Make sure iptables and conntrack don't interfere with our traffic

gistfile1.txt

Example
client$ iptables -I INPUT 1 --src 192.168.254.0/24 -j ACCEPT
client$ iptables -t raw -I PREROUTING 1 --src 192.168.254.0/24 -j NOTRACK
server$ iptables -I INPUT 1 --src 192.168.254.0/24 -j ACCEPT
server$ iptables -t raw -I PREROUTING 1 --src 192.168.254.0/24 -j NOTRACK

Example
receiver$ iptables -I INPUT 1 -p udp --dport 4321 -j ACCEPT
receiver$ iptables -t raw -I PREROUTING 1 -p udp --dport 4321 -j NOTRACK

Example
iptables -t raw -I PREROUTING -d 198.18.0.12 -p udp -m udp --dport 1234 -j NOTRACK

Sources
https://blog.cloudflare.com/how-to-drop-10-million-packets/
https://blog.cloudflare.com/how-to-achieve-low-latency/
https://blog.cloudflare.com/how-to-receive-a-million-packets/