Merge changes from topic "nat64"

* changes:
  Catch ServiceSpecificException instead of IllegalStateException.
  Manage NAT64 prefix discovery lifecycle in the framework.
  Track NAT64 in the framework and start clatd iff NAT64 detected
  Change Nat464Xlat lifecycle.
  Minor improvements to verifyTcpBufferSizeChange.

services/core/java/com/android/server/ConnectivityService.java

@@ -71,6 +71,8 @@ import android.net.INetworkMonitorCallbacks;
 import android.net.INetworkPolicyListener;
 import android.net.INetworkPolicyManager;
 import android.net.INetworkStatsService;
+import android.net.InetAddresses;
+import android.net.IpPrefix;
 import android.net.LinkProperties;
 import android.net.LinkProperties.CompareResult;
 import android.net.MatchAllNetworkSpecifier;
@@ -1740,6 +1742,12 @@ public class ConnectivityService extends IConnectivityManager.Stub
                 }
             }
         }
+
+        @Override
+        public void onNat64PrefixEvent(int netId, boolean added,
+                                       String prefixString, int prefixLength) {
+            mHandler.post(() -> handleNat64PrefixEvent(netId, added, prefixString, prefixLength));
+        }
     };
 
     @VisibleForTesting
@@ -2767,6 +2775,29 @@ public class ConnectivityService extends IConnectivityManager.Stub
         handleUpdateLinkProperties(nai, new LinkProperties(nai.linkProperties));
     }
 
+    private void handleNat64PrefixEvent(int netId, boolean added, String prefixString,
+            int prefixLength) {
+        NetworkAgentInfo nai = mNetworkForNetId.get(netId);
+        if (nai == null) return;
+
+        log(String.format("NAT64 prefix %s on netId %d: %s/%d",
+                          (added ? "added" : "removed"), netId, prefixString, prefixLength));
+
+        IpPrefix prefix = null;
+        if (added) {
+            try {
+                prefix = new IpPrefix(InetAddresses.parseNumericAddress(prefixString),
+                        prefixLength);
+            } catch (IllegalArgumentException e) {
+                loge("Invalid NAT64 prefix " + prefixString + "/" + prefixLength);
+                return;
+            }
+        }
+
+        nai.clatd.setNat64Prefix(prefix);
+        handleUpdateLinkProperties(nai, new LinkProperties(nai.linkProperties));
+    }
+
     private void updateLingerState(NetworkAgentInfo nai, long now) {
         // 1. Update the linger timer. If it's changed, reschedule or cancel the alarm.
         // 2. If the network was lingering and there are now requests, unlinger it.
@@ -2882,7 +2913,7 @@ public class ConnectivityService extends IConnectivityManager.Stub
             e.rethrowFromSystemServer();
         }
         mNetworkAgentInfos.remove(nai.messenger);
-        nai.maybeStopClat();
+        nai.clatd.update();
         synchronized (mNetworkForNetId) {
             // Remove the NetworkAgent, but don't mark the netId as
             // available until we've told netd to delete it below.
@@ -5190,11 +5221,10 @@ public class ConnectivityService extends IConnectivityManager.Stub
             LinkProperties oldLp) {
         int netId = networkAgent.network.netId;
 
-        // The NetworkAgentInfo does not know whether clatd is running on its network or not. Before
+        // The NetworkAgentInfo does not know whether clatd is running on its network or not, or
-        // we do anything else, make sure its LinkProperties are accurate.
+        // whether there is a NAT64 prefix. Before we do anything else, make sure its LinkProperties
-        if (networkAgent.clatd != null) {
+        // are accurate.
-            networkAgent.clatd.fixupLinkProperties(oldLp, newLp);
+        networkAgent.clatd.fixupLinkProperties(oldLp, newLp);
-        }
 
         updateInterfaces(newLp, oldLp, netId, networkAgent.networkCapabilities);
         updateMtu(newLp, oldLp);
@@ -5224,8 +5254,8 @@ public class ConnectivityService extends IConnectivityManager.Stub
             synchronized (networkAgent) {
                 networkAgent.linkProperties = newLp;
             }
-            // Start or stop clat accordingly to network state.
+            // Start or stop DNS64 detection and 464xlat according to network state.
-            networkAgent.updateClat(mNMS);
+            networkAgent.clatd.update();
             notifyIfacesChangedForNetworkStats();
             if (networkAgent.everConnected) {
                 try {

services/core/java/com/android/server/connectivity/Nat464Xlat.java

@@ -18,19 +18,24 @@ package com.android.server.connectivity;
 
 import android.net.ConnectivityManager;
 import android.net.INetd;
+import android.net.InetAddresses;
 import android.net.InterfaceConfiguration;
+import android.net.IpPrefix;
 import android.net.LinkAddress;
 import android.net.LinkProperties;
 import android.net.NetworkInfo;
 import android.net.RouteInfo;
 import android.os.INetworkManagementService;
 import android.os.RemoteException;
+import android.os.ServiceSpecificException;
 import android.util.Slog;
 
+import com.android.internal.annotations.VisibleForTesting;
 import com.android.internal.util.ArrayUtils;
 import com.android.server.net.BaseNetworkObserver;
 
 import java.net.Inet4Address;
+import java.net.Inet6Address;
 import java.util.Objects;
 
 /**
@@ -67,15 +72,16 @@ public class Nat464Xlat extends BaseNetworkObserver {
     private final NetworkAgentInfo mNetwork;
 
     private enum State {
-        IDLE,       // start() not called. Base iface and stacked iface names are null.
+        IDLE,         // start() not called. Base iface and stacked iface names are null.
-        STARTING,   // start() called. Base iface and stacked iface names are known.
+        DISCOVERING,  // same as IDLE, except prefix discovery in progress.
-        RUNNING,    // start() called, and the stacked iface is known to be up.
+        STARTING,     // start() called. Base iface and stacked iface names are known.
-        STOPPING;   // stop() called, this Nat464Xlat is still registered as a network observer for
+        RUNNING,      // start() called, and the stacked iface is known to be up.
-                    // the stacked interface.
     }
 
+    private IpPrefix mNat64Prefix;
     private String mBaseIface;
     private String mIface;
+    private Inet6Address mIPv6Address;
     private State mState = State.IDLE;
 
     public Nat464Xlat(NetworkAgentInfo nai, INetd netd, INetworkManagementService nmService) {
@@ -85,20 +91,51 @@ public class Nat464Xlat extends BaseNetworkObserver {
     }
 
