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         struct sctp_stream_out *sout;
 388
 389         q->sched->unsched_all(&asoc->stream);
 390
 391         list_for_each_entry_safe(chk, temp, &q->out_chunk_list, list) {
 392                 if (!chk->msg->abandoned &&
 393                     (!(chk->chunk_hdr->flags & SCTP_DATA_FIRST_FRAG) ||
 394                      !SCTP_PR_PRIO_ENABLED(chk->sinfo.sinfo_flags) ||
 395                      chk->sinfo.sinfo_timetolive <= sinfo->sinfo_timetolive))
 396                         continue;
 397
 398                 chk->msg->abandoned = 1;
 399                 sctp_sched_dequeue_common(q, chk);
 400                 asoc->sent_cnt_removable--;
 401                 asoc->abandoned_unsent[SCTP_PR_INDEX(PRIO)]++;
 402
 403                 sout = SCTP_SO(&asoc->stream, chk->sinfo.sinfo_stream);
 404                 sout->ext->abandoned_unsent[SCTP_PR_INDEX(PRIO)]++;
 405
 406                 /* clear out_curr if all frag chunks are pruned */
 407                 if (asoc->stream.out_curr == sout &&
 408                     list_is_last(&chk->frag_list, &chk->msg->chunks))
 409                         asoc->stream.out_curr = NULL;
 410
 411                 msg_len -= chk->skb->truesize + sizeof(struct sctp_chunk);
 412                 sctp_chunk_free(chk);
 413                 if (msg_len <= 0)
 414                         break;
 415         }
 416
 417         q->sched->sched_all(&asoc->stream);
 418
 419         return msg_len;
 420 }
 421
 422 /* Abandon the chunks according their priorities */
 423 void sctp_prsctp_prune(struct sctp_association *asoc,
 424                        struct sctp_sndrcvinfo *sinfo, int msg_len)
 425 {
 426         struct sctp_transport *transport;
 427
 428         if (!asoc->peer.prsctp_capable || !asoc->sent_cnt_removable)
 429                 return;
 430
 431         msg_len = sctp_prsctp_prune_sent(asoc, sinfo,
 432                                          &asoc->outqueue.retransmit,
 433                                          msg_len);
 434         if (msg_len <= 0)
 435                 return;
 436
 437         list_for_each_entry(transport, &asoc->peer.transport_addr_list,
 438                             transports) {
 439                 msg_len = sctp_prsctp_prune_sent(asoc, sinfo,
 440                                                  &transport->transmitted,
 441                                                  msg_len);
 442                 if (msg_len <= 0)
 443                         return;
 444         }
 445
 446         sctp_prsctp_prune_unsent(asoc, sinfo, msg_len);
 447 }
 448
 449 /* Mark all the eligible packets on a transport for retransmission.  */
 450 void sctp_retransmit_mark(struct sctp_outq *q,
 451                           struct sctp_transport *transport,
 452                           __u8 reason)
 453 {
 454         struct list_head *lchunk, *ltemp;
 455         struct sctp_chunk *chunk;
 456
 457         /* Walk through the specified transmitted queue.  */
 458         list_for_each_safe(lchunk, ltemp, &transport->transmitted) {
 459                 chunk = list_entry(lchunk, struct sctp_chunk,
 460                                    transmitted_list);
 461
 462                 /* If the chunk is abandoned, move it to abandoned list. */
 463                 if (sctp_chunk_abandoned(chunk)) {
 464                         list_del_init(lchunk);
 465                         sctp_insert_list(&q->abandoned, lchunk);
 466
 467                         /* If this chunk has not been previousely acked,
 468                          * stop considering it 'outstanding'.  Our peer
 469                          * will most likely never see it since it will
 470                          * not be retransmitted
 471                          */
 472                         if (!chunk->tsn_gap_acked) {
 473                                 if (chunk->transport)
 474                                         chunk->transport->flight_size -=
 475                                                         sctp_data_size(chunk);
 476                                 q->outstanding_bytes -= sctp_data_size(chunk);
 477                                 q->asoc->peer.rwnd += sctp_data_size(chunk);
 478                         }
 479                         continue;
 480                 }
 481
 482                 /* If we are doing  retransmission due to a timeout or pmtu
 483                  * discovery, only the  chunks that are not yet acked should
 484                  * be added to the retransmit queue.
 485                  */
 486                 if ((reason == SCTP_RTXR_FAST_RTX  &&
 487                             (chunk->fast_retransmit == SCTP_NEED_FRTX)) ||
 488                     (reason != SCTP_RTXR_FAST_RTX  && !chunk->tsn_gap_acked)) {
 489                         /* RFC 2960 6.2.1 Processing a Received SACK
 490                          *
 491                          * C) Any time a DATA chunk is marked for
 492                          * retransmission (via either T3-rtx timer expiration
 493                          * (Section 6.3.3) or via fast retransmit
 494                          * (Section 7.2.4)), add the data size of those
 495                          * chunks to the rwnd.
 496                          */
 497                         q->asoc->peer.rwnd += sctp_data_size(chunk);
 498                         q->outstanding_bytes -= sctp_data_size(chunk);
 499                         if (chunk->transport)
 500                                 transport->flight_size -= sctp_data_size(chunk);
 501
 502                         /* sctpimpguide-05 Section 2.8.2
 503                          * M5) If a T3-rtx timer expires, the
 504                          * 'TSN.Missing.Report' of all affected TSNs is set
 505                          * to 0.
 506                          */
 507                         chunk->tsn_missing_report = 0;
 508
 509                         /* If a chunk that is being used for RTT measurement
 510                          * has to be retransmitted, we cannot use this chunk
 511                          * anymore for RTT measurements. Reset rto_pending so
 512                          * that a new RTT measurement is started when a new
 513                          * data chunk is sent.
 514                          */
 515                         if (chunk->rtt_in_progress) {
 516                                 chunk->rtt_in_progress = 0;
 517                                 transport->rto_pending = 0;
 518                         }
 519
 520                         /* Move the chunk to the retransmit queue. The chunks
 521                          * on the retransmit queue are always kept in order.
 522                          */
 523                         list_del_init(lchunk);
 524                         sctp_insert_list(&q->retransmit, lchunk);
 525                 }
 526         }
 527
 528         pr_debug("%s: transport:%p, reason:%d, cwnd:%d, ssthresh:%d, "
 529                  "flight_size:%d, pba:%d\n", __func__, transport, reason,
 530                  transport->cwnd, transport->ssthresh, transport->flight_size,
 531                  transport->partial_bytes_acked);
 532 }
 533
 534 /* Mark all the eligible packets on a transport for retransmission and force
 535  * one packet out.
 536  */
 537 void sctp_retransmit(struct sctp_outq *q, struct sctp_transport *transport,
 538                      enum sctp_retransmit_reason reason)
 539 {
 540         struct net *net = q->asoc->base.net;
 541
 542         switch (reason) {
 543         case SCTP_RTXR_T3_RTX:
 544                 SCTP_INC_STATS(net, SCTP_MIB_T3_RETRANSMITS);
 545                 sctp_transport_lower_cwnd(transport, SCTP_LOWER_CWND_T3_RTX);
 546                 /* Update the retran path if the T3-rtx timer has expired for
 547                  * the current retran path.
 548                  */
 549                 if (transport == transport->asoc->peer.retran_path)
 550                         sctp_assoc_update_retran_path(transport->asoc);
 551                 transport->asoc->rtx_data_chunks +=
 552                         transport->asoc->unack_data;
 553                 if (transport->pl.state == SCTP_PL_COMPLETE &&
 554                     transport->asoc->unack_data)
 555                         sctp_transport_reset_probe_timer(transport);
 556                 break;
 557         case SCTP_RTXR_FAST_RTX:
 558                 SCTP_INC_STATS(net, SCTP_MIB_FAST_RETRANSMITS);
 559                 sctp_transport_lower_cwnd(transport, SCTP_LOWER_CWND_FAST_RTX);
 560                 q->fast_rtx = 1;
 561                 break;
 562         case SCTP_RTXR_PMTUD:
 563                 SCTP_INC_STATS(net, SCTP_MIB_PMTUD_RETRANSMITS);
 564                 break;
 565         case SCTP_RTXR_T1_RTX:
 566                 SCTP_INC_STATS(net, SCTP_MIB_T1_RETRANSMITS);
 567                 transport->asoc->init_retries++;
 568                 break;
 569         default:
 570                 BUG();
 571         }
 572
 573         sctp_retransmit_mark(q, transport, reason);
 574
 575         /* PR-SCTP A5) Any time the T3-rtx timer expires, on any destination,
 576          * the sender SHOULD try to advance the "Advanced.Peer.Ack.Point" by
 577          * following the procedures outlined in C1 - C5.
