net/dccp/ackvec.c

   1 /*
   2  *  net/dccp/ackvec.c
   3  *
   4  *  An implementation of Ack Vectors for the DCCP protocol
   5  *  Copyright (c) 2007 University of Aberdeen, Scotland, UK
   6  *  Copyright (c) 2005 Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
   7  *
   8  *      This program is free software; you can redistribute it and/or modify it
   9  *      under the terms of the GNU General Public License as published by the
  10  *      Free Software Foundation; version 2 of the License;
  11  */
  12
  13 #include "ackvec.h"
  14 #include "dccp.h"
  15
  16 #include <linux/init.h>
  17 #include <linux/errno.h>
  18 #include <linux/kernel.h>
  19 #include <linux/skbuff.h>
  20 #include <linux/slab.h>
  21
  22 #include <net/sock.h>
  23
  24 static struct kmem_cache *dccp_ackvec_slab;
  25 static struct kmem_cache *dccp_ackvec_record_slab;
  26
  27 struct dccp_ackvec *dccp_ackvec_alloc(const gfp_t priority)
  28 {
  29         struct dccp_ackvec *av = kmem_cache_zalloc(dccp_ackvec_slab, priority);
  30
  31         if (av != NULL) {
  32                 av->av_buf_head = av->av_buf_tail = DCCPAV_MAX_ACKVEC_LEN - 1;
  33                 INIT_LIST_HEAD(&av->av_records);
  34         }
  35         return av;
  36 }
  37
  38 static void dccp_ackvec_purge_records(struct dccp_ackvec *av)
  39 {
  40         struct dccp_ackvec_record *cur, *next;
  41
  42         list_for_each_entry_safe(cur, next, &av->av_records, avr_node)
  43                 kmem_cache_free(dccp_ackvec_record_slab, cur);
  44         INIT_LIST_HEAD(&av->av_records);
  45 }
  46
  47 void dccp_ackvec_free(struct dccp_ackvec *av)
  48 {
  49         if (likely(av != NULL)) {
  50                 dccp_ackvec_purge_records(av);
  51                 kmem_cache_free(dccp_ackvec_slab, av);
  52         }
  53 }
  54
  55 /**
  56  * dccp_ackvec_update_records  -  Record information about sent Ack Vectors
  57  * @av:         Ack Vector records to update
  58  * @seqno:      Sequence number of the packet carrying the Ack Vector just sent
  59  * @nonce_sum:  The sum of all buffer nonces contained in the Ack Vector
  60  */
  61 int dccp_ackvec_update_records(struct dccp_ackvec *av, u64 seqno, u8 nonce_sum)
  62 {
  63         struct dccp_ackvec_record *avr;
  64
  65         avr = kmem_cache_alloc(dccp_ackvec_record_slab, GFP_ATOMIC);
  66         if (avr == NULL)
  67                 return -ENOBUFS;
  68
  69         avr->avr_ack_seqno  = seqno;
  70         avr->avr_ack_ptr    = av->av_buf_head;
  71         avr->avr_ack_ackno  = av->av_buf_ackno;
  72         avr->avr_ack_nonce  = nonce_sum;
  73         avr->avr_ack_runlen = dccp_ackvec_runlen(av->av_buf + av->av_buf_head);
  74         /*
  75          * When the buffer overflows, we keep no more than one record. This is
  76          * the simplest way of disambiguating sender-Acks dating from before the
  77          * overflow from sender-Acks which refer to after the overflow; a simple
  78          * solution is preferable here since we are handling an exception.
  79          */
  80         if (av->av_overflow)
  81                 dccp_ackvec_purge_records(av);
  82         /*
  83          * Since GSS is incremented for each packet, the list is automatically
  84          * arranged in descending order of @ack_seqno.
