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. */
sctp_transport_init(struct net * net,struct sctp_transport * peer,const union sctp_addr * addr,gfp_t gfp)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. */
sctp_transport_new(struct net * net,const union sctp_addr * addr,gfp_t gfp)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 */
sctp_transport_free(struct sctp_transport * transport)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
sctp_transport_destroy_rcu(struct rcu_head * head)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 */
sctp_transport_destroy(struct sctp_transport * transport)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 */
sctp_transport_reset_t3_rtx(struct sctp_transport * transport)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
sctp_transport_reset_hb_timer(struct sctp_transport * transport)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 ((time_before(transport->hb_timer.expires, expires) ||
200 !timer_pending(&transport->hb_timer)) &&
201 !mod_timer(&transport->hb_timer,
202 expires + prandom_u32_max(transport->rto)))
203 sctp_transport_hold(transport);
204 }
205
sctp_transport_reset_reconf_timer(struct sctp_transport * transport)206 void sctp_transport_reset_reconf_timer(struct sctp_transport *transport)
207 {
208 if (!timer_pending(&transport->reconf_timer))
209 if (!mod_timer(&transport->reconf_timer,
210 jiffies + transport->rto))
211 sctp_transport_hold(transport);
212 }
213
sctp_transport_reset_probe_timer(struct sctp_transport * transport)214 void sctp_transport_reset_probe_timer(struct sctp_transport *transport)
215 {
216 if (timer_pending(&transport->probe_timer))
217 return;
218 if (!mod_timer(&transport->probe_timer,
219 jiffies + transport->probe_interval))
220 sctp_transport_hold(transport);
221 }
222
223 /* This transport has been assigned to an association.
224 * Initialize fields from the association or from the sock itself.
225 * Register the reference count in the association.
226 */
sctp_transport_set_owner(struct sctp_transport * transport,struct sctp_association * asoc)227 void sctp_transport_set_owner(struct sctp_transport *transport,
228 struct sctp_association *asoc)
229 {
230 transport->asoc = asoc;
231 sctp_association_hold(asoc);
232 }
233
234 /* Initialize the pmtu of a transport. */
sctp_transport_pmtu(struct sctp_transport * transport,struct sock * sk)235 void sctp_transport_pmtu(struct sctp_transport *transport, struct sock *sk)
236 {
237 /* If we don't have a fresh route, look one up */
238 if (!transport->dst || transport->dst->obsolete) {
239 sctp_transport_dst_release(transport);
240 transport->af_specific->get_dst(transport, &transport->saddr,
241 &transport->fl, sk);
242 }
243
244 if (transport->param_flags & SPP_PMTUD_DISABLE) {
245 struct sctp_association *asoc = transport->asoc;
246
247 if (!transport->pathmtu && asoc && asoc->pathmtu)
248 transport->pathmtu = asoc->pathmtu;
249 if (transport->pathmtu)
250 return;
251 }
252
