Mini Internet Stack (Rust)

A minimal user-space implementation of core Internet networking protocols built from scratch in Rust, integrated with Linux using TUN/TAP virtual network interfaces. This project implements packet parsing, protocol handling, and buffering.

Features

• Ethernet
  • Frame parsing and construction
• ARP (IPv4)
  • ARP request parsing
  • ARP reply generation for local IP
• IPv4
  • Header parsing and payload extraction
• UDP
  • Datagram parsing
• TCP (Basic)
  • TCP header parsing
  • Sequence and acknowledgment tracking
  • Send/receive buffering
  • Basic retransmission logic
• Kernel Integration
  • Real packet transmission and reception using Linux TUN/TAP
• Debugging & Validation
  • Packet inspection using tcpdump and Wireshark

Architecture

Application -> TCP / UDP -> IPv4 -> ARP / Ethernet -> TUN/TAP → Linux Kernel → Network Interface

Each protocol layer is implemented in its own Rust module.

Project Structure

src/ main.rs # Packet loop and protocol dispatch tun.rs # TUN/TAP device setup and ioctl handling eth.rs # Ethernet frame parsing arp.rs # ARP parsing and reply generation ipv4.rs # IPv4 header parsing udp.rs # UDP datagram parsing tcp.rs # Basic TCP state machine and buffering

How It Works

1. Attaches to a Linux TAP interface (tap0)
2. Reads raw Ethernet frames from the kernel
3. Parses protocol layers (Ethernet → ARP / IPv4 → UDP / TCP)
4. Handles:
   • ARP requests for the local IP
   • TCP SYN packets and connection state
5. Writes frames back to the TAP interface for real network transmission

Requirements

• Linux
• Rust (stable)
• Root permissions (required for TUN/TAP)

Dependencies

• nix
• libc

Running

Create and configure TAP device:

1. sudo ip tuntap add dev tap0 mode tap
2. sudo ip link set tap0 up
3. sudo ip addr add 10.0.0.1/24 dev tap0

Run the stack:

sudo cargo run

You can test ARP, ICMP, and TCP traffic using:

1. ping 10.0.0.1
2. tcpdump -i tap0