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
 166static void sctp_transport_destroy_rcu(struct rcu_head *head)
 167{
 168        struct sctp_transport *transport;
 169
 170        transport = container_of(head, struct sctp_transport, rcu);
 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/* Destroy the transport data structure.
 182 * Assumes there are no more users of this structure.
 183 */
 184static void sctp_transport_destroy(struct sctp_transport *transport)
 185{
 186        SCTP_ASSERT(transport->dead, "Transport is not dead", return);
 187
 188        call_rcu(&transport->rcu, sctp_transport_destroy_rcu);
 189}
 190
 191/* Start T3_rtx timer if it is not already running and update the heartbeat
 192 * timer.  This routine is called every time a DATA chunk is sent.
 193 */
 194void sctp_transport_reset_timers(struct sctp_transport *transport)
 195{
 196        /* RFC 2960 6.3.2 Retransmission Timer Rules
 197         *
 198         * R1) Every time a DATA chunk is sent to any address(including a
 199         * retransmission), if the T3-rtx timer of that address is not running
 200         * start it running so that it will expire after the RTO of that
 201         * address.
 202         */
 203
 204        if (!timer_pending(&transport->T3_rtx_timer))
 205                if (!mod_timer(&transport->T3_rtx_timer,
 206                               jiffies + transport->rto))
 207                        sctp_transport_hold(transport);
 208
 209        /* When a data chunk is sent, reset the heartbeat interval.  */
 210        if (!mod_timer(&transport->hb_timer,
 211                       sctp_transport_timeout(transport)))
 212            sctp_transport_hold(transport);
 213}
 214
 215/* This transport has been assigned to an association.
 216 * Initialize fields from the association or from the sock itself.
 217 * Register the reference count in the association.
 218 */
 219void sctp_transport_set_owner(struct sctp_transport *transport,
 220                              struct sctp_association *asoc)
 221{
 222        transport->asoc = asoc;
 223        sctp_association_hold(asoc);
 224}
 225
 226/* Initialize the pmtu of a transport. */
 227void sctp_transport_pmtu(struct sctp_transport *transport, struct sock *sk)
 228{
 229        /* If we don't have a fresh route, look one up */
 230        if (!transport->dst || transport->dst->obsolete) {
 231                dst_release(transport->dst);
 232                transport->af_specific->get_dst(transport, &transport->saddr,
 233                                                &transport->fl, sk);
 234        }
 235
 236        if (transport->dst) {
 237                transport->pathmtu = dst_mtu(transport->dst);
 238        } else
 239                transport->pathmtu = SCTP_DEFAULT_MAXSEGMENT;
 240}
 241
 242void sctp_transport_update_pmtu(struct sock *sk, struct sctp_transport *t, u32 pmtu)
 243{
 244        struct dst_entry *dst;
 245
 246        if (unlikely(pmtu < SCTP_DEFAULT_MINSEGMENT)) {
 247                pr_warn("%s: Reported pmtu %d too low, using default minimum of %d\n",
 248                        __func__, pmtu,
 249                        SCTP_DEFAULT_MINSEGMENT);
 250                /* Use default minimum segment size and disable
 251                 * pmtu discovery on this transport.
 252                 */
 253                t->pathmtu = SCTP_DEFAULT_MINSEGMENT;
 254        } else {
 255                t->pathmtu = pmtu;
 256        }
 257
 258        dst = sctp_transport_dst_check(t);
 259        if (!dst)
 260                t->af_specific->get_dst(t, &t->saddr, &t->fl, sk);
 261
 262        if (dst) {
 263                dst->ops->update_pmtu(dst, sk, NULL, pmtu);
 264
 265                dst = sctp_transport_dst_check(t);
 266                if (!dst)
 267                        t->af_specific->get_dst(t, &t->saddr, &t->fl, sk);
 268        }
 269}
 270
 271/* Caches the dst entry and source address for a transport's destination
 272 * address.
