netdev - Re: [ethtool] ethtool: Remove UDP Fragmentation Offload use from ethtool

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Message-ID: <20170829104452.b6n5ikxxioib7766@unicorn.suse.cz>
Date:   Tue, 29 Aug 2017 12:44:53 +0200
From:   Michal Kubecek <mkubecek@...e.cz>
To:     Tariq Toukan <tariqt@...lanox.com>
Cc:     "John W. Linville" <linville@...driver.com>,
        Eric Dumazet <eric.dumazet@...il.com>,
        David Miller <davem@...emloft.net>, netdev@...r.kernel.org,
        Eran Ben Elisha <eranbe@...lanox.com>,
        Shaker Daibes <shakerd@...lanox.com>
Subject: Re: [ethtool] ethtool: Remove UDP Fragmentation Offload use from
 ethtool

On Tue, Aug 29, 2017 at 10:50:20AM +0300, Tariq Toukan wrote:
> On 28/08/2017 9:22 PM, John W. Linville wrote:
> > On Mon, Aug 28, 2017 at 08:00:11AM -0700, Eric Dumazet wrote:
> > > On Mon, 2017-08-28 at 15:38 +0300, Tariq Toukan wrote:
> > > > From: Shaker Daibes <shakerd@...lanox.com>
> > > > 
> > > > UFO was removed in kernel, here we remove it in ethtool app.
> > > > 
> > > > Fixes the following issue:
> > > > Features for ens8:
> > > > Cannot get device udp-fragmentation-offload settings: Operation not supported
> 
> But I wonder how the warning removal should be done??
> 
> I have some suggestions in mind:
> 1) Have a special condition that does not print a warning only in the case
> of UFO?
> 2) Remove the warning totally? I don't like this option.
> 3) Add a max_kernel_ver field in struct off_flag_def, and use it to not
> print the warning, or to mark the feature 'off [fixed]'.

IMHO there is nothing wrong with not writing a warning for "get"
operation, after all it's just "ethtool -k", i.e. "show me all
offloading flags" and we do not warn about unsupported named features
either. IMHO the only question should be how friendly we should be to
old scripts expecting the line in the output:

  (a) omit the "udp-fragmentation-offload:" line (be consistent)
  (b) say something like "udp-fragmentation-offload: n/a"
  (c) pretend it's there and is off (most careful but misleading)

Personally, I would prefer (a) but some badly written scripts might have
problem with this approach.

On the other hand, an attempt to _set_ the flag with "ethtool -K" should
issue an error.

Michal Kubecek