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, see
  26  * <http://www.gnu.org/licenses/>.
  27  *
  28  * Please send any bug reports or fixes you make to the
  29  * email address(es):
  30  *    lksctp developers <linux-sctp@vger.kernel.org>
  31  *
  32  * Written or modified by:
  33  *    La Monte H.P. Yarroll <piggy@acm.org>
  34  *    Karl Knutson          <karl@athena.chicago.il.us>
  35  *    Perry Melange         <pmelange@null.cc.uic.edu>
  36  *    Xingang Guo           <xingang.guo@intel.com>
  37  *    Hui Huang             <hui.huang@nokia.com>
  38  *    Sridhar Samudrala     <sri@us.ibm.com>
  39  *    Jon Grimm             <jgrimm@us.ibm.com>
  40  */
  41
  42 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  43
  44 #include <linux/types.h>
  45 #include <linux/list.h>   /* For struct list_head */
  46 #include <linux/socket.h>
  47 #include <linux/ip.h>
  48 #include <linux/slab.h>
  49 #include <net/sock.h>     /* For skb_set_owner_w */
  50
  51 #include <net/sctp/sctp.h>
  52 #include <net/sctp/sm.h>
  53 #include <net/sctp/stream_sched.h>
  54
  55 /* Declare internal functions here.  */
  56 static int sctp_acked(struct sctp_sackhdr *sack, __u32 tsn);
  57 static void sctp_check_transmitted(struct sctp_outq *q,
  58                                    struct list_head *transmitted_queue,
  59                                    struct sctp_transport *transport,
  60                                    union sctp_addr *saddr,
  61                                    struct sctp_sackhdr *sack,
  62                                    __u32 *highest_new_tsn);
  63
  64 static void sctp_mark_missing(struct sctp_outq *q,
  65                               struct list_head *transmitted_queue,
  66                               struct sctp_transport *transport,
  67                               __u32 highest_new_tsn,
  68                               int count_of_newacks);
  69
  70 static void sctp_outq_flush(struct sctp_outq *q, int rtx_timeout, gfp_t gfp);
  71
  72 /* Add data to the front of the queue. */
  73 static inline void sctp_outq_head_data(struct sctp_outq *q,
  74                                        struct sctp_chunk *ch)
  75 {
  76         struct sctp_stream_out_ext *oute;
  77         __u16 stream;
  78
  79         list_add(&ch->list, &q->out_chunk_list);
  80         q->out_qlen += ch->skb->len;
  81
  82         stream = sctp_chunk_stream_no(ch);
  83         oute = SCTP_SO(&q->asoc->stream, stream)->ext;
  84         list_add(&ch->stream_list, &oute->outq);
  85 }
  86
  87 /* Take data from the front of the queue. */
  88 static inline struct sctp_chunk *sctp_outq_dequeue_data(struct sctp_outq *q)
  89 {
  90         return q->sched->dequeue(q);
  91 }
  92
  93 /* Add data chunk to the end of the queue. */
  94 static inline void sctp_outq_tail_data(struct sctp_outq *q,
  95                                        struct sctp_chunk *ch)
  96 {
  97         struct sctp_stream_out_ext *oute;
  98         __u16 stream;
  99
 100         list_add_tail(&ch->list, &q->out_chunk_list);
 101         q->out_qlen += ch->skb->len;
 102
 103         stream = sctp_chunk_stream_no(ch);
 104         oute = SCTP_SO(&q->asoc->stream, stream)->ext;
 105         list_add_tail(&ch->stream_list, &oute->outq);
 106 }
 107
 108 /*
 109  * SFR-CACC algorithm:
 110  * D) If count_of_newacks is greater than or equal to 2
 111  * and t was not sent to the current primary then the
 112  * sender MUST NOT increment missing report count for t.
 113  */
 114 static inline int sctp_cacc_skip_3_1_d(struct sctp_transport *primary,
 115                                        struct sctp_transport *transport,
 116                                        int count_of_newacks)
 117 {
 118         if (count_of_newacks >= 2 && transport != primary)
 119                 return 1;
 120         return 0;
 121 }
 122
 123 /*
 124  * SFR-CACC algorithm:
 125  * F) If count_of_newacks is less than 2, let d be the
 126  * destination to which t was sent. If cacc_saw_newack
 127  * is 0 for destination d, then the sender MUST NOT
 128  * increment missing report count for t.
 129  */
 130 static inline int sctp_cacc_skip_3_1_f(struct sctp_transport *transport,
 131                                        int count_of_newacks)
 132 {
 133         if (count_of_newacks < 2 &&
 134                         (transport && !transport->cacc.cacc_saw_newack))
 135                 return 1;
 136         return 0;
 137 }
 138
 139 /*
 140  * SFR-CACC algorithm:
 141  * 3.1) If CYCLING_CHANGEOVER is 0, the sender SHOULD
 142  * execute steps C, D, F.
 143  *
 144  * C has been implemented in sctp_outq_sack
 145  */
 146 static inline int sctp_cacc_skip_3_1(struct sctp_transport *primary,
 147                                      struct sctp_transport *transport,
 148                                      int count_of_newacks)
 149 {
 150         if (!primary->cacc.cycling_changeover) {
 151                 if (sctp_cacc_skip_3_1_d(primary, transport, count_of_newacks))
 152                         return 1;
 153                 if (sctp_cacc_skip_3_1_f(transport, count_of_newacks))
 154                         return 1;
 155                 return 0;
 156         }
 157         return 0;
 158 }
 159
 160 /*
 161  * SFR-CACC algorithm:
 162  * 3.2) Else if CYCLING_CHANGEOVER is 1, and t is less
 163  * than next_tsn_at_change of the current primary, then
 164  * the sender MUST NOT increment missing report count
 165  * for t.
 166  */
 167 static inline int sctp_cacc_skip_3_2(struct sctp_transport *primary, __u32 tsn)
 168 {
 169         if (primary->cacc.cycling_changeover &&
 170             TSN_lt(tsn, primary->cacc.next_tsn_at_change))
 171                 return 1;
 172         return 0;
 173 }
 174
 175 /*
 176  * SFR-CACC algorithm:
 177  * 3) If the missing report count for TSN t is to be
 178  * incremented according to [RFC2960] and
 179  * [SCTP_STEWART-2002], and CHANGEOVER_ACTIVE is set,
 180  * then the sender MUST further execute steps 3.1 and
 181  * 3.2 to determine if the missing report count for
 182  * TSN t SHOULD NOT be incremented.
 183  *
 184  * 3.3) If 3.1 and 3.2 do not dictate that the missing
 185  * report count for t should not be incremented, then
 186  * the sender SHOULD increment missing report count for
 187  * t (according to [RFC2960] and [SCTP_STEWART_2002]).
 188  */
 189 static inline int sctp_cacc_skip(struct sctp_transport *primary,
 190                                  struct sctp_transport *transport,
 191                                  int count_of_newacks,
 192                                  __u32 tsn)
 193 {
 194         if (primary->cacc.changeover_active &&
 195             (sctp_cacc_skip_3_1(primary, transport, count_of_newacks) ||
 196              sctp_cacc_skip_3_2(primary, tsn)))
 197                 return 1;
 198         return 0;
 199 }
 200
 201 /* Initialize an existing sctp_outq.  This does the boring stuff.
 202  * You still need to define handlers if you really want to DO
 203  * something with this structure...
 204  */
 205 void sctp_outq_init(struct sctp_association *asoc, struct sctp_outq *q)
 206 {
 207         memset(q, 0, sizeof(struct sctp_outq));
 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         sctp_sched_set_sched(asoc, sctp_sk(asoc->base.sk)->default_ss);
 216 }
 217
 218 /* Free the outqueue structure and any related pending chunks.
 219  */
 220 static void __sctp_outq_teardown(struct sctp_outq *q)
 221 {
 222         struct sctp_transport *transport;
 223         struct list_head *lchunk, *temp;
 224         struct sctp_chunk *chunk, *tmp;
 225
 226         /* Throw away unacknowledged chunks. */
 227         list_for_each_entry(transport, &q->asoc->peer.transport_addr_list,
 228                         transports) {
 229                 while ((lchunk = sctp_list_dequeue(&transport->transmitted)) != NULL) {
 230                         chunk = list_entry(lchunk, struct sctp_chunk,
 231                                            transmitted_list);
 232                         /* Mark as part of a failed message. */
 233                         sctp_chunk_fail(chunk, q->error);
 234                         sctp_chunk_free(chunk);
 235                 }
 236         }
 237
 238         /* Throw away chunks that have been gap ACKed.  */
 239         list_for_each_safe(lchunk, temp, &q->sacked) {
 240                 list_del_init(lchunk);
 241                 chunk = list_entry(lchunk, struct sctp_chunk,
 242                                    transmitted_list);
 243                 sctp_chunk_fail(chunk, q->error);
 244                 sctp_chunk_free(chunk);
 245         }
 246
 247         /* Throw away any chunks in the retransmit queue. */
 248         list_for_each_safe(lchunk, temp, &q->retransmit) {
 249                 list_del_init(lchunk);
 250                 chunk = list_entry(lchunk, struct sctp_chunk,
 251                                    transmitted_list);
 252                 sctp_chunk_fail(chunk, q->error);
 253                 sctp_chunk_free(chunk);
 254         }
 255
 256         /* Throw away any chunks that are in the abandoned queue. */
 257         list_for_each_safe(lchunk, temp, &q->abandoned) {
 258                 list_del_init(lchunk);
 259                 chunk = list_entry(lchunk, struct sctp_chunk,
 260                                    transmitted_list);
 261                 sctp_chunk_fail(chunk, q->error);
 262                 sctp_chunk_free(chunk);
 263         }
 264
 265         /* Throw away any leftover data chunks. */
 266         while ((chunk = sctp_outq_dequeue_data(q)) != NULL) {
 267                 sctp_sched_dequeue_done(q, chunk);
 268
 269                 /* Mark as send failure. */
 270                 sctp_chunk_fail(chunk, q->error);
 271                 sctp_chunk_free(chunk);
 272         }
 273
 274         /* Throw away any leftover control chunks. */
 275         list_for_each_entry_safe(chunk, tmp, &q->control_chunk_list, list) {
 276                 list_del_init(&chunk->list);
 277                 sctp_chunk_free(chunk);
 278         }
 279 }
 280
 281 void sctp_outq_teardown(struct sctp_outq *q)
 282 {
 283         __sctp_outq_teardown(q);
 284         sctp_outq_init(q->asoc, q);
 285 }
 286
 287 /* Free the outqueue structure and any related pending chunks.  */
 288 void sctp_outq_free(struct sctp_outq *q)
 289 {
 290         /* Throw away leftover chunks. */
 291         __sctp_outq_teardown(q);
 292 }
 293
 294 /* Put a new chunk in an sctp_outq.  */
 295 void sctp_outq_tail(struct sctp_outq *q, struct sctp_chunk *chunk, gfp_t gfp)
 296 {
 297         struct net *net = sock_net(q->asoc->base.sk);
 298
 299         pr_debug("%s: outq:%p, chunk:%p[%s]\n", __func__, q, chunk,
 300                  chunk && chunk->chunk_hdr ?
