diff --git a/Tethering/common/TetheringLib/Android.bp b/Tethering/common/TetheringLib/Android.bp
index 7ac9d25..79a1782 100644
--- a/Tethering/common/TetheringLib/Android.bp
+++ b/Tethering/common/TetheringLib/Android.bp
@@ -13,49 +13,11 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-// AIDL interfaces between the core system and the tethering mainline module.
-aidl_interface {
-    name: "tethering-aidl-interfaces",
-    unstable: true,
-    local_include_dir: "src",
-    include_dirs: ["frameworks/base/core/java"], // For framework parcelables.
-    srcs: [
-        // @JavaOnlyStableParcelable aidl declarations must not be listed here, as this would cause
-        // compilation to fail (b/148001843).
-        "src/android/net/IIntResultListener.aidl",
-        "src/android/net/ITetheringConnector.aidl",
-        "src/android/net/ITetheringEventCallback.aidl",
-        "src/android/net/TetheringCallbackStartedParcel.aidl",
-        "src/android/net/TetheringConfigurationParcel.aidl",
-        "src/android/net/TetheringRequestParcel.aidl",
-        "src/android/net/TetherStatesParcel.aidl",
-    ],
-    backend: {
-        ndk: {
-            enabled: false,
-        },
-        cpp: {
-            enabled: false,
-        },
-        java: {
-            apex_available: [
-                "//apex_available:platform",
-                "com.android.tethering",
-            ],
-        },
-    },
-}
-
 java_library {
     name: "framework-tethering",
     sdk_version: "module_current",
     srcs: [
-        "src/android/net/TetheredClient.java",
-        "src/android/net/TetheringManager.java",
-        "src/android/net/TetheringConstants.java",
-    ],
-    static_libs: [
-        "tethering-aidl-interfaces-java",
+        ":framework-tethering-srcs",
     ],
     jarjar_rules: "jarjar-rules.txt",
     installable: true,
diff --git a/Tethering/src/com/android/networkstack/tethering/OffloadHardwareInterface.java b/Tethering/src/com/android/networkstack/tethering/OffloadHardwareInterface.java
index 293f8ea..fe92204 100644
--- a/Tethering/src/com/android/networkstack/tethering/OffloadHardwareInterface.java
+++ b/Tethering/src/com/android/networkstack/tethering/OffloadHardwareInterface.java
@@ -66,6 +66,7 @@
 
     private final Handler mHandler;
     private final SharedLog mLog;
+    private final Dependencies mDeps;
     private IOffloadControl mOffloadControl;
     private TetheringOffloadCallback mTetheringOffloadCallback;
     private ControlCallback mControlCallback;
@@ -126,8 +127,76 @@
     }
 
     public OffloadHardwareInterface(Handler h, SharedLog log) {
+        this(h, log, new Dependencies(log));
+    }
+
+    OffloadHardwareInterface(Handler h, SharedLog log, Dependencies deps) {
         mHandler = h;
         mLog = log.forSubComponent(TAG);
+        mDeps = deps;
+    }
+
+    /** Capture OffloadHardwareInterface dependencies, for injection. */
+    static class Dependencies {
+        private final SharedLog mLog;
+
+        Dependencies(SharedLog log) {
+            mLog = log;
+        }
+
+        public IOffloadConfig getOffloadConfig() {
+            try {
+                return IOffloadConfig.getService(true /*retry*/);
+            } catch (RemoteException | NoSuchElementException e) {
+                mLog.e("getIOffloadConfig error " + e);
+                return null;
+            }
+        }
+
+        public IOffloadControl getOffloadControl() {
+            try {
+                return IOffloadControl.getService(true /*retry*/);
+            } catch (RemoteException | NoSuchElementException e) {
+                mLog.e("tethering offload control not supported: " + e);
+                return null;
+            }
+        }
+
+        public NativeHandle createConntrackSocket(final int groups) {
+            final 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);
+        }
     }
 
