netdev - Re: [PATCH] net/tls: Fix return values for setsockopt

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Message-ID: <CA+FuTSdcDW1oJU=BK-rifxm1n4kh0tkj0qQQfOGSoUOkkBKrFg@mail.gmail.com>
Date:   Wed, 4 Dec 2019 14:22:55 -0500
From:   Willem de Bruijn <willemdebruijn.kernel@...il.com>
To:     Jakub Kicinski <jakub.kicinski@...ronome.com>
Cc:     Valentin Vidic <vvidic@...entin-vidic.from.hr>,
        Boris Pismenny <borisp@...lanox.com>,
        Aviad Yehezkel <aviadye@...lanox.com>,
        John Fastabend <john.fastabend@...il.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        "David S. Miller" <davem@...emloft.net>,
        Network Development <netdev@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] net/tls: Fix return values for setsockopt

On Tue, Dec 3, 2019 at 6:08 PM Jakub Kicinski
<jakub.kicinski@...ronome.com> 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@...entin-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?

>
>
> 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.