How to see debug logs for WireGuard (e.g. to see authentication attempts)

I've successfully set up a WireGuard VPN on my Debian 10 server. It was incredibly straight forward compared to the setup of OpenVPN, and it's working fine.

However, I can't see any logs beyond those from journalctl -u [email protected]. I'd like to know, for example, when there are failed authentication attempts. Is there a way to monitor that? e.g. with openvpn I could use fail2ban based on auth attempts.

Assuming you are running a 5.6 kernel which supports dynamic debugging, you can enable debug logs by executing:

# modprobe wireguard 
# echo module wireguard +p > /sys/kernel/debug/dynamic_debug/control

The logs can than be consumed via dmesg or journalctl. With dmesg, just use following command:

$ dmesg -wH

(-H, --human enables user-friendly features like colors, relative time)

(-w, --follow)

Also on systems with systemd you can use:

$ journalctl -kf