netdev - RE: [PATCH v2 00/10] Low-level Ethernet debugging features.

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Message-ID: <1328881897.2443.20.camel@edumazet-laptop>
Date:	Fri, 10 Feb 2012 14:51:37 +0100
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	David Laight <David.Laight@...LAB.COM>
Cc:	Ben Greear <greearb@...delatech.com>, jeffrey.t.kirsher@...el.com,
	Jeff Kirsher <tarbal@...il.com>, netdev@...r.kernel.org
Subject: RE: [PATCH v2 00/10] Low-level Ethernet debugging features.

Le vendredi 10 février 2012 à 13:45 +0000, David Laight a écrit :
> > > I was thinking I might could get at least some NICs to generate Runt
> frames
> > > by sending small pkts and disabling frame padding, but haven't
> looked into
> > > it too hard yet.
> > 
> > I am interested by this, do you know some NICs able to disable frame
> > padding ?
> 
> I'm reasonably sure some old NICs like the AMD lance will send runts.
> Quite likely any that require the drives to set the padded frame length.
> 
> The same will be true when semi-generic HDLC controllers are used
> to send packets from DSPs, FPGAs and SOCs.
> 

Apparently, drivers/net/ethernet/dlink/de620.c does this in its
de620_start_xmit() function :

	if ((len = skb->len) < RUNT)
		len = RUNT;

Thats interesting for two reasons :

1) We probably can remove the test to send runts if we want to test
things...

2) As is, we can leak kernel memory content to wire since we dont
initialize the padding data.



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