diff --git a/tetheroffload/control/1.0/ITetheringOffloadCallback.hal b/tetheroffload/control/1.0/ITetheringOffloadCallback.hal
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+++ b/tetheroffload/control/1.0/ITetheringOffloadCallback.hal
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+/*
+ * 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 android.hardware.tetheroffload.control@1.0;
+
+/**
+ * Callback providing information about status of hardware management process
+ * as well as providing a way to keep offloaded connections from timing out.
+ */
+interface ITetheringOffloadCallback {
+  /**
+   * Called when an asynchronous event is generated by the hardware management
+   * process.
+   */
+  oneway onEvent(OffloadCallbackEvent event);
+
+  /**
+   *  Provide a way for the management process to request that a connections
+   *  timeout be updated in kernel.
+   *
+   *  This is necessary to ensure that offloaded traffic is not cleaned up
+   *  by the kernel connection tracking module for IPv4.
+   */
+   oneway updateTimeout(NatTimeoutUpdate params);
+};