NeighSet comment and implementation differ

[robertcankney]

Hi - NeighSet says in that comment that it will create or update an existing ARP entry (the semantics of NLM_F_CREATE not ORed with any other flags). However, the code ORs that with NLM_F_REPLACE.

Per https://docs.kernel.org/userspace-api/netlink/intro.html#other-request-type-specific-flags, that means it will fail if the neighbor does not exist. I can confirm from using this code that this is the case.

Happy to open a PR to either change the doc comment, or change the flags so the behavior matches the doc comment!

[aboch]

Thank you @robertcankney
Please open a PR with the change you find proper. Somebody will review it.