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 <linux/slab.h>
  54 #include <net/sock.h>     /* For skb_set_owner_w */
  55
  56 #include <net/sctp/sctp.h>
  57 #include <net/sctp/sm.h>
  58
  59 /* Declare internal functions here.  */
  60 static int sctp_acked(struct sctp_sackhdr *sack, __u32 tsn);
  61 static void sctp_check_transmitted(struct sctp_outq *q,
  62                                    struct list_head *transmitted_queue,
  63                                    struct sctp_transport *transport,
  64                                    struct sctp_sackhdr *sack,
  65                                    __u32 highest_new_tsn);
  66
  67 static void sctp_mark_missing(struct sctp_outq *q,
  68                               struct list_head *transmitted_queue,
  69                               struct sctp_transport *transport,
  70                               __u32 highest_new_tsn,
  71                               int count_of_newacks);
  72
  73 static void sctp_generate_fwdtsn(struct sctp_outq *q, __u32 sack_ctsn);
  74
  75 static int sctp_outq_flush(struct sctp_outq *q, int rtx_timeout);
  76
  77 /* Add data to the front of the queue. */
  78 static inline void sctp_outq_head_data(struct sctp_outq *q,
  79                                         struct sctp_chunk *ch)
  80 {
  81         list_add(&ch->list, &q->out_chunk_list);
  82         q->out_qlen += ch->skb->len;
  83         return;
  84 }
  85
  86 /* Take data from the front of the queue. */
  87 static inline struct sctp_chunk *sctp_outq_dequeue_data(struct sctp_outq *q)
  88 {
  89         struct sctp_chunk *ch = NULL;
  90
  91         if (!list_empty(&q->out_chunk_list)) {
  92                 struct list_head *entry = q->out_chunk_list.next;
  93
  94                 ch = list_entry(entry, struct sctp_chunk, list);
  95                 list_del_init(entry);
  96                 q->out_qlen -= ch->skb->len;
  97         }
  98         return ch;
  99 }
 100 /* Add data chunk to the end of the queue. */
 101 static inline void sctp_outq_tail_data(struct sctp_outq *q,
 102                                        struct sctp_chunk *ch)
 103 {
 104         list_add_tail(&ch->list, &q->out_chunk_list);
 105         q->out_qlen += ch->skb->len;
 106         return;
 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 futher 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 SOULD 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_CID_DATA == chunk->chunk_hdr->type) {
 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         struct sctp_association *asoc;
 549         int fast_rtx;
 550         int error = 0;
 551         int timer = 0;
 552         int done = 0;
 553
 554         asoc = q->asoc;
 555         lqueue = &q->retransmit;
 556         fast_rtx = q->fast_rtx;
 557
 558         /* This loop handles time-out retransmissions, fast retransmissions,
 559          * and retransmissions due to opening of whindow.
 560          *
 561          * RFC 2960 6.3.3 Handle T3-rtx Expiration
 562          *
 563          * E3) Determine how many of the earliest (i.e., lowest TSN)
 564          * outstanding DATA chunks for the address for which the
 565          * T3-rtx has expired will fit into a single packet, subject
 566          * to the MTU constraint for the path corresponding to the
 567          * destination transport address to which the retransmission
 568          * is being sent (this may be different from the address for
 569          * which the timer expires [see Section 6.4]). Call this value
 570          * K. Bundle and retransmit those K DATA chunks in a single
 571          * packet to the destination endpoint.
 572          *
 573          * [Just to be painfully clear, if we are retransmitting
 574          * because a timeout just happened, we should send only ONE
 575          * packet of retransmitted data.]
 576          *
 577          * For fast retransmissions we also send only ONE packet.  However,
 578          * if we are just flushing the queue due to open window, we'll
 579          * try to send as much as possible.
 580          */
 581         list_for_each_entry_safe(chunk, chunk1, lqueue, transmitted_list) {
 582
 583                 /* Make sure that Gap Acked TSNs are not retransmitted.  A
 584                  * simple approach is just to move such TSNs out of the
 585                  * way and into a 'transmitted' queue and skip to the
 586                  * next chunk.
 587                  */
 588                 if (chunk->tsn_gap_acked) {
 589                         list_del(&chunk->transmitted_list);
 590                         list_add_tail(&chunk->transmitted_list,
 591                                         &transport->transmitted);
 592                         continue;
 593                 }
 594
 595                 /* If we are doing fast retransmit, ignore non-fast_rtransmit
 596                  * chunks
 597                  */
 598                 if (fast_rtx && !chunk->fast_retransmit)
 599                         continue;
 600
 601 redo:
 602                 /* Attempt to append this chunk to the packet. */
 603                 status = sctp_packet_append_chunk(pkt, chunk);
 604
 605                 switch (status) {
 606                 case SCTP_XMIT_PMTU_FULL:
 607                         if (!pkt->has_data && !pkt->has_cookie_echo) {
 608                                 /* If this packet did not contain DATA then
 609                                  * retransmission did not happen, so do it
 610                                  * again.  We'll ignore the error here since
 611                                  * control chunks are already freed so there
 612                                  * is nothing we can do.
 613                                  */
 614                                 sctp_packet_transmit(pkt);
 615                                 goto redo;
 616                         }
 617
 618                         /* Send this packet.  */
 619                         error = sctp_packet_transmit(pkt);
 620
 621                         /* If we are retransmitting, we should only
 622                          * send a single packet.
 623                          */
 624                         if (rtx_timeout || fast_rtx)
 625                                 done = 1;
 626
 627                         /* Bundle next chunk in the next round.  */
 628                         break;
 629
 630                 case SCTP_XMIT_RWND_FULL:
 631                         /* Send this packet. */
 632                         error = sctp_packet_transmit(pkt);
 633
 634                         /* Stop sending DATA as there is no more room
 635                          * at the receiver.
 636                          */
 637                         done = 1;
 638                         break;
 639
 640                 case SCTP_XMIT_NAGLE_DELAY:
 641                         /* Send this packet. */
 642                         error = sctp_packet_transmit(pkt);
 643
 644                         /* Stop sending DATA because of nagle delay. */
 645                         done = 1;
 646                         break;
 647
 648                 default:
 649                         /* The append was successful, so add this chunk to
 650                          * the transmitted list.
 651                          */
 652                         list_del(&chunk->transmitted_list);
 653                         list_add_tail(&chunk->transmitted_list,
 654                                         &transport->transmitted);
 655
 656                         /* Mark the chunk as ineligible for fast retransmit
 657                          * after it is retransmitted.
 658                          */
 659                         if (chunk->fast_retransmit == SCTP_NEED_FRTX)
 660                                 chunk->fast_retransmit = SCTP_DONT_FRTX;
 661
 662                         /* Force start T3-rtx timer when fast retransmitting
 663                          * the earliest outstanding TSN
 664                          */
 665                         if (!timer && fast_rtx &&
 666                             ntohl(chunk->subh.data_hdr->tsn) ==
 667                                              asoc->ctsn_ack_point + 1)
 668                                 timer = 2;
 669
 670                         q->empty = 0;
 671                         break;
 672                 }
 673
 674                 /* Set the timer if there were no errors */
 675                 if (!error && !timer)
 676                         timer = 1;
 677
 678                 if (done)
 679                         break;
 680         }
 681
 682         /* If we are here due to a retransmit timeout or a fast
 683          * retransmit and if there are any chunks left in the retransmit
 684          * queue that could not fit in the PMTU sized packet, they need
 685          * to be marked as ineligible for a subsequent fast retransmit.
