/*
 * Copyright (C) 2007 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package android.net;

import android.annotation.SystemApi;
import android.app.DownloadManager;
import android.app.backup.BackupManager;
import android.app.usage.NetworkStatsManager;
import android.content.Context;
import android.media.MediaPlayer;
import android.os.RemoteException;
import android.os.ServiceManager;

import com.android.server.NetworkManagementSocketTagger;

import dalvik.system.SocketTagger;

import java.net.DatagramSocket;
import java.net.Socket;
import java.net.SocketException;

/**
 * Class that provides network traffic statistics. These statistics include
 * bytes transmitted and received and network packets transmitted and received,
 * over all interfaces, over the mobile interface, and on a per-UID basis.
 * <p>
 * These statistics may not be available on all platforms. If the statistics are
 * not supported by this device, {@link #UNSUPPORTED} will be returned.
 * <p>
 * Note that the statistics returned by this class reset and start from zero
 * after every reboot. To access more robust historical network statistics data,
 * use {@link NetworkStatsManager} instead.
 */
public class TrafficStats {
    /**
     * The return value to indicate that the device does not support the statistic.
     */
    public final static int UNSUPPORTED = -1;

    /** @hide */
    public static final long KB_IN_BYTES = 1024;
    /** @hide */
    public static final long MB_IN_BYTES = KB_IN_BYTES * 1024;
    /** @hide */
    public static final long GB_IN_BYTES = MB_IN_BYTES * 1024;
    /** @hide */
    public static final long TB_IN_BYTES = GB_IN_BYTES * 1024;
    /** @hide */
    public static final long PB_IN_BYTES = TB_IN_BYTES * 1024;

    /**
     * Special UID value used when collecting {@link NetworkStatsHistory} for
     * removed applications.
     *
     * @hide
     */
    public static final int UID_REMOVED = -4;

    /**
     * Special UID value used when collecting {@link NetworkStatsHistory} for
     * tethering traffic.
     *
     * @hide
     */
    public static final int UID_TETHERING = -5;

    /**
     * Default tag value for {@link DownloadManager} traffic.
     *
     * @hide
     */
    public static final int TAG_SYSTEM_DOWNLOAD = 0xFFFFFF01;

    /**
     * Default tag value for {@link MediaPlayer} traffic.
     *
     * @hide
     */
    public static final int TAG_SYSTEM_MEDIA = 0xFFFFFF02;

    /**
     * Default tag value for {@link BackupManager} backup traffic; that is,
     * traffic from the device to the storage backend.
     *
     * @hide
     */
    public static final int TAG_SYSTEM_BACKUP = 0xFFFFFF03;

    /**
     * Default tag value for {@link BackupManager} restore traffic; that is,
     * app data retrieved from the storage backend at install time.
     *
     * @hide
     */
    public static final int TAG_SYSTEM_RESTORE = 0xFFFFFF04;

    /** @hide */
    public static final int TAG_SYSTEM_DHCP = 0xFFFFFF05;
    /** @hide */
    public static final int TAG_SYSTEM_NTP = 0xFFFFFF06;
    /** @hide */
    public static final int TAG_SYSTEM_PROBE = 0xFFFFFF07;
    /** @hide */
    public static final int TAG_SYSTEM_NEIGHBOR = 0xFFFFFF08;
    /** @hide */
    public static final int TAG_SYSTEM_GPS = 0xFFFFFF09;
    /** @hide */
    public static final int TAG_SYSTEM_PAC = 0xFFFFFF0A;

    /**
     * Sockets that are strictly local on device; never hits network.
     *
     * @hide
     */
    public static final int TAG_SYSTEM_LOCAL = 0xFFFFFFAA;

    private static INetworkStatsService sStatsService;

    private synchronized static INetworkStatsService getStatsService() {
        if (sStatsService == null) {
            sStatsService = INetworkStatsService.Stub.asInterface(
                    ServiceManager.getService(Context.NETWORK_STATS_SERVICE));
        }
        return sStatsService;
    }

    /**
     * Snapshot of {@link NetworkStats} when the currently active profiling
     * session started, or {@code null} if no session active.
     *
     * @see #startDataProfiling(Context)
     * @see #stopDataProfiling(Context)
     */
    private static NetworkStats sActiveProfilingStart;

    private static Object sProfilingLock = new Object();

