ping before ssh

ping-before-ssh.sh

iptables --table filter --append INPUT --match conntrack --ctstate ESTABLISHED,RELATED --match comment --comment "Allow established and related connections" --jump ACCEPT

iptables --table filter --append INPUT --protocol icmp --icmp-type echo-request --match length --length 84 --match recent --set --name openSSH --rsource --match comment --comment "ping before ssh" --jump LOG --log-prefix "OpenDoor SSH: " --log-level 7
iptables --table filter --append INPUT --protocol tcp --dport ssh --syn --match recent ! --rcheck --seconds 30 --name openSSH --rsource --match comment --comment "Drop SSH connection not pinged recently" --jump DROP