RE: Reconnecting GSM profile after a long period of no signal

[Matthew Starr <mstarr hedonline com>]

> -----Original Message-----
> From: Thomas Haller [mailto:thaller redhat com]
> Sent: Thursday, June 20, 2019 3:22 AM
>
> On Tue, 2019-06-18 at 22:58 +0000, Matthew Starr wrote:
> > I am running NetworkManager 1.12.0 on an embedded Linux device that
> > has Ethernet, Wi-Fi, and cellular.  I am seeing a connection issue on
> > GSM profiles that are setup for autoconnect=true.  If I am able to
> > establish a connection on cellular, then lose signal (move out of
> > range) for 20-60 minutes, and then come back within range of the
> > cellular signal, NetworkManager will not attempt to reconnect to these
> > networks.  I can see that ModemManager (version 1.8.0) is fully
> > registered with the cellular network and that NetworkManager is just
> > not requesting to connect a data session.
> >
> > I know NetworkManager has a 300 second autoconnect reset retry timer.
> > I modified that timeout to be 60 seconds to make NetworkManager more
> > aggressive on retry attempts. I have given NetworkManager over an hour
> > and have seen no attempt to connect to the cellular network after a
> > long period of no signal.  A simple “nmcli con up <PROFILE>” command
> > will instantly connect when run, but I want NetworkManager to
> > automatically connect without user intervention on the command line.
> >
> > I believe I had someone explain before that this is based on the logic
> > of a connection that is having issues with getting data is eventually
> > assumed to be a bad connection after enough failed attempts and that
> > knowledge is somehow stored somewhere so NetworkManager doesn’t
> try to
> > connect to that network again.  In my case I have an embedded device
> > that is attached to mobile assets so the cell and Wi-Fi signal will
> > come and go, the whole time the device is never turned off.
> >
> > I have also seen this issue with Wi-Fi previously, but I am not sure
> > if that is the same issue I am seeing now with cellular.
> >
> > Is there some way to force NetworkManager to always keep retrying to
> > connect to networks defined in profiles that have autoconnect set to
> > true until successfully connected, no matter how many times it fails
> > to connect?
>
> Hi,
>
> when NetworkManager thinks that the connection failure happend due to a
> bad pin, then it might block autoconnect indefinitely. That is to prevent
> blocking the pin.
>
> Another reason why autoconnect be blocked is if NetworkManager thinks
> that the secret
> (Pin) was wrong, but there is no secret-agent around to provide a secret.
>
> But probably something is not right here. What does the level=TRACE log say
> about this? See [1] for infos about logging, in particular about rate-limiting.
>
> [1]
> https://cgit.freedesktop.org/NetworkManager/NetworkManager/tree/cont
> rib/fedora/rpm/NetworkManager.conf#n28
>
>
> best,
> Thomas

Thomas,

I have had the condition where NM does not attempt to reestablish a data connection a few times, but now that 
I am trying to reproduce it, to get better logs, it isn't happening.  I will keep trying.

Where in the NM code is the logic blocking autoconnect indefinitely when an autoconnect profile is repeatedly 
not able to connect?

In my use case of an embedded device, I always want to retry even if it wasn't working previously.  I am 
considering making my own modifications to disable blocking autoconnect indefinitely.  Maybe this could lead 
to a configuration option to enable/disable this logic.

Best regards,
Matthew Starr