[PATCH v2 11/22] doc: add PDCP library guide

[Anoob Joseph <anoobj@marvell.com>]

Add guide for PDCP library.

Signed-off-by: Anoob Joseph <anoobj@marvell.com>
Signed-off-by: Kiran Kumar K <kirankumark@marvell.com>
Signed-off-by: Volodymyr Fialko <vfialko@marvell.com>
---
 .../img/pdcp_functional_overview.svg          |   1 +
 doc/guides/prog_guide/index.rst               |   1 +
 doc/guides/prog_guide/pdcp_lib.rst            | 246 ++++++++++++++++++
 3 files changed, 248 insertions(+)
 create mode 100644 doc/guides/prog_guide/img/pdcp_functional_overview.svg
 create mode 100644 doc/guides/prog_guide/pdcp_lib.rst

diff --git a/doc/guides/prog_guide/img/pdcp_functional_overview.svg b/doc/guides/prog_guide/img/pdcp_functional_overview.svg
new file mode 100644
index 0000000000..287daafc21
--- /dev/null
+++ b/doc/guides/prog_guide/img/pdcp_functional_overview.svg
@@ -0,0 +1 @@
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fill="none" fill-rule="evenodd"/><path d="M331.5 71.5001C331.5 65.9772 349.633 61.5001 372 61.5001 394.368 61.5001 412.5 65.9772 412.5 71.5001 412.5 77.0229 394.368 81.5001 372 81.5001 349.633 81.5001 331.5 77.0229 331.5 71.5001Z" stroke="#000000" stroke-width="1.33333" stroke-miterlimit="8" fill="#FFFFFF" fill-rule="evenodd"/><path d="M353.5 90.5001 363.5 90.5001 363.5 48.5001 383.5 48.5001 383.5 90.5001 393.5 90.5001 373.5 110.5Z" stroke="#000000" stroke-width="1.33333" stroke-miterlimit="8" fill="#FFFFFF" fill-rule="evenodd"/><path d="M877.364 82.6549 760.5 82.5001" stroke="#000000" stroke-width="0.666667" stroke-miterlimit="8" fill="none" fill-rule="evenodd"/><path d="M860.5 83.5001C860.5 89.0229 842.368 93.5001 820 93.5001 797.633 93.5001 779.5 89.0229 779.5 83.5001 779.5 77.9772 797.633 73.5001 820 73.5001 842.368 73.5001 860.5 77.9772 860.5 83.5001Z" stroke="#000000" stroke-width="1.33333" stroke-miterlimit="8" fill="#FFFFFF" fill-rule="evenodd"/><path d="M838.5 64.5 828.5 64.5 828.5 106.5 808.5 106.5 808.5 64.5 798.5 64.5 818.5 44.5001Z" stroke="#000000" stroke-width="1.33333" stroke-miterlimit="8" fill="#FFFFFF" fill-rule="evenodd"/><rect x="244.5" y="128.5" width="285" height="55" stroke="#000000" stroke-width="1.33333" stroke-miterlimit="8" fill="#FFFFFF"/><text font-family="Arial,Arial_MSFontService,sans-serif" font-weight="400" font-size="19" transform="translate(302.494 150)">Transmission buffer:<tspan font-size="19" x="-4.67999" y="23">Sequence</tspan><tspan font-size="19" x="84.32" y="23">numberin</tspan>g</text><rect x="244.5" y="199.5" width="285" height="55" stroke="#000000" stroke-width="1.33333" stroke-miterlimit="8" fill="#FFFFFF"/><text font-family="Arial,Arial_MSFontService,sans-serif" font-weight="400" font-size="19" transform="translate(297.314 222)">Header or uplink data<tspan font-size="19" x="34.08" y="23">Compressio</tspan>n</text><rect x="682.5" y="141.5" width="285" height="55" stroke="#000000" stroke-width="1.33333" stroke-miterlimit="8" fill="#FFFFFF"/><text font-family="Arial,Arial_MSFontService,sans-serif" font-weight="400" font-size="19" transform="translate(735.782 164)">Header or uplink data<tspan font-size="19" x="24.2466" y="23">Decompressio</tspan>n</text><rect x="244.5" y="482.5" width="285" height="33" stroke="#000000" stroke-width="1.33333" stroke-miterlimit="8" fill="#FFFFFF"/><text font-family="Arial,Arial_MSFontService,sans-serif" font-weight="400" font-size="19" transform="translate(300.314 505)">Routing / Duplication</text><rect x="244.5" y="437.5" width="285" height="32" stroke="#000000" stroke-width="1.33333" stroke-miterlimit="8" fill="#FFFFFF"/><text font-family="Arial,Arial_MSFontService,sans-serif" font-weight="400" font-size="19" transform="translate(309.734 460)">Add PDCP header</text><rect x="244.5" y="383.5" width="189" height="33" stroke="#000000" stroke-width="1.33333" stroke-miterlimit="8" fill="#FFFFFF"/><text font-family="Arial,Arial_MSFontService,sans-serif" font-weight="400" font-size="19" transform="translate(298.62 406)">Ciphering</text><rect x="244.5" y="333.5" width="189" height="32" stroke="#000000" stroke-width="1.33333" stroke-miterlimit="8" fill="#FFFFFF"/><text font-family="Arial,Arial_MSFontService,sans-serif" font-weight="400" font-size="19" transform="translate(261.953 356)">Integrity protection</text><path d="M472.167 267.5 472.167 409.802 470.833 409.802 470.833 267.5ZM475.5 408.468 471.5 416.468 467.5 408.468Z"/><path d="M332.167 267.5 332.167 319.552 330.833 319.552 330.833 267.5ZM335.5 318.218 331.5 326.218 327.5 318.219Z"/><text font-family="Arial,Arial_MSFontService,sans-serif" font-weight="400" font-size="19" transform="translate(253.644 291)">Packets associated <tspan font-size="19" x="14.0067" y="23">to a PDCP SDU</tspan></text><text font-family="Arial,Arial_MSFontService,sans-serif" font-weight="400" font-size="19" transform="matrix(6.12323e-17 1 -1 6.12323e-17 499.312 299)">Packets not <tspan font-size="19" x="-14" y="23">associated to a </tspan><tspan font-size="19" x="-2.75546e-15" y="45">PDCP SDU</tspan></text><rect x="682.5" y="482.5" width="285" height="33" stroke="#000000" stroke-width="1.33333" stroke-miterlimit="8" fill="#FFFFFF"/><text font-family="Arial,Arial_MSFontService,sans-serif" font-weight="400" font-size="19" transform="translate(728.535 505)">Remove PDCP Header</text><rect x="682.5" y="437.5" width="203" height="32" stroke="#000000" stroke-width="1.33333" stroke-miterlimit="8" fill="#FFFFFF"/><text font-family="Arial,Arial_MSFontService,sans-serif" font-weight="400" font-size="19" transform="translate(733.729 460)">Deciphering</text><rect x="682.5" y="389.5" width="203" height="33" stroke="#000000" stroke-width="1.33333" stroke-miterlimit="8" fill="#FFFFFF"/><text font-family="Arial,Arial_MSFontService,sans-serif" font-weight="400" font-size="19" transform="translate(702.159 412)">Integrity Verification</text><rect x="682.5" y="303.5" width="203" height="77" stroke="#000000" 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\ No newline at end of file
diff --git a/doc/guides/prog_guide/index.rst b/doc/guides/prog_guide/index.rst
index 87333ee84a..6099ff63cd 100644
--- a/doc/guides/prog_guide/index.rst
+++ b/doc/guides/prog_guide/index.rst
@@ -77,4 +77,5 @@ Programmer's Guide
     lto
     profile_app
     asan
+    pdcp_lib
     glossary
diff --git a/doc/guides/prog_guide/pdcp_lib.rst b/doc/guides/prog_guide/pdcp_lib.rst
new file mode 100644
index 0000000000..abd874f2cc
--- /dev/null
+++ b/doc/guides/prog_guide/pdcp_lib.rst
@@ -0,0 +1,246 @@
+..  SPDX-License-Identifier: BSD-3-Clause
+    Copyright(C) 2023 Marvell.
+
+PDCP Protocol Processing Library
+================================
+
+DPDK provides a library for PDCP protocol processing. The library utilizes
+other DPDK libraries such as cryptodev, reorder, etc., to provide the
+application with a transparent and high performant PDCP protocol processing
+library.
