Re: Stable/14 dropping ssh connections to FT232 usb-serial adapter

On Sat, Oct 28, 2023 at 04:11:53PM -0700, Mark Millard wrote:
> So, if I understand correctly, the general structure here is something like:
> 
> RPi4B: ssh to RPi2 v1.1 #0 (to invent simple naming).
> . . .
> RPi2 v1.1 #0: tip ucom (which gets to RPi2 v1.1 #1)
> . . .
> (Does each RPi2 v1.1 get its own ssh session too? If yes: all from the same RPi4B?)
> RPi2 v1.1 #1: tip ucom (which gets to RPi2 v1.1 #2)
> . . .
> (ssh session to RPi2 v1.1 #N ?)
> RPi2 v1.1 #N: tip ucom (which gets to RPi2 v1.1 #0)
> 

I think you've got the picture. Here's an ASCII-art diagram:
http://www.zefox.net/~fbsd/netmap

Each connection originates on a single WiFi-connected Pi4 running RasPiOS (top right).
The sessions are separate shells, each running in a tab in one lxterminal window.


> (An accurate/complete indication of the sessions/connections
> command sequence for the set up could be useful.)
>

Here's a verbatim sample, including MOTD and usbconfig output:
bob@raspberrypi:~ $ ssh 50.1.20.26
Password for [email protected]:
Last login: Sun Oct 29 03:34:28 2023 from 50.1.20.31
FreeBSD 14.0-RC3 (GENERIC) #39 releng/14.0-n265368-c6cfdc130554-dirty: Fri Oct 27 21:27:20 PDT 2023

Welcome to FreeBSD!

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To change this login announcement, see motd(5).
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		-- Benedict Reuschling <[email protected]>
bob@www:~ % su
Password:
# usbconfig
ugen1.1: <DWCOTG OTG Root HUB> at usbus1, cfg=0 md=HOST spd=HIGH (480Mbps) pwr=SAVE (0mA)
ugen1.2: <vendor 0x0424 product 0x9514> at usbus1, cfg=0 md=HOST spd=HIGH (480Mbps) pwr=SAVE (2mA)
ugen1.3: <vendor 0x0424 product 0xec00> at usbus1, cfg=0 md=HOST spd=HIGH (480Mbps) pwr=ON (2mA)
ugen1.4: <FTDI USB - Serial> at usbus1, cfg=0 md=HOST spd=FULL (12Mbps) pwr=ON (90mA)
ugen1.5: <GenesysLogic USB2.0 Hub> at usbus1, cfg=0 md=HOST spd=HIGH (480Mbps) pwr=SAVE (100mA)
ugen1.6: <JMicron External USB 3.0> at usbus1, cfg=0 md=HOST spd=HIGH (480Mbps) pwr=ON (500mA)
# tip ucom
Stale lock on cuaU0 PID=1272... overriding.
connected


FreeBSD/arm64 (pelorus.zefox.org) (ttyu0)

 
> As I understand, you are seeing the ssh session abort, not just a tip
> session abort.
>

That's correct. On the RasPiOS host I see simply
client_loop: send disconnect: Broken pipe
 
> An interesting test might be having another ssh session paired with
> each one that does a remote tip --but that is not used for any tip
> or other activity beyond sitting at a shell prompt. The question for
> each paired ssh session would be:
>
> A) Do both ssh sessions of the pair fail/abort at the same time?
> B) Does only one? If yes: is it always just the one that had used tip?
> 
> So, a comparison/contrast test.
>

At present I have only one usb-serial adapter per RPi2/3/4. However,
that still gives me seven tip sessions up at any one time and the one
on releng/14 drops reliably. There are usually half a dozen ssh connections
running interactive shells from the RasPiOS host to random FreeBSD Pi's
and as a rule they only drop when I crash or reboot the RasPiOS host. 

> As I remember, there were notes about avoiding special character
> sequences from getting special interpretations for ssh. That sort of
> thing could be important to both ssh [-e none] and tip [-n] for
> testing if that avoids some problems.
> 
> I've no clue if "tip -n -v" might report anything interesting around
> a failure (via the -v).

I've tried ssh -e none, it didn't make an obvious difference. I overlooked 
tip -v, will try it next time. As it happens the tip sessions sometimes
come up "stuck", reporting a connection but refusing to display any 
output. In that case it's useful to use ~~. to escape back to a root
prompt, run usbconfig [-u 0 -a 4] power_off and then power_on to reset
the usb-serial adapter, which generally gets a working connection. 
I'll try tip -n -v at the next opportunity. 

Thanks for writing!

bob prohaska