Though I've really liked DDWRT in the past, that whole community has
seemingly fallen apart and trying to follow the
documentation/FAQs/updates to understand what images will/won't work
will drive you crazy. As such, I generally recommend people to use
OpenWRT these days and indeed your Dlink unit is supported (depending on
which specific revision of DIR-615 you have):
https://wiki.openwrt.org/toh/d-link/dir-615
Once installed and running OpenWRT (or even DDWRT) compared to your
stock vendor firmware, it's instantly like you're using a highend
enterprise piece of equipment. The richness of features, logging, etc.
is very impressive! I encourage everyone to give it a try as it really
does breath new life into old equipment (keeps it secure too!).
--David
KI6ZHD