    /**
     * Set active tag to use when accounting {@link Socket} traffic originating
     * from the current thread. Only one active tag per thread is supported.
     * <p>
     * Changes only take effect during subsequent calls to
     * {@link #tagSocket(Socket)}.
     * <p>
     * Tags between {@code 0xFFFFFF00} and {@code 0xFFFFFFFF} are reserved and
     * used internally by system services like {@link DownloadManager} when
     * performing traffic on behalf of an application.
     *
     * @see #clearThreadStatsTag()
     */
    public static void setThreadStatsTag(int tag) {
        NetworkManagementSocketTagger.setThreadSocketStatsTag(tag);
    }

    /**
     * Set active tag to use when accounting {@link Socket} traffic originating
     * from the current thread. The tag used internally is well-defined to
     * distinguish all backup-related traffic.
     *
     * @hide
     */
    @SystemApi
    public static void setThreadStatsTagBackup() {
        setThreadStatsTag(TAG_SYSTEM_BACKUP);
    }

    /**
     * Set active tag to use when accounting {@link Socket} traffic originating
     * from the current thread. The tag used internally is well-defined to
     * distinguish all restore-related traffic.
     *
     * @hide
     */
    @SystemApi
    public static void setThreadStatsTagRestore() {
        setThreadStatsTag(TAG_SYSTEM_RESTORE);
    }

    /**
     * Get the active tag used when accounting {@link Socket} traffic originating
     * from the current thread. Only one active tag per thread is supported.
     * {@link #tagSocket(Socket)}.
     *
     * @see #setThreadStatsTag(int)
     */
    public static int getThreadStatsTag() {
        return NetworkManagementSocketTagger.getThreadSocketStatsTag();
    }

    /**
     * Clear any active tag set to account {@link Socket} traffic originating
     * from the current thread.
     *
     * @see #setThreadStatsTag(int)
     */
    public static void clearThreadStatsTag() {
        NetworkManagementSocketTagger.setThreadSocketStatsTag(-1);
    }

    /**
     * Set specific UID to use when accounting {@link Socket} traffic
     * originating from the current thread. Designed for use when performing an
     * operation on behalf of another application.
     * <p>
     * Changes only take effect during subsequent calls to
     * {@link #tagSocket(Socket)}.
     * <p>
     * To take effect, caller must hold
     * {@link android.Manifest.permission#UPDATE_DEVICE_STATS} permission.
     *
     * @hide
     */
    @SystemApi
    public static void setThreadStatsUid(int uid) {
        NetworkManagementSocketTagger.setThreadSocketStatsUid(uid);
    }

    /**
     * Clear any active UID set to account {@link Socket} traffic originating
     * from the current thread.
     *
     * @see #setThreadStatsUid(int)
     * @hide
     */
    @SystemApi
    public static void clearThreadStatsUid() {
        NetworkManagementSocketTagger.setThreadSocketStatsUid(-1);
    }

    /**
     * Tag the given {@link Socket} with any statistics parameters active for
     * the current thread. Subsequent calls always replace any existing
     * parameters. When finished, call {@link #untagSocket(Socket)} to remove
     * statistics parameters.
     *
     * @see #setThreadStatsTag(int)
     */
    public static void tagSocket(Socket socket) throws SocketException {
        SocketTagger.get().tag(socket);
    }

    /**
     * Remove any statistics parameters from the given {@link Socket}.
     */
    public static void untagSocket(Socket socket) throws SocketException {
        SocketTagger.get().untag(socket);
    }

    /**
     * Tag the given {@link DatagramSocket} with any statistics parameters
     * active for the current thread. Subsequent calls always replace any
     * existing parameters. When finished, call
     * {@link #untagDatagramSocket(DatagramSocket)} to remove statistics
     * parameters.
     *
     * @see #setThreadStatsTag(int)
     */
    public static void tagDatagramSocket(DatagramSocket socket) throws SocketException {
        SocketTagger.get().tag(socket);
    }

    /**
     * Remove any statistics parameters from the given {@link DatagramSocket}.
     */
    public static void untagDatagramSocket(DatagramSocket socket) throws SocketException {
        SocketTagger.get().untag(socket);
    }

    /**
     * Start profiling data usage for current UID. Only one profiling session
     * can be active at a time.
     *
     * @hide
     */
    public static void startDataProfiling(Context context) {
        synchronized (sProfilingLock) {
            if (sActiveProfilingStart != null) {
                throw new IllegalStateException("already profiling data");
            }