+
+The library abstracts complete PDCP protocol processing conforming to
+``ETSI TS 138 323 V17.1.0 (2022-08)``.
+https://www.etsi.org/deliver/etsi_ts/138300_138399/138323/17.01.00_60/ts_138323v170100p.pdf
+
+PDCP would involve the following operations,
+
+1. Transfer of user plane data
+2. Transfer of control plane data
+3. Header compression
+4. Uplink data compression
+5. Ciphering and integrity protection
+
+.. _figure_pdcp_functional_overview:
+
+.. figure:: img/pdcp_functional_overview.*
+
+   PDCP functional overview new
+
+PDCP library would abstract the protocol offload features of the cryptodev and
+would provide a uniform interface and consistent API usage to work with
+cryptodev irrespective of the protocol offload features supported.
+
+PDCP entity API
+---------------
+
+PDCP library provides following control path APIs that is used to
+configure various PDCP entities,
+
+1. ``rte_pdcp_entity_establish()``
+2. ``rte_pdcp_entity_suspend()``
+3. ``rte_pdcp_entity_release()``
+
+A PDCP entity would translate to one ``rte_cryptodev_sym_session`` or
+``rte_security_session`` based on the config. The sessions would be created/
+destroyed while corresponding PDCP entity operations are performed.
+
+PDCP PDU (Protocol Data Unit)
+-----------------------------
+
+PDCP PDUs can be categorized as,
+
+1. Control PDU
+2. Data PDU
+
+Control PDUs are used for signalling between entities on either end and can be
+one of the following,
+
+1. PDCP status report
+2. ROHC feedback
+3. EHC feedback
+
+Control PDUs are not ciphered or authenticated, and so such packets are not
+submitted to cryptodev for processing.
+
+Data PDUs are regular packets submitted by upper layers for transmission to
+other end. Such packets would need to be ciphered and authenticated based on
+the entity configuration.
+
+PDCP packet processing API for data PDU
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+PDCP processing is split into 2 parts. One before cryptodev processing
+(``rte_pdcp_pkt_pre_process()``) and one after cryptodev processing
+(``rte_pdcp_pkt_post_process()``). Since cryptodev dequeue can return crypto
+operations belonging to multiple entities, ``rte_pdcp_pkt_crypto_group()``
+is added to help grouping crypto operations belonging to same PDCP entity.
+
+Lib PDCP would allow application to use same API sequence while leveraging
+protocol offload features enabled by ``rte_security`` library. Lib PDCP would
+internally change the handles registered for ``pre_process`` and
+``post_process`` based on features enabled in the entity.
+
+Lib PDCP would create the required sessions on the device provided in entity to
+minimize the application requirements. Also, the crypto_op allocation and free
+would also be done internally by lib PDCP to allow the library to create
+crypto ops as required for the input packets. For example, when control PDUs are
+received, no cryptodev enqueue-dequeue is expected for the same and lib PDCP
+is expected to handle it differently.
+
+Sample API usage
+----------------
+
+The ``rte_pdcp_entity_conf`` structure is used to pass the configuration
+parameters for entity creation.
+
+.. literalinclude:: ../../../lib/pdcp/rte_pdcp.h
+   :language: c
+   :start-after: Structure rte_pdcp_entity_conf 8<
+   :end-before: >8 End of structure rte_pdcp_entity_conf.
+
+.. code-block:: c
+
+	struct rte_mbuf **out_mb, *pkts[MAX_BURST_SIZE];
+	struct rte_crypto_op *cop[MAX_BURST_SIZE];
+	struct rte_pdcp_group grp[MAX_BURST_SIZE];
+	struct rte_pdcp_entity *pdcp_entity;
+	int nb_max_out_mb, ret, nb_grp;
+	uint16_t nb_ops;
+
+	/* Create PDCP entity */
+	pdcp_entity = rte_pdcp_entity_establish(&conf);
+
+	/**
+	 * Allocate buffer for holding mbufs returned during PDCP suspend,
+	 * release & post-process APIs.
