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Date:   Wed, 04 Dec 2019 12:51:35 -0800 (PST)
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Subject: Re: [PATCH] net/tls: Fix return values for setsockopt
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From: Willem de Bruijn <willemdebruijn.kernel@gmail.com>
Date: Wed, 4 Dec 2019 15:43:00 -0500

> On Wed, Dec 4, 2019 at 2:36 PM Jakub Kicinski
> <jakub.kicinski@netronome.com> wrote:
>>
>> (there is a v2, in case you missed)
> 
> Thanks. I meant to respond to your comment. (but should have done sooner :)
> 
>> 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.
> 
> Good idea if not exposing this in UAPI.

I'm trying to understand this part of the discussion.

If we have been returning a non-valid error code, this 524 internal
kernel thing, it is _NOT_ an exposed UAPI.

It is a kernel bug and we should fix it.

If userspace anywhere is checking for 524, that is what needs to be fixed.

Do we agree on this point?