Merge changes from topic \'tethering-ownership\' into nyc-mr1-dev

am: 281ec3272f

Change-Id: Ia8b234bcfdd479ef1ecda6b9102cf7cd5b3f217c

services/core/java/com/android/server/connectivity/tethering/IControlsTethering.java

@@ -0,0 +1,27 @@
+/*
+ * Copyright (C) 2016 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.tethering;
+
+/**
+ * @hide
+ *
+ * Interface with methods necessary to notify that a given interface is ready for tethering.
+ */
+public interface IControlsTethering {
+    void sendTetherStateChangedBroadcast();
+    void notifyInterfaceTetheringReadiness(boolean isReady, TetherInterfaceStateMachine who);
+}

services/core/java/com/android/server/connectivity/tethering/TetherInterfaceStateMachine.java

@@ -0,0 +1,360 @@
+/*
+ * Copyright (C) 2016 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.tethering;
+
+import android.net.ConnectivityManager;
+import android.net.INetworkStatsService;
+import android.net.InterfaceConfiguration;
+import android.net.LinkAddress;
+import android.net.NetworkUtils;
+import android.os.INetworkManagementService;
+import android.os.Looper;
+import android.os.Message;
+import android.util.Log;
+import android.util.SparseArray;
+
+import com.android.internal.util.IState;
+import com.android.internal.util.MessageUtils;
+import com.android.internal.util.Protocol;
+import com.android.internal.util.State;
+import com.android.internal.util.StateMachine;
+
+import java.net.InetAddress;
+
+/**
+ * @hide
+ *
+ * Tracks the eligibility of a given network interface for tethering.
+ */
+public class TetherInterfaceStateMachine extends StateMachine {
+    private static final String USB_NEAR_IFACE_ADDR = "192.168.42.129";
+    private static final int USB_PREFIX_LENGTH = 24;
+    private static final String WIFI_HOST_IFACE_ADDR = "192.168.43.1";
+    private static final int WIFI_HOST_IFACE_PREFIX_LENGTH = 24;
+
+    private final static String TAG = "TetherInterfaceSM";
+    private final static boolean DBG = false;
+    private final static boolean VDBG = false;
+    private static final Class[] messageClasses = {
+            TetherInterfaceStateMachine.class
+    };
+    private static final SparseArray<String> sMagicDecoderRing =
+            MessageUtils.findMessageNames(messageClasses);
+
+    private static final int BASE_IFACE              = Protocol.BASE_TETHERING + 100;
+    // request from the user that it wants to tether
+    public static final int CMD_TETHER_REQUESTED            = BASE_IFACE + 2;
+    // request from the user that it wants to untether
+    public static final int CMD_TETHER_UNREQUESTED          = BASE_IFACE + 3;
+    // notification that this interface is down
+    public static final int CMD_INTERFACE_DOWN              = BASE_IFACE + 4;
+    // notification from the master SM that it had trouble enabling IP Forwarding
+    public static final int CMD_IP_FORWARDING_ENABLE_ERROR  = BASE_IFACE + 7;
+    // notification from the master SM that it had trouble disabling IP Forwarding
+    public static final int CMD_IP_FORWARDING_DISABLE_ERROR = BASE_IFACE + 8;
+    // notification from the master SM that it had trouble starting tethering
+    public static final int CMD_START_TETHERING_ERROR       = BASE_IFACE + 9;
+    // notification from the master SM that it had trouble stopping tethering
+    public static final int CMD_STOP_TETHERING_ERROR        = BASE_IFACE + 10;
+    // notification from the master SM that it had trouble setting the DNS forwarders
+    public static final int CMD_SET_DNS_FORWARDERS_ERROR    = BASE_IFACE + 11;
+    // the upstream connection has changed
+    public static final int CMD_TETHER_CONNECTION_CHANGED   = BASE_IFACE + 12;
+
+    private final State mInitialState;
+    private final State mTetheredState;
+    private final State mUnavailableState;
+
+    private final INetworkManagementService mNMService;
+    private final INetworkStatsService mStatsService;
+    private final IControlsTethering mTetherController;
+
+    private final String mIfaceName;
+    private final int mInterfaceType;
+
+    private int mLastError;
+    private String mMyUpstreamIfaceName;  // may change over time
+
+    public TetherInterfaceStateMachine(String ifaceName, Looper looper, int interfaceType,
+                    INetworkManagementService nMService, INetworkStatsService statsService,
+                    IControlsTethering tetherController) {
+        super(ifaceName, looper);
+        mNMService = nMService;
+        mStatsService = statsService;
+        mTetherController = tetherController;
+        mIfaceName = ifaceName;
+        mInterfaceType = interfaceType;
+        setLastError(ConnectivityManager.TETHER_ERROR_NO_ERROR);
+
+        mInitialState = new InitialState();
+        addState(mInitialState);
+        mTetheredState = new TetheredState();
+        addState(mTetheredState);
+        mUnavailableState = new UnavailableState();
+        addState(mUnavailableState);
