Thanks Lisa, just to clarify:
I am compiling EVERYTHING from the kernel up, either 32 or 64, so the 
'64-in-32-userland' issue does not apply.
This box will have everything freshly compiled from source from day one.
It will be a 'pure' 64 (or 32) box. 

Now, from distant times I remember that 16 bit processors were generally 
faster than 8 bit, 32 were faster than 16, how come the 64 bit processor is 
slower than the 32? 

In a 'pure 64' environment does that still apply? 

I can understand that iptables has not been thoroughly tested in a 'pure 64' 
environment, but why would it run slower?
Inquiring minds would like to know...
ET 

 

Lisa Kachold writes: 

> Hi! 
> 
> Great question: 
> 
> On Sun, Jul 22, 2012 at 4:04 AM, kitepilot@kitepilot.com <
> kitepilot@kitepilot.com> wrote: 
> 
>> Hello World:
>> I run my firewall on a LFS box. 
>>
> 
> You might also consider a hardened kernel with: 
> 
> http://grsecurity.net/ 
> 
> 
>> Everything on it is compiled from source.
>> No bells and whistles, only the essential software is installed.
>> The hardware is 64 bits but I've been running 32 bit OS. 
>>
> 
> 32-bit iptables doesn't work on a machine running amd64 kernel, when run
> it reports:
> ===
> # iptables -L
> iptables v1.2.11: can't initialize iptables table `filter': Module is
> wrong version Perhaps iptables or your kernel needs to be upgraded 
> 
> iptables has to be 64bit to talk to a 64bit kernel due to an alignment
> issue in the kernel structures for iptables.  So you do need at least
> the 64bit iptables binary and associated libs. 
> 
> 
> This time around I am wondering...
>> The question is:
>> Is there any advantage to compiling the whole iptables enchilada in 64
>> bits? 
>>
>  
> 
>    - 32 bit is faster than 64 bit
>    - 32 bit is well tested, 64 bit isn't tested at all
>    - 2039 is still long way off 
> 
> The only reasons to compile anything in 64bit architecture: 
> 
>    - It needs to access more than 4GB of memory. In the real world this
>    only applies to huge databases.
>    - It needs to talk to the kernel directly. Some applications, like
>    iptables, contain ugly hacks to support the 64 bit kernel/32 bit
>    userland thing.
>    - It is a kernel. 
> 
> For you to talk with your 64bit kernel, you need 64bit iptables! 
> 
> 
>> Should it be avoided?
>> Please note that the 'normal' rules like 'more than 4GB and/or
>> 32-bit-adobe' do not apply here, what I am looking for is whether
>> filtering/marking will be faster/slower and (if known) why.
>> Any ideas?
>> Tnx
>> ET 
>>
> 
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