i386/73832: adding ipfw2 "fwd/forward" rule results in "Invalid Argument" error in FreeBSD 5.3

[Stephen Wylie]

>Number:         73832
>Category:       i386
>Synopsis:       adding ipfw2 "fwd/forward" rule results in "Invalid Argument" error in FreeBSD 5.3
>Confidential:   no
>Severity:       non-critical
>Priority:       medium
>Responsible:    freebsd-i386
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Thu Nov 11 19:40:23 GMT 2004
>Closed-Date:
>Last-Modified:
>Originator:     Stephen Wylie
>Release:        5.3-Release
>Organization:
American Megatrends, Inc.
>Environment:
14:14:55}gonzo:/etc# uname -a
FreeBSD gonzo.int.wylie.com 5.3-RELEASE FreeBSD 5.3-RELEASE #7: Tue Nov  9 18:22:33 EST 2004     root at kingkong.int.wylie.com:/usr/obj/usr/src/sys/gonzo  i386
14:28:46}gonzo:/etc#
>Description:
14:14:47}gonzo:/etc# ipfw add 300 fwd xxx.xxx.xxx.xxx all from xxx.xxx.xxx.xxx/xx to any
ipfw: getsockopt(IP_FW_ADD): Invalid argument

the above is (with the x's replaced with actual #'s to make a valid IP address / network address) a snip from my screen showing the command entered and the output from it. I updated the box (via cvsup) just the other day from 5.2.1 to 5.3 and this one firewall rule has quit working. I am using the same kernel config that I was using with 5.2.1 when everything was working perfectly.
>How-To-Repeat:
enter a command like this:
ipfw add 300 fwd xxx.xxx.xxx.xxx all from xxx.xxx.xxx.xxx/xx to any

replace the x's with numbers to make a valid IP address and network address.
>Fix:
n/a
>Release-Note:
>Audit-Trail:
>Unformatted: