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 #include <net/sctp/stream_sched.h>
  54
  55 /* Declare internal functions here.  */
  56 static int sctp_acked(struct sctp_sackhdr *sack, __u32 tsn);
  57 static void sctp_check_transmitted(struct sctp_outq *q,
  58                                    struct list_head *transmitted_queue,
  59                                    struct sctp_transport *transport,
  60                                    union sctp_addr *saddr,
  61                                    struct sctp_sackhdr *sack,
  62                                    __u32 *highest_new_tsn);
  63
  64 static void sctp_mark_missing(struct sctp_outq *q,
  65                               struct list_head *transmitted_queue,
  66                               struct sctp_transport *transport,
  67                               __u32 highest_new_tsn,
  68                               int count_of_newacks);
  69
  70 static void sctp_outq_flush(struct sctp_outq *q, int rtx_timeout, gfp_t gfp);
  71
  72 /* Add data to the front of the queue. */
  73 static inline void sctp_outq_head_data(struct sctp_outq *q,
  74                                        struct sctp_chunk *ch)
  75 {
  76         struct sctp_stream_out_ext *oute;
  77         __u16 stream;
  78
  79         list_add(&ch->list, &q->out_chunk_list);
  80         q->out_qlen += ch->skb->len;
  81
  82         stream = sctp_chunk_stream_no(ch);
  83         oute = q->asoc->stream.out[stream].ext;
  84         list_add(&ch->stream_list, &oute->outq);
  85 }
  86
  87 /* Take data from the front of the queue. */
  88 static inline struct sctp_chunk *sctp_outq_dequeue_data(struct sctp_outq *q)
  89 {
  90         return q->sched->dequeue(q);
  91 }
  92
  93 /* Add data chunk to the end of the queue. */
  94 static inline void sctp_outq_tail_data(struct sctp_outq *q,
  95                                        struct sctp_chunk *ch)
  96 {
  97         struct sctp_stream_out_ext *oute;
  98         __u16 stream;
  99
 100         list_add_tail(&ch->list, &q->out_chunk_list);
 101         q->out_qlen += ch->skb->len;
 102
 103         stream = sctp_chunk_stream_no(ch);
 104         oute = q->asoc->stream.out[stream].ext;
 105         list_add_tail(&ch->stream_list, &oute->outq);
 106 }
 107
 108 /*
 109  * SFR-CACC algorithm:
 110  * D) If count_of_newacks is greater than or equal to 2
 111  * and t was not sent to the current primary then the
 112  * sender MUST NOT increment missing report count for t.
 113  */
 114 static inline int sctp_cacc_skip_3_1_d(struct sctp_transport *primary,
 115                                        struct sctp_transport *transport,
 116                                        int count_of_newacks)
 117 {
 118         if (count_of_newacks >= 2 && transport != primary)
 119                 return 1;
 120         return 0;
 121 }
 122
 123 /*
 124  * SFR-CACC algorithm:
 125  * F) If count_of_newacks is less than 2, let d be the
 126  * destination to which t was sent. If cacc_saw_newack
 127  * is 0 for destination d, then the sender MUST NOT
 128  * increment missing report count for t.
 129  */
 130 static inline int sctp_cacc_skip_3_1_f(struct sctp_transport *transport,
 131                                        int count_of_newacks)
 132 {
 133         if (count_of_newacks < 2 &&
 134                         (transport && !transport->cacc.cacc_saw_newack))
 135                 return 1;
 136         return 0;
 137 }
 138
 139 /*
 140  * SFR-CACC algorithm:
 141  * 3.1) If CYCLING_CHANGEOVER is 0, the sender SHOULD
 142  * execute steps C, D, F.
 143  *
 144  * C has been implemented in sctp_outq_sack
 145  */
 146 static inline int sctp_cacc_skip_3_1(struct sctp_transport *primary,
 147                                      struct sctp_transport *transport,
 148                                      int count_of_newacks)
 149 {
 150         if (!primary->cacc.cycling_changeover) {
 151                 if (sctp_cacc_skip_3_1_d(primary, transport, count_of_newacks))
 152                         return 1;
 153                 if (sctp_cacc_skip_3_1_f(transport, count_of_newacks))
 154                         return 1;
 155                 return 0;
 156         }
 157         return 0;
 158 }
 159
 160 /*
 161  * SFR-CACC algorithm:
 162  * 3.2) Else if CYCLING_CHANGEOVER is 1, and t is less
 163  * than next_tsn_at_change of the current primary, then
 164  * the sender MUST NOT increment missing report count
 165  * for t.
 166  */
 167 static inline int sctp_cacc_skip_3_2(struct sctp_transport *primary, __u32 tsn)
 168 {
 169         if (primary->cacc.cycling_changeover &&
 170             TSN_lt(tsn, primary->cacc.next_tsn_at_change))
 171                 return 1;
 172         return 0;
 173 }
 174
 175 /*
 176  * SFR-CACC algorithm:
 177  * 3) If the missing report count for TSN t is to be
 178  * incremented according to [RFC2960] and
 179  * [SCTP_STEWART-2002], and CHANGEOVER_ACTIVE is set,
 180  * then the sender MUST further execute steps 3.1 and
 181  * 3.2 to determine if the missing report count for
 182  * TSN t SHOULD NOT be incremented.
 183  *
 184  * 3.3) If 3.1 and 3.2 do not dictate that the missing
 185  * report count for t should not be incremented, then
 186  * the sender SHOULD increment missing report count for
 187  * t (according to [RFC2960] and [SCTP_STEWART_2002]).
 188  */
 189 static inline int sctp_cacc_skip(struct sctp_transport *primary,
 190                                  struct sctp_transport *transport,
 191                                  int count_of_newacks,
 192                                  __u32 tsn)
 193 {
 194         if (primary->cacc.changeover_active &&
 195             (sctp_cacc_skip_3_1(primary, transport, count_of_newacks) ||
 196              sctp_cacc_skip_3_2(primary, tsn)))
 197                 return 1;
 198         return 0;
 199 }
 200
 201 /* Initialize an existing sctp_outq.  This does the boring stuff.
 202  * You still need to define handlers if you really want to DO
 203  * something with this structure...
 204  */
 205 void sctp_outq_init(struct sctp_association *asoc, struct sctp_outq *q)
 206 {
 207         memset(q, 0, sizeof(struct sctp_outq));
 208
 209         q->asoc = asoc;
 210         INIT_LIST_HEAD(&q->out_chunk_list);
 211         INIT_LIST_HEAD(&q->control_chunk_list);
 212         INIT_LIST_HEAD(&q->retransmit);
 213         INIT_LIST_HEAD(&q->sacked);
 214         INIT_LIST_HEAD(&q->abandoned);
 215         sctp_sched_set_sched(asoc, SCTP_SS_FCFS);
 216 }
 217
 218 /* Free the outqueue structure and any related pending chunks.
 219  */
 220 static void __sctp_outq_teardown(struct sctp_outq *q)
 221 {
 222         struct sctp_transport *transport;
 223         struct list_head *lchunk, *temp;
 224         struct sctp_chunk *chunk, *tmp;
 225
 226         /* Throw away unacknowledged chunks. */
 227         list_for_each_entry(transport, &q->asoc->peer.transport_addr_list,
 228                         transports) {
 229                 while ((lchunk = sctp_list_dequeue(&transport->transmitted)) != NULL) {
 230                         chunk = list_entry(lchunk, struct sctp_chunk,
 231                                            transmitted_list);
 232                         /* Mark as part of a failed message. */
 233                         sctp_chunk_fail(chunk, q->error);
 234                         sctp_chunk_free(chunk);
 235                 }
 236         }
 237
 238         /* Throw away chunks that have been gap ACKed.  */
 239         list_for_each_safe(lchunk, temp, &q->sacked) {
 240                 list_del_init(lchunk);
 241                 chunk = list_entry(lchunk, struct sctp_chunk,
 242                                    transmitted_list);
 243                 sctp_chunk_fail(chunk, q->error);
 244                 sctp_chunk_free(chunk);
 245         }
 246
 247         /* Throw away any chunks in the retransmit queue. */
 248         list_for_each_safe(lchunk, temp, &q->retransmit) {
 249                 list_del_init(lchunk);
 250                 chunk = list_entry(lchunk, struct sctp_chunk,
 251                                    transmitted_list);
 252                 sctp_chunk_fail(chunk, q->error);
 253                 sctp_chunk_free(chunk);
 254         }
 255
 256         /* Throw away any chunks that are in the abandoned queue. */
 257         list_for_each_safe(lchunk, temp, &q->abandoned) {
 258                 list_del_init(lchunk);
 259                 chunk = list_entry(lchunk, struct sctp_chunk,
 260                                    transmitted_list);
 261                 sctp_chunk_fail(chunk, q->error);
 262                 sctp_chunk_free(chunk);
 263         }
 264
 265         /* Throw away any leftover data chunks. */
 266         while ((chunk = sctp_outq_dequeue_data(q)) != NULL) {
 267                 sctp_sched_dequeue_done(q, chunk);
 268
 269                 /* Mark as send failure. */
 270                 sctp_chunk_fail(chunk, q->error);
 271                 sctp_chunk_free(chunk);
 272         }
 273
 274         /* Throw away any leftover control chunks. */
 275         list_for_each_entry_safe(chunk, tmp, &q->control_chunk_list, list) {
 276                 list_del_init(&chunk->list);
 277                 sctp_chunk_free(chunk);
 278         }
 279 }
 280
 281 void sctp_outq_teardown(struct sctp_outq *q)
 282 {
 283         __sctp_outq_teardown(q);
 284         sctp_outq_init(q->asoc, q);
 285 }
 286
 287 /* Free the outqueue structure and any related pending chunks.  */
 288 void sctp_outq_free(struct sctp_outq *q)
 289 {
 290         /* Throw away leftover chunks. */
 291         __sctp_outq_teardown(q);
 292 }
 293
 294 /* Put a new chunk in an sctp_outq.  */
 295 void sctp_outq_tail(struct sctp_outq *q, struct sctp_chunk *chunk, gfp_t gfp)
 296 {
 297         struct net *net = sock_net(q->asoc->base.sk);
 298
 299         pr_debug("%s: outq:%p, chunk:%p[%s]\n", __func__, q, chunk,
 300                  chunk && chunk->chunk_hdr ?
