diff --git a/Tethering/common/TetheringLib/src/android/net/TetheringManager.java b/Tethering/common/TetheringLib/src/android/net/TetheringManager.java
index c137b49..9e6e34e 100644
--- a/Tethering/common/TetheringLib/src/android/net/TetheringManager.java
+++ b/Tethering/common/TetheringLib/src/android/net/TetheringManager.java
@@ -290,6 +290,23 @@
         getConnector(c -> c.registerTetheringEventCallback(mCallback, pkgName));
     }
 
+    /** @hide */
+    @Override
+    protected void finalize() throws Throwable {
+        final String pkgName = mContext.getOpPackageName();
+        Log.i(TAG, "unregisterTetheringEventCallback:" + pkgName);
+        // 1. It's generally not recommended to perform long operations in finalize, but while
+        // unregisterTetheringEventCallback does an IPC, it's a oneway IPC so should not block.
+        // 2. If the connector is not yet connected, TetheringManager is impossible to finalize
+        // because the connector polling thread strong reference the TetheringManager object. So
+        // it's guaranteed that registerTetheringEventCallback was already called before calling
+        // unregisterTetheringEventCallback in finalize.
+        if (mConnector == null) Log.wtf(TAG, "null connector in finalize!");
+        getConnector(c -> c.unregisterTetheringEventCallback(mCallback, pkgName));
+
+        super.finalize();
+    }
+
     private void startPollingForConnector() {
         new Thread(() -> {
             while (true) {
diff --git a/Tethering/tests/unit/src/com/android/networkstack/tethering/TetheringServiceTest.java b/Tethering/tests/unit/src/com/android/networkstack/tethering/TetheringServiceTest.java
index 0052267..f664d5d 100644
--- a/Tethering/tests/unit/src/com/android/networkstack/tethering/TetheringServiceTest.java
+++ b/Tethering/tests/unit/src/com/android/networkstack/tethering/TetheringServiceTest.java
@@ -28,6 +28,7 @@
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertNotNull;
 import static org.junit.Assert.assertNull;
+import static org.junit.Assert.fail;
 import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.ArgumentMatchers.anyBoolean;
 import static org.mockito.ArgumentMatchers.eq;
@@ -46,6 +47,7 @@
 import android.net.TetheringRequestParcel;
 import android.net.ip.IpServer;
 import android.os.Bundle;
+import android.os.ConditionVariable;
 import android.os.Handler;
 import android.os.IBinder;
 import android.os.ResultReceiver;
@@ -63,7 +65,6 @@
 import org.junit.Rule;
 import org.junit.Test;
 import org.junit.runner.RunWith;
-import org.mockito.Matchers;
 import org.mockito.Mock;
 import org.mockito.MockitoAnnotations;
 
@@ -503,38 +504,80 @@
         });
     }
 
+    private class ConnectorSupplier<T> implements Supplier<T> {
+        private T mResult = null;
+
+        public void set(T result) {
+            mResult = result;
+        }
+
+        @Override
+        public T get() {
+            return mResult;
+        }
+    }
+
+    private void forceGc() {
+        System.gc();
+        System.runFinalization();
+        System.gc();
+    }
+
     @Test
     public void testTetheringManagerLeak() throws Exception {
         runAsAccessNetworkState((none) -> {
             final ArrayList<ITetheringEventCallback> callbacks = new ArrayList<>();
+            final ConditionVariable registeredCv = new ConditionVariable(false);
             doAnswer((invocation) -> {
                 final Object[] args = invocation.getArguments();
                 callbacks.add((ITetheringEventCallback) args[0]);
+                registeredCv.open();
                 return null;
-            }).when(mTethering).registerTetheringEventCallback(Matchers.anyObject());
+            }).when(mTethering).registerTetheringEventCallback(any());
 
-            final Supplier<IBinder> supplier = () -> mMockConnector.getIBinder();
+            doAnswer((invocation) -> {
+                final Object[] args = invocation.getArguments();
+                callbacks.remove((ITetheringEventCallback) args[0]);
+                return null;
+            }).when(mTethering).unregisterTetheringEventCallback(any());
+
+            final ConnectorSupplier<IBinder> supplier = new ConnectorSupplier<>();
 
             TetheringManager tm = new TetheringManager(mMockConnector.getService(), supplier);
             assertNotNull(tm);
-            assertEquals("Internal callback is not registered", 1, callbacks.size());
+            assertEquals("Internal callback should not be registered", 0, callbacks.size());
 
