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 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  50
  51 #include <linux/types.h>
  52 #include <linux/list.h>   /* For struct list_head */
  53 #include <linux/socket.h>
  54 #include <linux/ip.h>
  55 #include <linux/slab.h>
  56 #include <net/sock.h>     /* For skb_set_owner_w */
  57
  58 #include <net/sctp/sctp.h>
  59 #include <net/sctp/sm.h>
  60
  61 /* Declare internal functions here.  */
  62 static int sctp_acked(struct sctp_sackhdr *sack, __u32 tsn);
  63 static void sctp_check_transmitted(struct sctp_outq *q,
  64                                    struct list_head *transmitted_queue,
  65                                    struct sctp_transport *transport,
  66                                    struct sctp_sackhdr *sack,
  67                                    __u32 *highest_new_tsn);
  68
  69 static void sctp_mark_missing(struct sctp_outq *q,
  70                               struct list_head *transmitted_queue,
  71                               struct sctp_transport *transport,
  72                               __u32 highest_new_tsn,
  73                               int count_of_newacks);
  74
  75 static void sctp_generate_fwdtsn(struct sctp_outq *q, __u32 sack_ctsn);
  76
  77 static int sctp_outq_flush(struct sctp_outq *q, int rtx_timeout);
  78
  79 /* Add data to the front of the queue. */
  80 static inline void sctp_outq_head_data(struct sctp_outq *q,
  81                                         struct sctp_chunk *ch)
  82 {
  83         list_add(&ch->list, &q->out_chunk_list);
  84         q->out_qlen += ch->skb->len;
  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         struct sctp_chunk *ch = NULL;
  91
  92         if (!list_empty(&q->out_chunk_list)) {
  93                 struct list_head *entry = q->out_chunk_list.next;
  94
  95                 ch = list_entry(entry, struct sctp_chunk, list);
  96                 list_del_init(entry);
  97                 q->out_qlen -= ch->skb->len;
  98         }
  99         return ch;
 100 }
 101 /* Add data chunk to the end of the queue. */
 102 static inline void sctp_outq_tail_data(struct sctp_outq *q,
 103                                        struct sctp_chunk *ch)
 104 {
 105         list_add_tail(&ch->list, &q->out_chunk_list);
 106         q->out_qlen += ch->skb->len;
 107 }
 108
 109 /*
 110  * SFR-CACC algorithm:
 111  * D) If count_of_newacks is greater than or equal to 2
 112  * and t was not sent to the current primary then the
 113  * sender MUST NOT increment missing report count for t.
 114  */
 115 static inline int sctp_cacc_skip_3_1_d(struct sctp_transport *primary,
 116                                        struct sctp_transport *transport,
 117                                        int count_of_newacks)
 118 {
 119         if (count_of_newacks >=2 && transport != primary)
 120                 return 1;
 121         return 0;
 122 }
 123
 124 /*
 125  * SFR-CACC algorithm:
 126  * F) If count_of_newacks is less than 2, let d be the
 127  * destination to which t was sent. If cacc_saw_newack
 128  * is 0 for destination d, then the sender MUST NOT
 129  * increment missing report count for t.
 130  */
 131 static inline int sctp_cacc_skip_3_1_f(struct sctp_transport *transport,
 132                                        int count_of_newacks)
 133 {
 134         if (count_of_newacks < 2 && !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         q->asoc = asoc;
 208         INIT_LIST_HEAD(&q->out_chunk_list);
 209         INIT_LIST_HEAD(&q->control_chunk_list);
 210         INIT_LIST_HEAD(&q->retransmit);
 211         INIT_LIST_HEAD(&q->sacked);
 212         INIT_LIST_HEAD(&q->abandoned);
 213
 214         q->fast_rtx = 0;
 215         q->outstanding_bytes = 0;
 216         q->empty = 1;
 217         q->cork  = 0;
 218
 219         q->malloced = 0;
 220         q->out_qlen = 0;
 221 }
 222
 223 /* Free the outqueue structure and any related pending chunks.
 224  */
 225 void sctp_outq_teardown(struct sctp_outq *q)
 226 {
 227         struct sctp_transport *transport;
 228         struct list_head *lchunk, *temp;
 229         struct sctp_chunk *chunk, *tmp;
 230
 231         /* Throw away unacknowledged chunks. */
 232         list_for_each_entry(transport, &q->asoc->peer.transport_addr_list,
 233                         transports) {
 234                 while ((lchunk = sctp_list_dequeue(&transport->transmitted)) != NULL) {
 235                         chunk = list_entry(lchunk, struct sctp_chunk,
 236                                            transmitted_list);
 237                         /* Mark as part of a failed message. */
 238                         sctp_chunk_fail(chunk, q->error);
 239                         sctp_chunk_free(chunk);
 240                 }
 241         }
 242
 243         /* Throw away chunks that have been gap ACKed.  */
 244         list_for_each_safe(lchunk, temp, &q->sacked) {
 245                 list_del_init(lchunk);
 246                 chunk = list_entry(lchunk, struct sctp_chunk,
 247                                    transmitted_list);
 248                 sctp_chunk_fail(chunk, q->error);
 249                 sctp_chunk_free(chunk);
 250         }
 251
 252         /* Throw away any chunks in the retransmit queue. */
 253         list_for_each_safe(lchunk, temp, &q->retransmit) {
 254                 list_del_init(lchunk);
 255                 chunk = list_entry(lchunk, struct sctp_chunk,
 256                                    transmitted_list);
 257                 sctp_chunk_fail(chunk, q->error);
 258                 sctp_chunk_free(chunk);
 259         }
 260
 261         /* Throw away any chunks that are in the abandoned queue. */
 262         list_for_each_safe(lchunk, temp, &q->abandoned) {
 263                 list_del_init(lchunk);
 264                 chunk = list_entry(lchunk, struct sctp_chunk,
 265                                    transmitted_list);
 266                 sctp_chunk_fail(chunk, q->error);
 267                 sctp_chunk_free(chunk);
 268         }
 269
 270         /* Throw away any leftover data chunks. */
 271         while ((chunk = sctp_outq_dequeue_data(q)) != NULL) {
 272
 273                 /* Mark as send failure. */
 274                 sctp_chunk_fail(chunk, q->error);
 275                 sctp_chunk_free(chunk);
 276         }
 277
 278         q->error = 0;
 279
 280         /* Throw away any leftover control chunks. */
 281         list_for_each_entry_safe(chunk, tmp, &q->control_chunk_list, list) {
 282                 list_del_init(&chunk->list);
 283                 sctp_chunk_free(chunk);
 284         }
 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         /* If we were kmalloc()'d, free the memory.  */
 294         if (q->malloced)
 295                 kfree(q);
 296 }
 297
 298 /* Put a new chunk in an sctp_outq.  */
 299 int sctp_outq_tail(struct sctp_outq *q, struct sctp_chunk *chunk)
 300 {
 301         int error = 0;
 302
 303         SCTP_DEBUG_PRINTK("sctp_outq_tail(%p, %p[%s])\n",
 304                           q, chunk, chunk && chunk->chunk_hdr ?
 305                           sctp_cname(SCTP_ST_CHUNK(chunk->chunk_hdr->type))
 306                           : "Illegal Chunk");
 307
 308         /* If it is data, queue it up, otherwise, send it
 309          * immediately.
 310          */
 311         if (sctp_chunk_is_data(chunk)) {
 312                 /* Is it OK to queue data chunks?  */
 313                 /* From 9. Termination of Association
 314                  *
 315                  * When either endpoint performs a shutdown, the
 316                  * association on each peer will stop accepting new
 317                  * data from its user and only deliver data in queue
 318                  * at the time of sending or receiving the SHUTDOWN
 319                  * chunk.
 320                  */
 321                 switch (q->asoc->state) {
 322                 case SCTP_STATE_EMPTY:
 323                 case SCTP_STATE_CLOSED:
 324                 case SCTP_STATE_SHUTDOWN_PENDING:
 325                 case SCTP_STATE_SHUTDOWN_SENT:
 326                 case SCTP_STATE_SHUTDOWN_RECEIVED:
 327                 case SCTP_STATE_SHUTDOWN_ACK_SENT:
 328                         /* Cannot send after transport endpoint shutdown */
 329                         error = -ESHUTDOWN;
 330                         break;
 331
 332                 default:
 333                         SCTP_DEBUG_PRINTK("outqueueing (%p, %p[%s])\n",
 334                           q, chunk, chunk && chunk->chunk_hdr ?
 335                           sctp_cname(SCTP_ST_CHUNK(chunk->chunk_hdr->type))
 336                           : "Illegal Chunk");
 337
 338                         sctp_outq_tail_data(q, chunk);
 339                         if (chunk->chunk_hdr->flags & SCTP_DATA_UNORDERED)
 340                                 SCTP_INC_STATS(SCTP_MIB_OUTUNORDERCHUNKS);
 341                         else
 342                                 SCTP_INC_STATS(SCTP_MIB_OUTORDERCHUNKS);
 343                         q->empty = 0;
 344                         break;
 345                 }
 346         } else {
 347                 list_add_tail(&chunk->list, &q->control_chunk_list);
 348                 SCTP_INC_STATS(SCTP_MIB_OUTCTRLCHUNKS);
 349         }
 350
 351         if (error < 0)
 352                 return error;
 353
 354         if (!q->cork)
 355                 error = sctp_outq_flush(q, 0);
 356
 357         return error;
 358 }
 359
 360 /* Insert a chunk into the sorted list based on the TSNs.  The retransmit list
 361  * and the abandoned list are in ascending order.