  85          */
  86         list_add(&avr->avr_node, &av->av_records);
  87
  88         dccp_pr_debug("Added Vector, ack_seqno=%llu, ack_ackno=%llu (rl=%u)\n",
  89                       (unsigned long long)avr->avr_ack_seqno,
  90                       (unsigned long long)avr->avr_ack_ackno,
  91                       avr->avr_ack_runlen);
  92         return 0;
  93 }
  94
  95 static struct dccp_ackvec_record *dccp_ackvec_lookup(struct list_head *av_list,
  96                                                      const u64 ackno)
  97 {
  98         struct dccp_ackvec_record *avr;
  99         /*
 100          * Exploit that records are inserted in descending order of sequence
 101          * number, start with the oldest record first. If @ackno is `before'
 102          * the earliest ack_ackno, the packet is too old to be considered.
 103          */
 104         list_for_each_entry_reverse(avr, av_list, avr_node) {
 105                 if (avr->avr_ack_seqno == ackno)
 106                         return avr;
 107                 if (before48(ackno, avr->avr_ack_seqno))
 108                         break;
 109         }
 110         return NULL;
 111 }
 112
 113 /*
 114  * Buffer index and length computation using modulo-buffersize arithmetic.
 115  * Note that, as pointers move from right to left, head is `before' tail.
 116  */
 117 static inline u16 __ackvec_idx_add(const u16 a, const u16 b)
 118 {
 119         return (a + b) % DCCPAV_MAX_ACKVEC_LEN;
 120 }
 121
 122 static inline u16 __ackvec_idx_sub(const u16 a, const u16 b)
 123 {
 124         return __ackvec_idx_add(a, DCCPAV_MAX_ACKVEC_LEN - b);
 125 }
 126
 127 u16 dccp_ackvec_buflen(const struct dccp_ackvec *av)
 128 {
 129         if (unlikely(av->av_overflow))
 130                 return DCCPAV_MAX_ACKVEC_LEN;
 131         return __ackvec_idx_sub(av->av_buf_tail, av->av_buf_head);
 132 }
 133
 134 /**
 135  * dccp_ackvec_update_old  -  Update previous state as per RFC 4340, 11.4.1
 136  * @av:         non-empty buffer to update
 137  * @distance:   negative or zero distance of @seqno from buf_ackno downward
 138  * @seqno:      the (old) sequence number whose record is to be updated
 139  * @state:      state in which packet carrying @seqno was received
 140  */
 141 static void dccp_ackvec_update_old(struct dccp_ackvec *av, s64 distance,
 142                                    u64 seqno, enum dccp_ackvec_states state)
 143 {
 144         u16 ptr = av->av_buf_head;
 145
 146         BUG_ON(distance > 0);
 147         if (unlikely(dccp_ackvec_is_empty(av)))
 148                 return;
 149
 150         do {
 151                 u8 runlen = dccp_ackvec_runlen(av->av_buf + ptr);
 152
 153                 if (distance + runlen >= 0) {
 154                         /*
 155                          * Only update the state if packet has not been received
 156                          * yet. This is OK as per the second table in RFC 4340,
 157                          * 11.4.1; i.e. here we are using the following table:
 158                          *                     RECEIVED
 159                          *                      0   1   3
 160                          *              S     +---+---+---+
 161                          *              T   0 | 0 | 0 | 0 |
 162                          *              O     +---+---+---+
 163                          *              R   1 | 1 | 1 | 1 |
 164                          *              E     +---+---+---+
 165                          *              D   3 | 0 | 1 | 3 |
 166                          *                    +---+---+---+
 167                          * The "Not Received" state was set by reserve_seats().
