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
 221         q->malloced = 0;
 222         q->out_qlen = 0;
 223 }
 224
 225 /* Free the outqueue structure and any related pending chunks.
 226  */
 227 void sctp_outq_teardown(struct sctp_outq *q)
 228 {
 229         struct sctp_transport *transport;
 230         struct list_head *lchunk, *temp;
 231         struct sctp_chunk *chunk, *tmp;
 232
 233         /* Throw away unacknowledged chunks. */
 234         list_for_each_entry(transport, &q->asoc->peer.transport_addr_list,
 235                         transports) {
 236                 while ((lchunk = sctp_list_dequeue(&transport->transmitted)) != NULL) {
 237                         chunk = list_entry(lchunk, struct sctp_chunk,
 238                                            transmitted_list);
 239                         /* Mark as part of a failed message. */
 240                         sctp_chunk_fail(chunk, q->error);
 241                         sctp_chunk_free(chunk);
 242                 }
 243         }
 244
 245         /* Throw away chunks that have been gap ACKed.  */
 246         list_for_each_safe(lchunk, temp, &q->sacked) {
 247                 list_del_init(lchunk);
 248                 chunk = list_entry(lchunk, struct sctp_chunk,
 249                                    transmitted_list);
 250                 sctp_chunk_fail(chunk, q->error);
 251                 sctp_chunk_free(chunk);
 252         }
 253
 254         /* Throw away any chunks in the retransmit queue. */
 255         list_for_each_safe(lchunk, temp, &q->retransmit) {
 256                 list_del_init(lchunk);
 257                 chunk = list_entry(lchunk, struct sctp_chunk,
 258                                    transmitted_list);
 259                 sctp_chunk_fail(chunk, q->error);
 260                 sctp_chunk_free(chunk);
 261         }
 262
 263         /* Throw away any chunks that are in the abandoned queue. */
 264         list_for_each_safe(lchunk, temp, &q->abandoned) {
 265                 list_del_init(lchunk);
 266                 chunk = list_entry(lchunk, struct sctp_chunk,
 267                                    transmitted_list);
 268                 sctp_chunk_fail(chunk, q->error);
 269                 sctp_chunk_free(chunk);
 270         }
 271
 272         /* Throw away any leftover data chunks. */
 273         while ((chunk = sctp_outq_dequeue_data(q)) != NULL) {
 274
 275                 /* Mark as send failure. */
 276                 sctp_chunk_fail(chunk, q->error);
 277                 sctp_chunk_free(chunk);
 278         }
 279
 280         q->error = 0;
 281
 282         /* Throw away any leftover control chunks. */
 283         list_for_each_entry_safe(chunk, tmp, &q->control_chunk_list, list) {
 284                 list_del_init(&chunk->list);
 285                 sctp_chunk_free(chunk);
 286         }
 287 }
 288
 289 /* Free the outqueue structure and any related pending chunks.  */
 290 void sctp_outq_free(struct sctp_outq *q)
 291 {
 292         /* Throw away leftover chunks. */
 293         sctp_outq_teardown(q);
 294
 295         /* If we were kmalloc()'d, free the memory.  */
 296         if (q->malloced)
 297                 kfree(q);
 298 }
 299
 300 /* Put a new chunk in an sctp_outq.  */
 301 int sctp_outq_tail(struct sctp_outq *q, struct sctp_chunk *chunk)
 302 {
 303         struct net *net = sock_net(q->asoc->base.sk);
 304         int error = 0;
 305
 306         SCTP_DEBUG_PRINTK("sctp_outq_tail(%p, %p[%s])\n",
 307                           q, chunk, chunk && chunk->chunk_hdr ?
 308                           sctp_cname(SCTP_ST_CHUNK(chunk->chunk_hdr->type))
 309                           : "Illegal Chunk");
 310
 311         /* If it is data, queue it up, otherwise, send it
 312          * immediately.
 313          */
 314         if (sctp_chunk_is_data(chunk)) {
 315                 /* Is it OK to queue data chunks?  */
 316                 /* From 9. Termination of Association
 317                  *
 318                  * When either endpoint performs a shutdown, the
 319                  * association on each peer will stop accepting new
 320                  * data from its user and only deliver data in queue
 321                  * at the time of sending or receiving the SHUTDOWN
 322                  * chunk.
 323                  */
 324                 switch (q->asoc->state) {
 325                 case SCTP_STATE_CLOSED:
 326                 case SCTP_STATE_SHUTDOWN_PENDING:
 327                 case SCTP_STATE_SHUTDOWN_SENT:
 328                 case SCTP_STATE_SHUTDOWN_RECEIVED:
 329                 case SCTP_STATE_SHUTDOWN_ACK_SENT:
 330                         /* Cannot send after transport endpoint shutdown */
 331                         error = -ESHUTDOWN;
 332                         break;
 333
 334                 default:
 335                         SCTP_DEBUG_PRINTK("outqueueing (%p, %p[%s])\n",
 336                           q, chunk, chunk && chunk->chunk_hdr ?
 337                           sctp_cname(SCTP_ST_CHUNK(chunk->chunk_hdr->type))
 338                           : "Illegal Chunk");
 339
 340                         sctp_outq_tail_data(q, chunk);
 341                         if (chunk->chunk_hdr->flags & SCTP_DATA_UNORDERED)
 342                                 SCTP_INC_STATS(net, SCTP_MIB_OUTUNORDERCHUNKS);
 343                         else
 344                                 SCTP_INC_STATS(net, SCTP_MIB_OUTORDERCHUNKS);
 345                         q->empty = 0;
 346                         break;
 347                 }
 348         } else {
 349                 list_add_tail(&chunk->list, &q->control_chunk_list);
 350                 SCTP_INC_STATS(net, SCTP_MIB_OUTCTRLCHUNKS);
 351         }
 352
 353         if (error < 0)
 354                 return error;
 355
 356         if (!q->cork)
 357                 error = sctp_outq_flush(q, 0);
 358
 359         return error;
 360 }
 361
 362 /* Insert a chunk into the sorted list based on the TSNs.  The retransmit list
 363  * and the abandoned list are in ascending order.
 364  */
 365 static void sctp_insert_list(struct list_head *head, struct list_head *new)
 366 {
 367         struct list_head *pos;
 368         struct sctp_chunk *nchunk, *lchunk;
 369         __u32 ntsn, ltsn;
 370         int done = 0;
 371
 372         nchunk = list_entry(new, struct sctp_chunk, transmitted_list);
 373         ntsn = ntohl(nchunk->subh.data_hdr->tsn);
 374
 375         list_for_each(pos, head) {
 376                 lchunk = list_entry(pos, struct sctp_chunk, transmitted_list);
 377                 ltsn = ntohl(lchunk->subh.data_hdr->tsn);
 378                 if (TSN_lt(ntsn, ltsn)) {
 379                         list_add(new, pos->prev);
 380                         done = 1;
 381                         break;
 382                 }
 383         }
 384         if (!done)
 385                 list_add_tail(new, head);
 386 }
 387
 388 /* Mark all the eligible packets on a transport for retransmission.  */
 389 void sctp_retransmit_mark(struct sctp_outq *q,
 390                           struct sctp_transport *transport,
 391                           __u8 reason)
 392 {
 393         struct list_head *lchunk, *ltemp;
 394         struct sctp_chunk *chunk;
 395
 396         /* Walk through the specified transmitted queue.  */
 397         list_for_each_safe(lchunk, ltemp, &transport->transmitted) {
 398                 chunk = list_entry(lchunk, struct sctp_chunk,
 399                                    transmitted_list);
 400
 401                 /* If the chunk is abandoned, move it to abandoned list. */
 402                 if (sctp_chunk_abandoned(chunk)) {
 403                         list_del_init(lchunk);
 404                         sctp_insert_list(&q->abandoned, lchunk);
 405
 406                         /* If this chunk has not been previousely acked,
 407                          * stop considering it 'outstanding'.  Our peer
 408                          * will most likely never see it since it will
 409                          * not be retransmitted
 410                          */
 411                         if (!chunk->tsn_gap_acked) {
 412                                 if (chunk->transport)
 413                                         chunk->transport->flight_size -=
 414                                                         sctp_data_size(chunk);
 415                                 q->outstanding_bytes -= sctp_data_size(chunk);
 416                                 q->asoc->peer.rwnd += sctp_data_size(chunk);
 417                         }
 418                         continue;
 419                 }
 420
 421                 /* If we are doing  retransmission due to a timeout or pmtu
 422                  * discovery, only the  chunks that are not yet acked should
 423                  * be added to the retransmit queue.
 424                  */
 425                 if ((reason == SCTP_RTXR_FAST_RTX  &&
 426                             (chunk->fast_retransmit == SCTP_NEED_FRTX)) ||
 427                     (reason != SCTP_RTXR_FAST_RTX  && !chunk->tsn_gap_acked)) {
 428                         /* RFC 2960 6.2.1 Processing a Received SACK
 429                          *
 430                          * C) Any time a DATA chunk is marked for
 431                          * retransmission (via either T3-rtx timer expiration
 432                          * (Section 6.3.3) or via fast retransmit
 433                          * (Section 7.2.4)), add the data size of those
 434                          * chunks to the rwnd.
