Re: [RFC PATCH v1 00/21] Building a better rte_flow parser

[Stephen Hemminger <stephen@networkplumber.org>]

On Mon, 16 Mar 2026 17:27:28 +0000
Anatoly Burakov <anatoly.burakov@intel.com> wrote:

> Most rte_flow parsers in DPDK suffer from huge implementation complexity because
> even though 99% of what people use rte_flow parsers for is parsing protocol
> graphs, no parser is written explicitly as a graph. This patchset attempts to
> suggest a viable model to build rte_flow parsers as graphs, by offering a
> lightweight header only library to build rte_flow parsering graphs without too
> much boilerplate and complexity.
> 
> Most of the patchset is about Intel drivers, but they are meant as
> reimplementations as well as examples for the rest of the community to assess
> how to build parsers using this new infrastructure. I expect the first two
> patches will be of most interest to non-Intel reviewers, as they deal with
> building two reusable parser architecture pieces.
> 
> The first piece is a new flow graph helper in ethdev. Its purpose is
> deliberately narrow: it targets the protocol-graph part of rte_flow pattern
> parsing, where drivers walk packet headers and validate legal item sequences and
> parameters. That does not cover all possible rte_flow features, especially more
> exotic flow items, but it does cover a large and widely shared part of what
> existing drivers need to do. Or, to put it in other words, the only flow items
> this infrastructure *doesn't* cover is things that do not lend themselves well
> to be parsed as a graph of protocol headers (e.g. conntrack items). Everything
> else should be covered or cover-able.
> 
> The second piece is a reusable flow engine framework for Intel Ethernet drivers.
> This is kept Intel-local for now because I do not feel it is generic enough to
> be presented as an ethdev-wide engine model. Even so, the intent is to establish
> a cleaner parser architecture with a defined interaction model, explicit memory
> ownership rules, and engine definitions that do not block secondary-process-safe
> usage. It is my hope that we could also promote something like this into ethdev
> proper and remove the necessity for drivers to build so much boilerplate around
> rte_flow parsing (and more often than not doing it in a way that is more complex
> than it needs to be).
> 
> Most of the rest of the series is parser reimplementation, but that is mainly
> the vehicle for demonstrating and validating those two pieces. ixgbe and i40e
> are wired into the new common parsing path, and their existing parsers are
> migrated incrementally to the graph-based model. Besides reducing ad hoc parser
> code, this also makes validation more explicit and more consistent with the
> actual install path. In a few places that means invalid inputs that were
> previously ignored, deferred, or interpreted loosely are now rejected earlier
> and more strictly, without any increase in code complexity (in fact, with marked
> *decrease* of it!).
> 
> Series depends on previously submitted patchsets:
> 
> - IAVF global buffer fix [1]
> - Common attr parsing stuff [2]
> 
> [1] https://patches.dpdk.org/project/dpdk/list/?series=37585&state=*
> [2] https://patches.dpdk.org/project/dpdk/list/?series=37663&state=*
> 
> Anatoly Burakov (21):
>   ethdev: add flow graph API
>   net/intel/common: add flow engines infrastructure
>   net/intel/common: add utility functions
>   net/ixgbe: add support for common flow parsing
>   net/ixgbe: reimplement ethertype parser
>   net/ixgbe: reimplement syn parser
>   net/ixgbe: reimplement L2 tunnel parser
>   net/ixgbe: reimplement ntuple parser
>   net/ixgbe: reimplement security parser
>   net/ixgbe: reimplement FDIR parser
>   net/ixgbe: reimplement hash parser
>   net/i40e: add support for common flow parsing
>   net/i40e: reimplement ethertype parser
>   net/i40e: reimplement FDIR parser
>   net/i40e: reimplement tunnel QinQ parser
>   net/i40e: reimplement VXLAN parser
>   net/i40e: reimplement NVGRE parser
>   net/i40e: reimplement MPLS parser
>   net/i40e: reimplement gtp parser
>   net/i40e: reimplement L4 cloud parser
>   net/i40e: reimplement hash parser
> 
>  drivers/net/intel/common/flow_engine.h        | 1003 ++++
>  drivers/net/intel/common/flow_util.h          |  165 +
>  drivers/net/intel/i40e/i40e_ethdev.c          |   56 +-
>  drivers/net/intel/i40e/i40e_ethdev.h          |   49 +-
>  drivers/net/intel/i40e/i40e_fdir.c            |   47 -
>  drivers/net/intel/i40e/i40e_flow.c            | 4092 +----------------
>  drivers/net/intel/i40e/i40e_flow.h            |   44 +
>  drivers/net/intel/i40e/i40e_flow_ethertype.c  |  258 ++
>  drivers/net/intel/i40e/i40e_flow_fdir.c       | 1806 ++++++++
>  drivers/net/intel/i40e/i40e_flow_hash.c       | 1289 ++++++
>  drivers/net/intel/i40e/i40e_flow_tunnel.c     | 1510 ++++++
>  drivers/net/intel/i40e/i40e_hash.c            |  980 +---
>  drivers/net/intel/i40e/i40e_hash.h            |    8 +-
>  drivers/net/intel/i40e/meson.build            |    4 +
>  drivers/net/intel/ixgbe/ixgbe_ethdev.c        |   40 +-
>  drivers/net/intel/ixgbe/ixgbe_ethdev.h        |   13 +-
>  drivers/net/intel/ixgbe/ixgbe_fdir.c          |   13 +-
>  drivers/net/intel/ixgbe/ixgbe_flow.c          | 3130 +------------
>  drivers/net/intel/ixgbe/ixgbe_flow.h          |   38 +
>  .../net/intel/ixgbe/ixgbe_flow_ethertype.c    |  240 +
>  drivers/net/intel/ixgbe/ixgbe_flow_fdir.c     | 1510 ++++++
>  drivers/net/intel/ixgbe/ixgbe_flow_hash.c     |  182 +
>  drivers/net/intel/ixgbe/ixgbe_flow_l2tun.c    |  228 +
>  drivers/net/intel/ixgbe/ixgbe_flow_ntuple.c   |  483 ++
>  drivers/net/intel/ixgbe/ixgbe_flow_security.c |  297 ++
>  drivers/net/intel/ixgbe/ixgbe_flow_syn.c      |  280 ++
>  drivers/net/intel/ixgbe/meson.build           |    7 +
>  lib/ethdev/meson.build                        |    1 +
>  lib/ethdev/rte_flow_graph.h                   |  414 ++
>  29 files changed, 9867 insertions(+), 8320 deletions(-)
>  create mode 100644 drivers/net/intel/common/flow_engine.h
>  create mode 100644 drivers/net/intel/common/flow_util.h
>  create mode 100644 drivers/net/intel/i40e/i40e_flow.h
>  create mode 100644 drivers/net/intel/i40e/i40e_flow_ethertype.c
>  create mode 100644 drivers/net/intel/i40e/i40e_flow_fdir.c
>  create mode 100644 drivers/net/intel/i40e/i40e_flow_hash.c
>  create mode 100644 drivers/net/intel/i40e/i40e_flow_tunnel.c
>  create mode 100644 drivers/net/intel/ixgbe/ixgbe_flow.h
>  create mode 100644 drivers/net/intel/ixgbe/ixgbe_flow_ethertype.c
>  create mode 100644 drivers/net/intel/ixgbe/ixgbe_flow_fdir.c
>  create mode 100644 drivers/net/intel/ixgbe/ixgbe_flow_hash.c
>  create mode 100644 drivers/net/intel/ixgbe/ixgbe_flow_l2tun.c
>  create mode 100644 drivers/net/intel/ixgbe/ixgbe_flow_ntuple.c
>  create mode 100644 drivers/net/intel/ixgbe/ixgbe_flow_security.c
>  create mode 100644 drivers/net/intel/ixgbe/ixgbe_flow_syn.c
>  create mode 100644 lib/ethdev/rte_flow_graph.h
> 