+
+        setInitialState(mInitialState);
+    }
+
+    @Override
+    public String toString() {
+        String res = new String();
+        res += mIfaceName + " - ";
+        IState current = getCurrentState();
+        if (current == mInitialState) res += "InitialState";
+        if (current == mTetheredState) res += "TetheredState";
+        if (current == mUnavailableState) res += "UnavailableState";
+        if (isAvailable()) res += " - Available";
+        if (isTethered()) res += " - Tethered";
+        res += " - lastError =" + getLastError();
+        return res;
+    }
+
+    public int getLastError() {
+        return mLastError;
+    }
+
+    private void setLastError(int error) {
+        mLastError = error;
+    }
+
+    public boolean isAvailable() {
+        return getCurrentState() == mInitialState;
+    }
+
+    public boolean isTethered() {
+        return getCurrentState() == mTetheredState;
+    }
+
+    public boolean isErrored() {
+        return (mLastError != ConnectivityManager.TETHER_ERROR_NO_ERROR);
+    }
+
+    // configured when we start tethering and unconfig'd on error or conclusion
+    private boolean configureIfaceIp(boolean enabled) {
+        if (VDBG) Log.d(TAG, "configureIfaceIp(" + enabled + ")");
+
+        String ipAsString = null;
+        int prefixLen = 0;
+        if (mInterfaceType == ConnectivityManager.TETHERING_USB) {
+            ipAsString = USB_NEAR_IFACE_ADDR;
+            prefixLen = USB_PREFIX_LENGTH;
+        } else if (mInterfaceType == ConnectivityManager.TETHERING_WIFI) {
+            ipAsString = WIFI_HOST_IFACE_ADDR;
+            prefixLen = WIFI_HOST_IFACE_PREFIX_LENGTH;
+        } else {
+            // Nothing to do, BT does this elsewhere.
+            return true;
+        }
+
+        InterfaceConfiguration ifcg = null;
+        try {
+            ifcg = mNMService.getInterfaceConfig(mIfaceName);
+            if (ifcg != null) {
+                InetAddress addr = NetworkUtils.numericToInetAddress(ipAsString);
+                ifcg.setLinkAddress(new LinkAddress(addr, prefixLen));
+                if (enabled) {
+                    ifcg.setInterfaceUp();
+                } else {
+                    ifcg.setInterfaceDown();
+                }
+                ifcg.clearFlag("running");
+                mNMService.setInterfaceConfig(mIfaceName, ifcg);
+            }
+        } catch (Exception e) {
+            Log.e(TAG, "Error configuring interface " + mIfaceName, e);
+            return false;
+        }
+
+        return true;
+    }
+
+    private void maybeLogMessage(State state, int what) {
+        if (DBG) {
+            Log.d(TAG, state.getName() + " got " +
+                    sMagicDecoderRing.get(what, Integer.toString(what)));
+        }
+    }
+
+    class InitialState extends State {
+        @Override
+        public void enter() {
+            mTetherController.sendTetherStateChangedBroadcast();
+        }
+
+        @Override
+        public boolean processMessage(Message message) {
+            maybeLogMessage(this, message.what);
+            boolean retValue = true;
+            switch (message.what) {
+                case CMD_TETHER_REQUESTED:
+                    setLastError(ConnectivityManager.TETHER_ERROR_NO_ERROR);
+                    mTetherController.notifyInterfaceTetheringReadiness(true, TetherInterfaceStateMachine.this);
+                    transitionTo(mTetheredState);
+                    break;
+                case CMD_INTERFACE_DOWN:
+                    transitionTo(mUnavailableState);
+                    break;
+                default:
+                    retValue = false;
+                    break;
+            }
+            return retValue;
+        }
+    }
+
+    class TetheredState extends State {
+        @Override
+        public void enter() {
+            if (!configureIfaceIp(true)) {
+                setLastError(ConnectivityManager.TETHER_ERROR_IFACE_CFG_ERROR);
+                transitionTo(mInitialState);
+                return;
+            }
+
+            try {
+                mNMService.tetherInterface(mIfaceName);
+            } catch (Exception e) {
+                Log.e(TAG, "Error Tethering: " + e.toString());
+                setLastError(ConnectivityManager.TETHER_ERROR_TETHER_IFACE_ERROR);
+                transitionTo(mInitialState);
+                return;
+            }
+            if (DBG) Log.d(TAG, "Tethered " + mIfaceName);
+            mTetherController.sendTetherStateChangedBroadcast();
+        }
+
+        @Override
+        public void exit() {
+            mTetherController.notifyInterfaceTetheringReadiness(false,
+                    TetherInterfaceStateMachine.this);
+
+            // Note that at this point, we're leaving the tethered state.  We can fail any
+            // of these operations, but it doesn't really change that we have to try them
+            // all in sequence.
