No IPFW binary compat across versions ?

[K. Macy]

On Mon, Sep 5, 2011 at 11:44 PM, Arnaud Lacombe <lacombar at gmail.com> wrote:
> Hi,
>
> On Mon, Sep 5, 2011 at 4:18 PM, Arnaud Lacombe <lacombar at gmail.com> wrote:
>> Hi,
>>
>> On Mon, Sep 5, 2011 at 3:14 PM, K. Macy <kmacy at freebsd.org> wrote:
>>> -STABLE only implies that the ABI does not change during that release
>>> line. It makes no guarantees when moving from one branch to the next.
>>>
>> IIUC, FreeBSD does not provide binary backward compatibility between
>> version at all, is that it ?
>>
> I guess the answer is "NO", on the same system:
>

Netstat depends on specific structures in kernel memory, ipfw depends
on specific ioctls whose arguments may vary. Netstat in particular
breaks on head on a quasi daily basis because of changes to networking
structures. STABLE implies STABLE for things that depend on libc and
are not dependent on obscure kernel interfaces. There is some work
going on (off and on) to decouple netstat from kvm which would fix
that. N-1 compatibility for ipfw is probably possible, anything more
than that is probably infeasible from an interface tracking
standpoint.