Loading...
1/* SCTP kernel implementation
2 * Copyright (c) 1999-2000 Cisco, Inc.
3 * Copyright (c) 1999-2001 Motorola, Inc.
4 * Copyright (c) 2001-2003 International Business Machines Corp.
5 * Copyright (c) 2001 Intel Corp.
6 * Copyright (c) 2001 La Monte H.P. Yarroll
7 *
8 * This file is part of the SCTP kernel implementation
9 *
10 * This module provides the abstraction for an SCTP tranport representing
11 * a remote transport address. For local transport addresses, we just use
12 * union sctp_addr.
13 *
14 * This SCTP implementation is free software;
15 * you can redistribute it and/or modify it under the terms of
16 * the GNU General Public License as published by
17 * the Free Software Foundation; either version 2, or (at your option)
18 * any later version.
19 *
20 * This SCTP implementation is distributed in the hope that it
21 * will be useful, but WITHOUT ANY WARRANTY; without even the implied
22 * ************************
23 * warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
24 * See the GNU General Public License for more details.
25 *
26 * You should have received a copy of the GNU General Public License
27 * along with GNU CC; see the file COPYING. If not, write to
28 * the Free Software Foundation, 59 Temple Place - Suite 330,
29 * Boston, MA 02111-1307, USA.
30 *
31 * Please send any bug reports or fixes you make to the
32 * email address(es):
33 * lksctp developers <lksctp-developers@lists.sourceforge.net>
34 *
35 * Or submit a bug report through the following website:
36 * http://www.sf.net/projects/lksctp
37 *
38 * Written or modified by:
39 * La Monte H.P. Yarroll <piggy@acm.org>
40 * Karl Knutson <karl@athena.chicago.il.us>
41 * Jon Grimm <jgrimm@us.ibm.com>
42 * Xingang Guo <xingang.guo@intel.com>
43 * Hui Huang <hui.huang@nokia.com>
44 * Sridhar Samudrala <sri@us.ibm.com>
45 * Ardelle Fan <ardelle.fan@intel.com>
46 *
47 * Any bugs reported given to us we will try to fix... any fixes shared will
48 * be incorporated into the next SCTP release.
49 */
50
51#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
52
53#include <linux/slab.h>
54#include <linux/types.h>
55#include <linux/random.h>
56#include <net/sctp/sctp.h>
57#include <net/sctp/sm.h>
58
59/* 1st Level Abstractions. */
60
61/* Initialize a new transport from provided memory. */
62static struct sctp_transport *sctp_transport_init(struct 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 peer->sack_generation = 0;
72
73 /* From 6.3.1 RTO Calculation:
74 *
75 * C1) Until an RTT measurement has been made for a packet sent to the
76 * given destination transport address, set RTO to the protocol
77 * parameter 'RTO.Initial'.
78 */
79 peer->rto = msecs_to_jiffies(sctp_rto_initial);
80
81 peer->last_time_heard = jiffies;
82 peer->last_time_ecne_reduced = jiffies;
83
84 peer->param_flags = SPP_HB_DISABLE |
85 SPP_PMTUD_ENABLE |
86 SPP_SACKDELAY_ENABLE;
87
88 /* Initialize the default path max_retrans. */
89 peer->pathmaxrxt = sctp_max_retrans_path;
90
91 INIT_LIST_HEAD(&peer->transmitted);
92 INIT_LIST_HEAD(&peer->send_ready);
93 INIT_LIST_HEAD(&peer->transports);
94
95 setup_timer(&peer->T3_rtx_timer, sctp_generate_t3_rtx_event,
96 (unsigned long)peer);
97 setup_timer(&peer->hb_timer, sctp_generate_heartbeat_event,
98 (unsigned long)peer);
99 setup_timer(&peer->proto_unreach_timer,
100 sctp_generate_proto_unreach_event, (unsigned long)peer);
101
102 /* Initialize the 64-bit random nonce sent with heartbeat. */
103 get_random_bytes(&peer->hb_nonce, sizeof(peer->hb_nonce));
104
105 atomic_set(&peer->refcnt, 1);
106
107 return peer;
108}
109
110/* Allocate and initialize a new transport. */
111struct sctp_transport *sctp_transport_new(const union sctp_addr *addr,
112 gfp_t gfp)
113{
114 struct sctp_transport *transport;
115
116 transport = t_new(struct sctp_transport, gfp);
117 if (!transport)
118 goto fail;
119
120 if (!sctp_transport_init(transport, addr, gfp))
121 goto fail_init;
122
123 transport->malloced = 1;
124 SCTP_DBG_OBJCNT_INC(transport);
125
126 return transport;
127
128fail_init:
129 kfree(transport);
130
131fail:
132 return NULL;
133}
134
135/* This transport is no longer needed. Free up if possible, or
136 * delay until it last reference count.
137 */
138void sctp_transport_free(struct sctp_transport *transport)
139{
140 transport->dead = 1;
141
142 /* Try to delete the heartbeat timer. */
143 if (del_timer(&transport->hb_timer))
144 sctp_transport_put(transport);
145
146 /* Delete the T3_rtx timer if it's active.
