1/*
2 * Copyright (C) 2012 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17package com.android.server.connectivity;
18
19import java.net.Inet4Address;
20
21import android.content.Context;
22import android.net.InterfaceConfiguration;
23import android.net.ConnectivityManager;
24import android.net.LinkAddress;
25import android.net.LinkProperties;
26import android.net.NetworkAgent;
27import android.net.RouteInfo;
28import android.os.Handler;
29import android.os.Message;
30import android.os.INetworkManagementService;
31import android.os.RemoteException;
32import android.util.Slog;
33
34import com.android.server.net.BaseNetworkObserver;
35import com.android.internal.util.ArrayUtils;
36
37/**
38 * @hide
39 *
40 * Class to manage a 464xlat CLAT daemon.
41 */
42public class Nat464Xlat extends BaseNetworkObserver {
43    private static final String TAG = "Nat464Xlat";
44
45    // This must match the interface prefix in clatd.c.
46    private static final String CLAT_PREFIX = "v4-";
47
48    // The network types we will start clatd on.
49    private static final int[] NETWORK_TYPES = {
50            ConnectivityManager.TYPE_MOBILE,
51            ConnectivityManager.TYPE_WIFI,
52            ConnectivityManager.TYPE_ETHERNET,
53    };
54
55    private final INetworkManagementService mNMService;
56
57    // ConnectivityService Handler for LinkProperties updates.
58    private final Handler mHandler;
59
60    // The network we're running on, and its type.
61    private final NetworkAgentInfo mNetwork;
62
63    // Internal state variables.
64    //
65    // The possible states are:
66    //  - Idle: start() not called. Everything is null.
67    //  - Starting: start() called. Interfaces are non-null. isStarted() returns true.
68    //    mIsRunning is false.
69    //  - Running: start() called, and interfaceLinkStateChanged() told us that mIface is up.
70    //    mIsRunning is true.
71    //
72    // Once mIface is non-null and isStarted() is true, methods called by ConnectivityService on
73    // its handler thread must not modify any internal state variables; they are only updated by the
74    // interface observers, called on the notification threads.
75    private String mBaseIface;
76    private String mIface;
77    private boolean mIsRunning;
78
79    public Nat464Xlat(
80            Context context, INetworkManagementService nmService,
81            Handler handler, NetworkAgentInfo nai) {
82        mNMService = nmService;
83        mHandler = handler;
84        mNetwork = nai;
85    }
86
87    /**
88     * Determines whether a network requires clat.
89     * @param network the NetworkAgentInfo corresponding to the network.
90     * @return true if the network requires clat, false otherwise.
91     */
92    public static boolean requiresClat(NetworkAgentInfo nai) {
93        final int netType = nai.networkInfo.getType();
94        final boolean connected = nai.networkInfo.isConnected();
95        final boolean hasIPv4Address =
96                (nai.linkProperties != null) ? nai.linkProperties.hasIPv4Address() : false;
97        // Only support clat on mobile and wifi for now, because these are the only IPv6-only
98        // networks we can connect to.
99        return connected && !hasIPv4Address && ArrayUtils.contains(NETWORK_TYPES, netType);
100    }
101
102    /**
103     * Determines whether clatd is started. Always true, except a) if start has not yet been called,
104     * or b) if our interface was removed.
105     */
106    public boolean isStarted() {
107        return mIface != null;
108    }
109
110    /**
111     * Clears internal state. Must not be called by ConnectivityService.
112     */
113    private void clear() {
114        mIface = null;
115        mBaseIface = null;
116        mIsRunning = false;
117    }
118
119    /**
120     * Starts the clat daemon. Called by ConnectivityService on the handler thread.
121     */
122    public void start() {
123        if (isStarted()) {
124            Slog.e(TAG, "startClat: already started");
125            return;
126        }
127
128        if (mNetwork.linkProperties == null) {
129            Slog.e(TAG, "startClat: Can't start clat with null LinkProperties");
130            return;
131        }
132
133        try {
134            mNMService.registerObserver(this);
135        } catch(RemoteException e) {
136            Slog.e(TAG, "startClat: Can't register interface observer for clat on " + mNetwork);
137            return;
138        }
139
140        mBaseIface = mNetwork.linkProperties.getInterfaceName();
141        if (mBaseIface == null) {
142            Slog.e(TAG, "startClat: Can't start clat on null interface");
143            return;
144        }
145        mIface = CLAT_PREFIX + mBaseIface;
146        // From now on, isStarted() will return true.
147
148        Slog.i(TAG, "Starting clatd on " + mBaseIface);
149        try {
150            mNMService.startClatd(mBaseIface);
151        } catch(RemoteException|IllegalStateException e) {
152            Slog.e(TAG, "Error starting clatd: " + e);
153        }
154    }
155
156    /**
157     * Stops the clat daemon. Called by ConnectivityService on the handler thread.
158     */
159    public void stop() {
160        if (isStarted()) {
161            Slog.i(TAG, "Stopping clatd");
162            try {
163                mNMService.stopClatd(mBaseIface);
164            } catch(RemoteException|IllegalStateException e) {
165                Slog.e(TAG, "Error stopping clatd: " + e);
166            }
167            // When clatd stops and its interface is deleted, interfaceRemoved() will notify
168            // ConnectivityService and call clear().
