diff --git a/Tethering/common/TetheringLib/src/android/net/ITetheringEventCallback.aidl b/Tethering/common/TetheringLib/src/android/net/ITetheringEventCallback.aidl
index a554193..b4e3ba4 100644
--- a/Tethering/common/TetheringLib/src/android/net/ITetheringEventCallback.aidl
+++ b/Tethering/common/TetheringLib/src/android/net/ITetheringEventCallback.aidl
@@ -35,4 +35,5 @@
     void onConfigurationChanged(in TetheringConfigurationParcel config);
     void onTetherStatesChanged(in TetherStatesParcel states);
     void onTetherClientsChanged(in List<TetheredClient> clients);
+    void onOffloadStatusChanged(int status);
 }
diff --git a/Tethering/common/TetheringLib/src/android/net/TetheringCallbackStartedParcel.aidl b/Tethering/common/TetheringLib/src/android/net/TetheringCallbackStartedParcel.aidl
index c064aa4..253eacb 100644
--- a/Tethering/common/TetheringLib/src/android/net/TetheringCallbackStartedParcel.aidl
+++ b/Tethering/common/TetheringLib/src/android/net/TetheringCallbackStartedParcel.aidl
@@ -31,4 +31,5 @@
     TetheringConfigurationParcel config;
     TetherStatesParcel states;
     List<TetheredClient> tetheredClients;
-}
\ No newline at end of file
+    int offloadStatus;
+}
diff --git a/Tethering/common/TetheringLib/src/android/net/TetheringManager.java b/Tethering/common/TetheringLib/src/android/net/TetheringManager.java
index 79242c5..7f831ce 100644
--- a/Tethering/common/TetheringLib/src/android/net/TetheringManager.java
+++ b/Tethering/common/TetheringLib/src/android/net/TetheringManager.java
@@ -18,6 +18,7 @@
 import static android.annotation.SystemApi.Client.MODULE_LIBRARIES;
 
 import android.Manifest;
+import android.annotation.IntDef;
 import android.annotation.NonNull;
 import android.annotation.Nullable;
 import android.annotation.RequiresPermission;
@@ -34,6 +35,8 @@
 
 import com.android.internal.annotations.GuardedBy;
 
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collection;
@@ -172,6 +175,23 @@
     public static final int TETHER_ERROR_NO_CHANGE_TETHERING_PERMISSION = 14;
     public static final int TETHER_ERROR_NO_ACCESS_TETHERING_PERMISSION = 15;
 
+    /** @hide */
+    @Retention(RetentionPolicy.SOURCE)
+    @IntDef(flag = false, value = {
+            TETHER_HARDWARE_OFFLOAD_STOPPED,
+            TETHER_HARDWARE_OFFLOAD_STARTED,
+            TETHER_HARDWARE_OFFLOAD_FAILED,
+    })
+    public @interface TetherOffloadStatus {
+    }
+
+    /** Tethering offload status is stopped. */
+    public static final int TETHER_HARDWARE_OFFLOAD_STOPPED = 0;
+    /** Tethering offload status is started. */
+    public static final int TETHER_HARDWARE_OFFLOAD_STARTED = 1;
+    /** Fail to start tethering offload. */
+    public static final int TETHER_HARDWARE_OFFLOAD_FAILED = 2;
+
     /**
      * Create a TetheringManager object for interacting with the tethering service.
      *
@@ -378,6 +398,9 @@
         @Override
         public void onTetherClientsChanged(List<TetheredClient> clients) { }
 
+        @Override
+        public void onOffloadStatusChanged(int status) { }
+
         public void waitForStarted() {
             mWaitForCallback.block(DEFAULT_TIMEOUT_MS);
             throwIfPermissionFailure(mError);
@@ -802,6 +825,14 @@
          * @param clients The new set of tethered clients; the collection is not ordered.
          */
         public void onClientsChanged(@NonNull Collection<TetheredClient> clients) {}
+
+        /**
+         * Called when tethering offload status changes.
+         *
+         * <p>This will be called immediately after the callback is registered.
+         * @param status The offload status.
+         */
+        public void onOffloadStatusChanged(@TetherOffloadStatus int status) {}
     }
 
     /**
@@ -925,6 +956,7 @@
                         maybeSendTetherableIfacesChangedCallback(parcel.states);
                         maybeSendTetheredIfacesChangedCallback(parcel.states);
                         callback.onClientsChanged(parcel.tetheredClients);
+                        callback.onOffloadStatusChanged(parcel.offloadStatus);
                     });
                 }
 