 435                          */
 436                         q->asoc->peer.rwnd += sctp_data_size(chunk);
 437                         q->outstanding_bytes -= sctp_data_size(chunk);
 438                         if (chunk->transport)
 439                                 transport->flight_size -= sctp_data_size(chunk);
 440
 441                         /* sctpimpguide-05 Section 2.8.2
 442                          * M5) If a T3-rtx timer expires, the
 443                          * 'TSN.Missing.Report' of all affected TSNs is set
 444                          * to 0.
 445                          */
 446                         chunk->tsn_missing_report = 0;
 447
 448                         /* If a chunk that is being used for RTT measurement
 449                          * has to be retransmitted, we cannot use this chunk
 450                          * anymore for RTT measurements. Reset rto_pending so
 451                          * that a new RTT measurement is started when a new
 452                          * data chunk is sent.
 453                          */
 454                         if (chunk->rtt_in_progress) {
 455                                 chunk->rtt_in_progress = 0;
 456                                 transport->rto_pending = 0;
 457                         }
 458
 459                         /* Move the chunk to the retransmit queue. The chunks
 460                          * on the retransmit queue are always kept in order.
 461                          */
 462                         list_del_init(lchunk);
 463                         sctp_insert_list(&q->retransmit, lchunk);
 464                 }
 465         }
 466
 467         SCTP_DEBUG_PRINTK("%s: transport: %p, reason: %d, "
 468                           "cwnd: %d, ssthresh: %d, flight_size: %d, "
 469                           "pba: %d\n", __func__,
 470                           transport, reason,
 471                           transport->cwnd, transport->ssthresh,
 472                           transport->flight_size,
 473                           transport->partial_bytes_acked);
 474
 475 }
 476
 477 /* Mark all the eligible packets on a transport for retransmission and force
 478  * one packet out.
 479  */
 480 void sctp_retransmit(struct sctp_outq *q, struct sctp_transport *transport,
 481                      sctp_retransmit_reason_t reason)
 482 {
 483         struct net *net = sock_net(q->asoc->base.sk);
 484         int error = 0;
 485
 486         switch(reason) {
 487         case SCTP_RTXR_T3_RTX:
 488                 SCTP_INC_STATS(net, SCTP_MIB_T3_RETRANSMITS);
 489                 sctp_transport_lower_cwnd(transport, SCTP_LOWER_CWND_T3_RTX);
 490                 /* Update the retran path if the T3-rtx timer has expired for
 491                  * the current retran path.
 492                  */
 493                 if (transport == transport->asoc->peer.retran_path)
 494                         sctp_assoc_update_retran_path(transport->asoc);
 495                 transport->asoc->rtx_data_chunks +=
 496                         transport->asoc->unack_data;
 497                 break;
 498         case SCTP_RTXR_FAST_RTX:
 499                 SCTP_INC_STATS(net, SCTP_MIB_FAST_RETRANSMITS);
 500                 sctp_transport_lower_cwnd(transport, SCTP_LOWER_CWND_FAST_RTX);
 501                 q->fast_rtx = 1;
 502                 break;
 503         case SCTP_RTXR_PMTUD:
 504                 SCTP_INC_STATS(net, SCTP_MIB_PMTUD_RETRANSMITS);
 505                 break;
 506         case SCTP_RTXR_T1_RTX:
 507                 SCTP_INC_STATS(net, SCTP_MIB_T1_RETRANSMITS);
 508                 transport->asoc->init_retries++;
 509                 break;
 510         default:
 511                 BUG();
 512         }
 513
 514         sctp_retransmit_mark(q, transport, reason);
 515
 516         /* PR-SCTP A5) Any time the T3-rtx timer expires, on any destination,
 517          * the sender SHOULD try to advance the "Advanced.Peer.Ack.Point" by
 518          * following the procedures outlined in C1 - C5.
 519          */
 520         if (reason == SCTP_RTXR_T3_RTX)
 521                 sctp_generate_fwdtsn(q, q->asoc->ctsn_ack_point);
 522
 523         /* Flush the queues only on timeout, since fast_rtx is only
 524          * triggered during sack processing and the queue
 525          * will be flushed at the end.
 526          */
 527         if (reason != SCTP_RTXR_FAST_RTX)
 528                 error = sctp_outq_flush(q, /* rtx_timeout */ 1);
 529
 530         if (error)
 531                 q->asoc->base.sk->sk_err = -error;
 532 }
 533
 534 /*
 535  * Transmit DATA chunks on the retransmit queue.  Upon return from
 536  * sctp_outq_flush_rtx() the packet 'pkt' may contain chunks which
 537  * need to be transmitted by the caller.
 538  * We assume that pkt->transport has already been set.
 539  *
 540  * The return value is a normal kernel error return value.
 541  */
 542 static int sctp_outq_flush_rtx(struct sctp_outq *q, struct sctp_packet *pkt,
 543                                int rtx_timeout, int *start_timer)
 544 {
 545         struct list_head *lqueue;
 546         struct sctp_transport *transport = pkt->transport;
 547         sctp_xmit_t status;
 548         struct sctp_chunk *chunk, *chunk1;
 549         int fast_rtx;
 550         int error = 0;
 551         int timer = 0;
 552         int done = 0;
 553
 554         lqueue = &q->retransmit;
 555         fast_rtx = q->fast_rtx;
 556
 557         /* This loop handles time-out retransmissions, fast retransmissions,
 558          * and retransmissions due to opening of whindow.
 559          *
 560          * RFC 2960 6.3.3 Handle T3-rtx Expiration
 561          *
 562          * E3) Determine how many of the earliest (i.e., lowest TSN)
 563          * outstanding DATA chunks for the address for which the
 564          * T3-rtx has expired will fit into a single packet, subject
 565          * to the MTU constraint for the path corresponding to the
 566          * destination transport address to which the retransmission
 567          * is being sent (this may be different from the address for
 568          * which the timer expires [see Section 6.4]). Call this value
 569          * K. Bundle and retransmit those K DATA chunks in a single
 570          * packet to the destination endpoint.
 571          *
 572          * [Just to be painfully clear, if we are retransmitting
 573          * because a timeout just happened, we should send only ONE
 574          * packet of retransmitted data.]
 575          *
 576          * For fast retransmissions we also send only ONE packet.  However,
 577          * if we are just flushing the queue due to open window, we'll
 578          * try to send as much as possible.
 579          */
 580         list_for_each_entry_safe(chunk, chunk1, lqueue, transmitted_list) {
 581                 /* If the chunk is abandoned, move it to abandoned list. */
 582                 if (sctp_chunk_abandoned(chunk)) {
 583                         list_del_init(&chunk->transmitted_list);
 584                         sctp_insert_list(&q->abandoned,
 585                                          &chunk->transmitted_list);
 586                         continue;
 587                 }
 588
 589                 /* Make sure that Gap Acked TSNs are not retransmitted.  A
 590                  * simple approach is just to move such TSNs out of the
 591                  * way and into a 'transmitted' queue and skip to the
 592                  * next chunk.
 593                  */
 594                 if (chunk->tsn_gap_acked) {
 595                         list_move_tail(&chunk->transmitted_list,
 596                                        &transport->transmitted);
 597                         continue;
 598                 }
 599
 600                 /* If we are doing fast retransmit, ignore non-fast_rtransmit
 601                  * chunks
 602                  */
 603                 if (fast_rtx && !chunk->fast_retransmit)
 604                         continue;
 605
 606 redo:
 607                 /* Attempt to append this chunk to the packet. */
 608                 status = sctp_packet_append_chunk(pkt, chunk);
 609
 610                 switch (status) {
 611                 case SCTP_XMIT_PMTU_FULL:
 612                         if (!pkt->has_data && !pkt->has_cookie_echo) {
 613                                 /* If this packet did not contain DATA then
 614                                  * retransmission did not happen, so do it
 615                                  * again.  We'll ignore the error here since
 616                                  * control chunks are already freed so there
 617                                  * is nothing we can do.
 618                                  */
 619                                 sctp_packet_transmit(pkt);
 620                                 goto redo;
 621                         }
 622
 623                         /* Send this packet.  */
 624                         error = sctp_packet_transmit(pkt);
 625
 626                         /* If we are retransmitting, we should only
 627                          * send a single packet.
 628                          * Otherwise, try appending this chunk again.
 629                          */
 630                         if (rtx_timeout || fast_rtx)
 631                                 done = 1;
 632                         else
 633                                 goto redo;
 634
 635                         /* Bundle next chunk in the next round.  */
 636                         break;
 637
 638                 case SCTP_XMIT_RWND_FULL:
 639                         /* Send this packet. */
 640                         error = sctp_packet_transmit(pkt);
 641
 642                         /* Stop sending DATA as there is no more room
 643                          * at the receiver.
