F9 - cups - windows shared printer

[Andy Eager]

OK, for anyone interested (and as a way of documenting the problem), I 
finally got to the bottom of this issue.
It has absolutely nothing to do with users, groups, cups authentication, 
Firefox or much else discussed in this thread!!

I was using ipp as the printing protocol to talk to the printer:- A 
Konica-Minolta MC2450.
ipp://printer_hostname:631/ipp

Not sure whether the problem is with CUPS implementation of ipp or the 
printer itself, but if I change to JetDirect 
(socket://printer_hostname), then everything works just fine.

Now for the gory details:

* printers.conf is setup initially without the AuthInfoRequired line 
(which is the same AuthInfoRequired none)
* When I try to print I get the following:
   E [25/Jul/2008:17:20:53 +1000] [Job 1] Unable to get job 1997 
attributes (client-error-not-authorized)!
   I [25/Jul/2008:17:20:53 +1000] Saving printers.conf...
   E [25/Jul/2008:17:20:53 +1000] PID 5314 (/usr/lib/cups/backend/ipp) 
stopped with status 2!
   D [25/Jul/2008:17:20:53 +1000] [Job 1] File 0 is complete.
   I [25/Jul/2008:17:20:53 +1000] [Job 1] Backend returned status 2 
(authentication required)
* When cupsd saves printers.conf, it decides (incorrectly) that 
authentication is required and inserts the AuthInfoRequired negotiate 
line into printers.conf

For any cups developers reading this, here's the code that does this 
from job.c: (which I believe is semantically incorrect)
if ((attr = cupsGetOption("auth-info-required", num_attrs,  attrs)) != NULL)
      {
         cupsdLogMessage(CUPSD_LOG_ERROR, "WOULD BE SETTING attribute 
%s", attr);
         // cupsdSetAuthInfoRequired(job->printer, attr, NULL);
        cupsdSetPrinterAttrs(job->printer);
        cupsdSaveAllPrinters();
      }
The first line is me wanting to see this event in the log file
The second line is me commenting out the change to AuthInfoRequired.

When I run this modified version of cups, I still see same output in the 
log file, but the job does print (as do any subsequent jobs) and there 
is no change made to printers.conf.

Anyway, that's the full story.
I now know the anatomy of cups way more than I ever wanted to!

Andy