[PATCH v2 16/22] pdcp: add timer expiry handle

[Anoob Joseph]

Hi Akhil,

Please see inline.

Thanks,
Anoob

> -----Original Message-----
> From: Akhil Goyal <gakhil at marvell.com>
> Sent: Thursday, May 18, 2023 3:13 PM
> To: Anoob Joseph <anoobj at marvell.com>; Thomas Monjalon
> <thomas at monjalon.net>; Jerin Jacob Kollanukkaran <jerinj at marvell.com>;
> Konstantin Ananyev <konstantin.v.ananyev at yandex.ru>; Bernard
> Iremonger <bernard.iremonger at intel.com>
> Cc: Volodymyr Fialko <vfialko at marvell.com>; Hemant Agrawal
> <hemant.agrawal at nxp.com>; Mattias Rönnblom
> <mattias.ronnblom at ericsson.com>; Kiran Kumar Kokkilagadda
> <kirankumark at marvell.com>; dev at dpdk.org; Olivier Matz
> <olivier.matz at 6wind.com>
> Subject: RE: [PATCH v2 16/22] pdcp: add timer expiry handle
> 
> > Subject: [PATCH v2 16/22] pdcp: add timer expiry handle
> >
> > From: Volodymyr Fialko <vfialko at marvell.com>
> >
> > The PDCP protocol requires usage of timers to keep track of how long
> > an out-of-order packet should be buffered while waiting for missing
> > packets. Applications can register a desired timer implementation with
> > the PDCP library. Once the timer expires, the application will be
> > notified, and further handling of the event will be performed in the PDCP
> library.
> >
> > When the timer expires, the PDCP library will return the cached
> > packets, and PDCP internal state variables (like RX_REORD, RX_DELIV
> > etc) will be updated accordingly.
> >
> > Signed-off-by: Anoob Joseph <anoobj at marvell.com>
> > Signed-off-by: Volodymyr Fialko <vfialko at marvell.com>
> > ---
> >  doc/guides/prog_guide/pdcp_lib.rst | 29 ++++++++++++++++++
> >  lib/pdcp/pdcp_process.c            | 49 ++++++++++++++++++++++++++++++
> >  lib/pdcp/rte_pdcp.h                | 31 +++++++++++++++++++
> >  lib/pdcp/version.map               |  2 ++
> >  4 files changed, 111 insertions(+)
> >
> > diff --git a/doc/guides/prog_guide/pdcp_lib.rst
> > b/doc/guides/prog_guide/pdcp_lib.rst
> > index f23360dfc3..32370633e5 100644
> > --- a/doc/guides/prog_guide/pdcp_lib.rst
> > +++ b/doc/guides/prog_guide/pdcp_lib.rst
> > @@ -229,6 +229,35 @@ parameters for entity creation.
> >  		}
> >  	}
> >
> > +Timers
> > +------
> > +
> > +PDCP utilizes a reception window mechanism to limit the bits of COUNT
> > +value transmitted in the packet. It utilizes state variables such as
> > +RX_REORD, RX_DELIV to define the window and uses RX_DELIV as the
> > +lower pivot point of
> > the
> > +window.
> > +
> > +RX_DELIV would be updated only when packets are received in-order.
> > +Any
> > missing
> > +packet would mean RX_DELIV won't be updated. A timer, t-Reordering,
> > +helps
> > PDCP
> > +to slide the window if the missing packet is not received in a
> > +specified time duration.
> > +
> > +While starting and stopping the timer need to be done by lib PDCP,
> > +application could register its own timer implementation. This is to
> > +make sure application can choose between timers such as rte_timer and
> rte_event based timers.
> > Starting
> > +and stopping of timer would happen during pre & post process API.
> > +
> > +When the t-Reordering timer expires, application would receive the
> > +expiry
> > event.
> > +To perform the PDCP handling of the expiry event,
> > +``rte_pdcp_t_reordering_expiry_handle`` can be used. Expiry handling
> > +would involve sliding the window by updating state variables and
> > +passing the expired packets to the application.
> > +
> > +.. literalinclude:: ../../../lib/pdcp/rte_pdcp.h
> > +   :language: c
> > +   :start-after: Structure rte_pdcp_t_reordering 8<
> > +   :end-before: >8 End of structure rte_pdcp_t_reordering.
> > +
> >
> >  Supported features
> >  ------------------
> > diff --git a/lib/pdcp/pdcp_process.c b/lib/pdcp/pdcp_process.c index
> > 9ba07d5255..91b87a2a81 100644
> > --- a/lib/pdcp/pdcp_process.c
> > +++ b/lib/pdcp/pdcp_process.c
> > @@ -1285,3 +1285,52 @@ pdcp_process_func_set(struct rte_pdcp_entity
> > *entity, const struct rte_pdcp_enti
> >
> >  	return 0;
> >  }
> > +
> > +uint16_t
> > +rte_pdcp_t_reordering_expiry_handle(const struct rte_pdcp_entity
> > +*entity,
> > struct rte_mbuf *out_mb[])
> 
> Move this public API implementation to rte_pdcp.c

[Anoob] Agreed. Will make this change in next version.