+            cleanupUpstream();
+
+            try {
+                mNMService.untetherInterface(mIfaceName);
+            } catch (Exception ee) {
+                setLastError(ConnectivityManager.TETHER_ERROR_UNTETHER_IFACE_ERROR);
+                Log.e(TAG, "Failed to untether interface: " + ee.toString());
+            }
+
+            configureIfaceIp(false);
+        }
+
+        private void cleanupUpstream() {
+            if (mMyUpstreamIfaceName != null) {
+                // note that we don't care about errors here.
+                // sometimes interfaces are gone before we get
+                // to remove their rules, which generates errors.
+                // just do the best we can.
+                try {
+                    // about to tear down NAT; gather remaining statistics
+                    mStatsService.forceUpdate();
+                } catch (Exception e) {
+                    if (VDBG) Log.e(TAG, "Exception in forceUpdate: " + e.toString());
+                }
+                try {
+                    mNMService.stopInterfaceForwarding(mIfaceName, mMyUpstreamIfaceName);
+                } catch (Exception e) {
+                    if (VDBG) Log.e(
+                            TAG, "Exception in removeInterfaceForward: " + e.toString());
+                }
+                try {
+                    mNMService.disableNat(mIfaceName, mMyUpstreamIfaceName);
+                } catch (Exception e) {
+                    if (VDBG) Log.e(TAG, "Exception in disableNat: " + e.toString());
+                }
+                mMyUpstreamIfaceName = null;
+            }
+            return;
+        }
+
+        @Override
+        public boolean processMessage(Message message) {
+            maybeLogMessage(this, message.what);
+            boolean retValue = true;
+            switch (message.what) {
+                case CMD_TETHER_UNREQUESTED:
+                    transitionTo(mInitialState);
+                    if (DBG) Log.d(TAG, "Untethered (unrequested)" + mIfaceName);
+                    break;
+                case CMD_INTERFACE_DOWN:
+                    transitionTo(mUnavailableState);
+                    if (DBG) Log.d(TAG, "Untethered (ifdown)" + mIfaceName);
+                    break;
+                case CMD_TETHER_CONNECTION_CHANGED:
+                    String newUpstreamIfaceName = (String)(message.obj);
+                    if ((mMyUpstreamIfaceName == null && newUpstreamIfaceName == null) ||
+                            (mMyUpstreamIfaceName != null &&
+                            mMyUpstreamIfaceName.equals(newUpstreamIfaceName))) {
+                        if (VDBG) Log.d(TAG, "Connection changed noop - dropping");
+                        break;
+                    }
+                    cleanupUpstream();
+                    if (newUpstreamIfaceName != null) {
+                        try {
+                            mNMService.enableNat(mIfaceName, newUpstreamIfaceName);
+                            mNMService.startInterfaceForwarding(mIfaceName,
+                                    newUpstreamIfaceName);
+                        } catch (Exception e) {
+                            Log.e(TAG, "Exception enabling Nat: " + e.toString());
+                            setLastError(ConnectivityManager.TETHER_ERROR_ENABLE_NAT_ERROR);
+                            transitionTo(mInitialState);
+                            return true;
+                        }
+                    }
+                    mMyUpstreamIfaceName = newUpstreamIfaceName;
+                    break;
+                case CMD_IP_FORWARDING_ENABLE_ERROR:
+                case CMD_IP_FORWARDING_DISABLE_ERROR:
+                case CMD_START_TETHERING_ERROR:
+                case CMD_STOP_TETHERING_ERROR:
+                case CMD_SET_DNS_FORWARDERS_ERROR:
+                    setLastErrorAndTransitionToInitialState(
+                            ConnectivityManager.TETHER_ERROR_MASTER_ERROR);
+                    break;
+                default:
+                    retValue = false;
+                    break;
+            }
+            return retValue;
+        }
+    }
+
+    /**
+     * This state is terminal for the per interface state machine.  At this
+     * point, the master state machine should have removed this interface
+     * specific state machine from its list of possible recipients of
+     * tethering requests.  The state machine itself will hang around until
+     * the garbage collector finds it.
