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

On Mon, Oct 26, 2020 at 09:13:23AM +0000, David Laight wrote:

From: Stefano Garzarella

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Sent: 26 October 2020 08:43

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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