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Date: Thu, 10 Apr 1997 13:02:35 +1000
From: Bruce Evans <bde@zeta.org.au>
Message-Id: <199704100302.NAA16451@godzilla.zeta.org.au>
To: mishania@demos.su, proff@suburbia.net
Subject: Re: ipfilter/2.2.1 / devfs (general)
Cc: hackers@freebsd.org
Sender: owner-hackers@freebsd.org
X-Loop: FreeBSD.org
Precedence: bulk

>These devfs errors are because you didn't build your kernel with
>devfs support enabled.  You can turn off devfs support by commenting
>out the -DDEVFS in /usr/src/lkm/if_ipf/Makefile.
>
>While I'm on this subject - by default devfs support is not included with
>any modules, due to nothing defining #DEVFS during compilation. Seems
>to be something that needs addressing - either devfs should become
>non-optional, or stubs should be included.

Ifdefed options are fundamentally incompatible with LKMs.  This means
that LKMs must not use nonstandard options like DEVFS, except possibly
if you keep the LKMs carefully synchronised with the kernel.

The IPFILTER and IPFILTER_LKM options are more of a problem than DEVFS
because they affect standard objects (ip_input.o and ip_output.o).  A
GENERIC kernel can't possibly support an ipfilter LKM since GENERIC
isn't configured with these options.  The corresponding problem for
ipfw is handled by using a negative option - COMPAT_IPFW defaults to 1.

The corresponding problem for file systems is very old and usually
not worried about.   The union filesystem can't be an LKM because of
a couple of `#ifdef UNION's in "machine-independent" code.  The ext2fs
filesystem can't be an LKM because of many `#ifdef EXT2FS's in ufs.

Bruce