diff --git a/Tethering/tests/unit/Android.bp b/Tethering/tests/unit/Android.bp
index 5564bd6..7c06e5f 100644
--- a/Tethering/tests/unit/Android.bp
+++ b/Tethering/tests/unit/Android.bp
@@ -47,6 +47,7 @@
     srcs: [
         "src/com/android/server/connectivity/tethering/EntitlementManagerTest.java",
         "src/com/android/server/connectivity/tethering/TetheringConfigurationTest.java",
+        "src/com/android/server/connectivity/tethering/UpstreamNetworkMonitorTest.java",
         "src/android/net/dhcp/DhcpServingParamsParcelExtTest.java",
         "src/android/net/ip/IpServerTest.java",
         "src/android/net/util/InterfaceSetTest.java",
diff --git a/Tethering/tests/unit/src/com/android/server/connectivity/tethering/UpstreamNetworkMonitorTest.java b/Tethering/tests/unit/src/com/android/server/connectivity/tethering/UpstreamNetworkMonitorTest.java
new file mode 100644
index 0000000..c028d6d
--- /dev/null
+++ b/Tethering/tests/unit/src/com/android/server/connectivity/tethering/UpstreamNetworkMonitorTest.java
@@ -0,0 +1,798 @@
+/*
+ * 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.ConnectivityManager.TYPE_MOBILE_DUN;
+import static android.net.ConnectivityManager.TYPE_MOBILE_HIPRI;
+import static android.net.ConnectivityManager.TYPE_NONE;
+import static android.net.ConnectivityManager.TYPE_WIFI;
+import static android.net.NetworkCapabilities.NET_CAPABILITY_DUN;
+import static android.net.NetworkCapabilities.NET_CAPABILITY_INTERNET;
+import static android.net.NetworkCapabilities.TRANSPORT_CELLULAR;
+import static android.net.NetworkCapabilities.TRANSPORT_WIFI;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+import static org.junit.Assert.fail;
+import static org.mockito.Mockito.any;
+import static org.mockito.Mockito.anyInt;
+import static org.mockito.Mockito.anyString;
+import static org.mockito.Mockito.eq;
+import static org.mockito.Mockito.reset;
+import static org.mockito.Mockito.spy;
+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.net.ConnectivityManager;
+import android.net.ConnectivityManager.NetworkCallback;
+import android.net.IConnectivityManager;
+import android.net.IpPrefix;
+import android.net.LinkAddress;
+import android.net.LinkProperties;
+import android.net.Network;
+import android.net.NetworkCapabilities;
+import android.net.NetworkRequest;
+import android.net.NetworkState;
+import android.net.util.SharedLog;
+import android.os.Handler;
+import android.os.Message;
+
+import androidx.test.filters.SmallTest;
+import androidx.test.runner.AndroidJUnit4;
+
+import com.android.internal.util.State;
+import com.android.internal.util.StateMachine;
+
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mockito.Mock;
+import org.mockito.MockitoAnnotations;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.Map;
+import java.util.Objects;
+import java.util.Set;
+
+@RunWith(AndroidJUnit4.class)
+@SmallTest
+public class UpstreamNetworkMonitorTest {
+    private static final int EVENT_UNM_UPDATE = 1;
+
+    private static final boolean INCLUDES = true;
+    private static final boolean EXCLUDES = false;
+
+    // Actual contents of the request don't matter for this test. The lack of
+    // any specific TRANSPORT_* is sufficient to identify this request.