 578          */
 579         if (reason == SCTP_RTXR_T3_RTX)
 580                 q->asoc->stream.si->generate_ftsn(q, q->asoc->ctsn_ack_point);
 581
 582         /* Flush the queues only on timeout, since fast_rtx is only
 583          * triggered during sack processing and the queue
 584          * will be flushed at the end.
 585          */
 586         if (reason != SCTP_RTXR_FAST_RTX)
 587                 sctp_outq_flush(q, /* rtx_timeout */ 1, GFP_ATOMIC);
 588 }
 589
 590 /*
 591  * Transmit DATA chunks on the retransmit queue.  Upon return from
 592  * __sctp_outq_flush_rtx() the packet 'pkt' may contain chunks which
 593  * need to be transmitted by the caller.
 594  * We assume that pkt->transport has already been set.
 595  *
 596  * The return value is a normal kernel error return value.
 597  */
 598 static int __sctp_outq_flush_rtx(struct sctp_outq *q, struct sctp_packet *pkt,
 599                                  int rtx_timeout, int *start_timer, gfp_t gfp)
 600 {
 601         struct sctp_transport *transport = pkt->transport;
 602         struct sctp_chunk *chunk, *chunk1;
 603         struct list_head *lqueue;
 604         enum sctp_xmit status;
 605         int error = 0;
 606         int timer = 0;
 607         int done = 0;
 608         int fast_rtx;
 609
 610         lqueue = &q->retransmit;
 611         fast_rtx = q->fast_rtx;
 612
 613         /* This loop handles time-out retransmissions, fast retransmissions,
 614          * and retransmissions due to opening of whindow.
 615          *
 616          * RFC 2960 6.3.3 Handle T3-rtx Expiration
 617          *
 618          * E3) Determine how many of the earliest (i.e., lowest TSN)
 619          * outstanding DATA chunks for the address for which the
 620          * T3-rtx has expired will fit into a single packet, subject
 621          * to the MTU constraint for the path corresponding to the
 622          * destination transport address to which the retransmission
 623          * is being sent (this may be different from the address for
 624          * which the timer expires [see Section 6.4]). Call this value
 625          * K. Bundle and retransmit those K DATA chunks in a single
 626          * packet to the destination endpoint.
 627          *
 628          * [Just to be painfully clear, if we are retransmitting
 629          * because a timeout just happened, we should send only ONE
 630          * packet of retransmitted data.]
 631          *
 632          * For fast retransmissions we also send only ONE packet.  However,
 633          * if we are just flushing the queue due to open window, we'll
 634          * try to send as much as possible.
 635          */
 636         list_for_each_entry_safe(chunk, chunk1, lqueue, transmitted_list) {
 637                 /* If the chunk is abandoned, move it to abandoned list. */
 638                 if (sctp_chunk_abandoned(chunk)) {
 639                         list_del_init(&chunk->transmitted_list);
 640                         sctp_insert_list(&q->abandoned,
 641                                          &chunk->transmitted_list);
 642                         continue;
 643                 }
 644
 645                 /* Make sure that Gap Acked TSNs are not retransmitted.  A
 646                  * simple approach is just to move such TSNs out of the
 647                  * way and into a 'transmitted' queue and skip to the
 648                  * next chunk.
 649                  */
 650                 if (chunk->tsn_gap_acked) {
 651                         list_move_tail(&chunk->transmitted_list,
 652                                        &transport->transmitted);
 653                         continue;
 654                 }
 655
 656                 /* If we are doing fast retransmit, ignore non-fast_rtransmit
 657                  * chunks
 658                  */
 659                 if (fast_rtx && !chunk->fast_retransmit)
 660                         continue;
 661
 662 redo:
 663                 /* Attempt to append this chunk to the packet. */
 664                 status = sctp_packet_append_chunk(pkt, chunk);
 665
 666                 switch (status) {
 667                 case SCTP_XMIT_PMTU_FULL:
 668                         if (!pkt->has_data && !pkt->has_cookie_echo) {
 669                                 /* If this packet did not contain DATA then
 670                                  * retransmission did not happen, so do it
 671                                  * again.  We'll ignore the error here since
 672                                  * control chunks are already freed so there
 673                                  * is nothing we can do.
 674                                  */
 675                                 sctp_packet_transmit(pkt, gfp);
 676                                 goto redo;
 677                         }
 678
 679                         /* Send this packet.  */
 680                         error = sctp_packet_transmit(pkt, gfp);
 681
 682                         /* If we are retransmitting, we should only
 683                          * send a single packet.
 684                          * Otherwise, try appending this chunk again.
 685                          */
 686                         if (rtx_timeout || fast_rtx)
 687                                 done = 1;
 688                         else
 689                                 goto redo;
 690
 691                         /* Bundle next chunk in the next round.  */
 692                         break;
 693
 694                 case SCTP_XMIT_RWND_FULL:
 695                         /* Send this packet. */
 696                         error = sctp_packet_transmit(pkt, gfp);
 697
 698                         /* Stop sending DATA as there is no more room
 699                          * at the receiver.
 700                          */
 701                         done = 1;
 702                         break;
 703
 704                 case SCTP_XMIT_DELAY:
 705                         /* Send this packet. */
 706                         error = sctp_packet_transmit(pkt, gfp);
 707
 708                         /* Stop sending DATA because of nagle delay. */
 709                         done = 1;
 710                         break;
 711
 712                 default:
 713                         /* The append was successful, so add this chunk to
 714                          * the transmitted list.
 715                          */
 716                         list_move_tail(&chunk->transmitted_list,
 717                                        &transport->transmitted);
 718
 719                         /* Mark the chunk as ineligible for fast retransmit
 720                          * after it is retransmitted.
 721                          */
 722                         if (chunk->fast_retransmit == SCTP_NEED_FRTX)
 723                                 chunk->fast_retransmit = SCTP_DONT_FRTX;
 724
 725                         q->asoc->stats.rtxchunks++;
 726                         break;
 727                 }
 728
 729                 /* Set the timer if there were no errors */
 730                 if (!error && !timer)
 731                         timer = 1;
 732
 733                 if (done)
 734                         break;
 735         }
 736
 737         /* If we are here due to a retransmit timeout or a fast
 738          * retransmit and if there are any chunks left in the retransmit
 739          * queue that could not fit in the PMTU sized packet, they need
 740          * to be marked as ineligible for a subsequent fast retransmit.
