Hi Denis,
On 15/03/2019 02:27, Denis Kenzior wrote:
Hi Jonas,
On 03/14/2019 05:37 PM, Jonas Bonn wrote:
---
Funny, I was looking at this code today and thought it was wrong. Was
going to point this out to you, but you beat me to it ;)
Here's something that I'm having trouble understanding. The ublox
plugin creates 8 gprs_context atoms. As far as I can tell, this means
that ofono will allow it to activate 8 contexts simultaneously... right?
Correct. Each context driver added to gprs allows a concurrent context
to be activated. E.g. if you have 2 drivers, you can activate 2
contexts simultaneously. Obviously you need a high speed / ppp
interface for each active context.
Why is the ublox plugin the only one that does this? Do other modems
not support multiple active contexts? Or is this plugin wrong?
From what I recall, ublox does claim to support multiple PDP contexts
active at the same time. However, I don't know how this works in
practice as you need a unique network interface for each one. As it
stands today, given the udevng detection logic, this plugin is wrong.
Right, so the way this works is that the modem looks like either a
"bridge" or a "router". If configured as a "bridge", the outbound
packet's source address is used to determine which context to use; if
configured as a "router", the outbound packet's destination _network_ is
used to determine which context to use and a default route is set via
the _first activated context_ for packets that don't match the network
of any active context. That's a mouthful...!!!
The short of it is that this probably works in practice.
Is it ok for the connection manager interface to see multiple active
contexts with the same Interface and the IP settings set to method
"dhcp". Will it run a DHCP client on each interface or is it expected
to be smart enough to recognize the common interface??? What would the
point be since the only thing that differs the contexts is the APN and
the connection manager shouldn't care about that particular detail...???
This all applies to "router" mode only, really.
In "bridge" mode, the above is probably moot since each context would
announce different IP settings and the connection manager would be
expected to apply those settings to the common interface. No idea if
this works in practice.
Do you know how these multiple, active contexts are used in practice?
In particular with regard to ofono?
If I were to follow the model of other plugins, the below patch would
seem appropriate...
A bit of insight here would be appreciated.
There are drivers for USB based modems that do this properly. See
xmm7xxx for example. Multiple PDP context support was added to that
recently.
Modems that used multiplexing had support for multiple PDP contexts for
quite some time. E.g. plugins/ifx, etc.
Anyway, patch looks fine to me. Let me know if you want me to apply it
or you want to take a stab at fixing the detection logic.
From this, it sounds like the multiple gprs-context atoms are probably
correct. I'll take a look at the xmm7xxx driver and see how it handles
things.
Thanks,
Jonas
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