     /**
-     * Determines whether a network requires clat.
+     * Whether to attempt 464xlat on this network. This is true for an IPv6-only network that is
+     * currently connected and where the NetworkAgent has not disabled 464xlat. It is the signal to
+     * enable NAT64 prefix discovery.
+     *
      * @param network the NetworkAgentInfo corresponding to the network.
      * @return true if the network requires clat, false otherwise.
      */
-    public static boolean requiresClat(NetworkAgentInfo nai) {
+    @VisibleForTesting
+    protected static boolean requiresClat(NetworkAgentInfo nai) {
         // TODO: migrate to NetworkCapabilities.TRANSPORT_*.
         final boolean supported = ArrayUtils.contains(NETWORK_TYPES, nai.networkInfo.getType());
         final boolean connected = ArrayUtils.contains(NETWORK_STATES, nai.networkInfo.getState());
-        // We only run clat on networks that don't have a native IPv4 address.
+
-        final boolean hasIPv4Address =
+        // Only run clat on networks that have a global IPv6 address and don't have a native IPv4
-                (nai.linkProperties != null) && nai.linkProperties.hasIPv4Address();
+        // address.
-        final boolean skip464xlat =
+        LinkProperties lp = nai.linkProperties;
-                (nai.netMisc() != null) && nai.netMisc().skip464xlat;
+        final boolean isIpv6OnlyNetwork = (lp != null) && lp.hasGlobalIPv6Address()
-        return supported && connected && !hasIPv4Address && !skip464xlat;
+                && !lp.hasIPv4Address();
+
+        // If the network tells us it doesn't use clat, respect that.
+        final boolean skip464xlat = (nai.netMisc() != null) && nai.netMisc().skip464xlat;
+
+        return supported && connected && isIpv6OnlyNetwork && !skip464xlat;
+    }
+
+    /**
+     * Whether the clat demon should be started on this network now. This is true if requiresClat is
+     * true and a NAT64 prefix has been discovered.
+     *
+     * @param nai the NetworkAgentInfo corresponding to the network.
+     * @return true if the network should start clat, false otherwise.
+     */
+    @VisibleForTesting
+    protected static boolean shouldStartClat(NetworkAgentInfo nai) {
+        LinkProperties lp = nai.linkProperties;
+        return requiresClat(nai) && lp != null && lp.getNat64Prefix() != null;
+    }
+
+    /**
+     * @return true if we have started prefix discovery and not yet stopped it (regardless of
+     * whether it is still running or has succeeded).
+     * A true result corresponds to internal states DISCOVERING, STARTING and RUNNING.
+     */
+    public boolean isPrefixDiscoveryStarted() {
+        return mState == State.DISCOVERING || isStarted();
     }
 
     /**
@@ -106,7 +143,7 @@ public class Nat464Xlat extends BaseNetworkObserver {
      * A true result corresponds to internal states STARTING and RUNNING.
      */
     public boolean isStarted() {
-        return mState != State.IDLE;
+        return (mState == State.STARTING || mState == State.RUNNING);
     }
 
     /**
@@ -123,13 +160,6 @@ public class Nat464Xlat extends BaseNetworkObserver {
         return mState == State.RUNNING;
     }
 
-    /**
-     * @return true if clatd has been stopped.
-     */
-    public boolean isStopping() {
-        return mState == State.STOPPING;
-    }
-
     /**
      * Start clatd, register this Nat464Xlat as a network observer for the stacked interface,
      * and set internal state.
@@ -137,19 +167,25 @@ public class Nat464Xlat extends BaseNetworkObserver {
     private void enterStartingState(String baseIface) {
         try {
             mNMService.registerObserver(this);
-        } catch(RemoteException e) {
+        } catch (RemoteException e) {
-            Slog.e(TAG,
+            Slog.e(TAG, "Can't register interface observer for clat on " + mNetwork.name());
-                    "startClat: Can't register interface observer for clat on " + mNetwork.name());
             return;
         }
+
+        String addrStr = null;
         try {
-            mNetd.clatdStart(baseIface);
+            addrStr = mNetd.clatdStart(baseIface, mNat64Prefix.toString());
-        } catch(RemoteException|IllegalStateException e) {
+        } catch (RemoteException | ServiceSpecificException e) {
-            Slog.e(TAG, "Error starting clatd on " + baseIface, e);
+            Slog.e(TAG, "Error starting clatd on " + baseIface + ": " + e);
         }
         mIface = CLAT_PREFIX + baseIface;
         mBaseIface = baseIface;
         mState = State.STARTING;
+        try {
+            mIPv6Address = (Inet6Address) InetAddresses.parseNumericAddress(addrStr);
+        } catch (ClassCastException | IllegalArgumentException | NullPointerException e) {
+            Slog.e(TAG, "Invalid IPv6 address " + addrStr);
+        }
     }
 
     /**
@@ -160,38 +196,28 @@ public class Nat464Xlat extends BaseNetworkObserver {
         mState = State.RUNNING;
     }
 
-    /**
-     * Stop clatd, and turn ND offload on if it had been turned off.
-     */
-    private void enterStoppingState() {
-        try {
-            mNetd.clatdStop(mBaseIface);
-        } catch(RemoteException|IllegalStateException e) {
-            Slog.e(TAG, "Error stopping clatd on " + mBaseIface, e);
-        }
-
-        mState = State.STOPPING;
-    }
-
     /**
      * Unregister as a base observer for the stacked interface, and clear internal state.
      */
-    private void enterIdleState() {
+    private void leaveStartedState() {
         try {
             mNMService.unregisterObserver(this);
-        } catch(RemoteException|IllegalStateException e) {
+        } catch (RemoteException | IllegalStateException e) {
-            Slog.e(TAG, "Error unregistering clatd observer on " + mBaseIface, e);
+            Slog.e(TAG, "Error unregistering clatd observer on " + mBaseIface + ": " + e);
         }
-
         mIface = null;
         mBaseIface = null;
         mState = State.IDLE;
+        if (requiresClat(mNetwork)) {
+            mState = State.DISCOVERING;
+        } else {
+            stopPrefixDiscovery();
+            mState = State.IDLE;
+        }
     }
 
