'port forced close' after failed ppp

[Dan Williams]

On Thu, 2017-03-09 at 09:19 +0000, Colin Helliwell wrote:
> > On 08 March 2017 at 14:38 Aleksander Morgado <aleksander at aleksander
> > .es> wrote:
> > 
> > On Wed, Mar 8, 2017 at 3:08 PM, Colin Helliwell
> > 
> > <colin.helliwell at ln-systems.com> wrote:
> > 
> > > But this brings me back (in a round-the-houses way!) to my
> > > original question: when the PPP fails, for example with the ports
> > > assigned the right way round, but on 'faulty' SIM1, why is the
> > > PPP port getting "forced closed" and then unable to be retried?
> > > My concern being if PPP fails for an external reason e.g. at the
> > > remote end, then it can't retry?
> > 
> > Forgive my bad memory here. I think the HUP that triggers the
> > "forced
> > close" in the TTY shouldn't be received by ModemManager, it should
> > be
> > processed by pppd, which is the one that handles that
> > disconnection.
> > pppd resets all modem control lines on exit, IIRC. I recall a
> > similar
> > problem when playing with the NetworkManager integration, which is
> > the
> > one that would call pppd to establish the connection; I think I
> > solved
> > it just by making sure pppd is completely closed before
> > Disconnect()
> > is called for the modem in ModemManager (i.e. so that pppd could
> > recover the original state of the control lines before passing the
> > control of the TTY to MM through the Disconnect() call). Does that
> > make any sense at all?
> > 
> 
> Ermmm, some...!
> However I've found that the same thing is happening even when the PPP
> is successful - MM is getting the "unexpected port hangup!" when I
> close PPP. I'm doing:
>   mmcli -m 0 --enable
>   mmcli -m 0 --simple-connect="apn=wap.vodafone.co.uk"
>   pon
>   ... success ...
>   poff
>   mmcli -m 0 --simple-disconnect
> 
> Then trying again to connect fails with 'forced close'

I'd consider this an MM bug then.  But as a workaround, try passing the
"local" option to pppd, which disables its munging of modem control
lines and thus prevents a port hangup.  Does that help?

Dan