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, write to
  26  * the Free Software Foundation, 59 Temple Place - Suite 330,
  27  * Boston, MA 02111-1307, USA.
  28  *
  29  * Please send any bug reports or fixes you make to the
  30  * email address(es):
  31  *    lksctp developers <lksctp-developers@lists.sourceforge.net>
  32  *
  33  * Or submit a bug report through the following website:
  34  *    http://www.sf.net/projects/lksctp
  35  *
  36  * Written or modified by:
  37  *    La Monte H.P. Yarroll <piggy@acm.org>
  38  *    Karl Knutson          <karl@athena.chicago.il.us>
  39  *    Perry Melange         <pmelange@null.cc.uic.edu>
  40  *    Xingang Guo           <xingang.guo@intel.com>
  41  *    Hui Huang             <hui.huang@nokia.com>
  42  *    Sridhar Samudrala     <sri@us.ibm.com>
  43  *    Jon Grimm             <jgrimm@us.ibm.com>
  44  *
  45  * Any bugs reported given to us we will try to fix... any fixes shared will
  46  * be incorporated into the next SCTP release.
  47  */
  48
  49 #include <linux/types.h>
  50 #include <linux/list.h>   /* For struct list_head */
  51 #include <linux/socket.h>
  52 #include <linux/ip.h>
  53 #include <net/sock.h>     /* For skb_set_owner_w */
  54
  55 #include <net/sctp/sctp.h>
  56 #include <net/sctp/sm.h>
  57
  58 /* Declare internal functions here.  */
  59 static int sctp_acked(struct sctp_sackhdr *sack, __u32 tsn);
  60 static void sctp_check_transmitted(struct sctp_outq *q,
  61                                    struct list_head *transmitted_queue,
  62                                    struct sctp_transport *transport,
  63                                    struct sctp_sackhdr *sack,
  64                                    __u32 highest_new_tsn);
  65
  66 static void sctp_mark_missing(struct sctp_outq *q,
  67                               struct list_head *transmitted_queue,
  68                               struct sctp_transport *transport,
  69                               __u32 highest_new_tsn,
  70                               int count_of_newacks);
  71
  72 static void sctp_generate_fwdtsn(struct sctp_outq *q, __u32 sack_ctsn);
  73
  74 static int sctp_outq_flush(struct sctp_outq *q, int rtx_timeout);
  75
  76 /* Add data to the front of the queue. */
  77 static inline void sctp_outq_head_data(struct sctp_outq *q,
  78                                         struct sctp_chunk *ch)
  79 {
  80         list_add(&ch->list, &q->out_chunk_list);
  81         q->out_qlen += ch->skb->len;
  82         return;
  83 }
  84
  85 /* Take data from the front of the queue. */
  86 static inline struct sctp_chunk *sctp_outq_dequeue_data(struct sctp_outq *q)
  87 {
  88         struct sctp_chunk *ch = NULL;
  89
  90         if (!list_empty(&q->out_chunk_list)) {
  91                 struct list_head *entry = q->out_chunk_list.next;
  92
  93                 ch = list_entry(entry, struct sctp_chunk, list);
  94                 list_del_init(entry);
  95                 q->out_qlen -= ch->skb->len;
  96         }
  97         return ch;
  98 }
  99 /* Add data chunk to the end of the queue. */
 100 static inline void sctp_outq_tail_data(struct sctp_outq *q,
 101                                        struct sctp_chunk *ch)
 102 {
 103         list_add_tail(&ch->list, &q->out_chunk_list);
 104         q->out_qlen += ch->skb->len;
 105         return;
 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 && !transport->cacc.cacc_saw_newack)
 134                 return 1;
 135         return 0;
 136 }
 137
 138 /*
 139  * SFR-CACC algorithm:
 140  * 3.1) If CYCLING_CHANGEOVER is 0, the sender SHOULD
 141  * execute steps C, D, F.
 142  *
 143  * C has been implemented in sctp_outq_sack
 144  */
 145 static inline int sctp_cacc_skip_3_1(struct sctp_transport *primary,
 146                                      struct sctp_transport *transport,
 147                                      int count_of_newacks)
 148 {
 149         if (!primary->cacc.cycling_changeover) {
 150                 if (sctp_cacc_skip_3_1_d(primary, transport, count_of_newacks))
 151                         return 1;
 152                 if (sctp_cacc_skip_3_1_f(transport, count_of_newacks))
 153                         return 1;
 154                 return 0;
 155         }
 156         return 0;
 157 }
 158
 159 /*
 160  * SFR-CACC algorithm:
 161  * 3.2) Else if CYCLING_CHANGEOVER is 1, and t is less
 162  * than next_tsn_at_change of the current primary, then
 163  * the sender MUST NOT increment missing report count
 164  * for t.
 165  */
 166 static inline int sctp_cacc_skip_3_2(struct sctp_transport *primary, __u32 tsn)
 167 {
 168         if (primary->cacc.cycling_changeover &&
 169             TSN_lt(tsn, primary->cacc.next_tsn_at_change))
 170                 return 1;
 171         return 0;
 172 }
 173
 174 /*
 175  * SFR-CACC algorithm:
 176  * 3) If the missing report count for TSN t is to be
 177  * incremented according to [RFC2960] and
 178  * [SCTP_STEWART-2002], and CHANGEOVER_ACTIVE is set,
 179  * then the sender MUST futher execute steps 3.1 and
 180  * 3.2 to determine if the missing report count for
 181  * TSN t SHOULD NOT be incremented.
 182  *
 183  * 3.3) If 3.1 and 3.2 do not dictate that the missing
 184  * report count for t should not be incremented, then
 185  * the sender SOULD increment missing report count for
 186  * t (according to [RFC2960] and [SCTP_STEWART_2002]).
 187  */
 188 static inline int sctp_cacc_skip(struct sctp_transport *primary,
 189                                  struct sctp_transport *transport,
 190                                  int count_of_newacks,
 191                                  __u32 tsn)
 192 {
 193         if (primary->cacc.changeover_active &&
 194             (sctp_cacc_skip_3_1(primary, transport, count_of_newacks)
 195              || sctp_cacc_skip_3_2(primary, tsn)))
 196                 return 1;
 197         return 0;
 198 }
 199
 200 /* Initialize an existing sctp_outq.  This does the boring stuff.
 201  * You still need to define handlers if you really want to DO
 202  * something with this structure...
 203  */
 204 void sctp_outq_init(struct sctp_association *asoc, struct sctp_outq *q)
 205 {
 206         q->asoc = asoc;
 207         INIT_LIST_HEAD(&q->out_chunk_list);
 208         INIT_LIST_HEAD(&q->control_chunk_list);
 209         INIT_LIST_HEAD(&q->retransmit);
 210         INIT_LIST_HEAD(&q->sacked);
 211         INIT_LIST_HEAD(&q->abandoned);
 212
 213         q->fast_rtx = 0;
 214         q->outstanding_bytes = 0;
 215         q->empty = 1;
 216         q->cork  = 0;
 217
 218         q->malloced = 0;
 219         q->out_qlen = 0;
 220 }
 221
 222 /* Free the outqueue structure and any related pending chunks.
 223  */
 224 void sctp_outq_teardown(struct sctp_outq *q)
 225 {
 226         struct sctp_transport *transport;
 227         struct list_head *lchunk, *temp;
 228         struct sctp_chunk *chunk, *tmp;
 229
 230         /* Throw away unacknowledged chunks. */
 231         list_for_each_entry(transport, &q->asoc->peer.transport_addr_list,
 232                         transports) {
 233                 while ((lchunk = sctp_list_dequeue(&transport->transmitted)) != NULL) {
 234                         chunk = list_entry(lchunk, struct sctp_chunk,
 235                                            transmitted_list);
 236                         /* Mark as part of a failed message. */
 237                         sctp_chunk_fail(chunk, q->error);
 238                         sctp_chunk_free(chunk);
 239                 }
 240         }
 241
 242         /* Throw away chunks that have been gap ACKed.  */
 243         list_for_each_safe(lchunk, temp, &q->sacked) {
 244                 list_del_init(lchunk);
 245                 chunk = list_entry(lchunk, struct sctp_chunk,
 246                                    transmitted_list);
 247                 sctp_chunk_fail(chunk, q->error);
 248                 sctp_chunk_free(chunk);
 249         }
 250
 251         /* Throw away any chunks in the retransmit queue. */
 252         list_for_each_safe(lchunk, temp, &q->retransmit) {
 253                 list_del_init(lchunk);
 254                 chunk = list_entry(lchunk, struct sctp_chunk,
 255                                    transmitted_list);
 256                 sctp_chunk_fail(chunk, q->error);
 257                 sctp_chunk_free(chunk);
 258         }
 259
 260         /* Throw away any chunks that are in the abandoned queue. */
 261         list_for_each_safe(lchunk, temp, &q->abandoned) {
 262                 list_del_init(lchunk);
 263                 chunk = list_entry(lchunk, struct sctp_chunk,
 264                                    transmitted_list);
 265                 sctp_chunk_fail(chunk, q->error);
 266                 sctp_chunk_free(chunk);
 267         }
 268
 269         /* Throw away any leftover data chunks. */
 270         while ((chunk = sctp_outq_dequeue_data(q)) != NULL) {
 271
 272                 /* Mark as send failure. */
 273                 sctp_chunk_fail(chunk, q->error);
 274                 sctp_chunk_free(chunk);
 275         }
 276
 277         q->error = 0;
 278
 279         /* Throw away any leftover control chunks. */
 280         list_for_each_entry_safe(chunk, tmp, &q->control_chunk_list, list) {
 281                 list_del_init(&chunk->list);
 282                 sctp_chunk_free(chunk);
 283         }
 284 }
 285
 286 /* Free the outqueue structure and any related pending chunks.  */
 287 void sctp_outq_free(struct sctp_outq *q)
 288 {
 289         /* Throw away leftover chunks. */
 290         sctp_outq_teardown(q);
 291
 292         /* If we were kmalloc()'d, free the memory.  */
 293         if (q->malloced)
 294                 kfree(q);
 295 }
 296
 297 /* Put a new chunk in an sctp_outq.  */
 298 int sctp_outq_tail(struct sctp_outq *q, struct sctp_chunk *chunk)
 299 {
 300         int error = 0;
 301
 302         SCTP_DEBUG_PRINTK("sctp_outq_tail(%p, %p[%s])\n",
 303                           q, chunk, chunk && chunk->chunk_hdr ?