 273 */
 274void sctp_transport_route(struct sctp_transport *transport,
 275                          union sctp_addr *saddr, struct sctp_sock *opt)
 276{
 277        struct sctp_association *asoc = transport->asoc;
 278        struct sctp_af *af = transport->af_specific;
 279
 280        af->get_dst(transport, saddr, &transport->fl, sctp_opt2sk(opt));
 281
 282        if (saddr)
 283                memcpy(&transport->saddr, saddr, sizeof(union sctp_addr));
 284        else
 285                af->get_saddr(opt, transport, &transport->fl);
 286
 287        if ((transport->param_flags & SPP_PMTUD_DISABLE) && transport->pathmtu) {
 288                return;
 289        }
 290        if (transport->dst) {
 291                transport->pathmtu = dst_mtu(transport->dst);
 292
 293                /* Initialize sk->sk_rcv_saddr, if the transport is the
 294                 * association's active path for getsockname().
 295                 */
 296                if (asoc && (!asoc->peer.primary_path ||
 297                                (transport == asoc->peer.active_path)))
 298                        opt->pf->af->to_sk_saddr(&transport->saddr,
 299                                                 asoc->base.sk);
 300        } else
 301                transport->pathmtu = SCTP_DEFAULT_MAXSEGMENT;
 302}
 303
 304/* Hold a reference to a transport.  */
 305void sctp_transport_hold(struct sctp_transport *transport)
 306{
 307        atomic_inc(&transport->refcnt);
 308}
 309
 310/* Release a reference to a transport and clean up
 311 * if there are no more references.
 312 */
 313void sctp_transport_put(struct sctp_transport *transport)
 314{
 315        if (atomic_dec_and_test(&transport->refcnt))
 316                sctp_transport_destroy(transport);
 317}
 318
 319/* Update transport's RTO based on the newly calculated RTT. */
 320void sctp_transport_update_rto(struct sctp_transport *tp, __u32 rtt)
 321{
 322        /* Check for valid transport.  */
 323        SCTP_ASSERT(tp, "NULL transport", return);
 324
 325        /* We should not be doing any RTO updates unless rto_pending is set.  */
 326        SCTP_ASSERT(tp->rto_pending, "rto_pending not set", return);
 327
 328        if (tp->rttvar || tp->srtt) {
 329                struct net *net = sock_net(tp->asoc->base.sk);
 330                /* 6.3.1 C3) When a new RTT measurement R' is made, set
 331                 * RTTVAR <- (1 - RTO.Beta) * RTTVAR + RTO.Beta * |SRTT - R'|
 332                 * SRTT <- (1 - RTO.Alpha) * SRTT + RTO.Alpha * R'
 333                 */
 334
 335                /* Note:  The above algorithm has been rewritten to
 336                 * express rto_beta and rto_alpha as inverse powers
 337                 * of two.
 338                 * For example, assuming the default value of RTO.Alpha of
 339                 * 1/8, rto_alpha would be expressed as 3.
 340                 */
 341                tp->rttvar = tp->rttvar - (tp->rttvar >> net->sctp.rto_beta)
 342                        + (((__u32)abs64((__s64)tp->srtt - (__s64)rtt)) >> net->sctp.rto_beta);
 343                tp->srtt = tp->srtt - (tp->srtt >> net->sctp.rto_alpha)
 344                        + (rtt >> net->sctp.rto_alpha);
 345        } else {
 346                /* 6.3.1 C2) When the first RTT measurement R is made, set
 347                 * SRTT <- R, RTTVAR <- R/2.
 348                 */
 349                tp->srtt = rtt;
 350                tp->rttvar = rtt >> 1;
 351        }
 352
 353        /* 6.3.1 G1) Whenever RTTVAR is computed, if RTTVAR = 0, then
 354         * adjust RTTVAR <- G, where G is the CLOCK GRANULARITY.
 355         */
 356        if (tp->rttvar == 0)
 357                tp->rttvar = SCTP_CLOCK_GRANULARITY;
 358
 359        /* 6.3.1 C3) After the computation, update RTO <- SRTT + 4 * RTTVAR. */
 360        tp->rto = tp->srtt + (tp->rttvar << 2);
 361
 362        /* 6.3.1 C6) Whenever RTO is computed, if it is less than RTO.Min
 363         * seconds then it is rounded up to RTO.Min seconds.
 364         */
 365        if (tp->rto < tp->asoc->rto_min)
 366                tp->rto = tp->asoc->rto_min;
 367
 368        /* 6.3.1 C7) A maximum value may be placed on RTO provided it is
 369         * at least RTO.max seconds.
 370         */
 371        if (tp->rto > tp->asoc->rto_max)
 372                tp->rto = tp->asoc->rto_max;
 373
 374        sctp_max_rto(tp->asoc, tp);
 375        tp->rtt = rtt;
 376
 377        /* Reset rto_pending so that a new RTT measurement is started when a
 378         * new data chunk is sent.
