Add a registerSystemDefaultNetworkCallback method.

This method allows internal components to track the system
default network. This differs from registerDefaultNetworkCallback
because that method sends callbacks for the default network for
the UID that called it. This may not be the system default
network, for example, when a VPN is up and applies to the UID.

Bug: 173331190
Test: new unit tests in ConnectivityServiceTest
Test: new unit tests in ConnectivityManagerTest
Test: new CTS tests in ConnectivityServiceTest
Test: new CTS tests in HostsideVpnTests in other CL in this topic
Change-Id: Id02748a2183f71b71ff2a53a580466b9dcecaa93

framework/src/android/net/ConnectivityManager.java

@@ -21,6 +21,7 @@ import static android.net.NetworkRequest.Type.BACKGROUND_REQUEST;
 import static android.net.NetworkRequest.Type.LISTEN;
 import static android.net.NetworkRequest.Type.REQUEST;
 import static android.net.NetworkRequest.Type.TRACK_DEFAULT;
+import static android.net.NetworkRequest.Type.TRACK_SYSTEM_DEFAULT;
 import static android.net.QosCallback.QosCallbackRegistrationException;
 
 import android.annotation.CallbackExecutor;
@@ -3721,7 +3722,8 @@ public class ConnectivityManager {
         printStackTrace();
         checkCallbackNotNull(callback);
         Preconditions.checkArgument(
-                reqType == TRACK_DEFAULT || need != null, "null NetworkCapabilities");
+                reqType == TRACK_DEFAULT || reqType == TRACK_SYSTEM_DEFAULT || need != null,
+                "null NetworkCapabilities");
         final NetworkRequest request;
         final String callingPackageName = mContext.getOpPackageName();
         try {
@@ -4192,8 +4194,9 @@ public class ConnectivityManager {
     }
 
     /**
-     * Registers to receive notifications about changes in the system default network. The callbacks
+     * Registers to receive notifications about changes in the application's default network. This
-     * will continue to be called until either the application exits or
+     * may be a physical network or a virtual network, such as a VPN that applies to the
+     * application. The callbacks will continue to be called until either the application exits or
      * {@link #unregisterNetworkCallback(NetworkCallback)} is called.
      *
      * <p>To avoid performance issues due to apps leaking callbacks, the system will limit the
@@ -4206,7 +4209,7 @@ public class ConnectivityManager {
      * {@link #unregisterNetworkCallback(NetworkCallback)}.
      *
      * @param networkCallback The {@link NetworkCallback} that the system will call as the
-     *                        system default network changes.
+     *                        application's default network changes.
      *                        The callback is invoked on the default internal Handler.
      * @throws RuntimeException if the app already has too many callbacks registered.
      */
@@ -4215,11 +4218,47 @@ public class ConnectivityManager {
         registerDefaultNetworkCallback(networkCallback, getDefaultHandler());
     }
 
