Merge changes from topic "vpn_data_accounting" into qt-dev (b33d2ca2) · Commits · e / os / android_frameworks_base

core/java/android/net/NetworkStats.java

+232 −125

Original line number	Diff line number	Diff line
		@@ -18,6 +18,7 @@ package android.net;

		import static android.os.Process.CLAT_UID;

		import android.annotation.NonNull;
		import android.annotation.UnsupportedAppUsage;
		import android.os.Parcel;
		import android.os.Parcelable;
		@@ -33,6 +34,7 @@ import libcore.util.EmptyArray;
		import java.io.CharArrayWriter;
		import java.io.PrintWriter;
		import java.util.Arrays;
		import java.util.function.Predicate;
		import java.util.HashSet;
		import java.util.Map;
		import java.util.Objects;
		@@ -993,23 +995,33 @@ public class NetworkStats implements Parcelable {
		if (limitUid == UID_ALL && limitTag == TAG_ALL && limitIfaces == INTERFACES_ALL) {
		return;
		}
		filter(e -> (limitUid == UID_ALL \|\| limitUid == e.uid)
		&& (limitTag == TAG_ALL \|\| limitTag == e.tag)
		&& (limitIfaces == INTERFACES_ALL
		\|\| ArrayUtils.contains(limitIfaces, e.iface)));
		}

		/**
		* Only keep entries with {@link #set} value less than {@link #SET_DEBUG_START}.
		*
		* <p>This mutates the original structure in place.
		*/
		public void filterDebugEntries() {
		filter(e -> e.set < SET_DEBUG_START);
		}

		private void filter(Predicate<Entry> predicate) {
		Entry entry = new Entry();
		int nextOutputEntry = 0;
		for (int i = 0; i < size; i++) {
		entry = getValues(i, entry);
		final boolean matches =
		(limitUid == UID_ALL \|\| limitUid == entry.uid)
		&& (limitTag == TAG_ALL \|\| limitTag == entry.tag)
		&& (limitIfaces == INTERFACES_ALL
		\|\| ArrayUtils.contains(limitIfaces, entry.iface));

		if (matches) {
		if (predicate.test(entry)) {
		if (nextOutputEntry != i) {
		setValues(nextOutputEntry, entry);
		}
		nextOutputEntry++;
		}
		}

		size = nextOutputEntry;
		}

		@@ -1175,133 +1187,221 @@ public class NetworkStats implements Parcelable {
		/**
		* VPN accounting. Move some VPN's underlying traffic to other UIDs that use tun0 iface.
		*
		* This method should only be called on delta NetworkStats. Do not call this method on a
		* snapshot {@link NetworkStats} object because the tunUid and/or the underlyingIface may
		* change over time.
		*
		* This method performs adjustments for one active VPN package and one VPN iface at a time.
		* <p>This method should only be called on delta NetworkStats. Do not call this method on a
		* snapshot {@link NetworkStats} object because the tunUid and/or the underlyingIface may change
		* over time.
		*
		* It is possible for the VPN software to use multiple underlying networks. This method
		* only migrates traffic for the primary underlying network.
		* <p>This method performs adjustments for one active VPN package and one VPN iface at a time.
		*
		* @param tunUid uid of the VPN application
		* @param tunIface iface of the vpn tunnel
		* @param underlyingIface the primary underlying network iface used by the VPN application
		* @return true if it successfully adjusts the accounting for VPN, false otherwise
		* @param underlyingIfaces underlying network ifaces used by the VPN application
		*/
		public boolean migrateTun(int tunUid, String tunIface, String underlyingIface) {
		Entry tunIfaceTotal = new Entry();
		Entry underlyingIfaceTotal = new Entry();
		public void migrateTun(int tunUid, @NonNull String tunIface,
		@NonNull String[] underlyingIfaces) {
		// Combined usage by all apps using VPN.
		final Entry tunIfaceTotal = new Entry();
		// Usage by VPN, grouped by its {@code underlyingIfaces}.
		final Entry[] perInterfaceTotal = new Entry[underlyingIfaces.length];
		// Usage by VPN, summed across all its {@code underlyingIfaces}.
		final Entry underlyingIfacesTotal = new Entry();

		tunAdjustmentInit(tunUid, tunIface, underlyingIface, tunIfaceTotal, underlyingIfaceTotal);

