diff --git a/Tethering/tests/unit/Android.bp b/Tethering/tests/unit/Android.bp
index 7c06e5f..363be18 100644
--- a/Tethering/tests/unit/Android.bp
+++ b/Tethering/tests/unit/Android.bp
@@ -25,6 +25,7 @@
     static_libs: [
         "androidx.test.rules",
         "frameworks-base-testutils",
+        "net-tests-utils",
         "mockito-target-extended-minus-junit4",
         "TetheringApiCurrentLib",
         "testables",
@@ -46,6 +47,7 @@
     name: "tethering-tests-src",
     srcs: [
         "src/com/android/server/connectivity/tethering/EntitlementManagerTest.java",
+        "src/com/android/server/connectivity/tethering/OffloadControllerTest.java",
         "src/com/android/server/connectivity/tethering/TetheringConfigurationTest.java",
         "src/com/android/server/connectivity/tethering/UpstreamNetworkMonitorTest.java",
         "src/android/net/dhcp/DhcpServingParamsParcelExtTest.java",
diff --git a/Tethering/tests/unit/src/com/android/server/connectivity/tethering/OffloadControllerTest.java b/Tethering/tests/unit/src/com/android/server/connectivity/tethering/OffloadControllerTest.java
new file mode 100644
index 0000000..8574f54
--- /dev/null
+++ b/Tethering/tests/unit/src/com/android/server/connectivity/tethering/OffloadControllerTest.java
@@ -0,0 +1,730 @@
+/*
+ * Copyright (C) 2017 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 android.net.NetworkStats.SET_DEFAULT;
+import static android.net.NetworkStats.STATS_PER_IFACE;
+import static android.net.NetworkStats.STATS_PER_UID;
+import static android.net.NetworkStats.TAG_NONE;
+import static android.net.NetworkStats.UID_ALL;
+import static android.net.TrafficStats.UID_TETHERING;
+import static android.provider.Settings.Global.TETHER_OFFLOAD_DISABLED;
+
+import static com.android.server.connectivity.tethering.OffloadHardwareInterface.ForwardedStats;
+import static com.android.testutils.MiscAssertsKt.assertContainsAll;
+import static com.android.testutils.MiscAssertsKt.assertThrows;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+import static org.mockito.Matchers.any;
+import static org.mockito.Matchers.anyLong;
+import static org.mockito.Matchers.anyObject;
+import static org.mockito.Matchers.anyString;
+import static org.mockito.Matchers.eq;
+import static org.mockito.Mockito.clearInvocations;
+import static org.mockito.Mockito.inOrder;
+import static org.mockito.Mockito.never;
+import static org.mockito.Mockito.times;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.verifyNoMoreInteractions;
+import static org.mockito.Mockito.when;
+
+import android.content.Context;
+import android.content.pm.ApplicationInfo;
+import android.net.ITetheringStatsProvider;
+import android.net.IpPrefix;
+import android.net.LinkAddress;
+import android.net.LinkProperties;
+import android.net.NetworkStats;
+import android.net.RouteInfo;
+import android.net.util.SharedLog;
+import android.os.Handler;
+import android.os.INetworkManagementService;
+import android.os.Looper;
+import android.provider.Settings;
+import android.provider.Settings.SettingNotFoundException;
+import android.test.mock.MockContentResolver;
+
+import androidx.test.filters.SmallTest;
+import androidx.test.runner.AndroidJUnit4;
+
+import com.android.internal.util.test.FakeSettingsProvider;
+import com.android.testutils.HandlerUtilsKt;
+
+import org.junit.After;
+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;
+
+import java.net.InetAddress;
+import java.util.ArrayList;
+import java.util.HashSet;
+import java.util.Set;
+
+@RunWith(AndroidJUnit4.class)
+@SmallTest
+public class OffloadControllerTest {
+    private static final String RNDIS0 = "test_rndis0";
+    private static final String RMNET0 = "test_rmnet_data0";
+    private static final String WLAN0 = "test_wlan0";
+
+    private static final String IPV6_LINKLOCAL = "fe80::/64";
+    private static final String IPV6_DOC_PREFIX = "2001:db8::/64";
+    private static final String IPV6_DISCARD_PREFIX = "100::/64";
+    private static final String USB_PREFIX = "192.168.42.0/24";
+    private static final String WIFI_PREFIX = "192.168.43.0/24";
+    private static final long WAIT_FOR_IDLE_TIMEOUT = 2 * 1000;
+
+    @Mock private OffloadHardwareInterface mHardware;
+    @Mock private ApplicationInfo mApplicationInfo;
+    @Mock private Context mContext;
+    @Mock private INetworkManagementService mNMService;
+    private final ArgumentCaptor<ArrayList> mStringArrayCaptor =
+            ArgumentCaptor.forClass(ArrayList.class);
+    private final ArgumentCaptor<ITetheringStatsProvider.Stub> mTetherStatsProviderCaptor =
+            ArgumentCaptor.forClass(ITetheringStatsProvider.Stub.class);
+    private final ArgumentCaptor<OffloadHardwareInterface.ControlCallback> mControlCallbackCaptor =
+            ArgumentCaptor.forClass(OffloadHardwareInterface.ControlCallback.class);
+    private MockContentResolver mContentResolver;
+
+    @Before public void setUp() {
+        MockitoAnnotations.initMocks(this);
+        when(mContext.getApplicationInfo()).thenReturn(mApplicationInfo);
+        when(mContext.getPackageName()).thenReturn("OffloadControllerTest");
+        mContentResolver = new MockContentResolver(mContext);
+        mContentResolver.addProvider(Settings.AUTHORITY, new FakeSettingsProvider());
