Merge changes from topic "am-be6a9190f28c4c1fa3990ea22425f5b8-rvc-dev" into rvc-dev

* changes:
  [BOT.6] Make BpfCoordinator to support data limit
  [BOT.9] Add unit test for data warning in BpfCoordinator
  [BOT.4] Make BpfCoordinator to support data warning
  [BOT.5] Move class Ipv6ForwardingRule from IpServer to the coordinator
  [BOT.3] Add unit test for polling network stats in the coordinator
  [BOT.2] Create a coordinator and stats provider to provide tether stats
  [BOT.1] Add a class ForwardedStats in TetheringUtils

packages/Tethering/src/android/net/ip/IpServer.java

@@ -33,7 +33,6 @@ import android.net.LinkAddress;
 import android.net.LinkProperties;
 import android.net.MacAddress;
 import android.net.RouteInfo;
-import android.net.TetherOffloadRuleParcel;
 import android.net.TetheredClient;
 import android.net.TetheringManager;
 import android.net.TetheringRequestParcel;
@@ -65,6 +64,8 @@ import androidx.annotation.Nullable;
 import com.android.internal.util.MessageUtils;
 import com.android.internal.util.State;
 import com.android.internal.util.StateMachine;
+import com.android.networkstack.tethering.BpfCoordinator;
+import com.android.networkstack.tethering.BpfCoordinator.Ipv6ForwardingRule;
 import com.android.networkstack.tethering.PrivateAddressCoordinator;
 
 import java.io.IOException;
@@ -76,7 +77,6 @@ import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collections;
 import java.util.HashSet;
-import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Objects;
 import java.util.Random;
@@ -225,6 +225,8 @@ public class IpServer extends StateMachine {
 
     private final SharedLog mLog;
     private final INetd mNetd;
+    @NonNull
+    private final BpfCoordinator mBpfCoordinator;
     private final Callback mCallback;
     private final InterfaceController mInterfaceCtrl;
     private final PrivateAddressCoordinator mPrivateAddressCoordinator;
@@ -269,43 +271,6 @@ public class IpServer extends StateMachine {
         }
     }
 
-    static class Ipv6ForwardingRule {
-        public final int upstreamIfindex;
-        public final int downstreamIfindex;
-        public final Inet6Address address;
-        public final MacAddress srcMac;
-        public final MacAddress dstMac;
-
-        Ipv6ForwardingRule(int upstreamIfindex, int downstreamIfIndex, Inet6Address address,
-                MacAddress srcMac, MacAddress dstMac) {
-            this.upstreamIfindex = upstreamIfindex;
-            this.downstreamIfindex = downstreamIfIndex;
-            this.address = address;
-            this.srcMac = srcMac;
-            this.dstMac = dstMac;
-        }
-
-        public Ipv6ForwardingRule onNewUpstream(int newUpstreamIfindex) {
-            return new Ipv6ForwardingRule(newUpstreamIfindex, downstreamIfindex, address, srcMac,
-                    dstMac);
-        }
-
-        // Don't manipulate TetherOffloadRuleParcel directly because implementing onNewUpstream()
-        // would be error-prone due to generated stable AIDL classes not having a copy constructor.
-        public TetherOffloadRuleParcel toTetherOffloadRuleParcel() {
-            final TetherOffloadRuleParcel parcel = new TetherOffloadRuleParcel();
-            parcel.inputInterfaceIndex = upstreamIfindex;
-            parcel.outputInterfaceIndex = downstreamIfindex;
-            parcel.destination = address.getAddress();
-            parcel.prefixLength = 128;
-            parcel.srcL2Address = srcMac.toByteArray();
-            parcel.dstL2Address = dstMac.toByteArray();
-            return parcel;
-        }
-    }
-    private final LinkedHashMap<Inet6Address, Ipv6ForwardingRule> mIpv6ForwardingRules =
-            new LinkedHashMap<>();
-
     private final IpNeighborMonitor mIpNeighborMonitor;
 
     private LinkAddress mIpv4Address;
@@ -314,11 +279,13 @@ public class IpServer extends StateMachine {
     // object. It helps to reduce the arguments of the constructor.
     public IpServer(
             String ifaceName, Looper looper, int interfaceType, SharedLog log,
-            INetd netd, Callback callback, boolean usingLegacyDhcp, boolean usingBpfOffload,
+            INetd netd, @NonNull BpfCoordinator coordinator, Callback callback,
+            boolean usingLegacyDhcp, boolean usingBpfOffload,
             PrivateAddressCoordinator addressCoordinator, Dependencies deps) {
         super(ifaceName, looper);
         mLog = log.forSubComponent(ifaceName);
         mNetd = netd;
+        mBpfCoordinator = coordinator;
         mCallback = callback;
         mInterfaceCtrl = new InterfaceController(ifaceName, mNetd, mLog);
         mIfaceName = ifaceName;
@@ -749,6 +716,14 @@ public class IpServer extends StateMachine {
             }
 
             upstreamIfindex = mDeps.getIfindex(upstreamIface);
+
+            // Add upstream index to name mapping for the tether stats usage in the coordinator.
+            // Although this mapping could be added by both class Tethering and IpServer, adding
+            // mapping from IpServer guarantees that the mapping is added before the adding
+            // forwarding rules. That is because there are different state machines in both
+            // classes. It is hard to guarantee the link property update order between multiple
+            // state machines.
+            mBpfCoordinator.addUpstreamNameToLookupTable(upstreamIfindex, upstreamIface);
         }
 
         // If v6only is null, we pass in null to setRaParams(), which handles
@@ -864,43 +839,29 @@ public class IpServer extends StateMachine {
         // TODO: Perhaps remove this protection check.
         if (!mUsingBpfOffload) return;
 
-        try {
+        mBpfCoordinator.tetherOffloadRuleAdd(this, rule);
-            mNetd.tetherOffloadRuleAdd(rule.toTetherOffloadRuleParcel());
-            mIpv6ForwardingRules.put(rule.address, rule);
-        } catch (RemoteException | ServiceSpecificException e) {
-            mLog.e("Could not add IPv6 downstream rule: ", e);
-        }
     }
 
-    private void removeIpv6ForwardingRule(Ipv6ForwardingRule rule, boolean removeFromMap) {
+    private void removeIpv6ForwardingRule(Ipv6ForwardingRule rule) {
-        // Theoretically, we don't need this check because IP neighbor monitor doesn't start if BPF
-        // offload is disabled. Add this check just in case.
         // TODO: Perhaps remove this protection check.
+        // See the related comment in #addIpv6ForwardingRule.
         if (!mUsingBpfOffload) return;
 
-        try {
+        mBpfCoordinator.tetherOffloadRuleRemove(this, rule);
-            mNetd.tetherOffloadRuleRemove(rule.toTetherOffloadRuleParcel());
-            if (removeFromMap) {
-                mIpv6ForwardingRules.remove(rule.address);
-            }
-        } catch (RemoteException | ServiceSpecificException e) {
-            mLog.e("Could not remove IPv6 downstream rule: ", e);
-        }
     }
 
     private void clearIpv6ForwardingRules() {
-        for (Ipv6ForwardingRule rule : mIpv6ForwardingRules.values()) {
+        if (!mUsingBpfOffload) return;
-            removeIpv6ForwardingRule(rule, false /*removeFromMap*/);
+
-        }
+        mBpfCoordinator.tetherOffloadRuleClear(this);
-        mIpv6ForwardingRules.clear();
     }
 
-    // Convenience method to replace a rule with the same rule on a new upstream interface.
+    private void updateIpv6ForwardingRule(int newIfindex) {
-    // Allows replacing the rules in one iteration pass without ConcurrentModificationExceptions.
+        // TODO: Perhaps remove this protection check.
-    // Relies on the fact that rules are in a map indexed by IP address.
+        // See the related comment in #addIpv6ForwardingRule.
-    private void updateIpv6ForwardingRule(Ipv6ForwardingRule rule, int newIfindex) {
+        if (!mUsingBpfOffload) return;
-        addIpv6ForwardingRule(rule.onNewUpstream(newIfindex));
+
-        removeIpv6ForwardingRule(rule, false /*removeFromMap*/);
+        mBpfCoordinator.tetherOffloadRuleUpdate(this, newIfindex);
     }
 
     // Handles all updates to IPv6 forwarding rules. These can currently change only if the upstream
@@ -916,9 +877,7 @@ public class IpServer extends StateMachine {
         // If the upstream interface has changed, remove all rules and re-add them with the new
         // upstream interface.
         if (prevUpstreamIfindex != upstreamIfindex) {
-            for (Ipv6ForwardingRule rule : mIpv6ForwardingRules.values()) {
+            updateIpv6ForwardingRule(upstreamIfindex);
-                updateIpv6ForwardingRule(rule, upstreamIfindex);
-            }
         }
 
         // If we're here to process a NeighborEvent, do so now.
@@ -938,7 +897,7 @@ public class IpServer extends StateMachine {
         if (e.isValid()) {
             addIpv6ForwardingRule(rule);
         } else {
-            removeIpv6ForwardingRule(rule, true /*removeFromMap*/);
+            removeIpv6ForwardingRule(rule);
         }
     }
 

packages/Tethering/src/android/net/util/TetheringUtils.java

@@ -15,18 +15,93 @@
  */
 package android.net.util;
 
+import android.net.TetherStatsParcel;
 import android.net.TetheringRequestParcel;
 