147 * There is no point in not doing this now and letting
148 * structure hang around in memory since we know
149 * the tranport is going away.
150 */
151 if (timer_pending(&transport->T3_rtx_timer) &&
152 del_timer(&transport->T3_rtx_timer))
153 sctp_transport_put(transport);
154
155 /* Delete the ICMP proto unreachable timer if it's active. */
156 if (timer_pending(&transport->proto_unreach_timer) &&
157 del_timer(&transport->proto_unreach_timer))
158 sctp_association_put(transport->asoc);
159
160 sctp_transport_put(transport);
161}
162
163/* Destroy the transport data structure.
164 * Assumes there are no more users of this structure.
165 */
166static void sctp_transport_destroy(struct sctp_transport *transport)
167{
168 SCTP_ASSERT(transport->dead, "Transport is not dead", return);
169
170 if (transport->asoc)
171 sctp_association_put(transport->asoc);
172
173 sctp_packet_free(&transport->packet);
174
175 dst_release(transport->dst);
176 kfree(transport);
177 SCTP_DBG_OBJCNT_DEC(transport);
178}
179
180/* Start T3_rtx timer if it is not already running and update the heartbeat
181 * timer. This routine is called every time a DATA chunk is sent.
182 */
183void sctp_transport_reset_timers(struct sctp_transport *transport)
184{
185 /* RFC 2960 6.3.2 Retransmission Timer Rules
186 *
187 * R1) Every time a DATA chunk is sent to any address(including a
188 * retransmission), if the T3-rtx timer of that address is not running
189 * start it running so that it will expire after the RTO of that
190 * address.
191 */
192
193 if (!timer_pending(&transport->T3_rtx_timer))
194 if (!mod_timer(&transport->T3_rtx_timer,
195 jiffies + transport->rto))
196 sctp_transport_hold(transport);
197
198 /* When a data chunk is sent, reset the heartbeat interval. */
199 if (!mod_timer(&transport->hb_timer,
200 sctp_transport_timeout(transport)))
201 sctp_transport_hold(transport);
202}
203
204/* This transport has been assigned to an association.
205 * Initialize fields from the association or from the sock itself.
206 * Register the reference count in the association.
207 */
208void sctp_transport_set_owner(struct sctp_transport *transport,
209 struct sctp_association *asoc)
210{
211 transport->asoc = asoc;
212 sctp_association_hold(asoc);
213}
214
215/* Initialize the pmtu of a transport. */
216void sctp_transport_pmtu(struct sctp_transport *transport, struct sock *sk)
217{
218 /* If we don't have a fresh route, look one up */
219 if (!transport->dst || transport->dst->obsolete > 1) {
220 dst_release(transport->dst);
221 transport->af_specific->get_dst(transport, &transport->saddr,
222 &transport->fl, sk);
223 }
224
225 if (transport->dst) {
226 transport->pathmtu = dst_mtu(transport->dst);
227 } else
228 transport->pathmtu = SCTP_DEFAULT_MAXSEGMENT;
229}
230
231void sctp_transport_update_pmtu(struct sctp_transport *t, u32 pmtu)
232{
233 struct dst_entry *dst;
234
235 if (unlikely(pmtu < SCTP_DEFAULT_MINSEGMENT)) {
236 pr_warn("%s: Reported pmtu %d too low, using default minimum of %d\n",
237 __func__, pmtu,
238 SCTP_DEFAULT_MINSEGMENT);
239 /* Use default minimum segment size and disable
240 * pmtu discovery on this transport.
241 */
242 t->pathmtu = SCTP_DEFAULT_MINSEGMENT;
243 } else {
244 t->pathmtu = pmtu;
245 }
246
247 dst = sctp_transport_dst_check(t);
248 if (dst)
249 dst->ops->update_pmtu(dst, pmtu);
250}
251
252/* Caches the dst entry and source address for a transport's destination
253 * address.
254 */
255void sctp_transport_route(struct sctp_transport *transport,
256 union sctp_addr *saddr, struct sctp_sock *opt)
257{
258 struct sctp_association *asoc = transport->asoc;
259 struct sctp_af *af = transport->af_specific;
260
261 af->get_dst(transport, saddr, &transport->fl, sctp_opt2sk(opt));
262
263 if (saddr)
264 memcpy(&transport->saddr, saddr, sizeof(union sctp_addr));
265 else
266 af->get_saddr(opt, transport, &transport->fl);
267
268 if ((transport->param_flags & SPP_PMTUD_DISABLE) && transport->pathmtu) {
269 return;
270 }
271 if (transport->dst) {
272 transport->pathmtu = dst_mtu(transport->dst);
273
274 /* Initialize sk->sk_rcv_saddr, if the transport is the
275 * association's active path for getsockname().
276 */
277 if (asoc && (!asoc->peer.primary_path ||
278 (transport == asoc->peer.active_path)))
279 opt->pf->af->to_sk_saddr(&transport->saddr,
280 asoc->base.sk);
281 } else
282 transport->pathmtu = SCTP_DEFAULT_MAXSEGMENT;
283}
284
285/* Hold a reference to a transport. */
286void sctp_transport_hold(struct sctp_transport *transport)
287{
288 atomic_inc(&transport->refcnt);
289}
290
291/* Release a reference to a transport and clean up
292 * if there are no more references.
