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 int 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 int 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         int error = 0;
 292
 293         pr_debug("%s: outq:%p, chunk:%p[%s]\n", __func__, q, chunk,
 294                  chunk && chunk->chunk_hdr ?
 295                  sctp_cname(SCTP_ST_CHUNK(chunk->chunk_hdr->type)) :
 296                  "illegal chunk");
 297
 298         /* If it is data, queue it up, otherwise, send it
 299          * immediately.
 300          */
 301         if (sctp_chunk_is_data(chunk)) {
 302                 /* Is it OK to queue data chunks?  */
 303                 /* From 9. Termination of Association
 304                  *
 305                  * When either endpoint performs a shutdown, the
 306                  * association on each peer will stop accepting new
 307                  * data from its user and only deliver data in queue
 308                  * at the time of sending or receiving the SHUTDOWN
 309                  * chunk.
 310                  */
 311                 switch (q->asoc->state) {
 312                 case SCTP_STATE_CLOSED:
 313                 case SCTP_STATE_SHUTDOWN_PENDING:
 314                 case SCTP_STATE_SHUTDOWN_SENT:
 315                 case SCTP_STATE_SHUTDOWN_RECEIVED:
 316                 case SCTP_STATE_SHUTDOWN_ACK_SENT:
 317                         /* Cannot send after transport endpoint shutdown */
 318                         error = -ESHUTDOWN;
 319                         break;
 320
 321                 default:
 322                         pr_debug("%s: outqueueing: outq:%p, chunk:%p[%s])\n",
 323                                  __func__, q, chunk, chunk && chunk->chunk_hdr ?
 324                                  sctp_cname(SCTP_ST_CHUNK(chunk->chunk_hdr->type)) :
 325                                  "illegal chunk");
 326
 327                         sctp_chunk_hold(chunk);
 328                         sctp_outq_tail_data(q, chunk);
 329                         if (chunk->asoc->peer.prsctp_capable &&
 330                             SCTP_PR_PRIO_ENABLED(chunk->sinfo.sinfo_flags))
 331                                 chunk->asoc->sent_cnt_removable++;
 332                         if (chunk->chunk_hdr->flags & SCTP_DATA_UNORDERED)
 333                                 SCTP_INC_STATS(net, SCTP_MIB_OUTUNORDERCHUNKS);
 334                         else
 335                                 SCTP_INC_STATS(net, SCTP_MIB_OUTORDERCHUNKS);
 336                         break;
 337                 }
 338         } else {
 339                 list_add_tail(&chunk->list, &q->control_chunk_list);
 340                 SCTP_INC_STATS(net, SCTP_MIB_OUTCTRLCHUNKS);
 341         }
 342
 343         if (error < 0)
 344                 return error;
 345
 346         if (!q->cork)
 347                 error = sctp_outq_flush(q, 0, gfp);
 348
 349         return error;
 350 }
 351
 352 /* Insert a chunk into the sorted list based on the TSNs.  The retransmit list
 353  * and the abandoned list are in ascending order.
 354  */
 355 static void sctp_insert_list(struct list_head *head, struct list_head *new)
 356 {
 357         struct list_head *pos;
 358         struct sctp_chunk *nchunk, *lchunk;
 359         __u32 ntsn, ltsn;
 360         int done = 0;
 361
 362         nchunk = list_entry(new, struct sctp_chunk, transmitted_list);
 363         ntsn = ntohl(nchunk->subh.data_hdr->tsn);
 364
 365         list_for_each(pos, head) {
 366                 lchunk = list_entry(pos, struct sctp_chunk, transmitted_list);
 367                 ltsn = ntohl(lchunk->subh.data_hdr->tsn);
 368                 if (TSN_lt(ntsn, ltsn)) {
 369                         list_add(new, pos->prev);
 370                         done = 1;
 371                         break;
 372                 }
 373         }
 374         if (!done)
 375                 list_add_tail(new, head);
 376 }
 377
 378 static int sctp_prsctp_prune_sent(struct sctp_association *asoc,
 379                                   struct sctp_sndrcvinfo *sinfo,
 380                                   struct list_head *queue, int msg_len)
 381 {
 382         struct sctp_chunk *chk, *temp;
 383
 384         list_for_each_entry_safe(chk, temp, queue, transmitted_list) {
 385                 if (!SCTP_PR_PRIO_ENABLED(chk->sinfo.sinfo_flags) ||
 386                     chk->sinfo.sinfo_timetolive <= sinfo->sinfo_timetolive)
 387                         continue;
 388
 389                 list_del_init(&chk->transmitted_list);
 390                 sctp_insert_list(&asoc->outqueue.abandoned,
 391                                  &chk->transmitted_list);
 392
 393                 asoc->sent_cnt_removable--;
 394                 asoc->abandoned_sent[SCTP_PR_INDEX(PRIO)]++;
 395
 396                 if (!chk->tsn_gap_acked) {
 397                         if (chk->transport)
 398                                 chk->transport->flight_size -=
 399                                                 sctp_data_size(chk);
 400                         asoc->outqueue.outstanding_bytes -= sctp_data_size(chk);
 401                 }
 402
 403                 msg_len -= SCTP_DATA_SNDSIZE(chk) +
 404                            sizeof(struct sk_buff) +
 405                            sizeof(struct sctp_chunk);
 406                 if (msg_len <= 0)
 407                         break;
 408         }
 409
 410         return msg_len;
 411 }
 412
 413 static int sctp_prsctp_prune_unsent(struct sctp_association *asoc,
 414                                     struct sctp_sndrcvinfo *sinfo,
 415                                     struct list_head *queue, int msg_len)
 416 {
 417         struct sctp_chunk *chk, *temp;
 418
 419         list_for_each_entry_safe(chk, temp, queue, list) {
 420                 if (!SCTP_PR_PRIO_ENABLED(chk->sinfo.sinfo_flags) ||
 421                     chk->sinfo.sinfo_timetolive <= sinfo->sinfo_timetolive)
 422                         continue;
 423
 424                 list_del_init(&chk->list);
 425                 asoc->sent_cnt_removable--;
 426                 asoc->abandoned_unsent[SCTP_PR_INDEX(PRIO)]++;
 427
 428                 msg_len -= SCTP_DATA_SNDSIZE(chk) +
 429                            sizeof(struct sk_buff) +
 430                            sizeof(struct sctp_chunk);
 431                 sctp_chunk_free(chk);
 432                 if (msg_len <= 0)
 433                         break;
 434         }
 435
 436         return msg_len;
 437 }
 438
 439 /* Abandon the chunks according their priorities */
 440 void sctp_prsctp_prune(struct sctp_association *asoc,
 441                        struct sctp_sndrcvinfo *sinfo, int msg_len)
 442 {
 443         struct sctp_transport *transport;
 444
 445         if (!asoc->peer.prsctp_capable || !asoc->sent_cnt_removable)
 446                 return;
 447
 448         msg_len = sctp_prsctp_prune_sent(asoc, sinfo,
 449                                          &asoc->outqueue.retransmit,
 450                                          msg_len);
 451         if (msg_len <= 0)
 452                 return;
 453
 454         list_for_each_entry(transport, &asoc->peer.transport_addr_list,
 455                             transports) {
 456                 msg_len = sctp_prsctp_prune_sent(asoc, sinfo,
 457                                                  &transport->transmitted,
 458                                                  msg_len);
 459                 if (msg_len <= 0)
 460                         return;
 461         }
 462
 463         sctp_prsctp_prune_unsent(asoc, sinfo,
 464                                  &asoc->outqueue.out_chunk_list,
 465                                  msg_len);
 466 }
 467
 468 /* Mark all the eligible packets on a transport for retransmission.  */
 469 void sctp_retransmit_mark(struct sctp_outq *q,
 470                           struct sctp_transport *transport,
 471                           __u8 reason)
 472 {
 473         struct list_head *lchunk, *ltemp;
 474         struct sctp_chunk *chunk;
 475
 476         /* Walk through the specified transmitted queue.  */
 477         list_for_each_safe(lchunk, ltemp, &transport->transmitted) {
 478                 chunk = list_entry(lchunk, struct sctp_chunk,
 479                                    transmitted_list);
 480
 481                 /* If the chunk is abandoned, move it to abandoned list. */
 482                 if (sctp_chunk_abandoned(chunk)) {
 483                         list_del_init(lchunk);
 484                         sctp_insert_list(&q->abandoned, lchunk);
 485
 486                         /* If this chunk has not been previousely acked,
 487                          * stop considering it 'outstanding'.  Our peer
 488                          * will most likely never see it since it will
 489                          * not be retransmitted
 490                          */
 491                         if (!chunk->tsn_gap_acked) {
 492                                 if (chunk->transport)
 493                                         chunk->transport->flight_size -=
 494                                                         sctp_data_size(chunk);
 495                                 q->outstanding_bytes -= sctp_data_size(chunk);
 496                                 q->asoc->peer.rwnd += sctp_data_size(chunk);
 497                         }
 498                         continue;
 499                 }
 500
 501                 /* If we are doing  retransmission due to a timeout or pmtu
 502                  * discovery, only the  chunks that are not yet acked should
 503                  * be added to the retransmit queue.
