# IPv4
domain ip {
    table filter {
        chain INPUT {
            policy DROP;
            interface lo ACCEPT;
            # Make sure not to allow flooding via ICMP ping packages by sending them
            # to flood chain before state module kicks in.
            proto icmp icmp-type echo-request jump flood;
            mod state state (ESTABLISHED RELATED) ACCEPT;
            # For TCP packages we perform floods checks after state module took care
            # of established and related connections.
            proto tcp tcp-flags (FIN SYN RST ACK) SYN jump flood;
            # Accept some common incoming connections.
            proto icmp icmp-type echo-request ACCEPT;
            proto tcp dport 22 ACCEPT;
{% if maintenance %}
            # Validate source IP against list of allowed hosts in maintenance mode.
            jump allowed_hosts;
{% endif %}
        }

        # The flood chain is used for controlling the rate of the incoming connections.
        chain flood {
            # Rate-limit the ping requests.
            proto icmp icmp-type echo-request {
                mod hashlimit hashlimit {{ incoming_connection_limit }} hashlimit-burst {{ incoming_connection_limit_burst }}
                    hashlimit-mode srcip hashlimit-name icmp RETURN;
                DROP;
            }
            # Rate-limit the TCP connections.
            proto tcp tcp-flags (FIN SYN RST ACK) SYN {
                mod hashlimit hashlimit {{ incoming_connection_limit }} hashlimit-burst {{ incoming_connection_limit_burst }}
                    hashlimit-mode srcip hashlimit-name icmp RETURN;
                LOG;
                DROP;
            }
        }
{% if maintenance %}
        # Resume processing in case of allowed hosts, drop packets for
        # any other hosts.
        chain allowed_hosts {
            {% for host in maintenance_allowed_hosts %}
            saddr {{ host }} RETURN;
            {% endfor %}
            DROP;
        }
{% endif %}
    }
}

# IPv6, same as IPv4 config, with addition of a couple of ICMP packets.
domain ip6 {
    table filter {
        chain INPUT {
            policy DROP;
            interface lo ACCEPT;
            # Make sure not to allow flooding via ICMP ping packages by sending them
            # to flood chain before state module kicks in.
            proto icmp icmp-type echo-request jump flood;
            mod state state (ESTABLISHED RELATED) ACCEPT;
            # For TCP packages we perform floods checks after state module took care
            # of established and related connections.
            proto tcp tcp-flags (FIN SYN RST ACK) SYN jump flood;
            # ICMPv6 packets required for proper functioning of IPv6.
            proto icmp icmp-type router-advertisement ACCEPT;
            proto icmp icmp-type neighbor-solicitation ACCEPT;
            proto icmp icmp-type neighbor-advertisement ACCEPT;
            # Accept some common incoming connections.
            proto icmp icmp-type echo-request ACCEPT;
            proto tcp dport 22 ACCEPT;
{% if maintenance %}
            # Validate source IP against list of allowed hosts in maintenance mode.
            jump allowed_hosts;
{% endif %}
        }

        # The flood chain is used for controlling the rate of the incoming connections.
        chain flood {
            # Rate-limit the ping requests.
            proto icmp icmp-type echo-request {
                mod hashlimit hashlimit {{ incoming_connection_limit }} hashlimit-burst {{ incoming_connection_limit_burst }}
                    hashlimit-mode srcip hashlimit-name icmp RETURN;
                DROP;
            }
            # Rate-limit the TCP connections.
            proto tcp tcp-flags (FIN SYN RST ACK) SYN {
                mod hashlimit hashlimit {{ incoming_connection_limit }} hashlimit-burst {{ incoming_connection_limit_burst }}
                    hashlimit-mode srcip hashlimit-name icmp RETURN;
                LOG;
                DROP;
            }
        }
{% if maintenance %}
        # Resume processing in case of allowed hosts, drop packets for
        # any other hosts.
        chain allowed_hosts {
            {% for host in maintenance_allowed_hosts %}
                {% if lookup('dig', host + '/AAAA') not in ['NXDOMAIN', ''] %}
            saddr {{ host }} RETURN;
                {% endif %}
            {% endfor %}
            DROP;
        }
{% endif %}
    }
}