 301                  sctp_cname(SCTP_ST_CHUNK(chunk->chunk_hdr->type)) :
 302                  "illegal chunk");
 303
 304         /* If it is data, queue it up, otherwise, send it
 305          * immediately.
 306          */
 307         if (sctp_chunk_is_data(chunk)) {
 308                 pr_debug("%s: outqueueing: outq:%p, chunk:%p[%s])\n",
 309                          __func__, q, chunk, chunk && chunk->chunk_hdr ?
 310                          sctp_cname(SCTP_ST_CHUNK(chunk->chunk_hdr->type)) :
 311                          "illegal chunk");
 312
 313                 sctp_outq_tail_data(q, chunk);
 314                 if (chunk->asoc->peer.prsctp_capable &&
 315                     SCTP_PR_PRIO_ENABLED(chunk->sinfo.sinfo_flags))
 316                         chunk->asoc->sent_cnt_removable++;
 317                 if (chunk->chunk_hdr->flags & SCTP_DATA_UNORDERED)
 318                         SCTP_INC_STATS(net, SCTP_MIB_OUTUNORDERCHUNKS);
 319                 else
 320                         SCTP_INC_STATS(net, SCTP_MIB_OUTORDERCHUNKS);
 321         } else {
 322                 list_add_tail(&chunk->list, &q->control_chunk_list);
 323                 SCTP_INC_STATS(net, SCTP_MIB_OUTCTRLCHUNKS);
 324         }
 325
 326         if (!q->cork)
 327                 sctp_outq_flush(q, 0, gfp);
 328 }
 329
 330 /* Insert a chunk into the sorted list based on the TSNs.  The retransmit list
 331  * and the abandoned list are in ascending order.
 332  */
 333 static void sctp_insert_list(struct list_head *head, struct list_head *new)
 334 {
 335         struct list_head *pos;
 336         struct sctp_chunk *nchunk, *lchunk;
 337         __u32 ntsn, ltsn;
 338         int done = 0;
 339
 340         nchunk = list_entry(new, struct sctp_chunk, transmitted_list);
 341         ntsn = ntohl(nchunk->subh.data_hdr->tsn);
 342
 343         list_for_each(pos, head) {
 344                 lchunk = list_entry(pos, struct sctp_chunk, transmitted_list);
 345                 ltsn = ntohl(lchunk->subh.data_hdr->tsn);
 346                 if (TSN_lt(ntsn, ltsn)) {
 347                         list_add(new, pos->prev);
 348                         done = 1;
 349                         break;
 350                 }
 351         }
 352         if (!done)
 353                 list_add_tail(new, head);
 354 }
 355
 356 static int sctp_prsctp_prune_sent(struct sctp_association *asoc,
 357                                   struct sctp_sndrcvinfo *sinfo,
 358                                   struct list_head *queue, int msg_len)
 359 {
 360         struct sctp_chunk *chk, *temp;
 361
 362         list_for_each_entry_safe(chk, temp, queue, transmitted_list) {
 363                 struct sctp_stream_out *streamout;
 364
 365                 if (!chk->msg->abandoned &&
 366                     (!SCTP_PR_PRIO_ENABLED(chk->sinfo.sinfo_flags) ||
 367                      chk->sinfo.sinfo_timetolive <= sinfo->sinfo_timetolive))
 368                         continue;
 369
 370                 chk->msg->abandoned = 1;
 371                 list_del_init(&chk->transmitted_list);
 372                 sctp_insert_list(&asoc->outqueue.abandoned,
 373                                  &chk->transmitted_list);
 374
 375                 streamout = SCTP_SO(&asoc->stream, chk->sinfo.sinfo_stream);
 376                 asoc->sent_cnt_removable--;
 377                 asoc->abandoned_sent[SCTP_PR_INDEX(PRIO)]++;
 378                 streamout->ext->abandoned_sent[SCTP_PR_INDEX(PRIO)]++;
 379
 380                 if (queue != &asoc->outqueue.retransmit &&
 381                     !chk->tsn_gap_acked) {
 382                         if (chk->transport)
 383                                 chk->transport->flight_size -=
 384                                                 sctp_data_size(chk);
 385                         asoc->outqueue.outstanding_bytes -= sctp_data_size(chk);
 386                 }
 387
 388                 msg_len -= chk->skb->truesize + sizeof(struct sctp_chunk);
 389                 if (msg_len <= 0)
 390                         break;
 391         }
 392
 393         return msg_len;
 394 }
 395
 396 static int sctp_prsctp_prune_unsent(struct sctp_association *asoc,
 397                                     struct sctp_sndrcvinfo *sinfo, int msg_len)
 398 {
 399         struct sctp_outq *q = &asoc->outqueue;
 400         struct sctp_chunk *chk, *temp;
 401
 402         q->sched->unsched_all(&asoc->stream);
 403
 404         list_for_each_entry_safe(chk, temp, &q->out_chunk_list, list) {
 405                 if (!chk->msg->abandoned &&
 406                     (!(chk->chunk_hdr->flags & SCTP_DATA_FIRST_FRAG) ||
 407                      !SCTP_PR_PRIO_ENABLED(chk->sinfo.sinfo_flags) ||
 408                      chk->sinfo.sinfo_timetolive <= sinfo->sinfo_timetolive))
 409                         continue;
 410
 411                 chk->msg->abandoned = 1;
 412                 sctp_sched_dequeue_common(q, chk);
 413                 asoc->sent_cnt_removable--;
 414                 asoc->abandoned_unsent[SCTP_PR_INDEX(PRIO)]++;
 415                 if (chk->sinfo.sinfo_stream < asoc->stream.outcnt) {
 416                         struct sctp_stream_out *streamout =
 417                                 SCTP_SO(&asoc->stream, chk->sinfo.sinfo_stream);
 418
 419                         streamout->ext->abandoned_unsent[SCTP_PR_INDEX(PRIO)]++;
 420                 }
 421
 422                 msg_len -= chk->skb->truesize + sizeof(struct sctp_chunk);
 423                 sctp_chunk_free(chk);
 424                 if (msg_len <= 0)
 425                         break;
 426         }
 427
 428         q->sched->sched_all(&asoc->stream);
 429
 430         return msg_len;
 431 }
 432
 433 /* Abandon the chunks according their priorities */
 434 void sctp_prsctp_prune(struct sctp_association *asoc,
 435                        struct sctp_sndrcvinfo *sinfo, int msg_len)
 436 {
 437         struct sctp_transport *transport;
 438
 439         if (!asoc->peer.prsctp_capable || !asoc->sent_cnt_removable)
 440                 return;
 441
 442         msg_len = sctp_prsctp_prune_sent(asoc, sinfo,
 443                                          &asoc->outqueue.retransmit,
 444                                          msg_len);
 445         if (msg_len <= 0)
 446                 return;
 447
 448         list_for_each_entry(transport, &asoc->peer.transport_addr_list,
 449                             transports) {
 450                 msg_len = sctp_prsctp_prune_sent(asoc, sinfo,
 451                                                  &transport->transmitted,
 452                                                  msg_len);
 453                 if (msg_len <= 0)
 454                         return;
 455         }
 456
 457         sctp_prsctp_prune_unsent(asoc, sinfo, msg_len);
 458 }
 459
 460 /* Mark all the eligible packets on a transport for retransmission.  */
 461 void sctp_retransmit_mark(struct sctp_outq *q,
 462                           struct sctp_transport *transport,
 463                           __u8 reason)
 464 {
 465         struct list_head *lchunk, *ltemp;
 466         struct sctp_chunk *chunk;
 467
 468         /* Walk through the specified transmitted queue.  */
 469         list_for_each_safe(lchunk, ltemp, &transport->transmitted) {
 470                 chunk = list_entry(lchunk, struct sctp_chunk,
 471                                    transmitted_list);
 472
 473                 /* If the chunk is abandoned, move it to abandoned list. */
 474                 if (sctp_chunk_abandoned(chunk)) {
 475                         list_del_init(lchunk);
 476                         sctp_insert_list(&q->abandoned, lchunk);
 477
 478                         /* If this chunk has not been previousely acked,
 479                          * stop considering it 'outstanding'.  Our peer
 480                          * will most likely never see it since it will
 481                          * not be retransmitted
 482                          */
 483                         if (!chunk->tsn_gap_acked) {
 484                                 if (chunk->transport)
 485                                         chunk->transport->flight_size -=
 486                                                         sctp_data_size(chunk);
 487                                 q->outstanding_bytes -= sctp_data_size(chunk);
 488                                 q->asoc->peer.rwnd += sctp_data_size(chunk);
 489                         }
 490                         continue;
 491                 }
 492
 493                 /* If we are doing  retransmission due to a timeout or pmtu
 494                  * discovery, only the  chunks that are not yet acked should
 495                  * be added to the retransmit queue.
