Re: [PATCH libnftnl 0/3] add description infrastructure

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

On Wed, Apr 06, 2022 at 01:06:13PM +0200, Phil Sutter wrote:
> Hi Pablo,
> 
> On Thu, Jan 20, 2022 at 01:03:59AM +0100, Pablo Neira Ayuso wrote:
> > This is my proposal to address the snprintf data printing depending on
> > the arch. The idea is to add description objects that can be used to
> > build the userdata area as well as to parse the userdata to create the
> > description object.
> > 
> > This is revisiting 6e48df5329ea ("src: add "typeof" build/parse/print
> > support") in nftables which adds build and parse userdata callbacks to
> > expression in libnftables. My proposal is to move this to libnftnl.
> 
> Looking at your PoC again, I assume it was meant for use by applications
> to create and populate an nftnl_set_desc object and serialize it into
> nftnl_set's userdata using nftnl_set_desc_build_udata(). Since the
> information is needed within libnftnl though, the whole API does not
> make sense anymore and nftnl_set_desc must be serialized by libnftnl
> itself. This in turn means one may just integrate the data structure
> into nftnl_set's 'desc' field directly and extend nftnl_set_set_data()
> to allow populating the new fields, plus
> nftnl_set_desc_add_{expr,datatype}() I guess.
> 
> Am I on the right track there?
> 
> Maybe it's quicker for me to add the missing bits to my stuff instead of
> adjusting it to your series after making it work for the intended
> purpose. Especially since I'm not quite sure what goal we're trying to
> achieve.

Goal is to consolidate code. Move the existing code in nftables to
libnftnl so there is a desc object that can be use to build the
userdata and to all assist the libnftnl print functions.

This will take a bit of work.