Add an Ethernet tethering test.

This test uses EthernetManager's ability to use test network
interfaces to test tethering. This provides a fairly realistic
integration test for Tethering and its callbacks, IpServer and
DhcpServer, and so on.

It is in a new integration/ directory under Tethering because I
didn't really know where to put it. It's fast enough to run in
presubmit, but it didn't seem to be appropriate to call it a
unit test, and in the future we could also use this test to do
some limited testing of real Ethernet tethering as well.

Bug: 150644681
Test: atest TetheringIntegrationTests:EthernetTetheringTest --rerun-until-failure 100
Merged-In: Ifcda70b73848b1fd4c26b031e53f0a6500cc93d4
Change-Id: Ifcda70b73848b1fd4c26b031e53f0a6500cc93d4

Tethering/tests/integration/Android.bp

+//
+// Copyright (C) 2020 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.
+//
+
+android_test {
+    name: "TetheringIntegrationTests",
+    certificate: "platform",
+    platform_apis: true,
+    srcs: [
+        "src/**/*.java",
+        "src/**/*.kt",
+    ],
+    test_suites: [
+        "device-tests",
+        "mts",
+    ],
+    static_libs: [
+        "NetworkStackApiStableLib",
+        "androidx.test.rules",
+        "frameworks-base-testutils",
+        "mockito-target-extended-minus-junit4",
+        "net-tests-utils",
+        "testables",
+    ],
+    libs: [
+        "android.test.runner",
+        "android.test.base",
+        "android.test.mock",
+    ],
+}

Tethering/tests/integration/AndroidManifest.xml

+<?xml version="1.0" encoding="utf-8"?>
+<!-- Copyright (C) 2020 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.
+-->
+<manifest xmlns:android="http://schemas.android.com/apk/res/android"
+          package="com.android.networkstack.tethering.tests.integration">
+
+    <uses-permission android:name="android.permission.INTERNET"/>
+    <uses-permission android:name="android.permission.TETHER_PRIVILEGED"/>
+
+    <application android:debuggable="true">
+        <uses-library android:name="android.test.runner" />
+    </application>
+    <instrumentation android:name="androidx.test.runner.AndroidJUnitRunner"
+        android:targetPackage="com.android.networkstack.tethering.tests.integration"
+        android:label="Tethering integration tests">
+    </instrumentation>
+</manifest>

