Generic flow string parser

[Cliff Burdick]

Hi Stephen, it would definitely not be worthwhile to repeat everything
that's already tested with testpmd. I was thinking that given that there
already is a "flow_parse" function that does almost everything needed,
something like that could be exposed. If we think of the testpmd flow
string as a sort of "IR" for string flow specification, that would allow
others to implement higher-level transform of a schema like JSON or YAML
into the testpmd language. Due to the complexity of testpmd and how it's
the source of true for testing flows, I think it's too great of an ask to
have testpmd support a new type of parsing. My only suggestion would be to
take what already exists and expose it in a public API that is included in
a DPDK install.

If you look at the "flow_classify" example in DPDK you can already see that
for that application someone had to write another flow text parser for a
format they made up. Instead, that example could be converted over to this
other API as well.

On Fri, Apr 28, 2023 at 11:09 AM Stephen Hemminger <
stephen at networkplumber.org> wrote:

> On Fri, 28 Apr 2023 17:36:51 +0000
> Tom Barbette <tom.barbette at uclouvain.be> wrote:
>
> > Hi all!
> >
> > I totally agree with this.
> >
> > In FastClick we link against a copy of the test-pmd source code to call
> the parser externally. We just have to patch a bit some files (see
> https://github.com/tbarbette/fastclick/blob/main/userlevel/rte_parse.mk,
> and used here :
> https://github.com/tbarbette/fastclick/blob/main/lib/flowruleparser.cc).
> It actually worked fairly well until a structure named "template" appeared,
> which is a registered keyword in C++, and prevent compilation now even
> under extern "C". This can be patched too but did not find the time yet.
> >
> > So a clean solution would be more than nice. It's not only the 12K lines
> of codes, it's also the "testpmd syntax" which is known, and appears in a
> lot of examples here and there.
> >
> > Given the relatively easy (but hacky) integration we have, a clean
> library wouldn't probably be very difficult.
> >
> >
> > Tom
> >
> > Le 27/04/23 à 15:19, Cliff Burdick a écrit :
> > Hi Thomas, testpmd has a 12,000 line parser just for taking in strings
> and converting it to flow rules. This is obviously useful for testing
> flows, but it also is an interface for any type of flow imaginable since
> this is where they're tested.
> >
> > Now imagine you're developing an application that allows the user to
> specify custom flows in a config. Your only option is to make your own flow
> string input (json, etc) and convert that to to the flow spec. This is
> reinventing almost all of what testpmd already does, and it's extremely
> error-prone. I think it would be very useful to have this as an API call
> rather than a user constructing each flow by hand so that all these other
> applications can benefit and not be worries about bugs during conversions.
> >
> >
> >
> > On Thu, Apr 27, 2023, 01:37 Thomas Monjalon <thomas at monjalon.net<mailto:
> thomas at monjalon.net>> wrote:
> > 26/04/2023 07:47, David Marchand:
> > > On Wed, Apr 26, 2023 at 6:47 AM Cliff Burdick <shaklee3 at gmail.com
> <mailto:shaklee3 at gmail.com>> wrote:
> > > >
> > > > Does anyone know if a generic parser for flow strings exists
> anywhere? The one inside of testpmd is ideal, but unfortunately it's
> self-contained and not distributed as part of a normal DPDK install. This
> seems like something that is likely reinvented over and over and it would
> be useful if there was a single API to take in strings and generate flows.
> > >
> > > I heard this same question in the past, but I don't remember the
> answer.
> > > Copying Thomas and Ori who might know.
> >
> > I'm not sure how the testpmd code could help another application.
> > And in general, if your application has a CLI,
> > you need to integrate the flow commands in a broader context.
>
> Exposing the parser for use, would require some renaming of functions,
> documentation
> and a test suite. The testing would be the hardest part.
>
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