 496                  */
 497                 if ((reason == SCTP_RTXR_FAST_RTX  &&
 498                             (chunk->fast_retransmit == SCTP_NEED_FRTX)) ||
 499                     (reason != SCTP_RTXR_FAST_RTX  && !chunk->tsn_gap_acked)) {
 500                         /* RFC 2960 6.2.1 Processing a Received SACK
 501                          *
 502                          * C) Any time a DATA chunk is marked for
 503                          * retransmission (via either T3-rtx timer expiration
 504                          * (Section 6.3.3) or via fast retransmit
 505                          * (Section 7.2.4)), add the data size of those
 506                          * chunks to the rwnd.
 507                          */
 508                         q->asoc->peer.rwnd += sctp_data_size(chunk);
 509                         q->outstanding_bytes -= sctp_data_size(chunk);
 510                         if (chunk->transport)
 511                                 transport->flight_size -= sctp_data_size(chunk);
 512
 513                         /* sctpimpguide-05 Section 2.8.2
 514                          * M5) If a T3-rtx timer expires, the
 515                          * 'TSN.Missing.Report' of all affected TSNs is set
 516                          * to 0.
 517                          */
 518                         chunk->tsn_missing_report = 0;
 519
 520                         /* If a chunk that is being used for RTT measurement
 521                          * has to be retransmitted, we cannot use this chunk
 522                          * anymore for RTT measurements. Reset rto_pending so
 523                          * that a new RTT measurement is started when a new
 524                          * data chunk is sent.
 525                          */
 526                         if (chunk->rtt_in_progress) {
 527                                 chunk->rtt_in_progress = 0;
 528                                 transport->rto_pending = 0;
 529                         }
 530
 531                         /* Move the chunk to the retransmit queue. The chunks
 532                          * on the retransmit queue are always kept in order.
 533                          */
 534                         list_del_init(lchunk);
 535                         sctp_insert_list(&q->retransmit, lchunk);
 536                 }
 537         }
 538
 539         pr_debug("%s: transport:%p, reason:%d, cwnd:%d, ssthresh:%d, "
 540                  "flight_size:%d, pba:%d\n", __func__, transport, reason,
 541                  transport->cwnd, transport->ssthresh, transport->flight_size,
 542                  transport->partial_bytes_acked);
 543 }
 544
 545 /* Mark all the eligible packets on a transport for retransmission and force
 546  * one packet out.
 547  */
 548 void sctp_retransmit(struct sctp_outq *q, struct sctp_transport *transport,
 549                      enum sctp_retransmit_reason reason)
 550 {
 551         struct net *net = sock_net(q->asoc->base.sk);
 552
 553         switch (reason) {
 554         case SCTP_RTXR_T3_RTX:
 555                 SCTP_INC_STATS(net, SCTP_MIB_T3_RETRANSMITS);
 556                 sctp_transport_lower_cwnd(transport, SCTP_LOWER_CWND_T3_RTX);
 557                 /* Update the retran path if the T3-rtx timer has expired for
 558                  * the current retran path.
 559                  */
 560                 if (transport == transport->asoc->peer.retran_path)
 561                         sctp_assoc_update_retran_path(transport->asoc);
 562                 transport->asoc->rtx_data_chunks +=
 563                         transport->asoc->unack_data;
 564                 break;
 565         case SCTP_RTXR_FAST_RTX:
 566                 SCTP_INC_STATS(net, SCTP_MIB_FAST_RETRANSMITS);
 567                 sctp_transport_lower_cwnd(transport, SCTP_LOWER_CWND_FAST_RTX);
 568                 q->fast_rtx = 1;
 569                 break;
 570         case SCTP_RTXR_PMTUD:
 571                 SCTP_INC_STATS(net, SCTP_MIB_PMTUD_RETRANSMITS);
 572                 break;
 573         case SCTP_RTXR_T1_RTX:
 574                 SCTP_INC_STATS(net, SCTP_MIB_T1_RETRANSMITS);
 575                 transport->asoc->init_retries++;
 576                 break;
 577         default:
 578                 BUG();
 579         }
 580
 581         sctp_retransmit_mark(q, transport, reason);
 582
 583         /* PR-SCTP A5) Any time the T3-rtx timer expires, on any destination,
 584          * the sender SHOULD try to advance the "Advanced.Peer.Ack.Point" by
 585          * following the procedures outlined in C1 - C5.
 586          */
 587         if (reason == SCTP_RTXR_T3_RTX)
 588                 q->asoc->stream.si->generate_ftsn(q, q->asoc->ctsn_ack_point);
 589
 590         /* Flush the queues only on timeout, since fast_rtx is only
 591          * triggered during sack processing and the queue
 592          * will be flushed at the end.
 593          */
 594         if (reason != SCTP_RTXR_FAST_RTX)
 595                 sctp_outq_flush(q, /* rtx_timeout */ 1, GFP_ATOMIC);
 596 }
 597
 598 /*
 599  * Transmit DATA chunks on the retransmit queue.  Upon return from
 600  * __sctp_outq_flush_rtx() the packet 'pkt' may contain chunks which
 601  * need to be transmitted by the caller.
 602  * We assume that pkt->transport has already been set.
 603  *
 604  * The return value is a normal kernel error return value.
 605  */
 606 static int __sctp_outq_flush_rtx(struct sctp_outq *q, struct sctp_packet *pkt,
 607                                  int rtx_timeout, int *start_timer, gfp_t gfp)
 608 {
 609         struct sctp_transport *transport = pkt->transport;
 610         struct sctp_chunk *chunk, *chunk1;
 611         struct list_head *lqueue;
 612         enum sctp_xmit status;
 613         int error = 0;
 614         int timer = 0;
 615         int done = 0;
 616         int fast_rtx;
 617
 618         lqueue = &q->retransmit;
 619         fast_rtx = q->fast_rtx;
 620
 621         /* This loop handles time-out retransmissions, fast retransmissions,
 622          * and retransmissions due to opening of whindow.
 623          *
 624          * RFC 2960 6.3.3 Handle T3-rtx Expiration
 625          *
 626          * E3) Determine how many of the earliest (i.e., lowest TSN)
 627          * outstanding DATA chunks for the address for which the
 628          * T3-rtx has expired will fit into a single packet, subject
 629          * to the MTU constraint for the path corresponding to the
 630          * destination transport address to which the retransmission
 631          * is being sent (this may be different from the address for
 632          * which the timer expires [see Section 6.4]). Call this value
 633          * K. Bundle and retransmit those K DATA chunks in a single
 634          * packet to the destination endpoint.
 635          *
 636          * [Just to be painfully clear, if we are retransmitting
 637          * because a timeout just happened, we should send only ONE
 638          * packet of retransmitted data.]
 639          *
 640          * For fast retransmissions we also send only ONE packet.  However,
 641          * if we are just flushing the queue due to open window, we'll
 642          * try to send as much as possible.
 643          */
 644         list_for_each_entry_safe(chunk, chunk1, lqueue, transmitted_list) {
 645                 /* If the chunk is abandoned, move it to abandoned list. */
 646                 if (sctp_chunk_abandoned(chunk)) {
 647                         list_del_init(&chunk->transmitted_list);
 648                         sctp_insert_list(&q->abandoned,
 649                                          &chunk->transmitted_list);
 650                         continue;
 651                 }
 652
 653                 /* Make sure that Gap Acked TSNs are not retransmitted.  A
 654                  * simple approach is just to move such TSNs out of the
 655                  * way and into a 'transmitted' queue and skip to the
 656                  * next chunk.
 657                  */
 658                 if (chunk->tsn_gap_acked) {
 659                         list_move_tail(&chunk->transmitted_list,
 660                                        &transport->transmitted);
 661                         continue;
 662                 }
 663
 664                 /* If we are doing fast retransmit, ignore non-fast_rtransmit
 665                  * chunks
 666                  */
 667                 if (fast_rtx && !chunk->fast_retransmit)
 668                         continue;
 669
 670 redo:
 671                 /* Attempt to append this chunk to the packet. */
 672                 status = sctp_packet_append_chunk(pkt, chunk);
 673
 674                 switch (status) {
 675                 case SCTP_XMIT_PMTU_FULL:
 676                         if (!pkt->has_data && !pkt->has_cookie_echo) {
 677                                 /* If this packet did not contain DATA then
 678                                  * retransmission did not happen, so do it
 679                                  * again.  We'll ignore the error here since
 680                                  * control chunks are already freed so there
 681                                  * is nothing we can do.
 682                                  */
 683                                 sctp_packet_transmit(pkt, gfp);
 684                                 goto redo;
 685                         }
 686
 687                         /* Send this packet.  */
 688                         error = sctp_packet_transmit(pkt, gfp);
 689
 690                         /* If we are retransmitting, we should only
 691                          * send a single packet.
 692                          * Otherwise, try appending this chunk again.
 693                          */
 694                         if (rtx_timeout || fast_rtx)
 695                                 done = 1;
 696                         else
 697                                 goto redo;
 698
 699                         /* Bundle next chunk in the next round.  */
 700                         break;
 701
 702                 case SCTP_XMIT_RWND_FULL:
 703                         /* Send this packet. */
 704                         error = sctp_packet_transmit(pkt, gfp);
 705
 706                         /* Stop sending DATA as there is no more room
 707                          * at the receiver.
 708                          */
 709                         done = 1;
 710                         break;
 711
 712                 case SCTP_XMIT_DELAY:
 713                         /* Send this packet. */
 714                         error = sctp_packet_transmit(pkt, gfp);
 715
 716                         /* Stop sending DATA because of nagle delay. */
 717                         done = 1;
 718                         break;
 719
 720                 default:
 721                         /* The append was successful, so add this chunk to
 722                          * the transmitted list.
 723                          */
 724                         list_move_tail(&chunk->transmitted_list,
 725                                        &transport->transmitted);
 726
 727                         /* Mark the chunk as ineligible for fast retransmit
 728                          * after it is retransmitted.