 362  */
 363 static void sctp_insert_list(struct list_head *head, struct list_head *new)
 364 {
 365         struct list_head *pos;
 366         struct sctp_chunk *nchunk, *lchunk;
 367         __u32 ntsn, ltsn;
 368         int done = 0;
 369
 370         nchunk = list_entry(new, struct sctp_chunk, transmitted_list);
 371         ntsn = ntohl(nchunk->subh.data_hdr->tsn);
 372
 373         list_for_each(pos, head) {
 374                 lchunk = list_entry(pos, struct sctp_chunk, transmitted_list);
 375                 ltsn = ntohl(lchunk->subh.data_hdr->tsn);
 376                 if (TSN_lt(ntsn, ltsn)) {
 377                         list_add(new, pos->prev);
 378                         done = 1;
 379                         break;
 380                 }
 381         }
 382         if (!done)
 383                 list_add_tail(new, head);
 384 }
 385
 386 /* Mark all the eligible packets on a transport for retransmission.  */
 387 void sctp_retransmit_mark(struct sctp_outq *q,
 388                           struct sctp_transport *transport,
 389                           __u8 reason)
 390 {
 391         struct list_head *lchunk, *ltemp;
 392         struct sctp_chunk *chunk;
 393
 394         /* Walk through the specified transmitted queue.  */
 395         list_for_each_safe(lchunk, ltemp, &transport->transmitted) {
 396                 chunk = list_entry(lchunk, struct sctp_chunk,
 397                                    transmitted_list);
 398
 399                 /* If the chunk is abandoned, move it to abandoned list. */
 400                 if (sctp_chunk_abandoned(chunk)) {
 401                         list_del_init(lchunk);
 402                         sctp_insert_list(&q->abandoned, lchunk);
 403
 404                         /* If this chunk has not been previousely acked,
 405                          * stop considering it 'outstanding'.  Our peer
 406                          * will most likely never see it since it will
 407                          * not be retransmitted
 408                          */
 409                         if (!chunk->tsn_gap_acked) {
 410                                 if (chunk->transport)
 411                                         chunk->transport->flight_size -=
 412                                                         sctp_data_size(chunk);
 413                                 q->outstanding_bytes -= sctp_data_size(chunk);
 414                                 q->asoc->peer.rwnd += (sctp_data_size(chunk) +
 415                                                         sizeof(struct sk_buff));
 416                         }
 417                         continue;
 418                 }
 419
 420                 /* If we are doing  retransmission due to a timeout or pmtu
 421                  * discovery, only the  chunks that are not yet acked should
 422                  * be added to the retransmit queue.
 423                  */
 424                 if ((reason == SCTP_RTXR_FAST_RTX  &&
 425                             (chunk->fast_retransmit == SCTP_NEED_FRTX)) ||
 426                     (reason != SCTP_RTXR_FAST_RTX  && !chunk->tsn_gap_acked)) {
 427                         /* RFC 2960 6.2.1 Processing a Received SACK
 428                          *
 429                          * C) Any time a DATA chunk is marked for
 430                          * retransmission (via either T3-rtx timer expiration
 431                          * (Section 6.3.3) or via fast retransmit
 432                          * (Section 7.2.4)), add the data size of those
 433                          * chunks to the rwnd.
 434                          */
 435                         q->asoc->peer.rwnd += (sctp_data_size(chunk) +
 436                                                 sizeof(struct sk_buff));
 437                         q->outstanding_bytes -= sctp_data_size(chunk);
 438                         if (chunk->transport)
 439                                 transport->flight_size -= sctp_data_size(chunk);
 440
 441                         /* sctpimpguide-05 Section 2.8.2
 442                          * M5) If a T3-rtx timer expires, the
 443                          * 'TSN.Missing.Report' of all affected TSNs is set
 444                          * to 0.
 445                          */
 446                         chunk->tsn_missing_report = 0;
 447
 448                         /* If a chunk that is being used for RTT measurement
 449                          * has to be retransmitted, we cannot use this chunk
 450                          * anymore for RTT measurements. Reset rto_pending so
 451                          * that a new RTT measurement is started when a new
 452                          * data chunk is sent.
 453                          */
 454                         if (chunk->rtt_in_progress) {
 455                                 chunk->rtt_in_progress = 0;
 456                                 transport->rto_pending = 0;
 457                         }
 458
 459                         /* Move the chunk to the retransmit queue. The chunks
 460                          * on the retransmit queue are always kept in order.
 461                          */
 462                         list_del_init(lchunk);
 463                         sctp_insert_list(&q->retransmit, lchunk);
 464                 }
 465         }
 466
 467         SCTP_DEBUG_PRINTK("%s: transport: %p, reason: %d, "
 468                           "cwnd: %d, ssthresh: %d, flight_size: %d, "
 469                           "pba: %d\n", __func__,
 470                           transport, reason,
 471                           transport->cwnd, transport->ssthresh,
 472                           transport->flight_size,
 473                           transport->partial_bytes_acked);
 474
 475 }
 476
 477 /* Mark all the eligible packets on a transport for retransmission and force
 478  * one packet out.
 479  */
 480 void sctp_retransmit(struct sctp_outq *q, struct sctp_transport *transport,
 481                      sctp_retransmit_reason_t reason)
 482 {
 483         int error = 0;
 484
 485         switch(reason) {
 486         case SCTP_RTXR_T3_RTX:
 487                 SCTP_INC_STATS(SCTP_MIB_T3_RETRANSMITS);
 488                 sctp_transport_lower_cwnd(transport, SCTP_LOWER_CWND_T3_RTX);
 489                 /* Update the retran path if the T3-rtx timer has expired for
 490                  * the current retran path.
 491                  */
 492                 if (transport == transport->asoc->peer.retran_path)
 493                         sctp_assoc_update_retran_path(transport->asoc);
 494                 transport->asoc->rtx_data_chunks +=
 495                         transport->asoc->unack_data;
 496                 break;
 497         case SCTP_RTXR_FAST_RTX:
 498                 SCTP_INC_STATS(SCTP_MIB_FAST_RETRANSMITS);
 499                 sctp_transport_lower_cwnd(transport, SCTP_LOWER_CWND_FAST_RTX);
 500                 q->fast_rtx = 1;
 501                 break;
 502         case SCTP_RTXR_PMTUD:
 503                 SCTP_INC_STATS(SCTP_MIB_PMTUD_RETRANSMITS);
 504                 break;
 505         case SCTP_RTXR_T1_RTX:
 506                 SCTP_INC_STATS(SCTP_MIB_T1_RETRANSMITS);
 507                 transport->asoc->init_retries++;
 508                 break;
 509         default:
 510                 BUG();
 511         }
 512
 513         sctp_retransmit_mark(q, transport, reason);
 514
 515         /* PR-SCTP A5) Any time the T3-rtx timer expires, on any destination,
 516          * the sender SHOULD try to advance the "Advanced.Peer.Ack.Point" by
 517          * following the procedures outlined in C1 - C5.
 518          */
 519         if (reason == SCTP_RTXR_T3_RTX)
 520                 sctp_generate_fwdtsn(q, q->asoc->ctsn_ack_point);
 521
 522         /* Flush the queues only on timeout, since fast_rtx is only
 523          * triggered during sack processing and the queue
 524          * will be flushed at the end.
 525          */
 526         if (reason != SCTP_RTXR_FAST_RTX)
 527                 error = sctp_outq_flush(q, /* rtx_timeout */ 1);
 528
 529         if (error)
 530                 q->asoc->base.sk->sk_err = -error;
 531 }
 532
 533 /*
 534  * Transmit DATA chunks on the retransmit queue.  Upon return from
 535  * sctp_outq_flush_rtx() the packet 'pkt' may contain chunks which
 536  * need to be transmitted by the caller.
 537  * We assume that pkt->transport has already been set.
 538  *
 539  * The return value is a normal kernel error return value.
 540  */
 541 static int sctp_outq_flush_rtx(struct sctp_outq *q, struct sctp_packet *pkt,
 542                                int rtx_timeout, int *start_timer)
 543 {
 544         struct list_head *lqueue;
 545         struct sctp_transport *transport = pkt->transport;
 546         sctp_xmit_t status;
 547         struct sctp_chunk *chunk, *chunk1;
 548         int fast_rtx;
 549         int error = 0;
 550         int timer = 0;
 551         int done = 0;
 552
 553         lqueue = &q->retransmit;
 554         fast_rtx = q->fast_rtx;
 555
 556         /* This loop handles time-out retransmissions, fast retransmissions,
 557          * and retransmissions due to opening of whindow.
