linux/net/sctp/transport.c
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   1/* SCTP kernel implementation
   2 * Copyright (c) 1999-2000 Cisco, Inc.
   3 * Copyright (c) 1999-2001 Motorola, Inc.
   4 * Copyright (c) 2001-2003 International Business Machines Corp.
   5 * Copyright (c) 2001 Intel Corp.
   6 * Copyright (c) 2001 La Monte H.P. Yarroll
   7 *
   8 * This file is part of the SCTP kernel implementation
   9 *
  10 * This module provides the abstraction for an SCTP tranport representing
  11 * a remote transport address.  For local transport addresses, we just use
  12 * union sctp_addr.
  13 *
  14 * This SCTP implementation is free software;
  15 * you can redistribute it and/or modify it under the terms of
  16 * the GNU General Public License as published by
  17 * the Free Software Foundation; either version 2, or (at your option)
  18 * any later version.
  19 *
  20 * This SCTP implementation is distributed in the hope that it
  21 * will be useful, but WITHOUT ANY WARRANTY; without even the implied
  22 *                 ************************
  23 * warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
  24 * See the GNU General Public License for more details.
  25 *
  26 * You should have received a copy of the GNU General Public License
  27 * along with GNU CC; see the file COPYING.  If not, write to
  28 * the Free Software Foundation, 59 Temple Place - Suite 330,
  29 * Boston, MA 02111-1307, USA.
  30 *
  31 * Please send any bug reports or fixes you make to the
  32 * email address(es):
  33 *    lksctp developers <lksctp-developers@lists.sourceforge.net>
  34 *
  35 * Or submit a bug report through the following website:
  36 *    http://www.sf.net/projects/lksctp
  37 *
  38 * Written or modified by:
  39 *    La Monte H.P. Yarroll <piggy@acm.org>
  40 *    Karl Knutson          <karl@athena.chicago.il.us>
  41 *    Jon Grimm             <jgrimm@us.ibm.com>
  42 *    Xingang Guo           <xingang.guo@intel.com>
  43 *    Hui Huang             <hui.huang@nokia.com>
  44 *    Sridhar Samudrala     <sri@us.ibm.com>
  45 *    Ardelle Fan           <ardelle.fan@intel.com>
  46 *
  47 * Any bugs reported given to us we will try to fix... any fixes shared will
  48 * be incorporated into the next SCTP release.
  49 */
  50
  51#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  52
  53#include <linux/slab.h>
  54#include <linux/types.h>
  55#include <linux/random.h>
  56#include <net/sctp/sctp.h>
  57#include <net/sctp/sm.h>
  58
  59/* 1st Level Abstractions.  */
  60
  61/* Initialize a new transport from provided memory.  */
  62static struct sctp_transport *sctp_transport_init(struct sctp_transport *peer,
  63                                                  const union sctp_addr *addr,
  64                                                  gfp_t gfp)
  65{
  66        /* Copy in the address.  */
  67        peer->ipaddr = *addr;
  68        peer->af_specific = sctp_get_af_specific(addr->sa.sa_family);
  69        memset(&peer->saddr, 0, sizeof(union sctp_addr));
  70
  71        peer->sack_generation = 0;
  72
  73        /* From 6.3.1 RTO Calculation:
  74         *
  75         * C1) Until an RTT measurement has been made for a packet sent to the
  76         * given destination transport address, set RTO to the protocol
  77         * parameter 'RTO.Initial'.
