1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* SCTP kernel implementation 3 * Copyright (c) 1999-2000 Cisco, Inc. 4 * Copyright (c) 1999-2001 Motorola, Inc. 5 * Copyright (c) 2001-2003 International Business Machines Corp. 6 * Copyright (c) 2001 Intel Corp. 7 * Copyright (c) 2001 La Monte H.P. Yarroll 8 * 9 * This file is part of the SCTP kernel implementation 10 * 11 * This module provides the abstraction for an SCTP transport representing 12 * a remote transport address. For local transport addresses, we just use 13 * union sctp_addr. 14 * 15 * Please send any bug reports or fixes you make to the 16 * email address(es): 17 * lksctp developers <linux-sctp@vger.kernel.org> 18 * 19 * Written or modified by: 20 * La Monte H.P. Yarroll <piggy@acm.org> 21 * Karl Knutson <karl@athena.chicago.il.us> 22 * Jon Grimm <jgrimm@us.ibm.com> 23 * Xingang Guo <xingang.guo@intel.com> 24 * Hui Huang <hui.huang@nokia.com> 25 * Sridhar Samudrala <sri@us.ibm.com> 26 * Ardelle Fan <ardelle.fan@intel.com> 27 */ 28 29 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 30 31 #include <linux/slab.h> 32 #include <linux/types.h> 33 #include <linux/random.h> 34 #include <net/sctp/sctp.h> 35 #include <net/sctp/sm.h> 36 37 /* 1st Level Abstractions. */ 38 39 /* Initialize a new transport from provided memory. */ 40 static struct sctp_transport *sctp_transport_init(struct net *net, 41 struct sctp_transport *peer, 42 const union sctp_addr *addr, 43 gfp_t gfp) 44 { 45 /* Copy in the address. */ 46 peer->af_specific = sctp_get_af_specific(addr->sa.sa_family); 47 memcpy(&peer->ipaddr, addr, peer->af_specific->sockaddr_len); 48 memset(&peer->saddr, 0, sizeof(union sctp_addr)); 49 50 peer->sack_generation = 0; 51 52 /* From 6.3.1 RTO Calculation: 53 * 54 * C1) Until an RTT measurement has been made for a packet sent to the 55 * given destination transport address, set RTO to the protocol 56 * parameter 'RTO.Initial'. 57 */ 58 peer->rto = msecs_to_jiffies(net->sctp.rto_initial); 59 60 peer->last_time_heard = 0; 61 peer->last_time_ecne_reduced = jiffies; 62 63 peer->param_flags = SPP_HB_DISABLE | 64 SPP_PMTUD_ENABLE | 65 SPP_SACKDELAY_ENABLE; 66 67 /* Initialize the default path max_retrans. */ 68 peer->pathmaxrxt = net->sctp.max_retrans_path; 69 peer->pf_retrans = net->sctp.pf_retrans; 70 71 INIT_LIST_HEAD(&peer->transmitted); 72 INIT_LIST_HEAD(&peer->send_ready); 73 INIT_LIST_HEAD(&peer->transports); 74 75 timer_setup(&peer->T3_rtx_timer, sctp_generate_t3_rtx_event, 0); 76 timer_setup(&peer->hb_timer, sctp_generate_heartbeat_event, 0); 77 timer_setup(&peer->reconf_timer, sctp_generate_reconf_event, 0); 78 timer_setup(&peer->probe_timer, sctp_generate_probe_event, 0); 79 timer_setup(&peer->proto_unreach_timer, 80 sctp_generate_proto_unreach_event, 0); 81 82 /* Initialize the 64-bit random nonce sent with heartbeat. */ 83 get_random_bytes(&peer->hb_nonce, sizeof(peer->hb_nonce)); 84 85 refcount_set(&peer->refcnt, 1); 86 87 return peer; 88 } 89 90 /* Allocate and initialize a new transport. */ 91 struct sctp_transport *sctp_transport_new(struct net *net, 92 const union sctp_addr *addr, 93 gfp_t gfp) 94 { 95 struct sctp_transport *transport; 96 97 transport = kzalloc(sizeof(*transport), gfp); 98 if (!transport) 99 goto fail; 100 101 if (!sctp_transport_init(net, transport, addr, gfp)) 102 goto fail_init; 103 104 SCTP_DBG_OBJCNT_INC(transport); 105 106 return transport; 107 108 fail_init: 109 kfree(transport); 110 111 fail: 112 return NULL; 113 } 114 115 /* This transport is no longer needed. Free up if possible, or 116 * delay until it last reference count. 