 558          *
 559          * RFC 2960 6.3.3 Handle T3-rtx Expiration
 560          *
 561          * E3) Determine how many of the earliest (i.e., lowest TSN)
 562          * outstanding DATA chunks for the address for which the
 563          * T3-rtx has expired will fit into a single packet, subject
 564          * to the MTU constraint for the path corresponding to the
 565          * destination transport address to which the retransmission
 566          * is being sent (this may be different from the address for
 567          * which the timer expires [see Section 6.4]). Call this value
 568          * K. Bundle and retransmit those K DATA chunks in a single
 569          * packet to the destination endpoint.
 570          *
 571          * [Just to be painfully clear, if we are retransmitting
 572          * because a timeout just happened, we should send only ONE
 573          * packet of retransmitted data.]
 574          *
 575          * For fast retransmissions we also send only ONE packet.  However,
 576          * if we are just flushing the queue due to open window, we'll
 577          * try to send as much as possible.
 578          */
 579         list_for_each_entry_safe(chunk, chunk1, lqueue, transmitted_list) {
 580
 581                 /* Make sure that Gap Acked TSNs are not retransmitted.  A
 582                  * simple approach is just to move such TSNs out of the
 583                  * way and into a 'transmitted' queue and skip to the
 584                  * next chunk.
 585                  */
 586                 if (chunk->tsn_gap_acked) {
 587                         list_del(&chunk->transmitted_list);
 588                         list_add_tail(&chunk->transmitted_list,
 589                                         &transport->transmitted);
 590                         continue;
 591                 }
 592
 593                 /* If we are doing fast retransmit, ignore non-fast_rtransmit
 594                  * chunks
 595                  */
 596                 if (fast_rtx && !chunk->fast_retransmit)
 597                         continue;
 598
 599 redo:
 600                 /* Attempt to append this chunk to the packet. */
 601                 status = sctp_packet_append_chunk(pkt, chunk);
 602
 603                 switch (status) {
 604                 case SCTP_XMIT_PMTU_FULL:
 605                         if (!pkt->has_data && !pkt->has_cookie_echo) {
 606                                 /* If this packet did not contain DATA then
 607                                  * retransmission did not happen, so do it
 608                                  * again.  We'll ignore the error here since
 609                                  * control chunks are already freed so there
 610                                  * is nothing we can do.
 611                                  */
 612                                 sctp_packet_transmit(pkt);
 613                                 goto redo;
 614                         }
 615
 616                         /* Send this packet.  */
 617                         error = sctp_packet_transmit(pkt);
 618
 619                         /* If we are retransmitting, we should only
 620                          * send a single packet.
 621                          */
 622                         if (rtx_timeout || fast_rtx)
 623                                 done = 1;
 624
 625                         /* Bundle next chunk in the next round.  */
 626                         break;
 627
 628                 case SCTP_XMIT_RWND_FULL:
 629                         /* Send this packet. */
 630                         error = sctp_packet_transmit(pkt);
 631
 632                         /* Stop sending DATA as there is no more room
 633                          * at the receiver.
 634                          */
 635                         done = 1;
 636                         break;
 637
 638                 case SCTP_XMIT_NAGLE_DELAY:
 639                         /* Send this packet. */
 640                         error = sctp_packet_transmit(pkt);
 641
 642                         /* Stop sending DATA because of nagle delay. */
 643                         done = 1;
 644                         break;
 645
 646                 default:
 647                         /* The append was successful, so add this chunk to
 648                          * the transmitted list.
 649                          */
 650                         list_del(&chunk->transmitted_list);
 651                         list_add_tail(&chunk->transmitted_list,
 652                                         &transport->transmitted);
 653
 654                         /* Mark the chunk as ineligible for fast retransmit
 655                          * after it is retransmitted.
 656                          */
 657                         if (chunk->fast_retransmit == SCTP_NEED_FRTX)
 658                                 chunk->fast_retransmit = SCTP_DONT_FRTX;
 659
 660                         q->empty = 0;
 661                         break;
 662                 }
 663
 664                 /* Set the timer if there were no errors */
 665                 if (!error && !timer)
 666                         timer = 1;
 667
 668                 if (done)
 669                         break;
 670         }
 671
 672         /* If we are here due to a retransmit timeout or a fast
 673          * retransmit and if there are any chunks left in the retransmit
 674          * queue that could not fit in the PMTU sized packet, they need
 675          * to be marked as ineligible for a subsequent fast retransmit.
 676          */
 677         if (rtx_timeout || fast_rtx) {
 678                 list_for_each_entry(chunk1, lqueue, transmitted_list) {
 679                         if (chunk1->fast_retransmit == SCTP_NEED_FRTX)
 680                                 chunk1->fast_retransmit = SCTP_DONT_FRTX;
 681                 }
 682         }
 683
 684         *start_timer = timer;
 685
 686         /* Clear fast retransmit hint */
 687         if (fast_rtx)
 688                 q->fast_rtx = 0;
 689
 690         return error;
 691 }
 692
 693 /* Cork the outqueue so queued chunks are really queued. */
 694 int sctp_outq_uncork(struct sctp_outq *q)
 695 {
 696         int error = 0;
 697         if (q->cork)
 698                 q->cork = 0;
 699         error = sctp_outq_flush(q, 0);
 700         return error;
 701 }
 702
 703
 704 /*
 705  * Try to flush an outqueue.
 706  *
 707  * Description: Send everything in q which we legally can, subject to
 708  * congestion limitations.
 709  * * Note: This function can be called from multiple contexts so appropriate
 710  * locking concerns must be made.  Today we use the sock lock to protect
 711  * this function.
 712  */
 713 static int sctp_outq_flush(struct sctp_outq *q, int rtx_timeout)
 714 {
 715         struct sctp_packet *packet;
 716         struct sctp_packet singleton;
 717         struct sctp_association *asoc = q->asoc;
 718         __u16 sport = asoc->base.bind_addr.port;
 719         __u16 dport = asoc->peer.port;
 720         __u32 vtag = asoc->peer.i.init_tag;
 721         struct sctp_transport *transport = NULL;
 722         struct sctp_transport *new_transport;
 723         struct sctp_chunk *chunk, *tmp;
 724         sctp_xmit_t status;
 725         int error = 0;
 726         int start_timer = 0;
 727         int one_packet = 0;
 728
 729         /* These transports have chunks to send. */
 730         struct list_head transport_list;
 731         struct list_head *ltransport;
 732
 733         INIT_LIST_HEAD(&transport_list);
 734         packet = NULL;
 735
 736         /*
 737          * 6.10 Bundling
 738          *   ...
 739          *   When bundling control chunks with DATA chunks, an
 740          *   endpoint MUST place control chunks first in the outbound
 741          *   SCTP packet.  The transmitter MUST transmit DATA chunks
 742          *   within a SCTP packet in increasing order of TSN.
 743          *   ...
 744          */
 745
 746         list_for_each_entry_safe(chunk, tmp, &q->control_chunk_list, list) {
 747                 list_del_init(&chunk->list);
 748
 749                 /* Pick the right transport to use. */
 750                 new_transport = chunk->transport;
 751
 752                 if (!new_transport) {
 753                         /*
 754                          * If we have a prior transport pointer, see if
 755                          * the destination address of the chunk
 756                          * matches the destination address of the
 757                          * current transport.  If not a match, then
 758                          * try to look up the transport with a given
 759                          * destination address.  We do this because
 760                          * after processing ASCONFs, we may have new
 761                          * transports created.
 762                          */
 763                         if (transport &&
 764                             sctp_cmp_addr_exact(&chunk->dest,
 765                                                 &transport->ipaddr))
 766                                         new_transport = transport;
 767                         else
 768                                 new_transport = sctp_assoc_lookup_paddr(asoc,
 769                                                                 &chunk->dest);
 770
 771                         /* if we still don't have a new transport, then
 772                          * use the current active path.
 773                          */
 774                         if (!new_transport)
 775                                 new_transport = asoc->peer.active_path;
 776                 } else if ((new_transport->state == SCTP_INACTIVE) ||
 777                            (new_transport->state == SCTP_UNCONFIRMED)) {
 778                         /* If the chunk is Heartbeat or Heartbeat Ack,
 779                          * send it to chunk->transport, even if it's
 780                          * inactive.
 781                          *
 782                          * 3.3.6 Heartbeat Acknowledgement:
 783                          * ...
 784                          * A HEARTBEAT ACK is always sent to the source IP
 785                          * address of the IP datagram containing the
 786                          * HEARTBEAT chunk to which this ack is responding.
 787                          * ...
 788                          *
 789                          * ASCONF_ACKs also must be sent to the source.
 790                          */
 791                         if (chunk->chunk_hdr->type != SCTP_CID_HEARTBEAT &&
 792                             chunk->chunk_hdr->type != SCTP_CID_HEARTBEAT_ACK &&
 793                             chunk->chunk_hdr->type != SCTP_CID_ASCONF_ACK)
 794                                 new_transport = asoc->peer.active_path;
 795                 }
 796
 797                 /* Are we switching transports?