+     */
+    class UnavailableState extends State {
+        @Override
+        public void enter() {
+            setLastError(ConnectivityManager.TETHER_ERROR_NO_ERROR);
+            mTetherController.sendTetherStateChangedBroadcast();
+        }
+    }
+
+    void setLastErrorAndTransitionToInitialState(int error) {
+        setLastError(error);
+        transitionTo(mInitialState);
+    }
+}

services/tests/servicestests/Android.mk

@@ -12,6 +12,7 @@ LOCAL_MODULE_TAGS := tests
 LOCAL_SRC_FILES := $(call all-java-files-under, src)
 
 LOCAL_STATIC_JAVA_LIBRARIES := \
+    frameworks-base-testutils \
     services.core \
     services.devicepolicy \
     services.net \

services/tests/servicestests/src/com/android/server/connectivity/tethering/TetherInterfaceStateMachineTest.java

@@ -0,0 +1,298 @@
+/*
+ * Copyright (C) 2016 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.tethering;
+
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+import static org.mockito.Matchers.anyString;
+import static org.mockito.Mockito.doThrow;
+import static org.mockito.Mockito.inOrder;
+import static org.mockito.Mockito.reset;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.verifyNoMoreInteractions;
+import static org.mockito.Mockito.when;
+
+import android.net.ConnectivityManager;
+import android.net.INetworkStatsService;
+import android.net.InterfaceConfiguration;
+import android.os.INetworkManagementService;
+import android.os.RemoteException;
+import android.os.test.TestLooper;
+import android.support.test.filters.SmallTest;
+import android.support.test.runner.AndroidJUnit4;
+
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mockito.InOrder;
+import org.mockito.Mock;
+import org.mockito.MockitoAnnotations;
+
+@RunWith(AndroidJUnit4.class)
+@SmallTest
+public class TetherInterfaceStateMachineTest {
+    private static final String IFACE_NAME = "testnet1";
+    private static final String UPSTREAM_IFACE = "upstream0";
+    private static final String UPSTREAM_IFACE2 = "upstream1";
+
+    @Mock private INetworkManagementService mNMService;
+    @Mock private INetworkStatsService mStatsService;
+    @Mock private IControlsTethering mTetherHelper;
+    @Mock private InterfaceConfiguration mInterfaceConfiguration;
+
+    private final TestLooper mLooper = new TestLooper();
+    private TetherInterfaceStateMachine mTestedSm;
+
+    private void initStateMachine(int interfaceType) throws Exception {
+        mTestedSm = new TetherInterfaceStateMachine(IFACE_NAME, mLooper.getLooper(), interfaceType,
+                mNMService, mStatsService, mTetherHelper);
+        mTestedSm.start();
+        // Starting the state machine always puts us in a consistent state and notifies
+        // the test of the world that we've changed from an unknown to available state.
