dd0fc992b042beafd80340e3d87178add3756ee2
[linux-2.6.git] / net / dccp / ccids / lib / loss_interval.c
1 /*
2  *  net/dccp/ccids/lib/loss_interval.c
3  *
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  *  This program is free software; you can redistribute it and/or modify
9  *  it under the terms of the GNU General Public License as published by
10  *  the Free Software Foundation; either version 2 of the License, or
11  *  (at your option) any later version.
12  */
13
14 #include <linux/module.h>
15 #include <net/sock.h>
16 #include "../../dccp.h"
17 #include "loss_interval.h"
18 #include "packet_history.h"
19 #include "tfrc.h"
20
21 #define DCCP_LI_HIST_IVAL_F_LENGTH  8
22
23 struct dccp_li_hist_entry {
24         struct list_head dccplih_node;
25         u64              dccplih_seqno:48,
26                          dccplih_win_count:4;
27         u32              dccplih_interval;
28 };
29
30 static struct kmem_cache *dccp_li_cachep __read_mostly;
31
32 static inline struct dccp_li_hist_entry *dccp_li_hist_entry_new(const gfp_t prio)
33 {
34         return kmem_cache_alloc(dccp_li_cachep, prio);
35 }
36
37 static inline void dccp_li_hist_entry_delete(struct dccp_li_hist_entry *entry)
38 {
39         if (entry != NULL)
40                 kmem_cache_free(dccp_li_cachep, entry);
41 }
42
43 void dccp_li_hist_purge(struct list_head *list)
44 {
45         struct dccp_li_hist_entry *entry, *next;
46
47         list_for_each_entry_safe(entry, next, list, dccplih_node) {
48                 list_del_init(&entry->dccplih_node);
49                 kmem_cache_free(dccp_li_cachep, entry);
50         }
51 }
52
53 EXPORT_SYMBOL_GPL(dccp_li_hist_purge);
54
55 /* Weights used to calculate loss event rate */
56 /*
57  * These are integers as per section 8 of RFC3448. We can then divide by 4 *
58  * when we use it.
59  */
60 static const int dccp_li_hist_w[DCCP_LI_HIST_IVAL_F_LENGTH] = {
61         4, 4, 4, 4, 3, 2, 1, 1,
62 };
63
64 u32 dccp_li_hist_calc_i_mean(struct list_head *list)
65 {
66         struct dccp_li_hist_entry *li_entry, *li_next;
67         int i = 0;
68         u32 i_tot;
69         u32 i_tot0 = 0;
70         u32 i_tot1 = 0;
71         u32 w_tot  = 0;
72
73         list_for_each_entry_safe(li_entry, li_next, list, dccplih_node) {
74                 if (li_entry->dccplih_interval != ~0U) {
75                         i_tot0 += li_entry->dccplih_interval * dccp_li_hist_w[i];
76                         w_tot  += dccp_li_hist_w[i];
77                         if (i != 0)
78                                 i_tot1 += li_entry->dccplih_interval * dccp_li_hist_w[i - 1];
79                 }
80
81
82                 if (++i > DCCP_LI_HIST_IVAL_F_LENGTH)
83                         break;
84         }
85
86         if (i != DCCP_LI_HIST_IVAL_F_LENGTH)
87                 return 0;
88
89         i_tot = max(i_tot0, i_tot1);
90
91         if (!w_tot) {
92                 DCCP_WARN("w_tot = 0\n");
93                 return 1;
94         }
95
96         return i_tot / w_tot;
97 }
98
99 EXPORT_SYMBOL_GPL(dccp_li_hist_calc_i_mean);
100
101 static int dccp_li_hist_interval_new(struct list_head *list,
102                                      const u64 seq_loss, const u8 win_loss)
103 {
104         struct dccp_li_hist_entry *entry;
105         int i;
106
107         for (i = 0; i < DCCP_LI_HIST_IVAL_F_LENGTH; i++) {
108                 entry = dccp_li_hist_entry_new(GFP_ATOMIC);
109                 if (entry == NULL) {
110                         dccp_li_hist_purge(list);
111                         DCCP_BUG("loss interval list entry is NULL");
112                         return 0;
113                 }
114                 entry->dccplih_interval = ~0;
115                 list_add(&entry->dccplih_node, list);
116         }
117
118         entry->dccplih_seqno     = seq_loss;
119         entry->dccplih_win_count = win_loss;
120         return 1;
121 }
122
123 /* calculate first loss interval
124  *
125  * returns estimated loss interval in usecs */
126 static u32 dccp_li_calc_first_li(struct sock *sk,
127                                  struct list_head *hist_list,
128                                  struct timeval *last_feedback,
129                                  u16 s, u32 bytes_recv,
130                                  u32 previous_x_recv)
131 {
132         struct dccp_rx_hist_entry *entry, *next, *tail = NULL;
133         u32 x_recv, p;
134         suseconds_t rtt, delta;
135         struct timeval tstamp = { 0, 0 };
136         int interval = 0;
137         int win_count = 0;
138         int step = 0;
139         u64 fval;
140
141         list_for_each_entry_safe(entry, next, hist_list, dccphrx_node) {
142                 if (dccp_rx_hist_entry_data_packet(entry)) {
143                         tail = entry;
144
145                         switch (step) {
146                         case 0:
147                                 tstamp    = entry->dccphrx_tstamp;
148                                 win_count = entry->dccphrx_ccval;
149                                 step = 1;
150                                 break;
151                         case 1:
152                                 interval = win_count - entry->dccphrx_ccval;
153                                 if (interval < 0)
154                                         interval += TFRC_WIN_COUNT_LIMIT;
155                                 if (interval > 4)
156                                         goto found;
157                                 break;
158                         }
159                 }
160         }
161
162         if (unlikely(step == 0)) {
163                 DCCP_WARN("%s(%p), packet history has no data packets!\n",
164                           dccp_role(sk), sk);
165                 return ~0;