-    /**
+    @VisibleForTesting
-     * Starts the clat daemon.
+    protected void start() {
-     */
-    public void start() {
         if (isStarted()) {
             Slog.e(TAG, "startClat: already started");
             return;
@@ -212,20 +238,82 @@ public class Nat464Xlat extends BaseNetworkObserver {
         enterStartingState(baseIface);
     }
 
-    /**
+    @VisibleForTesting
-     * Stops the clat daemon.
+    protected void stop() {
-     */
-    public void stop() {
         if (!isStarted()) {
+            Slog.e(TAG, "stopClat: already stopped");
             return;
         }
-        Slog.i(TAG, "Stopping clatd on " + mBaseIface);
 
-        boolean wasStarting = isStarting();
+        Slog.i(TAG, "Stopping clatd on " + mBaseIface);
-        enterStoppingState();
+        try {
-        if (wasStarting) {
+            mNetd.clatdStop(mBaseIface);
-            enterIdleState();
+        } catch (RemoteException | ServiceSpecificException e) {
+            Slog.e(TAG, "Error stopping clatd on " + mBaseIface + ": " + e);
         }
+
+        String iface = mIface;
+        boolean wasRunning = isRunning();
+
+        // Change state before updating LinkProperties. handleUpdateLinkProperties ends up calling
+        // fixupLinkProperties, and if at that time the state is still RUNNING, fixupLinkProperties
+        // would wrongly inform ConnectivityService that there is still a stacked interface.
+        leaveStartedState();
+
+        if (wasRunning) {
+            LinkProperties lp = new LinkProperties(mNetwork.linkProperties);
+            lp.removeStackedLink(iface);
+            mNetwork.connService().handleUpdateLinkProperties(mNetwork, lp);
+        }
+    }
+
+    private void startPrefixDiscovery() {
+        try {
+            mNetd.resolverStartPrefix64Discovery(getNetId());
+            mState = State.DISCOVERING;
+        } catch (RemoteException | ServiceSpecificException e) {
+            Slog.e(TAG, "Error starting prefix discovery on netId " + getNetId() + ": " + e);
+        }
+    }
+
+    private void stopPrefixDiscovery() {
+        try {
+            mNetd.resolverStopPrefix64Discovery(getNetId());
+        } catch (RemoteException | ServiceSpecificException e) {
+            Slog.e(TAG, "Error stopping prefix discovery on netId " + getNetId() + ": " + e);
+        }
+    }
+
+    /**
+     * Starts/stops NAT64 prefix discovery and clatd as necessary.
+     */
+    public void update() {
+        // TODO: turn this class into a proper StateMachine. // http://b/126113090
+        if (requiresClat(mNetwork)) {
+            if (!isPrefixDiscoveryStarted()) {
+                startPrefixDiscovery();
+            } else if (shouldStartClat(mNetwork)) {
+                // NAT64 prefix detected. Start clatd.
+                // TODO: support the NAT64 prefix changing after it's been discovered. There is no
+                // need to support this at the moment because it cannot happen without changes to
+                // the Dns64Configuration code in netd.
+                start();
+            } else {
+                // NAT64 prefix removed. Stop clatd and go back into DISCOVERING state.
+                stop();
+            }
+        } else {
+            // Network no longer requires clat. Stop clat and prefix discovery.
+            if (isStarted()) {
+                stop();
+            } else if (isPrefixDiscoveryStarted()) {
+                leaveStartedState();
+            }
+        }
+    }
+
+    public void setNat64Prefix(IpPrefix nat64Prefix) {
+        mNat64Prefix = nat64Prefix;
     }
 
     /**
@@ -234,6 +322,8 @@ public class Nat464Xlat extends BaseNetworkObserver {
      * has no idea that 464xlat is running on top of it.
      */
     public void fixupLinkProperties(LinkProperties oldLp, LinkProperties lp) {
+        lp.setNat64Prefix(mNat64Prefix);
+
         if (!isRunning()) {
             return;
         }
@@ -272,7 +362,7 @@ public class Nat464Xlat extends BaseNetworkObserver {
         try {
             InterfaceConfiguration config = mNMService.getInterfaceConfig(iface);
             return config.getLinkAddress();
-        } catch(RemoteException|IllegalStateException e) {
+        } catch (RemoteException | IllegalStateException e) {
             Slog.e(TAG, "Error getting link properties: " + e);
             return null;
         }
@@ -282,6 +372,20 @@ public class Nat464Xlat extends BaseNetworkObserver {
      * Adds stacked link on base link and transitions to RUNNING state.
      */
     private void handleInterfaceLinkStateChanged(String iface, boolean up) {
+        // TODO: if we call start(), then stop(), then start() again, and the
+        // interfaceLinkStateChanged notification for the first start is delayed past the first
+        // stop, then the code becomes out of sync with system state and will behave incorrectly.
+        //
+        // This is not trivial to fix because:
+        // 1. It is not guaranteed that start() will eventually result in the interface coming up,
+        //    because there could be an error starting clat (e.g., if the interface goes down before
+        //    the packet socket can be bound).
+        // 2. If start is called multiple times, there is nothing in the interfaceLinkStateChanged
+        //    notification that says which start() call the interface was created by.
+        //
+        // Once this code is converted to StateMachine, it will be possible to use deferMessage to
+        // ensure it stays in STARTING state until the interfaceLinkStateChanged notification fires,
+        // and possibly use a timeout (or provide some guarantees at the lower layer) to address #1.
         if (!isStarting() || !up || !Objects.equals(mIface, iface)) {
             return;
         }
@@ -307,20 +411,16 @@ public class Nat464Xlat extends BaseNetworkObserver {
         if (!Objects.equals(mIface, iface)) {
             return;
         }
-        if (!isRunning() && !isStopping()) {
+        if (!isRunning()) {
             return;
         }
 
         Slog.i(TAG, "interface " + iface + " removed");
-        if (!isStopping()) {
+        // If we're running, and the interface was removed, then we didn't call stop(), and it's
-            // Ensure clatd is stopped if stop() has not been called: this likely means that clatd
+        // likely that clatd crashed. Ensure we call stop() so we can start clatd again. Calling
-            // has crashed.
+        // stop() will also update LinkProperties, and if clatd crashed, the LinkProperties update
-            enterStoppingState();
+        // will cause ConnectivityService to call start() again.
-        }
+        stop();
-        enterIdleState();
-        LinkProperties lp = new LinkProperties(mNetwork.linkProperties);
-        lp.removeStackedLink(iface);
-        mNetwork.connService().handleUpdateLinkProperties(mNetwork, lp);
     }
 
