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Date:      Tue, 26 Sep 2006 20:21:17 +0200
From:      "Magnus Ringman" <bmr@google.com>
To:        "Brandon S. Allbery KF8NH" <allbery@ece.cmu.edu>
Cc:        current@freebsd.org
Subject:   Re: What do you think ?: How should pseundo terminals behave ...
Message-ID:  <4f674ca50609261121v5ed0b2dalad3607634c965271@mail.google.com>
In-Reply-To: <F0E30165-89B1-4A79-A376-615AF1655234@ece.cmu.edu>
References:  <20060926111452.J91466@godot.imp.ch> <0C4B0125-11AA-4BDB-A4E3-163A6194AB68@alumni.cwru.edu> <98FD6058-7220-48DB-AC24-F989FCB2AE11@ece.cmu.edu> <4f674ca50609261029s76432971yfc15171a3e89cb72@mail.google.com> <8EECEF0C-8C94-4A7C-862A-633F67D3D229@ece.cmu.edu> <4f674ca50609261109s78a26d3dh1dd0a6dc8c112ca2@mail.google.com> <F0E30165-89B1-4A79-A376-615AF1655234@ece.cmu.edu>

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On 9/26/06, Brandon S. Allbery KF8NH <allbery@ece.cmu.edu> wrote:
>
> On Sep 26, 2006, at 14:09 , Magnus Ringman wrote:
>
> > Methinks Sir has it the wrong way around!
> > Hangup on a hardware device -doesn't- void a program's access to the
> > device.  It just (optionally) sends the process a SIGHUP.  That is why
> > somebody (iirc, for SunOS < 5) invented vhangup(2) as a means for a
> > new session owner to insure it was the only process using the
> > terminal.
>
> I think you misunderstood:  yes, physically you do not lose access,
> but for security reasons *logically you should*, and that is why
> vhangup() was invented.  And, this being done, it is also a
> reasonable --- and, more to the point, consistent --- model for what
> happens when a pty slave loses its master (which *is* equivalent to
> physically losing access).

Ah, yes - my bad.  We agree!
My poor brain stem objected to the use of SIGHUP for losing master, on
grounds that a hangup is a perfetly valid terminal event.
Invalidating the fd is the important point.

Magnus



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