253 if (transport->dst)
254 transport->pathmtu = sctp_dst_mtu(transport->dst);
255 else
256 transport->pathmtu = SCTP_DEFAULT_MAXSEGMENT;
257
258 sctp_transport_pl_update(transport);
259 }
260
sctp_transport_pl_send(struct sctp_transport * t)261 bool sctp_transport_pl_send(struct sctp_transport *t)
262 {
263 if (t->pl.probe_count < SCTP_MAX_PROBES)
264 goto out;
265
266 t->pl.last_rtx_chunks = t->asoc->rtx_data_chunks;
267 t->pl.probe_count = 0;
268 if (t->pl.state == SCTP_PL_BASE) {
269 if (t->pl.probe_size == SCTP_BASE_PLPMTU) { /* BASE_PLPMTU Confirmation Failed */
270 t->pl.state = SCTP_PL_ERROR; /* Base -> Error */
271
272 t->pl.pmtu = SCTP_MIN_PLPMTU;
273 t->pathmtu = t->pl.pmtu + sctp_transport_pl_hlen(t);
274 sctp_assoc_sync_pmtu(t->asoc);
275 }
276 } else if (t->pl.state == SCTP_PL_SEARCH) {
277 if (t->pl.pmtu == t->pl.probe_size) { /* Black Hole Detected */
278 t->pl.state = SCTP_PL_BASE; /* Search -> Base */
279 t->pl.probe_size = SCTP_BASE_PLPMTU;
280 t->pl.probe_high = 0;
281
282 t->pl.pmtu = SCTP_BASE_PLPMTU;
283 t->pathmtu = t->pl.pmtu + sctp_transport_pl_hlen(t);
284 sctp_assoc_sync_pmtu(t->asoc);
285 } else { /* Normal probe failure. */
286 t->pl.probe_high = t->pl.probe_size;
287 t->pl.probe_size = t->pl.pmtu;
288 }
289 } else if (t->pl.state == SCTP_PL_COMPLETE) {
290 if (t->pl.pmtu == t->pl.probe_size) { /* Black Hole Detected */
291 t->pl.state = SCTP_PL_BASE; /* Search Complete -> Base */
292 t->pl.probe_size = SCTP_BASE_PLPMTU;
293
294 t->pl.pmtu = SCTP_BASE_PLPMTU;
295 t->pathmtu = t->pl.pmtu + sctp_transport_pl_hlen(t);
296 sctp_assoc_sync_pmtu(t->asoc);
297 }
298 }
299
300 out:
301 if (t->pl.state == SCTP_PL_COMPLETE && t->pl.raise_count < 30 &&
302 !t->pl.probe_count && t->pl.last_rtx_chunks == t->asoc->rtx_data_chunks) {
303 t->pl.raise_count++;
304 return false;
305 }
306
307 pr_debug("%s: PLPMTUD: transport: %p, state: %d, pmtu: %d, size: %d, high: %d\n",
308 __func__, t, t->pl.state, t->pl.pmtu, t->pl.probe_size, t->pl.probe_high);
309
310 t->pl.probe_count++;
311 return true;
312 }
313
sctp_transport_pl_recv(struct sctp_transport * t)314 bool sctp_transport_pl_recv(struct sctp_transport *t)
315 {
316 pr_debug("%s: PLPMTUD: transport: %p, state: %d, pmtu: %d, size: %d, high: %d\n",
317 __func__, t, t->pl.state, t->pl.pmtu, t->pl.probe_size, t->pl.probe_high);
318
319 t->pl.last_rtx_chunks = t->asoc->rtx_data_chunks;
320 t->pl.pmtu = t->pl.probe_size;
321 t->pl.probe_count = 0;
322 if (t->pl.state == SCTP_PL_BASE) {
323 t->pl.state = SCTP_PL_SEARCH; /* Base -> Search */
324 t->pl.probe_size += SCTP_PL_BIG_STEP;
325 } else if (t->pl.state == SCTP_PL_ERROR) {
326 t->pl.state = SCTP_PL_SEARCH; /* Error -> Search */
327
328 t->pl.pmtu = t->pl.probe_size;
329 t->pathmtu = t->pl.pmtu + sctp_transport_pl_hlen(t);
330 sctp_assoc_sync_pmtu(t->asoc);
331 t->pl.probe_size += SCTP_PL_BIG_STEP;
332 } else if (t->pl.state == SCTP_PL_SEARCH) {
333 if (!t->pl.probe_high) {
334 t->pl.probe_size = min(t->pl.probe_size + SCTP_PL_BIG_STEP,