 301                  sctp_cname(SCTP_ST_CHUNK(chunk->chunk_hdr->type)) :
 302                  "illegal chunk");
 303
 304         /* If it is data, queue it up, otherwise, send it
 305          * immediately.
 306          */
 307         if (sctp_chunk_is_data(chunk)) {
 308                 pr_debug("%s: outqueueing: outq:%p, chunk:%p[%s])\n",
 309                          __func__, q, chunk, chunk && chunk->chunk_hdr ?
 310                          sctp_cname(SCTP_ST_CHUNK(chunk->chunk_hdr->type)) :
 311                          "illegal chunk");
 312
 313                 sctp_outq_tail_data(q, chunk);
 314                 if (chunk->asoc->peer.prsctp_capable &&
 315                     SCTP_PR_PRIO_ENABLED(chunk->sinfo.sinfo_flags))
 316                         chunk->asoc->sent_cnt_removable++;
 317                 if (chunk->chunk_hdr->flags & SCTP_DATA_UNORDERED)
 318                         SCTP_INC_STATS(net, SCTP_MIB_OUTUNORDERCHUNKS);
 319                 else
 320                         SCTP_INC_STATS(net, SCTP_MIB_OUTORDERCHUNKS);
 321         } else {
 322                 list_add_tail(&chunk->list, &q->control_chunk_list);
 323                 SCTP_INC_STATS(net, SCTP_MIB_OUTCTRLCHUNKS);
 324         }
 325
 326         if (!q->cork)
 327                 sctp_outq_flush(q, 0, gfp);
 328 }
 329
 330 /* Insert a chunk into the sorted list based on the TSNs.  The retransmit list
 331  * and the abandoned list are in ascending order.
 332  */
 333 static void sctp_insert_list(struct list_head *head, struct list_head *new)
 334 {
 335         struct list_head *pos;
 336         struct sctp_chunk *nchunk, *lchunk;
 337         __u32 ntsn, ltsn;
 338         int done = 0;
 339
 340         nchunk = list_entry(new, struct sctp_chunk, transmitted_list);
 341         ntsn = ntohl(nchunk->subh.data_hdr->tsn);
 342
 343         list_for_each(pos, head) {
 344                 lchunk = list_entry(pos, struct sctp_chunk, transmitted_list);
 345                 ltsn = ntohl(lchunk->subh.data_hdr->tsn);
 346                 if (TSN_lt(ntsn, ltsn)) {
 347                         list_add(new, pos->prev);
 348                         done = 1;
 349                         break;
 350                 }
 351         }
 352         if (!done)
 353                 list_add_tail(new, head);
 354 }
 355
 356 static int sctp_prsctp_prune_sent(struct sctp_association *asoc,
 357                                   struct sctp_sndrcvinfo *sinfo,
 358                                   struct list_head *queue, int msg_len)
 359 {
 360         struct sctp_chunk *chk, *temp;
 361
 362         list_for_each_entry_safe(chk, temp, queue, transmitted_list) {
 363                 struct sctp_stream_out *streamout;
 364
 365                 if (!chk->msg->abandoned &&
 366                     (!SCTP_PR_PRIO_ENABLED(chk->sinfo.sinfo_flags) ||
 367                      chk->sinfo.sinfo_timetolive <= sinfo->sinfo_timetolive))
 368                         continue;
 369
 370                 chk->msg->abandoned = 1;
 371                 list_del_init(&chk->transmitted_list);
 372                 sctp_insert_list(&asoc->outqueue.abandoned,
 373                                  &chk->transmitted_list);
 374
 375                 streamout = &asoc->stream.out[chk->sinfo.sinfo_stream];
 376                 asoc->sent_cnt_removable--;
 377                 asoc->abandoned_sent[SCTP_PR_INDEX(PRIO)]++;
 378                 streamout->ext->abandoned_sent[SCTP_PR_INDEX(PRIO)]++;
 379
 380                 if (queue != &asoc->outqueue.retransmit &&
 381                     !chk->tsn_gap_acked) {
 382                         if (chk->transport)
 383                                 chk->transport->flight_size -=
 384                                                 sctp_data_size(chk);
 385                         asoc->outqueue.outstanding_bytes -= sctp_data_size(chk);
 386                 }
 387
 388                 msg_len -= SCTP_DATA_SNDSIZE(chk) +
 389                            sizeof(struct sk_buff) +
 390                            sizeof(struct sctp_chunk);
 391                 if (msg_len <= 0)
 392                         break;
 393         }
 394
 395         return msg_len;
 396 }
 397
 398 static int sctp_prsctp_prune_unsent(struct sctp_association *asoc,
 399                                     struct sctp_sndrcvinfo *sinfo, int msg_len)
 400 {
 401         struct sctp_outq *q = &asoc->outqueue;
 402         struct sctp_chunk *chk, *temp;
 403
 404         q->sched->unsched_all(&asoc->stream);
 405
 406         list_for_each_entry_safe(chk, temp, &q->out_chunk_list, list) {
 407                 if (!chk->msg->abandoned &&
 408                     (!(chk->chunk_hdr->flags & SCTP_DATA_FIRST_FRAG) ||
 409                      !SCTP_PR_PRIO_ENABLED(chk->sinfo.sinfo_flags) ||
 410                      chk->sinfo.sinfo_timetolive <= sinfo->sinfo_timetolive))
 411                         continue;
 412
 413                 chk->msg->abandoned = 1;
 414                 sctp_sched_dequeue_common(q, chk);
 415                 asoc->sent_cnt_removable--;
 416                 asoc->abandoned_unsent[SCTP_PR_INDEX(PRIO)]++;
 417                 if (chk->sinfo.sinfo_stream < asoc->stream.outcnt) {
 418                         struct sctp_stream_out *streamout =
 419                                 &asoc->stream.out[chk->sinfo.sinfo_stream];
 420
 421                         streamout->ext->abandoned_unsent[SCTP_PR_INDEX(PRIO)]++;
 422                 }
 423
 424                 msg_len -= SCTP_DATA_SNDSIZE(chk) +
 425                            sizeof(struct sk_buff) +
 426                            sizeof(struct sctp_chunk);
 427                 sctp_chunk_free(chk);
 428                 if (msg_len <= 0)
 429                         break;
 430         }
 431
 432         q->sched->sched_all(&asoc->stream);
 433
 434         return msg_len;
 435 }
 436
 437 /* Abandon the chunks according their priorities */
 438 void sctp_prsctp_prune(struct sctp_association *asoc,
 439                        struct sctp_sndrcvinfo *sinfo, int msg_len)
 440 {
 441         struct sctp_transport *transport;
 442
 443         if (!asoc->peer.prsctp_capable || !asoc->sent_cnt_removable)
 444                 return;
 445
 446         msg_len = sctp_prsctp_prune_sent(asoc, sinfo,
 447                                          &asoc->outqueue.retransmit,
 448                                          msg_len);
 449         if (msg_len <= 0)
 450                 return;
 451
 452         list_for_each_entry(transport, &asoc->peer.transport_addr_list,
 453                             transports) {
 454                 msg_len = sctp_prsctp_prune_sent(asoc, sinfo,
 455                                                  &transport->transmitted,
 456                                                  msg_len);
 457                 if (msg_len <= 0)
 458                         return;
 459         }
 460
 461         sctp_prsctp_prune_unsent(asoc, sinfo, msg_len);
 462 }
 463
 464 /* Mark all the eligible packets on a transport for retransmission.  */
 465 void sctp_retransmit_mark(struct sctp_outq *q,
 466                           struct sctp_transport *transport,
 467                           __u8 reason)
 468 {
 469         struct list_head *lchunk, *ltemp;
 470         struct sctp_chunk *chunk;
 471
 472         /* Walk through the specified transmitted queue.  */
 473         list_for_each_safe(lchunk, ltemp, &transport->transmitted) {
 474                 chunk = list_entry(lchunk, struct sctp_chunk,
 475                                    transmitted_list);
 476
 477                 /* If the chunk is abandoned, move it to abandoned list. */
 478                 if (sctp_chunk_abandoned(chunk)) {
 479                         list_del_init(lchunk);
 480                         sctp_insert_list(&q->abandoned, lchunk);
 481
 482                         /* If this chunk has not been previousely acked,
 483                          * stop considering it 'outstanding'.  Our peer
 484                          * will most likely never see it since it will
 485                          * not be retransmitted
 486                          */
 487                         if (!chunk->tsn_gap_acked) {
 488                                 if (chunk->transport)
 489                                         chunk->transport->flight_size -=
 490                                                         sctp_data_size(chunk);
 491                                 q->outstanding_bytes -= sctp_data_size(chunk);
 492                                 q->asoc->peer.rwnd += sctp_data_size(chunk);
 493                         }
 494                         continue;
 495                 }
 496
 497                 /* If we are doing  retransmission due to a timeout or pmtu
 498                  * discovery, only the  chunks that are not yet acked should
 499                  * be added to the retransmit queue.
 500                  */
 501                 if ((reason == SCTP_RTXR_FAST_RTX  &&
 502                             (chunk->fast_retransmit == SCTP_NEED_FRTX)) ||
 503                     (reason != SCTP_RTXR_FAST_RTX  && !chunk->tsn_gap_acked)) {
 504                         /* RFC 2960 6.2.1 Processing a Received SACK
 505                          *
 506                          * C) Any time a DATA chunk is marked for
 507                          * retransmission (via either T3-rtx timer expiration
 508                          * (Section 6.3.3) or via fast retransmit
 509                          * (Section 7.2.4)), add the data size of those
 510                          * chunks to the rwnd.
