Nat464Xlat.java revision 72479c0373c7be75fb6bf752949a8f728911542f 
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 android.net.InterfaceConfiguration;
20import android.net.ConnectivityManager;
21import android.net.LinkAddress;
22import android.net.LinkProperties;
23import android.net.RouteInfo;
24import android.os.INetworkManagementService;
25import android.os.RemoteException;
26import android.util.Slog;
27
28import com.android.internal.util.ArrayUtils;
29import com.android.server.net.BaseNetworkObserver;
30
31import java.net.Inet4Address;
32import java.util.Objects;
33
34/**
35 * Class to manage a 464xlat CLAT daemon. Nat464Xlat is not thread safe and should be manipulated
36 * from a consistent and unique thread context. It is the responsability of ConnectivityService to
37 * call into this class from its own Handler thread.
38 *
39 * @hide
40 */
41public class Nat464Xlat extends BaseNetworkObserver {
42    private static final String TAG = Nat464Xlat.class.getSimpleName();
43
44    // This must match the interface prefix in clatd.c.
45    private static final String CLAT_PREFIX = "v4-";
46
47    // The network types we will start clatd on,
48    // allowing clat only on networks for which we can support IPv6-only.
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    // The network we're running on, and its type.
58    private final NetworkAgentInfo mNetwork;
59
60    private enum State {
61        IDLE,       // start() not called. Base iface and stacked iface names are null.
62        STARTING,   // start() called. Base iface and stacked iface names are known.
63        RUNNING;    // start() called, and the stacked iface is known to be up.
64    }
65
66    private String mBaseIface;
67    private String mIface;
68    private State mState = State.IDLE;
69
70    public Nat464Xlat(INetworkManagementService nmService, NetworkAgentInfo nai) {
71        mNMService = nmService;
72        mNetwork = nai;
73    }
74
75    /**
76     * Determines whether a network requires clat.
77     * @param network the NetworkAgentInfo corresponding to the network.
78     * @return true if the network requires clat, false otherwise.
79     */
80    public static boolean requiresClat(NetworkAgentInfo nai) {
81        // TODO: migrate to NetworkCapabilities.TRANSPORT_*.
82        final int netType = nai.networkInfo.getType();
83        final boolean supported = ArrayUtils.contains(NETWORK_TYPES, nai.networkInfo.getType());
84        final boolean connected = nai.networkInfo.isConnected();
85        // We only run clat on networks that don't have a native IPv4 address.
86        final boolean hasIPv4Address =
87                (nai.linkProperties != null) && nai.linkProperties.hasIPv4Address();
88        return supported && connected && !hasIPv4Address;
89    }
90
91    /**
92     * @return true if clatd has been started and has not yet stopped.
93     * A true result corresponds to internal states STARTING and RUNNING.
94     */
95    public boolean isStarted() {
96        return mState != State.IDLE;
97    }
98
99    /**
100     * @return true if clatd has been started but the stacked interface is not yet up.
101     */
102    public boolean isStarting() {
103        return mState == State.STARTING;
104    }
105
106    /**
107     * @return true if clatd has been started and the stacked interface is up.
108     */
109    public boolean isRunning() {
110        return mState == State.RUNNING;
111    }
112
113    /**
114     * Sets internal state.
115     */
116    private void enterStartingState(String baseIface) {
117        mIface = CLAT_PREFIX + baseIface;
118        mBaseIface = baseIface;
119        mState = State.STARTING;
120    }
121
122    /**
123     * Clears internal state.
124     */
125    private void enterIdleState() {
126        mIface = null;
127        mBaseIface = null;
128        mState = State.IDLE;
129    }
130
131    /**
132     * Starts the clat daemon.
133     */
134    public void start() {
135        if (isStarted()) {
136            Slog.e(TAG, "startClat: already started");
137            return;
138        }
139
140        if (mNetwork.linkProperties == null) {
141            Slog.e(TAG, "startClat: Can't start clat with null LinkProperties");
142            return;
143        }
144
145        try {
146            mNMService.registerObserver(this);
147        } catch(RemoteException e) {
148            Slog.e(TAG, "startClat: Can't register interface observer for clat on " + mNetwork);
149            return;
150        }
151
152        String baseIface = mNetwork.linkProperties.getInterfaceName();
153        if (baseIface == null) {
154            Slog.e(TAG, "startClat: Can't start clat on null interface");
155            return;
156        }
157        // TODO: should we only do this if mNMService.startClatd() succeeds?
158        enterStartingState(baseIface);
159
160        Slog.i(TAG, "Starting clatd on " + mBaseIface);
161        try {
162            mNMService.startClatd(mBaseIface);
163        } catch(RemoteException|IllegalStateException e) {
164            Slog.e(TAG, "Error starting clatd on " + mBaseIface, e);
165        }
166    }
167
168    /**
169     * Stops the clat daemon.
170     */
171    public void stop() {
172        if (!isStarted()) {
173            Slog.e(TAG, "stopClat: already stopped or not started");
174            return;
175        }
176
177        Slog.i(TAG, "Stopping clatd on " + mBaseIface);
178        try {
179            mNMService.stopClatd(mBaseIface);
180        } catch(RemoteException|IllegalStateException e) {
181            Slog.e(TAG, "Error stopping clatd on " + mBaseIface, e);
182        }
183        // When clatd stops and its interface is deleted, handleInterfaceRemoved() will trigger
184        // ConnectivityService#handleUpdateLinkProperties and call enterIdleState().