+    /**
+     * Registers to receive notifications about changes in the application's default network. This
+     * may be a physical network or a virtual network, such as a VPN that applies to the
+     * application. The callbacks will continue to be called until either the application exits or
+     * {@link #unregisterNetworkCallback(NetworkCallback)} is called.
+     *
+     * <p>To avoid performance issues due to apps leaking callbacks, the system will limit the
+     * number of outstanding requests to 100 per app (identified by their UID), shared with
+     * all variants of this method, of {@link #requestNetwork} as well as
+     * {@link ConnectivityDiagnosticsManager#registerConnectivityDiagnosticsCallback}.
+     * Requesting a network with this method will count toward this limit. If this limit is
+     * exceeded, an exception will be thrown. To avoid hitting this issue and to conserve resources,
+     * make sure to unregister the callbacks with
+     * {@link #unregisterNetworkCallback(NetworkCallback)}.
+     *
+     * @param networkCallback The {@link NetworkCallback} that the system will call as the
+     *                        application's default network changes.
+     * @param handler {@link Handler} to specify the thread upon which the callback will be invoked.
+     * @throws RuntimeException if the app already has too many callbacks registered.
+     */
+    @RequiresPermission(android.Manifest.permission.ACCESS_NETWORK_STATE)
+    public void registerDefaultNetworkCallback(@NonNull NetworkCallback networkCallback,
+            @NonNull Handler handler) {
+        CallbackHandler cbHandler = new CallbackHandler(handler);
+        sendRequestForNetwork(null /* NetworkCapabilities need */, networkCallback, 0,
+                TRACK_DEFAULT, TYPE_NONE, cbHandler);
+    }
+
     /**
      * Registers to receive notifications about changes in the system default network. The callbacks
      * will continue to be called until either the application exits or
      * {@link #unregisterNetworkCallback(NetworkCallback)} is called.
      *
+     * This method should not be used to determine networking state seen by applications, because in
+     * many cases, most or even all application traffic may not use the default network directly,
+     * and traffic from different applications may go on different networks by default. As an
+     * example, if a VPN is connected, traffic from all applications might be sent through the VPN
+     * and not onto the system default network. Applications or system components desiring to do
+     * determine network state as seen by applications should use other methods such as
+     * {@link #registerDefaultNetworkCallback(NetworkCallback, Handler)}.
+     *
      * <p>To avoid performance issues due to apps leaking callbacks, the system will limit the
      * number of outstanding requests to 100 per app (identified by their UID), shared with
      * all variants of this method, of {@link #requestNetwork} as well as
@@ -4233,20 +4272,19 @@ public class ConnectivityManager {
      *                        system default network changes.
      * @param handler {@link Handler} to specify the thread upon which the callback will be invoked.
      * @throws RuntimeException if the app already has too many callbacks registered.
+     *
+     * @hide
      */
-    @RequiresPermission(android.Manifest.permission.ACCESS_NETWORK_STATE)
+    @SystemApi(client = MODULE_LIBRARIES)
-    public void registerDefaultNetworkCallback(@NonNull NetworkCallback networkCallback,
+    @SuppressLint({"ExecutorRegistration", "PairedRegistration"})
+    @RequiresPermission(anyOf = {
+            NetworkStack.PERMISSION_MAINLINE_NETWORK_STACK,
+            android.Manifest.permission.NETWORK_SETTINGS})
+    public void registerSystemDefaultNetworkCallback(@NonNull NetworkCallback networkCallback,
             @NonNull Handler handler) {
-        // This works because if the NetworkCapabilities are null,
-        // ConnectivityService takes them from the default request.
-        //
-        // Since the capabilities are exactly the same as the default request's
-        // capabilities, this request is guaranteed, at all times, to be
-        // satisfied by the same network, if any, that satisfies the default
-        // request, i.e., the system default network.
         CallbackHandler cbHandler = new CallbackHandler(handler);
         sendRequestForNetwork(null /* NetworkCapabilities need */, networkCallback, 0,
-                TRACK_DEFAULT, TYPE_NONE, cbHandler);
+                TRACK_SYSTEM_DEFAULT, TYPE_NONE, cbHandler);
     }
 
     /**

framework/src/android/net/NetworkRequest.java

@@ -104,17 +104,14 @@ public class NetworkRequest implements Parcelable {
      *       callbacks about the single, highest scoring current network
      *       (if any) that matches the specified NetworkCapabilities, or
      *
-     *     - TRACK_DEFAULT, a hybrid of the two designed such that the
+     *     - TRACK_DEFAULT, which causes the framework to issue callbacks for
-     *       framework will issue callbacks for the single, highest scoring
+     *       the single, highest scoring current network (if any) that will
-     *       current network (if any) that matches the capabilities of the
+     *       be chosen for an app, but which cannot cause the framework to
-     *       default Internet request (mDefaultRequest), but which cannot cause
+     *       either create or retain the existence of any specific network.
-     *       the framework to either create or retain the existence of any
+     *
-     *       specific network. Note that from the point of view of the request
+     *     - TRACK_SYSTEM_DEFAULT, which causes the framework to send callbacks
-     *       matching code, TRACK_DEFAULT is identical to REQUEST: its special
+     *       for the network (if any) that satisfies the default Internet
-     *       behaviour is not due to different semantics, but to the fact that
+     *       request.
-     *       the system will only ever create a TRACK_DEFAULT with capabilities
-     *       that are identical to the default request's capabilities, thus
-     *       causing it to share fate in every way with the default request.
      *
      *     - BACKGROUND_REQUEST, like REQUEST but does not cause any networks
      *       to retain the NET_CAPABILITY_FOREGROUND capability. A network with
@@ -137,6 +134,7 @@ public class NetworkRequest implements Parcelable {
         TRACK_DEFAULT,
         REQUEST,
         BACKGROUND_REQUEST,
+        TRACK_SYSTEM_DEFAULT,
     };
 
