diff --git a/Tethering/src/com/android/networkstack/tethering/PrivateAddressCoordinator.java b/Tethering/src/com/android/networkstack/tethering/PrivateAddressCoordinator.java
index 6c0ca82..6f3e865 100644
--- a/Tethering/src/com/android/networkstack/tethering/PrivateAddressCoordinator.java
+++ b/Tethering/src/com/android/networkstack/tethering/PrivateAddressCoordinator.java
@@ -79,6 +79,7 @@
     private final TetheringConfiguration mConfig;
     // keyed by downstream type(TetheringManager.TETHERING_*).
     private final ArrayMap<AddressKey, LinkAddress> mCachedAddresses;
+    private final Random mRandom;
 
     public PrivateAddressCoordinator(Context context, TetheringConfiguration config) {
         mDownstreams = new ArraySet<>();
@@ -95,6 +96,7 @@
 
         mTetheringPrefixes = new ArrayList<>(Arrays.asList(new IpPrefix("192.168.0.0/16"),
             new IpPrefix("172.16.0.0/12"), new IpPrefix("10.0.0.0/8")));
+        mRandom = new Random();
     }
 
     /**
@@ -263,12 +265,13 @@
         // is less than 127.0.0.0 = 0x7f000000 = 2130706432.
         //
         // Additionally, it makes debug output easier to read by making the numbers smaller.
-        final int randomPrefixStart = getRandomInt() & ~prefixRangeMask & prefixMask;
+        final int randomInt = getRandomInt();
+        final int randomPrefixStart = randomInt & ~prefixRangeMask & prefixMask;
 
         // A random offset within the prefix. Used to determine the local address once the prefix
         // is selected. It does not result in an IPv4 address ending in .0, .1, or .255
-        // For a PREFIX_LENGTH of 255, this is a number between 2 and 254.
-        final int subAddress = getSanitizedSubAddr(~prefixMask);
+        // For a PREFIX_LENGTH of 24, this is a number between 2 and 254.
+        final int subAddress = getSanitizedSubAddr(randomInt, ~prefixMask);
 
         // Find a prefix length PREFIX_LENGTH between randomPrefixStart and the end of the block,
         // such that the prefix does not conflict with any upstream.
@@ -310,12 +313,12 @@
     /** Get random int which could be used to generate random address. */
     @VisibleForTesting
     public int getRandomInt() {
-        return (new Random()).nextInt();
+        return mRandom.nextInt();
     }
 
     /** Get random subAddress and avoid selecting x.x.x.0, x.x.x.1 and x.x.x.255 address. */
-    private int getSanitizedSubAddr(final int subAddrMask) {
-        final int randomSubAddr = getRandomInt() & subAddrMask;
+    private int getSanitizedSubAddr(final int randomInt, final int subAddrMask) {
+        final int randomSubAddr = randomInt & subAddrMask;
         // If prefix length > 30, the selecting speace would be less than 4 which may be hard to
         // avoid 3 consecutive address.
         if (PREFIX_LENGTH > 30) return randomSubAddr;
diff --git a/service/ServiceConnectivityResources/res/values/strings.xml b/service/ServiceConnectivityResources/res/values/strings.xml
index b2fa5f5..246155e 100644
--- a/service/ServiceConnectivityResources/res/values/strings.xml
+++ b/service/ServiceConnectivityResources/res/values/strings.xml
@@ -29,6 +29,15 @@
     <!-- A notification is shown when a captive portal network is detected.  This is the notification's message. -->
     <string name="network_available_sign_in_detailed"><xliff:g id="network_ssid">%1$s</xliff:g></string>
 
+    <!-- A notification is shown when the system detected no internet access on a mobile network, possibly because the user is out of data, and a webpage is available to get Internet access (possibly by topping up or getting a subscription).  This is the notification's title. -->
+    <string name="mobile_network_available_no_internet">No internet</string>
+
+    <!-- A notification is shown when the system detected no internet access on a mobile network, possibly because the user is out of data, and a webpage is available to get Internet access (possibly by topping up or getting a subscription).  This is the notification's message. -->
+    <string name="mobile_network_available_no_internet_detailed">You may be out of data from <xliff:g id="network_carrier" example="Android Mobile">%1$s</xliff:g>. Tap for options.</string>
+
+    <!-- A notification is shown when the system detected no internet access on a mobile network, possibly because the user is out of data, and a webpage is available to get Internet access (possibly by topping up or getting a subscription).  This is the notification's message when the carrier is unknown. -->
+    <string name="mobile_network_available_no_internet_detailed_unknown_carrier">You may be out of data. Tap for options.</string>
+
     <!-- A notification is shown when the user connects to a Wi-Fi network and the system detects that that network has no Internet access. This is the notification's title. -->
     <string name="wifi_no_internet"><xliff:g id="network_ssid" example="GoogleGuest">%1$s</xliff:g> has no internet access</string>
 
