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