 504                  */
 505                 if ((reason == SCTP_RTXR_FAST_RTX  &&
 506                             (chunk->fast_retransmit == SCTP_NEED_FRTX)) ||
 507                     (reason != SCTP_RTXR_FAST_RTX  && !chunk->tsn_gap_acked)) {
 508                         /* RFC 2960 6.2.1 Processing a Received SACK
 509                          *
 510                          * C) Any time a DATA chunk is marked for
 511                          * retransmission (via either T3-rtx timer expiration
 512                          * (Section 6.3.3) or via fast retransmit
 513                          * (Section 7.2.4)), add the data size of those
 514                          * chunks to the rwnd.
 515                          */
 516                         q->asoc->peer.rwnd += sctp_data_size(chunk);
 517                         q->outstanding_bytes -= sctp_data_size(chunk);
 518                         if (chunk->transport)
 519                                 transport->flight_size -= sctp_data_size(chunk);
 520
 521                         /* sctpimpguide-05 Section 2.8.2
 522                          * M5) If a T3-rtx timer expires, the
 523                          * 'TSN.Missing.Report' of all affected TSNs is set
 524                          * to 0.
 525                          */
 526                         chunk->tsn_missing_report = 0;
 527
 528                         /* If a chunk that is being used for RTT measurement
 529                          * has to be retransmitted, we cannot use this chunk
 530                          * anymore for RTT measurements. Reset rto_pending so
 531                          * that a new RTT measurement is started when a new
 532                          * data chunk is sent.
 533                          */
 534                         if (chunk->rtt_in_progress) {
 535                                 chunk->rtt_in_progress = 0;
 536                                 transport->rto_pending = 0;
 537                         }
 538
 539                         chunk->resent = 1;
 540
 541                         /* Move the chunk to the retransmit queue. The chunks
 542                          * on the retransmit queue are always kept in order.
 543                          */
 544                         list_del_init(lchunk);
 545                         sctp_insert_list(&q->retransmit, lchunk);
 546                 }
 547         }
 548
 549         pr_debug("%s: transport:%p, reason:%d, cwnd:%d, ssthresh:%d, "
 550                  "flight_size:%d, pba:%d\n", __func__, transport, reason,
 551                  transport->cwnd, transport->ssthresh, transport->flight_size,
 552                  transport->partial_bytes_acked);
 553 }
 554
 555 /* Mark all the eligible packets on a transport for retransmission and force
 556  * one packet out.
 557  */
 558 void sctp_retransmit(struct sctp_outq *q, struct sctp_transport *transport,
 559                      sctp_retransmit_reason_t reason)
 560 {
 561         struct net *net = sock_net(q->asoc->base.sk);
 562         int error = 0;
 563
 564         switch (reason) {
 565         case SCTP_RTXR_T3_RTX:
 566                 SCTP_INC_STATS(net, SCTP_MIB_T3_RETRANSMITS);
 567                 sctp_transport_lower_cwnd(transport, SCTP_LOWER_CWND_T3_RTX);
 568                 /* Update the retran path if the T3-rtx timer has expired for
 569                  * the current retran path.
 570                  */
 571                 if (transport == transport->asoc->peer.retran_path)
 572                         sctp_assoc_update_retran_path(transport->asoc);
 573                 transport->asoc->rtx_data_chunks +=
 574                         transport->asoc->unack_data;
 575                 break;
 576         case SCTP_RTXR_FAST_RTX:
 577                 SCTP_INC_STATS(net, SCTP_MIB_FAST_RETRANSMITS);
 578                 sctp_transport_lower_cwnd(transport, SCTP_LOWER_CWND_FAST_RTX);
 579                 q->fast_rtx = 1;
 580                 break;
 581         case SCTP_RTXR_PMTUD:
 582                 SCTP_INC_STATS(net, SCTP_MIB_PMTUD_RETRANSMITS);
 583                 break;
 584         case SCTP_RTXR_T1_RTX:
 585                 SCTP_INC_STATS(net, SCTP_MIB_T1_RETRANSMITS);
 586                 transport->asoc->init_retries++;
 587                 break;
 588         default:
 589                 BUG();
 590         }
 591
 592         sctp_retransmit_mark(q, transport, reason);
 593
 594         /* PR-SCTP A5) Any time the T3-rtx timer expires, on any destination,
 595          * the sender SHOULD try to advance the "Advanced.Peer.Ack.Point" by
 596          * following the procedures outlined in C1 - C5.
 597          */
 598         if (reason == SCTP_RTXR_T3_RTX)
 599                 sctp_generate_fwdtsn(q, q->asoc->ctsn_ack_point);
 600
 601         /* Flush the queues only on timeout, since fast_rtx is only
 602          * triggered during sack processing and the queue
 603          * will be flushed at the end.
 604          */
 605         if (reason != SCTP_RTXR_FAST_RTX)
 606                 error = sctp_outq_flush(q, /* rtx_timeout */ 1, GFP_ATOMIC);
 607
 608         if (error)
 609                 q->asoc->base.sk->sk_err = -error;
 610 }
 611
 612 /*
 613  * Transmit DATA chunks on the retransmit queue.  Upon return from
 614  * sctp_outq_flush_rtx() the packet 'pkt' may contain chunks which
 615  * need to be transmitted by the caller.
 616  * We assume that pkt->transport has already been set.
 617  *
 618  * The return value is a normal kernel error return value.
 619  */
 620 static int sctp_outq_flush_rtx(struct sctp_outq *q, struct sctp_packet *pkt,
 621                                int rtx_timeout, int *start_timer)
 622 {
 623         struct list_head *lqueue;
 624         struct sctp_transport *transport = pkt->transport;
 625         sctp_xmit_t status;
 626         struct sctp_chunk *chunk, *chunk1;
 627         int fast_rtx;
 628         int error = 0;
 629         int timer = 0;
 630         int done = 0;
 631
 632         lqueue = &q->retransmit;
 633         fast_rtx = q->fast_rtx;
 634
 635         /* This loop handles time-out retransmissions, fast retransmissions,
 636          * and retransmissions due to opening of whindow.
 637          *
 638          * RFC 2960 6.3.3 Handle T3-rtx Expiration
 639          *
 640          * E3) Determine how many of the earliest (i.e., lowest TSN)
 641          * outstanding DATA chunks for the address for which the
 642          * T3-rtx has expired will fit into a single packet, subject
 643          * to the MTU constraint for the path corresponding to the
 644          * destination transport address to which the retransmission
 645          * is being sent (this may be different from the address for
 646          * which the timer expires [see Section 6.4]). Call this value
 647          * K. Bundle and retransmit those K DATA chunks in a single
 648          * packet to the destination endpoint.
 649          *
 650          * [Just to be painfully clear, if we are retransmitting
 651          * because a timeout just happened, we should send only ONE
 652          * packet of retransmitted data.]
 653          *
 654          * For fast retransmissions we also send only ONE packet.  However,
 655          * if we are just flushing the queue due to open window, we'll
 656          * try to send as much as possible.
 657          */
 658         list_for_each_entry_safe(chunk, chunk1, lqueue, transmitted_list) {
 659                 /* If the chunk is abandoned, move it to abandoned list. */
 660                 if (sctp_chunk_abandoned(chunk)) {
 661                         list_del_init(&chunk->transmitted_list);
 662                         sctp_insert_list(&q->abandoned,
 663                                          &chunk->transmitted_list);
 664                         continue;
 665                 }
 666
 667                 /* Make sure that Gap Acked TSNs are not retransmitted.  A
 668                  * simple approach is just to move such TSNs out of the
 669                  * way and into a 'transmitted' queue and skip to the
 670                  * next chunk.