 304                           sctp_cname(SCTP_ST_CHUNK(chunk->chunk_hdr->type))
 305                           : "Illegal Chunk");
 306
 307         /* If it is data, queue it up, otherwise, send it
 308          * immediately.
 309          */
 310         if (SCTP_CID_DATA == chunk->chunk_hdr->type) {
 311                 /* Is it OK to queue data chunks?  */
 312                 /* From 9. Termination of Association
 313                  *
 314                  * When either endpoint performs a shutdown, the
 315                  * association on each peer will stop accepting new
 316                  * data from its user and only deliver data in queue
 317                  * at the time of sending or receiving the SHUTDOWN
 318                  * chunk.
 319                  */
 320                 switch (q->asoc->state) {
 321                 case SCTP_STATE_EMPTY:
 322                 case SCTP_STATE_CLOSED:
 323                 case SCTP_STATE_SHUTDOWN_PENDING:
 324                 case SCTP_STATE_SHUTDOWN_SENT:
 325                 case SCTP_STATE_SHUTDOWN_RECEIVED:
 326                 case SCTP_STATE_SHUTDOWN_ACK_SENT:
 327                         /* Cannot send after transport endpoint shutdown */
 328                         error = -ESHUTDOWN;
 329                         break;
 330
 331                 default:
 332                         SCTP_DEBUG_PRINTK("outqueueing (%p, %p[%s])\n",
 333                           q, chunk, chunk && chunk->chunk_hdr ?
 334                           sctp_cname(SCTP_ST_CHUNK(chunk->chunk_hdr->type))
 335                           : "Illegal Chunk");
 336
 337                         sctp_outq_tail_data(q, chunk);
 338                         if (chunk->chunk_hdr->flags & SCTP_DATA_UNORDERED)
 339                                 SCTP_INC_STATS(SCTP_MIB_OUTUNORDERCHUNKS);
 340                         else
 341                                 SCTP_INC_STATS(SCTP_MIB_OUTORDERCHUNKS);
 342                         q->empty = 0;
 343                         break;
 344                 }
 345         } else {
 346                 list_add_tail(&chunk->list, &q->control_chunk_list);
 347                 SCTP_INC_STATS(SCTP_MIB_OUTCTRLCHUNKS);
 348         }
 349
 350         if (error < 0)
 351                 return error;
 352
 353         if (!q->cork)
 354                 error = sctp_outq_flush(q, 0);
 355
 356         return error;
 357 }
 358
 359 /* Insert a chunk into the sorted list based on the TSNs.  The retransmit list
 360  * and the abandoned list are in ascending order.
 361  */
 362 static void sctp_insert_list(struct list_head *head, struct list_head *new)
 363 {
 364         struct list_head *pos;
 365         struct sctp_chunk *nchunk, *lchunk;
 366         __u32 ntsn, ltsn;
 367         int done = 0;
 368
 369         nchunk = list_entry(new, struct sctp_chunk, transmitted_list);
 370         ntsn = ntohl(nchunk->subh.data_hdr->tsn);
 371
 372         list_for_each(pos, head) {
 373                 lchunk = list_entry(pos, struct sctp_chunk, transmitted_list);
 374                 ltsn = ntohl(lchunk->subh.data_hdr->tsn);
 375                 if (TSN_lt(ntsn, ltsn)) {
 376                         list_add(new, pos->prev);
 377                         done = 1;
 378                         break;
 379                 }
 380         }
 381         if (!done)
 382                 list_add_tail(new, head);
 383 }
 384
 385 /* Mark all the eligible packets on a transport for retransmission.  */
 386 void sctp_retransmit_mark(struct sctp_outq *q,
 387                           struct sctp_transport *transport,
 388                           __u8 reason)
 389 {
 390         struct list_head *lchunk, *ltemp;
 391         struct sctp_chunk *chunk;
 392
 393         /* Walk through the specified transmitted queue.  */
 394         list_for_each_safe(lchunk, ltemp, &transport->transmitted) {
 395                 chunk = list_entry(lchunk, struct sctp_chunk,
 396                                    transmitted_list);
 397
 398                 /* If the chunk is abandoned, move it to abandoned list. */
 399                 if (sctp_chunk_abandoned(chunk)) {
 400                         list_del_init(lchunk);
 401                         sctp_insert_list(&q->abandoned, lchunk);
 402
 403                         /* If this chunk has not been previousely acked,
 404                          * stop considering it 'outstanding'.  Our peer
 405                          * will most likely never see it since it will
 406                          * not be retransmitted
 407                          */
 408                         if (!chunk->tsn_gap_acked) {
 409                                 chunk->transport->flight_size -=
 410                                                 sctp_data_size(chunk);
 411                                 q->outstanding_bytes -= sctp_data_size(chunk);
 412                                 q->asoc->peer.rwnd += (sctp_data_size(chunk) +
 413                                                         sizeof(struct sk_buff));
 414                         }
 415                         continue;
 416                 }
 417
 418                 /* If we are doing  retransmission due to a timeout or pmtu
 419                  * discovery, only the  chunks that are not yet acked should
 420                  * be added to the retransmit queue.
 421                  */
 422                 if ((reason == SCTP_RTXR_FAST_RTX  &&
 423                             (chunk->fast_retransmit > 0)) ||
 424                     (reason != SCTP_RTXR_FAST_RTX  && !chunk->tsn_gap_acked)) {
 425                         /* If this chunk was sent less then 1 rto ago, do not
 426                          * retransmit this chunk, but give the peer time
 427                          * to acknowlege it.  Do this only when
 428                          * retransmitting due to T3 timeout.
 429                          */
 430                         if (reason == SCTP_RTXR_T3_RTX &&
 431                             (jiffies - chunk->sent_at) < transport->last_rto)
 432                                 continue;
 433
 434                         /* RFC 2960 6.2.1 Processing a Received SACK
 435                          *
 436                          * C) Any time a DATA chunk is marked for
 437                          * retransmission (via either T3-rtx timer expiration
 438                          * (Section 6.3.3) or via fast retransmit
 439                          * (Section 7.2.4)), add the data size of those
 440                          * chunks to the rwnd.
 441                          */
 442                         q->asoc->peer.rwnd += (sctp_data_size(chunk) +
 443                                                 sizeof(struct sk_buff));
 444                         q->outstanding_bytes -= sctp_data_size(chunk);
 445                         transport->flight_size -= sctp_data_size(chunk);
 446
 447                         /* sctpimpguide-05 Section 2.8.2
 448                          * M5) If a T3-rtx timer expires, the
 449                          * 'TSN.Missing.Report' of all affected TSNs is set
 450                          * to 0.
 451                          */
 452                         chunk->tsn_missing_report = 0;
 453
 454                         /* If a chunk that is being used for RTT measurement
 455                          * has to be retransmitted, we cannot use this chunk
 456                          * anymore for RTT measurements. Reset rto_pending so
 457                          * that a new RTT measurement is started when a new
 458                          * data chunk is sent.
 459                          */
 460                         if (chunk->rtt_in_progress) {
 461                                 chunk->rtt_in_progress = 0;
 462                                 transport->rto_pending = 0;
 463                         }
 464
 465                         /* Move the chunk to the retransmit queue. The chunks
 466                          * on the retransmit queue are always kept in order.
 467                          */
 468                         list_del_init(lchunk);
 469                         sctp_insert_list(&q->retransmit, lchunk);
 470                 }
 471         }
 472
 473         SCTP_DEBUG_PRINTK("%s: transport: %p, reason: %d, "
 474                           "cwnd: %d, ssthresh: %d, flight_size: %d, "
 475                           "pba: %d\n", __func__,
 476                           transport, reason,
 477                           transport->cwnd, transport->ssthresh,
 478                           transport->flight_size,
 479                           transport->partial_bytes_acked);
 480
 481 }
 482
 483 /* Mark all the eligible packets on a transport for retransmission and force
 484  * one packet out.
 485  */
 486 void sctp_retransmit(struct sctp_outq *q, struct sctp_transport *transport,
 487                      sctp_retransmit_reason_t reason)
 488 {
 489         int error = 0;
 490
 491         switch(reason) {
 492         case SCTP_RTXR_T3_RTX:
 493                 SCTP_INC_STATS(SCTP_MIB_T3_RETRANSMITS);
 494                 sctp_transport_lower_cwnd(transport, SCTP_LOWER_CWND_T3_RTX);
 495                 /* Update the retran path if the T3-rtx timer has expired for
 496                  * the current retran path.
