Change tethering file structure to respect its package name

Bug: 145099347
Test: atest TetheringTests
      atest CtsTetheringTest
Change-Id: I7401c550fbafd17a5ed2d925b5d0e17e358af467

Tethering/AndroidManifest.xml

@@ -43,7 +43,7 @@
         android:process="com.android.networkstack.process"
         android:extractNativeLibs="false"
         android:persistent="true">
-        <service android:name="com.android.server.connectivity.tethering.TetheringService"
+        <service android:name="com.android.networkstack.tethering.TetheringService"
                  android:permission="android.permission.MAINLINE_NETWORK_STACK"
                  android:exported="true">
             <intent-filter>

Tethering/AndroidManifest_InProcess.xml

@@ -22,7 +22,7 @@
           android:process="system">
     <uses-sdk android:minSdkVersion="29" android:targetSdkVersion="29" />
     <application>
-        <service android:name="com.android.server.connectivity.tethering.TetheringService"
+        <service android:name="com.android.networkstack.tethering.TetheringService"
                  android:process="system"
                  android:permission="android.permission.MAINLINE_NETWORK_STACK"
                  android:exported="true">

Tethering/proguard.flags

@@ -1,5 +1,5 @@
 # Keep class's integer static field for MessageUtils to parsing their name.
--keep class com.android.server.connectivity.tethering.Tethering$TetherMasterSM {
+-keep class com.android.networkstack.tethering.Tethering$TetherMasterSM {
     static final int CMD_*;
     static final int EVENT_*;
 }

Tethering/res/values/config.xml

@@ -87,7 +87,7 @@
                         TYPE_MOBILE_HIPRI is appended.
 
          For other changes applied to this list, now and in the future, see
-         com.android.server.connectivity.tethering.TetheringConfiguration.
+         com.android.networkstack.tethering.TetheringConfiguration.
 
          Note also: the order of this is important. The first upstream type
          for which a satisfying network exists is used.

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

@@ -0,0 +1,183 @@
+/*
+ * 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.TetheringManager.TETHERING_WIFI;
+
+import android.net.MacAddress;
+import android.net.TetheredClient;
+import android.net.TetheredClient.AddressInfo;
+import android.net.ip.IpServer;
+import android.net.wifi.WifiClient;
+import android.os.SystemClock;
+
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+import androidx.annotation.VisibleForTesting;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+
+/**
+ * Tracker for clients connected to downstreams.
+ *
+ * <p>This class is not thread safe, it is intended to be used only from the tethering handler
+ * thread.
+ */
+public class ConnectedClientsTracker {
+    private final Clock mClock;
+
+    @NonNull
+    private List<WifiClient> mLastWifiClients = Collections.emptyList();
+    @NonNull
+    private List<TetheredClient> mLastTetheredClients = Collections.emptyList();
+
+    @VisibleForTesting
+    static class Clock {
+        public long elapsedRealtime() {
+            return SystemClock.elapsedRealtime();
+        }
+    }
+
+    public ConnectedClientsTracker() {
+        this(new Clock());
+    }
+
+    @VisibleForTesting
+    ConnectedClientsTracker(Clock clock) {
+        mClock = clock;
+    }
+
+    /**
+     * Update the tracker with new connected clients.
+     *
+     * <p>The new list can be obtained through {@link #getLastTetheredClients()}.
+     * @param ipServers The IpServers used to assign addresses to clients.
+     * @param wifiClients The list of L2-connected WiFi clients. Null for no change since last
+     *                    update.
+     * @return True if the list of clients changed since the last calculation.
+     */
+    public boolean updateConnectedClients(
+            Iterable<IpServer> ipServers, @Nullable List<WifiClient> wifiClients) {
+        final long now = mClock.elapsedRealtime();
+
+        if (wifiClients != null) {
+            mLastWifiClients = wifiClients;
+        }
+        final Set<MacAddress> wifiClientMacs = getClientMacs(mLastWifiClients);
+
+        // Build the list of non-expired leases from all IpServers, grouped by mac address
+        final Map<MacAddress, TetheredClient> clientsMap = new HashMap<>();
+        for (IpServer server : ipServers) {
+            for (TetheredClient client : server.getAllLeases()) {
+                if (client.getTetheringType() == TETHERING_WIFI
+                        && !wifiClientMacs.contains(client.getMacAddress())) {
+                    // Skip leases of WiFi clients that are not (or no longer) L2-connected
+                    continue;
+                }
+                final TetheredClient prunedClient = pruneExpired(client, now);
+                if (prunedClient == null) continue; // All addresses expired
+
+                addLease(clientsMap, prunedClient);
+            }
+        }
+
+        // TODO: add IPv6 addresses from netlink
+
+        // Add connected WiFi clients that do not have any known address
+        for (MacAddress client : wifiClientMacs) {
+            if (clientsMap.containsKey(client)) continue;
+            clientsMap.put(client, new TetheredClient(
+                    client, Collections.emptyList() /* addresses */, TETHERING_WIFI));
+        }
+
+        final HashSet<TetheredClient> clients = new HashSet<>(clientsMap.values());
+        final boolean clientsChanged = clients.size() != mLastTetheredClients.size()
+                || !clients.containsAll(mLastTetheredClients);
+        mLastTetheredClients = Collections.unmodifiableList(new ArrayList<>(clients));
+        return clientsChanged;
+    }
+
+    private static void addLease(Map<MacAddress, TetheredClient> clientsMap, TetheredClient lease) {
+        final TetheredClient aggregateClient = clientsMap.getOrDefault(
+                lease.getMacAddress(), lease);
+        if (aggregateClient == lease) {
+            // This is the first lease with this mac address
+            clientsMap.put(lease.getMacAddress(), lease);
+            return;
+        }
+
+        // Only add the address info; this assumes that the tethering type is the same when the mac
+        // address is the same. If a client is connected through different tethering types with the
+        // same mac address, connected clients callbacks will report all of its addresses under only
+        // one of these tethering types. This keeps the API simple considering that such a scenario
+        // would really be a rare edge case.
+        clientsMap.put(lease.getMacAddress(), aggregateClient.addAddresses(lease));
+    }
+
+    /**
+     * Get the last list of tethered clients, as calculated in {@link #updateConnectedClients}.
+     *
+     * <p>The returned list is immutable.
+     */
+    @NonNull
+    public List<TetheredClient> getLastTetheredClients() {
+        return mLastTetheredClients;
+    }
+
+    private static boolean hasExpiredAddress(List<AddressInfo> addresses, long now) {
+        for (AddressInfo info : addresses) {
+            if (info.getExpirationTime() <= now) {
+                return true;
+            }
+        }
+        return false;
+    }
+
+    @Nullable
+    private static TetheredClient pruneExpired(TetheredClient client, long now) {
+        final List<AddressInfo> addresses = client.getAddresses();
+        if (addresses.size() == 0) return null;
+        if (!hasExpiredAddress(addresses, now)) return client;
+
+        final ArrayList<AddressInfo> newAddrs = new ArrayList<>(addresses.size() - 1);
+        for (AddressInfo info : addresses) {
+            if (info.getExpirationTime() > now) {
+                newAddrs.add(info);
+            }
+        }
+
+        if (newAddrs.size() == 0) {
+            return null;
+        }
+        return new TetheredClient(client.getMacAddress(), newAddrs, client.getTetheringType());
+    }
+
+    @NonNull
+    private static Set<MacAddress> getClientMacs(@NonNull List<WifiClient> clients) {
+        final Set<MacAddress> macs = new HashSet<>(clients.size());
+        for (WifiClient c : clients) {
+            macs.add(c.getMacAddress());
+        }
+        return macs;
+    }
+}

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

@@ -0,0 +1,674 @@
+/*
+ * Copyright (C) 2018 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.TetheringConstants.EXTRA_ADD_TETHER_TYPE;
+import static android.net.TetheringConstants.EXTRA_PROVISION_CALLBACK;
+import static android.net.TetheringConstants.EXTRA_RUN_PROVISION;
+import static android.net.TetheringManager.TETHERING_BLUETOOTH;
+import static android.net.TetheringManager.TETHERING_ETHERNET;
+import static android.net.TetheringManager.TETHERING_INVALID;
+import static android.net.TetheringManager.TETHERING_USB;
+import static android.net.TetheringManager.TETHERING_WIFI;
+import static android.net.TetheringManager.TETHER_ERROR_ENTITLEMENT_UNKNOWN;
+import static android.net.TetheringManager.TETHER_ERROR_NO_ERROR;
+import static android.net.TetheringManager.TETHER_ERROR_PROVISIONING_FAILED;
+
+import android.app.AlarmManager;
+import android.app.PendingIntent;
+import android.content.BroadcastReceiver;
+import android.content.ComponentName;
+import android.content.Context;
+import android.content.Intent;
+import android.content.IntentFilter;
+import android.net.util.SharedLog;
+import android.os.Bundle;
+import android.os.Handler;
+import android.os.Looper;
+import android.os.Message;
+import android.os.Parcel;
+import android.os.PersistableBundle;
+import android.os.ResultReceiver;
+import android.os.SystemClock;
+import android.os.SystemProperties;
+import android.provider.Settings;
+import android.telephony.CarrierConfigManager;
+import android.util.ArraySet;
+import android.util.SparseIntArray;
+
+import com.android.internal.annotations.VisibleForTesting;
+import com.android.internal.util.StateMachine;
+
+import java.io.PrintWriter;
+
+/**
+ * Re-check tethering provisioning for enabled downstream tether types.
+ * Reference TetheringManager.TETHERING_{@code *} for each tether type.
+ *
+ * All methods of this class must be accessed from the thread of tethering
+ * state machine.
+ * @hide
+ */
+public class EntitlementManager {
+    private static final String TAG = EntitlementManager.class.getSimpleName();
+    private static final boolean DBG = false;
+
+    @VisibleForTesting
+    protected static final String DISABLE_PROVISIONING_SYSPROP_KEY = "net.tethering.noprovisioning";
+    private static final String ACTION_PROVISIONING_ALARM =
+            "com.android.networkstack.tethering.PROVISIONING_RECHECK_ALARM";
+    private static final String EXTRA_SUBID = "subId";
+
+    private final ComponentName mSilentProvisioningService;
+    private static final int MS_PER_HOUR = 60 * 60 * 1000;
+    private static final int EVENT_START_PROVISIONING = 0;
+    private static final int EVENT_STOP_PROVISIONING = 1;
+    private static final int EVENT_UPSTREAM_CHANGED = 2;
+    private static final int EVENT_MAYBE_RUN_PROVISIONING = 3;
+    private static final int EVENT_GET_ENTITLEMENT_VALUE = 4;
+
+    // The ArraySet contains enabled downstream types, ex:
+    // {@link TetheringManager.TETHERING_WIFI}
+    // {@link TetheringManager.TETHERING_USB}
+    // {@link TetheringManager.TETHERING_BLUETOOTH}
+    private final ArraySet<Integer> mCurrentTethers;
+    private final Context mContext;
+    private final int mPermissionChangeMessageCode;
+    private final SharedLog mLog;
+    private final SparseIntArray mEntitlementCacheValue;
+    private final EntitlementHandler mHandler;
+    private final StateMachine mTetherMasterSM;
+    // Key: TetheringManager.TETHERING_*(downstream).
+    // Value: TetheringManager.TETHER_ERROR_{NO_ERROR or PROVISION_FAILED}(provisioning result).
+    private final SparseIntArray mCellularPermitted;
+    private PendingIntent mProvisioningRecheckAlarm;
+    private boolean mCellularUpstreamPermitted = true;
+    private boolean mUsingCellularAsUpstream = false;
+    private boolean mNeedReRunProvisioningUi = false;
+    private OnUiEntitlementFailedListener mListener;
+    private TetheringConfigurationFetcher mFetcher;
+
+    public EntitlementManager(Context ctx, StateMachine tetherMasterSM, SharedLog log,
+            int permissionChangeMessageCode) {
+
+        mContext = ctx;
+        mLog = log.forSubComponent(TAG);
+        mCurrentTethers = new ArraySet<Integer>();
+        mCellularPermitted = new SparseIntArray();
+        mEntitlementCacheValue = new SparseIntArray();
+        mTetherMasterSM = tetherMasterSM;
+        mPermissionChangeMessageCode = permissionChangeMessageCode;
+        final Handler masterHandler = tetherMasterSM.getHandler();
+        // Create entitlement's own handler which is associated with TetherMaster thread
+        // let all entitlement processes run in the same thread.
+        mHandler = new EntitlementHandler(masterHandler.getLooper());
+        mContext.registerReceiver(mReceiver, new IntentFilter(ACTION_PROVISIONING_ALARM),
+                null, mHandler);
+        mSilentProvisioningService = ComponentName.unflattenFromString(
+                mContext.getResources().getString(R.string.config_wifi_tether_enable));
+    }
+
+    public void setOnUiEntitlementFailedListener(final OnUiEntitlementFailedListener listener) {
+        mListener = listener;
+    }
+
+    /** Callback fired when UI entitlement failed. */
+    public interface OnUiEntitlementFailedListener {
+        /**
+         * Ui entitlement check fails in |downstream|.
+         *
+         * @param downstream tethering type from TetheringManager.TETHERING_{@code *}.
+         */
+        void onUiEntitlementFailed(int downstream);
+    }
+
+    public void setTetheringConfigurationFetcher(final TetheringConfigurationFetcher fetcher) {
+        mFetcher = fetcher;
+    }
+
+    /** Interface to fetch TetheringConfiguration. */
+    public interface TetheringConfigurationFetcher {
+        /**
+         * Fetch current tethering configuration. This will be called to ensure whether entitlement
+         * check is needed.
+         * @return TetheringConfiguration instance.
+         */
+        TetheringConfiguration fetchTetheringConfiguration();
+    }
+
+    /**
+     * Check if cellular upstream is permitted.
+     */
+    public boolean isCellularUpstreamPermitted() {
+        // If provisioning is required and EntitlementManager don't know any downstream,
+        // cellular upstream should not be allowed.
+        final TetheringConfiguration config = mFetcher.fetchTetheringConfiguration();
+        if (mCurrentTethers.size() == 0 && isTetherProvisioningRequired(config)) {
+            return false;
+        }
+        return mCellularUpstreamPermitted;
+    }
+
+    /**
+     * This is called when tethering starts.
+     * Launch provisioning app if upstream is cellular.
+     *
+     * @param downstreamType tethering type from TetheringManager.TETHERING_{@code *}
+     * @param showProvisioningUi a boolean indicating whether to show the
+     *        provisioning app UI if there is one.
+     */
+    public void startProvisioningIfNeeded(int downstreamType, boolean showProvisioningUi) {
+        mHandler.sendMessage(mHandler.obtainMessage(EVENT_START_PROVISIONING,
+                downstreamType, encodeBool(showProvisioningUi)));
+    }
+
+    private void handleStartProvisioningIfNeeded(int type, boolean showProvisioningUi) {
+        if (!isValidDownstreamType(type)) return;
+
+        if (!mCurrentTethers.contains(type)) mCurrentTethers.add(type);
+
+        final TetheringConfiguration config = mFetcher.fetchTetheringConfiguration();
+        if (isTetherProvisioningRequired(config)) {
+            // If provisioning is required and the result is not available yet,
+            // cellular upstream should not be allowed.
+            if (mCellularPermitted.size() == 0) {
+                mCellularUpstreamPermitted = false;
+            }
+            // If upstream is not cellular, provisioning app would not be launched
+            // till upstream change to cellular.
+            if (mUsingCellularAsUpstream) {
+                if (showProvisioningUi) {
+                    runUiTetherProvisioning(type, config.activeDataSubId);
+                } else {
+                    runSilentTetherProvisioning(type, config.activeDataSubId);
+                }
+                mNeedReRunProvisioningUi = false;
+            } else {
+                mNeedReRunProvisioningUi |= showProvisioningUi;
+            }
+        } else {
+            mCellularUpstreamPermitted = true;
+        }
+    }
+
+    /**
+     * Tell EntitlementManager that a given type of tethering has been disabled
+     *
+     * @param type tethering type from TetheringManager.TETHERING_{@code *}
+     */
+    public void stopProvisioningIfNeeded(int type) {
+        mHandler.sendMessage(mHandler.obtainMessage(EVENT_STOP_PROVISIONING, type, 0));
+    }
+
+    private void handleStopProvisioningIfNeeded(int type) {
+        if (!isValidDownstreamType(type)) return;
+
+        mCurrentTethers.remove(type);
+        // There are lurking bugs where the notion of "provisioning required" or
+        // "tethering supported" may change without without tethering being notified properly.
+        // Remove the mapping all the time no matter provisioning is required or not.
+        removeDownstreamMapping(type);
+    }
+
+    /**
+     * Notify EntitlementManager if upstream is cellular or not.
+     *
+     * @param isCellular whether tethering upstream is cellular.
+     */
+    public void notifyUpstream(boolean isCellular) {
+        mHandler.sendMessage(mHandler.obtainMessage(
+                EVENT_UPSTREAM_CHANGED, encodeBool(isCellular), 0));
+    }
+
+    private void handleNotifyUpstream(boolean isCellular) {
+        if (DBG) {
+            mLog.i("notifyUpstream: " + isCellular
+                    + ", mCellularUpstreamPermitted: " + mCellularUpstreamPermitted
+                    + ", mNeedReRunProvisioningUi: " + mNeedReRunProvisioningUi);
+        }
+        mUsingCellularAsUpstream = isCellular;
+
+        if (mUsingCellularAsUpstream) {
+            final TetheringConfiguration config = mFetcher.fetchTetheringConfiguration();
+            handleMaybeRunProvisioning(config);
+        }
+    }
+
+    /** Run provisioning if needed */
+    public void maybeRunProvisioning() {
+        mHandler.sendMessage(mHandler.obtainMessage(EVENT_MAYBE_RUN_PROVISIONING));
+    }
+
+    private void handleMaybeRunProvisioning(final TetheringConfiguration config) {
+        if (mCurrentTethers.size() == 0 || !isTetherProvisioningRequired(config)) {
+            return;
+        }
+
+        // Whenever any entitlement value changes, all downstreams will re-evaluate whether they
+        // are allowed. Therefore even if the silent check here ends in a failure and the UI later
+        // yields success, then the downstream that got a failure will re-evaluate as a result of
+        // the change and get the new correct value.
+        for (Integer downstream : mCurrentTethers) {
+            if (mCellularPermitted.indexOfKey(downstream) < 0) {
+                if (mNeedReRunProvisioningUi) {
+                    mNeedReRunProvisioningUi = false;
+                    runUiTetherProvisioning(downstream, config.activeDataSubId);
+                } else {
+                    runSilentTetherProvisioning(downstream, config.activeDataSubId);
+                }
+            }
+        }
+    }
+
+    /**
+     * Check if the device requires a provisioning check in order to enable tethering.
+     *
+     * @param config an object that encapsulates the various tethering configuration elements.
+     * @return a boolean - {@code true} indicating tether provisioning is required by the carrier.
+     */
+    @VisibleForTesting
+    protected boolean isTetherProvisioningRequired(final TetheringConfiguration config) {
+        if (SystemProperties.getBoolean(DISABLE_PROVISIONING_SYSPROP_KEY, false)
+                || config.provisioningApp.length == 0) {
+            return false;
+        }
+        if (carrierConfigAffirmsEntitlementCheckNotRequired(config)) {
+            return false;
+        }
+        return (config.provisioningApp.length == 2);
+    }
+
+    /**
+     * Re-check tethering provisioning for all enabled tether types.
+     * Reference TetheringManager.TETHERING_{@code *} for each tether type.
+     *
+     * @param config an object that encapsulates the various tethering configuration elements.
+     * Note: this method is only called from TetherMaster on the handler thread.
+     * If there are new callers from different threads, the logic should move to
+     * masterHandler to avoid race conditions.
+     */
+    public void reevaluateSimCardProvisioning(final TetheringConfiguration config) {
+        if (DBG) mLog.i("reevaluateSimCardProvisioning");
+
+        if (!mHandler.getLooper().isCurrentThread()) {
+            // Except for test, this log should not appear in normal flow.
+            mLog.log("reevaluateSimCardProvisioning() don't run in TetherMaster thread");
+        }
+        mEntitlementCacheValue.clear();
+        mCellularPermitted.clear();
+
+        // TODO: refine provisioning check to isTetherProvisioningRequired() ??
+        if (!config.hasMobileHotspotProvisionApp()
+                || carrierConfigAffirmsEntitlementCheckNotRequired(config)) {
+            evaluateCellularPermission(config);
+            return;
+        }
+
+        if (mUsingCellularAsUpstream) {
+            handleMaybeRunProvisioning(config);
+        }
+    }
+
+    /**
+     * Get carrier configuration bundle.
+     * @param config an object that encapsulates the various tethering configuration elements.
+     * */
+    public PersistableBundle getCarrierConfig(final TetheringConfiguration config) {
+        final CarrierConfigManager configManager = (CarrierConfigManager) mContext
+                .getSystemService(Context.CARRIER_CONFIG_SERVICE);
+        if (configManager == null) return null;
+
+        final PersistableBundle carrierConfig = configManager.getConfigForSubId(
+                config.activeDataSubId);
+
+        if (CarrierConfigManager.isConfigForIdentifiedCarrier(carrierConfig)) {
+            return carrierConfig;
+        }
+
+        return null;
+    }
+
+    // The logic here is aimed solely at confirming that a CarrierConfig exists
+    // and affirms that entitlement checks are not required.
+    //
+    // TODO: find a better way to express this, or alter the checking process
+    // entirely so that this is more intuitive.
+    private boolean carrierConfigAffirmsEntitlementCheckNotRequired(
+            final TetheringConfiguration config) {
+        // Check carrier config for entitlement checks
+        final PersistableBundle carrierConfig = getCarrierConfig(config);
+        if (carrierConfig == null) return false;
+
+        // A CarrierConfigManager was found and it has a config.
+        final boolean isEntitlementCheckRequired = carrierConfig.getBoolean(
+                CarrierConfigManager.KEY_REQUIRE_ENTITLEMENT_CHECKS_BOOL);
+        return !isEntitlementCheckRequired;
+    }
+
+    /**
+     * Run no UI tethering provisioning check.
+     * @param type tethering type from TetheringManager.TETHERING_{@code *}
+     * @param subId default data subscription ID.
+     */
+    @VisibleForTesting
+    protected void runSilentTetherProvisioning(int type, int subId) {
+        if (DBG) mLog.i("runSilentTetherProvisioning: " + type);
+        // For silent provisioning, settings would stop tethering when entitlement fail.
+        ResultReceiver receiver = buildProxyReceiver(type, false/* notifyFail */, null);
+
+        Intent intent = new Intent();
+        intent.putExtra(EXTRA_ADD_TETHER_TYPE, type);
+        intent.putExtra(EXTRA_RUN_PROVISION, true);
+        intent.putExtra(EXTRA_PROVISION_CALLBACK, receiver);
+        intent.putExtra(EXTRA_SUBID, subId);
+        intent.setComponent(mSilentProvisioningService);
+        // Only admin user can change tethering and SilentTetherProvisioning don't need to
+        // show UI, it is fine to always start setting's background service as system user.
+        mContext.startService(intent);
+    }
+
+    private void runUiTetherProvisioning(int type, int subId) {
+        ResultReceiver receiver = buildProxyReceiver(type, true/* notifyFail */, null);
+        runUiTetherProvisioning(type, subId, receiver);
+    }
+
+    /**
+     * Run the UI-enabled tethering provisioning check.
+     * @param type tethering type from TetheringManager.TETHERING_{@code *}
+     * @param subId default data subscription ID.
+     * @param receiver to receive entitlement check result.
+     */
+    @VisibleForTesting
+    protected void runUiTetherProvisioning(int type, int subId, ResultReceiver receiver) {
+        if (DBG) mLog.i("runUiTetherProvisioning: " + type);
+
+        Intent intent = new Intent(Settings.ACTION_TETHER_PROVISIONING_UI);
+        intent.putExtra(EXTRA_ADD_TETHER_TYPE, type);
+        intent.putExtra(EXTRA_PROVISION_CALLBACK, receiver);
+        intent.putExtra(EXTRA_SUBID, subId);
+        intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
+        // Only launch entitlement UI for system user. Entitlement UI should not appear for other
+        // user because only admin user is allowed to change tethering.
+        mContext.startActivity(intent);
+    }
+
+    // Not needed to check if this don't run on the handler thread because it's private.
+    private void scheduleProvisioningRechecks(final TetheringConfiguration config) {
+        if (mProvisioningRecheckAlarm == null) {
+            final int period = config.provisioningCheckPeriod;
+            if (period <= 0) return;
+
+            Intent intent = new Intent(ACTION_PROVISIONING_ALARM);
+            mProvisioningRecheckAlarm = PendingIntent.getBroadcast(mContext, 0, intent, 0);
+            AlarmManager alarmManager = (AlarmManager) mContext.getSystemService(
+                    Context.ALARM_SERVICE);
+            long periodMs = period * MS_PER_HOUR;
+            long firstAlarmTime = SystemClock.elapsedRealtime() + periodMs;
+            alarmManager.setRepeating(AlarmManager.ELAPSED_REALTIME, firstAlarmTime, periodMs,
+                    mProvisioningRecheckAlarm);
+        }
+    }
+
+    private void cancelTetherProvisioningRechecks() {
+        if (mProvisioningRecheckAlarm != null) {
+            AlarmManager alarmManager = (AlarmManager) mContext.getSystemService(
+                    Context.ALARM_SERVICE);
+            alarmManager.cancel(mProvisioningRecheckAlarm);
+            mProvisioningRecheckAlarm = null;
+        }
+    }
+
+    private void evaluateCellularPermission(final TetheringConfiguration config) {
+        final boolean oldPermitted = mCellularUpstreamPermitted;
+        mCellularUpstreamPermitted = (!isTetherProvisioningRequired(config)
+                || mCellularPermitted.indexOfValue(TETHER_ERROR_NO_ERROR) > -1);
+
+        if (DBG) {
+            mLog.i("Cellular permission change from " + oldPermitted
+                    + " to " + mCellularUpstreamPermitted);
+        }
+
+        if (mCellularUpstreamPermitted != oldPermitted) {
+            mLog.log("Cellular permission change: " + mCellularUpstreamPermitted);
+            mTetherMasterSM.sendMessage(mPermissionChangeMessageCode);
+        }
+        // Only schedule periodic re-check when tether is provisioned
+        // and the result is ok.
+        if (mCellularUpstreamPermitted && mCellularPermitted.size() > 0) {
+            scheduleProvisioningRechecks(config);
+        } else {
+            cancelTetherProvisioningRechecks();
+        }
+    }
+
+    /**
+     * Add the mapping between provisioning result and tethering type.
+     * Notify UpstreamNetworkMonitor if Cellular permission changes.
+     *
+     * @param type tethering type from TetheringManager.TETHERING_{@code *}
+     * @param resultCode Provisioning result
+     */
+    protected void addDownstreamMapping(int type, int resultCode) {
+        mLog.i("addDownstreamMapping: " + type + ", result: " + resultCode
+                + " ,TetherTypeRequested: " + mCurrentTethers.contains(type));
+        if (!mCurrentTethers.contains(type)) return;
+
+        mCellularPermitted.put(type, resultCode);
+        final TetheringConfiguration config = mFetcher.fetchTetheringConfiguration();
+        evaluateCellularPermission(config);
+    }
+
+    /**
+     * Remove the mapping for input tethering type.
+     * @param type tethering type from TetheringManager.TETHERING_{@code *}
+     */
+    protected void removeDownstreamMapping(int type) {
+        mLog.i("removeDownstreamMapping: " + type);
+        mCellularPermitted.delete(type);
+        final TetheringConfiguration config = mFetcher.fetchTetheringConfiguration();
+        evaluateCellularPermission(config);
+    }
+
+    private final BroadcastReceiver mReceiver = new BroadcastReceiver() {
+        @Override
+        public void onReceive(Context context, Intent intent) {
+            if (ACTION_PROVISIONING_ALARM.equals(intent.getAction())) {
+                mLog.log("Received provisioning alarm");
+                final TetheringConfiguration config = mFetcher.fetchTetheringConfiguration();
+                reevaluateSimCardProvisioning(config);
+            }
+        }
+    };
+
+    private class EntitlementHandler extends Handler {
+        EntitlementHandler(Looper looper) {
+            super(looper);
+        }
+
+        @Override
+        public void handleMessage(Message msg) {
+            switch (msg.what) {
+                case EVENT_START_PROVISIONING:
+                    handleStartProvisioningIfNeeded(msg.arg1, toBool(msg.arg2));
+                    break;
+                case EVENT_STOP_PROVISIONING:
+                    handleStopProvisioningIfNeeded(msg.arg1);
+                    break;
+                case EVENT_UPSTREAM_CHANGED:
+                    handleNotifyUpstream(toBool(msg.arg1));
+                    break;
+                case EVENT_MAYBE_RUN_PROVISIONING:
+                    final TetheringConfiguration config = mFetcher.fetchTetheringConfiguration();
+                    handleMaybeRunProvisioning(config);
+                    break;
+                case EVENT_GET_ENTITLEMENT_VALUE:
+                    handleRequestLatestTetheringEntitlementValue(msg.arg1,
+                            (ResultReceiver) msg.obj, toBool(msg.arg2));
+                    break;
+                default:
+                    mLog.log("Unknown event: " + msg.what);
+                    break;
+            }
+        }
+    }
+
+    private static boolean toBool(int encodedBoolean) {
+        return encodedBoolean != 0;
+    }
+
+    private static int encodeBool(boolean b) {
+        return b ? 1 : 0;
+    }
+
+    private static boolean isValidDownstreamType(int type) {
+        switch (type) {
+            case TETHERING_BLUETOOTH:
+            case TETHERING_ETHERNET:
+            case TETHERING_USB:
+            case TETHERING_WIFI:
+                return true;
+            default:
+                return false;
+        }
+    }
+
+    /**
+     * Dump the infromation of EntitlementManager.
+     * @param pw {@link PrintWriter} is used to print formatted
+     */
+    public void dump(PrintWriter pw) {
+        pw.print("mCellularUpstreamPermitted: ");
+        pw.println(mCellularUpstreamPermitted);
+        for (Integer type : mCurrentTethers) {
+            pw.print("Type: ");
+            pw.print(typeString(type));
+            if (mCellularPermitted.indexOfKey(type) > -1) {
+                pw.print(", Value: ");
+                pw.println(errorString(mCellularPermitted.get(type)));
+            } else {
+                pw.println(", Value: empty");
+            }
+        }
+    }
+
+    private static String typeString(int type) {
+        switch (type) {
+            case TETHERING_BLUETOOTH: return "TETHERING_BLUETOOTH";
+            case TETHERING_INVALID: return "TETHERING_INVALID";
+            case TETHERING_USB: return "TETHERING_USB";
+            case TETHERING_WIFI: return "TETHERING_WIFI";
+            default:
+                return String.format("TETHERING UNKNOWN TYPE (%d)", type);
+        }
+    }
+
+    private static String errorString(int value) {
+        switch (value) {
+            case TETHER_ERROR_ENTITLEMENT_UNKNOWN: return "TETHER_ERROR_ENTITLEMENT_UNKONWN";
+            case TETHER_ERROR_NO_ERROR: return "TETHER_ERROR_NO_ERROR";
+            case TETHER_ERROR_PROVISIONING_FAILED: return "TETHER_ERROR_PROVISIONING_FAILED";
+            default:
+                return String.format("UNKNOWN ERROR (%d)", value);
+        }
+    }
+
+    private ResultReceiver buildProxyReceiver(int type, boolean notifyFail,
+            final ResultReceiver receiver) {
+        ResultReceiver rr = new ResultReceiver(mHandler) {
+            @Override
+            protected void onReceiveResult(int resultCode, Bundle resultData) {
+                int updatedCacheValue = updateEntitlementCacheValue(type, resultCode);
+                addDownstreamMapping(type, updatedCacheValue);
+                if (updatedCacheValue == TETHER_ERROR_PROVISIONING_FAILED && notifyFail) {
+                    mListener.onUiEntitlementFailed(type);
+                }
+                if (receiver != null) receiver.send(updatedCacheValue, null);
+            }
+        };
+
+        return writeToParcel(rr);
+    }
+
+    // Instances of ResultReceiver need to be public classes for remote processes to be able
+    // to load them (otherwise, ClassNotFoundException). For private classes, this method
+    // performs a trick : round-trip parceling any instance of ResultReceiver will return a
+    // vanilla instance of ResultReceiver sharing the binder token with the original receiver.
+    // The binder token has a reference to the original instance of the private class and will
+    // still call its methods, and can be sent over. However it cannot be used for anything
+    // else than sending over a Binder call.
+    // While round-trip parceling is not great, there is currently no other way of generating
+    // a vanilla instance of ResultReceiver because all its fields are private.
+    private ResultReceiver writeToParcel(final ResultReceiver receiver) {
+        Parcel parcel = Parcel.obtain();
+        receiver.writeToParcel(parcel, 0);
+        parcel.setDataPosition(0);
+        ResultReceiver receiverForSending = ResultReceiver.CREATOR.createFromParcel(parcel);
+        parcel.recycle();
+        return receiverForSending;
+    }
+
+    /**
+     * Update the last entitlement value to internal cache
+     *
+     * @param type tethering type from TetheringManager.TETHERING_{@code *}
+     * @param resultCode last entitlement value
+     * @return the last updated entitlement value
+     */
+    private int updateEntitlementCacheValue(int type, int resultCode) {
+        if (DBG) {
+            mLog.i("updateEntitlementCacheValue: " + type + ", result: " + resultCode);
+        }
+        if (resultCode == TETHER_ERROR_NO_ERROR) {
+            mEntitlementCacheValue.put(type, resultCode);
+            return resultCode;
+        } else {
+            mEntitlementCacheValue.put(type, TETHER_ERROR_PROVISIONING_FAILED);
+            return TETHER_ERROR_PROVISIONING_FAILED;
+        }
+    }
+
+    /** Get the last value of the tethering entitlement check. */
+    public void requestLatestTetheringEntitlementResult(int downstream, ResultReceiver receiver,
+            boolean showEntitlementUi) {
+        mHandler.sendMessage(mHandler.obtainMessage(EVENT_GET_ENTITLEMENT_VALUE,
+                downstream, encodeBool(showEntitlementUi), receiver));
+
+    }
+
+    private void handleRequestLatestTetheringEntitlementValue(int downstream,
+            ResultReceiver receiver, boolean showEntitlementUi) {
+        if (!isValidDownstreamType(downstream)) {
+            receiver.send(TETHER_ERROR_ENTITLEMENT_UNKNOWN, null);
+            return;
+        }
+
+        final TetheringConfiguration config = mFetcher.fetchTetheringConfiguration();
+        if (!isTetherProvisioningRequired(config)) {
+            receiver.send(TETHER_ERROR_NO_ERROR, null);
+            return;
+        }
+
+        final int cacheValue = mEntitlementCacheValue.get(
+                downstream, TETHER_ERROR_ENTITLEMENT_UNKNOWN);
+        if (cacheValue == TETHER_ERROR_NO_ERROR || !showEntitlementUi) {
+            receiver.send(cacheValue, null);
+        } else {
+            ResultReceiver proxy = buildProxyReceiver(downstream, false/* notifyFail */, receiver);
+            runUiTetherProvisioning(downstream, config.activeDataSubId, proxy);
+        }
+    }
+}

