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                         }
 416                         continue;
 417                 }
 418
 419                 /* If we are doing  retransmission due to a timeout or pmtu
 420                  * discovery, only the  chunks that are not yet acked should
 421                  * be added to the retransmit queue.
 422                  */
 423                 if ((reason == SCTP_RTXR_FAST_RTX  &&
 424                             (chunk->fast_retransmit == SCTP_NEED_FRTX)) ||
 425                     (reason != SCTP_RTXR_FAST_RTX  && !chunk->tsn_gap_acked)) {
 426                         /* RFC 2960 6.2.1 Processing a Received SACK
 427                          *
 428                          * C) Any time a DATA chunk is marked for
 429                          * retransmission (via either T3-rtx timer expiration
 430                          * (Section 6.3.3) or via fast retransmit
 431                          * (Section 7.2.4)), add the data size of those
 432                          * chunks to the rwnd.
 433                          */
 434                         q->asoc->peer.rwnd += sctp_data_size(chunk);
 435                         q->outstanding_bytes -= sctp_data_size(chunk);
 436                         if (chunk->transport)
 437                                 transport->flight_size -= sctp_data_size(chunk);
 438
 439                         /* sctpimpguide-05 Section 2.8.2
 440                          * M5) If a T3-rtx timer expires, the
 441                          * 'TSN.Missing.Report' of all affected TSNs is set
 442                          * to 0.
 443                          */
 444                         chunk->tsn_missing_report = 0;
 445
 446                         /* If a chunk that is being used for RTT measurement
 447                          * has to be retransmitted, we cannot use this chunk
 448                          * anymore for RTT measurements. Reset rto_pending so
 449                          * that a new RTT measurement is started when a new
 450                          * data chunk is sent.
 451                          */
 452                         if (chunk->rtt_in_progress) {
 453                                 chunk->rtt_in_progress = 0;
 454                                 transport->rto_pending = 0;
 455                         }
 456
 457                         /* Move the chunk to the retransmit queue. The chunks
 458                          * on the retransmit queue are always kept in order.
 459                          */
 460                         list_del_init(lchunk);
 461                         sctp_insert_list(&q->retransmit, lchunk);
 462                 }
 463         }
 464
 465         SCTP_DEBUG_PRINTK("%s: transport: %p, reason: %d, "
 466                           "cwnd: %d, ssthresh: %d, flight_size: %d, "
 467                           "pba: %d\n", __func__,
 468                           transport, reason,
 469                           transport->cwnd, transport->ssthresh,
 470                           transport->flight_size,
 471                           transport->partial_bytes_acked);
 472
 473 }
 474
 475 /* Mark all the eligible packets on a transport for retransmission and force
 476  * one packet out.
 477  */
 478 void sctp_retransmit(struct sctp_outq *q, struct sctp_transport *transport,
 479                      sctp_retransmit_reason_t reason)
 480 {
 481         int error = 0;
 482
 483         switch(reason) {
 484         case SCTP_RTXR_T3_RTX:
 485                 SCTP_INC_STATS(SCTP_MIB_T3_RETRANSMITS);
 486                 sctp_transport_lower_cwnd(transport, SCTP_LOWER_CWND_T3_RTX);
 487                 /* Update the retran path if the T3-rtx timer has expired for
 488                  * the current retran path.
 489                  */
 490                 if (transport == transport->asoc->peer.retran_path)
 491                         sctp_assoc_update_retran_path(transport->asoc);
 492                 transport->asoc->rtx_data_chunks +=
 493                         transport->asoc->unack_data;
 494                 break;
 495         case SCTP_RTXR_FAST_RTX:
 496                 SCTP_INC_STATS(SCTP_MIB_FAST_RETRANSMITS);
 497                 sctp_transport_lower_cwnd(transport, SCTP_LOWER_CWND_FAST_RTX);
 498                 q->fast_rtx = 1;
 499                 break;
 500         case SCTP_RTXR_PMTUD:
 501                 SCTP_INC_STATS(SCTP_MIB_PMTUD_RETRANSMITS);
 502                 break;
 503         case SCTP_RTXR_T1_RTX:
 504                 SCTP_INC_STATS(SCTP_MIB_T1_RETRANSMITS);
 505                 transport->asoc->init_retries++;
 506                 break;
 507         default:
 508                 BUG();
 509         }
 510
 511         sctp_retransmit_mark(q, transport, reason);
 512
 513         /* PR-SCTP A5) Any time the T3-rtx timer expires, on any destination,
 514          * the sender SHOULD try to advance the "Advanced.Peer.Ack.Point" by
 515          * following the procedures outlined in C1 - C5.
 516          */
 517         if (reason == SCTP_RTXR_T3_RTX)
 518                 sctp_generate_fwdtsn(q, q->asoc->ctsn_ack_point);
 519
 520         /* Flush the queues only on timeout, since fast_rtx is only
 521          * triggered during sack processing and the queue
 522          * will be flushed at the end.
 523          */
 524         if (reason != SCTP_RTXR_FAST_RTX)
 525                 error = sctp_outq_flush(q, /* rtx_timeout */ 1);
 526
 527         if (error)
 528                 q->asoc->base.sk->sk_err = -error;
 529 }
 530
 531 /*
 532  * Transmit DATA chunks on the retransmit queue.  Upon return from
 533  * sctp_outq_flush_rtx() the packet 'pkt' may contain chunks which
 534  * need to be transmitted by the caller.
 535  * We assume that pkt->transport has already been set.
 536  *
 537  * The return value is a normal kernel error return value.
 538  */
 539 static int sctp_outq_flush_rtx(struct sctp_outq *q, struct sctp_packet *pkt,
 540                                int rtx_timeout, int *start_timer)
 541 {
 542         struct list_head *lqueue;
 543         struct sctp_transport *transport = pkt->transport;
 544         sctp_xmit_t status;
 545         struct sctp_chunk *chunk, *chunk1;
 546         int fast_rtx;
 547         int error = 0;
 548         int timer = 0;
 549         int done = 0;
 550
 551         lqueue = &q->retransmit;
 552         fast_rtx = q->fast_rtx;
 553
 554         /* This loop handles time-out retransmissions, fast retransmissions,
 555          * and retransmissions due to opening of whindow.
 556          *
 557          * RFC 2960 6.3.3 Handle T3-rtx Expiration
 558          *
 559          * E3) Determine how many of the earliest (i.e., lowest TSN)
 560          * outstanding DATA chunks for the address for which the
 561          * T3-rtx has expired will fit into a single packet, subject
 562          * to the MTU constraint for the path corresponding to the
 563          * destination transport address to which the retransmission
 564          * is being sent (this may be different from the address for
 565          * which the timer expires [see Section 6.4]). Call this value
 566          * K. Bundle and retransmit those K DATA chunks in a single
 567          * packet to the destination endpoint.
 568          *
 569          * [Just to be painfully clear, if we are retransmitting
 570          * because a timeout just happened, we should send only ONE
 571          * packet of retransmitted data.]
 572          *
 573          * For fast retransmissions we also send only ONE packet.  However,
 574          * if we are just flushing the queue due to open window, we'll
 575          * try to send as much as possible.
 576          */
 577         list_for_each_entry_safe(chunk, chunk1, lqueue, transmitted_list) {
 578                 /* If the chunk is abandoned, move it to abandoned list. */
 579                 if (sctp_chunk_abandoned(chunk)) {
 580                         list_del_init(&chunk->transmitted_list);
 581                         sctp_insert_list(&q->abandoned,
 582                                          &chunk->transmitted_list);
 583                         continue;
 584                 }
 585
 586                 /* Make sure that Gap Acked TSNs are not retransmitted.  A
 587                  * simple approach is just to move such TSNs out of the
 588                  * way and into a 'transmitted' queue and skip to the
 589                  * next chunk.
