This is the test case to check if it's possible for other applications (system-config-printer in this case) to modify the firewall.
How to test
system-config-printer >= 1.3.11-5.fc18
2. Run system-config-printer
Click the blue 'plus' button. After entering your password you should see a dialog asking you if you want to adjust firewall. Whether you see the dialog and what items the dialog contains depends on what zone the interface is in. For example: In 'trusted' zone you won't see the dialog at all because all traffic is trusted. In 'home' and 'work' zones you won't see it either because all needed services are already allowed. In 'public' (the default) it will ask you for allowing of 'incoming IPP Browse packets'. Press 'Adjust Firewall'.
After this the needed services should be allowed, see
and check that you see ipp-client, mdns and ipp services.
In the output of system-config-printer --debug you should see something similar to:
Using /org/fedoraproject/FirewallD1 Examining firewall Firewall data obtained Using cached firewall data Asking for permission to adjust firewall: The firewall may need adjusting in order to detect network printers. Adjust the firewall now? - Allow all incoming IPP Browse packets Fetching devices after firewall dialog response
Now quit system-config-printer, do 'service firewalld restart' and try again to test whether the changes previously done to firewall are permanent, i.e. system-config-printer shouldn't ask again to allow once allowed service.