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   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 static inline void tfrc_rx_hist_entry_from_skb(struct tfrc_rx_hist_entry *entry,
 155                                                const struct sk_buff *skb,
 156                                                const u64 ndp)
 157 {
 158         const struct dccp_hdr *dh = dccp_hdr(skb);
 159
 160         entry->tfrchrx_seqno = DCCP_SKB_CB(skb)->dccpd_seq;
 161         entry->tfrchrx_ccval = dh->dccph_ccval;
 162         entry->tfrchrx_type  = dh->dccph_type;
 163         entry->tfrchrx_ndp   = ndp;
 164         entry->tfrchrx_tstamp = ktime_get_real();
 165 }
 166
 167 void tfrc_rx_hist_add_packet(struct tfrc_rx_hist *h,
 168                              const struct sk_buff *skb,
 169                              const u64 ndp)
 170 {
 171         struct tfrc_rx_hist_entry *entry = tfrc_rx_hist_last_rcv(h);
 172
 173         tfrc_rx_hist_entry_from_skb(entry, skb, ndp);
 174 }
 175 EXPORT_SYMBOL_GPL(tfrc_rx_hist_add_packet);
 176
 177 /* has the packet contained in skb been seen before? */
 178 int tfrc_rx_hist_duplicate(struct tfrc_rx_hist *h, struct sk_buff *skb)
 179 {
 180         const u64 seq = DCCP_SKB_CB(skb)->dccpd_seq;
 181         int i;
 182
 183         if (dccp_delta_seqno(tfrc_rx_hist_loss_prev(h)->tfrchrx_seqno, seq) <= 0)
 184                 return 1;
 185
 186         for (i = 1; i <= h->loss_count; i++)
 187                 if (tfrc_rx_hist_entry(h, i)->tfrchrx_seqno == seq)
 188                         return 1;
 189
 190         return 0;
 191 }
 192 EXPORT_SYMBOL_GPL(tfrc_rx_hist_duplicate);
 193
 194 static void tfrc_rx_hist_swap(struct tfrc_rx_hist *h, const u8 a, const u8 b)
 195 {
 196         const u8 idx_a = tfrc_rx_hist_index(h, a),
 197                  idx_b = tfrc_rx_hist_index(h, b);
 198         struct tfrc_rx_hist_entry *tmp = h->ring[idx_a];
 199
 200         h->ring[idx_a] = h->ring[idx_b];
 201         h->ring[idx_b] = tmp;
 202 }
 203
 204 /*
 205  * Private helper functions for loss detection.
 206  *
 207  * In the descriptions, `Si' refers to the sequence number of entry number i,
 208  * whose NDP count is `Ni' (lower case is used for variables).
 209  * Note: All __xxx_loss functions expect that a test against duplicates has been
 210  *       performed already: the seqno of the skb must not be less than the seqno
 211  *       of loss_prev; and it must not equal that of any valid history entry.
 212  */
 213 static void __do_track_loss(struct tfrc_rx_hist *h, struct sk_buff *skb, u64 n1)
 214 {
 215         u64 s0 = tfrc_rx_hist_loss_prev(h)->tfrchrx_seqno,
 216             s1 = DCCP_SKB_CB(skb)->dccpd_seq;
 217
 218         if (!dccp_loss_free(s0, s1, n1)) {      /* gap between S0 and S1 */
 219                 h->loss_count = 1;
 220                 tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_entry(h, 1), skb, n1);
 221         }
 222 }
 223
 224 static void __one_after_loss(struct tfrc_rx_hist *h, struct sk_buff *skb, u32 n2)
 225 {
 226         u64 s0 = tfrc_rx_hist_loss_prev(h)->tfrchrx_seqno,
 227             s1 = tfrc_rx_hist_entry(h, 1)->tfrchrx_seqno,
 228             s2 = DCCP_SKB_CB(skb)->dccpd_seq;
 229
 230         if (likely(dccp_delta_seqno(s1, s2) > 0)) {     /* S1  <  S2 */
 231                 h->loss_count = 2;
 232                 tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_entry(h, 2), skb, n2);
 233                 return;
 234         }
 235
 236         /* S0  <  S2  <  S1 */
 237
 238         if (dccp_loss_free(s0, s2, n2)) {
 239                 u64 n1 = tfrc_rx_hist_entry(h, 1)->tfrchrx_ndp;
 240
 241                 if (dccp_loss_free(s2, s1, n1)) {
 242                         /* hole is filled: S0, S2, and S1 are consecutive */
 243                         h->loss_count = 0;
 244                         h->loss_start = tfrc_rx_hist_index(h, 1);
