diff --git a/staticlibs/framework/com/android/net/module/util/ConnectivitySettingsUtils.java b/staticlibs/framework/com/android/net/module/util/ConnectivitySettingsUtils.java
new file mode 100644
index 0000000..b7eb70b
--- /dev/null
+++ b/staticlibs/framework/com/android/net/module/util/ConnectivitySettingsUtils.java
@@ -0,0 +1,127 @@
+/*
+ * 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.annotation.NonNull;
+import android.annotation.Nullable;
+import android.content.ContentResolver;
+import android.content.Context;
+import android.provider.Settings;
+import android.text.TextUtils;
+
+/**
+ * Collection of connectivity settings utilities.
+ *
+ * @hide
+ */
+public class ConnectivitySettingsUtils {
+    public static final int PRIVATE_DNS_MODE_OFF = 1;
+    public static final int PRIVATE_DNS_MODE_OPPORTUNISTIC = 2;
+    public static final int PRIVATE_DNS_MODE_PROVIDER_HOSTNAME = 3;
+
+    public static final String PRIVATE_DNS_DEFAULT_MODE = "private_dns_default_mode";
+    public static final String PRIVATE_DNS_MODE = "private_dns_mode";
+    public static final String PRIVATE_DNS_MODE_OFF_STRING = "off";
+    public static final String PRIVATE_DNS_MODE_OPPORTUNISTIC_STRING = "opportunistic";
+    public static final String PRIVATE_DNS_MODE_PROVIDER_HOSTNAME_STRING = "hostname";
+    public static final String PRIVATE_DNS_SPECIFIER = "private_dns_specifier";
+
+    /**
+     * Get private DNS mode as string.
+     *
+     * @param mode One of the private DNS values.
+     * @return A string of private DNS mode.
+     */
+    public static String getPrivateDnsModeAsString(int mode) {
+        switch (mode) {
+            case PRIVATE_DNS_MODE_OFF:
+                return PRIVATE_DNS_MODE_OFF_STRING;
+            case PRIVATE_DNS_MODE_OPPORTUNISTIC:
+                return PRIVATE_DNS_MODE_OPPORTUNISTIC_STRING;
+            case PRIVATE_DNS_MODE_PROVIDER_HOSTNAME:
+                return PRIVATE_DNS_MODE_PROVIDER_HOSTNAME_STRING;
+            default:
+                throw new IllegalArgumentException("Invalid private dns mode: " + mode);
+        }
+    }
+
+    private static int getPrivateDnsModeAsInt(String mode) {
+        switch (mode) {
+            case "off":
+                return PRIVATE_DNS_MODE_OFF;
+            case "hostname":
+                return PRIVATE_DNS_MODE_PROVIDER_HOSTNAME;
+            case "opportunistic":
+                return PRIVATE_DNS_MODE_OPPORTUNISTIC;
+            default:
+                throw new IllegalArgumentException("Invalid private dns mode: " + mode);
+        }
+    }
+
+    /**
+     * Get private DNS mode from settings.
+     *
+     * @param context The Context to query the private DNS mode from settings.
+     * @return An integer of private DNS mode.
+     */
+    public static int getPrivateDnsMode(@NonNull Context context) {
+        final ContentResolver cr = context.getContentResolver();
+        String mode = Settings.Global.getString(cr, PRIVATE_DNS_MODE);
+        if (TextUtils.isEmpty(mode)) mode = Settings.Global.getString(cr, PRIVATE_DNS_DEFAULT_MODE);
+        // If both PRIVATE_DNS_MODE and PRIVATE_DNS_DEFAULT_MODE are not set, choose
+        // PRIVATE_DNS_MODE_OPPORTUNISTIC as default mode.
+        if (TextUtils.isEmpty(mode)) return PRIVATE_DNS_MODE_OPPORTUNISTIC;
+        return getPrivateDnsModeAsInt(mode);
+    }
+
+    /**
+     * Set private DNS mode to settings.
+     *
+     * @param context The {@link Context} to set the private DNS mode.
+     * @param mode The private dns mode. This should be one of the PRIVATE_DNS_MODE_* constants.
+     */
+    public static void setPrivateDnsMode(@NonNull Context context, int mode) {
+        if (!(mode == PRIVATE_DNS_MODE_OFF
+                || mode == PRIVATE_DNS_MODE_OPPORTUNISTIC
+                || mode == PRIVATE_DNS_MODE_PROVIDER_HOSTNAME)) {
+            throw new IllegalArgumentException("Invalid private dns mode: " + mode);
+        }
+        Settings.Global.putString(context.getContentResolver(), PRIVATE_DNS_MODE,
+                getPrivateDnsModeAsString(mode));
+    }
+
+    /**
+     * Get specific private dns provider name from {@link Settings}.
+     *
+     * @param context The {@link Context} to query the setting.
+     * @return The specific private dns provider name, or null if no setting value.
+     */
+    @Nullable
+    public static String getPrivateDnsHostname(@NonNull Context context) {
+        return Settings.Global.getString(context.getContentResolver(), PRIVATE_DNS_SPECIFIER);
+    }
+
+    /**
+     * Set specific private dns provider name to {@link Settings}.
+     *
+     * @param context The {@link Context} to set the setting.
+     * @param specifier The specific private dns provider name.
+     */
+    public static void setPrivateDnsHostname(@NonNull Context context, @Nullable String specifier) {
+        Settings.Global.putString(context.getContentResolver(), PRIVATE_DNS_SPECIFIER, specifier);
+    }
+}
diff --git a/staticlibs/framework/com/android/net/module/util/NetworkStackConstants.java b/staticlibs/framework/com/android/net/module/util/NetworkStackConstants.java
index b7062e7..f7151d7 100644
--- a/staticlibs/framework/com/android/net/module/util/NetworkStackConstants.java
+++ b/staticlibs/framework/com/android/net/module/util/NetworkStackConstants.java
@@ -148,7 +148,10 @@
     public static final int ICMPV6_ND_OPTION_RDNSS = 25;
     public static final int ICMPV6_ND_OPTION_PREF64 = 38;
 
