natd, DNAT of UDP traffic

[Sergey Vavilov]

Hello, all!
I want to make DNAT (Destination NAT) on FreeBSD 5.3 with saving of 
source IP in translated packets.
As I understood, natd always changes source IP to  value of 
"-alias_address"  or IP of "-interface".
As I understood, remaining source IP unchanged possible with 
"-proxy_only". But "proxy-only" works with TCP traffic only,
but I want to process UDP traffic via natd.

Please, give me some advice how I can to do this.
Thank you beforehand!

The Schema:
srcipA-----> ipB(DNAT)------->dstipC

Now I using redirect_address, but I want to see in server's logs at 
dstipC original client's ip address (srcipA - is a pool of 30 addresses).

-- 
Sergey Vavilov, Perm, Russia