@@ -960,6 +992,11 @@
                 public void onTetherClientsChanged(final List<TetheredClient> clients) {
                     executor.execute(() -> callback.onClientsChanged(clients));
                 }
+
+                @Override
+                public void onOffloadStatusChanged(final int status) {
+                    executor.execute(() -> callback.onOffloadStatusChanged(status));
+                }
             };
             getConnector(c -> c.registerTetheringEventCallback(remoteCallback, callerPkg));
             mTetheringEventCallbacks.put(callback, remoteCallback);
diff --git a/Tethering/src/com/android/server/connectivity/tethering/Tethering.java b/Tethering/src/com/android/server/connectivity/tethering/Tethering.java
index 864f35c..f89da84 100644
--- a/Tethering/src/com/android/server/connectivity/tethering/Tethering.java
+++ b/Tethering/src/com/android/server/connectivity/tethering/Tethering.java
@@ -44,6 +44,9 @@
 import static android.net.TetheringManager.TETHER_ERROR_SERVICE_UNAVAIL;
 import static android.net.TetheringManager.TETHER_ERROR_UNAVAIL_IFACE;
 import static android.net.TetheringManager.TETHER_ERROR_UNKNOWN_IFACE;
+import static android.net.TetheringManager.TETHER_HARDWARE_OFFLOAD_FAILED;
+import static android.net.TetheringManager.TETHER_HARDWARE_OFFLOAD_STARTED;
+import static android.net.TetheringManager.TETHER_HARDWARE_OFFLOAD_STOPPED;
 import static android.net.util.TetheringMessageBase.BASE_MASTER;
 import static android.net.wifi.WifiManager.EXTRA_WIFI_AP_INTERFACE_NAME;
 import static android.net.wifi.WifiManager.EXTRA_WIFI_AP_MODE;
@@ -237,6 +240,7 @@
     private TetherStatesParcel mTetherStatesParcel;
     private boolean mDataSaverEnabled = false;
     private String mWifiP2pTetherInterface = null;
+    private int mOffloadStatus = TETHER_HARDWARE_OFFLOAD_STOPPED;
 
     @GuardedBy("mPublicSync")
     private EthernetManager.TetheredInterfaceRequest mEthernetIfaceRequest;
@@ -1901,12 +1905,15 @@
         // OffloadController implementation.
         class OffloadWrapper {
             public void start() {
-                mOffloadController.start();
+                final int status = mOffloadController.start() ? TETHER_HARDWARE_OFFLOAD_STARTED
+                        : TETHER_HARDWARE_OFFLOAD_FAILED;
+                updateOffloadStatus(status);
                 sendOffloadExemptPrefixes();
             }
 
             public void stop() {
                 mOffloadController.stop();
+                updateOffloadStatus(TETHER_HARDWARE_OFFLOAD_STOPPED);
             }
 
             public void updateUpstreamNetworkState(UpstreamNetworkState ns) {
@@ -1967,6 +1974,13 @@
 
                 mOffloadController.setLocalPrefixes(localPrefixes);
             }
+
+            private void updateOffloadStatus(final int newStatus) {
+                if (newStatus == mOffloadStatus) return;
+
+                mOffloadStatus = newStatus;
+                reportOffloadStatusChanged(mOffloadStatus);
+            }
         }
     }
 
@@ -2001,6 +2015,7 @@
             parcel.tetheredClients = hasListPermission
                     ? mConnectedClientsTracker.getLastTetheredClients()
                     : Collections.emptyList();
+            parcel.offloadStatus = mOffloadStatus;
             try {
                 callback.onCallbackStarted(parcel);
             } catch (RemoteException e) {
@@ -2095,6 +2110,21 @@
         }
     }
 
