netdev - Re: [PATCH 001/001] smsc95xx: Fix hard_header

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Message-ID: <1345139973.2832.3.camel@bwh-desktop.uk.solarflarecom.com>
Date:	Thu, 16 Aug 2012 18:59:33 +0100
From:	Ben Hutchings <bhutchings@...arflare.com>
To:	Steve Glendinning <steve@...well.net>
CC:	JamesBetts <jimbob.betts@...glemail.com>, <netdev@...r.kernel.org>,
	David Miller <davem@...emloft.net>
Subject: Re: [PATCH 001/001] smsc95xx: Fix hard_header_len

On Thu, 2012-08-16 at 10:57 +0100, Steve Glendinning wrote:
> Hi James,
> 
> Thanks for spotting this, I don't think I've ever tested this device with IMQ.
> 
> > -       dev->net->hard_header_len += SMSC95XX_TX_OVERHEAD_CSUM;
> > -       dev->hard_mtu = dev->net->mtu + dev->net->hard_header_len;
> > +       dev->net->needed_headroom = SMSC95XX_TX_OVERHEAD_CSUM;
> > +       dev->hard_mtu = dev->net->mtu + dev->net->hard_header_len +
> > dev->net->needed_headroom;
> 
> I'm unsure what we *should* be setting hard_header_len and
> needed_headroom to.  David?

hard_header_len is set to ETH_HLEN by alloc_etherdev() (in the
ether_setup() callback).  Any extra headroom you want before the
Ethernet header should indeed be specified in needed_headroom.

Ben.

-- 
Ben Hutchings, Staff Engineer, Solarflare
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.

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