     /** Get default value indicating whether offload is supported. */
@@ -141,13 +210,7 @@
      * share them with offload management process.
      */
     public boolean initOffloadConfig() {
-        IOffloadConfig offloadConfig;
-        try {
-            offloadConfig = IOffloadConfig.getService(true /*retry*/);
-        } catch (RemoteException | NoSuchElementException e) {
-            mLog.e("getIOffloadConfig error " + e);
-            return false;
-        }
+        final IOffloadConfig offloadConfig = mDeps.getOffloadConfig();
         if (offloadConfig == null) {
             mLog.e("Could not find IOffloadConfig service");
             return false;
@@ -159,11 +222,11 @@
         //
         // h2    provides a file descriptor bound to the following netlink groups
         //       (NF_NETLINK_CONNTRACK_UPDATE | NF_NETLINK_CONNTRACK_DESTROY).
-        final NativeHandle h1 = createConntrackSocket(
+        final NativeHandle h1 = mDeps.createConntrackSocket(
                 NF_NETLINK_CONNTRACK_NEW | NF_NETLINK_CONNTRACK_DESTROY);
         if (h1 == null) return false;
 
-        final NativeHandle h2 = createConntrackSocket(
+        final NativeHandle h2 = mDeps.createConntrackSocket(
                 NF_NETLINK_CONNTRACK_UPDATE | NF_NETLINK_CONNTRACK_DESTROY);
         if (h2 == null) {
             closeFdInNativeHandle(h1);
@@ -198,53 +261,12 @@
         }
     }
 
-    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(true /*retry*/);
-            } catch (RemoteException | NoSuchElementException e) {
-                mLog.e("tethering offload control not supported: " + e);
-                return false;
-            }
+            mOffloadControl = mDeps.getOffloadControl();
             if (mOffloadControl == null) {
                 mLog.e("tethering IOffloadControl.getService() returned null");
                 return false;
diff --git a/Tethering/src/com/android/networkstack/tethering/Tethering.java b/Tethering/src/com/android/networkstack/tethering/Tethering.java
index bca86ca..3ce3b45 100644
--- a/Tethering/src/com/android/networkstack/tethering/Tethering.java
+++ b/Tethering/src/com/android/networkstack/tethering/Tethering.java
@@ -109,8 +109,10 @@
 import android.os.RemoteException;
 import android.os.ResultReceiver;
 import android.os.ServiceSpecificException;
+import android.os.SystemProperties;
 import android.os.UserHandle;
 import android.os.UserManager;
+import android.provider.Settings;
 import android.telephony.PhoneStateListener;
 import android.telephony.TelephonyManager;
 import android.text.TextUtils;
@@ -228,6 +230,7 @@
     private final ConnectedClientsTracker mConnectedClientsTracker;
     private final TetheringThreadExecutor mExecutor;
     private final TetheringNotificationUpdater mNotificationUpdater;
+    private final UserManager mUserManager;
     private int mActiveDataSubId = INVALID_SUBSCRIPTION_ID;
     // All the usage of mTetheringEventCallback should run in the same thread.
     private ITetheringEventCallback mTetheringEventCallback = null;
@@ -305,23 +308,24 @@
 
         mStateReceiver = new StateReceiver();
 
-        final UserManager userManager = (UserManager) mContext.getSystemService(
-                Context.USER_SERVICE);
+        mUserManager = (UserManager) mContext.getSystemService(Context.USER_SERVICE);
         mTetheringRestriction = new UserRestrictionActionListener(
-                userManager, this, mNotificationUpdater);
+                mUserManager, this, mNotificationUpdater);
         mExecutor = new TetheringThreadExecutor(mHandler);
         mActiveDataSubIdListener = new ActiveDataSubIdListener(mExecutor);
         mNetdCallback = new NetdCallback();
 
         // Load tethering configuration.
         updateConfiguration();
+
+        startStateMachineUpdaters();
     }
 
     /**
      * Start to register callbacks.
      * Call this function when tethering is ready to handle callback events.
      */
-    public void startStateMachineUpdaters() {
+    private void startStateMachineUpdaters() {
         try {
             mNetd.registerUnsolicitedEventListener(mNetdCallback);
         } catch (RemoteException e) {
@@ -779,7 +783,7 @@
 
     // TODO: Figure out how to update for local hotspot mode interfaces.
     private void sendTetherStateChangedBroadcast() {
-        if (!mDeps.isTetheringSupported()) return;
+        if (!isTetheringSupported()) return;
 
         final ArrayList<String> availableList = new ArrayList<>();
         final ArrayList<String> tetherList = new ArrayList<>();
@@ -1020,14 +1024,14 @@
 