Tethering/src/com/android/networkstack/tethering/IPv6TetheringCoordinator.java

@@ -0,0 +1,311 @@
+/*
+ * Copyright (C) 2016 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.networkstack.tethering;
+
+import android.net.IpPrefix;
+import android.net.LinkAddress;
+import android.net.LinkProperties;
+import android.net.Network;
+import android.net.NetworkCapabilities;
+import android.net.RouteInfo;
+import android.net.ip.IpServer;
+import android.net.util.NetworkConstants;
+import android.net.util.SharedLog;
+import android.util.Log;
+
+import java.net.Inet6Address;
+import java.net.InetAddress;
+import java.net.UnknownHostException;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.LinkedList;
+import java.util.Random;
+
+
+/**
+ * IPv6 tethering is rather different from IPv4 owing to the absence of NAT.
+ * This coordinator is responsible for evaluating the dedicated prefixes
+ * assigned to the device and deciding how to divvy them up among downstream
+ * interfaces.
+ *
+ * @hide
+ */
+public class IPv6TetheringCoordinator {
+    private static final String TAG = IPv6TetheringCoordinator.class.getSimpleName();
+    private static final boolean DBG = false;
+    private static final boolean VDBG = false;
+
+    private static class Downstream {
+        public final IpServer ipServer;
+        public final int mode;  // IpServer.STATE_*
+        // Used to append to a ULA /48, constructing a ULA /64 for local use.
+        public final short subnetId;
+
+        Downstream(IpServer ipServer, int mode, short subnetId) {
+            this.ipServer = ipServer;
+            this.mode = mode;
+            this.subnetId = subnetId;
+        }
+    }
+
+    private final ArrayList<IpServer> mNotifyList;
+    private final SharedLog mLog;
+    // NOTE: mActiveDownstreams is a list and not a hash data structure because
+    // we keep active downstreams in arrival order.  This is done so /64s can
+    // be parceled out on a "first come, first served" basis and a /64 used by
+    // a downstream that is no longer active can be redistributed to any next
+    // waiting active downstream (again, in arrival order).
+    private final LinkedList<Downstream> mActiveDownstreams;
+    private final byte[] mUniqueLocalPrefix;
+    private short mNextSubnetId;
+    private UpstreamNetworkState mUpstreamNetworkState;
+
+    public IPv6TetheringCoordinator(ArrayList<IpServer> notifyList, SharedLog log) {
+        mNotifyList = notifyList;
+        mLog = log.forSubComponent(TAG);
+        mActiveDownstreams = new LinkedList<>();
+        mUniqueLocalPrefix = generateUniqueLocalPrefix();
+        mNextSubnetId = 0;
+    }
+
+    /** Add active downstream to ipv6 tethering candidate list. */
+    public void addActiveDownstream(IpServer downstream, int mode) {
+        if (findDownstream(downstream) == null) {
+            // Adding a new downstream appends it to the list. Adding a
+            // downstream a second time without first removing it has no effect.
+            // We never change the mode of a downstream except by first removing
+            // it and then re-adding it (with its new mode specified);
+            if (mActiveDownstreams.offer(new Downstream(downstream, mode, mNextSubnetId))) {
+                // Make sure subnet IDs are always positive. They are appended
+                // to a ULA /48 to make a ULA /64 for local use.
+                mNextSubnetId = (short) Math.max(0, mNextSubnetId + 1);
+            }
+            updateIPv6TetheringInterfaces();
+        }
+    }
+
+    /** Remove downstream from ipv6 tethering candidate list. */
+    public void removeActiveDownstream(IpServer downstream) {
+        stopIPv6TetheringOn(downstream);
+        if (mActiveDownstreams.remove(findDownstream(downstream))) {
+            updateIPv6TetheringInterfaces();
+        }
+
+        // When tethering is stopping we can reset the subnet counter.
+        if (mNotifyList.isEmpty()) {
+            if (!mActiveDownstreams.isEmpty()) {
+                Log.wtf(TAG, "Tethering notify list empty, IPv6 downstreams non-empty.");
+            }
+            mNextSubnetId = 0;
+        }
+    }
+
+    /**
+     * Call when UpstreamNetworkState may be changed.
+     * If upstream has ipv6 for tethering, update this new UpstreamNetworkState
+     * to IpServer. Otherwise stop ipv6 tethering on downstream interfaces.
+     */
+    public void updateUpstreamNetworkState(UpstreamNetworkState ns) {
+        if (VDBG) {
+            Log.d(TAG, "updateUpstreamNetworkState: " + toDebugString(ns));
+        }
+        if (TetheringInterfaceUtils.getIPv6Interface(ns) == null) {
+            stopIPv6TetheringOnAllInterfaces();
+            setUpstreamNetworkState(null);
+            return;
+        }
+
+        if (mUpstreamNetworkState != null
+                && !ns.network.equals(mUpstreamNetworkState.network)) {
+            stopIPv6TetheringOnAllInterfaces();
+        }
+
+        setUpstreamNetworkState(ns);
+        updateIPv6TetheringInterfaces();
+    }
+
+    private void stopIPv6TetheringOnAllInterfaces() {
+        for (IpServer ipServer : mNotifyList) {
+            stopIPv6TetheringOn(ipServer);
+        }
+    }
+
+    private void setUpstreamNetworkState(UpstreamNetworkState ns) {
+        if (ns == null) {
+            mUpstreamNetworkState = null;
+        } else {
+            // Make a deep copy of the parts we need.
+            mUpstreamNetworkState = new UpstreamNetworkState(
+                    new LinkProperties(ns.linkProperties),
+                    new NetworkCapabilities(ns.networkCapabilities),
+                    new Network(ns.network));
+        }
+
+        mLog.log("setUpstreamNetworkState: " + toDebugString(mUpstreamNetworkState));
+    }
+
+    private void updateIPv6TetheringInterfaces() {
+        for (IpServer ipServer : mNotifyList) {
+            final LinkProperties lp = getInterfaceIPv6LinkProperties(ipServer);
+            ipServer.sendMessage(IpServer.CMD_IPV6_TETHER_UPDATE, 0, 0, lp);
+            break;
+        }
+    }
+
+    private LinkProperties getInterfaceIPv6LinkProperties(IpServer ipServer) {
+        final Downstream ds = findDownstream(ipServer);
+        if (ds == null) return null;
+
+        if (ds.mode == IpServer.STATE_LOCAL_ONLY) {
+            // Build a Unique Locally-assigned Prefix configuration.
+            return getUniqueLocalConfig(mUniqueLocalPrefix, ds.subnetId);
+        }
+
+        // This downstream is in IpServer.STATE_TETHERED mode.
+        if (mUpstreamNetworkState == null || mUpstreamNetworkState.linkProperties == null) {
+            return null;
+        }
+
+        // NOTE: Here, in future, we would have policies to decide how to divvy
+        // up the available dedicated prefixes among downstream interfaces.
+        // At this time we have no such mechanism--we only support tethering
+        // IPv6 toward the oldest (first requested) active downstream.
+
+        final Downstream currentActive = mActiveDownstreams.peek();
+        if (currentActive != null && currentActive.ipServer == ipServer) {
+            final LinkProperties lp = getIPv6OnlyLinkProperties(
+                    mUpstreamNetworkState.linkProperties);
+            if (lp.hasIpv6DefaultRoute() && lp.hasGlobalIpv6Address()) {
+                return lp;
+            }
+        }
+
+        return null;
+    }
+
+    Downstream findDownstream(IpServer ipServer) {
+        for (Downstream ds : mActiveDownstreams) {
+            if (ds.ipServer == ipServer) return ds;
+        }
+        return null;
+    }
+
+    private static LinkProperties getIPv6OnlyLinkProperties(LinkProperties lp) {
+        final LinkProperties v6only = new LinkProperties();
+        if (lp == null) {
+            return v6only;
+        }
+
+        // NOTE: At this time we don't copy over any information about any
+        // stacked links. No current stacked link configuration has IPv6.
+
+        v6only.setInterfaceName(lp.getInterfaceName());
+
+        v6only.setMtu(lp.getMtu());
+
+        for (LinkAddress linkAddr : lp.getLinkAddresses()) {
+            if (linkAddr.isGlobalPreferred() && linkAddr.getPrefixLength() == 64) {
+                v6only.addLinkAddress(linkAddr);
+            }
+        }
+
+        for (RouteInfo routeInfo : lp.getRoutes()) {
+            final IpPrefix destination = routeInfo.getDestination();
+            if ((destination.getAddress() instanceof Inet6Address)
+                    && (destination.getPrefixLength() <= 64)) {
+                v6only.addRoute(routeInfo);
+            }
+        }
+
+        for (InetAddress dnsServer : lp.getDnsServers()) {
+            if (isIPv6GlobalAddress(dnsServer)) {
+                // For now we include ULAs.
+                v6only.addDnsServer(dnsServer);
+            }
+        }
+
+        v6only.setDomains(lp.getDomains());
+
+        return v6only;
+    }
+
+    // TODO: Delete this and switch to LinkAddress#isGlobalPreferred once we
+    // announce our own IPv6 address as DNS server.
+    private static boolean isIPv6GlobalAddress(InetAddress ip) {
+        return (ip instanceof Inet6Address)
+               && !ip.isAnyLocalAddress()
+               && !ip.isLoopbackAddress()
+               && !ip.isLinkLocalAddress()
+               && !ip.isSiteLocalAddress()
+               && !ip.isMulticastAddress();
+    }
+
+    private static LinkProperties getUniqueLocalConfig(byte[] ulp, short subnetId) {
+        final LinkProperties lp = new LinkProperties();
+
+        final IpPrefix local48 = makeUniqueLocalPrefix(ulp, (short) 0, 48);
+        lp.addRoute(new RouteInfo(local48, null, null, RouteInfo.RTN_UNICAST));
+
+        final IpPrefix local64 = makeUniqueLocalPrefix(ulp, subnetId, 64);
+        // Because this is a locally-generated ULA, we don't have an upstream
+        // address. But because the downstream IP address management code gets
+        // its prefix from the upstream's IP address, we create a fake one here.
+        lp.addLinkAddress(new LinkAddress(local64.getAddress(), 64));
+
+        lp.setMtu(NetworkConstants.ETHER_MTU);
+        return lp;
+    }
+
+    private static IpPrefix makeUniqueLocalPrefix(byte[] in6addr, short subnetId, int prefixlen) {
+        final byte[] bytes = Arrays.copyOf(in6addr, in6addr.length);
+        bytes[7] = (byte) (subnetId >> 8);
+        bytes[8] = (byte) subnetId;
+        final InetAddress addr;
+        try {
+            addr = InetAddress.getByAddress(bytes);
+        } catch (UnknownHostException e) {
+            throw new IllegalStateException("Invalid address length: " + bytes.length, e);
+        }
+        return new IpPrefix(addr, prefixlen);
+    }
+
+    // Generates a Unique Locally-assigned Prefix:
+    //
+    //     https://tools.ietf.org/html/rfc4193#section-3.1
+    //
+    // The result is a /48 that can be used for local-only communications.
+    private static byte[] generateUniqueLocalPrefix() {
+        final byte[] ulp = new byte[6];  // 6 = 48bits / 8bits/byte
+        (new Random()).nextBytes(ulp);
+
+        final byte[] in6addr = Arrays.copyOf(ulp, NetworkConstants.IPV6_ADDR_LEN);
+        in6addr[0] = (byte) 0xfd;  // fc00::/7 and L=1
+
+        return in6addr;
+    }
+
+    private static String toDebugString(UpstreamNetworkState ns) {
+        if (ns == null) {
+            return "UpstreamNetworkState{null}";
+        }
+        return ns.toString();
+    }
+
+    private static void stopIPv6TetheringOn(IpServer ipServer) {
+        ipServer.sendMessage(IpServer.CMD_IPV6_TETHER_UPDATE, 0, 0, null);
+    }
+}