293 */
294void sctp_transport_put(struct sctp_transport *transport)
295{
296 if (atomic_dec_and_test(&transport->refcnt))
297 sctp_transport_destroy(transport);
298}
299
300/* Update transport's RTO based on the newly calculated RTT. */
301void sctp_transport_update_rto(struct sctp_transport *tp, __u32 rtt)
302{
303 /* Check for valid transport. */
304 SCTP_ASSERT(tp, "NULL transport", return);
305
306 /* We should not be doing any RTO updates unless rto_pending is set. */
307 SCTP_ASSERT(tp->rto_pending, "rto_pending not set", return);
308
309 if (tp->rttvar || tp->srtt) {
310 /* 6.3.1 C3) When a new RTT measurement R' is made, set
311 * RTTVAR <- (1 - RTO.Beta) * RTTVAR + RTO.Beta * |SRTT - R'|
312 * SRTT <- (1 - RTO.Alpha) * SRTT + RTO.Alpha * R'
313 */
314
315 /* Note: The above algorithm has been rewritten to
316 * express rto_beta and rto_alpha as inverse powers
317 * of two.
318 * For example, assuming the default value of RTO.Alpha of
319 * 1/8, rto_alpha would be expressed as 3.
320 */
321 tp->rttvar = tp->rttvar - (tp->rttvar >> sctp_rto_beta)
322 + ((abs(tp->srtt - rtt)) >> sctp_rto_beta);
323 tp->srtt = tp->srtt - (tp->srtt >> sctp_rto_alpha)
324 + (rtt >> sctp_rto_alpha);
325 } else {
326 /* 6.3.1 C2) When the first RTT measurement R is made, set
327 * SRTT <- R, RTTVAR <- R/2.
328 */
329 tp->srtt = rtt;
330 tp->rttvar = rtt >> 1;
331 }
332
333 /* 6.3.1 G1) Whenever RTTVAR is computed, if RTTVAR = 0, then
334 * adjust RTTVAR <- G, where G is the CLOCK GRANULARITY.
335 */
336 if (tp->rttvar == 0)
337 tp->rttvar = SCTP_CLOCK_GRANULARITY;
338
339 /* 6.3.1 C3) After the computation, update RTO <- SRTT + 4 * RTTVAR. */
340 tp->rto = tp->srtt + (tp->rttvar << 2);
341
342 /* 6.3.1 C6) Whenever RTO is computed, if it is less than RTO.Min
343 * seconds then it is rounded up to RTO.Min seconds.
344 */
345 if (tp->rto < tp->asoc->rto_min)
346 tp->rto = tp->asoc->rto_min;
347
348 /* 6.3.1 C7) A maximum value may be placed on RTO provided it is
349 * at least RTO.max seconds.
350 */
351 if (tp->rto > tp->asoc->rto_max)
352 tp->rto = tp->asoc->rto_max;
353
354 tp->rtt = rtt;
355
356 /* Reset rto_pending so that a new RTT measurement is started when a
357 * new data chunk is sent.
358 */
359 tp->rto_pending = 0;
360
361 SCTP_DEBUG_PRINTK("%s: transport: %p, rtt: %d, srtt: %d "
362 "rttvar: %d, rto: %ld\n", __func__,
363 tp, rtt, tp->srtt, tp->rttvar, tp->rto);
364}
365
366/* This routine updates the transport's cwnd and partial_bytes_acked
367 * parameters based on the bytes acked in the received SACK.
368 */
369void sctp_transport_raise_cwnd(struct sctp_transport *transport,
370 __u32 sack_ctsn, __u32 bytes_acked)
371{
372 struct sctp_association *asoc = transport->asoc;
373 __u32 cwnd, ssthresh, flight_size, pba, pmtu;
374
375 cwnd = transport->cwnd;
376 flight_size = transport->flight_size;
377
378 /* See if we need to exit Fast Recovery first */
379 if (asoc->fast_recovery &&
380 TSN_lte(asoc->fast_recovery_exit, sack_ctsn))
381 asoc->fast_recovery = 0;
382
383 /* The appropriate cwnd increase algorithm is performed if, and only
384 * if the cumulative TSN whould advanced and the congestion window is
385 * being fully utilized.
386 */
387 if (TSN_lte(sack_ctsn, transport->asoc->ctsn_ack_point) ||
388 (flight_size < cwnd))
389 return;
390
391 ssthresh = transport->ssthresh;
392 pba = transport->partial_bytes_acked;
393 pmtu = transport->asoc->pathmtu;
394
395 if (cwnd <= ssthresh) {
396 /* RFC 4960 7.2.1
397 * o When cwnd is less than or equal to ssthresh, an SCTP
398 * endpoint MUST use the slow-start algorithm to increase
399 * cwnd only if the current congestion window is being fully
400 * utilized, an incoming SACK advances the Cumulative TSN
401 * Ack Point, and the data sender is not in Fast Recovery.
402 * Only when these three conditions are met can the cwnd be
403 * increased; otherwise, the cwnd MUST not be increased.
