Re: ebtables broken for kernel above 2.6.28

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

Jan Engelhardt schreef:
> Patrick McHardy wrote on  2009-06-02 12:20:45:
>   
>> Jan Engelhardt wrote:
>>     
>>>
>>> Since the kernel uses xt_align already, it's best for userspace to do 
>>> the same.
>>>       
>> But that doesn't work for older kernels. Please don't dismiss
>> compatibility issues that easily. Sometimes things unfortunately
>> do slip through, but I expect people to do their best to fix the
>> problem properly when this happens.
>>     
>
> I compiled myself an ARM crosscompiler, just to see what's going on. Not 
> that I could run the binaries, but I could at least look at the objdump 
> output. The first impression was: "the state before the supposed 
> regression was introduced could not have worked on ARM in the first 
> place had I run this".
>
> It turns out that ebtables is completely unusable on at least three 
> arches with given ABI configurations even if things were still 
> calculated against ebt_replace instead of _xt_align. One case has been 
> verified by me since it's consumer hardware, and it surprises me 
> the Debian project has not found this earlier, because they actually 
> produced one affected binary distribution in the past (x86 with 
> k64_u32).
>
> Affected arches are all with k64_u32. (Perhaps almost all — I did not 
> recall seeing it on sparc64, and, as I am just checking up on ebtables's 
> Makefile, it has a hack for sparc.) The other configuration I see 
> problems in is a (rather normal) k32_u32 ARM setup with a kernel 
> compiled with CONFIG_EABI=no.
>
> The userspace patch proposed by Sachin Nasap is, IMHO, one to fix the 
> alignment problems (both old and recent) in one clap.
>   

Thanks, I'll have a look at it this weekend.

cheers,
Bart

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