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
  98 void tfrc_tx_hist_purge(struct tfrc_tx_hist_entry **headp)
  99 {
 100         struct tfrc_tx_hist_entry *head = *headp;
 101
 102         while (head != NULL) {
 103                 struct tfrc_tx_hist_entry *next = head->next;
 104
 105                 kmem_cache_free(tfrc_tx_hist_slab, head);
 106                 head = next;
 107         }
 108
 109         *headp = NULL;
 110 }
 111
 112 u32 tfrc_tx_hist_rtt(struct tfrc_tx_hist_entry *head, const u64 seqno,
 113                      const ktime_t now)
 114 {
 115         u32 rtt = 0;
 116         struct tfrc_tx_hist_entry *packet = tfrc_tx_hist_find_entry(head, seqno);
 117
 118         if (packet != NULL) {
 119                 rtt = ktime_us_delta(now, packet->stamp);
 120                 /*
 121                  * Garbage-collect older (irrelevant) entries:
 122                  */
 123                 tfrc_tx_hist_purge(&packet->next);
 124         }
 125
 126         return rtt;
 127 }
 128
 129
 130 /*
 131  *      Receiver History Routines
 132  */
 133 static struct kmem_cache *tfrc_rx_hist_slab;
 134
 135 int __init tfrc_rx_packet_history_init(void)
 136 {
 137         tfrc_rx_hist_slab = kmem_cache_create("tfrc_rxh_cache",
 138                                               sizeof(struct tfrc_rx_hist_entry),
 139                                               0, SLAB_HWCACHE_ALIGN, NULL);
 140         return tfrc_rx_hist_slab == NULL ? -ENOBUFS : 0;
 141 }
 142
 143 void tfrc_rx_packet_history_exit(void)
 144 {
 145         if (tfrc_rx_hist_slab != NULL) {
 146                 kmem_cache_destroy(tfrc_rx_hist_slab);
 147                 tfrc_rx_hist_slab = NULL;
 148         }
 149 }
 150
 151 static inline void tfrc_rx_hist_entry_from_skb(struct tfrc_rx_hist_entry *entry,
 152                                                const struct sk_buff *skb,
 153                                                const u64 ndp)
 154 {
 155         const struct dccp_hdr *dh = dccp_hdr(skb);
 156
 157         entry->tfrchrx_seqno = DCCP_SKB_CB(skb)->dccpd_seq;
 158         entry->tfrchrx_ccval = dh->dccph_ccval;
 159         entry->tfrchrx_type  = dh->dccph_type;
 160         entry->tfrchrx_ndp   = ndp;
 161         entry->tfrchrx_tstamp = ktime_get_real();
 162 }
 163
 164 void tfrc_rx_hist_add_packet(struct tfrc_rx_hist *h,
 165                              const struct sk_buff *skb,
 166                              const u64 ndp)
 167 {
 168         struct tfrc_rx_hist_entry *entry = tfrc_rx_hist_last_rcv(h);
 169
 170         tfrc_rx_hist_entry_from_skb(entry, skb, ndp);
 171 }
 172
 173 /* has the packet contained in skb been seen before? */
 174 int tfrc_rx_hist_duplicate(struct tfrc_rx_hist *h, struct sk_buff *skb)
 175 {
 176         const u64 seq = DCCP_SKB_CB(skb)->dccpd_seq;
 177         int i;
 178
 179         if (dccp_delta_seqno(tfrc_rx_hist_loss_prev(h)->tfrchrx_seqno, seq) <= 0)
 180                 return 1;
 181
 182         for (i = 1; i <= h->loss_count; i++)
 183                 if (tfrc_rx_hist_entry(h, i)->tfrchrx_seqno == seq)
 184                         return 1;
 185
 186         return 0;
 187 }
 188
 189 static void tfrc_rx_hist_swap(struct tfrc_rx_hist *h, const u8 a, const u8 b)
 190 {
 191         const u8 idx_a = tfrc_rx_hist_index(h, a),
 192                  idx_b = tfrc_rx_hist_index(h, b);
 193         struct tfrc_rx_hist_entry *tmp = h->ring[idx_a];
 194
 195         h->ring[idx_a] = h->ring[idx_b];
 196         h->ring[idx_b] = tmp;
 197 }
 198
 199 /*
 200  * Private helper functions for loss detection.
 201  *
 202  * In the descriptions, `Si' refers to the sequence number of entry number i,
 203  * whose NDP count is `Ni' (lower case is used for variables).