 168                          */
 169                         if (av->av_buf[ptr] == DCCPAV_NOT_RECEIVED)
 170                                 av->av_buf[ptr] = state;
 171                         else
 172                                 dccp_pr_debug("Not changing %llu state to %u\n",
 173                                               (unsigned long long)seqno, state);
 174                         break;
 175                 }
 176
 177                 distance += runlen + 1;
 178                 ptr       = __ackvec_idx_add(ptr, 1);
 179
 180         } while (ptr != av->av_buf_tail);
 181 }
 182
 183 /* Mark @num entries after buf_head as "Not yet received". */
 184 static void dccp_ackvec_reserve_seats(struct dccp_ackvec *av, u16 num)
 185 {
 186         u16 start = __ackvec_idx_add(av->av_buf_head, 1),
 187             len   = DCCPAV_MAX_ACKVEC_LEN - start;
 188
 189         /* check for buffer wrap-around */
 190         if (num > len) {
 191                 memset(av->av_buf + start, DCCPAV_NOT_RECEIVED, len);
 192                 start = 0;
 193                 num  -= len;
 194         }
 195         if (num)
 196                 memset(av->av_buf + start, DCCPAV_NOT_RECEIVED, num);
 197 }
 198
 199 /**
 200  * dccp_ackvec_add_new  -  Record one or more new entries in Ack Vector buffer
 201  * @av:          container of buffer to update (can be empty or non-empty)
 202  * @num_packets: number of packets to register (must be >= 1)
 203  * @seqno:       sequence number of the first packet in @num_packets
 204  * @state:       state in which packet carrying @seqno was received
 205  */
 206 static void dccp_ackvec_add_new(struct dccp_ackvec *av, u32 num_packets,
 207                                 u64 seqno, enum dccp_ackvec_states state)
 208 {
 209         u32 num_cells = num_packets;
 210
 211         if (num_packets > DCCPAV_BURST_THRESH) {
 212                 u32 lost_packets = num_packets - 1;
 213
 214                 DCCP_WARN("Warning: large burst loss (%u)\n", lost_packets);
 215                 /*
 216                  * We received 1 packet and have a loss of size "num_packets-1"
 217                  * which we squeeze into num_cells-1 rather than reserving an
 218                  * entire byte for each lost packet.
 219                  * The reason is that the vector grows in O(burst_length); when
 220                  * it grows too large there will no room left for the payload.
 221                  * This is a trade-off: if a few packets out of the burst show
 222                  * up later, their state will not be changed; it is simply too
 223                  * costly to reshuffle/reallocate/copy the buffer each time.
 224                  * Should such problems persist, we will need to switch to a
 225                  * different underlying data structure.
 226                  */
 227                 for (num_packets = num_cells = 1; lost_packets; ++num_cells) {
 228                         u8 len = min(lost_packets, (u32)DCCPAV_MAX_RUNLEN);
 229
 230                         av->av_buf_head = __ackvec_idx_sub(av->av_buf_head, 1);
 231                         av->av_buf[av->av_buf_head] = DCCPAV_NOT_RECEIVED | len;
 232
 233                         lost_packets -= len;
 234                 }
 235         }
 236
 237         if (num_cells + dccp_ackvec_buflen(av) >= DCCPAV_MAX_ACKVEC_LEN) {
 238                 DCCP_CRIT("Ack Vector buffer overflow: dropping old entries\n");
 239                 av->av_overflow = true;
 240         }
 241
 242         av->av_buf_head = __ackvec_idx_sub(av->av_buf_head, num_packets);
 243         if (av->av_overflow)
 244                 av->av_buf_tail = av->av_buf_head;
 245
 246         av->av_buf[av->av_buf_head] = state;
 247         av->av_buf_ackno            = seqno;
 248
 249         if (num_packets > 1)
 250                 dccp_ackvec_reserve_seats(av, num_packets - 1);
 251 }
 252
 253 /**
 254  * dccp_ackvec_input  -  Register incoming packet in the buffer
 255  */
 256 void dccp_ackvec_input(struct dccp_ackvec *av, struct sk_buff *skb)
 257 {
 258         u64 seqno = DCCP_SKB_CB(skb)->dccpd_seq;
 259         enum dccp_ackvec_states state = DCCPAV_RECEIVED;
 260
 261         if (dccp_ackvec_is_empty(av)) {
 262                 dccp_ackvec_add_new(av, 1, seqno, state);
 263                 av->av_tail_ackno = seqno;
 264
 265         } else {
 266                 s64 num_packets = dccp_delta_seqno(av->av_buf_ackno, seqno);
 267                 u8 *current_head = av->av_buf + av->av_buf_head;
 268
 269                 if (num_packets == 1 &&
 270                     dccp_ackvec_state(current_head) == state &&
 271                     dccp_ackvec_runlen(current_head) < DCCPAV_MAX_RUNLEN) {
 272
 273                         *current_head   += 1;
 274                         av->av_buf_ackno = seqno;
 275
 276                 } else if (num_packets > 0) {
 277                         dccp_ackvec_add_new(av, num_packets, seqno, state);
 278                 } else {
 279                         dccp_ackvec_update_old(av, num_packets, seqno, state);
 280                 }
 281         }
 282 }
 283
 284 /*
 285  * If several packets are missing, the HC-Receiver may prefer to enter multiple
 286  * bytes with run length 0, rather than a single byte with a larger run length;
 287  * this simplifies table updates if one of the missing packets arrives.