 644                          */
 645                         done = 1;
 646                         break;
 647
 648                 case SCTP_XMIT_NAGLE_DELAY:
 649                         /* Send this packet. */
 650                         error = sctp_packet_transmit(pkt);
 651
 652                         /* Stop sending DATA because of nagle delay. */
 653                         done = 1;
 654                         break;
 655
 656                 default:
 657                         /* The append was successful, so add this chunk to
 658                          * the transmitted list.
 659                          */
 660                         list_move_tail(&chunk->transmitted_list,
 661                                        &transport->transmitted);
 662
 663                         /* Mark the chunk as ineligible for fast retransmit
 664                          * after it is retransmitted.
 665                          */
 666                         if (chunk->fast_retransmit == SCTP_NEED_FRTX)
 667                                 chunk->fast_retransmit = SCTP_DONT_FRTX;
 668
 669                         q->empty = 0;
 670                         q->asoc->stats.rtxchunks++;
 671                         break;
 672                 }
 673
 674                 /* Set the timer if there were no errors */
 675                 if (!error && !timer)
 676                         timer = 1;
 677
 678                 if (done)
 679                         break;
 680         }
 681
 682         /* If we are here due to a retransmit timeout or a fast
 683          * retransmit and if there are any chunks left in the retransmit
 684          * queue that could not fit in the PMTU sized packet, they need
 685          * to be marked as ineligible for a subsequent fast retransmit.
 686          */
 687         if (rtx_timeout || fast_rtx) {
 688                 list_for_each_entry(chunk1, lqueue, transmitted_list) {
 689                         if (chunk1->fast_retransmit == SCTP_NEED_FRTX)
 690                                 chunk1->fast_retransmit = SCTP_DONT_FRTX;
 691                 }
 692         }
 693
 694         *start_timer = timer;
 695
 696         /* Clear fast retransmit hint */
 697         if (fast_rtx)
 698                 q->fast_rtx = 0;
 699
 700         return error;
 701 }
 702
 703 /* Cork the outqueue so queued chunks are really queued. */
 704 int sctp_outq_uncork(struct sctp_outq *q)
 705 {
 706         int error = 0;
 707         if (q->cork)
 708                 q->cork = 0;
 709         error = sctp_outq_flush(q, 0);
 710         return error;
 711 }
 712
 713
 714 /*
 715  * Try to flush an outqueue.
 716  *
 717  * Description: Send everything in q which we legally can, subject to
 718  * congestion limitations.
 719  * * Note: This function can be called from multiple contexts so appropriate
 720  * locking concerns must be made.  Today we use the sock lock to protect
 721  * this function.
 722  */
 723 static int sctp_outq_flush(struct sctp_outq *q, int rtx_timeout)
 724 {
 725         struct sctp_packet *packet;
 726         struct sctp_packet singleton;
 727         struct sctp_association *asoc = q->asoc;
 728         __u16 sport = asoc->base.bind_addr.port;
 729         __u16 dport = asoc->peer.port;
 730         __u32 vtag = asoc->peer.i.init_tag;
 731         struct sctp_transport *transport = NULL;
 732         struct sctp_transport *new_transport;
 733         struct sctp_chunk *chunk, *tmp;
 734         sctp_xmit_t status;
 735         int error = 0;
 736         int start_timer = 0;
 737         int one_packet = 0;
 738
 739         /* These transports have chunks to send. */
 740         struct list_head transport_list;
 741         struct list_head *ltransport;
 742
 743         INIT_LIST_HEAD(&transport_list);
 744         packet = NULL;
 745
 746         /*
 747          * 6.10 Bundling
 748          *   ...
 749          *   When bundling control chunks with DATA chunks, an
 750          *   endpoint MUST place control chunks first in the outbound
 751          *   SCTP packet.  The transmitter MUST transmit DATA chunks
 752          *   within a SCTP packet in increasing order of TSN.
 753          *   ...
 754          */
 755
 756         list_for_each_entry_safe(chunk, tmp, &q->control_chunk_list, list) {
 757                 /* RFC 5061, 5.3
 758                  * F1) This means that until such time as the ASCONF
 759                  * containing the add is acknowledged, the sender MUST
 760                  * NOT use the new IP address as a source for ANY SCTP
 761                  * packet except on carrying an ASCONF Chunk.
 762                  */
 763                 if (asoc->src_out_of_asoc_ok &&
 764                     chunk->chunk_hdr->type != SCTP_CID_ASCONF)
 765                         continue;
 766
 767                 list_del_init(&chunk->list);
 768
 769                 /* Pick the right transport to use. */
 770                 new_transport = chunk->transport;
 771
 772                 if (!new_transport) {
 773                         /*
 774                          * If we have a prior transport pointer, see if
 775                          * the destination address of the chunk
 776                          * matches the destination address of the
 777                          * current transport.  If not a match, then
 778                          * try to look up the transport with a given
 779                          * destination address.  We do this because
 780                          * after processing ASCONFs, we may have new
 781                          * transports created.
 782                          */
 783                         if (transport &&
 784                             sctp_cmp_addr_exact(&chunk->dest,
 785                                                 &transport->ipaddr))
 786                                         new_transport = transport;
 787                         else
 788                                 new_transport = sctp_assoc_lookup_paddr(asoc,
 789                                                                 &chunk->dest);
 790
 791                         /* if we still don't have a new transport, then
 792                          * use the current active path.
 793                          */
 794                         if (!new_transport)
 795                                 new_transport = asoc->peer.active_path;
 796                 } else if ((new_transport->state == SCTP_INACTIVE) ||
 797                            (new_transport->state == SCTP_UNCONFIRMED) ||
 798                            (new_transport->state == SCTP_PF)) {
 799                         /* If the chunk is Heartbeat or Heartbeat Ack,
 800                          * send it to chunk->transport, even if it's
 801                          * inactive.
 802                          *
 803                          * 3.3.6 Heartbeat Acknowledgement:
 804                          * ...
 805                          * A HEARTBEAT ACK is always sent to the source IP
 806                          * address of the IP datagram containing the
 807                          * HEARTBEAT chunk to which this ack is responding.
 808                          * ...
 809                          *
 810                          * ASCONF_ACKs also must be sent to the source.
 811                          */
 812                         if (chunk->chunk_hdr->type != SCTP_CID_HEARTBEAT &&
 813                             chunk->chunk_hdr->type != SCTP_CID_HEARTBEAT_ACK &&
 814                             chunk->chunk_hdr->type != SCTP_CID_ASCONF_ACK)
 815                                 new_transport = asoc->peer.active_path;
 816                 }
 817
 818                 /* Are we switching transports?
 819                  * Take care of transport locks.
 820                  */
 821                 if (new_transport != transport) {
 822                         transport = new_transport;
 823                         if (list_empty(&transport->send_ready)) {
 824                                 list_add_tail(&transport->send_ready,
 825                                               &transport_list);
 826                         }
 827                         packet = &transport->packet;
 828                         sctp_packet_config(packet, vtag,
 829                                            asoc->peer.ecn_capable);
 830                 }
 831
 832                 switch (chunk->chunk_hdr->type) {
 833                 /*
 834                  * 6.10 Bundling
 835                  *   ...
 836                  *   An endpoint MUST NOT bundle INIT, INIT ACK or SHUTDOWN
 837                  *   COMPLETE with any other chunks.  [Send them immediately.]
 838                  */
 839                 case SCTP_CID_INIT:
 840                 case SCTP_CID_INIT_ACK:
 841                 case SCTP_CID_SHUTDOWN_COMPLETE:
 842                         sctp_packet_init(&singleton, transport, sport, dport);
 843                         sctp_packet_config(&singleton, vtag, 0);
 844                         sctp_packet_append_chunk(&singleton, chunk);
 845                         error = sctp_packet_transmit(&singleton);
 846                         if (error < 0)
 847                                 return error;
 848                         break;
 849
 850                 case SCTP_CID_ABORT:
 851                         if (sctp_test_T_bit(chunk)) {
 852                                 packet->vtag = asoc->c.my_vtag;
 853                         }
 854                 /* The following chunks are "response" chunks, i.e.
 855                  * they are generated in response to something we
 856                  * received.  If we are sending these, then we can
 857                  * send only 1 packet containing these chunks.
 858                  */
 859                 case SCTP_CID_HEARTBEAT_ACK:
 860                 case SCTP_CID_SHUTDOWN_ACK:
 861                 case SCTP_CID_COOKIE_ACK:
 862                 case SCTP_CID_COOKIE_ECHO:
 863                 case SCTP_CID_ERROR:
 864                 case SCTP_CID_ECN_CWR:
 865                 case SCTP_CID_ASCONF_ACK:
 866                         one_packet = 1;
 867                         /* Fall through */
 868
 869                 case SCTP_CID_SACK:
 870                 case SCTP_CID_HEARTBEAT:
 871                 case SCTP_CID_SHUTDOWN:
 872                 case SCTP_CID_ECN_ECNE:
 873                 case SCTP_CID_ASCONF:
 874                 case SCTP_CID_FWD_TSN:
 875                         status = sctp_packet_transmit_chunk(packet, chunk,
 876                                                             one_packet);
 877                         if (status  != SCTP_XMIT_OK) {
 878                                 /* put the chunk back */
 879                                 list_add(&chunk->list, &q->control_chunk_list);
 880                         } else {
 881                                 asoc->stats.octrlchunks++;
 882                                 /* PR-SCTP C5) If a FORWARD TSN is sent, the
 883                                  * sender MUST assure that at least one T3-rtx
 884                                  * timer is running.