     /**
@@ -601,6 +599,8 @@ public class NetworkRequest implements Parcelable {
                 return NetworkRequestProto.TYPE_REQUEST;
             case BACKGROUND_REQUEST:
                 return NetworkRequestProto.TYPE_BACKGROUND_REQUEST;
+            case TRACK_SYSTEM_DEFAULT:
+                return NetworkRequestProto.TYPE_TRACK_SYSTEM_DEFAULT;
             default:
                 return NetworkRequestProto.TYPE_UNKNOWN;
         }

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

@@ -5746,6 +5746,7 @@ public class ConnectivityService extends IConnectivityManager.Stub
                 throw new SecurityException("Insufficient permissions to specify legacy type");
             }
         }
+        final NetworkCapabilities defaultNc = mDefaultRequest.mRequests.get(0).networkCapabilities;
         final int callingUid = mDeps.getCallingUid();
         final NetworkRequest.Type reqType;
         try {
@@ -5756,11 +5757,15 @@ public class ConnectivityService extends IConnectivityManager.Stub
         switch (reqType) {
             case TRACK_DEFAULT:
                 // If the request type is TRACK_DEFAULT, the passed {@code networkCapabilities}
-                // is unused and will be replaced by the one from the default network request.
+                // is unused and will be replaced by ones appropriate for the caller.
-                // This allows callers to keep track of the system default network.
+                // This allows callers to keep track of the default network for their app.
                 networkCapabilities = createDefaultNetworkCapabilitiesForUid(callingUid);
                 enforceAccessPermission();
                 break;
+            case TRACK_SYSTEM_DEFAULT:
+                enforceSettingsPermission();
+                networkCapabilities = new NetworkCapabilities(defaultNc);
+                break;
             case BACKGROUND_REQUEST:
                 enforceNetworkStackOrSettingsPermission();
                 // Fall-through since other checks are the same with normal requests.
@@ -5779,6 +5784,7 @@ public class ConnectivityService extends IConnectivityManager.Stub
         ensureRequestableCapabilities(networkCapabilities);
         ensureSufficientPermissionsForRequest(networkCapabilities,
                 Binder.getCallingPid(), callingUid, callingPackageName);
+
         // Set the UID range for this request to the single UID of the requester, or to an empty
         // set of UIDs if the caller has the appropriate permission and UIDs have not been set.
         // This will overwrite any allowed UIDs in the requested capabilities. Though there
@@ -5798,6 +5804,16 @@ public class ConnectivityService extends IConnectivityManager.Stub
                 new NetworkRequestInfo(messenger, networkRequest, binder, callingAttributionTag);
         if (DBG) log("requestNetwork for " + nri);
 
+        // For TRACK_SYSTEM_DEFAULT callbacks, the capabilities have been modified since they were
+        // copied from the default request above. (This is necessary to ensure, for example, that
+        // the callback does not leak sensitive information to unprivileged apps.) Check that the
+        // changes don't alter request matching.
+        if (reqType == NetworkRequest.Type.TRACK_SYSTEM_DEFAULT &&
+                (!networkCapabilities.equalRequestableCapabilities(defaultNc))) {
+            Log.wtf(TAG, "TRACK_SYSTEM_DEFAULT capabilities don't match default request: "
+                    + networkCapabilities + " vs. " + defaultNc);
+        }
+
         mHandler.sendMessage(mHandler.obtainMessage(EVENT_REGISTER_NETWORK_REQUEST, nri));
         if (timeoutMs > 0) {
             mHandler.sendMessageDelayed(mHandler.obtainMessage(EVENT_TIMEOUT_NETWORK_REQUEST,

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

@@ -717,8 +717,9 @@ public class NetworkAgentInfo implements Comparable<NetworkAgentInfo> {
                 mNumBackgroundNetworkRequests += delta;
                 break;
 
