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 &&
 135                         (transport && !transport->cacc.cacc_saw_newack))
 136                 return 1;
 137         return 0;
 138 }
 139
 140 /*
 141  * SFR-CACC algorithm:
 142  * 3.1) If CYCLING_CHANGEOVER is 0, the sender SHOULD
 143  * execute steps C, D, F.
 144  *
 145  * C has been implemented in sctp_outq_sack
 146  */
 147 static inline int sctp_cacc_skip_3_1(struct sctp_transport *primary,
 148                                      struct sctp_transport *transport,
 149                                      int count_of_newacks)
 150 {
 151         if (!primary->cacc.cycling_changeover) {
 152                 if (sctp_cacc_skip_3_1_d(primary, transport, count_of_newacks))
 153                         return 1;
 154                 if (sctp_cacc_skip_3_1_f(transport, count_of_newacks))
 155                         return 1;
 156                 return 0;
 157         }
 158         return 0;
 159 }
 160
 161 /*
 162  * SFR-CACC algorithm:
 163  * 3.2) Else if CYCLING_CHANGEOVER is 1, and t is less
 164  * than next_tsn_at_change of the current primary, then
 165  * the sender MUST NOT increment missing report count
 166  * for t.
 167  */
 168 static inline int sctp_cacc_skip_3_2(struct sctp_transport *primary, __u32 tsn)
 169 {
 170         if (primary->cacc.cycling_changeover &&
 171             TSN_lt(tsn, primary->cacc.next_tsn_at_change))
 172                 return 1;
 173         return 0;
 174 }
 175
 176 /*
 177  * SFR-CACC algorithm:
 178  * 3) If the missing report count for TSN t is to be
 179  * incremented according to [RFC2960] and
 180  * [SCTP_STEWART-2002], and CHANGEOVER_ACTIVE is set,
 181  * then the sender MUST further execute steps 3.1 and
 182  * 3.2 to determine if the missing report count for
 183  * TSN t SHOULD NOT be incremented.
 184  *
 185  * 3.3) If 3.1 and 3.2 do not dictate that the missing
 186  * report count for t should not be incremented, then
 187  * the sender SHOULD increment missing report count for
 188  * t (according to [RFC2960] and [SCTP_STEWART_2002]).
 189  */
 190 static inline int sctp_cacc_skip(struct sctp_transport *primary,
 191                                  struct sctp_transport *transport,
 192                                  int count_of_newacks,
 193                                  __u32 tsn)
 194 {
 195         if (primary->cacc.changeover_active &&
 196             (sctp_cacc_skip_3_1(primary, transport, count_of_newacks) ||
 197              sctp_cacc_skip_3_2(primary, tsn)))
 198                 return 1;
 199         return 0;
 200 }
 201
 202 /* Initialize an existing sctp_outq.  This does the boring stuff.
 203  * You still need to define handlers if you really want to DO
 204  * something with this structure...
 205  */
 206 void sctp_outq_init(struct sctp_association *asoc, struct sctp_outq *q)
 207 {
 208         q->asoc = asoc;
 209         INIT_LIST_HEAD(&q->out_chunk_list);
 210         INIT_LIST_HEAD(&q->control_chunk_list);
 211         INIT_LIST_HEAD(&q->retransmit);
 212         INIT_LIST_HEAD(&q->sacked);
 213         INIT_LIST_HEAD(&q->abandoned);
 214
 215         q->fast_rtx = 0;
 216         q->outstanding_bytes = 0;
 217         q->empty = 1;
 218         q->cork  = 0;
 219
 220         q->malloced = 0;
 221         q->out_qlen = 0;
 222 }
 223
 224 /* Free the outqueue structure and any related pending chunks.
 225  */
 226 void sctp_outq_teardown(struct sctp_outq *q)
 227 {
 228         struct sctp_transport *transport;
 229         struct list_head *lchunk, *temp;
 230         struct sctp_chunk *chunk, *tmp;
 231
 232         /* Throw away unacknowledged chunks. */
 233         list_for_each_entry(transport, &q->asoc->peer.transport_addr_list,
 234                         transports) {
 235                 while ((lchunk = sctp_list_dequeue(&transport->transmitted)) != NULL) {
 236                         chunk = list_entry(lchunk, struct sctp_chunk,
 237                                            transmitted_list);
 238                         /* Mark as part of a failed message. */
 239                         sctp_chunk_fail(chunk, q->error);
 240                         sctp_chunk_free(chunk);
 241                 }
 242         }
 243
 244         /* Throw away chunks that have been gap ACKed.  */
 245         list_for_each_safe(lchunk, temp, &q->sacked) {
 246                 list_del_init(lchunk);
 247                 chunk = list_entry(lchunk, struct sctp_chunk,
 248                                    transmitted_list);
 249                 sctp_chunk_fail(chunk, q->error);
 250                 sctp_chunk_free(chunk);
 251         }
 252
 253         /* Throw away any chunks in the retransmit queue. */
 254         list_for_each_safe(lchunk, temp, &q->retransmit) {
 255                 list_del_init(lchunk);
 256                 chunk = list_entry(lchunk, struct sctp_chunk,
 257                                    transmitted_list);
 258                 sctp_chunk_fail(chunk, q->error);
 259                 sctp_chunk_free(chunk);
 260         }
 261
 262         /* Throw away any chunks that are in the abandoned queue. */
 263         list_for_each_safe(lchunk, temp, &q->abandoned) {
 264                 list_del_init(lchunk);
 265                 chunk = list_entry(lchunk, struct sctp_chunk,
 266                                    transmitted_list);
 267                 sctp_chunk_fail(chunk, q->error);
 268                 sctp_chunk_free(chunk);
 269         }
 270
 271         /* Throw away any leftover data chunks. */
 272         while ((chunk = sctp_outq_dequeue_data(q)) != NULL) {
 273
 274                 /* Mark as send failure. */
 275                 sctp_chunk_fail(chunk, q->error);
 276                 sctp_chunk_free(chunk);
 277         }
 278
 279         q->error = 0;
 280
 281         /* Throw away any leftover control chunks. */
 282         list_for_each_entry_safe(chunk, tmp, &q->control_chunk_list, list) {
 283                 list_del_init(&chunk->list);
 284                 sctp_chunk_free(chunk);
 285         }
 286 }
 287
 288 /* Free the outqueue structure and any related pending chunks.  */
 289 void sctp_outq_free(struct sctp_outq *q)
 290 {
 291         /* Throw away leftover chunks. */
 292         sctp_outq_teardown(q);
 293
 294         /* If we were kmalloc()'d, free the memory.  */
 295         if (q->malloced)
 296                 kfree(q);
 297 }
 298
 299 /* Put a new chunk in an sctp_outq.  */
 300 int sctp_outq_tail(struct sctp_outq *q, struct sctp_chunk *chunk)
 301 {
 302         int error = 0;
 303
 304         SCTP_DEBUG_PRINTK("sctp_outq_tail(%p, %p[%s])\n",
 305                           q, chunk, chunk && chunk->chunk_hdr ?