+    private static final NetworkRequest sDefaultRequest = new NetworkRequest.Builder().build();
+
+    @Mock private Context mContext;
+    @Mock private EntitlementManager mEntitleMgr;
+    @Mock private IConnectivityManager mCS;
+    @Mock private SharedLog mLog;
+
+    private TestStateMachine mSM;
+    private TestConnectivityManager mCM;
+    private UpstreamNetworkMonitor mUNM;
+
+    @Before public void setUp() throws Exception {
+        MockitoAnnotations.initMocks(this);
+        reset(mContext);
+        reset(mCS);
+        reset(mLog);
+        when(mLog.forSubComponent(anyString())).thenReturn(mLog);
+        when(mEntitleMgr.isCellularUpstreamPermitted()).thenReturn(true);
+
+        mCM = spy(new TestConnectivityManager(mContext, mCS));
+        mSM = new TestStateMachine();
+        mUNM = new UpstreamNetworkMonitor(
+                (ConnectivityManager) mCM, mSM, mLog, EVENT_UNM_UPDATE);
+    }
+
+    @After public void tearDown() throws Exception {
+        if (mSM != null) {
+            mSM.quit();
+            mSM = null;
+        }
+    }
+
+    @Test
+    public void testStopWithoutStartIsNonFatal() {
+        mUNM.stop();
+        mUNM.stop();
+        mUNM.stop();
+    }
+
+    @Test
+    public void testDoesNothingBeforeTrackDefaultAndStarted() throws Exception {
+        assertTrue(mCM.hasNoCallbacks());
+        assertFalse(mUNM.mobileNetworkRequested());
+
+        mUNM.updateMobileRequiresDun(true);
+        assertTrue(mCM.hasNoCallbacks());
+        mUNM.updateMobileRequiresDun(false);
+        assertTrue(mCM.hasNoCallbacks());
+    }
+
+    @Test
+    public void testDefaultNetworkIsTracked() throws Exception {
+        assertTrue(mCM.hasNoCallbacks());
+        mUNM.startTrackDefaultNetwork(sDefaultRequest, mEntitleMgr);
+
+        mUNM.startObserveAllNetworks();
+        assertEquals(1, mCM.trackingDefault.size());
+
+        mUNM.stop();
+        assertTrue(mCM.onlyHasDefaultCallbacks());
+    }
+
+    @Test
+    public void testListensForAllNetworks() throws Exception {
+        assertTrue(mCM.listening.isEmpty());
+
+        mUNM.startTrackDefaultNetwork(sDefaultRequest, mEntitleMgr);
+        mUNM.startObserveAllNetworks();
+        assertFalse(mCM.listening.isEmpty());
+        assertTrue(mCM.isListeningForAll());
+
+        mUNM.stop();
+        assertTrue(mCM.onlyHasDefaultCallbacks());
+    }
+
+    @Test
+    public void testCallbacksRegistered() {
+        mUNM.startTrackDefaultNetwork(sDefaultRequest, mEntitleMgr);
+        verify(mCM, times(1)).requestNetwork(
+                eq(sDefaultRequest), any(NetworkCallback.class), any(Handler.class));
+        mUNM.startObserveAllNetworks();
+        verify(mCM, times(1)).registerNetworkCallback(
+                any(NetworkRequest.class), any(NetworkCallback.class), any(Handler.class));
+
+        mUNM.stop();
+        verify(mCM, times(1)).unregisterNetworkCallback(any(NetworkCallback.class));
+    }
+
+    @Test
+    public void testRequestsMobileNetwork() throws Exception {
+        assertFalse(mUNM.mobileNetworkRequested());
+        assertEquals(0, mCM.requested.size());
+
+        mUNM.startObserveAllNetworks();
+        assertFalse(mUNM.mobileNetworkRequested());
+        assertEquals(0, mCM.requested.size());
+
+        mUNM.updateMobileRequiresDun(false);
+        assertFalse(mUNM.mobileNetworkRequested());
+        assertEquals(0, mCM.requested.size());
+
+        mUNM.registerMobileNetworkRequest();
+        assertTrue(mUNM.mobileNetworkRequested());
+        assertUpstreamTypeRequested(TYPE_MOBILE_HIPRI);
+        assertFalse(isDunRequested());
+
+        mUNM.stop();
+        assertFalse(mUNM.mobileNetworkRequested());
+        assertTrue(mCM.hasNoCallbacks());
+    }
+
+    @Test
+    public void testDuplicateMobileRequestsIgnored() throws Exception {
+        assertFalse(mUNM.mobileNetworkRequested());
+        assertEquals(0, mCM.requested.size());
+
+        mUNM.startObserveAllNetworks();
+        verify(mCM, times(1)).registerNetworkCallback(
+                any(NetworkRequest.class), any(NetworkCallback.class), any(Handler.class));
+        assertFalse(mUNM.mobileNetworkRequested());
+        assertEquals(0, mCM.requested.size());
+
+        mUNM.updateMobileRequiresDun(true);
+        mUNM.registerMobileNetworkRequest();
+        verify(mCM, times(1)).requestNetwork(
+                any(NetworkRequest.class), any(NetworkCallback.class), anyInt(), anyInt(),
+                any(Handler.class));
+
+        assertTrue(mUNM.mobileNetworkRequested());
+        assertUpstreamTypeRequested(TYPE_MOBILE_DUN);
+        assertTrue(isDunRequested());
+
+        // Try a few things that must not result in any state change.