 288  */
 289 static inline int dccp_ackvec_set_buf_head_state(struct dccp_ackvec *av,
 290                                                  const unsigned int packets,
 291                                                  const unsigned char state)
 292 {
 293         long gap;
 294         long new_head;
 295
 296         if (av->av_vec_len + packets > DCCPAV_MAX_ACKVEC_LEN)
 297                 return -ENOBUFS;
 298
 299         gap      = packets - 1;
 300         new_head = av->av_buf_head - packets;
 301
 302         if (new_head < 0) {
 303                 if (gap > 0) {
 304                         memset(av->av_buf, DCCPAV_NOT_RECEIVED,
 305                                gap + new_head + 1);
 306                         gap = -new_head;
 307                 }
 308                 new_head += DCCPAV_MAX_ACKVEC_LEN;
 309         }
 310
 311         av->av_buf_head = new_head;
 312
 313         if (gap > 0)
 314                 memset(av->av_buf + av->av_buf_head + 1,
 315                        DCCPAV_NOT_RECEIVED, gap);
 316
 317         av->av_buf[av->av_buf_head] = state;
 318         av->av_vec_len += packets;
 319         return 0;
 320 }
 321
 322 /*
 323  * Implements the RFC 4340, Appendix A
 324  */
 325 int dccp_ackvec_add(struct dccp_ackvec *av, const struct sock *sk,
 326                     const u64 ackno, const u8 state)
 327 {
 328         u8 *cur_head = av->av_buf + av->av_buf_head,
 329            *buf_end  = av->av_buf + DCCPAV_MAX_ACKVEC_LEN;
 330         /*
 331          * Check at the right places if the buffer is full, if it is, tell the
 332          * caller to start dropping packets till the HC-Sender acks our ACK
 333          * vectors, when we will free up space in av_buf.
 334          *
 335          * We may well decide to do buffer compression, etc, but for now lets
 336          * just drop.
 337          *
 338          * From Appendix A.1.1 (`New Packets'):
 339          *
 340          *      Of course, the circular buffer may overflow, either when the
 341          *      HC-Sender is sending data at a very high rate, when the
 342          *      HC-Receiver's acknowledgements are not reaching the HC-Sender,
 343          *      or when the HC-Sender is forgetting to acknowledge those acks
 344          *      (so the HC-Receiver is unable to clean up old state). In this
 345          *      case, the HC-Receiver should either compress the buffer (by
 346          *      increasing run lengths when possible), transfer its state to
 347          *      a larger buffer, or, as a last resort, drop all received
 348          *      packets, without processing them whatsoever, until its buffer
 349          *      shrinks again.
 350          */
 351
 352         /* See if this is the first ackno being inserted */
 353         if (av->av_vec_len == 0) {
 354                 *cur_head = state;
 355                 av->av_vec_len = 1;
 356         } else if (after48(ackno, av->av_buf_ackno)) {
 357                 const u64 delta = dccp_delta_seqno(av->av_buf_ackno, ackno);
 358
 359                 /*
 360                  * Look if the state of this packet is the same as the
 361                  * previous ackno and if so if we can bump the head len.