335 SCTP_MAX_PLPMTU);
336 return false;
337 }
338 t->pl.probe_size += SCTP_PL_MIN_STEP;
339 if (t->pl.probe_size >= t->pl.probe_high) {
340 t->pl.probe_high = 0;
341 t->pl.raise_count = 0;
342 t->pl.state = SCTP_PL_COMPLETE; /* Search -> Search Complete */
343
344 t->pl.probe_size = t->pl.pmtu;
345 t->pathmtu = t->pl.pmtu + sctp_transport_pl_hlen(t);
346 sctp_assoc_sync_pmtu(t->asoc);
347 }
348 } else if (t->pl.state == SCTP_PL_COMPLETE && t->pl.raise_count == 30) {
349 /* Raise probe_size again after 30 * interval in Search Complete */
350 t->pl.state = SCTP_PL_SEARCH; /* Search Complete -> Search */
351 t->pl.probe_size += SCTP_PL_MIN_STEP;
352 }
353
354 return t->pl.state == SCTP_PL_COMPLETE;
355 }
356
sctp_transport_pl_toobig(struct sctp_transport * t,u32 pmtu)357 static bool sctp_transport_pl_toobig(struct sctp_transport *t, u32 pmtu)
358 {
359 pr_debug("%s: PLPMTUD: transport: %p, state: %d, pmtu: %d, size: %d, ptb: %d\n",
360 __func__, t, t->pl.state, t->pl.pmtu, t->pl.probe_size, pmtu);
361
362 if (pmtu < SCTP_MIN_PLPMTU || pmtu >= t->pl.probe_size)
363 return false;
364
365 if (t->pl.state == SCTP_PL_BASE) {
366 if (pmtu >= SCTP_MIN_PLPMTU && pmtu < SCTP_BASE_PLPMTU) {
367 t->pl.state = SCTP_PL_ERROR; /* Base -> Error */
368
369 t->pl.pmtu = SCTP_MIN_PLPMTU;
370 t->pathmtu = t->pl.pmtu + sctp_transport_pl_hlen(t);
371 }
372 } else if (t->pl.state == SCTP_PL_SEARCH) {
373 if (pmtu >= SCTP_BASE_PLPMTU && pmtu < t->pl.pmtu) {
374 t->pl.state = SCTP_PL_BASE; /* Search -> Base */
375 t->pl.probe_size = SCTP_BASE_PLPMTU;
376 t->pl.probe_count = 0;
377
378 t->pl.probe_high = 0;
379 t->pl.pmtu = SCTP_BASE_PLPMTU;
380 t->pathmtu = t->pl.pmtu + sctp_transport_pl_hlen(t);
381 } else if (pmtu > t->pl.pmtu && pmtu < t->pl.probe_size) {
382 t->pl.probe_size = pmtu;
383 t->pl.probe_count = 0;
384
385 return false;
386 }
387 } else if (t->pl.state == SCTP_PL_COMPLETE) {
388 if (pmtu >= SCTP_BASE_PLPMTU && pmtu < t->pl.pmtu) {
389 t->pl.state = SCTP_PL_BASE; /* Complete -> Base */
390 t->pl.probe_size = SCTP_BASE_PLPMTU;
391 t->pl.probe_count = 0;
392
393 t->pl.probe_high = 0;
394 t->pl.pmtu = SCTP_BASE_PLPMTU;
395 t->pathmtu = t->pl.pmtu + sctp_transport_pl_hlen(t);
396 }
397 }
398
399 return true;
400 }
401
sctp_transport_update_pmtu(struct sctp_transport * t,u32 pmtu)402 bool sctp_transport_update_pmtu(struct sctp_transport *t, u32 pmtu)
403 {
404 struct sock *sk = t->asoc->base.sk;
405 struct dst_entry *dst;
406 bool change = true;
407
408 if (unlikely(pmtu < SCTP_DEFAULT_MINSEGMENT)) {
409 pr_warn_ratelimited("%s: Reported pmtu %d too low, using default minimum of %d\n",
410 __func__, pmtu, SCTP_DEFAULT_MINSEGMENT);
411 /* Use default minimum segment instead */
412 pmtu = SCTP_DEFAULT_MINSEGMENT;
413 }
414 pmtu = SCTP_TRUNC4(pmtu);
415
416 if (sctp_transport_pl_enabled(t))
417 return sctp_transport_pl_toobig(t, pmtu - sctp_transport_pl_hlen(t));
418
419 dst = sctp_transport_dst_check(t);
420 if (dst) {