166         }
167
168         if (unlikely(interval == 0)) {
169                 DCCP_WARN("%s(%p), Could not find a win_count interval > 0."
170                           "Defaulting to 1\n", dccp_role(sk), sk);
171                 interval = 1;
172         }
173 found:
174         if (!tail) {
175                 DCCP_CRIT("tail is null\n");
176                 return ~0;
177         }
178
179         delta = timeval_delta(&tstamp, &tail->dccphrx_tstamp);
180         DCCP_BUG_ON(delta < 0);
181
182         rtt = delta * 4 / interval;
183         dccp_pr_debug("%s(%p), approximated RTT to %dus\n",
184                       dccp_role(sk), sk, (int)rtt);
185
186         /*
187          * Determine the length of the first loss interval via inverse lookup.
188          * Assume that X_recv can be computed by the throughput equation
189          *                  s
190          *      X_recv = --------
191          *               R * fval
192          * Find some p such that f(p) = fval; return 1/p [RFC 3448, 6.3.1].
193          */
194         if (rtt == 0) {                 /* would result in divide-by-zero */
195                 DCCP_WARN("RTT==0\n");
196                 return ~0;
197         }
198
199         dccp_timestamp(sk, &tstamp);
200         delta = timeval_delta(&tstamp, last_feedback);
201         DCCP_BUG_ON(delta <= 0);
202
203         x_recv = scaled_div32(bytes_recv, delta);
204         if (x_recv == 0) {              /* would also trigger divide-by-zero */
205                 DCCP_WARN("X_recv==0\n");
206                 if (previous_x_recv == 0) {
207                         DCCP_BUG("stored value of X_recv is zero");
208                         return ~0;
209                 }
210                 x_recv = previous_x_recv;
211         }
212
213         fval = scaled_div(s, rtt);
214         fval = scaled_div32(fval, x_recv);
215         p = tfrc_calc_x_reverse_lookup(fval);
216
217         dccp_pr_debug("%s(%p), receive rate=%u bytes/s, implied "
218                       "loss rate=%u\n", dccp_role(sk), sk, x_recv, p);
219
220         if (p == 0)
221                 return ~0;
222         else
223                 return 1000000 / p;
224 }
225
226 void dccp_li_update_li(struct sock *sk,
227                        struct list_head *li_hist_list,
228                        struct list_head *hist_list,
229                        struct timeval *last_feedback, u16 s, u32 bytes_recv,
230                        u32 previous_x_recv, u64 seq_loss, u8 win_loss)
231 {
232         struct dccp_li_hist_entry *head;
233         u64 seq_temp;
234
235         if (list_empty(li_hist_list)) {
236                 if (!dccp_li_hist_interval_new(li_hist_list, seq_loss,
237                                                win_loss))
238                         return;
239
240                 head = list_entry(li_hist_list->next, struct dccp_li_hist_entry,
241                                   dccplih_node);
242                 head->dccplih_interval = dccp_li_calc_first_li(sk, hist_list,
243                                                                last_feedback,
244                                                                s, bytes_recv,
245                                                                previous_x_recv);
246         } else {
247                 struct dccp_li_hist_entry *entry;
248                 struct list_head *tail;
249
250                 head = list_entry(li_hist_list->next, struct dccp_li_hist_entry,
251                                   dccplih_node);
252                 /* FIXME win count check removed as was wrong */
253                 /* should make this check with receive history */
254                 /* and compare there as per section 10.2 of RFC4342 */
255
256                 /* new loss event detected */
257                 /* calculate last interval length */
258                 seq_temp = dccp_delta_seqno(head->dccplih_seqno, seq_loss);
259                 entry = dccp_li_hist_entry_new(GFP_ATOMIC);
260
261                 if (entry == NULL) {
262                         DCCP_BUG("out of memory - can not allocate entry");
263                         return;
264                 }
265
266                 list_add(&entry->dccplih_node, li_hist_list);
267
268                 tail = li_hist_list->prev;
269                 list_del(tail);
270                 kmem_cache_free(dccp_li_cachep, tail);
271
272                 /* Create the newest interval */
273                 entry->dccplih_seqno = seq_loss;
274                 entry->dccplih_interval = seq_temp;
275                 entry->dccplih_win_count = win_loss;
276         }
277 }
278
279 EXPORT_SYMBOL_GPL(dccp_li_update_li);
280
281 static __init int dccp_li_init(void)
282 {
283         dccp_li_cachep = kmem_cache_create("dccp_li_hist",
284                                            sizeof(struct dccp_li_hist_entry),
285                                            0, SLAB_HWCACHE_ALIGN, NULL, NULL);
286         return dccp_li_cachep == NULL ? -ENOBUFS : 0;
287 }
288
289 static __exit void dccp_li_exit(void)
290 {
291         kmem_cache_destroy(dccp_li_cachep);
292 }
293
294 module_init(dccp_li_init);
295 module_exit(dccp_li_exit);