Issues regarding multiple MBIM bearer support

Bjørn Mork bjorn at
Mon Jun 21 15:14:15 UTC 2021

Aleksander Morgado <aleksander at> writes:

>> With master (83ac82470589a3672092a0ba0be855093b1cf5e2) I had problems. MM did want to enable multiplexing, but it failed for some reason, probably at sub-interface creation:
>> 2021-06-16 10:04:05.630664 +00:00 test-host NetworkManager[457]: <INFO>  <info>  [1623837845.6302] modem["cdc-wdm0"]: modem state changed, 'registered' --> 'connecting' (reason: user-r
>> equested)
>> 2021-06-16 10:04:05.636959 +00:00 test-host ModemManager[455]: <DEBUG>  Using dynamic session ID 0
>> 2021-06-16 10:04:05.637483 +00:00 test-host ModemManager[455]: <WARNING>  <warn>  [modem0/bearer4] connection attempt #1 failed: failed to create net link for device: failed to add lin
>> k for device: Could not allocate link: Failed to add link with session id 0: Netlink message with transaction 5 failed: Unknown error -1
>> 2021-06-16 10:04:05.638678 +00:00 test-host ModemManager[455]: <INFO>  <info>  [modem0] state changed (connecting -> registered)
>> On the device I have 5.11.19 kernel with 802.1Q enabled. Again, I can provide you with detailed logs if this wasn't fixed already.
> Please, provide detailed logs, we need to understand why this failed
> in the kernel. @Bjørn Mork any idea why it may have failed like this?
> does the kernel need any additional thing on top of MBIM and VLAN
> support?

I have no idea what happened here. If that's an ENOENT error then I
don't see any way it could be trggered.


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