CoreOS cloud-config for DigitalOcean with iptables firewall

cloud-config.yml

#cloud-config

coreos:
  etcd:
    # generate a new token for each unique cluster from https://discovery.etcd.io/new
    discovery: https://discovery.etcd.io/<token>
    # multi-region deployments, multi-cloud deployments, and droplets without
    # private networking need to use $public_ipv4
    addr: $private_ipv4:4001
    peer-addr: $private_ipv4:7001
  fleet:
    public-ip: $private_ipv4
  units:
    - name: etcd.service
      command: start
    - name: fleet.service
      command: start
    - name: iptables-restore.service
      enable: true
write_files:
  - path: /var/lib/iptables/rules-save
    permissions: 0644
    owner: root:root
    content: |
      *filter
      :INPUT DROP [0:0]
      :FORWARD DROP [0:0]
      :OUTPUT ACCEPT [0:0]
      -A INPUT -i lo -j ACCEPT
      -A INPUT -i eth1 -j ACCEPT
      -A INPUT -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT
      -A INPUT -p tcp -m tcp --dport 22 -j ACCEPT
      -A INPUT -p tcp -m tcp --dport 80 -j ACCEPT
      -A INPUT -p tcp -m tcp --dport 443 -j ACCEPT
      -A INPUT -p icmp -m icmp --icmp-type 0 -j ACCEPT
      -A INPUT -p icmp -m icmp --icmp-type 3 -j ACCEPT
      -A INPUT -p icmp -m icmp --icmp-type 11 -j ACCEPT
      COMMIT

@sjlu @socketwiz @oliver006 Any solution found for the private network security concern?