| Message ID | 20240223131728.116717-1-jhs@mojatatu.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | Introducing P4TC (series 1) | expand |
On Fri, 23 Feb 2024 08:17:23 -0500 Jamal Hadi Salim wrote: > This is the first patchset of two. In this patch we are only submitting 5 > patches which touch the general TC code given these are trivial. We will be > posting a second patchset which handles the P4 objects and associated infra > (which includes 10 patches that we have already been posting to hit the 15 > limit). Don't use the limit as a justification for questionable tactics :| If there's still BPF in it, it's not getting merged without BPF maintainers's acks. So we're going to merge these 5 and then what? BTW the diffstat at the end of the commit message is from the full set.
On Fri, Feb 23, 2024 at 07:38:02AM -0800, Jakub Kicinski wrote: > On Fri, 23 Feb 2024 08:17:23 -0500 Jamal Hadi Salim wrote: > > This is the first patchset of two. In this patch we are only submitting 5 > > patches which touch the general TC code given these are trivial. We will be > > posting a second patchset which handles the P4 objects and associated infra > > (which includes 10 patches that we have already been posting to hit the 15 > > limit). > > Don't use the limit as a justification for questionable tactics :| > If there's still BPF in it, it's not getting merged without BPF > maintainers's acks. So we're going to merge these 5 and then what? > > BTW the diffstat at the end of the commit message is from the full set. ...and it is followed by the current one, but that old scary diffstat sould better go away ;) >
On Fri, Feb 23, 2024 at 10:38 AM Jakub Kicinski <kuba@kernel.org> wrote: > > On Fri, 23 Feb 2024 08:17:23 -0500 Jamal Hadi Salim wrote: > > This is the first patchset of two. In this patch we are only submitting 5 > > patches which touch the general TC code given these are trivial. We will be > > posting a second patchset which handles the P4 objects and associated infra > > (which includes 10 patches that we have already been posting to hit the 15 > > limit). > > Don't use the limit as a justification for questionable tactics :| The discussion with Daniel was on removing the XDP referencing in the filter which in my last email exchange i offered to remove. I believe that removing the XDP reference should resolve the issue. Instead of waiting for Daniel to respond (the last response took a while), at the last minute i decided to only do the first five which are trivial and have been posted for over a year now and have been reviewd by multiple people. I had no intention to make this a conspiracy of any sort. > If there's still BPF in it, it's not getting merged without BPF > maintainers's acks. So we're going to merge these 5 and then what? > Look, this is getting to be too much navigation (which is what scares most newbies from participating and i have been here for 100 years now). I dont have a problem removing the XDP reference - but now we are treading into subsystem territories; this is about P4 abstraction and the infra around it, it is really not about eBPF. We dont need anything "new" from ebpf i.e none of these patches make any eBPF changes. This is a tc classifier that happens to use ebpf, whose domain is that? The exhausting part is some feedback is "you do it our way or else" thing: I apologize i dont want to lump everyone in that pool, and it is nothing to do specifically with ebpf people rather a failure in reaching compromise within this community. > BTW the diffstat at the end of the commit message is from the full set Yeah, sorry - this was last minute "should i send all or just these five to make space for the remainder 5 that we havent posted since V8". We have 5 more patches on top of what we posted on V10 - merging these would open the door to post the rest with 15 limit. I can repost all 15 if that works better. cheers, jamal
