Merge branch 'media_fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab...
[cris-mirror.git] / net / dccp / ccids / lib / loss_interval.c
blob497723c4d4bbccf1a584230d99739a2799f80932
1 /*
2 * Copyright (c) 2007 The University of Aberdeen, Scotland, UK
3 * Copyright (c) 2005-7 The University of Waikato, Hamilton, New Zealand.
4 * Copyright (c) 2005-7 Ian McDonald <ian.mcdonald@jandi.co.nz>
5 * Copyright (c) 2005 Arnaldo Carvalho de Melo <acme@conectiva.com.br>
7 * This program is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License as published by
9 * the Free Software Foundation; either version 2 of the License, or
10 * (at your option) any later version.
12 #include <net/sock.h>
13 #include "tfrc.h"
15 static struct kmem_cache *tfrc_lh_slab __read_mostly;
16 /* Loss Interval weights from [RFC 3448, 5.4], scaled by 10 */
17 static const int tfrc_lh_weights[NINTERVAL] = { 10, 10, 10, 10, 8, 6, 4, 2 };
19 /* implements LIFO semantics on the array */
20 static inline u8 LIH_INDEX(const u8 ctr)
22 return LIH_SIZE - 1 - (ctr % LIH_SIZE);
25 /* the `counter' index always points at the next entry to be populated */
26 static inline struct tfrc_loss_interval *tfrc_lh_peek(struct tfrc_loss_hist *lh)
28 return lh->counter ? lh->ring[LIH_INDEX(lh->counter - 1)] : NULL;
31 /* given i with 0 <= i <= k, return I_i as per the rfc3448bis notation */
32 static inline u32 tfrc_lh_get_interval(struct tfrc_loss_hist *lh, const u8 i)
34 BUG_ON(i >= lh->counter);
35 return lh->ring[LIH_INDEX(lh->counter - i - 1)]->li_length;
39 * On-demand allocation and de-allocation of entries
41 static struct tfrc_loss_interval *tfrc_lh_demand_next(struct tfrc_loss_hist *lh)
43 if (lh->ring[LIH_INDEX(lh->counter)] == NULL)
44 lh->ring[LIH_INDEX(lh->counter)] = kmem_cache_alloc(tfrc_lh_slab,
45 GFP_ATOMIC);
46 return lh->ring[LIH_INDEX(lh->counter)];
49 void tfrc_lh_cleanup(struct tfrc_loss_hist *lh)
51 if (!tfrc_lh_is_initialised(lh))
52 return;
54 for (lh->counter = 0; lh->counter < LIH_SIZE; lh->counter++)
55 if (lh->ring[LIH_INDEX(lh->counter)] != NULL) {
56 kmem_cache_free(tfrc_lh_slab,
57 lh->ring[LIH_INDEX(lh->counter)]);
58 lh->ring[LIH_INDEX(lh->counter)] = NULL;
62 static void tfrc_lh_calc_i_mean(struct tfrc_loss_hist *lh)
64 u32 i_i, i_tot0 = 0, i_tot1 = 0, w_tot = 0;
65 int i, k = tfrc_lh_length(lh) - 1; /* k is as in rfc3448bis, 5.4 */
67 if (k <= 0)
68 return;
70 for (i = 0; i <= k; i++) {
71 i_i = tfrc_lh_get_interval(lh, i);
73 if (i < k) {
74 i_tot0 += i_i * tfrc_lh_weights[i];
75 w_tot += tfrc_lh_weights[i];
77 if (i > 0)
78 i_tot1 += i_i * tfrc_lh_weights[i-1];
81 lh->i_mean = max(i_tot0, i_tot1) / w_tot;
84 /**
85 * tfrc_lh_update_i_mean - Update the `open' loss interval I_0
86 * For recomputing p: returns `true' if p > p_prev <=> 1/p < 1/p_prev
88 u8 tfrc_lh_update_i_mean(struct tfrc_loss_hist *lh, struct sk_buff *skb)
90 struct tfrc_loss_interval *cur = tfrc_lh_peek(lh);
91 u32 old_i_mean = lh->i_mean;
92 s64 len;
94 if (cur == NULL) /* not initialised */
95 return 0;
97 len = dccp_delta_seqno(cur->li_seqno, DCCP_SKB_CB(skb)->dccpd_seq) + 1;
99 if (len - (s64)cur->li_length <= 0) /* duplicate or reordered */
100 return 0;
102 if (SUB16(dccp_hdr(skb)->dccph_ccval, cur->li_ccval) > 4)
104 * Implements RFC 4342, 10.2:
105 * If a packet S (skb) exists whose seqno comes `after' the one
106 * starting the current loss interval (cur) and if the modulo-16
107 * distance from C(cur) to C(S) is greater than 4, consider all
108 * subsequent packets as belonging to a new loss interval. This
109 * test is necessary since CCVal may wrap between intervals.
111 cur->li_is_closed = 1;
113 if (tfrc_lh_length(lh) == 1) /* due to RFC 3448, 6.3.1 */
114 return 0;
116 cur->li_length = len;
117 tfrc_lh_calc_i_mean(lh);
119 return lh->i_mean < old_i_mean;
122 /* Determine if `new_loss' does begin a new loss interval [RFC 4342, 10.2] */
123 static inline u8 tfrc_lh_is_new_loss(struct tfrc_loss_interval *cur,
124 struct tfrc_rx_hist_entry *new_loss)
126 return dccp_delta_seqno(cur->li_seqno, new_loss->tfrchrx_seqno) > 0 &&
127 (cur->li_is_closed || SUB16(new_loss->tfrchrx_ccval, cur->li_ccval) > 4);
131 * tfrc_lh_interval_add - Insert new record into the Loss Interval database
132 * @lh: Loss Interval database
133 * @rh: Receive history containing a fresh loss event
134 * @calc_first_li: Caller-dependent routine to compute length of first interval
135 * @sk: Used by @calc_first_li in caller-specific way (subtyping)
136 * Updates I_mean and returns 1 if a new interval has in fact been added to @lh.
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)
141 struct tfrc_loss_interval *cur = tfrc_lh_peek(lh), *new;
143 if (cur != NULL && !tfrc_lh_is_new_loss(cur, tfrc_rx_hist_loss_prev(rh)))
144 return 0;
146 new = tfrc_lh_demand_next(lh);
147 if (unlikely(new == NULL)) {
148 DCCP_CRIT("Cannot allocate/add loss record.");
149 return 0;
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;
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;
165 tfrc_lh_calc_i_mean(lh);
167 return 1;
170 int __init tfrc_li_init(void)
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;
178 void tfrc_li_exit(void)
180 if (tfrc_lh_slab != NULL) {
181 kmem_cache_destroy(tfrc_lh_slab);
182 tfrc_lh_slab = NULL;