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
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