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

@@ -0,0 +1,721 @@
+/*
+ * Copyright (C) 2017 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.provider.Settings.Global.TETHER_OFFLOAD_DISABLED;
+
+import android.annotation.NonNull;
+import android.annotation.Nullable;
+import android.app.usage.NetworkStatsManager;
+import android.content.ContentResolver;
+import android.net.InetAddresses;
+import android.net.IpPrefix;
+import android.net.LinkAddress;
+import android.net.LinkProperties;
+import android.net.NetworkStats;
+import android.net.NetworkStats.Entry;
+import android.net.RouteInfo;
+import android.net.netlink.ConntrackMessage;
+import android.net.netlink.NetlinkConstants;
+import android.net.netlink.NetlinkSocket;
+import android.net.netstats.provider.NetworkStatsProvider;
+import android.net.util.SharedLog;
+import android.os.Handler;
+import android.provider.Settings;
+import android.system.ErrnoException;
+import android.system.OsConstants;
+import android.text.TextUtils;
+import android.util.Log;
+
+import com.android.internal.annotations.VisibleForTesting;
+import com.android.internal.util.IndentingPrintWriter;
+import com.android.networkstack.tethering.OffloadHardwareInterface.ForwardedStats;
+
+import java.net.Inet4Address;
+import java.net.Inet6Address;
+import java.net.InetAddress;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Map;
+import java.util.Objects;
+import java.util.Set;
+import java.util.concurrent.ConcurrentHashMap;
+
+/**
+ * A class to encapsulate the business logic of programming the tethering
+ * hardware offload interface.
+ *
+ * @hide
+ */
+public class OffloadController {
+    private static final String TAG = OffloadController.class.getSimpleName();
+    private static final boolean DBG = false;
+    private static final String ANYIP = "0.0.0.0";
+    private static final ForwardedStats EMPTY_STATS = new ForwardedStats();
+
+    @VisibleForTesting
+    enum StatsType {
+        STATS_PER_IFACE,
+        STATS_PER_UID,
+    }
+
+    private enum UpdateType { IF_NEEDED, FORCE };
+
+    private final Handler mHandler;
+    private final OffloadHardwareInterface mHwInterface;
+    private final ContentResolver mContentResolver;
+    @Nullable
+    private final OffloadTetheringStatsProvider mStatsProvider;
+    private final SharedLog mLog;
+    private final HashMap<String, LinkProperties> mDownstreams;
+    private boolean mConfigInitialized;
+    private boolean mControlInitialized;
+    private LinkProperties mUpstreamLinkProperties;
+    // The complete set of offload-exempt prefixes passed in via Tethering from
+    // all upstream and downstream sources.
+    private Set<IpPrefix> mExemptPrefixes;
+    // A strictly "smaller" set of prefixes, wherein offload-approved prefixes
+    // (e.g. downstream on-link prefixes) have been removed and replaced with
+    // prefixes representing only the locally-assigned IP addresses.
+    private Set<String> mLastLocalPrefixStrs;
+
+    // Maps upstream interface names to offloaded traffic statistics.
+    // Always contains the latest value received from the hardware for each interface, regardless of
+    // whether offload is currently running on that interface.
+    private ConcurrentHashMap<String, ForwardedStats> mForwardedStats =
+            new ConcurrentHashMap<>(16, 0.75F, 1);
+
+    // 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 upstream interfaces that have a quota set.
+    private HashMap<String, Long> mInterfaceQuotas = new HashMap<>();
+
+    private int mNatUpdateCallbacksReceived;
+    private int mNatUpdateNetlinkErrors;
+
+    public OffloadController(Handler h, OffloadHardwareInterface hwi,
+            ContentResolver contentResolver, NetworkStatsManager nsm, SharedLog log) {
+        mHandler = h;
+        mHwInterface = hwi;
+        mContentResolver = contentResolver;
+        mLog = log.forSubComponent(TAG);
+        mDownstreams = new HashMap<>();
+        mExemptPrefixes = new HashSet<>();
+        mLastLocalPrefixStrs = new HashSet<>();
+        OffloadTetheringStatsProvider provider = new OffloadTetheringStatsProvider();
+        try {
+            nsm.registerNetworkStatsProvider(getClass().getSimpleName(), provider);
+        } catch (RuntimeException e) {
+            Log.wtf(TAG, "Cannot register offload stats provider: " + e);
+            provider = null;
+        }
+        mStatsProvider = provider;
+    }
+
+    /** Start hardware offload. */
+    public boolean start() {
+        if (started()) return true;
+
+        if (isOffloadDisabled()) {
+            mLog.i("tethering offload disabled");
+            return false;
+        }
+
+        if (!mConfigInitialized) {
+            mConfigInitialized = mHwInterface.initOffloadConfig();
+            if (!mConfigInitialized) {
+                mLog.i("tethering offload config not supported");
+                stop();
+                return false;
+            }
+        }
+
+        mControlInitialized = mHwInterface.initOffloadControl(
+                // OffloadHardwareInterface guarantees that these callback
+                // methods are called on the handler passed to it, which is the
+                // same as mHandler, as coordinated by the setup in Tethering.
+                new OffloadHardwareInterface.ControlCallback() {
+                    @Override
+                    public void onStarted() {
+                        if (!started()) return;
+                        mLog.log("onStarted");
+                    }
+
+                    @Override
+                    public void onStoppedError() {
+                        if (!started()) return;
+                        mLog.log("onStoppedError");
+                    }
+
+                    @Override
+                    public void onStoppedUnsupported() {
+                        if (!started()) return;
+                        mLog.log("onStoppedUnsupported");
+                        // Poll for statistics and trigger a sweep of tethering
+                        // stats by observers. This might not succeed, but it's
+                        // worth trying anyway. We need to do this because from
+                        // this point on we continue with software forwarding,
+                        // and we need to synchronize stats and limits between
+                        // software and hardware forwarding.
+                        updateStatsForAllUpstreams();
+                        if (mStatsProvider != null) mStatsProvider.pushTetherStats();
+                    }
+
+                    @Override
+                    public void onSupportAvailable() {
+                        if (!started()) return;
+                        mLog.log("onSupportAvailable");
+
+                        // [1] Poll for statistics and trigger a sweep of stats
+                        // by observers. We need to do this to ensure that any
+                        // limits set take into account any software tethering
+                        // traffic that has been happening in the meantime.
+                        updateStatsForAllUpstreams();
+                        if (mStatsProvider != null) mStatsProvider.pushTetherStats();
+                        // [2] (Re)Push all state.
+                        computeAndPushLocalPrefixes(UpdateType.FORCE);
+                        pushAllDownstreamState();
+                        pushUpstreamParameters(null);
+                    }
+
+                    @Override
+                    public void onStoppedLimitReached() {
+                        if (!started()) return;
+                        mLog.log("onStoppedLimitReached");
+
+                        // We cannot reliably determine on which interface the limit was reached,
+                        // because the HAL interface does not specify it. We cannot just use the
+                        // current upstream, because that might have changed since the time that
+                        // the HAL queued the callback.
+                        // TODO: rev the HAL so that it provides an interface name.
+
+                        updateStatsForCurrentUpstream();
+                        if (mStatsProvider != null) {
+                            mStatsProvider.pushTetherStats();
+                            // Push stats to service does not cause the service react to it
+                            // immediately. Inform the service about limit reached.
+                            mStatsProvider.notifyLimitReached();
+                        }
+                    }
+
+                    @Override
+                    public void onNatTimeoutUpdate(int proto,
+                                                   String srcAddr, int srcPort,
+                                                   String dstAddr, int dstPort) {
+                        if (!started()) return;
+                        updateNatTimeout(proto, srcAddr, srcPort, dstAddr, dstPort);
+                    }
+                });
+
+        final boolean isStarted = started();
+        if (!isStarted) {
+            mLog.i("tethering offload control not supported");
+            stop();
+        } else {
+            mLog.log("tethering offload started");
+            mNatUpdateCallbacksReceived = 0;
+            mNatUpdateNetlinkErrors = 0;
+        }
+        return isStarted;
+    }
+
+    /** Stop hardware offload. */
+    public void stop() {
+        // Completely stops tethering offload. After this method is called, it is no longer safe to
+        // call any HAL method, no callbacks from the hardware will be delivered, and any in-flight
+        // callbacks must be ignored. Offload may be started again by calling start().
+        final boolean wasStarted = started();
+        updateStatsForCurrentUpstream();
+        mUpstreamLinkProperties = null;
+        mHwInterface.stopOffloadControl();
+        mControlInitialized = false;
+        mConfigInitialized = false;
+        if (wasStarted) mLog.log("tethering offload stopped");
+    }
+
+    private boolean started() {
+        return mConfigInitialized && mControlInitialized;
+    }
+
+    @VisibleForTesting
+    class OffloadTetheringStatsProvider extends NetworkStatsProvider {
+        // These stats must only ever be touched on the handler thread.
+        @NonNull
+        private NetworkStats mIfaceStats = new NetworkStats(0L, 0);
+        @NonNull
+        private NetworkStats mUidStats = new NetworkStats(0L, 0);
+
+        /**
+         * A helper function that collect tether stats from local hashmap. Note that this does not
+         * invoke binder call.
+         */
+        @VisibleForTesting
+        @NonNull
+        NetworkStats getTetherStats(@NonNull StatsType how) {
+            NetworkStats stats = new NetworkStats(0L, 0);
+            final int uid = (how == StatsType.STATS_PER_UID) ? UID_TETHERING : UID_ALL;
+
+            for (final Map.Entry<String, ForwardedStats> kv : mForwardedStats.entrySet()) {
+                final ForwardedStats value = kv.getValue();
+                final Entry entry = new Entry(kv.getKey(), uid, SET_DEFAULT, TAG_NONE, METERED_NO,
+                        ROAMING_NO, DEFAULT_NETWORK_NO, value.rxBytes, 0L, value.txBytes, 0L, 0L);
+                stats = stats.addEntry(entry);
+            }
+
+            return stats;
+        }
+
+        @Override
+        public void onSetLimit(String iface, long quotaBytes) {
+            // Listen for all iface is necessary since upstream might be changed after limit
+            // is set.
+            mHandler.post(() -> {
+                final Long curIfaceQuota = mInterfaceQuotas.get(iface);
+
+                // If the quota is set to unlimited, the value set to HAL is Long.MAX_VALUE,
+                // which is ~8.4 x 10^6 TiB, no one can actually reach it. Thus, it is not
+                // useful to set it multiple times.
+                // Otherwise, the quota needs to be updated to tell HAL to re-count from now even
+                // if the quota is the same as the existing one.
+                if (null == curIfaceQuota && QUOTA_UNLIMITED == quotaBytes) return;
+
+                if (quotaBytes == QUOTA_UNLIMITED) {
+                    mInterfaceQuotas.remove(iface);
+                } else {
+                    mInterfaceQuotas.put(iface, quotaBytes);
+                }
+                maybeUpdateDataLimit(iface);
+            });
+        }
+
+        /**
+         * Push stats to service, but does not cause a force polling. Note that this can only be
+         * called on the handler thread.
+         */
+        public void pushTetherStats() {
+            // TODO: remove the accumulated stats and report the diff from HAL directly.
+            final NetworkStats ifaceDiff =
+                    getTetherStats(StatsType.STATS_PER_IFACE).subtract(mIfaceStats);
+            final NetworkStats uidDiff =
+                    getTetherStats(StatsType.STATS_PER_UID).subtract(mUidStats);
+            try {
+                notifyStatsUpdated(0 /* token */, ifaceDiff, uidDiff);
+                mIfaceStats = mIfaceStats.add(ifaceDiff);
+                mUidStats = mUidStats.add(uidDiff);
+            } catch (RuntimeException e) {
+                mLog.e("Cannot report network stats: ", e);
+            }
+        }
+
+        @Override
+        public void onRequestStatsUpdate(int token) {
+            // Do not attempt to update stats by querying the offload HAL
+            // synchronously from a different thread than the Handler thread. http://b/64771555.
+            mHandler.post(() -> {
+                updateStatsForCurrentUpstream();
+                pushTetherStats();
+            });
+        }
+
+        @Override
+        public void onSetAlert(long quotaBytes) {
+            // TODO: Ask offload HAL to notify alert without stopping traffic.
+        }
+    }
+
+    private String currentUpstreamInterface() {
+        return (mUpstreamLinkProperties != null)
+                ? mUpstreamLinkProperties.getInterfaceName() : null;
+    }
+
+    private void maybeUpdateStats(String iface) {
+        if (TextUtils.isEmpty(iface)) {
+            return;
+        }
+
+        // Always called on the handler thread.
+        //
+        // Use get()/put() instead of updating ForwardedStats in place because we can be called
+        // concurrently with getTetherStats. In combination with the guarantees provided by
+        // ConcurrentHashMap, this ensures that getTetherStats always gets the most recent copy of
+        // the stats for each interface, and does not observe partial writes where rxBytes is
+        // updated and txBytes is not.
+        ForwardedStats diff = mHwInterface.getForwardedStats(iface);
+        ForwardedStats base = mForwardedStats.get(iface);
+        if (base != null) {
+            diff.add(base);
+        }
+        mForwardedStats.put(iface, diff);
+        // diff is a new object, just created by getForwardedStats(). Therefore, anyone reading from
+        // mForwardedStats (i.e., any caller of getTetherStats) will see the new stats immediately.
+    }
+
+    private boolean maybeUpdateDataLimit(String iface) {
+        // setDataLimit may only be called while offload is occurring on this upstream.
+        if (!started() || !TextUtils.equals(iface, currentUpstreamInterface())) {
+            return true;
+        }
+
+        Long limit = mInterfaceQuotas.get(iface);
+        if (limit == null) {
+            limit = Long.MAX_VALUE;
+        }
+
+        return mHwInterface.setDataLimit(iface, limit);
+    }
+
+    private void updateStatsForCurrentUpstream() {
+        maybeUpdateStats(currentUpstreamInterface());
+    }
+
+    private void updateStatsForAllUpstreams() {
+        // In practice, there should only ever be a single digit number of
+        // upstream interfaces over the lifetime of an active tethering session.
+        // Roughly speaking, imagine a very ambitious one or two of each of the
+        // following interface types: [ "rmnet_data", "wlan", "eth", "rndis" ].
+        for (Map.Entry<String, ForwardedStats> kv : mForwardedStats.entrySet()) {
+            maybeUpdateStats(kv.getKey());
+        }
+    }
+
+    /** Set current tethering upstream LinkProperties. */
+    public void setUpstreamLinkProperties(LinkProperties lp) {
+        if (!started() || Objects.equals(mUpstreamLinkProperties, lp)) return;
+
+        final String prevUpstream = currentUpstreamInterface();
+
+        mUpstreamLinkProperties = (lp != null) ? new LinkProperties(lp) : null;
+        // Make sure we record this interface in the ForwardedStats map.
+        final String iface = currentUpstreamInterface();
+        if (!TextUtils.isEmpty(iface)) mForwardedStats.putIfAbsent(iface, EMPTY_STATS);
+
+        // TODO: examine return code and decide what to do if programming
+        // upstream parameters fails (probably just wait for a subsequent
+        // onOffloadEvent() callback to tell us offload is available again and
+        // then reapply all state).
+        computeAndPushLocalPrefixes(UpdateType.IF_NEEDED);
+        pushUpstreamParameters(prevUpstream);
+    }
+
+    /** Set local prefixes. */
+    public void setLocalPrefixes(Set<IpPrefix> localPrefixes) {
+        mExemptPrefixes = localPrefixes;
+
+        if (!started()) return;
+        computeAndPushLocalPrefixes(UpdateType.IF_NEEDED);
+    }
+
+    /** Update current downstream LinkProperties. */
+    public void notifyDownstreamLinkProperties(LinkProperties lp) {
+        final String ifname = lp.getInterfaceName();
+        final LinkProperties oldLp = mDownstreams.put(ifname, new LinkProperties(lp));
+        if (Objects.equals(oldLp, lp)) return;
+
+        if (!started()) return;
+        pushDownstreamState(oldLp, lp);
+    }
+
+    private void pushDownstreamState(LinkProperties oldLp, LinkProperties newLp) {
+        final String ifname = newLp.getInterfaceName();
+        final List<RouteInfo> oldRoutes =
+                (oldLp != null) ? oldLp.getRoutes() : Collections.EMPTY_LIST;
+        final List<RouteInfo> newRoutes = newLp.getRoutes();
+
+        // For each old route, if not in new routes: remove.
+        for (RouteInfo ri : oldRoutes) {
+            if (shouldIgnoreDownstreamRoute(ri)) continue;
+            if (!newRoutes.contains(ri)) {
+                mHwInterface.removeDownstreamPrefix(ifname, ri.getDestination().toString());
+            }
+        }
+
+        // For each new route, if not in old routes: add.
+        for (RouteInfo ri : newRoutes) {
+            if (shouldIgnoreDownstreamRoute(ri)) continue;
+            if (!oldRoutes.contains(ri)) {
+                mHwInterface.addDownstreamPrefix(ifname, ri.getDestination().toString());
+            }
+        }
+    }
+
+    private void pushAllDownstreamState() {
+        for (LinkProperties lp : mDownstreams.values()) {
+            pushDownstreamState(null, lp);
+        }
+    }
+
+    /** Remove downstream interface from offload hardware. */
+    public void removeDownstreamInterface(String ifname) {
+        final LinkProperties lp = mDownstreams.remove(ifname);
+        if (lp == null) return;
+
+        if (!started()) return;
+
+        for (RouteInfo route : lp.getRoutes()) {
+            if (shouldIgnoreDownstreamRoute(route)) continue;
+            mHwInterface.removeDownstreamPrefix(ifname, route.getDestination().toString());
+        }
+    }
+
+    private boolean isOffloadDisabled() {
+        final int defaultDisposition = mHwInterface.getDefaultTetherOffloadDisabled();
+        return (Settings.Global.getInt(
+                mContentResolver, TETHER_OFFLOAD_DISABLED, defaultDisposition) != 0);
+    }
+
+    private boolean pushUpstreamParameters(String prevUpstream) {
+        final String iface = currentUpstreamInterface();
+
+        if (TextUtils.isEmpty(iface)) {
+            final boolean rval = mHwInterface.setUpstreamParameters("", ANYIP, ANYIP, null);
+            // Update stats after we've told the hardware to stop forwarding so
+            // we don't miss packets.
+            maybeUpdateStats(prevUpstream);
+            return rval;
+        }
+
+        // A stacked interface cannot be an upstream for hardware offload.
+        // Consequently, we examine only the primary interface name, look at
+        // getAddresses() rather than getAllAddresses(), and check getRoutes()
+        // rather than getAllRoutes().
+        final ArrayList<String> v6gateways = new ArrayList<>();
+        String v4addr = null;
+        String v4gateway = null;
+
+        for (InetAddress ip : mUpstreamLinkProperties.getAddresses()) {
+            if (ip instanceof Inet4Address) {
+                v4addr = ip.getHostAddress();
+                break;
+            }
+        }
+
+        // Find the gateway addresses of all default routes of either address family.
+        for (RouteInfo ri : mUpstreamLinkProperties.getRoutes()) {
+            if (!ri.hasGateway()) continue;
+
+            final String gateway = ri.getGateway().getHostAddress();
+            final InetAddress address = ri.getDestination().getAddress();
+            if (ri.isDefaultRoute() && address instanceof Inet4Address) {
+                v4gateway = gateway;
+            } else if (ri.isDefaultRoute() && address instanceof Inet6Address) {
+                v6gateways.add(gateway);
+            }
+        }
+
+        boolean success = mHwInterface.setUpstreamParameters(
+                iface, v4addr, v4gateway, (v6gateways.isEmpty() ? null : v6gateways));
+
+        if (!success) {
+            return success;
+        }
+
+        // Update stats after we've told the hardware to change routing so we don't miss packets.
+        maybeUpdateStats(prevUpstream);
+
+        // Data limits can only be set once offload is running on the upstream.
+        success = maybeUpdateDataLimit(iface);
+        if (!success) {
+            // If we failed to set a data limit, don't use this upstream, because we don't want to
+            // blow through the data limit that we were told to apply.
+            mLog.log("Setting data limit for " + iface + " failed, disabling offload.");
+            stop();
+        }
+
+        return success;
+    }
+
+    private boolean computeAndPushLocalPrefixes(UpdateType how) {
+        final boolean force = (how == UpdateType.FORCE);
+        final Set<String> localPrefixStrs = computeLocalPrefixStrings(
+                mExemptPrefixes, mUpstreamLinkProperties);
+        if (!force && mLastLocalPrefixStrs.equals(localPrefixStrs)) return true;
+
+        mLastLocalPrefixStrs = localPrefixStrs;
+        return mHwInterface.setLocalPrefixes(new ArrayList<>(localPrefixStrs));
+    }
+
+    // TODO: Factor in downstream LinkProperties once that information is available.
+    private static Set<String> computeLocalPrefixStrings(
+            Set<IpPrefix> localPrefixes, LinkProperties upstreamLinkProperties) {
+        // Create an editable copy.
+        final Set<IpPrefix> prefixSet = new HashSet<>(localPrefixes);
+
+        // TODO: If a downstream interface (not currently passed in) is reusing
+        // the /64 of the upstream (64share) then:
+        //
+        //     [a] remove that /64 from the local prefixes
+        //     [b] add in /128s for IP addresses on the downstream interface
+        //     [c] add in /128s for IP addresses on the upstream interface
+        //
+        // Until downstream information is available here, simply add /128s from
+        // the upstream network; they'll just be redundant with their /64.
+        if (upstreamLinkProperties != null) {
+            for (LinkAddress linkAddr : upstreamLinkProperties.getLinkAddresses()) {
+                if (!linkAddr.isGlobalPreferred()) continue;
+                final InetAddress ip = linkAddr.getAddress();
+                if (!(ip instanceof Inet6Address)) continue;
+                prefixSet.add(new IpPrefix(ip, 128));
+            }
+        }
+
+        final HashSet<String> localPrefixStrs = new HashSet<>();
+        for (IpPrefix pfx : prefixSet) localPrefixStrs.add(pfx.toString());
+        return localPrefixStrs;
+    }
+
+    private static boolean shouldIgnoreDownstreamRoute(RouteInfo route) {
+        // Ignore any link-local routes.
+        final IpPrefix destination = route.getDestination();
+        final LinkAddress linkAddr = new LinkAddress(destination.getAddress(),
+                destination.getPrefixLength());
+        if (!linkAddr.isGlobalPreferred()) return true;
+
+        return false;
+    }
+
+    /** Dump information. */
+    public void dump(IndentingPrintWriter pw) {
+        if (isOffloadDisabled()) {
+            pw.println("Offload disabled");
+            return;
+        }
+        final boolean isStarted = started();
+        pw.println("Offload HALs " + (isStarted ? "started" : "not started"));
+        LinkProperties lp = mUpstreamLinkProperties;
+        String upstream = (lp != null) ? lp.getInterfaceName() : null;
+        pw.println("Current upstream: " + upstream);
+        pw.println("Exempt prefixes: " + mLastLocalPrefixStrs);
+        pw.println("NAT timeout update callbacks received during the "
+                + (isStarted ? "current" : "last")
+                + " offload session: "
+                + mNatUpdateCallbacksReceived);
+        pw.println("NAT timeout update netlink errors during the "
+                + (isStarted ? "current" : "last")
+                + " offload session: "
+                + mNatUpdateNetlinkErrors);
+    }
+
+    private void updateNatTimeout(
+            int proto, String srcAddr, int srcPort, String dstAddr, int dstPort) {
+        final String protoName = protoNameFor(proto);
+        if (protoName == null) {
+            mLog.e("Unknown NAT update callback protocol: " + proto);
+            return;
+        }
+
+        final Inet4Address src = parseIPv4Address(srcAddr);
+        if (src == null) {
+            mLog.e("Failed to parse IPv4 address: " + srcAddr);
+            return;
+        }
+
+        if (!isValidUdpOrTcpPort(srcPort)) {
+            mLog.e("Invalid src port: " + srcPort);
+            return;
+        }
+
+        final Inet4Address dst = parseIPv4Address(dstAddr);
+        if (dst == null) {
+            mLog.e("Failed to parse IPv4 address: " + dstAddr);
+            return;
+        }
+
+        if (!isValidUdpOrTcpPort(dstPort)) {
+            mLog.e("Invalid dst port: " + dstPort);
+            return;
+        }
+
+        mNatUpdateCallbacksReceived++;
+        final String natDescription = String.format("%s (%s, %s) -> (%s, %s)",
+                protoName, srcAddr, srcPort, dstAddr, dstPort);
+        if (DBG) {
+            mLog.log("NAT timeout update: " + natDescription);
+        }
+
+        final int timeoutSec = connectionTimeoutUpdateSecondsFor(proto);
+        final byte[] msg = ConntrackMessage.newIPv4TimeoutUpdateRequest(
+                proto, src, srcPort, dst, dstPort, timeoutSec);
+
+        try {
+            NetlinkSocket.sendOneShotKernelMessage(OsConstants.NETLINK_NETFILTER, msg);
+        } catch (ErrnoException e) {
+            mNatUpdateNetlinkErrors++;
+            mLog.e("Error updating NAT conntrack entry >" + natDescription + "<: " + e
+                    + ", msg: " + NetlinkConstants.hexify(msg));
+            mLog.log("NAT timeout update callbacks received: " + mNatUpdateCallbacksReceived);
+            mLog.log("NAT timeout update netlink errors: " + mNatUpdateNetlinkErrors);
+        }
+    }
+
+    private static Inet4Address parseIPv4Address(String addrString) {
+        try {
+            final InetAddress ip = InetAddresses.parseNumericAddress(addrString);
+            // TODO: Consider other sanitization steps here, including perhaps:
+            //           not eql to 0.0.0.0
+            //           not within 169.254.0.0/16
+            //           not within ::ffff:0.0.0.0/96
+            //           not within ::/96
+            // et cetera.
+            if (ip instanceof Inet4Address) {
+                return (Inet4Address) ip;
+            }
+        } catch (IllegalArgumentException iae) { }
+        return null;
+    }
+
+    private static String protoNameFor(int proto) {
+        // OsConstants values are not constant expressions; no switch statement.
+        if (proto == OsConstants.IPPROTO_UDP) {
+            return "UDP";
+        } else if (proto == OsConstants.IPPROTO_TCP) {
+            return "TCP";
+        }
+        return null;
+    }
+
+    private static int connectionTimeoutUpdateSecondsFor(int proto) {
+        // TODO: Replace this with more thoughtful work, perhaps reading from
+        // and maybe writing to any required
+        //
+        //     /proc/sys/net/netfilter/nf_conntrack_tcp_timeout_*
+        //     /proc/sys/net/netfilter/nf_conntrack_udp_timeout{,_stream}
+        //
+        // entries.  TBD.
+        if (proto == OsConstants.IPPROTO_TCP) {
+            // Cf. /proc/sys/net/netfilter/nf_conntrack_tcp_timeout_established
+            return 432000;
+        } else {
+            // Cf. /proc/sys/net/netfilter/nf_conntrack_udp_timeout_stream
+            return 180;
+        }
+    }
+
+    private static boolean isValidUdpOrTcpPort(int port) {
+        return port > 0 && port < 65536;
+    }
+}