+        when(mContext.getContentResolver()).thenReturn(mContentResolver);
+        FakeSettingsProvider.clearSettingsProvider();
+    }
+
+    @After public void tearDown() throws Exception {
+        FakeSettingsProvider.clearSettingsProvider();
+    }
+
+    private void setupFunctioningHardwareInterface() {
+        when(mHardware.initOffloadConfig()).thenReturn(true);
+        when(mHardware.initOffloadControl(mControlCallbackCaptor.capture()))
+                .thenReturn(true);
+        when(mHardware.setUpstreamParameters(anyString(), any(), any(), any())).thenReturn(true);
+        when(mHardware.getForwardedStats(any())).thenReturn(new ForwardedStats());
+        when(mHardware.setDataLimit(anyString(), anyLong())).thenReturn(true);
+    }
+
+    private void enableOffload() {
+        Settings.Global.putInt(mContentResolver, TETHER_OFFLOAD_DISABLED, 0);
+    }
+
+    private void waitForIdle() {
+        HandlerUtilsKt.waitForIdle(new Handler(Looper.getMainLooper()), WAIT_FOR_IDLE_TIMEOUT);
+    }
+
+    private OffloadController makeOffloadController() throws Exception {
+        OffloadController offload = new OffloadController(new Handler(Looper.getMainLooper()),
+                mHardware, mContentResolver, mNMService, new SharedLog("test"));
+        verify(mNMService).registerTetheringStatsProvider(
+                mTetherStatsProviderCaptor.capture(), anyString());
+        return offload;
+    }
+
+    @Test
+    public void testNoSettingsValueDefaultDisabledDoesNotStart() throws Exception {
+        setupFunctioningHardwareInterface();
+        when(mHardware.getDefaultTetherOffloadDisabled()).thenReturn(1);
+        assertThrows(SettingNotFoundException.class, () ->
+                Settings.Global.getInt(mContentResolver, TETHER_OFFLOAD_DISABLED));
+
+        final OffloadController offload = makeOffloadController();
+        offload.start();
+
+        final InOrder inOrder = inOrder(mHardware);
+        inOrder.verify(mHardware, times(1)).getDefaultTetherOffloadDisabled();
+        inOrder.verify(mHardware, never()).initOffloadConfig();
+        inOrder.verify(mHardware, never()).initOffloadControl(
+                any(OffloadHardwareInterface.ControlCallback.class));
+        inOrder.verifyNoMoreInteractions();
+    }
+
+    @Test
+    public void testNoSettingsValueDefaultEnabledDoesStart() throws Exception {
+        setupFunctioningHardwareInterface();
+        when(mHardware.getDefaultTetherOffloadDisabled()).thenReturn(0);
+        assertThrows(SettingNotFoundException.class, () ->
+                Settings.Global.getInt(mContentResolver, TETHER_OFFLOAD_DISABLED));
+
+        final OffloadController offload = makeOffloadController();
+        offload.start();
+
+        final InOrder inOrder = inOrder(mHardware);
+        inOrder.verify(mHardware, times(1)).getDefaultTetherOffloadDisabled();
+        inOrder.verify(mHardware, times(1)).initOffloadConfig();
+        inOrder.verify(mHardware, times(1)).initOffloadControl(
+                any(OffloadHardwareInterface.ControlCallback.class));
+        inOrder.verifyNoMoreInteractions();
+    }
+
+    @Test
+    public void testSettingsAllowsStart() throws Exception {
+        setupFunctioningHardwareInterface();
+        Settings.Global.putInt(mContentResolver, TETHER_OFFLOAD_DISABLED, 0);
+
+        final OffloadController offload = makeOffloadController();
+        offload.start();
+
+        final InOrder inOrder = inOrder(mHardware);
+        inOrder.verify(mHardware, times(1)).getDefaultTetherOffloadDisabled();
+        inOrder.verify(mHardware, times(1)).initOffloadConfig();
+        inOrder.verify(mHardware, times(1)).initOffloadControl(
+                any(OffloadHardwareInterface.ControlCallback.class));
+        inOrder.verifyNoMoreInteractions();
+    }
+
+    @Test
+    public void testSettingsDisablesStart() throws Exception {
+        setupFunctioningHardwareInterface();
+        Settings.Global.putInt(mContentResolver, TETHER_OFFLOAD_DISABLED, 1);
+
+        final OffloadController offload = makeOffloadController();
+        offload.start();
+
+        final InOrder inOrder = inOrder(mHardware);
+        inOrder.verify(mHardware, times(1)).getDefaultTetherOffloadDisabled();
+        inOrder.verify(mHardware, never()).initOffloadConfig();
+        inOrder.verify(mHardware, never()).initOffloadControl(anyObject());
+        inOrder.verifyNoMoreInteractions();
+    }
+
+    @Test
+    public void testSetUpstreamLinkPropertiesWorking() throws Exception {
+        setupFunctioningHardwareInterface();
+        enableOffload();
+
+        final OffloadController offload = makeOffloadController();
+        offload.start();
+
+        final InOrder inOrder = inOrder(mHardware);
+        inOrder.verify(mHardware, times(1)).getDefaultTetherOffloadDisabled();
+        inOrder.verify(mHardware, times(1)).initOffloadConfig();
+        inOrder.verify(mHardware, times(1)).initOffloadControl(
+                any(OffloadHardwareInterface.ControlCallback.class));
+        inOrder.verifyNoMoreInteractions();
+
+        // In reality, the UpstreamNetworkMonitor would have passed down to us
+        // a covering set of local prefixes representing a minimum essential
+        // set plus all the prefixes on networks with network agents.