     @Override
@@ -337,4 +437,9 @@ public class Nat464Xlat extends BaseNetworkObserver {
     public String toString() {
         return "mBaseIface: " + mBaseIface + ", mIface: " + mIface + ", mState: " + mState;
     }
+
+    @VisibleForTesting
+    protected int getNetId() {
+        return mNetwork.network.netId;
+    }
 }

services/core/java/com/android/server/connectivity/NetworkAgentInfo.java

@@ -236,7 +236,7 @@ public class NetworkAgentInfo implements Comparable<NetworkAgentInfo> {
     public final AsyncChannel asyncChannel;
 
     // Used by ConnectivityService to keep track of 464xlat.
-    public Nat464Xlat clatd;
+    public final Nat464Xlat clatd;
 
     // Set after asynchronous creation of the NetworkMonitor.
     private volatile INetworkMonitor mNetworkMonitor;
@@ -244,8 +244,6 @@ public class NetworkAgentInfo implements Comparable<NetworkAgentInfo> {
     private static final String TAG = ConnectivityService.class.getSimpleName();
     private static final boolean VDBG = false;
     private final ConnectivityService mConnService;
-    private final INetd mNetd;
-    private final INetworkManagementService mNMS;
     private final Context mContext;
     private final Handler mHandler;
 
@@ -260,9 +258,8 @@ public class NetworkAgentInfo implements Comparable<NetworkAgentInfo> {
         linkProperties = lp;
         networkCapabilities = nc;
         currentScore = score;
+        clatd = new Nat464Xlat(this, netd, nms);
         mConnService = connService;
-        mNetd = netd;
-        mNMS = nms;
         mContext = context;
         mHandler = handler;
         networkMisc = misc;
@@ -595,32 +592,6 @@ public class NetworkAgentInfo implements Comparable<NetworkAgentInfo> {
         for (LingerTimer timer : mLingerTimers) { pw.println(timer); }
     }
 
-    public void updateClat(INetworkManagementService netd) {
-        if (Nat464Xlat.requiresClat(this)) {
-            maybeStartClat();
-        } else {
-            maybeStopClat();
-        }
-    }
-
-    /** Ensure clat has started for this network. */
-    public void maybeStartClat() {
-        if (clatd != null && clatd.isStarted()) {
-            return;
-        }
-        clatd = new Nat464Xlat(this, mNetd, mNMS);
-        clatd.start();
-    }
-
-    /** Ensure clat has stopped for this network. */
-    public void maybeStopClat() {
-        if (clatd == null) {
-            return;
-        }
-        clatd.stop();
-        clatd = null;
-    }
-
     public String toString() {
         return "NetworkAgentInfo{ ni{" + networkInfo + "}  "
                 + "network{" + network + "}  nethandle{" + network.getNetworkHandle() + "}  "

tests/net/java/com/android/server/ConnectivityServiceTest.java

@@ -17,10 +17,10 @@
 package com.android.server;
 
 import static android.net.ConnectivityManager.CONNECTIVITY_ACTION;
+import static android.net.ConnectivityManager.NETID_UNSET;
 import static android.net.ConnectivityManager.PRIVATE_DNS_MODE_OFF;
 import static android.net.ConnectivityManager.PRIVATE_DNS_MODE_OPPORTUNISTIC;
 import static android.net.ConnectivityManager.PRIVATE_DNS_MODE_PROVIDER_HOSTNAME;
-import static android.net.ConnectivityManager.NETID_UNSET;
 import static android.net.ConnectivityManager.TYPE_ETHERNET;
 import static android.net.ConnectivityManager.TYPE_MOBILE;
 import static android.net.ConnectivityManager.TYPE_MOBILE_FOTA;
@@ -1798,6 +1798,12 @@ public class ConnectivityServiceTest {
                     fn.test((NetworkCapabilities) cbi.arg));
         }
 
+        void expectLinkPropertiesLike(Predicate<LinkProperties> fn, MockNetworkAgent agent) {
+            CallbackInfo cbi = expectCallback(CallbackState.LINK_PROPERTIES, agent);
+            assertTrue("Received LinkProperties don't match expectations : " + cbi.arg,
+                    fn.test((LinkProperties) cbi.arg));
+        }
+
         void expectBlockedStatusCallback(boolean expectBlocked, MockNetworkAgent agent) {
             CallbackInfo cbi = expectCallback(CallbackState.BLOCKED_STATUS, agent);
             boolean actualBlocked = (boolean) cbi.arg;
@@ -5087,6 +5093,9 @@ public class ConnectivityServiceTest {
     public void testStackedLinkProperties() throws UnknownHostException, RemoteException {
         final LinkAddress myIpv4 = new LinkAddress("1.2.3.4/24");
         final LinkAddress myIpv6 = new LinkAddress("2001:db8:1::1/64");
+        final String kNat64PrefixString = "2001:db8:64:64:64:64::";
+        final IpPrefix kNat64Prefix = new IpPrefix(InetAddress.getByName(kNat64PrefixString), 96);
+
         final NetworkRequest networkRequest = new NetworkRequest.Builder()
                 .addTransportType(TRANSPORT_CELLULAR)
                 .addCapability(NET_CAPABILITY_INTERNET)
@@ -5094,8 +5103,9 @@ public class ConnectivityServiceTest {
         final TestNetworkCallback networkCallback = new TestNetworkCallback();
         mCm.registerNetworkCallback(networkRequest, networkCallback);
 
-        // Prepare ipv6 only link properties and connect.
+        // Prepare ipv6 only link properties.
         mCellNetworkAgent = new MockNetworkAgent(TRANSPORT_CELLULAR);
+        final int cellNetId = mCellNetworkAgent.getNetwork().netId;
         final LinkProperties cellLp = new LinkProperties();
         cellLp.setInterfaceName(MOBILE_IFNAME);
         cellLp.addLinkAddress(myIpv6);
@@ -5105,15 +5115,44 @@ public class ConnectivityServiceTest {
         when(mNetworkManagementService.getInterfaceConfig(CLAT_PREFIX + MOBILE_IFNAME))
                 .thenReturn(getClatInterfaceConfig(myIpv4));
 
