Re: alignment problem with ebt_among on ppc

[Pablo Neira Ayuso <pablo@netfilter.org>]

On Tue, Feb 14, 2012 at 07:31:03PM +0100, Bart De Schuymer wrote:
> Op 10/02/2012 13:17, Joerg Willmann schreef:
> >On Thu, 9 Feb 2012, Bart De Schuymer wrote:
> >
> >>Op 3/02/2012 8:21, joe@clnt.de schreef:
> >>>What I've seen is that ebt_among extension of ebtables uses
> >>>__alignof__(_xt_align) while the corresponding kernel module uses
> >>>__alignof__(ebt_replace) to determin the alignment in EBT_ALIGN().
> >>>
> >>>These are the results of these values on different platforms:
> >>>
> >>>x86 x86_64 ppc
> >>>__alignof__(_xt_align) 4 8 8
> >>>__alignof__(ebt_replace) 4 8 4
> >>>
> >>>So I assume here we can see why ebtales fails to add rules
> >>>which use the
> >>>among extension.
> >>>
> >>>I'm using kernel 2.6.33 and ebtables 2.0.10-4
> >>>
> >>>Is this a known issue or are there any suggestions how to
> >>>circumvent this
> >>>problem?
> >>>Thankyou very much.
> >>
> >>The userspace alignment was changed to _xt_align to fix an
> >>alignment issue on a userspace32-kernel64 system (I think it was
> >>for an ARM device). So userspace must be right. The kernel
> >>alignment macro needs to change so it also uses _xt_align
> >>instead of ebt_replace. The userspace changes date back from
> >>June 29, 2009.
> >>Can you do these changes and provide a patch?
> >>
> >Thank you very much for the input. I did the proposed changes
> >which solved my problem.
> >See below for the patch (hopefully it's the way you expect it...)
> >
> >Best regards,
> >Joerg
> >
> >---
> >
> >
> >diff -rupN a/include/linux/netfilter_bridge/ebtables.h
> >b/include/linux/netfilter_bridge/ebtables.h
> >--- a/include/linux/netfilter_bridge/ebtables.h    2010-08-02
> >19:27:18.000000000 +0200
> >+++ b/include/linux/netfilter_bridge/ebtables.h    2012-02-10
> >12:01:56.464822589 +0100
> >@@ -285,8 +285,8 @@ struct ebt_table {
> >     struct module *me;
> > };
> >
> >-#define EBT_ALIGN(s) (((s) + (__alignof__(struct ebt_replace)-1)) & \
> >-             ~(__alignof__(struct ebt_replace)-1))
> >+#define EBT_ALIGN(s) (((s) + (__alignof__(struct _xt_align)-1)) & \
> >+             ~(__alignof__(struct _xt_align)-1))
> > extern struct ebt_table *ebt_register_table(struct net *net,
> >                         const struct ebt_table *table);
> > extern void ebt_unregister_table(struct ebt_table *table);
> >
> >
> This patch is fine by me... Please apply.
> 
> Signed-off by: Bart De Schuymer <bdschuym@pandora.be>

I'd appreciate if you can send me a well-formed patch that I can
easily apply, it's composed of:

1) title

2) description

3) signed-off-by section

4) patch

Thank you!