+        mLooper.dispatchAll();
+        reset(mNMService, mStatsService, mTetherHelper);
+        when(mNMService.getInterfaceConfig(IFACE_NAME)).thenReturn(mInterfaceConfiguration);
+    }
+
+    private void initTetheredStateMachine(int interfaceType, String upstreamIface) throws Exception {
+        initStateMachine(interfaceType);
+        dispatchCommand(TetherInterfaceStateMachine.CMD_TETHER_REQUESTED);
+        if (upstreamIface != null) {
+            dispatchTetherConnectionChanged(upstreamIface);
+        }
+        reset(mNMService, mStatsService, mTetherHelper);
+        when(mNMService.getInterfaceConfig(IFACE_NAME)).thenReturn(mInterfaceConfiguration);
+    }
+
+    @Before
+    public void setUp() throws Exception {
+        MockitoAnnotations.initMocks(this);
+    }
+
+    @Test
+    public void startsOutAvailable() {
+        mTestedSm = new TetherInterfaceStateMachine(IFACE_NAME, mLooper.getLooper(),
+                ConnectivityManager.TETHERING_BLUETOOTH, mNMService, mStatsService, mTetherHelper);
+        mTestedSm.start();
+        mLooper.dispatchAll();
+        assertTrue("Should start out available for tethering", mTestedSm.isAvailable());
+        assertFalse("Should not be tethered initially", mTestedSm.isTethered());
+        assertFalse("Should have no errors initially", mTestedSm.isErrored());
+        verify(mTetherHelper).sendTetherStateChangedBroadcast();
+        verifyNoMoreInteractions(mTetherHelper, mNMService, mStatsService);
+    }
+
+    @Test
+    public void shouldDoNothingUntilRequested() throws Exception {
+        initStateMachine(ConnectivityManager.TETHERING_BLUETOOTH);
+        final int [] NOOP_COMMANDS = {
+            TetherInterfaceStateMachine.CMD_TETHER_UNREQUESTED,
+            TetherInterfaceStateMachine.CMD_IP_FORWARDING_ENABLE_ERROR,
+            TetherInterfaceStateMachine.CMD_IP_FORWARDING_DISABLE_ERROR,
+            TetherInterfaceStateMachine.CMD_START_TETHERING_ERROR,
+            TetherInterfaceStateMachine.CMD_STOP_TETHERING_ERROR,
+            TetherInterfaceStateMachine.CMD_SET_DNS_FORWARDERS_ERROR,
+            TetherInterfaceStateMachine.CMD_TETHER_CONNECTION_CHANGED
+        };
+        for (int command : NOOP_COMMANDS) {
+            // None of these commands should trigger us to request action from
+            // the rest of the system.
+            dispatchCommand(command);
+            verifyNoMoreInteractions(mNMService, mStatsService, mTetherHelper);
+        }
+    }
+
+    @Test
+    public void handlesImmediateInterfaceDown() throws Exception {
+        initStateMachine(ConnectivityManager.TETHERING_BLUETOOTH);
+        dispatchCommand(TetherInterfaceStateMachine.CMD_INTERFACE_DOWN);
+        verify(mTetherHelper).sendTetherStateChangedBroadcast();
+        verifyNoMoreInteractions(mNMService, mStatsService, mTetherHelper);
+        assertFalse("Should not be tetherable when the interface is down", mTestedSm.isAvailable());
+        assertFalse("Should not be tethered when the interface is down", mTestedSm.isTethered());
+        assertFalse("Should have no errors when the interface goes immediately down",
+                mTestedSm.isErrored());
+    }
+
+    @Test
+    public void canBeTethered() throws Exception {
+        initStateMachine(ConnectivityManager.TETHERING_BLUETOOTH);
+        dispatchCommand(TetherInterfaceStateMachine.CMD_TETHER_REQUESTED);
+        InOrder inOrder = inOrder(mTetherHelper, mNMService);
+        inOrder.verify(mTetherHelper).notifyInterfaceTetheringReadiness(true, mTestedSm);
+        inOrder.verify(mNMService).tetherInterface(IFACE_NAME);
+        inOrder.verify(mTetherHelper).sendTetherStateChangedBroadcast();
+
+        verifyNoMoreInteractions(mNMService, mStatsService, mTetherHelper);
+        assertFalse("Should not be tetherable when tethered", mTestedSm.isAvailable());
+        assertTrue("Should be in a tethered state", mTestedSm.isTethered());
+        assertFalse("Should have no errors when tethered", mTestedSm.isErrored());
+    }
+
+    @Test
+    public void canUnrequestTethering() throws Exception {
