netdev - Re: [PATCH net-next 3/3] selftests/net: remove unnecessary MTU config in big

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Message-ID: <d252363c-4791-43da-89d7-4410eb16af5c@gmail.com>
Date: Tue, 6 Jan 2026 10:26:32 +0100
From: Mariusz Klimek <maklimek97@...il.com>
To: Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org
Subject: Re: [PATCH net-next 3/3] selftests/net: remove unnecessary MTU config
 in big_tcp.sh

On 12/2/25 17:46, Mariusz Klimek wrote:
> On 12/2/25 13:01, Paolo Abeni wrote:
>> On 11/27/25 10:13 AM, Mariusz Klimek wrote:
>>> This patch removes the manual lowering of the client MTU in big_tcp.sh. The
>>> MTU lowering was previously required as a work-around due to a bug in the
>>> MTU validation of BIG TCP jumbograms. The MTU was lowered to 1442, but note
>>> that 1492 (1500 - 8) would of worked just as well. Now that the bug has
>>> been fixed, the manual client MTU modification can be removed entirely.
>>>
>>> Signed-off-by: Mariusz Klimek <maklimek97@...il.com>
>>
>> While touching this self-tests, I think it would be nice to additionally
>> add the 'negative' case, i.e. egress mtu lower than ingress and bit tcp
>> segmentation taking place.
>>
>> /P
>>
> 
> Good idea. I'll update the tests.
> 

Actually, this idea doesn't really work. When lowering the egress MTU, the MSS
is also lowered, so no segmentation will (or should) occur, and so the negative
case will never fail.

-- 
Mariusz K.