iptables-translate -A INPUT -p icmp -m length --length 86:0xffff -j DROP nft add rule ip filter INPUT ip protocol icmp meta length 86-65535 counter drop iptables-translate -A INPUT -p udp -m length --length :400 nft add rule ip filter INPUT ip protocol udp meta length 0-400 counter iptables-translate -A INPUT -p udp -m length --length 40 nft add rule ip filter INPUT ip protocol udp meta length 40 counter iptables-translate -A INPUT -p udp -m length ! --length 40 nft add rule ip filter INPUT ip protocol udp meta length != 40 counter