 511                          */
 512                         q->asoc->peer.rwnd += sctp_data_size(chunk);
 513                         q->outstanding_bytes -= sctp_data_size(chunk);
 514                         if (chunk->transport)
 515                                 transport->flight_size -= sctp_data_size(chunk);
 516
 517                         /* sctpimpguide-05 Section 2.8.2
 518                          * M5) If a T3-rtx timer expires, the
 519                          * 'TSN.Missing.Report' of all affected TSNs is set
 520                          * to 0.
 521                          */
 522                         chunk->tsn_missing_report = 0;
 523
 524                         /* If a chunk that is being used for RTT measurement
 525                          * has to be retransmitted, we cannot use this chunk
 526                          * anymore for RTT measurements. Reset rto_pending so
 527                          * that a new RTT measurement is started when a new
 528                          * data chunk is sent.
 529                          */
 530                         if (chunk->rtt_in_progress) {
 531                                 chunk->rtt_in_progress = 0;
 532                                 transport->rto_pending = 0;
 533                         }
 534
 535                         /* Move the chunk to the retransmit queue. The chunks
 536                          * on the retransmit queue are always kept in order.
 537                          */
 538                         list_del_init(lchunk);
 539                         sctp_insert_list(&q->retransmit, lchunk);
 540                 }
 541         }
 542
 543         pr_debug("%s: transport:%p, reason:%d, cwnd:%d, ssthresh:%d, "
 544                  "flight_size:%d, pba:%d\n", __func__, transport, reason,
 545                  transport->cwnd, transport->ssthresh, transport->flight_size,
 546                  transport->partial_bytes_acked);
 547 }
 548
 549 /* Mark all the eligible packets on a transport for retransmission and force
 550  * one packet out.
 551  */
 552 void sctp_retransmit(struct sctp_outq *q, struct sctp_transport *transport,
 553                      enum sctp_retransmit_reason reason)
 554 {
 555         struct net *net = sock_net(q->asoc->base.sk);
 556
 557         switch (reason) {
 558         case SCTP_RTXR_T3_RTX:
 559                 SCTP_INC_STATS(net, SCTP_MIB_T3_RETRANSMITS);
 560                 sctp_transport_lower_cwnd(transport, SCTP_LOWER_CWND_T3_RTX);
 561                 /* Update the retran path if the T3-rtx timer has expired for
 562                  * the current retran path.
 563                  */
 564                 if (transport == transport->asoc->peer.retran_path)
 565                         sctp_assoc_update_retran_path(transport->asoc);
 566                 transport->asoc->rtx_data_chunks +=
 567                         transport->asoc->unack_data;
 568                 break;
 569         case SCTP_RTXR_FAST_RTX:
 570                 SCTP_INC_STATS(net, SCTP_MIB_FAST_RETRANSMITS);
 571                 sctp_transport_lower_cwnd(transport, SCTP_LOWER_CWND_FAST_RTX);
 572                 q->fast_rtx = 1;
 573                 break;
 574         case SCTP_RTXR_PMTUD:
 575                 SCTP_INC_STATS(net, SCTP_MIB_PMTUD_RETRANSMITS);
 576                 break;
 577         case SCTP_RTXR_T1_RTX:
 578                 SCTP_INC_STATS(net, SCTP_MIB_T1_RETRANSMITS);
 579                 transport->asoc->init_retries++;
 580                 break;
 581         default:
 582                 BUG();
 583         }
 584
 585         sctp_retransmit_mark(q, transport, reason);
 586
 587         /* PR-SCTP A5) Any time the T3-rtx timer expires, on any destination,
 588          * the sender SHOULD try to advance the "Advanced.Peer.Ack.Point" by
 589          * following the procedures outlined in C1 - C5.
 590          */
 591         if (reason == SCTP_RTXR_T3_RTX)
 592                 q->asoc->stream.si->generate_ftsn(q, q->asoc->ctsn_ack_point);
 593
 594         /* Flush the queues only on timeout, since fast_rtx is only
 595          * triggered during sack processing and the queue
 596          * will be flushed at the end.
 597          */
 598         if (reason != SCTP_RTXR_FAST_RTX)
 599                 sctp_outq_flush(q, /* rtx_timeout */ 1, GFP_ATOMIC);
 600 }
 601
 602 /*
 603  * Transmit DATA chunks on the retransmit queue.  Upon return from
 604  * __sctp_outq_flush_rtx() the packet 'pkt' may contain chunks which
 605  * need to be transmitted by the caller.
 606  * We assume that pkt->transport has already been set.
 607  *
 608  * The return value is a normal kernel error return value.
 609  */
 610 static int __sctp_outq_flush_rtx(struct sctp_outq *q, struct sctp_packet *pkt,
 611                                  int rtx_timeout, int *start_timer, gfp_t gfp)
 612 {
 613         struct sctp_transport *transport = pkt->transport;
 614         struct sctp_chunk *chunk, *chunk1;
 615         struct list_head *lqueue;
 616         enum sctp_xmit status;
 617         int error = 0;
 618         int timer = 0;
 619         int done = 0;
 620         int fast_rtx;
 621
 622         lqueue = &q->retransmit;
 623         fast_rtx = q->fast_rtx;
 624
 625         /* This loop handles time-out retransmissions, fast retransmissions,
 626          * and retransmissions due to opening of whindow.
 627          *
 628          * RFC 2960 6.3.3 Handle T3-rtx Expiration
 629          *
 630          * E3) Determine how many of the earliest (i.e., lowest TSN)
 631          * outstanding DATA chunks for the address for which the
 632          * T3-rtx has expired will fit into a single packet, subject
 633          * to the MTU constraint for the path corresponding to the
 634          * destination transport address to which the retransmission
 635          * is being sent (this may be different from the address for
 636          * which the timer expires [see Section 6.4]). Call this value
 637          * K. Bundle and retransmit those K DATA chunks in a single
 638          * packet to the destination endpoint.
 639          *
 640          * [Just to be painfully clear, if we are retransmitting
 641          * because a timeout just happened, we should send only ONE
 642          * packet of retransmitted data.]
 643          *
 644          * For fast retransmissions we also send only ONE packet.  However,
 645          * if we are just flushing the queue due to open window, we'll
 646          * try to send as much as possible.
 647          */
 648         list_for_each_entry_safe(chunk, chunk1, lqueue, transmitted_list) {
 649                 /* If the chunk is abandoned, move it to abandoned list. */
 650                 if (sctp_chunk_abandoned(chunk)) {
 651                         list_del_init(&chunk->transmitted_list);
 652                         sctp_insert_list(&q->abandoned,
 653                                          &chunk->transmitted_list);
 654                         continue;
 655                 }
 656
 657                 /* Make sure that Gap Acked TSNs are not retransmitted.  A
 658                  * simple approach is just to move such TSNs out of the
 659                  * way and into a 'transmitted' queue and skip to the
 660                  * next chunk.
 661                  */
 662                 if (chunk->tsn_gap_acked) {
 663                         list_move_tail(&chunk->transmitted_list,
 664                                        &transport->transmitted);
 665                         continue;
 666                 }
 667
 668                 /* If we are doing fast retransmit, ignore non-fast_rtransmit
 669                  * chunks
 670                  */
 671                 if (fast_rtx && !chunk->fast_retransmit)
 672                         continue;
 673
 674 redo:
 675                 /* Attempt to append this chunk to the packet. */
 676                 status = sctp_packet_append_chunk(pkt, chunk);
 677
 678                 switch (status) {
 679                 case SCTP_XMIT_PMTU_FULL:
 680                         if (!pkt->has_data && !pkt->has_cookie_echo) {
 681                                 /* If this packet did not contain DATA then
 682                                  * retransmission did not happen, so do it
 683                                  * again.  We'll ignore the error here since
 684                                  * control chunks are already freed so there
 685                                  * is nothing we can do.
 686                                  */
 687                                 sctp_packet_transmit(pkt, gfp);
 688                                 goto redo;
 689                         }
 690
 691                         /* Send this packet.  */
 692                         error = sctp_packet_transmit(pkt, gfp);
 693
 694                         /* If we are retransmitting, we should only
 695                          * send a single packet.
 696                          * Otherwise, try appending this chunk again.
 697                          */
 698                         if (rtx_timeout || fast_rtx)
 699                                 done = 1;
 700                         else
 701                                 goto redo;
 702
 703                         /* Bundle next chunk in the next round.  */
 704                         break;
 705
 706                 case SCTP_XMIT_RWND_FULL:
 707                         /* Send this packet. */
 708                         error = sctp_packet_transmit(pkt, gfp);
 709
 710                         /* Stop sending DATA as there is no more room
 711                          * at the receiver.
 712                          */
 713                         done = 1;
 714                         break;
 715
 716                 case SCTP_XMIT_DELAY:
 717                         /* Send this packet. */
 718                         error = sctp_packet_transmit(pkt, gfp);
 719
 720                         /* Stop sending DATA because of nagle delay. */
 721                         done = 1;
 722                         break;
 723
 724                 default:
 725                         /* The append was successful, so add this chunk to
 726                          * the transmitted list.
 727                          */
 728                         list_move_tail(&chunk->transmitted_list,
 729                                        &transport->transmitted);
 730
 731                         /* Mark the chunk as ineligible for fast retransmit
 732                          * after it is retransmitted.
 733                          */
 734                         if (chunk->fast_retransmit == SCTP_NEED_FRTX)
 735                                 chunk->fast_retransmit = SCTP_DONT_FRTX;
 736
 737                         q->asoc->stats.rtxchunks++;
 738                         break;
 739                 }
 740
 741                 /* Set the timer if there were no errors */
 742                 if (!error && !timer)
 743                         timer = 1;
 744
 745                 if (done)
 746                         break;
 747         }
 748
 749         /* If we are here due to a retransmit timeout or a fast
 750          * retransmit and if there are any chunks left in the retransmit
 751          * queue that could not fit in the PMTU sized packet, they need
 752          * to be marked as ineligible for a subsequent fast retransmit.
