> From: Dumitrescu, Cristian [mailto:cristian.dumitre...@intel.com] > Sent: Wednesday, 2 August 2023 19.23 > > > From: Ori Kam <or...@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 <or...@nvidia.com> > > > Sent: Wednesday, August 2, 2023 6:47 PM > > > > > > Hi Qi > > > > > > > -----Original Message----- > > > > From: Morten Brørup <m...@smartsharesystems.com> > > > > Sent: Wednesday, August 2, 2023 6:25 PM > > > > > > > > > From: Dumitrescu, Cristian > [mailto:cristian.dumitre...@intel.com] > > > > > Sent: Wednesday, 2 August 2023 16.06 > > > > > > > > > > > From: Jerin Jacob <jerinjac...@gmail.com> > > > > > > Sent: Wednesday, August 2, 2023 12:22 PM > > > > > > > > > > > > On Wed, Aug 2, 2023 at 4:31 PM Morten Brørup > > > > > > <m...@smartsharesystems.com> wrote: > > > > > > > > > > > > > > > From: Morten Brørup [mailto:m...@smartsharesystems.com] > > > > > > > > Sent: Wednesday, 2 August 2023 12.25 > > > > > > > > > > > > > > > > > From: Qi Zhang [mailto:qi.z.zh...@intel.com] > > > > > > > > > Sent: Wednesday, 2 August 2023 19.35 > > > > > > > > > > > > > > > > > > From: Cristian Dumitrescu > <cristian.dumitre...@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
