hang on exit bug under Linux

[Nicolas Williams]

On Fri, Dec 14, 2001 at 01:58:42AM +0100, Peter Stuge wrote:
> On Thu, Dec 13, 2001 at 05:35:49PM +0100, Wichert Akkerman wrote:
> > Previously John Hardin wrote:
> > > ...so you're saying having a "hung" ssh session is okay if it's
> > > backgrounded?
> > 
> > It is if the backgrounded program has not disconnected itself from
> > the pty.
> 
> My point exactly.  And nothing has hung.  The client is lingering, waiting
> for all remote tasks to complete.  This is the same behaviour you get if you
> set SO_LINGER on a socket.  Check out socket(7)..  If/when the program in
> the background (on remotehost) exits, the ssh client and the sshd on the
> server will also exit.  And if the xterm (or virtual console) gets closed,
> the ssh client will be killed off, as the sshd on remotehost.  If the
> backgrounded program on remotehost catches HUP it will stay alive, but any
> data output from it will be lost.  That's however hard to change from within
> ssh.
> 
> Now off to code up this patch.  Or at least I'll try, had a look at some of
> the code yesterday too but didn't get anywhere..

Cool.

You need options processing code (readconf.c) and session-exit
processing code. When the client gets a session-exit message, and that
was the last session still "alive", then do as the user wanted. The
things to do could be many, as I've suggested before and as I'll repeat:

 - do nothing ("hang" until the session's channels are closed)
 - background the client (what you suggest)
 - force the channels closed and exit (what many users want)
 - pass a SIGHUP to the session in question (reading the drafts this can
   be done because the session exit message is really associated with the
   session's channel, therefore, though the session has exited it
   continues to exist until the channels are closed. The server should
   kill the process group of the session leader whose exiting elicited
   the session-exit message).

You needn't implement all of those options. The first two will do for
you, apparently, so implement that. The others can be added later.


> //Peter
> 

Cheers,

Nico
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