 590                  */
 591                 if (chunk->tsn_gap_acked) {
 592                         list_del(&chunk->transmitted_list);
 593                         list_add_tail(&chunk->transmitted_list,
 594                                         &transport->transmitted);
 595                         continue;
 596                 }
 597
 598                 /* If we are doing fast retransmit, ignore non-fast_rtransmit
 599                  * chunks
 600                  */
 601                 if (fast_rtx && !chunk->fast_retransmit)
 602                         continue;
 603
 604 redo:
 605                 /* Attempt to append this chunk to the packet. */
 606                 status = sctp_packet_append_chunk(pkt, chunk);
 607
 608                 switch (status) {
 609                 case SCTP_XMIT_PMTU_FULL:
 610                         if (!pkt->has_data && !pkt->has_cookie_echo) {
 611                                 /* If this packet did not contain DATA then
 612                                  * retransmission did not happen, so do it
 613                                  * again.  We'll ignore the error here since
 614                                  * control chunks are already freed so there
 615                                  * is nothing we can do.
 616                                  */
 617                                 sctp_packet_transmit(pkt);
 618                                 goto redo;
 619                         }
 620
 621                         /* Send this packet.  */
 622                         error = sctp_packet_transmit(pkt);
 623
 624                         /* If we are retransmitting, we should only
 625                          * send a single packet.
 626                          * Otherwise, try appending this chunk again.
 627                          */
 628                         if (rtx_timeout || fast_rtx)
 629                                 done = 1;
 630                         else
 631                                 goto redo;
 632
 633                         /* Bundle next chunk in the next round.  */
 634                         break;
 635
 636                 case SCTP_XMIT_RWND_FULL:
 637                         /* Send this packet. */
 638                         error = sctp_packet_transmit(pkt);
 639
 640                         /* Stop sending DATA as there is no more room
 641                          * at the receiver.
 642                          */
 643                         done = 1;
 644                         break;
 645
 646                 case SCTP_XMIT_NAGLE_DELAY:
 647                         /* Send this packet. */
 648                         error = sctp_packet_transmit(pkt);
 649
 650                         /* Stop sending DATA because of nagle delay. */
 651                         done = 1;
 652                         break;
 653
 654                 default:
 655                         /* The append was successful, so add this chunk to
 656                          * the transmitted list.
 657                          */
 658                         list_del(&chunk->transmitted_list);
 659                         list_add_tail(&chunk->transmitted_list,
 660                                         &transport->transmitted);
 661
 662                         /* Mark the chunk as ineligible for fast retransmit
 663                          * after it is retransmitted.
 664                          */
 665                         if (chunk->fast_retransmit == SCTP_NEED_FRTX)
 666                                 chunk->fast_retransmit = SCTP_DONT_FRTX;
 667
 668                         q->empty = 0;
 669                         break;
 670                 }
 671
 672                 /* Set the timer if there were no errors */
 673                 if (!error && !timer)
 674                         timer = 1;
 675
 676                 if (done)
 677                         break;
 678         }
 679
 680         /* If we are here due to a retransmit timeout or a fast
 681          * retransmit and if there are any chunks left in the retransmit
 682          * queue that could not fit in the PMTU sized packet, they need
 683          * to be marked as ineligible for a subsequent fast retransmit.
 684          */
 685         if (rtx_timeout || fast_rtx) {
 686                 list_for_each_entry(chunk1, lqueue, transmitted_list) {
 687                         if (chunk1->fast_retransmit == SCTP_NEED_FRTX)
 688                                 chunk1->fast_retransmit = SCTP_DONT_FRTX;
 689                 }
 690         }
 691
 692         *start_timer = timer;
 693
 694         /* Clear fast retransmit hint */
 695         if (fast_rtx)
 696                 q->fast_rtx = 0;
 697
 698         return error;
 699 }
 700
 701 /* Cork the outqueue so queued chunks are really queued. */
 702 int sctp_outq_uncork(struct sctp_outq *q)
 703 {
 704         int error = 0;
 705         if (q->cork)
 706                 q->cork = 0;
 707         error = sctp_outq_flush(q, 0);
 708         return error;
 709 }
 710
 711
 712 /*
 713  * Try to flush an outqueue.
 714  *
 715  * Description: Send everything in q which we legally can, subject to
 716  * congestion limitations.
 717  * * Note: This function can be called from multiple contexts so appropriate
 718  * locking concerns must be made.  Today we use the sock lock to protect
 719  * this function.
 720  */
 721 static int sctp_outq_flush(struct sctp_outq *q, int rtx_timeout)
 722 {
 723         struct sctp_packet *packet;
 724         struct sctp_packet singleton;
 725         struct sctp_association *asoc = q->asoc;
 726         __u16 sport = asoc->base.bind_addr.port;
 727         __u16 dport = asoc->peer.port;
 728         __u32 vtag = asoc->peer.i.init_tag;
 729         struct sctp_transport *transport = NULL;
 730         struct sctp_transport *new_transport;
 731         struct sctp_chunk *chunk, *tmp;
 732         sctp_xmit_t status;
 733         int error = 0;
 734         int start_timer = 0;
 735         int one_packet = 0;
 736
 737         /* These transports have chunks to send. */
 738         struct list_head transport_list;
 739         struct list_head *ltransport;
 740
 741         INIT_LIST_HEAD(&transport_list);
 742         packet = NULL;
 743
 744         /*
 745          * 6.10 Bundling
 746          *   ...
 747          *   When bundling control chunks with DATA chunks, an
 748          *   endpoint MUST place control chunks first in the outbound
 749          *   SCTP packet.  The transmitter MUST transmit DATA chunks
 750          *   within a SCTP packet in increasing order of TSN.
 751          *   ...
 752          */
 753
 754         list_for_each_entry_safe(chunk, tmp, &q->control_chunk_list, list) {
 755                 list_del_init(&chunk->list);
 756
 757                 /* Pick the right transport to use. */
 758                 new_transport = chunk->transport;
 759
 760                 if (!new_transport) {
 761                         /*
 762                          * If we have a prior transport pointer, see if
 763                          * the destination address of the chunk
 764                          * matches the destination address of the
 765                          * current transport.  If not a match, then
 766                          * try to look up the transport with a given
 767                          * destination address.  We do this because
 768                          * after processing ASCONFs, we may have new
 769                          * transports created.
 770                          */
 771                         if (transport &&
 772                             sctp_cmp_addr_exact(&chunk->dest,
 773                                                 &transport->ipaddr))
 774                                         new_transport = transport;
 775                         else
 776                                 new_transport = sctp_assoc_lookup_paddr(asoc,
 777                                                                 &chunk->dest);
 778
 779                         /* if we still don't have a new transport, then
 780                          * use the current active path.
 781                          */
 782                         if (!new_transport)
 783                                 new_transport = asoc->peer.active_path;
 784                 } else if ((new_transport->state == SCTP_INACTIVE) ||
 785                            (new_transport->state == SCTP_UNCONFIRMED)) {
 786                         /* If the chunk is Heartbeat or Heartbeat Ack,
 787                          * send it to chunk->transport, even if it's
 788                          * inactive.
 789                          *
 790                          * 3.3.6 Heartbeat Acknowledgement:
 791                          * ...
 792                          * A HEARTBEAT ACK is always sent to the source IP
 793                          * address of the IP datagram containing the
 794                          * HEARTBEAT chunk to which this ack is responding.
 795                          * ...
 796                          *
 797                          * ASCONF_ACKs also must be sent to the source.
 798                          */
 799                         if (chunk->chunk_hdr->type != SCTP_CID_HEARTBEAT &&
 800                             chunk->chunk_hdr->type != SCTP_CID_HEARTBEAT_ACK &&
 801                             chunk->chunk_hdr->type != SCTP_CID_ASCONF_ACK)
 802                                 new_transport = asoc->peer.active_path;
 803                 }
 804
 805                 /* Are we switching transports?