421 struct sctp_pf *pf = sctp_get_pf_specific(dst->ops->family);
422 union sctp_addr addr;
423
424 pf->af->from_sk(&addr, sk);
425 pf->to_sk_daddr(&t->ipaddr, sk);
426 dst->ops->update_pmtu(dst, sk, NULL, pmtu, true);
427 pf->to_sk_daddr(&addr, sk);
428
429 dst = sctp_transport_dst_check(t);
430 }
431
432 if (!dst) {
433 t->af_specific->get_dst(t, &t->saddr, &t->fl, sk);
434 dst = t->dst;
435 }
436
437 if (dst) {
438 /* Re-fetch, as under layers may have a higher minimum size */
439 pmtu = sctp_dst_mtu(dst);
440 change = t->pathmtu != pmtu;
441 }
442 t->pathmtu = pmtu;
443
444 return change;
445 }
446
447 /* Caches the dst entry and source address for a transport's destination
448 * address.
449 */
sctp_transport_route(struct sctp_transport * transport,union sctp_addr * saddr,struct sctp_sock * opt)450 void sctp_transport_route(struct sctp_transport *transport,
451 union sctp_addr *saddr, struct sctp_sock *opt)
452 {
453 struct sctp_association *asoc = transport->asoc;
454 struct sctp_af *af = transport->af_specific;
455
456 sctp_transport_dst_release(transport);
457 af->get_dst(transport, saddr, &transport->fl, sctp_opt2sk(opt));
458
459 if (saddr)
460 memcpy(&transport->saddr, saddr, sizeof(union sctp_addr));
461 else
462 af->get_saddr(opt, transport, &transport->fl);
463
464 sctp_transport_pmtu(transport, sctp_opt2sk(opt));
465
466 /* Initialize sk->sk_rcv_saddr, if the transport is the
467 * association's active path for getsockname().
468 */
469 if (transport->dst && asoc &&
470 (!asoc->peer.primary_path || transport == asoc->peer.active_path))
471 opt->pf->to_sk_saddr(&transport->saddr, asoc->base.sk);
472 }
473
474 /* Hold a reference to a transport. */
sctp_transport_hold(struct sctp_transport * transport)475 int sctp_transport_hold(struct sctp_transport *transport)
476 {
477 return refcount_inc_not_zero(&transport->refcnt);
478 }
479
480 /* Release a reference to a transport and clean up
481 * if there are no more references.
482 */
sctp_transport_put(struct sctp_transport * transport)483 void sctp_transport_put(struct sctp_transport *transport)
484 {
485 if (refcount_dec_and_test(&transport->refcnt))
486 sctp_transport_destroy(transport);
487 }
488
489 /* Update transport's RTO based on the newly calculated RTT. */
sctp_transport_update_rto(struct sctp_transport * tp,__u32 rtt)490 void sctp_transport_update_rto(struct sctp_transport *tp, __u32 rtt)
491 {
492 if (unlikely(!tp->rto_pending))
493 /* We should not be doing any RTO updates unless rto_pending is set. */
494 pr_debug("%s: rto_pending not set on transport %p!\n", __func__, tp);
495
496 if (tp->rttvar || tp->srtt) {
497 struct net *net = tp->asoc->base.net;
498 /* 6.3.1 C3) When a new RTT measurement R' is made, set
499 * RTTVAR <- (1 - RTO.Beta) * RTTVAR + RTO.Beta * |SRTT - R'|
500 * SRTT <- (1 - RTO.Alpha) * SRTT + RTO.Alpha * R'
501 */
502
503 /* Note: The above algorithm has been rewritten to
504 * express rto_beta and rto_alpha as inverse powers
505 * of two.
