[dpdk-dev] [RFC] ethdev: introduce configurable flexible item

[Viacheslav Ovsiienko <viacheslavo@nvidia.com>]

1. Introduction and Retrospective

Nowadays the networks are evolving fast and wide, the network
structures are getting more and more complicated, the new
application areas are emerging. To address these challenges
the new network protocols are continuously being developed,
considered by technical communities, adopted by industry and,
eventually implemented in hardware and software. The DPDK
framework follows the common trends and if we bother
to glance at the RTE Flow API header we see the multiple
new items were introduced during the last years since
the initial release.

The new protocol adoption and implementation process is
not straightforward and takes time, the new protocol passes
development, consideration, adoption, and implementation
phases. The industry tries to mitigate and address the
forthcoming network protocols, for example, many hardware
vendors are implementing flexible and configurable network
protocol parsers. As DPDK developers, could we anticipate
the near future in the same fashion and introduce the similar
flexibility in RTE Flow API?

Let's check what we already have merged in our project, and
we see the nice raw item (rte_flow_item_raw). At the first
glance, it looks superior and we can try to implement a flow
matching on the header of some relatively new tunnel protocol,
say on the GENEVE header with variable length options. And,
under further consideration, we run into the raw item
limitations:

- only fixed size network header can be represented
- the entire network header pattern of fixed format
  (header field offsets are fixed) must be provided
- the search for patterns is not robust (the wrong matches
  might be triggered), and actually is not supported
  by existing PMDs
- no explicitly specified relations with preceding
  and following items
- no tunnel hint support

As the result, implementing the support for tunnel protocols
like aforementioned GENEVE with variable extra protocol option
with flow raw item becomes very complicated and would require
multiple flows and multiple raw items chained in the same
flow (by the way, there is no support found for chained raw
items in implemented drivers).

This RFC introduces the dedicated flex item (rte_flow_item_flex)
to handle matches with existing and new network protocol headers
in a unified fashion.

2. Flex Item Lifecycle

Let's assume there are the requirements to support the new
network protocol with RTE Flows. What is given within protocol
specification:

  - header format
  - header length, (can be variable, depending on options)
  - potential presence of extra options following or included
    in the header the header
  - the relations with preceding protocols. For example,
    the GENEVE follows UDP, eCPRI can follow either UDP
    or L2 header
  - the relations with following protocols. For example,
    the next layer after tunnel header can be L2 or L3
  - whether the new protocol is a tunnel and the header
    is a splitting point between outer and inner layers

The supposed way to operate with flex item:

  - application defines the header structures according to
    protocol specification

  - application calls rte_flow_flex_item_create() with desired
    configuration according to the protocol specification, it
    creates the flex item object over specified ethernet device
    and prepares PMD and underlying hardware to handle flex
    item. On item creation call PMD backing the specified
    ethernet device returns the opaque handle identifying
    the object have been created

  - application uses the rte_flow_item_flex with obtained handle
    in the flows, the values/masks to match with fields in the
    header are specified in the flex item per flow as for regular
    items (except that pattern buffer combines all fields)

  - flows with flex items match with packets in a regular fashion,
    the values and masks for the new protocol header match are
    taken from the flex items in the flows

  - application destroys flows with flex items

  - application calls rte_flow_flex_item_release() as part of
    ethernet device API and destroys the flex item object in
    PMD and releases the engaged hardware resources

3. Flex Item Structure

The flex item structure is intended to be used as part of the flow
pattern like regular RTE flow items and provides the mask and
value to match with fields of the protocol item was configured
for.

  struct rte_flow_item_flex {
    void *handle;
    uint32_t length;
    const uint8_t* pattern;
  };

The handle is some opaque object maintained on per device basis
by underlying driver.

The protocol header fields are considered as bit fields, all
offsets and widths are expressed in bits. The pattern is the
buffer containing the bit concatenation of all the fields
presented at item configuration time, in the same order and
same amount. If byte boundary alignment is needed an application
can use a dummy type field, this is just some kind of gap filler.

