Work in progress. Come back soon.
*fsck*, I've lost the source code and documentatio in a major hard drive crash :/ .. err.. no backups, but I just saved a FreeBSD/i386 binary that should work more or less as natd does, going back to the old days as the file date I think I compiled it on FreeBSD-2.2. If you wanna try it, just download it here.
rlucia@elisa:~/public_html/bwd$ ./bwd -help
bwd: unknown option help
Recognized options:
-verbose [yes|no]
-v [yes|no]
verbose mode, dump packet information
-port number|service_name
-p number|service_name
set port (defaults to bwd)
-bandwidth bandwidth
-b bandwidth
set bandwidth of the data flow