[Printing-architecture] IPP Validate-Job operation and its implementation in CUPS

[Ira McDonald]

Hi,

Commenting just on one point in your note.

Validate-Job has been REQUIRED for all IPP implementations since
original IPP/1.1 (RFC 2911) and is REQUIRED in IETF Standard IPP/1.1
(RFC 8011).  It is NOT optional to support.

Cheers,
- Ira (co-chair of IPP WG)

*Ira McDonald (Musician / Software Architect)*

*Chair - SAE Trust Anchors and Authentication TF*
*Co-Chair - TCG Trusted Mobility Solutions WG*

*Co-Chair - TCG Metadata Access Protocol SG*








*Chair - Linux Foundation Open Printing WGSecretary - IEEE-ISTO Printer
Working GroupCo-Chair - IEEE-ISTO PWG Internet Printing Protocol WGIETF
Designated Expert - IPP & Printer MIBBlue Roof Music / High North
Inchttp://sites.google.com/site/blueroofmusic
<http://sites.google.com/site/blueroofmusic>http://sites.google.com/site/highnorthinc
<http://sites.google.com/site/highnorthinc>mailto: blueroofmusic at gmail.com
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906-494-2434*


On Wed, Oct 21, 2020 at 9:19 AM Zdenek Dohnal <zdohnal at redhat.com> wrote:

> Hi all,
>
> one of our RHEL customers hit an issue with IPP Validate-Job operation
> when using Lexmark CX727de printer.
>
> A print job occasionally fails after IPP backend sends IPP Validate-Job
> request to the printer, but the printer only sends TCP ACK packet after
> receiving the request, and doesn't send 'HTTP/1.1 100 Continue' or full
> response. When an user resubmits the job later, the printer sends the
> correct response and the print job ends successfully.
>
> I came to the conclusion it is a printer firmware bug and recommended
> reporting it to printer vendor, because the printer reports it is capable
> of Validate-Job operation (checked via ipptool), but it occasionally fails.
>
> In this email I would like to ask if there can be a way how to work around
> such printer issues within CUPS, which can be aligned with RFC and PWG
> standards, and can be merged into OpenPrinting/cups project.
>
> I have several ideas:
>
> 1) Validate-Job operation is 'only' recommended since IPP 2.0, so the
> backend would have printed only warning if Validate-Job failed and the IPP
> protocol used for communication is 2.0 or newer
>
> 2) configurable retries for Validate-Job operation - this idea came up
> from printer behavior (Validate-Job works after N retries) and from
> knowledge there are already configurable variables in backends via device
> uri
>
> 3) define a specific IPP_STATUS_* enum variable for failing Validate-Job,
> let the backend fail if ipp_status is that variable and let error-policy
> handle the possible retry
>
> Is some of them acceptable to implement it in CUPS?
>
> Thank you in advance for any suggestions!
>
> Have a nice day,
>
>
> Zdenek
>
> --
> Zdenek Dohnal
> Software Engineer
> Red Hat Czech - Brno TPB-C
>
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>
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