diff --git a/service-t/Sources.bp b/service-t/Sources.bp
index 529f58d..6a64910 100644
--- a/service-t/Sources.bp
+++ b/service-t/Sources.bp
@@ -19,13 +19,45 @@
     default_applicable_licenses: ["Android-Apache-2.0"],
 }
 
+// NetworkStats related libraries.
+
+filegroup {
+    name: "services.connectivity-netstats-sources",
+    srcs: [
+        "src/com/android/server/net/NetworkIdentity*.java",
+        "src/com/android/server/net/NetworkStats*.java",
+    ],
+    path: "src",
+    visibility: [
+        "//visibility:private",
+    ],
+}
+
+// Nsd related libraries.
+
 filegroup {
     name: "services.connectivity-nsd-sources",
     srcs: [
-        "src/**/*.java",
+        "src/com/android/server/INativeDaemon*.java",
+        "src/com/android/server/NativeDaemon*.java",
+        "src/com/android/server/Nsd*.java",
+    ],
+    path: "src",
+    visibility: [
+        "//visibility:private",
+    ],
+}
+
+// Connectivity-T common libraries.
+
+filegroup {
+    name: "services.connectivity-tiramisu-sources",
+    srcs: [
+        ":services.connectivity-netstats-sources",
+        ":services.connectivity-nsd-sources",
     ],
     path: "src",
     visibility: [
         "//frameworks/base/services/core",
     ],
-}
+}
\ No newline at end of file
diff --git a/service-t/src/com/android/server/net/NetworkIdentitySet.java b/service-t/src/com/android/server/net/NetworkIdentitySet.java
new file mode 100644
index 0000000..22ed781
--- /dev/null
+++ b/service-t/src/com/android/server/net/NetworkIdentitySet.java
@@ -0,0 +1,191 @@
+/*
+ * Copyright (C) 2011 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.net;
+
+import android.net.NetworkIdentity;
+import android.service.NetworkIdentitySetProto;
+import android.util.proto.ProtoOutputStream;
+
+import java.io.DataInput;
+import java.io.DataOutput;
+import java.io.IOException;
+import java.util.HashSet;
+
+import static android.net.ConnectivityManager.TYPE_MOBILE;
+
+/**
+ * Identity of a {@code iface}, defined by the set of {@link NetworkIdentity}
+ * active on that interface.
+ *
+ * @hide
+ */
+public class NetworkIdentitySet extends HashSet<NetworkIdentity> implements
+        Comparable<NetworkIdentitySet> {
+    private static final int VERSION_INIT = 1;
+    private static final int VERSION_ADD_ROAMING = 2;
+    private static final int VERSION_ADD_NETWORK_ID = 3;
+    private static final int VERSION_ADD_METERED = 4;
+    private static final int VERSION_ADD_DEFAULT_NETWORK = 5;
+    private static final int VERSION_ADD_OEM_MANAGED_NETWORK = 6;
+
+    public NetworkIdentitySet() {
+    }
+
+    public NetworkIdentitySet(DataInput in) throws IOException {
+        final int version = in.readInt();
+        final int size = in.readInt();
+        for (int i = 0; i < size; i++) {
+            if (version <= VERSION_INIT) {
+                final int ignored = in.readInt();
+            }
+            final int type = in.readInt();
+            final int subType = in.readInt();
+            final String subscriberId = readOptionalString(in);
+            final String networkId;
+            if (version >= VERSION_ADD_NETWORK_ID) {
+                networkId = readOptionalString(in);
+            } else {
+                networkId = null;
+            }
+            final boolean roaming;
+            if (version >= VERSION_ADD_ROAMING) {
+                roaming = in.readBoolean();
+            } else {
+                roaming = false;
+            }
+
+            final boolean metered;
+            if (version >= VERSION_ADD_METERED) {
+                metered = in.readBoolean();
+            } else {
+                // If this is the old data and the type is mobile, treat it as metered. (Note that
+                // if this is a mobile network, TYPE_MOBILE is the only possible type that could be
+                // used.)
+                metered = (type == TYPE_MOBILE);
+            }
+
+            final boolean defaultNetwork;
+            if (version >= VERSION_ADD_DEFAULT_NETWORK) {
+                defaultNetwork = in.readBoolean();
+            } else {
+                defaultNetwork = true;
+            }
+
+            final int oemNetCapabilities;
+            if (version >= VERSION_ADD_OEM_MANAGED_NETWORK) {
+                oemNetCapabilities = in.readInt();
+            } else {
+                oemNetCapabilities = NetworkIdentity.OEM_NONE;
+            }
+
+            add(new NetworkIdentity(type, subType, subscriberId, networkId, roaming, metered,
+                    defaultNetwork, oemNetCapabilities));
+        }
+    }
+
+    public void writeToStream(DataOutput out) throws IOException {
+        out.writeInt(VERSION_ADD_OEM_MANAGED_NETWORK);
+        out.writeInt(size());
+        for (NetworkIdentity ident : this) {
+            out.writeInt(ident.getType());
+            out.writeInt(ident.getSubType());
+            writeOptionalString(out, ident.getSubscriberId());
+            writeOptionalString(out, ident.getNetworkId());
+            out.writeBoolean(ident.getRoaming());
+            out.writeBoolean(ident.getMetered());
+            out.writeBoolean(ident.getDefaultNetwork());
+            out.writeInt(ident.getOemManaged());
+        }
+    }
+
+    /** @return whether any {@link NetworkIdentity} in this set is considered metered. */
+    public boolean isAnyMemberMetered() {
+        if (isEmpty()) {
+            return false;
+        }
+        for (NetworkIdentity ident : this) {
+            if (ident.getMetered()) {
+                return true;
+            }
+        }
+        return false;
+    }
+
+    /** @return whether any {@link NetworkIdentity} in this set is considered roaming. */
+    public boolean isAnyMemberRoaming() {
+        if (isEmpty()) {
+            return false;
+        }
+        for (NetworkIdentity ident : this) {
+            if (ident.getRoaming()) {
+                return true;
+            }
+        }
+        return false;
+    }
+
+    /** @return whether any {@link NetworkIdentity} in this set is considered on the default
+            network. */
+    public boolean areAllMembersOnDefaultNetwork() {
+        if (isEmpty()) {
+            return true;
+        }
+        for (NetworkIdentity ident : this) {
+            if (!ident.getDefaultNetwork()) {
+                return false;
+            }
+        }
+        return true;
+    }
+
+    private static void writeOptionalString(DataOutput out, String value) throws IOException {
+        if (value != null) {
+            out.writeByte(1);
+            out.writeUTF(value);
+        } else {
+            out.writeByte(0);
+        }
+    }
+
+    private static String readOptionalString(DataInput in) throws IOException {
+        if (in.readByte() != 0) {
+            return in.readUTF();
+        } else {
+            return null;
+        }
+    }
+
+    @Override
+    public int compareTo(NetworkIdentitySet another) {
+        if (isEmpty()) return -1;
+        if (another.isEmpty()) return 1;
+
+        final NetworkIdentity ident = iterator().next();
+        final NetworkIdentity anotherIdent = another.iterator().next();
+        return ident.compareTo(anotherIdent);
+    }
+
+    public void dumpDebug(ProtoOutputStream proto, long tag) {
+        final long start = proto.start(tag);
+
+        for (NetworkIdentity ident : this) {
+            ident.dumpDebug(proto, NetworkIdentitySetProto.IDENTITIES);
+        }
+
+        proto.end(start);
+    }
+}
diff --git a/service-t/src/com/android/server/net/NetworkStatsAccess.java b/service-t/src/com/android/server/net/NetworkStatsAccess.java
new file mode 100644
index 0000000..d25eae4
--- /dev/null
+++ b/service-t/src/com/android/server/net/NetworkStatsAccess.java
@@ -0,0 +1,199 @@
+/*
+ * Copyright (C) 2015 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.net;
+
+import static android.Manifest.permission.READ_NETWORK_USAGE_HISTORY;
+import static android.net.NetworkStats.UID_ALL;
+import static android.net.TrafficStats.UID_REMOVED;
+import static android.net.TrafficStats.UID_TETHERING;
+
+import android.Manifest;
+import android.annotation.IntDef;
+import android.app.AppOpsManager;
+import android.app.admin.DevicePolicyManagerInternal;
+import android.content.Context;
+import android.content.pm.PackageManager;
+import android.os.Binder;
+import android.os.Process;
+import android.os.UserHandle;
+import android.telephony.TelephonyManager;
+
+import com.android.server.LocalServices;
+
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+
+/** Utility methods for controlling access to network stats APIs. */
+public final class NetworkStatsAccess {
+    private NetworkStatsAccess() {}
+
+    /**
+     * Represents an access level for the network usage history and statistics APIs.
+     *
+     * <p>Access levels are in increasing order; that is, it is reasonable to check access by
+     * verifying that the caller's access level is at least the minimum required level.
+     */
+    @IntDef({
+            Level.DEFAULT,
+            Level.USER,
+            Level.DEVICESUMMARY,
+            Level.DEVICE,
+    })
+    @Retention(RetentionPolicy.SOURCE)
+    public @interface Level {
+        /**
+         * Default, unprivileged access level.
+         *
+         * <p>Can only access usage for one's own UID.
+         *
+         * <p>Every app will have at least this access level.
+         */
+        int DEFAULT = 0;
+
+        /**
+         * Access level for apps which can access usage for any app running in the same user.
+         *
+         * <p>Granted to:
+         * <ul>
+         * <li>Profile owners.
+         * </ul>
+         */
+        int USER = 1;
+
+        /**
+         * Access level for apps which can access usage summary of device. Device summary includes
+         * usage by apps running in any profiles/users, however this access level does not
+         * allow querying usage of individual apps running in other profiles/users.
+         *
+         * <p>Granted to:
+         * <ul>
+         * <li>Apps with the PACKAGE_USAGE_STATS permission granted. Note that this is an AppOps bit
+         * so it is not necessarily sufficient to declare this in the manifest.
+         * <li>Apps with the (signature/privileged) READ_NETWORK_USAGE_HISTORY permission.
+         * </ul>
+         */
+        int DEVICESUMMARY = 2;
+
+        /**
+         * Access level for apps which can access usage for any app on the device, including apps
+         * running on other users/profiles.
+         *
+         * <p>Granted to:
+         * <ul>
+         * <li>Device owners.
+         * <li>Carrier-privileged applications.
+         * <li>The system UID.
+         * </ul>
+         */
+        int DEVICE = 3;
+    }
+
+    /** Returns the {@link NetworkStatsAccess.Level} for the given caller. */
+    public static @NetworkStatsAccess.Level int checkAccessLevel(
+            Context context, int callingUid, String callingPackage) {
+        final DevicePolicyManagerInternal dpmi = LocalServices.getService(
+                DevicePolicyManagerInternal.class);
+        final TelephonyManager tm = (TelephonyManager)
+                context.getSystemService(Context.TELEPHONY_SERVICE);
+        boolean hasCarrierPrivileges;
+        final long token = Binder.clearCallingIdentity();
+        try {
+            hasCarrierPrivileges = tm != null
+                    && tm.checkCarrierPrivilegesForPackageAnyPhone(callingPackage)
+                            == TelephonyManager.CARRIER_PRIVILEGE_STATUS_HAS_ACCESS;
+        } finally {
+            Binder.restoreCallingIdentity(token);
+        }
+
+        final boolean isDeviceOwner = dpmi != null && dpmi.isActiveDeviceOwner(callingUid);
+        final int appId = UserHandle.getAppId(callingUid);
+        if (hasCarrierPrivileges || isDeviceOwner
+                || appId == Process.SYSTEM_UID || appId == Process.NETWORK_STACK_UID) {
+            // Carrier-privileged apps and device owners, and the system (including the
+            // network stack) can access data usage for all apps on the device.
+            return NetworkStatsAccess.Level.DEVICE;
+        }
+
+        boolean hasAppOpsPermission = hasAppOpsPermission(context, callingUid, callingPackage);
+        if (hasAppOpsPermission || context.checkCallingOrSelfPermission(
+                READ_NETWORK_USAGE_HISTORY) == PackageManager.PERMISSION_GRANTED) {
+            return NetworkStatsAccess.Level.DEVICESUMMARY;
+        }
+
+        //TODO(b/169395065) Figure out if this flow makes sense in Device Owner mode.
+        boolean isProfileOwner = dpmi != null && (dpmi.isActiveProfileOwner(callingUid)
+                || dpmi.isActiveDeviceOwner(callingUid));
+        if (isProfileOwner) {
+            // Apps with the AppOps permission, profile owners, and apps with the privileged
+            // permission can access data usage for all apps in this user/profile.
+            return NetworkStatsAccess.Level.USER;
+        }
+
+        // Everyone else gets default access (only to their own UID).
+        return NetworkStatsAccess.Level.DEFAULT;
+    }
+
+    /**
+     * Returns whether the given caller should be able to access the given UID when the caller has
+     * the given {@link NetworkStatsAccess.Level}.
+     */
+    public static boolean isAccessibleToUser(int uid, int callerUid,
+            @NetworkStatsAccess.Level int accessLevel) {
+        switch (accessLevel) {
+            case NetworkStatsAccess.Level.DEVICE:
+                // Device-level access - can access usage for any uid.
+                return true;
+            case NetworkStatsAccess.Level.DEVICESUMMARY:
+                // Can access usage for any app running in the same user, along
+                // with some special uids (system, removed, or tethering) and
+                // anonymized uids
+                return uid == android.os.Process.SYSTEM_UID || uid == UID_REMOVED
+                        || uid == UID_TETHERING || uid == UID_ALL
+                        || UserHandle.getUserId(uid) == UserHandle.getUserId(callerUid);
+            case NetworkStatsAccess.Level.USER:
+                // User-level access - can access usage for any app running in the same user, along
+                // with some special uids (system, removed, or tethering).
+                return uid == android.os.Process.SYSTEM_UID || uid == UID_REMOVED
+                        || uid == UID_TETHERING
+                        || UserHandle.getUserId(uid) == UserHandle.getUserId(callerUid);
+            case NetworkStatsAccess.Level.DEFAULT:
+            default:
+                // Default access level - can only access one's own usage.
+                return uid == callerUid;
+        }
+    }
+
+    private static boolean hasAppOpsPermission(
+            Context context, int callingUid, String callingPackage) {
+        if (callingPackage != null) {
+            AppOpsManager appOps = (AppOpsManager) context.getSystemService(
+                    Context.APP_OPS_SERVICE);
+
+            final int mode = appOps.noteOp(AppOpsManager.OP_GET_USAGE_STATS,
+                    callingUid, callingPackage);
+            if (mode == AppOpsManager.MODE_DEFAULT) {
+                // The default behavior here is to check if PackageManager has given the app
+                // permission.
+                final int permissionCheck = context.checkCallingPermission(
+                        Manifest.permission.PACKAGE_USAGE_STATS);
+                return permissionCheck == PackageManager.PERMISSION_GRANTED;
+            }
+            return (mode == AppOpsManager.MODE_ALLOWED);
+        }
+        return false;
+    }
+}
diff --git a/service-t/src/com/android/server/net/NetworkStatsCollection.java b/service-t/src/com/android/server/net/NetworkStatsCollection.java
new file mode 100644
index 0000000..213ea40
--- /dev/null
+++ b/service-t/src/com/android/server/net/NetworkStatsCollection.java
@@ -0,0 +1,820 @@
+/*
+ * Copyright (C) 2012 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.net;
+
+import static android.net.NetworkStats.DEFAULT_NETWORK_NO;
+import static android.net.NetworkStats.DEFAULT_NETWORK_YES;
+import static android.net.NetworkStats.IFACE_ALL;
+import static android.net.NetworkStats.METERED_NO;
+import static android.net.NetworkStats.METERED_YES;
+import static android.net.NetworkStats.ROAMING_NO;
+import static android.net.NetworkStats.ROAMING_YES;
+import static android.net.NetworkStats.SET_ALL;
+import static android.net.NetworkStats.SET_DEFAULT;
+import static android.net.NetworkStats.TAG_NONE;
+import static android.net.NetworkStats.UID_ALL;
+import static android.net.TrafficStats.UID_REMOVED;
+import static android.text.format.DateUtils.WEEK_IN_MILLIS;
+
+import static com.android.internal.net.NetworkUtilsInternal.multiplySafeByRational;
+import static com.android.server.net.NetworkStatsService.TAG;
+
+import android.net.NetworkIdentity;
+import android.net.NetworkStats;
+import android.net.NetworkStatsHistory;
+import android.net.NetworkTemplate;
+import android.net.TrafficStats;
+import android.os.Binder;
+import android.service.NetworkStatsCollectionKeyProto;
+import android.service.NetworkStatsCollectionProto;
+import android.service.NetworkStatsCollectionStatsProto;
+import android.telephony.SubscriptionPlan;
+import android.text.format.DateUtils;
+import android.util.ArrayMap;
+import android.util.AtomicFile;
+import android.util.IntArray;
+import android.util.MathUtils;
+import android.util.Range;
+import android.util.Slog;
+import android.util.proto.ProtoOutputStream;
+
+import com.android.internal.annotations.VisibleForTesting;
+import com.android.internal.util.ArrayUtils;
+import com.android.internal.util.FastDataInput;
+import com.android.internal.util.FastDataOutput;
+import com.android.internal.util.FileRotator;
+import com.android.internal.util.IndentingPrintWriter;
+
+import com.google.android.collect.Lists;
+import com.google.android.collect.Maps;
+
+import libcore.io.IoUtils;
+
+import java.io.BufferedInputStream;
+import java.io.DataInput;
+import java.io.DataInputStream;
+import java.io.DataOutput;
+import java.io.File;
+import java.io.FileNotFoundException;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.OutputStream;
+import java.io.PrintWriter;
+import java.net.ProtocolException;
+import java.time.ZonedDateTime;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.Iterator;
+import java.util.Objects;
+
+/**
+ * Collection of {@link NetworkStatsHistory}, stored based on combined key of
+ * {@link NetworkIdentitySet}, UID, set, and tag. Knows how to persist itself.
+ */
+public class NetworkStatsCollection implements FileRotator.Reader, FileRotator.Writer {
+    /** File header magic number: "ANET" */
+    private static final int FILE_MAGIC = 0x414E4554;
+
+    /** Default buffer size from BufferedInputStream */
+    private static final int BUFFER_SIZE = 8192;
+
+    private static final int VERSION_NETWORK_INIT = 1;
+
+    private static final int VERSION_UID_INIT = 1;
+    private static final int VERSION_UID_WITH_IDENT = 2;
+    private static final int VERSION_UID_WITH_TAG = 3;
+    private static final int VERSION_UID_WITH_SET = 4;
+
+    private static final int VERSION_UNIFIED_INIT = 16;
+
+    private ArrayMap<Key, NetworkStatsHistory> mStats = new ArrayMap<>();
+
+    private final long mBucketDuration;
+
+    private long mStartMillis;
+    private long mEndMillis;
+    private long mTotalBytes;
+    private boolean mDirty;
+
+    public NetworkStatsCollection(long bucketDuration) {
+        mBucketDuration = bucketDuration;
+        reset();
+    }
+
+    public void clear() {
+        reset();
+    }
+
+    public void reset() {
+        mStats.clear();
+        mStartMillis = Long.MAX_VALUE;
+        mEndMillis = Long.MIN_VALUE;
+        mTotalBytes = 0;
+        mDirty = false;
+    }
+
+    public long getStartMillis() {
+        return mStartMillis;
+    }
+
+    /**
+     * Return first atomic bucket in this collection, which is more conservative
+     * than {@link #mStartMillis}.
+     */
+    public long getFirstAtomicBucketMillis() {
+        if (mStartMillis == Long.MAX_VALUE) {
+            return Long.MAX_VALUE;
+        } else {
+            return mStartMillis + mBucketDuration;
+        }
+    }
+
+    public long getEndMillis() {
+        return mEndMillis;
+    }
+
+    public long getTotalBytes() {
+        return mTotalBytes;
+    }
+
+    public boolean isDirty() {
+        return mDirty;
+    }
+
+    public void clearDirty() {
+        mDirty = false;
+    }
+
+    public boolean isEmpty() {
+        return mStartMillis == Long.MAX_VALUE && mEndMillis == Long.MIN_VALUE;
+    }
+
+    @VisibleForTesting
+    public long roundUp(long time) {
+        if (time == Long.MIN_VALUE || time == Long.MAX_VALUE
+                || time == SubscriptionPlan.TIME_UNKNOWN) {
+            return time;
+        } else {
+            final long mod = time % mBucketDuration;
+            if (mod > 0) {
+                time -= mod;
+                time += mBucketDuration;
+            }
+            return time;
+        }
+    }
+
+    @VisibleForTesting
+    public long roundDown(long time) {
+        if (time == Long.MIN_VALUE || time == Long.MAX_VALUE
+                || time == SubscriptionPlan.TIME_UNKNOWN) {
+            return time;
+        } else {
+            final long mod = time % mBucketDuration;
+            if (mod > 0) {
+                time -= mod;
+            }
+            return time;
+        }
+    }
+
+    public int[] getRelevantUids(@NetworkStatsAccess.Level int accessLevel) {
+        return getRelevantUids(accessLevel, Binder.getCallingUid());
+    }
+
+    public int[] getRelevantUids(@NetworkStatsAccess.Level int accessLevel,
+                final int callerUid) {
+        IntArray uids = new IntArray();
+        for (int i = 0; i < mStats.size(); i++) {
+            final Key key = mStats.keyAt(i);
+            if (NetworkStatsAccess.isAccessibleToUser(key.uid, callerUid, accessLevel)) {
+                int j = uids.binarySearch(key.uid);
+
+                if (j < 0) {
+                    j = ~j;
+                    uids.add(j, key.uid);
+                }
+            }
+        }
+        return uids.toArray();
+    }
+
+    /**
+     * Combine all {@link NetworkStatsHistory} in this collection which match
+     * the requested parameters.
+     */
+    public NetworkStatsHistory getHistory(NetworkTemplate template, SubscriptionPlan augmentPlan,
+            int uid, int set, int tag, int fields, long start, long end,
+            @NetworkStatsAccess.Level int accessLevel, int callerUid) {
+        if (!NetworkStatsAccess.isAccessibleToUser(uid, callerUid, accessLevel)) {
+            throw new SecurityException("Network stats history of uid " + uid
+                    + " is forbidden for caller " + callerUid);
+        }
+
+        // 180 days of history should be enough for anyone; if we end up needing
+        // more, we'll dynamically grow the history object.
+        final int bucketEstimate = (int) MathUtils.constrain(((end - start) / mBucketDuration), 0,
+                (180 * DateUtils.DAY_IN_MILLIS) / mBucketDuration);
+        final NetworkStatsHistory combined = new NetworkStatsHistory(
+                mBucketDuration, bucketEstimate, fields);
+
+        // shortcut when we know stats will be empty
+        if (start == end) return combined;
+
+        // Figure out the window of time that we should be augmenting (if any)
+        long augmentStart = SubscriptionPlan.TIME_UNKNOWN;
+        long augmentEnd = (augmentPlan != null) ? augmentPlan.getDataUsageTime()
+                : SubscriptionPlan.TIME_UNKNOWN;
+        // And if augmenting, we might need to collect more data to adjust with
+        long collectStart = start;
+        long collectEnd = end;
+
+        if (augmentEnd != SubscriptionPlan.TIME_UNKNOWN) {
+            final Iterator<Range<ZonedDateTime>> it = augmentPlan.cycleIterator();
+            while (it.hasNext()) {
+                final Range<ZonedDateTime> cycle = it.next();
+                final long cycleStart = cycle.getLower().toInstant().toEpochMilli();
+                final long cycleEnd = cycle.getUpper().toInstant().toEpochMilli();
+                if (cycleStart <= augmentEnd && augmentEnd < cycleEnd) {
+                    augmentStart = cycleStart;
+                    collectStart = Long.min(collectStart, augmentStart);
+                    collectEnd = Long.max(collectEnd, augmentEnd);
+                    break;
+                }
+            }
+        }
+
+        if (augmentStart != SubscriptionPlan.TIME_UNKNOWN) {
+            // Shrink augmentation window so we don't risk undercounting.
+            augmentStart = roundUp(augmentStart);
+            augmentEnd = roundDown(augmentEnd);
+            // Grow collection window so we get all the stats needed.
+            collectStart = roundDown(collectStart);
+            collectEnd = roundUp(collectEnd);
+        }
+
+        for (int i = 0; i < mStats.size(); i++) {
+            final Key key = mStats.keyAt(i);
+            if (key.uid == uid && NetworkStats.setMatches(set, key.set) && key.tag == tag
+                    && templateMatches(template, key.ident)) {
+                final NetworkStatsHistory value = mStats.valueAt(i);
+                combined.recordHistory(value, collectStart, collectEnd);
+            }
+        }
+
+        if (augmentStart != SubscriptionPlan.TIME_UNKNOWN) {
+            final NetworkStatsHistory.Entry entry = combined.getValues(
+                    augmentStart, augmentEnd, null);
+
+            // If we don't have any recorded data for this time period, give
+            // ourselves something to scale with.
