net/sctp/outqueue.c

   1 /* SCTP kernel implementation
   2  * (C) Copyright IBM Corp. 2001, 2004
   3  * Copyright (c) 1999-2000 Cisco, Inc.
   4  * Copyright (c) 1999-2001 Motorola, Inc.
   5  * Copyright (c) 2001-2003 Intel Corp.
   6  *
   7  * This file is part of the SCTP kernel implementation
   8  *
   9  * These functions implement the sctp_outq class.   The outqueue handles
  10  * bundling and queueing of outgoing SCTP chunks.
  11  *
  12  * This SCTP implementation is free software;
  13  * you can redistribute it and/or modify it under the terms of
  14  * the GNU General Public License as published by
  15  * the Free Software Foundation; either version 2, or (at your option)
  16  * any later version.
  17  *
  18  * This SCTP implementation is distributed in the hope that it
  19  * will be useful, but WITHOUT ANY WARRANTY; without even the implied
  20  *                 ************************
  21  * warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
  22  * See the GNU General Public License for more details.
  23  *
  24  * You should have received a copy of the GNU General Public License
  25  * along with GNU CC; see the file COPYING.  If not, see
  26  * <http://www.gnu.org/licenses/>.
  27  *
  28  * Please send any bug reports or fixes you make to the
  29  * email address(es):
  30  *    lksctp developers <linux-sctp@vger.kernel.org>
  31  *
  32  * Written or modified by:
  33  *    La Monte H.P. Yarroll <piggy@acm.org>
  34  *    Karl Knutson          <karl@athena.chicago.il.us>
  35  *    Perry Melange         <pmelange@null.cc.uic.edu>
  36  *    Xingang Guo           <xingang.guo@intel.com>
  37  *    Hui Huang             <hui.huang@nokia.com>
  38  *    Sridhar Samudrala     <sri@us.ibm.com>
  39  *    Jon Grimm             <jgrimm@us.ibm.com>
  40  */
  41
  42 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  43
  44 #include <linux/types.h>
  45 #include <linux/list.h>   /* For struct list_head */
  46 #include <linux/socket.h>
  47 #include <linux/ip.h>
  48 #include <linux/slab.h>
  49 #include <net/sock.h>     /* For skb_set_owner_w */
  50
  51 #include <net/sctp/sctp.h>
  52 #include <net/sctp/sm.h>
  53
  54 /* Declare internal functions here.  */
  55 static int sctp_acked(struct sctp_sackhdr *sack, __u32 tsn);
  56 static void sctp_check_transmitted(struct sctp_outq *q,
  57                                    struct list_head *transmitted_queue,
  58                                    struct sctp_transport *transport,
  59                                    union sctp_addr *saddr,
  60                                    struct sctp_sackhdr *sack,
  61                                    __u32 *highest_new_tsn);
  62
  63 static void sctp_mark_missing(struct sctp_outq *q,
  64                               struct list_head *transmitted_queue,
  65                               struct sctp_transport *transport,
  66                               __u32 highest_new_tsn,
  67                               int count_of_newacks);
  68
  69 static void sctp_generate_fwdtsn(struct sctp_outq *q, __u32 sack_ctsn);
  70
  71 static void sctp_outq_flush(struct sctp_outq *q, int rtx_timeout, gfp_t gfp);
  72
  73 /* Add data to the front of the queue. */
  74 static inline void sctp_outq_head_data(struct sctp_outq *q,
  75                                         struct sctp_chunk *ch)
  76 {
  77         list_add(&ch->list, &q->out_chunk_list);
  78         q->out_qlen += ch->skb->len;
  79 }
  80
  81 /* Take data from the front of the queue. */
  82 static inline struct sctp_chunk *sctp_outq_dequeue_data(struct sctp_outq *q)
  83 {
  84         struct sctp_chunk *ch = NULL;
  85
  86         if (!list_empty(&q->out_chunk_list)) {
  87                 struct list_head *entry = q->out_chunk_list.next;
  88
  89                 ch = list_entry(entry, struct sctp_chunk, list);
  90                 list_del_init(entry);
  91                 q->out_qlen -= ch->skb->len;
  92         }
  93         return ch;
  94 }
  95 /* Add data chunk to the end of the queue. */
  96 static inline void sctp_outq_tail_data(struct sctp_outq *q,
  97                                        struct sctp_chunk *ch)
  98 {
  99         list_add_tail(&ch->list, &q->out_chunk_list);
 100         q->out_qlen += ch->skb->len;
 101 }
 102
 103 /*
 104  * SFR-CACC algorithm:
 105  * D) If count_of_newacks is greater than or equal to 2
 106  * and t was not sent to the current primary then the
 107  * sender MUST NOT increment missing report count for t.
 108  */
 109 static inline int sctp_cacc_skip_3_1_d(struct sctp_transport *primary,
 110                                        struct sctp_transport *transport,
 111                                        int count_of_newacks)
 112 {
 113         if (count_of_newacks >= 2 && transport != primary)
 114                 return 1;
 115         return 0;
 116 }
 117
 118 /*
 119  * SFR-CACC algorithm:
 120  * F) If count_of_newacks is less than 2, let d be the
 121  * destination to which t was sent. If cacc_saw_newack
 122  * is 0 for destination d, then the sender MUST NOT
 123  * increment missing report count for t.
 124  */
 125 static inline int sctp_cacc_skip_3_1_f(struct sctp_transport *transport,
 126                                        int count_of_newacks)
 127 {
 128         if (count_of_newacks < 2 &&
 129                         (transport && !transport->cacc.cacc_saw_newack))
 130                 return 1;
 131         return 0;
 132 }
 133
 134 /*
 135  * SFR-CACC algorithm:
 136  * 3.1) If CYCLING_CHANGEOVER is 0, the sender SHOULD
 137  * execute steps C, D, F.
 138  *
 139  * C has been implemented in sctp_outq_sack
 140  */
 141 static inline int sctp_cacc_skip_3_1(struct sctp_transport *primary,
 142                                      struct sctp_transport *transport,
 143                                      int count_of_newacks)
 144 {
 145         if (!primary->cacc.cycling_changeover) {
 146                 if (sctp_cacc_skip_3_1_d(primary, transport, count_of_newacks))
 147                         return 1;
 148                 if (sctp_cacc_skip_3_1_f(transport, count_of_newacks))
 149                         return 1;
 150                 return 0;
 151         }
 152         return 0;
 153 }
 154
 155 /*
 156  * SFR-CACC algorithm:
 157  * 3.2) Else if CYCLING_CHANGEOVER is 1, and t is less
 158  * than next_tsn_at_change of the current primary, then
 159  * the sender MUST NOT increment missing report count
 160  * for t.
 161  */
 162 static inline int sctp_cacc_skip_3_2(struct sctp_transport *primary, __u32 tsn)
 163 {
 164         if (primary->cacc.cycling_changeover &&
 165             TSN_lt(tsn, primary->cacc.next_tsn_at_change))
 166                 return 1;
 167         return 0;
 168 }
 169
 170 /*
 171  * SFR-CACC algorithm:
 172  * 3) If the missing report count for TSN t is to be
 173  * incremented according to [RFC2960] and
 174  * [SCTP_STEWART-2002], and CHANGEOVER_ACTIVE is set,
 175  * then the sender MUST further execute steps 3.1 and
 176  * 3.2 to determine if the missing report count for
 177  * TSN t SHOULD NOT be incremented.
 178  *
 179  * 3.3) If 3.1 and 3.2 do not dictate that the missing
 180  * report count for t should not be incremented, then
 181  * the sender SHOULD increment missing report count for
 182  * t (according to [RFC2960] and [SCTP_STEWART_2002]).
 183  */
 184 static inline int sctp_cacc_skip(struct sctp_transport *primary,
 185                                  struct sctp_transport *transport,
 186                                  int count_of_newacks,
 187                                  __u32 tsn)
 188 {
 189         if (primary->cacc.changeover_active &&
 190             (sctp_cacc_skip_3_1(primary, transport, count_of_newacks) ||
 191              sctp_cacc_skip_3_2(primary, tsn)))
 192                 return 1;
 193         return 0;
 194 }
 195
 196 /* Initialize an existing sctp_outq.  This does the boring stuff.
 197  * You still need to define handlers if you really want to DO
 198  * something with this structure...
 199  */
 200 void sctp_outq_init(struct sctp_association *asoc, struct sctp_outq *q)
 201 {
 202         memset(q, 0, sizeof(struct sctp_outq));
 203
 204         q->asoc = asoc;
 205         INIT_LIST_HEAD(&q->out_chunk_list);
 206         INIT_LIST_HEAD(&q->control_chunk_list);
 207         INIT_LIST_HEAD(&q->retransmit);
 208         INIT_LIST_HEAD(&q->sacked);
 209         INIT_LIST_HEAD(&q->abandoned);
 210 }
 211
 212 /* Free the outqueue structure and any related pending chunks.
