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

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

On 10/3/22 14:06, Ori Kam wrote:
> Hi Andrew,
> 
>> -----Original Message-----
>> From: Andrew Rybchenko <andrew.rybchenko@oktetlabs.ru>
>> Sent: Monday, 3 October 2022 13:47
>>
>> 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?
>>
> 
> +1

Michael,

please, send v5 with release notes update. Don't forget to
rebase in on current next-net/main, please.

Thanks,
Andrew.

> 
>> Acked-by: Andrew Rybchenko <andrew.rybchenko@oktetlabs.ru>
>>
>>>
>>>>>
>>>>>>
>>>>>>> +	 *
>>>>>>> +	 * No associated configuration structure.
>>>>>>> +	 */
>>>>>>> +	RTE_FLOW_ACTION_TYPE_SEND_TO_KERNEL,
>>>>>>>      };
>>>>>>>
>>>>>>>      /**
>>>>>
>>>
>