#!/usr/sbin/nft -f

# Start with clean NAT table
flush table nat

{% if helper_functions == 'remove' %}
{# NAT if going to be disabled - remove rules and targets from nftables #}

{% set base_command = "delete rule ip raw" %}
{{ base_command }} PREROUTING handle {{ pre_ct_ignore }}
{{ base_command }} OUTPUT     handle {{ out_ct_ignore }}
{{ base_command }} PREROUTING handle {{ pre_ct_conntrack }}
{{ base_command }} OUTPUT     handle {{ out_ct_conntrack }}

delete chain ip raw NAT_CONNTRACK

{% elif helper_functions == 'add' %}
{# NAT if enabled - add targets to nftables #}
add chain ip raw NAT_CONNTRACK
add rule ip raw NAT_CONNTRACK counter accept

{% set base_command = "add rule ip raw" %}

{{ base_command }} PREROUTING position {{ pre_ct_ignore }}    counter jump VYATTA_CT_HELPER
{{ base_command }} OUTPUT     position {{ out_ct_ignore }}    counter jump VYATTA_CT_HELPER
{{ base_command }} PREROUTING position {{ pre_ct_conntrack }} counter jump NAT_CONNTRACK
{{ base_command }} OUTPUT     position {{ out_ct_conntrack }} counter jump NAT_CONNTRACK
{% endif %}

{% macro nat_rule(rule, chain) %}
{%   set src_addr  = "ip saddr " + rule.source_address if rule.source_address %}
{%   set src_port  = "sport { " + rule.source_port +" }" if rule.source_port %}
{%   set dst_addr  = "ip daddr " + rule.dest_address if rule.dest_address %}
{%   set dst_port  = "dport { " + rule.dest_port +" }" if rule.dest_port %}
{%   set comment   = "DST-NAT-" + rule.number %}

{%   if chain == "PREROUTING" %}
{%     set interface = " iifname \"" + rule.interface_in + "\"" %}
{%     set trns_addr = "dnat to " + rule.translation_address %}
{%   elif chain == "POSTROUTING" %}
{%     set interface = " oifname \"" + rule.interface_out + "\"" %}
{%     set trns_addr = rule.translation_address %}
{%     if rule.translation_address != 'masquerade' %}
{%       set trns_addr = "snat to " + trns_addr %}
{%     endif %}
{%   endif %}
{%   set trns_port = ":" + rule.translation_port if rule.translation_port %}

{%   if rule.protocol == "tcp_udp" %}
{%     set protocol  = "tcp" %}
{%     set comment   = comment + " tcp_udp" %}
{%   else %}
{%     set protocol  = rule.protocol %}
{%   endif %}

{%   if rule.log %}
{%     set base_log = "[NAT-DST-" + rule.number %}
{%     if rule.exclude %}
{%       set log = base_log + "-EXCL]" %}
{%     elif rule.translation_address == 'masquerade' %}
{%       set log = base_log + "-MASQ]" %}
{%     else %}
{%       set log = base_log + "]" %}
{%     endif %}
{%   endif %}

{%   if rule.exclude %}
{#     rule has been marked as "exclude" thus we simply return here #}
{%     set trns_addr = "return" %}
{%     set trns_port = "" %}
{%   endif %}

{%   set output = "add rule ip nat " + chain + interface %}

{%   if protocol != "all" %}
{%     set output = output + " ip protocol " + protocol %}
{%   endif %}

{%   if src_addr %}
{%     set output = output + " " + src_addr %}
{%   endif %}
{%   if src_port %}
{%     set output = output + " " + protocol + " " + src_port %}
{%   endif %}

{%   if dst_addr %}
{%     set output = output + " " + dst_addr %}
{%   endif %}
{%   if dst_port %}
{%     set output = output + " " + protocol + " " + dst_port %}
{%   endif %}

{#   Count packets #}
{%     set output = output + " counter" %}

{#   Special handling of log option, we must repeat the entire rule before the #}
{#   NAT translation options are added, this is essential                      #}
{%   if log %}
{%     set log_output = output + " log prefix \"" + log + "\" comment \"" + comment + "\"" %}
{%   endif %}

{%   if trns_addr %}
{%     set output = output + " " + trns_addr %}
{%   endif %}

{%   if trns_port %}
{#     Do not add a whitespace here, translation port must be directly added after IP address #}
{#     e.g. 192.0.2.10:3389                                                                   #}
{%     set output = output + trns_port %}
{%   endif %}

{%   if comment %}
{%     set output = output + " comment \"" + comment + "\"" %}
{%   endif %}

{{ log_output if log_output }}
{{ output }}

{#   Special handling if protocol is tcp_udp, we must repeat the entire rule with udp as protocol #}
{%   if rule.protocol == "tcp_udp" %}
{#     Beware of trailing whitespace, without it the comment tcp_udp will be changed to udp_udp   #}
{{ log_output | replace("tcp ", "udp ") if log_output }}
{{ output | replace("tcp ", "udp ") }}
{%   endif %}
{% endmacro %}

#
# Destination NAT rules build up here
#
{% for rule in destination if not rule.disabled -%}
{{ nat_rule(rule, 'PREROUTING') }}
{% endfor %}

#
# Source NAT rules build up here
#
{% for rule in source if not rule.disabled -%}
{{ nat_rule(rule, 'POSTROUTING') }}
{% endfor %}