  78         */
  79        peer->rto = msecs_to_jiffies(sctp_rto_initial);
  80
  81        peer->last_time_heard = jiffies;
  82        peer->last_time_ecne_reduced = jiffies;
  83
  84        peer->param_flags = SPP_HB_DISABLE |
  85                            SPP_PMTUD_ENABLE |
  86                            SPP_SACKDELAY_ENABLE;
  87
  88        /* Initialize the default path max_retrans.  */
  89        peer->pathmaxrxt  = sctp_max_retrans_path;
  90        peer->pf_retrans  = sctp_pf_retrans;
  91
  92        INIT_LIST_HEAD(&peer->transmitted);
  93        INIT_LIST_HEAD(&peer->send_ready);
  94        INIT_LIST_HEAD(&peer->transports);
  95
  96        setup_timer(&peer->T3_rtx_timer, sctp_generate_t3_rtx_event,
  97                        (unsigned long)peer);
  98        setup_timer(&peer->hb_timer, sctp_generate_heartbeat_event,
  99                        (unsigned long)peer);
 100        setup_timer(&peer->proto_unreach_timer,
 101                    sctp_generate_proto_unreach_event, (unsigned long)peer);
 102
 103        /* Initialize the 64-bit random nonce sent with heartbeat. */
 104        get_random_bytes(&peer->hb_nonce, sizeof(peer->hb_nonce));
 105
 106        atomic_set(&peer->refcnt, 1);
 107
 108        return peer;
 109}
 110
 111/* Allocate and initialize a new transport.  */
 112struct sctp_transport *sctp_transport_new(const union sctp_addr *addr,
 113                                          gfp_t gfp)
 114{
 115        struct sctp_transport *transport;
 116
 117        transport = t_new(struct sctp_transport, gfp);
 118        if (!transport)
 119                goto fail;
 120
 121        if (!sctp_transport_init(transport, addr, gfp))
 122                goto fail_init;
 123
 124        transport->malloced = 1;
 125        SCTP_DBG_OBJCNT_INC(transport);
 126
 127        return transport;
 128
 129fail_init:
 130        kfree(transport);
 131
 132fail:
 133        return NULL;
 134}
 135
 136/* This transport is no longer needed.  Free up if possible, or
 137 * delay until it last reference count.
 138 */
 139void sctp_transport_free(struct sctp_transport *transport)
 140{
 141        transport->dead = 1;
 142
 143        /* Try to delete the heartbeat timer.  */
 144        if (del_timer(&transport->hb_timer))
 145                sctp_transport_put(transport);
 146
 147        /* Delete the T3_rtx timer if it's active.
 148         * There is no point in not doing this now and letting
 149         * structure hang around in memory since we know
 150         * the tranport is going away.
 151         */
 152        if (timer_pending(&transport->T3_rtx_timer) &&
 153            del_timer(&transport->T3_rtx_timer))
 154                sctp_transport_put(transport);
 155
 156        /* Delete the ICMP proto unreachable timer if it's active. */
 157        if (timer_pending(&transport->proto_unreach_timer) &&
 158            del_timer(&transport->proto_unreach_timer))
 159                sctp_association_put(transport->asoc);
 160
 161        sctp_transport_put(transport);
 162}
 163
 164/* Destroy the transport data structure.
 165 * Assumes there are no more users of this structure.
 166 */
 167static void sctp_transport_destroy(struct sctp_transport *transport)
 168{
 169        SCTP_ASSERT(transport->dead, "Transport is not dead", return);
 170
 171        if (transport->asoc)
 172                sctp_association_put(transport->asoc);
 173
 174        sctp_packet_free(&transport->packet);
 175
 176        dst_release(transport->dst);
 177        kfree(transport);
 178        SCTP_DBG_OBJCNT_DEC(transport);
 179}
 180
 181/* Start T3_rtx timer if it is not already running and update the heartbeat
 182 * timer.  This routine is called every time a DATA chunk is sent.
 183 */
 184void sctp_transport_reset_timers(struct sctp_transport *transport)
 185{
 186        /* RFC 2960 6.3.2 Retransmission Timer Rules
 187         *
 188         * R1) Every time a DATA chunk is sent to any address(including a
 189         * retransmission), if the T3-rtx timer of that address is not running
 190         * start it running so that it will expire after the RTO of that
 191         * address.
 192         */
 193
 194        if (!timer_pending(&transport->T3_rtx_timer))
 195                if (!mod_timer(&transport->T3_rtx_timer,
 196                               jiffies + transport->rto))
 197                        sctp_transport_hold(transport);
 198
 199        /* When a data chunk is sent, reset the heartbeat interval.  */
 200        if (!mod_timer(&transport->hb_timer,
 201                       sctp_transport_timeout(transport)))
 202            sctp_transport_hold(transport);
 203}
 204
 205/* This transport has been assigned to an association.
