linux/net/sctp/outqueue.c
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   1/* SCTP kernel implementation
   2 * (C) Copyright IBM Corp. 2001, 2004
   3 * Copyright (c) 1999-2000 Cisco, Inc.
   4 * Copyright (c) 1999-2001 Motorola, Inc.
   5 * Copyright (c) 2001-2003 Intel Corp.
   6 *
   7 * This file is part of the SCTP kernel implementation
   8 *
   9 * These functions implement the sctp_outq class.   The outqueue handles
  10 * bundling and queueing of outgoing SCTP chunks.
  11 *
  12 * This SCTP implementation is free software;
  13 * you can redistribute it and/or modify it under the terms of
  14 * the GNU General Public License as published by
  15 * the Free Software Foundation; either version 2, or (at your option)
  16 * any later version.
  17 *
  18 * This SCTP implementation is distributed in the hope that it
  19 * will be useful, but WITHOUT ANY WARRANTY; without even the implied
  20 *                 ************************
  21 * warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
  22 * See the GNU General Public License for more details.
  23 *
  24 * You should have received a copy of the GNU General Public License
  25 * along with GNU CC; see the file COPYING.  If not, write to
  26 * the Free Software Foundation, 59 Temple Place - Suite 330,
  27 * Boston, MA 02111-1307, USA.
  28 *
  29 * Please send any bug reports or fixes you make to the
  30 * email address(es):
  31 *    lksctp developers <lksctp-developers@lists.sourceforge.net>
  32 *
  33 * Or submit a bug report through the following website:
  34 *    http://www.sf.net/projects/lksctp
  35 *
  36 * Written or modified by:
  37 *    La Monte H.P. Yarroll <piggy@acm.org>
  38 *    Karl Knutson          <karl@athena.chicago.il.us>
  39 *    Perry Melange         <pmelange@null.cc.uic.edu>
  40 *    Xingang Guo           <xingang.guo@intel.com>
  41 *    Hui Huang             <hui.huang@nokia.com>
  42 *    Sridhar Samudrala     <sri@us.ibm.com>
  43 *    Jon Grimm             <jgrimm@us.ibm.com>
  44 *
  45 * Any bugs reported given to us we will try to fix... any fixes shared will
  46 * be incorporated into the next SCTP release.
  47 */
  48
  49#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  50
  51#include <linux/types.h>
  52#include <linux/list.h>   /* For struct list_head */
  53#include <linux/socket.h>
  54#include <linux/ip.h>
  55#include <linux/slab.h>
  56#include <net/sock.h>     /* For skb_set_owner_w */
  57
  58#include <net/sctp/sctp.h>
  59#include <net/sctp/sm.h>
  60
  61/* Declare internal functions here.  */
  62static int sctp_acked(struct sctp_sackhdr *sack, __u32 tsn);
  63static void sctp_check_transmitted(struct sctp_outq *q,
  64                                   struct list_head *transmitted_queue,
  65                                   struct sctp_transport *transport,
  66                                   struct sctp_sackhdr *sack,
  67                                   __u32 *highest_new_tsn);
  68
  69static void sctp_mark_missing(struct sctp_outq *q,
  70                              struct list_head *transmitted_queue,
  71                              struct sctp_transport *transport,
  72                              __u32 highest_new_tsn,
  73                              int count_of_newacks);
  74
  75static void sctp_generate_fwdtsn(struct sctp_outq *q, __u32 sack_ctsn);
  76
  77static int sctp_outq_flush(struct sctp_outq *q, int rtx_timeout);
  78
  79/* Add data to the front of the queue. */
  80static inline void sctp_outq_head_data(struct sctp_outq *q,
  81                                        struct sctp_chunk *ch)
  82{
  83        list_add(&ch->list, &q->out_chunk_list);
  84        q->out_qlen += ch->skb->len;
  85}
  86
  87/* Take data from the front of the queue. */
  88static inline struct sctp_chunk *sctp_outq_dequeue_data(struct sctp_outq *q)
  89{
  90        struct sctp_chunk *ch = NULL;
  91
  92        if (!list_empty(&q->out_chunk_list)) {
  93                struct list_head *entry = q->out_chunk_list.next;
  94
  95                ch = list_entry(entry, struct sctp_chunk, list);
  96                list_del_init(entry);
  97                q->out_qlen -= ch->skb->len;
  98        }
  99        return ch;
 100}
 101/* Add data chunk to the end of the queue. */
 102static inline void sctp_outq_tail_data(struct sctp_outq *q,
 103                                       struct sctp_chunk *ch)
 104{
 105        list_add_tail(&ch->list, &q->out_chunk_list);
 106        q->out_qlen += ch->skb->len;
 107}
 108
 109/*
 110 * SFR-CACC algorithm:
 111 * D) If count_of_newacks is greater than or equal to 2
 112 * and t was not sent to the current primary then the
 113 * sender MUST NOT increment missing report count for t.
 114 */
 115static inline int sctp_cacc_skip_3_1_d(struct sctp_transport *primary,
 116                                       struct sctp_transport *transport,
 117                                       int count_of_newacks)
 118{
 119        if (count_of_newacks >=2 && transport != primary)
 120                return 1;
 121        return 0;
 122}
 123
 124/*
 125 * SFR-CACC algorithm:
 126 * F) If count_of_newacks is less than 2, let d be the
 127 * destination to which t was sent. If cacc_saw_newack
 128 * is 0 for destination d, then the sender MUST NOT
 129 * increment missing report count for t.
 130 */
 131static inline int sctp_cacc_skip_3_1_f(struct sctp_transport *transport,
 132                                       int count_of_newacks)
 133{
 134        if (count_of_newacks < 2 &&
 135                        (transport && !transport->cacc.cacc_saw_newack))
 136                return 1;
 137        return 0;
 138}
 139
 140/*
 141 * SFR-CACC algorithm:
 142 * 3.1) If CYCLING_CHANGEOVER is 0, the sender SHOULD
 143 * execute steps C, D, F.
 144 *
 145 * C has been implemented in sctp_outq_sack
 146 */
 147static inline int sctp_cacc_skip_3_1(struct sctp_transport *primary,
 148                                     struct sctp_transport *transport,
 149                                     int count_of_newacks)
 150{
 151        if (!primary->cacc.cycling_changeover) {
 152                if (sctp_cacc_skip_3_1_d(primary, transport, count_of_newacks))
 153                        return 1;
 154                if (sctp_cacc_skip_3_1_f(transport, count_of_newacks))
 155                        return 1;
 156                return 0;
 157        }
 158        return 0;
 159}
 160
 161/*
 162 * SFR-CACC algorithm:
 163 * 3.2) Else if CYCLING_CHANGEOVER is 1, and t is less
 164 * than next_tsn_at_change of the current primary, then
 165 * the sender MUST NOT increment missing report count
 166 * for t.
 167 */
 168static inline int sctp_cacc_skip_3_2(struct sctp_transport *primary, __u32 tsn)
 169{
 170        if (primary->cacc.cycling_changeover &&
 171            TSN_lt(tsn, primary->cacc.next_tsn_at_change))
 172                return 1;
 173        return 0;
 174}
 175
 176/*
 177 * SFR-CACC algorithm:
 178 * 3) If the missing report count for TSN t is to be
 179 * incremented according to [RFC2960] and
 180 * [SCTP_STEWART-2002], and CHANGEOVER_ACTIVE is set,
 181 * then the sender MUST further execute steps 3.1 and
 182 * 3.2 to determine if the missing report count for
 183 * TSN t SHOULD NOT be incremented.
 184 *
 185 * 3.3) If 3.1 and 3.2 do not dictate that the missing
 186 * report count for t should not be incremented, then
 187 * the sender SHOULD increment missing report count for
 188 * t (according to [RFC2960] and [SCTP_STEWART_2002]).
 189 */
 190static inline int sctp_cacc_skip(struct sctp_transport *primary,
 191                                 struct sctp_transport *transport,
 192                                 int count_of_newacks,
 193                                 __u32 tsn)
 194{
 195        if (primary->cacc.changeover_active &&
 196            (sctp_cacc_skip_3_1(primary, transport, count_of_newacks) ||
 197             sctp_cacc_skip_3_2(primary, tsn)))
 198                return 1;
 199        return 0;
 200}
 201
 202/* Initialize an existing sctp_outq.  This does the boring stuff.
 203 * You still need to define handlers if you really want to DO
 204 * something with this structure...
 205 */
 206void sctp_outq_init(struct sctp_association *asoc, struct sctp_outq *q)
 207{
 208        q->asoc = asoc;
 209        INIT_LIST_HEAD(&q->out_chunk_list);
 210        INIT_LIST_HEAD(&q->control_chunk_list);
 211        INIT_LIST_HEAD(&q->retransmit);
 212        INIT_LIST_HEAD(&q->sacked);
 213        INIT_LIST_HEAD(&q->abandoned);
 214
 215        q->fast_rtx = 0;
 216        q->outstanding_bytes = 0;
 217        q->empty = 1;
 218        q->cork  = 0;
 219
 220        q->malloced = 0;
 221        q->out_qlen = 0;
 222}
 223
 224/* Free the outqueue structure and any related pending chunks.
