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                                   union sctp_addr *saddr,
  67                                   struct sctp_sackhdr *sack,
  68                                   __u32 *highest_new_tsn);
  69
  70static void sctp_mark_missing(struct sctp_outq *q,
  71                              struct list_head *transmitted_queue,
  72                              struct sctp_transport *transport,
  73                              __u32 highest_new_tsn,
  74                              int count_of_newacks);
  75
  76static void sctp_generate_fwdtsn(struct sctp_outq *q, __u32 sack_ctsn);
  77
  78static int sctp_outq_flush(struct sctp_outq *q, int rtx_timeout);
  79
  80/* Add data to the front of the queue. */
  81static inline void sctp_outq_head_data(struct sctp_outq *q,
  82                                        struct sctp_chunk *ch)
  83{
  84        list_add(&ch->list, &q->out_chunk_list);
  85        q->out_qlen += ch->skb->len;
  86}
  87
  88/* Take data from the front of the queue. */
  89static inline struct sctp_chunk *sctp_outq_dequeue_data(struct sctp_outq *q)
  90{
  91        struct sctp_chunk *ch = NULL;
  92
  93        if (!list_empty(&q->out_chunk_list)) {
  94                struct list_head *entry = q->out_chunk_list.next;
  95
  96                ch = list_entry(entry, struct sctp_chunk, list);
  97                list_del_init(entry);
  98                q->out_qlen -= ch->skb->len;
  99        }
 100        return ch;
 101}
 102/* Add data chunk to the end of the queue. */
 103static inline void sctp_outq_tail_data(struct sctp_outq *q,
 104                                       struct sctp_chunk *ch)
 105{
 106        list_add_tail(&ch->list, &q->out_chunk_list);
 107        q->out_qlen += ch->skb->len;
 108}
 109
 110/*
 111 * SFR-CACC algorithm:
 112 * D) If count_of_newacks is greater than or equal to 2
 113 * and t was not sent to the current primary then the
 114 * sender MUST NOT increment missing report count for t.
 115 */
 116static inline int sctp_cacc_skip_3_1_d(struct sctp_transport *primary,
 117                                       struct sctp_transport *transport,
 118                                       int count_of_newacks)
 119{
 120        if (count_of_newacks >=2 && transport != primary)
 121                return 1;
 122        return 0;
 123}
 124
 125/*
 126 * SFR-CACC algorithm:
 127 * F) If count_of_newacks is less than 2, let d be the
 128 * destination to which t was sent. If cacc_saw_newack
 129 * is 0 for destination d, then the sender MUST NOT
 130 * increment missing report count for t.
 131 */
 132static inline int sctp_cacc_skip_3_1_f(struct sctp_transport *transport,
 133                                       int count_of_newacks)
 134{
 135        if (count_of_newacks < 2 &&
 136                        (transport && !transport->cacc.cacc_saw_newack))
 137                return 1;
 138        return 0;
 139}
 140
 141/*
 142 * SFR-CACC algorithm:
 143 * 3.1) If CYCLING_CHANGEOVER is 0, the sender SHOULD
 144 * execute steps C, D, F.
 145 *
 146 * C has been implemented in sctp_outq_sack
 147 */
 148static inline int sctp_cacc_skip_3_1(struct sctp_transport *primary,
 149                                     struct sctp_transport *transport,
 150                                     int count_of_newacks)
 151{
 152        if (!primary->cacc.cycling_changeover) {
 153                if (sctp_cacc_skip_3_1_d(primary, transport, count_of_newacks))
 154                        return 1;
 155                if (sctp_cacc_skip_3_1_f(transport, count_of_newacks))
 156                        return 1;
 157                return 0;
 158        }
 159        return 0;
 160}
 161
 162/*
 163 * SFR-CACC algorithm:
 164 * 3.2) Else if CYCLING_CHANGEOVER is 1, and t is less
 165 * than next_tsn_at_change of the current primary, then
 166 * the sender MUST NOT increment missing report count
 167 * for t.
 168 */
 169static inline int sctp_cacc_skip_3_2(struct sctp_transport *primary, __u32 tsn)
 170{
 171        if (primary->cacc.cycling_changeover &&
 172            TSN_lt(tsn, primary->cacc.next_tsn_at_change))
 173                return 1;
 174        return 0;
 175}
 176
 177/*
 178 * SFR-CACC algorithm:
 179 * 3) If the missing report count for TSN t is to be
 180 * incremented according to [RFC2960] and
 181 * [SCTP_STEWART-2002], and CHANGEOVER_ACTIVE is set,
 182 * then the sender MUST further execute steps 3.1 and
 183 * 3.2 to determine if the missing report count for
 184 * TSN t SHOULD NOT be incremented.
 185 *
 186 * 3.3) If 3.1 and 3.2 do not dictate that the missing
 187 * report count for t should not be incremented, then
 188 * the sender SHOULD increment missing report count for
 189 * t (according to [RFC2960] and [SCTP_STEWART_2002]).
 190 */
 191static inline int sctp_cacc_skip(struct sctp_transport *primary,
 192                                 struct sctp_transport *transport,
 193                                 int count_of_newacks,
 194                                 __u32 tsn)
 195{
 196        if (primary->cacc.changeover_active &&
 197            (sctp_cacc_skip_3_1(primary, transport, count_of_newacks) ||
 198             sctp_cacc_skip_3_2(primary, tsn)))
 199                return 1;
 200        return 0;
 201}
 202
 203/* Initialize an existing sctp_outq.  This does the boring stuff.
 204 * You still need to define handlers if you really want to DO
 205 * something with this structure...
 206 */
 207void sctp_outq_init(struct sctp_association *asoc, struct sctp_outq *q)
 208{
 209        q->asoc = asoc;
 210        INIT_LIST_HEAD(&q->out_chunk_list);
 211        INIT_LIST_HEAD(&q->control_chunk_list);
 212        INIT_LIST_HEAD(&q->retransmit);
 213        INIT_LIST_HEAD(&q->sacked);
 214        INIT_LIST_HEAD(&q->abandoned);
 215
 216        q->fast_rtx = 0;
 217        q->outstanding_bytes = 0;
 218        q->empty = 1;
 219        q->cork  = 0;
 220
 221        q->malloced = 0;
 222        q->out_qlen = 0;
 223}
 224
 225/* Free the outqueue structure and any related pending chunks.
 226 */
 227static void __sctp_outq_teardown(struct sctp_outq *q)
 228{
 229        struct sctp_transport *transport;
 230        struct list_head *lchunk, *temp;
 231        struct sctp_chunk *chunk, *tmp;
 232
 233        /* Throw away unacknowledged chunks. */
 234        list_for_each_entry(transport, &q->asoc->peer.transport_addr_list,
 235                        transports) {
 236                while ((lchunk = sctp_list_dequeue(&transport->transmitted)) != NULL) {
 237                        chunk = list_entry(lchunk, struct sctp_chunk,
 238                                           transmitted_list);
 239                        /* Mark as part of a failed message. */
 240                        sctp_chunk_fail(chunk, q->error);
 241                        sctp_chunk_free(chunk);
 242                }
 243        }
 244
 245        /* Throw away chunks that have been gap ACKed.  */
 246        list_for_each_safe(lchunk, temp, &q->sacked) {
 247                list_del_init(lchunk);
 248                chunk = list_entry(lchunk, struct sctp_chunk,
 249                                   transmitted_list);
 250                sctp_chunk_fail(chunk, q->error);
 251                sctp_chunk_free(chunk);
 252        }
 253
 254        /* Throw away any chunks in the retransmit queue. */
 255        list_for_each_safe(lchunk, temp, &q->retransmit) {
 256                list_del_init(lchunk);
 257                chunk = list_entry(lchunk, struct sctp_chunk,
 258                                   transmitted_list);
 259                sctp_chunk_fail(chunk, q->error);
 260                sctp_chunk_free(chunk);
 261        }
 262
 263        /* Throw away any chunks that are in the abandoned queue. */
 264        list_for_each_safe(lchunk, temp, &q->abandoned) {
 265                list_del_init(lchunk);
 266                chunk = list_entry(lchunk, struct sctp_chunk,
 267                                   transmitted_list);
 268                sctp_chunk_fail(chunk, q->error);
 269                sctp_chunk_free(chunk);
 270        }
 271
 272        /* Throw away any leftover data chunks. */
 273        while ((chunk = sctp_outq_dequeue_data(q)) != NULL) {
 274
 275                /* Mark as send failure. */
 276                sctp_chunk_fail(chunk, q->error);
 277                sctp_chunk_free(chunk);
 278        }
 279
 280        /* Throw away any leftover control chunks. */
 281        list_for_each_entry_safe(chunk, tmp, &q->control_chunk_list, list) {
 282                list_del_init(&chunk->list);
 283                sctp_chunk_free(chunk);
 284        }
 285}
 286
 287void sctp_outq_teardown(struct sctp_outq *q)
 288{
 289        __sctp_outq_teardown(q);
 290        sctp_outq_init(q->asoc, q);
 291}
 292
 293/* Free the outqueue structure and any related pending chunks.  */
 294void sctp_outq_free(struct sctp_outq *q)
 295{
 296        /* Throw away leftover chunks. */
 297        __sctp_outq_teardown(q);
 298
 299        /* If we were kmalloc()'d, free the memory.  */
 300        if (q->malloced)
 301                kfree(q);
 302}
 303
 304/* Put a new chunk in an sctp_outq.  */
 305int sctp_outq_tail(struct sctp_outq *q, struct sctp_chunk *chunk)
 306{
 307        struct net *net = sock_net(q->asoc->base.sk);
 308        int error = 0;
 309
 310        SCTP_DEBUG_PRINTK("sctp_outq_tail(%p, %p[%s])\n",
 311                          q, chunk, chunk && chunk->chunk_hdr ?