 798                  * Take care of transport locks.
 799                  */
 800                 if (new_transport != transport) {
 801                         transport = new_transport;
 802                         if (list_empty(&transport->send_ready)) {
 803                                 list_add_tail(&transport->send_ready,
 804                                               &transport_list);
 805                         }
 806                         packet = &transport->packet;
 807                         sctp_packet_config(packet, vtag,
 808                                            asoc->peer.ecn_capable);
 809                 }
 810
 811                 switch (chunk->chunk_hdr->type) {
 812                 /*
 813                  * 6.10 Bundling
 814                  *   ...
 815                  *   An endpoint MUST NOT bundle INIT, INIT ACK or SHUTDOWN
 816                  *   COMPLETE with any other chunks.  [Send them immediately.]
 817                  */
 818                 case SCTP_CID_INIT:
 819                 case SCTP_CID_INIT_ACK:
 820                 case SCTP_CID_SHUTDOWN_COMPLETE:
 821                         sctp_packet_init(&singleton, transport, sport, dport);
 822                         sctp_packet_config(&singleton, vtag, 0);
 823                         sctp_packet_append_chunk(&singleton, chunk);
 824                         error = sctp_packet_transmit(&singleton);
 825                         if (error < 0)
 826                                 return error;
 827                         break;
 828
 829                 case SCTP_CID_ABORT:
 830                         if (sctp_test_T_bit(chunk)) {
 831                                 packet->vtag = asoc->c.my_vtag;
 832                         }
 833                 /* The following chunks are "response" chunks, i.e.
 834                  * they are generated in response to something we
 835                  * received.  If we are sending these, then we can
 836                  * send only 1 packet containing these chunks.
 837                  */
 838                 case SCTP_CID_HEARTBEAT_ACK:
 839                 case SCTP_CID_SHUTDOWN_ACK:
 840                 case SCTP_CID_COOKIE_ACK:
 841                 case SCTP_CID_COOKIE_ECHO:
 842                 case SCTP_CID_ERROR:
 843                 case SCTP_CID_ECN_CWR:
 844                 case SCTP_CID_ASCONF_ACK:
 845                         one_packet = 1;
 846                         /* Fall through */
 847
 848                 case SCTP_CID_SACK:
 849                 case SCTP_CID_HEARTBEAT:
 850                 case SCTP_CID_SHUTDOWN:
 851                 case SCTP_CID_ECN_ECNE:
 852                 case SCTP_CID_ASCONF:
 853                 case SCTP_CID_FWD_TSN:
 854                         status = sctp_packet_transmit_chunk(packet, chunk,
 855                                                             one_packet);
 856                         if (status  != SCTP_XMIT_OK) {
 857                                 /* put the chunk back */
 858                                 list_add(&chunk->list, &q->control_chunk_list);
 859                         } else if (chunk->chunk_hdr->type == SCTP_CID_FWD_TSN) {
 860                                 /* PR-SCTP C5) If a FORWARD TSN is sent, the
 861                                  * sender MUST assure that at least one T3-rtx
 862                                  * timer is running.
 863                                  */
 864                                 sctp_transport_reset_timers(transport);
 865                         }
 866                         break;
 867
 868                 default:
 869                         /* We built a chunk with an illegal type! */
 870                         BUG();
 871                 }
 872         }
 873
 874         /* Is it OK to send data chunks?  */
 875         switch (asoc->state) {
 876         case SCTP_STATE_COOKIE_ECHOED:
 877                 /* Only allow bundling when this packet has a COOKIE-ECHO
 878                  * chunk.
 879                  */
 880                 if (!packet || !packet->has_cookie_echo)
 881                         break;
 882
 883                 /* fallthru */
 884         case SCTP_STATE_ESTABLISHED:
 885         case SCTP_STATE_SHUTDOWN_PENDING:
 886         case SCTP_STATE_SHUTDOWN_RECEIVED:
 887                 /*
 888                  * RFC 2960 6.1  Transmission of DATA Chunks
 889                  *
 890                  * C) When the time comes for the sender to transmit,
 891                  * before sending new DATA chunks, the sender MUST
 892                  * first transmit any outstanding DATA chunks which
 893                  * are marked for retransmission (limited by the
 894                  * current cwnd).
 895                  */
 896                 if (!list_empty(&q->retransmit)) {
 897                         if (transport == asoc->peer.retran_path)
 898                                 goto retran;
 899
 900                         /* Switch transports & prepare the packet.  */
 901
 902                         transport = asoc->peer.retran_path;
 903
 904                         if (list_empty(&transport->send_ready)) {
 905                                 list_add_tail(&transport->send_ready,
 906                                               &transport_list);
 907                         }
 908
 909                         packet = &transport->packet;
 910                         sctp_packet_config(packet, vtag,
 911                                            asoc->peer.ecn_capable);
 912                 retran:
 913                         error = sctp_outq_flush_rtx(q, packet,
 914                                                     rtx_timeout, &start_timer);
 915
 916                         if (start_timer)
 917                                 sctp_transport_reset_timers(transport);
 918
 919                         /* This can happen on COOKIE-ECHO resend.  Only
 920                          * one chunk can get bundled with a COOKIE-ECHO.
 921                          */
 922                         if (packet->has_cookie_echo)
 923                                 goto sctp_flush_out;
 924
 925                         /* Don't send new data if there is still data
 926                          * waiting to retransmit.
 927                          */
 928                         if (!list_empty(&q->retransmit))
 929                                 goto sctp_flush_out;
 930                 }
 931
 932                 /* Apply Max.Burst limitation to the current transport in
 933                  * case it will be used for new data.  We are going to
 934                  * rest it before we return, but we want to apply the limit
 935                  * to the currently queued data.
 936                  */
 937                 if (transport)
 938                         sctp_transport_burst_limited(transport);
 939
 940                 /* Finally, transmit new packets.  */
 941                 while ((chunk = sctp_outq_dequeue_data(q)) != NULL) {
 942                         /* RFC 2960 6.5 Every DATA chunk MUST carry a valid
 943                          * stream identifier.
 944                          */
 945                         if (chunk->sinfo.sinfo_stream >=
 946                             asoc->c.sinit_num_ostreams) {
 947
 948                                 /* Mark as failed send. */
 949                                 sctp_chunk_fail(chunk, SCTP_ERROR_INV_STRM);
 950                                 sctp_chunk_free(chunk);
 951                                 continue;
 952                         }
 953
 954                         /* Has this chunk expired? */
 955                         if (sctp_chunk_abandoned(chunk)) {
 956                                 sctp_chunk_fail(chunk, 0);
 957                                 sctp_chunk_free(chunk);
 958                                 continue;
 959                         }
 960
 961                         /* If there is a specified transport, use it.
 962                          * Otherwise, we want to use the active path.
 963                          */
 964                         new_transport = chunk->transport;
 965                         if (!new_transport ||
 966                             ((new_transport->state == SCTP_INACTIVE) ||
 967                              (new_transport->state == SCTP_UNCONFIRMED)))
 968                                 new_transport = asoc->peer.active_path;
 969
 970                         /* Change packets if necessary.  */
 971                         if (new_transport != transport) {
 972                                 transport = new_transport;
 973
 974                                 /* Schedule to have this transport's
 975                                  * packet flushed.
 976                                  */
 977                                 if (list_empty(&transport->send_ready)) {
 978                                         list_add_tail(&transport->send_ready,
 979                                                       &transport_list);
 980                                 }
 981
 982                                 packet = &transport->packet;
 983                                 sctp_packet_config(packet, vtag,
 984                                                    asoc->peer.ecn_capable);
 985                                 /* We've switched transports, so apply the
 986                                  * Burst limit to the new transport.
 987                                  */
 988                                 sctp_transport_burst_limited(transport);
 989                         }
 990
 991                         SCTP_DEBUG_PRINTK("sctp_outq_flush(%p, %p[%s]), ",
 992                                           q, chunk,
 993                                           chunk && chunk->chunk_hdr ?
 994                                           sctp_cname(SCTP_ST_CHUNK(
 995                                                   chunk->chunk_hdr->type))
 996                                           : "Illegal Chunk");
 997
 998                         SCTP_DEBUG_PRINTK("TX TSN 0x%x skb->head "
 999                                         "%p skb->users %d.\n",
1000                                         ntohl(chunk->subh.data_hdr->tsn),
1001                                         chunk->skb ?chunk->skb->head : NULL,
1002                                         chunk->skb ?
1003                                         atomic_read(&chunk->skb->users) : -1);
1004
1005                         /* Add the chunk to the packet.  */
1006                         status = sctp_packet_transmit_chunk(packet, chunk, 0);
1007
1008                         switch (status) {
1009                         case SCTP_XMIT_PMTU_FULL:
1010                         case SCTP_XMIT_RWND_FULL:
1011                         case SCTP_XMIT_NAGLE_DELAY:
1012                                 /* We could not append this chunk, so put
1013                                  * the chunk back on the output queue.