 806                  * Take care of transport locks.
 807                  */
 808                 if (new_transport != transport) {
 809                         transport = new_transport;
 810                         if (list_empty(&transport->send_ready)) {
 811                                 list_add_tail(&transport->send_ready,
 812                                               &transport_list);
 813                         }
 814                         packet = &transport->packet;
 815                         sctp_packet_config(packet, vtag,
 816                                            asoc->peer.ecn_capable);
 817                 }
 818
 819                 switch (chunk->chunk_hdr->type) {
 820                 /*
 821                  * 6.10 Bundling
 822                  *   ...
 823                  *   An endpoint MUST NOT bundle INIT, INIT ACK or SHUTDOWN
 824                  *   COMPLETE with any other chunks.  [Send them immediately.]
 825                  */
 826                 case SCTP_CID_INIT:
 827                 case SCTP_CID_INIT_ACK:
 828                 case SCTP_CID_SHUTDOWN_COMPLETE:
 829                         sctp_packet_init(&singleton, transport, sport, dport);
 830                         sctp_packet_config(&singleton, vtag, 0);
 831                         sctp_packet_append_chunk(&singleton, chunk);
 832                         error = sctp_packet_transmit(&singleton);
 833                         if (error < 0)
 834                                 return error;
 835                         break;
 836
 837                 case SCTP_CID_ABORT:
 838                         if (sctp_test_T_bit(chunk)) {
 839                                 packet->vtag = asoc->c.my_vtag;
 840                         }
 841                 /* The following chunks are "response" chunks, i.e.
 842                  * they are generated in response to something we
 843                  * received.  If we are sending these, then we can
 844                  * send only 1 packet containing these chunks.
 845                  */
 846                 case SCTP_CID_HEARTBEAT_ACK:
 847                 case SCTP_CID_SHUTDOWN_ACK:
 848                 case SCTP_CID_COOKIE_ACK:
 849                 case SCTP_CID_COOKIE_ECHO:
 850                 case SCTP_CID_ERROR:
 851                 case SCTP_CID_ECN_CWR:
 852                 case SCTP_CID_ASCONF_ACK:
 853                         one_packet = 1;
 854                         /* Fall through */
 855
 856                 case SCTP_CID_SACK:
 857                 case SCTP_CID_HEARTBEAT:
 858                 case SCTP_CID_SHUTDOWN:
 859                 case SCTP_CID_ECN_ECNE:
 860                 case SCTP_CID_ASCONF:
 861                 case SCTP_CID_FWD_TSN:
 862                         status = sctp_packet_transmit_chunk(packet, chunk,
 863                                                             one_packet);
 864                         if (status  != SCTP_XMIT_OK) {
 865                                 /* put the chunk back */
 866                                 list_add(&chunk->list, &q->control_chunk_list);
 867                         } else if (chunk->chunk_hdr->type == SCTP_CID_FWD_TSN) {
 868                                 /* PR-SCTP C5) If a FORWARD TSN is sent, the
 869                                  * sender MUST assure that at least one T3-rtx
 870                                  * timer is running.
 871                                  */
 872                                 sctp_transport_reset_timers(transport);
 873                         }
 874                         break;
 875
 876                 default:
 877                         /* We built a chunk with an illegal type! */
 878                         BUG();
 879                 }
 880         }
 881
 882         /* Is it OK to send data chunks?  */
 883         switch (asoc->state) {
 884         case SCTP_STATE_COOKIE_ECHOED:
 885                 /* Only allow bundling when this packet has a COOKIE-ECHO
 886                  * chunk.
 887                  */
 888                 if (!packet || !packet->has_cookie_echo)
 889                         break;
 890
 891                 /* fallthru */
 892         case SCTP_STATE_ESTABLISHED:
 893         case SCTP_STATE_SHUTDOWN_PENDING:
 894         case SCTP_STATE_SHUTDOWN_RECEIVED:
 895                 /*
 896                  * RFC 2960 6.1  Transmission of DATA Chunks
 897                  *
 898                  * C) When the time comes for the sender to transmit,
 899                  * before sending new DATA chunks, the sender MUST
 900                  * first transmit any outstanding DATA chunks which
 901                  * are marked for retransmission (limited by the
 902                  * current cwnd).
 903                  */
 904                 if (!list_empty(&q->retransmit)) {
 905                         if (transport == asoc->peer.retran_path)
 906                                 goto retran;
 907
 908                         /* Switch transports & prepare the packet.  */
 909
 910                         transport = asoc->peer.retran_path;
 911
 912                         if (list_empty(&transport->send_ready)) {
 913                                 list_add_tail(&transport->send_ready,
 914                                               &transport_list);
 915                         }
 916
 917                         packet = &transport->packet;
 918                         sctp_packet_config(packet, vtag,
 919                                            asoc->peer.ecn_capable);
 920                 retran:
 921                         error = sctp_outq_flush_rtx(q, packet,
 922                                                     rtx_timeout, &start_timer);
 923
 924                         if (start_timer)
 925                                 sctp_transport_reset_timers(transport);
 926
 927                         /* This can happen on COOKIE-ECHO resend.  Only
 928                          * one chunk can get bundled with a COOKIE-ECHO.
 929                          */
 930                         if (packet->has_cookie_echo)
 931                                 goto sctp_flush_out;
 932
 933                         /* Don't send new data if there is still data
 934                          * waiting to retransmit.
 935                          */
 936                         if (!list_empty(&q->retransmit))
 937                                 goto sctp_flush_out;
 938                 }
 939
 940                 /* Apply Max.Burst limitation to the current transport in
 941                  * case it will be used for new data.  We are going to
 942                  * rest it before we return, but we want to apply the limit
 943                  * to the currently queued data.
 944                  */
 945                 if (transport)
 946                         sctp_transport_burst_limited(transport);
 947
 948                 /* Finally, transmit new packets.  */
 949                 while ((chunk = sctp_outq_dequeue_data(q)) != NULL) {
 950                         /* RFC 2960 6.5 Every DATA chunk MUST carry a valid
 951                          * stream identifier.
 952                          */
 953                         if (chunk->sinfo.sinfo_stream >=
 954                             asoc->c.sinit_num_ostreams) {
 955
 956                                 /* Mark as failed send. */
 957                                 sctp_chunk_fail(chunk, SCTP_ERROR_INV_STRM);
 958                                 sctp_chunk_free(chunk);
 959                                 continue;
 960                         }
 961
 962                         /* Has this chunk expired? */
 963                         if (sctp_chunk_abandoned(chunk)) {
 964                                 sctp_chunk_fail(chunk, 0);
 965                                 sctp_chunk_free(chunk);
 966                                 continue;
 967                         }
 968
 969                         /* If there is a specified transport, use it.
 970                          * Otherwise, we want to use the active path.
 971                          */
 972                         new_transport = chunk->transport;
 973                         if (!new_transport ||
 974                             ((new_transport->state == SCTP_INACTIVE) ||
 975                              (new_transport->state == SCTP_UNCONFIRMED)))
 976                                 new_transport = asoc->peer.active_path;
 977
 978                         /* Change packets if necessary.  */
 979                         if (new_transport != transport) {
 980                                 transport = new_transport;
 981
 982                                 /* Schedule to have this transport's
 983                                  * packet flushed.
 984                                  */
 985                                 if (list_empty(&transport->send_ready)) {
 986                                         list_add_tail(&transport->send_ready,
 987                                                       &transport_list);
 988                                 }
 989
 990                                 packet = &transport->packet;
 991                                 sctp_packet_config(packet, vtag,
 992                                                    asoc->peer.ecn_capable);
 993                                 /* We've switched transports, so apply the
 994                                  * Burst limit to the new transport.
