Re: [dpdk-dev] [PATCH v2 1/5] ethdev: update modify field flow action

[Andrew Rybchenko <andrew.rybchenko@oktetlabs.ru>]

On 10/11/21 2:45 AM, Viacheslav Ovsiienko wrote:
> The generic modify field flow action introduced in [1] has
> some issues related to the immediate source operand:
> 
>   - immediate source can be presented either as an unsigned
>     64-bit integer or pointer to data pattern in memory.
>     There was no explicit pointer field defined in the union.
> 
>   - the byte ordering for 64-bit integer was not specified.
>     Many fields have shorter lengths and byte ordering
>     is crucial.
> 
>   - how the bit offset is applied to the immediate source
>     field was not defined and documented.
> 
>   - 64-bit integer size is not enough to provide IPv6
>     addresses.
> 
> In order to cover the issues and exclude any ambiguities
> the following is done:
> 
>   - introduce the explicit pointer field
>     in rte_flow_action_modify_data structure
> 
>   - replace the 64-bit unsigned integer with 16-byte array
> 
>   - update the modify field flow action documentation
> 
> [1] commit 73b68f4c54a0 ("ethdev: introduce generic modify flow action")
> 
> Signed-off-by: Viacheslav Ovsiienko <viacheslavo@nvidia.com>
> ---
>  doc/guides/prog_guide/rte_flow.rst     | 16 ++++++++++++++++
>  doc/guides/rel_notes/release_21_11.rst |  9 +++++++++
>  lib/ethdev/rte_flow.h                  | 17 ++++++++++++++---
>  3 files changed, 39 insertions(+), 3 deletions(-)
> 
> diff --git a/doc/guides/prog_guide/rte_flow.rst b/doc/guides/prog_guide/rte_flow.rst
> index 2b42d5ec8c..1ceecb399f 100644
> --- a/doc/guides/prog_guide/rte_flow.rst
> +++ b/doc/guides/prog_guide/rte_flow.rst
> @@ -2835,6 +2835,22 @@ a packet to any other part of it.
>  ``value`` sets an immediate value to be used as a source or points to a
>  location of the value in memory. It is used instead of ``level`` and ``offset``
>  for ``RTE_FLOW_FIELD_VALUE`` and ``RTE_FLOW_FIELD_POINTER`` respectively.
> +The data in memory should be presented exactly in the same byte order and
> +length as in the relevant flow item, i.e. data for field with type
> +RTE_FLOW_FIELD_MAC_DST should follow the conventions of dst field
> +in rte_flow_item_eth structure, with type RTE_FLOW_FIELD_IPV6_SRC -
> +rte_flow_item_ipv6 conventions, and so on. If the field size is large than

large -> larger

> +16 bytes the pattern can be provided as pointer only.

RTE_FLOW_FIELD_MAC_DST, dst, rte_flow_item_eth, RTE_FLOW_FIELD_IPV6_SRC,
rte_flow_item_ipv6 should be ``x``.

> +
> +The bitfield extracted from the memory being applied as second operation
> +parameter is defined by action width and by the destination field offset.
> +Application should provide the data in immediate value memory (either as
> +buffer or by pointer) exactly as item field without any applied explicit offset,
> +and destination packet field (with specified width and bit offset) will be
> +replaced by immediate source bits from the same bit offset. For example,
> +to replace the third byte of MAC address with value 0x85, application should
> +specify destination width as 8, destination width as 16, and provide immediate

destination width twice above

> +value as sequence of bytes {xxx, xxx, 0x85, xxx, xxx, xxx}.
>  
>  .. _table_rte_flow_action_modify_field:

pvalue should be added in the "destination/source field
definition".

dst and src members documentation should be improved to
highlight the difference. Destination cannot be "immediate" and
"pointer". In fact, "pointer" is a kind of "immediate". May be
it is better to use "constant value" instead of "immediate".

>  
> diff --git a/doc/guides/rel_notes/release_21_11.rst b/doc/guides/rel_notes/release_21_11.rst
> index dfc2cbdeed..41a087d7c1 100644
> --- a/doc/guides/rel_notes/release_21_11.rst
> +++ b/doc/guides/rel_notes/release_21_11.rst
> @@ -187,6 +187,13 @@ API Changes
>    the crypto/security operation. This field will be used to communicate
>    events such as soft expiry with IPsec in lookaside mode.
>  
> +* ethdev: ``rte_flow_action_modify_data`` structure udpdated, immediate data

udpdated -> updated

> +  array is extended, data pointer field is explicitly added to union, the
> +  action behavior is defined in more strict fashion and documentation updated.
> +  The immediate value behavior has been changed, the entire immediate field
> +  should be provided, and offset for immediate source bitfield is assigned
> +  from destination one.
> +
>  
>  ABI Changes
>  -----------
> @@ -222,6 +229,8 @@ ABI Changes
>    ``rte_security_ipsec_xform`` to allow applications to configure SA soft
>    and hard expiry limits. Limits can be either in number of packets or bytes.
>  
> +* ethdev: ``rte_flow_action_modify_data`` structure udpdated.

udpdated -> updated
I'm not sure that it makes sense to duplicate ABI changes if
API is changed.

> +
>  
>  Known Issues
>  ------------
> diff --git a/lib/ethdev/rte_flow.h b/lib/ethdev/rte_flow.h
> index 7b1ed7f110..953924d42b 100644
> --- a/lib/ethdev/rte_flow.h
> +++ b/lib/ethdev/rte_flow.h
> @@ -3204,6 +3204,9 @@ enum rte_flow_field_id {
>  };
>  
>  /**
> + * @warning
> + * @b EXPERIMENTAL: this structure may change without prior notice
> + *

Isn't a separate fix to add missing experimental header?

>   * Field description for MODIFY_FIELD action.
>   */

"Another packet field" in the next paragraph I read as
a field of another packet which sounds confusing.
I guess it is "Another field of the packet" in fact.
I think it would be nice to clarify as well.

>  struct rte_flow_action_modify_data {
> @@ -3217,10 +3220,18 @@ struct rte_flow_action_modify_data {
>  			uint32_t offset;
>  		};
>  		/**
> -		 * Immediate value for RTE_FLOW_FIELD_VALUE or
> -		 * memory address for RTE_FLOW_FIELD_POINTER.
> +		 * Immediate value for RTE_FLOW_FIELD_VALUE, presented in the
> +		 * same byte order and length as in relevant rte_flow_item_xxx.
> +		 * The immediate source bitfield offset is inherited from
> +		 * the destination's one.
>  		 */
> -		uint64_t value;
> +		uint8_t value[16];
> +		/*

It should be a Doxygen style comment.

> +		 * Memory address for RTE_FLOW_FIELD_POINTER, memory layout
> +		 * should be the same as for relevant field in the
> +		 * rte_flow_item_xxx structure.
> +		 */
> +		void *pvalue;
>  	};
>  };
>  
>