 204  * Note: All __xxx_loss functions expect that a test against duplicates has been
 205  *       performed already: the seqno of the skb must not be less than the seqno
 206  *       of loss_prev; and it must not equal that of any valid history entry.
 207  */
 208 static void __do_track_loss(struct tfrc_rx_hist *h, struct sk_buff *skb, u64 n1)
 209 {
 210         u64 s0 = tfrc_rx_hist_loss_prev(h)->tfrchrx_seqno,
 211             s1 = DCCP_SKB_CB(skb)->dccpd_seq;
 212
 213         if (!dccp_loss_free(s0, s1, n1)) {      /* gap between S0 and S1 */
 214                 h->loss_count = 1;
 215                 tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_entry(h, 1), skb, n1);
 216         }
 217 }
 218
 219 static void __one_after_loss(struct tfrc_rx_hist *h, struct sk_buff *skb, u32 n2)
 220 {
 221         u64 s0 = tfrc_rx_hist_loss_prev(h)->tfrchrx_seqno,
 222             s1 = tfrc_rx_hist_entry(h, 1)->tfrchrx_seqno,
 223             s2 = DCCP_SKB_CB(skb)->dccpd_seq;
 224
 225         if (likely(dccp_delta_seqno(s1, s2) > 0)) {     /* S1  <  S2 */
 226                 h->loss_count = 2;
 227                 tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_entry(h, 2), skb, n2);
 228                 return;
 229         }
 230
 231         /* S0  <  S2  <  S1 */
 232
 233         if (dccp_loss_free(s0, s2, n2)) {
 234                 u64 n1 = tfrc_rx_hist_entry(h, 1)->tfrchrx_ndp;
 235
 236                 if (dccp_loss_free(s2, s1, n1)) {
 237                         /* hole is filled: S0, S2, and S1 are consecutive */
 238                         h->loss_count = 0;
 239                         h->loss_start = tfrc_rx_hist_index(h, 1);
 240                 } else
 241                         /* gap between S2 and S1: just update loss_prev */
 242                         tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_loss_prev(h), skb, n2);
 243
 244         } else {        /* gap between S0 and S2 */
 245                 /*
 246                  * Reorder history to insert S2 between S0 and S1
 247                  */
 248                 tfrc_rx_hist_swap(h, 0, 3);
 249                 h->loss_start = tfrc_rx_hist_index(h, 3);
 250                 tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_entry(h, 1), skb, n2);
 251                 h->loss_count = 2;
 252         }
 253 }
 254
 255 /* return 1 if a new loss event has been identified */
 256 static int __two_after_loss(struct tfrc_rx_hist *h, struct sk_buff *skb, u32 n3)
 257 {
 258         u64 s0 = tfrc_rx_hist_loss_prev(h)->tfrchrx_seqno,
 259             s1 = tfrc_rx_hist_entry(h, 1)->tfrchrx_seqno,
 260             s2 = tfrc_rx_hist_entry(h, 2)->tfrchrx_seqno,
 261             s3 = DCCP_SKB_CB(skb)->dccpd_seq;
 262
 263         if (likely(dccp_delta_seqno(s2, s3) > 0)) {     /* S2  <  S3 */
 264                 h->loss_count = 3;
 265                 tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_entry(h, 3), skb, n3);
 266                 return 1;
 267         }
 268
 269         /* S3  <  S2 */
 270
 271         if (dccp_delta_seqno(s1, s3) > 0) {             /* S1  <  S3  <  S2 */
 272                 /*
 273                  * Reorder history to insert S3 between S1 and S2
 274                  */
 275                 tfrc_rx_hist_swap(h, 2, 3);
 276                 tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_entry(h, 2), skb, n3);
 277                 h->loss_count = 3;
 278                 return 1;
 279         }
 280
 281         /* S0  <  S3  <  S1 */
 282
 283         if (dccp_loss_free(s0, s3, n3)) {
 284                 u64 n1 = tfrc_rx_hist_entry(h, 1)->tfrchrx_ndp;
 285
 286                 if (dccp_loss_free(s3, s1, n1)) {
 287                         /* hole between S0 and S1 filled by S3 */
 288                         u64 n2 = tfrc_rx_hist_entry(h, 2)->tfrchrx_ndp;
 289
 290                         if (dccp_loss_free(s1, s2, n2)) {
 291                                 /* entire hole filled by S0, S3, S1, S2 */
 292                                 h->loss_start = tfrc_rx_hist_index(h, 2);
 293                                 h->loss_count = 0;
 294                         } else {
 295                                 /* gap remains between S1 and S2 */
 296                                 h->loss_start = tfrc_rx_hist_index(h, 1);
 297                                 h->loss_count = 1;
 298                         }
 299
 300                 } else /* gap exists between S3 and S1, loss_count stays at 2 */
 301                         tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_loss_prev(h), skb, n3);
 302
 303                 return 0;
 304         }
 305
 306         /*
 307          * The remaining case:  S0  <  S3  <  S1  <  S2;  gap between S0 and S3
 308          * Reorder history to insert S3 between S0 and S1.