 686          */
 687         if (rtx_timeout || fast_rtx) {
 688                 list_for_each_entry(chunk1, lqueue, transmitted_list) {
 689                         if (chunk1->fast_retransmit == SCTP_NEED_FRTX)
 690                                 chunk1->fast_retransmit = SCTP_DONT_FRTX;
 691                 }
 692         }
 693
 694         *start_timer = timer;
 695
 696         /* Clear fast retransmit hint */
 697         if (fast_rtx)
 698                 q->fast_rtx = 0;
 699
 700         return error;
 701 }
 702
 703 /* Cork the outqueue so queued chunks are really queued. */
 704 int sctp_outq_uncork(struct sctp_outq *q)
 705 {
 706         int error = 0;
 707         if (q->cork)
 708                 q->cork = 0;
 709         error = sctp_outq_flush(q, 0);
 710         return error;
 711 }
 712
 713
 714 /*
 715  * Try to flush an outqueue.
 716  *
 717  * Description: Send everything in q which we legally can, subject to
 718  * congestion limitations.
 719  * * Note: This function can be called from multiple contexts so appropriate
 720  * locking concerns must be made.  Today we use the sock lock to protect
 721  * this function.
 722  */
 723 static int sctp_outq_flush(struct sctp_outq *q, int rtx_timeout)
 724 {
 725         struct sctp_packet *packet;
 726         struct sctp_packet singleton;
 727         struct sctp_association *asoc = q->asoc;
 728         __u16 sport = asoc->base.bind_addr.port;
 729         __u16 dport = asoc->peer.port;
 730         __u32 vtag = asoc->peer.i.init_tag;
 731         struct sctp_transport *transport = NULL;
 732         struct sctp_transport *new_transport;
 733         struct sctp_chunk *chunk, *tmp;
 734         sctp_xmit_t status;
 735         int error = 0;
 736         int start_timer = 0;
 737         int one_packet = 0;
 738
 739         /* These transports have chunks to send. */
 740         struct list_head transport_list;
 741         struct list_head *ltransport;
 742
 743         INIT_LIST_HEAD(&transport_list);
 744         packet = NULL;
 745
 746         /*
 747          * 6.10 Bundling
 748          *   ...
 749          *   When bundling control chunks with DATA chunks, an
 750          *   endpoint MUST place control chunks first in the outbound
 751          *   SCTP packet.  The transmitter MUST transmit DATA chunks
 752          *   within a SCTP packet in increasing order of TSN.
 753          *   ...
 754          */
 755
 756         list_for_each_entry_safe(chunk, tmp, &q->control_chunk_list, list) {
 757                 list_del_init(&chunk->list);
 758
 759                 /* Pick the right transport to use. */
 760                 new_transport = chunk->transport;
 761
 762                 if (!new_transport) {
 763                         /*
 764                          * If we have a prior transport pointer, see if
 765                          * the destination address of the chunk
 766                          * matches the destination address of the
 767                          * current transport.  If not a match, then
 768                          * try to look up the transport with a given
 769                          * destination address.  We do this because
 770                          * after processing ASCONFs, we may have new
 771                          * transports created.
 772                          */
 773                         if (transport &&
 774                             sctp_cmp_addr_exact(&chunk->dest,
 775                                                 &transport->ipaddr))
 776                                         new_transport = transport;
 777                         else
 778                                 new_transport = sctp_assoc_lookup_paddr(asoc,
 779                                                                 &chunk->dest);
 780
 781                         /* if we still don't have a new transport, then
 782                          * use the current active path.
 783                          */
 784                         if (!new_transport)
 785                                 new_transport = asoc->peer.active_path;
 786                 } else if ((new_transport->state == SCTP_INACTIVE) ||
 787                            (new_transport->state == SCTP_UNCONFIRMED)) {
 788                         /* If the chunk is Heartbeat or Heartbeat Ack,
 789                          * send it to chunk->transport, even if it's
 790                          * inactive.
 791                          *
 792                          * 3.3.6 Heartbeat Acknowledgement:
 793                          * ...
 794                          * A HEARTBEAT ACK is always sent to the source IP
 795                          * address of the IP datagram containing the
 796                          * HEARTBEAT chunk to which this ack is responding.
 797                          * ...
 798                          *
 799                          * ASCONF_ACKs also must be sent to the source.
 800                          */
 801                         if (chunk->chunk_hdr->type != SCTP_CID_HEARTBEAT &&
 802                             chunk->chunk_hdr->type != SCTP_CID_HEARTBEAT_ACK &&
 803                             chunk->chunk_hdr->type != SCTP_CID_ASCONF_ACK)
 804                                 new_transport = asoc->peer.active_path;
 805                 }
 806
 807                 /* Are we switching transports?
 808                  * Take care of transport locks.
 809                  */
 810                 if (new_transport != transport) {
 811                         transport = new_transport;
 812                         if (list_empty(&transport->send_ready)) {
 813                                 list_add_tail(&transport->send_ready,
 814                                               &transport_list);
 815                         }
 816                         packet = &transport->packet;
 817                         sctp_packet_config(packet, vtag,
 818                                            asoc->peer.ecn_capable);
 819                 }
 820
 821                 switch (chunk->chunk_hdr->type) {
 822                 /*
 823                  * 6.10 Bundling
 824                  *   ...
 825                  *   An endpoint MUST NOT bundle INIT, INIT ACK or SHUTDOWN
 826                  *   COMPLETE with any other chunks.  [Send them immediately.]
 827                  */
 828                 case SCTP_CID_INIT:
 829                 case SCTP_CID_INIT_ACK:
 830                 case SCTP_CID_SHUTDOWN_COMPLETE:
 831                         sctp_packet_init(&singleton, transport, sport, dport);
 832                         sctp_packet_config(&singleton, vtag, 0);
 833                         sctp_packet_append_chunk(&singleton, chunk);
 834                         error = sctp_packet_transmit(&singleton);
 835                         if (error < 0)
 836                                 return error;
 837                         break;
 838
 839                 case SCTP_CID_ABORT:
 840                         if (sctp_test_T_bit(chunk)) {
 841                                 packet->vtag = asoc->c.my_vtag;
 842                         }
 843                 /* The following chunks are "response" chunks, i.e.
 844                  * they are generated in response to something we
 845                  * received.  If we are sending these, then we can
 846                  * send only 1 packet containing these chunks.
 847                  */
 848                 case SCTP_CID_HEARTBEAT_ACK:
 849                 case SCTP_CID_SHUTDOWN_ACK:
 850                 case SCTP_CID_COOKIE_ACK:
 851                 case SCTP_CID_COOKIE_ECHO:
 852                 case SCTP_CID_ERROR:
 853                 case SCTP_CID_ECN_CWR:
 854                 case SCTP_CID_ASCONF_ACK:
 855                         one_packet = 1;
 856                         /* Fall throught */
 857
 858                 case SCTP_CID_SACK:
 859                 case SCTP_CID_HEARTBEAT:
 860                 case SCTP_CID_SHUTDOWN:
 861                 case SCTP_CID_ECN_ECNE:
 862                 case SCTP_CID_ASCONF:
 863                 case SCTP_CID_FWD_TSN:
 864                         status = sctp_packet_transmit_chunk(packet, chunk,
 865                                                             one_packet);
 866                         if (status  != SCTP_XMIT_OK) {
 867                                 /* put the chunk back */
 868                                 list_add(&chunk->list, &q->control_chunk_list);
 869                         } else if (chunk->chunk_hdr->type == SCTP_CID_FWD_TSN) {
 870                                 /* PR-SCTP C5) If a FORWARD TSN is sent, the
 871                                  * sender MUST assure that at least one T3-rtx
 872                                  * timer is running.
