WSL : nl80211 not found fix & 8814au drivers

Quick facts

• Do not save kernel source to a /mnt/c path, compile from the linux user home directory. Windows is case-insensitive, will cause random "file not found" compilation errors.
• I'm using the Kali Windows store installation to do all these steps, this is especially important if you plan on using 8814au drivers (I don't believe they are compatible with Ubuntu)
• Windows 10, latest windows updates & WSL.
• The steps related to 8814au drivers can be modified as necessary.
• For changes to take effect, WSL requires the "6 second rule" between restarts when modifying WSL related configuration files. Meaning if you issue a wsl --shutdown wait 6 seconds before issuing wsl.

Dependencies

sudo apt update && sudo apt upgrade
sudo apt install flex bison libssl-dev libelf-dev git dwarves bc make libncurses-dev python3

Change working directory to home

Make sure you're not inside a /mnt/c path.

cd ~

Pull kernel source & extract

Credit to kevin for this ingenius method, much faster than cloning github repo.

wget https://github.com/microsoft/WSL2-Linux-Kernel/archive/refs/tags/linux-msft-wsl-$(uname -r | cut -d- -f 1).tar.gz
tar -xvf linux-msft-wsl-$(uname -r | cut -d- -f 1).tar.gz

Change directory into kernel source

What would we do without auto-complete..

cd WSL{TAB}

Use current kernel config as template

cat /proc/config.gz | gunzip > .config

Configure kernel

make menuconfig

Enable the following in kernel config (*), exit & save

I opted to integrate into the kernel (*), you can also choose to compile as modules (M) this will require more setting up later (auto starting at boot)

• Networking support
  • Wireless (*)
    • cfg80211 (*)

Compile kernel, modules_install needed for DKMS

make modules -j $(expr $(nproc) - 1)
sudo make modules_install

Build kernel bzImage

make -j $(expr $(nproc) - 1)

Move kernel image to %UserProfile%

Replace USERNAME with your own (duh)

mv arch/x86/boot/bzImage /mnt/c/Users/USERNAME

Some useful tools & 8814au drivers

sudo apt install usbip usbutils iw wireshark realtek-rtl8814au-dkms

Enable systemd, needed for module autostart & other useful services

sudo nano /etc/wsl.conf

Contents:

[boot]
systemd = true

Auto start kernel module on WSL startup

If you decided to configure cfg80211 as a module, you want to also create a autostart conf for it also

echo "8814au" | sudo tee -a /etc/modules-load.d/8814au.conf

Shut down WSL on host machine

wsl --shutdown

Create .wslconfig in %UserProfile%

Replace USERNAME with your own (duh)

Contents:

# Settings apply across all Linux distros running on WSL 2
[wsl2]

# Specify a custom Linux kernel to use with your installed distros. The default kernel used can be found at https://github.com/microsoft/WSL2-Linux-Kernel
kernel=C:\\Users\\USERNAME\\bzImage

Restart WSL on host machine

wsl

Verify kernel module is loaded

lsmod

Output:

Module                  Size  Used by
8814au               2682880  0

Attach Wireless USB (8814au)

Either on host with

usbipd wsl attach -b <BUSID>

or on VM

sudo usbip attach -r <HOSTIP/172.20.32.1> -b <BUSID>

Verify 8814au attached & more importantly driver is being used

lsusb -t

Output:

/:  Bus 02.Port 1: Dev 1, Class=root_hub, Driver=vhci_hcd/8p, 5000M
/:  Bus 01.Port 1: Dev 1, Class=root_hub, Driver=vhci_hcd/8p, 480M
    |__ Port 1: Dev 2, If 0, Class=Vendor Specific Class, Driver=rtl8814au, 480M

Auto attach USB on startup & set monitor mode on wlan0

sudo nano ~/wsl.sh

Contents:

#!/bin/sh

sudo usbip attach --remote 172.20.32.1 --busid=3-2

while true; do
    if [ -z $(sudo iw dev | grep -o wlan0) ]; then
        sleep 1  # network not yet up
    else
        break   # network up
    fi
done

sudo ip link set wlan0 down
sudo iw wlan0 set monitor control
sudo ip link set wlan0 up

Set permissions & enable in crontab

sudo chmod +x ~/wsl.sh
sudo crontab -e

May have to select editor if first time running crontab -e (obviously nano, unless you're a masochist).. contents:

# Edit this file to introduce tasks to be run by cron.
#
# Each task to run has to be defined through a single line
# indicating with different fields when the task will be run
# and what command to run for the task
#
# To define the time you can provide concrete values for
# minute (m), hour (h), day of month (dom), month (mon),
# and day of week (dow) or use '*' in these fields (for 'any').
#
# Notice that tasks will be started based on the cron's system
# daemon's notion of time and timezones.
#
# Output of the crontab jobs (including errors) is sent through
# email to the user the crontab file belongs to (unless redirected).
#
# For example, you can run a backup of all your user accounts
# at 5 a.m every week with:
# 0 5 * * 1 tar -zcf /var/backups/home.tgz /home/
#
# For more information see the manual pages of crontab(5) and cron(8)
#
# m h  dom mon dow   command

@reboot sh /home/ruckus/wsl.sh

Shutdown WSL on host machine

Shutdown & wait for USB chime, USB chime is used as an indication it's safe to reboot.

wsl --shutdown

Start WSL on host machine

At this stage kernel module should auto load, USB should auto attach & wireless interface should be set in monitor mode.

wsl

Test wireshark

Launch as sudo, otherwise you won't see network adapters

sudo wireshark

Refrences

• WSL
• WSL kernel source
• Kevins excellent gist writeup