'port forced close' after failed ppp

[Colin Helliwell]

> On 14 March 2017 at 14:18 Colin Helliwell <colin.helliwell at ln-systems.com> wrote:
> 
> > On 13 March 2017 at 09:53 Colin Helliwell <colin.helliwell at ln-systems.com> wrote:
> > 
> > > On 13 March 2017 at 09:06 Colin Helliwell <colin.helliwell at ln-systems.com> wrote:
> > > 
...
> > > Tracing in the driver, I can see the TCSETFS ioctl being called at the 'pon' and at the 'poff'. Presumably this *is* from pppd - nothing else is using the port except MM.
> > > The respective c_cflag values in the args seem to be
> > >  pon 020000012267
> > >  poff 016261
> > > So, yes, it appears that CLOCAL [04000] is being set? (and CRTSCTS cleared)
> > 
> > Using 'local' instead of 'modem' in the ppp settings:
> > pon 20000014267
> > poff 016261
> > i.e. CLOCAL *staying* set, and setting HUPCL?
> 
> Still trying to get to the bottom of this problem.
> What are the events which can cause the G_IO_HUP (in MM)?
> I only plan to use the driver with MM/NM/ppp, so I *could* make mods if necessary, but I'm not even sure it's the driver that needs alteration. Or, at least, that that's the best place.
> I also came across this old thread - https://mail.gnome.org/archives/networkmanager-list/2010-March/msg00140.html - dunno if it's relevant to my problem.
> 


I've done some stripping back of the driver, yet still getting the 'hangup'. I'm tracing the ioctl 'set' functions in the driver, and can currently only see
pon sending a TCSETSF cflag = 020000014262  (CRTSCTS  CLOCAL !HUPCL)
and
poff then sending a TCSETSF cflag = 14261 (!CRTSCTS  CLOCAL !HUPCL)

So is it just the change in CRTSCTS that is triggering the hangup? (I'd have expected it to be set anyway, so I'm not sure why/when it's getting cleared - I can maybe track this down if it's pertinent)