 885                                  */
 886                                 if (chunk->chunk_hdr->type == SCTP_CID_FWD_TSN)
 887                                         sctp_transport_reset_timers(transport);
 888                         }
 889                         break;
 890
 891                 default:
 892                         /* We built a chunk with an illegal type! */
 893                         BUG();
 894                 }
 895         }
 896
 897         if (q->asoc->src_out_of_asoc_ok)
 898                 goto sctp_flush_out;
 899
 900         /* Is it OK to send data chunks?  */
 901         switch (asoc->state) {
 902         case SCTP_STATE_COOKIE_ECHOED:
 903                 /* Only allow bundling when this packet has a COOKIE-ECHO
 904                  * chunk.
 905                  */
 906                 if (!packet || !packet->has_cookie_echo)
 907                         break;
 908
 909                 /* fallthru */
 910         case SCTP_STATE_ESTABLISHED:
 911         case SCTP_STATE_SHUTDOWN_PENDING:
 912         case SCTP_STATE_SHUTDOWN_RECEIVED:
 913                 /*
 914                  * RFC 2960 6.1  Transmission of DATA Chunks
 915                  *
 916                  * C) When the time comes for the sender to transmit,
 917                  * before sending new DATA chunks, the sender MUST
 918                  * first transmit any outstanding DATA chunks which
 919                  * are marked for retransmission (limited by the
 920                  * current cwnd).
 921                  */
 922                 if (!list_empty(&q->retransmit)) {
 923                         if (asoc->peer.retran_path->state == SCTP_UNCONFIRMED)
 924                                 goto sctp_flush_out;
 925                         if (transport == asoc->peer.retran_path)
 926                                 goto retran;
 927
 928                         /* Switch transports & prepare the packet.  */
 929
 930                         transport = asoc->peer.retran_path;
 931
 932                         if (list_empty(&transport->send_ready)) {
 933                                 list_add_tail(&transport->send_ready,
 934                                               &transport_list);
 935                         }
 936
 937                         packet = &transport->packet;
 938                         sctp_packet_config(packet, vtag,
 939                                            asoc->peer.ecn_capable);
 940                 retran:
 941                         error = sctp_outq_flush_rtx(q, packet,
 942                                                     rtx_timeout, &start_timer);
 943
 944                         if (start_timer)
 945                                 sctp_transport_reset_timers(transport);
 946
 947                         /* This can happen on COOKIE-ECHO resend.  Only
 948                          * one chunk can get bundled with a COOKIE-ECHO.
 949                          */
 950                         if (packet->has_cookie_echo)
 951                                 goto sctp_flush_out;
 952
 953                         /* Don't send new data if there is still data
 954                          * waiting to retransmit.
 955                          */
 956                         if (!list_empty(&q->retransmit))
 957                                 goto sctp_flush_out;
 958                 }
 959
 960                 /* Apply Max.Burst limitation to the current transport in
 961                  * case it will be used for new data.  We are going to
 962                  * rest it before we return, but we want to apply the limit
 963                  * to the currently queued data.
 964                  */
 965                 if (transport)
 966                         sctp_transport_burst_limited(transport);
 967
 968                 /* Finally, transmit new packets.  */
 969                 while ((chunk = sctp_outq_dequeue_data(q)) != NULL) {
 970                         /* RFC 2960 6.5 Every DATA chunk MUST carry a valid
 971                          * stream identifier.
 972                          */
 973                         if (chunk->sinfo.sinfo_stream >=
 974                             asoc->c.sinit_num_ostreams) {
 975
 976                                 /* Mark as failed send. */
 977                                 sctp_chunk_fail(chunk, SCTP_ERROR_INV_STRM);
 978                                 sctp_chunk_free(chunk);
 979                                 continue;
 980                         }
 981
 982                         /* Has this chunk expired? */
 983                         if (sctp_chunk_abandoned(chunk)) {
 984                                 sctp_chunk_fail(chunk, 0);
 985                                 sctp_chunk_free(chunk);
 986                                 continue;
 987                         }
 988
 989                         /* If there is a specified transport, use it.
 990                          * Otherwise, we want to use the active path.
 991                          */
 992                         new_transport = chunk->transport;
 993                         if (!new_transport ||
 994                             ((new_transport->state == SCTP_INACTIVE) ||
 995                              (new_transport->state == SCTP_UNCONFIRMED) ||
 996                              (new_transport->state == SCTP_PF)))
 997                                 new_transport = asoc->peer.active_path;
 998                         if (new_transport->state == SCTP_UNCONFIRMED)
 999                                 continue;
1000
1001                         /* Change packets if necessary.  */
1002                         if (new_transport != transport) {
1003                                 transport = new_transport;
1004
1005                                 /* Schedule to have this transport's
1006                                  * packet flushed.
1007                                  */
1008                                 if (list_empty(&transport->send_ready)) {
1009                                         list_add_tail(&transport->send_ready,
1010                                                       &transport_list);
1011                                 }
1012
1013                                 packet = &transport->packet;
1014                                 sctp_packet_config(packet, vtag,
1015                                                    asoc->peer.ecn_capable);
1016                                 /* We've switched transports, so apply the
1017                                  * Burst limit to the new transport.
1018                                  */
1019                                 sctp_transport_burst_limited(transport);
1020                         }
1021
1022                         SCTP_DEBUG_PRINTK("sctp_outq_flush(%p, %p[%s]), ",
1023                                           q, chunk,
1024                                           chunk && chunk->chunk_hdr ?
1025                                           sctp_cname(SCTP_ST_CHUNK(
1026                                                   chunk->chunk_hdr->type))
1027                                           : "Illegal Chunk");
1028
1029                         SCTP_DEBUG_PRINTK("TX TSN 0x%x skb->head "
1030                                         "%p skb->users %d.\n",
1031                                         ntohl(chunk->subh.data_hdr->tsn),
1032                                         chunk->skb ?chunk->skb->head : NULL,
1033                                         chunk->skb ?
1034                                         atomic_read(&chunk->skb->users) : -1);
1035
1036                         /* Add the chunk to the packet.  */
1037                         status = sctp_packet_transmit_chunk(packet, chunk, 0);
1038
1039                         switch (status) {
1040                         case SCTP_XMIT_PMTU_FULL:
1041                         case SCTP_XMIT_RWND_FULL:
1042                         case SCTP_XMIT_NAGLE_DELAY:
1043                                 /* We could not append this chunk, so put
1044                                  * the chunk back on the output queue.
1045                                  */
1046                                 SCTP_DEBUG_PRINTK("sctp_outq_flush: could "
1047                                         "not transmit TSN: 0x%x, status: %d\n",
1048                                         ntohl(chunk->subh.data_hdr->tsn),
1049                                         status);
1050                                 sctp_outq_head_data(q, chunk);
1051                                 goto sctp_flush_out;
1052                                 break;
1053
1054                         case SCTP_XMIT_OK:
1055                                 /* The sender is in the SHUTDOWN-PENDING state,
1056                                  * The sender MAY set the I-bit in the DATA
1057                                  * chunk header.
1058                                  */
1059                                 if (asoc->state == SCTP_STATE_SHUTDOWN_PENDING)
1060                                         chunk->chunk_hdr->flags |= SCTP_DATA_SACK_IMM;
1061                                 if (chunk->chunk_hdr->flags & SCTP_DATA_UNORDERED)
1062                                         asoc->stats.ouodchunks++;
1063                                 else
1064                                         asoc->stats.oodchunks++;
1065
1066                                 break;
1067
1068                         default:
1069                                 BUG();
1070                         }
1071
1072                         /* BUG: We assume that the sctp_packet_transmit()
1073                          * call below will succeed all the time and add the
1074                          * chunk to the transmitted list and restart the
1075                          * timers.
1076                          * It is possible that the call can fail under OOM
1077                          * conditions.
1078                          *
1079                          * Is this really a problem?  Won't this behave
1080                          * like a lost TSN?
1081                          */
1082                         list_add_tail(&chunk->transmitted_list,
1083                                       &transport->transmitted);
1084
1085                         sctp_transport_reset_timers(transport);
1086
1087                         q->empty = 0;
1088
1089                         /* Only let one DATA chunk get bundled with a
1090                          * COOKIE-ECHO chunk.
