diff --git a/staticlibs/device/com/android/net/module/util/netlink/OsAccess.java b/staticlibs/device/com/android/net/module/util/netlink/OsAccess.java
new file mode 100644
index 0000000..7591d5c
--- /dev/null
+++ b/staticlibs/device/com/android/net/module/util/netlink/OsAccess.java
@@ -0,0 +1,37 @@
+/*
+ * Copyright (C) 2024 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;
+
+import android.system.Os;
+
+import androidx.annotation.NonNull;
+
+/**
+ * This class wraps the static methods of {@link android.system.Os} for mocking and testing.
+ */
+public class OsAccess {
+    /**
+     * Constant indicating that the {@code if_nametoindex()} function could not find the network
+     * interface index corresponding to the given interface name.
+     */
+    public static int INVALID_INTERFACE_INDEX = 0;
+
+    /** Wraps {@link Os#if_nametoindex(String)}. */
+    public int if_nametoindex(@NonNull String name) {
+        return Os.if_nametoindex(name);
+    }
+}
diff --git a/staticlibs/device/com/android/net/module/util/netlink/RtNetlinkLinkMessage.java b/staticlibs/device/com/android/net/module/util/netlink/RtNetlinkLinkMessage.java
index 72c770a..887a701 100644
--- a/staticlibs/device/com/android/net/module/util/netlink/RtNetlinkLinkMessage.java
+++ b/staticlibs/device/com/android/net/module/util/netlink/RtNetlinkLinkMessage.java
@@ -16,7 +16,12 @@
 
 package com.android.net.module.util.netlink;
 
+import static android.system.OsConstants.AF_UNSPEC;
+
 import static com.android.net.module.util.NetworkStackConstants.ETHER_ADDR_LEN;
+import static com.android.net.module.util.netlink.NetlinkConstants.IFF_UP;
+import static com.android.net.module.util.netlink.NetlinkConstants.RTM_NEWLINK;
+import static com.android.net.module.util.netlink.StructNlMsgHdr.NLM_F_REQUEST_ACK;
 
 import android.net.MacAddress;
 import android.system.OsConstants;
@@ -218,6 +223,35 @@
         return length;
     }
 
+    /**
+     * Create a link message to set the operational state (up or down) of a network interface.
+     *
+     * @param interfaceName  The network interface name.
+     * @param sequenceNumber The sequence number to use for the Netlink message.
+     * @param isUp           {@code true} to set the interface up, {@code false} to set it down.
+     * @return A `RtNetlinkLinkMessage` instance configured to set the link state.
+     */
+    @Nullable
+    public static RtNetlinkLinkMessage createSetLinkStateMessage(@NonNull String interfaceName,
+            int sequenceNumber, boolean isUp) {
+        return createSetLinkStateMessage(interfaceName, sequenceNumber, isUp, new OsAccess());
+    }
+
+    @VisibleForTesting
+    @Nullable
+    protected static RtNetlinkLinkMessage createSetLinkStateMessage(@NonNull String interfaceName,
+            int sequenceNumber, boolean isUp, OsAccess osAccess) {
+        final int interfaceIndex = osAccess.if_nametoindex(interfaceName);
+        if (interfaceIndex == OsAccess.INVALID_INTERFACE_INDEX) {
+            return null;
+        }
+
+        return RtNetlinkLinkMessage.build(
+                new StructNlMsgHdr(0, RTM_NEWLINK, NLM_F_REQUEST_ACK, sequenceNumber),
+                new StructIfinfoMsg((short) AF_UNSPEC, (short) 0, interfaceIndex,
+                                    isUp ? IFF_UP : 0, IFF_UP), DEFAULT_MTU, null, null);
+    }
+
     @Override
     public String toString() {
         return "RtNetlinkLinkMessage{ "
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 5272366..7cc95de 100644
--- a/staticlibs/device/com/android/net/module/util/netlink/StructNlMsgHdr.java
+++ b/staticlibs/device/com/android/net/module/util/netlink/StructNlMsgHdr.java
@@ -32,10 +32,11 @@
     // Already aligned.
     public static final int STRUCT_SIZE = 16;
 