 995                                  */
 996                                 sctp_transport_burst_limited(transport);
 997                         }
 998
 999                         SCTP_DEBUG_PRINTK("sctp_outq_flush(%p, %p[%s]), ",
1000                                           q, chunk,
1001                                           chunk && chunk->chunk_hdr ?
1002                                           sctp_cname(SCTP_ST_CHUNK(
1003                                                   chunk->chunk_hdr->type))
1004                                           : "Illegal Chunk");
1005
1006                         SCTP_DEBUG_PRINTK("TX TSN 0x%x skb->head "
1007                                         "%p skb->users %d.\n",
1008                                         ntohl(chunk->subh.data_hdr->tsn),
1009                                         chunk->skb ?chunk->skb->head : NULL,
1010                                         chunk->skb ?
1011                                         atomic_read(&chunk->skb->users) : -1);
1012
1013                         /* Add the chunk to the packet.  */
1014                         status = sctp_packet_transmit_chunk(packet, chunk, 0);
1015
1016                         switch (status) {
1017                         case SCTP_XMIT_PMTU_FULL:
1018                         case SCTP_XMIT_RWND_FULL:
1019                         case SCTP_XMIT_NAGLE_DELAY:
1020                                 /* We could not append this chunk, so put
1021                                  * the chunk back on the output queue.
1022                                  */
1023                                 SCTP_DEBUG_PRINTK("sctp_outq_flush: could "
1024                                         "not transmit TSN: 0x%x, status: %d\n",
1025                                         ntohl(chunk->subh.data_hdr->tsn),
1026                                         status);
1027                                 sctp_outq_head_data(q, chunk);
1028                                 goto sctp_flush_out;
1029                                 break;
1030
1031                         case SCTP_XMIT_OK:
1032                                 /* The sender is in the SHUTDOWN-PENDING state,
1033                                  * The sender MAY set the I-bit in the DATA
1034                                  * chunk header.
1035                                  */
1036                                 if (asoc->state == SCTP_STATE_SHUTDOWN_PENDING)
1037                                         chunk->chunk_hdr->flags |= SCTP_DATA_SACK_IMM;
1038
1039                                 break;
1040
1041                         default:
1042                                 BUG();
1043                         }
1044
1045                         /* BUG: We assume that the sctp_packet_transmit()
1046                          * call below will succeed all the time and add the
1047                          * chunk to the transmitted list and restart the
1048                          * timers.
1049                          * It is possible that the call can fail under OOM
1050                          * conditions.
1051                          *
1052                          * Is this really a problem?  Won't this behave
1053                          * like a lost TSN?
1054                          */
1055                         list_add_tail(&chunk->transmitted_list,
1056                                       &transport->transmitted);
1057
1058                         sctp_transport_reset_timers(transport);
1059
1060                         q->empty = 0;
1061
1062                         /* Only let one DATA chunk get bundled with a
1063                          * COOKIE-ECHO chunk.
1064                          */
1065                         if (packet->has_cookie_echo)
1066                                 goto sctp_flush_out;
1067                 }
1068                 break;
1069
1070         default:
1071                 /* Do nothing.  */
1072                 break;
1073         }
1074
1075 sctp_flush_out:
1076
1077         /* Before returning, examine all the transports touched in
1078          * this call.  Right now, we bluntly force clear all the
1079          * transports.  Things might change after we implement Nagle.
1080          * But such an examination is still required.
1081          *
1082          * --xguo
1083          */
1084         while ((ltransport = sctp_list_dequeue(&transport_list)) != NULL ) {
1085                 struct sctp_transport *t = list_entry(ltransport,
1086                                                       struct sctp_transport,
1087                                                       send_ready);
1088                 packet = &t->packet;
1089                 if (!sctp_packet_empty(packet))
1090                         error = sctp_packet_transmit(packet);
1091
1092                 /* Clear the burst limited state, if any */
1093                 sctp_transport_burst_reset(t);
1094         }
1095
1096         return error;
1097 }
1098
1099 /* Update unack_data based on the incoming SACK chunk */
1100 static void sctp_sack_update_unack_data(struct sctp_association *assoc,
1101                                         struct sctp_sackhdr *sack)
1102 {
1103         sctp_sack_variable_t *frags;
1104         __u16 unack_data;
1105         int i;
1106
1107         unack_data = assoc->next_tsn - assoc->ctsn_ack_point - 1;
1108
1109         frags = sack->variable;
1110         for (i = 0; i < ntohs(sack->num_gap_ack_blocks); i++) {
1111                 unack_data -= ((ntohs(frags[i].gab.end) -
1112                                 ntohs(frags[i].gab.start) + 1));
1113         }
1114
1115         assoc->unack_data = unack_data;
1116 }
1117
1118 /* This is where we REALLY process a SACK.
1119  *
1120  * Process the SACK against the outqueue.  Mostly, this just frees
1121  * things off the transmitted queue.
1122  */
1123 int sctp_outq_sack(struct sctp_outq *q, struct sctp_sackhdr *sack)
1124 {
1125         struct sctp_association *asoc = q->asoc;
1126         struct sctp_transport *transport;
1127         struct sctp_chunk *tchunk = NULL;
1128         struct list_head *lchunk, *transport_list, *temp;
1129         sctp_sack_variable_t *frags = sack->variable;
1130         __u32 sack_ctsn, ctsn, tsn;
1131         __u32 highest_tsn, highest_new_tsn;
1132         __u32 sack_a_rwnd;
1133         unsigned outstanding;
1134         struct sctp_transport *primary = asoc->peer.primary_path;
1135         int count_of_newacks = 0;
1136         int gap_ack_blocks;
1137         u8 accum_moved = 0;
1138
1139         /* Grab the association's destination address list. */
1140         transport_list = &asoc->peer.transport_addr_list;
1141
1142         sack_ctsn = ntohl(sack->cum_tsn_ack);
1143         gap_ack_blocks = ntohs(sack->num_gap_ack_blocks);
1144         /*
1145          * SFR-CACC algorithm:
1146          * On receipt of a SACK the sender SHOULD execute the
1147          * following statements.
1148          *
1149          * 1) If the cumulative ack in the SACK passes next tsn_at_change
1150          * on the current primary, the CHANGEOVER_ACTIVE flag SHOULD be
1151          * cleared. The CYCLING_CHANGEOVER flag SHOULD also be cleared for
1152          * all destinations.
1153          * 2) If the SACK contains gap acks and the flag CHANGEOVER_ACTIVE
1154          * is set the receiver of the SACK MUST take the following actions:
1155          *
1156          * A) Initialize the cacc_saw_newack to 0 for all destination
1157          * addresses.
1158          *
1159          * Only bother if changeover_active is set. Otherwise, this is
1160          * totally suboptimal to do on every SACK.
1161          */
1162         if (primary->cacc.changeover_active) {
1163                 u8 clear_cycling = 0;
1164
1165                 if (TSN_lte(primary->cacc.next_tsn_at_change, sack_ctsn)) {
1166                         primary->cacc.changeover_active = 0;
1167                         clear_cycling = 1;
1168                 }
1169
1170                 if (clear_cycling || gap_ack_blocks) {
1171                         list_for_each_entry(transport, transport_list,
1172                                         transports) {
1173                                 if (clear_cycling)
1174                                         transport->cacc.cycling_changeover = 0;
1175                                 if (gap_ack_blocks)
1176                                         transport->cacc.cacc_saw_newack = 0;
1177                         }
1178                 }
1179         }
1180
1181         /* Get the highest TSN in the sack. */
1182         highest_tsn = sack_ctsn;
1183         if (gap_ack_blocks)
1184                 highest_tsn += ntohs(frags[gap_ack_blocks - 1].gab.end);
1185
1186         if (TSN_lt(asoc->highest_sacked, highest_tsn))
1187                 asoc->highest_sacked = highest_tsn;
1188
1189         highest_new_tsn = sack_ctsn;
1190
1191         /* Run through the retransmit queue.  Credit bytes received
1192          * and free those chunks that we can.