     @VisibleForTesting
     protected static class UserRestrictionActionListener {
-        private final UserManager mUserManager;
+        private final UserManager mUserMgr;
         private final Tethering mWrapper;
         private final TetheringNotificationUpdater mNotificationUpdater;
         public boolean mDisallowTethering;
 
         public UserRestrictionActionListener(@NonNull UserManager um, @NonNull Tethering wrapper,
                 @NonNull TetheringNotificationUpdater updater) {
-            mUserManager = um;
+            mUserMgr = um;
             mWrapper = wrapper;
             mNotificationUpdater = updater;
             mDisallowTethering = false;
@@ -1037,7 +1041,7 @@
             // getUserRestrictions gets restriction for this process' user, which is the primary
             // user. This is fine because DISALLOW_CONFIG_TETHERING can only be set on the primary
             // user. See UserManager.DISALLOW_CONFIG_TETHERING.
-            final Bundle restrictions = mUserManager.getUserRestrictions();
+            final Bundle restrictions = mUserMgr.getUserRestrictions();
             final boolean newlyDisallowed =
                     restrictions.getBoolean(UserManager.DISALLOW_CONFIG_TETHERING);
             final boolean prevDisallowed = mDisallowTethering;
@@ -1988,7 +1992,7 @@
         mHandler.post(() -> {
             mTetheringEventCallbacks.register(callback, new CallbackCookie(hasListPermission));
             final TetheringCallbackStartedParcel parcel = new TetheringCallbackStartedParcel();
-            parcel.tetheringSupported = mDeps.isTetheringSupported();
+            parcel.tetheringSupported = isTetheringSupported();
             parcel.upstreamNetwork = mTetherUpstream;
             parcel.config = mConfig.toStableParcelable();
             parcel.states =
@@ -2111,6 +2115,20 @@
         }
     }
 
+    // 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.
+    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 && hasTetherableConfiguration();
+    }
+
     void dump(@NonNull FileDescriptor fd, @NonNull PrintWriter writer, @Nullable String[] args) {
         // Binder.java closes the resource for us.
         @SuppressWarnings("resource")
diff --git a/Tethering/src/com/android/networkstack/tethering/TetheringService.java b/Tethering/src/com/android/networkstack/tethering/TetheringService.java
index af349f2..7d01273 100644
--- a/Tethering/src/com/android/networkstack/tethering/TetheringService.java
+++ b/Tethering/src/com/android/networkstack/tethering/TetheringService.java
@@ -40,15 +40,12 @@
 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;
 
@@ -68,21 +65,14 @@
 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();
+        final TetheringDependencies deps = makeTetheringDependencies();
+        // The Tethering object needs a fully functional context to start, so this can't be done
+        // in the constructor.
+        mConnector = new TetheringConnector(makeTethering(deps), TetheringService.this);
     }
 
     /**
@@ -94,21 +84,10 @@
         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();
+        return mConnector;
     }
 
     private static class TetheringConnector extends ITetheringConnector.Stub {
@@ -248,7 +227,7 @@
                     listener.onResult(TETHER_ERROR_NO_CHANGE_TETHERING_PERMISSION);
                     return true;
                 }
-                if (!mService.isTetheringSupported()) {
+                if (!mTethering.isTetheringSupported()) {
                     listener.onResult(TETHER_ERROR_UNSUPPORTED);
                     return true;
                 }
@@ -266,7 +245,7 @@
                 receiver.send(TETHER_ERROR_NO_CHANGE_TETHERING_PERMISSION, null);
                 return true;
             }
-            if (!mService.isTetheringSupported()) {
+            if (!mTethering.isTetheringSupported()) {
                 receiver.send(TETHER_ERROR_UNSUPPORTED, null);
                 return true;
             }
@@ -300,20 +279,6 @@
         }
     }
 
-    // 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();
-    }
-
     /**
      * Check if the package is a allowed to write settings. This also accounts that such an access
      * happened.
@@ -332,87 +297,79 @@
      * 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;
-                }
+    public TetheringDependencies makeTetheringDependencies() {
+        return 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 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 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;
 
