| /* |
| * Copyright (C) 2020 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 android.net.netlink; |
| |
| import java.nio.ByteBuffer; |
| |
| /** |
| * Base class for IPv6 neighbour discovery options. |
| */ |
| public class NdOption { |
| public static final int STRUCT_SIZE = 2; |
| |
| /** The option type. */ |
| public final byte type; |
| /** The length of the option in 8-byte units. Actually an unsigned 8-bit integer */ |
| public final int length; |
| |
| /** Constructs a new NdOption. */ |
| NdOption(byte type, int length) { |
| this.type = type; |
| this.length = length; |
| } |
| |
| /** |
| * Parses a neighbour discovery option. |
| * |
| * Parses (and consumes) the option if it is of a known type. If the option is of an unknown |
| * type, advances the buffer (so the caller can continue parsing if desired) and returns |
| * {@link #UNKNOWN}. If the option claims a length of 0, returns null because parsing cannot |
| * continue. |
| * |
| * No checks are performed on the length other than ensuring it is not 0, so if a caller wants |
| * to deal with options that might overflow the structure that contains them, it must explicitly |
| * set the buffer's limit to the position at which that structure ends. |
| * |
| * @param buf the buffer to parse. |
| * @return a subclass of {@link NdOption}, or {@code null} for an unknown or malformed option. |
| */ |
| public static NdOption parse(ByteBuffer buf) { |
| if (buf == null || buf.remaining() < STRUCT_SIZE) return null; |
| |
| // Peek the type without advancing the buffer. |
| byte type = buf.get(buf.position()); |
| int length = Byte.toUnsignedInt(buf.get(buf.position() + 1)); |
| if (length == 0) return null; |
| |
| switch (type) { |
| case StructNdOptPref64.TYPE: |
| return StructNdOptPref64.parse(buf); |
| |
| default: |
| int newPosition = Math.min(buf.limit(), buf.position() + length * 8); |
| buf.position(newPosition); |
| return UNKNOWN; |
| } |
| } |
| |
| void writeToByteBuffer(ByteBuffer buf) { |
| buf.put(type); |
| buf.put((byte) length); |
| } |
| |
| @Override |
| public String toString() { |
| return String.format("NdOption(%d, %d)", Byte.toUnsignedInt(type), length); |
| } |
| |
| public static final NdOption UNKNOWN = new NdOption((byte) 0, 0); |
| } |