1091                          */
1092                         if (packet->has_cookie_echo)
1093                                 goto sctp_flush_out;
1094                 }
1095                 break;
1096
1097         default:
1098                 /* Do nothing.  */
1099                 break;
1100         }
1101
1102 sctp_flush_out:
1103
1104         /* Before returning, examine all the transports touched in
1105          * this call.  Right now, we bluntly force clear all the
1106          * transports.  Things might change after we implement Nagle.
1107          * But such an examination is still required.
1108          *
1109          * --xguo
1110          */
1111         while ((ltransport = sctp_list_dequeue(&transport_list)) != NULL ) {
1112                 struct sctp_transport *t = list_entry(ltransport,
1113                                                       struct sctp_transport,
1114                                                       send_ready);
1115                 packet = &t->packet;
1116                 if (!sctp_packet_empty(packet))
1117                         error = sctp_packet_transmit(packet);
1118
1119                 /* Clear the burst limited state, if any */
1120                 sctp_transport_burst_reset(t);
1121         }
1122
1123         return error;
1124 }
1125
1126 /* Update unack_data based on the incoming SACK chunk */
1127 static void sctp_sack_update_unack_data(struct sctp_association *assoc,
1128                                         struct sctp_sackhdr *sack)
1129 {
1130         sctp_sack_variable_t *frags;
1131         __u16 unack_data;
1132         int i;
1133
1134         unack_data = assoc->next_tsn - assoc->ctsn_ack_point - 1;
1135
1136         frags = sack->variable;
1137         for (i = 0; i < ntohs(sack->num_gap_ack_blocks); i++) {
1138                 unack_data -= ((ntohs(frags[i].gab.end) -
1139                                 ntohs(frags[i].gab.start) + 1));
1140         }
1141
1142         assoc->unack_data = unack_data;
1143 }
1144
1145 /* This is where we REALLY process a SACK.
1146  *
1147  * Process the SACK against the outqueue.  Mostly, this just frees
1148  * things off the transmitted queue.
1149  */
1150 int sctp_outq_sack(struct sctp_outq *q, struct sctp_chunk *chunk)
1151 {
1152         struct sctp_association *asoc = q->asoc;
1153         struct sctp_sackhdr *sack = chunk->subh.sack_hdr;
1154         struct sctp_transport *transport;
1155         struct sctp_chunk *tchunk = NULL;
1156         struct list_head *lchunk, *transport_list, *temp;
1157         sctp_sack_variable_t *frags = sack->variable;
1158         __u32 sack_ctsn, ctsn, tsn;
1159         __u32 highest_tsn, highest_new_tsn;
1160         __u32 sack_a_rwnd;
1161         unsigned int outstanding;
1162         struct sctp_transport *primary = asoc->peer.primary_path;
1163         int count_of_newacks = 0;
1164         int gap_ack_blocks;
1165         u8 accum_moved = 0;
1166
1167         /* Grab the association's destination address list. */
1168         transport_list = &asoc->peer.transport_addr_list;
1169
1170         sack_ctsn = ntohl(sack->cum_tsn_ack);
1171         gap_ack_blocks = ntohs(sack->num_gap_ack_blocks);
1172         asoc->stats.gapcnt += gap_ack_blocks;
1173         /*
1174          * SFR-CACC algorithm:
1175          * On receipt of a SACK the sender SHOULD execute the
1176          * following statements.
1177          *
1178          * 1) If the cumulative ack in the SACK passes next tsn_at_change
1179          * on the current primary, the CHANGEOVER_ACTIVE flag SHOULD be
1180          * cleared. The CYCLING_CHANGEOVER flag SHOULD also be cleared for
1181          * all destinations.
1182          * 2) If the SACK contains gap acks and the flag CHANGEOVER_ACTIVE
1183          * is set the receiver of the SACK MUST take the following actions:
1184          *
1185          * A) Initialize the cacc_saw_newack to 0 for all destination
1186          * addresses.
1187          *
1188          * Only bother if changeover_active is set. Otherwise, this is
1189          * totally suboptimal to do on every SACK.
1190          */
1191         if (primary->cacc.changeover_active) {
1192                 u8 clear_cycling = 0;
1193
1194                 if (TSN_lte(primary->cacc.next_tsn_at_change, sack_ctsn)) {
1195                         primary->cacc.changeover_active = 0;
1196                         clear_cycling = 1;
1197                 }
1198
1199                 if (clear_cycling || gap_ack_blocks) {
1200                         list_for_each_entry(transport, transport_list,
1201                                         transports) {
1202                                 if (clear_cycling)
1203                                         transport->cacc.cycling_changeover = 0;
1204                                 if (gap_ack_blocks)
1205                                         transport->cacc.cacc_saw_newack = 0;
1206                         }
1207                 }
1208         }
1209
1210         /* Get the highest TSN in the sack. */
1211         highest_tsn = sack_ctsn;
1212         if (gap_ack_blocks)
1213                 highest_tsn += ntohs(frags[gap_ack_blocks - 1].gab.end);
1214
1215         if (TSN_lt(asoc->highest_sacked, highest_tsn))
1216                 asoc->highest_sacked = highest_tsn;
1217
1218         highest_new_tsn = sack_ctsn;
1219
1220         /* Run through the retransmit queue.  Credit bytes received
1221          * and free those chunks that we can.
1222          */
1223         sctp_check_transmitted(q, &q->retransmit, NULL, NULL, sack, &highest_new_tsn);
1224
1225         /* Run through the transmitted queue.
1226          * Credit bytes received and free those chunks which we can.
1227          *
1228          * This is a MASSIVE candidate for optimization.
1229          */
1230         list_for_each_entry(transport, transport_list, transports) {
1231                 sctp_check_transmitted(q, &transport->transmitted,
1232                                        transport, &chunk->source, sack,
1233                                        &highest_new_tsn);
1234                 /*
1235                  * SFR-CACC algorithm:
1236                  * C) Let count_of_newacks be the number of
1237                  * destinations for which cacc_saw_newack is set.
1238                  */
1239                 if (transport->cacc.cacc_saw_newack)
1240                         count_of_newacks ++;
1241         }
1242
1243         /* Move the Cumulative TSN Ack Point if appropriate.  */
1244         if (TSN_lt(asoc->ctsn_ack_point, sack_ctsn)) {
1245                 asoc->ctsn_ack_point = sack_ctsn;
1246                 accum_moved = 1;
1247         }
1248
1249         if (gap_ack_blocks) {
1250
1251                 if (asoc->fast_recovery && accum_moved)
1252                         highest_new_tsn = highest_tsn;
1253
1254                 list_for_each_entry(transport, transport_list, transports)
1255                         sctp_mark_missing(q, &transport->transmitted, transport,
1256                                           highest_new_tsn, count_of_newacks);
1257         }
1258
1259         /* Update unack_data field in the assoc. */
1260         sctp_sack_update_unack_data(asoc, sack);
1261
1262         ctsn = asoc->ctsn_ack_point;
1263
1264         /* Throw away stuff rotting on the sack queue.  */
1265         list_for_each_safe(lchunk, temp, &q->sacked) {
1266                 tchunk = list_entry(lchunk, struct sctp_chunk,
1267                                     transmitted_list);
1268                 tsn = ntohl(tchunk->subh.data_hdr->tsn);
1269                 if (TSN_lte(tsn, ctsn)) {
1270                         list_del_init(&tchunk->transmitted_list);
1271                         sctp_chunk_free(tchunk);
1272                 }
1273         }
1274
1275         /* ii) Set rwnd equal to the newly received a_rwnd minus the
1276          *     number of bytes still outstanding after processing the
1277          *     Cumulative TSN Ack and the Gap Ack Blocks.
1278          */
1279
1280         sack_a_rwnd = ntohl(sack->a_rwnd);
1281         outstanding = q->outstanding_bytes;
1282
1283         if (outstanding < sack_a_rwnd)
1284                 sack_a_rwnd -= outstanding;
1285         else
1286                 sack_a_rwnd = 0;
1287
1288         asoc->peer.rwnd = sack_a_rwnd;
1289
1290         sctp_generate_fwdtsn(q, sack_ctsn);
1291
1292         SCTP_DEBUG_PRINTK("%s: sack Cumulative TSN Ack is 0x%x.\n",
1293                           __func__, sack_ctsn);
1294         SCTP_DEBUG_PRINTK("%s: Cumulative TSN Ack of association, "
1295                           "%p is 0x%x. Adv peer ack point: 0x%x\n",
1296                           __func__, asoc, ctsn, asoc->adv_peer_ack_point);
1297
1298         /* See if all chunks are acked.
1299          * Make sure the empty queue handler will get run later.
1300          */
1301         q->empty = (list_empty(&q->out_chunk_list) &&
1302                     list_empty(&q->retransmit));
1303         if (!q->empty)
1304                 goto finish;
1305
1306         list_for_each_entry(transport, transport_list, transports) {
1307                 q->empty = q->empty && list_empty(&transport->transmitted);
1308                 if (!q->empty)
1309                         goto finish;
1310         }
1311
1312         SCTP_DEBUG_PRINTK("sack queue is empty.\n");
1313 finish:
1314         return q->empty;
1315 }
1316
1317 /* Is the outqueue empty?  */
1318 int sctp_outq_is_empty(const struct sctp_outq *q)
1319 {
1320         return q->empty;
1321 }
1322
1323 /********************************************************************
1324  * 2nd Level Abstractions
1325  ********************************************************************/
1326
1327 /* Go through a transport's transmitted list or the association's retransmit
1328  * list and move chunks that are acked by the Cumulative TSN Ack to q->sacked.
