From: "Morten Brørup" <mb@smartsharesystems.com>
To: "Dumitrescu, Cristian" <cristian.dumitrescu@intel.com>,
"Ori Kam" <orika@nvidia.com>,
"Jerin Jacob" <jerinjacobk@gmail.com>
Cc: "Zhang, Qi Z" <qi.z.zhang@intel.com>,
"NBU-Contact-Thomas Monjalon (EXTERNAL)" <thomas@monjalon.net>,
<david.marchand@redhat.com>,
"Richardson, Bruce" <bruce.richardson@intel.com>,
<jerinj@marvell.com>, <ferruh.yigit@amd.com>,
<techboard@dpdk.org>, "Mcnamara, John" <john.mcnamara@intel.com>,
"Zhang, Helin" <helin.zhang@intel.com>, <dev@dpdk.org>
Subject: RE: [PATCH] ethdev: introduce generic flow item and action
Date: Wed, 2 Aug 2023 19:56:03 +0200 [thread overview]
Message-ID: <98CBD80474FA8B44BF855DF32C47DC35D87AC2@smartserver.smartshare.dk> (raw)
In-Reply-To: <PH7PR11MB7450AA53C689604CCA00E4BEEB0BA@PH7PR11MB7450.namprd11.prod.outlook.com>
> From: Dumitrescu, Cristian [mailto:cristian.dumitrescu@intel.com]
> Sent: Wednesday, 2 August 2023 19.23
>
> > From: Ori Kam <orika@nvidia.com>
> > Sent: Wednesday, August 2, 2023 5:06 PM
> >
> > Hi Qi,
> >
> > In addition to my previous email,
> > I fully support you’re your idea to update the rte_flow API
> > so it will be easier for P4 integration, I just think the suggested
> approach is not
> > the correct one at least not as appears in the RFC.
> >
> > I think it will be good if we can discuss some uses cases you are
> having
> > with the API/implementation and see what is the best way to solve
> them.
> > The main idea is not to re-invent the wheel, but to solve issues.
>
> Yes, fully agree, it would be great meet and talk through this, as we
> did it in the
> past for other issues. What days & time next week would be good for
> people?
My calendar is pretty much all open these days, so anytime work hours in the Central European time zone works for me.
>
> Meanwhile, some answers below.
>
> >
> > To summarize, as I see it there are several issues:
> > 1. no protocol is defined so different PMD can't translate it.
>
> The format of the flow items is defined by the P4 program, so all the HW
> devices
> (from the same or from different vendors) that are able to successfully
> load the
> given P4 program will have the same understanding of the flow items.
If the P4 flow items/actions are standardized by some P4 organization or similar, they can be enumerated and defined as DPDK flow items/actions. At least the ones that are standardized.
And if you (for flexibility or other reasons) need to bypass the RTE_FLOW standardization process (getting ACKs etc. on the DPDK mailing list) for faster integration of new DPDK flow items/actions, it does make sense to define a generic flow item (and action) for this purpose (and not just for P4).
In order to avoid conflicts between P4 and non-P4 generic flow items/actions, the generic type should include information about how to interpret the information, which is why I suggest making it a Vendor-Specific type, with vendor-specific TLV's (managed by the vendor), like the RADIUS Vendor-Specific attributes I compared to, instead of just an opaque blob.
The P4 standardized items/actions can use the Vendor ID of the P4 standards organization.
The non-standardized items/actions can use the Vendor ID of the hardware vendor or the application developer.
>
> > 2. even the same PMD doesn't know what is the action, unless you plan
> that
> > this will move
> > directly to the HW, in this case, the action will be HW dependent.
>
> The processing of each flow action, as well as the number of arguments
> and the
> format of each action argument, is defined by the P4 program, so all the
> HW
> devices (from the same or from different vendors) that are able to
> successfully
> load the given P4 program will have the same understanding of the flow
> actions.
>
> > 3. when application should use this new action or the old ones.