 306                           sctp_cname(SCTP_ST_CHUNK(chunk->chunk_hdr->type))
 307                           : "Illegal Chunk");
 308
 309         /* If it is data, queue it up, otherwise, send it
 310          * immediately.
 311          */
 312         if (sctp_chunk_is_data(chunk)) {
 313                 /* Is it OK to queue data chunks?  */
 314                 /* From 9. Termination of Association
 315                  *
 316                  * When either endpoint performs a shutdown, the
 317                  * association on each peer will stop accepting new
 318                  * data from its user and only deliver data in queue
 319                  * at the time of sending or receiving the SHUTDOWN
 320                  * chunk.
 321                  */
 322                 switch (q->asoc->state) {
 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                 /* If the chunk is abandoned, move it to abandoned list. */
 581                 if (sctp_chunk_abandoned(chunk)) {
 582                         list_del_init(&chunk->transmitted_list);
 583                         sctp_insert_list(&q->abandoned,
 584                                          &chunk->transmitted_list);
 585                         continue;
 586                 }
 587
 588                 /* Make sure that Gap Acked TSNs are not retransmitted.  A
 589                  * simple approach is just to move such TSNs out of the
 590                  * way and into a 'transmitted' queue and skip to the
 591                  * next chunk.
 592                  */
 593                 if (chunk->tsn_gap_acked) {
 594                         list_del(&chunk->transmitted_list);
 595                         list_add_tail(&chunk->transmitted_list,
 596                                         &transport->transmitted);
 597                         continue;
 598                 }
 599
 600                 /* If we are doing fast retransmit, ignore non-fast_rtransmit
 601                  * chunks
 602                  */
 603                 if (fast_rtx && !chunk->fast_retransmit)
 604                         continue;
 605
 606 redo:
 607                 /* Attempt to append this chunk to the packet. */
 608                 status = sctp_packet_append_chunk(pkt, chunk);
 609
 610                 switch (status) {
 611                 case SCTP_XMIT_PMTU_FULL:
 612                         if (!pkt->has_data && !pkt->has_cookie_echo) {
 613                                 /* If this packet did not contain DATA then
 614                                  * retransmission did not happen, so do it
 615                                  * again.  We'll ignore the error here since
 616                                  * control chunks are already freed so there
 617                                  * is nothing we can do.
 618                                  */
 619                                 sctp_packet_transmit(pkt);
 620                                 goto redo;
 621                         }
 622
 623                         /* Send this packet.  */
 624                         error = sctp_packet_transmit(pkt);
 625
 626                         /* If we are retransmitting, we should only
 627                          * send a single packet.
 628                          * Otherwise, try appending this chunk again.
 629                          */
 630                         if (rtx_timeout || fast_rtx)
 631                                 done = 1;
 632                         else
 633                                 goto redo;
 634
 635                         /* Bundle next chunk in the next round.  */
 636                         break;
 637
 638                 case SCTP_XMIT_RWND_FULL:
 639                         /* Send this packet. */
 640                         error = sctp_packet_transmit(pkt);
 641
 642                         /* Stop sending DATA as there is no more room
 643                          * at the receiver.
 644                          */
 645                         done = 1;
 646                         break;
 647
 648                 case SCTP_XMIT_NAGLE_DELAY:
 649                         /* Send this packet. */
 650                         error = sctp_packet_transmit(pkt);
 651
 652                         /* Stop sending DATA because of nagle delay. */
 653                         done = 1;
 654                         break;
 655
 656                 default:
 657                         /* The append was successful, so add this chunk to
 658                          * the transmitted list.
 659                          */
 660                         list_del(&chunk->transmitted_list);
 661                         list_add_tail(&chunk->transmitted_list,
 662                                         &transport->transmitted);
 663
 664                         /* Mark the chunk as ineligible for fast retransmit
 665                          * after it is retransmitted.
 666                          */
 667                         if (chunk->fast_retransmit == SCTP_NEED_FRTX)
 668                                 chunk->fast_retransmit = SCTP_DONT_FRTX;
 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 through */
 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);
 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
 929                         /* This can happen on COOKIE-ECHO resend.  Only
 930                          * one chunk can get bundled with a COOKIE-ECHO.
 931                          */
 932                         if (packet->has_cookie_echo)
 933                                 goto sctp_flush_out;
 934
 935                         /* Don't send new data if there is still data
 936                          * waiting to retransmit.
 937                          */
 938                         if (!list_empty(&q->retransmit))
 939                                 goto sctp_flush_out;
 940                 }
 941
 942                 /* Apply Max.Burst limitation to the current transport in
 943                  * case it will be used for new data.  We are going to
 944                  * rest it before we return, but we want to apply the limit
 945                  * to the currently queued data.
 946                  */
 947                 if (transport)
 948                         sctp_transport_burst_limited(transport);
 949
 950                 /* Finally, transmit new packets.  */
 951                 while ((chunk = sctp_outq_dequeue_data(q)) != NULL) {
 952                         /* RFC 2960 6.5 Every DATA chunk MUST carry a valid
 953                          * stream identifier.
 954                          */
 955                         if (chunk->sinfo.sinfo_stream >=
 956                             asoc->c.sinit_num_ostreams) {
 957
 958                                 /* Mark as failed send. */
 959                                 sctp_chunk_fail(chunk, SCTP_ERROR_INV_STRM);
 960                                 sctp_chunk_free(chunk);
 961                                 continue;
 962                         }
 963
 964                         /* Has this chunk expired? */
 965                         if (sctp_chunk_abandoned(chunk)) {
 966                                 sctp_chunk_fail(chunk, 0);
 967                                 sctp_chunk_free(chunk);
 968                                 continue;
 969                         }
 970
 971                         /* If there is a specified transport, use it.
 972                          * Otherwise, we want to use the active path.
 973                          */
 974                         new_transport = chunk->transport;
 975                         if (!new_transport ||
 976                             ((new_transport->state == SCTP_INACTIVE) ||
 977                              (new_transport->state == SCTP_UNCONFIRMED)))
 978                                 new_transport = asoc->peer.active_path;
 979
 980                         /* Change packets if necessary.  */
 981                         if (new_transport != transport) {
 982                                 transport = new_transport;
 983
 984                                 /* Schedule to have this transport's
 985                                  * packet flushed.