+import androidx.annotation.NonNull;
+
 import java.io.FileDescriptor;
 import java.net.SocketException;
 import java.util.Objects;
 
 /**
- * Native methods for tethering utilization.
+ * The classes and the methods for tethering utilization.
  *
  * {@hide}
  */
 public class TetheringUtils {
+    /**
+     *  The object which records offload Tx/Rx forwarded bytes/packets.
+     *  TODO: Replace the inner class ForwardedStats of class OffloadHardwareInterface with
+     *  this class as well.
+     */
+    public static class ForwardedStats {
+        public final long rxBytes;
+        public final long rxPackets;
+        public final long txBytes;
+        public final long txPackets;
+
+        public ForwardedStats() {
+            rxBytes = 0;
+            rxPackets = 0;
+            txBytes = 0;
+            txPackets = 0;
+        }
+
+        public ForwardedStats(long rxBytes, long txBytes) {
+            this.rxBytes = rxBytes;
+            this.rxPackets = 0;
+            this.txBytes = txBytes;
+            this.txPackets = 0;
+        }
+
+        public ForwardedStats(long rxBytes, long rxPackets, long txBytes, long txPackets) {
+            this.rxBytes = rxBytes;
+            this.rxPackets = rxPackets;
+            this.txBytes = txBytes;
+            this.txPackets = txPackets;
+        }
+
+        public ForwardedStats(@NonNull TetherStatsParcel tetherStats) {
+            rxBytes = tetherStats.rxBytes;
+            rxPackets = tetherStats.rxPackets;
+            txBytes = tetherStats.txBytes;
+            txPackets = tetherStats.txPackets;
+        }
+
+        public ForwardedStats(@NonNull ForwardedStats other) {
+            rxBytes = other.rxBytes;
+            rxPackets = other.rxPackets;
+            txBytes = other.txBytes;
+            txPackets = other.txPackets;
+        }
+
+        /** Add Tx/Rx bytes/packets and return the result as a new object. */
+        @NonNull
+        public ForwardedStats add(@NonNull ForwardedStats other) {
+            return new ForwardedStats(rxBytes + other.rxBytes, rxPackets + other.rxPackets,
+                    txBytes + other.txBytes, txPackets + other.txPackets);
+        }
+
+        /** Subtract Tx/Rx bytes/packets and return the result as a new object. */
+        @NonNull
+        public ForwardedStats subtract(@NonNull ForwardedStats other) {
+            // TODO: Perhaps throw an exception if any negative difference value just in case.
+            final long rxBytesDiff = Math.max(rxBytes - other.rxBytes, 0);
+            final long rxPacketsDiff = Math.max(rxPackets - other.rxPackets, 0);
+            final long txBytesDiff = Math.max(txBytes - other.txBytes, 0);
+            final long txPacketsDiff = Math.max(txPackets - other.txPackets, 0);
+            return new ForwardedStats(rxBytesDiff, rxPacketsDiff, txBytesDiff, txPacketsDiff);
+        }
+
+        /** Returns the string representation of this object. */
+        @NonNull
+        public String toString() {
+            return String.format("ForwardedStats(rxb: %d, rxp: %d, txb: %d, txp: %d)", rxBytes,
+                    rxPackets, txBytes, txPackets);
+        }
+    }
+
     /**
      * Configures a socket for receiving ICMPv6 router solicitations and sending advertisements.
      * @param fd the socket's {@link FileDescriptor}.