 309          */
 310         tfrc_rx_hist_swap(h, 0, 3);
 311         h->loss_start = tfrc_rx_hist_index(h, 3);
 312         tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_entry(h, 1), skb, n3);
 313         h->loss_count = 3;
 314
 315         return 1;
 316 }
 317
 318 /* recycle RX history records to continue loss detection if necessary */
 319 static void __three_after_loss(struct tfrc_rx_hist *h)
 320 {
 321         /*
 322          * At this stage we know already that there is a gap between S0 and S1
 323          * (since S0 was the highest sequence number received before detecting
 324          * the loss). To recycle the loss record, it is thus only necessary to
 325          * check for other possible gaps between S1/S2 and between S2/S3.
 326          */
 327         u64 s1 = tfrc_rx_hist_entry(h, 1)->tfrchrx_seqno,
 328             s2 = tfrc_rx_hist_entry(h, 2)->tfrchrx_seqno,
 329             s3 = tfrc_rx_hist_entry(h, 3)->tfrchrx_seqno;
 330         u64 n2 = tfrc_rx_hist_entry(h, 2)->tfrchrx_ndp,
 331             n3 = tfrc_rx_hist_entry(h, 3)->tfrchrx_ndp;
 332
 333         if (dccp_loss_free(s1, s2, n2)) {
 334
 335                 if (dccp_loss_free(s2, s3, n3)) {
 336                         /* no gap between S2 and S3: entire hole is filled */
 337                         h->loss_start = tfrc_rx_hist_index(h, 3);
 338                         h->loss_count = 0;
 339                 } else {
 340                         /* gap between S2 and S3 */
 341                         h->loss_start = tfrc_rx_hist_index(h, 2);
 342                         h->loss_count = 1;
 343                 }
 344
 345         } else {        /* gap between S1 and S2 */
 346                 h->loss_start = tfrc_rx_hist_index(h, 1);
 347                 h->loss_count = 2;
 348         }
 349 }
 350
 351 /**
 352  *  tfrc_rx_handle_loss  -  Loss detection and further processing
 353  *  @h:             The non-empty RX history object
 354  *  @lh:            Loss Intervals database to update
 355  *  @skb:           Currently received packet
 356  *  @ndp:           The NDP count belonging to @skb
 357  *  @calc_first_li: Caller-dependent computation of first loss interval in @lh
 358  *  @sk:            Used by @calc_first_li (see tfrc_lh_interval_add)
 359  *  Chooses action according to pending loss, updates LI database when a new
 360  *  loss was detected, and does required post-processing. Returns 1 when caller
 361  *  should send feedback, 0 otherwise.
 362  *  Since it also takes care of reordering during loss detection and updates the
 363  *  records accordingly, the caller should not perform any more RX history
 364  *  operations when loss_count is greater than 0 after calling this function.
