Change NetworkTimeUpdateServiceImpl behavior

This change moves some logic associated with time detection out of the
NetworkTimeUpdateServiceImpl and moves it to the TimeDetectorStrategy
called by the TimeDetectorService.

The TimeDetectorStategy implementation now decides when to use an
NTP-derived time instead. The logic implemented here is effectively the
same as it was: NITZ takes priority over NTP until the latest NITZ
signal becomes "too old".

The motivating reasons for the change:
1) The "what signal is used when several are available?" logic should be
in one place: the TimeDetectoryStrategy not scattered around the
platform. Centralizing will enable different strategies and time sources
to be introduced over time.

2) It will allow removal of the ACTION_NETWORK_SET_TIME intent in a
follow-up commit; this intent was used to coordinate the NTP vs NITZ
logic should no longer be required.

The "bonus" effect of this change is that NetworkTimeUpdateServiceImpl
becomes more general: It can now be the authority for the NTP time on a
device independently of how the system clock should be set. e.g. it
could be used in future to back the
AlarmManager.currentNetworkTimeMillis() API call.  Anything that needs a
"what is the best time according to NTP?" answer could use this service.

Note: The NetworkTimeUpdateServiceImpl still observes the AUTO_TIME
setting and will perform an NTP lookup "on demand" (if required) when
the user enables the setting. This should be a temporary state and
likely to be removed in future; knowledge of AUTO_TIME shouldn't be
required for the NTP info to be correct and if
NetworkTimeUpdateServiceImpl is doing the right thing.

Bug: 140712361
Test: atest com.android.server.timedetector
Test: atest android.app.timedetector
Change-Id: I4b2936a42c552c4dd4cb55010306bb81bca0c712

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);
+    }
+
 }