d-link dwm 157 B1 - mbim

[Bjørn Mork]

Thomas Schäfer <tschaefer at t-online.de> writes:

> In serial/ppp-mode the modem works now. The mbim-mode has still problems.
>
> I attached the usb-trace unter linux while trying to ping 8.8.8.8 in mbim-
> mode.

Thanks.  But there's not much to learn from that, I'm afraid.  Looks
like we are sending perfectly fine MBIM frames, but not getting anything
back.

I guess the fact that Windows end up using PPP is an indication of where
we stand.  I wonder how they get there, though?  Do they detect some
problem with the MBIM implementation and switch to PPP automatically?
Or is this a hardcoded device specific thing?

I must admit that I find these problems a bit surprising. The hardware
and firmware should be pretty much the same as in the D-Link DWM-156 A7
I got from Mediatek many years ago:

[/dev/cdc-wdm2] Device capabilities retrieved:
              Device type: 'removable'
           Cellular class: 'gsm'
              Voice class: 'simultaneous-voice-data'
                Sim class: 'removable'
               Data class: 'gprs, edge, umts, hsdpa, hsupa'
                 SMS caps: 'pdu-receive, pdu-send'
                Ctrl caps: 'reg-manual'
             Max sessions: '2'
        Custom data class: 'unknown'
                Device ID: '355619050151297'
            Firmware info: 'MOLY.WR8.W1231.DC.WG.MP.V3'
            Hardware info: 'MTK2'

AFAIR, this device had no major problems with our MBIM implementation.
It lacked a DHCP server, and it had a bit non-standard wMaxSegmentSize,
but it worked fine without any driver quirks.  So why should similar
hardware and firmware have developed a problem now?

Just to be sure that we haven't developed a problem over time, I dug out
that modem again and tried.  It still works fine.  Not useful for much,
but I attached the pcap for reference.

So I'm a bit lost here.  Think I'm going to lean on the Windows
behaviour for now...

Bjørn
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