506 * For example, assuming the default value of RTO.Alpha of
507 * 1/8, rto_alpha would be expressed as 3.
508 */
509 tp->rttvar = tp->rttvar - (tp->rttvar >> net->sctp.rto_beta)
510 + (((__u32)abs((__s64)tp->srtt - (__s64)rtt)) >> net->sctp.rto_beta);
511 tp->srtt = tp->srtt - (tp->srtt >> net->sctp.rto_alpha)
512 + (rtt >> net->sctp.rto_alpha);
513 } else {
514 /* 6.3.1 C2) When the first RTT measurement R is made, set
515 * SRTT <- R, RTTVAR <- R/2.
516 */
517 tp->srtt = rtt;
518 tp->rttvar = rtt >> 1;
519 }
520
521 /* 6.3.1 G1) Whenever RTTVAR is computed, if RTTVAR = 0, then
522 * adjust RTTVAR <- G, where G is the CLOCK GRANULARITY.
523 */
524 if (tp->rttvar == 0)
525 tp->rttvar = SCTP_CLOCK_GRANULARITY;
526
527 /* 6.3.1 C3) After the computation, update RTO <- SRTT + 4 * RTTVAR. */
528 tp->rto = tp->srtt + (tp->rttvar << 2);
529
530 /* 6.3.1 C6) Whenever RTO is computed, if it is less than RTO.Min
531 * seconds then it is rounded up to RTO.Min seconds.
532 */
533 if (tp->rto < tp->asoc->rto_min)
534 tp->rto = tp->asoc->rto_min;
535
536 /* 6.3.1 C7) A maximum value may be placed on RTO provided it is
537 * at least RTO.max seconds.
538 */
539 if (tp->rto > tp->asoc->rto_max)
540 tp->rto = tp->asoc->rto_max;
541
542 sctp_max_rto(tp->asoc, tp);
543 tp->rtt = rtt;
544
545 /* Reset rto_pending so that a new RTT measurement is started when a
546 * new data chunk is sent.
547 */
548 tp->rto_pending = 0;
549
550 pr_debug("%s: transport:%p, rtt:%d, srtt:%d rttvar:%d, rto:%ld\n",
551 __func__, tp, rtt, tp->srtt, tp->rttvar, tp->rto);
552 }
553
554 /* This routine updates the transport's cwnd and partial_bytes_acked
555 * parameters based on the bytes acked in the received SACK.
556 */
sctp_transport_raise_cwnd(struct sctp_transport * transport,__u32 sack_ctsn,__u32 bytes_acked)557 void sctp_transport_raise_cwnd(struct sctp_transport *transport,
558 __u32 sack_ctsn, __u32 bytes_acked)
559 {
560 struct sctp_association *asoc = transport->asoc;
561 __u32 cwnd, ssthresh, flight_size, pba, pmtu;
562
563 cwnd = transport->cwnd;
564 flight_size = transport->flight_size;
565
566 /* See if we need to exit Fast Recovery first */
567 if (asoc->fast_recovery &&
568 TSN_lte(asoc->fast_recovery_exit, sack_ctsn))
569 asoc->fast_recovery = 0;
570
571 ssthresh = transport->ssthresh;
572 pba = transport->partial_bytes_acked;
573 pmtu = transport->asoc->pathmtu;
574
575 if (cwnd <= ssthresh) {
576 /* RFC 4960 7.2.1
577 * o When cwnd is less than or equal to ssthresh, an SCTP
578 * endpoint MUST use the slow-start algorithm to increase
579 * cwnd only if the current congestion window is being fully
580 * utilized, an incoming SACK advances the Cumulative TSN
581 * Ack Point, and the data sender is not in Fast Recovery.
582 * Only when these three conditions are met can the cwnd be
583 * increased; otherwise, the cwnd MUST not be increased.