 312                          sctp_cname(SCTP_ST_CHUNK(chunk->chunk_hdr->type))
 313                          : "Illegal Chunk");
 314
 315        /* If it is data, queue it up, otherwise, send it
 316         * immediately.
 317         */
 318        if (sctp_chunk_is_data(chunk)) {
 319                /* Is it OK to queue data chunks?  */
 320                /* From 9. Termination of Association
 321                 *
 322                 * When either endpoint performs a shutdown, the
 323                 * association on each peer will stop accepting new
 324                 * data from its user and only deliver data in queue
 325                 * at the time of sending or receiving the SHUTDOWN
 326                 * chunk.
 327                 */
 328                switch (q->asoc->state) {
 329                case SCTP_STATE_CLOSED:
 330                case SCTP_STATE_SHUTDOWN_PENDING:
 331                case SCTP_STATE_SHUTDOWN_SENT:
 332                case SCTP_STATE_SHUTDOWN_RECEIVED:
 333                case SCTP_STATE_SHUTDOWN_ACK_SENT:
 334                        /* Cannot send after transport endpoint shutdown */
 335                        error = -ESHUTDOWN;
 336                        break;
 337
 338                default:
 339                        SCTP_DEBUG_PRINTK("outqueueing (%p, %p[%s])\n",
 340                          q, chunk, chunk && chunk->chunk_hdr ?
 341                          sctp_cname(SCTP_ST_CHUNK(chunk->chunk_hdr->type))
 342                          : "Illegal Chunk");
 343
 344                        sctp_outq_tail_data(q, chunk);
 345                        if (chunk->chunk_hdr->flags & SCTP_DATA_UNORDERED)
 346                                SCTP_INC_STATS(net, SCTP_MIB_OUTUNORDERCHUNKS);
 347                        else
 348                                SCTP_INC_STATS(net, SCTP_MIB_OUTORDERCHUNKS);
 349                        q->empty = 0;
 350                        break;
 351                }
 352        } else {
 353                list_add_tail(&chunk->list, &q->control_chunk_list);
 354                SCTP_INC_STATS(net, SCTP_MIB_OUTCTRLCHUNKS);
 355        }
 356
 357        if (error < 0)
 358                return error;
 359
 360        if (!q->cork)
 361                error = sctp_outq_flush(q, 0);
 362
 363        return error;
 364}
 365
 366/* Insert a chunk into the sorted list based on the TSNs.  The retransmit list
 367 * and the abandoned list are in ascending order.
 368 */
 369static void sctp_insert_list(struct list_head *head, struct list_head *new)
 370{
 371        struct list_head *pos;
 372        struct sctp_chunk *nchunk, *lchunk;
 373        __u32 ntsn, ltsn;
 374        int done = 0;
 375
 376        nchunk = list_entry(new, struct sctp_chunk, transmitted_list);
 377        ntsn = ntohl(nchunk->subh.data_hdr->tsn);
 378
 379        list_for_each(pos, head) {
 380                lchunk = list_entry(pos, struct sctp_chunk, transmitted_list);
 381                ltsn = ntohl(lchunk->subh.data_hdr->tsn);
 382                if (TSN_lt(ntsn, ltsn)) {
 383                        list_add(new, pos->prev);
 384                        done = 1;
 385                        break;
 386                }
 387        }
 388        if (!done)
 389                list_add_tail(new, head);
 390}
 391
 392/* Mark all the eligible packets on a transport for retransmission.  */
 393void sctp_retransmit_mark(struct sctp_outq *q,
 394                          struct sctp_transport *transport,
 395                          __u8 reason)
 396{
 397        struct list_head *lchunk, *ltemp;
 398        struct sctp_chunk *chunk;
 399
 400        /* Walk through the specified transmitted queue.  */
 401        list_for_each_safe(lchunk, ltemp, &transport->transmitted) {
 402                chunk = list_entry(lchunk, struct sctp_chunk,
 403                                   transmitted_list);
 404
 405                /* If the chunk is abandoned, move it to abandoned list. */
 406                if (sctp_chunk_abandoned(chunk)) {
 407                        list_del_init(lchunk);
 408                        sctp_insert_list(&q->abandoned, lchunk);
 409
 410                        /* If this chunk has not been previousely acked,
 411                         * stop considering it 'outstanding'.  Our peer
 412                         * will most likely never see it since it will
 413                         * not be retransmitted
 414                         */
 415                        if (!chunk->tsn_gap_acked) {
 416                                if (chunk->transport)
 417                                        chunk->transport->flight_size -=
 418                                                        sctp_data_size(chunk);
 419                                q->outstanding_bytes -= sctp_data_size(chunk);
 420                                q->asoc->peer.rwnd += sctp_data_size(chunk);
 421                        }
 422                        continue;
 423                }
 424
 425                /* If we are doing  retransmission due to a timeout or pmtu
 426                 * discovery, only the  chunks that are not yet acked should
 427                 * be added to the retransmit queue.
 428                 */
 429                if ((reason == SCTP_RTXR_FAST_RTX  &&
 430                            (chunk->fast_retransmit == SCTP_NEED_FRTX)) ||
 431                    (reason != SCTP_RTXR_FAST_RTX  && !chunk->tsn_gap_acked)) {
 432                        /* RFC 2960 6.2.1 Processing a Received SACK
 433                         *
 434                         * C) Any time a DATA chunk is marked for
 435                         * retransmission (via either T3-rtx timer expiration
 436                         * (Section 6.3.3) or via fast retransmit
 437                         * (Section 7.2.4)), add the data size of those
 438                         * chunks to the rwnd.
 439                         */
 440                        q->asoc->peer.rwnd += sctp_data_size(chunk);
 441                        q->outstanding_bytes -= sctp_data_size(chunk);
 442                        if (chunk->transport)
 443                                transport->flight_size -= sctp_data_size(chunk);
 444
 445                        /* sctpimpguide-05 Section 2.8.2
 446                         * M5) If a T3-rtx timer expires, the
 447                         * 'TSN.Missing.Report' of all affected TSNs is set
 448                         * to 0.
 449                         */
 450                        chunk->tsn_missing_report = 0;
 451
 452                        /* If a chunk that is being used for RTT measurement
 453                         * has to be retransmitted, we cannot use this chunk
 454                         * anymore for RTT measurements. Reset rto_pending so
 455                         * that a new RTT measurement is started when a new
 456                         * data chunk is sent.
 457                         */
 458                        if (chunk->rtt_in_progress) {
 459                                chunk->rtt_in_progress = 0;
 460                                transport->rto_pending = 0;
 461                        }
 462
 463                        /* Move the chunk to the retransmit queue. The chunks
 464                         * on the retransmit queue are always kept in order.
 465                         */
 466                        list_del_init(lchunk);
 467                        sctp_insert_list(&q->retransmit, lchunk);
 468                }
 469        }
 470
 471        SCTP_DEBUG_PRINTK("%s: transport: %p, reason: %d, "
 472                          "cwnd: %d, ssthresh: %d, flight_size: %d, "
 473                          "pba: %d\n", __func__,
 474                          transport, reason,
 475                          transport->cwnd, transport->ssthresh,
 476                          transport->flight_size,
 477                          transport->partial_bytes_acked);
 478
 479}
 480
 481/* Mark all the eligible packets on a transport for retransmission and force
 482 * one packet out.
 483 */
 484void sctp_retransmit(struct sctp_outq *q, struct sctp_transport *transport,
 485                     sctp_retransmit_reason_t reason)
 486{
 487        struct net *net = sock_net(q->asoc->base.sk);
 488        int error = 0;
 489
 490        switch(reason) {
 491        case SCTP_RTXR_T3_RTX:
 492                SCTP_INC_STATS(net, SCTP_MIB_T3_RETRANSMITS);
 493                sctp_transport_lower_cwnd(transport, SCTP_LOWER_CWND_T3_RTX);
 494                /* Update the retran path if the T3-rtx timer has expired for
 495                 * the current retran path.
 496                 */
 497                if (transport == transport->asoc->peer.retran_path)
 498                        sctp_assoc_update_retran_path(transport->asoc);
 499                transport->asoc->rtx_data_chunks +=
 500                        transport->asoc->unack_data;
 501                break;
 502        case SCTP_RTXR_FAST_RTX:
 503                SCTP_INC_STATS(net, SCTP_MIB_FAST_RETRANSMITS);
 504                sctp_transport_lower_cwnd(transport, SCTP_LOWER_CWND_FAST_RTX);
 505                q->fast_rtx = 1;
 506                break;
 507        case SCTP_RTXR_PMTUD:
 508                SCTP_INC_STATS(net, SCTP_MIB_PMTUD_RETRANSMITS);
 509                break;
 510        case SCTP_RTXR_T1_RTX:
 511                SCTP_INC_STATS(net, SCTP_MIB_T1_RETRANSMITS);
 512                transport->asoc->init_retries++;
 513                break;
 514        default:
 515                BUG();
 516        }
 517
 518        sctp_retransmit_mark(q, transport, reason);
 519
 520        /* PR-SCTP A5) Any time the T3-rtx timer expires, on any destination,
 521         * the sender SHOULD try to advance the "Advanced.Peer.Ack.Point" by
 522         * following the procedures outlined in C1 - C5.
 523         */
 524        if (reason == SCTP_RTXR_T3_RTX)
 525                sctp_generate_fwdtsn(q, q->asoc->ctsn_ack_point);
 526
 527        /* Flush the queues only on timeout, since fast_rtx is only
 528         * triggered during sack processing and the queue
 529         * will be flushed at the end.
