err.no Git - linux-2.6/blob - net/dccp/ccids/lib/packet_history.c

   1 /*
   2  *  net/dccp/packet_history.c
   3  *
   4  *  Copyright (c) 2007   The University of Aberdeen, Scotland, UK
   5  *  Copyright (c) 2005-7 The University of Waikato, Hamilton, New Zealand.
   6  *
   7  *  An implementation of the DCCP protocol
   8  *
   9  *  This code has been developed by the University of Waikato WAND
  10  *  research group. For further information please see http://www.wand.net.nz/
  11  *  or e-mail Ian McDonald - ian.mcdonald@jandi.co.nz
  12  *
  13  *  This code also uses code from Lulea University, rereleased as GPL by its
  14  *  authors:
  15  *  Copyright (c) 2003 Nils-Erik Mattsson, Joacim Haggmark, Magnus Erixzon
  16  *
  17  *  Changes to meet Linux coding standards, to make it meet latest ccid3 draft
  18  *  and to make it work as a loadable module in the DCCP stack written by
  19  *  Arnaldo Carvalho de Melo <acme@conectiva.com.br>.
  20  *
  21  *  Copyright (c) 2005 Arnaldo Carvalho de Melo <acme@conectiva.com.br>
  22  *
  23  *  This program is free software; you can redistribute it and/or modify
  24  *  it under the terms of the GNU General Public License as published by
  25  *  the Free Software Foundation; either version 2 of the License, or
  26  *  (at your option) any later version.
  27  *
  28  *  This program is distributed in the hope that it will be useful,
  29  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  30  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  31  *  GNU General Public License for more details.
  32  *
  33  *  You should have received a copy of the GNU General Public License
  34  *  along with this program; if not, write to the Free Software
  35  *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  36  */
  37
  38 #include <linux/string.h>
  39 #include <linux/slab.h>
  40 #include "packet_history.h"
  41 #include "../../dccp.h"
  42
  43 /**
  44  *  tfrc_tx_hist_entry  -  Simple singly-linked TX history list
  45  *  @next:  next oldest entry (LIFO order)
  46  *  @seqno: sequence number of this entry
  47  *  @stamp: send time of packet with sequence number @seqno
  48  */
  49 struct tfrc_tx_hist_entry {
  50         struct tfrc_tx_hist_entry *next;
  51         u64                       seqno;
  52         ktime_t                   stamp;
  53 };
  54
  55 /*
  56  * Transmitter History Routines
  57  */
  58 static struct kmem_cache *tfrc_tx_hist_slab;
  59
  60 int __init tfrc_tx_packet_history_init(void)
  61 {
  62         tfrc_tx_hist_slab = kmem_cache_create("tfrc_tx_hist",
  63                                               sizeof(struct tfrc_tx_hist_entry),
  64                                               0, SLAB_HWCACHE_ALIGN, NULL);
  65         return tfrc_tx_hist_slab == NULL ? -ENOBUFS : 0;
  66 }
  67
  68 void tfrc_tx_packet_history_exit(void)
  69 {
  70         if (tfrc_tx_hist_slab != NULL) {
  71                 kmem_cache_destroy(tfrc_tx_hist_slab);
  72                 tfrc_tx_hist_slab = NULL;
  73         }
  74 }
  75
  76 static struct tfrc_tx_hist_entry *
  77         tfrc_tx_hist_find_entry(struct tfrc_tx_hist_entry *head, u64 seqno)
  78 {
  79         while (head != NULL && head->seqno != seqno)
  80                 head = head->next;
  81
  82         return head;
  83 }
  84