 671                  */
 672                 if (chunk->tsn_gap_acked) {
 673                         list_move_tail(&chunk->transmitted_list,
 674                                        &transport->transmitted);
 675                         continue;
 676                 }
 677
 678                 /* If we are doing fast retransmit, ignore non-fast_rtransmit
 679                  * chunks
 680                  */
 681                 if (fast_rtx && !chunk->fast_retransmit)
 682                         continue;
 683
 684 redo:
 685                 /* Attempt to append this chunk to the packet. */
 686                 status = sctp_packet_append_chunk(pkt, chunk);
 687
 688                 switch (status) {
 689                 case SCTP_XMIT_PMTU_FULL:
 690                         if (!pkt->has_data && !pkt->has_cookie_echo) {
 691                                 /* If this packet did not contain DATA then
 692                                  * retransmission did not happen, so do it
 693                                  * again.  We'll ignore the error here since
 694                                  * control chunks are already freed so there
 695                                  * is nothing we can do.
 696                                  */
 697                                 sctp_packet_transmit(pkt, GFP_ATOMIC);
 698                                 goto redo;
 699                         }
 700
 701                         /* Send this packet.  */
 702                         error = sctp_packet_transmit(pkt, GFP_ATOMIC);
 703
 704                         /* If we are retransmitting, we should only
 705                          * send a single packet.
 706                          * Otherwise, try appending this chunk again.
 707                          */
 708                         if (rtx_timeout || fast_rtx)
 709                                 done = 1;
 710                         else
 711                                 goto redo;
 712
 713                         /* Bundle next chunk in the next round.  */
 714                         break;
 715
 716                 case SCTP_XMIT_RWND_FULL:
 717                         /* Send this packet. */
 718                         error = sctp_packet_transmit(pkt, GFP_ATOMIC);
 719
 720                         /* Stop sending DATA as there is no more room
 721                          * at the receiver.
 722                          */
 723                         done = 1;
 724                         break;
 725
 726                 case SCTP_XMIT_DELAY:
 727                         /* Send this packet. */
 728                         error = sctp_packet_transmit(pkt, GFP_ATOMIC);
 729
 730                         /* Stop sending DATA because of nagle delay. */
 731                         done = 1;
 732                         break;
 733
 734                 default:
 735                         /* The append was successful, so add this chunk to
 736                          * the transmitted list.
 737                          */
 738                         list_move_tail(&chunk->transmitted_list,
 739                                        &transport->transmitted);
 740
 741                         /* Mark the chunk as ineligible for fast retransmit
 742                          * after it is retransmitted.
 743                          */
 744                         if (chunk->fast_retransmit == SCTP_NEED_FRTX)
 745                                 chunk->fast_retransmit = SCTP_DONT_FRTX;
 746
 747                         q->asoc->stats.rtxchunks++;
 748                         break;
 749                 }
 750
 751                 /* Set the timer if there were no errors */
 752                 if (!error && !timer)
 753                         timer = 1;
 754
 755                 if (done)
 756                         break;
 757         }
 758
 759         /* If we are here due to a retransmit timeout or a fast
 760          * retransmit and if there are any chunks left in the retransmit
 761          * queue that could not fit in the PMTU sized packet, they need
 762          * to be marked as ineligible for a subsequent fast retransmit.
 763          */
 764         if (rtx_timeout || fast_rtx) {
 765                 list_for_each_entry(chunk1, lqueue, transmitted_list) {
 766                         if (chunk1->fast_retransmit == SCTP_NEED_FRTX)
 767                                 chunk1->fast_retransmit = SCTP_DONT_FRTX;
 768                 }
 769         }
 770
 771         *start_timer = timer;
 772
 773         /* Clear fast retransmit hint */
 774         if (fast_rtx)
 775                 q->fast_rtx = 0;
 776
 777         return error;
 778 }
 779
 780 /* Cork the outqueue so queued chunks are really queued. */
 781 int sctp_outq_uncork(struct sctp_outq *q, gfp_t gfp)
 782 {
 783         if (q->cork)
 784                 q->cork = 0;
 785
 786         return sctp_outq_flush(q, 0, gfp);
 787 }
 788
 789
 790 /*
 791  * Try to flush an outqueue.
 792  *
 793  * Description: Send everything in q which we legally can, subject to
 794  * congestion limitations.
 795  * * Note: This function can be called from multiple contexts so appropriate
 796  * locking concerns must be made.  Today we use the sock lock to protect
 797  * this function.
 798  */
 799 static int sctp_outq_flush(struct sctp_outq *q, int rtx_timeout, gfp_t gfp)
 800 {
 801         struct sctp_packet *packet;
 802         struct sctp_packet singleton;
 803         struct sctp_association *asoc = q->asoc;
 804         __u16 sport = asoc->base.bind_addr.port;
 805         __u16 dport = asoc->peer.port;
 806         __u32 vtag = asoc->peer.i.init_tag;
 807         struct sctp_transport *transport = NULL;
 808         struct sctp_transport *new_transport;
 809         struct sctp_chunk *chunk, *tmp;
 810         sctp_xmit_t status;
 811         int error = 0;
 812         int start_timer = 0;
 813         int one_packet = 0;
 814
 815         /* These transports have chunks to send. */
 816         struct list_head transport_list;
 817         struct list_head *ltransport;
 818
 819         INIT_LIST_HEAD(&transport_list);
 820         packet = NULL;
 821
 822         /*
 823          * 6.10 Bundling
 824          *   ...
 825          *   When bundling control chunks with DATA chunks, an
 826          *   endpoint MUST place control chunks first in the outbound
 827          *   SCTP packet.  The transmitter MUST transmit DATA chunks
 828          *   within a SCTP packet in increasing order of TSN.
 829          *   ...
 830          */
 831
 832         list_for_each_entry_safe(chunk, tmp, &q->control_chunk_list, list) {
 833                 /* RFC 5061, 5.3
 834                  * F1) This means that until such time as the ASCONF
 835                  * containing the add is acknowledged, the sender MUST
 836                  * NOT use the new IP address as a source for ANY SCTP
 837                  * packet except on carrying an ASCONF Chunk.
 838                  */
 839                 if (asoc->src_out_of_asoc_ok &&
 840                     chunk->chunk_hdr->type != SCTP_CID_ASCONF)
 841                         continue;
 842
 843                 list_del_init(&chunk->list);
 844
 845                 /* Pick the right transport to use. */
 846                 new_transport = chunk->transport;
 847
 848                 if (!new_transport) {
 849                         /*
 850                          * If we have a prior transport pointer, see if
 851                          * the destination address of the chunk
 852                          * matches the destination address of the
 853                          * current transport.  If not a match, then
 854                          * try to look up the transport with a given
 855                          * destination address.  We do this because
 856                          * after processing ASCONFs, we may have new
 857                          * transports created.
 858                          */
 859                         if (transport &&
 860                             sctp_cmp_addr_exact(&chunk->dest,
 861                                                 &transport->ipaddr))
 862                                         new_transport = transport;
 863                         else
 864                                 new_transport = sctp_assoc_lookup_paddr(asoc,
 865                                                                 &chunk->dest);
 866
 867                         /* if we still don't have a new transport, then
 868                          * use the current active path.
 869                          */
 870                         if (!new_transport)
 871                                 new_transport = asoc->peer.active_path;
 872                 } else if ((new_transport->state == SCTP_INACTIVE) ||
 873                            (new_transport->state == SCTP_UNCONFIRMED) ||
 874                            (new_transport->state == SCTP_PF)) {
 875                         /* If the chunk is Heartbeat or Heartbeat Ack,
 876                          * send it to chunk->transport, even if it's
 877                          * inactive.
 878                          *
 879                          * 3.3.6 Heartbeat Acknowledgement:
 880                          * ...
 881                          * A HEARTBEAT ACK is always sent to the source IP
 882                          * address of the IP datagram containing the
 883                          * HEARTBEAT chunk to which this ack is responding.
 884                          * ...
 885                          *
 886                          * ASCONF_ACKs also must be sent to the source.
 887                          */
 888                         if (chunk->chunk_hdr->type != SCTP_CID_HEARTBEAT &&
 889                             chunk->chunk_hdr->type != SCTP_CID_HEARTBEAT_ACK &&
 890                             chunk->chunk_hdr->type != SCTP_CID_ASCONF_ACK)
 891                                 new_transport = asoc->peer.active_path;
 892                 }
 893
 894                 /* Are we switching transports?
 895                  * Take care of transport locks.