 225 */
 226void sctp_outq_teardown(struct sctp_outq *q)
 227{
 228        struct sctp_transport *transport;
 229        struct list_head *lchunk, *temp;
 230        struct sctp_chunk *chunk, *tmp;
 231
 232        /* Throw away unacknowledged chunks. */
 233        list_for_each_entry(transport, &q->asoc->peer.transport_addr_list,
 234                        transports) {
 235                while ((lchunk = sctp_list_dequeue(&transport->transmitted)) != NULL) {
 236                        chunk = list_entry(lchunk, struct sctp_chunk,
 237                                           transmitted_list);
 238                        /* Mark as part of a failed message. */
 239                        sctp_chunk_fail(chunk, q->error);
 240                        sctp_chunk_free(chunk);
 241                }
 242        }
 243
 244        /* Throw away chunks that have been gap ACKed.  */
 245        list_for_each_safe(lchunk, temp, &q->sacked) {
 246                list_del_init(lchunk);
 247                chunk = list_entry(lchunk, struct sctp_chunk,
 248                                   transmitted_list);
 249                sctp_chunk_fail(chunk, q->error);
 250                sctp_chunk_free(chunk);
 251        }
 252
 253        /* Throw away any chunks in the retransmit queue. */
 254        list_for_each_safe(lchunk, temp, &q->retransmit) {
 255                list_del_init(lchunk);
 256                chunk = list_entry(lchunk, struct sctp_chunk,
 257                                   transmitted_list);
 258                sctp_chunk_fail(chunk, q->error);
 259                sctp_chunk_free(chunk);
 260        }
 261
 262        /* Throw away any chunks that are in the abandoned queue. */
 263        list_for_each_safe(lchunk, temp, &q->abandoned) {
 264                list_del_init(lchunk);
 265                chunk = list_entry(lchunk, struct sctp_chunk,
 266                                   transmitted_list);
 267                sctp_chunk_fail(chunk, q->error);
 268                sctp_chunk_free(chunk);
 269        }
 270
 271        /* Throw away any leftover data chunks. */
 272        while ((chunk = sctp_outq_dequeue_data(q)) != NULL) {
 273
 274                /* Mark as send failure. */
 275                sctp_chunk_fail(chunk, q->error);
 276                sctp_chunk_free(chunk);
 277        }
 278
 279        q->error = 0;
 280
 281        /* Throw away any leftover control chunks. */
 282        list_for_each_entry_safe(chunk, tmp, &q->control_chunk_list, list) {
 283                list_del_init(&chunk->list);
 284                sctp_chunk_free(chunk);
 285        }
 286}
 287
 288/* Free the outqueue structure and any related pending chunks.  */
 289void sctp_outq_free(struct sctp_outq *q)
 290{
 291        /* Throw away leftover chunks. */
 292        sctp_outq_teardown(q);
 293
 294        /* If we were kmalloc()'d, free the memory.  */
 295        if (q->malloced)
 296                kfree(q);
 297}
 298
 299/* Put a new chunk in an sctp_outq.  */
 300int sctp_outq_tail(struct sctp_outq *q, struct sctp_chunk *chunk)
 301{
 302        int error = 0;
 303
 304        SCTP_DEBUG_PRINTK("sctp_outq_tail(%p, %p[%s])\n",
 305                          q, chunk, chunk && chunk->chunk_hdr ?
 306                          sctp_cname(SCTP_ST_CHUNK(chunk->chunk_hdr->type))
 307                          : "Illegal Chunk");
 308
 309        /* If it is data, queue it up, otherwise, send it
 310         * immediately.
 311         */
 312        if (sctp_chunk_is_data(chunk)) {
 313                /* Is it OK to queue data chunks?  */
 314                /* From 9. Termination of Association
 315                 *
 316                 * When either endpoint performs a shutdown, the
 317                 * association on each peer will stop accepting new
 318                 * data from its user and only deliver data in queue
 319                 * at the time of sending or receiving the SHUTDOWN
 320                 * chunk.
 321                 */
 322                switch (q->asoc->state) {
 323                case SCTP_STATE_CLOSED:
 324                case SCTP_STATE_SHUTDOWN_PENDING:
 325                case SCTP_STATE_SHUTDOWN_SENT:
 326                case SCTP_STATE_SHUTDOWN_RECEIVED:
 327                case SCTP_STATE_SHUTDOWN_ACK_SENT:
 328                        /* Cannot send after transport endpoint shutdown */
 329                        error = -ESHUTDOWN;
 330                        break;
 331
 332                default:
 333                        SCTP_DEBUG_PRINTK("outqueueing (%p, %p[%s])\n",
 334                          q, chunk, chunk && chunk->chunk_hdr ?
 335                          sctp_cname(SCTP_ST_CHUNK(chunk->chunk_hdr->type))
 336                          : "Illegal Chunk");
 337
 338                        sctp_outq_tail_data(q, chunk);
 339                        if (chunk->chunk_hdr->flags & SCTP_DATA_UNORDERED)
 340                                SCTP_INC_STATS(SCTP_MIB_OUTUNORDERCHUNKS);
 341                        else
 342                                SCTP_INC_STATS(SCTP_MIB_OUTORDERCHUNKS);
 343                        q->empty = 0;
 344                        break;
 345                }
 346        } else {
 347                list_add_tail(&chunk->list, &q->control_chunk_list);
 348                SCTP_INC_STATS(SCTP_MIB_OUTCTRLCHUNKS);
 349        }
 350
 351        if (error < 0)
 352                return error;
 353
 354        if (!q->cork)
 355                error = sctp_outq_flush(q, 0);
 356
 357        return error;
 358}
 359
 360/* Insert a chunk into the sorted list based on the TSNs.  The retransmit list
 361 * and the abandoned list are in ascending order.
 362 */
 363static void sctp_insert_list(struct list_head *head, struct list_head *new)
 364{
 365        struct list_head *pos;
 366        struct sctp_chunk *nchunk, *lchunk;
 367        __u32 ntsn, ltsn;
 368        int done = 0;
 369
 370        nchunk = list_entry(new, struct sctp_chunk, transmitted_list);
 371        ntsn = ntohl(nchunk->subh.data_hdr->tsn);
 372
 373        list_for_each(pos, head) {
 374                lchunk = list_entry(pos, struct sctp_chunk, transmitted_list);
 375                ltsn = ntohl(lchunk->subh.data_hdr->tsn);
 376                if (TSN_lt(ntsn, ltsn)) {
 377                        list_add(new, pos->prev);
 378                        done = 1;
 379                        break;
 380                }
 381        }
 382        if (!done)
 383                list_add_tail(new, head);
 384}
 385
 386/* Mark all the eligible packets on a transport for retransmission.  */
 387void sctp_retransmit_mark(struct sctp_outq *q,
 388                          struct sctp_transport *transport,
 389                          __u8 reason)
 390{
 391        struct list_head *lchunk, *ltemp;
 392        struct sctp_chunk *chunk;
 393
 394        /* Walk through the specified transmitted queue.  */
 395        list_for_each_safe(lchunk, ltemp, &transport->transmitted) {
 396                chunk = list_entry(lchunk, struct sctp_chunk,
 397                                   transmitted_list);
 398
 399                /* If the chunk is abandoned, move it to abandoned list. */
 400                if (sctp_chunk_abandoned(chunk)) {
 401                        list_del_init(lchunk);
 402                        sctp_insert_list(&q->abandoned, lchunk);
 403
 404                        /* If this chunk has not been previousely acked,
 405                         * stop considering it 'outstanding'.  Our peer
 406                         * will most likely never see it since it will
 407                         * not be retransmitted
 408                         */
 409                        if (!chunk->tsn_gap_acked) {
 410                                if (chunk->transport)
 411                                        chunk->transport->flight_size -=
 412                                                        sctp_data_size(chunk);
 413                                q->outstanding_bytes -= sctp_data_size(chunk);
 414                                q->asoc->peer.rwnd += sctp_data_size(chunk);
 415                        }
 416                        continue;
 417                }
 418
 419                /* If we are doing  retransmission due to a timeout or pmtu
 420                 * discovery, only the  chunks that are not yet acked should
 421                 * be added to the retransmit queue.
 422                 */
 423                if ((reason == SCTP_RTXR_FAST_RTX  &&
 424                            (chunk->fast_retransmit == SCTP_NEED_FRTX)) ||
 425                    (reason != SCTP_RTXR_FAST_RTX  && !chunk->tsn_gap_acked)) {
 426                        /* RFC 2960 6.2.1 Processing a Received SACK
 427                         *
 428                         * C) Any time a DATA chunk is marked for
 429                         * retransmission (via either T3-rtx timer expiration
 430                         * (Section 6.3.3) or via fast retransmit
 431                         * (Section 7.2.4)), add the data size of those
 432                         * chunks to the rwnd.
 433                         */
 434                        q->asoc->peer.rwnd += sctp_data_size(chunk);
 435                        q->outstanding_bytes -= sctp_data_size(chunk);
 436                        if (chunk->transport)
 437                                transport->flight_size -= sctp_data_size(chunk);
 438
 439                        /* sctpimpguide-05 Section 2.8.2
 440                         * M5) If a T3-rtx timer expires, the
 441                         * 'TSN.Missing.Report' of all affected TSNs is set
 442                         * to 0.