 741          */
 742         if (rtx_timeout || fast_rtx) {
 743                 list_for_each_entry(chunk1, lqueue, transmitted_list) {
 744                         if (chunk1->fast_retransmit == SCTP_NEED_FRTX)
 745                                 chunk1->fast_retransmit = SCTP_DONT_FRTX;
 746                 }
 747         }
 748
 749         *start_timer = timer;
 750
 751         /* Clear fast retransmit hint */
 752         if (fast_rtx)
 753                 q->fast_rtx = 0;
 754
 755         return error;
 756 }
 757
 758 /* Cork the outqueue so queued chunks are really queued. */
 759 void sctp_outq_uncork(struct sctp_outq *q, gfp_t gfp)
 760 {
 761         if (q->cork)
 762                 q->cork = 0;
 763
 764         sctp_outq_flush(q, 0, gfp);
 765 }
 766
 767 static int sctp_packet_singleton(struct sctp_transport *transport,
 768                                  struct sctp_chunk *chunk, gfp_t gfp)
 769 {
 770         const struct sctp_association *asoc = transport->asoc;
 771         const __u16 sport = asoc->base.bind_addr.port;
 772         const __u16 dport = asoc->peer.port;
 773         const __u32 vtag = asoc->peer.i.init_tag;
 774         struct sctp_packet singleton;
 775
 776         sctp_packet_init(&singleton, transport, sport, dport);
 777         sctp_packet_config(&singleton, vtag, 0);
 778         if (sctp_packet_append_chunk(&singleton, chunk) != SCTP_XMIT_OK) {
 779                 list_del_init(&chunk->list);
 780                 sctp_chunk_free(chunk);
 781                 return -ENOMEM;
 782         }
 783         return sctp_packet_transmit(&singleton, gfp);
 784 }
 785
 786 /* Struct to hold the context during sctp outq flush */
 787 struct sctp_flush_ctx {
 788         struct sctp_outq *q;
 789         /* Current transport being used. It's NOT the same as curr active one */
 790         struct sctp_transport *transport;
 791         /* These transports have chunks to send. */
 792         struct list_head transport_list;
 793         struct sctp_association *asoc;
 794         /* Packet on the current transport above */
 795         struct sctp_packet *packet;
 796         gfp_t gfp;
 797 };
 798
 799 /* transport: current transport */
 800 static void sctp_outq_select_transport(struct sctp_flush_ctx *ctx,
 801                                        struct sctp_chunk *chunk)
 802 {
 803         struct sctp_transport *new_transport = chunk->transport;
 804
 805         if (!new_transport) {
 806                 if (!sctp_chunk_is_data(chunk)) {
 807                         /* If we have a prior transport pointer, see if
 808                          * the destination address of the chunk
 809                          * matches the destination address of the
 810                          * current transport.  If not a match, then
 811                          * try to look up the transport with a given
 812                          * destination address.  We do this because
 813                          * after processing ASCONFs, we may have new
 814                          * transports created.
 815                          */
 816                         if (ctx->transport && sctp_cmp_addr_exact(&chunk->dest,
 817                                                         &ctx->transport->ipaddr))
 818                                 new_transport = ctx->transport;
 819                         else
 820                                 new_transport = sctp_assoc_lookup_paddr(ctx->asoc,
 821                                                                   &chunk->dest);
 822                 }
 823
 824                 /* if we still don't have a new transport, then
 825                  * use the current active path.
 826                  */
 827                 if (!new_transport)
 828                         new_transport = ctx->asoc->peer.active_path;
 829         } else {
 830                 __u8 type;
 831
 832                 switch (new_transport->state) {
 833                 case SCTP_INACTIVE:
 834                 case SCTP_UNCONFIRMED:
 835                 case SCTP_PF:
 836                         /* If the chunk is Heartbeat or Heartbeat Ack,
 837                          * send it to chunk->transport, even if it's
 838                          * inactive.
 839                          *
 840                          * 3.3.6 Heartbeat Acknowledgement:
 841                          * ...
 842                          * A HEARTBEAT ACK is always sent to the source IP
 843                          * address of the IP datagram containing the
 844                          * HEARTBEAT chunk to which this ack is responding.
 845                          * ...
 846                          *
 847                          * ASCONF_ACKs also must be sent to the source.
 848                          */
 849                         type = chunk->chunk_hdr->type;
 850                         if (type != SCTP_CID_HEARTBEAT &&
 851                             type != SCTP_CID_HEARTBEAT_ACK &&
 852                             type != SCTP_CID_ASCONF_ACK)
 853                                 new_transport = ctx->asoc->peer.active_path;
 854                         break;
 855                 default:
 856                         break;
 857                 }
 858         }
 859
 860         /* Are we switching transports? Take care of transport locks. */
 861         if (new_transport != ctx->transport) {
 862                 ctx->transport = new_transport;
 863                 ctx->packet = &ctx->transport->packet;
 864
 865                 if (list_empty(&ctx->transport->send_ready))
 866                         list_add_tail(&ctx->transport->send_ready,
 867                                       &ctx->transport_list);
 868
 869                 sctp_packet_config(ctx->packet,
 870                                    ctx->asoc->peer.i.init_tag,
 871                                    ctx->asoc->peer.ecn_capable);
 872                 /* We've switched transports, so apply the
 873                  * Burst limit to the new transport.
 874                  */
 875                 sctp_transport_burst_limited(ctx->transport);
 876         }
 877 }
 878
 879 static void sctp_outq_flush_ctrl(struct sctp_flush_ctx *ctx)
 880 {
 881         struct sctp_chunk *chunk, *tmp;
 882         enum sctp_xmit status;
 883         int one_packet, error;
 884
 885         list_for_each_entry_safe(chunk, tmp, &ctx->q->control_chunk_list, list) {
 886                 one_packet = 0;
 887
 888                 /* RFC 5061, 5.3
 889                  * F1) This means that until such time as the ASCONF
 890                  * containing the add is acknowledged, the sender MUST
 891                  * NOT use the new IP address as a source for ANY SCTP
 892                  * packet except on carrying an ASCONF Chunk.
 893                  */
 894                 if (ctx->asoc->src_out_of_asoc_ok &&
 895                     chunk->chunk_hdr->type != SCTP_CID_ASCONF)
 896                         continue;
 897
 898                 list_del_init(&chunk->list);
 899
 900                 /* Pick the right transport to use. Should always be true for
 901                  * the first chunk as we don't have a transport by then.
 902                  */
 903                 sctp_outq_select_transport(ctx, chunk);
 904
 905                 switch (chunk->chunk_hdr->type) {
 906                 /* 6.10 Bundling
 907                  *   ...
 908                  *   An endpoint MUST NOT bundle INIT, INIT ACK or SHUTDOWN
 909                  *   COMPLETE with any other chunks.  [Send them immediately.]
 910                  */
 911                 case SCTP_CID_INIT:
 912                 case SCTP_CID_INIT_ACK:
 913                 case SCTP_CID_SHUTDOWN_COMPLETE:
 914                         error = sctp_packet_singleton(ctx->transport, chunk,
 915                                                       ctx->gfp);
 916                         if (error < 0) {
 917                                 ctx->asoc->base.sk->sk_err = -error;
 918                                 return;
 919                         }
 920                         ctx->asoc->stats.octrlchunks++;
 921                         break;
 922
 923                 case SCTP_CID_ABORT:
 924                         if (sctp_test_T_bit(chunk))
 925                                 ctx->packet->vtag = ctx->asoc->c.my_vtag;
 926                         fallthrough;
 927
 928                 /* The following chunks are "response" chunks, i.e.
 929                  * they are generated in response to something we
 930                  * received.  If we are sending these, then we can
 931                  * send only 1 packet containing these chunks.
 932                  */
 933                 case SCTP_CID_HEARTBEAT_ACK:
 934                 case SCTP_CID_SHUTDOWN_ACK:
 935                 case SCTP_CID_COOKIE_ACK:
 936                 case SCTP_CID_COOKIE_ECHO:
 937                 case SCTP_CID_ERROR:
 938                 case SCTP_CID_ECN_CWR:
 939                 case SCTP_CID_ASCONF_ACK:
 940                         one_packet = 1;
 941                         fallthrough;
 942
 943                 case SCTP_CID_HEARTBEAT:
 944                         if (chunk->pmtu_probe) {
 945                                 error = sctp_packet_singleton(ctx->transport,
 946                                                               chunk, ctx->gfp);
 947                                 if (!error)
 948                                         ctx->asoc->stats.octrlchunks++;
 949                                 break;
 950                         }
 951                         fallthrough;
 952                 case SCTP_CID_SACK:
 953                 case SCTP_CID_SHUTDOWN:
 954                 case SCTP_CID_ECN_ECNE:
 955                 case SCTP_CID_ASCONF:
 956                 case SCTP_CID_FWD_TSN:
 957                 case SCTP_CID_I_FWD_TSN:
 958                 case SCTP_CID_RECONF:
 959                         status = sctp_packet_transmit_chunk(ctx->packet, chunk,
 960                                                             one_packet, ctx->gfp);
 961                         if (status != SCTP_XMIT_OK) {
 962                                 /* put the chunk back */
 963                                 list_add(&chunk->list, &ctx->q->control_chunk_list);
 964                                 break;
 965                         }
 966
 967                         ctx->asoc->stats.octrlchunks++;
 968                         /* PR-SCTP C5) If a FORWARD TSN is sent, the
 969                          * sender MUST assure that at least one T3-rtx
 970                          * timer is running.
