[sane-devel] Setting backend capabilities

Johannes Meixner jsmeix at suse.de
Mon Mar 9 09:37:02 GMT 2020


On Mar 7 18:17 Ralph Little wrote (excerpt):
> I think most proprietary scan software implementations that I have observed
> use a polling loop of some sort, some utilizing USB INTERRUPT, some not.

I think polling directly connected devices (e.g. via USB) should be OK
but polling devices that are not directly connected (e.g. via network)
is likely not OK in general.

Think about whatever organization network (e.g. company or university)
where many users may have many scanning frontend applications open
that may continuously poll various devices in the network.

We experienced something similar in our SUSE company network
where a naive desktop printing application had been installed
and activated by default as part of a particular Linux desktop.
On each workstation with that Linux desktop its desktop printing
application was continuously monitoring all print queues
to provide continuously up to date user feedback.
That caused network admin alerts because of zillions continuously
happening requests to our CUPS print server which even lead to some
minor kind of denial of service because at that time our CUPS server
was not prepared to deal well with so many simultaneous connections.

What works OK for a single user or in a small private home network
can become a severe annoyance in a bigger network and in a public
network it might even lead to some kind of security issue or things
like that (e.g. continuously polling hosts might get banned).

Kind Regards
Johannes Meixner
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5 - 90409 Nuernberg - Germany
(HRB 36809, AG Nuernberg) GF: Felix Imendoerffer

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