-            final WeakReference weakTm = new WeakReference(tm);
+            final WeakReference<TetheringManager> weakTm = new WeakReference(tm);
             assertNotNull(weakTm.get());
 
+            // TetheringManager couldn't be GCed because pollingConnector thread implicitly
+            // reference TetheringManager object.
             tm = null;
+            forceGc();
+            assertNotNull(weakTm.get());
+
+            // After getting connector, pollingConnector thread stops and internal callback is
+            // registered.
+            supplier.set(mMockConnector.getIBinder());
+            final long timeout = 500L;
+            if (!registeredCv.block(timeout)) {
+                fail("TetheringManager poll connector fail after " + timeout + " ms");
+            }
+            assertEquals("Internal callback is not registered", 1, callbacks.size());
+            assertNotNull(weakTm.get());
+
             final int attempts = 100;
             final long waitIntervalMs = 50;
             for (int i = 0; i < attempts; i++) {
-                System.gc();
-                System.runFinalization();
-                System.gc();
+                forceGc();
                 if (weakTm.get() == null) break;
 
                 Thread.sleep(waitIntervalMs);
             }
             assertNull("TetheringManager weak reference still not null after " + attempts
                     + " attempts", weakTm.get());
+
+            assertEquals("Internal callback is not unregistered", 0, callbacks.size());
         });
     }
 }
diff --git a/framework/src/android/net/NetworkInfo.java b/framework/src/android/net/NetworkInfo.java
index bb23494..433933f 100644
--- a/framework/src/android/net/NetworkInfo.java
+++ b/framework/src/android/net/NetworkInfo.java
@@ -179,21 +179,19 @@
 
     /** {@hide} */
     @UnsupportedAppUsage
-    public NetworkInfo(NetworkInfo source) {
-        if (source != null) {
-            synchronized (source) {
-                mNetworkType = source.mNetworkType;
-                mSubtype = source.mSubtype;
-                mTypeName = source.mTypeName;
-                mSubtypeName = source.mSubtypeName;
-                mState = source.mState;
-                mDetailedState = source.mDetailedState;
-                mReason = source.mReason;
-                mExtraInfo = source.mExtraInfo;
-                mIsFailover = source.mIsFailover;
-                mIsAvailable = source.mIsAvailable;
-                mIsRoaming = source.mIsRoaming;
-            }
+    public NetworkInfo(@NonNull NetworkInfo source) {
+        synchronized (source) {
+            mNetworkType = source.mNetworkType;
+            mSubtype = source.mSubtype;
+            mTypeName = source.mTypeName;
+            mSubtypeName = source.mSubtypeName;
+            mState = source.mState;
+            mDetailedState = source.mDetailedState;
+            mReason = source.mReason;
+            mExtraInfo = source.mExtraInfo;
+            mIsFailover = source.mIsFailover;
+            mIsAvailable = source.mIsAvailable;
+            mIsRoaming = source.mIsRoaming;
         }
     }
 
@@ -479,7 +477,7 @@
      * @param detailedState the {@link DetailedState}.
      * @param reason a {@code String} indicating the reason for the state change,
      * if one was supplied. May be {@code null}.
-     * @param extraInfo an optional {@code String} providing addditional network state
+     * @param extraInfo an optional {@code String} providing additional network state
      * information passed up from the lower networking layers.
      * @deprecated Use {@link NetworkCapabilities} instead.
      */
@@ -491,6 +489,11 @@
             this.mState = stateMap.get(detailedState);
             this.mReason = reason;
             this.mExtraInfo = extraInfo;
+            // Catch both the case where detailedState is null and the case where it's some
+            // unknown value
+            if (null == mState) {
+                throw new NullPointerException("Unknown DetailedState : " + detailedState);
+            }
         }
     }
 
diff --git a/tests/cts/net/src/android/net/cts/ConnectivityManagerTest.java b/tests/cts/net/src/android/net/cts/ConnectivityManagerTest.java
index 99cfdc2..9606960 100644
--- a/tests/cts/net/src/android/net/cts/ConnectivityManagerTest.java
+++ b/tests/cts/net/src/android/net/cts/ConnectivityManagerTest.java
@@ -2829,6 +2829,19 @@
             });
     }
 
