Set Country code before scanning for WiFi

[agners]

Description

Problem

By default WiFi interfaces are in the global domain (country code "00"). However, in this domain WiFis running on certain frequencies (e.g. Channel 153 running on 5765MHz) is disabled, thus not allowing to even see the access point.

This came up previously in the OS issue tracker: https://github.com/home-assistant/operating-system/issues/785 https://github.com/home-assistant/operating-system/issues/1530 https://github.com/home-assistant/operating-system/issues/2755

Solution

Setting the country before scanning allows to scan those APs.

WPA supplicant allows to set the country code per WiFi interface. According to the D-Bus documentation (https://w1.fi/wpa_supplicant/devel/dbus.html#dbus_interface) this matches the setting in wpa_supplicant.conf.

In a quick test setting the country before scanning enables frequencies which are otherwise disabled (as shown by iw reg get)

busctl set-property fi.w1.wpa_supplicant1 /fi/w1/wpa_supplicant1/Interfaces/0 fi.w1.wpa_supplicant1.Interface Country s US

Implementation

The country code used in WiFi regulatory domain is a ISO3166-alpha2 country code. From what I can tell this is what our whoami server is using, so we can reuse this information. However, in case the user wants to on-board via terminal/CLI, we should offer a override/fallback, e.g.

ha network scan --country=US

Open quesitons:

Do we need to store that override country? What if it differes with what the API returns?

busctl get-property org.freedesktop.NetworkManager /org/freedesktop/NetworkManager/Devices/3 org.freedesktop.NetworkManager.Device Interface
busctl get-property fi.w1.wpa_supplicant1 /fi/w1/wpa_supplicant1/Interfaces/0 fi.w1.wpa_supplicant1.Interface Ifname

Additional context

No response

[agners]

The NetworkManager and WPA Supplicant interface can be linked using

busctl get-property org.freedesktop.NetworkManager /org/freedesktop/NetworkManager/Devices/3 org.freedesktop.NetworkManager.Device Interface
busctl get-property fi.w1.wpa_supplicant1 /fi/w1/wpa_supplicant1/Interfaces/0 fi.w1.wpa_supplicant1.Interface Ifname

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