-            case TRACK_DEFAULT:
             case LISTEN:
+            case TRACK_DEFAULT:
+            case TRACK_SYSTEM_DEFAULT:
                 break;
 
             case NONE:

tests/net/java/android/net/ConnectivityManagerTest.java

@@ -35,6 +35,7 @@ import static android.net.NetworkCapabilities.TRANSPORT_WIFI;
 import static android.net.NetworkRequest.Type.BACKGROUND_REQUEST;
 import static android.net.NetworkRequest.Type.REQUEST;
 import static android.net.NetworkRequest.Type.TRACK_DEFAULT;
+import static android.net.NetworkRequest.Type.TRACK_SYSTEM_DEFAULT;
 
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertNotNull;
@@ -329,6 +330,9 @@ public class ConnectivityManagerTest {
         mustFail(() -> { manager.registerDefaultNetworkCallback(null, handler); });
         mustFail(() -> { manager.registerDefaultNetworkCallback(callback, null); });
 
+        mustFail(() -> { manager.registerSystemDefaultNetworkCallback(null, handler); });
+        mustFail(() -> { manager.registerSystemDefaultNetworkCallback(callback, null); });
+
         mustFail(() -> { manager.unregisterNetworkCallback(nullCallback); });
         mustFail(() -> { manager.unregisterNetworkCallback(nullIntent); });
         mustFail(() -> { manager.releaseNetworkRequest(nullIntent); });
@@ -377,6 +381,13 @@ public class ConnectivityManagerTest {
                 eq(BACKGROUND_REQUEST.ordinal()), any(), anyInt(), any(), eq(TYPE_NONE),
                 eq(testPkgName), eq(testAttributionTag));
         reset(mService);
+
+        Handler handler = new Handler(ConnectivityThread.getInstanceLooper());
+        manager.registerSystemDefaultNetworkCallback(callback, handler);
+        verify(mService).requestNetwork(eq(null),
+                eq(TRACK_SYSTEM_DEFAULT.ordinal()), any(), anyInt(), any(), eq(TYPE_NONE),
+                eq(testPkgName), eq(testAttributionTag));
+        reset(mService);
     }
 
     static Message makeMessage(NetworkRequest req, int messageType) {

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

@@ -3649,10 +3649,19 @@ public class ConnectivityServiceTest {
 
     @Test
     public void testRegisterDefaultNetworkCallback() throws Exception {
+        // NETWORK_SETTINGS is necessary to call registerSystemDefaultNetworkCallback.
+        mServiceContext.setPermission(Manifest.permission.NETWORK_SETTINGS,
+                PERMISSION_GRANTED);
+
         final TestNetworkCallback defaultNetworkCallback = new TestNetworkCallback();
         mCm.registerDefaultNetworkCallback(defaultNetworkCallback);
         defaultNetworkCallback.assertNoCallback();
 
+        final Handler handler = new Handler(ConnectivityThread.getInstanceLooper());
+        final TestNetworkCallback systemDefaultCallback = new TestNetworkCallback();
+        mCm.registerSystemDefaultNetworkCallback(systemDefaultCallback, handler);
+        systemDefaultCallback.assertNoCallback();
+
         // Create a TRANSPORT_CELLULAR request to keep the mobile interface up
         // whenever Wi-Fi is up. Without this, the mobile network agent is
         // reaped before any other activity can take place.
@@ -3667,27 +3676,35 @@ public class ConnectivityServiceTest {
         mCellNetworkAgent.connect(true);
         cellNetworkCallback.expectAvailableThenValidatedCallbacks(mCellNetworkAgent);
         defaultNetworkCallback.expectAvailableThenValidatedCallbacks(mCellNetworkAgent);
+        systemDefaultCallback.expectAvailableThenValidatedCallbacks(mCellNetworkAgent);
         assertEquals(defaultNetworkCallback.getLastAvailableNetwork(), mCm.getActiveNetwork());
+        assertEquals(systemDefaultCallback.getLastAvailableNetwork(), mCm.getActiveNetwork());
 
         // Bring up wifi and expect CALLBACK_AVAILABLE.
         mWiFiNetworkAgent = new TestNetworkAgentWrapper(TRANSPORT_WIFI);
         mWiFiNetworkAgent.connect(true);
         cellNetworkCallback.assertNoCallback();
         defaultNetworkCallback.expectAvailableDoubleValidatedCallbacks(mWiFiNetworkAgent);
+        systemDefaultCallback.expectAvailableDoubleValidatedCallbacks(mWiFiNetworkAgent);
         assertEquals(defaultNetworkCallback.getLastAvailableNetwork(), mCm.getActiveNetwork());
+        assertEquals(systemDefaultCallback.getLastAvailableNetwork(), mCm.getActiveNetwork());
 
