netdev - Re: [PATCH v6 net-next 13/13] mlx5: support BIG TCP packets

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Date:   Thu, 12 May 2022 11:02:19 +0200
From:   Paolo Abeni <pabeni@...hat.com>
To:     Saeed Mahameed <saeedm@...dia.com>,
        Eric Dumazet <eric.dumazet@...il.com>
Cc:     "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        netdev <netdev@...r.kernel.org>,
        Alexander Duyck <alexanderduyck@...com>,
        Coco Li <lixiaoyan@...gle.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Tariq Toukan <tariqt@...dia.com>,
        Leon Romanovsky <leon@...nel.org>
Subject: Re: [PATCH v6 net-next 13/13] mlx5: support BIG TCP packets

On Thu, 2022-05-12 at 01:40 -0700, Saeed Mahameed wrote:
> On 09 May 20:32, Eric Dumazet wrote:
> > From: Coco Li <lixiaoyan@...gle.com>
> > 
> > mlx5 supports LSOv2.
> > 
> > IPv6 gro/tcp stacks insert a temporary Hop-by-Hop header
> > with JUMBO TLV for big packets.
> > 
> > We need to ignore/skip this HBH header when populating TX descriptor.
> > 
> 
> Sorry i didn't go through all the documentations or previous discussions,
> please bare with me, so why not clear HBH just before calling the
> driver xmit ndo ? 

I guess this way is more efficient: the driver copies IP hdr and TCP
hdr directly in the correct/final location into the tx descriptor,
otherwise the caller would have to memmove L2/L3 just before the driver
copies them again.
> 
> Or if HBH has to stick, 

My understanding is that this is not the case.

Cheers,

Paolo