 362                  */
 363                 if (delta == 1 && dccp_ackvec_state(cur_head) == state &&
 364                     dccp_ackvec_runlen(cur_head) < DCCPAV_MAX_RUNLEN)
 365                         *cur_head += 1;
 366                 else if (dccp_ackvec_set_buf_head_state(av, delta, state))
 367                         return -ENOBUFS;
 368         } else {
 369                 /*
 370                  * A.1.2.  Old Packets
 371                  *
 372                  *      When a packet with Sequence Number S <= buf_ackno
 373                  *      arrives, the HC-Receiver will scan the table for
 374                  *      the byte corresponding to S. (Indexing structures
 375                  *      could reduce the complexity of this scan.)
 376                  */
 377                 u64 delta = dccp_delta_seqno(ackno, av->av_buf_ackno);
 378
 379                 while (1) {
 380                         const u8 len = dccp_ackvec_runlen(cur_head);
 381                         /*
 382                          * valid packets not yet in av_buf have a reserved
 383                          * entry, with a len equal to 0.
 384                          */
 385                         if (*cur_head == DCCPAV_NOT_RECEIVED && delta == 0) {
 386                                 dccp_pr_debug("Found %llu reserved seat!\n",
 387                                               (unsigned long long)ackno);
 388                                 *cur_head = state;
 389                                 goto out;
 390                         }
 391                         /* len == 0 means one packet */
 392                         if (delta < len + 1)
 393                                 goto out_duplicate;
 394
 395                         delta -= len + 1;
 396                         if (++cur_head == buf_end)
 397                                 cur_head = av->av_buf;
 398                 }
 399         }
 400
 401         av->av_buf_ackno = ackno;
 402 out:
 403         return 0;
 404
 405 out_duplicate:
 406         /* Duplicate packet */
 407         dccp_pr_debug("Received a dup or already considered lost "
 408                       "packet: %llu\n", (unsigned long long)ackno);
 409         return -EILSEQ;
 410 }
 411
 412 static void dccp_ackvec_throw_record(struct dccp_ackvec *av,
 413                                      struct dccp_ackvec_record *avr)
 414 {
 415         struct dccp_ackvec_record *next;
 416
 417         /* sort out vector length */
 418         if (av->av_buf_head <= avr->avr_ack_ptr)
 419                 av->av_vec_len = avr->avr_ack_ptr - av->av_buf_head;
 420         else
 421                 av->av_vec_len = DCCPAV_MAX_ACKVEC_LEN - 1 -
 422                                  av->av_buf_head + avr->avr_ack_ptr;
 423
 424         /* free records */
 425         list_for_each_entry_safe_from(avr, next, &av->av_records, avr_node) {
 426                 list_del(&avr->avr_node);
 427                 kmem_cache_free(dccp_ackvec_record_slab, avr);
 428         }
 429 }
 430
 431 void dccp_ackvec_check_rcv_ackno(struct dccp_ackvec *av, struct sock *sk,
 432                                  const u64 ackno)
 433 {
 434         struct dccp_ackvec_record *avr;
 435
 436         /*
 437          * If we traverse backwards, it should be faster when we have large
 438          * windows. We will be receiving ACKs for stuff we sent a while back
 439          * -sorbo.