 873                                  */
 874                                 sctp_transport_reset_timers(transport, 0);
 875                         }
 876                         break;
 877
 878                 default:
 879                         /* We built a chunk with an illegal type! */
 880                         BUG();
 881                 }
 882         }
 883
 884         /* Is it OK to send data chunks?  */
 885         switch (asoc->state) {
 886         case SCTP_STATE_COOKIE_ECHOED:
 887                 /* Only allow bundling when this packet has a COOKIE-ECHO
 888                  * chunk.
 889                  */
 890                 if (!packet || !packet->has_cookie_echo)
 891                         break;
 892
 893                 /* fallthru */
 894         case SCTP_STATE_ESTABLISHED:
 895         case SCTP_STATE_SHUTDOWN_PENDING:
 896         case SCTP_STATE_SHUTDOWN_RECEIVED:
 897                 /*
 898                  * RFC 2960 6.1  Transmission of DATA Chunks
 899                  *
 900                  * C) When the time comes for the sender to transmit,
 901                  * before sending new DATA chunks, the sender MUST
 902                  * first transmit any outstanding DATA chunks which
 903                  * are marked for retransmission (limited by the
 904                  * current cwnd).
 905                  */
 906                 if (!list_empty(&q->retransmit)) {
 907                         if (transport == asoc->peer.retran_path)
 908                                 goto retran;
 909
 910                         /* Switch transports & prepare the packet.  */
 911
 912                         transport = asoc->peer.retran_path;
 913
 914                         if (list_empty(&transport->send_ready)) {
 915                                 list_add_tail(&transport->send_ready,
 916                                               &transport_list);
 917                         }
 918
 919                         packet = &transport->packet;
 920                         sctp_packet_config(packet, vtag,
 921                                            asoc->peer.ecn_capable);
 922                 retran:
 923                         error = sctp_outq_flush_rtx(q, packet,
 924                                                     rtx_timeout, &start_timer);
 925
 926                         if (start_timer)
 927                                 sctp_transport_reset_timers(transport,
 928                                                             start_timer-1);
 929
 930                         /* This can happen on COOKIE-ECHO resend.  Only
 931                          * one chunk can get bundled with a COOKIE-ECHO.
 932                          */
 933                         if (packet->has_cookie_echo)
 934                                 goto sctp_flush_out;
 935
 936                         /* Don't send new data if there is still data
 937                          * waiting to retransmit.
 938                          */
 939                         if (!list_empty(&q->retransmit))
 940                                 goto sctp_flush_out;
 941                 }
 942
 943                 /* Apply Max.Burst limitation to the current transport in
 944                  * case it will be used for new data.  We are going to
 945                  * rest it before we return, but we want to apply the limit
 946                  * to the currently queued data.
 947                  */
 948                 if (transport)
 949                         sctp_transport_burst_limited(transport);
 950
 951                 /* Finally, transmit new packets.  */
 952                 while ((chunk = sctp_outq_dequeue_data(q)) != NULL) {
 953                         /* RFC 2960 6.5 Every DATA chunk MUST carry a valid
 954                          * stream identifier.
 955                          */
 956                         if (chunk->sinfo.sinfo_stream >=
 957                             asoc->c.sinit_num_ostreams) {
 958
 959                                 /* Mark as failed send. */
 960                                 sctp_chunk_fail(chunk, SCTP_ERROR_INV_STRM);
 961                                 sctp_chunk_free(chunk);
 962                                 continue;
 963                         }
 964
 965                         /* Has this chunk expired? */
 966                         if (sctp_chunk_abandoned(chunk)) {
 967                                 sctp_chunk_fail(chunk, 0);
 968                                 sctp_chunk_free(chunk);
 969                                 continue;
 970                         }
 971
 972                         /* If there is a specified transport, use it.
 973                          * Otherwise, we want to use the active path.
 974                          */
 975                         new_transport = chunk->transport;
 976                         if (!new_transport ||
 977                             ((new_transport->state == SCTP_INACTIVE) ||
 978                              (new_transport->state == SCTP_UNCONFIRMED)))
 979                                 new_transport = asoc->peer.active_path;
 980
 981                         /* Change packets if necessary.  */
 982                         if (new_transport != transport) {
 983                                 transport = new_transport;
 984
 985                                 /* Schedule to have this transport's
 986                                  * packet flushed.
 987                                  */
 988                                 if (list_empty(&transport->send_ready)) {
 989                                         list_add_tail(&transport->send_ready,
 990                                                       &transport_list);
 991                                 }
 992
 993                                 packet = &transport->packet;
 994                                 sctp_packet_config(packet, vtag,
 995                                                    asoc->peer.ecn_capable);
 996                                 /* We've switched transports, so apply the
 997                                  * Burst limit to the new transport.
 998                                  */
 999                                 sctp_transport_burst_limited(transport);
1000                         }
1001
1002                         SCTP_DEBUG_PRINTK("sctp_outq_flush(%p, %p[%s]), ",
1003                                           q, chunk,
1004                                           chunk && chunk->chunk_hdr ?
1005                                           sctp_cname(SCTP_ST_CHUNK(
1006                                                   chunk->chunk_hdr->type))
1007                                           : "Illegal Chunk");
1008
1009                         SCTP_DEBUG_PRINTK("TX TSN 0x%x skb->head "
1010                                         "%p skb->users %d.\n",
1011                                         ntohl(chunk->subh.data_hdr->tsn),
1012                                         chunk->skb ?chunk->skb->head : NULL,
1013                                         chunk->skb ?
1014                                         atomic_read(&chunk->skb->users) : -1);
1015
1016                         /* Add the chunk to the packet.  */
1017                         status = sctp_packet_transmit_chunk(packet, chunk, 0);
1018
1019                         switch (status) {
1020                         case SCTP_XMIT_PMTU_FULL:
1021                         case SCTP_XMIT_RWND_FULL:
1022                         case SCTP_XMIT_NAGLE_DELAY:
1023                                 /* We could not append this chunk, so put
1024                                  * the chunk back on the output queue.
1025                                  */
1026                                 SCTP_DEBUG_PRINTK("sctp_outq_flush: could "
1027                                         "not transmit TSN: 0x%x, status: %d\n",
1028                                         ntohl(chunk->subh.data_hdr->tsn),
1029                                         status);
1030                                 sctp_outq_head_data(q, chunk);
1031                                 goto sctp_flush_out;
1032                                 break;
1033
1034                         case SCTP_XMIT_OK:
1035                                 /* The sender is in the SHUTDOWN-PENDING state,
1036                                  * The sender MAY set the I-bit in the DATA
1037                                  * chunk header.