-                @Override
-                public IpServer.Dependencies getIpServerDependencies() {
-                    return new IpServer.Dependencies() {
-                        @Override
-                        public void makeDhcpServer(String ifName, DhcpServingParamsParcel params,
-                                DhcpServerCallbacks cb) {
+                            service.makeDhcpServer(ifName, params, cb);
+                        } catch (RemoteException e) {
+                            Log.e(TAG, "Fail to make dhcp server");
                             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) { }
-                            }
+                                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();
+            // 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 mDeps;
+                return INetworkStackConnector.Stub.asInterface(connector);
+            }
+
+            @Override
+            public BluetoothAdapter getBluetoothAdapter() {
+                return BluetoothAdapter.getDefaultAdapter();
+            }
+        };
     }
 }
diff --git a/Tethering/tests/unit/src/com/android/networkstack/tethering/OffloadHardwareInterfaceTest.java b/Tethering/tests/unit/src/com/android/networkstack/tethering/OffloadHardwareInterfaceTest.java
new file mode 100644
index 0000000..f8ff1cb
--- /dev/null
+++ b/Tethering/tests/unit/src/com/android/networkstack/tethering/OffloadHardwareInterfaceTest.java
@@ -0,0 +1,215 @@
+/*
+ * 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.util.TetheringUtils.uint16;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotNull;
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.ArgumentMatchers.eq;
+import static org.mockito.Mockito.spy;
+import static org.mockito.Mockito.verify;
+
+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.util.SharedLog;
+import android.os.Handler;
+import android.os.NativeHandle;
+import android.os.test.TestLooper;
+import android.system.OsConstants;
+
+import androidx.test.filters.SmallTest;
+import androidx.test.runner.AndroidJUnit4;
+
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mockito.ArgumentCaptor;
+import org.mockito.Mock;
+import org.mockito.MockitoAnnotations;
+
+import java.util.ArrayList;
+
+@RunWith(AndroidJUnit4.class)
+@SmallTest
+public final class OffloadHardwareInterfaceTest {
+    private static final String RMNET0 = "test_rmnet_data0";
+
+    private final TestLooper mTestLooper = new TestLooper();
+
+    private OffloadHardwareInterface mOffloadHw;
+    private ITetheringOffloadCallback mTetheringOffloadCallback;
+    private OffloadHardwareInterface.ControlCallback mControlCallback;
+
+    @Mock private IOffloadConfig mIOffloadConfig;
+    @Mock private IOffloadControl mIOffloadControl;
+    @Mock private NativeHandle mNativeHandle;
+
+    class MyDependencies extends OffloadHardwareInterface.Dependencies {
+        MyDependencies(SharedLog log) {
+            super(log);
+        }
+
+        @Override
+        public IOffloadConfig getOffloadConfig() {
+            return mIOffloadConfig;
+        }
+
+        @Override
+        public IOffloadControl getOffloadControl() {
+            return mIOffloadControl;
+        }
+
+        @Override
+        public NativeHandle createConntrackSocket(final int groups) {
+            return mNativeHandle;
+        }
+    }
+
+    @Before
+    public void setUp() {
+        MockitoAnnotations.initMocks(this);
+        final SharedLog log = new SharedLog("test");
+        mOffloadHw = new OffloadHardwareInterface(new Handler(mTestLooper.getLooper()), log,
+                new MyDependencies(log));
+        mControlCallback = spy(new OffloadHardwareInterface.ControlCallback());
+    }
+
+    private void startOffloadHardwareInterface() throws Exception {
+        mOffloadHw.initOffloadConfig();
+        mOffloadHw.initOffloadControl(mControlCallback);
+        final ArgumentCaptor<ITetheringOffloadCallback> mOffloadCallbackCaptor =
+                ArgumentCaptor.forClass(ITetheringOffloadCallback.class);
+        verify(mIOffloadControl).initOffload(mOffloadCallbackCaptor.capture(), any());
+        mTetheringOffloadCallback = mOffloadCallbackCaptor.getValue();
+    }
+
+    @Test
+    public void testGetForwardedStats() throws Exception {
+        startOffloadHardwareInterface();
+        final OffloadHardwareInterface.ForwardedStats stats = mOffloadHw.getForwardedStats(RMNET0);
+        verify(mIOffloadControl).getForwardedStats(eq(RMNET0), any());
+        assertNotNull(stats);
+    }
+
+    @Test
+    public void testSetLocalPrefixes() throws Exception {
+        startOffloadHardwareInterface();
+        final ArrayList<String> localPrefixes = new ArrayList<>();
+        localPrefixes.add("127.0.0.0/8");
+        localPrefixes.add("fe80::/64");
+        mOffloadHw.setLocalPrefixes(localPrefixes);