-        // Connect with ipv6 link properties, then expect clat setup ipv4 and update link
+        // Connect with ipv6 link properties. Expect prefix discovery to be started.
-        // properties properly.
         mCellNetworkAgent.sendLinkProperties(cellLp);
         mCellNetworkAgent.connect(true);
         networkCallback.expectAvailableThenValidatedCallbacks(mCellNetworkAgent);
-        verify(mMockNetd, times(1)).clatdStart(MOBILE_IFNAME);
+        verify(mMockNetd, times(1)).resolverStartPrefix64Discovery(cellNetId);
-        Nat464Xlat clat = mService.getNat464Xlat(mCellNetworkAgent);
 
-        // Clat iface up, expect stack link updated.
+        // Switching default network updates TCP buffer sizes.
+        verifyTcpBufferSizeChange(ConnectivityService.DEFAULT_TCP_BUFFER_SIZES);
+
+        // Add an IPv4 address. Expect prefix discovery to be stopped. Netd doesn't tell us that
+        // the NAT64 prefix was removed because one was never discovered.
+        cellLp.addLinkAddress(myIpv4);
+        mCellNetworkAgent.sendLinkProperties(cellLp);
+        networkCallback.expectCallback(CallbackState.LINK_PROPERTIES, mCellNetworkAgent);
+        verify(mMockNetd, times(1)).resolverStopPrefix64Discovery(cellNetId);
+
+        verifyNoMoreInteractions(mMockNetd);
+        reset(mMockNetd);
+
+        // Remove IPv4 address. Expect prefix discovery to be started again.
+        cellLp.removeLinkAddress(myIpv4);
+        cellLp.removeRoute(new RouteInfo(myIpv4, null, MOBILE_IFNAME));
+        mCellNetworkAgent.sendLinkProperties(cellLp);
+        networkCallback.expectCallback(CallbackState.LINK_PROPERTIES, mCellNetworkAgent);
+        verify(mMockNetd, times(1)).resolverStartPrefix64Discovery(cellNetId);
+
+        // When NAT64 prefix discovery succeeds, LinkProperties are updated and clatd is started.
+        Nat464Xlat clat = mService.getNat464Xlat(mCellNetworkAgent);
+        assertNull(mCm.getLinkProperties(mCellNetworkAgent.getNetwork()).getNat64Prefix());
+        mService.mNetdEventCallback.onNat64PrefixEvent(cellNetId, true /* added */,
+                kNat64PrefixString, 96);
+        LinkProperties lpBeforeClat = (LinkProperties) networkCallback.expectCallback(
+                CallbackState.LINK_PROPERTIES, mCellNetworkAgent).arg;
+        assertEquals(0, lpBeforeClat.getStackedLinks().size());
+        assertEquals(kNat64Prefix, lpBeforeClat.getNat64Prefix());
+        verify(mMockNetd, times(1)).clatdStart(MOBILE_IFNAME, kNat64Prefix.toString());
+
+        // Clat iface comes up. Expect stacked link to be added.
         clat.interfaceLinkStateChanged(CLAT_PREFIX + MOBILE_IFNAME, true);
         networkCallback.expectCallback(CallbackState.LINK_PROPERTIES, mCellNetworkAgent);
         List<LinkProperties> stackedLps = mCm.getLinkProperties(mCellNetworkAgent.getNetwork())
@@ -5130,20 +5169,66 @@ public class ConnectivityServiceTest {
         assertNotEquals(stackedLpsAfterChange, Collections.EMPTY_LIST);
         assertEquals(makeClatLinkProperties(myIpv4), stackedLpsAfterChange.get(0));
 
-        // Add ipv4 address, expect stacked linkproperties be cleaned up
+        // Add ipv4 address, expect that clatd and prefix discovery are stopped and stacked
+        // linkproperties are cleaned up.
         cellLp.addLinkAddress(myIpv4);
         cellLp.addRoute(new RouteInfo(myIpv4, null, MOBILE_IFNAME));
         mCellNetworkAgent.sendLinkProperties(cellLp);
         networkCallback.expectCallback(CallbackState.LINK_PROPERTIES, mCellNetworkAgent);
         verify(mMockNetd, times(1)).clatdStop(MOBILE_IFNAME);
+        verify(mMockNetd, times(1)).resolverStopPrefix64Discovery(cellNetId);
 
-        // Clat iface removed, expect linkproperties revert to original one
+        // As soon as stop is called, the linkproperties lose the stacked interface.
-        clat.interfaceRemoved(CLAT_PREFIX + MOBILE_IFNAME);
         networkCallback.expectCallback(CallbackState.LINK_PROPERTIES, mCellNetworkAgent);
         LinkProperties actualLpAfterIpv4 = mCm.getLinkProperties(mCellNetworkAgent.getNetwork());
-        assertEquals(cellLp, actualLpAfterIpv4);
+        LinkProperties expected = new LinkProperties(cellLp);
+        expected.setNat64Prefix(kNat64Prefix);
+        assertEquals(expected, actualLpAfterIpv4);
+        assertEquals(0, actualLpAfterIpv4.getStackedLinks().size());
 
-        // Clean up
+        // The interface removed callback happens but has no effect after stop is called.
+        clat.interfaceRemoved(CLAT_PREFIX + MOBILE_IFNAME);
+        networkCallback.assertNoCallback();
+
+        verifyNoMoreInteractions(mMockNetd);
+        reset(mMockNetd);
+
+        // Stopping prefix discovery causes netd to tell us that the NAT64 prefix is gone.
+        mService.mNetdEventCallback.onNat64PrefixEvent(cellNetId, false /* added */,
+                kNat64PrefixString, 96);
+        networkCallback.expectLinkPropertiesLike((lp) -> lp.getNat64Prefix() == null,
+                mCellNetworkAgent);
+
+        // Remove IPv4 address and expect prefix discovery and clatd to be started again.
+        cellLp.removeLinkAddress(myIpv4);
+        cellLp.removeRoute(new RouteInfo(myIpv4, null, MOBILE_IFNAME));
+        cellLp.removeDnsServer(InetAddress.getByName("8.8.8.8"));
+        mCellNetworkAgent.sendLinkProperties(cellLp);
+        networkCallback.expectCallback(CallbackState.LINK_PROPERTIES, mCellNetworkAgent);
+        verify(mMockNetd, times(1)).resolverStartPrefix64Discovery(cellNetId);
+        mService.mNetdEventCallback.onNat64PrefixEvent(cellNetId, true /* added */,
+                kNat64PrefixString, 96);
+        networkCallback.expectCallback(CallbackState.LINK_PROPERTIES, mCellNetworkAgent);
+        verify(mMockNetd, times(1)).clatdStart(MOBILE_IFNAME, kNat64Prefix.toString());
+
+
+        // Clat iface comes up. Expect stacked link to be added.
+        clat.interfaceLinkStateChanged(CLAT_PREFIX + MOBILE_IFNAME, true);
+        networkCallback.expectLinkPropertiesLike(
+                (lp) -> lp.getStackedLinks().size() == 1 && lp.getNat64Prefix() != null,
+                mCellNetworkAgent);
+
+        // NAT64 prefix is removed. Expect that clat is stopped.
+        mService.mNetdEventCallback.onNat64PrefixEvent(cellNetId, false /* added */,
+                kNat64PrefixString, 96);
+        networkCallback.expectLinkPropertiesLike(
+                (lp) -> lp.getStackedLinks().size() == 0 && lp.getNat64Prefix() == null,
+                mCellNetworkAgent);
+        verify(mMockNetd, times(1)).clatdStop(MOBILE_IFNAME);
+        networkCallback.expectLinkPropertiesLike((lp) -> lp.getStackedLinks().size() == 0,
+                mCellNetworkAgent);
+
+        // Clean up.
         mCellNetworkAgent.disconnect();
         networkCallback.expectCallback(CallbackState.LOST, mCellNetworkAgent);
         networkCallback.assertNoCallback();
@@ -5224,30 +5309,34 @@ public class ConnectivityServiceTest {
         mCm.unregisterNetworkCallback(networkCallback);
     }
 