 530         */
 531        if (reason != SCTP_RTXR_FAST_RTX)
 532                error = sctp_outq_flush(q, /* rtx_timeout */ 1);
 533
 534        if (error)
 535                q->asoc->base.sk->sk_err = -error;
 536}
 537
 538/*
 539 * Transmit DATA chunks on the retransmit queue.  Upon return from
 540 * sctp_outq_flush_rtx() the packet 'pkt' may contain chunks which
 541 * need to be transmitted by the caller.
 542 * We assume that pkt->transport has already been set.
 543 *
 544 * The return value is a normal kernel error return value.
 545 */
 546static int sctp_outq_flush_rtx(struct sctp_outq *q, struct sctp_packet *pkt,
 547                               int rtx_timeout, int *start_timer)
 548{
 549        struct list_head *lqueue;
 550        struct sctp_transport *transport = pkt->transport;
 551        sctp_xmit_t status;
 552        struct sctp_chunk *chunk, *chunk1;
 553        int fast_rtx;
 554        int error = 0;
 555        int timer = 0;
 556        int done = 0;
 557
 558        lqueue = &q->retransmit;
 559        fast_rtx = q->fast_rtx;
 560
 561        /* This loop handles time-out retransmissions, fast retransmissions,
 562         * and retransmissions due to opening of whindow.
 563         *
 564         * RFC 2960 6.3.3 Handle T3-rtx Expiration
 565         *
 566         * E3) Determine how many of the earliest (i.e., lowest TSN)
 567         * outstanding DATA chunks for the address for which the
 568         * T3-rtx has expired will fit into a single packet, subject
 569         * to the MTU constraint for the path corresponding to the
 570         * destination transport address to which the retransmission
 571         * is being sent (this may be different from the address for
 572         * which the timer expires [see Section 6.4]). Call this value
 573         * K. Bundle and retransmit those K DATA chunks in a single
 574         * packet to the destination endpoint.
 575         *
 576         * [Just to be painfully clear, if we are retransmitting
 577         * because a timeout just happened, we should send only ONE
 578         * packet of retransmitted data.]
 579         *
 580         * For fast retransmissions we also send only ONE packet.  However,
 581         * if we are just flushing the queue due to open window, we'll
 582         * try to send as much as possible.
 583         */
 584        list_for_each_entry_safe(chunk, chunk1, lqueue, transmitted_list) {
 585                /* If the chunk is abandoned, move it to abandoned list. */
 586                if (sctp_chunk_abandoned(chunk)) {
 587                        list_del_init(&chunk->transmitted_list);
 588                        sctp_insert_list(&q->abandoned,
 589                                         &chunk->transmitted_list);
 590                        continue;
 591                }
 592
 593                /* Make sure that Gap Acked TSNs are not retransmitted.  A
 594                 * simple approach is just to move such TSNs out of the
 595                 * way and into a 'transmitted' queue and skip to the
 596                 * next chunk.
 597                 */
 598                if (chunk->tsn_gap_acked) {
 599                        list_move_tail(&chunk->transmitted_list,
 600                                       &transport->transmitted);
 601                        continue;
 602                }
 603
 604                /* If we are doing fast retransmit, ignore non-fast_rtransmit
 605                 * chunks
 606                 */
 607                if (fast_rtx && !chunk->fast_retransmit)
 608                        continue;
 609
 610redo:
 611                /* Attempt to append this chunk to the packet. */
 612                status = sctp_packet_append_chunk(pkt, chunk);
 613
 614                switch (status) {
 615                case SCTP_XMIT_PMTU_FULL:
 616                        if (!pkt->has_data && !pkt->has_cookie_echo) {
 617                                /* If this packet did not contain DATA then
 618                                 * retransmission did not happen, so do it
 619                                 * again.  We'll ignore the error here since
 620                                 * control chunks are already freed so there
 621                                 * is nothing we can do.
 622                                 */
 623                                sctp_packet_transmit(pkt);
 624                                goto redo;
 625                        }
 626
 627                        /* Send this packet.  */
 628                        error = sctp_packet_transmit(pkt);
 629
 630                        /* If we are retransmitting, we should only
 631                         * send a single packet.
 632                         * Otherwise, try appending this chunk again.
 633                         */
 634                        if (rtx_timeout || fast_rtx)
 635                                done = 1;
 636                        else
 637                                goto redo;
 638
 639                        /* Bundle next chunk in the next round.  */
 640                        break;
 641
 642                case SCTP_XMIT_RWND_FULL:
 643                        /* Send this packet. */
 644                        error = sctp_packet_transmit(pkt);
 645
 646                        /* Stop sending DATA as there is no more room
 647                         * at the receiver.
 648                         */
 649                        done = 1;
 650                        break;
 651
 652                case SCTP_XMIT_NAGLE_DELAY:
 653                        /* Send this packet. */
 654                        error = sctp_packet_transmit(pkt);
 655
 656                        /* Stop sending DATA because of nagle delay. */
 657                        done = 1;
 658                        break;
 659
 660                default:
 661                        /* The append was successful, so add this chunk to
 662                         * the transmitted list.
 663                         */
 664                        list_move_tail(&chunk->transmitted_list,
 665                                       &transport->transmitted);
 666
 667                        /* Mark the chunk as ineligible for fast retransmit
 668                         * after it is retransmitted.
 669                         */
 670                        if (chunk->fast_retransmit == SCTP_NEED_FRTX)
 671                                chunk->fast_retransmit = SCTP_DONT_FRTX;
 672
 673                        q->empty = 0;
 674                        q->asoc->stats.rtxchunks++;
 675                        break;
 676                }
 677
 678                /* Set the timer if there were no errors */
 679                if (!error && !timer)
 680                        timer = 1;
 681
 682                if (done)
 683                        break;
 684        }
 685
 686        /* If we are here due to a retransmit timeout or a fast
 687         * retransmit and if there are any chunks left in the retransmit
 688         * queue that could not fit in the PMTU sized packet, they need
 689         * to be marked as ineligible for a subsequent fast retransmit.
 690         */
 691        if (rtx_timeout || fast_rtx) {
 692                list_for_each_entry(chunk1, lqueue, transmitted_list) {
 693                        if (chunk1->fast_retransmit == SCTP_NEED_FRTX)
 694                                chunk1->fast_retransmit = SCTP_DONT_FRTX;
 695                }
 696        }
 697
 698        *start_timer = timer;
 699
 700        /* Clear fast retransmit hint */
 701        if (fast_rtx)
 702                q->fast_rtx = 0;
 703
 704        return error;
 705}
 706
 707/* Cork the outqueue so queued chunks are really queued. */
 708int sctp_outq_uncork(struct sctp_outq *q)
 709{
 710        int error = 0;
 711        if (q->cork)
 712                q->cork = 0;
 713        error = sctp_outq_flush(q, 0);
 714        return error;
 715}
 716
 717
 718/*
 719 * Try to flush an outqueue.
 720 *
 721 * Description: Send everything in q which we legally can, subject to
 722 * congestion limitations.
 723 * * Note: This function can be called from multiple contexts so appropriate
 724 * locking concerns must be made.  Today we use the sock lock to protect
 725 * this function.
 726 */
 727static int sctp_outq_flush(struct sctp_outq *q, int rtx_timeout)
 728{
 729        struct sctp_packet *packet;
 730        struct sctp_packet singleton;
 731        struct sctp_association *asoc = q->asoc;
 732        __u16 sport = asoc->base.bind_addr.port;
 733        __u16 dport = asoc->peer.port;
 734        __u32 vtag = asoc->peer.i.init_tag;
 735        struct sctp_transport *transport = NULL;
 736        struct sctp_transport *new_transport;
 737        struct sctp_chunk *chunk, *tmp;
 738        sctp_xmit_t status;
 739        int error = 0;
 740        int start_timer = 0;
 741        int one_packet = 0;
 742
 743        /* These transports have chunks to send. */
 744        struct list_head transport_list;
 745        struct list_head *ltransport;
 746
 747        INIT_LIST_HEAD(&transport_list);
 748        packet = NULL;
 749
 750        /*
 751         * 6.10 Bundling
 752         *   ...
 753         *   When bundling control chunks with DATA chunks, an
 754         *   endpoint MUST place control chunks first in the outbound
 755         *   SCTP packet.  The transmitter MUST transmit DATA chunks
 756         *   within a SCTP packet in increasing order of TSN.
 757         *   ...
 758         */
 759
 760        list_for_each_entry_safe(chunk, tmp, &q->control_chunk_list, list) {
 761                /* RFC 5061, 5.3
 762                 * F1) This means that until such time as the ASCONF
 763                 * containing the add is acknowledged, the sender MUST
 764                 * NOT use the new IP address as a source for ANY SCTP
 765                 * packet except on carrying an ASCONF Chunk.
 766                 */
 767                if (asoc->src_out_of_asoc_ok &&
 768                    chunk->chunk_hdr->type != SCTP_CID_ASCONF)
 769                        continue;
 770
 771                list_del_init(&chunk->list);
 772
 773                /* Pick the right transport to use. */
 774                new_transport = chunk->transport;
 775
 776                if (!new_transport) {
 777                        /*
 778                         * If we have a prior transport pointer, see if
 779                         * the destination address of the chunk
 780                         * matches the destination address of the
 781                         * current transport.  If not a match, then
 782                         * try to look up the transport with a given
 783                         * destination address.  We do this because
 784                         * after processing ASCONFs, we may have new
 785                         * transports created.