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

@@ -0,0 +1,509 @@
+/*
+ * Copyright (C) 2017 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.util.TetheringUtils.uint16;
+
+import android.hardware.tetheroffload.config.V1_0.IOffloadConfig;
+import android.hardware.tetheroffload.control.V1_0.IOffloadControl;
+import android.hardware.tetheroffload.control.V1_0.ITetheringOffloadCallback;
+import android.hardware.tetheroffload.control.V1_0.NatTimeoutUpdate;
+import android.hardware.tetheroffload.control.V1_0.NetworkProtocol;
+import android.hardware.tetheroffload.control.V1_0.OffloadCallbackEvent;
+import android.net.netlink.NetlinkSocket;
+import android.net.util.SharedLog;
+import android.net.util.SocketUtils;
+import android.os.Handler;
+import android.os.NativeHandle;
+import android.os.RemoteException;
+import android.system.ErrnoException;
+import android.system.Os;
+import android.system.OsConstants;
+
+import com.android.internal.annotations.VisibleForTesting;
+
+import java.io.FileDescriptor;
+import java.io.IOException;
+import java.net.SocketAddress;
+import java.net.SocketException;
+import java.util.ArrayList;
+
+
+/**
+ * Capture tethering dependencies, for injection.
+ *
+ * @hide
+ */
+public class OffloadHardwareInterface {
+    private static final String TAG = OffloadHardwareInterface.class.getSimpleName();
+    private static final String YIELDS = " -> ";
+    // Change this value to control whether tether offload is enabled or
+    // disabled by default in the absence of an explicit Settings value.
+    // See accompanying unittest to distinguish 0 from non-0 values.
+    private static final int DEFAULT_TETHER_OFFLOAD_DISABLED = 0;
+    private static final String NO_INTERFACE_NAME = "";
+    private static final String NO_IPV4_ADDRESS = "";
+    private static final String NO_IPV4_GATEWAY = "";
+    // Reference kernel/uapi/linux/netfilter/nfnetlink_compat.h
+    private static final int NF_NETLINK_CONNTRACK_NEW = 1;
+    private static final int NF_NETLINK_CONNTRACK_UPDATE = 2;
+    private static final int NF_NETLINK_CONNTRACK_DESTROY = 4;
+
+    private final Handler mHandler;
+    private final SharedLog mLog;
+    private IOffloadControl mOffloadControl;
+    private TetheringOffloadCallback mTetheringOffloadCallback;
+    private ControlCallback mControlCallback;
+
+    /** The callback to notify status of offload management process. */
+    public static class ControlCallback {
+        /** Offload started. */
+        public void onStarted() {}
+        /**
+         * Offload stopped because an error has occurred in lower layer.
+         */
+        public void onStoppedError() {}
+        /**
+         * Offload stopped because the device has moved to a bearer on which hardware offload is
+         * not supported. Subsequent calls to setUpstreamParameters and add/removeDownstream will
+         * likely fail and cannot be presumed to be saved inside of the hardware management process.
+         * Upon receiving #onSupportAvailable(), the caller should reprogram the hardware to begin
+         * offload again.
+         */
+        public void onStoppedUnsupported() {}
+        /** Indicate that offload is able to proivde support for this time. */
+        public void onSupportAvailable() {}
+        /** Offload stopped because of usage limit reached. */
+        public void onStoppedLimitReached() {}
+
+        /** Indicate to update NAT timeout. */
+        public void onNatTimeoutUpdate(int proto,
+                                       String srcAddr, int srcPort,
+                                       String dstAddr, int dstPort) {}
+    }
+
+    /** The object which records Tx/Rx forwarded bytes. */
+    public static class ForwardedStats {
+        public long rxBytes;
+        public long txBytes;
+
+        public ForwardedStats() {
+            rxBytes = 0;
+            txBytes = 0;
+        }
+
+        @VisibleForTesting
+        public ForwardedStats(long rxBytes, long txBytes) {
+            this.rxBytes = rxBytes;
+            this.txBytes = txBytes;
+        }
+
+        /** Add Tx/Rx bytes. */
+        public void add(ForwardedStats other) {
+            rxBytes += other.rxBytes;
+            txBytes += other.txBytes;
+        }
+
+        /** Returns the string representation of this object. */
+        public String toString() {
+            return String.format("rx:%s tx:%s", rxBytes, txBytes);
+        }
+    }
+
+    public OffloadHardwareInterface(Handler h, SharedLog log) {
+        mHandler = h;
+        mLog = log.forSubComponent(TAG);
+    }
+
+    /** Get default value indicating whether offload is supported. */
+    public int getDefaultTetherOffloadDisabled() {
+        return DEFAULT_TETHER_OFFLOAD_DISABLED;
+    }
+
+    /**
+     * Offload management process need to know conntrack rules to support NAT, but it may not have
+     * permission to create netlink netfilter sockets. Create two netlink netfilter sockets and
+     * share them with offload management process.
+     */
+    public boolean initOffloadConfig() {
+        IOffloadConfig offloadConfig;
+        try {
+            offloadConfig = IOffloadConfig.getService();
+        } catch (RemoteException e) {
+            mLog.e("getIOffloadConfig error " + e);
+            return false;
+        }
+        if (offloadConfig == null) {
+            mLog.e("Could not find IOffloadConfig service");
+            return false;
+        }
+        // Per the IConfigOffload definition:
+        //
+        // h1    provides a file descriptor bound to the following netlink groups
+        //       (NF_NETLINK_CONNTRACK_NEW | NF_NETLINK_CONNTRACK_DESTROY).
+        //
+        // h2    provides a file descriptor bound to the following netlink groups
+        //       (NF_NETLINK_CONNTRACK_UPDATE | NF_NETLINK_CONNTRACK_DESTROY).
+        final NativeHandle h1 = createConntrackSocket(
+                NF_NETLINK_CONNTRACK_NEW | NF_NETLINK_CONNTRACK_DESTROY);
+        if (h1 == null) return false;
+
+        final NativeHandle h2 = createConntrackSocket(
+                NF_NETLINK_CONNTRACK_UPDATE | NF_NETLINK_CONNTRACK_DESTROY);
+        if (h2 == null) {
+            closeFdInNativeHandle(h1);
+            return false;
+        }
+
+        final CbResults results = new CbResults();
+        try {
+            offloadConfig.setHandles(h1, h2,
+                    (boolean success, String errMsg) -> {
+                        results.mSuccess = success;
+                        results.mErrMsg = errMsg;
+                    });
+        } catch (RemoteException e) {
+            record("initOffloadConfig, setHandles fail", e);
+            return false;
+        }
+        // Explicitly close FDs.
+        closeFdInNativeHandle(h1);
+        closeFdInNativeHandle(h2);
+
+        record("initOffloadConfig, setHandles results:", results);
+        return results.mSuccess;
+    }
+
+    private void closeFdInNativeHandle(final NativeHandle h) {
+        try {
+            h.close();
+        } catch (IOException | IllegalStateException e) {
+            // IllegalStateException means fd is already closed, do nothing here.
+            // Also nothing we can do if IOException.
+        }
+    }
+
+    private NativeHandle createConntrackSocket(final int groups) {
+        FileDescriptor fd;
+        try {
+            fd = NetlinkSocket.forProto(OsConstants.NETLINK_NETFILTER);
+        } catch (ErrnoException e) {
+            mLog.e("Unable to create conntrack socket " + e);
+            return null;
+        }
+
+        final SocketAddress sockAddr = SocketUtils.makeNetlinkSocketAddress(0, groups);
+        try {
+            Os.bind(fd, sockAddr);
+        } catch (ErrnoException | SocketException e) {
+            mLog.e("Unable to bind conntrack socket for groups " + groups + " error: " + e);
+            try {
+                SocketUtils.closeSocket(fd);
+            } catch (IOException ie) {
+                // Nothing we can do here
+            }
+            return null;
+        }
+        try {
+            Os.connect(fd, sockAddr);
+        } catch (ErrnoException | SocketException e) {
+            mLog.e("connect to kernel fail for groups " + groups + " error: " + e);
+            try {
+                SocketUtils.closeSocket(fd);
+            } catch (IOException ie) {
+                // Nothing we can do here
+            }
+            return null;
+        }
+
+        return new NativeHandle(fd, true);
+    }
+
+    /** Initialize the tethering offload HAL. */
+    public boolean initOffloadControl(ControlCallback controlCb) {
+        mControlCallback = controlCb;
+
+        if (mOffloadControl == null) {
+            try {
+                mOffloadControl = IOffloadControl.getService();
+            } catch (RemoteException e) {
+                mLog.e("tethering offload control not supported: " + e);
+                return false;
+            }
+            if (mOffloadControl == null) {
+                mLog.e("tethering IOffloadControl.getService() returned null");
+                return false;
+            }
+        }
+
+        final String logmsg = String.format("initOffloadControl(%s)",
+                (controlCb == null) ? "null"
+                        : "0x" + Integer.toHexString(System.identityHashCode(controlCb)));
+
+        mTetheringOffloadCallback = new TetheringOffloadCallback(mHandler, mControlCallback, mLog);
+        final CbResults results = new CbResults();
+        try {
+            mOffloadControl.initOffload(
+                    mTetheringOffloadCallback,
+                    (boolean success, String errMsg) -> {
+                        results.mSuccess = success;
+                        results.mErrMsg = errMsg;
+                    });
+        } catch (RemoteException e) {
+            record(logmsg, e);
+            return false;
+        }
+
+        record(logmsg, results);
+        return results.mSuccess;
+    }
+
+    /** Stop IOffloadControl. */
+    public void stopOffloadControl() {
+        if (mOffloadControl != null) {
+            try {
+                mOffloadControl.stopOffload(
+                        (boolean success, String errMsg) -> {
+                            if (!success) mLog.e("stopOffload failed: " + errMsg);
+                        });
+            } catch (RemoteException e) {
+                mLog.e("failed to stopOffload: " + e);
+            }
+        }
+        mOffloadControl = null;
+        mTetheringOffloadCallback = null;
+        mControlCallback = null;
+        mLog.log("stopOffloadControl()");
+    }
+
+    /** Get Tx/Rx usage from last query. */
+    public ForwardedStats getForwardedStats(String upstream) {
+        final String logmsg = String.format("getForwardedStats(%s)",  upstream);
+
+        final ForwardedStats stats = new ForwardedStats();
+        try {
+            mOffloadControl.getForwardedStats(
+                    upstream,
+                    (long rxBytes, long txBytes) -> {
+                        stats.rxBytes = (rxBytes > 0) ? rxBytes : 0;
+                        stats.txBytes = (txBytes > 0) ? txBytes : 0;
+                    });
+        } catch (RemoteException e) {
+            record(logmsg, e);
+            return stats;
+        }
+
+        mLog.log(logmsg + YIELDS + stats);
+        return stats;
+    }
+
+    /** Set local prefixes to offload management process. */
+    public boolean setLocalPrefixes(ArrayList<String> localPrefixes) {
+        final String logmsg = String.format("setLocalPrefixes([%s])",
+                String.join(",", localPrefixes));
+
+        final CbResults results = new CbResults();
+        try {
+            mOffloadControl.setLocalPrefixes(localPrefixes,
+                    (boolean success, String errMsg) -> {
+                        results.mSuccess = success;
+                        results.mErrMsg = errMsg;
+                    });
+        } catch (RemoteException e) {
+            record(logmsg, e);
+            return false;
+        }
+
+        record(logmsg, results);
+        return results.mSuccess;
+    }
+
+    /** Set data limit value to offload management process. */
+    public boolean setDataLimit(String iface, long limit) {
+
+        final String logmsg = String.format("setDataLimit(%s, %d)", iface, limit);
+
+        final CbResults results = new CbResults();
+        try {
+            mOffloadControl.setDataLimit(
+                    iface, limit,
+                    (boolean success, String errMsg) -> {
+                        results.mSuccess = success;
+                        results.mErrMsg = errMsg;
+                    });
+        } catch (RemoteException e) {
+            record(logmsg, e);
+            return false;
+        }
+
+        record(logmsg, results);
+        return results.mSuccess;
+    }
+
+    /** Set upstream parameters to offload management process. */
+    public boolean setUpstreamParameters(
+            String iface, String v4addr, String v4gateway, ArrayList<String> v6gws) {
+        iface = (iface != null) ? iface : NO_INTERFACE_NAME;
+        v4addr = (v4addr != null) ? v4addr : NO_IPV4_ADDRESS;
+        v4gateway = (v4gateway != null) ? v4gateway : NO_IPV4_GATEWAY;
+        v6gws = (v6gws != null) ? v6gws : new ArrayList<>();
+
+        final String logmsg = String.format("setUpstreamParameters(%s, %s, %s, [%s])",
+                iface, v4addr, v4gateway, String.join(",", v6gws));
+
+        final CbResults results = new CbResults();
+        try {
+            mOffloadControl.setUpstreamParameters(
+                    iface, v4addr, v4gateway, v6gws,
+                    (boolean success, String errMsg) -> {
+                        results.mSuccess = success;
+                        results.mErrMsg = errMsg;
+                    });
+        } catch (RemoteException e) {
+            record(logmsg, e);
+            return false;
+        }
+
+        record(logmsg, results);
+        return results.mSuccess;
+    }
+
+    /** Add downstream prefix to offload management process. */
+    public boolean addDownstreamPrefix(String ifname, String prefix) {
+        final String logmsg = String.format("addDownstreamPrefix(%s, %s)", ifname, prefix);
+
+        final CbResults results = new CbResults();
+        try {
+            mOffloadControl.addDownstream(ifname, prefix,
+                    (boolean success, String errMsg) -> {
+                        results.mSuccess = success;
+                        results.mErrMsg = errMsg;
+                    });
+        } catch (RemoteException e) {
+            record(logmsg, e);
+            return false;
+        }
+
+        record(logmsg, results);
+        return results.mSuccess;
+    }
+
+    /** Remove downstream prefix from offload management process. */
+    public boolean removeDownstreamPrefix(String ifname, String prefix) {
+        final String logmsg = String.format("removeDownstreamPrefix(%s, %s)", ifname, prefix);
+
+        final CbResults results = new CbResults();
+        try {
+            mOffloadControl.removeDownstream(ifname, prefix,
+                    (boolean success, String errMsg) -> {
+                        results.mSuccess = success;
+                        results.mErrMsg = errMsg;
+                    });
+        } catch (RemoteException e) {
+            record(logmsg, e);
+            return false;
+        }
+
+        record(logmsg, results);
+        return results.mSuccess;
+    }
+
+    private void record(String msg, Throwable t) {
+        mLog.e(msg + YIELDS + "exception: " + t);
+    }
+
+    private void record(String msg, CbResults results) {
+        final String logmsg = msg + YIELDS + results;
+        if (!results.mSuccess) {
+            mLog.e(logmsg);
+        } else {
+            mLog.log(logmsg);
+        }
+    }
+
+    private static class TetheringOffloadCallback extends ITetheringOffloadCallback.Stub {
+        public final Handler handler;
+        public final ControlCallback controlCb;
+        public final SharedLog log;
+
+        TetheringOffloadCallback(Handler h, ControlCallback cb, SharedLog sharedLog) {
+            handler = h;
+            controlCb = cb;
+            log = sharedLog;
+        }
+
+        @Override
+        public void onEvent(int event) {
+            handler.post(() -> {
+                switch (event) {
+                    case OffloadCallbackEvent.OFFLOAD_STARTED:
+                        controlCb.onStarted();
+                        break;
+                    case OffloadCallbackEvent.OFFLOAD_STOPPED_ERROR:
+                        controlCb.onStoppedError();
+                        break;
+                    case OffloadCallbackEvent.OFFLOAD_STOPPED_UNSUPPORTED:
+                        controlCb.onStoppedUnsupported();
+                        break;
+                    case OffloadCallbackEvent.OFFLOAD_SUPPORT_AVAILABLE:
+                        controlCb.onSupportAvailable();
+                        break;
+                    case OffloadCallbackEvent.OFFLOAD_STOPPED_LIMIT_REACHED:
+                        controlCb.onStoppedLimitReached();
+                        break;
+                    default:
+                        log.e("Unsupported OffloadCallbackEvent: " + event);
+                }
+            });
+        }
+
+        @Override
+        public void updateTimeout(NatTimeoutUpdate params) {
+            handler.post(() -> {
+                controlCb.onNatTimeoutUpdate(
+                        networkProtocolToOsConstant(params.proto),
+                        params.src.addr, uint16(params.src.port),
+                        params.dst.addr, uint16(params.dst.port));
+            });
+        }
+    }
+
+    private static int networkProtocolToOsConstant(int proto) {
+        switch (proto) {
+            case NetworkProtocol.TCP: return OsConstants.IPPROTO_TCP;
+            case NetworkProtocol.UDP: return OsConstants.IPPROTO_UDP;
+            default:
+                // The caller checks this value and will log an error. Just make
+                // sure it won't collide with valid OsContants.IPPROTO_* values.
+                return -Math.abs(proto);
+        }
+    }
+
+    private static class CbResults {
+        boolean mSuccess;
+        String mErrMsg;
+
+        @Override
+        public String toString() {
+            if (mSuccess) {
+                return "ok";
+            } else {
+                return "fail: " + mErrMsg;
+            }
+        }
+    }
+}