The length field specifies the pattern buffer length in bytes
and is needed to allow rte_flow_copy() operations. The approach
of multiple pattern pointers and lengths (per field) was
considered and found clumsy - it seems to be much suitable for
the application to maintain the single structure within the
sinlge pattern buffer.

4. Flex Item Configuration

The flex item configuration consists of the following parts:

  - header field descriptors:
    - next header
    - next protocol
    - sample to match
  - input link descriptors
  - output link descriptors

The field descriptors tell driver and hardware what data should
be extracted from the packet and then presented to match in the
flows. Each field is a bit pattern. It has width, offset from
the header beginning, mode of offset calculation, and offset
related parameters.

The next header field is special, no data are actually taken
from the packet, but its offset is used as pointer to the next
header in the packet, in other word the next header offset
specifies the size of the header being parsed by flex item.

There is one more special field - next protocol, it specifies
where the next protocol identifier is contained and packet data
sampled from this field will be used to determine the next
protocol header type to continue packet pasring. The next
protocol field is like eth_type field in MAC2, or proto field
in IPv4/v6 headers.

The sample fields are used to represent the data be sampled
from the packet and then matched with established flows.

There are several methods supposed to calculate field offset
in runtime depending on configuration and packet content:

  - FIELD_MODE_FIXED - fixed offset. The bit offset from
    header beginning is permanent and defined by field_base
    configuration parameter.

  - FIELD_MODE_OFFSET - the field bit offset is extracted
    from other header field (indirect offset field). The
    resulting field offset to match is calculated from as:

  field_base + (*field_offset & offset_mask) << field_shift

    This mode is useful to sample some extra options following
    the main header with field containing main header length.
    Also, this mode can be used to calculate offset to the
    next protocol header, for example - IPv4 header contains
    the 4-bit field with IPv4 header length expressed in dwords.
    One more example - this mode would allow us to skip GENEVE
    header variable length options.

  - FIELD_MODE_BITMASK - the field bit offset is extracted
    from other header field (indirect offset field), the latter
    is considered as bitmask containing some number of one bits,
    the resulting field offset to match is calculated as:

  field_base + bitcount(*field_offset & offset_mask) << field_shift

    This mode would be useful to skip the GTP header and its
    extra options with specified flags.

  - FIELD_MODE_DUMMY - dummy field, optionally used for byte
    boundary alignment in pattern. Pattern mask and data are
    ignored in the match. All configuration parameters besides
    field size are ignored.

The offset mode list can be extended by vendors according to
hardware supported options.

Signed-off-by: Viacheslav Ovsiienko <viacheslavo@nvidia.com>
---
 lib/ethdev/rte_flow.h | 218 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 218 insertions(+)

diff --git a/lib/ethdev/rte_flow.h b/lib/ethdev/rte_flow.h
index 70f455d47d..589fe513bf 100644
--- a/lib/ethdev/rte_flow.h
+++ b/lib/ethdev/rte_flow.h
@@ -573,6 +573,15 @@ enum rte_flow_item_type {
 	 * @see struct rte_flow_item_conntrack.
 	 */
 	RTE_FLOW_ITEM_TYPE_CONNTRACK,
+
+	/**
+	 * Matches a configured set of fields at runtime calculated offsets
+	 * over the generic network header with variable length and
+	 * flexible pattern
+	 *
+	 * See struct rte_flow_item_flex.
+	 */
+	RTE_FLOW_ITEM_TYPE_FLEX,
 };
 
 /**
@@ -1839,6 +1848,150 @@ struct rte_flow_item {
 	const void *mask; /**< Bit-mask applied to spec and last. */
 };
 
