netdev - Re: [PATCH] gianfar: Fix oversized packets handling

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Date:	Wed, 16 Jun 2010 18:09:49 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	avorontsov@...sta.com
Cc:	Sandeep.Kumar@...escale.com, afleming@...escale.com,
	netdev@...r.kernel.org, linuxppc-dev@...abs.org
Subject: Re: [PATCH] gianfar: Fix oversized packets handling

From: Anton Vorontsov <avorontsov@...sta.com>
Date: Sat, 12 Jun 2010 00:51:03 +0400

> Issuing the following command on host:
> 
> $ ifconfig eth2 mtu 1600 ; ping 10.0.0.27 -s 1485 -c 1
> 
> Makes some boards (tested with MPC8315 rev 1.1 and MPC8313 rev 1.0)
> oops like this:
 ...
> Dumped buffer descriptors showed that eTSEC's length/truncation
> logic sometimes passes oversized packets, i.e. for the above ICMP
> packet the following two buffer descriptors may become ready:
> 
>   status=1400 length=1536
>   status=1800 length=1541
> 
> So, it seems that gianfar actually receives the whole big frame,
> and it tries to place the packet into two BDs. This situation
> confuses the driver, and so the skb_put() sanity check fails.
> 
> This patch fixes the issue by adding an appropriate check, i.e.
> the driver should not try to process frames with buffer
> descriptor's length over rx_buffer_size (i.e. maxfrm and mrblr).
> 
> Note that sometimes eTSEC works correctly, i.e. in the second
> (last) buffer descriptor bits 'truncated' and 'crcerr' are set,
> and so there's no oops. Though I couldn't find any logic when
> it works correctly and when not.
> 
> Signed-off-by: Anton Vorontsov <avorontsov@...sta.com>

Applied, thanks Anton.
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