From mboxrd@z Thu Jan  1 00:00:00 1970
From: Ben Warren <biggerbadderben@gmail.com>
Date: Wed, 28 Jan 2009 09:55:45 -0800
Subject: [U-Boot] IP_t should be a "packed" struct
In-Reply-To: <200901271932.11060.luigi.mantellini.ml@gmail.com>
References: <200901271932.11060.luigi.mantellini.ml@gmail.com>
Message-ID: <49809C21.6070004@gmail.com>
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To: u-boot@lists.denx.de

Luigi 'Comio' Mantellini wrote:
> Hi ML,
>
> I'm working on a mips target and I used qemu_mips target to simulate my target 
> (that I hope to have in the next week...)
>
> Following my activities I noticed that IP_t structure is no defined with 
> attribute "packed". I noticed this issue because using a self-made toolchain 
> (gcc4.2.4+binutils2.8+uclibc0.9.30) the compiler has aligned all bytes to 
> 32bit boundary. This is not ok, because the packets IP_t can be non aligned 
> (see the /net/net.c PingSend function, for an example).
>
>   
Why is your compiler aligning all bytes to 32-bit boundary?  Seems like 
an awful waste of space.  This struct should pack itself nicely, and 
does on the small sample of toolchains I've tried (gcc 4.3.2 x86_64 and 
gcc 4.0.0 ppc_4xx).
> The dirty solution is to define the structure with the 
> __attribute__((__packed__))... but, from my point of view, a better packet 
> forging mechanism should be implemented into the net.c stack.
>
> I attached a trivial patch that solved the issue on my target.
>
> Any comments is welcome.
>
> best regards,
>
> luigi
>
>  
I'd focus on fixing your toolchain.  Your problem will not be confined 
to protocol headers.
>  
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regards,
Ben