Centos VPN server block P2P traffic

I have a Centos6.9 VPN proxy server with kernel 3.9.3-x86_64, I need to set iptables to block and record the P2P traffic such as BT through this server . Preliminary considering application-layer protocol filtering module such as ipp2p or l7-filter , looking for an expert to do the deployment. Other filtering solutions are also welcomed.