 206 * Initialize fields from the association or from the sock itself.
 207 * Register the reference count in the association.
 208 */
 209void sctp_transport_set_owner(struct sctp_transport *transport,
 210                              struct sctp_association *asoc)
 211{
 212        transport->asoc = asoc;
 213        sctp_association_hold(asoc);
 214}
 215
 216/* Initialize the pmtu of a transport. */
 217void sctp_transport_pmtu(struct sctp_transport *transport, struct sock *sk)
 218{
 219        /* If we don't have a fresh route, look one up */
 220        if (!transport->dst || transport->dst->obsolete) {
 221                dst_release(transport->dst);
 222                transport->af_specific->get_dst(transport, &transport->saddr,
 223                                                &transport->fl, sk);
 224        }
 225
 226        if (transport->dst) {
 227                transport->pathmtu = dst_mtu(transport->dst);
 228        } else
 229                transport->pathmtu = SCTP_DEFAULT_MAXSEGMENT;
 230}
 231
 232void sctp_transport_update_pmtu(struct sock *sk, struct sctp_transport *t, u32 pmtu)
 233{
 234        struct dst_entry *dst;
 235
 236        if (unlikely(pmtu < SCTP_DEFAULT_MINSEGMENT)) {
 237                pr_warn("%s: Reported pmtu %d too low, using default minimum of %d\n",
 238                        __func__, pmtu,
 239                        SCTP_DEFAULT_MINSEGMENT);
 240                /* Use default minimum segment size and disable
 241                 * pmtu discovery on this transport.
 242                 */
 243                t->pathmtu = SCTP_DEFAULT_MINSEGMENT;
 244        } else {
 245                t->pathmtu = pmtu;
 246        }
 247
 248        dst = sctp_transport_dst_check(t);
 249        if (!dst)
 250                t->af_specific->get_dst(t, &t->saddr, &t->fl, sk);
 251
 252        if (dst) {
 253                dst->ops->update_pmtu(dst, sk, NULL, pmtu);
 254
 255                dst = sctp_transport_dst_check(t);
 256                if (!dst)
 257                        t->af_specific->get_dst(t, &t->saddr, &t->fl, sk);
 258        }
 259}
 260
 261/* Caches the dst entry and source address for a transport's destination
 262 * address.
 263 */
 264void sctp_transport_route(struct sctp_transport *transport,
 265                          union sctp_addr *saddr, struct sctp_sock *opt)
 266{
 267        struct sctp_association *asoc = transport->asoc;
 268        struct sctp_af *af = transport->af_specific;
 269
 270        af->get_dst(transport, saddr, &transport->fl, sctp_opt2sk(opt));
 271
 272        if (saddr)
 273                memcpy(&transport->saddr, saddr, sizeof(union sctp_addr));
 274        else
 275                af->get_saddr(opt, transport, &transport->fl);
 276
 277        if ((transport->param_flags & SPP_PMTUD_DISABLE) && transport->pathmtu) {
 278                return;
 279        }
 280        if (transport->dst) {
 281                transport->pathmtu = dst_mtu(transport->dst);
 282
 283                /* Initialize sk->sk_rcv_saddr, if the transport is the
 284                 * association's active path for getsockname().
 285                 */
 286                if (asoc && (!asoc->peer.primary_path ||
 287                                (transport == asoc->peer.active_path)))
 288                        opt->pf->af->to_sk_saddr(&transport->saddr,
 289                                                 asoc->base.sk);
 290        } else
 291                transport->pathmtu = SCTP_DEFAULT_MAXSEGMENT;
 292}
 293
 294/* Hold a reference to a transport.  */
 295void sctp_transport_hold(struct sctp_transport *transport)
 296{
 297        atomic_inc(&transport->refcnt);
 298}
 299
 300/* Release a reference to a transport and clean up
 301 * if there are no more references.
