units: introduce network-pre.target as place to hook in firewalls network-pre.target is a passive target that should be pulled in by services that want to be executed before any network is configured (for example: firewall scrips). network-pre.target should be ordered before all network managemet services (but not be pulled in by them). network-pre.target should be order after all services that want to be executed before any network is configured (and be pulled in by them).