 971                          */
 972                         if (chunk->chunk_hdr->type == SCTP_CID_FWD_TSN ||
 973                             chunk->chunk_hdr->type == SCTP_CID_I_FWD_TSN) {
 974                                 sctp_transport_reset_t3_rtx(ctx->transport);
 975                                 ctx->transport->last_time_sent = jiffies;
 976                         }
 977
 978                         if (chunk == ctx->asoc->strreset_chunk)
 979                                 sctp_transport_reset_reconf_timer(ctx->transport);
 980
 981                         break;
 982
 983                 default:
 984                         /* We built a chunk with an illegal type! */
 985                         BUG();
 986                 }
 987         }
 988 }
 989
 990 /* Returns false if new data shouldn't be sent */
 991 static bool sctp_outq_flush_rtx(struct sctp_flush_ctx *ctx,
 992                                 int rtx_timeout)
 993 {
 994         int error, start_timer = 0;
 995
 996         if (ctx->asoc->peer.retran_path->state == SCTP_UNCONFIRMED)
 997                 return false;
 998
 999         if (ctx->transport != ctx->asoc->peer.retran_path) {
1000                 /* Switch transports & prepare the packet.  */
1001                 ctx->transport = ctx->asoc->peer.retran_path;
1002                 ctx->packet = &ctx->transport->packet;
1003
1004                 if (list_empty(&ctx->transport->send_ready))
1005                         list_add_tail(&ctx->transport->send_ready,
1006                                       &ctx->transport_list);
1007
1008                 sctp_packet_config(ctx->packet, ctx->asoc->peer.i.init_tag,
1009                                    ctx->asoc->peer.ecn_capable);
1010         }
1011
1012         error = __sctp_outq_flush_rtx(ctx->q, ctx->packet, rtx_timeout,
1013                                       &start_timer, ctx->gfp);
1014         if (error < 0)
1015                 ctx->asoc->base.sk->sk_err = -error;
1016
1017         if (start_timer) {
1018                 sctp_transport_reset_t3_rtx(ctx->transport);
1019                 ctx->transport->last_time_sent = jiffies;
1020         }
1021
1022         /* This can happen on COOKIE-ECHO resend.  Only
1023          * one chunk can get bundled with a COOKIE-ECHO.
1024          */
1025         if (ctx->packet->has_cookie_echo)
1026                 return false;
1027
1028         /* Don't send new data if there is still data
1029          * waiting to retransmit.
1030          */
1031         if (!list_empty(&ctx->q->retransmit))
1032                 return false;
1033
1034         return true;
1035 }
1036
1037 static void sctp_outq_flush_data(struct sctp_flush_ctx *ctx,
1038                                  int rtx_timeout)
1039 {
1040         struct sctp_chunk *chunk;
1041         enum sctp_xmit status;
1042
1043         /* Is it OK to send data chunks?  */
1044         switch (ctx->asoc->state) {
1045         case SCTP_STATE_COOKIE_ECHOED:
1046                 /* Only allow bundling when this packet has a COOKIE-ECHO
1047                  * chunk.
1048                  */
1049                 if (!ctx->packet || !ctx->packet->has_cookie_echo)
1050                         return;
1051
1052                 fallthrough;
1053         case SCTP_STATE_ESTABLISHED:
1054         case SCTP_STATE_SHUTDOWN_PENDING:
1055         case SCTP_STATE_SHUTDOWN_RECEIVED:
1056                 break;
1057
1058         default:
1059                 /* Do nothing. */
1060                 return;
1061         }
1062
1063         /* RFC 2960 6.1  Transmission of DATA Chunks
1064          *
1065          * C) When the time comes for the sender to transmit,
1066          * before sending new DATA chunks, the sender MUST
1067          * first transmit any outstanding DATA chunks which
1068          * are marked for retransmission (limited by the
1069          * current cwnd).
1070          */
1071         if (!list_empty(&ctx->q->retransmit) &&
1072             !sctp_outq_flush_rtx(ctx, rtx_timeout))
1073                 return;
1074
1075         /* Apply Max.Burst limitation to the current transport in
1076          * case it will be used for new data.  We are going to
1077          * rest it before we return, but we want to apply the limit
1078          * to the currently queued data.
1079          */
1080         if (ctx->transport)
1081                 sctp_transport_burst_limited(ctx->transport);
1082
1083         /* Finally, transmit new packets.  */
1084         while ((chunk = sctp_outq_dequeue_data(ctx->q)) != NULL) {
1085                 __u32 sid = ntohs(chunk->subh.data_hdr->stream);
1086                 __u8 stream_state = SCTP_SO(&ctx->asoc->stream, sid)->state;
1087
1088                 /* Has this chunk expired? */
1089                 if (sctp_chunk_abandoned(chunk)) {
1090                         sctp_sched_dequeue_done(ctx->q, chunk);
1091                         sctp_chunk_fail(chunk, 0);
1092                         sctp_chunk_free(chunk);
1093                         continue;
1094                 }
1095
1096                 if (stream_state == SCTP_STREAM_CLOSED) {
1097                         sctp_outq_head_data(ctx->q, chunk);
1098                         break;
1099                 }
1100
1101                 sctp_outq_select_transport(ctx, chunk);
1102
1103                 pr_debug("%s: outq:%p, chunk:%p[%s], tx-tsn:0x%x skb->head:%p skb->users:%d\n",
1104                          __func__, ctx->q, chunk, chunk && chunk->chunk_hdr ?
1105                          sctp_cname(SCTP_ST_CHUNK(chunk->chunk_hdr->type)) :
1106                          "illegal chunk", ntohl(chunk->subh.data_hdr->tsn),
1107                          chunk->skb ? chunk->skb->head : NULL, chunk->skb ?
1108                          refcount_read(&chunk->skb->users) : -1);
1109
1110                 /* Add the chunk to the packet.  */
1111                 status = sctp_packet_transmit_chunk(ctx->packet, chunk, 0,
1112                                                     ctx->gfp);
1113                 if (status != SCTP_XMIT_OK) {
1114                         /* We could not append this chunk, so put
1115                          * the chunk back on the output queue.
1116                          */
1117                         pr_debug("%s: could not transmit tsn:0x%x, status:%d\n",
1118                                  __func__, ntohl(chunk->subh.data_hdr->tsn),
1119                                  status);
1120
1121                         sctp_outq_head_data(ctx->q, chunk);
1122                         break;
1123                 }
1124
1125                 /* The sender is in the SHUTDOWN-PENDING state,
1126                  * The sender MAY set the I-bit in the DATA
1127                  * chunk header.
1128                  */
1129                 if (ctx->asoc->state == SCTP_STATE_SHUTDOWN_PENDING)
1130                         chunk->chunk_hdr->flags |= SCTP_DATA_SACK_IMM;
1131                 if (chunk->chunk_hdr->flags & SCTP_DATA_UNORDERED)
1132                         ctx->asoc->stats.ouodchunks++;
1133                 else
1134                         ctx->asoc->stats.oodchunks++;
1135
1136                 /* Only now it's safe to consider this
1137                  * chunk as sent, sched-wise.
1138                  */
1139                 sctp_sched_dequeue_done(ctx->q, chunk);
1140
1141                 list_add_tail(&chunk->transmitted_list,
1142                               &ctx->transport->transmitted);
1143
1144                 sctp_transport_reset_t3_rtx(ctx->transport);
1145                 ctx->transport->last_time_sent = jiffies;
1146
1147                 /* Only let one DATA chunk get bundled with a
1148                  * COOKIE-ECHO chunk.
1149                  */
1150                 if (ctx->packet->has_cookie_echo)
1151                         break;
1152         }
1153 }
1154
1155 static void sctp_outq_flush_transports(struct sctp_flush_ctx *ctx)
1156 {
1157         struct sock *sk = ctx->asoc->base.sk;
1158         struct list_head *ltransport;
1159         struct sctp_packet *packet;
1160         struct sctp_transport *t;
1161         int error = 0;
1162
1163         while ((ltransport = sctp_list_dequeue(&ctx->transport_list)) != NULL) {
1164                 t = list_entry(ltransport, struct sctp_transport, send_ready);
1165                 packet = &t->packet;
1166                 if (!sctp_packet_empty(packet)) {
1167                         rcu_read_lock();
1168                         if (t->dst && __sk_dst_get(sk) != t->dst) {
1169                                 dst_hold(t->dst);
1170                                 sk_setup_caps(sk, t->dst);
1171                         }
1172                         rcu_read_unlock();
1173                         error = sctp_packet_transmit(packet, ctx->gfp);
1174                         if (error < 0)
1175                                 ctx->q->asoc->base.sk->sk_err = -error;
1176                 }
1177
1178                 /* Clear the burst limited state, if any */
1179                 sctp_transport_burst_reset(t);
1180         }
1181 }
1182
1183 /* Try to flush an outqueue.