This is the first patchset of two. In this patch we are only submitting 5 patches which touch the general TC code given these are trivial. We will be posting a second patchset which handles the P4 objects and associated infra (which includes 10 patches that we have already been posting to hit the 15 limit). One call that was hard to make was whether to include this cover letter which talks about all of P4 and P4TC details or not. In the end we are putting a slightly abbreviated version of the original cover letter and describe the P4 objects and associated infra further below. __Description of these Patches__ Patch #1 adds infrastructure for per-netns P4 actions that can be created on as need basis for the P4 program requirement. This patch makes a small incision into act_api. Patches 2-4 are minimalist enablers for P4TC and have no effect the classical tc action (example patch#2 just increases the size of the action names from 16->64B). Patch 5 adds infrastructure support for preallocation of dynamic actions. None of these patches affect the performance (or functionality) of the existing actions What is P4? ----------- The Programming Protocol-independent Packet Processors (P4) is an open source, domain-specific programming language for specifying data plane behavior. The current P4 landscape includes an extensive range of deployments, products, projects and services, etc[9][12]. Two major NIC vendors, Intel[10] and AMD[11] currently offer P4-native NICs. P4 is currently curated by the Linux Foundation[9]. On why P4 - see small treatise here:[4]. What is P4TC? ------------- P4TC is a net-namespace aware P4 implementation over TC; meaning, a P4 program and its associated objects and state are attachend to a kernel _netns_ structure. IOW, if we had two programs across netns' or within a netns they have no visibility to each others objects (unlike for example TC actions whose kinds are "global" in nature or eBPF maps visavis bpftool). P4TC builds on top of many years of Linux TC experiences of a netlink control path interface coupled with a software datapath with an equivalent offloadable hardware datapath. In this patch series we are focussing only on the s/w datapath. The s/w and h/w path equivalence that TC provides is relevant for a primary use case of P4 where some (currently) large consumers of NICs provide vendors their datapath specs in P4. In such a case one could generate specified datapaths in s/w and test/validate the requirements before hardware acquisition(example [12]). Unlike other approaches such as TC Flower which require kernel and user space changes when new datapath objects like packet headers are introduced P4TC, with these patches, provides _kernel and user space code change independence_. Meaning: A P4 program describes headers, parsers, etc alongside the datapath processing; the compiler uses the P4 program as input and generates several artifacts which are then loaded into the kernel to manifest the intended datapath. In addition to the generated datapath, control path constructs are generated. The process is described further below in "P4TC Workflow". There have been many discussions and meetings within the community since about 2015 in regards to P4 over TC[2] and we are finally proving to the naysayers that we do get stuff done! A lot more of the P4TC motivation is captured at: https://github.com/p4tc-dev/docs/blob/main/why-p4tc.md __P4TC Architecture__ The current architecture was described at netdevconf 0x17[14] and if you prefer academic conference papers, a short paper is available here[15]. There are 4 parts: 1) A Template CRUD provisioning API for manifesting a P4 program and its associated objects in the kernel. The template provisioning API uses netlink. See patch in part 2. 2) A Runtime CRUD+ API code which is used for controlling the different runtime behavior of the P4 objects. The runtime API uses netlink. See notes further down. See patch description later.. 3) P4 objects and their control interfaces: tables, actions, externs, etc. Any object that requires control plane interaction resides in the TC domain and is subject to the CRUD runtime API. The intended goal is to make use of the tc semantics of skip_sw/hw to target P4 program objects either in s/w or h/w. 4) S/W Datapath code hooks. The s/w datapath is eBPF based and is generated by a compiler based on the P4 spec. When accessing any P4 object that requires control plane interfaces, the eBPF code accesses the P4TC side from #3 above using kfuncs. The generated eBPF code is derived from [13] with enhancements and fixes to meet our requirements. __P4TC Workflow__ The Development and instantiation workflow for P4TC is as follows: A) A developer writes a P4 program, "myprog" B) Compiles it using the P4C compiler[8]. The compiler generates 3 outputs: a) A shell script which form template definitions for the different P4 objects "myprog" utilizes (tables, externs, actions etc). See #1 above.. b) the parser and the rest of the datapath are generated as eBPF and need to be compiled into binaries. At