Snort 3.0 is still in Alpha.. we should probably try to upgrade to 2.9.8.2 which is the latest. The shield as well as the OpenWRT repo is on 2.9.7.2 which is EOL and was released Dec 2014. I had someone try to make a package of 2.9.8.2 but was having compiling errors and couldn't get it. Anyone knowledgeable in building OpenWRT packages out there?
Running the latest OpenWrt stable release