+/**
+ * @warning
+ * @b EXPERIMENTAL: this structure may change without prior notice
+ *
+ * RTE_FLOW_ITEM_TYPE_FLEX
+ *
+ * Matches a specified set of fields within the network protocol
+ * header. Each field is presented as set of bits with specified width, and
+ * bit offset (this is dynamic one - can be calulated by several methods
+ * in runtime) from the header beginning.
+ *
+ * The pattern is concatenation of all bit fields configured at item creation
+ * by rte_flow_flex_item_create() exactly in the same order and amount, no
+ * fields can be omitted or swapped. The dummy mode field can be used for
+ * pattern byte boundary alignment, least significant bit in byte goes first.
+ * Only the fields specified in sample_data configuration parameter participate
+ * in pattern construction.
+ *
+ * If pattern length is smaller than configured fields overall length it is
+ * extended with trailing zeroes, both for value and mask.
+ *
+ * This type does not support ranges (struct rte_flow_item.last).
+ */
+struct rte_flow_item_flex {
+	struct rte_flow_item_flex_handle *handle; /**< Opaque item handle. */
+	uint32_t length; /**< Pattern length in bytes. */
+	const uint8_t *pattern; /**< Combined bitfields pattern to match. */
+};
+
+/**
+ * Field bit offset calculation mode.
+ */
+enum rte_flow_item_flex_field_mode {
+	/**
+	 * Dummy field, used for byte boundary alignment in pattern.
+	 * Pattern mask and data are ignored in the match. All configuration
+	 * parameters besides field size are ignored.
+	 */
+	FIELD_MODE_DUMMY = 0,
+	/**
+	 * Fixed offset field. The bit offset from header beginning is
+	 * is permanent and defined by field_base parameter.
+	 */
+	FIELD_MODE_FIXED,
+	/**
+	 * The field bit offset is extracted from other header field (indirect
+	 * offset field). The resulting field offset to match is calculated as:
+	 *
+	 *    field_base + (*field_offset & offset_mask) << field_shift
+	 */
+	FIELD_MODE_OFFSET,
+	/**
+	 * The field bit offset is extracted from other header field (indirect
+	 * offset field), the latter is considered as bitmask containing some
+	 * number of one bits, the resulting field offset to match is
+	 * calculated as:
+	 *
+	 *    field_base + bitcount(*field_offset & offset_mask) << field_shift
+	 */
+	FIELD_MODE_BITMASK,
+};
+
+/**
+ * @warning
+ * @b EXPERIMENTAL: this structure may change without prior notice
+ */
+struct rte_flow_item_flex_field {
+	/** Defines how match field offset is calculated over the packet. */
+	enum rte_flow_item_flex_field_mode field_mode;
+	uint32_t field_size; /**< Match field size in bits. */
+	int32_t field_base; /**< Match field offset in bits. */
+	uint32_t offset_base; /**< Indirect offset field offset in bits. */
+	uint32_t offset_mask; /**< Indirect offset field bit mask. */
+	int32_t offset_shift; /**< Indirect offset multiply factor. */
+	uint32_t tunnel_count; /**< 0-first occurrence, 1-outer, 2-inner.*/
+	uint32_t field_id; /**< device hint, for flows with multiple items. */
+};
+
+/**
+ * @warning
+ * @b EXPERIMENTAL: this structure may change without prior notice
+ */
+struct rte_flow_item_flex_link {
+	/**
+	 * Preceding/following header. The item type must be always provided.
+	 * For preceding one item must specify the header value/mask to match
+	 * for the link be taken and start the flex item header parsing.
+	 */
+	struct rte_flow_item item;
+	/**
+	 * Next field value to match to continue with one of the configured
+	 * next protocols.
+	 */
+	uint32_t next;
+	/**
+	 * Specifies whether flex item represents tunnel protocol
+	 */
+	bool tunnel;
+};
+
+/**
+ * @warning
+ * @b EXPERIMENTAL: this structure may change without prior notice
+ */
+struct rte_flow_item_flex_conf {
+	/**
