net/sctp/outqueue.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /* SCTP kernel implementation
   3  * (C) Copyright IBM Corp. 2001, 2004
   4  * Copyright (c) 1999-2000 Cisco, Inc.
   5  * Copyright (c) 1999-2001 Motorola, Inc.
   6  * Copyright (c) 2001-2003 Intel Corp.
   7  *
   8  * This file is part of the SCTP kernel implementation
   9  *
  10  * These functions implement the sctp_outq class.   The outqueue handles
  11  * bundling and queueing of outgoing SCTP chunks.
  12  *
  13  * Please send any bug reports or fixes you make to the
  14  * email address(es):
  15  *    lksctp developers <linux-sctp@vger.kernel.org>
  16  *
  17  * Written or modified by:
  18  *    La Monte H.P. Yarroll <piggy@acm.org>
  19  *    Karl Knutson          <karl@athena.chicago.il.us>
  20  *    Perry Melange         <pmelange@null.cc.uic.edu>
  21  *    Xingang Guo           <xingang.guo@intel.com>
  22  *    Hui Huang             <hui.huang@nokia.com>
  23  *    Sridhar Samudrala     <sri@us.ibm.com>
  24  *    Jon Grimm             <jgrimm@us.ibm.com>
  25  */
  26
  27 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  28
  29 #include <linux/types.h>
  30 #include <linux/list.h>   /* For struct list_head */
  31 #include <linux/socket.h>
  32 #include <linux/ip.h>
  33 #include <linux/slab.h>
  34 #include <net/sock.h>     /* For skb_set_owner_w */
  35
  36 #include <net/sctp/sctp.h>
  37 #include <net/sctp/sm.h>
  38 #include <net/sctp/stream_sched.h>
  39 #include <trace/events/sctp.h>
  40
  41 /* Declare internal functions here.  */
  42 static int sctp_acked(struct sctp_sackhdr *sack, __u32 tsn);
  43 static void sctp_check_transmitted(struct sctp_outq *q,
  44                                    struct list_head *transmitted_queue,
  45                                    struct sctp_transport *transport,
  46                                    union sctp_addr *saddr,
  47                                    struct sctp_sackhdr *sack,
  48                                    __u32 *highest_new_tsn);
  49
  50 static void sctp_mark_missing(struct sctp_outq *q,
  51                               struct list_head *transmitted_queue,
  52                               struct sctp_transport *transport,
  53                               __u32 highest_new_tsn,
  54                               int count_of_newacks);
  55
  56 static void sctp_outq_flush(struct sctp_outq *q, int rtx_timeout, gfp_t gfp);
  57
  58 /* Add data to the front of the queue. */
  59 static inline void sctp_outq_head_data(struct sctp_outq *q,
  60                                        struct sctp_chunk *ch)
  61 {
  62         struct sctp_stream_out_ext *oute;
  63         __u16 stream;
  64
  65         list_add(&ch->list, &q->out_chunk_list);
  66         q->out_qlen += ch->skb->len;
  67
  68         stream = sctp_chunk_stream_no(ch);
  69         oute = SCTP_SO(&q->asoc->stream, stream)->ext;
  70         list_add(&ch->stream_list, &oute->outq);
  71 }
  72
  73 /* Take data from the front of the queue. */
  74 static inline struct sctp_chunk *sctp_outq_dequeue_data(struct sctp_outq *q)
  75 {
  76         return q->sched->dequeue(q);
  77 }
  78
  79 /* Add data chunk to the end of the queue. */
  80 static inline void sctp_outq_tail_data(struct sctp_outq *q,
  81                                        struct sctp_chunk *ch)
  82 {
  83         struct sctp_stream_out_ext *oute;
  84         __u16 stream;
  85
  86         list_add_tail(&ch->list, &q->out_chunk_list);
  87         q->out_qlen += ch->skb->len;
  88
  89         stream = sctp_chunk_stream_no(ch);
  90         oute = SCTP_SO(&q->asoc->stream, stream)->ext;
  91         list_add_tail(&ch->stream_list, &oute->outq);
  92 }
  93
  94 /*
  95  * SFR-CACC algorithm:
  96  * D) If count_of_newacks is greater than or equal to 2
  97  * and t was not sent to the current primary then the
  98  * sender MUST NOT increment missing report count for t.
  99  */
 100 static inline int sctp_cacc_skip_3_1_d(struct sctp_transport *primary,
 101                                        struct sctp_transport *transport,
 102                                        int count_of_newacks)
 103 {
 104         if (count_of_newacks >= 2 && transport != primary)
 105                 return 1;
 106         return 0;
 107 }
 108
 109 /*
 110  * SFR-CACC algorithm:
 111  * F) If count_of_newacks is less than 2, let d be the
 112  * destination to which t was sent. If cacc_saw_newack
 113  * is 0 for destination d, then the sender MUST NOT
 114  * increment missing report count for t.
 115  */
 116 static inline int sctp_cacc_skip_3_1_f(struct sctp_transport *transport,
 117                                        int count_of_newacks)
 118 {
 119         if (count_of_newacks < 2 &&
 120                         (transport && !transport->cacc.cacc_saw_newack))
 121                 return 1;
 122         return 0;
 123 }
 124
 125 /*
 126  * SFR-CACC algorithm:
 127  * 3.1) If CYCLING_CHANGEOVER is 0, the sender SHOULD
 128  * execute steps C, D, F.
 129  *
 130  * C has been implemented in sctp_outq_sack
 131  */
 132 static inline int sctp_cacc_skip_3_1(struct sctp_transport *primary,
 133                                      struct sctp_transport *transport,
 134                                      int count_of_newacks)
 135 {
 136         if (!primary->cacc.cycling_changeover) {
 137                 if (sctp_cacc_skip_3_1_d(primary, transport, count_of_newacks))
 138                         return 1;
 139                 if (sctp_cacc_skip_3_1_f(transport, count_of_newacks))
 140                         return 1;
 141                 return 0;
 142         }
 143         return 0;
 144 }
 145
 146 /*
 147  * SFR-CACC algorithm:
 148  * 3.2) Else if CYCLING_CHANGEOVER is 1, and t is less
 149  * than next_tsn_at_change of the current primary, then
 150  * the sender MUST NOT increment missing report count
 151  * for t.
 152  */
 153 static inline int sctp_cacc_skip_3_2(struct sctp_transport *primary, __u32 tsn)
 154 {
 155         if (primary->cacc.cycling_changeover &&
 156             TSN_lt(tsn, primary->cacc.next_tsn_at_change))
 157                 return 1;
 158         return 0;
 159 }
 160
 161 /*
 162  * SFR-CACC algorithm:
 163  * 3) If the missing report count for TSN t is to be
 164  * incremented according to [RFC2960] and
 165  * [SCTP_STEWART-2002], and CHANGEOVER_ACTIVE is set,
 166  * then the sender MUST further execute steps 3.1 and
 167  * 3.2 to determine if the missing report count for
 168  * TSN t SHOULD NOT be incremented.
 169  *
 170  * 3.3) If 3.1 and 3.2 do not dictate that the missing
 171  * report count for t should not be incremented, then
 172  * the sender SHOULD increment missing report count for
 173  * t (according to [RFC2960] and [SCTP_STEWART_2002]).
 174  */
 175 static inline int sctp_cacc_skip(struct sctp_transport *primary,
 176                                  struct sctp_transport *transport,
 177                                  int count_of_newacks,
 178                                  __u32 tsn)
 179 {
 180         if (primary->cacc.changeover_active &&
 181             (sctp_cacc_skip_3_1(primary, transport, count_of_newacks) ||
 182              sctp_cacc_skip_3_2(primary, tsn)))
 183                 return 1;
 184         return 0;
 185 }
 186
 187 /* Initialize an existing sctp_outq.  This does the boring stuff.
 188  * You still need to define handlers if you really want to DO
 189  * something with this structure...
 190  */
 191 void sctp_outq_init(struct sctp_association *asoc, struct sctp_outq *q)
 192 {
 193         memset(q, 0, sizeof(struct sctp_outq));
 194
 195         q->asoc = asoc;
 196         INIT_LIST_HEAD(&q->out_chunk_list);
 197         INIT_LIST_HEAD(&q->control_chunk_list);
 198         INIT_LIST_HEAD(&q->retransmit);
 199         INIT_LIST_HEAD(&q->sacked);
 200         INIT_LIST_HEAD(&q->abandoned);
 201         sctp_sched_set_sched(asoc, sctp_sk(asoc->base.sk)->default_ss);
 202 }
 203
 204 /* Free the outqueue structure and any related pending chunks.
