Delay in starting programs on FreeBSD via ssh after upgrade OpenBSD from 7.3 to 7.4

[Damien Miller]

On Fri, 27 Oct 2023, Roger Marsh wrote:

This is missing a lot of context, and I had to go to the misc@ archives to
find out the actual command that is running slow for you.

AFAIK, it's 
ssh -Y opendev xterm -title roger at opendev

Please get a debug trace from the ssh connection, e.g. "ssh -vvv -Y ..."
and annotate where the delay happens. Without this, we're not in a position
to help.

-d

> Context is provided by the forwarded message: the most recent (final?) post on
> 
> Subject: Re: Delay in starting xterm via ssh after upgrade from 7.3 to 7.4
> 
> on misc at openbsd.org
> 
> Begin forwarded message:
> 
> On 2023-10-25, Roger Marsh <r.m at rmswch.plus.com> wrote:
> > On 23 Oct 2023 09:32:19 -0600
> > "Andy Bradford" <amb-sendok-1700667140.jgjncfcjadjlnbiepadd at bradfords.org> wrote:
> >
> >> Thus said Roger Marsh on Thu, 19 Oct 2023 17:23:47 -0000:
> >> 
> >> > fixes the delay  problem, but was the delay  a predictable consequence
> >> > of some change? Or perhaps the  entry should never have been expressed
> >> > in the way that led to the delay?  
> >> 
> >> Most likely the cause is an unexpected side effect of some other change.
> >> There  have been  some interesting  changes  to SSH  with this  release,
> >> perhaps try disabling:
> >> 
> >> http://man.openbsd.org/OpenBSD-7.4/ssh_config#ObscureKeystrokeTiming
> >> 
> >> I would be surprised  if this is actually the cause, but  it is a change
> >> that was introduced and something that is easily tested.
> >> 
> >> You could also look through:
> >> 
> >> http://www.openbsd.org/plus74.html
> >> 
> >> See if any of the changes stand out as relevant and try to test them.
> >> 
> >> Andy
> >> 
> >
> > Thanks.
> >
> > ObscureKeystokeTiming turned out to be the cause, or so it seemed after reading the ssh_config reference.  Setting this option to 'no' whereever ssh is used in the .fvwmrc configuration file got rid of the response time problem.
> >
> > I remember looking at plus74.html some time before formal release.  If ObscureKeystrokeTiming had caught my eye I think I would not have associated it with the possibility of a large increase in response time.
> >
> > The line in plus74.html immediately before the one about ObscureKeystokeTiming states 'Limit artificial login delay ...'.  That change looks a more likely cause than 'ObscureKeystokeTiming' measures.
> >
> > Roger
> >
> >
> 
> Almost the first thing done after adjusting the .fvwmrc file was open up a Python Idle session on a FreeBSD 13.2 installation by ssh from the OpenBSD 7.4 box in the Xserver role.  The delay was instantly obvious, both starting the session and opening *.py files (or anything else I suppose) from the Idle menu.
> 
> This was unexpected too.
> 
> After reverting the OpenBSD Xserver box to 7.3 response times are back to what they were before any OpenBSD boxes were upgraded from 7.3 to 7.4.  The plan is to keep the OpenBSD Xserver box at 7.3 until the next upgrade of the FreeBSD 13.2 box when 14.0 is released (it's well into release candidates right now) and hope it has OpenSSH 9.4 and fixes the problem.
> 
> On the FreeBSD 13.2 box 'ssh -V' says OpenSSH_9.3p1 and 'sshd -V' says OpenSSH_9.3, while both say OpenSSH_9.3 on the OpenBSD 7.3 box.
> 
> I would rather not be relying on hope.
> 
> Roger
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