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 net *net,
  63                                                  struct sctp_transport *peer,
  64                                                  const union sctp_addr *addr,
  65                                                  gfp_t gfp)
  66{
  67        /* Copy in the address.  */
  68        peer->ipaddr = *addr;
  69        peer->af_specific = sctp_get_af_specific(addr->sa.sa_family);
  70        memset(&peer->saddr, 0, sizeof(union sctp_addr));
  71
  72        peer->sack_generation = 0;
  73
  74        /* From 6.3.1 RTO Calculation:
  75         *
  76         * C1) Until an RTT measurement has been made for a packet sent to the
  77         * given destination transport address, set RTO to the protocol
  78         * parameter 'RTO.Initial'.
  79         */
  80        peer->rto = msecs_to_jiffies(net->sctp.rto_initial);
  81
  82        peer->last_time_heard = jiffies;
  83        peer->last_time_ecne_reduced = jiffies;
  84
  85        peer->param_flags = SPP_HB_DISABLE |
  86                            SPP_PMTUD_ENABLE |
  87                            SPP_SACKDELAY_ENABLE;
  88
  89        /* Initialize the default path max_retrans.  */
  90        peer->pathmaxrxt  = net->sctp.max_retrans_path;
  91        peer->pf_retrans  = net->sctp.pf_retrans;
  92
  93        INIT_LIST_HEAD(&peer->transmitted);
  94        INIT_LIST_HEAD(&peer->send_ready);
  95        INIT_LIST_HEAD(&peer->transports);
  96
  97        setup_timer(&peer->T3_rtx_timer, sctp_generate_t3_rtx_event,
  98                        (unsigned long)peer);
  99        setup_timer(&peer->hb_timer, sctp_generate_heartbeat_event,
 100                        (unsigned long)peer);
 101        setup_timer(&peer->proto_unreach_timer,
 102                    sctp_generate_proto_unreach_event, (unsigned long)peer);
 103
 104        /* Initialize the 64-bit random nonce sent with heartbeat. */
 105        get_random_bytes(&peer->hb_nonce, sizeof(peer->hb_nonce));
 106
 107        atomic_set(&peer->refcnt, 1);
 108
 109        return peer;
 110}
 111
 112/* Allocate and initialize a new transport.  */
 113struct sctp_transport *sctp_transport_new(struct net *net,
 114                                          const union sctp_addr *addr,
 115                                          gfp_t gfp)
 116{
 117        struct sctp_transport *transport;
 118
 119        transport = t_new(struct sctp_transport, gfp);
 120        if (!transport)
 121                goto fail;
 122
 123        if (!sctp_transport_init(net, transport, addr, gfp))
 124                goto fail_init;
 125
 126        transport->malloced = 1;
 127        SCTP_DBG_OBJCNT_INC(transport);
 128
 129        return transport;
 130
 131fail_init:
 132        kfree(transport);
 133
 134fail:
 135        return NULL;
 136}
 137
 138/* This transport is no longer needed.  Free up if possible, or
 139 * delay until it last reference count.
 140 */
 141void sctp_transport_free(struct sctp_transport *transport)
 142{
 143        transport->dead = 1;
 144
 145        /* Try to delete the heartbeat timer.  */
 146        if (del_timer(&transport->hb_timer))
 147                sctp_transport_put(transport);
 148
 149        /* Delete the T3_rtx timer if it's active.
 150         * There is no point in not doing this now and letting
 151         * structure hang around in memory since we know
 152         * the tranport is going away.
 153         */
 154        if (timer_pending(&transport->T3_rtx_timer) &&
 155            del_timer(&transport->T3_rtx_timer))
 156                sctp_transport_put(transport);
 157
 158        /* Delete the ICMP proto unreachable timer if it's active. */
 159        if (timer_pending(&transport->proto_unreach_timer) &&
 160            del_timer(&transport->proto_unreach_timer))
 161                sctp_association_put(transport->asoc);
 162
 163        sctp_transport_put(transport);
 164}
 165
 166/* Destroy the transport data structure.
 167 * Assumes there are no more users of this structure.