584 * If these conditions are met, then cwnd MUST be increased
585 * by, at most, the lesser of 1) the total size of the
586 * previously outstanding DATA chunk(s) acknowledged, and
587 * 2) the destination's path MTU. This upper bound protects
588 * against the ACK-Splitting attack outlined in [SAVAGE99].
589 */
590 if (asoc->fast_recovery)
591 return;
592
593 /* The appropriate cwnd increase algorithm is performed
594 * if, and only if the congestion window is being fully
595 * utilized. Note that RFC4960 Errata 3.22 removed the
596 * other condition on ctsn moving.
597 */
598 if (flight_size < cwnd)
599 return;
600
601 if (bytes_acked > pmtu)
602 cwnd += pmtu;
603 else
604 cwnd += bytes_acked;
605
606 pr_debug("%s: slow start: transport:%p, bytes_acked:%d, "
607 "cwnd:%d, ssthresh:%d, flight_size:%d, pba:%d\n",
608 __func__, transport, bytes_acked, cwnd, ssthresh,
609 flight_size, pba);
610 } else {
611 /* RFC 2960 7.2.2 Whenever cwnd is greater than ssthresh,
612 * upon each SACK arrival, increase partial_bytes_acked
613 * by the total number of bytes of all new chunks
614 * acknowledged in that SACK including chunks
615 * acknowledged by the new Cumulative TSN Ack and by Gap
616 * Ack Blocks. (updated by RFC4960 Errata 3.22)
617 *
618 * When partial_bytes_acked is greater than cwnd and
619 * before the arrival of the SACK the sender had less
620 * bytes of data outstanding than cwnd (i.e., before
621 * arrival of the SACK, flightsize was less than cwnd),
622 * reset partial_bytes_acked to cwnd. (RFC 4960 Errata
623 * 3.26)
624 *
625 * When partial_bytes_acked is equal to or greater than
626 * cwnd and before the arrival of the SACK the sender
627 * had cwnd or more bytes of data outstanding (i.e.,
628 * before arrival of the SACK, flightsize was greater
629 * than or equal to cwnd), partial_bytes_acked is reset
630 * to (partial_bytes_acked - cwnd). Next, cwnd is
631 * increased by MTU. (RFC 4960 Errata 3.12)
632 */
633 pba += bytes_acked;
634 if (pba > cwnd && flight_size < cwnd)
635 pba = cwnd;
636 if (pba >= cwnd && flight_size >= cwnd) {
637 pba = pba - cwnd;
638 cwnd += pmtu;
639 }
640
641 pr_debug("%s: congestion avoidance: transport:%p, "
642 "bytes_acked:%d, cwnd:%d, ssthresh:%d, "
643 "flight_size:%d, pba:%d\n", __func__,
644 transport, bytes_acked, cwnd, ssthresh,
645 flight_size, pba);
646 }
647
648 transport->cwnd = cwnd;
649 transport->partial_bytes_acked = pba;
650 }
651
652 /* This routine is used to lower the transport's cwnd when congestion is
653 * detected.
654 */
sctp_transport_lower_cwnd(struct sctp_transport * transport,enum sctp_lower_cwnd reason)655 void sctp_transport_lower_cwnd(struct sctp_transport *transport,
656 enum sctp_lower_cwnd reason)
657 {
658 struct sctp_association *asoc = transport->asoc;
659
660 switch (reason) {
661 case SCTP_LOWER_CWND_T3_RTX:
662 /* RFC 2960 Section 7.2.3, sctpimpguide
663 * When the T3-rtx timer expires on an address, SCTP should
664 * perform slow start by:
665 * ssthresh = max(cwnd/2, 4*MTU)
666 * cwnd = 1*MTU
667 * partial_bytes_acked = 0
668 */
669 transport->ssthresh = max(transport->cwnd/2,
670 4*asoc->pathmtu);
671 transport->cwnd = asoc->pathmtu;
672
673 /* T3-rtx also clears fast recovery */
674 asoc->fast_recovery = 0;
675 break;
676
677 case SCTP_LOWER_CWND_FAST_RTX:
678 /* RFC 2960 7.2.4 Adjust the ssthresh and cwnd of the
679 * destination address(es) to which the missing DATA chunks
680 * were last sent, according to the formula described in
681 * Section 7.2.3.
