services/core/java/com/android/server/connectivity/tethering/OffloadController.java

/*
 * 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.server.connectivity.tethering;

import static android.provider.Settings.Global.TETHER_OFFLOAD_DISABLED;

import android.content.ContentResolver;
import android.net.LinkProperties;
import android.net.util.SharedLog;
import android.os.Handler;
import android.provider.Settings;

/**
 * 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 final Handler mHandler;
    private final OffloadHardwareInterface mHwInterface;
    private final ContentResolver mContentResolver;
    private final SharedLog mLog;
    private boolean mConfigInitialized;
    private boolean mControlInitialized;
    private LinkProperties mUpstreamLinkProperties;

    public OffloadController(Handler h, OffloadHardwareInterface hwi,
            ContentResolver contentResolver, SharedLog log) {
        mHandler = h;
        mHwInterface = hwi;
        mContentResolver = contentResolver;
        mLog = log.forSubComponent(TAG);
    }

    public void start() {
        if (isOffloadDisabled() || started()) return;

        if (!mConfigInitialized) {
            mConfigInitialized = mHwInterface.initOffloadConfig();
            if (!mConfigInitialized) {
                mLog.i("tethering offload config not supported");
                stop();
                return;
            }
        }

        mControlInitialized = mHwInterface.initOffloadControl(
                new OffloadHardwareInterface.ControlCallback() {
                    @Override
                    public void onOffloadEvent(int event) {
                        mLog.log("got offload event: " + event);
                    }

                    @Override
                    public void onNatTimeoutUpdate(int proto,
                                                   String srcAddr, int srcPort,
                                                   String dstAddr, int dstPort) {
                        mLog.log(String.format("NAT timeout update: %s (%s,%s) -> (%s,%s)",
                                proto, srcAddr, srcPort, dstAddr, dstPort));
                    }
                });
        if (!mControlInitialized) {
            mLog.i("tethering offload control not supported");
            stop();
        }
    }

    public void stop() {
        mUpstreamLinkProperties = null;
        mHwInterface.stopOffloadControl();
        mControlInitialized = false;
        mConfigInitialized = false;
    }

    public void setUpstreamLinkProperties(LinkProperties lp) {
        if (!started()) return;

        // TODO: setUpstreamParameters().
        mUpstreamLinkProperties = lp;
    }

    // TODO: public void addDownStream(...)

    private boolean isOffloadDisabled() {
        // Defaults to |false| if not present.
        return (Settings.Global.getInt(mContentResolver, TETHER_OFFLOAD_DISABLED, 0) != 0);
    }

    private boolean started() {
        return mConfigInitialized && mControlInitialized;
    }
}