isisd: fix building asla at first flex-algo config

When an color affinity is set on an interface before configuring the
flex-algorithm, the ASLA (Application Specific Link-Attribute) sub-TLV
is not build. Flex-algo fails to build the paths when a affinity
constraint is required because of the lacking of information contained
in ASLA. There are no problems when the configuration order is reversed.
For example:

> affinity-map red bit-position 1
>
> interface eth2
>  link-params
>   affinity red
>
> router isis 1
>  mpls-te on
>  flex-algo 129
>   dataplane sr-mpls
>   advertise-definition
>   affinity include-any green

In isis_link_params_update_asla(), the ASLA sub-TLV is not build when
the list of flex-algos is empty.

Update ASLA when the first flex-algorithm is configured.

Fixes: 893882e ("isisd: add isis flex-algo configuration backend")
Signed-off-by: Louis Scalbert <louis.scalbert@6wind.com>

isisd/isis_nb_config.c

@@ -2838,7 +2838,9 @@ int isis_instance_flex_algo_create(struct nb_cb_create_args *args)
 {
 	struct isis_area *area;
 	struct flex_algo *fa;
-	bool advertise;
+	bool advertise, update_te;
+	struct isis_circuit *circuit;
+	struct listnode *node;
 	uint32_t algorithm;
 	uint32_t priority = FLEX_ALGO_PRIO_DEFAULT;
 	struct isis_flex_algo_alloc_arg arg;
@@ -2851,6 +2853,7 @@ int isis_instance_flex_algo_create(struct nb_cb_create_args *args)
 		area = nb_running_get_entry(args->dnode, NULL, true);
 		arg.algorithm = algorithm;
 		arg.area = area;
+		update_te = list_isempty(area->flex_algos->flex_algos);
 		fa = flex_algo_alloc(area->flex_algos, algorithm, &arg);
 		fa->priority = priority;
 		fa->advertise_definition = advertise;
@@ -2862,6 +2865,12 @@ int isis_instance_flex_algo_create(struct nb_cb_create_args *args)
 			admin_group_allow_explicit_zero(
 				&fa->admin_group_include_all);
 		}
+		if (update_te) {
+			for (ALL_LIST_ELEMENTS_RO(area->circuit_list, node,
+						  circuit))
+				isis_link_params_update_asla(circuit,
+							     circuit->interface);
+		}
 		lsp_regenerate_schedule(area, area->is_type, 0);
 		break;
 	case NB_EV_VALIDATE:

isisd/isis_te.c

@@ -164,8 +164,8 @@ void isis_mpls_te_term(struct isis_area *area)
 	XFREE(MTYPE_ISIS_MPLS_TE, area->mta);
 }
 
-static void isis_link_params_update_asla(struct isis_circuit *circuit,
-					 struct interface *ifp)
+void isis_link_params_update_asla(struct isis_circuit *circuit,
+				  struct interface *ifp)
 {
 	struct isis_asla_subtlvs *asla;
 	struct listnode *node, *nnode;

isisd/isis_te.h

@@ -112,6 +112,8 @@ void isis_mpls_te_init(void);
 void isis_mpls_te_create(struct isis_area *area);
 void isis_mpls_te_disable(struct isis_area *area);
 void isis_mpls_te_term(struct isis_area *area);
+void isis_link_params_update_asla(struct isis_circuit *circuit,
+				  struct interface *ifp);
 void isis_link_params_update(struct isis_circuit *, struct interface *);
 int isis_mpls_te_update(struct interface *);
 void isis_te_lsp_event(struct isis_lsp *lsp, enum lsp_event event);