 896                  */
 897                 if (new_transport != transport) {
 898                         transport = new_transport;
 899                         if (list_empty(&transport->send_ready)) {
 900                                 list_add_tail(&transport->send_ready,
 901                                               &transport_list);
 902                         }
 903                         packet = &transport->packet;
 904                         sctp_packet_config(packet, vtag,
 905                                            asoc->peer.ecn_capable);
 906                 }
 907
 908                 switch (chunk->chunk_hdr->type) {
 909                 /*
 910                  * 6.10 Bundling
 911                  *   ...
 912                  *   An endpoint MUST NOT bundle INIT, INIT ACK or SHUTDOWN
 913                  *   COMPLETE with any other chunks.  [Send them immediately.]
 914                  */
 915                 case SCTP_CID_INIT:
 916                 case SCTP_CID_INIT_ACK:
 917                 case SCTP_CID_SHUTDOWN_COMPLETE:
 918                         sctp_packet_init(&singleton, transport, sport, dport);
 919                         sctp_packet_config(&singleton, vtag, 0);
 920                         sctp_packet_append_chunk(&singleton, chunk);
 921                         error = sctp_packet_transmit(&singleton, gfp);
 922                         if (error < 0)
 923                                 return error;
 924                         break;
 925
 926                 case SCTP_CID_ABORT:
 927                         if (sctp_test_T_bit(chunk)) {
 928                                 packet->vtag = asoc->c.my_vtag;
 929                         }
 930                 /* The following chunks are "response" chunks, i.e.
 931                  * they are generated in response to something we
 932                  * received.  If we are sending these, then we can
 933                  * send only 1 packet containing these chunks.
 934                  */
 935                 case SCTP_CID_HEARTBEAT_ACK:
 936                 case SCTP_CID_SHUTDOWN_ACK:
 937                 case SCTP_CID_COOKIE_ACK:
 938                 case SCTP_CID_COOKIE_ECHO:
 939                 case SCTP_CID_ERROR:
 940                 case SCTP_CID_ECN_CWR:
 941                 case SCTP_CID_ASCONF_ACK:
 942                         one_packet = 1;
 943                         /* Fall through */
 944
 945                 case SCTP_CID_SACK:
 946                 case SCTP_CID_HEARTBEAT:
 947                 case SCTP_CID_SHUTDOWN:
 948                 case SCTP_CID_ECN_ECNE:
 949                 case SCTP_CID_ASCONF:
 950                 case SCTP_CID_FWD_TSN:
 951                         status = sctp_packet_transmit_chunk(packet, chunk,
 952                                                             one_packet, gfp);
 953                         if (status  != SCTP_XMIT_OK) {
 954                                 /* put the chunk back */
 955                                 list_add(&chunk->list, &q->control_chunk_list);
 956                         } else {
 957                                 asoc->stats.octrlchunks++;
 958                                 /* PR-SCTP C5) If a FORWARD TSN is sent, the
 959                                  * sender MUST assure that at least one T3-rtx
 960                                  * timer is running.
 961                                  */
 962                                 if (chunk->chunk_hdr->type == SCTP_CID_FWD_TSN) {
 963                                         sctp_transport_reset_t3_rtx(transport);
 964                                         transport->last_time_sent = jiffies;
 965                                 }
 966                         }
 967                         break;
 968
 969                 default:
 970                         /* We built a chunk with an illegal type! */
 971                         BUG();
 972                 }
 973         }
 974
 975         if (q->asoc->src_out_of_asoc_ok)
 976                 goto sctp_flush_out;
 977
 978         /* Is it OK to send data chunks?  */
 979         switch (asoc->state) {
 980         case SCTP_STATE_COOKIE_ECHOED:
 981                 /* Only allow bundling when this packet has a COOKIE-ECHO
 982                  * chunk.
 983                  */
 984                 if (!packet || !packet->has_cookie_echo)
 985                         break;
 986
 987                 /* fallthru */
 988         case SCTP_STATE_ESTABLISHED:
 989         case SCTP_STATE_SHUTDOWN_PENDING:
 990         case SCTP_STATE_SHUTDOWN_RECEIVED:
 991                 /*
 992                  * RFC 2960 6.1  Transmission of DATA Chunks
 993                  *
 994                  * C) When the time comes for the sender to transmit,
 995                  * before sending new DATA chunks, the sender MUST
 996                  * first transmit any outstanding DATA chunks which
 997                  * are marked for retransmission (limited by the
 998                  * current cwnd).
 999                  */
1000                 if (!list_empty(&q->retransmit)) {
1001                         if (asoc->peer.retran_path->state == SCTP_UNCONFIRMED)
1002                                 goto sctp_flush_out;
1003                         if (transport == asoc->peer.retran_path)
1004                                 goto retran;
1005
1006                         /* Switch transports & prepare the packet.  */
1007
1008                         transport = asoc->peer.retran_path;
1009
1010                         if (list_empty(&transport->send_ready)) {
1011                                 list_add_tail(&transport->send_ready,
1012                                               &transport_list);
1013                         }
1014
1015                         packet = &transport->packet;
1016                         sctp_packet_config(packet, vtag,
1017                                            asoc->peer.ecn_capable);
1018                 retran:
1019                         error = sctp_outq_flush_rtx(q, packet,
1020                                                     rtx_timeout, &start_timer);
1021
1022                         if (start_timer) {
1023                                 sctp_transport_reset_t3_rtx(transport);
1024                                 transport->last_time_sent = jiffies;
1025                         }
1026
1027                         /* This can happen on COOKIE-ECHO resend.  Only
1028                          * one chunk can get bundled with a COOKIE-ECHO.
1029                          */
1030                         if (packet->has_cookie_echo)
1031                                 goto sctp_flush_out;
1032
1033                         /* Don't send new data if there is still data
1034                          * waiting to retransmit.
1035                          */
1036                         if (!list_empty(&q->retransmit))
1037                                 goto sctp_flush_out;
1038                 }
1039
1040                 /* Apply Max.Burst limitation to the current transport in
1041                  * case it will be used for new data.  We are going to
1042                  * rest it before we return, but we want to apply the limit
1043                  * to the currently queued data.
1044                  */
1045                 if (transport)
1046                         sctp_transport_burst_limited(transport);
1047
1048                 /* Finally, transmit new packets.  */
1049                 while ((chunk = sctp_outq_dequeue_data(q)) != NULL) {
1050                         /* RFC 2960 6.5 Every DATA chunk MUST carry a valid
1051                          * stream identifier.
1052                          */
1053                         if (chunk->sinfo.sinfo_stream >=
1054                             asoc->c.sinit_num_ostreams) {
1055
1056                                 /* Mark as failed send. */
1057                                 sctp_chunk_fail(chunk, SCTP_ERROR_INV_STRM);
1058                                 if (asoc->peer.prsctp_capable &&
1059                                     SCTP_PR_PRIO_ENABLED(chunk->sinfo.sinfo_flags))
1060                                         asoc->sent_cnt_removable--;
1061                                 sctp_chunk_free(chunk);
1062                                 continue;
1063                         }
1064
1065                         /* Has this chunk expired? */
1066                         if (sctp_chunk_abandoned(chunk)) {
1067                                 sctp_chunk_fail(chunk, 0);
1068                                 sctp_chunk_free(chunk);
1069                                 continue;
1070                         }
1071
1072                         /* If there is a specified transport, use it.
1073                          * Otherwise, we want to use the active path.
1074                          */
1075                         new_transport = chunk->transport;
1076                         if (!new_transport ||
1077                             ((new_transport->state == SCTP_INACTIVE) ||
1078                              (new_transport->state == SCTP_UNCONFIRMED) ||
1079                              (new_transport->state == SCTP_PF)))
1080                                 new_transport = asoc->peer.active_path;
1081                         if (new_transport->state == SCTP_UNCONFIRMED) {
1082                                 WARN_ONCE(1, "Atempt to send packet on unconfirmed path.");
1083                                 sctp_chunk_fail(chunk, 0);
1084                                 sctp_chunk_free(chunk);
1085                                 continue;
1086                         }
1087
1088                         /* Change packets if necessary.  */
1089                         if (new_transport != transport) {
1090                                 transport = new_transport;
1091
1092                                 /* Schedule to have this transport's
1093                                  * packet flushed.
1094                                  */
1095                                 if (list_empty(&transport->send_ready)) {
1096                                         list_add_tail(&transport->send_ready,
1097                                                       &transport_list);
1098                                 }
1099
1100                                 packet = &transport->packet;
1101                                 sctp_packet_config(packet, vtag,
1102                                                    asoc->peer.ecn_capable);
1103                                 /* We've switched transports, so apply the
1104                                  * Burst limit to the new transport.