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

@@ -0,0 +1,415 @@
+/*
+ * Copyright (C) 2017 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.content.Context.TELEPHONY_SERVICE;
+import static android.net.ConnectivityManager.TYPE_ETHERNET;
+import static android.net.ConnectivityManager.TYPE_MOBILE;
+import static android.net.ConnectivityManager.TYPE_MOBILE_DUN;
+import static android.net.ConnectivityManager.TYPE_MOBILE_HIPRI;
+import static android.provider.DeviceConfig.NAMESPACE_CONNECTIVITY;
+
+import android.content.Context;
+import android.content.res.Resources;
+import android.net.TetheringConfigurationParcel;
+import android.net.util.SharedLog;
+import android.provider.DeviceConfig;
+import android.telephony.SubscriptionManager;
+import android.telephony.TelephonyManager;
+import android.text.TextUtils;
+
+import com.android.internal.annotations.VisibleForTesting;
+
+import java.io.PrintWriter;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.StringJoiner;
+
+
+/**
+ * A utility class to encapsulate the various tethering configuration elements.
+ *
+ * This configuration data includes elements describing upstream properties
+ * (preferred and required types of upstream connectivity as well as default
+ * DNS servers to use if none are available) and downstream properties (such
+ * as regular expressions use to match suitable downstream interfaces and the
+ * DHCPv4 ranges to use).
+ *
+ * @hide
+ */
+public class TetheringConfiguration {
+    private static final String TAG = TetheringConfiguration.class.getSimpleName();
+
+    private static final String[] EMPTY_STRING_ARRAY = new String[0];
+
+    // Default ranges used for the legacy DHCP server.
+    // USB is  192.168.42.1 and 255.255.255.0
+    // Wifi is 192.168.43.1 and 255.255.255.0
+    // BT is limited to max default of 5 connections. 192.168.44.1 to 192.168.48.1
+    // with 255.255.255.0
+    // P2P is 192.168.49.1 and 255.255.255.0
+    private static final String[] LEGACY_DHCP_DEFAULT_RANGE = {
+        "192.168.42.2", "192.168.42.254", "192.168.43.2", "192.168.43.254",
+        "192.168.44.2", "192.168.44.254", "192.168.45.2", "192.168.45.254",
+        "192.168.46.2", "192.168.46.254", "192.168.47.2", "192.168.47.254",
+        "192.168.48.2", "192.168.48.254", "192.168.49.2", "192.168.49.254",
+    };
+
+    private static final String[] DEFAULT_IPV4_DNS = {"8.8.4.4", "8.8.8.8"};
+
+    /**
+     * Use the old dnsmasq DHCP server for tethering instead of the framework implementation.
+     */
+    public static final String TETHER_ENABLE_LEGACY_DHCP_SERVER =
+            "tether_enable_legacy_dhcp_server";
+
+    public final String[] tetherableUsbRegexs;
+    public final String[] tetherableWifiRegexs;
+    public final String[] tetherableWifiP2pRegexs;
+    public final String[] tetherableBluetoothRegexs;
+    public final String[] tetherableNcmRegexs;
+    public final boolean isDunRequired;
+    public final boolean chooseUpstreamAutomatically;
+    public final Collection<Integer> preferredUpstreamIfaceTypes;
+    public final String[] legacyDhcpRanges;
+    public final String[] defaultIPv4DNS;
+    public final boolean enableLegacyDhcpServer;
+
+    public final String[] provisioningApp;
+    public final String provisioningAppNoUi;
+    public final int provisioningCheckPeriod;
+
+    public final int activeDataSubId;
+
+    public TetheringConfiguration(Context ctx, SharedLog log, int id) {
+        final SharedLog configLog = log.forSubComponent("config");
+
+        activeDataSubId = id;
+        Resources res = getResources(ctx, activeDataSubId);
+
+        tetherableUsbRegexs = getResourceStringArray(res, R.array.config_tether_usb_regexs);
+        tetherableNcmRegexs = getResourceStringArray(res, R.array.config_tether_ncm_regexs);
+        // TODO: Evaluate deleting this altogether now that Wi-Fi always passes
+        // us an interface name. Careful consideration needs to be given to
+        // implications for Settings and for provisioning checks.
+        tetherableWifiRegexs = getResourceStringArray(res, R.array.config_tether_wifi_regexs);
+        tetherableWifiP2pRegexs = getResourceStringArray(
+                res, R.array.config_tether_wifi_p2p_regexs);
+        tetherableBluetoothRegexs = getResourceStringArray(
+                res, R.array.config_tether_bluetooth_regexs);
+
+        isDunRequired = checkDunRequired(ctx);
+
+        chooseUpstreamAutomatically = getResourceBoolean(
+                res, R.bool.config_tether_upstream_automatic);
+        preferredUpstreamIfaceTypes = getUpstreamIfaceTypes(res, isDunRequired);
+
+        legacyDhcpRanges = getLegacyDhcpRanges(res);
+        defaultIPv4DNS = copy(DEFAULT_IPV4_DNS);
+        enableLegacyDhcpServer = getEnableLegacyDhcpServer(res);
+
+        provisioningApp = getResourceStringArray(res, R.array.config_mobile_hotspot_provision_app);
+        provisioningAppNoUi = getProvisioningAppNoUi(res);
+        provisioningCheckPeriod = getResourceInteger(res,
+                R.integer.config_mobile_hotspot_provision_check_period,
+                0 /* No periodic re-check */);
+
+        configLog.log(toString());
+    }
+
+    /** Check whether input interface belong to usb.*/
+    public boolean isUsb(String iface) {
+        return matchesDownstreamRegexs(iface, tetherableUsbRegexs);
+    }
+
+    /** Check whether input interface belong to wifi.*/
+    public boolean isWifi(String iface) {
+        return matchesDownstreamRegexs(iface, tetherableWifiRegexs);
+    }
+
+    /** Check whether this interface is Wifi P2P interface. */
+    public boolean isWifiP2p(String iface) {
+        return matchesDownstreamRegexs(iface, tetherableWifiP2pRegexs);
+    }
+
+    /** Check whether using legacy mode for wifi P2P. */
+    public boolean isWifiP2pLegacyTetheringMode() {
+        return (tetherableWifiP2pRegexs == null || tetherableWifiP2pRegexs.length == 0);
+    }
+
+    /** Check whether input interface belong to bluetooth.*/
+    public boolean isBluetooth(String iface) {
+        return matchesDownstreamRegexs(iface, tetherableBluetoothRegexs);
+    }
+
+    /** Check if interface is ncm */
+    public boolean isNcm(String iface) {
+        return matchesDownstreamRegexs(iface, tetherableNcmRegexs);
+    }
+
+    /** Check whether no ui entitlement application is available.*/
+    public boolean hasMobileHotspotProvisionApp() {
+        return !TextUtils.isEmpty(provisioningAppNoUi);
+    }
+
+    /** Does the dumping.*/
+    public void dump(PrintWriter pw) {
+        pw.print("activeDataSubId: ");
+        pw.println(activeDataSubId);
+
+        dumpStringArray(pw, "tetherableUsbRegexs", tetherableUsbRegexs);
+        dumpStringArray(pw, "tetherableWifiRegexs", tetherableWifiRegexs);
+        dumpStringArray(pw, "tetherableWifiP2pRegexs", tetherableWifiP2pRegexs);
+        dumpStringArray(pw, "tetherableBluetoothRegexs", tetherableBluetoothRegexs);
+        dumpStringArray(pw, "tetherableNcmRegexs", tetherableNcmRegexs);
+
+        pw.print("isDunRequired: ");
+        pw.println(isDunRequired);
+
+        pw.print("chooseUpstreamAutomatically: ");
+        pw.println(chooseUpstreamAutomatically);
+        pw.print("legacyPreredUpstreamIfaceTypes: ");
+        pw.println(Arrays.toString(toIntArray(preferredUpstreamIfaceTypes)));
+
+        dumpStringArray(pw, "legacyDhcpRanges", legacyDhcpRanges);
+        dumpStringArray(pw, "defaultIPv4DNS", defaultIPv4DNS);
+
+        dumpStringArray(pw, "provisioningApp", provisioningApp);
+        pw.print("provisioningAppNoUi: ");
+        pw.println(provisioningAppNoUi);
+
+        pw.print("enableLegacyDhcpServer: ");
+        pw.println(enableLegacyDhcpServer);
+    }
+
+    /** Returns the string representation of this object.*/
+    public String toString() {
+        final StringJoiner sj = new StringJoiner(" ");
+        sj.add(String.format("activeDataSubId:%d", activeDataSubId));
+        sj.add(String.format("tetherableUsbRegexs:%s", makeString(tetherableUsbRegexs)));
+        sj.add(String.format("tetherableWifiRegexs:%s", makeString(tetherableWifiRegexs)));
+        sj.add(String.format("tetherableWifiP2pRegexs:%s", makeString(tetherableWifiP2pRegexs)));
+        sj.add(String.format("tetherableBluetoothRegexs:%s",
+                makeString(tetherableBluetoothRegexs)));
+        sj.add(String.format("isDunRequired:%s", isDunRequired));
+        sj.add(String.format("chooseUpstreamAutomatically:%s", chooseUpstreamAutomatically));
+        sj.add(String.format("preferredUpstreamIfaceTypes:%s",
+                toIntArray(preferredUpstreamIfaceTypes)));
+        sj.add(String.format("provisioningApp:%s", makeString(provisioningApp)));
+        sj.add(String.format("provisioningAppNoUi:%s", provisioningAppNoUi));
+        sj.add(String.format("enableLegacyDhcpServer:%s", enableLegacyDhcpServer));
+        return String.format("TetheringConfiguration{%s}", sj.toString());
+    }
+
+    private static void dumpStringArray(PrintWriter pw, String label, String[] values) {
+        pw.print(label);
+        pw.print(": ");
+
+        if (values != null) {
+            final StringJoiner sj = new StringJoiner(", ", "[", "]");
+            for (String value : values) sj.add(value);
+            pw.print(sj.toString());
+        } else {
+            pw.print("null");
+        }
+
+        pw.println();
+    }
+
+    private static String makeString(String[] strings) {
+        if (strings == null) return "null";
+        final StringJoiner sj = new StringJoiner(",", "[", "]");
+        for (String s : strings) sj.add(s);
+        return sj.toString();
+    }
+
+    /** Check whether dun is required. */
+    public static boolean checkDunRequired(Context ctx) {
+        final TelephonyManager tm = (TelephonyManager) ctx.getSystemService(TELEPHONY_SERVICE);
+        // TelephonyManager would uses the active data subscription, which should be the one used
+        // by tethering.
+        return (tm != null) ? tm.isTetheringApnRequired() : false;
+    }
+
+    private static Collection<Integer> getUpstreamIfaceTypes(Resources res, boolean dunRequired) {
+        final int[] ifaceTypes = res.getIntArray(R.array.config_tether_upstream_types);
+        final ArrayList<Integer> upstreamIfaceTypes = new ArrayList<>(ifaceTypes.length);
+        for (int i : ifaceTypes) {
+            switch (i) {
+                case TYPE_MOBILE:
+                case TYPE_MOBILE_HIPRI:
+                    if (dunRequired) continue;
+                    break;
+                case TYPE_MOBILE_DUN:
+                    if (!dunRequired) continue;
+                    break;
+            }
+            upstreamIfaceTypes.add(i);
+        }
+
+        // Fix up upstream interface types for DUN or mobile. NOTE: independent
+        // of the value of |dunRequired|, cell data of one form or another is
+        // *always* an upstream, regardless of the upstream interface types
+        // specified by configuration resources.
+        if (dunRequired) {
+            appendIfNotPresent(upstreamIfaceTypes, TYPE_MOBILE_DUN);
+        } else {
+            // Do not modify if a cellular interface type is already present in the
+            // upstream interface types. Add TYPE_MOBILE and TYPE_MOBILE_HIPRI if no
+            // cellular interface types are found in the upstream interface types.
+            // This preserves backwards compatibility and prevents the DUN and default
+            // mobile types incorrectly appearing together, which could happen on
+            // previous releases in the common case where checkDunRequired returned
+            // DUN_UNSPECIFIED.
+            if (!containsOneOf(upstreamIfaceTypes, TYPE_MOBILE, TYPE_MOBILE_HIPRI)) {
+                upstreamIfaceTypes.add(TYPE_MOBILE);
+                upstreamIfaceTypes.add(TYPE_MOBILE_HIPRI);
+            }
+        }
+
+        // Always make sure our good friend Ethernet is present.
+        // TODO: consider unilaterally forcing this at the front.
+        prependIfNotPresent(upstreamIfaceTypes, TYPE_ETHERNET);
+
+        return upstreamIfaceTypes;
+    }
+
+    private static boolean matchesDownstreamRegexs(String iface, String[] regexs) {
+        for (String regex : regexs) {
+            if (iface.matches(regex)) return true;
+        }
+        return false;
+    }
+
+    private static String[] getLegacyDhcpRanges(Resources res) {
+        final String[] fromResource = getResourceStringArray(res, R.array.config_tether_dhcp_range);
+        if ((fromResource.length > 0) && (fromResource.length % 2 == 0)) {
+            return fromResource;
+        }
+        return copy(LEGACY_DHCP_DEFAULT_RANGE);
+    }
+
+    private static String getProvisioningAppNoUi(Resources res) {
+        try {
+            return res.getString(R.string.config_mobile_hotspot_provision_app_no_ui);
+        } catch (Resources.NotFoundException e) {
+            return "";
+        }
+    }
+
+    private static boolean getResourceBoolean(Resources res, int resId) {
+        try {
+            return res.getBoolean(resId);
+        } catch (Resources.NotFoundException e404) {
+            return false;
+        }
+    }
+
+    private static String[] getResourceStringArray(Resources res, int resId) {
+        try {
+            final String[] strArray = res.getStringArray(resId);
+            return (strArray != null) ? strArray : EMPTY_STRING_ARRAY;
+        } catch (Resources.NotFoundException e404) {
+            return EMPTY_STRING_ARRAY;
+        }
+    }
+
+    private static int getResourceInteger(Resources res, int resId, int defaultValue) {
+        try {
+            return res.getInteger(resId);
+        } catch (Resources.NotFoundException e404) {
+            return defaultValue;
+        }
+    }
+
+    private boolean getEnableLegacyDhcpServer(final Resources res) {
+        return getResourceBoolean(res, R.bool.config_tether_enable_legacy_dhcp_server)
+                || getDeviceConfigBoolean(TETHER_ENABLE_LEGACY_DHCP_SERVER);
+    }
+
+    @VisibleForTesting
+    protected boolean getDeviceConfigBoolean(final String name) {
+        return DeviceConfig.getBoolean(NAMESPACE_CONNECTIVITY, name, false /** defaultValue */);
+    }
+
+    private Resources getResources(Context ctx, int subId) {
+        if (subId != SubscriptionManager.INVALID_SUBSCRIPTION_ID) {
+            return getResourcesForSubIdWrapper(ctx, subId);
+        } else {
+            return ctx.getResources();
+        }
+    }
+
+    @VisibleForTesting
+    protected Resources getResourcesForSubIdWrapper(Context ctx, int subId) {
+        return SubscriptionManager.getResourcesForSubId(ctx, subId);
+    }
+
+    private static String[] copy(String[] strarray) {
+        return Arrays.copyOf(strarray, strarray.length);
+    }
+
+    private static void prependIfNotPresent(ArrayList<Integer> list, int value) {
+        if (list.contains(value)) return;
+        list.add(0, value);
+    }
+
+    private static void appendIfNotPresent(ArrayList<Integer> list, int value) {
+        if (list.contains(value)) return;
+        list.add(value);
+    }
+
+    private static boolean containsOneOf(ArrayList<Integer> list, Integer... values) {
+        for (Integer value : values) {
+            if (list.contains(value)) return true;
+        }
+        return false;
+    }
+
+    private static int[] toIntArray(Collection<Integer> values) {
+        final int[] result = new int[values.size()];
+        int index = 0;
+        for (Integer value : values) {
+            result[index++] = value;
+        }
+        return result;
+    }
+
+    /**
+     * Convert this TetheringConfiguration to a TetheringConfigurationParcel.
+     */
+    public TetheringConfigurationParcel toStableParcelable() {
+        final TetheringConfigurationParcel parcel = new TetheringConfigurationParcel();
+        parcel.subId = activeDataSubId;
+        parcel.tetherableUsbRegexs = tetherableUsbRegexs;
+        parcel.tetherableWifiRegexs = tetherableWifiRegexs;
+        parcel.tetherableBluetoothRegexs = tetherableBluetoothRegexs;
+        parcel.isDunRequired = isDunRequired;
+        parcel.chooseUpstreamAutomatically = chooseUpstreamAutomatically;
+
+        parcel.preferredUpstreamIfaceTypes = toIntArray(preferredUpstreamIfaceTypes);
+
+        parcel.legacyDhcpRanges = legacyDhcpRanges;
+        parcel.defaultIPv4DNS = defaultIPv4DNS;
+        parcel.enableLegacyDhcpServer = enableLegacyDhcpServer;
+        parcel.provisioningApp = provisioningApp;
+        parcel.provisioningAppNoUi = provisioningAppNoUi;
+        parcel.provisioningCheckPeriod = provisioningCheckPeriod;
+        return parcel;
+    }
+}

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

@@ -0,0 +1,127 @@
+/*
+ * Copyright (C) 2017 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 android.bluetooth.BluetoothAdapter;
+import android.content.Context;
+import android.net.INetd;
+import android.net.NetworkRequest;
+import android.net.ip.IpServer;
+import android.net.util.SharedLog;
+import android.os.Handler;
+import android.os.IBinder;
+import android.os.Looper;
+
+import androidx.annotation.NonNull;
+
+import com.android.internal.util.StateMachine;
+
+import java.util.ArrayList;
+
+
+/**
+ * Capture tethering dependencies, for injection.
+ *
+ * @hide
+ */
+public abstract class TetheringDependencies {
+    /**
+     * Get a reference to the offload hardware interface to be used by tethering.
+     */
+    public OffloadHardwareInterface getOffloadHardwareInterface(Handler h, SharedLog log) {
+        return new OffloadHardwareInterface(h, log);
+    }
+
+    /**
+     * Get a reference to the UpstreamNetworkMonitor to be used by tethering.
+     */
+    public UpstreamNetworkMonitor getUpstreamNetworkMonitor(Context ctx, StateMachine target,
+            SharedLog log, int what) {
+        return new UpstreamNetworkMonitor(ctx, target, log, what);
+    }
+
+    /**
+     * Get a reference to the IPv6TetheringCoordinator to be used by tethering.
+     */
+    public IPv6TetheringCoordinator getIPv6TetheringCoordinator(
+            ArrayList<IpServer> notifyList, SharedLog log) {
+        return new IPv6TetheringCoordinator(notifyList, log);
+    }
+
+    /**
+     * Get dependencies to be used by IpServer.
+     */
+    public abstract IpServer.Dependencies getIpServerDependencies();
+
+    /**
+     * Indicates whether tethering is supported on the device.
+     */
+    public boolean isTetheringSupported() {
+        return true;
+    }
+
+    /**
+     * Get the NetworkRequest that should be fulfilled by the default network.
+     */
+    public abstract NetworkRequest getDefaultNetworkRequest();
+
+    /**
+     * Get a reference to the EntitlementManager to be used by tethering.
+     */
+    public EntitlementManager getEntitlementManager(Context ctx, StateMachine target,
+            SharedLog log, int what) {
+        return new EntitlementManager(ctx, target, log, what);
+    }
+
+    /**
+     * Generate a new TetheringConfiguration according to input sub Id.
+     */
+    public TetheringConfiguration generateTetheringConfiguration(Context ctx, SharedLog log,
+            int subId) {
+        return new TetheringConfiguration(ctx, log, subId);
+    }
+
+    /**
+     * Get a reference to INetd to be used by tethering.
+     */
+    public INetd getINetd(Context context) {
+        return INetd.Stub.asInterface(
+                (IBinder) context.getSystemService(Context.NETD_SERVICE));
+    }
+
+    /**
+     * Get a reference to the TetheringNotificationUpdater to be used by tethering.
+     */
+    public TetheringNotificationUpdater getNotificationUpdater(@NonNull final Context ctx) {
+        return new TetheringNotificationUpdater(ctx);
+    }
+
+    /**
+     * Get tethering thread looper.
+     */
+    public abstract Looper getTetheringLooper();
+
+    /**
+     *  Get Context of TetheringSerice.
+     */
+    public abstract Context getContext();
+
+    /**
+     * Get a reference to BluetoothAdapter to be used by tethering.
+     */
+    public abstract BluetoothAdapter getBluetoothAdapter();
+}

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

@@ -0,0 +1,102 @@
+/*
+ * Copyright (C) 2018 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 android.annotation.Nullable;
+import android.net.LinkProperties;
+import android.net.NetworkCapabilities;
+import android.net.RouteInfo;
+import android.net.util.InterfaceSet;
+
+import com.android.net.module.util.NetUtils;
+
+import java.net.InetAddress;
+import java.net.UnknownHostException;
+
+/**
+ * @hide
+ */
+public final class TetheringInterfaceUtils {
+    private static final InetAddress IN6ADDR_ANY = getByAddress(
+            new byte[] {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0});
+    private static final InetAddress INADDR_ANY = getByAddress(new byte[] {0, 0, 0, 0});
+
+    /**
+     * Get upstream interfaces for tethering based on default routes for IPv4/IPv6.
+     * @return null if there is no usable interface, or a set of at least one interface otherwise.
+     */
+    public static @Nullable InterfaceSet getTetheringInterfaces(UpstreamNetworkState ns) {
+        if (ns == null) {
+            return null;
+        }
+
+        final LinkProperties lp = ns.linkProperties;
+        final String if4 = getInterfaceForDestination(lp, INADDR_ANY);
+        final String if6 = getIPv6Interface(ns);
+
+        return (if4 == null && if6 == null) ? null : new InterfaceSet(if4, if6);
+    }
+
+    /**
+     * Get the upstream interface for IPv6 tethering.
+     * @return null if there is no usable interface, or the interface name otherwise.
+     */
+    public static @Nullable String getIPv6Interface(UpstreamNetworkState ns) {
+        // Broadly speaking:
+        //
+        //     [1] does the upstream have an IPv6 default route?
+        //
+        // and
+        //
+        //     [2] does the upstream have one or more global IPv6 /64s
+        //         dedicated to this device?
+        //
+        // In lieu of Prefix Delegation and other evaluation of whether a
+        // prefix may or may not be dedicated to this device, for now just
+        // check whether the upstream is TRANSPORT_CELLULAR. This works
+        // because "[t]he 3GPP network allocates each default bearer a unique
+        // /64 prefix", per RFC 6459, Section 5.2.
+        final boolean canTether =
+                (ns != null) && (ns.network != null)
+                && (ns.linkProperties != null) && (ns.networkCapabilities != null)
+                // At least one upstream DNS server:
+                && ns.linkProperties.hasIpv6DnsServer()
+                // Minimal amount of IPv6 provisioning:
+                && ns.linkProperties.hasGlobalIpv6Address()
+                // Temporary approximation of "dedicated prefix":
+                && ns.networkCapabilities.hasTransport(NetworkCapabilities.TRANSPORT_CELLULAR);
+
+        return canTether
+                ? getInterfaceForDestination(ns.linkProperties, IN6ADDR_ANY)
+                : null;
+    }
+
+    private static String getInterfaceForDestination(LinkProperties lp, InetAddress dst) {
+        final RouteInfo ri = (lp != null)
+                ? NetUtils.selectBestRoute(lp.getAllRoutes(), dst)
+                : null;
+        return (ri != null) ? ri.getInterface() : null;
+    }
+
+    private static InetAddress getByAddress(final byte[] addr) {
+        try {
+            return InetAddress.getByAddress(null, addr);
+        } catch (UnknownHostException e) {
+            throw new AssertionError("illegal address length" + addr.length);
+        }
+    }
+}

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

@@ -0,0 +1,243 @@
+/*
+ * Copyright (C) 2020 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.networkstack.tethering;
+
+import static android.net.TetheringManager.TETHERING_BLUETOOTH;
+import static android.net.TetheringManager.TETHERING_USB;
+import static android.net.TetheringManager.TETHERING_WIFI;
+
+import android.app.Notification;
+import android.app.NotificationChannel;
+import android.app.NotificationManager;
+import android.app.PendingIntent;
+import android.content.Context;
+import android.content.Intent;
+import android.content.res.Resources;
+import android.os.UserHandle;
+import android.provider.Settings;
+import android.telephony.SubscriptionManager;
+import android.text.TextUtils;
+import android.util.Log;
+import android.util.SparseArray;
+
+import androidx.annotation.ArrayRes;
+import androidx.annotation.DrawableRes;
+import androidx.annotation.IntDef;
+import androidx.annotation.IntRange;
+import androidx.annotation.NonNull;
+
+import com.android.internal.annotations.VisibleForTesting;
+
+/**
+ * A class to display tethering-related notifications.
+ *
+ * <p>This class is not thread safe, it is intended to be used only from the tethering handler
+ * thread. However the constructor is an exception, as it is called on another thread ;
+ * therefore for thread safety all members of this class MUST either be final or initialized
+ * to their default value (0, false or null).
+ *
+ * @hide
+ */
+public class TetheringNotificationUpdater {
+    private static final String TAG = TetheringNotificationUpdater.class.getSimpleName();
+    private static final String CHANNEL_ID = "TETHERING_STATUS";
+    private static final String WIFI_DOWNSTREAM = "WIFI";
+    private static final String USB_DOWNSTREAM = "USB";
+    private static final String BLUETOOTH_DOWNSTREAM = "BT";
+    private static final boolean NOTIFY_DONE = true;
+    private static final boolean NO_NOTIFY = false;
+    // Id to update and cancel tethering notification. Must be unique within the tethering app.
+    private static final int ENABLE_NOTIFICATION_ID = 1000;
+    // Id to update and cancel restricted notification. Must be unique within the tethering app.
+    private static final int RESTRICTED_NOTIFICATION_ID = 1001;
+    @VisibleForTesting
+    static final int NO_ICON_ID = 0;
+    @VisibleForTesting
+    static final int DOWNSTREAM_NONE = 0;
+    private final Context mContext;
+    private final NotificationManager mNotificationManager;
+    private final NotificationChannel mChannel;
+
+    // WARNING : the constructor is called on a different thread. Thread safety therefore
+    // relies on this value being initialized to 0, and not any other value. If you need
+    // to change this, you will need to change the thread where the constructor is invoked,
+    // or to introduce synchronization.
+    // Downstream type is one of ConnectivityManager.TETHERING_* constants, 0 1 or 2.
+    // This value has to be made 1 2 and 4, and OR'd with the others.
+    private int mDownstreamTypesMask = DOWNSTREAM_NONE;
+
+    // WARNING : this value is not able to being initialized to 0 and must have volatile because
+    // telephony service is not guaranteed that is up before tethering service starts. If telephony
+    // is up later than tethering, TetheringNotificationUpdater will use incorrect and valid
+    // subscription id(0) to query resources. Therefore, initialized subscription id must be
+    // INVALID_SUBSCRIPTION_ID.
+    private volatile int mActiveDataSubId = SubscriptionManager.INVALID_SUBSCRIPTION_ID;
+
+    @IntDef({ENABLE_NOTIFICATION_ID, RESTRICTED_NOTIFICATION_ID})
+    @interface NotificationId {}
+
+    public TetheringNotificationUpdater(@NonNull final Context context) {
+        mContext = context;
+        mNotificationManager = (NotificationManager) context.createContextAsUser(UserHandle.ALL, 0)
+                .getSystemService(Context.NOTIFICATION_SERVICE);
+        mChannel = new NotificationChannel(
+                CHANNEL_ID,
+                context.getResources().getString(R.string.notification_channel_tethering_status),
+                NotificationManager.IMPORTANCE_LOW);
+        mNotificationManager.createNotificationChannel(mChannel);
+    }
+
+    /** Called when downstream has changed */
+    public void onDownstreamChanged(@IntRange(from = 0, to = 7) final int downstreamTypesMask) {
+        if (mDownstreamTypesMask == downstreamTypesMask) return;
+        mDownstreamTypesMask = downstreamTypesMask;
+        updateEnableNotification();
+    }
+
+    /** Called when active data subscription id changed */
+    public void onActiveDataSubscriptionIdChanged(final int subId) {
+        if (mActiveDataSubId == subId) return;
+        mActiveDataSubId = subId;
+        updateEnableNotification();
+    }
+
+    @VisibleForTesting
+    Resources getResourcesForSubId(@NonNull final Context c, final int subId) {
+        return SubscriptionManager.getResourcesForSubId(c, subId);
+    }
+
+    private void updateEnableNotification() {
+        final boolean tetheringInactive = mDownstreamTypesMask <= DOWNSTREAM_NONE;
+
+        if (tetheringInactive || setupNotification() == NO_NOTIFY) {
+            clearNotification(ENABLE_NOTIFICATION_ID);
+        }
+    }
+
+    @VisibleForTesting
+    void tetheringRestrictionLifted() {
+        clearNotification(RESTRICTED_NOTIFICATION_ID);
+    }
+
+    private void clearNotification(@NotificationId final int id) {
+        mNotificationManager.cancel(null /* tag */, id);
+    }
+
+    @VisibleForTesting
+    void notifyTetheringDisabledByRestriction() {
+        final Resources res = getResourcesForSubId(mContext, mActiveDataSubId);
+        final String title = res.getString(R.string.disable_tether_notification_title);
+        final String message = res.getString(R.string.disable_tether_notification_message);
+
+        showNotification(R.drawable.stat_sys_tether_general, title, message,
+                RESTRICTED_NOTIFICATION_ID);
+    }
+
+    /**
+     * Returns the downstream types mask which convert from given string.
+     *
+     * @param types This string has to be made by "WIFI", "USB", "BT", and OR'd with the others.
+     *
+     * @return downstream types mask value.
+     */
+    @VisibleForTesting
+    @IntRange(from = 0, to = 7)
+    int getDownstreamTypesMask(@NonNull final String types) {
+        int downstreamTypesMask = DOWNSTREAM_NONE;
+        final String[] downstreams = types.split("\\|");
+        for (String downstream : downstreams) {
+            if (USB_DOWNSTREAM.equals(downstream.trim())) {
+                downstreamTypesMask |= (1 << TETHERING_USB);
+            } else if (WIFI_DOWNSTREAM.equals(downstream.trim())) {
+                downstreamTypesMask |= (1 << TETHERING_WIFI);
+            } else if (BLUETOOTH_DOWNSTREAM.equals(downstream.trim())) {
+                downstreamTypesMask |= (1 << TETHERING_BLUETOOTH);
+            }
+        }
+        return downstreamTypesMask;
+    }
+
+    /**
+     * Returns the icons {@link android.util.SparseArray} which get from given string-array resource
+     * id.
+     *
+     * @param id String-array resource id
+     *
+     * @return {@link android.util.SparseArray} with downstream types and icon id info.
+     */
+    @VisibleForTesting
+    SparseArray<Integer> getIcons(@ArrayRes int id, @NonNull Resources res) {
+        final String[] array = res.getStringArray(id);
+        final SparseArray<Integer> icons = new SparseArray<>();
+        for (String config : array) {
+            if (TextUtils.isEmpty(config)) continue;
+
+            final String[] elements = config.split(";");
+            if (elements.length != 2) {
+                Log.wtf(TAG,
+                        "Unexpected format in Tethering notification configuration : " + config);
+                continue;
+            }
+
+            final String[] types = elements[0].split(",");
+            for (String type : types) {
+                int mask = getDownstreamTypesMask(type);
+                if (mask == DOWNSTREAM_NONE) continue;
+                icons.put(mask, res.getIdentifier(
+                        elements[1].trim(), null /* defType */, null /* defPackage */));
+            }
+        }
+        return icons;
+    }
+
+    private boolean setupNotification() {
+        final Resources res = getResourcesForSubId(mContext, mActiveDataSubId);
+        final SparseArray<Integer> downstreamIcons =
+                getIcons(R.array.tethering_notification_icons, res);
+
+        final int iconId = downstreamIcons.get(mDownstreamTypesMask, NO_ICON_ID);
+        if (iconId == NO_ICON_ID) return NO_NOTIFY;
+
+        final String title = res.getString(R.string.tethering_notification_title);
+        final String message = res.getString(R.string.tethering_notification_message);
+
+        showNotification(iconId, title, message, ENABLE_NOTIFICATION_ID);
+        return NOTIFY_DONE;
+    }
+
+    private void showNotification(@DrawableRes final int iconId, @NonNull final String title,
+            @NonNull final String message, @NotificationId final int id) {
+        final Intent intent = new Intent(Settings.ACTION_TETHER_SETTINGS);
+        final PendingIntent pi = PendingIntent.getActivity(
+                mContext.createContextAsUser(UserHandle.CURRENT, 0),
+                0 /* requestCode */, intent, 0 /* flags */, null /* options */);
+        final Notification notification =
+                new Notification.Builder(mContext, mChannel.getId())
+                        .setSmallIcon(iconId)
+                        .setContentTitle(title)
+                        .setContentText(message)
+                        .setOngoing(true)
+                        .setColor(mContext.getColor(
+                                android.R.color.system_notification_accent_color))
+                        .setVisibility(Notification.VISIBILITY_PUBLIC)
+                        .setCategory(Notification.CATEGORY_STATUS)
+                        .setContentIntent(pi)
+                        .build();
+
+        mNotificationManager.notify(null /* tag */, id, notification);
+    }
+}