         // Bring down cell. Expect no default network callback, since it wasn't the default.
         mCellNetworkAgent.disconnect();
         cellNetworkCallback.expectCallback(CallbackEntry.LOST, mCellNetworkAgent);
         defaultNetworkCallback.assertNoCallback();
+        systemDefaultCallback.assertNoCallback();
         assertEquals(defaultNetworkCallback.getLastAvailableNetwork(), mCm.getActiveNetwork());
+        assertEquals(systemDefaultCallback.getLastAvailableNetwork(), mCm.getActiveNetwork());
 
         // Bring up cell. Expect no default network callback, since it won't be the default.
         mCellNetworkAgent = new TestNetworkAgentWrapper(TRANSPORT_CELLULAR);
         mCellNetworkAgent.connect(true);
         cellNetworkCallback.expectAvailableThenValidatedCallbacks(mCellNetworkAgent);
         defaultNetworkCallback.assertNoCallback();
+        systemDefaultCallback.assertNoCallback();
         assertEquals(defaultNetworkCallback.getLastAvailableNetwork(), mCm.getActiveNetwork());
+        assertEquals(systemDefaultCallback.getLastAvailableNetwork(), mCm.getActiveNetwork());
 
         // Bring down wifi. Expect the default network callback to notified of LOST wifi
         // followed by AVAILABLE cell.
@@ -3695,19 +3712,25 @@ public class ConnectivityServiceTest {
         cellNetworkCallback.assertNoCallback();
         defaultNetworkCallback.expectCallback(CallbackEntry.LOST, mWiFiNetworkAgent);
         defaultNetworkCallback.expectAvailableCallbacksValidated(mCellNetworkAgent);
+        systemDefaultCallback.expectCallback(CallbackEntry.LOST, mWiFiNetworkAgent);
+        systemDefaultCallback.expectAvailableCallbacksValidated(mCellNetworkAgent);
         mCellNetworkAgent.disconnect();
         cellNetworkCallback.expectCallback(CallbackEntry.LOST, mCellNetworkAgent);
         defaultNetworkCallback.expectCallback(CallbackEntry.LOST, mCellNetworkAgent);
+        systemDefaultCallback.expectCallback(CallbackEntry.LOST, mCellNetworkAgent);
         waitForIdle();
         assertEquals(null, mCm.getActiveNetwork());
 
         mMockVpn.establishForMyUid();
         assertUidRangesUpdatedForMyUid(true);
         defaultNetworkCallback.expectAvailableThenValidatedCallbacks(mMockVpn);
+        systemDefaultCallback.assertNoCallback();
         assertEquals(defaultNetworkCallback.getLastAvailableNetwork(), mCm.getActiveNetwork());
+        assertEquals(null, systemDefaultCallback.getLastAvailableNetwork());
 
         mMockVpn.disconnect();
         defaultNetworkCallback.expectCallback(CallbackEntry.LOST, mMockVpn);
+        systemDefaultCallback.assertNoCallback();
         waitForIdle();
         assertEquals(null, mCm.getActiveNetwork());
     }
@@ -6134,6 +6157,10 @@ public class ConnectivityServiceTest {
 
     @Test
     public void testVpnNetworkActive() throws Exception {
+        // NETWORK_SETTINGS is necessary to call registerSystemDefaultNetworkCallback.
+        mServiceContext.setPermission(Manifest.permission.NETWORK_SETTINGS,
+                PERMISSION_GRANTED);
+
         final int uid = Process.myUid();
 
         final TestNetworkCallback genericNetworkCallback = new TestNetworkCallback();
@@ -6141,6 +6168,7 @@ public class ConnectivityServiceTest {
         final TestNetworkCallback wifiNetworkCallback = new TestNetworkCallback();
         final TestNetworkCallback vpnNetworkCallback = new TestNetworkCallback();
         final TestNetworkCallback defaultCallback = new TestNetworkCallback();
+        final TestNetworkCallback systemDefaultCallback = new TestNetworkCallback();
         final NetworkRequest genericNotVpnRequest = new NetworkRequest.Builder().build();
         final NetworkRequest genericRequest = new NetworkRequest.Builder()
                 .removeCapability(NET_CAPABILITY_NOT_VPN).build();
@@ -6154,6 +6182,8 @@ public class ConnectivityServiceTest {
         mCm.registerNetworkCallback(wifiRequest, wifiNetworkCallback);
         mCm.registerNetworkCallback(vpnNetworkRequest, vpnNetworkCallback);
         mCm.registerDefaultNetworkCallback(defaultCallback);
+        mCm.registerSystemDefaultNetworkCallback(systemDefaultCallback,
+                new Handler(ConnectivityThread.getInstanceLooper()));
         defaultCallback.assertNoCallback();
 