the moment the parser and the main control block are generated as separate eBPF program but this could change in the future (without affecting any kernel code). See #4 above. c) A json introspection file used for the control plane (by iproute2/tc). C) At this point the artifacts from #1,#4 could be handed to an operator (the operator could be the same person as the developer from #A, #B). i) For the eBPF part, either the operator is handed an ebpf binary or source which they compile at this point into a binary. The operator executes the shell script(s) to manifest the functional "myprog" into the kernel. ii) The operator instantiates "myprog" pipeline via the tc P4 filter to ingress/egress (depending on P4 arch) of one or more netdevs/ports (illustrated below as "block 22"). Example instantion where the parser is a separate action: "tc filter add block 22 ingress protocol all prio 10 p4 pname myprog \ action bpf obj $PARSER.o section p4tc/parse \ action bpf obj $PROGNAME.o section p4tc/main" See individual patches in partc for more examples tc vs xdp etc. Also see section on "challenges" (further below on this cover letter). Once "myprog" P4 program is instantiated one can start performing operations on table entries and/or actions at runtime as described below. __P4TC Runtime Control Path__ The control interface builds on past tc experience and tries to get things right from the beginning (example filtering is separated from depending on existing object TLVs and made generic); also the code is written in such a way it is mostly lockless. The P4TC control interface, using netlink, provides what we call a CRUDPS abstraction which stands for: Create, Read(get), Update, Delete, Subscribe, Publish. From a high level PoV the following describes a conformant high level API (both on netlink data model and code level): Create(</path/to/object, DATA>+) Read(</path/to/object>, [optional filter]) Update(</path/to/object>, DATA>+) Delete(</path/to/object>, [optional filter]) Subscribe(</path/to/object>, [optional filter]) Note, we _dont_ treat "dump" or "flush" as speacial. If "path/to/object" points to a table then a "Delete" implies "flush" and a "Read" implies dump but if it points to an entry (by specifying a key) then "Delete" implies deleting and entry and "Read" implies reading that single entry. It should be noted that both "Delete" and "Read" take an optional filter parameter. The filter can define further refinements to what the control plane wants read or deleted. "Subscribe" uses built in netlink event management. It, as well, takes a filter which can further refine what events get generated to the control plane (taken out of this patchset, to be re-added with consideration of [16]). Lets show some runtime samples: ..create an entry, if we match ip address 10.0.1.2 send packet out eno1 tc p4ctrl create myprog/table/mytable \ dstAddr 10.0.1.2/32 action send_to_port param port eno1 ..Batch create entries tc p4ctrl create myprog/table/mytable \ entry dstAddr 10.1.1.2/32 action send_to_port param port eno1 \ entry dstAddr 10.1.10.2/32 action send_to_port param port eno10 \ entry dstAddr 10.0.2.2/32 action send_to_port param port eno2 ..Get an entry (note "read" is interchangeably used as "get" which is a common semantic in tc): tc p4ctrl read myprog/table/mytable \ dstAddr 10.0.2.2/32 ..dump mytable tc p4ctrl read myprog/table/mytable ..dump mytable for all entries whose key fits within 10.1.0.0/16 tc p4ctrl read myprog/table/mytable \ filter key/myprog/mytable/dstAddr = 10.1.0.0/16 ..dump all mytable entries which have an action send_to_port with param "eno1" tc p4ctrl get myprog/table/mytable \ filter param/act/myprog/send_to_port/port = "eno1" The filter expression is powerful, f.e you could say: tc p4ctrl get myprog/table/mytable \ filter param/act/myprog/send_to_port/port = "eno1" && \ key/myprog/mytable/dstAddr = 10.1.0.0/16 It also works on built in metadata, example in the following case dumping entries from mytable that have seen activity in the last 10 secs: tc p4ctrl get myprog/table/mytable \ filter msecs_since < 10000 Delete follows the same syntax as get/read, so for sake of brevity we won't show more example than how to flush mytable: tc p4ctrl delete myprog/table/mytable Mystery question: How do we achieve iproute2-kernel independence and how does "tc p4ctrl" as a cli know how to program the kernel given an arbitrary command line as shown above? Answer(s): It queries the compiler generated json