kern/50508: ipnat doesn't work without INET6 kernel option

[scole_mail%gmx.com@localhost]

>Number:         50508
>Category:       kern
>Synopsis:       ipnat doesn't work without INET6 kernel option
>Confidential:   no
>Severity:       non-critical
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Wed Dec 09 17:05:00 +0000 2015
>Originator:     scole_mail
>Release:        NetBSD 7.0 GENERIC
>Organization:
>Environment:
NetBSD dstar 7.0.0_PATCH NetBSD 7.0.0_PATCH (GENERIC) #0: Wed Dec  9 10:55:42 EST 2015  scole@dstar:/usr/src/sys/arch/i386/compile/GENERIC i386

>Description:
ipnat doesn't work without INET6 kernel option:

# /etc/rc.d/ipnat restart
70:ioctl(SIOCGNATS) object size mismatch for copying out ipfobj

freebsd used to have a similar bug:
 https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=190964

It'd be nice to have ipnat without necessarily requiring ipv6 in the kernel.

>How-To-Repeat:
Build GENERIC kernel without INET6, run ipnat.
>Fix: