Ethernet-briding a MBIM-interface

[Markus Gothe]

The rationale for having a null mac adress as the ethernet source adress would be nice to know. Wouldnt it be better to keep it the same as the ethernet destination adress (like some CDC ECM implementations)??? This is afaik to be considered a bug. :-)

//M

Skickat ifrån min mobil.
Den 24 okt 2014 09:23 skrev Markus Gothe <nietzsche at lysator.liu.se>:
>
> Well… 
> The DirectIP and CDC ECM behaves differently at least because you put the logic inside the modem firmware :-) 
>
> Having a DHCP-server inside cdc_mbim.c should not be too difficult, look at an old version of sierra_net.c 
>
> Well, MBIM is supposed to be like QMI ‘raw-ip’-mode. Maybe we could do the same mess up for that case. ;-) 
>
> //M 
>
> On 24 Oct 2014, at 09:04 , Bjørn Mork <bjorn at mork.no> wrote: 
>
> > Markus Gothe <nietzsche at lysator.liu.se> writes: 
> > 
> >> Hi, Björn and thanks for your feedback. 
> >> 
> >> 2G/3G networks are circuit switch running PPP over the backhaul. LTE 
> >> is circuit switch and talking IP over the backhaul.  This is why 
> >> Sierra’s DirectIP / sierra_net.c is a half-bridge. It is by an old 
> >> design. Hiding the PPP and using a DHCP-hack (older DirectIP devices 
> >> actually wants the DHCP-server to be implemented in sierra_net.c using 
> >> CnS/HIP). 
> > 
> > Yes, I have wondered if that wouldn't have been a better design after 
> > all.  Having a DHCP server inside the driver would be messy, of course. 
> > But having it inside the modem firmware isn't less messy, and prevents 
> > us from fixing it if that should become necessary.  Luckily it hasn't. 
> > 
> > For MBIM, I believe the best option for the host is to use the IP 
> > configuration request instead of trusting some random DHCP server 
> > implementation in the firmware. 
> > 
> >> The local MAC-issue will be overcome by using eatables to do MAC-DNAT 
> >> (been there done that before).  The use case for being able to bridge 
> >> MBIM is of course embedded devices. Not computers. 
> >> 
> >> Playing around with proxy arp / parprouted might be a good starter. :-) 
> >> 
> >> So basically you are saying that MBIM and Sierra DirecIP is 
> >> reassembling each other very close? 
> > 
> > Yup. And also any other modem presenting an ethernet like interface, 
> > like NCM or ECM (with or without a QMI channel) 
> > 
> > Some might argue that MBIM should be different because there are no 
> > ethernet headers, but we messed that up in the Linux driver :-) 
> > 
> > 
> > Bjørn 
> > _______________________________________________ 
> > libmbim-devel mailing list 
> > libmbim-devel at lists.freedesktop.org 
> > http://lists.freedesktop.org/mailman/listinfo/libmbim-devel 
>
>
>
> //Markus - The panama-hat hacker 
>
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