Netlink failure when attempting to add multiplexed link in MBIM modem

[Aleksander Morgado]

Hey Bjørn,

I'm getting some strange reports of failures in the netlink
communication when adding new multiplexed links in a MBIM modem, using
cdc_mbim. I also have the kernel dmesg but it doesn't give any
reference to the error, the only valid thing I have is the MM debug
log.

Any idea why this may fail? If I'm not mistaken, the actual
multiplexed net interface creation is a process done by the kernel
alone, without any interaction with the device, so not sure what could
be happening.

2024-01-15T06:52:20.192634Z NOTICE ModemManager[4658]: <msg> [modem6]
state changed (registered -> connecting)
2024-01-15T06:52:20.192901Z DEBUG ModemManager[4658]: <dbg>
[modem6/bearer2] launching multiplexed connection with data port
(net/wwan0)
2024-01-15T06:52:20.192912Z DEBUG ModemManager[4658]: <dbg>
[modem6/bearer2] setting up new multiplexed link...
2024-01-15T06:52:20.193219Z DEBUG ModemManager[4658]: <dbg> Using
dynamic session ID 1
2024-01-15T06:52:20.193259Z DEBUG ModemManager[4658]: <dbg> Using
ifname 'mbimmux6.1' and vlan id 1
2024-01-15T06:52:20.193506Z WARNING ModemManager[4658]: <wrn>
[modem6/bearer2] 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 session id 1: Netlink message with
transaction 1 failed: Unknown error -1
2024-01-15T06:52:20.193634Z DEBUG ModemManager[4658]: <dbg>
[modem6/bearer2] cannot set unhandled domain error as connection
error: failed to create net link for device: failed to add link for
device: Could not allocate link: Failed to add link with session id 1:
Netlink message with transaction 1 failed: Unknown error -1
2024-01-15T06:52:20.193684Z NOTICE ModemManager[4658]: <msg> [modem6]
state changed (connecting -> registered)
2024-01-15T06:52:20.193973Z NOTICE ModemManager[4658]: <msg>
[modem6/bearer2] connection #1 finished: duration 0s
2024-01-15T06:52:20.193996Z WARNING ModemManager[4658]: <wrn> [modem6]
couldn't connect bearer: failed to create net link for device: failed
to add link for device: Could not allocate link: Failed to add link
with session id 1: Netlink message with transaction 1 failed: Unknown
error -1


-- 
Aleksander