1/* SPDX-License-Identifier: GPL-2.0-or-later */
2/*
3 *  Packet RX/TX history data structures and routines for TFRC-based protocols.
4 *
5 *  Copyright (c) 2007   The University of Aberdeen, Scotland, UK
6 *  Copyright (c) 2005-6 The University of Waikato, Hamilton, New Zealand.
7 *
8 *  This code has been developed by the University of Waikato WAND
9 *  research group. For further information please see https://www.wand.net.nz/
10 *  or e-mail Ian McDonald - ian.mcdonald@jandi.co.nz
11 *
12 *  This code also uses code from Lulea University, rereleased as GPL by its
13 *  authors:
14 *  Copyright (c) 2003 Nils-Erik Mattsson, Joacim Haggmark, Magnus Erixzon
15 *
16 *  Changes to meet Linux coding standards, to make it meet latest ccid3 draft
17 *  and to make it work as a loadable module in the DCCP stack written by
18 *  Arnaldo Carvalho de Melo <acme@conectiva.com.br>.
19 *
20 *  Copyright (c) 2005 Arnaldo Carvalho de Melo <acme@conectiva.com.br>
21 */
22
23#ifndef _DCCP_PKT_HIST_
24#define _DCCP_PKT_HIST_
25
26#include <linux/list.h>
27#include <linux/slab.h>
28#include "tfrc.h"
29
30/**
31 *  tfrc_tx_hist_entry  -  Simple singly-linked TX history list
32 *  @next:  next oldest entry (LIFO order)
33 *  @seqno: sequence number of this entry
34 *  @stamp: send time of packet with sequence number @seqno
35 */
36struct tfrc_tx_hist_entry {
37	struct tfrc_tx_hist_entry *next;
38	u64			  seqno;
39	ktime_t			  stamp;
40};
41
42static inline struct tfrc_tx_hist_entry *
43	tfrc_tx_hist_find_entry(struct tfrc_tx_hist_entry *head, u64 seqno)
44{
45	while (head != NULL && head->seqno != seqno)
46		head = head->next;
47	return head;
48}
49
50int tfrc_tx_hist_add(struct tfrc_tx_hist_entry **headp, u64 seqno);
51void tfrc_tx_hist_purge(struct tfrc_tx_hist_entry **headp);
52
53/* Subtraction a-b modulo-16, respects circular wrap-around */
54#define SUB16(a, b) (((a) + 16 - (b)) & 0xF)
55
56/* Number of packets to wait after a missing packet (RFC 4342, 6.1) */
57#define TFRC_NDUPACK 3
58
59/**
60 * tfrc_rx_hist_entry - Store information about a single received packet
61 * @tfrchrx_seqno:	DCCP packet sequence number
62 * @tfrchrx_ccval:	window counter value of packet (RFC 4342, 8.1)
63 * @tfrchrx_ndp:	the NDP count (if any) of the packet
64 * @tfrchrx_tstamp:	actual receive time of packet
65 */
66struct tfrc_rx_hist_entry {
67	u64		 tfrchrx_seqno:48,
68			 tfrchrx_ccval:4,
69			 tfrchrx_type:4;
70	u64		 tfrchrx_ndp:48;
71	ktime_t		 tfrchrx_tstamp;
72};
73
74/**
75 * tfrc_rx_hist  -  RX history structure for TFRC-based protocols
76 * @ring:		Packet history for RTT sampling and loss detection
77 * @loss_count:		Number of entries in circular history
78 * @loss_start:		Movable index (for loss detection)
79 * @rtt_sample_prev:	Used during RTT sampling, points to candidate entry
80 */
81struct tfrc_rx_hist {
82	struct tfrc_rx_hist_entry *ring[TFRC_NDUPACK + 1];
83	u8			  loss_count:2,
84				  loss_start:2;
85#define rtt_sample_prev		  loss_start
86};
87
88/**
89 * tfrc_rx_hist_index - index to reach n-th entry after loss_start
90 */
91static inline u8 tfrc_rx_hist_index(const struct tfrc_rx_hist *h, const u8 n)
92{
93	return (h->loss_start + n) & TFRC_NDUPACK;
94}
95
96/**
97 * tfrc_rx_hist_last_rcv - entry with highest-received-seqno so far
98 */
99static inline struct tfrc_rx_hist_entry *
100			tfrc_rx_hist_last_rcv(const struct tfrc_rx_hist *h)
101{
102	return h->ring[tfrc_rx_hist_index(h, h->loss_count)];
103}
104
105/**
106 * tfrc_rx_hist_entry - return the n-th history entry after loss_start
107 */
108static inline struct tfrc_rx_hist_entry *
109			tfrc_rx_hist_entry(const struct tfrc_rx_hist *h, const u8 n)
110{
111	return h->ring[tfrc_rx_hist_index(h, n)];
112}
113
114/**
115 * tfrc_rx_hist_loss_prev - entry with highest-received-seqno before loss was detected
116 */
117static inline struct tfrc_rx_hist_entry *
118			tfrc_rx_hist_loss_prev(const struct tfrc_rx_hist *h)
119{
120	return h->ring[h->loss_start];
121}
122
123/* indicate whether previously a packet was detected missing */
124static inline bool tfrc_rx_hist_loss_pending(const struct tfrc_rx_hist *h)
125{
126	return h->loss_count > 0;
127}
128
129void tfrc_rx_hist_add_packet(struct tfrc_rx_hist *h, const struct sk_buff *skb,
130			     const u64 ndp);
131
132int tfrc_rx_hist_duplicate(struct tfrc_rx_hist *h, struct sk_buff *skb);
133
134struct tfrc_loss_hist;
135int tfrc_rx_handle_loss(struct tfrc_rx_hist *h, struct tfrc_loss_hist *lh,
136			struct sk_buff *skb, const u64 ndp,
137			u32 (*first_li)(struct sock *sk), struct sock *sk);
138u32 tfrc_rx_hist_sample_rtt(struct tfrc_rx_hist *h, const struct sk_buff *skb);
139int tfrc_rx_hist_alloc(struct tfrc_rx_hist *h);
140void tfrc_rx_hist_purge(struct tfrc_rx_hist *h);
141
142#endif /* _DCCP_PKT_HIST_ */
143