>
> I guess it is good to clarify that there are two application: a data
> path application
> (the P4 program) that defines the packet processing pipeline, and a
> control path
> application that invokes RTE_FLOW to add/delete the flows on the device.
> I guess
> we are now referring to the control path app.
>
> Whenever the P4 program (the data path app) that is currently loaded on
> the
> device is defining and using flow actions that perform identical
> processing to one
> of the existing pre-defined RTE_FLOW actions (such as packet drop,
> packet
> redirection to a given output queue, packet modifications, etc), then
> the app
> (the control path app) can accept these actions as well.
>
> But in the (frequent) case that the user's P4 program defines actions
> that do not
> map to an RTE_FLOW action from the pre-defined list, then the app has no
> other
> option but to use the newly proposed generic flow action in order to
> specify
> (through the action_id field) the exact flow action from the P4 program.
>
> Makes sense?
>
> >
> >
> > Thanks,
> > Ori
> >
>
> Regards,
> Cristian
>
> > > -----Original Message-----
> > > From: Ori Kam <orika@nvidia.com>
> > > Sent: Wednesday, August 2, 2023 6:47 PM
> > >
> > > Hi Qi
> > >
> > > > -----Original Message-----
> > > > From: Morten Brørup <mb@smartsharesystems.com>
> > > > Sent: Wednesday, August 2, 2023 6:25 PM
> > > >
> > > > > From: Dumitrescu, Cristian
> [mailto:cristian.dumitrescu@intel.com]
> > > > > Sent: Wednesday, 2 August 2023 16.06
> > > > >
> > > > > > From: Jerin Jacob <jerinjacobk@gmail.com>
> > > > > > Sent: Wednesday, August 2, 2023 12:22 PM
> > > > > >
> > > > > > On Wed, Aug 2, 2023 at 4:31 PM Morten Brørup
> > > > > > <mb@smartsharesystems.com> wrote:
> > > > > > >
> > > > > > > > From: Morten Brørup [mailto:mb@smartsharesystems.com]
> > > > > > > > Sent: Wednesday, 2 August 2023 12.25
> > > > > > > >
> > > > > > > > > From: Qi Zhang [mailto:qi.z.zhang@intel.com]
> > > > > > > > > Sent: Wednesday, 2 August 2023 19.35
> > > > > > > > >
> > > > > > > > > From: Cristian Dumitrescu
> <cristian.dumitrescu@intel.com>
> > > > > > > > >
> > > > > > > > > For network devices that are programmable through
> languages
> > such
> > > as
> > > > > > > > > the P4 language, there are no pre-defined flow items and
> actions.
> > > > > > > > >
> > > > > > > > > The format of the protocol header and metadata fields
> that are
> > used
> > > to
> > > > > > > > > specify the flow items that make up the flow pattern, as
> well as
> > the
> > > > > > > > > flow actions, are all defined by the program, with an
> infinity of
> > > > > > > > > possible combinations, as opposed to being selected from
> a
> > finite
> > > > > > > > > pre-defined list.
> > > > > > > > >
> > > > > > > > > It is virtually impossible to pre-define all the flow
> items and the
> > > > > > > > > flow actions that programs might ever use, as these are
> only
> > limited
> > > > > > > > > by the set of HW resources and the program developer's
> > > imagination.
> > > > > > > > >
> > > > > > > > > To support the programmable network devices, we are
> > introducing:
> > > > > > > > >
> > > > > > > > > * A generic flow item: The flow item is expressed as an
> array of
> > bytes
> > > > > > > > > of a given length, whose meaning is defined by the
> program
> > loaded
> > > by
> > > > > > > > > the network device.
> > > > > > > >
> > > > > > > > The flow item is not "generic", it is "opaque": Only the
> application
> > > > > knows
> > > > > > > > what this flow item does.
> > > > > > > >
> > > > > > > > I hate the concept for two reasons:
> > > > > > > > 1. The inability for applications to detect which flow
> items the
> > > > > underlying
> > > > > > > > hardware supports.
