Re: [PATCH] vsock: ratelimit unknown ioctl error message

[Stefano Garzarella]

On Mon, Oct 26, 2020 at 09:13:23AM +0000, David Laight wrote:
> From: Stefano Garzarella
> > Sent: 26 October 2020 08:43
> ...
> > >Isn't the canonical error for unknown ioctl codes -ENOTTY?
> > >
> >
> > Oh, thanks for pointing that out!
> >
> > I had not paid attention to the error returned, but looking at it I
> > noticed that perhaps the most appropriate would be -ENOIOCTLCMD.
> > In the ioctl syscall we return -ENOTTY, if the callback returns
> > -ENOIOCTLCMD.
> >
> > What do you think?
>
> It is 729 v 443 in favour of ENOTTY (based on grep).

Under net/ it is 6 vs 83 in favour of ENOIOCTLCMD.

> No idea where ENOIOCTLCMD comes from, but ENOTTY probably
> goes back to the early 1970s.

Me too.

> The fact that the ioctl wrapper converts the value is a good
> hint that userspace expects ENOTTY.

Agree on that, but since we are not interfacing directly with userspace, 
I think it is better to return the more specific error (ENOIOCTLCMD).

Thanks,
Stefano