iptables-translate -t filter -A INPUT -m conntrack --ctstate NEW,RELATED -j ACCEPT
nft add rule ip filter INPUT ct state new,related counter accept

ip6tables-translate -t filter -A INPUT -m conntrack ! --ctstate NEW,RELATED -j ACCEPT
nft add rule ip6 filter INPUT ct state != new,related counter accept

iptables-translate -t filter -A INPUT -m conntrack --ctproto UDP -j ACCEPT
nft add rule ip filter INPUT ct original protocol 17 counter accept

iptables-translate -t filter -A INPUT -m conntrack ! --ctproto UDP -j ACCEPT
nft add rule ip filter INPUT ct original protocol != 17 counter accept

iptables-translate -t filter -A INPUT -m conntrack --ctorigsrc 10.100.2.131 -j ACCEPT
nft add rule ip filter INPUT ct original saddr 10.100.2.131 counter accept

iptables-translate -t filter -A INPUT -m conntrack --ctorigsrc 10.100.0.0/255.255.0.0 -j ACCEPT
nft add rule ip filter INPUT ct original saddr 10.100.0.0/16 counter accept

iptables-translate -t filter -A INPUT -m conntrack --ctorigdst 10.100.2.131 -j ACCEPT
nft add rule ip filter INPUT ct original daddr 10.100.2.131 counter accept

iptables-translate -t filter -A INPUT -m conntrack --ctreplsrc 10.100.2.131 -j ACCEPT
nft add rule ip filter INPUT ct reply saddr 10.100.2.131 counter accept

iptables-translate -t filter -A INPUT -m conntrack --ctrepldst 10.100.2.131 -j ACCEPT
nft add rule ip filter INPUT ct reply daddr 10.100.2.131 counter accept

iptables-translate -t filter -A INPUT -m conntrack --ctproto tcp --ctorigsrcport 443:444 -j ACCEPT
nft add rule ip filter INPUT ct original protocol 6 ct original proto-src 443-444 counter accept

iptables-translate -t filter -A INPUT -m conntrack --ctstatus EXPECTED -j ACCEPT
nft add rule ip filter INPUT ct status expected counter accept

iptables-translate -t filter -A INPUT -m conntrack ! --ctstatus CONFIRMED -j ACCEPT
nft add rule ip filter INPUT ct status != confirmed counter accept

iptables-translate -t filter -A INPUT -m conntrack --ctexpire 3 -j ACCEPT
nft add rule ip filter INPUT ct expiration 3 counter accept

iptables-translate -t filter -A INPUT -m conntrack --ctdir ORIGINAL -j ACCEPT
nft add rule ip filter INPUT ct direction original counter accept

iptables-translate -t filter -A INPUT -m conntrack --ctstate NEW --ctproto tcp --ctorigsrc 192.168.0.1 --ctorigdst 192.168.0.1 --ctreplsrc 192.168.0.1 --ctrepldst 192.168.0.1 --ctorigsrcport 12 --ctorigdstport 14 --ctreplsrcport 16 --ctrepldstport 18 --ctexpire 10 --ctstatus SEEN_REPLY --ctdir ORIGINAL -j ACCEPT
nft add rule ip filter INPUT ct direction original ct original protocol 6 ct state new ct status seen-reply ct expiration 10 ct original saddr 192.168.0.1 ct original daddr 192.168.0.1 ct reply saddr 192.168.0.1 ct reply daddr 192.168.0.1 ct original proto-src 12 ct original proto-dst 14 ct reply proto-src 16 ct reply proto-dst 18 counter accept