 443                         */
 444                        chunk->tsn_missing_report = 0;
 445
 446                        /* If a chunk that is being used for RTT measurement
 447                         * has to be retransmitted, we cannot use this chunk
 448                         * anymore for RTT measurements. Reset rto_pending so
 449                         * that a new RTT measurement is started when a new
 450                         * data chunk is sent.
 451                         */
 452                        if (chunk->rtt_in_progress) {
 453                                chunk->rtt_in_progress = 0;
 454                                transport->rto_pending = 0;
 455                        }
 456
 457                        /* Move the chunk to the retransmit queue. The chunks
 458                         * on the retransmit queue are always kept in order.
 459                         */
 460                        list_del_init(lchunk);
 461                        sctp_insert_list(&q->retransmit, lchunk);
 462                }
 463        }
 464
 465        SCTP_DEBUG_PRINTK("%s: transport: %p, reason: %d, "
 466                          "cwnd: %d, ssthresh: %d, flight_size: %d, "
 467                          "pba: %d\n", __func__,
 468                          transport, reason,
 469                          transport->cwnd, transport->ssthresh,
 470                          transport->flight_size,
 471                          transport->partial_bytes_acked);
 472
 473}
 474
 475/* Mark all the eligible packets on a transport for retransmission and force
 476 * one packet out.
 477 */
 478void sctp_retransmit(struct sctp_outq *q, struct sctp_transport *transport,
 479                     sctp_retransmit_reason_t reason)
 480{
 481        int error = 0;
 482
 483        switch(reason) {
 484        case SCTP_RTXR_T3_RTX:
 485                SCTP_INC_STATS(SCTP_MIB_T3_RETRANSMITS);
 486                sctp_transport_lower_cwnd(transport, SCTP_LOWER_CWND_T3_RTX);
 487                /* Update the retran path if the T3-rtx timer has expired for
 488                 * the current retran path.
 489                 */
 490                if (transport == transport->asoc->peer.retran_path)
 491                        sctp_assoc_update_retran_path(transport->asoc);
 492                transport->asoc->rtx_data_chunks +=
 493                        transport->asoc->unack_data;
 494                break;
 495        case SCTP_RTXR_FAST_RTX:
 496                SCTP_INC_STATS(SCTP_MIB_FAST_RETRANSMITS);
 497                sctp_transport_lower_cwnd(transport, SCTP_LOWER_CWND_FAST_RTX);
 498                q->fast_rtx = 1;
 499                break;
 500        case SCTP_RTXR_PMTUD:
 501                SCTP_INC_STATS(SCTP_MIB_PMTUD_RETRANSMITS);
 502                break;
 503        case SCTP_RTXR_T1_RTX:
 504                SCTP_INC_STATS(SCTP_MIB_T1_RETRANSMITS);
 505                transport->asoc->init_retries++;
 506                break;
 507        default:
 508                BUG();
 509        }
 510
 511        sctp_retransmit_mark(q, transport, reason);
 512
 513        /* PR-SCTP A5) Any time the T3-rtx timer expires, on any destination,
 514         * the sender SHOULD try to advance the "Advanced.Peer.Ack.Point" by
 515         * following the procedures outlined in C1 - C5.
 516         */
 517        if (reason == SCTP_RTXR_T3_RTX)
 518                sctp_generate_fwdtsn(q, q->asoc->ctsn_ack_point);
 519
 520        /* Flush the queues only on timeout, since fast_rtx is only
 521         * triggered during sack processing and the queue
 522         * will be flushed at the end.
 523         */
 524        if (reason != SCTP_RTXR_FAST_RTX)
 525                error = sctp_outq_flush(q, /* rtx_timeout */ 1);
 526
 527        if (error)
 528                q->asoc->base.sk->sk_err = -error;
 529}
 530
 531/*
 532 * Transmit DATA chunks on the retransmit queue.  Upon return from
 533 * sctp_outq_flush_rtx() the packet 'pkt' may contain chunks which
 534 * need to be transmitted by the caller.
 535 * We assume that pkt->transport has already been set.
 536 *
 537 * The return value is a normal kernel error return value.
 538 */
 539static int sctp_outq_flush_rtx(struct sctp_outq *q, struct sctp_packet *pkt,
 540                               int rtx_timeout, int *start_timer)
 541{
 542        struct list_head *lqueue;
 543        struct sctp_transport *transport = pkt->transport;
 544        sctp_xmit_t status;
 545        struct sctp_chunk *chunk, *chunk1;
 546        int fast_rtx;
 547        int error = 0;
 548        int timer = 0;
 549        int done = 0;
 550
 551        lqueue = &q->retransmit;
 552        fast_rtx = q->fast_rtx;
 553
 554        /* This loop handles time-out retransmissions, fast retransmissions,
 555         * and retransmissions due to opening of whindow.
 556         *
 557         * RFC 2960 6.3.3 Handle T3-rtx Expiration
 558         *
 559         * E3) Determine how many of the earliest (i.e., lowest TSN)
 560         * outstanding DATA chunks for the address for which the
 561         * T3-rtx has expired will fit into a single packet, subject
 562         * to the MTU constraint for the path corresponding to the
 563         * destination transport address to which the retransmission
 564         * is being sent (this may be different from the address for
 565         * which the timer expires [see Section 6.4]). Call this value
 566         * K. Bundle and retransmit those K DATA chunks in a single
 567         * packet to the destination endpoint.
 568         *
 569         * [Just to be painfully clear, if we are retransmitting
 570         * because a timeout just happened, we should send only ONE
 571         * packet of retransmitted data.]
 572         *
 573         * For fast retransmissions we also send only ONE packet.  However,
 574         * if we are just flushing the queue due to open window, we'll
 575         * try to send as much as possible.
 576         */
 577        list_for_each_entry_safe(chunk, chunk1, lqueue, transmitted_list) {
 578                /* If the chunk is abandoned, move it to abandoned list. */
 579                if (sctp_chunk_abandoned(chunk)) {
 580                        list_del_init(&chunk->transmitted_list);
 581                        sctp_insert_list(&q->abandoned,
 582                                         &chunk->transmitted_list);
 583                        continue;
 584                }
 585
 586                /* Make sure that Gap Acked TSNs are not retransmitted.  A
 587                 * simple approach is just to move such TSNs out of the
 588                 * way and into a 'transmitted' queue and skip to the
 589                 * next chunk.
 590                 */
 591                if (chunk->tsn_gap_acked) {
 592                        list_del(&chunk->transmitted_list);
 593                        list_add_tail(&chunk->transmitted_list,
 594                                        &transport->transmitted);
 595                        continue;
 596                }
 597
 598                /* If we are doing fast retransmit, ignore non-fast_rtransmit
 599                 * chunks
 600                 */
 601                if (fast_rtx && !chunk->fast_retransmit)
 602                        continue;
 603
 604redo:
 605                /* Attempt to append this chunk to the packet. */
 606                status = sctp_packet_append_chunk(pkt, chunk);
 607
 608                switch (status) {
 609                case SCTP_XMIT_PMTU_FULL:
 610                        if (!pkt->has_data && !pkt->has_cookie_echo) {
 611                                /* If this packet did not contain DATA then
 612                                 * retransmission did not happen, so do it
 613                                 * again.  We'll ignore the error here since
 614                                 * control chunks are already freed so there
 615                                 * is nothing we can do.
 616                                 */
 617                                sctp_packet_transmit(pkt);
 618                                goto redo;
 619                        }
 620
 621                        /* Send this packet.  */
 622                        error = sctp_packet_transmit(pkt);
 623
 624                        /* If we are retransmitting, we should only
 625                         * send a single packet.
 626                         * Otherwise, try appending this chunk again.
 627                         */
 628                        if (rtx_timeout || fast_rtx)
 629                                done = 1;
 630                        else
 631                                goto redo;
 632
 633                        /* Bundle next chunk in the next round.  */
 634                        break;
 635
 636                case SCTP_XMIT_RWND_FULL:
 637                        /* Send this packet. */
 638                        error = sctp_packet_transmit(pkt);
 639
 640                        /* Stop sending DATA as there is no more room
 641                         * at the receiver.
 642                         */
 643                        done = 1;
 644                        break;
 645
 646                case SCTP_XMIT_NAGLE_DELAY:
 647                        /* Send this packet. */
 648                        error = sctp_packet_transmit(pkt);
 649
 650                        /* Stop sending DATA because of nagle delay. */
 651                        done = 1;
 652                        break;
 653
 654                default:
 655                        /* The append was successful, so add this chunk to
 656                         * the transmitted list.
 657                         */
 658                        list_del(&chunk->transmitted_list);
 659                        list_add_tail(&chunk->transmitted_list,
 660                                        &transport->transmitted);
 661
 662                        /* Mark the chunk as ineligible for fast retransmit
 663                         * after it is retransmitted.
