TCP/IP

What is this?

This is a user-land implementation of the TCP/IP protocol using the Linux TAP interface. The goal was to have a deeper understanding about TCP/IP and other network protocols by implementing them myself. It also seemed like an interesting project to exercise Zig programming. I started by following this guide and then filled the missing parts by reading the related RFCs.

How to run it

You will need Zig (version 0.14.0) to build.

# Clone project
git clone https://github.com/LvMalware/tcp-ip

# cd into the folder
cd tcp-ip/

# build project
zig build

# Add `cap_net_admin` capability to the file:
sudo setcap cap_net_admin=ep zig-out/bin/stack

# Run the executable
./zig-out/bin/stack

By default, the tap interface will have the IP 10.0.0.4 and the program will run a TCP echo server listenning on port 5501. Now you can use a tcp client like netcat to interact with it.

nc 10.0.0.4 5501

Implemented

Basics of:

• Ethernet
• IP functionality
• ICMP echo (ping)
• ARP request/response
• TCP functionality (connection, retransmission, etc.)

Missing/TODO

• Handle Urgent data on the TCP

• Implement IP options and fragmentation

• Implement timeouts

• Many more