Hello

Its been a while when I visited you guys.

Is there any way to block connections at as soon as Layer2? programming related.
Do I HAVE to study tc (traffic control) INSTEAD ?
I am able to create AF_PACKET+SOCK_RAW sockets but I can only listen... or not?

I require a guaranteed block, unless my program makes decision - traffic goes nowhere.

If you want to block connections that means TCP protocol? For same effect simply block remote address via iptables

I never wrote a firewall before. Can somebody throw at a few IOCTLs or a set to functions with correct params.
Unfortunately use iptables or install pfsense on separate computer is typical response.

There's this article on "How to create a micro-firewall with kernel modules and packet filtering". There's also this related packet filtering diagram from Wikipedia which can provide a visual.

Hacking iptables is also possible, which may be what Melissa meant.

I only have a 'barely-working' OpenSUSE on Windows 10 from the Windows Store at the moment, so I can't really test anything out, but converting the LinuxJournal C functions to fasm should be possible. If that example still works (a better, newer approach may have replaced this), it could at least provide a quick running example so you can see if that's what you're looking for. May not be low-enough level for you, however..