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

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

On 10/3/22 12:57, Ori Kam wrote:
> Hi Andrew,
> 
>> -----Original Message-----
>> From: Andrew Rybchenko <andrew.rybchenko@oktetlabs.ru>
>> Sent: Monday, 3 October 2022 12:44
>>
>> On 10/3/22 11:23, Ori Kam wrote:
>>> 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"
>>
>> Yes, I meant intercept packet on egress and send to kernel.
>> But we still need loopback+send_to_kernel. Loopback itself
>> cannot send to kernel. Moreover it should be two rules:
>> loopback on egress plus send-to-kernel on ingress. Does
>> it really worse it? I'm not sure. Yes, it sounds a bit
>> better from arch point of view, but I'm still unsure.
>> I'd allow send-to-kernel on egress. Up to you.
>>
> 
> It looks more correct with loop_back on the egress and send-to-kernel on egress
> I suggest to keep the current design,
> and if we see that we can merge those to commands, we will change it

OK. And the last question: do we need to announce it in release
notes?

Acked-by: Andrew Rybchenko <andrew.rybchenko@oktetlabs.ru>

> 
>>>
>>>>
>>>>> +	 *
>>>>> +	 * No associated configuration structure.
>>>>> +	 */
>>>>> +	RTE_FLOW_ACTION_TYPE_SEND_TO_KERNEL,
>>>>>     };
>>>>>
>>>>>     /**
>>>
>