[v10,net-next,00/15] Introducing P4TC

Message

Jamal Hadi Salim Jan. 22, 2024, 7:47 p.m. UTC

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.

Unlike other approaches like 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 since within the community since
about 2015 in regards to P4 over TC[2] and we are finally proving (if the drama
ends soon) 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 description further down..

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 further down..

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 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 (see "Restating Our Requirements" further below).

__P4TC Workflow__

The workflow is as follows:

  1) A developer writes a P4 program, "myprog"

  2) 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).
     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).
     c) A json introspection file used for the control plane (by iproute2/tc).

  3) At this point the artifacts from #2 could be handed to an operator.
     Either the operator is handed an ebpf binary or source which they compile
     at this point.
     The operator executes the shell script(s) to manifest the functional
     "myprog" into the kernel.

  4) 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"). Note the tc filter here is used
     to manage the P4 program pipeline which may include pieces in h/w,
     tc(eBPF) and XDP(eBPF).

     Several ways to instantiate:

     Example1: parser is an action:
       "tc filter add block 22 ingress protocol all prio 10 p4 pname myprog \
        action bpf obj $PARSER.o section p4parser/tc-ingress \
        action bpf obj $PROGNAME.o section p4prog/tc"

     Example2: parser explicitly bound and rest of dpath as an action:
       "tc filter add block 22 ingress protocol all prio 10 p4 pname myprog \
        prog tc obj $PARSER.o section p4parser/tc-ingress \
        action bpf obj $PROGNAME.o section p4prog/tc"

     Example3: parser is at XDP, rest of dpath as an action:
       "tc filter add block 22 ingress protocol all prio 10 p4 pname myprog \
        prog type xdp obj $PARSER.o section p4parser/xdp-ingress \
	pinned_link /path/to/xdp-prog-link \
        action bpf obj $PROGNAME.o section p4prog/tc"

     Example4: parser+prog at XDP:
       "tc filter add block 22 ingress protocol all prio 10 p4 pname myprog \
        prog type xdp obj $PROGNAME.o section p4prog/xdp \
	pinned_link /path/to/xdp-prog-link"

See individual patches 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 updating table entries
and/or creating actions at runtime.
Example, creating an entry matched with a dstAddr 10.0.1.2/32 in myprog's table
named "mytable" which  redirect to eno1:

  tc p4ctrl create myprog/table/mytable dstAddr 10.0.1.2/32 \
    action send_to_port param port eno1

__P4TC Runtime Control Path__

The control interface builds on past 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 samples:

..create an entry
  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 #2c 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 in 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 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.

__Description of Patches__

P4TC is designed to have no impact on the core code for other users of the
kernel. IOW, you either can compile it out (or even compile it in and if you
dont use it) then there should be no impact on your workload performance or
functionality.

We do make small kernel changes (only on tc code, and not intrusive at all in
the first 5 patches). Patch #1 adds infrastructure for P4 actions that can
be created on as need basis for the P4 program requirement.  This patch makes
a small incision into act_api which shouldn't affect the performance (or
functionality) of the existing actions. Patches 2-4 are minimalist enablers for
P4TC and have no effect the classical tc action.
Patch 5 adds infrastructure support for preallocation of dynamic actions.

The core P4TC code implements several P4 objects.

1) Patch #6 introduces P4 data types which are consumed by the rest of the code
2) Patch #7 introduces the templating API. i.e CRUD commands for templates
3) Patch #8 introduces the concept of templating Pipelines. i.e CRUD commands
   for P4 pipelines.
4) Patch #9 introduces the action templates and associated CRUD commands.
5) Patch #10 introduce the action runtime infrastructure.
6) Patch #11 introduces the concept of P4 table templates and associated
   CRUD commands for tables.
7) Patch #12 introduces runtime table entry infra and associated CU commands.
8) Patch #13 introduces runtime table entry infra and associated RD commands.
9) Patch #14 introduces interaction of eBPF to P4TC tables via kfunc.
10) Patch #15 introduces the TC classifier P4 used at runtime.

Note, to have the minimal viable implementation we need to have extern patch(es)
on top of these. There are a few more patches (2-5) not in this patchset that
deal with P4 Extern objects. So consider this patchset to be "part 1"; "part2"
will come later. Now if we could only push the trivial patches 1-5... then we
can fit all in the max allowed 15.

__Testing__

Speaking of testing - we have ~300 tdc test cases. This number is growing as
we are adjusting to accommodate for eBPF.
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 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 is still work in progress and will be generated by the P4
compiler.
Note: We have other code that test parallelization etc which we are trying to
find a fit for in the kernel tree's testing infra.

__Restating Our Requirements__

Given this code is not intrusive at all, it is amazing the kind of noise these
patches have generated;-> We would like to emphasize that _we see eBPF as
infrastructure tooling available to us and not the end goal_. Please help us
with technical input on for example how we can do better kfuncs, etc. If you
want to critique, then our requirements should be your guide and please be
considerate that this is about P4, not eBPF. IOW:
We would appreciate technical commentary instead of bikeshedding on how _you_
would have implemented this probably with more eBPF. Moreover, it is sad to
see there was zero input from anyone in the eBPF world for 7 RFC postings.
If i am ranting here is because we have spent over a year now on this topic - we
have taken the initial input and have given you eBPF. So lets make progress
please.

The initial release was presented in October 2022[20] and RFC in January/2023
had a "scriptable" datapath (the idea built on the u32 classifier[17] and pedit
action[18] approach). Post RFC V1, we made changes to fit the feedback to
integrate eBPF to replace the "scriptable" software datapath. On our part, the
goal for the change was to meet folks in the middle as a compromise.
No regrets on the journey since after all the effort because we ended getting
XDP which was not in the original picture. Some of our efforts are captured
at [1][3] and in the patch history.