 168 */
 169static void sctp_transport_destroy(struct sctp_transport *transport)
 170{
 171        SCTP_ASSERT(transport->dead, "Transport is not dead", return);
 172
 173        if (transport->asoc)
 174                sctp_association_put(transport->asoc);
 175
 176        sctp_packet_free(&transport->packet);
 177
 178        dst_release(transport->dst);
 179        kfree(transport);
 180        SCTP_DBG_OBJCNT_DEC(transport);
 181}
 182
 183/* Start T3_rtx timer if it is not already running and update the heartbeat
 184 * timer.  This routine is called every time a DATA chunk is sent.
 185 */
 186void sctp_transport_reset_timers(struct sctp_transport *transport)
 187{
 188        /* RFC 2960 6.3.2 Retransmission Timer Rules
 189         *
 190         * R1) Every time a DATA chunk is sent to any address(including a
 191         * retransmission), if the T3-rtx timer of that address is not running
 192         * start it running so that it will expire after the RTO of that
 193         * address.
 194         */
 195
 196        if (!timer_pending(&transport->T3_rtx_timer))
 197                if (!mod_timer(&transport->T3_rtx_timer,
 198                               jiffies + transport->rto))
 199                        sctp_transport_hold(transport);
 200
 201        /* When a data chunk is sent, reset the heartbeat interval.  */
 202        if (!mod_timer(&transport->hb_timer,
 203                       sctp_transport_timeout(transport)))
 204            sctp_transport_hold(transport);
 205}
 206
 207/* This transport has been assigned to an association.
 208 * Initialize fields from the association or from the sock itself.
 209 * Register the reference count in the association.
 210 */
 211void sctp_transport_set_owner(struct sctp_transport *transport,
 212                              struct sctp_association *asoc)
 213{
 214        transport->asoc = asoc;
 215        sctp_association_hold(asoc);
 216}
 217
 218/* Initialize the pmtu of a transport. */
 219void sctp_transport_pmtu(struct sctp_transport *transport, struct sock *sk)
 220{
 221        /* If we don't have a fresh route, look one up */
 222        if (!transport->dst || transport->dst->obsolete) {
 223                dst_release(transport->dst);
 224                transport->af_specific->get_dst(transport, &transport->saddr,
 225                                                &transport->fl, sk);
 226        }
 227
 228        if (transport->dst) {
 229                transport->pathmtu = dst_mtu(transport->dst);
 230        } else
 231                transport->pathmtu = SCTP_DEFAULT_MAXSEGMENT;
 232}
 233
 234void sctp_transport_update_pmtu(struct sock *sk, struct sctp_transport *t, u32 pmtu)
 235{
 236        struct dst_entry *dst;
 237
 238        if (unlikely(pmtu < SCTP_DEFAULT_MINSEGMENT)) {
 239                pr_warn("%s: Reported pmtu %d too low, using default minimum of %d\n",
 240                        __func__, pmtu,
 241                        SCTP_DEFAULT_MINSEGMENT);
 242                /* Use default minimum segment size and disable
 243                 * pmtu discovery on this transport.
 244                 */
 245                t->pathmtu = SCTP_DEFAULT_MINSEGMENT;
 246        } else {
 247                t->pathmtu = pmtu;
 248        }
 249
 250        dst = sctp_transport_dst_check(t);
 251        if (!dst)
 252                t->af_specific->get_dst(t, &t->saddr, &t->fl, sk);
 253
 254        if (dst) {
 255                dst->ops->update_pmtu(dst, sk, NULL, pmtu);
 256
 257                dst = sctp_transport_dst_check(t);
 258                if (!dst)
 259                        t->af_specific->get_dst(t, &t->saddr, &t->fl, sk);
 260        }
 261}
 262
 263/* Caches the dst entry and source address for a transport's destination
 264 * address.
 265 */
 266void sctp_transport_route(struct sctp_transport *transport,
 267                          union sctp_addr *saddr, struct sctp_sock *opt)
 268{
 269        struct sctp_association *asoc = transport->asoc;
 270        struct sctp_af *af = transport->af_specific;
 271
 272        af->get_dst(transport, saddr, &transport->fl, sctp_opt2sk(opt));
 273
 274        if (saddr)
 275                memcpy(&transport->saddr, saddr, sizeof(union sctp_addr));
 276        else
 277                af->get_saddr(opt, transport, &transport->fl);
 278
 279        if ((transport->param_flags & SPP_PMTUD_DISABLE) && transport->pathmtu) {
 280                return;
 281        }
 282        if (transport->dst) {
 283                transport->pathmtu = dst_mtu(transport->dst);
 284
 285                /* Initialize sk->sk_rcv_saddr, if the transport is the
 286                 * association's active path for getsockname().
