From 849e48c58b76b98e25be6d0ee458bd2940b186c8 Mon Sep 17 00:00:00 2001
From: Guillaume Girol <symphorien+git@xlumurb.eu>
Date: Sun, 25 Feb 2024 12:00:00 +0000
Subject: [PATCH] saned: add option to allow relaying network scanners

My intended use case is the following:
I want to compile saned backends with different libraries (for example
glibc) than a specific application (as if it were a chroot of another
distro version). This application cannot dlopen sane
backends because of the library mismatch.
The specific application will be
built with a stripped down libsane that only has the net backend,
and therefore very few dependencies. The net backend points to saned.
saned has a full config and set of backends, and is responsible for
exporting all scanners to the application. This option allows to
reexport network scanners this way. I only have to make sure saned does
not contact itself.
---
 doc/saned.man    | 12 ++++++++++++
 frontend/saned.c | 11 +++++++++--
 2 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/doc/saned.man b/doc/saned.man
index 400ab6c62..f7f6504f7 100644
--- a/doc/saned.man
+++ b/doc/saned.man
@@ -92,6 +92,18 @@ will request
 .B saned
 to detach from the console and run in the background.
 
+.TP
+.BR \-n ", " \-\-allow\-network
+allows
+.B saned
+to use network scanners. By default this is forbidden to prevent
+.B saned
+from contacting itself. When enabled, the configuration of the
+.BR sane-net (5)
+backend should not mention the address on which
+.B saned
+is listening.
+
 .TP
 .BR \-o ", " \-\-once
 requests that
diff --git a/frontend/saned.c b/frontend/saned.c
index d71d428c5..842a74181 100644
--- a/frontend/saned.c
+++ b/frontend/saned.c
@@ -254,6 +254,7 @@ static int debug;
 static int run_mode;
 static int run_foreground;
 static int run_once;
+static int allow_network;
 static int data_connect_timeout = 4000;
 static Handle *handle;
 static char *bind_addr;
@@ -1869,7 +1870,7 @@ process_request (Wire * w)
 
 	reply.status =
 	  sane_get_devices ((const SANE_Device ***) &reply.device_list,
-			    SANE_TRUE);
+			    !allow_network);
 	sanei_w_reply (w, (WireCodecFunc) sanei_w_get_devices_reply, &reply);
       }
       break;
@@ -3436,6 +3437,7 @@ static void usage(char *me, int err)
        "  -a, --alone[=user]	        equal to `-l -D -u user'\n"
        "  -l, --listen		        run in standalone mode (listen for connection)\n"
        "  -u, --user=user	        run as `user'\n"
+       "  -n, --allow-network	        allow saned to use network scanners\n"
        "  -D, --daemonize	        run in background\n"
        "  -o, --once		        exit after first client disconnects\n"
        "  -d, --debug=level	        set debug level `level' (default is 2)\n"
@@ -3457,6 +3459,7 @@ static struct option long_options[] =
   {"alone",             optional_argument,      0, 'a'},
   {"listen",            no_argument,            0, 'l'},
   {"user",              required_argument,      0, 'u'},
+  {"allow-network",     no_argument,            0, 'n'},
   {"daemonize",         no_argument,            0, 'D'},
   {"once",              no_argument,            0, 'o'},
   {"debug",             required_argument,      0, 'd'},
@@ -3488,8 +3491,9 @@ main (int argc, char *argv[])
   run_mode = SANED_RUN_INETD;
   run_foreground = SANE_TRUE;
   run_once = SANE_FALSE;
+  allow_network = SANE_FALSE;
 
-  while((c = getopt_long(argc, argv,"ha::lu:Dod:eb:p:B:", long_options, &long_index )) != -1)
+  while((c = getopt_long(argc, argv,"ha::lu:nDod:eb:p:B:", long_options, &long_index )) != -1)
     {
       switch(c) {
       case 'a':
@@ -3504,6 +3508,9 @@ main (int argc, char *argv[])
       case 'u':
 	user = optarg;
 	break;
+      case 'n':
+	allow_network = SANE_TRUE;
+	break;
       case 'D':
 	run_foreground = SANE_FALSE;
 	break;