packages/Tethering/src/com/android/networkstack/tethering/BpfCoordinator.java

@@ -0,0 +1,637 @@
+/*
+ * 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.networkstack.tethering;
+
+import static android.net.NetworkStats.DEFAULT_NETWORK_NO;
+import static android.net.NetworkStats.METERED_NO;
+import static android.net.NetworkStats.ROAMING_NO;
+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.NetworkStats.UID_TETHERING;
+import static android.net.netstats.provider.NetworkStatsProvider.QUOTA_UNLIMITED;
+
+import android.app.usage.NetworkStatsManager;
+import android.net.INetd;
+import android.net.MacAddress;
+import android.net.NetworkStats;
+import android.net.NetworkStats.Entry;
+import android.net.TetherOffloadRuleParcel;
+import android.net.TetherStatsParcel;
+import android.net.ip.IpServer;
+import android.net.netstats.provider.NetworkStatsProvider;
+import android.net.util.SharedLog;
+import android.net.util.TetheringUtils.ForwardedStats;
+import android.os.Handler;
+import android.os.RemoteException;
+import android.os.ServiceSpecificException;
+import android.text.TextUtils;
+import android.util.Log;
+import android.util.SparseArray;
+
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+
+import com.android.internal.annotations.VisibleForTesting;
+
+import java.net.Inet6Address;
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.LinkedHashMap;
+import java.util.Objects;
+
+/**
+ *  This coordinator is responsible for providing BPF offload relevant functionality.
+ *  - Get tethering stats.
+ *  - Set data limit.
+ *  - Set global alert.
+ *  - Add/remove forwarding rules.
+ *
+ * @hide
+ */
+public class BpfCoordinator {
+    private static final String TAG = BpfCoordinator.class.getSimpleName();
+    @VisibleForTesting
+    static final int DEFAULT_PERFORM_POLL_INTERVAL_MS = 5000; // TODO: Make it customizable.
+
+    @VisibleForTesting
+    enum StatsType {
+        STATS_PER_IFACE,
+        STATS_PER_UID,
+    }
+
+    @NonNull
+    private final Handler mHandler;
+    @NonNull
+    private final INetd mNetd;
+    @NonNull
+    private final SharedLog mLog;
+    @NonNull
+    private final Dependencies mDeps;
+    @Nullable
+    private final BpfTetherStatsProvider mStatsProvider;
+
+    // Tracks whether BPF tethering is started or not. This is set by tethering before it
+    // starts the first IpServer and is cleared by tethering shortly before the last IpServer
+    // is stopped. Note that rule updates (especially deletions, but sometimes additions as
+    // well) may arrive when this is false. If they do, they must be communicated to netd.
+    // Changes in data limits may also arrive when this is false, and if they do, they must
+    // also be communicated to netd.
+    private boolean mPollingStarted = false;
+
+    // Tracking remaining alert quota. Unlike limit quota is subject to interface, the alert
+    // quota is interface independent and global for tether offload.
+    private long mRemainingAlertQuota = QUOTA_UNLIMITED;
+
+    // Maps upstream interface index to offloaded traffic statistics.
+    // Always contains the latest total bytes/packets, since each upstream was started, received
+    // from the BPF maps for each interface.
+    private final SparseArray<ForwardedStats> mStats = new SparseArray<>();
+
+    // Maps upstream interface names to interface quotas.
+    // Always contains the latest value received from the framework for each interface, regardless
+    // of whether offload is currently running (or is even supported) on that interface. Only
+    // includes interfaces that have a quota set. Note that this map is used for storing the quota
+    // which is set from the service. Because the service uses the interface name to present the
+    // interface, this map uses the interface name to be the mapping index.
+    private final HashMap<String, Long> mInterfaceQuotas = new HashMap<>();
+
+    // Maps upstream interface index to interface names.
+    // Store all interface name since boot. Used for lookup what interface name it is from the
+    // tether stats got from netd because netd reports interface index to present an interface.
+    // TODO: Remove the unused interface name.
+    private final SparseArray<String> mInterfaceNames = new SparseArray<>();
+
+    // Map of downstream rule maps. Each of these maps represents the IPv6 forwarding rules for a
+    // given downstream. Each map:
+    // - Is owned by the IpServer that is responsible for that downstream.
+    // - Must only be modified by that IpServer.
+    // - Is created when the IpServer adds its first rule, and deleted when the IpServer deletes
+    //   its last rule (or clears its rules).
+    // TODO: Perhaps seal the map and rule operations which communicates with netd into a class.
+    // TODO: Does this need to be a LinkedHashMap or can it just be a HashMap? Also, could it be
+    // a ConcurrentHashMap, in order to avoid the copies in tetherOffloadRuleClear
+    // and tetherOffloadRuleUpdate?
+    // TODO: Perhaps use one-dimensional map and access specific downstream rules via downstream
+    // index. For doing that, IpServer must guarantee that it always has a valid IPv6 downstream
+    // interface index while calling function to clear all rules. IpServer may be calling clear
+    // rules function without a valid IPv6 downstream interface index even if it may have one
+    // before. IpServer would need to call getInterfaceParams() in the constructor instead of when
+    // startIpv6() is called, and make mInterfaceParams final.
+    private final HashMap<IpServer, LinkedHashMap<Inet6Address, Ipv6ForwardingRule>>
+            mIpv6ForwardingRules = new LinkedHashMap<>();
+
+    // Runnable that used by scheduling next polling of stats.
+    private final Runnable mScheduledPollingTask = () -> {
+        updateForwardedStatsFromNetd();
+        maybeSchedulePollingStats();
+    };
+
+    @VisibleForTesting
+    public static class Dependencies {
+        int getPerformPollInterval() {
+            // TODO: Consider make this configurable.
+            return DEFAULT_PERFORM_POLL_INTERVAL_MS;
+        }
+    }
+
+    @VisibleForTesting
+    public BpfCoordinator(@NonNull Handler handler, @NonNull INetd netd,
+            @NonNull NetworkStatsManager nsm, @NonNull SharedLog log, @NonNull Dependencies deps) {
+        mHandler = handler;
+        mNetd = netd;
+        mLog = log.forSubComponent(TAG);
+        BpfTetherStatsProvider provider = new BpfTetherStatsProvider();
+        try {
+            nsm.registerNetworkStatsProvider(getClass().getSimpleName(), provider);
+        } catch (RuntimeException e) {
+            // TODO: Perhaps not allow to use BPF offload because the reregistration failure
+            // implied that no data limit could be applies on a metered upstream if any.
+            Log.wtf(TAG, "Cannot register offload stats provider: " + e);
+            provider = null;
+        }
+        mStatsProvider = provider;
+        mDeps = deps;
+    }
+
+    /**
+     * Start BPF tethering offload stats polling when the first upstream is started.
+     * Note that this can be only called on handler thread.
+     * TODO: Perhaps check BPF support before starting.
+     * TODO: Start the stats polling only if there is any client on the downstream.
+     */
+    public void startPolling() {
+        if (mPollingStarted) return;
+
+        mPollingStarted = true;
+        maybeSchedulePollingStats();
+
+        mLog.i("Polling started");
+    }
+
+    /**
+     * Stop BPF tethering offload stats polling.
+     * The data limit cleanup and the tether stats maps cleanup are not implemented here.
+     * These cleanups rely on all IpServers calling #tetherOffloadRuleRemove. After the
+     * last rule is removed from the upstream, #tetherOffloadRuleRemove does the cleanup
+     * functionality.
+     * Note that this can be only called on handler thread.
+     */
+    public void stopPolling() {
+        if (!mPollingStarted) return;
+
+        // Stop scheduled polling tasks and poll the latest stats from BPF maps.
+        if (mHandler.hasCallbacks(mScheduledPollingTask)) {
+            mHandler.removeCallbacks(mScheduledPollingTask);
+        }
+        updateForwardedStatsFromNetd();
+        mPollingStarted = false;
+
+        mLog.i("Polling stopped");
+    }
+
+    /**
+     * Add forwarding rule. After adding the first rule on a given upstream, must add the data
+     * limit on the given upstream.
+     * Note that this can be only called on handler thread.
+     */
+    public void tetherOffloadRuleAdd(
+            @NonNull final IpServer ipServer, @NonNull final Ipv6ForwardingRule rule) {
+        try {
+            // TODO: Perhaps avoid to add a duplicate rule.
+            mNetd.tetherOffloadRuleAdd(rule.toTetherOffloadRuleParcel());
+        } catch (RemoteException | ServiceSpecificException e) {
+            mLog.e("Could not add IPv6 forwarding rule: ", e);
+            return;
+        }
+
+        if (!mIpv6ForwardingRules.containsKey(ipServer)) {
+            mIpv6ForwardingRules.put(ipServer, new LinkedHashMap<Inet6Address,
+                    Ipv6ForwardingRule>());
+        }
+        LinkedHashMap<Inet6Address, Ipv6ForwardingRule> rules = mIpv6ForwardingRules.get(ipServer);
+
+        // Setup the data limit on the given upstream if the first rule is added.
+        final int upstreamIfindex = rule.upstreamIfindex;
+        if (!isAnyRuleOnUpstream(upstreamIfindex)) {
+            // If failed to set a data limit, probably should not use this upstream, because
+            // the upstream may not want to blow through the data limit that was told to apply.
+            // TODO: Perhaps stop the coordinator.
+            boolean success = updateDataLimit(upstreamIfindex);
+            if (!success) {
+                final String iface = mInterfaceNames.get(upstreamIfindex);
+                mLog.e("Setting data limit for " + iface + " failed.");
+            }
+        }
+
+        // Must update the adding rule after calling #isAnyRuleOnUpstream because it needs to
+        // check if it is about adding a first rule for a given upstream.
+        rules.put(rule.address, rule);
+    }
+
+    /**
+     * Remove forwarding rule. After removing the last rule on a given upstream, must clear
+     * data limit, update the last tether stats and remove the tether stats in the BPF maps.
+     * Note that this can be only called on handler thread.
+     */
+    public void tetherOffloadRuleRemove(
+            @NonNull final IpServer ipServer, @NonNull final Ipv6ForwardingRule rule) {
+        try {
+            // TODO: Perhaps avoid to remove a non-existent rule.
+            mNetd.tetherOffloadRuleRemove(rule.toTetherOffloadRuleParcel());
+        } catch (RemoteException | ServiceSpecificException e) {
+            mLog.e("Could not remove IPv6 forwarding rule: ", e);
+            return;
+        }
+
+        LinkedHashMap<Inet6Address, Ipv6ForwardingRule> rules = mIpv6ForwardingRules.get(ipServer);
+        if (rules == null) return;
+
+        // Must remove rules before calling #isAnyRuleOnUpstream because it needs to check if
+        // the last rule is removed for a given upstream. If no rule is removed, return early.
+        // Avoid unnecessary work on a non-existent rule which may have never been added or
+        // removed already.
+        if (rules.remove(rule.address) == null) return;
+
+        // Remove the downstream entry if it has no more rule.
+        if (rules.isEmpty()) {
+            mIpv6ForwardingRules.remove(ipServer);
+        }
+
+        // Do cleanup functionality if there is no more rule on the given upstream.
+        final int upstreamIfindex = rule.upstreamIfindex;
+        if (!isAnyRuleOnUpstream(upstreamIfindex)) {
+            try {
+                final TetherStatsParcel stats =
+                        mNetd.tetherOffloadGetAndClearStats(upstreamIfindex);
+                // Update the last stats delta and delete the local cache for a given upstream.
+                updateQuotaAndStatsFromSnapshot(new TetherStatsParcel[] {stats});
+                mStats.remove(upstreamIfindex);
+            } catch (RemoteException | ServiceSpecificException e) {
+                Log.wtf(TAG, "Exception when cleanup tether stats for upstream index "
+                        + upstreamIfindex + ": ", e);
+            }
+        }
+    }
+
+    /**
+     * Clear all forwarding rules for a given downstream.
+     * Note that this can be only called on handler thread.
+     */
+    public void tetherOffloadRuleClear(@NonNull final IpServer ipServer) {
+        final LinkedHashMap<Inet6Address, Ipv6ForwardingRule> rules = mIpv6ForwardingRules.get(
+                ipServer);
+        if (rules == null) return;
+
+        // Need to build a rule list because the rule map may be changed in the iteration.
+        for (final Ipv6ForwardingRule rule : new ArrayList<Ipv6ForwardingRule>(rules.values())) {
+            tetherOffloadRuleRemove(ipServer, rule);
+        }
+    }
+
+    /**
+     * Update existing forwarding rules to new upstream for a given downstream.
+     * Note that this can be only called on handler thread.
+     */
+    public void tetherOffloadRuleUpdate(@NonNull final IpServer ipServer, int newUpstreamIfindex) {
+        final LinkedHashMap<Inet6Address, Ipv6ForwardingRule> rules = mIpv6ForwardingRules.get(
+                ipServer);
+        if (rules == null) return;
+
+        // Need to build a rule list because the rule map may be changed in the iteration.
+        for (final Ipv6ForwardingRule rule : new ArrayList<Ipv6ForwardingRule>(rules.values())) {
+            // Remove the old rule before adding the new one because the map uses the same key for
