Framework changes for 464xlat.

1. Add a Nat464Xlat service that ConnectivityService can use
   to start and stop clat. When clat is started, the service
   waits for the clat interface to come up and then calls
   ConnectivityService to add the appropriate routes.
2. Make ConnectivityService start clat when an IPv6-only mobile
   interface is connected. We only support clat on mobile for
   now.
3. Make tethering use the interface that has the IPv4 default
   route insted of using the base interface of the
   LinkProperties. This allows us to tether to a stacked
   interface, which is needed for tethering with 464xlat.

Bug: 8276725
Change-Id: I24480af69ee280f504399062638af0836a56268e

2 files changed, 205 insertions, 1 deletions

diff --git a/services/java/com/android/server/connectivity/Nat464Xlat.java b/services/java/com/android/server/connectivity/Nat464Xlat.java
new file mode 100644
index 0000000..2884eaf
--- /dev/null
+++ b/services/java/com/android/server/connectivity/Nat464Xlat.java
@@ -0,0 +1,189 @@
+/*
+ * Copyright (C) 2012 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;
+
+import static android.net.ConnectivityManager.TYPE_MOBILE;
+
+import java.net.Inet4Address;
+
+import android.content.Context;
+import android.net.IConnectivityManager;
+import android.net.InterfaceConfiguration;
+import android.net.LinkAddress;
+import android.net.LinkProperties;
+import android.net.NetworkStateTracker;
+import android.net.NetworkUtils;
+import android.net.RouteInfo;
+import android.os.Handler;
+import android.os.Message;
+import android.os.INetworkManagementService;
+import android.os.RemoteException;
+import android.util.Slog;
+
+import com.android.server.net.BaseNetworkObserver;
+
+/**
+ * @hide
+ *
+ * Class to manage a 464xlat CLAT daemon.
+ */
+public class Nat464Xlat extends BaseNetworkObserver {
+    private Context mContext;
+    private INetworkManagementService mNMService;
+    private IConnectivityManager mConnService;
+    private NetworkStateTracker mTracker;
+    private Handler mHandler;
+
+    // Whether we started clatd and expect it to be running.
+    private boolean mIsStarted;
+    // Whether the clatd interface exists (i.e., clatd is running).
+    private boolean mIsRunning;
+    // The LinkProperties of the clat interface.
+    private LinkProperties mLP;
+
+    // This must match the interface name in clatd.conf.
+    private static final String CLAT_INTERFACE_NAME = "clat4";
+
+    private static final String TAG = "Nat464Xlat";
+
+    public Nat464Xlat(Context context, INetworkManagementService nmService,
+                      IConnectivityManager connService, Handler handler) {
+        mContext = context;
+        mNMService = nmService;
+        mConnService = connService;
+        mHandler = handler;
+
+        mIsStarted = false;
+        mIsRunning = false;
+        mLP = new LinkProperties();
+    }
+
+    /**
+     * Determines whether an interface requires clat.
+     * @param netType the network type (one of the
+     *   android.net.ConnectivityManager.TYPE_* constants)
+     * @param tracker the NetworkStateTracker corresponding to the network type.
+     * @return true if the interface requires clat, false otherwise.
+     */
+    public boolean requiresClat(int netType, NetworkStateTracker tracker) {
+        LinkProperties lp = tracker.getLinkProperties();
+        // Only support clat on mobile for now.
+        Slog.d(TAG, "requiresClat: netType=" + netType + ", hasIPv4Address=" +
+               lp.hasIPv4Address());
+        return netType == TYPE_MOBILE && !lp.hasIPv4Address();
+    }
+
+    /**
+     * Starts the clat daemon.
+     * @param lp The link properties of the interface to start clatd on.
+     */
+    public void startClat(NetworkStateTracker tracker) {
+        if (mIsStarted) {
+            Slog.e(TAG, "startClat: already started");
+            return;
+        }
+        mTracker = tracker;
+        LinkProperties lp = mTracker.getLinkProperties();
+        String iface = lp.getInterfaceName();
+        Slog.i(TAG, "Starting clatd on " + iface + ", lp=" + lp);
+        try {
+            mNMService.startClatd(iface);
+        } catch(RemoteException e) {
+            Slog.e(TAG, "Error starting clat daemon: " + e);
+        }
+        mIsStarted = true;
+    }
+
+    /**
+     * Stops the clat daemon.
+     */
+    public void stopClat() {
+        if (mIsStarted) {
+            Slog.i(TAG, "Stopping clatd");
+            try {
+                mNMService.stopClatd();
+            } catch(RemoteException e) {
+                Slog.e(TAG, "Error stopping clat daemon: " + e);