 753          */
 754         if (rtx_timeout || fast_rtx) {
 755                 list_for_each_entry(chunk1, lqueue, transmitted_list) {
 756                         if (chunk1->fast_retransmit == SCTP_NEED_FRTX)
 757                                 chunk1->fast_retransmit = SCTP_DONT_FRTX;
 758                 }
 759         }
 760
 761         *start_timer = timer;
 762
 763         /* Clear fast retransmit hint */
 764         if (fast_rtx)
 765                 q->fast_rtx = 0;
 766
 767         return error;
 768 }
 769
 770 /* Cork the outqueue so queued chunks are really queued. */
 771 void sctp_outq_uncork(struct sctp_outq *q, gfp_t gfp)
 772 {
 773         if (q->cork)
 774                 q->cork = 0;
 775
 776         sctp_outq_flush(q, 0, gfp);
 777 }
 778
 779 static int sctp_packet_singleton(struct sctp_transport *transport,
 780                                  struct sctp_chunk *chunk, gfp_t gfp)
 781 {
 782         const struct sctp_association *asoc = transport->asoc;
 783         const __u16 sport = asoc->base.bind_addr.port;
 784         const __u16 dport = asoc->peer.port;
 785         const __u32 vtag = asoc->peer.i.init_tag;
 786         struct sctp_packet singleton;
 787
 788         sctp_packet_init(&singleton, transport, sport, dport);
 789         sctp_packet_config(&singleton, vtag, 0);
 790         sctp_packet_append_chunk(&singleton, chunk);
 791         return sctp_packet_transmit(&singleton, gfp);
 792 }
 793
 794 /* Struct to hold the context during sctp outq flush */
 795 struct sctp_flush_ctx {
 796         struct sctp_outq *q;
 797         /* Current transport being used. It's NOT the same as curr active one */
 798         struct sctp_transport *transport;
 799         /* These transports have chunks to send. */
 800         struct list_head transport_list;
 801         struct sctp_association *asoc;
 802         /* Packet on the current transport above */
 803         struct sctp_packet *packet;
 804         gfp_t gfp;
 805 };
 806
 807 /* transport: current transport */
 808 static void sctp_outq_select_transport(struct sctp_flush_ctx *ctx,
 809                                        struct sctp_chunk *chunk)
 810 {
 811         struct sctp_transport *new_transport = chunk->transport;
 812
 813         if (!new_transport) {
 814                 if (!sctp_chunk_is_data(chunk)) {
 815                         /* If we have a prior transport pointer, see if
 816                          * the destination address of the chunk
 817                          * matches the destination address of the
 818                          * current transport.  If not a match, then
 819                          * try to look up the transport with a given
 820                          * destination address.  We do this because
 821                          * after processing ASCONFs, we may have new
 822                          * transports created.
 823                          */
 824                         if (ctx->transport && sctp_cmp_addr_exact(&chunk->dest,
 825                                                         &ctx->transport->ipaddr))
 826                                 new_transport = ctx->transport;
 827                         else
 828                                 new_transport = sctp_assoc_lookup_paddr(ctx->asoc,
 829                                                                   &chunk->dest);
 830                 }
 831
 832                 /* if we still don't have a new transport, then
 833                  * use the current active path.
 834                  */
 835                 if (!new_transport)
 836                         new_transport = ctx->asoc->peer.active_path;
 837         } else {
 838                 __u8 type;
 839
 840                 switch (new_transport->state) {
 841                 case SCTP_INACTIVE:
 842                 case SCTP_UNCONFIRMED:
 843                 case SCTP_PF:
 844                         /* If the chunk is Heartbeat or Heartbeat Ack,
 845                          * send it to chunk->transport, even if it's
 846                          * inactive.
 847                          *
 848                          * 3.3.6 Heartbeat Acknowledgement:
 849                          * ...
 850                          * A HEARTBEAT ACK is always sent to the source IP
 851                          * address of the IP datagram containing the
 852                          * HEARTBEAT chunk to which this ack is responding.
 853                          * ...
 854                          *
 855                          * ASCONF_ACKs also must be sent to the source.
 856                          */
 857                         type = chunk->chunk_hdr->type;
 858                         if (type != SCTP_CID_HEARTBEAT &&
 859                             type != SCTP_CID_HEARTBEAT_ACK &&
 860                             type != SCTP_CID_ASCONF_ACK)
 861                                 new_transport = ctx->asoc->peer.active_path;
 862                         break;
 863                 default:
 864                         break;
 865                 }
 866         }
 867
 868         /* Are we switching transports? Take care of transport locks. */
 869         if (new_transport != ctx->transport) {
 870                 ctx->transport = new_transport;
 871                 ctx->packet = &ctx->transport->packet;
 872
 873                 if (list_empty(&ctx->transport->send_ready))
 874                         list_add_tail(&ctx->transport->send_ready,
 875                                       &ctx->transport_list);
 876
 877                 sctp_packet_config(ctx->packet,
 878                                    ctx->asoc->peer.i.init_tag,
 879                                    ctx->asoc->peer.ecn_capable);
 880                 /* We've switched transports, so apply the
 881                  * Burst limit to the new transport.
 882                  */
 883                 sctp_transport_burst_limited(ctx->transport);
 884         }
 885 }
 886
 887 static void sctp_outq_flush_ctrl(struct sctp_flush_ctx *ctx)
 888 {
 889         struct sctp_chunk *chunk, *tmp;
 890         enum sctp_xmit status;
 891         int one_packet, error;
 892
 893         list_for_each_entry_safe(chunk, tmp, &ctx->q->control_chunk_list, list) {
 894                 one_packet = 0;
 895
 896                 /* RFC 5061, 5.3
 897                  * F1) This means that until such time as the ASCONF
 898                  * containing the add is acknowledged, the sender MUST
 899                  * NOT use the new IP address as a source for ANY SCTP
 900                  * packet except on carrying an ASCONF Chunk.
 901                  */
 902                 if (ctx->asoc->src_out_of_asoc_ok &&
 903                     chunk->chunk_hdr->type != SCTP_CID_ASCONF)
 904                         continue;
 905
 906                 list_del_init(&chunk->list);
 907
 908                 /* Pick the right transport to use. Should always be true for
 909                  * the first chunk as we don't have a transport by then.
 910                  */
 911                 sctp_outq_select_transport(ctx, chunk);
 912
 913                 switch (chunk->chunk_hdr->type) {
 914                 /* 6.10 Bundling
 915                  *   ...
 916                  *   An endpoint MUST NOT bundle INIT, INIT ACK or SHUTDOWN
 917                  *   COMPLETE with any other chunks.  [Send them immediately.]
 918                  */
 919                 case SCTP_CID_INIT:
 920                 case SCTP_CID_INIT_ACK:
 921                 case SCTP_CID_SHUTDOWN_COMPLETE:
 922                         error = sctp_packet_singleton(ctx->transport, chunk,
 923                                                       ctx->gfp);
 924                         if (error < 0) {
 925                                 ctx->asoc->base.sk->sk_err = -error;
 926                                 return;
 927                         }
 928                         break;
 929
 930                 case SCTP_CID_ABORT:
 931                         if (sctp_test_T_bit(chunk))
 932                                 ctx->packet->vtag = ctx->asoc->c.my_vtag;
 933                         /* fallthru */
 934
 935                 /* The following chunks are "response" chunks, i.e.
 936                  * they are generated in response to something we
 937                  * received.  If we are sending these, then we can
 938                  * send only 1 packet containing these chunks.
 939                  */
 940                 case SCTP_CID_HEARTBEAT_ACK:
 941                 case SCTP_CID_SHUTDOWN_ACK:
 942                 case SCTP_CID_COOKIE_ACK:
 943                 case SCTP_CID_COOKIE_ECHO:
 944                 case SCTP_CID_ERROR:
 945                 case SCTP_CID_ECN_CWR:
 946                 case SCTP_CID_ASCONF_ACK:
 947                         one_packet = 1;
 948                         /* Fall through */
 949
 950                 case SCTP_CID_SACK:
 951                 case SCTP_CID_HEARTBEAT:
 952                 case SCTP_CID_SHUTDOWN:
 953                 case SCTP_CID_ECN_ECNE:
 954                 case SCTP_CID_ASCONF:
 955                 case SCTP_CID_FWD_TSN:
 956                 case SCTP_CID_I_FWD_TSN:
 957                 case SCTP_CID_RECONF:
 958                         status = sctp_packet_transmit_chunk(ctx->packet, chunk,
 959                                                             one_packet, ctx->gfp);
 960                         if (status != SCTP_XMIT_OK) {
 961                                 /* put the chunk back */
 962                                 list_add(&chunk->list, &ctx->q->control_chunk_list);
 963                                 break;
 964                         }
 965
 966                         ctx->asoc->stats.octrlchunks++;
 967                         /* PR-SCTP C5) If a FORWARD TSN is sent, the
 968                          * sender MUST assure that at least one T3-rtx
 969                          * timer is running.