 986                                  */
 987                                 if (list_empty(&transport->send_ready)) {
 988                                         list_add_tail(&transport->send_ready,
 989                                                       &transport_list);
 990                                 }
 991
 992                                 packet = &transport->packet;
 993                                 sctp_packet_config(packet, vtag,
 994                                                    asoc->peer.ecn_capable);
 995                                 /* We've switched transports, so apply the
 996                                  * Burst limit to the new transport.
 997                                  */
 998                                 sctp_transport_burst_limited(transport);
 999                         }
1000
1001                         SCTP_DEBUG_PRINTK("sctp_outq_flush(%p, %p[%s]), ",
1002                                           q, chunk,
1003                                           chunk && chunk->chunk_hdr ?
1004                                           sctp_cname(SCTP_ST_CHUNK(
1005                                                   chunk->chunk_hdr->type))
1006                                           : "Illegal Chunk");
1007
1008                         SCTP_DEBUG_PRINTK("TX TSN 0x%x skb->head "
1009                                         "%p skb->users %d.\n",
1010                                         ntohl(chunk->subh.data_hdr->tsn),
1011                                         chunk->skb ?chunk->skb->head : NULL,
1012                                         chunk->skb ?
1013                                         atomic_read(&chunk->skb->users) : -1);
1014
1015                         /* Add the chunk to the packet.  */
1016                         status = sctp_packet_transmit_chunk(packet, chunk, 0);
1017
1018                         switch (status) {
1019                         case SCTP_XMIT_PMTU_FULL:
1020                         case SCTP_XMIT_RWND_FULL:
1021                         case SCTP_XMIT_NAGLE_DELAY:
1022                                 /* We could not append this chunk, so put
1023                                  * the chunk back on the output queue.
1024                                  */
1025                                 SCTP_DEBUG_PRINTK("sctp_outq_flush: could "
1026                                         "not transmit TSN: 0x%x, status: %d\n",
1027                                         ntohl(chunk->subh.data_hdr->tsn),
1028                                         status);
1029                                 sctp_outq_head_data(q, chunk);
1030                                 goto sctp_flush_out;
1031                                 break;
1032
1033                         case SCTP_XMIT_OK:
1034                                 /* The sender is in the SHUTDOWN-PENDING state,
1035                                  * The sender MAY set the I-bit in the DATA
1036                                  * chunk header.
1037                                  */
1038                                 if (asoc->state == SCTP_STATE_SHUTDOWN_PENDING)
1039                                         chunk->chunk_hdr->flags |= SCTP_DATA_SACK_IMM;
1040
1041                                 break;
1042
1043                         default:
1044                                 BUG();
1045                         }
1046
1047                         /* BUG: We assume that the sctp_packet_transmit()
1048                          * call below will succeed all the time and add the
1049                          * chunk to the transmitted list and restart the
1050                          * timers.
1051                          * It is possible that the call can fail under OOM
1052                          * conditions.
1053                          *
1054                          * Is this really a problem?  Won't this behave
1055                          * like a lost TSN?
1056                          */
1057                         list_add_tail(&chunk->transmitted_list,
1058                                       &transport->transmitted);
1059
1060                         sctp_transport_reset_timers(transport);
1061
1062                         q->empty = 0;
1063
1064                         /* Only let one DATA chunk get bundled with a
1065                          * COOKIE-ECHO chunk.
1066                          */
1067                         if (packet->has_cookie_echo)
1068                                 goto sctp_flush_out;
1069                 }
1070                 break;
1071
1072         default:
1073                 /* Do nothing.  */
1074                 break;
1075         }
1076
1077 sctp_flush_out:
1078
1079         /* Before returning, examine all the transports touched in
1080          * this call.  Right now, we bluntly force clear all the
1081          * transports.  Things might change after we implement Nagle.
1082          * But such an examination is still required.
1083          *
1084          * --xguo
1085          */
1086         while ((ltransport = sctp_list_dequeue(&transport_list)) != NULL ) {
1087                 struct sctp_transport *t = list_entry(ltransport,
1088                                                       struct sctp_transport,
1089                                                       send_ready);
1090                 packet = &t->packet;
1091                 if (!sctp_packet_empty(packet))
1092                         error = sctp_packet_transmit(packet);
1093
1094                 /* Clear the burst limited state, if any */
1095                 sctp_transport_burst_reset(t);
1096         }
1097
1098         return error;
1099 }
1100
1101 /* Update unack_data based on the incoming SACK chunk */
1102 static void sctp_sack_update_unack_data(struct sctp_association *assoc,
1103                                         struct sctp_sackhdr *sack)
1104 {
1105         sctp_sack_variable_t *frags;
1106         __u16 unack_data;
1107         int i;
1108
1109         unack_data = assoc->next_tsn - assoc->ctsn_ack_point - 1;
1110
1111         frags = sack->variable;
1112         for (i = 0; i < ntohs(sack->num_gap_ack_blocks); i++) {
1113                 unack_data -= ((ntohs(frags[i].gab.end) -
1114                                 ntohs(frags[i].gab.start) + 1));
1115         }
1116
1117         assoc->unack_data = unack_data;
1118 }
1119
1120 /* This is where we REALLY process a SACK.
1121  *
1122  * Process the SACK against the outqueue.  Mostly, this just frees
1123  * things off the transmitted queue.
1124  */
1125 int sctp_outq_sack(struct sctp_outq *q, struct sctp_sackhdr *sack)
1126 {
1127         struct sctp_association *asoc = q->asoc;
1128         struct sctp_transport *transport;
1129         struct sctp_chunk *tchunk = NULL;
1130         struct list_head *lchunk, *transport_list, *temp;
1131         sctp_sack_variable_t *frags = sack->variable;
1132         __u32 sack_ctsn, ctsn, tsn;
1133         __u32 highest_tsn, highest_new_tsn;
1134         __u32 sack_a_rwnd;
1135         unsigned outstanding;
1136         struct sctp_transport *primary = asoc->peer.primary_path;
1137         int count_of_newacks = 0;
1138         int gap_ack_blocks;
1139         u8 accum_moved = 0;
1140
1141         /* Grab the association's destination address list. */
1142         transport_list = &asoc->peer.transport_addr_list;
1143
1144         sack_ctsn = ntohl(sack->cum_tsn_ack);
1145         gap_ack_blocks = ntohs(sack->num_gap_ack_blocks);
1146         /*
1147          * SFR-CACC algorithm:
1148          * On receipt of a SACK the sender SHOULD execute the
1149          * following statements.