682 *
683 * RFC 2960 7.2.3, sctpimpguide Upon detection of packet
684 * losses from SACK (see Section 7.2.4), An endpoint
685 * should do the following:
686 * ssthresh = max(cwnd/2, 4*MTU)
687 * cwnd = ssthresh
688 * partial_bytes_acked = 0
689 */
690 if (asoc->fast_recovery)
691 return;
692
693 /* Mark Fast recovery */
694 asoc->fast_recovery = 1;
695 asoc->fast_recovery_exit = asoc->next_tsn - 1;
696
697 transport->ssthresh = max(transport->cwnd/2,
698 4*asoc->pathmtu);
699 transport->cwnd = transport->ssthresh;
700 break;
701
702 case SCTP_LOWER_CWND_ECNE:
703 /* RFC 2481 Section 6.1.2.
704 * If the sender receives an ECN-Echo ACK packet
705 * then the sender knows that congestion was encountered in the
706 * network on the path from the sender to the receiver. The
707 * indication of congestion should be treated just as a
708 * congestion loss in non-ECN Capable TCP. That is, the TCP
709 * source halves the congestion window "cwnd" and reduces the
710 * slow start threshold "ssthresh".
711 * A critical condition is that TCP does not react to
712 * congestion indications more than once every window of
713 * data (or more loosely more than once every round-trip time).
714 */
715 if (time_after(jiffies, transport->last_time_ecne_reduced +
716 transport->rtt)) {
717 transport->ssthresh = max(transport->cwnd/2,
718 4*asoc->pathmtu);
719 transport->cwnd = transport->ssthresh;
720 transport->last_time_ecne_reduced = jiffies;
721 }
722 break;
723
724 case SCTP_LOWER_CWND_INACTIVE:
725 /* RFC 2960 Section 7.2.1, sctpimpguide
726 * When the endpoint does not transmit data on a given
727 * transport address, the cwnd of the transport address
728 * should be adjusted to max(cwnd/2, 4*MTU) per RTO.
729 * NOTE: Although the draft recommends that this check needs
730 * to be done every RTO interval, we do it every hearbeat
731 * interval.
732 */
733 transport->cwnd = max(transport->cwnd/2,
734 4*asoc->pathmtu);
735 /* RFC 4960 Errata 3.27.2: also adjust sshthresh */
736 transport->ssthresh = transport->cwnd;
737 break;
738 }
739
740 transport->partial_bytes_acked = 0;
741
742 pr_debug("%s: transport:%p, reason:%d, cwnd:%d, ssthresh:%d\n",
743 __func__, transport, reason, transport->cwnd,
744 transport->ssthresh);
745 }
746
747 /* Apply Max.Burst limit to the congestion window:
748 * sctpimpguide-05 2.14.2
749 * D) When the time comes for the sender to
750 * transmit new DATA chunks, the protocol parameter Max.Burst MUST
751 * first be applied to limit how many new DATA chunks may be sent.
752 * The limit is applied by adjusting cwnd as follows:
753 * if ((flightsize+ Max.Burst * MTU) < cwnd)
754 * cwnd = flightsize + Max.Burst * MTU
755 */
756
sctp_transport_burst_limited(struct sctp_transport * t)757 void sctp_transport_burst_limited(struct sctp_transport *t)
758 {
759 struct sctp_association *asoc = t->asoc;
760 u32 old_cwnd = t->cwnd;
761 u32 max_burst_bytes;
762
763 if (t->burst_limited || asoc->max_burst == 0)
764 return;
765
766 max_burst_bytes = t->flight_size + (asoc->max_burst * asoc->pathmtu);
767 if (max_burst_bytes < old_cwnd) {
768 t->cwnd = max_burst_bytes;
769 t->burst_limited = old_cwnd;
770 }
771 }
772
773 /* Restore the old cwnd congestion window, after the burst had it's
774 * desired effect.