1038                                  */
1039                                 if (asoc->state == SCTP_STATE_SHUTDOWN_PENDING)
1040                                         chunk->chunk_hdr->flags |= SCTP_DATA_SACK_IMM;
1041
1042                                 break;
1043
1044                         default:
1045                                 BUG();
1046                         }
1047
1048                         /* BUG: We assume that the sctp_packet_transmit()
1049                          * call below will succeed all the time and add the
1050                          * chunk to the transmitted list and restart the
1051                          * timers.
1052                          * It is possible that the call can fail under OOM
1053                          * conditions.
1054                          *
1055                          * Is this really a problem?  Won't this behave
1056                          * like a lost TSN?
1057                          */
1058                         list_add_tail(&chunk->transmitted_list,
1059                                       &transport->transmitted);
1060
1061                         sctp_transport_reset_timers(transport, 0);
1062
1063                         q->empty = 0;
1064
1065                         /* Only let one DATA chunk get bundled with a
1066                          * COOKIE-ECHO chunk.
1067                          */
1068                         if (packet->has_cookie_echo)
1069                                 goto sctp_flush_out;
1070                 }
1071                 break;
1072
1073         default:
1074                 /* Do nothing.  */
1075                 break;
1076         }
1077
1078 sctp_flush_out:
1079
1080         /* Before returning, examine all the transports touched in
1081          * this call.  Right now, we bluntly force clear all the
1082          * transports.  Things might change after we implement Nagle.
1083          * But such an examination is still required.
1084          *
1085          * --xguo
1086          */
1087         while ((ltransport = sctp_list_dequeue(&transport_list)) != NULL ) {
1088                 struct sctp_transport *t = list_entry(ltransport,
1089                                                       struct sctp_transport,
1090                                                       send_ready);
1091                 packet = &t->packet;
1092                 if (!sctp_packet_empty(packet))
1093                         error = sctp_packet_transmit(packet);
1094
1095                 /* Clear the burst limited state, if any */
1096                 sctp_transport_burst_reset(t);
1097         }
1098
1099         return error;
1100 }
1101
1102 /* Update unack_data based on the incoming SACK chunk */
1103 static void sctp_sack_update_unack_data(struct sctp_association *assoc,
1104                                         struct sctp_sackhdr *sack)
1105 {
1106         sctp_sack_variable_t *frags;
1107         __u16 unack_data;
1108         int i;
1109
1110         unack_data = assoc->next_tsn - assoc->ctsn_ack_point - 1;
1111
1112         frags = sack->variable;
1113         for (i = 0; i < ntohs(sack->num_gap_ack_blocks); i++) {
1114                 unack_data -= ((ntohs(frags[i].gab.end) -
1115                                 ntohs(frags[i].gab.start) + 1));
1116         }
1117
1118         assoc->unack_data = unack_data;
1119 }
1120
1121 /* Return the highest new tsn that is acknowledged by the given SACK chunk. */
1122 static __u32 sctp_highest_new_tsn(struct sctp_sackhdr *sack,
1123                                   struct sctp_association *asoc)
1124 {
1125         struct sctp_transport *transport;
1126         struct sctp_chunk *chunk;
1127         __u32 highest_new_tsn, tsn;
1128         struct list_head *transport_list = &asoc->peer.transport_addr_list;
1129
1130         highest_new_tsn = ntohl(sack->cum_tsn_ack);
1131
1132         list_for_each_entry(transport, transport_list, transports) {
1133                 list_for_each_entry(chunk, &transport->transmitted,
1134                                 transmitted_list) {
1135                         tsn = ntohl(chunk->subh.data_hdr->tsn);
1136
1137                         if (!chunk->tsn_gap_acked &&
1138                             TSN_lt(highest_new_tsn, tsn) &&
1139                             sctp_acked(sack, tsn))
1140                                 highest_new_tsn = tsn;
1141                 }
1142         }
1143
1144         return highest_new_tsn;
1145 }
1146
1147 /* This is where we REALLY process a SACK.
1148  *
1149  * Process the SACK against the outqueue.  Mostly, this just frees
1150  * things off the transmitted queue.
1151  */
1152 int sctp_outq_sack(struct sctp_outq *q, struct sctp_sackhdr *sack)
1153 {
1154         struct sctp_association *asoc = q->asoc;
1155         struct sctp_transport *transport;
1156         struct sctp_chunk *tchunk = NULL;
1157         struct list_head *lchunk, *transport_list, *temp;
1158         sctp_sack_variable_t *frags = sack->variable;
1159         __u32 sack_ctsn, ctsn, tsn;
1160         __u32 highest_tsn, highest_new_tsn;
1161         __u32 sack_a_rwnd;
1162         unsigned outstanding;
1163         struct sctp_transport *primary = asoc->peer.primary_path;
1164         int count_of_newacks = 0;
1165         int gap_ack_blocks;
1166
1167         /* Grab the association's destination address list. */
1168         transport_list = &asoc->peer.transport_addr_list;
1169
1170         sack_ctsn = ntohl(sack->cum_tsn_ack);
1171         gap_ack_blocks = ntohs(sack->num_gap_ack_blocks);
1172         /*
1173          * SFR-CACC algorithm:
1174          * On receipt of a SACK the sender SHOULD execute the
1175          * following statements.
1176          *
1177          * 1) If the cumulative ack in the SACK passes next tsn_at_change
1178          * on the current primary, the CHANGEOVER_ACTIVE flag SHOULD be
1179          * cleared. The CYCLING_CHANGEOVER flag SHOULD also be cleared for
1180          * all destinations.
1181          * 2) If the SACK contains gap acks and the flag CHANGEOVER_ACTIVE
1182          * is set the receiver of the SACK MUST take the following actions:
1183          *
1184          * A) Initialize the cacc_saw_newack to 0 for all destination
1185          * addresses.
1186          *
1187          * Only bother if changeover_active is set. Otherwise, this is
1188          * totally suboptimal to do on every SACK.
1189          */
1190         if (primary->cacc.changeover_active) {
1191                 u8 clear_cycling = 0;
1192
1193                 if (TSN_lte(primary->cacc.next_tsn_at_change, sack_ctsn)) {
1194                         primary->cacc.changeover_active = 0;
1195                         clear_cycling = 1;
1196                 }
1197
1198                 if (clear_cycling || gap_ack_blocks) {
1199                         list_for_each_entry(transport, transport_list,
1200                                         transports) {
1201                                 if (clear_cycling)
1202                                         transport->cacc.cycling_changeover = 0;
1203                                 if (gap_ack_blocks)
1204                                         transport->cacc.cacc_saw_newack = 0;
1205                         }
1206                 }
1207         }
1208
1209         /* Get the highest TSN in the sack. */
1210         highest_tsn = sack_ctsn;
1211         if (gap_ack_blocks)
1212                 highest_tsn += ntohs(frags[gap_ack_blocks - 1].gab.end);
1213
1214         if (TSN_lt(asoc->highest_sacked, highest_tsn)) {
1215                 highest_new_tsn = highest_tsn;
1216                 asoc->highest_sacked = highest_tsn;
1217         } else {
1218                 highest_new_tsn = sctp_highest_new_tsn(sack, asoc);
1219         }
1220
1221
1222         /* Run through the retransmit queue.  Credit bytes received
1223          * and free those chunks that we can.
1224          */
1225         sctp_check_transmitted(q, &q->retransmit, NULL, sack, highest_new_tsn);
1226
1227         /* Run through the transmitted queue.
