kern/157689: ipfw nat config does not accept nonexistent interfaces

[Viktor Štujber]

>Number:         157689
>Category:       kern
>Synopsis:       ipfw nat config does not accept nonexistent interfaces
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Tue Jun 07 15:00:21 UTC 2011
>Closed-Date:
>Last-Modified:
>Originator:     Viktor Štujber
>Release:        8.2-PRERELEASE
>Organization:
>Environment:
FreeBSD poring 8.2-PRERELEASE FreeBSD 8.2-PRERELEASE #4: Sun Feb 20 13:15:15 CET 2011     umage at poring:/usr/obj/usr/src/sys/PORING  i386

>Description:
ipfw accepts rules for interfaces that do not (yet) exist, and makes them work seamlessly as the interfaces come and go. However, the 'ipfw nat' addon feature is not compatible with ipfw's interface handling philosophy.
>How-To-Repeat:
# ipfw add 60000 allow via foobar
60000 allow ip from any to any via foobar
^-- works

# ipfw nat 100 config if foobar
ipfw: unknown interface name foobar
^-- doesn't work
>Fix:
A workaround using cloned_interfaces was suggested. This preemptively creates a dummy interface to satisfy ipfw.

>Release-Note:
>Audit-Trail:
>Unformatted: