[systemd-devel] network-online.target is not down when a physical network is down

[Dan Williams]

On Thu, 2015-01-22 at 19:51 +0300, Andrei Borzenkov wrote:
> В Thu, 22 Jan 2015 16:44:52 +0100
> Igor Bukanov <igor at mir2.org> пишет:
> 
> > For a service that should be shutdown when network is not available, I
> > tried to use Requires=network-online.target . However, on Fedora 21
> > with NetworkManager that does not work. When I switch off WiFi, the
> > only connection on my laptop that can configure default IP route and
> > setup /etc/resolv.conf, network-online.target still stays active and
> > my service continues to run. Is it a bug in Fedora? If not, what is a
> > canonical way to implement such dependency?
> 
> 
> No, it is not a bug. network-online was never intended to be used this
> way. It was intended to be used only during startup; when initial
> startup is finished, state of this service is largely irrelevant.
> 
> network-online.target itself does absolutely nothing. It is provided as
> well known name for other services to order itself after; and you need
> to provide implementation that orders itself before.
> 
> For NM implementation would be NetworkManager-wait-online.service that
> basically does nothing more than calling nm-online.
> 
> Note that "network down" does not cause any change state in systemd.
> NetworkManager still runs. systemd itself does not watch or manages
> network, so it cannot initiate any actions here. I suppose you really
> want to hook systemctl stop/systemctl start in NetworkManager
> dispatcher framework.

Yeah, a dispatcher script ("man NetworkManager" has more info) will be
executed whenever any network interface is deconfigured by
NetworkManager.  You could use this, in combination with 'nmcli -f STATE
-t g' (which reports the NM state as a single word, eg "connected" or
"disconnected" or "connecting"), to determine when no network
connections are active, and then run 'systemctl stop your-service".

See also
http://cgit.freedesktop.org/NetworkManager/NetworkManager/tree/examples/dispatcher

Dan