 497                  */
 498                 if (transport == transport->asoc->peer.retran_path)
 499                         sctp_assoc_update_retran_path(transport->asoc);
 500                 transport->asoc->rtx_data_chunks +=
 501                         transport->asoc->unack_data;
 502                 break;
 503         case SCTP_RTXR_FAST_RTX:
 504                 SCTP_INC_STATS(SCTP_MIB_FAST_RETRANSMITS);
 505                 sctp_transport_lower_cwnd(transport, SCTP_LOWER_CWND_FAST_RTX);
 506                 q->fast_rtx = 1;
 507                 break;
 508         case SCTP_RTXR_PMTUD:
 509                 SCTP_INC_STATS(SCTP_MIB_PMTUD_RETRANSMITS);
 510                 break;
 511         case SCTP_RTXR_T1_RTX:
 512                 SCTP_INC_STATS(SCTP_MIB_T1_RETRANSMITS);
 513                 transport->asoc->init_retries++;
 514                 break;
 515         default:
 516                 BUG();
 517         }
 518
 519         sctp_retransmit_mark(q, transport, reason);
 520
 521         /* PR-SCTP A5) Any time the T3-rtx timer expires, on any destination,
 522          * the sender SHOULD try to advance the "Advanced.Peer.Ack.Point" by
 523          * following the procedures outlined in C1 - C5.
 524          */
 525         if (reason == SCTP_RTXR_T3_RTX)
 526                 sctp_generate_fwdtsn(q, q->asoc->ctsn_ack_point);
 527
 528         /* Flush the queues only on timeout, since fast_rtx is only
 529          * triggered during sack processing and the queue
 530          * will be flushed at the end.
 531          */
 532         if (reason != SCTP_RTXR_FAST_RTX)
 533                 error = sctp_outq_flush(q, /* rtx_timeout */ 1);
 534
 535         if (error)
 536                 q->asoc->base.sk->sk_err = -error;
 537 }
 538
 539 /*
 540  * Transmit DATA chunks on the retransmit queue.  Upon return from
 541  * sctp_outq_flush_rtx() the packet 'pkt' may contain chunks which
 542  * need to be transmitted by the caller.
 543  * We assume that pkt->transport has already been set.
 544  *
 545  * The return value is a normal kernel error return value.
 546  */
 547 static int sctp_outq_flush_rtx(struct sctp_outq *q, struct sctp_packet *pkt,
 548                                int rtx_timeout, int *start_timer)
 549 {
 550         struct list_head *lqueue;
 551         struct sctp_transport *transport = pkt->transport;
 552         sctp_xmit_t status;
 553         struct sctp_chunk *chunk, *chunk1;
 554         struct sctp_association *asoc;
 555         int fast_rtx;
 556         int error = 0;
 557         int timer = 0;
 558         int done = 0;
 559
 560         asoc = q->asoc;
 561         lqueue = &q->retransmit;
 562         fast_rtx = q->fast_rtx;
 563
 564         /* This loop handles time-out retransmissions, fast retransmissions,
 565          * and retransmissions due to opening of whindow.
 566          *
 567          * RFC 2960 6.3.3 Handle T3-rtx Expiration
 568          *
 569          * E3) Determine how many of the earliest (i.e., lowest TSN)
 570          * outstanding DATA chunks for the address for which the
 571          * T3-rtx has expired will fit into a single packet, subject
 572          * to the MTU constraint for the path corresponding to the
 573          * destination transport address to which the retransmission
 574          * is being sent (this may be different from the address for
 575          * which the timer expires [see Section 6.4]). Call this value
 576          * K. Bundle and retransmit those K DATA chunks in a single
 577          * packet to the destination endpoint.
 578          *
 579          * [Just to be painfully clear, if we are retransmitting
 580          * because a timeout just happened, we should send only ONE
 581          * packet of retransmitted data.]
 582          *
 583          * For fast retransmissions we also send only ONE packet.  However,
 584          * if we are just flushing the queue due to open window, we'll
 585          * try to send as much as possible.
 586          */
 587         list_for_each_entry_safe(chunk, chunk1, lqueue, transmitted_list) {
 588
 589                 /* Make sure that Gap Acked TSNs are not retransmitted.  A
 590                  * simple approach is just to move such TSNs out of the
 591                  * way and into a 'transmitted' queue and skip to the
 592                  * next chunk.
 593                  */
 594                 if (chunk->tsn_gap_acked) {
 595                         list_del(&chunk->transmitted_list);
 596                         list_add_tail(&chunk->transmitted_list,
 597                                         &transport->transmitted);
 598                         continue;
 599                 }
 600
 601                 /* If we are doing fast retransmit, ignore non-fast_rtransmit
 602                  * chunks
 603                  */
 604                 if (fast_rtx && !chunk->fast_retransmit)
 605                         continue;
 606
 607                 /* Attempt to append this chunk to the packet. */
 608                 status = sctp_packet_append_chunk(pkt, chunk);
 609
 610                 switch (status) {
 611                 case SCTP_XMIT_PMTU_FULL:
 612                         /* Send this packet.  */
 613                         error = sctp_packet_transmit(pkt);
 614
 615                         /* If we are retransmitting, we should only
 616                          * send a single packet.
 617                          */
 618                         if (rtx_timeout || fast_rtx)
 619                                 done = 1;
 620
 621                         /* Bundle next chunk in the next round.  */
 622                         break;
 623
 624                 case SCTP_XMIT_RWND_FULL:
 625                         /* Send this packet. */
 626                         error = sctp_packet_transmit(pkt);
 627
 628                         /* Stop sending DATA as there is no more room
 629                          * at the receiver.
 630                          */
 631                         done = 1;
 632                         break;
 633
 634                 case SCTP_XMIT_NAGLE_DELAY:
 635                         /* Send this packet. */
 636                         error = sctp_packet_transmit(pkt);
 637
 638                         /* Stop sending DATA because of nagle delay. */
 639                         done = 1;
 640                         break;
 641
 642                 default:
 643                         /* The append was successful, so add this chunk to
 644                          * the transmitted list.
 645                          */
 646                         list_del(&chunk->transmitted_list);
 647                         list_add_tail(&chunk->transmitted_list,
 648                                         &transport->transmitted);
 649
 650                         /* Mark the chunk as ineligible for fast retransmit
 651                          * after it is retransmitted.
 652                          */
 653                         if (chunk->fast_retransmit > 0)
 654                                 chunk->fast_retransmit = -1;
 655
 656                         /* Force start T3-rtx timer when fast retransmitting
 657                          * the earliest outstanding TSN
 658                          */
 659                         if (!timer && fast_rtx &&
 660                             ntohl(chunk->subh.data_hdr->tsn) ==
 661                                              asoc->ctsn_ack_point + 1)
 662                                 timer = 2;
 663
 664                         q->empty = 0;
 665                         break;
 666                 }
 667
 668                 /* Set the timer if there were no errors */
 669                 if (!error && !timer)
 670                         timer = 1;
 671
 672                 if (done)
 673                         break;
 674         }
 675
 676         /* If we are here due to a retransmit timeout or a fast
 677          * retransmit and if there are any chunks left in the retransmit
 678          * queue that could not fit in the PMTU sized packet, they need
 679          * to be marked as ineligible for a subsequent fast retransmit.
 680          */
 681         if (rtx_timeout || fast_rtx) {
 682                 list_for_each_entry(chunk1, lqueue, transmitted_list) {
 683                         if (chunk1->fast_retransmit > 0)
 684                                 chunk1->fast_retransmit = -1;
 685                 }
 686         }
 687
 688         *start_timer = timer;
 689
 690         /* Clear fast retransmit hint */
 691         if (fast_rtx)
 692                 q->fast_rtx = 0;
 693
 694         return error;
 695 }
 696
 697 /* Cork the outqueue so queued chunks are really queued. */
 698 int sctp_outq_uncork(struct sctp_outq *q)
 699 {
 700         int error = 0;
 701         if (q->cork)
 702                 q->cork = 0;
 703         error = sctp_outq_flush(q, 0);
 704         return error;
 705 }
 706
 707
 708 /*
 709  * Try to flush an outqueue.
 710  *
 711  * Description: Send everything in q which we legally can, subject to
 712  * congestion limitations.
 713  * * Note: This function can be called from multiple contexts so appropriate
 714  * locking concerns must be made.  Today we use the sock lock to protect
 715  * this function.
 716  */
 717 static int sctp_outq_flush(struct sctp_outq *q, int rtx_timeout)
 718 {
 719         struct sctp_packet *packet;
 720         struct sctp_packet singleton;
 721         struct sctp_association *asoc = q->asoc;
 722         __u16 sport = asoc->base.bind_addr.port;
 723         __u16 dport = asoc->peer.port;
 724         __u32 vtag = asoc->peer.i.init_tag;
 725         struct sctp_transport *transport = NULL;
 726         struct sctp_transport *new_transport;
 727         struct sctp_chunk *chunk, *tmp;
 728         sctp_xmit_t status;
 729         int error = 0;
 730         int start_timer = 0;
 731         int one_packet = 0;
 732
 733         /* These transports have chunks to send. */
 734         struct list_head transport_list;
 735         struct list_head *ltransport;
 736
 737         INIT_LIST_HEAD(&transport_list);
 738         packet = NULL;
 739
 740         /*
 741          * 6.10 Bundling
 742          *   ...
