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                                    union sctp_addr *saddr,
  67                                    struct sctp_sackhdr *sack,
  68                                    __u32 *highest_new_tsn);
  69
  70 static void sctp_mark_missing(struct sctp_outq *q,
  71                               struct list_head *transmitted_queue,
  72                               struct sctp_transport *transport,
  73                               __u32 highest_new_tsn,
  74                               int count_of_newacks);
  75
  76 static void sctp_generate_fwdtsn(struct sctp_outq *q, __u32 sack_ctsn);
  77
  78 static int sctp_outq_flush(struct sctp_outq *q, int rtx_timeout);
  79
  80 /* Add data to the front of the queue. */
  81 static inline void sctp_outq_head_data(struct sctp_outq *q,
  82                                         struct sctp_chunk *ch)
  83 {
  84         list_add(&ch->list, &q->out_chunk_list);
  85         q->out_qlen += ch->skb->len;
  86 }
  87
  88 /* Take data from the front of the queue. */
  89 static inline struct sctp_chunk *sctp_outq_dequeue_data(struct sctp_outq *q)
  90 {
  91         struct sctp_chunk *ch = NULL;
  92
  93         if (!list_empty(&q->out_chunk_list)) {
  94                 struct list_head *entry = q->out_chunk_list.next;
  95
  96                 ch = list_entry(entry, struct sctp_chunk, list);
  97                 list_del_init(entry);
  98                 q->out_qlen -= ch->skb->len;
  99         }
 100         return ch;
 101 }
 102 /* Add data chunk to the end of the queue. */
 103 static inline void sctp_outq_tail_data(struct sctp_outq *q,
 104                                        struct sctp_chunk *ch)
 105 {
 106         list_add_tail(&ch->list, &q->out_chunk_list);
 107         q->out_qlen += ch->skb->len;
 108 }
 109
 110 /*
 111  * SFR-CACC algorithm:
 112  * D) If count_of_newacks is greater than or equal to 2
 113  * and t was not sent to the current primary then the
 114  * sender MUST NOT increment missing report count for t.
 115  */
 116 static inline int sctp_cacc_skip_3_1_d(struct sctp_transport *primary,
 117                                        struct sctp_transport *transport,
 118                                        int count_of_newacks)
 119 {
 120         if (count_of_newacks >=2 && transport != primary)
 121                 return 1;
 122         return 0;
 123 }
 124
 125 /*
 126  * SFR-CACC algorithm:
 127  * F) If count_of_newacks is less than 2, let d be the
 128  * destination to which t was sent. If cacc_saw_newack
 129  * is 0 for destination d, then the sender MUST NOT
 130  * increment missing report count for t.
 131  */
 132 static inline int sctp_cacc_skip_3_1_f(struct sctp_transport *transport,
 133                                        int count_of_newacks)
 134 {
 135         if (count_of_newacks < 2 &&
 136                         (transport && !transport->cacc.cacc_saw_newack))
 137                 return 1;
 138         return 0;
 139 }
 140
 141 /*
 142  * SFR-CACC algorithm:
 143  * 3.1) If CYCLING_CHANGEOVER is 0, the sender SHOULD
 144  * execute steps C, D, F.
 145  *
 146  * C has been implemented in sctp_outq_sack
 147  */
 148 static inline int sctp_cacc_skip_3_1(struct sctp_transport *primary,
 149                                      struct sctp_transport *transport,
 150                                      int count_of_newacks)
 151 {
 152         if (!primary->cacc.cycling_changeover) {
 153                 if (sctp_cacc_skip_3_1_d(primary, transport, count_of_newacks))
 154                         return 1;
 155                 if (sctp_cacc_skip_3_1_f(transport, count_of_newacks))
 156                         return 1;
 157                 return 0;
 158         }
 159         return 0;
 160 }
 161
 162 /*
 163  * SFR-CACC algorithm:
 164  * 3.2) Else if CYCLING_CHANGEOVER is 1, and t is less
 165  * than next_tsn_at_change of the current primary, then
 166  * the sender MUST NOT increment missing report count
 167  * for t.
 168  */
 169 static inline int sctp_cacc_skip_3_2(struct sctp_transport *primary, __u32 tsn)
 170 {
 171         if (primary->cacc.cycling_changeover &&
 172             TSN_lt(tsn, primary->cacc.next_tsn_at_change))
 173                 return 1;
 174         return 0;
 175 }
 176
 177 /*
 178  * SFR-CACC algorithm:
 179  * 3) If the missing report count for TSN t is to be
 180  * incremented according to [RFC2960] and
 181  * [SCTP_STEWART-2002], and CHANGEOVER_ACTIVE is set,
 182  * then the sender MUST further execute steps 3.1 and
 183  * 3.2 to determine if the missing report count for
 184  * TSN t SHOULD NOT be incremented.
 185  *
 186  * 3.3) If 3.1 and 3.2 do not dictate that the missing
 187  * report count for t should not be incremented, then
 188  * the sender SHOULD increment missing report count for
 189  * t (according to [RFC2960] and [SCTP_STEWART_2002]).
 190  */
 191 static inline int sctp_cacc_skip(struct sctp_transport *primary,
 192                                  struct sctp_transport *transport,
 193                                  int count_of_newacks,
 194                                  __u32 tsn)
 195 {
 196         if (primary->cacc.changeover_active &&
 197             (sctp_cacc_skip_3_1(primary, transport, count_of_newacks) ||
 198              sctp_cacc_skip_3_2(primary, tsn)))
 199                 return 1;
 200         return 0;
 201 }
 202
 203 /* Initialize an existing sctp_outq.  This does the boring stuff.
 204  * You still need to define handlers if you really want to DO
 205  * something with this structure...
 206  */
 207 void sctp_outq_init(struct sctp_association *asoc, struct sctp_outq *q)
 208 {
 209         q->asoc = asoc;
 210         INIT_LIST_HEAD(&q->out_chunk_list);
 211         INIT_LIST_HEAD(&q->control_chunk_list);
 212         INIT_LIST_HEAD(&q->retransmit);
 213         INIT_LIST_HEAD(&q->sacked);
 214         INIT_LIST_HEAD(&q->abandoned);
 215
 216         q->fast_rtx = 0;
 217         q->outstanding_bytes = 0;
 218         q->empty = 1;
 219         q->cork  = 0;
 220         q->out_qlen = 0;
 221 }
 222
 223 /* Free the outqueue structure and any related pending chunks.
 224  */
 225 static void __sctp_outq_teardown(struct sctp_outq *q)
 226 {
 227         struct sctp_transport *transport;
 228         struct list_head *lchunk, *temp;
 229         struct sctp_chunk *chunk, *tmp;
 230
 231         /* Throw away unacknowledged chunks. */
 232         list_for_each_entry(transport, &q->asoc->peer.transport_addr_list,
 233                         transports) {
 234                 while ((lchunk = sctp_list_dequeue(&transport->transmitted)) != NULL) {
 235                         chunk = list_entry(lchunk, struct sctp_chunk,
 236                                            transmitted_list);
 237                         /* Mark as part of a failed message. */
 238                         sctp_chunk_fail(chunk, q->error);
 239                         sctp_chunk_free(chunk);
 240                 }
 241         }
 242
 243         /* Throw away chunks that have been gap ACKed.  */
 244         list_for_each_safe(lchunk, temp, &q->sacked) {
 245                 list_del_init(lchunk);
 246                 chunk = list_entry(lchunk, struct sctp_chunk,
 247                                    transmitted_list);
 248                 sctp_chunk_fail(chunk, q->error);
 249                 sctp_chunk_free(chunk);
 250         }
 251
 252         /* Throw away any chunks in the retransmit queue. */
 253         list_for_each_safe(lchunk, temp, &q->retransmit) {
 254                 list_del_init(lchunk);
 255                 chunk = list_entry(lchunk, struct sctp_chunk,
 256                                    transmitted_list);
 257                 sctp_chunk_fail(chunk, q->error);
 258                 sctp_chunk_free(chunk);
 259         }
 260
 261         /* Throw away any chunks that are in the abandoned queue. */
 262         list_for_each_safe(lchunk, temp, &q->abandoned) {
 263                 list_del_init(lchunk);
 264                 chunk = list_entry(lchunk, struct sctp_chunk,
 265                                    transmitted_list);
 266                 sctp_chunk_fail(chunk, q->error);
 267                 sctp_chunk_free(chunk);
 268         }
 269
 270         /* Throw away any leftover data chunks. */
 271         while ((chunk = sctp_outq_dequeue_data(q)) != NULL) {
 272
 273                 /* Mark as send failure. */
 274                 sctp_chunk_fail(chunk, q->error);
 275                 sctp_chunk_free(chunk);
 276         }
 277
 278         /* Throw away any leftover control chunks. */
 279         list_for_each_entry_safe(chunk, tmp, &q->control_chunk_list, list) {
 280                 list_del_init(&chunk->list);
 281                 sctp_chunk_free(chunk);
 282         }
 283 }
 284
 285 void sctp_outq_teardown(struct sctp_outq *q)
 286 {
 287         __sctp_outq_teardown(q);
 288         sctp_outq_init(q->asoc, q);
 289 }
 290
 291 /* Free the outqueue structure and any related pending chunks.  */
 292 void sctp_outq_free(struct sctp_outq *q)
 293 {
 294         /* Throw away leftover chunks. */
 295         __sctp_outq_teardown(q);
 296 }
 297
 298 /* Put a new chunk in an sctp_outq.  */
 299 int sctp_outq_tail(struct sctp_outq *q, struct sctp_chunk *chunk)
 300 {
 301         struct net *net = sock_net(q->asoc->base.sk);
 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(net, SCTP_MIB_OUTUNORDERCHUNKS);
 341                         else
 342                                 SCTP_INC_STATS(net, 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(net, 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         struct net *net = sock_net(q->asoc->base.sk);
 482         int error = 0;
 483
 484         switch(reason) {
 485         case SCTP_RTXR_T3_RTX:
 486                 SCTP_INC_STATS(net, SCTP_MIB_T3_RETRANSMITS);
 487                 sctp_transport_lower_cwnd(transport, SCTP_LOWER_CWND_T3_RTX);
 488                 /* Update the retran path if the T3-rtx timer has expired for
 489                  * the current retran path.