169        } else {
170            Slog.e(TAG, "clatd: already stopped");
171        }
172    }
173
174    private void updateConnectivityService(LinkProperties lp) {
175        Message msg = mHandler.obtainMessage(NetworkAgent.EVENT_NETWORK_PROPERTIES_CHANGED, lp);
176        msg.replyTo = mNetwork.messenger;
177        Slog.i(TAG, "sending message to ConnectivityService: " + msg);
178        msg.sendToTarget();
179    }
180
181    /**
182     * Copies the stacked clat link in oldLp, if any, to the LinkProperties in mNetwork.
183     * This is necessary because the LinkProperties in mNetwork come from the transport layer, which
184     * has no idea that 464xlat is running on top of it.
185     */
186    public void fixupLinkProperties(LinkProperties oldLp) {
187        if (mNetwork.clatd != null &&
188                mIsRunning &&
189                mNetwork.linkProperties != null &&
190                !mNetwork.linkProperties.getAllInterfaceNames().contains(mIface)) {
191            Slog.d(TAG, "clatd running, updating NAI for " + mIface);
192            for (LinkProperties stacked: oldLp.getStackedLinks()) {
193                if (mIface.equals(stacked.getInterfaceName())) {
194                    mNetwork.linkProperties.addStackedLink(stacked);
195                    break;
196                }
197            }
198        }
199    }
200
201    private LinkProperties makeLinkProperties(LinkAddress clatAddress) {
202        LinkProperties stacked = new LinkProperties();
203        stacked.setInterfaceName(mIface);
204
205        // Although the clat interface is a point-to-point tunnel, we don't
206        // point the route directly at the interface because some apps don't
207        // understand routes without gateways (see, e.g., http://b/9597256
208        // http://b/9597516). Instead, set the next hop of the route to the
209        // clat IPv4 address itself (for those apps, it doesn't matter what
210        // the IP of the gateway is, only that there is one).
211        RouteInfo ipv4Default = new RouteInfo(
212                new LinkAddress(Inet4Address.ANY, 0),
213                clatAddress.getAddress(), mIface);
214        stacked.addRoute(ipv4Default);
215        stacked.addLinkAddress(clatAddress);
216        return stacked;
217    }
218
219    private LinkAddress getLinkAddress(String iface) {
220        try {
221            InterfaceConfiguration config = mNMService.getInterfaceConfig(iface);
222            return config.getLinkAddress();
223        } catch(RemoteException|IllegalStateException e) {
224            Slog.e(TAG, "Error getting link properties: " + e);
225            return null;
226        }
227    }
228
229    private void maybeSetIpv6NdOffload(String iface, boolean on) {
230        if (mNetwork.networkInfo.getType() != ConnectivityManager.TYPE_WIFI) {
231            return;
232        }
233        try {
234            Slog.d(TAG, (on ? "En" : "Dis") + "abling ND offload on " + iface);
235            mNMService.setInterfaceIpv6NdOffload(iface, on);
236        } catch(RemoteException|IllegalStateException e) {
237            Slog.w(TAG, "Changing IPv6 ND offload on " + iface + "failed: " + e);
238        }
239    }
240
241    @Override
242    public void interfaceLinkStateChanged(String iface, boolean up) {
243        // Called by the InterfaceObserver on its own thread, so can race with stop().
244        if (isStarted() && up && mIface.equals(iface)) {
245            Slog.i(TAG, "interface " + iface + " is up, mIsRunning " + mIsRunning + "->true");
246
247            if (!mIsRunning) {
248                LinkAddress clatAddress = getLinkAddress(iface);
249                if (clatAddress == null) {
250                    return;
251                }
252                mIsRunning = true;
253                maybeSetIpv6NdOffload(mBaseIface, false);
254                LinkProperties lp = new LinkProperties(mNetwork.linkProperties);
255                lp.addStackedLink(makeLinkProperties(clatAddress));
256                Slog.i(TAG, "Adding stacked link " + mIface + " on top of " + mBaseIface);
257                updateConnectivityService(lp);
258            }
259        }
260    }
261
262    @Override
263    public void interfaceRemoved(String iface) {
264        if (isStarted() && mIface.equals(iface)) {
265            Slog.i(TAG, "interface " + iface + " removed, mIsRunning " + mIsRunning + "->false");
266
267            if (mIsRunning) {
268                // The interface going away likely means clatd has crashed. Ask netd to stop it,
269                // because otherwise when we try to start it again on the same base interface netd
270                // will complain that it's already started.
271                //
272                // Note that this method can be called by the interface observer at the same time
273                // that ConnectivityService calls stop(). In this case, the second call to
274                // stopClatd() will just throw IllegalStateException, which we'll ignore.
275                try {
276                    mNMService.unregisterObserver(this);
277                    mNMService.stopClatd(mBaseIface);
278                } catch (RemoteException|IllegalStateException e) {
279                    // Well, we tried.
280                }
281                maybeSetIpv6NdOffload(mBaseIface, true);
282                LinkProperties lp = new LinkProperties(mNetwork.linkProperties);
283                lp.removeStackedLink(mIface);
284                clear();
285                updateConnectivityService(lp);
286            }
287        }
288    }
289}
290