iptables: drop instead accept all but SSH

templates/iptables_default_v6.j2

@@ -1,7 +1,12 @@
 # {{ ansible_managed }}
 
 *filter
-:INPUT ACCEPT [0:0]
-:FORWARD ACCEPT [0:0]
+:INPUT DROP [0:0]
+:FORWARD DROP [0:0]
 :OUTPUT ACCEPT [0:0]
+-A INPUT -p tcp --syn -j DROP
+-A INPUT -m state --state NEW -m tcp -p tcp --dport 22 -j ACCEPT
+-A INPUT -p ipv6-icmp -j ACCEPT
+-A INPUT -m conntrack --ctstate ESTABLISHED,RELATED -j ACCEPT
+-A INPUT -i lo -j ACCEPT
 COMMIT