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

[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.

> > 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.

> > depends on PMD implementation. An old rule must be destroyed first.
> > The index cannot be bigger than the size of the table.
> >
> > 2. Allow a user to specify the hash calculation function used in template
> > tables. The hash calculation type is responsible for the calculation of
> > the flow rule index a packet would hit upon arrival at the table.
> >
> > Control over this is useful for applications with custom RSS algorithms,
> > for example. An application can select various packet fields to serve as
> > a hash calculation source and jump to the appropriate flow rule location.
> > The RSS hash result will be used as the index in the table. For the linear
> > hash function, the mapping is one-to-one and the hash result is the index.
> > For other hash functions, the index is the hash result module table size.
> > The RSS hash result can be retrieved via modify_field API: HASH_RESULT.
> >
> > Signed-off-by: Alexander Kozyrev <akozyrev at nvidia.com>
> > ---
> >  doc/guides/prog_guide/rte_flow.rst | 20 +++++++
> >  lib/ethdev/rte_flow.c              | 24 ++++++++
> >  lib/ethdev/rte_flow.h              | 96 ++++++++++++++++++++++++++++++
> >  lib/ethdev/rte_flow_driver.h       | 11 ++++
> >  lib/ethdev/version.map             |  3 +
> >  5 files changed, 154 insertions(+)
> 
> Is there a PMD implementation available on the mailing list?
> This is required to accept a new API.

This is RFC. PMD implementation will follow in a v1 patches shortly.