Tethering/tests/integration/src/android/net/EthernetTetheringTest.java

+/*
+ * Copyright (C) 2020 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 android.net;
+
+import static android.Manifest.permission.MANAGE_TEST_NETWORKS;
+import static android.Manifest.permission.NETWORK_SETTINGS;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertNull;
+import static org.junit.Assert.assertTrue;
+import static org.junit.Assert.fail;
+import static org.junit.Assume.assumeFalse;
+import static org.junit.Assume.assumeTrue;
+
+import android.app.UiAutomation;
+import android.content.Context;
+import android.net.EthernetManager.TetheredInterfaceCallback;
+import android.net.EthernetManager.TetheredInterfaceRequest;
+import android.net.TetheringManager.StartTetheringCallback;
+import android.net.TetheringManager.TetheringEventCallback;
+import android.net.TetheringManager.TetheringRequest;
+import android.net.dhcp.DhcpAckPacket;
+import android.net.dhcp.DhcpOfferPacket;
+import android.net.dhcp.DhcpPacket;
+import android.os.Handler;
+import android.os.HandlerThread;
+import android.os.SystemClock;
+import android.system.Os;
+import android.util.Log;
+
+import androidx.test.InstrumentationRegistry;
+import androidx.test.filters.MediumTest;
+import androidx.test.runner.AndroidJUnit4;
+
+import com.android.testutils.HandlerUtilsKt;
+import com.android.testutils.TapPacketReader;
+
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+
+import java.io.FileDescriptor;
+import java.net.Inet4Address;
+import java.net.NetworkInterface;
+import java.net.SocketException;
+import java.nio.ByteBuffer;
+import java.util.Collection;
+import java.util.List;
+import java.util.Random;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.TimeUnit;
+
+@RunWith(AndroidJUnit4.class)
+@MediumTest
+public class EthernetTetheringTest {
+
+    private static final String TAG = EthernetTetheringTest.class.getSimpleName();
+    private static final int TIMEOUT_MS = 1000;
+    private static final int PACKET_READ_TIMEOUT_MS = 100;
+    private static final int DHCP_DISCOVER_ATTEMPTS = 10;
+    private static final byte[] DHCP_REQUESTED_PARAMS = new byte[] {
+            DhcpPacket.DHCP_SUBNET_MASK,
+            DhcpPacket.DHCP_ROUTER,
+            DhcpPacket.DHCP_DNS_SERVER,
+            DhcpPacket.DHCP_LEASE_TIME,
+    };
+    private static final String DHCP_HOSTNAME = "testhostname";
+
+    private final Context mContext = InstrumentationRegistry.getContext();
+    private final EthernetManager mEm = mContext.getSystemService(EthernetManager.class);
+    private final TetheringManager mTm = mContext.getSystemService(TetheringManager.class);
+
+    private TestNetworkInterface mTestIface;
+    private HandlerThread mHandlerThread;
+    private Handler mHandler;
+    private TapPacketReader mTapPacketReader;
+
+    private TetheredInterfaceRequester mTetheredInterfaceRequester;
+    private MyTetheringEventCallback mTetheringEventCallback;
+
+    private UiAutomation mUiAutomation =
+            InstrumentationRegistry.getInstrumentation().getUiAutomation();
+
+    @Before
+    public void setUp() throws Exception {
+        mHandlerThread = new HandlerThread(getClass().getSimpleName());
+        mHandlerThread.start();
+        mHandler = new Handler(mHandlerThread.getLooper());
+        mTetheredInterfaceRequester = new TetheredInterfaceRequester(mHandler, mEm);
+        // Needed to create a TestNetworkInterface, to call requestTetheredInterface, and to receive
+        // tethered client callbacks.
+        mUiAutomation.adoptShellPermissionIdentity(MANAGE_TEST_NETWORKS, NETWORK_SETTINGS);
+    }
+
+    private void cleanUp() throws Exception {
+        mTm.stopTethering(TetheringManager.TETHERING_ETHERNET);
+        if (mTetheringEventCallback != null) {
+            mTetheringEventCallback.awaitInterfaceUntethered();
+            mTetheringEventCallback.unregister();
+            mTetheringEventCallback = null;
+        }
+        if (mTapPacketReader != null) {
+            TapPacketReader reader = mTapPacketReader;
+            mHandler.post(() -> reader.stop());
+            mTapPacketReader = null;
+        }
+        mHandlerThread.quitSafely();
+        mTetheredInterfaceRequester.release();
+        mEm.setIncludeTestInterfaces(false);
+        maybeDeleteTestInterface();
+    }
+
+    @After
+    public void tearDown() throws Exception {
+        try {
+            cleanUp();
+        } finally {
+            mUiAutomation.dropShellPermissionIdentity();
+        }
+    }
+
+    @Test
+    public void testVirtualEthernetAlreadyExists() throws Exception {
+        // This test requires manipulating packets. Skip if there is a physical Ethernet connected.
+        assumeFalse(mEm.isAvailable());
+
+        mTestIface = createTestInterface();