1329  * The retransmit list will not have an associated transport.
1330  *
1331  * I added coherent debug information output.   --xguo
1332  *
1333  * Instead of printing 'sacked' or 'kept' for each TSN on the
1334  * transmitted_queue, we print a range: SACKED: TSN1-TSN2, TSN3, TSN4-TSN5.
1335  * KEPT TSN6-TSN7, etc.
1336  */
1337 static void sctp_check_transmitted(struct sctp_outq *q,
1338                                    struct list_head *transmitted_queue,
1339                                    struct sctp_transport *transport,
1340                                    union sctp_addr *saddr,
1341                                    struct sctp_sackhdr *sack,
1342                                    __u32 *highest_new_tsn_in_sack)
1343 {
1344         struct list_head *lchunk;
1345         struct sctp_chunk *tchunk;
1346         struct list_head tlist;
1347         __u32 tsn;
1348         __u32 sack_ctsn;
1349         __u32 rtt;
1350         __u8 restart_timer = 0;
1351         int bytes_acked = 0;
1352         int migrate_bytes = 0;
1353
1354         /* These state variables are for coherent debug output. --xguo */
1355
1356 #if SCTP_DEBUG
1357         __u32 dbg_ack_tsn = 0;  /* An ACKed TSN range starts here... */
1358         __u32 dbg_last_ack_tsn = 0;  /* ...and finishes here.        */
1359         __u32 dbg_kept_tsn = 0; /* An un-ACKed range starts here...  */
1360         __u32 dbg_last_kept_tsn = 0; /* ...and finishes here.        */
1361
1362         /* 0 : The last TSN was ACKed.
1363          * 1 : The last TSN was NOT ACKed (i.e. KEPT).
1364          * -1: We need to initialize.
1365          */
1366         int dbg_prt_state = -1;
1367 #endif /* SCTP_DEBUG */
1368
1369         sack_ctsn = ntohl(sack->cum_tsn_ack);
1370
1371         INIT_LIST_HEAD(&tlist);
1372
1373         /* The while loop will skip empty transmitted queues. */
1374         while (NULL != (lchunk = sctp_list_dequeue(transmitted_queue))) {
1375                 tchunk = list_entry(lchunk, struct sctp_chunk,
1376                                     transmitted_list);
1377
1378                 if (sctp_chunk_abandoned(tchunk)) {
1379                         /* Move the chunk to abandoned list. */
1380                         sctp_insert_list(&q->abandoned, lchunk);
1381
1382                         /* If this chunk has not been acked, stop
1383                          * considering it as 'outstanding'.
1384                          */
1385                         if (!tchunk->tsn_gap_acked) {
1386                                 if (tchunk->transport)
1387                                         tchunk->transport->flight_size -=
1388                                                         sctp_data_size(tchunk);
1389                                 q->outstanding_bytes -= sctp_data_size(tchunk);
1390                         }
1391                         continue;
1392                 }
1393
1394                 tsn = ntohl(tchunk->subh.data_hdr->tsn);
1395                 if (sctp_acked(sack, tsn)) {
1396                         /* If this queue is the retransmit queue, the
1397                          * retransmit timer has already reclaimed
1398                          * the outstanding bytes for this chunk, so only
1399                          * count bytes associated with a transport.
1400                          */
1401                         if (transport) {
1402                                 /* If this chunk is being used for RTT
1403                                  * measurement, calculate the RTT and update
1404                                  * the RTO using this value.
1405                                  *
1406                                  * 6.3.1 C5) Karn's algorithm: RTT measurements
1407                                  * MUST NOT be made using packets that were
1408                                  * retransmitted (and thus for which it is
1409                                  * ambiguous whether the reply was for the
1410                                  * first instance of the packet or a later
1411                                  * instance).
1412                                  */
1413                                 if (!tchunk->tsn_gap_acked &&
1414                                     tchunk->rtt_in_progress) {
1415                                         tchunk->rtt_in_progress = 0;
1416                                         rtt = jiffies - tchunk->sent_at;
1417                                         sctp_transport_update_rto(transport,
1418                                                                   rtt);
1419                                 }
1420                         }
1421
1422                         /* If the chunk hasn't been marked as ACKED,
1423                          * mark it and account bytes_acked if the
1424                          * chunk had a valid transport (it will not
1425                          * have a transport if ASCONF had deleted it
1426                          * while DATA was outstanding).
1427                          */
1428                         if (!tchunk->tsn_gap_acked) {
1429                                 tchunk->tsn_gap_acked = 1;
1430                                 *highest_new_tsn_in_sack = tsn;
1431                                 bytes_acked += sctp_data_size(tchunk);
1432                                 if (!tchunk->transport)
1433                                         migrate_bytes += sctp_data_size(tchunk);
1434                         }
1435
1436                         if (TSN_lte(tsn, sack_ctsn)) {
1437                                 /* RFC 2960  6.3.2 Retransmission Timer Rules
1438                                  *
1439                                  * R3) Whenever a SACK is received
1440                                  * that acknowledges the DATA chunk
1441                                  * with the earliest outstanding TSN
1442                                  * for that address, restart T3-rtx
1443                                  * timer for that address with its
1444                                  * current RTO.
1445                                  */
1446                                 restart_timer = 1;
1447
1448                                 if (!tchunk->tsn_gap_acked) {
1449                                         /*
1450                                          * SFR-CACC algorithm:
1451                                          * 2) If the SACK contains gap acks
1452                                          * and the flag CHANGEOVER_ACTIVE is
1453                                          * set the receiver of the SACK MUST
1454                                          * take the following action:
1455                                          *
1456                                          * B) For each TSN t being acked that
1457                                          * has not been acked in any SACK so
1458                                          * far, set cacc_saw_newack to 1 for
1459                                          * the destination that the TSN was
1460                                          * sent to.
1461                                          */
1462                                         if (transport &&
1463                                             sack->num_gap_ack_blocks &&
1464                                             q->asoc->peer.primary_path->cacc.
1465                                             changeover_active)
1466                                                 transport->cacc.cacc_saw_newack
1467                                                         = 1;
1468                                 }
1469
1470                                 list_add_tail(&tchunk->transmitted_list,
1471                                               &q->sacked);
1472                         } else {
1473                                 /* RFC2960 7.2.4, sctpimpguide-05 2.8.2
1474                                  * M2) Each time a SACK arrives reporting
1475                                  * 'Stray DATA chunk(s)' record the highest TSN
1476                                  * reported as newly acknowledged, call this
1477                                  * value 'HighestTSNinSack'. A newly
1478                                  * acknowledged DATA chunk is one not
1479                                  * previously acknowledged in a SACK.
1480                                  *
1481                                  * When the SCTP sender of data receives a SACK
1482                                  * chunk that acknowledges, for the first time,
1483                                  * the receipt of a DATA chunk, all the still
1484                                  * unacknowledged DATA chunks whose TSN is
1485                                  * older than that newly acknowledged DATA
1486                                  * chunk, are qualified as 'Stray DATA chunks'.
1487                                  */
1488                                 list_add_tail(lchunk, &tlist);
1489                         }
1490
1491 #if SCTP_DEBUG
1492                         switch (dbg_prt_state) {
1493                         case 0: /* last TSN was ACKed */
1494                                 if (dbg_last_ack_tsn + 1 == tsn) {
1495                                         /* This TSN belongs to the
1496                                          * current ACK range.
1497                                          */
1498                                         break;
1499                                 }
1500
1501                                 if (dbg_last_ack_tsn != dbg_ack_tsn) {
1502                                         /* Display the end of the
1503                                          * current range.