 664                         */
 665                        if (chunk->fast_retransmit == SCTP_NEED_FRTX)
 666                                chunk->fast_retransmit = SCTP_DONT_FRTX;
 667
 668                        q->empty = 0;
 669                        break;
 670                }
 671
 672                /* Set the timer if there were no errors */
 673                if (!error && !timer)
 674                        timer = 1;
 675
 676                if (done)
 677                        break;
 678        }
 679
 680        /* If we are here due to a retransmit timeout or a fast
 681         * retransmit and if there are any chunks left in the retransmit
 682         * queue that could not fit in the PMTU sized packet, they need
 683         * to be marked as ineligible for a subsequent fast retransmit.
 684         */
 685        if (rtx_timeout || fast_rtx) {
 686                list_for_each_entry(chunk1, lqueue, transmitted_list) {
 687                        if (chunk1->fast_retransmit == SCTP_NEED_FRTX)
 688                                chunk1->fast_retransmit = SCTP_DONT_FRTX;
 689                }
 690        }
 691
 692        *start_timer = timer;
 693
 694        /* Clear fast retransmit hint */
 695        if (fast_rtx)
 696                q->fast_rtx = 0;
 697
 698        return error;
 699}
 700
 701/* Cork the outqueue so queued chunks are really queued. */
 702int sctp_outq_uncork(struct sctp_outq *q)
 703{
 704        int error = 0;
 705        if (q->cork)
 706                q->cork = 0;
 707        error = sctp_outq_flush(q, 0);
 708        return error;
 709}
 710
 711
 712/*
 713 * Try to flush an outqueue.
 714 *
 715 * Description: Send everything in q which we legally can, subject to
 716 * congestion limitations.
 717 * * Note: This function can be called from multiple contexts so appropriate
 718 * locking concerns must be made.  Today we use the sock lock to protect
 719 * this function.
 720 */
 721static int sctp_outq_flush(struct sctp_outq *q, int rtx_timeout)
 722{
 723        struct sctp_packet *packet;
 724        struct sctp_packet singleton;
 725        struct sctp_association *asoc = q->asoc;
 726        __u16 sport = asoc->base.bind_addr.port;
 727        __u16 dport = asoc->peer.port;
 728        __u32 vtag = asoc->peer.i.init_tag;
 729        struct sctp_transport *transport = NULL;
 730        struct sctp_transport *new_transport;
 731        struct sctp_chunk *chunk, *tmp;
 732        sctp_xmit_t status;
 733        int error = 0;
 734        int start_timer = 0;
 735        int one_packet = 0;
 736
 737        /* These transports have chunks to send. */
 738        struct list_head transport_list;
 739        struct list_head *ltransport;
 740
 741        INIT_LIST_HEAD(&transport_list);
 742        packet = NULL;
 743
 744        /*
 745         * 6.10 Bundling
 746         *   ...
 747         *   When bundling control chunks with DATA chunks, an
 748         *   endpoint MUST place control chunks first in the outbound
 749         *   SCTP packet.  The transmitter MUST transmit DATA chunks
 750         *   within a SCTP packet in increasing order of TSN.
 751         *   ...
 752         */
 753
 754        list_for_each_entry_safe(chunk, tmp, &q->control_chunk_list, list) {
 755                /* RFC 5061, 5.3
 756                 * F1) This means that until such time as the ASCONF
 757                 * containing the add is acknowledged, the sender MUST
 758                 * NOT use the new IP address as a source for ANY SCTP
 759                 * packet except on carrying an ASCONF Chunk.
 760                 */
 761                if (asoc->src_out_of_asoc_ok &&
 762                    chunk->chunk_hdr->type != SCTP_CID_ASCONF)
 763                        continue;
 764
 765                list_del_init(&chunk->list);
 766
 767                /* Pick the right transport to use. */
 768                new_transport = chunk->transport;
 769
 770                if (!new_transport) {
 771                        /*
 772                         * If we have a prior transport pointer, see if
 773                         * the destination address of the chunk
 774                         * matches the destination address of the
 775                         * current transport.  If not a match, then
 776                         * try to look up the transport with a given
 777                         * destination address.  We do this because
 778                         * after processing ASCONFs, we may have new
 779                         * transports created.
 780                         */
 781                        if (transport &&
 782                            sctp_cmp_addr_exact(&chunk->dest,
 783                                                &transport->ipaddr))
 784                                        new_transport = transport;
 785                        else
 786                                new_transport = sctp_assoc_lookup_paddr(asoc,
 787                                                                &chunk->dest);
 788
 789                        /* if we still don't have a new transport, then
 790                         * use the current active path.
 791                         */
 792                        if (!new_transport)
 793                                new_transport = asoc->peer.active_path;
 794                } else if ((new_transport->state == SCTP_INACTIVE) ||
 795                           (new_transport->state == SCTP_UNCONFIRMED) ||
 796                           (new_transport->state == SCTP_PF)) {
 797                        /* If the chunk is Heartbeat or Heartbeat Ack,
 798                         * send it to chunk->transport, even if it's
 799                         * inactive.
 800                         *
 801                         * 3.3.6 Heartbeat Acknowledgement:
 802                         * ...
 803                         * A HEARTBEAT ACK is always sent to the source IP
 804                         * address of the IP datagram containing the
 805                         * HEARTBEAT chunk to which this ack is responding.
 806                         * ...
 807                         *
 808                         * ASCONF_ACKs also must be sent to the source.
 809                         */
 810                        if (chunk->chunk_hdr->type != SCTP_CID_HEARTBEAT &&
 811                            chunk->chunk_hdr->type != SCTP_CID_HEARTBEAT_ACK &&
 812                            chunk->chunk_hdr->type != SCTP_CID_ASCONF_ACK)
 813                                new_transport = asoc->peer.active_path;
 814                }
 815
 816                /* Are we switching transports?
 817                 * Take care of transport locks.
 818                 */
 819                if (new_transport != transport) {
 820                        transport = new_transport;
 821                        if (list_empty(&transport->send_ready)) {
 822                                list_add_tail(&transport->send_ready,
 823                                              &transport_list);
 824                        }
 825                        packet = &transport->packet;
 826                        sctp_packet_config(packet, vtag,
 827                                           asoc->peer.ecn_capable);
 828                }
 829
 830                switch (chunk->chunk_hdr->type) {
 831                /*
 832                 * 6.10 Bundling
 833                 *   ...
 834                 *   An endpoint MUST NOT bundle INIT, INIT ACK or SHUTDOWN
 835                 *   COMPLETE with any other chunks.  [Send them immediately.]
 836                 */
 837                case SCTP_CID_INIT:
 838                case SCTP_CID_INIT_ACK:
 839                case SCTP_CID_SHUTDOWN_COMPLETE:
 840                        sctp_packet_init(&singleton, transport, sport, dport);
 841                        sctp_packet_config(&singleton, vtag, 0);
 842                        sctp_packet_append_chunk(&singleton, chunk);
 843                        error = sctp_packet_transmit(&singleton);
 844                        if (error < 0)
 845                                return error;
 846                        break;
 847
 848                case SCTP_CID_ABORT:
 849                        if (sctp_test_T_bit(chunk)) {
 850                                packet->vtag = asoc->c.my_vtag;
 851                        }
 852                /* The following chunks are "response" chunks, i.e.
 853                 * they are generated in response to something we
 854                 * received.  If we are sending these, then we can
 855                 * send only 1 packet containing these chunks.
 856                 */
 857                case SCTP_CID_HEARTBEAT_ACK:
 858                case SCTP_CID_SHUTDOWN_ACK:
 859                case SCTP_CID_COOKIE_ACK:
 860                case SCTP_CID_COOKIE_ECHO:
 861                case SCTP_CID_ERROR:
 862                case SCTP_CID_ECN_CWR:
 863                case SCTP_CID_ASCONF_ACK:
 864                        one_packet = 1;
 865                        /* Fall through */
 866
 867                case SCTP_CID_SACK:
 868                case SCTP_CID_HEARTBEAT:
 869                case SCTP_CID_SHUTDOWN:
 870                case SCTP_CID_ECN_ECNE:
 871                case SCTP_CID_ASCONF:
 872                case SCTP_CID_FWD_TSN:
 873                        status = sctp_packet_transmit_chunk(packet, chunk,
 874                                                            one_packet);
 875                        if (status  != SCTP_XMIT_OK) {
 876                                /* put the chunk back */
 877                                list_add(&chunk->list, &q->control_chunk_list);
 878                        } else if (chunk->chunk_hdr->type == SCTP_CID_FWD_TSN) {
 879                                /* PR-SCTP C5) If a FORWARD TSN is sent, the
 880                                 * sender MUST assure that at least one T3-rtx
 881                                 * timer is running.
 882                                 */
 883                                sctp_transport_reset_timers(transport);
 884                        }
 885                        break;
 886
 887                default:
 888                        /* We built a chunk with an illegal type! */
 889                        BUG();
 890                }
 891        }
 892
 893        if (q->asoc->src_out_of_asoc_ok)
 894                goto sctp_flush_out;
 895
 896        /* Is it OK to send data chunks?  */
 897        switch (asoc->state) {
 898        case SCTP_STATE_COOKIE_ECHOED:
 899                /* Only allow bundling when this packet has a COOKIE-ECHO
 900                 * chunk.