         mWiFiNetworkAgent = new TestNetworkAgentWrapper(TRANSPORT_WIFI);
@@ -6163,6 +6193,7 @@ public class ConnectivityServiceTest {
         genericNotVpnNetworkCallback.expectAvailableCallbacksUnvalidated(mWiFiNetworkAgent);
         wifiNetworkCallback.expectAvailableCallbacksUnvalidated(mWiFiNetworkAgent);
         defaultCallback.expectAvailableCallbacksUnvalidated(mWiFiNetworkAgent);
+        systemDefaultCallback.expectAvailableCallbacksUnvalidated(mWiFiNetworkAgent);
         vpnNetworkCallback.assertNoCallback();
         assertEquals(defaultCallback.getLastAvailableNetwork(), mCm.getActiveNetwork());
 
@@ -6183,7 +6214,10 @@ public class ConnectivityServiceTest {
         wifiNetworkCallback.assertNoCallback();
         vpnNetworkCallback.expectAvailableThenValidatedCallbacks(mMockVpn);
         defaultCallback.expectAvailableThenValidatedCallbacks(mMockVpn);
+        systemDefaultCallback.assertNoCallback();
         assertEquals(defaultCallback.getLastAvailableNetwork(), mCm.getActiveNetwork());
+        assertEquals(mWiFiNetworkAgent.getNetwork(),
+                systemDefaultCallback.getLastAvailableNetwork());
 
         ranges.clear();
         mMockVpn.setUids(ranges);
@@ -6200,6 +6234,7 @@ public class ConnectivityServiceTest {
         // much, but that is the reason the test here has to check for an update to the
         // capabilities instead of the expected LOST then AVAILABLE.
         defaultCallback.expectCallback(CallbackEntry.NETWORK_CAPS_UPDATED, mMockVpn);
+        systemDefaultCallback.assertNoCallback();
 
         ranges.add(new UidRange(uid, uid));
         mMockVpn.setUids(ranges);
@@ -6211,6 +6246,7 @@ public class ConnectivityServiceTest {
         // TODO : Here like above, AVAILABLE would be correct, but because this can't actually
         // happen outside of the test, ConnectivityService does not rematch callbacks.
         defaultCallback.expectCallback(CallbackEntry.NETWORK_CAPS_UPDATED, mMockVpn);
+        systemDefaultCallback.assertNoCallback();
 
         mWiFiNetworkAgent.disconnect();
 
@@ -6219,6 +6255,7 @@ public class ConnectivityServiceTest {
         wifiNetworkCallback.expectCallback(CallbackEntry.LOST, mWiFiNetworkAgent);
         vpnNetworkCallback.assertNoCallback();
         defaultCallback.assertNoCallback();
+        systemDefaultCallback.expectCallback(CallbackEntry.LOST, mWiFiNetworkAgent);
 
         mMockVpn.disconnect();
 
@@ -6227,12 +6264,14 @@ public class ConnectivityServiceTest {
         wifiNetworkCallback.assertNoCallback();
         vpnNetworkCallback.expectCallback(CallbackEntry.LOST, mMockVpn);
         defaultCallback.expectCallback(CallbackEntry.LOST, mMockVpn);
+        systemDefaultCallback.assertNoCallback();
         assertEquals(null, mCm.getActiveNetwork());
 
         mCm.unregisterNetworkCallback(genericNetworkCallback);
         mCm.unregisterNetworkCallback(wifiNetworkCallback);
         mCm.unregisterNetworkCallback(vpnNetworkCallback);
         mCm.unregisterNetworkCallback(defaultCallback);
+        mCm.unregisterNetworkCallback(systemDefaultCallback);
     }
 
     @Test