1184  *
1185  * Description: Send everything in q which we legally can, subject to
1186  * congestion limitations.
1187  * * Note: This function can be called from multiple contexts so appropriate
1188  * locking concerns must be made.  Today we use the sock lock to protect
1189  * this function.
1190  */
1191
1192 static void sctp_outq_flush(struct sctp_outq *q, int rtx_timeout, gfp_t gfp)
1193 {
1194         struct sctp_flush_ctx ctx = {
1195                 .q = q,
1196                 .transport = NULL,
1197                 .transport_list = LIST_HEAD_INIT(ctx.transport_list),
1198                 .asoc = q->asoc,
1199                 .packet = NULL,
1200                 .gfp = gfp,
1201         };
1202
1203         /* 6.10 Bundling
1204          *   ...
1205          *   When bundling control chunks with DATA chunks, an
1206          *   endpoint MUST place control chunks first in the outbound
1207          *   SCTP packet.  The transmitter MUST transmit DATA chunks
1208          *   within a SCTP packet in increasing order of TSN.
1209          *   ...
1210          */
1211
1212         sctp_outq_flush_ctrl(&ctx);
1213
1214         if (q->asoc->src_out_of_asoc_ok)
1215                 goto sctp_flush_out;
1216
1217         sctp_outq_flush_data(&ctx, rtx_timeout);
1218
1219 sctp_flush_out:
1220
1221         sctp_outq_flush_transports(&ctx);
1222 }
1223
1224 /* Update unack_data based on the incoming SACK chunk */
1225 static void sctp_sack_update_unack_data(struct sctp_association *assoc,
1226                                         struct sctp_sackhdr *sack)
1227 {
1228         union sctp_sack_variable *frags;
1229         __u16 unack_data;
1230         int i;
1231
1232         unack_data = assoc->next_tsn - assoc->ctsn_ack_point - 1;
1233
1234         frags = (union sctp_sack_variable *)(sack + 1);
1235         for (i = 0; i < ntohs(sack->num_gap_ack_blocks); i++) {
1236                 unack_data -= ((ntohs(frags[i].gab.end) -
1237                                 ntohs(frags[i].gab.start) + 1));
1238         }
1239
1240         assoc->unack_data = unack_data;
1241 }
1242
1243 /* This is where we REALLY process a SACK.
1244  *
1245  * Process the SACK against the outqueue.  Mostly, this just frees
1246  * things off the transmitted queue.
1247  */
1248 int sctp_outq_sack(struct sctp_outq *q, struct sctp_chunk *chunk)
1249 {
1250         struct sctp_association *asoc = q->asoc;
1251         struct sctp_sackhdr *sack = chunk->subh.sack_hdr;
1252         struct sctp_transport *transport;
1253         struct sctp_chunk *tchunk = NULL;
1254         struct list_head *lchunk, *transport_list, *temp;
1255         __u32 sack_ctsn, ctsn, tsn;
1256         __u32 highest_tsn, highest_new_tsn;
1257         __u32 sack_a_rwnd;
1258         unsigned int outstanding;
1259         struct sctp_transport *primary = asoc->peer.primary_path;
1260         int count_of_newacks = 0;
1261         int gap_ack_blocks;
1262         u8 accum_moved = 0;
1263
1264         /* Grab the association's destination address list. */
1265         transport_list = &asoc->peer.transport_addr_list;
1266
1267         /* SCTP path tracepoint for congestion control debugging. */
1268         if (trace_sctp_probe_path_enabled()) {
1269                 list_for_each_entry(transport, transport_list, transports)
1270                         trace_sctp_probe_path(transport, asoc);
1271         }
1272
1273         sack_ctsn = ntohl(sack->cum_tsn_ack);
1274         gap_ack_blocks = ntohs(sack->num_gap_ack_blocks);
1275         asoc->stats.gapcnt += gap_ack_blocks;
1276         /*
1277          * SFR-CACC algorithm:
1278          * On receipt of a SACK the sender SHOULD execute the
1279          * following statements.
1280          *
1281          * 1) If the cumulative ack in the SACK passes next tsn_at_change
1282          * on the current primary, the CHANGEOVER_ACTIVE flag SHOULD be
1283          * cleared. The CYCLING_CHANGEOVER flag SHOULD also be cleared for
1284          * all destinations.
1285          * 2) If the SACK contains gap acks and the flag CHANGEOVER_ACTIVE
1286          * is set the receiver of the SACK MUST take the following actions:
1287          *
1288          * A) Initialize the cacc_saw_newack to 0 for all destination
1289          * addresses.
1290          *
1291          * Only bother if changeover_active is set. Otherwise, this is
1292          * totally suboptimal to do on every SACK.
1293          */
1294         if (primary->cacc.changeover_active) {
1295                 u8 clear_cycling = 0;
1296
1297                 if (TSN_lte(primary->cacc.next_tsn_at_change, sack_ctsn)) {
1298                         primary->cacc.changeover_active = 0;
1299                         clear_cycling = 1;
1300                 }
1301
1302                 if (clear_cycling || gap_ack_blocks) {
1303                         list_for_each_entry(transport, transport_list,
1304                                         transports) {
1305                                 if (clear_cycling)
1306                                         transport->cacc.cycling_changeover = 0;
1307                                 if (gap_ack_blocks)
1308                                         transport->cacc.cacc_saw_newack = 0;
1309                         }
1310                 }
1311         }
1312
1313         /* Get the highest TSN in the sack. */
1314         highest_tsn = sack_ctsn;
1315         if (gap_ack_blocks) {
1316                 union sctp_sack_variable *frags =
1317                         (union sctp_sack_variable *)(sack + 1);
1318
1319                 highest_tsn += ntohs(frags[gap_ack_blocks - 1].gab.end);
1320         }
1321
1322         if (TSN_lt(asoc->highest_sacked, highest_tsn))
1323                 asoc->highest_sacked = highest_tsn;
1324
1325         highest_new_tsn = sack_ctsn;
1326
1327         /* Run through the retransmit queue.  Credit bytes received
1328          * and free those chunks that we can.
1329          */
1330         sctp_check_transmitted(q, &q->retransmit, NULL, NULL, sack, &highest_new_tsn);
1331
1332         /* Run through the transmitted queue.
1333          * Credit bytes received and free those chunks which we can.
1334          *
1335          * This is a MASSIVE candidate for optimization.
1336          */
1337         list_for_each_entry(transport, transport_list, transports) {
1338                 sctp_check_transmitted(q, &transport->transmitted,
1339                                        transport, &chunk->source, sack,
1340                                        &highest_new_tsn);
1341                 /*
1342                  * SFR-CACC algorithm:
1343                  * C) Let count_of_newacks be the number of
1344                  * destinations for which cacc_saw_newack is set.
