RPI2 drops _some_ ssh connection

[Paul Mather]

On Aug 25, 2019, at 7:06 PM, bob prohaska <fbsd at www.zefox.net> wrote:

> I've an RPI2 running 11.3-STABLE FreeBSD 11.3-STABLE #0 r351178
> which seems to be dropping one of several active ssh connections.
>
> With four connections active from terminal windows on a Pi3 running
> raspbian, the one used to monitor a cu session keeps dropping every
> half-hour or so. All the other connections, running ordinary user
> processes like top or compiling a port, seem to stay up and running.
>
> There has been a tendency for -current to do this on a Pi3, but
> 11-stable didn't until the latest upgrade a few days ago.
>
> It doesn't look like a network problem, since all four sessions
> are over the same wifi and wired links. Could there be some odd
> interaction between cu and ssh?


Is the cu session producing regular output?  If not, could there be some  
sort of idle timeout at the remote end disconnecting it?  (All the other  
sessions you mention above [e.g., top] seem like they would be generating  
regular output.)

Are you using the ServerAliveInterval option at the client side of the SSH  
session to ensure semi-regular traffic is being sent through the  
connection?  This can help prevent the connection state being aged out with  
some stateful firewall setups.

Cheers,

Paul.