 379         */
 380        tp->rto_pending = 0;
 381
 382        SCTP_DEBUG_PRINTK("%s: transport: %p, rtt: %d, srtt: %d "
 383                          "rttvar: %d, rto: %ld\n", __func__,
 384                          tp, rtt, tp->srtt, tp->rttvar, tp->rto);
 385}
 386
 387/* This routine updates the transport's cwnd and partial_bytes_acked
 388 * parameters based on the bytes acked in the received SACK.
 389 */
 390void sctp_transport_raise_cwnd(struct sctp_transport *transport,
 391                               __u32 sack_ctsn, __u32 bytes_acked)
 392{
 393        struct sctp_association *asoc = transport->asoc;
 394        __u32 cwnd, ssthresh, flight_size, pba, pmtu;
 395
 396        cwnd = transport->cwnd;
 397        flight_size = transport->flight_size;
 398
 399        /* See if we need to exit Fast Recovery first */
 400        if (asoc->fast_recovery &&
 401            TSN_lte(asoc->fast_recovery_exit, sack_ctsn))
 402                asoc->fast_recovery = 0;
 403
 404        /* The appropriate cwnd increase algorithm is performed if, and only
 405         * if the cumulative TSN whould advanced and the congestion window is
 406         * being fully utilized.
 407         */
 408        if (TSN_lte(sack_ctsn, transport->asoc->ctsn_ack_point) ||
 409            (flight_size < cwnd))
 410                return;
 411
 412        ssthresh = transport->ssthresh;
 413        pba = transport->partial_bytes_acked;
 414        pmtu = transport->asoc->pathmtu;
 415
 416        if (cwnd <= ssthresh) {
 417                /* RFC 4960 7.2.1
 418                 * o  When cwnd is less than or equal to ssthresh, an SCTP
 419                 *    endpoint MUST use the slow-start algorithm to increase
 420                 *    cwnd only if the current congestion window is being fully
 421                 *    utilized, an incoming SACK advances the Cumulative TSN
 422                 *    Ack Point, and the data sender is not in Fast Recovery.
 423                 *    Only when these three conditions are met can the cwnd be
 424                 *    increased; otherwise, the cwnd MUST not be increased.
 425                 *    If these conditions are met, then cwnd MUST be increased
 426                 *    by, at most, the lesser of 1) the total size of the
 427                 *    previously outstanding DATA chunk(s) acknowledged, and
 428                 *    2) the destination's path MTU.  This upper bound protects
 429                 *    against the ACK-Splitting attack outlined in [SAVAGE99].
 430                 */
 431                if (asoc->fast_recovery)
 432                        return;
 433
 434                if (bytes_acked > pmtu)
 435                        cwnd += pmtu;
 436                else
 437                        cwnd += bytes_acked;
 438                SCTP_DEBUG_PRINTK("%s: SLOW START: transport: %p, "
 439                                  "bytes_acked: %d, cwnd: %d, ssthresh: %d, "
 440                                  "flight_size: %d, pba: %d\n",
 441                                  __func__,
 442                                  transport, bytes_acked, cwnd,
 443                                  ssthresh, flight_size, pba);
 444        } else {
 445                /* RFC 2960 7.2.2 Whenever cwnd is greater than ssthresh,
 446                 * upon each SACK arrival that advances the Cumulative TSN Ack
 447                 * Point, increase partial_bytes_acked by the total number of
 448                 * bytes of all new chunks acknowledged in that SACK including
 449                 * chunks acknowledged by the new Cumulative TSN Ack and by
 450                 * Gap Ack Blocks.
 451                 *
 452                 * When partial_bytes_acked is equal to or greater than cwnd
 453                 * and before the arrival of the SACK the sender had cwnd or
 454                 * more bytes of data outstanding (i.e., before arrival of the
 455                 * SACK, flightsize was greater than or equal to cwnd),
 456                 * increase cwnd by MTU, and reset partial_bytes_acked to
 457                 * (partial_bytes_acked - cwnd).