1105                                  */
1106                                 sctp_transport_burst_limited(transport);
1107                         }
1108
1109                         pr_debug("%s: outq:%p, chunk:%p[%s], tx-tsn:0x%x skb->head:%p "
1110                                  "skb->users:%d\n",
1111                                  __func__, q, chunk, chunk && chunk->chunk_hdr ?
1112                                  sctp_cname(SCTP_ST_CHUNK(chunk->chunk_hdr->type)) :
1113                                  "illegal chunk", ntohl(chunk->subh.data_hdr->tsn),
1114                                  chunk->skb ? chunk->skb->head : NULL, chunk->skb ?
1115                                  atomic_read(&chunk->skb->users) : -1);
1116
1117                         /* Add the chunk to the packet.  */
1118                         status = sctp_packet_transmit_chunk(packet, chunk, 0, gfp);
1119
1120                         switch (status) {
1121                         case SCTP_XMIT_PMTU_FULL:
1122                         case SCTP_XMIT_RWND_FULL:
1123                         case SCTP_XMIT_DELAY:
1124                                 /* We could not append this chunk, so put
1125                                  * the chunk back on the output queue.
1126                                  */
1127                                 pr_debug("%s: could not transmit tsn:0x%x, status:%d\n",
1128                                          __func__, ntohl(chunk->subh.data_hdr->tsn),
1129                                          status);
1130
1131                                 sctp_outq_head_data(q, chunk);
1132                                 goto sctp_flush_out;
1133
1134                         case SCTP_XMIT_OK:
1135                                 /* The sender is in the SHUTDOWN-PENDING state,
1136                                  * The sender MAY set the I-bit in the DATA
1137                                  * chunk header.
1138                                  */
1139                                 if (asoc->state == SCTP_STATE_SHUTDOWN_PENDING)
1140                                         chunk->chunk_hdr->flags |= SCTP_DATA_SACK_IMM;
1141                                 if (chunk->chunk_hdr->flags & SCTP_DATA_UNORDERED)
1142                                         asoc->stats.ouodchunks++;
1143                                 else
1144                                         asoc->stats.oodchunks++;
1145
1146                                 break;
1147
1148                         default:
1149                                 BUG();
1150                         }
1151
1152                         /* BUG: We assume that the sctp_packet_transmit()
1153                          * call below will succeed all the time and add the
1154                          * chunk to the transmitted list and restart the
1155                          * timers.
1156                          * It is possible that the call can fail under OOM
1157                          * conditions.
1158                          *
1159                          * Is this really a problem?  Won't this behave
1160                          * like a lost TSN?
1161                          */
1162                         list_add_tail(&chunk->transmitted_list,
1163                                       &transport->transmitted);
1164
1165                         sctp_transport_reset_t3_rtx(transport);
1166                         transport->last_time_sent = jiffies;
1167
1168                         /* Only let one DATA chunk get bundled with a
1169                          * COOKIE-ECHO chunk.
1170                          */
1171                         if (packet->has_cookie_echo)
1172                                 goto sctp_flush_out;
1173                 }
1174                 break;
1175
1176         default:
1177                 /* Do nothing.  */
1178                 break;
1179         }
1180
1181 sctp_flush_out:
1182
1183         /* Before returning, examine all the transports touched in
1184          * this call.  Right now, we bluntly force clear all the
1185          * transports.  Things might change after we implement Nagle.
1186          * But such an examination is still required.
1187          *
1188          * --xguo
1189          */
1190         while ((ltransport = sctp_list_dequeue(&transport_list)) != NULL) {
1191                 struct sctp_transport *t = list_entry(ltransport,
1192                                                       struct sctp_transport,
1193                                                       send_ready);
1194                 packet = &t->packet;
1195                 if (!sctp_packet_empty(packet))
1196                         error = sctp_packet_transmit(packet, gfp);
1197
1198                 /* Clear the burst limited state, if any */
1199                 sctp_transport_burst_reset(t);
1200         }
1201
1202         return error;
1203 }
1204
1205 /* Update unack_data based on the incoming SACK chunk */
1206 static void sctp_sack_update_unack_data(struct sctp_association *assoc,
1207                                         struct sctp_sackhdr *sack)
1208 {
1209         sctp_sack_variable_t *frags;
1210         __u16 unack_data;
1211         int i;
1212
1213         unack_data = assoc->next_tsn - assoc->ctsn_ack_point - 1;
1214
1215         frags = sack->variable;
1216         for (i = 0; i < ntohs(sack->num_gap_ack_blocks); i++) {
1217                 unack_data -= ((ntohs(frags[i].gab.end) -
1218                                 ntohs(frags[i].gab.start) + 1));
1219         }
1220
1221         assoc->unack_data = unack_data;
1222 }
1223
1224 /* This is where we REALLY process a SACK.
1225  *
1226  * Process the SACK against the outqueue.  Mostly, this just frees
1227  * things off the transmitted queue.
1228  */
1229 int sctp_outq_sack(struct sctp_outq *q, struct sctp_chunk *chunk)
1230 {
1231         struct sctp_association *asoc = q->asoc;
1232         struct sctp_sackhdr *sack = chunk->subh.sack_hdr;
1233         struct sctp_transport *transport;
1234         struct sctp_chunk *tchunk = NULL;
1235         struct list_head *lchunk, *transport_list, *temp;
1236         sctp_sack_variable_t *frags = sack->variable;
1237         __u32 sack_ctsn, ctsn, tsn;
1238         __u32 highest_tsn, highest_new_tsn;
1239         __u32 sack_a_rwnd;
1240         unsigned int outstanding;
1241         struct sctp_transport *primary = asoc->peer.primary_path;
1242         int count_of_newacks = 0;
1243         int gap_ack_blocks;
1244         u8 accum_moved = 0;
1245
1246         /* Grab the association's destination address list. */
1247         transport_list = &asoc->peer.transport_addr_list;
1248
1249         sack_ctsn = ntohl(sack->cum_tsn_ack);
1250         gap_ack_blocks = ntohs(sack->num_gap_ack_blocks);
1251         asoc->stats.gapcnt += gap_ack_blocks;
1252         /*
1253          * SFR-CACC algorithm:
1254          * On receipt of a SACK the sender SHOULD execute the
1255          * following statements.
1256          *
1257          * 1) If the cumulative ack in the SACK passes next tsn_at_change
1258          * on the current primary, the CHANGEOVER_ACTIVE flag SHOULD be
1259          * cleared. The CYCLING_CHANGEOVER flag SHOULD also be cleared for
1260          * all destinations.
1261          * 2) If the SACK contains gap acks and the flag CHANGEOVER_ACTIVE
1262          * is set the receiver of the SACK MUST take the following actions:
1263          *
1264          * A) Initialize the cacc_saw_newack to 0 for all destination
1265          * addresses.
1266          *
1267          * Only bother if changeover_active is set. Otherwise, this is
1268          * totally suboptimal to do on every SACK.
1269          */
1270         if (primary->cacc.changeover_active) {
1271                 u8 clear_cycling = 0;
1272
1273                 if (TSN_lte(primary->cacc.next_tsn_at_change, sack_ctsn)) {
1274                         primary->cacc.changeover_active = 0;
1275                         clear_cycling = 1;
1276                 }
1277
1278                 if (clear_cycling || gap_ack_blocks) {
1279                         list_for_each_entry(transport, transport_list,
1280                                         transports) {
1281                                 if (clear_cycling)
1282                                         transport->cacc.cycling_changeover = 0;
1283                                 if (gap_ack_blocks)
1284                                         transport->cacc.cacc_saw_newack = 0;
1285                         }
1286                 }
1287         }
1288
1289         /* Get the highest TSN in the sack. */
1290         highest_tsn = sack_ctsn;
1291         if (gap_ack_blocks)
1292                 highest_tsn += ntohs(frags[gap_ack_blocks - 1].gab.end);
1293
1294         if (TSN_lt(asoc->highest_sacked, highest_tsn))
1295                 asoc->highest_sacked = highest_tsn;
1296
1297         highest_new_tsn = sack_ctsn;
1298
1299         /* Run through the retransmit queue.  Credit bytes received
1300          * and free those chunks that we can.
1301          */
1302         sctp_check_transmitted(q, &q->retransmit, NULL, NULL, sack, &highest_new_tsn);
1303
1304         /* Run through the transmitted queue.
1305          * Credit bytes received and free those chunks which we can.
1306          *
1307          * This is a MASSIVE candidate for optimization.