 729                          */
 730                         if (chunk->fast_retransmit == SCTP_NEED_FRTX)
 731                                 chunk->fast_retransmit = SCTP_DONT_FRTX;
 732
 733                         q->asoc->stats.rtxchunks++;
 734                         break;
 735                 }
 736
 737                 /* Set the timer if there were no errors */
 738                 if (!error && !timer)
 739                         timer = 1;
 740
 741                 if (done)
 742                         break;
 743         }
 744
 745         /* If we are here due to a retransmit timeout or a fast
 746          * retransmit and if there are any chunks left in the retransmit
 747          * queue that could not fit in the PMTU sized packet, they need
 748          * to be marked as ineligible for a subsequent fast retransmit.
 749          */
 750         if (rtx_timeout || fast_rtx) {
 751                 list_for_each_entry(chunk1, lqueue, transmitted_list) {
 752                         if (chunk1->fast_retransmit == SCTP_NEED_FRTX)
 753                                 chunk1->fast_retransmit = SCTP_DONT_FRTX;
 754                 }
 755         }
 756
 757         *start_timer = timer;
 758
 759         /* Clear fast retransmit hint */
 760         if (fast_rtx)
 761                 q->fast_rtx = 0;
 762
 763         return error;
 764 }
 765
 766 /* Cork the outqueue so queued chunks are really queued. */
 767 void sctp_outq_uncork(struct sctp_outq *q, gfp_t gfp)
 768 {
 769         if (q->cork)
 770                 q->cork = 0;
 771
 772         sctp_outq_flush(q, 0, gfp);
 773 }
 774
 775 static int sctp_packet_singleton(struct sctp_transport *transport,
 776                                  struct sctp_chunk *chunk, gfp_t gfp)
 777 {
 778         const struct sctp_association *asoc = transport->asoc;
 779         const __u16 sport = asoc->base.bind_addr.port;
 780         const __u16 dport = asoc->peer.port;
 781         const __u32 vtag = asoc->peer.i.init_tag;
 782         struct sctp_packet singleton;
 783
 784         sctp_packet_init(&singleton, transport, sport, dport);
 785         sctp_packet_config(&singleton, vtag, 0);
 786         sctp_packet_append_chunk(&singleton, chunk);
 787         return sctp_packet_transmit(&singleton, gfp);
 788 }
 789
 790 /* Struct to hold the context during sctp outq flush */
 791 struct sctp_flush_ctx {
 792         struct sctp_outq *q;
 793         /* Current transport being used. It's NOT the same as curr active one */
 794         struct sctp_transport *transport;
 795         /* These transports have chunks to send. */
 796         struct list_head transport_list;
 797         struct sctp_association *asoc;
 798         /* Packet on the current transport above */
 799         struct sctp_packet *packet;
 800         gfp_t gfp;
 801 };
 802
 803 /* transport: current transport */
 804 static void sctp_outq_select_transport(struct sctp_flush_ctx *ctx,
 805                                        struct sctp_chunk *chunk)
 806 {
 807         struct sctp_transport *new_transport = chunk->transport;
 808
 809         if (!new_transport) {
 810                 if (!sctp_chunk_is_data(chunk)) {
 811                         /* If we have a prior transport pointer, see if
 812                          * the destination address of the chunk
 813                          * matches the destination address of the
 814                          * current transport.  If not a match, then
 815                          * try to look up the transport with a given
 816                          * destination address.  We do this because
 817                          * after processing ASCONFs, we may have new
 818                          * transports created.
 819                          */
 820                         if (ctx->transport && sctp_cmp_addr_exact(&chunk->dest,
 821                                                         &ctx->transport->ipaddr))
 822                                 new_transport = ctx->transport;
 823                         else
 824                                 new_transport = sctp_assoc_lookup_paddr(ctx->asoc,
 825                                                                   &chunk->dest);
 826                 }
 827
 828                 /* if we still don't have a new transport, then
 829                  * use the current active path.
 830                  */
 831                 if (!new_transport)
 832                         new_transport = ctx->asoc->peer.active_path;
 833         } else {
 834                 __u8 type;
 835
 836                 switch (new_transport->state) {
 837                 case SCTP_INACTIVE:
 838                 case SCTP_UNCONFIRMED:
 839                 case SCTP_PF:
 840                         /* If the chunk is Heartbeat or Heartbeat Ack,
 841                          * send it to chunk->transport, even if it's
 842                          * inactive.
 843                          *
 844                          * 3.3.6 Heartbeat Acknowledgement:
 845                          * ...
 846                          * A HEARTBEAT ACK is always sent to the source IP
 847                          * address of the IP datagram containing the
 848                          * HEARTBEAT chunk to which this ack is responding.
 849                          * ...
 850                          *
 851                          * ASCONF_ACKs also must be sent to the source.
 852                          */
 853                         type = chunk->chunk_hdr->type;
 854                         if (type != SCTP_CID_HEARTBEAT &&
 855                             type != SCTP_CID_HEARTBEAT_ACK &&
 856                             type != SCTP_CID_ASCONF_ACK)
 857                                 new_transport = ctx->asoc->peer.active_path;
 858                         break;
 859                 default:
 860                         break;
 861                 }
 862         }
 863
 864         /* Are we switching transports? Take care of transport locks. */
 865         if (new_transport != ctx->transport) {
 866                 ctx->transport = new_transport;
 867                 ctx->packet = &ctx->transport->packet;
 868
 869                 if (list_empty(&ctx->transport->send_ready))
 870                         list_add_tail(&ctx->transport->send_ready,
 871                                       &ctx->transport_list);
 872
 873                 sctp_packet_config(ctx->packet,
 874                                    ctx->asoc->peer.i.init_tag,
 875                                    ctx->asoc->peer.ecn_capable);
 876                 /* We've switched transports, so apply the
 877                  * Burst limit to the new transport.
 878                  */
 879                 sctp_transport_burst_limited(ctx->transport);
 880         }
 881 }
 882
 883 static void sctp_outq_flush_ctrl(struct sctp_flush_ctx *ctx)
 884 {
 885         struct sctp_chunk *chunk, *tmp;
 886         enum sctp_xmit status;
 887         int one_packet, error;
 888
 889         list_for_each_entry_safe(chunk, tmp, &ctx->q->control_chunk_list, list) {
 890                 one_packet = 0;
 891
 892                 /* RFC 5061, 5.3
 893                  * F1) This means that until such time as the ASCONF
 894                  * containing the add is acknowledged, the sender MUST
 895                  * NOT use the new IP address as a source for ANY SCTP
 896                  * packet except on carrying an ASCONF Chunk.
 897                  */
 898                 if (ctx->asoc->src_out_of_asoc_ok &&
 899                     chunk->chunk_hdr->type != SCTP_CID_ASCONF)
 900                         continue;
 901
 902                 list_del_init(&chunk->list);
 903
 904                 /* Pick the right transport to use. Should always be true for
 905                  * the first chunk as we don't have a transport by then.
 906                  */
 907                 sctp_outq_select_transport(ctx, chunk);
 908
 909                 switch (chunk->chunk_hdr->type) {
 910                 /* 6.10 Bundling
 911                  *   ...
 912                  *   An endpoint MUST NOT bundle INIT, INIT ACK or SHUTDOWN
 913                  *   COMPLETE with any other chunks.  [Send them immediately.]
 914                  */
 915                 case SCTP_CID_INIT:
 916                 case SCTP_CID_INIT_ACK:
 917                 case SCTP_CID_SHUTDOWN_COMPLETE:
 918                         error = sctp_packet_singleton(ctx->transport, chunk,
 919                                                       ctx->gfp);
 920                         if (error < 0) {
 921                                 ctx->asoc->base.sk->sk_err = -error;
 922                                 return;
 923                         }
 924                         break;
 925
 926                 case SCTP_CID_ABORT:
 927                         if (sctp_test_T_bit(chunk))
 928                                 ctx->packet->vtag = ctx->asoc->c.my_vtag;
 929                         /* fallthru */
 930
 931                 /* The following chunks are "response" chunks, i.e.
 932                  * they are generated in response to something we
 933                  * received.  If we are sending these, then we can
 934                  * send only 1 packet containing these chunks.
 935                  */
 936                 case SCTP_CID_HEARTBEAT_ACK:
 937                 case SCTP_CID_SHUTDOWN_ACK:
 938                 case SCTP_CID_COOKIE_ACK:
 939                 case SCTP_CID_COOKIE_ECHO:
 940                 case SCTP_CID_ERROR:
 941                 case SCTP_CID_ECN_CWR:
 942                 case SCTP_CID_ASCONF_ACK:
 943                         one_packet = 1;
 944                         /* Fall through */
 945
 946                 case SCTP_CID_SACK:
 947                 case SCTP_CID_HEARTBEAT:
 948                 case SCTP_CID_SHUTDOWN:
 949                 case SCTP_CID_ECN_ECNE:
 950                 case SCTP_CID_ASCONF:
 951                 case SCTP_CID_FWD_TSN:
 952                 case SCTP_CID_I_FWD_TSN:
 953                 case SCTP_CID_RECONF:
 954                         status = sctp_packet_transmit_chunk(ctx->packet, chunk,
 955                                                             one_packet, ctx->gfp);
 956                         if (status != SCTP_XMIT_OK) {
 957                                 /* put the chunk back */
 958                                 list_add(&chunk->list, &ctx->q->control_chunk_list);
 959                                 break;
 960                         }
 961
 962                         ctx->asoc->stats.octrlchunks++;
 963                         /* PR-SCTP C5) If a FORWARD TSN is sent, the
 964                          * sender MUST assure that at least one T3-rtx
 965                          * timer is running.