 490                  */
 491                 if (transport == transport->asoc->peer.retran_path)
 492                         sctp_assoc_update_retran_path(transport->asoc);
 493                 transport->asoc->rtx_data_chunks +=
 494                         transport->asoc->unack_data;
 495                 break;
 496         case SCTP_RTXR_FAST_RTX:
 497                 SCTP_INC_STATS(net, SCTP_MIB_FAST_RETRANSMITS);
 498                 sctp_transport_lower_cwnd(transport, SCTP_LOWER_CWND_FAST_RTX);
 499                 q->fast_rtx = 1;
 500                 break;
 501         case SCTP_RTXR_PMTUD:
 502                 SCTP_INC_STATS(net, SCTP_MIB_PMTUD_RETRANSMITS);
 503                 break;
 504         case SCTP_RTXR_T1_RTX:
 505                 SCTP_INC_STATS(net, SCTP_MIB_T1_RETRANSMITS);
 506                 transport->asoc->init_retries++;
 507                 break;
 508         default:
 509                 BUG();
 510         }
 511
 512         sctp_retransmit_mark(q, transport, reason);
 513
 514         /* PR-SCTP A5) Any time the T3-rtx timer expires, on any destination,
 515          * the sender SHOULD try to advance the "Advanced.Peer.Ack.Point" by
 516          * following the procedures outlined in C1 - C5.
 517          */
 518         if (reason == SCTP_RTXR_T3_RTX)
 519                 sctp_generate_fwdtsn(q, q->asoc->ctsn_ack_point);
 520
 521         /* Flush the queues only on timeout, since fast_rtx is only
 522          * triggered during sack processing and the queue
 523          * will be flushed at the end.
 524          */
 525         if (reason != SCTP_RTXR_FAST_RTX)
 526                 error = sctp_outq_flush(q, /* rtx_timeout */ 1);
 527
 528         if (error)
 529                 q->asoc->base.sk->sk_err = -error;
 530 }
 531
 532 /*
 533  * Transmit DATA chunks on the retransmit queue.  Upon return from
 534  * sctp_outq_flush_rtx() the packet 'pkt' may contain chunks which
 535  * need to be transmitted by the caller.
 536  * We assume that pkt->transport has already been set.
 537  *
 538  * The return value is a normal kernel error return value.
 539  */
 540 static int sctp_outq_flush_rtx(struct sctp_outq *q, struct sctp_packet *pkt,
 541                                int rtx_timeout, int *start_timer)
 542 {
 543         struct list_head *lqueue;
 544         struct sctp_transport *transport = pkt->transport;
 545         sctp_xmit_t status;
 546         struct sctp_chunk *chunk, *chunk1;
 547         int fast_rtx;
 548         int error = 0;
 549         int timer = 0;
 550         int done = 0;
 551
 552         lqueue = &q->retransmit;
 553         fast_rtx = q->fast_rtx;
 554
 555         /* This loop handles time-out retransmissions, fast retransmissions,
 556          * and retransmissions due to opening of whindow.
 557          *
 558          * RFC 2960 6.3.3 Handle T3-rtx Expiration
 559          *
 560          * E3) Determine how many of the earliest (i.e., lowest TSN)
 561          * outstanding DATA chunks for the address for which the
 562          * T3-rtx has expired will fit into a single packet, subject
 563          * to the MTU constraint for the path corresponding to the
 564          * destination transport address to which the retransmission
 565          * is being sent (this may be different from the address for
 566          * which the timer expires [see Section 6.4]). Call this value
 567          * K. Bundle and retransmit those K DATA chunks in a single
 568          * packet to the destination endpoint.
 569          *
 570          * [Just to be painfully clear, if we are retransmitting
 571          * because a timeout just happened, we should send only ONE
 572          * packet of retransmitted data.]
 573          *
 574          * For fast retransmissions we also send only ONE packet.  However,
 575          * if we are just flushing the queue due to open window, we'll
 576          * try to send as much as possible.
 577          */
 578         list_for_each_entry_safe(chunk, chunk1, lqueue, transmitted_list) {
 579                 /* If the chunk is abandoned, move it to abandoned list. */
 580                 if (sctp_chunk_abandoned(chunk)) {
 581                         list_del_init(&chunk->transmitted_list);
 582                         sctp_insert_list(&q->abandoned,
 583                                          &chunk->transmitted_list);
 584                         continue;
 585                 }
 586
 587                 /* Make sure that Gap Acked TSNs are not retransmitted.  A
 588                  * simple approach is just to move such TSNs out of the
 589                  * way and into a 'transmitted' queue and skip to the
 590                  * next chunk.
 591                  */
 592                 if (chunk->tsn_gap_acked) {
 593                         list_move_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_move_tail(&chunk->transmitted_list,
 659                                        &transport->transmitted);
 660
 661                         /* Mark the chunk as ineligible for fast retransmit
 662                          * after it is retransmitted.
 663                          */
 664                         if (chunk->fast_retransmit == SCTP_NEED_FRTX)
 665                                 chunk->fast_retransmit = SCTP_DONT_FRTX;
 666
 667                         q->empty = 0;
 668                         q->asoc->stats.rtxchunks++;
 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         if (q->cork)
 705                 q->cork = 0;
 706
 707         return sctp_outq_flush(q, 0);
 708 }
 709
 710
 711 /*
 712  * Try to flush an outqueue.
 713  *
 714  * Description: Send everything in q which we legally can, subject to
 715  * congestion limitations.
 716  * * Note: This function can be called from multiple contexts so appropriate
 717  * locking concerns must be made.  Today we use the sock lock to protect
 718  * this function.
 719  */
 720 static int sctp_outq_flush(struct sctp_outq *q, int rtx_timeout)
 721 {
 722         struct sctp_packet *packet;
 723         struct sctp_packet singleton;
 724         struct sctp_association *asoc = q->asoc;
 725         __u16 sport = asoc->base.bind_addr.port;
 726         __u16 dport = asoc->peer.port;
 727         __u32 vtag = asoc->peer.i.init_tag;
 728         struct sctp_transport *transport = NULL;
 729         struct sctp_transport *new_transport;
 730         struct sctp_chunk *chunk, *tmp;
 731         sctp_xmit_t status;
 732         int error = 0;
 733         int start_timer = 0;
 734         int one_packet = 0;
 735
 736         /* These transports have chunks to send. */
 737         struct list_head transport_list;
 738         struct list_head *ltransport;
 739
 740         INIT_LIST_HEAD(&transport_list);
 741         packet = NULL;
 742
 743         /*
 744          * 6.10 Bundling
 745          *   ...