 743          *   When bundling control chunks with DATA chunks, an
 744          *   endpoint MUST place control chunks first in the outbound
 745          *   SCTP packet.  The transmitter MUST transmit DATA chunks
 746          *   within a SCTP packet in increasing order of TSN.
 747          *   ...
 748          */
 749
 750         list_for_each_entry_safe(chunk, tmp, &q->control_chunk_list, list) {
 751                 list_del_init(&chunk->list);
 752
 753                 /* Pick the right transport to use. */
 754                 new_transport = chunk->transport;
 755
 756                 if (!new_transport) {
 757                         /*
 758                          * If we have a prior transport pointer, see if
 759                          * the destination address of the chunk
 760                          * matches the destination address of the
 761                          * current transport.  If not a match, then
 762                          * try to look up the transport with a given
 763                          * destination address.  We do this because
 764                          * after processing ASCONFs, we may have new
 765                          * transports created.
 766                          */
 767                         if (transport &&
 768                             sctp_cmp_addr_exact(&chunk->dest,
 769                                                 &transport->ipaddr))
 770                                         new_transport = transport;
 771                         else
 772                                 new_transport = sctp_assoc_lookup_paddr(asoc,
 773                                                                 &chunk->dest);
 774
 775                         /* if we still don't have a new transport, then
 776                          * use the current active path.
 777                          */
 778                         if (!new_transport)
 779                                 new_transport = asoc->peer.active_path;
 780                 } else if ((new_transport->state == SCTP_INACTIVE) ||
 781                            (new_transport->state == SCTP_UNCONFIRMED)) {
 782                         /* If the chunk is Heartbeat or Heartbeat Ack,
 783                          * send it to chunk->transport, even if it's
 784                          * inactive.
 785                          *
 786                          * 3.3.6 Heartbeat Acknowledgement:
 787                          * ...
 788                          * A HEARTBEAT ACK is always sent to the source IP
 789                          * address of the IP datagram containing the
 790                          * HEARTBEAT chunk to which this ack is responding.
 791                          * ...
 792                          *
 793                          * ASCONF_ACKs also must be sent to the source.
 794                          */
 795                         if (chunk->chunk_hdr->type != SCTP_CID_HEARTBEAT &&
 796                             chunk->chunk_hdr->type != SCTP_CID_HEARTBEAT_ACK &&
 797                             chunk->chunk_hdr->type != SCTP_CID_ASCONF_ACK)
 798                                 new_transport = asoc->peer.active_path;
 799                 }
 800
 801                 /* Are we switching transports?
 802                  * Take care of transport locks.
 803                  */
 804                 if (new_transport != transport) {
 805                         transport = new_transport;
 806                         if (list_empty(&transport->send_ready)) {
 807                                 list_add_tail(&transport->send_ready,
 808                                               &transport_list);
 809                         }
 810                         packet = &transport->packet;
 811                         sctp_packet_config(packet, vtag,
 812                                            asoc->peer.ecn_capable);
 813                 }
 814
 815                 switch (chunk->chunk_hdr->type) {
 816                 /*
 817                  * 6.10 Bundling
 818                  *   ...
 819                  *   An endpoint MUST NOT bundle INIT, INIT ACK or SHUTDOWN
 820                  *   COMPLETE with any other chunks.  [Send them immediately.]
 821                  */
 822                 case SCTP_CID_INIT:
 823                 case SCTP_CID_INIT_ACK:
 824                 case SCTP_CID_SHUTDOWN_COMPLETE:
 825                         sctp_packet_init(&singleton, transport, sport, dport);
 826                         sctp_packet_config(&singleton, vtag, 0);
 827                         sctp_packet_append_chunk(&singleton, chunk);
 828                         error = sctp_packet_transmit(&singleton);
 829                         if (error < 0)
 830                                 return error;
 831                         break;
 832
 833                 case SCTP_CID_ABORT:
 834                         if (sctp_test_T_bit(chunk)) {
 835                                 packet->vtag = asoc->c.my_vtag;
 836                         }
 837                 /* The following chunks are "response" chunks, i.e.
 838                  * they are generated in response to something we
 839                  * received.  If we are sending these, then we can
 840                  * send only 1 packet containing these chunks.
 841                  */
 842                 case SCTP_CID_HEARTBEAT_ACK:
 843                 case SCTP_CID_SHUTDOWN_ACK:
 844                 case SCTP_CID_COOKIE_ACK:
 845                 case SCTP_CID_COOKIE_ECHO:
 846                 case SCTP_CID_ERROR:
 847                 case SCTP_CID_ECN_CWR:
 848                 case SCTP_CID_ASCONF_ACK:
 849                         one_packet = 1;
 850                         /* Fall throught */
 851
 852                 case SCTP_CID_SACK:
 853                 case SCTP_CID_HEARTBEAT:
 854                 case SCTP_CID_SHUTDOWN:
 855                 case SCTP_CID_ECN_ECNE:
 856                 case SCTP_CID_ASCONF:
 857                 case SCTP_CID_FWD_TSN:
 858                         status = sctp_packet_transmit_chunk(packet, chunk,
 859                                                             one_packet);
 860                         if (status  != SCTP_XMIT_OK) {
 861                                 /* put the chunk back */
 862                                 list_add(&chunk->list, &q->control_chunk_list);
 863                         }
 864                         break;
 865
 866                 default:
 867                         /* We built a chunk with an illegal type! */
 868                         BUG();
 869                 }
 870         }
 871
 872         /* Is it OK to send data chunks?  */
 873         switch (asoc->state) {
 874         case SCTP_STATE_COOKIE_ECHOED:
 875                 /* Only allow bundling when this packet has a COOKIE-ECHO
 876                  * chunk.
 877                  */
 878                 if (!packet || !packet->has_cookie_echo)
 879                         break;
 880
 881                 /* fallthru */
 882         case SCTP_STATE_ESTABLISHED:
 883         case SCTP_STATE_SHUTDOWN_PENDING:
 884         case SCTP_STATE_SHUTDOWN_RECEIVED:
 885                 /*
 886                  * RFC 2960 6.1  Transmission of DATA Chunks
 887                  *
 888                  * C) When the time comes for the sender to transmit,
 889                  * before sending new DATA chunks, the sender MUST
 890                  * first transmit any outstanding DATA chunks which
 891                  * are marked for retransmission (limited by the
 892                  * current cwnd).
 893                  */
 894                 if (!list_empty(&q->retransmit)) {
 895                         if (transport == asoc->peer.retran_path)
 896                                 goto retran;
 897
 898                         /* Switch transports & prepare the packet.  */
 899
 900                         transport = asoc->peer.retran_path;
 901
 902                         if (list_empty(&transport->send_ready)) {
 903                                 list_add_tail(&transport->send_ready,
 904                                               &transport_list);
 905                         }
 906
 907                         packet = &transport->packet;
 908                         sctp_packet_config(packet, vtag,
 909                                            asoc->peer.ecn_capable);
 910                 retran:
 911                         error = sctp_outq_flush_rtx(q, packet,
 912                                                     rtx_timeout, &start_timer);
 913
 914                         if (start_timer)
 915                                 sctp_transport_reset_timers(transport,
 916                                                             start_timer-1);
 917
 918                         /* This can happen on COOKIE-ECHO resend.  Only
 919                          * one chunk can get bundled with a COOKIE-ECHO.
 920                          */
 921                         if (packet->has_cookie_echo)
 922                                 goto sctp_flush_out;
 923
 924                         /* Don't send new data if there is still data
 925                          * waiting to retransmit.
 926                          */
 927                         if (!list_empty(&q->retransmit))
 928                                 goto sctp_flush_out;
 929                 }
 930
 931                 /* Finally, transmit new packets.  */
 932                 start_timer = 0;
 933                 while ((chunk = sctp_outq_dequeue_data(q)) != NULL) {
 934                         /* RFC 2960 6.5 Every DATA chunk MUST carry a valid
 935                          * stream identifier.
 936                          */
 937                         if (chunk->sinfo.sinfo_stream >=
 938                             asoc->c.sinit_num_ostreams) {
 939
 940                                 /* Mark as failed send. */
 941                                 sctp_chunk_fail(chunk, SCTP_ERROR_INV_STRM);
 942                                 sctp_chunk_free(chunk);
 943                                 continue;
 944                         }
 945
 946                         /* Has this chunk expired? */
 947                         if (sctp_chunk_abandoned(chunk)) {
 948                                 sctp_chunk_fail(chunk, 0);
 949                                 sctp_chunk_free(chunk);
 950                                 continue;
 951                         }
 952
 953                         /* If there is a specified transport, use it.
 954                          * Otherwise, we want to use the active path.
 955                          */
 956                         new_transport = chunk->transport;
 957                         if (!new_transport ||
 958                             ((new_transport->state == SCTP_INACTIVE) ||
 959                              (new_transport->state == SCTP_UNCONFIRMED)))
 960                                 new_transport = asoc->peer.active_path;
 961
 962                         /* Change packets if necessary.  */
 963                         if (new_transport != transport) {
 964                                 transport = new_transport;
 965
 966                                 /* Schedule to have this transport's
 967                                  * packet flushed.
