         */
+        NetworkTimeSuggestion peekLatestValidNetworkSuggestion() {
+            return mTimeDetectorStrategy.findLatestValidNetworkSuggestionForTests();
+        }
+
         /**
          * Generates a ManualTimeSuggestion using the current elapsed realtime clock for the
          * reference time.
@@ -739,6 +900,24 @@ public class TimeDetectorStrategyImplTest {
             }
             return createPhoneTimeSuggestion(phoneId, time);
         }
+
+        /**
+         * Generates a NetworkTimeSuggestion using the current elapsed realtime clock for the
+         * reference time.
+         */
+        NetworkTimeSuggestion generateNetworkTimeSuggestion(long timeMillis) {
+            TimestampedValue<Long> utcTime =
+                    new TimestampedValue<>(mFakeCallback.peekElapsedRealtimeMillis(), timeMillis);
+            return new NetworkTimeSuggestion(utcTime);
+        }
+
+        /**
+         * Calculates what the supplied time would be when adjusted for the movement of the fake
+         * elapsed realtime clock.
+         */
+        long calculateTimeInMillisForNow(TimestampedValue<Long> utcTime) {
+            return TimeDetectorStrategy.getTimeAt(utcTime, peekElapsedRealtimeMillis());
+        }
     }
 
     private static PhoneTimeSuggestion createPhoneTimeSuggestion(int phoneId,