+            // both rules. Reversing the processing order causes that the new rule is removed as
+            // unexpected.
+            // TODO: Add new rule first to reduce the latency which has no rule.
+            tetherOffloadRuleRemove(ipServer, rule);
+            tetherOffloadRuleAdd(ipServer, rule.onNewUpstream(newUpstreamIfindex));
+        }
+    }
+
+    /**
+     * Add upstream name to lookup table. The lookup table is used for tether stats interface name
+     * lookup because the netd only reports interface index in BPF tether stats but the service
+     * expects the interface name in NetworkStats object.
+     * Note that this can be only called on handler thread.
+     */
+    public void addUpstreamNameToLookupTable(int upstreamIfindex, @NonNull String upstreamIface) {
+        if (upstreamIfindex == 0 || TextUtils.isEmpty(upstreamIface)) return;
+
+        // The same interface index to name mapping may be added by different IpServer objects or
+        // re-added by reconnection on the same upstream interface. Ignore the duplicate one.
+        final String iface = mInterfaceNames.get(upstreamIfindex);
+        if (iface == null) {
+            mInterfaceNames.put(upstreamIfindex, upstreamIface);
+        } else if (!TextUtils.equals(iface, upstreamIface)) {
+            Log.wtf(TAG, "The upstream interface name " + upstreamIface
+                    + " is different from the existing interface name "
+                    + iface + " for index " + upstreamIfindex);
+        }
+    }
+
+    /** IPv6 forwarding rule class. */
+    public static class Ipv6ForwardingRule {
+        public final int upstreamIfindex;
+        public final int downstreamIfindex;
+
+        @NonNull
+        public final Inet6Address address;
+        @NonNull
+        public final MacAddress srcMac;
+        @NonNull
+        public final MacAddress dstMac;
+
+        public Ipv6ForwardingRule(int upstreamIfindex, int downstreamIfIndex,
+                @NonNull Inet6Address address, @NonNull MacAddress srcMac,
+                @NonNull MacAddress dstMac) {
+            this.upstreamIfindex = upstreamIfindex;
+            this.downstreamIfindex = downstreamIfIndex;
+            this.address = address;
+            this.srcMac = srcMac;
+            this.dstMac = dstMac;
+        }
+
+        /** Return a new rule object which updates with new upstream index. */
+        @NonNull
+        public Ipv6ForwardingRule onNewUpstream(int newUpstreamIfindex) {
+            return new Ipv6ForwardingRule(newUpstreamIfindex, downstreamIfindex, address, srcMac,
+                    dstMac);
+        }
+
+        /**
+         * Don't manipulate TetherOffloadRuleParcel directly because implementing onNewUpstream()
+         * would be error-prone due to generated stable AIDL classes not having a copy constructor.
+         */
+        @NonNull
+        public TetherOffloadRuleParcel toTetherOffloadRuleParcel() {
+            final TetherOffloadRuleParcel parcel = new TetherOffloadRuleParcel();
+            parcel.inputInterfaceIndex = upstreamIfindex;
+            parcel.outputInterfaceIndex = downstreamIfindex;
+            parcel.destination = address.getAddress();
+            parcel.prefixLength = 128;
+            parcel.srcL2Address = srcMac.toByteArray();
+            parcel.dstL2Address = dstMac.toByteArray();
+            return parcel;
+        }
+
+        @Override
+        public boolean equals(Object o) {
+            if (!(o instanceof Ipv6ForwardingRule)) return false;
+            Ipv6ForwardingRule that = (Ipv6ForwardingRule) o;
+            return this.upstreamIfindex == that.upstreamIfindex
+                    && this.downstreamIfindex == that.downstreamIfindex
+                    && Objects.equals(this.address, that.address)
+                    && Objects.equals(this.srcMac, that.srcMac)
+                    && Objects.equals(this.dstMac, that.dstMac);
+        }
+
+        @Override
+        public int hashCode() {
+            // TODO: if this is ever used in production code, don't pass ifindices
+            // to Objects.hash() to avoid autoboxing overhead.
+            return Objects.hash(upstreamIfindex, downstreamIfindex, address, srcMac, dstMac);
+        }
+    }
+
+    /**
+     * A BPF tethering stats provider to provide network statistics to the system.
+     * Note that this class' data may only be accessed on the handler thread.
+     */
+    @VisibleForTesting
+    class BpfTetherStatsProvider extends NetworkStatsProvider {
+        // The offloaded traffic statistics per interface that has not been reported since the
+        // last call to pushTetherStats. Only the interfaces that were ever tethering upstreams
+        // and has pending tether stats delta are included in this NetworkStats object.
+        private NetworkStats mIfaceStats = new NetworkStats(0L, 0);
+
+        // The same stats as above, but counts network stats per uid.
+        private NetworkStats mUidStats = new NetworkStats(0L, 0);
+
+        @Override
+        public void onRequestStatsUpdate(int token) {
+            mHandler.post(() -> pushTetherStats());
+        }
+
+        @Override
+        public void onSetAlert(long quotaBytes) {
+            mHandler.post(() -> updateAlertQuota(quotaBytes));
+        }
+
+        @Override
+        public void onSetLimit(@NonNull String iface, long quotaBytes) {
+            if (quotaBytes < QUOTA_UNLIMITED) {
+                throw new IllegalArgumentException("invalid quota value " + quotaBytes);
+            }
+
+            mHandler.post(() -> {
+                final Long curIfaceQuota = mInterfaceQuotas.get(iface);
+
+                if (null == curIfaceQuota && QUOTA_UNLIMITED == quotaBytes) return;
+
+                if (quotaBytes == QUOTA_UNLIMITED) {
+                    mInterfaceQuotas.remove(iface);
+                } else {
+                    mInterfaceQuotas.put(iface, quotaBytes);
+                }
+                maybeUpdateDataLimit(iface);
+            });
+        }
+
+        @VisibleForTesting
+        void pushTetherStats() {
+            try {
+                // The token is not used for now. See b/153606961.
+                notifyStatsUpdated(0 /* token */, mIfaceStats, mUidStats);
+
+                // Clear the accumulated tether stats delta after reported. Note that create a new
+                // empty object because NetworkStats#clear is @hide.
+                mIfaceStats = new NetworkStats(0L, 0);
+                mUidStats = new NetworkStats(0L, 0);
+            } catch (RuntimeException e) {
+                mLog.e("Cannot report network stats: ", e);
+            }
+        }
+
+        private void accumulateDiff(@NonNull NetworkStats ifaceDiff,
+                @NonNull NetworkStats uidDiff) {
+            mIfaceStats = mIfaceStats.add(ifaceDiff);
+            mUidStats = mUidStats.add(uidDiff);
+        }
+    }
+
+    private int getInterfaceIndexFromRules(@NonNull String ifName) {
+        for (LinkedHashMap<Inet6Address, Ipv6ForwardingRule> rules : mIpv6ForwardingRules
+                .values()) {
+            for (Ipv6ForwardingRule rule : rules.values()) {
+                final int upstreamIfindex = rule.upstreamIfindex;
+                if (TextUtils.equals(ifName, mInterfaceNames.get(upstreamIfindex))) {
+                    return upstreamIfindex;
+                }
+            }
+        }
+        return 0;
+    }
+
+    private long getQuotaBytes(@NonNull String iface) {
+        final Long limit = mInterfaceQuotas.get(iface);
+        final long quotaBytes = (limit != null) ? limit : QUOTA_UNLIMITED;
+
+        return quotaBytes;
+    }
+
+    private boolean sendDataLimitToNetd(int ifIndex, long quotaBytes) {
+        if (ifIndex == 0) {
+            Log.wtf(TAG, "Invalid interface index.");
+            return false;
+        }
+
+        try {
+            mNetd.tetherOffloadSetInterfaceQuota(ifIndex, quotaBytes);
+        } catch (RemoteException | ServiceSpecificException e) {
+            mLog.e("Exception when updating quota " + quotaBytes + ": ", e);
+            return false;
+        }
+
+        return true;
+    }
+
+    // Handle the data limit update from the service which is the stats provider registered for.
+    private void maybeUpdateDataLimit(@NonNull String iface) {
+        // Set data limit only on a given upstream which has at least one rule. If we can't get
+        // an interface index for a given interface name, it means either there is no rule for
+        // a given upstream or the interface name is not an upstream which is monitored by the
+        // coordinator.
+        final int ifIndex = getInterfaceIndexFromRules(iface);
+        if (ifIndex == 0) return;
+
+        final long quotaBytes = getQuotaBytes(iface);
+        sendDataLimitToNetd(ifIndex, quotaBytes);
+    }
+
+    // Handle the data limit update while adding forwarding rules.
+    private boolean updateDataLimit(int ifIndex) {
+        final String iface = mInterfaceNames.get(ifIndex);
+        if (iface == null) {
+            mLog.e("Fail to get the interface name for index " + ifIndex);
+            return false;
+        }
+        final long quotaBytes = getQuotaBytes(iface);
+        return sendDataLimitToNetd(ifIndex, quotaBytes);
+    }
+
+    private boolean isAnyRuleOnUpstream(int upstreamIfindex) {
+        for (LinkedHashMap<Inet6Address, Ipv6ForwardingRule> rules : mIpv6ForwardingRules
+                .values()) {
+            for (Ipv6ForwardingRule rule : rules.values()) {
+                if (upstreamIfindex == rule.upstreamIfindex) return true;
+            }
+        }
+        return false;
+    }
+
+    @NonNull
+    private NetworkStats buildNetworkStats(@NonNull StatsType type, int ifIndex,
+            @NonNull final ForwardedStats diff) {
+        NetworkStats stats = new NetworkStats(0L, 0);
+        final String iface = mInterfaceNames.get(ifIndex);
+        if (iface == null) {
+            // TODO: Use Log.wtf once the coordinator owns full control of tether stats from netd.
+            // For now, netd may add the empty stats for the upstream which is not monitored by
+            // the coordinator. Silently ignore it.
+            return stats;
+        }
+        final int uid = (type == StatsType.STATS_PER_UID) ? UID_TETHERING : UID_ALL;
+        // Note that the argument 'metered', 'roaming' and 'defaultNetwork' are not recorded for
+        // network stats snapshot. See NetworkStatsRecorder#recordSnapshotLocked.
+        return stats.addEntry(new Entry(iface, uid, SET_DEFAULT, TAG_NONE, METERED_NO,
+                ROAMING_NO, DEFAULT_NETWORK_NO, diff.rxBytes, diff.rxPackets,
+                diff.txBytes, diff.txPackets, 0L /* operations */));
+    }
+
+    private void updateAlertQuota(long newQuota) {
+        if (newQuota < QUOTA_UNLIMITED) {
+            throw new IllegalArgumentException("invalid quota value " + newQuota);
+        }
+        if (mRemainingAlertQuota == newQuota) return;
+
+        mRemainingAlertQuota = newQuota;
+        if (mRemainingAlertQuota == 0) {
+            mLog.i("onAlertReached");
+            if (mStatsProvider != null) mStatsProvider.notifyAlertReached();
+        }
+    }
+
+    private void updateQuotaAndStatsFromSnapshot(
+            @NonNull final TetherStatsParcel[] tetherStatsList) {
+        long usedAlertQuota = 0;
+        for (TetherStatsParcel tetherStats : tetherStatsList) {
+            final Integer ifIndex = tetherStats.ifIndex;
+            final ForwardedStats curr = new ForwardedStats(tetherStats);
+            final ForwardedStats base = mStats.get(ifIndex);
+            final ForwardedStats diff = (base != null) ? curr.subtract(base) : curr;
+            usedAlertQuota += diff.rxBytes + diff.txBytes;
+
+            // Update the local cache for counting tether stats delta.
+            mStats.put(ifIndex, curr);
+
+            // Update the accumulated tether stats delta to the stats provider for the service
+            // querying.
+            if (mStatsProvider != null) {
+                try {
+                    mStatsProvider.accumulateDiff(
+                            buildNetworkStats(StatsType.STATS_PER_IFACE, ifIndex, diff),
+                            buildNetworkStats(StatsType.STATS_PER_UID, ifIndex, diff));
+                } catch (ArrayIndexOutOfBoundsException e) {
+                    Log.wtf(TAG, "Fail to update the accumulated stats delta for interface index "
+                            + ifIndex + " : ", e);
+                }
+            }
+        }
+
+        if (mRemainingAlertQuota > 0 && usedAlertQuota > 0) {
+            // Trim to zero if overshoot.
+            final long newQuota = Math.max(mRemainingAlertQuota - usedAlertQuota, 0);
+            updateAlertQuota(newQuota);
+        }
+
+        // TODO: Count the used limit quota for notifying data limit reached.
+    }
+
+    private void updateForwardedStatsFromNetd() {
+        final TetherStatsParcel[] tetherStatsList;
+        try {
+            // The reported tether stats are total data usage for all currently-active upstream
+            // interfaces since tethering start.
+            tetherStatsList = mNetd.tetherOffloadGetStats();
+        } catch (RemoteException | ServiceSpecificException e) {
+            mLog.e("Problem fetching tethering stats: ", e);
+            return;
+        }
+        updateQuotaAndStatsFromSnapshot(tetherStatsList);
+    }
+
+    private void maybeSchedulePollingStats() {
+        if (!mPollingStarted) return;
+
+        if (mHandler.hasCallbacks(mScheduledPollingTask)) {
+            mHandler.removeCallbacks(mScheduledPollingTask);
+        }
+
+        mHandler.postDelayed(mScheduledPollingTask, mDeps.getPerformPollInterval());
+    }
+}

