Re: [PATCH net v2] Revert "ipv6: preserve insertion order for same-scope addresses"

On 6/3/26 08:53, Íñigo Huguet wrote:
> Stating that the order is "random" implies that someone will change
> the default insertion order in the future, as the documentation says
> that it's not UAPI. So they'll cause the UAPI breakage that we are
> trying to avoid now. Moreover, if we consider the default order
> "random" and state that userspace programs must not rely on it, why
> can't we change it now?

Because the UAPI is only indirectly important, as it's "something that
used to work doesn't anymore" is what matters; you in fact can break the
UAPI all you want, as long as everything continues to work. Or to quote
Linus from:

https://www.kernel.org/doc/html/latest/process/handling-regressions.html#on-what-qualifies-as-userspace-interface-abi-api-documented-interfaces-etc

"I just wanted to point out that the argument about whether it's an ABI
change or not is irrelevant. If it turns out that some program - not a
test script, but something with relevance to conscious user expectations
~ depended on the old broken behavior, then it needs to be done some
other way.""

Yes, he talks about ABIs here, but it's the same for APIs.

Ciao, Thorsten