Re: [PATCH v2 nft] parser: tcpopt: fix tcp option parsing with NUM + length field

[Phil Sutter <phil@nwl.cc>]

On Wed, Dec 06, 2023 at 01:04:47PM +0100, Florian Westphal wrote:
> Florian Westphal <fw@strlen.de> wrote:
> > Thomas Haller <thaller@redhat.com> wrote:
> > > On Wed, 2023-12-06 at 12:38 +0100, Florian Westphal wrote:
> > > > Thomas Haller <thaller@redhat.com> wrote:
> > > > > Hi Florian,
> > > > > 
> > > > > On Tue, 2023-12-05 at 12:56 +0100, Florian Westphal wrote:
> > > > > >  .../packetpath/dumps/tcp_options.nft          | 14 +++++++
> > > > > 
> > > > > is there a reason not to also generate a .json-nft file?
> > > > 
> > > > Yes, I am not adding more one-line monsters.
> > > > 
> > > > I'll add one once there is a solution in place that has human
> > > > readable
> > > > json dumps that don't fail validation because of identical but
> > > > differently formatted output.
> > > > 
> > > 
> > > What about the "[PATCH nft 0/2] pretty print .json-nft files" patches?
> > 
> > I'm fine with that. Phil? Pablo? This is re:
> > 
> > https://patchwork.ozlabs.org/project/netfilter-devel/patch/20231124124759.3269219-3-thaller@redhat.com/

What I don't like is that we'll still get these huge patches/mails if
the dumps are converted. Those that remain are still hard to handle in
case of errors.

> What about making it so we NEVER compare json-nft at all?
> 
> Instead, feed the json-nft file to nft, then do a normal list-ruleset,
> then compare that vs. normal .nft file.
> 
> This avoids any and all formatting issues and also avoids breakage when
> the json-nft file is formatted differently.

We may hide problems because nft might inadvertently sanitize the input.
Also, conversion from standard syntax to JSON may be symmetrically
broken, so standard->JSON->standard won't detect the problem.

> Eg. postprocessing via json_pp won't match what this patch above
> expects.

Python natively supports JSON. Converting stuff into comparable strings
(which also look pretty when printed) is a simple matter of:

| import json
| 
| json.dumps(json.loads(<dump as string>), \
| 	   sort_keys = True, indent = 4, \
| 	   separators = (',', ': '))

We rely upon Python for the testsuite already, so I don't see why
there's all the fuss. JSON dump create, load and compare have not been a
problem in the 5 years tests/py does it.

Cheers, Phil