Hi Przemek,

thank you for trying the driverless and the investigation!

Would you mind checking if the similar bug isn't already reported on Avahi in Fedora and reporting it if not? Maybe Avahi maintainers can point out what is the best for debugging Avahi.

I recommend setting debug logging on avahi-daemon service file, maybe its logs will show something more.

There are so many moving pieces here that it's hard to get a handle on this. I had trouble seeing local network printers so I tried following the advice Zdenek published [1], but I ran into a nest of issues: printing depending on avahi, which fails quietly and is hard to debug.

Specifically, I did   avahi-browse -avrt  which just returns with
avahi_service_browser_new() failed: Invalid service type

This seems to be related to a bug where some devices are sending non-compliant data to avahi:  https://github.com/lathiat/avahi/issues/212 but we're already far away from the print subsystem.. I tried running avahi-browser under gdb but between the missing and not-autoloading debuginfo packages, and the callback-style structure, I wasn't able to catch it receiving the data that causes the problem.

I guess my point here is that we have a complex, interdependent system, and when it fails, it is fairly opaque. At this point I am not sure what to do: is the root cause here the avahi bug? I am willing to spend the effort getting to the bottom of it but I can't figure out where to start.

On 5/24/21 1:42 PM, Stephen John Smoogen wrote:

I have had very bad luck in setting up new network printers over the last 4 years. I can get all of them to print from Windows and Mac, but every one of them from HP, Brother, and some other brands could not print anything from Linux. They were all 'Linux ready' but were doing it via either Google Print or a set of proprietary software blobs to be put on the computer. [They even came with ipp filters but they called the blobs]. I have a Brother MFC-27100W in my office which I print to via my wife's Mac because of this.

 

I have written some basic info about how to find out whether your printer supports driverless [1] and how to setup it [2]. If you have at least F33 and have the device in your LAN, you can use temp queues for sure, otherwise you need to create a permanent queue via lpadmin:

$ lpadmin -p <name> -v <uri from lpinfo -l -v or ippfind> -m everywhere -E

If you still experience the issue, do feel free to file a bug for cups in bugzilla and I can look into it further.

[1] https://fedoraproject.org/wiki/How_to_debug_printing_problems#How_to_find_out_whether_my_printer_is_capable_of_driverless_printing.3F

[2] https://fedoraproject.org/wiki/How_to_debug_printing_problems#How_to_setup_CUPS_temporary_queues_with_network_printer

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Zdenek Dohnal
Software Engineer
Red Hat Czech - Brno TPB-C