Add a method helper to create RTM_NEWADDR message in user space.

Bug: 260934173
Test: atest NetworkStaticLibTests
Change-Id: I39a53a3d8b0cd10437aeed502657dd34d8b7775d

staticlibs/device/com/android/net/module/util/netlink/RtNetlinkAddressMessage.java

@@ -16,6 +16,10 @@
 
 package com.android.net.module.util.netlink;
 
+import static com.android.net.module.util.netlink.StructNlMsgHdr.NLM_F_ACK;
+import static com.android.net.module.util.netlink.StructNlMsgHdr.NLM_F_REPLACE;
+import static com.android.net.module.util.netlink.StructNlMsgHdr.NLM_F_REQUEST;
+
 import android.system.OsConstants;
 
 import androidx.annotation.NonNull;
@@ -24,8 +28,10 @@ import androidx.annotation.VisibleForTesting;
 
 import com.android.net.module.util.HexDump;
 
+import java.net.Inet6Address;
 import java.net.InetAddress;
 import java.nio.ByteBuffer;
+import java.nio.ByteOrder;
 
 /**
  * A NetlinkMessage subclass for rtnetlink address messages.
@@ -145,6 +151,47 @@ public class RtNetlinkAddressMessage extends NetlinkMessage {
         flags.pack(byteBuffer);
     }
 
+    /**
+     * A convenience method to create an RTM_NEWADDR message.
+     */
+    public static byte[] newRtmNewAddressMessage(int seqNo, final InetAddress ip, short prefixlen,
+            byte flags, byte scope, int ifIndex, long preferred, long valid) {
+        final StructNlMsgHdr nlmsghdr = new StructNlMsgHdr();
+        nlmsghdr.nlmsg_type = NetlinkConstants.RTM_NEWADDR;
+        nlmsghdr.nlmsg_flags = NLM_F_REQUEST | NLM_F_ACK | NLM_F_REPLACE;
+        nlmsghdr.nlmsg_seq = seqNo;
+
+        final RtNetlinkAddressMessage msg = new RtNetlinkAddressMessage(nlmsghdr);
+        final byte family =
+                (byte) ((ip instanceof Inet6Address) ? OsConstants.AF_INET6 : OsConstants.AF_INET);
+        msg.mIfaddrmsg = new StructIfaddrMsg(family, prefixlen, flags, scope, ifIndex);
+        msg.mIpAddress = ip;
+        msg.mIfacacheInfo = new StructIfacacheInfo(preferred, valid, 0 /* cstamp */,
+                0 /* tstamp */);
+        msg.mFlags = (int) (flags & 0xFF);
+
+        final byte[] bytes = new byte[msg.getRequiredSpace()];
+        nlmsghdr.nlmsg_len = bytes.length;
+        final ByteBuffer byteBuffer = ByteBuffer.wrap(bytes);
+        byteBuffer.order(ByteOrder.nativeOrder());
+        msg.pack(byteBuffer);
+        return bytes;
+    }
+
+    private int getRequiredSpace() {
+        int spaceRequired = StructNlMsgHdr.STRUCT_SIZE + StructIfaddrMsg.STRUCT_SIZE;
+        if (mIpAddress != null) {
+            spaceRequired += NetlinkConstants.alignedLengthOf(
+                    StructNlAttr.NLA_HEADERLEN + mIpAddress.getAddress().length);
+        }
+        if (mIfacacheInfo != null) {
+            spaceRequired += NetlinkConstants.alignedLengthOf(
+                    StructNlAttr.NLA_HEADERLEN + StructIfacacheInfo.STRUCT_SIZE);
+        }
+        spaceRequired += StructNlAttr.NLA_HEADERLEN + 4; // IFA_FLAGS "u32" attr
+        return spaceRequired;
+    }
+
     @Override
     public String toString() {
         return "RtNetlinkAddressMessage{ "

staticlibs/tests/unit/src/com/android/net/module/util/netlink/RtNetlinkAddressMessageTest.java

@@ -16,8 +16,11 @@
 
 package com.android.net.module.util.netlink;
 
+import static android.system.OsConstants.IFA_F_PERMANENT;
 import static android.system.OsConstants.NETLINK_ROUTE;
+import static android.system.OsConstants.RT_SCOPE_LINK;
 
+import static org.junit.Assert.assertArrayEquals;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertNotNull;
 import static org.junit.Assert.assertNull;
@@ -31,6 +34,8 @@ import androidx.test.runner.AndroidJUnit4;
 
 import com.android.net.module.util.HexDump;
 
+import libcore.util.HexEncoding;
+
 import org.junit.Test;
 import org.junit.runner.RunWith;
 
@@ -42,7 +47,7 @@ import java.nio.ByteOrder;
 @SmallTest
 public class RtNetlinkAddressMessageTest {
     private static final Inet6Address TEST_LINK_LOCAL =
-            (Inet6Address) InetAddresses.parseNumericAddress("fe80::2C41:5CFF:FE09:6665");
+            (Inet6Address) InetAddresses.parseNumericAddress("FE80::2C41:5CFF:FE09:6665");
 
     // An example of the full RTM_NEWADDR message.
     private static final String RTM_NEWADDR_HEX =
@@ -127,6 +132,47 @@ public class RtNetlinkAddressMessageTest {
         assertNull(msg);
     }
 
+    @Test
+    public void testCreateRtmNewAddressMessage() {
+        // Hexadecimal representation of our created packet.
+        final String expectedNewAddressHex =
+                // struct nlmsghdr
+                "48000000" +    // length = 72
+                "1400" +        // type = 20 (RTM_NEWADDR)
+                "0501" +        // flags = NLM_F_ACK | NLM_F_REQUEST | NLM_F_REPLACE
+                "01000000" +    // seqno = 1
+                "00000000" +    // pid = 0 (send to kernel)
+                // struct IfaddrMsg
+                "0A" +          // family = inet6
+                "40" +          // prefix len = 64
+                "80" +          // flags = IFA_F_PERMANENT
+                "FD" +          // scope = RT_SCOPE_LINK
+                "17000000" +    // ifindex = 23
+                // struct nlattr: IFA_ADDRESS
+                "1400" +        // len
+                "0100" +        // type
+                "FE800000000000002C415CFFFE096665" + // IP address = fe80::2C41:5cff:fe09:6665
+                // struct nlattr: IFA_CACHEINFO
+                "1400" +        // len
+                "0600" +        // type
+                "FFFFFFFF" +    // preferred = infinite
+                "FFFFFFFF" +    // valid = infinite
+                "00000000" +    // cstamp
+                "00000000" +    // tstamp
+                // struct nlattr: IFA_FLAGS
+                "0800" +        // len
+                "0800" +        // type
+                "80000000";     // flags = IFA_F_PERMANENT
+        final byte[] expectedNewAddress =
+                HexEncoding.decode(expectedNewAddressHex.toCharArray(), false);
+
+        final byte[] bytes = RtNetlinkAddressMessage.newRtmNewAddressMessage(1 /* seqno */,
+                TEST_LINK_LOCAL, (short) 64 /* prefix len */, (byte) IFA_F_PERMANENT /* flags */,
+                (byte) RT_SCOPE_LINK /* scope */, 23 /* ifindex */,
+                (long) 0xFFFFFFFF /* preferred */, (long) 0xFFFFFFFF /* valid */);
+        assertArrayEquals(expectedNewAddress, bytes);
+    }
+
     @Test
     public void testToString() {
         final ByteBuffer byteBuffer = toByteBuffer(RTM_NEWADDR_HEX);