Improve ethernet ping device handling

[ES-Alexander]

Some robustness improvements that will hopefully fix #2569.

I've tested this on my machine, and it doesn't seem to have any regressions, and the dropped network device handling works 👍 Not sure whether it fixes the duplication issue because I haven't run into it in the first place, so I've asked Aaron to see if the issue is fixed on his system.

Given the PR doesn't seem to hurt things we could potentially merge as-is, but it may also be worth waiting to see whether the issue is actually resolved (by testing from someone who can replicate it).