 213  */
 214 static void __sctp_outq_teardown(struct sctp_outq *q)
 215 {
 216         struct sctp_transport *transport;
 217         struct list_head *lchunk, *temp;
 218         struct sctp_chunk *chunk, *tmp;
 219
 220         /* Throw away unacknowledged chunks. */
 221         list_for_each_entry(transport, &q->asoc->peer.transport_addr_list,
 222                         transports) {
 223                 while ((lchunk = sctp_list_dequeue(&transport->transmitted)) != NULL) {
 224                         chunk = list_entry(lchunk, struct sctp_chunk,
 225                                            transmitted_list);
 226                         /* Mark as part of a failed message. */
 227                         sctp_chunk_fail(chunk, q->error);
 228                         sctp_chunk_free(chunk);
 229                 }
 230         }
 231
 232         /* Throw away chunks that have been gap ACKed.  */
 233         list_for_each_safe(lchunk, temp, &q->sacked) {
 234                 list_del_init(lchunk);
 235                 chunk = list_entry(lchunk, struct sctp_chunk,
 236                                    transmitted_list);
 237                 sctp_chunk_fail(chunk, q->error);
 238                 sctp_chunk_free(chunk);
 239         }
 240
 241         /* Throw away any chunks in the retransmit queue. */
 242         list_for_each_safe(lchunk, temp, &q->retransmit) {
 243                 list_del_init(lchunk);
 244                 chunk = list_entry(lchunk, struct sctp_chunk,
 245                                    transmitted_list);
 246                 sctp_chunk_fail(chunk, q->error);
 247                 sctp_chunk_free(chunk);
 248         }
 249
 250         /* Throw away any chunks that are in the abandoned queue. */
 251         list_for_each_safe(lchunk, temp, &q->abandoned) {
 252                 list_del_init(lchunk);
 253                 chunk = list_entry(lchunk, struct sctp_chunk,
 254                                    transmitted_list);
 255                 sctp_chunk_fail(chunk, q->error);
 256                 sctp_chunk_free(chunk);
 257         }
 258
 259         /* Throw away any leftover data chunks. */
 260         while ((chunk = sctp_outq_dequeue_data(q)) != NULL) {
 261
 262                 /* Mark as send failure. */
 263                 sctp_chunk_fail(chunk, q->error);
 264                 sctp_chunk_free(chunk);
 265         }
 266
 267         /* Throw away any leftover control chunks. */
 268         list_for_each_entry_safe(chunk, tmp, &q->control_chunk_list, list) {
 269                 list_del_init(&chunk->list);
 270                 sctp_chunk_free(chunk);
 271         }
 272 }
 273
 274 void sctp_outq_teardown(struct sctp_outq *q)
 275 {
 276         __sctp_outq_teardown(q);
 277         sctp_outq_init(q->asoc, q);
 278 }
 279
 280 /* Free the outqueue structure and any related pending chunks.  */
 281 void sctp_outq_free(struct sctp_outq *q)
 282 {
 283         /* Throw away leftover chunks. */
 284         __sctp_outq_teardown(q);
 285 }
 286
 287 /* Put a new chunk in an sctp_outq.  */
 288 void sctp_outq_tail(struct sctp_outq *q, struct sctp_chunk *chunk, gfp_t gfp)
 289 {
 290         struct net *net = sock_net(q->asoc->base.sk);
 291
 292         pr_debug("%s: outq:%p, chunk:%p[%s]\n", __func__, q, chunk,
 293                  chunk && chunk->chunk_hdr ?
 294                  sctp_cname(SCTP_ST_CHUNK(chunk->chunk_hdr->type)) :
 295                  "illegal chunk");
 296
 297         /* If it is data, queue it up, otherwise, send it
 298          * immediately.
 299          */
 300         if (sctp_chunk_is_data(chunk)) {
 301                 pr_debug("%s: outqueueing: outq:%p, chunk:%p[%s])\n",
 302                          __func__, q, chunk, chunk && chunk->chunk_hdr ?
 303                          sctp_cname(SCTP_ST_CHUNK(chunk->chunk_hdr->type)) :
 304                          "illegal chunk");
 305
 306                 sctp_outq_tail_data(q, chunk);
 307                 if (chunk->asoc->peer.prsctp_capable &&
 308                     SCTP_PR_PRIO_ENABLED(chunk->sinfo.sinfo_flags))
 309                         chunk->asoc->sent_cnt_removable++;
 310                 if (chunk->chunk_hdr->flags & SCTP_DATA_UNORDERED)
 311                         SCTP_INC_STATS(net, SCTP_MIB_OUTUNORDERCHUNKS);
 312                 else
 313                         SCTP_INC_STATS(net, SCTP_MIB_OUTORDERCHUNKS);
 314         } else {
 315                 list_add_tail(&chunk->list, &q->control_chunk_list);
 316                 SCTP_INC_STATS(net, SCTP_MIB_OUTCTRLCHUNKS);
 317         }
 318
 319         if (!q->cork)
 320                 sctp_outq_flush(q, 0, gfp);
 321 }
 322
 323 /* Insert a chunk into the sorted list based on the TSNs.  The retransmit list
 324  * and the abandoned list are in ascending order.
 325  */
 326 static void sctp_insert_list(struct list_head *head, struct list_head *new)
 327 {
 328         struct list_head *pos;
 329         struct sctp_chunk *nchunk, *lchunk;
 330         __u32 ntsn, ltsn;
 331         int done = 0;
 332
 333         nchunk = list_entry(new, struct sctp_chunk, transmitted_list);
 334         ntsn = ntohl(nchunk->subh.data_hdr->tsn);
 335
 336         list_for_each(pos, head) {
 337                 lchunk = list_entry(pos, struct sctp_chunk, transmitted_list);
 338                 ltsn = ntohl(lchunk->subh.data_hdr->tsn);
 339                 if (TSN_lt(ntsn, ltsn)) {
 340                         list_add(new, pos->prev);
 341                         done = 1;
 342                         break;
 343                 }
 344         }
 345         if (!done)
 346                 list_add_tail(new, head);
 347 }
 348
 349 static int sctp_prsctp_prune_sent(struct sctp_association *asoc,
 350                                   struct sctp_sndrcvinfo *sinfo,
 351                                   struct list_head *queue, int msg_len)
 352 {
 353         struct sctp_chunk *chk, *temp;
 354
 355         list_for_each_entry_safe(chk, temp, queue, transmitted_list) {
 356                 struct sctp_stream_out *streamout;
 357
 358                 if (!SCTP_PR_PRIO_ENABLED(chk->sinfo.sinfo_flags) ||
 359                     chk->sinfo.sinfo_timetolive <= sinfo->sinfo_timetolive)
 360                         continue;
 361
 362                 list_del_init(&chk->transmitted_list);
 363                 sctp_insert_list(&asoc->outqueue.abandoned,
 364                                  &chk->transmitted_list);
 365
 366                 streamout = &asoc->stream.out[chk->sinfo.sinfo_stream];
 367                 asoc->sent_cnt_removable--;
 368                 asoc->abandoned_sent[SCTP_PR_INDEX(PRIO)]++;
 369                 streamout->abandoned_sent[SCTP_PR_INDEX(PRIO)]++;
 370
 371                 if (queue != &asoc->outqueue.retransmit &&
 372                     !chk->tsn_gap_acked) {
 373                         if (chk->transport)
 374                                 chk->transport->flight_size -=
 375                                                 sctp_data_size(chk);
 376                         asoc->outqueue.outstanding_bytes -= sctp_data_size(chk);
 377                 }
 378
 379                 msg_len -= SCTP_DATA_SNDSIZE(chk) +
 380                            sizeof(struct sk_buff) +
 381                            sizeof(struct sctp_chunk);
 382                 if (msg_len <= 0)
 383                         break;
 384         }
 385
 386         return msg_len;
 387 }
 388
 389 static int sctp_prsctp_prune_unsent(struct sctp_association *asoc,
 390                                     struct sctp_sndrcvinfo *sinfo, int msg_len)
 391 {
 392         struct sctp_outq *q = &asoc->outqueue;
 393         struct sctp_chunk *chk, *temp;
 394
 395         list_for_each_entry_safe(chk, temp, &q->out_chunk_list, list) {
 396                 if (!SCTP_PR_PRIO_ENABLED(chk->sinfo.sinfo_flags) ||
 397                     chk->sinfo.sinfo_timetolive <= sinfo->sinfo_timetolive)
 398                         continue;
 399
 400                 list_del_init(&chk->list);
 401                 q->out_qlen -= chk->skb->len;
 402                 asoc->sent_cnt_removable--;
 403                 asoc->abandoned_unsent[SCTP_PR_INDEX(PRIO)]++;
 404                 if (chk->sinfo.sinfo_stream < asoc->stream.outcnt) {
 405                         struct sctp_stream_out *streamout =
 406                                 &asoc->stream.out[chk->sinfo.sinfo_stream];
 407
 408                         streamout->abandoned_unsent[SCTP_PR_INDEX(PRIO)]++;
 409                 }
 410
 411                 msg_len -= SCTP_DATA_SNDSIZE(chk) +
 412                            sizeof(struct sk_buff) +
 413                            sizeof(struct sctp_chunk);
 414                 sctp_chunk_free(chk);
 415                 if (msg_len <= 0)
 416                         break;
 417         }
 418
 419         return msg_len;
 420 }
 421
 422 /* Abandon the chunks according their priorities */
 423 void sctp_prsctp_prune(struct sctp_association *asoc,
 424                        struct sctp_sndrcvinfo *sinfo, int msg_len)
 425 {
 426         struct sctp_transport *transport;
 427
 428         if (!asoc->peer.prsctp_capable || !asoc->sent_cnt_removable)
 429                 return;
 430
 431         msg_len = sctp_prsctp_prune_sent(asoc, sinfo,
 432                                          &asoc->outqueue.retransmit,
 433                                          msg_len);
 434         if (msg_len <= 0)
 435                 return;
 436
 437         list_for_each_entry(transport, &asoc->peer.transport_addr_list,
 438                             transports) {
 439                 msg_len = sctp_prsctp_prune_sent(asoc, sinfo,
 440                                                  &transport->transmitted,
 441                                                  msg_len);
 442                 if (msg_len <= 0)
 443                         return;
 444         }
 445
 446         sctp_prsctp_prune_unsent(asoc, sinfo, msg_len);
 447 }
 448
 449 /* Mark all the eligible packets on a transport for retransmission.  */
 450 void sctp_retransmit_mark(struct sctp_outq *q,
 451                           struct sctp_transport *transport,
 452                           __u8 reason)
 453 {
 454         struct list_head *lchunk, *ltemp;
 455         struct sctp_chunk *chunk;
 456
 457         /* Walk through the specified transmitted queue.  */
 458         list_for_each_safe(lchunk, ltemp, &transport->transmitted) {
 459                 chunk = list_entry(lchunk, struct sctp_chunk,
 460                                    transmitted_list);
 461
 462                 /* If the chunk is abandoned, move it to abandoned list. */
 463                 if (sctp_chunk_abandoned(chunk)) {
 464                         list_del_init(lchunk);
 465                         sctp_insert_list(&q->abandoned, lchunk);
 466
 467                         /* If this chunk has not been previousely acked,
 468                          * stop considering it 'outstanding'.  Our peer
 469                          * will most likely never see it since it will
 470                          * not be retransmitted
 471                          */
 472                         if (!chunk->tsn_gap_acked) {
 473                                 if (chunk->transport)
 474                                         chunk->transport->flight_size -=
 475                                                         sctp_data_size(chunk);
 476                                 q->outstanding_bytes -= sctp_data_size(chunk);
 477                                 q->asoc->peer.rwnd += sctp_data_size(chunk);
 478                         }
 479                         continue;
 480                 }
 481
 482                 /* If we are doing  retransmission due to a timeout or pmtu
 483                  * discovery, only the  chunks that are not yet acked should
 484                  * be added to the retransmit queue.