		// If tunIface < underlyingIface, it leaves the overhead traffic in the VPN app.
		// If tunIface > underlyingIface, the VPN app doesn't get credit for data compression.
		// Negative stats should be avoided.
		Entry pool = tunGetPool(tunIfaceTotal, underlyingIfaceTotal);
		if (pool.isEmpty()) {
		return true;
		for (int i = 0; i < perInterfaceTotal.length; i++) {
		perInterfaceTotal[i] = new Entry();
		}
		Entry moved =
		addTrafficToApplications(tunUid, tunIface, underlyingIface, tunIfaceTotal, pool);
		deductTrafficFromVpnApp(tunUid, underlyingIface, moved);

		if (!moved.isEmpty()) {
		Slog.wtf(TAG, "Failed to deduct underlying network traffic from VPN package. Moved="
		+ moved);
		return false;
		}
		return true;
		tunAdjustmentInit(tunUid, tunIface, underlyingIfaces, tunIfaceTotal, perInterfaceTotal,
		underlyingIfacesTotal);

		// If tunIface < underlyingIfacesTotal, it leaves the overhead traffic in the VPN app.
		// If tunIface > underlyingIfacesTotal, the VPN app doesn't get credit for data compression.
		// Negative stats should be avoided.
		final Entry[] moved =
		addTrafficToApplications(tunUid, tunIface, underlyingIfaces, tunIfaceTotal,
		perInterfaceTotal, underlyingIfacesTotal);
		deductTrafficFromVpnApp(tunUid, underlyingIfaces, moved);
		}

		/**
		* Initializes the data used by the migrateTun() method.
		*
		* This is the first pass iteration which does the following work:
		* (1) Adds up all the traffic through the tunUid's underlyingIface
		* (both foreground and background).
		* (2) Adds up all the traffic through tun0 excluding traffic from the vpn app itself.
		* <p>This is the first pass iteration which does the following work:
		*
		* <ul>
		* <li>Adds up all the traffic through the tunUid's underlyingIfaces (both foreground and
		* background).
		* <li>Adds up all the traffic through tun0 excluding traffic from the vpn app itself.
		* </ul>
		*
		* @param tunUid uid of the VPN application
		* @param tunIface iface of the vpn tunnel
		* @param underlyingIfaces underlying network ifaces used by the VPN application
		* @param tunIfaceTotal output parameter; combined data usage by all apps using VPN
		* @param perInterfaceTotal output parameter; data usage by VPN app, grouped by its {@code
		* underlyingIfaces}
		* @param underlyingIfacesTotal output parameter; data usage by VPN, summed across all of its
		* {@code underlyingIfaces}
		*/
		private void tunAdjustmentInit(int tunUid, String tunIface, String underlyingIface,
		Entry tunIfaceTotal, Entry underlyingIfaceTotal) {
		Entry recycle = new Entry();
		private void tunAdjustmentInit(int tunUid, @NonNull String tunIface,
		@NonNull String[] underlyingIfaces, @NonNull Entry tunIfaceTotal,
		@NonNull Entry[] perInterfaceTotal, @NonNull Entry underlyingIfacesTotal) {
		final Entry recycle = new Entry();
		for (int i = 0; i < size; i++) {
		getValues(i, recycle);
		if (recycle.uid == UID_ALL) {
		throw new IllegalStateException(
		"Cannot adjust VPN accounting on an iface aggregated NetworkStats.");
		} if (recycle.set == SET_DBG_VPN_IN \|\| recycle.set == SET_DBG_VPN_OUT) {
		}
		if (recycle.set == SET_DBG_VPN_IN \|\| recycle.set == SET_DBG_VPN_OUT) {
		throw new IllegalStateException(
		"Cannot adjust VPN accounting on a NetworkStats containing SET_DBG_VPN_*");
		}

		if (recycle.uid == tunUid && recycle.tag == TAG_NONE
		&& Objects.equals(underlyingIface, recycle.iface)) {
		underlyingIfaceTotal.add(recycle);
		if (recycle.tag != TAG_NONE) {
		// TODO(b/123666283): Take all tags for tunUid into account.
		continue;
		}