 365  */
 366 int tfrc_rx_handle_loss(struct tfrc_rx_hist *h,
 367                         struct tfrc_loss_hist *lh,
 368                         struct sk_buff *skb, const u64 ndp,
 369                         u32 (*calc_first_li)(struct sock *), struct sock *sk)
 370 {
 371         int is_new_loss = 0;
 372
 373         if (h->loss_count == 0) {
 374                 __do_track_loss(h, skb, ndp);
 375         } else if (h->loss_count == 1) {
 376                 __one_after_loss(h, skb, ndp);
 377         } else if (h->loss_count != 2) {
 378                 DCCP_BUG("invalid loss_count %d", h->loss_count);
 379         } else if (__two_after_loss(h, skb, ndp)) {
 380                 /*
 381                  * Update Loss Interval database and recycle RX records
 382                  */
 383                 is_new_loss = tfrc_lh_interval_add(lh, h, calc_first_li, sk);
 384                 __three_after_loss(h);
 385         }
 386         return is_new_loss;
 387 }
 388
 389 int tfrc_rx_hist_alloc(struct tfrc_rx_hist *h)
 390 {
 391         int i;
 392
 393         for (i = 0; i <= TFRC_NDUPACK; i++) {
 394                 h->ring[i] = kmem_cache_alloc(tfrc_rx_hist_slab, GFP_ATOMIC);
 395                 if (h->ring[i] == NULL)
 396                         goto out_free;
 397         }
 398
 399         h->loss_count = h->loss_start = 0;
 400         return 0;
 401
 402 out_free:
 403         while (i-- != 0) {
 404                 kmem_cache_free(tfrc_rx_hist_slab, h->ring[i]);
 405                 h->ring[i] = NULL;
 406         }
 407         return -ENOBUFS;
 408 }
 409
 410 void tfrc_rx_hist_purge(struct tfrc_rx_hist *h)
 411 {
 412         int i;
 413
 414         for (i = 0; i <= TFRC_NDUPACK; ++i)
 415                 if (h->ring[i] != NULL) {
 416                         kmem_cache_free(tfrc_rx_hist_slab, h->ring[i]);
 417                         h->ring[i] = NULL;
 418                 }
 419 }
 420
 421 /**
 422  * tfrc_rx_hist_rtt_last_s - reference entry to compute RTT samples against
 423  */
 424 static inline struct tfrc_rx_hist_entry *
 425                         tfrc_rx_hist_rtt_last_s(const struct tfrc_rx_hist *h)
 426 {
 427         return h->ring[0];
 428 }
 429
 430 /**
 431  * tfrc_rx_hist_rtt_prev_s: previously suitable (wrt rtt_last_s) RTT-sampling entry
 432  */
 433 static inline struct tfrc_rx_hist_entry *
 434                         tfrc_rx_hist_rtt_prev_s(const struct tfrc_rx_hist *h)
 435 {
 436         return h->ring[h->rtt_sample_prev];
 437 }
 438
 439 /**
 440  * tfrc_rx_hist_sample_rtt  -  Sample RTT from timestamp / CCVal
 441  * Based on ideas presented in RFC 4342, 8.1. Returns 0 if it was not able
 442  * to compute a sample with given data - calling function should check this.
 443  */
 444 u32 tfrc_rx_hist_sample_rtt(struct tfrc_rx_hist *h, const struct sk_buff *skb)
 445 {
 446         u32 sample = 0,
 447             delta_v = SUB16(dccp_hdr(skb)->dccph_ccval,
 448                             tfrc_rx_hist_rtt_last_s(h)->tfrchrx_ccval);
 449
 450         if (delta_v < 1 || delta_v > 4) {       /* unsuitable CCVal delta */
 451                 if (h->rtt_sample_prev == 2) {  /* previous candidate stored */
 452                         sample = SUB16(tfrc_rx_hist_rtt_prev_s(h)->tfrchrx_ccval,
 453                                        tfrc_rx_hist_rtt_last_s(h)->tfrchrx_ccval);
 454                         if (sample)
 455                                 sample = 4 / sample *
 456                                          ktime_us_delta(tfrc_rx_hist_rtt_prev_s(h)->tfrchrx_tstamp,
 457                                                         tfrc_rx_hist_rtt_last_s(h)->tfrchrx_tstamp);
 458                         else    /*
 459                                  * FIXME: This condition is in principle not
 460                                  * possible but occurs when CCID is used for
 461                                  * two-way data traffic. I have tried to trace
 462                                  * it, but the cause does not seem to be here.
 463                                  */
 464                                 DCCP_BUG("please report to dccp@vger.kernel.org"
 465                                          " => prev = %u, last = %u",
 466                                          tfrc_rx_hist_rtt_prev_s(h)->tfrchrx_ccval,
 467                                          tfrc_rx_hist_rtt_last_s(h)->tfrchrx_ccval);
 468                 } else if (delta_v < 1) {
 469                         h->rtt_sample_prev = 1;
 470                         goto keep_ref_for_next_time;
 471                 }
 472
 473         } else if (delta_v == 4) /* optimal match */
 474                 sample = ktime_to_us(net_timedelta(tfrc_rx_hist_rtt_last_s(h)->tfrchrx_tstamp));
 475         else {                   /* suboptimal match */
 476                 h->rtt_sample_prev = 2;
 477                 goto keep_ref_for_next_time;
 478         }
 479
 480         if (unlikely(sample > DCCP_SANE_RTT_MAX)) {
 481                 DCCP_WARN("RTT sample %u too large, using max\n", sample);
 482                 sample = DCCP_SANE_RTT_MAX;
 483         }
 484
 485         h->rtt_sample_prev = 0;        /* use current entry as next reference */
 486 keep_ref_for_next_time:
 487
 488         return sample;
 489 }