int opkg_list_packages (opkg_package_callback_t callback, void *user_data);
int opkg_list_upgradable_packages (opkg_package_callback_t callback, void *user_data);
int opkg_list_packages (opkg_package_callback_t callback, void *user_data);
int opkg_list_upgradable_packages (opkg_package_callback_t callback, void *user_data);