Allow CloudFlare only

cloudflare.sh

# Source:
# https://www.cloudflare.com/ips
# https://support.cloudflare.com/hc/en-us/articles/200169166-How-do-I-whitelist-CloudFlare-s-IP-addresses-in-iptables-

# create new chains
iptables -N CF 2>/dev/null
ip6tables -N CF 2>/dev/null
# clear chains
iptables -F CF
ip6tables -F CF

# add cloudflare ips to CF chain
for i in `curl https://www.cloudflare.com/ips-v4`; do iptables -I CF -p tcp -m multiport --dports http,https -s $i -j ACCEPT; done
for i in `curl https://www.cloudflare.com/ips-v6`; do ip6tables -I CF -p tcp -m multiport --dports http,https -s $i -j ACCEPT; done

# drop packets from other ips
iptables -A CF -p tcp -m multiport --dports http,https -j DROP
ip6tables -A CF -p tcp -m multiport --dports http,https -j DROP

# delete chains from input
iptables -D INPUT -j CF 2>/dev/null
ip6tables -D INPUT -j CF 2>/dev/null

# add chains to input
iptables -A INPUT -j CF
ip6tables -A INPUT -j CF