185    }
186
187    /**
188     * Copies the stacked clat link in oldLp, if any, to the LinkProperties in mNetwork.
189     * This is necessary because the LinkProperties in mNetwork come from the transport layer, which
190     * has no idea that 464xlat is running on top of it.
191     */
192    public void fixupLinkProperties(LinkProperties oldLp) {
193        if (!isRunning()) {
194            return;
195        }
196        LinkProperties lp = mNetwork.linkProperties;
197        if (lp == null || lp.getAllInterfaceNames().contains(mIface)) {
198            return;
199        }
200
201        Slog.d(TAG, "clatd running, updating NAI for " + mIface);
202        for (LinkProperties stacked: oldLp.getStackedLinks()) {
203            if (Objects.equals(mIface, stacked.getInterfaceName())) {
204                lp.addStackedLink(stacked);
205                return;
206            }
207        }
208    }
209
210    private LinkProperties makeLinkProperties(LinkAddress clatAddress) {
211        LinkProperties stacked = new LinkProperties();
212        stacked.setInterfaceName(mIface);
213
214        // Although the clat interface is a point-to-point tunnel, we don't
215        // point the route directly at the interface because some apps don't
216        // understand routes without gateways (see, e.g., http://b/9597256
217        // http://b/9597516). Instead, set the next hop of the route to the
218        // clat IPv4 address itself (for those apps, it doesn't matter what
219        // the IP of the gateway is, only that there is one).
220        RouteInfo ipv4Default = new RouteInfo(
221                new LinkAddress(Inet4Address.ANY, 0),
222                clatAddress.getAddress(), mIface);
223        stacked.addRoute(ipv4Default);
224        stacked.addLinkAddress(clatAddress);
225        return stacked;
226    }
227
228    private LinkAddress getLinkAddress(String iface) {
229        try {
230            InterfaceConfiguration config = mNMService.getInterfaceConfig(iface);
231            return config.getLinkAddress();
232        } catch(RemoteException|IllegalStateException e) {
233            Slog.e(TAG, "Error getting link properties: " + e);
234            return null;
235        }
236    }
237
238    private void maybeSetIpv6NdOffload(String iface, boolean on) {
239        // TODO: migrate to NetworkCapabilities.TRANSPORT_*.
240        if (mNetwork.networkInfo.getType() != ConnectivityManager.TYPE_WIFI) {
241            return;
242        }
243        try {
244            Slog.d(TAG, (on ? "En" : "Dis") + "abling ND offload on " + iface);
245            mNMService.setInterfaceIpv6NdOffload(iface, on);
246        } catch(RemoteException|IllegalStateException e) {
247            Slog.w(TAG, "Changing IPv6 ND offload on " + iface + "failed: " + e);
248        }
249    }
250
251    /**
252     * Adds stacked link on base link and transitions to RUNNING state.
253     */
254    private void handleInterfaceLinkStateChanged(String iface, boolean up) {
255        if (!isStarting() || !up || !Objects.equals(mIface, iface)) {
256            return;
257        }
258        LinkAddress clatAddress = getLinkAddress(iface);
259        if (clatAddress == null) {
260            Slog.e(TAG, "cladAddress was null for stacked iface " + iface);
261            return;
262        }
263        mState = State.RUNNING;
264        Slog.i(TAG, String.format("interface %s is up, adding stacked link %s on top of %s",
265                mIface, mIface, mBaseIface));
266
267        maybeSetIpv6NdOffload(mBaseIface, false);
268        LinkProperties lp = new LinkProperties(mNetwork.linkProperties);
269        lp.addStackedLink(makeLinkProperties(clatAddress));
270        mNetwork.connService.handleUpdateLinkProperties(mNetwork, lp);
271    }
272
273    /**
274     * Removes stacked link on base link and transitions to IDLE state.
275     */
276    private void handleInterfaceRemoved(String iface) {
277        if (!isRunning() || !Objects.equals(mIface, iface)) {
278            return;
279        }
280
281        Slog.i(TAG, "interface " + iface + " removed");
282        // The interface going away likely means clatd has crashed. Ask netd to stop it,
283        // because otherwise when we try to start it again on the same base interface netd
284        // will complain that it's already started.
285        try {
286            mNMService.unregisterObserver(this);
287            // TODO: add STOPPING state to avoid calling stopClatd twice.
288            mNMService.stopClatd(mBaseIface);
289        } catch(RemoteException|IllegalStateException e) {
290            Slog.e(TAG, "Error stopping clatd on " + mBaseIface, e);
291        }
292        maybeSetIpv6NdOffload(mBaseIface, true);
293        LinkProperties lp = new LinkProperties(mNetwork.linkProperties);
294        lp.removeStackedLink(mIface);
295        enterIdleState();
296        mNetwork.connService.handleUpdateLinkProperties(mNetwork, lp);
297    }
298
299    @Override
300    public void interfaceLinkStateChanged(String iface, boolean up) {
301        mNetwork.handler.post(() -> { handleInterfaceLinkStateChanged(iface, up); });
302    }
303
304    @Override
305    public void interfaceRemoved(String iface) {
306        mNetwork.handler.post(() -> { handleInterfaceRemoved(iface); });
307    }
308
309    @Override
310    public String toString() {
311        return "mBaseIface: " + mBaseIface + ", mIface: " + mIface + ", mState: " + mState;
312    }
313}
314