  85 int tfrc_tx_hist_add(struct tfrc_tx_hist_entry **headp, u64 seqno)
  86 {
  87         struct tfrc_tx_hist_entry *entry = kmem_cache_alloc(tfrc_tx_hist_slab, gfp_any());
  88
  89         if (entry == NULL)
  90                 return -ENOBUFS;
  91         entry->seqno = seqno;
  92         entry->stamp = ktime_get_real();
  93         entry->next  = *headp;
  94         *headp       = entry;
  95         return 0;
  96 }
  97 EXPORT_SYMBOL_GPL(tfrc_tx_hist_add);
  98
  99 void tfrc_tx_hist_purge(struct tfrc_tx_hist_entry **headp)
 100 {
 101         struct tfrc_tx_hist_entry *head = *headp;
 102
 103         while (head != NULL) {
 104                 struct tfrc_tx_hist_entry *next = head->next;
 105
 106                 kmem_cache_free(tfrc_tx_hist_slab, head);
 107                 head = next;
 108         }
 109
 110         *headp = NULL;
 111 }
 112 EXPORT_SYMBOL_GPL(tfrc_tx_hist_purge);
 113
 114 u32 tfrc_tx_hist_rtt(struct tfrc_tx_hist_entry *head, const u64 seqno,
 115                      const ktime_t now)
 116 {
 117         u32 rtt = 0;
 118         struct tfrc_tx_hist_entry *packet = tfrc_tx_hist_find_entry(head, seqno);
 119
 120         if (packet != NULL) {
 121                 rtt = ktime_us_delta(now, packet->stamp);
 122                 /*
 123                  * Garbage-collect older (irrelevant) entries:
 124                  */
 125                 tfrc_tx_hist_purge(&packet->next);
 126         }
 127
 128         return rtt;
 129 }
 130 EXPORT_SYMBOL_GPL(tfrc_tx_hist_rtt);
 131
 132
 133 /*
 134  *      Receiver History Routines
 135  */
 136 static struct kmem_cache *tfrc_rx_hist_slab;
 137
 138 int __init tfrc_rx_packet_history_init(void)
 139 {
 140         tfrc_rx_hist_slab = kmem_cache_create("tfrc_rxh_cache",
 141                                               sizeof(struct tfrc_rx_hist_entry),
 142                                               0, SLAB_HWCACHE_ALIGN, NULL);
 143         return tfrc_rx_hist_slab == NULL ? -ENOBUFS : 0;
 144 }
 145
 146 void tfrc_rx_packet_history_exit(void)
 147 {
 148         if (tfrc_rx_hist_slab != NULL) {
 149                 kmem_cache_destroy(tfrc_rx_hist_slab);
 150                 tfrc_rx_hist_slab = NULL;
 151         }
 152 }
 153
 154 /**
 155  * tfrc_rx_hist_index - index to reach n-th entry after loss_start
 156  */
 157 static inline u8 tfrc_rx_hist_index(const struct tfrc_rx_hist *h, const u8 n)
 158 {
 159         return (h->loss_start + n) & TFRC_NDUPACK;
 160 }
 161
 162 /**
 163  * tfrc_rx_hist_last_rcv - entry with highest-received-seqno so far
 164  */
 165 static inline struct tfrc_rx_hist_entry *
 166                         tfrc_rx_hist_last_rcv(const struct tfrc_rx_hist *h)
 167 {
 168         return h->ring[tfrc_rx_hist_index(h, h->loss_count)];
 169 }
 170
 171 void tfrc_rx_hist_add_packet(struct tfrc_rx_hist *h,
 172                              const struct sk_buff *skb,
 173                              const u32 ndp)
 174 {
 175         struct tfrc_rx_hist_entry *entry = tfrc_rx_hist_last_rcv(h);
 176         const struct dccp_hdr *dh = dccp_hdr(skb);
 177
 178         entry->tfrchrx_seqno = DCCP_SKB_CB(skb)->dccpd_seq;
 179         entry->tfrchrx_ccval = dh->dccph_ccval;
 180         entry->tfrchrx_type  = dh->dccph_type;
 181         entry->tfrchrx_ndp   = ndp;
 182         entry->tfrchrx_tstamp = ktime_get_real();