1228          * Credit bytes received and free those chunks which we can.
1229          *
1230          * This is a MASSIVE candidate for optimization.
1231          */
1232         list_for_each_entry(transport, transport_list, transports) {
1233                 sctp_check_transmitted(q, &transport->transmitted,
1234                                        transport, sack, highest_new_tsn);
1235                 /*
1236                  * SFR-CACC algorithm:
1237                  * C) Let count_of_newacks be the number of
1238                  * destinations for which cacc_saw_newack is set.
1239                  */
1240                 if (transport->cacc.cacc_saw_newack)
1241                         count_of_newacks ++;
1242         }
1243
1244         if (gap_ack_blocks) {
1245                 list_for_each_entry(transport, transport_list, transports)
1246                         sctp_mark_missing(q, &transport->transmitted, transport,
1247                                           highest_new_tsn, count_of_newacks);
1248         }
1249
1250         /* Move the Cumulative TSN Ack Point if appropriate.  */
1251         if (TSN_lt(asoc->ctsn_ack_point, sack_ctsn))
1252                 asoc->ctsn_ack_point = sack_ctsn;
1253
1254         /* Update unack_data field in the assoc. */
1255         sctp_sack_update_unack_data(asoc, sack);
1256
1257         ctsn = asoc->ctsn_ack_point;
1258
1259         /* Throw away stuff rotting on the sack queue.  */
1260         list_for_each_safe(lchunk, temp, &q->sacked) {
1261                 tchunk = list_entry(lchunk, struct sctp_chunk,
1262                                     transmitted_list);
1263                 tsn = ntohl(tchunk->subh.data_hdr->tsn);
1264                 if (TSN_lte(tsn, ctsn)) {
1265                         list_del_init(&tchunk->transmitted_list);
1266                         sctp_chunk_free(tchunk);
1267                 }
1268         }
1269
1270         /* ii) Set rwnd equal to the newly received a_rwnd minus the
1271          *     number of bytes still outstanding after processing the
1272          *     Cumulative TSN Ack and the Gap Ack Blocks.
1273          */
1274
1275         sack_a_rwnd = ntohl(sack->a_rwnd);
1276         outstanding = q->outstanding_bytes;
1277
1278         if (outstanding < sack_a_rwnd)
1279                 sack_a_rwnd -= outstanding;
1280         else
1281                 sack_a_rwnd = 0;
1282
1283         asoc->peer.rwnd = sack_a_rwnd;
1284
1285         sctp_generate_fwdtsn(q, sack_ctsn);
1286
1287         SCTP_DEBUG_PRINTK("%s: sack Cumulative TSN Ack is 0x%x.\n",
1288                           __func__, sack_ctsn);
1289         SCTP_DEBUG_PRINTK("%s: Cumulative TSN Ack of association, "
1290                           "%p is 0x%x. Adv peer ack point: 0x%x\n",
1291                           __func__, asoc, ctsn, asoc->adv_peer_ack_point);
1292
1293         /* See if all chunks are acked.
1294          * Make sure the empty queue handler will get run later.
1295          */
1296         q->empty = (list_empty(&q->out_chunk_list) &&
1297                     list_empty(&q->retransmit));
1298         if (!q->empty)
1299                 goto finish;
1300
1301         list_for_each_entry(transport, transport_list, transports) {
1302                 q->empty = q->empty && list_empty(&transport->transmitted);
1303                 if (!q->empty)
1304                         goto finish;
1305         }
1306
1307         SCTP_DEBUG_PRINTK("sack queue is empty.\n");
1308 finish:
1309         return q->empty;
1310 }
1311
1312 /* Is the outqueue empty?  */
1313 int sctp_outq_is_empty(const struct sctp_outq *q)
1314 {
1315         return q->empty;
1316 }
1317
1318 /********************************************************************
1319  * 2nd Level Abstractions
1320  ********************************************************************/
1321
1322 /* Go through a transport's transmitted list or the association's retransmit
1323  * list and move chunks that are acked by the Cumulative TSN Ack to q->sacked.
1324  * The retransmit list will not have an associated transport.
1325  *
1326  * I added coherent debug information output.   --xguo
1327  *
1328  * Instead of printing 'sacked' or 'kept' for each TSN on the
1329  * transmitted_queue, we print a range: SACKED: TSN1-TSN2, TSN3, TSN4-TSN5.
1330  * KEPT TSN6-TSN7, etc.
1331  */
1332 static void sctp_check_transmitted(struct sctp_outq *q,
1333                                    struct list_head *transmitted_queue,
1334                                    struct sctp_transport *transport,
1335                                    struct sctp_sackhdr *sack,
1336                                    __u32 highest_new_tsn_in_sack)
1337 {
1338         struct list_head *lchunk;
1339         struct sctp_chunk *tchunk;
1340         struct list_head tlist;
1341         __u32 tsn;
1342         __u32 sack_ctsn;
1343         __u32 rtt;
1344         __u8 restart_timer = 0;
1345         int bytes_acked = 0;
1346         int migrate_bytes = 0;
1347
1348         /* These state variables are for coherent debug output. --xguo */
1349
1350 #if SCTP_DEBUG
1351         __u32 dbg_ack_tsn = 0;  /* An ACKed TSN range starts here... */
1352         __u32 dbg_last_ack_tsn = 0;  /* ...and finishes here.        */
1353         __u32 dbg_kept_tsn = 0; /* An un-ACKed range starts here...  */
1354         __u32 dbg_last_kept_tsn = 0; /* ...and finishes here.        */
1355
1356         /* 0 : The last TSN was ACKed.
1357          * 1 : The last TSN was NOT ACKed (i.e. KEPT).
1358          * -1: We need to initialize.
1359          */
1360         int dbg_prt_state = -1;
1361 #endif /* SCTP_DEBUG */
1362
1363         sack_ctsn = ntohl(sack->cum_tsn_ack);
1364
1365         INIT_LIST_HEAD(&tlist);
1366
1367         /* The while loop will skip empty transmitted queues. */
1368         while (NULL != (lchunk = sctp_list_dequeue(transmitted_queue))) {
1369                 tchunk = list_entry(lchunk, struct sctp_chunk,
1370                                     transmitted_list);
1371
1372                 if (sctp_chunk_abandoned(tchunk)) {
1373                         /* Move the chunk to abandoned list. */
1374                         sctp_insert_list(&q->abandoned, lchunk);
1375
1376                         /* If this chunk has not been acked, stop
1377                          * considering it as 'outstanding'.
1378                          */
1379                         if (!tchunk->tsn_gap_acked) {
1380                                 if (tchunk->transport)
1381                                         tchunk->transport->flight_size -=
1382                                                         sctp_data_size(tchunk);
1383                                 q->outstanding_bytes -= sctp_data_size(tchunk);
1384                         }
1385                         continue;
1386                 }
1387
1388                 tsn = ntohl(tchunk->subh.data_hdr->tsn);
1389                 if (sctp_acked(sack, tsn)) {
1390                         /* If this queue is the retransmit queue, the
1391                          * retransmit timer has already reclaimed
1392                          * the outstanding bytes for this chunk, so only
1393                          * count bytes associated with a transport.
1394                          */
1395                         if (transport) {
1396                                 /* If this chunk is being used for RTT
1397                                  * measurement, calculate the RTT and update
1398                                  * the RTO using this value.
