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 dccp_li_hist *dccp_li_hist_new(const char *name)
  22 {
  23         struct dccp_li_hist *hist = kmalloc(sizeof(*hist), GFP_ATOMIC);
  24         static const char dccp_li_hist_mask[] = "li_hist_%s";
  25         char *slab_name;
  26
  27         if (hist == NULL)
  28                 goto out;
  29
  30         slab_name = kmalloc(strlen(name) + sizeof(dccp_li_hist_mask) - 1,
  31                             GFP_ATOMIC);
  32         if (slab_name == NULL)
  33                 goto out_free_hist;
  34
  35         sprintf(slab_name, dccp_li_hist_mask, name);
  36         hist->dccplih_slab = kmem_cache_create(slab_name,
  37                                              sizeof(struct dccp_li_hist_entry),
  38                                                0, SLAB_HWCACHE_ALIGN,
  39                                                NULL, NULL);
  40         if (hist->dccplih_slab == NULL)
  41                 goto out_free_slab_name;
  42 out:
  43         return hist;
  44 out_free_slab_name:
  45         kfree(slab_name);
  46 out_free_hist:
  47         kfree(hist);
  48         hist = NULL;
  49         goto out;
  50 }
  51
  52 EXPORT_SYMBOL_GPL(dccp_li_hist_new);
  53
  54 void dccp_li_hist_delete(struct dccp_li_hist *hist)
  55 {
  56         const char* name = kmem_cache_name(hist->dccplih_slab);
  57
  58         kmem_cache_destroy(hist->dccplih_slab);
  59         kfree(name);
  60         kfree(hist);
  61 }
  62
  63 EXPORT_SYMBOL_GPL(dccp_li_hist_delete);
  64
  65 void dccp_li_hist_purge(struct dccp_li_hist *hist, struct list_head *list)
  66 {
  67         struct dccp_li_hist_entry *entry, *next;
  68
  69         list_for_each_entry_safe(entry, next, list, dccplih_node) {
  70                 list_del_init(&entry->dccplih_node);
  71                 kmem_cache_free(hist->dccplih_slab, entry);
  72         }
  73 }
  74
  75 EXPORT_SYMBOL_GPL(dccp_li_hist_purge);
  76
  77 /* Weights used to calculate loss event rate */
  78 /*
  79  * These are integers as per section 8 of RFC3448. We can then divide by 4 *
  80  * when we use it.
  81  */
  82 static const int dccp_li_hist_w[DCCP_LI_HIST_IVAL_F_LENGTH] = {
  83         4, 4, 4, 4, 3, 2, 1, 1,
  84 };
  85
  86 u32 dccp_li_hist_calc_i_mean(struct list_head *list)
  87 {
  88         struct dccp_li_hist_entry *li_entry, *li_next;
  89         int i = 0;
  90         u32 i_tot;
  91         u32 i_tot0 = 0;
  92         u32 i_tot1 = 0;
  93         u32 w_tot  = 0;
  94
  95         list_for_each_entry_safe(li_entry, li_next, list, dccplih_node) {
  96                 if (li_entry->dccplih_interval != ~0U) {
  97                         i_tot0 += li_entry->dccplih_interval * dccp_li_hist_w[i];
  98                         w_tot  += dccp_li_hist_w[i];
  99                         if (i != 0)
 100                                 i_tot1 += li_entry->dccplih_interval * dccp_li_hist_w[i - 1];
 101                 }
 102
 103
 104                 if (++i > DCCP_LI_HIST_IVAL_F_LENGTH)
 105                         break;
 106         }
 107
 108         if (i != DCCP_LI_HIST_IVAL_F_LENGTH)
 109                 return 0;
 110
 111         i_tot = max(i_tot0, i_tot1);
 112
 113         if (!w_tot) {
 114                 DCCP_WARN("w_tot = 0\n");
 115                 return 1;
 116         }
 117
 118         return i_tot / w_tot;
 119 }
 120
 121 EXPORT_SYMBOL_GPL(dccp_li_hist_calc_i_mean);
 122
 123 int dccp_li_hist_interval_new(struct dccp_li_hist *hist,
 124    struct list_head *list, const u64 seq_loss, const u8 win_loss)
 125 {
 126         struct dccp_li_hist_entry *entry;
 127         int i;
 128
 129         for (i = 0; i < DCCP_LI_HIST_IVAL_F_LENGTH; i++) {
 130                 entry = dccp_li_hist_entry_new(hist, GFP_ATOMIC);
 131                 if (entry == NULL) {
 132                         dccp_li_hist_purge(hist, list);
 133                         DCCP_BUG("loss interval list entry is NULL");
 134                         return 0;
 135                 }
 136                 entry->dccplih_interval = ~0;
 137                 list_add(&entry->dccplih_node, list);
 138         }
 139
 140         entry->dccplih_seqno     = seq_loss;
 141         entry->dccplih_win_count = win_loss;
 142         return 1;
 143 }
 144
 145 EXPORT_SYMBOL_GPL(dccp_li_hist_interval_new);
 146
 147 /* calculate first loss interval
 148  *
 149  * returns estimated loss interval in usecs */
 150 static u32 dccp_li_calc_first_li(struct sock *sk,
 151                                  struct list_head *hist_list,
 152                                  struct timeval *last_feedback,
 153                                  u16 s, u32 bytes_recv,
 154                                  u32 previous_x_recv)
 155 {
 156         struct dccp_rx_hist_entry *entry, *next, *tail = NULL;
 157         u32 x_recv, p;
 158         suseconds_t rtt, delta;
 159         struct timeval tstamp = { 0, 0 };
 160         int interval = 0;
 161         int win_count = 0;
 162         int step = 0;
 163         u64 fval;
 164
 165         list_for_each_entry_safe(entry, next, hist_list, dccphrx_node) {
 166                 if (dccp_rx_hist_entry_data_packet(entry)) {
 167                         tail = entry;
 168
 169                         switch (step) {
 170                         case 0:
 171                                 tstamp    = entry->dccphrx_tstamp;
 172                                 win_count = entry->dccphrx_ccval;
 173                                 step = 1;
 174                                 break;
 175                         case 1:
 176                                 interval = win_count - entry->dccphrx_ccval;
 177                                 if (interval < 0)
 178                                         interval += TFRC_WIN_COUNT_LIMIT;
 179                                 if (interval > 4)
 180                                         goto found;
 181                                 break;
 182                         }
 183                 }
 184         }
 185
 186         if (unlikely(step == 0)) {
 187                 DCCP_WARN("%s(%p), packet history has no data packets!\n",
 188                           dccp_role(sk), sk);
 189                 return ~0;