117 */ 118 void sctp_transport_free(struct sctp_transport *transport) 119 { 120 /* Try to delete the heartbeat timer. */ 121 if (del_timer(&transport->hb_timer)) 122 sctp_transport_put(transport); 123 124 /* Delete the T3_rtx timer if it's active. 125 * There is no point in not doing this now and letting 126 * structure hang around in memory since we know 127 * the transport is going away. 128 */ 129 if (del_timer(&transport->T3_rtx_timer)) 130 sctp_transport_put(transport); 131 132 if (del_timer(&transport->reconf_timer)) 133 sctp_transport_put(transport); 134 135 if (del_timer(&transport->probe_timer)) 136 sctp_transport_put(transport); 137 138 /* Delete the ICMP proto unreachable timer if it's active. */ 139 if (del_timer(&transport->proto_unreach_timer)) 140 sctp_transport_put(transport); 141 142 sctp_transport_put(transport); 143 } 144 145 static void sctp_transport_destroy_rcu(struct rcu_head *head) 146 { 147 struct sctp_transport *transport; 148 149 transport = container_of(head, struct sctp_transport, rcu); 150 151 dst_release(transport->dst); 152 kfree(transport); 153 SCTP_DBG_OBJCNT_DEC(transport); 154 } 155 156 /* Destroy the transport data structure. 157 * Assumes there are no more users of this structure. 158 */ 159 static void sctp_transport_destroy(struct sctp_transport *transport) 160 { 161 if (unlikely(refcount_read(&transport->refcnt))) { 162 WARN(1, "Attempt to destroy undead transport %p!\n", transport); 163 return; 164 } 165 166 sctp_packet_free(&transport->packet); 167 168 if (transport->asoc) 169 sctp_association_put(transport->asoc); 170 171 call_rcu(&transport->rcu, sctp_transport_destroy_rcu); 172 } 173 174 /* Start T3_rtx timer if it is not already running and update the heartbeat 175 * timer. This routine is called every time a DATA chunk is sent. 176 */ 177 void sctp_transport_reset_t3_rtx(struct sctp_transport *transport) 178 { 179 /* RFC 2960 6.3.2 Retransmission Timer Rules 180 * 181 * R1) Every time a DATA chunk is sent to any address(including a 182 * retransmission), if the T3-rtx timer of that address is not running 183 * start it running so that it will expire after the RTO of that 184 * address. 185 */ 186 187 if (!timer_pending(&transport->T3_rtx_timer)) 188 if (!mod_timer(&transport->T3_rtx_timer, 189 jiffies + transport->rto)) 190 sctp_transport_hold(transport); 191 } 192 193 void sctp_transport_reset_hb_timer(struct sctp_transport *transport) 194 { 195 unsigned long expires; 196 197 /* When a data chunk is sent, reset the heartbeat interval. */ 198 expires = jiffies + sctp_transport_timeout(transport); 199 if (!mod_timer(&transport->hb_timer, 200 expires + get_random_u32_below(transport->rto))) 201 sctp_transport_hold(transport); 202 } 203 204 void sctp_transport_reset_reconf_timer(struct sctp_transport *transport) 205 { 206 if (!timer_pending(&transport->reconf_timer)) 207 if (!mod_timer(&transport->reconf_timer, 208 jiffies + transport->rto)) 209 sctp_transport_hold(transport); 210 } 211 212 void sctp_transport_reset_probe_timer(struct sctp_transport *transport) 213 { 214 if (!mod_timer(&transport->probe_timer, 215 jiffies + transport->probe_interval)) 216 sctp_transport_hold(transport); 217 } 218 219 void sctp_transport_reset_raise_timer(struct sctp_transport *transport) 220 { 221 if (!mod_timer(&transport->probe_timer, 222 jiffies + transport->probe_interval * 30)) 223 sctp_transport_hold(transport); 224 } 225 226 /* This transport has been assigned to an association. 