> > > > > > > > 2. The risk that vendors will use this instead of
> introducing new
> > flow
> > > > > item
> > > > > > > > types, available for anyone to implement.
> > > > > > >
> > > > > > > After further consideration, there might be a middle ground.
> > > > > > >
> > > > > > > Consider Vendor-Specific attributes for DHCP and RADIUS, or
> SNMP
> > > > MIBs...
> > > > > > >
> > > > > > > Any vendor is free to add his own, proprietary special-
> purpose
> > > attributes,
> > > > > > without going through the standardization process. (This is
> the key
> > > > > challenge
> > > > > > this patch seems to be aiming at.)
> > > > > > >
> > > > > > > The vendor might publish these attributes, and other vendors
> may
> > > > > > implement them too.
> > > > > > >
> > > > > > > And in order to prevent collisions, the Vendor-Specific
> attributes
> > contain
> > > > > a
> > > > > > globally unique vendor ID, such as the Private Enterprise
> Number [1]
> > > > > > managed by IANA.
> > > > > > >
> > > > > > > If similar principles can be worked into the patch, I can
> support it.
> > > > > >
> > > > > > +1
> > > > > >
> > > +1 I understand that this is supposed to be generic, but how can it?
> > > how do you know if PMD supports this?
> > > what if each PMD needs different configurations?
> > >
> > > In addition how can you handle number of those action and items?
> > > For example if I have match on protocol X and Y and do actions Z and
> W
> > > each one of those can be generic item.
> > > if you have a way to define a standard why to read such actions then
> we
> > have
> > > something to talk about.
> > >
> > >
> > > > >
> > > > > Morten, Jerin,
> > > > >
> > > > > I think there is a fundamental misunderstanding here: we are not
> trying
> > to
> > > > > provide support for some non-standard vendor-specific features
> here.
> > What
> > > > > we are trying to do is add generic multi-vendor support in
> RTE_FLOW
> > for
> > > > > P4 programmable network devices, which requires supporting flow
> > items
> > > > > and actions that are defined directly by the user through their
> P4
> > programs
> > > > > as opposed to being selected from a pre-defined list.
> > > > >
> > > > > There are an infinity of flow items and actions that the users
> can define
> > > > > through
> > > > > their P4 programs, and they cannot be supported with a finite
> list of
> > > > RTE_FLOW
> > > > > items and actions:
> > > > >
> > > > > 1/ Some flow items map directly to the IETF defined protocols,
> while
> > some
> > > > > others do not, and only the user writing the program knows the
> exact
> > > answer;
> > > > >
> > > > > 2/ Some flow items are simply application-specific (not vendor
> specific)
> > > > > meta-data that (I hope we all accept) is outside of the
> standardization
> > > > > process.
> > > >
> > > > Such items can use a special "reserved" vendor-id.
> > > >
> > >
> > > Can you show me what items/actions are missing in rte_flow?
> > >
> > > > >
> > > > > 3/ Some flow actions map directly to the existing RTE_FLOW
> actions
> > > > (especially
> > > > > the more straightforward actions such as: packet drop, packet
> redirection
> > to
> > > > > an
> > > > > output queue, some specific packet modifications, etc), while
> the vast
> > > > > majority
> > > > > of possible actions do not.
> > > > >
> > > > > Are you saying that the P4 programmable network devices should
> NOT
> > be
> > > > > supported by DPDK and RTE_FLOW?
> > > >
> > > > No, I get the need for this. And I understand that since P4 is
> compiled to
> > > > hardware-specific binary blobs, there is a need to put such blobs
> into
> > DPDK as
> > > > flow items and actions, instead of the "uncompiled" P4 program.
> > > >
> > > > I am suggesting that instead of adding a completely opaque data
> type:
> > > >
> > > > Struct item {
> > > > Int len; // Length of value in bytes.
> > > > Char value[]; // Application specific meaning.