 901                 */
 902                if (!packet || !packet->has_cookie_echo)
 903                        break;
 904
 905                /* fallthru */
 906        case SCTP_STATE_ESTABLISHED:
 907        case SCTP_STATE_SHUTDOWN_PENDING:
 908        case SCTP_STATE_SHUTDOWN_RECEIVED:
 909                /*
 910                 * RFC 2960 6.1  Transmission of DATA Chunks
 911                 *
 912                 * C) When the time comes for the sender to transmit,
 913                 * before sending new DATA chunks, the sender MUST
 914                 * first transmit any outstanding DATA chunks which
 915                 * are marked for retransmission (limited by the
 916                 * current cwnd).
 917                 */
 918                if (!list_empty(&q->retransmit)) {
 919                        if (asoc->peer.retran_path->state == SCTP_UNCONFIRMED)
 920                                goto sctp_flush_out;
 921                        if (transport == asoc->peer.retran_path)
 922                                goto retran;
 923
 924                        /* Switch transports & prepare the packet.  */
 925
 926                        transport = asoc->peer.retran_path;
 927
 928                        if (list_empty(&transport->send_ready)) {
 929                                list_add_tail(&transport->send_ready,
 930                                              &transport_list);
 931                        }
 932
 933                        packet = &transport->packet;
 934                        sctp_packet_config(packet, vtag,
 935                                           asoc->peer.ecn_capable);
 936                retran:
 937                        error = sctp_outq_flush_rtx(q, packet,
 938                                                    rtx_timeout, &start_timer);
 939
 940                        if (start_timer)
 941                                sctp_transport_reset_timers(transport);
 942
 943                        /* This can happen on COOKIE-ECHO resend.  Only
 944                         * one chunk can get bundled with a COOKIE-ECHO.
 945                         */
 946                        if (packet->has_cookie_echo)
 947                                goto sctp_flush_out;
 948
 949                        /* Don't send new data if there is still data
 950                         * waiting to retransmit.
 951                         */
 952                        if (!list_empty(&q->retransmit))
 953                                goto sctp_flush_out;
 954                }
 955
 956                /* Apply Max.Burst limitation to the current transport in
 957                 * case it will be used for new data.  We are going to
 958                 * rest it before we return, but we want to apply the limit
 959                 * to the currently queued data.
 960                 */
 961                if (transport)
 962                        sctp_transport_burst_limited(transport);
 963
 964                /* Finally, transmit new packets.  */
 965                while ((chunk = sctp_outq_dequeue_data(q)) != NULL) {
 966                        /* RFC 2960 6.5 Every DATA chunk MUST carry a valid
 967                         * stream identifier.
 968                         */
 969                        if (chunk->sinfo.sinfo_stream >=
 970                            asoc->c.sinit_num_ostreams) {
 971
 972                                /* Mark as failed send. */
 973                                sctp_chunk_fail(chunk, SCTP_ERROR_INV_STRM);
 974                                sctp_chunk_free(chunk);
 975                                continue;
 976                        }
 977
 978                        /* Has this chunk expired? */
 979                        if (sctp_chunk_abandoned(chunk)) {
 980                                sctp_chunk_fail(chunk, 0);
 981                                sctp_chunk_free(chunk);
 982                                continue;
 983                        }
 984
 985                        /* If there is a specified transport, use it.
 986                         * Otherwise, we want to use the active path.
 987                         */
 988                        new_transport = chunk->transport;
 989                        if (!new_transport ||
 990                            ((new_transport->state == SCTP_INACTIVE) ||
 991                             (new_transport->state == SCTP_UNCONFIRMED) ||
 992                             (new_transport->state == SCTP_PF)))
 993                                new_transport = asoc->peer.active_path;
 994                        if (new_transport->state == SCTP_UNCONFIRMED)
 995                                continue;
 996
 997                        /* Change packets if necessary.  */
 998                        if (new_transport != transport) {
 999                                transport = new_transport;
1000
1001                                /* Schedule to have this transport's
1002                                 * packet flushed.
1003                                 */
1004                                if (list_empty(&transport->send_ready)) {
1005                                        list_add_tail(&transport->send_ready,
1006                                                      &transport_list);
1007                                }
1008
1009                                packet = &transport->packet;
1010                                sctp_packet_config(packet, vtag,
1011                                                   asoc->peer.ecn_capable);
1012                                /* We've switched transports, so apply the
1013                                 * Burst limit to the new transport.
1014                                 */
1015                                sctp_transport_burst_limited(transport);
1016                        }
1017
1018                        SCTP_DEBUG_PRINTK("sctp_outq_flush(%p, %p[%s]), ",
1019                                          q, chunk,
1020                                          chunk && chunk->chunk_hdr ?
1021                                          sctp_cname(SCTP_ST_CHUNK(
1022                                                  chunk->chunk_hdr->type))
1023                                          : "Illegal Chunk");
1024
1025                        SCTP_DEBUG_PRINTK("TX TSN 0x%x skb->head "
1026                                        "%p skb->users %d.\n",
1027                                        ntohl(chunk->subh.data_hdr->tsn),
1028                                        chunk->skb ?chunk->skb->head : NULL,
1029                                        chunk->skb ?
1030                                        atomic_read(&chunk->skb->users) : -1);
1031
1032                        /* Add the chunk to the packet.  */
1033                        status = sctp_packet_transmit_chunk(packet, chunk, 0);
1034
1035                        switch (status) {
1036                        case SCTP_XMIT_PMTU_FULL:
1037                        case SCTP_XMIT_RWND_FULL:
1038                        case SCTP_XMIT_NAGLE_DELAY:
1039                                /* We could not append this chunk, so put
1040                                 * the chunk back on the output queue.
1041                                 */
1042                                SCTP_DEBUG_PRINTK("sctp_outq_flush: could "
1043                                        "not transmit TSN: 0x%x, status: %d\n",
1044                                        ntohl(chunk->subh.data_hdr->tsn),
1045                                        status);
1046                                sctp_outq_head_data(q, chunk);
1047                                goto sctp_flush_out;
1048                                break;
1049
1050                        case SCTP_XMIT_OK:
1051                                /* The sender is in the SHUTDOWN-PENDING state,
1052                                 * The sender MAY set the I-bit in the DATA
1053                                 * chunk header.
1054                                 */
1055                                if (asoc->state == SCTP_STATE_SHUTDOWN_PENDING)
1056                                        chunk->chunk_hdr->flags |= SCTP_DATA_SACK_IMM;
1057
1058                                break;
1059
1060                        default:
1061                                BUG();
1062                        }
1063
1064                        /* BUG: We assume that the sctp_packet_transmit()
1065                         * call below will succeed all the time and add the
1066                         * chunk to the transmitted list and restart the
1067                         * timers.
1068                         * It is possible that the call can fail under OOM
1069                         * conditions.
1070                         *
1071                         * Is this really a problem?  Won't this behave
1072                         * like a lost TSN?
1073                         */
1074                        list_add_tail(&chunk->transmitted_list,
1075                                      &transport->transmitted);
1076
1077                        sctp_transport_reset_timers(transport);
1078
1079                        q->empty = 0;
1080
1081                        /* Only let one DATA chunk get bundled with a
1082                         * COOKIE-ECHO chunk.
1083                         */
1084                        if (packet->has_cookie_echo)
1085                                goto sctp_flush_out;
1086                }
1087                break;
1088
1089        default:
1090                /* Do nothing.  */
1091                break;
1092        }
1093
1094sctp_flush_out:
1095
1096        /* Before returning, examine all the transports touched in
1097         * this call.  Right now, we bluntly force clear all the
1098         * transports.  Things might change after we implement Nagle.
1099         * But such an examination is still required.
1100         *
1101         * --xguo
1102         */
1103        while ((ltransport = sctp_list_dequeue(&transport_list)) != NULL ) {
1104                struct sctp_transport *t = list_entry(ltransport,
1105                                                      struct sctp_transport,
1106                                                      send_ready);
1107                packet = &t->packet;
1108                if (!sctp_packet_empty(packet))
1109                        error = sctp_packet_transmit(packet);
1110
1111                /* Clear the burst limited state, if any */
1112                sctp_transport_burst_reset(t);
1113        }
1114
1115        return error;
1116}
1117
1118/* Update unack_data based on the incoming SACK chunk */
1119static void sctp_sack_update_unack_data(struct sctp_association *assoc,
1120                                        struct sctp_sackhdr *sack)
1121{
1122        sctp_sack_variable_t *frags;
1123        __u16 unack_data;
1124        int i;
1125
1126        unack_data = assoc->next_tsn - assoc->ctsn_ack_point - 1;
1127
1128        frags = sack->variable;
1129        for (i = 0; i < ntohs(sack->num_gap_ack_blocks); i++) {
1130                unack_data -= ((ntohs(frags[i].gab.end) -
1131                                ntohs(frags[i].gab.start) + 1));
1132        }
1133
1134        assoc->unack_data = unack_data;
1135}
1136
1137/* This is where we REALLY process a SACK.