1150          *
1151          * 1) If the cumulative ack in the SACK passes next tsn_at_change
1152          * on the current primary, the CHANGEOVER_ACTIVE flag SHOULD be
1153          * cleared. The CYCLING_CHANGEOVER flag SHOULD also be cleared for
1154          * all destinations.
1155          * 2) If the SACK contains gap acks and the flag CHANGEOVER_ACTIVE
1156          * is set the receiver of the SACK MUST take the following actions:
1157          *
1158          * A) Initialize the cacc_saw_newack to 0 for all destination
1159          * addresses.
1160          *
1161          * Only bother if changeover_active is set. Otherwise, this is
1162          * totally suboptimal to do on every SACK.
1163          */
1164         if (primary->cacc.changeover_active) {
1165                 u8 clear_cycling = 0;
1166
1167                 if (TSN_lte(primary->cacc.next_tsn_at_change, sack_ctsn)) {
1168                         primary->cacc.changeover_active = 0;
1169                         clear_cycling = 1;
1170                 }
1171
1172                 if (clear_cycling || gap_ack_blocks) {
1173                         list_for_each_entry(transport, transport_list,
1174                                         transports) {
1175                                 if (clear_cycling)
1176                                         transport->cacc.cycling_changeover = 0;
1177                                 if (gap_ack_blocks)
1178                                         transport->cacc.cacc_saw_newack = 0;
1179                         }
1180                 }
1181         }
1182
1183         /* Get the highest TSN in the sack. */
1184         highest_tsn = sack_ctsn;
1185         if (gap_ack_blocks)
1186                 highest_tsn += ntohs(frags[gap_ack_blocks - 1].gab.end);
1187
1188         if (TSN_lt(asoc->highest_sacked, highest_tsn))
1189                 asoc->highest_sacked = highest_tsn;
1190
1191         highest_new_tsn = sack_ctsn;
1192
1193         /* Run through the retransmit queue.  Credit bytes received
1194          * and free those chunks that we can.
1195          */
1196         sctp_check_transmitted(q, &q->retransmit, NULL, sack, &highest_new_tsn);
1197
1198         /* Run through the transmitted queue.
1199          * Credit bytes received and free those chunks which we can.
1200          *
1201          * This is a MASSIVE candidate for optimization.
1202          */
1203         list_for_each_entry(transport, transport_list, transports) {
1204                 sctp_check_transmitted(q, &transport->transmitted,
1205                                        transport, sack, &highest_new_tsn);
1206                 /*
1207                  * SFR-CACC algorithm:
1208                  * C) Let count_of_newacks be the number of
1209                  * destinations for which cacc_saw_newack is set.
1210                  */
1211                 if (transport->cacc.cacc_saw_newack)
1212                         count_of_newacks ++;
1213         }
1214
1215         /* Move the Cumulative TSN Ack Point if appropriate.  */
1216         if (TSN_lt(asoc->ctsn_ack_point, sack_ctsn)) {
1217                 asoc->ctsn_ack_point = sack_ctsn;
1218                 accum_moved = 1;
1219         }
1220
1221         if (gap_ack_blocks) {
1222
1223                 if (asoc->fast_recovery && accum_moved)
1224                         highest_new_tsn = highest_tsn;
1225
1226                 list_for_each_entry(transport, transport_list, transports)
1227                         sctp_mark_missing(q, &transport->transmitted, transport,
1228                                           highest_new_tsn, count_of_newacks);
1229         }
1230
1231         /* Update unack_data field in the assoc. */
1232         sctp_sack_update_unack_data(asoc, sack);
1233
1234         ctsn = asoc->ctsn_ack_point;
1235
1236         /* Throw away stuff rotting on the sack queue.  */
1237         list_for_each_safe(lchunk, temp, &q->sacked) {
1238                 tchunk = list_entry(lchunk, struct sctp_chunk,
1239                                     transmitted_list);
1240                 tsn = ntohl(tchunk->subh.data_hdr->tsn);
1241                 if (TSN_lte(tsn, ctsn)) {
1242                         list_del_init(&tchunk->transmitted_list);
1243                         sctp_chunk_free(tchunk);
1244                 }
1245         }
1246
1247         /* ii) Set rwnd equal to the newly received a_rwnd minus the
1248          *     number of bytes still outstanding after processing the
1249          *     Cumulative TSN Ack and the Gap Ack Blocks.
1250          */
1251
1252         sack_a_rwnd = ntohl(sack->a_rwnd);
1253         outstanding = q->outstanding_bytes;
1254
1255         if (outstanding < sack_a_rwnd)
1256                 sack_a_rwnd -= outstanding;
1257         else
1258                 sack_a_rwnd = 0;
1259
1260         asoc->peer.rwnd = sack_a_rwnd;
1261
1262         sctp_generate_fwdtsn(q, sack_ctsn);
1263
1264         SCTP_DEBUG_PRINTK("%s: sack Cumulative TSN Ack is 0x%x.\n",
1265                           __func__, sack_ctsn);
1266         SCTP_DEBUG_PRINTK("%s: Cumulative TSN Ack of association, "
1267                           "%p is 0x%x. Adv peer ack point: 0x%x\n",
1268                           __func__, asoc, ctsn, asoc->adv_peer_ack_point);
1269
1270         /* See if all chunks are acked.
1271          * Make sure the empty queue handler will get run later.
1272          */
1273         q->empty = (list_empty(&q->out_chunk_list) &&
1274                     list_empty(&q->retransmit));
1275         if (!q->empty)
1276                 goto finish;
1277
1278         list_for_each_entry(transport, transport_list, transports) {
1279                 q->empty = q->empty && list_empty(&transport->transmitted);
1280                 if (!q->empty)
1281                         goto finish;
1282         }
1283
1284         SCTP_DEBUG_PRINTK("sack queue is empty.\n");
1285 finish:
1286         return q->empty;
1287 }
1288
1289 /* Is the outqueue empty?  */
1290 int sctp_outq_is_empty(const struct sctp_outq *q)
1291 {
1292         return q->empty;
1293 }
1294
1295 /********************************************************************
1296  * 2nd Level Abstractions
1297  ********************************************************************/
1298
1299 /* Go through a transport's transmitted list or the association's retransmit
1300  * list and move chunks that are acked by the Cumulative TSN Ack to q->sacked.
1301  * The retransmit list will not have an associated transport.