 183 }
 184 EXPORT_SYMBOL_GPL(tfrc_rx_hist_add_packet);
 185
 186 /**
 187  * tfrc_rx_hist_entry - return the n-th history entry after loss_start
 188  */
 189 static inline struct tfrc_rx_hist_entry *
 190                 tfrc_rx_hist_entry(const struct tfrc_rx_hist *h, const u8 n)
 191 {
 192         return h->ring[tfrc_rx_hist_index(h, n)];
 193 }
 194
 195 /**
 196  * tfrc_rx_hist_loss_prev - entry with highest-received-seqno before loss was detected
 197  */
 198 static inline struct tfrc_rx_hist_entry *
 199                         tfrc_rx_hist_loss_prev(const struct tfrc_rx_hist *h)
 200 {
 201         return h->ring[h->loss_start];
 202 }
 203
 204 /* has the packet contained in skb been seen before? */
 205 int tfrc_rx_hist_duplicate(struct tfrc_rx_hist *h, struct sk_buff *skb)
 206 {
 207         const u64 seq = DCCP_SKB_CB(skb)->dccpd_seq;
 208         int i;
 209
 210         if (dccp_delta_seqno(tfrc_rx_hist_loss_prev(h)->tfrchrx_seqno, seq) <= 0)
 211                 return 1;
 212
 213         for (i = 1; i <= h->loss_count; i++)
 214                 if (tfrc_rx_hist_entry(h, i)->tfrchrx_seqno == seq)
 215                         return 1;
 216
 217         return 0;
 218 }
 219 EXPORT_SYMBOL_GPL(tfrc_rx_hist_duplicate);
 220
 221 /* initialise loss detection and disable RTT sampling */
 222 static inline void tfrc_rx_hist_loss_indicated(struct tfrc_rx_hist *h)
 223 {
 224         h->loss_count = 1;
 225 }
 226
 227 /* indicate whether previously a packet was detected missing */
 228 static inline int tfrc_rx_hist_loss_pending(const struct tfrc_rx_hist *h)
 229 {
 230         return h->loss_count;
 231 }
 232
 233 /* any data packets missing between last reception and skb ? */
 234 int tfrc_rx_hist_new_loss_indicated(struct tfrc_rx_hist *h,
 235                                     const struct sk_buff *skb, u32 ndp)
 236 {
 237         int delta = dccp_delta_seqno(tfrc_rx_hist_last_rcv(h)->tfrchrx_seqno,
 238                                      DCCP_SKB_CB(skb)->dccpd_seq);
 239
 240         if (delta > 1 && ndp < delta)
 241                 tfrc_rx_hist_loss_indicated(h);
 242
 243         return tfrc_rx_hist_loss_pending(h);
 244 }
 245 EXPORT_SYMBOL_GPL(tfrc_rx_hist_new_loss_indicated);
 246
 247 int tfrc_rx_hist_alloc(struct tfrc_rx_hist *h)
 248 {
 249         int i;
 250
 251         for (i = 0; i <= TFRC_NDUPACK; i++) {
 252                 h->ring[i] = kmem_cache_alloc(tfrc_rx_hist_slab, GFP_ATOMIC);
 253                 if (h->ring[i] == NULL)
 254                         goto out_free;
 255         }
 256
 257         h->loss_count = h->loss_start = 0;
 258         return 0;
 259
 260 out_free:
 261         while (i-- != 0) {
 262                 kmem_cache_free(tfrc_rx_hist_slab, h->ring[i]);
 263                 h->ring[i] = NULL;
 264         }
 265         return -ENOBUFS;
 266 }
 267 EXPORT_SYMBOL_GPL(tfrc_rx_hist_alloc);
 268
 269 void tfrc_rx_hist_purge(struct tfrc_rx_hist *h)
 270 {
 271         int i;
 272
 273         for (i = 0; i <= TFRC_NDUPACK; ++i)
 274                 if (h->ring[i] != NULL) {
 275                         kmem_cache_free(tfrc_rx_hist_slab, h->ring[i]);
 276                         h->ring[i] = NULL;
 277                 }
 278 }
 279 EXPORT_SYMBOL_GPL(tfrc_rx_hist_purge);
 280
 281 /**
 282  * tfrc_rx_hist_rtt_last_s - reference entry to compute RTT samples against
