linux/net/dccp/ccids/lib/packet_history.c

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *  Copyright (c) 2007   The University of Aberdeen, Scotland, UK
 *  Copyright (c) 2005-7 The University of Waikato, Hamilton, New Zealand.
 *
 *  An implementation of the DCCP protocol
 *
 *  This code has been developed by the University of Waikato WAND
 *  research group. For further information please see https://www.wand.net.nz/
 *  or e-mail Ian McDonald - [email protected]
 *
 *  This code also uses code from Lulea University, rereleased as GPL by its
 *  authors:
 *  Copyright (c) 2003 Nils-Erik Mattsson, Joacim Haggmark, Magnus Erixzon
 *
 *  Changes to meet Linux coding standards, to make it meet latest ccid3 draft
 *  and to make it work as a loadable module in the DCCP stack written by
 *  Arnaldo Carvalho de Melo <[email protected]>.
 *
 *  Copyright (c) 2005 Arnaldo Carvalho de Melo <[email protected]>
 */

#include <linux/string.h>
#include <linux/slab.h>
#include "packet_history.h"
#include "../../dccp.h"

/*
 * Transmitter History Routines
 */
static struct kmem_cache *tfrc_tx_hist_slab;

int __init tfrc_tx_packet_history_init(void)
{ … }

void tfrc_tx_packet_history_exit(void)
{ … }

int tfrc_tx_hist_add(struct tfrc_tx_hist_entry **headp, u64 seqno)
{ … }

void tfrc_tx_hist_purge(struct tfrc_tx_hist_entry **headp)
{ … }

/*
 *	Receiver History Routines
 */
static struct kmem_cache *tfrc_rx_hist_slab;

int __init tfrc_rx_packet_history_init(void)
{ … }

void tfrc_rx_packet_history_exit(void)
{ … }

static inline void tfrc_rx_hist_entry_from_skb(struct tfrc_rx_hist_entry *entry,
					       const struct sk_buff *skb,
					       const u64 ndp)
{ … }

void tfrc_rx_hist_add_packet(struct tfrc_rx_hist *h,
			     const struct sk_buff *skb,
			     const u64 ndp)
{ … }

/* has the packet contained in skb been seen before? */
int tfrc_rx_hist_duplicate(struct tfrc_rx_hist *h, struct sk_buff *skb)
{ … }

static void tfrc_rx_hist_swap(struct tfrc_rx_hist *h, const u8 a, const u8 b)
{ … }

/*
 * Private helper functions for loss detection.
 *
 * In the descriptions, `Si' refers to the sequence number of entry number i,
 * whose NDP count is `Ni' (lower case is used for variables).
 * Note: All __xxx_loss functions expect that a test against duplicates has been
 *       performed already: the seqno of the skb must not be less than the seqno
 *       of loss_prev; and it must not equal that of any valid history entry.
 */
static void __do_track_loss(struct tfrc_rx_hist *h, struct sk_buff *skb, u64 n1)
{ … }

static void __one_after_loss(struct tfrc_rx_hist *h, struct sk_buff *skb, u32 n2)
{ … }

/* return 1 if a new loss event has been identified */
static int __two_after_loss(struct tfrc_rx_hist *h, struct sk_buff *skb, u32 n3)
{ … }

/* recycle RX history records to continue loss detection if necessary */
static void __three_after_loss(struct tfrc_rx_hist *h)
{ … }

/**
 *  tfrc_rx_handle_loss  -  Loss detection and further processing
 *  @h:		    The non-empty RX history object
 *  @lh:	    Loss Intervals database to update
 *  @skb:	    Currently received packet
 *  @ndp:	    The NDP count belonging to @skb
 *  @calc_first_li: Caller-dependent computation of first loss interval in @lh
 *  @sk:	    Used by @calc_first_li (see tfrc_lh_interval_add)
 *
 *  Chooses action according to pending loss, updates LI database when a new
 *  loss was detected, and does required post-processing. Returns 1 when caller
 *  should send feedback, 0 otherwise.
 *  Since it also takes care of reordering during loss detection and updates the
 *  records accordingly, the caller should not perform any more RX history
 *  operations when loss_count is greater than 0 after calling this function.
 */
int tfrc_rx_handle_loss(struct tfrc_rx_hist *h,
			struct tfrc_loss_hist *lh,
			struct sk_buff *skb, const u64 ndp,
			u32 (*calc_first_li)(struct sock *), struct sock *sk)
{ … }

int tfrc_rx_hist_alloc(struct tfrc_rx_hist *h)
{ … }

void tfrc_rx_hist_purge(struct tfrc_rx_hist *h)
{ … }

/**
 * tfrc_rx_hist_rtt_last_s - reference entry to compute RTT samples against
 * @h:	The non-empty RX history object
 */
static inline struct tfrc_rx_hist_entry *
			tfrc_rx_hist_rtt_last_s(const struct tfrc_rx_hist *h)
{ … }

/**
 * tfrc_rx_hist_rtt_prev_s - previously suitable (wrt rtt_last_s) RTT-sampling entry
 * @h:	The non-empty RX history object
 */
static inline struct tfrc_rx_hist_entry *
			tfrc_rx_hist_rtt_prev_s(const struct tfrc_rx_hist *h)
{ … }

/**
 * tfrc_rx_hist_sample_rtt  -  Sample RTT from timestamp / CCVal
 * @h: receive histogram
 * @skb: packet containing timestamp.
 *
 * Based on ideas presented in RFC 4342, 8.1. Returns 0 if it was not able
 * to compute a sample with given data - calling function should check this.
 */
u32 tfrc_rx_hist_sample_rtt(struct tfrc_rx_hist *h, const struct sk_buff *skb)
{ … }