+        //
+        // We simulate that there, and then add upstream elements one by one
+        // and watch what happens.
+        final Set<IpPrefix> minimumLocalPrefixes = new HashSet<>();
+        for (String s : new String[]{
+                "127.0.0.0/8", "192.0.2.0/24", "fe80::/64", "2001:db8::/64"}) {
+            minimumLocalPrefixes.add(new IpPrefix(s));
+        }
+        offload.setLocalPrefixes(minimumLocalPrefixes);
+        inOrder.verify(mHardware, times(1)).setLocalPrefixes(mStringArrayCaptor.capture());
+        ArrayList<String> localPrefixes = mStringArrayCaptor.getValue();
+        assertEquals(4, localPrefixes.size());
+        assertContainsAll(localPrefixes,
+                "127.0.0.0/8", "192.0.2.0/24", "fe80::/64", "2001:db8::/64");
+        inOrder.verifyNoMoreInteractions();
+
+        offload.setUpstreamLinkProperties(null);
+        // No change in local addresses means no call to setLocalPrefixes().
+        inOrder.verify(mHardware, never()).setLocalPrefixes(mStringArrayCaptor.capture());
+        // This LinkProperties value does not differ from the default upstream.
+        // There should be no extraneous call to setUpstreamParameters().
+        inOrder.verify(mHardware, never()).setUpstreamParameters(
+                anyObject(), anyObject(), anyObject(), anyObject());
+        inOrder.verifyNoMoreInteractions();
+
+        final LinkProperties lp = new LinkProperties();
+
+        final String testIfName = "rmnet_data17";
+        lp.setInterfaceName(testIfName);
+        offload.setUpstreamLinkProperties(lp);
+        // No change in local addresses means no call to setLocalPrefixes().
+        inOrder.verify(mHardware, never()).setLocalPrefixes(mStringArrayCaptor.capture());
+        inOrder.verify(mHardware, times(1)).setUpstreamParameters(
+                eq(testIfName), eq(null), eq(null), eq(null));
+        inOrder.verify(mHardware, times(1)).setDataLimit(eq(testIfName), eq(Long.MAX_VALUE));
+        inOrder.verifyNoMoreInteractions();
+
+        final String ipv4Addr = "192.0.2.5";
+        final String linkAddr = ipv4Addr + "/24";
+        lp.addLinkAddress(new LinkAddress(linkAddr));
+        lp.addRoute(new RouteInfo(new IpPrefix("192.0.2.0/24")));
+        offload.setUpstreamLinkProperties(lp);
+        // IPv4 prefixes and addresses on the upstream are simply left as whole
+        // prefixes (already passed in from UpstreamNetworkMonitor code). If a
+        // tethering client sends traffic to the IPv4 default router or other
+        // clients on the upstream this will not be hardware-forwarded, and that
+        // should be fine for now. Ergo: no change in local addresses, no call
+        // to setLocalPrefixes().
+        inOrder.verify(mHardware, never()).setLocalPrefixes(mStringArrayCaptor.capture());
+        inOrder.verify(mHardware, times(1)).setUpstreamParameters(
+                eq(testIfName), eq(ipv4Addr), eq(null), eq(null));
+        inOrder.verify(mHardware, times(1)).getForwardedStats(eq(testIfName));
+        inOrder.verify(mHardware, times(1)).setDataLimit(eq(testIfName), eq(Long.MAX_VALUE));
+        inOrder.verifyNoMoreInteractions();
+
+        final String ipv4Gateway = "192.0.2.1";
+        lp.addRoute(new RouteInfo(InetAddress.getByName(ipv4Gateway)));
+        offload.setUpstreamLinkProperties(lp);
+        // No change in local addresses means no call to setLocalPrefixes().
