Re: [PATCH 1/3] security: introduce out of place support for inline ingress

[Jerin Jacob <jerinjacobk@gmail.com>]

> > > > > +      */
> > > > > +     uint32_t ingress_oop : 1;
> > > > > +
> > > > >       /** Reserved bit fields for future extension
> > > > >        *
> > > > >        * User should ensure reserved_opts is cleared as it may change in
> > > > > @@ -282,7 +293,7 @@ struct rte_security_ipsec_sa_options {
> > > > >        *
> > > > >        * Note: Reduce number of bits in reserved_opts for every new option.
> > > > >        */
> > > > > -     uint32_t reserved_opts : 17;
> > > > > +     uint32_t reserved_opts : 16;
> > > > >  };
> > > >
> > > > NAK
> > > > Let me repeat the reserved bit rant. YAGNI
> > > >
> > > > Reserved space is not usable without ABI breakage unless the existing
> > > > code enforces that reserved space has to be zero.
> > > >
> > > > Just saying "User should ensure reserved_opts is cleared" is not enough.
> > >
> > > Yes. I think, we need to enforce to have _init functions for the
> > > structures which is using reserved filed.
> > >
> > > On the same note on YAGNI, I am wondering why NOT introduce
> > > RTE_NEXT_ABI marco kind of scheme to compile out ABI breaking changes.
> > > By keeping RTE_NEXT_ABI disable by default, enable explicitly if user
> > > wants it to avoid waiting for one year any ABI breaking changes.
> > > There are a lot of "fixed appliance" customers (not OS distribution
> > > driven customer) they are willing to recompile DPDK for new feature.
> > > What we are loosing with this scheme?
> >
> > RTE_NEXT_ABI is described in the ABI policy.
> > We are not doing it currently, but I think we could
> > when it is not too much complicate in the code.
> >
> > The only problems I see are:
> > - more #ifdef clutter
> > - 2 binary versions to test
> > - CI and checks must handle RTE_NEXT_ABI version
>
> I think, we have two buckets of ABI breakages via RTE_NEXT_ABI
>
> 1) Changes that introduces compilation failures like adding new
> argument to API or change API name etc
> 2) Structure size change which won't affect the compilation but breaks
> the ABI for shared library usage.
>
> I think, (1) is very distributive, and I don't see recently such
> changes. I think, we should avoid (1) for non XX.11 releases.(or two
> or three-year cycles if we decide that path)
>
> The (2) comes are very common due to the fact HW features are
> evolving. I think, to address the (2), we have two options
> a) Have reserved fields and have _init() function to initialize the structures
> b) Follow YAGNI style and introduce RTE_NEXT_ABI for structure size change.
>
> The above concerns[1] can greatly reduce with option b OR option a.
>
> [1]
>  1) more #ifdef clutter
> For option (a) this is not needed or option (b) the clutter will be
> limited, it will be around structure which add the new filed and
> around the FULL block where new functions are added (not inside the
> functions)
>
> 2) 2 binary versions to test
> For option (a) this is not needed, for option (b) it is limited as for
> new features only one needs to test another binary (rather than NOT
> adding a new feature).
>
>  3) CI and checks must handle RTE_NEXT_ABI version
>
> I think, it is cheap to add this, at least for compilation test.
>
> IMO, We need to change the API break release to 3 year kind of time
> frame to have very good end user experience
> and allow ABI related change to get in every release and force
> _rebuild_ shared objects in major LTS release.
>
> I think, in this major LTS version(23.11) if we can decide (a) vs (b)
> then we can align the code accordingly . e.s.p for (a) we need to add
> _init() functions.
>
> Thoughts?

Not much input from mailing list. Can we discuss this next TB meeting?
Especially how to align with next LTS release on
-YAGNI vs reserved fileds with init()
-What it takes to Extend the API breaking release more than a year as
first step.