From mboxrd@z Thu Jan  1 00:00:00 1970
From: Eric Dumazet <eric.dumazet@gmail.com>
Subject: Re: [PATCH] Applying inappropriate ioctl operation on socket
 should return ENOTTY
Date: Wed, 27 Apr 2011 08:57:37 +0200
Message-ID: <1303887457.2699.60.camel@edumazet-laptop>
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	 <20110427063730.GA20313@md5.ntu.edu.sg>
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Cc: linux-kernel@vger.kernel.org, netdev <netdev@vger.kernel.org>
To: Lifeng Sun <lifongsun@gmail.com>
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Le mercredi 27 avril 2011 =C3=A0 14:37 +0800, Lifeng Sun a =C3=A9crit :
> On 07:58 Wed 04/27/11 Apr, Eric Dumazet wrote:
> > Really ?
> >=20
> > EINVAL is ok too : Request or argp is not valid.
>=20
> I'm afraid not. SUSv4 specifies, say,
>=20
>   int tcsetattr(int fildes, int optional_actions,
>          const struct termios *termios_p);
>=20
>  ERROR:
>   [EINVAL]
>       The optional_actions argument is not a supported value, or an
>       attempt was made to change an attribute represented in the
>       termios structure to an unsupported value.
>=20
>   [ENOTTY]
>       The file associated with fildes is not a terminal.
>=20
> which means when we apply tcsetattr (implemented by ioctl) to _any_
> non-terminal file descriptor, it should set errno to ENOTTY rather
> than EINVAL.
>=20

You quote manpage for a library call, not a system call.

If you feel your glibc doesnt implement well this, please complain to
glibc maintainer.