+        inOrder.verify(mHardware, never()).setLocalPrefixes(mStringArrayCaptor.capture());
+        inOrder.verify(mHardware, times(1)).setUpstreamParameters(
+                eq(testIfName), eq(ipv4Addr), eq(ipv4Gateway), eq(null));
+        inOrder.verify(mHardware, times(1)).getForwardedStats(eq(testIfName));
+        inOrder.verify(mHardware, times(1)).setDataLimit(eq(testIfName), eq(Long.MAX_VALUE));
+        inOrder.verifyNoMoreInteractions();
+
+        final String ipv6Gw1 = "fe80::cafe";
+        lp.addRoute(new RouteInfo(InetAddress.getByName(ipv6Gw1)));
+        offload.setUpstreamLinkProperties(lp);
+        // No change in local addresses means no call to setLocalPrefixes().
+        inOrder.verify(mHardware, never()).setLocalPrefixes(mStringArrayCaptor.capture());
+        inOrder.verify(mHardware, times(1)).setUpstreamParameters(
+                eq(testIfName), eq(ipv4Addr), eq(ipv4Gateway), mStringArrayCaptor.capture());
+        inOrder.verify(mHardware, times(1)).getForwardedStats(eq(testIfName));
+        ArrayList<String> v6gws = mStringArrayCaptor.getValue();
+        assertEquals(1, v6gws.size());
+        assertTrue(v6gws.contains(ipv6Gw1));
+        inOrder.verify(mHardware, times(1)).setDataLimit(eq(testIfName), eq(Long.MAX_VALUE));
+        inOrder.verifyNoMoreInteractions();
+
+        final String ipv6Gw2 = "fe80::d00d";
+        lp.addRoute(new RouteInfo(InetAddress.getByName(ipv6Gw2)));
+        offload.setUpstreamLinkProperties(lp);
+        // No change in local addresses means no call to setLocalPrefixes().
+        inOrder.verify(mHardware, never()).setLocalPrefixes(mStringArrayCaptor.capture());
+        inOrder.verify(mHardware, times(1)).setUpstreamParameters(
+                eq(testIfName), eq(ipv4Addr), eq(ipv4Gateway), mStringArrayCaptor.capture());
+        inOrder.verify(mHardware, times(1)).getForwardedStats(eq(testIfName));
+        v6gws = mStringArrayCaptor.getValue();
+        assertEquals(2, v6gws.size());
+        assertTrue(v6gws.contains(ipv6Gw1));
+        assertTrue(v6gws.contains(ipv6Gw2));
+        inOrder.verify(mHardware, times(1)).setDataLimit(eq(testIfName), eq(Long.MAX_VALUE));
+        inOrder.verifyNoMoreInteractions();
+
+        final LinkProperties stacked = new LinkProperties();
+        stacked.setInterfaceName("stacked");
+        stacked.addLinkAddress(new LinkAddress("192.0.2.129/25"));
+        stacked.addRoute(new RouteInfo(InetAddress.getByName("192.0.2.254")));
+        stacked.addRoute(new RouteInfo(InetAddress.getByName("fe80::bad:f00")));
+        assertTrue(lp.addStackedLink(stacked));
+        offload.setUpstreamLinkProperties(lp);
+        // No change in local addresses means no call to setLocalPrefixes().
+        inOrder.verify(mHardware, never()).setLocalPrefixes(mStringArrayCaptor.capture());
+        inOrder.verify(mHardware, times(1)).setUpstreamParameters(
+                eq(testIfName), eq(ipv4Addr), eq(ipv4Gateway), mStringArrayCaptor.capture());
+        inOrder.verify(mHardware, times(1)).getForwardedStats(eq(testIfName));
+        v6gws = mStringArrayCaptor.getValue();
+        assertEquals(2, v6gws.size());
+        assertTrue(v6gws.contains(ipv6Gw1));
+        assertTrue(v6gws.contains(ipv6Gw2));
+        inOrder.verify(mHardware, times(1)).setDataLimit(eq(testIfName), eq(Long.MAX_VALUE));
+        inOrder.verifyNoMoreInteractions();
+
+        // Add in some IPv6 upstream info. When there is a tethered downstream
+        // making use of the IPv6 prefix we would expect to see the /64 route
+        // removed from "local prefixes" and /128s added for the upstream IPv6
+        // addresses.  This is not yet implemented, and for now we simply
+        // expect to see these /128s.
+        lp.addRoute(new RouteInfo(new IpPrefix("2001:db8::/64")));
+        // "2001:db8::/64" plus "assigned" ASCII in hex
+        lp.addLinkAddress(new LinkAddress("2001:db8::6173:7369:676e:6564/64"));
+        // "2001:db8::/64" plus "random" ASCII in hex
+        lp.addLinkAddress(new LinkAddress("2001:db8::7261:6e64:6f6d/64"));
+        offload.setUpstreamLinkProperties(lp);
+        inOrder.verify(mHardware, times(1)).setLocalPrefixes(mStringArrayCaptor.capture());
+        localPrefixes = mStringArrayCaptor.getValue();
+        assertEquals(6, localPrefixes.size());
+        assertContainsAll(localPrefixes,
+                "127.0.0.0/8", "192.0.2.0/24", "fe80::/64", "2001:db8::/64",
+                "2001:db8::6173:7369:676e:6564/128", "2001:db8::7261:6e64:6f6d/128");
+        // The relevant parts of the LinkProperties have not changed, but at the
+        // moment we do not de-dup upstream LinkProperties this carefully.
