iptables: drop instead accept all but SSH

templates/iptables_default_v4.j2

@@ -1,7 +1,14 @@
 # {{ 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 -m tcp --dport 22 -j ACCEPT
+-A INPUT -p icmp -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
+-A INPUT -j REJECT --reject-with icmp-proto-unreachable
 COMMIT