404 * If these conditions are met, then cwnd MUST be increased
405 * by, at most, the lesser of 1) the total size of the
406 * previously outstanding DATA chunk(s) acknowledged, and
407 * 2) the destination's path MTU. This upper bound protects
408 * against the ACK-Splitting attack outlined in [SAVAGE99].
409 */
410 if (asoc->fast_recovery)
411 return;
412
413 if (bytes_acked > pmtu)
414 cwnd += pmtu;
415 else
416 cwnd += bytes_acked;
417 SCTP_DEBUG_PRINTK("%s: SLOW START: transport: %p, "
418 "bytes_acked: %d, cwnd: %d, ssthresh: %d, "
419 "flight_size: %d, pba: %d\n",
420 __func__,
421 transport, bytes_acked, cwnd,
422 ssthresh, flight_size, pba);
423 } else {
424 /* RFC 2960 7.2.2 Whenever cwnd is greater than ssthresh,
425 * upon each SACK arrival that advances the Cumulative TSN Ack
426 * Point, increase partial_bytes_acked by the total number of
427 * bytes of all new chunks acknowledged in that SACK including
428 * chunks acknowledged by the new Cumulative TSN Ack and by
429 * Gap Ack Blocks.
430 *
431 * When partial_bytes_acked is equal to or greater than cwnd
432 * and before the arrival of the SACK the sender had cwnd or
433 * more bytes of data outstanding (i.e., before arrival of the
434 * SACK, flightsize was greater than or equal to cwnd),
435 * increase cwnd by MTU, and reset partial_bytes_acked to
436 * (partial_bytes_acked - cwnd).
437 */
438 pba += bytes_acked;
439 if (pba >= cwnd) {
440 cwnd += pmtu;
441 pba = ((cwnd < pba) ? (pba - cwnd) : 0);
442 }
443 SCTP_DEBUG_PRINTK("%s: CONGESTION AVOIDANCE: "
444 "transport: %p, bytes_acked: %d, cwnd: %d, "
445 "ssthresh: %d, flight_size: %d, pba: %d\n",
446 __func__,
447 transport, bytes_acked, cwnd,
448 ssthresh, flight_size, pba);
449 }
450
451 transport->cwnd = cwnd;
452 transport->partial_bytes_acked = pba;
453}
454
455/* This routine is used to lower the transport's cwnd when congestion is
456 * detected.
457 */
458void sctp_transport_lower_cwnd(struct sctp_transport *transport,
459 sctp_lower_cwnd_t reason)
460{
461 struct sctp_association *asoc = transport->asoc;
462
463 switch (reason) {
464 case SCTP_LOWER_CWND_T3_RTX:
465 /* RFC 2960 Section 7.2.3, sctpimpguide
466 * When the T3-rtx timer expires on an address, SCTP should
467 * perform slow start by:
468 * ssthresh = max(cwnd/2, 4*MTU)
469 * cwnd = 1*MTU
470 * partial_bytes_acked = 0
471 */
472 transport->ssthresh = max(transport->cwnd/2,
473 4*asoc->pathmtu);
474 transport->cwnd = asoc->pathmtu;
475
476 /* T3-rtx also clears fast recovery */
477 asoc->fast_recovery = 0;
478 break;
479
480 case SCTP_LOWER_CWND_FAST_RTX:
481 /* RFC 2960 7.2.4 Adjust the ssthresh and cwnd of the
482 * destination address(es) to which the missing DATA chunks
483 * were last sent, according to the formula described in
484 * Section 7.2.3.
485 *
486 * RFC 2960 7.2.3, sctpimpguide Upon detection of packet
487 * losses from SACK (see Section 7.2.4), An endpoint
488 * should do the following:
489 * ssthresh = max(cwnd/2, 4*MTU)
490 * cwnd = ssthresh
491 * partial_bytes_acked = 0
492 */
493 if (asoc->fast_recovery)
494 return;
495
496 /* Mark Fast recovery */
497 asoc->fast_recovery = 1;
498 asoc->fast_recovery_exit = asoc->next_tsn - 1;
499
500 transport->ssthresh = max(transport->cwnd/2,
501 4*asoc->pathmtu);
502 transport->cwnd = transport->ssthresh;
503 break;
504
505 case SCTP_LOWER_CWND_ECNE:
506 /* RFC 2481 Section 6.1.2.
507 * If the sender receives an ECN-Echo ACK packet
508 * then the sender knows that congestion was encountered in the
509 * network on the path from the sender to the receiver. The
510 * indication of congestion should be treated just as a
511 * congestion loss in non-ECN Capable TCP. That is, the TCP
512 * source halves the congestion window "cwnd" and reduces the
513 * slow start threshold "ssthresh".
514 * A critical condition is that TCP does not react to
515 * congestion indications more than once every window of
516 * data (or more loosely more than once every round-trip time).
517 */
518 if (time_after(jiffies, transport->last_time_ecne_reduced +
519 transport->rtt)) {
520 transport->ssthresh = max(transport->cwnd/2,
521 4*asoc->pathmtu);
522 transport->cwnd = transport->ssthresh;
523 transport->last_time_ecne_reduced = jiffies;
524 }
525 break;
526
527 case SCTP_LOWER_CWND_INACTIVE:
528 /* RFC 2960 Section 7.2.1, sctpimpguide
529 * When the endpoint does not transmit data on a given
530 * transport address, the cwnd of the transport address
531 * should be adjusted to max(cwnd/2, 4*MTU) per RTO.
