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

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Message-ID: <AE90C24D6B3A694183C094C60CF0A2F6026B705D@saturn3.aculab.com>
Date:	Tue, 23 Oct 2012 16:25:49 +0100
From:	"David Laight" <David.Laight@...LAB.COM>
To:	"Jeff Kirsher" <jeffrey.t.kirsher@...el.com>, <davem@...emloft.net>
Cc:	"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

> 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



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