file in "P4TC Workflow" #B.c above. The json file has enough details to figure out that we have a program called "myprog" which has a table "mytable" that has a key name "dstAddr" which happens to be type ipv4 address prefix. The json file also provides details to show that the table "mytable" supports an action called "send_to_port" which accepts a parameter "port" of type netdev (see the types patch for all supported P4 data types). All P4 components have names, IDs, and types - so this makes it very easy to map into netlink. Once user space tc/p4ctrl validates the human command input, it creates standard binary netlink structures (TLVs etc) which are sent to the kernel. See the runtime table entry patch for more details. __P4TC Datapath__ The P4TC s/w datapath execution is generated as eBPF. Any objects that require control interfacing reside in the "P4TC domain" and are controlled via netlink as described above. Per packet execution and state and even objects that do not require control interfacing (like the P4 parser) are generated as eBPF. A packet arriving on s/w ingress of any of the ports on block 22 will first be exercised via the (generated eBPF) parser component to extract the headers (the ip destination address in labelled "dstAddr" above). The datapath then proceeds to use "dstAddr", table ID and pipeline ID as a key to do a lookup in myprog's "mytable" which returns the action params which are then used to execute the action in the eBPF datapath (eventually sending out packets to eno1). On a table miss, mytable's default miss action (not described) is executed. __Testing__ Speaking of testing - we have 2-300 tdc test cases (which will be in the second patchset). These tests are run on our CICD system on pull requests and after commits are approved. The CICD does a lot of other tests (more since v2, thanks to Simon's input)including: checkpatch, sparse, smatch, coccinelle, 32 bit and 64 bit builds tested on both X86, ARM 64 and emulated BE via qemu s390. We trigger performance testing in the CICD to catch performance regressions (currently only on the control path, but in the future for the datapath). Syzkaller runs 24/7 on dedicated hardware, originally we focussed only on memory sanitizer but recently added support for concurrency sanitizer. Before main releases we ensure each patch will compile on its own to help in git bisect and run the xmas tree tool. We eventually put the code via coverity. In addition we are working on enabling a tool that will take a P4 program, run it through the compiler, and generate permutations of traffic patterns via symbolic execution that will test both positive and negative datapath code paths. The test generator tool integration is still work in progress. Also: We have other code that test parallelization etc which we are trying to find a fit for in the kernel tree's testing infra. __References__ [1]https://github.com/p4tc-dev/docs/blob/main/p4-conference-2023/2023P4WorkshopP4TC.pdf [2]https://github.com/p4tc-dev/docs/blob/main/why-p4tc.md#historical-perspective-for-p4tc [3]https://2023p4workshop.sched.com/event/1KsAe/p4tc-linux-kernel-p4-implementation-approaches-and-evaluation [4]https://github.com/p4tc-dev/docs/blob/main/why-p4tc.md#so-why-p4-and-how-does-p4-help-here [5]https://lore.kernel.org/netdev/20230517110232.29349-3-jhs@mojatatu.com/T/#mf59be7abc5df3473cff3879c8cc3e2369c0640a6 [6]https://lore.kernel.org/netdev/20230517110232.29349-3-jhs@mojatatu.com/T/#m783cfd79e9d755cf0e7afc1a7d5404635a5b1919 [7]https://lore.kernel.org/netdev/20230517110232.29349-3-jhs@mojatatu.com/T/#ma8c84df0f7043d17b98f3d67aab0f4904c600469 [8]https://github.com/p4lang/p4c/tree/main/backends/tc [9]https://p4.org/ [10]https://www.intel.com/content/www/us/en/products/details/network-io/ipu/e2000-asic.html [11]https://www.amd.com/en/accelerators/pensando [12]https://github.com/sonic-net/DASH/tree/main [13]https://github.com/p4lang/p4c/tree/main/backends/ebpf [14]https://netdevconf.info/0x17/sessions/talk/integrating-ebpf-into-the-p4tc-datapath.html [15]https://dl.acm.org/doi/10.1145/3630047.3630193 [16]https://lore.kernel.org/netdev/20231216123001.1293639-1-jiri@resnulli.us/ [17.a]https://netdevconf.info/0x13/session.html?talk-tc-u-classifier [17.b]man tc-u32 [18]man tc-pedit [19] https://lore.kernel.org/netdev/20231219181623.3845083-6-victor@mojatatu.com/T/#m86e71743d1d83b728bb29d5b877797cb4942e835 [20.a] https://netdevconf.info/0x16/sessions/talk/your-network-datapath-will-be-p4-scripted.html [20.b] https://netdevconf.info/0x16/sessions/workshop/p4tc-workshop.html -------- HISTORY -------- Changes in Version 11 ---------------------- 1) Split the series into two. Original patches 1-5 in this patchset. The rest will go out after this is merged. 