 746          *   When bundling control chunks with DATA chunks, an
 747          *   endpoint MUST place control chunks first in the outbound
 748          *   SCTP packet.  The transmitter MUST transmit DATA chunks
 749          *   within a SCTP packet in increasing order of TSN.
 750          *   ...
 751          */
 752
 753         list_for_each_entry_safe(chunk, tmp, &q->control_chunk_list, list) {
 754                 /* RFC 5061, 5.3
 755                  * F1) This means that until such time as the ASCONF
 756                  * containing the add is acknowledged, the sender MUST
 757                  * NOT use the new IP address as a source for ANY SCTP
 758                  * packet except on carrying an ASCONF Chunk.
 759                  */
 760                 if (asoc->src_out_of_asoc_ok &&
 761                     chunk->chunk_hdr->type != SCTP_CID_ASCONF)
 762                         continue;
 763
 764                 list_del_init(&chunk->list);
 765
 766                 /* Pick the right transport to use. */
 767                 new_transport = chunk->transport;
 768
 769                 if (!new_transport) {
 770                         /*
 771                          * If we have a prior transport pointer, see if
 772                          * the destination address of the chunk
 773                          * matches the destination address of the
 774                          * current transport.  If not a match, then
 775                          * try to look up the transport with a given
 776                          * destination address.  We do this because
 777                          * after processing ASCONFs, we may have new
 778                          * transports created.
 779                          */
 780                         if (transport &&
 781                             sctp_cmp_addr_exact(&chunk->dest,
 782                                                 &transport->ipaddr))
 783                                         new_transport = transport;
 784                         else
 785                                 new_transport = sctp_assoc_lookup_paddr(asoc,
 786                                                                 &chunk->dest);
 787
 788                         /* if we still don't have a new transport, then
 789                          * use the current active path.
 790                          */
 791                         if (!new_transport)
 792                                 new_transport = asoc->peer.active_path;
 793                 } else if ((new_transport->state == SCTP_INACTIVE) ||
 794                            (new_transport->state == SCTP_UNCONFIRMED) ||
 795                            (new_transport->state == SCTP_PF)) {
 796                         /* If the chunk is Heartbeat or Heartbeat Ack,
 797                          * send it to chunk->transport, even if it's
 798                          * inactive.
 799                          *
 800                          * 3.3.6 Heartbeat Acknowledgement:
 801                          * ...
 802                          * A HEARTBEAT ACK is always sent to the source IP
 803                          * address of the IP datagram containing the
 804                          * HEARTBEAT chunk to which this ack is responding.
 805                          * ...
 806                          *
 807                          * ASCONF_ACKs also must be sent to the source.
 808                          */
 809                         if (chunk->chunk_hdr->type != SCTP_CID_HEARTBEAT &&
 810                             chunk->chunk_hdr->type != SCTP_CID_HEARTBEAT_ACK &&
 811                             chunk->chunk_hdr->type != SCTP_CID_ASCONF_ACK)
 812                                 new_transport = asoc->peer.active_path;
 813                 }
 814
 815                 /* Are we switching transports?
 816                  * Take care of transport locks.
 817                  */
 818                 if (new_transport != transport) {
 819                         transport = new_transport;
 820                         if (list_empty(&transport->send_ready)) {
 821                                 list_add_tail(&transport->send_ready,
 822                                               &transport_list);
 823                         }
 824                         packet = &transport->packet;
 825                         sctp_packet_config(packet, vtag,
 826                                            asoc->peer.ecn_capable);
 827                 }
 828
 829                 switch (chunk->chunk_hdr->type) {
 830                 /*
 831                  * 6.10 Bundling
 832                  *   ...
 833                  *   An endpoint MUST NOT bundle INIT, INIT ACK or SHUTDOWN
 834                  *   COMPLETE with any other chunks.  [Send them immediately.]
 835                  */
 836                 case SCTP_CID_INIT:
 837                 case SCTP_CID_INIT_ACK:
 838                 case SCTP_CID_SHUTDOWN_COMPLETE:
 839                         sctp_packet_init(&singleton, transport, sport, dport);
 840                         sctp_packet_config(&singleton, vtag, 0);
 841                         sctp_packet_append_chunk(&singleton, chunk);
 842                         error = sctp_packet_transmit(&singleton);
 843                         if (error < 0)
 844                                 return error;
 845                         break;
 846
 847                 case SCTP_CID_ABORT:
 848                         if (sctp_test_T_bit(chunk)) {
 849                                 packet->vtag = asoc->c.my_vtag;
 850                         }
 851                 /* The following chunks are "response" chunks, i.e.
 852                  * they are generated in response to something we
 853                  * received.  If we are sending these, then we can
 854                  * send only 1 packet containing these chunks.
 855                  */
 856                 case SCTP_CID_HEARTBEAT_ACK:
 857                 case SCTP_CID_SHUTDOWN_ACK:
 858                 case SCTP_CID_COOKIE_ACK:
 859                 case SCTP_CID_COOKIE_ECHO:
 860                 case SCTP_CID_ERROR:
 861                 case SCTP_CID_ECN_CWR:
 862                 case SCTP_CID_ASCONF_ACK:
 863                         one_packet = 1;
 864                         /* Fall through */
 865
 866                 case SCTP_CID_SACK:
 867                 case SCTP_CID_HEARTBEAT:
 868                 case SCTP_CID_SHUTDOWN:
 869                 case SCTP_CID_ECN_ECNE:
 870                 case SCTP_CID_ASCONF:
 871                 case SCTP_CID_FWD_TSN:
 872                         status = sctp_packet_transmit_chunk(packet, chunk,
 873                                                             one_packet);
 874                         if (status  != SCTP_XMIT_OK) {
 875                                 /* put the chunk back */
 876                                 list_add(&chunk->list, &q->control_chunk_list);
 877                         } else {
 878                                 asoc->stats.octrlchunks++;
 879                                 /* PR-SCTP C5) If a FORWARD TSN is sent, the
 880                                  * sender MUST assure that at least one T3-rtx
 881                                  * timer is running.
 882                                  */
 883                                 if (chunk->chunk_hdr->type == SCTP_CID_FWD_TSN)
 884                                         sctp_transport_reset_timers(transport);
 885                         }
 886                         break;
 887
 888                 default:
 889                         /* We built a chunk with an illegal type! */
 890                         BUG();
 891                 }
 892         }
 893
 894         if (q->asoc->src_out_of_asoc_ok)
 895                 goto sctp_flush_out;
 896
 897         /* Is it OK to send data chunks?  */
 898         switch (asoc->state) {
 899         case SCTP_STATE_COOKIE_ECHOED:
 900                 /* Only allow bundling when this packet has a COOKIE-ECHO
 901                  * chunk.
 902                  */
 903                 if (!packet || !packet->has_cookie_echo)
 904                         break;
 905
 906                 /* fallthru */
 907         case SCTP_STATE_ESTABLISHED:
 908         case SCTP_STATE_SHUTDOWN_PENDING:
 909         case SCTP_STATE_SHUTDOWN_RECEIVED:
 910                 /*
 911                  * RFC 2960 6.1  Transmission of DATA Chunks
 912                  *
 913                  * C) When the time comes for the sender to transmit,
 914                  * before sending new DATA chunks, the sender MUST
 915                  * first transmit any outstanding DATA chunks which
 916                  * are marked for retransmission (limited by the
 917                  * current cwnd).
 918                  */
 919                 if (!list_empty(&q->retransmit)) {
 920                         if (asoc->peer.retran_path->state == SCTP_UNCONFIRMED)
 921                                 goto sctp_flush_out;
 922                         if (transport == asoc->peer.retran_path)
 923                                 goto retran;
 924
 925                         /* Switch transports & prepare the packet.  */
 926
 927                         transport = asoc->peer.retran_path;
 928
 929                         if (list_empty(&transport->send_ready)) {
 930                                 list_add_tail(&transport->send_ready,
 931                                               &transport_list);
 932                         }
 933
 934                         packet = &transport->packet;
 935                         sctp_packet_config(packet, vtag,
 936                                            asoc->peer.ecn_capable);
 937                 retran:
 938                         error = sctp_outq_flush_rtx(q, packet,
 939                                                     rtx_timeout, &start_timer);
 940
 941                         if (start_timer)
 942                                 sctp_transport_reset_timers(transport);
 943
 944                         /* This can happen on COOKIE-ECHO resend.  Only
 945                          * one chunk can get bundled with a COOKIE-ECHO.
