netdev - Re: "TCP: eth0: Driver has suspect GRO implementation, TCP performance may be compromised." message with "ethtool -K eth0 gro off"

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Message-ID: <1486133253.21871.89.camel@edumazet-glaptop3.roam.corp.google.com>
Date:   Fri, 03 Feb 2017 06:47:33 -0800
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
Cc:     Markus Trippelsdorf <markus@...ppelsdorf.de>,
        netdev@...r.kernel.org
Subject: Re: "TCP: eth0: Driver has suspect GRO implementation, TCP
 performance may be compromised." message with "ethtool -K eth0 gro off"

On Fri, 2017-02-03 at 12:28 -0200, Marcelo Ricardo Leitner wrote:

> Aren't you mixing the endpoints here? MSS is the largest amount of data
> that the peer can receive in a single segment, and not how much it will
> send. For the sending part, that depends on what the other peer
> announced, and we can have 2 different MSS in a single connection, one
> for each peer.
> 
> If a peer later wants to send larger segments, it can, but it must
> respect the mss advertised by the other peer during handshake.
> 

I am not mixing endpoints, you are.

If you need to be convinced, please grab :
https://patchwork.ozlabs.org/patch/723028/

And just watch "ss -temoi ..."