		if (recycle.uid != tunUid && recycle.tag == TAG_NONE
		&& Objects.equals(tunIface, recycle.iface)) {
		if (recycle.uid == tunUid) {
		// Add up traffic through tunUid's underlying interfaces.
		for (int j = 0; j < underlyingIfaces.length; j++) {
		if (Objects.equals(underlyingIfaces[j], recycle.iface)) {
		perInterfaceTotal[j].add(recycle);
		underlyingIfacesTotal.add(recycle);
		break;
		}
		}
		} else if (tunIface.equals(recycle.iface)) {
		// Add up all tunIface traffic excluding traffic from the vpn app itself.
		tunIfaceTotal.add(recycle);
		}
		}
		}

		private static Entry tunGetPool(Entry tunIfaceTotal, Entry underlyingIfaceTotal) {
		Entry pool = new Entry();
		pool.rxBytes = Math.min(tunIfaceTotal.rxBytes, underlyingIfaceTotal.rxBytes);
		pool.rxPackets = Math.min(tunIfaceTotal.rxPackets, underlyingIfaceTotal.rxPackets);
		pool.txBytes = Math.min(tunIfaceTotal.txBytes, underlyingIfaceTotal.txBytes);
		pool.txPackets = Math.min(tunIfaceTotal.txPackets, underlyingIfaceTotal.txPackets);
		pool.operations = Math.min(tunIfaceTotal.operations, underlyingIfaceTotal.operations);
		return pool;
		/**
		* Distributes traffic across apps that are using given {@code tunIface}, and returns the total
		* traffic that should be moved off of {@code tunUid} grouped by {@code underlyingIfaces}.
		*
		* @param tunUid uid of the VPN application
		* @param tunIface iface of the vpn tunnel
		* @param underlyingIfaces underlying network ifaces used by the VPN application
		* @param tunIfaceTotal combined data usage across all apps using {@code tunIface}
		* @param perInterfaceTotal data usage by VPN app, grouped by its {@code underlyingIfaces}
		* @param underlyingIfacesTotal data usage by VPN, summed across all of its {@code
		* underlyingIfaces}
		*/
		private Entry[] addTrafficToApplications(int tunUid, @NonNull String tunIface,
		@NonNull String[] underlyingIfaces, @NonNull Entry tunIfaceTotal,
		@NonNull Entry[] perInterfaceTotal, @NonNull Entry underlyingIfacesTotal) {
		// Traffic that should be moved off of each underlying interface for tunUid (see
		// deductTrafficFromVpnApp below).
		final Entry[] moved = new Entry[underlyingIfaces.length];
		for (int i = 0; i < underlyingIfaces.length; i++) {
		moved[i] = new Entry();
		}

		final Entry tmpEntry = new Entry();
		final int origSize = size;
		for (int i = 0; i < origSize; i++) {
		if (!Objects.equals(iface[i], tunIface)) {
		// Consider only entries that go onto the VPN interface.
		continue;
		}
		if (uid[i] == tunUid) {
		// Exclude VPN app from the redistribution, as it can choose to create packet
		// streams by writing to itself.
		continue;
		}
		tmpEntry.uid = uid[i];
		tmpEntry.tag = tag[i];
		tmpEntry.metered = metered[i];
		tmpEntry.roaming = roaming[i];
		tmpEntry.defaultNetwork = defaultNetwork[i];