1014                                  */
1015                                 SCTP_DEBUG_PRINTK("sctp_outq_flush: could "
1016                                         "not transmit TSN: 0x%x, status: %d\n",
1017                                         ntohl(chunk->subh.data_hdr->tsn),
1018                                         status);
1019                                 sctp_outq_head_data(q, chunk);
1020                                 goto sctp_flush_out;
1021                                 break;
1022
1023                         case SCTP_XMIT_OK:
1024                                 /* The sender is in the SHUTDOWN-PENDING state,
1025                                  * The sender MAY set the I-bit in the DATA
1026                                  * chunk header.
1027                                  */
1028                                 if (asoc->state == SCTP_STATE_SHUTDOWN_PENDING)
1029                                         chunk->chunk_hdr->flags |= SCTP_DATA_SACK_IMM;
1030
1031                                 break;
1032
1033                         default:
1034                                 BUG();
1035                         }
1036
1037                         /* BUG: We assume that the sctp_packet_transmit()
1038                          * call below will succeed all the time and add the
1039                          * chunk to the transmitted list and restart the
1040                          * timers.
1041                          * It is possible that the call can fail under OOM
1042                          * conditions.
1043                          *
1044                          * Is this really a problem?  Won't this behave
1045                          * like a lost TSN?
1046                          */
1047                         list_add_tail(&chunk->transmitted_list,
1048                                       &transport->transmitted);
1049
1050                         sctp_transport_reset_timers(transport);
1051
1052                         q->empty = 0;
1053
1054                         /* Only let one DATA chunk get bundled with a
1055                          * COOKIE-ECHO chunk.
1056                          */
1057                         if (packet->has_cookie_echo)
1058                                 goto sctp_flush_out;
1059                 }
1060                 break;
1061
1062         default:
1063                 /* Do nothing.  */
1064                 break;
1065         }
1066
1067 sctp_flush_out:
1068
1069         /* Before returning, examine all the transports touched in
1070          * this call.  Right now, we bluntly force clear all the
1071          * transports.  Things might change after we implement Nagle.
1072          * But such an examination is still required.
1073          *
1074          * --xguo
1075          */
1076         while ((ltransport = sctp_list_dequeue(&transport_list)) != NULL ) {
1077                 struct sctp_transport *t = list_entry(ltransport,
1078                                                       struct sctp_transport,
1079                                                       send_ready);
1080                 packet = &t->packet;
1081                 if (!sctp_packet_empty(packet))
1082                         error = sctp_packet_transmit(packet);
1083
1084                 /* Clear the burst limited state, if any */
1085                 sctp_transport_burst_reset(t);
1086         }
1087
1088         return error;
1089 }
1090
1091 /* Update unack_data based on the incoming SACK chunk */
1092 static void sctp_sack_update_unack_data(struct sctp_association *assoc,
1093                                         struct sctp_sackhdr *sack)
1094 {
1095         sctp_sack_variable_t *frags;
1096         __u16 unack_data;
1097         int i;
1098
1099         unack_data = assoc->next_tsn - assoc->ctsn_ack_point - 1;
1100
1101         frags = sack->variable;
1102         for (i = 0; i < ntohs(sack->num_gap_ack_blocks); i++) {
1103                 unack_data -= ((ntohs(frags[i].gab.end) -
1104                                 ntohs(frags[i].gab.start) + 1));
1105         }
1106
1107         assoc->unack_data = unack_data;
1108 }
1109
1110 /* This is where we REALLY process a SACK.
1111  *
1112  * Process the SACK against the outqueue.  Mostly, this just frees
1113  * things off the transmitted queue.
1114  */
1115 int sctp_outq_sack(struct sctp_outq *q, struct sctp_sackhdr *sack)
1116 {
1117         struct sctp_association *asoc = q->asoc;
1118         struct sctp_transport *transport;
1119         struct sctp_chunk *tchunk = NULL;
1120         struct list_head *lchunk, *transport_list, *temp;
1121         sctp_sack_variable_t *frags = sack->variable;
1122         __u32 sack_ctsn, ctsn, tsn;
1123         __u32 highest_tsn, highest_new_tsn;
1124         __u32 sack_a_rwnd;
1125         unsigned outstanding;
1126         struct sctp_transport *primary = asoc->peer.primary_path;
1127         int count_of_newacks = 0;
1128         int gap_ack_blocks;
1129         u8 accum_moved = 0;
1130
1131         /* Grab the association's destination address list. */
1132         transport_list = &asoc->peer.transport_addr_list;
1133
1134         sack_ctsn = ntohl(sack->cum_tsn_ack);
1135         gap_ack_blocks = ntohs(sack->num_gap_ack_blocks);
1136         /*
1137          * SFR-CACC algorithm:
1138          * On receipt of a SACK the sender SHOULD execute the
1139          * following statements.
1140          *
1141          * 1) If the cumulative ack in the SACK passes next tsn_at_change
1142          * on the current primary, the CHANGEOVER_ACTIVE flag SHOULD be
1143          * cleared. The CYCLING_CHANGEOVER flag SHOULD also be cleared for
1144          * all destinations.
1145          * 2) If the SACK contains gap acks and the flag CHANGEOVER_ACTIVE
1146          * is set the receiver of the SACK MUST take the following actions:
1147          *
1148          * A) Initialize the cacc_saw_newack to 0 for all destination
1149          * addresses.
1150          *
1151          * Only bother if changeover_active is set. Otherwise, this is
1152          * totally suboptimal to do on every SACK.
1153          */
1154         if (primary->cacc.changeover_active) {
1155                 u8 clear_cycling = 0;
1156
1157                 if (TSN_lte(primary->cacc.next_tsn_at_change, sack_ctsn)) {
1158                         primary->cacc.changeover_active = 0;
1159                         clear_cycling = 1;
1160                 }
1161
1162                 if (clear_cycling || gap_ack_blocks) {
1163                         list_for_each_entry(transport, transport_list,
1164                                         transports) {
1165                                 if (clear_cycling)
1166                                         transport->cacc.cycling_changeover = 0;
1167                                 if (gap_ack_blocks)
1168                                         transport->cacc.cacc_saw_newack = 0;
1169                         }
1170                 }
1171         }
1172
1173         /* Get the highest TSN in the sack. */
1174         highest_tsn = sack_ctsn;
1175         if (gap_ack_blocks)
1176                 highest_tsn += ntohs(frags[gap_ack_blocks - 1].gab.end);
1177
1178         if (TSN_lt(asoc->highest_sacked, highest_tsn))
1179                 asoc->highest_sacked = highest_tsn;
1180
1181         highest_new_tsn = sack_ctsn;
1182
1183         /* Run through the retransmit queue.  Credit bytes received
1184          * and free those chunks that we can.
1185          */
1186         sctp_check_transmitted(q, &q->retransmit, NULL, sack, &highest_new_tsn);
1187
1188         /* Run through the transmitted queue.
1189          * Credit bytes received and free those chunks which we can.
1190          *
1191          * This is a MASSIVE candidate for optimization.
1192          */
1193         list_for_each_entry(transport, transport_list, transports) {
1194                 sctp_check_transmitted(q, &transport->transmitted,
1195                                        transport, sack, &highest_new_tsn);
1196                 /*
1197                  * SFR-CACC algorithm:
1198                  * C) Let count_of_newacks be the number of
1199                  * destinations for which cacc_saw_newack is set.
1200                  */
1201                 if (transport->cacc.cacc_saw_newack)
1202                         count_of_newacks ++;
1203         }
1204
1205         /* Move the Cumulative TSN Ack Point if appropriate.  */
1206         if (TSN_lt(asoc->ctsn_ack_point, sack_ctsn)) {
1207                 asoc->ctsn_ack_point = sack_ctsn;
1208                 accum_moved = 1;
1209         }
1210
1211         if (gap_ack_blocks) {
1212
1213                 if (asoc->fast_recovery && accum_moved)
1214                         highest_new_tsn = highest_tsn;
1215
1216                 list_for_each_entry(transport, transport_list, transports)
1217                         sctp_mark_missing(q, &transport->transmitted, transport,
1218                                           highest_new_tsn, count_of_newacks);
1219         }
1220
1221         /* Update unack_data field in the assoc. */
1222         sctp_sack_update_unack_data(asoc, sack);
1223
1224         ctsn = asoc->ctsn_ack_point;
1225
1226         /* Throw away stuff rotting on the sack queue.  */
1227         list_for_each_safe(lchunk, temp, &q->sacked) {
1228                 tchunk = list_entry(lchunk, struct sctp_chunk,
1229                                     transmitted_list);
1230                 tsn = ntohl(tchunk->subh.data_hdr->tsn);
1231                 if (TSN_lte(tsn, ctsn)) {
1232                         list_del_init(&tchunk->transmitted_list);
1233                         sctp_chunk_free(tchunk);
1234                 }
1235         }
1236
1237         /* ii) Set rwnd equal to the newly received a_rwnd minus the
1238          *     number of bytes still outstanding after processing the
1239          *     Cumulative TSN Ack and the Gap Ack Blocks.
