ike: Optionally use DPD to check if the current path still works

We could maybe check the duration of the last stale condition or when
the last packet was sent as filter to avoid unnecessary updates.

src/libcharon/sa/ike_sa.c

@@ -2708,6 +2708,14 @@ METHOD(ike_sa_t, roam, status_t,
 			this->task_manager->queue_mobike(this->task_manager, FALSE, TRUE);
 			return this->task_manager->initiate(this->task_manager);
 		}
+		if (lib->settings->get_bool(lib->settings,
+								"%s.check_current_path", FALSE, lib->ns) &&
+			!this->task_manager->busy(this->task_manager))
+		{
+			DBG1(DBG_IKE, "checking if current path still works using DPD");
+			this->task_manager->queue_dpd(this->task_manager);
+			return this->task_manager->initiate(this->task_manager);
+		}
 		return SUCCESS;
 	}