 946                          */
 947                         if (packet->has_cookie_echo)
 948                                 goto sctp_flush_out;
 949
 950                         /* Don't send new data if there is still data
 951                          * waiting to retransmit.
 952                          */
 953                         if (!list_empty(&q->retransmit))
 954                                 goto sctp_flush_out;
 955                 }
 956
 957                 /* Apply Max.Burst limitation to the current transport in
 958                  * case it will be used for new data.  We are going to
 959                  * rest it before we return, but we want to apply the limit
 960                  * to the currently queued data.
 961                  */
 962                 if (transport)
 963                         sctp_transport_burst_limited(transport);
 964
 965                 /* Finally, transmit new packets.  */
 966                 while ((chunk = sctp_outq_dequeue_data(q)) != NULL) {
 967                         /* RFC 2960 6.5 Every DATA chunk MUST carry a valid
 968                          * stream identifier.
 969                          */
 970                         if (chunk->sinfo.sinfo_stream >=
 971                             asoc->c.sinit_num_ostreams) {
 972
 973                                 /* Mark as failed send. */
 974                                 sctp_chunk_fail(chunk, SCTP_ERROR_INV_STRM);
 975                                 sctp_chunk_free(chunk);
 976                                 continue;
 977                         }
 978
 979                         /* Has this chunk expired? */
 980                         if (sctp_chunk_abandoned(chunk)) {
 981                                 sctp_chunk_fail(chunk, 0);
 982                                 sctp_chunk_free(chunk);
 983                                 continue;
 984                         }
 985
 986                         /* If there is a specified transport, use it.
 987                          * Otherwise, we want to use the active path.
 988                          */
 989                         new_transport = chunk->transport;
 990                         if (!new_transport ||
 991                             ((new_transport->state == SCTP_INACTIVE) ||
 992                              (new_transport->state == SCTP_UNCONFIRMED) ||
 993                              (new_transport->state == SCTP_PF)))
 994                                 new_transport = asoc->peer.active_path;
 995                         if (new_transport->state == SCTP_UNCONFIRMED)
 996                                 continue;
 997
 998                         /* Change packets if necessary.  */
 999                         if (new_transport != transport) {
1000                                 transport = new_transport;
1001
1002                                 /* Schedule to have this transport's
1003                                  * packet flushed.
1004                                  */
1005                                 if (list_empty(&transport->send_ready)) {
1006                                         list_add_tail(&transport->send_ready,
1007                                                       &transport_list);
1008                                 }
1009
1010                                 packet = &transport->packet;
1011                                 sctp_packet_config(packet, vtag,
1012                                                    asoc->peer.ecn_capable);
1013                                 /* We've switched transports, so apply the
1014                                  * Burst limit to the new transport.
1015                                  */
1016                                 sctp_transport_burst_limited(transport);
1017                         }
1018
1019                         SCTP_DEBUG_PRINTK("sctp_outq_flush(%p, %p[%s]), ",
1020                                           q, chunk,
1021                                           chunk && chunk->chunk_hdr ?
1022                                           sctp_cname(SCTP_ST_CHUNK(
1023                                                   chunk->chunk_hdr->type))
1024                                           : "Illegal Chunk");
1025
1026                         SCTP_DEBUG_PRINTK("TX TSN 0x%x skb->head "
1027                                         "%p skb->users %d.\n",
1028                                         ntohl(chunk->subh.data_hdr->tsn),
1029                                         chunk->skb ?chunk->skb->head : NULL,
1030                                         chunk->skb ?
1031                                         atomic_read(&chunk->skb->users) : -1);
1032
1033                         /* Add the chunk to the packet.  */
1034                         status = sctp_packet_transmit_chunk(packet, chunk, 0);
1035
1036                         switch (status) {
1037                         case SCTP_XMIT_PMTU_FULL:
1038                         case SCTP_XMIT_RWND_FULL:
1039                         case SCTP_XMIT_NAGLE_DELAY:
1040                                 /* We could not append this chunk, so put
1041                                  * the chunk back on the output queue.
1042                                  */
1043                                 SCTP_DEBUG_PRINTK("sctp_outq_flush: could "
1044                                         "not transmit TSN: 0x%x, status: %d\n",
1045                                         ntohl(chunk->subh.data_hdr->tsn),
1046                                         status);
1047                                 sctp_outq_head_data(q, chunk);
1048                                 goto sctp_flush_out;
1049                                 break;
1050
1051                         case SCTP_XMIT_OK:
1052                                 /* The sender is in the SHUTDOWN-PENDING state,
1053                                  * The sender MAY set the I-bit in the DATA
1054                                  * chunk header.
1055                                  */
1056                                 if (asoc->state == SCTP_STATE_SHUTDOWN_PENDING)
1057                                         chunk->chunk_hdr->flags |= SCTP_DATA_SACK_IMM;
1058                                 if (chunk->chunk_hdr->flags & SCTP_DATA_UNORDERED)
1059                                         asoc->stats.ouodchunks++;
1060                                 else
1061                                         asoc->stats.oodchunks++;
1062
1063                                 break;
1064
1065                         default:
1066                                 BUG();
1067                         }
1068
1069                         /* BUG: We assume that the sctp_packet_transmit()
1070                          * call below will succeed all the time and add the
1071                          * chunk to the transmitted list and restart the
1072                          * timers.
1073                          * It is possible that the call can fail under OOM
1074                          * conditions.
1075                          *
1076                          * Is this really a problem?  Won't this behave
1077                          * like a lost TSN?
1078                          */
1079                         list_add_tail(&chunk->transmitted_list,
1080                                       &transport->transmitted);
1081
1082                         sctp_transport_reset_timers(transport);
1083
1084                         q->empty = 0;
1085
1086                         /* Only let one DATA chunk get bundled with a
1087                          * COOKIE-ECHO chunk.
1088                          */
1089                         if (packet->has_cookie_echo)
1090                                 goto sctp_flush_out;
1091                 }
1092                 break;
1093
1094         default:
1095                 /* Do nothing.  */
1096                 break;
1097         }
1098
1099 sctp_flush_out:
1100
1101         /* Before returning, examine all the transports touched in
1102          * this call.  Right now, we bluntly force clear all the
1103          * transports.  Things might change after we implement Nagle.
1104          * But such an examination is still required.
1105          *
1106          * --xguo
1107          */
1108         while ((ltransport = sctp_list_dequeue(&transport_list)) != NULL ) {
1109                 struct sctp_transport *t = list_entry(ltransport,
1110                                                       struct sctp_transport,
1111                                                       send_ready);
1112                 packet = &t->packet;
1113                 if (!sctp_packet_empty(packet))
1114                         error = sctp_packet_transmit(packet);
1115
1116                 /* Clear the burst limited state, if any */
1117                 sctp_transport_burst_reset(t);
1118         }
1119
1120         return error;
1121 }
1122
1123 /* Update unack_data based on the incoming SACK chunk */
1124 static void sctp_sack_update_unack_data(struct sctp_association *assoc,
1125                                         struct sctp_sackhdr *sack)
1126 {
1127         sctp_sack_variable_t *frags;
1128         __u16 unack_data;
1129         int i;
1130
1131         unack_data = assoc->next_tsn - assoc->ctsn_ack_point - 1;
1132
1133         frags = sack->variable;
1134         for (i = 0; i < ntohs(sack->num_gap_ack_blocks); i++) {
1135                 unack_data -= ((ntohs(frags[i].gab.end) -
1136                                 ntohs(frags[i].gab.start) + 1));
1137         }
1138
1139         assoc->unack_data = unack_data;
1140 }
1141
1142 /* This is where we REALLY process a SACK.
1143  *
1144  * Process the SACK against the outqueue.  Mostly, this just frees
1145  * things off the transmitted queue.