1138 *
1139 * Process the SACK against the outqueue.  Mostly, this just frees
1140 * things off the transmitted queue.
1141 */
1142int sctp_outq_sack(struct sctp_outq *q, struct sctp_sackhdr *sack)
1143{
1144        struct sctp_association *asoc = q->asoc;
1145        struct sctp_transport *transport;
1146        struct sctp_chunk *tchunk = NULL;
1147        struct list_head *lchunk, *transport_list, *temp;
1148        sctp_sack_variable_t *frags = sack->variable;
1149        __u32 sack_ctsn, ctsn, tsn;
1150        __u32 highest_tsn, highest_new_tsn;
1151        __u32 sack_a_rwnd;
1152        unsigned int outstanding;
1153        struct sctp_transport *primary = asoc->peer.primary_path;
1154        int count_of_newacks = 0;
1155        int gap_ack_blocks;
1156        u8 accum_moved = 0;
1157
1158        /* Grab the association's destination address list. */
1159        transport_list = &asoc->peer.transport_addr_list;
1160
1161        sack_ctsn = ntohl(sack->cum_tsn_ack);
1162        gap_ack_blocks = ntohs(sack->num_gap_ack_blocks);
1163        /*
1164         * SFR-CACC algorithm:
1165         * On receipt of a SACK the sender SHOULD execute the
1166         * following statements.
1167         *
1168         * 1) If the cumulative ack in the SACK passes next tsn_at_change
1169         * on the current primary, the CHANGEOVER_ACTIVE flag SHOULD be
1170         * cleared. The CYCLING_CHANGEOVER flag SHOULD also be cleared for
1171         * all destinations.
1172         * 2) If the SACK contains gap acks and the flag CHANGEOVER_ACTIVE
1173         * is set the receiver of the SACK MUST take the following actions:
1174         *
1175         * A) Initialize the cacc_saw_newack to 0 for all destination
1176         * addresses.
1177         *
1178         * Only bother if changeover_active is set. Otherwise, this is
1179         * totally suboptimal to do on every SACK.
1180         */
1181        if (primary->cacc.changeover_active) {
1182                u8 clear_cycling = 0;
1183
1184                if (TSN_lte(primary->cacc.next_tsn_at_change, sack_ctsn)) {
1185                        primary->cacc.changeover_active = 0;
1186                        clear_cycling = 1;
1187                }
1188
1189                if (clear_cycling || gap_ack_blocks) {
1190                        list_for_each_entry(transport, transport_list,
1191                                        transports) {
1192                                if (clear_cycling)
1193                                        transport->cacc.cycling_changeover = 0;
1194                                if (gap_ack_blocks)
1195                                        transport->cacc.cacc_saw_newack = 0;
1196                        }
1197                }
1198        }
1199
1200        /* Get the highest TSN in the sack. */
1201        highest_tsn = sack_ctsn;
1202        if (gap_ack_blocks)
1203                highest_tsn += ntohs(frags[gap_ack_blocks - 1].gab.end);
1204
1205        if (TSN_lt(asoc->highest_sacked, highest_tsn))
1206                asoc->highest_sacked = highest_tsn;
1207
1208        highest_new_tsn = sack_ctsn;
1209
1210        /* Run through the retransmit queue.  Credit bytes received
1211         * and free those chunks that we can.
1212         */
1213        sctp_check_transmitted(q, &q->retransmit, NULL, sack, &highest_new_tsn);
1214
1215        /* Run through the transmitted queue.
1216         * Credit bytes received and free those chunks which we can.
1217         *
1218         * This is a MASSIVE candidate for optimization.
1219         */
1220        list_for_each_entry(transport, transport_list, transports) {
1221                sctp_check_transmitted(q, &transport->transmitted,
1222                                       transport, sack, &highest_new_tsn);
1223                /*
1224                 * SFR-CACC algorithm:
1225                 * C) Let count_of_newacks be the number of
1226                 * destinations for which cacc_saw_newack is set.
1227                 */
1228                if (transport->cacc.cacc_saw_newack)
1229                        count_of_newacks ++;
1230        }
1231
1232        /* Move the Cumulative TSN Ack Point if appropriate.  */
1233        if (TSN_lt(asoc->ctsn_ack_point, sack_ctsn)) {
1234                asoc->ctsn_ack_point = sack_ctsn;
1235                accum_moved = 1;
1236        }
1237
1238        if (gap_ack_blocks) {
1239
1240                if (asoc->fast_recovery && accum_moved)
1241                        highest_new_tsn = highest_tsn;
1242
1243                list_for_each_entry(transport, transport_list, transports)
1244                        sctp_mark_missing(q, &transport->transmitted, transport,
1245                                          highest_new_tsn, count_of_newacks);
1246        }
1247
1248        /* Update unack_data field in the assoc. */
1249        sctp_sack_update_unack_data(asoc, sack);
1250
1251        ctsn = asoc->ctsn_ack_point;
1252
1253        /* Throw away stuff rotting on the sack queue.  */
1254        list_for_each_safe(lchunk, temp, &q->sacked) {
1255                tchunk = list_entry(lchunk, struct sctp_chunk,
1256                                    transmitted_list);
1257                tsn = ntohl(tchunk->subh.data_hdr->tsn);
1258                if (TSN_lte(tsn, ctsn)) {
1259                        list_del_init(&tchunk->transmitted_list);
1260                        sctp_chunk_free(tchunk);
1261                }
1262        }
1263
1264        /* ii) Set rwnd equal to the newly received a_rwnd minus the
1265         *     number of bytes still outstanding after processing the
1266         *     Cumulative TSN Ack and the Gap Ack Blocks.
1267         */
1268
1269        sack_a_rwnd = ntohl(sack->a_rwnd);
1270        outstanding = q->outstanding_bytes;
1271
1272        if (outstanding < sack_a_rwnd)
1273                sack_a_rwnd -= outstanding;
1274        else
1275                sack_a_rwnd = 0;
1276
1277        asoc->peer.rwnd = sack_a_rwnd;
1278
1279        sctp_generate_fwdtsn(q, sack_ctsn);
1280
1281        SCTP_DEBUG_PRINTK("%s: sack Cumulative TSN Ack is 0x%x.\n",
1282                          __func__, sack_ctsn);
1283        SCTP_DEBUG_PRINTK("%s: Cumulative TSN Ack of association, "
1284                          "%p is 0x%x. Adv peer ack point: 0x%x\n",
1285                          __func__, asoc, ctsn, asoc->adv_peer_ack_point);
1286
1287        /* See if all chunks are acked.
1288         * Make sure the empty queue handler will get run later.
1289         */
1290        q->empty = (list_empty(&q->out_chunk_list) &&
1291                    list_empty(&q->retransmit));
1292        if (!q->empty)
1293                goto finish;
1294
1295        list_for_each_entry(transport, transport_list, transports) {
1296                q->empty = q->empty && list_empty(&transport->transmitted);
1297                if (!q->empty)
1298                        goto finish;
1299        }
1300
1301        SCTP_DEBUG_PRINTK("sack queue is empty.\n");
1302finish:
1303        return q->empty;
1304}
1305
1306/* Is the outqueue empty?  */
1307int sctp_outq_is_empty(const struct sctp_outq *q)
1308{
1309        return q->empty;
1310}
1311
1312/********************************************************************
1313 * 2nd Level Abstractions
1314 ********************************************************************/
1315
1316/* Go through a transport's transmitted list or the association's retransmit
1317 * list and move chunks that are acked by the Cumulative TSN Ack to q->sacked.
1318 * The retransmit list will not have an associated transport.
1319 *
1320 * I added coherent debug information output.   --xguo
1321 *
1322 * Instead of printing 'sacked' or 'kept' for each TSN on the
1323 * transmitted_queue, we print a range: SACKED: TSN1-TSN2, TSN3, TSN4-TSN5.
1324 * KEPT TSN6-TSN7, etc.
1325 */
1326static void sctp_check_transmitted(struct sctp_outq *q,
1327                                   struct list_head *transmitted_queue,
1328                                   struct sctp_transport *transport,
1329                                   struct sctp_sackhdr *sack,
1330                                   __u32 *highest_new_tsn_in_sack)
1331{
1332        struct list_head *lchunk;
1333        struct sctp_chunk *tchunk;
1334        struct list_head tlist;
1335        __u32 tsn;
1336        __u32 sack_ctsn;
1337        __u32 rtt;
1338        __u8 restart_timer = 0;
1339        int bytes_acked = 0;
1340        int migrate_bytes = 0;
1341
1342        /* These state variables are for coherent debug output. --xguo */
1343
1344#if SCTP_DEBUG
1345        __u32 dbg_ack_tsn = 0;  /* An ACKed TSN range starts here... */
1346        __u32 dbg_last_ack_tsn = 0;  /* ...and finishes here.        */
1347        __u32 dbg_kept_tsn = 0; /* An un-ACKed range starts here...  */
1348        __u32 dbg_last_kept_tsn = 0; /* ...and finishes here.        */
1349
1350        /* 0 : The last TSN was ACKed.
1351         * 1 : The last TSN was NOT ACKed (i.e. KEPT).
1352         * -1: We need to initialize.
