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/*
* Copyright (C) 2021 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.ICMPV6_ND_OPTION_MTU;
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;
/**
* ICMPv6 MTU option, as per https://tools.ietf.org/html/rfc4861.
*
* 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
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | Type | Length | Reserved |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | MTU |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
*/
public class MtuOption extends Struct {
@Field(order = 0, type = Type.S8)
public final byte type;
@Field(order = 1, type = Type.S8)
public final byte length; // Length in 8-byte units
@Field(order = 2, type = Type.S16)
public final short reserved;
@Field(order = 3, type = Type.U32)
public final long mtu;
MtuOption(final byte type, final byte length, final short reserved,
final long mtu) {
this.type = type;
this.length = length;
this.reserved = reserved;
this.mtu = mtu;
}
/**
* Build a MTU option from the required specified parameters.
*/
public static ByteBuffer build(final long mtu) {
final MtuOption option = new MtuOption((byte) ICMPV6_ND_OPTION_MTU,
(byte) 1 /* option len */, (short) 0 /* reserved */, mtu);
return ByteBuffer.wrap(option.writeToBytes(ByteOrder.BIG_ENDIAN));
}
}
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