+        inOrder.verify(mHardware, times(1)).setUpstreamParameters(
+                eq(testIfName), eq(ipv4Addr), eq(ipv4Gateway), mStringArrayCaptor.capture());
+        v6gws = mStringArrayCaptor.getValue();
+        assertEquals(2, v6gws.size());
+        assertTrue(v6gws.contains(ipv6Gw1));
+        assertTrue(v6gws.contains(ipv6Gw2));
+        inOrder.verify(mHardware, times(1)).getForwardedStats(eq(testIfName));
+        inOrder.verify(mHardware, times(1)).setDataLimit(eq(testIfName), eq(Long.MAX_VALUE));
+        inOrder.verifyNoMoreInteractions();
+
+        // Completely identical LinkProperties updates are de-duped.
+        offload.setUpstreamLinkProperties(lp);
+        // This LinkProperties value does not differ from the default upstream.
+        // There should be no extraneous call to setUpstreamParameters().
+        inOrder.verify(mHardware, never()).setUpstreamParameters(
+                anyObject(), anyObject(), anyObject(), anyObject());
+        inOrder.verifyNoMoreInteractions();
+    }
+
+    private void assertNetworkStats(String iface, ForwardedStats stats, NetworkStats.Entry entry) {
+        assertEquals(iface, entry.iface);
+        assertEquals(stats.rxBytes, entry.rxBytes);
+        assertEquals(stats.txBytes, entry.txBytes);
+        assertEquals(SET_DEFAULT, entry.set);
+        assertEquals(TAG_NONE, entry.tag);
+    }
+
+    @Test
+    public void testGetForwardedStats() throws Exception {
+        setupFunctioningHardwareInterface();
+        enableOffload();
+
+        final OffloadController offload = makeOffloadController();
+        offload.start();
+
+        final String ethernetIface = "eth1";
+        final String mobileIface = "rmnet_data0";
+
+        ForwardedStats ethernetStats = new ForwardedStats();
+        ethernetStats.rxBytes = 12345;
+        ethernetStats.txBytes = 54321;
+
+        ForwardedStats mobileStats = new ForwardedStats();
+        mobileStats.rxBytes = 999;
+        mobileStats.txBytes = 99999;
+
+        when(mHardware.getForwardedStats(eq(ethernetIface))).thenReturn(ethernetStats);
+        when(mHardware.getForwardedStats(eq(mobileIface))).thenReturn(mobileStats);
+
+        InOrder inOrder = inOrder(mHardware);
+
+        final LinkProperties lp = new LinkProperties();
+        lp.setInterfaceName(ethernetIface);
+        offload.setUpstreamLinkProperties(lp);
+        // Previous upstream was null, so no stats are fetched.
+        inOrder.verify(mHardware, never()).getForwardedStats(any());
+
+        lp.setInterfaceName(mobileIface);
+        offload.setUpstreamLinkProperties(lp);
+        // Expect that we fetch stats from the previous upstream.
+        inOrder.verify(mHardware, times(1)).getForwardedStats(eq(ethernetIface));
+
+        lp.setInterfaceName(ethernetIface);
+        offload.setUpstreamLinkProperties(lp);
+        // Expect that we fetch stats from the previous upstream.
+        inOrder.verify(mHardware, times(1)).getForwardedStats(eq(mobileIface));
+
+        ethernetStats = new ForwardedStats();
+        ethernetStats.rxBytes = 100000;
+        ethernetStats.txBytes = 100000;
+        when(mHardware.getForwardedStats(eq(ethernetIface))).thenReturn(ethernetStats);
+        offload.setUpstreamLinkProperties(null);
+        // Expect that we first clear the HAL's upstream parameters.
+        inOrder.verify(mHardware, times(1)).setUpstreamParameters(
+                eq(""), eq("0.0.0.0"), eq("0.0.0.0"), eq(null));
+        // Expect that we fetch stats from the previous upstream.
+        inOrder.verify(mHardware, times(1)).getForwardedStats(eq(ethernetIface));
+
+        ITetheringStatsProvider provider = mTetherStatsProviderCaptor.getValue();
+        NetworkStats stats = provider.getTetherStats(STATS_PER_IFACE);
+        NetworkStats perUidStats = provider.getTetherStats(STATS_PER_UID);
+        waitForIdle();
+        // There is no current upstream, so no stats are fetched.
