Add DHCPv6 IA Prefix Option structure.

Bug: 260934173
Test: m
Change-Id: Iba9be5ad6c696b6b44c39bd50f5f27ade3e33846
diff --git a/staticlibs/device/com/android/net/module/util/structs/IaPrefixOption.java b/staticlibs/device/com/android/net/module/util/structs/IaPrefixOption.java
new file mode 100644
index 0000000..1ac21ff
--- /dev/null
+++ b/staticlibs/device/com/android/net/module/util/structs/IaPrefixOption.java
@@ -0,0 +1,89 @@
+/*
+ * 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.structs;
+
+import static com.android.net.module.util.NetworkStackConstants.DHCP6_OPTION_IAPREFIX;
+
+import com.android.net.module.util.Struct;
+import com.android.net.module.util.Struct.Field;
+import com.android.net.module.util.Struct.Type;
+
+import java.nio.ByteBuffer;
+import java.nio.ByteOrder;
+
+/**
+ * DHCPv6 IA Prefix Option.
+ * https://tools.ietf.org/html/rfc8415. This does not contain any option.
+ *
+ * 0                   1                   2                   3
+ * 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * |        OPTION_IAPREFIX        |           option-len          |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * |                      preferred-lifetime                       |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * |                        valid-lifetime                         |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * | prefix-length |                                               |
+ * +-+-+-+-+-+-+-+-+          IPv6-prefix                          |
+ * |                           (16 octets)                         |
+ * |                                                               |
+ * |                                                               |
+ * |                                                               |
+ * |               +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * |               |                                               .
+ * +-+-+-+-+-+-+-+-+                                               .
+ * .                       IAprefix-options                        .
+ * .                                                               .
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ */
+public class IaPrefixOption extends Struct {
+    public static final int LENGTH = 25; // option length excluding IAprefix-options
+
+    @Field(order = 0, type = Type.S16)
+    public short code;
+    @Field(order = 1, type = Type.S16)
+    public short length;
+    @Field(order = 2, type = Type.U32)
+    public long preferred;
+    @Field(order = 3, type = Type.U32)
+    public long valid;
+    @Field(order = 4, type = Type.U8)
+    public short prefixLen;
+    @Field(order = 5, type = Type.ByteArray, arraysize = 16)
+    public byte[] prefix;
+
+    IaPrefixOption(final short code, final short length, final long preferred,
+            final long valid, final short prefixLen, final byte[] prefix) {
+        this.code = code;
+        this.length = length;
+        this.preferred = preferred;
+        this.valid = valid;
+        this.prefixLen = prefixLen;
+        this.prefix = prefix.clone();
+    }
+
+    /**
+     * Build an IA_PD prefix option with given specific parameters.
+     */
+    public static ByteBuffer build(final short length, final long preferred, final long valid,
+            final short prefixLen, final byte[] prefix) {
+        final IaPrefixOption option = new IaPrefixOption((byte) DHCP6_OPTION_IAPREFIX,
+                length /* 25 + IAPrefix options length */, preferred, valid, prefixLen, prefix);
+        return ByteBuffer.wrap(option.writeToBytes(ByteOrder.BIG_ENDIAN));
+    }
+}