isisd: Fix isisd to generate lsps after config processing is complete

Before:
isisd generates its initial lsp before fully processing the written config. Ex: lsp_generate() is called in isis_instance_area_address_create(), before other configs that may affect the lsp are loaded in, like set-overload-bit.

After:
isisd generates its initial lsp as soon as the config is fully processed. This was done by utilizing the initialization config callbacks, similar to bgp's implementation.

Signed-off-by: Isabella de Leon <ideleon@microsoft.com>

isisd/isis_lsp.c

@@ -1377,6 +1377,10 @@ int lsp_generate(struct isis_area *area, int level)
 	if ((area == NULL) || (area->is_type & level) != level)
 		return ISIS_ERROR;
 
+	/* Check if config is still being processed */
+	if (thread_is_scheduled(t_isis_cfg))
+		return ISIS_OK;
+
 	memset(&lspid, 0, ISIS_SYS_ID_LEN + 2);
 
 	memcpy(&lspid, area->isis->sysid, ISIS_SYS_ID_LEN);

isisd/isis_main.c

@@ -181,6 +181,40 @@ static const struct frr_yang_module_info *const isisd_yang_modules[] = {
 };
 /* clang-format on */
 
+
+static void isis_config_finish(struct thread *t)
+{
+	struct listnode *node, *inode;
+	struct isis *isis;
+	struct isis_area *area;
+
+	for (ALL_LIST_ELEMENTS_RO(im->isis, inode, isis)) {
+		for (ALL_LIST_ELEMENTS_RO(isis->area_list, node, area))
+			config_end_lsp_generate(area);
+	}
+}
+
+static void isis_config_start(void)
+{
+	/* Max wait time for config to load before generating lsp */
+#define ISIS_PRE_CONFIG_MAX_WAIT_SECONDS 600
+	THREAD_OFF(t_isis_cfg);
+	thread_add_timer(im->master, isis_config_finish, NULL,
+			 ISIS_PRE_CONFIG_MAX_WAIT_SECONDS, &t_isis_cfg);
+}
+
+static void isis_config_end(void)
+{
+	/* If ISIS config processing thread isn't running, then
+	 * we can return and rely it's properly handled.
+	 */
+	if (!thread_is_scheduled(t_isis_cfg))
+		return;
+
+	THREAD_OFF(t_isis_cfg);
+	isis_config_finish(t_isis_cfg);
+}
+
 #ifdef FABRICD
 FRR_DAEMON_INFO(fabricd, OPEN_FABRIC, .vty_port = FABRICD_VTY_PORT,
 
@@ -244,6 +278,7 @@ int main(int argc, char **argv, char **envp)
 	/*
 	 *  initializations
 	 */
+	cmd_init_config_callbacks(isis_config_start, isis_config_end);
 	isis_error_init();
 	access_list_init();
 	access_list_add_hook(isis_filter_update);

isisd/isisd.c

@@ -100,6 +100,9 @@ static struct isis_master isis_master;
 /* ISIS process wide configuration pointer to export. */
 struct isis_master *im;
 
+/* ISIS config processing thread */
+struct thread *t_isis_cfg;
+
 #ifndef FABRICD
 DEFINE_HOOK(isis_hook_db_overload, (const struct isis_area *area), (area));
 #endif /* ifndef FABRICD */
@@ -3247,6 +3250,16 @@ void isis_area_overload_on_startup_set(struct isis_area *area,
 	}
 }
 
+void config_end_lsp_generate(struct isis_area *area)
+{
+	if (listcount(area->area_addrs) > 0) {
+		if (CHECK_FLAG(area->is_type, IS_LEVEL_1))
+			lsp_generate(area, IS_LEVEL_1);
+		if (CHECK_FLAG(area->is_type, IS_LEVEL_2))
+			lsp_generate(area, IS_LEVEL_2);
+	}
+}
+
 /*
  * Returns the path of the file (non-volatile memory) that contains restart
  * information.

isisd/isisd.h

@@ -112,6 +112,8 @@ struct isis {
 
 extern struct isis_master *im;
 
+extern struct thread *t_isis_cfg;
+
 enum spf_tree_id {
 	SPFTREE_IPV4 = 0,
 	SPFTREE_IPV6,
@@ -327,6 +329,8 @@ char *isis_restart_filepath(void);
 void isis_restart_write_overload_time(struct isis_area *isis_area,
 				      uint32_t overload_time);
 uint32_t isis_restart_read_overload_time(struct isis_area *isis_area);
+void config_end_lsp_generate(struct isis_area *area);
+
 /* YANG paths */
 #define ISIS_INSTANCE	"/frr-isisd:isis/instance"
 #define ISIS_SR		"/frr-isisd:isis/instance/segment-routing"