+            if (entry.rxBytes == 0 || entry.txBytes == 0) {
+                combined.recordData(augmentStart, augmentEnd,
+                        new NetworkStats.Entry(1, 0, 1, 0, 0));
+                combined.getValues(augmentStart, augmentEnd, entry);
+            }
+
+            final long rawBytes = (entry.rxBytes + entry.txBytes) == 0 ? 1 :
+                    (entry.rxBytes + entry.txBytes);
+            final long rawRxBytes = entry.rxBytes == 0 ? 1 : entry.rxBytes;
+            final long rawTxBytes = entry.txBytes == 0 ? 1 : entry.txBytes;
+            final long targetBytes = augmentPlan.getDataUsageBytes();
+
+            final long targetRxBytes = multiplySafeByRational(targetBytes, rawRxBytes, rawBytes);
+            final long targetTxBytes = multiplySafeByRational(targetBytes, rawTxBytes, rawBytes);
+
+
+            // Scale all matching buckets to reach anchor target
+            final long beforeTotal = combined.getTotalBytes();
+            for (int i = 0; i < combined.size(); i++) {
+                combined.getValues(i, entry);
+                if (entry.bucketStart >= augmentStart
+                        && entry.bucketStart + entry.bucketDuration <= augmentEnd) {
+                    entry.rxBytes = multiplySafeByRational(
+                            targetRxBytes, entry.rxBytes, rawRxBytes);
+                    entry.txBytes = multiplySafeByRational(
+                            targetTxBytes, entry.txBytes, rawTxBytes);
+                    // We purposefully clear out packet counters to indicate
+                    // that this data has been augmented.
+                    entry.rxPackets = 0;
+                    entry.txPackets = 0;
+                    combined.setValues(i, entry);
+                }
+            }
+
+            final long deltaTotal = combined.getTotalBytes() - beforeTotal;
+            if (deltaTotal != 0) {
+                Slog.d(TAG, "Augmented network usage by " + deltaTotal + " bytes");
+            }
+
+            // Finally we can slice data as originally requested
+            final NetworkStatsHistory sliced = new NetworkStatsHistory(
+                    mBucketDuration, bucketEstimate, fields);
+            sliced.recordHistory(combined, start, end);
+            return sliced;
+        } else {
+            return combined;
+        }
+    }
+
+    /**
+     * Summarize all {@link NetworkStatsHistory} in this collection which match
+     * the requested parameters across the requested range.
+     *
+     * @param template - a predicate for filtering netstats.
+     * @param start - start of the range, timestamp in milliseconds since the epoch.
+     * @param end - end of the range, timestamp in milliseconds since the epoch.
+     * @param accessLevel - caller access level.
+     * @param callerUid - caller UID.
+     */
+    public NetworkStats getSummary(NetworkTemplate template, long start, long end,
+            @NetworkStatsAccess.Level int accessLevel, int callerUid) {
+        final long now = System.currentTimeMillis();
+
+        final NetworkStats stats = new NetworkStats(end - start, 24);
+
+        // shortcut when we know stats will be empty
+        if (start == end) return stats;
+
+        final NetworkStats.Entry entry = new NetworkStats.Entry();
+        NetworkStatsHistory.Entry historyEntry = null;
+
+        for (int i = 0; i < mStats.size(); i++) {
+            final Key key = mStats.keyAt(i);
+            if (templateMatches(template, key.ident)
+                    && NetworkStatsAccess.isAccessibleToUser(key.uid, callerUid, accessLevel)
+                    && key.set < NetworkStats.SET_DEBUG_START) {
+                final NetworkStatsHistory value = mStats.valueAt(i);
+                historyEntry = value.getValues(start, end, now, historyEntry);
+
+                entry.iface = IFACE_ALL;
+                entry.uid = key.uid;
+                entry.set = key.set;
+                entry.tag = key.tag;
+                entry.defaultNetwork = key.ident.areAllMembersOnDefaultNetwork() ?
+                        DEFAULT_NETWORK_YES : DEFAULT_NETWORK_NO;
+                entry.metered = key.ident.isAnyMemberMetered() ? METERED_YES : METERED_NO;
+                entry.roaming = key.ident.isAnyMemberRoaming() ? ROAMING_YES : ROAMING_NO;
+                entry.rxBytes = historyEntry.rxBytes;
+                entry.rxPackets = historyEntry.rxPackets;
+                entry.txBytes = historyEntry.txBytes;
+                entry.txPackets = historyEntry.txPackets;
+                entry.operations = historyEntry.operations;
+
+                if (!entry.isEmpty()) {
+                    stats.combineValues(entry);
+                }
+            }
+        }
+
+        return stats;
+    }
+
+    /**
+     * Record given {@link android.net.NetworkStats.Entry} into this collection.
+     */
+    public void recordData(NetworkIdentitySet ident, int uid, int set, int tag, long start,
+            long end, NetworkStats.Entry entry) {
+        final NetworkStatsHistory history = findOrCreateHistory(ident, uid, set, tag);
+        history.recordData(start, end, entry);
+        noteRecordedHistory(history.getStart(), history.getEnd(), entry.rxBytes + entry.txBytes);
+    }
+
+    /**
+     * Record given {@link NetworkStatsHistory} into this collection.
+     */
+    private void recordHistory(Key key, NetworkStatsHistory history) {
+        if (history.size() == 0) return;
+        noteRecordedHistory(history.getStart(), history.getEnd(), history.getTotalBytes());
+
+        NetworkStatsHistory target = mStats.get(key);
+        if (target == null) {
+            target = new NetworkStatsHistory(history.getBucketDuration());
+            mStats.put(key, target);
+        }
+        target.recordEntireHistory(history);
+    }
+
+    /**
+     * Record all {@link NetworkStatsHistory} contained in the given collection
+     * into this collection.
+     */
+    public void recordCollection(NetworkStatsCollection another) {
+        for (int i = 0; i < another.mStats.size(); i++) {
+            final Key key = another.mStats.keyAt(i);
+            final NetworkStatsHistory value = another.mStats.valueAt(i);
+            recordHistory(key, value);
+        }
+    }
+
+    private NetworkStatsHistory findOrCreateHistory(
+            NetworkIdentitySet ident, int uid, int set, int tag) {
+        final Key key = new Key(ident, uid, set, tag);
+        final NetworkStatsHistory existing = mStats.get(key);
+
+        // update when no existing, or when bucket duration changed
+        NetworkStatsHistory updated = null;
+        if (existing == null) {
+            updated = new NetworkStatsHistory(mBucketDuration, 10);
+        } else if (existing.getBucketDuration() != mBucketDuration) {
+            updated = new NetworkStatsHistory(existing, mBucketDuration);
+        }
+
+        if (updated != null) {
+            mStats.put(key, updated);
+            return updated;
+        } else {
+            return existing;
+        }
+    }
+
+    @Override
+    public void read(InputStream in) throws IOException {
+        final FastDataInput dataIn = new FastDataInput(in, BUFFER_SIZE);
+        read(dataIn);
+    }
+
+    private void read(DataInput in) throws IOException {
+        // verify file magic header intact
+        final int magic = in.readInt();
+        if (magic != FILE_MAGIC) {
+            throw new ProtocolException("unexpected magic: " + magic);
+        }
+
+        final int version = in.readInt();
+        switch (version) {
+            case VERSION_UNIFIED_INIT: {
+                // uid := size *(NetworkIdentitySet size *(uid set tag NetworkStatsHistory))
+                final int identSize = in.readInt();
+                for (int i = 0; i < identSize; i++) {
+                    final NetworkIdentitySet ident = new NetworkIdentitySet(in);
+
+                    final int size = in.readInt();
+                    for (int j = 0; j < size; j++) {
+                        final int uid = in.readInt();
+                        final int set = in.readInt();
+                        final int tag = in.readInt();
+
+                        final Key key = new Key(ident, uid, set, tag);
+                        final NetworkStatsHistory history = new NetworkStatsHistory(in);
+                        recordHistory(key, history);
+                    }
+                }
+                break;
+            }
+            default: {
+                throw new ProtocolException("unexpected version: " + version);
+            }
+        }
+    }
+
+    @Override
+    public void write(OutputStream out) throws IOException {
+        final FastDataOutput dataOut = new FastDataOutput(out, BUFFER_SIZE);
+        write(dataOut);
+        dataOut.flush();
+    }
+
+    private void write(DataOutput out) throws IOException {
+        // cluster key lists grouped by ident
+        final HashMap<NetworkIdentitySet, ArrayList<Key>> keysByIdent = Maps.newHashMap();
+        for (Key key : mStats.keySet()) {
+            ArrayList<Key> keys = keysByIdent.get(key.ident);
+            if (keys == null) {
+                keys = Lists.newArrayList();
+                keysByIdent.put(key.ident, keys);
+            }
+            keys.add(key);
+        }
+
+        out.writeInt(FILE_MAGIC);
+        out.writeInt(VERSION_UNIFIED_INIT);
+
+        out.writeInt(keysByIdent.size());
+        for (NetworkIdentitySet ident : keysByIdent.keySet()) {
+            final ArrayList<Key> keys = keysByIdent.get(ident);
+            ident.writeToStream(out);
+
+            out.writeInt(keys.size());
+            for (Key key : keys) {
+                final NetworkStatsHistory history = mStats.get(key);
+                out.writeInt(key.uid);
+                out.writeInt(key.set);
+                out.writeInt(key.tag);
+                history.writeToStream(out);
+            }
+        }
+    }
+
+    @Deprecated
+    public void readLegacyNetwork(File file) throws IOException {
+        final AtomicFile inputFile = new AtomicFile(file);
+
+        DataInputStream in = null;
+        try {
+            in = new DataInputStream(new BufferedInputStream(inputFile.openRead()));
+
+            // verify file magic header intact
+            final int magic = in.readInt();
+            if (magic != FILE_MAGIC) {
+                throw new ProtocolException("unexpected magic: " + magic);
+            }
+
+            final int version = in.readInt();
+            switch (version) {
+                case VERSION_NETWORK_INIT: {
+                    // network := size *(NetworkIdentitySet NetworkStatsHistory)
+                    final int size = in.readInt();
+                    for (int i = 0; i < size; i++) {
+                        final NetworkIdentitySet ident = new NetworkIdentitySet(in);
+                        final NetworkStatsHistory history = new NetworkStatsHistory(in);
+
+                        final Key key = new Key(ident, UID_ALL, SET_ALL, TAG_NONE);
+                        recordHistory(key, history);
+                    }
+                    break;
+                }
+                default: {
+                    throw new ProtocolException("unexpected version: " + version);
+                }
+            }
+        } catch (FileNotFoundException e) {
+            // missing stats is okay, probably first boot
+        } finally {
+            IoUtils.closeQuietly(in);
+        }
+    }
+
+    @Deprecated
+    public void readLegacyUid(File file, boolean onlyTags) throws IOException {
+        final AtomicFile inputFile = new AtomicFile(file);
+
+        DataInputStream in = null;
+        try {
+            in = new DataInputStream(new BufferedInputStream(inputFile.openRead()));
+
+            // verify file magic header intact
+            final int magic = in.readInt();
+            if (magic != FILE_MAGIC) {
+                throw new ProtocolException("unexpected magic: " + magic);
+            }
+
+            final int version = in.readInt();
+            switch (version) {
+                case VERSION_UID_INIT: {
+                    // uid := size *(UID NetworkStatsHistory)
+
+                    // drop this data version, since we don't have a good
+                    // mapping into NetworkIdentitySet.
+                    break;
+                }
+                case VERSION_UID_WITH_IDENT: {
+                    // uid := size *(NetworkIdentitySet size *(UID NetworkStatsHistory))
+
+                    // drop this data version, since this version only existed
+                    // for a short time.
+                    break;
+                }
+                case VERSION_UID_WITH_TAG:
+                case VERSION_UID_WITH_SET: {
+                    // uid := size *(NetworkIdentitySet size *(uid set tag NetworkStatsHistory))
+                    final int identSize = in.readInt();
+                    for (int i = 0; i < identSize; i++) {
+                        final NetworkIdentitySet ident = new NetworkIdentitySet(in);
+
+                        final int size = in.readInt();
+                        for (int j = 0; j < size; j++) {
+                            final int uid = in.readInt();
+                            final int set = (version >= VERSION_UID_WITH_SET) ? in.readInt()
+                                    : SET_DEFAULT;
+                            final int tag = in.readInt();
+
+                            final Key key = new Key(ident, uid, set, tag);
+                            final NetworkStatsHistory history = new NetworkStatsHistory(in);
+
+                            if ((tag == TAG_NONE) != onlyTags) {
+                                recordHistory(key, history);
+                            }
+                        }
+                    }
+                    break;
+                }
+                default: {
+                    throw new ProtocolException("unexpected version: " + version);
+                }
+            }
+        } catch (FileNotFoundException e) {
+            // missing stats is okay, probably first boot
+        } finally {
+            IoUtils.closeQuietly(in);
+        }
+    }
+
+    /**
+     * Remove any {@link NetworkStatsHistory} attributed to the requested UID,
+     * moving any {@link NetworkStats#TAG_NONE} series to
+     * {@link TrafficStats#UID_REMOVED}.
+     */
+    public void removeUids(int[] uids) {
+        final ArrayList<Key> knownKeys = Lists.newArrayList();
+        knownKeys.addAll(mStats.keySet());
+
+        // migrate all UID stats into special "removed" bucket
+        for (Key key : knownKeys) {
+            if (ArrayUtils.contains(uids, key.uid)) {
+                // only migrate combined TAG_NONE history
+                if (key.tag == TAG_NONE) {
+                    final NetworkStatsHistory uidHistory = mStats.get(key);
+                    final NetworkStatsHistory removedHistory = findOrCreateHistory(
+                            key.ident, UID_REMOVED, SET_DEFAULT, TAG_NONE);
+                    removedHistory.recordEntireHistory(uidHistory);
+                }
+                mStats.remove(key);
+                mDirty = true;
+            }
+        }
+    }
+
+    private void noteRecordedHistory(long startMillis, long endMillis, long totalBytes) {
+        if (startMillis < mStartMillis) mStartMillis = startMillis;
+        if (endMillis > mEndMillis) mEndMillis = endMillis;
+        mTotalBytes += totalBytes;
+        mDirty = true;
+    }
+
+    private int estimateBuckets() {
+        return (int) (Math.min(mEndMillis - mStartMillis, WEEK_IN_MILLIS * 5)
+                / mBucketDuration);
+    }
+
+    private ArrayList<Key> getSortedKeys() {
+        final ArrayList<Key> keys = Lists.newArrayList();
+        keys.addAll(mStats.keySet());
+        Collections.sort(keys);
+        return keys;
+    }
+
+    public void dump(IndentingPrintWriter pw) {
+        for (Key key : getSortedKeys()) {
+            pw.print("ident="); pw.print(key.ident.toString());
+            pw.print(" uid="); pw.print(key.uid);
+            pw.print(" set="); pw.print(NetworkStats.setToString(key.set));
+            pw.print(" tag="); pw.println(NetworkStats.tagToString(key.tag));
+
+            final NetworkStatsHistory history = mStats.get(key);
+            pw.increaseIndent();
+            history.dump(pw, true);
+            pw.decreaseIndent();
+        }
+    }
+
+    public void dumpDebug(ProtoOutputStream proto, long tag) {
+        final long start = proto.start(tag);
+
+        for (Key key : getSortedKeys()) {
+            final long startStats = proto.start(NetworkStatsCollectionProto.STATS);
+
+            // Key
+            final long startKey = proto.start(NetworkStatsCollectionStatsProto.KEY);
+            key.ident.dumpDebug(proto, NetworkStatsCollectionKeyProto.IDENTITY);
+            proto.write(NetworkStatsCollectionKeyProto.UID, key.uid);
+            proto.write(NetworkStatsCollectionKeyProto.SET, key.set);
+            proto.write(NetworkStatsCollectionKeyProto.TAG, key.tag);
+            proto.end(startKey);
+
+            // Value
+            final NetworkStatsHistory history = mStats.get(key);
+            history.dumpDebug(proto, NetworkStatsCollectionStatsProto.HISTORY);
+            proto.end(startStats);
+        }
+
+        proto.end(start);
+    }
+
+    public void dumpCheckin(PrintWriter pw, long start, long end) {
+        dumpCheckin(pw, start, end, NetworkTemplate.buildTemplateMobileWildcard(), "cell");
+        dumpCheckin(pw, start, end, NetworkTemplate.buildTemplateWifiWildcard(), "wifi");
+        dumpCheckin(pw, start, end, NetworkTemplate.buildTemplateEthernet(), "eth");
+        dumpCheckin(pw, start, end, NetworkTemplate.buildTemplateBluetooth(), "bt");
+    }
+
+    /**
+     * Dump all contained stats that match requested parameters, but group
+     * together all matching {@link NetworkTemplate} under a single prefix.
+     */
+    private void dumpCheckin(PrintWriter pw, long start, long end, NetworkTemplate groupTemplate,
+            String groupPrefix) {
+        final ArrayMap<Key, NetworkStatsHistory> grouped = new ArrayMap<>();
+
+        // Walk through all history, grouping by matching network templates
+        for (int i = 0; i < mStats.size(); i++) {
+            final Key key = mStats.keyAt(i);
+            final NetworkStatsHistory value = mStats.valueAt(i);
+
+            if (!templateMatches(groupTemplate, key.ident)) continue;
+            if (key.set >= NetworkStats.SET_DEBUG_START) continue;
+
+            final Key groupKey = new Key(null, key.uid, key.set, key.tag);
+            NetworkStatsHistory groupHistory = grouped.get(groupKey);
+            if (groupHistory == null) {
+                groupHistory = new NetworkStatsHistory(value.getBucketDuration());
+                grouped.put(groupKey, groupHistory);
+            }
+            groupHistory.recordHistory(value, start, end);
+        }
+
+        for (int i = 0; i < grouped.size(); i++) {
+            final Key key = grouped.keyAt(i);
+            final NetworkStatsHistory value = grouped.valueAt(i);
+
+            if (value.size() == 0) continue;
+
+            pw.print("c,");
+            pw.print(groupPrefix); pw.print(',');
+            pw.print(key.uid); pw.print(',');
+            pw.print(NetworkStats.setToCheckinString(key.set)); pw.print(',');
+            pw.print(key.tag);
+            pw.println();
+
+            value.dumpCheckin(pw);
+        }
+    }
+
+    /**
+     * Test if given {@link NetworkTemplate} matches any {@link NetworkIdentity}
+     * in the given {@link NetworkIdentitySet}.
+     */
+    private static boolean templateMatches(NetworkTemplate template, NetworkIdentitySet identSet) {
+        for (NetworkIdentity ident : identSet) {
+            if (template.matches(ident)) {
+                return true;
+            }
+        }
+        return false;
+    }
+
+    private static class Key implements Comparable<Key> {
+        public final NetworkIdentitySet ident;
+        public final int uid;
+        public final int set;
+        public final int tag;
+
+        private final int hashCode;
+
+        public Key(NetworkIdentitySet ident, int uid, int set, int tag) {
+            this.ident = ident;
+            this.uid = uid;
+            this.set = set;
+            this.tag = tag;
+            hashCode = Objects.hash(ident, uid, set, tag);
+        }
+
+        @Override
+        public int hashCode() {
+            return hashCode;
+        }
+
+        @Override
+        public boolean equals(Object obj) {
+            if (obj instanceof Key) {
+                final Key key = (Key) obj;
+                return uid == key.uid && set == key.set && tag == key.tag
+                        && Objects.equals(ident, key.ident);
+            }
+            return false;
+        }
+
+        @Override
+        public int compareTo(Key another) {
+            int res = 0;
+            if (ident != null && another.ident != null) {
+                res = ident.compareTo(another.ident);
+            }
+            if (res == 0) {
+                res = Integer.compare(uid, another.uid);
+            }
+            if (res == 0) {
+                res = Integer.compare(set, another.set);
+            }
+            if (res == 0) {
+                res = Integer.compare(tag, another.tag);
+            }
+            return res;
+        }
+    }
+}
diff --git a/service-t/src/com/android/server/net/NetworkStatsFactory.java b/service-t/src/com/android/server/net/NetworkStatsFactory.java
new file mode 100644
index 0000000..e6433db
--- /dev/null
+++ b/service-t/src/com/android/server/net/NetworkStatsFactory.java
@@ -0,0 +1,489 @@
+/*
+ * Copyright (C) 2011 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.net;
+
+import static android.net.NetworkStats.INTERFACES_ALL;
+import static android.net.NetworkStats.SET_ALL;
+import static android.net.NetworkStats.TAG_ALL;
+import static android.net.NetworkStats.TAG_NONE;
+import static android.net.NetworkStats.UID_ALL;
+
+import static com.android.server.NetworkManagementSocketTagger.kernelToTag;
+
+import android.annotation.Nullable;
+import android.net.INetd;
+import android.net.NetworkStats;
+import android.net.UnderlyingNetworkInfo;
+import android.net.util.NetdService;
+import android.os.RemoteException;
+import android.os.StrictMode;
+import android.os.SystemClock;
+
+import com.android.internal.annotations.GuardedBy;
+import com.android.internal.annotations.VisibleForTesting;
+import com.android.internal.util.ArrayUtils;
+import com.android.internal.util.ProcFileReader;
+
+import libcore.io.IoUtils;
+
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.IOException;
+import java.net.ProtocolException;
+import java.util.Arrays;
+import java.util.HashSet;
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
+
+/**
+ * Creates {@link NetworkStats} instances by parsing various {@code /proc/}
+ * files as needed.
+ *
+ * @hide
+ */
+public class NetworkStatsFactory {
+    private static final String TAG = "NetworkStatsFactory";
+
+    private static final boolean USE_NATIVE_PARSING = true;
+    private static final boolean VALIDATE_NATIVE_STATS = false;
+
+    /** Path to {@code /proc/net/xt_qtaguid/iface_stat_all}. */
+    private final File mStatsXtIfaceAll;
+    /** Path to {@code /proc/net/xt_qtaguid/iface_stat_fmt}. */
+    private final File mStatsXtIfaceFmt;
+    /** Path to {@code /proc/net/xt_qtaguid/stats}. */
+    private final File mStatsXtUid;
+
+    private final boolean mUseBpfStats;
+
+    private INetd mNetdService;
+
+    /**
+     * Guards persistent data access in this class
+     *
+     * <p>In order to prevent deadlocks, critical sections protected by this lock SHALL NOT call out
+     * to other code that will acquire other locks within the system server. See b/134244752.
+     */
+    private final Object mPersistentDataLock = new Object();
+
+    /** Set containing info about active VPNs and their underlying networks. */
+    private volatile UnderlyingNetworkInfo[] mUnderlyingNetworkInfos = new UnderlyingNetworkInfo[0];
+
+    // A persistent snapshot of cumulative stats since device start
+    @GuardedBy("mPersistentDataLock")
+    private NetworkStats mPersistSnapshot;
+
+    // The persistent snapshot of tun and 464xlat adjusted stats since device start
+    @GuardedBy("mPersistentDataLock")
+    private NetworkStats mTunAnd464xlatAdjustedStats;
+
+    /**
+     * (Stacked interface) -> (base interface) association for all connected ifaces since boot.
+     *
+     * Because counters must never roll backwards, once a given interface is stacked on top of an
+     * underlying interface, the stacked interface can never be stacked on top of
+     * another interface. */
+    private final ConcurrentHashMap<String, String> mStackedIfaces
+            = new ConcurrentHashMap<>();
+
+    /** Informs the factory of a new stacked interface. */
+    public void noteStackedIface(String stackedIface, String baseIface) {
+        if (stackedIface != null && baseIface != null) {
+            mStackedIfaces.put(stackedIface, baseIface);
+        }
+    }
+
+    /**
+     * Set active VPN information for data usage migration purposes
+     *
+     * <p>Traffic on TUN-based VPNs inherently all appear to be originated from the VPN providing
+     * app's UID. This method is used to support migration of VPN data usage, ensuring data is
+     * accurately billed to the real owner of the traffic.
+     *
+     * @param vpnArray The snapshot of the currently-running VPNs.
+     */
+    public void updateUnderlyingNetworkInfos(UnderlyingNetworkInfo[] vpnArray) {
+        mUnderlyingNetworkInfos = vpnArray.clone();
+    }
+
+    /**
+     * Get a set of interfaces containing specified ifaces and stacked interfaces.
+     *
+     * <p>The added stacked interfaces are ifaces stacked on top of the specified ones, or ifaces
+     * on which the specified ones are stacked. Stacked interfaces are those noted with
+     * {@link #noteStackedIface(String, String)}, but only interfaces noted before this method
+     * is called are guaranteed to be included.
+     */
+    public String[] augmentWithStackedInterfaces(@Nullable String[] requiredIfaces) {
+        if (requiredIfaces == NetworkStats.INTERFACES_ALL) {
+            return null;
+        }
+
+        HashSet<String> relatedIfaces = new HashSet<>(Arrays.asList(requiredIfaces));
+        // ConcurrentHashMap's EntrySet iterators are "guaranteed to traverse
+        // elements as they existed upon construction exactly once, and may
+        // (but are not guaranteed to) reflect any modifications subsequent to construction".
+        // This is enough here.
+        for (Map.Entry<String, String> entry : mStackedIfaces.entrySet()) {
+            if (relatedIfaces.contains(entry.getKey())) {
+                relatedIfaces.add(entry.getValue());
+            } else if (relatedIfaces.contains(entry.getValue())) {
+                relatedIfaces.add(entry.getKey());
+            }
+        }
+
+        String[] outArray = new String[relatedIfaces.size()];
+        return relatedIfaces.toArray(outArray);
+    }
+
+    /**
+     * Applies 464xlat adjustments with ifaces noted with {@link #noteStackedIface(String, String)}.
