ftp over nat: ftp-proxy (OpenBSD 3.8 and earlier equivalents such as NetBSD, FreeBSD pre-7.0)
/etc/inetd.conf
127.0.0.1:8021 stream tcp nowait root /usr/libexec/ftp-proxy ftp-proxy -n
- restart inetd
FreeBSD+NetBSD$ sudo /etc/rc.d/inetd restart
/etc/pf.conf
rdr on $int_if proto tcp from any to any port ftp -> 127.0.0.1 \ port 8021 # [...] pass in on $ext_if inet proto tcp from port ftp-data to ($ext_if) \ user proxy flags S/SA keep state
- load your new rules
$ sudo pfctl -f /etc/pf.conf