 966                          */
 967                         if (chunk->chunk_hdr->type == SCTP_CID_FWD_TSN ||
 968                             chunk->chunk_hdr->type == SCTP_CID_I_FWD_TSN) {
 969                                 sctp_transport_reset_t3_rtx(ctx->transport);
 970                                 ctx->transport->last_time_sent = jiffies;
 971                         }
 972
 973                         if (chunk == ctx->asoc->strreset_chunk)
 974                                 sctp_transport_reset_reconf_timer(ctx->transport);
 975
 976                         break;
 977
 978                 default:
 979                         /* We built a chunk with an illegal type! */
 980                         BUG();
 981                 }
 982         }
 983 }
 984
 985 /* Returns false if new data shouldn't be sent */
 986 static bool sctp_outq_flush_rtx(struct sctp_flush_ctx *ctx,
 987                                 int rtx_timeout)
 988 {
 989         int error, start_timer = 0;
 990
 991         if (ctx->asoc->peer.retran_path->state == SCTP_UNCONFIRMED)
 992                 return false;
 993
 994         if (ctx->transport != ctx->asoc->peer.retran_path) {
 995                 /* Switch transports & prepare the packet.  */
 996                 ctx->transport = ctx->asoc->peer.retran_path;
 997                 ctx->packet = &ctx->transport->packet;
 998
 999                 if (list_empty(&ctx->transport->send_ready))
1000                         list_add_tail(&ctx->transport->send_ready,
1001                                       &ctx->transport_list);
1002
1003                 sctp_packet_config(ctx->packet, ctx->asoc->peer.i.init_tag,
1004                                    ctx->asoc->peer.ecn_capable);
1005         }
1006
1007         error = __sctp_outq_flush_rtx(ctx->q, ctx->packet, rtx_timeout,
1008                                       &start_timer, ctx->gfp);
1009         if (error < 0)
1010                 ctx->asoc->base.sk->sk_err = -error;
1011
1012         if (start_timer) {
1013                 sctp_transport_reset_t3_rtx(ctx->transport);
1014                 ctx->transport->last_time_sent = jiffies;
1015         }
1016
1017         /* This can happen on COOKIE-ECHO resend.  Only
1018          * one chunk can get bundled with a COOKIE-ECHO.
1019          */
1020         if (ctx->packet->has_cookie_echo)
1021                 return false;
1022
1023         /* Don't send new data if there is still data
1024          * waiting to retransmit.
1025          */
1026         if (!list_empty(&ctx->q->retransmit))
1027                 return false;
1028
1029         return true;
1030 }
1031
1032 static void sctp_outq_flush_data(struct sctp_flush_ctx *ctx,
1033                                  int rtx_timeout)
1034 {
1035         struct sctp_chunk *chunk;
1036         enum sctp_xmit status;
1037
1038         /* Is it OK to send data chunks?  */
1039         switch (ctx->asoc->state) {
1040         case SCTP_STATE_COOKIE_ECHOED:
1041                 /* Only allow bundling when this packet has a COOKIE-ECHO
1042                  * chunk.
1043                  */
1044                 if (!ctx->packet || !ctx->packet->has_cookie_echo)
1045                         return;
1046
1047                 /* fall through */
1048         case SCTP_STATE_ESTABLISHED:
1049         case SCTP_STATE_SHUTDOWN_PENDING:
1050         case SCTP_STATE_SHUTDOWN_RECEIVED:
1051                 break;
1052
1053         default:
1054                 /* Do nothing. */
1055                 return;
1056         }
1057
1058         /* RFC 2960 6.1  Transmission of DATA Chunks
1059          *
1060          * C) When the time comes for the sender to transmit,
1061          * before sending new DATA chunks, the sender MUST
1062          * first transmit any outstanding DATA chunks which
1063          * are marked for retransmission (limited by the
1064          * current cwnd).
1065          */
1066         if (!list_empty(&ctx->q->retransmit) &&
1067             !sctp_outq_flush_rtx(ctx, rtx_timeout))
1068                 return;
1069
1070         /* Apply Max.Burst limitation to the current transport in
1071          * case it will be used for new data.  We are going to
1072          * rest it before we return, but we want to apply the limit
1073          * to the currently queued data.
1074          */
1075         if (ctx->transport)
1076                 sctp_transport_burst_limited(ctx->transport);
1077
1078         /* Finally, transmit new packets.  */
1079         while ((chunk = sctp_outq_dequeue_data(ctx->q)) != NULL) {
1080                 __u32 sid = ntohs(chunk->subh.data_hdr->stream);
1081                 __u8 stream_state = SCTP_SO(&ctx->asoc->stream, sid)->state;
1082
1083                 /* Has this chunk expired? */
1084                 if (sctp_chunk_abandoned(chunk)) {
1085                         sctp_sched_dequeue_done(ctx->q, chunk);
1086                         sctp_chunk_fail(chunk, 0);
1087                         sctp_chunk_free(chunk);
1088                         continue;
1089                 }
1090
1091                 if (stream_state == SCTP_STREAM_CLOSED) {
1092                         sctp_outq_head_data(ctx->q, chunk);
1093                         break;
1094                 }
1095
1096                 sctp_outq_select_transport(ctx, chunk);
1097
1098                 pr_debug("%s: outq:%p, chunk:%p[%s], tx-tsn:0x%x skb->head:%p skb->users:%d\n",
1099                          __func__, ctx->q, chunk, chunk && chunk->chunk_hdr ?
1100                          sctp_cname(SCTP_ST_CHUNK(chunk->chunk_hdr->type)) :
1101                          "illegal chunk", ntohl(chunk->subh.data_hdr->tsn),
1102                          chunk->skb ? chunk->skb->head : NULL, chunk->skb ?
1103                          refcount_read(&chunk->skb->users) : -1);
1104
1105                 /* Add the chunk to the packet.  */
1106                 status = sctp_packet_transmit_chunk(ctx->packet, chunk, 0,
1107                                                     ctx->gfp);
1108                 if (status != SCTP_XMIT_OK) {
1109                         /* We could not append this chunk, so put
1110                          * the chunk back on the output queue.
1111                          */
1112                         pr_debug("%s: could not transmit tsn:0x%x, status:%d\n",
1113                                  __func__, ntohl(chunk->subh.data_hdr->tsn),
1114                                  status);
1115
1116                         sctp_outq_head_data(ctx->q, chunk);
1117                         break;
1118                 }
1119
1120                 /* The sender is in the SHUTDOWN-PENDING state,
1121                  * The sender MAY set the I-bit in the DATA
1122                  * chunk header.
1123                  */
1124                 if (ctx->asoc->state == SCTP_STATE_SHUTDOWN_PENDING)
1125                         chunk->chunk_hdr->flags |= SCTP_DATA_SACK_IMM;
1126                 if (chunk->chunk_hdr->flags & SCTP_DATA_UNORDERED)
1127                         ctx->asoc->stats.ouodchunks++;
1128                 else
1129                         ctx->asoc->stats.oodchunks++;
1130
1131                 /* Only now it's safe to consider this
1132                  * chunk as sent, sched-wise.
1133                  */
1134                 sctp_sched_dequeue_done(ctx->q, chunk);
1135
1136                 list_add_tail(&chunk->transmitted_list,
1137                               &ctx->transport->transmitted);
1138
1139                 sctp_transport_reset_t3_rtx(ctx->transport);
1140                 ctx->transport->last_time_sent = jiffies;
1141
1142                 /* Only let one DATA chunk get bundled with a
1143                  * COOKIE-ECHO chunk.
1144                  */
1145                 if (ctx->packet->has_cookie_echo)
1146                         break;
1147         }
1148 }
1149
1150 static void sctp_outq_flush_transports(struct sctp_flush_ctx *ctx)
1151 {
1152         struct list_head *ltransport;
1153         struct sctp_packet *packet;
1154         struct sctp_transport *t;
1155         int error = 0;
1156
1157         while ((ltransport = sctp_list_dequeue(&ctx->transport_list)) != NULL) {
1158                 t = list_entry(ltransport, struct sctp_transport, send_ready);
1159                 packet = &t->packet;
1160                 if (!sctp_packet_empty(packet)) {
1161                         error = sctp_packet_transmit(packet, ctx->gfp);
1162                         if (error < 0)
1163                                 ctx->q->asoc->base.sk->sk_err = -error;
1164                 }
1165
1166                 /* Clear the burst limited state, if any */
1167                 sctp_transport_burst_reset(t);
1168         }
1169 }
1170
1171 /* Try to flush an outqueue.
1172  *
1173  * Description: Send everything in q which we legally can, subject to
1174  * congestion limitations.
1175  * * Note: This function can be called from multiple contexts so appropriate
1176  * locking concerns must be made.  Today we use the sock lock to protect
1177  * this function.
1178  */
1179
1180 static void sctp_outq_flush(struct sctp_outq *q, int rtx_timeout, gfp_t gfp)
1181 {
1182         struct sctp_flush_ctx ctx = {
1183                 .q = q,
1184                 .transport = NULL,
1185                 .transport_list = LIST_HEAD_INIT(ctx.transport_list),
1186                 .asoc = q->asoc,
1187                 .packet = NULL,
1188                 .gfp = gfp,
1189         };
1190
1191         /* 6.10 Bundling
1192          *   ...
1193          *   When bundling control chunks with DATA chunks, an
1194          *   endpoint MUST place control chunks first in the outbound
1195          *   SCTP packet.  The transmitter MUST transmit DATA chunks
1196          *   within a SCTP packet in increasing order of TSN.
1197          *   ...
1198          */
1199
1200         sctp_outq_flush_ctrl(&ctx);
1201
1202         if (q->asoc->src_out_of_asoc_ok)
1203                 goto sctp_flush_out;
1204
1205         sctp_outq_flush_data(&ctx, rtx_timeout);
1206
1207 sctp_flush_out:
1208
1209         sctp_outq_flush_transports(&ctx);
1210 }
1211
1212 /* Update unack_data based on the incoming SACK chunk */
1213 static void sctp_sack_update_unack_data(struct sctp_association *assoc,
1214                                         struct sctp_sackhdr *sack)
1215 {
1216         union sctp_sack_variable *frags;
1217         __u16 unack_data;
1218         int i;
1219
1220         unack_data = assoc->next_tsn - assoc->ctsn_ack_point - 1;
1221
1222         frags = sack->variable;
1223         for (i = 0; i < ntohs(sack->num_gap_ack_blocks); i++) {
1224                 unack_data -= ((ntohs(frags[i].gab.end) -
1225                                 ntohs(frags[i].gab.start) + 1));
1226         }
1227
1228         assoc->unack_data = unack_data;
1229 }
1230
1231 /* This is where we REALLY process a SACK.
