The program used in this thread appears to send 4096 byte packets. Cant you just change your csgo packet size and then drop larger packets using iptables?
sm_cvar net_maxroutable 768
sm_cvar net_minroutable 768
iptables -N CHECK1
iptables -A INPUT -p udp -m length --length 829 -j CHECK1
iptables -A CHECK1 -p udp -m length --length 829:65535 -m limit --limit 128/second -j ACCEPT
iptables -A CHECK1 -j DROP