examples/gnrc_border_router: pass variables to docker

[maribu]

Contribution description

This passes environment variables used to configure e.g. the uplink of the border router to the docker container, so that configuration works with BUILD_IN_DOCKER=1.

Testing procedure

Run:

USEMODULE="sock_dns gnrc_ipv6_nib_dns" make -C examples/gnrc_border_router BOARD=esp32-mh-et-live-minikit BUILD_IN_DOCKER=1 UPLINK=wifi WIFI_SSID=foobar WIFI_PASS=foobar1337 flash term
make: Entering directory '/home/maribu/Repos/software/RIOT/master/examples/gnrc_border_router'

In master, you'll see "crazy" serial output, as the build system on the host expects normal stdio and WiFi as uplink, but the build system in the docker container expected slip as uplink and multiplexes the uplink with stdio.

With this PR, the serial is no longer multiplexed with the uplink, but WiFi is used as configured.

Issues/PRs references

None

[MrKevinWeiss]

Ahh, that makes sense :)

[riot-ci]

Murdock results

✔️ PASSED

276ad18 examples/gnrc_border_router: pass UPLINK etc to docker

Success	Failures	Total	Runtime
10065	0	10066	20m:56s

Artifacts

• Documentation preview

[mguetschow]

Are those defined and documented anywhere in a generic way? grepping through the RIOT repo only shows them being mentioned in esp-common and atwinc15x0 driver documentation, where they are expected to be passed within CFLAGS anyway.

So instead of adding them here, I would use the same approach as for the other Makefile variables just for examples/gnrc_border_router.

[maribu]

They are actually not used by the example, but used by the only two WIFI drivers (ESP* and ATWINC15x0) we have.

They are documented separately in both drivers.

[mguetschow]

I'm not sure I follow. The example defines the environment variables in https://github.com/RIOT-OS/RIOT/blob/master/examples/gnrc_border_router/Makefile#L19-L20 and uses them in https://github.com/RIOT-OS/RIOT/blob/master/examples/gnrc_border_router/Makefile.wifi.conf to add them to CFLAGS.

The documentation of both ESP* and the ATWINC15x0 explicitly adds them to CFLAGS as well (e.g., https://github.com/RIOT-OS/RIOT/blob/master/cpu/esp32/doc.txt#L1639). The only other example I could find that uses these environment variables is examples/paho-mqtt which also explicitly adds them to CFLAGS later on: https://github.com/RIOT-OS/RIOT/blob/master/examples/paho-mqtt/Makefile#L62-L63.

So my point was that the environment variables themselves are not generically defined, but only custom to specific examples, and therefore I think those examples should add the respective DOCKER_ENV_VARS themselves.