[Ovmsdev] A promiscous wifi client

Stephen Casner casner at acm.org
Sat Nov 18 05:05:53 HKT 2017

There is more to do on this conversion of the Telnet Console to use

  - When wifi service is shut down by command, my old implementation
    would close the connections to the clients cleanly.  The new
    implementation with mongoose leaves them hanging.  The way to
    improve this may lie in the shutdown steps in ovms_netmanager.

  - It looks like there may be a memory blocked leaked at each client
    disconnection.  I need to find that.

  - I think I can improve how I handle the receive buffer and save
    some more RAM.

I've also thought more about how to convert the SSH Console and will
take a stab at that as well.

                                                        -- Steve

On Fri, 17 Nov 2017, Stephen Casner wrote:

> On Thu, 16 Nov 2017, Mark Webb-Johnson wrote:
> > We don't seem to have this issue with the webserver listener; that
> > uses mongoose (in netmanager). That doesn't have long-lived client
> > side connections, but the socket listen/accept functionality should
> > be similar. Not sure how mongoose handles it internally, but the
> > library seems quite robust.
> Mongoose wakes up from the select() periodically to do polling so the
> deletion of the task would not happen while in select().
> > I'm wondering if we can migrate to use that? It would probably save
> > a bunch of ram (as it doesn't need a task for each thread). We are
> > mostly single-user anyway.
> I have converted console_telnet to use mongoose and netmanager in the
> same manner as ovms_webserver.  This eliminates the TelnetServer and
> TelnetReceiver tasks and saves about 3KB.  I have kept TelnetConsole
> as a separate task from NetManTask.  I'm not convinced that combining
> the console functionality into NetManTask is a good idea; I'm afraid
> it would introduce some problems with interference between various
> operations and may get into trouble with the Log() mechanism.  Even if
> not, much more surgery would be required.
> > Perhaps a generic extension to ovms_netmanager where you give it a
> > tcp port and an object type. Then, it listens on that port and
> > launches objects of that type (pre-configured to receive mongoose
> > events as appropriate) for each new connection? Have a base virtual
> > connection class, that gets inherited by each implementation (ssh,
> > telnet, etc).
> I didn't do it that way for this telnet conversion, but we could
> evolve to that if appropriate.
> Converting ssh may be possible but would be significantly harder.  The
> libtelnet design calls for all the actual I/O (recv/send) to be done
> outside of the library.  That fits with the design of mongoose where
> it owns that I/O.  However, the wolfssh library is designed for the
> library itself to be in control of the I/O.
>                                                         -- Steve
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