+	 * The next header offset, it presents the network header size covered
+	 * by the flex item and can be obtained with all supported offset
+	 * calculating methods (fixed, dedicated field, bitmask, etc).
+	 */
+	struct rte_flow_item_flex_field *next_header;
+	/**
+	 * Specifies the next protocol field to match with link next protocol
+	 * values and continue packet parsing with matching link.
+	 */
+	struct rte_flow_item_flex_field *next_protocol;
+	/**
+	 * The fields will be sampled and presented for explicit match
+	 * with pattern in the rte_flow_flex_item. There can be multiple
+	 * fields descriptors, the number should be specified by sample_num.
+	 */
+	struct rte_flow_item_flex_field *sample_data;
+	/** Number of field descriptors in the sample_data array. */
+	uint32_t sample_num;
+	/**
+	 * Input link defines the flex item relation with preceding
+	 * header. It specified the preceding item type and provides pattern
+	 * to match. The flex item will continue parsing and will provide the
+	 * data to flow match in case if there is the match with one of input
+	 * links.
+	 */
+	struct rte_flow_item_flex_link *input_link;
+	/** Number of link descriptors in the input link array. */
+	uint32_t input_num;
+	/**
+	 * Output link defines the next protocol field value to match and
+	 * the following protocol header to continue packet parsing. Also
+	 * defines the tunnel-related behaviour.
+	 */
+	struct rte_flow_item_flex_link *output_link;
+	/** Number of link descriptors in the output link array. */
+	uint32_t output_num;
+};
+
 /**
  * Action types.
  *
@@ -4288,6 +4441,71 @@ rte_flow_tunnel_item_release(uint16_t port_id,
 			     struct rte_flow_item *items,
 			     uint32_t num_of_items,
 			     struct rte_flow_error *error);
+
+/**
+ * Create the flex item with specified configuration over
+ * the Ethernet device.
+ *
+ * @param port_id
+ *   Port identifier of Ethernet device.
+ * @param[in] conf
+ *   Item configuration.
+ * @param[out] error
+ *   Perform verbose error reporting if not NULL. PMDs initialize this
+ *   structure in case of error only.
+ *
+ * @return
+ *   Non-NULL opaque pointer on success, NULL otherwise and rte_errno is set.
+ */
+__rte_experimental
+struct rte_flow_item_flex_handle *
+rte_flow_flex_item_create(uint16_t port_id,
+			  const struct rte_flow_item_flex_conf *conf,
+			  struct rte_flow_error error);
+
+/**
+ * Release the flex item on the specified Ethernet device.
+ *
+ * @param port_id
+ *   Port identifier of Ethernet device.
+ * @param[in] handle
+ *   Handle of the item existing on the specified device.
+ * @param[out] error
+ *   Perform verbose error reporting if not NULL. PMDs initialize this
+ *   structure in case of error only.
+ *
+ * @return
+ *   0 on success, a negative errno value otherwise and rte_errno is set.
+ */
+__rte_experimental
+int
+rte_flow_flex_item_release(uint16_t port_id,
+			   const struct rte_flow_item_flex_handle *handle,
+			   struct rte_flow_error error);
+
+/**
+ * Modify the flex item on the specified Ethernet device.
+ *
+ * @param port_id
+ *   Port identifier of Ethernet device.
+ * @param[in] handle
+ *   Handle of the item existing on the specified device.
+ * @param[in] conf
+ *   Item new configuration.
+ * @param[out] error
+ *   Perform verbose error reporting if not NULL. PMDs initialize this
+ *   structure in case of error only.
+ *
+ * @return
+ *   0 on success, a negative errno value otherwise and rte_errno is set.
+ */
+__rte_experimental
+int
+rte_flow_flex_item_update(uint16_t port_id,
+			  const struct rte_flow_item_flex_handle *handle,
+			  const struct rte_flow_item_flex_conf *conf,
+			  struct rte_flow_error error);
+
 #ifdef __cplusplus
 }
 #endif
-- 
2.18.1