532 * NOTE: Although the draft recommends that this check needs
533 * to be done every RTO interval, we do it every hearbeat
534 * interval.
535 */
536 transport->cwnd = max(transport->cwnd/2,
537 4*asoc->pathmtu);
538 break;
539 }
540
541 transport->partial_bytes_acked = 0;
542 SCTP_DEBUG_PRINTK("%s: transport: %p reason: %d cwnd: "
543 "%d ssthresh: %d\n", __func__,
544 transport, reason,
545 transport->cwnd, transport->ssthresh);
546}
547
548/* Apply Max.Burst limit to the congestion window:
549 * sctpimpguide-05 2.14.2
550 * D) When the time comes for the sender to
551 * transmit new DATA chunks, the protocol parameter Max.Burst MUST
552 * first be applied to limit how many new DATA chunks may be sent.
553 * The limit is applied by adjusting cwnd as follows:
554 * if ((flightsize+ Max.Burst * MTU) < cwnd)
555 * cwnd = flightsize + Max.Burst * MTU
556 */
557
558void sctp_transport_burst_limited(struct sctp_transport *t)
559{
560 struct sctp_association *asoc = t->asoc;
561 u32 old_cwnd = t->cwnd;
562 u32 max_burst_bytes;
563
564 if (t->burst_limited)
565 return;
566
567 max_burst_bytes = t->flight_size + (asoc->max_burst * asoc->pathmtu);
568 if (max_burst_bytes < old_cwnd) {
569 t->cwnd = max_burst_bytes;
570 t->burst_limited = old_cwnd;
571 }
572}
573
574/* Restore the old cwnd congestion window, after the burst had it's
575 * desired effect.
576 */
577void sctp_transport_burst_reset(struct sctp_transport *t)
578{
579 if (t->burst_limited) {
580 t->cwnd = t->burst_limited;
581 t->burst_limited = 0;
582 }
583}
584
585/* What is the next timeout value for this transport? */
586unsigned long sctp_transport_timeout(struct sctp_transport *t)
587{
588 unsigned long timeout;
589 timeout = t->rto + sctp_jitter(t->rto);
590 if (t->state != SCTP_UNCONFIRMED)
591 timeout += t->hbinterval;
592 timeout += jiffies;
593 return timeout;
594}
595
596/* Reset transport variables to their initial values */
597void sctp_transport_reset(struct sctp_transport *t)
598{
599 struct sctp_association *asoc = t->asoc;
600
601 /* RFC 2960 (bis), Section 5.2.4
602 * All the congestion control parameters (e.g., cwnd, ssthresh)
603 * related to this peer MUST be reset to their initial values
604 * (see Section 6.2.1)
605 */
606 t->cwnd = min(4*asoc->pathmtu, max_t(__u32, 2*asoc->pathmtu, 4380));
607 t->burst_limited = 0;
608 t->ssthresh = asoc->peer.i.a_rwnd;
609 t->rto = asoc->rto_initial;
610 t->rtt = 0;
611 t->srtt = 0;
612 t->rttvar = 0;
613
614 /* Reset these additional varibles so that we have a clean
615 * slate.
616 */
617 t->partial_bytes_acked = 0;
618 t->flight_size = 0;
619 t->error_count = 0;
620 t->rto_pending = 0;
621 t->hb_sent = 0;
622
623 /* Initialize the state information for SFR-CACC */
624 t->cacc.changeover_active = 0;
625 t->cacc.cycling_changeover = 0;
626 t->cacc.next_tsn_at_change = 0;
627 t->cacc.cacc_saw_newack = 0;
628}
629
630/* Schedule retransmission on the given transport */
631void sctp_transport_immediate_rtx(struct sctp_transport *t)
632{
633 /* Stop pending T3_rtx_timer */
634 if (timer_pending(&t->T3_rtx_timer)) {
635 (void)del_timer(&t->T3_rtx_timer);
636 sctp_transport_put(t);
637 }
638 sctp_retransmit(&t->asoc->outqueue, t, SCTP_RTXR_T3_RTX);
639 if (!timer_pending(&t->T3_rtx_timer)) {
640 if (!mod_timer(&t->T3_rtx_timer, jiffies + t->rto))
641 sctp_transport_hold(t);
642 }
643 return;
644}
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, see
28 * <http://www.gnu.org/licenses/>.
