Establishing connections to multiple PDPs simultaneously with MBIM

[Dan Williams]

On Wed, 2015-08-05 at 17:47 +0200, Markus Gothe wrote:
> Per specification MBIM allows you to have up to 256 simultanous data connections IIRC.
> 
> You can use the command line interface for mbimcli or even better modemmanager to allocate simultanous connections. Then you need to do vlan-tagging etc on the "ethernet device".
> 
> It is kinda complex but doable.

Bjorn implemented this on the kernel side, so he'd know exactly what has
to happen.

But I think what you do is create a new VLAN interface on top of the
ethernet interface that gets created for the device.  Then each VLAN
interface gets mapped to a specific data session that you've created.

https://www.kernel.org/doc/Documentation/networking/cdc_mbim.txt

I guess this is one area where ModemManager would help, since it would
create these interfaces for you and just hand you the interface name and
the IP details (though this isn't all implemented yet).

Otherwise you get to poke the kernel yourself.  Something like:

1) make sure the device supports multiple sessions using
"--query-device-caps".  My XMM7160 device only supports 16.
2) create a kernel VLAN interface on top of the MBIM network interface
using the session ID you'd like to use; you get to manage the session
IDs :)
3) run the mbimcli connect and send it the session ID you chose
4) assign the IP address information that mbimcli returns from the
connect request to the VLAN interface
5) send some packets

But it doesn't actually look like mbimcli supports multiple sessions
since it always passes '0' to the functions that deal with connect.  So
we'd need to fix that up and allow passing a specific session ID to
--connect, --disconnect, and --query-connection-state.  

Dan