[v5,1/2] ethdev: introduce generic modify rte flow action

diff --git a/doc/guides/prog_guide/rte_flow.rst b/doc/guides/prog_guide/rte_flow.rst
index 86b3444803..3b1babd587 100644
--- a/doc/guides/prog_guide/rte_flow.rst
+++ b/doc/guides/prog_guide/rte_flow.rst
@@ -2766,6 +2766,71 @@  The behaviour of the shared action defined by ``action`` argument of type
    | no properties |
    +---------------+
 
+Action: ``MODIFY_FIELD``
+^^^^^^^^^^^^^^^^^^^^^^^^
+
+Modify ``dst`` field according to ``op`` selected (move, addition,
+substraction) with ``width`` bits of data from ``src`` field.
+
+Any arbitrary header field (as well as mark, metadata or tag values)
+can be used as both source and destination fields as set by ``field``.
+The immediate value ``RTE_FLOW_FIELD_VALUE`` (or a pointer to it
+``RTE_FLOW_FIELD_POINTER``) is allowed as a source only.
+``RTE_FLOW_FIELD_START`` is used to point to the beginning of a packet.
+
+``op`` selects the operation to perform on a destination field.
+- ``mov`` copies the data from ``src`` field to ``dst`` field.
+- ``add`` adds together ``dst`` and ``src`` and stores the result into ``dst``.
+- ``sub`` substracts ``src`` from ``dst`` and stores the result into ``dst``
+
+ ``width`` defines a number of bits to use from ``src`` field.
+
+ ``level`` is used to access any packet field on any encapsulation level
+ as well as any tag element in the tag array.
+- ``0`` means the default behaviour. Depending on the packet type, it can
+  mean outermost, innermost or anything in between.
+- ``1`` requests access to the outermost packet encapsulation level.
+- ``2`` and subsequent values requests access to the specified packet
+  encapsulation level, from outermost to innermost (lower to higher values).
+  For the tag array ``level`` translates directly into the array index.
+
+``offset`` specifies the number of bits to skip from a field's start.
+That allows performing a partial copy of the needed part or to divide a big
+packet field into multiple smaller fields. Alternatively, ``offset`` allows
+going past the specified packet field boundary to copy a field to an
+arbitrary place in a packet, essentially providing a way to copy any part of
+a packet to any other part of it if supported by an underlying PMD driver.
+
+``value`` sets an immediate value to be used as a source or points to a
+location of the value in memory. It is used instead of ``level`` and ``offset``
+for ``RTE_FLOW_FIELD_VALUE`` and ``RTE_FLOW_FIELD_POINTER`` respectively.
+
+.. _table_rte_flow_action_modify_field:
+
+.. table:: MODIFY_FIELD
+
+   +-----------------------------------------+
+   | Field         | Value                   |
+   +===============+=========================+
+   | ``op``        | operation to perform    |
+   | ``dst``       | destination field       |
+   | ``src``       | source field            |
+   | ``width``     | number of bits to use   |
+   +---------------+-------------------------+
+
+.. _table_rte_flow_action_modify_data:
+
+.. table:: destination/source field definition
+
+   +--------------------------------------------------------------------------+
+   | Field         | Value                                                    |
+   +===============+==========================================================+
+   | ``field``     | ID: packet field, mark, meta, tag, immediate, pointer    |
+   | ``level``     | encapsulation level of a packet field or tag array index |
+   | ``offset``    | number of bits to skip at the beginning                  |
+   | ``value``     | immediate value or a poiner to it                        |
+   +---------------+----------------------------------------------------------+
+
 Negative types
 ~~~~~~~~~~~~~~
 
diff --git a/doc/guides/rel_notes/release_21_02.rst b/doc/guides/rel_notes/release_21_02.rst
index c64294e7a6..fc828cb21d 100644
--- a/doc/guides/rel_notes/release_21_02.rst
+++ b/doc/guides/rel_notes/release_21_02.rst
@@ -55,6 +55,14 @@  New Features
      Also, make sure to start the actual text at the margin.
      =======================================================
 
+* **Added support of modify field action in the flow API.**
+
+  Added modify action support to perform various operations on
+  any arbitrary header field (as well as mark, metadata or tag values):
+  ``RTE_FLOW_ACTION_TYPE_MODIFY_FIELD``.
+  supported operations are: overwriting the field with the content from
+  another field, addition and subtraction of an immediate value.