 970                          */
 971                         if (chunk->chunk_hdr->type == SCTP_CID_FWD_TSN ||
 972                             chunk->chunk_hdr->type == SCTP_CID_I_FWD_TSN) {
 973                                 sctp_transport_reset_t3_rtx(ctx->transport);
 974                                 ctx->transport->last_time_sent = jiffies;
 975                         }
 976
 977                         if (chunk == ctx->asoc->strreset_chunk)
 978                                 sctp_transport_reset_reconf_timer(ctx->transport);
 979
 980                         break;
 981
 982                 default:
 983                         /* We built a chunk with an illegal type! */
 984                         BUG();
 985                 }
 986         }
 987 }
 988
 989 /* Returns false if new data shouldn't be sent */
 990 static bool sctp_outq_flush_rtx(struct sctp_flush_ctx *ctx,
 991                                 int rtx_timeout)
 992 {
 993         int error, start_timer = 0;
 994
 995         if (ctx->asoc->peer.retran_path->state == SCTP_UNCONFIRMED)
 996                 return false;
 997
 998         if (ctx->transport != ctx->asoc->peer.retran_path) {
 999                 /* Switch transports & prepare the packet.  */
1000                 ctx->transport = ctx->asoc->peer.retran_path;
1001                 ctx->packet = &ctx->transport->packet;
1002
1003                 if (list_empty(&ctx->transport->send_ready))
1004                         list_add_tail(&ctx->transport->send_ready,
1005                                       &ctx->transport_list);
1006
1007                 sctp_packet_config(ctx->packet, ctx->asoc->peer.i.init_tag,
1008                                    ctx->asoc->peer.ecn_capable);
1009         }
1010
1011         error = __sctp_outq_flush_rtx(ctx->q, ctx->packet, rtx_timeout,
1012                                       &start_timer, ctx->gfp);
1013         if (error < 0)
1014                 ctx->asoc->base.sk->sk_err = -error;
1015
1016         if (start_timer) {
1017                 sctp_transport_reset_t3_rtx(ctx->transport);
1018                 ctx->transport->last_time_sent = jiffies;
1019         }
1020
1021         /* This can happen on COOKIE-ECHO resend.  Only
1022          * one chunk can get bundled with a COOKIE-ECHO.
1023          */
1024         if (ctx->packet->has_cookie_echo)
1025                 return false;
1026
1027         /* Don't send new data if there is still data
1028          * waiting to retransmit.
1029          */
1030         if (!list_empty(&ctx->q->retransmit))
1031                 return false;
1032
1033         return true;
1034 }
1035
1036 static void sctp_outq_flush_data(struct sctp_flush_ctx *ctx,
1037                                  int rtx_timeout)
1038 {
1039         struct sctp_chunk *chunk;
1040         enum sctp_xmit status;
1041
1042         /* Is it OK to send data chunks?  */
1043         switch (ctx->asoc->state) {
1044         case SCTP_STATE_COOKIE_ECHOED:
1045                 /* Only allow bundling when this packet has a COOKIE-ECHO
1046                  * chunk.
1047                  */
1048                 if (!ctx->packet || !ctx->packet->has_cookie_echo)
1049                         return;
1050
1051                 /* fallthru */
1052         case SCTP_STATE_ESTABLISHED:
1053         case SCTP_STATE_SHUTDOWN_PENDING:
1054         case SCTP_STATE_SHUTDOWN_RECEIVED:
1055                 break;
1056
1057         default:
1058                 /* Do nothing. */
1059                 return;
1060         }
1061
1062         /* RFC 2960 6.1  Transmission of DATA Chunks
1063          *
1064          * C) When the time comes for the sender to transmit,
1065          * before sending new DATA chunks, the sender MUST
1066          * first transmit any outstanding DATA chunks which
1067          * are marked for retransmission (limited by the
1068          * current cwnd).
1069          */
1070         if (!list_empty(&ctx->q->retransmit) &&
1071             !sctp_outq_flush_rtx(ctx, rtx_timeout))
1072                 return;
1073
1074         /* Apply Max.Burst limitation to the current transport in
1075          * case it will be used for new data.  We are going to
1076          * rest it before we return, but we want to apply the limit
1077          * to the currently queued data.
1078          */
1079         if (ctx->transport)
1080                 sctp_transport_burst_limited(ctx->transport);
1081
1082         /* Finally, transmit new packets.  */
1083         while ((chunk = sctp_outq_dequeue_data(ctx->q)) != NULL) {
1084                 __u32 sid = ntohs(chunk->subh.data_hdr->stream);
1085
1086                 /* Has this chunk expired? */
1087                 if (sctp_chunk_abandoned(chunk)) {
1088                         sctp_sched_dequeue_done(ctx->q, chunk);
1089                         sctp_chunk_fail(chunk, 0);
1090                         sctp_chunk_free(chunk);
1091                         continue;
1092                 }
1093
1094                 if (ctx->asoc->stream.out[sid].state == SCTP_STREAM_CLOSED) {
1095                         sctp_outq_head_data(ctx->q, chunk);
1096                         break;
1097                 }
1098
1099                 sctp_outq_select_transport(ctx, chunk);
1100
1101                 pr_debug("%s: outq:%p, chunk:%p[%s], tx-tsn:0x%x skb->head:%p skb->users:%d\n",
1102                          __func__, ctx->q, chunk, chunk && chunk->chunk_hdr ?
1103                          sctp_cname(SCTP_ST_CHUNK(chunk->chunk_hdr->type)) :
1104                          "illegal chunk", ntohl(chunk->subh.data_hdr->tsn),
1105                          chunk->skb ? chunk->skb->head : NULL, chunk->skb ?
1106                          refcount_read(&chunk->skb->users) : -1);
1107
1108                 /* Add the chunk to the packet.  */
1109                 status = sctp_packet_transmit_chunk(ctx->packet, chunk, 0,
1110                                                     ctx->gfp);
1111                 if (status != SCTP_XMIT_OK) {
1112                         /* We could not append this chunk, so put
1113                          * the chunk back on the output queue.
1114                          */
1115                         pr_debug("%s: could not transmit tsn:0x%x, status:%d\n",
1116                                  __func__, ntohl(chunk->subh.data_hdr->tsn),
1117                                  status);
1118
1119                         sctp_outq_head_data(ctx->q, chunk);
1120                         break;
1121                 }
1122
1123                 /* The sender is in the SHUTDOWN-PENDING state,
1124                  * The sender MAY set the I-bit in the DATA
1125                  * chunk header.
1126                  */
1127                 if (ctx->asoc->state == SCTP_STATE_SHUTDOWN_PENDING)
1128                         chunk->chunk_hdr->flags |= SCTP_DATA_SACK_IMM;
1129                 if (chunk->chunk_hdr->flags & SCTP_DATA_UNORDERED)
1130                         ctx->asoc->stats.ouodchunks++;
1131                 else
1132                         ctx->asoc->stats.oodchunks++;
1133
1134                 /* Only now it's safe to consider this
1135                  * chunk as sent, sched-wise.
1136                  */
1137                 sctp_sched_dequeue_done(ctx->q, chunk);
1138
1139                 list_add_tail(&chunk->transmitted_list,
1140                               &ctx->transport->transmitted);
1141
1142                 sctp_transport_reset_t3_rtx(ctx->transport);
1143                 ctx->transport->last_time_sent = jiffies;
1144
1145                 /* Only let one DATA chunk get bundled with a
1146                  * COOKIE-ECHO chunk.
1147                  */
1148                 if (ctx->packet->has_cookie_echo)
1149                         break;
1150         }
1151 }
1152
1153 static void sctp_outq_flush_transports(struct sctp_flush_ctx *ctx)
1154 {
1155         struct list_head *ltransport;
1156         struct sctp_packet *packet;
1157         struct sctp_transport *t;
1158         int error = 0;
1159
1160         while ((ltransport = sctp_list_dequeue(&ctx->transport_list)) != NULL) {
1161                 t = list_entry(ltransport, struct sctp_transport, send_ready);
1162                 packet = &t->packet;
1163                 if (!sctp_packet_empty(packet)) {
1164                         error = sctp_packet_transmit(packet, ctx->gfp);
1165                         if (error < 0)
1166                                 ctx->q->asoc->base.sk->sk_err = -error;
1167                 }
1168
1169                 /* Clear the burst limited state, if any */
1170                 sctp_transport_burst_reset(t);
1171         }
1172 }
1173
1174 /* Try to flush an outqueue.
1175  *
1176  * Description: Send everything in q which we legally can, subject to
1177  * congestion limitations.
1178  * * Note: This function can be called from multiple contexts so appropriate
1179  * locking concerns must be made.  Today we use the sock lock to protect
1180  * this function.
1181  */
1182
1183 static void sctp_outq_flush(struct sctp_outq *q, int rtx_timeout, gfp_t gfp)
1184 {
1185         struct sctp_flush_ctx ctx = {
1186                 .q = q,
1187                 .transport = NULL,
1188                 .transport_list = LIST_HEAD_INIT(ctx.transport_list),
1189                 .asoc = q->asoc,
1190                 .packet = NULL,
1191                 .gfp = gfp,
1192         };
1193
1194         /* 6.10 Bundling
1195          *   ...
1196          *   When bundling control chunks with DATA chunks, an
1197          *   endpoint MUST place control chunks first in the outbound
1198          *   SCTP packet.  The transmitter MUST transmit DATA chunks
1199          *   within a SCTP packet in increasing order of TSN.
1200          *   ...
1201          */
1202
1203         sctp_outq_flush_ctrl(&ctx);
1204
1205         if (q->asoc->src_out_of_asoc_ok)
1206                 goto sctp_flush_out;
1207
1208         sctp_outq_flush_data(&ctx, rtx_timeout);
1209
1210 sctp_flush_out:
1211
1212         sctp_outq_flush_transports(&ctx);
1213 }
1214
1215 /* Update unack_data based on the incoming SACK chunk */
1216 static void sctp_sack_update_unack_data(struct sctp_association *assoc,
1217                                         struct sctp_sackhdr *sack)
1218 {
1219         union sctp_sack_variable *frags;
1220         __u16 unack_data;
1221         int i;
1222
1223         unack_data = assoc->next_tsn - assoc->ctsn_ack_point - 1;
1224
1225         frags = sack->variable;
1226         for (i = 0; i < ntohs(sack->num_gap_ack_blocks); i++) {
1227                 unack_data -= ((ntohs(frags[i].gab.end) -
1228                                 ntohs(frags[i].gab.start) + 1));
1229         }
1230
1231         assoc->unack_data = unack_data;
1232 }
1233
1234 /* This is where we REALLY process a SACK.