diff --git a/service/src/com/android/server/connectivity/NetworkNotificationManager.java b/service/src/com/android/server/connectivity/NetworkNotificationManager.java
index bc13592..7707122 100644
--- a/service/src/com/android/server/connectivity/NetworkNotificationManager.java
+++ b/service/src/com/android/server/connectivity/NetworkNotificationManager.java
@@ -243,7 +243,7 @@
                     details = r.getString(R.string.network_available_sign_in_detailed, name);
                     break;
                 case TRANSPORT_CELLULAR:
-                    title = r.getString(R.string.network_available_sign_in, 0);
+                    title = r.getString(R.string.mobile_network_available_no_internet);
                     // TODO: Change this to pull from NetworkInfo once a printable
                     // name has been added to it
                     NetworkSpecifier specifier = nai.networkCapabilities.getNetworkSpecifier();
@@ -252,8 +252,16 @@
                         subId = ((TelephonyNetworkSpecifier) specifier).getSubscriptionId();
                     }
 
-                    details = mTelephonyManager.createForSubscriptionId(subId)
+                    final String operatorName = mTelephonyManager.createForSubscriptionId(subId)
                             .getNetworkOperatorName();
+                    if (TextUtils.isEmpty(operatorName)) {
+                        details = r.getString(R.string
+                                .mobile_network_available_no_internet_detailed_unknown_carrier);
+                    } else {
+                        details = r.getString(
+                                R.string.mobile_network_available_no_internet_detailed,
+                                operatorName);
+                    }
                     break;
                 default:
                     title = r.getString(R.string.network_available_sign_in, 0);
diff --git a/staticlibs/device/com/android/net/module/util/netlink/NetlinkMessage.java b/staticlibs/device/com/android/net/module/util/netlink/NetlinkMessage.java
index 9e1e26e..111e0ba 100644
--- a/staticlibs/device/com/android/net/module/util/netlink/NetlinkMessage.java
+++ b/staticlibs/device/com/android/net/module/util/netlink/NetlinkMessage.java
@@ -16,12 +16,17 @@
 
 package com.android.net.module.util.netlink;
 
+import static com.android.net.module.util.netlink.xfrm.XfrmNetlinkMessage.NETLINK_XFRM;
+
 import android.system.OsConstants;
 
 import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
 
+import com.android.net.module.util.netlink.xfrm.XfrmNetlinkMessage;
+
 import java.nio.ByteBuffer;
+import java.nio.ByteOrder;
 
 /**
  * NetlinkMessage base class for other, more specific netlink message types.
@@ -75,6 +80,8 @@
             parsed = parseInetDiagMessage(nlmsghdr, byteBuffer);
         } else if (nlFamily == OsConstants.NETLINK_NETFILTER) {
             parsed = parseNfMessage(nlmsghdr, byteBuffer);
+        } else if (nlFamily == NETLINK_XFRM) {
+            parsed = parseXfrmMessage(nlmsghdr, byteBuffer);
         } else {
             parsed = null;
         }
@@ -168,4 +175,19 @@
             default: return null;
         }
     }
+
+    @Nullable
+    private static NetlinkMessage parseXfrmMessage(
+            @NonNull final StructNlMsgHdr nlmsghdr, @NonNull final ByteBuffer byteBuffer) {
+        return (NetlinkMessage) XfrmNetlinkMessage.parseXfrmInternal(nlmsghdr, byteBuffer);
+    }
+
+    /** A convenient method to create a ByteBuffer for encoding a new message */
+    protected static ByteBuffer newNlMsgByteBuffer(int payloadLen) {
+        final int length = StructNlMsgHdr.STRUCT_SIZE + payloadLen;
+        final ByteBuffer byteBuffer = ByteBuffer.allocate(length);
+        byteBuffer.order(ByteOrder.nativeOrder());
+
+        return byteBuffer;
+    }
 }
diff --git a/staticlibs/device/com/android/net/module/util/netlink/StructNlMsgHdr.java b/staticlibs/device/com/android/net/module/util/netlink/StructNlMsgHdr.java
index 5052cb8..ff37639 100644
--- a/staticlibs/device/com/android/net/module/util/netlink/StructNlMsgHdr.java
+++ b/staticlibs/device/com/android/net/module/util/netlink/StructNlMsgHdr.java
@@ -128,6 +128,14 @@
         nlmsg_pid = 0;
     }
 