1146  */
1147 int sctp_outq_sack(struct sctp_outq *q, struct sctp_chunk *chunk)
1148 {
1149         struct sctp_association *asoc = q->asoc;
1150         struct sctp_sackhdr *sack = chunk->subh.sack_hdr;
1151         struct sctp_transport *transport;
1152         struct sctp_chunk *tchunk = NULL;
1153         struct list_head *lchunk, *transport_list, *temp;
1154         sctp_sack_variable_t *frags = sack->variable;
1155         __u32 sack_ctsn, ctsn, tsn;
1156         __u32 highest_tsn, highest_new_tsn;
1157         __u32 sack_a_rwnd;
1158         unsigned int outstanding;
1159         struct sctp_transport *primary = asoc->peer.primary_path;
1160         int count_of_newacks = 0;
1161         int gap_ack_blocks;
1162         u8 accum_moved = 0;
1163
1164         /* Grab the association's destination address list. */
1165         transport_list = &asoc->peer.transport_addr_list;
1166
1167         sack_ctsn = ntohl(sack->cum_tsn_ack);
1168         gap_ack_blocks = ntohs(sack->num_gap_ack_blocks);
1169         asoc->stats.gapcnt += gap_ack_blocks;
1170         /*
1171          * SFR-CACC algorithm:
1172          * On receipt of a SACK the sender SHOULD execute the
1173          * following statements.
1174          *
1175          * 1) If the cumulative ack in the SACK passes next tsn_at_change
1176          * on the current primary, the CHANGEOVER_ACTIVE flag SHOULD be
1177          * cleared. The CYCLING_CHANGEOVER flag SHOULD also be cleared for
1178          * all destinations.
1179          * 2) If the SACK contains gap acks and the flag CHANGEOVER_ACTIVE
1180          * is set the receiver of the SACK MUST take the following actions:
1181          *
1182          * A) Initialize the cacc_saw_newack to 0 for all destination
1183          * addresses.
1184          *
1185          * Only bother if changeover_active is set. Otherwise, this is
1186          * totally suboptimal to do on every SACK.
1187          */
1188         if (primary->cacc.changeover_active) {
1189                 u8 clear_cycling = 0;
1190
1191                 if (TSN_lte(primary->cacc.next_tsn_at_change, sack_ctsn)) {
1192                         primary->cacc.changeover_active = 0;
1193                         clear_cycling = 1;
1194                 }
1195
1196                 if (clear_cycling || gap_ack_blocks) {
1197                         list_for_each_entry(transport, transport_list,
1198                                         transports) {
1199                                 if (clear_cycling)
1200                                         transport->cacc.cycling_changeover = 0;
1201                                 if (gap_ack_blocks)
1202                                         transport->cacc.cacc_saw_newack = 0;
1203                         }
1204                 }
1205         }
1206
1207         /* Get the highest TSN in the sack. */
1208         highest_tsn = sack_ctsn;
1209         if (gap_ack_blocks)
1210                 highest_tsn += ntohs(frags[gap_ack_blocks - 1].gab.end);
1211
1212         if (TSN_lt(asoc->highest_sacked, highest_tsn))
1213                 asoc->highest_sacked = highest_tsn;
1214
1215         highest_new_tsn = sack_ctsn;
1216
1217         /* Run through the retransmit queue.  Credit bytes received
1218          * and free those chunks that we can.
1219          */
1220         sctp_check_transmitted(q, &q->retransmit, NULL, NULL, sack, &highest_new_tsn);
1221
1222         /* Run through the transmitted queue.
1223          * Credit bytes received and free those chunks which we can.
1224          *
1225          * This is a MASSIVE candidate for optimization.
1226          */
1227         list_for_each_entry(transport, transport_list, transports) {
1228                 sctp_check_transmitted(q, &transport->transmitted,
1229                                        transport, &chunk->source, sack,
1230                                        &highest_new_tsn);
1231                 /*
1232                  * SFR-CACC algorithm:
1233                  * C) Let count_of_newacks be the number of
1234                  * destinations for which cacc_saw_newack is set.
1235                  */
1236                 if (transport->cacc.cacc_saw_newack)
1237                         count_of_newacks ++;
1238         }
1239
1240         /* Move the Cumulative TSN Ack Point if appropriate.  */
1241         if (TSN_lt(asoc->ctsn_ack_point, sack_ctsn)) {
1242                 asoc->ctsn_ack_point = sack_ctsn;
1243                 accum_moved = 1;
1244         }
1245
1246         if (gap_ack_blocks) {
1247
1248                 if (asoc->fast_recovery && accum_moved)
1249                         highest_new_tsn = highest_tsn;
1250
1251                 list_for_each_entry(transport, transport_list, transports)
1252                         sctp_mark_missing(q, &transport->transmitted, transport,
1253                                           highest_new_tsn, count_of_newacks);
1254         }
1255
1256         /* Update unack_data field in the assoc. */
1257         sctp_sack_update_unack_data(asoc, sack);
1258
1259         ctsn = asoc->ctsn_ack_point;
1260
1261         /* Throw away stuff rotting on the sack queue.  */
1262         list_for_each_safe(lchunk, temp, &q->sacked) {
1263                 tchunk = list_entry(lchunk, struct sctp_chunk,
1264                                     transmitted_list);
1265                 tsn = ntohl(tchunk->subh.data_hdr->tsn);
1266                 if (TSN_lte(tsn, ctsn)) {
1267                         list_del_init(&tchunk->transmitted_list);
1268                         sctp_chunk_free(tchunk);
1269                 }
1270         }
1271
1272         /* ii) Set rwnd equal to the newly received a_rwnd minus the
1273          *     number of bytes still outstanding after processing the
1274          *     Cumulative TSN Ack and the Gap Ack Blocks.
1275          */
1276
1277         sack_a_rwnd = ntohl(sack->a_rwnd);
1278         outstanding = q->outstanding_bytes;
1279
1280         if (outstanding < sack_a_rwnd)
1281                 sack_a_rwnd -= outstanding;
1282         else
1283                 sack_a_rwnd = 0;
1284
1285         asoc->peer.rwnd = sack_a_rwnd;
1286
1287         sctp_generate_fwdtsn(q, sack_ctsn);
1288
1289         SCTP_DEBUG_PRINTK("%s: sack Cumulative TSN Ack is 0x%x.\n",
1290                           __func__, sack_ctsn);
1291         SCTP_DEBUG_PRINTK("%s: Cumulative TSN Ack of association, "
1292                           "%p is 0x%x. Adv peer ack point: 0x%x\n",
1293                           __func__, asoc, ctsn, asoc->adv_peer_ack_point);
1294
1295         /* See if all chunks are acked.
1296          * Make sure the empty queue handler will get run later.
1297          */
1298         q->empty = (list_empty(&q->out_chunk_list) &&
1299                     list_empty(&q->retransmit));
1300         if (!q->empty)
1301                 goto finish;
1302
1303         list_for_each_entry(transport, transport_list, transports) {
1304                 q->empty = q->empty && list_empty(&transport->transmitted);
1305                 if (!q->empty)
1306                         goto finish;
1307         }
1308
1309         SCTP_DEBUG_PRINTK("sack queue is empty.\n");
1310 finish:
1311         return q->empty;
1312 }
1313
1314 /* Is the outqueue empty?  */
1315 int sctp_outq_is_empty(const struct sctp_outq *q)
1316 {
1317         return q->empty;
1318 }
1319
1320 /********************************************************************
1321  * 2nd Level Abstractions
1322  ********************************************************************/
1323
1324 /* Go through a transport's transmitted list or the association's retransmit
1325  * list and move chunks that are acked by the Cumulative TSN Ack to q->sacked.
1326  * The retransmit list will not have an associated transport.
1327  *
1328  * I added coherent debug information output.   --xguo
1329  *
1330  * Instead of printing 'sacked' or 'kept' for each TSN on the
1331  * transmitted_queue, we print a range: SACKED: TSN1-TSN2, TSN3, TSN4-TSN5.
1332  * KEPT TSN6-TSN7, etc.
1333  */
1334 static void sctp_check_transmitted(struct sctp_outq *q,
1335                                    struct list_head *transmitted_queue,
1336                                    struct sctp_transport *transport,
1337                                    union sctp_addr *saddr,
1338                                    struct sctp_sackhdr *sack,
1339                                    __u32 *highest_new_tsn_in_sack)
1340 {
1341         struct list_head *lchunk;
1342         struct sctp_chunk *tchunk;
1343         struct list_head tlist;
1344         __u32 tsn;
1345         __u32 sack_ctsn;
1346         __u32 rtt;
1347         __u8 restart_timer = 0;
1348         int bytes_acked = 0;
1349         int migrate_bytes = 0;
1350
1351         /* These state variables are for coherent debug output. --xguo */
1352
1353 #if SCTP_DEBUG
1354         __u32 dbg_ack_tsn = 0;  /* An ACKed TSN range starts here... */
1355         __u32 dbg_last_ack_tsn = 0;  /* ...and finishes here.        */
1356         __u32 dbg_kept_tsn = 0; /* An un-ACKed range starts here...  */
1357         __u32 dbg_last_kept_tsn = 0; /* ...and finishes here.        */
1358
1359         /* 0 : The last TSN was ACKed.