1302  *
1303  * I added coherent debug information output.   --xguo
1304  *
1305  * Instead of printing 'sacked' or 'kept' for each TSN on the
1306  * transmitted_queue, we print a range: SACKED: TSN1-TSN2, TSN3, TSN4-TSN5.
1307  * KEPT TSN6-TSN7, etc.
1308  */
1309 static void sctp_check_transmitted(struct sctp_outq *q,
1310                                    struct list_head *transmitted_queue,
1311                                    struct sctp_transport *transport,
1312                                    struct sctp_sackhdr *sack,
1313                                    __u32 *highest_new_tsn_in_sack)
1314 {
1315         struct list_head *lchunk;
1316         struct sctp_chunk *tchunk;
1317         struct list_head tlist;
1318         __u32 tsn;
1319         __u32 sack_ctsn;
1320         __u32 rtt;
1321         __u8 restart_timer = 0;
1322         int bytes_acked = 0;
1323         int migrate_bytes = 0;
1324
1325         /* These state variables are for coherent debug output. --xguo */
1326
1327 #if SCTP_DEBUG
1328         __u32 dbg_ack_tsn = 0;  /* An ACKed TSN range starts here... */
1329         __u32 dbg_last_ack_tsn = 0;  /* ...and finishes here.        */
1330         __u32 dbg_kept_tsn = 0; /* An un-ACKed range starts here...  */
1331         __u32 dbg_last_kept_tsn = 0; /* ...and finishes here.        */
1332
1333         /* 0 : The last TSN was ACKed.
1334          * 1 : The last TSN was NOT ACKed (i.e. KEPT).
1335          * -1: We need to initialize.
1336          */
1337         int dbg_prt_state = -1;
1338 #endif /* SCTP_DEBUG */
1339
1340         sack_ctsn = ntohl(sack->cum_tsn_ack);
1341
1342         INIT_LIST_HEAD(&tlist);
1343
1344         /* The while loop will skip empty transmitted queues. */
1345         while (NULL != (lchunk = sctp_list_dequeue(transmitted_queue))) {
1346                 tchunk = list_entry(lchunk, struct sctp_chunk,
1347                                     transmitted_list);
1348
1349                 if (sctp_chunk_abandoned(tchunk)) {
1350                         /* Move the chunk to abandoned list. */
1351                         sctp_insert_list(&q->abandoned, lchunk);
1352
1353                         /* If this chunk has not been acked, stop
1354                          * considering it as 'outstanding'.
1355                          */
1356                         if (!tchunk->tsn_gap_acked) {
1357                                 if (tchunk->transport)
1358                                         tchunk->transport->flight_size -=
1359                                                         sctp_data_size(tchunk);
1360                                 q->outstanding_bytes -= sctp_data_size(tchunk);
1361                         }
1362                         continue;
1363                 }
1364
1365                 tsn = ntohl(tchunk->subh.data_hdr->tsn);
1366                 if (sctp_acked(sack, tsn)) {
1367                         /* If this queue is the retransmit queue, the
1368                          * retransmit timer has already reclaimed
1369                          * the outstanding bytes for this chunk, so only
1370                          * count bytes associated with a transport.
1371                          */
1372                         if (transport) {
1373                                 /* If this chunk is being used for RTT
1374                                  * measurement, calculate the RTT and update
1375                                  * the RTO using this value.
1376                                  *
1377                                  * 6.3.1 C5) Karn's algorithm: RTT measurements
1378                                  * MUST NOT be made using packets that were
1379                                  * retransmitted (and thus for which it is
1380                                  * ambiguous whether the reply was for the
1381                                  * first instance of the packet or a later
1382                                  * instance).
1383                                  */
1384                                 if (!tchunk->tsn_gap_acked &&
1385                                     tchunk->rtt_in_progress) {
1386                                         tchunk->rtt_in_progress = 0;
1387                                         rtt = jiffies - tchunk->sent_at;
1388                                         sctp_transport_update_rto(transport,
1389                                                                   rtt);
1390                                 }
1391                         }
1392
1393                         /* If the chunk hasn't been marked as ACKED,
1394                          * mark it and account bytes_acked if the
1395                          * chunk had a valid transport (it will not
1396                          * have a transport if ASCONF had deleted it
1397                          * while DATA was outstanding).
1398                          */
1399                         if (!tchunk->tsn_gap_acked) {
1400                                 tchunk->tsn_gap_acked = 1;
1401                                 *highest_new_tsn_in_sack = tsn;
1402                                 bytes_acked += sctp_data_size(tchunk);
1403                                 if (!tchunk->transport)
1404                                         migrate_bytes += sctp_data_size(tchunk);
1405                         }
1406
1407                         if (TSN_lte(tsn, sack_ctsn)) {
1408                                 /* RFC 2960  6.3.2 Retransmission Timer Rules
1409                                  *
1410                                  * R3) Whenever a SACK is received
1411                                  * that acknowledges the DATA chunk
1412                                  * with the earliest outstanding TSN
1413                                  * for that address, restart T3-rtx
1414                                  * timer for that address with its
1415                                  * current RTO.
1416                                  */
1417                                 restart_timer = 1;
1418
1419                                 if (!tchunk->tsn_gap_acked) {
1420                                         /*
1421                                          * SFR-CACC algorithm:
1422                                          * 2) If the SACK contains gap acks
1423                                          * and the flag CHANGEOVER_ACTIVE is
1424                                          * set the receiver of the SACK MUST
1425                                          * take the following action:
1426                                          *
1427                                          * B) For each TSN t being acked that
1428                                          * has not been acked in any SACK so
1429                                          * far, set cacc_saw_newack to 1 for
1430                                          * the destination that the TSN was
1431                                          * sent to.
1432                                          */
1433                                         if (transport &&
1434                                             sack->num_gap_ack_blocks &&
1435                                             q->asoc->peer.primary_path->cacc.
1436                                             changeover_active)
1437                                                 transport->cacc.cacc_saw_newack
1438                                                         = 1;
1439                                 }
1440
1441                                 list_add_tail(&tchunk->transmitted_list,
1442                                               &q->sacked);
1443                         } else {
1444                                 /* RFC2960 7.2.4, sctpimpguide-05 2.8.2
1445                                  * M2) Each time a SACK arrives reporting
1446                                  * 'Stray DATA chunk(s)' record the highest TSN
1447                                  * reported as newly acknowledged, call this
1448                                  * value 'HighestTSNinSack'. A newly
1449                                  * acknowledged DATA chunk is one not
1450                                  * previously acknowledged in a SACK.
