Re: alignment problem with ebt_among on ppc

[Joerg Willmann <joe@clnt.de>]

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);