 205  */
 206 static void __sctp_outq_teardown(struct sctp_outq *q)
 207 {
 208         struct sctp_transport *transport;
 209         struct list_head *lchunk, *temp;
 210         struct sctp_chunk *chunk, *tmp;
 211
 212         /* Throw away unacknowledged chunks. */
 213         list_for_each_entry(transport, &q->asoc->peer.transport_addr_list,
 214                         transports) {
 215                 while ((lchunk = sctp_list_dequeue(&transport->transmitted)) != NULL) {
 216                         chunk = list_entry(lchunk, struct sctp_chunk,
 217                                            transmitted_list);
 218                         /* Mark as part of a failed message. */
 219                         sctp_chunk_fail(chunk, q->error);
 220                         sctp_chunk_free(chunk);
 221                 }
 222         }
 223
 224         /* Throw away chunks that have been gap ACKed.  */
 225         list_for_each_safe(lchunk, temp, &q->sacked) {
 226                 list_del_init(lchunk);
 227                 chunk = list_entry(lchunk, struct sctp_chunk,
 228                                    transmitted_list);
 229                 sctp_chunk_fail(chunk, q->error);
 230                 sctp_chunk_free(chunk);
 231         }
 232
 233         /* Throw away any chunks in the retransmit queue. */
 234         list_for_each_safe(lchunk, temp, &q->retransmit) {
 235                 list_del_init(lchunk);
 236                 chunk = list_entry(lchunk, struct sctp_chunk,
 237                                    transmitted_list);
 238                 sctp_chunk_fail(chunk, q->error);
 239                 sctp_chunk_free(chunk);
 240         }
 241
 242         /* Throw away any chunks that are in the abandoned queue. */
 243         list_for_each_safe(lchunk, temp, &q->abandoned) {
 244                 list_del_init(lchunk);
 245                 chunk = list_entry(lchunk, struct sctp_chunk,
 246                                    transmitted_list);
 247                 sctp_chunk_fail(chunk, q->error);
 248                 sctp_chunk_free(chunk);
 249         }
 250
 251         /* Throw away any leftover data chunks. */
 252         while ((chunk = sctp_outq_dequeue_data(q)) != NULL) {
 253                 sctp_sched_dequeue_done(q, chunk);
 254
 255                 /* Mark as send failure. */
 256                 sctp_chunk_fail(chunk, q->error);
 257                 sctp_chunk_free(chunk);
 258         }
 259
 260         /* Throw away any leftover control chunks. */
 261         list_for_each_entry_safe(chunk, tmp, &q->control_chunk_list, list) {
 262                 list_del_init(&chunk->list);
 263                 sctp_chunk_free(chunk);
 264         }
 265 }
 266
 267 void sctp_outq_teardown(struct sctp_outq *q)
 268 {
 269         __sctp_outq_teardown(q);
 270         sctp_outq_init(q->asoc, q);
 271 }
 272
 273 /* Free the outqueue structure and any related pending chunks.  */
 274 void sctp_outq_free(struct sctp_outq *q)
 275 {
 276         /* Throw away leftover chunks. */
 277         __sctp_outq_teardown(q);
 278 }
 279
 280 /* Put a new chunk in an sctp_outq.  */
 281 void sctp_outq_tail(struct sctp_outq *q, struct sctp_chunk *chunk, gfp_t gfp)
 282 {
 283         struct net *net = q->asoc->base.net;
 284
 285         pr_debug("%s: outq:%p, chunk:%p[%s]\n", __func__, q, chunk,
 286                  chunk && chunk->chunk_hdr ?
 287                  sctp_cname(SCTP_ST_CHUNK(chunk->chunk_hdr->type)) :
 288                  "illegal chunk");
 289
 290         /* If it is data, queue it up, otherwise, send it
 291          * immediately.
 292          */
 293         if (sctp_chunk_is_data(chunk)) {
 294                 pr_debug("%s: outqueueing: outq:%p, chunk:%p[%s])\n",
 295                          __func__, q, chunk, chunk && chunk->chunk_hdr ?
 296                          sctp_cname(SCTP_ST_CHUNK(chunk->chunk_hdr->type)) :
 297                          "illegal chunk");
 298
 299                 sctp_outq_tail_data(q, chunk);
 300                 if (chunk->asoc->peer.prsctp_capable &&
 301                     SCTP_PR_PRIO_ENABLED(chunk->sinfo.sinfo_flags))
 302                         chunk->asoc->sent_cnt_removable++;
 303                 if (chunk->chunk_hdr->flags & SCTP_DATA_UNORDERED)
 304                         SCTP_INC_STATS(net, SCTP_MIB_OUTUNORDERCHUNKS);
 305                 else
 306                         SCTP_INC_STATS(net, SCTP_MIB_OUTORDERCHUNKS);
 307         } else {
 308                 list_add_tail(&chunk->list, &q->control_chunk_list);
 309                 SCTP_INC_STATS(net, SCTP_MIB_OUTCTRLCHUNKS);
 310         }
 311
 312         if (!q->cork)
 313                 sctp_outq_flush(q, 0, gfp);
 314 }
 315
 316 /* Insert a chunk into the sorted list based on the TSNs.  The retransmit list
 317  * and the abandoned list are in ascending order.
 318  */
 319 static void sctp_insert_list(struct list_head *head, struct list_head *new)
 320 {
 321         struct list_head *pos;
 322         struct sctp_chunk *nchunk, *lchunk;
 323         __u32 ntsn, ltsn;
 324         int done = 0;
 325
 326         nchunk = list_entry(new, struct sctp_chunk, transmitted_list);
 327         ntsn = ntohl(nchunk->subh.data_hdr->tsn);
 328
 329         list_for_each(pos, head) {
 330                 lchunk = list_entry(pos, struct sctp_chunk, transmitted_list);
 331                 ltsn = ntohl(lchunk->subh.data_hdr->tsn);
 332                 if (TSN_lt(ntsn, ltsn)) {
 333                         list_add(new, pos->prev);
 334                         done = 1;
 335                         break;
 336                 }
 337         }
 338         if (!done)
 339                 list_add_tail(new, head);
 340 }
 341
 342 static int sctp_prsctp_prune_sent(struct sctp_association *asoc,
 343                                   struct sctp_sndrcvinfo *sinfo,
 344                                   struct list_head *queue, int msg_len)
 345 {
 346         struct sctp_chunk *chk, *temp;
 347
 348         list_for_each_entry_safe(chk, temp, queue, transmitted_list) {
 349                 struct sctp_stream_out *streamout;
 350
 351                 if (!chk->msg->abandoned &&
 352                     (!SCTP_PR_PRIO_ENABLED(chk->sinfo.sinfo_flags) ||
 353                      chk->sinfo.sinfo_timetolive <= sinfo->sinfo_timetolive))
 354                         continue;
 355
 356                 chk->msg->abandoned = 1;
 357                 list_del_init(&chk->transmitted_list);
 358                 sctp_insert_list(&asoc->outqueue.abandoned,
 359                                  &chk->transmitted_list);
 360
 361                 streamout = SCTP_SO(&asoc->stream, chk->sinfo.sinfo_stream);
 362                 asoc->sent_cnt_removable--;
 363                 asoc->abandoned_sent[SCTP_PR_INDEX(PRIO)]++;
 364                 streamout->ext->abandoned_sent[SCTP_PR_INDEX(PRIO)]++;
 365
 366                 if (queue != &asoc->outqueue.retransmit &&
 367                     !chk->tsn_gap_acked) {
 368                         if (chk->transport)
 369                                 chk->transport->flight_size -=
 370                                                 sctp_data_size(chk);
 371                         asoc->outqueue.outstanding_bytes -= sctp_data_size(chk);
 372                 }
 373
 374                 msg_len -= chk->skb->truesize + sizeof(struct sctp_chunk);
 375                 if (msg_len <= 0)
 376                         break;
 377         }
 378
 379         return msg_len;
 380 }
 381
 382 static int sctp_prsctp_prune_unsent(struct sctp_association *asoc,
 383                                     struct sctp_sndrcvinfo *sinfo, int msg_len)
 384 {
 385         struct sctp_outq *q = &asoc->outqueue;
 386         struct sctp_chunk *chk, *temp;
 387
 388         q->sched->unsched_all(&asoc->stream);
 389
 390         list_for_each_entry_safe(chk, temp, &q->out_chunk_list, list) {
 391                 if (!chk->msg->abandoned &&
 392                     (!(chk->chunk_hdr->flags & SCTP_DATA_FIRST_FRAG) ||
 393                      !SCTP_PR_PRIO_ENABLED(chk->sinfo.sinfo_flags) ||
 394                      chk->sinfo.sinfo_timetolive <= sinfo->sinfo_timetolive))
 395                         continue;
 396
 397                 chk->msg->abandoned = 1;
 398                 sctp_sched_dequeue_common(q, chk);
 399                 asoc->sent_cnt_removable--;
 400                 asoc->abandoned_unsent[SCTP_PR_INDEX(PRIO)]++;
 401                 if (chk->sinfo.sinfo_stream < asoc->stream.outcnt) {
 402                         struct sctp_stream_out *streamout =
 403                                 SCTP_SO(&asoc->stream, chk->sinfo.sinfo_stream);
 404
 405                         streamout->ext->abandoned_unsent[SCTP_PR_INDEX(PRIO)]++;
 406                 }
 407
 408                 msg_len -= chk->skb->truesize + sizeof(struct sctp_chunk);
 409                 sctp_chunk_free(chk);
 410                 if (msg_len <= 0)
 411                         break;
 412         }
 413
 414         q->sched->sched_all(&asoc->stream);
 415
 416         return msg_len;
 417 }
 418
 419 /* Abandon the chunks according their priorities */
 420 void sctp_prsctp_prune(struct sctp_association *asoc,
 421                        struct sctp_sndrcvinfo *sinfo, int msg_len)
 422 {
 423         struct sctp_transport *transport;
 424
 425         if (!asoc->peer.prsctp_capable || !asoc->sent_cnt_removable)
 426                 return;
 427
 428         msg_len = sctp_prsctp_prune_sent(asoc, sinfo,
 429                                          &asoc->outqueue.retransmit,
 430                                          msg_len);
 431         if (msg_len <= 0)
 432                 return;
 433
 434         list_for_each_entry(transport, &asoc->peer.transport_addr_list,
 435                             transports) {
 436                 msg_len = sctp_prsctp_prune_sent(asoc, sinfo,
 437                                                  &transport->transmitted,
 438                                                  msg_len);
 439                 if (msg_len <= 0)
 440                         return;
 441         }
 442
 443         sctp_prsctp_prune_unsent(asoc, sinfo, msg_len);
 444 }
 445
 446 /* Mark all the eligible packets on a transport for retransmission.  */
 447 void sctp_retransmit_mark(struct sctp_outq *q,
 448                           struct sctp_transport *transport,
 449                           __u8 reason)
 450 {
 451         struct list_head *lchunk, *ltemp;
 452         struct sctp_chunk *chunk;
 453
 454         /* Walk through the specified transmitted queue.  */
 455         list_for_each_safe(lchunk, ltemp, &transport->transmitted) {
 456                 chunk = list_entry(lchunk, struct sctp_chunk,
 457                                    transmitted_list);
 458
 459                 /* If the chunk is abandoned, move it to abandoned list. */
 460                 if (sctp_chunk_abandoned(chunk)) {
 461                         list_del_init(lchunk);
 462                         sctp_insert_list(&q->abandoned, lchunk);
 463
 464                         /* If this chunk has not been previousely acked,
 465                          * stop considering it 'outstanding'.  Our peer
 466                          * will most likely never see it since it will
 467                          * not be retransmitted
 468                          */
 469                         if (!chunk->tsn_gap_acked) {
 470                                 if (chunk->transport)
 471                                         chunk->transport->flight_size -=
 472                                                         sctp_data_size(chunk);
 473                                 q->outstanding_bytes -= sctp_data_size(chunk);
 474                                 q->asoc->peer.rwnd += sctp_data_size(chunk);
 475                         }
 476                         continue;
 477                 }
 478
 479                 /* If we are doing  retransmission due to a timeout or pmtu
 480                  * discovery, only the  chunks that are not yet acked should
 481                  * be added to the retransmit queue.