1451                                  *
1452                                  * When the SCTP sender of data receives a SACK
1453                                  * chunk that acknowledges, for the first time,
1454                                  * the receipt of a DATA chunk, all the still
1455                                  * unacknowledged DATA chunks whose TSN is
1456                                  * older than that newly acknowledged DATA
1457                                  * chunk, are qualified as 'Stray DATA chunks'.
1458                                  */
1459                                 list_add_tail(lchunk, &tlist);
1460                         }
1461
1462 #if SCTP_DEBUG
1463                         switch (dbg_prt_state) {
1464                         case 0: /* last TSN was ACKed */
1465                                 if (dbg_last_ack_tsn + 1 == tsn) {
1466                                         /* This TSN belongs to the
1467                                          * current ACK range.
1468                                          */
1469                                         break;
1470                                 }
1471
1472                                 if (dbg_last_ack_tsn != dbg_ack_tsn) {
1473                                         /* Display the end of the
1474                                          * current range.
1475                                          */
1476                                         SCTP_DEBUG_PRINTK_CONT("-%08x",
1477                                                                dbg_last_ack_tsn);
1478                                 }
1479
1480                                 /* Start a new range.  */
1481                                 SCTP_DEBUG_PRINTK_CONT(",%08x", tsn);
1482                                 dbg_ack_tsn = tsn;
1483                                 break;
1484
1485                         case 1: /* The last TSN was NOT ACKed. */
1486                                 if (dbg_last_kept_tsn != dbg_kept_tsn) {
1487                                         /* Display the end of current range. */
1488                                         SCTP_DEBUG_PRINTK_CONT("-%08x",
1489                                                                dbg_last_kept_tsn);
1490                                 }
1491
1492                                 SCTP_DEBUG_PRINTK_CONT("\n");
1493
1494                                 /* FALL THROUGH... */
1495                         default:
1496                                 /* This is the first-ever TSN we examined.  */
1497                                 /* Start a new range of ACK-ed TSNs.  */
1498                                 SCTP_DEBUG_PRINTK("ACKed: %08x", tsn);
1499                                 dbg_prt_state = 0;
1500                                 dbg_ack_tsn = tsn;
1501                         }
1502
1503                         dbg_last_ack_tsn = tsn;
1504 #endif /* SCTP_DEBUG */
1505
1506                 } else {
1507                         if (tchunk->tsn_gap_acked) {
1508                                 SCTP_DEBUG_PRINTK("%s: Receiver reneged on "
1509                                                   "data TSN: 0x%x\n",
1510                                                   __func__,
1511                                                   tsn);
1512                                 tchunk->tsn_gap_acked = 0;
1513
1514                                 if (tchunk->transport)
1515                                         bytes_acked -= sctp_data_size(tchunk);
1516
1517                                 /* RFC 2960 6.3.2 Retransmission Timer Rules
1518                                  *
1519                                  * R4) Whenever a SACK is received missing a
1520                                  * TSN that was previously acknowledged via a
1521                                  * Gap Ack Block, start T3-rtx for the
1522                                  * destination address to which the DATA
1523                                  * chunk was originally
1524                                  * transmitted if it is not already running.
1525                                  */
1526                                 restart_timer = 1;
1527                         }
1528
1529                         list_add_tail(lchunk, &tlist);
1530
1531 #if SCTP_DEBUG
1532                         /* See the above comments on ACK-ed TSNs. */
1533                         switch (dbg_prt_state) {
1534                         case 1:
1535                                 if (dbg_last_kept_tsn + 1 == tsn)
1536                                         break;
1537
1538                                 if (dbg_last_kept_tsn != dbg_kept_tsn)
1539                                         SCTP_DEBUG_PRINTK_CONT("-%08x",
1540                                                                dbg_last_kept_tsn);
1541
1542                                 SCTP_DEBUG_PRINTK_CONT(",%08x", tsn);
1543                                 dbg_kept_tsn = tsn;
1544                                 break;
1545
1546                         case 0:
1547                                 if (dbg_last_ack_tsn != dbg_ack_tsn)
1548                                         SCTP_DEBUG_PRINTK_CONT("-%08x",
1549                                                                dbg_last_ack_tsn);
1550                                 SCTP_DEBUG_PRINTK_CONT("\n");
1551
1552                                 /* FALL THROUGH... */
1553                         default:
1554                                 SCTP_DEBUG_PRINTK("KEPT: %08x",tsn);
1555                                 dbg_prt_state = 1;
1556                                 dbg_kept_tsn = tsn;
1557                         }
1558
1559                         dbg_last_kept_tsn = tsn;
1560 #endif /* SCTP_DEBUG */
1561                 }
1562         }
1563
1564 #if SCTP_DEBUG
1565         /* Finish off the last range, displaying its ending TSN.  */
1566         switch (dbg_prt_state) {
1567         case 0:
1568                 if (dbg_last_ack_tsn != dbg_ack_tsn) {
1569                         SCTP_DEBUG_PRINTK_CONT("-%08x\n", dbg_last_ack_tsn);
1570                 } else {
1571                         SCTP_DEBUG_PRINTK_CONT("\n");
1572                 }
1573         break;
1574
1575         case 1:
1576                 if (dbg_last_kept_tsn != dbg_kept_tsn) {
1577                         SCTP_DEBUG_PRINTK_CONT("-%08x\n", dbg_last_kept_tsn);
1578                 } else {
1579                         SCTP_DEBUG_PRINTK_CONT("\n");
1580                 }
1581         }
1582 #endif /* SCTP_DEBUG */
1583         if (transport) {
1584                 if (bytes_acked) {
1585                         struct sctp_association *asoc = transport->asoc;
1586
1587                         /* We may have counted DATA that was migrated
1588                          * to this transport due to DEL-IP operation.
1589                          * Subtract those bytes, since the were never
1590                          * send on this transport and shouldn't be
1591                          * credited to this transport.
1592                          */
1593                         bytes_acked -= migrate_bytes;
1594
1595                         /* 8.2. When an outstanding TSN is acknowledged,
1596                          * the endpoint shall clear the error counter of
1597                          * the destination transport address to which the
1598                          * DATA chunk was last sent.
1599                          * The association's overall error counter is
1600                          * also cleared.
1601                          */
1602                         transport->error_count = 0;
1603                         transport->asoc->overall_error_count = 0;
1604
1605                         /*
1606                          * While in SHUTDOWN PENDING, we may have started
1607                          * the T5 shutdown guard timer after reaching the
1608                          * retransmission limit. Stop that timer as soon
1609                          * as the receiver acknowledged any data.