+
 * **Updated Broadcom bnxt driver.**
 
   Updated the Broadcom bnxt driver with fixes and improvements, including:
diff --git a/lib/librte_ethdev/rte_flow.c b/lib/librte_ethdev/rte_flow.c
index a06f64c271..9dd051f3c2 100644
--- a/lib/librte_ethdev/rte_flow.c
+++ b/lib/librte_ethdev/rte_flow.c
@@ -176,6 +176,8 @@  static const struct rte_flow_desc_data rte_flow_desc_action[] = {
 	MK_FLOW_ACTION(SET_IPV6_DSCP, sizeof(struct rte_flow_action_set_dscp)),
 	MK_FLOW_ACTION(AGE, sizeof(struct rte_flow_action_age)),
 	MK_FLOW_ACTION(SAMPLE, sizeof(struct rte_flow_action_sample)),
+	MK_FLOW_ACTION(MODIFY_FIELD,
+		       sizeof(struct rte_flow_action_modify_field)),
 	/**
 	 * Shared action represented as handle of type
 	 * (struct rte_flow_shared action *) stored in conf field (see
diff --git a/lib/librte_ethdev/rte_flow.h b/lib/librte_ethdev/rte_flow.h
index 0977a78270..6610e638d7 100644
--- a/lib/librte_ethdev/rte_flow.h
+++ b/lib/librte_ethdev/rte_flow.h
@@ -2198,6 +2198,17 @@  enum rte_flow_action_type {
 	 * struct rte_flow_shared_action).
 	 */
 	RTE_FLOW_ACTION_TYPE_SHARED,
+
+	/**
+	 * Modify a packet header field, tag, mark or metadata.
+	 *
+	 * Allow the modification of an arbitrary header field via
+	 * set, add and sub operations or copying its content into
+	 * tag, meta or mark for future processing.
+	 *
+	 * See struct rte_flow_action_modify_field.
+	 */
+	RTE_FLOW_ACTION_TYPE_MODIFY_FIELD,
 };
 
 /**
@@ -2777,7 +2788,6 @@  struct rte_flow_action_set_dscp {
 	uint8_t dscp;
 };
 
-
 /**
  * RTE_FLOW_ACTION_TYPE_SHARED
  *
@@ -2791,6 +2801,73 @@  struct rte_flow_action_set_dscp {
  */
 struct rte_flow_shared_action;
 
+enum rte_flow_field_id {
+	RTE_FLOW_FIELD_START = 0,
+	RTE_FLOW_FIELD_MAC_DST,
+	RTE_FLOW_FIELD_MAC_SRC,
+	RTE_FLOW_FIELD_VLAN_TYPE,
+	RTE_FLOW_FIELD_VLAN_ID,
+	RTE_FLOW_FIELD_MAC_TYPE,
+	RTE_FLOW_FIELD_IPV4_DSCP,
+	RTE_FLOW_FIELD_IPV4_TTL,
+	RTE_FLOW_FIELD_IPV4_SRC,
+	RTE_FLOW_FIELD_IPV4_DST,
+	RTE_FLOW_FIELD_IPV6_HOPLIMIT,
+	RTE_FLOW_FIELD_IPV6_SRC,
+	RTE_FLOW_FIELD_IPV6_DST,
+	RTE_FLOW_FIELD_TCP_PORT_SRC,
+	RTE_FLOW_FIELD_TCP_PORT_DST,
+	RTE_FLOW_FIELD_TCP_SEQ_NUM,
+	RTE_FLOW_FIELD_TCP_ACK_NUM,
+	RTE_FLOW_FIELD_TCP_FLAGS,
+	RTE_FLOW_FIELD_UDP_PORT_SRC,
+	RTE_FLOW_FIELD_UDP_PORT_DST,
+	RTE_FLOW_FIELD_VXLAN_VNI,
+	RTE_FLOW_FIELD_GENEVE_VNI,
+	RTE_FLOW_FIELD_GTP_TEID,
+	RTE_FLOW_FIELD_TAG,
+	RTE_FLOW_FIELD_MARK,
+	RTE_FLOW_FIELD_META,
+	RTE_FLOW_FIELD_POINTER,
+	RTE_FLOW_FIELD_VALUE,
+};
+
+struct rte_flow_action_modify_data {
+	enum rte_flow_field_id field;
+	RTE_STD_C11
+	union {
+		struct {
+			uint32_t level;
+			uint32_t offset;
+		};
+		uint64_t value;
+	};
+};
+
+enum rte_flow_modify_op {
+	RTE_FLOW_MODIFY_MOV = 0,
+	RTE_FLOW_MODIFY_ADD,
+	RTE_FLOW_MODIFY_SUB,
+};
+
+/**
+ * @warning
+ * @b EXPERIMENTAL: this structure may change without prior notice
+ *
+ * RTE_FLOW_ACTION_TYPE_MODIFY_FIELD
+ *
+ * Modifies a destination header field according to the specified
+ * operation. Another packet field can be used as a source as well
+ * as tag, mark, metadata or an immediate value or a pointer to it.
+ * Width is the number of bits used from the source item.
+ */
+struct rte_flow_action_modify_field {
+	enum rte_flow_modify_op operation;
+	struct rte_flow_action_modify_data dst;
+	struct rte_flow_action_modify_data src;
+	uint32_t width;
+};
+
 /* Mbuf dynamic field offset for metadata. */
 extern int32_t rte_flow_dynf_metadata_offs;