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(ctr: 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(ctr: 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(ctr: lh->counter)] == NULL) |
40 | lh->ring[LIH_INDEX(ctr: lh->counter)] = kmem_cache_alloc(cachep: tfrc_lh_slab, |
41 | GFP_ATOMIC); |
42 | return lh->ring[LIH_INDEX(ctr: 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(ctr: lh->counter)] != NULL) { |
52 | kmem_cache_free(s: tfrc_lh_slab, |
53 | objp: lh->ring[LIH_INDEX(ctr: lh->counter)]); |
54 | lh->ring[LIH_INDEX(ctr: 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(seqno1: 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(seqno1: cur->li_seqno, seqno2: 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, new_loss: tfrc_rx_hist_loss_prev(h: 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(h: rh)->tfrchrx_seqno; |
153 | new->li_ccval = tfrc_rx_hist_loss_prev(h: 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(seqno1: cur->li_seqno, seqno2: new->li_seqno); |
160 | new->li_length = dccp_delta_seqno(seqno1: new->li_seqno, |
161 | seqno2: tfrc_rx_hist_last_rcv(h: 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(name: "tfrc_li_hist" , |
173 | size: sizeof(struct tfrc_loss_interval), align: 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(s: tfrc_lh_slab); |
182 | tfrc_lh_slab = NULL; |
183 | } |
184 | } |
185 | |