-    public static final short NLM_F_REQUEST = 0x0001;
-    public static final short NLM_F_MULTI   = 0x0002;
-    public static final short NLM_F_ACK     = 0x0004;
-    public static final short NLM_F_ECHO    = 0x0008;
+    public static final short NLM_F_REQUEST     = 0x0001;
+    public static final short NLM_F_MULTI       = 0x0002;
+    public static final short NLM_F_ACK         = 0x0004;
+    public static final short NLM_F_ECHO        = 0x0008;
+    public static final short NLM_F_REQUEST_ACK = NLM_F_REQUEST | NLM_F_ACK;
     // Flags for a GET request.
     public static final short NLM_F_ROOT    = 0x0100;
     public static final short NLM_F_MATCH   = 0x0200;
diff --git a/staticlibs/tests/unit/src/com/android/net/module/util/netlink/RtNetlinkLinkMessageTest.java b/staticlibs/tests/unit/src/com/android/net/module/util/netlink/RtNetlinkLinkMessageTest.java
index afe220f..b9f3661 100644
--- a/staticlibs/tests/unit/src/com/android/net/module/util/netlink/RtNetlinkLinkMessageTest.java
+++ b/staticlibs/tests/unit/src/com/android/net/module/util/netlink/RtNetlinkLinkMessageTest.java
@@ -24,24 +24,29 @@
 import static org.junit.Assert.assertNotNull;
 import static org.junit.Assert.assertNull;
 import static org.junit.Assert.assertTrue;
+import static org.mockito.Mockito.when;
 
+import android.annotation.SuppressLint;
 import android.net.MacAddress;
 import android.system.OsConstants;
 
 import androidx.test.filters.SmallTest;
-import androidx.test.runner.AndroidJUnit4;
 
 import com.android.net.module.util.HexDump;
 
 import org.junit.Test;
 import org.junit.runner.RunWith;
+import org.mockito.Mock;
+import org.mockito.junit.MockitoJUnitRunner;
 
 import java.nio.ByteBuffer;
 import java.nio.ByteOrder;
 
-@RunWith(AndroidJUnit4.class)
+@RunWith(MockitoJUnitRunner.class)
 @SmallTest
 public class RtNetlinkLinkMessageTest {
+    @Mock
+    private OsAccess mOsAccess;
 
     // An example of the full RTM_NEWLINK message.
     private static final String RTM_NEWLINK_HEX =
@@ -186,6 +191,57 @@
     }
 
     @Test
+    public void testCreateSetLinkUpMessage() {
+        final String expectedHexBytes =
+                "20000000100005006824000000000000"     // struct nlmsghdr
+                + "00000000080000000100000001000000";  // struct ifinfomsg
+        final String interfaceName = "wlan0";
+        final int interfaceIndex = 8;
+        final int sequenceNumber = 0x2468;
+        final boolean isUp = true;
+
+        when(mOsAccess.if_nametoindex(interfaceName)).thenReturn(interfaceIndex);
+
+        final RtNetlinkLinkMessage msg = RtNetlinkLinkMessage.createSetLinkStateMessage(
+                interfaceName, sequenceNumber, isUp, mOsAccess);
+        assertNotNull(msg);
+        final byte[] bytes = msg.pack(ByteOrder.LITTLE_ENDIAN);  // For testing.
+        assertEquals(expectedHexBytes, HexDump.toHexString(bytes));
+    }
+
+    @Test
+    public void testCreateSetLinkDownMessage() {
+        final String expectedHexBytes =
+                "20000000100005006824000000000000"     // struct nlmsghdr
+                        + "00000000080000000000000001000000";  // struct ifinfomsg
+        final String interfaceName = "wlan0";
+        final int interfaceIndex = 8;
+        final int sequenceNumber = 0x2468;
+        final boolean isUp = false;
+
+        when(mOsAccess.if_nametoindex(interfaceName)).thenReturn(interfaceIndex);
+
+        final RtNetlinkLinkMessage msg = RtNetlinkLinkMessage.createSetLinkStateMessage(
+                interfaceName, sequenceNumber, isUp, mOsAccess);
+        assertNotNull(msg);
+        final byte[] bytes = msg.pack(ByteOrder.LITTLE_ENDIAN);  // For testing.
+        assertEquals(expectedHexBytes, HexDump.toHexString(bytes));
+    }
+
+    @Test
+    public void testCreateSetLinkStateMessage_InvalidInterface() {
+        final String interfaceName = "wlan0";
+        final int sequenceNumber = 0x2468;
+        final boolean isUp = false;
+
+        when(mOsAccess.if_nametoindex(interfaceName)).thenReturn(OsAccess.INVALID_INTERFACE_INDEX);
+
+        final RtNetlinkLinkMessage msg = RtNetlinkLinkMessage.createSetLinkStateMessage(
+                interfaceName, sequenceNumber, isUp, mOsAccess);
+        assertNull(msg);
+    }
+
+    @Test
     public void testToString() {
         final ByteBuffer byteBuffer = toByteBuffer(RTM_NEWLINK_HEX);
         byteBuffer.order(ByteOrder.LITTLE_ENDIAN);  // For testing.