 482                  */
 483                 if ((reason == SCTP_RTXR_FAST_RTX  &&
 484                             (chunk->fast_retransmit == SCTP_NEED_FRTX)) ||
 485                     (reason != SCTP_RTXR_FAST_RTX  && !chunk->tsn_gap_acked)) {
 486                         /* RFC 2960 6.2.1 Processing a Received SACK
 487                          *
 488                          * C) Any time a DATA chunk is marked for
 489                          * retransmission (via either T3-rtx timer expiration
 490                          * (Section 6.3.3) or via fast retransmit
 491                          * (Section 7.2.4)), add the data size of those
 492                          * chunks to the rwnd.
 493                          */
 494                         q->asoc->peer.rwnd += sctp_data_size(chunk);
 495                         q->outstanding_bytes -= sctp_data_size(chunk);
 496                         if (chunk->transport)
 497                                 transport->flight_size -= sctp_data_size(chunk);
 498
 499                         /* sctpimpguide-05 Section 2.8.2
 500                          * M5) If a T3-rtx timer expires, the
 501                          * 'TSN.Missing.Report' of all affected TSNs is set
 502                          * to 0.
 503                          */
 504                         chunk->tsn_missing_report = 0;
 505
 506                         /* If a chunk that is being used for RTT measurement
 507                          * has to be retransmitted, we cannot use this chunk
 508                          * anymore for RTT measurements. Reset rto_pending so
 509                          * that a new RTT measurement is started when a new
 510                          * data chunk is sent.
 511                          */
 512                         if (chunk->rtt_in_progress) {
 513                                 chunk->rtt_in_progress = 0;
 514                                 transport->rto_pending = 0;
 515                         }
 516
 517                         /* Move the chunk to the retransmit queue. The chunks
 518                          * on the retransmit queue are always kept in order.
 519                          */
 520                         list_del_init(lchunk);
 521                         sctp_insert_list(&q->retransmit, lchunk);
 522                 }
 523         }
 524
 525         pr_debug("%s: transport:%p, reason:%d, cwnd:%d, ssthresh:%d, "
 526                  "flight_size:%d, pba:%d\n", __func__, transport, reason,
 527                  transport->cwnd, transport->ssthresh, transport->flight_size,
 528                  transport->partial_bytes_acked);
 529 }
 530
 531 /* Mark all the eligible packets on a transport for retransmission and force
 532  * one packet out.
 533  */
 534 void sctp_retransmit(struct sctp_outq *q, struct sctp_transport *transport,
 535                      enum sctp_retransmit_reason reason)
 536 {
 537         struct net *net = q->asoc->base.net;
 538
 539         switch (reason) {
 540         case SCTP_RTXR_T3_RTX:
 541                 SCTP_INC_STATS(net, SCTP_MIB_T3_RETRANSMITS);
 542                 sctp_transport_lower_cwnd(transport, SCTP_LOWER_CWND_T3_RTX);
 543                 /* Update the retran path if the T3-rtx timer has expired for
 544                  * the current retran path.
 545                  */
 546                 if (transport == transport->asoc->peer.retran_path)
 547                         sctp_assoc_update_retran_path(transport->asoc);
 548                 transport->asoc->rtx_data_chunks +=
 549                         transport->asoc->unack_data;
 550                 if (transport->pl.state == SCTP_PL_COMPLETE &&
 551                     transport->asoc->unack_data)
 552                         sctp_transport_reset_probe_timer(transport);
 553                 break;
 554         case SCTP_RTXR_FAST_RTX:
 555                 SCTP_INC_STATS(net, SCTP_MIB_FAST_RETRANSMITS);
 556                 sctp_transport_lower_cwnd(transport, SCTP_LOWER_CWND_FAST_RTX);
 557                 q->fast_rtx = 1;
 558                 break;
 559         case SCTP_RTXR_PMTUD:
 560                 SCTP_INC_STATS(net, SCTP_MIB_PMTUD_RETRANSMITS);
 561                 break;
 562         case SCTP_RTXR_T1_RTX:
 563                 SCTP_INC_STATS(net, SCTP_MIB_T1_RETRANSMITS);
 564                 transport->asoc->init_retries++;
 565                 break;
 566         default:
 567                 BUG();
 568         }
 569
 570         sctp_retransmit_mark(q, transport, reason);
 571
 572         /* PR-SCTP A5) Any time the T3-rtx timer expires, on any destination,
 573          * the sender SHOULD try to advance the "Advanced.Peer.Ack.Point" by
 574          * following the procedures outlined in C1 - C5.
 575          */
 576         if (reason == SCTP_RTXR_T3_RTX)
 577                 q->asoc->stream.si->generate_ftsn(q, q->asoc->ctsn_ack_point);
 578
 579         /* Flush the queues only on timeout, since fast_rtx is only
 580          * triggered during sack processing and the queue
 581          * will be flushed at the end.
 582          */
 583         if (reason != SCTP_RTXR_FAST_RTX)
 584                 sctp_outq_flush(q, /* rtx_timeout */ 1, GFP_ATOMIC);
 585 }
 586
 587 /*
 588  * Transmit DATA chunks on the retransmit queue.  Upon return from
 589  * __sctp_outq_flush_rtx() the packet 'pkt' may contain chunks which
 590  * need to be transmitted by the caller.
 591  * We assume that pkt->transport has already been set.
 592  *
 593  * The return value is a normal kernel error return value.
 594  */
 595 static int __sctp_outq_flush_rtx(struct sctp_outq *q, struct sctp_packet *pkt,
 596                                  int rtx_timeout, int *start_timer, gfp_t gfp)
 597 {
 598         struct sctp_transport *transport = pkt->transport;
 599         struct sctp_chunk *chunk, *chunk1;
 600         struct list_head *lqueue;
 601         enum sctp_xmit status;
 602         int error = 0;
 603         int timer = 0;
 604         int done = 0;
 605         int fast_rtx;
 606
 607         lqueue = &q->retransmit;
 608         fast_rtx = q->fast_rtx;
 609
 610         /* This loop handles time-out retransmissions, fast retransmissions,
 611          * and retransmissions due to opening of whindow.
 612          *
 613          * RFC 2960 6.3.3 Handle T3-rtx Expiration
 614          *
 615          * E3) Determine how many of the earliest (i.e., lowest TSN)
 616          * outstanding DATA chunks for the address for which the
 617          * T3-rtx has expired will fit into a single packet, subject
 618          * to the MTU constraint for the path corresponding to the
 619          * destination transport address to which the retransmission
 620          * is being sent (this may be different from the address for
 621          * which the timer expires [see Section 6.4]). Call this value
 622          * K. Bundle and retransmit those K DATA chunks in a single
 623          * packet to the destination endpoint.
 624          *
 625          * [Just to be painfully clear, if we are retransmitting
 626          * because a timeout just happened, we should send only ONE
 627          * packet of retransmitted data.]
 628          *
 629          * For fast retransmissions we also send only ONE packet.  However,
 630          * if we are just flushing the queue due to open window, we'll
 631          * try to send as much as possible.
 632          */
 633         list_for_each_entry_safe(chunk, chunk1, lqueue, transmitted_list) {
 634                 /* If the chunk is abandoned, move it to abandoned list. */
 635                 if (sctp_chunk_abandoned(chunk)) {
 636                         list_del_init(&chunk->transmitted_list);
 637                         sctp_insert_list(&q->abandoned,
 638                                          &chunk->transmitted_list);
 639                         continue;
 640                 }
 641
 642                 /* Make sure that Gap Acked TSNs are not retransmitted.  A
 643                  * simple approach is just to move such TSNs out of the
 644                  * way and into a 'transmitted' queue and skip to the
 645                  * next chunk.
 646                  */
 647                 if (chunk->tsn_gap_acked) {
 648                         list_move_tail(&chunk->transmitted_list,
 649                                        &transport->transmitted);
 650                         continue;
 651                 }
 652
 653                 /* If we are doing fast retransmit, ignore non-fast_rtransmit
 654                  * chunks
 655                  */
 656                 if (fast_rtx && !chunk->fast_retransmit)
 657                         continue;
 658
 659 redo:
 660                 /* Attempt to append this chunk to the packet. */
 661                 status = sctp_packet_append_chunk(pkt, chunk);
 662
 663                 switch (status) {
 664                 case SCTP_XMIT_PMTU_FULL:
 665                         if (!pkt->has_data && !pkt->has_cookie_echo) {
 666                                 /* If this packet did not contain DATA then
 667                                  * retransmission did not happen, so do it
 668                                  * again.  We'll ignore the error here since
 669                                  * control chunks are already freed so there
 670                                  * is nothing we can do.
 671                                  */
 672                                 sctp_packet_transmit(pkt, gfp);
 673                                 goto redo;
 674                         }
 675
 676                         /* Send this packet.  */
 677                         error = sctp_packet_transmit(pkt, gfp);
 678
 679                         /* If we are retransmitting, we should only
 680                          * send a single packet.
 681                          * Otherwise, try appending this chunk again.
 682                          */
 683                         if (rtx_timeout || fast_rtx)
 684                                 done = 1;
 685                         else
 686                                 goto redo;
 687
 688                         /* Bundle next chunk in the next round.  */
 689                         break;
 690
 691                 case SCTP_XMIT_RWND_FULL:
 692                         /* Send this packet. */
 693                         error = sctp_packet_transmit(pkt, gfp);
 694
 695                         /* Stop sending DATA as there is no more room
 696                          * at the receiver.
 697                          */
 698                         done = 1;
 699                         break;
 700
 701                 case SCTP_XMIT_DELAY:
 702                         /* Send this packet. */
 703                         error = sctp_packet_transmit(pkt, gfp);
 704
 705                         /* Stop sending DATA because of nagle delay. */
 706                         done = 1;
 707                         break;
 708
 709                 default:
 710                         /* The append was successful, so add this chunk to
 711                          * the transmitted list.