1345                  */
1346                 if (transport->cacc.cacc_saw_newack)
1347                         count_of_newacks++;
1348         }
1349
1350         /* Move the Cumulative TSN Ack Point if appropriate.  */
1351         if (TSN_lt(asoc->ctsn_ack_point, sack_ctsn)) {
1352                 asoc->ctsn_ack_point = sack_ctsn;
1353                 accum_moved = 1;
1354         }
1355
1356         if (gap_ack_blocks) {
1357
1358                 if (asoc->fast_recovery && accum_moved)
1359                         highest_new_tsn = highest_tsn;
1360
1361                 list_for_each_entry(transport, transport_list, transports)
1362                         sctp_mark_missing(q, &transport->transmitted, transport,
1363                                           highest_new_tsn, count_of_newacks);
1364         }
1365
1366         /* Update unack_data field in the assoc. */
1367         sctp_sack_update_unack_data(asoc, sack);
1368
1369         ctsn = asoc->ctsn_ack_point;
1370
1371         /* Throw away stuff rotting on the sack queue.  */
1372         list_for_each_safe(lchunk, temp, &q->sacked) {
1373                 tchunk = list_entry(lchunk, struct sctp_chunk,
1374                                     transmitted_list);
1375                 tsn = ntohl(tchunk->subh.data_hdr->tsn);
1376                 if (TSN_lte(tsn, ctsn)) {
1377                         list_del_init(&tchunk->transmitted_list);
1378                         if (asoc->peer.prsctp_capable &&
1379                             SCTP_PR_PRIO_ENABLED(chunk->sinfo.sinfo_flags))
1380                                 asoc->sent_cnt_removable--;
1381                         sctp_chunk_free(tchunk);
1382                 }
1383         }
1384
1385         /* ii) Set rwnd equal to the newly received a_rwnd minus the
1386          *     number of bytes still outstanding after processing the
1387          *     Cumulative TSN Ack and the Gap Ack Blocks.
1388          */
1389
1390         sack_a_rwnd = ntohl(sack->a_rwnd);
1391         asoc->peer.zero_window_announced = !sack_a_rwnd;
1392         outstanding = q->outstanding_bytes;
1393
1394         if (outstanding < sack_a_rwnd)
1395                 sack_a_rwnd -= outstanding;
1396         else
1397                 sack_a_rwnd = 0;
1398
1399         asoc->peer.rwnd = sack_a_rwnd;
1400
1401         asoc->stream.si->generate_ftsn(q, sack_ctsn);
1402
1403         pr_debug("%s: sack cumulative tsn ack:0x%x\n", __func__, sack_ctsn);
1404         pr_debug("%s: cumulative tsn ack of assoc:%p is 0x%x, "
1405                  "advertised peer ack point:0x%x\n", __func__, asoc, ctsn,
1406                  asoc->adv_peer_ack_point);
1407
1408         return sctp_outq_is_empty(q);
1409 }
1410
1411 /* Is the outqueue empty?
1412  * The queue is empty when we have not pending data, no in-flight data
1413  * and nothing pending retransmissions.
1414  */
1415 int sctp_outq_is_empty(const struct sctp_outq *q)
1416 {
1417         return q->out_qlen == 0 && q->outstanding_bytes == 0 &&
1418                list_empty(&q->retransmit);
1419 }
1420
1421 /********************************************************************
1422  * 2nd Level Abstractions
1423  ********************************************************************/
1424
1425 /* Go through a transport's transmitted list or the association's retransmit
1426  * list and move chunks that are acked by the Cumulative TSN Ack to q->sacked.
1427  * The retransmit list will not have an associated transport.
1428  *
1429  * I added coherent debug information output.   --xguo
1430  *
1431  * Instead of printing 'sacked' or 'kept' for each TSN on the
1432  * transmitted_queue, we print a range: SACKED: TSN1-TSN2, TSN3, TSN4-TSN5.
1433  * KEPT TSN6-TSN7, etc.
1434  */
1435 static void sctp_check_transmitted(struct sctp_outq *q,
1436                                    struct list_head *transmitted_queue,
1437                                    struct sctp_transport *transport,
1438                                    union sctp_addr *saddr,
1439                                    struct sctp_sackhdr *sack,
1440                                    __u32 *highest_new_tsn_in_sack)
1441 {
1442         struct list_head *lchunk;
1443         struct sctp_chunk *tchunk;
1444         struct list_head tlist;
1445         __u32 tsn;
1446         __u32 sack_ctsn;
1447         __u32 rtt;
1448         __u8 restart_timer = 0;
1449         int bytes_acked = 0;
1450         int migrate_bytes = 0;
1451         bool forward_progress = false;
1452
1453         sack_ctsn = ntohl(sack->cum_tsn_ack);
1454
1455         INIT_LIST_HEAD(&tlist);
1456
1457         /* The while loop will skip empty transmitted queues. */
1458         while (NULL != (lchunk = sctp_list_dequeue(transmitted_queue))) {
1459                 tchunk = list_entry(lchunk, struct sctp_chunk,
1460                                     transmitted_list);
1461
1462                 if (sctp_chunk_abandoned(tchunk)) {
1463                         /* Move the chunk to abandoned list. */
1464                         sctp_insert_list(&q->abandoned, lchunk);
1465
1466                         /* If this chunk has not been acked, stop
1467                          * considering it as 'outstanding'.
1468                          */
1469                         if (transmitted_queue != &q->retransmit &&
1470                             !tchunk->tsn_gap_acked) {
1471                                 if (tchunk->transport)
1472                                         tchunk->transport->flight_size -=
1473                                                         sctp_data_size(tchunk);
1474                                 q->outstanding_bytes -= sctp_data_size(tchunk);
1475                         }
1476                         continue;
1477                 }
1478
1479                 tsn = ntohl(tchunk->subh.data_hdr->tsn);
1480                 if (sctp_acked(sack, tsn)) {
1481                         /* If this queue is the retransmit queue, the
1482                          * retransmit timer has already reclaimed
1483                          * the outstanding bytes for this chunk, so only
1484                          * count bytes associated with a transport.
1485                          */
1486                         if (transport && !tchunk->tsn_gap_acked) {
1487                                 /* If this chunk is being used for RTT
1488                                  * measurement, calculate the RTT and update
1489                                  * the RTO using this value.
1490                                  *
1491                                  * 6.3.1 C5) Karn's algorithm: RTT measurements
1492                                  * MUST NOT be made using packets that were
1493                                  * retransmitted (and thus for which it is
1494                                  * ambiguous whether the reply was for the
1495                                  * first instance of the packet or a later
1496                                  * instance).
1497                                  */
1498                                 if (!sctp_chunk_retransmitted(tchunk) &&
1499                                     tchunk->rtt_in_progress) {
1500                                         tchunk->rtt_in_progress = 0;
1501                                         rtt = jiffies - tchunk->sent_at;
1502                                         sctp_transport_update_rto(transport,
1503                                                                   rtt);
1504                                 }
1505
1506                                 if (TSN_lte(tsn, sack_ctsn)) {
1507                                         /*
1508                                          * SFR-CACC algorithm:
1509                                          * 2) If the SACK contains gap acks
1510                                          * and the flag CHANGEOVER_ACTIVE is
1511                                          * set the receiver of the SACK MUST
1512                                          * take the following action:
1513                                          *
1514                                          * B) For each TSN t being acked that
1515                                          * has not been acked in any SACK so
1516                                          * far, set cacc_saw_newack to 1 for
1517                                          * the destination that the TSN was
1518                                          * sent to.
1519                                          */
1520                                         if (sack->num_gap_ack_blocks &&
1521                                             q->asoc->peer.primary_path->cacc.
1522                                             changeover_active)
1523                                                 transport->cacc.cacc_saw_newack
1524                                                         = 1;
1525                                 }
1526                         }
1527
1528                         /* If the chunk hasn't been marked as ACKED,
1529                          * mark it and account bytes_acked if the
1530                          * chunk had a valid transport (it will not
1531                          * have a transport if ASCONF had deleted it
1532                          * while DATA was outstanding).
1533                          */
1534                         if (!tchunk->tsn_gap_acked) {
1535                                 tchunk->tsn_gap_acked = 1;
1536                                 if (TSN_lt(*highest_new_tsn_in_sack, tsn))
1537                                         *highest_new_tsn_in_sack = tsn;
1538                                 bytes_acked += sctp_data_size(tchunk);
1539                                 if (!tchunk->transport)
1540                                         migrate_bytes += sctp_data_size(tchunk);
1541                                 forward_progress = true;
1542                         }
1543
1544                         if (TSN_lte(tsn, sack_ctsn)) {
1545                                 /* RFC 2960  6.3.2 Retransmission Timer Rules
1546                                  *
1547                                  * R3) Whenever a SACK is received
1548                                  * that acknowledges the DATA chunk
1549                                  * with the earliest outstanding TSN
1550                                  * for that address, restart T3-rtx
1551                                  * timer for that address with its
1552                                  * current RTO.