		private Entry addTrafficToApplications(int tunUid, String tunIface, String underlyingIface,
		Entry tunIfaceTotal, Entry pool) {
		Entry moved = new Entry();
		Entry tmpEntry = new Entry();
		tmpEntry.iface = underlyingIface;
		for (int i = 0; i < size; i++) {
		// the vpn app is excluded from the redistribution but all moved traffic will be
		// deducted from the vpn app (see deductTrafficFromVpnApp below).
		if (Objects.equals(iface[i], tunIface) && uid[i] != tunUid) {
		// In a first pass, compute this entry's total share of data across all
		// underlyingIfaces. This is computed on the basis of the share of this entry's usage
		// over tunIface.
		// TODO: Consider refactoring first pass into a separate helper method.
		long totalRxBytes = 0;
		if (tunIfaceTotal.rxBytes > 0) {
		tmpEntry.rxBytes = pool.rxBytes * rxBytes[i] / tunIfaceTotal.rxBytes;
		} else {
		// Note - The multiplication below should not overflow since NetworkStatsService
		// processes this every time device has transmitted/received amount equivalent to
		// global threshold alert (~ 2MB) across all interfaces.
		final long rxBytesAcrossUnderlyingIfaces =
		underlyingIfacesTotal.rxBytes * rxBytes[i] / tunIfaceTotal.rxBytes;
		// app must not be blamed for more than it consumed on tunIface
		totalRxBytes = Math.min(rxBytes[i], rxBytesAcrossUnderlyingIfaces);
		}
		long totalRxPackets = 0;
		if (tunIfaceTotal.rxPackets > 0) {
		final long rxPacketsAcrossUnderlyingIfaces =
		underlyingIfacesTotal.rxPackets * rxPackets[i] / tunIfaceTotal.rxPackets;
		totalRxPackets = Math.min(rxPackets[i], rxPacketsAcrossUnderlyingIfaces);
		}
		long totalTxBytes = 0;
		if (tunIfaceTotal.txBytes > 0) {
		final long txBytesAcrossUnderlyingIfaces =
		underlyingIfacesTotal.txBytes * txBytes[i] / tunIfaceTotal.txBytes;
		totalTxBytes = Math.min(txBytes[i], txBytesAcrossUnderlyingIfaces);
		}
		long totalTxPackets = 0;
		if (tunIfaceTotal.txPackets > 0) {
		final long txPacketsAcrossUnderlyingIfaces =
		underlyingIfacesTotal.txPackets * txPackets[i] / tunIfaceTotal.txPackets;
		totalTxPackets = Math.min(txPackets[i], txPacketsAcrossUnderlyingIfaces);
		}
		long totalOperations = 0;
		if (tunIfaceTotal.operations > 0) {
		final long operationsAcrossUnderlyingIfaces =
		underlyingIfacesTotal.operations * operations[i] / tunIfaceTotal.operations;
		totalOperations = Math.min(operations[i], operationsAcrossUnderlyingIfaces);
		}
		// In a second pass, distribute these values across interfaces in the proportion that
		// each interface represents of the total traffic of the underlying interfaces.
		for (int j = 0; j < underlyingIfaces.length; j++) {
		tmpEntry.iface = underlyingIfaces[j];
		tmpEntry.rxBytes = 0;
		// Reset 'set' to correct value since it gets updated when adding debug info below.
		tmpEntry.set = set[i];
		if (underlyingIfacesTotal.rxBytes > 0) {
		tmpEntry.rxBytes =
		totalRxBytes
		* perInterfaceTotal[j].rxBytes
		/ underlyingIfacesTotal.rxBytes;
		}
		if (tunIfaceTotal.rxPackets > 0) {
		tmpEntry.rxPackets = pool.rxPackets * rxPackets[i] / tunIfaceTotal.rxPackets;
		} else {
		tmpEntry.rxPackets = 0;
		if (underlyingIfacesTotal.rxPackets > 0) {
		tmpEntry.rxPackets =
		totalRxPackets
		* perInterfaceTotal[j].rxPackets
		/ underlyingIfacesTotal.rxPackets;
		}
		if (tunIfaceTotal.txBytes > 0) {
		tmpEntry.txBytes = pool.txBytes * txBytes[i] / tunIfaceTotal.txBytes;
		} else {
		tmpEntry.txBytes = 0;
		if (underlyingIfacesTotal.txBytes > 0) {
		tmpEntry.txBytes =
		totalTxBytes
		* perInterfaceTotal[j].txBytes
		/ underlyingIfacesTotal.txBytes;
		}
		if (tunIfaceTotal.txPackets > 0) {
		tmpEntry.txPackets = pool.txPackets * txPackets[i] / tunIfaceTotal.txPackets;
		} else {
		tmpEntry.txPackets = 0;
		if (underlyingIfacesTotal.txPackets > 0) {
		tmpEntry.txPackets =
		totalTxPackets
		* perInterfaceTotal[j].txPackets
		/ underlyingIfacesTotal.txPackets;
		}
		if (tunIfaceTotal.operations > 0) {
		tmpEntry.operations =
		pool.operations * operations[i] / tunIfaceTotal.operations;
		} else {
		tmpEntry.operations = 0;
		if (underlyingIfacesTotal.operations > 0) {
		tmpEntry.operations =
		totalOperations
		* perInterfaceTotal[j].operations
		/ underlyingIfacesTotal.operations;
		}
		tmpEntry.uid = uid[i];
		tmpEntry.tag = tag[i];
		tmpEntry.set = set[i];
		tmpEntry.metered = metered[i];
		tmpEntry.roaming = roaming[i];
		tmpEntry.defaultNetwork = defaultNetwork[i];
		// tmpEntry now contains the migrated data of the i-th entry for the j-th underlying
		// interface. Add that data usage to this object.
		combineValues(tmpEntry);
		if (tag[i] == TAG_NONE) {
		moved.add(tmpEntry);
		// Add the migrated data to moved so it is deducted from the VPN app later.
		moved[j].add(tmpEntry);
		// Add debug info
		tmpEntry.set = SET_DBG_VPN_IN;
		combineValues(tmpEntry);
		@@ -1311,38 +1411,45 @@ public class NetworkStats implements Parcelable {
		return moved;
		}

