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                                  ktime_t 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         ktime_t tstamp = ktime_set(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 = ktime_us_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         delta = ktime_us_delta(ktime_get_real(), last_feedback);
 200         DCCP_BUG_ON(delta <= 0);
 201
 202         x_recv = scaled_div32(bytes_recv, delta);
 203         if (x_recv == 0) {              /* would also trigger divide-by-zero */
 204                 DCCP_WARN("X_recv==0\n");
 205                 if (previous_x_recv == 0) {
 206                         DCCP_BUG("stored value of X_recv is zero");
 207                         return ~0;
 208                 }
 209                 x_recv = previous_x_recv;
 210         }
 211
 212         fval = scaled_div(s, rtt);
 213         fval = scaled_div32(fval, x_recv);
 214         p = tfrc_calc_x_reverse_lookup(fval);
 215
 216         dccp_pr_debug("%s(%p), receive rate=%u bytes/s, implied "
 217                       "loss rate=%u\n", dccp_role(sk), sk, x_recv, p);
 218
 219         if (p == 0)
 220                 return ~0;
 221         else
 222                 return 1000000 / p;
 223 }
 224
 225 void dccp_li_update_li(struct sock *sk,
 226                        struct list_head *li_hist_list,
 227                        struct list_head *hist_list,
 228                        ktime_t last_feedback, u16 s, u32 bytes_recv,
 229                        u32 previous_x_recv, u64 seq_loss, u8 win_loss)
 230 {
 231         struct dccp_li_hist_entry *head;
 232         u64 seq_temp;
 233
 234         if (list_empty(li_hist_list)) {
 235                 if (!dccp_li_hist_interval_new(li_hist_list, seq_loss,
 236                                                win_loss))
 237                         return;
 238
 239                 head = list_entry(li_hist_list->next, struct dccp_li_hist_entry,
 240                                   dccplih_node);
 241                 head->dccplih_interval = dccp_li_calc_first_li(sk, hist_list,
 242                                                                last_feedback,
 243                                                                s, bytes_recv,
 244                                                                previous_x_recv);
 245         } else {
 246                 struct dccp_li_hist_entry *entry;
 247                 struct list_head *tail;
 248
 249                 head = list_entry(li_hist_list->next, struct dccp_li_hist_entry,
 250                                   dccplih_node);
 251                 /* FIXME win count check removed as was wrong */
 252                 /* should make this check with receive history */
 253                 /* and compare there as per section 10.2 of RFC4342 */
 254
 255                 /* new loss event detected */
 256                 /* calculate last interval length */
 257                 seq_temp = dccp_delta_seqno(head->dccplih_seqno, seq_loss);
 258                 entry = dccp_li_hist_entry_new(GFP_ATOMIC);
 259
 260                 if (entry == NULL) {
 261                         DCCP_BUG("out of memory - can not allocate entry");
 262                         return;
 263                 }
 264
 265                 list_add(&entry->dccplih_node, li_hist_list);
 266
 267                 tail = li_hist_list->prev;
 268                 list_del(tail);
 269                 kmem_cache_free(dccp_li_cachep, tail);
 270
 271                 /* Create the newest interval */
 272                 entry->dccplih_seqno = seq_loss;
 273                 entry->dccplih_interval = seq_temp;
 274                 entry->dccplih_win_count = win_loss;
 275         }
 276 }
 277
 278 EXPORT_SYMBOL_GPL(dccp_li_update_li);
 279
 280 static __init int dccp_li_init(void)
 281 {
 282         dccp_li_cachep = kmem_cache_create("dccp_li_hist",
 283                                            sizeof(struct dccp_li_hist_entry),
 284                                            0, SLAB_HWCACHE_ALIGN, NULL);
 285         return dccp_li_cachep == NULL ? -ENOBUFS : 0;
 286 }
 287
 288 static __exit void dccp_li_exit(void)
 289 {
 290         kmem_cache_destroy(dccp_li_cachep);
 291 }
 292
 293 module_init(dccp_li_init);
 294 module_exit(dccp_li_exit);