 485                  */
 486                 if ((reason == SCTP_RTXR_FAST_RTX  &&
 487                             (chunk->fast_retransmit == SCTP_NEED_FRTX)) ||
 488                     (reason != SCTP_RTXR_FAST_RTX  && !chunk->tsn_gap_acked)) {
 489                         /* RFC 2960 6.2.1 Processing a Received SACK
 490                          *
 491                          * C) Any time a DATA chunk is marked for
 492                          * retransmission (via either T3-rtx timer expiration
 493                          * (Section 6.3.3) or via fast retransmit
 494                          * (Section 7.2.4)), add the data size of those
 495                          * chunks to the rwnd.
 496                          */
 497                         q->asoc->peer.rwnd += sctp_data_size(chunk);
 498                         q->outstanding_bytes -= sctp_data_size(chunk);
 499                         if (chunk->transport)
 500                                 transport->flight_size -= sctp_data_size(chunk);
 501
 502                         /* sctpimpguide-05 Section 2.8.2
 503                          * M5) If a T3-rtx timer expires, the
 504                          * 'TSN.Missing.Report' of all affected TSNs is set
 505                          * to 0.
 506                          */
 507                         chunk->tsn_missing_report = 0;
 508
 509                         /* If a chunk that is being used for RTT measurement
 510                          * has to be retransmitted, we cannot use this chunk
 511                          * anymore for RTT measurements. Reset rto_pending so
 512                          * that a new RTT measurement is started when a new
 513                          * data chunk is sent.
 514                          */
 515                         if (chunk->rtt_in_progress) {
 516                                 chunk->rtt_in_progress = 0;
 517                                 transport->rto_pending = 0;
 518                         }
 519
 520                         /* Move the chunk to the retransmit queue. The chunks
 521                          * on the retransmit queue are always kept in order.
 522                          */
 523                         list_del_init(lchunk);
 524                         sctp_insert_list(&q->retransmit, lchunk);
 525                 }
 526         }
 527
 528         pr_debug("%s: transport:%p, reason:%d, cwnd:%d, ssthresh:%d, "
 529                  "flight_size:%d, pba:%d\n", __func__, transport, reason,
 530                  transport->cwnd, transport->ssthresh, transport->flight_size,
 531                  transport->partial_bytes_acked);
 532 }
 533
 534 /* Mark all the eligible packets on a transport for retransmission and force
 535  * one packet out.
 536  */
 537 void sctp_retransmit(struct sctp_outq *q, struct sctp_transport *transport,
 538                      enum sctp_retransmit_reason reason)
 539 {
 540         struct net *net = sock_net(q->asoc->base.sk);
 541
 542         switch (reason) {
 543         case SCTP_RTXR_T3_RTX:
 544                 SCTP_INC_STATS(net, SCTP_MIB_T3_RETRANSMITS);
 545                 sctp_transport_lower_cwnd(transport, SCTP_LOWER_CWND_T3_RTX);
 546                 /* Update the retran path if the T3-rtx timer has expired for
 547                  * the current retran path.
 548                  */
 549                 if (transport == transport->asoc->peer.retran_path)
 550                         sctp_assoc_update_retran_path(transport->asoc);
 551                 transport->asoc->rtx_data_chunks +=
 552                         transport->asoc->unack_data;
 553                 break;
 554         case SCTP_RTXR_FAST_RTX:
 555                 SCTP_INC_STATS(net, SCTP_MIB_FAST_RETRANSMITS);
 556                 sctp_transport_lower_cwnd(transport, SCTP_LOWER_CWND_FAST_RTX);
 557                 q->fast_rtx = 1;
 558                 break;
 559         case SCTP_RTXR_PMTUD:
 560                 SCTP_INC_STATS(net, SCTP_MIB_PMTUD_RETRANSMITS);
 561                 break;
 562         case SCTP_RTXR_T1_RTX:
 563                 SCTP_INC_STATS(net, SCTP_MIB_T1_RETRANSMITS);
 564                 transport->asoc->init_retries++;
 565                 break;
 566         default:
 567                 BUG();
 568         }
 569
 570         sctp_retransmit_mark(q, transport, reason);
 571
 572         /* PR-SCTP A5) Any time the T3-rtx timer expires, on any destination,
 573          * the sender SHOULD try to advance the "Advanced.Peer.Ack.Point" by
 574          * following the procedures outlined in C1 - C5.
 575          */
 576         if (reason == SCTP_RTXR_T3_RTX)
 577                 sctp_generate_fwdtsn(q, q->asoc->ctsn_ack_point);
 578
 579         /* Flush the queues only on timeout, since fast_rtx is only
 580          * triggered during sack processing and the queue
 581          * will be flushed at the end.
 582          */
 583         if (reason != SCTP_RTXR_FAST_RTX)
 584                 sctp_outq_flush(q, /* rtx_timeout */ 1, GFP_ATOMIC);
 585 }
 586
 587 /*
 588  * Transmit DATA chunks on the retransmit queue.  Upon return from
 589  * sctp_outq_flush_rtx() the packet 'pkt' may contain chunks which
 590  * need to be transmitted by the caller.
 591  * We assume that pkt->transport has already been set.
 592  *
 593  * The return value is a normal kernel error return value.
 594  */
 595 static int sctp_outq_flush_rtx(struct sctp_outq *q, struct sctp_packet *pkt,
 596                                int rtx_timeout, int *start_timer)
 597 {
 598         struct sctp_transport *transport = pkt->transport;
 599         struct sctp_chunk *chunk, *chunk1;
 600         struct list_head *lqueue;
 601         enum sctp_xmit status;
 602         int error = 0;
 603         int timer = 0;
 604         int done = 0;
 605         int fast_rtx;
 606
 607         lqueue = &q->retransmit;
 608         fast_rtx = q->fast_rtx;
 609
 610         /* This loop handles time-out retransmissions, fast retransmissions,
 611          * and retransmissions due to opening of whindow.
 612          *
 613          * RFC 2960 6.3.3 Handle T3-rtx Expiration
 614          *
 615          * E3) Determine how many of the earliest (i.e., lowest TSN)
 616          * outstanding DATA chunks for the address for which the
 617          * T3-rtx has expired will fit into a single packet, subject
 618          * to the MTU constraint for the path corresponding to the
 619          * destination transport address to which the retransmission
 620          * is being sent (this may be different from the address for
 621          * which the timer expires [see Section 6.4]). Call this value
 622          * K. Bundle and retransmit those K DATA chunks in a single
 623          * packet to the destination endpoint.
 624          *
 625          * [Just to be painfully clear, if we are retransmitting
 626          * because a timeout just happened, we should send only ONE
 627          * packet of retransmitted data.]
 628          *
 629          * For fast retransmissions we also send only ONE packet.  However,
 630          * if we are just flushing the queue due to open window, we'll
 631          * try to send as much as possible.
 632          */
 633         list_for_each_entry_safe(chunk, chunk1, lqueue, transmitted_list) {
 634                 /* If the chunk is abandoned, move it to abandoned list. */
 635                 if (sctp_chunk_abandoned(chunk)) {
 636                         list_del_init(&chunk->transmitted_list);
 637                         sctp_insert_list(&q->abandoned,
 638                                          &chunk->transmitted_list);
 639                         continue;
 640                 }
 641
 642                 /* Make sure that Gap Acked TSNs are not retransmitted.  A
 643                  * simple approach is just to move such TSNs out of the
 644                  * way and into a 'transmitted' queue and skip to the
 645                  * next chunk.
 646                  */
 647                 if (chunk->tsn_gap_acked) {
 648                         list_move_tail(&chunk->transmitted_list,
 649                                        &transport->transmitted);
 650                         continue;
 651                 }
 652
 653                 /* If we are doing fast retransmit, ignore non-fast_rtransmit
 654                  * chunks
 655                  */
 656                 if (fast_rtx && !chunk->fast_retransmit)
 657                         continue;
 658
 659 redo:
 660                 /* Attempt to append this chunk to the packet. */
 661                 status = sctp_packet_append_chunk(pkt, chunk);
 662
 663                 switch (status) {
 664                 case SCTP_XMIT_PMTU_FULL:
 665                         if (!pkt->has_data && !pkt->has_cookie_echo) {
 666                                 /* If this packet did not contain DATA then
 667                                  * retransmission did not happen, so do it
 668                                  * again.  We'll ignore the error here since
 669                                  * control chunks are already freed so there
 670                                  * is nothing we can do.
 671                                  */
 672                                 sctp_packet_transmit(pkt, GFP_ATOMIC);
 673                                 goto redo;
 674                         }
 675
 676                         /* Send this packet.  */
 677                         error = sctp_packet_transmit(pkt, GFP_ATOMIC);
 678
 679                         /* If we are retransmitting, we should only
 680                          * send a single packet.
 681                          * Otherwise, try appending this chunk again.
 682                          */
 683                         if (rtx_timeout || fast_rtx)
 684                                 done = 1;
 685                         else
 686                                 goto redo;
 687
 688                         /* Bundle next chunk in the next round.  */
 689                         break;
 690
 691                 case SCTP_XMIT_RWND_FULL:
 692                         /* Send this packet. */
 693                         error = sctp_packet_transmit(pkt, GFP_ATOMIC);
 694
 695                         /* Stop sending DATA as there is no more room
 696                          * at the receiver.