In this section we review the original scriptable version against the current
implementation which uses eBPF and in the process re-enumerate our requirements.

To be very clear: Our intention for P4TC is to target _the TC crowd_.
Essentially developers and ops people already familiar and deploying TC based
infra.
More importantly the original intent for P4TC was to enable _ops folks_ more
than devs (given code is being generated and doesn't need humans to write it).

With TC, we gain the whole "familiar" package of match-action pipeline
abstraction++, meaning from the control plane(see discussion above) all the
way to the tooling infra, i.e iproute2/tc cli, netlink infra interface
(request/response, event subscribe/multicast-publish, congestion control etc),
s/w and h/w symbiosis, the autonomous kernel control, etc.
The main advantage over vendor specific implementations(which is the current
alternative) is: with P4TC we have a singular vendor-neutral interface via the
kernel using well understood mechanisms that have gained learnings from
deployment experience.

So lets list some of these requirements and compare whether moving to eBPF
affected us or gave us an advantage.

0) Understood Control Plane semantics

This requirement is unaffected.
The control plane remains as netlink and therefore we get the classical
multi-user CRUD+Publish/subscribe APIs built in.

1) Must support SW/HW equivalence

This requirement is unaffected. The control plane is netlink. Any semantics to
select between sw and hw via skip_sw/hw semantics is maintained.

2) Supporting expressibility of the universe set of P4 progs

It is a must to support 100% of all possible P4 programs. In the past the eBPF
verifier, for example in [13], had to be worked around and even then there are
cases where we couldnt avoid path explosion when branching is involved and
failed to run. So we were skeptical about using eBPF to begin with.
Kfuncs changed our minds. Note, there are still challenges running all
potential P4 programs at the XDP level - but the pipeline could be split
between XDP and TC in such cases. The compiler can be told to generate pieces
that run on XDP and other on TC (see examples).
Summary: This requirement is unaffected.

3) Operational usability

By maintaining the TC control plane (even in presence of eBPF datapath)
runtime aspects remain unchanged. So for our target audience of folks
who have deployed tc, including offloads, the comfort zone is unchanged.

There is some loss in operational usability because we now have more knobs:
the extra compilation, loading and syncing of ebpf binaries, etc.
IOW, I can no longer just ship someone a shell script(ascii) in an email to
someone and say "go run this and "myprog" will just work".

4) Operational and development Debuggability

If something goes wrong, the tc craftsperson is now required to have additional
knowledge of eBPF code and process.
Our intent is to compensate this challenge with debug tools that ease the
craftperson's debugging.

5) Opportunity for rapid prototyping of new ideas

This is not exactly a requirement but something that became a useful
feature during the P4TC development phase. When the compiler was lagging behind
in features was to often handcode the template scripts.
Then you would dump back the template from the kernel and do a diff to ensure
the kernel didn't get something wrong. Essentially, this was a nice debug
feature. During development, we wrote scripts that covered a range of P4
architectures(PSA, V1, etc) which required no kernel code changes.

Over time the debug feature morphed into: a) start by handcoding scripts then
b) read it back and then c) generate the P4 code.
It means one could start with the template scripts outside of the constraints
of a P4 architecture spec(PNA/PSA) or even within a P4 architecture then test
some ideas and eventually feed back the concepts to the compiler authors or
modify or create a new P4 architecture and share with the P4 standards folks.

To summarize in presence of eBPF: The debugging idea is probably still alive.
One could dump, with proper tooling(bpftool for example), the loaded eBPF code
and be able to check for differences. But this is not the interesting part.
The concept of going back from whats in the kernel to P4 is a lot more difficult
to implement mostly due to scoping of DSL vs general purpose. It may be lost.
We have been thinking of ways to use BTF and embedding annotations in the eBPF
code and binary but more thought is required and we welcome suggestions.

6) Supporting per namespace program

In P4TC every program and its associated objects have unique IDs which are
generated by the compiler. Multiple or the same P4 program(s) can run
independently in different namespaces alongside their appropriate state and
object instance parameterization (despite name or ID collission).
This requirement is still met (by virtue of keeping P4 program control
objects within the TC domain and attaching to a netns).

__Challenges__

1) Concept of tc block in XDP is _very tedious_ to implement. It would be nice
   if we can use concept there as well, since we expect P4 to work with many
   ports. It will likely work now with patch [19].

2) Right now we are using "packed" construct to enforce alignment in kfunc data
   exchange; but we're wondering if there is potential to use BTF to understand
   parameters and their offsets and encode this information at the compiler
   level.

3) At the moment we are creating a static buffer of 128B to retrieve the action
   parameters. If you have a lot of table entries and individual(non-shared)
   action instances with actions that require very little (or no) param space
   a lot of memory is wasted. There may also be cases where 128B may not be
   enough; (likely this is something we can teach the P4C compiler). If we can
   have dynamic pointers instead for kfunc fixed length parameterization then
   this issue is resolvable.

4) See "Restating Our Requirements" #5.
   We would really appreciate ideas/suggestions, etc.

__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/[e-mail]/T/#mf59be7abc5df3473cff3879c8cc3e2369c0640a6
[6]https://lore.kernel.org/netdev/[e-mail]/T/#m783cfd79e9d755cf0e7afc1a7d5404635a5b1919
[7]https://lore.kernel.org/netdev/[e-mail]/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/[e-mail]/
[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/[e-mail]/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 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