 712                          */
 713                         list_move_tail(&chunk->transmitted_list,
 714                                        &transport->transmitted);
 715
 716                         /* Mark the chunk as ineligible for fast retransmit
 717                          * after it is retransmitted.
 718                          */
 719                         if (chunk->fast_retransmit == SCTP_NEED_FRTX)
 720                                 chunk->fast_retransmit = SCTP_DONT_FRTX;
 721
 722                         q->asoc->stats.rtxchunks++;
 723                         break;
 724                 }
 725
 726                 /* Set the timer if there were no errors */
 727                 if (!error && !timer)
 728                         timer = 1;
 729
 730                 if (done)
 731                         break;
 732         }
 733
 734         /* If we are here due to a retransmit timeout or a fast
 735          * retransmit and if there are any chunks left in the retransmit
 736          * queue that could not fit in the PMTU sized packet, they need
 737          * to be marked as ineligible for a subsequent fast retransmit.
 738          */
 739         if (rtx_timeout || fast_rtx) {
 740                 list_for_each_entry(chunk1, lqueue, transmitted_list) {
 741                         if (chunk1->fast_retransmit == SCTP_NEED_FRTX)
 742                                 chunk1->fast_retransmit = SCTP_DONT_FRTX;
 743                 }
 744         }
 745
 746         *start_timer = timer;
 747
 748         /* Clear fast retransmit hint */
 749         if (fast_rtx)
 750                 q->fast_rtx = 0;
 751
 752         return error;
 753 }
 754
 755 /* Cork the outqueue so queued chunks are really queued. */
 756 void sctp_outq_uncork(struct sctp_outq *q, gfp_t gfp)
 757 {
 758         if (q->cork)
 759                 q->cork = 0;
 760
 761         sctp_outq_flush(q, 0, gfp);
 762 }
 763
 764 static int sctp_packet_singleton(struct sctp_transport *transport,
 765                                  struct sctp_chunk *chunk, gfp_t gfp)
 766 {
 767         const struct sctp_association *asoc = transport->asoc;
 768         const __u16 sport = asoc->base.bind_addr.port;
 769         const __u16 dport = asoc->peer.port;
 770         const __u32 vtag = asoc->peer.i.init_tag;
 771         struct sctp_packet singleton;
 772
 773         sctp_packet_init(&singleton, transport, sport, dport);
 774         sctp_packet_config(&singleton, vtag, 0);
 775         if (sctp_packet_append_chunk(&singleton, chunk) != SCTP_XMIT_OK) {
 776                 list_del_init(&chunk->list);
 777                 sctp_chunk_free(chunk);
 778                 return -ENOMEM;
 779         }
 780         return sctp_packet_transmit(&singleton, gfp);
 781 }
 782
 783 /* Struct to hold the context during sctp outq flush */
 784 struct sctp_flush_ctx {
 785         struct sctp_outq *q;
 786         /* Current transport being used. It's NOT the same as curr active one */
 787         struct sctp_transport *transport;
 788         /* These transports have chunks to send. */
 789         struct list_head transport_list;
 790         struct sctp_association *asoc;
 791         /* Packet on the current transport above */
 792         struct sctp_packet *packet;
 793         gfp_t gfp;
 794 };
 795
 796 /* transport: current transport */
 797 static void sctp_outq_select_transport(struct sctp_flush_ctx *ctx,
 798                                        struct sctp_chunk *chunk)
 799 {
 800         struct sctp_transport *new_transport = chunk->transport;
 801
 802         if (!new_transport) {
 803                 if (!sctp_chunk_is_data(chunk)) {
 804                         /* If we have a prior transport pointer, see if
 805                          * the destination address of the chunk
 806                          * matches the destination address of the
 807                          * current transport.  If not a match, then
 808                          * try to look up the transport with a given
 809                          * destination address.  We do this because
 810                          * after processing ASCONFs, we may have new
 811                          * transports created.
 812                          */
 813                         if (ctx->transport && sctp_cmp_addr_exact(&chunk->dest,
 814                                                         &ctx->transport->ipaddr))
 815                                 new_transport = ctx->transport;
 816                         else
 817                                 new_transport = sctp_assoc_lookup_paddr(ctx->asoc,
 818                                                                   &chunk->dest);
 819                 }
 820
 821                 /* if we still don't have a new transport, then
 822                  * use the current active path.
 823                  */
 824                 if (!new_transport)
 825                         new_transport = ctx->asoc->peer.active_path;
 826         } else {
 827                 __u8 type;
 828
 829                 switch (new_transport->state) {
 830                 case SCTP_INACTIVE:
 831                 case SCTP_UNCONFIRMED:
 832                 case SCTP_PF:
 833                         /* If the chunk is Heartbeat or Heartbeat Ack,
 834                          * send it to chunk->transport, even if it's
 835                          * inactive.
 836                          *
 837                          * 3.3.6 Heartbeat Acknowledgement:
 838                          * ...
 839                          * A HEARTBEAT ACK is always sent to the source IP
 840                          * address of the IP datagram containing the
 841                          * HEARTBEAT chunk to which this ack is responding.
 842                          * ...
 843                          *
 844                          * ASCONF_ACKs also must be sent to the source.
 845                          */
 846                         type = chunk->chunk_hdr->type;
 847                         if (type != SCTP_CID_HEARTBEAT &&
 848                             type != SCTP_CID_HEARTBEAT_ACK &&
 849                             type != SCTP_CID_ASCONF_ACK)
 850                                 new_transport = ctx->asoc->peer.active_path;
 851                         break;
 852                 default:
 853                         break;
 854                 }
 855         }
 856
 857         /* Are we switching transports? Take care of transport locks. */
 858         if (new_transport != ctx->transport) {
 859                 ctx->transport = new_transport;
 860                 ctx->packet = &ctx->transport->packet;
 861
 862                 if (list_empty(&ctx->transport->send_ready))
 863                         list_add_tail(&ctx->transport->send_ready,
 864                                       &ctx->transport_list);
 865
 866                 sctp_packet_config(ctx->packet,
 867                                    ctx->asoc->peer.i.init_tag,
 868                                    ctx->asoc->peer.ecn_capable);
 869                 /* We've switched transports, so apply the
 870                  * Burst limit to the new transport.
 871                  */
 872                 sctp_transport_burst_limited(ctx->transport);
 873         }
 874 }
 875
 876 static void sctp_outq_flush_ctrl(struct sctp_flush_ctx *ctx)
 877 {
 878         struct sctp_chunk *chunk, *tmp;
 879         enum sctp_xmit status;
 880         int one_packet, error;
 881
 882         list_for_each_entry_safe(chunk, tmp, &ctx->q->control_chunk_list, list) {
 883                 one_packet = 0;
 884
 885                 /* RFC 5061, 5.3
 886                  * F1) This means that until such time as the ASCONF
 887                  * containing the add is acknowledged, the sender MUST
 888                  * NOT use the new IP address as a source for ANY SCTP
 889                  * packet except on carrying an ASCONF Chunk.
 890                  */
 891                 if (ctx->asoc->src_out_of_asoc_ok &&
 892                     chunk->chunk_hdr->type != SCTP_CID_ASCONF)
 893                         continue;
 894
 895                 list_del_init(&chunk->list);
 896
 897                 /* Pick the right transport to use. Should always be true for
 898                  * the first chunk as we don't have a transport by then.
 899                  */
 900                 sctp_outq_select_transport(ctx, chunk);
 901
 902                 switch (chunk->chunk_hdr->type) {
 903                 /* 6.10 Bundling
 904                  *   ...
 905                  *   An endpoint MUST NOT bundle INIT, INIT ACK or SHUTDOWN
 906                  *   COMPLETE with any other chunks.  [Send them immediately.]
 907                  */
 908                 case SCTP_CID_INIT:
 909                 case SCTP_CID_INIT_ACK:
 910                 case SCTP_CID_SHUTDOWN_COMPLETE:
 911                         error = sctp_packet_singleton(ctx->transport, chunk,
 912                                                       ctx->gfp);
 913                         if (error < 0) {
 914                                 ctx->asoc->base.sk->sk_err = -error;
 915                                 return;
 916                         }
 917                         ctx->asoc->stats.octrlchunks++;
 918                         break;
 919
 920                 case SCTP_CID_ABORT:
 921                         if (sctp_test_T_bit(chunk))
 922                                 ctx->packet->vtag = ctx->asoc->c.my_vtag;
 923                         fallthrough;
 924
 925                 /* The following chunks are "response" chunks, i.e.
 926                  * they are generated in response to something we
 927                  * received.  If we are sending these, then we can
 928                  * send only 1 packet containing these chunks.
 929                  */
 930                 case SCTP_CID_HEARTBEAT_ACK:
 931                 case SCTP_CID_SHUTDOWN_ACK:
 932                 case SCTP_CID_COOKIE_ACK:
 933                 case SCTP_CID_COOKIE_ECHO:
 934                 case SCTP_CID_ERROR:
 935                 case SCTP_CID_ECN_CWR:
 936                 case SCTP_CID_ASCONF_ACK:
 937                         one_packet = 1;
 938                         fallthrough;
 939
 940                 case SCTP_CID_HEARTBEAT:
 941                         if (chunk->pmtu_probe) {
 942                                 error = sctp_packet_singleton(ctx->transport,
 943                                                               chunk, ctx->gfp);
 944                                 if (!error)
 945                                         ctx->asoc->stats.octrlchunks++;
 946                                 break;
 947                         }
 948                         fallthrough;
 949                 case SCTP_CID_SACK:
 950                 case SCTP_CID_SHUTDOWN:
 951                 case SCTP_CID_ECN_ECNE:
 952                 case SCTP_CID_ASCONF:
 953                 case SCTP_CID_FWD_TSN:
 954                 case SCTP_CID_I_FWD_TSN:
 955                 case SCTP_CID_RECONF:
 956                         status = sctp_packet_transmit_chunk(ctx->packet, chunk,
 957                                                             one_packet, ctx->gfp);
 958                         if (status != SCTP_XMIT_OK) {
 959                                 /* put the chunk back */
 960                                 list_add(&chunk->list, &ctx->q->control_chunk_list);
 961                                 break;
 962                         }
 963
 964                         ctx->asoc->stats.octrlchunks++;
 965                         /* PR-SCTP C5) If a FORWARD TSN is sent, the
 966                          * sender MUST assure that at least one T3-rtx
 967                          * timer is running.