 440          */
 441         list_for_each_entry_reverse(avr, &av->av_records, avr_node) {
 442                 if (ackno == avr->avr_ack_seqno) {
 443                         dccp_pr_debug("%s ACK packet 0, len=%d, ack_seqno=%llu, "
 444                                       "ack_ackno=%llu, ACKED!\n",
 445                                       dccp_role(sk), avr->avr_ack_runlen,
 446                                       (unsigned long long)avr->avr_ack_seqno,
 447                                       (unsigned long long)avr->avr_ack_ackno);
 448                         dccp_ackvec_throw_record(av, avr);
 449                         break;
 450                 } else if (avr->avr_ack_seqno > ackno)
 451                         break; /* old news */
 452         }
 453 }
 454
 455 static void dccp_ackvec_check_rcv_ackvector(struct dccp_ackvec *av,
 456                                             struct sock *sk, u64 *ackno,
 457                                             const unsigned char len,
 458                                             const unsigned char *vector)
 459 {
 460         unsigned char i;
 461         struct dccp_ackvec_record *avr;
 462
 463         /* Check if we actually sent an ACK vector */
 464         if (list_empty(&av->av_records))
 465                 return;
 466
 467         i = len;
 468         /*
 469          * XXX
 470          * I think it might be more efficient to work backwards. See comment on
 471          * rcv_ackno. -sorbo.
 472          */
 473         avr = list_entry(av->av_records.next, struct dccp_ackvec_record, avr_node);
 474         while (i--) {
 475                 const u8 rl = dccp_ackvec_runlen(vector);
 476                 u64 ackno_end_rl;
 477
 478                 dccp_set_seqno(&ackno_end_rl, *ackno - rl);
 479
 480                 /*
 481                  * If our AVR sequence number is greater than the ack, go
 482                  * forward in the AVR list until it is not so.
 483                  */
 484                 list_for_each_entry_from(avr, &av->av_records, avr_node) {
 485                         if (!after48(avr->avr_ack_seqno, *ackno))
 486                                 goto found;
 487                 }
 488                 /* End of the av_records list, not found, exit */
 489                 break;
 490 found:
 491                 if (between48(avr->avr_ack_seqno, ackno_end_rl, *ackno)) {
 492                         if (dccp_ackvec_state(vector) != DCCPAV_NOT_RECEIVED) {
 493                                 dccp_pr_debug("%s ACK vector 0, len=%d, "
 494                                               "ack_seqno=%llu, ack_ackno=%llu, "
 495                                               "ACKED!\n",
 496                                               dccp_role(sk), len,
 497                                               (unsigned long long)
 498                                               avr->avr_ack_seqno,
 499                                               (unsigned long long)
 500                                               avr->avr_ack_ackno);
 501                                 dccp_ackvec_throw_record(av, avr);
 502                                 break;
 503                         }
 504                         /*
 505                          * If it wasn't received, continue scanning... we might
 506                          * find another one.
 507                          */
 508                 }
 509
 510                 dccp_set_seqno(ackno, ackno_end_rl - 1);
 511                 ++vector;
 512         }
 513 }
 514
 515 int dccp_ackvec_parse(struct sock *sk, const struct sk_buff *skb,
 516                       u64 *ackno, const u8 opt, const u8 *value, const u8 len)
 517 {
 518         if (len > DCCP_SINGLE_OPT_MAXLEN)
 519                 return -1;
 520
 521         /* dccp_ackvector_print(DCCP_SKB_CB(skb)->dccpd_ack_seq, value, len); */
 522         dccp_ackvec_check_rcv_ackvector(dccp_sk(sk)->dccps_hc_rx_ackvec, sk,
 523                                         ackno, len, value);
 524         return 0;
 525 }
 526
 527 /**
 528  * dccp_ackvec_clear_state  -  Perform house-keeping / garbage-collection
 529  * This routine is called when the peer acknowledges the receipt of Ack Vectors
 530  * up to and including @ackno. While based on on section A.3 of RFC 4340, here
 531  * are additional precautions to prevent corrupted buffer state. In particular,
 532  * we use tail_ackno to identify outdated records; it always marks the earliest
 533  * packet of group (2) in 11.4.2.
 534  */
 535 void dccp_ackvec_clear_state(struct dccp_ackvec *av, const u64 ackno)
 536  {
 537         struct dccp_ackvec_record *avr, *next;
 538         u8 runlen_now, eff_runlen;
 539         s64 delta;
 540
 541         avr = dccp_ackvec_lookup(&av->av_records, ackno);
 542         if (avr == NULL)
 543                 return;
 544         /*
 545          * Deal with outdated acknowledgments: this arises when e.g. there are
 546          * several old records and the acks from the peer come in slowly. In
 547          * that case we may still have records that pre-date tail_ackno.