-    private static final String TEST_TCP_BUFFER_SIZES = "1,2,3,4,5,6";
+    private void verifyTcpBufferSizeChange(String tcpBufferSizes) {
-
-    private void verifyTcpBufferSizeChange(String tcpBufferSizes) throws Exception {
         String[] values = tcpBufferSizes.split(",");
         String rmemValues = String.join(" ", values[0], values[1], values[2]);
         String wmemValues = String.join(" ", values[3], values[4], values[5]);
         waitForIdle();
-        verify(mMockNetd, atLeastOnce()).setTcpRWmemorySize(rmemValues, wmemValues);
+        try {
+            verify(mMockNetd, atLeastOnce()).setTcpRWmemorySize(rmemValues, wmemValues);
+        } catch (RemoteException e) {
+            fail("mMockNetd should never throw RemoteException");
+        }
         reset(mMockNetd);
     }
 
     @Test
-    public void testTcpBufferReset() throws Exception {
+    public void testTcpBufferReset() {
+        final String testTcpBufferSizes = "1,2,3,4,5,6";
+
         mCellNetworkAgent = new MockNetworkAgent(TRANSPORT_CELLULAR);
         reset(mMockNetd);
-        // Simple connection should have updated tcp buffer size.
+        // Switching default network updates TCP buffer sizes.
         mCellNetworkAgent.connect(false);
         verifyTcpBufferSizeChange(ConnectivityService.DEFAULT_TCP_BUFFER_SIZES);
 
         // Change link Properties should have updated tcp buffer size.
         LinkProperties lp = new LinkProperties();
-        lp.setTcpBufferSizes(TEST_TCP_BUFFER_SIZES);
+        lp.setTcpBufferSizes(testTcpBufferSizes);
         mCellNetworkAgent.sendLinkProperties(lp);
-        verifyTcpBufferSizeChange(TEST_TCP_BUFFER_SIZES);
+        verifyTcpBufferSizeChange(testTcpBufferSizes);
     }
 
     @Test

tests/net/java/com/android/server/connectivity/Nat464XlatTest.java

@@ -16,9 +16,11 @@
 
 package com.android.server.connectivity;
 
+import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertTrue;
 import static org.mockito.Mockito.eq;
+import static org.mockito.Mockito.inOrder;
 import static org.mockito.Mockito.times;
 import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.verifyNoMoreInteractions;
@@ -27,6 +29,7 @@ import static org.mockito.Mockito.when;
 import android.net.ConnectivityManager;
 import android.net.INetd;
 import android.net.InterfaceConfiguration;
+import android.net.IpPrefix;
 import android.net.LinkAddress;
 import android.net.LinkProperties;
 import android.net.NetworkInfo;
@@ -43,6 +46,7 @@ import org.junit.Before;
 import org.junit.Test;
 import org.junit.runner.RunWith;
 import org.mockito.ArgumentCaptor;
+import org.mockito.InOrder;
 import org.mockito.Mock;
 import org.mockito.MockitoAnnotations;
 
@@ -53,6 +57,8 @@ public class Nat464XlatTest {
     static final String BASE_IFACE = "test0";
     static final String STACKED_IFACE = "v4-test0";
     static final LinkAddress ADDR = new LinkAddress("192.0.2.5/29");
+    static final String NAT64_PREFIX = "64:ff9b::/96";
+    static final int NETID = 42;
 
     @Mock ConnectivityService mConnectivity;
     @Mock NetworkMisc mMisc;
@@ -65,7 +71,11 @@ public class Nat464XlatTest {
     Handler mHandler;
 
     Nat464Xlat makeNat464Xlat() {
-        return new Nat464Xlat(mNai, mNetd, mNms);
+        return new Nat464Xlat(mNai, mNetd, mNms) {
+            @Override protected int getNetId() {
+                return NETID;
+            }
+        };
     }
 
     @Before
@@ -87,6 +97,24 @@ public class Nat464XlatTest {
         when(mConfig.getLinkAddress()).thenReturn(ADDR);
     }
 
+    private void assertRequiresClat(boolean expected, NetworkAgentInfo nai) {
+        String msg = String.format("requiresClat expected %b for type=%d state=%s skip=%b "
+                + "nat64Prefix=%s addresses=%s", expected, nai.networkInfo.getType(),
+                nai.networkInfo.getDetailedState(),
+                mMisc.skip464xlat, nai.linkProperties.getNat64Prefix(),
+                nai.linkProperties.getLinkAddresses());
+        assertEquals(msg, expected, Nat464Xlat.requiresClat(nai));
+    }
+
+    private void assertShouldStartClat(boolean expected, NetworkAgentInfo nai) {
+        String msg = String.format("shouldStartClat expected %b for type=%d state=%s skip=%b "
+                + "nat64Prefix=%s addresses=%s", expected, nai.networkInfo.getType(),
+                nai.networkInfo.getDetailedState(),
+                mMisc.skip464xlat, nai.linkProperties.getNat64Prefix(),
+                nai.linkProperties.getLinkAddresses());
+        assertEquals(msg, expected, Nat464Xlat.shouldStartClat(nai));
+    }
+
     @Test
     public void testRequiresClat() throws Exception {
         final int[] supportedTypes = {
@@ -102,20 +130,45 @@ public class Nat464XlatTest {
             NetworkInfo.DetailedState.SUSPENDED,
         };
 
