Re: [PATCH nft] datatype, meta: add new ifname_type for iifname/oifname

[Florian Westphal <fw@strlen.de>]

Pablo Neira Ayuso <pablo@netfilter.org> wrote:
> > Ok, but how do you plan to handle the key length?
> 
> Right, in concatenations we can infer this from the lhs, but in set
> definitions there is not way.

Okay.  So whats the plan there?

> What I would suggest is to recover a patch that Patrick submitted that
> introduces typeof(X) so we can use this from set definitions. We can
> store in the TLV the original subtype X as a string. Thus, when
> listing back to userspace we can use this information to display back
> the typeof(X).

So you mean you'd use something like

nft add set filter ifnames '{typeof(meta iifname); }' ?

That should indeed work since we can derive the size
from the meta iifname (or whatever other field),

> We have to potentially support every meta and packet selector,
> including crazy ones as 48 bits fields, and last time we discussed
> this, we agreed that adding one type per field size is not the way to
> go.

Ok, yes, I see your point.

> Let me know your opinion on this, thanks!

I think typeof would be good; we could indeed derive the key size with
this without the need for a new type.