Merge "Use netlink to set interface up/down in EthernetTracker(1/2)" into main
diff --git a/staticlibs/device/com/android/net/module/util/netlink/NetlinkUtils.java b/staticlibs/device/com/android/net/module/util/netlink/NetlinkUtils.java
index 541a375..e2544d3 100644
--- a/staticlibs/device/com/android/net/module/util/netlink/NetlinkUtils.java
+++ b/staticlibs/device/com/android/net/module/util/netlink/NetlinkUtils.java
@@ -55,6 +55,7 @@
 import java.nio.ByteBuffer;
 import java.nio.ByteOrder;
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.List;
 import java.util.Objects;
 import java.util.function.Consumer;
@@ -469,4 +470,31 @@
             // Nothing we can do here
         }
     }
+
+    /**
+     * Sends a netlink request to set flags for given interface
+     *
+     * @param interfaceName The name of the network interface to query.
+     * @param flags power-of-two integer flags to set or unset. A flag to set should be passed as
+     *        is as a power-of-two value, and a flag to remove should be passed inversed as -1 with
+     *        a single bit down. For example: IFF_UP, ~IFF_BROADCAST...
+     * @return true if the request finished successfully, otherwise false.
+     */
+    public static boolean setInterfaceFlags(@NonNull String interfaceName, int... flags) {
+        final RtNetlinkLinkMessage ntMsg =
+                RtNetlinkLinkMessage.createSetFlagsMessage(interfaceName, /*seqNo*/ 0, flags);
+        if (ntMsg == null) {
+            Log.e(TAG, "Failed to create message to set interface flags for interface "
+                    + interfaceName + ", input flags are: " + Arrays.toString(flags));
+            return false;
+        }
+        final byte[] msg = ntMsg.pack(ByteOrder.nativeOrder());
+        try {
+            NetlinkUtils.sendOneShotKernelMessage(NETLINK_ROUTE, msg);
+            return true;
+        } catch (ErrnoException e) {
+            Log.e(TAG, "Failed to set flags for: " + interfaceName, e);
+            return false;
+        }
+    }
 }
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 037d95f..1afe3b8 100644
--- a/staticlibs/device/com/android/net/module/util/netlink/RtNetlinkLinkMessage.java
+++ b/staticlibs/device/com/android/net/module/util/netlink/RtNetlinkLinkMessage.java
@@ -312,6 +312,57 @@
                 DEFAULT_MTU, null, null);
     }
 
+    /**
+     * Creates an {@link RtNetlinkLinkMessage} instance that can be used to set the flags of a
+     * network interface.
+     *
+     * @param interfaceName The name of the network interface to query.
+     * @param sequenceNumber The sequence number for the Netlink message.
+     * @param flags power-of-two integer flags to set or unset. A flag to set should be passed as
+     *        is as a power-of-two value, and a flag to remove should be passed inversed as -1 with
+     *        a single bit down. For example: IFF_UP, ~IFF_BROADCAST...
+     * @return An `RtNetlinkLinkMessage` instance representing the request to query the interface.
+     */
+    @Nullable
+    public static RtNetlinkLinkMessage createSetFlagsMessage(@NonNull String interfaceName,
+            int sequenceNumber, int... flags) {
+        return createSetFlagsMessage(
+                interfaceName, sequenceNumber, new OsAccess(), flags);
+    }
+
+    @VisibleForTesting
+    @Nullable
+    protected static RtNetlinkLinkMessage createSetFlagsMessage(
+            @NonNull String interfaceName, int sequenceNumber, @NonNull OsAccess osAccess,
+            int... flags) {
+        final int interfaceIndex = osAccess.if_nametoindex(interfaceName);
+        if (interfaceIndex == OsAccess.INVALID_INTERFACE_INDEX) {
+            return null;
+        }
+
+        int flagsBits = 0;
+        int changeBits = 0;
+        for (int f : flags) {
+            if (Integer.bitCount(f) == 1) {
+                flagsBits |= f;
+                changeBits |= f;
+            } else if (Integer.bitCount(~f) == 1) {
+                flagsBits &= f;
+                changeBits |= ~f;
+            } else {
+                return null;
+            }
+        }
+        // RTM_NEWLINK is used here for create, modify, or notify changes about a internet
+        // interface, including change in administrative state. While RTM_SETLINK is used to
+        // modify an existing link rather than creating a new one.
+        return RtNetlinkLinkMessage.build(
+                new StructNlMsgHdr(/*payloadLen*/ 0, RTM_NEWLINK, NLM_F_REQUEST, sequenceNumber),
+                new StructIfinfoMsg((short) AF_UNSPEC, /*type*/ 0, interfaceIndex,
+                        flagsBits, changeBits),
+                DEFAULT_MTU, /*hardwareAddress*/ null, /*interfaceName*/ null);
+    }
+
     @Override
     public String toString() {
         return "RtNetlinkLinkMessage{ "
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 bd0e31d..8104e3a 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
@@ -306,6 +306,28 @@
     }
 
     @Test
+    public void testCreateSetInterfaceFlagsMessage() {
+        final String expectedHexBytes =
+                "20000000100001006824000000000000"    // struct nlmsghdr
+                        + "00000000080000000100000001000100"; // struct ifinfomsg
+        final String interfaceName = "wlan0";
+        final int interfaceIndex = 8;
+        final int sequenceNumber = 0x2468;
+
+        when(mOsAccess.if_nametoindex(interfaceName)).thenReturn(interfaceIndex);
+
+        final RtNetlinkLinkMessage msg = RtNetlinkLinkMessage.createSetFlagsMessage(
+                interfaceName,
+                sequenceNumber,
+                mOsAccess,
+                NetlinkConstants.IFF_UP,
+                ~NetlinkConstants.IFF_LOWER_UP);
+        assertNotNull(msg);
+        final byte[] bytes = msg.pack(ByteOrder.LITTLE_ENDIAN);  // For testing.
+        assertEquals(expectedHexBytes, HexDump.toHexString(bytes));
+    }
+
+    @Test
     public void testToString() {
         final ByteBuffer byteBuffer = toByteBuffer(RTM_NEWLINK_HEX);
         byteBuffer.order(ByteOrder.LITTLE_ENDIAN);  // For testing.