+        LinkProperties oldLp = new LinkProperties(mNai.linkProperties);
         for (int type : supportedTypes) {
             mNai.networkInfo.setType(type);
             for (NetworkInfo.DetailedState state : supportedDetailedStates) {
                 mNai.networkInfo.setDetailedState(state, "reason", "extraInfo");
-                String msg = String.format("requiresClat expected for type=%d state=%s",
+
-                        type, state);
+                mNai.linkProperties.setNat64Prefix(new IpPrefix("2001:db8:0:64::/96"));
+                assertRequiresClat(false, mNai);
+                assertShouldStartClat(false, mNai);
+
+                mNai.linkProperties.addLinkAddress(new LinkAddress("fc00::1/64"));
+                assertRequiresClat(false, mNai);
+                assertShouldStartClat(false, mNai);
+
+                mNai.linkProperties.addLinkAddress(new LinkAddress("2001:db8::1/64"));
+                assertRequiresClat(true, mNai);
+                assertShouldStartClat(true, mNai);
 
                 mMisc.skip464xlat = true;
-                String errorMsg = msg + String.format(" skip464xlat=%b", mMisc.skip464xlat);
+                assertRequiresClat(false, mNai);
-                assertFalse(errorMsg, Nat464Xlat.requiresClat(mNai));
+                assertShouldStartClat(false, mNai);
 
                 mMisc.skip464xlat = false;
-                errorMsg = msg + String.format(" skip464xlat=%b", mMisc.skip464xlat);
+                assertRequiresClat(true, mNai);
-                assertTrue(errorMsg, Nat464Xlat.requiresClat(mNai));
+                assertShouldStartClat(true, mNai);
+
+                mNai.linkProperties.addLinkAddress(new LinkAddress("192.0.2.2/24"));
+                assertRequiresClat(false, mNai);
+                assertShouldStartClat(false, mNai);
+
+                mNai.linkProperties.removeLinkAddress(new LinkAddress("192.0.2.2/24"));
+                assertRequiresClat(true, mNai);
+                assertShouldStartClat(true, mNai);
+
+                mNai.linkProperties.setNat64Prefix(null);
+                assertRequiresClat(true, mNai);
+                assertShouldStartClat(false, mNai);
+
+                mNai.linkProperties = new LinkProperties(oldLp);
             }
         }
     }
@@ -125,11 +178,13 @@ public class Nat464XlatTest {
         Nat464Xlat nat = makeNat464Xlat();
         ArgumentCaptor<LinkProperties> c = ArgumentCaptor.forClass(LinkProperties.class);
 
-        // ConnectivityService starts clat.
+        nat.setNat64Prefix(new IpPrefix(NAT64_PREFIX));
+
+        // Start clat.
         nat.start();
 
         verify(mNms).registerObserver(eq(nat));
-        verify(mNetd).clatdStart(eq(BASE_IFACE));
+        verify(mNetd).clatdStart(eq(BASE_IFACE), eq(NAT64_PREFIX));
 
         // Stacked interface up notification arrives.
         nat.interfaceLinkStateChanged(STACKED_IFACE, true);
@@ -141,22 +196,109 @@ public class Nat464XlatTest {
         assertTrue(c.getValue().getAllInterfaceNames().contains(STACKED_IFACE));
         assertRunning(nat);
 
-        // ConnectivityService stops clat (Network disconnects, IPv4 addr appears, ...).
+        // Stop clat (Network disconnects, IPv4 addr appears, ...).
         nat.stop();
 
         verify(mNetd).clatdStop(eq(BASE_IFACE));
+        verify(mConnectivity, times(2)).handleUpdateLinkProperties(eq(mNai), c.capture());
+        verify(mNms).unregisterObserver(eq(nat));
+        assertTrue(c.getValue().getStackedLinks().isEmpty());
+        assertFalse(c.getValue().getAllInterfaceNames().contains(STACKED_IFACE));
+        verify(mNetd).resolverStopPrefix64Discovery(eq(NETID));
+        assertIdle(nat);
 
-        // Stacked interface removed notification arrives.
+        // Stacked interface removed notification arrives and is ignored.
         nat.interfaceRemoved(STACKED_IFACE);
         mLooper.dispatchNext();
 
-        verify(mNms).unregisterObserver(eq(nat));
+        verifyNoMoreInteractions(mNetd, mNms, mConnectivity);
-        verify(mConnectivity, times(2)).handleUpdateLinkProperties(eq(mNai), c.capture());
+    }
+
+    private void checkStartStopStart(boolean interfaceRemovedFirst) throws Exception {
+        Nat464Xlat nat = makeNat464Xlat();
+        ArgumentCaptor<LinkProperties> c = ArgumentCaptor.forClass(LinkProperties.class);
+        InOrder inOrder = inOrder(mNetd, mConnectivity);
+
+        nat.setNat64Prefix(new IpPrefix(NAT64_PREFIX));
+
+        nat.start();
+
+        inOrder.verify(mNetd).clatdStart(eq(BASE_IFACE), eq(NAT64_PREFIX));
+
+        // Stacked interface up notification arrives.
+        nat.interfaceLinkStateChanged(STACKED_IFACE, true);
+        mLooper.dispatchNext();
+
+        inOrder.verify(mConnectivity).handleUpdateLinkProperties(eq(mNai), c.capture());
+        assertFalse(c.getValue().getStackedLinks().isEmpty());
+        assertTrue(c.getValue().getAllInterfaceNames().contains(STACKED_IFACE));
+        assertRunning(nat);
+
+        // ConnectivityService stops clat (Network disconnects, IPv4 addr appears, ...).
+        nat.stop();
+
+        inOrder.verify(mNetd).clatdStop(eq(BASE_IFACE));
+
+        inOrder.verify(mConnectivity, times(1)).handleUpdateLinkProperties(eq(mNai), c.capture());
         assertTrue(c.getValue().getStackedLinks().isEmpty());
         assertFalse(c.getValue().getAllInterfaceNames().contains(STACKED_IFACE));
         assertIdle(nat);
 