+        verify(mIOffloadControl).setLocalPrefixes(eq(localPrefixes), any());
+    }
+
+    @Test
+    public void testSetDataLimit() throws Exception {
+        startOffloadHardwareInterface();
+        final long limit = 12345;
+        mOffloadHw.setDataLimit(RMNET0, limit);
+        verify(mIOffloadControl).setDataLimit(eq(RMNET0), eq(limit), any());
+    }
+
+    @Test
+    public void testSetUpstreamParameters() throws Exception {
+        startOffloadHardwareInterface();
+        final String v4addr = "192.168.10.1";
+        final String v4gateway = "192.168.10.255";
+        final ArrayList<String> v6gws = new ArrayList<>(0);
+        v6gws.add("2001:db8::1");
+        mOffloadHw.setUpstreamParameters(RMNET0, v4addr, v4gateway, v6gws);
+        verify(mIOffloadControl).setUpstreamParameters(eq(RMNET0), eq(v4addr), eq(v4gateway),
+                eq(v6gws), any());
+
+        final ArgumentCaptor<ArrayList<String>> mArrayListCaptor =
+                ArgumentCaptor.forClass(ArrayList.class);
+        mOffloadHw.setUpstreamParameters(null, null, null, null);
+        verify(mIOffloadControl).setUpstreamParameters(eq(""), eq(""), eq(""),
+                mArrayListCaptor.capture(), any());
+        assertEquals(mArrayListCaptor.getValue().size(), 0);
+    }
+
+    @Test
+    public void testUpdateDownstreamPrefix() throws Exception {
+        startOffloadHardwareInterface();
+        final String ifName = "wlan1";
+        final String prefix = "192.168.43.0/24";
+        mOffloadHw.addDownstreamPrefix(ifName, prefix);
+        verify(mIOffloadControl).addDownstream(eq(ifName), eq(prefix), any());
+
+        mOffloadHw.removeDownstreamPrefix(ifName, prefix);
+        verify(mIOffloadControl).removeDownstream(eq(ifName), eq(prefix), any());
+    }
+
+    @Test
+    public void testTetheringOffloadCallback() throws Exception {
+        startOffloadHardwareInterface();
+
+        mTetheringOffloadCallback.onEvent(OffloadCallbackEvent.OFFLOAD_STARTED);
+        mTestLooper.dispatchAll();
+        verify(mControlCallback).onStarted();
+
+        mTetheringOffloadCallback.onEvent(OffloadCallbackEvent.OFFLOAD_STOPPED_ERROR);
+        mTestLooper.dispatchAll();
+        verify(mControlCallback).onStoppedError();
+
+        mTetheringOffloadCallback.onEvent(OffloadCallbackEvent.OFFLOAD_STOPPED_UNSUPPORTED);
+        mTestLooper.dispatchAll();
+        verify(mControlCallback).onStoppedUnsupported();
+
+        mTetheringOffloadCallback.onEvent(OffloadCallbackEvent.OFFLOAD_SUPPORT_AVAILABLE);
+        mTestLooper.dispatchAll();
+        verify(mControlCallback).onSupportAvailable();
+
+        mTetheringOffloadCallback.onEvent(OffloadCallbackEvent.OFFLOAD_STOPPED_LIMIT_REACHED);
+        mTestLooper.dispatchAll();
+        verify(mControlCallback).onStoppedLimitReached();
+
+        final NatTimeoutUpdate tcpParams = buildNatTimeoutUpdate(NetworkProtocol.TCP);
+        mTetheringOffloadCallback.updateTimeout(tcpParams);
+        mTestLooper.dispatchAll();
+        verify(mControlCallback).onNatTimeoutUpdate(eq(OsConstants.IPPROTO_TCP),
+                eq(tcpParams.src.addr),
+                eq(uint16(tcpParams.src.port)),
+                eq(tcpParams.dst.addr),
+                eq(uint16(tcpParams.dst.port)));
+
+        final NatTimeoutUpdate udpParams = buildNatTimeoutUpdate(NetworkProtocol.UDP);
+        mTetheringOffloadCallback.updateTimeout(udpParams);
+        mTestLooper.dispatchAll();
+        verify(mControlCallback).onNatTimeoutUpdate(eq(OsConstants.IPPROTO_UDP),
+                eq(udpParams.src.addr),
+                eq(uint16(udpParams.src.port)),
+                eq(udpParams.dst.addr),
+                eq(uint16(udpParams.dst.port)));
+    }
+
+    private NatTimeoutUpdate buildNatTimeoutUpdate(final int proto) {
+        final NatTimeoutUpdate params = new NatTimeoutUpdate();
+        params.proto = proto;
+        params.src.addr = "192.168.43.200";
+        params.src.port = 100;
+        params.dst.addr = "172.50.46.169";
+        params.dst.port = 150;
+        return params;
+    }
+}
diff --git a/Tethering/tests/unit/src/com/android/networkstack/tethering/TetheringServiceTest.java b/Tethering/tests/unit/src/com/android/networkstack/tethering/TetheringServiceTest.java
index 7df9fc6..3dc6a13 100644
--- a/Tethering/tests/unit/src/com/android/networkstack/tethering/TetheringServiceTest.java
+++ b/Tethering/tests/unit/src/com/android/networkstack/tethering/TetheringServiceTest.java
@@ -83,8 +83,7 @@
         mTetheringConnector = mockConnector.getTetheringConnector();
         final MockTetheringService service = mockConnector.getService();
         mTethering = service.getTethering();
-        verify(mTethering).startStateMachineUpdaters();
-        when(mTethering.hasTetherableConfiguration()).thenReturn(true);
+        when(mTethering.isTetheringSupported()).thenReturn(true);
     }
 
