[RFC] ethdev: introduce entropy calculation

[Ferruh Yigit]

On 12/10/2023 8:30 AM, Ori Kam wrote:
> When offloading rules with the encap action, the HW may calculate entropy based on the encap protocol.
> Each HW can implement a different algorithm.
> 

Hi Ori,

Can you please provide more details what this 'entropy' is used for,
what is the usecase?


> When the application receives packets that should have been
> encaped by the HW, but didn't reach this stage yet (for example TCP SYN packets),
> then when encap is done in SW, application must apply
> the same entropy calculation algorithm.
>> Using the new API application can request the PMD to calculate the
> value as if the packet passed in the HW.
> 

So is this new API a datapath API? Is the intention that application
call this API per packet that is missing 'entropy' information?

> Signed-off-by: Ori Kam <orika at nvidia.com>
> ---
>  lib/ethdev/rte_flow.h | 49 +++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 49 insertions(+)
> 
> diff --git a/lib/ethdev/rte_flow.h b/lib/ethdev/rte_flow.h
> index affdc8121b..3989b089dd 100644
> --- a/lib/ethdev/rte_flow.h
> +++ b/lib/ethdev/rte_flow.h
> @@ -6753,6 +6753,55 @@ rte_flow_calc_table_hash(uint16_t port_id, const struct rte_flow_template_table
>  			 const struct rte_flow_item pattern[], uint8_t pattern_template_index,
>  			 uint32_t *hash, struct rte_flow_error *error);
>  
> +/**
> + * @warning
> + * @b EXPERIMENTAL: this API may change without prior notice.
> + *
> + * Destination field type for the entropy calculation.
> + *
> + * @see function rte_flow_calc_encap_entropy
> + */
> +enum rte_flow_entropy_dest {
> +	/* Calculate entropy placed in UDP source port field. */
> +	RTE_FLOW_ENTROPY_DEST_UDP_SRC_PORT,
> +	/* Calculate entropy placed in NVGRE flow ID field. */
> +	RTE_FLOW_ENTROPY_DEST_NVGRE_FLOW_ID,
> +};
> +
> +/**
> + * @warning
> + * @b EXPERIMENTAL: this API may change without prior notice.
> + *
> + * Calculate the entropy generated by the HW for a given pattern,
> + * when encapsulation flow action is executed.
> + *
> + * @param[in] port_id
> + *   Port identifier of Ethernet device.
> + * @param[in] pattern
> + *   The values to be used in the entropy calculation.
> + * @param[in] dest_field
> + *   Type of destination field for entropy calculation.
> + * @param[out] entropy
> + *   Used to return the calculated entropy. It will be written in network order,
> + *   so entropy[0] is the MSB.
> + *   The number of bytes is based on the destination field type.
>


Is the size same as field size in the 'dest_field'?
Like for 'RTE_FLOW_ENTROPY_DEST_UDP_SRC_PORT' is it two bytes?


> + * @param[out] error
> + *   Perform verbose error reporting if not NULL.
> + *   PMDs initialize this structure in case of error only.
> + *
> + * @return
> + *   - (0) if success.
> + *   - (-ENODEV) if *port_id* invalid.
> + *   - (-ENOTSUP) if underlying device does not support this functionality.
> + *   - (-EINVAL) if *pattern* doesn't hold enough information to calculate the entropy
> + *               or the dest is not supported.
> + */
> +__rte_experimental
> +int
> +rte_flow_calc_encap_entropy(uint16_t port_id, const struct rte_flow_item pattern[],
> +			    enum rte_flow_entropy_dest dest_field, uint8_t *entropy,
> +			    struct rte_flow_error *error);
> +
>  #ifdef __cplusplus
>  }
>  #endif