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

@@ -0,0 +1,391 @@
+/*
+ * Copyright (C) 2019 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.networkstack.tethering;
+
+import static android.content.pm.PackageManager.PERMISSION_GRANTED;
+import static android.net.TetheringManager.TETHER_ERROR_NO_ACCESS_TETHERING_PERMISSION;
+import static android.net.TetheringManager.TETHER_ERROR_NO_CHANGE_TETHERING_PERMISSION;
+import static android.net.TetheringManager.TETHER_ERROR_NO_ERROR;
+import static android.net.TetheringManager.TETHER_ERROR_UNSUPPORTED;
+import static android.net.dhcp.IDhcpServer.STATUS_UNKNOWN_ERROR;
+
+import android.app.Service;
+import android.bluetooth.BluetoothAdapter;
+import android.content.Context;
+import android.content.Intent;
+import android.net.IIntResultListener;
+import android.net.INetworkStackConnector;
+import android.net.ITetheringConnector;
+import android.net.ITetheringEventCallback;
+import android.net.NetworkCapabilities;
+import android.net.NetworkRequest;
+import android.net.NetworkStack;
+import android.net.TetheringRequestParcel;
+import android.net.dhcp.DhcpServerCallbacks;
+import android.net.dhcp.DhcpServingParamsParcel;
+import android.net.ip.IpServer;
+import android.net.util.SharedLog;
+import android.os.Binder;
+import android.os.HandlerThread;
+import android.os.IBinder;
+import android.os.Looper;
+import android.os.RemoteException;
+import android.os.ResultReceiver;
+import android.os.SystemProperties;
+import android.os.UserManager;
+import android.provider.Settings;
+import android.util.Log;
+
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+
+import com.android.internal.annotations.VisibleForTesting;
+
+import java.io.FileDescriptor;
+import java.io.PrintWriter;
+
+/**
+ * Android service used to manage tethering.
+ *
+ * <p>The service returns a binder for the system server to communicate with the tethering.
+ */
+public class TetheringService extends Service {
+    private static final String TAG = TetheringService.class.getSimpleName();
+
+    private final SharedLog mLog = new SharedLog(TAG);
+    private TetheringConnector mConnector;
+    private Context mContext;
+    private TetheringDependencies mDeps;
+    private Tethering mTethering;
+    private UserManager mUserManager;
+
+    @Override
+    public void onCreate() {
+        mLog.mark("onCreate");
+        mDeps = getTetheringDependencies();
+        mContext = mDeps.getContext();
+        mUserManager = (UserManager) mContext.getSystemService(Context.USER_SERVICE);
+        mTethering = makeTethering(mDeps);
+        mTethering.startStateMachineUpdaters();
+    }
+
+    /**
+     * Make a reference to Tethering object.
+     */
+    @VisibleForTesting
+    public Tethering makeTethering(TetheringDependencies deps) {
+        System.loadLibrary("tetherutilsjni");
+        return new Tethering(deps);
+    }
+
+    /**
+     * Create a binder connector for the system server to communicate with the tethering.
+     */
+    private synchronized IBinder makeConnector() {
+        if (mConnector == null) {
+            mConnector = new TetheringConnector(mTethering, TetheringService.this);
+        }
+        return mConnector;
+    }
+
+    @NonNull
+    @Override
+    public IBinder onBind(Intent intent) {
+        mLog.mark("onBind");
+        return makeConnector();
+    }
+
+    private static class TetheringConnector extends ITetheringConnector.Stub {
+        private final TetheringService mService;
+        private final Tethering mTethering;
+
+        TetheringConnector(Tethering tether, TetheringService service) {
+            mTethering = tether;
+            mService = service;
+        }
+
+        @Override
+        public void tether(String iface, String callerPkg, IIntResultListener listener) {
+            if (checkAndNotifyCommonError(callerPkg, listener)) return;
+
+            try {
+                listener.onResult(mTethering.tether(iface));
+            } catch (RemoteException e) { }
+        }
+
+        @Override
+        public void untether(String iface, String callerPkg, IIntResultListener listener) {
+            if (checkAndNotifyCommonError(callerPkg, listener)) return;
+
+            try {
+                listener.onResult(mTethering.untether(iface));
+            } catch (RemoteException e) { }
+        }
+
+        @Override
+        public void setUsbTethering(boolean enable, String callerPkg, IIntResultListener listener) {
+            if (checkAndNotifyCommonError(callerPkg, listener)) return;
+
+            try {
+                listener.onResult(mTethering.setUsbTethering(enable));
+            } catch (RemoteException e) { }
+        }
+
+        @Override
+        public void startTethering(TetheringRequestParcel request, String callerPkg,
+                IIntResultListener listener) {
+            if (checkAndNotifyCommonError(callerPkg, listener)) return;
+
+            mTethering.startTethering(request, listener);
+        }
+
+        @Override
+        public void stopTethering(int type, String callerPkg, IIntResultListener listener) {
+            if (checkAndNotifyCommonError(callerPkg, listener)) return;
+
+            try {
+                mTethering.stopTethering(type);
+                listener.onResult(TETHER_ERROR_NO_ERROR);
+            } catch (RemoteException e) { }
+        }
+
+        @Override
+        public void requestLatestTetheringEntitlementResult(int type, ResultReceiver receiver,
+                boolean showEntitlementUi, String callerPkg) {
+            if (checkAndNotifyCommonError(callerPkg, receiver)) return;
+
+            mTethering.requestLatestTetheringEntitlementResult(type, receiver, showEntitlementUi);
+        }
+
+        @Override
+        public void registerTetheringEventCallback(ITetheringEventCallback callback,
+                String callerPkg) {
+            try {
+                if (!mService.hasTetherAccessPermission()) {
+                    callback.onCallbackStopped(TETHER_ERROR_NO_ACCESS_TETHERING_PERMISSION);
+                    return;
+                }
+                mTethering.registerTetheringEventCallback(callback);
+            } catch (RemoteException e) { }
+        }
+
+        @Override
+        public void unregisterTetheringEventCallback(ITetheringEventCallback callback,
+                String callerPkg) {
+            try {
+                if (!mService.hasTetherAccessPermission()) {
+                    callback.onCallbackStopped(TETHER_ERROR_NO_ACCESS_TETHERING_PERMISSION);
+                    return;
+                }
+                mTethering.unregisterTetheringEventCallback(callback);
+            } catch (RemoteException e) { }
+        }
+
+        @Override
+        public void stopAllTethering(String callerPkg, IIntResultListener listener) {
+            if (checkAndNotifyCommonError(callerPkg, listener)) return;
+
+            try {
+                mTethering.untetherAll();
+                listener.onResult(TETHER_ERROR_NO_ERROR);
+            } catch (RemoteException e) { }
+        }
+
+        @Override
+        public void isTetheringSupported(String callerPkg, IIntResultListener listener) {
+            if (checkAndNotifyCommonError(callerPkg, listener)) return;
+
+            try {
+                listener.onResult(TETHER_ERROR_NO_ERROR);
+            } catch (RemoteException e) { }
+        }
+
+        @Override
+        protected void dump(@NonNull FileDescriptor fd, @NonNull PrintWriter writer,
+                    @Nullable String[] args) {
+            mTethering.dump(fd, writer, args);
+        }
+
+        private boolean checkAndNotifyCommonError(String callerPkg, IIntResultListener listener) {
+            try {
+                if (!mService.hasTetherChangePermission(callerPkg)) {
+                    listener.onResult(TETHER_ERROR_NO_CHANGE_TETHERING_PERMISSION);
+                    return true;
+                }
+                if (!mService.isTetheringSupported()) {
+                    listener.onResult(TETHER_ERROR_UNSUPPORTED);
+                    return true;
+                }
+            } catch (RemoteException e) {
+                return true;
+            }
+
+            return false;
+        }
+
+        private boolean checkAndNotifyCommonError(String callerPkg, ResultReceiver receiver) {
+            if (!mService.hasTetherChangePermission(callerPkg)) {
+                receiver.send(TETHER_ERROR_NO_CHANGE_TETHERING_PERMISSION, null);
+                return true;
+            }
+            if (!mService.isTetheringSupported()) {
+                receiver.send(TETHER_ERROR_UNSUPPORTED, null);
+                return true;
+            }
+
+            return false;
+        }
+
+    }
+
+    // if ro.tether.denied = true we default to no tethering
+    // gservices could set the secure setting to 1 though to enable it on a build where it
+    // had previously been turned off.
+    private boolean isTetheringSupported() {
+        final int defaultVal =
+                SystemProperties.get("ro.tether.denied").equals("true") ? 0 : 1;
+        final boolean tetherSupported = Settings.Global.getInt(mContext.getContentResolver(),
+                Settings.Global.TETHER_SUPPORTED, defaultVal) != 0;
+        final boolean tetherEnabledInSettings = tetherSupported
+                && !mUserManager.hasUserRestriction(UserManager.DISALLOW_CONFIG_TETHERING);
+
+        return tetherEnabledInSettings && mTethering.hasTetherableConfiguration();
+    }
+
+    private boolean hasTetherChangePermission(String callerPkg) {
+        if (checkCallingOrSelfPermission(
+                android.Manifest.permission.TETHER_PRIVILEGED) == PERMISSION_GRANTED) {
+            return true;
+        }
+
+        if (mTethering.isTetherProvisioningRequired()) return false;
+
+
+        int uid = Binder.getCallingUid();
+        // If callerPkg's uid is not same as Binder.getCallingUid(),
+        // checkAndNoteWriteSettingsOperation will return false and the operation will be denied.
+        if (Settings.checkAndNoteWriteSettingsOperation(mContext, uid, callerPkg,
+                false /* throwException */)) {
+            return true;
+        }
+
+        return false;
+    }
+
+    private boolean hasTetherAccessPermission() {
+        if (checkCallingOrSelfPermission(
+                android.Manifest.permission.TETHER_PRIVILEGED) == PERMISSION_GRANTED) {
+            return true;
+        }
+
+        if (checkCallingOrSelfPermission(
+                android.Manifest.permission.ACCESS_NETWORK_STATE) == PERMISSION_GRANTED) {
+            return true;
+        }
+
+        return false;
+    }
+
+
+    /**
+     * An injection method for testing.
+     */
+    @VisibleForTesting
+    public TetheringDependencies getTetheringDependencies() {
+        if (mDeps == null) {
+            mDeps = new TetheringDependencies() {
+                @Override
+                public NetworkRequest getDefaultNetworkRequest() {
+                    // TODO: b/147280869, add a proper system API to replace this.
+                    final NetworkRequest trackDefaultRequest = new NetworkRequest.Builder()
+                            .clearCapabilities()
+                            .addCapability(NetworkCapabilities.NET_CAPABILITY_NOT_RESTRICTED)
+                            .addCapability(NetworkCapabilities.NET_CAPABILITY_TRUSTED)
+                            .addCapability(NetworkCapabilities.NET_CAPABILITY_NOT_VPN)
+                            .addCapability(NetworkCapabilities.NET_CAPABILITY_INTERNET)
+                            .build();
+                    return trackDefaultRequest;
+                }
+
+                @Override
+                public Looper getTetheringLooper() {
+                    final HandlerThread tetherThread = new HandlerThread("android.tethering");
+                    tetherThread.start();
+                    return tetherThread.getLooper();
+                }
+
+                @Override
+                public boolean isTetheringSupported() {
+                    return TetheringService.this.isTetheringSupported();
+                }
+
+                @Override
+                public Context getContext() {
+                    return TetheringService.this;
+                }
+
+                @Override
+                public IpServer.Dependencies getIpServerDependencies() {
+                    return new IpServer.Dependencies() {
+                        @Override
+                        public void makeDhcpServer(String ifName, DhcpServingParamsParcel params,
+                                DhcpServerCallbacks cb) {
+                            try {
+                                final INetworkStackConnector service = getNetworkStackConnector();
+                                if (service == null) return;
+
+                                service.makeDhcpServer(ifName, params, cb);
+                            } catch (RemoteException e) {
+                                Log.e(TAG, "Fail to make dhcp server");
+                                try {
+                                    cb.onDhcpServerCreated(STATUS_UNKNOWN_ERROR, null);
+                                } catch (RemoteException re) { }
+                            }
+                        }
+                    };
+                }
+
+                // TODO: replace this by NetworkStackClient#getRemoteConnector after refactoring
+                // networkStackClient.
+                static final int NETWORKSTACK_TIMEOUT_MS = 60_000;
+                private INetworkStackConnector getNetworkStackConnector() {
+                    IBinder connector;
+                    try {
+                        final long before = System.currentTimeMillis();
+                        while ((connector = NetworkStack.getService()) == null) {
+                            if (System.currentTimeMillis() - before > NETWORKSTACK_TIMEOUT_MS) {
+                                Log.wtf(TAG, "Timeout, fail to get INetworkStackConnector");
+                                return null;
+                            }
+                            Thread.sleep(200);
+                        }
+                    } catch (InterruptedException e) {
+                        Log.wtf(TAG, "Interrupted, fail to get INetworkStackConnector");
+                        return null;
+                    }
+                    return INetworkStackConnector.Stub.asInterface(connector);
+                }
+
+                @Override
+                public BluetoothAdapter getBluetoothAdapter() {
+                    return BluetoothAdapter.getDefaultAdapter();
+                }
+            };
+        }
+        return mDeps;
+    }
+}