+        // This must be done now because as soon as setIncludeTestInterfaces(true) is called, the
+        // interface will be placed in client mode, which will delete the link-local address.
+        // At that point NetworkInterface.getByName() will cease to work on the interface, because
+        // starting in R NetworkInterface can no longer see interfaces without IP addresses.
+        int mtu = getMTU(mTestIface);
+
+        Log.d(TAG, "Including test interfaces");
+        mEm.setIncludeTestInterfaces(true);
+
+        Log.d(TAG, "Requesting tethered interface");
+        mTetheredInterfaceRequester.requestInterface();
+
+        final String iface = mTetheredInterfaceRequester.awaitRequestedInterface();
+        assertEquals("TetheredInterfaceCallback for unexpected interface",
+                mTestIface.getInterfaceName(), iface);
+
+        checkVirtualEthernet(mTestIface, mtu);
+    }
+
+    @Test
+    public void testVirtualEthernet() throws Exception {
+        // This test requires manipulating packets. Skip if there is a physical Ethernet connected.
+        assumeFalse(mEm.isAvailable());
+
+        Log.d(TAG, "Requesting tethered interface");
+        mTetheredInterfaceRequester.requestInterface();
+
+        mEm.setIncludeTestInterfaces(true);
+
+        mTestIface = createTestInterface();
+
+        final String iface = mTetheredInterfaceRequester.awaitRequestedInterface();
+        assertEquals("TetheredInterfaceCallback for unexpected interface",
+                mTestIface.getInterfaceName(), iface);
+
+        checkVirtualEthernet(mTestIface, getMTU(mTestIface));
+    }
+
+    @Test
+    public void testPhysicalEthernet() throws Exception {
+        assumeTrue(mEm.isAvailable());
+
+        // Get an interface to use.
+        mTetheredInterfaceRequester.requestInterface();
+        String iface = mTetheredInterfaceRequester.awaitRequestedInterface();
+
+        // Enable Ethernet tethering and check that it starts.
+        mTetheringEventCallback = enableEthernetTethering(iface);
+
+        // There is nothing more we can do on a physical interface without connecting an actual
+        // client, which is not possible in this test.
+    }
+
+    private static final class MyTetheringEventCallback implements TetheringEventCallback {
+        private final TetheringManager mTm;
+        private final CountDownLatch mTetheringStartedLatch = new CountDownLatch(1);
+        private final CountDownLatch mTetheringStoppedLatch = new CountDownLatch(1);
+        private final CountDownLatch mClientConnectedLatch = new CountDownLatch(1);
+        private final String mIface;
+
+        private volatile boolean mInterfaceWasTethered = false;
+        private volatile boolean mUnregistered = false;
+        private volatile Collection<TetheredClient> mClients = null;
+
+        MyTetheringEventCallback(TetheringManager tm, String iface) {
+            mTm = tm;
+            mIface = iface;
+        }
+
+        public void unregister() {
+            mTm.unregisterTetheringEventCallback(this);
+            mUnregistered = true;
+        }
+
+        @Override
+        public void onTetheredInterfacesChanged(List<String> interfaces) {
+            // Ignore stale callbacks registered by previous test cases.
+            if (mUnregistered) return;
+
+            final boolean wasTethered = mTetheringStartedLatch.getCount() == 0;
+            if (!mInterfaceWasTethered && (mIface == null || interfaces.contains(mIface))) {
+                // This interface is being tethered for the first time.
+                Log.d(TAG, "Tethering started: " + interfaces);
+                mInterfaceWasTethered = true;
+                mTetheringStartedLatch.countDown();
+            } else if (mInterfaceWasTethered && !interfaces.contains(mIface)) {
+                Log.d(TAG, "Tethering stopped: " + interfaces);
+                mTetheringStoppedLatch.countDown();
+            }
+        }
+
+        public void awaitInterfaceTethered() throws Exception {
+            assertTrue("Ethernet not tethered after " + TIMEOUT_MS + "ms",
+                    mTetheringStartedLatch.await(TIMEOUT_MS, TimeUnit.MILLISECONDS));
+        }
+
+        public void awaitInterfaceUntethered() throws Exception {
+            // Don't block teardown if the interface was never tethered.
+            // This is racy because the interface might become tethered right after this check, but
+            // that can only happen in tearDown if startTethering timed out, which likely means
+            // the test has already failed.
+            if (!mInterfaceWasTethered) return;
+
+            assertTrue(mIface + " not untethered after " + TIMEOUT_MS + "ms",
+                    mTetheringStoppedLatch.await(TIMEOUT_MS, TimeUnit.MILLISECONDS));