     @After
@@ -97,7 +96,7 @@
         when(mTethering.tether(TEST_IFACE_NAME)).thenReturn(TETHER_ERROR_NO_ERROR);
         final TestTetheringResult result = new TestTetheringResult();
         mTetheringConnector.tether(TEST_IFACE_NAME, TEST_CALLER_PKG, TEST_ATTRIBUTION_TAG, result);
-        verify(mTethering).hasTetherableConfiguration();
+        verify(mTethering).isTetheringSupported();
         verify(mTethering).tether(TEST_IFACE_NAME);
         verifyNoMoreInteractions(mTethering);
         result.assertResult(TETHER_ERROR_NO_ERROR);
@@ -109,7 +108,7 @@
         final TestTetheringResult result = new TestTetheringResult();
         mTetheringConnector.untether(TEST_IFACE_NAME, TEST_CALLER_PKG, TEST_ATTRIBUTION_TAG,
                 result);
-        verify(mTethering).hasTetherableConfiguration();
+        verify(mTethering).isTetheringSupported();
         verify(mTethering).untether(TEST_IFACE_NAME);
         verifyNoMoreInteractions(mTethering);
         result.assertResult(TETHER_ERROR_NO_ERROR);
@@ -121,7 +120,7 @@
         final TestTetheringResult result = new TestTetheringResult();
         mTetheringConnector.setUsbTethering(true /* enable */, TEST_CALLER_PKG,
                 TEST_ATTRIBUTION_TAG, result);
-        verify(mTethering).hasTetherableConfiguration();
+        verify(mTethering).isTetheringSupported();
         verify(mTethering).setUsbTethering(true /* enable */);
         verifyNoMoreInteractions(mTethering);
         result.assertResult(TETHER_ERROR_NO_ERROR);
@@ -133,7 +132,7 @@
         final TetheringRequestParcel request = new TetheringRequestParcel();
         request.tetheringType = TETHERING_WIFI;
         mTetheringConnector.startTethering(request, TEST_CALLER_PKG, TEST_ATTRIBUTION_TAG, result);
-        verify(mTethering).hasTetherableConfiguration();
+        verify(mTethering).isTetheringSupported();
         verify(mTethering).startTethering(eq(request), eq(result));
         verifyNoMoreInteractions(mTethering);
     }
@@ -143,7 +142,7 @@
         final TestTetheringResult result = new TestTetheringResult();
         mTetheringConnector.stopTethering(TETHERING_WIFI, TEST_CALLER_PKG, TEST_ATTRIBUTION_TAG,
                 result);
-        verify(mTethering).hasTetherableConfiguration();
+        verify(mTethering).isTetheringSupported();
         verify(mTethering).stopTethering(TETHERING_WIFI);
         verifyNoMoreInteractions(mTethering);
         result.assertResult(TETHER_ERROR_NO_ERROR);
@@ -154,7 +153,7 @@
         final ResultReceiver result = new ResultReceiver(null);
         mTetheringConnector.requestLatestTetheringEntitlementResult(TETHERING_WIFI, result,
                 true /* showEntitlementUi */, TEST_CALLER_PKG, TEST_ATTRIBUTION_TAG);
-        verify(mTethering).hasTetherableConfiguration();
+        verify(mTethering).isTetheringSupported();
         verify(mTethering).requestLatestTetheringEntitlementResult(eq(TETHERING_WIFI),
                 eq(result), eq(true) /* showEntitlementUi */);
         verifyNoMoreInteractions(mTethering);
@@ -181,7 +180,7 @@
     public void testStopAllTethering() throws Exception {
         final TestTetheringResult result = new TestTetheringResult();
         mTetheringConnector.stopAllTethering(TEST_CALLER_PKG, TEST_ATTRIBUTION_TAG, result);
-        verify(mTethering).hasTetherableConfiguration();
+        verify(mTethering).isTetheringSupported();
         verify(mTethering).untetherAll();
         verifyNoMoreInteractions(mTethering);
         result.assertResult(TETHER_ERROR_NO_ERROR);
@@ -191,7 +190,7 @@
     public void testIsTetheringSupported() throws Exception {
         final TestTetheringResult result = new TestTetheringResult();
         mTetheringConnector.isTetheringSupported(TEST_CALLER_PKG, TEST_ATTRIBUTION_TAG, result);
-        verify(mTethering).hasTetherableConfiguration();
+        verify(mTethering).isTetheringSupported();
         verifyNoMoreInteractions(mTethering);
         result.assertResult(TETHER_ERROR_NO_ERROR);
     }
diff --git a/Tethering/tests/unit/src/com/android/networkstack/tethering/TetheringTest.java b/Tethering/tests/unit/src/com/android/networkstack/tethering/TetheringTest.java
index 85c2f2b..b665acc 100644
--- a/Tethering/tests/unit/src/com/android/networkstack/tethering/TetheringTest.java
+++ b/Tethering/tests/unit/src/com/android/networkstack/tethering/TetheringTest.java
@@ -485,18 +485,6 @@
         MockitoAnnotations.initMocks(this);
         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[] { "test_rndis\\d" });
-        when(mResources.getStringArray(R.array.config_tether_wifi_regexs))
-                .thenReturn(new String[]{ "test_wlan\\d" });
-        when(mResources.getStringArray(R.array.config_tether_wifi_p2p_regexs))
-                .thenReturn(new String[]{ "test_p2p-p2p\\d-.*" });
-        when(mResources.getStringArray(R.array.config_tether_bluetooth_regexs))
-                .thenReturn(new String[0]);
-        when(mResources.getStringArray(R.array.config_tether_ncm_regexs))
-                .thenReturn(new String[] { "test_ncm\\d" });
-        when(mResources.getIntArray(R.array.config_tether_upstream_types)).thenReturn(new int[0]);
-        when(mResources.getBoolean(R.bool.config_tether_upstream_automatic)).thenReturn(false);
         when(mResources.getBoolean(R.bool.config_tether_enable_legacy_dhcp_server)).thenReturn(
                 false);
         when(mNetd.interfaceGetList())
@@ -515,6 +503,7 @@
         mServiceContext = new TestContext(mContext);
         mContentResolver = new MockContentResolver(mServiceContext);
         mContentResolver.addProvider(Settings.AUTHORITY, new FakeSettingsProvider());
+        setTetheringSupported(true /* supported */);
         mIntents = new Vector<>();
         mBroadcastReceiver = new BroadcastReceiver() {
             @Override
@@ -525,7 +514,6 @@
         mServiceContext.registerReceiver(mBroadcastReceiver,
                 new IntentFilter(ACTION_TETHER_STATE_CHANGED));
         mTethering = makeTethering();
-        mTethering.startStateMachineUpdaters();
         verify(mStatsManager, times(1)).registerNetworkStatsProvider(anyString(), any());
         verify(mNetd).registerUnsolicitedEventListener(any());
         final ArgumentCaptor<PhoneStateListener> phoneListenerCaptor =
@@ -536,6 +524,31 @@
         mPhoneStateListener = phoneListenerCaptor.getValue();
     }
 
