Switch to nft interface by default

source-files/rules/simple_firewall.rules

@@ -3,7 +3,7 @@
 :FORWARD DROP [0:0]
 :OUTPUT ACCEPT [0:0]
 -A INPUT -p icmp -j ACCEPT 
--A INPUT -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT 
+-A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT 
 -A INPUT -i lo -j ACCEPT 
 -A INPUT -p tcp -j REJECT --reject-with tcp-reset 
 -A INPUT -p udp -j REJECT --reject-with icmp-port-unreachable