+	 */
+
+	/* Max packets that can be cached in entity + burst size */
+	nb_max_out_mb = pdcp_entity->max_pkt_cache + MAX_BURST_SIZE;
+	out_mb = rte_malloc(NULL, nb_max_out_mb * sizeof(uintptr_t), 0);
+	if (out_mb == NULL) {
+		/* Handle error */
+	}
+
+	while (1) {
+		/* Receive packet and form mbuf */
+
+		/**
+		 * Prepare packets for crypto operation. Following operations
+		 * would be done,
+		 *
+		 * Transmitting entity/UL (only data PDUs):
+		 *  - Perform compression
+		 *  - Assign sequence number
+		 *  - Add PDCP header
+		 *  - Create & prepare crypto_op
+		 *  - Prepare IV for crypto operation (auth_gen, encrypt)
+		 *  - Save original PDCP SDU (during PDCP re-establishment,
+		 *    unconfirmed PDCP SDUs need to crypto processed again and
+		 *    transmitted/re-transmitted)
+		 *
+		 *  Receiving entity/DL:
+		 *  - Any control PDUs received would be processed and
+		 *    appropriate actions taken. If data PDU, continue.
+		 *  - Determine sequence number (based on HFN & per packet SN)
+		 *  - Prepare crypto_op
+		 *  - Prepare IV for crypto operation (decrypt, auth_verify)
+		 */
+		nb_success = rte_pdcp_pkt_pre_process(pdcp_entity, pkts, cop,
+						      nb_rx, &nb_err);
+		if (nb_err != 0) {
+			/* Handle error packets */
+		}
+
+		if ((rte_cryptodev_enqueue_burst(dev_id, qp_id, cop, nb_success)
+				!= nb_success) {
+			/* Retry for enqueue failure packets */
+		}
+
+		...
+
+		nb_ops = rte_cryptodev_dequeue_burst(dev_id, qp_id, cop,
+						  MAX_BURST_SIZE);
+		if (nb_ops == 0)
+			continue;
+
+		/**
+		 * Received a burst of completed crypto ops from cryptodev. It
+		 * may belong to various entities. Group similar ones together
+		 * for entity specific post-processing.
+		 */
+
+		/**
+		 * Groups similar entities together. Frees crypto op and based
+		 * on crypto_op status, set mbuf->ol_flags which would be
+		 * checked in rte_pdcp_pkt_post_process().
+		 */
+		nb_grp = rte_pdcp_pkt_crypto_group(cop, pkts, grp, ret);
+
+		for (i = 0; i != nb_grp; i++) {
+
+			/**
+			 * Post process packets after crypto completion.
+			 * Following operations would be done,
+			 *
+			 *  Transmitting entity/UL:
+			 *  - Check crypto result
+			 *
+			 *  Receiving entity/DL:
+			 *  - Check crypto operation status
+			 *  - Check for duplication (if yes, drop duplicate)
+			 *  - Perform decompression
+			 *  - Trim PDCP header
+			 *  - Hold packet (SDU) for in-order delivery (return
+			 *    completed packets as and when sequence is
+			 *    completed)
+			 *  - If not in sequence, cache the packet and start
+			 *    t-Reordering timer. When timer expires, the
+			 *    packets need to delivered to upper layers (not
+			 *    treated as error packets).
+			 */
+			nb_success = rte_pdcp_pkt_post_process(grp[i].id.ptr,
+							       grp[i].m, out_mb,
+							       grp[i].cnt,
+							       &nb_err);
+			if (nb_err != 0) {
+				/* Handle error packets */
+			}
+
+			/* Perform additional operations */
+
+			/**
+			 * Transmitting entity/UL
+			 * - If duplication is enabled, duplicate PDCP PDUs
+			 * - When lower layers confirm reception of a PDCP PDU,
+			 *   it should be communicated to PDCP layer so that
+			 *   PDCP can drop the corresponding SDU
+			 */
+		}
+	}
+
+
+Supported features
+------------------
+
+- 12 bit & 18 bit sequence numbers
+- Uplink & downlink traffic
+- HFN increment
+- IV generation as required per algorithm
+
+Supported ciphering algorithms
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+- NULL
+- AES-CTR
+- SNOW3G-CIPHER
+- ZUC-CIPHER
+
+Supported integrity protection algorithms
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+- NULL
+- AES-CMAC
+- SNOW3G-AUTH
+- ZUC-AUTH
-- 
2.25.1