 697                          */
 698                         done = 1;
 699                         break;
 700
 701                 case SCTP_XMIT_DELAY:
 702                         /* Send this packet. */
 703                         error = sctp_packet_transmit(pkt, GFP_ATOMIC);
 704
 705                         /* Stop sending DATA because of nagle delay. */
 706                         done = 1;
 707                         break;
 708
 709                 default:
 710                         /* The append was successful, so add this chunk to
 711                          * the transmitted list.
 712                          */
 713                         list_move_tail(&chunk->transmitted_list,
 714                                        &transport->transmitted);
 715
 716                         /* Mark the chunk as ineligible for fast retransmit
 717                          * after it is retransmitted.
 718                          */
 719                         if (chunk->fast_retransmit == SCTP_NEED_FRTX)
 720                                 chunk->fast_retransmit = SCTP_DONT_FRTX;
 721
 722                         q->asoc->stats.rtxchunks++;
 723                         break;
 724                 }
 725
 726                 /* Set the timer if there were no errors */
 727                 if (!error && !timer)
 728                         timer = 1;
 729
 730                 if (done)
 731                         break;
 732         }
 733
 734         /* If we are here due to a retransmit timeout or a fast
 735          * retransmit and if there are any chunks left in the retransmit
 736          * queue that could not fit in the PMTU sized packet, they need
 737          * to be marked as ineligible for a subsequent fast retransmit.
 738          */
 739         if (rtx_timeout || fast_rtx) {
 740                 list_for_each_entry(chunk1, lqueue, transmitted_list) {
 741                         if (chunk1->fast_retransmit == SCTP_NEED_FRTX)
 742                                 chunk1->fast_retransmit = SCTP_DONT_FRTX;
 743                 }
 744         }
 745
 746         *start_timer = timer;
 747
 748         /* Clear fast retransmit hint */
 749         if (fast_rtx)
 750                 q->fast_rtx = 0;
 751
 752         return error;
 753 }
 754
 755 /* Cork the outqueue so queued chunks are really queued. */
 756 void sctp_outq_uncork(struct sctp_outq *q, gfp_t gfp)
 757 {
 758         if (q->cork)
 759                 q->cork = 0;
 760
 761         sctp_outq_flush(q, 0, gfp);
 762 }
 763
 764
 765 /*
 766  * Try to flush an outqueue.
 767  *
 768  * Description: Send everything in q which we legally can, subject to
 769  * congestion limitations.
 770  * * Note: This function can be called from multiple contexts so appropriate
 771  * locking concerns must be made.  Today we use the sock lock to protect
 772  * this function.
 773  */
 774 static void sctp_outq_flush(struct sctp_outq *q, int rtx_timeout, gfp_t gfp)
 775 {
 776         struct sctp_packet *packet;
 777         struct sctp_packet singleton;
 778         struct sctp_association *asoc = q->asoc;
 779         __u16 sport = asoc->base.bind_addr.port;
 780         __u16 dport = asoc->peer.port;
 781         __u32 vtag = asoc->peer.i.init_tag;
 782         struct sctp_transport *transport = NULL;
 783         struct sctp_transport *new_transport;
 784         struct sctp_chunk *chunk, *tmp;
 785         enum sctp_xmit status;
 786         int error = 0;
 787         int start_timer = 0;
 788         int one_packet = 0;
 789
 790         /* These transports have chunks to send. */
 791         struct list_head transport_list;
 792         struct list_head *ltransport;
 793
 794         INIT_LIST_HEAD(&transport_list);
 795         packet = NULL;
 796
 797         /*
 798          * 6.10 Bundling
 799          *   ...
 800          *   When bundling control chunks with DATA chunks, an
 801          *   endpoint MUST place control chunks first in the outbound
 802          *   SCTP packet.  The transmitter MUST transmit DATA chunks
 803          *   within a SCTP packet in increasing order of TSN.
 804          *   ...
 805          */
 806
 807         list_for_each_entry_safe(chunk, tmp, &q->control_chunk_list, list) {
 808                 /* RFC 5061, 5.3
 809                  * F1) This means that until such time as the ASCONF
 810                  * containing the add is acknowledged, the sender MUST
 811                  * NOT use the new IP address as a source for ANY SCTP
 812                  * packet except on carrying an ASCONF Chunk.
 813                  */
 814                 if (asoc->src_out_of_asoc_ok &&
 815                     chunk->chunk_hdr->type != SCTP_CID_ASCONF)
 816                         continue;
 817
 818                 list_del_init(&chunk->list);
 819
 820                 /* Pick the right transport to use. */
 821                 new_transport = chunk->transport;
 822
 823                 if (!new_transport) {
 824                         /*
 825                          * If we have a prior transport pointer, see if
 826                          * the destination address of the chunk
 827                          * matches the destination address of the
 828                          * current transport.  If not a match, then
 829                          * try to look up the transport with a given
 830                          * destination address.  We do this because
 831                          * after processing ASCONFs, we may have new
 832                          * transports created.
 833                          */
 834                         if (transport &&
 835                             sctp_cmp_addr_exact(&chunk->dest,
 836                                                 &transport->ipaddr))
 837                                         new_transport = transport;
 838                         else
 839                                 new_transport = sctp_assoc_lookup_paddr(asoc,
 840                                                                 &chunk->dest);
 841
 842                         /* if we still don't have a new transport, then
 843                          * use the current active path.
 844                          */
 845                         if (!new_transport)
 846                                 new_transport = asoc->peer.active_path;
 847                 } else if ((new_transport->state == SCTP_INACTIVE) ||
 848                            (new_transport->state == SCTP_UNCONFIRMED) ||
 849                            (new_transport->state == SCTP_PF)) {
 850                         /* If the chunk is Heartbeat or Heartbeat Ack,
 851                          * send it to chunk->transport, even if it's
 852                          * inactive.
 853                          *
 854                          * 3.3.6 Heartbeat Acknowledgement:
 855                          * ...
 856                          * A HEARTBEAT ACK is always sent to the source IP
 857                          * address of the IP datagram containing the
 858                          * HEARTBEAT chunk to which this ack is responding.
 859                          * ...
 860                          *
 861                          * ASCONF_ACKs also must be sent to the source.
 862                          */
 863                         if (chunk->chunk_hdr->type != SCTP_CID_HEARTBEAT &&
 864                             chunk->chunk_hdr->type != SCTP_CID_HEARTBEAT_ACK &&
 865                             chunk->chunk_hdr->type != SCTP_CID_ASCONF_ACK)
 866                                 new_transport = asoc->peer.active_path;
 867                 }
 868
 869                 /* Are we switching transports?
 870                  * Take care of transport locks.
 871                  */
 872                 if (new_transport != transport) {
 873                         transport = new_transport;
 874                         if (list_empty(&transport->send_ready)) {
 875                                 list_add_tail(&transport->send_ready,
 876                                               &transport_list);
 877                         }
 878                         packet = &transport->packet;
 879                         sctp_packet_config(packet, vtag,
 880                                            asoc->peer.ecn_capable);
 881                 }
 882
 883                 switch (chunk->chunk_hdr->type) {
 884                 /*
 885                  * 6.10 Bundling
 886                  *   ...
 887                  *   An endpoint MUST NOT bundle INIT, INIT ACK or SHUTDOWN
 888                  *   COMPLETE with any other chunks.  [Send them immediately.]
 889                  */
 890                 case SCTP_CID_INIT:
 891                 case SCTP_CID_INIT_ACK:
 892                 case SCTP_CID_SHUTDOWN_COMPLETE:
 893                         sctp_packet_init(&singleton, transport, sport, dport);
 894                         sctp_packet_config(&singleton, vtag, 0);
 895                         sctp_packet_append_chunk(&singleton, chunk);
 896                         error = sctp_packet_transmit(&singleton, gfp);
 897                         if (error < 0) {
 898                                 asoc->base.sk->sk_err = -error;
 899                                 return;
 900                         }
 901                         break;
 902
 903                 case SCTP_CID_ABORT:
 904                         if (sctp_test_T_bit(chunk)) {
 905                                 packet->vtag = asoc->c.my_vtag;
 906                         }
 907                 /* The following chunks are "response" chunks, i.e.
 908                  * they are generated in response to something we
 909                  * received.  If we are sending these, then we can
 910                  * send only 1 packet containing these chunks.
 911                  */
 912                 case SCTP_CID_HEARTBEAT_ACK:
 913                 case SCTP_CID_SHUTDOWN_ACK:
 914                 case SCTP_CID_COOKIE_ACK:
 915                 case SCTP_CID_COOKIE_ECHO:
 916                 case SCTP_CID_ERROR:
 917                 case SCTP_CID_ECN_CWR:
 918                 case SCTP_CID_ASCONF_ACK:
 919                         one_packet = 1;
 920                         /* Fall through */
 921
 922                 case SCTP_CID_SACK:
 923                 case SCTP_CID_HEARTBEAT:
 924                 case SCTP_CID_SHUTDOWN:
 925                 case SCTP_CID_ECN_ECNE:
 926                 case SCTP_CID_ASCONF:
 927                 case SCTP_CID_FWD_TSN:
 928                 case SCTP_CID_RECONF:
 929                         status = sctp_packet_transmit_chunk(packet, chunk,
 930                                                             one_packet, gfp);
 931                         if (status  != SCTP_XMIT_OK) {
 932                                 /* put the chunk back */
 933                                 list_add(&chunk->list, &q->control_chunk_list);
 934                                 break;
 935                         }
 936
 937                         asoc->stats.octrlchunks++;
 938                         /* PR-SCTP C5) If a FORWARD TSN is sent, the
 939                          * sender MUST assure that at least one T3-rtx
 940                          * timer is running.