+    public StructNlMsgHdr(int payloadLen, short type, short flags, int seq) {
+        nlmsg_len = StructNlMsgHdr.STRUCT_SIZE + payloadLen;
+        nlmsg_type = type;
+        nlmsg_flags = flags;
+        nlmsg_seq = seq;
+        nlmsg_pid = 0;
+    }
+
     /**
      * Write netlink message header to ByteBuffer.
      */
diff --git a/staticlibs/device/com/android/net/module/util/netlink/xfrm/XfrmNetlinkGetSaMessage.java b/staticlibs/device/com/android/net/module/util/netlink/xfrm/XfrmNetlinkGetSaMessage.java
new file mode 100644
index 0000000..680a7ca
--- /dev/null
+++ b/staticlibs/device/com/android/net/module/util/netlink/xfrm/XfrmNetlinkGetSaMessage.java
@@ -0,0 +1,116 @@
+/*
+ * Copyright (C) 2023 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.netlink.xfrm;
+
+import static com.android.net.module.util.netlink.StructNlMsgHdr.NLM_F_REQUEST;
+import static com.android.net.module.util.netlink.xfrm.XfrmNetlinkMessage.XFRM_MSG_GETSA;
+
+import android.system.OsConstants;
+
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+
+import com.android.net.module.util.Struct;
+import com.android.net.module.util.netlink.StructNlMsgHdr;
+
+import java.net.Inet4Address;
+import java.net.InetAddress;
+import java.nio.ByteBuffer;
+
+/**
+ * An XfrmNetlinkMessage subclass for XFRM_MSG_GETSA messages.
+ *
+ * <p>see include/uapi/linux/xfrm.h
+ *
+ * <p>XFRM_MSG_GETSA syntax
+ *
+ * <ul>
+ *   <li>TLV: xfrm_usersa_id
+ *   <li>Optional Attributes: XFRMA_MARK, XFRMA_SRCADDR
+ * </ul>
+ *
+ * @hide
+ */
+public class XfrmNetlinkGetSaMessage extends XfrmNetlinkMessage {
+    @NonNull private final StructXfrmUsersaId mXfrmUsersaId;
+
+    private XfrmNetlinkGetSaMessage(
+            @NonNull final StructNlMsgHdr header, @NonNull final StructXfrmUsersaId xfrmUsersaId) {
+        super(header);
+        mXfrmUsersaId = xfrmUsersaId;
+    }
+
+    private XfrmNetlinkGetSaMessage(
+            @NonNull final StructNlMsgHdr header,
+            @NonNull final InetAddress destAddress,
+            long spi,
+            short proto) {
+        super(header);
+
+        final int family =
+                destAddress instanceof Inet4Address ? OsConstants.AF_INET : OsConstants.AF_INET6;
+        mXfrmUsersaId = new StructXfrmUsersaId(destAddress, spi, family, proto);
+    }
+
+    @Override
+    protected void packPayload(@NonNull final ByteBuffer byteBuffer) {
+        mXfrmUsersaId.writeToByteBuffer(byteBuffer);
+    }
+
+    /**
+     * Parse XFRM_MSG_GETSA message from ByteBuffer.
+     *
+     * <p>This method should be called from NetlinkMessage#parse(ByteBuffer, int) for generic
+     * message validation and processing
+     *
+     * @param nlmsghdr netlink message header.
+     * @param byteBuffer the ByteBuffer instance that wraps the raw netlink message bytes. MUST be
+     *                   host order
+     */
+    @Nullable
+    static XfrmNetlinkGetSaMessage parseInternal(
+            @NonNull final StructNlMsgHdr nlmsghdr, @NonNull final ByteBuffer byteBuffer) {
+        final StructXfrmUsersaId xfrmUsersaId = Struct.parse(StructXfrmUsersaId.class, byteBuffer);
+        if (xfrmUsersaId == null) {
+            return null;
+        }
+
+        // Attributes not supported. Don't bother handling them.
+
+        return new XfrmNetlinkGetSaMessage(nlmsghdr, xfrmUsersaId);
+    }
+
+    /** A convenient method to create a XFRM_MSG_GETSA message. */
+    public static byte[] newXfrmNetlinkGetSaMessage(
+            @NonNull final InetAddress destAddress, long spi, short proto) {
+        final int payloadLen = StructXfrmUsersaId.STRUCT_SIZE;
+
+        final StructNlMsgHdr nlmsghdr =
+                new StructNlMsgHdr(payloadLen, XFRM_MSG_GETSA, NLM_F_REQUEST, 0);
+        final XfrmNetlinkGetSaMessage message =
+                new XfrmNetlinkGetSaMessage(nlmsghdr, destAddress, spi, proto);
+
+        final ByteBuffer byteBuffer = newNlMsgByteBuffer(payloadLen);
+        message.pack(byteBuffer);
+
+        return byteBuffer.array();
+    }
+
+    public StructXfrmUsersaId getStructXfrmUsersaId() {
+        return mXfrmUsersaId;
+    }
+}
diff --git a/staticlibs/device/com/android/net/module/util/netlink/xfrm/XfrmNetlinkMessage.java b/staticlibs/device/com/android/net/module/util/netlink/xfrm/XfrmNetlinkMessage.java
index ee34e57..e15342b 100644
--- a/staticlibs/device/com/android/net/module/util/netlink/xfrm/XfrmNetlinkMessage.java
+++ b/staticlibs/device/com/android/net/module/util/netlink/xfrm/XfrmNetlinkMessage.java
@@ -17,10 +17,13 @@
 package com.android.net.module.util.netlink.xfrm;
 