1360          * 1 : The last TSN was NOT ACKed (i.e. KEPT).
1361          * -1: We need to initialize.
1362          */
1363         int dbg_prt_state = -1;
1364 #endif /* SCTP_DEBUG */
1365
1366         sack_ctsn = ntohl(sack->cum_tsn_ack);
1367
1368         INIT_LIST_HEAD(&tlist);
1369
1370         /* The while loop will skip empty transmitted queues. */
1371         while (NULL != (lchunk = sctp_list_dequeue(transmitted_queue))) {
1372                 tchunk = list_entry(lchunk, struct sctp_chunk,
1373                                     transmitted_list);
1374
1375                 if (sctp_chunk_abandoned(tchunk)) {
1376                         /* Move the chunk to abandoned list. */
1377                         sctp_insert_list(&q->abandoned, lchunk);
1378
1379                         /* If this chunk has not been acked, stop
1380                          * considering it as 'outstanding'.
1381                          */
1382                         if (!tchunk->tsn_gap_acked) {
1383                                 if (tchunk->transport)
1384                                         tchunk->transport->flight_size -=
1385                                                         sctp_data_size(tchunk);
1386                                 q->outstanding_bytes -= sctp_data_size(tchunk);
1387                         }
1388                         continue;
1389                 }
1390
1391                 tsn = ntohl(tchunk->subh.data_hdr->tsn);
1392                 if (sctp_acked(sack, tsn)) {
1393                         /* If this queue is the retransmit queue, the
1394                          * retransmit timer has already reclaimed
1395                          * the outstanding bytes for this chunk, so only
1396                          * count bytes associated with a transport.
1397                          */
1398                         if (transport) {
1399                                 /* If this chunk is being used for RTT
1400                                  * measurement, calculate the RTT and update
1401                                  * the RTO using this value.
1402                                  *
1403                                  * 6.3.1 C5) Karn's algorithm: RTT measurements
1404                                  * MUST NOT be made using packets that were
1405                                  * retransmitted (and thus for which it is
1406                                  * ambiguous whether the reply was for the
1407                                  * first instance of the packet or a later
1408                                  * instance).
1409                                  */
1410                                 if (!tchunk->tsn_gap_acked &&
1411                                     tchunk->rtt_in_progress) {
1412                                         tchunk->rtt_in_progress = 0;
1413                                         rtt = jiffies - tchunk->sent_at;
1414                                         sctp_transport_update_rto(transport,
1415                                                                   rtt);
1416                                 }
1417                         }
1418
1419                         /* If the chunk hasn't been marked as ACKED,
1420                          * mark it and account bytes_acked if the
1421                          * chunk had a valid transport (it will not
1422                          * have a transport if ASCONF had deleted it
1423                          * while DATA was outstanding).
1424                          */
1425                         if (!tchunk->tsn_gap_acked) {
1426                                 tchunk->tsn_gap_acked = 1;
1427                                 *highest_new_tsn_in_sack = tsn;
1428                                 bytes_acked += sctp_data_size(tchunk);
1429                                 if (!tchunk->transport)
1430                                         migrate_bytes += sctp_data_size(tchunk);
1431                         }
1432
1433                         if (TSN_lte(tsn, sack_ctsn)) {
1434                                 /* RFC 2960  6.3.2 Retransmission Timer Rules
1435                                  *
1436                                  * R3) Whenever a SACK is received
1437                                  * that acknowledges the DATA chunk
1438                                  * with the earliest outstanding TSN
1439                                  * for that address, restart T3-rtx
1440                                  * timer for that address with its
1441                                  * current RTO.
1442                                  */
1443                                 restart_timer = 1;
1444
1445                                 if (!tchunk->tsn_gap_acked) {
1446                                         /*
1447                                          * SFR-CACC algorithm:
1448                                          * 2) If the SACK contains gap acks
1449                                          * and the flag CHANGEOVER_ACTIVE is
1450                                          * set the receiver of the SACK MUST
1451                                          * take the following action:
1452                                          *
1453                                          * B) For each TSN t being acked that
1454                                          * has not been acked in any SACK so
1455                                          * far, set cacc_saw_newack to 1 for
1456                                          * the destination that the TSN was
1457                                          * sent to.
1458                                          */
1459                                         if (transport &&
1460                                             sack->num_gap_ack_blocks &&
1461                                             q->asoc->peer.primary_path->cacc.
1462                                             changeover_active)
1463                                                 transport->cacc.cacc_saw_newack
1464                                                         = 1;
1465                                 }
1466
1467                                 list_add_tail(&tchunk->transmitted_list,
1468                                               &q->sacked);
1469                         } else {
1470                                 /* RFC2960 7.2.4, sctpimpguide-05 2.8.2
1471                                  * M2) Each time a SACK arrives reporting
1472                                  * 'Stray DATA chunk(s)' record the highest TSN
1473                                  * reported as newly acknowledged, call this
1474                                  * value 'HighestTSNinSack'. A newly
1475                                  * acknowledged DATA chunk is one not
1476                                  * previously acknowledged in a SACK.
1477                                  *
1478                                  * When the SCTP sender of data receives a SACK
1479                                  * chunk that acknowledges, for the first time,
1480                                  * the receipt of a DATA chunk, all the still
1481                                  * unacknowledged DATA chunks whose TSN is
1482                                  * older than that newly acknowledged DATA
1483                                  * chunk, are qualified as 'Stray DATA chunks'.
1484                                  */
1485                                 list_add_tail(lchunk, &tlist);
1486                         }
1487
1488 #if SCTP_DEBUG
1489                         switch (dbg_prt_state) {
1490                         case 0: /* last TSN was ACKed */
1491                                 if (dbg_last_ack_tsn + 1 == tsn) {
1492                                         /* This TSN belongs to the
1493                                          * current ACK range.
1494                                          */
1495                                         break;
1496                                 }
1497
1498                                 if (dbg_last_ack_tsn != dbg_ack_tsn) {
1499                                         /* Display the end of the
1500                                          * current range.
1501                                          */
1502                                         SCTP_DEBUG_PRINTK_CONT("-%08x",
1503                                                                dbg_last_ack_tsn);
1504                                 }
1505
1506                                 /* Start a new range.  */
1507                                 SCTP_DEBUG_PRINTK_CONT(",%08x", tsn);
1508                                 dbg_ack_tsn = tsn;
1509                                 break;
1510
1511                         case 1: /* The last TSN was NOT ACKed. */
1512                                 if (dbg_last_kept_tsn != dbg_kept_tsn) {
1513                                         /* Display the end of current range. */
1514                                         SCTP_DEBUG_PRINTK_CONT("-%08x",
1515                                                                dbg_last_kept_tsn);
1516                                 }
1517
1518                                 SCTP_DEBUG_PRINTK_CONT("\n");
1519
1520                                 /* FALL THROUGH... */
1521                         default:
1522                                 /* This is the first-ever TSN we examined.  */
1523                                 /* Start a new range of ACK-ed TSNs.  */
1524                                 SCTP_DEBUG_PRINTK("ACKed: %08x", tsn);
1525                                 dbg_prt_state = 0;
1526                                 dbg_ack_tsn = tsn;
1527                         }
1528
1529                         dbg_last_ack_tsn = tsn;
1530 #endif /* SCTP_DEBUG */
1531
1532                 } else {
1533                         if (tchunk->tsn_gap_acked) {
1534                                 SCTP_DEBUG_PRINTK("%s: Receiver reneged on "
1535                                                   "data TSN: 0x%x\n",
1536                                                   __func__,
1537                                                   tsn);
1538                                 tchunk->tsn_gap_acked = 0;
1539
1540                                 if (tchunk->transport)
1541                                         bytes_acked -= sctp_data_size(tchunk);
1542
1543                                 /* RFC 2960 6.3.2 Retransmission Timer Rules
1544                                  *
1545                                  * R4) Whenever a SACK is received missing a
1546                                  * TSN that was previously acknowledged via a
1547                                  * Gap Ack Block, start T3-rtx for the
1548                                  * destination address to which the DATA
1549                                  * chunk was originally
1550                                  * transmitted if it is not already running.
