Re: [PATCH nft] src: allow to map key to nfqueue number

[Florian Westphal <fw@strlen.de>]

Pablo Neira Ayuso <pablo@netfilter.org> wrote:
> > @@ -447,6 +457,9 @@ extern struct expr *relational_expr_alloc(const struct location *loc, enum ops o
> >  extern void relational_expr_pctx_update(struct proto_ctx *ctx,
> >  					const struct expr *expr);
> >  
> > +extern struct expr *typeof_expr_alloc(const struct location *loc,
> > +				      enum expr_typeof_key key);
> 
> I think it should be possible to follow an alternative path to achieve
> this, that is, use integer_expr and attach a new internal datatype,
> ie. queue_type, for this queue number.
> 
> No need for new TYPE_* in enum, that is only required by
> concatenations and this datatype will not ever be used in that case.
> 
> For reference, there is also use of this alias datatypes such as
> xinteger_type which is used to print integers in hexadecimal.
> 
> From userdata path it should be possible to check for this special
> internal queue_datatype then encode the queue number type in the TLV.

I have no idea how to do any of this.  I don't even know what a "queue number
type" is.

How on earth do i flip the data type on postprocessing without any idea
what "2 octets worth of data" is?