1232  *
1233  * Process the SACK against the outqueue.  Mostly, this just frees
1234  * things off the transmitted queue.
1235  */
1236 int sctp_outq_sack(struct sctp_outq *q, struct sctp_chunk *chunk)
1237 {
1238         struct sctp_association *asoc = q->asoc;
1239         struct sctp_sackhdr *sack = chunk->subh.sack_hdr;
1240         struct sctp_transport *transport;
1241         struct sctp_chunk *tchunk = NULL;
1242         struct list_head *lchunk, *transport_list, *temp;
1243         union sctp_sack_variable *frags = sack->variable;
1244         __u32 sack_ctsn, ctsn, tsn;
1245         __u32 highest_tsn, highest_new_tsn;
1246         __u32 sack_a_rwnd;
1247         unsigned int outstanding;
1248         struct sctp_transport *primary = asoc->peer.primary_path;
1249         int count_of_newacks = 0;
1250         int gap_ack_blocks;
1251         u8 accum_moved = 0;
1252
1253         /* Grab the association's destination address list. */
1254         transport_list = &asoc->peer.transport_addr_list;
1255
1256         sack_ctsn = ntohl(sack->cum_tsn_ack);
1257         gap_ack_blocks = ntohs(sack->num_gap_ack_blocks);
1258         asoc->stats.gapcnt += gap_ack_blocks;
1259         /*
1260          * SFR-CACC algorithm:
1261          * On receipt of a SACK the sender SHOULD execute the
1262          * following statements.
1263          *
1264          * 1) If the cumulative ack in the SACK passes next tsn_at_change
1265          * on the current primary, the CHANGEOVER_ACTIVE flag SHOULD be
1266          * cleared. The CYCLING_CHANGEOVER flag SHOULD also be cleared for
1267          * all destinations.
1268          * 2) If the SACK contains gap acks and the flag CHANGEOVER_ACTIVE
1269          * is set the receiver of the SACK MUST take the following actions:
1270          *
1271          * A) Initialize the cacc_saw_newack to 0 for all destination
1272          * addresses.
1273          *
1274          * Only bother if changeover_active is set. Otherwise, this is
1275          * totally suboptimal to do on every SACK.
1276          */
1277         if (primary->cacc.changeover_active) {
1278                 u8 clear_cycling = 0;
1279
1280                 if (TSN_lte(primary->cacc.next_tsn_at_change, sack_ctsn)) {
1281                         primary->cacc.changeover_active = 0;
1282                         clear_cycling = 1;
1283                 }
1284
1285                 if (clear_cycling || gap_ack_blocks) {
1286                         list_for_each_entry(transport, transport_list,
1287                                         transports) {
1288                                 if (clear_cycling)
1289                                         transport->cacc.cycling_changeover = 0;
1290                                 if (gap_ack_blocks)
1291                                         transport->cacc.cacc_saw_newack = 0;
1292                         }
1293                 }
1294         }
1295
1296         /* Get the highest TSN in the sack. */
1297         highest_tsn = sack_ctsn;
1298         if (gap_ack_blocks)
1299                 highest_tsn += ntohs(frags[gap_ack_blocks - 1].gab.end);
1300
1301         if (TSN_lt(asoc->highest_sacked, highest_tsn))
1302                 asoc->highest_sacked = highest_tsn;
1303
1304         highest_new_tsn = sack_ctsn;
1305
1306         /* Run through the retransmit queue.  Credit bytes received
1307          * and free those chunks that we can.
1308          */
1309         sctp_check_transmitted(q, &q->retransmit, NULL, NULL, sack, &highest_new_tsn);
1310
1311         /* Run through the transmitted queue.
1312          * Credit bytes received and free those chunks which we can.
1313          *
1314          * This is a MASSIVE candidate for optimization.
1315          */
1316         list_for_each_entry(transport, transport_list, transports) {
1317                 sctp_check_transmitted(q, &transport->transmitted,
1318                                        transport, &chunk->source, sack,
1319                                        &highest_new_tsn);
1320                 /*
1321                  * SFR-CACC algorithm:
1322                  * C) Let count_of_newacks be the number of
1323                  * destinations for which cacc_saw_newack is set.
1324                  */
1325                 if (transport->cacc.cacc_saw_newack)
1326                         count_of_newacks++;
1327         }
1328
1329         /* Move the Cumulative TSN Ack Point if appropriate.  */
1330         if (TSN_lt(asoc->ctsn_ack_point, sack_ctsn)) {
1331                 asoc->ctsn_ack_point = sack_ctsn;
1332                 accum_moved = 1;
1333         }
1334
1335         if (gap_ack_blocks) {
1336
1337                 if (asoc->fast_recovery && accum_moved)
1338                         highest_new_tsn = highest_tsn;
1339
1340                 list_for_each_entry(transport, transport_list, transports)
1341                         sctp_mark_missing(q, &transport->transmitted, transport,
1342                                           highest_new_tsn, count_of_newacks);
1343         }
1344
1345         /* Update unack_data field in the assoc. */
1346         sctp_sack_update_unack_data(asoc, sack);
1347
1348         ctsn = asoc->ctsn_ack_point;
1349
1350         /* Throw away stuff rotting on the sack queue.  */
1351         list_for_each_safe(lchunk, temp, &q->sacked) {
1352                 tchunk = list_entry(lchunk, struct sctp_chunk,
1353                                     transmitted_list);
1354                 tsn = ntohl(tchunk->subh.data_hdr->tsn);
1355                 if (TSN_lte(tsn, ctsn)) {
1356                         list_del_init(&tchunk->transmitted_list);
1357                         if (asoc->peer.prsctp_capable &&
1358                             SCTP_PR_PRIO_ENABLED(chunk->sinfo.sinfo_flags))
1359                                 asoc->sent_cnt_removable--;
1360                         sctp_chunk_free(tchunk);
1361                 }
1362         }
1363
1364         /* ii) Set rwnd equal to the newly received a_rwnd minus the
1365          *     number of bytes still outstanding after processing the
1366          *     Cumulative TSN Ack and the Gap Ack Blocks.
1367          */
1368
1369         sack_a_rwnd = ntohl(sack->a_rwnd);
1370         asoc->peer.zero_window_announced = !sack_a_rwnd;
1371         outstanding = q->outstanding_bytes;
1372
1373         if (outstanding < sack_a_rwnd)
1374                 sack_a_rwnd -= outstanding;
1375         else
1376                 sack_a_rwnd = 0;
1377
1378         asoc->peer.rwnd = sack_a_rwnd;
1379
1380         asoc->stream.si->generate_ftsn(q, sack_ctsn);
1381
1382         pr_debug("%s: sack cumulative tsn ack:0x%x\n", __func__, sack_ctsn);
1383         pr_debug("%s: cumulative tsn ack of assoc:%p is 0x%x, "
1384                  "advertised peer ack point:0x%x\n", __func__, asoc, ctsn,
1385                  asoc->adv_peer_ack_point);
1386
1387         return sctp_outq_is_empty(q);
1388 }
1389
1390 /* Is the outqueue empty?
1391  * The queue is empty when we have not pending data, no in-flight data
1392  * and nothing pending retransmissions.
1393  */
1394 int sctp_outq_is_empty(const struct sctp_outq *q)
1395 {
1396         return q->out_qlen == 0 && q->outstanding_bytes == 0 &&
1397                list_empty(&q->retransmit);
1398 }
1399
1400 /********************************************************************
1401  * 2nd Level Abstractions
1402  ********************************************************************/
1403
1404 /* Go through a transport's transmitted list or the association's retransmit
1405  * list and move chunks that are acked by the Cumulative TSN Ack to q->sacked.
1406  * The retransmit list will not have an associated transport.
1407  *
1408  * I added coherent debug information output.   --xguo
1409  *
1410  * Instead of printing 'sacked' or 'kept' for each TSN on the
1411  * transmitted_queue, we print a range: SACKED: TSN1-TSN2, TSN3, TSN4-TSN5.
1412  * KEPT TSN6-TSN7, etc.
1413  */
1414 static void sctp_check_transmitted(struct sctp_outq *q,
1415                                    struct list_head *transmitted_queue,
1416                                    struct sctp_transport *transport,
1417                                    union sctp_addr *saddr,
1418                                    struct sctp_sackhdr *sack,
1419                                    __u32 *highest_new_tsn_in_sack)
1420 {
1421         struct list_head *lchunk;
1422         struct sctp_chunk *tchunk;
1423         struct list_head tlist;
1424         __u32 tsn;
1425         __u32 sack_ctsn;
1426         __u32 rtt;
1427         __u8 restart_timer = 0;
1428         int bytes_acked = 0;
1429         int migrate_bytes = 0;
1430         bool forward_progress = false;
1431
1432         sack_ctsn = ntohl(sack->cum_tsn_ack);
1433
1434         INIT_LIST_HEAD(&tlist);
1435
1436         /* The while loop will skip empty transmitted queues. */
1437         while (NULL != (lchunk = sctp_list_dequeue(transmitted_queue))) {
1438                 tchunk = list_entry(lchunk, struct sctp_chunk,
1439                                     transmitted_list);
1440
1441                 if (sctp_chunk_abandoned(tchunk)) {
1442                         /* Move the chunk to abandoned list. */
1443                         sctp_insert_list(&q->abandoned, lchunk);
1444
1445                         /* If this chunk has not been acked, stop
1446                          * considering it as 'outstanding'.
