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