Ok, of course this didn't go as planned. It took longer than expected to figure out how to best test my DNS library, which by itself seems to work ok but also only is a thin wrapper around tdgram, so it doesn't do anything fancy yet.
I played with getting some code into the server, but I think I'm not quite doing the right thing there yet. I've set myself a deadline until tomorrow 11:00, if I haven't got it by then, I'm back to TSIG et al.
All in all, I notice that with all the python programming I've been doing recently, my C-fu has rusted a bit. I hope today will prove to be the WD-40 I needed to get going again. :)
Oh well, enough for today, more Samba DNS work will come tomorrow.