I blogged here about adding SQL support to dhcpd. I’ve fixed a couple of issues – mainly memory leaks. I have no idea how I missed these before (sigh). The good news is that the server ran for sufficiently long for the process to get to many gigabytes in size, and nothing crashed!
You can find a new patch, against dhcpd 4.2.0-P1 (but should work against dhcpd 4.2.1-RC1) here.
See the original post here for build instructions and documentation.