 968                          */
 969                         if (chunk->chunk_hdr->type == SCTP_CID_FWD_TSN ||
 970                             chunk->chunk_hdr->type == SCTP_CID_I_FWD_TSN) {
 971                                 sctp_transport_reset_t3_rtx(ctx->transport);
 972                                 ctx->transport->last_time_sent = jiffies;
 973                         }
 974
 975                         if (chunk == ctx->asoc->strreset_chunk)
 976                                 sctp_transport_reset_reconf_timer(ctx->transport);
 977
 978                         break;
 979
 980                 default:
 981                         /* We built a chunk with an illegal type! */
 982                         BUG();
 983                 }
 984         }
 985 }
 986
 987 /* Returns false if new data shouldn't be sent */
 988 static bool sctp_outq_flush_rtx(struct sctp_flush_ctx *ctx,
 989                                 int rtx_timeout)
 990 {
 991         int error, start_timer = 0;
 992
 993         if (ctx->asoc->peer.retran_path->state == SCTP_UNCONFIRMED)
 994                 return false;
 995
 996         if (ctx->transport != ctx->asoc->peer.retran_path) {
 997                 /* Switch transports & prepare the packet.  */
 998                 ctx->transport = ctx->asoc->peer.retran_path;
 999                 ctx->packet = &ctx->transport->packet;
1000
1001                 if (list_empty(&ctx->transport->send_ready))
1002                         list_add_tail(&ctx->transport->send_ready,
1003                                       &ctx->transport_list);
1004
1005                 sctp_packet_config(ctx->packet, ctx->asoc->peer.i.init_tag,
1006                                    ctx->asoc->peer.ecn_capable);
1007         }
1008
1009         error = __sctp_outq_flush_rtx(ctx->q, ctx->packet, rtx_timeout,
1010                                       &start_timer, ctx->gfp);
1011         if (error < 0)
1012                 ctx->asoc->base.sk->sk_err = -error;
1013
1014         if (start_timer) {
1015                 sctp_transport_reset_t3_rtx(ctx->transport);
1016                 ctx->transport->last_time_sent = jiffies;
1017         }
1018
1019         /* This can happen on COOKIE-ECHO resend.  Only
1020          * one chunk can get bundled with a COOKIE-ECHO.
1021          */
1022         if (ctx->packet->has_cookie_echo)
1023                 return false;
1024
1025         /* Don't send new data if there is still data
1026          * waiting to retransmit.
1027          */
1028         if (!list_empty(&ctx->q->retransmit))
1029                 return false;
1030
1031         return true;
1032 }
1033
1034 static void sctp_outq_flush_data(struct sctp_flush_ctx *ctx,
1035                                  int rtx_timeout)
1036 {
1037         struct sctp_chunk *chunk;
1038         enum sctp_xmit status;
1039
1040         /* Is it OK to send data chunks?  */
1041         switch (ctx->asoc->state) {
1042         case SCTP_STATE_COOKIE_ECHOED:
1043                 /* Only allow bundling when this packet has a COOKIE-ECHO
1044                  * chunk.
1045                  */
1046                 if (!ctx->packet || !ctx->packet->has_cookie_echo)
1047                         return;
1048
1049                 fallthrough;
1050         case SCTP_STATE_ESTABLISHED:
1051         case SCTP_STATE_SHUTDOWN_PENDING:
1052         case SCTP_STATE_SHUTDOWN_RECEIVED:
1053                 break;
1054
1055         default:
1056                 /* Do nothing. */
1057                 return;
1058         }
1059
1060         /* RFC 2960 6.1  Transmission of DATA Chunks
1061          *
1062          * C) When the time comes for the sender to transmit,
1063          * before sending new DATA chunks, the sender MUST
1064          * first transmit any outstanding DATA chunks which
1065          * are marked for retransmission (limited by the
1066          * current cwnd).
1067          */
1068         if (!list_empty(&ctx->q->retransmit) &&
1069             !sctp_outq_flush_rtx(ctx, rtx_timeout))
1070                 return;
1071
1072         /* Apply Max.Burst limitation to the current transport in
1073          * case it will be used for new data.  We are going to
1074          * rest it before we return, but we want to apply the limit
1075          * to the currently queued data.
1076          */
1077         if (ctx->transport)
1078                 sctp_transport_burst_limited(ctx->transport);
1079
1080         /* Finally, transmit new packets.  */
1081         while ((chunk = sctp_outq_dequeue_data(ctx->q)) != NULL) {
1082                 __u32 sid = ntohs(chunk->subh.data_hdr->stream);
1083                 __u8 stream_state = SCTP_SO(&ctx->asoc->stream, sid)->state;
1084
1085                 /* Has this chunk expired? */
1086                 if (sctp_chunk_abandoned(chunk)) {
1087                         sctp_sched_dequeue_done(ctx->q, chunk);
1088                         sctp_chunk_fail(chunk, 0);
1089                         sctp_chunk_free(chunk);
1090                         continue;
1091                 }
1092
1093                 if (stream_state == SCTP_STREAM_CLOSED) {
1094                         sctp_outq_head_data(ctx->q, chunk);
1095                         break;
1096                 }
1097
1098                 sctp_outq_select_transport(ctx, chunk);
1099
1100                 pr_debug("%s: outq:%p, chunk:%p[%s], tx-tsn:0x%x skb->head:%p skb->users:%d\n",
1101                          __func__, ctx->q, chunk, chunk && chunk->chunk_hdr ?
1102                          sctp_cname(SCTP_ST_CHUNK(chunk->chunk_hdr->type)) :
1103                          "illegal chunk", ntohl(chunk->subh.data_hdr->tsn),
1104                          chunk->skb ? chunk->skb->head : NULL, chunk->skb ?
1105                          refcount_read(&chunk->skb->users) : -1);
1106
1107                 /* Add the chunk to the packet.  */
1108                 status = sctp_packet_transmit_chunk(ctx->packet, chunk, 0,
1109                                                     ctx->gfp);
1110                 if (status != SCTP_XMIT_OK) {
1111                         /* We could not append this chunk, so put
1112                          * the chunk back on the output queue.
1113                          */
1114                         pr_debug("%s: could not transmit tsn:0x%x, status:%d\n",
1115                                  __func__, ntohl(chunk->subh.data_hdr->tsn),
1116                                  status);
1117
1118                         sctp_outq_head_data(ctx->q, chunk);
1119                         break;
1120                 }
1121
1122                 /* The sender is in the SHUTDOWN-PENDING state,
1123                  * The sender MAY set the I-bit in the DATA
1124                  * chunk header.
1125                  */
1126                 if (ctx->asoc->state == SCTP_STATE_SHUTDOWN_PENDING)
1127                         chunk->chunk_hdr->flags |= SCTP_DATA_SACK_IMM;
1128                 if (chunk->chunk_hdr->flags & SCTP_DATA_UNORDERED)
1129                         ctx->asoc->stats.ouodchunks++;
1130                 else
1131                         ctx->asoc->stats.oodchunks++;
1132
1133                 /* Only now it's safe to consider this
1134                  * chunk as sent, sched-wise.
1135                  */
1136                 sctp_sched_dequeue_done(ctx->q, chunk);
1137
1138                 list_add_tail(&chunk->transmitted_list,
1139                               &ctx->transport->transmitted);
1140
1141                 sctp_transport_reset_t3_rtx(ctx->transport);
1142                 ctx->transport->last_time_sent = jiffies;
1143
1144                 /* Only let one DATA chunk get bundled with a
1145                  * COOKIE-ECHO chunk.
1146                  */
1147                 if (ctx->packet->has_cookie_echo)
1148                         break;
1149         }
1150 }
1151
1152 static void sctp_outq_flush_transports(struct sctp_flush_ctx *ctx)
1153 {
1154         struct sock *sk = ctx->asoc->base.sk;
1155         struct list_head *ltransport;
1156         struct sctp_packet *packet;
1157         struct sctp_transport *t;
1158         int error = 0;
1159
1160         while ((ltransport = sctp_list_dequeue(&ctx->transport_list)) != NULL) {
1161                 t = list_entry(ltransport, struct sctp_transport, send_ready);
1162                 packet = &t->packet;
1163                 if (!sctp_packet_empty(packet)) {
1164                         rcu_read_lock();
1165                         if (t->dst && __sk_dst_get(sk) != t->dst) {
1166                                 dst_hold(t->dst);
1167                                 sk_setup_caps(sk, t->dst);
1168                         }
1169                         rcu_read_unlock();
1170                         error = sctp_packet_transmit(packet, ctx->gfp);
1171                         if (error < 0)
1172                                 ctx->q->asoc->base.sk->sk_err = -error;
1173                 }
1174
1175                 /* Clear the burst limited state, if any */
1176                 sctp_transport_burst_reset(t);
1177         }
1178 }
1179
1180 /* Try to flush an outqueue.
1181  *
1182  * Description: Send everything in q which we legally can, subject to
1183  * congestion limitations.
1184  * * Note: This function can be called from multiple contexts so appropriate
1185  * locking concerns must be made.  Today we use the sock lock to protect
1186  * this function.
1187  */
1188
1189 static void sctp_outq_flush(struct sctp_outq *q, int rtx_timeout, gfp_t gfp)
1190 {
1191         struct sctp_flush_ctx ctx = {
1192                 .q = q,
1193                 .transport = NULL,
1194                 .transport_list = LIST_HEAD_INIT(ctx.transport_list),
1195                 .asoc = q->asoc,
1196                 .packet = NULL,
1197                 .gfp = gfp,
1198         };
1199
1200         /* 6.10 Bundling
1201          *   ...
1202          *   When bundling control chunks with DATA chunks, an
1203          *   endpoint MUST place control chunks first in the outbound
1204          *   SCTP packet.  The transmitter MUST transmit DATA chunks
1205          *   within a SCTP packet in increasing order of TSN.
1206          *   ...
