linuxshellnetworkmanager

Detect if current connection is metered with NetworkManager

How can I detect whether the current connection is marked as metered on a system with NetworkManager?

This is from a shell script, but I can easily call any C functions via Python.

Solution

  • With the nmcli utility, the necessary steps are:

    1. verify NetworkManager is version 1.0.6+:

      $ nmcli -v nmcli tool, version 1.9.0

    2. check GENERAL.METERED on an interface:

      $ nmcli -t -f GENERAL.METERED dev show eth1 GENERAL.METERED:unknown

    3. values are: unknown, yes, no, yes (guessed), no (guessed)

    4. Forcing the value is done like this:

      $ nmcli dev modify wlan1 connection.METERED yes Connection successfully reapplied to device 'wlan1' $ nmcli -t -f GENERAL.METERED dev show wlan1 GENERAL.METERED:yes

    And, to get a list grouped by device:

      $ nmcli -t -f GENERAL.DEVICE,GENERAL.METERED dev show

  GENERAL.DEVICE:wlan1
  GENERAL.METERED:yes

  GENERAL.DEVICE:eth1
  GENERAL.METERED:unknown

  GENERAL.DEVICE:lo
  GENERAL.METERED:unknown

    Trying to cut this down to info on just the default route would still require a call to another command as NetworkManager doesn't try to distinguish between multiple devices in a connected state:

      $ nmcli -t -f GENERAL.DEVICE,GENERAL.METERED dev show `ip route list 0/0 | sed -r 's/.*dev (\S*).*/\1/g'`