1193          */
1194         sctp_check_transmitted(q, &q->retransmit, NULL, sack, &highest_new_tsn);
1195
1196         /* Run through the transmitted queue.
1197          * Credit bytes received and free those chunks which we can.
1198          *
1199          * This is a MASSIVE candidate for optimization.
1200          */
1201         list_for_each_entry(transport, transport_list, transports) {
1202                 sctp_check_transmitted(q, &transport->transmitted,
1203                                        transport, sack, &highest_new_tsn);
1204                 /*
1205                  * SFR-CACC algorithm:
1206                  * C) Let count_of_newacks be the number of
1207                  * destinations for which cacc_saw_newack is set.
1208                  */
1209                 if (transport->cacc.cacc_saw_newack)
1210                         count_of_newacks ++;
1211         }
1212
1213         /* Move the Cumulative TSN Ack Point if appropriate.  */
1214         if (TSN_lt(asoc->ctsn_ack_point, sack_ctsn)) {
1215                 asoc->ctsn_ack_point = sack_ctsn;
1216                 accum_moved = 1;
1217         }
1218
1219         if (gap_ack_blocks) {
1220
1221                 if (asoc->fast_recovery && accum_moved)
1222                         highest_new_tsn = highest_tsn;
1223
1224                 list_for_each_entry(transport, transport_list, transports)
1225                         sctp_mark_missing(q, &transport->transmitted, transport,
1226                                           highest_new_tsn, count_of_newacks);
1227         }
1228
1229         /* Update unack_data field in the assoc. */
1230         sctp_sack_update_unack_data(asoc, sack);
1231
1232         ctsn = asoc->ctsn_ack_point;
1233
1234         /* Throw away stuff rotting on the sack queue.  */
1235         list_for_each_safe(lchunk, temp, &q->sacked) {
1236                 tchunk = list_entry(lchunk, struct sctp_chunk,
1237                                     transmitted_list);
1238                 tsn = ntohl(tchunk->subh.data_hdr->tsn);
1239                 if (TSN_lte(tsn, ctsn)) {
1240                         list_del_init(&tchunk->transmitted_list);
1241                         sctp_chunk_free(tchunk);
1242                 }
1243         }
1244
1245         /* ii) Set rwnd equal to the newly received a_rwnd minus the
1246          *     number of bytes still outstanding after processing the
1247          *     Cumulative TSN Ack and the Gap Ack Blocks.
1248          */
1249
1250         sack_a_rwnd = ntohl(sack->a_rwnd);
1251         outstanding = q->outstanding_bytes;
1252
1253         if (outstanding < sack_a_rwnd)
1254                 sack_a_rwnd -= outstanding;
1255         else
1256                 sack_a_rwnd = 0;
1257
1258         asoc->peer.rwnd = sack_a_rwnd;
1259
1260         sctp_generate_fwdtsn(q, sack_ctsn);
1261
1262         SCTP_DEBUG_PRINTK("%s: sack Cumulative TSN Ack is 0x%x.\n",
1263                           __func__, sack_ctsn);
1264         SCTP_DEBUG_PRINTK("%s: Cumulative TSN Ack of association, "
1265                           "%p is 0x%x. Adv peer ack point: 0x%x\n",
1266                           __func__, asoc, ctsn, asoc->adv_peer_ack_point);
1267
1268         /* See if all chunks are acked.
1269          * Make sure the empty queue handler will get run later.
1270          */
1271         q->empty = (list_empty(&q->out_chunk_list) &&
1272                     list_empty(&q->retransmit));
1273         if (!q->empty)
1274                 goto finish;
1275
1276         list_for_each_entry(transport, transport_list, transports) {
1277                 q->empty = q->empty && list_empty(&transport->transmitted);
1278                 if (!q->empty)
1279                         goto finish;
1280         }
1281
1282         SCTP_DEBUG_PRINTK("sack queue is empty.\n");
1283 finish:
1284         return q->empty;
1285 }
1286
1287 /* Is the outqueue empty?  */
1288 int sctp_outq_is_empty(const struct sctp_outq *q)
1289 {
1290         return q->empty;
1291 }
1292
1293 /********************************************************************
1294  * 2nd Level Abstractions
1295  ********************************************************************/
1296
1297 /* Go through a transport's transmitted list or the association's retransmit
1298  * list and move chunks that are acked by the Cumulative TSN Ack to q->sacked.
1299  * The retransmit list will not have an associated transport.
1300  *
1301  * I added coherent debug information output.   --xguo
1302  *
1303  * Instead of printing 'sacked' or 'kept' for each TSN on the
1304  * transmitted_queue, we print a range: SACKED: TSN1-TSN2, TSN3, TSN4-TSN5.
1305  * KEPT TSN6-TSN7, etc.
1306  */
1307 static void sctp_check_transmitted(struct sctp_outq *q,
1308                                    struct list_head *transmitted_queue,
1309                                    struct sctp_transport *transport,
1310                                    struct sctp_sackhdr *sack,
1311                                    __u32 *highest_new_tsn_in_sack)
1312 {
1313         struct list_head *lchunk;
1314         struct sctp_chunk *tchunk;
1315         struct list_head tlist;
1316         __u32 tsn;
1317         __u32 sack_ctsn;
1318         __u32 rtt;
1319         __u8 restart_timer = 0;
1320         int bytes_acked = 0;
1321         int migrate_bytes = 0;
1322
1323         /* These state variables are for coherent debug output. --xguo */
1324
1325 #if SCTP_DEBUG
1326         __u32 dbg_ack_tsn = 0;  /* An ACKed TSN range starts here... */
1327         __u32 dbg_last_ack_tsn = 0;  /* ...and finishes here.        */
1328         __u32 dbg_kept_tsn = 0; /* An un-ACKed range starts here...  */
1329         __u32 dbg_last_kept_tsn = 0; /* ...and finishes here.        */
1330
1331         /* 0 : The last TSN was ACKed.
1332          * 1 : The last TSN was NOT ACKed (i.e. KEPT).
1333          * -1: We need to initialize.
1334          */
1335         int dbg_prt_state = -1;
1336 #endif /* SCTP_DEBUG */
1337
1338         sack_ctsn = ntohl(sack->cum_tsn_ack);
1339
1340         INIT_LIST_HEAD(&tlist);
1341
1342         /* The while loop will skip empty transmitted queues. */
1343         while (NULL != (lchunk = sctp_list_dequeue(transmitted_queue))) {
1344                 tchunk = list_entry(lchunk, struct sctp_chunk,
1345                                     transmitted_list);
1346
1347                 if (sctp_chunk_abandoned(tchunk)) {
1348                         /* Move the chunk to abandoned list. */
1349                         sctp_insert_list(&q->abandoned, lchunk);
1350
1351                         /* If this chunk has not been acked, stop
1352                          * considering it as 'outstanding'.
1353                          */
1354                         if (!tchunk->tsn_gap_acked) {
1355                                 if (tchunk->transport)
1356                                         tchunk->transport->flight_size -=
1357                                                         sctp_data_size(tchunk);
1358                                 q->outstanding_bytes -= sctp_data_size(tchunk);
1359                         }
1360                         continue;
1361                 }
1362
1363                 tsn = ntohl(tchunk->subh.data_hdr->tsn);
1364                 if (sctp_acked(sack, tsn)) {
1365                         /* If this queue is the retransmit queue, the
1366                          * retransmit timer has already reclaimed
1367                          * the outstanding bytes for this chunk, so only
1368                          * count bytes associated with a transport.