1447                          */
1448                         if (transmitted_queue != &q->retransmit &&
1449                             !tchunk->tsn_gap_acked) {
1450                                 if (tchunk->transport)
1451                                         tchunk->transport->flight_size -=
1452                                                         sctp_data_size(tchunk);
1453                                 q->outstanding_bytes -= sctp_data_size(tchunk);
1454                         }
1455                         continue;
1456                 }
1457
1458                 tsn = ntohl(tchunk->subh.data_hdr->tsn);
1459                 if (sctp_acked(sack, tsn)) {
1460                         /* If this queue is the retransmit queue, the
1461                          * retransmit timer has already reclaimed
1462                          * the outstanding bytes for this chunk, so only
1463                          * count bytes associated with a transport.
1464                          */
1465                         if (transport && !tchunk->tsn_gap_acked) {
1466                                 /* If this chunk is being used for RTT
1467                                  * measurement, calculate the RTT and update
1468                                  * the RTO using this value.
1469                                  *
1470                                  * 6.3.1 C5) Karn's algorithm: RTT measurements
1471                                  * MUST NOT be made using packets that were
1472                                  * retransmitted (and thus for which it is
1473                                  * ambiguous whether the reply was for the
1474                                  * first instance of the packet or a later
1475                                  * instance).
1476                                  */
1477                                 if (!sctp_chunk_retransmitted(tchunk) &&
1478                                     tchunk->rtt_in_progress) {
1479                                         tchunk->rtt_in_progress = 0;
1480                                         rtt = jiffies - tchunk->sent_at;
1481                                         sctp_transport_update_rto(transport,
1482                                                                   rtt);
1483                                 }
1484
1485                                 if (TSN_lte(tsn, sack_ctsn)) {
1486                                         /*
1487                                          * SFR-CACC algorithm:
1488                                          * 2) If the SACK contains gap acks
1489                                          * and the flag CHANGEOVER_ACTIVE is
1490                                          * set the receiver of the SACK MUST
1491                                          * take the following action:
1492                                          *
1493                                          * B) For each TSN t being acked that
1494                                          * has not been acked in any SACK so
1495                                          * far, set cacc_saw_newack to 1 for
1496                                          * the destination that the TSN was
1497                                          * sent to.
1498                                          */
1499                                         if (sack->num_gap_ack_blocks &&
1500                                             q->asoc->peer.primary_path->cacc.
1501                                             changeover_active)
1502                                                 transport->cacc.cacc_saw_newack
1503                                                         = 1;
1504                                 }
1505                         }
1506
1507                         /* If the chunk hasn't been marked as ACKED,
1508                          * mark it and account bytes_acked if the
1509                          * chunk had a valid transport (it will not
1510                          * have a transport if ASCONF had deleted it
1511                          * while DATA was outstanding).
1512                          */
1513                         if (!tchunk->tsn_gap_acked) {
1514                                 tchunk->tsn_gap_acked = 1;
1515                                 if (TSN_lt(*highest_new_tsn_in_sack, tsn))
1516                                         *highest_new_tsn_in_sack = tsn;
1517                                 bytes_acked += sctp_data_size(tchunk);
1518                                 if (!tchunk->transport)
1519                                         migrate_bytes += sctp_data_size(tchunk);
1520                                 forward_progress = true;
1521                         }
1522
1523                         if (TSN_lte(tsn, sack_ctsn)) {
1524                                 /* RFC 2960  6.3.2 Retransmission Timer Rules
1525                                  *
1526                                  * R3) Whenever a SACK is received
1527                                  * that acknowledges the DATA chunk
1528                                  * with the earliest outstanding TSN
1529                                  * for that address, restart T3-rtx
1530                                  * timer for that address with its
1531                                  * current RTO.
1532                                  */
1533                                 restart_timer = 1;
1534                                 forward_progress = true;
1535
1536                                 list_add_tail(&tchunk->transmitted_list,
1537                                               &q->sacked);
1538                         } else {
1539                                 /* RFC2960 7.2.4, sctpimpguide-05 2.8.2
1540                                  * M2) Each time a SACK arrives reporting
1541                                  * 'Stray DATA chunk(s)' record the highest TSN
1542                                  * reported as newly acknowledged, call this
1543                                  * value 'HighestTSNinSack'. A newly
1544                                  * acknowledged DATA chunk is one not
1545                                  * previously acknowledged in a SACK.
1546                                  *
1547                                  * When the SCTP sender of data receives a SACK
1548                                  * chunk that acknowledges, for the first time,
1549                                  * the receipt of a DATA chunk, all the still
1550                                  * unacknowledged DATA chunks whose TSN is
1551                                  * older than that newly acknowledged DATA
1552                                  * chunk, are qualified as 'Stray DATA chunks'.
1553                                  */
1554                                 list_add_tail(lchunk, &tlist);
1555                         }
1556                 } else {
1557                         if (tchunk->tsn_gap_acked) {
1558                                 pr_debug("%s: receiver reneged on data TSN:0x%x\n",
1559                                          __func__, tsn);
1560
1561                                 tchunk->tsn_gap_acked = 0;
1562
1563                                 if (tchunk->transport)
1564                                         bytes_acked -= sctp_data_size(tchunk);
1565
1566                                 /* RFC 2960 6.3.2 Retransmission Timer Rules
1567                                  *
1568                                  * R4) Whenever a SACK is received missing a
1569                                  * TSN that was previously acknowledged via a
1570                                  * Gap Ack Block, start T3-rtx for the
1571                                  * destination address to which the DATA
1572                                  * chunk was originally
1573                                  * transmitted if it is not already running.
1574                                  */
1575                                 restart_timer = 1;
1576                         }
1577
1578                         list_add_tail(lchunk, &tlist);
1579                 }
1580         }
1581
1582         if (transport) {
1583                 if (bytes_acked) {
1584                         struct sctp_association *asoc = transport->asoc;
1585
1586                         /* We may have counted DATA that was migrated
1587                          * to this transport due to DEL-IP operation.
1588                          * Subtract those bytes, since the were never
1589                          * send on this transport and shouldn't be
1590                          * credited to this transport.
1591                          */
1592                         bytes_acked -= migrate_bytes;
1593
1594                         /* 8.2. When an outstanding TSN is acknowledged,
1595                          * the endpoint shall clear the error counter of
1596                          * the destination transport address to which the
1597                          * DATA chunk was last sent.
1598                          * The association's overall error counter is
1599                          * also cleared.
1600                          */
1601                         transport->error_count = 0;
1602                         transport->asoc->overall_error_count = 0;
1603                         forward_progress = true;
1604
1605                         /*
1606                          * While in SHUTDOWN PENDING, we may have started
1607                          * the T5 shutdown guard timer after reaching the
1608                          * retransmission limit. Stop that timer as soon
1609                          * as the receiver acknowledged any data.
1610                          */
1611                         if (asoc->state == SCTP_STATE_SHUTDOWN_PENDING &&
1612                             del_timer(&asoc->timers
1613                                 [SCTP_EVENT_TIMEOUT_T5_SHUTDOWN_GUARD]))
1614                                         sctp_association_put(asoc);
1615
1616                         /* Mark the destination transport address as
1617                          * active if it is not so marked.
1618                          */
1619                         if ((transport->state == SCTP_INACTIVE ||
1620                              transport->state == SCTP_UNCONFIRMED) &&
1621                             sctp_cmp_addr_exact(&transport->ipaddr, saddr)) {
1622                                 sctp_assoc_control_transport(
1623                                         transport->asoc,
1624                                         transport,
1625                                         SCTP_TRANSPORT_UP,
1626                                         SCTP_RECEIVED_SACK);
1627                         }
1628
1629                         sctp_transport_raise_cwnd(transport, sack_ctsn,
1630                                                   bytes_acked);
1631
1632                         transport->flight_size -= bytes_acked;
1633                         if (transport->flight_size == 0)
1634                                 transport->partial_bytes_acked = 0;
1635                         q->outstanding_bytes -= bytes_acked + migrate_bytes;
1636                 } else {
1637                         /* RFC 2960 6.1, sctpimpguide-06 2.15.2
1638                          * When a sender is doing zero window probing, it
1639                          * should not timeout the association if it continues
1640                          * to receive new packets from the receiver. The
1641                          * reason is that the receiver MAY keep its window
1642                          * closed for an indefinite time.
1643                          * A sender is doing zero window probing when the
1644                          * receiver's advertised window is zero, and there is
1645                          * only one data chunk in flight to the receiver.
1646                          *
1647                          * Allow the association to timeout while in SHUTDOWN
1648                          * PENDING or SHUTDOWN RECEIVED in case the receiver
1649                          * stays in zero window mode forever.
1650                          */
1651                         if (!q->asoc->peer.rwnd &&
1652                             !list_empty(&tlist) &&
1653                             (sack_ctsn+2 == q->asoc->next_tsn) &&
1654                             q->asoc->state < SCTP_STATE_SHUTDOWN_PENDING) {
1655                                 pr_debug("%s: sack received for zero window "
1656                                          "probe:%u\n", __func__, sack_ctsn);
1657
1658                                 q->asoc->overall_error_count = 0;
1659                                 transport->error_count = 0;
1660                         }
1661                 }
1662
1663                 /* RFC 2960 6.3.2 Retransmission Timer Rules
1664                  *
1665                  * R2) Whenever all outstanding data sent to an address have
1666                  * been acknowledged, turn off the T3-rtx timer of that
1667                  * address.