+        mUNM.registerMobileNetworkRequest();
+        mUNM.updateMobileRequiresDun(true);
+        mUNM.registerMobileNetworkRequest();
+
+        assertTrue(mUNM.mobileNetworkRequested());
+        assertUpstreamTypeRequested(TYPE_MOBILE_DUN);
+        assertTrue(isDunRequested());
+
+        mUNM.stop();
+        verify(mCM, times(2)).unregisterNetworkCallback(any(NetworkCallback.class));
+
+        verifyNoMoreInteractions(mCM);
+    }
+
+    @Test
+    public void testRequestsDunNetwork() throws Exception {
+        assertFalse(mUNM.mobileNetworkRequested());
+        assertEquals(0, mCM.requested.size());
+
+        mUNM.startObserveAllNetworks();
+        assertFalse(mUNM.mobileNetworkRequested());
+        assertEquals(0, mCM.requested.size());
+
+        mUNM.updateMobileRequiresDun(true);
+        assertFalse(mUNM.mobileNetworkRequested());
+        assertEquals(0, mCM.requested.size());
+
+        mUNM.registerMobileNetworkRequest();
+        assertTrue(mUNM.mobileNetworkRequested());
+        assertUpstreamTypeRequested(TYPE_MOBILE_DUN);
+        assertTrue(isDunRequested());
+
+        mUNM.stop();
+        assertFalse(mUNM.mobileNetworkRequested());
+        assertTrue(mCM.hasNoCallbacks());
+    }
+
+    @Test
+    public void testUpdateMobileRequiresDun() throws Exception {
+        mUNM.startObserveAllNetworks();
+
+        // Test going from no-DUN to DUN correctly re-registers callbacks.
+        mUNM.updateMobileRequiresDun(false);
+        mUNM.registerMobileNetworkRequest();
+        assertTrue(mUNM.mobileNetworkRequested());
+        assertUpstreamTypeRequested(TYPE_MOBILE_HIPRI);
+        assertFalse(isDunRequested());
+        mUNM.updateMobileRequiresDun(true);
+        assertTrue(mUNM.mobileNetworkRequested());
+        assertUpstreamTypeRequested(TYPE_MOBILE_DUN);
+        assertTrue(isDunRequested());
+
+        // Test going from DUN to no-DUN correctly re-registers callbacks.
+        mUNM.updateMobileRequiresDun(false);
+        assertTrue(mUNM.mobileNetworkRequested());
+        assertUpstreamTypeRequested(TYPE_MOBILE_HIPRI);
+        assertFalse(isDunRequested());
+
+        mUNM.stop();
+        assertFalse(mUNM.mobileNetworkRequested());
+    }
+
+    @Test
+    public void testSelectPreferredUpstreamType() throws Exception {
+        final Collection<Integer> preferredTypes = new ArrayList<>();
+        preferredTypes.add(TYPE_WIFI);
+
+        mUNM.startTrackDefaultNetwork(sDefaultRequest, mEntitleMgr);
+        mUNM.startObserveAllNetworks();
+        // There are no networks, so there is nothing to select.
+        assertSatisfiesLegacyType(TYPE_NONE, mUNM.selectPreferredUpstreamType(preferredTypes));
+
+        final TestNetworkAgent wifiAgent = new TestNetworkAgent(mCM, TRANSPORT_WIFI);
+        wifiAgent.fakeConnect();
+        // WiFi is up, we should prefer it.
+        assertSatisfiesLegacyType(TYPE_WIFI, mUNM.selectPreferredUpstreamType(preferredTypes));
+        wifiAgent.fakeDisconnect();
+        // There are no networks, so there is nothing to select.
+        assertSatisfiesLegacyType(TYPE_NONE, mUNM.selectPreferredUpstreamType(preferredTypes));
+
+        final TestNetworkAgent cellAgent = new TestNetworkAgent(mCM, TRANSPORT_CELLULAR);
+        cellAgent.fakeConnect();
+        assertSatisfiesLegacyType(TYPE_NONE, mUNM.selectPreferredUpstreamType(preferredTypes));
+
+        preferredTypes.add(TYPE_MOBILE_DUN);
+        // This is coupled with preferred types in TetheringConfiguration.
+        mUNM.updateMobileRequiresDun(true);
+        // DUN is available, but only use regular cell: no upstream selected.
+        assertSatisfiesLegacyType(TYPE_NONE, mUNM.selectPreferredUpstreamType(preferredTypes));
+        preferredTypes.remove(TYPE_MOBILE_DUN);
+        // No WiFi, but our preferred flavour of cell is up.
+        preferredTypes.add(TYPE_MOBILE_HIPRI);
+        // This is coupled with preferred types in TetheringConfiguration.
