diff --git a/staticlibs/framework/com/android/net/module/util/BestClock.java b/staticlibs/framework/com/android/net/module/util/BestClock.java
new file mode 100644
index 0000000..35391ad
--- /dev/null
+++ b/staticlibs/framework/com/android/net/module/util/BestClock.java
@@ -0,0 +1,78 @@
+/*
+ * Copyright (C) 2021 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.net.module.util;
+
+import android.util.Log;
+
+import java.time.Clock;
+import java.time.DateTimeException;
+import java.time.Instant;
+import java.time.ZoneId;
+import java.util.Arrays;
+
+/**
+ * Single {@link Clock} that will return the best available time from a set of
+ * prioritized {@link Clock} instances.
+ * <p>
+ * For example, when {@link SystemClock#currentNetworkTimeClock()} isn't able to
+ * provide the time, this class could use {@link Clock#systemUTC()} instead.
+ *
+ * Note that this is re-implemented based on {@code android.os.BestClock} to be used inside
+ * the mainline module. And the class does NOT support serialization.
+ *
+ * @hide
+ */
+final public class BestClock extends Clock {
+    private static final String TAG = "BestClock";
+    private final ZoneId mZone;
+    private final Clock[] mClocks;
+
+    public BestClock(ZoneId zone, Clock... clocks) {
+        super();
+        this.mZone = zone;
+        this.mClocks = clocks;
+    }
+
+    @Override
+    public long millis() {
+        for (Clock clock : mClocks) {
+            try {
+                return clock.millis();
+            } catch (DateTimeException e) {
+                // Ignore and attempt the next clock
+                Log.w(TAG, e.toString());
+            }
+        }
+        throw new DateTimeException(
+                "No clocks in " + Arrays.toString(mClocks) + " were able to provide time");
+    }
+
+    @Override
+    public ZoneId getZone() {
+        return mZone;
+    }
+
+    @Override
+    public Clock withZone(ZoneId zone) {
+        return new BestClock(zone, mClocks);
+    }
+
+    @Override
+    public Instant instant() {
+        return Instant.ofEpochMilli(millis());
+    }
+}
diff --git a/staticlibs/framework/com/android/net/module/util/PermissionUtils.java b/staticlibs/framework/com/android/net/module/util/PermissionUtils.java
index 3ab2070..0f3dc15 100644
--- a/staticlibs/framework/com/android/net/module/util/PermissionUtils.java
+++ b/staticlibs/framework/com/android/net/module/util/PermissionUtils.java
@@ -16,11 +16,14 @@
 
 package com.android.net.module.util;
 
+import static android.Manifest.permission.ACCESS_NETWORK_STATE;
+import static android.Manifest.permission.CONNECTIVITY_USE_RESTRICTED_NETWORKS;
 import static android.Manifest.permission.NETWORK_STACK;
 import static android.content.pm.PackageManager.PERMISSION_GRANTED;
 import static android.net.NetworkStack.PERMISSION_MAINLINE_NETWORK_STACK;
 
 import android.annotation.NonNull;
+import android.annotation.Nullable;
 import android.content.Context;
 import android.os.Binder;
 
@@ -84,6 +87,30 @@
     }
 
     /**
+     * If the CONNECTIVITY_USE_RESTRICTED_NETWORKS is not allowed for a particular process, throw a
+     * {@link SecurityException}.
+     *
+     * @param context {@link android.content.Context} for the process.
+     * @param message A message to include in the exception if it is thrown.
+     */
+    public static void enforceRestrictedNetworkPermission(
+            final @NonNull Context context, final @Nullable String message) {
+        context.enforceCallingOrSelfPermission(CONNECTIVITY_USE_RESTRICTED_NETWORKS, message);
+    }
+
+    /**
+     * If the ACCESS_NETWORK_STATE is not allowed for a particular process, throw a
+     * {@link SecurityException}.
+     *
+     * @param context {@link android.content.Context} for the process.
+     * @param message A message to include in the exception if it is thrown.
+     */
+    public static void enforceAccessNetworkStatePermission(
+            final @NonNull Context context, final @Nullable String message) {
+        context.enforceCallingOrSelfPermission(ACCESS_NETWORK_STATE, message);
+    }
+
+    /**
      * Return true if the context has DUMP permission.
      */
     public static boolean checkDumpPermission(Context context, String tag, PrintWriter pw) {
@@ -97,4 +124,24 @@
             return true;
         }
     }
+
+    /**
+     * Enforce that a given feature is available and if not, throw an
+     * {@link UnsupportedOperationException}.
+     *
+     * @param context {@link android.content.Context} for the process.
+     * @param feature the feature name to enforce.
+     * @param errorMessage an optional error message to include.
+     */
+    public static void enforceSystemFeature(final @NonNull Context context,
+            final @NonNull String feature, final @Nullable String errorMessage) {
+        final boolean hasSystemFeature =
+                context.getPackageManager().hasSystemFeature(feature);
+        if (!hasSystemFeature) {
+            if (null == errorMessage) {
+                throw new UnsupportedOperationException();
+            }
+            throw new UnsupportedOperationException(errorMessage);
+        }
+    }
 }
diff --git a/staticlibs/netd/libnetdutils/include/netdutils/Status.h b/staticlibs/netd/libnetdutils/include/netdutils/Status.h
index bc347d5..7b0bd47 100644
--- a/staticlibs/netd/libnetdutils/include/netdutils/Status.h
+++ b/staticlibs/netd/libnetdutils/include/netdutils/Status.h
@@ -42,7 +42,7 @@
     Status(int code, std::string msg) : mCode(code), mMsg(std::move(msg)) { assert(!ok()); }
 
