diff --git a/Tethering/tests/unit/src/com/android/server/connectivity/tethering/IPv6TetheringCoordinatorTest.java b/Tethering/tests/unit/src/com/android/server/connectivity/tethering/IPv6TetheringCoordinatorTest.java
new file mode 100644
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+++ b/Tethering/tests/unit/src/com/android/server/connectivity/tethering/IPv6TetheringCoordinatorTest.java
@@ -0,0 +1,156 @@
+/*
+ * 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 com.android.server.connectivity.tethering;
+
+import static android.net.NetworkCapabilities.TRANSPORT_CELLULAR;
+import static android.net.RouteInfo.RTN_UNICAST;
+import static android.net.ip.IpServer.STATE_LOCAL_ONLY;
+import static android.net.ip.IpServer.STATE_TETHERED;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNotEquals;
+import static org.junit.Assert.assertNotNull;
+import static org.mockito.ArgumentMatchers.anyString;
+import static org.mockito.ArgumentMatchers.eq;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.reset;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.verifyNoMoreInteractions;
+import static org.mockito.Mockito.when;
+
+import android.net.InetAddresses;
+import android.net.IpPrefix;
+import android.net.LinkAddress;
+import android.net.LinkProperties;
+import android.net.Network;
+import android.net.NetworkCapabilities;
+import android.net.RouteInfo;
+import android.net.ip.IpServer;
+import android.net.util.SharedLog;
+
+import androidx.test.filters.SmallTest;
+import androidx.test.runner.AndroidJUnit4;
+
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mockito.ArgumentCaptor;
+import org.mockito.Mock;
+import org.mockito.MockitoAnnotations;
+
+import java.net.InetAddress;
+import java.util.ArrayList;
+import java.util.List;
+
+@RunWith(AndroidJUnit4.class)
+@SmallTest
+public class IPv6TetheringCoordinatorTest {
+    private static final String TEST_DNS_SERVER = "2001:4860:4860::8888";
+    private static final String TEST_INTERFACE = "test_rmnet0";
+    private static final String TEST_IPV6_ADDRESS = "2001:db8::1/64";
+    private static final String TEST_IPV4_ADDRESS = "192.168.100.1/24";
+
+    private IPv6TetheringCoordinator mIPv6TetheringCoordinator;
+    private ArrayList<IpServer> mNotifyList;
+
+    @Mock private SharedLog mSharedLog;
+
+    @Before
+    public void setUp() throws Exception {
+        MockitoAnnotations.initMocks(this);
+        when(mSharedLog.forSubComponent(anyString())).thenReturn(mSharedLog);
+        mNotifyList = new ArrayList<IpServer>();
+        mIPv6TetheringCoordinator = new IPv6TetheringCoordinator(mNotifyList, mSharedLog);
+    }
+
+    private UpstreamNetworkState createDualStackUpstream(final int transportType) {
+        final Network network = mock(Network.class);
+        final NetworkCapabilities netCap =
+                new NetworkCapabilities.Builder().addTransportType(transportType).build();
+        final InetAddress dns = InetAddresses.parseNumericAddress(TEST_DNS_SERVER);
+        final LinkProperties linkProp = new LinkProperties();
+        linkProp.setInterfaceName(TEST_INTERFACE);
+        linkProp.addLinkAddress(new LinkAddress(TEST_IPV6_ADDRESS));
+        linkProp.addLinkAddress(new LinkAddress(TEST_IPV4_ADDRESS));
+        linkProp.addRoute(new RouteInfo(new IpPrefix("::/0"), null, TEST_INTERFACE, RTN_UNICAST));
+        linkProp.addRoute(new RouteInfo(new IpPrefix("0.0.0.0/0"), null, TEST_INTERFACE,
+                    RTN_UNICAST));
+        linkProp.addDnsServer(dns);
+        return new UpstreamNetworkState(linkProp, netCap, network);
+    }
+
+    private void assertOnlyOneV6AddressAndNoV4(LinkProperties lp) {
+        assertEquals(lp.getInterfaceName(), TEST_INTERFACE);
+        assertFalse(lp.hasIpv4Address());
+        final List<LinkAddress> addresses = lp.getLinkAddresses();
+        assertEquals(addresses.size(), 1);
+        final LinkAddress v6Address = addresses.get(0);
+        assertEquals(v6Address, new LinkAddress(TEST_IPV6_ADDRESS));
+    }
+
+    @Test
+    public void testUpdateIpv6Upstream() throws Exception {
+        // 1. Add first IpServer.
+        final IpServer firstServer = mock(IpServer.class);
+        mNotifyList.add(firstServer);
+        mIPv6TetheringCoordinator.addActiveDownstream(firstServer, STATE_TETHERED);
+        verify(firstServer).sendMessage(IpServer.CMD_IPV6_TETHER_UPDATE, 0, 0, null);
+        verifyNoMoreInteractions(firstServer);
+
+        // 2. Add second IpServer and it would not have ipv6 tethering.
+        final IpServer secondServer = mock(IpServer.class);
+        mNotifyList.add(secondServer);
+        mIPv6TetheringCoordinator.addActiveDownstream(secondServer, STATE_LOCAL_ONLY);
+        verifyNoMoreInteractions(secondServer);
+        reset(firstServer, secondServer);
+
+        // 3. No upstream.
+        mIPv6TetheringCoordinator.updateUpstreamNetworkState(null);
+        verify(secondServer).sendMessage(IpServer.CMD_IPV6_TETHER_UPDATE, 0, 0, null);
+        reset(firstServer, secondServer);
+
+        // 4. Update ipv6 mobile upstream.
+        final UpstreamNetworkState mobileUpstream = createDualStackUpstream(TRANSPORT_CELLULAR);
+        final ArgumentCaptor<LinkProperties> lp = ArgumentCaptor.forClass(LinkProperties.class);
+        mIPv6TetheringCoordinator.updateUpstreamNetworkState(mobileUpstream);
+        verify(firstServer).sendMessage(eq(IpServer.CMD_IPV6_TETHER_UPDATE), eq(0), eq(0),
+                lp.capture());
+        final LinkProperties v6OnlyLink = lp.getValue();
+        assertOnlyOneV6AddressAndNoV4(v6OnlyLink);
+        verifyNoMoreInteractions(firstServer);
+        verifyNoMoreInteractions(secondServer);
+        reset(firstServer, secondServer);
+
+        // 5. Remove first IpServer.
+        mNotifyList.remove(firstServer);
+        mIPv6TetheringCoordinator.removeActiveDownstream(firstServer);
+        verify(firstServer).sendMessage(IpServer.CMD_IPV6_TETHER_UPDATE, 0, 0, null);
+        verify(secondServer).sendMessage(eq(IpServer.CMD_IPV6_TETHER_UPDATE), eq(0), eq(0),
+                lp.capture());
+        final LinkProperties localOnlyLink = lp.getValue();
+        assertNotNull(localOnlyLink);
+        assertNotEquals(localOnlyLink, v6OnlyLink);
+        reset(firstServer, secondServer);
+
+        // 6. Remove second IpServer.
+        mNotifyList.remove(secondServer);
+        mIPv6TetheringCoordinator.removeActiveDownstream(secondServer);
+        verifyNoMoreInteractions(firstServer);
+        verify(secondServer).sendMessage(IpServer.CMD_IPV6_TETHER_UPDATE, 0, 0, null);
+    }
+}