pkg/lwip: implement netif_get_name()

[benpicco]

Contribution description

This function is needed so we can use netutils_get_ipv6() with LWIP.
The code is from _netif_list().

Testing procedure

Issues/PRs references

#16739

[miri64]

You forgot to add testing procedures. How can I test this?

[benpicco]

I'm afraid there is no test case for netif_get_name()

[miri64]

You could use the function in tests/lwip ;-).

[chrysn]

Well as for testing, I can recommend the procedure of #16378:

• Inside the gcoap example, remove all gnrc USEMODULE lines, and add the ones listed there in green.
• Run on native. Before this PR, this produces build errors; after, it builds.

I don't know an actual code path to trigger the new function, though: I would have expected the breakpoint on the function to be hit when entering coap get fe80::157b:e0b6:d952:d2ca%ET0 5683 /.well-known/core, but it wasn't, because netif_get_by_name_buffer iterates over netif_list, and that's NULL in my debugger ... which is where I don't know the lwip/netif parts well enough to follow further.

[miri64]

I don't know an actual code path to trigger the new function, though:[…]

I guess ifconfig should suffice, once the function is added to the shell command :-)

[chrysn]

There was an ifconfig in the example, but that already printed "ET0" without triggering the new function. (Maybe the command was lwip specific? Not sure, can't test from mobile...)

[miri64]

Yepp, the new function's functionality was taken from there, but it is at the moment only duplicating the code there instead of calling the function straight-away (which I was asking both to decrease duplication and allow for testing this function :-))

[benpicco]

Well there you go

main(): This is RIOT! (Version: 2021.10-devel-358-g11089-net_lwip_netif_get_name)
Running mqtt paho example. Type help for commands info
> ifconfig
ifconfig
Iface ET0 HWaddr: 7a:37:fc:7d:1a:af Link: up State: up
        Link type: wired
        inet6 addr: fe80:0:0:0:7837:fcff:fe7d:1aaf scope: link

[miri64]

ACK! Ran tests/lwip on both master and this PR. The test still passes and the ifconfig output stays the same.

[miri64]

(only ran on native, but the code looks very portable, so it should pass on other boards too).

[miri64]

🚀 🎉