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