 786                         */
 787                        if (transport &&
 788                            sctp_cmp_addr_exact(&chunk->dest,
 789                                                &transport->ipaddr))
 790                                        new_transport = transport;
 791                        else
 792                                new_transport = sctp_assoc_lookup_paddr(asoc,
 793                                                                &chunk->dest);
 794
 795                        /* if we still don't have a new transport, then
 796                         * use the current active path.
 797                         */
 798                        if (!new_transport)
 799                                new_transport = asoc->peer.active_path;
 800                } else if ((new_transport->state == SCTP_INACTIVE) ||
 801                           (new_transport->state == SCTP_UNCONFIRMED) ||
 802                           (new_transport->state == SCTP_PF)) {
 803                        /* If the chunk is Heartbeat or Heartbeat Ack,
 804                         * send it to chunk->transport, even if it's
 805                         * inactive.
 806                         *
 807                         * 3.3.6 Heartbeat Acknowledgement:
 808                         * ...
 809                         * A HEARTBEAT ACK is always sent to the source IP
 810                         * address of the IP datagram containing the
 811                         * HEARTBEAT chunk to which this ack is responding.
 812                         * ...
 813                         *
 814                         * ASCONF_ACKs also must be sent to the source.
 815                         */
 816                        if (chunk->chunk_hdr->type != SCTP_CID_HEARTBEAT &&
 817                            chunk->chunk_hdr->type != SCTP_CID_HEARTBEAT_ACK &&
 818                            chunk->chunk_hdr->type != SCTP_CID_ASCONF_ACK)
 819                                new_transport = asoc->peer.active_path;
 820                }
 821
 822                /* Are we switching transports?
 823                 * Take care of transport locks.
 824                 */
 825                if (new_transport != transport) {
 826                        transport = new_transport;
 827                        if (list_empty(&transport->send_ready)) {
 828                                list_add_tail(&transport->send_ready,
 829                                              &transport_list);
 830                        }
 831                        packet = &transport->packet;
 832                        sctp_packet_config(packet, vtag,
 833                                           asoc->peer.ecn_capable);
 834                }
 835
 836                switch (chunk->chunk_hdr->type) {
 837                /*
 838                 * 6.10 Bundling
 839                 *   ...
 840                 *   An endpoint MUST NOT bundle INIT, INIT ACK or SHUTDOWN
 841                 *   COMPLETE with any other chunks.  [Send them immediately.]
 842                 */
 843                case SCTP_CID_INIT:
 844                case SCTP_CID_INIT_ACK:
 845                case SCTP_CID_SHUTDOWN_COMPLETE:
 846                        sctp_packet_init(&singleton, transport, sport, dport);
 847                        sctp_packet_config(&singleton, vtag, 0);
 848                        sctp_packet_append_chunk(&singleton, chunk);
 849                        error = sctp_packet_transmit(&singleton);
 850                        if (error < 0)
 851                                return error;
 852                        break;
 853
 854                case SCTP_CID_ABORT:
 855                        if (sctp_test_T_bit(chunk)) {
 856                                packet->vtag = asoc->c.my_vtag;
 857                        }
 858                /* The following chunks are "response" chunks, i.e.
 859                 * they are generated in response to something we
 860                 * received.  If we are sending these, then we can
 861                 * send only 1 packet containing these chunks.
 862                 */
 863                case SCTP_CID_HEARTBEAT_ACK:
 864                case SCTP_CID_SHUTDOWN_ACK:
 865                case SCTP_CID_COOKIE_ACK:
 866                case SCTP_CID_COOKIE_ECHO:
 867                case SCTP_CID_ERROR:
 868                case SCTP_CID_ECN_CWR:
 869                case SCTP_CID_ASCONF_ACK:
 870                        one_packet = 1;
 871                        /* Fall through */
 872
 873                case SCTP_CID_SACK:
 874                case SCTP_CID_HEARTBEAT:
 875                case SCTP_CID_SHUTDOWN:
 876                case SCTP_CID_ECN_ECNE:
 877                case SCTP_CID_ASCONF:
 878                case SCTP_CID_FWD_TSN:
 879                        status = sctp_packet_transmit_chunk(packet, chunk,
 880                                                            one_packet);
 881                        if (status  != SCTP_XMIT_OK) {
 882                                /* put the chunk back */
 883                                list_add(&chunk->list, &q->control_chunk_list);
 884                        } else {
 885                                asoc->stats.octrlchunks++;
 886                                /* PR-SCTP C5) If a FORWARD TSN is sent, the
 887                                 * sender MUST assure that at least one T3-rtx
 888                                 * timer is running.
 889                                 */
 890                                if (chunk->chunk_hdr->type == SCTP_CID_FWD_TSN)
 891                                        sctp_transport_reset_timers(transport);
 892                        }
 893                        break;
 894
 895                default:
 896                        /* We built a chunk with an illegal type! */
 897                        BUG();
 898                }
 899        }
 900
 901        if (q->asoc->src_out_of_asoc_ok)
 902                goto sctp_flush_out;
 903
 904        /* Is it OK to send data chunks?  */
 905        switch (asoc->state) {
 906        case SCTP_STATE_COOKIE_ECHOED:
 907                /* Only allow bundling when this packet has a COOKIE-ECHO
 908                 * chunk.
 909                 */
 910                if (!packet || !packet->has_cookie_echo)
 911                        break;
 912
 913                /* fallthru */
 914        case SCTP_STATE_ESTABLISHED:
 915        case SCTP_STATE_SHUTDOWN_PENDING:
 916        case SCTP_STATE_SHUTDOWN_RECEIVED:
 917                /*
 918                 * RFC 2960 6.1  Transmission of DATA Chunks
 919                 *
 920                 * C) When the time comes for the sender to transmit,
 921                 * before sending new DATA chunks, the sender MUST
 922                 * first transmit any outstanding DATA chunks which
 923                 * are marked for retransmission (limited by the
 924                 * current cwnd).
 925                 */
 926                if (!list_empty(&q->retransmit)) {
 927                        if (asoc->peer.retran_path->state == SCTP_UNCONFIRMED)
 928                                goto sctp_flush_out;
 929                        if (transport == asoc->peer.retran_path)
 930                                goto retran;
 931
 932                        /* Switch transports & prepare the packet.  */
 933
 934                        transport = asoc->peer.retran_path;
 935
 936                        if (list_empty(&transport->send_ready)) {
 937                                list_add_tail(&transport->send_ready,
 938                                              &transport_list);
 939                        }
 940
 941                        packet = &transport->packet;
 942                        sctp_packet_config(packet, vtag,
 943                                           asoc->peer.ecn_capable);
 944                retran:
 945                        error = sctp_outq_flush_rtx(q, packet,
 946                                                    rtx_timeout, &start_timer);
 947
 948                        if (start_timer)
 949                                sctp_transport_reset_timers(transport);
 950
 951                        /* This can happen on COOKIE-ECHO resend.  Only
 952                         * one chunk can get bundled with a COOKIE-ECHO.
 953                         */
 954                        if (packet->has_cookie_echo)
 955                                goto sctp_flush_out;
 956
 957                        /* Don't send new data if there is still data
 958                         * waiting to retransmit.
 959                         */
 960                        if (!list_empty(&q->retransmit))
 961                                goto sctp_flush_out;
 962                }
 963
 964                /* Apply Max.Burst limitation to the current transport in
 965                 * case it will be used for new data.  We are going to
 966                 * rest it before we return, but we want to apply the limit
 967                 * to the currently queued data.
 968                 */
 969                if (transport)
 970                        sctp_transport_burst_limited(transport);
 971
 972                /* Finally, transmit new packets.  */
 973                while ((chunk = sctp_outq_dequeue_data(q)) != NULL) {
 974                        /* RFC 2960 6.5 Every DATA chunk MUST carry a valid
 975                         * stream identifier.
 976                         */
 977                        if (chunk->sinfo.sinfo_stream >=
 978                            asoc->c.sinit_num_ostreams) {
 979
 980                                /* Mark as failed send. */
 981                                sctp_chunk_fail(chunk, SCTP_ERROR_INV_STRM);
 982                                sctp_chunk_free(chunk);
 983                                continue;
 984                        }
 985
 986                        /* Has this chunk expired? */
 987                        if (sctp_chunk_abandoned(chunk)) {
 988                                sctp_chunk_fail(chunk, 0);
 989                                sctp_chunk_free(chunk);
 990                                continue;
 991                        }
 992
 993                        /* If there is a specified transport, use it.
 994                         * Otherwise, we want to use the active path.
 995                         */
 996                        new_transport = chunk->transport;
 997                        if (!new_transport ||
 998                            ((new_transport->state == SCTP_INACTIVE) ||
 999                             (new_transport->state == SCTP_UNCONFIRMED) ||
1000                             (new_transport->state == SCTP_PF)))
1001                                new_transport = asoc->peer.active_path;
1002                        if (new_transport->state == SCTP_UNCONFIRMED)
1003                                continue;
1004
1005                        /* Change packets if necessary.  */
1006                        if (new_transport != transport) {
1007                                transport = new_transport;
1008
1009                                /* Schedule to have this transport's
1010                                 * packet flushed.
1011                                 */
1012                                if (list_empty(&transport->send_ready)) {
1013                                        list_add_tail(&transport->send_ready,
1014                                                      &transport_list);
1015                                }
1016
1017                                packet = &transport->packet;
1018                                sctp_packet_config(packet, vtag,
1019                                                   asoc->peer.ecn_capable);
1020                                /* We've switched transports, so apply the
1021                                 * Burst limit to the new transport.