 458                 */
 459                pba += bytes_acked;
 460                if (pba >= cwnd) {
 461                        cwnd += pmtu;
 462                        pba = ((cwnd < pba) ? (pba - cwnd) : 0);
 463                }
 464                SCTP_DEBUG_PRINTK("%s: CONGESTION AVOIDANCE: "
 465                                  "transport: %p, bytes_acked: %d, cwnd: %d, "
 466                                  "ssthresh: %d, flight_size: %d, pba: %d\n",
 467                                  __func__,
 468                                  transport, bytes_acked, cwnd,
 469                                  ssthresh, flight_size, pba);
 470        }
 471
 472        transport->cwnd = cwnd;
 473        transport->partial_bytes_acked = pba;
 474}
 475
 476/* This routine is used to lower the transport's cwnd when congestion is
 477 * detected.
 478 */
 479void sctp_transport_lower_cwnd(struct sctp_transport *transport,
 480                               sctp_lower_cwnd_t reason)
 481{
 482        struct sctp_association *asoc = transport->asoc;
 483
 484        switch (reason) {
 485        case SCTP_LOWER_CWND_T3_RTX:
 486                /* RFC 2960 Section 7.2.3, sctpimpguide
 487                 * When the T3-rtx timer expires on an address, SCTP should
 488                 * perform slow start by:
 489                 *      ssthresh = max(cwnd/2, 4*MTU)
 490                 *      cwnd = 1*MTU
 491                 *      partial_bytes_acked = 0
 492                 */
 493                transport->ssthresh = max(transport->cwnd/2,
 494                                          4*asoc->pathmtu);
 495                transport->cwnd = asoc->pathmtu;
 496
 497                /* T3-rtx also clears fast recovery */
 498                asoc->fast_recovery = 0;
 499                break;
 500
 501        case SCTP_LOWER_CWND_FAST_RTX:
 502                /* RFC 2960 7.2.4 Adjust the ssthresh and cwnd of the
 503                 * destination address(es) to which the missing DATA chunks
 504                 * were last sent, according to the formula described in
 505                 * Section 7.2.3.
 506                 *
 507                 * RFC 2960 7.2.3, sctpimpguide Upon detection of packet
 508                 * losses from SACK (see Section 7.2.4), An endpoint
 509                 * should do the following:
 510                 *      ssthresh = max(cwnd/2, 4*MTU)
 511                 *      cwnd = ssthresh
 512                 *      partial_bytes_acked = 0
 513                 */
 514                if (asoc->fast_recovery)
 515                        return;
 516
 517                /* Mark Fast recovery */
 518                asoc->fast_recovery = 1;
 519                asoc->fast_recovery_exit = asoc->next_tsn - 1;
 520
 521                transport->ssthresh = max(transport->cwnd/2,
 522                                          4*asoc->pathmtu);
 523                transport->cwnd = transport->ssthresh;
 524                break;
 525
 526        case SCTP_LOWER_CWND_ECNE:
 527                /* RFC 2481 Section 6.1.2.
 528                 * If the sender receives an ECN-Echo ACK packet
 529                 * then the sender knows that congestion was encountered in the
 530                 * network on the path from the sender to the receiver. The
 531                 * indication of congestion should be treated just as a
 532                 * congestion loss in non-ECN Capable TCP. That is, the TCP
 533                 * source halves the congestion window "cwnd" and reduces the
 534                 * slow start threshold "ssthresh".
 535                 * A critical condition is that TCP does not react to
 536                 * congestion indications more than once every window of
 537                 * data (or more loosely more than once every round-trip time).
 538                 */
 539                if (time_after(jiffies, transport->last_time_ecne_reduced +
 540                                        transport->rtt)) {
 541                        transport->ssthresh = max(transport->cwnd/2,
 542                                                  4*asoc->pathmtu);
 543                        transport->cwnd = transport->ssthresh;
 544                        transport->last_time_ecne_reduced = jiffies;
 545                }
 546                break;
 547
 548        case SCTP_LOWER_CWND_INACTIVE:
 549                /* RFC 2960 Section 7.2.1, sctpimpguide
 550                 * When the endpoint does not transmit data on a given
 551                 * transport address, the cwnd of the transport address
 552                 * should be adjusted to max(cwnd/2, 4*MTU) per RTO.
 553                 * NOTE: Although the draft recommends that this check needs
 554                 * to be done every RTO interval, we do it every hearbeat
 555                 * interval.
