evbuffer_cb_clear_flags(struct evbuffer *buffer,
		      struct evbuffer_cb_entry *cb, ev_uint32_t flags)
{
	/* the user isn't allowed to mess with these. */
	flags &= ~EVBUFFER_CB_INTERNAL_FLAGS;
	EVBUFFER_LOCK(buffer);
	cb->flags &= ~flags;
	EVBUFFER_UNLOCK(buffer);
	return 0;
}