packages/Tethering/src/com/android/networkstack/tethering/Tethering.java

@@ -232,6 +232,7 @@ public class Tethering {
     private final TetheringThreadExecutor mExecutor;
     private final TetheringNotificationUpdater mNotificationUpdater;
     private final UserManager mUserManager;
+    private final BpfCoordinator mBpfCoordinator;
     private final PrivateAddressCoordinator mPrivateAddressCoordinator;
     private int mActiveDataSubId = INVALID_SUBSCRIPTION_ID;
     // All the usage of mTetheringEventCallback should run in the same thread.
@@ -284,6 +285,8 @@ public class Tethering {
         mUpstreamNetworkMonitor = mDeps.getUpstreamNetworkMonitor(mContext, mTetherMasterSM, mLog,
                 TetherMasterSM.EVENT_UPSTREAM_CALLBACK);
         mForwardedDownstreams = new LinkedHashSet<>();
+        mBpfCoordinator = mDeps.getBpfCoordinator(
+                mHandler, mNetd, mLog, new BpfCoordinator.Dependencies());
 
         IntentFilter filter = new IntentFilter();
         filter.addAction(ACTION_CARRIER_CONFIG_CHANGED);
@@ -1704,6 +1707,9 @@ public class Tethering {
                     chooseUpstreamType(true);
                     mTryCell = false;
                 }
+
+                // TODO: Check the upstream interface if it is managed by BPF offload.
+                mBpfCoordinator.startPolling();
             }
 
             @Override
@@ -1716,6 +1722,7 @@ public class Tethering {
                     mTetherUpstream = null;
                     reportUpstreamChanged(null);
                 }
+                mBpfCoordinator.stopPolling();
             }
 
             private boolean updateUpstreamWanted() {
@@ -2341,7 +2348,7 @@ public class Tethering {
 
         mLog.log("adding TetheringInterfaceStateMachine for: " + iface);
         final TetherState tetherState = new TetherState(
-                new IpServer(iface, mLooper, interfaceType, mLog, mNetd,
+                new IpServer(iface, mLooper, interfaceType, mLog, mNetd, mBpfCoordinator,
                              makeControlCallback(), mConfig.enableLegacyDhcpServer,
                              mConfig.enableBpfOffload, mPrivateAddressCoordinator,
                              mDeps.getIpServerDependencies()));

packages/Tethering/src/com/android/networkstack/tethering/TetheringDependencies.java

@@ -40,6 +40,17 @@ import java.util.ArrayList;
  * @hide
  */
 public abstract class TetheringDependencies {
+    /**
+     * Get a reference to the BpfCoordinator to be used by tethering.
+     */
+    public @NonNull BpfCoordinator getBpfCoordinator(
+            @NonNull Handler handler, @NonNull INetd netd, @NonNull SharedLog log,
+            @NonNull BpfCoordinator.Dependencies deps) {
+        final NetworkStatsManager statsManager =
+                (NetworkStatsManager) getContext().getSystemService(Context.NETWORK_STATS_SERVICE);
+        return new BpfCoordinator(handler, netd, statsManager, log, deps);
+    }
+
     /**
      * Get a reference to the offload hardware interface to be used by tethering.
      */

packages/Tethering/tests/unit/src/android/net/ip/IpServerTest.java

@@ -54,12 +54,14 @@ import static org.mockito.Mockito.doThrow;
 import static org.mockito.Mockito.inOrder;
 import static org.mockito.Mockito.never;
 import static org.mockito.Mockito.reset;
+import static org.mockito.Mockito.spy;
 import static org.mockito.Mockito.timeout;
 import static org.mockito.Mockito.times;
 import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.verifyNoMoreInteractions;
 import static org.mockito.Mockito.when;
 
+import android.app.usage.NetworkStatsManager;
 import android.net.INetd;
 import android.net.InetAddresses;
 import android.net.InterfaceConfigurationParcel;
@@ -69,6 +71,7 @@ import android.net.LinkProperties;
 import android.net.MacAddress;
 import android.net.RouteInfo;
 import android.net.TetherOffloadRuleParcel;
+import android.net.TetherStatsParcel;
 import android.net.dhcp.DhcpServingParamsParcel;
 import android.net.dhcp.IDhcpEventCallbacks;
 import android.net.dhcp.IDhcpServer;
@@ -80,13 +83,17 @@ import android.net.util.InterfaceParams;
 import android.net.util.InterfaceSet;
 import android.net.util.PrefixUtils;
 import android.net.util.SharedLog;
+import android.os.Handler;
 import android.os.RemoteException;
 import android.os.test.TestLooper;
 import android.text.TextUtils;
 
+import androidx.annotation.NonNull;
 import androidx.test.filters.SmallTest;
 import androidx.test.runner.AndroidJUnit4;
 
+import com.android.networkstack.tethering.BpfCoordinator;
+import com.android.networkstack.tethering.BpfCoordinator.Ipv6ForwardingRule;
 import com.android.networkstack.tethering.PrivateAddressCoordinator;
 
 import org.junit.Before;
@@ -100,6 +107,7 @@ import org.mockito.Mock;
 import org.mockito.MockitoAnnotations;
 
 import java.net.Inet4Address;
+import java.net.Inet6Address;
 import java.net.InetAddress;
 import java.util.Arrays;
 import java.util.List;
@@ -133,6 +141,7 @@ public class IpServerTest {
     @Mock private IpNeighborMonitor mIpNeighborMonitor;
     @Mock private IpServer.Dependencies mDependencies;
     @Mock private PrivateAddressCoordinator mAddressCoordinator;
+    @Mock private NetworkStatsManager mStatsManager;
 
     @Captor private ArgumentCaptor<DhcpServingParamsParcel> mDhcpParamsCaptor;
 
@@ -142,6 +151,7 @@ public class IpServerTest {
     private IpServer mIpServer;
     private InterfaceConfigurationParcel mInterfaceConfiguration;
     private NeighborEventConsumer mNeighborEventConsumer;
+    private BpfCoordinator mBpfCoordinator;
 
     private void initStateMachine(int interfaceType) throws Exception {
         initStateMachine(interfaceType, false /* usingLegacyDhcp */, DEFAULT_USING_BPF_OFFLOAD);
@@ -179,7 +189,7 @@ public class IpServerTest {
                 neighborCaptor.capture());
 
         mIpServer = new IpServer(
-                IFACE_NAME, mLooper.getLooper(), interfaceType, mSharedLog, mNetd,
+                IFACE_NAME, mLooper.getLooper(), interfaceType, mSharedLog, mNetd, mBpfCoordinator,
                 mCallback, usingLegacyDhcp, usingBpfOffload, mAddressCoordinator, mDependencies);
         mIpServer.start();
         mNeighborEventConsumer = neighborCaptor.getValue();
@@ -215,6 +225,10 @@ public class IpServerTest {
         MockitoAnnotations.initMocks(this);
         when(mSharedLog.forSubComponent(anyString())).thenReturn(mSharedLog);
         when(mAddressCoordinator.requestDownstreamAddress(any())).thenReturn(mTestAddress);
+
+        BpfCoordinator bc = new BpfCoordinator(new Handler(mLooper.getLooper()), mNetd,
+                mStatsManager, mSharedLog, new BpfCoordinator.Dependencies());
+        mBpfCoordinator = spy(bc);
     }
 