 968                                  */
 969                                 if (list_empty(&transport->send_ready)) {
 970                                         list_add_tail(&transport->send_ready,
 971                                                       &transport_list);
 972                                 }
 973
 974                                 packet = &transport->packet;
 975                                 sctp_packet_config(packet, vtag,
 976                                                    asoc->peer.ecn_capable);
 977                         }
 978
 979                         SCTP_DEBUG_PRINTK("sctp_outq_flush(%p, %p[%s]), ",
 980                                           q, chunk,
 981                                           chunk && chunk->chunk_hdr ?
 982                                           sctp_cname(SCTP_ST_CHUNK(
 983                                                   chunk->chunk_hdr->type))
 984                                           : "Illegal Chunk");
 985
 986                         SCTP_DEBUG_PRINTK("TX TSN 0x%x skb->head "
 987                                         "%p skb->users %d.\n",
 988                                         ntohl(chunk->subh.data_hdr->tsn),
 989                                         chunk->skb ?chunk->skb->head : NULL,
 990                                         chunk->skb ?
 991                                         atomic_read(&chunk->skb->users) : -1);
 992
 993                         /* Add the chunk to the packet.  */
 994                         status = sctp_packet_transmit_chunk(packet, chunk, 0);
 995
 996                         switch (status) {
 997                         case SCTP_XMIT_PMTU_FULL:
 998                         case SCTP_XMIT_RWND_FULL:
 999                         case SCTP_XMIT_NAGLE_DELAY:
1000                                 /* We could not append this chunk, so put
1001                                  * the chunk back on the output queue.
1002                                  */
1003                                 SCTP_DEBUG_PRINTK("sctp_outq_flush: could "
1004                                         "not transmit TSN: 0x%x, status: %d\n",
1005                                         ntohl(chunk->subh.data_hdr->tsn),
1006                                         status);
1007                                 sctp_outq_head_data(q, chunk);
1008                                 goto sctp_flush_out;
1009                                 break;
1010
1011                         case SCTP_XMIT_OK:
1012                                 break;
1013
1014                         default:
1015                                 BUG();
1016                         }
1017
1018                         /* BUG: We assume that the sctp_packet_transmit()
1019                          * call below will succeed all the time and add the
1020                          * chunk to the transmitted list and restart the
1021                          * timers.
1022                          * It is possible that the call can fail under OOM
1023                          * conditions.
1024                          *
1025                          * Is this really a problem?  Won't this behave
1026                          * like a lost TSN?
1027                          */
1028                         list_add_tail(&chunk->transmitted_list,
1029                                       &transport->transmitted);
1030
1031                         sctp_transport_reset_timers(transport, start_timer-1);
1032
1033                         q->empty = 0;
1034
1035                         /* Only let one DATA chunk get bundled with a
1036                          * COOKIE-ECHO chunk.
1037                          */
1038                         if (packet->has_cookie_echo)
1039                                 goto sctp_flush_out;
1040                 }
1041                 break;
1042
1043         default:
1044                 /* Do nothing.  */
1045                 break;
1046         }
1047
1048 sctp_flush_out:
1049
1050         /* Before returning, examine all the transports touched in
1051          * this call.  Right now, we bluntly force clear all the
1052          * transports.  Things might change after we implement Nagle.
1053          * But such an examination is still required.
1054          *
1055          * --xguo
1056          */
1057         while ((ltransport = sctp_list_dequeue(&transport_list)) != NULL ) {
1058                 struct sctp_transport *t = list_entry(ltransport,
1059                                                       struct sctp_transport,
1060                                                       send_ready);
1061                 packet = &t->packet;
1062                 if (!sctp_packet_empty(packet))
1063                         error = sctp_packet_transmit(packet);
1064         }
1065
1066         return error;
1067 }
1068
1069 /* Update unack_data based on the incoming SACK chunk */
1070 static void sctp_sack_update_unack_data(struct sctp_association *assoc,
1071                                         struct sctp_sackhdr *sack)
1072 {
1073         sctp_sack_variable_t *frags;
1074         __u16 unack_data;
1075         int i;
1076
1077         unack_data = assoc->next_tsn - assoc->ctsn_ack_point - 1;
1078
1079         frags = sack->variable;
1080         for (i = 0; i < ntohs(sack->num_gap_ack_blocks); i++) {
1081                 unack_data -= ((ntohs(frags[i].gab.end) -
1082                                 ntohs(frags[i].gab.start) + 1));
1083         }
1084
1085         assoc->unack_data = unack_data;
1086 }
1087
1088 /* Return the highest new tsn that is acknowledged by the given SACK chunk. */
1089 static __u32 sctp_highest_new_tsn(struct sctp_sackhdr *sack,
1090                                   struct sctp_association *asoc)
1091 {
1092         struct sctp_transport *transport;
1093         struct sctp_chunk *chunk;
1094         __u32 highest_new_tsn, tsn;
1095         struct list_head *transport_list = &asoc->peer.transport_addr_list;
1096
1097         highest_new_tsn = ntohl(sack->cum_tsn_ack);
1098
1099         list_for_each_entry(transport, transport_list, transports) {
1100                 list_for_each_entry(chunk, &transport->transmitted,
1101                                 transmitted_list) {
1102                         tsn = ntohl(chunk->subh.data_hdr->tsn);
1103
1104                         if (!chunk->tsn_gap_acked &&
1105                             TSN_lt(highest_new_tsn, tsn) &&
1106                             sctp_acked(sack, tsn))
1107                                 highest_new_tsn = tsn;
1108                 }
1109         }
1110
1111         return highest_new_tsn;
1112 }
1113
1114 /* This is where we REALLY process a SACK.
1115  *
1116  * Process the SACK against the outqueue.  Mostly, this just frees
1117  * things off the transmitted queue.
1118  */
1119 int sctp_outq_sack(struct sctp_outq *q, struct sctp_sackhdr *sack)
1120 {
1121         struct sctp_association *asoc = q->asoc;
1122         struct sctp_transport *transport;
1123         struct sctp_chunk *tchunk = NULL;
1124         struct list_head *lchunk, *transport_list, *temp;
1125         sctp_sack_variable_t *frags = sack->variable;
1126         __u32 sack_ctsn, ctsn, tsn;
1127         __u32 highest_tsn, highest_new_tsn;
1128         __u32 sack_a_rwnd;
1129         unsigned outstanding;
1130         struct sctp_transport *primary = asoc->peer.primary_path;
1131         int count_of_newacks = 0;
1132
1133         /* Grab the association's destination address list. */
1134         transport_list = &asoc->peer.transport_addr_list;
1135
1136         sack_ctsn = ntohl(sack->cum_tsn_ack);
1137
1138         /*
1139          * SFR-CACC algorithm:
1140          * On receipt of a SACK the sender SHOULD execute the
1141          * following statements.
1142          *
1143          * 1) If the cumulative ack in the SACK passes next tsn_at_change
1144          * on the current primary, the CHANGEOVER_ACTIVE flag SHOULD be
1145          * cleared. The CYCLING_CHANGEOVER flag SHOULD also be cleared for
1146          * all destinations.
1147          */
1148         if (TSN_lte(primary->cacc.next_tsn_at_change, sack_ctsn)) {
1149                 primary->cacc.changeover_active = 0;
1150                 list_for_each_entry(transport, transport_list,
1151                                 transports) {
1152                         transport->cacc.cycling_changeover = 0;
1153                 }
1154         }
1155
1156         /*
1157          * SFR-CACC algorithm:
1158          * 2) If the SACK contains gap acks and the flag CHANGEOVER_ACTIVE
1159          * is set the receiver of the SACK MUST take the following actions:
1160          *
1161          * A) Initialize the cacc_saw_newack to 0 for all destination
1162          * addresses.
1163          */
1164         if (sack->num_gap_ack_blocks &&
1165             primary->cacc.changeover_active) {
1166                 list_for_each_entry(transport, transport_list, transports) {
1167                         transport->cacc.cacc_saw_newack = 0;
1168                 }
1169         }
1170
1171         /* Get the highest TSN in the sack. */
1172         highest_tsn = sack_ctsn;
1173         if (sack->num_gap_ack_blocks)
1174                 highest_tsn +=
1175                     ntohs(frags[ntohs(sack->num_gap_ack_blocks) - 1].gab.end);
1176
1177         if (TSN_lt(asoc->highest_sacked, highest_tsn)) {
1178                 highest_new_tsn = highest_tsn;
1179                 asoc->highest_sacked = highest_tsn;
1180         } else {
1181                 highest_new_tsn = sctp_highest_new_tsn(sack, asoc);
1182         }
1183
1184         /* Run through the retransmit queue.  Credit bytes received
1185          * and free those chunks that we can.
1186          */
1187         sctp_check_transmitted(q, &q->retransmit, NULL, sack, highest_new_tsn);
1188         sctp_mark_missing(q, &q->retransmit, NULL, highest_new_tsn, 0);
1189
1190         /* Run through the transmitted queue.
1191          * Credit bytes received and free those chunks which we can.
1192          *
1193          * This is a MASSIVE candidate for optimization.