		private void deductTrafficFromVpnApp(int tunUid, String underlyingIface, Entry moved) {
		private void deductTrafficFromVpnApp(
		int tunUid,
		@NonNull String[] underlyingIfaces,
		@NonNull Entry[] moved) {
		for (int i = 0; i < underlyingIfaces.length; i++) {
		moved[i].uid = tunUid;
		// Add debug info
		moved.uid = tunUid;
		moved.set = SET_DBG_VPN_OUT;
		moved.tag = TAG_NONE;
		moved.iface = underlyingIface;
		moved.metered = METERED_ALL;
		moved.roaming = ROAMING_ALL;
		moved.defaultNetwork = DEFAULT_NETWORK_ALL;
		combineValues(moved);
		moved[i].set = SET_DBG_VPN_OUT;
		moved[i].tag = TAG_NONE;
		moved[i].iface = underlyingIfaces[i];
		moved[i].metered = METERED_ALL;
		moved[i].roaming = ROAMING_ALL;
		moved[i].defaultNetwork = DEFAULT_NETWORK_ALL;
		combineValues(moved[i]);

		// Caveat: if the vpn software uses tag, the total tagged traffic may be greater than
		// the TAG_NONE traffic.
		//
		// Relies on the fact that the underlying traffic only has state ROAMING_NO and METERED_NO,
		// which should be the case as it comes directly from the /proc file. We only blend in the
		// roaming data after applying these adjustments, by checking the NetworkIdentity of the
		// underlying iface.
		int idxVpnBackground = findIndex(underlyingIface, tunUid, SET_DEFAULT, TAG_NONE,
		METERED_NO, ROAMING_NO, DEFAULT_NETWORK_NO);
		// Relies on the fact that the underlying traffic only has state ROAMING_NO and
		// METERED_NO, which should be the case as it comes directly from the /proc file.
		// We only blend in the roaming data after applying these adjustments, by checking the
		// NetworkIdentity of the underlying iface.
		final int idxVpnBackground = findIndex(underlyingIfaces[i], tunUid, SET_DEFAULT,
		TAG_NONE, METERED_NO, ROAMING_NO, DEFAULT_NETWORK_NO);
		if (idxVpnBackground != -1) {
		tunSubtract(idxVpnBackground, this, moved);
		// Note - tunSubtract also updates moved[i]; whatever traffic that's left is removed
		// from foreground usage.
		tunSubtract(idxVpnBackground, this, moved[i]);
		}

		int idxVpnForeground = findIndex(underlyingIface, tunUid, SET_FOREGROUND, TAG_NONE,
		METERED_NO, ROAMING_NO, DEFAULT_NETWORK_NO);
		final int idxVpnForeground = findIndex(underlyingIfaces[i], tunUid, SET_FOREGROUND,
		TAG_NONE, METERED_NO, ROAMING_NO, DEFAULT_NETWORK_NO);
		if (idxVpnForeground != -1) {
		tunSubtract(idxVpnForeground, this, moved);
		tunSubtract(idxVpnForeground, this, moved[i]);
		}
		}
		}

		private static void tunSubtract(int i, NetworkStats left, Entry right) {
		private static void tunSubtract(int i, @NonNull NetworkStats left, @NonNull Entry right) {
		long rxBytes = Math.min(left.rxBytes[i], right.rxBytes);
		left.rxBytes[i] -= rxBytes;
		right.rxBytes -= rxBytes;

core/java/com/android/internal/net/VpnInfo.java

+6 −4

Original line number	Diff line number	Diff line
		@@ -19,6 +19,8 @@ package com.android.internal.net;
		import android.os.Parcel;
		import android.os.Parcelable;

		import java.util.Arrays;