1399                                  *
1400                                  * 6.3.1 C5) Karn's algorithm: RTT measurements
1401                                  * MUST NOT be made using packets that were
1402                                  * retransmitted (and thus for which it is
1403                                  * ambiguous whether the reply was for the
1404                                  * first instance of the packet or a later
1405                                  * instance).
1406                                  */
1407                                 if (!tchunk->tsn_gap_acked &&
1408                                     !tchunk->resent &&
1409                                     tchunk->rtt_in_progress) {
1410                                         tchunk->rtt_in_progress = 0;
1411                                         rtt = jiffies - tchunk->sent_at;
1412                                         sctp_transport_update_rto(transport,
1413                                                                   rtt);
1414                                 }
1415                         }
1416
1417                         /* If the chunk hasn't been marked as ACKED,
1418                          * mark it and account bytes_acked if the
1419                          * chunk had a valid transport (it will not
1420                          * have a transport if ASCONF had deleted it
1421                          * while DATA was outstanding).
1422                          */
1423                         if (!tchunk->tsn_gap_acked) {
1424                                 tchunk->tsn_gap_acked = 1;
1425                                 bytes_acked += sctp_data_size(tchunk);
1426                                 if (!tchunk->transport)
1427                                         migrate_bytes += sctp_data_size(tchunk);
1428                         }
1429
1430                         if (TSN_lte(tsn, sack_ctsn)) {
1431                                 /* RFC 2960  6.3.2 Retransmission Timer Rules
1432                                  *
1433                                  * R3) Whenever a SACK is received
1434                                  * that acknowledges the DATA chunk
1435                                  * with the earliest outstanding TSN
1436                                  * for that address, restart T3-rtx
1437                                  * timer for that address with its
1438                                  * current RTO.
1439                                  */
1440                                 restart_timer = 1;
1441
1442                                 if (!tchunk->tsn_gap_acked) {
1443                                         /*
1444                                          * SFR-CACC algorithm:
1445                                          * 2) If the SACK contains gap acks
1446                                          * and the flag CHANGEOVER_ACTIVE is
1447                                          * set the receiver of the SACK MUST
1448                                          * take the following action:
1449                                          *
1450                                          * B) For each TSN t being acked that
1451                                          * has not been acked in any SACK so
1452                                          * far, set cacc_saw_newack to 1 for
1453                                          * the destination that the TSN was
1454                                          * sent to.
1455                                          */
1456                                         if (transport &&
1457                                             sack->num_gap_ack_blocks &&
1458                                             q->asoc->peer.primary_path->cacc.
1459                                             changeover_active)
1460                                                 transport->cacc.cacc_saw_newack
1461                                                         = 1;
1462                                 }
1463
1464                                 list_add_tail(&tchunk->transmitted_list,
1465                                               &q->sacked);
1466                         } else {
1467                                 /* RFC2960 7.2.4, sctpimpguide-05 2.8.2
1468                                  * M2) Each time a SACK arrives reporting
1469                                  * 'Stray DATA chunk(s)' record the highest TSN
1470                                  * reported as newly acknowledged, call this
1471                                  * value 'HighestTSNinSack'. A newly
1472                                  * acknowledged DATA chunk is one not
1473                                  * previously acknowledged in a SACK.
1474                                  *
1475                                  * When the SCTP sender of data receives a SACK
1476                                  * chunk that acknowledges, for the first time,
1477                                  * the receipt of a DATA chunk, all the still
1478                                  * unacknowledged DATA chunks whose TSN is
1479                                  * older than that newly acknowledged DATA
1480                                  * chunk, are qualified as 'Stray DATA chunks'.
1481                                  */
1482                                 list_add_tail(lchunk, &tlist);
1483                         }
1484
1485 #if SCTP_DEBUG
1486                         switch (dbg_prt_state) {
1487                         case 0: /* last TSN was ACKed */
1488                                 if (dbg_last_ack_tsn + 1 == tsn) {
1489                                         /* This TSN belongs to the
1490                                          * current ACK range.
1491                                          */
1492                                         break;
1493                                 }
1494
1495                                 if (dbg_last_ack_tsn != dbg_ack_tsn) {
1496                                         /* Display the end of the
1497                                          * current range.
1498                                          */
1499                                         SCTP_DEBUG_PRINTK("-%08x",
1500                                                           dbg_last_ack_tsn);
1501                                 }
1502
1503                                 /* Start a new range.  */
1504                                 SCTP_DEBUG_PRINTK(",%08x", tsn);
1505                                 dbg_ack_tsn = tsn;
1506                                 break;
1507
1508                         case 1: /* The last TSN was NOT ACKed. */
1509                                 if (dbg_last_kept_tsn != dbg_kept_tsn) {
1510                                         /* Display the end of current range. */
1511                                         SCTP_DEBUG_PRINTK("-%08x",
1512                                                           dbg_last_kept_tsn);
1513                                 }
1514
1515                                 SCTP_DEBUG_PRINTK("\n");
1516
1517                                 /* FALL THROUGH... */
1518                         default:
1519                                 /* This is the first-ever TSN we examined.  */
1520                                 /* Start a new range of ACK-ed TSNs.  */
1521                                 SCTP_DEBUG_PRINTK("ACKed: %08x", tsn);
1522                                 dbg_prt_state = 0;
1523                                 dbg_ack_tsn = tsn;
1524                         }
1525
1526                         dbg_last_ack_tsn = tsn;
1527 #endif /* SCTP_DEBUG */
1528
1529                 } else {
1530                         if (tchunk->tsn_gap_acked) {
1531                                 SCTP_DEBUG_PRINTK("%s: Receiver reneged on "
1532                                                   "data TSN: 0x%x\n",
1533                                                   __func__,
1534                                                   tsn);
1535                                 tchunk->tsn_gap_acked = 0;
1536
1537                                 if (tchunk->transport)
1538                                         bytes_acked -= sctp_data_size(tchunk);
1539
1540                                 /* RFC 2960 6.3.2 Retransmission Timer Rules
1541                                  *
1542                                  * R4) Whenever a SACK is received missing a
1543                                  * TSN that was previously acknowledged via a
1544                                  * Gap Ack Block, start T3-rtx for the
1545                                  * destination address to which the DATA
1546                                  * chunk was originally
1547                                  * transmitted if it is not already running.