 245                 } else
 246                         /* gap between S2 and S1: just update loss_prev */
 247                         tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_loss_prev(h), skb, n2);
 248
 249         } else {        /* gap between S0 and S2 */
 250                 /*
 251                  * Reorder history to insert S2 between S0 and S1
 252                  */
 253                 tfrc_rx_hist_swap(h, 0, 3);
 254                 h->loss_start = tfrc_rx_hist_index(h, 3);
 255                 tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_entry(h, 1), skb, n2);
 256                 h->loss_count = 2;
 257         }
 258 }
 259
 260 /* return 1 if a new loss event has been identified */
 261 static int __two_after_loss(struct tfrc_rx_hist *h, struct sk_buff *skb, u32 n3)
 262 {
 263         u64 s0 = tfrc_rx_hist_loss_prev(h)->tfrchrx_seqno,
 264             s1 = tfrc_rx_hist_entry(h, 1)->tfrchrx_seqno,
 265             s2 = tfrc_rx_hist_entry(h, 2)->tfrchrx_seqno,
 266             s3 = DCCP_SKB_CB(skb)->dccpd_seq;
 267
 268         if (likely(dccp_delta_seqno(s2, s3) > 0)) {     /* S2  <  S3 */
 269                 h->loss_count = 3;
 270                 tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_entry(h, 3), skb, n3);
 271                 return 1;
 272         }
 273
 274         /* S3  <  S2 */
 275
 276         if (dccp_delta_seqno(s1, s3) > 0) {             /* S1  <  S3  <  S2 */
 277                 /*
 278                  * Reorder history to insert S3 between S1 and S2
 279                  */
 280                 tfrc_rx_hist_swap(h, 2, 3);
 281                 tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_entry(h, 2), skb, n3);
 282                 h->loss_count = 3;
 283                 return 1;
 284         }
 285
 286         /* S0  <  S3  <  S1 */
 287
 288         if (dccp_loss_free(s0, s3, n3)) {
 289                 u64 n1 = tfrc_rx_hist_entry(h, 1)->tfrchrx_ndp;
 290
 291                 if (dccp_loss_free(s3, s1, n1)) {
 292                         /* hole between S0 and S1 filled by S3 */
 293                         u64 n2 = tfrc_rx_hist_entry(h, 2)->tfrchrx_ndp;
 294
 295                         if (dccp_loss_free(s1, s2, n2)) {
 296                                 /* entire hole filled by S0, S3, S1, S2 */
 297                                 h->loss_start = tfrc_rx_hist_index(h, 2);
 298                                 h->loss_count = 0;
 299                         } else {
 300                                 /* gap remains between S1 and S2 */
 301                                 h->loss_start = tfrc_rx_hist_index(h, 1);
 302                                 h->loss_count = 1;
 303                         }
 304
 305                 } else /* gap exists between S3 and S1, loss_count stays at 2 */
 306                         tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_loss_prev(h), skb, n3);
 307
 308                 return 0;
 309         }
 310
 311         /*
 312          * The remaining case:  S0  <  S3  <  S1  <  S2;  gap between S0 and S3
 313          * Reorder history to insert S3 between S0 and S1.
 314          */
 315         tfrc_rx_hist_swap(h, 0, 3);
 316         h->loss_start = tfrc_rx_hist_index(h, 3);
 317         tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_entry(h, 1), skb, n3);
 318         h->loss_count = 3;
 319
 320         return 1;
 321 }
 322
 323 /* recycle RX history records to continue loss detection if necessary */
 324 static void __three_after_loss(struct tfrc_rx_hist *h)
 325 {
 326         /*
 327          * At this stage we know already that there is a gap between S0 and S1
 328          * (since S0 was the highest sequence number received before detecting
 329          * the loss). To recycle the loss record, it is thus only necessary to
 330          * check for other possible gaps between S1/S2 and between S2/S3.