     @Test
@@ -222,8 +236,8 @@ public class IpServerTest {
         when(mDependencies.getIpNeighborMonitor(any(), any(), any()))
                 .thenReturn(mIpNeighborMonitor);
         mIpServer = new IpServer(IFACE_NAME, mLooper.getLooper(), TETHERING_BLUETOOTH, mSharedLog,
-                mNetd, mCallback, false /* usingLegacyDhcp */, DEFAULT_USING_BPF_OFFLOAD,
+                mNetd, mBpfCoordinator, mCallback, false /* usingLegacyDhcp */,
-                mAddressCoordinator, mDependencies);
+                DEFAULT_USING_BPF_OFFLOAD, mAddressCoordinator, mDependencies);
         mIpServer.start();
         mLooper.dispatchAll();
         verify(mCallback).updateInterfaceState(
@@ -619,6 +633,10 @@ public class IpServerTest {
      * (actual: "android.net.TetherOffloadRuleParcel@8c827b0" or some such), but at least it does
      * work.
      *
+     * TODO: consider making the error message more readable by adding a method that catching the
+     * AssertionFailedError and throwing a new assertion with more details. See
+     * NetworkMonitorTest#verifyNetworkTested.
+     *
      * See ConnectivityServiceTest#assertRoutesAdded for an alternative approach which solves the
      * TooManyActualInvocations problem described above by forcing the caller of the custom assert
      * method to specify all expected invocations in one call. This is useful when the stable
@@ -658,6 +676,27 @@ public class IpServerTest {
         return argThat(new TetherOffloadRuleParcelMatcher(upstreamIfindex, dst, dstMac));
     }
 
+    private static Ipv6ForwardingRule makeForwardingRule(
+            int upstreamIfindex, @NonNull InetAddress dst, @NonNull MacAddress dstMac) {
+        return new Ipv6ForwardingRule(upstreamIfindex, TEST_IFACE_PARAMS.index,
+                (Inet6Address) dst, TEST_IFACE_PARAMS.macAddr, dstMac);
+    }
+
+    private TetherStatsParcel buildEmptyTetherStatsParcel(int ifIndex) {
+        TetherStatsParcel parcel = new TetherStatsParcel();
+        parcel.ifIndex = ifIndex;
+        return parcel;
+    }
+
+    private void resetNetdAndBpfCoordinator() throws Exception {
+        reset(mNetd, mBpfCoordinator);
+        when(mNetd.tetherOffloadGetStats()).thenReturn(new TetherStatsParcel[0]);
+        when(mNetd.tetherOffloadGetAndClearStats(UPSTREAM_IFINDEX))
+                .thenReturn(buildEmptyTetherStatsParcel(UPSTREAM_IFINDEX));
+        when(mNetd.tetherOffloadGetAndClearStats(UPSTREAM_IFINDEX2))
+                .thenReturn(buildEmptyTetherStatsParcel(UPSTREAM_IFINDEX2));
+    }
+
     @Test
     public void addRemoveipv6ForwardingRules() throws Exception {
         initTetheredStateMachine(TETHERING_WIFI, UPSTREAM_IFACE, false /* usingLegacyDhcp */,
@@ -675,75 +714,100 @@ public class IpServerTest {
         final MacAddress macA = MacAddress.fromString("00:00:00:00:00:0a");
         final MacAddress macB = MacAddress.fromString("11:22:33:00:00:0b");
 
-        reset(mNetd);
+        resetNetdAndBpfCoordinator();
+        verifyNoMoreInteractions(mBpfCoordinator, mNetd);
+
+        // TODO: Perhaps verify the interaction of tetherOffloadSetInterfaceQuota and
+        // tetherOffloadGetAndClearStats in netd while the rules are changed.
 
         // Events on other interfaces are ignored.
         recvNewNeigh(notMyIfindex, neighA, NUD_REACHABLE, macA);
-        verifyNoMoreInteractions(mNetd);
+        verifyNoMoreInteractions(mBpfCoordinator, mNetd);
 
         // Events on this interface are received and sent to netd.
         recvNewNeigh(myIfindex, neighA, NUD_REACHABLE, macA);
+        verify(mBpfCoordinator).tetherOffloadRuleAdd(
+                mIpServer, makeForwardingRule(UPSTREAM_IFINDEX, neighA, macA));
         verify(mNetd).tetherOffloadRuleAdd(matches(UPSTREAM_IFINDEX, neighA, macA));
-        reset(mNetd);
+        resetNetdAndBpfCoordinator();
 
         recvNewNeigh(myIfindex, neighB, NUD_REACHABLE, macB);
+        verify(mBpfCoordinator).tetherOffloadRuleAdd(
+                mIpServer, makeForwardingRule(UPSTREAM_IFINDEX, neighB, macB));
         verify(mNetd).tetherOffloadRuleAdd(matches(UPSTREAM_IFINDEX, neighB, macB));
-        reset(mNetd);
+        resetNetdAndBpfCoordinator();
 
         // Link-local and multicast neighbors are ignored.
         recvNewNeigh(myIfindex, neighLL, NUD_REACHABLE, macA);
-        verifyNoMoreInteractions(mNetd);
+        verifyNoMoreInteractions(mBpfCoordinator, mNetd);
         recvNewNeigh(myIfindex, neighMC, NUD_REACHABLE, macA);
-        verifyNoMoreInteractions(mNetd);
+        verifyNoMoreInteractions(mBpfCoordinator, mNetd);
 
         // A neighbor that is no longer valid causes the rule to be removed.
         // NUD_FAILED events do not have a MAC address.
         recvNewNeigh(myIfindex, neighA, NUD_FAILED, null);
+        verify(mBpfCoordinator).tetherOffloadRuleRemove(
+                mIpServer, makeForwardingRule(UPSTREAM_IFINDEX, neighA, macNull));
         verify(mNetd).tetherOffloadRuleRemove(matches(UPSTREAM_IFINDEX, neighA, macNull));
-        reset(mNetd);
+        resetNetdAndBpfCoordinator();
 
         // A neighbor that is deleted causes the rule to be removed.
         recvDelNeigh(myIfindex, neighB, NUD_STALE, macB);
+        verify(mBpfCoordinator).tetherOffloadRuleRemove(
+                mIpServer,  makeForwardingRule(UPSTREAM_IFINDEX, neighB, macNull));
         verify(mNetd).tetherOffloadRuleRemove(matches(UPSTREAM_IFINDEX, neighB, macNull));
-        reset(mNetd);
+        resetNetdAndBpfCoordinator();
 
-        // Upstream changes result in deleting and re-adding the rules.
+        // Upstream changes result in updating the rules.
         recvNewNeigh(myIfindex, neighA, NUD_REACHABLE, macA);
         recvNewNeigh(myIfindex, neighB, NUD_REACHABLE, macB);
-        reset(mNetd);
+        resetNetdAndBpfCoordinator();
 
         InOrder inOrder = inOrder(mNetd);
         LinkProperties lp = new LinkProperties();
         lp.setInterfaceName(UPSTREAM_IFACE2);
         dispatchTetherConnectionChanged(UPSTREAM_IFACE2, lp, -1);
-        inOrder.verify(mNetd).tetherOffloadRuleAdd(matches(UPSTREAM_IFINDEX2, neighA, macA));
+        verify(mBpfCoordinator).tetherOffloadRuleUpdate(mIpServer, UPSTREAM_IFINDEX2);
         inOrder.verify(mNetd).tetherOffloadRuleRemove(matches(UPSTREAM_IFINDEX, neighA, macA));
-        inOrder.verify(mNetd).tetherOffloadRuleAdd(matches(UPSTREAM_IFINDEX2, neighB, macB));
+        inOrder.verify(mNetd).tetherOffloadRuleAdd(matches(UPSTREAM_IFINDEX2, neighA, macA));
         inOrder.verify(mNetd).tetherOffloadRuleRemove(matches(UPSTREAM_IFINDEX, neighB, macB));
-        reset(mNetd);
+        inOrder.verify(mNetd).tetherOffloadRuleAdd(matches(UPSTREAM_IFINDEX2, neighB, macB));
+        resetNetdAndBpfCoordinator();
 
         // When the upstream is lost, rules are removed.
         dispatchTetherConnectionChanged(null, null, 0);
+        // Clear function is called two times by:
+        // - processMessage CMD_TETHER_CONNECTION_CHANGED for the upstream is lost.
+        // - processMessage CMD_IPV6_TETHER_UPDATE for the IPv6 upstream is lost.
+        // See dispatchTetherConnectionChanged.
+        verify(mBpfCoordinator, times(2)).tetherOffloadRuleClear(mIpServer);
         verify(mNetd).tetherOffloadRuleRemove(matches(UPSTREAM_IFINDEX2, neighA, macA));
         verify(mNetd).tetherOffloadRuleRemove(matches(UPSTREAM_IFINDEX2, neighB, macB));
-        reset(mNetd);
+        resetNetdAndBpfCoordinator();
 
         // If the upstream is IPv4-only, no rules are added.
         dispatchTetherConnectionChanged(UPSTREAM_IFACE);
-        reset(mNetd);
+        resetNetdAndBpfCoordinator();
         recvNewNeigh(myIfindex, neighA, NUD_REACHABLE, macA);
-        verifyNoMoreInteractions(mNetd);
+        // Clear function is called by #updateIpv6ForwardingRules for the IPv6 upstream is lost.
+        verify(mBpfCoordinator).tetherOffloadRuleClear(mIpServer);
+        verifyNoMoreInteractions(mBpfCoordinator, mNetd);
 