29 *
30 * Please send any bug reports or fixes you make to the
31 * email address(es):
32 * lksctp developers <linux-sctp@vger.kernel.org>
33 *
34 * Written or modified by:
35 * La Monte H.P. Yarroll <piggy@acm.org>
36 * Karl Knutson <karl@athena.chicago.il.us>
37 * Jon Grimm <jgrimm@us.ibm.com>
38 * Xingang Guo <xingang.guo@intel.com>
39 * Hui Huang <hui.huang@nokia.com>
40 * Sridhar Samudrala <sri@us.ibm.com>
41 * Ardelle Fan <ardelle.fan@intel.com>
42 */
43
44#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
45
46#include <linux/slab.h>
47#include <linux/types.h>
48#include <linux/random.h>
49#include <net/sctp/sctp.h>
50#include <net/sctp/sm.h>
51
52/* 1st Level Abstractions. */
53
54/* Initialize a new transport from provided memory. */
55static struct sctp_transport *sctp_transport_init(struct net *net,
56 struct sctp_transport *peer,
57 const union sctp_addr *addr,
58 gfp_t gfp)
59{
60 /* Copy in the address. */
61 peer->ipaddr = *addr;
62 peer->af_specific = sctp_get_af_specific(addr->sa.sa_family);
63 memset(&peer->saddr, 0, sizeof(union sctp_addr));
64
65 peer->sack_generation = 0;
66
67 /* From 6.3.1 RTO Calculation:
68 *
69 * C1) Until an RTT measurement has been made for a packet sent to the
70 * given destination transport address, set RTO to the protocol
71 * parameter 'RTO.Initial'.
72 */
73 peer->rto = msecs_to_jiffies(net->sctp.rto_initial);
74
75 peer->last_time_heard = ktime_set(0, 0);
76 peer->last_time_ecne_reduced = jiffies;
77
78 peer->param_flags = SPP_HB_DISABLE |
79 SPP_PMTUD_ENABLE |
80 SPP_SACKDELAY_ENABLE;
81
82 /* Initialize the default path max_retrans. */
83 peer->pathmaxrxt = net->sctp.max_retrans_path;
84 peer->pf_retrans = net->sctp.pf_retrans;
85
86 INIT_LIST_HEAD(&peer->transmitted);
87 INIT_LIST_HEAD(&peer->send_ready);
88 INIT_LIST_HEAD(&peer->transports);
89
90 setup_timer(&peer->T3_rtx_timer, sctp_generate_t3_rtx_event,
91 (unsigned long)peer);
92 setup_timer(&peer->hb_timer, sctp_generate_heartbeat_event,
93 (unsigned long)peer);
94 setup_timer(&peer->proto_unreach_timer,
95 sctp_generate_proto_unreach_event, (unsigned long)peer);
96
97 /* Initialize the 64-bit random nonce sent with heartbeat. */
98 get_random_bytes(&peer->hb_nonce, sizeof(peer->hb_nonce));
99
100 atomic_set(&peer->refcnt, 1);
101
102 return peer;
103}
104
105/* Allocate and initialize a new transport. */
106struct sctp_transport *sctp_transport_new(struct net *net,
107 const union sctp_addr *addr,
108 gfp_t gfp)
109{
110 struct sctp_transport *transport;
111
112 transport = kzalloc(sizeof(*transport), gfp);
113 if (!transport)
114 goto fail;
115
116 if (!sctp_transport_init(net, transport, addr, gfp))
117 goto fail_init;
118
119 SCTP_DBG_OBJCNT_INC(transport);
120
121 return transport;
122
123fail_init:
124 kfree(transport);
125
126fail:
127 return NULL;
128}
129
130/* This transport is no longer needed. Free up if possible, or
131 * delay until it last reference count.
132 */
133void sctp_transport_free(struct sctp_transport *transport)
134{
135 /* Try to delete the heartbeat timer. */
136 if (del_timer(&transport->hb_timer))
137 sctp_transport_put(transport);
138
139 /* Delete the T3_rtx timer if it's active.
140 * There is no point in not doing this now and letting
141 * structure hang around in memory since we know
142 * the tranport is going away.
143 */
144 if (del_timer(&transport->T3_rtx_timer))
145 sctp_transport_put(transport);
146
147 /* Delete the ICMP proto unreachable timer if it's active. */
148 if (del_timer(&transport->proto_unreach_timer))
149 sctp_association_put(transport->asoc);
150
151 sctp_transport_put(transport);
152}
153
154static void sctp_transport_destroy_rcu(struct rcu_head *head)
155{
156 struct sctp_transport *transport;
157
158 transport = container_of(head, struct sctp_transport, rcu);
159
160 dst_release(transport->dst);
161 kfree(transport);
162 SCTP_DBG_OBJCNT_DEC(transport);
163}
164
165/* Destroy the transport data structure.
166 * Assumes there are no more users of this structure.
167 */
168static void sctp_transport_destroy(struct sctp_transport *transport)
169{
170 if (unlikely(atomic_read(&transport->refcnt))) {
171 WARN(1, "Attempt to destroy undead transport %p!\n", transport);
172 return;
173 }
174
175 sctp_packet_free(&transport->packet);
176
177 if (transport->asoc)
178 sctp_association_put(transport->asoc);
179
180 call_rcu(&transport->rcu, sctp_transport_destroy_rcu);
181}
182
183/* Start T3_rtx timer if it is not already running and update the heartbeat
184 * timer. This routine is called every time a DATA chunk is sent.
185 */
186void sctp_transport_reset_t3_rtx(struct sctp_transport *transport)
187{
188 /* RFC 2960 6.3.2 Retransmission Timer Rules
189 *
190 * R1) Every time a DATA chunk is sent to any address(including a
191 * retransmission), if the T3-rtx timer of that address is not running
192 * start it running so that it will expire after the RTO of that
193 * address.
