[knot-dns-users] Is it possible to inhibit a response?

I've written aknot module, which is functioning well.  I've been asked to add functionality to it that would inhibit any response from knot, based upon the client's identity.  I know the identity; I just need to figure out how to inhibit a response. I just noticed the rrl module, and I looked at what it does.  I emulated what I saw and set pkt->size = 0 and returned KNOTD_STATE_DONE. When I ran host -a, it returned that no servers could be reached.  When I ran dig ANY, I ultimately got the same response, but dig complained three times about receiving a message that was too short in length. I really want NO message to be returned.  How do I force this?