1504                                          */
1505                                         SCTP_DEBUG_PRINTK_CONT("-%08x",
1506                                                                dbg_last_ack_tsn);
1507                                 }
1508
1509                                 /* Start a new range.  */
1510                                 SCTP_DEBUG_PRINTK_CONT(",%08x", tsn);
1511                                 dbg_ack_tsn = tsn;
1512                                 break;
1513
1514                         case 1: /* The last TSN was NOT ACKed. */
1515                                 if (dbg_last_kept_tsn != dbg_kept_tsn) {
1516                                         /* Display the end of current range. */
1517                                         SCTP_DEBUG_PRINTK_CONT("-%08x",
1518                                                                dbg_last_kept_tsn);
1519                                 }
1520
1521                                 SCTP_DEBUG_PRINTK_CONT("\n");
1522
1523                                 /* FALL THROUGH... */
1524                         default:
1525                                 /* This is the first-ever TSN we examined.  */
1526                                 /* Start a new range of ACK-ed TSNs.  */
1527                                 SCTP_DEBUG_PRINTK("ACKed: %08x", tsn);
1528                                 dbg_prt_state = 0;
1529                                 dbg_ack_tsn = tsn;
1530                         }
1531
1532                         dbg_last_ack_tsn = tsn;
1533 #endif /* SCTP_DEBUG */
1534
1535                 } else {
1536                         if (tchunk->tsn_gap_acked) {
1537                                 SCTP_DEBUG_PRINTK("%s: Receiver reneged on "
1538                                                   "data TSN: 0x%x\n",
1539                                                   __func__,
1540                                                   tsn);
1541                                 tchunk->tsn_gap_acked = 0;
1542
1543                                 if (tchunk->transport)
1544                                         bytes_acked -= sctp_data_size(tchunk);
1545
1546                                 /* RFC 2960 6.3.2 Retransmission Timer Rules
1547                                  *
1548                                  * R4) Whenever a SACK is received missing a
1549                                  * TSN that was previously acknowledged via a
1550                                  * Gap Ack Block, start T3-rtx for the
1551                                  * destination address to which the DATA
1552                                  * chunk was originally
1553                                  * transmitted if it is not already running.
1554                                  */
1555                                 restart_timer = 1;
1556                         }
1557
1558                         list_add_tail(lchunk, &tlist);
1559
1560 #if SCTP_DEBUG
1561                         /* See the above comments on ACK-ed TSNs. */
1562                         switch (dbg_prt_state) {
1563                         case 1:
1564                                 if (dbg_last_kept_tsn + 1 == tsn)
1565                                         break;
1566
1567                                 if (dbg_last_kept_tsn != dbg_kept_tsn)
1568                                         SCTP_DEBUG_PRINTK_CONT("-%08x",
1569                                                                dbg_last_kept_tsn);
1570
1571                                 SCTP_DEBUG_PRINTK_CONT(",%08x", tsn);
1572                                 dbg_kept_tsn = tsn;
1573                                 break;
1574
1575                         case 0:
1576                                 if (dbg_last_ack_tsn != dbg_ack_tsn)
1577                                         SCTP_DEBUG_PRINTK_CONT("-%08x",
1578                                                                dbg_last_ack_tsn);
1579                                 SCTP_DEBUG_PRINTK_CONT("\n");
1580
1581                                 /* FALL THROUGH... */
1582                         default:
1583                                 SCTP_DEBUG_PRINTK("KEPT: %08x",tsn);
1584                                 dbg_prt_state = 1;
1585                                 dbg_kept_tsn = tsn;
1586                         }
1587
1588                         dbg_last_kept_tsn = tsn;
1589 #endif /* SCTP_DEBUG */
1590                 }
1591         }
1592
1593 #if SCTP_DEBUG
1594         /* Finish off the last range, displaying its ending TSN.  */
1595         switch (dbg_prt_state) {
1596         case 0:
1597                 if (dbg_last_ack_tsn != dbg_ack_tsn) {
1598                         SCTP_DEBUG_PRINTK_CONT("-%08x\n", dbg_last_ack_tsn);
1599                 } else {
1600                         SCTP_DEBUG_PRINTK_CONT("\n");
1601                 }
1602         break;
1603
1604         case 1:
1605                 if (dbg_last_kept_tsn != dbg_kept_tsn) {
1606                         SCTP_DEBUG_PRINTK_CONT("-%08x\n", dbg_last_kept_tsn);
1607                 } else {
1608                         SCTP_DEBUG_PRINTK_CONT("\n");
1609                 }
1610         }
1611 #endif /* SCTP_DEBUG */
1612         if (transport) {
1613                 if (bytes_acked) {
1614                         struct sctp_association *asoc = transport->asoc;
1615
1616                         /* We may have counted DATA that was migrated
1617                          * to this transport due to DEL-IP operation.
1618                          * Subtract those bytes, since the were never
1619                          * send on this transport and shouldn't be
1620                          * credited to this transport.
1621                          */
1622                         bytes_acked -= migrate_bytes;
1623
1624                         /* 8.2. When an outstanding TSN is acknowledged,
1625                          * the endpoint shall clear the error counter of
1626                          * the destination transport address to which the
1627                          * DATA chunk was last sent.
1628                          * The association's overall error counter is
1629                          * also cleared.
1630                          */
1631                         transport->error_count = 0;
1632                         transport->asoc->overall_error_count = 0;
1633
1634                         /*
1635                          * While in SHUTDOWN PENDING, we may have started
1636                          * the T5 shutdown guard timer after reaching the
1637                          * retransmission limit. Stop that timer as soon
1638                          * as the receiver acknowledged any data.
1639                          */
1640                         if (asoc->state == SCTP_STATE_SHUTDOWN_PENDING &&
1641                             del_timer(&asoc->timers
1642                                 [SCTP_EVENT_TIMEOUT_T5_SHUTDOWN_GUARD]))
1643                                         sctp_association_put(asoc);
1644
1645                         /* Mark the destination transport address as
1646                          * active if it is not so marked.
1647                          */
1648                         if ((transport->state == SCTP_INACTIVE ||
1649                              transport->state == SCTP_UNCONFIRMED) &&
1650                             sctp_cmp_addr_exact(&transport->ipaddr, saddr)) {
1651                                 sctp_assoc_control_transport(
1652                                         transport->asoc,
1653                                         transport,
1654                                         SCTP_TRANSPORT_UP,
1655                                         SCTP_RECEIVED_SACK);
1656                         }
1657
1658                         sctp_transport_raise_cwnd(transport, sack_ctsn,
1659                                                   bytes_acked);
1660
1661                         transport->flight_size -= bytes_acked;
1662                         if (transport->flight_size == 0)
1663                                 transport->partial_bytes_acked = 0;
1664                         q->outstanding_bytes -= bytes_acked + migrate_bytes;
1665                 } else {
1666                         /* RFC 2960 6.1, sctpimpguide-06 2.15.2
1667                          * When a sender is doing zero window probing, it
1668                          * should not timeout the association if it continues
1669                          * to receive new packets from the receiver. The
1670                          * reason is that the receiver MAY keep its window
1671                          * closed for an indefinite time.
1672                          * A sender is doing zero window probing when the
1673                          * receiver's advertised window is zero, and there is
1674                          * only one data chunk in flight to the receiver.
1675                          *
1676                          * Allow the association to timeout while in SHUTDOWN
1677                          * PENDING or SHUTDOWN RECEIVED in case the receiver
1678                          * stays in zero window mode forever.
1679                          */
1680                         if (!q->asoc->peer.rwnd &&
1681                             !list_empty(&tlist) &&
1682                             (sack_ctsn+2 == q->asoc->next_tsn) &&
1683                             q->asoc->state < SCTP_STATE_SHUTDOWN_PENDING) {
1684                                 SCTP_DEBUG_PRINTK("%s: SACK received for zero "
1685                                                   "window probe: %u\n",
1686                                                   __func__, sack_ctsn);
1687                                 q->asoc->overall_error_count = 0;
1688                                 transport->error_count = 0;
1689                         }
1690                 }
1691
1692                 /* RFC 2960 6.3.2 Retransmission Timer Rules
1693                  *
1694                  * R2) Whenever all outstanding data sent to an address have
1695                  * been acknowledged, turn off the T3-rtx timer of that
1696                  * address.
1697                  */
1698                 if (!transport->flight_size) {
1699                         if (timer_pending(&transport->T3_rtx_timer) &&
1700                             del_timer(&transport->T3_rtx_timer)) {
1701                                 sctp_transport_put(transport);
1702                         }
1703                 } else if (restart_timer) {
1704                         if (!mod_timer(&transport->T3_rtx_timer,
1705                                        jiffies + transport->rto))
1706                                 sctp_transport_hold(transport);
1707                 }
1708         }
1709
1710         list_splice(&tlist, transmitted_queue);
1711 }
1712
1713 /* Mark chunks as missing and consequently may get retransmitted. */
1714 static void sctp_mark_missing(struct sctp_outq *q,
1715                               struct list_head *transmitted_queue,
1716                               struct sctp_transport *transport,
1717                               __u32 highest_new_tsn_in_sack,
1718                               int count_of_newacks)
1719 {
1720         struct sctp_chunk *chunk;
1721         __u32 tsn;
1722         char do_fast_retransmit = 0;
1723         struct sctp_association *asoc = q->asoc;
1724         struct sctp_transport *primary = asoc->peer.primary_path;
1725
1726         list_for_each_entry(chunk, transmitted_queue, transmitted_list) {
1727
1728                 tsn = ntohl(chunk->subh.data_hdr->tsn);
1729
1730                 /* RFC 2960 7.2.4, sctpimpguide-05 2.8.2 M3) Examine all
1731                  * 'Unacknowledged TSN's', if the TSN number of an
1732                  * 'Unacknowledged TSN' is smaller than the 'HighestTSNinSack'
1733                  * value, increment the 'TSN.Missing.Report' count on that
1734                  * chunk if it has NOT been fast retransmitted or marked for
1735                  * fast retransmit already.
