Send offload status changed callback

The callback would be fired when offload started, stopped, or failed.
If offload is not supported, "failed" callback would be fired when user
enable tethering. Enabling multiple tethering would not have multiple
offload status callbacks because offload should already be started or
failed.

Bug: 130596697
Test: -build, flash, boot
      -atest TetheringTests
      -ON/OFF hotspot
Change-Id: Ia0398601144b0e5f61dc0c5771eacf13e7cfbb59

Tethering/common/TetheringLib/src/android/net/ITetheringEventCallback.aidl

@@ -35,4 +35,5 @@ oneway interface ITetheringEventCallback
     void onConfigurationChanged(in TetheringConfigurationParcel config);
     void onTetherStatesChanged(in TetherStatesParcel states);
     void onTetherClientsChanged(in List<TetheredClient> clients);
+    void onOffloadStatusChanged(int status);
 }

Tethering/common/TetheringLib/src/android/net/TetheringCallbackStartedParcel.aidl

@@ -31,4 +31,5 @@ parcelable TetheringCallbackStartedParcel {
     TetheringConfigurationParcel config;
     TetherStatesParcel states;
     List<TetheredClient> tetheredClients;
-}
+    int offloadStatus;
+}

Tethering/common/TetheringLib/src/android/net/TetheringManager.java

@@ -18,6 +18,7 @@ package android.net;
 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 android.util.Log;
 
 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 class TetheringManager {
     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 @@ public class TetheringManager {
         @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 @@ public class TetheringManager {
          * @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 @@ public class TetheringManager {
                         maybeSendTetherableIfacesChangedCallback(parcel.states);
                         maybeSendTetheredIfacesChangedCallback(parcel.states);
                         callback.onClientsChanged(parcel.tetheredClients);
+                        callback.onOffloadStatusChanged(parcel.offloadStatus);
                     });
                 }
 
@@ -960,6 +992,11 @@ public class TetheringManager {
                 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);