		/**
		* A lightweight container used to carry information of the ongoing VPN.
		* Internal use only..
		@@ -28,14 +30,14 @@ import android.os.Parcelable;
		public class VpnInfo implements Parcelable {
		public int ownerUid;
		public String vpnIface;
		public String primaryUnderlyingIface;
		public String[] underlyingIfaces;

		@Override
		public String toString() {
		return "VpnInfo{"
		+ "ownerUid=" + ownerUid
		+ ", vpnIface='" + vpnIface + '\''
		+ ", primaryUnderlyingIface='" + primaryUnderlyingIface + '\''
		+ ", underlyingIfaces='" + Arrays.toString(underlyingIfaces) + '\''
		+ '}';
		}

		@@ -48,7 +50,7 @@ public class VpnInfo implements Parcelable {
		public void writeToParcel(Parcel dest, int flags) {
		dest.writeInt(ownerUid);
		dest.writeString(vpnIface);
		dest.writeString(primaryUnderlyingIface);
		dest.writeStringArray(underlyingIfaces);
		}

		public static final Parcelable.Creator<VpnInfo> CREATOR = new Parcelable.Creator<VpnInfo>() {
		@@ -57,7 +59,7 @@ public class VpnInfo implements Parcelable {
		VpnInfo info = new VpnInfo();
		info.ownerUid = source.readInt();
		info.vpnIface = source.readString();
		info.primaryUnderlyingIface = source.readString();
		info.underlyingIfaces = source.readStringArray();
		return info;
		}

core/tests/benchmarks/src/android/net/NetworkStatsBenchmark.java

+41 −13

File changed.

Preview size limit exceeded, changes collapsed.

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

+16 −9

Original line number	Diff line number	Diff line
		@@ -4363,7 +4363,7 @@ public class ConnectivityService extends IConnectivityManager.Stub

		/**
		* @return VPN information for accounting, or null if we can't retrieve all required
		* information, e.g primary underlying iface.
		* information, e.g underlying ifaces.
		*/
		@Nullable
		private VpnInfo createVpnInfo(Vpn vpn) {
		@@ -4375,17 +4375,24 @@ public class ConnectivityService extends IConnectivityManager.Stub
		// see VpnService.setUnderlyingNetworks()'s javadoc about how to interpret
		// the underlyingNetworks list.
		if (underlyingNetworks == null) {
		NetworkAgentInfo defaultNetwork = getDefaultNetwork();
		if (defaultNetwork != null && defaultNetwork.linkProperties != null) {
		info.primaryUnderlyingIface = getDefaultNetwork().linkProperties.getInterfaceName();
		NetworkAgentInfo defaultNai = getDefaultNetwork();
		if (defaultNai != null) {
		underlyingNetworks = new Network[] { defaultNai.network };
		}
		}
		if (underlyingNetworks != null && underlyingNetworks.length > 0) {
		List<String> interfaces = new ArrayList<>();
		for (Network network : underlyingNetworks) {
		LinkProperties lp = getLinkProperties(network);
		if (lp != null && !TextUtils.isEmpty(lp.getInterfaceName())) {
		interfaces.add(lp.getInterfaceName());
		}
		}
		} else if (underlyingNetworks.length > 0) {
		LinkProperties linkProperties = getLinkProperties(underlyingNetworks[0]);
		if (linkProperties != null) {
		info.primaryUnderlyingIface = linkProperties.getInterfaceName();
		if (!interfaces.isEmpty()) {
		info.underlyingIfaces = interfaces.toArray(new String[interfaces.size()]);
		}
		}
		return info.primaryUnderlyingIface == null ? null : info;
		return info.underlyingIfaces == null ? null : info;
		}

		/**

services/core/java/com/android/server/net/NetworkStatsFactory.java

+4 −0

Original line number	Diff line number	Diff line
		@@ -263,6 +263,10 @@ public class NetworkStatsFactory {
		return stats;
		}

		/**
		* @deprecated Use NetworkStatsService#getDetailedUidStats which also accounts for
		* VPN traffic
		*/
		public NetworkStats readNetworkStatsDetail() throws IOException {
		return readNetworkStatsDetail(UID_ALL, null, TAG_ALL, null);
		}