1548                                  */
1549                                 restart_timer = 1;
1550                         }
1551
1552                         list_add_tail(lchunk, &tlist);
1553
1554 #if SCTP_DEBUG
1555                         /* See the above comments on ACK-ed TSNs. */
1556                         switch (dbg_prt_state) {
1557                         case 1:
1558                                 if (dbg_last_kept_tsn + 1 == tsn)
1559                                         break;
1560
1561                                 if (dbg_last_kept_tsn != dbg_kept_tsn)
1562                                         SCTP_DEBUG_PRINTK("-%08x",
1563                                                           dbg_last_kept_tsn);
1564
1565                                 SCTP_DEBUG_PRINTK(",%08x", tsn);
1566                                 dbg_kept_tsn = tsn;
1567                                 break;
1568
1569                         case 0:
1570                                 if (dbg_last_ack_tsn != dbg_ack_tsn)
1571                                         SCTP_DEBUG_PRINTK("-%08x",
1572                                                           dbg_last_ack_tsn);
1573                                 SCTP_DEBUG_PRINTK("\n");
1574
1575                                 /* FALL THROUGH... */
1576                         default:
1577                                 SCTP_DEBUG_PRINTK("KEPT: %08x",tsn);
1578                                 dbg_prt_state = 1;
1579                                 dbg_kept_tsn = tsn;
1580                         }
1581
1582                         dbg_last_kept_tsn = tsn;
1583 #endif /* SCTP_DEBUG */
1584                 }
1585         }
1586
1587 #if SCTP_DEBUG
1588         /* Finish off the last range, displaying its ending TSN.  */
1589         switch (dbg_prt_state) {
1590         case 0:
1591                 if (dbg_last_ack_tsn != dbg_ack_tsn) {
1592                         SCTP_DEBUG_PRINTK("-%08x\n", dbg_last_ack_tsn);
1593                 } else {
1594                         SCTP_DEBUG_PRINTK("\n");
1595                 }
1596         break;
1597
1598         case 1:
1599                 if (dbg_last_kept_tsn != dbg_kept_tsn) {
1600                         SCTP_DEBUG_PRINTK("-%08x\n", dbg_last_kept_tsn);
1601                 } else {
1602                         SCTP_DEBUG_PRINTK("\n");
1603                 }
1604         }
1605 #endif /* SCTP_DEBUG */
1606         if (transport) {
1607                 if (bytes_acked) {
1608                         /* We may have counted DATA that was migrated
1609                          * to this transport due to DEL-IP operation.
1610                          * Subtract those bytes, since the were never
1611                          * send on this transport and shouldn't be
1612                          * credited to this transport.
1613                          */
1614                         bytes_acked -= migrate_bytes;
1615
1616                         /* 8.2. When an outstanding TSN is acknowledged,
1617                          * the endpoint shall clear the error counter of
1618                          * the destination transport address to which the
1619                          * DATA chunk was last sent.
1620                          * The association's overall error counter is
1621                          * also cleared.
1622                          */
1623                         transport->error_count = 0;
1624                         transport->asoc->overall_error_count = 0;
1625
1626                         /* Mark the destination transport address as
1627                          * active if it is not so marked.
1628                          */
1629                         if ((transport->state == SCTP_INACTIVE) ||
1630                             (transport->state == SCTP_UNCONFIRMED)) {
1631                                 sctp_assoc_control_transport(
1632                                         transport->asoc,
1633                                         transport,
1634                                         SCTP_TRANSPORT_UP,
1635                                         SCTP_RECEIVED_SACK);
1636                         }
1637
1638                         sctp_transport_raise_cwnd(transport, sack_ctsn,
1639                                                   bytes_acked);
1640
1641                         transport->flight_size -= bytes_acked;
1642                         if (transport->flight_size == 0)
1643                                 transport->partial_bytes_acked = 0;
1644                         q->outstanding_bytes -= bytes_acked + migrate_bytes;
1645                 } else {
1646                         /* RFC 2960 6.1, sctpimpguide-06 2.15.2
1647                          * When a sender is doing zero window probing, it
1648                          * should not timeout the association if it continues
1649                          * to receive new packets from the receiver. The
1650                          * reason is that the receiver MAY keep its window
1651                          * closed for an indefinite time.
1652                          * A sender is doing zero window probing when the
1653                          * receiver's advertised window is zero, and there is
1654                          * only one data chunk in flight to the receiver.
1655                          */
1656                         if (!q->asoc->peer.rwnd &&
1657                             !list_empty(&tlist) &&
1658                             (sack_ctsn+2 == q->asoc->next_tsn)) {
1659                                 SCTP_DEBUG_PRINTK("%s: SACK received for zero "
1660                                                   "window probe: %u\n",
1661                                                   __func__, sack_ctsn);
1662                                 q->asoc->overall_error_count = 0;
1663                                 transport->error_count = 0;
1664                         }
1665                 }
1666
1667                 /* RFC 2960 6.3.2 Retransmission Timer Rules
1668                  *
1669                  * R2) Whenever all outstanding data sent to an address have
1670                  * been acknowledged, turn off the T3-rtx timer of that
1671                  * address.
1672                  */
1673                 if (!transport->flight_size) {
1674                         if (timer_pending(&transport->T3_rtx_timer) &&
1675                             del_timer(&transport->T3_rtx_timer)) {
1676                                 sctp_transport_put(transport);
1677                         }
1678                 } else if (restart_timer) {
1679                         if (!mod_timer(&transport->T3_rtx_timer,
1680                                        jiffies + transport->rto))
1681                                 sctp_transport_hold(transport);
1682                 }
1683         }
1684
1685         list_splice(&tlist, transmitted_queue);
1686 }
1687
1688 /* Mark chunks as missing and consequently may get retransmitted. */
1689 static void sctp_mark_missing(struct sctp_outq *q,
1690                               struct list_head *transmitted_queue,
1691                               struct sctp_transport *transport,
1692                               __u32 highest_new_tsn_in_sack,
1693                               int count_of_newacks)
1694 {
1695         struct sctp_chunk *chunk;
1696         __u32 tsn;
1697         char do_fast_retransmit = 0;
1698         struct sctp_transport *primary = q->asoc->peer.primary_path;
1699
1700         list_for_each_entry(chunk, transmitted_queue, transmitted_list) {
1701
1702                 tsn = ntohl(chunk->subh.data_hdr->tsn);
1703
1704                 /* RFC 2960 7.2.4, sctpimpguide-05 2.8.2 M3) Examine all
1705                  * 'Unacknowledged TSN's', if the TSN number of an
1706                  * 'Unacknowledged TSN' is smaller than the 'HighestTSNinSack'
1707                  * value, increment the 'TSN.Missing.Report' count on that
1708                  * chunk if it has NOT been fast retransmitted or marked for
1709                  * fast retransmit already.
1710                  */
1711                 if (chunk->fast_retransmit == SCTP_CAN_FRTX &&
1712                     !chunk->tsn_gap_acked &&
1713                     TSN_lt(tsn, highest_new_tsn_in_sack)) {
1714
1715                         /* SFR-CACC may require us to skip marking
1716                          * this chunk as missing.
1717                          */
1718                         if (!transport || !sctp_cacc_skip(primary, transport,
1719                                             count_of_newacks, tsn)) {
1720                                 chunk->tsn_missing_report++;
1721
1722                                 SCTP_DEBUG_PRINTK(
1723                                         "%s: TSN 0x%x missing counter: %d\n",
1724                                         __func__, tsn,
1725                                         chunk->tsn_missing_report);
1726                         }
1727                 }
1728                 /*
1729                  * M4) If any DATA chunk is found to have a
1730                  * 'TSN.Missing.Report'
1731                  * value larger than or equal to 3, mark that chunk for
1732                  * retransmission and start the fast retransmit procedure.