1022                                 */
1023                                sctp_transport_burst_limited(transport);
1024                        }
1025
1026                        SCTP_DEBUG_PRINTK("sctp_outq_flush(%p, %p[%s]), ",
1027                                          q, chunk,
1028                                          chunk && chunk->chunk_hdr ?
1029                                          sctp_cname(SCTP_ST_CHUNK(
1030                                                  chunk->chunk_hdr->type))
1031                                          : "Illegal Chunk");
1032
1033                        SCTP_DEBUG_PRINTK("TX TSN 0x%x skb->head "
1034                                        "%p skb->users %d.\n",
1035                                        ntohl(chunk->subh.data_hdr->tsn),
1036                                        chunk->skb ?chunk->skb->head : NULL,
1037                                        chunk->skb ?
1038                                        atomic_read(&chunk->skb->users) : -1);
1039
1040                        /* Add the chunk to the packet.  */
1041                        status = sctp_packet_transmit_chunk(packet, chunk, 0);
1042
1043                        switch (status) {
1044                        case SCTP_XMIT_PMTU_FULL:
1045                        case SCTP_XMIT_RWND_FULL:
1046                        case SCTP_XMIT_NAGLE_DELAY:
1047                                /* We could not append this chunk, so put
1048                                 * the chunk back on the output queue.
1049                                 */
1050                                SCTP_DEBUG_PRINTK("sctp_outq_flush: could "
1051                                        "not transmit TSN: 0x%x, status: %d\n",
1052                                        ntohl(chunk->subh.data_hdr->tsn),
1053                                        status);
1054                                sctp_outq_head_data(q, chunk);
1055                                goto sctp_flush_out;
1056                                break;
1057
1058                        case SCTP_XMIT_OK:
1059                                /* The sender is in the SHUTDOWN-PENDING state,
1060                                 * The sender MAY set the I-bit in the DATA
1061                                 * chunk header.
1062                                 */
1063                                if (asoc->state == SCTP_STATE_SHUTDOWN_PENDING)
1064                                        chunk->chunk_hdr->flags |= SCTP_DATA_SACK_IMM;
1065                                if (chunk->chunk_hdr->flags & SCTP_DATA_UNORDERED)
1066                                        asoc->stats.ouodchunks++;
1067                                else
1068                                        asoc->stats.oodchunks++;
1069
1070                                break;
1071
1072                        default:
1073                                BUG();
1074                        }
1075
1076                        /* BUG: We assume that the sctp_packet_transmit()
1077                         * call below will succeed all the time and add the
1078                         * chunk to the transmitted list and restart the
1079                         * timers.
1080                         * It is possible that the call can fail under OOM
1081                         * conditions.
1082                         *
1083                         * Is this really a problem?  Won't this behave
1084                         * like a lost TSN?
1085                         */
1086                        list_add_tail(&chunk->transmitted_list,
1087                                      &transport->transmitted);
1088
1089                        sctp_transport_reset_timers(transport);
1090
1091                        q->empty = 0;
1092
1093                        /* Only let one DATA chunk get bundled with a
1094                         * COOKIE-ECHO chunk.
1095                         */
1096                        if (packet->has_cookie_echo)
1097                                goto sctp_flush_out;
1098                }
1099                break;
1100
1101        default:
1102                /* Do nothing.  */
1103                break;
1104        }
1105
1106sctp_flush_out:
1107
1108        /* Before returning, examine all the transports touched in
1109         * this call.  Right now, we bluntly force clear all the
1110         * transports.  Things might change after we implement Nagle.
1111         * But such an examination is still required.
1112         *
1113         * --xguo
1114         */
1115        while ((ltransport = sctp_list_dequeue(&transport_list)) != NULL ) {
1116                struct sctp_transport *t = list_entry(ltransport,
1117                                                      struct sctp_transport,
1118                                                      send_ready);
1119                packet = &t->packet;
1120                if (!sctp_packet_empty(packet))
1121                        error = sctp_packet_transmit(packet);
1122
1123                /* Clear the burst limited state, if any */
1124                sctp_transport_burst_reset(t);
1125        }
1126
1127        return error;
1128}
1129
1130/* Update unack_data based on the incoming SACK chunk */
1131static void sctp_sack_update_unack_data(struct sctp_association *assoc,
1132                                        struct sctp_sackhdr *sack)
1133{
1134        sctp_sack_variable_t *frags;
1135        __u16 unack_data;
1136        int i;
1137
1138        unack_data = assoc->next_tsn - assoc->ctsn_ack_point - 1;
1139
1140        frags = sack->variable;
1141        for (i = 0; i < ntohs(sack->num_gap_ack_blocks); i++) {
1142                unack_data -= ((ntohs(frags[i].gab.end) -
1143                                ntohs(frags[i].gab.start) + 1));
1144        }
1145
1146        assoc->unack_data = unack_data;
1147}
1148
1149/* This is where we REALLY process a SACK.
1150 *
1151 * Process the SACK against the outqueue.  Mostly, this just frees
1152 * things off the transmitted queue.
1153 */
1154int sctp_outq_sack(struct sctp_outq *q, struct sctp_chunk *chunk)
1155{
1156        struct sctp_association *asoc = q->asoc;
1157        struct sctp_sackhdr *sack = chunk->subh.sack_hdr;
1158        struct sctp_transport *transport;
1159        struct sctp_chunk *tchunk = NULL;
1160        struct list_head *lchunk, *transport_list, *temp;
1161        sctp_sack_variable_t *frags = sack->variable;
1162        __u32 sack_ctsn, ctsn, tsn;
1163        __u32 highest_tsn, highest_new_tsn;
1164        __u32 sack_a_rwnd;
1165        unsigned int outstanding;
1166        struct sctp_transport *primary = asoc->peer.primary_path;
1167        int count_of_newacks = 0;
1168        int gap_ack_blocks;
1169        u8 accum_moved = 0;
1170
1171        /* Grab the association's destination address list. */
1172        transport_list = &asoc->peer.transport_addr_list;
1173
1174        sack_ctsn = ntohl(sack->cum_tsn_ack);
1175        gap_ack_blocks = ntohs(sack->num_gap_ack_blocks);
1176        asoc->stats.gapcnt += gap_ack_blocks;
1177        /*
1178         * SFR-CACC algorithm:
1179         * On receipt of a SACK the sender SHOULD execute the
1180         * following statements.
1181         *
1182         * 1) If the cumulative ack in the SACK passes next tsn_at_change
1183         * on the current primary, the CHANGEOVER_ACTIVE flag SHOULD be
1184         * cleared. The CYCLING_CHANGEOVER flag SHOULD also be cleared for
1185         * all destinations.
1186         * 2) If the SACK contains gap acks and the flag CHANGEOVER_ACTIVE
1187         * is set the receiver of the SACK MUST take the following actions:
1188         *
1189         * A) Initialize the cacc_saw_newack to 0 for all destination
1190         * addresses.
1191         *
1192         * Only bother if changeover_active is set. Otherwise, this is
1193         * totally suboptimal to do on every SACK.
1194         */
1195        if (primary->cacc.changeover_active) {
1196                u8 clear_cycling = 0;
1197
1198                if (TSN_lte(primary->cacc.next_tsn_at_change, sack_ctsn)) {
1199                        primary->cacc.changeover_active = 0;
1200                        clear_cycling = 1;
1201                }
1202
1203                if (clear_cycling || gap_ack_blocks) {
1204                        list_for_each_entry(transport, transport_list,
1205                                        transports) {
1206                                if (clear_cycling)
1207                                        transport->cacc.cycling_changeover = 0;
1208                                if (gap_ack_blocks)
1209                                        transport->cacc.cacc_saw_newack = 0;
1210                        }
1211                }
1212        }
1213
1214        /* Get the highest TSN in the sack. */
1215        highest_tsn = sack_ctsn;
1216        if (gap_ack_blocks)
1217                highest_tsn += ntohs(frags[gap_ack_blocks - 1].gab.end);
1218
1219        if (TSN_lt(asoc->highest_sacked, highest_tsn))
1220                asoc->highest_sacked = highest_tsn;
1221
1222        highest_new_tsn = sack_ctsn;
1223
1224        /* Run through the retransmit queue.  Credit bytes received
1225         * and free those chunks that we can.
1226         */
1227        sctp_check_transmitted(q, &q->retransmit, NULL, NULL, sack, &highest_new_tsn);
1228
1229        /* Run through the transmitted queue.
1230         * Credit bytes received and free those chunks which we can.
1231         *
1232         * This is a MASSIVE candidate for optimization.
1233         */
1234        list_for_each_entry(transport, transport_list, transports) {
1235                sctp_check_transmitted(q, &transport->transmitted,
1236                                       transport, &chunk->source, sack,
1237                                       &highest_new_tsn);
1238                /*
1239                 * SFR-CACC algorithm:
1240                 * C) Let count_of_newacks be the number of
1241                 * destinations for which cacc_saw_newack is set.
