netdev - Re: [net-next 1/8] e1000e: Minimum packet size must be 17 bytes

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Message-ID: <5086C7B4.6060202@intel.com>
Date:	Tue, 23 Oct 2012 09:37:08 -0700
From:	Alexander Duyck <alexander.h.duyck@...el.com>
To:	David Laight <David.Laight@...LAB.COM>
CC:	Jeff Kirsher <jeffrey.t.kirsher@...el.com>, davem@...emloft.net,
	Tushar Dave <tushar.n.dave@...el.com>, netdev@...r.kernel.org,
	gospo@...hat.com, sassmann@...hat.com
Subject: Re: [net-next 1/8] e1000e: Minimum packet size must be 17 bytes

On 10/23/2012 08:25 AM, David Laight wrote:
>> This is a HW requirement. Although a buffer as short as 1 byte is allowed,
>> the total length of packet before, padding and CRC insertion, must be at
>> least 17 bytes.  So pad all small packets manually up to 17 bytes before
>> delivering them to HW.
> Where do such very short packets come from?
> The shortest one I know of have:
>  6 bytes dest-mac
>  6 bytes src-mac
>  2 bytes length
>  3 bytes llc header (eg reflect request).
> 17 bytes total.
>
> 	David
>

This mostly has to do with security fuzz testers sending raw packets at
the interface trying to see what can cause it to hang.  As far as I know
nothing from the stack will be that small, but we still have to support
raw packets that size.

Thanks,

Alex
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