+        mUNM.updateMobileRequiresDun(false);
+        assertSatisfiesLegacyType(TYPE_MOBILE_HIPRI,
+                mUNM.selectPreferredUpstreamType(preferredTypes));
+        // Check to see we filed an explicit request.
+        assertEquals(1, mCM.requested.size());
+        NetworkRequest netReq = (NetworkRequest) mCM.requested.values().toArray()[0];
+        assertTrue(netReq.networkCapabilities.hasTransport(TRANSPORT_CELLULAR));
+        assertFalse(netReq.networkCapabilities.hasCapability(NET_CAPABILITY_DUN));
+        // mobile is not permitted, we should not use HIPRI.
+        when(mEntitleMgr.isCellularUpstreamPermitted()).thenReturn(false);
+        assertSatisfiesLegacyType(TYPE_NONE, mUNM.selectPreferredUpstreamType(preferredTypes));
+        assertEquals(0, mCM.requested.size());
+        // mobile change back to permitted, HIRPI should come back
+        when(mEntitleMgr.isCellularUpstreamPermitted()).thenReturn(true);
+        assertSatisfiesLegacyType(TYPE_MOBILE_HIPRI,
+                mUNM.selectPreferredUpstreamType(preferredTypes));
+
+        wifiAgent.fakeConnect();
+        // WiFi is up, and we should prefer it over cell.
+        assertSatisfiesLegacyType(TYPE_WIFI, mUNM.selectPreferredUpstreamType(preferredTypes));
+        assertEquals(0, mCM.requested.size());
+
+        preferredTypes.remove(TYPE_MOBILE_HIPRI);
+        preferredTypes.add(TYPE_MOBILE_DUN);
+        // This is coupled with preferred types in TetheringConfiguration.
+        mUNM.updateMobileRequiresDun(true);
+        assertSatisfiesLegacyType(TYPE_WIFI, mUNM.selectPreferredUpstreamType(preferredTypes));
+
+        final TestNetworkAgent dunAgent = new TestNetworkAgent(mCM, TRANSPORT_CELLULAR);
+        dunAgent.networkCapabilities.addCapability(NET_CAPABILITY_DUN);
+        dunAgent.fakeConnect();
+
+        // WiFi is still preferred.
+        assertSatisfiesLegacyType(TYPE_WIFI, mUNM.selectPreferredUpstreamType(preferredTypes));
+
+        // WiFi goes down, cell and DUN are still up but only DUN is preferred.
+        wifiAgent.fakeDisconnect();
+        assertSatisfiesLegacyType(TYPE_MOBILE_DUN,
+                mUNM.selectPreferredUpstreamType(preferredTypes));
+        // Check to see we filed an explicit request.
+        assertEquals(1, mCM.requested.size());
+        netReq = (NetworkRequest) mCM.requested.values().toArray()[0];
+        assertTrue(netReq.networkCapabilities.hasTransport(TRANSPORT_CELLULAR));
+        assertTrue(netReq.networkCapabilities.hasCapability(NET_CAPABILITY_DUN));
+        // mobile is not permitted, we should not use DUN.
+        when(mEntitleMgr.isCellularUpstreamPermitted()).thenReturn(false);
+        assertSatisfiesLegacyType(TYPE_NONE, mUNM.selectPreferredUpstreamType(preferredTypes));
+        assertEquals(0, mCM.requested.size());
+        // mobile change back to permitted, DUN should come back
+        when(mEntitleMgr.isCellularUpstreamPermitted()).thenReturn(true);
+        assertSatisfiesLegacyType(TYPE_MOBILE_DUN,
+                mUNM.selectPreferredUpstreamType(preferredTypes));
+    }
+
+    @Test
+    public void testGetCurrentPreferredUpstream() throws Exception {
+        mUNM.startTrackDefaultNetwork(sDefaultRequest, mEntitleMgr);
+        mUNM.startObserveAllNetworks();
+        mUNM.updateMobileRequiresDun(false);
+
+        // [0] Mobile connects, DUN not required -> mobile selected.
+        final TestNetworkAgent cellAgent = new TestNetworkAgent(mCM, TRANSPORT_CELLULAR);
+        cellAgent.fakeConnect();
+        mCM.makeDefaultNetwork(cellAgent);
+        assertEquals(cellAgent.networkId, mUNM.getCurrentPreferredUpstream().network);
+
+        // [1] Mobile connects but not permitted -> null selected
+        when(mEntitleMgr.isCellularUpstreamPermitted()).thenReturn(false);
+        assertEquals(null, mUNM.getCurrentPreferredUpstream());
+        when(mEntitleMgr.isCellularUpstreamPermitted()).thenReturn(true);
+
+        // [2] WiFi connects but not validated/promoted to default -> mobile selected.
