How to turn off Wireless power management permanently using systemd-networkd?

Question

This question is very much related to How to turn off Wireless power management permanently, albeit when using systemd-networkd to manage hardware.

I have a headless Raspberry Pi Model 3 connected to a printer whose only job it is to collect print jobs (CUPS) and forward them to the printer (using the AirPrint protocol mostly). Sometimes I cannot ping it. I suspect that the wireless card powers down after awhile. I can rule out connectivity issues because it is near an access point. Is there any way to influence this in my unit configuration? I could not find it documented anywhere.

wlan0.network 
[Match]
Name=wlan0

[Network]
DHCP=yes
#Domains=local

[DHCP]
RouteMetric=20

And yes, I know I can do iwconfig wlan0 power off to disable power management on the device. I just like having static configuration files:

So I am looking for an equivalent to NetworkManager's

/etc/NetworkManager/conf.d/default-wifi-powersave-on.conf

[connection]
wifi.powersave = 2

Answer 1

I ended up writing a parameterized unit configuration to do it.

wlan-always-on@.service

[Unit]
Description=Keep wireless device %i from sleeping.
After=network.target

[Service]
ExecStart=/usr/bin/iw %i set power_save off

[Install]
WantedBy=default.target

Usage

systemctl enable —now wlan-always-on@wlan0.service