1353         */
1354        int dbg_prt_state = -1;
1355#endif /* SCTP_DEBUG */
1356
1357        sack_ctsn = ntohl(sack->cum_tsn_ack);
1358
1359        INIT_LIST_HEAD(&tlist);
1360
1361        /* The while loop will skip empty transmitted queues. */
1362        while (NULL != (lchunk = sctp_list_dequeue(transmitted_queue))) {
1363                tchunk = list_entry(lchunk, struct sctp_chunk,
1364                                    transmitted_list);
1365
1366                if (sctp_chunk_abandoned(tchunk)) {
1367                        /* Move the chunk to abandoned list. */
1368                        sctp_insert_list(&q->abandoned, lchunk);
1369
1370                        /* If this chunk has not been acked, stop
1371                         * considering it as 'outstanding'.
1372                         */
1373                        if (!tchunk->tsn_gap_acked) {
1374                                if (tchunk->transport)
1375                                        tchunk->transport->flight_size -=
1376                                                        sctp_data_size(tchunk);
1377                                q->outstanding_bytes -= sctp_data_size(tchunk);
1378                        }
1379                        continue;
1380                }
1381
1382                tsn = ntohl(tchunk->subh.data_hdr->tsn);
1383                if (sctp_acked(sack, tsn)) {
1384                        /* If this queue is the retransmit queue, the
1385                         * retransmit timer has already reclaimed
1386                         * the outstanding bytes for this chunk, so only
1387                         * count bytes associated with a transport.
1388                         */
1389                        if (transport) {
1390                                /* If this chunk is being used for RTT
1391                                 * measurement, calculate the RTT and update
1392                                 * the RTO using this value.
1393                                 *
1394                                 * 6.3.1 C5) Karn's algorithm: RTT measurements
1395                                 * MUST NOT be made using packets that were
1396                                 * retransmitted (and thus for which it is
1397                                 * ambiguous whether the reply was for the
1398                                 * first instance of the packet or a later
1399                                 * instance).
1400                                 */
1401                                if (!tchunk->tsn_gap_acked &&
1402                                    tchunk->rtt_in_progress) {
1403                                        tchunk->rtt_in_progress = 0;
1404                                        rtt = jiffies - tchunk->sent_at;
1405                                        sctp_transport_update_rto(transport,
1406                                                                  rtt);
1407                                }
1408                        }
1409
1410                        /* If the chunk hasn't been marked as ACKED,
1411                         * mark it and account bytes_acked if the
1412                         * chunk had a valid transport (it will not
1413                         * have a transport if ASCONF had deleted it
1414                         * while DATA was outstanding).
1415                         */
1416                        if (!tchunk->tsn_gap_acked) {
1417                                tchunk->tsn_gap_acked = 1;
1418                                *highest_new_tsn_in_sack = tsn;
1419                                bytes_acked += sctp_data_size(tchunk);
1420                                if (!tchunk->transport)
1421                                        migrate_bytes += sctp_data_size(tchunk);
1422                        }
1423
1424                        if (TSN_lte(tsn, sack_ctsn)) {
1425                                /* RFC 2960  6.3.2 Retransmission Timer Rules
1426                                 *
1427                                 * R3) Whenever a SACK is received
1428                                 * that acknowledges the DATA chunk
1429                                 * with the earliest outstanding TSN
1430                                 * for that address, restart T3-rtx
1431                                 * timer for that address with its
1432                                 * current RTO.
1433                                 */
1434                                restart_timer = 1;
1435
1436                                if (!tchunk->tsn_gap_acked) {
1437                                        /*
1438                                         * SFR-CACC algorithm:
1439                                         * 2) If the SACK contains gap acks
1440                                         * and the flag CHANGEOVER_ACTIVE is
1441                                         * set the receiver of the SACK MUST
1442                                         * take the following action:
1443                                         *
1444                                         * B) For each TSN t being acked that
1445                                         * has not been acked in any SACK so
1446                                         * far, set cacc_saw_newack to 1 for
1447                                         * the destination that the TSN was
1448                                         * sent to.
1449                                         */
1450                                        if (transport &&
1451                                            sack->num_gap_ack_blocks &&
1452                                            q->asoc->peer.primary_path->cacc.
1453                                            changeover_active)
1454                                                transport->cacc.cacc_saw_newack
1455                                                        = 1;
1456                                }
1457
1458                                list_add_tail(&tchunk->transmitted_list,
1459                                              &q->sacked);
1460                        } else {
1461                                /* RFC2960 7.2.4, sctpimpguide-05 2.8.2
1462                                 * M2) Each time a SACK arrives reporting
1463                                 * 'Stray DATA chunk(s)' record the highest TSN
1464                                 * reported as newly acknowledged, call this
1465                                 * value 'HighestTSNinSack'. A newly
1466                                 * acknowledged DATA chunk is one not
1467                                 * previously acknowledged in a SACK.
1468                                 *
1469                                 * When the SCTP sender of data receives a SACK
1470                                 * chunk that acknowledges, for the first time,
1471                                 * the receipt of a DATA chunk, all the still
1472                                 * unacknowledged DATA chunks whose TSN is
1473                                 * older than that newly acknowledged DATA
1474                                 * chunk, are qualified as 'Stray DATA chunks'.
1475                                 */
1476                                list_add_tail(lchunk, &tlist);
1477                        }
1478
1479#if SCTP_DEBUG
1480                        switch (dbg_prt_state) {
1481                        case 0: /* last TSN was ACKed */
1482                                if (dbg_last_ack_tsn + 1 == tsn) {
1483                                        /* This TSN belongs to the
1484                                         * current ACK range.
1485                                         */
1486                                        break;
1487                                }
1488
1489                                if (dbg_last_ack_tsn != dbg_ack_tsn) {
1490                                        /* Display the end of the
1491                                         * current range.
1492                                         */
1493                                        SCTP_DEBUG_PRINTK_CONT("-%08x",
1494                                                               dbg_last_ack_tsn);
1495                                }
1496
1497                                /* Start a new range.  */
1498                                SCTP_DEBUG_PRINTK_CONT(",%08x", tsn);
1499                                dbg_ack_tsn = tsn;
1500                                break;
1501
1502                        case 1: /* The last TSN was NOT ACKed. */
1503                                if (dbg_last_kept_tsn != dbg_kept_tsn) {
1504                                        /* Display the end of current range. */
1505                                        SCTP_DEBUG_PRINTK_CONT("-%08x",
1506                                                               dbg_last_kept_tsn);
1507                                }
1508
1509                                SCTP_DEBUG_PRINTK_CONT("\n");
1510
1511                                /* FALL THROUGH... */
1512                        default:
1513                                /* This is the first-ever TSN we examined.  */
1514                                /* Start a new range of ACK-ed TSNs.  */
1515                                SCTP_DEBUG_PRINTK("ACKed: %08x", tsn);
1516                                dbg_prt_state = 0;
1517                                dbg_ack_tsn = tsn;
1518                        }
1519
1520                        dbg_last_ack_tsn = tsn;
1521#endif /* SCTP_DEBUG */
1522
1523                } else {
1524                        if (tchunk->tsn_gap_acked) {
1525                                SCTP_DEBUG_PRINTK("%s: Receiver reneged on "
1526                                                  "data TSN: 0x%x\n",
1527                                                  __func__,
1528                                                  tsn);
1529                                tchunk->tsn_gap_acked = 0;
1530
1531                                if (tchunk->transport)
1532                                        bytes_acked -= sctp_data_size(tchunk);
1533
1534                                /* RFC 2960 6.3.2 Retransmission Timer Rules
1535                                 *
1536                                 * R4) Whenever a SACK is received missing a
1537                                 * TSN that was previously acknowledged via a
1538                                 * Gap Ack Block, start T3-rtx for the
1539                                 * destination address to which the DATA
1540                                 * chunk was originally
1541                                 * transmitted if it is not already running.