1308          */
1309         list_for_each_entry(transport, transport_list, transports) {
1310                 sctp_check_transmitted(q, &transport->transmitted,
1311                                        transport, &chunk->source, sack,
1312                                        &highest_new_tsn);
1313                 /*
1314                  * SFR-CACC algorithm:
1315                  * C) Let count_of_newacks be the number of
1316                  * destinations for which cacc_saw_newack is set.
1317                  */
1318                 if (transport->cacc.cacc_saw_newack)
1319                         count_of_newacks++;
1320         }
1321
1322         /* Move the Cumulative TSN Ack Point if appropriate.  */
1323         if (TSN_lt(asoc->ctsn_ack_point, sack_ctsn)) {
1324                 asoc->ctsn_ack_point = sack_ctsn;
1325                 accum_moved = 1;
1326         }
1327
1328         if (gap_ack_blocks) {
1329
1330                 if (asoc->fast_recovery && accum_moved)
1331                         highest_new_tsn = highest_tsn;
1332
1333                 list_for_each_entry(transport, transport_list, transports)
1334                         sctp_mark_missing(q, &transport->transmitted, transport,
1335                                           highest_new_tsn, count_of_newacks);
1336         }
1337
1338         /* Update unack_data field in the assoc. */
1339         sctp_sack_update_unack_data(asoc, sack);
1340
1341         ctsn = asoc->ctsn_ack_point;
1342
1343         /* Throw away stuff rotting on the sack queue.  */
1344         list_for_each_safe(lchunk, temp, &q->sacked) {
1345                 tchunk = list_entry(lchunk, struct sctp_chunk,
1346                                     transmitted_list);
1347                 tsn = ntohl(tchunk->subh.data_hdr->tsn);
1348                 if (TSN_lte(tsn, ctsn)) {
1349                         list_del_init(&tchunk->transmitted_list);
1350                         if (asoc->peer.prsctp_capable &&
1351                             SCTP_PR_PRIO_ENABLED(chunk->sinfo.sinfo_flags))
1352                                 asoc->sent_cnt_removable--;
1353                         sctp_chunk_free(tchunk);
1354                 }
1355         }
1356
1357         /* ii) Set rwnd equal to the newly received a_rwnd minus the
1358          *     number of bytes still outstanding after processing the
1359          *     Cumulative TSN Ack and the Gap Ack Blocks.
1360          */
1361
1362         sack_a_rwnd = ntohl(sack->a_rwnd);
1363         asoc->peer.zero_window_announced = !sack_a_rwnd;
1364         outstanding = q->outstanding_bytes;
1365
1366         if (outstanding < sack_a_rwnd)
1367                 sack_a_rwnd -= outstanding;
1368         else
1369                 sack_a_rwnd = 0;
1370
1371         asoc->peer.rwnd = sack_a_rwnd;
1372
1373         sctp_generate_fwdtsn(q, sack_ctsn);
1374
1375         pr_debug("%s: sack cumulative tsn ack:0x%x\n", __func__, sack_ctsn);
1376         pr_debug("%s: cumulative tsn ack of assoc:%p is 0x%x, "
1377                  "advertised peer ack point:0x%x\n", __func__, asoc, ctsn,
1378                  asoc->adv_peer_ack_point);
1379
1380         return sctp_outq_is_empty(q);
1381 }
1382
1383 /* Is the outqueue empty?
1384  * The queue is empty when we have not pending data, no in-flight data
1385  * and nothing pending retransmissions.
1386  */
1387 int sctp_outq_is_empty(const struct sctp_outq *q)
1388 {
1389         return q->out_qlen == 0 && q->outstanding_bytes == 0 &&
1390                list_empty(&q->retransmit);
1391 }
1392
1393 /********************************************************************
1394  * 2nd Level Abstractions
1395  ********************************************************************/
1396
1397 /* Go through a transport's transmitted list or the association's retransmit
1398  * list and move chunks that are acked by the Cumulative TSN Ack to q->sacked.
1399  * The retransmit list will not have an associated transport.
1400  *
1401  * I added coherent debug information output.   --xguo
1402  *
1403  * Instead of printing 'sacked' or 'kept' for each TSN on the
1404  * transmitted_queue, we print a range: SACKED: TSN1-TSN2, TSN3, TSN4-TSN5.
1405  * KEPT TSN6-TSN7, etc.
1406  */
1407 static void sctp_check_transmitted(struct sctp_outq *q,
1408                                    struct list_head *transmitted_queue,
1409                                    struct sctp_transport *transport,
1410                                    union sctp_addr *saddr,
1411                                    struct sctp_sackhdr *sack,
1412                                    __u32 *highest_new_tsn_in_sack)
1413 {
1414         struct list_head *lchunk;
1415         struct sctp_chunk *tchunk;
1416         struct list_head tlist;
1417         __u32 tsn;
1418         __u32 sack_ctsn;
1419         __u32 rtt;
1420         __u8 restart_timer = 0;
1421         int bytes_acked = 0;
1422         int migrate_bytes = 0;
1423         bool forward_progress = false;
1424
1425         sack_ctsn = ntohl(sack->cum_tsn_ack);
1426
1427         INIT_LIST_HEAD(&tlist);
1428
1429         /* The while loop will skip empty transmitted queues. */
1430         while (NULL != (lchunk = sctp_list_dequeue(transmitted_queue))) {
1431                 tchunk = list_entry(lchunk, struct sctp_chunk,
1432                                     transmitted_list);
1433
1434                 if (sctp_chunk_abandoned(tchunk)) {
1435                         /* Move the chunk to abandoned list. */
1436                         sctp_insert_list(&q->abandoned, lchunk);
1437
1438                         /* If this chunk has not been acked, stop
1439                          * considering it as 'outstanding'.
1440                          */
1441                         if (!tchunk->tsn_gap_acked) {
1442                                 if (tchunk->transport)
1443                                         tchunk->transport->flight_size -=
1444                                                         sctp_data_size(tchunk);
1445                                 q->outstanding_bytes -= sctp_data_size(tchunk);
1446                         }
1447                         continue;
1448                 }
1449
1450                 tsn = ntohl(tchunk->subh.data_hdr->tsn);
1451                 if (sctp_acked(sack, tsn)) {
1452                         /* If this queue is the retransmit queue, the
1453                          * retransmit timer has already reclaimed
1454                          * the outstanding bytes for this chunk, so only
1455                          * count bytes associated with a transport.
1456                          */
1457                         if (transport) {
1458                                 /* If this chunk is being used for RTT
1459                                  * measurement, calculate the RTT and update
1460                                  * the RTO using this value.
1461                                  *
1462                                  * 6.3.1 C5) Karn's algorithm: RTT measurements
1463                                  * MUST NOT be made using packets that were
1464                                  * retransmitted (and thus for which it is
1465                                  * ambiguous whether the reply was for the
1466                                  * first instance of the packet or a later
1467                                  * instance).
1468                                  */
1469                                 if (!tchunk->tsn_gap_acked &&
1470                                     !tchunk->resent &&
1471                                     tchunk->rtt_in_progress) {
1472                                         tchunk->rtt_in_progress = 0;
1473                                         rtt = jiffies - tchunk->sent_at;
1474                                         sctp_transport_update_rto(transport,
1475                                                                   rtt);
1476                                 }
1477                         }
1478
1479                         /* If the chunk hasn't been marked as ACKED,
1480                          * mark it and account bytes_acked if the
1481                          * chunk had a valid transport (it will not
1482                          * have a transport if ASCONF had deleted it
1483                          * while DATA was outstanding).
1484                          */
1485                         if (!tchunk->tsn_gap_acked) {
1486                                 tchunk->tsn_gap_acked = 1;
1487                                 if (TSN_lt(*highest_new_tsn_in_sack, tsn))
1488                                         *highest_new_tsn_in_sack = tsn;
1489                                 bytes_acked += sctp_data_size(tchunk);
1490                                 if (!tchunk->transport)
1491                                         migrate_bytes += sctp_data_size(tchunk);
1492                                 forward_progress = true;
1493                         }
1494
1495                         if (TSN_lte(tsn, sack_ctsn)) {
1496                                 /* RFC 2960  6.3.2 Retransmission Timer Rules
1497                                  *
1498                                  * R3) Whenever a SACK is received
1499                                  * that acknowledges the DATA chunk
1500                                  * with the earliest outstanding TSN
1501                                  * for that address, restart T3-rtx
1502                                  * timer for that address with its
1503                                  * current RTO.
