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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 com.android.net.module.util.Struct;
import com.android.net.module.util.Struct.Field;
import com.android.net.module.util.Struct.Type;
/**
* L4 TCP header as per https://tools.ietf.org/html/rfc793.
* This class does not contain option and data fields.
*
* 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
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | Source Port | Destination Port |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | Sequence Number |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | Acknowledgment Number |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | Data | |U|A|P|R|S|F| |
* | Offset| Reserved |R|C|S|S|Y|I| Window |
* | | |G|K|H|T|N|N| |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | Checksum | Urgent Pointer |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | Options | Padding |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | data |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
*/
public class TcpHeader extends Struct {
@Field(order = 0, type = Type.U16)
public final int srcPort;
@Field(order = 1, type = Type.U16)
public final int dstPort;
@Field(order = 2, type = Type.U32)
public final long seq;
@Field(order = 3, type = Type.U32)
public final long ack;
@Field(order = 4, type = Type.S16)
// data Offset (4 bits), reserved (6 bits), control bits (6 bits)
// TODO: update with bitfields once class Struct supports it
public final short dataOffsetAndControlBits;
@Field(order = 5, type = Type.U16)
public final int window;
@Field(order = 6, type = Type.S16)
public final short checksum;
@Field(order = 7, type = Type.U16)
public final int urgentPointer;
public TcpHeader(final int srcPort, final int dstPort, final long seq, final long ack,
final short dataOffsetAndControlBits, final int window, final short checksum,
final int urgentPointer) {
this.srcPort = srcPort;
this.dstPort = dstPort;
this.seq = seq;
this.ack = ack;
this.dataOffsetAndControlBits = dataOffsetAndControlBits;
this.window = window;
this.checksum = checksum;
this.urgentPointer = urgentPointer;
}
}
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