1668                  */
1669                 if (!transport->flight_size) {
1670                         if (del_timer(&transport->T3_rtx_timer))
1671                                 sctp_transport_put(transport);
1672                 } else if (restart_timer) {
1673                         if (!mod_timer(&transport->T3_rtx_timer,
1674                                        jiffies + transport->rto))
1675                                 sctp_transport_hold(transport);
1676                 }
1677
1678                 if (forward_progress) {
1679                         if (transport->dst)
1680                                 sctp_transport_dst_confirm(transport);
1681                 }
1682         }
1683
1684         list_splice(&tlist, transmitted_queue);
1685 }
1686
1687 /* Mark chunks as missing and consequently may get retransmitted. */
1688 static void sctp_mark_missing(struct sctp_outq *q,
1689                               struct list_head *transmitted_queue,
1690                               struct sctp_transport *transport,
1691                               __u32 highest_new_tsn_in_sack,
1692                               int count_of_newacks)
1693 {
1694         struct sctp_chunk *chunk;
1695         __u32 tsn;
1696         char do_fast_retransmit = 0;
1697         struct sctp_association *asoc = q->asoc;
1698         struct sctp_transport *primary = asoc->peer.primary_path;
1699
1700         list_for_each_entry(chunk, transmitted_queue, transmitted_list) {
1701
1702                 tsn = ntohl(chunk->subh.data_hdr->tsn);
1703
1704                 /* RFC 2960 7.2.4, sctpimpguide-05 2.8.2 M3) Examine all
1705                  * 'Unacknowledged TSN's', if the TSN number of an
1706                  * 'Unacknowledged TSN' is smaller than the 'HighestTSNinSack'
1707                  * value, increment the 'TSN.Missing.Report' count on that
1708                  * chunk if it has NOT been fast retransmitted or marked for
1709                  * fast retransmit already.
1710                  */
1711                 if (chunk->fast_retransmit == SCTP_CAN_FRTX &&
1712                     !chunk->tsn_gap_acked &&
1713                     TSN_lt(tsn, highest_new_tsn_in_sack)) {
1714
1715                         /* SFR-CACC may require us to skip marking
1716                          * this chunk as missing.
1717                          */
1718                         if (!transport || !sctp_cacc_skip(primary,
1719                                                 chunk->transport,
1720                                                 count_of_newacks, tsn)) {
1721                                 chunk->tsn_missing_report++;
1722
1723                                 pr_debug("%s: tsn:0x%x missing counter:%d\n",
1724                                          __func__, tsn, chunk->tsn_missing_report);
1725                         }
1726                 }
1727                 /*
1728                  * M4) If any DATA chunk is found to have a
1729                  * 'TSN.Missing.Report'
1730                  * value larger than or equal to 3, mark that chunk for
1731                  * retransmission and start the fast retransmit procedure.
1732                  */
1733
1734                 if (chunk->tsn_missing_report >= 3) {
1735                         chunk->fast_retransmit = SCTP_NEED_FRTX;
1736                         do_fast_retransmit = 1;
1737                 }
1738         }
1739
1740         if (transport) {
1741                 if (do_fast_retransmit)
1742                         sctp_retransmit(q, transport, SCTP_RTXR_FAST_RTX);
1743
1744                 pr_debug("%s: transport:%p, cwnd:%d, ssthresh:%d, "
1745                          "flight_size:%d, pba:%d\n",  __func__, transport,
1746                          transport->cwnd, transport->ssthresh,
1747                          transport->flight_size, transport->partial_bytes_acked);
1748         }
1749 }
1750
1751 /* Is the given TSN acked by this packet?  */
1752 static int sctp_acked(struct sctp_sackhdr *sack, __u32 tsn)
1753 {
1754         __u32 ctsn = ntohl(sack->cum_tsn_ack);
1755         union sctp_sack_variable *frags;
1756         __u16 tsn_offset, blocks;
1757         int i;
1758
1759         if (TSN_lte(tsn, ctsn))
1760                 goto pass;
1761
1762         /* 3.3.4 Selective Acknowledgment (SACK) (3):
1763          *
1764          * Gap Ack Blocks:
1765          *  These fields contain the Gap Ack Blocks. They are repeated
1766          *  for each Gap Ack Block up to the number of Gap Ack Blocks
1767          *  defined in the Number of Gap Ack Blocks field. All DATA
1768          *  chunks with TSNs greater than or equal to (Cumulative TSN
1769          *  Ack + Gap Ack Block Start) and less than or equal to
1770          *  (Cumulative TSN Ack + Gap Ack Block End) of each Gap Ack
1771          *  Block are assumed to have been received correctly.
1772          */
1773
1774         frags = sack->variable;
1775         blocks = ntohs(sack->num_gap_ack_blocks);
1776         tsn_offset = tsn - ctsn;
1777         for (i = 0; i < blocks; ++i) {
1778                 if (tsn_offset >= ntohs(frags[i].gab.start) &&
1779                     tsn_offset <= ntohs(frags[i].gab.end))
1780                         goto pass;
1781         }
1782
1783         return 0;
1784 pass:
1785         return 1;
1786 }
1787
1788 static inline int sctp_get_skip_pos(struct sctp_fwdtsn_skip *skiplist,
1789                                     int nskips, __be16 stream)
1790 {
1791         int i;
1792
1793         for (i = 0; i < nskips; i++) {
1794                 if (skiplist[i].stream == stream)
1795                         return i;
1796         }
1797         return i;
1798 }
1799
1800 /* Create and add a fwdtsn chunk to the outq's control queue if needed. */
1801 void sctp_generate_fwdtsn(struct sctp_outq *q, __u32 ctsn)
1802 {
1803         struct sctp_association *asoc = q->asoc;
1804         struct sctp_chunk *ftsn_chunk = NULL;
1805         struct sctp_fwdtsn_skip ftsn_skip_arr[10];
1806         int nskips = 0;
1807         int skip_pos = 0;
1808         __u32 tsn;
1809         struct sctp_chunk *chunk;
1810         struct list_head *lchunk, *temp;
1811
1812         if (!asoc->peer.prsctp_capable)
1813                 return;
1814
1815         /* PR-SCTP C1) Let SackCumAck be the Cumulative TSN ACK carried in the
1816          * received SACK.
1817          *
1818          * If (Advanced.Peer.Ack.Point < SackCumAck), then update
1819          * Advanced.Peer.Ack.Point to be equal to SackCumAck.
1820          */
1821         if (TSN_lt(asoc->adv_peer_ack_point, ctsn))
1822                 asoc->adv_peer_ack_point = ctsn;
1823
1824         /* PR-SCTP C2) Try to further advance the "Advanced.Peer.Ack.Point"
1825          * locally, that is, to move "Advanced.Peer.Ack.Point" up as long as
1826          * the chunk next in the out-queue space is marked as "abandoned" as
1827          * shown in the following example:
1828          *
1829          * Assuming that a SACK arrived with the Cumulative TSN ACK 102
1830          * and the Advanced.Peer.Ack.Point is updated to this value:
1831          *
1832          *   out-queue at the end of  ==>   out-queue after Adv.Ack.Point
1833          *   normal SACK processing           local advancement
1834          *                ...                           ...
1835          *   Adv.Ack.Pt-> 102 acked                     102 acked
1836          *                103 abandoned                 103 abandoned
1837          *                104 abandoned     Adv.Ack.P-> 104 abandoned
1838          *                105                           105
1839          *                106 acked                     106 acked
1840          *                ...                           ...
1841          *
1842          * In this example, the data sender successfully advanced the
1843          * "Advanced.Peer.Ack.Point" from 102 to 104 locally.
1844          */
1845         list_for_each_safe(lchunk, temp, &q->abandoned) {
1846                 chunk = list_entry(lchunk, struct sctp_chunk,
1847                                         transmitted_list);
1848                 tsn = ntohl(chunk->subh.data_hdr->tsn);
1849
1850                 /* Remove any chunks in the abandoned queue that are acked by
1851                  * the ctsn.
1852                  */
1853                 if (TSN_lte(tsn, ctsn)) {
1854                         list_del_init(lchunk);
1855                         sctp_chunk_free(chunk);
1856                 } else {
1857                         if (TSN_lte(tsn, asoc->adv_peer_ack_point+1)) {
1858                                 asoc->adv_peer_ack_point = tsn;
1859                                 if (chunk->chunk_hdr->flags &
1860                                          SCTP_DATA_UNORDERED)
1861                                         continue;
1862                                 skip_pos = sctp_get_skip_pos(&ftsn_skip_arr[0],
1863                                                 nskips,
1864                                                 chunk->subh.data_hdr->stream);
1865                                 ftsn_skip_arr[skip_pos].stream =
1866                                         chunk->subh.data_hdr->stream;
1867                                 ftsn_skip_arr[skip_pos].ssn =
1868                                          chunk->subh.data_hdr->ssn;
1869                                 if (skip_pos == nskips)
1870                                         nskips++;
1871                                 if (nskips == 10)
1872                                         break;
1873                         } else
1874                                 break;
1875                 }
1876         }
1877
1878         /* PR-SCTP C3) If, after step C1 and C2, the "Advanced.Peer.Ack.Point"
1879          * is greater than the Cumulative TSN ACK carried in the received
1880          * SACK, the data sender MUST send the data receiver a FORWARD TSN
1881          * chunk containing the latest value of the
1882          * "Advanced.Peer.Ack.Point".
1883          *
1884          * C4) For each "abandoned" TSN the sender of the FORWARD TSN SHOULD
1885          * list each stream and sequence number in the forwarded TSN. This
1886          * information will enable the receiver to easily find any
1887          * stranded TSN's waiting on stream reorder queues. Each stream
1888          * SHOULD only be reported once; this means that if multiple
1889          * abandoned messages occur in the same stream then only the
1890          * highest abandoned stream sequence number is reported. If the
1891          * total size of the FORWARD TSN does NOT fit in a single MTU then
1892          * the sender of the FORWARD TSN SHOULD lower the
1893          * Advanced.Peer.Ack.Point to the last TSN that will fit in a
1894          * single MTU.
1895          */
1896         if (asoc->adv_peer_ack_point > ctsn)
1897                 ftsn_chunk = sctp_make_fwdtsn(asoc, asoc->adv_peer_ack_point,
1898                                               nskips, &ftsn_skip_arr[0]);
1899
1900         if (ftsn_chunk) {
1901                 list_add_tail(&ftsn_chunk->list, &q->control_chunk_list);
1902                 SCTP_INC_STATS(sock_net(asoc->base.sk), SCTP_MIB_OUTCTRLCHUNKS);
1903         }
1904 }