Re: [nft PATCH 2/2] meta: use reentrant localtime_r()/gmtime_r() functions

[Pablo Neira Ayuso <pablo@netfilter.org>]

On Tue, Aug 22, 2023 at 01:39:20PM +0200, Thomas Haller wrote:
> Hi Pablo,
> 
> One more consideration, that I didn't realize before. Sorry about that.
> 
> localtime() will always call tzset(). And localtime_r() is documented
> that it may not call it.
> 
>   https://linux.die.net/man/3/localtime_r
> 
> I checked implementations, AFAIS, musl will always call do_tzset()
> ([1]). glibc will only ensure that tzset() was called at least once
> ([2]).
> 
> [1] https://git.musl-libc.org/cgit/musl/tree/src/time/__tz.c?id=83b858f83b658bd34eca5d8ad4d145f673ae7e5e#n369
> [2] https://codebrowser.dev/glibc/glibc/time/tzset.c.html#577
> 
> It's not clear to me, whether it would be more correct/desirable to
> always call tzset() before localtime_r(). I think it would only matter,
> if the timezone were to change (e.g. update /etc/localtime).
>
> nftables calls localtime_r() from print/parse functions. Presumably, we
> will print/parse several timestamps during a larger operation, it would
> be odd to change/reload the timezone in between or to meaningfully
> support that.

You mean, timezone change while there is a 'list ruleset' command
might be an issue is what you mean?

> I think it is all good, nothing to change. Just to be aware of.