         // Rules can be added again once upstream IPv6 connectivity is available.
         lp.setInterfaceName(UPSTREAM_IFACE);
         dispatchTetherConnectionChanged(UPSTREAM_IFACE, lp, -1);
         recvNewNeigh(myIfindex, neighB, NUD_REACHABLE, macB);
+        verify(mBpfCoordinator).tetherOffloadRuleAdd(
+                mIpServer, makeForwardingRule(UPSTREAM_IFINDEX, neighB, macB));
         verify(mNetd).tetherOffloadRuleAdd(matches(UPSTREAM_IFINDEX, neighB, macB));
+        verify(mBpfCoordinator, never()).tetherOffloadRuleAdd(
+                mIpServer, makeForwardingRule(UPSTREAM_IFINDEX, neighA, macA));
         verify(mNetd, never()).tetherOffloadRuleAdd(matches(UPSTREAM_IFINDEX, neighA, macA));
 
         // If upstream IPv6 connectivity is lost, rules are removed.
-        reset(mNetd);
+        resetNetdAndBpfCoordinator();
         dispatchTetherConnectionChanged(UPSTREAM_IFACE, null, 0);
+        verify(mBpfCoordinator).tetherOffloadRuleClear(mIpServer);
         verify(mNetd).tetherOffloadRuleRemove(matches(UPSTREAM_IFINDEX, neighB, macB));
 
         // When the interface goes down, rules are removed.
@@ -751,15 +815,20 @@ public class IpServerTest {
         dispatchTetherConnectionChanged(UPSTREAM_IFACE, lp, -1);
         recvNewNeigh(myIfindex, neighA, NUD_REACHABLE, macA);
         recvNewNeigh(myIfindex, neighB, NUD_REACHABLE, macB);
+        verify(mBpfCoordinator).tetherOffloadRuleAdd(
+                mIpServer, makeForwardingRule(UPSTREAM_IFINDEX, neighA, macA));
         verify(mNetd).tetherOffloadRuleAdd(matches(UPSTREAM_IFINDEX, neighA, macA));
+        verify(mBpfCoordinator).tetherOffloadRuleAdd(
+                mIpServer, makeForwardingRule(UPSTREAM_IFINDEX, neighB, macB));
         verify(mNetd).tetherOffloadRuleAdd(matches(UPSTREAM_IFINDEX, neighB, macB));
-        reset(mNetd);
+        resetNetdAndBpfCoordinator();
 
         mIpServer.stop();
         mLooper.dispatchAll();
+        verify(mBpfCoordinator).tetherOffloadRuleClear(mIpServer);
         verify(mNetd).tetherOffloadRuleRemove(matches(UPSTREAM_IFINDEX, neighA, macA));
         verify(mNetd).tetherOffloadRuleRemove(matches(UPSTREAM_IFINDEX, neighB, macB));
-        reset(mNetd);
+        resetNetdAndBpfCoordinator();
     }
 
     @Test
@@ -769,35 +838,46 @@ public class IpServerTest {
         final MacAddress macA = MacAddress.fromString("00:00:00:00:00:0a");
         final MacAddress macNull = MacAddress.fromString("00:00:00:00:00:00");
 
-        reset(mNetd);
-
         // Expect that rules can be only added/removed when the BPF offload config is enabled.
-        // Note that the usingBpfOffload false case is not a realistic test case. Because IP
+        // Note that the BPF offload disabled case is not a realistic test case. Because IP
         // neighbor monitor doesn't start if BPF offload is disabled, there should have no
         // neighbor event listening. This is used for testing the protection check just in case.
-        // TODO: Perhaps remove this test once we don't need this check anymore.
+        // TODO: Perhaps remove the BPF offload disabled case test once this check isn't needed
-        for (boolean usingBpfOffload : new boolean[]{true, false}) {
+        // anymore.
+
+        // [1] Enable BPF offload.
+        // A neighbor that is added or deleted causes the rule to be added or removed.
         initTetheredStateMachine(TETHERING_WIFI, UPSTREAM_IFACE, false /* usingLegacyDhcp */,
-                    usingBpfOffload);
+                true /* usingBpfOffload */);
+        resetNetdAndBpfCoordinator();
 
-            // A neighbor is added.
         recvNewNeigh(myIfindex, neigh, NUD_REACHABLE, macA);
-            if (usingBpfOffload) {
+        verify(mBpfCoordinator).tetherOffloadRuleAdd(
+                mIpServer, makeForwardingRule(UPSTREAM_IFINDEX, neigh, macA));
         verify(mNetd).tetherOffloadRuleAdd(matches(UPSTREAM_IFINDEX, neigh, macA));
-            } else {
+        resetNetdAndBpfCoordinator();
-                verify(mNetd, never()).tetherOffloadRuleAdd(any());
-            }
-            reset(mNetd);
 
-            // A neighbor is deleted.
         recvDelNeigh(myIfindex, neigh, NUD_STALE, macA);
-            if (usingBpfOffload) {
+        verify(mBpfCoordinator).tetherOffloadRuleRemove(
+                mIpServer, makeForwardingRule(UPSTREAM_IFINDEX, neigh, macNull));
         verify(mNetd).tetherOffloadRuleRemove(matches(UPSTREAM_IFINDEX, neigh, macNull));
-            } else {
+        resetNetdAndBpfCoordinator();
+
+        // [2] Disable BPF offload.
+        // A neighbor that is added or deleted doesn’t cause the rule to be added or removed.
+        initTetheredStateMachine(TETHERING_WIFI, UPSTREAM_IFACE, false /* usingLegacyDhcp */,
+                false /* usingBpfOffload */);
+        resetNetdAndBpfCoordinator();
+
+        recvNewNeigh(myIfindex, neigh, NUD_REACHABLE, macA);
+        verify(mBpfCoordinator, never()).tetherOffloadRuleAdd(any(), any());
+        verify(mNetd, never()).tetherOffloadRuleAdd(any());
+        resetNetdAndBpfCoordinator();
+
+        recvDelNeigh(myIfindex, neigh, NUD_STALE, macA);
+        verify(mBpfCoordinator, never()).tetherOffloadRuleRemove(any(), any());
         verify(mNetd, never()).tetherOffloadRuleRemove(any());
-            }
+        resetNetdAndBpfCoordinator();
-            reset(mNetd);
-        }
     }
 
     @Test

packages/Tethering/tests/unit/src/com/android/networkstack/tethering/BpfCoordinatorTest.java