 import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
 
 import com.android.net.module.util.netlink.NetlinkMessage;
 import com.android.net.module.util.netlink.StructNlMsgHdr;
 
+import java.nio.ByteBuffer;
+
 /** Base calss for XFRM netlink messages */
 // Developer notes: The Linux kernel includes a number of XFRM structs that are not standard netlink
 // attributes (e.g., xfrm_usersa_id). These structs are unlikely to change size, so this XFRM
@@ -28,12 +31,45 @@
 // struct size changes, it should be caught by CTS and then developers should add
 // kernel-version-based behvaiours.
 public abstract class XfrmNetlinkMessage extends NetlinkMessage {
-    // TODO: STOPSHIP: b/308011229 Remove it when OsConstants.IPPROTO_ESP is exposed
+    // TODO: b/312498032 Remove it when OsConstants.IPPROTO_ESP is stable
     public static final int IPPROTO_ESP = 50;
+    // TODO: b/312498032 Remove it when OsConstants.NETLINK_XFRM is stable
+    public static final int NETLINK_XFRM = 6;
+
+    /* see include/uapi/linux/xfrm.h */
+    public static final short XFRM_MSG_NEWSA = 16;
+    public static final short XFRM_MSG_GETSA = 18;
 
     public XfrmNetlinkMessage(@NonNull final StructNlMsgHdr header) {
         super(header);
     }
 
-    // TODO: Add the support for parsing messages
+    /**
+     * Parse XFRM message from ByteBuffer.
+     *
+     * <p>This method should be called from NetlinkMessage#parse(ByteBuffer, int) for generic
+     * message validation and processing
+     *
+     * @param nlmsghdr netlink message header.
+     * @param byteBuffer the ByteBuffer instance that wraps the raw netlink message bytes. MUST be
+     *                   host order
+     */
+    @Nullable
+    public static XfrmNetlinkMessage parseXfrmInternal(
+            @NonNull final StructNlMsgHdr nlmsghdr, @NonNull final ByteBuffer byteBuffer) {
+        switch (nlmsghdr.nlmsg_type) {
+            case XFRM_MSG_GETSA:
+                return XfrmNetlinkGetSaMessage.parseInternal(nlmsghdr, byteBuffer);
+            default:
+                return null;
+        }
+    }
+
+    protected abstract void packPayload(@NonNull final ByteBuffer byteBuffer);
+
+    /** Write a XFRM message to {@link ByteBuffer}. */
+    public void pack(@NonNull final ByteBuffer byteBuffer) {
+        getHeader().pack(byteBuffer);
+        packPayload(byteBuffer);
+    }
 }
diff --git a/staticlibs/tests/unit/src/com/android/net/module/util/netlink/xfrm/StructXfrmUsersaIdTest.java b/staticlibs/tests/unit/src/com/android/net/module/util/netlink/xfrm/StructXfrmUsersaIdTest.java
index 52fd591..b659f62 100644
--- a/staticlibs/tests/unit/src/com/android/net/module/util/netlink/xfrm/StructXfrmUsersaIdTest.java
+++ b/staticlibs/tests/unit/src/com/android/net/module/util/netlink/xfrm/StructXfrmUsersaIdTest.java
@@ -52,7 +52,7 @@
     public void testEncode() throws Exception {
         final StructXfrmUsersaId struct = new StructXfrmUsersaId(DEST_ADDRESS, SPI, FAMILY, PROTO);
 
