It is safer to enable send-sci by default because, at the cost of
8-byte overhead, it makes MACsec work over bridges (note that kernel
also enables it by default). While at it, also make the option
configurable.
https://bugzilla.redhat.com/show_bug.cgi?id=1588041
The new NMSettingMacsec contains information necessary to establish a
MACsec connection. At the moment we support two different MACsec
modes, both using wpa_supplicant: PSK and EAP.
PSK mode is based on a static CAK key for the MACsec key agreement
protocol, while EAP mode derives keys from a 802.1x authentication and
thus requires the presence of a NMSetting8021x in the connection.