Description:

When cupsd is instructed in /etc/cups/cupsd.conf to listen only on some selected interfaces (IPs), instead on all (by “Port” directive), it may happen, that the daemon ends up listening on the wrong IP, if “Listen” directive was supplied with hostname (instead of explicit IP address) and cupsd wasn't able to query DNS to supply proper IP for the hostname. It's most likely to happen, when the host running cupsd relies on DHCP to configure its interfaces and cupsd is started before relevant interfaces are brought up.

For example:

I'm booting my host. In /etc/cups/cupsd.conf (original attached to this report) I've got 3 “Listen” directives: one set to localhost, one to socket and one to my hostname (“gizmo:631”). When the host is up and running, I can see (ss -tuln | grep -i 631) that cupsd listens on localhost (127.0.0.1) and on 127.0.0.2, instead on the IP assigned to my host via DHCP. Restarting cupsd service (I'm using systemd), of course, solves the problem, but it's at least inconvenient to do.

Obviously setting IP to some explicit value would be, most of the time, a feasible option, but that kind of hard-coding things may be dangerous too.

Maybe dependency on network would be in order in cupsd service?


Additional info:
* any



Steps to reproduce:
* Make sure cupsd listens only on interfaces defined by “Listen” directives in /etc/cups/cupsd.conf and at least one of these interfaces is defined as a hostname.
* Make sure that previously given hostname's IP can be retrieved by DNS query.
* Make sure org.cups.cupsd.service is enabled and appropriate interface is configured by DHCP.
* Boot the system.
* Check the IPs of the interfaces the cups daemon listens on.