1553                                  */
1554                                 restart_timer = 1;
1555                                 forward_progress = true;
1556
1557                                 list_add_tail(&tchunk->transmitted_list,
1558                                               &q->sacked);
1559                         } else {
1560                                 /* RFC2960 7.2.4, sctpimpguide-05 2.8.2
1561                                  * M2) Each time a SACK arrives reporting
1562                                  * 'Stray DATA chunk(s)' record the highest TSN
1563                                  * reported as newly acknowledged, call this
1564                                  * value 'HighestTSNinSack'. A newly
1565                                  * acknowledged DATA chunk is one not
1566                                  * previously acknowledged in a SACK.
1567                                  *
1568                                  * When the SCTP sender of data receives a SACK
1569                                  * chunk that acknowledges, for the first time,
1570                                  * the receipt of a DATA chunk, all the still
1571                                  * unacknowledged DATA chunks whose TSN is
1572                                  * older than that newly acknowledged DATA
1573                                  * chunk, are qualified as 'Stray DATA chunks'.
1574                                  */
1575                                 list_add_tail(lchunk, &tlist);
1576                         }
1577                 } else {
1578                         if (tchunk->tsn_gap_acked) {
1579                                 pr_debug("%s: receiver reneged on data TSN:0x%x\n",
1580                                          __func__, tsn);
1581
1582                                 tchunk->tsn_gap_acked = 0;
1583
1584                                 if (tchunk->transport)
1585                                         bytes_acked -= sctp_data_size(tchunk);
1586
1587                                 /* RFC 2960 6.3.2 Retransmission Timer Rules
1588                                  *
1589                                  * R4) Whenever a SACK is received missing a
1590                                  * TSN that was previously acknowledged via a
1591                                  * Gap Ack Block, start T3-rtx for the
1592                                  * destination address to which the DATA
1593                                  * chunk was originally
1594                                  * transmitted if it is not already running.
1595                                  */
1596                                 restart_timer = 1;
1597                         }
1598
1599                         list_add_tail(lchunk, &tlist);
1600                 }
1601         }
1602
1603         if (transport) {
1604                 if (bytes_acked) {
1605                         struct sctp_association *asoc = transport->asoc;
1606
1607                         /* We may have counted DATA that was migrated
1608                          * to this transport due to DEL-IP operation.
1609                          * Subtract those bytes, since the were never
1610                          * send on this transport and shouldn't be
1611                          * credited to this transport.
1612                          */
1613                         bytes_acked -= migrate_bytes;
1614
1615                         /* 8.2. When an outstanding TSN is acknowledged,
1616                          * the endpoint shall clear the error counter of
1617                          * the destination transport address to which the
1618                          * DATA chunk was last sent.
1619                          * The association's overall error counter is
1620                          * also cleared.
1621                          */
1622                         transport->error_count = 0;
1623                         transport->asoc->overall_error_count = 0;
1624                         forward_progress = true;
1625
1626                         /*
1627                          * While in SHUTDOWN PENDING, we may have started
1628                          * the T5 shutdown guard timer after reaching the
1629                          * retransmission limit. Stop that timer as soon
1630                          * as the receiver acknowledged any data.
1631                          */
1632                         if (asoc->state == SCTP_STATE_SHUTDOWN_PENDING &&
1633                             del_timer(&asoc->timers
1634                                 [SCTP_EVENT_TIMEOUT_T5_SHUTDOWN_GUARD]))
1635                                         sctp_association_put(asoc);
1636
1637                         /* Mark the destination transport address as
1638                          * active if it is not so marked.
1639                          */
1640                         if ((transport->state == SCTP_INACTIVE ||
1641                              transport->state == SCTP_UNCONFIRMED) &&
1642                             sctp_cmp_addr_exact(&transport->ipaddr, saddr)) {
1643                                 sctp_assoc_control_transport(
1644                                         transport->asoc,
1645                                         transport,
1646                                         SCTP_TRANSPORT_UP,
1647                                         SCTP_RECEIVED_SACK);
1648                         }
1649
1650                         sctp_transport_raise_cwnd(transport, sack_ctsn,
1651                                                   bytes_acked);
1652
1653                         transport->flight_size -= bytes_acked;
1654                         if (transport->flight_size == 0)
1655                                 transport->partial_bytes_acked = 0;
1656                         q->outstanding_bytes -= bytes_acked + migrate_bytes;
1657                 } else {
1658                         /* RFC 2960 6.1, sctpimpguide-06 2.15.2
1659                          * When a sender is doing zero window probing, it
1660                          * should not timeout the association if it continues
1661                          * to receive new packets from the receiver. The
1662                          * reason is that the receiver MAY keep its window
1663                          * closed for an indefinite time.
1664                          * A sender is doing zero window probing when the
1665                          * receiver's advertised window is zero, and there is
1666                          * only one data chunk in flight to the receiver.
1667                          *
1668                          * Allow the association to timeout while in SHUTDOWN
1669                          * PENDING or SHUTDOWN RECEIVED in case the receiver
1670                          * stays in zero window mode forever.
1671                          */
1672                         if (!q->asoc->peer.rwnd &&
1673                             !list_empty(&tlist) &&
1674                             (sack_ctsn+2 == q->asoc->next_tsn) &&
1675                             q->asoc->state < SCTP_STATE_SHUTDOWN_PENDING) {
1676                                 pr_debug("%s: sack received for zero window "
1677                                          "probe:%u\n", __func__, sack_ctsn);
1678
1679                                 q->asoc->overall_error_count = 0;
1680                                 transport->error_count = 0;
1681                         }
1682                 }
1683
1684                 /* RFC 2960 6.3.2 Retransmission Timer Rules
1685                  *
1686                  * R2) Whenever all outstanding data sent to an address have
1687                  * been acknowledged, turn off the T3-rtx timer of that
1688                  * address.
1689                  */
1690                 if (!transport->flight_size) {
1691                         if (del_timer(&transport->T3_rtx_timer))
1692                                 sctp_transport_put(transport);
1693                 } else if (restart_timer) {
1694                         if (!mod_timer(&transport->T3_rtx_timer,
1695                                        jiffies + transport->rto))
1696                                 sctp_transport_hold(transport);
1697                 }
1698
1699                 if (forward_progress) {
1700                         if (transport->dst)
1701                                 sctp_transport_dst_confirm(transport);
1702                 }
1703         }
1704
1705         list_splice(&tlist, transmitted_queue);
1706 }
1707
1708 /* Mark chunks as missing and consequently may get retransmitted. */
1709 static void sctp_mark_missing(struct sctp_outq *q,
1710                               struct list_head *transmitted_queue,
1711                               struct sctp_transport *transport,
1712                               __u32 highest_new_tsn_in_sack,
1713                               int count_of_newacks)
1714 {
1715         struct sctp_chunk *chunk;
1716         __u32 tsn;
1717         char do_fast_retransmit = 0;
1718         struct sctp_association *asoc = q->asoc;
1719         struct sctp_transport *primary = asoc->peer.primary_path;
1720
1721         list_for_each_entry(chunk, transmitted_queue, transmitted_list) {
1722
1723                 tsn = ntohl(chunk->subh.data_hdr->tsn);
1724
1725                 /* RFC 2960 7.2.4, sctpimpguide-05 2.8.2 M3) Examine all
1726                  * 'Unacknowledged TSN's', if the TSN number of an
1727                  * 'Unacknowledged TSN' is smaller than the 'HighestTSNinSack'
1728                  * value, increment the 'TSN.Missing.Report' count on that
1729                  * chunk if it has NOT been fast retransmitted or marked for
1730                  * fast retransmit already.
1731                  */
1732                 if (chunk->fast_retransmit == SCTP_CAN_FRTX &&
1733                     !chunk->tsn_gap_acked &&
1734                     TSN_lt(tsn, highest_new_tsn_in_sack)) {
1735
1736                         /* SFR-CACC may require us to skip marking
1737                          * this chunk as missing.
1738                          */
1739                         if (!transport || !sctp_cacc_skip(primary,
1740                                                 chunk->transport,
1741                                                 count_of_newacks, tsn)) {
1742                                 chunk->tsn_missing_report++;
1743
1744                                 pr_debug("%s: tsn:0x%x missing counter:%d\n",
1745                                          __func__, tsn, chunk->tsn_missing_report);
1746                         }
1747                 }
1748                 /*
1749                  * M4) If any DATA chunk is found to have a
1750                  * 'TSN.Missing.Report'
1751                  * value larger than or equal to 3, mark that chunk for
1752                  * retransmission and start the fast retransmit procedure.
