Since the modem iface and the GGSN iface are on the same host/netns,
it's really difficult to conveniently test data plane without getting
routing loops. As a result, either GGSN or modem iface must be moved to
a different namespace. The decision after a few discussions was finally
to move modem interfaces to a different netns.
Expected setup:
* ofono is patched to avoid removing modem if it detects
through udev that its net iface was removed (due to for instance, net
iface being moved to another netns and thus not being reachable anymore
by systemd-udev process running in root netns).
* After ofono is started (and successfully configured all the modems and
detected its net ifaces through syfs/udev), script "modem-netns-setup.py
start" which creates a netns for each modem, naming it after its usb
path ID. net ifaces for that modem are moved into its netns.
* Modem is configured to use 802-3 data format, and as a result the net
iface is configured through DHCP (DHCP req only replied AFTER pdp ctx is
activated!).
* Since osmo-gsm-tester knowns the modem USB path ID (available in
resources.conf), it can run required steps (ifup, DHCP) to configure the
interface. The interface name is provided by ofono to osmo-gsm-tester.
* As a result, any process willing to transmit data through the modem
must be in the modem netns.
Related: OS#2308
Change-Id: Icb06bdfcdd37c797be95ab5addb28da2d9f6681c
Pau Espin
fd4c144049