1207          */
1208
1209         sctp_outq_flush_ctrl(&ctx);
1210
1211         if (q->asoc->src_out_of_asoc_ok)
1212                 goto sctp_flush_out;
1213
1214         sctp_outq_flush_data(&ctx, rtx_timeout);
1215
1216 sctp_flush_out:
1217
1218         sctp_outq_flush_transports(&ctx);
1219 }
1220
1221 /* Update unack_data based on the incoming SACK chunk */
1222 static void sctp_sack_update_unack_data(struct sctp_association *assoc,
1223                                         struct sctp_sackhdr *sack)
1224 {
1225         union sctp_sack_variable *frags;
1226         __u16 unack_data;
1227         int i;
1228
1229         unack_data = assoc->next_tsn - assoc->ctsn_ack_point - 1;
1230
1231         frags = sack->variable;
1232         for (i = 0; i < ntohs(sack->num_gap_ack_blocks); i++) {
1233                 unack_data -= ((ntohs(frags[i].gab.end) -
1234                                 ntohs(frags[i].gab.start) + 1));
1235         }
1236
1237         assoc->unack_data = unack_data;
1238 }
1239
1240 /* This is where we REALLY process a SACK.
1241  *
1242  * Process the SACK against the outqueue.  Mostly, this just frees
1243  * things off the transmitted queue.
1244  */
1245 int sctp_outq_sack(struct sctp_outq *q, struct sctp_chunk *chunk)
1246 {
1247         struct sctp_association *asoc = q->asoc;
1248         struct sctp_sackhdr *sack = chunk->subh.sack_hdr;
1249         struct sctp_transport *transport;
1250         struct sctp_chunk *tchunk = NULL;
1251         struct list_head *lchunk, *transport_list, *temp;
1252         union sctp_sack_variable *frags = sack->variable;
1253         __u32 sack_ctsn, ctsn, tsn;
1254         __u32 highest_tsn, highest_new_tsn;
1255         __u32 sack_a_rwnd;
1256         unsigned int outstanding;
1257         struct sctp_transport *primary = asoc->peer.primary_path;
1258         int count_of_newacks = 0;
1259         int gap_ack_blocks;
1260         u8 accum_moved = 0;
1261
1262         /* Grab the association's destination address list. */
1263         transport_list = &asoc->peer.transport_addr_list;
1264
1265         /* SCTP path tracepoint for congestion control debugging. */
1266         if (trace_sctp_probe_path_enabled()) {
1267                 list_for_each_entry(transport, transport_list, transports)
1268                         trace_sctp_probe_path(transport, asoc);
1269         }
1270
1271         sack_ctsn = ntohl(sack->cum_tsn_ack);
1272         gap_ack_blocks = ntohs(sack->num_gap_ack_blocks);
1273         asoc->stats.gapcnt += gap_ack_blocks;
1274         /*
1275          * SFR-CACC algorithm:
1276          * On receipt of a SACK the sender SHOULD execute the
1277          * following statements.
1278          *
1279          * 1) If the cumulative ack in the SACK passes next tsn_at_change
1280          * on the current primary, the CHANGEOVER_ACTIVE flag SHOULD be
1281          * cleared. The CYCLING_CHANGEOVER flag SHOULD also be cleared for
1282          * all destinations.
1283          * 2) If the SACK contains gap acks and the flag CHANGEOVER_ACTIVE
1284          * is set the receiver of the SACK MUST take the following actions:
1285          *
1286          * A) Initialize the cacc_saw_newack to 0 for all destination
1287          * addresses.
1288          *
1289          * Only bother if changeover_active is set. Otherwise, this is
1290          * totally suboptimal to do on every SACK.
1291          */
1292         if (primary->cacc.changeover_active) {
1293                 u8 clear_cycling = 0;
1294
1295                 if (TSN_lte(primary->cacc.next_tsn_at_change, sack_ctsn)) {
1296                         primary->cacc.changeover_active = 0;
1297                         clear_cycling = 1;
1298                 }
1299
1300                 if (clear_cycling || gap_ack_blocks) {
1301                         list_for_each_entry(transport, transport_list,
1302                                         transports) {
1303                                 if (clear_cycling)
1304                                         transport->cacc.cycling_changeover = 0;
1305                                 if (gap_ack_blocks)
1306                                         transport->cacc.cacc_saw_newack = 0;
1307                         }
1308                 }
1309         }
1310
1311         /* Get the highest TSN in the sack. */
1312         highest_tsn = sack_ctsn;
1313         if (gap_ack_blocks)
1314                 highest_tsn += ntohs(frags[gap_ack_blocks - 1].gab.end);
1315
1316         if (TSN_lt(asoc->highest_sacked, highest_tsn))
1317                 asoc->highest_sacked = highest_tsn;
1318
1319         highest_new_tsn = sack_ctsn;
1320
1321         /* Run through the retransmit queue.  Credit bytes received
1322          * and free those chunks that we can.
1323          */
1324         sctp_check_transmitted(q, &q->retransmit, NULL, NULL, sack, &highest_new_tsn);
1325
1326         /* Run through the transmitted queue.
1327          * Credit bytes received and free those chunks which we can.
1328          *
1329          * This is a MASSIVE candidate for optimization.
1330          */
1331         list_for_each_entry(transport, transport_list, transports) {
1332                 sctp_check_transmitted(q, &transport->transmitted,
1333                                        transport, &chunk->source, sack,
1334                                        &highest_new_tsn);
1335                 /*
1336                  * SFR-CACC algorithm:
1337                  * C) Let count_of_newacks be the number of
1338                  * destinations for which cacc_saw_newack is set.
1339                  */
1340                 if (transport->cacc.cacc_saw_newack)
1341                         count_of_newacks++;
1342         }
1343
1344         /* Move the Cumulative TSN Ack Point if appropriate.  */
1345         if (TSN_lt(asoc->ctsn_ack_point, sack_ctsn)) {
1346                 asoc->ctsn_ack_point = sack_ctsn;
1347                 accum_moved = 1;
1348         }
1349
1350         if (gap_ack_blocks) {
1351
1352                 if (asoc->fast_recovery && accum_moved)
1353                         highest_new_tsn = highest_tsn;
1354
1355                 list_for_each_entry(transport, transport_list, transports)
1356                         sctp_mark_missing(q, &transport->transmitted, transport,
1357                                           highest_new_tsn, count_of_newacks);
1358         }
1359
1360         /* Update unack_data field in the assoc. */
1361         sctp_sack_update_unack_data(asoc, sack);
1362
1363         ctsn = asoc->ctsn_ack_point;
1364
1365         /* Throw away stuff rotting on the sack queue.  */
1366         list_for_each_safe(lchunk, temp, &q->sacked) {
1367                 tchunk = list_entry(lchunk, struct sctp_chunk,
1368                                     transmitted_list);
1369                 tsn = ntohl(tchunk->subh.data_hdr->tsn);
1370                 if (TSN_lte(tsn, ctsn)) {
1371                         list_del_init(&tchunk->transmitted_list);
1372                         if (asoc->peer.prsctp_capable &&
1373                             SCTP_PR_PRIO_ENABLED(chunk->sinfo.sinfo_flags))
1374                                 asoc->sent_cnt_removable--;
1375                         sctp_chunk_free(tchunk);
1376                 }
1377         }
1378
1379         /* ii) Set rwnd equal to the newly received a_rwnd minus the
1380          *     number of bytes still outstanding after processing the
1381          *     Cumulative TSN Ack and the Gap Ack Blocks.
1382          */
1383
1384         sack_a_rwnd = ntohl(sack->a_rwnd);
1385         asoc->peer.zero_window_announced = !sack_a_rwnd;
1386         outstanding = q->outstanding_bytes;
1387
1388         if (outstanding < sack_a_rwnd)
1389                 sack_a_rwnd -= outstanding;
1390         else
1391                 sack_a_rwnd = 0;
1392
1393         asoc->peer.rwnd = sack_a_rwnd;
1394
1395         asoc->stream.si->generate_ftsn(q, sack_ctsn);
1396
1397         pr_debug("%s: sack cumulative tsn ack:0x%x\n", __func__, sack_ctsn);
1398         pr_debug("%s: cumulative tsn ack of assoc:%p is 0x%x, "
1399                  "advertised peer ack point:0x%x\n", __func__, asoc, ctsn,
1400                  asoc->adv_peer_ack_point);
1401
1402         return sctp_outq_is_empty(q);
1403 }
1404
1405 /* Is the outqueue empty?
1406  * The queue is empty when we have not pending data, no in-flight data
1407  * and nothing pending retransmissions.
1408  */
1409 int sctp_outq_is_empty(const struct sctp_outq *q)
1410 {
1411         return q->out_qlen == 0 && q->outstanding_bytes == 0 &&
1412                list_empty(&q->retransmit);
1413 }
1414
1415 /********************************************************************
1416  * 2nd Level Abstractions
1417  ********************************************************************/
1418
1419 /* Go through a transport's transmitted list or the association's retransmit
1420  * list and move chunks that are acked by the Cumulative TSN Ack to q->sacked.
1421  * The retransmit list will not have an associated transport.
1422  *
1423  * I added coherent debug information output.   --xguo
1424  *
1425  * Instead of printing 'sacked' or 'kept' for each TSN on the
1426  * transmitted_queue, we print a range: SACKED: TSN1-TSN2, TSN3, TSN4-TSN5.
1427  * KEPT TSN6-TSN7, etc.
1428  */
1429 static void sctp_check_transmitted(struct sctp_outq *q,
1430                                    struct list_head *transmitted_queue,
1431                                    struct sctp_transport *transport,
1432                                    union sctp_addr *saddr,
1433                                    struct sctp_sackhdr *sack,
1434                                    __u32 *highest_new_tsn_in_sack)
1435 {
1436         struct list_head *lchunk;
1437         struct sctp_chunk *tchunk;
1438         struct list_head tlist;
1439         __u32 tsn;
1440         __u32 sack_ctsn;
1441         __u32 rtt;
1442         __u8 restart_timer = 0;
1443         int bytes_acked = 0;
1444         int migrate_bytes = 0;
1445         bool forward_progress = false;
1446
1447         sack_ctsn = ntohl(sack->cum_tsn_ack);
1448
1449         INIT_LIST_HEAD(&tlist);
1450
1451         /* The while loop will skip empty transmitted queues. */
1452         while (NULL != (lchunk = sctp_list_dequeue(transmitted_queue))) {
1453                 tchunk = list_entry(lchunk, struct sctp_chunk,
1454                                     transmitted_list);
1455
1456                 if (sctp_chunk_abandoned(tchunk)) {
1457                         /* Move the chunk to abandoned list. */
1458                         sctp_insert_list(&q->abandoned, lchunk);
1459
1460                         /* If this chunk has not been acked, stop
1461                          * considering it as 'outstanding'.