227 * Initialize fields from the association or from the sock itself. 228 * Register the reference count in the association. 229 */ 230 void sctp_transport_set_owner(struct sctp_transport *transport, 231 struct sctp_association *asoc) 232 { 233 transport->asoc = asoc; 234 sctp_association_hold(asoc); 235 } 236 237 /* Initialize the pmtu of a transport. */ 238 void sctp_transport_pmtu(struct sctp_transport *transport, struct sock *sk) 239 { 240 /* If we don't have a fresh route, look one up */ 241 if (!transport->dst || transport->dst->obsolete) { 242 sctp_transport_dst_release(transport); 243 transport->af_specific->get_dst(transport, &transport->saddr, 244 &transport->fl, sk); 245 } 246 247 if (transport->param_flags & SPP_PMTUD_DISABLE) { 248 struct sctp_association *asoc = transport->asoc; 249 250 if (!transport->pathmtu && asoc && asoc->pathmtu) 251 transport->pathmtu = asoc->pathmtu; 252 if (transport->pathmtu) 253 return; 254 } 255 256 if (transport->dst) 257 transport->pathmtu = sctp_dst_mtu(transport->dst); 258 else 259 transport->pathmtu = SCTP_DEFAULT_MAXSEGMENT; 260 261 sctp_transport_pl_update(transport); 262 } 263 264 void sctp_transport_pl_send(struct sctp_transport *t) 265 { 266 if (t->pl.probe_count < SCTP_MAX_PROBES) 267 goto out; 268 269 t->pl.probe_count = 0; 270 if (t->pl.state == SCTP_PL_BASE) { 271 if (t->pl.probe_size == SCTP_BASE_PLPMTU) { /* BASE_PLPMTU Confirmation Failed */ 272 t->pl.state = SCTP_PL_ERROR; /* Base -> Error */ 273 274 t->pl.pmtu = SCTP_BASE_PLPMTU; 275 t->pathmtu = t->pl.pmtu + sctp_transport_pl_hlen(t); 276 sctp_assoc_sync_pmtu(t->asoc); 277 } 278 } else if (t->pl.state == SCTP_PL_SEARCH) { 279 if (t->pl.pmtu == t->pl.probe_size) { /* Black Hole Detected */ 280 t->pl.state = SCTP_PL_BASE; /* Search -> Base */ 281 t->pl.probe_size = SCTP_BASE_PLPMTU; 282 t->pl.probe_high = 0; 283 284 t->pl.pmtu = SCTP_BASE_PLPMTU; 285 t->pathmtu = t->pl.pmtu + sctp_transport_pl_hlen(t); 286 sctp_assoc_sync_pmtu(t->asoc); 287 } else { /* Normal probe failure. */ 288 t->pl.probe_high = t->pl.probe_size; 289 t->pl.probe_size = t->pl.pmtu; 290 } 291 } else if (t->pl.state == SCTP_PL_COMPLETE) { 292 if (t->pl.pmtu == t->pl.probe_size) { /* Black Hole Detected */ 293 t->pl.state = SCTP_PL_BASE; /* Search Complete -> Base */ 294 t->pl.probe_size = SCTP_BASE_PLPMTU; 295 296 t->pl.pmtu = SCTP_BASE_PLPMTU; 297 t->pathmtu = t->pl.pmtu + sctp_transport_pl_hlen(t); 298 sctp_assoc_sync_pmtu(t->asoc); 299 } 300 } 301 302 out: 303 pr_debug("%s: PLPMTUD: transport: %p, state: %d, pmtu: %d, size: %d, high: %d\n", 304 __func__, t, t->pl.state, t->pl.pmtu, t->pl.probe_size, t->pl.probe_high); 305 t->pl.probe_count++; 306 } 307 308 bool sctp_transport_pl_recv(struct sctp_transport *t) 309 { 310 pr_debug("%s: PLPMTUD: transport: %p, state: %d, pmtu: %d, size: %d, high: %d\n", 311 __func__, t, t->pl.state, t->pl.pmtu, t->pl.probe_size, t->pl.probe_high); 312 313 t->pl.pmtu = t->pl.probe_size; 314 t->pl.probe_count = 0; 315 if (t->pl.state == SCTP_PL_BASE) { 316 t->pl.state = SCTP_PL_SEARCH; /* Base -> Search */ 317 t->pl.probe_size += SCTP_PL_BIG_STEP; 318 } else if (t->pl.state == SCTP_PL_ERROR) { 319 t->pl.state = SCTP_PL_SEARCH; /* Error -> Search */ 320 321 t->pl.pmtu = t->pl.probe_size; 322 t->pathmtu = t->pl.pmtu + sctp_transport_pl_hlen(t); 323 sctp_assoc_sync_pmtu(t->asoc); 324 t->pl.probe_size += SCTP_PL_BIG_STEP; 325 } else if (t->pl.state == SCTP_PL_SEARCH) { 326 if (!t->pl.probe_high) { 