-        verifyNoMoreInteractions(mNetd, mNms, mConnectivity);
+        if (interfaceRemovedFirst) {
+            // Stacked interface removed notification arrives and is ignored.
+            nat.interfaceRemoved(STACKED_IFACE);
+            mLooper.dispatchNext();
+            nat.interfaceLinkStateChanged(STACKED_IFACE, false);
+            mLooper.dispatchNext();
+        }
+
+        assertTrue(c.getValue().getStackedLinks().isEmpty());
+        assertFalse(c.getValue().getAllInterfaceNames().contains(STACKED_IFACE));
+        assertIdle(nat);
+        inOrder.verifyNoMoreInteractions();
+
+        nat.start();
+
+        inOrder.verify(mNetd).clatdStart(eq(BASE_IFACE), eq(NAT64_PREFIX));
+
+        if (!interfaceRemovedFirst) {
+            // Stacked interface removed notification arrives and is ignored.
+            nat.interfaceRemoved(STACKED_IFACE);
+            mLooper.dispatchNext();
+            nat.interfaceLinkStateChanged(STACKED_IFACE, false);
+            mLooper.dispatchNext();
+        }
+
+        // Stacked interface up notification arrives.
+        nat.interfaceLinkStateChanged(STACKED_IFACE, true);
+        mLooper.dispatchNext();
+
+        inOrder.verify(mConnectivity).handleUpdateLinkProperties(eq(mNai), c.capture());
+        assertFalse(c.getValue().getStackedLinks().isEmpty());
+        assertTrue(c.getValue().getAllInterfaceNames().contains(STACKED_IFACE));
+        assertRunning(nat);
+
+        // ConnectivityService stops clat again.
+        nat.stop();
+
+        inOrder.verify(mNetd).clatdStop(eq(BASE_IFACE));
+
+        inOrder.verify(mConnectivity, times(1)).handleUpdateLinkProperties(eq(mNai), c.capture());
+        assertTrue(c.getValue().getStackedLinks().isEmpty());
+        assertFalse(c.getValue().getAllInterfaceNames().contains(STACKED_IFACE));
+        assertIdle(nat);
+
+        inOrder.verifyNoMoreInteractions();
+    }
+
+    @Test
+    public void testStartStopStart() throws Exception {
+        checkStartStopStart(true);
+    }
+
+    @Test
+    public void testStartStopStartBeforeInterfaceRemoved() throws Exception {
+        checkStartStopStart(false);
     }
 
     @Test
@@ -164,11 +306,12 @@ public class Nat464XlatTest {
         Nat464Xlat nat = makeNat464Xlat();
         ArgumentCaptor<LinkProperties> c = ArgumentCaptor.forClass(LinkProperties.class);
 
-        // ConnectivityService starts clat.
+        nat.setNat64Prefix(new IpPrefix(NAT64_PREFIX));
+
         nat.start();
 
         verify(mNms).registerObserver(eq(nat));
-        verify(mNetd).clatdStart(eq(BASE_IFACE));
+        verify(mNetd).clatdStart(eq(BASE_IFACE), eq(NAT64_PREFIX));
 
         // Stacked interface up notification arrives.
         nat.interfaceLinkStateChanged(STACKED_IFACE, true);
@@ -184,9 +327,10 @@ public class Nat464XlatTest {
         nat.interfaceRemoved(STACKED_IFACE);
         mLooper.dispatchNext();
 
-        verify(mNms).unregisterObserver(eq(nat));
         verify(mNetd).clatdStop(eq(BASE_IFACE));
         verify(mConnectivity, times(2)).handleUpdateLinkProperties(eq(mNai), c.capture());
+        verify(mNms).unregisterObserver(eq(nat));
+        verify(mNetd).resolverStopPrefix64Discovery(eq(NETID));
         assertTrue(c.getValue().getStackedLinks().isEmpty());
         assertFalse(c.getValue().getAllInterfaceNames().contains(STACKED_IFACE));
         assertIdle(nat);
@@ -201,24 +345,25 @@ public class Nat464XlatTest {
     public void testStopBeforeClatdStarts() throws Exception {
         Nat464Xlat nat = makeNat464Xlat();
 
-        // ConnectivityService starts clat.
+        nat.setNat64Prefix(new IpPrefix(NAT64_PREFIX));
+
         nat.start();
 
         verify(mNms).registerObserver(eq(nat));
-        verify(mNetd).clatdStart(eq(BASE_IFACE));
+        verify(mNetd).clatdStart(eq(BASE_IFACE), eq(NAT64_PREFIX));
 
         // ConnectivityService immediately stops clat (Network disconnects, IPv4 addr appears, ...)
         nat.stop();
 
-        verify(mNms).unregisterObserver(eq(nat));
         verify(mNetd).clatdStop(eq(BASE_IFACE));
+        verify(mNms).unregisterObserver(eq(nat));
+        verify(mNetd).resolverStopPrefix64Discovery(eq(NETID));
         assertIdle(nat);
 
         // In-flight interface up notification arrives: no-op
         nat.interfaceLinkStateChanged(STACKED_IFACE, true);
         mLooper.dispatchNext();
 
-
         // Interface removed notification arrives after stopClatd() takes effect: no-op.
         nat.interfaceRemoved(STACKED_IFACE);
         mLooper.dispatchNext();
@@ -232,17 +377,19 @@ public class Nat464XlatTest {
     public void testStopAndClatdNeverStarts() throws Exception {
         Nat464Xlat nat = makeNat464Xlat();
 
-        // ConnectivityService starts clat.
+        nat.setNat64Prefix(new IpPrefix(NAT64_PREFIX));
+
         nat.start();
 
         verify(mNms).registerObserver(eq(nat));
-        verify(mNetd).clatdStart(eq(BASE_IFACE));
+        verify(mNetd).clatdStart(eq(BASE_IFACE), eq(NAT64_PREFIX));
 
         // ConnectivityService immediately stops clat (Network disconnects, IPv4 addr appears, ...)
         nat.stop();
 
-        verify(mNms).unregisterObserver(eq(nat));
         verify(mNetd).clatdStop(eq(BASE_IFACE));
+        verify(mNms).unregisterObserver(eq(nat));
+        verify(mNetd).resolverStopPrefix64Discovery(eq(NETID));
         assertIdle(nat);
 
         verifyNoMoreInteractions(mNetd, mNms, mConnectivity);