1551                                  */
1552                                 restart_timer = 1;
1553                         }
1554
1555                         list_add_tail(lchunk, &tlist);
1556
1557 #if SCTP_DEBUG
1558                         /* See the above comments on ACK-ed TSNs. */
1559                         switch (dbg_prt_state) {
1560                         case 1:
1561                                 if (dbg_last_kept_tsn + 1 == tsn)
1562                                         break;
1563
1564                                 if (dbg_last_kept_tsn != dbg_kept_tsn)
1565                                         SCTP_DEBUG_PRINTK_CONT("-%08x",
1566                                                                dbg_last_kept_tsn);
1567
1568                                 SCTP_DEBUG_PRINTK_CONT(",%08x", tsn);
1569                                 dbg_kept_tsn = tsn;
1570                                 break;
1571
1572                         case 0:
1573                                 if (dbg_last_ack_tsn != dbg_ack_tsn)
1574                                         SCTP_DEBUG_PRINTK_CONT("-%08x",
1575                                                                dbg_last_ack_tsn);
1576                                 SCTP_DEBUG_PRINTK_CONT("\n");
1577
1578                                 /* FALL THROUGH... */
1579                         default:
1580                                 SCTP_DEBUG_PRINTK("KEPT: %08x",tsn);
1581                                 dbg_prt_state = 1;
1582                                 dbg_kept_tsn = tsn;
1583                         }
1584
1585                         dbg_last_kept_tsn = tsn;
1586 #endif /* SCTP_DEBUG */
1587                 }
1588         }
1589
1590 #if SCTP_DEBUG
1591         /* Finish off the last range, displaying its ending TSN.  */
1592         switch (dbg_prt_state) {
1593         case 0:
1594                 if (dbg_last_ack_tsn != dbg_ack_tsn) {
1595                         SCTP_DEBUG_PRINTK_CONT("-%08x\n", dbg_last_ack_tsn);
1596                 } else {
1597                         SCTP_DEBUG_PRINTK_CONT("\n");
1598                 }
1599         break;
1600
1601         case 1:
1602                 if (dbg_last_kept_tsn != dbg_kept_tsn) {
1603                         SCTP_DEBUG_PRINTK_CONT("-%08x\n", dbg_last_kept_tsn);
1604                 } else {
1605                         SCTP_DEBUG_PRINTK_CONT("\n");
1606                 }
1607         }
1608 #endif /* SCTP_DEBUG */
1609         if (transport) {
1610                 if (bytes_acked) {
1611                         struct sctp_association *asoc = transport->asoc;
1612
1613                         /* We may have counted DATA that was migrated
1614                          * to this transport due to DEL-IP operation.
1615                          * Subtract those bytes, since the were never
1616                          * send on this transport and shouldn't be
1617                          * credited to this transport.
1618                          */
1619                         bytes_acked -= migrate_bytes;
1620
1621                         /* 8.2. When an outstanding TSN is acknowledged,
1622                          * the endpoint shall clear the error counter of
1623                          * the destination transport address to which the
1624                          * DATA chunk was last sent.
1625                          * The association's overall error counter is
1626                          * also cleared.
1627                          */
1628                         transport->error_count = 0;
1629                         transport->asoc->overall_error_count = 0;
1630
1631                         /*
1632                          * While in SHUTDOWN PENDING, we may have started
1633                          * the T5 shutdown guard timer after reaching the
1634                          * retransmission limit. Stop that timer as soon
1635                          * as the receiver acknowledged any data.
1636                          */
1637                         if (asoc->state == SCTP_STATE_SHUTDOWN_PENDING &&
1638                             del_timer(&asoc->timers
1639                                 [SCTP_EVENT_TIMEOUT_T5_SHUTDOWN_GUARD]))
1640                                         sctp_association_put(asoc);
1641
1642                         /* Mark the destination transport address as
1643                          * active if it is not so marked.
1644                          */
1645                         if ((transport->state == SCTP_INACTIVE ||
1646                              transport->state == SCTP_UNCONFIRMED) &&
1647                             sctp_cmp_addr_exact(&transport->ipaddr, saddr)) {
1648                                 sctp_assoc_control_transport(
1649                                         transport->asoc,
1650                                         transport,
1651                                         SCTP_TRANSPORT_UP,
1652                                         SCTP_RECEIVED_SACK);
1653                         }
1654
1655                         sctp_transport_raise_cwnd(transport, sack_ctsn,
1656                                                   bytes_acked);
1657
1658                         transport->flight_size -= bytes_acked;
1659                         if (transport->flight_size == 0)
1660                                 transport->partial_bytes_acked = 0;
1661                         q->outstanding_bytes -= bytes_acked + migrate_bytes;
1662                 } else {
1663                         /* RFC 2960 6.1, sctpimpguide-06 2.15.2
1664                          * When a sender is doing zero window probing, it
1665                          * should not timeout the association if it continues
1666                          * to receive new packets from the receiver. The
1667                          * reason is that the receiver MAY keep its window
1668                          * closed for an indefinite time.
1669                          * A sender is doing zero window probing when the
1670                          * receiver's advertised window is zero, and there is
1671                          * only one data chunk in flight to the receiver.
1672                          *
1673                          * Allow the association to timeout while in SHUTDOWN
1674                          * PENDING or SHUTDOWN RECEIVED in case the receiver
1675                          * stays in zero window mode forever.
1676                          */
1677                         if (!q->asoc->peer.rwnd &&
1678                             !list_empty(&tlist) &&
1679                             (sack_ctsn+2 == q->asoc->next_tsn) &&
1680                             q->asoc->state < SCTP_STATE_SHUTDOWN_PENDING) {
1681                                 SCTP_DEBUG_PRINTK("%s: SACK received for zero "
1682                                                   "window probe: %u\n",
1683                                                   __func__, sack_ctsn);
1684                                 q->asoc->overall_error_count = 0;
1685                                 transport->error_count = 0;
1686                         }
1687                 }
1688
1689                 /* RFC 2960 6.3.2 Retransmission Timer Rules
1690                  *
1691                  * R2) Whenever all outstanding data sent to an address have
1692                  * been acknowledged, turn off the T3-rtx timer of that
1693                  * address.
1694                  */
1695                 if (!transport->flight_size) {
1696                         if (del_timer(&transport->T3_rtx_timer))
1697                                 sctp_transport_put(transport);
1698                 } else if (restart_timer) {
1699                         if (!mod_timer(&transport->T3_rtx_timer,
1700                                        jiffies + transport->rto))
1701                                 sctp_transport_hold(transport);
1702                 }
1703         }
1704
1705         list_splice(&tlist, transmitted_queue);
1706 }
1707
1708 /* Mark chunks as missing and consequently may get retransmitted. */
1709 static void sctp_mark_missing(struct sctp_outq *q,
1710                               struct list_head *transmitted_queue,
1711                               struct sctp_transport *transport,
1712                               __u32 highest_new_tsn_in_sack,
1713                               int count_of_newacks)
1714 {
1715         struct sctp_chunk *chunk;
1716         __u32 tsn;
1717         char do_fast_retransmit = 0;
1718         struct sctp_association *asoc = q->asoc;
1719         struct sctp_transport *primary = asoc->peer.primary_path;
1720
1721         list_for_each_entry(chunk, transmitted_queue, transmitted_list) {
1722
1723                 tsn = ntohl(chunk->subh.data_hdr->tsn);
1724
1725                 /* RFC 2960 7.2.4, sctpimpguide-05 2.8.2 M3) Examine all
1726                  * 'Unacknowledged TSN's', if the TSN number of an
1727                  * 'Unacknowledged TSN' is smaller than the 'HighestTSNinSack'
1728                  * value, increment the 'TSN.Missing.Report' count on that
1729                  * chunk if it has NOT been fast retransmitted or marked for
1730                  * fast retransmit already.
1731                  */
1732                 if (chunk->fast_retransmit == SCTP_CAN_FRTX &&
1733                     !chunk->tsn_gap_acked &&
1734                     TSN_lt(tsn, highest_new_tsn_in_sack)) {
1735
1736                         /* SFR-CACC may require us to skip marking
1737                          * this chunk as missing.