+        initTetheredStateMachine(ConnectivityManager.TETHERING_BLUETOOTH, null);
+
+        dispatchCommand(TetherInterfaceStateMachine.CMD_TETHER_UNREQUESTED);
+        InOrder inOrder = inOrder(mNMService, mStatsService, mTetherHelper);
+        inOrder.verify(mTetherHelper).notifyInterfaceTetheringReadiness(false, mTestedSm);
+        inOrder.verify(mNMService).untetherInterface(IFACE_NAME);
+        inOrder.verify(mTetherHelper).sendTetherStateChangedBroadcast();
+        verifyNoMoreInteractions(mNMService, mStatsService, mTetherHelper);
+        assertTrue("Should be ready for tethering again", mTestedSm.isAvailable());
+        assertFalse("Should not be tethered", mTestedSm.isTethered());
+        assertFalse("Should have no errors", mTestedSm.isErrored());
+    }
+
+    @Test
+    public void canBeTetheredAsUsb() throws Exception {
+        initStateMachine(ConnectivityManager.TETHERING_USB);
+
+        dispatchCommand(TetherInterfaceStateMachine.CMD_TETHER_REQUESTED);
+        InOrder inOrder = inOrder(mTetherHelper, mNMService);
+        inOrder.verify(mTetherHelper).notifyInterfaceTetheringReadiness(true, mTestedSm);
+        inOrder.verify(mNMService).getInterfaceConfig(IFACE_NAME);
+        inOrder.verify(mNMService).setInterfaceConfig(IFACE_NAME, mInterfaceConfiguration);
+        inOrder.verify(mNMService).tetherInterface(IFACE_NAME);
+        inOrder.verify(mTetherHelper).sendTetherStateChangedBroadcast();
+
+        verifyNoMoreInteractions(mNMService, mStatsService, mTetherHelper);
+        assertFalse("Should not be tetherable when tethered", mTestedSm.isAvailable());
+        assertTrue("Should be in a tethered state", mTestedSm.isTethered());
+        assertFalse("Should have no errors when tethered", mTestedSm.isErrored());
+    }
+
+    @Test
+    public void handlesFirstUpstreamChange() throws Exception {
+        initTetheredStateMachine(ConnectivityManager.TETHERING_BLUETOOTH, null);
+
+        // Telling the state machine about its upstream interface triggers a little more configuration.
+        dispatchTetherConnectionChanged(UPSTREAM_IFACE);
+        InOrder inOrder = inOrder(mNMService);
+        inOrder.verify(mNMService).enableNat(IFACE_NAME, UPSTREAM_IFACE);
+        inOrder.verify(mNMService).startInterfaceForwarding(IFACE_NAME, UPSTREAM_IFACE);
+        verifyNoMoreInteractions(mNMService, mStatsService, mTetherHelper);
+        assertFalse("Should not be tetherable when tethered", mTestedSm.isAvailable());
+        assertTrue("Should be in a tethered state", mTestedSm.isTethered());
+        assertFalse("Should have no errors when tethered", mTestedSm.isErrored());
+    }
+
+    @Test
+    public void handlesChangingUpstream() throws Exception {
+        initTetheredStateMachine(ConnectivityManager.TETHERING_BLUETOOTH, UPSTREAM_IFACE);
+
+        dispatchTetherConnectionChanged(UPSTREAM_IFACE2);
+        InOrder inOrder = inOrder(mNMService, mStatsService);
+        inOrder.verify(mStatsService).forceUpdate();
+        inOrder.verify(mNMService).stopInterfaceForwarding(IFACE_NAME, UPSTREAM_IFACE);
+        inOrder.verify(mNMService).disableNat(IFACE_NAME, UPSTREAM_IFACE);
+        inOrder.verify(mNMService).enableNat(IFACE_NAME, UPSTREAM_IFACE2);
+        inOrder.verify(mNMService).startInterfaceForwarding(IFACE_NAME, UPSTREAM_IFACE2);
+        verifyNoMoreInteractions(mNMService, mStatsService, mTetherHelper);
+        assertFalse("Should not be tetherable when tethered", mTestedSm.isAvailable());
+        assertTrue("Should be in a tethered state", mTestedSm.isTethered());
+        assertFalse("Should have no errors when tethered", mTestedSm.isErrored());
+    }
+
+    @Test
+    public void canUnrequestTetheringWithUpstream() throws Exception {
+        initTetheredStateMachine(ConnectivityManager.TETHERING_BLUETOOTH, UPSTREAM_IFACE);
+
+        dispatchCommand(TetherInterfaceStateMachine.CMD_TETHER_UNREQUESTED);
+        InOrder inOrder = inOrder(mNMService, mStatsService, mTetherHelper);
+        inOrder.verify(mTetherHelper).notifyInterfaceTetheringReadiness(false, mTestedSm);
+        inOrder.verify(mStatsService).forceUpdate();
