netdev - Re: i386 vs x86_64 struct tpacket

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Message-Id: <20131220.133854.672157982782686878.davem@davemloft.net>
Date:	Fri, 20 Dec 2013 13:38:54 -0500 (EST)
From:	David Miller <davem@...emloft.net>
To:	nvbolhuis@...valley.nl
Cc:	netdev@...r.kernel.org, linux-net@...r.kernel.org
Subject: Re: i386 vs x86_64 struct tpacket_hdr layout

From: Norbert van Bolhuis <nvbolhuis@...valley.nl>
Date: Fri, 20 Dec 2013 14:30:06 +0100

> 
> I'm compiling my 32bit application with -m32 on a x86_64
> system/kernel.
> 
> Things aren't working because for my application tp_len is at offset 4
> but for the kernel it is at offset 8.
> 
> struct tpacket_hdr {
>         unsigned long   tp_status;
>         unsigned int    tp_len;
>         unsigned int    tp_snaplen;
>         unsigned short  tp_mac;
>         unsigned short  tp_net;
>         unsigned int    tp_sec;
>         unsigned int    tp_usec;
> };
> 
> How is this suppose to work ?

This is why you should use tpacket layout v2 or v3, rather than v1,
they fix these issues.
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