 287                 */
 288                if (asoc && (!asoc->peer.primary_path ||
 289                                (transport == asoc->peer.active_path)))
 290                        opt->pf->af->to_sk_saddr(&transport->saddr,
 291                                                 asoc->base.sk);
 292        } else
 293                transport->pathmtu = SCTP_DEFAULT_MAXSEGMENT;
 294}
 295
 296/* Hold a reference to a transport.  */
 297void sctp_transport_hold(struct sctp_transport *transport)
 298{
 299        atomic_inc(&transport->refcnt);
 300}
 301
 302/* Release a reference to a transport and clean up
 303 * if there are no more references.
 304 */
 305void sctp_transport_put(struct sctp_transport *transport)
 306{
 307        if (atomic_dec_and_test(&transport->refcnt))
 308                sctp_transport_destroy(transport);
 309}
 310
 311/* Update transport's RTO based on the newly calculated RTT. */
 312void sctp_transport_update_rto(struct sctp_transport *tp, __u32 rtt)
 313{
 314        /* Check for valid transport.  */
 315        SCTP_ASSERT(tp, "NULL transport", return);
 316
 317        /* We should not be doing any RTO updates unless rto_pending is set.  */
 318        SCTP_ASSERT(tp->rto_pending, "rto_pending not set", return);
 319
 320        if (tp->rttvar || tp->srtt) {
 321                struct net *net = sock_net(tp->asoc->base.sk);
 322                /* 6.3.1 C3) When a new RTT measurement R' is made, set
 323                 * RTTVAR <- (1 - RTO.Beta) * RTTVAR + RTO.Beta * |SRTT - R'|
 324                 * SRTT <- (1 - RTO.Alpha) * SRTT + RTO.Alpha * R'
 325                 */
 326
 327                /* Note:  The above algorithm has been rewritten to
 328                 * express rto_beta and rto_alpha as inverse powers
 329                 * of two.
 330                 * For example, assuming the default value of RTO.Alpha of
 331                 * 1/8, rto_alpha would be expressed as 3.
 332                 */
 333                tp->rttvar = tp->rttvar - (tp->rttvar >> net->sctp.rto_beta)
 334                        + (((__u32)abs64((__s64)tp->srtt - (__s64)rtt)) >> net->sctp.rto_beta);
 335                tp->srtt = tp->srtt - (tp->srtt >> net->sctp.rto_alpha)
 336                        + (rtt >> net->sctp.rto_alpha);
 337        } else {
 338                /* 6.3.1 C2) When the first RTT measurement R is made, set
 339                 * SRTT <- R, RTTVAR <- R/2.
 340                 */
 341                tp->srtt = rtt;
 342                tp->rttvar = rtt >> 1;
 343        }
 344
 345        /* 6.3.1 G1) Whenever RTTVAR is computed, if RTTVAR = 0, then
 346         * adjust RTTVAR <- G, where G is the CLOCK GRANULARITY.
 347         */
 348        if (tp->rttvar == 0)
 349                tp->rttvar = SCTP_CLOCK_GRANULARITY;
 350
 351        /* 6.3.1 C3) After the computation, update RTO <- SRTT + 4 * RTTVAR. */
 352        tp->rto = tp->srtt + (tp->rttvar << 2);
 353
 354        /* 6.3.1 C6) Whenever RTO is computed, if it is less than RTO.Min
 355         * seconds then it is rounded up to RTO.Min seconds.
 356         */
 357        if (tp->rto < tp->asoc->rto_min)
 358                tp->rto = tp->asoc->rto_min;
 359
 360        /* 6.3.1 C7) A maximum value may be placed on RTO provided it is
 361         * at least RTO.max seconds.
 362         */
 363        if (tp->rto > tp->asoc->rto_max)
 364                tp->rto = tp->asoc->rto_max;
 365
 366        tp->rtt = rtt;
 367
 368        /* Reset rto_pending so that a new RTT measurement is started when a
 369         * new data chunk is sent.