1504                                  */
1505                                 restart_timer = 1;
1506                                 forward_progress = true;
1507
1508                                 if (!tchunk->tsn_gap_acked) {
1509                                         /*
1510                                          * SFR-CACC algorithm:
1511                                          * 2) If the SACK contains gap acks
1512                                          * and the flag CHANGEOVER_ACTIVE is
1513                                          * set the receiver of the SACK MUST
1514                                          * take the following action:
1515                                          *
1516                                          * B) For each TSN t being acked that
1517                                          * has not been acked in any SACK so
1518                                          * far, set cacc_saw_newack to 1 for
1519                                          * the destination that the TSN was
1520                                          * sent to.
1521                                          */
1522                                         if (transport &&
1523                                             sack->num_gap_ack_blocks &&
1524                                             q->asoc->peer.primary_path->cacc.
1525                                             changeover_active)
1526                                                 transport->cacc.cacc_saw_newack
1527                                                         = 1;
1528                                 }
1529
1530                                 list_add_tail(&tchunk->transmitted_list,
1531                                               &q->sacked);
1532                         } else {
1533                                 /* RFC2960 7.2.4, sctpimpguide-05 2.8.2
1534                                  * M2) Each time a SACK arrives reporting
1535                                  * 'Stray DATA chunk(s)' record the highest TSN
1536                                  * reported as newly acknowledged, call this
1537                                  * value 'HighestTSNinSack'. A newly
1538                                  * acknowledged DATA chunk is one not
1539                                  * previously acknowledged in a SACK.
1540                                  *
1541                                  * When the SCTP sender of data receives a SACK
1542                                  * chunk that acknowledges, for the first time,
1543                                  * the receipt of a DATA chunk, all the still
1544                                  * unacknowledged DATA chunks whose TSN is
1545                                  * older than that newly acknowledged DATA
1546                                  * chunk, are qualified as 'Stray DATA chunks'.
1547                                  */
1548                                 list_add_tail(lchunk, &tlist);
1549                         }
1550                 } else {
1551                         if (tchunk->tsn_gap_acked) {
1552                                 pr_debug("%s: receiver reneged on data TSN:0x%x\n",
1553                                          __func__, tsn);
1554
1555                                 tchunk->tsn_gap_acked = 0;
1556
1557                                 if (tchunk->transport)
1558                                         bytes_acked -= sctp_data_size(tchunk);
1559
1560                                 /* RFC 2960 6.3.2 Retransmission Timer Rules
1561                                  *
1562                                  * R4) Whenever a SACK is received missing a
1563                                  * TSN that was previously acknowledged via a
1564                                  * Gap Ack Block, start T3-rtx for the
1565                                  * destination address to which the DATA
1566                                  * chunk was originally
1567                                  * transmitted if it is not already running.
1568                                  */
1569                                 restart_timer = 1;
1570                         }
1571
1572                         list_add_tail(lchunk, &tlist);
1573                 }
1574         }
1575
1576         if (transport) {
1577                 if (bytes_acked) {
1578                         struct sctp_association *asoc = transport->asoc;
1579
1580                         /* We may have counted DATA that was migrated
1581                          * to this transport due to DEL-IP operation.
1582                          * Subtract those bytes, since the were never
1583                          * send on this transport and shouldn't be
1584                          * credited to this transport.
1585                          */
1586                         bytes_acked -= migrate_bytes;
1587
1588                         /* 8.2. When an outstanding TSN is acknowledged,
1589                          * the endpoint shall clear the error counter of
1590                          * the destination transport address to which the
1591                          * DATA chunk was last sent.
1592                          * The association's overall error counter is
1593                          * also cleared.
1594                          */
1595                         transport->error_count = 0;
1596                         transport->asoc->overall_error_count = 0;
1597                         forward_progress = true;
1598
1599                         /*
1600                          * While in SHUTDOWN PENDING, we may have started
1601                          * the T5 shutdown guard timer after reaching the
1602                          * retransmission limit. Stop that timer as soon
1603                          * as the receiver acknowledged any data.
1604                          */
1605                         if (asoc->state == SCTP_STATE_SHUTDOWN_PENDING &&
1606                             del_timer(&asoc->timers
1607                                 [SCTP_EVENT_TIMEOUT_T5_SHUTDOWN_GUARD]))
1608                                         sctp_association_put(asoc);
1609
1610                         /* Mark the destination transport address as
1611                          * active if it is not so marked.
1612                          */
1613                         if ((transport->state == SCTP_INACTIVE ||
1614                              transport->state == SCTP_UNCONFIRMED) &&
1615                             sctp_cmp_addr_exact(&transport->ipaddr, saddr)) {
1616                                 sctp_assoc_control_transport(
1617                                         transport->asoc,
1618                                         transport,
1619                                         SCTP_TRANSPORT_UP,
1620                                         SCTP_RECEIVED_SACK);
1621                         }
1622
1623                         sctp_transport_raise_cwnd(transport, sack_ctsn,
1624                                                   bytes_acked);
1625
1626                         transport->flight_size -= bytes_acked;
1627                         if (transport->flight_size == 0)
1628                                 transport->partial_bytes_acked = 0;
1629                         q->outstanding_bytes -= bytes_acked + migrate_bytes;
1630                 } else {
1631                         /* RFC 2960 6.1, sctpimpguide-06 2.15.2
1632                          * When a sender is doing zero window probing, it
1633                          * should not timeout the association if it continues
1634                          * to receive new packets from the receiver. The
1635                          * reason is that the receiver MAY keep its window
1636                          * closed for an indefinite time.
1637                          * A sender is doing zero window probing when the
1638                          * receiver's advertised window is zero, and there is
1639                          * only one data chunk in flight to the receiver.
1640                          *
1641                          * Allow the association to timeout while in SHUTDOWN
1642                          * PENDING or SHUTDOWN RECEIVED in case the receiver
1643                          * stays in zero window mode forever.
1644                          */
1645                         if (!q->asoc->peer.rwnd &&
1646                             !list_empty(&tlist) &&
1647                             (sack_ctsn+2 == q->asoc->next_tsn) &&
1648                             q->asoc->state < SCTP_STATE_SHUTDOWN_PENDING) {
1649                                 pr_debug("%s: sack received for zero window "
1650                                          "probe:%u\n", __func__, sack_ctsn);
1651
1652                                 q->asoc->overall_error_count = 0;
1653                                 transport->error_count = 0;
1654                         }
1655                 }
1656
1657                 /* RFC 2960 6.3.2 Retransmission Timer Rules
1658                  *
1659                  * R2) Whenever all outstanding data sent to an address have
1660                  * been acknowledged, turn off the T3-rtx timer of that
1661                  * address.
1662                  */
1663                 if (!transport->flight_size) {
1664                         if (del_timer(&transport->T3_rtx_timer))
1665                                 sctp_transport_put(transport);
1666                 } else if (restart_timer) {
1667                         if (!mod_timer(&transport->T3_rtx_timer,
1668                                        jiffies + transport->rto))
1669                                 sctp_transport_hold(transport);
1670                 }
1671
1672                 if (forward_progress) {
1673                         if (transport->dst)
1674                                 dst_confirm(transport->dst);
1675                 }
1676         }
1677
1678         list_splice(&tlist, transmitted_queue);
1679 }
1680
1681 /* Mark chunks as missing and consequently may get retransmitted. */
1682 static void sctp_mark_missing(struct sctp_outq *q,
1683                               struct list_head *transmitted_queue,
1684                               struct sctp_transport *transport,
1685                               __u32 highest_new_tsn_in_sack,
1686                               int count_of_newacks)
1687 {
1688         struct sctp_chunk *chunk;
1689         __u32 tsn;
1690         char do_fast_retransmit = 0;
1691         struct sctp_association *asoc = q->asoc;
1692         struct sctp_transport *primary = asoc->peer.primary_path;
1693
1694         list_for_each_entry(chunk, transmitted_queue, transmitted_list) {
1695
1696                 tsn = ntohl(chunk->subh.data_hdr->tsn);
1697
1698                 /* RFC 2960 7.2.4, sctpimpguide-05 2.8.2 M3) Examine all
1699                  * 'Unacknowledged TSN's', if the TSN number of an
1700                  * 'Unacknowledged TSN' is smaller than the 'HighestTSNinSack'
1701                  * value, increment the 'TSN.Missing.Report' count on that
1702                  * chunk if it has NOT been fast retransmitted or marked for
1703                  * fast retransmit already.
1704                  */
1705                 if (chunk->fast_retransmit == SCTP_CAN_FRTX &&
1706                     !chunk->tsn_gap_acked &&
1707                     TSN_lt(tsn, highest_new_tsn_in_sack)) {
1708
1709                         /* SFR-CACC may require us to skip marking
1710                          * this chunk as missing.