1753                  */
1754
1755                 if (chunk->tsn_missing_report >= 3) {
1756                         chunk->fast_retransmit = SCTP_NEED_FRTX;
1757                         do_fast_retransmit = 1;
1758                 }
1759         }
1760
1761         if (transport) {
1762                 if (do_fast_retransmit)
1763                         sctp_retransmit(q, transport, SCTP_RTXR_FAST_RTX);
1764
1765                 pr_debug("%s: transport:%p, cwnd:%d, ssthresh:%d, "
1766                          "flight_size:%d, pba:%d\n",  __func__, transport,
1767                          transport->cwnd, transport->ssthresh,
1768                          transport->flight_size, transport->partial_bytes_acked);
1769         }
1770 }
1771
1772 /* Is the given TSN acked by this packet?  */
1773 static int sctp_acked(struct sctp_sackhdr *sack, __u32 tsn)
1774 {
1775         __u32 ctsn = ntohl(sack->cum_tsn_ack);
1776         union sctp_sack_variable *frags;
1777         __u16 tsn_offset, blocks;
1778         int i;
1779
1780         if (TSN_lte(tsn, ctsn))
1781                 goto pass;
1782
1783         /* 3.3.4 Selective Acknowledgment (SACK) (3):
1784          *
1785          * Gap Ack Blocks:
1786          *  These fields contain the Gap Ack Blocks. They are repeated
1787          *  for each Gap Ack Block up to the number of Gap Ack Blocks
1788          *  defined in the Number of Gap Ack Blocks field. All DATA
1789          *  chunks with TSNs greater than or equal to (Cumulative TSN
1790          *  Ack + Gap Ack Block Start) and less than or equal to
1791          *  (Cumulative TSN Ack + Gap Ack Block End) of each Gap Ack
1792          *  Block are assumed to have been received correctly.
1793          */
1794
1795         frags = (union sctp_sack_variable *)(sack + 1);
1796         blocks = ntohs(sack->num_gap_ack_blocks);
1797         tsn_offset = tsn - ctsn;
1798         for (i = 0; i < blocks; ++i) {
1799                 if (tsn_offset >= ntohs(frags[i].gab.start) &&
1800                     tsn_offset <= ntohs(frags[i].gab.end))
1801                         goto pass;
1802         }
1803
1804         return 0;
1805 pass:
1806         return 1;
1807 }
1808
1809 static inline int sctp_get_skip_pos(struct sctp_fwdtsn_skip *skiplist,
1810                                     int nskips, __be16 stream)
1811 {
1812         int i;
1813
1814         for (i = 0; i < nskips; i++) {
1815                 if (skiplist[i].stream == stream)
1816                         return i;
1817         }
1818         return i;
1819 }
1820
1821 /* Create and add a fwdtsn chunk to the outq's control queue if needed. */
1822 void sctp_generate_fwdtsn(struct sctp_outq *q, __u32 ctsn)
1823 {
1824         struct sctp_association *asoc = q->asoc;
1825         struct sctp_chunk *ftsn_chunk = NULL;
1826         struct sctp_fwdtsn_skip ftsn_skip_arr[10];
1827         int nskips = 0;
1828         int skip_pos = 0;
1829         __u32 tsn;
1830         struct sctp_chunk *chunk;
1831         struct list_head *lchunk, *temp;
1832
1833         if (!asoc->peer.prsctp_capable)
1834                 return;
1835
1836         /* PR-SCTP C1) Let SackCumAck be the Cumulative TSN ACK carried in the
1837          * received SACK.
1838          *
1839          * If (Advanced.Peer.Ack.Point < SackCumAck), then update
1840          * Advanced.Peer.Ack.Point to be equal to SackCumAck.
1841          */
1842         if (TSN_lt(asoc->adv_peer_ack_point, ctsn))
1843                 asoc->adv_peer_ack_point = ctsn;
1844
1845         /* PR-SCTP C2) Try to further advance the "Advanced.Peer.Ack.Point"
1846          * locally, that is, to move "Advanced.Peer.Ack.Point" up as long as
1847          * the chunk next in the out-queue space is marked as "abandoned" as
1848          * shown in the following example:
1849          *
1850          * Assuming that a SACK arrived with the Cumulative TSN ACK 102
1851          * and the Advanced.Peer.Ack.Point is updated to this value:
1852          *
1853          *   out-queue at the end of  ==>   out-queue after Adv.Ack.Point
1854          *   normal SACK processing           local advancement
1855          *                ...                           ...
1856          *   Adv.Ack.Pt-> 102 acked                     102 acked
1857          *                103 abandoned                 103 abandoned
1858          *                104 abandoned     Adv.Ack.P-> 104 abandoned
1859          *                105                           105
1860          *                106 acked                     106 acked
1861          *                ...                           ...
1862          *
1863          * In this example, the data sender successfully advanced the
1864          * "Advanced.Peer.Ack.Point" from 102 to 104 locally.
1865          */
1866         list_for_each_safe(lchunk, temp, &q->abandoned) {
1867                 chunk = list_entry(lchunk, struct sctp_chunk,
1868                                         transmitted_list);
1869                 tsn = ntohl(chunk->subh.data_hdr->tsn);
1870
1871                 /* Remove any chunks in the abandoned queue that are acked by
1872                  * the ctsn.
1873                  */
1874                 if (TSN_lte(tsn, ctsn)) {
1875                         list_del_init(lchunk);
1876                         sctp_chunk_free(chunk);
1877                 } else {
1878                         if (TSN_lte(tsn, asoc->adv_peer_ack_point+1)) {
1879                                 asoc->adv_peer_ack_point = tsn;
1880                                 if (chunk->chunk_hdr->flags &
1881                                          SCTP_DATA_UNORDERED)
1882                                         continue;
1883                                 skip_pos = sctp_get_skip_pos(&ftsn_skip_arr[0],
1884                                                 nskips,
1885                                                 chunk->subh.data_hdr->stream);
1886                                 ftsn_skip_arr[skip_pos].stream =
1887                                         chunk->subh.data_hdr->stream;
1888                                 ftsn_skip_arr[skip_pos].ssn =
1889                                          chunk->subh.data_hdr->ssn;
1890                                 if (skip_pos == nskips)
1891                                         nskips++;
1892                                 if (nskips == 10)
1893                                         break;
1894                         } else
1895                                 break;
1896                 }
1897         }
1898
1899         /* PR-SCTP C3) If, after step C1 and C2, the "Advanced.Peer.Ack.Point"
1900          * is greater than the Cumulative TSN ACK carried in the received
1901          * SACK, the data sender MUST send the data receiver a FORWARD TSN
1902          * chunk containing the latest value of the
1903          * "Advanced.Peer.Ack.Point".
1904          *
1905          * C4) For each "abandoned" TSN the sender of the FORWARD TSN SHOULD
1906          * list each stream and sequence number in the forwarded TSN. This
1907          * information will enable the receiver to easily find any
1908          * stranded TSN's waiting on stream reorder queues. Each stream
1909          * SHOULD only be reported once; this means that if multiple
1910          * abandoned messages occur in the same stream then only the
1911          * highest abandoned stream sequence number is reported. If the
1912          * total size of the FORWARD TSN does NOT fit in a single MTU then
1913          * the sender of the FORWARD TSN SHOULD lower the
1914          * Advanced.Peer.Ack.Point to the last TSN that will fit in a
1915          * single MTU.
1916          */
1917         if (asoc->adv_peer_ack_point > ctsn)
1918                 ftsn_chunk = sctp_make_fwdtsn(asoc, asoc->adv_peer_ack_point,
1919                                               nskips, &ftsn_skip_arr[0]);
1920
1921         if (ftsn_chunk) {
1922                 list_add_tail(&ftsn_chunk->list, &q->control_chunk_list);
1923                 SCTP_INC_STATS(asoc->base.net, SCTP_MIB_OUTCTRLCHUNKS);
1924         }
1925 }