Running C++ .so filters in Big Ip using iRules or any other way

There's no supported way to make a binary library call, but perhaps you could look at using the ICAP protocol to get your requests and replies to a different box, and implement your filter there.

https://support.f5.com/kb/en-us/products/big-ip_ltm/manuals/product/ltm-implementations-12-0-0/16.html?sr=53781983

Alternatively, you could look at implementing the logic of your filter in an iRule, and apply that to the virtual server(s) required.