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Date:   Wed, 4 Dec 2019 11:35:44 -0800
From:   Jakub Kicinski <jakub.kicinski@netronome.com>
To:     Willem de Bruijn <willemdebruijn.kernel@gmail.com>
Cc:     Valentin Vidic <vvidic@valentin-vidic.from.hr>,
        Boris Pismenny <borisp@mellanox.com>,
        Aviad Yehezkel <aviadye@mellanox.com>,
        John Fastabend <john.fastabend@gmail.com>,
        Daniel Borkmann <daniel@iogearbox.net>,
        "David S. Miller" <davem@davemloft.net>,
        Network Development <netdev@vger.kernel.org>,
        linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] net/tls: Fix return values for setsockopt
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(there is a v2, in case you missed)

On Wed, 4 Dec 2019 14:22:55 -0500, Willem de Bruijn wrote:
> On Tue, Dec 3, 2019 at 6:08 PM Jakub Kicinski wrote:
> > On Tue,  3 Dec 2019 23:44:58 +0100, Valentin Vidic wrote:  
> > > ENOTSUPP is not available in userspace:
> > >
> > >   setsockopt failed, 524, Unknown error 524
> > >
> > > Signed-off-by: Valentin Vidic <vvidic@valentin-vidic.from.hr>  
> >
> > I'm not 100% clear on whether we can change the return codes after they
> > had been exposed to user space for numerous releases..  
> 
> This has also come up in the context of SO_ZEROCOPY in the past. In my
> opinion the answer is no. A quick grep | wc -l in net/ shows 99
> matches for this error code. Only a fraction of those probably make it
> to userspace, but definitely more than this single case.
> 
> If anything, it may be time to define it in uapi?

No opinion but FWIW I'm toying with some CI for netdev, I've added a
check for use of ENOTSUPP, apparently checkpatch already sniffs out
uses of ENOSYS, so seems appropriate to add this one.

> > But if we can - please fix the tools/testing/selftests/net/tls.c test
> > as well, because it expects ENOTSUPP.  
> 
> Even if changing the error code, EOPNOTSUPP is arguably a better
> replacement. The request itself is valid. Also considering forward
> compatibility.

For the case TLS version case?