+        final TestNetworkAgent wifiAgent = new TestNetworkAgent(mCM, TRANSPORT_WIFI);
+        wifiAgent.fakeConnect();
+        assertEquals(cellAgent.networkId, mUNM.getCurrentPreferredUpstream().network);
+
+        // [3] WiFi validates and is promoted to the default network -> WiFi selected.
+        mCM.makeDefaultNetwork(wifiAgent);
+        assertEquals(wifiAgent.networkId, mUNM.getCurrentPreferredUpstream().network);
+
+        // [4] DUN required, no other changes -> WiFi still selected
+        mUNM.updateMobileRequiresDun(true);
+        assertEquals(wifiAgent.networkId, mUNM.getCurrentPreferredUpstream().network);
+
+        // [5] WiFi no longer validated, mobile becomes default, DUN required -> null selected.
+        mCM.makeDefaultNetwork(cellAgent);
+        assertEquals(null, mUNM.getCurrentPreferredUpstream());
+        // TODO: make sure that a DUN request has been filed. This is currently
+        // triggered by code over in Tethering, but once that has been moved
+        // into UNM we should test for this here.
+
+        // [6] DUN network arrives -> DUN selected
+        final TestNetworkAgent dunAgent = new TestNetworkAgent(mCM, TRANSPORT_CELLULAR);
+        dunAgent.networkCapabilities.addCapability(NET_CAPABILITY_DUN);
+        dunAgent.networkCapabilities.removeCapability(NET_CAPABILITY_INTERNET);
+        dunAgent.fakeConnect();
+        assertEquals(dunAgent.networkId, mUNM.getCurrentPreferredUpstream().network);
+
+        // [7] Mobile is not permitted -> null selected
+        when(mEntitleMgr.isCellularUpstreamPermitted()).thenReturn(false);
+        assertEquals(null, mUNM.getCurrentPreferredUpstream());
+    }
+
+    @Test
+    public void testLocalPrefixes() throws Exception {
+        mUNM.startTrackDefaultNetwork(sDefaultRequest, mEntitleMgr);
+        mUNM.startObserveAllNetworks();
+
+        // [0] Test minimum set of local prefixes.
+        Set<IpPrefix> local = mUNM.getLocalPrefixes();
+        assertTrue(local.isEmpty());
+
+        final Set<String> alreadySeen = new HashSet<>();
+
+        // [1] Pretend Wi-Fi connects.
+        final TestNetworkAgent wifiAgent = new TestNetworkAgent(mCM, TRANSPORT_WIFI);
+        final LinkProperties wifiLp = wifiAgent.linkProperties;
+        wifiLp.setInterfaceName("wlan0");
+        final String[] wifi_addrs = {
+                "fe80::827a:bfff:fe6f:374d", "100.112.103.18",
+                "2001:db8:4:fd00:827a:bfff:fe6f:374d",
+                "2001:db8:4:fd00:6dea:325a:fdae:4ef4",
+                "fd6a:a640:60bf:e985::123",  // ULA address for good measure.
+        };
+        for (String addrStr : wifi_addrs) {
+            final String cidr = addrStr.contains(":") ? "/64" : "/20";
+            wifiLp.addLinkAddress(new LinkAddress(addrStr + cidr));
+        }
+        wifiAgent.fakeConnect();
+        wifiAgent.sendLinkProperties();
+
+        local = mUNM.getLocalPrefixes();
+        assertPrefixSet(local, INCLUDES, alreadySeen);
+        final String[] wifiLinkPrefixes = {
+                // Link-local prefixes are excluded and dealt with elsewhere.
+                "100.112.96.0/20", "2001:db8:4:fd00::/64", "fd6a:a640:60bf:e985::/64",
+        };
+        assertPrefixSet(local, INCLUDES, wifiLinkPrefixes);
+        Collections.addAll(alreadySeen, wifiLinkPrefixes);
+        assertEquals(alreadySeen.size(), local.size());
+
+        // [2] Pretend mobile connects.