> > > > };
> > > >
> > >
> > > But since you didn't define a known protocol for PMD to read the
> data how
> > > 2 pmds can use the same action?
> > >
> > > > ...add a semi-opaque data type:
> > > >
> > > > Struct tlv {
> > > > Int type; // Vendor specific type.
> > > > Int len; // Length of value in bytes.
> > > > Char value[]; // (Vendor, Type) specific meaning.
> > > > };
> > > >
> > > > Struct item {
> > > > Int vendor; // Vendor ID.
> > > > Int len; // Length of values in bytes.
> > > > Struct tlv values[]; // Array of TLVs.
> > > > };
> > > >
> > > > Like RADIUS Vendor-Specific attributes:
> > > > https://datatracker.ietf.org/doc/html/rfc2138#section-5.26
> > > >
> > > > Then some (Vendor, Type) fields can be documented (and thus
> generally
> > > > understood by DPDK), and some undocumented.
> > > >
> > > > E.g. like Microsoft documented some of theirs in RFC 2548:
> > > > https://datatracker.ietf.org/doc/html/rfc2548
> > > >
> > > >
> > > > Another benefit is that these new "VENDOR-SPECIFIC" flow types can
> be
> > > reused
> > > > for other purposes than compiled P4 programs.
> > > >
> > > > >
> > > > > >
> > > > > > >
> > > > > > > Preferably, there should also be a means for applications to
> query if
> > > > > specific
> > > > > > Vendor-Specific flow items and actions are supported or not.
> > > > > > >
> > > > > > >
> > > > > > > [1]: https://www.iana.org/assignments/enterprise-numbers/
> > > > > > >
> > > > >
> > > > > Regards,
> > > > > Cristian
next prev parent reply other threads:[~2023-08-02 17:56 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-08-02 17:34 Qi Zhang
2023-08-02 9:37 ` Zhang, Qi Z
2023-08-02 10:25 ` Morten Brørup
2023-08-02 11:01 ` Morten Brørup
2023-08-02 11:21 ` Jerin Jacob
2023-08-02 14:06 ` Dumitrescu, Cristian
2023-08-02 15:24 ` Morten Brørup
2023-08-02 15:47 ` Ori Kam
2023-08-02 16:06 ` Ori Kam
2023-08-02 17:22 ` Dumitrescu, Cristian
2023-08-02 17:56 ` Morten Brørup [this message]
2023-08-03 1:05 ` Zhang, Qi Z
2023-08-03 13:57 ` Morten Brørup
2023-08-16 13:23 ` Dumitrescu, Cristian
2023-08-16 14:20 ` Morten Brørup
2023-08-16 17:08 ` Ferruh Yigit
2023-08-16 17:18 ` Dumitrescu, Cristian
2023-08-16 16:19 ` DPDK community: RTE_FLOW support for P4-programmable devices Dumitrescu, Cristian
2023-08-27 7:48 ` Ori Kam
2023-08-28 16:12 ` Dumitrescu, Cristian
2023-08-29 7:38 ` Jerin Jacob
2023-08-29 10:18 ` Ferruh Yigit
2023-08-31 10:32 ` Ori Kam
2023-08-31 13:42 ` Stephen Hemminger
2023-09-01 2:07 ` Jerin Jacob
2023-09-01 6:57 ` Ori Kam
2023-09-01 9:52 ` Jerin Jacob
2023-09-04 7:45 ` Ferruh Yigit
2023-09-06 8:30 ` Ori Kam
2023-09-11 20:20 ` Dumitrescu, Cristian
2023-08-02 16:56 ` [PATCH] ethdev: introduce generic flow item and action Dumitrescu, Cristian
2023-08-03 8:39 ` Ori Kam
2023-08-16 13:12 ` Dumitrescu, Cristian
2023-08-02 16:14 ` Dumitrescu, Cristian
2023-08-02 14:06 ` Dumitrescu, Cristian
2023-08-02 14:54 ` Morten Brørup
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