+    private void reportOffloadStatusChanged(final int status) {
+        final int length = mTetheringEventCallbacks.beginBroadcast();
+        try {
+            for (int i = 0; i < length; i++) {
+                try {
+                    mTetheringEventCallbacks.getBroadcastItem(i).onOffloadStatusChanged(status);
+                } catch (RemoteException e) {
+                    // Not really very much to do here.
+                }
+            }
+        } finally {
+            mTetheringEventCallbacks.finishBroadcast();
+        }
+    }
+
     void dump(@NonNull FileDescriptor fd, @NonNull PrintWriter writer, @Nullable String[] args) {
         // Binder.java closes the resource for us.
         @SuppressWarnings("resource")
diff --git a/Tethering/tests/unit/src/com/android/server/connectivity/tethering/TetheringTest.java b/Tethering/tests/unit/src/com/android/server/connectivity/tethering/TetheringTest.java
index 72c3435..af7ad66 100644
--- a/Tethering/tests/unit/src/com/android/server/connectivity/tethering/TetheringTest.java
+++ b/Tethering/tests/unit/src/com/android/server/connectivity/tethering/TetheringTest.java
@@ -34,6 +34,9 @@
 import static android.net.TetheringManager.TETHERING_WIFI;
 import static android.net.TetheringManager.TETHER_ERROR_NO_ERROR;
 import static android.net.TetheringManager.TETHER_ERROR_UNKNOWN_IFACE;
+import static android.net.TetheringManager.TETHER_HARDWARE_OFFLOAD_FAILED;
+import static android.net.TetheringManager.TETHER_HARDWARE_OFFLOAD_STARTED;
+import static android.net.TetheringManager.TETHER_HARDWARE_OFFLOAD_STOPPED;
 import static android.net.dhcp.IDhcpServer.STATUS_SUCCESS;
 import static android.net.wifi.WifiManager.EXTRA_WIFI_AP_INTERFACE_NAME;
 import static android.net.wifi.WifiManager.EXTRA_WIFI_AP_MODE;
@@ -169,6 +172,7 @@
     @Mock private Context mContext;
     @Mock private NetworkStatsManager mStatsManager;
     @Mock private OffloadHardwareInterface mOffloadHardwareInterface;
+    @Mock private OffloadHardwareInterface.ForwardedStats mForwardedStats;
     @Mock private Resources mResources;
     @Mock private TelephonyManager mTelephonyManager;
     @Mock private UsbManager mUsbManager;
@@ -463,6 +467,9 @@
         mInterfaceConfiguration.flags = new String[0];
         when(mRouterAdvertisementDaemon.start())
                 .thenReturn(true);
+        initOffloadConfiguration(true /* offloadConfig */, true /* offloadControl */,
+                0 /* defaultDisabled */);
+        when(mOffloadHardwareInterface.getForwardedStats(any())).thenReturn(mForwardedStats);
 
         mServiceContext = new TestContext(mContext);
         when(mContext.getSystemService(Context.NOTIFICATION_SERVICE)).thenReturn(null);
@@ -1136,6 +1143,7 @@
         private final ArrayList<TetheringConfigurationParcel> mTetheringConfigs =
                 new ArrayList<>();
         private final ArrayList<TetherStatesParcel> mTetherStates = new ArrayList<>();
+        private final ArrayList<Integer> mOffloadStatus = new ArrayList<>();
 
         // This function will remove the recorded callbacks, so it must be called once for
         // each callback. If this is called after multiple callback, the order matters.
@@ -1171,6 +1179,11 @@
             assertNoConfigChangeCallback();
         }
 
+        public void expectOffloadStatusChanged(final int expectedStatus) {
+            assertOffloadStatusChangedCallback();
+            assertEquals(mOffloadStatus.remove(0), new Integer(expectedStatus));
+        }
+
         public TetherStatesParcel pollTetherStatesChanged() {
             assertStateChangeCallback();
             return mTetherStates.remove(0);
@@ -1197,10 +1210,16 @@
         }
 
         @Override
+        public void onOffloadStatusChanged(final int status) {
+            mOffloadStatus.add(status);
+        }
+
+        @Override
         public void onCallbackStarted(TetheringCallbackStartedParcel parcel) {
             mActualUpstreams.add(parcel.upstreamNetwork);
             mTetheringConfigs.add(parcel.config);
             mTetherStates.add(parcel.states);
+            mOffloadStatus.add(parcel.offloadStatus);
         }
 
         @Override
@@ -1222,6 +1241,10 @@
             assertFalse(mTetherStates.isEmpty());
         }
 
+        public void assertOffloadStatusChangedCallback() {
+            assertFalse(mOffloadStatus.isEmpty());
+        }
+
         public void assertNoCallback() {
             assertNoUpstreamChangeCallback();
             assertNoConfigChangeCallback();
@@ -1270,6 +1293,7 @@
                 mTethering.getTetheringConfiguration().toStableParcelable());
         TetherStatesParcel tetherState = callback.pollTetherStatesChanged();
         assertTetherStatesNotNullButEmpty(tetherState);
+        callback.expectOffloadStatusChanged(TETHER_HARDWARE_OFFLOAD_STOPPED);
         // 2. Enable wifi tethering.
         UpstreamNetworkState upstreamState = buildMobileDualStackUpstreamState();
         when(mUpstreamNetworkMonitor.getCurrentPreferredUpstream()).thenReturn(upstreamState);
@@ -1287,6 +1311,7 @@
         tetherState = callback.pollTetherStatesChanged();
         assertArrayEquals(tetherState.tetheredList, new String[] {TEST_WLAN_IFNAME});
         callback.expectUpstreamChanged(upstreamState.network);
+        callback.expectOffloadStatusChanged(TETHER_HARDWARE_OFFLOAD_STARTED);
 
