tcp-rust

A TCP/IP stack implementation in Rust from scratch, built on top of a TUN device.

Overview

This project implements the core TCP protocol following RFC 793 specifications. It creates a virtual network interface (TUN device) and handles TCP connections at the packet level, including connection establishment (three-way handshake) and state management.

Features

• Custom TCP state machine (Listen, SynRcvd, Closed)
• Three-way handshake implementation (SYN, SYN-ACK, ACK)
• Send and Receive Sequence Space management
• Connection tracking using a quad (source IP:port, destination IP:port)
• Raw packet parsing and construction

Dependencies

• etherparse - For parsing and constructing IP and TCP headers
• tun-tap - For creating and managing TUN/TAP devices

How It Works

1. Creates a TUN device named "tun0"
2. Listens for incoming packets on the interface
3. Parses IPv4 and TCP headers
4. Manages TCP connections in a HashMap indexed by connection quads
5. Handles TCP state transitions and sends appropriate responses

Usage

# Run with appropriate permissions (requires root/sudo for TUN device creation)
# Better to run the shell command ./run.sh
/run.sh

Project Structure

• main.rs - Main event loop, packet reception, and connection management
• tcp.rs - TCP connection state machine and packet handling logic

Learning Goals

This project is designed to understand:

• How TCP works at a low level
• Network packet structure and parsing
• State machine implementation
• Systems programming in Rust