Detailed AI review found some issues here.

Review: [RFC PATCH v1 00/21] Intel flow parser rework (flow graph + engine framework)

No Reviewed-by: a functional bug remains (see patch 02).

Patch 02/21 - net/intel/common: add flow engines (flow_engine.h)

Error: created flows are never tracked; destroy corrupts memory, flush/reset leak.
  ci_flow_create() allocates, parses, installs, and returns a flow but never links
  it into engine_conf->flows. The series has TAILQ_INIT + 3x TAILQ_REMOVE + 2x
  FOREACH over that list, but no TAILQ_INSERT into it anywhere. Once an engine is
  registered:
    - ci_flow_destroy() runs TAILQ_REMOVE on a node never inserted. ci_flow_alloc()
      zeroes the ci_flow header, so node.tqe_prev == NULL, and TAILQ_REMOVE's
      "*(elm)->field.tqe_prev = ..." is a NULL-pointer write -> crash/corruption on
      first rule destroy.
    - ci_flow_flush() and ci_flow_engine_conf_reset() iterate an always-empty list,
      so created rules are never uninstalled from HW and are leaked (incl. at close).
  Fix: on the success path in ci_flow_create(), before goto unlock:
      TAILQ_INSERT_TAIL(&engine_conf->flows, flow, node);

Info: ci_flow_engine_conf_reset() calls ci_flow_free(engine, flow) without the
  "if (engine == NULL) continue;" guard that ci_flow_flush() has; ci_flow_free()
  dereferences engine->ops. Unreachable today (list always empty) but inconsistent.

Patch 01/21 - ethdev: add flow graph API (rte_flow_graph.h)

Warning: __rte_internal is applied to six static inline functions. That macro is a
  symbol-visibility attribute for exported (non-inline) symbols; on static inline it
  is meaningless and, without ALLOW_INTERNAL_API, expands to
  __attribute__((error("Symbol is not public ABI"))). Verified against current main:
  a TU including the header and calling rte_flow_graph_parse() fails at -O0 without
  ALLOW_INTERNAL_API ("Symbol is not public ABI", x8); clean with it. In-tree drivers
  set the flag so CI passes, but the header ships in driver_sdk_headers and the
  section(".text.internal") placement is still wrong. Also applied inconsistently
  (the two constraint helpers omit it). Recommend dropping __rte_internal from the
  inlines.

Warning: doc references nonexistent macro. struct rte_flow_graph_edge comment and the
  next field comment say "terminated by RTE_FLOW_EDGE_END"; the defined sentinel is
  RTE_FLOW_NODE_EDGE_END.

Info: rte_flow_graph_parse() visits node[0] with item == NULL. If a driver gives
  node[0] constraints or a validate/process callback, __flow_graph_node_is_expected()
  dereferences item->spec (NULL) or passes NULL to the callback. Default empty graph
  is safe; the "node[0] is a bare start node" contract is implicit - document/guard.

Design (RFC-level): both the graph (per-node validate/process fn-pointers) and
  ci_flow_engine_ops (13 callbacks) are callback-table frameworks. The header aims to
  avoid a "driver-within-a-driver framework" - worth confirming the callback surface
  is minimal (e.g. optional ctx_validate, separate flow_alloc/flow_free) before the
  non-RFC spin.