-        ByteBuffer buffer = ByteBuffer.allocate(EXPECTED_HEX.length);
+        final ByteBuffer buffer = ByteBuffer.allocate(EXPECTED_HEX.length);
         buffer.order(ByteOrder.nativeOrder());
         struct.writeToByteBuffer(buffer);
 
diff --git a/staticlibs/tests/unit/src/com/android/net/module/util/netlink/xfrm/XfrmNetlinkGetSaMessageTest.java b/staticlibs/tests/unit/src/com/android/net/module/util/netlink/xfrm/XfrmNetlinkGetSaMessageTest.java
new file mode 100644
index 0000000..0ab36e7
--- /dev/null
+++ b/staticlibs/tests/unit/src/com/android/net/module/util/netlink/xfrm/XfrmNetlinkGetSaMessageTest.java
@@ -0,0 +1,75 @@
+/*
+ * Copyright (C) 2023 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.netlink.xfrm;
+
+import static com.android.net.module.util.netlink.xfrm.XfrmNetlinkMessage.IPPROTO_ESP;
+import static com.android.net.module.util.netlink.xfrm.XfrmNetlinkMessage.NETLINK_XFRM;
+
+import static org.junit.Assert.assertArrayEquals;
+import static org.junit.Assert.assertEquals;
+
+import android.net.InetAddresses;
+import android.system.OsConstants;
+
+import androidx.test.filters.SmallTest;
+import androidx.test.runner.AndroidJUnit4;
+
+import com.android.net.module.util.HexDump;
+import com.android.net.module.util.netlink.NetlinkMessage;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+
+import java.net.InetAddress;
+import java.nio.ByteBuffer;
+import java.nio.ByteOrder;
+
+@RunWith(AndroidJUnit4.class)
+@SmallTest
+public class XfrmNetlinkGetSaMessageTest {
+    private static final String EXPECTED_HEX_STRING =
+            "28000000120001000000000000000000"
+                    + "C0000201000000000000000000000000"
+                    + "7768440002003200";
+    private static final byte[] EXPECTED_HEX = HexDump.hexStringToByteArray(EXPECTED_HEX_STRING);
+    private static final InetAddress DEST_ADDRESS = InetAddresses.parseNumericAddress("192.0.2.1");
+    private static final long SPI = 0x77684400;
+    private static final int FAMILY = OsConstants.AF_INET;
+    private static final short PROTO = IPPROTO_ESP;
+
+    @Test
+    public void testEncode() throws Exception {
+        final byte[] result =
+                XfrmNetlinkGetSaMessage.newXfrmNetlinkGetSaMessage(DEST_ADDRESS, SPI, PROTO);
+        assertArrayEquals(EXPECTED_HEX, result);
+    }
+
+    @Test
+    public void testDecode() throws Exception {
+        final ByteBuffer buffer = ByteBuffer.wrap(EXPECTED_HEX);
+        buffer.order(ByteOrder.nativeOrder());
+        final XfrmNetlinkGetSaMessage message =
+                (XfrmNetlinkGetSaMessage) NetlinkMessage.parse(buffer, NETLINK_XFRM);
+        final StructXfrmUsersaId struct = message.getStructXfrmUsersaId();
+
+        assertEquals(DEST_ADDRESS, struct.getDestAddress());
+        assertEquals(SPI, struct.spi);
+        assertEquals(FAMILY, struct.family);
+        assertEquals(PROTO, struct.proto);
+        assertEquals(0, buffer.remaining());
+    }
+}
diff --git a/tests/cts/hostside/AndroidTest.xml b/tests/cts/hostside/AndroidTest.xml
index 90b7875..0ffe81e 100644
--- a/tests/cts/hostside/AndroidTest.xml
+++ b/tests/cts/hostside/AndroidTest.xml
@@ -36,6 +36,7 @@
     <target_preparer class="com.android.tradefed.targetprep.DeviceSetup">
         <option name="force-skip-system-props" value="true" />
         <option name="set-global-setting" key="verifier_verify_adb_installs" value="0" />
+        <option name="set-global-setting" key="low_power_standby_enabled" value="0" />
     </target_preparer>
 
