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