Re: [RFC] ethdev: add template table insertion and matching types

[Thomas Monjalon <thomas@monjalon.net>]

21/01/2023 00:06, Alexander Kozyrev:
> > 14/12/2022 03:21, Alexander Kozyrev:
> > > Bring more flexibility and control over both flow rule insertion
> > > and packet matching mechanisms. Introduce 2 new flow table types:
> > >
> > > 1. Allow a user to specify the insertion type used in template tables.
> > > The insertion type is responsible for choosing the appropriate key
> > > value used to map inserted flow rules into a template table.
> > >
> > > Flow rules can be inserted by calculating the hash value for
> > > the pattern or inserted by index via the new create_by_index() API.
> > > The idea of the index-based insertion is to avoid additional matches
> > > and simply execute predefined actions after jumping to the index.
> > 
> > I don't understand the idea.
> > Why is it avoiding additional matches?
> 
> If you jump directly to an index in a table, you don't need to match anything.
> For the regular pattern-based table you must calculate the hash and match on it.

I don't get it. I think it would be simpler with an example.

> > > The insertion to an already existing index is undefined and
> > 
> > Why is it undefined?
> 
> The behavior is up to a PMD to decide. It is free to replace the rule or throw an error.

An undefined behavior of an API makes applications not portable.
Why not deciding of a behavior? You are not sure what is best?