[RFC] ethdev: sharing indirect actions between ports

[Thomas Monjalon]

28/12/2022 17:54, Viacheslav Ovsiienko:
> The RTE Flow API implements the concept of shared objects,
> known as indirect actions (RTE_FLOW_ACTION_TYPE_INDIRECT).
> An application can create the indirect action of desired
> type and configuration with rte_flow_action_handle_create
> call and then specify the obtained action handle in multiple
> flows.
> 
> The initial concept supposes the action handle has strict
> attachment to the port it was created on and to be used
> exclusively in the flows being installed on the port.
> 
> Nowadays the multipath network topologies are quite common,
> packets belonging to the same connection might arrive and
> be sent over multiple ports, and there is the raising demand
> to handle these "spread" connections. To fulfil this demand
> it is proposed to extend indirect action sharing across the
> multiple ports. This kind of sharing would be extremely useful
> for the meters and counters, allowing to manage the single
> connection over the multiple ports.
> 
> This cross-port object sharing is hard to implement in
> generic way merely with software on the upper layers, but
> can be provided by the driver over the single hardware
> instance, where  multiple ports reside on the same physical
> NIC and share the same hardware context.
> 
> To allow this action sharing application should specify
> the "host port" during flow configuring to claim the intention
> to share the indirect actions. All indirect actions reside within
> "host port" context and can be shared in flows being installed

I don't like the word "host" because it may refer to the host CPU.
Also if I understand well, the application must choose one port
between all ports of the NIC and keep using the same.
I guess we don't want to create a NIC id.
So I would suggest to rename to nic_ref_port or something like that.

> on the host port and on all the ports referencing this one.

Not "all the ports" but only on sibling ports (ports of the same NIC).

> If sharing between host and port being configured is not supported
> the configuration should be rejected with error. There might be
> multiple independent (mutual exclusive) sharing domains with
> dedicated host and referencing ports.
> 
> To manage the shared indirect action any port from sharing domain
> can be specified. To share or not the created action is up to
> application, no API change is needed.
[...]
> +	/**
> +	 * Port to base shared objects on.
> +	 */
> +	uint16_t host_port_id;

Is it a DPDK ethdev port ID?

You should add this feature to the release notes and in rte_flow guide.

PS: please Cc ethdev maintainers.