     <test class="com.android.compatibility.common.tradefed.testtype.JarHostTest" >
diff --git a/tests/cts/net/src/android/net/cts/DnsResolverTest.java b/tests/cts/net/src/android/net/cts/DnsResolverTest.java
index 308aead..9ff0f2f 100644
--- a/tests/cts/net/src/android/net/cts/DnsResolverTest.java
+++ b/tests/cts/net/src/android/net/cts/DnsResolverTest.java
@@ -860,4 +860,9 @@
             assertEquals(DnsResolver.ERROR_SYSTEM, e.code);
         }
     }
+
+    @Test
+    public void testNoRawBinderAccess() {
+        assertNull(mContext.getSystemService("dnsresolver"));
+    }
 }
diff --git a/tests/unit/java/com/android/server/connectivity/NetworkNotificationManagerTest.java b/tests/unit/java/com/android/server/connectivity/NetworkNotificationManagerTest.java
index b319c30..7121ed4 100644
--- a/tests/unit/java/com/android/server/connectivity/NetworkNotificationManagerTest.java
+++ b/tests/unit/java/com/android/server/connectivity/NetworkNotificationManagerTest.java
@@ -54,6 +54,7 @@
 import android.content.res.Resources;
 import android.net.NetworkCapabilities;
 import android.net.NetworkInfo;
+import android.net.TelephonyNetworkSpecifier;
 import android.os.Build;
 import android.os.Bundle;
 import android.os.PowerManager;
@@ -107,12 +108,16 @@
     private static final long TEST_TIMEOUT_MS = 10_000L;
     private static final long UI_AUTOMATOR_WAIT_TIME_MILLIS = TEST_TIMEOUT_MS;
 
-    static final NetworkCapabilities CELL_CAPABILITIES = new NetworkCapabilities();
-    static final NetworkCapabilities WIFI_CAPABILITIES = new NetworkCapabilities();
-    static final NetworkCapabilities VPN_CAPABILITIES = new NetworkCapabilities();
+    private static final int TEST_SUB_ID = 43;
+    private static final String TEST_OPERATOR_NAME = "Test Operator";
+    private static final NetworkCapabilities CELL_CAPABILITIES = new NetworkCapabilities();
+    private static final NetworkCapabilities WIFI_CAPABILITIES = new NetworkCapabilities();
+    private static final NetworkCapabilities VPN_CAPABILITIES = new NetworkCapabilities();
     static {
         CELL_CAPABILITIES.addTransportType(NetworkCapabilities.TRANSPORT_CELLULAR);
         CELL_CAPABILITIES.addCapability(NetworkCapabilities.NET_CAPABILITY_INTERNET);
+        CELL_CAPABILITIES.setNetworkSpecifier(new TelephonyNetworkSpecifier.Builder()
+                .setSubscriptionId(TEST_SUB_ID).build());
 
