RE: [PATCH v4] ethdev: add send to kernel action

[Ori Kam <orika@nvidia.com>]

Hi Andrew

> -----Original Message-----
> From: Andrew Rybchenko <andrew.rybchenko@oktetlabs.ru>
> Sent: Monday, 3 October 2022 10:54
> On 9/29/22 17:54, 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>
> > Acked-by: Ori Kam <orika@nvidia.com>
> > ---
> > v4:
> > - improve description comment above
> RTE_FLOW_ACTION_TYPE_SEND_TO_KERNEL
> >
> > v3:
> > http://patches.dpdk.org/project/dpdk/patch/20220919155013.61473-1-
> michaelsav@nvidia.com/
> >
> > v2:
> > http://patches.dpdk.org/project/dpdk/patch/20220914093219.11728-1-
> 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                       | 12 ++++++++++++
> >   4 files changed, 24 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..2c15279a3b 100644
> > --- a/lib/ethdev/rte_flow.h
> > +++ b/lib/ethdev/rte_flow.h
> > @@ -2879,6 +2879,18 @@ 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
> > +	 * the same device as the DPDK port on which this action is
> > +	 * configured. This action is mostly suits bifurcated driver
> > +	 * model.
> > +	 * This is an ingress non-transfer action only.
> 
> May be we should not limit the definition to ingress only?
> It could be useful on egress as a way to reroute packet
> back to kernel.
> 

Interesting, but there are no Kernel queues on egress that can receive packets (by definition of egress)
do you mean that this will also do loopback from the egress back to the ingress of the same port and then
send to kernel?
if so, I think we need a new action "loop_back" 
 
> 
> > +	 *
> > +	 * No associated configuration structure.
> > +	 */
> > +	RTE_FLOW_ACTION_TYPE_SEND_TO_KERNEL,
> >   };
> >
> >   /**