Never take your wifi for granted with Linux ! After updating to Ubuntu 17.10 on your dell XPS 13, did you find yourself devoid of wifi ?
Fortunately the solution is simple, just run this command :
sudo apt install --reinstall bcmwl-kernel-source
It will reinstall the driver for the Broadcom Wireless Card of your laptop.
You might need to
sudo reboot after, but I didn't.
More detailed instructions can be found here : https://askubuntu.com/a/60395/649516
Good luck sir !