1194          */
1195         list_for_each_entry(transport, transport_list, transports) {
1196                 sctp_check_transmitted(q, &transport->transmitted,
1197                                        transport, sack, highest_new_tsn);
1198                 /*
1199                  * SFR-CACC algorithm:
1200                  * C) Let count_of_newacks be the number of
1201                  * destinations for which cacc_saw_newack is set.
1202                  */
1203                 if (transport->cacc.cacc_saw_newack)
1204                         count_of_newacks ++;
1205         }
1206
1207         list_for_each_entry(transport, transport_list, transports) {
1208                 sctp_mark_missing(q, &transport->transmitted, transport,
1209                                   highest_new_tsn, count_of_newacks);
1210         }
1211
1212         /* Move the Cumulative TSN Ack Point if appropriate.  */
1213         if (TSN_lt(asoc->ctsn_ack_point, sack_ctsn))
1214                 asoc->ctsn_ack_point = sack_ctsn;
1215
1216         /* Update unack_data field in the assoc. */
1217         sctp_sack_update_unack_data(asoc, sack);
1218
1219         ctsn = asoc->ctsn_ack_point;
1220
1221         /* Throw away stuff rotting on the sack queue.  */
1222         list_for_each_safe(lchunk, temp, &q->sacked) {
1223                 tchunk = list_entry(lchunk, struct sctp_chunk,
1224                                     transmitted_list);
1225                 tsn = ntohl(tchunk->subh.data_hdr->tsn);
1226                 if (TSN_lte(tsn, ctsn)) {
1227                         list_del_init(&tchunk->transmitted_list);
1228                         sctp_chunk_free(tchunk);
1229                 }
1230         }
1231
1232         /* ii) Set rwnd equal to the newly received a_rwnd minus the
1233          *     number of bytes still outstanding after processing the
1234          *     Cumulative TSN Ack and the Gap Ack Blocks.
1235          */
1236
1237         sack_a_rwnd = ntohl(sack->a_rwnd);
1238         outstanding = q->outstanding_bytes;
1239
1240         if (outstanding < sack_a_rwnd)
1241                 sack_a_rwnd -= outstanding;
1242         else
1243                 sack_a_rwnd = 0;
1244
1245         asoc->peer.rwnd = sack_a_rwnd;
1246
1247         sctp_generate_fwdtsn(q, sack_ctsn);
1248
1249         SCTP_DEBUG_PRINTK("%s: sack Cumulative TSN Ack is 0x%x.\n",
1250                           __func__, sack_ctsn);
1251         SCTP_DEBUG_PRINTK("%s: Cumulative TSN Ack of association, "
1252                           "%p is 0x%x. Adv peer ack point: 0x%x\n",
1253                           __func__, asoc, ctsn, asoc->adv_peer_ack_point);
1254
1255         /* See if all chunks are acked.
1256          * Make sure the empty queue handler will get run later.
1257          */
1258         q->empty = (list_empty(&q->out_chunk_list) &&
1259                     list_empty(&q->retransmit));
1260         if (!q->empty)
1261                 goto finish;
1262
1263         list_for_each_entry(transport, transport_list, transports) {
1264                 q->empty = q->empty && list_empty(&transport->transmitted);
1265                 if (!q->empty)
1266                         goto finish;
1267         }
1268
1269         SCTP_DEBUG_PRINTK("sack queue is empty.\n");
1270 finish:
1271         return q->empty;
1272 }
1273
1274 /* Is the outqueue empty?  */
1275 int sctp_outq_is_empty(const struct sctp_outq *q)
1276 {
1277         return q->empty;
1278 }
1279
1280 /********************************************************************
1281  * 2nd Level Abstractions
1282  ********************************************************************/
1283
1284 /* Go through a transport's transmitted list or the association's retransmit
1285  * list and move chunks that are acked by the Cumulative TSN Ack to q->sacked.
1286  * The retransmit list will not have an associated transport.
1287  *
1288  * I added coherent debug information output.   --xguo
1289  *
1290  * Instead of printing 'sacked' or 'kept' for each TSN on the
1291  * transmitted_queue, we print a range: SACKED: TSN1-TSN2, TSN3, TSN4-TSN5.
1292  * KEPT TSN6-TSN7, etc.
1293  */
1294 static void sctp_check_transmitted(struct sctp_outq *q,
1295                                    struct list_head *transmitted_queue,
1296                                    struct sctp_transport *transport,
1297                                    struct sctp_sackhdr *sack,
1298                                    __u32 highest_new_tsn_in_sack)
1299 {
1300         struct list_head *lchunk;
1301         struct sctp_chunk *tchunk;
1302         struct list_head tlist;
1303         __u32 tsn;
1304         __u32 sack_ctsn;
1305         __u32 rtt;
1306         __u8 restart_timer = 0;
1307         int bytes_acked = 0;
1308
1309         /* These state variables are for coherent debug output. --xguo */
1310
1311 #if SCTP_DEBUG
1312         __u32 dbg_ack_tsn = 0;  /* An ACKed TSN range starts here... */
1313         __u32 dbg_last_ack_tsn = 0;  /* ...and finishes here.        */
1314         __u32 dbg_kept_tsn = 0; /* An un-ACKed range starts here...  */
1315         __u32 dbg_last_kept_tsn = 0; /* ...and finishes here.        */
1316
1317         /* 0 : The last TSN was ACKed.
1318          * 1 : The last TSN was NOT ACKed (i.e. KEPT).
1319          * -1: We need to initialize.
1320          */
1321         int dbg_prt_state = -1;
1322 #endif /* SCTP_DEBUG */
1323
1324         sack_ctsn = ntohl(sack->cum_tsn_ack);
1325
1326         INIT_LIST_HEAD(&tlist);
1327
1328         /* The while loop will skip empty transmitted queues. */
1329         while (NULL != (lchunk = sctp_list_dequeue(transmitted_queue))) {
1330                 tchunk = list_entry(lchunk, struct sctp_chunk,
1331                                     transmitted_list);
1332
1333                 if (sctp_chunk_abandoned(tchunk)) {
1334                         /* Move the chunk to abandoned list. */
1335                         sctp_insert_list(&q->abandoned, lchunk);
1336
1337                         /* If this chunk has not been acked, stop
1338                          * considering it as 'outstanding'.
1339                          */
1340                         if (!tchunk->tsn_gap_acked) {
1341                                 tchunk->transport->flight_size -=
1342                                                 sctp_data_size(tchunk);
1343                                 q->outstanding_bytes -= sctp_data_size(tchunk);
1344                         }
1345                         continue;
1346                 }
1347
1348                 tsn = ntohl(tchunk->subh.data_hdr->tsn);
1349                 if (sctp_acked(sack, tsn)) {
1350                         /* If this queue is the retransmit queue, the
1351                          * retransmit timer has already reclaimed
1352                          * the outstanding bytes for this chunk, so only
1353                          * count bytes associated with a transport.
1354                          */
1355                         if (transport) {
1356                                 /* If this chunk is being used for RTT
1357                                  * measurement, calculate the RTT and update
1358                                  * the RTO using this value.
1359                                  *
1360                                  * 6.3.1 C5) Karn's algorithm: RTT measurements
1361                                  * MUST NOT be made using packets that were
1362                                  * retransmitted (and thus for which it is
1363                                  * ambiguous whether the reply was for the
1364                                  * first instance of the packet or a later
1365                                  * instance).
1366                                  */
1367                                 if (!tchunk->tsn_gap_acked &&
1368                                     !tchunk->resent &&
1369                                     tchunk->rtt_in_progress) {
1370                                         tchunk->rtt_in_progress = 0;
1371                                         rtt = jiffies - tchunk->sent_at;
1372                                         sctp_transport_update_rto(transport,
1373                                                                   rtt);
1374                                 }
1375                         }
1376                         if (TSN_lte(tsn, sack_ctsn)) {
1377                                 /* RFC 2960  6.3.2 Retransmission Timer Rules
1378                                  *
1379                                  * R3) Whenever a SACK is received
1380                                  * that acknowledges the DATA chunk
1381                                  * with the earliest outstanding TSN
1382                                  * for that address, restart T3-rtx
1383                                  * timer for that address with its
1384                                  * current RTO.
1385                                  */
1386                                 restart_timer = 1;
1387
1388                                 if (!tchunk->tsn_gap_acked) {
1389                                         tchunk->tsn_gap_acked = 1;
1390                                         bytes_acked += sctp_data_size(tchunk);
1391                                         /*
1392                                          * SFR-CACC algorithm:
1393                                          * 2) If the SACK contains gap acks
1394                                          * and the flag CHANGEOVER_ACTIVE is
1395                                          * set the receiver of the SACK MUST
1396                                          * take the following action:
1397                                          *
1398                                          * B) For each TSN t being acked that
1399                                          * has not been acked in any SACK so
1400                                          * far, set cacc_saw_newack to 1 for
1401                                          * the destination that the TSN was
1402                                          * sent to.
1403                                          */
1404                                         if (transport &&
1405                                             sack->num_gap_ack_blocks &&
1406                                             q->asoc->peer.primary_path->cacc.
1407                                             changeover_active)
1408                                                 transport->cacc.cacc_saw_newack
1409                                                         = 1;
1410                                 }
1411
1412                                 list_add_tail(&tchunk->transmitted_list,
1413                                               &q->sacked);
1414                         } else {
1415                                 /* RFC2960 7.2.4, sctpimpguide-05 2.8.2
1416                                  * M2) Each time a SACK arrives reporting
1417                                  * 'Stray DATA chunk(s)' record the highest TSN
1418                                  * reported as newly acknowledged, call this
1419                                  * value 'HighestTSNinSack'. A newly
1420                                  * acknowledged DATA chunk is one not
1421                                  * previously acknowledged in a SACK.