            // take snapshot in time; we calculate delta later
            sActiveProfilingStart = getDataLayerSnapshotForUid(context);
        }
    }

    /**
     * Stop profiling data usage for current UID.
     *
     * @return Detailed {@link NetworkStats} of data that occurred since last
     *         {@link #startDataProfiling(Context)} call.
     * @hide
     */
    public static NetworkStats stopDataProfiling(Context context) {
        synchronized (sProfilingLock) {
            if (sActiveProfilingStart == null) {
                throw new IllegalStateException("not profiling data");
            }

            // subtract starting values and return delta
            final NetworkStats profilingStop = getDataLayerSnapshotForUid(context);
            final NetworkStats profilingDelta = NetworkStats.subtract(
                    profilingStop, sActiveProfilingStart, null, null);
            sActiveProfilingStart = null;
            return profilingDelta;
        }
    }

    /**
     * Increment count of network operations performed under the accounting tag
     * currently active on the calling thread. This can be used to derive
     * bytes-per-operation.
     *
     * @param operationCount Number of operations to increment count by.
     */
    public static void incrementOperationCount(int operationCount) {
        final int tag = getThreadStatsTag();
        incrementOperationCount(tag, operationCount);
    }

    /**
     * Increment count of network operations performed under the given
     * accounting tag. This can be used to derive bytes-per-operation.
     *
     * @param tag Accounting tag used in {@link #setThreadStatsTag(int)}.
     * @param operationCount Number of operations to increment count by.
     */
    public static void incrementOperationCount(int tag, int operationCount) {
        final int uid = android.os.Process.myUid();
        try {
            getStatsService().incrementOperationCount(uid, tag, operationCount);
        } catch (RemoteException e) {
            throw e.rethrowFromSystemServer();
        }
    }

    /** {@hide} */
    public static void closeQuietly(INetworkStatsSession session) {
        // TODO: move to NetworkStatsService once it exists
        if (session != null) {
            try {
                session.close();
            } catch (RuntimeException rethrown) {
                throw rethrown;
            } catch (Exception ignored) {
            }
        }
    }

    /**
     * Return number of packets transmitted across mobile networks since device
     * boot. Counts packets across all mobile network interfaces, and always
     * increases monotonically since device boot. Statistics are measured at the
     * network layer, so they include both TCP and UDP usage.
     * <p>
     * Before {@link android.os.Build.VERSION_CODES#JELLY_BEAN_MR2}, this may
     * return {@link #UNSUPPORTED} on devices where statistics aren't available.
     */
    public static long getMobileTxPackets() {
        long total = 0;
        for (String iface : getMobileIfaces()) {
            total += getTxPackets(iface);
        }
        return total;
    }

    /**
     * Return number of packets received across mobile networks since device
     * boot. Counts packets across all mobile network interfaces, and always
     * increases monotonically since device boot. Statistics are measured at the
     * network layer, so they include both TCP and UDP usage.
     * <p>
     * Before {@link android.os.Build.VERSION_CODES#JELLY_BEAN_MR2}, this may
     * return {@link #UNSUPPORTED} on devices where statistics aren't available.
     */
    public static long getMobileRxPackets() {
        long total = 0;
        for (String iface : getMobileIfaces()) {
            total += getRxPackets(iface);
        }
        return total;
    }

    /**
     * Return number of bytes transmitted across mobile networks since device
     * boot. Counts packets across all mobile network interfaces, and always
     * increases monotonically since device boot. Statistics are measured at the
     * network layer, so they include both TCP and UDP usage.
     * <p>
     * Before {@link android.os.Build.VERSION_CODES#JELLY_BEAN_MR2}, this may
     * return {@link #UNSUPPORTED} on devices where statistics aren't available.
     */
    public static long getMobileTxBytes() {
        long total = 0;
        for (String iface : getMobileIfaces()) {
            total += getTxBytes(iface);
        }
        return total;
    }

    /**
     * Return number of bytes received across mobile networks since device boot.
     * Counts packets across all mobile network interfaces, and always increases
     * monotonically since device boot. Statistics are measured at the network
     * layer, so they include both TCP and UDP usage.
     * <p>
     * Before {@link android.os.Build.VERSION_CODES#JELLY_BEAN_MR2}, this may
     * return {@link #UNSUPPORTED} on devices where statistics aren't available.
     */
    public static long getMobileRxBytes() {
        long total = 0;
        for (String iface : getMobileIfaces()) {
            total += getRxBytes(iface);
        }
        return total;
    }