1733                  */
1734
1735                 if (chunk->tsn_missing_report >= 3) {
1736                         chunk->fast_retransmit = SCTP_NEED_FRTX;
1737                         do_fast_retransmit = 1;
1738                 }
1739         }
1740
1741         if (transport) {
1742                 if (do_fast_retransmit)
1743                         sctp_retransmit(q, transport, SCTP_RTXR_FAST_RTX);
1744
1745                 SCTP_DEBUG_PRINTK("%s: transport: %p, cwnd: %d, "
1746                                   "ssthresh: %d, flight_size: %d, pba: %d\n",
1747                                   __func__, transport, transport->cwnd,
1748                                   transport->ssthresh, transport->flight_size,
1749                                   transport->partial_bytes_acked);
1750         }
1751 }
1752
1753 /* Is the given TSN acked by this packet?  */
1754 static int sctp_acked(struct sctp_sackhdr *sack, __u32 tsn)
1755 {
1756         int i;
1757         sctp_sack_variable_t *frags;
1758         __u16 gap;
1759         __u32 ctsn = ntohl(sack->cum_tsn_ack);
1760
1761         if (TSN_lte(tsn, ctsn))
1762                 goto pass;
1763
1764         /* 3.3.4 Selective Acknowledgement (SACK) (3):
1765          *
1766          * Gap Ack Blocks:
1767          *  These fields contain the Gap Ack Blocks. They are repeated
1768          *  for each Gap Ack Block up to the number of Gap Ack Blocks
1769          *  defined in the Number of Gap Ack Blocks field. All DATA
1770          *  chunks with TSNs greater than or equal to (Cumulative TSN
1771          *  Ack + Gap Ack Block Start) and less than or equal to
1772          *  (Cumulative TSN Ack + Gap Ack Block End) of each Gap Ack
1773          *  Block are assumed to have been received correctly.
1774          */
1775
1776         frags = sack->variable;
1777         gap = tsn - ctsn;
1778         for (i = 0; i < ntohs(sack->num_gap_ack_blocks); ++i) {
1779                 if (TSN_lte(ntohs(frags[i].gab.start), gap) &&
1780                     TSN_lte(gap, ntohs(frags[i].gab.end)))
1781                         goto pass;
1782         }
1783
1784         return 0;
1785 pass:
1786         return 1;
1787 }
1788
1789 static inline int sctp_get_skip_pos(struct sctp_fwdtsn_skip *skiplist,
1790                                     int nskips, __be16 stream)
1791 {
1792         int i;
1793
1794         for (i = 0; i < nskips; i++) {
1795                 if (skiplist[i].stream == stream)
1796                         return i;
1797         }
1798         return i;
1799 }
1800
1801 /* Create and add a fwdtsn chunk to the outq's control queue if needed. */
1802 static void sctp_generate_fwdtsn(struct sctp_outq *q, __u32 ctsn)
1803 {
1804         struct sctp_association *asoc = q->asoc;
1805         struct sctp_chunk *ftsn_chunk = NULL;
1806         struct sctp_fwdtsn_skip ftsn_skip_arr[10];
1807         int nskips = 0;
1808         int skip_pos = 0;
1809         __u32 tsn;
1810         struct sctp_chunk *chunk;
1811         struct list_head *lchunk, *temp;
1812
1813         if (!asoc->peer.prsctp_capable)
1814                 return;
1815
1816         /* PR-SCTP C1) Let SackCumAck be the Cumulative TSN ACK carried in the
1817          * received SACK.
1818          *
1819          * If (Advanced.Peer.Ack.Point < SackCumAck), then update
1820          * Advanced.Peer.Ack.Point to be equal to SackCumAck.
1821          */
1822         if (TSN_lt(asoc->adv_peer_ack_point, ctsn))
1823                 asoc->adv_peer_ack_point = ctsn;
1824
1825         /* PR-SCTP C2) Try to further advance the "Advanced.Peer.Ack.Point"
1826          * locally, that is, to move "Advanced.Peer.Ack.Point" up as long as
1827          * the chunk next in the out-queue space is marked as "abandoned" as
1828          * shown in the following example:
1829          *
1830          * Assuming that a SACK arrived with the Cumulative TSN ACK 102
1831          * and the Advanced.Peer.Ack.Point is updated to this value:
1832          *
1833          *   out-queue at the end of  ==>   out-queue after Adv.Ack.Point
1834          *   normal SACK processing           local advancement
1835          *                ...                           ...
1836          *   Adv.Ack.Pt-> 102 acked                     102 acked
1837          *                103 abandoned                 103 abandoned
1838          *                104 abandoned     Adv.Ack.P-> 104 abandoned
1839          *                105                           105
1840          *                106 acked                     106 acked
1841          *                ...                           ...
1842          *
1843          * In this example, the data sender successfully advanced the
1844          * "Advanced.Peer.Ack.Point" from 102 to 104 locally.
1845          */
1846         list_for_each_safe(lchunk, temp, &q->abandoned) {
1847                 chunk = list_entry(lchunk, struct sctp_chunk,
1848                                         transmitted_list);
1849                 tsn = ntohl(chunk->subh.data_hdr->tsn);
1850
1851                 /* Remove any chunks in the abandoned queue that are acked by
1852                  * the ctsn.
1853                  */
1854                 if (TSN_lte(tsn, ctsn)) {
1855                         list_del_init(lchunk);
1856                         sctp_chunk_free(chunk);
1857                 } else {
1858                         if (TSN_lte(tsn, asoc->adv_peer_ack_point+1)) {
1859                                 asoc->adv_peer_ack_point = tsn;
1860                                 if (chunk->chunk_hdr->flags &
1861                                          SCTP_DATA_UNORDERED)
1862                                         continue;
1863                                 skip_pos = sctp_get_skip_pos(&ftsn_skip_arr[0],
1864                                                 nskips,
1865                                                 chunk->subh.data_hdr->stream);
1866                                 ftsn_skip_arr[skip_pos].stream =
1867                                         chunk->subh.data_hdr->stream;
1868                                 ftsn_skip_arr[skip_pos].ssn =
1869                                          chunk->subh.data_hdr->ssn;
1870                                 if (skip_pos == nskips)
1871                                         nskips++;
1872                                 if (nskips == 10)
1873                                         break;
1874                         } else
1875                                 break;
1876                 }
1877         }
1878
1879         /* PR-SCTP C3) If, after step C1 and C2, the "Advanced.Peer.Ack.Point"
1880          * is greater than the Cumulative TSN ACK carried in the received
1881          * SACK, the data sender MUST send the data receiver a FORWARD TSN
1882          * chunk containing the latest value of the
1883          * "Advanced.Peer.Ack.Point".
1884          *
1885          * C4) For each "abandoned" TSN the sender of the FORWARD TSN SHOULD
1886          * list each stream and sequence number in the forwarded TSN. This
1887          * information will enable the receiver to easily find any
1888          * stranded TSN's waiting on stream reorder queues. Each stream
1889          * SHOULD only be reported once; this means that if multiple
1890          * abandoned messages occur in the same stream then only the
1891          * highest abandoned stream sequence number is reported. If the
1892          * total size of the FORWARD TSN does NOT fit in a single MTU then
1893          * the sender of the FORWARD TSN SHOULD lower the
1894          * Advanced.Peer.Ack.Point to the last TSN that will fit in a
1895          * single MTU.
1896          */
1897         if (asoc->adv_peer_ack_point > ctsn)
1898                 ftsn_chunk = sctp_make_fwdtsn(asoc, asoc->adv_peer_ack_point,
1899                                               nskips, &ftsn_skip_arr[0]);
1900
1901         if (ftsn_chunk) {
1902                 list_add_tail(&ftsn_chunk->list, &q->control_chunk_list);
1903                 SCTP_INC_STATS(SCTP_MIB_OUTCTRLCHUNKS);
1904         }
1905 }