linux-kernel - Re: [PATCH net-next 2/4] net: add support for segmenting TCP fraglist GSO packets

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Message-ID: <1bc0ac3d-b18d-4969-a090-6803fa4dd5b4@nbd.name>
Date: Thu, 25 Apr 2024 09:51:12 +0200
From: Felix Fietkau <nbd@....name>
To: Willem de Bruijn <willemdebruijn.kernel@...il.com>,
 netdev@...r.kernel.org, Eric Dumazet <edumazet@...gle.com>,
 "David S. Miller" <davem@...emloft.net>, David Ahern <dsahern@...nel.org>,
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>
Cc: linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next 2/4] net: add support for segmenting TCP fraglist
 GSO packets

On 25.04.24 05:03, Willem de Bruijn wrote:
> Felix Fietkau wrote:
>> Preparation for adding TCP fraglist GRO support. It expects packets to be
>> combined in a similar way as UDP fraglist GSO packets.
>> One difference is the fact that this code assumes that the TCP flags of
>> all packets have the same value. This allows simple handling of flags
>> mutations.
> 
> Can you clarify this some more? We expect potentially different flags
> on first and last packet in a TSO train. With fraglist, the segments
> keep their original flags, as the headers are only pulled. When do
> segment flags need to be replaced with those of the first segment?

Maybe I just misunderstood a comment that Paolo made earlier regarding 
TCP header mutations. Will review this again and compare with regular TSO.

- Felix