Lprint is sensitive to both system hostname and server name

[mairas]

Here's something very, very weird that I've been struggling with for the past 10 hours or so. lprint seems to be very finicky about the system hostname settings.

Here's what I have:

My home office network uses both mDNS (*.local) and and actual DNS server (with the domain *.hal, dynamically populated by the router from the DHCP data) to resolve host addresses.

I have an existing print server, let's call it print.local, that is a proxmox container running Debian bookworm (amd64) with a self-built lprint server (I had trouble getting snap to work inside the container).

I have two USB label printers connected to print.local:

• Munbyn ITPP941, a generic 203dpi TSPL printer
• Vevor Y428BT, a generic 300dpi TSPL printer.

Both have been working without any issues: I've been printing to both on Mac command line and GUI apps.

Next, I got a Raspberry Pi CM4 device called pi.hal (arm64, running Raspeberry Pi OS Bookworm) and installed lprint on it using snap. Fairly straightforward. I can print a .png file to both printers using lprint on the command line.

Then, the troubles start. On pi.hal command line, lp -d VevorPi debug_output_ADDRESSLABEL_20240506173419.pdf results in no output. Debug logging gives the following:

Validate-Job request:   print-quality enum 0
...
Validate-Job response: IPP/2.0 request-id=2, status-code=client-error-attributes-or-values-not-supported
...
Validate-Job response:   status-message textWithoutLanguage Unsupported print-quality enum value.

Same happens with the Munbyn printer.

Mac behavior is even stranger. I could see and install the printers on the system print dialog but printing a PDF label using the preview app is first stuck in "Processing page: 1" and then after a longish time, in Print Center, the print job appears and the printer goes offline. As soon as I pause the job, the printer immediately comes back online.

This all worked on print.local. I went through the lprint.state files on both machines and couldn't find any differences, and also the server command line arguments were identical. I tried also a self-built lprint on pi.hal, but that didn't make a difference.

Changing the server-name option on pi.hal to either pi.hal or pi.local seemed to cause some change in the Mac behavior, and then I noticed the other server /etc/hostname was print.local, so I tried changing the Pi /etc/hostname to pi.local. After that, printing to either printer worked, both locally, from a remote Linux host, and from the Mac laptop.

I also tried setting /etc/hostname to a "bare" hostname: pi. This resulted in printing from the Mac laptop still working, but when printing from another Linux with lp, I got the same "print-quality enum 0" thing as above.

As said, I spent quite a few hours debugging this issue. There was really no hint that any of the errors would be related to the hostname. At some point I got errors in the debug level log about bad hostname or something similar - I wonder is lprint too restrictive in its hostname matching? I think none of this would've happened if only the bare hostname was matched to the request.

[mairas]

The blabbering above was of course coincidental. Now I am getting that error regardless of the hostname:

May 13 14:09:22 shopship.local lprint.lprint-server[694]: I [2024-05-13T11:09:22.916Z] [Client 12] Validate-Job client-error-attributes-or-values-not-supported (Unsupported print-quality enum value.)

I will continue investigating and will report when I find anything.

[mairas]

Printing succeeds if I set -o cupsPrintQuality=Normal:

lp -d VevorPi -o media=101x220mm -o cupsPrintQuality=Normal -o print-scaling=none debug_output_shipping_label_20240513105329.pdf```

Setting the same option as default does not help:

sudo lpadmin -d VevorPi -o cupsPrintQuality-default=Normal

[michaelrsweet]

OK, so you are having a bunch of problems, and not all of them related I think.

The CUPS "lp" and "lpadmin" command issues are specific to CUPS and not LPrint. The "print-quality" option is what IPP calls an enum value - 3 is draft, 4 is normal, and 5 is high or best quality. The strings are only supported for the "cupsPrintQuality" option which is part of the PPD options. The default PPD option name is "DefaultcupsPrintQuality", not "cupsPrintQuality-default"...