diff --git a/Tethering/common/TetheringLib/src/android/net/TetheredClient.java b/Tethering/common/TetheringLib/src/android/net/TetheredClient.java
index 645b000..0b223f4 100644
--- a/Tethering/common/TetheringLib/src/android/net/TetheredClient.java
+++ b/Tethering/common/TetheringLib/src/android/net/TetheredClient.java
@@ -19,7 +19,6 @@
 import android.annotation.NonNull;
 import android.annotation.Nullable;
 import android.annotation.SystemApi;
-import android.annotation.TestApi;
 import android.os.Parcel;
 import android.os.Parcelable;
 
@@ -34,7 +33,6 @@
  * @hide
  */
 @SystemApi
-@TestApi
 public final class TetheredClient implements Parcelable {
     @NonNull
     private final MacAddress mMacAddress;
diff --git a/Tethering/common/TetheringLib/src/android/net/TetheringManager.java b/Tethering/common/TetheringLib/src/android/net/TetheringManager.java
index 88e0b42..97fb497 100644
--- a/Tethering/common/TetheringLib/src/android/net/TetheringManager.java
+++ b/Tethering/common/TetheringLib/src/android/net/TetheringManager.java
@@ -23,7 +23,6 @@
 import android.annotation.Nullable;
 import android.annotation.RequiresPermission;
 import android.annotation.SystemApi;
-import android.annotation.TestApi;
 import android.content.Context;
 import android.os.Bundle;
 import android.os.ConditionVariable;
@@ -55,7 +54,6 @@
  * @hide
  */
 @SystemApi
-@TestApi
 public class TetheringManager {
     private static final String TAG = TetheringManager.class.getSimpleName();
     private static final int DEFAULT_TIMEOUT_MS = 60_000;
diff --git a/Tethering/tests/privileged/src/android/net/ip/DadProxyTest.java b/Tethering/tests/privileged/src/android/net/ip/DadProxyTest.java
index 95e36fa..42a91aa 100644
--- a/Tethering/tests/privileged/src/android/net/ip/DadProxyTest.java
+++ b/Tethering/tests/privileged/src/android/net/ip/DadProxyTest.java
@@ -17,9 +17,9 @@
 package android.net.ip;
 
 import static android.system.OsConstants.IPPROTO_ICMPV6;
-import static android.system.OsConstants.IPPROTO_TCP;
 
-import static com.android.internal.util.BitUtils.uint16;
+import static com.android.net.module.util.IpUtils.icmpv6Checksum;
+import static com.android.net.module.util.NetworkStackConstants.ETHER_SRC_ADDR_OFFSET;
 
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertNotNull;
@@ -30,34 +30,29 @@
 import android.net.INetd;
 import android.net.InetAddresses;
 import android.net.MacAddress;
-import android.net.TestNetworkInterface;
-import android.net.TestNetworkManager;
 import android.net.util.InterfaceParams;
 import android.net.util.TetheringUtils;
 import android.os.Handler;
 import android.os.HandlerThread;
 import android.os.IBinder;
 import android.os.Looper;
-import android.system.ErrnoException;
-import android.system.Os;
 
 import androidx.test.InstrumentationRegistry;
 import androidx.test.filters.SmallTest;
 import androidx.test.runner.AndroidJUnit4;
 
-import com.android.net.module.util.IpUtils;
 import com.android.testutils.TapPacketReader;
+import com.android.testutils.TapPacketReaderRule;
 
 import org.junit.After;
 import org.junit.Before;
 import org.junit.BeforeClass;
+import org.junit.Rule;
 import org.junit.Test;
 import org.junit.runner.RunWith;
 import org.mockito.MockitoAnnotations;
 
-import java.io.FileDescriptor;
 import java.nio.ByteBuffer;
-import java.util.concurrent.atomic.AtomicReference;
 
 @RunWith(AndroidJUnit4.class)
 @SmallTest
@@ -65,16 +60,18 @@
     private static final int DATA_BUFFER_LEN = 4096;
     private static final int PACKET_TIMEOUT_MS = 5_000;
 
-    // TODO: make NetworkStackConstants accessible to this test and use the constant from there.
-    private static final int ETHER_SRC_ADDR_OFFSET = 6;
+    // Start the readers manually on a common handler shared with DadProxy, for simplicity
+    @Rule
+    public final TapPacketReaderRule mUpstreamReader = new TapPacketReaderRule(
+            DATA_BUFFER_LEN, false /* autoStart */);
+    @Rule
+    public final TapPacketReaderRule mTetheredReader = new TapPacketReaderRule(
+            DATA_BUFFER_LEN, false /* autoStart */);
 
-    private DadProxy mProxy;
-    TestNetworkInterface mUpstreamTestIface, mTetheredTestIface;
     private InterfaceParams mUpstreamParams, mTetheredParams;
     private HandlerThread mHandlerThread;
     private Handler mHandler;
     private TapPacketReader mUpstreamPacketReader, mTetheredPacketReader;
-    private FileDescriptor mUpstreamTapFd, mTetheredTapFd;
 
     private static INetd sNetd;
 
