Issue with 5G Slices and Bearer Connection Failure on Telit FN990 Modem

[Dan Williams]

On Sun, 2024-12-29 at 19:08 -0800, Pradeep Gopanapalli wrote:
> Hello,
> I am trying to establish multiple 5G multiplex slices on a Telit
> FN990 modem running in QMI mode. These 5G slices represent multiple
> PDNs managed by ModemManager (via mmcli).
> 
> When using the "--test-multiplex-requested" option, the bearer setup
> fails with the following Netlink error:
> GDBus.Error:org.gtk.GDBus.UnmappedGError.Quark._g_2dio_2derror_2dquar
> k.Code0: failed to create net link for device: failed to add link for
> device: Could not allocate link: Failed to add link with mux id 1:
> Netlink message with transaction 9 failed

Unfortunately libqmi-glib doesn't print out the actual error we get
from netlink, which I've fixed here:

https://gitlab.freedesktop.org/mobile-broadband/libqmi/-/merge_requests/389

would you be able to apply that patch locally and reproduce the issue,
so that we can figure out the actual error code netlink is returning?

Thanks,
Dan

> 
> Environment:
>  * Modem: Telit FN990A28 in QMI mode
>  * ModemManager: 1.22.0
>  * libqmi: 1.34.0-2
>  * libmbim: 1.30.0-2
>  * Kernel: 5.15.150
>  * OpenWrt: Based on 22.03 using netifd
> Debug Logs During Bearer Connection:
> (PFA message_modem_debug)
> 2024-12-28T00:38:03.709 DEBUG daemon ModemManager[9676]: 
> [1735346283.709521] [modem0/bearer1] connecting...
> 2024-12-28T00:38:03.709 NOTICE daemon ModemManager[9676]: 
> [1735346283.709796] [modem0] state changed (registered -> connecting)
> 2024-12-28T00:38:03.709 DEBUG daemon ModemManager[9676]: 
> [1735346283.709904] [modem0/bearer1] launching connection with QMI
> port (cdc-wdm0) and data port (wwan0) (multiplex requested)
> 2024-12-28T00:38:03.709 DEBUG daemon ModemManager[9676]: 
> [1735346283.709916] [cdc-wdm0/qmi] bringing down data interface
> 'wwan0'
> 2024-12-28T00:38:03.710 DEBUG daemon ModemManager[9676]: 
> [1735346283.710309] [cdc-wdm0/qmi] resetting expected kernel data
> format to 802.3 in data interface 'wwan0'
> 2024-12-28T00:38:03.897 WARN daemon ModemManager[9676]: 
> [1735346283.897197] [modem0/bearer1] connection attempt #1 failed:
> failed to create net link for device: failed to add link for device:
> Could not allocate link: Failed to add link with mux id 1: Netlink
> message with transaction 1 failed
> 2024-12-28T00:38:03.898 NOTICE daemon netifd: CELL1 (19170): error:
> couldn't connect the modem:
> 'GDBus.Error:org.gtk.GDBus.UnmappedGError.Quark._g_2dio_2derror_2dqua
> rk.Code0: failed to create net link for device: failed to add link
> for device: Could not allocate link: Failed to add link with mux id
> 1: Netlink message with transaction 1 failed'
> Similar Issue Reported:
> This issue has been reported in the following GitLab issue:
> GitLab ModemManager Issue #533, but I have not seen a resolution for
> it.
> Reference Links:
>  * ModemManager Mailing List - March 2022
> Any assistance or suggestions on resolving this issue would be
> greatly appreciated.
> Thanks,
> Pradeep G
> 
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