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  */
36 struct tfrc_tx_hist_entry {
37 	struct tfrc_tx_hist_entry *next;
38 	u64			  seqno;
39 	ktime_t			  stamp;
40 };
41 
42 static 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 
50 int tfrc_tx_hist_add(struct tfrc_tx_hist_entry **headp, u64 seqno);
51 void 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  */
66 struct 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  */
81 struct 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  */
91 static 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  */
99 static 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  */
108 static 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  */
117 static 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 */
124 static inline bool tfrc_rx_hist_loss_pending(const struct tfrc_rx_hist *h)
125 {
126 	return h->loss_count > 0;
127 }
128 
129 void tfrc_rx_hist_add_packet(struct tfrc_rx_hist *h, const struct sk_buff *skb,
130 			     const u64 ndp);
131 
132 int tfrc_rx_hist_duplicate(struct tfrc_rx_hist *h, struct sk_buff *skb);
133 
134 struct tfrc_loss_hist;
135 int 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);
138 u32 tfrc_rx_hist_sample_rtt(struct tfrc_rx_hist *h, const struct sk_buff *skb);
139 int tfrc_rx_hist_alloc(struct tfrc_rx_hist *h);
140 void tfrc_rx_hist_purge(struct tfrc_rx_hist *h);
141 
142 #endif /* _DCCP_PKT_HIST_ */
143