If We Have To: ftp-proxy With divert-to (Or Redirection)

In the base system, load the daemon if you need it

/etc/rc.conf[.local]

ftpproxy_flags=""

FreeBSD also needs

ftpproxy_enable="YES"

/etc/pf.conf

anchor "ftp-proxy/*"

the redirection

pass in quick inet proto tcp to port ftp divert-to 127.0.0.1 port 8021
pass in quick inet6 proto tcp to port ftp divert-to ::1 port 8021

Pre-OpenBSD 5.0, proxies used rdr-to:

pass in quick inet proto tcp to port ftp rdr-to 127.0.0.1 port 8021
pass in quick inet6 proto tcp to port ftp rdr-to ::1 port 8021

pass out proto tcp from $proxy to port ftp