    /** {@hide} */
    public static long getMobileTcpRxPackets() {
        long total = 0;
        for (String iface : getMobileIfaces()) {
            final long stat = nativeGetIfaceStat(iface, TYPE_TCP_RX_PACKETS);
            if (stat != UNSUPPORTED) {
                total += stat;
            }
        }
        return total;
    }

    /** {@hide} */
    public static long getMobileTcpTxPackets() {
        long total = 0;
        for (String iface : getMobileIfaces()) {
            final long stat = nativeGetIfaceStat(iface, TYPE_TCP_TX_PACKETS);
            if (stat != UNSUPPORTED) {
                total += stat;
            }
        }
        return total;
    }

    /** {@hide} */
    public static long getTxPackets(String iface) {
        return nativeGetIfaceStat(iface, TYPE_TX_PACKETS);
    }

    /** {@hide} */
    public static long getRxPackets(String iface) {
        return nativeGetIfaceStat(iface, TYPE_RX_PACKETS);
    }

    /** {@hide} */
    public static long getTxBytes(String iface) {
        return nativeGetIfaceStat(iface, TYPE_TX_BYTES);
    }

    /** {@hide} */
    public static long getRxBytes(String iface) {
        return nativeGetIfaceStat(iface, TYPE_RX_BYTES);
    }

    /**
     * Return number of packets transmitted since device boot. Counts packets
     * across all network interfaces, and always increases monotonically since
     * device boot. Statistics are measured at the network layer, so they
     * include both TCP and UDP usage.
     * <p>
     * Before {@link android.os.Build.VERSION_CODES#JELLY_BEAN_MR2}, this may
     * return {@link #UNSUPPORTED} on devices where statistics aren't available.
     */
    public static long getTotalTxPackets() {
        return nativeGetTotalStat(TYPE_TX_PACKETS);
    }

    /**
     * Return number of packets received since device boot. Counts packets
     * across all network interfaces, and always increases monotonically since
     * device boot. Statistics are measured at the network layer, so they
     * include both TCP and UDP usage.
     * <p>
     * Before {@link android.os.Build.VERSION_CODES#JELLY_BEAN_MR2}, this may
     * return {@link #UNSUPPORTED} on devices where statistics aren't available.
     */
    public static long getTotalRxPackets() {
        return nativeGetTotalStat(TYPE_RX_PACKETS);
    }

    /**
     * Return number of bytes transmitted since device boot. Counts packets
     * across all network interfaces, and always increases monotonically since
     * device boot. Statistics are measured at the network layer, so they
     * include both TCP and UDP usage.
     * <p>
     * Before {@link android.os.Build.VERSION_CODES#JELLY_BEAN_MR2}, this may
     * return {@link #UNSUPPORTED} on devices where statistics aren't available.
     */
    public static long getTotalTxBytes() {
        return nativeGetTotalStat(TYPE_TX_BYTES);
    }

    /**
     * Return number of bytes received since device boot. Counts packets across
     * all network interfaces, and always increases monotonically since device
     * boot. Statistics are measured at the network layer, so they include both
     * TCP and UDP usage.
     * <p>
     * Before {@link android.os.Build.VERSION_CODES#JELLY_BEAN_MR2}, this may
     * return {@link #UNSUPPORTED} on devices where statistics aren't available.
     */
    public static long getTotalRxBytes() {
        return nativeGetTotalStat(TYPE_RX_BYTES);
    }

    /**
     * Return number of bytes transmitted by the given UID since device boot.
     * Counts packets across all network interfaces, and always increases
     * monotonically since device boot. Statistics are measured at the network
     * layer, so they include both TCP and UDP usage.
     * <p>
     * Before {@link android.os.Build.VERSION_CODES#JELLY_BEAN_MR2}, this may
     * return {@link #UNSUPPORTED} on devices where statistics aren't available.
     * <p>
     * Starting in {@link android.os.Build.VERSION_CODES#N} this will only
     * report traffic statistics for the calling UID. It will return
     * {@link #UNSUPPORTED} for all other UIDs for privacy reasons. To access
     * historical network statistics belonging to other UIDs, use
     * {@link NetworkStatsManager}.
     *
     * @see android.os.Process#myUid()
     * @see android.content.pm.ApplicationInfo#uid
     */
    public static long getUidTxBytes(int uid) {
        // This isn't actually enforcing any security; it just returns the
        // unsupported value. The real filtering is done at the kernel level.
        final int callingUid = android.os.Process.myUid();
        if (callingUid == android.os.Process.SYSTEM_UID || callingUid == uid) {
            return nativeGetUidStat(uid, TYPE_TX_BYTES);
        } else {
            return UNSUPPORTED;
        }
    }