327 if (t->pl.probe_size < SCTP_MAX_PLPMTU) { 328 t->pl.probe_size = min(t->pl.probe_size + SCTP_PL_BIG_STEP, 329 SCTP_MAX_PLPMTU); 330 return false; 331 } 332 t->pl.probe_high = SCTP_MAX_PLPMTU; 333 } 334 t->pl.probe_size += SCTP_PL_MIN_STEP; 335 if (t->pl.probe_size >= t->pl.probe_high) { 336 t->pl.probe_high = 0; 337 t->pl.state = SCTP_PL_COMPLETE; /* Search -> Search Complete */ 338 339 t->pl.probe_size = t->pl.pmtu; 340 t->pathmtu = t->pl.pmtu + sctp_transport_pl_hlen(t); 341 sctp_assoc_sync_pmtu(t->asoc); 342 sctp_transport_reset_raise_timer(t); 343 } 344 } else if (t->pl.state == SCTP_PL_COMPLETE) { 345 /* Raise probe_size again after 30 * interval in Search Complete */ 346 t->pl.state = SCTP_PL_SEARCH; /* Search Complete -> Search */ 347 t->pl.probe_size = min(t->pl.probe_size + SCTP_PL_MIN_STEP, SCTP_MAX_PLPMTU); 348 } 349 350 return t->pl.state == SCTP_PL_COMPLETE; 351 } 352 353 static bool sctp_transport_pl_toobig(struct sctp_transport *t, u32 pmtu) 354 { 355 pr_debug("%s: PLPMTUD: transport: %p, state: %d, pmtu: %d, size: %d, ptb: %d\n", 356 __func__, t, t->pl.state, t->pl.pmtu, t->pl.probe_size, pmtu); 357 358 if (pmtu < SCTP_MIN_PLPMTU || pmtu >= t->pl.probe_size) 359 return false; 360 361 if (t->pl.state == SCTP_PL_BASE) { 362 if (pmtu >= SCTP_MIN_PLPMTU && pmtu < SCTP_BASE_PLPMTU) { 363 t->pl.state = SCTP_PL_ERROR; /* Base -> Error */ 364 365 t->pl.pmtu = SCTP_BASE_PLPMTU; 366 t->pathmtu = t->pl.pmtu + sctp_transport_pl_hlen(t); 367 return true; 368 } 369 } else if (t->pl.state == SCTP_PL_SEARCH) { 370 if (pmtu >= SCTP_BASE_PLPMTU && pmtu < t->pl.pmtu) { 371 t->pl.state = SCTP_PL_BASE; /* Search -> Base */ 372 t->pl.probe_size = SCTP_BASE_PLPMTU; 373 t->pl.probe_count = 0; 374 375 t->pl.probe_high = 0; 376 t->pl.pmtu = SCTP_BASE_PLPMTU; 377 t->pathmtu = t->pl.pmtu + sctp_transport_pl_hlen(t); 378 return true; 379 } else if (pmtu > t->pl.pmtu && pmtu < t->pl.probe_size) { 380 t->pl.probe_size = pmtu; 381 t->pl.probe_count = 0; 382 } 383 } else if (t->pl.state == SCTP_PL_COMPLETE) { 384 if (pmtu >= SCTP_BASE_PLPMTU && pmtu < t->pl.pmtu) { 385 t->pl.state = SCTP_PL_BASE; /* Complete -> Base */ 386 t->pl.probe_size = SCTP_BASE_PLPMTU; 387 t->pl.probe_count = 0; 388 389 t->pl.probe_high = 0; 390 t->pl.pmtu = SCTP_BASE_PLPMTU; 391 t->pathmtu = t->pl.pmtu + sctp_transport_pl_hlen(t); 392 sctp_transport_reset_probe_timer(t); 393 return true; 394 } 395 } 396 397 return false; 398 } 399 400 bool sctp_transport_update_pmtu(struct sctp_transport *t, u32 pmtu) 401 { 402 struct sock *sk = t->asoc->base.sk; 403 struct dst_entry *dst; 404 bool change = true; 405 406 if (unlikely(pmtu < SCTP_DEFAULT_MINSEGMENT)) { 407 pr_warn_ratelimited("%s: Reported pmtu %d too low, using default minimum of %d\n", 408 __func__, pmtu, SCTP_DEFAULT_MINSEGMENT); 409 /* Use default minimum segment instead */ 410 pmtu = SCTP_DEFAULT_MINSEGMENT; 411 } 412 pmtu = SCTP_TRUNC4(pmtu); 413 414 if (sctp_transport_pl_enabled(t)) 415 return sctp_transport_pl_toobig(t, pmtu - sctp_transport_pl_hlen(t)); 416 417 dst = sctp_transport_dst_check(t); 418 if (dst) { 419 struct sctp_pf *pf = sctp_get_pf_specific(dst->ops->family); 420 union sctp_addr addr; 421 422 pf->af->from_sk(&addr, sk); 423 pf->to_sk_daddr(&t->ipaddr, sk); 424 dst->ops->update_pmtu(dst, sk, NULL, pmtu, true); 425 pf->to_sk_daddr(&addr, sk); 426 427 dst = sctp_transport_dst_check(t); 428 } 429 430 if (!dst) { 431 t->af_specific->get_dst(t, &t->saddr, &t->fl, sk); 432 dst = t->dst; 433 } 434 435 if (dst) { 436 /* Re-fetch, as under layers may have a higher minimum size */ 437 pmtu = sctp_dst_mtu(dst); 438 change = t->pathmtu != pmtu; 439 } 440 t->pathmtu = pmtu; 441 442 return change; 443 } 444 445 /* Caches the dst entry and source address for a transport's destination 446 * address. 