Re: -current dropping ssh connections

On Wed, Jun 21, 2023 at 10:45:25AM -0700, Mark Millard wrote:
> On Jun 21, 2023, at 10:24, bob prohaska <fbsd@www.zefox.net> wrote:
> 
> > I've got a Pi4 running -current that seems to selectively drop ssh connections.
> 
> Only when the ssh has text streaming over it? Even when it
> is idle? Any other types of context differences that lead
> to observable differences of some type related to the
> disconnects (vs. lack of them)?

I can't detect any consistent pattern. For a while I thought load on the
sshd-host end made a difference, but the latest disconnect was on an idle
system with serial console output the only traffic on the dropped connection. 
 
> > Connections running a shell seem to stay up, but a session running tip to a
> > usb-serial adapter (FTDI TTL232R-3V3) seems go away within a few hours. 
> 
> The way that reads, ssh to a shell and then running tip in
> that shell would stay up. (Does it?) tip is being run
> without ssh running a shell? May be more detail about the
> two contexts of establishing the connection is needed here?
> 

No, other way 'round. In both cases an ssh connection was made which
started a shell. In one a tip session was started, which seems prone 
to dropping. In the other an active shell (typically running buildworld, 
or maybe idle) kept running. This makes me think (perhaps wrongly) that 
tip is involved with the disconnection. Both shells are started as a
regular user and then su-d to root.

I'm fairly confident this isn't a client-side or NAT problem, simply because
there are a dozen or so other ssh sessions running from the ssh client to the
various Pi2/3/4 hosts in my collection which stay up basically until they're
taken down deliberately.

I seem to (vaguely) recall a discussion of ssh problems over NAT some months 
ago, something about tolerating misssing ts (timestamps?). Is that still possible?

Thanks for writing!

bob prohaska