+        final TestNetworkAgent cellAgent = new TestNetworkAgent(mCM, TRANSPORT_CELLULAR);
+        final LinkProperties cellLp = cellAgent.linkProperties;
+        cellLp.setInterfaceName("rmnet_data0");
+        final String[] cell_addrs = {
+                "10.102.211.48", "2001:db8:0:1:b50e:70d9:10c9:433d",
+        };
+        for (String addrStr : cell_addrs) {
+            final String cidr = addrStr.contains(":") ? "/64" : "/27";
+            cellLp.addLinkAddress(new LinkAddress(addrStr + cidr));
+        }
+        cellAgent.fakeConnect();
+        cellAgent.sendLinkProperties();
+
+        local = mUNM.getLocalPrefixes();
+        assertPrefixSet(local, INCLUDES, alreadySeen);
+        final String[] cellLinkPrefixes = { "10.102.211.32/27", "2001:db8:0:1::/64" };
+        assertPrefixSet(local, INCLUDES, cellLinkPrefixes);
+        Collections.addAll(alreadySeen, cellLinkPrefixes);
+        assertEquals(alreadySeen.size(), local.size());
+
+        // [3] Pretend DUN connects.
+        final TestNetworkAgent dunAgent = new TestNetworkAgent(mCM, TRANSPORT_CELLULAR);
+        dunAgent.networkCapabilities.addCapability(NET_CAPABILITY_DUN);
+        dunAgent.networkCapabilities.removeCapability(NET_CAPABILITY_INTERNET);
+        final LinkProperties dunLp = dunAgent.linkProperties;
+        dunLp.setInterfaceName("rmnet_data1");
+        final String[] dun_addrs = {
+                "192.0.2.48", "2001:db8:1:2:b50e:70d9:10c9:433d",
+        };
+        for (String addrStr : dun_addrs) {
+            final String cidr = addrStr.contains(":") ? "/64" : "/27";
+            dunLp.addLinkAddress(new LinkAddress(addrStr + cidr));
+        }
+        dunAgent.fakeConnect();
+        dunAgent.sendLinkProperties();
+
+        local = mUNM.getLocalPrefixes();
+        assertPrefixSet(local, INCLUDES, alreadySeen);
+        final String[] dunLinkPrefixes = { "192.0.2.32/27", "2001:db8:1:2::/64" };
+        assertPrefixSet(local, INCLUDES, dunLinkPrefixes);
+        Collections.addAll(alreadySeen, dunLinkPrefixes);
+        assertEquals(alreadySeen.size(), local.size());
+
+        // [4] Pretend Wi-Fi disconnected.  It's addresses/prefixes should no
+        // longer be included (should be properly removed).
+        wifiAgent.fakeDisconnect();
+        local = mUNM.getLocalPrefixes();
+        assertPrefixSet(local, EXCLUDES, wifiLinkPrefixes);
+        assertPrefixSet(local, INCLUDES, cellLinkPrefixes);
+        assertPrefixSet(local, INCLUDES, dunLinkPrefixes);
+
+        // [5] Pretend mobile disconnected.
+        cellAgent.fakeDisconnect();
+        local = mUNM.getLocalPrefixes();
+        assertPrefixSet(local, EXCLUDES, wifiLinkPrefixes);
+        assertPrefixSet(local, EXCLUDES, cellLinkPrefixes);
+        assertPrefixSet(local, INCLUDES, dunLinkPrefixes);
+
+        // [6] Pretend DUN disconnected.
+        dunAgent.fakeDisconnect();
+        local = mUNM.getLocalPrefixes();
+        assertTrue(local.isEmpty());
+    }
+
+    @Test
+    public void testSelectMobileWhenMobileIsNotDefault() {
+        final Collection<Integer> preferredTypes = new ArrayList<>();
+        // Mobile has higher pirority than wifi.
+        preferredTypes.add(TYPE_MOBILE_HIPRI);
+        preferredTypes.add(TYPE_WIFI);
+        mUNM.startTrackDefaultNetwork(sDefaultRequest, mEntitleMgr);
+        mUNM.startObserveAllNetworks();
+        // Setup wifi and make wifi as default network.
+        final TestNetworkAgent wifiAgent = new TestNetworkAgent(mCM, TRANSPORT_WIFI);
+        wifiAgent.fakeConnect();
+        mCM.makeDefaultNetwork(wifiAgent);
+        // Setup mobile network.