    /**
     * Return number of bytes received by the given UID since device boot.
     * Counts packets across all network interfaces, and always increases
     * monotonically since device boot. Statistics are measured at the network
     * layer, so they include both TCP and UDP usage.
     * <p>
     * Before {@link android.os.Build.VERSION_CODES#JELLY_BEAN_MR2}, this may return
     * {@link #UNSUPPORTED} on devices where statistics aren't available.
     * <p>
     * Starting in {@link android.os.Build.VERSION_CODES#N} this will only
     * report traffic statistics for the calling UID. It will return
     * {@link #UNSUPPORTED} for all other UIDs for privacy reasons. To access
     * historical network statistics belonging to other UIDs, use
     * {@link NetworkStatsManager}.
     *
     * @see android.os.Process#myUid()
     * @see android.content.pm.ApplicationInfo#uid
     */
    public static long getUidRxBytes(int uid) {
        // This isn't actually enforcing any security; it just returns the
        // unsupported value. The real filtering is done at the kernel level.
        final int callingUid = android.os.Process.myUid();
        if (callingUid == android.os.Process.SYSTEM_UID || callingUid == uid) {
            return nativeGetUidStat(uid, TYPE_RX_BYTES);
        } else {
            return UNSUPPORTED;
        }
    }

    /**
     * Return number of packets transmitted by the given UID since device boot.
     * Counts packets across all network interfaces, and always increases
     * monotonically since device boot. Statistics are measured at the network
     * layer, so they include both TCP and UDP usage.
     * <p>
     * Before {@link android.os.Build.VERSION_CODES#JELLY_BEAN_MR2}, this may return
     * {@link #UNSUPPORTED} on devices where statistics aren't available.
     * <p>
     * Starting in {@link android.os.Build.VERSION_CODES#N} this will only
     * report traffic statistics for the calling UID. It will return
     * {@link #UNSUPPORTED} for all other UIDs for privacy reasons. To access
     * historical network statistics belonging to other UIDs, use
     * {@link NetworkStatsManager}.
     *
     * @see android.os.Process#myUid()
     * @see android.content.pm.ApplicationInfo#uid
     */
    public static long getUidTxPackets(int uid) {
        // This isn't actually enforcing any security; it just returns the
        // unsupported value. The real filtering is done at the kernel level.
        final int callingUid = android.os.Process.myUid();
        if (callingUid == android.os.Process.SYSTEM_UID || callingUid == uid) {
            return nativeGetUidStat(uid, TYPE_TX_PACKETS);
        } else {
            return UNSUPPORTED;
        }
    }

    /**
     * Return number of packets received by the given UID since device boot.
     * Counts packets across all network interfaces, and always increases
     * monotonically since device boot. Statistics are measured at the network
     * layer, so they include both TCP and UDP usage.
     * <p>
     * Before {@link android.os.Build.VERSION_CODES#JELLY_BEAN_MR2}, this may return
     * {@link #UNSUPPORTED} on devices where statistics aren't available.
     * <p>
     * Starting in {@link android.os.Build.VERSION_CODES#N} this will only
     * report traffic statistics for the calling UID. It will return
     * {@link #UNSUPPORTED} for all other UIDs for privacy reasons. To access
     * historical network statistics belonging to other UIDs, use
     * {@link NetworkStatsManager}.
     *
     * @see android.os.Process#myUid()
     * @see android.content.pm.ApplicationInfo#uid
     */
    public static long getUidRxPackets(int uid) {
        // This isn't actually enforcing any security; it just returns the
        // unsupported value. The real filtering is done at the kernel level.
        final int callingUid = android.os.Process.myUid();
        if (callingUid == android.os.Process.SYSTEM_UID || callingUid == uid) {
            return nativeGetUidStat(uid, TYPE_RX_PACKETS);
        } else {
            return UNSUPPORTED;
        }
    }