+     * @see NetworkStats#apply464xlatAdjustments(NetworkStats, NetworkStats, Map)
+     */
+    public void apply464xlatAdjustments(NetworkStats baseTraffic, NetworkStats stackedTraffic) {
+        NetworkStats.apply464xlatAdjustments(baseTraffic, stackedTraffic, mStackedIfaces);
+    }
+
+    public NetworkStatsFactory() {
+        this(new File("/proc/"), true);
+    }
+
+    @VisibleForTesting
+    public NetworkStatsFactory(File procRoot, boolean useBpfStats) {
+        mStatsXtIfaceAll = new File(procRoot, "net/xt_qtaguid/iface_stat_all");
+        mStatsXtIfaceFmt = new File(procRoot, "net/xt_qtaguid/iface_stat_fmt");
+        mStatsXtUid = new File(procRoot, "net/xt_qtaguid/stats");
+        mUseBpfStats = useBpfStats;
+        synchronized (mPersistentDataLock) {
+            mPersistSnapshot = new NetworkStats(SystemClock.elapsedRealtime(), -1);
+            mTunAnd464xlatAdjustedStats = new NetworkStats(SystemClock.elapsedRealtime(), -1);
+        }
+    }
+
+    public NetworkStats readBpfNetworkStatsDev() throws IOException {
+        final NetworkStats stats = new NetworkStats(SystemClock.elapsedRealtime(), 6);
+        if (nativeReadNetworkStatsDev(stats) != 0) {
+            throw new IOException("Failed to parse bpf iface stats");
+        }
+        return stats;
+    }
+
+    /**
+     * Parse and return interface-level summary {@link NetworkStats} measured
+     * using {@code /proc/net/dev} style hooks, which may include non IP layer
+     * traffic. Values monotonically increase since device boot, and may include
+     * details about inactive interfaces.
+     *
+     * @throws IllegalStateException when problem parsing stats.
+     */
+    public NetworkStats readNetworkStatsSummaryDev() throws IOException {
+
+        // Return xt_bpf stats if switched to bpf module.
+        if (mUseBpfStats)
+            return readBpfNetworkStatsDev();
+
+        final StrictMode.ThreadPolicy savedPolicy = StrictMode.allowThreadDiskReads();
+
+        final NetworkStats stats = new NetworkStats(SystemClock.elapsedRealtime(), 6);
+        final NetworkStats.Entry entry = new NetworkStats.Entry();
+
+        ProcFileReader reader = null;
+        try {
+            reader = new ProcFileReader(new FileInputStream(mStatsXtIfaceAll));
+
+            while (reader.hasMoreData()) {
+                entry.iface = reader.nextString();
+                entry.uid = UID_ALL;
+                entry.set = SET_ALL;
+                entry.tag = TAG_NONE;
+
+                final boolean active = reader.nextInt() != 0;
+
+                // always include snapshot values
+                entry.rxBytes = reader.nextLong();
+                entry.rxPackets = reader.nextLong();
+                entry.txBytes = reader.nextLong();
+                entry.txPackets = reader.nextLong();
+
+                // fold in active numbers, but only when active
+                if (active) {
+                    entry.rxBytes += reader.nextLong();
+                    entry.rxPackets += reader.nextLong();
+                    entry.txBytes += reader.nextLong();
+                    entry.txPackets += reader.nextLong();
+                }
+
+                stats.insertEntry(entry);
+                reader.finishLine();
+            }
+        } catch (NullPointerException|NumberFormatException e) {
+            throw protocolExceptionWithCause("problem parsing stats", e);
+        } finally {
+            IoUtils.closeQuietly(reader);
+            StrictMode.setThreadPolicy(savedPolicy);
+        }
+        return stats;
+    }
+
+    /**
+     * Parse and return interface-level summary {@link NetworkStats}. Designed
+     * to return only IP layer traffic. Values monotonically increase since
+     * device boot, and may include details about inactive interfaces.
+     *
+     * @throws IllegalStateException when problem parsing stats.
+     */
+    public NetworkStats readNetworkStatsSummaryXt() throws IOException {
+
+        // Return xt_bpf stats if qtaguid  module is replaced.
+        if (mUseBpfStats)
+            return readBpfNetworkStatsDev();
+
+        final StrictMode.ThreadPolicy savedPolicy = StrictMode.allowThreadDiskReads();
+
+        // return null when kernel doesn't support
+        if (!mStatsXtIfaceFmt.exists()) return null;
+
+        final NetworkStats stats = new NetworkStats(SystemClock.elapsedRealtime(), 6);
+        final NetworkStats.Entry entry = new NetworkStats.Entry();
+
+        ProcFileReader reader = null;
+        try {
+            // open and consume header line
+            reader = new ProcFileReader(new FileInputStream(mStatsXtIfaceFmt));
+            reader.finishLine();
+
+            while (reader.hasMoreData()) {
+                entry.iface = reader.nextString();
+                entry.uid = UID_ALL;
+                entry.set = SET_ALL;
+                entry.tag = TAG_NONE;
+
+                entry.rxBytes = reader.nextLong();
+                entry.rxPackets = reader.nextLong();
+                entry.txBytes = reader.nextLong();
+                entry.txPackets = reader.nextLong();
+
+                stats.insertEntry(entry);
+                reader.finishLine();
+            }
+        } catch (NullPointerException|NumberFormatException e) {
+            throw protocolExceptionWithCause("problem parsing stats", e);
+        } finally {
+            IoUtils.closeQuietly(reader);
+            StrictMode.setThreadPolicy(savedPolicy);
+        }
+        return stats;
+    }
+
+    public NetworkStats readNetworkStatsDetail() throws IOException {
+        return readNetworkStatsDetail(UID_ALL, INTERFACES_ALL, TAG_ALL);
+    }
+
+    @GuardedBy("mPersistentDataLock")
+    private void requestSwapActiveStatsMapLocked() throws RemoteException {
+        // Ask netd to do a active map stats swap. When the binder call successfully returns,
+        // the system server should be able to safely read and clean the inactive map
+        // without race problem.
+        if (mNetdService == null) {
+            mNetdService = NetdService.getInstance();
+        }
+        mNetdService.trafficSwapActiveStatsMap();
+    }
+
+    /**
+     * Reads the detailed UID stats based on the provided parameters
+     *
+     * @param limitUid the UID to limit this query to
+     * @param limitIfaces the interfaces to limit this query to. Use {@link
+     *     NetworkStats.INTERFACES_ALL} to select all interfaces
+     * @param limitTag the tags to limit this query to
+     * @return the NetworkStats instance containing network statistics at the present time.
+     */
+    public NetworkStats readNetworkStatsDetail(
+            int limitUid, String[] limitIfaces, int limitTag) throws IOException {
+        // In order to prevent deadlocks, anything protected by this lock MUST NOT call out to other
+        // code that will acquire other locks within the system server. See b/134244752.
+        synchronized (mPersistentDataLock) {
+            // Take a reference. If this gets swapped out, we still have the old reference.
+            final UnderlyingNetworkInfo[] vpnArray = mUnderlyingNetworkInfos;
+            // Take a defensive copy. mPersistSnapshot is mutated in some cases below
+            final NetworkStats prev = mPersistSnapshot.clone();
+
+            if (USE_NATIVE_PARSING) {
+                final NetworkStats stats =
+                        new NetworkStats(SystemClock.elapsedRealtime(), 0 /* initialSize */);
+                if (mUseBpfStats) {
+                    try {
+                        requestSwapActiveStatsMapLocked();
+                    } catch (RemoteException e) {
+                        throw new IOException(e);
+                    }
+                    // Stats are always read from the inactive map, so they must be read after the
+                    // swap
+                    if (nativeReadNetworkStatsDetail(stats, mStatsXtUid.getAbsolutePath(), UID_ALL,
+                            INTERFACES_ALL, TAG_ALL, mUseBpfStats) != 0) {
+                        throw new IOException("Failed to parse network stats");
+                    }
+
+                    // BPF stats are incremental; fold into mPersistSnapshot.
+                    mPersistSnapshot.setElapsedRealtime(stats.getElapsedRealtime());
+                    mPersistSnapshot.combineAllValues(stats);
+                } else {
+                    if (nativeReadNetworkStatsDetail(stats, mStatsXtUid.getAbsolutePath(), UID_ALL,
+                            INTERFACES_ALL, TAG_ALL, mUseBpfStats) != 0) {
+                        throw new IOException("Failed to parse network stats");
+                    }
+                    if (VALIDATE_NATIVE_STATS) {
+                        final NetworkStats javaStats = javaReadNetworkStatsDetail(mStatsXtUid,
+                                UID_ALL, INTERFACES_ALL, TAG_ALL);
+                        assertEquals(javaStats, stats);
+                    }
+
+                    mPersistSnapshot = stats;
+                }
+            } else {
+                mPersistSnapshot = javaReadNetworkStatsDetail(mStatsXtUid, UID_ALL, INTERFACES_ALL,
+                        TAG_ALL);
+            }
+
+            NetworkStats adjustedStats = adjustForTunAnd464Xlat(mPersistSnapshot, prev, vpnArray);
+
+            // Filter return values
+            adjustedStats.filter(limitUid, limitIfaces, limitTag);
+            return adjustedStats;
+        }
+    }
+
+    @GuardedBy("mPersistentDataLock")
+    private NetworkStats adjustForTunAnd464Xlat(NetworkStats uidDetailStats,
+            NetworkStats previousStats, UnderlyingNetworkInfo[] vpnArray) {
+        // Calculate delta from last snapshot
+        final NetworkStats delta = uidDetailStats.subtract(previousStats);
+
+        // Apply 464xlat adjustments before VPN adjustments. If VPNs are using v4 on a v6 only
+        // network, the overhead is their fault.
+        // No locking here: apply464xlatAdjustments behaves fine with an add-only
+        // ConcurrentHashMap.
+        delta.apply464xlatAdjustments(mStackedIfaces);
+
+        // Migrate data usage over a VPN to the TUN network.
+        for (UnderlyingNetworkInfo info : vpnArray) {
+            delta.migrateTun(info.getOwnerUid(), info.getInterface(),
+                    info.getUnderlyingInterfaces());
+            // Filter out debug entries as that may lead to over counting.
+            delta.filterDebugEntries();
+        }
+
+        // Update mTunAnd464xlatAdjustedStats with migrated delta.
+        mTunAnd464xlatAdjustedStats.combineAllValues(delta);
+        mTunAnd464xlatAdjustedStats.setElapsedRealtime(uidDetailStats.getElapsedRealtime());
+
+        return mTunAnd464xlatAdjustedStats.clone();
+    }
+
+    /**
+     * Parse and return {@link NetworkStats} with UID-level details. Values are
+     * expected to monotonically increase since device boot.
+     */
+    @VisibleForTesting
+    public static NetworkStats javaReadNetworkStatsDetail(File detailPath, int limitUid,
+            String[] limitIfaces, int limitTag)
+            throws IOException {
+        final StrictMode.ThreadPolicy savedPolicy = StrictMode.allowThreadDiskReads();
+
+        final NetworkStats stats = new NetworkStats(SystemClock.elapsedRealtime(), 24);
+        final NetworkStats.Entry entry = new NetworkStats.Entry();
+
+        int idx = 1;
+        int lastIdx = 1;
+
+        ProcFileReader reader = null;
+        try {
+            // open and consume header line
+            reader = new ProcFileReader(new FileInputStream(detailPath));
+            reader.finishLine();
+
+            while (reader.hasMoreData()) {
+                idx = reader.nextInt();
+                if (idx != lastIdx + 1) {
+                    throw new ProtocolException(
+                            "inconsistent idx=" + idx + " after lastIdx=" + lastIdx);
+                }
+                lastIdx = idx;
+
+                entry.iface = reader.nextString();
+                entry.tag = kernelToTag(reader.nextString());
+                entry.uid = reader.nextInt();
+                entry.set = reader.nextInt();
+                entry.rxBytes = reader.nextLong();
+                entry.rxPackets = reader.nextLong();
+                entry.txBytes = reader.nextLong();
+                entry.txPackets = reader.nextLong();
+
+                if ((limitIfaces == null || ArrayUtils.contains(limitIfaces, entry.iface))
+                        && (limitUid == UID_ALL || limitUid == entry.uid)
+                        && (limitTag == TAG_ALL || limitTag == entry.tag)) {
+                    stats.insertEntry(entry);
+                }
+
+                reader.finishLine();
+            }
+        } catch (NullPointerException|NumberFormatException e) {
+            throw protocolExceptionWithCause("problem parsing idx " + idx, e);
+        } finally {
+            IoUtils.closeQuietly(reader);
+            StrictMode.setThreadPolicy(savedPolicy);
+        }
+
+        return stats;
+    }
+
+    public void assertEquals(NetworkStats expected, NetworkStats actual) {
+        if (expected.size() != actual.size()) {
+            throw new AssertionError(
+                    "Expected size " + expected.size() + ", actual size " + actual.size());
+        }
+
+        NetworkStats.Entry expectedRow = null;
+        NetworkStats.Entry actualRow = null;
+        for (int i = 0; i < expected.size(); i++) {
+            expectedRow = expected.getValues(i, expectedRow);
+            actualRow = actual.getValues(i, actualRow);
+            if (!expectedRow.equals(actualRow)) {
+                throw new AssertionError(
+                        "Expected row " + i + ": " + expectedRow + ", actual row " + actualRow);
+            }
+        }
+    }
+
+    /**
+     * Parse statistics from file into given {@link NetworkStats} object. Values
+     * are expected to monotonically increase since device boot.
+     */
+    @VisibleForTesting
+    public static native int nativeReadNetworkStatsDetail(NetworkStats stats, String path,
+        int limitUid, String[] limitIfaces, int limitTag, boolean useBpfStats);
+
+    @VisibleForTesting
+    public static native int nativeReadNetworkStatsDev(NetworkStats stats);
+
+    private static ProtocolException protocolExceptionWithCause(String message, Throwable cause) {
+        ProtocolException pe = new ProtocolException(message);
+        pe.initCause(cause);
+        return pe;
+    }
+}
diff --git a/service-t/src/com/android/server/net/NetworkStatsObservers.java b/service-t/src/com/android/server/net/NetworkStatsObservers.java
new file mode 100644
index 0000000..2564dae
--- /dev/null
+++ b/service-t/src/com/android/server/net/NetworkStatsObservers.java
@@ -0,0 +1,442 @@
+/*
+ * Copyright (C) 2016 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.net;
+
+import static android.app.usage.NetworkStatsManager.MIN_THRESHOLD_BYTES;
+
+import static com.android.internal.util.Preconditions.checkArgument;
+
+import android.app.usage.NetworkStatsManager;
+import android.net.DataUsageRequest;
+import android.net.NetworkStats;
+import android.net.NetworkStatsHistory;
+import android.net.NetworkTemplate;
+import android.os.Bundle;
+import android.os.Handler;
+import android.os.HandlerThread;
+import android.os.IBinder;
+import android.os.Looper;
+import android.os.Message;
+import android.os.Messenger;
+import android.os.Process;
+import android.os.RemoteException;
+import android.util.ArrayMap;
+import android.util.Slog;
+import android.util.SparseArray;
+
+import com.android.internal.annotations.VisibleForTesting;
+
+import java.util.concurrent.atomic.AtomicInteger;
+
+/**
+ * Manages observers of {@link NetworkStats}. Allows observers to be notified when
+ * data usage has been reported in {@link NetworkStatsService}. An observer can set
+ * a threshold of how much data it cares about to be notified.
+ */
+class NetworkStatsObservers {
+    private static final String TAG = "NetworkStatsObservers";
+    private static final boolean LOGV = false;
+
+    private static final int MSG_REGISTER = 1;
+    private static final int MSG_UNREGISTER = 2;
+    private static final int MSG_UPDATE_STATS = 3;
+
+    // All access to this map must be done from the handler thread.
+    // indexed by DataUsageRequest#requestId
+    private final SparseArray<RequestInfo> mDataUsageRequests = new SparseArray<>();
+
+    // Sequence number of DataUsageRequests
+    private final AtomicInteger mNextDataUsageRequestId = new AtomicInteger();
+
+    // Lazily instantiated when an observer is registered.
+    private volatile Handler mHandler;
+
+    /**
+     * Creates a wrapper that contains the caller context and a normalized request.
+     * The request should be returned to the caller app, and the wrapper should be sent to this
+     * object through #addObserver by the service handler.
+     *
+     * <p>It will register the observer asynchronously, so it is safe to call from any thread.
+     *
+     * @return the normalized request wrapped within {@link RequestInfo}.
+     */
+    public DataUsageRequest register(DataUsageRequest inputRequest, Messenger messenger,
+                IBinder binder, int callingUid, @NetworkStatsAccess.Level int accessLevel) {
+        DataUsageRequest request = buildRequest(inputRequest);
+        RequestInfo requestInfo = buildRequestInfo(request, messenger, binder, callingUid,
+                accessLevel);
+
+        if (LOGV) Slog.v(TAG, "Registering observer for " + request);
+        getHandler().sendMessage(mHandler.obtainMessage(MSG_REGISTER, requestInfo));
+        return request;
+    }
+
+    /**
+     * Unregister a data usage observer.
+     *
+     * <p>It will unregister the observer asynchronously, so it is safe to call from any thread.
+     */
+    public void unregister(DataUsageRequest request, int callingUid) {
+        getHandler().sendMessage(mHandler.obtainMessage(MSG_UNREGISTER, callingUid, 0 /* ignore */,
+                request));
+    }
+
+    /**
+     * Updates data usage statistics of registered observers and notifies if limits are reached.
+     *
+     * <p>It will update stats asynchronously, so it is safe to call from any thread.
+     */
+    public void updateStats(NetworkStats xtSnapshot, NetworkStats uidSnapshot,
+                ArrayMap<String, NetworkIdentitySet> activeIfaces,
+                ArrayMap<String, NetworkIdentitySet> activeUidIfaces,
+                long currentTime) {
+        StatsContext statsContext = new StatsContext(xtSnapshot, uidSnapshot, activeIfaces,
+                activeUidIfaces, currentTime);
+        getHandler().sendMessage(mHandler.obtainMessage(MSG_UPDATE_STATS, statsContext));
+    }
+
+    private Handler getHandler() {
+        if (mHandler == null) {
+            synchronized (this) {
+                if (mHandler == null) {
+                    if (LOGV) Slog.v(TAG, "Creating handler");
+                    mHandler = new Handler(getHandlerLooperLocked(), mHandlerCallback);
+                }
+            }
+        }
+        return mHandler;
+    }
+
+    @VisibleForTesting
+    protected Looper getHandlerLooperLocked() {
+        HandlerThread handlerThread = new HandlerThread(TAG);
+        handlerThread.start();
+        return handlerThread.getLooper();
+    }
+
+    private Handler.Callback mHandlerCallback = new Handler.Callback() {
+        @Override
+        public boolean handleMessage(Message msg) {
+            switch (msg.what) {
+                case MSG_REGISTER: {
+                    handleRegister((RequestInfo) msg.obj);
+                    return true;
+                }
+                case MSG_UNREGISTER: {
+                    handleUnregister((DataUsageRequest) msg.obj, msg.arg1 /* callingUid */);
+                    return true;
+                }
+                case MSG_UPDATE_STATS: {
+                    handleUpdateStats((StatsContext) msg.obj);
+                    return true;
+                }
+                default: {
+                    return false;
+                }
+            }
+        }
+    };
+
+    /**
+     * Adds a {@link RequestInfo} as an observer.
+     * Should only be called from the handler thread otherwise there will be a race condition
+     * on mDataUsageRequests.
+     */
+    private void handleRegister(RequestInfo requestInfo) {
+        mDataUsageRequests.put(requestInfo.mRequest.requestId, requestInfo);
+    }
+
+    /**
+     * Removes a {@link DataUsageRequest} if the calling uid is authorized.
+     * Should only be called from the handler thread otherwise there will be a race condition
+     * on mDataUsageRequests.
+     */
+    private void handleUnregister(DataUsageRequest request, int callingUid) {
+        RequestInfo requestInfo;
+        requestInfo = mDataUsageRequests.get(request.requestId);
+        if (requestInfo == null) {
+            if (LOGV) Slog.v(TAG, "Trying to unregister unknown request " + request);
+            return;
+        }
+        if (Process.SYSTEM_UID != callingUid && requestInfo.mCallingUid != callingUid) {
+            Slog.w(TAG, "Caller uid " + callingUid + " is not owner of " + request);
+            return;
+        }
+
+        if (LOGV) Slog.v(TAG, "Unregistering " + request);
+        mDataUsageRequests.remove(request.requestId);
+        requestInfo.unlinkDeathRecipient();
+        requestInfo.callCallback(NetworkStatsManager.CALLBACK_RELEASED);
+    }
+
+    private void handleUpdateStats(StatsContext statsContext) {
+        if (mDataUsageRequests.size() == 0) {
+            return;
+        }
+
+        for (int i = 0; i < mDataUsageRequests.size(); i++) {
+            RequestInfo requestInfo = mDataUsageRequests.valueAt(i);
+            requestInfo.updateStats(statsContext);
+        }
+    }
+
+    private DataUsageRequest buildRequest(DataUsageRequest request) {
+        // Cap the minimum threshold to a safe default to avoid too many callbacks
+        long thresholdInBytes = Math.max(MIN_THRESHOLD_BYTES, request.thresholdInBytes);
+        if (thresholdInBytes < request.thresholdInBytes) {
+            Slog.w(TAG, "Threshold was too low for " + request
+                    + ". Overriding to a safer default of " + thresholdInBytes + " bytes");
+        }
+        return new DataUsageRequest(mNextDataUsageRequestId.incrementAndGet(),
+                request.template, thresholdInBytes);
+    }
+
+    private RequestInfo buildRequestInfo(DataUsageRequest request,
+                Messenger messenger, IBinder binder, int callingUid,
+                @NetworkStatsAccess.Level int accessLevel) {
+        if (accessLevel <= NetworkStatsAccess.Level.USER) {
+            return new UserUsageRequestInfo(this, request, messenger, binder, callingUid,
+                    accessLevel);
+        } else {
+            // Safety check in case a new access level is added and we forgot to update this
+            checkArgument(accessLevel >= NetworkStatsAccess.Level.DEVICESUMMARY);
+            return new NetworkUsageRequestInfo(this, request, messenger, binder, callingUid,
+                    accessLevel);
+        }
+    }
+
+    /**
+     * Tracks information relevant to a data usage observer.
+     * It will notice when the calling process dies so we can self-expire.
+     */
+    private abstract static class RequestInfo implements IBinder.DeathRecipient {
+        private final NetworkStatsObservers mStatsObserver;
+        protected final DataUsageRequest mRequest;
+        private final Messenger mMessenger;
+        private final IBinder mBinder;
+        protected final int mCallingUid;
+        protected final @NetworkStatsAccess.Level int mAccessLevel;
+        protected NetworkStatsRecorder mRecorder;
+        protected NetworkStatsCollection mCollection;
+
+        RequestInfo(NetworkStatsObservers statsObserver, DataUsageRequest request,
+                    Messenger messenger, IBinder binder, int callingUid,
+                    @NetworkStatsAccess.Level int accessLevel) {
+            mStatsObserver = statsObserver;
+            mRequest = request;
+            mMessenger = messenger;
+            mBinder = binder;
+            mCallingUid = callingUid;
+            mAccessLevel = accessLevel;
+
+            try {
+                mBinder.linkToDeath(this, 0);
+            } catch (RemoteException e) {
+                binderDied();
+            }
+        }
+
+        @Override
+        public void binderDied() {
+            if (LOGV) Slog.v(TAG, "RequestInfo binderDied("
+                    + mRequest + ", " + mBinder + ")");
+            mStatsObserver.unregister(mRequest, Process.SYSTEM_UID);
+            callCallback(NetworkStatsManager.CALLBACK_RELEASED);
+        }
+
+        @Override
+        public String toString() {
+            return "RequestInfo from uid:" + mCallingUid
+                    + " for " + mRequest + " accessLevel:" + mAccessLevel;
+        }
+
+        private void unlinkDeathRecipient() {
+            if (mBinder != null) {
+                mBinder.unlinkToDeath(this, 0);
+            }
+        }
+
+        /**
+         * Update stats given the samples and interface to identity mappings.
+         */
+        private void updateStats(StatsContext statsContext) {
+            if (mRecorder == null) {
+                // First run; establish baseline stats
+                resetRecorder();
+                recordSample(statsContext);
+                return;
+            }
+            recordSample(statsContext);
+
+            if (checkStats()) {
+                resetRecorder();
+                callCallback(NetworkStatsManager.CALLBACK_LIMIT_REACHED);
+            }
+        }
+
+        private void callCallback(int callbackType) {
+            Bundle bundle = new Bundle();
+            bundle.putParcelable(DataUsageRequest.PARCELABLE_KEY, mRequest);
+            Message msg = Message.obtain();
+            msg.what = callbackType;
+            msg.setData(bundle);
+            try {
+                if (LOGV) {
+                    Slog.v(TAG, "sending notification " + callbackTypeToName(callbackType)
+                            + " for " + mRequest);
+                }
+                mMessenger.send(msg);
+            } catch (RemoteException e) {
+                // May occur naturally in the race of binder death.
+                Slog.w(TAG, "RemoteException caught trying to send a callback msg for " + mRequest);
+            }
+        }
+
+        private void resetRecorder() {
+            mRecorder = new NetworkStatsRecorder();
+            mCollection = mRecorder.getSinceBoot();
+        }
+
+        protected abstract boolean checkStats();
+
+        protected abstract void recordSample(StatsContext statsContext);
+
+        private String callbackTypeToName(int callbackType) {
+            switch (callbackType) {
+                case NetworkStatsManager.CALLBACK_LIMIT_REACHED:
+                    return "LIMIT_REACHED";
+                case NetworkStatsManager.CALLBACK_RELEASED:
+                    return "RELEASED";
+                default:
+                    return "UNKNOWN";
+            }
+        }
+    }
+
+    private static class NetworkUsageRequestInfo extends RequestInfo {
+        NetworkUsageRequestInfo(NetworkStatsObservers statsObserver, DataUsageRequest request,
+                    Messenger messenger, IBinder binder, int callingUid,
+                    @NetworkStatsAccess.Level int accessLevel) {
+            super(statsObserver, request, messenger, binder, callingUid, accessLevel);
+        }
+
+        @Override
+        protected boolean checkStats() {
+            long bytesSoFar = getTotalBytesForNetwork(mRequest.template);
+            if (LOGV) {
+                Slog.v(TAG, bytesSoFar + " bytes so far since notification for "
+                        + mRequest.template);
+            }
+            if (bytesSoFar > mRequest.thresholdInBytes) {
+                return true;
+            }
+            return false;
+        }
+
+        @Override
+        protected void recordSample(StatsContext statsContext) {
+            // Recorder does not need to be locked in this context since only the handler
+            // thread will update it. We pass a null VPN array because usage is aggregated by uid
+            // for this snapshot, so VPN traffic can't be reattributed to responsible apps.