+    public static final int ICMPV6_RS_HEADER_LEN = 8;
     public static final int ICMPV6_RA_HEADER_LEN = 16;
+    public static final int ICMPV6_NS_HEADER_LEN = 24;
+    public static final int ICMPV6_NA_HEADER_LEN = 24;
 
     public static final int NEIGHBOR_ADVERTISEMENT_FLAG_ROUTER    = 1 << 31;
     public static final int NEIGHBOR_ADVERTISEMENT_FLAG_SOLICITED = 1 << 30;
diff --git a/staticlibs/tests/unit/Android.bp b/staticlibs/tests/unit/Android.bp
index 45a89b0..5c5a431 100644
--- a/staticlibs/tests/unit/Android.bp
+++ b/staticlibs/tests/unit/Android.bp
@@ -23,7 +23,8 @@
     ],
     visibility: [
         "//frameworks/base/packages/Tethering/tests/integration",
-        "//packages/modules/Connectivity/Tethering/tests/integration",
+        "//packages/modules/Connectivity/tests:__subpackages__",
+        "//packages/modules/Connectivity/Tethering/tests:__subpackages__",
         "//packages/modules/NetworkStack/tests/integration",
     ]
 }
diff --git a/staticlibs/testutils/devicetests/com/android/testutils/TestHttpServer.kt b/staticlibs/testutils/devicetests/com/android/testutils/TestHttpServer.kt
index 7aae8e3..39ce487 100644
--- a/staticlibs/testutils/devicetests/com/android/testutils/TestHttpServer.kt
+++ b/staticlibs/testutils/devicetests/com/android/testutils/TestHttpServer.kt
@@ -54,12 +54,12 @@
     fun addResponse(
         uri: Uri,
         statusCode: Response.IStatus,
-        locationHeader: String? = null,
+        headers: Map<String, String>? = null,
         content: String = ""
     ) {
         addResponse(Request(uri.path
                 ?: "", Method.GET, uri.query ?: ""),
-                statusCode, locationHeader, content)
+                statusCode, headers, content)
     }
 