+    /**
+     *  The networks used in this test are real networks and as such they can see seemingly random
+     *  updates of their capabilities or link properties as conditions change, e.g. the network
+     *  loses validation or IPv4 shows up. Many tests should simply treat these callbacks as
+     *  spurious.
+     */
+    private void assertNoCallbackExceptCapOrLpChange(
+            @NonNull final TestableNetworkCallback cb) {
+        cb.assertNoCallbackThat(NO_CALLBACK_TIMEOUT_MS,
+                c -> !(c instanceof CallbackEntry.CapabilitiesChanged
+                        || c instanceof CallbackEntry.LinkPropertiesChanged));
+    }
+
     @AppModeFull(reason = "Cannot get WifiManager in instant app mode")
     @Test
     public void testMobileDataPreferredUids() throws Exception {
@@ -2861,8 +2874,7 @@
             // CtsNetTestCases uid is not listed in MOBILE_DATA_PREFERRED_UIDS setting, so the
             // per-app default network should be same as system default network.
             waitForAvailable(systemDefaultCb, wifiNetwork);
-            defaultTrackingCb.eventuallyExpect(CallbackEntry.AVAILABLE, NETWORK_CALLBACK_TIMEOUT_MS,
-                    entry -> wifiNetwork.equals(entry.getNetwork()));
+            waitForAvailable(defaultTrackingCb, wifiNetwork);
             // Active network for CtsNetTestCases uid should be wifi now.
             assertEquals(wifiNetwork, mCm.getActiveNetwork());
 
@@ -2872,10 +2884,10 @@
             newMobileDataPreferredUids.add(uid);
             ConnectivitySettingsManager.setMobileDataPreferredUids(
                     mContext, newMobileDataPreferredUids);
-            defaultTrackingCb.eventuallyExpect(CallbackEntry.AVAILABLE, NETWORK_CALLBACK_TIMEOUT_MS,
-                    entry -> cellNetwork.equals(entry.getNetwork()));
-            // System default network doesn't change.
-            systemDefaultCb.assertNoCallback();
+            waitForAvailable(defaultTrackingCb, cellNetwork);
+            // No change for system default network. Expect no callback except CapabilitiesChanged
+            // or LinkPropertiesChanged which may be triggered randomly from wifi network.
+            assertNoCallbackExceptCapOrLpChange(systemDefaultCb);
             // Active network for CtsNetTestCases uid should change to cell, too.
             assertEquals(cellNetwork, mCm.getActiveNetwork());
 
@@ -2884,10 +2896,10 @@
             newMobileDataPreferredUids.remove(uid);
             ConnectivitySettingsManager.setMobileDataPreferredUids(
                     mContext, newMobileDataPreferredUids);
-            defaultTrackingCb.eventuallyExpect(CallbackEntry.AVAILABLE, NETWORK_CALLBACK_TIMEOUT_MS,
-                    entry -> wifiNetwork.equals(entry.getNetwork()));
-            // System default network still doesn't change.
-            systemDefaultCb.assertNoCallback();
+            waitForAvailable(defaultTrackingCb, wifiNetwork);
+            // No change for system default network. Expect no callback except CapabilitiesChanged
+            // or LinkPropertiesChanged which may be triggered randomly from wifi network.
+            assertNoCallbackExceptCapOrLpChange(systemDefaultCb);
             // Active network for CtsNetTestCases uid should change back to wifi.
             assertEquals(wifiNetwork, mCm.getActiveNetwork());
         } finally {
diff --git a/tests/unit/java/com/android/server/connectivity/Nat464XlatTest.java b/tests/unit/java/com/android/server/connectivity/Nat464XlatTest.java
index f358726..aa4c4e3 100644
--- a/tests/unit/java/com/android/server/connectivity/Nat464XlatTest.java
+++ b/tests/unit/java/com/android/server/connectivity/Nat464XlatTest.java
@@ -109,8 +109,8 @@
 
         mNai.linkProperties = new LinkProperties();
         mNai.linkProperties.setInterfaceName(BASE_IFACE);
-        mNai.networkInfo = new NetworkInfo(null);
-        mNai.networkInfo.setType(ConnectivityManager.TYPE_WIFI);
+        mNai.networkInfo = new NetworkInfo(ConnectivityManager.TYPE_WIFI, 0 /* subtype */,
+                null /* typeName */, null /* subtypeName */);
         mNai.networkCapabilities = new NetworkCapabilities();
         markNetworkConnected();
         when(mNai.connService()).thenReturn(mConnectivity);