+    private void setTetheringSupported(final boolean supported) {
+        Settings.Global.putInt(mContentResolver, Settings.Global.TETHER_SUPPORTED,
+                supported ? 1 : 0);
+        when(mUserManager.hasUserRestriction(
+                UserManager.DISALLOW_CONFIG_TETHERING)).thenReturn(!supported);
+        // Setup tetherable configuration.
+        when(mResources.getStringArray(R.array.config_tether_usb_regexs))
+                .thenReturn(new String[] { "test_rndis\\d" });
+        when(mResources.getStringArray(R.array.config_tether_wifi_regexs))
+                .thenReturn(new String[]{ "test_wlan\\d" });
+        when(mResources.getStringArray(R.array.config_tether_wifi_p2p_regexs))
+                .thenReturn(new String[]{ "test_p2p-p2p\\d-.*" });
+        when(mResources.getStringArray(R.array.config_tether_bluetooth_regexs))
+                .thenReturn(new String[0]);
+        when(mResources.getStringArray(R.array.config_tether_ncm_regexs))
+                .thenReturn(new String[] { "test_ncm\\d" });
+        when(mResources.getIntArray(R.array.config_tether_upstream_types)).thenReturn(new int[0]);
+        when(mResources.getBoolean(R.bool.config_tether_upstream_automatic)).thenReturn(true);
+    }
+
+    private void initTetheringUpstream(UpstreamNetworkState upstreamState) {
+        when(mUpstreamNetworkMonitor.getCurrentPreferredUpstream()).thenReturn(upstreamState);
+        when(mUpstreamNetworkMonitor.selectPreferredUpstreamType(any())).thenReturn(upstreamState);
+    }
+
     private Tethering makeTethering() {
         mTetheringDependencies.reset();
         return new Tethering(mTetheringDependencies);
@@ -672,9 +685,7 @@
     }
 