         WIFI_CAPABILITIES.addTransportType(NetworkCapabilities.TRANSPORT_WIFI);
         WIFI_CAPABILITIES.addCapability(NetworkCapabilities.NET_CAPABILITY_INTERNET);
@@ -149,6 +154,7 @@
     @Mock DisplayMetrics mDisplayMetrics;
     @Mock PackageManager mPm;
     @Mock TelephonyManager mTelephonyManager;
+    @Mock TelephonyManager mTestSubIdTelephonyManager;
     @Mock NotificationManager mNotificationManager;
     @Mock NetworkAgentInfo mWifiNai;
     @Mock NetworkAgentInfo mCellNai;
@@ -170,18 +176,21 @@
         mVpnNai.networkInfo = mNetworkInfo;
         mDisplayMetrics.density = 2.275f;
         doReturn(true).when(mVpnNai).isVPN();
-        when(mCtx.getResources()).thenReturn(mResources);
-        when(mCtx.getPackageManager()).thenReturn(mPm);
-        when(mCtx.getApplicationInfo()).thenReturn(new ApplicationInfo());
+        doReturn(mResources).when(mCtx).getResources();
+        doReturn(mPm).when(mCtx).getPackageManager();
+        doReturn(new ApplicationInfo()).when(mCtx).getApplicationInfo();
         final Context asUserCtx = mock(Context.class, AdditionalAnswers.delegatesTo(mCtx));
         doReturn(UserHandle.ALL).when(asUserCtx).getUser();
-        when(mCtx.createContextAsUser(eq(UserHandle.ALL), anyInt())).thenReturn(asUserCtx);
-        when(mCtx.getSystemService(eq(Context.NOTIFICATION_SERVICE)))
-                .thenReturn(mNotificationManager);
-        when(mNetworkInfo.getExtraInfo()).thenReturn(TEST_EXTRA_INFO);
+        doReturn(asUserCtx).when(mCtx).createContextAsUser(eq(UserHandle.ALL), anyInt());
+        doReturn(mNotificationManager).when(mCtx)
+                .getSystemService(eq(Context.NOTIFICATION_SERVICE));
+        doReturn(TEST_EXTRA_INFO).when(mNetworkInfo).getExtraInfo();
         ConnectivityResources.setResourcesContextForTest(mCtx);
-        when(mResources.getColor(anyInt(), any())).thenReturn(0xFF607D8B);
-        when(mResources.getDisplayMetrics()).thenReturn(mDisplayMetrics);
+        doReturn(0xFF607D8B).when(mResources).getColor(anyInt(), any());
+        doReturn(mDisplayMetrics).when(mResources).getDisplayMetrics();
+        doReturn(mTestSubIdTelephonyManager).when(mTelephonyManager)
+                .createForSubscriptionId(TEST_SUB_ID);
+        doReturn(TEST_OPERATOR_NAME).when(mTestSubIdTelephonyManager).getNetworkOperatorName();
 
         // Come up with some credible-looking transport names. The actual values do not matter.
         String[] transportNames = new String[NetworkCapabilities.MAX_TRANSPORT + 1];
@@ -532,4 +541,44 @@
                 R.string.wifi_no_internet, TEST_EXTRA_INFO,
                 R.string.wifi_no_internet_detailed);
     }
+
+    private void runTelephonySignInNotificationTest(String testTitle, String testContents) {
+        final int id = 101;
+        final String tag = NetworkNotificationManager.tagFor(id);
+        mManager.showNotification(id, SIGN_IN, mCellNai, null, null, false);
+
+        final ArgumentCaptor<Notification> noteCaptor = ArgumentCaptor.forClass(Notification.class);
+        verify(mNotificationManager).notify(eq(tag), eq(SIGN_IN.eventId), noteCaptor.capture());
+        final Bundle noteExtras = noteCaptor.getValue().extras;
+        assertEquals(testTitle, noteExtras.getString(Notification.EXTRA_TITLE));
+        assertEquals(testContents, noteExtras.getString(Notification.EXTRA_TEXT));
+    }
+
+    @Test
+    public void testTelephonySignInNotification() {
+        final String testTitle = "Telephony no internet title";
+        final String testContents = "Add data for " + TEST_OPERATOR_NAME;
+        // The test does not use real resources as they are in the ConnectivityResources package,
+        // which is tricky to use (requires resolving the package, QUERY_ALL_PACKAGES permission).
+        doReturn(testTitle).when(mResources).getString(
+                R.string.mobile_network_available_no_internet);
+        doReturn(testContents).when(mResources).getString(
+                R.string.mobile_network_available_no_internet_detailed, TEST_OPERATOR_NAME);
+
+        runTelephonySignInNotificationTest(testTitle, testContents);
+    }
+
+    @Test
+    public void testTelephonySignInNotification_NoOperator() {
+        doReturn("").when(mTestSubIdTelephonyManager).getNetworkOperatorName();
+
+        final String testTitle = "Telephony no internet title";
+        final String testContents = "Add data";
+        doReturn(testTitle).when(mResources).getString(
+                R.string.mobile_network_available_no_internet);
+        doReturn(testContents).when(mResources).getString(
+                R.string.mobile_network_available_no_internet_detailed_unknown_carrier);
+
+        runTelephonySignInNotificationTest(testTitle, testContents);
+    }
 }