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

@@ -0,0 +1,606 @@
+/*
+ * Copyright (C) 2017 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.ConnectivityManager.TYPE_BLUETOOTH;
+import static android.net.ConnectivityManager.TYPE_ETHERNET;
+import static android.net.ConnectivityManager.TYPE_MOBILE;
+import static android.net.ConnectivityManager.TYPE_MOBILE_DUN;
+import static android.net.ConnectivityManager.TYPE_MOBILE_HIPRI;
+import static android.net.ConnectivityManager.TYPE_WIFI;
+import static android.net.NetworkCapabilities.NET_CAPABILITY_DUN;
+import static android.net.NetworkCapabilities.NET_CAPABILITY_INTERNET;
+import static android.net.NetworkCapabilities.NET_CAPABILITY_NOT_RESTRICTED;
+import static android.net.NetworkCapabilities.NET_CAPABILITY_NOT_VPN;
+import static android.net.NetworkCapabilities.TRANSPORT_CELLULAR;
+
+import android.content.Context;
+import android.net.ConnectivityManager;
+import android.net.ConnectivityManager.NetworkCallback;
+import android.net.IpPrefix;
+import android.net.LinkProperties;
+import android.net.Network;
+import android.net.NetworkCapabilities;
+import android.net.NetworkRequest;
+import android.net.util.PrefixUtils;
+import android.net.util.SharedLog;
+import android.os.Handler;
+import android.util.Log;
+import android.util.SparseIntArray;
+
+import com.android.internal.annotations.VisibleForTesting;
+import com.android.internal.util.Preconditions;
+import com.android.internal.util.StateMachine;
+
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.Set;
+
+
+/**
+ * A class to centralize all the network and link properties information
+ * pertaining to the current and any potential upstream network.
+ *
+ * The owner of UNM gets it to register network callbacks by calling the
+ * following methods :
+ * Calling #startTrackDefaultNetwork() to track the system default network.
+ * Calling #startObserveAllNetworks() to observe all networks. Listening all
+ * networks is necessary while the expression of preferred upstreams remains
+ * a list of legacy connectivity types.  In future, this can be revisited.
+ * Calling #registerMobileNetworkRequest() to bring up mobile DUN/HIPRI network.
+ *
+ * The methods and data members of this class are only to be accessed and
+ * modified from the tethering master state machine thread. Any other
+ * access semantics would necessitate the addition of locking.
+ *
+ * TODO: Move upstream selection logic here.
+ *
+ * All callback methods are run on the same thread as the specified target
+ * state machine.  This class does not require locking when accessed from this
+ * thread.  Access from other threads is not advised.
+ *
+ * @hide
+ */
+public class UpstreamNetworkMonitor {
+    private static final String TAG = UpstreamNetworkMonitor.class.getSimpleName();
+    private static final boolean DBG = false;
+    private static final boolean VDBG = false;
+
+    public static final int EVENT_ON_CAPABILITIES   = 1;
+    public static final int EVENT_ON_LINKPROPERTIES = 2;
+    public static final int EVENT_ON_LOST           = 3;
+    public static final int NOTIFY_LOCAL_PREFIXES   = 10;
+    // This value is used by deprecated preferredUpstreamIfaceTypes selection which is default
+    // disabled.
+    @VisibleForTesting
+    public static final int TYPE_NONE = -1;
+
+    private static final int CALLBACK_LISTEN_ALL = 1;
+    private static final int CALLBACK_DEFAULT_INTERNET = 2;
+    private static final int CALLBACK_MOBILE_REQUEST = 3;
+
+    private static final SparseIntArray sLegacyTypeToTransport = new SparseIntArray();
+    static {
+        sLegacyTypeToTransport.put(TYPE_MOBILE,       NetworkCapabilities.TRANSPORT_CELLULAR);
+        sLegacyTypeToTransport.put(TYPE_MOBILE_DUN,   NetworkCapabilities.TRANSPORT_CELLULAR);
+        sLegacyTypeToTransport.put(TYPE_MOBILE_HIPRI, NetworkCapabilities.TRANSPORT_CELLULAR);
+        sLegacyTypeToTransport.put(TYPE_WIFI,         NetworkCapabilities.TRANSPORT_WIFI);
+        sLegacyTypeToTransport.put(TYPE_BLUETOOTH,    NetworkCapabilities.TRANSPORT_BLUETOOTH);
+        sLegacyTypeToTransport.put(TYPE_ETHERNET,     NetworkCapabilities.TRANSPORT_ETHERNET);
+    }
+
+    private final Context mContext;
+    private final SharedLog mLog;
+    private final StateMachine mTarget;
+    private final Handler mHandler;
+    private final int mWhat;
+    private final HashMap<Network, UpstreamNetworkState> mNetworkMap = new HashMap<>();
+    private HashSet<IpPrefix> mLocalPrefixes;
+    private ConnectivityManager mCM;
+    private EntitlementManager mEntitlementMgr;
+    private NetworkCallback mListenAllCallback;
+    private NetworkCallback mDefaultNetworkCallback;
+    private NetworkCallback mMobileNetworkCallback;
+    private boolean mDunRequired;
+    // Whether the current default upstream is mobile or not.
+    private boolean mIsDefaultCellularUpstream;
+    // The current system default network (not really used yet).
+    private Network mDefaultInternetNetwork;
+    // The current upstream network used for tethering.
+    private Network mTetheringUpstreamNetwork;
+
+    public UpstreamNetworkMonitor(Context ctx, StateMachine tgt, SharedLog log, int what) {
+        mContext = ctx;
+        mTarget = tgt;
+        mHandler = mTarget.getHandler();
+        mLog = log.forSubComponent(TAG);
+        mWhat = what;
+        mLocalPrefixes = new HashSet<>();
+        mIsDefaultCellularUpstream = false;
+    }
+
+    @VisibleForTesting
+    public UpstreamNetworkMonitor(
+            ConnectivityManager cm, StateMachine tgt, SharedLog log, int what) {
+        this((Context) null, tgt, log, what);
+        mCM = cm;
+    }
+
+    /**
+     * Tracking the system default network. This method should be called when system is ready.
+     *
+     * @param defaultNetworkRequest should be the same as ConnectivityService default request
+     * @param entitle a EntitlementManager object to communicate between EntitlementManager and
+     * UpstreamNetworkMonitor
+     */
+    public void startTrackDefaultNetwork(NetworkRequest defaultNetworkRequest,
+            EntitlementManager entitle) {
+
+        // defaultNetworkRequest is not really a "request", just a way of tracking the system
+        // default network. It's guaranteed not to actually bring up any networks because it's
+        // the should be the same request as the ConnectivityService default request, and thus
+        // shares fate with it. We can't use registerDefaultNetworkCallback because it will not
+        // track the system default network if there is a VPN that applies to our UID.
+        if (mDefaultNetworkCallback == null) {
+            mDefaultNetworkCallback = new UpstreamNetworkCallback(CALLBACK_DEFAULT_INTERNET);
+            cm().requestNetwork(defaultNetworkRequest, mDefaultNetworkCallback, mHandler);
+        }
+        if (mEntitlementMgr == null) {
+            mEntitlementMgr = entitle;
+        }
+    }
+
+    /** Listen all networks. */
+    public void startObserveAllNetworks() {
+        stop();
+
+        final NetworkRequest listenAllRequest = new NetworkRequest.Builder()
+                .clearCapabilities().build();
+        mListenAllCallback = new UpstreamNetworkCallback(CALLBACK_LISTEN_ALL);
+        cm().registerNetworkCallback(listenAllRequest, mListenAllCallback, mHandler);
+    }
+
+    /**
+     * Stop tracking candidate tethering upstreams and release mobile network request.
+     * Note: this function is used when tethering is stopped because tethering do not need to
+     * choose upstream anymore. But it would not stop default network tracking because
+     * EntitlementManager may need to know default network to decide whether to request entitlement
+     * check even tethering is not active yet.
+     */
+    public void stop() {
+        releaseMobileNetworkRequest();
+
+        releaseCallback(mListenAllCallback);
+        mListenAllCallback = null;
+
+        mTetheringUpstreamNetwork = null;
+        mNetworkMap.clear();
+    }
+
+    /** Setup or teardown DUN connection according to |dunRequired|. */
+    public void updateMobileRequiresDun(boolean dunRequired) {
+        final boolean valueChanged = (mDunRequired != dunRequired);
+        mDunRequired = dunRequired;
+        if (valueChanged && mobileNetworkRequested()) {
+            releaseMobileNetworkRequest();
+            registerMobileNetworkRequest();
+        }
+    }
+
+    /** Whether mobile network is requested. */
+    public boolean mobileNetworkRequested() {
+        return (mMobileNetworkCallback != null);
+    }
+
+    /** Request mobile network if mobile upstream is permitted. */
+    public void registerMobileNetworkRequest() {
+        if (!isCellularUpstreamPermitted()) {
+            mLog.i("registerMobileNetworkRequest() is not permitted");
+            releaseMobileNetworkRequest();
+            return;
+        }
+        if (mMobileNetworkCallback != null) {
+            mLog.e("registerMobileNetworkRequest() already registered");
+            return;
+        }
+
+        final NetworkRequest mobileUpstreamRequest;
+        if (mDunRequired) {
+            mobileUpstreamRequest = new NetworkRequest.Builder()
+                    .addCapability(NET_CAPABILITY_DUN)
+                    .removeCapability(NET_CAPABILITY_NOT_RESTRICTED)
+                    .addTransportType(TRANSPORT_CELLULAR).build();
+        } else {
+            mobileUpstreamRequest = new NetworkRequest.Builder()
+                    .addCapability(NET_CAPABILITY_INTERNET)
+                    .addTransportType(TRANSPORT_CELLULAR).build();
+        }
+
+        // The existing default network and DUN callbacks will be notified.
+        // Therefore, to avoid duplicate notifications, we only register a no-op.
+        mMobileNetworkCallback = new UpstreamNetworkCallback(CALLBACK_MOBILE_REQUEST);
+
+        // The following use of the legacy type system cannot be removed until
+        // upstream selection no longer finds networks by legacy type.
+        // See also http://b/34364553 .
+        final int legacyType = mDunRequired ? TYPE_MOBILE_DUN : TYPE_MOBILE_HIPRI;
+
+        // TODO: Change the timeout from 0 (no onUnavailable callback) to some
+        // moderate callback timeout. This might be useful for updating some UI.
+        // Additionally, we log a message to aid in any subsequent debugging.
+        mLog.i("requesting mobile upstream network: " + mobileUpstreamRequest);
+
+        cm().requestNetwork(mobileUpstreamRequest, 0, legacyType, mHandler,
+                mMobileNetworkCallback);
+    }
+
+    /** Release mobile network request. */
+    public void releaseMobileNetworkRequest() {
+        if (mMobileNetworkCallback == null) return;
+
+        cm().unregisterNetworkCallback(mMobileNetworkCallback);
+        mMobileNetworkCallback = null;
+    }
+
+    // So many TODOs here, but chief among them is: make this functionality an
+    // integral part of this class such that whenever a higher priority network
+    // becomes available and useful we (a) file a request to keep it up as
+    // necessary and (b) change all upstream tracking state accordingly (by
+    // passing LinkProperties up to Tethering).
+    /**
+     * Select the first available network from |perferredTypes|.
+     */
+    public UpstreamNetworkState selectPreferredUpstreamType(Iterable<Integer> preferredTypes) {
+        final TypeStatePair typeStatePair = findFirstAvailableUpstreamByType(
+                mNetworkMap.values(), preferredTypes, isCellularUpstreamPermitted());
+
+        mLog.log("preferred upstream type: " + typeStatePair.type);
+
+        switch (typeStatePair.type) {
+            case TYPE_MOBILE_DUN:
+            case TYPE_MOBILE_HIPRI:
+                // Tethering just selected mobile upstream in spite of the default network being
+                // not mobile. This can happen because of the priority list.
+                // Notify EntitlementManager to check permission for using mobile upstream.
+                if (!mIsDefaultCellularUpstream) {
+                    mEntitlementMgr.maybeRunProvisioning();
+                }
+                // If we're on DUN, put our own grab on it.
+                registerMobileNetworkRequest();
+                break;
+            case TYPE_NONE:
+                // If we found NONE and mobile upstream is permitted we don't want to do this
+                // as we want any previous requests to keep trying to bring up something we can use.
+                if (!isCellularUpstreamPermitted()) releaseMobileNetworkRequest();
+                break;
+            default:
+                // If we've found an active upstream connection that's not DUN/HIPRI
+                // we should stop any outstanding DUN/HIPRI requests.
+                releaseMobileNetworkRequest();
+                break;
+        }
+
+        return typeStatePair.ns;
+    }
+
+    /**
+     * Get current preferred upstream network. If default network is cellular and DUN is required,
+     * preferred upstream would be DUN otherwise preferred upstream is the same as default network.
+     * Returns null if no current upstream is available.
+     */
+    public UpstreamNetworkState getCurrentPreferredUpstream() {
+        final UpstreamNetworkState dfltState = (mDefaultInternetNetwork != null)
+                ? mNetworkMap.get(mDefaultInternetNetwork)
+                : null;
+        if (isNetworkUsableAndNotCellular(dfltState)) return dfltState;
+
+        if (!isCellularUpstreamPermitted()) return null;
+
+        if (!mDunRequired) return dfltState;
+
+        // Find a DUN network. Note that code in Tethering causes a DUN request
+        // to be filed, but this might be moved into this class in future.
+        return findFirstDunNetwork(mNetworkMap.values());
+    }
+
+    /** Tell UpstreamNetworkMonitor which network is the current upstream of tethering. */
+    public void setCurrentUpstream(Network upstream) {
+        mTetheringUpstreamNetwork = upstream;
+    }
+
+    /** Return local prefixes. */
+    public Set<IpPrefix> getLocalPrefixes() {
+        return (Set<IpPrefix>) mLocalPrefixes.clone();
+    }
+
+    private boolean isCellularUpstreamPermitted() {
+        if (mEntitlementMgr != null) {
+            return mEntitlementMgr.isCellularUpstreamPermitted();
+        } else {
+            // This flow should only happens in testing.
+            return true;
+        }
+    }
+
+    private void handleAvailable(Network network) {
+        if (mNetworkMap.containsKey(network)) return;
+
+        if (VDBG) Log.d(TAG, "onAvailable for " + network);
+        mNetworkMap.put(network, new UpstreamNetworkState(null, null, network));
+    }
+
+    private void handleNetCap(Network network, NetworkCapabilities newNc) {
+        final UpstreamNetworkState prev = mNetworkMap.get(network);
+        if (prev == null || newNc.equals(prev.networkCapabilities)) {
+            // Ignore notifications about networks for which we have not yet
+            // received onAvailable() (should never happen) and any duplicate
+            // notifications (e.g. matching more than one of our callbacks).
+            return;
+        }
+
+        if (VDBG) {
+            Log.d(TAG, String.format("EVENT_ON_CAPABILITIES for %s: %s",
+                    network, newNc));
+        }
+
+        mNetworkMap.put(network, new UpstreamNetworkState(
+                prev.linkProperties, newNc, network));
+        // TODO: If sufficient information is available to select a more
+        // preferable upstream, do so now and notify the target.
+        notifyTarget(EVENT_ON_CAPABILITIES, network);
+    }
+
+    private void handleLinkProp(Network network, LinkProperties newLp) {
+        final UpstreamNetworkState prev = mNetworkMap.get(network);
+        if (prev == null || newLp.equals(prev.linkProperties)) {
+            // Ignore notifications about networks for which we have not yet
+            // received onAvailable() (should never happen) and any duplicate
+            // notifications (e.g. matching more than one of our callbacks).
+            return;
+        }
+
+        if (VDBG) {
+            Log.d(TAG, String.format("EVENT_ON_LINKPROPERTIES for %s: %s",
+                    network, newLp));
+        }
+
+        mNetworkMap.put(network, new UpstreamNetworkState(
+                newLp, prev.networkCapabilities, network));
+        // TODO: If sufficient information is available to select a more
+        // preferable upstream, do so now and notify the target.
+        notifyTarget(EVENT_ON_LINKPROPERTIES, network);
+    }
+
+    private void handleLost(Network network) {
+        // There are few TODOs within ConnectivityService's rematching code
+        // pertaining to spurious onLost() notifications.
+        //
+        // TODO: simplify this, probably if favor of code that:
+        //     - selects a new upstream if mTetheringUpstreamNetwork has
+        //       been lost (by any callback)
+        //     - deletes the entry from the map only when the LISTEN_ALL
+        //       callback gets notified.
+
+        if (!mNetworkMap.containsKey(network)) {
+            // Ignore loss of networks about which we had not previously
+            // learned any information or for which we have already processed
+            // an onLost() notification.
+            return;
+        }
+
+        if (VDBG) Log.d(TAG, "EVENT_ON_LOST for " + network);
+
+        // TODO: If sufficient information is available to select a more
+        // preferable upstream, do so now and notify the target.  Likewise,
+        // if the current upstream network is gone, notify the target of the
+        // fact that we now have no upstream at all.
+        notifyTarget(EVENT_ON_LOST, mNetworkMap.remove(network));
+    }
+
+    private void recomputeLocalPrefixes() {
+        final HashSet<IpPrefix> localPrefixes = allLocalPrefixes(mNetworkMap.values());
+        if (!mLocalPrefixes.equals(localPrefixes)) {
+            mLocalPrefixes = localPrefixes;
+            notifyTarget(NOTIFY_LOCAL_PREFIXES, localPrefixes.clone());
+        }
+    }
+
+    // Fetch (and cache) a ConnectivityManager only if and when we need one.
+    private ConnectivityManager cm() {
+        if (mCM == null) {
+            // MUST call the String variant to be able to write unittests.
+            mCM = (ConnectivityManager) mContext.getSystemService(Context.CONNECTIVITY_SERVICE);
+        }
+        return mCM;
+    }
+
+    /**
+     * A NetworkCallback class that handles information of interest directly
+     * in the thread on which it is invoked. To avoid locking, this MUST be
+     * run on the same thread as the target state machine's handler.
+     */
+    private class UpstreamNetworkCallback extends NetworkCallback {
+        private final int mCallbackType;
+
+        UpstreamNetworkCallback(int callbackType) {
+            mCallbackType = callbackType;
+        }
+
+        @Override
+        public void onAvailable(Network network) {
+            handleAvailable(network);
+        }
+
+        @Override
+        public void onCapabilitiesChanged(Network network, NetworkCapabilities newNc) {
+            if (mCallbackType == CALLBACK_DEFAULT_INTERNET) {
+                mDefaultInternetNetwork = network;
+                final boolean newIsCellular = isCellular(newNc);
+                if (mIsDefaultCellularUpstream != newIsCellular) {
+                    mIsDefaultCellularUpstream = newIsCellular;
+                    mEntitlementMgr.notifyUpstream(newIsCellular);
+                }
+                return;
+            }
+
+            handleNetCap(network, newNc);
+        }
+
+        @Override
+        public void onLinkPropertiesChanged(Network network, LinkProperties newLp) {
+            if (mCallbackType == CALLBACK_DEFAULT_INTERNET) return;
+
+            handleLinkProp(network, newLp);
+            // Any non-LISTEN_ALL callback will necessarily concern a network that will
+            // also match the LISTEN_ALL callback by construction of the LISTEN_ALL callback.
+            // So it's not useful to do this work for non-LISTEN_ALL callbacks.
+            if (mCallbackType == CALLBACK_LISTEN_ALL) {
+                recomputeLocalPrefixes();
+            }
+        }
+
+        @Override
+        public void onLost(Network network) {
+            if (mCallbackType == CALLBACK_DEFAULT_INTERNET) {
+                mDefaultInternetNetwork = null;
+                mIsDefaultCellularUpstream = false;
+                mEntitlementMgr.notifyUpstream(false);
+                return;
+            }
+
+            handleLost(network);
+            // Any non-LISTEN_ALL callback will necessarily concern a network that will
+            // also match the LISTEN_ALL callback by construction of the LISTEN_ALL callback.
+            // So it's not useful to do this work for non-LISTEN_ALL callbacks.
+            if (mCallbackType == CALLBACK_LISTEN_ALL) {
+                recomputeLocalPrefixes();
+            }
+        }
+    }
+
+    private void releaseCallback(NetworkCallback cb) {
+        if (cb != null) cm().unregisterNetworkCallback(cb);
+    }
+
+    private void notifyTarget(int which, Network network) {
+        notifyTarget(which, mNetworkMap.get(network));
+    }
+
+    private void notifyTarget(int which, Object obj) {
+        mTarget.sendMessage(mWhat, which, 0, obj);
+    }
+
+    private static class TypeStatePair {
+        public int type = TYPE_NONE;
+        public UpstreamNetworkState ns = null;
+    }
+
+    private static TypeStatePair findFirstAvailableUpstreamByType(
+            Iterable<UpstreamNetworkState> netStates, Iterable<Integer> preferredTypes,
+            boolean isCellularUpstreamPermitted) {
+        final TypeStatePair result = new TypeStatePair();
+
+        for (int type : preferredTypes) {
+            NetworkCapabilities nc;
+            try {
+                nc = networkCapabilitiesForType(type);
+            } catch (IllegalArgumentException iae) {
+                Log.e(TAG, "No NetworkCapabilities mapping for legacy type: " + type);
+                continue;
+            }
+            if (!isCellularUpstreamPermitted && isCellular(nc)) {
+                continue;
+            }
+
+            for (UpstreamNetworkState value : netStates) {
+                if (!nc.satisfiedByNetworkCapabilities(value.networkCapabilities)) {
+                    continue;
+                }
+
+                result.type = type;
+                result.ns = value;
+                return result;
+            }
+        }
+
+        return result;
+    }
+
+    private static HashSet<IpPrefix> allLocalPrefixes(Iterable<UpstreamNetworkState> netStates) {
+        final HashSet<IpPrefix> prefixSet = new HashSet<>();
+
+        for (UpstreamNetworkState ns : netStates) {
+            final LinkProperties lp = ns.linkProperties;
+            if (lp == null) continue;
+            prefixSet.addAll(PrefixUtils.localPrefixesFrom(lp));
+        }
+
+        return prefixSet;
+    }
+
+    private static boolean isCellular(UpstreamNetworkState ns) {
+        return (ns != null) && isCellular(ns.networkCapabilities);
+    }
+
+    private static boolean isCellular(NetworkCapabilities nc) {
+        return (nc != null) && nc.hasTransport(TRANSPORT_CELLULAR)
+               && nc.hasCapability(NET_CAPABILITY_NOT_VPN);
+    }
+
+    private static boolean hasCapability(UpstreamNetworkState ns, int netCap) {
+        return (ns != null) && (ns.networkCapabilities != null)
+               && ns.networkCapabilities.hasCapability(netCap);
+    }
+
+    private static boolean isNetworkUsableAndNotCellular(UpstreamNetworkState ns) {
+        return (ns != null) && (ns.networkCapabilities != null) && (ns.linkProperties != null)
+               && !isCellular(ns.networkCapabilities);
+    }
+
+    private static UpstreamNetworkState findFirstDunNetwork(
+            Iterable<UpstreamNetworkState> netStates) {
+        for (UpstreamNetworkState ns : netStates) {
+            if (isCellular(ns) && hasCapability(ns, NET_CAPABILITY_DUN)) return ns;
+        }
+
+        return null;
+    }
+
+    /**
+     * Given a legacy type (TYPE_WIFI, ...) returns the corresponding NetworkCapabilities instance.
+     * This function is used for deprecated legacy type and be disabled by default.
+     */
+    @VisibleForTesting
+    public static NetworkCapabilities networkCapabilitiesForType(int type) {
+        final NetworkCapabilities.Builder builder = new NetworkCapabilities.Builder();
+
+        // Map from type to transports.
+        final int notFound = -1;
+        final int transport = sLegacyTypeToTransport.get(type, notFound);
+        Preconditions.checkArgument(transport != notFound, "unknown legacy type: " + type);
+        builder.addTransportType(transport);
+
+        if (type == TYPE_MOBILE_DUN) {
+            builder.addCapability(NetworkCapabilities.NET_CAPABILITY_DUN);
+            // DUN is restricted network, see NetworkCapabilities#FORCE_RESTRICTED_CAPABILITIES.
+            builder.removeCapability(NetworkCapabilities.NET_CAPABILITY_NOT_RESTRICTED);
+        } else {
+            builder.addCapability(NetworkCapabilities.NET_CAPABILITY_INTERNET);
+        }
+        return builder.build();
+    }
+}

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

@@ -0,0 +1,51 @@
+/*
+ * Copyright (C) 2019 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.android.networkstack.tethering;
+
+import android.net.LinkProperties;
+import android.net.Network;
+import android.net.NetworkCapabilities;
+
+import androidx.annotation.NonNull;
+
+/**
+ * Snapshot of tethering upstream network state.
+ */
+public class UpstreamNetworkState {
+    /** {@link LinkProperties}. */
+    public final LinkProperties linkProperties;
+    /** {@link NetworkCapabilities}. */
+    public final NetworkCapabilities networkCapabilities;
+    /** {@link Network}. */
+    public final Network network;
+
+    /** Constructs a new UpstreamNetworkState. */
+    public UpstreamNetworkState(LinkProperties linkProperties,
+            NetworkCapabilities networkCapabilities, Network network) {
+        this.linkProperties = linkProperties;
+        this.networkCapabilities = networkCapabilities;
+        this.network = network;
+    }
+
+    @NonNull
+    @Override
+    public String toString() {
+        return String.format("UpstreamNetworkState{%s, %s, %s}",
+                network == null ? "null" : network,
+                networkCapabilities == null ? "null" : networkCapabilities,
+                linkProperties == null ? "null" : linkProperties);
+    }
+}

Tethering/tests/unit/AndroidManifest.xml

@@ -21,11 +21,11 @@
     <application android:debuggable="true">
         <uses-library android:name="android.test.runner" />
         <service
-            android:name="com.android.server.connectivity.tethering.MockTetheringService"
+            android:name="com.android.networkstack.tethering.MockTetheringService"
             android:permission="android.permission.TETHER_PRIVILEGED"
             android:exported="true">
             <intent-filter>
-                <action android:name="com.android.server.connectivity.tethering.TetheringService"/>
+                <action android:name="com.android.networkstack.tethering.TetheringService"/>
             </intent-filter>
         </service>
     </application>

Tethering/tests/unit/src/com/android/networkstack/tethering/ConnectedClientsTrackerTest.kt

@@ -0,0 +1,162 @@
+/*
+ * 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 android.net.LinkAddress
+import android.net.MacAddress
+import android.net.TetheredClient
+import android.net.TetheredClient.AddressInfo
+import android.net.TetheringManager.TETHERING_USB
+import android.net.TetheringManager.TETHERING_WIFI
+import android.net.ip.IpServer
+import android.net.wifi.WifiClient
+import androidx.test.filters.SmallTest
+import androidx.test.runner.AndroidJUnit4
+import org.junit.Test
+import org.junit.runner.RunWith
+import org.mockito.Mockito.doReturn
+import org.mockito.Mockito.mock
+import kotlin.test.assertEquals
+import kotlin.test.assertFalse
+import kotlin.test.assertTrue
+
+@RunWith(AndroidJUnit4::class)
+@SmallTest
+class ConnectedClientsTrackerTest {
+
+    private val server1 = mock(IpServer::class.java)
+    private val server2 = mock(IpServer::class.java)
+    private val servers = listOf(server1, server2)
+
+    private val clock = TestClock(1324L)
+
+    private val client1Addr = MacAddress.fromString("01:23:45:67:89:0A")
+    private val client1 = TetheredClient(client1Addr, listOf(
+            makeAddrInfo("192.168.43.44/32", null /* hostname */, clock.time + 20)),
+            TETHERING_WIFI)
+    private val wifiClient1 = makeWifiClient(client1Addr)
+    private val client2Addr = MacAddress.fromString("02:34:56:78:90:AB")
+    private val client2Exp30AddrInfo = makeAddrInfo(
+            "192.168.43.45/32", "my_hostname", clock.time + 30)
+    private val client2 = TetheredClient(client2Addr, listOf(
+            client2Exp30AddrInfo,
+            makeAddrInfo("2001:db8:12::34/72", "other_hostname", clock.time + 10)),
+            TETHERING_WIFI)
+    private val wifiClient2 = makeWifiClient(client2Addr)
+    private val client3Addr = MacAddress.fromString("03:45:67:89:0A:BC")
+    private val client3 = TetheredClient(client3Addr,
+            listOf(makeAddrInfo("2001:db8:34::34/72", "other_other_hostname", clock.time + 10)),
+            TETHERING_USB)
+
+    private fun makeAddrInfo(addr: String, hostname: String?, expTime: Long) =
+            LinkAddress(addr).let {
+                AddressInfo(LinkAddress(it.address, it.prefixLength, it.flags, it.scope,
+                        expTime /* deprecationTime */, expTime /* expirationTime */), hostname)
+            }
+
+    @Test
+    fun testUpdateConnectedClients() {
+        doReturn(emptyList<TetheredClient>()).`when`(server1).allLeases
+        doReturn(emptyList<TetheredClient>()).`when`(server2).allLeases
+
+        val tracker = ConnectedClientsTracker(clock)
+        assertFalse(tracker.updateConnectedClients(servers, null))
+
+        // Obtain a lease for client 1
+        doReturn(listOf(client1)).`when`(server1).allLeases
+        assertSameClients(listOf(client1), assertNewClients(tracker, servers, listOf(wifiClient1)))
+
+        // Client 2 L2-connected, no lease yet
+        val client2WithoutAddr = TetheredClient(client2Addr, emptyList(), TETHERING_WIFI)
+        assertSameClients(listOf(client1, client2WithoutAddr),
+                assertNewClients(tracker, servers, listOf(wifiClient1, wifiClient2)))
+
+        // Client 2 lease obtained
+        doReturn(listOf(client1, client2)).`when`(server1).allLeases
+        assertSameClients(listOf(client1, client2), assertNewClients(tracker, servers, null))
+
+        // Client 3 lease obtained
+        doReturn(listOf(client3)).`when`(server2).allLeases
+        assertSameClients(listOf(client1, client2, client3),
+                assertNewClients(tracker, servers, null))
+
+        // Client 2 L2-disconnected
+        assertSameClients(listOf(client1, client3),
+                assertNewClients(tracker, servers, listOf(wifiClient1)))
+
+        // Client 1 L2-disconnected
+        assertSameClients(listOf(client3), assertNewClients(tracker, servers, emptyList()))
+
+        // Client 1 comes back
+        assertSameClients(listOf(client1, client3),
+                assertNewClients(tracker, servers, listOf(wifiClient1)))
+
+        // Leases lost, client 1 still L2-connected
+        doReturn(emptyList<TetheredClient>()).`when`(server1).allLeases
+        doReturn(emptyList<TetheredClient>()).`when`(server2).allLeases
+        assertSameClients(listOf(TetheredClient(client1Addr, emptyList(), TETHERING_WIFI)),
+                assertNewClients(tracker, servers, null))
+    }
+
+    @Test
+    fun testUpdateConnectedClients_LeaseExpiration() {
+        val tracker = ConnectedClientsTracker(clock)
+        doReturn(listOf(client1, client2)).`when`(server1).allLeases
+        doReturn(listOf(client3)).`when`(server2).allLeases
+        assertSameClients(listOf(client1, client2, client3), assertNewClients(
+                tracker, servers, listOf(wifiClient1, wifiClient2)))
+
+        clock.time += 20
+        // Client 3 has no remaining lease: removed
+        val expectedClients = listOf(
+                // Client 1 has no remaining lease but is L2-connected
+                TetheredClient(client1Addr, emptyList(), TETHERING_WIFI),
+                // Client 2 has some expired leases
+                TetheredClient(
+                        client2Addr,
+                        // Only the "t + 30" address is left, the "t + 10" address expired
+                        listOf(client2Exp30AddrInfo),
+                        TETHERING_WIFI))
+        assertSameClients(expectedClients, assertNewClients(tracker, servers, null))
+    }
+
+    private fun assertNewClients(
+        tracker: ConnectedClientsTracker,
+        ipServers: Iterable<IpServer>,
+        wifiClients: List<WifiClient>?
+    ): List<TetheredClient> {
+        assertTrue(tracker.updateConnectedClients(ipServers, wifiClients))
+        return tracker.lastTetheredClients
+    }
+
+    private fun assertSameClients(expected: List<TetheredClient>, actual: List<TetheredClient>) {
+        val expectedSet = HashSet(expected)
+        assertEquals(expected.size, expectedSet.size)
+        assertEquals(expectedSet, HashSet(actual))
+    }
+
+    private fun makeWifiClient(macAddr: MacAddress): WifiClient {
+        // Use a mock WifiClient as the constructor is not part of the WiFi module exported API.
+        return mock(WifiClient::class.java).apply { doReturn(macAddr).`when`(this).macAddress }
+    }
+
+    private class TestClock(var time: Long) : ConnectedClientsTracker.Clock() {
+        override fun elapsedRealtime(): Long {
+            return time
+        }
+    }
+}