 370         */
 371        tp->rto_pending = 0;
 372
 373        SCTP_DEBUG_PRINTK("%s: transport: %p, rtt: %d, srtt: %d "
 374                          "rttvar: %d, rto: %ld\n", __func__,
 375                          tp, rtt, tp->srtt, tp->rttvar, tp->rto);
 376}
 377
 378/* This routine updates the transport's cwnd and partial_bytes_acked
 379 * parameters based on the bytes acked in the received SACK.
 380 */
 381void sctp_transport_raise_cwnd(struct sctp_transport *transport,
 382                               __u32 sack_ctsn, __u32 bytes_acked)
 383{
 384        struct sctp_association *asoc = transport->asoc;
 385        __u32 cwnd, ssthresh, flight_size, pba, pmtu;
 386
 387        cwnd = transport->cwnd;
 388        flight_size = transport->flight_size;
 389
 390        /* See if we need to exit Fast Recovery first */
 391        if (asoc->fast_recovery &&
 392            TSN_lte(asoc->fast_recovery_exit, sack_ctsn))
 393                asoc->fast_recovery = 0;
 394
 395        /* The appropriate cwnd increase algorithm is performed if, and only
 396         * if the cumulative TSN whould advanced and the congestion window is
 397         * being fully utilized.
 398         */
 399        if (TSN_lte(sack_ctsn, transport->asoc->ctsn_ack_point) ||
 400            (flight_size < cwnd))
 401                return;
 402
 403        ssthresh = transport->ssthresh;
 404        pba = transport->partial_bytes_acked;
 405        pmtu = transport->asoc->pathmtu;
 406
 407        if (cwnd <= ssthresh) {
 408                /* RFC 4960 7.2.1
 409                 * o  When cwnd is less than or equal to ssthresh, an SCTP
 410                 *    endpoint MUST use the slow-start algorithm to increase
 411                 *    cwnd only if the current congestion window is being fully
 412                 *    utilized, an incoming SACK advances the Cumulative TSN
 413                 *    Ack Point, and the data sender is not in Fast Recovery.
 414                 *    Only when these three conditions are met can the cwnd be
 415                 *    increased; otherwise, the cwnd MUST not be increased.
 416                 *    If these conditions are met, then cwnd MUST be increased
 417                 *    by, at most, the lesser of 1) the total size of the
 418                 *    previously outstanding DATA chunk(s) acknowledged, and
 419                 *    2) the destination's path MTU.  This upper bound protects
 420                 *    against the ACK-Splitting attack outlined in [SAVAGE99].
 421                 */
 422                if (asoc->fast_recovery)
 423                        return;
 424
 425                if (bytes_acked > pmtu)
 426                        cwnd += pmtu;
 427                else
 428                        cwnd += bytes_acked;
 429                SCTP_DEBUG_PRINTK("%s: SLOW START: transport: %p, "
 430                                  "bytes_acked: %d, cwnd: %d, ssthresh: %d, "
 431                                  "flight_size: %d, pba: %d\n",
 432                                  __func__,
 433                                  transport, bytes_acked, cwnd,
 434                                  ssthresh, flight_size, pba);
 435        } else {
 436                /* RFC 2960 7.2.2 Whenever cwnd is greater than ssthresh,
 437                 * upon each SACK arrival that advances the Cumulative TSN Ack
 438                 * Point, increase partial_bytes_acked by the total number of
 439                 * bytes of all new chunks acknowledged in that SACK including
 440                 * chunks acknowledged by the new Cumulative TSN Ack and by
 441                 * Gap Ack Blocks.
 442                 *
 443                 * When partial_bytes_acked is equal to or greater than cwnd
 444                 * and before the arrival of the SACK the sender had cwnd or
 445                 * more bytes of data outstanding (i.e., before arrival of the
 446                 * SACK, flightsize was greater than or equal to cwnd),
 447                 * increase cwnd by MTU, and reset partial_bytes_acked to
 448                 * (partial_bytes_acked - cwnd).
