Systemd metered connection dependency

Execute systemd services if current connection is not metered.

Installation

Install `unmetered-connection.service` in `/usr/local/lib/systemd/system`.
Install `check-metered-connection.sh` in `/usr/local/bin`.
Execute `systemctl daemon-reload`

/!\ If you want it to be available to your users:

Install `unmetered-connection.service` in `/usr/local/lib/systemd/user`.
Execute `systemctl --user daemon-reload`

Usage

Systemd

Add the following to any unit you do not want to execute on a metered connection

[Unit]
Requires=unmetered-connection.service
After=unmetered-connection.service

See exemple.service for an exemple usage.

Network Manager

Network Manager might not guess the metered connection status. If so, use the following to mark a connection as metered:

$ nmcli con modify <connection-name> connection.metered yes

How does it work ?

1. When you add the unmetered-connection.service dependency to your service with Requires and After, on activation, your service will start unmetered-connection.service.
2. unmetered-connection.service will execute the check-metered-connection.sh bash script.
3. check-metered-connection.sh then uses DBUS and NetworkManager to check on the current connection status. It returns 0 for an unmetered connection and 1 for a metered connection.
4. If the script returns zero, unmetered-connection.service will fail, preventing execution of your service.

Things to improve

Support other connection managers

Display better logs

Package it (AUR)

Manage multiple connections

Disable metered verification through a service

Directly hook DBUS to systemd service

Use systemd target to start/stop services ?