make sure we process PhysicalAddress on Linux

[wfurt]

This is regression to 3.1 caused by dotnet/corefx#41490. Somehow the lack of MAC address got unnoticed as GetPhysicalAddress() simple returns empty address instead of failing.

I modified tests to ensure valid length at least for Ethernet type.
Provided repro now shows correct output:

Selected interface:enp0s5
MAC:001C42E4302E
False
Bytes:6
Hash code:-465423824

fixes #42870

[ghost]

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[geoffkizer]

This is regression to 3.1 caused by #41490

Looks like wrong issue?

[wfurt]

updated. correct number wrong repo - this was done back in corefx before the consolidation.

[geoffkizer]

Can you help me understand what in that change broke this?

[wfurt]

In the past, we would walk the interface list and then for each address type we would invoke appropriate managed callback which would be building the resulting structure. That was inefficient as well as we could not handle certain cases. So with the change we put everything to single array passed from native side and we processes it in two linear passes on managed side.
The issue is that we never processed returned AddressBytes (effectively ignoring) them) and that created PhysicalAddress with no content. It got missed since we did not have test to validate that besides existence of the object. The fix is to create PhysicalAddress from returned data.

I hope this makes some sense @geoffkizer. Updated test would be sufficient to catch this e.g. test for some specific data.

[danmoseley]

Thanks for quick fix @wfurt. Let's get a 5.0 PR up with the template?

Are there any other missing test cases you see around this API?

[wfurt]

/backport release/5.0

[wfurt]

/backport to release/5.0

[github-actions]

Started backporting to release/5.0: https://github.com/dotnet/runtime/actions/runs/279989116