+        inOrder.verify(mHardware, never()).getForwardedStats(any());
+        inOrder.verifyNoMoreInteractions();
+
+        assertEquals(2, stats.size());
+        assertEquals(2, perUidStats.size());
+
+        NetworkStats.Entry entry = null;
+        for (int i = 0; i < stats.size(); i++) {
+            assertEquals(UID_ALL, stats.getValues(i, entry).uid);
+            assertEquals(UID_TETHERING, perUidStats.getValues(i, entry).uid);
+        }
+
+        int ethernetPosition = ethernetIface.equals(stats.getValues(0, entry).iface) ? 0 : 1;
+        int mobilePosition = 1 - ethernetPosition;
+
+        entry = stats.getValues(mobilePosition, entry);
+        assertNetworkStats(mobileIface, mobileStats, entry);
+        entry = perUidStats.getValues(mobilePosition, entry);
+        assertNetworkStats(mobileIface, mobileStats, entry);
+
+        ethernetStats.rxBytes = 12345 + 100000;
+        ethernetStats.txBytes = 54321 + 100000;
+        entry = stats.getValues(ethernetPosition, entry);
+        assertNetworkStats(ethernetIface, ethernetStats, entry);
+        entry = perUidStats.getValues(ethernetPosition, entry);
+        assertNetworkStats(ethernetIface, ethernetStats, entry);
+    }
+
+    @Test
+    public void testSetInterfaceQuota() throws Exception {
+        setupFunctioningHardwareInterface();
+        enableOffload();
+
+        final OffloadController offload = makeOffloadController();
+        offload.start();
+
+        final String ethernetIface = "eth1";
+        final String mobileIface = "rmnet_data0";
+        final long ethernetLimit = 12345;
+        final long mobileLimit = 12345678;
+
+        final LinkProperties lp = new LinkProperties();
+        lp.setInterfaceName(ethernetIface);
+        offload.setUpstreamLinkProperties(lp);
+
+        ITetheringStatsProvider provider = mTetherStatsProviderCaptor.getValue();
+        final InOrder inOrder = inOrder(mHardware);
+        when(mHardware.setUpstreamParameters(any(), any(), any(), any())).thenReturn(true);
+        when(mHardware.setDataLimit(anyString(), anyLong())).thenReturn(true);
+
+        // Applying an interface quota to the current upstream immediately sends it to the hardware.
+        provider.setInterfaceQuota(ethernetIface, ethernetLimit);
+        waitForIdle();
+        inOrder.verify(mHardware).setDataLimit(ethernetIface, ethernetLimit);
+        inOrder.verifyNoMoreInteractions();
+
+        // Applying an interface quota to another upstream does not take any immediate action.
+        provider.setInterfaceQuota(mobileIface, mobileLimit);
+        waitForIdle();
+        inOrder.verify(mHardware, never()).setDataLimit(anyString(), anyLong());
+
+        // Switching to that upstream causes the quota to be applied if the parameters were applied
+        // correctly.
+        lp.setInterfaceName(mobileIface);
+        offload.setUpstreamLinkProperties(lp);
+        waitForIdle();
+        inOrder.verify(mHardware).setDataLimit(mobileIface, mobileLimit);
+
+        // Setting a limit of ITetheringStatsProvider.QUOTA_UNLIMITED causes the limit to be set
+        // to Long.MAX_VALUE.
+        provider.setInterfaceQuota(mobileIface, ITetheringStatsProvider.QUOTA_UNLIMITED);
+        waitForIdle();
+        inOrder.verify(mHardware).setDataLimit(mobileIface, Long.MAX_VALUE);
+
+        // If setting upstream parameters fails, then the data limit is not set.
+        when(mHardware.setUpstreamParameters(any(), any(), any(), any())).thenReturn(false);
+        lp.setInterfaceName(ethernetIface);
+        offload.setUpstreamLinkProperties(lp);
+        provider.setInterfaceQuota(mobileIface, mobileLimit);
+        waitForIdle();
+        inOrder.verify(mHardware, never()).setDataLimit(anyString(), anyLong());
+
+        // If setting the data limit fails while changing upstreams, offload is stopped.
+        when(mHardware.setUpstreamParameters(any(), any(), any(), any())).thenReturn(true);
+        when(mHardware.setDataLimit(anyString(), anyLong())).thenReturn(false);
+        lp.setInterfaceName(mobileIface);
+        offload.setUpstreamLinkProperties(lp);
+        provider.setInterfaceQuota(mobileIface, mobileLimit);
+        waitForIdle();
+        inOrder.verify(mHardware).getForwardedStats(ethernetIface);
+        inOrder.verify(mHardware).stopOffloadControl();
+    }
+
+    @Test
+    public void testDataLimitCallback() throws Exception {
+        setupFunctioningHardwareInterface();
+        enableOffload();
+
+        final OffloadController offload = makeOffloadController();
+        offload.start();
+
+        OffloadHardwareInterface.ControlCallback callback = mControlCallbackCaptor.getValue();
+        callback.onStoppedLimitReached();
+        verify(mNMService, times(1)).tetherLimitReached(mTetherStatsProviderCaptor.getValue());
+    }
+
+    @Test
+    public void testAddRemoveDownstreams() throws Exception {
+        setupFunctioningHardwareInterface();
+        enableOffload();
+
+        final OffloadController offload = makeOffloadController();
+        offload.start();
+
+        final InOrder inOrder = inOrder(mHardware);
+        inOrder.verify(mHardware, times(1)).initOffloadConfig();
+        inOrder.verify(mHardware, times(1)).initOffloadControl(
+                any(OffloadHardwareInterface.ControlCallback.class));
+        inOrder.verifyNoMoreInteractions();
+
+        // Tethering makes several calls to setLocalPrefixes() before add/remove
+        // downstream calls are made. This is not tested here; only the behavior
+        // of notifyDownstreamLinkProperties() and removeDownstreamInterface()
+        // are tested.