1240          */
1241
1242         sack_a_rwnd = ntohl(sack->a_rwnd);
1243         outstanding = q->outstanding_bytes;
1244
1245         if (outstanding < sack_a_rwnd)
1246                 sack_a_rwnd -= outstanding;
1247         else
1248                 sack_a_rwnd = 0;
1249
1250         asoc->peer.rwnd = sack_a_rwnd;
1251
1252         sctp_generate_fwdtsn(q, sack_ctsn);
1253
1254         SCTP_DEBUG_PRINTK("%s: sack Cumulative TSN Ack is 0x%x.\n",
1255                           __func__, sack_ctsn);
1256         SCTP_DEBUG_PRINTK("%s: Cumulative TSN Ack of association, "
1257                           "%p is 0x%x. Adv peer ack point: 0x%x\n",
1258                           __func__, asoc, ctsn, asoc->adv_peer_ack_point);
1259
1260         /* See if all chunks are acked.
1261          * Make sure the empty queue handler will get run later.
1262          */
1263         q->empty = (list_empty(&q->out_chunk_list) &&
1264                     list_empty(&q->retransmit));
1265         if (!q->empty)
1266                 goto finish;
1267
1268         list_for_each_entry(transport, transport_list, transports) {
1269                 q->empty = q->empty && list_empty(&transport->transmitted);
1270                 if (!q->empty)
1271                         goto finish;
1272         }
1273
1274         SCTP_DEBUG_PRINTK("sack queue is empty.\n");
1275 finish:
1276         return q->empty;
1277 }
1278
1279 /* Is the outqueue empty?  */
1280 int sctp_outq_is_empty(const struct sctp_outq *q)
1281 {
1282         return q->empty;
1283 }
1284
1285 /********************************************************************
1286  * 2nd Level Abstractions
1287  ********************************************************************/
1288
1289 /* Go through a transport's transmitted list or the association's retransmit
1290  * list and move chunks that are acked by the Cumulative TSN Ack to q->sacked.
1291  * The retransmit list will not have an associated transport.
1292  *
1293  * I added coherent debug information output.   --xguo
1294  *
1295  * Instead of printing 'sacked' or 'kept' for each TSN on the
1296  * transmitted_queue, we print a range: SACKED: TSN1-TSN2, TSN3, TSN4-TSN5.
1297  * KEPT TSN6-TSN7, etc.
1298  */
1299 static void sctp_check_transmitted(struct sctp_outq *q,
1300                                    struct list_head *transmitted_queue,
1301                                    struct sctp_transport *transport,
1302                                    struct sctp_sackhdr *sack,
1303                                    __u32 *highest_new_tsn_in_sack)
1304 {
1305         struct list_head *lchunk;
1306         struct sctp_chunk *tchunk;
1307         struct list_head tlist;
1308         __u32 tsn;
1309         __u32 sack_ctsn;
1310         __u32 rtt;
1311         __u8 restart_timer = 0;
1312         int bytes_acked = 0;
1313         int migrate_bytes = 0;
1314
1315         /* These state variables are for coherent debug output. --xguo */
1316
1317 #if SCTP_DEBUG
1318         __u32 dbg_ack_tsn = 0;  /* An ACKed TSN range starts here... */
1319         __u32 dbg_last_ack_tsn = 0;  /* ...and finishes here.        */
1320         __u32 dbg_kept_tsn = 0; /* An un-ACKed range starts here...  */
1321         __u32 dbg_last_kept_tsn = 0; /* ...and finishes here.        */
1322
1323         /* 0 : The last TSN was ACKed.
1324          * 1 : The last TSN was NOT ACKed (i.e. KEPT).
1325          * -1: We need to initialize.
1326          */
1327         int dbg_prt_state = -1;
1328 #endif /* SCTP_DEBUG */
1329
1330         sack_ctsn = ntohl(sack->cum_tsn_ack);
1331
1332         INIT_LIST_HEAD(&tlist);
1333
1334         /* The while loop will skip empty transmitted queues. */
1335         while (NULL != (lchunk = sctp_list_dequeue(transmitted_queue))) {
1336                 tchunk = list_entry(lchunk, struct sctp_chunk,
1337                                     transmitted_list);
1338
1339                 if (sctp_chunk_abandoned(tchunk)) {
1340                         /* Move the chunk to abandoned list. */
1341                         sctp_insert_list(&q->abandoned, lchunk);
1342
1343                         /* If this chunk has not been acked, stop
1344                          * considering it as 'outstanding'.
1345                          */
1346                         if (!tchunk->tsn_gap_acked) {
1347                                 if (tchunk->transport)
1348                                         tchunk->transport->flight_size -=
1349                                                         sctp_data_size(tchunk);
1350                                 q->outstanding_bytes -= sctp_data_size(tchunk);
1351                         }
1352                         continue;
1353                 }
1354
1355                 tsn = ntohl(tchunk->subh.data_hdr->tsn);
1356                 if (sctp_acked(sack, tsn)) {
1357                         /* If this queue is the retransmit queue, the
1358                          * retransmit timer has already reclaimed
1359                          * the outstanding bytes for this chunk, so only
1360                          * count bytes associated with a transport.
1361                          */
1362                         if (transport) {
1363                                 /* If this chunk is being used for RTT
1364                                  * measurement, calculate the RTT and update
1365                                  * the RTO using this value.
1366                                  *
1367                                  * 6.3.1 C5) Karn's algorithm: RTT measurements
1368                                  * MUST NOT be made using packets that were
1369                                  * retransmitted (and thus for which it is
1370                                  * ambiguous whether the reply was for the
1371                                  * first instance of the packet or a later
1372                                  * instance).
1373                                  */
1374                                 if (!tchunk->tsn_gap_acked &&
1375                                     tchunk->rtt_in_progress) {
1376                                         tchunk->rtt_in_progress = 0;
1377                                         rtt = jiffies - tchunk->sent_at;
1378                                         sctp_transport_update_rto(transport,
1379                                                                   rtt);
1380                                 }
1381                         }
1382
1383                         /* If the chunk hasn't been marked as ACKED,
1384                          * mark it and account bytes_acked if the
1385                          * chunk had a valid transport (it will not
1386                          * have a transport if ASCONF had deleted it
1387                          * while DATA was outstanding).
1388                          */
1389                         if (!tchunk->tsn_gap_acked) {
1390                                 tchunk->tsn_gap_acked = 1;
1391                                 *highest_new_tsn_in_sack = tsn;
1392                                 bytes_acked += sctp_data_size(tchunk);
1393                                 if (!tchunk->transport)
1394                                         migrate_bytes += sctp_data_size(tchunk);
1395                         }
1396
1397                         if (TSN_lte(tsn, sack_ctsn)) {
1398                                 /* RFC 2960  6.3.2 Retransmission Timer Rules
1399                                  *
1400                                  * R3) Whenever a SACK is received
1401                                  * that acknowledges the DATA chunk
1402                                  * with the earliest outstanding TSN
1403                                  * for that address, restart T3-rtx
1404                                  * timer for that address with its
1405                                  * current RTO.
1406                                  */
1407                                 restart_timer = 1;
1408
1409                                 if (!tchunk->tsn_gap_acked) {
1410                                         /*
1411                                          * SFR-CACC algorithm:
1412                                          * 2) If the SACK contains gap acks
1413                                          * and the flag CHANGEOVER_ACTIVE is
1414                                          * set the receiver of the SACK MUST
1415                                          * take the following action:
1416                                          *
1417                                          * B) For each TSN t being acked that
1418                                          * has not been acked in any SACK so
1419                                          * far, set cacc_saw_newack to 1 for
1420                                          * the destination that the TSN was
1421                                          * sent to.
1422                                          */
1423                                         if (transport &&
1424                                             sack->num_gap_ack_blocks &&
1425                                             q->asoc->peer.primary_path->cacc.
1426                                             changeover_active)
1427                                                 transport->cacc.cacc_saw_newack
1428                                                         = 1;
1429                                 }
1430
1431                                 list_add_tail(&tchunk->transmitted_list,
1432                                               &q->sacked);
1433                         } else {
1434                                 /* RFC2960 7.2.4, sctpimpguide-05 2.8.2
1435                                  * M2) Each time a SACK arrives reporting
1436                                  * 'Stray DATA chunk(s)' record the highest TSN
1437                                  * reported as newly acknowledged, call this
1438                                  * value 'HighestTSNinSack'. A newly
1439                                  * acknowledged DATA chunk is one not
1440                                  * previously acknowledged in a SACK.
1441                                  *
1442                                  * When the SCTP sender of data receives a SACK
1443                                  * chunk that acknowledges, for the first time,
1444                                  * the receipt of a DATA chunk, all the still
1445                                  * unacknowledged DATA chunks whose TSN is
1446                                  * older than that newly acknowledged DATA
1447                                  * chunk, are qualified as 'Stray DATA chunks'.
1448                                  */
1449                                 list_add_tail(lchunk, &tlist);
1450                         }
1451
1452 #if SCTP_DEBUG
1453                         switch (dbg_prt_state) {
1454                         case 0: /* last TSN was ACKed */
1455                                 if (dbg_last_ack_tsn + 1 == tsn) {
1456                                         /* This TSN belongs to the
1457                                          * current ACK range.
