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

[Thomas Monjalon <thomas@monjalon.net>]

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?

> The insertion to an already existing index is undefined and

Why is it undefined?

> 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@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.