Start of research: Introduction to OpenWiFi

by Stef Pletinck

OpenWiFi is an FPGA¹ and SDR² implementation of the IEEE 802.11 a/g/n standard (WiFi, for us common folk). Essentially, it’s a WiFi chip, like you’d find in your phone or a router, but open source and written in Verilog. For more introductory reading, see the paper³ or the talk on FOSDEM. This series of blog posts will document my experiences learning and researching.

Why?

OpenWiFi exists for research and very little else at this point, as FPGA’s are expensive and quite large. It allows one to test even some very funky ideas. The FPGA can do all kinds of fun stuff that normal WiFi cards don’t support (they tend to be really cost-oriented) or won’t allow.

For this research project, we’ll look at using the openwifi project to do security testing of WiFi networks and develop testing equipment.

How does it work

Let’s go top-down. First there’s Linux userspace. The card is seen as a perfectly normal WiFi card and works exactly as you’d expect. There are some extra userpace tools for managing the FPGA and SDR hardware, but those aren’t essential.

Then there’s a driver that implements Linux mac80211⁴. This is what makes it so simple for userspace. Finally, there’s the FPGA code, written in Verilog. I happen to only know VHDL, so this will be fun.

Goals for this research

It’s something about developing test equipment with Keysight. Honestly I don’t really know either, I’m just trying to get a grasp of the subject right now. If I could figure out how to download the standard, that’d be great.

---

1. Field Programmable Gate Array ↩

2. Software Defined Radio ↩

3. X. Jiao, W. Liu, M. Mehari, M. Aslam, and I. Moerman, ‘openwifi: a free and open-source IEEE802.11 SDR implementation on SoC’, in 2020 IEEE 91st Vehicular Technology Conference (VTC2020-Spring), Antwerp, Belgium, May 2020, pp. 1–2, doi: 10.1109/VTC2020-Spring48590.2020.9128614. ↩

4. https://wireless.wiki.kernel.org/en/users ↩