1458                                          */
1459                                         break;
1460                                 }
1461
1462                                 if (dbg_last_ack_tsn != dbg_ack_tsn) {
1463                                         /* Display the end of the
1464                                          * current range.
1465                                          */
1466                                         SCTP_DEBUG_PRINTK_CONT("-%08x",
1467                                                                dbg_last_ack_tsn);
1468                                 }
1469
1470                                 /* Start a new range.  */
1471                                 SCTP_DEBUG_PRINTK_CONT(",%08x", tsn);
1472                                 dbg_ack_tsn = tsn;
1473                                 break;
1474
1475                         case 1: /* The last TSN was NOT ACKed. */
1476                                 if (dbg_last_kept_tsn != dbg_kept_tsn) {
1477                                         /* Display the end of current range. */
1478                                         SCTP_DEBUG_PRINTK_CONT("-%08x",
1479                                                                dbg_last_kept_tsn);
1480                                 }
1481
1482                                 SCTP_DEBUG_PRINTK_CONT("\n");
1483
1484                                 /* FALL THROUGH... */
1485                         default:
1486                                 /* This is the first-ever TSN we examined.  */
1487                                 /* Start a new range of ACK-ed TSNs.  */
1488                                 SCTP_DEBUG_PRINTK("ACKed: %08x", tsn);
1489                                 dbg_prt_state = 0;
1490                                 dbg_ack_tsn = tsn;
1491                         }
1492
1493                         dbg_last_ack_tsn = tsn;
1494 #endif /* SCTP_DEBUG */
1495
1496                 } else {
1497                         if (tchunk->tsn_gap_acked) {
1498                                 SCTP_DEBUG_PRINTK("%s: Receiver reneged on "
1499                                                   "data TSN: 0x%x\n",
1500                                                   __func__,
1501                                                   tsn);
1502                                 tchunk->tsn_gap_acked = 0;
1503
1504                                 if (tchunk->transport)
1505                                         bytes_acked -= sctp_data_size(tchunk);
1506
1507                                 /* RFC 2960 6.3.2 Retransmission Timer Rules
1508                                  *
1509                                  * R4) Whenever a SACK is received missing a
1510                                  * TSN that was previously acknowledged via a
1511                                  * Gap Ack Block, start T3-rtx for the
1512                                  * destination address to which the DATA
1513                                  * chunk was originally
1514                                  * transmitted if it is not already running.
1515                                  */
1516                                 restart_timer = 1;
1517                         }
1518
1519                         list_add_tail(lchunk, &tlist);
1520
1521 #if SCTP_DEBUG
1522                         /* See the above comments on ACK-ed TSNs. */
1523                         switch (dbg_prt_state) {
1524                         case 1:
1525                                 if (dbg_last_kept_tsn + 1 == tsn)
1526                                         break;
1527
1528                                 if (dbg_last_kept_tsn != dbg_kept_tsn)
1529                                         SCTP_DEBUG_PRINTK_CONT("-%08x",
1530                                                                dbg_last_kept_tsn);
1531
1532                                 SCTP_DEBUG_PRINTK_CONT(",%08x", tsn);
1533                                 dbg_kept_tsn = tsn;
1534                                 break;
1535
1536                         case 0:
1537                                 if (dbg_last_ack_tsn != dbg_ack_tsn)
1538                                         SCTP_DEBUG_PRINTK_CONT("-%08x",
1539                                                                dbg_last_ack_tsn);
1540                                 SCTP_DEBUG_PRINTK_CONT("\n");
1541
1542                                 /* FALL THROUGH... */
1543                         default:
1544                                 SCTP_DEBUG_PRINTK("KEPT: %08x",tsn);
1545                                 dbg_prt_state = 1;
1546                                 dbg_kept_tsn = tsn;
1547                         }
1548
1549                         dbg_last_kept_tsn = tsn;
1550 #endif /* SCTP_DEBUG */
1551                 }
1552         }
1553
1554 #if SCTP_DEBUG
1555         /* Finish off the last range, displaying its ending TSN.  */
1556         switch (dbg_prt_state) {
1557         case 0:
1558                 if (dbg_last_ack_tsn != dbg_ack_tsn) {
1559                         SCTP_DEBUG_PRINTK_CONT("-%08x\n", dbg_last_ack_tsn);
1560                 } else {
1561                         SCTP_DEBUG_PRINTK_CONT("\n");
1562                 }
1563         break;
1564
1565         case 1:
1566                 if (dbg_last_kept_tsn != dbg_kept_tsn) {
1567                         SCTP_DEBUG_PRINTK_CONT("-%08x\n", dbg_last_kept_tsn);
1568                 } else {
1569                         SCTP_DEBUG_PRINTK_CONT("\n");
1570                 }
1571         }
1572 #endif /* SCTP_DEBUG */
1573         if (transport) {
1574                 if (bytes_acked) {
1575                         /* We may have counted DATA that was migrated
1576                          * to this transport due to DEL-IP operation.
1577                          * Subtract those bytes, since the were never
1578                          * send on this transport and shouldn't be
1579                          * credited to this transport.
1580                          */
1581                         bytes_acked -= migrate_bytes;
1582
1583                         /* 8.2. When an outstanding TSN is acknowledged,
1584                          * the endpoint shall clear the error counter of
1585                          * the destination transport address to which the
1586                          * DATA chunk was last sent.
1587                          * The association's overall error counter is
1588                          * also cleared.
1589                          */
1590                         transport->error_count = 0;
1591                         transport->asoc->overall_error_count = 0;
1592
1593                         /* Mark the destination transport address as
1594                          * active if it is not so marked.
1595                          */
1596                         if ((transport->state == SCTP_INACTIVE) ||
1597                             (transport->state == SCTP_UNCONFIRMED)) {
1598                                 sctp_assoc_control_transport(
1599                                         transport->asoc,
1600                                         transport,
1601                                         SCTP_TRANSPORT_UP,
1602                                         SCTP_RECEIVED_SACK);
1603                         }
1604
1605                         sctp_transport_raise_cwnd(transport, sack_ctsn,
1606                                                   bytes_acked);
1607
1608                         transport->flight_size -= bytes_acked;
1609                         if (transport->flight_size == 0)
1610                                 transport->partial_bytes_acked = 0;
1611                         q->outstanding_bytes -= bytes_acked + migrate_bytes;
1612                 } else {
1613                         /* RFC 2960 6.1, sctpimpguide-06 2.15.2
1614                          * When a sender is doing zero window probing, it
1615                          * should not timeout the association if it continues
1616                          * to receive new packets from the receiver. The
1617                          * reason is that the receiver MAY keep its window
1618                          * closed for an indefinite time.
1619                          * A sender is doing zero window probing when the
1620                          * receiver's advertised window is zero, and there is
1621                          * only one data chunk in flight to the receiver.
1622                          */
1623                         if (!q->asoc->peer.rwnd &&
1624                             !list_empty(&tlist) &&
1625                             (sack_ctsn+2 == q->asoc->next_tsn)) {
1626                                 SCTP_DEBUG_PRINTK("%s: SACK received for zero "
1627                                                   "window probe: %u\n",
1628                                                   __func__, sack_ctsn);
1629                                 q->asoc->overall_error_count = 0;
1630                                 transport->error_count = 0;
1631                         }
1632                 }
1633
1634                 /* RFC 2960 6.3.2 Retransmission Timer Rules
1635                  *
1636                  * R2) Whenever all outstanding data sent to an address have
1637                  * been acknowledged, turn off the T3-rtx timer of that
1638                  * address.
1639                  */
1640                 if (!transport->flight_size) {
1641                         if (timer_pending(&transport->T3_rtx_timer) &&
1642                             del_timer(&transport->T3_rtx_timer)) {
1643                                 sctp_transport_put(transport);
1644                         }
1645                 } else if (restart_timer) {
1646                         if (!mod_timer(&transport->T3_rtx_timer,
1647                                        jiffies + transport->rto))
1648                                 sctp_transport_hold(transport);
1649                 }
1650         }
1651
1652         list_splice(&tlist, transmitted_queue);
1653 }
1654
1655 /* Mark chunks as missing and consequently may get retransmitted. */
1656 static void sctp_mark_missing(struct sctp_outq *q,
1657                               struct list_head *transmitted_queue,
1658                               struct sctp_transport *transport,
1659                               __u32 highest_new_tsn_in_sack,
1660                               int count_of_newacks)
1661 {
1662         struct sctp_chunk *chunk;
1663         __u32 tsn;
1664         char do_fast_retransmit = 0;
1665         struct sctp_association *asoc = q->asoc;
1666         struct sctp_transport *primary = asoc->peer.primary_path;
1667
1668         list_for_each_entry(chunk, transmitted_queue, transmitted_list) {
1669
1670                 tsn = ntohl(chunk->subh.data_hdr->tsn);
1671
1672                 /* RFC 2960 7.2.4, sctpimpguide-05 2.8.2 M3) Examine all
1673                  * 'Unacknowledged TSN's', if the TSN number of an
1674                  * 'Unacknowledged TSN' is smaller than the 'HighestTSNinSack'
1675                  * value, increment the 'TSN.Missing.Report' count on that
1676                  * chunk if it has NOT been fast retransmitted or marked for
1677                  * fast retransmit already.