775 */
sctp_transport_burst_reset(struct sctp_transport * t)776 void sctp_transport_burst_reset(struct sctp_transport *t)
777 {
778 if (t->burst_limited) {
779 t->cwnd = t->burst_limited;
780 t->burst_limited = 0;
781 }
782 }
783
784 /* What is the next timeout value for this transport? */
sctp_transport_timeout(struct sctp_transport * trans)785 unsigned long sctp_transport_timeout(struct sctp_transport *trans)
786 {
787 /* RTO + timer slack +/- 50% of RTO */
788 unsigned long timeout = trans->rto >> 1;
789
790 if (trans->state != SCTP_UNCONFIRMED &&
791 trans->state != SCTP_PF)
792 timeout += trans->hbinterval;
793
794 return max_t(unsigned long, timeout, HZ / 5);
795 }
796
797 /* Reset transport variables to their initial values */
sctp_transport_reset(struct sctp_transport * t)798 void sctp_transport_reset(struct sctp_transport *t)
799 {
800 struct sctp_association *asoc = t->asoc;
801
802 /* RFC 2960 (bis), Section 5.2.4
803 * All the congestion control parameters (e.g., cwnd, ssthresh)
804 * related to this peer MUST be reset to their initial values
805 * (see Section 6.2.1)
806 */
807 t->cwnd = min(4*asoc->pathmtu, max_t(__u32, 2*asoc->pathmtu, 4380));
808 t->burst_limited = 0;
809 t->ssthresh = asoc->peer.i.a_rwnd;
810 t->rto = asoc->rto_initial;
811 sctp_max_rto(asoc, t);
812 t->rtt = 0;
813 t->srtt = 0;
814 t->rttvar = 0;
815
816 /* Reset these additional variables so that we have a clean slate. */
817 t->partial_bytes_acked = 0;
818 t->flight_size = 0;
819 t->error_count = 0;
820 t->rto_pending = 0;
821 t->hb_sent = 0;
822
823 /* Initialize the state information for SFR-CACC */
824 t->cacc.changeover_active = 0;
825 t->cacc.cycling_changeover = 0;
826 t->cacc.next_tsn_at_change = 0;
827 t->cacc.cacc_saw_newack = 0;
828 }
829
830 /* Schedule retransmission on the given transport */
sctp_transport_immediate_rtx(struct sctp_transport * t)831 void sctp_transport_immediate_rtx(struct sctp_transport *t)
832 {
833 /* Stop pending T3_rtx_timer */
834 if (del_timer(&t->T3_rtx_timer))
835 sctp_transport_put(t);
836
837 sctp_retransmit(&t->asoc->outqueue, t, SCTP_RTXR_T3_RTX);
838 if (!timer_pending(&t->T3_rtx_timer)) {
839 if (!mod_timer(&t->T3_rtx_timer, jiffies + t->rto))
840 sctp_transport_hold(t);
841 }
842 }
843
844 /* Drop dst */
sctp_transport_dst_release(struct sctp_transport * t)845 void sctp_transport_dst_release(struct sctp_transport *t)
846 {
847 dst_release(t->dst);
848 t->dst = NULL;
849 t->dst_pending_confirm = 0;
850 }
851
852 /* Schedule neighbour confirm */
sctp_transport_dst_confirm(struct sctp_transport * t)853 void sctp_transport_dst_confirm(struct sctp_transport *t)
854 {
855 t->dst_pending_confirm = 1;
856 }
857