+            mRecorder.recordSnapshotLocked(statsContext.mXtSnapshot, statsContext.mActiveIfaces,
+                    statsContext.mCurrentTime);
+        }
+
+        /**
+         * Reads stats matching the given template. {@link NetworkStatsCollection} will aggregate
+         * over all buckets, which in this case should be only one since we built it big enough
+         * that it will outlive the caller. If it doesn't, then there will be multiple buckets.
+         */
+        private long getTotalBytesForNetwork(NetworkTemplate template) {
+            NetworkStats stats = mCollection.getSummary(template,
+                    Long.MIN_VALUE /* start */, Long.MAX_VALUE /* end */,
+                    mAccessLevel, mCallingUid);
+            return stats.getTotalBytes();
+        }
+    }
+
+    private static class UserUsageRequestInfo extends RequestInfo {
+        UserUsageRequestInfo(NetworkStatsObservers statsObserver, DataUsageRequest request,
+                    Messenger messenger, IBinder binder, int callingUid,
+                    @NetworkStatsAccess.Level int accessLevel) {
+            super(statsObserver, request, messenger, binder, callingUid, accessLevel);
+        }
+
+        @Override
+        protected boolean checkStats() {
+            int[] uidsToMonitor = mCollection.getRelevantUids(mAccessLevel, mCallingUid);
+
+            for (int i = 0; i < uidsToMonitor.length; i++) {
+                long bytesSoFar = getTotalBytesForNetworkUid(mRequest.template, uidsToMonitor[i]);
+                if (bytesSoFar > mRequest.thresholdInBytes) {
+                    return true;
+                }
+            }
+            return false;
+        }
+
+        @Override
+        protected void recordSample(StatsContext statsContext) {
+            // Recorder does not need to be locked in this context since only the handler
+            // thread will update it. We pass the VPN info so VPN traffic is reattributed to
+            // responsible apps.
+            mRecorder.recordSnapshotLocked(statsContext.mUidSnapshot, statsContext.mActiveUidIfaces,
+                    statsContext.mCurrentTime);
+        }
+
+        /**
+         * Reads all stats matching the given template and uid. Ther history will likely only
+         * contain one bucket per ident since we build it big enough that it will outlive the
+         * caller lifetime.
+         */
+        private long getTotalBytesForNetworkUid(NetworkTemplate template, int uid) {
+            try {
+                NetworkStatsHistory history = mCollection.getHistory(template, null, uid,
+                        NetworkStats.SET_ALL, NetworkStats.TAG_NONE,
+                        NetworkStatsHistory.FIELD_ALL,
+                        Long.MIN_VALUE /* start */, Long.MAX_VALUE /* end */,
+                        mAccessLevel, mCallingUid);
+                return history.getTotalBytes();
+            } catch (SecurityException e) {
+                if (LOGV) {
+                    Slog.w(TAG, "CallerUid " + mCallingUid + " may have lost access to uid "
+                            + uid);
+                }
+                return 0;
+            }
+        }
+    }
+
+    private static class StatsContext {
+        NetworkStats mXtSnapshot;
+        NetworkStats mUidSnapshot;
+        ArrayMap<String, NetworkIdentitySet> mActiveIfaces;
+        ArrayMap<String, NetworkIdentitySet> mActiveUidIfaces;
+        long mCurrentTime;
+
+        StatsContext(NetworkStats xtSnapshot, NetworkStats uidSnapshot,
+                ArrayMap<String, NetworkIdentitySet> activeIfaces,
+                ArrayMap<String, NetworkIdentitySet> activeUidIfaces,
+                long currentTime) {
+            mXtSnapshot = xtSnapshot;
+            mUidSnapshot = uidSnapshot;
+            mActiveIfaces = activeIfaces;
+            mActiveUidIfaces = activeUidIfaces;
+            mCurrentTime = currentTime;
+        }
+    }
+}
diff --git a/service-t/src/com/android/server/net/NetworkStatsRecorder.java b/service-t/src/com/android/server/net/NetworkStatsRecorder.java
new file mode 100644
index 0000000..978ae87
--- /dev/null
+++ b/service-t/src/com/android/server/net/NetworkStatsRecorder.java
@@ -0,0 +1,505 @@
+/*
+ * Copyright (C) 2012 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.net;
+
+import static android.net.NetworkStats.TAG_NONE;
+import static android.net.TrafficStats.KB_IN_BYTES;
+import static android.net.TrafficStats.MB_IN_BYTES;
+import static android.text.format.DateUtils.YEAR_IN_MILLIS;
+
+import android.net.NetworkStats;
+import android.net.NetworkStats.NonMonotonicObserver;
+import android.net.NetworkStatsHistory;
+import android.net.NetworkTemplate;
+import android.net.TrafficStats;
+import android.os.Binder;
+import android.os.DropBoxManager;
+import android.service.NetworkStatsRecorderProto;
+import android.util.Log;
+import android.util.MathUtils;
+import android.util.Slog;
+import android.util.proto.ProtoOutputStream;
+
+import com.android.internal.util.FileRotator;
+import com.android.internal.util.IndentingPrintWriter;
+
+import com.google.android.collect.Sets;
+
+import libcore.io.IoUtils;
+
+import java.io.ByteArrayOutputStream;
+import java.io.File;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.OutputStream;
+import java.io.PrintWriter;
+import java.lang.ref.WeakReference;
+import java.util.Arrays;
+import java.util.HashSet;
+import java.util.Map;
+import java.util.Objects;
+
+/**
+ * Logic to record deltas between periodic {@link NetworkStats} snapshots into
+ * {@link NetworkStatsHistory} that belong to {@link NetworkStatsCollection}.
+ * Keeps pending changes in memory until they pass a specific threshold, in
+ * bytes. Uses {@link FileRotator} for persistence logic if present.
+ * <p>
+ * Not inherently thread safe.
+ */
+public class NetworkStatsRecorder {
+    private static final String TAG = "NetworkStatsRecorder";
+    private static final boolean LOGD = false;
+    private static final boolean LOGV = false;
+
+    private static final String TAG_NETSTATS_DUMP = "netstats_dump";
+
+    /** Dump before deleting in {@link #recoverFromWtf()}. */
+    private static final boolean DUMP_BEFORE_DELETE = true;
+
+    private final FileRotator mRotator;
+    private final NonMonotonicObserver<String> mObserver;
+    private final DropBoxManager mDropBox;
+    private final String mCookie;
+
+    private final long mBucketDuration;
+    private final boolean mOnlyTags;
+
+    private long mPersistThresholdBytes = 2 * MB_IN_BYTES;
+    private NetworkStats mLastSnapshot;
+
+    private final NetworkStatsCollection mPending;
+    private final NetworkStatsCollection mSinceBoot;
+
+    private final CombiningRewriter mPendingRewriter;
+
+    private WeakReference<NetworkStatsCollection> mComplete;
+
+    /**
+     * Non-persisted recorder, with only one bucket. Used by {@link NetworkStatsObservers}.
+     */
+    public NetworkStatsRecorder() {
+        mRotator = null;
+        mObserver = null;
+        mDropBox = null;
+        mCookie = null;
+
+        // set the bucket big enough to have all data in one bucket, but allow some
+        // slack to avoid overflow
+        mBucketDuration = YEAR_IN_MILLIS;
+        mOnlyTags = false;
+
+        mPending = null;
+        mSinceBoot = new NetworkStatsCollection(mBucketDuration);
+
+        mPendingRewriter = null;
+    }
+
+    /**
+     * Persisted recorder.
+     */
+    public NetworkStatsRecorder(FileRotator rotator, NonMonotonicObserver<String> observer,
+            DropBoxManager dropBox, String cookie, long bucketDuration, boolean onlyTags) {
+        mRotator = Objects.requireNonNull(rotator, "missing FileRotator");
+        mObserver = Objects.requireNonNull(observer, "missing NonMonotonicObserver");
+        mDropBox = Objects.requireNonNull(dropBox, "missing DropBoxManager");
+        mCookie = cookie;
+
+        mBucketDuration = bucketDuration;
+        mOnlyTags = onlyTags;
+
+        mPending = new NetworkStatsCollection(bucketDuration);
+        mSinceBoot = new NetworkStatsCollection(bucketDuration);
+
+        mPendingRewriter = new CombiningRewriter(mPending);
+    }
+
+    public void setPersistThreshold(long thresholdBytes) {
+        if (LOGV) Slog.v(TAG, "setPersistThreshold() with " + thresholdBytes);
+        mPersistThresholdBytes = MathUtils.constrain(
+                thresholdBytes, 1 * KB_IN_BYTES, 100 * MB_IN_BYTES);
+    }
+
+    public void resetLocked() {
+        mLastSnapshot = null;
+        if (mPending != null) {
+            mPending.reset();
+        }
+        if (mSinceBoot != null) {
+            mSinceBoot.reset();
+        }
+        if (mComplete != null) {
+            mComplete.clear();
+        }
+    }
+
+    public NetworkStats.Entry getTotalSinceBootLocked(NetworkTemplate template) {
+        return mSinceBoot.getSummary(template, Long.MIN_VALUE, Long.MAX_VALUE,
+                NetworkStatsAccess.Level.DEVICE, Binder.getCallingUid()).getTotal(null);
+    }
+
+    public NetworkStatsCollection getSinceBoot() {
+        return mSinceBoot;
+    }
+
+    /**
+     * Load complete history represented by {@link FileRotator}. Caches
+     * internally as a {@link WeakReference}, and updated with future
+     * {@link #recordSnapshotLocked(NetworkStats, Map, long)} snapshots as long
+     * as reference is valid.
+     */
+    public NetworkStatsCollection getOrLoadCompleteLocked() {
+        Objects.requireNonNull(mRotator, "missing FileRotator");
+        NetworkStatsCollection res = mComplete != null ? mComplete.get() : null;
+        if (res == null) {
+            res = loadLocked(Long.MIN_VALUE, Long.MAX_VALUE);
+            mComplete = new WeakReference<NetworkStatsCollection>(res);
+        }
+        return res;
+    }
+
+    public NetworkStatsCollection getOrLoadPartialLocked(long start, long end) {
+        Objects.requireNonNull(mRotator, "missing FileRotator");
+        NetworkStatsCollection res = mComplete != null ? mComplete.get() : null;
+        if (res == null) {
+            res = loadLocked(start, end);
+        }
+        return res;
+    }
+
+    private NetworkStatsCollection loadLocked(long start, long end) {
+        if (LOGD) Slog.d(TAG, "loadLocked() reading from disk for " + mCookie);
+        final NetworkStatsCollection res = new NetworkStatsCollection(mBucketDuration);
+        try {
+            mRotator.readMatching(res, start, end);
+            res.recordCollection(mPending);
+        } catch (IOException e) {
+            Log.wtf(TAG, "problem completely reading network stats", e);
+            recoverFromWtf();
+        } catch (OutOfMemoryError e) {
+            Log.wtf(TAG, "problem completely reading network stats", e);
+            recoverFromWtf();
+        }
+        return res;
+    }
+
+    /**
+     * Record any delta that occurred since last {@link NetworkStats} snapshot, using the given
+     * {@link Map} to identify network interfaces. First snapshot is considered bootstrap, and is
+     * not counted as delta.
+     */
+    public void recordSnapshotLocked(NetworkStats snapshot,
+            Map<String, NetworkIdentitySet> ifaceIdent, long currentTimeMillis) {
+        final HashSet<String> unknownIfaces = Sets.newHashSet();
+
+        // skip recording when snapshot missing
+        if (snapshot == null) return;
+
+        // assume first snapshot is bootstrap and don't record
+        if (mLastSnapshot == null) {
+            mLastSnapshot = snapshot;
+            return;
+        }
+
+        final NetworkStatsCollection complete = mComplete != null ? mComplete.get() : null;
+
+        final NetworkStats delta = NetworkStats.subtract(
+                snapshot, mLastSnapshot, mObserver, mCookie);
+        final long end = currentTimeMillis;
+        final long start = end - delta.getElapsedRealtime();
+
+        NetworkStats.Entry entry = null;
+        for (int i = 0; i < delta.size(); i++) {
+            entry = delta.getValues(i, entry);
+
+            // As a last-ditch check, report any negative values and
+            // clamp them so recording below doesn't croak.
+            if (entry.isNegative()) {
+                if (mObserver != null) {
+                    mObserver.foundNonMonotonic(delta, i, mCookie);
+                }
+                entry.rxBytes = Math.max(entry.rxBytes, 0);
+                entry.rxPackets = Math.max(entry.rxPackets, 0);
+                entry.txBytes = Math.max(entry.txBytes, 0);
+                entry.txPackets = Math.max(entry.txPackets, 0);
+                entry.operations = Math.max(entry.operations, 0);
+            }
+
+            final NetworkIdentitySet ident = ifaceIdent.get(entry.iface);
+            if (ident == null) {
+                unknownIfaces.add(entry.iface);
+                continue;
+            }
+
+            // skip when no delta occurred
+            if (entry.isEmpty()) continue;
+
+            // only record tag data when requested
+            if ((entry.tag == TAG_NONE) != mOnlyTags) {
+                if (mPending != null) {
+                    mPending.recordData(ident, entry.uid, entry.set, entry.tag, start, end, entry);
+                }
+
+                // also record against boot stats when present
+                if (mSinceBoot != null) {
+                    mSinceBoot.recordData(ident, entry.uid, entry.set, entry.tag, start, end, entry);
+                }
+
+                // also record against complete dataset when present
+                if (complete != null) {
+                    complete.recordData(ident, entry.uid, entry.set, entry.tag, start, end, entry);
+                }
+            }
+        }
+
+        mLastSnapshot = snapshot;
+
+        if (LOGV && unknownIfaces.size() > 0) {
+            Slog.w(TAG, "unknown interfaces " + unknownIfaces + ", ignoring those stats");
+        }
+    }
+
+    /**
+     * Consider persisting any pending deltas, if they are beyond
+     * {@link #mPersistThresholdBytes}.
+     */
+    public void maybePersistLocked(long currentTimeMillis) {
+        Objects.requireNonNull(mRotator, "missing FileRotator");
+        final long pendingBytes = mPending.getTotalBytes();
+        if (pendingBytes >= mPersistThresholdBytes) {
+            forcePersistLocked(currentTimeMillis);
+        } else {
+            mRotator.maybeRotate(currentTimeMillis);
+        }
+    }
+
+    /**
+     * Force persisting any pending deltas.
+     */
+    public void forcePersistLocked(long currentTimeMillis) {
+        Objects.requireNonNull(mRotator, "missing FileRotator");
+        if (mPending.isDirty()) {
+            if (LOGD) Slog.d(TAG, "forcePersistLocked() writing for " + mCookie);
+            try {
+                mRotator.rewriteActive(mPendingRewriter, currentTimeMillis);
+                mRotator.maybeRotate(currentTimeMillis);
+                mPending.reset();
+            } catch (IOException e) {
+                Log.wtf(TAG, "problem persisting pending stats", e);
+                recoverFromWtf();
+            } catch (OutOfMemoryError e) {
+                Log.wtf(TAG, "problem persisting pending stats", e);
+                recoverFromWtf();
+            }
+        }
+    }
+
+    /**
+     * Remove the given UID from all {@link FileRotator} history, migrating it
+     * to {@link TrafficStats#UID_REMOVED}.
+     */
+    public void removeUidsLocked(int[] uids) {
+        if (mRotator != null) {
+            try {
+                // Rewrite all persisted data to migrate UID stats
+                mRotator.rewriteAll(new RemoveUidRewriter(mBucketDuration, uids));
+            } catch (IOException e) {
+                Log.wtf(TAG, "problem removing UIDs " + Arrays.toString(uids), e);
+                recoverFromWtf();
+            } catch (OutOfMemoryError e) {
+                Log.wtf(TAG, "problem removing UIDs " + Arrays.toString(uids), e);
+                recoverFromWtf();
+            }
+        }
+
+        // Remove any pending stats
+        if (mPending != null) {
+            mPending.removeUids(uids);
+        }
+        if (mSinceBoot != null) {
+            mSinceBoot.removeUids(uids);
+        }
+
+        // Clear UID from current stats snapshot
+        if (mLastSnapshot != null) {
+            mLastSnapshot.removeUids(uids);
+        }
+
+        final NetworkStatsCollection complete = mComplete != null ? mComplete.get() : null;
+        if (complete != null) {
+            complete.removeUids(uids);
+        }
+    }
+
+    /**
+     * Rewriter that will combine current {@link NetworkStatsCollection} values
+     * with anything read from disk, and write combined set to disk. Clears the
+     * original {@link NetworkStatsCollection} when finished writing.
+     */
+    private static class CombiningRewriter implements FileRotator.Rewriter {
+        private final NetworkStatsCollection mCollection;
+
+        public CombiningRewriter(NetworkStatsCollection collection) {
+            mCollection = Objects.requireNonNull(collection, "missing NetworkStatsCollection");
+        }
+
+        @Override
+        public void reset() {
+            // ignored
+        }
+
+        @Override
+        public void read(InputStream in) throws IOException {
+            mCollection.read(in);
+        }
+
+        @Override
+        public boolean shouldWrite() {
+            return true;
+        }
+
+        @Override
+        public void write(OutputStream out) throws IOException {
+            mCollection.write(out);
+            mCollection.reset();
+        }
+    }
+
+    /**
+     * Rewriter that will remove any {@link NetworkStatsHistory} attributed to
+     * the requested UID, only writing data back when modified.
+     */
+    public static class RemoveUidRewriter implements FileRotator.Rewriter {
+        private final NetworkStatsCollection mTemp;
+        private final int[] mUids;
+
+        public RemoveUidRewriter(long bucketDuration, int[] uids) {
+            mTemp = new NetworkStatsCollection(bucketDuration);
+            mUids = uids;
+        }
+
+        @Override
+        public void reset() {
+            mTemp.reset();
+        }
+
+        @Override
+        public void read(InputStream in) throws IOException {
+            mTemp.read(in);
+            mTemp.clearDirty();
+            mTemp.removeUids(mUids);
+        }
+
+        @Override
+        public boolean shouldWrite() {
+            return mTemp.isDirty();
+        }
+
+        @Override
+        public void write(OutputStream out) throws IOException {
+            mTemp.write(out);
+        }
+    }
+
+    public void importLegacyNetworkLocked(File file) throws IOException {
+        Objects.requireNonNull(mRotator, "missing FileRotator");
+
+        // legacy file still exists; start empty to avoid double importing
+        mRotator.deleteAll();
+
+        final NetworkStatsCollection collection = new NetworkStatsCollection(mBucketDuration);
+        collection.readLegacyNetwork(file);
+
+        final long startMillis = collection.getStartMillis();
+        final long endMillis = collection.getEndMillis();
+
+        if (!collection.isEmpty()) {
+            // process legacy data, creating active file at starting time, then
+            // using end time to possibly trigger rotation.
+            mRotator.rewriteActive(new CombiningRewriter(collection), startMillis);
+            mRotator.maybeRotate(endMillis);
+        }
+    }
+
+    public void importLegacyUidLocked(File file) throws IOException {
+        Objects.requireNonNull(mRotator, "missing FileRotator");
+
+        // legacy file still exists; start empty to avoid double importing
+        mRotator.deleteAll();
+
+        final NetworkStatsCollection collection = new NetworkStatsCollection(mBucketDuration);
+        collection.readLegacyUid(file, mOnlyTags);
+
+        final long startMillis = collection.getStartMillis();
+        final long endMillis = collection.getEndMillis();
+
+        if (!collection.isEmpty()) {
+            // process legacy data, creating active file at starting time, then
+            // using end time to possibly trigger rotation.
+            mRotator.rewriteActive(new CombiningRewriter(collection), startMillis);
+            mRotator.maybeRotate(endMillis);
+        }
+    }
+
+    public void dumpLocked(IndentingPrintWriter pw, boolean fullHistory) {
+        if (mPending != null) {
+            pw.print("Pending bytes: "); pw.println(mPending.getTotalBytes());
+        }
+        if (fullHistory) {
+            pw.println("Complete history:");
+            getOrLoadCompleteLocked().dump(pw);
+        } else {
+            pw.println("History since boot:");
+            mSinceBoot.dump(pw);
+        }
+    }
+
+    public void dumpDebugLocked(ProtoOutputStream proto, long tag) {
+        final long start = proto.start(tag);
+        if (mPending != null) {
+            proto.write(NetworkStatsRecorderProto.PENDING_TOTAL_BYTES, mPending.getTotalBytes());
+        }
+        getOrLoadCompleteLocked().dumpDebug(proto, NetworkStatsRecorderProto.COMPLETE_HISTORY);
+        proto.end(start);
+    }
+
+    public void dumpCheckin(PrintWriter pw, long start, long end) {
+        // Only load and dump stats from the requested window
+        getOrLoadPartialLocked(start, end).dumpCheckin(pw, start, end);
+    }
+
+    /**
+     * Recover from {@link FileRotator} failure by dumping state to
+     * {@link DropBoxManager} and deleting contents.
