1 /*
2 * Copyright 2020 The Netty Project
3 *
4 * The Netty Project licenses this file to you under the Apache License,
5 * version 2.0 (the "License"); you may not use this file except in compliance
6 * with the License. You may obtain a copy of the License at:
7 *
8 * https://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
12 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
13 * License for the specific language governing permissions and limitations
14 * under the License.
15 */
16 package io.netty.handler.pcap;
17
18 import io.netty.buffer.ByteBuf;
19
20 final class TCPPacket {
21
22 /**
23 * Data Offset + Reserved Bits.
24 */
25 private static final short OFFSET = 0x5000;
26
27 private TCPPacket() {
28 // Prevent outside initialization
29 }
30
31 /**
32 * Write TCP Packet
33 *
34 * @param byteBuf ByteBuf where Packet data will be set
35 * @param payload Payload of this Packet
36 * @param srcPort Source Port
37 * @param dstPort Destination Port
38 */
39 static void writePacket(ByteBuf byteBuf, ByteBuf payload, long segmentNumber, long ackNumber, int srcPort,
40 int dstPort, TCPFlag... tcpFlags) {
41
42 byteBuf.writeShort(srcPort); // Source Port
43 byteBuf.writeShort(dstPort); // Destination Port
44 byteBuf.writeInt((int) segmentNumber); // Segment Number
45 byteBuf.writeInt((int) ackNumber); // Acknowledgment Number
46 byteBuf.writeShort(OFFSET | TCPFlag.getFlag(tcpFlags)); // Flags
47 byteBuf.writeShort(65535); // Window Size
48 byteBuf.writeShort(0x0001); // Checksum
49 byteBuf.writeShort(0); // Urgent Pointer
50
51 if (payload != null) {
52 byteBuf.writeBytes(payload); // Payload of Data
53 }
54 }
55
56 enum TCPFlag {
57 FIN(1),
58 SYN(1 << 1),
59 RST(1 << 2),
60 PSH(1 << 3),
61 ACK(1 << 4),
62 URG(1 << 5),
63 ECE(1 << 6),
64 CWR(1 << 7);
65
66 private final int value;
67
68 TCPFlag(int value) {
69 this.value = value;
70 }
71
72 static int getFlag(TCPFlag... tcpFlags) {
73 int flags = 0;
74
75 for (TCPFlag tcpFlag : tcpFlags) {
76 flags |= tcpFlag.value;
77 }
78
79 return flags;
80 }
81 }
82 }