+        final TestNetworkAgent cellAgent = new TestNetworkAgent(mCM, TRANSPORT_CELLULAR);
+        cellAgent.fakeConnect();
+
+        assertSatisfiesLegacyType(TYPE_MOBILE_HIPRI,
+                mUNM.selectPreferredUpstreamType(preferredTypes));
+        verify(mEntitleMgr, times(1)).maybeRunProvisioning();
+    }
+    private void assertSatisfiesLegacyType(int legacyType, NetworkState ns) {
+        if (legacyType == TYPE_NONE) {
+            assertTrue(ns == null);
+            return;
+        }
+
+        final NetworkCapabilities nc = ConnectivityManager.networkCapabilitiesForType(legacyType);
+        assertTrue(nc.satisfiedByNetworkCapabilities(ns.networkCapabilities));
+    }
+
+    private void assertUpstreamTypeRequested(int upstreamType) throws Exception {
+        assertEquals(1, mCM.requested.size());
+        assertEquals(1, mCM.legacyTypeMap.size());
+        assertEquals(Integer.valueOf(upstreamType),
+                mCM.legacyTypeMap.values().iterator().next());
+    }
+
+    private boolean isDunRequested() {
+        for (NetworkRequest req : mCM.requested.values()) {
+            if (req.networkCapabilities.hasCapability(NET_CAPABILITY_DUN)) {
+                return true;
+            }
+        }
+        return false;
+    }
+
+    public static class TestConnectivityManager extends ConnectivityManager {
+        public Map<NetworkCallback, Handler> allCallbacks = new HashMap<>();
+        public Set<NetworkCallback> trackingDefault = new HashSet<>();
+        public TestNetworkAgent defaultNetwork = null;
+        public Map<NetworkCallback, NetworkRequest> listening = new HashMap<>();
+        public Map<NetworkCallback, NetworkRequest> requested = new HashMap<>();
+        public Map<NetworkCallback, Integer> legacyTypeMap = new HashMap<>();
+
+        private int mNetworkId = 100;
+
+        public TestConnectivityManager(Context ctx, IConnectivityManager svc) {
+            super(ctx, svc);
+        }
+
+        boolean hasNoCallbacks() {
+            return allCallbacks.isEmpty()
+                    && trackingDefault.isEmpty()
+                    && listening.isEmpty()
+                    && requested.isEmpty()
+                    && legacyTypeMap.isEmpty();
+        }
+
+        boolean onlyHasDefaultCallbacks() {
+            return (allCallbacks.size() == 1)
+                    && (trackingDefault.size() == 1)
+                    && listening.isEmpty()
+                    && requested.isEmpty()
+                    && legacyTypeMap.isEmpty();
+        }
+
+        boolean isListeningForAll() {
+            final NetworkCapabilities empty = new NetworkCapabilities();
+            empty.clearAll();
+
+            for (NetworkRequest req : listening.values()) {
+                if (req.networkCapabilities.equalRequestableCapabilities(empty)) {
+                    return true;
+                }
+            }
+            return false;
+        }
+
+        int getNetworkId() {
+            return ++mNetworkId;
+        }
+
+        void makeDefaultNetwork(TestNetworkAgent agent) {
+            if (Objects.equals(defaultNetwork, agent)) return;
+
+            final TestNetworkAgent formerDefault = defaultNetwork;
+            defaultNetwork = agent;
+
+            for (NetworkCallback cb : trackingDefault) {
+                if (defaultNetwork != null) {
+                    cb.onAvailable(defaultNetwork.networkId);
+                    cb.onCapabilitiesChanged(
+                            defaultNetwork.networkId, defaultNetwork.networkCapabilities);
+                    cb.onLinkPropertiesChanged(
+                            defaultNetwork.networkId, defaultNetwork.linkProperties);
+                }
+            }
+        }
+
+        @Override
+        public void requestNetwork(NetworkRequest req, NetworkCallback cb, Handler h) {
+            assertFalse(allCallbacks.containsKey(cb));
+            allCallbacks.put(cb, h);
+            if (sDefaultRequest.equals(req)) {
+                assertFalse(trackingDefault.contains(cb));
+                trackingDefault.add(cb);
+            } else {
+                assertFalse(requested.containsKey(cb));
+                requested.put(cb, req);
+            }
+        }
+
+        @Override
+        public void requestNetwork(NetworkRequest req, NetworkCallback cb) {
+            fail("Should never be called.");
+        }
+
+        @Override
+        public void requestNetwork(NetworkRequest req, NetworkCallback cb,
+                int timeoutMs, int legacyType, Handler h) {
+            assertFalse(allCallbacks.containsKey(cb));
+            allCallbacks.put(cb, h);
+            assertFalse(requested.containsKey(cb));
+            requested.put(cb, req);
+            assertFalse(legacyTypeMap.containsKey(cb));
+            if (legacyType != ConnectivityManager.TYPE_NONE) {
+                legacyTypeMap.put(cb, legacyType);
+            }
+        }
+
+        @Override