+     */
+    private void recoverFromWtf() {
+        if (DUMP_BEFORE_DELETE) {
+            final ByteArrayOutputStream os = new ByteArrayOutputStream();
+            try {
+                mRotator.dumpAll(os);
+            } catch (IOException e) {
+                // ignore partial contents
+                os.reset();
+            } finally {
+                IoUtils.closeQuietly(os);
+            }
+            mDropBox.addData(TAG_NETSTATS_DUMP, os.toByteArray(), 0);
+        }
+
+        mRotator.deleteAll();
+    }
+}
diff --git a/service-t/src/com/android/server/net/NetworkStatsService.java b/service-t/src/com/android/server/net/NetworkStatsService.java
new file mode 100644
index 0000000..c876d41
--- /dev/null
+++ b/service-t/src/com/android/server/net/NetworkStatsService.java
@@ -0,0 +1,2253 @@
+/*
+ * Copyright (C) 2011 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.net;
+
+import static android.Manifest.permission.NETWORK_STATS_PROVIDER;
+import static android.Manifest.permission.READ_NETWORK_USAGE_HISTORY;
+import static android.Manifest.permission.UPDATE_DEVICE_STATS;
+import static android.content.Intent.ACTION_SHUTDOWN;
+import static android.content.Intent.ACTION_UID_REMOVED;
+import static android.content.Intent.ACTION_USER_REMOVED;
+import static android.content.Intent.EXTRA_UID;
+import static android.content.pm.PackageManager.PERMISSION_GRANTED;
+import static android.net.NetworkIdentity.SUBTYPE_COMBINED;
+import static android.net.NetworkStack.checkNetworkStackPermission;
+import static android.net.NetworkStats.DEFAULT_NETWORK_ALL;
+import static android.net.NetworkStats.IFACE_ALL;
+import static android.net.NetworkStats.IFACE_VT;
+import static android.net.NetworkStats.INTERFACES_ALL;
+import static android.net.NetworkStats.METERED_ALL;
+import static android.net.NetworkStats.ROAMING_ALL;
+import static android.net.NetworkStats.SET_ALL;
+import static android.net.NetworkStats.SET_DEFAULT;
+import static android.net.NetworkStats.SET_FOREGROUND;
+import static android.net.NetworkStats.STATS_PER_IFACE;
+import static android.net.NetworkStats.STATS_PER_UID;
+import static android.net.NetworkStats.TAG_ALL;
+import static android.net.NetworkStats.TAG_NONE;
+import static android.net.NetworkStats.UID_ALL;
+import static android.net.NetworkStatsHistory.FIELD_ALL;
+import static android.net.NetworkTemplate.buildTemplateMobileWildcard;
+import static android.net.NetworkTemplate.buildTemplateWifiWildcard;
+import static android.net.TetheringManager.ACTION_TETHER_STATE_CHANGED;
+import static android.net.TrafficStats.KB_IN_BYTES;
+import static android.net.TrafficStats.MB_IN_BYTES;
+import static android.net.TrafficStats.UNSUPPORTED;
+import static android.os.Trace.TRACE_TAG_NETWORK;
+import static android.provider.Settings.Global.NETSTATS_AUGMENT_ENABLED;
+import static android.provider.Settings.Global.NETSTATS_COMBINE_SUBTYPE_ENABLED;
+import static android.provider.Settings.Global.NETSTATS_DEV_BUCKET_DURATION;
+import static android.provider.Settings.Global.NETSTATS_DEV_DELETE_AGE;
+import static android.provider.Settings.Global.NETSTATS_DEV_PERSIST_BYTES;
+import static android.provider.Settings.Global.NETSTATS_DEV_ROTATE_AGE;
+import static android.provider.Settings.Global.NETSTATS_GLOBAL_ALERT_BYTES;
+import static android.provider.Settings.Global.NETSTATS_POLL_INTERVAL;
+import static android.provider.Settings.Global.NETSTATS_SAMPLE_ENABLED;
+import static android.provider.Settings.Global.NETSTATS_UID_BUCKET_DURATION;
+import static android.provider.Settings.Global.NETSTATS_UID_DELETE_AGE;
+import static android.provider.Settings.Global.NETSTATS_UID_PERSIST_BYTES;
+import static android.provider.Settings.Global.NETSTATS_UID_ROTATE_AGE;
+import static android.provider.Settings.Global.NETSTATS_UID_TAG_BUCKET_DURATION;
+import static android.provider.Settings.Global.NETSTATS_UID_TAG_DELETE_AGE;
+import static android.provider.Settings.Global.NETSTATS_UID_TAG_PERSIST_BYTES;
+import static android.provider.Settings.Global.NETSTATS_UID_TAG_ROTATE_AGE;
+import static android.telephony.SubscriptionManager.INVALID_SUBSCRIPTION_ID;
+import static android.text.format.DateUtils.DAY_IN_MILLIS;
+import static android.text.format.DateUtils.HOUR_IN_MILLIS;
+import static android.text.format.DateUtils.MINUTE_IN_MILLIS;
+import static android.text.format.DateUtils.SECOND_IN_MILLIS;
+
+import static com.android.net.module.util.NetworkCapabilitiesUtils.getDisplayTransport;
+import static com.android.server.NetworkManagementService.LIMIT_GLOBAL_ALERT;
+import static com.android.server.NetworkManagementSocketTagger.resetKernelUidStats;
+import static com.android.server.NetworkManagementSocketTagger.setKernelCounterSet;
+
+import android.annotation.NonNull;
+import android.annotation.Nullable;
+import android.app.AlarmManager;
+import android.app.PendingIntent;
+import android.app.usage.NetworkStatsManager;
+import android.content.BroadcastReceiver;
+import android.content.ContentResolver;
+import android.content.Context;
+import android.content.Intent;
+import android.content.IntentFilter;
+import android.content.pm.ApplicationInfo;
+import android.content.pm.PackageManager;
+import android.database.ContentObserver;
+import android.net.DataUsageRequest;
+import android.net.INetworkManagementEventObserver;
+import android.net.INetworkStatsService;
+import android.net.INetworkStatsSession;
+import android.net.Network;
+import android.net.NetworkCapabilities;
+import android.net.NetworkIdentity;
+import android.net.NetworkSpecifier;
+import android.net.NetworkStack;
+import android.net.NetworkStateSnapshot;
+import android.net.NetworkStats;
+import android.net.NetworkStats.NonMonotonicObserver;
+import android.net.NetworkStatsHistory;
+import android.net.NetworkTemplate;
+import android.net.TelephonyNetworkSpecifier;
+import android.net.TrafficStats;
+import android.net.UnderlyingNetworkInfo;
+import android.net.Uri;
+import android.net.netstats.provider.INetworkStatsProvider;
+import android.net.netstats.provider.INetworkStatsProviderCallback;
+import android.net.netstats.provider.NetworkStatsProvider;
+import android.os.BestClock;
+import android.os.Binder;
+import android.os.DropBoxManager;
+import android.os.Environment;
+import android.os.Handler;
+import android.os.HandlerExecutor;
+import android.os.HandlerThread;
+import android.os.IBinder;
+import android.os.INetworkManagementService;
+import android.os.Looper;
+import android.os.Message;
+import android.os.Messenger;
+import android.os.PowerManager;
+import android.os.RemoteException;
+import android.os.SystemClock;
+import android.os.Trace;
+import android.os.UserHandle;
+import android.provider.Settings;
+import android.provider.Settings.Global;
+import android.service.NetworkInterfaceProto;
+import android.service.NetworkStatsServiceDumpProto;
+import android.telephony.PhoneStateListener;
+import android.telephony.SubscriptionPlan;
+import android.text.TextUtils;
+import android.text.format.DateUtils;
+import android.util.ArrayMap;
+import android.util.ArraySet;
+import android.util.EventLog;
+import android.util.Log;
+import android.util.MathUtils;
+import android.util.Slog;
+import android.util.SparseIntArray;
+import android.util.proto.ProtoOutputStream;
+
+import com.android.internal.annotations.GuardedBy;
+import com.android.internal.annotations.VisibleForTesting;
+import com.android.internal.util.ArrayUtils;
+import com.android.internal.util.DumpUtils;
+import com.android.internal.util.FileRotator;
+import com.android.internal.util.IndentingPrintWriter;
+import com.android.net.module.util.BinderUtils;
+import com.android.server.EventLogTags;
+import com.android.server.LocalServices;
+
+import java.io.File;
+import java.io.FileDescriptor;
+import java.io.IOException;
+import java.io.PrintWriter;
+import java.time.Clock;
+import java.time.ZoneOffset;
+import java.util.Arrays;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Objects;
+import java.util.concurrent.CopyOnWriteArrayList;
+import java.util.concurrent.Executor;
+import java.util.concurrent.Semaphore;
+import java.util.concurrent.TimeUnit;
+
+/**
+ * Collect and persist detailed network statistics, and provide this data to
+ * other system services.
+ */
+public class NetworkStatsService extends INetworkStatsService.Stub {
+    static final String TAG = "NetworkStats";
+    static final boolean LOGD = Log.isLoggable(TAG, Log.DEBUG);
+    static final boolean LOGV = Log.isLoggable(TAG, Log.VERBOSE);
+
+    // Perform polling and persist all (FLAG_PERSIST_ALL).
+    private static final int MSG_PERFORM_POLL = 1;
+    // Perform polling, persist network, and register the global alert again.
+    private static final int MSG_PERFORM_POLL_REGISTER_ALERT = 2;
+    private static final int MSG_NOTIFY_NETWORK_STATUS = 3;
+    // A message for broadcasting ACTION_NETWORK_STATS_UPDATED in handler thread to prevent
+    // deadlock.
+    private static final int MSG_BROADCAST_NETWORK_STATS_UPDATED = 4;
+
+    /** Flags to control detail level of poll event. */
+    private static final int FLAG_PERSIST_NETWORK = 0x1;
+    private static final int FLAG_PERSIST_UID = 0x2;
+    private static final int FLAG_PERSIST_ALL = FLAG_PERSIST_NETWORK | FLAG_PERSIST_UID;
+    private static final int FLAG_PERSIST_FORCE = 0x100;
+
+    /**
+     * When global alert quota is high, wait for this delay before processing each polling,
+     * and do not schedule further polls once there is already one queued.
+     * This avoids firing the global alert too often on devices with high transfer speeds and
+     * high quota.
+     */
+    private static final int DEFAULT_PERFORM_POLL_DELAY_MS = 1000;
+
+    private static final String TAG_NETSTATS_ERROR = "netstats_error";
+
+    private final Context mContext;
+    private final INetworkManagementService mNetworkManager;
+    private final NetworkStatsFactory mStatsFactory;
+    private final AlarmManager mAlarmManager;
+    private final Clock mClock;
+    private final NetworkStatsSettings mSettings;
+    private final NetworkStatsObservers mStatsObservers;
+
+    private final File mSystemDir;
+    private final File mBaseDir;
+
+    private final PowerManager.WakeLock mWakeLock;
+
+    private final ContentObserver mContentObserver;
+    private final ContentResolver mContentResolver;
+
+    @VisibleForTesting
+    public static final String ACTION_NETWORK_STATS_POLL =
+            "com.android.server.action.NETWORK_STATS_POLL";
+    public static final String ACTION_NETWORK_STATS_UPDATED =
+            "com.android.server.action.NETWORK_STATS_UPDATED";
+
+    private PendingIntent mPollIntent;
+
+    private static final String PREFIX_DEV = "dev";
+    private static final String PREFIX_XT = "xt";
+    private static final String PREFIX_UID = "uid";
+    private static final String PREFIX_UID_TAG = "uid_tag";
+
+    /**
+     * Settings that can be changed externally.
+     */
+    public interface NetworkStatsSettings {
+        long getPollInterval();
+        long getPollDelay();
+        boolean getSampleEnabled();
+        boolean getAugmentEnabled();
+        /**
+         * When enabled, all mobile data is reported under {@link NetworkIdentity#SUBTYPE_COMBINED}.
+         * When disabled, mobile data is broken down by a granular subtype representative of the
+         * actual subtype. {@see NetworkTemplate#getCollapsedRatType}.
+         * Enabling this decreases the level of detail but saves performance, disk space and
+         * amount of data logged.
+         */
+        boolean getCombineSubtypeEnabled();
+
+        class Config {
+            public final long bucketDuration;
+            public final long rotateAgeMillis;
+            public final long deleteAgeMillis;
+
+            public Config(long bucketDuration, long rotateAgeMillis, long deleteAgeMillis) {
+                this.bucketDuration = bucketDuration;
+                this.rotateAgeMillis = rotateAgeMillis;
+                this.deleteAgeMillis = deleteAgeMillis;
+            }
+        }
+
+        Config getDevConfig();
+        Config getXtConfig();
+        Config getUidConfig();
+        Config getUidTagConfig();
+
+        long getGlobalAlertBytes(long def);
+        long getDevPersistBytes(long def);
+        long getXtPersistBytes(long def);
+        long getUidPersistBytes(long def);
+        long getUidTagPersistBytes(long def);
+    }
+
+    private final Object mStatsLock = new Object();
+
+    /** Set of currently active ifaces. */
+    @GuardedBy("mStatsLock")
+    private final ArrayMap<String, NetworkIdentitySet> mActiveIfaces = new ArrayMap<>();
+
+    /** Set of currently active ifaces for UID stats. */
+    @GuardedBy("mStatsLock")
+    private final ArrayMap<String, NetworkIdentitySet> mActiveUidIfaces = new ArrayMap<>();
+
+    /** Current default active iface. */
+    @GuardedBy("mStatsLock")
+    private String mActiveIface;
+
+    /** Set of any ifaces associated with mobile networks since boot. */
+    private volatile String[] mMobileIfaces = new String[0];
+
+    /** Set of all ifaces currently used by traffic that does not explicitly specify a Network. */
+    @GuardedBy("mStatsLock")
+    private Network[] mDefaultNetworks = new Network[0];
+
+    /** Last states of all networks sent from ConnectivityService. */
+    @GuardedBy("mStatsLock")
+    @Nullable
+    private NetworkStateSnapshot[] mLastNetworkStateSnapshots = null;
+
+    private final DropBoxNonMonotonicObserver mNonMonotonicObserver =
+            new DropBoxNonMonotonicObserver();
+
+    private static final int MAX_STATS_PROVIDER_POLL_WAIT_TIME_MS = 100;
+    private final CopyOnWriteArrayList<NetworkStatsProviderCallbackImpl> mStatsProviderCbList =
+            new CopyOnWriteArrayList<>();
+    /** Semaphore used to wait for stats provider to respond to request stats update. */
+    private final Semaphore mStatsProviderSem = new Semaphore(0, true);
+
+    @GuardedBy("mStatsLock")
+    private NetworkStatsRecorder mDevRecorder;
+    @GuardedBy("mStatsLock")
+    private NetworkStatsRecorder mXtRecorder;
+    @GuardedBy("mStatsLock")
+    private NetworkStatsRecorder mUidRecorder;
+    @GuardedBy("mStatsLock")
+    private NetworkStatsRecorder mUidTagRecorder;
+
+    /** Cached {@link #mXtRecorder} stats. */
+    @GuardedBy("mStatsLock")
+    private NetworkStatsCollection mXtStatsCached;
+
+    /** Current counter sets for each UID. */
+    private SparseIntArray mActiveUidCounterSet = new SparseIntArray();
+
+    /** Data layer operation counters for splicing into other structures. */
+    private NetworkStats mUidOperations = new NetworkStats(0L, 10);
+
+    @NonNull
+    private final Handler mHandler;
+
+    private volatile boolean mSystemReady;
+    private long mPersistThreshold = 2 * MB_IN_BYTES;
+    private long mGlobalAlertBytes;
+
+    private static final long POLL_RATE_LIMIT_MS = 15_000;
+
+    private long mLastStatsSessionPoll;
+
+    /** Map from UID to number of opened sessions */
+    @GuardedBy("mOpenSessionCallsPerUid")
+    private final SparseIntArray mOpenSessionCallsPerUid = new SparseIntArray();
+
+    private final static int DUMP_STATS_SESSION_COUNT = 20;
+
+    @NonNull
+    private final Dependencies mDeps;
+
+    @NonNull
+    private final NetworkStatsSubscriptionsMonitor mNetworkStatsSubscriptionsMonitor;
+
+    private static @NonNull File getDefaultSystemDir() {
+        return new File(Environment.getDataDirectory(), "system");
+    }
+
+    private static @NonNull File getDefaultBaseDir() {
+        File baseDir = new File(getDefaultSystemDir(), "netstats");
+        baseDir.mkdirs();
+        return baseDir;
+    }
+
+    private static @NonNull Clock getDefaultClock() {
+        return new BestClock(ZoneOffset.UTC, SystemClock.currentNetworkTimeClock(),
+                Clock.systemUTC());
+    }
+
+    private final class NetworkStatsHandler extends Handler {
+        NetworkStatsHandler(@NonNull Looper looper) {
+            super(looper);
+        }
+
+        @Override
+        public void handleMessage(Message msg) {
+            switch (msg.what) {
+                case MSG_PERFORM_POLL: {
+                    performPoll(FLAG_PERSIST_ALL);
+                    break;
+                }
+                case MSG_NOTIFY_NETWORK_STATUS: {
+                    // If no cached states, ignore.
+                    if (mLastNetworkStateSnapshots == null) break;
+                    // TODO (b/181642673): Protect mDefaultNetworks from concurrent accessing.
+                    handleNotifyNetworkStatus(
+                            mDefaultNetworks, mLastNetworkStateSnapshots, mActiveIface);
+                    break;
+                }
+                case MSG_PERFORM_POLL_REGISTER_ALERT: {
+                    performPoll(FLAG_PERSIST_NETWORK);
+                    registerGlobalAlert();
+                    break;
+                }
+                case MSG_BROADCAST_NETWORK_STATS_UPDATED: {
+                    final Intent updatedIntent = new Intent(ACTION_NETWORK_STATS_UPDATED);
+                    updatedIntent.setFlags(Intent.FLAG_RECEIVER_REGISTERED_ONLY);
+                    mContext.sendBroadcastAsUser(updatedIntent, UserHandle.ALL,
+                            READ_NETWORK_USAGE_HISTORY);
+                    break;
+                }
+            }
+        }
+    }
+
+    public static NetworkStatsService create(Context context,
+                INetworkManagementService networkManager) {
+        AlarmManager alarmManager = (AlarmManager) context.getSystemService(Context.ALARM_SERVICE);
+        PowerManager powerManager = (PowerManager) context.getSystemService(Context.POWER_SERVICE);
+        PowerManager.WakeLock wakeLock =
+                powerManager.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK, TAG);
+
+        final NetworkStatsService service = new NetworkStatsService(context, networkManager,
+                alarmManager, wakeLock, getDefaultClock(),
+                new DefaultNetworkStatsSettings(context), new NetworkStatsFactory(),
+                new NetworkStatsObservers(), getDefaultSystemDir(), getDefaultBaseDir(),
+                new Dependencies());
+        service.registerLocalService();
+
+        return service;
+    }
+
+    // This must not be called outside of tests, even within the same package, as this constructor
+    // does not register the local service. Use the create() helper above.
+    @VisibleForTesting
+    NetworkStatsService(Context context, INetworkManagementService networkManager,
+            AlarmManager alarmManager, PowerManager.WakeLock wakeLock, Clock clock,
+            NetworkStatsSettings settings, NetworkStatsFactory factory,
+            NetworkStatsObservers statsObservers, File systemDir, File baseDir,
+            @NonNull Dependencies deps) {
+        mContext = Objects.requireNonNull(context, "missing Context");
+        mNetworkManager = Objects.requireNonNull(networkManager,
+                "missing INetworkManagementService");
+        mAlarmManager = Objects.requireNonNull(alarmManager, "missing AlarmManager");
+        mClock = Objects.requireNonNull(clock, "missing Clock");
+        mSettings = Objects.requireNonNull(settings, "missing NetworkStatsSettings");
+        mWakeLock = Objects.requireNonNull(wakeLock, "missing WakeLock");
+        mStatsFactory = Objects.requireNonNull(factory, "missing factory");
+        mStatsObservers = Objects.requireNonNull(statsObservers, "missing NetworkStatsObservers");
+        mSystemDir = Objects.requireNonNull(systemDir, "missing systemDir");
+        mBaseDir = Objects.requireNonNull(baseDir, "missing baseDir");
+        mDeps = Objects.requireNonNull(deps, "missing Dependencies");
+
+        final HandlerThread handlerThread = mDeps.makeHandlerThread();
+        handlerThread.start();
+        mHandler = new NetworkStatsHandler(handlerThread.getLooper());
+        mNetworkStatsSubscriptionsMonitor = deps.makeSubscriptionsMonitor(mContext,
+                mHandler.getLooper(), new HandlerExecutor(mHandler), this);
+        mContentResolver = mContext.getContentResolver();
+        mContentObserver = mDeps.makeContentObserver(mHandler, mSettings,
+                mNetworkStatsSubscriptionsMonitor);
+    }
+
+    /**
+     * Dependencies of NetworkStatsService, for injection in tests.
+     */
+    // TODO: Move more stuff into dependencies object.
+    @VisibleForTesting
+    public static class Dependencies {
+        /**
+         * Create a HandlerThread to use in NetworkStatsService.
+         */
+        @NonNull
+        public HandlerThread makeHandlerThread() {
+            return new HandlerThread(TAG);
+        }
+
+        /**
+         * Create a {@link NetworkStatsSubscriptionsMonitor}, can be used to monitor RAT change
+         * event in NetworkStatsService.
+         */
+        @NonNull
+        public NetworkStatsSubscriptionsMonitor makeSubscriptionsMonitor(@NonNull Context context,
+                @NonNull Looper looper, @NonNull Executor executor,
+                @NonNull NetworkStatsService service) {
+            // TODO: Update RatType passively in NSS, instead of querying into the monitor
+            //  when notifyNetworkStatus.
+            return new NetworkStatsSubscriptionsMonitor(context, looper, executor,
+                    (subscriberId, type) -> service.handleOnCollapsedRatTypeChanged());
+        }
+
+        /**
+         * Create a ContentObserver instance which is used to observe settings changes,
+         * and dispatch onChange events on handler thread.
+         */
+        public @NonNull ContentObserver makeContentObserver(@NonNull Handler handler,
+                @NonNull NetworkStatsSettings settings,
+                @NonNull NetworkStatsSubscriptionsMonitor monitor) {
+            return new ContentObserver(handler) {
+                @Override
+                public void onChange(boolean selfChange, @NonNull Uri uri) {
+                    if (!settings.getCombineSubtypeEnabled()) {
+                        monitor.start();
+                    } else {
+                        monitor.stop();
+                    }
+                }
+            };
+        }
+    }
+
+    private void registerLocalService() {
+        LocalServices.addService(NetworkStatsManagerInternal.class,
+                new NetworkStatsManagerInternalImpl());
+    }
+
+    public void systemReady() {
+        synchronized (mStatsLock) {
+            mSystemReady = true;
+
+            // create data recorders along with historical rotators
+            mDevRecorder = buildRecorder(PREFIX_DEV, mSettings.getDevConfig(), false);
+            mXtRecorder = buildRecorder(PREFIX_XT, mSettings.getXtConfig(), false);
+            mUidRecorder = buildRecorder(PREFIX_UID, mSettings.getUidConfig(), false);
+            mUidTagRecorder = buildRecorder(PREFIX_UID_TAG, mSettings.getUidTagConfig(), true);
+
+            updatePersistThresholdsLocked();
+
+            // upgrade any legacy stats, migrating them to rotated files
+            maybeUpgradeLegacyStatsLocked();
+
+            // read historical network stats from disk, since policy service
+            // might need them right away.
+            mXtStatsCached = mXtRecorder.getOrLoadCompleteLocked();
+
+            // bootstrap initial stats to prevent double-counting later
+            bootstrapStatsLocked();
+        }
+
+        // watch for tethering changes
+        final IntentFilter tetherFilter = new IntentFilter(ACTION_TETHER_STATE_CHANGED);
+        mContext.registerReceiver(mTetherReceiver, tetherFilter, null, mHandler);
+
+        // listen for periodic polling events
+        final IntentFilter pollFilter = new IntentFilter(ACTION_NETWORK_STATS_POLL);
+        mContext.registerReceiver(mPollReceiver, pollFilter, READ_NETWORK_USAGE_HISTORY, mHandler);
+
+        // listen for uid removal to clean stats
+        final IntentFilter removedFilter = new IntentFilter(ACTION_UID_REMOVED);
+        mContext.registerReceiver(mRemovedReceiver, removedFilter, null, mHandler);
+
+        // listen for user changes to clean stats
+        final IntentFilter userFilter = new IntentFilter(ACTION_USER_REMOVED);
+        mContext.registerReceiver(mUserReceiver, userFilter, null, mHandler);
+
+        // persist stats during clean shutdown
+        final IntentFilter shutdownFilter = new IntentFilter(ACTION_SHUTDOWN);
+        mContext.registerReceiver(mShutdownReceiver, shutdownFilter);
+
+        try {
+            mNetworkManager.registerObserver(mAlertObserver);
+        } catch (RemoteException e) {
+            // ignored; service lives in system_server
+        }
+
+        //  schedule periodic pall alarm based on {@link NetworkStatsSettings#getPollInterval()}.
+        final PendingIntent pollIntent =
+                PendingIntent.getBroadcast(mContext, 0, new Intent(ACTION_NETWORK_STATS_POLL),
+                        PendingIntent.FLAG_IMMUTABLE);
+
+        final long currentRealtime = SystemClock.elapsedRealtime();
+        mAlarmManager.setInexactRepeating(AlarmManager.ELAPSED_REALTIME, currentRealtime,
+                mSettings.getPollInterval(), pollIntent);
+
+        mContentResolver.registerContentObserver(Settings.Global
+                .getUriFor(Settings.Global.NETSTATS_COMBINE_SUBTYPE_ENABLED),
+                        false /* notifyForDescendants */, mContentObserver);
+
+        // Post a runnable on handler thread to call onChange(). It's for getting current value of
+        // NETSTATS_COMBINE_SUBTYPE_ENABLED to decide start or stop monitoring RAT type changes.
+        mHandler.post(() -> mContentObserver.onChange(false, Settings.Global
+                .getUriFor(Settings.Global.NETSTATS_COMBINE_SUBTYPE_ENABLED)));
+
+        registerGlobalAlert();
+    }
+
+    private NetworkStatsRecorder buildRecorder(
+            String prefix, NetworkStatsSettings.Config config, boolean includeTags) {
+        final DropBoxManager dropBox = (DropBoxManager) mContext.getSystemService(
+                Context.DROPBOX_SERVICE);
+        return new NetworkStatsRecorder(new FileRotator(
+                mBaseDir, prefix, config.rotateAgeMillis, config.deleteAgeMillis),
+                mNonMonotonicObserver, dropBox, prefix, config.bucketDuration, includeTags);
+    }
+
+    @GuardedBy("mStatsLock")
+    private void shutdownLocked() {
+        mContext.unregisterReceiver(mTetherReceiver);
+        mContext.unregisterReceiver(mPollReceiver);
+        mContext.unregisterReceiver(mRemovedReceiver);
+        mContext.unregisterReceiver(mUserReceiver);
+        mContext.unregisterReceiver(mShutdownReceiver);
+
+        if (!mSettings.getCombineSubtypeEnabled()) {
+            mNetworkStatsSubscriptionsMonitor.stop();
+        }
+
+        mContentResolver.unregisterContentObserver(mContentObserver);
+
+        final long currentTime = mClock.millis();
+
+        // persist any pending stats
+        mDevRecorder.forcePersistLocked(currentTime);
+        mXtRecorder.forcePersistLocked(currentTime);
+        mUidRecorder.forcePersistLocked(currentTime);
+        mUidTagRecorder.forcePersistLocked(currentTime);
+
+        mSystemReady = false;
+    }
+
+    @GuardedBy("mStatsLock")
+    private void maybeUpgradeLegacyStatsLocked() {
+        File file;
+        try {
+            file = new File(mSystemDir, "netstats.bin");
+            if (file.exists()) {
+                mDevRecorder.importLegacyNetworkLocked(file);
+                file.delete();
+            }
+
+            file = new File(mSystemDir, "netstats_xt.bin");
+            if (file.exists()) {
+                file.delete();
+            }
+
+            file = new File(mSystemDir, "netstats_uid.bin");
+            if (file.exists()) {
+                mUidRecorder.importLegacyUidLocked(file);
+                mUidTagRecorder.importLegacyUidLocked(file);
+                file.delete();
+            }
+        } catch (IOException e) {
+            Log.wtf(TAG, "problem during legacy upgrade", e);
+        } catch (OutOfMemoryError e) {
+            Log.wtf(TAG, "problem during legacy upgrade", e);
+        }
+    }
+
+    /**
+     * Register for a global alert that is delivered through {@link INetworkManagementEventObserver}
+     * or {@link NetworkStatsProviderCallback#onAlertReached()} once a threshold amount of data has
+     * been transferred.