1738                          */
1739                         if (!transport || !sctp_cacc_skip(primary,
1740                                                 chunk->transport,
1741                                                 count_of_newacks, tsn)) {
1742                                 chunk->tsn_missing_report++;
1743
1744                                 SCTP_DEBUG_PRINTK(
1745                                         "%s: TSN 0x%x missing counter: %d\n",
1746                                         __func__, tsn,
1747                                         chunk->tsn_missing_report);
1748                         }
1749                 }
1750                 /*
1751                  * M4) If any DATA chunk is found to have a
1752                  * 'TSN.Missing.Report'
1753                  * value larger than or equal to 3, mark that chunk for
1754                  * retransmission and start the fast retransmit procedure.
1755                  */
1756
1757                 if (chunk->tsn_missing_report >= 3) {
1758                         chunk->fast_retransmit = SCTP_NEED_FRTX;
1759                         do_fast_retransmit = 1;
1760                 }
1761         }
1762
1763         if (transport) {
1764                 if (do_fast_retransmit)
1765                         sctp_retransmit(q, transport, SCTP_RTXR_FAST_RTX);
1766
1767                 SCTP_DEBUG_PRINTK("%s: transport: %p, cwnd: %d, "
1768                                   "ssthresh: %d, flight_size: %d, pba: %d\n",
1769                                   __func__, transport, transport->cwnd,
1770                                   transport->ssthresh, transport->flight_size,
1771                                   transport->partial_bytes_acked);
1772         }
1773 }
1774
1775 /* Is the given TSN acked by this packet?  */
1776 static int sctp_acked(struct sctp_sackhdr *sack, __u32 tsn)
1777 {
1778         int i;
1779         sctp_sack_variable_t *frags;
1780         __u16 gap;
1781         __u32 ctsn = ntohl(sack->cum_tsn_ack);
1782
1783         if (TSN_lte(tsn, ctsn))
1784                 goto pass;
1785
1786         /* 3.3.4 Selective Acknowledgement (SACK) (3):
1787          *
1788          * Gap Ack Blocks:
1789          *  These fields contain the Gap Ack Blocks. They are repeated
1790          *  for each Gap Ack Block up to the number of Gap Ack Blocks
1791          *  defined in the Number of Gap Ack Blocks field. All DATA
1792          *  chunks with TSNs greater than or equal to (Cumulative TSN
1793          *  Ack + Gap Ack Block Start) and less than or equal to
1794          *  (Cumulative TSN Ack + Gap Ack Block End) of each Gap Ack
1795          *  Block are assumed to have been received correctly.
1796          */
1797
1798         frags = sack->variable;
1799         gap = tsn - ctsn;
1800         for (i = 0; i < ntohs(sack->num_gap_ack_blocks); ++i) {
1801                 if (TSN_lte(ntohs(frags[i].gab.start), gap) &&
1802                     TSN_lte(gap, ntohs(frags[i].gab.end)))
1803                         goto pass;
1804         }
1805
1806         return 0;
1807 pass:
1808         return 1;
1809 }
1810
1811 static inline int sctp_get_skip_pos(struct sctp_fwdtsn_skip *skiplist,
1812                                     int nskips, __be16 stream)
1813 {
1814         int i;
1815
1816         for (i = 0; i < nskips; i++) {
1817                 if (skiplist[i].stream == stream)
1818                         return i;
1819         }
1820         return i;
1821 }
1822
1823 /* Create and add a fwdtsn chunk to the outq's control queue if needed. */
1824 static void sctp_generate_fwdtsn(struct sctp_outq *q, __u32 ctsn)
1825 {
1826         struct sctp_association *asoc = q->asoc;
1827         struct sctp_chunk *ftsn_chunk = NULL;
1828         struct sctp_fwdtsn_skip ftsn_skip_arr[10];
1829         int nskips = 0;
1830         int skip_pos = 0;
1831         __u32 tsn;
1832         struct sctp_chunk *chunk;
1833         struct list_head *lchunk, *temp;
1834
1835         if (!asoc->peer.prsctp_capable)
1836                 return;
1837
1838         /* PR-SCTP C1) Let SackCumAck be the Cumulative TSN ACK carried in the
1839          * received SACK.
1840          *
1841          * If (Advanced.Peer.Ack.Point < SackCumAck), then update
1842          * Advanced.Peer.Ack.Point to be equal to SackCumAck.
1843          */
1844         if (TSN_lt(asoc->adv_peer_ack_point, ctsn))
1845                 asoc->adv_peer_ack_point = ctsn;
1846
1847         /* PR-SCTP C2) Try to further advance the "Advanced.Peer.Ack.Point"
1848          * locally, that is, to move "Advanced.Peer.Ack.Point" up as long as
1849          * the chunk next in the out-queue space is marked as "abandoned" as
1850          * shown in the following example:
1851          *
1852          * Assuming that a SACK arrived with the Cumulative TSN ACK 102
1853          * and the Advanced.Peer.Ack.Point is updated to this value:
1854          *
1855          *   out-queue at the end of  ==>   out-queue after Adv.Ack.Point
1856          *   normal SACK processing           local advancement
1857          *                ...                           ...
1858          *   Adv.Ack.Pt-> 102 acked                     102 acked
1859          *                103 abandoned                 103 abandoned
1860          *                104 abandoned     Adv.Ack.P-> 104 abandoned
1861          *                105                           105
1862          *                106 acked                     106 acked
1863          *                ...                           ...
1864          *
1865          * In this example, the data sender successfully advanced the
1866          * "Advanced.Peer.Ack.Point" from 102 to 104 locally.
1867          */
1868         list_for_each_safe(lchunk, temp, &q->abandoned) {
1869                 chunk = list_entry(lchunk, struct sctp_chunk,
1870                                         transmitted_list);
1871                 tsn = ntohl(chunk->subh.data_hdr->tsn);
1872
1873                 /* Remove any chunks in the abandoned queue that are acked by
1874                  * the ctsn.
1875                  */
1876                 if (TSN_lte(tsn, ctsn)) {
1877                         list_del_init(lchunk);
1878                         sctp_chunk_free(chunk);
1879                 } else {
1880                         if (TSN_lte(tsn, asoc->adv_peer_ack_point+1)) {
1881                                 asoc->adv_peer_ack_point = tsn;
1882                                 if (chunk->chunk_hdr->flags &
1883                                          SCTP_DATA_UNORDERED)
1884                                         continue;
1885                                 skip_pos = sctp_get_skip_pos(&ftsn_skip_arr[0],
1886                                                 nskips,
1887                                                 chunk->subh.data_hdr->stream);
1888                                 ftsn_skip_arr[skip_pos].stream =
1889                                         chunk->subh.data_hdr->stream;
1890                                 ftsn_skip_arr[skip_pos].ssn =
1891                                          chunk->subh.data_hdr->ssn;
1892                                 if (skip_pos == nskips)
1893                                         nskips++;
1894                                 if (nskips == 10)
1895                                         break;
1896                         } else
1897                                 break;
1898                 }
1899         }
1900
1901         /* PR-SCTP C3) If, after step C1 and C2, the "Advanced.Peer.Ack.Point"
1902          * is greater than the Cumulative TSN ACK carried in the received
1903          * SACK, the data sender MUST send the data receiver a FORWARD TSN
1904          * chunk containing the latest value of the
1905          * "Advanced.Peer.Ack.Point".
1906          *
1907          * C4) For each "abandoned" TSN the sender of the FORWARD TSN SHOULD
1908          * list each stream and sequence number in the forwarded TSN. This
1909          * information will enable the receiver to easily find any
1910          * stranded TSN's waiting on stream reorder queues. Each stream
1911          * SHOULD only be reported once; this means that if multiple
1912          * abandoned messages occur in the same stream then only the
1913          * highest abandoned stream sequence number is reported. If the
1914          * total size of the FORWARD TSN does NOT fit in a single MTU then
1915          * the sender of the FORWARD TSN SHOULD lower the
1916          * Advanced.Peer.Ack.Point to the last TSN that will fit in a
1917          * single MTU.
1918          */
1919         if (asoc->adv_peer_ack_point > ctsn)
1920                 ftsn_chunk = sctp_make_fwdtsn(asoc, asoc->adv_peer_ack_point,
1921                                               nskips, &ftsn_skip_arr[0]);
1922
1923         if (ftsn_chunk) {
1924                 list_add_tail(&ftsn_chunk->list, &q->control_chunk_list);
1925                 SCTP_INC_STATS(sock_net(asoc->base.sk), SCTP_MIB_OUTCTRLCHUNKS);
1926         }
1927 }