1610                          */
1611                         if (asoc->state == SCTP_STATE_SHUTDOWN_PENDING &&
1612                             del_timer(&asoc->timers
1613                                 [SCTP_EVENT_TIMEOUT_T5_SHUTDOWN_GUARD]))
1614                                         sctp_association_put(asoc);
1615
1616                         /* Mark the destination transport address as
1617                          * active if it is not so marked.
1618                          */
1619                         if ((transport->state == SCTP_INACTIVE) ||
1620                             (transport->state == SCTP_UNCONFIRMED)) {
1621                                 sctp_assoc_control_transport(
1622                                         transport->asoc,
1623                                         transport,
1624                                         SCTP_TRANSPORT_UP,
1625                                         SCTP_RECEIVED_SACK);
1626                         }
1627
1628                         sctp_transport_raise_cwnd(transport, sack_ctsn,
1629                                                   bytes_acked);
1630
1631                         transport->flight_size -= bytes_acked;
1632                         if (transport->flight_size == 0)
1633                                 transport->partial_bytes_acked = 0;
1634                         q->outstanding_bytes -= bytes_acked + migrate_bytes;
1635                 } else {
1636                         /* RFC 2960 6.1, sctpimpguide-06 2.15.2
1637                          * When a sender is doing zero window probing, it
1638                          * should not timeout the association if it continues
1639                          * to receive new packets from the receiver. The
1640                          * reason is that the receiver MAY keep its window
1641                          * closed for an indefinite time.
1642                          * A sender is doing zero window probing when the
1643                          * receiver's advertised window is zero, and there is
1644                          * only one data chunk in flight to the receiver.
1645                          *
1646                          * Allow the association to timeout while in SHUTDOWN
1647                          * PENDING or SHUTDOWN RECEIVED in case the receiver
1648                          * stays in zero window mode forever.
1649                          */
1650                         if (!q->asoc->peer.rwnd &&
1651                             !list_empty(&tlist) &&
1652                             (sack_ctsn+2 == q->asoc->next_tsn) &&
1653                             q->asoc->state < SCTP_STATE_SHUTDOWN_PENDING) {
1654                                 SCTP_DEBUG_PRINTK("%s: SACK received for zero "
1655                                                   "window probe: %u\n",
1656                                                   __func__, sack_ctsn);
1657                                 q->asoc->overall_error_count = 0;
1658                                 transport->error_count = 0;
1659                         }
1660                 }
1661
1662                 /* RFC 2960 6.3.2 Retransmission Timer Rules
1663                  *
1664                  * R2) Whenever all outstanding data sent to an address have
1665                  * been acknowledged, turn off the T3-rtx timer of that
1666                  * address.
1667                  */
1668                 if (!transport->flight_size) {
1669                         if (timer_pending(&transport->T3_rtx_timer) &&
1670                             del_timer(&transport->T3_rtx_timer)) {
1671                                 sctp_transport_put(transport);
1672                         }
1673                 } else if (restart_timer) {
1674                         if (!mod_timer(&transport->T3_rtx_timer,
1675                                        jiffies + transport->rto))
1676                                 sctp_transport_hold(transport);
1677                 }
1678         }
1679
1680         list_splice(&tlist, transmitted_queue);
1681 }
1682
1683 /* Mark chunks as missing and consequently may get retransmitted. */
1684 static void sctp_mark_missing(struct sctp_outq *q,
1685                               struct list_head *transmitted_queue,
1686                               struct sctp_transport *transport,
1687                               __u32 highest_new_tsn_in_sack,
1688                               int count_of_newacks)
1689 {
1690         struct sctp_chunk *chunk;
1691         __u32 tsn;
1692         char do_fast_retransmit = 0;
1693         struct sctp_association *asoc = q->asoc;
1694         struct sctp_transport *primary = asoc->peer.primary_path;
1695
1696         list_for_each_entry(chunk, transmitted_queue, transmitted_list) {
1697
1698                 tsn = ntohl(chunk->subh.data_hdr->tsn);
1699
1700                 /* RFC 2960 7.2.4, sctpimpguide-05 2.8.2 M3) Examine all
1701                  * 'Unacknowledged TSN's', if the TSN number of an
1702                  * 'Unacknowledged TSN' is smaller than the 'HighestTSNinSack'
1703                  * value, increment the 'TSN.Missing.Report' count on that
1704                  * chunk if it has NOT been fast retransmitted or marked for
1705                  * fast retransmit already.
1706                  */
1707                 if (chunk->fast_retransmit == SCTP_CAN_FRTX &&
1708                     !chunk->tsn_gap_acked &&
1709                     TSN_lt(tsn, highest_new_tsn_in_sack)) {
1710
1711                         /* SFR-CACC may require us to skip marking
1712                          * this chunk as missing.
1713                          */
1714                         if (!transport || !sctp_cacc_skip(primary,
1715                                                 chunk->transport,
1716                                                 count_of_newacks, tsn)) {
1717                                 chunk->tsn_missing_report++;
1718
1719                                 SCTP_DEBUG_PRINTK(
1720                                         "%s: TSN 0x%x missing counter: %d\n",
1721                                         __func__, tsn,
1722                                         chunk->tsn_missing_report);
1723                         }
1724                 }
1725                 /*
1726                  * M4) If any DATA chunk is found to have a
1727                  * 'TSN.Missing.Report'
1728                  * value larger than or equal to 3, mark that chunk for
1729                  * retransmission and start the fast retransmit procedure.
1730                  */
1731
1732                 if (chunk->tsn_missing_report >= 3) {
1733                         chunk->fast_retransmit = SCTP_NEED_FRTX;
1734                         do_fast_retransmit = 1;
1735                 }
1736         }
1737
1738         if (transport) {
1739                 if (do_fast_retransmit)
1740                         sctp_retransmit(q, transport, SCTP_RTXR_FAST_RTX);
1741
1742                 SCTP_DEBUG_PRINTK("%s: transport: %p, cwnd: %d, "
1743                                   "ssthresh: %d, flight_size: %d, pba: %d\n",
1744                                   __func__, transport, transport->cwnd,
1745                                   transport->ssthresh, transport->flight_size,
1746                                   transport->partial_bytes_acked);
1747         }
1748 }
1749
1750 /* Is the given TSN acked by this packet?  */
1751 static int sctp_acked(struct sctp_sackhdr *sack, __u32 tsn)
1752 {
1753         int i;
1754         sctp_sack_variable_t *frags;
1755         __u16 gap;
1756         __u32 ctsn = ntohl(sack->cum_tsn_ack);
1757
1758         if (TSN_lte(tsn, ctsn))
1759                 goto pass;
1760
1761         /* 3.3.4 Selective Acknowledgement (SACK) (3):
1762          *
1763          * Gap Ack Blocks:
1764          *  These fields contain the Gap Ack Blocks. They are repeated
1765          *  for each Gap Ack Block up to the number of Gap Ack Blocks
1766          *  defined in the Number of Gap Ack Blocks field. All DATA
1767          *  chunks with TSNs greater than or equal to (Cumulative TSN
1768          *  Ack + Gap Ack Block Start) and less than or equal to
1769          *  (Cumulative TSN Ack + Gap Ack Block End) of each Gap Ack
1770          *  Block are assumed to have been received correctly.
