Will modem inhibition truly release MBIM port ?

[Bjørn Mork]

Bjørn Mork <bjorn at mork.no> writes:
> Aleksander Morgado <aleksander at aleksander.es> writes:
>
>> I've opened a new issue in gitlab for your problem:
>> https://gitlab.freedesktop.org/mobile-broadband/libmbim/-/issues/9
>> Will take a look at the problem sometime this week.
>
> Something is incrementing the transaction id between each fragment:
>
> [21  九  2020, 09:55:23] [Debug] [/dev/cdc-wdm_pcie] Sent message (translated)...
> <<<<<< Header:
> <<<<<<   length      = 4096
> <<<<<<   type        = command (0x00000003)
> <<<<<<   transaction = 4
> <<<<<< Fragment header:
> <<<<<<   total   = 65
> <<<<<<   current = 0
> <<<<<< Contents:
> <<<<<<   service = 'qdu' (6427015f-579d-48f5-8c54-f43ed1e76f83)
> <<<<<<   cid     = 'file-write' (0x00000003)
> <<<<<<   type    = 'set' (0x00000001)
> <<<<<< Fields:
> <<<<<<   DataBuffer = 
> ..
>
> <<<<<< Header:
> <<<<<<   length      = 4096
> <<<<<<   type        = command (0x00000003)
> <<<<<<   transaction = 5
> <<<<<< Fragment header:
> <<<<<<   total   = 65
> <<<<<<   current = 1
> <<<<<< Contents:
> <<<<<<   service = 'invalid' (00000000-0000-0000-0000-000000000000)
> <<<<<<   cid     = '(null)' (0x00000000)
> <<<<<<   type    = 'query' (0x00000000)
>
>
>
> That's not good.  The function is supposed to err out both transactions
> when it sees this second fragment with a new transaction id:
>
>  If the function receives a fragment that is not the first fragment of a
>  new command with a new TransactionId, both commands shall be
>  discarded. One MBIM_FUNCTION_ERROR_MSG message per TransactionId shall
>  be sent.

A proposed quickfix here:
https://gitlab.freedesktop.org/mobile-broadband/libmbim/-/merge_requests/32

But as noted: A real fix for proxied fragments will have to prevent
other clients from interfering.  Access to a device should be blocked
once a client starts a fragmented transaction, until either all
fragments have been submitted or some reasonable timeout. I guess
MAX_TIME_BETWEEN_FRAGMENTS_MS could be re-used.

This means that fragmented transactions must be tracked by the proxy.


Bjørn