@@ -0,0 +1,246 @@
+/*
+ * 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.networkstack.tethering;
+
+import static android.net.NetworkStats.DEFAULT_NETWORK_NO;
+import static android.net.NetworkStats.METERED_NO;
+import static android.net.NetworkStats.ROAMING_NO;
+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.NetworkStats.UID_TETHERING;
+import static android.net.netstats.provider.NetworkStatsProvider.QUOTA_UNLIMITED;
+
+import static com.android.networkstack.tethering.BpfCoordinator
+        .DEFAULT_PERFORM_POLL_INTERVAL_MS;
+import static com.android.networkstack.tethering.BpfCoordinator.StatsType;
+import static com.android.networkstack.tethering.BpfCoordinator.StatsType.STATS_PER_IFACE;
+import static com.android.networkstack.tethering.BpfCoordinator.StatsType.STATS_PER_UID;
+
+import static junit.framework.Assert.assertNotNull;
+
+import static org.mockito.Matchers.anyString;
+import static org.mockito.Mockito.clearInvocations;
+import static org.mockito.Mockito.never;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
+
+import android.annotation.NonNull;
+import android.app.usage.NetworkStatsManager;
+import android.net.INetd;
+import android.net.NetworkStats;
+import android.net.TetherStatsParcel;
+import android.net.util.SharedLog;
+import android.os.Handler;
+import android.os.test.TestLooper;
+
+import androidx.test.filters.SmallTest;
+import androidx.test.runner.AndroidJUnit4;
+
+import com.android.testutils.TestableNetworkStatsProviderCbBinder;
+
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mockito.ArgumentCaptor;
+import org.mockito.Mock;
+import org.mockito.MockitoAnnotations;
+
+import java.util.ArrayList;
+
+@RunWith(AndroidJUnit4.class)
+@SmallTest
+public class BpfCoordinatorTest {
+    @Mock private NetworkStatsManager mStatsManager;
+    @Mock private INetd mNetd;
+    // Late init since methods must be called by the thread that created this object.
+    private TestableNetworkStatsProviderCbBinder mTetherStatsProviderCb;
+    private BpfCoordinator.BpfTetherStatsProvider mTetherStatsProvider;
+    private final ArgumentCaptor<ArrayList> mStringArrayCaptor =
+            ArgumentCaptor.forClass(ArrayList.class);
+    private final TestLooper mTestLooper = new TestLooper();
+    private BpfCoordinator.Dependencies mDeps =
+            new BpfCoordinator.Dependencies() {
+            @Override
+            int getPerformPollInterval() {
+                return DEFAULT_PERFORM_POLL_INTERVAL_MS;
+            }
+    };
+
+    @Before public void setUp() {
+        MockitoAnnotations.initMocks(this);
+    }
+
+    private void waitForIdle() {
+        mTestLooper.dispatchAll();
+    }
+
+    private void setupFunctioningNetdInterface() throws Exception {
+        when(mNetd.tetherOffloadGetStats()).thenReturn(new TetherStatsParcel[0]);
+    }
+
+    @NonNull
+    private BpfCoordinator makeBpfCoordinator() throws Exception {
+        BpfCoordinator coordinator = new BpfCoordinator(
+                new Handler(mTestLooper.getLooper()), mNetd, mStatsManager, new SharedLog("test"),
+                mDeps);
+        final ArgumentCaptor<BpfCoordinator.BpfTetherStatsProvider>
+                tetherStatsProviderCaptor =
+                ArgumentCaptor.forClass(BpfCoordinator.BpfTetherStatsProvider.class);
+        verify(mStatsManager).registerNetworkStatsProvider(anyString(),
+                tetherStatsProviderCaptor.capture());
+        mTetherStatsProvider = tetherStatsProviderCaptor.getValue();
+        assertNotNull(mTetherStatsProvider);
+        mTetherStatsProviderCb = new TestableNetworkStatsProviderCbBinder();
+        mTetherStatsProvider.setProviderCallbackBinder(mTetherStatsProviderCb);
+        return coordinator;
+    }
+
+    @NonNull
+    private static NetworkStats.Entry buildTestEntry(@NonNull StatsType how,
+            @NonNull String iface, long rxBytes, long rxPackets, long txBytes, long txPackets) {
+        return new NetworkStats.Entry(iface, how == STATS_PER_IFACE ? UID_ALL : UID_TETHERING,
+                SET_DEFAULT, TAG_NONE, METERED_NO, ROAMING_NO, DEFAULT_NETWORK_NO, rxBytes,
+                rxPackets, txBytes, txPackets, 0L);
+    }
+
+    @NonNull
+    private static TetherStatsParcel buildTestTetherStatsParcel(@NonNull Integer ifIndex,
+            long rxBytes, long rxPackets, long txBytes, long txPackets) {
+        final TetherStatsParcel parcel = new TetherStatsParcel();
+        parcel.ifIndex = ifIndex;
+        parcel.rxBytes = rxBytes;
+        parcel.rxPackets = rxPackets;
+        parcel.txBytes = txBytes;
+        parcel.txPackets = txPackets;
+        return parcel;
+    }
+
+    private void setTetherOffloadStatsList(TetherStatsParcel[] tetherStatsList) throws Exception {
+        when(mNetd.tetherOffloadGetStats()).thenReturn(tetherStatsList);
+        mTestLooper.moveTimeForward(DEFAULT_PERFORM_POLL_INTERVAL_MS);
+        waitForIdle();
+    }
+
+    @Test
+    public void testGetForwardedStats() throws Exception {
+        setupFunctioningNetdInterface();
+
+        final BpfCoordinator coordinator = makeBpfCoordinator();
+        coordinator.startPolling();
+
+        final String wlanIface = "wlan0";
+        final Integer wlanIfIndex = 100;
+        final String mobileIface = "rmnet_data0";
+        final Integer mobileIfIndex = 101;
+
+        // Add interface name to lookup table. In realistic case, the upstream interface name will
+        // be added by IpServer when IpServer has received with a new IPv6 upstream update event.
+        coordinator.addUpstreamNameToLookupTable(wlanIfIndex, wlanIface);
+        coordinator.addUpstreamNameToLookupTable(mobileIfIndex, mobileIface);
+
+        // [1] Both interface stats are changed.
+        // Setup the tether stats of wlan and mobile interface. Note that move forward the time of
+        // the looper to make sure the new tether stats has been updated by polling update thread.
+        setTetherOffloadStatsList(new TetherStatsParcel[] {
+                buildTestTetherStatsParcel(wlanIfIndex, 1000, 100, 2000, 200),
+                buildTestTetherStatsParcel(mobileIfIndex, 3000, 300, 4000, 400)});
+
+        final NetworkStats expectedIfaceStats = new NetworkStats(0L, 2)
+                .addEntry(buildTestEntry(STATS_PER_IFACE, wlanIface, 1000, 100, 2000, 200))
+                .addEntry(buildTestEntry(STATS_PER_IFACE, mobileIface, 3000, 300, 4000, 400));
+
+        final NetworkStats expectedUidStats = new NetworkStats(0L, 2)
+                .addEntry(buildTestEntry(STATS_PER_UID, wlanIface, 1000, 100, 2000, 200))
+                .addEntry(buildTestEntry(STATS_PER_UID, mobileIface, 3000, 300, 4000, 400));
+
+        // Force pushing stats update to verify the stats reported.
+        // TODO: Perhaps make #expectNotifyStatsUpdated to use test TetherStatsParcel object for
+        // verifying the notification.
+        mTetherStatsProvider.pushTetherStats();
+        mTetherStatsProviderCb.expectNotifyStatsUpdated(expectedIfaceStats, expectedUidStats);
+
+        // [2] Only one interface stats is changed.
+        // The tether stats of mobile interface is accumulated and The tether stats of wlan
+        // interface is the same.
+        setTetherOffloadStatsList(new TetherStatsParcel[] {
+                buildTestTetherStatsParcel(wlanIfIndex, 1000, 100, 2000, 200),
+                buildTestTetherStatsParcel(mobileIfIndex, 3010, 320, 4030, 440)});
+
+        final NetworkStats expectedIfaceStatsDiff = new NetworkStats(0L, 2)
+                .addEntry(buildTestEntry(STATS_PER_IFACE, wlanIface, 0, 0, 0, 0))
+                .addEntry(buildTestEntry(STATS_PER_IFACE, mobileIface, 10, 20, 30, 40));
+
+        final NetworkStats expectedUidStatsDiff = new NetworkStats(0L, 2)
+                .addEntry(buildTestEntry(STATS_PER_UID, wlanIface, 0, 0, 0, 0))
+                .addEntry(buildTestEntry(STATS_PER_UID, mobileIface, 10, 20, 30, 40));
+
+        // Force pushing stats update to verify that only diff of stats is reported.
+        mTetherStatsProvider.pushTetherStats();
+        mTetherStatsProviderCb.expectNotifyStatsUpdated(expectedIfaceStatsDiff,
+                expectedUidStatsDiff);
+
+        // [3] Stop coordinator.
+        // Shutdown the coordinator and clear the invocation history, especially the
+        // tetherOffloadGetStats() calls.
+        coordinator.stopPolling();
+        clearInvocations(mNetd);
+
+        // Verify the polling update thread stopped.
+        mTestLooper.moveTimeForward(DEFAULT_PERFORM_POLL_INTERVAL_MS);
+        waitForIdle();
+        verify(mNetd, never()).tetherOffloadGetStats();
+    }
+
+    @Test
+    public void testOnSetAlert() throws Exception {
+        setupFunctioningNetdInterface();
+
+        final BpfCoordinator coordinator = makeBpfCoordinator();
+        coordinator.startPolling();
+
+        final String mobileIface = "rmnet_data0";
+        final Integer mobileIfIndex = 100;
+        coordinator.addUpstreamNameToLookupTable(mobileIfIndex, mobileIface);
+
+        // Verify that set quota to 0 will immediately triggers a callback.
+        mTetherStatsProvider.onSetAlert(0);
+        waitForIdle();
+        mTetherStatsProviderCb.expectNotifyAlertReached();
+
+        // Verify that notifyAlertReached never fired if quota is not yet reached.
+        when(mNetd.tetherOffloadGetStats()).thenReturn(
+                new TetherStatsParcel[] {buildTestTetherStatsParcel(mobileIfIndex, 0, 0, 0, 0)});
+        mTetherStatsProvider.onSetAlert(100);
+        mTestLooper.moveTimeForward(DEFAULT_PERFORM_POLL_INTERVAL_MS);
+        waitForIdle();
+        mTetherStatsProviderCb.assertNoCallback();
+
+        // Verify that notifyAlertReached fired when quota is reached.
+        when(mNetd.tetherOffloadGetStats()).thenReturn(
+                new TetherStatsParcel[] {buildTestTetherStatsParcel(mobileIfIndex, 50, 0, 50, 0)});
+        mTestLooper.moveTimeForward(DEFAULT_PERFORM_POLL_INTERVAL_MS);
+        waitForIdle();
+        mTetherStatsProviderCb.expectNotifyAlertReached();
+
+        // Verify that set quota with UNLIMITED won't trigger any callback.
+        mTetherStatsProvider.onSetAlert(QUOTA_UNLIMITED);
+        mTestLooper.moveTimeForward(DEFAULT_PERFORM_POLL_INTERVAL_MS);
+        waitForIdle();
+        mTetherStatsProviderCb.assertNoCallback();
+    }
+}

packages/Tethering/tests/unit/src/com/android/networkstack/tethering/TetheringTest.java

@@ -203,6 +203,7 @@ public class TetheringTest {
     @Mock private ConnectivityManager mCm;
     @Mock private EthernetManager mEm;
     @Mock private TetheringNotificationUpdater mNotificationUpdater;
+    @Mock private BpfCoordinator mBpfCoordinator;
 
     private final MockIpServerDependencies mIpServerDependencies =
             spy(new MockIpServerDependencies());
@@ -336,6 +337,12 @@ public class TetheringTest {
             mIpv6CoordinatorNotifyList = null;
         }
 
+        @Override
+        public BpfCoordinator getBpfCoordinator(Handler handler, INetd netd,
+                SharedLog log, BpfCoordinator.Dependencies deps) {
+            return mBpfCoordinator;
+        }
+
         @Override
         public OffloadHardwareInterface getOffloadHardwareInterface(Handler h, SharedLog log) {
             return mOffloadHardwareInterface;