Just to keep an update. After some tests, and a lot of work, I couldn't trust only in netifyd for application detection. It works, at some level, but for sure there are many work to do about netfyd. So, let's take some considerations:
There's no support for their firewall utility, thus if you need to take any action from the netifyd, it must be implemented by a third script/software. This issue itself doesn't botters me at all, because I'm a developer, so It's something I can do. But if it doesn't your case, it will not work.
The detection itself aren't that much trustful, sometimes it takes so long to identify a connection from an appliance, and it for sure can't detect all conections from youtube, whatsapp, facebook and some of the most popular apps.
It lack's in documentation. I had a hard time to make it run for the first time as a socket. Part of that was because of the output format that wasn't clear how it should be.
So, after that, I gave up about implement my Layer 7 firewall application using only the netifyd. For this purpose, the openappid + snort, did a much more reliable detection. About the snort itself, to prevent it from consuming all processing power and a huge amount of memory, my solution was to implement it in IDS mode, and write some scripts to configure firewall rules from the alert output. It isn't perfect too, and can't detect all traffic from some applications too, like youtube ( it's really annoying trying to block youtube). Maybe writing some more rules for the openappid itself can help to improve the results.
So far, it isn't that simple to track app connections. Maybe I'm lacking in knowledge to do it, but for now it's my solution architecture:
The Image descriptions are in Portuguese, but basically, on top I wrote an application to configure snort and netify to watch the network traffic, this application then read netify and snort notifications and writes iptables and QoS rules to block/control/monitoring application's traffic.
So far so good, it isn't perfect, but works well enough for my needs.
Suggestions are welcome too!