 941                          */
 942                         if (chunk->chunk_hdr->type == SCTP_CID_FWD_TSN) {
 943                                 sctp_transport_reset_t3_rtx(transport);
 944                                 transport->last_time_sent = jiffies;
 945                         }
 946
 947                         if (chunk == asoc->strreset_chunk)
 948                                 sctp_transport_reset_reconf_timer(transport);
 949
 950                         break;
 951
 952                 default:
 953                         /* We built a chunk with an illegal type! */
 954                         BUG();
 955                 }
 956         }
 957
 958         if (q->asoc->src_out_of_asoc_ok)
 959                 goto sctp_flush_out;
 960
 961         /* Is it OK to send data chunks?  */
 962         switch (asoc->state) {
 963         case SCTP_STATE_COOKIE_ECHOED:
 964                 /* Only allow bundling when this packet has a COOKIE-ECHO
 965                  * chunk.
 966                  */
 967                 if (!packet || !packet->has_cookie_echo)
 968                         break;
 969
 970                 /* fallthru */
 971         case SCTP_STATE_ESTABLISHED:
 972         case SCTP_STATE_SHUTDOWN_PENDING:
 973         case SCTP_STATE_SHUTDOWN_RECEIVED:
 974                 /*
 975                  * RFC 2960 6.1  Transmission of DATA Chunks
 976                  *
 977                  * C) When the time comes for the sender to transmit,
 978                  * before sending new DATA chunks, the sender MUST
 979                  * first transmit any outstanding DATA chunks which
 980                  * are marked for retransmission (limited by the
 981                  * current cwnd).
 982                  */
 983                 if (!list_empty(&q->retransmit)) {
 984                         if (asoc->peer.retran_path->state == SCTP_UNCONFIRMED)
 985                                 goto sctp_flush_out;
 986                         if (transport == asoc->peer.retran_path)
 987                                 goto retran;
 988
 989                         /* Switch transports & prepare the packet.  */
 990
 991                         transport = asoc->peer.retran_path;
 992
 993                         if (list_empty(&transport->send_ready)) {
 994                                 list_add_tail(&transport->send_ready,
 995                                               &transport_list);
 996                         }
 997
 998                         packet = &transport->packet;
 999                         sctp_packet_config(packet, vtag,
1000                                            asoc->peer.ecn_capable);
1001                 retran:
1002                         error = sctp_outq_flush_rtx(q, packet,
1003                                                     rtx_timeout, &start_timer);
1004                         if (error < 0)
1005                                 asoc->base.sk->sk_err = -error;
1006
1007                         if (start_timer) {
1008                                 sctp_transport_reset_t3_rtx(transport);
1009                                 transport->last_time_sent = jiffies;
1010                         }
1011
1012                         /* This can happen on COOKIE-ECHO resend.  Only
1013                          * one chunk can get bundled with a COOKIE-ECHO.
1014                          */
1015                         if (packet->has_cookie_echo)
1016                                 goto sctp_flush_out;
1017
1018                         /* Don't send new data if there is still data
1019                          * waiting to retransmit.
1020                          */
1021                         if (!list_empty(&q->retransmit))
1022                                 goto sctp_flush_out;
1023                 }
1024
1025                 /* Apply Max.Burst limitation to the current transport in
1026                  * case it will be used for new data.  We are going to
1027                  * rest it before we return, but we want to apply the limit
1028                  * to the currently queued data.
1029                  */
1030                 if (transport)
1031                         sctp_transport_burst_limited(transport);
1032
1033                 /* Finally, transmit new packets.  */
1034                 while ((chunk = sctp_outq_dequeue_data(q)) != NULL) {
1035                         __u32 sid = ntohs(chunk->subh.data_hdr->stream);
1036
1037                         /* RFC 2960 6.5 Every DATA chunk MUST carry a valid
1038                          * stream identifier.
1039                          */
1040                         if (chunk->sinfo.sinfo_stream >= asoc->stream.outcnt) {
1041
1042                                 /* Mark as failed send. */
1043                                 sctp_chunk_fail(chunk, SCTP_ERROR_INV_STRM);
1044                                 if (asoc->peer.prsctp_capable &&
1045                                     SCTP_PR_PRIO_ENABLED(chunk->sinfo.sinfo_flags))
1046                                         asoc->sent_cnt_removable--;
1047                                 sctp_chunk_free(chunk);
1048                                 continue;
1049                         }
1050
1051                         /* Has this chunk expired? */
1052                         if (sctp_chunk_abandoned(chunk)) {
1053                                 sctp_chunk_fail(chunk, 0);
1054                                 sctp_chunk_free(chunk);
1055                                 continue;
1056                         }
1057
1058                         if (asoc->stream.out[sid].state == SCTP_STREAM_CLOSED) {
1059                                 sctp_outq_head_data(q, chunk);
1060                                 goto sctp_flush_out;
1061                         }
1062
1063                         /* If there is a specified transport, use it.
1064                          * Otherwise, we want to use the active path.
1065                          */
1066                         new_transport = chunk->transport;
1067                         if (!new_transport ||
1068                             ((new_transport->state == SCTP_INACTIVE) ||
1069                              (new_transport->state == SCTP_UNCONFIRMED) ||
1070                              (new_transport->state == SCTP_PF)))
1071                                 new_transport = asoc->peer.active_path;
1072                         if (new_transport->state == SCTP_UNCONFIRMED) {
1073                                 WARN_ONCE(1, "Attempt to send packet on unconfirmed path.");
1074                                 sctp_chunk_fail(chunk, 0);
1075                                 sctp_chunk_free(chunk);
1076                                 continue;
1077                         }
1078
1079                         /* Change packets if necessary.  */
1080                         if (new_transport != transport) {
1081                                 transport = new_transport;
1082
1083                                 /* Schedule to have this transport's
1084                                  * packet flushed.
1085                                  */
1086                                 if (list_empty(&transport->send_ready)) {
1087                                         list_add_tail(&transport->send_ready,
1088                                                       &transport_list);
1089                                 }
1090
1091                                 packet = &transport->packet;
1092                                 sctp_packet_config(packet, vtag,
1093                                                    asoc->peer.ecn_capable);
1094                                 /* We've switched transports, so apply the
1095                                  * Burst limit to the new transport.
1096                                  */
1097                                 sctp_transport_burst_limited(transport);
1098                         }
1099
1100                         pr_debug("%s: outq:%p, chunk:%p[%s], tx-tsn:0x%x skb->head:%p "
1101                                  "skb->users:%d\n",
1102                                  __func__, q, chunk, chunk && chunk->chunk_hdr ?
1103                                  sctp_cname(SCTP_ST_CHUNK(chunk->chunk_hdr->type)) :
1104                                  "illegal chunk", ntohl(chunk->subh.data_hdr->tsn),
1105                                  chunk->skb ? chunk->skb->head : NULL, chunk->skb ?
1106                                  refcount_read(&chunk->skb->users) : -1);
1107
1108                         /* Add the chunk to the packet.  */
1109                         status = sctp_packet_transmit_chunk(packet, chunk, 0, gfp);
1110
1111                         switch (status) {
1112                         case SCTP_XMIT_PMTU_FULL:
1113                         case SCTP_XMIT_RWND_FULL:
1114                         case SCTP_XMIT_DELAY:
1115                                 /* We could not append this chunk, so put
1116                                  * the chunk back on the output queue.
1117                                  */
1118                                 pr_debug("%s: could not transmit tsn:0x%x, status:%d\n",
1119                                          __func__, ntohl(chunk->subh.data_hdr->tsn),
1120                                          status);
1121
1122                                 sctp_outq_head_data(q, chunk);
1123                                 goto sctp_flush_out;
1124
1125                         case SCTP_XMIT_OK:
1126                                 /* The sender is in the SHUTDOWN-PENDING state,
1127                                  * The sender MAY set the I-bit in the DATA
1128                                  * chunk header.
1129                                  */
1130                                 if (asoc->state == SCTP_STATE_SHUTDOWN_PENDING)
1131                                         chunk->chunk_hdr->flags |= SCTP_DATA_SACK_IMM;
1132                                 if (chunk->chunk_hdr->flags & SCTP_DATA_UNORDERED)
1133                                         asoc->stats.ouodchunks++;
1134                                 else
1135                                         asoc->stats.oodchunks++;
1136
1137                                 break;
1138
1139                         default:
1140                                 BUG();
1141                         }
1142
1143                         /* BUG: We assume that the sctp_packet_transmit()
1144                          * call below will succeed all the time and add the
1145                          * chunk to the transmitted list and restart the
1146                          * timers.
1147                          * It is possible that the call can fail under OOM
1148                          * conditions.
1149                          *
1150                          * Is this really a problem?  Won't this behave
1151                          * like a lost TSN?
1152                          */
1153                         list_add_tail(&chunk->transmitted_list,
1154                                       &transport->transmitted);
1155
1156                         sctp_transport_reset_t3_rtx(transport);
1157                         transport->last_time_sent = jiffies;
1158
1159                         /* Only let one DATA chunk get bundled with a
1160                          * COOKIE-ECHO chunk.
1161                          */
1162                         if (packet->has_cookie_echo)
1163                                 goto sctp_flush_out;
1164                 }
1165                 break;
1166
1167         default:
1168                 /* Do nothing.  */
1169                 break;
1170         }
1171
1172 sctp_flush_out:
1173
1174         /* Before returning, examine all the transports touched in
1175          * this call.  Right now, we bluntly force clear all the
1176          * transports.  Things might change after we implement Nagle.
1177          * But such an examination is still required.
1178          *
1179          * --xguo
1180          */
1181         while ((ltransport = sctp_list_dequeue(&transport_list)) != NULL) {
1182                 struct sctp_transport *t = list_entry(ltransport,
1183                                                       struct sctp_transport,
1184                                                       send_ready);
1185                 packet = &t->packet;
1186                 if (!sctp_packet_empty(packet)) {
1187                         error = sctp_packet_transmit(packet, gfp);
1188                         if (error < 0)
1189                                 asoc->base.sk->sk_err = -error;
1190                 }
1191
1192                 /* Clear the burst limited state, if any */
1193                 sctp_transport_burst_reset(t);
1194         }
1195 }
1196
1197 /* Update unack_data based on the incoming SACK chunk */
1198 static void sctp_sack_update_unack_data(struct sctp_association *assoc,
1199                                         struct sctp_sackhdr *sack)
1200 {
1201         union sctp_sack_variable *frags;
1202         __u16 unack_data;
1203         int i;
1204
1205         unack_data = assoc->next_tsn - assoc->ctsn_ack_point - 1;
1206
1207         frags = sack->variable;
1208         for (i = 0; i < ntohs(sack->num_gap_ack_blocks); i++) {
1209                 unack_data -= ((ntohs(frags[i].gab.end) -
1210                                 ntohs(frags[i].gab.start) + 1));
1211         }
1212
1213         assoc->unack_data = unack_data;
1214 }
1215
1216 /* This is where we REALLY process a SACK.