+        }
+
+        @Override
+        public void onError(String ifName, int error) {
+            // Ignore stale callbacks registered by previous test cases.
+            if (mUnregistered) return;
+
+            fail("TetheringEventCallback got error:" + error + " on iface " + ifName);
+        }
+
+        @Override
+        public void onClientsChanged(Collection<TetheredClient> clients) {
+            // Ignore stale callbacks registered by previous test cases.
+            if (mUnregistered) return;
+
+            Log.d(TAG, "Got clients changed: " + clients);
+            mClients = clients;
+            if (clients.size() > 0) {
+                mClientConnectedLatch.countDown();
+            }
+        }
+
+        public Collection<TetheredClient> awaitClientConnected() throws Exception {
+            assertTrue("Did not receive client connected callback after " + TIMEOUT_MS + "ms",
+                    mClientConnectedLatch.await(TIMEOUT_MS, TimeUnit.MILLISECONDS));
+            return mClients;
+        }
+    }
+
+    private MyTetheringEventCallback enableEthernetTethering(String iface) throws Exception {
+        MyTetheringEventCallback callback = new MyTetheringEventCallback(mTm, iface);
+        mTm.registerTetheringEventCallback(mHandler::post, callback);
+
+        StartTetheringCallback startTetheringCallback = new StartTetheringCallback() {
+            @Override
+            public void onTetheringFailed(int resultCode) {
+                fail("Unexpectedly got onTetheringFailed");
+            }
+        };
+        Log.d(TAG, "Starting Ethernet tethering");
+        mTm.startTethering(
+                new TetheringRequest.Builder(TetheringManager.TETHERING_ETHERNET).build(),
+                mHandler::post /* executor */,  startTetheringCallback);
+        callback.awaitInterfaceTethered();
+        return callback;
+    }
+
+    private int getMTU(TestNetworkInterface iface) throws SocketException {
+        NetworkInterface nif = NetworkInterface.getByName(iface.getInterfaceName());
+        assertNotNull("Can't get NetworkInterface object for " + iface.getInterfaceName(), nif);
+        return nif.getMTU();
+    }
+
+    private void checkVirtualEthernet(TestNetworkInterface iface, int mtu) throws Exception {
+        FileDescriptor fd = iface.getFileDescriptor().getFileDescriptor();
+        mTapPacketReader = new TapPacketReader(mHandler, fd, mtu);
+        mHandler.post(() -> mTapPacketReader.start());
+        HandlerUtilsKt.waitForIdle(mHandler, TIMEOUT_MS);
+
+        mTetheringEventCallback = enableEthernetTethering(iface.getInterfaceName());
+        checkTetheredClientCallbacks(fd);
+    }
+
+    private void checkTetheredClientCallbacks(FileDescriptor fd) throws Exception {
+        // Create a fake client.
+        byte[] clientMacAddr = new byte[6];
+        new Random().nextBytes(clientMacAddr);
+
+        // We have to retransmit DHCP requests because IpServer declares itself to be ready before
+        // its DhcpServer is actually started. TODO: fix this race and remove this loop.
+        DhcpPacket offerPacket = null;
+        for (int i = 0; i < DHCP_DISCOVER_ATTEMPTS; i++) {
+            Log.d(TAG, "Sending DHCP discover");
+            sendDhcpDiscover(fd, clientMacAddr);
+            offerPacket = getNextDhcpPacket();
+            if (offerPacket instanceof DhcpOfferPacket) break;
+        }
+        assertTrue("No DHCPOFFER received on interface within timeout",
+                offerPacket instanceof DhcpOfferPacket);
+
+        sendDhcpRequest(fd, offerPacket, clientMacAddr);
+        DhcpPacket ackPacket = getNextDhcpPacket();
+        assertTrue("No DHCPACK received on interface within timeout",
+                ackPacket instanceof DhcpAckPacket);
+
+        final Collection<TetheredClient> clients = mTetheringEventCallback.awaitClientConnected();
+        assertEquals(1, clients.size());
+        final TetheredClient client = clients.iterator().next();
+
+        // Check the MAC address.
+        assertEquals(MacAddress.fromBytes(clientMacAddr), client.getMacAddress());
+        assertEquals(TetheringManager.TETHERING_ETHERNET, client.getTetheringType());
+
+        // Check the hostname.
+        assertEquals(1, client.getAddresses().size());
+        TetheredClient.AddressInfo info = client.getAddresses().get(0);
+        assertEquals(DHCP_HOSTNAME, info.getHostname());
+
+        // Check the address is the one that was handed out in the DHCP ACK.
+        DhcpResults dhcpResults = offerPacket.toDhcpResults();
+        assertLinkAddressMatches(dhcpResults.ipAddress, info.getAddress());
+
+        // Check that the lifetime is correct +/- 10s.
+        final long now = SystemClock.elapsedRealtime();