194 */
195
196 if (!timer_pending(&transport->T3_rtx_timer))
197 if (!mod_timer(&transport->T3_rtx_timer,
198 jiffies + transport->rto))
199 sctp_transport_hold(transport);
200}
201
202void sctp_transport_reset_hb_timer(struct sctp_transport *transport)
203{
204 unsigned long expires;
205
206 /* When a data chunk is sent, reset the heartbeat interval. */
207 expires = jiffies + sctp_transport_timeout(transport);
208 if (time_before(transport->hb_timer.expires, expires) &&
209 !mod_timer(&transport->hb_timer,
210 expires + prandom_u32_max(transport->rto)))
211 sctp_transport_hold(transport);
212}
213
214/* This transport has been assigned to an association.
215 * Initialize fields from the association or from the sock itself.
216 * Register the reference count in the association.
217 */
218void sctp_transport_set_owner(struct sctp_transport *transport,
219 struct sctp_association *asoc)
220{
221 transport->asoc = asoc;
222 sctp_association_hold(asoc);
223}
224
225/* Initialize the pmtu of a transport. */
226void sctp_transport_pmtu(struct sctp_transport *transport, struct sock *sk)
227{
228 /* If we don't have a fresh route, look one up */
229 if (!transport->dst || transport->dst->obsolete) {
230 dst_release(transport->dst);
231 transport->af_specific->get_dst(transport, &transport->saddr,
232 &transport->fl, sk);
233 }
234
235 if (transport->dst) {
236 transport->pathmtu = WORD_TRUNC(dst_mtu(transport->dst));
237 } else
238 transport->pathmtu = SCTP_DEFAULT_MAXSEGMENT;
239}
240
241void sctp_transport_update_pmtu(struct sock *sk, struct sctp_transport *t, u32 pmtu)
242{
243 struct dst_entry *dst;
244
245 if (unlikely(pmtu < SCTP_DEFAULT_MINSEGMENT)) {
246 pr_warn("%s: Reported pmtu %d too low, using default minimum of %d\n",
247 __func__, pmtu,
248 SCTP_DEFAULT_MINSEGMENT);
249 /* Use default minimum segment size and disable
250 * pmtu discovery on this transport.
251 */
252 t->pathmtu = SCTP_DEFAULT_MINSEGMENT;
253 } else {
254 t->pathmtu = pmtu;
255 }
256
257 dst = sctp_transport_dst_check(t);
258 if (!dst)
259 t->af_specific->get_dst(t, &t->saddr, &t->fl, sk);
260
261 if (dst) {
262 dst->ops->update_pmtu(dst, sk, NULL, pmtu);
263
264 dst = sctp_transport_dst_check(t);
265 if (!dst)
266 t->af_specific->get_dst(t, &t->saddr, &t->fl, sk);
267 }
268}
269
270/* Caches the dst entry and source address for a transport's destination
271 * address.
272 */
273void sctp_transport_route(struct sctp_transport *transport,
274 union sctp_addr *saddr, struct sctp_sock *opt)
275{
276 struct sctp_association *asoc = transport->asoc;
277 struct sctp_af *af = transport->af_specific;
278
279 af->get_dst(transport, saddr, &transport->fl, sctp_opt2sk(opt));
280
281 if (saddr)
282 memcpy(&transport->saddr, saddr, sizeof(union sctp_addr));
283 else
284 af->get_saddr(opt, transport, &transport->fl);
285
286 if ((transport->param_flags & SPP_PMTUD_DISABLE) && transport->pathmtu) {
287 return;
288 }
289 if (transport->dst) {
290 transport->pathmtu = WORD_TRUNC(dst_mtu(transport->dst));
291
292 /* Initialize sk->sk_rcv_saddr, if the transport is the
293 * association's active path for getsockname().
294 */
295 if (asoc && (!asoc->peer.primary_path ||
296 (transport == asoc->peer.active_path)))
297 opt->pf->to_sk_saddr(&transport->saddr,
298 asoc->base.sk);
299 } else
300 transport->pathmtu = SCTP_DEFAULT_MAXSEGMENT;
301}
302
303/* Hold a reference to a transport. */
304int sctp_transport_hold(struct sctp_transport *transport)
305{
306 return atomic_add_unless(&transport->refcnt, 1, 0);
307}
308
309/* Release a reference to a transport and clean up
310 * if there are no more references.
311 */
312void sctp_transport_put(struct sctp_transport *transport)
313{
314 if (atomic_dec_and_test(&transport->refcnt))
315 sctp_transport_destroy(transport);
316}
317
318/* Update transport's RTO based on the newly calculated RTT. */
319void sctp_transport_update_rto(struct sctp_transport *tp, __u32 rtt)
320{
321 if (unlikely(!tp->rto_pending))
322 /* We should not be doing any RTO updates unless rto_pending is set. */
323 pr_debug("%s: rto_pending not set on transport %p!\n", __func__, tp);
324
325 if (tp->rttvar || tp->srtt) {
326 struct net *net = sock_net(tp->asoc->base.sk);
327 /* 6.3.1 C3) When a new RTT measurement R' is made, set
328 * RTTVAR <- (1 - RTO.Beta) * RTTVAR + RTO.Beta * |SRTT - R'|
329 * SRTT <- (1 - RTO.Alpha) * SRTT + RTO.Alpha * R'
330 */
331
332 /* Note: The above algorithm has been rewritten to
333 * express rto_beta and rto_alpha as inverse powers
334 * of two.
