Hi
On 2022-08-09 20:27, Guy B wrote:
So, I went ahead and gave this a try (specifically, option B) and it
seems to work perfectly well (both via the scanimage commandline and
gscan2pdf). I attempted to rig up enabling this with a flag, but
couldn't grok how sane's flag system worked from just staring at the
code. I've included the diff below in case it is helpful. For now,
I'll leave my dodgy "one-random custom-built so-file" setup in place,
but +1 for making this a mainline feature and thanks for
the assistance. It is most appreciated.
That's great. I will perhaps do a change for the net backend to allow to
allow this to be enabled.
Probably a net.conf option.
Cheers,
Ralph
-Guy
diff --git a/backend/net.c b/backend/net.c
index d16119a81..4acb92730 100644
--- a/backend/net.c
+++ b/backend/net.c
@@ -120,6 +120,7 @@static int client_big_endian; /* 1 == big endian; 0
== little endian */
static int server_big_endian; /* 1 == big endian; 0 == little endian */
static int depth; /* bits per pixel */
static int connect_timeout = -1; /* timeout for connection to saned */
+static SANE_Bool reshare_net = SANE_FALSE; /* if true, reshare
network-connected */
#ifndef NET_USES_AF_INDEP
static int saned_port;
@@ -1117,6 +1118,14 @@sane_init (SANE_Int * version_code,
SANE_Auth_Callback authorize)
DBG (2, "sane_init: connect timeout set to %d seconds from
env\n", connect_timeout);
}
+ DBG (2, "sane_init: evaluating environment variable
SANE_NET_RESHARE\n");
+ env = getenv("SANE_NET_RESHARE");
+ if (env)
+ {
+ reshare_net = SANE_TRUE;
+ DBG (2, "sane_init: resharing of net scanners enabled\n");
+ }
+
DBG (2, "sane_init: done\n");
return SANE_STATUS_GOOD;
}
@@ -1220,7 +1229,7 @@sane_get_devices (const SANE_Device ***
device_list, SANE_Bool local_only)
DBG (3, "sane_get_devices: local_only = %d\n", local_only);
- if (local_only)
+ if (local_only && !reshare_net)
{
*device_list = empty_devlist;
return SANE_STATUS_GOOD;
On Sun, Aug 7, 2022 at 7:39 AM Ralph Little <[email protected]> wrote:
Hi,
On 2022-08-02 12:46, Guy B wrote:
I'm trying to determine if this setup can actually be made to
function (and Googling has given no obvious answer).
Server A - connected to scanner via USB, exposed via network
↓
Server B - connected to A via the "net" interface, re-exposes
scanner to another net via "net" interface
↓
Server C - connects to B via "net"
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 /any/ network). "B" is then a real machine that I want to use
to expose it to the rest of the network.
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.
-Guy
So to summarise:
- Server A (VM) will be running the binary driver and saned,
- Server B will be running SANE with the "net" backend
(configured to connect to Server A's saned) and also saned,
- Server C will be running SANE with the "net" backend
(configured to connect to Server B's saned).
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.
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.
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.
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.
Do one of:
A. Rebuild saned with a small change to the code here around line
1851 of saned.c:
sane_get_devices ((const SANE_Device ***) &reply.device_list,
SANE_TRUE);
to
sane_get_devices ((const SANE_Device ***) &reply.device_list,
SANE_FALSE);
This removes the restriction on local-only devices.
or:
B. Rebuild the net backend with a small change to the code around
line 1223 of net.c:
if (local_only)
{
*device_list = empty_devlist;
return SANE_STATUS_GOOD;
}
...by removing this code entirely.
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.
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.
Probably not a good permanent solution but a place to start at least.
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.
Anyway, let us know if you need help giving that a try.
Cheers,
Ralph