 302 */
 303void sctp_transport_put(struct sctp_transport *transport)
 304{
 305        if (atomic_dec_and_test(&transport->refcnt))
 306                sctp_transport_destroy(transport);
 307}
 308
 309/* Update transport's RTO based on the newly calculated RTT. */
 310void sctp_transport_update_rto(struct sctp_transport *tp, __u32 rtt)
 311{
 312        /* Check for valid transport.  */
 313        SCTP_ASSERT(tp, "NULL transport", return);
 314
 315        /* We should not be doing any RTO updates unless rto_pending is set.  */
 316        SCTP_ASSERT(tp->rto_pending, "rto_pending not set", return);
 317
 318        if (tp->rttvar || tp->srtt) {
 319                /* 6.3.1 C3) When a new RTT measurement R' is made, set
 320                 * RTTVAR <- (1 - RTO.Beta) * RTTVAR + RTO.Beta * |SRTT - R'|
 321                 * SRTT <- (1 - RTO.Alpha) * SRTT + RTO.Alpha * R'
 322                 */
 323
 324                /* Note:  The above algorithm has been rewritten to
 325                 * express rto_beta and rto_alpha as inverse powers
 326                 * of two.
 327                 * For example, assuming the default value of RTO.Alpha of
 328                 * 1/8, rto_alpha would be expressed as 3.
 329                 */
 330                tp->rttvar = tp->rttvar - (tp->rttvar >> sctp_rto_beta)
 331                        + ((abs(tp->srtt - rtt)) >> sctp_rto_beta);
 332                tp->srtt = tp->srtt - (tp->srtt >> sctp_rto_alpha)
 333                        + (rtt >> sctp_rto_alpha);
 334        } else {
 335                /* 6.3.1 C2) When the first RTT measurement R is made, set
 336                 * SRTT <- R, RTTVAR <- R/2.
 337                 */
 338                tp->srtt = rtt;
 339                tp->rttvar = rtt >> 1;
 340        }
 341
 342        /* 6.3.1 G1) Whenever RTTVAR is computed, if RTTVAR = 0, then
 343         * adjust RTTVAR <- G, where G is the CLOCK GRANULARITY.
 344         */
 345        if (tp->rttvar == 0)
 346                tp->rttvar = SCTP_CLOCK_GRANULARITY;
 347
 348        /* 6.3.1 C3) After the computation, update RTO <- SRTT + 4 * RTTVAR. */
 349        tp->rto = tp->srtt + (tp->rttvar << 2);
 350
 351        /* 6.3.1 C6) Whenever RTO is computed, if it is less than RTO.Min
 352         * seconds then it is rounded up to RTO.Min seconds.
 353         */
 354        if (tp->rto < tp->asoc->rto_min)
 355                tp->rto = tp->asoc->rto_min;
 356
 357        /* 6.3.1 C7) A maximum value may be placed on RTO provided it is
 358         * at least RTO.max seconds.
 359         */
 360        if (tp->rto > tp->asoc->rto_max)
 361                tp->rto = tp->asoc->rto_max;
 362
 363        tp->rtt = rtt;
 364
 365        /* Reset rto_pending so that a new RTT measurement is started when a
 366         * new data chunk is sent.
 367         */
 368        tp->rto_pending = 0;
 369
 370        SCTP_DEBUG_PRINTK("%s: transport: %p, rtt: %d, srtt: %d "
 371                          "rttvar: %d, rto: %ld\n", __func__,
 372                          tp, rtt, tp->srtt, tp->rttvar, tp->rto);
 373}
 374
 375/* This routine updates the transport's cwnd and partial_bytes_acked
 376 * parameters based on the bytes acked in the received SACK.