1217  *
1218  * Process the SACK against the outqueue.  Mostly, this just frees
1219  * things off the transmitted queue.
1220  */
1221 int sctp_outq_sack(struct sctp_outq *q, struct sctp_chunk *chunk)
1222 {
1223         struct sctp_association *asoc = q->asoc;
1224         struct sctp_sackhdr *sack = chunk->subh.sack_hdr;
1225         struct sctp_transport *transport;
1226         struct sctp_chunk *tchunk = NULL;
1227         struct list_head *lchunk, *transport_list, *temp;
1228         union sctp_sack_variable *frags = sack->variable;
1229         __u32 sack_ctsn, ctsn, tsn;
1230         __u32 highest_tsn, highest_new_tsn;
1231         __u32 sack_a_rwnd;
1232         unsigned int outstanding;
1233         struct sctp_transport *primary = asoc->peer.primary_path;
1234         int count_of_newacks = 0;
1235         int gap_ack_blocks;
1236         u8 accum_moved = 0;
1237
1238         /* Grab the association's destination address list. */
1239         transport_list = &asoc->peer.transport_addr_list;
1240
1241         sack_ctsn = ntohl(sack->cum_tsn_ack);
1242         gap_ack_blocks = ntohs(sack->num_gap_ack_blocks);
1243         asoc->stats.gapcnt += gap_ack_blocks;
1244         /*
1245          * SFR-CACC algorithm:
1246          * On receipt of a SACK the sender SHOULD execute the
1247          * following statements.
1248          *
1249          * 1) If the cumulative ack in the SACK passes next tsn_at_change
1250          * on the current primary, the CHANGEOVER_ACTIVE flag SHOULD be
1251          * cleared. The CYCLING_CHANGEOVER flag SHOULD also be cleared for
1252          * all destinations.
1253          * 2) If the SACK contains gap acks and the flag CHANGEOVER_ACTIVE
1254          * is set the receiver of the SACK MUST take the following actions:
1255          *
1256          * A) Initialize the cacc_saw_newack to 0 for all destination
1257          * addresses.
1258          *
1259          * Only bother if changeover_active is set. Otherwise, this is
1260          * totally suboptimal to do on every SACK.
1261          */
1262         if (primary->cacc.changeover_active) {
1263                 u8 clear_cycling = 0;
1264
1265                 if (TSN_lte(primary->cacc.next_tsn_at_change, sack_ctsn)) {
1266                         primary->cacc.changeover_active = 0;
1267                         clear_cycling = 1;
1268                 }
1269
1270                 if (clear_cycling || gap_ack_blocks) {
1271                         list_for_each_entry(transport, transport_list,
1272                                         transports) {
1273                                 if (clear_cycling)
1274                                         transport->cacc.cycling_changeover = 0;
1275                                 if (gap_ack_blocks)
1276                                         transport->cacc.cacc_saw_newack = 0;
1277                         }
1278                 }
1279         }
1280
1281         /* Get the highest TSN in the sack. */
1282         highest_tsn = sack_ctsn;
1283         if (gap_ack_blocks)
1284                 highest_tsn += ntohs(frags[gap_ack_blocks - 1].gab.end);
1285
1286         if (TSN_lt(asoc->highest_sacked, highest_tsn))
1287                 asoc->highest_sacked = highest_tsn;
1288
1289         highest_new_tsn = sack_ctsn;
1290
1291         /* Run through the retransmit queue.  Credit bytes received
1292          * and free those chunks that we can.
1293          */
1294         sctp_check_transmitted(q, &q->retransmit, NULL, NULL, sack, &highest_new_tsn);
1295
1296         /* Run through the transmitted queue.
1297          * Credit bytes received and free those chunks which we can.
1298          *
1299          * This is a MASSIVE candidate for optimization.
1300          */
1301         list_for_each_entry(transport, transport_list, transports) {
1302                 sctp_check_transmitted(q, &transport->transmitted,
1303                                        transport, &chunk->source, sack,
1304                                        &highest_new_tsn);
1305                 /*
1306                  * SFR-CACC algorithm:
1307                  * C) Let count_of_newacks be the number of
1308                  * destinations for which cacc_saw_newack is set.
1309                  */
1310                 if (transport->cacc.cacc_saw_newack)
1311                         count_of_newacks++;
1312         }
1313
1314         /* Move the Cumulative TSN Ack Point if appropriate.  */
1315         if (TSN_lt(asoc->ctsn_ack_point, sack_ctsn)) {
1316                 asoc->ctsn_ack_point = sack_ctsn;
1317                 accum_moved = 1;
1318         }
1319
1320         if (gap_ack_blocks) {
1321
1322                 if (asoc->fast_recovery && accum_moved)
1323                         highest_new_tsn = highest_tsn;
1324
1325                 list_for_each_entry(transport, transport_list, transports)
1326                         sctp_mark_missing(q, &transport->transmitted, transport,
1327                                           highest_new_tsn, count_of_newacks);
1328         }
1329
1330         /* Update unack_data field in the assoc. */
1331         sctp_sack_update_unack_data(asoc, sack);
1332
1333         ctsn = asoc->ctsn_ack_point;
1334
1335         /* Throw away stuff rotting on the sack queue.  */
1336         list_for_each_safe(lchunk, temp, &q->sacked) {
1337                 tchunk = list_entry(lchunk, struct sctp_chunk,
1338                                     transmitted_list);
1339                 tsn = ntohl(tchunk->subh.data_hdr->tsn);
1340                 if (TSN_lte(tsn, ctsn)) {
1341                         list_del_init(&tchunk->transmitted_list);
1342                         if (asoc->peer.prsctp_capable &&
1343                             SCTP_PR_PRIO_ENABLED(chunk->sinfo.sinfo_flags))
1344                                 asoc->sent_cnt_removable--;
1345                         sctp_chunk_free(tchunk);
1346                 }
1347         }
1348
1349         /* ii) Set rwnd equal to the newly received a_rwnd minus the
1350          *     number of bytes still outstanding after processing the
1351          *     Cumulative TSN Ack and the Gap Ack Blocks.
1352          */
1353
1354         sack_a_rwnd = ntohl(sack->a_rwnd);
1355         asoc->peer.zero_window_announced = !sack_a_rwnd;
1356         outstanding = q->outstanding_bytes;
1357
1358         if (outstanding < sack_a_rwnd)
1359                 sack_a_rwnd -= outstanding;
1360         else
1361                 sack_a_rwnd = 0;
1362
1363         asoc->peer.rwnd = sack_a_rwnd;
1364
1365         sctp_generate_fwdtsn(q, sack_ctsn);
1366
1367         pr_debug("%s: sack cumulative tsn ack:0x%x\n", __func__, sack_ctsn);
1368         pr_debug("%s: cumulative tsn ack of assoc:%p is 0x%x, "
1369                  "advertised peer ack point:0x%x\n", __func__, asoc, ctsn,
1370                  asoc->adv_peer_ack_point);
1371
1372         return sctp_outq_is_empty(q);
1373 }
1374
1375 /* Is the outqueue empty?
1376  * The queue is empty when we have not pending data, no in-flight data
1377  * and nothing pending retransmissions.
1378  */
1379 int sctp_outq_is_empty(const struct sctp_outq *q)
1380 {
1381         return q->out_qlen == 0 && q->outstanding_bytes == 0 &&
1382                list_empty(&q->retransmit);
1383 }
1384
1385 /********************************************************************
1386  * 2nd Level Abstractions
1387  ********************************************************************/
1388
1389 /* Go through a transport's transmitted list or the association's retransmit
1390  * list and move chunks that are acked by the Cumulative TSN Ack to q->sacked.
1391  * The retransmit list will not have an associated transport.
1392  *
1393  * I added coherent debug information output.   --xguo
1394  *
1395  * Instead of printing 'sacked' or 'kept' for each TSN on the
1396  * transmitted_queue, we print a range: SACKED: TSN1-TSN2, TSN3, TSN4-TSN5.
1397  * KEPT TSN6-TSN7, etc.
1398  */
1399 static void sctp_check_transmitted(struct sctp_outq *q,
1400                                    struct list_head *transmitted_queue,
1401                                    struct sctp_transport *transport,
1402                                    union sctp_addr *saddr,
1403                                    struct sctp_sackhdr *sack,
1404                                    __u32 *highest_new_tsn_in_sack)
1405 {
1406         struct list_head *lchunk;
1407         struct sctp_chunk *tchunk;
1408         struct list_head tlist;
1409         __u32 tsn;
1410         __u32 sack_ctsn;
1411         __u32 rtt;
1412         __u8 restart_timer = 0;
1413         int bytes_acked = 0;
1414         int migrate_bytes = 0;
1415         bool forward_progress = false;
1416
1417         sack_ctsn = ntohl(sack->cum_tsn_ack);
1418
1419         INIT_LIST_HEAD(&tlist);
1420
1421         /* The while loop will skip empty transmitted queues. */
1422         while (NULL != (lchunk = sctp_list_dequeue(transmitted_queue))) {
1423                 tchunk = list_entry(lchunk, struct sctp_chunk,
1424                                     transmitted_list);
1425
1426                 if (sctp_chunk_abandoned(tchunk)) {
1427                         /* Move the chunk to abandoned list. */
1428                         sctp_insert_list(&q->abandoned, lchunk);
1429
1430                         /* If this chunk has not been acked, stop
1431                          * considering it as 'outstanding'.
