[RFC] No multiplexing by default in MM 1.18

Daniele Palmas dnlplm at gmail.com
Tue Aug 3 10:23:37 UTC 2021

Hi Aleksander,

Il giorno lun 2 ago 2021 alle ore 16:41 Aleksander Morgado <
aleksander at aleksander.es> ha scritto:

> Hey all,
> I've been testing with all my modems for the next 1.18 release, and
> for the QMI and MBIM ones I've done tests with and without
> multiplexing support (i.e. connecting normally as we did until now,
> and also connecting with multiplexing enabled).
> All the QMI modems I have tested with have worked fine. If QMAP wasn't
> supported by the modem and we were requesting multiplexing, it would
> automatically just fallback to no multiplexing (802.3 or plain
> raw-ip), and that was it.
> Most of the MBIM modems I have tested with have worked fine as well,
> with the exception of the Netgear AC340U, which would reply with
> "InvalidParameters" if we were attempting to connect any session with
> id != 0. All the other modems have been able to correctly setup
> multiplexing when requested without issues.
> Even if the tests have been quite satisfactory overall (I've tested
> >60 different modems in the past month), I think that for 1.18 we
> should not enable multiplexing by default (except for IPA), and still
> leave it as a requirement from the user at connect time. So, if the
> user wants to setup a connection with multiplexing enabled, it should
> pass either "multiplex=requested" or "multiplex=required" in the
> connection settings explicitly
I think it makes sense.


> I've also updated the daemon to have a "--test-multiplex-requested"
> option, so that if given, the default would be back to attempt to
> enable multiplexing whenever possible.
> The main reason for this decision is that the network interface that
> gets connected if multiplexing is enabled would change between 1.16
> and 1.18, because with multiplexing we're connecting an ephemeral
> network link that we have created during runtime  (e.g. for a QMI
> modem that had a connected net interface named wwan0 in 1.16, the
> connected net interface in 1.18 would be named qmapmux0.0 instead).
> This connected net interface name change wasn't an issue for
> NetworkManager or standard distributions, but it would have been a
> major change for every other custom system using ModemManager, if e.g.
> custom firewall or routing rules were configured based on the network
> interface name and such. I think we should provide more information
> about the feature to system integrators, and give some more time for
> the feature to be used and tested, before discussing again whether it
> should be the default or not in 1.20.
> The MR that includes the changes to update the multiplexing default is
> this one, including some other related fixes:
> https://gitlab.freedesktop.org/mobile-broadband/ModemManager/-/merge_requests/598
> Comments welcome!
> --
> Aleksander
> https://aleksander.es
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