+     */
+    private void registerGlobalAlert() {
+        try {
+            mNetworkManager.setGlobalAlert(mGlobalAlertBytes);
+        } catch (IllegalStateException e) {
+            Slog.w(TAG, "problem registering for global alert: " + e);
+        } catch (RemoteException e) {
+            // ignored; service lives in system_server
+        }
+        invokeForAllStatsProviderCallbacks((cb) -> cb.mProvider.onSetAlert(mGlobalAlertBytes));
+    }
+
+    @Override
+    public INetworkStatsSession openSession() {
+        // NOTE: if callers want to get non-augmented data, they should go
+        // through the public API
+        return openSessionInternal(NetworkStatsManager.FLAG_AUGMENT_WITH_SUBSCRIPTION_PLAN, null);
+    }
+
+    @Override
+    public INetworkStatsSession openSessionForUsageStats(int flags, String callingPackage) {
+        return openSessionInternal(flags, callingPackage);
+    }
+
+    private boolean isRateLimitedForPoll(int callingUid) {
+        if (callingUid == android.os.Process.SYSTEM_UID) {
+            return false;
+        }
+
+        final long lastCallTime;
+        final long now = SystemClock.elapsedRealtime();
+        synchronized (mOpenSessionCallsPerUid) {
+            int calls = mOpenSessionCallsPerUid.get(callingUid, 0);
+            mOpenSessionCallsPerUid.put(callingUid, calls + 1);
+            lastCallTime = mLastStatsSessionPoll;
+            mLastStatsSessionPoll = now;
+        }
+
+        return now - lastCallTime < POLL_RATE_LIMIT_MS;
+    }
+
+    private INetworkStatsSession openSessionInternal(final int flags, final String callingPackage) {
+        final int callingUid = Binder.getCallingUid();
+        final int usedFlags = isRateLimitedForPoll(callingUid)
+                ? flags & (~NetworkStatsManager.FLAG_POLL_ON_OPEN)
+                : flags;
+        if ((usedFlags & (NetworkStatsManager.FLAG_POLL_ON_OPEN
+                | NetworkStatsManager.FLAG_POLL_FORCE)) != 0) {
+            final long ident = Binder.clearCallingIdentity();
+            try {
+                performPoll(FLAG_PERSIST_ALL);
+            } finally {
+                Binder.restoreCallingIdentity(ident);
+            }
+        }
+
+        // return an IBinder which holds strong references to any loaded stats
+        // for its lifetime; when caller closes only weak references remain.
+
+        return new INetworkStatsSession.Stub() {
+            private final int mCallingUid = callingUid;
+            private final String mCallingPackage = callingPackage;
+            private final @NetworkStatsAccess.Level int mAccessLevel = checkAccessLevel(
+                    callingPackage);
+
+            private NetworkStatsCollection mUidComplete;
+            private NetworkStatsCollection mUidTagComplete;
+
+            private NetworkStatsCollection getUidComplete() {
+                synchronized (mStatsLock) {
+                    if (mUidComplete == null) {
+                        mUidComplete = mUidRecorder.getOrLoadCompleteLocked();
+                    }
+                    return mUidComplete;
+                }
+            }
+
+            private NetworkStatsCollection getUidTagComplete() {
+                synchronized (mStatsLock) {
+                    if (mUidTagComplete == null) {
+                        mUidTagComplete = mUidTagRecorder.getOrLoadCompleteLocked();
+                    }
+                    return mUidTagComplete;
+                }
+            }
+
+            @Override
+            public int[] getRelevantUids() {
+                return getUidComplete().getRelevantUids(mAccessLevel);
+            }
+
+            @Override
+            public NetworkStats getDeviceSummaryForNetwork(
+                    NetworkTemplate template, long start, long end) {
+                return internalGetSummaryForNetwork(template, usedFlags, start, end, mAccessLevel,
+                        mCallingUid);
+            }
+
+            @Override
+            public NetworkStats getSummaryForNetwork(
+                    NetworkTemplate template, long start, long end) {
+                return internalGetSummaryForNetwork(template, usedFlags, start, end, mAccessLevel,
+                        mCallingUid);
+            }
+
+            @Override
+            public NetworkStatsHistory getHistoryForNetwork(NetworkTemplate template, int fields) {
+                return internalGetHistoryForNetwork(template, usedFlags, fields, mAccessLevel,
+                        mCallingUid);
+            }
+
+            @Override
+            public NetworkStats getSummaryForAllUid(
+                    NetworkTemplate template, long start, long end, boolean includeTags) {
+                try {
+                    final NetworkStats stats = getUidComplete()
+                            .getSummary(template, start, end, mAccessLevel, mCallingUid);
+                    if (includeTags) {
+                        final NetworkStats tagStats = getUidTagComplete()
+                                .getSummary(template, start, end, mAccessLevel, mCallingUid);
+                        stats.combineAllValues(tagStats);
+                    }
+                    return stats;
+                } catch (NullPointerException e) {
+                    // TODO: Track down and fix the cause of this crash and remove this catch block.
+                    Slog.wtf(TAG, "NullPointerException in getSummaryForAllUid", e);
+                    throw e;
+                }
+            }
+
+            @Override
+            public NetworkStatsHistory getHistoryForUid(
+                    NetworkTemplate template, int uid, int set, int tag, int fields) {
+                // NOTE: We don't augment UID-level statistics
+                if (tag == TAG_NONE) {
+                    return getUidComplete().getHistory(template, null, uid, set, tag, fields,
+                            Long.MIN_VALUE, Long.MAX_VALUE, mAccessLevel, mCallingUid);
+                } else {
+                    return getUidTagComplete().getHistory(template, null, uid, set, tag, fields,
+                            Long.MIN_VALUE, Long.MAX_VALUE, mAccessLevel, mCallingUid);
+                }
+            }
+
+            @Override
+            public NetworkStatsHistory getHistoryIntervalForUid(
+                    NetworkTemplate template, int uid, int set, int tag, int fields,
+                    long start, long end) {
+                // NOTE: We don't augment UID-level statistics
+                if (tag == TAG_NONE) {
+                    return getUidComplete().getHistory(template, null, uid, set, tag, fields,
+                            start, end, mAccessLevel, mCallingUid);
+                } else if (uid == Binder.getCallingUid()) {
+                    return getUidTagComplete().getHistory(template, null, uid, set, tag, fields,
+                            start, end, mAccessLevel, mCallingUid);
+                } else {
+                    throw new SecurityException("Calling package " + mCallingPackage
+                            + " cannot access tag information from a different uid");
+                }
+            }
+
+            @Override
+            public void close() {
+                mUidComplete = null;
+                mUidTagComplete = null;
+            }
+        };
+    }
+
+    private @NetworkStatsAccess.Level int checkAccessLevel(String callingPackage) {
+        return NetworkStatsAccess.checkAccessLevel(
+                mContext, Binder.getCallingUid(), callingPackage);
+    }
+
+    /**
+     * Find the most relevant {@link SubscriptionPlan} for the given
+     * {@link NetworkTemplate} and flags. This is typically used to augment
+     * local measurement results to match a known anchor from the carrier.
+     */
+    private SubscriptionPlan resolveSubscriptionPlan(NetworkTemplate template, int flags) {
+        SubscriptionPlan plan = null;
+        if ((flags & NetworkStatsManager.FLAG_AUGMENT_WITH_SUBSCRIPTION_PLAN) != 0
+                && mSettings.getAugmentEnabled()) {
+            if (LOGD) Slog.d(TAG, "Resolving plan for " + template);
+            final long token = Binder.clearCallingIdentity();
+            try {
+                plan = LocalServices.getService(NetworkPolicyManagerInternal.class)
+                        .getSubscriptionPlan(template);
+            } finally {
+                Binder.restoreCallingIdentity(token);
+            }
+            if (LOGD) Slog.d(TAG, "Resolved to plan " + plan);
+        }
+        return plan;
+    }
+
+    /**
+     * Return network summary, splicing between DEV and XT stats when
+     * appropriate.
+     */
+    private NetworkStats internalGetSummaryForNetwork(NetworkTemplate template, int flags,
+            long start, long end, @NetworkStatsAccess.Level int accessLevel, int callingUid) {
+        // We've been using pure XT stats long enough that we no longer need to
+        // splice DEV and XT together.
+        final NetworkStatsHistory history = internalGetHistoryForNetwork(template, flags, FIELD_ALL,
+                accessLevel, callingUid);
+
+        final long now = System.currentTimeMillis();
+        final NetworkStatsHistory.Entry entry = history.getValues(start, end, now, null);
+
+        final NetworkStats stats = new NetworkStats(end - start, 1);
+        stats.insertEntry(new NetworkStats.Entry(IFACE_ALL, UID_ALL, SET_ALL, TAG_NONE,
+                METERED_ALL, ROAMING_ALL, DEFAULT_NETWORK_ALL, entry.rxBytes, entry.rxPackets,
+                entry.txBytes, entry.txPackets, entry.operations));
+        return stats;
+    }
+
+    /**
+     * Return network history, splicing between DEV and XT stats when
+     * appropriate.
+     */
+    private NetworkStatsHistory internalGetHistoryForNetwork(NetworkTemplate template,
+            int flags, int fields, @NetworkStatsAccess.Level int accessLevel, int callingUid) {
+        // We've been using pure XT stats long enough that we no longer need to
+        // splice DEV and XT together.
+        final SubscriptionPlan augmentPlan = resolveSubscriptionPlan(template, flags);
+        synchronized (mStatsLock) {
+            return mXtStatsCached.getHistory(template, augmentPlan,
+                    UID_ALL, SET_ALL, TAG_NONE, fields, Long.MIN_VALUE, Long.MAX_VALUE,
+                    accessLevel, callingUid);
+        }
+    }
+
+    private long getNetworkTotalBytes(NetworkTemplate template, long start, long end) {
+        assertSystemReady();
+
+        // NOTE: if callers want to get non-augmented data, they should go
+        // through the public API
+        return internalGetSummaryForNetwork(template,
+                NetworkStatsManager.FLAG_AUGMENT_WITH_SUBSCRIPTION_PLAN, start, end,
+                NetworkStatsAccess.Level.DEVICE, Binder.getCallingUid()).getTotalBytes();
+    }
+
+    private NetworkStats getNetworkUidBytes(NetworkTemplate template, long start, long end) {
+        assertSystemReady();
+
+        final NetworkStatsCollection uidComplete;
+        synchronized (mStatsLock) {
+            uidComplete = mUidRecorder.getOrLoadCompleteLocked();
+        }
+        return uidComplete.getSummary(template, start, end, NetworkStatsAccess.Level.DEVICE,
+                android.os.Process.SYSTEM_UID);
+    }
+
+    @Override
+    public NetworkStats getDataLayerSnapshotForUid(int uid) throws RemoteException {
+        if (Binder.getCallingUid() != uid) {
+            Log.w(TAG, "Snapshots only available for calling UID");
+            return new NetworkStats(SystemClock.elapsedRealtime(), 0);
+        }
+
+        // TODO: switch to data layer stats once kernel exports
+        // for now, read network layer stats and flatten across all ifaces
+        final NetworkStats networkLayer = readNetworkStatsUidDetail(uid, INTERFACES_ALL, TAG_ALL);
+
+        // splice in operation counts
+        networkLayer.spliceOperationsFrom(mUidOperations);
+
+        final NetworkStats dataLayer = new NetworkStats(
+                networkLayer.getElapsedRealtime(), networkLayer.size());
+
+        NetworkStats.Entry entry = null;
+        for (int i = 0; i < networkLayer.size(); i++) {
+            entry = networkLayer.getValues(i, entry);
+            entry.iface = IFACE_ALL;
+            dataLayer.combineValues(entry);
+        }
+
+        return dataLayer;
+    }
+
+    @Override
+    public NetworkStats getDetailedUidStats(String[] requiredIfaces) {
+        try {
+            final String[] ifacesToQuery =
+                    mStatsFactory.augmentWithStackedInterfaces(requiredIfaces);
+            return getNetworkStatsUidDetail(ifacesToQuery);
+        } catch (RemoteException e) {
+            Log.wtf(TAG, "Error compiling UID stats", e);
+            return new NetworkStats(0L, 0);
+        }
+    }
+
+    @Override
+    public String[] getMobileIfaces() {
+        // TODO (b/192758557): Remove debug log.
+        if (ArrayUtils.contains(mMobileIfaces, null)) {
+            throw new NullPointerException(
+                    "null element in mMobileIfaces: " + Arrays.toString(mMobileIfaces));
+        }
+        return mMobileIfaces.clone();
+    }
+
+    @Override
+    public void incrementOperationCount(int uid, int tag, int operationCount) {
+        if (Binder.getCallingUid() != uid) {
+            mContext.enforceCallingOrSelfPermission(UPDATE_DEVICE_STATS, TAG);
+        }
+
+        if (operationCount < 0) {
+            throw new IllegalArgumentException("operation count can only be incremented");
+        }
+        if (tag == TAG_NONE) {
+            throw new IllegalArgumentException("operation count must have specific tag");
+        }
+
+        synchronized (mStatsLock) {
+            final int set = mActiveUidCounterSet.get(uid, SET_DEFAULT);
+            mUidOperations.combineValues(
+                    mActiveIface, uid, set, tag, 0L, 0L, 0L, 0L, operationCount);
+            mUidOperations.combineValues(
+                    mActiveIface, uid, set, TAG_NONE, 0L, 0L, 0L, 0L, operationCount);
+        }
+    }
+
+    @VisibleForTesting
+    void setUidForeground(int uid, boolean uidForeground) {
+        synchronized (mStatsLock) {
+            final int set = uidForeground ? SET_FOREGROUND : SET_DEFAULT;
+            final int oldSet = mActiveUidCounterSet.get(uid, SET_DEFAULT);
+            if (oldSet != set) {
+                mActiveUidCounterSet.put(uid, set);
+                setKernelCounterSet(uid, set);
+            }
+        }
+    }
+
+    /**
+     * Notify {@code NetworkStatsService} about network status changed.
+     */
+    public void notifyNetworkStatus(
+            @NonNull Network[] defaultNetworks,
+            @NonNull NetworkStateSnapshot[] networkStates,
+            @Nullable String activeIface,
+            @NonNull UnderlyingNetworkInfo[] underlyingNetworkInfos) {
+        checkNetworkStackPermission(mContext);
+
+        final long token = Binder.clearCallingIdentity();
+        try {
+            handleNotifyNetworkStatus(defaultNetworks, networkStates, activeIface);
+        } finally {
+            Binder.restoreCallingIdentity(token);
+        }
+
+        // Update the VPN underlying interfaces only after the poll is made and tun data has been
+        // migrated. Otherwise the migration would use the new interfaces instead of the ones that
+        // were current when the polled data was transferred.
+        mStatsFactory.updateUnderlyingNetworkInfos(underlyingNetworkInfos);
+    }
+
+    @Override
+    public void forceUpdate() {
+        mContext.enforceCallingOrSelfPermission(READ_NETWORK_USAGE_HISTORY, TAG);
+
+        final long token = Binder.clearCallingIdentity();
+        try {
+            performPoll(FLAG_PERSIST_ALL);
+        } finally {
+            Binder.restoreCallingIdentity(token);
+        }
+    }
+
+    private void advisePersistThreshold(long thresholdBytes) {
+        // clamp threshold into safe range
+        mPersistThreshold = MathUtils.constrain(thresholdBytes, 128 * KB_IN_BYTES, 2 * MB_IN_BYTES);
+        if (LOGV) {
+            Slog.v(TAG, "advisePersistThreshold() given " + thresholdBytes + ", clamped to "
+                    + mPersistThreshold);
+        }
+
+        final long oldGlobalAlertBytes = mGlobalAlertBytes;
+
+        // update and persist if beyond new thresholds
+        final long currentTime = mClock.millis();
+        synchronized (mStatsLock) {
+            if (!mSystemReady) return;
+
+            updatePersistThresholdsLocked();
+
+            mDevRecorder.maybePersistLocked(currentTime);
+            mXtRecorder.maybePersistLocked(currentTime);
+            mUidRecorder.maybePersistLocked(currentTime);
+            mUidTagRecorder.maybePersistLocked(currentTime);
+        }
+
+        if (oldGlobalAlertBytes != mGlobalAlertBytes) {
+            registerGlobalAlert();
+        }
+    }
+
+    @Override
+    public DataUsageRequest registerUsageCallback(String callingPackage,
+                DataUsageRequest request, Messenger messenger, IBinder binder) {
+        Objects.requireNonNull(callingPackage, "calling package is null");
+        Objects.requireNonNull(request, "DataUsageRequest is null");
+        Objects.requireNonNull(request.template, "NetworkTemplate is null");
+        Objects.requireNonNull(messenger, "messenger is null");
+        Objects.requireNonNull(binder, "binder is null");
+
+        int callingUid = Binder.getCallingUid();
+        @NetworkStatsAccess.Level int accessLevel = checkAccessLevel(callingPackage);
+        DataUsageRequest normalizedRequest;
+        final long token = Binder.clearCallingIdentity();
+        try {
+            normalizedRequest = mStatsObservers.register(request, messenger, binder,
+                    callingUid, accessLevel);
+        } finally {
+            Binder.restoreCallingIdentity(token);
+        }
+
+        // Create baseline stats
+        mHandler.sendMessage(mHandler.obtainMessage(MSG_PERFORM_POLL));
+
+        return normalizedRequest;
+   }
+
+    @Override
+    public void unregisterUsageRequest(DataUsageRequest request) {
+        Objects.requireNonNull(request, "DataUsageRequest is null");
+
+        int callingUid = Binder.getCallingUid();
+        final long token = Binder.clearCallingIdentity();
+        try {
+            mStatsObservers.unregister(request, callingUid);
+        } finally {
+            Binder.restoreCallingIdentity(token);
+        }
+    }
+
+    @Override
+    public long getUidStats(int uid, int type) {
+        final int callingUid = Binder.getCallingUid();
+        if (callingUid != android.os.Process.SYSTEM_UID && callingUid != uid) {
+            return UNSUPPORTED;
+        }
+        return nativeGetUidStat(uid, type);
+    }
+
+    @Override
+    public long getIfaceStats(@NonNull String iface, int type) {
+        Objects.requireNonNull(iface);
+        long nativeIfaceStats = nativeGetIfaceStat(iface, type);
+        if (nativeIfaceStats == -1) {
+            return nativeIfaceStats;
+        } else {
+            // When tethering offload is in use, nativeIfaceStats does not contain usage from
+            // offload, add it back here. Note that the included statistics might be stale
+            // since polling newest stats from hardware might impact system health and not
+            // suitable for TrafficStats API use cases.
+            return nativeIfaceStats + getProviderIfaceStats(iface, type);
+        }
+    }
+
+    @Override
+    public long getTotalStats(int type) {
+        long nativeTotalStats = nativeGetTotalStat(type);
+        if (nativeTotalStats == -1) {
+            return nativeTotalStats;
+        } else {
+            // Refer to comment in getIfaceStats
+            return nativeTotalStats + getProviderIfaceStats(IFACE_ALL, type);
+        }
+    }
+
+    private long getProviderIfaceStats(@Nullable String iface, int type) {
+        final NetworkStats providerSnapshot = getNetworkStatsFromProviders(STATS_PER_IFACE);
+        final HashSet<String> limitIfaces;
+        if (iface == IFACE_ALL) {
+            limitIfaces = null;
+        } else {
+            limitIfaces = new HashSet<>();
+            limitIfaces.add(iface);
+        }
+        final NetworkStats.Entry entry = providerSnapshot.getTotal(null, limitIfaces);
+        switch (type) {
+            case TrafficStats.TYPE_RX_BYTES:
+                return entry.rxBytes;
+            case TrafficStats.TYPE_RX_PACKETS:
+                return entry.rxPackets;
+            case TrafficStats.TYPE_TX_BYTES:
+                return entry.txBytes;
+            case TrafficStats.TYPE_TX_PACKETS:
+                return entry.txPackets;
+            default:
+                return 0;
+        }
+    }
+
+    /**
+     * Update {@link NetworkStatsRecorder} and {@link #mGlobalAlertBytes} to
+     * reflect current {@link #mPersistThreshold} value. Always defers to
+     * {@link Global} values when defined.
+     */
+    @GuardedBy("mStatsLock")
+    private void updatePersistThresholdsLocked() {
+        mDevRecorder.setPersistThreshold(mSettings.getDevPersistBytes(mPersistThreshold));
+        mXtRecorder.setPersistThreshold(mSettings.getXtPersistBytes(mPersistThreshold));
+        mUidRecorder.setPersistThreshold(mSettings.getUidPersistBytes(mPersistThreshold));
+        mUidTagRecorder.setPersistThreshold(mSettings.getUidTagPersistBytes(mPersistThreshold));
+        mGlobalAlertBytes = mSettings.getGlobalAlertBytes(mPersistThreshold);
+    }
+
+    /**
+     * Receiver that watches for {@link Tethering} to claim interface pairs.
+     */
+    private BroadcastReceiver mTetherReceiver = new BroadcastReceiver() {
+        @Override
+        public void onReceive(Context context, Intent intent) {
+            performPoll(FLAG_PERSIST_NETWORK);
+        }
+    };
+
+    private BroadcastReceiver mPollReceiver = new BroadcastReceiver() {
+        @Override
+        public void onReceive(Context context, Intent intent) {
+            // on background handler thread, and verified UPDATE_DEVICE_STATS
+            // permission above.
+            performPoll(FLAG_PERSIST_ALL);
+
+            // verify that we're watching global alert
+            registerGlobalAlert();
+        }
+    };
+
+    private BroadcastReceiver mRemovedReceiver = new BroadcastReceiver() {
+        @Override
+        public void onReceive(Context context, Intent intent) {
+            // on background handler thread, and UID_REMOVED is protected
+            // broadcast.
+
+            final int uid = intent.getIntExtra(EXTRA_UID, -1);
+            if (uid == -1) return;
+
+            synchronized (mStatsLock) {
+                mWakeLock.acquire();
+                try {
+                    removeUidsLocked(uid);
+                } finally {
+                    mWakeLock.release();
+                }
+            }
+        }
+    };
+
+    private BroadcastReceiver mUserReceiver = new BroadcastReceiver() {
+        @Override
+        public void onReceive(Context context, Intent intent) {
+            // On background handler thread, and USER_REMOVED is protected
+            // broadcast.
+
+            final int userId = intent.getIntExtra(Intent.EXTRA_USER_HANDLE, -1);
+            if (userId == -1) return;
+
+            synchronized (mStatsLock) {
+                mWakeLock.acquire();
+                try {
+                    removeUserLocked(userId);
+                } finally {
+                    mWakeLock.release();
+                }
+            }
+        }
+    };
+
+    private BroadcastReceiver mShutdownReceiver = new BroadcastReceiver() {
+        @Override
+        public void onReceive(Context context, Intent intent) {
+            // SHUTDOWN is protected broadcast.
+            synchronized (mStatsLock) {
+                shutdownLocked();
+            }
+        }
+    };
+
+    /**
+     * Observer that watches for {@link INetworkManagementService} alerts.
+     */
+    private final INetworkManagementEventObserver mAlertObserver = new BaseNetworkObserver() {
+        @Override
+        public void limitReached(String limitName, String iface) {
+            // only someone like NMS should be calling us
+            NetworkStack.checkNetworkStackPermission(mContext);
+
+            if (LIMIT_GLOBAL_ALERT.equals(limitName)) {
+                // kick off background poll to collect network stats unless there is already
+                // such a call pending; UID stats are handled during normal polling interval.
+                if (!mHandler.hasMessages(MSG_PERFORM_POLL_REGISTER_ALERT)) {
+                    mHandler.sendEmptyMessageDelayed(MSG_PERFORM_POLL_REGISTER_ALERT,
+                            mSettings.getPollDelay());
+                }
+            }
+        }
+    };
+
+    /**
+     * Handle collapsed RAT type changed event.
+     */
+    @VisibleForTesting
+    public void handleOnCollapsedRatTypeChanged() {
+        // Protect service from frequently updating. Remove pending messages if any.
+        mHandler.removeMessages(MSG_NOTIFY_NETWORK_STATUS);
+        mHandler.sendMessageDelayed(
+                mHandler.obtainMessage(MSG_NOTIFY_NETWORK_STATUS), mSettings.getPollDelay());
+    }
+
+    private void handleNotifyNetworkStatus(
+            Network[] defaultNetworks,
+            NetworkStateSnapshot[] snapshots,
+            String activeIface) {
+        synchronized (mStatsLock) {
+            mWakeLock.acquire();
+            try {
+                mActiveIface = activeIface;
+                handleNotifyNetworkStatusLocked(defaultNetworks, snapshots);
+            } finally {
+                mWakeLock.release();
+            }
+        }
+    }
+
+    /**
+     * Inspect all current {@link NetworkStateSnapshot}s to derive mapping from {@code iface} to
+     * {@link NetworkStatsHistory}. When multiple networks are active on a single {@code iface},
+     * they are combined under a single {@link NetworkIdentitySet}.
+     */
+    @GuardedBy("mStatsLock")
+    private void handleNotifyNetworkStatusLocked(@NonNull Network[] defaultNetworks,
+            @NonNull NetworkStateSnapshot[] snapshots) {
+        if (!mSystemReady) return;
+        if (LOGV) Slog.v(TAG, "handleNotifyNetworkStatusLocked()");
+
+        // take one last stats snapshot before updating iface mapping. this
+        // isn't perfect, since the kernel may already be counting traffic from
+        // the updated network.
+
+        // poll, but only persist network stats to keep codepath fast. UID stats
+        // will be persisted during next alarm poll event.
+        performPollLocked(FLAG_PERSIST_NETWORK);
+
+        // Rebuild active interfaces based on connected networks
+        mActiveIfaces.clear();
+        mActiveUidIfaces.clear();
+        // Update the list of default networks.
+        mDefaultNetworks = defaultNetworks;
+
+        mLastNetworkStateSnapshots = snapshots;
+
+        final boolean combineSubtypeEnabled = mSettings.getCombineSubtypeEnabled();
+        final ArraySet<String> mobileIfaces = new ArraySet<>();
+        for (NetworkStateSnapshot snapshot : snapshots) {
+            final int displayTransport =
+                    getDisplayTransport(snapshot.getNetworkCapabilities().getTransportTypes());
+            final boolean isMobile = (NetworkCapabilities.TRANSPORT_CELLULAR == displayTransport);
+            final boolean isDefault = ArrayUtils.contains(mDefaultNetworks, snapshot.getNetwork());
+            final int subType = combineSubtypeEnabled ? SUBTYPE_COMBINED
+                    : getSubTypeForStateSnapshot(snapshot);
+            final NetworkIdentity ident = NetworkIdentity.buildNetworkIdentity(mContext, snapshot,
+                    isDefault, subType);
+
+            // Traffic occurring on the base interface is always counted for
+            // both total usage and UID details.