         // 3. Register second callback.
         mTethering.registerTetheringEventCallback(callback2);
@@ -1296,6 +1321,7 @@
                 mTethering.getTetheringConfiguration().toStableParcelable());
         tetherState = callback2.pollTetherStatesChanged();
         assertEquals(tetherState.tetheredList, new String[] {TEST_WLAN_IFNAME});
+        callback2.expectOffloadStatusChanged(TETHER_HARDWARE_OFFLOAD_STARTED);
 
         // 4. Unregister first callback and disable wifi tethering
         mTethering.unregisterTetheringEventCallback(callback);
@@ -1307,10 +1333,59 @@
         assertArrayEquals(tetherState.availableList, new String[] {TEST_WLAN_IFNAME});
         mLooper.dispatchAll();
         callback2.expectUpstreamChanged(new Network[] {null});
+        callback2.expectOffloadStatusChanged(TETHER_HARDWARE_OFFLOAD_STOPPED);
         callback.assertNoCallback();
     }
 
     @Test
+    public void testReportFailCallbackIfOffloadNotSupported() throws Exception {
+        final UpstreamNetworkState upstreamState = buildMobileDualStackUpstreamState();
+        TestTetheringEventCallback callback = new TestTetheringEventCallback();
+        mTethering.registerTetheringEventCallback(callback);
+        mLooper.dispatchAll();
+        callback.expectOffloadStatusChanged(TETHER_HARDWARE_OFFLOAD_STOPPED);
+
+        // 1. Offload fail if no OffloadConfig.
+        initOffloadConfiguration(false /* offloadConfig */, true /* offloadControl */,
+                0 /* defaultDisabled */);
+        runUsbTethering(upstreamState);
+        callback.expectOffloadStatusChanged(TETHER_HARDWARE_OFFLOAD_FAILED);
+        runStopUSBTethering();
+        callback.expectOffloadStatusChanged(TETHER_HARDWARE_OFFLOAD_STOPPED);
+        reset(mUsbManager);
+        // 2. Offload fail if no OffloadControl.
+        initOffloadConfiguration(true /* offloadConfig */, false /* offloadControl */,
+                0 /* defaultDisabled */);
+        runUsbTethering(upstreamState);
+        callback.expectOffloadStatusChanged(TETHER_HARDWARE_OFFLOAD_FAILED);
+        runStopUSBTethering();
+        callback.expectOffloadStatusChanged(TETHER_HARDWARE_OFFLOAD_STOPPED);
+        reset(mUsbManager);
+        // 3. Offload fail if disabled by settings.
+        initOffloadConfiguration(true /* offloadConfig */, true /* offloadControl */,
+                1 /* defaultDisabled */);
+        runUsbTethering(upstreamState);
+        callback.expectOffloadStatusChanged(TETHER_HARDWARE_OFFLOAD_FAILED);
+        runStopUSBTethering();
+        callback.expectOffloadStatusChanged(TETHER_HARDWARE_OFFLOAD_STOPPED);
+    }
+
+    private void runStopUSBTethering() {
+        mTethering.stopTethering(TETHERING_USB);
+        mLooper.dispatchAll();
+        mTethering.interfaceRemoved(TEST_USB_IFNAME);
+        mLooper.dispatchAll();
+    }
+
+    private void initOffloadConfiguration(final boolean offloadConfig,
+            final boolean offloadControl, final int defaultDisabled) {
+        when(mOffloadHardwareInterface.initOffloadConfig()).thenReturn(offloadConfig);
+        when(mOffloadHardwareInterface.initOffloadControl(any())).thenReturn(offloadControl);
+        when(mOffloadHardwareInterface.getDefaultTetherOffloadDisabled()).thenReturn(
+                defaultDisabled);
+    }
+
+    @Test
     public void testMultiSimAware() throws Exception {
         final TetheringConfiguration initailConfig = mTethering.getTetheringConfiguration();
         assertEquals(INVALID_SUBSCRIPTION_ID, initailConfig.activeDataSubId);