447 */ 448 void sctp_transport_route(struct sctp_transport *transport, 449 union sctp_addr *saddr, struct sctp_sock *opt) 450 { 451 struct sctp_association *asoc = transport->asoc; 452 struct sctp_af *af = transport->af_specific; 453 454 sctp_transport_dst_release(transport); 455 af->get_dst(transport, saddr, &transport->fl, sctp_opt2sk(opt)); 456 457 if (saddr) 458 memcpy(&transport->saddr, saddr, sizeof(union sctp_addr)); 459 else 460 af->get_saddr(opt, transport, &transport->fl); 461 462 sctp_transport_pmtu(transport, sctp_opt2sk(opt)); 463 464 /* Initialize sk->sk_rcv_saddr, if the transport is the 465 * association's active path for getsockname(). 466 */ 467 if (transport->dst && asoc && 468 (!asoc->peer.primary_path || transport == asoc->peer.active_path)) 469 opt->pf->to_sk_saddr(&transport->saddr, asoc->base.sk); 470 } 471 472 /* Hold a reference to a transport. */ 473 int sctp_transport_hold(struct sctp_transport *transport) 474 { 475 return refcount_inc_not_zero(&transport->refcnt); 476 } 477 478 /* Release a reference to a transport and clean up 479 * if there are no more references. 480 */ 481 void sctp_transport_put(struct sctp_transport *transport) 482 { 483 if (refcount_dec_and_test(&transport->refcnt)) 484 sctp_transport_destroy(transport); 485 } 486 487 /* Update transport's RTO based on the newly calculated RTT. */ 488 void sctp_transport_update_rto(struct sctp_transport *tp, __u32 rtt) 489 { 490 if (unlikely(!tp->rto_pending)) 491 /* We should not be doing any RTO updates unless rto_pending is set. */ 492 pr_debug("%s: rto_pending not set on transport %p!\n", __func__, tp); 493 494 if (tp->rttvar || tp->srtt) { 495 struct net *net = tp->asoc->base.net; 496 /* 6.3.1 C3) When a new RTT measurement R' is made, set 497 * RTTVAR <- (1 - RTO.Beta) * RTTVAR + RTO.Beta * |SRTT - R'| 498 * SRTT <- (1 - RTO.Alpha) * SRTT + RTO.Alpha * R' 499 */ 500 501 /* Note: The above algorithm has been rewritten to 502 * express rto_beta and rto_alpha as inverse powers 503 * of two. 504 * For example, assuming the default value of RTO.Alpha of 505 * 1/8, rto_alpha would be expressed as 3. 506 */ 507 tp->rttvar = tp->rttvar - (tp->rttvar >> net->sctp.rto_beta) 508 + (((__u32)abs((__s64)tp->srtt - (__s64)rtt)) >> net->sctp.rto_beta); 509 tp->srtt = tp->srtt - (tp->srtt >> net->sctp.rto_alpha) 510 + (rtt >> net->sctp.rto_alpha); 511 } else { 512 /* 6.3.1 C2) When the first RTT measurement R is made, set 513 * SRTT <- R, RTTVAR <- R/2. 514 */ 515 tp->srtt = rtt; 516 tp->rttvar = rtt >> 1; 517 } 518 519 /* 6.3.1 G1) Whenever RTTVAR is computed, if RTTVAR = 0, then 520 * adjust RTTVAR <- G, where G is the CLOCK GRANULARITY. 521 */ 522 if (tp->rttvar == 0) 523 tp->rttvar = SCTP_CLOCK_GRANULARITY; 524 525 /* 6.3.1 C3) After the computation, update RTO <- SRTT + 4 * RTTVAR. */ 526 tp->rto = tp->srtt + (tp->rttvar << 2); 527 528 /* 6.3.1 C6) Whenever RTO is computed, if it is less than RTO.Min 529 * seconds then it is rounded up to RTO.Min seconds. 530 */ 531 if (tp->rto < tp->asoc->rto_min) 532 tp->rto = tp->asoc->rto_min; 533 534 /* 6.3.1 C7) A maximum value may be placed on RTO provided it is 535 * at least RTO.max seconds. 