2) Change any references of IFNAMSIZ in the action code when referencing the action name size to ACTNAMSIZ. Thanks to Marcelo. Changes in Version 10 ---------------------- 1) A couple of patches from the earlier version were clean enough to submit, so we did. This gave us room to split the two largest patches each into two. Even though the split is not git-bisactable and really some of it didn't make much sense (eg spliting a create, and update in one patch and delete and get into another) we made sure each of the split patches compiled independently. The idea is to reduce the number of lines of code to review and when we get sufficient reviews we will put the splits together again. See patch #12 and #13 as well as patches #7 and #8). 2) Add more context in patch 0. Please READ! 3) Added dump/delete filters back to the code - we had taken them out in the earlier patches to reduce the amount of code for review - but in retrospect we feel they are important enough to push earlier rather than later. Changes In version 9 --------------------- 1) Remove the largest patch (externs) to ease review. 2) Break up action patches into two to ease review bringing down the patches that need more scrutiny to 8 (the first 7 are almost trivial). 3) Fixup prefix naming convention to p4tc_xxx for uapi and p4a_xxx for actions to provide consistency(Jiri). 4) Silence sparse warning "was not declared. Should it be static?" for kfuncs by making them static. TBH, not sure if this is the right solution but it makes sparse happy and hopefully someone will comment. Changes In Version 8 --------------------- 1) Fix all the patchwork warnings and improve our ci to catch them in the future 2) Reduce the number of patches to basic max(15) to ease review. Changes In Version 7 ------------------------- 0) First time removing the RFC tag! 1) Removed XDP cookie. It turns out as was pointed out by Toke(Thanks!) - that using bpf links was sufficient to protect us from someone replacing or deleting a eBPF program after it has been bound to a netdev. 2) Add some reviewed-bys from Vlad. 3) Small bug fixes from v6 based on testing for ebpf. 4) Added the counter extern as a sample extern. Illustrating this example because it is slightly complex since it is possible to invoke it directly from the P4TC domain (in case of direct counters) or from eBPF (indirect counters). It is not exactly the most efficient implementation (a reasonable counter impl should be per-cpu). Changes In RFC Version 6 ------------------------- 1) Completed integration from scriptable view to eBPF. Completed integration of externs integration. 2) Small bug fixes from v5 based on testing. Changes In RFC Version 5 ------------------------- 1) More integration from scriptable view to eBPF. Small bug fixes from last integration. 2) More streamlining support of externs via kfunc (create-on-miss, etc) 3) eBPF linking for XDP. There is more eBPF integration/streamlining coming (we are getting close to conversion from scriptable domain). Changes In RFC Version 4 ------------------------- 1) More integration from scriptable to eBPF. Small bug fixes. 2) More streamlining support of externs via kfunc (one additional kfunc). 3) Removed per-cpu scratchpad per Toke's suggestion and instead use XDP metadata. There is more eBPF integration coming. One thing we looked at but is not in this patchset but should be in the next is use of eBPF link in our loading (see "challenge #1" further below). Changes In RFC Version 3 ------------------------- These patches are still in a little bit of flux as we adjust to integrating eBPF. So there are small constructs that are used in V1 and 2 but no longer used in this version. We will make a V4 which will remove those. The changes from V2 are as follows: 1) Feedback we got in V2 is to try stick to one of the two modes. In this version we are taking one more step and going the path of mode2 vs v2 where we had 2 modes. 2) The P4 Register extern is no longer standalone. Instead, as part of integrating into eBPF we introduce another kfunc which encapsulates Register as part of the extern interface. 