1235  *
1236  * Process the SACK against the outqueue.  Mostly, this just frees
1237  * things off the transmitted queue.
1238  */
1239 int sctp_outq_sack(struct sctp_outq *q, struct sctp_chunk *chunk)
1240 {
1241         struct sctp_association *asoc = q->asoc;
1242         struct sctp_sackhdr *sack = chunk->subh.sack_hdr;
1243         struct sctp_transport *transport;
1244         struct sctp_chunk *tchunk = NULL;
1245         struct list_head *lchunk, *transport_list, *temp;
1246         union sctp_sack_variable *frags = sack->variable;
1247         __u32 sack_ctsn, ctsn, tsn;
1248         __u32 highest_tsn, highest_new_tsn;
1249         __u32 sack_a_rwnd;
1250         unsigned int outstanding;
1251         struct sctp_transport *primary = asoc->peer.primary_path;
1252         int count_of_newacks = 0;
1253         int gap_ack_blocks;
1254         u8 accum_moved = 0;
1255
1256         /* Grab the association's destination address list. */
1257         transport_list = &asoc->peer.transport_addr_list;
1258
1259         sack_ctsn = ntohl(sack->cum_tsn_ack);
1260         gap_ack_blocks = ntohs(sack->num_gap_ack_blocks);
1261         asoc->stats.gapcnt += gap_ack_blocks;
1262         /*
1263          * SFR-CACC algorithm:
1264          * On receipt of a SACK the sender SHOULD execute the
1265          * following statements.
1266          *
1267          * 1) If the cumulative ack in the SACK passes next tsn_at_change
1268          * on the current primary, the CHANGEOVER_ACTIVE flag SHOULD be
1269          * cleared. The CYCLING_CHANGEOVER flag SHOULD also be cleared for
1270          * all destinations.
1271          * 2) If the SACK contains gap acks and the flag CHANGEOVER_ACTIVE
1272          * is set the receiver of the SACK MUST take the following actions:
1273          *
1274          * A) Initialize the cacc_saw_newack to 0 for all destination
1275          * addresses.
1276          *
1277          * Only bother if changeover_active is set. Otherwise, this is
1278          * totally suboptimal to do on every SACK.
1279          */
1280         if (primary->cacc.changeover_active) {
1281                 u8 clear_cycling = 0;
1282
1283                 if (TSN_lte(primary->cacc.next_tsn_at_change, sack_ctsn)) {
1284                         primary->cacc.changeover_active = 0;
1285                         clear_cycling = 1;
1286                 }
1287
1288                 if (clear_cycling || gap_ack_blocks) {
1289                         list_for_each_entry(transport, transport_list,
1290                                         transports) {
1291                                 if (clear_cycling)
1292                                         transport->cacc.cycling_changeover = 0;
1293                                 if (gap_ack_blocks)
1294                                         transport->cacc.cacc_saw_newack = 0;
1295                         }
1296                 }
1297         }
1298
1299         /* Get the highest TSN in the sack. */
1300         highest_tsn = sack_ctsn;
1301         if (gap_ack_blocks)
1302                 highest_tsn += ntohs(frags[gap_ack_blocks - 1].gab.end);
1303
1304         if (TSN_lt(asoc->highest_sacked, highest_tsn))
1305                 asoc->highest_sacked = highest_tsn;
1306
1307         highest_new_tsn = sack_ctsn;
1308
1309         /* Run through the retransmit queue.  Credit bytes received
1310          * and free those chunks that we can.
1311          */
1312         sctp_check_transmitted(q, &q->retransmit, NULL, NULL, sack, &highest_new_tsn);
1313
1314         /* Run through the transmitted queue.
1315          * Credit bytes received and free those chunks which we can.
1316          *
1317          * This is a MASSIVE candidate for optimization.
1318          */
1319         list_for_each_entry(transport, transport_list, transports) {
1320                 sctp_check_transmitted(q, &transport->transmitted,
1321                                        transport, &chunk->source, sack,
1322                                        &highest_new_tsn);
1323                 /*
1324                  * SFR-CACC algorithm:
1325                  * C) Let count_of_newacks be the number of
1326                  * destinations for which cacc_saw_newack is set.
1327                  */
1328                 if (transport->cacc.cacc_saw_newack)
1329                         count_of_newacks++;
1330         }
1331
1332         /* Move the Cumulative TSN Ack Point if appropriate.  */
1333         if (TSN_lt(asoc->ctsn_ack_point, sack_ctsn)) {
1334                 asoc->ctsn_ack_point = sack_ctsn;
1335                 accum_moved = 1;
1336         }
1337
1338         if (gap_ack_blocks) {
1339
1340                 if (asoc->fast_recovery && accum_moved)
1341                         highest_new_tsn = highest_tsn;
1342
1343                 list_for_each_entry(transport, transport_list, transports)
1344                         sctp_mark_missing(q, &transport->transmitted, transport,
1345                                           highest_new_tsn, count_of_newacks);
1346         }
1347
1348         /* Update unack_data field in the assoc. */
1349         sctp_sack_update_unack_data(asoc, sack);
1350
1351         ctsn = asoc->ctsn_ack_point;
1352
1353         /* Throw away stuff rotting on the sack queue.  */
1354         list_for_each_safe(lchunk, temp, &q->sacked) {
1355                 tchunk = list_entry(lchunk, struct sctp_chunk,
1356                                     transmitted_list);
1357                 tsn = ntohl(tchunk->subh.data_hdr->tsn);
1358                 if (TSN_lte(tsn, ctsn)) {
1359                         list_del_init(&tchunk->transmitted_list);
1360                         if (asoc->peer.prsctp_capable &&
1361                             SCTP_PR_PRIO_ENABLED(chunk->sinfo.sinfo_flags))
1362                                 asoc->sent_cnt_removable--;
1363                         sctp_chunk_free(tchunk);
1364                 }
1365         }
1366
1367         /* ii) Set rwnd equal to the newly received a_rwnd minus the
1368          *     number of bytes still outstanding after processing the
1369          *     Cumulative TSN Ack and the Gap Ack Blocks.
1370          */
1371
1372         sack_a_rwnd = ntohl(sack->a_rwnd);
1373         asoc->peer.zero_window_announced = !sack_a_rwnd;
1374         outstanding = q->outstanding_bytes;
1375
1376         if (outstanding < sack_a_rwnd)
1377                 sack_a_rwnd -= outstanding;
1378         else
1379                 sack_a_rwnd = 0;
1380
1381         asoc->peer.rwnd = sack_a_rwnd;
1382
1383         asoc->stream.si->generate_ftsn(q, sack_ctsn);
1384
1385         pr_debug("%s: sack cumulative tsn ack:0x%x\n", __func__, sack_ctsn);
1386         pr_debug("%s: cumulative tsn ack of assoc:%p is 0x%x, "
1387                  "advertised peer ack point:0x%x\n", __func__, asoc, ctsn,
1388                  asoc->adv_peer_ack_point);
1389
1390         return sctp_outq_is_empty(q);
1391 }
1392
1393 /* Is the outqueue empty?
1394  * The queue is empty when we have not pending data, no in-flight data
1395  * and nothing pending retransmissions.
1396  */
1397 int sctp_outq_is_empty(const struct sctp_outq *q)
1398 {
1399         return q->out_qlen == 0 && q->outstanding_bytes == 0 &&
1400                list_empty(&q->retransmit);
1401 }
1402
1403 /********************************************************************
1404  * 2nd Level Abstractions
1405  ********************************************************************/
1406
1407 /* Go through a transport's transmitted list or the association's retransmit
1408  * list and move chunks that are acked by the Cumulative TSN Ack to q->sacked.
1409  * The retransmit list will not have an associated transport.
1410  *
1411  * I added coherent debug information output.   --xguo
1412  *
1413  * Instead of printing 'sacked' or 'kept' for each TSN on the
1414  * transmitted_queue, we print a range: SACKED: TSN1-TSN2, TSN3, TSN4-TSN5.
1415  * KEPT TSN6-TSN7, etc.
1416  */
1417 static void sctp_check_transmitted(struct sctp_outq *q,
1418                                    struct list_head *transmitted_queue,
1419                                    struct sctp_transport *transport,
1420                                    union sctp_addr *saddr,
1421                                    struct sctp_sackhdr *sack,
1422                                    __u32 *highest_new_tsn_in_sack)
1423 {
1424         struct list_head *lchunk;
1425         struct sctp_chunk *tchunk;
1426         struct list_head tlist;
1427         __u32 tsn;
1428         __u32 sack_ctsn;
1429         __u32 rtt;
1430         __u8 restart_timer = 0;
1431         int bytes_acked = 0;
1432         int migrate_bytes = 0;
1433         bool forward_progress = false;
1434
1435         sack_ctsn = ntohl(sack->cum_tsn_ack);
1436
1437         INIT_LIST_HEAD(&tlist);
1438
1439         /* The while loop will skip empty transmitted queues. */
1440         while (NULL != (lchunk = sctp_list_dequeue(transmitted_queue))) {
1441                 tchunk = list_entry(lchunk, struct sctp_chunk,
1442                                     transmitted_list);
1443
1444                 if (sctp_chunk_abandoned(tchunk)) {
1445                         /* Move the chunk to abandoned list. */
1446                         sctp_insert_list(&q->abandoned, lchunk);
1447
1448                         /* If this chunk has not been acked, stop
1449                          * considering it as 'outstanding'.