 331          */
 332         u64 s1 = tfrc_rx_hist_entry(h, 1)->tfrchrx_seqno,
 333             s2 = tfrc_rx_hist_entry(h, 2)->tfrchrx_seqno,
 334             s3 = tfrc_rx_hist_entry(h, 3)->tfrchrx_seqno;
 335         u64 n2 = tfrc_rx_hist_entry(h, 2)->tfrchrx_ndp,
 336             n3 = tfrc_rx_hist_entry(h, 3)->tfrchrx_ndp;
 337
 338         if (dccp_loss_free(s1, s2, n2)) {
 339
 340                 if (dccp_loss_free(s2, s3, n3)) {
 341                         /* no gap between S2 and S3: entire hole is filled */
 342                         h->loss_start = tfrc_rx_hist_index(h, 3);
 343                         h->loss_count = 0;
 344                 } else {
 345                         /* gap between S2 and S3 */
 346                         h->loss_start = tfrc_rx_hist_index(h, 2);
 347                         h->loss_count = 1;
 348                 }
 349
 350         } else {        /* gap between S1 and S2 */
 351                 h->loss_start = tfrc_rx_hist_index(h, 1);
 352                 h->loss_count = 2;
 353         }
 354 }
 355
 356 /**
 357  *  tfrc_rx_handle_loss  -  Loss detection and further processing
 358  *  @h:             The non-empty RX history object
 359  *  @lh:            Loss Intervals database to update
 360  *  @skb:           Currently received packet
 361  *  @ndp:           The NDP count belonging to @skb
 362  *  @calc_first_li: Caller-dependent computation of first loss interval in @lh
 363  *  @sk:            Used by @calc_first_li (see tfrc_lh_interval_add)
 364  *  Chooses action according to pending loss, updates LI database when a new
 365  *  loss was detected, and does required post-processing. Returns 1 when caller
 366  *  should send feedback, 0 otherwise.
 367  *  Since it also takes care of reordering during loss detection and updates the
 368  *  records accordingly, the caller should not perform any more RX history
 369  *  operations when loss_count is greater than 0 after calling this function.
 370  */
 371 int tfrc_rx_handle_loss(struct tfrc_rx_hist *h,
 372                         struct tfrc_loss_hist *lh,
 373                         struct sk_buff *skb, const u64 ndp,
 374                         u32 (*calc_first_li)(struct sock *), struct sock *sk)
 375 {
 376         int is_new_loss = 0;
 377
 378         if (h->loss_count == 0) {
 379                 __do_track_loss(h, skb, ndp);
 380         } else if (h->loss_count == 1) {
 381                 __one_after_loss(h, skb, ndp);
 382         } else if (h->loss_count != 2) {
 383                 DCCP_BUG("invalid loss_count %d", h->loss_count);
 384         } else if (__two_after_loss(h, skb, ndp)) {
 385                 /*
 386                  * Update Loss Interval database and recycle RX records
 387                  */
 388                 is_new_loss = tfrc_lh_interval_add(lh, h, calc_first_li, sk);
 389                 __three_after_loss(h);
 390         }
 391         return is_new_loss;
 392 }
 393 EXPORT_SYMBOL_GPL(tfrc_rx_handle_loss);
 394
 395 int tfrc_rx_hist_alloc(struct tfrc_rx_hist *h)
 396 {
 397         int i;
 398
 399         for (i = 0; i <= TFRC_NDUPACK; i++) {
 400                 h->ring[i] = kmem_cache_alloc(tfrc_rx_hist_slab, GFP_ATOMIC);
 401                 if (h->ring[i] == NULL)
 402                         goto out_free;
 403         }
 404
 405         h->loss_count = h->loss_start = 0;
 406         return 0;
 407
 408 out_free:
 409         while (i-- != 0) {
 410                 kmem_cache_free(tfrc_rx_hist_slab, h->ring[i]);
 411                 h->ring[i] = NULL;
 412         }
 413         return -ENOBUFS;
 414 }
 415 EXPORT_SYMBOL_GPL(tfrc_rx_hist_alloc);
 416
 417 void tfrc_rx_hist_purge(struct tfrc_rx_hist *h)
 418 {
 419         int i;
