SS/USSD: make NCSS session timeout configurable

It may happen that either the MS or an ESME would become
unresponsive, e.g. due to a bug, or a dropped message.
This is why we have SS session timeout, that prevents
keeping 'stalled' sessions forever.

Let's introduce a VTY option, which can be used to configure
this timer (by default it's set to 30 seconds):

hlr
  ...
  ! Use 0 to disable this timer
  ncss-guard-timeout 30

Change-Id: I971fc2cee6fd46d4d5d6dac6c634e0b22fff183d
Related: OS#3717

src/hlr.c

@@ -611,6 +611,9 @@ int main(int argc, char **argv)
 	INIT_LLIST_HEAD(&g_hlr->ss_sessions);
 	INIT_LLIST_HEAD(&g_hlr->ussd_routes);
 
+	/* Init default (call independent) SS session guard timeout value */
+	g_hlr->ncss_guard_timeout = NCSS_GUARD_TIMEOUT_DEFAULT;
+
 	rc = osmo_init_logging2(hlr_ctx, &hlr_log_info);
 	if (rc < 0) {
 		fprintf(stderr, "Error initializing logging\n");

src/hlr.h

@@ -45,6 +45,9 @@ struct hlr {
 	struct hlr_euse *euse_default;
 	struct llist_head iuse_list;
 
+	/* NCSS (call independent) session guard timeout value */
+	int ncss_guard_timeout;
+
 	struct llist_head ussd_routes;
 
 	struct llist_head ss_sessions;

src/hlr_ussd.c

@@ -209,10 +209,11 @@ struct ss_session *ss_session_alloc(struct hlr *hlr, const char *imsi, uint32_t
 	OSMO_STRLCPY_ARRAY(ss->imsi, imsi);
 	ss->session_id = session_id;
 	osmo_timer_setup(&ss->timeout, ss_session_timeout, ss);
-	/* NOTE: The timeout is currently global and not refreshed with subsequent messages
-	 * within the SS/USSD session.  So 30s after the initial SS message, the session will
-	 * timeout! */
-	osmo_timer_schedule(&ss->timeout, 30, 0);
+	/* NOTE: The timeout is currently not refreshed with subsequent messages
+	 * within the SS/USSD session. So X seconds after the initial SS message,
+	 * the session will timeout! */
+	if (g_hlr->ncss_guard_timeout > 0)
+		osmo_timer_schedule(&ss->timeout, g_hlr->ncss_guard_timeout, 0);
 
 	llist_add_tail(&ss->list, &hlr->ss_sessions);
 	return ss;

src/hlr_ussd.h

@@ -7,6 +7,8 @@
 
 #include "gsup_server.h"
 
+#define NCSS_GUARD_TIMEOUT_DEFAULT 30
+
 struct hlr_ussd_route {
 	/* g_hlr.routes */
 	struct llist_head list;

src/hlr_vty.c

@@ -35,6 +35,7 @@
 #include "hlr.h"
 #include "hlr_vty.h"
 #include "hlr_vty_subscr.h"
+#include "hlr_ussd.h"
 #include "gsup_server.h"
 
 struct cmd_node hlr_node = {
@@ -288,9 +289,22 @@ static int config_write_euse(struct vty *vty)
 	if (g_hlr->euse_default)
 		vty_out(vty, " ussd default-route external %s%s", g_hlr->euse_default->name, VTY_NEWLINE);
 
+	if (g_hlr->ncss_guard_timeout != NCSS_GUARD_TIMEOUT_DEFAULT)
+		vty_out(vty, " ncss-guard-timeout %i%s",
+			g_hlr->ncss_guard_timeout, VTY_NEWLINE);
+
 	return 0;
 }
 
+DEFUN(cfg_ncss_guard_timeout, cfg_ncss_guard_timeout_cmd,
+	"ncss-guard-timeout <0-255>",
+	"Set guard timer for NCSS (call independent SS) session activity\n"
+	"Guard timer value (sec.), or 0 to disable")
+{
+	g_hlr->ncss_guard_timeout = atoi(argv[0]);
+	return CMD_SUCCESS;
+}
+
 /***********************************************************************
  * Common Code
  ***********************************************************************/
@@ -353,6 +367,7 @@ void hlr_vty_init(const struct log_info *cat)
 	install_element(HLR_NODE, &cfg_ussd_no_route_pfx_cmd);
 	install_element(HLR_NODE, &cfg_ussd_defaultroute_cmd);
 	install_element(HLR_NODE, &cfg_ussd_no_defaultroute_cmd);
+	install_element(HLR_NODE, &cfg_ncss_guard_timeout_cmd);
 
 	hlr_vty_subscriber_init();
 }

tests/test_nodes.vty

@@ -78,6 +78,7 @@ OsmoHLR(config-hlr)# list
   no ussd route prefix PREFIX
   ussd default-route external EUSE
   no ussd default-route
+  ncss-guard-timeout <0-255>
 
 OsmoHLR(config-hlr)# gsup
 OsmoHLR(config-hlr-gsup)# list