> 
> 
> > +{
> > +	struct entity_priv_dl_part *dl = entity_dl_part_get(entity);
> > +	struct entity_priv *en_priv = entity_priv_get(entity);
> > +	uint16_t capacity = entity->max_pkt_cache;
> > +	uint16_t nb_out, nb_seq;
> > +
> > +	/* 5.2.2.2 Actions when a t-Reordering expires */
> > +
> > +	/*
> > +	 * - deliver to upper layers in ascending order of the associated
> > +COUNT
> > value after
> > +	 *   performing header decompression, if not decompressed before:
> > +	 */
> > +
> > +	/*   - all stored PDCP SDU(s) with associated COUNT value(s) <
> > RX_REORD; */
> > +	nb_out = pdcp_reorder_up_to_get(&dl->reorder, out_mb, capacity,
> > en_priv->state.rx_reord);
> > +	capacity -= nb_out;
> > +	out_mb = &out_mb[nb_out];
> > +
> > +	/*
> > +	 *   - all stored PDCP SDU(s) with consecutively associated COUNT
> > value(s) starting from
> > +	 *     RX_REORD;
> > +	 */
> > +	nb_seq = pdcp_reorder_get_sequential(&dl->reorder, out_mb,
> > capacity);
> > +	nb_out += nb_seq;
> > +
> > +	/*
> > +	 * - update RX_DELIV to the COUNT value of the first PDCP SDU
> which
> > has not been delivered
> > +	 *   to upper layers, with COUNT value >= RX_REORD;
> > +	 */
> > +	en_priv->state.rx_deliv = en_priv->state.rx_reord + nb_seq;
> > +
> > +	/*
> > +	 * - if RX_DELIV < RX_NEXT:
> > +	 *   - update RX_REORD to RX_NEXT;
> > +	 *   - start t-Reordering.
> > +	 */
> > +	if (en_priv->state.rx_deliv < en_priv->state.rx_next) {
> > +		en_priv->state.rx_reord = en_priv->state.rx_next;
> > +		dl->t_reorder.state = TIMER_RUNNING;
> > +		dl->t_reorder.handle.start(dl->t_reorder.handle.timer, dl-
> > >t_reorder.handle.args);
> > +	} else {
> > +		dl->t_reorder.state = TIMER_EXPIRED;
> > +	}
> > +
> > +	return nb_out;
> > +}
> > diff --git a/lib/pdcp/rte_pdcp.h b/lib/pdcp/rte_pdcp.h index
> > 55e57c3b9b..c077acce63 100644
> > --- a/lib/pdcp/rte_pdcp.h
> > +++ b/lib/pdcp/rte_pdcp.h
> > @@ -100,6 +100,7 @@ typedef void
> > (*rte_pdcp_t_reordering_stop_cb_t)(void
> > *timer, void *args);
> >   *
> >   * Configuration provided by user, that PDCP library will invoke
> > according to timer behaviour.
> >   */
> > +/* Structure rte_pdcp_t_reordering 8< */
> >  struct rte_pdcp_t_reordering {
> >  	/** Timer pointer, stored for later use in callback functions */
> >  	void *timer;
> > @@ -110,6 +111,7 @@ struct rte_pdcp_t_reordering {
> >  	/** Timer start callback handle */
> >  	rte_pdcp_t_reordering_stop_cb_t stop;  };
> > +/* >8 End of structure rte_pdcp_t_reordering. */
> >
> >  /**
> >   * PDCP entity configuration to be used for establishing an entity.
> > @@ -327,6 +329,35 @@ rte_pdcp_pkt_post_process(const struct
> > rte_pdcp_entity *entity,
> >  	return entity->post_process(entity, in_mb, out_mb, num, nb_err);  }
> >
> > +/**
> > + * @warning
> > + * @b EXPERIMENTAL: this API may change without prior notice
> > + *
> > + * 5.2.2.2 Actions when a t-Reordering expires
> > + *
> > + * When t-Reordering timer expires, PDCP is required to slide the
> > +reception
> > + * window by updating state variables such as RX_REORD & RX_DELIV.
> > +PDCP
> > would
> > + * need to deliver some of the buffered packets based on the state
> > + variables
> > and
> > + * conditions described.
> > + *
> > + * The expiry handle need to be invoked by the application when
> > + t-Reordering
> > + * timer expires. In addition to returning buffered packets, it may
> > + also restart
> > + * timer based on the state variables.
> > + *
> > + * @param entity
> > + *   Pointer to the *rte_pdcp_entity* for which the timer expired.
> > + * @param[out] out_mb
> > + *   The address of an array that can hold up to
> > *rte_pdcp_entity.max_pkt_cache*
> > + *   pointers to *rte_mbuf* structures. Used to return buffered packets
> that are
> > + *   expired.
> > + * @return
> > + *   Number of packets returned in *out_mb* buffer.
> > + */
> > +__rte_experimental
> > +uint16_t
> > +rte_pdcp_t_reordering_expiry_handle(const struct rte_pdcp_entity
> *entity,
> > +				    struct rte_mbuf *out_mb[]);
> > +
> >  #include <rte_pdcp_group.h>
> >
> >  #ifdef __cplusplus
> > diff --git a/lib/pdcp/version.map b/lib/pdcp/version.map index
> > d0cf338e1f..89b0463be6 100644
> > --- a/lib/pdcp/version.map
> > +++ b/lib/pdcp/version.map
> > @@ -11,5 +11,7 @@ EXPERIMENTAL {
> >  	rte_pdcp_pkt_post_process;
> >  	rte_pdcp_pkt_pre_process;
> >
> > +	rte_pdcp_t_reordering_expiry_handle;
> > +
> >  	local: *;
> >  };
> > --
> > 2.25.1