res_pjsip_pubsub: update RLS to reflect the changes to the lists

This patch makes the Resource List Subscriptions (RLS) dynamic.
The asterisk updates the current subscriptions to reflect the changes
to the list on the subscriptions refresh. If list items are added,
removed, updated or do not exist anymore, the asterisk regenerates
the resource list.

ASTERISK-29906 #close

Change-Id: Icee8c00459a7aaa43c643d77ce6f16fb7ab037d3

doc/CHANGES-staging/rls_refresh.txt

@@ -0,0 +1,7 @@
+Subject: res_pjsip_pubsub
+
+The Resource List Subscriptions (RLS) is dynamic now.
+The asterisk now updates current subscriptions to reflect the changes
+to the list on subscription refresh. If list items are added,
+removed, updated or do not exist anymore, the asterisk regenerates
+the resource list.

res/res_pjsip_pubsub.c

@@ -475,6 +475,10 @@ struct sip_subscription_tree {
 	 * Only used for reliable transports.
 	 */
 	pjsip_transport *transport;
+	/*! Indicator if initial notify should be generated.
+	 * Used to refresh modified RLS.
+	 */
+	unsigned int generate_initial_notify;
 };
 
 /*!
@@ -3902,6 +3906,15 @@ static int pubsub_on_refresh_timeout(void *userdata)
 		set_state_terminated(sub_tree->root);
 	}
 
+	if (sub_tree->generate_initial_notify) {
+		sub_tree->generate_initial_notify = 0;
+		if (generate_initial_notify(sub_tree->root)) {
+			pjsip_evsub_terminate(sub_tree->evsub, PJ_TRUE);
+			pjsip_dlg_dec_lock(dlg);
+			return 0;
+		}
+	}
+
 	send_notify(sub_tree, 1);
 
 	ast_test_suite_event_notify(sub_tree->root->subscription_state == PJSIP_EVSUB_STATE_TERMINATED ?
@@ -3926,6 +3939,52 @@ static int serialized_pubsub_on_refresh_timeout(void *userdata)
 	return 0;
 }
 
+/*!
+ * \brief Compare strings for equality checking for NULL.
+ *
+ * This function considers NULL values as empty strings.
+ * This means NULL or empty strings are equal.
+ *
+ * \retval 0 The strings are equal
+ * \retval 1 The strings are not equal
+ */
+static int cmp_strings(char *s1, char *s2)
+{
+	if (!ast_strlen_zero(s1) && !ast_strlen_zero(s2)) {
+		return strcmp(s1, s2);
+	}
+
+	return ast_strlen_zero(s1) == ast_strlen_zero(s2) ? 0 : 1;
+}
+
+/*!
+ * \brief compares the childrens of two ast_sip_subscription s1 and s2
+ *
+ * \retval 0 The s1 childrens match the s2 childrens
+ * \retval 1 The s1 childrens do not match the s2 childrens
+ */
+static int cmp_subscription_childrens(struct ast_sip_subscription *s1, struct ast_sip_subscription *s2)
+{
+	int i;
+
+	if (AST_VECTOR_SIZE(&s1->children) != AST_VECTOR_SIZE(&s2->children)) {
+		return 1;
+	}
+
+	for (i = 0; i < AST_VECTOR_SIZE(&s1->children); ++i) {
+		struct ast_sip_subscription *c1 = AST_VECTOR_GET(&s1->children, i);
+		struct ast_sip_subscription *c2 = AST_VECTOR_GET(&s2->children, i);
+
+		if (cmp_strings(c1->resource, c2->resource)
+			|| cmp_strings(c1->display_name, c2->display_name)) {
+
+			return 1;
+		}
+	}
+
+	return 0;
+}
+
 /*!
  * \brief Called whenever an in-dialog SUBSCRIBE is received
  *
@@ -3966,6 +4025,48 @@ static void pubsub_on_rx_refresh(pjsip_evsub *evsub, pjsip_rx_data *rdata,
 		sub_tree->state = SIP_SUB_TREE_TERMINATE_PENDING;
 	}
 
+	if (sub_tree->state == SIP_SUB_TREE_NORMAL && sub_tree->is_list) {
+		/* update RLS */
+		const char *resource = sub_tree->root->resource;
+		struct ast_sip_subscription *old_root = sub_tree->root;
+		struct ast_sip_subscription *new_root = NULL;
+		RAII_VAR(struct ast_sip_endpoint *, endpoint, NULL, ao2_cleanup);
+		struct ast_sip_subscription_handler *handler = NULL;
+		struct ast_sip_pubsub_body_generator *generator = NULL;
+
+		if ((endpoint = ast_pjsip_rdata_get_endpoint(rdata))
+			&& (handler = subscription_get_handler_from_rdata(rdata, ast_sorcery_object_get_id(endpoint)))
+			&& (generator = subscription_get_generator_from_rdata(rdata, handler))) {
+
+			struct resource_tree tree;
+			int resp;
+
+			memset(&tree, 0, sizeof(tree));
+			resp = build_resource_tree(endpoint, handler, resource, &tree,
+				ast_sip_pubsub_has_eventlist_support(rdata));
+			if (PJSIP_IS_STATUS_IN_CLASS(resp, 200)) {
+				new_root = create_virtual_subscriptions(handler, resource, generator, sub_tree, tree.root);
+				if (new_root) {
+					if (cmp_subscription_childrens(old_root, new_root)) {
+						ast_debug(1, "RLS '%s->%s' was modified, regenerate it\n", ast_sorcery_object_get_id(endpoint), old_root->resource);
+						new_root->version = old_root->version;
+						sub_tree->root = new_root;
+						sub_tree->generate_initial_notify = 1;
+						shutdown_subscriptions(old_root);
+						destroy_subscriptions(old_root);
+					} else {
+						destroy_subscriptions(new_root);
+					}
+				}
+			} else {
+				sub_tree->state = SIP_SUB_TREE_TERMINATE_PENDING;
+				pjsip_evsub_terminate(sub_tree->evsub, PJ_TRUE);
+			}
+
+			resource_tree_destroy(&tree);
+		}
+	}
+
 	subscription_persistence_update(sub_tree, rdata, SUBSCRIPTION_PERSISTENCE_REFRESHED);
 
 	if (ast_sip_push_task(sub_tree->serializer, serialized_pubsub_on_refresh_timeout, ao2_bump(sub_tree))) {