io.netty.handler.pcap.TCPPacket Maven / Gradle / Ivy
/*
* Copyright 2020 The Netty Project
*
* The Netty Project licenses this file to you 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:
*
* https://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 io.netty.handler.pcap;
import io.netty.buffer.ByteBuf;
final class TCPPacket {
/**
* Data Offset + Reserved Bits.
*/
private static final short OFFSET = 0x5000;
private TCPPacket() {
// Prevent outside initialization
}
/**
* Write TCP Packet
*
* @param byteBuf ByteBuf where Packet data will be set
* @param payload Payload of this Packet
* @param srcPort Source Port
* @param dstPort Destination Port
*/
static void writePacket(ByteBuf byteBuf, ByteBuf payload, int segmentNumber, int ackNumber, int srcPort,
int dstPort, TCPFlag... tcpFlags) {
byteBuf.writeShort(srcPort); // Source Port
byteBuf.writeShort(dstPort); // Destination Port
byteBuf.writeInt(segmentNumber); // Segment Number
byteBuf.writeInt(ackNumber); // Acknowledgment Number
byteBuf.writeShort(OFFSET | TCPFlag.getFlag(tcpFlags)); // Flags
byteBuf.writeShort(65535); // Window Size
byteBuf.writeShort(0x0001); // Checksum
byteBuf.writeShort(0); // Urgent Pointer
if (payload != null) {
byteBuf.writeBytes(payload); // Payload of Data
}
}
enum TCPFlag {
FIN(1),
SYN(1 << 1),
RST(1 << 2),
PSH(1 << 3),
ACK(1 << 4),
URG(1 << 5),
ECE(1 << 6),
CWR(1 << 7);
private final int value;
TCPFlag(int value) {
this.value = value;
}
static int getFlag(TCPFlag... tcpFlags) {
int flags = 0;
for (TCPFlag tcpFlag : tcpFlags) {
flags |= tcpFlag.value;
}
return flags;
}
}
}