[sane-devel] run saned on ephemeral port

[James Ring]

Hi all,

In developing jfreesane (pure Java client for saned,
https://github.com/sjamesr/jfreesane), I've found that it's useful to
run saned locally with a known configuration (e.g. 1 test device, 4
test devices, various test device configurations). This is complicated
by the fact that saned will only ever listen on sane-port as specified
in /etc/services, or 6566 if that entry is not present.

Would there be any interest in patching saned to accept a -p (port)
argument, which may be zero if an ephemeral port is desired? In the
ephemeral port case, the selected port is logged so the test may find
it.

I attached a proposed patch. What do you think?

Regards,
James

diff --git a/frontend/saned.c b/frontend/saned.c
index 03175428c..23841c47b 100644
--- a/frontend/saned.c
+++ b/frontend/saned.c
@@ -256,6 +256,7 @@ static int run_once;
 static int data_connect_timeout = 4000;
 static Handle *handle;
 static char *bind_addr;
+static short bind_port = -1;
 static union
 {
   int w;
@@ -2841,6 +2842,7 @@ do_bindings_family (int family, int *nfds, struct pollfd **fds, struct addrinfo
   int on = 1;
   int i;
 
+  sane_port = bind_port;
   fdp = *fds;
 
   for (resp = res, i = 0; resp != NULL; resp = resp->ai_next, i++)
@@ -2851,12 +2853,14 @@ do_bindings_family (int family, int *nfds, struct pollfd **fds, struct addrinfo
 
       if (resp->ai_family == AF_INET)
 	{
-	  sane_port = ntohs (((struct sockaddr_in *) resp->ai_addr)->sin_port);
+        if (sane_port != -1) ((struct sockaddr_in *) resp->ai_addr)->sin_port = htons(sane_port);
+        else sane_port = ntohs(((struct sockaddr_in *) resp->ai_addr)->sin_port);
 	}
 #ifdef ENABLE_IPV6
       else if (resp->ai_family == AF_INET6)
 	{
-	  sane_port = ntohs (((struct sockaddr_in6 *) resp->ai_addr)->sin6_port);
+        if (sane_port != -1) ((struct sockaddr_in6 *) resp->ai_addr)->sin6_port = htons(sane_port);
+        else sane_port = ntohs (((struct sockaddr_in6 *) resp->ai_addr)->sin6_port);
 	}
 #endif /* ENABLE_IPV6 */
       else
@@ -2903,6 +2907,28 @@ do_bindings_family (int family, int *nfds, struct pollfd **fds, struct addrinfo
 	  continue;
 	}
 
+      if (sane_port == 0)
+    {
+      /* sane was asked to bind to an ephemeral port, log it */
+      socklen_t len = sizeof (*resp->ai_addr);
+        if (getsockname(fd, resp->ai_addr, &len) != -1)
+      {
+          if (resp->ai_family == AF_INET)
+        {
+          DBG (DBG_INFO, "do_bindings: [%d] selected ephemeral port: %d\n", i, ntohs(((struct sockaddr_in *) resp->ai_addr)->sin_port));
+        }
+
+#ifdef ENABLE_IPV6
+          if (resp->ai_family == AF_INET6)
+        {
+          DBG (DBG_INFO, "do_bindings: [%d] selected ephemeral port: %d\n", i, ntohs(((struct sockaddr_in6 *) resp->ai_addr)->sin6_port));
+        }
+
+#endif /* ENABLE_IPV6 */
+
+      }
+    }
+
       fdp->fd = fd;
       fdp->events = POLLIN;
 
@@ -3391,6 +3417,7 @@ static void usage(char *me, int err)
        "  -d, --debug=level	set debug level `level' (default is 2)\n"
        "  -e, --stderr		output to stderr\n"
        "  -b, --bind=addr	bind address `addr' (default all interfaces)\n"
+       "  -p, --port=port   bind port `port` (default sane-port or 6566)\n"
        "  -h, --help		show this help message and exit\n", me);
 
   exit(err);
@@ -3410,6 +3437,7 @@ static struct option long_options[] =
   {"debug",	required_argument,	0, 'd'},
   {"stderr",	no_argument,		0, 'e'},
   {"bind",	required_argument,	0, 'b'},
+  {"port",	required_argument,	0, 'p'},
   {0,		0,			0,  0 }
 };
 
@@ -3435,7 +3463,7 @@ main (int argc, char *argv[])
   run_foreground = SANE_TRUE;
   run_once = SANE_FALSE;
 
-  while((c = getopt_long(argc, argv,"ha::lu:Dod:eb:", long_options, &long_index )) != -1)
+  while((c = getopt_long(argc, argv,"ha::lu:Dod:eb:p:", long_options, &long_index )) != -1)
     {
       switch(c) {
       case 'a':
@@ -3465,6 +3493,9 @@ main (int argc, char *argv[])
       case 'b':
 	bind_addr = optarg;
 	break;
+      case 'p':
+	bind_port = atoi(optarg);
+	break;
       case 'h':
 	usage(argv[0], EXIT_SUCCESS);
 	break;