+        final long actualLeaseDuration = (info.getAddress().getExpirationTime() - now) / 1000;
+        final String msg = String.format("IP address should have lifetime of %d, got %d",
+                dhcpResults.leaseDuration, actualLeaseDuration);
+        assertTrue(msg, Math.abs(dhcpResults.leaseDuration - actualLeaseDuration) < 10);
+    }
+
+    private DhcpPacket getNextDhcpPacket() throws ParseException {
+        byte[] packet;
+        while ((packet = mTapPacketReader.popPacket(PACKET_READ_TIMEOUT_MS)) != null) {
+            try {
+                return DhcpPacket.decodeFullPacket(packet, packet.length, DhcpPacket.ENCAP_L2);
+            } catch (DhcpPacket.ParseException e) {
+                // Not a DHCP packet. Continue.
+            }
+        }
+        return null;
+    }
+
+    private static final class TetheredInterfaceRequester implements TetheredInterfaceCallback {
+        private final CountDownLatch mInterfaceAvailableLatch = new CountDownLatch(1);
+        private final Handler mHandler;
+        private final EthernetManager mEm;
+
+        private volatile TetheredInterfaceRequest mRequest;
+        private volatile String mIface;
+
+        TetheredInterfaceRequester(Handler handler, EthernetManager em) {
+            mHandler = handler;
+            mEm = em;
+        }
+
+        @Override
+        public void onAvailable(String iface) {
+            Log.d(TAG, "Ethernet interface available: " + iface);
+            mIface = iface;
+            mInterfaceAvailableLatch.countDown();
+        }
+        @Override
+        public void onUnavailable() {}
+
+        public void requestInterface() {
+            assertNull("BUG: more than one tethered interface request", mRequest);
+            mRequest = mEm.requestTetheredInterface(mHandler::post, this);
+        }
+
+        public String awaitRequestedInterface() throws InterruptedException {
+            assertTrue("No tethered interface available after " + TIMEOUT_MS + "ms",
+                    mInterfaceAvailableLatch.await(TIMEOUT_MS, TimeUnit.MILLISECONDS));
+            return mIface;
+        }
+
+        public void release() {
+            if (mRequest != null) {
+                mRequest.release();
+                mRequest = null;
+            }
+        }
+    }
+
+    private void sendDhcpDiscover(FileDescriptor fd, byte[] macAddress) throws Exception {
+        ByteBuffer packet = DhcpPacket.buildDiscoverPacket(DhcpPacket.ENCAP_L2,
+                new Random().nextInt() /* transactionId */, (short) 0 /* secs */,
+                macAddress,  false /* unicast */, DHCP_REQUESTED_PARAMS,
+                false /* rapid commit */,  DHCP_HOSTNAME);
+        sendPacket(fd, packet);
+    }
+
+    private void sendDhcpRequest(FileDescriptor fd, DhcpPacket offerPacket, byte[] macAddress)
+            throws Exception {
+        DhcpResults results = offerPacket.toDhcpResults();
+        Inet4Address clientIp = (Inet4Address) results.ipAddress.getAddress();
+        Inet4Address serverIdentifier = results.serverAddress;
+        ByteBuffer packet = DhcpPacket.buildRequestPacket(DhcpPacket.ENCAP_L2,
+                0 /* transactionId */, (short) 0 /* secs */, DhcpPacket.INADDR_ANY /* clientIp */,
+                false /* broadcast */, macAddress, clientIp /* requestedIpAddress */,
+                serverIdentifier, DHCP_REQUESTED_PARAMS, DHCP_HOSTNAME);
+        sendPacket(fd, packet);
+    }
+
+    private void sendPacket(FileDescriptor fd, ByteBuffer packet) throws Exception {
+        assertNotNull("Only tests on virtual interfaces can send packets", fd);
+        Os.write(fd, packet);
+    }
+
+    public void assertLinkAddressMatches(LinkAddress l1, LinkAddress l2) {
+        // Check all fields except the deprecation and expiry times.
+        String msg = String.format("LinkAddresses do not match. expected: %s actual: %s", l1, l2);
+        assertTrue(msg, l1.isSameAddressAs(l2));
+        assertEquals("LinkAddress flags do not match", l1.getFlags(), l2.getFlags());
+        assertEquals("LinkAddress scope does not match", l1.getScope(), l2.getScope());
+    }
+
+    private TestNetworkInterface createTestInterface() throws Exception {
+        TestNetworkManager tnm = mContext.getSystemService(TestNetworkManager.class);
+        TestNetworkInterface iface = tnm.createTapInterface();
+        Log.d(TAG, "Created test interface " + iface.getInterfaceName());
+        assertNotNull(NetworkInterface.getByName(iface.getInterfaceName()));
+        return iface;
+    }
+
+    private void maybeDeleteTestInterface() throws Exception {
+        if (mTestIface != null) {
+            mTestIface.getFileDescriptor().close();
+            Log.d(TAG, "Deleted test interface " + mTestIface.getInterfaceName());
+            mTestIface = null;
+        }
+    }
+}