 190         }
 191
 192         if (unlikely(interval == 0)) {
 193                 DCCP_WARN("%s(%p), Could not find a win_count interval > 0."
 194                           "Defaulting to 1\n", dccp_role(sk), sk);
 195                 interval = 1;
 196         }
 197 found:
 198         if (!tail) {
 199                 DCCP_CRIT("tail is null\n");
 200                 return ~0;
 201         }
 202
 203         delta = timeval_delta(&tstamp, &tail->dccphrx_tstamp);
 204         DCCP_BUG_ON(delta < 0);
 205
 206         rtt = delta * 4 / interval;
 207         dccp_pr_debug("%s(%p), approximated RTT to %dus\n",
 208                       dccp_role(sk), sk, (int)rtt);
 209
 210         /*
 211          * Determine the length of the first loss interval via inverse lookup.
 212          * Assume that X_recv can be computed by the throughput equation
 213          *                  s
 214          *      X_recv = --------
 215          *               R * fval
 216          * Find some p such that f(p) = fval; return 1/p [RFC 3448, 6.3.1].
 217          */
 218         if (rtt == 0) {                 /* would result in divide-by-zero */
 219                 DCCP_WARN("RTT==0\n");
 220                 return ~0;
 221         }
 222
 223         dccp_timestamp(sk, &tstamp);
 224         delta = timeval_delta(&tstamp, last_feedback);
 225         DCCP_BUG_ON(delta <= 0);
 226
 227         x_recv = scaled_div32(bytes_recv, delta);
 228         if (x_recv == 0) {              /* would also trigger divide-by-zero */
 229                 DCCP_WARN("X_recv==0\n");
 230                 if (previous_x_recv == 0) {
 231                         DCCP_BUG("stored value of X_recv is zero");
 232                         return ~0;
 233                 }
 234                 x_recv = previous_x_recv;
 235         }
 236
 237         fval = scaled_div(s, rtt);
 238         fval = scaled_div32(fval, x_recv);
 239         p = tfrc_calc_x_reverse_lookup(fval);
 240
 241         dccp_pr_debug("%s(%p), receive rate=%u bytes/s, implied "
 242                       "loss rate=%u\n", dccp_role(sk), sk, x_recv, p);
 243
 244         if (p == 0)
 245                 return ~0;
 246         else
 247                 return 1000000 / p;
 248 }
 249
 250 void dccp_li_update_li(struct sock *sk, struct dccp_li_hist *li_hist,
 251                        struct list_head *li_hist_list,
 252                        struct list_head *hist_list,
 253                        struct timeval *last_feedback, u16 s, u32 bytes_recv,
 254                        u32 previous_x_recv, u64 seq_loss, u8 win_loss)
 255 {
 256         struct dccp_li_hist_entry *head;
 257         u64 seq_temp;
 258
 259         if (list_empty(li_hist_list)) {
 260                 if (!dccp_li_hist_interval_new(li_hist, li_hist_list,
 261                                                seq_loss, win_loss))
 262                         return;
 263
 264                 head = list_entry(li_hist_list->next, struct dccp_li_hist_entry,
 265                                   dccplih_node);
 266                 head->dccplih_interval = dccp_li_calc_first_li(sk, hist_list,
 267                                                                last_feedback,
 268                                                                s, bytes_recv,
 269                                                                previous_x_recv);
 270         } else {
 271                 struct dccp_li_hist_entry *entry;
 272                 struct list_head *tail;
 273
 274                 head = list_entry(li_hist_list->next, struct dccp_li_hist_entry,
 275                                   dccplih_node);
 276                 /* FIXME win count check removed as was wrong */
 277                 /* should make this check with receive history */
 278                 /* and compare there as per section 10.2 of RFC4342 */
 279
 280                 /* new loss event detected */
 281                 /* calculate last interval length */
 282                 seq_temp = dccp_delta_seqno(head->dccplih_seqno, seq_loss);
 283                 entry = dccp_li_hist_entry_new(li_hist, GFP_ATOMIC);
 284
 285                 if (entry == NULL) {
 286                         DCCP_BUG("out of memory - can not allocate entry");
 287                         return;
 288                 }
 289
 290                 list_add(&entry->dccplih_node, li_hist_list);
 291
 292                 tail = li_hist_list->prev;
 293                 list_del(tail);
 294                 kmem_cache_free(li_hist->dccplih_slab, tail);
 295
 296                 /* Create the newest interval */
 297                 entry->dccplih_seqno = seq_loss;
 298                 entry->dccplih_interval = seq_temp;
 299                 entry->dccplih_win_count = win_loss;
 300         }
 301 }
 302
 303 EXPORT_SYMBOL_GPL(dccp_li_update_li);