     Status(android::base::Result<void> result)
-        : mCode(result.ok() ? 0 : result.error().code()),
+        : mCode(result.ok() ? 0 : static_cast<int>(result.error().code())),
           mMsg(result.ok() ? "" : result.error().message()) {}
 
     int code() const { return mCode; }
diff --git a/staticlibs/tests/unit/src/com/android/net/module/util/PermissionUtilsTest.kt b/staticlibs/tests/unit/src/com/android/net/module/util/PermissionUtilsTest.kt
index 6da5e7d..1b6cbcb 100644
--- a/staticlibs/tests/unit/src/com/android/net/module/util/PermissionUtilsTest.kt
+++ b/staticlibs/tests/unit/src/com/android/net/module/util/PermissionUtilsTest.kt
@@ -18,22 +18,28 @@
 
 import android.Manifest.permission.NETWORK_STACK
 import android.content.Context
+import android.content.pm.PackageManager
 import android.content.pm.PackageManager.PERMISSION_DENIED
 import android.content.pm.PackageManager.PERMISSION_GRANTED
 import android.net.NetworkStack.PERMISSION_MAINLINE_NETWORK_STACK
 import androidx.test.filters.SmallTest
 import androidx.test.runner.AndroidJUnit4
 import com.android.net.module.util.PermissionUtils.checkAnyPermissionOf
+import com.android.net.module.util.PermissionUtils.enforceAnyPermissionOf
 import com.android.net.module.util.PermissionUtils.enforceNetworkStackPermission
 import com.android.net.module.util.PermissionUtils.enforceNetworkStackPermissionOr
-import com.android.net.module.util.PermissionUtils.enforceAnyPermissionOf
+import com.android.net.module.util.PermissionUtils.enforceSystemFeature
+import org.junit.Assert
 import org.junit.Assert.assertFalse
 import org.junit.Assert.assertTrue
+import org.junit.Before
 import org.junit.Test
 import org.junit.runner.RunWith
+import org.mockito.ArgumentMatchers
 import org.mockito.ArgumentMatchers.any
 import org.mockito.Mockito.doReturn
 import org.mockito.Mockito.mock
+import kotlin.test.assertEquals
 import kotlin.test.assertFailsWith
 
 /** Tests for PermissionUtils */
@@ -43,6 +49,12 @@
     private val TEST_PERMISSION1 = "android.permission.TEST_PERMISSION1"
     private val TEST_PERMISSION2 = "android.permission.TEST_PERMISSION2"
     private val context = mock(Context::class.java)
+    private val packageManager = mock(PackageManager::class.java)
+
+    @Before
+    fun setup() {
+        doReturn(packageManager).`when`(context).packageManager
+    }
 
     @Test
     fun testEnforceAnyPermissionOf() {
@@ -90,4 +102,26 @@
         assertFailsWith<SecurityException>("Expect fail but permission granted.") {
             enforceNetworkStackPermissionOr(context, TEST_PERMISSION2) }
     }
+
+    private fun mockHasSystemFeature(featureName: String, hasFeature: Boolean) {
+        doReturn(hasFeature).`when`(packageManager)
+                .hasSystemFeature(ArgumentMatchers.eq(featureName))
+    }
+
+    @Test
+    fun testEnforceSystemFeature() {
+        val systemFeature = "test.system.feature"
+        val exceptionMessage = "test exception message"
+        mockHasSystemFeature(featureName = systemFeature, hasFeature = false)
+        val e = assertFailsWith<UnsupportedOperationException>("Should fail without feature") {
+            enforceSystemFeature(context, systemFeature, exceptionMessage) }
+        assertEquals(exceptionMessage, e.message)
+
+        mockHasSystemFeature(featureName = systemFeature, hasFeature = true)
+        try {
+            enforceSystemFeature(context, systemFeature, "")
+        } catch (e: UnsupportedOperationException) {
+            Assert.fail("Exception should have not been thrown with system feature enabled")
+        }
+    }
 }