Re: Fwd: ebtables broken for kernel above 2.6.28

[Bart De Schuymer <bdschuym@pandora.be>]

Hi,

I think it's best to fix this in the kernel if it's possible, since we 
don't want to break compatibility.
If the fix has to be in userspace, then it must be a fix that still 
works for older kernels.

cheers,
Bart

sachin sanap schreef:
> Sorry dint inform you earlier that iam on 32bit ARM machine.
> The real problem is the kernel is computing the alignment on
> __alignof__(struct _xt_align) and the userspace ebtables is computing
> it on __alignof__(struct ebt_entry_target) , which are two different
> structs.
>
> I have the following patch for ebtables-v2.0.8-2 that fixes this.
>
>
>
> --- ebtables-v2.0.8-2.orig/include/ebtables_u.h 2009-05-29
> 21:41:32.000000000 +0530
> +++ ebtables-v2.0.8-2/include/ebtables_u.h      2009-05-29
> 21:43:32.000000000 +0530
> @@ -25,6 +25,7 @@
>  #define EBTABLES_U_H
>  #include <netinet/in.h>
>  #include <linux/netfilter_bridge/ebtables.h>
> +#include <linux/netfilter/x_tables.h>
>
>  #ifndef IPPROTO_SCTP
>  #define IPPROTO_SCTP           132
> @@ -37,7 +38,7 @@
>  #define EXEC_STYLE_DAEMON      1
>
>  #ifndef EBT_MIN_ALIGN
> -#define EBT_MIN_ALIGN (__alignof__(struct ebt_entry_target))
> +#define EBT_MIN_ALIGN (__alignof__(struct _xt_align))
>  #endif
>  #define EBT_ALIGN(s) (((s) + (EBT_MIN_ALIGN-1)) & ~(EBT_MIN_ALIGN-1))
>  #define ERRORMSG_MAXLEN 128
>
>
> -Sachin
>
>
>
>
> On Fri, May 29, 2009 at 3:32 PM, Jan Engelhardt <jengelh@medozas.de> wrote:
>   
>> On Friday 2009-05-29 07:51, sachin sanap wrote:
>>
>>     
>>> Iam facing problem with ebtables binay on 2.6.28 kernel (same binary
>>> works well with 2.6.27). Its mostly a structure alignment issue with
>>> standard targets like DROP,ACCEPT etc. Message seen by user is
>>> "eb_tables: standard target: invalid size 8 != 4"
>>> Iam trying to fix it, this mail is just to check if its already fixed
>>> by someone else?
>>>       
>> Indeed this seems to happen, but only when using a mixed-bitness
>> combination:
>>
>> /tmp/usr/sbin # LD_LIBRARY_PATH=../lib ./ebtables -A INPUT -j ACCEPT
>> The kernel doesn't support the ebtables 'filter' table.
>>
>> /tmp/usr/sbin # uname -a
>> Linux sovereign 2.6.29.3-jen80-default #1 SMP 2009-04-06 18:10:58 +0200
>> x86_64 x86_64 x86_64 GNU/Linux
>>
>> /tmp/usr/sbin # file ebtables
>> ebtables: ELF 32-bit LSB executable, Intel 80386, version 1 (SYSV), for
>> GNU/Linux 2.6.4, dynamically linked (uses shared libs), stripped
>>
>> ebtables does work when it is 64-bit too, so the immediate workaround —
>> assuming you are on x86 — is to not use a 32-bit userspace with a
>> 64-bit kernel.
>>
>>     
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>   

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