Move netlink updates to a new NetlinkTracker class.

/*

 * Copyright (C) 2014 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.net;

import android.net.LinkAddress;

import android.net.LinkProperties;

import android.util.Log;

/**

 * Keeps track of link configuration received from Netlink.

 *

 * Instances of this class are expected to be owned by subsystems such as Wi-Fi

 * or Ethernet that manage one or more network interfaces. Each interface to be

 * tracked needs its own {@code NetlinkTracker}.

 *

 * An instance of this class is constructed by passing in an interface name and

 * a callback. The owner is then responsible for registering the tracker with

 * NetworkManagementService. When the class receives update notifications from

 * the NetworkManagementService notification threads, it applies the update to

 * its local LinkProperties, and if something has changed, notifies its owner of

 * the update via the callback.

 *

 * The owner can then call {@code getLinkProperties()} in order to find out

 * what changed. If in the meantime the LinkProperties stored here have changed,

 * this class will return the current LinkProperties. Because each change

 * triggers an update callback after the change is made, the owner may get more

 * callbacks than strictly necessary (some of which may be no-ops), but will not

 * be out of sync once all callbacks have been processed.

 *

 * Threading model:

 *

 * - The owner of this class is expected to create it, register it, and call

 *   getLinkProperties or clearLinkProperties on its thread.

 * - Most of the methods in the class are inherited from BaseNetworkObserver

 *   and are called by NetworkManagementService notification threads.

 * - All accesses to mLinkProperties must be synchronized(this). All the other

 *   member variables are immutable once the object is constructed.

 *

 * This class currently tracks IPv4 and IPv6 addresses. In the future it will

 * track routes and DNS servers.

 *

 * @hide

 */

public class NetlinkTracker extends BaseNetworkObserver {

    private final String TAG;

    public interface Callback {

        public void update();

    }

    private final String mInterfaceName;

    private final Callback mCallback;

    private final LinkProperties mLinkProperties;

    private static final boolean DBG = true;

    public NetlinkTracker(String iface, Callback callback) {

        TAG = "NetlinkTracker/" + iface;

        mInterfaceName = iface;

        mCallback = callback;

        mLinkProperties = new LinkProperties();

        mLinkProperties.setInterfaceName(mInterfaceName);

    }

    private void maybeLog(String operation, String iface, LinkAddress address) {

        if (DBG) {

            Log.d(TAG, operation + ": " + address + " on " + iface +

                    " flags " + address.getFlags() + " scope " + address.getScope());

        }

    }

    @Override

    public void addressUpdated(String iface, LinkAddress address) {

        if (mInterfaceName.equals(iface)) {

            maybeLog("addressUpdated", iface, address);

            boolean changed;

            synchronized (this) {

                changed = mLinkProperties.addLinkAddress(address);

            }

            if (changed) {

                mCallback.update();

            }

        }

    }

    @Override

    public void addressRemoved(String iface, LinkAddress address) {

        if (mInterfaceName.equals(iface)) {

            maybeLog("addressRemoved", iface, address);

            boolean changed;

            synchronized (this) {

                changed = mLinkProperties.removeLinkAddress(address);

            }

            if (changed) {

                mCallback.update();

            }

        }

    }

    /**

     * Returns a copy of this object's LinkProperties.

     */

    public synchronized LinkProperties getLinkProperties() {

        return new LinkProperties(mLinkProperties);

    }

    public synchronized void clearLinkProperties() {

        mLinkProperties.clear();

        mLinkProperties.setInterfaceName(mInterfaceName);

    }

}