[cups-devel] IPP backend bug

Vadim A. Misbakh-Soloviov mva at mva.name
Sun Oct 26 21:39:30 PDT 2014


Hi there!
I've discovered, that CUPS, starting from 1.6.2 (tested on 1.6.2, 1.6.3, 1.7 and 2.0) has some issue in 
IPP backend.

When I using my printer (Epson Stylus TX210), or my parents one (TX410) via usb backend — it 
works flawlessly.

But when I setup it as IPP (and other symlinked backends like http/https/ipps) even on the same 
host (even ipp://localhost/ !) cups silently finishes jobs (like successfully completed), but don't 
print anything. All, that it says in error log is:

>> E [22/Aug/2013:19:52:18 +0700] [Job 643] Invalid printer command "!

With exactly one double-qoute and exclamation mark.

After some debugging I discovered that:

>> I [22/Aug/2013:21:20:09 +0700] [Job 648] Started filter /usr/libexec/cups/filter/commandtoepson 
(PID 3330)
>> I [22/Aug/2013:21:20:09 +0700] [Job 648] Started backend /usr/libexec/cups/backend/ipps (PID 
3331)
>> D [22/Aug/2013:21:20:14 +0700] Discarding unused job-progress event...
>> D [22/Aug/2013:21:20:14 +0700] [Job 649] PID 3333 (/usr/libexec/cups/filter/gziptoany) exited with 
no errors.
>> E [22/Aug/2013:21:20:14 +0700] [Job 649] Invalid printer command "!

That was make me think, that error can be somewhere in compression and encryption, but 
unfortunately even with force-disabled encryption and compression i get:
>> D [22/Aug/2013:21:38:10 +0700] [Job 655] PID 6324 (/usr/libexec/cups/filter/commandtoepson) 
exited with no errors.
>> E [22/Aug/2013:21:38:10 +0700] [Job 655] Invalid printer command "!

Only once, after long debug session, I even get something more informative then quote-
exclamationmark error:
>> D [22/Aug/2013:21:48:44 +0700] [Job 663] Set job-printer-state-message to "Invalid printer 
command "<1B>@<1B>(R<08>"!", current level=INFO


I mostly debugged it on cups-1.6.3 (since, 1.6.2 has broken russian web-interface and don't wont to 
work at all for me), but as I mentioned above, all newer versions affected too.
When I downgraded to, for example, 1.5.2 and removed cups-filters package (filters was bubdled 
at 1.5's time) and doesn't touch (!!!) gutenprint, conatining 'commandtoepson' filter — it start to 
work fine again (but, it seems, every client should downgrade to 1.5 to work with it).

I'm sure it is not guttenprint fault, since same "commandtoepson" filter works like a charm 
with USB backend on any version (including 2.0), and with IPP on <1.6. So, I bet, it is some broken 
API in IPP backend, but I can't get exactly part.
Can somebody confirm the issue and say me, if I should report that on bugtracker or stop and 
discuss here?

-- 
Best regards,
mva


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