Questions about ipfw

[Egoitz Aurrekoetxea]

Good afternoon,

I wanted to formulate a couple of questions I’m doing my self some time ago. 

1 - With Linux, Iptables and mod_conntrack_ftp you can allow only connecting to unprivileged port ranges for 
ftp passive mode to ip addresses who have properly established a tcp/21 port connection. Is this possible in 
FreeBSD with ipfw?.

2.- I am a client A connecting to public ip 1.1.1.1 (for example) of host B. I want this packets at B to be redirected to host C
but changing the source address of A from that packets with the ip address of B. Later when B receives back the answer of C
that packets from the answer to be redirected to A changing B destination ip address to A destination ip address. So when telnetting
from client A to host B for example to port 5000, really, to be telnetting host C port 5000 for example and work this telnet properly from A.

The most important question is number two. Could you help me please?.

Best regards.