1432                          */
1433                         if (transmitted_queue != &q->retransmit &&
1434                             !tchunk->tsn_gap_acked) {
1435                                 if (tchunk->transport)
1436                                         tchunk->transport->flight_size -=
1437                                                         sctp_data_size(tchunk);
1438                                 q->outstanding_bytes -= sctp_data_size(tchunk);
1439                         }
1440                         continue;
1441                 }
1442
1443                 tsn = ntohl(tchunk->subh.data_hdr->tsn);
1444                 if (sctp_acked(sack, tsn)) {
1445                         /* If this queue is the retransmit queue, the
1446                          * retransmit timer has already reclaimed
1447                          * the outstanding bytes for this chunk, so only
1448                          * count bytes associated with a transport.
1449                          */
1450                         if (transport) {
1451                                 /* If this chunk is being used for RTT
1452                                  * measurement, calculate the RTT and update
1453                                  * the RTO using this value.
1454                                  *
1455                                  * 6.3.1 C5) Karn's algorithm: RTT measurements
1456                                  * MUST NOT be made using packets that were
1457                                  * retransmitted (and thus for which it is
1458                                  * ambiguous whether the reply was for the
1459                                  * first instance of the packet or a later
1460                                  * instance).
1461                                  */
1462                                 if (!tchunk->tsn_gap_acked &&
1463                                     !sctp_chunk_retransmitted(tchunk) &&
1464                                     tchunk->rtt_in_progress) {
1465                                         tchunk->rtt_in_progress = 0;
1466                                         rtt = jiffies - tchunk->sent_at;
1467                                         sctp_transport_update_rto(transport,
1468                                                                   rtt);
1469                                 }
1470                         }
1471
1472                         /* If the chunk hasn't been marked as ACKED,
1473                          * mark it and account bytes_acked if the
1474                          * chunk had a valid transport (it will not
1475                          * have a transport if ASCONF had deleted it
1476                          * while DATA was outstanding).
1477                          */
1478                         if (!tchunk->tsn_gap_acked) {
1479                                 tchunk->tsn_gap_acked = 1;
1480                                 if (TSN_lt(*highest_new_tsn_in_sack, tsn))
1481                                         *highest_new_tsn_in_sack = tsn;
1482                                 bytes_acked += sctp_data_size(tchunk);
1483                                 if (!tchunk->transport)
1484                                         migrate_bytes += sctp_data_size(tchunk);
1485                                 forward_progress = true;
1486                         }
1487
1488                         if (TSN_lte(tsn, sack_ctsn)) {
1489                                 /* RFC 2960  6.3.2 Retransmission Timer Rules
1490                                  *
1491                                  * R3) Whenever a SACK is received
1492                                  * that acknowledges the DATA chunk
1493                                  * with the earliest outstanding TSN
1494                                  * for that address, restart T3-rtx
1495                                  * timer for that address with its
1496                                  * current RTO.
1497                                  */
1498                                 restart_timer = 1;
1499                                 forward_progress = true;
1500
1501                                 if (!tchunk->tsn_gap_acked) {
1502                                         /*
1503                                          * SFR-CACC algorithm:
1504                                          * 2) If the SACK contains gap acks
1505                                          * and the flag CHANGEOVER_ACTIVE is
1506                                          * set the receiver of the SACK MUST
1507                                          * take the following action:
1508                                          *
1509                                          * B) For each TSN t being acked that
1510                                          * has not been acked in any SACK so
1511                                          * far, set cacc_saw_newack to 1 for
1512                                          * the destination that the TSN was
1513                                          * sent to.
1514                                          */
1515                                         if (transport &&
1516                                             sack->num_gap_ack_blocks &&
1517                                             q->asoc->peer.primary_path->cacc.
1518                                             changeover_active)
1519                                                 transport->cacc.cacc_saw_newack
1520                                                         = 1;
1521                                 }
1522
1523                                 list_add_tail(&tchunk->transmitted_list,
1524                                               &q->sacked);
1525                         } else {
1526                                 /* RFC2960 7.2.4, sctpimpguide-05 2.8.2
1527                                  * M2) Each time a SACK arrives reporting
1528                                  * 'Stray DATA chunk(s)' record the highest TSN
1529                                  * reported as newly acknowledged, call this
1530                                  * value 'HighestTSNinSack'. A newly
1531                                  * acknowledged DATA chunk is one not
1532                                  * previously acknowledged in a SACK.
1533                                  *
1534                                  * When the SCTP sender of data receives a SACK
1535                                  * chunk that acknowledges, for the first time,
1536                                  * the receipt of a DATA chunk, all the still
1537                                  * unacknowledged DATA chunks whose TSN is
1538                                  * older than that newly acknowledged DATA
1539                                  * chunk, are qualified as 'Stray DATA chunks'.
1540                                  */
1541                                 list_add_tail(lchunk, &tlist);
1542                         }
1543                 } else {
1544                         if (tchunk->tsn_gap_acked) {
1545                                 pr_debug("%s: receiver reneged on data TSN:0x%x\n",
1546                                          __func__, tsn);
1547
1548                                 tchunk->tsn_gap_acked = 0;
1549
1550                                 if (tchunk->transport)
1551                                         bytes_acked -= sctp_data_size(tchunk);
1552
1553                                 /* RFC 2960 6.3.2 Retransmission Timer Rules
1554                                  *
1555                                  * R4) Whenever a SACK is received missing a
1556                                  * TSN that was previously acknowledged via a
1557                                  * Gap Ack Block, start T3-rtx for the
1558                                  * destination address to which the DATA
1559                                  * chunk was originally
1560                                  * transmitted if it is not already running.
1561                                  */
1562                                 restart_timer = 1;
1563                         }
1564
1565                         list_add_tail(lchunk, &tlist);
1566                 }
1567         }
1568
1569         if (transport) {
1570                 if (bytes_acked) {
1571                         struct sctp_association *asoc = transport->asoc;
1572
1573                         /* We may have counted DATA that was migrated
1574                          * to this transport due to DEL-IP operation.
1575                          * Subtract those bytes, since the were never
1576                          * send on this transport and shouldn't be
1577                          * credited to this transport.
1578                          */
1579                         bytes_acked -= migrate_bytes;
1580
1581                         /* 8.2. When an outstanding TSN is acknowledged,
1582                          * the endpoint shall clear the error counter of
1583                          * the destination transport address to which the
1584                          * DATA chunk was last sent.
1585                          * The association's overall error counter is
1586                          * also cleared.
1587                          */
1588                         transport->error_count = 0;
1589                         transport->asoc->overall_error_count = 0;
1590                         forward_progress = true;
1591
1592                         /*
1593                          * While in SHUTDOWN PENDING, we may have started
1594                          * the T5 shutdown guard timer after reaching the
1595                          * retransmission limit. Stop that timer as soon
1596                          * as the receiver acknowledged any data.
1597                          */
1598                         if (asoc->state == SCTP_STATE_SHUTDOWN_PENDING &&
1599                             del_timer(&asoc->timers
1600                                 [SCTP_EVENT_TIMEOUT_T5_SHUTDOWN_GUARD]))
1601                                         sctp_association_put(asoc);
1602
1603                         /* Mark the destination transport address as
1604                          * active if it is not so marked.
1605                          */
1606                         if ((transport->state == SCTP_INACTIVE ||
1607                              transport->state == SCTP_UNCONFIRMED) &&
1608                             sctp_cmp_addr_exact(&transport->ipaddr, saddr)) {
1609                                 sctp_assoc_control_transport(
1610                                         transport->asoc,
1611                                         transport,
1612                                         SCTP_TRANSPORT_UP,
1613                                         SCTP_RECEIVED_SACK);
1614                         }
1615
1616                         sctp_transport_raise_cwnd(transport, sack_ctsn,
1617                                                   bytes_acked);
1618
1619                         transport->flight_size -= bytes_acked;
1620                         if (transport->flight_size == 0)
1621                                 transport->partial_bytes_acked = 0;
1622                         q->outstanding_bytes -= bytes_acked + migrate_bytes;
1623                 } else {
1624                         /* RFC 2960 6.1, sctpimpguide-06 2.15.2
1625                          * When a sender is doing zero window probing, it
1626                          * should not timeout the association if it continues
1627                          * to receive new packets from the receiver. The
1628                          * reason is that the receiver MAY keep its window
1629                          * closed for an indefinite time.
1630                          * A sender is doing zero window probing when the
1631                          * receiver's advertised window is zero, and there is
1632                          * only one data chunk in flight to the receiver.
1633                          *
1634                          * Allow the association to timeout while in SHUTDOWN
1635                          * PENDING or SHUTDOWN RECEIVED in case the receiver
1636                          * stays in zero window mode forever.
1637                          */
1638                         if (!q->asoc->peer.rwnd &&
1639                             !list_empty(&tlist) &&
1640                             (sack_ctsn+2 == q->asoc->next_tsn) &&
1641                             q->asoc->state < SCTP_STATE_SHUTDOWN_PENDING) {
1642                                 pr_debug("%s: sack received for zero window "
1643                                          "probe:%u\n", __func__, sack_ctsn);
1644
1645                                 q->asoc->overall_error_count = 0;
1646                                 transport->error_count = 0;
1647                         }
1648                 }
1649
1650                 /* RFC 2960 6.3.2 Retransmission Timer Rules
1651                  *
1652                  * R2) Whenever all outstanding data sent to an address have
1653                  * been acknowledged, turn off the T3-rtx timer of that
1654                  * address.