1422                                  *
1423                                  * When the SCTP sender of data receives a SACK
1424                                  * chunk that acknowledges, for the first time,
1425                                  * the receipt of a DATA chunk, all the still
1426                                  * unacknowledged DATA chunks whose TSN is
1427                                  * older than that newly acknowledged DATA
1428                                  * chunk, are qualified as 'Stray DATA chunks'.
1429                                  */
1430                                 if (!tchunk->tsn_gap_acked) {
1431                                         tchunk->tsn_gap_acked = 1;
1432                                         bytes_acked += sctp_data_size(tchunk);
1433                                 }
1434                                 list_add_tail(lchunk, &tlist);
1435                         }
1436
1437 #if SCTP_DEBUG
1438                         switch (dbg_prt_state) {
1439                         case 0: /* last TSN was ACKed */
1440                                 if (dbg_last_ack_tsn + 1 == tsn) {
1441                                         /* This TSN belongs to the
1442                                          * current ACK range.
1443                                          */
1444                                         break;
1445                                 }
1446
1447                                 if (dbg_last_ack_tsn != dbg_ack_tsn) {
1448                                         /* Display the end of the
1449                                          * current range.
1450                                          */
1451                                         SCTP_DEBUG_PRINTK("-%08x",
1452                                                           dbg_last_ack_tsn);
1453                                 }
1454
1455                                 /* Start a new range.  */
1456                                 SCTP_DEBUG_PRINTK(",%08x", tsn);
1457                                 dbg_ack_tsn = tsn;
1458                                 break;
1459
1460                         case 1: /* The last TSN was NOT ACKed. */
1461                                 if (dbg_last_kept_tsn != dbg_kept_tsn) {
1462                                         /* Display the end of current range. */
1463                                         SCTP_DEBUG_PRINTK("-%08x",
1464                                                           dbg_last_kept_tsn);
1465                                 }
1466
1467                                 SCTP_DEBUG_PRINTK("\n");
1468
1469                                 /* FALL THROUGH... */
1470                         default:
1471                                 /* This is the first-ever TSN we examined.  */
1472                                 /* Start a new range of ACK-ed TSNs.  */
1473                                 SCTP_DEBUG_PRINTK("ACKed: %08x", tsn);
1474                                 dbg_prt_state = 0;
1475                                 dbg_ack_tsn = tsn;
1476                         }
1477
1478                         dbg_last_ack_tsn = tsn;
1479 #endif /* SCTP_DEBUG */
1480
1481                 } else {
1482                         if (tchunk->tsn_gap_acked) {
1483                                 SCTP_DEBUG_PRINTK("%s: Receiver reneged on "
1484                                                   "data TSN: 0x%x\n",
1485                                                   __func__,
1486                                                   tsn);
1487                                 tchunk->tsn_gap_acked = 0;
1488
1489                                 bytes_acked -= sctp_data_size(tchunk);
1490
1491                                 /* RFC 2960 6.3.2 Retransmission Timer Rules
1492                                  *
1493                                  * R4) Whenever a SACK is received missing a
1494                                  * TSN that was previously acknowledged via a
1495                                  * Gap Ack Block, start T3-rtx for the
1496                                  * destination address to which the DATA
1497                                  * chunk was originally
1498                                  * transmitted if it is not already running.
1499                                  */
1500                                 restart_timer = 1;
1501                         }
1502
1503                         list_add_tail(lchunk, &tlist);
1504
1505 #if SCTP_DEBUG
1506                         /* See the above comments on ACK-ed TSNs. */
1507                         switch (dbg_prt_state) {
1508                         case 1:
1509                                 if (dbg_last_kept_tsn + 1 == tsn)
1510                                         break;
1511
1512                                 if (dbg_last_kept_tsn != dbg_kept_tsn)
1513                                         SCTP_DEBUG_PRINTK("-%08x",
1514                                                           dbg_last_kept_tsn);
1515
1516                                 SCTP_DEBUG_PRINTK(",%08x", tsn);
1517                                 dbg_kept_tsn = tsn;
1518                                 break;
1519
1520                         case 0:
1521                                 if (dbg_last_ack_tsn != dbg_ack_tsn)
1522                                         SCTP_DEBUG_PRINTK("-%08x",
1523                                                           dbg_last_ack_tsn);
1524                                 SCTP_DEBUG_PRINTK("\n");
1525
1526                                 /* FALL THROUGH... */
1527                         default:
1528                                 SCTP_DEBUG_PRINTK("KEPT: %08x",tsn);
1529                                 dbg_prt_state = 1;
1530                                 dbg_kept_tsn = tsn;
1531                         }
1532
1533                         dbg_last_kept_tsn = tsn;
1534 #endif /* SCTP_DEBUG */
1535                 }
1536         }
1537
1538 #if SCTP_DEBUG
1539         /* Finish off the last range, displaying its ending TSN.  */
1540         switch (dbg_prt_state) {
1541         case 0:
1542                 if (dbg_last_ack_tsn != dbg_ack_tsn) {
1543                         SCTP_DEBUG_PRINTK("-%08x\n", dbg_last_ack_tsn);
1544                 } else {
1545                         SCTP_DEBUG_PRINTK("\n");
1546                 }
1547         break;
1548
1549         case 1:
1550                 if (dbg_last_kept_tsn != dbg_kept_tsn) {
1551                         SCTP_DEBUG_PRINTK("-%08x\n", dbg_last_kept_tsn);
1552                 } else {
1553                         SCTP_DEBUG_PRINTK("\n");
1554                 }
1555         }
1556 #endif /* SCTP_DEBUG */
1557         if (transport) {
1558                 if (bytes_acked) {
1559                         /* 8.2. When an outstanding TSN is acknowledged,
1560                          * the endpoint shall clear the error counter of
1561                          * the destination transport address to which the
1562                          * DATA chunk was last sent.
1563                          * The association's overall error counter is
1564                          * also cleared.
1565                          */
1566                         transport->error_count = 0;
1567                         transport->asoc->overall_error_count = 0;
1568
1569                         /* Mark the destination transport address as
1570                          * active if it is not so marked.
1571                          */
1572                         if ((transport->state == SCTP_INACTIVE) ||
1573                             (transport->state == SCTP_UNCONFIRMED)) {
1574                                 sctp_assoc_control_transport(
1575                                         transport->asoc,
1576                                         transport,
1577                                         SCTP_TRANSPORT_UP,
1578                                         SCTP_RECEIVED_SACK);
1579                         }
1580
1581                         sctp_transport_raise_cwnd(transport, sack_ctsn,
1582                                                   bytes_acked);
1583
1584                         transport->flight_size -= bytes_acked;
1585                         if (transport->flight_size == 0)
1586                                 transport->partial_bytes_acked = 0;
1587                         q->outstanding_bytes -= bytes_acked;
1588                 } else {
1589                         /* RFC 2960 6.1, sctpimpguide-06 2.15.2
1590                          * When a sender is doing zero window probing, it
1591                          * should not timeout the association if it continues
1592                          * to receive new packets from the receiver. The
1593                          * reason is that the receiver MAY keep its window
1594                          * closed for an indefinite time.
1595                          * A sender is doing zero window probing when the
1596                          * receiver's advertised window is zero, and there is
1597                          * only one data chunk in flight to the receiver.
1598                          */
1599                         if (!q->asoc->peer.rwnd &&
1600                             !list_empty(&tlist) &&
1601                             (sack_ctsn+2 == q->asoc->next_tsn)) {
1602                                 SCTP_DEBUG_PRINTK("%s: SACK received for zero "
1603                                                   "window probe: %u\n",
1604                                                   __func__, sack_ctsn);
1605                                 q->asoc->overall_error_count = 0;
1606                                 transport->error_count = 0;
1607                         }
1608                 }
1609
1610                 /* RFC 2960 6.3.2 Retransmission Timer Rules
1611                  *
1612                  * R2) Whenever all outstanding data sent to an address have
1613                  * been acknowledged, turn off the T3-rtx timer of that
1614                  * address.
1615                  */
1616                 if (!transport->flight_size) {
1617                         if (timer_pending(&transport->T3_rtx_timer) &&
1618                             del_timer(&transport->T3_rtx_timer)) {
1619                                 sctp_transport_put(transport);
1620                         }
1621                 } else if (restart_timer) {
1622                         if (!mod_timer(&transport->T3_rtx_timer,
1623                                        jiffies + transport->rto))
1624                                 sctp_transport_hold(transport);
1625                 }
1626         }
1627
1628         list_splice(&tlist, transmitted_queue);
1629 }
1630
1631 /* Mark chunks as missing and consequently may get retransmitted. */
1632 static void sctp_mark_missing(struct sctp_outq *q,
1633                               struct list_head *transmitted_queue,
1634                               struct sctp_transport *transport,
1635                               __u32 highest_new_tsn_in_sack,
1636                               int count_of_newacks)
1637 {
1638         struct sctp_chunk *chunk;
1639         __u32 tsn;
1640         char do_fast_retransmit = 0;
1641         struct sctp_transport *primary = q->asoc->peer.primary_path;
1642
1643         list_for_each_entry(chunk, transmitted_queue, transmitted_list) {
1644
1645                 tsn = ntohl(chunk->subh.data_hdr->tsn);
1646
1647                 /* RFC 2960 7.2.4, sctpimpguide-05 2.8.2 M3) Examine all
1648                  * 'Unacknowledged TSN's', if the TSN number of an
1649                  * 'Unacknowledged TSN' is smaller than the 'HighestTSNinSack'
1650                  * value, increment the 'TSN.Missing.Report' count on that
1651                  * chunk if it has NOT been fast retransmitted or marked for
1652                  * fast retransmit already.