 449                 */
 450                pba += bytes_acked;
 451                if (pba >= cwnd) {
 452                        cwnd += pmtu;
 453                        pba = ((cwnd < pba) ? (pba - cwnd) : 0);
 454                }
 455                SCTP_DEBUG_PRINTK("%s: CONGESTION AVOIDANCE: "
 456                                  "transport: %p, bytes_acked: %d, cwnd: %d, "
 457                                  "ssthresh: %d, flight_size: %d, pba: %d\n",
 458                                  __func__,
 459                                  transport, bytes_acked, cwnd,
 460                                  ssthresh, flight_size, pba);
 461        }
 462
 463        transport->cwnd = cwnd;
 464        transport->partial_bytes_acked = pba;
 465}
 466
 467/* This routine is used to lower the transport's cwnd when congestion is
 468 * detected.
 469 */
 470void sctp_transport_lower_cwnd(struct sctp_transport *transport,
 471                               sctp_lower_cwnd_t reason)
 472{
 473        struct sctp_association *asoc = transport->asoc;
 474
 475        switch (reason) {
 476        case SCTP_LOWER_CWND_T3_RTX:
 477                /* RFC 2960 Section 7.2.3, sctpimpguide
 478                 * When the T3-rtx timer expires on an address, SCTP should
 479                 * perform slow start by:
 480                 *      ssthresh = max(cwnd/2, 4*MTU)
 481                 *      cwnd = 1*MTU
 482                 *      partial_bytes_acked = 0
 483                 */
 484                transport->ssthresh = max(transport->cwnd/2,
 485                                          4*asoc->pathmtu);
 486                transport->cwnd = asoc->pathmtu;
 487
 488                /* T3-rtx also clears fast recovery */
 489                asoc->fast_recovery = 0;
 490                break;
 491
 492        case SCTP_LOWER_CWND_FAST_RTX:
 493                /* RFC 2960 7.2.4 Adjust the ssthresh and cwnd of the
 494                 * destination address(es) to which the missing DATA chunks
 495                 * were last sent, according to the formula described in
 496                 * Section 7.2.3.
 497                 *
 498                 * RFC 2960 7.2.3, sctpimpguide Upon detection of packet
 499                 * losses from SACK (see Section 7.2.4), An endpoint
 500                 * should do the following:
 501                 *      ssthresh = max(cwnd/2, 4*MTU)
 502                 *      cwnd = ssthresh
 503                 *      partial_bytes_acked = 0
 504                 */
 505                if (asoc->fast_recovery)
 506                        return;
 507
 508                /* Mark Fast recovery */
 509                asoc->fast_recovery = 1;
 510                asoc->fast_recovery_exit = asoc->next_tsn - 1;
 511
 512                transport->ssthresh = max(transport->cwnd/2,
 513                                          4*asoc->pathmtu);
 514                transport->cwnd = transport->ssthresh;
 515                break;
 516
 517        case SCTP_LOWER_CWND_ECNE:
 518                /* RFC 2481 Section 6.1.2.
 519                 * If the sender receives an ECN-Echo ACK packet
 520                 * then the sender knows that congestion was encountered in the
 521                 * network on the path from the sender to the receiver. The
 522                 * indication of congestion should be treated just as a
 523                 * congestion loss in non-ECN Capable TCP. That is, the TCP
 524                 * source halves the congestion window "cwnd" and reduces the
 525                 * slow start threshold "ssthresh".
 526                 * A critical condition is that TCP does not react to
 527                 * congestion indications more than once every window of
 528                 * data (or more loosely more than once every round-trip time).
 529                 */
 530                if (time_after(jiffies, transport->last_time_ecne_reduced +
 531                                        transport->rtt)) {
 532                        transport->ssthresh = max(transport->cwnd/2,
 533                                                  4*asoc->pathmtu);
 534                        transport->cwnd = transport->ssthresh;
 535                        transport->last_time_ecne_reduced = jiffies;
 536                }
 537                break;
 538
 539        case SCTP_LOWER_CWND_INACTIVE:
 540                /* RFC 2960 Section 7.2.1, sctpimpguide
 541                 * When the endpoint does not transmit data on a given
 542                 * transport address, the cwnd of the transport address
 543                 * should be adjusted to max(cwnd/2, 4*MTU) per RTO.
 544                 * NOTE: Although the draft recommends that this check needs
 545                 * to be done every RTO interval, we do it every hearbeat
 546                 * interval.
