The postinst script tries parsing the wireless MAC address from the sysfs, and
in case of failure, obtains a random string from /dev/urandom. This caused two
problems when booting with systemd:
* The wifi interface's sysfs entry is not available because the interface
hasn't had time to start up yet, forcing the script to always resort to the
/dev/urandom fallback.
* Even though the postinst scripts are run after populating the volatile
filesystems (as can be seen in run-postinsts.service's dependencies), trying
to read either /dev/random or /dev/urandom at this point in the system's
initialization causes it to lock up indefinitely.
To avoid either situation, add the following changes:
* Immediately exit when running on a non-wireless target, as the script isn't
necessary in this use case.
* Parse the wireless mac address from /proc/device-tree/wireless, which is
guaranteed to always be available when the script runs. By doing this, we can
remove the /dev/urandom fallback entirely.
https://jira.digi.com/browse/DEL-6415
Signed-off-by: Gabriel Valcazar <gabriel.valcazar@digi.com>
b769f90e2a