 377 */
 378void sctp_transport_raise_cwnd(struct sctp_transport *transport,
 379                               __u32 sack_ctsn, __u32 bytes_acked)
 380{
 381        struct sctp_association *asoc = transport->asoc;
 382        __u32 cwnd, ssthresh, flight_size, pba, pmtu;
 383
 384        cwnd = transport->cwnd;
 385        flight_size = transport->flight_size;
 386
 387        /* See if we need to exit Fast Recovery first */
 388        if (asoc->fast_recovery &&
 389            TSN_lte(asoc->fast_recovery_exit, sack_ctsn))
 390                asoc->fast_recovery = 0;
 391
 392        /* The appropriate cwnd increase algorithm is performed if, and only
 393         * if the cumulative TSN whould advanced and the congestion window is
 394         * being fully utilized.
 395         */
 396        if (TSN_lte(sack_ctsn, transport->asoc->ctsn_ack_point) ||
 397            (flight_size < cwnd))
 398                return;
 399
 400        ssthresh = transport->ssthresh;
 401        pba = transport->partial_bytes_acked;
 402        pmtu = transport->asoc->pathmtu;
 403
 404        if (cwnd <= ssthresh) {
 405                /* RFC 4960 7.2.1
 406                 * o  When cwnd is less than or equal to ssthresh, an SCTP
 407                 *    endpoint MUST use the slow-start algorithm to increase
 408                 *    cwnd only if the current congestion window is being fully
 409                 *    utilized, an incoming SACK advances the Cumulative TSN
 410                 *    Ack Point, and the data sender is not in Fast Recovery.
 411                 *    Only when these three conditions are met can the cwnd be
 412                 *    increased; otherwise, the cwnd MUST not be increased.
 413                 *    If these conditions are met, then cwnd MUST be increased
 414                 *    by, at most, the lesser of 1) the total size of the
 415                 *    previously outstanding DATA chunk(s) acknowledged, and
 416                 *    2) the destination's path MTU.  This upper bound protects
 417                 *    against the ACK-Splitting attack outlined in [SAVAGE99].
 418                 */
 419                if (asoc->fast_recovery)
 420                        return;
 421
 422                if (bytes_acked > pmtu)
 423                        cwnd += pmtu;
 424                else
 425                        cwnd += bytes_acked;
 426                SCTP_DEBUG_PRINTK("%s: SLOW START: transport: %p, "
 427                                  "bytes_acked: %d, cwnd: %d, ssthresh: %d, "
 428                                  "flight_size: %d, pba: %d\n",
 429                                  __func__,
 430                                  transport, bytes_acked, cwnd,
 431                                  ssthresh, flight_size, pba);
 432        } else {
 433                /* RFC 2960 7.2.2 Whenever cwnd is greater than ssthresh,
 434                 * upon each SACK arrival that advances the Cumulative TSN Ack
 435                 * Point, increase partial_bytes_acked by the total number of
 436                 * bytes of all new chunks acknowledged in that SACK including
 437                 * chunks acknowledged by the new Cumulative TSN Ack and by
 438                 * Gap Ack Blocks.
 439                 *
 440                 * When partial_bytes_acked is equal to or greater than cwnd
 441                 * and before the arrival of the SACK the sender had cwnd or
 442                 * more bytes of data outstanding (i.e., before arrival of the
 443                 * SACK, flightsize was greater than or equal to cwnd),
 444                 * increase cwnd by MTU, and reset partial_bytes_acked to
 445                 * (partial_bytes_acked - cwnd).
 446                 */
 447                pba += bytes_acked;
 448                if (pba >= cwnd) {
 449                        cwnd += pmtu;
 450                        pba = ((cwnd < pba) ? (pba - cwnd) : 0);
 451                }
 452                SCTP_DEBUG_PRINTK("%s: CONGESTION AVOIDANCE: "
 453                                  "transport: %p, bytes_acked: %d, cwnd: %d, "
 454                                  "ssthresh: %d, flight_size: %d, pba: %d\n",
 455                                  __func__,
 456                                  transport, bytes_acked, cwnd,
 457                                  ssthresh, flight_size, pba);
 458        }
 459
 460        transport->cwnd = cwnd;
 461        transport->partial_bytes_acked = pba;
 462}
 463
 464/* This routine is used to lower the transport's cwnd when congestion is
 465 * detected.