     private void prepareUsbTethering(UpstreamNetworkState upstreamState) {
-        when(mUpstreamNetworkMonitor.getCurrentPreferredUpstream()).thenReturn(upstreamState);
-        when(mUpstreamNetworkMonitor.selectPreferredUpstreamType(any()))
-                .thenReturn(upstreamState);
+        initTetheringUpstream(upstreamState);
 
         // Emulate pressing the USB tethering button in Settings UI.
         mTethering.startTethering(createTetheringRequestParcel(TETHERING_USB), null);
@@ -700,7 +711,7 @@
         verify(mNetd, times(1)).interfaceGetList();
 
         // UpstreamNetworkMonitor should receive selected upstream
-        verify(mUpstreamNetworkMonitor, times(1)).selectPreferredUpstreamType(any());
+        verify(mUpstreamNetworkMonitor, times(1)).getCurrentPreferredUpstream();
         verify(mUpstreamNetworkMonitor, times(1)).setCurrentUpstream(upstreamState.network);
     }
 
@@ -872,8 +883,7 @@
 
         // Then 464xlat comes up
         upstreamState = buildMobile464xlatUpstreamState();
-        when(mUpstreamNetworkMonitor.selectPreferredUpstreamType(any()))
-                .thenReturn(upstreamState);
+        initTetheringUpstream(upstreamState);
 
         // Upstream LinkProperties changed: UpstreamNetworkMonitor sends EVENT_ON_LINKPROPERTIES.
         mTetheringDependencies.mUpstreamNetworkMonitorMasterSM.sendMessage(
@@ -1344,9 +1354,7 @@
         callback.expectOffloadStatusChanged(TETHER_HARDWARE_OFFLOAD_STOPPED);
         // 2. Enable wifi tethering.
         UpstreamNetworkState upstreamState = buildMobileDualStackUpstreamState();
-        when(mUpstreamNetworkMonitor.getCurrentPreferredUpstream()).thenReturn(upstreamState);
-        when(mUpstreamNetworkMonitor.selectPreferredUpstreamType(any()))
-                .thenReturn(upstreamState);
+        initTetheringUpstream(upstreamState);
         when(mWifiManager.startSoftAp(any(WifiConfiguration.class))).thenReturn(true);
         mTethering.interfaceStatusChanged(TEST_WLAN_IFNAME, true);
         mLooper.dispatchAll();
@@ -1723,7 +1731,7 @@
         final Tethering.TetherMasterSM stateMachine = (Tethering.TetherMasterSM)
                 mTetheringDependencies.mUpstreamNetworkMonitorMasterSM;
         final UpstreamNetworkState upstreamState = buildMobileIPv4UpstreamState();
-        when(mUpstreamNetworkMonitor.selectPreferredUpstreamType(any())).thenReturn(upstreamState);
+        initTetheringUpstream(upstreamState);
         stateMachine.chooseUpstreamType(true);
 
         verify(mUpstreamNetworkMonitor, times(1)).setCurrentUpstream(eq(upstreamState.network));
@@ -1735,7 +1743,7 @@
         final Tethering.TetherMasterSM stateMachine = (Tethering.TetherMasterSM)
                 mTetheringDependencies.mUpstreamNetworkMonitorMasterSM;
         final UpstreamNetworkState upstreamState = buildMobileIPv4UpstreamState();
-        when(mUpstreamNetworkMonitor.selectPreferredUpstreamType(any())).thenReturn(upstreamState);
+        initTetheringUpstream(upstreamState);
         stateMachine.chooseUpstreamType(true);
 
         stateMachine.handleUpstreamNetworkMonitorCallback(EVENT_ON_CAPABILITIES, upstreamState);