RE: [PATCH v3] ethdev: add send to kernel action

[Michael Savisko <michaelsav@nvidia.com>]

> -----Original Message-----
> From: Andrew Rybchenko <andrew.rybchenko@oktetlabs.ru>
> Sent: Monday, 26 September 2022 16:07
> 
> On 9/19/22 18:50, Michael Savisko wrote:
> > In some cases application may receive a packet that should have been
> > received by the kernel. In this case application uses KNI or other
> > means to transfer the packet to the kernel.
> >
> > With bifurcated driver we can have a rule to route packets matching a
> > pattern (example: IPv4 packets) to the DPDK application and the rest
> > of the traffic will be received by the kernel.
> > But if we want to receive most of the traffic in DPDK except specific
> > pattern (example: ICMP packets) that should be processed by the
> > kernel, then it's easier to re-route these packets with a single rule.
> >
> > This commit introduces new rte_flow action which allows application to
> > re-route packets directly to the kernel without software involvement.
> >
> > Add new testpmd rte_flow action 'send_to_kernel'. The application may
> > use this action to route the packet to the kernel while still in the
> > HW.
> >
> > Example with testpmd command:
> >
> > flow create 0 ingress priority 0 group 1 pattern eth type spec 0x0800
> > type mask 0xffff / end actions send_to_kernel / end
> >
> > Signed-off-by: Michael Savisko <michaelsav@nvidia.com>
> > ---
> >   app/test-pmd/cmdline_flow.c                 |  9 +++++++++
> >   doc/guides/testpmd_app_ug/testpmd_funcs.rst |  2 ++
> >   lib/ethdev/rte_flow.c                       |  1 +
> >   lib/ethdev/rte_flow.h                       | 10 ++++++++++
> >   4 files changed, 22 insertions(+)
> >
> > diff --git a/app/test-pmd/cmdline_flow.c b/app/test-pmd/cmdline_flow.c
> > index 7f50028eb7..042f6b34a6 100644
> > --- a/app/test-pmd/cmdline_flow.c
> > +++ b/app/test-pmd/cmdline_flow.c
> > @@ -612,6 +612,7 @@ enum index {
> >   	ACTION_PORT_REPRESENTOR_PORT_ID,
> >   	ACTION_REPRESENTED_PORT,
> >   	ACTION_REPRESENTED_PORT_ETHDEV_PORT_ID,
> > +	ACTION_SEND_TO_KERNEL,
> >   };
> >
> >   /** Maximum size for pattern in struct rte_flow_item_raw. */ @@
> > -1872,6 +1873,7 @@ static const enum index next_action[] = {
> >   	ACTION_CONNTRACK_UPDATE,
> >   	ACTION_PORT_REPRESENTOR,
> >   	ACTION_REPRESENTED_PORT,
> > +	ACTION_SEND_TO_KERNEL,
> >   	ZERO,
> >   };
> >
> > @@ -6341,6 +6343,13 @@ static const struct token token_list[] = {
> >   		.help = "submit a list of associated actions for red",
> >   		.next = NEXT(next_action),
> >   	},
> > +	[ACTION_SEND_TO_KERNEL] = {
> > +		.name = "send_to_kernel",
> > +		.help = "send packets to kernel",
> > +		.priv = PRIV_ACTION(SEND_TO_KERNEL, 0),
> > +		.next = NEXT(NEXT_ENTRY(ACTION_NEXT)),
> > +		.call = parse_vc,
> > +	},
> >
> >   	/* Top-level command. */
> >   	[ADD] = {
> > diff --git a/doc/guides/testpmd_app_ug/testpmd_funcs.rst
> > b/doc/guides/testpmd_app_ug/testpmd_funcs.rst
> > index 330e34427d..c259c8239a 100644
> > --- a/doc/guides/testpmd_app_ug/testpmd_funcs.rst
> > +++ b/doc/guides/testpmd_app_ug/testpmd_funcs.rst
> > @@ -4189,6 +4189,8 @@ This section lists supported actions and their
> attributes, if any.
> >
> >     - ``ethdev_port_id {unsigned}``: ethdev port ID
> >
> > +- ``send_to_kernel``: send packets to kernel.
> > +
> >   Destroying flow rules
> >   ~~~~~~~~~~~~~~~~~~~~~
> >
> > diff --git a/lib/ethdev/rte_flow.c b/lib/ethdev/rte_flow.c index
> > 501be9d602..627c671ce4 100644
> > --- a/lib/ethdev/rte_flow.c
> > +++ b/lib/ethdev/rte_flow.c
> > @@ -259,6 +259,7 @@ static const struct rte_flow_desc_data
> rte_flow_desc_action[] = {
> >   	MK_FLOW_ACTION(CONNTRACK, sizeof(struct
> rte_flow_action_conntrack)),
> >   	MK_FLOW_ACTION(PORT_REPRESENTOR, sizeof(struct
> rte_flow_action_ethdev)),
> >   	MK_FLOW_ACTION(REPRESENTED_PORT, sizeof(struct
> > rte_flow_action_ethdev)),
> > +	MK_FLOW_ACTION(SEND_TO_KERNEL, 0),
> >   };
> >
> >   int
> > diff --git a/lib/ethdev/rte_flow.h b/lib/ethdev/rte_flow.h index
> > a79f1e7ef0..bf076087b3 100644
> > --- a/lib/ethdev/rte_flow.h
> > +++ b/lib/ethdev/rte_flow.h
> > @@ -2879,6 +2879,16 @@ enum rte_flow_action_type {
> >   	 * @see struct rte_flow_action_ethdev
> >   	 */
> >   	RTE_FLOW_ACTION_TYPE_REPRESENTED_PORT,
> > +
> > +	/**
> > +	 * Send packets to the kernel, without going to userspace at all.
> > +	 * The packets will be received by the kernel driver sharing
> 
> May be it is better to mentioned bifurcated driver model and add a reference to
> the documentation.

Yes, I will add mentioning bifurcated driver model.

> 
> > +	 * the same device as the DPDK port.
> 
> Which DPDK port? There is no control structure associated with the action.
> 
> I guess it is the port used to create the flow rule.
> If so, it should be documented that it is non-transfer action and highlighted that
> the port used to create the action.

Yes, its is the port used to create the flow rule. I will add this to the comment.
I will emphasize that it's non-transfer action as well.

I will provide a new version of the patch with better documentation.

Thank you,
Michael Savisko

> 
> > +	 * This is an ingress action only.
> > +	 *
> > +	 * No associated configuration structure.
> > +	 */
> > +	RTE_FLOW_ACTION_TYPE_SEND_TO_KERNEL,
> >   };
> >
> >   /**