1462                          */
1463                         if (transmitted_queue != &q->retransmit &&
1464                             !tchunk->tsn_gap_acked) {
1465                                 if (tchunk->transport)
1466                                         tchunk->transport->flight_size -=
1467                                                         sctp_data_size(tchunk);
1468                                 q->outstanding_bytes -= sctp_data_size(tchunk);
1469                         }
1470                         continue;
1471                 }
1472
1473                 tsn = ntohl(tchunk->subh.data_hdr->tsn);
1474                 if (sctp_acked(sack, tsn)) {
1475                         /* If this queue is the retransmit queue, the
1476                          * retransmit timer has already reclaimed
1477                          * the outstanding bytes for this chunk, so only
1478                          * count bytes associated with a transport.
1479                          */
1480                         if (transport && !tchunk->tsn_gap_acked) {
1481                                 /* If this chunk is being used for RTT
1482                                  * measurement, calculate the RTT and update
1483                                  * the RTO using this value.
1484                                  *
1485                                  * 6.3.1 C5) Karn's algorithm: RTT measurements
1486                                  * MUST NOT be made using packets that were
1487                                  * retransmitted (and thus for which it is
1488                                  * ambiguous whether the reply was for the
1489                                  * first instance of the packet or a later
1490                                  * instance).
1491                                  */
1492                                 if (!sctp_chunk_retransmitted(tchunk) &&
1493                                     tchunk->rtt_in_progress) {
1494                                         tchunk->rtt_in_progress = 0;
1495                                         rtt = jiffies - tchunk->sent_at;
1496                                         sctp_transport_update_rto(transport,
1497                                                                   rtt);
1498                                 }
1499
1500                                 if (TSN_lte(tsn, sack_ctsn)) {
1501                                         /*
1502                                          * SFR-CACC algorithm:
1503                                          * 2) If the SACK contains gap acks
1504                                          * and the flag CHANGEOVER_ACTIVE is
1505                                          * set the receiver of the SACK MUST
1506                                          * take the following action:
1507                                          *
1508                                          * B) For each TSN t being acked that
1509                                          * has not been acked in any SACK so
1510                                          * far, set cacc_saw_newack to 1 for
1511                                          * the destination that the TSN was
1512                                          * sent to.
1513                                          */
1514                                         if (sack->num_gap_ack_blocks &&
1515                                             q->asoc->peer.primary_path->cacc.
1516                                             changeover_active)
1517                                                 transport->cacc.cacc_saw_newack
1518                                                         = 1;
1519                                 }
1520                         }
1521
1522                         /* If the chunk hasn't been marked as ACKED,
1523                          * mark it and account bytes_acked if the
1524                          * chunk had a valid transport (it will not
1525                          * have a transport if ASCONF had deleted it
1526                          * while DATA was outstanding).
1527                          */
1528                         if (!tchunk->tsn_gap_acked) {
1529                                 tchunk->tsn_gap_acked = 1;
1530                                 if (TSN_lt(*highest_new_tsn_in_sack, tsn))
1531                                         *highest_new_tsn_in_sack = tsn;
1532                                 bytes_acked += sctp_data_size(tchunk);
1533                                 if (!tchunk->transport)
1534                                         migrate_bytes += sctp_data_size(tchunk);
1535                                 forward_progress = true;
1536                         }
1537
1538                         if (TSN_lte(tsn, sack_ctsn)) {
1539                                 /* RFC 2960  6.3.2 Retransmission Timer Rules
1540                                  *
1541                                  * R3) Whenever a SACK is received
1542                                  * that acknowledges the DATA chunk
1543                                  * with the earliest outstanding TSN
1544                                  * for that address, restart T3-rtx
1545                                  * timer for that address with its
1546                                  * current RTO.
1547                                  */
1548                                 restart_timer = 1;
1549                                 forward_progress = true;
1550
1551                                 list_add_tail(&tchunk->transmitted_list,
1552                                               &q->sacked);
1553                         } else {
1554                                 /* RFC2960 7.2.4, sctpimpguide-05 2.8.2
1555                                  * M2) Each time a SACK arrives reporting
1556                                  * 'Stray DATA chunk(s)' record the highest TSN
1557                                  * reported as newly acknowledged, call this
1558                                  * value 'HighestTSNinSack'. A newly
1559                                  * acknowledged DATA chunk is one not
1560                                  * previously acknowledged in a SACK.
1561                                  *
1562                                  * When the SCTP sender of data receives a SACK
1563                                  * chunk that acknowledges, for the first time,
1564                                  * the receipt of a DATA chunk, all the still
1565                                  * unacknowledged DATA chunks whose TSN is
1566                                  * older than that newly acknowledged DATA
1567                                  * chunk, are qualified as 'Stray DATA chunks'.
1568                                  */
1569                                 list_add_tail(lchunk, &tlist);
1570                         }
1571                 } else {
1572                         if (tchunk->tsn_gap_acked) {
1573                                 pr_debug("%s: receiver reneged on data TSN:0x%x\n",
1574                                          __func__, tsn);
1575
1576                                 tchunk->tsn_gap_acked = 0;
1577
1578                                 if (tchunk->transport)
1579                                         bytes_acked -= sctp_data_size(tchunk);
1580
1581                                 /* RFC 2960 6.3.2 Retransmission Timer Rules
1582                                  *
1583                                  * R4) Whenever a SACK is received missing a
1584                                  * TSN that was previously acknowledged via a
1585                                  * Gap Ack Block, start T3-rtx for the
1586                                  * destination address to which the DATA
1587                                  * chunk was originally
1588                                  * transmitted if it is not already running.
1589                                  */
1590                                 restart_timer = 1;
1591                         }
1592
1593                         list_add_tail(lchunk, &tlist);
1594                 }
1595         }
1596
1597         if (transport) {
1598                 if (bytes_acked) {
1599                         struct sctp_association *asoc = transport->asoc;
1600
1601                         /* We may have counted DATA that was migrated
1602                          * to this transport due to DEL-IP operation.
1603                          * Subtract those bytes, since the were never
1604                          * send on this transport and shouldn't be
1605                          * credited to this transport.
1606                          */
1607                         bytes_acked -= migrate_bytes;
1608
1609                         /* 8.2. When an outstanding TSN is acknowledged,
1610                          * the endpoint shall clear the error counter of
1611                          * the destination transport address to which the
1612                          * DATA chunk was last sent.
1613                          * The association's overall error counter is
1614                          * also cleared.
1615                          */
1616                         transport->error_count = 0;
1617                         transport->asoc->overall_error_count = 0;
1618                         forward_progress = true;
1619
1620                         /*
1621                          * While in SHUTDOWN PENDING, we may have started
1622                          * the T5 shutdown guard timer after reaching the
1623                          * retransmission limit. Stop that timer as soon
1624                          * as the receiver acknowledged any data.
1625                          */
1626                         if (asoc->state == SCTP_STATE_SHUTDOWN_PENDING &&
1627                             del_timer(&asoc->timers
1628                                 [SCTP_EVENT_TIMEOUT_T5_SHUTDOWN_GUARD]))
1629                                         sctp_association_put(asoc);
1630
1631                         /* Mark the destination transport address as
1632                          * active if it is not so marked.
1633                          */
1634                         if ((transport->state == SCTP_INACTIVE ||
1635                              transport->state == SCTP_UNCONFIRMED) &&
1636                             sctp_cmp_addr_exact(&transport->ipaddr, saddr)) {
1637                                 sctp_assoc_control_transport(
1638                                         transport->asoc,
1639                                         transport,
1640                                         SCTP_TRANSPORT_UP,
1641                                         SCTP_RECEIVED_SACK);
1642                         }
1643
1644                         sctp_transport_raise_cwnd(transport, sack_ctsn,
1645                                                   bytes_acked);
1646
1647                         transport->flight_size -= bytes_acked;
1648                         if (transport->flight_size == 0)
1649                                 transport->partial_bytes_acked = 0;
1650                         q->outstanding_bytes -= bytes_acked + migrate_bytes;
1651                 } else {
1652                         /* RFC 2960 6.1, sctpimpguide-06 2.15.2
1653                          * When a sender is doing zero window probing, it
1654                          * should not timeout the association if it continues
1655                          * to receive new packets from the receiver. The
1656                          * reason is that the receiver MAY keep its window
1657                          * closed for an indefinite time.
1658                          * A sender is doing zero window probing when the
1659                          * receiver's advertised window is zero, and there is
1660                          * only one data chunk in flight to the receiver.
1661                          *
1662                          * Allow the association to timeout while in SHUTDOWN
1663                          * PENDING or SHUTDOWN RECEIVED in case the receiver
1664                          * stays in zero window mode forever.
1665                          */
1666                         if (!q->asoc->peer.rwnd &&
1667                             !list_empty(&tlist) &&
1668                             (sack_ctsn+2 == q->asoc->next_tsn) &&
1669                             q->asoc->state < SCTP_STATE_SHUTDOWN_PENDING) {
1670                                 pr_debug("%s: sack received for zero window "
1671                                          "probe:%u\n", __func__, sack_ctsn);
1672
1673                                 q->asoc->overall_error_count = 0;
1674                                 transport->error_count = 0;
1675                         }
1676                 }
1677
1678                 /* RFC 2960 6.3.2 Retransmission Timer Rules
1679                  *
1680                  * R2) Whenever all outstanding data sent to an address have
1681                  * been acknowledged, turn off the T3-rtx timer of that
1682                  * address.