 556                 */
 557                transport->cwnd = max(transport->cwnd/2,
 558                                         4*asoc->pathmtu);
 559                break;
 560        }
 561
 562        transport->partial_bytes_acked = 0;
 563        SCTP_DEBUG_PRINTK("%s: transport: %p reason: %d cwnd: "
 564                          "%d ssthresh: %d\n", __func__,
 565                          transport, reason,
 566                          transport->cwnd, transport->ssthresh);
 567}
 568
 569/* Apply Max.Burst limit to the congestion window:
 570 * sctpimpguide-05 2.14.2
 571 * D) When the time comes for the sender to
 572 * transmit new DATA chunks, the protocol parameter Max.Burst MUST
 573 * first be applied to limit how many new DATA chunks may be sent.
 574 * The limit is applied by adjusting cwnd as follows:
 575 *      if ((flightsize+ Max.Burst * MTU) < cwnd)
 576 *              cwnd = flightsize + Max.Burst * MTU
 577 */
 578
 579void sctp_transport_burst_limited(struct sctp_transport *t)
 580{
 581        struct sctp_association *asoc = t->asoc;
 582        u32 old_cwnd = t->cwnd;
 583        u32 max_burst_bytes;
 584
 585        if (t->burst_limited)
 586                return;
 587
 588        max_burst_bytes = t->flight_size + (asoc->max_burst * asoc->pathmtu);
 589        if (max_burst_bytes < old_cwnd) {
 590                t->cwnd = max_burst_bytes;
 591                t->burst_limited = old_cwnd;
 592        }
 593}
 594
 595/* Restore the old cwnd congestion window, after the burst had it's
 596 * desired effect.
 597 */
 598void sctp_transport_burst_reset(struct sctp_transport *t)
 599{
 600        if (t->burst_limited) {
 601                t->cwnd = t->burst_limited;
 602                t->burst_limited = 0;
 603        }
 604}
 605
 606/* What is the next timeout value for this transport? */
 607unsigned long sctp_transport_timeout(struct sctp_transport *t)
 608{
 609        unsigned long timeout;
 610        timeout = t->rto + sctp_jitter(t->rto);
 611        if ((t->state != SCTP_UNCONFIRMED) &&
 612            (t->state != SCTP_PF))
 613                timeout += t->hbinterval;
 614        timeout += jiffies;
 615        return timeout;
 616}
 617
 618/* Reset transport variables to their initial values */
 619void sctp_transport_reset(struct sctp_transport *t)
 620{
 621        struct sctp_association *asoc = t->asoc;
 622
 623        /* RFC 2960 (bis), Section 5.2.4
 624         * All the congestion control parameters (e.g., cwnd, ssthresh)
 625         * related to this peer MUST be reset to their initial values
 626         * (see Section 6.2.1)
 627         */
 628        t->cwnd = min(4*asoc->pathmtu, max_t(__u32, 2*asoc->pathmtu, 4380));
 629        t->burst_limited = 0;
 630        t->ssthresh = asoc->peer.i.a_rwnd;
 631        t->rto = asoc->rto_initial;
 632        sctp_max_rto(asoc, t);
 633        t->rtt = 0;
 634        t->srtt = 0;
 635        t->rttvar = 0;
 636
 637        /* Reset these additional varibles so that we have a clean
 638         * slate.
 639         */
 640        t->partial_bytes_acked = 0;
 641        t->flight_size = 0;
 642        t->error_count = 0;
 643        t->rto_pending = 0;
 644        t->hb_sent = 0;
 645
 646        /* Initialize the state information for SFR-CACC */
 647        t->cacc.changeover_active = 0;
 648        t->cacc.cycling_changeover = 0;
 649        t->cacc.next_tsn_at_change = 0;
 650        t->cacc.cacc_saw_newack = 0;
 651}
 652
 653/* Schedule retransmission on the given transport */
 654void sctp_transport_immediate_rtx(struct sctp_transport *t)
 655{
 656        /* Stop pending T3_rtx_timer */
 657        if (timer_pending(&t->T3_rtx_timer)) {
 658                (void)del_timer(&t->T3_rtx_timer);
 659                sctp_transport_put(t);
 660        }
 661        sctp_retransmit(&t->asoc->outqueue, t, SCTP_RTXR_T3_RTX);
 662        if (!timer_pending(&t->T3_rtx_timer)) {
 663                if (!mod_timer(&t->T3_rtx_timer, jiffies + t->rto))
 664                        sctp_transport_hold(t);
 665        }
 666        return;
 667}
 668
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