WSL was a great introduction in Windows for developers who were familiar with working in a Linux environment; however one of the main pain points of WSL 1 was the extremely slowness when working with files. That changed in better with WSL 2, but the new virtualization system came with a fully NATted VM. Unfortunately that led WSL 2 to not being usable for some environments, for example when UDP communication or broadcasting is needed.
Recently I had some USB Ethernet adapters laying around, and I thought about making it work with WSL 2, with the help
of the usbipd tool.
Recompiling the WSL kernel
The first step to make the adapter work under the WSL is to recompile its kernel so that the necessary drivers are added.
Open a WSL terminal and run:
# Install the building dependencies
$ sudo apt install build-essential flex bison libssl-dev libelf-dev git dwarves libncurses-dev bc
$ git clone https://github.com/microsoft/WSL2-Linux-Kernel.git
$ cd WSL2-Linux-Kernel
$ cp Microsoft/config-wsl .config
Now that we have the sources available, the next thing to do is to update the kernel configuration so that our ethernet
adapter is supported. In my case, I had USBNET already enabled but I needed an additional driver.
# Enter the configuration menu
$ make menuconfig
Search the relevant driver using /; in my case it was RTL8152. Press 1 to navigate to the corresponding
configuration entry and Y to add it to the configuration. Using the arrow keys navigate to < Save >, leave the
default .config name and the configuration menu.
Now build the updated kernel:
# Use your core count as the -j argument
$ make -j16
Starting the WSL with the custom kernel
Now that we have a custom kernel, we need to configure the WSL so that it's used when starting it up. Copy the kernel binary to Windows:
$ cp arch/x86/boot/bzImage /mnt/c/Users/<username>
Then create a file in %userprofile%\.wslconfig with the following content:
[wsl2]
; Double backslashes are required!
kernel=C:\\Users\\<username>\\bzimage
Close all the WSL terminals, then in Powershell run:
> wsl --shutdown
Reopen a WSL terminal.
Insalling usbipd
To use a USB device from the WSL, we can follow the instructions found at https://learn.microsoft.com/it-it/windows/wsl/connect-usb: go to the release page for usbipd and download the setup file from the latest release; then install it. In the WSL terminal, run:
$ sudo apt install linux-tools-generic hwdata
$ sudo update-alternatives --install /usr/local/bin/usbip usbip /usr/lib/linux-tools/*-generic/usbip 20
Using a USB device
Every time a USB device must be used from within the WSL, open a Powershell and run:
> usbipd wsl list
This will list the available USB devices together with a bus identifier; search for the USB ethernet adapter device, then run:
> usbipd wsl attach --busid <busid>
In the WSL terminal, run:
$ lsusb
This should print the ethernet adapter in the device list; this procedure must be followed every time the PC is turned on.
By default, no network manager is installed in WSL, so I had to manually turn on the interface and start a DHCP client for the new interface, then it was fully working.