TRANSLATION RULES:
nat-anchor "ftp-proxy/*" all
rdr-anchor "ftp-proxy/*" all
rdr on em1 inet proto tcp from any to any port = ftp -> 127.0.0.1 port 8021

FILTER RULES:
scrub in on em0 all fragment reassemble
scrub in on em1 all fragment reassemble
anchor "ftp-proxy/*" all
pass out quick on em0 inet proto tcp from x.x.x.x to any port = ftp flags S/SA keep state