536 */ 537 if (tp->rto > tp->asoc->rto_max) 538 tp->rto = tp->asoc->rto_max; 539 540 sctp_max_rto(tp->asoc, tp); 541 tp->rtt = rtt; 542 543 /* Reset rto_pending so that a new RTT measurement is started when a 544 * new data chunk is sent. 545 */ 546 tp->rto_pending = 0; 547 548 pr_debug("%s: transport:%p, rtt:%d, srtt:%d rttvar:%d, rto:%ld\n", 549 __func__, tp, rtt, tp->srtt, tp->rttvar, tp->rto); 550 } 551 552 /* This routine updates the transport's cwnd and partial_bytes_acked 553 * parameters based on the bytes acked in the received SACK. 554 */ 555 void sctp_transport_raise_cwnd(struct sctp_transport *transport, 556 __u32 sack_ctsn, __u32 bytes_acked) 557 { 558 struct sctp_association *asoc = transport->asoc; 559 __u32 cwnd, ssthresh, flight_size, pba, pmtu; 560 561 cwnd = transport->cwnd; 562 flight_size = transport->flight_size; 563 564 /* See if we need to exit Fast Recovery first */ 565 if (asoc->fast_recovery && 566 TSN_lte(asoc->fast_recovery_exit, sack_ctsn)) 567 asoc->fast_recovery = 0; 568 569 ssthresh = transport->ssthresh; 570 pba = transport->partial_bytes_acked; 571 pmtu = transport->asoc->pathmtu; 572 573 if (cwnd <= ssthresh) { 574 /* RFC 4960 7.2.1 575 * o When cwnd is less than or equal to ssthresh, an SCTP 576 * endpoint MUST use the slow-start algorithm to increase 577 * cwnd only if the current congestion window is being fully 578 * utilized, an incoming SACK advances the Cumulative TSN 579 * Ack Point, and the data sender is not in Fast Recovery. 580 * Only when these three conditions are met can the cwnd be 581 * increased; otherwise, the cwnd MUST not be increased. 582 * If these conditions are met, then cwnd MUST be increased 583 * by, at most, the lesser of 1) the total size of the 584 * previously outstanding DATA chunk(s) acknowledged, and 585 * 2) the destination's path MTU. This upper bound protects 586 * against the ACK-Splitting attack outlined in [SAVAGE99]. 587 */ 588 if (asoc->fast_recovery) 589 return; 590 591 /* The appropriate cwnd increase algorithm is performed 592 * if, and only if the congestion window is being fully 593 * utilized. Note that RFC4960 Errata 3.22 removed the 594 * other condition on ctsn moving. 595 */ 596 if (flight_size < cwnd) 597 return; 598 599 if (bytes_acked > pmtu) 600 cwnd += pmtu; 601 else 602 cwnd += bytes_acked; 603 604 pr_debug("%s: slow start: transport:%p, bytes_acked:%d, " 605 "cwnd:%d, ssthresh:%d, flight_size:%d, pba:%d\n", 606 __func__, transport, bytes_acked, cwnd, ssthresh, 607 flight_size, pba); 608 } else { 609 /* RFC 2960 7.2.2 Whenever cwnd is greater than ssthresh, 610 * upon each SACK arrival, increase partial_bytes_acked 611 * by the total number of bytes of all new chunks 612 * acknowledged in that SACK including chunks 613 * acknowledged by the new Cumulative TSN Ack and by Gap 614 * Ack Blocks. (updated by RFC4960 Errata 3.22) 615 * 616 * When partial_bytes_acked is greater than cwnd and 617 * before the arrival of the SACK the sender had less 618 * bytes of data outstanding than cwnd (i.e., before 619 * arrival of the SACK, flightsize was less than cwnd), 620 * reset partial_bytes_acked to cwnd. (RFC 4960 Errata 621 * 3.26) 622 * 623 * When partial_bytes_acked is equal to or greater than 624 * cwnd and before the arrival of the SACK the sender 625 * had cwnd or more bytes of data outstanding (i.e., 626 * before arrival of the SACK, flightsize was greater 627 * than or equal to cwnd), partial_bytes_acked is reset 628 * to (partial_bytes_acked - cwnd). Next, cwnd is 629 * increased by MTU. (RFC 4960 Errata 3.12) 630 */ 631 pba += bytes_acked; 632 if (pba > cwnd && flight_size < cwnd) 633 pba = cwnd; 634 if (pba >= cwnd && flight_size >= cwnd) { 635 pba = pba - cwnd; 636 cwnd += pmtu; 637 } 638 639 pr_debug("%s: congestion avoidance: transport:%p, " 640 "bytes_acked:%d, cwnd:%d, ssthresh:%d, " 641 "flight_size:%d, pba:%d\n", __func__, 642 transport, bytes_acked, cwnd, ssthresh, 643 flight_size, pba); 644 } 645 646 transport->cwnd = cwnd; 647 transport->partial_bytes_acked = pba; 648 } 649 650 /* This routine is used to lower the transport's cwnd when congestion is 651 * detected. 652 */ 653 void sctp_transport_lower_cwnd(struct sctp_transport *transport, 654 enum sctp_lower_cwnd reason) 655 { 656 struct sctp_association *asoc = transport->asoc; 657 658 switch (reason) { 659 case SCTP_LOWER_CWND_T3_RTX: 660 /* RFC 2960 Section 7.2.3, sctpimpguide 661 * When the T3-rtx timer expires on an address, SCTP should 662 * perform slow start by: 663 * ssthresh = max(cwnd/2, 4*MTU) 664 * cwnd = 1*MTU 665 * partial_bytes_acked = 0 666 */ 667 transport->ssthresh = max(transport->cwnd/2, 668 4*asoc->pathmtu); 669 transport->cwnd = asoc->pathmtu; 670 671 /* T3-rtx also clears fast recovery */ 672 asoc->fast_recovery = 0; 673 break; 674 675 case SCTP_LOWER_CWND_FAST_RTX: 676 /* RFC 2960 7.2.4 Adjust the ssthresh and cwnd of the 677 * destination address(es) to which the missing DATA chunks 678 * were last sent, according to the formula described in 679 * Section 7.2.3. 680 * 681 * RFC 2960 7.2.3, sctpimpguide Upon detection of packet 682 * losses from SACK (see Section 7.2.4), An endpoint 683 * should do the following: 684 * ssthresh = max(cwnd/2, 4*MTU) 685 * cwnd = ssthresh 686 * partial_bytes_acked = 0 687 */ 688 if (asoc->fast_recovery) 689 return; 690 691 /* Mark Fast recovery */ 692 asoc->fast_recovery = 1; 693 asoc->fast_recovery_exit = asoc->next_tsn - 1; 694 695 transport->ssthresh = max(transport->cwnd/2, 696 4*asoc->pathmtu); 697 transport->cwnd = transport->ssthresh; 698 break; 699 700 case SCTP_LOWER_CWND_ECNE: 701 /* RFC 2481 Section 6.1.2. 702 * If the sender receives an ECN-Echo ACK packet 703 * then the sender knows that congestion was encountered in the 704 * network on the path from the sender to the receiver. The 705 * indication of congestion should be treated just as a 706 * congestion loss in non-ECN Capable TCP. That is, the TCP 707 * source halves the congestion window "cwnd" and reduces the 708 * slow start threshold "ssthresh". 709 * A critical condition is that TCP does not react to 710 * congestion indications more than once every window of 711 * data (or more loosely more than once every round-trip time). 712 */ 713 if (time_after(jiffies, transport->last_time_ecne_reduced + 714 transport->rtt)) { 715 transport->ssthresh = max(transport->cwnd/2, 716 4*asoc->pathmtu); 717 transport->cwnd = transport->ssthresh; 718 transport->last_time_ecne_reduced = jiffies; 719 } 720 break; 721 722 case SCTP_LOWER_CWND_INACTIVE: 723 /* RFC 2960 Section 7.2.1, sctpimpguide 724 * When the endpoint does not transmit data on a given 725 * transport address, the cwnd of the transport address 726 * should be adjusted to max(cwnd/2, 4*MTU) per RTO. 727 * NOTE: Although the draft recommends that this check needs 728 * to be done every RTO interval, we do it every hearbeat 729 * interval. 