1653                  */
1654                 if (!chunk->fast_retransmit &&
1655                     !chunk->tsn_gap_acked &&
1656                     TSN_lt(tsn, highest_new_tsn_in_sack)) {
1657
1658                         /* SFR-CACC may require us to skip marking
1659                          * this chunk as missing.
1660                          */
1661                         if (!transport || !sctp_cacc_skip(primary, transport,
1662                                             count_of_newacks, tsn)) {
1663                                 chunk->tsn_missing_report++;
1664
1665                                 SCTP_DEBUG_PRINTK(
1666                                         "%s: TSN 0x%x missing counter: %d\n",
1667                                         __func__, tsn,
1668                                         chunk->tsn_missing_report);
1669                         }
1670                 }
1671                 /*
1672                  * M4) If any DATA chunk is found to have a
1673                  * 'TSN.Missing.Report'
1674                  * value larger than or equal to 3, mark that chunk for
1675                  * retransmission and start the fast retransmit procedure.
1676                  */
1677
1678                 if (chunk->tsn_missing_report >= 3) {
1679                         chunk->fast_retransmit = 1;
1680                         do_fast_retransmit = 1;
1681                 }
1682         }
1683
1684         if (transport) {
1685                 if (do_fast_retransmit)
1686                         sctp_retransmit(q, transport, SCTP_RTXR_FAST_RTX);
1687
1688                 SCTP_DEBUG_PRINTK("%s: transport: %p, cwnd: %d, "
1689                                   "ssthresh: %d, flight_size: %d, pba: %d\n",
1690                                   __func__, transport, transport->cwnd,
1691                                   transport->ssthresh, transport->flight_size,
1692                                   transport->partial_bytes_acked);
1693         }
1694 }
1695
1696 /* Is the given TSN acked by this packet?  */
1697 static int sctp_acked(struct sctp_sackhdr *sack, __u32 tsn)
1698 {
1699         int i;
1700         sctp_sack_variable_t *frags;
1701         __u16 gap;
1702         __u32 ctsn = ntohl(sack->cum_tsn_ack);
1703
1704         if (TSN_lte(tsn, ctsn))
1705                 goto pass;
1706
1707         /* 3.3.4 Selective Acknowledgement (SACK) (3):
1708          *
1709          * Gap Ack Blocks:
1710          *  These fields contain the Gap Ack Blocks. They are repeated
1711          *  for each Gap Ack Block up to the number of Gap Ack Blocks
1712          *  defined in the Number of Gap Ack Blocks field. All DATA
1713          *  chunks with TSNs greater than or equal to (Cumulative TSN
1714          *  Ack + Gap Ack Block Start) and less than or equal to
1715          *  (Cumulative TSN Ack + Gap Ack Block End) of each Gap Ack
1716          *  Block are assumed to have been received correctly.
1717          */
1718
1719         frags = sack->variable;
1720         gap = tsn - ctsn;
1721         for (i = 0; i < ntohs(sack->num_gap_ack_blocks); ++i) {
1722                 if (TSN_lte(ntohs(frags[i].gab.start), gap) &&
1723                     TSN_lte(gap, ntohs(frags[i].gab.end)))
1724                         goto pass;
1725         }
1726
1727         return 0;
1728 pass:
1729         return 1;
1730 }
1731
1732 static inline int sctp_get_skip_pos(struct sctp_fwdtsn_skip *skiplist,
1733                                     int nskips, __be16 stream)
1734 {
1735         int i;
1736
1737         for (i = 0; i < nskips; i++) {
1738                 if (skiplist[i].stream == stream)
1739                         return i;
1740         }
1741         return i;
1742 }
1743
1744 /* Create and add a fwdtsn chunk to the outq's control queue if needed. */
1745 static void sctp_generate_fwdtsn(struct sctp_outq *q, __u32 ctsn)
1746 {
1747         struct sctp_association *asoc = q->asoc;
1748         struct sctp_chunk *ftsn_chunk = NULL;
1749         struct sctp_fwdtsn_skip ftsn_skip_arr[10];
1750         int nskips = 0;
1751         int skip_pos = 0;
1752         __u32 tsn;
1753         struct sctp_chunk *chunk;
1754         struct list_head *lchunk, *temp;
1755
1756         /* PR-SCTP C1) Let SackCumAck be the Cumulative TSN ACK carried in the
1757          * received SACK.
1758          *
1759          * If (Advanced.Peer.Ack.Point < SackCumAck), then update
1760          * Advanced.Peer.Ack.Point to be equal to SackCumAck.
1761          */
1762         if (TSN_lt(asoc->adv_peer_ack_point, ctsn))
1763                 asoc->adv_peer_ack_point = ctsn;
1764
1765         /* PR-SCTP C2) Try to further advance the "Advanced.Peer.Ack.Point"
1766          * locally, that is, to move "Advanced.Peer.Ack.Point" up as long as
1767          * the chunk next in the out-queue space is marked as "abandoned" as
1768          * shown in the following example:
1769          *
1770          * Assuming that a SACK arrived with the Cumulative TSN ACK 102
1771          * and the Advanced.Peer.Ack.Point is updated to this value:
1772          *
1773          *   out-queue at the end of  ==>   out-queue after Adv.Ack.Point
1774          *   normal SACK processing           local advancement
1775          *                ...                           ...
1776          *   Adv.Ack.Pt-> 102 acked                     102 acked
1777          *                103 abandoned                 103 abandoned
1778          *                104 abandoned     Adv.Ack.P-> 104 abandoned
1779          *                105                           105
1780          *                106 acked                     106 acked
1781          *                ...                           ...
1782          *
1783          * In this example, the data sender successfully advanced the
1784          * "Advanced.Peer.Ack.Point" from 102 to 104 locally.
1785          */
1786         list_for_each_safe(lchunk, temp, &q->abandoned) {
1787                 chunk = list_entry(lchunk, struct sctp_chunk,
1788                                         transmitted_list);
1789                 tsn = ntohl(chunk->subh.data_hdr->tsn);
1790
1791                 /* Remove any chunks in the abandoned queue that are acked by
1792                  * the ctsn.
1793                  */
1794                 if (TSN_lte(tsn, ctsn)) {
1795                         list_del_init(lchunk);
1796                         sctp_chunk_free(chunk);
1797                 } else {
1798                         if (TSN_lte(tsn, asoc->adv_peer_ack_point+1)) {
1799                                 asoc->adv_peer_ack_point = tsn;
1800                                 if (chunk->chunk_hdr->flags &
1801                                          SCTP_DATA_UNORDERED)
1802                                         continue;
1803                                 skip_pos = sctp_get_skip_pos(&ftsn_skip_arr[0],
1804                                                 nskips,
1805                                                 chunk->subh.data_hdr->stream);
1806                                 ftsn_skip_arr[skip_pos].stream =
1807                                         chunk->subh.data_hdr->stream;
1808                                 ftsn_skip_arr[skip_pos].ssn =
1809                                          chunk->subh.data_hdr->ssn;
1810                                 if (skip_pos == nskips)
1811                                         nskips++;
1812                                 if (nskips == 10)
1813                                         break;
1814                         } else
1815                                 break;
1816                 }
1817         }
1818
1819         /* PR-SCTP C3) If, after step C1 and C2, the "Advanced.Peer.Ack.Point"
1820          * is greater than the Cumulative TSN ACK carried in the received
1821          * SACK, the data sender MUST send the data receiver a FORWARD TSN
1822          * chunk containing the latest value of the
1823          * "Advanced.Peer.Ack.Point".
1824          *
1825          * C4) For each "abandoned" TSN the sender of the FORWARD TSN SHOULD
1826          * list each stream and sequence number in the forwarded TSN. This
1827          * information will enable the receiver to easily find any
1828          * stranded TSN's waiting on stream reorder queues. Each stream
1829          * SHOULD only be reported once; this means that if multiple
1830          * abandoned messages occur in the same stream then only the
1831          * highest abandoned stream sequence number is reported. If the
1832          * total size of the FORWARD TSN does NOT fit in a single MTU then
1833          * the sender of the FORWARD TSN SHOULD lower the
1834          * Advanced.Peer.Ack.Point to the last TSN that will fit in a
1835          * single MTU.
1836          */
1837         if (asoc->adv_peer_ack_point > ctsn)
1838                 ftsn_chunk = sctp_make_fwdtsn(asoc, asoc->adv_peer_ack_point,
1839                                               nskips, &ftsn_skip_arr[0]);
1840
1841         if (ftsn_chunk) {
1842                 list_add_tail(&ftsn_chunk->list, &q->control_chunk_list);
1843                 SCTP_INC_STATS(SCTP_MIB_OUTCTRLCHUNKS);
1844         }
1845 }