Hi,
On 4/3/19 4:49 PM, Marcel Holtmann wrote:
Wouldn’t it generally be better for reading the name after oFono has brought up
the interface. In case we need this for the D-Bus API somehow. And for sake of
matching we start and handing this to the plugins and drivers we should start
using the ifindex.
I'm sorry but I didn't fully understand you here. Can you
rephrase/extend your thoughts? We need it for the D-Bus API, it is
announced to dbus clients when activating a PDP Context tgether with
other IP information in order to let the clients know which iface to use
for it.
== General scenario for the patch:
You have a modem and it has iface name wwan0. You decide you want to
rename it manually:
ip link set wwan0 down && ip link set wwan0 name mymodem && ip link set
wwan0 up
Currently ofono is unable to catch this change and will continue to
advertise "wwan0" on the DBUs API.
== Our specific scenario:
As you may have heard already before, at Osmocom [1] we use ofono in
order to operate QMI modems (EC20, SierraW, gobi2000, etc.) to test our
core networks on a wired HW setup, all orchestrated by osmo-gsm-tester
[2][3].
In order to provide correct routing (avoid loops) from different modems
to different GGSNs on the same machine, we move modem network interfaces
to their own network namespace. In order to do that, we required adding
a small hack-patch [4] into our own ofono branch [5] to prevent ofono
from dropping the whole modem when the net iface disappears (because
udev is unable to track different net namespaces than default, which
means from udev point of view the iface is not there).
Furthermore, we experience sporadic crashes in the modem firmware while
executing tests, which from linux system point of view means the
interface is removed and re-appears. When it is re-registered with the
kernel, it may give a new different iface name than the previous one.
That also means the ifindex of this new interface is not the same it
used to be before. Since due to our patch we didn't drop the modem
during netif removed (moved to different netns), the modem is kept alive
during crash but still points to old net iface name. More information
about this scenario can be found in [6].
I'm so far fixing it using persistent naming in our net ifaces by means
of udev rules.
[1] https://osmocom.org/
[2] https://osmocom.org/projects/osmo-gsm-tester
[3] https://git.osmocom.org/osmo-gsm-tester/
[4]
https://git.sysmocom.de/ofono/commit/?h=osmo-gsm-tester&id=e77b82a1bd1986aab42a119e0556c5941795992e
[5] https://git.sysmocom.de/ofono/log/?h=osmo-gsm-tester
[6] https://osmocom.org/issues/3881
--
- Pau Espin Pedrol <pes...@sysmocom.de> http://www.sysmocom.de/
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* sysmocom - systems for mobile communications GmbH
* Alt-Moabit 93
* 10559 Berlin, Germany
* Sitz / Registered office: Berlin, HRB 134158 B
* Geschaeftsfuehrer / Managing Director: Harald Welte
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