 548          */
 549         delta = dccp_delta_seqno(av->av_tail_ackno, avr->avr_ack_ackno);
 550         if (delta < 0)
 551                 goto free_records;
 552         /*
 553          * Deal with overlapping Ack Vectors: don't subtract more than the
 554          * number of packets between tail_ackno and ack_ackno.
 555          */
 556         eff_runlen = delta < avr->avr_ack_runlen ? delta : avr->avr_ack_runlen;
 557
 558         runlen_now = dccp_ackvec_runlen(av->av_buf + avr->avr_ack_ptr);
 559         /*
 560          * The run length of Ack Vector cells does not decrease over time. If
 561          * the run length is the same as at the time the Ack Vector was sent, we
 562          * free the ack_ptr cell. That cell can however not be freed if the run
 563          * length has increased: in this case we need to move the tail pointer
 564          * backwards (towards higher indices), to its next-oldest neighbour.
 565          */
 566         if (runlen_now > eff_runlen) {
 567
 568                 av->av_buf[avr->avr_ack_ptr] -= eff_runlen + 1;
 569                 av->av_buf_tail = __ackvec_idx_add(avr->avr_ack_ptr, 1);
 570
 571                 /* This move may not have cleared the overflow flag. */
 572                 if (av->av_overflow)
 573                         av->av_overflow = (av->av_buf_head == av->av_buf_tail);
 574         } else {
 575                 av->av_buf_tail = avr->avr_ack_ptr;
 576                 /*
 577                  * We have made sure that avr points to a valid cell within the
 578                  * buffer. This cell is either older than head, or equals head
 579                  * (empty buffer): in both cases we no longer have any overflow.
 580                  */
 581                 av->av_overflow = 0;
 582         }
 583
 584         /*
 585          * The peer has acknowledged up to and including ack_ackno. Hence the
 586          * first packet in group (2) of 11.4.2 is the successor of ack_ackno.
 587          */
 588         av->av_tail_ackno = ADD48(avr->avr_ack_ackno, 1);
 589
 590 free_records:
 591         list_for_each_entry_safe_from(avr, next, &av->av_records, avr_node) {
 592                 list_del(&avr->avr_node);
 593                 kmem_cache_free(dccp_ackvec_record_slab, avr);
 594         }
 595 }
 596
 597 int __init dccp_ackvec_init(void)
 598 {
 599         dccp_ackvec_slab = kmem_cache_create("dccp_ackvec",
 600                                              sizeof(struct dccp_ackvec), 0,
 601                                              SLAB_HWCACHE_ALIGN, NULL);
 602         if (dccp_ackvec_slab == NULL)
 603                 goto out_err;
 604
 605         dccp_ackvec_record_slab = kmem_cache_create("dccp_ackvec_record",
 606                                              sizeof(struct dccp_ackvec_record),
 607                                              0, SLAB_HWCACHE_ALIGN, NULL);
 608         if (dccp_ackvec_record_slab == NULL)
 609                 goto out_destroy_slab;
 610
 611         return 0;
 612
 613 out_destroy_slab:
 614         kmem_cache_destroy(dccp_ackvec_slab);
 615         dccp_ackvec_slab = NULL;
 616 out_err:
 617         DCCP_CRIT("Unable to create Ack Vector slab cache");
 618         return -ENOBUFS;
 619 }
 620
 621 void dccp_ackvec_exit(void)
 622 {
 623         if (dccp_ackvec_slab != NULL) {
 624                 kmem_cache_destroy(dccp_ackvec_slab);
 625                 dccp_ackvec_slab = NULL;
 626         }
 627         if (dccp_ackvec_record_slab != NULL) {
 628                 kmem_cache_destroy(dccp_ackvec_record_slab);
 629                 dccp_ackvec_record_slab = NULL;
 630         }
 631 }