Re: [dpdk-dev] [PATCH] ethdev: introduce generic copy rte flow action

[Alexander Kozyrev <akozyrev@nvidia.com>]

> From: Jerin Jacob <jerinjacobk@gmail.com> on  Friday, January 15, 2021 9:01
> Subject: Re: [dpdk-dev] [PATCH] ethdev: introduce generic copy rte flow
> action
> 
> On Thu, Jan 14, 2021 at 8:32 PM Ori Kam <orika@nvidia.com> wrote:
> >
> > Hi Jerin,
> >
> > > -----Original Message-----
> > > From: Jerin Jacob <jerinjacobk@gmail.com>
> > > Sent: Thursday, January 14, 2021 4:00 PM
> > > Subject: Re: [dpdk-dev] [PATCH] ethdev: introduce generic copy rte flow
> action
> > >
> > > On Fri, Jan 8, 2021 at 12:02 PM Alexander Kozyrev
> <akozyrev@nvidia.com>
> > > wrote:
> > > >
> > > > Implement a generic copy flow API to allow copying of an arbitrary
> > > > header field (as well as mark, metadata or tag) to another item.
> > > >
> > > > This generic copy mechanism removes the necessity to implement a
> > > > separate RTE Flow action every time we need to modify a new packet
> > > > field in the future. A user-provided value can be used from a
> > > > specified tag/metadata or directly copied from other packet field.
> > > >
> > > > The number of bits to copy as well as the offset to start from can
> > > > be specified to allow a partial copy or copy into an arbitrary
> > > > place in a packet for greater flexibility.
> > > >
> > > > RFC:
> > >
> https://nam11.safelinks.protection.outlook.com/?url=http%3A%2F%2Fpatch
> es.d
> > >
> pdk.org%2Fpatch%2F85384%2F&amp;data=04%7C01%7Corika%40nvidia.com
> %
> > >
> 7C62ab41b9ed5948d056c308d8b894af02%7C43083d15727340c1b7db39efd9cc
> > >
> c17a%7C0%7C0%7C637462296023413253%7CUnknown%7CTWFpbGZsb3d8ey
> J
> > >
> WIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%
> 7C
> > >
> 1000&amp;sdata=ovpEss3%2B7TgZRYFiDkrvuMFW52747Gno5oOIeDLwrBQ%
> 3D
> > > &amp;reserved=0
> > > >
> > > > Signed-off-by: Alexander Kozyrev <akozyrev@nvidia.com>
> > > > ---
> > >
> > > >
> > > > +Action: ``COPY_ITEM``
> > > > +^^^^^^^^^^^^^^^^^^^^^
> > > > +
> > > > +Copy ``width`` bits from ``src`` item to ``dst`` item.
> > > > +
> > > > +An arbitrary header field (as well as mark, metadata or tag values)
> > > > +can be used as both source and destination items as set by ``item``.
> > > > +
> > > > +Inner packet header fields can be accessed using the ``index`` and
> > > > +it is possible to start the copy from the ``offset`` bits in an item.
> > > > +
> > > > +.. _table_rte_flow_action_copy_item:
> > > > +
> > > > +.. table:: COPY_ITEM
> > > > +
> > > > +   +-----------------------------------------+
> > > > +   | Field         | Value                   |
> > > > +   +===============+=========================+
> > > > +   | ``dst``       | destination item        |
> > > > +   | ``src``       | source item             |
> > > > +   | ``width``     | number of bits to copy  |
> > >
> > >
> > >
> > > Overall it is a good improvement.
> > >
> > > I think, if we add transform "op" here then it can be more generic. In
> > > other words, A generic packet transform and copy operation is just one
> > > of the operations.
> > > ie.. making it as rte_flow_action_xform_item and introduce COPY, ADD,
> > > SUB, etc transform along with existing rte_flow_action_copy_item
> > > fields.
> > >
> > > It may useful for expressing P4 packet transforms to rte_flow.
> > >
> > > The current generation of Marvell HW does not have COPY transform so I
> > > am leaving suggestions to vendors with this HW capablity.
> > >
> > >
> >
> > +1
> > Lest have dst, src, width, op members,
> > and change the action name to rte_flow_action_modify_field()
> >
> > also lest add new field name immediate  so the copy can be used as set.
> > (copy of an immediate value is a set)
> >
> > Possible op = copy / add / sub
> 
> +1
Thank you, Jerin, for a great idea. I'm issuing a v4 patch with generic modify_field design. 

> 
> >
> > > > +   +---------------+-------------------------+
> > >
> > >
> > >
> > >
> > > > +
> > > > +.. _table_rte_flow_action_copy_data:
> > > > +
> > > > +.. table:: destination/source item definition
> > > > +
> > > > +   +----------------------------------------------------------+
> > > > +   | Field         | Value                                    |
> > > > +
> +===============+=========================================
> =+
> > > > +   | ``item``      | ID of a packet field/mark/metadata/tag   |
> > > > +   | ``index``     | index of outer/inner header or tag array |
> > > > +   | ``offset``    | number of bits to skip during the copy   |
> > > > +   +---------------+------------------------------------------+
> > > > +