1711                          */
1712                         if (!transport || !sctp_cacc_skip(primary,
1713                                                 chunk->transport,
1714                                                 count_of_newacks, tsn)) {
1715                                 chunk->tsn_missing_report++;
1716
1717                                 pr_debug("%s: tsn:0x%x missing counter:%d\n",
1718                                          __func__, tsn, chunk->tsn_missing_report);
1719                         }
1720                 }
1721                 /*
1722                  * M4) If any DATA chunk is found to have a
1723                  * 'TSN.Missing.Report'
1724                  * value larger than or equal to 3, mark that chunk for
1725                  * retransmission and start the fast retransmit procedure.
1726                  */
1727
1728                 if (chunk->tsn_missing_report >= 3) {
1729                         chunk->fast_retransmit = SCTP_NEED_FRTX;
1730                         do_fast_retransmit = 1;
1731                 }
1732         }
1733
1734         if (transport) {
1735                 if (do_fast_retransmit)
1736                         sctp_retransmit(q, transport, SCTP_RTXR_FAST_RTX);
1737
1738                 pr_debug("%s: transport:%p, cwnd:%d, ssthresh:%d, "
1739                          "flight_size:%d, pba:%d\n",  __func__, transport,
1740                          transport->cwnd, transport->ssthresh,
1741                          transport->flight_size, transport->partial_bytes_acked);
1742         }
1743 }
1744
1745 /* Is the given TSN acked by this packet?  */
1746 static int sctp_acked(struct sctp_sackhdr *sack, __u32 tsn)
1747 {
1748         int i;
1749         sctp_sack_variable_t *frags;
1750         __u16 gap;
1751         __u32 ctsn = ntohl(sack->cum_tsn_ack);
1752
1753         if (TSN_lte(tsn, ctsn))
1754                 goto pass;
1755
1756         /* 3.3.4 Selective Acknowledgement (SACK) (3):
1757          *
1758          * Gap Ack Blocks:
1759          *  These fields contain the Gap Ack Blocks. They are repeated
1760          *  for each Gap Ack Block up to the number of Gap Ack Blocks
1761          *  defined in the Number of Gap Ack Blocks field. All DATA
1762          *  chunks with TSNs greater than or equal to (Cumulative TSN
1763          *  Ack + Gap Ack Block Start) and less than or equal to
1764          *  (Cumulative TSN Ack + Gap Ack Block End) of each Gap Ack
1765          *  Block are assumed to have been received correctly.
1766          */
1767
1768         frags = sack->variable;
1769         gap = tsn - ctsn;
1770         for (i = 0; i < ntohs(sack->num_gap_ack_blocks); ++i) {
1771                 if (TSN_lte(ntohs(frags[i].gab.start), gap) &&
1772                     TSN_lte(gap, ntohs(frags[i].gab.end)))
1773                         goto pass;
1774         }
1775
1776         return 0;
1777 pass:
1778         return 1;
1779 }
1780
1781 static inline int sctp_get_skip_pos(struct sctp_fwdtsn_skip *skiplist,
1782                                     int nskips, __be16 stream)
1783 {
1784         int i;
1785
1786         for (i = 0; i < nskips; i++) {
1787                 if (skiplist[i].stream == stream)
1788                         return i;
1789         }
1790         return i;
1791 }
1792
1793 /* Create and add a fwdtsn chunk to the outq's control queue if needed. */
1794 static void sctp_generate_fwdtsn(struct sctp_outq *q, __u32 ctsn)
1795 {
1796         struct sctp_association *asoc = q->asoc;
1797         struct sctp_chunk *ftsn_chunk = NULL;
1798         struct sctp_fwdtsn_skip ftsn_skip_arr[10];
1799         int nskips = 0;
1800         int skip_pos = 0;
1801         __u32 tsn;
1802         struct sctp_chunk *chunk;
1803         struct list_head *lchunk, *temp;
1804
1805         if (!asoc->peer.prsctp_capable)
1806                 return;
1807
1808         /* PR-SCTP C1) Let SackCumAck be the Cumulative TSN ACK carried in the
1809          * received SACK.
1810          *
1811          * If (Advanced.Peer.Ack.Point < SackCumAck), then update
1812          * Advanced.Peer.Ack.Point to be equal to SackCumAck.
1813          */
1814         if (TSN_lt(asoc->adv_peer_ack_point, ctsn))
1815                 asoc->adv_peer_ack_point = ctsn;
1816
1817         /* PR-SCTP C2) Try to further advance the "Advanced.Peer.Ack.Point"
1818          * locally, that is, to move "Advanced.Peer.Ack.Point" up as long as
1819          * the chunk next in the out-queue space is marked as "abandoned" as
1820          * shown in the following example:
1821          *
1822          * Assuming that a SACK arrived with the Cumulative TSN ACK 102
1823          * and the Advanced.Peer.Ack.Point is updated to this value:
1824          *
1825          *   out-queue at the end of  ==>   out-queue after Adv.Ack.Point
1826          *   normal SACK processing           local advancement
1827          *                ...                           ...
1828          *   Adv.Ack.Pt-> 102 acked                     102 acked
1829          *                103 abandoned                 103 abandoned
1830          *                104 abandoned     Adv.Ack.P-> 104 abandoned
1831          *                105                           105
1832          *                106 acked                     106 acked
1833          *                ...                           ...
1834          *
1835          * In this example, the data sender successfully advanced the
1836          * "Advanced.Peer.Ack.Point" from 102 to 104 locally.
1837          */
1838         list_for_each_safe(lchunk, temp, &q->abandoned) {
1839                 chunk = list_entry(lchunk, struct sctp_chunk,
1840                                         transmitted_list);
1841                 tsn = ntohl(chunk->subh.data_hdr->tsn);
1842
1843                 /* Remove any chunks in the abandoned queue that are acked by
1844                  * the ctsn.
1845                  */
1846                 if (TSN_lte(tsn, ctsn)) {
1847                         list_del_init(lchunk);
1848                         sctp_chunk_free(chunk);
1849                 } else {
1850                         if (TSN_lte(tsn, asoc->adv_peer_ack_point+1)) {
1851                                 asoc->adv_peer_ack_point = tsn;
1852                                 if (chunk->chunk_hdr->flags &
1853                                          SCTP_DATA_UNORDERED)
1854                                         continue;
1855                                 skip_pos = sctp_get_skip_pos(&ftsn_skip_arr[0],
1856                                                 nskips,
1857                                                 chunk->subh.data_hdr->stream);
1858                                 ftsn_skip_arr[skip_pos].stream =
1859                                         chunk->subh.data_hdr->stream;
1860                                 ftsn_skip_arr[skip_pos].ssn =
1861                                          chunk->subh.data_hdr->ssn;
1862                                 if (skip_pos == nskips)
1863                                         nskips++;
1864                                 if (nskips == 10)
1865                                         break;
1866                         } else
1867                                 break;
1868                 }
1869         }
1870
1871         /* PR-SCTP C3) If, after step C1 and C2, the "Advanced.Peer.Ack.Point"
1872          * is greater than the Cumulative TSN ACK carried in the received
1873          * SACK, the data sender MUST send the data receiver a FORWARD TSN
1874          * chunk containing the latest value of the
1875          * "Advanced.Peer.Ack.Point".
1876          *
1877          * C4) For each "abandoned" TSN the sender of the FORWARD TSN SHOULD
1878          * list each stream and sequence number in the forwarded TSN. This
1879          * information will enable the receiver to easily find any
1880          * stranded TSN's waiting on stream reorder queues. Each stream
1881          * SHOULD only be reported once; this means that if multiple
1882          * abandoned messages occur in the same stream then only the
1883          * highest abandoned stream sequence number is reported. If the
1884          * total size of the FORWARD TSN does NOT fit in a single MTU then
1885          * the sender of the FORWARD TSN SHOULD lower the
1886          * Advanced.Peer.Ack.Point to the last TSN that will fit in a
1887          * single MTU.
1888          */
1889         if (asoc->adv_peer_ack_point > ctsn)
1890                 ftsn_chunk = sctp_make_fwdtsn(asoc, asoc->adv_peer_ack_point,
1891                                               nskips, &ftsn_skip_arr[0]);
1892
1893         if (ftsn_chunk) {
1894                 list_add_tail(&ftsn_chunk->list, &q->control_chunk_list);
1895                 SCTP_INC_STATS(sock_net(asoc->base.sk), SCTP_MIB_OUTCTRLCHUNKS);
1896         }
1897 }