[PATCH v5 11/21] 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>
---
 MAINTAINERS                                   |   1 +
 .../img/pdcp_functional_overview.svg          |   1 +
 doc/guides/prog_guide/index.rst               |   1 +
 doc/guides/prog_guide/pdcp_lib.rst            | 254 ++++++++++++++++++
 doc/guides/rel_notes/release_23_07.rst        |  12 +
 5 files changed, 269 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/MAINTAINERS b/MAINTAINERS
index 15dd88af3a..4345ae21b6 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -1555,6 +1555,7 @@ M: Volodymyr Fialko <vfialko@marvell.com>
 T: git://dpdk.org/next/dpdk-next-crypto
 F: lib/pdcp/
 F: app/test/test_pdcp*
+F: doc/guides/prog_guide/pdcp_lib.rst
 
 
 Packet Framework
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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\ 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..8369c71600
--- /dev/null
+++ b/doc/guides/prog_guide/pdcp_lib.rst
@@ -0,0 +1,254 @@
+..  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.
+
+When upper layers request a PDCP entity suspend (``rte_pdcp_entity_suspend()``),
+it would result in flushing out of all cached packets. Internal state variables
+are updated as described in 5.1.4.
+
+When upper layers request a PDCP entity release (``rte_pdcp_entity_release()``),
+it would result in flushing out of all cached packets and releasing of all
+memory associated with the entity. It would internally free any crypto/security
+sessions created. All procedures mentioned in 5.1.3 would be performed.
+
+PDCP PDU (Protocol Data Unit) API
+---------------------------------
+
+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.
+
+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
+
+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
+			 */
+		}
+	}
diff --git a/doc/guides/rel_notes/release_23_07.rst b/doc/guides/rel_notes/release_23_07.rst
index 75079ca7d6..bb48514637 100644
--- a/doc/guides/rel_notes/release_23_07.rst
+++ b/doc/guides/rel_notes/release_23_07.rst
@@ -65,6 +65,18 @@ New Features
   * Added support for SM3 hash operations.
   * Added support for AES-CCM in cn9k and cn10k drivers.
 
+* **Added PDCP Library.**
+
+  Added an experimental library ``lib_pdcp`` to provide PDCP UL and DL
+  processing of packets.
+
+  The library supports all PDCP algorithms and leverages lookaside crypto
+  offloads to cryptodevs for crypto processing. PDCP features such as IV
+  generation, sequence number handling etc are supported. It is planned to add
+  more features such as packet caching in future releases.
+
+  See :doc:`../prog_guide/pdcp_lib` for more information.
+
 
 Removed Items
 -------------
-- 
2.25.1