Re: [PATCH nftables 0/8] add typeof keyword

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

Hi Florian,

On Sun, Aug 18, 2019 at 04:33:15PM +0200, Arturo Borrero Gonzalez wrote:
> On 8/17/19 10:55 PM, Florian Westphal wrote:
> > Pablo Neira Ayuso <pablo@netfilter.org> wrote:
> >> I know I sent a RFC using typeof(), I wonder if you could just use the
> >> selector instead, it's a bit of a lot of type typeof() . typeof()
> >> probably.
> >>
> >> So this is left as this:
> >>
> >>         type osf name
> >>
> >> in concatenations, like this:
> >>
> >>         nft add set ip filter allowed "{ type ip daddr . tcp dport; }"
> >>
> >> Probably I would ask my sysadmin friends what they think.
> > 
> > Yes, please do, it would be good to get a non-developer perspective.
> > 
> > I'm very used to things like sizeof(), so typeof() felt natural to me.
> > 
> > Might be very un-intuitive for non-developers though, so it would be
> > good to get outside perspective.
> 
> From my point of view, this is a rather advanced operation. As long as it is
> properly documented, I don't see any problem with `typeof()`.
> 
> Also, just `typeof` would work of course. Up to you.

My suggestion is:

        typeof ip saddr . tcp dport . meta mark

but, not to allow the use of the existing datatypes with typeof.

So either the user picks:

        type ipv4_addr . inet_service . mark

or this:

        typeof ip saddr . tcp dport . meta mark

Then, for the notation:

        integer,bits

I would suggest this one can only be used from 'type'.

Goal is basically:

* Avoiding repetitive typeof() that looks a bit like C programming.
* Mixing datatype with inferred datatypes looks a bit sloppy to me
  from syntax consistency point of view.

This approach is flexible enough to cover all use cases this patchset
is dealing with I think.

If you like this approach, I would suggest you just update the
patchset to support this and then push this out, I'll catch up later
on to revisit this before the next release, in case I can propose you
some refinement for your review.

Let me know, thanks.