1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * Copyright (c) 2007 The University of Aberdeen, Scotland, UK
4 * Copyright (c) 2005-7 The University of Waikato, Hamilton, New Zealand.
5 * Copyright (c) 2005-7 Ian McDonald <ian.mcdonald@jandi.co.nz>
6 * Copyright (c) 2005 Arnaldo Carvalho de Melo <acme@conectiva.com.br>
7 */
8 #include <net/sock.h>
9 #include "tfrc.h"
10
11 static struct kmem_cache *tfrc_lh_slab __read_mostly;
12 /* Loss Interval weights from [RFC 3448, 5.4], scaled by 10 */
13 static const int tfrc_lh_weights[NINTERVAL] = { 10, 10, 10, 10, 8, 6, 4, 2 };
14
15 /* implements LIFO semantics on the array */
16 static inline u8 LIH_INDEX(const u8 ctr)
17 {
18 return LIH_SIZE - 1 - (ctr % LIH_SIZE);
19 }
20
21 /* the `counter' index always points at the next entry to be populated */
22 static inline struct tfrc_loss_interval *tfrc_lh_peek(struct tfrc_loss_hist *lh)
23 {
24 return lh->counter ? lh->ring[LIH_INDEX(lh->counter - 1)] : NULL;
25 }
26
27 /* given i with 0 <= i <= k, return I_i as per the rfc3448bis notation */
28 static inline u32 tfrc_lh_get_interval(struct tfrc_loss_hist *lh, const u8 i)
29 {
30 BUG_ON(i >= lh->counter);
31 return lh->ring[LIH_INDEX(lh->counter - i - 1)]->li_length;
32 }
33
34 /*
35 * On-demand allocation and de-allocation of entries
36 */
37 static struct tfrc_loss_interval *tfrc_lh_demand_next(struct tfrc_loss_hist *lh)
38 {
39 if (lh->ring[LIH_INDEX(lh->counter)] == NULL)
40 lh->ring[LIH_INDEX(lh->counter)] = kmem_cache_alloc(tfrc_lh_slab,
41 GFP_ATOMIC);
42 return lh->ring[LIH_INDEX(lh->counter)];
43 }
44
45 void tfrc_lh_cleanup(struct tfrc_loss_hist *lh)
46 {
47 if (!tfrc_lh_is_initialised(lh))
48 return;
49
50 for (lh->counter = 0; lh->counter < LIH_SIZE; lh->counter++)
51 if (lh->ring[LIH_INDEX(lh->counter)] != NULL) {
52 kmem_cache_free(tfrc_lh_slab,
53 lh->ring[LIH_INDEX(lh->counter)]);
54 lh->ring[LIH_INDEX(lh->counter)] = NULL;
55 }
56 }
57
58 static void tfrc_lh_calc_i_mean(struct tfrc_loss_hist *lh)
59 {
60 u32 i_i, i_tot0 = 0, i_tot1 = 0, w_tot = 0;
61 int i, k = tfrc_lh_length(lh) - 1; /* k is as in rfc3448bis, 5.4 */
62
63 if (k <= 0)
64 return;
65
66 for (i = 0; i <= k; i++) {
67 i_i = tfrc_lh_get_interval(lh, i);
68
69 if (i < k) {
70 i_tot0 += i_i * tfrc_lh_weights[i];
71 w_tot += tfrc_lh_weights[i];
72 }
73 if (i > 0)
74 i_tot1 += i_i * tfrc_lh_weights[i-1];
75 }
76
77 lh->i_mean = max(i_tot0, i_tot1) / w_tot;
78 }
79
80 /**
81 * tfrc_lh_update_i_mean - Update the `open' loss interval I_0
82 * @lh: histogram to update
83 * @skb: received socket triggering loss interval update
84 *
85 * For recomputing p: returns `true' if p > p_prev <=> 1/p < 1/p_prev
86 */
87 u8 tfrc_lh_update_i_mean(struct tfrc_loss_hist *lh, struct sk_buff *skb)
88 {
89 struct tfrc_loss_interval *cur = tfrc_lh_peek(lh);
90 u32 old_i_mean = lh->i_mean;
91 s64 len;
92
93 if (cur == NULL) /* not initialised */
94 return 0;
95
96 len = dccp_delta_seqno(cur->li_seqno, DCCP_SKB_CB(skb)->dccpd_seq) + 1;
97
98 if (len - (s64)cur->li_length <= 0) /* duplicate or reordered */
99 return 0;
100
101 if (SUB16(dccp_hdr(skb)->dccph_ccval, cur->li_ccval) > 4)
102 /*
103 * Implements RFC 4342, 10.2:
104 * If a packet S (skb) exists whose seqno comes `after' the one
105 * starting the current loss interval (cur) and if the modulo-16
106 * distance from C(cur) to C(S) is greater than 4, consider all
107 * subsequent packets as belonging to a new loss interval. This
108 * test is necessary since CCVal may wrap between intervals.