 466 */
 467void sctp_transport_lower_cwnd(struct sctp_transport *transport,
 468                               sctp_lower_cwnd_t reason)
 469{
 470        struct sctp_association *asoc = transport->asoc;
 471
 472        switch (reason) {
 473        case SCTP_LOWER_CWND_T3_RTX:
 474                /* RFC 2960 Section 7.2.3, sctpimpguide
 475                 * When the T3-rtx timer expires on an address, SCTP should
 476                 * perform slow start by:
 477                 *      ssthresh = max(cwnd/2, 4*MTU)
 478                 *      cwnd = 1*MTU
 479                 *      partial_bytes_acked = 0
 480                 */
 481                transport->ssthresh = max(transport->cwnd/2,
 482                                          4*asoc->pathmtu);
 483                transport->cwnd = asoc->pathmtu;
 484
 485                /* T3-rtx also clears fast recovery */
 486                asoc->fast_recovery = 0;
 487                break;
 488
 489        case SCTP_LOWER_CWND_FAST_RTX:
 490                /* RFC 2960 7.2.4 Adjust the ssthresh and cwnd of the
 491                 * destination address(es) to which the missing DATA chunks
 492                 * were last sent, according to the formula described in
 493                 * Section 7.2.3.
 494                 *
 495                 * RFC 2960 7.2.3, sctpimpguide Upon detection of packet
 496                 * losses from SACK (see Section 7.2.4), An endpoint
 497                 * should do the following:
 498                 *      ssthresh = max(cwnd/2, 4*MTU)
 499                 *      cwnd = ssthresh
 500                 *      partial_bytes_acked = 0
 501                 */
 502                if (asoc->fast_recovery)
 503                        return;
 504
 505                /* Mark Fast recovery */
 506                asoc->fast_recovery = 1;
 507                asoc->fast_recovery_exit = asoc->next_tsn - 1;
 508
 509                transport->ssthresh = max(transport->cwnd/2,
 510                                          4*asoc->pathmtu);
 511                transport->cwnd = transport->ssthresh;
 512                break;
 513
 514        case SCTP_LOWER_CWND_ECNE:
 515                /* RFC 2481 Section 6.1.2.
 516                 * If the sender receives an ECN-Echo ACK packet
 517                 * then the sender knows that congestion was encountered in the
 518                 * network on the path from the sender to the receiver. The
 519                 * indication of congestion should be treated just as a
 520                 * congestion loss in non-ECN Capable TCP. That is, the TCP
 521                 * source halves the congestion window "cwnd" and reduces the
 522                 * slow start threshold "ssthresh".
 523                 * A critical condition is that TCP does not react to
 524                 * congestion indications more than once every window of
 525                 * data (or more loosely more than once every round-trip time).
 526                 */
 527                if (time_after(jiffies, transport->last_time_ecne_reduced +
 528                                        transport->rtt)) {
 529                        transport->ssthresh = max(transport->cwnd/2,
 530                                                  4*asoc->pathmtu);
 531                        transport->cwnd = transport->ssthresh;
 532                        transport->last_time_ecne_reduced = jiffies;
 533                }
 534                break;
 535
 536        case SCTP_LOWER_CWND_INACTIVE:
 537                /* RFC 2960 Section 7.2.1, sctpimpguide
 538                 * When the endpoint does not transmit data on a given
 539                 * transport address, the cwnd of the transport address
 540                 * should be adjusted to max(cwnd/2, 4*MTU) per RTO.
 541                 * NOTE: Although the draft recommends that this check needs
 542                 * to be done every RTO interval, we do it every hearbeat
 543                 * interval.
 544                 */
 545                transport->cwnd = max(transport->cwnd/2,
 546                                         4*asoc->pathmtu);
 547                break;
 548        }
 549
 550        transport->partial_bytes_acked = 0;
 551        SCTP_DEBUG_PRINTK("%s: transport: %p reason: %d cwnd: "
 552                          "%d ssthresh: %d\n", __func__,
 553                          transport, reason,
 554                          transport->cwnd, transport->ssthresh);
 555}
 556
 557/* Apply Max.Burst limit to the congestion window:
 558 * sctpimpguide-05 2.14.2
 559 * D) When the time comes for the sender to
 560 * transmit new DATA chunks, the protocol parameter Max.Burst MUST
 561 * first be applied to limit how many new DATA chunks may be sent.
