LC

Use a TUN/TAP Interface to Inject Your TCP Stack

hard8/8

Implement a Simple Congestion Control AlgorithmNext

Language

Compiler

2.0s Limit 256MB

Implementation

Implement a program that sets up a TUN interface and demonstrates packet I/O.

Requirements:

Open /dev/net/tun device
Use ioctl(TUNSETIFF) to create/configure interface
Support both TUN (IFF_TUN) and TAP (IFF_TAP) modes
Read raw packets from the interface
Show how to inject response packets back
Display packet type (IP for TUN, Ethernet for TAP)
Explain differences between TUN and TAP
Handle errors for open, ioctl, and read operations
Print interface name after successful creation

Why This Matters

WireGuard and OpenVPN both create a TUN device exactly this way to intercept IP packets in user space before encrypting and re-injecting them over a UDP tunnel, while Docker and QEMU networking rely on the TAP variant to bridge Ethernet frames into virtual machines and containers. This is the same kernel interface that lets you build and test a user-space TCP/IP stack without touching kernel code.

Hints

0 / 3 revealed

Validation Suite

main.c

Workspace 1.0