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Hi,<br>
<br>
<div class="moz-cite-prefix">On 2022-08-02 12:46, Guy B wrote:<br>
</div>
<blockquote type="cite"
cite="mid:CAB-P8TZeF1qNgAjVNpn=YRMsYJsA__6V+CPM7Fi9dsTVjCb8bQ@mail.gmail.com">
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<div dir="ltr">I'm trying to determine if this setup can actually
be made to function (and Googling has given no obvious answer).<br>
<br>
Server A - connected to scanner via USB, exposed via network
<div> ↓<br>
Server B - connected to A via the "net" interface, re-exposes
scanner to another net via "net" interface<br>
↓<br>
Server C - connects to B via "net"<br>
<br>
The reason that I'm trying to do this is because "A" in this
use case is actually a VM running an ancient version of Ubuntu
because that's the only place I can make the binary-only
drivers work (and I don't want a 10+ year old version of
Ubuntu exposed to <i>any</i> network). "B" is then a real
machine that I want to use to expose it to the rest of the
network.<br>
<br>
While I've had no trouble plumbing things through to "B", I
can't figure out how (or if it is possible) to re-share the
network scanner again.</div>
<div><br>
</div>
<div>-Guy</div>
</div>
</blockquote>
<br>
So to summarise:<br>
- Server A (VM) will be running the binary driver and saned,<br>
- Server B will be running SANE with the "net" backend
(configured to connect to Server A's saned) and also saned,<br>
- Server C will be running SANE with the "net" backend
(configured to connect to Server B's saned).<br>
<br>
Although this sounds reasonable, the only issue that I can see with
this setup is that saned running on Server B will not pick up the
devices through the "net" backend.<br>
The reason for this is that saned is intended to advertise local
devices only and when asking the "net" backend for local devices, it
will simply return with an empty list.<br>
Partly the reason for this is to stop deadly embrace loops where the
"net" backend and saned could conceivably keep re-advertising each
other's devices in an endless loop.<br>
<br>
Without changing code, I don't see an obvious way around this
restriction. However, there are two ways you could get around this
in your circumstance if you are willing do some minor code changes
and rebuild.<br>
<br>
Do one of:<br>
<br>
A. Rebuild saned with a small change to the code here around line
1851 of saned.c:<br>
<br>
sane_get_devices ((const SANE_Device ***)
&reply.device_list,<br>
SANE_TRUE);<br>
<br>
to <br>
<br>
sane_get_devices ((const SANE_Device ***)
&reply.device_list,<br>
SANE_FALSE);<br>
<br>
This removes the restriction on local-only devices.<br>
<br>
or:<br>
<br>
B. Rebuild the net backend with a small change to the code around
line 1223 of net.c:<br>
<br>
if (local_only)<br>
{<br>
*device_list = empty_devlist;<br>
return SANE_STATUS_GOOD;<br>
}<br>
<br>
...by removing this code entirely.<br>
<br>
If you are willing to give this a try, I would say that changing the
net backend and using that is probably the easiest solution.<br>
To give it a go, I would clone the backends repo, make the change,
build it, take the built net backend files (libsane-net.*) and
temporarily replace your regular ones on Server B with the built
ones so that Server B's saned will see them.<br>
Probably not a good permanent solution but a place to start at
least.<br>
<br>
Actually, since we have had this question come up a couple of times
in the past, it might be an optional feature that we could add,
switched off by default, to the core code.<br>
<br>
Anyway, let us know if you need help giving that a try.<br>
<br>
Cheers,<br>
Ralph<br>
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