1450                          */
1451                         if (transmitted_queue != &q->retransmit &&
1452                             !tchunk->tsn_gap_acked) {
1453                                 if (tchunk->transport)
1454                                         tchunk->transport->flight_size -=
1455                                                         sctp_data_size(tchunk);
1456                                 q->outstanding_bytes -= sctp_data_size(tchunk);
1457                         }
1458                         continue;
1459                 }
1460
1461                 tsn = ntohl(tchunk->subh.data_hdr->tsn);
1462                 if (sctp_acked(sack, tsn)) {
1463                         /* If this queue is the retransmit queue, the
1464                          * retransmit timer has already reclaimed
1465                          * the outstanding bytes for this chunk, so only
1466                          * count bytes associated with a transport.
1467                          */
1468                         if (transport && !tchunk->tsn_gap_acked) {
1469                                 /* If this chunk is being used for RTT
1470                                  * measurement, calculate the RTT and update
1471                                  * the RTO using this value.
1472                                  *
1473                                  * 6.3.1 C5) Karn's algorithm: RTT measurements
1474                                  * MUST NOT be made using packets that were
1475                                  * retransmitted (and thus for which it is
1476                                  * ambiguous whether the reply was for the
1477                                  * first instance of the packet or a later
1478                                  * instance).
1479                                  */
1480                                 if (!sctp_chunk_retransmitted(tchunk) &&
1481                                     tchunk->rtt_in_progress) {
1482                                         tchunk->rtt_in_progress = 0;
1483                                         rtt = jiffies - tchunk->sent_at;
1484                                         sctp_transport_update_rto(transport,
1485                                                                   rtt);
1486                                 }
1487
1488                                 if (TSN_lte(tsn, sack_ctsn)) {
1489                                         /*
1490                                          * SFR-CACC algorithm:
1491                                          * 2) If the SACK contains gap acks
1492                                          * and the flag CHANGEOVER_ACTIVE is
1493                                          * set the receiver of the SACK MUST
1494                                          * take the following action:
1495                                          *
1496                                          * B) For each TSN t being acked that
1497                                          * has not been acked in any SACK so
1498                                          * far, set cacc_saw_newack to 1 for
1499                                          * the destination that the TSN was
1500                                          * sent to.
1501                                          */
1502                                         if (sack->num_gap_ack_blocks &&
1503                                             q->asoc->peer.primary_path->cacc.
1504                                             changeover_active)
1505                                                 transport->cacc.cacc_saw_newack
1506                                                         = 1;
1507                                 }
1508                         }
1509
1510                         /* If the chunk hasn't been marked as ACKED,
1511                          * mark it and account bytes_acked if the
1512                          * chunk had a valid transport (it will not
1513                          * have a transport if ASCONF had deleted it
1514                          * while DATA was outstanding).
1515                          */
1516                         if (!tchunk->tsn_gap_acked) {
1517                                 tchunk->tsn_gap_acked = 1;
1518                                 if (TSN_lt(*highest_new_tsn_in_sack, tsn))
1519                                         *highest_new_tsn_in_sack = tsn;
1520                                 bytes_acked += sctp_data_size(tchunk);
1521                                 if (!tchunk->transport)
1522                                         migrate_bytes += sctp_data_size(tchunk);
1523                                 forward_progress = true;
1524                         }
1525
1526                         if (TSN_lte(tsn, sack_ctsn)) {
1527                                 /* RFC 2960  6.3.2 Retransmission Timer Rules
1528                                  *
1529                                  * R3) Whenever a SACK is received
1530                                  * that acknowledges the DATA chunk
1531                                  * with the earliest outstanding TSN
1532                                  * for that address, restart T3-rtx
1533                                  * timer for that address with its
1534                                  * current RTO.
1535                                  */
1536                                 restart_timer = 1;
1537                                 forward_progress = true;
1538
1539                                 list_add_tail(&tchunk->transmitted_list,
1540                                               &q->sacked);
1541                         } else {
1542                                 /* RFC2960 7.2.4, sctpimpguide-05 2.8.2
1543                                  * M2) Each time a SACK arrives reporting
1544                                  * 'Stray DATA chunk(s)' record the highest TSN
1545                                  * reported as newly acknowledged, call this
1546                                  * value 'HighestTSNinSack'. A newly
1547                                  * acknowledged DATA chunk is one not
1548                                  * previously acknowledged in a SACK.
1549                                  *
1550                                  * When the SCTP sender of data receives a SACK
1551                                  * chunk that acknowledges, for the first time,
1552                                  * the receipt of a DATA chunk, all the still
1553                                  * unacknowledged DATA chunks whose TSN is
1554                                  * older than that newly acknowledged DATA
1555                                  * chunk, are qualified as 'Stray DATA chunks'.
1556                                  */
1557                                 list_add_tail(lchunk, &tlist);
1558                         }
1559                 } else {
1560                         if (tchunk->tsn_gap_acked) {
1561                                 pr_debug("%s: receiver reneged on data TSN:0x%x\n",
1562                                          __func__, tsn);
1563
1564                                 tchunk->tsn_gap_acked = 0;
1565
1566                                 if (tchunk->transport)
1567                                         bytes_acked -= sctp_data_size(tchunk);
1568
1569                                 /* RFC 2960 6.3.2 Retransmission Timer Rules
1570                                  *
1571                                  * R4) Whenever a SACK is received missing a
1572                                  * TSN that was previously acknowledged via a
1573                                  * Gap Ack Block, start T3-rtx for the
1574                                  * destination address to which the DATA
1575                                  * chunk was originally
1576                                  * transmitted if it is not already running.
1577                                  */
1578                                 restart_timer = 1;
1579                         }
1580
1581                         list_add_tail(lchunk, &tlist);
1582                 }
1583         }
1584
1585         if (transport) {
1586                 if (bytes_acked) {
1587                         struct sctp_association *asoc = transport->asoc;
1588
1589                         /* We may have counted DATA that was migrated
1590                          * to this transport due to DEL-IP operation.
1591                          * Subtract those bytes, since the were never
1592                          * send on this transport and shouldn't be
1593                          * credited to this transport.
1594                          */
1595                         bytes_acked -= migrate_bytes;
1596
1597                         /* 8.2. When an outstanding TSN is acknowledged,
1598                          * the endpoint shall clear the error counter of
1599                          * the destination transport address to which the
1600                          * DATA chunk was last sent.
1601                          * The association's overall error counter is
1602                          * also cleared.
1603                          */
1604                         transport->error_count = 0;
1605                         transport->asoc->overall_error_count = 0;
1606                         forward_progress = true;
1607
1608                         /*
1609                          * While in SHUTDOWN PENDING, we may have started
1610                          * the T5 shutdown guard timer after reaching the
1611                          * retransmission limit. Stop that timer as soon
1612                          * as the receiver acknowledged any data.
1613                          */
1614                         if (asoc->state == SCTP_STATE_SHUTDOWN_PENDING &&
1615                             del_timer(&asoc->timers
1616                                 [SCTP_EVENT_TIMEOUT_T5_SHUTDOWN_GUARD]))
1617                                         sctp_association_put(asoc);
1618
1619                         /* Mark the destination transport address as
1620                          * active if it is not so marked.
1621                          */
1622                         if ((transport->state == SCTP_INACTIVE ||
1623                              transport->state == SCTP_UNCONFIRMED) &&
1624                             sctp_cmp_addr_exact(&transport->ipaddr, saddr)) {
1625                                 sctp_assoc_control_transport(
1626                                         transport->asoc,
1627                                         transport,
1628                                         SCTP_TRANSPORT_UP,
1629                                         SCTP_RECEIVED_SACK);
1630                         }
1631
1632                         sctp_transport_raise_cwnd(transport, sack_ctsn,
1633                                                   bytes_acked);
1634
1635                         transport->flight_size -= bytes_acked;
1636                         if (transport->flight_size == 0)
1637                                 transport->partial_bytes_acked = 0;
1638                         q->outstanding_bytes -= bytes_acked + migrate_bytes;
1639                 } else {
1640                         /* RFC 2960 6.1, sctpimpguide-06 2.15.2
1641                          * When a sender is doing zero window probing, it
1642                          * should not timeout the association if it continues
1643                          * to receive new packets from the receiver. The
1644                          * reason is that the receiver MAY keep its window
1645                          * closed for an indefinite time.
1646                          * A sender is doing zero window probing when the
1647                          * receiver's advertised window is zero, and there is
1648                          * only one data chunk in flight to the receiver.
1649                          *
1650                          * Allow the association to timeout while in SHUTDOWN
1651                          * PENDING or SHUTDOWN RECEIVED in case the receiver
1652                          * stays in zero window mode forever.
1653                          */
1654                         if (!q->asoc->peer.rwnd &&
1655                             !list_empty(&tlist) &&
1656                             (sack_ctsn+2 == q->asoc->next_tsn) &&
1657                             q->asoc->state < SCTP_STATE_SHUTDOWN_PENDING) {
1658                                 pr_debug("%s: sack received for zero window "
1659                                          "probe:%u\n", __func__, sack_ctsn);
1660
1661                                 q->asoc->overall_error_count = 0;
1662                                 transport->error_count = 0;
1663                         }
1664                 }
1665
1666                 /* RFC 2960 6.3.2 Retransmission Timer Rules
1667                  *
1668                  * R2) Whenever all outstanding data sent to an address have
1669                  * been acknowledged, turn off the T3-rtx timer of that
1670                  * address.
