Issues regarding multiple MBIM bearer support

Aleksander Morgado aleksander at
Mon Jun 21 13:04:16 UTC 2021


> Just to let you know - I cherry-picked e5305498b7ddbc5e419cf51fc0c30aa6593a40d2 over 1.16.6 tag, and it did fix the VLAN issue - new bearers objects appear, but all use session 0.
> Without the fix it didn't - the issue was caught exactly on vanilla 1.16.6, but we didn't gather the logs at the time.

I've cherry-picked that commit for MM 1.16.

> I prefer this over updating configuration on units deployed in the field. I can still provide you with the logs if you wish.

What configuration would you need to update?

> 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

Also, by default the multiplexing setup is "requested" (not
"required") and so, if for any reason it fails to setup multiplexing,
we should allow setting it up as a non-multiplexed session. In your
case, we should have fallen back without breaking the connection
attempt. I need to work on that in the next few weeks, so if it's not
much to ask, I may ping you again once I have a fix to see if you
could retest it... :)


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