@@ -106,12 +103,12 @@
 
     @After
     public void tearDown() throws Exception {
+        mUpstreamReader.stop();
+        mTetheredReader.stop();
+
         if (mHandlerThread != null) {
-            mHandler.post(mUpstreamPacketReader::stop); // Also closes the socket
-            mHandler.post(mTetheredPacketReader::stop); // Also closes the socket
-            mUpstreamTapFd = null;
-            mTetheredTapFd = null;
             mHandlerThread.quitSafely();
+            mHandlerThread.join(PACKET_TIMEOUT_MS);
         }
 
         if (mTetheredParams != null) {
@@ -120,54 +117,20 @@
         if (mUpstreamParams != null) {
             sNetd.networkRemoveInterface(INetd.LOCAL_NET_ID, mUpstreamParams.name);
         }
-
-        if (mUpstreamTestIface != null) {
-            try {
-                Os.close(mUpstreamTestIface.getFileDescriptor().getFileDescriptor());
-            } catch (ErrnoException e) { }
-        }
-
-        if (mTetheredTestIface != null) {
-            try {
-                Os.close(mTetheredTestIface.getFileDescriptor().getFileDescriptor());
-            } catch (ErrnoException e) { }
-        }
-    }
-
-    private TestNetworkInterface setupTapInterface() {
-        final Instrumentation inst = InstrumentationRegistry.getInstrumentation();
-        AtomicReference<TestNetworkInterface> iface = new AtomicReference<>();
-
-        inst.getUiAutomation().adoptShellPermissionIdentity();
-        try {
-            final TestNetworkManager tnm = (TestNetworkManager) inst.getContext().getSystemService(
-                    Context.TEST_NETWORK_SERVICE);
-            iface.set(tnm.createTapInterface());
-        } finally {
-            inst.getUiAutomation().dropShellPermissionIdentity();
-        }
-
-        return iface.get();
     }
 
     private void setupTapInterfaces() {
         // Create upstream test iface.
-        mUpstreamTestIface = setupTapInterface();
-        mUpstreamParams = InterfaceParams.getByName(mUpstreamTestIface.getInterfaceName());
+        mUpstreamReader.start(mHandler);
+        mUpstreamParams = InterfaceParams.getByName(mUpstreamReader.iface.getInterfaceName());
         assertNotNull(mUpstreamParams);
-        mUpstreamTapFd = mUpstreamTestIface.getFileDescriptor().getFileDescriptor();
-        mUpstreamPacketReader = new TapPacketReader(mHandler, mUpstreamTapFd,
-                                                    DATA_BUFFER_LEN);
-        mHandler.post(mUpstreamPacketReader::start);
+        mUpstreamPacketReader = mUpstreamReader.getReader();
 
         // Create tethered test iface.
-        mTetheredTestIface = setupTapInterface();
-        mTetheredParams = InterfaceParams.getByName(mTetheredTestIface.getInterfaceName());
+        mTetheredReader.start(mHandler);
+        mTetheredParams = InterfaceParams.getByName(mTetheredReader.getIface().getInterfaceName());
         assertNotNull(mTetheredParams);
-        mTetheredTapFd = mTetheredTestIface.getFileDescriptor().getFileDescriptor();
-        mTetheredPacketReader = new TapPacketReader(mHandler, mTetheredTapFd,
-                                                    DATA_BUFFER_LEN);
-        mHandler.post(mTetheredPacketReader::start);
+        mTetheredPacketReader = mTetheredReader.getReader();
     }
 
     private static final int IPV6_HEADER_LEN = 40;
@@ -177,31 +140,6 @@
     private static final int ICMPV6_CHECKSUM_OFFSET = 2;
     private static final int ETHER_TYPE_IPV6 = 0x86dd;
 
-    // TODO: move the IpUtils code to frameworks/lib/net and link it statically.
-    private static int checksumFold(int sum) {
-        while (sum > 0xffff) {
-            sum = (sum >> 16) + (sum & 0xffff);
-        }
-        return sum;
-    }
-
-    // TODO: move the IpUtils code to frameworks/lib/net and link it statically.
-    private static short checksumAdjust(short checksum, short oldWord, short newWord) {
-        checksum = (short) ~checksum;
-        int tempSum = checksumFold(uint16(checksum) + uint16(newWord) + 0xffff - uint16(oldWord));
-        return (short) ~tempSum;
-    }
-
-    // TODO: move the IpUtils code to frameworks/lib/net and link it statically.
-    private static short icmpv6Checksum(ByteBuffer buf, int ipOffset, int transportOffset,
-            int transportLen) {
-        // The ICMPv6 checksum is the same as the TCP checksum, except the pseudo-header uses
-        // 58 (ICMPv6) instead of 6 (TCP). Calculate the TCP checksum, and then do an incremental
-        // checksum adjustment  for the change in the next header byte.
-        short checksum = IpUtils.tcpChecksum(buf, ipOffset, transportOffset, transportLen);
-        return checksumAdjust(checksum, (short) IPPROTO_TCP, (short) IPPROTO_ICMPV6);
-    }
-
     private static ByteBuffer createDadPacket(int type) {
         // Refer to buildArpPacket()
         int icmpLen = ICMPV6_NA_NS_LEN