1678                  */
1679                 if (chunk->fast_retransmit == SCTP_CAN_FRTX &&
1680                     !chunk->tsn_gap_acked &&
1681                     TSN_lt(tsn, highest_new_tsn_in_sack)) {
1682
1683                         /* SFR-CACC may require us to skip marking
1684                          * this chunk as missing.
1685                          */
1686                         if (!transport || !sctp_cacc_skip(primary, transport,
1687                                             count_of_newacks, tsn)) {
1688                                 chunk->tsn_missing_report++;
1689
1690                                 SCTP_DEBUG_PRINTK(
1691                                         "%s: TSN 0x%x missing counter: %d\n",
1692                                         __func__, tsn,
1693                                         chunk->tsn_missing_report);
1694                         }
1695                 }
1696                 /*
1697                  * M4) If any DATA chunk is found to have a
1698                  * 'TSN.Missing.Report'
1699                  * value larger than or equal to 3, mark that chunk for
1700                  * retransmission and start the fast retransmit procedure.
1701                  */
1702
1703                 if (chunk->tsn_missing_report >= 3) {
1704                         chunk->fast_retransmit = SCTP_NEED_FRTX;
1705                         do_fast_retransmit = 1;
1706                 }
1707         }
1708
1709         if (transport) {
1710                 if (do_fast_retransmit)
1711                         sctp_retransmit(q, transport, SCTP_RTXR_FAST_RTX);
1712
1713                 SCTP_DEBUG_PRINTK("%s: transport: %p, cwnd: %d, "
1714                                   "ssthresh: %d, flight_size: %d, pba: %d\n",
1715                                   __func__, transport, transport->cwnd,
1716                                   transport->ssthresh, transport->flight_size,
1717                                   transport->partial_bytes_acked);
1718         }
1719 }
1720
1721 /* Is the given TSN acked by this packet?  */
1722 static int sctp_acked(struct sctp_sackhdr *sack, __u32 tsn)
1723 {
1724         int i;
1725         sctp_sack_variable_t *frags;
1726         __u16 gap;
1727         __u32 ctsn = ntohl(sack->cum_tsn_ack);
1728
1729         if (TSN_lte(tsn, ctsn))
1730                 goto pass;
1731
1732         /* 3.3.4 Selective Acknowledgement (SACK) (3):
1733          *
1734          * Gap Ack Blocks:
1735          *  These fields contain the Gap Ack Blocks. They are repeated
1736          *  for each Gap Ack Block up to the number of Gap Ack Blocks
1737          *  defined in the Number of Gap Ack Blocks field. All DATA
1738          *  chunks with TSNs greater than or equal to (Cumulative TSN
1739          *  Ack + Gap Ack Block Start) and less than or equal to
1740          *  (Cumulative TSN Ack + Gap Ack Block End) of each Gap Ack
1741          *  Block are assumed to have been received correctly.
1742          */
1743
1744         frags = sack->variable;
1745         gap = tsn - ctsn;
1746         for (i = 0; i < ntohs(sack->num_gap_ack_blocks); ++i) {
1747                 if (TSN_lte(ntohs(frags[i].gab.start), gap) &&
1748                     TSN_lte(gap, ntohs(frags[i].gab.end)))
1749                         goto pass;
1750         }
1751
1752         return 0;
1753 pass:
1754         return 1;
1755 }
1756
1757 static inline int sctp_get_skip_pos(struct sctp_fwdtsn_skip *skiplist,
1758                                     int nskips, __be16 stream)
1759 {
1760         int i;
1761
1762         for (i = 0; i < nskips; i++) {
1763                 if (skiplist[i].stream == stream)
1764                         return i;
1765         }
1766         return i;
1767 }
1768
1769 /* Create and add a fwdtsn chunk to the outq's control queue if needed. */
1770 static void sctp_generate_fwdtsn(struct sctp_outq *q, __u32 ctsn)
1771 {
1772         struct sctp_association *asoc = q->asoc;
1773         struct sctp_chunk *ftsn_chunk = NULL;
1774         struct sctp_fwdtsn_skip ftsn_skip_arr[10];
1775         int nskips = 0;
1776         int skip_pos = 0;
1777         __u32 tsn;
1778         struct sctp_chunk *chunk;
1779         struct list_head *lchunk, *temp;
1780
1781         if (!asoc->peer.prsctp_capable)
1782                 return;
1783
1784         /* PR-SCTP C1) Let SackCumAck be the Cumulative TSN ACK carried in the
1785          * received SACK.
1786          *
1787          * If (Advanced.Peer.Ack.Point < SackCumAck), then update
1788          * Advanced.Peer.Ack.Point to be equal to SackCumAck.
1789          */
1790         if (TSN_lt(asoc->adv_peer_ack_point, ctsn))
1791                 asoc->adv_peer_ack_point = ctsn;
1792
1793         /* PR-SCTP C2) Try to further advance the "Advanced.Peer.Ack.Point"
1794          * locally, that is, to move "Advanced.Peer.Ack.Point" up as long as
1795          * the chunk next in the out-queue space is marked as "abandoned" as
1796          * shown in the following example:
1797          *
1798          * Assuming that a SACK arrived with the Cumulative TSN ACK 102
1799          * and the Advanced.Peer.Ack.Point is updated to this value:
1800          *
1801          *   out-queue at the end of  ==>   out-queue after Adv.Ack.Point
1802          *   normal SACK processing           local advancement
1803          *                ...                           ...
1804          *   Adv.Ack.Pt-> 102 acked                     102 acked
1805          *                103 abandoned                 103 abandoned
1806          *                104 abandoned     Adv.Ack.P-> 104 abandoned
1807          *                105                           105
1808          *                106 acked                     106 acked
1809          *                ...                           ...
1810          *
1811          * In this example, the data sender successfully advanced the
1812          * "Advanced.Peer.Ack.Point" from 102 to 104 locally.
1813          */
1814         list_for_each_safe(lchunk, temp, &q->abandoned) {
1815                 chunk = list_entry(lchunk, struct sctp_chunk,
1816                                         transmitted_list);
1817                 tsn = ntohl(chunk->subh.data_hdr->tsn);
1818
1819                 /* Remove any chunks in the abandoned queue that are acked by
1820                  * the ctsn.
1821                  */
1822                 if (TSN_lte(tsn, ctsn)) {
1823                         list_del_init(lchunk);
1824                         sctp_chunk_free(chunk);
1825                 } else {
1826                         if (TSN_lte(tsn, asoc->adv_peer_ack_point+1)) {
1827                                 asoc->adv_peer_ack_point = tsn;
1828                                 if (chunk->chunk_hdr->flags &
1829                                          SCTP_DATA_UNORDERED)
1830                                         continue;
1831                                 skip_pos = sctp_get_skip_pos(&ftsn_skip_arr[0],
1832                                                 nskips,
1833                                                 chunk->subh.data_hdr->stream);
1834                                 ftsn_skip_arr[skip_pos].stream =
1835                                         chunk->subh.data_hdr->stream;
1836                                 ftsn_skip_arr[skip_pos].ssn =
1837                                          chunk->subh.data_hdr->ssn;
1838                                 if (skip_pos == nskips)
1839                                         nskips++;
1840                                 if (nskips == 10)
1841                                         break;
1842                         } else
1843                                 break;
1844                 }
1845         }
1846
1847         /* PR-SCTP C3) If, after step C1 and C2, the "Advanced.Peer.Ack.Point"
1848          * is greater than the Cumulative TSN ACK carried in the received
1849          * SACK, the data sender MUST send the data receiver a FORWARD TSN
1850          * chunk containing the latest value of the
1851          * "Advanced.Peer.Ack.Point".
1852          *
1853          * C4) For each "abandoned" TSN the sender of the FORWARD TSN SHOULD
1854          * list each stream and sequence number in the forwarded TSN. This
1855          * information will enable the receiver to easily find any
1856          * stranded TSN's waiting on stream reorder queues. Each stream
1857          * SHOULD only be reported once; this means that if multiple
1858          * abandoned messages occur in the same stream then only the
1859          * highest abandoned stream sequence number is reported. If the
1860          * total size of the FORWARD TSN does NOT fit in a single MTU then
1861          * the sender of the FORWARD TSN SHOULD lower the
1862          * Advanced.Peer.Ack.Point to the last TSN that will fit in a
1863          * single MTU.
1864          */
1865         if (asoc->adv_peer_ack_point > ctsn)
1866                 ftsn_chunk = sctp_make_fwdtsn(asoc, asoc->adv_peer_ack_point,
1867                                               nskips, &ftsn_skip_arr[0]);
1868
1869         if (ftsn_chunk) {
1870                 list_add_tail(&ftsn_chunk->list, &q->control_chunk_list);
1871                 SCTP_INC_STATS(SCTP_MIB_OUTCTRLCHUNKS);
1872         }
1873 }