+
+        // [1] USB tethering is started.
+        final LinkProperties usbLinkProperties = new LinkProperties();
+        usbLinkProperties.setInterfaceName(RNDIS0);
+        usbLinkProperties.addLinkAddress(new LinkAddress("192.168.42.1/24"));
+        usbLinkProperties.addRoute(new RouteInfo(new IpPrefix(USB_PREFIX)));
+        offload.notifyDownstreamLinkProperties(usbLinkProperties);
+        inOrder.verify(mHardware, times(1)).addDownstreamPrefix(RNDIS0, USB_PREFIX);
+        inOrder.verifyNoMoreInteractions();
+
+        // [2] Routes for IPv6 link-local prefixes should never be added.
+        usbLinkProperties.addRoute(new RouteInfo(new IpPrefix(IPV6_LINKLOCAL)));
+        offload.notifyDownstreamLinkProperties(usbLinkProperties);
+        inOrder.verify(mHardware, never()).addDownstreamPrefix(eq(RNDIS0), anyString());
+        inOrder.verifyNoMoreInteractions();
+
+        // [3] Add an IPv6 prefix for good measure. Only new offload-able
+        // prefixes should be passed to the HAL.
+        usbLinkProperties.addLinkAddress(new LinkAddress("2001:db8::1/64"));
+        usbLinkProperties.addRoute(new RouteInfo(new IpPrefix(IPV6_DOC_PREFIX)));
+        offload.notifyDownstreamLinkProperties(usbLinkProperties);
+        inOrder.verify(mHardware, times(1)).addDownstreamPrefix(RNDIS0, IPV6_DOC_PREFIX);
+        inOrder.verifyNoMoreInteractions();
+
+        // [4] Adding addresses doesn't affect notifyDownstreamLinkProperties().
+        // The address is passed in by a separate setLocalPrefixes() invocation.
+        usbLinkProperties.addLinkAddress(new LinkAddress("2001:db8::2/64"));
+        offload.notifyDownstreamLinkProperties(usbLinkProperties);
+        inOrder.verify(mHardware, never()).addDownstreamPrefix(eq(RNDIS0), anyString());
+
+        // [5] Differences in local routes are converted into addDownstream()
+        // and removeDownstream() invocations accordingly.
+        usbLinkProperties.removeRoute(new RouteInfo(new IpPrefix(IPV6_DOC_PREFIX), null, RNDIS0));
+        usbLinkProperties.addRoute(new RouteInfo(new IpPrefix(IPV6_DISCARD_PREFIX)));
+        offload.notifyDownstreamLinkProperties(usbLinkProperties);
+        inOrder.verify(mHardware, times(1)).removeDownstreamPrefix(RNDIS0, IPV6_DOC_PREFIX);
+        inOrder.verify(mHardware, times(1)).addDownstreamPrefix(RNDIS0, IPV6_DISCARD_PREFIX);
+        inOrder.verifyNoMoreInteractions();
+
+        // [6] Removing a downstream interface which was never added causes no
+        // interactions with the HAL.
+        offload.removeDownstreamInterface(WLAN0);
+        inOrder.verifyNoMoreInteractions();
+
+        // [7] Removing an active downstream removes all remaining prefixes.
+        offload.removeDownstreamInterface(RNDIS0);
+        inOrder.verify(mHardware, times(1)).removeDownstreamPrefix(RNDIS0, USB_PREFIX);
+        inOrder.verify(mHardware, times(1)).removeDownstreamPrefix(RNDIS0, IPV6_DISCARD_PREFIX);
+        inOrder.verifyNoMoreInteractions();
+    }
+
+    @Test
+    public void testControlCallbackOnStoppedUnsupportedFetchesAllStats() throws Exception {
+        setupFunctioningHardwareInterface();
+        enableOffload();
+
+        final OffloadController offload = makeOffloadController();
+        offload.start();
+
+        // Pretend to set a few different upstreams (only the interface name
+        // matters for this test; we're ignoring IP and route information).
+        final LinkProperties upstreamLp = new LinkProperties();
+        for (String ifname : new String[]{RMNET0, WLAN0, RMNET0}) {
+            upstreamLp.setInterfaceName(ifname);
+            offload.setUpstreamLinkProperties(upstreamLp);
+        }
+
+        // Clear invocation history, especially the getForwardedStats() calls
+        // that happen with setUpstreamParameters().
+        clearInvocations(mHardware);
+
+        OffloadHardwareInterface.ControlCallback callback = mControlCallbackCaptor.getValue();
+        callback.onStoppedUnsupported();
+
+        // Verify forwarded stats behaviour.
