#!/bin/bash

RULESET='add table ip filter

add chain ip filter filter { type filter hook prerouting priority mangle; policy accept; }

add ct helper ip filter ftp { type "ftp" protocol tcp; };

add rule ip filter filter tcp dport 33 ct helper set "ftp"'

set -e

$NFT -f - <<< "$RULESET"

RULESET='flush chain ip filter filter

delete chain filter filter

delete ct helper ip filter ftp'

$NFT -f - <<< "$RULESET"