1671                  */
1672                 if (!transport->flight_size) {
1673                         if (del_timer(&transport->T3_rtx_timer))
1674                                 sctp_transport_put(transport);
1675                 } else if (restart_timer) {
1676                         if (!mod_timer(&transport->T3_rtx_timer,
1677                                        jiffies + transport->rto))
1678                                 sctp_transport_hold(transport);
1679                 }
1680
1681                 if (forward_progress) {
1682                         if (transport->dst)
1683                                 sctp_transport_dst_confirm(transport);
1684                 }
1685         }
1686
1687         list_splice(&tlist, transmitted_queue);
1688 }
1689
1690 /* Mark chunks as missing and consequently may get retransmitted. */
1691 static void sctp_mark_missing(struct sctp_outq *q,
1692                               struct list_head *transmitted_queue,
1693                               struct sctp_transport *transport,
1694                               __u32 highest_new_tsn_in_sack,
1695                               int count_of_newacks)
1696 {
1697         struct sctp_chunk *chunk;
1698         __u32 tsn;
1699         char do_fast_retransmit = 0;
1700         struct sctp_association *asoc = q->asoc;
1701         struct sctp_transport *primary = asoc->peer.primary_path;
1702
1703         list_for_each_entry(chunk, transmitted_queue, transmitted_list) {
1704
1705                 tsn = ntohl(chunk->subh.data_hdr->tsn);
1706
1707                 /* RFC 2960 7.2.4, sctpimpguide-05 2.8.2 M3) Examine all
1708                  * 'Unacknowledged TSN's', if the TSN number of an
1709                  * 'Unacknowledged TSN' is smaller than the 'HighestTSNinSack'
1710                  * value, increment the 'TSN.Missing.Report' count on that
1711                  * chunk if it has NOT been fast retransmitted or marked for
1712                  * fast retransmit already.
1713                  */
1714                 if (chunk->fast_retransmit == SCTP_CAN_FRTX &&
1715                     !chunk->tsn_gap_acked &&
1716                     TSN_lt(tsn, highest_new_tsn_in_sack)) {
1717
1718                         /* SFR-CACC may require us to skip marking
1719                          * this chunk as missing.
1720                          */
1721                         if (!transport || !sctp_cacc_skip(primary,
1722                                                 chunk->transport,
1723                                                 count_of_newacks, tsn)) {
1724                                 chunk->tsn_missing_report++;
1725
1726                                 pr_debug("%s: tsn:0x%x missing counter:%d\n",
1727                                          __func__, tsn, chunk->tsn_missing_report);
1728                         }
1729                 }
1730                 /*
1731                  * M4) If any DATA chunk is found to have a
1732                  * 'TSN.Missing.Report'
1733                  * value larger than or equal to 3, mark that chunk for
1734                  * retransmission and start the fast retransmit procedure.
1735                  */
1736
1737                 if (chunk->tsn_missing_report >= 3) {
1738                         chunk->fast_retransmit = SCTP_NEED_FRTX;
1739                         do_fast_retransmit = 1;
1740                 }
1741         }
1742
1743         if (transport) {
1744                 if (do_fast_retransmit)
1745                         sctp_retransmit(q, transport, SCTP_RTXR_FAST_RTX);
1746
1747                 pr_debug("%s: transport:%p, cwnd:%d, ssthresh:%d, "
1748                          "flight_size:%d, pba:%d\n",  __func__, transport,
1749                          transport->cwnd, transport->ssthresh,
1750                          transport->flight_size, transport->partial_bytes_acked);
1751         }
1752 }
1753
1754 /* Is the given TSN acked by this packet?  */
1755 static int sctp_acked(struct sctp_sackhdr *sack, __u32 tsn)
1756 {
1757         __u32 ctsn = ntohl(sack->cum_tsn_ack);
1758         union sctp_sack_variable *frags;
1759         __u16 tsn_offset, blocks;
1760         int i;
1761
1762         if (TSN_lte(tsn, ctsn))
1763                 goto pass;
1764
1765         /* 3.3.4 Selective Acknowledgment (SACK) (3):
1766          *
1767          * Gap Ack Blocks:
1768          *  These fields contain the Gap Ack Blocks. They are repeated
1769          *  for each Gap Ack Block up to the number of Gap Ack Blocks
1770          *  defined in the Number of Gap Ack Blocks field. All DATA
1771          *  chunks with TSNs greater than or equal to (Cumulative TSN
1772          *  Ack + Gap Ack Block Start) and less than or equal to
1773          *  (Cumulative TSN Ack + Gap Ack Block End) of each Gap Ack
1774          *  Block are assumed to have been received correctly.
1775          */
1776
1777         frags = sack->variable;
1778         blocks = ntohs(sack->num_gap_ack_blocks);
1779         tsn_offset = tsn - ctsn;
1780         for (i = 0; i < blocks; ++i) {
1781                 if (tsn_offset >= ntohs(frags[i].gab.start) &&
1782                     tsn_offset <= ntohs(frags[i].gab.end))
1783                         goto pass;
1784         }
1785
1786         return 0;
1787 pass:
1788         return 1;
1789 }
1790
1791 static inline int sctp_get_skip_pos(struct sctp_fwdtsn_skip *skiplist,
1792                                     int nskips, __be16 stream)
1793 {
1794         int i;
1795
1796         for (i = 0; i < nskips; i++) {
1797                 if (skiplist[i].stream == stream)
1798                         return i;
1799         }
1800         return i;
1801 }
1802
1803 /* Create and add a fwdtsn chunk to the outq's control queue if needed. */
1804 void sctp_generate_fwdtsn(struct sctp_outq *q, __u32 ctsn)
1805 {
1806         struct sctp_association *asoc = q->asoc;
1807         struct sctp_chunk *ftsn_chunk = NULL;
1808         struct sctp_fwdtsn_skip ftsn_skip_arr[10];
1809         int nskips = 0;
1810         int skip_pos = 0;
1811         __u32 tsn;
1812         struct sctp_chunk *chunk;
1813         struct list_head *lchunk, *temp;
1814
1815         if (!asoc->peer.prsctp_capable)
1816                 return;
1817
1818         /* PR-SCTP C1) Let SackCumAck be the Cumulative TSN ACK carried in the
1819          * received SACK.
1820          *
1821          * If (Advanced.Peer.Ack.Point < SackCumAck), then update
1822          * Advanced.Peer.Ack.Point to be equal to SackCumAck.
1823          */
1824         if (TSN_lt(asoc->adv_peer_ack_point, ctsn))
1825                 asoc->adv_peer_ack_point = ctsn;
1826
1827         /* PR-SCTP C2) Try to further advance the "Advanced.Peer.Ack.Point"
1828          * locally, that is, to move "Advanced.Peer.Ack.Point" up as long as
1829          * the chunk next in the out-queue space is marked as "abandoned" as
1830          * shown in the following example:
1831          *
1832          * Assuming that a SACK arrived with the Cumulative TSN ACK 102
1833          * and the Advanced.Peer.Ack.Point is updated to this value:
1834          *
1835          *   out-queue at the end of  ==>   out-queue after Adv.Ack.Point
1836          *   normal SACK processing           local advancement
1837          *                ...                           ...
1838          *   Adv.Ack.Pt-> 102 acked                     102 acked
1839          *                103 abandoned                 103 abandoned
1840          *                104 abandoned     Adv.Ack.P-> 104 abandoned
1841          *                105                           105
1842          *                106 acked                     106 acked
1843          *                ...                           ...
1844          *
1845          * In this example, the data sender successfully advanced the
1846          * "Advanced.Peer.Ack.Point" from 102 to 104 locally.
1847          */
1848         list_for_each_safe(lchunk, temp, &q->abandoned) {
1849                 chunk = list_entry(lchunk, struct sctp_chunk,
1850                                         transmitted_list);
1851                 tsn = ntohl(chunk->subh.data_hdr->tsn);
1852
1853                 /* Remove any chunks in the abandoned queue that are acked by
1854                  * the ctsn.
1855                  */
1856                 if (TSN_lte(tsn, ctsn)) {
1857                         list_del_init(lchunk);
1858                         sctp_chunk_free(chunk);
1859                 } else {
1860                         if (TSN_lte(tsn, asoc->adv_peer_ack_point+1)) {
1861                                 asoc->adv_peer_ack_point = tsn;
1862                                 if (chunk->chunk_hdr->flags &
1863                                          SCTP_DATA_UNORDERED)
1864                                         continue;
1865                                 skip_pos = sctp_get_skip_pos(&ftsn_skip_arr[0],
1866                                                 nskips,
1867                                                 chunk->subh.data_hdr->stream);
1868                                 ftsn_skip_arr[skip_pos].stream =
1869                                         chunk->subh.data_hdr->stream;
1870                                 ftsn_skip_arr[skip_pos].ssn =
1871                                          chunk->subh.data_hdr->ssn;
1872                                 if (skip_pos == nskips)
1873                                         nskips++;
1874                                 if (nskips == 10)
1875                                         break;
1876                         } else
1877                                 break;
1878                 }
1879         }
1880
1881         /* PR-SCTP C3) If, after step C1 and C2, the "Advanced.Peer.Ack.Point"
1882          * is greater than the Cumulative TSN ACK carried in the received
1883          * SACK, the data sender MUST send the data receiver a FORWARD TSN
1884          * chunk containing the latest value of the
1885          * "Advanced.Peer.Ack.Point".
1886          *
1887          * C4) For each "abandoned" TSN the sender of the FORWARD TSN SHOULD
1888          * list each stream and sequence number in the forwarded TSN. This
1889          * information will enable the receiver to easily find any
1890          * stranded TSN's waiting on stream reorder queues. Each stream
1891          * SHOULD only be reported once; this means that if multiple
1892          * abandoned messages occur in the same stream then only the
1893          * highest abandoned stream sequence number is reported. If the
1894          * total size of the FORWARD TSN does NOT fit in a single MTU then
1895          * the sender of the FORWARD TSN SHOULD lower the
1896          * Advanced.Peer.Ack.Point to the last TSN that will fit in a
1897          * single MTU.
1898          */
1899         if (asoc->adv_peer_ack_point > ctsn)
1900                 ftsn_chunk = sctp_make_fwdtsn(asoc, asoc->adv_peer_ack_point,
1901                                               nskips, &ftsn_skip_arr[0]);
1902
1903         if (ftsn_chunk) {
1904                 list_add_tail(&ftsn_chunk->list, &q->control_chunk_list);
1905                 SCTP_INC_STATS(sock_net(asoc->base.sk), SCTP_MIB_OUTCTRLCHUNKS);
1906         }
1907 }