debian: fix network targets order for systemd unit

[sohorx]

This PR make network.target up after ifupdown2 is finished. Before this, no service would bring up network.target which is a main dependency for ordering services around network.

As explain in the systemd documentation¹, network.target is not pulled by any services. Instead, it is pulled in by the network management service, which we are.

For further examples the ifupdown package (on bullseye) is bundled with this unit:

[Unit]
Description=Raise network interfaces
Documentation=man:interfaces(5)
DefaultDependencies=no
Requires=ifupdown-pre.service
Wants=network.target
After=local-fs.target network-pre.target apparmor.service systemd-sysctl.service systemd-modules-load.service ifupdown-pre.service
Before=network.target shutdown.target network-online.target
Conflicts=shutdown.target

[Install]
WantedBy=multi-user.target
WantedBy=network-online.target

[Service]
Type=oneshot
EnvironmentFile=-/etc/default/networking
ExecStart=/sbin/ifup -a --read-environment
ExecStop=/sbin/ifdown -a --read-environment --exclude=lo
RemainAfterExit=true
TimeoutStartSec=5min

And systemd-networkd also work by pulling in network.target.

Footnotes

1. https://www.freedesktop.org/wiki/Software/systemd/NetworkTarget/#conceptsinsystemd ↩

[sohorx]

While I'm uncertain if this would cause issues with known services (except for some of mine), it's still preferable to do things correctly.