 283  */
 284 static inline struct tfrc_rx_hist_entry *
 285                         tfrc_rx_hist_rtt_last_s(const struct tfrc_rx_hist *h)
 286 {
 287         return h->ring[0];
 288 }
 289
 290 /**
 291  * tfrc_rx_hist_rtt_prev_s: previously suitable (wrt rtt_last_s) RTT-sampling entry
 292  */
 293 static inline struct tfrc_rx_hist_entry *
 294                         tfrc_rx_hist_rtt_prev_s(const struct tfrc_rx_hist *h)
 295 {
 296         return h->ring[h->rtt_sample_prev];
 297 }
 298
 299 /**
 300  * tfrc_rx_hist_sample_rtt  -  Sample RTT from timestamp / CCVal
 301  * Based on ideas presented in RFC 4342, 8.1. Returns 0 if it was not able
 302  * to compute a sample with given data - calling function should check this.
 303  */
 304 u32 tfrc_rx_hist_sample_rtt(struct tfrc_rx_hist *h, const struct sk_buff *skb)
 305 {
 306         u32 sample = 0,
 307             delta_v = SUB16(dccp_hdr(skb)->dccph_ccval,
 308                             tfrc_rx_hist_rtt_last_s(h)->tfrchrx_ccval);
 309
 310         if (delta_v < 1 || delta_v > 4) {       /* unsuitable CCVal delta */
 311                 if (h->rtt_sample_prev == 2) {  /* previous candidate stored */
 312                         sample = SUB16(tfrc_rx_hist_rtt_prev_s(h)->tfrchrx_ccval,
 313                                        tfrc_rx_hist_rtt_last_s(h)->tfrchrx_ccval);
 314                         if (sample)
 315                                 sample = 4 / sample *
 316                                          ktime_us_delta(tfrc_rx_hist_rtt_prev_s(h)->tfrchrx_tstamp,
 317                                                         tfrc_rx_hist_rtt_last_s(h)->tfrchrx_tstamp);
 318                         else    /*
 319                                  * FIXME: This condition is in principle not
 320                                  * possible but occurs when CCID is used for
 321                                  * two-way data traffic. I have tried to trace
 322                                  * it, but the cause does not seem to be here.
 323                                  */
 324                                 DCCP_BUG("please report to dccp@vger.kernel.org"
 325                                          " => prev = %u, last = %u",
 326                                          tfrc_rx_hist_rtt_prev_s(h)->tfrchrx_ccval,
 327                                          tfrc_rx_hist_rtt_last_s(h)->tfrchrx_ccval);
 328                 } else if (delta_v < 1) {
 329                         h->rtt_sample_prev = 1;
 330                         goto keep_ref_for_next_time;
 331                 }
 332
 333         } else if (delta_v == 4) /* optimal match */
 334                 sample = ktime_to_us(net_timedelta(tfrc_rx_hist_rtt_last_s(h)->tfrchrx_tstamp));
 335         else {                   /* suboptimal match */
 336                 h->rtt_sample_prev = 2;
 337                 goto keep_ref_for_next_time;
 338         }
 339
 340         if (unlikely(sample > DCCP_SANE_RTT_MAX)) {
 341                 DCCP_WARN("RTT sample %u too large, using max\n", sample);
 342                 sample = DCCP_SANE_RTT_MAX;
 343         }
 344
 345         h->rtt_sample_prev = 0;        /* use current entry as next reference */
 346 keep_ref_for_next_time:
 347
 348         return sample;
 349 }
 350 EXPORT_SYMBOL_GPL(tfrc_rx_hist_sample_rtt);