Randomize mac address

macchanger莫名奇妙的失效了，結果在wiki裏搜到好方法，簡直太好用了。

Configuring MAC Address Randomization

As of version 1.4.0, NetworkManager supports two types MAC Address Randomization: randomization during scanning, and stable randomization. Both modes can be configured by modifying /etc/NetworkManager/NetworkManager.conf.

Randomization during Wi-Fi scanning is enabled by default starting on version 1.2.0, and it can be disabled by adding the following lines to /etc/NetworkManager/NetworkManager.conf:

[device]
wifi.scan-rand-mac-address=no

In contrast, stable randomization generates a different MAC address for each different connection. This is specially useful when, for example, a portal remembers your login status based on your MAC address. To enable this mode, you can use the option

[connection]
wifi.cloned-mac-address=random

or

[connection]
ethernet.cloned-mac-address=random

You can read more about it here