1242                 */
1243                if (transport->cacc.cacc_saw_newack)
1244                        count_of_newacks ++;
1245        }
1246
1247        /* Move the Cumulative TSN Ack Point if appropriate.  */
1248        if (TSN_lt(asoc->ctsn_ack_point, sack_ctsn)) {
1249                asoc->ctsn_ack_point = sack_ctsn;
1250                accum_moved = 1;
1251        }
1252
1253        if (gap_ack_blocks) {
1254
1255                if (asoc->fast_recovery && accum_moved)
1256                        highest_new_tsn = highest_tsn;
1257
1258                list_for_each_entry(transport, transport_list, transports)
1259                        sctp_mark_missing(q, &transport->transmitted, transport,
1260                                          highest_new_tsn, count_of_newacks);
1261        }
1262
1263        /* Update unack_data field in the assoc. */
1264        sctp_sack_update_unack_data(asoc, sack);
1265
1266        ctsn = asoc->ctsn_ack_point;
1267
1268        /* Throw away stuff rotting on the sack queue.  */
1269        list_for_each_safe(lchunk, temp, &q->sacked) {
1270                tchunk = list_entry(lchunk, struct sctp_chunk,
1271                                    transmitted_list);
1272                tsn = ntohl(tchunk->subh.data_hdr->tsn);
1273                if (TSN_lte(tsn, ctsn)) {
1274                        list_del_init(&tchunk->transmitted_list);
1275                        sctp_chunk_free(tchunk);
1276                }
1277        }
1278
1279        /* ii) Set rwnd equal to the newly received a_rwnd minus the
1280         *     number of bytes still outstanding after processing the
1281         *     Cumulative TSN Ack and the Gap Ack Blocks.
1282         */
1283
1284        sack_a_rwnd = ntohl(sack->a_rwnd);
1285        outstanding = q->outstanding_bytes;
1286
1287        if (outstanding < sack_a_rwnd)
1288                sack_a_rwnd -= outstanding;
1289        else
1290                sack_a_rwnd = 0;
1291
1292        asoc->peer.rwnd = sack_a_rwnd;
1293
1294        sctp_generate_fwdtsn(q, sack_ctsn);
1295
1296        SCTP_DEBUG_PRINTK("%s: sack Cumulative TSN Ack is 0x%x.\n",
1297                          __func__, sack_ctsn);
1298        SCTP_DEBUG_PRINTK("%s: Cumulative TSN Ack of association, "
1299                          "%p is 0x%x. Adv peer ack point: 0x%x\n",
1300                          __func__, asoc, ctsn, asoc->adv_peer_ack_point);
1301
1302        /* See if all chunks are acked.
1303         * Make sure the empty queue handler will get run later.
1304         */
1305        q->empty = (list_empty(&q->out_chunk_list) &&
1306                    list_empty(&q->retransmit));
1307        if (!q->empty)
1308                goto finish;
1309
1310        list_for_each_entry(transport, transport_list, transports) {
1311                q->empty = q->empty && list_empty(&transport->transmitted);
1312                if (!q->empty)
1313                        goto finish;
1314        }
1315
1316        SCTP_DEBUG_PRINTK("sack queue is empty.\n");
1317finish:
1318        return q->empty;
1319}
1320
1321/* Is the outqueue empty?  */
1322int sctp_outq_is_empty(const struct sctp_outq *q)
1323{
1324        return q->empty;
1325}
1326
1327/********************************************************************
1328 * 2nd Level Abstractions
1329 ********************************************************************/
1330
1331/* Go through a transport's transmitted list or the association's retransmit
1332 * list and move chunks that are acked by the Cumulative TSN Ack to q->sacked.
1333 * The retransmit list will not have an associated transport.
1334 *
1335 * I added coherent debug information output.   --xguo
1336 *
1337 * Instead of printing 'sacked' or 'kept' for each TSN on the
1338 * transmitted_queue, we print a range: SACKED: TSN1-TSN2, TSN3, TSN4-TSN5.
1339 * KEPT TSN6-TSN7, etc.
1340 */
1341static void sctp_check_transmitted(struct sctp_outq *q,
1342                                   struct list_head *transmitted_queue,
1343                                   struct sctp_transport *transport,
1344                                   union sctp_addr *saddr,
1345                                   struct sctp_sackhdr *sack,
1346                                   __u32 *highest_new_tsn_in_sack)
1347{
1348        struct list_head *lchunk;
1349        struct sctp_chunk *tchunk;
1350        struct list_head tlist;
1351        __u32 tsn;
1352        __u32 sack_ctsn;
1353        __u32 rtt;
1354        __u8 restart_timer = 0;
1355        int bytes_acked = 0;
1356        int migrate_bytes = 0;
1357
1358        /* These state variables are for coherent debug output. --xguo */
1359
1360#if SCTP_DEBUG
1361        __u32 dbg_ack_tsn = 0;  /* An ACKed TSN range starts here... */
1362        __u32 dbg_last_ack_tsn = 0;  /* ...and finishes here.        */
1363        __u32 dbg_kept_tsn = 0; /* An un-ACKed range starts here...  */
1364        __u32 dbg_last_kept_tsn = 0; /* ...and finishes here.        */
1365
1366        /* 0 : The last TSN was ACKed.
1367         * 1 : The last TSN was NOT ACKed (i.e. KEPT).
1368         * -1: We need to initialize.
1369         */
1370        int dbg_prt_state = -1;
1371#endif /* SCTP_DEBUG */
1372
1373        sack_ctsn = ntohl(sack->cum_tsn_ack);
1374
1375        INIT_LIST_HEAD(&tlist);
1376
1377        /* The while loop will skip empty transmitted queues. */
1378        while (NULL != (lchunk = sctp_list_dequeue(transmitted_queue))) {
1379                tchunk = list_entry(lchunk, struct sctp_chunk,
1380                                    transmitted_list);
1381
1382                if (sctp_chunk_abandoned(tchunk)) {
1383                        /* Move the chunk to abandoned list. */
1384                        sctp_insert_list(&q->abandoned, lchunk);
1385
1386                        /* If this chunk has not been acked, stop
1387                         * considering it as 'outstanding'.
1388                         */
1389                        if (!tchunk->tsn_gap_acked) {
1390                                if (tchunk->transport)
1391                                        tchunk->transport->flight_size -=
1392                                                        sctp_data_size(tchunk);
1393                                q->outstanding_bytes -= sctp_data_size(tchunk);
1394                        }
1395                        continue;
1396                }
1397
1398                tsn = ntohl(tchunk->subh.data_hdr->tsn);
1399                if (sctp_acked(sack, tsn)) {
1400                        /* If this queue is the retransmit queue, the
1401                         * retransmit timer has already reclaimed
1402                         * the outstanding bytes for this chunk, so only
1403                         * count bytes associated with a transport.
1404                         */
1405                        if (transport) {
1406                                /* If this chunk is being used for RTT
1407                                 * measurement, calculate the RTT and update
1408                                 * the RTO using this value.
1409                                 *
1410                                 * 6.3.1 C5) Karn's algorithm: RTT measurements
1411                                 * MUST NOT be made using packets that were
1412                                 * retransmitted (and thus for which it is
1413                                 * ambiguous whether the reply was for the
1414                                 * first instance of the packet or a later
1415                                 * instance).
1416                                 */
1417                                if (!tchunk->tsn_gap_acked &&
1418                                    tchunk->rtt_in_progress) {
1419                                        tchunk->rtt_in_progress = 0;
1420                                        rtt = jiffies - tchunk->sent_at;
1421                                        sctp_transport_update_rto(transport,
1422                                                                  rtt);
1423                                }
1424                        }
1425
1426                        /* If the chunk hasn't been marked as ACKED,
1427                         * mark it and account bytes_acked if the
1428                         * chunk had a valid transport (it will not
1429                         * have a transport if ASCONF had deleted it
1430                         * while DATA was outstanding).
1431                         */
1432                        if (!tchunk->tsn_gap_acked) {
1433                                tchunk->tsn_gap_acked = 1;
1434                                *highest_new_tsn_in_sack = tsn;
1435                                bytes_acked += sctp_data_size(tchunk);
1436                                if (!tchunk->transport)
1437                                        migrate_bytes += sctp_data_size(tchunk);
1438                        }
1439
1440                        if (TSN_lte(tsn, sack_ctsn)) {
1441                                /* RFC 2960  6.3.2 Retransmission Timer Rules
1442                                 *
1443                                 * R3) Whenever a SACK is received
1444                                 * that acknowledges the DATA chunk
1445                                 * with the earliest outstanding TSN
1446                                 * for that address, restart T3-rtx
1447                                 * timer for that address with its
1448                                 * current RTO.
1449                                 */
1450                                restart_timer = 1;
1451
1452                                if (!tchunk->tsn_gap_acked) {
1453                                        /*
1454                                         * SFR-CACC algorithm:
1455                                         * 2) If the SACK contains gap acks
1456                                         * and the flag CHANGEOVER_ACTIVE is
1457                                         * set the receiver of the SACK MUST
1458                                         * take the following action:
1459                                         *
1460                                         * B) For each TSN t being acked that
1461                                         * has not been acked in any SACK so
1462                                         * far, set cacc_saw_newack to 1 for
1463                                         * the destination that the TSN was
1464                                         * sent to.
1465                                         */
1466                                        if (transport &&
1467                                            sack->num_gap_ack_blocks &&
1468                                            q->asoc->peer.primary_path->cacc.
1469                                            changeover_active)
1470                                                transport->cacc.cacc_saw_newack
1471                                                        = 1;
1472                                }
1473
1474                                list_add_tail(&tchunk->transmitted_list,
1475                                              &q->sacked);
1476                        } else {
1477                                /* RFC2960 7.2.4, sctpimpguide-05 2.8.2
1478                                 * M2) Each time a SACK arrives reporting
1479                                 * 'Stray DATA chunk(s)' record the highest TSN
1480                                 * reported as newly acknowledged, call this
1481                                 * value 'HighestTSNinSack'. A newly
1482                                 * acknowledged DATA chunk is one not
1483                                 * previously acknowledged in a SACK.
1484                                 *
1485                                 * When the SCTP sender of data receives a SACK
1486                                 * chunk that acknowledges, for the first time,
1487                                 * the receipt of a DATA chunk, all the still
1488                                 * unacknowledged DATA chunks whose TSN is
1489                                 * older than that newly acknowledged DATA
1490                                 * chunk, are qualified as 'Stray DATA chunks'.