1771          */
1772
1773         frags = sack->variable;
1774         gap = tsn - ctsn;
1775         for (i = 0; i < ntohs(sack->num_gap_ack_blocks); ++i) {
1776                 if (TSN_lte(ntohs(frags[i].gab.start), gap) &&
1777                     TSN_lte(gap, ntohs(frags[i].gab.end)))
1778                         goto pass;
1779         }
1780
1781         return 0;
1782 pass:
1783         return 1;
1784 }
1785
1786 static inline int sctp_get_skip_pos(struct sctp_fwdtsn_skip *skiplist,
1787                                     int nskips, __be16 stream)
1788 {
1789         int i;
1790
1791         for (i = 0; i < nskips; i++) {
1792                 if (skiplist[i].stream == stream)
1793                         return i;
1794         }
1795         return i;
1796 }
1797
1798 /* Create and add a fwdtsn chunk to the outq's control queue if needed. */
1799 static void sctp_generate_fwdtsn(struct sctp_outq *q, __u32 ctsn)
1800 {
1801         struct sctp_association *asoc = q->asoc;
1802         struct sctp_chunk *ftsn_chunk = NULL;
1803         struct sctp_fwdtsn_skip ftsn_skip_arr[10];
1804         int nskips = 0;
1805         int skip_pos = 0;
1806         __u32 tsn;
1807         struct sctp_chunk *chunk;
1808         struct list_head *lchunk, *temp;
1809
1810         if (!asoc->peer.prsctp_capable)
1811                 return;
1812
1813         /* PR-SCTP C1) Let SackCumAck be the Cumulative TSN ACK carried in the
1814          * received SACK.
1815          *
1816          * If (Advanced.Peer.Ack.Point < SackCumAck), then update
1817          * Advanced.Peer.Ack.Point to be equal to SackCumAck.
1818          */
1819         if (TSN_lt(asoc->adv_peer_ack_point, ctsn))
1820                 asoc->adv_peer_ack_point = ctsn;
1821
1822         /* PR-SCTP C2) Try to further advance the "Advanced.Peer.Ack.Point"
1823          * locally, that is, to move "Advanced.Peer.Ack.Point" up as long as
1824          * the chunk next in the out-queue space is marked as "abandoned" as
1825          * shown in the following example:
1826          *
1827          * Assuming that a SACK arrived with the Cumulative TSN ACK 102
1828          * and the Advanced.Peer.Ack.Point is updated to this value:
1829          *
1830          *   out-queue at the end of  ==>   out-queue after Adv.Ack.Point
1831          *   normal SACK processing           local advancement
1832          *                ...                           ...
1833          *   Adv.Ack.Pt-> 102 acked                     102 acked
1834          *                103 abandoned                 103 abandoned
1835          *                104 abandoned     Adv.Ack.P-> 104 abandoned
1836          *                105                           105
1837          *                106 acked                     106 acked
1838          *                ...                           ...
1839          *
1840          * In this example, the data sender successfully advanced the
1841          * "Advanced.Peer.Ack.Point" from 102 to 104 locally.
1842          */
1843         list_for_each_safe(lchunk, temp, &q->abandoned) {
1844                 chunk = list_entry(lchunk, struct sctp_chunk,
1845                                         transmitted_list);
1846                 tsn = ntohl(chunk->subh.data_hdr->tsn);
1847
1848                 /* Remove any chunks in the abandoned queue that are acked by
1849                  * the ctsn.
1850                  */
1851                 if (TSN_lte(tsn, ctsn)) {
1852                         list_del_init(lchunk);
1853                         sctp_chunk_free(chunk);
1854                 } else {
1855                         if (TSN_lte(tsn, asoc->adv_peer_ack_point+1)) {
1856                                 asoc->adv_peer_ack_point = tsn;
1857                                 if (chunk->chunk_hdr->flags &
1858                                          SCTP_DATA_UNORDERED)
1859                                         continue;
1860                                 skip_pos = sctp_get_skip_pos(&ftsn_skip_arr[0],
1861                                                 nskips,
1862                                                 chunk->subh.data_hdr->stream);
1863                                 ftsn_skip_arr[skip_pos].stream =
1864                                         chunk->subh.data_hdr->stream;
1865                                 ftsn_skip_arr[skip_pos].ssn =
1866                                          chunk->subh.data_hdr->ssn;
1867                                 if (skip_pos == nskips)
1868                                         nskips++;
1869                                 if (nskips == 10)
1870                                         break;
1871                         } else
1872                                 break;
1873                 }
1874         }
1875
1876         /* PR-SCTP C3) If, after step C1 and C2, the "Advanced.Peer.Ack.Point"
1877          * is greater than the Cumulative TSN ACK carried in the received
1878          * SACK, the data sender MUST send the data receiver a FORWARD TSN
1879          * chunk containing the latest value of the
1880          * "Advanced.Peer.Ack.Point".
1881          *
1882          * C4) For each "abandoned" TSN the sender of the FORWARD TSN SHOULD
1883          * list each stream and sequence number in the forwarded TSN. This
1884          * information will enable the receiver to easily find any
1885          * stranded TSN's waiting on stream reorder queues. Each stream
1886          * SHOULD only be reported once; this means that if multiple
1887          * abandoned messages occur in the same stream then only the
1888          * highest abandoned stream sequence number is reported. If the
1889          * total size of the FORWARD TSN does NOT fit in a single MTU then
1890          * the sender of the FORWARD TSN SHOULD lower the
1891          * Advanced.Peer.Ack.Point to the last TSN that will fit in a
1892          * single MTU.
1893          */
1894         if (asoc->adv_peer_ack_point > ctsn)
1895                 ftsn_chunk = sctp_make_fwdtsn(asoc, asoc->adv_peer_ack_point,
1896                                               nskips, &ftsn_skip_arr[0]);
1897
1898         if (ftsn_chunk) {
1899                 list_add_tail(&ftsn_chunk->list, &q->control_chunk_list);
1900                 SCTP_INC_STATS(SCTP_MIB_OUTCTRLCHUNKS);
1901         }
1902 }