1369                          */
1370                         if (transport) {
1371                                 /* If this chunk is being used for RTT
1372                                  * measurement, calculate the RTT and update
1373                                  * the RTO using this value.
1374                                  *
1375                                  * 6.3.1 C5) Karn's algorithm: RTT measurements
1376                                  * MUST NOT be made using packets that were
1377                                  * retransmitted (and thus for which it is
1378                                  * ambiguous whether the reply was for the
1379                                  * first instance of the packet or a later
1380                                  * instance).
1381                                  */
1382                                 if (!tchunk->tsn_gap_acked &&
1383                                     tchunk->rtt_in_progress) {
1384                                         tchunk->rtt_in_progress = 0;
1385                                         rtt = jiffies - tchunk->sent_at;
1386                                         sctp_transport_update_rto(transport,
1387                                                                   rtt);
1388                                 }
1389                         }
1390
1391                         /* If the chunk hasn't been marked as ACKED,
1392                          * mark it and account bytes_acked if the
1393                          * chunk had a valid transport (it will not
1394                          * have a transport if ASCONF had deleted it
1395                          * while DATA was outstanding).
1396                          */
1397                         if (!tchunk->tsn_gap_acked) {
1398                                 tchunk->tsn_gap_acked = 1;
1399                                 *highest_new_tsn_in_sack = tsn;
1400                                 bytes_acked += sctp_data_size(tchunk);
1401                                 if (!tchunk->transport)
1402                                         migrate_bytes += sctp_data_size(tchunk);
1403                         }
1404
1405                         if (TSN_lte(tsn, sack_ctsn)) {
1406                                 /* RFC 2960  6.3.2 Retransmission Timer Rules
1407                                  *
1408                                  * R3) Whenever a SACK is received
1409                                  * that acknowledges the DATA chunk
1410                                  * with the earliest outstanding TSN
1411                                  * for that address, restart T3-rtx
1412                                  * timer for that address with its
1413                                  * current RTO.
1414                                  */
1415                                 restart_timer = 1;
1416
1417                                 if (!tchunk->tsn_gap_acked) {
1418                                         /*
1419                                          * SFR-CACC algorithm:
1420                                          * 2) If the SACK contains gap acks
1421                                          * and the flag CHANGEOVER_ACTIVE is
1422                                          * set the receiver of the SACK MUST
1423                                          * take the following action:
1424                                          *
1425                                          * B) For each TSN t being acked that
1426                                          * has not been acked in any SACK so
1427                                          * far, set cacc_saw_newack to 1 for
1428                                          * the destination that the TSN was
1429                                          * sent to.
1430                                          */
1431                                         if (transport &&
1432                                             sack->num_gap_ack_blocks &&
1433                                             q->asoc->peer.primary_path->cacc.
1434                                             changeover_active)
1435                                                 transport->cacc.cacc_saw_newack
1436                                                         = 1;
1437                                 }
1438
1439                                 list_add_tail(&tchunk->transmitted_list,
1440                                               &q->sacked);
1441                         } else {
1442                                 /* RFC2960 7.2.4, sctpimpguide-05 2.8.2
1443                                  * M2) Each time a SACK arrives reporting
1444                                  * 'Stray DATA chunk(s)' record the highest TSN
1445                                  * reported as newly acknowledged, call this
1446                                  * value 'HighestTSNinSack'. A newly
1447                                  * acknowledged DATA chunk is one not
1448                                  * previously acknowledged in a SACK.
1449                                  *
1450                                  * When the SCTP sender of data receives a SACK
1451                                  * chunk that acknowledges, for the first time,
1452                                  * the receipt of a DATA chunk, all the still
1453                                  * unacknowledged DATA chunks whose TSN is
1454                                  * older than that newly acknowledged DATA
1455                                  * chunk, are qualified as 'Stray DATA chunks'.
1456                                  */
1457                                 list_add_tail(lchunk, &tlist);
1458                         }
1459
1460 #if SCTP_DEBUG
1461                         switch (dbg_prt_state) {
1462                         case 0: /* last TSN was ACKed */
1463                                 if (dbg_last_ack_tsn + 1 == tsn) {
1464                                         /* This TSN belongs to the
1465                                          * current ACK range.
1466                                          */
1467                                         break;
1468                                 }
1469
1470                                 if (dbg_last_ack_tsn != dbg_ack_tsn) {
1471                                         /* Display the end of the
1472                                          * current range.
1473                                          */
1474                                         SCTP_DEBUG_PRINTK_CONT("-%08x",
1475                                                                dbg_last_ack_tsn);
1476                                 }
1477
1478                                 /* Start a new range.  */
1479                                 SCTP_DEBUG_PRINTK_CONT(",%08x", tsn);
1480                                 dbg_ack_tsn = tsn;
1481                                 break;
1482
1483                         case 1: /* The last TSN was NOT ACKed. */
1484                                 if (dbg_last_kept_tsn != dbg_kept_tsn) {
1485                                         /* Display the end of current range. */
1486                                         SCTP_DEBUG_PRINTK_CONT("-%08x",
1487                                                                dbg_last_kept_tsn);
1488                                 }
1489
1490                                 SCTP_DEBUG_PRINTK_CONT("\n");
1491
1492                                 /* FALL THROUGH... */
1493                         default:
1494                                 /* This is the first-ever TSN we examined.  */
1495                                 /* Start a new range of ACK-ed TSNs.  */
1496                                 SCTP_DEBUG_PRINTK("ACKed: %08x", tsn);
1497                                 dbg_prt_state = 0;
1498                                 dbg_ack_tsn = tsn;
1499                         }
1500
1501                         dbg_last_ack_tsn = tsn;
1502 #endif /* SCTP_DEBUG */
1503
1504                 } else {
1505                         if (tchunk->tsn_gap_acked) {
1506                                 SCTP_DEBUG_PRINTK("%s: Receiver reneged on "
1507                                                   "data TSN: 0x%x\n",
1508                                                   __func__,
1509                                                   tsn);
1510                                 tchunk->tsn_gap_acked = 0;
1511
1512                                 if (tchunk->transport)
1513                                         bytes_acked -= sctp_data_size(tchunk);
1514
1515                                 /* RFC 2960 6.3.2 Retransmission Timer Rules
1516                                  *
1517                                  * R4) Whenever a SACK is received missing a
1518                                  * TSN that was previously acknowledged via a
1519                                  * Gap Ack Block, start T3-rtx for the
1520                                  * destination address to which the DATA
1521                                  * chunk was originally
1522                                  * transmitted if it is not already running.