     /**
@@ -68,11 +68,13 @@
     fun addResponse(
         request: Request,
         statusCode: Response.IStatus,
-        locationHeader: String? = null,
+        headers: Map<String, String>? = null,
         content: String = ""
     ) {
         val response = newFixedLengthResponse(statusCode, "text/plain", content)
-        locationHeader?.let { response.addHeader("Location", it) }
+        headers?.forEach {
+            (key, value) -> response.addHeader(key, value)
+        }
         responses[request] = response
     }
 
diff --git a/staticlibs/testutils/devicetests/com/android/testutils/TestableNetworkOfferCallback.kt b/staticlibs/testutils/devicetests/com/android/testutils/TestableNetworkOfferCallback.kt
new file mode 100644
index 0000000..21bd60c
--- /dev/null
+++ b/staticlibs/testutils/devicetests/com/android/testutils/TestableNetworkOfferCallback.kt
@@ -0,0 +1,75 @@
+/*
+ * 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.testutils
+
+import android.net.NetworkCapabilities
+import android.net.NetworkProvider
+import android.net.NetworkRequest
+import android.util.Log
+import com.android.net.module.util.ArrayTrackRecord
+import kotlin.test.fail
+
+class TestableNetworkOfferCallback(val timeoutMs: Long, private val noCallbackTimeoutMs: Long)
+            : NetworkProvider.NetworkOfferCallback {
+    private val TAG = this::class.simpleName
+    val history = ArrayTrackRecord<CallbackEntry>().newReadHead()
+
+    sealed class CallbackEntry {
+        data class OnNetworkNeeded(val request: NetworkRequest) : CallbackEntry()
+        data class OnNetworkUnneeded(val request: NetworkRequest) : CallbackEntry()
+    }
+
+    /**
+     * Called by the system when a network for this offer is needed to satisfy some
+     * networking request.
+     */
+    override fun onNetworkNeeded(request: NetworkRequest) {
+        Log.d(TAG, "onNetworkNeeded $request")
+        history.add(CallbackEntry.OnNetworkNeeded(request))
+    }
+
+    /**
+     * Called by the system when this offer is no longer valuable for this request.
+     */
+    override fun onNetworkUnneeded(request: NetworkRequest) {
+        Log.d(TAG, "onNetworkUnneeded $request")
+        history.add(CallbackEntry.OnNetworkUnneeded(request))
+    }
+
+    inline fun <reified T : CallbackEntry> expectCallbackThat(
+        crossinline predicate: (T) -> Boolean
+    ) {
+        val event = history.poll(timeoutMs)
+                ?: fail("Did not receive callback after ${timeoutMs}ms")
+        if (event !is T || !predicate(event)) fail("Received unexpected callback $event")
+    }
+
+    fun expectOnNetworkNeeded(capabilities: NetworkCapabilities) =
+            expectCallbackThat<CallbackEntry.OnNetworkNeeded> {
+                it.request.canBeSatisfiedBy(capabilities)
+            }
+
+    fun expectOnNetworkUnneeded(capabilities: NetworkCapabilities) =
+            expectCallbackThat<CallbackEntry.OnNetworkUnneeded> {
+                it.request.canBeSatisfiedBy(capabilities)
+            }
+
+    fun assertNoCallback() {
+        val cb = history.poll(noCallbackTimeoutMs)
+        if (null != cb) fail("Expected no callback but got $cb")
+    }
+}
\ No newline at end of file
diff --git a/staticlibs/testutils/devicetests/com/android/testutils/TestableNetworkStatsProvider.kt b/staticlibs/testutils/devicetests/com/android/testutils/TestableNetworkStatsProvider.kt
index d5c3a2a..d034a7d 100644
--- a/staticlibs/testutils/devicetests/com/android/testutils/TestableNetworkStatsProvider.kt
+++ b/staticlibs/testutils/devicetests/com/android/testutils/TestableNetworkStatsProvider.kt
@@ -23,6 +23,7 @@
 import kotlin.test.fail
 
 private const val DEFAULT_TIMEOUT_MS = 200L
+const val TOKEN_ANY = -1
 
 open class TestableNetworkStatsProvider(
     val defaultTimeoutMs: Long = DEFAULT_TIMEOUT_MS
@@ -49,8 +50,13 @@
         history.add(CallbackType.OnSetAlert(quotaBytes))
     }
 
-    fun expectOnRequestStatsUpdate(token: Int, timeout: Long = defaultTimeoutMs) {
-        assertEquals(CallbackType.OnRequestStatsUpdate(token), history.poll(timeout))
+    fun expectOnRequestStatsUpdate(token: Int, timeout: Long = defaultTimeoutMs): Int {
+        val event = history.poll(timeout)
+        assertTrue(event is CallbackType.OnRequestStatsUpdate)
+        if (token != TOKEN_ANY) {
+            assertEquals(token, event.token)
+        }
+        return token
     }
 
     fun expectOnSetLimit(iface: String?, quotaBytes: Long, timeout: Long = defaultTimeoutMs) {