109 */
110 cur->li_is_closed = 1;
111
112 if (tfrc_lh_length(lh) == 1) /* due to RFC 3448, 6.3.1 */
113 return 0;
114
115 cur->li_length = len;
116 tfrc_lh_calc_i_mean(lh);
117
118 return lh->i_mean < old_i_mean;
119 }
120
121 /* Determine if `new_loss' does begin a new loss interval [RFC 4342, 10.2] */
122 static inline u8 tfrc_lh_is_new_loss(struct tfrc_loss_interval *cur,
123 struct tfrc_rx_hist_entry *new_loss)
124 {
125 return dccp_delta_seqno(cur->li_seqno, new_loss->tfrchrx_seqno) > 0 &&
126 (cur->li_is_closed || SUB16(new_loss->tfrchrx_ccval, cur->li_ccval) > 4);
127 }
128
129 /**
130 * tfrc_lh_interval_add - Insert new record into the Loss Interval database
131 * @lh: Loss Interval database
132 * @rh: Receive history containing a fresh loss event
133 * @calc_first_li: Caller-dependent routine to compute length of first interval
134 * @sk: Used by @calc_first_li in caller-specific way (subtyping)
135 *
136 * Updates I_mean and returns 1 if a new interval has in fact been added to @lh.
137 */
138 int tfrc_lh_interval_add(struct tfrc_loss_hist *lh, struct tfrc_rx_hist *rh,
139 u32 (*calc_first_li)(struct sock *), struct sock *sk)
140 {
141 struct tfrc_loss_interval *cur = tfrc_lh_peek(lh), *new;
142
143 if (cur != NULL && !tfrc_lh_is_new_loss(cur, tfrc_rx_hist_loss_prev(rh)))
144 return 0;
145
146 new = tfrc_lh_demand_next(lh);
147 if (unlikely(new == NULL)) {
148 DCCP_CRIT("Cannot allocate/add loss record.");
149 return 0;
150 }
151
152 new->li_seqno = tfrc_rx_hist_loss_prev(rh)->tfrchrx_seqno;
153 new->li_ccval = tfrc_rx_hist_loss_prev(rh)->tfrchrx_ccval;
154 new->li_is_closed = 0;
155
156 if (++lh->counter == 1)
157 lh->i_mean = new->li_length = (*calc_first_li)(sk);
158 else {
159 cur->li_length = dccp_delta_seqno(cur->li_seqno, new->li_seqno);
160 new->li_length = dccp_delta_seqno(new->li_seqno,
161 tfrc_rx_hist_last_rcv(rh)->tfrchrx_seqno) + 1;
162 if (lh->counter > (2*LIH_SIZE))
163 lh->counter -= LIH_SIZE;
164
165 tfrc_lh_calc_i_mean(lh);
166 }
167 return 1;
168 }
169
170 int __init tfrc_li_init(void)
171 {
172 tfrc_lh_slab = kmem_cache_create("tfrc_li_hist",
173 sizeof(struct tfrc_loss_interval), 0,
174 SLAB_HWCACHE_ALIGN, NULL);
175 return tfrc_lh_slab == NULL ? -ENOBUFS : 0;
176 }
177
178 void tfrc_li_exit(void)
179 {
180 if (tfrc_lh_slab != NULL) {
181 kmem_cache_destroy(tfrc_lh_slab);
182 tfrc_lh_slab = NULL;
183 }
184 }
185
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