1523                                  */
1524                                 restart_timer = 1;
1525                         }
1526
1527                         list_add_tail(lchunk, &tlist);
1528
1529 #if SCTP_DEBUG
1530                         /* See the above comments on ACK-ed TSNs. */
1531                         switch (dbg_prt_state) {
1532                         case 1:
1533                                 if (dbg_last_kept_tsn + 1 == tsn)
1534                                         break;
1535
1536                                 if (dbg_last_kept_tsn != dbg_kept_tsn)
1537                                         SCTP_DEBUG_PRINTK_CONT("-%08x",
1538                                                                dbg_last_kept_tsn);
1539
1540                                 SCTP_DEBUG_PRINTK_CONT(",%08x", tsn);
1541                                 dbg_kept_tsn = tsn;
1542                                 break;
1543
1544                         case 0:
1545                                 if (dbg_last_ack_tsn != dbg_ack_tsn)
1546                                         SCTP_DEBUG_PRINTK_CONT("-%08x",
1547                                                                dbg_last_ack_tsn);
1548                                 SCTP_DEBUG_PRINTK_CONT("\n");
1549
1550                                 /* FALL THROUGH... */
1551                         default:
1552                                 SCTP_DEBUG_PRINTK("KEPT: %08x",tsn);
1553                                 dbg_prt_state = 1;
1554                                 dbg_kept_tsn = tsn;
1555                         }
1556
1557                         dbg_last_kept_tsn = tsn;
1558 #endif /* SCTP_DEBUG */
1559                 }
1560         }
1561
1562 #if SCTP_DEBUG
1563         /* Finish off the last range, displaying its ending TSN.  */
1564         switch (dbg_prt_state) {
1565         case 0:
1566                 if (dbg_last_ack_tsn != dbg_ack_tsn) {
1567                         SCTP_DEBUG_PRINTK_CONT("-%08x\n", dbg_last_ack_tsn);
1568                 } else {
1569                         SCTP_DEBUG_PRINTK_CONT("\n");
1570                 }
1571         break;
1572
1573         case 1:
1574                 if (dbg_last_kept_tsn != dbg_kept_tsn) {
1575                         SCTP_DEBUG_PRINTK_CONT("-%08x\n", dbg_last_kept_tsn);
1576                 } else {
1577                         SCTP_DEBUG_PRINTK_CONT("\n");
1578                 }
1579         }
1580 #endif /* SCTP_DEBUG */
1581         if (transport) {
1582                 if (bytes_acked) {
1583                         struct sctp_association *asoc = transport->asoc;
1584
1585                         /* We may have counted DATA that was migrated
1586                          * to this transport due to DEL-IP operation.
1587                          * Subtract those bytes, since the were never
1588                          * send on this transport and shouldn't be
1589                          * credited to this transport.
1590                          */
1591                         bytes_acked -= migrate_bytes;
1592
1593                         /* 8.2. When an outstanding TSN is acknowledged,
1594                          * the endpoint shall clear the error counter of
1595                          * the destination transport address to which the
1596                          * DATA chunk was last sent.
1597                          * The association's overall error counter is
1598                          * also cleared.
1599                          */
1600                         transport->error_count = 0;
1601                         transport->asoc->overall_error_count = 0;
1602
1603                         /*
1604                          * While in SHUTDOWN PENDING, we may have started
1605                          * the T5 shutdown guard timer after reaching the
1606                          * retransmission limit. Stop that timer as soon
1607                          * as the receiver acknowledged any data.
1608                          */
1609                         if (asoc->state == SCTP_STATE_SHUTDOWN_PENDING &&
1610                             del_timer(&asoc->timers
1611                                 [SCTP_EVENT_TIMEOUT_T5_SHUTDOWN_GUARD]))
1612                                         sctp_association_put(asoc);
1613
1614                         /* Mark the destination transport address as
1615                          * active if it is not so marked.
1616                          */
1617                         if ((transport->state == SCTP_INACTIVE) ||
1618                             (transport->state == SCTP_UNCONFIRMED)) {
1619                                 sctp_assoc_control_transport(
1620                                         transport->asoc,
1621                                         transport,
1622                                         SCTP_TRANSPORT_UP,
1623                                         SCTP_RECEIVED_SACK);
1624                         }
1625
1626                         sctp_transport_raise_cwnd(transport, sack_ctsn,
1627                                                   bytes_acked);
1628
1629                         transport->flight_size -= bytes_acked;
1630                         if (transport->flight_size == 0)
1631                                 transport->partial_bytes_acked = 0;
1632                         q->outstanding_bytes -= bytes_acked + migrate_bytes;
1633                 } else {
1634                         /* RFC 2960 6.1, sctpimpguide-06 2.15.2
1635                          * When a sender is doing zero window probing, it
1636                          * should not timeout the association if it continues
1637                          * to receive new packets from the receiver. The
1638                          * reason is that the receiver MAY keep its window
1639                          * closed for an indefinite time.
1640                          * A sender is doing zero window probing when the
1641                          * receiver's advertised window is zero, and there is
1642                          * only one data chunk in flight to the receiver.
1643                          *
1644                          * Allow the association to timeout while in SHUTDOWN
1645                          * PENDING or SHUTDOWN RECEIVED in case the receiver
1646                          * stays in zero window mode forever.
1647                          */
1648                         if (!q->asoc->peer.rwnd &&
1649                             !list_empty(&tlist) &&
1650                             (sack_ctsn+2 == q->asoc->next_tsn) &&
1651                             q->asoc->state < SCTP_STATE_SHUTDOWN_PENDING) {
1652                                 SCTP_DEBUG_PRINTK("%s: SACK received for zero "
1653                                                   "window probe: %u\n",
1654                                                   __func__, sack_ctsn);
1655                                 q->asoc->overall_error_count = 0;
1656                                 transport->error_count = 0;
1657                         }
1658                 }
1659
1660                 /* RFC 2960 6.3.2 Retransmission Timer Rules
1661                  *
1662                  * R2) Whenever all outstanding data sent to an address have
1663                  * been acknowledged, turn off the T3-rtx timer of that
1664                  * address.
1665                  */
1666                 if (!transport->flight_size) {
1667                         if (timer_pending(&transport->T3_rtx_timer) &&
1668                             del_timer(&transport->T3_rtx_timer)) {
1669                                 sctp_transport_put(transport);
1670                         }
1671                 } else if (restart_timer) {
1672                         if (!mod_timer(&transport->T3_rtx_timer,
1673                                        jiffies + transport->rto))
1674                                 sctp_transport_hold(transport);
1675                 }
1676         }
1677
1678         list_splice(&tlist, transmitted_queue);
1679 }
1680
1681 /* Mark chunks as missing and consequently may get retransmitted. */
1682 static void sctp_mark_missing(struct sctp_outq *q,
1683                               struct list_head *transmitted_queue,
1684                               struct sctp_transport *transport,
1685                               __u32 highest_new_tsn_in_sack,
1686                               int count_of_newacks)
1687 {
1688         struct sctp_chunk *chunk;
1689         __u32 tsn;
1690         char do_fast_retransmit = 0;
1691         struct sctp_association *asoc = q->asoc;
1692         struct sctp_transport *primary = asoc->peer.primary_path;
1693
1694         list_for_each_entry(chunk, transmitted_queue, transmitted_list) {
1695
1696                 tsn = ntohl(chunk->subh.data_hdr->tsn);
1697
1698                 /* RFC 2960 7.2.4, sctpimpguide-05 2.8.2 M3) Examine all
1699                  * 'Unacknowledged TSN's', if the TSN number of an
1700                  * 'Unacknowledged TSN' is smaller than the 'HighestTSNinSack'
1701                  * value, increment the 'TSN.Missing.Report' count on that
1702                  * chunk if it has NOT been fast retransmitted or marked for
1703                  * fast retransmit already.
1704                  */
1705                 if (chunk->fast_retransmit == SCTP_CAN_FRTX &&
1706                     !chunk->tsn_gap_acked &&
1707                     TSN_lt(tsn, highest_new_tsn_in_sack)) {
1708
1709                         /* SFR-CACC may require us to skip marking
1710                          * this chunk as missing.
1711                          */
1712                         if (!transport || !sctp_cacc_skip(primary,
1713                                                 chunk->transport,
1714                                                 count_of_newacks, tsn)) {
1715                                 chunk->tsn_missing_report++;
1716
1717                                 SCTP_DEBUG_PRINTK(
1718                                         "%s: TSN 0x%x missing counter: %d\n",
1719                                         __func__, tsn,
1720                                         chunk->tsn_missing_report);
1721                         }
1722                 }
1723                 /*
1724                  * M4) If any DATA chunk is found to have a
1725                  * 'TSN.Missing.Report'
1726                  * value larger than or equal to 3, mark that chunk for
1727                  * retransmission and start the fast retransmit procedure.