    /**
     * @deprecated Starting in {@link android.os.Build.VERSION_CODES#JELLY_BEAN_MR2},
     *             transport layer statistics are no longer available, and will
     *             always return {@link #UNSUPPORTED}.
     * @see #getUidTxBytes(int)
     */
    @Deprecated
    public static long getUidTcpTxBytes(int uid) {
        return UNSUPPORTED;
    }

    /**
     * @deprecated Starting in {@link android.os.Build.VERSION_CODES#JELLY_BEAN_MR2},
     *             transport layer statistics are no longer available, and will
     *             always return {@link #UNSUPPORTED}.
     * @see #getUidRxBytes(int)
     */
    @Deprecated
    public static long getUidTcpRxBytes(int uid) {
        return UNSUPPORTED;
    }

    /**
     * @deprecated Starting in {@link android.os.Build.VERSION_CODES#JELLY_BEAN_MR2},
     *             transport layer statistics are no longer available, and will
     *             always return {@link #UNSUPPORTED}.
     * @see #getUidTxBytes(int)
     */
    @Deprecated
    public static long getUidUdpTxBytes(int uid) {
        return UNSUPPORTED;
    }

    /**
     * @deprecated Starting in {@link android.os.Build.VERSION_CODES#JELLY_BEAN_MR2},
     *             transport layer statistics are no longer available, and will
     *             always return {@link #UNSUPPORTED}.
     * @see #getUidRxBytes(int)
     */
    @Deprecated
    public static long getUidUdpRxBytes(int uid) {
        return UNSUPPORTED;
    }

    /**
     * @deprecated Starting in {@link android.os.Build.VERSION_CODES#JELLY_BEAN_MR2},
     *             transport layer statistics are no longer available, and will
     *             always return {@link #UNSUPPORTED}.
     * @see #getUidTxPackets(int)
     */
    @Deprecated
    public static long getUidTcpTxSegments(int uid) {
        return UNSUPPORTED;
    }

    /**
     * @deprecated Starting in {@link android.os.Build.VERSION_CODES#JELLY_BEAN_MR2},
     *             transport layer statistics are no longer available, and will
     *             always return {@link #UNSUPPORTED}.
     * @see #getUidRxPackets(int)
     */
    @Deprecated
    public static long getUidTcpRxSegments(int uid) {
        return UNSUPPORTED;
    }

    /**
     * @deprecated Starting in {@link android.os.Build.VERSION_CODES#JELLY_BEAN_MR2},
     *             transport layer statistics are no longer available, and will
     *             always return {@link #UNSUPPORTED}.
     * @see #getUidTxPackets(int)
     */
    @Deprecated
    public static long getUidUdpTxPackets(int uid) {
        return UNSUPPORTED;
    }

    /**
     * @deprecated Starting in {@link android.os.Build.VERSION_CODES#JELLY_BEAN_MR2},
     *             transport layer statistics are no longer available, and will
     *             always return {@link #UNSUPPORTED}.
     * @see #getUidRxPackets(int)
     */
    @Deprecated
    public static long getUidUdpRxPackets(int uid) {
        return UNSUPPORTED;
    }

    /**
     * Return detailed {@link NetworkStats} for the current UID. Requires no
     * special permission.
     */
    private static NetworkStats getDataLayerSnapshotForUid(Context context) {
        // TODO: take snapshot locally, since proc file is now visible
        final int uid = android.os.Process.myUid();
        try {
            return getStatsService().getDataLayerSnapshotForUid(uid);
        } catch (RemoteException e) {
            throw e.rethrowFromSystemServer();
        }
    }

    /**
     * Return set of any ifaces associated with mobile networks since boot.
     * Interfaces are never removed from this list, so counters should always be
     * monotonic.
     */
    private static String[] getMobileIfaces() {
        try {
            return getStatsService().getMobileIfaces();
        } catch (RemoteException e) {
            throw e.rethrowFromSystemServer();
        }
    }

    // NOTE: keep these in sync with android_net_TrafficStats.cpp
    private static final int TYPE_RX_BYTES = 0;
    private static final int TYPE_RX_PACKETS = 1;
    private static final int TYPE_TX_BYTES = 2;
    private static final int TYPE_TX_PACKETS = 3;
    private static final int TYPE_TCP_RX_PACKETS = 4;
    private static final int TYPE_TCP_TX_PACKETS = 5;

    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);
}