Userspace TCP protocol implementation using TUN device

This project is a minimal, custom implementation of the Transmission Control Protocol (TCP), as defined in RFC 793, operating entirely in userspace. It leverages a TUN virtual network device to process IPv4 and IPv6 packets. The purpose of this project is purely for self-education.

Usage

1. Compile and run

The run.sh script executes the binary with sudo to create a TUN device (see device.rs), which requires root privileges due to its interaction with the network stack.

./scripts/run.sh

2. Monitor network traffic

Capture and inspect TCP packets on the tun0 interface using tcpdump:

sudo tcpdump -i tun0 tcp -n

3. Test with a client

Use netcat to establish a TCP connection to the server. The host portions and ports are up to you:

nc -N 10.0.0.10 8080

or/both(as the program spawns 2 listeners):

nc -N fd00:dead:beef::10 8081

Acknowledgments

• Portions of the connection management logic are inspired by Jon Gjengset’s TCP implementation.
• Socket API design influenced by Rust's std::net module.