Ssh sessions running top keep disconnecting

[Robert Crowston]

To debug, you can launch a debug sshd instance with “sshd -ddd -p 12345” (or whatever alternative port you like) and your ssh client with “ssh -vvv -p 12345 bob at whatever”.

This will produce a great deal of debug info which can help figure out what is going on. You can reduce the number of “v”s or “d”s to decrease verbosity if it becomes unusable. Server side logs are more useful but at max debug level may have compromising information in them, so read them carefully before sharing. sshd -d can be run in parallel with regular sshd, just run it from the command line with a different port. It will quit automatically after the client disconnects.

On Fri, Jun 5, 2020 at 21:23, bob prohaska <fbsd at www.zefox.net> wrote:

> On Wed, Jun 03, 2020 at 07:39:44PM -0700, Mark Millard wrote:
>>
>>
>> On 2020-Jun-3, at 19:02, bob prohaska <fbsd at www.zefox.net> wrote:
>>
>> > For some reason, ssh sessions running top seem to be quitting
>> > with
>> > packet_write_wait: Connection to 50.1.20.25 port 22: Broken pipe
>> >
>> > I'm in the habit of leaving an ssh session running top going on
>> > machines running long jobs like world or port builds. On my Pi3
>> > running 12.1-stable those sessions keep disconnecting. No other
>> > ssh sessions, among the four open, seem to be affected.
>> >
>> > The client is a Pi3b+ running raspberry pi os. It has a dozen
>> > or so ssh sessions open, no others are affected.
>> >
>> > Any ideas what might be going on?
>> >
>>
>> No clue. But a possible kind of experiment . . .
>>
>> top keeps its ssh connection in use on a rather
>> frequent basis, even if the mount of traffic is
>> not large.
>>
>> Try having some other ssh session into the 12.1
>> Stable FreeBSD system that also keeps its ssh
>> connection in use on a rather frequent basis.
>> Does it get the same issue as the top sessions
>> do? (Need not be at the same times but if the
>> times were near each other for failures that
>> might indicate something.)
>>
>> Of course, it may be that some of your other ssh
>> connections to the same system already do this
>> test --or it may be they all rarely put their
>> connection to use (compared to top).
>>
> In a couple of cases top sessions disconnected as
> described while gstat sessions kep running. The
> statistics aren't very good on this, with only
> three or four cases total and at least one where
> no disconnection occurred.
>
> The client machine from which all the sessions are
> observed is a Pi3B+ running Raspberry Pi Buster. It's
> been found that all ssh sessions are more stable if
> there's an ongoing ping -i 10 to the WAP. I don't
> see how that would be significant but maybe it is.
>
> Thanks for writing,
>
> bob prohaska
>
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