#!/bin/bash
mc_port=25565
users=('DerMetzgerFlo' 'pc')

regex="^([[:alpha:]]+).*\((.*)\)$"
ssh_users=()
ips=()
while read -r line ; do
    [[ $line =~ $regex ]]
    for i in "${users[@]}"
    do
        if [ "$i" == "${BASH_REMATCH[1]}" ] ; then
            ssh_users+=(${BASH_REMATCH[1]})
            ips+=(${BASH_REMATCH[2]})
        fi
    done
done < <(who | grep -v localhost | grep -v "(:0)")

#flush existing rules
/sbin/iptables -F
for i in "${!ssh_users[@]}"
do
    #allow connection for user ${ssh_users[$i]} on ip ${ips[$i]}
    /sbin/iptables -A INPUT -p tcp --destination-port $mc_port -s ${ips[$i]} -j ACCEPT
done

#disallow all other connections
/sbin/iptables -A INPUT -p tcp --destination-port $mc_port -j DROP