1736                  */
1737                 if (chunk->fast_retransmit == SCTP_CAN_FRTX &&
1738                     !chunk->tsn_gap_acked &&
1739                     TSN_lt(tsn, highest_new_tsn_in_sack)) {
1740
1741                         /* SFR-CACC may require us to skip marking
1742                          * this chunk as missing.
1743                          */
1744                         if (!transport || !sctp_cacc_skip(primary,
1745                                                 chunk->transport,
1746                                                 count_of_newacks, tsn)) {
1747                                 chunk->tsn_missing_report++;
1748
1749                                 SCTP_DEBUG_PRINTK(
1750                                         "%s: TSN 0x%x missing counter: %d\n",
1751                                         __func__, tsn,
1752                                         chunk->tsn_missing_report);
1753                         }
1754                 }
1755                 /*
1756                  * M4) If any DATA chunk is found to have a
1757                  * 'TSN.Missing.Report'
1758                  * value larger than or equal to 3, mark that chunk for
1759                  * retransmission and start the fast retransmit procedure.
1760                  */
1761
1762                 if (chunk->tsn_missing_report >= 3) {
1763                         chunk->fast_retransmit = SCTP_NEED_FRTX;
1764                         do_fast_retransmit = 1;
1765                 }
1766         }
1767
1768         if (transport) {
1769                 if (do_fast_retransmit)
1770                         sctp_retransmit(q, transport, SCTP_RTXR_FAST_RTX);
1771
1772                 SCTP_DEBUG_PRINTK("%s: transport: %p, cwnd: %d, "
1773                                   "ssthresh: %d, flight_size: %d, pba: %d\n",
1774                                   __func__, transport, transport->cwnd,
1775                                   transport->ssthresh, transport->flight_size,
1776                                   transport->partial_bytes_acked);
1777         }
1778 }
1779
1780 /* Is the given TSN acked by this packet?  */
1781 static int sctp_acked(struct sctp_sackhdr *sack, __u32 tsn)
1782 {
1783         int i;
1784         sctp_sack_variable_t *frags;
1785         __u16 gap;
1786         __u32 ctsn = ntohl(sack->cum_tsn_ack);
1787
1788         if (TSN_lte(tsn, ctsn))
1789                 goto pass;
1790
1791         /* 3.3.4 Selective Acknowledgement (SACK) (3):
1792          *
1793          * Gap Ack Blocks:
1794          *  These fields contain the Gap Ack Blocks. They are repeated
1795          *  for each Gap Ack Block up to the number of Gap Ack Blocks
1796          *  defined in the Number of Gap Ack Blocks field. All DATA
1797          *  chunks with TSNs greater than or equal to (Cumulative TSN
1798          *  Ack + Gap Ack Block Start) and less than or equal to
1799          *  (Cumulative TSN Ack + Gap Ack Block End) of each Gap Ack
1800          *  Block are assumed to have been received correctly.
1801          */
1802
1803         frags = sack->variable;
1804         gap = tsn - ctsn;
1805         for (i = 0; i < ntohs(sack->num_gap_ack_blocks); ++i) {
1806                 if (TSN_lte(ntohs(frags[i].gab.start), gap) &&
1807                     TSN_lte(gap, ntohs(frags[i].gab.end)))
1808                         goto pass;
1809         }
1810
1811         return 0;
1812 pass:
1813         return 1;
1814 }
1815
1816 static inline int sctp_get_skip_pos(struct sctp_fwdtsn_skip *skiplist,
1817                                     int nskips, __be16 stream)
1818 {
1819         int i;
1820
1821         for (i = 0; i < nskips; i++) {
1822                 if (skiplist[i].stream == stream)
1823                         return i;
1824         }
1825         return i;
1826 }
1827
1828 /* Create and add a fwdtsn chunk to the outq's control queue if needed. */
1829 static void sctp_generate_fwdtsn(struct sctp_outq *q, __u32 ctsn)
1830 {
1831         struct sctp_association *asoc = q->asoc;
1832         struct sctp_chunk *ftsn_chunk = NULL;
1833         struct sctp_fwdtsn_skip ftsn_skip_arr[10];
1834         int nskips = 0;
1835         int skip_pos = 0;
1836         __u32 tsn;
1837         struct sctp_chunk *chunk;
1838         struct list_head *lchunk, *temp;
1839
1840         if (!asoc->peer.prsctp_capable)
1841                 return;
1842
1843         /* PR-SCTP C1) Let SackCumAck be the Cumulative TSN ACK carried in the
1844          * received SACK.
1845          *
1846          * If (Advanced.Peer.Ack.Point < SackCumAck), then update
1847          * Advanced.Peer.Ack.Point to be equal to SackCumAck.
1848          */
1849         if (TSN_lt(asoc->adv_peer_ack_point, ctsn))
1850                 asoc->adv_peer_ack_point = ctsn;
1851
1852         /* PR-SCTP C2) Try to further advance the "Advanced.Peer.Ack.Point"
1853          * locally, that is, to move "Advanced.Peer.Ack.Point" up as long as
1854          * the chunk next in the out-queue space is marked as "abandoned" as
1855          * shown in the following example:
1856          *
1857          * Assuming that a SACK arrived with the Cumulative TSN ACK 102
1858          * and the Advanced.Peer.Ack.Point is updated to this value:
1859          *
1860          *   out-queue at the end of  ==>   out-queue after Adv.Ack.Point
1861          *   normal SACK processing           local advancement
1862          *                ...                           ...
1863          *   Adv.Ack.Pt-> 102 acked                     102 acked
1864          *                103 abandoned                 103 abandoned
1865          *                104 abandoned     Adv.Ack.P-> 104 abandoned
1866          *                105                           105
1867          *                106 acked                     106 acked
1868          *                ...                           ...
1869          *
1870          * In this example, the data sender successfully advanced the
1871          * "Advanced.Peer.Ack.Point" from 102 to 104 locally.
1872          */
1873         list_for_each_safe(lchunk, temp, &q->abandoned) {
1874                 chunk = list_entry(lchunk, struct sctp_chunk,
1875                                         transmitted_list);
1876                 tsn = ntohl(chunk->subh.data_hdr->tsn);
1877
1878                 /* Remove any chunks in the abandoned queue that are acked by
1879                  * the ctsn.
1880                  */
1881                 if (TSN_lte(tsn, ctsn)) {
1882                         list_del_init(lchunk);
1883                         sctp_chunk_free(chunk);
1884                 } else {
1885                         if (TSN_lte(tsn, asoc->adv_peer_ack_point+1)) {
1886                                 asoc->adv_peer_ack_point = tsn;
1887                                 if (chunk->chunk_hdr->flags &
1888                                          SCTP_DATA_UNORDERED)
1889                                         continue;
1890                                 skip_pos = sctp_get_skip_pos(&ftsn_skip_arr[0],
1891                                                 nskips,
1892                                                 chunk->subh.data_hdr->stream);
1893                                 ftsn_skip_arr[skip_pos].stream =
1894                                         chunk->subh.data_hdr->stream;
1895                                 ftsn_skip_arr[skip_pos].ssn =
1896                                          chunk->subh.data_hdr->ssn;
1897                                 if (skip_pos == nskips)
1898                                         nskips++;
1899                                 if (nskips == 10)
1900                                         break;
1901                         } else
1902                                 break;
1903                 }
1904         }
1905
1906         /* PR-SCTP C3) If, after step C1 and C2, the "Advanced.Peer.Ack.Point"
1907          * is greater than the Cumulative TSN ACK carried in the received
1908          * SACK, the data sender MUST send the data receiver a FORWARD TSN
1909          * chunk containing the latest value of the
1910          * "Advanced.Peer.Ack.Point".
1911          *
1912          * C4) For each "abandoned" TSN the sender of the FORWARD TSN SHOULD
1913          * list each stream and sequence number in the forwarded TSN. This
1914          * information will enable the receiver to easily find any
1915          * stranded TSN's waiting on stream reorder queues. Each stream
1916          * SHOULD only be reported once; this means that if multiple
1917          * abandoned messages occur in the same stream then only the
1918          * highest abandoned stream sequence number is reported. If the
1919          * total size of the FORWARD TSN does NOT fit in a single MTU then
1920          * the sender of the FORWARD TSN SHOULD lower the
1921          * Advanced.Peer.Ack.Point to the last TSN that will fit in a
1922          * single MTU.
1923          */
1924         if (asoc->adv_peer_ack_point > ctsn)
1925                 ftsn_chunk = sctp_make_fwdtsn(asoc, asoc->adv_peer_ack_point,
1926                                               nskips, &ftsn_skip_arr[0]);
1927
1928         if (ftsn_chunk) {
1929                 list_add_tail(&ftsn_chunk->list, &q->control_chunk_list);
1930                 SCTP_INC_STATS(sock_net(asoc->base.sk), SCTP_MIB_OUTCTRLCHUNKS);
1931         }
1932 }