netdev - Re: [PATCH] sky2: make sure ethernet header is in transmit skb

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Message-ID: <20100104084049.4d9cd0e4@nehalam>
Date:	Mon, 4 Jan 2010 08:40:49 -0800
From:	Stephen Hemminger <shemminger@...ux-foundation.org>
To:	David Miller <davem@...emloft.net>
Cc:	mbreuer@...jas.com, akpm@...ux-foundation.org, flyboy@...il.com,
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH] sky2: make sure ethernet header is in transmit skb

On Sun, 03 Jan 2010 21:32:58 -0800 (PST)
David Miller <davem@...emloft.net> wrote:

> From: David Miller <davem@...emloft.net>
> Date: Sat, 26 Dec 2009 20:11:07 -0800 (PST)
> 
> > From: David Miller <davem@...emloft.net>
> > Date: Sat, 26 Dec 2009 19:44:18 -0800 (PST)
> > 
> >> From: Stephen Hemminger <shemminger@...ux-foundation.org>
> >> Date: Sat, 26 Dec 2009 14:05:44 -0800
> >> 
> >>> Other drivers may have same problem, I really think this ought
> >>> to be done at higher level.
> >> 
> >> I tend to agree with you, and I thought we had handled all
> >> cases.  Let's simply make AF_PACKET linearize the link
> >> level header before sending things out to the transmit path.
> >> 
> >> I can work on this if you want.
> > 
> > Actually Stephen, I took a look and I can't see how AF_PACKET
> > can create this situation.
> > 
> > It always copies into the linear area of the SKB it allocates
> > for sendmsg() processing.  Whether the data comes from sendmsg
> > data or the mmap() ring buffer.
> 
> Stephen can you get a backtrace of the code path which triggers
> this?  I want to fix it at a higher level too, but I can't
> do that until I know where it actually happens.

Ignore it, the problem is outside the sky2 driver in some other
place causing corrupt skb's. I never reproduced this (with added BUG_ON
and WARN_ON), only seen by Michael.
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