1728                  */
1729
1730                 if (chunk->tsn_missing_report >= 3) {
1731                         chunk->fast_retransmit = SCTP_NEED_FRTX;
1732                         do_fast_retransmit = 1;
1733                 }
1734         }
1735
1736         if (transport) {
1737                 if (do_fast_retransmit)
1738                         sctp_retransmit(q, transport, SCTP_RTXR_FAST_RTX);
1739
1740                 SCTP_DEBUG_PRINTK("%s: transport: %p, cwnd: %d, "
1741                                   "ssthresh: %d, flight_size: %d, pba: %d\n",
1742                                   __func__, transport, transport->cwnd,
1743                                   transport->ssthresh, transport->flight_size,
1744                                   transport->partial_bytes_acked);
1745         }
1746 }
1747
1748 /* Is the given TSN acked by this packet?  */
1749 static int sctp_acked(struct sctp_sackhdr *sack, __u32 tsn)
1750 {
1751         int i;
1752         sctp_sack_variable_t *frags;
1753         __u16 gap;
1754         __u32 ctsn = ntohl(sack->cum_tsn_ack);
1755
1756         if (TSN_lte(tsn, ctsn))
1757                 goto pass;
1758
1759         /* 3.3.4 Selective Acknowledgement (SACK) (3):
1760          *
1761          * Gap Ack Blocks:
1762          *  These fields contain the Gap Ack Blocks. They are repeated
1763          *  for each Gap Ack Block up to the number of Gap Ack Blocks
1764          *  defined in the Number of Gap Ack Blocks field. All DATA
1765          *  chunks with TSNs greater than or equal to (Cumulative TSN
1766          *  Ack + Gap Ack Block Start) and less than or equal to
1767          *  (Cumulative TSN Ack + Gap Ack Block End) of each Gap Ack
1768          *  Block are assumed to have been received correctly.
1769          */
1770
1771         frags = sack->variable;
1772         gap = tsn - ctsn;
1773         for (i = 0; i < ntohs(sack->num_gap_ack_blocks); ++i) {
1774                 if (TSN_lte(ntohs(frags[i].gab.start), gap) &&
1775                     TSN_lte(gap, ntohs(frags[i].gab.end)))
1776                         goto pass;
1777         }
1778
1779         return 0;
1780 pass:
1781         return 1;
1782 }
1783
1784 static inline int sctp_get_skip_pos(struct sctp_fwdtsn_skip *skiplist,
1785                                     int nskips, __be16 stream)
1786 {
1787         int i;
1788
1789         for (i = 0; i < nskips; i++) {
1790                 if (skiplist[i].stream == stream)
1791                         return i;
1792         }
1793         return i;
1794 }
1795
1796 /* Create and add a fwdtsn chunk to the outq's control queue if needed. */
1797 static void sctp_generate_fwdtsn(struct sctp_outq *q, __u32 ctsn)
1798 {
1799         struct sctp_association *asoc = q->asoc;
1800         struct sctp_chunk *ftsn_chunk = NULL;
1801         struct sctp_fwdtsn_skip ftsn_skip_arr[10];
1802         int nskips = 0;
1803         int skip_pos = 0;
1804         __u32 tsn;
1805         struct sctp_chunk *chunk;
1806         struct list_head *lchunk, *temp;
1807
1808         if (!asoc->peer.prsctp_capable)
1809                 return;
1810
1811         /* PR-SCTP C1) Let SackCumAck be the Cumulative TSN ACK carried in the
1812          * received SACK.
1813          *
1814          * If (Advanced.Peer.Ack.Point < SackCumAck), then update
1815          * Advanced.Peer.Ack.Point to be equal to SackCumAck.
1816          */
1817         if (TSN_lt(asoc->adv_peer_ack_point, ctsn))
1818                 asoc->adv_peer_ack_point = ctsn;
1819
1820         /* PR-SCTP C2) Try to further advance the "Advanced.Peer.Ack.Point"
1821          * locally, that is, to move "Advanced.Peer.Ack.Point" up as long as
1822          * the chunk next in the out-queue space is marked as "abandoned" as
1823          * shown in the following example:
1824          *
1825          * Assuming that a SACK arrived with the Cumulative TSN ACK 102
1826          * and the Advanced.Peer.Ack.Point is updated to this value:
1827          *
1828          *   out-queue at the end of  ==>   out-queue after Adv.Ack.Point
1829          *   normal SACK processing           local advancement
1830          *                ...                           ...
1831          *   Adv.Ack.Pt-> 102 acked                     102 acked
1832          *                103 abandoned                 103 abandoned
1833          *                104 abandoned     Adv.Ack.P-> 104 abandoned
1834          *                105                           105
1835          *                106 acked                     106 acked
1836          *                ...                           ...
1837          *
1838          * In this example, the data sender successfully advanced the
1839          * "Advanced.Peer.Ack.Point" from 102 to 104 locally.
1840          */
1841         list_for_each_safe(lchunk, temp, &q->abandoned) {
1842                 chunk = list_entry(lchunk, struct sctp_chunk,
1843                                         transmitted_list);
1844                 tsn = ntohl(chunk->subh.data_hdr->tsn);
1845
1846                 /* Remove any chunks in the abandoned queue that are acked by
1847                  * the ctsn.
1848                  */
1849                 if (TSN_lte(tsn, ctsn)) {
1850                         list_del_init(lchunk);
1851                         sctp_chunk_free(chunk);
1852                 } else {
1853                         if (TSN_lte(tsn, asoc->adv_peer_ack_point+1)) {
1854                                 asoc->adv_peer_ack_point = tsn;
1855                                 if (chunk->chunk_hdr->flags &
1856                                          SCTP_DATA_UNORDERED)
1857                                         continue;
1858                                 skip_pos = sctp_get_skip_pos(&ftsn_skip_arr[0],
1859                                                 nskips,
1860                                                 chunk->subh.data_hdr->stream);
1861                                 ftsn_skip_arr[skip_pos].stream =
1862                                         chunk->subh.data_hdr->stream;
1863                                 ftsn_skip_arr[skip_pos].ssn =
1864                                          chunk->subh.data_hdr->ssn;
1865                                 if (skip_pos == nskips)
1866                                         nskips++;
1867                                 if (nskips == 10)
1868                                         break;
1869                         } else
1870                                 break;
1871                 }
1872         }
1873
1874         /* PR-SCTP C3) If, after step C1 and C2, the "Advanced.Peer.Ack.Point"
1875          * is greater than the Cumulative TSN ACK carried in the received
1876          * SACK, the data sender MUST send the data receiver a FORWARD TSN
1877          * chunk containing the latest value of the
1878          * "Advanced.Peer.Ack.Point".
1879          *
1880          * C4) For each "abandoned" TSN the sender of the FORWARD TSN SHOULD
1881          * list each stream and sequence number in the forwarded TSN. This
1882          * information will enable the receiver to easily find any
1883          * stranded TSN's waiting on stream reorder queues. Each stream
1884          * SHOULD only be reported once; this means that if multiple
1885          * abandoned messages occur in the same stream then only the
1886          * highest abandoned stream sequence number is reported. If the
1887          * total size of the FORWARD TSN does NOT fit in a single MTU then
1888          * the sender of the FORWARD TSN SHOULD lower the
1889          * Advanced.Peer.Ack.Point to the last TSN that will fit in a
1890          * single MTU.
1891          */
1892         if (asoc->adv_peer_ack_point > ctsn)
1893                 ftsn_chunk = sctp_make_fwdtsn(asoc, asoc->adv_peer_ack_point,
1894                                               nskips, &ftsn_skip_arr[0]);
1895
1896         if (ftsn_chunk) {
1897                 list_add_tail(&ftsn_chunk->list, &q->control_chunk_list);
1898                 SCTP_INC_STATS(SCTP_MIB_OUTCTRLCHUNKS);
1899         }
1900 }