+            final String baseIface = snapshot.getLinkProperties().getInterfaceName();
+            if (baseIface != null) {
+                findOrCreateNetworkIdentitySet(mActiveIfaces, baseIface).add(ident);
+                findOrCreateNetworkIdentitySet(mActiveUidIfaces, baseIface).add(ident);
+
+                // Build a separate virtual interface for VT (Video Telephony) data usage.
+                // Only do this when IMS is not metered, but VT is metered.
+                // If IMS is metered, then the IMS network usage has already included VT usage.
+                // VT is considered always metered in framework's layer. If VT is not metered
+                // per carrier's policy, modem will report 0 usage for VT calls.
+                if (snapshot.getNetworkCapabilities().hasCapability(
+                        NetworkCapabilities.NET_CAPABILITY_IMS) && !ident.getMetered()) {
+
+                    // Copy the identify from IMS one but mark it as metered.
+                    NetworkIdentity vtIdent = new NetworkIdentity(ident.getType(),
+                            ident.getSubType(), ident.getSubscriberId(), ident.getNetworkId(),
+                            ident.getRoaming(), true /* metered */,
+                            true /* onDefaultNetwork */, ident.getOemManaged());
+                    final String ifaceVt = IFACE_VT + getSubIdForMobile(snapshot);
+                    findOrCreateNetworkIdentitySet(mActiveIfaces, ifaceVt).add(vtIdent);
+                    findOrCreateNetworkIdentitySet(mActiveUidIfaces, ifaceVt).add(vtIdent);
+                }
+
+                if (isMobile) {
+                    mobileIfaces.add(baseIface);
+                }
+            }
+
+            // Traffic occurring on stacked interfaces is usually clatd.
+            //
+            // UID stats are always counted on the stacked interface and never on the base
+            // interface, because the packets on the base interface do not actually match
+            // application sockets (they're not IPv4) and thus the app uid is not known.
+            // For receive this is obvious: packets must be translated from IPv6 to IPv4
+            // before the application socket can be found.
+            // For transmit: either they go through the clat daemon which by virtue of going
+            // through userspace strips the original socket association during the IPv4 to
+            // IPv6 translation process, or they are offloaded by eBPF, which doesn't:
+            // However, on an ebpf device the accounting is done in cgroup ebpf hooks,
+            // which don't trigger again post ebpf translation.
+            // (as such stats accounted to the clat uid are ignored)
+            //
+            // Interface stats are more complicated.
+            //
+            // eBPF offloaded 464xlat'ed packets never hit base interface ip6tables, and thus
+            // *all* statistics are collected by iptables on the stacked v4-* interface.
+            //
+            // Additionally for ingress all packets bound for the clat IPv6 address are dropped
+            // in ip6tables raw prerouting and thus even non-offloaded packets are only
+            // accounted for on the stacked interface.
+            //
+            // For egress, packets subject to eBPF offload never appear on the base interface
+            // and only appear on the stacked interface. Thus to ensure packets increment
+            // interface stats, we must collate data from stacked interfaces. For xt_qtaguid
+            // (or non eBPF offloaded) TX they would appear on both, however egress interface
+            // accounting is explicitly bypassed for traffic from the clat uid.
+            //
+            // TODO: This code might be combined to above code.
+            for (String iface : snapshot.getLinkProperties().getAllInterfaceNames()) {
+                // baseIface has been handled, so ignore it.
+                if (TextUtils.equals(baseIface, iface)) continue;
+                if (iface != null) {
+                    findOrCreateNetworkIdentitySet(mActiveIfaces, iface).add(ident);
+                    findOrCreateNetworkIdentitySet(mActiveUidIfaces, iface).add(ident);
+                    if (isMobile) {
+                        mobileIfaces.add(iface);
+                    }
+
+                    mStatsFactory.noteStackedIface(iface, baseIface);
+                }
+            }
+        }
+
+        mMobileIfaces = mobileIfaces.toArray(new String[0]);
+        // TODO (b/192758557): Remove debug log.
+        if (ArrayUtils.contains(mMobileIfaces, null)) {
+            throw new NullPointerException(
+                    "null element in mMobileIfaces: " + Arrays.toString(mMobileIfaces));
+        }
+    }
+
+    private static int getSubIdForMobile(@NonNull NetworkStateSnapshot state) {
+        if (!state.getNetworkCapabilities().hasTransport(NetworkCapabilities.TRANSPORT_CELLULAR)) {
+            throw new IllegalArgumentException("Mobile state need capability TRANSPORT_CELLULAR");
+        }
+
+        final NetworkSpecifier spec = state.getNetworkCapabilities().getNetworkSpecifier();
+        if (spec instanceof TelephonyNetworkSpecifier) {
+             return ((TelephonyNetworkSpecifier) spec).getSubscriptionId();
+        } else {
+            Slog.wtf(TAG, "getSubIdForState invalid NetworkSpecifier");
+            return INVALID_SUBSCRIPTION_ID;
+        }
+    }
+
+    /**
+     * For networks with {@code TRANSPORT_CELLULAR}, get subType that was obtained through
+     * {@link PhoneStateListener}. Otherwise, return 0 given that other networks with different
+     * transport types do not actually fill this value.
+     */
+    private int getSubTypeForStateSnapshot(@NonNull NetworkStateSnapshot state) {
+        if (!state.getNetworkCapabilities().hasTransport(NetworkCapabilities.TRANSPORT_CELLULAR)) {
+            return 0;
+        }
+
+        return mNetworkStatsSubscriptionsMonitor.getRatTypeForSubscriberId(state.getSubscriberId());
+    }
+
+    private static <K> NetworkIdentitySet findOrCreateNetworkIdentitySet(
+            ArrayMap<K, NetworkIdentitySet> map, K key) {
+        NetworkIdentitySet ident = map.get(key);
+        if (ident == null) {
+            ident = new NetworkIdentitySet();
+            map.put(key, ident);
+        }
+        return ident;
+    }
+
+    @GuardedBy("mStatsLock")
+    private void recordSnapshotLocked(long currentTime) throws RemoteException {
+        // snapshot and record current counters; read UID stats first to
+        // avoid over counting dev stats.
+        Trace.traceBegin(TRACE_TAG_NETWORK, "snapshotUid");
+        final NetworkStats uidSnapshot = getNetworkStatsUidDetail(INTERFACES_ALL);
+        Trace.traceEnd(TRACE_TAG_NETWORK);
+        Trace.traceBegin(TRACE_TAG_NETWORK, "snapshotXt");
+        final NetworkStats xtSnapshot = readNetworkStatsSummaryXt();
+        Trace.traceEnd(TRACE_TAG_NETWORK);
+        Trace.traceBegin(TRACE_TAG_NETWORK, "snapshotDev");
+        final NetworkStats devSnapshot = readNetworkStatsSummaryDev();
+        Trace.traceEnd(TRACE_TAG_NETWORK);
+
+        // Snapshot for dev/xt stats from all custom stats providers. Counts per-interface data
+        // from stats providers that isn't already counted by dev and XT stats.
+        Trace.traceBegin(TRACE_TAG_NETWORK, "snapshotStatsProvider");
+        final NetworkStats providersnapshot = getNetworkStatsFromProviders(STATS_PER_IFACE);
+        Trace.traceEnd(TRACE_TAG_NETWORK);
+        xtSnapshot.combineAllValues(providersnapshot);
+        devSnapshot.combineAllValues(providersnapshot);
+
+        // For xt/dev, we pass a null VPN array because usage is aggregated by UID, so VPN traffic
+        // can't be reattributed to responsible apps.
+        Trace.traceBegin(TRACE_TAG_NETWORK, "recordDev");
+        mDevRecorder.recordSnapshotLocked(devSnapshot, mActiveIfaces, currentTime);
+        Trace.traceEnd(TRACE_TAG_NETWORK);
+        Trace.traceBegin(TRACE_TAG_NETWORK, "recordXt");
+        mXtRecorder.recordSnapshotLocked(xtSnapshot, mActiveIfaces, currentTime);
+        Trace.traceEnd(TRACE_TAG_NETWORK);
+
+        // For per-UID stats, pass the VPN info so VPN traffic is reattributed to responsible apps.
+        Trace.traceBegin(TRACE_TAG_NETWORK, "recordUid");
+        mUidRecorder.recordSnapshotLocked(uidSnapshot, mActiveUidIfaces, currentTime);
+        Trace.traceEnd(TRACE_TAG_NETWORK);
+        Trace.traceBegin(TRACE_TAG_NETWORK, "recordUidTag");
+        mUidTagRecorder.recordSnapshotLocked(uidSnapshot, mActiveUidIfaces, currentTime);
+        Trace.traceEnd(TRACE_TAG_NETWORK);
+
+        // We need to make copies of member fields that are sent to the observer to avoid
+        // a race condition between the service handler thread and the observer's
+        mStatsObservers.updateStats(xtSnapshot, uidSnapshot, new ArrayMap<>(mActiveIfaces),
+                new ArrayMap<>(mActiveUidIfaces), currentTime);
+    }
+
+    /**
+     * Bootstrap initial stats snapshot, usually during {@link #systemReady()}
+     * so we have baseline values without double-counting.
+     */
+    @GuardedBy("mStatsLock")
+    private void bootstrapStatsLocked() {
+        final long currentTime = mClock.millis();
+
+        try {
+            recordSnapshotLocked(currentTime);
+        } catch (IllegalStateException e) {
+            Slog.w(TAG, "problem reading network stats: " + e);
+        } catch (RemoteException e) {
+            // ignored; service lives in system_server
+        }
+    }
+
+    private void performPoll(int flags) {
+        synchronized (mStatsLock) {
+            mWakeLock.acquire();
+
+            try {
+                performPollLocked(flags);
+            } finally {
+                mWakeLock.release();
+            }
+        }
+    }
+
+    /**
+     * Periodic poll operation, reading current statistics and recording into
+     * {@link NetworkStatsHistory}.
+     */
+    @GuardedBy("mStatsLock")
+    private void performPollLocked(int flags) {
+        if (!mSystemReady) return;
+        if (LOGV) Slog.v(TAG, "performPollLocked(flags=0x" + Integer.toHexString(flags) + ")");
+        Trace.traceBegin(TRACE_TAG_NETWORK, "performPollLocked");
+
+        final boolean persistNetwork = (flags & FLAG_PERSIST_NETWORK) != 0;
+        final boolean persistUid = (flags & FLAG_PERSIST_UID) != 0;
+        final boolean persistForce = (flags & FLAG_PERSIST_FORCE) != 0;
+
+        performPollFromProvidersLocked();
+
+        // TODO: consider marking "untrusted" times in historical stats
+        final long currentTime = mClock.millis();
+
+        try {
+            recordSnapshotLocked(currentTime);
+        } catch (IllegalStateException e) {
+            Log.wtf(TAG, "problem reading network stats", e);
+            return;
+        } catch (RemoteException e) {
+            // ignored; service lives in system_server
+            return;
+        }
+
+        // persist any pending data depending on requested flags
+        Trace.traceBegin(TRACE_TAG_NETWORK, "[persisting]");
+        if (persistForce) {
+            mDevRecorder.forcePersistLocked(currentTime);
+            mXtRecorder.forcePersistLocked(currentTime);
+            mUidRecorder.forcePersistLocked(currentTime);
+            mUidTagRecorder.forcePersistLocked(currentTime);
+        } else {
+            if (persistNetwork) {
+                mDevRecorder.maybePersistLocked(currentTime);
+                mXtRecorder.maybePersistLocked(currentTime);
+            }
+            if (persistUid) {
+                mUidRecorder.maybePersistLocked(currentTime);
+                mUidTagRecorder.maybePersistLocked(currentTime);
+            }
+        }
+        Trace.traceEnd(TRACE_TAG_NETWORK);
+
+        if (mSettings.getSampleEnabled()) {
+            // sample stats after each full poll
+            performSampleLocked();
+        }
+
+        // finally, dispatch updated event to any listeners
+        mHandler.sendMessage(mHandler.obtainMessage(MSG_BROADCAST_NETWORK_STATS_UPDATED));
+
+        Trace.traceEnd(TRACE_TAG_NETWORK);
+    }
+
+    @GuardedBy("mStatsLock")
+    private void performPollFromProvidersLocked() {
+        // Request asynchronous stats update from all providers for next poll. And wait a bit of
+        // time to allow providers report-in given that normally binder call should be fast. Note
+        // that size of list might be changed because addition/removing at the same time. For
+        // addition, the stats of the missed provider can only be collected in next poll;
+        // for removal, wait might take up to MAX_STATS_PROVIDER_POLL_WAIT_TIME_MS
+        // once that happened.
+        // TODO: request with a valid token.
+        Trace.traceBegin(TRACE_TAG_NETWORK, "provider.requestStatsUpdate");
+        final int registeredCallbackCount = mStatsProviderCbList.size();
+        mStatsProviderSem.drainPermits();
+        invokeForAllStatsProviderCallbacks(
+                (cb) -> cb.mProvider.onRequestStatsUpdate(0 /* unused */));
+        try {
+            mStatsProviderSem.tryAcquire(registeredCallbackCount,
+                    MAX_STATS_PROVIDER_POLL_WAIT_TIME_MS, TimeUnit.MILLISECONDS);
+        } catch (InterruptedException e) {
+            // Strictly speaking it's possible a provider happened to deliver between the timeout
+            // and the log, and that doesn't matter too much as this is just a debug log.
+            Log.d(TAG, "requestStatsUpdate - providers responded "
+                    + mStatsProviderSem.availablePermits()
+                    + "/" + registeredCallbackCount + " : " + e);
+        }
+        Trace.traceEnd(TRACE_TAG_NETWORK);
+    }
+
+    /**
+     * Sample recent statistics summary into {@link EventLog}.
+     */
+    @GuardedBy("mStatsLock")
+    private void performSampleLocked() {
+        // TODO: migrate trustedtime fixes to separate binary log events
+        final long currentTime = mClock.millis();
+
+        NetworkTemplate template;
+        NetworkStats.Entry devTotal;
+        NetworkStats.Entry xtTotal;
+        NetworkStats.Entry uidTotal;
+
+        // collect mobile sample
+        template = buildTemplateMobileWildcard();
+        devTotal = mDevRecorder.getTotalSinceBootLocked(template);
+        xtTotal = mXtRecorder.getTotalSinceBootLocked(template);
+        uidTotal = mUidRecorder.getTotalSinceBootLocked(template);
+
+        EventLogTags.writeNetstatsMobileSample(
+                devTotal.rxBytes, devTotal.rxPackets, devTotal.txBytes, devTotal.txPackets,
+                xtTotal.rxBytes, xtTotal.rxPackets, xtTotal.txBytes, xtTotal.txPackets,
+                uidTotal.rxBytes, uidTotal.rxPackets, uidTotal.txBytes, uidTotal.txPackets,
+                currentTime);
+
+        // collect wifi sample
+        template = buildTemplateWifiWildcard();
+        devTotal = mDevRecorder.getTotalSinceBootLocked(template);
+        xtTotal = mXtRecorder.getTotalSinceBootLocked(template);
+        uidTotal = mUidRecorder.getTotalSinceBootLocked(template);
+
+        EventLogTags.writeNetstatsWifiSample(
+                devTotal.rxBytes, devTotal.rxPackets, devTotal.txBytes, devTotal.txPackets,
+                xtTotal.rxBytes, xtTotal.rxPackets, xtTotal.txBytes, xtTotal.txPackets,
+                uidTotal.rxBytes, uidTotal.rxPackets, uidTotal.txBytes, uidTotal.txPackets,
+                currentTime);
+    }
+
+    /**
+     * Clean up {@link #mUidRecorder} after UID is removed.
+     */
+    @GuardedBy("mStatsLock")
+    private void removeUidsLocked(int... uids) {
+        if (LOGV) Slog.v(TAG, "removeUidsLocked() for UIDs " + Arrays.toString(uids));
+
+        // Perform one last poll before removing
+        performPollLocked(FLAG_PERSIST_ALL);
+
+        mUidRecorder.removeUidsLocked(uids);
+        mUidTagRecorder.removeUidsLocked(uids);
+
+        // Clear kernel stats associated with UID
+        for (int uid : uids) {
+            resetKernelUidStats(uid);
+        }
+    }
+
+    /**
+     * Clean up {@link #mUidRecorder} after user is removed.
+     */
+    @GuardedBy("mStatsLock")
+    private void removeUserLocked(int userId) {
+        if (LOGV) Slog.v(TAG, "removeUserLocked() for userId=" + userId);
+
+        // Build list of UIDs that we should clean up
+        int[] uids = new int[0];
+        final List<ApplicationInfo> apps = mContext.getPackageManager().getInstalledApplications(
+                PackageManager.MATCH_ANY_USER
+                | PackageManager.MATCH_DISABLED_COMPONENTS);
+        for (ApplicationInfo app : apps) {
+            final int uid = UserHandle.getUid(userId, app.uid);
+            uids = ArrayUtils.appendInt(uids, uid);
+        }
+
+        removeUidsLocked(uids);
+    }
+
+    private class NetworkStatsManagerInternalImpl extends NetworkStatsManagerInternal {
+        @Override
+        public long getNetworkTotalBytes(NetworkTemplate template, long start, long end) {
+            Trace.traceBegin(TRACE_TAG_NETWORK, "getNetworkTotalBytes");
+            try {
+                return NetworkStatsService.this.getNetworkTotalBytes(template, start, end);
+            } finally {
+                Trace.traceEnd(TRACE_TAG_NETWORK);
+            }
+        }
+
+        @Override
+        public NetworkStats getNetworkUidBytes(NetworkTemplate template, long start, long end) {
+            Trace.traceBegin(TRACE_TAG_NETWORK, "getNetworkUidBytes");
+            try {
+                return NetworkStatsService.this.getNetworkUidBytes(template, start, end);
+            } finally {
+                Trace.traceEnd(TRACE_TAG_NETWORK);
+            }
+        }
+
+        @Override
+        public void setUidForeground(int uid, boolean uidForeground) {
+            NetworkStatsService.this.setUidForeground(uid, uidForeground);
+        }
+
+        @Override
+        public void advisePersistThreshold(long thresholdBytes) {
+            NetworkStatsService.this.advisePersistThreshold(thresholdBytes);
+        }
+
+        @Override
+        public void forceUpdate() {
+            NetworkStatsService.this.forceUpdate();
+        }
+
+        @Override
+        public void setStatsProviderWarningAndLimitAsync(
+                @NonNull String iface, long warning, long limit) {
+            if (LOGV) {
+                Slog.v(TAG, "setStatsProviderWarningAndLimitAsync("
+                        + iface + "," + warning + "," + limit + ")");
+            }
+            invokeForAllStatsProviderCallbacks((cb) -> cb.mProvider.onSetWarningAndLimit(iface,
+                    warning, limit));
+        }
+    }
+
+    @Override
+    protected void dump(FileDescriptor fd, PrintWriter rawWriter, String[] args) {
+        if (!DumpUtils.checkDumpPermission(mContext, TAG, rawWriter)) return;
+
+        long duration = DateUtils.DAY_IN_MILLIS;
+        final HashSet<String> argSet = new HashSet<String>();
+        for (String arg : args) {
+            argSet.add(arg);
+
+            if (arg.startsWith("--duration=")) {
+                try {
+                    duration = Long.parseLong(arg.substring(11));
+                } catch (NumberFormatException ignored) {
+                }
+            }
+        }
+
+        // usage: dumpsys netstats --full --uid --tag --poll --checkin
+        final boolean poll = argSet.contains("--poll") || argSet.contains("poll");
+        final boolean checkin = argSet.contains("--checkin");
+        final boolean fullHistory = argSet.contains("--full") || argSet.contains("full");
+        final boolean includeUid = argSet.contains("--uid") || argSet.contains("detail");
+        final boolean includeTag = argSet.contains("--tag") || argSet.contains("detail");
+
+        final IndentingPrintWriter pw = new IndentingPrintWriter(rawWriter, "  ");
+
+        synchronized (mStatsLock) {
+            if (args.length > 0 && "--proto".equals(args[0])) {
+                // In this case ignore all other arguments.
+                dumpProtoLocked(fd);
+                return;
+            }
+
+            if (poll) {
+                performPollLocked(FLAG_PERSIST_ALL | FLAG_PERSIST_FORCE);
+                pw.println("Forced poll");
+                return;
+            }
+
+            if (checkin) {
+                final long end = System.currentTimeMillis();
+                final long start = end - duration;
+
+                pw.print("v1,");
+                pw.print(start / SECOND_IN_MILLIS); pw.print(',');
+                pw.print(end / SECOND_IN_MILLIS); pw.println();
+
+                pw.println("xt");
+                mXtRecorder.dumpCheckin(rawWriter, start, end);
+
+                if (includeUid) {
+                    pw.println("uid");
+                    mUidRecorder.dumpCheckin(rawWriter, start, end);
+                }
+                if (includeTag) {
+                    pw.println("tag");
+                    mUidTagRecorder.dumpCheckin(rawWriter, start, end);
+                }
+                return;
+            }
+
+            pw.println("Configs:");
+            pw.increaseIndent();
+            pw.printPair(NETSTATS_COMBINE_SUBTYPE_ENABLED, mSettings.getCombineSubtypeEnabled());
+            pw.println();
+            pw.decreaseIndent();
+
+            pw.println("Active interfaces:");
+            pw.increaseIndent();
+            for (int i = 0; i < mActiveIfaces.size(); i++) {
+                pw.printPair("iface", mActiveIfaces.keyAt(i));
+                pw.printPair("ident", mActiveIfaces.valueAt(i));
+                pw.println();
+            }
+            pw.decreaseIndent();
+
+            pw.println("Active UID interfaces:");
+            pw.increaseIndent();
+            for (int i = 0; i < mActiveUidIfaces.size(); i++) {
+                pw.printPair("iface", mActiveUidIfaces.keyAt(i));
+                pw.printPair("ident", mActiveUidIfaces.valueAt(i));
+                pw.println();
+            }
+            pw.decreaseIndent();
+
+            // Get the top openSession callers
+            final SparseIntArray calls;
+            synchronized (mOpenSessionCallsPerUid) {
+                calls = mOpenSessionCallsPerUid.clone();
+            }
+
+            final int N = calls.size();
+            final long[] values = new long[N];
+            for (int j = 0; j < N; j++) {
+                values[j] = ((long) calls.valueAt(j) << 32) | calls.keyAt(j);
+            }
+            Arrays.sort(values);
+
+            pw.println("Top openSession callers (uid=count):");
+            pw.increaseIndent();
+            final int end = Math.max(0, N - DUMP_STATS_SESSION_COUNT);
+            for (int j = N - 1; j >= end; j--) {
+                final int uid = (int) (values[j] & 0xffffffff);
+                final int count = (int) (values[j] >> 32);
+                pw.print(uid); pw.print("="); pw.println(count);
+            }
+            pw.decreaseIndent();
+            pw.println();
+
+            pw.println("Stats Providers:");
+            pw.increaseIndent();
+            invokeForAllStatsProviderCallbacks((cb) -> {
+                pw.println(cb.mTag + " Xt:");
+                pw.increaseIndent();
+                pw.print(cb.getCachedStats(STATS_PER_IFACE).toString());
+                pw.decreaseIndent();
+                if (includeUid) {
+                    pw.println(cb.mTag + " Uid:");
+                    pw.increaseIndent();
+                    pw.print(cb.getCachedStats(STATS_PER_UID).toString());
+                    pw.decreaseIndent();
+                }
+            });
+            pw.decreaseIndent();
+
+            pw.println("Dev stats:");
+            pw.increaseIndent();
+            mDevRecorder.dumpLocked(pw, fullHistory);
+            pw.decreaseIndent();
+
+            pw.println("Xt stats:");
+            pw.increaseIndent();
+            mXtRecorder.dumpLocked(pw, fullHistory);
+            pw.decreaseIndent();
+
+            if (includeUid) {
+                pw.println("UID stats:");
+                pw.increaseIndent();
+                mUidRecorder.dumpLocked(pw, fullHistory);
+                pw.decreaseIndent();
+            }
+
+            if (includeTag) {
+                pw.println("UID tag stats:");
+                pw.increaseIndent();
+                mUidTagRecorder.dumpLocked(pw, fullHistory);
+                pw.decreaseIndent();
+            }
+        }
+    }
+
+    @GuardedBy("mStatsLock")
+    private void dumpProtoLocked(FileDescriptor fd) {
+        final ProtoOutputStream proto = new ProtoOutputStream(fd);
+
+        // TODO Right now it writes all history.  Should it limit to the "since-boot" log?