 547                 */
 548                transport->cwnd = max(transport->cwnd/2,
 549                                         4*asoc->pathmtu);
 550                break;
 551        }
 552
 553        transport->partial_bytes_acked = 0;
 554        SCTP_DEBUG_PRINTK("%s: transport: %p reason: %d cwnd: "
 555                          "%d ssthresh: %d\n", __func__,
 556                          transport, reason,
 557                          transport->cwnd, transport->ssthresh);
 558}
 559
 560/* Apply Max.Burst limit to the congestion window:
 561 * sctpimpguide-05 2.14.2
 562 * D) When the time comes for the sender to
 563 * transmit new DATA chunks, the protocol parameter Max.Burst MUST
 564 * first be applied to limit how many new DATA chunks may be sent.
 565 * The limit is applied by adjusting cwnd as follows:
 566 *      if ((flightsize+ Max.Burst * MTU) < cwnd)
 567 *              cwnd = flightsize + Max.Burst * MTU
 568 */
 569
 570void sctp_transport_burst_limited(struct sctp_transport *t)
 571{
 572        struct sctp_association *asoc = t->asoc;
 573        u32 old_cwnd = t->cwnd;
 574        u32 max_burst_bytes;
 575
 576        if (t->burst_limited)
 577                return;
 578
 579        max_burst_bytes = t->flight_size + (asoc->max_burst * asoc->pathmtu);
 580        if (max_burst_bytes < old_cwnd) {
 581                t->cwnd = max_burst_bytes;
 582                t->burst_limited = old_cwnd;
 583        }
 584}
 585
 586/* Restore the old cwnd congestion window, after the burst had it's
 587 * desired effect.
 588 */
 589void sctp_transport_burst_reset(struct sctp_transport *t)
 590{
 591        if (t->burst_limited) {
 592                t->cwnd = t->burst_limited;
 593                t->burst_limited = 0;
 594        }
 595}
 596
 597/* What is the next timeout value for this transport? */
 598unsigned long sctp_transport_timeout(struct sctp_transport *t)
 599{
 600        unsigned long timeout;
 601        timeout = t->rto + sctp_jitter(t->rto);
 602        if ((t->state != SCTP_UNCONFIRMED) &&
 603            (t->state != SCTP_PF))
 604                timeout += t->hbinterval;
 605        timeout += jiffies;
 606        return timeout;
 607}
 608
 609/* Reset transport variables to their initial values */
 610void sctp_transport_reset(struct sctp_transport *t)
 611{
 612        struct sctp_association *asoc = t->asoc;
 613
 614        /* RFC 2960 (bis), Section 5.2.4
 615         * All the congestion control parameters (e.g., cwnd, ssthresh)
 616         * related to this peer MUST be reset to their initial values
 617         * (see Section 6.2.1)
 618         */
 619        t->cwnd = min(4*asoc->pathmtu, max_t(__u32, 2*asoc->pathmtu, 4380));
 620        t->burst_limited = 0;
 621        t->ssthresh = asoc->peer.i.a_rwnd;
 622        t->rto = asoc->rto_initial;
 623        t->rtt = 0;
 624        t->srtt = 0;
 625        t->rttvar = 0;
 626
 627        /* Reset these additional varibles so that we have a clean
 628         * slate.
 629         */
 630        t->partial_bytes_acked = 0;
 631        t->flight_size = 0;
 632        t->error_count = 0;
 633        t->rto_pending = 0;
 634        t->hb_sent = 0;
 635
 636        /* Initialize the state information for SFR-CACC */
 637        t->cacc.changeover_active = 0;
 638        t->cacc.cycling_changeover = 0;
 639        t->cacc.next_tsn_at_change = 0;
 640        t->cacc.cacc_saw_newack = 0;
 641}
 642
 643/* Schedule retransmission on the given transport */
 644void sctp_transport_immediate_rtx(struct sctp_transport *t)
 645{
 646        /* Stop pending T3_rtx_timer */
 647        if (timer_pending(&t->T3_rtx_timer)) {
 648                (void)del_timer(&t->T3_rtx_timer);
 649                sctp_transport_put(t);
 650        }
 651        sctp_retransmit(&t->asoc->outqueue, t, SCTP_RTXR_T3_RTX);
 652        if (!timer_pending(&t->T3_rtx_timer)) {
 653                if (!mod_timer(&t->T3_rtx_timer, jiffies + t->rto))
 654                        sctp_transport_hold(t);
 655        }
 656        return;
 657}
 658
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