1491                                 */
1492                                list_add_tail(lchunk, &tlist);
1493                        }
1494
1495#if SCTP_DEBUG
1496                        switch (dbg_prt_state) {
1497                        case 0: /* last TSN was ACKed */
1498                                if (dbg_last_ack_tsn + 1 == tsn) {
1499                                        /* This TSN belongs to the
1500                                         * current ACK range.
1501                                         */
1502                                        break;
1503                                }
1504
1505                                if (dbg_last_ack_tsn != dbg_ack_tsn) {
1506                                        /* Display the end of the
1507                                         * current range.
1508                                         */
1509                                        SCTP_DEBUG_PRINTK_CONT("-%08x",
1510                                                               dbg_last_ack_tsn);
1511                                }
1512
1513                                /* Start a new range.  */
1514                                SCTP_DEBUG_PRINTK_CONT(",%08x", tsn);
1515                                dbg_ack_tsn = tsn;
1516                                break;
1517
1518                        case 1: /* The last TSN was NOT ACKed. */
1519                                if (dbg_last_kept_tsn != dbg_kept_tsn) {
1520                                        /* Display the end of current range. */
1521                                        SCTP_DEBUG_PRINTK_CONT("-%08x",
1522                                                               dbg_last_kept_tsn);
1523                                }
1524
1525                                SCTP_DEBUG_PRINTK_CONT("\n");
1526
1527                                /* FALL THROUGH... */
1528                        default:
1529                                /* This is the first-ever TSN we examined.  */
1530                                /* Start a new range of ACK-ed TSNs.  */
1531                                SCTP_DEBUG_PRINTK("ACKed: %08x", tsn);
1532                                dbg_prt_state = 0;
1533                                dbg_ack_tsn = tsn;
1534                        }
1535
1536                        dbg_last_ack_tsn = tsn;
1537#endif /* SCTP_DEBUG */
1538
1539                } else {
1540                        if (tchunk->tsn_gap_acked) {
1541                                SCTP_DEBUG_PRINTK("%s: Receiver reneged on "
1542                                                  "data TSN: 0x%x\n",
1543                                                  __func__,
1544                                                  tsn);
1545                                tchunk->tsn_gap_acked = 0;
1546
1547                                if (tchunk->transport)
1548                                        bytes_acked -= sctp_data_size(tchunk);
1549
1550                                /* RFC 2960 6.3.2 Retransmission Timer Rules
1551                                 *
1552                                 * R4) Whenever a SACK is received missing a
1553                                 * TSN that was previously acknowledged via a
1554                                 * Gap Ack Block, start T3-rtx for the
1555                                 * destination address to which the DATA
1556                                 * chunk was originally
1557                                 * transmitted if it is not already running.
1558                                 */
1559                                restart_timer = 1;
1560                        }
1561
1562                        list_add_tail(lchunk, &tlist);
1563
1564#if SCTP_DEBUG
1565                        /* See the above comments on ACK-ed TSNs. */
1566                        switch (dbg_prt_state) {
1567                        case 1:
1568                                if (dbg_last_kept_tsn + 1 == tsn)
1569                                        break;
1570
1571                                if (dbg_last_kept_tsn != dbg_kept_tsn)
1572                                        SCTP_DEBUG_PRINTK_CONT("-%08x",
1573                                                               dbg_last_kept_tsn);
1574
1575                                SCTP_DEBUG_PRINTK_CONT(",%08x", tsn);
1576                                dbg_kept_tsn = tsn;
1577                                break;
1578
1579                        case 0:
1580                                if (dbg_last_ack_tsn != dbg_ack_tsn)
1581                                        SCTP_DEBUG_PRINTK_CONT("-%08x",
1582                                                               dbg_last_ack_tsn);
1583                                SCTP_DEBUG_PRINTK_CONT("\n");
1584
1585                                /* FALL THROUGH... */
1586                        default:
1587                                SCTP_DEBUG_PRINTK("KEPT: %08x",tsn);
1588                                dbg_prt_state = 1;
1589                                dbg_kept_tsn = tsn;
1590                        }
1591
1592                        dbg_last_kept_tsn = tsn;
1593#endif /* SCTP_DEBUG */
1594                }
1595        }
1596
1597#if SCTP_DEBUG
1598        /* Finish off the last range, displaying its ending TSN.  */
1599        switch (dbg_prt_state) {
1600        case 0:
1601                if (dbg_last_ack_tsn != dbg_ack_tsn) {
1602                        SCTP_DEBUG_PRINTK_CONT("-%08x\n", dbg_last_ack_tsn);
1603                } else {
1604                        SCTP_DEBUG_PRINTK_CONT("\n");
1605                }
1606        break;
1607
1608        case 1:
1609                if (dbg_last_kept_tsn != dbg_kept_tsn) {
1610                        SCTP_DEBUG_PRINTK_CONT("-%08x\n", dbg_last_kept_tsn);
1611                } else {
1612                        SCTP_DEBUG_PRINTK_CONT("\n");
1613                }
1614        }
1615#endif /* SCTP_DEBUG */
1616        if (transport) {
1617                if (bytes_acked) {
1618                        struct sctp_association *asoc = transport->asoc;
1619
1620                        /* We may have counted DATA that was migrated
1621                         * to this transport due to DEL-IP operation.
1622                         * Subtract those bytes, since the were never
1623                         * send on this transport and shouldn't be
1624                         * credited to this transport.
1625                         */
1626                        bytes_acked -= migrate_bytes;
1627
1628                        /* 8.2. When an outstanding TSN is acknowledged,
1629                         * the endpoint shall clear the error counter of
1630                         * the destination transport address to which the
1631                         * DATA chunk was last sent.
1632                         * The association's overall error counter is
1633                         * also cleared.
1634                         */
1635                        transport->error_count = 0;
1636                        transport->asoc->overall_error_count = 0;
1637
1638                        /*
1639                         * While in SHUTDOWN PENDING, we may have started
1640                         * the T5 shutdown guard timer after reaching the
1641                         * retransmission limit. Stop that timer as soon
1642                         * as the receiver acknowledged any data.
1643                         */
1644                        if (asoc->state == SCTP_STATE_SHUTDOWN_PENDING &&
1645                            del_timer(&asoc->timers
1646                                [SCTP_EVENT_TIMEOUT_T5_SHUTDOWN_GUARD]))
1647                                        sctp_association_put(asoc);
1648
1649                        /* Mark the destination transport address as
1650                         * active if it is not so marked.
1651                         */
1652                        if ((transport->state == SCTP_INACTIVE ||
1653                             transport->state == SCTP_UNCONFIRMED) &&
1654                            sctp_cmp_addr_exact(&transport->ipaddr, saddr)) {
1655                                sctp_assoc_control_transport(
1656                                        transport->asoc,
1657                                        transport,
1658                                        SCTP_TRANSPORT_UP,
1659                                        SCTP_RECEIVED_SACK);
1660                        }
1661
1662                        sctp_transport_raise_cwnd(transport, sack_ctsn,
1663                                                  bytes_acked);
1664
1665                        transport->flight_size -= bytes_acked;
1666                        if (transport->flight_size == 0)
1667                                transport->partial_bytes_acked = 0;
1668                        q->outstanding_bytes -= bytes_acked + migrate_bytes;
1669                } else {
1670                        /* RFC 2960 6.1, sctpimpguide-06 2.15.2
1671                         * When a sender is doing zero window probing, it
1672                         * should not timeout the association if it continues
1673                         * to receive new packets from the receiver. The
1674                         * reason is that the receiver MAY keep its window
1675                         * closed for an indefinite time.
1676                         * A sender is doing zero window probing when the
1677                         * receiver's advertised window is zero, and there is
1678                         * only one data chunk in flight to the receiver.
1679                         *
1680                         * Allow the association to timeout while in SHUTDOWN
1681                         * PENDING or SHUTDOWN RECEIVED in case the receiver
1682                         * stays in zero window mode forever.
1683                         */
1684                        if (!q->asoc->peer.rwnd &&
1685                            !list_empty(&tlist) &&
1686                            (sack_ctsn+2 == q->asoc->next_tsn) &&
1687                            q->asoc->state < SCTP_STATE_SHUTDOWN_PENDING) {
1688                                SCTP_DEBUG_PRINTK("%s: SACK received for zero "
1689                                                  "window probe: %u\n",
1690                                                  __func__, sack_ctsn);
1691                                q->asoc->overall_error_count = 0;
1692                                transport->error_count = 0;
1693                        }
1694                }
1695
1696                /* RFC 2960 6.3.2 Retransmission Timer Rules
1697                 *
1698                 * R2) Whenever all outstanding data sent to an address have
1699                 * been acknowledged, turn off the T3-rtx timer of that
1700                 * address.
1701                 */
1702                if (!transport->flight_size) {
1703                        if (timer_pending(&transport->T3_rtx_timer) &&
1704                            del_timer(&transport->T3_rtx_timer)) {
1705                                sctp_transport_put(transport);
1706                        }
1707                } else if (restart_timer) {
1708                        if (!mod_timer(&transport->T3_rtx_timer,
1709                                       jiffies + transport->rto))
1710                                sctp_transport_hold(transport);
1711                }
1712        }
1713
1714        list_splice(&tlist, transmitted_queue);
1715}
1716
1717/* Mark chunks as missing and consequently may get retransmitted. */
1718static void sctp_mark_missing(struct sctp_outq *q,
1719                              struct list_head *transmitted_queue,
1720                              struct sctp_transport *transport,
1721                              __u32 highest_new_tsn_in_sack,
1722                              int count_of_newacks)
1723{
1724        struct sctp_chunk *chunk;
1725        __u32 tsn;
1726        char do_fast_retransmit = 0;
1727        struct sctp_association *asoc = q->asoc;
1728        struct sctp_transport *primary = asoc->peer.primary_path;
1729
1730        list_for_each_entry(chunk, transmitted_queue, transmitted_list) {
1731
1732                tsn = ntohl(chunk->subh.data_hdr->tsn);
1733
1734                /* RFC 2960 7.2.4, sctpimpguide-05 2.8.2 M3) Examine all
1735                 * 'Unacknowledged TSN's', if the TSN number of an
1736                 * 'Unacknowledged TSN' is smaller than the 'HighestTSNinSack'
1737                 * value, increment the 'TSN.Missing.Report' count on that
1738                 * chunk if it has NOT been fast retransmitted or marked for
1739                 * fast retransmit already.
