[solved] Raspbian Stretch: how to identify built-in ethernet adapter

[beta-tester]

i have a problem with Raspbian Stretch (2017-07-05-raspbian-jessie.img).
with Raspbian/Debian Stretch the method of naming network adapters has changes.
on Raspbian Jessie the built-in ethernet adapter got always the name eth0.
on Raspbian Stretch the built-in ethernet adapter get a name with the MAC address in it (e.g. enx112233445566).
but this makes it impossible for scripts to find the built-in ehternet adapter without the knowledge of the MAC of that adapter.

in the past, i simply could grab necessary information by using the name eth0.
how can i identify the built-in ethernet adapter without knowing the MAC address and existence of multiple ethernet adapters at the same time.
e.g.

Code: Select all

pi@raspberry:~ $ ifconfig
enx112233445566: ...
enx998877665544: ...
enx556677889900: ...
lo: ...

how can the script find out which of the listed adapters is the built-in adapter of the RPi, when the MAC address is unknown by the script?
(the script is running on different RPis - so i can not hardcode the MAC or adapter name)

PS.: i am not able to do any preparations before the script is running. the script has to work out of the box on each RPi.

[beta-tester]

hmm... it is ugly, but at the moment i don't find an other solution...
i am fetching the network adapter that sitts on the first USB adapter on the first "port".

Code: Select all

pi@raspberry:~ $ ls /sys/devices/platform/soc/*.usb/usb1/1-1/1-1.1/1-1.1:1.0/net
enx112233445566