 562 * The limit is applied by adjusting cwnd as follows:
 563 *      if ((flightsize+ Max.Burst * MTU) < cwnd)
 564 *              cwnd = flightsize + Max.Burst * MTU
 565 */
 566
 567void sctp_transport_burst_limited(struct sctp_transport *t)
 568{
 569        struct sctp_association *asoc = t->asoc;
 570        u32 old_cwnd = t->cwnd;
 571        u32 max_burst_bytes;
 572
 573        if (t->burst_limited)
 574                return;
 575
 576        max_burst_bytes = t->flight_size + (asoc->max_burst * asoc->pathmtu);
 577        if (max_burst_bytes < old_cwnd) {
 578                t->cwnd = max_burst_bytes;
 579                t->burst_limited = old_cwnd;
 580        }
 581}
 582
 583/* Restore the old cwnd congestion window, after the burst had it's
 584 * desired effect.
 585 */
 586void sctp_transport_burst_reset(struct sctp_transport *t)
 587{
 588        if (t->burst_limited) {
 589                t->cwnd = t->burst_limited;
 590                t->burst_limited = 0;
 591        }
 592}
 593
 594/* What is the next timeout value for this transport? */
 595unsigned long sctp_transport_timeout(struct sctp_transport *t)
 596{
 597        unsigned long timeout;
 598        timeout = t->rto + sctp_jitter(t->rto);
 599        if ((t->state != SCTP_UNCONFIRMED) &&
 600            (t->state != SCTP_PF))
 601                timeout += t->hbinterval;
 602        timeout += jiffies;
 603        return timeout;
 604}
 605
 606/* Reset transport variables to their initial values */
 607void sctp_transport_reset(struct sctp_transport *t)
 608{
 609        struct sctp_association *asoc = t->asoc;
 610
 611        /* RFC 2960 (bis), Section 5.2.4
 612         * All the congestion control parameters (e.g., cwnd, ssthresh)
 613         * related to this peer MUST be reset to their initial values
 614         * (see Section 6.2.1)
 615         */
 616        t->cwnd = min(4*asoc->pathmtu, max_t(__u32, 2*asoc->pathmtu, 4380));
 617        t->burst_limited = 0;
 618        t->ssthresh = asoc->peer.i.a_rwnd;
 619        t->rto = asoc->rto_initial;
 620        t->rtt = 0;
 621        t->srtt = 0;
 622        t->rttvar = 0;
 623
 624        /* Reset these additional varibles so that we have a clean
 625         * slate.
 626         */
 627        t->partial_bytes_acked = 0;
 628        t->flight_size = 0;
 629        t->error_count = 0;
 630        t->rto_pending = 0;
 631        t->hb_sent = 0;
 632
 633        /* Initialize the state information for SFR-CACC */
 634        t->cacc.changeover_active = 0;
 635        t->cacc.cycling_changeover = 0;
 636        t->cacc.next_tsn_at_change = 0;
 637        t->cacc.cacc_saw_newack = 0;
 638}
 639
 640/* Schedule retransmission on the given transport */
 641void sctp_transport_immediate_rtx(struct sctp_transport *t)
 642{
 643        /* Stop pending T3_rtx_timer */
 644        if (timer_pending(&t->T3_rtx_timer)) {
 645                (void)del_timer(&t->T3_rtx_timer);
 646                sctp_transport_put(t);
 647        }
 648        sctp_retransmit(&t->asoc->outqueue, t, SCTP_RTXR_T3_RTX);
 649        if (!timer_pending(&t->T3_rtx_timer)) {
 650                if (!mod_timer(&t->T3_rtx_timer, jiffies + t->rto))
 651                        sctp_transport_hold(t);
 652        }
 653        return;
 654}
 655
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