+
+        dumpInterfaces(proto, NetworkStatsServiceDumpProto.ACTIVE_INTERFACES, mActiveIfaces);
+        dumpInterfaces(proto, NetworkStatsServiceDumpProto.ACTIVE_UID_INTERFACES, mActiveUidIfaces);
+        mDevRecorder.dumpDebugLocked(proto, NetworkStatsServiceDumpProto.DEV_STATS);
+        mXtRecorder.dumpDebugLocked(proto, NetworkStatsServiceDumpProto.XT_STATS);
+        mUidRecorder.dumpDebugLocked(proto, NetworkStatsServiceDumpProto.UID_STATS);
+        mUidTagRecorder.dumpDebugLocked(proto, NetworkStatsServiceDumpProto.UID_TAG_STATS);
+
+        proto.flush();
+    }
+
+    private static void dumpInterfaces(ProtoOutputStream proto, long tag,
+            ArrayMap<String, NetworkIdentitySet> ifaces) {
+        for (int i = 0; i < ifaces.size(); i++) {
+            final long start = proto.start(tag);
+
+            proto.write(NetworkInterfaceProto.INTERFACE, ifaces.keyAt(i));
+            ifaces.valueAt(i).dumpDebug(proto, NetworkInterfaceProto.IDENTITIES);
+
+            proto.end(start);
+        }
+    }
+
+    private NetworkStats readNetworkStatsSummaryDev() {
+        try {
+            return mStatsFactory.readNetworkStatsSummaryDev();
+        } catch (IOException e) {
+            throw new IllegalStateException(e);
+        }
+    }
+
+    private NetworkStats readNetworkStatsSummaryXt() {
+        try {
+            return mStatsFactory.readNetworkStatsSummaryXt();
+        } catch (IOException e) {
+            throw new IllegalStateException(e);
+        }
+    }
+
+    private NetworkStats readNetworkStatsUidDetail(int uid, String[] ifaces, int tag) {
+        try {
+            return mStatsFactory.readNetworkStatsDetail(uid, ifaces, tag);
+        } catch (IOException e) {
+            throw new IllegalStateException(e);
+        }
+    }
+
+    /**
+     * Return snapshot of current UID statistics, including any
+     * {@link TrafficStats#UID_TETHERING}, video calling data usage, and {@link #mUidOperations}
+     * values.
+     *
+     * @param ifaces A list of interfaces the stats should be restricted to, or
+     *               {@link NetworkStats#INTERFACES_ALL}.
+     */
+    private NetworkStats getNetworkStatsUidDetail(String[] ifaces)
+            throws RemoteException {
+        final NetworkStats uidSnapshot = readNetworkStatsUidDetail(UID_ALL,  ifaces, TAG_ALL);
+
+        // fold tethering stats and operations into uid snapshot
+        final NetworkStats tetherSnapshot = getNetworkStatsTethering(STATS_PER_UID);
+        tetherSnapshot.filter(UID_ALL, ifaces, TAG_ALL);
+        mStatsFactory.apply464xlatAdjustments(uidSnapshot, tetherSnapshot);
+        uidSnapshot.combineAllValues(tetherSnapshot);
+
+        // get a stale copy of uid stats snapshot provided by providers.
+        final NetworkStats providerStats = getNetworkStatsFromProviders(STATS_PER_UID);
+        providerStats.filter(UID_ALL, ifaces, TAG_ALL);
+        mStatsFactory.apply464xlatAdjustments(uidSnapshot, providerStats);
+        uidSnapshot.combineAllValues(providerStats);
+
+        uidSnapshot.combineAllValues(mUidOperations);
+
+        return uidSnapshot;
+    }
+
+    /**
+     * Return snapshot of current non-offloaded tethering statistics. Will return empty
+     * {@link NetworkStats} if any problems are encountered, or queried by {@code STATS_PER_IFACE}
+     * since it is already included by {@link #nativeGetIfaceStat}.
+     * See {@code OffloadTetheringStatsProvider} for offloaded tethering stats.
+     */
+    // TODO: Remove this by implementing {@link NetworkStatsProvider} for non-offloaded
+    //  tethering stats.
+    private NetworkStats getNetworkStatsTethering(int how) throws RemoteException {
+        try {
+            return mNetworkManager.getNetworkStatsTethering(how);
+        } catch (IllegalStateException e) {
+            Log.wtf(TAG, "problem reading network stats", e);
+            return new NetworkStats(0L, 10);
+        }
+    }
+
+    // TODO: It is copied from ConnectivityService, consider refactor these check permission
+    //  functions to a proper util.
+    private boolean checkAnyPermissionOf(String... permissions) {
+        for (String permission : permissions) {
+            if (mContext.checkCallingOrSelfPermission(permission) == PERMISSION_GRANTED) {
+                return true;
+            }
+        }
+        return false;
+    }
+
+    private void enforceAnyPermissionOf(String... permissions) {
+        if (!checkAnyPermissionOf(permissions)) {
+            throw new SecurityException("Requires one of the following permissions: "
+                    + String.join(", ", permissions) + ".");
+        }
+    }
+
+    /**
+     * Registers a custom provider of {@link android.net.NetworkStats} to combine the network
+     * statistics that cannot be seen by the kernel to system. To unregister, invoke the
+     * {@code unregister()} of the returned callback.
+     *
+     * @param tag a human readable identifier of the custom network stats provider.
+     * @param provider the {@link INetworkStatsProvider} binder corresponding to the
+     *                 {@link NetworkStatsProvider} to be registered.
+     *
+     * @return a {@link INetworkStatsProviderCallback} binder
+     *         interface, which can be used to report events to the system.
+     */
+    public @NonNull INetworkStatsProviderCallback registerNetworkStatsProvider(
+            @NonNull String tag, @NonNull INetworkStatsProvider provider) {
+        enforceAnyPermissionOf(NETWORK_STATS_PROVIDER,
+                NetworkStack.PERMISSION_MAINLINE_NETWORK_STACK);
+        Objects.requireNonNull(provider, "provider is null");
+        Objects.requireNonNull(tag, "tag is null");
+        try {
+            NetworkStatsProviderCallbackImpl callback = new NetworkStatsProviderCallbackImpl(
+                    tag, provider, mStatsProviderSem, mAlertObserver,
+                    mStatsProviderCbList);
+            mStatsProviderCbList.add(callback);
+            Log.d(TAG, "registerNetworkStatsProvider from " + callback.mTag + " uid/pid="
+                    + getCallingUid() + "/" + getCallingPid());
+            return callback;
+        } catch (RemoteException e) {
+            Log.e(TAG, "registerNetworkStatsProvider failed", e);
+        }
+        return null;
+    }
+
+    // Collect stats from local cache of providers.
+    private @NonNull NetworkStats getNetworkStatsFromProviders(int how) {
+        final NetworkStats ret = new NetworkStats(0L, 0);
+        invokeForAllStatsProviderCallbacks((cb) -> ret.combineAllValues(cb.getCachedStats(how)));
+        return ret;
+    }
+
+    @FunctionalInterface
+    private interface ThrowingConsumer<S, T extends Throwable> {
+        void accept(S s) throws T;
+    }
+
+    private void invokeForAllStatsProviderCallbacks(
+            @NonNull ThrowingConsumer<NetworkStatsProviderCallbackImpl, RemoteException> task) {
+        for (final NetworkStatsProviderCallbackImpl cb : mStatsProviderCbList) {
+            try {
+                task.accept(cb);
+            } catch (RemoteException e) {
+                Log.e(TAG, "Fail to broadcast to provider: " + cb.mTag, e);
+            }
+        }
+    }
+
+    private static class NetworkStatsProviderCallbackImpl extends INetworkStatsProviderCallback.Stub
+            implements IBinder.DeathRecipient {
+        @NonNull final String mTag;
+
+        @NonNull final INetworkStatsProvider mProvider;
+        @NonNull private final Semaphore mSemaphore;
+        @NonNull final INetworkManagementEventObserver mAlertObserver;
+        @NonNull final CopyOnWriteArrayList<NetworkStatsProviderCallbackImpl> mStatsProviderCbList;
+
+        @NonNull private final Object mProviderStatsLock = new Object();
+
+        @GuardedBy("mProviderStatsLock")
+        // Track STATS_PER_IFACE and STATS_PER_UID separately.
+        private final NetworkStats mIfaceStats = new NetworkStats(0L, 0);
+        @GuardedBy("mProviderStatsLock")
+        private final NetworkStats mUidStats = new NetworkStats(0L, 0);
+
+        NetworkStatsProviderCallbackImpl(
+                @NonNull String tag, @NonNull INetworkStatsProvider provider,
+                @NonNull Semaphore semaphore,
+                @NonNull INetworkManagementEventObserver alertObserver,
+                @NonNull CopyOnWriteArrayList<NetworkStatsProviderCallbackImpl> cbList)
+                throws RemoteException {
+            mTag = tag;
+            mProvider = provider;
+            mProvider.asBinder().linkToDeath(this, 0);
+            mSemaphore = semaphore;
+            mAlertObserver = alertObserver;
+            mStatsProviderCbList = cbList;
+        }
+
+        @NonNull
+        public NetworkStats getCachedStats(int how) {
+            synchronized (mProviderStatsLock) {
+                NetworkStats stats;
+                switch (how) {
+                    case STATS_PER_IFACE:
+                        stats = mIfaceStats;
+                        break;
+                    case STATS_PER_UID:
+                        stats = mUidStats;
+                        break;
+                    default:
+                        throw new IllegalArgumentException("Invalid type: " + how);
+                }
+                // Callers might be able to mutate the returned object. Return a defensive copy
+                // instead of local reference.
+                return stats.clone();
+            }
+        }
+
+        @Override
+        public void notifyStatsUpdated(int token, @Nullable NetworkStats ifaceStats,
+                @Nullable NetworkStats uidStats) {
+            // TODO: 1. Use token to map ifaces to correct NetworkIdentity.
+            //       2. Store the difference and store it directly to the recorder.
+            synchronized (mProviderStatsLock) {
+                if (ifaceStats != null) mIfaceStats.combineAllValues(ifaceStats);
+                if (uidStats != null) mUidStats.combineAllValues(uidStats);
+            }
+            mSemaphore.release();
+        }
+
+        @Override
+        public void notifyAlertReached() throws RemoteException {
+            // This binder object can only have been obtained by a process that holds
+            // NETWORK_STATS_PROVIDER. Thus, no additional permission check is required.
+            BinderUtils.withCleanCallingIdentity(() ->
+                    mAlertObserver.limitReached(LIMIT_GLOBAL_ALERT, null /* unused */));
+        }
+
+        @Override
+        public void notifyWarningOrLimitReached() {
+            Log.d(TAG, mTag + ": notifyWarningOrLimitReached");
+            BinderUtils.withCleanCallingIdentity(() ->
+                    LocalServices.getService(NetworkPolicyManagerInternal.class)
+                            .onStatsProviderWarningOrLimitReached(mTag));
+        }
+
+        @Override
+        public void binderDied() {
+            Log.d(TAG, mTag + ": binderDied");
+            mStatsProviderCbList.remove(this);
+        }
+
+        @Override
+        public void unregister() {
+            Log.d(TAG, mTag + ": unregister");
+            mStatsProviderCbList.remove(this);
+        }
+
+    }
+
+    private void assertSystemReady() {
+        if (!mSystemReady) {
+            throw new IllegalStateException("System not ready");
+        }
+    }
+
+    private class DropBoxNonMonotonicObserver implements NonMonotonicObserver<String> {
+        @Override
+        public void foundNonMonotonic(NetworkStats left, int leftIndex, NetworkStats right,
+                int rightIndex, String cookie) {
+            Log.w(TAG, "Found non-monotonic values; saving to dropbox");
+
+            // record error for debugging
+            final StringBuilder builder = new StringBuilder();
+            builder.append("found non-monotonic " + cookie + " values at left[" + leftIndex
+                    + "] - right[" + rightIndex + "]\n");
+            builder.append("left=").append(left).append('\n');
+            builder.append("right=").append(right).append('\n');
+
+            mContext.getSystemService(DropBoxManager.class).addText(TAG_NETSTATS_ERROR,
+                    builder.toString());
+        }
+
+        @Override
+        public void foundNonMonotonic(
+                NetworkStats stats, int statsIndex, String cookie) {
+            Log.w(TAG, "Found non-monotonic values; saving to dropbox");
+
+            final StringBuilder builder = new StringBuilder();
+            builder.append("Found non-monotonic " + cookie + " values at [" + statsIndex + "]\n");
+            builder.append("stats=").append(stats).append('\n');
+
+            mContext.getSystemService(DropBoxManager.class).addText(TAG_NETSTATS_ERROR,
+                    builder.toString());
+        }
+    }
+
+    /**
+     * Default external settings that read from
+     * {@link android.provider.Settings.Global}.
+     */
+    private static class DefaultNetworkStatsSettings implements NetworkStatsSettings {
+        private final ContentResolver mResolver;
+
+        public DefaultNetworkStatsSettings(Context context) {
+            mResolver = Objects.requireNonNull(context.getContentResolver());
+            // TODO: adjust these timings for production builds
+        }
+
+        private long getGlobalLong(String name, long def) {
+            return Settings.Global.getLong(mResolver, name, def);
+        }
+        private boolean getGlobalBoolean(String name, boolean def) {
+            final int defInt = def ? 1 : 0;
+            return Settings.Global.getInt(mResolver, name, defInt) != 0;
+        }
+
+        @Override
+        public long getPollInterval() {
+            return getGlobalLong(NETSTATS_POLL_INTERVAL, 30 * MINUTE_IN_MILLIS);
+        }
+        @Override
+        public long getPollDelay() {
+            return DEFAULT_PERFORM_POLL_DELAY_MS;
+        }
+        @Override
+        public long getGlobalAlertBytes(long def) {
+            return getGlobalLong(NETSTATS_GLOBAL_ALERT_BYTES, def);
+        }
+        @Override
+        public boolean getSampleEnabled() {
+            return getGlobalBoolean(NETSTATS_SAMPLE_ENABLED, true);
+        }
+        @Override
+        public boolean getAugmentEnabled() {
+            return getGlobalBoolean(NETSTATS_AUGMENT_ENABLED, true);
+        }
+        @Override
+        public boolean getCombineSubtypeEnabled() {
+            return getGlobalBoolean(NETSTATS_COMBINE_SUBTYPE_ENABLED, false);
+        }
+        @Override
+        public Config getDevConfig() {
+            return new Config(getGlobalLong(NETSTATS_DEV_BUCKET_DURATION, HOUR_IN_MILLIS),
+                    getGlobalLong(NETSTATS_DEV_ROTATE_AGE, 15 * DAY_IN_MILLIS),
+                    getGlobalLong(NETSTATS_DEV_DELETE_AGE, 90 * DAY_IN_MILLIS));
+        }
+        @Override
+        public Config getXtConfig() {
+            return getDevConfig();
+        }
+        @Override
+        public Config getUidConfig() {
+            return new Config(getGlobalLong(NETSTATS_UID_BUCKET_DURATION, 2 * HOUR_IN_MILLIS),
+                    getGlobalLong(NETSTATS_UID_ROTATE_AGE, 15 * DAY_IN_MILLIS),
+                    getGlobalLong(NETSTATS_UID_DELETE_AGE, 90 * DAY_IN_MILLIS));
+        }
+        @Override
+        public Config getUidTagConfig() {
+            return new Config(getGlobalLong(NETSTATS_UID_TAG_BUCKET_DURATION, 2 * HOUR_IN_MILLIS),
+                    getGlobalLong(NETSTATS_UID_TAG_ROTATE_AGE, 5 * DAY_IN_MILLIS),
+                    getGlobalLong(NETSTATS_UID_TAG_DELETE_AGE, 15 * DAY_IN_MILLIS));
+        }
+        @Override
+        public long getDevPersistBytes(long def) {
+            return getGlobalLong(NETSTATS_DEV_PERSIST_BYTES, def);
+        }
+        @Override
+        public long getXtPersistBytes(long def) {
+            return getDevPersistBytes(def);
+        }
+        @Override
+        public long getUidPersistBytes(long def) {
+            return getGlobalLong(NETSTATS_UID_PERSIST_BYTES, def);
+        }
+        @Override
+        public long getUidTagPersistBytes(long def) {
+            return getGlobalLong(NETSTATS_UID_TAG_PERSIST_BYTES, def);
+        }
+    }
+
+    private static native long nativeGetTotalStat(int type);
+    private static native long nativeGetIfaceStat(String iface, int type);
+    private static native long nativeGetUidStat(int uid, int type);
+}
diff --git a/service-t/src/com/android/server/net/NetworkStatsSubscriptionsMonitor.java b/service-t/src/com/android/server/net/NetworkStatsSubscriptionsMonitor.java
new file mode 100644
index 0000000..5646c75
--- /dev/null
+++ b/service-t/src/com/android/server/net/NetworkStatsSubscriptionsMonitor.java
@@ -0,0 +1,243 @@
+/*
+ * Copyright (C) 2020 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.net;
+
+import static android.net.NetworkTemplate.NETWORK_TYPE_5G_NSA;
+import static android.net.NetworkTemplate.getCollapsedRatType;
+
+import android.annotation.NonNull;
+import android.content.Context;
+import android.os.Looper;
+import android.telephony.Annotation;
+import android.telephony.NetworkRegistrationInfo;
+import android.telephony.PhoneStateListener;
+import android.telephony.ServiceState;
+import android.telephony.SubscriptionManager;
+import android.telephony.TelephonyManager;
+import android.text.TextUtils;
+import android.util.Log;
+import android.util.Pair;
+
+import com.android.internal.annotations.VisibleForTesting;
+import com.android.internal.util.CollectionUtils;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.concurrent.CopyOnWriteArrayList;
+import java.util.concurrent.Executor;
+
+/**
+ * Helper class that watches for events that are triggered per subscription.
+ */
+public class NetworkStatsSubscriptionsMonitor extends
+        SubscriptionManager.OnSubscriptionsChangedListener {
+
+    /**
+     * Interface that this monitor uses to delegate event handling to NetworkStatsService.
+     */
+    public interface Delegate {
+        /**
+         * Notify that the collapsed RAT type has been changed for any subscription. The method
+         * will also be triggered for any existing sub when start and stop monitoring.
+         *
+         * @param subscriberId IMSI of the subscription.
+         * @param collapsedRatType collapsed RAT type.
+         *                         @see android.net.NetworkTemplate#getCollapsedRatType(int).
+         */
+        void onCollapsedRatTypeChanged(@NonNull String subscriberId,
+                @Annotation.NetworkType int collapsedRatType);
+    }
+    private final Delegate mDelegate;
+
+    /**
+     * Receivers that watches for {@link ServiceState} changes for each subscription, to
+     * monitor the transitioning between Radio Access Technology(RAT) types for each sub.
+     */
+    @NonNull
+    private final CopyOnWriteArrayList<RatTypeListener> mRatListeners =
+            new CopyOnWriteArrayList<>();
+
+    @NonNull
+    private final SubscriptionManager mSubscriptionManager;
+    @NonNull
+    private final TelephonyManager mTeleManager;
+
+    @NonNull
+    private final Executor mExecutor;
+
+    NetworkStatsSubscriptionsMonitor(@NonNull Context context, @NonNull Looper looper,
+            @NonNull Executor executor, @NonNull Delegate delegate) {
+        super(looper);
+        mSubscriptionManager = (SubscriptionManager) context.getSystemService(
+                Context.TELEPHONY_SUBSCRIPTION_SERVICE);
+        mTeleManager = (TelephonyManager) context.getSystemService(Context.TELEPHONY_SERVICE);
+        mExecutor = executor;
+        mDelegate = delegate;
+    }
+
+    @Override
+    public void onSubscriptionsChanged() {
+        // Collect active subId list, hidden subId such as opportunistic subscriptions are
+        // also needed to track CBRS.
+        final List<Integer> newSubs = getActiveSubIdList(mSubscriptionManager);
+
+        // IMSI is needed for every newly added sub. Listener stores subscriberId into it to
+        // prevent binder call to telephony when querying RAT. Keep listener registration with empty
+        // IMSI is meaningless since the RAT type changed is ambiguous for multi-SIM if reported
+        // with empty IMSI. So filter the subs w/o a valid IMSI to prevent such registration.
+        final List<Pair<Integer, String>> filteredNewSubs =
+                CollectionUtils.mapNotNull(newSubs, subId -> {
+                    final String subscriberId = mTeleManager.getSubscriberId(subId);
+                    return TextUtils.isEmpty(subscriberId) ? null : new Pair(subId, subscriberId);
+                });
+
+        for (final Pair<Integer, String> sub : filteredNewSubs) {
+            // Fully match listener with subId and IMSI, since in some rare cases, IMSI might be
+            // suddenly change regardless of subId, such as switch IMSI feature in modem side.
+            // If that happens, register new listener with new IMSI and remove old one later.
+            if (CollectionUtils.find(mRatListeners,
+                    it -> it.equalsKey(sub.first, sub.second)) != null) {
+                continue;
+            }
+
+            final RatTypeListener listener =
+                    new RatTypeListener(mExecutor, this, sub.first, sub.second);
+            mRatListeners.add(listener);
+
+            // Register listener to the telephony manager that associated with specific sub.
+            mTeleManager.createForSubscriptionId(sub.first)
+                    .listen(listener, PhoneStateListener.LISTEN_SERVICE_STATE);
+            Log.d(NetworkStatsService.TAG, "RAT type listener registered for sub " + sub.first);
+        }
+
+        for (final RatTypeListener listener : new ArrayList<>(mRatListeners)) {
+            // If there is no subId and IMSI matched the listener, removes it.
+            if (CollectionUtils.find(filteredNewSubs,
+                    it -> listener.equalsKey(it.first, it.second)) == null) {
+                handleRemoveRatTypeListener(listener);
+            }
+        }
+    }
+
+    @NonNull
+    private List<Integer> getActiveSubIdList(@NonNull SubscriptionManager subscriptionManager) {
+        final ArrayList<Integer> ret = new ArrayList<>();
+        final int[] ids = subscriptionManager.getCompleteActiveSubscriptionIdList();
+        for (int id : ids) ret.add(id);
+        return ret;
+    }
+
+    /**
+     * Get a collapsed RatType for the given subscriberId.
+     *
+     * @param subscriberId the target subscriberId
+     * @return collapsed RatType for the given subscriberId
+     */
+    public int getRatTypeForSubscriberId(@NonNull String subscriberId) {
+        final RatTypeListener match = CollectionUtils.find(mRatListeners,
+                it -> TextUtils.equals(subscriberId, it.mSubscriberId));
+        return match != null ? match.mLastCollapsedRatType : TelephonyManager.NETWORK_TYPE_UNKNOWN;
+    }
+
+    /**
+     * Start monitoring events that triggered per subscription.
+     */
+    public void start() {
+        mSubscriptionManager.addOnSubscriptionsChangedListener(mExecutor, this);
+    }
+
+    /**
+     * Unregister subscription changes and all listeners for each subscription.
+     */
+    public void stop() {
+        mSubscriptionManager.removeOnSubscriptionsChangedListener(this);
+
+        for (final RatTypeListener listener : new ArrayList<>(mRatListeners)) {
+            handleRemoveRatTypeListener(listener);
+        }
+    }
+
+    private void handleRemoveRatTypeListener(@NonNull RatTypeListener listener) {
+        mTeleManager.createForSubscriptionId(listener.mSubId)
+                .listen(listener, PhoneStateListener.LISTEN_NONE);
+        Log.d(NetworkStatsService.TAG, "RAT type listener unregistered for sub " + listener.mSubId);
+        mRatListeners.remove(listener);
+
+        // Removal of subscriptions doesn't generate RAT changed event, fire it for every
+        // RatTypeListener.
+        mDelegate.onCollapsedRatTypeChanged(
+                listener.mSubscriberId, TelephonyManager.NETWORK_TYPE_UNKNOWN);
+    }
+
+    static class RatTypeListener extends PhoneStateListener {
+        // Unique id for the subscription. See {@link SubscriptionInfo#getSubscriptionId}.
+        @NonNull
+        private final int mSubId;
+
+        // IMSI to identifying the corresponding network from {@link NetworkState}.
+        // See {@link TelephonyManager#getSubscriberId}.
+        @NonNull
+        private final String mSubscriberId;
+
+        private volatile int mLastCollapsedRatType = TelephonyManager.NETWORK_TYPE_UNKNOWN;
+        @NonNull
+        private final NetworkStatsSubscriptionsMonitor mMonitor;
+
+        RatTypeListener(@NonNull Executor executor,
+                @NonNull NetworkStatsSubscriptionsMonitor monitor, int subId,
+                @NonNull String subscriberId) {
+            super(executor);
+            mSubId = subId;
+            mSubscriberId = subscriberId;
+            mMonitor = monitor;
+        }
+
+        @Override
+        public void onServiceStateChanged(@NonNull ServiceState ss) {
+            // In 5G SA (Stand Alone) mode, the primary cell itself will be 5G hence telephony
+            // would report RAT = 5G_NR.
+            // However, in 5G NSA (Non Stand Alone) mode, the primary cell is still LTE and
+            // network allocates a secondary 5G cell so telephony reports RAT = LTE along with
+            // NR state as connected. In such case, attributes the data usage to NR.
+            // See b/160727498.
+            final boolean is5GNsa = (ss.getDataNetworkType() == TelephonyManager.NETWORK_TYPE_LTE
+                    || ss.getDataNetworkType() == TelephonyManager.NETWORK_TYPE_LTE_CA)
+                    && ss.getNrState() == NetworkRegistrationInfo.NR_STATE_CONNECTED;
+
+            final int networkType =
+                    (is5GNsa ? NETWORK_TYPE_5G_NSA : ss.getDataNetworkType());
+            final int collapsedRatType = getCollapsedRatType(networkType);
+            if (collapsedRatType == mLastCollapsedRatType) return;
+
+            if (NetworkStatsService.LOGD) {
+                Log.d(NetworkStatsService.TAG, "subtype changed for sub(" + mSubId + "): "
+                        + mLastCollapsedRatType + " -> " + collapsedRatType);
+            }
+            mLastCollapsedRatType = collapsedRatType;
+            mMonitor.mDelegate.onCollapsedRatTypeChanged(mSubscriberId, mLastCollapsedRatType);
+        }
+
+        @VisibleForTesting
+        public int getSubId() {
+            return mSubId;
+        }
+
+        boolean equalsKey(int subId, @NonNull String subscriberId) {
+            return mSubId == subId && TextUtils.equals(mSubscriberId, subscriberId);
+        }
+    }
+}