Re: [PATCH v5 2/2] netfilter: nft_meta: support for time matching

[Florian Westphal <fw@strlen.de>]

Jones Desougi <jones.desougi+netfilter@gmail.com> wrote:
> On Sun, Aug 18, 2019 at 8:22 PM Ander Juaristi <a@juaristi.eus> wrote:
> >
> > On 17/8/19 15:43, Jones Desougi wrote:
> > >> diff --git a/include/uapi/linux/netfilter/nf_tables.h b/include/uapi/linux/netfilter/nf_tables.h
> > >> index 82abaa183fc3..b83b62eb4b01 100644
> > >> --- a/include/uapi/linux/netfilter/nf_tables.h
> > >> +++ b/include/uapi/linux/netfilter/nf_tables.h
> > >> @@ -799,6 +799,9 @@ enum nft_exthdr_attributes {
> > >>   * @NFT_META_OIFKIND: packet output interface kind name (dev->rtnl_link_ops->kind)
> > >>   * @NFT_META_BRI_IIFPVID: packet input bridge port pvid
> > >>   * @NFT_META_BRI_IIFVPROTO: packet input bridge vlan proto
> > >> + * @NFT_META_TIME_NS: time since epoch (in nanoseconds)
> > >> + * @NFT_META_TIME_DAY: day of week (from 0 = Sunday to 6 = Saturday)
> > >
> > > This would be clearer as NFT_META_TIME_WEEKDAY. Just day can mean a
> > > lot of things.
> > > Matches nicely with the added nft_meta_weekday function too.
> >
> > I agree with you here. Seems to me WEEKDAY is clearer.
> >
> > >
> > >> + * @NFT_META_TIME_HOUR: hour of day (in seconds)
> > >
> > > This isn't really an hour, so why call it that (confuses unit at least)?
> > > Something like NFT_META_TIME_TIMEOFDAY? Alternatively TIMEINDAY.
> > > Presumably the added nft_meta_hour function also derives its name from
> > > this, but otherwise has nothing to do with hours.
> > >
> >
> > But not so sure on this one. TIMEOFDAY sounds to me equivalent to HOUR,
> > though less explicit (more ambiguous).
> 
> HOUR is a unit, much like NS, but its use is quite different with no
> clear hint as to how. Unlike the latter it's also not the unit of the
> value. From that perspective the name comes up empty of meaning. If
> you already know what it means, the name can be put in context, but
> that's not explicit at all.

If the NFT_META_TIME_* names are off, then those for the
frontend are too.

I think
meta time <iso-date>
meta hour <relative to this day>
meta day <weekday>

are fine, and thus so are the uapi enums.

Examples:

meta time < "2019-06-06 17:20:20" drop
meta hour 11:00-17:00 accept
meta day "Sat" drop

What would you suggest as alternatives?