+        inOrder.verify(mNMService).stopInterfaceForwarding(IFACE_NAME, UPSTREAM_IFACE);
+        inOrder.verify(mNMService).disableNat(IFACE_NAME, UPSTREAM_IFACE);
+        inOrder.verify(mNMService).untetherInterface(IFACE_NAME);
+        inOrder.verify(mTetherHelper).sendTetherStateChangedBroadcast();
+        verifyNoMoreInteractions(mNMService, mStatsService, mTetherHelper);
+        assertTrue("Should be ready for tethering again", mTestedSm.isAvailable());
+        assertFalse("Should not be tethered", mTestedSm.isTethered());
+        assertFalse("Should have no errors", mTestedSm.isErrored());
+    }
+
+    @Test
+    public void interfaceDownLeadsToUnavailable() throws Exception {
+        for (boolean shouldThrow : new boolean[]{true, false}) {
+            initTetheredStateMachine(ConnectivityManager.TETHERING_USB, null);
+
+            if (shouldThrow) {
+                doThrow(RemoteException.class).when(mNMService).untetherInterface(IFACE_NAME);
+            }
+            dispatchCommand(TetherInterfaceStateMachine.CMD_INTERFACE_DOWN);
+            InOrder usbTeardownOrder = inOrder(mNMService, mInterfaceConfiguration);
+            usbTeardownOrder.verify(mInterfaceConfiguration).setInterfaceDown();
+            usbTeardownOrder.verify(mNMService).setInterfaceConfig(
+                    IFACE_NAME, mInterfaceConfiguration);
+            verify(mTetherHelper).notifyInterfaceTetheringReadiness(false, mTestedSm);
+            assertFalse("Should not be available", mTestedSm.isAvailable());
+            assertFalse("Should not be tethered", mTestedSm.isTethered());
+        }
+    }
+
+    @Test
+    public void usbShouldBeTornDownOnTetherError() throws Exception {
+        initStateMachine(ConnectivityManager.TETHERING_USB);
+
+        doThrow(RemoteException.class).when(mNMService).tetherInterface(IFACE_NAME);
+        dispatchCommand(TetherInterfaceStateMachine.CMD_TETHER_REQUESTED);
+        InOrder usbTeardownOrder = inOrder(mNMService, mInterfaceConfiguration);
+        usbTeardownOrder.verify(mInterfaceConfiguration).setInterfaceDown();
+        usbTeardownOrder.verify(mNMService).setInterfaceConfig(
+                IFACE_NAME, mInterfaceConfiguration);
+        // Initial call is when we transition to the tethered state on request.
+        verify(mTetherHelper).notifyInterfaceTetheringReadiness(true, mTestedSm);
+        // And this call is to notify that we really aren't requested tethering.
+        verify(mTetherHelper).notifyInterfaceTetheringReadiness(false, mTestedSm);
+        assertTrue("Expected to see an error reported", mTestedSm.isErrored());
+    }
+
+    @Test
+    public void shouldTearDownUsbOnUpstreamError() throws Exception {
+        initTetheredStateMachine(ConnectivityManager.TETHERING_USB, null);
+
+        doThrow(RemoteException.class).when(mNMService).enableNat(anyString(), anyString());
+        dispatchTetherConnectionChanged(UPSTREAM_IFACE);
+        InOrder usbTeardownOrder = inOrder(mNMService, mInterfaceConfiguration);
+        usbTeardownOrder.verify(mInterfaceConfiguration).setInterfaceDown();
+        usbTeardownOrder.verify(mNMService).setInterfaceConfig(IFACE_NAME, mInterfaceConfiguration);
+        verify(mTetherHelper).notifyInterfaceTetheringReadiness(false, mTestedSm);
+    }
+
+    /**
+     * Send a command to the state machine under test, and run the event loop to idle.
+     *
+     * @param command One of the TetherInterfaceStateMachine.CMD_* constants.
+     */
+    private void dispatchCommand(int command) {
+        mTestedSm.sendMessage(command);
+        mLooper.dispatchAll();
+    }
+
+    /**
+     * Special override to tell the state machine that the upstream interface has changed.
+     *
+     * @see #dispatchCommand(int)
+     * @param upstreamIface String name of upstream interface (or null)
+     */
+    private void dispatchTetherConnectionChanged(String upstreamIface) {
+        mTestedSm.sendMessage(TetherInterfaceStateMachine.CMD_TETHER_CONNECTION_CHANGED,
+                upstreamIface);
+        mLooper.dispatchAll();
+    }
+}