3) We have improved our CICD to include tools pointed to us by Simon. See "Testing" further below. Thanks to Simon for that and other issues he caught. Simon, we discussed on issue [7] but decided to keep that log since we think it is useful. 4) A lot of small cleanups. Thanks Marcelo. There are two things we need to re-discuss though; see: [5], [6]. 5) We removed the need for a range of IDs for dynamic actions. Thanks Jakub. 6) Clarify ambiguity caused by smatch in an if(A) else if(B) condition. We are guaranteed that either A or B must exist; however, lets make smatch happy. Thanks to Simon and Dan Carpenter. Changes In RFC Version 2 ------------------------- Version 2 is the initial integration of the eBPF datapath. We took into consideration suggestions provided to use eBPF and put effort into analyzing eBPF as datapath which involved extensive testing. We implemented 6 approaches with eBPF and ran performance analysis and presented our results at the P4 2023 workshop in Santa Clara[see: 1, 3] on each of the 6 vs the scriptable P4TC and concluded that 2 of the approaches are sensible (4 if you account for XDP or TC separately). Conclusions from the exercise: We lose the simple operational model we had prior to integrating eBPF. We do gain performance in most cases when the datapath is less compute-bound. For more discussion on our requirements vs journeying the eBPF path please scroll down to "Restating Our Requirements" and "Challenges". This patch set presented two modes. mode1: the parser is entirely based on eBPF - whereas the rest of the SW datapath stays as _scriptable_ as in Version 1. mode2: All of the kernel s/w datapath (including parser) is in eBPF. The key ingredient for eBPF, that we did not have access to in the past, is kfunc (it made a big difference for us to reconsider eBPF). In V2 the two modes are mutually exclusive (IOW, you get to choose one or the other via Kconfig). Jamal Hadi Salim (15): net: sched: act_api: Introduce P4 actions list net/sched: act_api: increase action kind string length net/sched: act_api: Update tc_action_ops to account for P4 actions net/sched: act_api: add struct p4tc_action_ops as a parameter to lookup callback net: sched: act_api: Add support for preallocated P4 action instances p4tc: add P4 data types p4tc: add template API p4tc: add template pipeline create, get, update, delete p4tc: add template action create, update, delete, get, flush and dump p4tc: add runtime action support p4tc: add template table create, update, delete, get, flush and dump p4tc: add runtime table entry create and update p4tc: add runtime table entry get, delete, flush and dump p4tc: add set of P4TC table kfuncs p4tc: add P4 classifier include/linux/bitops.h | 1 + include/net/act_api.h | 23 +- include/net/p4tc.h | 642 ++++++ include/net/p4tc_types.h | 91 + include/net/tc_act/p4tc.h | 52 + include/uapi/linux/p4tc.h | 433 ++++ include/uapi/linux/pkt_cls.h | 19 + include/uapi/linux/rtnetlink.h | 18 + include/uapi/linux/tc_act/tc_p4.h | 11 + net/sched/Kconfig | 23 + net/sched/Makefile | 3 + net/sched/act_api.c | 190 +- net/sched/cls_api.c | 2 +- net/sched/cls_p4.c | 450 +++++ net/sched/p4tc/Makefile | 8 + net/sched/p4tc/p4tc_action.c | 2305 ++++++++++++++++++++++ net/sched/p4tc/p4tc_bpf.c | 338 ++++ net/sched/p4tc/p4tc_filter.c | 872 +++++++++ net/sched/p4tc/p4tc_pipeline.c | 678 +++++++ net/sched/p4tc/p4tc_runtime_api.c | 145 ++ net/sched/p4tc/p4tc_table.c | 1779 +++++++++++++++++ net/sched/p4tc/p4tc_tbl_entry.c | 3044 +++++++++++++++++++++++++++++ net/sched/p4tc/p4tc_tmpl_api.c | 609 ++++++ net/sched/p4tc/p4tc_types.c | 1287 ++++++++++++ net/sched/p4tc/trace.c | 10 + net/sched/p4tc/trace.h | 44 + security/selinux/nlmsgtab.c | 10 +- 27 files changed, 13052 insertions(+), 35 deletions(-) create mode 100644 include/net/p4tc.h create mode 100644 include/net/p4tc_types.h create mode 100644 include/net/tc_act/p4tc.h create mode 100644 include/uapi/linux/p4tc.h create mode 100644 include/uapi/linux/tc_act/tc_p4.h create mode 100644 net/sched/cls_p4.c create mode 100644 net/sched/p4tc/Makefile create mode 100644 net/sched/p4tc/p4tc_action.c create mode 100644 net/sched/p4tc/p4tc_bpf.c create mode 100644 net/sched/p4tc/p4tc_filter.c create mode 100644 net/sched/p4tc/p4tc_pipeline.c create mode 100644 net/sched/p4tc/p4tc_runtime_api.c create mode 100644 net/sched/p4tc/p4tc_table.c create mode 100644 net/sched/p4tc/p4tc_tbl_entry.c create mode 100644 net/sched/p4tc/p4tc_tmpl_api.c create mode 100644 net/sched/p4tc/p4tc_types.c create mode 100644 net/sched/p4tc/trace.c create mode 100644 net/sched/p4tc/trace.h