 420
 421         for (i = 0; i <= TFRC_NDUPACK; ++i)
 422                 if (h->ring[i] != NULL) {
 423                         kmem_cache_free(tfrc_rx_hist_slab, h->ring[i]);
 424                         h->ring[i] = NULL;
 425                 }
 426 }
 427 EXPORT_SYMBOL_GPL(tfrc_rx_hist_purge);
 428
 429 /**
 430  * tfrc_rx_hist_rtt_last_s - reference entry to compute RTT samples against
 431  */
 432 static inline struct tfrc_rx_hist_entry *
 433                         tfrc_rx_hist_rtt_last_s(const struct tfrc_rx_hist *h)
 434 {
 435         return h->ring[0];
 436 }
 437
 438 /**
 439  * tfrc_rx_hist_rtt_prev_s: previously suitable (wrt rtt_last_s) RTT-sampling entry
 440  */
 441 static inline struct tfrc_rx_hist_entry *
 442                         tfrc_rx_hist_rtt_prev_s(const struct tfrc_rx_hist *h)
 443 {
 444         return h->ring[h->rtt_sample_prev];
 445 }
 446
 447 /**
 448  * tfrc_rx_hist_sample_rtt  -  Sample RTT from timestamp / CCVal
 449  * Based on ideas presented in RFC 4342, 8.1. Returns 0 if it was not able
 450  * to compute a sample with given data - calling function should check this.
 451  */
 452 u32 tfrc_rx_hist_sample_rtt(struct tfrc_rx_hist *h, const struct sk_buff *skb)
 453 {
 454         u32 sample = 0,
 455             delta_v = SUB16(dccp_hdr(skb)->dccph_ccval,
 456                             tfrc_rx_hist_rtt_last_s(h)->tfrchrx_ccval);
 457
 458         if (delta_v < 1 || delta_v > 4) {       /* unsuitable CCVal delta */
 459                 if (h->rtt_sample_prev == 2) {  /* previous candidate stored */
 460                         sample = SUB16(tfrc_rx_hist_rtt_prev_s(h)->tfrchrx_ccval,
 461                                        tfrc_rx_hist_rtt_last_s(h)->tfrchrx_ccval);
 462                         if (sample)
 463                                 sample = 4 / sample *
 464                                          ktime_us_delta(tfrc_rx_hist_rtt_prev_s(h)->tfrchrx_tstamp,
 465                                                         tfrc_rx_hist_rtt_last_s(h)->tfrchrx_tstamp);
 466                         else    /*
 467                                  * FIXME: This condition is in principle not
 468                                  * possible but occurs when CCID is used for
 469                                  * two-way data traffic. I have tried to trace
 470                                  * it, but the cause does not seem to be here.
 471                                  */
 472                                 DCCP_BUG("please report to dccp@vger.kernel.org"
 473                                          " => prev = %u, last = %u",
 474                                          tfrc_rx_hist_rtt_prev_s(h)->tfrchrx_ccval,
 475                                          tfrc_rx_hist_rtt_last_s(h)->tfrchrx_ccval);
 476                 } else if (delta_v < 1) {
 477                         h->rtt_sample_prev = 1;
 478                         goto keep_ref_for_next_time;
 479                 }
 480
 481         } else if (delta_v == 4) /* optimal match */
 482                 sample = ktime_to_us(net_timedelta(tfrc_rx_hist_rtt_last_s(h)->tfrchrx_tstamp));
 483         else {                   /* suboptimal match */
 484                 h->rtt_sample_prev = 2;
 485                 goto keep_ref_for_next_time;
 486         }
 487
 488         if (unlikely(sample > DCCP_SANE_RTT_MAX)) {
 489                 DCCP_WARN("RTT sample %u too large, using max\n", sample);
 490                 sample = DCCP_SANE_RTT_MAX;
 491         }
 492
 493         h->rtt_sample_prev = 0;        /* use current entry as next reference */
 494 keep_ref_for_next_time:
 495
 496         return sample;
 497 }
 498 EXPORT_SYMBOL_GPL(tfrc_rx_hist_sample_rtt);