+            }
+            mIsStarted = false;
+            mIsRunning = false;
+            mTracker = null;
+            mLP.clear();
+        } else {
+            Slog.e(TAG, "stopClat: already stopped");
+        }
+    }
+
+    public boolean isStarted() {
+        return mIsStarted;
+    }
+
+    public boolean isRunning() {
+        return mIsRunning;
+    }
+
+    @Override
+    public void interfaceAdded(String iface) {
+        if (iface.equals(CLAT_INTERFACE_NAME)) {
+            Slog.i(TAG, "interface " + CLAT_INTERFACE_NAME +
+                   " added, mIsRunning = " + mIsRunning + " -> true");
+            mIsRunning = true;
+
+            // Get the network configuration of the clat interface, store it
+            // in our link properties, and stack it on top of the interface
+            // it's running on.
+            try {
+                InterfaceConfiguration config = mNMService.getInterfaceConfig(iface);
+                mLP.clear();
+                mLP.setInterfaceName(iface);
+                RouteInfo ipv4Default = new RouteInfo(new LinkAddress(Inet4Address.ANY, 0), null,
+                                                      iface);
+                mLP.addRoute(ipv4Default);
+                mLP.addLinkAddress(config.getLinkAddress());
+                mTracker.addStackedLink(mLP);
+                Slog.i(TAG, "Adding stacked link. tracker LP: " +
+                       mTracker.getLinkProperties());
+            } catch(RemoteException e) {
+                Slog.e(TAG, "Error getting link properties: " + e);
+            }
+
+            // Inform ConnectivityService that things have changed.
+            Message msg = mHandler.obtainMessage(
+                NetworkStateTracker.EVENT_CONFIGURATION_CHANGED,
+                mTracker.getNetworkInfo());
+            Slog.i(TAG, "sending message to ConnectivityService: " + msg);
+            msg.sendToTarget();
+        }
+    }
+
+    @Override
+    public void interfaceRemoved(String iface) {
+        if (iface == CLAT_INTERFACE_NAME) {
+            if (mIsRunning) {
+                NetworkUtils.resetConnections(
+                    CLAT_INTERFACE_NAME,
+                    NetworkUtils.RESET_IPV4_ADDRESSES);
+            }
+            Slog.i(TAG, "interface " + CLAT_INTERFACE_NAME +
+                   " removed, mIsRunning = " + mIsRunning + " -> false");
+            mIsRunning = false;
+            mTracker.removeStackedLink(mLP);
+            mLP.clear();
+            Slog.i(TAG, "mLP = " + mLP);
+        }
+    }
+};
diff --git a/services/java/com/android/server/connectivity/Tethering.java b/services/java/com/android/server/connectivity/Tethering.java
index e4a7ead..32f39b7 100644
--- a/services/java/com/android/server/connectivity/Tethering.java
+++ b/services/java/com/android/server/connectivity/Tethering.java
@@ -35,6 +35,7 @@ import android.net.LinkAddress;
 import android.net.LinkProperties;
 import android.net.NetworkInfo;
 import android.net.NetworkUtils;
+import android.net.RouteInfo;
 import android.os.Binder;
 import android.os.HandlerThread;
 import android.os.IBinder;
@@ -1345,7 +1346,21 @@ public class Tethering extends INetworkManagementEventObserver.Stub {
                         linkProperties = mConnService.getLinkProperties(upType);
                     } catch (RemoteException e) { }
                     if (linkProperties != null) {
-                        iface = linkProperties.getInterfaceName();
+                        // Find the interface with the default IPv4 route. It may be the
+                        // interface described by linkProperties, or one of the interfaces
+                        // stacked on top of it.
+                        Log.i(TAG, "Finding IPv4 upstream interface on: " + linkProperties);
+                        RouteInfo ipv4Default = RouteInfo.selectBestRoute(
+                            linkProperties.getAllRoutes(), Inet4Address.ANY);
+                        if (ipv4Default != null) {
+                            iface = ipv4Default.getInterface();
+                            Log.i(TAG, "Found interface " + ipv4Default.getInterface());
+                        } else {
+                            Log.i(TAG, "No IPv4 upstream interface, giving up.");
+                        }
+                    }
+
+                    if (iface != null) {
                         String[] dnsServers = mDefaultDnsServers;
                         Collection<InetAddress> dnses = linkProperties.getDnses();
                         if (dnses != null) {