1542                                 */
1543                                restart_timer = 1;
1544                        }
1545
1546                        list_add_tail(lchunk, &tlist);
1547
1548#if SCTP_DEBUG
1549                        /* See the above comments on ACK-ed TSNs. */
1550                        switch (dbg_prt_state) {
1551                        case 1:
1552                                if (dbg_last_kept_tsn + 1 == tsn)
1553                                        break;
1554
1555                                if (dbg_last_kept_tsn != dbg_kept_tsn)
1556                                        SCTP_DEBUG_PRINTK_CONT("-%08x",
1557                                                               dbg_last_kept_tsn);
1558
1559                                SCTP_DEBUG_PRINTK_CONT(",%08x", tsn);
1560                                dbg_kept_tsn = tsn;
1561                                break;
1562
1563                        case 0:
1564                                if (dbg_last_ack_tsn != dbg_ack_tsn)
1565                                        SCTP_DEBUG_PRINTK_CONT("-%08x",
1566                                                               dbg_last_ack_tsn);
1567                                SCTP_DEBUG_PRINTK_CONT("\n");
1568
1569                                /* FALL THROUGH... */
1570                        default:
1571                                SCTP_DEBUG_PRINTK("KEPT: %08x",tsn);
1572                                dbg_prt_state = 1;
1573                                dbg_kept_tsn = tsn;
1574                        }
1575
1576                        dbg_last_kept_tsn = tsn;
1577#endif /* SCTP_DEBUG */
1578                }
1579        }
1580
1581#if SCTP_DEBUG
1582        /* Finish off the last range, displaying its ending TSN.  */
1583        switch (dbg_prt_state) {
1584        case 0:
1585                if (dbg_last_ack_tsn != dbg_ack_tsn) {
1586                        SCTP_DEBUG_PRINTK_CONT("-%08x\n", dbg_last_ack_tsn);
1587                } else {
1588                        SCTP_DEBUG_PRINTK_CONT("\n");
1589                }
1590        break;
1591
1592        case 1:
1593                if (dbg_last_kept_tsn != dbg_kept_tsn) {
1594                        SCTP_DEBUG_PRINTK_CONT("-%08x\n", dbg_last_kept_tsn);
1595                } else {
1596                        SCTP_DEBUG_PRINTK_CONT("\n");
1597                }
1598        }
1599#endif /* SCTP_DEBUG */
1600        if (transport) {
1601                if (bytes_acked) {
1602                        struct sctp_association *asoc = transport->asoc;
1603
1604                        /* We may have counted DATA that was migrated
1605                         * to this transport due to DEL-IP operation.
1606                         * Subtract those bytes, since the were never
1607                         * send on this transport and shouldn't be
1608                         * credited to this transport.
1609                         */
1610                        bytes_acked -= migrate_bytes;
1611
1612                        /* 8.2. When an outstanding TSN is acknowledged,
1613                         * the endpoint shall clear the error counter of
1614                         * the destination transport address to which the
1615                         * DATA chunk was last sent.
1616                         * The association's overall error counter is
1617                         * also cleared.
1618                         */
1619                        transport->error_count = 0;
1620                        transport->asoc->overall_error_count = 0;
1621
1622                        /*
1623                         * While in SHUTDOWN PENDING, we may have started
1624                         * the T5 shutdown guard timer after reaching the
1625                         * retransmission limit. Stop that timer as soon
1626                         * as the receiver acknowledged any data.
1627                         */
1628                        if (asoc->state == SCTP_STATE_SHUTDOWN_PENDING &&
1629                            del_timer(&asoc->timers
1630                                [SCTP_EVENT_TIMEOUT_T5_SHUTDOWN_GUARD]))
1631                                        sctp_association_put(asoc);
1632
1633                        /* Mark the destination transport address as
1634                         * active if it is not so marked.
1635                         */
1636                        if ((transport->state == SCTP_INACTIVE) ||
1637                            (transport->state == SCTP_UNCONFIRMED)) {
1638                                sctp_assoc_control_transport(
1639                                        transport->asoc,
1640                                        transport,
1641                                        SCTP_TRANSPORT_UP,
1642                                        SCTP_RECEIVED_SACK);
1643                        }
1644
1645                        sctp_transport_raise_cwnd(transport, sack_ctsn,
1646                                                  bytes_acked);
1647
1648                        transport->flight_size -= bytes_acked;
1649                        if (transport->flight_size == 0)
1650                                transport->partial_bytes_acked = 0;
1651                        q->outstanding_bytes -= bytes_acked + migrate_bytes;
1652                } else {
1653                        /* RFC 2960 6.1, sctpimpguide-06 2.15.2
1654                         * When a sender is doing zero window probing, it
1655                         * should not timeout the association if it continues
1656                         * to receive new packets from the receiver. The
1657                         * reason is that the receiver MAY keep its window
1658                         * closed for an indefinite time.
1659                         * A sender is doing zero window probing when the
1660                         * receiver's advertised window is zero, and there is
1661                         * only one data chunk in flight to the receiver.
1662                         *
1663                         * Allow the association to timeout while in SHUTDOWN
1664                         * PENDING or SHUTDOWN RECEIVED in case the receiver
1665                         * stays in zero window mode forever.
1666                         */
1667                        if (!q->asoc->peer.rwnd &&
1668                            !list_empty(&tlist) &&
1669                            (sack_ctsn+2 == q->asoc->next_tsn) &&
1670                            q->asoc->state < SCTP_STATE_SHUTDOWN_PENDING) {
1671                                SCTP_DEBUG_PRINTK("%s: SACK received for zero "
1672                                                  "window probe: %u\n",
1673                                                  __func__, sack_ctsn);
1674                                q->asoc->overall_error_count = 0;
1675                                transport->error_count = 0;
1676                        }
1677                }
1678
1679                /* RFC 2960 6.3.2 Retransmission Timer Rules
1680                 *
1681                 * R2) Whenever all outstanding data sent to an address have
1682                 * been acknowledged, turn off the T3-rtx timer of that
1683                 * address.
1684                 */
1685                if (!transport->flight_size) {
1686                        if (timer_pending(&transport->T3_rtx_timer) &&
1687                            del_timer(&transport->T3_rtx_timer)) {
1688                                sctp_transport_put(transport);
1689                        }
1690                } else if (restart_timer) {
1691                        if (!mod_timer(&transport->T3_rtx_timer,
1692                                       jiffies + transport->rto))
1693                                sctp_transport_hold(transport);
1694                }
1695        }
1696
1697        list_splice(&tlist, transmitted_queue);
1698}
1699
1700/* Mark chunks as missing and consequently may get retransmitted. */
1701static void sctp_mark_missing(struct sctp_outq *q,
1702                              struct list_head *transmitted_queue,
1703                              struct sctp_transport *transport,
1704                              __u32 highest_new_tsn_in_sack,
1705                              int count_of_newacks)
1706{
1707        struct sctp_chunk *chunk;
1708        __u32 tsn;
1709        char do_fast_retransmit = 0;
1710        struct sctp_association *asoc = q->asoc;
1711        struct sctp_transport *primary = asoc->peer.primary_path;
1712
1713        list_for_each_entry(chunk, transmitted_queue, transmitted_list) {
1714
1715                tsn = ntohl(chunk->subh.data_hdr->tsn);
1716
1717                /* RFC 2960 7.2.4, sctpimpguide-05 2.8.2 M3) Examine all
1718                 * 'Unacknowledged TSN's', if the TSN number of an
1719                 * 'Unacknowledged TSN' is smaller than the 'HighestTSNinSack'
1720                 * value, increment the 'TSN.Missing.Report' count on that
1721                 * chunk if it has NOT been fast retransmitted or marked for
1722                 * fast retransmit already.
1723                 */
1724                if (chunk->fast_retransmit == SCTP_CAN_FRTX &&
1725                    !chunk->tsn_gap_acked &&
1726                    TSN_lt(tsn, highest_new_tsn_in_sack)) {
1727
1728                        /* SFR-CACC may require us to skip marking
1729                         * this chunk as missing.
1730                         */
1731                        if (!transport || !sctp_cacc_skip(primary,
1732                                                chunk->transport,
1733                                                count_of_newacks, tsn)) {
1734                                chunk->tsn_missing_report++;
1735
1736                                SCTP_DEBUG_PRINTK(
1737                                        "%s: TSN 0x%x missing counter: %d\n",
1738                                        __func__, tsn,
1739                                        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                SCTP_DEBUG_PRINTK("%s: transport: %p, cwnd: %d, "
1760                                  "ssthresh: %d, flight_size: %d, pba: %d\n",
1761                                  __func__, transport, transport->cwnd,
1762                                  transport->ssthresh, transport->flight_size,
1763                                  transport->partial_bytes_acked);
1764        }
1765}
1766
1767/* Is the given TSN acked by this packet?  */
1768static int sctp_acked(struct sctp_sackhdr *sack, __u32 tsn)
1769{
1770        int i;
1771        sctp_sack_variable_t *frags;
1772        __u16 gap;
1773        __u32 ctsn = ntohl(sack->cum_tsn_ack);
1774
1775        if (TSN_lte(tsn, ctsn))
1776                goto pass;
1777
1778        /* 3.3.4 Selective Acknowledgement (SACK) (3):
1779         *
1780         * Gap Ack Blocks:
1781         *  These fields contain the Gap Ack Blocks. They are repeated
1782         *  for each Gap Ack Block up to the number of Gap Ack Blocks
1783         *  defined in the Number of Gap Ack Blocks field. All DATA
1784         *  chunks with TSNs greater than or equal to (Cumulative TSN
1785         *  Ack + Gap Ack Block Start) and less than or equal to
1786         *  (Cumulative TSN Ack + Gap Ack Block End) of each Gap Ack
1787         *  Block are assumed to have been received correctly.
1788         */
1789
1790        frags = sack->variable;
1791        gap = tsn - ctsn;
1792        for (i = 0; i < ntohs(sack->num_gap_ack_blocks); ++i) {
1793                if (TSN_lte(ntohs(frags[i].gab.start), gap) &&
1794                    TSN_lte(gap, ntohs(frags[i].gab.end)))
1795                        goto pass;
1796        }
1797
1798        return 0;
1799pass:
1800        return 1;
1801}
1802
1803static 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. */
1816static 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(SCTP_MIB_OUTCTRLCHUNKS);
1918        }
1919}
1920
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