+        public void registerNetworkCallback(NetworkRequest req, NetworkCallback cb, Handler h) {
+            assertFalse(allCallbacks.containsKey(cb));
+            allCallbacks.put(cb, h);
+            assertFalse(listening.containsKey(cb));
+            listening.put(cb, req);
+        }
+
+        @Override
+        public void registerNetworkCallback(NetworkRequest req, NetworkCallback cb) {
+            fail("Should never be called.");
+        }
+
+        @Override
+        public void registerDefaultNetworkCallback(NetworkCallback cb, Handler h) {
+            fail("Should never be called.");
+        }
+
+        @Override
+        public void registerDefaultNetworkCallback(NetworkCallback cb) {
+            fail("Should never be called.");
+        }
+
+        @Override
+        public void unregisterNetworkCallback(NetworkCallback cb) {
+            if (trackingDefault.contains(cb)) {
+                trackingDefault.remove(cb);
+            } else if (listening.containsKey(cb)) {
+                listening.remove(cb);
+            } else if (requested.containsKey(cb)) {
+                requested.remove(cb);
+                legacyTypeMap.remove(cb);
+            } else {
+                fail("Unexpected callback removed");
+            }
+            allCallbacks.remove(cb);
+
+            assertFalse(allCallbacks.containsKey(cb));
+            assertFalse(trackingDefault.contains(cb));
+            assertFalse(listening.containsKey(cb));
+            assertFalse(requested.containsKey(cb));
+        }
+    }
+
+    public static class TestNetworkAgent {
+        public final TestConnectivityManager cm;
+        public final Network networkId;
+        public final int transportType;
+        public final NetworkCapabilities networkCapabilities;
+        public final LinkProperties linkProperties;
+
+        public TestNetworkAgent(TestConnectivityManager cm, int transportType) {
+            this.cm = cm;
+            this.networkId = new Network(cm.getNetworkId());
+            this.transportType = transportType;
+            networkCapabilities = new NetworkCapabilities();
+            networkCapabilities.addTransportType(transportType);
+            networkCapabilities.addCapability(NET_CAPABILITY_INTERNET);
+            linkProperties = new LinkProperties();
+        }
+
+        public void fakeConnect() {
+            for (NetworkCallback cb : cm.listening.keySet()) {
+                cb.onAvailable(networkId);
+                cb.onCapabilitiesChanged(networkId, copy(networkCapabilities));
+                cb.onLinkPropertiesChanged(networkId, copy(linkProperties));
+            }
+        }
+
+        public void fakeDisconnect() {
+            for (NetworkCallback cb : cm.listening.keySet()) {
+                cb.onLost(networkId);
+            }
+        }
+
+        public void sendLinkProperties() {
+            for (NetworkCallback cb : cm.listening.keySet()) {
+                cb.onLinkPropertiesChanged(networkId, copy(linkProperties));
+            }
+        }
+
+        @Override
+        public String toString() {
+            return String.format("TestNetworkAgent: %s %s", networkId, networkCapabilities);
+        }
+    }
+
+    public static class TestStateMachine extends StateMachine {
+        public final ArrayList<Message> messages = new ArrayList<>();
+        private final State mLoggingState = new LoggingState();
+
+        class LoggingState extends State {
+            @Override public void enter() {
+                messages.clear();
+            }
+
+            @Override public void exit() {
+                messages.clear();
+            }
+
+            @Override public boolean processMessage(Message msg) {
+                messages.add(msg);
+                return true;
+            }
+        }
+
+        public TestStateMachine() {
+            super("UpstreamNetworkMonitor.TestStateMachine");
+            addState(mLoggingState);
+            setInitialState(mLoggingState);
+            super.start();
+        }
+    }
+
+    static NetworkCapabilities copy(NetworkCapabilities nc) {
+        return new NetworkCapabilities(nc);
+    }
+
+    static LinkProperties copy(LinkProperties lp) {
+        return new LinkProperties(lp);
+    }
+
+    static void assertPrefixSet(Set<IpPrefix> prefixes, boolean expectation, String... expected) {
+        final Set<String> expectedSet = new HashSet<>();
+        Collections.addAll(expectedSet, expected);
+        assertPrefixSet(prefixes, expectation, expectedSet);
+    }
+
+    static void assertPrefixSet(Set<IpPrefix> prefixes, boolean expectation, Set<String> expected) {
+        for (String expectedPrefix : expected) {
+            final String errStr = expectation ? "did not find" : "found";
+            assertEquals(
+                    String.format("Failed expectation: %s prefix: %s", errStr, expectedPrefix),
+                    expectation, prefixes.contains(new IpPrefix(expectedPrefix)));
+        }
+    }
+}