so-called-hang-on-exit

[Ben Lindstrom]

FYI.. If you don't know this yet.. OpenBSD is not affected by this.  And
no one can explain it and how it relates to the issue.  Which has a
bearing on why it has not been fixed also.

- Ben

On Mon, 5 Aug 2002, Michael Robinton wrote:

> >Fair enough on the flushing of the pty. But sshd should still not close
> >the pty - it should wait for the background processes to exit and/or
> >dissassociate from the pty.
> >
> >The client does know that there are background processes left still
> >holding the pty open. How? Because the client requested and got a pty,
> >the sshd has sent a session-exit message, and the channel is still open.
> >
> >Cheers,
> >
> >Nico --
>
> This is an oversimplification of the problem and what I consider to be the
> main reason why the problem has not been fixed. Consider the situation
> where a sysadm needs to log into a host, kill and restart a daemon.
> Naturally the daemon has not been properly written through no fault of the
> sysadmin who is merely and innocent victim of the ssh server. Upon logout
> the terminal window hangs.... duh!!!! Again I ask, why should we be held
> hostage to poorly written daemons just so you purists can say that not a
> single byte of data has been lost that might someday be attempted to be
> sent to pty connection that is trying desperately to disconnect???
>
> The argument will not go away until some one fixes this BUG. Your argument
> that the "client knows" is simplistic. Sure, we know that people write
> buggy software and buggy daemons that do not properly redirect their
> STDOUT and STDERR. That does not meant that we should
> accomodate their stupidity and hang our own systems up because of it. At
> the very least, make it a server configuration option that connections
> will be closed unconditionally if requested by the client to do so. This
> way we can rid our systems of hung sshd processes that fill up the process
> table.
>
> Michael
>
>
> > -----Original Message-----
> > From: Jani Jaakkola [mailto:jjaakkol at cs.Helsinki.FI]
> > Sent: Monday, August 05, 2002 4:20 PM
> > To: Williams, Nicolas
> > Cc: openssh-unix-dev at mindrot.org
> > Subject: RE: so-called-hang-on-exit
> >
> >
> > On Mon, 5 Aug 2002 Nicolas.Williams at ubsw.com wrote:
> >
> > >
> > > I still think this sort of thing should be done by the client.
> > >
> > > The client knows everything that the server knows.
> >
> > Except this time is does not. If there is background
> > processses on the
> > tty, the client can either close the session and lose data or wait
> > indefinetely for data from the background processes.
> >
> > > So the client
> > > can choose to terminate the SSHv2 session when the PTY session
> > > process leader exits - and it can implement any other termination
> > > heuristic you wish too.
> >
> > It needs server modifications that data from the pty session process
> > leaders is not lost. I think rlogin and all other pty using
> > programs have
> > allready implemented this properly; which is that the pty buffer is
> > first emptied and the connection is closed _after_ that.
> >
> > - Jani
> >
> >
>
>
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