1683                  */
1684                 if (!transport->flight_size) {
1685                         if (del_timer(&transport->T3_rtx_timer))
1686                                 sctp_transport_put(transport);
1687                 } else if (restart_timer) {
1688                         if (!mod_timer(&transport->T3_rtx_timer,
1689                                        jiffies + transport->rto))
1690                                 sctp_transport_hold(transport);
1691                 }
1692
1693                 if (forward_progress) {
1694                         if (transport->dst)
1695                                 sctp_transport_dst_confirm(transport);
1696                 }
1697         }
1698
1699         list_splice(&tlist, transmitted_queue);
1700 }
1701
1702 /* Mark chunks as missing and consequently may get retransmitted. */
1703 static void sctp_mark_missing(struct sctp_outq *q,
1704                               struct list_head *transmitted_queue,
1705                               struct sctp_transport *transport,
1706                               __u32 highest_new_tsn_in_sack,
1707                               int count_of_newacks)
1708 {
1709         struct sctp_chunk *chunk;
1710         __u32 tsn;
1711         char do_fast_retransmit = 0;
1712         struct sctp_association *asoc = q->asoc;
1713         struct sctp_transport *primary = asoc->peer.primary_path;
1714
1715         list_for_each_entry(chunk, transmitted_queue, transmitted_list) {
1716
1717                 tsn = ntohl(chunk->subh.data_hdr->tsn);
1718
1719                 /* RFC 2960 7.2.4, sctpimpguide-05 2.8.2 M3) Examine all
1720                  * 'Unacknowledged TSN's', if the TSN number of an
1721                  * 'Unacknowledged TSN' is smaller than the 'HighestTSNinSack'
1722                  * value, increment the 'TSN.Missing.Report' count on that
1723                  * chunk if it has NOT been fast retransmitted or marked for
1724                  * fast retransmit already.
1725                  */
1726                 if (chunk->fast_retransmit == SCTP_CAN_FRTX &&
1727                     !chunk->tsn_gap_acked &&
1728                     TSN_lt(tsn, highest_new_tsn_in_sack)) {
1729
1730                         /* SFR-CACC may require us to skip marking
1731                          * this chunk as missing.
1732                          */
1733                         if (!transport || !sctp_cacc_skip(primary,
1734                                                 chunk->transport,
1735                                                 count_of_newacks, tsn)) {
1736                                 chunk->tsn_missing_report++;
1737
1738                                 pr_debug("%s: tsn:0x%x missing counter:%d\n",
1739                                          __func__, tsn, chunk->tsn_missing_report);
1740                         }
1741                 }
1742                 /*
1743                  * M4) If any DATA chunk is found to have a
1744                  * 'TSN.Missing.Report'
1745                  * value larger than or equal to 3, mark that chunk for
1746                  * retransmission and start the fast retransmit procedure.
1747                  */
1748
1749                 if (chunk->tsn_missing_report >= 3) {
1750                         chunk->fast_retransmit = SCTP_NEED_FRTX;
1751                         do_fast_retransmit = 1;
1752                 }
1753         }
1754
1755         if (transport) {
1756                 if (do_fast_retransmit)
1757                         sctp_retransmit(q, transport, SCTP_RTXR_FAST_RTX);
1758
1759                 pr_debug("%s: transport:%p, cwnd:%d, ssthresh:%d, "
1760                          "flight_size:%d, pba:%d\n",  __func__, transport,
1761                          transport->cwnd, transport->ssthresh,
1762                          transport->flight_size, transport->partial_bytes_acked);
1763         }
1764 }
1765
1766 /* Is the given TSN acked by this packet?  */
1767 static int sctp_acked(struct sctp_sackhdr *sack, __u32 tsn)
1768 {
1769         __u32 ctsn = ntohl(sack->cum_tsn_ack);
1770         union sctp_sack_variable *frags;
1771         __u16 tsn_offset, blocks;
1772         int i;
1773
1774         if (TSN_lte(tsn, ctsn))
1775                 goto pass;
1776
1777         /* 3.3.4 Selective Acknowledgment (SACK) (3):
1778          *
1779          * Gap Ack Blocks:
1780          *  These fields contain the Gap Ack Blocks. They are repeated
1781          *  for each Gap Ack Block up to the number of Gap Ack Blocks
1782          *  defined in the Number of Gap Ack Blocks field. All DATA
1783          *  chunks with TSNs greater than or equal to (Cumulative TSN
1784          *  Ack + Gap Ack Block Start) and less than or equal to
1785          *  (Cumulative TSN Ack + Gap Ack Block End) of each Gap Ack
1786          *  Block are assumed to have been received correctly.
1787          */
1788
1789         frags = sack->variable;
1790         blocks = ntohs(sack->num_gap_ack_blocks);
1791         tsn_offset = tsn - ctsn;
1792         for (i = 0; i < blocks; ++i) {
1793                 if (tsn_offset >= ntohs(frags[i].gab.start) &&
1794                     tsn_offset <= ntohs(frags[i].gab.end))
1795                         goto pass;
1796         }
1797
1798         return 0;
1799 pass:
1800         return 1;
1801 }
1802
1803 static inline int sctp_get_skip_pos(struct sctp_fwdtsn_skip *skiplist,
1804                                     int nskips, __be16 stream)
1805 {
1806         int i;
1807
1808         for (i = 0; i < nskips; i++) {
1809                 if (skiplist[i].stream == stream)
1810                         return i;
1811         }
1812         return i;
1813 }
1814
1815 /* Create and add a fwdtsn chunk to the outq's control queue if needed. */
1816 void sctp_generate_fwdtsn(struct sctp_outq *q, __u32 ctsn)
1817 {
1818         struct sctp_association *asoc = q->asoc;
1819         struct sctp_chunk *ftsn_chunk = NULL;
1820         struct sctp_fwdtsn_skip ftsn_skip_arr[10];
1821         int nskips = 0;
1822         int skip_pos = 0;
1823         __u32 tsn;
1824         struct sctp_chunk *chunk;
1825         struct list_head *lchunk, *temp;
1826
1827         if (!asoc->peer.prsctp_capable)
1828                 return;
1829
1830         /* PR-SCTP C1) Let SackCumAck be the Cumulative TSN ACK carried in the
1831          * received SACK.
1832          *
1833          * If (Advanced.Peer.Ack.Point < SackCumAck), then update
1834          * Advanced.Peer.Ack.Point to be equal to SackCumAck.
1835          */
1836         if (TSN_lt(asoc->adv_peer_ack_point, ctsn))
1837                 asoc->adv_peer_ack_point = ctsn;
1838
1839         /* PR-SCTP C2) Try to further advance the "Advanced.Peer.Ack.Point"
1840          * locally, that is, to move "Advanced.Peer.Ack.Point" up as long as
1841          * the chunk next in the out-queue space is marked as "abandoned" as
1842          * shown in the following example:
1843          *
1844          * Assuming that a SACK arrived with the Cumulative TSN ACK 102
1845          * and the Advanced.Peer.Ack.Point is updated to this value:
1846          *
1847          *   out-queue at the end of  ==>   out-queue after Adv.Ack.Point
1848          *   normal SACK processing           local advancement
1849          *                ...                           ...
1850          *   Adv.Ack.Pt-> 102 acked                     102 acked
1851          *                103 abandoned                 103 abandoned
1852          *                104 abandoned     Adv.Ack.P-> 104 abandoned
1853          *                105                           105
1854          *                106 acked                     106 acked
1855          *                ...                           ...
1856          *
1857          * In this example, the data sender successfully advanced the
1858          * "Advanced.Peer.Ack.Point" from 102 to 104 locally.
1859          */
1860         list_for_each_safe(lchunk, temp, &q->abandoned) {
1861                 chunk = list_entry(lchunk, struct sctp_chunk,
1862                                         transmitted_list);
1863                 tsn = ntohl(chunk->subh.data_hdr->tsn);
1864
1865                 /* Remove any chunks in the abandoned queue that are acked by
1866                  * the ctsn.
1867                  */
1868                 if (TSN_lte(tsn, ctsn)) {
1869                         list_del_init(lchunk);
1870                         sctp_chunk_free(chunk);
1871                 } else {
1872                         if (TSN_lte(tsn, asoc->adv_peer_ack_point+1)) {
1873                                 asoc->adv_peer_ack_point = tsn;
1874                                 if (chunk->chunk_hdr->flags &
1875                                          SCTP_DATA_UNORDERED)
1876                                         continue;
1877                                 skip_pos = sctp_get_skip_pos(&ftsn_skip_arr[0],
1878                                                 nskips,
1879                                                 chunk->subh.data_hdr->stream);
1880                                 ftsn_skip_arr[skip_pos].stream =
1881                                         chunk->subh.data_hdr->stream;
1882                                 ftsn_skip_arr[skip_pos].ssn =
1883                                          chunk->subh.data_hdr->ssn;
1884                                 if (skip_pos == nskips)
1885                                         nskips++;
1886                                 if (nskips == 10)
1887                                         break;
1888                         } else
1889                                 break;
1890                 }
1891         }
1892
1893         /* PR-SCTP C3) If, after step C1 and C2, the "Advanced.Peer.Ack.Point"
1894          * is greater than the Cumulative TSN ACK carried in the received
1895          * SACK, the data sender MUST send the data receiver a FORWARD TSN
1896          * chunk containing the latest value of the
1897          * "Advanced.Peer.Ack.Point".
1898          *
1899          * C4) For each "abandoned" TSN the sender of the FORWARD TSN SHOULD
1900          * list each stream and sequence number in the forwarded TSN. This
1901          * information will enable the receiver to easily find any
1902          * stranded TSN's waiting on stream reorder queues. Each stream
1903          * SHOULD only be reported once; this means that if multiple
1904          * abandoned messages occur in the same stream then only the
1905          * highest abandoned stream sequence number is reported. If the
1906          * total size of the FORWARD TSN does NOT fit in a single MTU then
1907          * the sender of the FORWARD TSN SHOULD lower the
1908          * Advanced.Peer.Ack.Point to the last TSN that will fit in a
1909          * single MTU.
1910          */
1911         if (asoc->adv_peer_ack_point > ctsn)
1912                 ftsn_chunk = sctp_make_fwdtsn(asoc, asoc->adv_peer_ack_point,
1913                                               nskips, &ftsn_skip_arr[0]);
1914
1915         if (ftsn_chunk) {
1916                 list_add_tail(&ftsn_chunk->list, &q->control_chunk_list);
1917                 SCTP_INC_STATS(asoc->base.net, SCTP_MIB_OUTCTRLCHUNKS);
1918         }
1919 }