730 */ 731 transport->cwnd = max(transport->cwnd/2, 732 4*asoc->pathmtu); 733 /* RFC 4960 Errata 3.27.2: also adjust sshthresh */ 734 transport->ssthresh = transport->cwnd; 735 break; 736 } 737 738 transport->partial_bytes_acked = 0; 739 740 pr_debug("%s: transport:%p, reason:%d, cwnd:%d, ssthresh:%d\n", 741 __func__, transport, reason, transport->cwnd, 742 transport->ssthresh); 743 } 744 745 /* Apply Max.Burst limit to the congestion window: 746 * sctpimpguide-05 2.14.2 747 * D) When the time comes for the sender to 748 * transmit new DATA chunks, the protocol parameter Max.Burst MUST 749 * first be applied to limit how many new DATA chunks may be sent. 750 * The limit is applied by adjusting cwnd as follows: 751 * if ((flightsize+ Max.Burst * MTU) < cwnd) 752 * cwnd = flightsize + Max.Burst * MTU 753 */ 754 755 void sctp_transport_burst_limited(struct sctp_transport *t) 756 { 757 struct sctp_association *asoc = t->asoc; 758 u32 old_cwnd = t->cwnd; 759 u32 max_burst_bytes; 760 761 if (t->burst_limited || asoc->max_burst == 0) 762 return; 763 764 max_burst_bytes = t->flight_size + (asoc->max_burst * asoc->pathmtu); 765 if (max_burst_bytes < old_cwnd) { 766 t->cwnd = max_burst_bytes; 767 t->burst_limited = old_cwnd; 768 } 769 } 770 771 /* Restore the old cwnd congestion window, after the burst had it's 772 * desired effect. 773 */ 774 void sctp_transport_burst_reset(struct sctp_transport *t) 775 { 776 if (t->burst_limited) { 777 t->cwnd = t->burst_limited; 778 t->burst_limited = 0; 779 } 780 } 781 782 /* What is the next timeout value for this transport? */ 783 unsigned long sctp_transport_timeout(struct sctp_transport *trans) 784 { 785 /* RTO + timer slack +/- 50% of RTO */ 786 unsigned long timeout = trans->rto >> 1; 787 788 if (trans->state != SCTP_UNCONFIRMED && 789 trans->state != SCTP_PF) 790 timeout += trans->hbinterval; 791 792 return max_t(unsigned long, timeout, HZ / 5); 793 } 794 795 /* Reset transport variables to their initial values */ 796 void sctp_transport_reset(struct sctp_transport *t) 797 { 798 struct sctp_association *asoc = t->asoc; 799 800 /* RFC 2960 (bis), Section 5.2.4 801 * All the congestion control parameters (e.g., cwnd, ssthresh) 802 * related to this peer MUST be reset to their initial values 803 * (see Section 6.2.1) 804 */ 805 t->cwnd = min(4*asoc->pathmtu, max_t(__u32, 2*asoc->pathmtu, 4380)); 806 t->burst_limited = 0; 807 t->ssthresh = asoc->peer.i.a_rwnd; 808 t->rto = asoc->rto_initial; 809 sctp_max_rto(asoc, t); 810 t->rtt = 0; 811 t->srtt = 0; 812 t->rttvar = 0; 813 814 /* Reset these additional variables so that we have a clean slate. */ 815 t->partial_bytes_acked = 0; 816 t->flight_size = 0; 817 t->error_count = 0; 818 t->rto_pending = 0; 819 t->hb_sent = 0; 820 821 /* Initialize the state information for SFR-CACC */ 822 t->cacc.changeover_active = 0; 823 t->cacc.cycling_changeover = 0; 824 t->cacc.next_tsn_at_change = 0; 825 t->cacc.cacc_saw_newack = 0; 826 } 827 828 /* Schedule retransmission on the given transport */ 829 void sctp_transport_immediate_rtx(struct sctp_transport *t) 830 { 831 /* Stop pending T3_rtx_timer */ 832 if (del_timer(&t->T3_rtx_timer)) 833 sctp_transport_put(t); 834 835 sctp_retransmit(&t->asoc->outqueue, t, SCTP_RTXR_T3_RTX); 836 if (!timer_pending(&t->T3_rtx_timer)) { 837 if (!mod_timer(&t->T3_rtx_timer, jiffies + t->rto)) 838 sctp_transport_hold(t); 839 } 840 } 841 842 /* Drop dst */ 843 void sctp_transport_dst_release(struct sctp_transport *t) 844 { 845 dst_release(t->dst); 846 t->dst = NULL; 847 t->dst_pending_confirm = 0; 848 } 849 850 /* Schedule neighbour confirm */ 851 void sctp_transport_dst_confirm(struct sctp_transport *t) 852 { 853 t->dst_pending_confirm = 1; 854 } 855