Let's code a TCP/IP stack, 1: Ethernet and ARP

Writing your own TCP/IP stack may seem like a daunting task. Indeed, TCP has accumulated many specifications over its lifetime of more than thirty years. The core specification, however, is seemingly compact - the important parts being TCP header parsing, the state machine, congestion control and retransmission timeout computation. The most common layer 2 and layer 3 protocols, Ethernet and IP respectively, pale in comparison to TCP’s complexity. In this blog series, we will implement a minimal userspace TCP/IP stack for Linux. The purpose of these posts and the resulting software is purely educational - to learn network and system programming at a deeper level. Contents TUN/TAP devices To intercept low-level network traffic from the Linux kernel, we will use a Linux TAP device. In short, a TUN/TAP device is often used by networking userspace applications to manipulate L3/L2 traffic, respectively. A popular example is tunneling, where a packet is wrapped inside the payload of anot ... Read full article.