1740                 */
1741                if (chunk->fast_retransmit == SCTP_CAN_FRTX &&
1742                    !chunk->tsn_gap_acked &&
1743                    TSN_lt(tsn, highest_new_tsn_in_sack)) {
1744
1745                        /* SFR-CACC may require us to skip marking
1746                         * this chunk as missing.
1747                         */
1748                        if (!transport || !sctp_cacc_skip(primary,
1749                                                chunk->transport,
1750                                                count_of_newacks, tsn)) {
1751                                chunk->tsn_missing_report++;
1752
1753                                SCTP_DEBUG_PRINTK(
1754                                        "%s: TSN 0x%x missing counter: %d\n",
1755                                        __func__, tsn,
1756                                        chunk->tsn_missing_report);
1757                        }
1758                }
1759                /*
1760                 * M4) If any DATA chunk is found to have a
1761                 * 'TSN.Missing.Report'
1762                 * value larger than or equal to 3, mark that chunk for
1763                 * retransmission and start the fast retransmit procedure.
1764                 */
1765
1766                if (chunk->tsn_missing_report >= 3) {
1767                        chunk->fast_retransmit = SCTP_NEED_FRTX;
1768                        do_fast_retransmit = 1;
1769                }
1770        }
1771
1772        if (transport) {
1773                if (do_fast_retransmit)
1774                        sctp_retransmit(q, transport, SCTP_RTXR_FAST_RTX);
1775
1776                SCTP_DEBUG_PRINTK("%s: transport: %p, cwnd: %d, "
1777                                  "ssthresh: %d, flight_size: %d, pba: %d\n",
1778                                  __func__, transport, transport->cwnd,
1779                                  transport->ssthresh, transport->flight_size,
1780                                  transport->partial_bytes_acked);
1781        }
1782}
1783
1784/* Is the given TSN acked by this packet?  */
1785static int sctp_acked(struct sctp_sackhdr *sack, __u32 tsn)
1786{
1787        int i;
1788        sctp_sack_variable_t *frags;
1789        __u16 gap;
1790        __u32 ctsn = ntohl(sack->cum_tsn_ack);
1791
1792        if (TSN_lte(tsn, ctsn))
1793                goto pass;
1794
1795        /* 3.3.4 Selective Acknowledgement (SACK) (3):
1796         *
1797         * Gap Ack Blocks:
1798         *  These fields contain the Gap Ack Blocks. They are repeated
1799         *  for each Gap Ack Block up to the number of Gap Ack Blocks
1800         *  defined in the Number of Gap Ack Blocks field. All DATA
1801         *  chunks with TSNs greater than or equal to (Cumulative TSN
1802         *  Ack + Gap Ack Block Start) and less than or equal to
1803         *  (Cumulative TSN Ack + Gap Ack Block End) of each Gap Ack
1804         *  Block are assumed to have been received correctly.
1805         */
1806
1807        frags = sack->variable;
1808        gap = tsn - ctsn;
1809        for (i = 0; i < ntohs(sack->num_gap_ack_blocks); ++i) {
1810                if (TSN_lte(ntohs(frags[i].gab.start), gap) &&
1811                    TSN_lte(gap, ntohs(frags[i].gab.end)))
1812                        goto pass;
1813        }
1814
1815        return 0;
1816pass:
1817        return 1;
1818}
1819
1820static inline int sctp_get_skip_pos(struct sctp_fwdtsn_skip *skiplist,
1821                                    int nskips, __be16 stream)
1822{
1823        int i;
1824
1825        for (i = 0; i < nskips; i++) {
1826                if (skiplist[i].stream == stream)
1827                        return i;
1828        }
1829        return i;
1830}
1831
1832/* Create and add a fwdtsn chunk to the outq's control queue if needed. */
1833static void sctp_generate_fwdtsn(struct sctp_outq *q, __u32 ctsn)
1834{
1835        struct sctp_association *asoc = q->asoc;
1836        struct sctp_chunk *ftsn_chunk = NULL;
1837        struct sctp_fwdtsn_skip ftsn_skip_arr[10];
1838        int nskips = 0;
1839        int skip_pos = 0;
1840        __u32 tsn;
1841        struct sctp_chunk *chunk;
1842        struct list_head *lchunk, *temp;
1843
1844        if (!asoc->peer.prsctp_capable)
1845                return;
1846
1847        /* PR-SCTP C1) Let SackCumAck be the Cumulative TSN ACK carried in the
1848         * received SACK.
1849         *
1850         * If (Advanced.Peer.Ack.Point < SackCumAck), then update
1851         * Advanced.Peer.Ack.Point to be equal to SackCumAck.
1852         */
1853        if (TSN_lt(asoc->adv_peer_ack_point, ctsn))
1854                asoc->adv_peer_ack_point = ctsn;
1855
1856        /* PR-SCTP C2) Try to further advance the "Advanced.Peer.Ack.Point"
1857         * locally, that is, to move "Advanced.Peer.Ack.Point" up as long as
1858         * the chunk next in the out-queue space is marked as "abandoned" as
1859         * shown in the following example:
1860         *
1861         * Assuming that a SACK arrived with the Cumulative TSN ACK 102
1862         * and the Advanced.Peer.Ack.Point is updated to this value:
1863         *
1864         *   out-queue at the end of  ==>   out-queue after Adv.Ack.Point
1865         *   normal SACK processing           local advancement
1866         *                ...                           ...
1867         *   Adv.Ack.Pt-> 102 acked                     102 acked
1868         *                103 abandoned                 103 abandoned
1869         *                104 abandoned     Adv.Ack.P-> 104 abandoned
1870         *                105                           105
1871         *                106 acked                     106 acked
1872         *                ...                           ...
1873         *
1874         * In this example, the data sender successfully advanced the
1875         * "Advanced.Peer.Ack.Point" from 102 to 104 locally.
1876         */
1877        list_for_each_safe(lchunk, temp, &q->abandoned) {
1878                chunk = list_entry(lchunk, struct sctp_chunk,
1879                                        transmitted_list);
1880                tsn = ntohl(chunk->subh.data_hdr->tsn);
1881
1882                /* Remove any chunks in the abandoned queue that are acked by
1883                 * the ctsn.
1884                 */
1885                if (TSN_lte(tsn, ctsn)) {
1886                        list_del_init(lchunk);
1887                        sctp_chunk_free(chunk);
1888                } else {
1889                        if (TSN_lte(tsn, asoc->adv_peer_ack_point+1)) {
1890                                asoc->adv_peer_ack_point = tsn;
1891                                if (chunk->chunk_hdr->flags &
1892                                         SCTP_DATA_UNORDERED)
1893                                        continue;
1894                                skip_pos = sctp_get_skip_pos(&ftsn_skip_arr[0],
1895                                                nskips,
1896                                                chunk->subh.data_hdr->stream);
1897                                ftsn_skip_arr[skip_pos].stream =
1898                                        chunk->subh.data_hdr->stream;
1899                                ftsn_skip_arr[skip_pos].ssn =
1900                                         chunk->subh.data_hdr->ssn;
1901                                if (skip_pos == nskips)
1902                                        nskips++;
1903                                if (nskips == 10)
1904                                        break;
1905                        } else
1906                                break;
1907                }
1908        }
1909
1910        /* PR-SCTP C3) If, after step C1 and C2, the "Advanced.Peer.Ack.Point"
1911         * is greater than the Cumulative TSN ACK carried in the received
1912         * SACK, the data sender MUST send the data receiver a FORWARD TSN
1913         * chunk containing the latest value of the
1914         * "Advanced.Peer.Ack.Point".
1915         *
1916         * C4) For each "abandoned" TSN the sender of the FORWARD TSN SHOULD
1917         * list each stream and sequence number in the forwarded TSN. This
1918         * information will enable the receiver to easily find any
1919         * stranded TSN's waiting on stream reorder queues. Each stream
1920         * SHOULD only be reported once; this means that if multiple
1921         * abandoned messages occur in the same stream then only the
1922         * highest abandoned stream sequence number is reported. If the
1923         * total size of the FORWARD TSN does NOT fit in a single MTU then
1924         * the sender of the FORWARD TSN SHOULD lower the
1925         * Advanced.Peer.Ack.Point to the last TSN that will fit in a
1926         * single MTU.
1927         */
1928        if (asoc->adv_peer_ack_point > ctsn)
1929                ftsn_chunk = sctp_make_fwdtsn(asoc, asoc->adv_peer_ack_point,
1930                                              nskips, &ftsn_skip_arr[0]);
1931
1932        if (ftsn_chunk) {
1933                list_add_tail(&ftsn_chunk->list, &q->control_chunk_list);
1934                SCTP_INC_STATS(sock_net(asoc->base.sk), SCTP_MIB_OUTCTRLCHUNKS);
1935        }
1936}
1937
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