1655                  */
1656                 if (!transport->flight_size) {
1657                         if (del_timer(&transport->T3_rtx_timer))
1658                                 sctp_transport_put(transport);
1659                 } else if (restart_timer) {
1660                         if (!mod_timer(&transport->T3_rtx_timer,
1661                                        jiffies + transport->rto))
1662                                 sctp_transport_hold(transport);
1663                 }
1664
1665                 if (forward_progress) {
1666                         if (transport->dst)
1667                                 sctp_transport_dst_confirm(transport);
1668                 }
1669         }
1670
1671         list_splice(&tlist, transmitted_queue);
1672 }
1673
1674 /* Mark chunks as missing and consequently may get retransmitted. */
1675 static void sctp_mark_missing(struct sctp_outq *q,
1676                               struct list_head *transmitted_queue,
1677                               struct sctp_transport *transport,
1678                               __u32 highest_new_tsn_in_sack,
1679                               int count_of_newacks)
1680 {
1681         struct sctp_chunk *chunk;
1682         __u32 tsn;
1683         char do_fast_retransmit = 0;
1684         struct sctp_association *asoc = q->asoc;
1685         struct sctp_transport *primary = asoc->peer.primary_path;
1686
1687         list_for_each_entry(chunk, transmitted_queue, transmitted_list) {
1688
1689                 tsn = ntohl(chunk->subh.data_hdr->tsn);
1690
1691                 /* RFC 2960 7.2.4, sctpimpguide-05 2.8.2 M3) Examine all
1692                  * 'Unacknowledged TSN's', if the TSN number of an
1693                  * 'Unacknowledged TSN' is smaller than the 'HighestTSNinSack'
1694                  * value, increment the 'TSN.Missing.Report' count on that
1695                  * chunk if it has NOT been fast retransmitted or marked for
1696                  * fast retransmit already.
1697                  */
1698                 if (chunk->fast_retransmit == SCTP_CAN_FRTX &&
1699                     !chunk->tsn_gap_acked &&
1700                     TSN_lt(tsn, highest_new_tsn_in_sack)) {
1701
1702                         /* SFR-CACC may require us to skip marking
1703                          * this chunk as missing.
1704                          */
1705                         if (!transport || !sctp_cacc_skip(primary,
1706                                                 chunk->transport,
1707                                                 count_of_newacks, tsn)) {
1708                                 chunk->tsn_missing_report++;
1709
1710                                 pr_debug("%s: tsn:0x%x missing counter:%d\n",
1711                                          __func__, tsn, chunk->tsn_missing_report);
1712                         }
1713                 }
1714                 /*
1715                  * M4) If any DATA chunk is found to have a
1716                  * 'TSN.Missing.Report'
1717                  * value larger than or equal to 3, mark that chunk for
1718                  * retransmission and start the fast retransmit procedure.
1719                  */
1720
1721                 if (chunk->tsn_missing_report >= 3) {
1722                         chunk->fast_retransmit = SCTP_NEED_FRTX;
1723                         do_fast_retransmit = 1;
1724                 }
1725         }
1726
1727         if (transport) {
1728                 if (do_fast_retransmit)
1729                         sctp_retransmit(q, transport, SCTP_RTXR_FAST_RTX);
1730
1731                 pr_debug("%s: transport:%p, cwnd:%d, ssthresh:%d, "
1732                          "flight_size:%d, pba:%d\n",  __func__, transport,
1733                          transport->cwnd, transport->ssthresh,
1734                          transport->flight_size, transport->partial_bytes_acked);
1735         }
1736 }
1737
1738 /* Is the given TSN acked by this packet?  */
1739 static int sctp_acked(struct sctp_sackhdr *sack, __u32 tsn)
1740 {
1741         __u32 ctsn = ntohl(sack->cum_tsn_ack);
1742         union sctp_sack_variable *frags;
1743         __u16 tsn_offset, blocks;
1744         int i;
1745
1746         if (TSN_lte(tsn, ctsn))
1747                 goto pass;
1748
1749         /* 3.3.4 Selective Acknowledgement (SACK) (3):
1750          *
1751          * Gap Ack Blocks:
1752          *  These fields contain the Gap Ack Blocks. They are repeated
1753          *  for each Gap Ack Block up to the number of Gap Ack Blocks
1754          *  defined in the Number of Gap Ack Blocks field. All DATA
1755          *  chunks with TSNs greater than or equal to (Cumulative TSN
1756          *  Ack + Gap Ack Block Start) and less than or equal to
1757          *  (Cumulative TSN Ack + Gap Ack Block End) of each Gap Ack
1758          *  Block are assumed to have been received correctly.
1759          */
1760
1761         frags = sack->variable;
1762         blocks = ntohs(sack->num_gap_ack_blocks);
1763         tsn_offset = tsn - ctsn;
1764         for (i = 0; i < blocks; ++i) {
1765                 if (tsn_offset >= ntohs(frags[i].gab.start) &&
1766                     tsn_offset <= ntohs(frags[i].gab.end))
1767                         goto pass;
1768         }
1769
1770         return 0;
1771 pass:
1772         return 1;
1773 }
1774
1775 static inline int sctp_get_skip_pos(struct sctp_fwdtsn_skip *skiplist,
1776                                     int nskips, __be16 stream)
1777 {
1778         int i;
1779
1780         for (i = 0; i < nskips; i++) {
1781                 if (skiplist[i].stream == stream)
1782                         return i;
1783         }
1784         return i;
1785 }
1786
1787 /* Create and add a fwdtsn chunk to the outq's control queue if needed. */
1788 static void sctp_generate_fwdtsn(struct sctp_outq *q, __u32 ctsn)
1789 {
1790         struct sctp_association *asoc = q->asoc;
1791         struct sctp_chunk *ftsn_chunk = NULL;
1792         struct sctp_fwdtsn_skip ftsn_skip_arr[10];
1793         int nskips = 0;
1794         int skip_pos = 0;
1795         __u32 tsn;
1796         struct sctp_chunk *chunk;
1797         struct list_head *lchunk, *temp;
1798
1799         if (!asoc->peer.prsctp_capable)
1800                 return;
1801
1802         /* PR-SCTP C1) Let SackCumAck be the Cumulative TSN ACK carried in the
1803          * received SACK.
1804          *
1805          * If (Advanced.Peer.Ack.Point < SackCumAck), then update
1806          * Advanced.Peer.Ack.Point to be equal to SackCumAck.
1807          */
1808         if (TSN_lt(asoc->adv_peer_ack_point, ctsn))
1809                 asoc->adv_peer_ack_point = ctsn;
1810
1811         /* PR-SCTP C2) Try to further advance the "Advanced.Peer.Ack.Point"
1812          * locally, that is, to move "Advanced.Peer.Ack.Point" up as long as
1813          * the chunk next in the out-queue space is marked as "abandoned" as
1814          * shown in the following example:
1815          *
1816          * Assuming that a SACK arrived with the Cumulative TSN ACK 102
1817          * and the Advanced.Peer.Ack.Point is updated to this value:
1818          *
1819          *   out-queue at the end of  ==>   out-queue after Adv.Ack.Point
1820          *   normal SACK processing           local advancement
1821          *                ...                           ...
1822          *   Adv.Ack.Pt-> 102 acked                     102 acked
1823          *                103 abandoned                 103 abandoned
1824          *                104 abandoned     Adv.Ack.P-> 104 abandoned
1825          *                105                           105
1826          *                106 acked                     106 acked
1827          *                ...                           ...
1828          *
1829          * In this example, the data sender successfully advanced the
1830          * "Advanced.Peer.Ack.Point" from 102 to 104 locally.
1831          */
1832         list_for_each_safe(lchunk, temp, &q->abandoned) {
1833                 chunk = list_entry(lchunk, struct sctp_chunk,
1834                                         transmitted_list);
1835                 tsn = ntohl(chunk->subh.data_hdr->tsn);
1836
1837                 /* Remove any chunks in the abandoned queue that are acked by
1838                  * the ctsn.
1839                  */
1840                 if (TSN_lte(tsn, ctsn)) {
1841                         list_del_init(lchunk);
1842                         sctp_chunk_free(chunk);
1843                 } else {
1844                         if (TSN_lte(tsn, asoc->adv_peer_ack_point+1)) {
1845                                 asoc->adv_peer_ack_point = tsn;
1846                                 if (chunk->chunk_hdr->flags &
1847                                          SCTP_DATA_UNORDERED)
1848                                         continue;
1849                                 skip_pos = sctp_get_skip_pos(&ftsn_skip_arr[0],
1850                                                 nskips,
1851                                                 chunk->subh.data_hdr->stream);
1852                                 ftsn_skip_arr[skip_pos].stream =
1853                                         chunk->subh.data_hdr->stream;
1854                                 ftsn_skip_arr[skip_pos].ssn =
1855                                          chunk->subh.data_hdr->ssn;
1856                                 if (skip_pos == nskips)
1857                                         nskips++;
1858                                 if (nskips == 10)
1859                                         break;
1860                         } else
1861                                 break;
1862                 }
1863         }
1864
1865         /* PR-SCTP C3) If, after step C1 and C2, the "Advanced.Peer.Ack.Point"
1866          * is greater than the Cumulative TSN ACK carried in the received
1867          * SACK, the data sender MUST send the data receiver a FORWARD TSN
1868          * chunk containing the latest value of the
1869          * "Advanced.Peer.Ack.Point".
1870          *
1871          * C4) For each "abandoned" TSN the sender of the FORWARD TSN SHOULD
1872          * list each stream and sequence number in the forwarded TSN. This
1873          * information will enable the receiver to easily find any
1874          * stranded TSN's waiting on stream reorder queues. Each stream
1875          * SHOULD only be reported once; this means that if multiple
1876          * abandoned messages occur in the same stream then only the
1877          * highest abandoned stream sequence number is reported. If the
1878          * total size of the FORWARD TSN does NOT fit in a single MTU then
1879          * the sender of the FORWARD TSN SHOULD lower the
1880          * Advanced.Peer.Ack.Point to the last TSN that will fit in a
1881          * single MTU.
1882          */
1883         if (asoc->adv_peer_ack_point > ctsn)
1884                 ftsn_chunk = sctp_make_fwdtsn(asoc, asoc->adv_peer_ack_point,
1885                                               nskips, &ftsn_skip_arr[0]);
1886
1887         if (ftsn_chunk) {
1888                 list_add_tail(&ftsn_chunk->list, &q->control_chunk_list);
1889                 SCTP_INC_STATS(sock_net(asoc->base.sk), SCTP_MIB_OUTCTRLCHUNKS);
1890         }
1891 }