Tethering/tests/unit/src/com/android/networkstack/tethering/EntitlementManagerTest.java

@@ -0,0 +1,522 @@
+/*
+ * Copyright (C) 2018 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.TetheringManager.TETHERING_BLUETOOTH;
+import static android.net.TetheringManager.TETHERING_ETHERNET;
+import static android.net.TetheringManager.TETHERING_USB;
+import static android.net.TetheringManager.TETHERING_WIFI;
+import static android.net.TetheringManager.TETHERING_WIFI_P2P;
+import static android.net.TetheringManager.TETHER_ERROR_ENTITLEMENT_UNKNOWN;
+import static android.net.TetheringManager.TETHER_ERROR_NO_ERROR;
+import static android.net.TetheringManager.TETHER_ERROR_PROVISIONING_FAILED;
+import static android.provider.DeviceConfig.NAMESPACE_CONNECTIVITY;
+import static android.telephony.SubscriptionManager.INVALID_SUBSCRIPTION_ID;
+
+import static com.android.dx.mockito.inline.extended.ExtendedMockito.doReturn;
+import static com.android.dx.mockito.inline.extended.ExtendedMockito.mockitoSession;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+import static org.mockito.Matchers.anyBoolean;
+import static org.mockito.Matchers.anyInt;
+import static org.mockito.Matchers.anyString;
+import static org.mockito.Matchers.eq;
+import static org.mockito.Mockito.times;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
+
+import android.content.Context;
+import android.content.res.Resources;
+import android.net.util.SharedLog;
+import android.os.Bundle;
+import android.os.Message;
+import android.os.PersistableBundle;
+import android.os.ResultReceiver;
+import android.os.SystemProperties;
+import android.os.test.TestLooper;
+import android.provider.DeviceConfig;
+import android.telephony.CarrierConfigManager;
+
+import androidx.test.filters.SmallTest;
+import androidx.test.runner.AndroidJUnit4;
+
+import com.android.internal.util.State;
+import com.android.internal.util.StateMachine;
+import com.android.internal.util.test.BroadcastInterceptingContext;
+
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mockito.Mock;
+import org.mockito.MockitoAnnotations;
+import org.mockito.MockitoSession;
+import org.mockito.quality.Strictness;
+
+import java.util.ArrayList;
+
+@RunWith(AndroidJUnit4.class)
+@SmallTest
+public final class EntitlementManagerTest {
+
+    private static final int EVENT_EM_UPDATE = 1;
+    private static final String[] PROVISIONING_APP_NAME = {"some", "app"};
+    private static final String PROVISIONING_NO_UI_APP_NAME = "no_ui_app";
+
+    @Mock private CarrierConfigManager mCarrierConfigManager;
+    @Mock private Context mContext;
+    @Mock private Resources mResources;
+    @Mock private SharedLog mLog;
+    @Mock private EntitlementManager.OnUiEntitlementFailedListener mEntitlementFailedListener;
+
+    // Like so many Android system APIs, these cannot be mocked because it is marked final.
+    // We have to use the real versions.
+    private final PersistableBundle mCarrierConfig = new PersistableBundle();
+    private final TestLooper mLooper = new TestLooper();
+    private Context mMockContext;
+
+    private TestStateMachine mSM;
+    private WrappedEntitlementManager mEnMgr;
+    private TetheringConfiguration mConfig;
+    private MockitoSession mMockingSession;
+
+    private class MockContext extends BroadcastInterceptingContext {
+        MockContext(Context base) {
+            super(base);
+        }
+
+        @Override
+        public Resources getResources() {
+            return mResources;
+        }
+    }
+
+    public class WrappedEntitlementManager extends EntitlementManager {
+        public int fakeEntitlementResult = TETHER_ERROR_ENTITLEMENT_UNKNOWN;
+        public int uiProvisionCount = 0;
+        public int silentProvisionCount = 0;
+
+        public WrappedEntitlementManager(Context ctx, StateMachine target,
+                SharedLog log, int what) {
+            super(ctx, target, log, what);
+        }
+
+        public void reset() {
+            fakeEntitlementResult = TETHER_ERROR_ENTITLEMENT_UNKNOWN;
+            uiProvisionCount = 0;
+            silentProvisionCount = 0;
+        }
+
+        @Override
+        protected void runUiTetherProvisioning(int type, int subId, ResultReceiver receiver) {
+            uiProvisionCount++;
+            receiver.send(fakeEntitlementResult, null);
+        }
+
+        @Override
+        protected void runSilentTetherProvisioning(int type, int subId) {
+            silentProvisionCount++;
+            addDownstreamMapping(type, fakeEntitlementResult);
+        }
+    }
+
+    @Before
+    public void setUp() {
+        MockitoAnnotations.initMocks(this);
+        mMockingSession = mockitoSession()
+                .initMocks(this)
+                .mockStatic(SystemProperties.class)
+                .mockStatic(DeviceConfig.class)
+                .strictness(Strictness.WARN)
+                .startMocking();
+        // Don't disable tethering provisioning unless requested.
+        doReturn(false).when(
+                () -> SystemProperties.getBoolean(
+                eq(EntitlementManager.DISABLE_PROVISIONING_SYSPROP_KEY), anyBoolean()));
+        doReturn(false).when(
+                () -> DeviceConfig.getBoolean(eq(NAMESPACE_CONNECTIVITY),
+                eq(TetheringConfiguration.TETHER_ENABLE_LEGACY_DHCP_SERVER), anyBoolean()));
+
+        when(mResources.getStringArray(R.array.config_tether_dhcp_range))
+                .thenReturn(new String[0]);
+        when(mResources.getStringArray(R.array.config_tether_usb_regexs))
+                .thenReturn(new String[0]);
+        when(mResources.getStringArray(R.array.config_tether_wifi_regexs))
+                .thenReturn(new String[0]);
+        when(mResources.getStringArray(R.array.config_tether_bluetooth_regexs))
+                .thenReturn(new String[0]);
+        when(mResources.getIntArray(R.array.config_tether_upstream_types))
+                .thenReturn(new int[0]);
+        when(mResources.getBoolean(R.bool.config_tether_enable_legacy_dhcp_server)).thenReturn(
+                false);
+        when(mResources.getString(R.string.config_wifi_tether_enable)).thenReturn("");
+        when(mLog.forSubComponent(anyString())).thenReturn(mLog);
+
+        mMockContext = new MockContext(mContext);
+        mSM = new TestStateMachine();
+        mEnMgr = new WrappedEntitlementManager(mMockContext, mSM, mLog, EVENT_EM_UPDATE);
+        mEnMgr.setOnUiEntitlementFailedListener(mEntitlementFailedListener);
+        mConfig = new TetheringConfiguration(mMockContext, mLog, INVALID_SUBSCRIPTION_ID);
+        mEnMgr.setTetheringConfigurationFetcher(() -> {
+            return mConfig;
+        });
+    }
+
+    @After
+    public void tearDown() throws Exception {
+        if (mSM != null) {
+            mSM.quit();
+            mSM = null;
+        }
+        mMockingSession.finishMocking();
+    }
+
+    private void setupForRequiredProvisioning() {
+        // Produce some acceptable looking provision app setting if requested.
+        when(mResources.getStringArray(R.array.config_mobile_hotspot_provision_app))
+                .thenReturn(PROVISIONING_APP_NAME);
+        when(mResources.getString(R.string.config_mobile_hotspot_provision_app_no_ui))
+                .thenReturn(PROVISIONING_NO_UI_APP_NAME);
+        // Act like the CarrierConfigManager is present and ready unless told otherwise.
+        when(mContext.getSystemService(Context.CARRIER_CONFIG_SERVICE))
+                .thenReturn(mCarrierConfigManager);
+        when(mCarrierConfigManager.getConfigForSubId(anyInt())).thenReturn(mCarrierConfig);
+        mCarrierConfig.putBoolean(CarrierConfigManager.KEY_REQUIRE_ENTITLEMENT_CHECKS_BOOL, true);
+        mCarrierConfig.putBoolean(CarrierConfigManager.KEY_CARRIER_CONFIG_APPLIED_BOOL, true);
+        mConfig = new TetheringConfiguration(mMockContext, mLog, INVALID_SUBSCRIPTION_ID);
+    }
+
+    @Test
+    public void canRequireProvisioning() {
+        setupForRequiredProvisioning();
+        assertTrue(mEnMgr.isTetherProvisioningRequired(mConfig));
+    }
+
+    @Test
+    public void toleratesCarrierConfigManagerMissing() {
+        setupForRequiredProvisioning();
+        when(mContext.getSystemService(Context.CARRIER_CONFIG_SERVICE))
+            .thenReturn(null);
+        mConfig = new TetheringConfiguration(mMockContext, mLog, INVALID_SUBSCRIPTION_ID);
+        // Couldn't get the CarrierConfigManager, but still had a declared provisioning app.
+        // Therefore provisioning still be required.
+        assertTrue(mEnMgr.isTetherProvisioningRequired(mConfig));
+    }
+
+    @Test
+    public void toleratesCarrierConfigMissing() {
+        setupForRequiredProvisioning();
+        when(mCarrierConfigManager.getConfig()).thenReturn(null);
+        mConfig = new TetheringConfiguration(mMockContext, mLog, INVALID_SUBSCRIPTION_ID);
+        // We still have a provisioning app configured, so still require provisioning.
+        assertTrue(mEnMgr.isTetherProvisioningRequired(mConfig));
+    }
+
+    @Test
+    public void toleratesCarrierConfigNotLoaded() {
+        setupForRequiredProvisioning();
+        mCarrierConfig.putBoolean(CarrierConfigManager.KEY_CARRIER_CONFIG_APPLIED_BOOL, false);
+        // We still have a provisioning app configured, so still require provisioning.
+        assertTrue(mEnMgr.isTetherProvisioningRequired(mConfig));
+    }
+
+    @Test
+    public void provisioningNotRequiredWhenAppNotFound() {
+        setupForRequiredProvisioning();
+        when(mResources.getStringArray(R.array.config_mobile_hotspot_provision_app))
+            .thenReturn(null);
+        mConfig = new TetheringConfiguration(mMockContext, mLog, INVALID_SUBSCRIPTION_ID);
+        assertFalse(mEnMgr.isTetherProvisioningRequired(mConfig));
+        when(mResources.getStringArray(R.array.config_mobile_hotspot_provision_app))
+            .thenReturn(new String[] {"malformedApp"});
+        mConfig = new TetheringConfiguration(mMockContext, mLog, INVALID_SUBSCRIPTION_ID);
+        assertFalse(mEnMgr.isTetherProvisioningRequired(mConfig));
+    }
+
+    @Test
+    public void testRequestLastEntitlementCacheValue() throws Exception {
+        // 1. Entitlement check is not required.
+        mEnMgr.fakeEntitlementResult = TETHER_ERROR_NO_ERROR;
+        ResultReceiver receiver = new ResultReceiver(null) {
+            @Override
+            protected void onReceiveResult(int resultCode, Bundle resultData) {
+                assertEquals(TETHER_ERROR_NO_ERROR, resultCode);
+            }
+        };
+        mEnMgr.requestLatestTetheringEntitlementResult(TETHERING_WIFI, receiver, true);
+        mLooper.dispatchAll();
+        assertEquals(0, mEnMgr.uiProvisionCount);
+        mEnMgr.reset();
+
+        setupForRequiredProvisioning();
+        // 2. No cache value and don't need to run entitlement check.
+        receiver = new ResultReceiver(null) {
+            @Override
+            protected void onReceiveResult(int resultCode, Bundle resultData) {
+                assertEquals(TETHER_ERROR_ENTITLEMENT_UNKNOWN, resultCode);
+            }
+        };
+        mEnMgr.requestLatestTetheringEntitlementResult(TETHERING_WIFI, receiver, false);
+        mLooper.dispatchAll();
+        assertEquals(0, mEnMgr.uiProvisionCount);
+        mEnMgr.reset();
+        // 3. No cache value and ui entitlement check is needed.
+        mEnMgr.fakeEntitlementResult = TETHER_ERROR_PROVISIONING_FAILED;
+        receiver = new ResultReceiver(null) {
+            @Override
+            protected void onReceiveResult(int resultCode, Bundle resultData) {
+                assertEquals(TETHER_ERROR_PROVISIONING_FAILED, resultCode);
+            }
+        };
+        mEnMgr.requestLatestTetheringEntitlementResult(TETHERING_WIFI, receiver, true);
+        mLooper.dispatchAll();
+        assertEquals(1, mEnMgr.uiProvisionCount);
+        mEnMgr.reset();
+        // 4. Cache value is TETHER_ERROR_PROVISIONING_FAILED and don't need to run entitlement
+        // check.
+        mEnMgr.fakeEntitlementResult = TETHER_ERROR_NO_ERROR;
+        receiver = new ResultReceiver(null) {
+            @Override
+            protected void onReceiveResult(int resultCode, Bundle resultData) {
+                assertEquals(TETHER_ERROR_PROVISIONING_FAILED, resultCode);
+            }
+        };
+        mEnMgr.requestLatestTetheringEntitlementResult(TETHERING_WIFI, receiver, false);
+        mLooper.dispatchAll();
+        assertEquals(0, mEnMgr.uiProvisionCount);
+        mEnMgr.reset();
+        // 5. Cache value is TETHER_ERROR_PROVISIONING_FAILED and ui entitlement check is needed.
+        mEnMgr.fakeEntitlementResult = TETHER_ERROR_NO_ERROR;
+        receiver = new ResultReceiver(null) {
+            @Override
+            protected void onReceiveResult(int resultCode, Bundle resultData) {
+                assertEquals(TETHER_ERROR_NO_ERROR, resultCode);
+            }
+        };
+        mEnMgr.requestLatestTetheringEntitlementResult(TETHERING_WIFI, receiver, true);
+        mLooper.dispatchAll();
+        assertEquals(1, mEnMgr.uiProvisionCount);
+        mEnMgr.reset();
+        // 6. Cache value is TETHER_ERROR_NO_ERROR.
+        mEnMgr.fakeEntitlementResult = TETHER_ERROR_NO_ERROR;
+        receiver = new ResultReceiver(null) {
+            @Override
+            protected void onReceiveResult(int resultCode, Bundle resultData) {
+                assertEquals(TETHER_ERROR_NO_ERROR, resultCode);
+            }
+        };
+        mEnMgr.requestLatestTetheringEntitlementResult(TETHERING_WIFI, receiver, true);
+        mLooper.dispatchAll();
+        assertEquals(0, mEnMgr.uiProvisionCount);
+        mEnMgr.reset();
+        // 7. Test get value for other downstream type.
+        receiver = new ResultReceiver(null) {
+            @Override
+            protected void onReceiveResult(int resultCode, Bundle resultData) {
+                assertEquals(TETHER_ERROR_ENTITLEMENT_UNKNOWN, resultCode);
+            }
+        };
+        mEnMgr.requestLatestTetheringEntitlementResult(TETHERING_USB, receiver, false);
+        mLooper.dispatchAll();
+        assertEquals(0, mEnMgr.uiProvisionCount);
+        mEnMgr.reset();
+        // 8. Test get value for invalid downstream type.
+        mEnMgr.fakeEntitlementResult = TETHER_ERROR_NO_ERROR;
+        receiver = new ResultReceiver(null) {
+            @Override
+            protected void onReceiveResult(int resultCode, Bundle resultData) {
+                assertEquals(TETHER_ERROR_ENTITLEMENT_UNKNOWN, resultCode);
+            }
+        };
+        mEnMgr.requestLatestTetheringEntitlementResult(TETHERING_WIFI_P2P, receiver, true);
+        mLooper.dispatchAll();
+        assertEquals(0, mEnMgr.uiProvisionCount);
+        mEnMgr.reset();
+    }
+
+    @Test
+    public void verifyPermissionResult() {
+        setupForRequiredProvisioning();
+        mEnMgr.notifyUpstream(true);
+        mEnMgr.fakeEntitlementResult = TETHER_ERROR_PROVISIONING_FAILED;
+        mEnMgr.startProvisioningIfNeeded(TETHERING_WIFI, true);
+        mLooper.dispatchAll();
+        assertFalse(mEnMgr.isCellularUpstreamPermitted());
+        mEnMgr.stopProvisioningIfNeeded(TETHERING_WIFI);
+        mLooper.dispatchAll();
+        mEnMgr.fakeEntitlementResult = TETHER_ERROR_NO_ERROR;
+        mEnMgr.startProvisioningIfNeeded(TETHERING_WIFI, true);
+        mLooper.dispatchAll();
+        assertTrue(mEnMgr.isCellularUpstreamPermitted());
+    }
+
+    @Test
+    public void verifyPermissionIfAllNotApproved() {
+        setupForRequiredProvisioning();
+        mEnMgr.notifyUpstream(true);
+        mEnMgr.fakeEntitlementResult = TETHER_ERROR_PROVISIONING_FAILED;
+        mEnMgr.startProvisioningIfNeeded(TETHERING_WIFI, true);
+        mLooper.dispatchAll();
+        assertFalse(mEnMgr.isCellularUpstreamPermitted());
+        mEnMgr.fakeEntitlementResult = TETHER_ERROR_PROVISIONING_FAILED;
+        mEnMgr.startProvisioningIfNeeded(TETHERING_USB, true);
+        mLooper.dispatchAll();
+        assertFalse(mEnMgr.isCellularUpstreamPermitted());
+        mEnMgr.fakeEntitlementResult = TETHER_ERROR_PROVISIONING_FAILED;
+        mEnMgr.startProvisioningIfNeeded(TETHERING_BLUETOOTH, true);
+        mLooper.dispatchAll();
+        assertFalse(mEnMgr.isCellularUpstreamPermitted());
+    }
+
+    @Test
+    public void verifyPermissionIfAnyApproved() {
+        setupForRequiredProvisioning();
+        mEnMgr.notifyUpstream(true);
+        mEnMgr.fakeEntitlementResult = TETHER_ERROR_NO_ERROR;
+        mEnMgr.startProvisioningIfNeeded(TETHERING_WIFI, true);
+        mLooper.dispatchAll();
+        assertTrue(mEnMgr.isCellularUpstreamPermitted());
+        mLooper.dispatchAll();
+        mEnMgr.fakeEntitlementResult = TETHER_ERROR_PROVISIONING_FAILED;
+        mEnMgr.startProvisioningIfNeeded(TETHERING_USB, true);
+        mLooper.dispatchAll();
+        assertTrue(mEnMgr.isCellularUpstreamPermitted());
+        mEnMgr.stopProvisioningIfNeeded(TETHERING_WIFI);
+        mLooper.dispatchAll();
+        assertFalse(mEnMgr.isCellularUpstreamPermitted());
+
+    }
+
+    @Test
+    public void verifyPermissionWhenProvisioningNotStarted() {
+        assertTrue(mEnMgr.isCellularUpstreamPermitted());
+        setupForRequiredProvisioning();
+        assertFalse(mEnMgr.isCellularUpstreamPermitted());
+    }
+
+    @Test
+    public void testRunTetherProvisioning() {
+        setupForRequiredProvisioning();
+        // 1. start ui provisioning, upstream is mobile
+        mEnMgr.fakeEntitlementResult = TETHER_ERROR_NO_ERROR;
+        mEnMgr.notifyUpstream(true);
+        mLooper.dispatchAll();
+        mEnMgr.startProvisioningIfNeeded(TETHERING_USB, true);
+        mLooper.dispatchAll();
+        assertEquals(1, mEnMgr.uiProvisionCount);
+        assertEquals(0, mEnMgr.silentProvisionCount);
+        assertTrue(mEnMgr.isCellularUpstreamPermitted());
+        mEnMgr.reset();
+        // 2. start no-ui provisioning
+        mEnMgr.fakeEntitlementResult = TETHER_ERROR_NO_ERROR;
+        mEnMgr.startProvisioningIfNeeded(TETHERING_WIFI, false);
+        mLooper.dispatchAll();
+        assertEquals(0, mEnMgr.uiProvisionCount);
+        assertEquals(1, mEnMgr.silentProvisionCount);
+        assertTrue(mEnMgr.isCellularUpstreamPermitted());
+        mEnMgr.reset();
+        // 3. tear down mobile, then start ui provisioning
+        mEnMgr.notifyUpstream(false);
+        mLooper.dispatchAll();
+        mEnMgr.startProvisioningIfNeeded(TETHERING_BLUETOOTH, true);
+        mLooper.dispatchAll();
+        assertEquals(0, mEnMgr.uiProvisionCount);
+        assertEquals(0, mEnMgr.silentProvisionCount);
+        mEnMgr.reset();
+        // 4. switch upstream back to mobile
+        mEnMgr.fakeEntitlementResult = TETHER_ERROR_NO_ERROR;
+        mEnMgr.notifyUpstream(true);
+        mLooper.dispatchAll();
+        assertEquals(1, mEnMgr.uiProvisionCount);
+        assertEquals(0, mEnMgr.silentProvisionCount);
+        assertTrue(mEnMgr.isCellularUpstreamPermitted());
+        mEnMgr.reset();
+        // 5. tear down mobile, then switch SIM
+        mEnMgr.notifyUpstream(false);
+        mLooper.dispatchAll();
+        mEnMgr.reevaluateSimCardProvisioning(mConfig);
+        assertEquals(0, mEnMgr.uiProvisionCount);
+        assertEquals(0, mEnMgr.silentProvisionCount);
+        mEnMgr.reset();
+        // 6. switch upstream back to mobile again
+        mEnMgr.fakeEntitlementResult = TETHER_ERROR_PROVISIONING_FAILED;
+        mEnMgr.notifyUpstream(true);
+        mLooper.dispatchAll();
+        assertEquals(0, mEnMgr.uiProvisionCount);
+        assertEquals(3, mEnMgr.silentProvisionCount);
+        assertFalse(mEnMgr.isCellularUpstreamPermitted());
+        mEnMgr.reset();
+        // 7. start ui provisioning, upstream is mobile, downstream is ethernet
+        mEnMgr.fakeEntitlementResult = TETHER_ERROR_NO_ERROR;
+        mEnMgr.startProvisioningIfNeeded(TETHERING_ETHERNET, true);
+        mLooper.dispatchAll();
+        assertEquals(1, mEnMgr.uiProvisionCount);
+        assertEquals(0, mEnMgr.silentProvisionCount);
+        assertTrue(mEnMgr.isCellularUpstreamPermitted());
+        mEnMgr.reset();
+        // 8. downstream is invalid
+        mEnMgr.fakeEntitlementResult = TETHER_ERROR_NO_ERROR;
+        mEnMgr.startProvisioningIfNeeded(TETHERING_WIFI_P2P, true);
+        mLooper.dispatchAll();
+        assertEquals(0, mEnMgr.uiProvisionCount);
+        assertEquals(0, mEnMgr.silentProvisionCount);
+        mEnMgr.reset();
+    }
+
+    @Test
+    public void testCallStopTetheringWhenUiProvisioningFail() {
+        setupForRequiredProvisioning();
+        verify(mEntitlementFailedListener, times(0)).onUiEntitlementFailed(TETHERING_WIFI);
+        mEnMgr.fakeEntitlementResult = TETHER_ERROR_PROVISIONING_FAILED;
+        mEnMgr.notifyUpstream(true);
+        mLooper.dispatchAll();
+        mEnMgr.startProvisioningIfNeeded(TETHERING_WIFI, true);
+        mLooper.dispatchAll();
+        assertEquals(1, mEnMgr.uiProvisionCount);
+        verify(mEntitlementFailedListener, times(1)).onUiEntitlementFailed(TETHERING_WIFI);
+    }
+
+    public class TestStateMachine extends StateMachine {
+        public final ArrayList<Message> messages = new ArrayList<>();
+        private final State
+                mLoggingState = new EntitlementManagerTest.TestStateMachine.LoggingState();
+
+        class LoggingState extends State {
+            @Override public void enter() {
+                messages.clear();
+            }
+
+            @Override public void exit() {
+                messages.clear();
+            }
+
+            @Override public boolean processMessage(Message msg) {
+                messages.add(msg);
+                return false;
+            }
+        }
+
+        public TestStateMachine() {
+            super("EntitlementManagerTest.TestStateMachine", mLooper.getLooper());
+            addState(mLoggingState);
+            setInitialState(mLoggingState);
+            super.start();
+        }
+    }
+}