nm-applet misses default option for ip6-privacy, breaks setting, leaks data
For IPv6 privacy extensions, network manager itself has the setting ip6-privacy which can have 4 different values: 0/1/2 similar to the sysctl use_tempaddr, and -1 which has the same effect as being not set. If a connection config file doesn't have this ip6-privacy setting, or has the value -1, NM looks next in a global config file, and if there isn't a conclusive answer either then it falls back to reading from /proc/sys/net/ipv6/conf/default/use_tempaddr
That part above is working. Problems are in nm-applet's connection configuration GUI:
a) If the setting is the connect file is -1 or not set, the GUI displays "Disabled" which means 0.
b) When changing something different in the GUI, or even just saving without doing anything else, it will add/overwrite use_tempaddr in the connection file to be 0.
So basically, if someone globally configures all connections to have privacy protections enabled except the connection explicitly is set different, then just using the GUI once breaks that connection config (makes it leaking the MAC etc. to the whole internet, enabling easy tracking etc.) and requires manual config file edits to fix it again (if the problem is noticed at all).
Therefore, would it please be possible to add another selection in that drop-down, like "System default" (value -1), to be used if the connection file has no setting yet etc.?