+        verify(mHardware, times(1)).getForwardedStats(eq(RMNET0));
+        verify(mHardware, times(1)).getForwardedStats(eq(WLAN0));
+        verifyNoMoreInteractions(mHardware);
+        verify(mNMService, times(1)).tetherLimitReached(mTetherStatsProviderCaptor.getValue());
+        verifyNoMoreInteractions(mNMService);
+    }
+
+    @Test
+    public void testControlCallbackOnSupportAvailableFetchesAllStatsAndPushesAllParameters()
+            throws Exception {
+        setupFunctioningHardwareInterface();
+        enableOffload();
+
+        final OffloadController offload = makeOffloadController();
+        offload.start();
+
+        // Pretend to set a few different upstreams (only the interface name
+        // matters for this test; we're ignoring IP and route information).
+        final LinkProperties upstreamLp = new LinkProperties();
+        for (String ifname : new String[]{RMNET0, WLAN0, RMNET0}) {
+            upstreamLp.setInterfaceName(ifname);
+            offload.setUpstreamLinkProperties(upstreamLp);
+        }
+
+        // Pretend that some local prefixes and downstreams have been added
+        // (and removed, for good measure).
+        final Set<IpPrefix> minimumLocalPrefixes = new HashSet<>();
+        for (String s : new String[]{
+                "127.0.0.0/8", "192.0.2.0/24", "fe80::/64", "2001:db8::/64"}) {
+            minimumLocalPrefixes.add(new IpPrefix(s));
+        }
+        offload.setLocalPrefixes(minimumLocalPrefixes);
+
+        final LinkProperties usbLinkProperties = new LinkProperties();
+        usbLinkProperties.setInterfaceName(RNDIS0);
+        usbLinkProperties.addLinkAddress(new LinkAddress("192.168.42.1/24"));
+        usbLinkProperties.addRoute(new RouteInfo(new IpPrefix(USB_PREFIX)));
+        offload.notifyDownstreamLinkProperties(usbLinkProperties);
+
+        final LinkProperties wifiLinkProperties = new LinkProperties();
+        wifiLinkProperties.setInterfaceName(WLAN0);
+        wifiLinkProperties.addLinkAddress(new LinkAddress("192.168.43.1/24"));
+        wifiLinkProperties.addRoute(new RouteInfo(new IpPrefix(WIFI_PREFIX)));
+        wifiLinkProperties.addRoute(new RouteInfo(new IpPrefix(IPV6_LINKLOCAL)));
+        // Use a benchmark prefix (RFC 5180 + erratum), since the documentation
+        // prefix is included in the excluded prefix list.
+        wifiLinkProperties.addLinkAddress(new LinkAddress("2001:2::1/64"));
+        wifiLinkProperties.addLinkAddress(new LinkAddress("2001:2::2/64"));
+        wifiLinkProperties.addRoute(new RouteInfo(new IpPrefix("2001:2::/64")));
+        offload.notifyDownstreamLinkProperties(wifiLinkProperties);
+
+        offload.removeDownstreamInterface(RNDIS0);
+
+        // Clear invocation history, especially the getForwardedStats() calls
+        // that happen with setUpstreamParameters().
+        clearInvocations(mHardware);
+
+        OffloadHardwareInterface.ControlCallback callback = mControlCallbackCaptor.getValue();
+        callback.onSupportAvailable();
+
+        // Verify forwarded stats behaviour.
+        verify(mHardware, times(1)).getForwardedStats(eq(RMNET0));
+        verify(mHardware, times(1)).getForwardedStats(eq(WLAN0));
+        verify(mNMService, times(1)).tetherLimitReached(mTetherStatsProviderCaptor.getValue());
+        verifyNoMoreInteractions(mNMService);
+
+        // TODO: verify local prefixes and downstreams are also pushed to the HAL.
+        verify(mHardware, times(1)).setLocalPrefixes(mStringArrayCaptor.capture());
+        ArrayList<String> localPrefixes = mStringArrayCaptor.getValue();
+        assertEquals(4, localPrefixes.size());
+        assertContainsAll(localPrefixes,
+                // TODO: The logic to find and exclude downstream IP prefixes
+                // is currently in Tethering's OffloadWrapper but must be moved
+                // into OffloadController proper. After this, also check for:
+                //     "192.168.43.1/32", "2001:2::1/128", "2001:2::2/128"
+                "127.0.0.0/8", "192.0.2.0/24", "fe80::/64", "2001:db8::/64");
+        verify(mHardware, times(1)).addDownstreamPrefix(WLAN0, "192.168.43.0/24");
+        verify(mHardware, times(1)).addDownstreamPrefix(WLAN0, "2001:2::/64");
+        verify(mHardware, times(1)).setUpstreamParameters(eq(RMNET0), any(), any(), any());
+        verify(mHardware, times(1)).setDataLimit(eq(RMNET0), anyLong());
+        verifyNoMoreInteractions(mHardware);
+    }
+
+}