335 * For example, assuming the default value of RTO.Alpha of
336 * 1/8, rto_alpha would be expressed as 3.
337 */
338 tp->rttvar = tp->rttvar - (tp->rttvar >> net->sctp.rto_beta)
339 + (((__u32)abs((__s64)tp->srtt - (__s64)rtt)) >> net->sctp.rto_beta);
340 tp->srtt = tp->srtt - (tp->srtt >> net->sctp.rto_alpha)
341 + (rtt >> net->sctp.rto_alpha);
342 } else {
343 /* 6.3.1 C2) When the first RTT measurement R is made, set
344 * SRTT <- R, RTTVAR <- R/2.
345 */
346 tp->srtt = rtt;
347 tp->rttvar = rtt >> 1;
348 }
349
350 /* 6.3.1 G1) Whenever RTTVAR is computed, if RTTVAR = 0, then
351 * adjust RTTVAR <- G, where G is the CLOCK GRANULARITY.
352 */
353 if (tp->rttvar == 0)
354 tp->rttvar = SCTP_CLOCK_GRANULARITY;
355
356 /* 6.3.1 C3) After the computation, update RTO <- SRTT + 4 * RTTVAR. */
357 tp->rto = tp->srtt + (tp->rttvar << 2);
358
359 /* 6.3.1 C6) Whenever RTO is computed, if it is less than RTO.Min
360 * seconds then it is rounded up to RTO.Min seconds.
361 */
362 if (tp->rto < tp->asoc->rto_min)
363 tp->rto = tp->asoc->rto_min;
364
365 /* 6.3.1 C7) A maximum value may be placed on RTO provided it is
366 * at least RTO.max seconds.
367 */
368 if (tp->rto > tp->asoc->rto_max)
369 tp->rto = tp->asoc->rto_max;
370
371 sctp_max_rto(tp->asoc, tp);
372 tp->rtt = rtt;
373
374 /* Reset rto_pending so that a new RTT measurement is started when a
375 * new data chunk is sent.
376 */
377 tp->rto_pending = 0;
378
379 pr_debug("%s: transport:%p, rtt:%d, srtt:%d rttvar:%d, rto:%ld\n",
380 __func__, tp, rtt, tp->srtt, tp->rttvar, tp->rto);
381}
382
383/* This routine updates the transport's cwnd and partial_bytes_acked
384 * parameters based on the bytes acked in the received SACK.
385 */
386void sctp_transport_raise_cwnd(struct sctp_transport *transport,
387 __u32 sack_ctsn, __u32 bytes_acked)
388{
389 struct sctp_association *asoc = transport->asoc;
390 __u32 cwnd, ssthresh, flight_size, pba, pmtu;
391
392 cwnd = transport->cwnd;
393 flight_size = transport->flight_size;
394
395 /* See if we need to exit Fast Recovery first */
396 if (asoc->fast_recovery &&
397 TSN_lte(asoc->fast_recovery_exit, sack_ctsn))
398 asoc->fast_recovery = 0;
399
400 /* The appropriate cwnd increase algorithm is performed if, and only
401 * if the cumulative TSN whould advanced and the congestion window is
402 * being fully utilized.
403 */
404 if (TSN_lte(sack_ctsn, transport->asoc->ctsn_ack_point) ||
405 (flight_size < cwnd))
406 return;
407
408 ssthresh = transport->ssthresh;
409 pba = transport->partial_bytes_acked;
410 pmtu = transport->asoc->pathmtu;
411
412 if (cwnd <= ssthresh) {
413 /* RFC 4960 7.2.1
414 * o When cwnd is less than or equal to ssthresh, an SCTP
415 * endpoint MUST use the slow-start algorithm to increase
416 * cwnd only if the current congestion window is being fully
417 * utilized, an incoming SACK advances the Cumulative TSN
418 * Ack Point, and the data sender is not in Fast Recovery.
419 * Only when these three conditions are met can the cwnd be
420 * increased; otherwise, the cwnd MUST not be increased.
421 * If these conditions are met, then cwnd MUST be increased
422 * by, at most, the lesser of 1) the total size of the
423 * previously outstanding DATA chunk(s) acknowledged, and
424 * 2) the destination's path MTU. This upper bound protects
425 * against the ACK-Splitting attack outlined in [SAVAGE99].
426 */
427 if (asoc->fast_recovery)
428 return;
429
430 if (bytes_acked > pmtu)
431 cwnd += pmtu;
432 else
433 cwnd += bytes_acked;
434
435 pr_debug("%s: slow start: transport:%p, bytes_acked:%d, "
436 "cwnd:%d, ssthresh:%d, flight_size:%d, pba:%d\n",
437 __func__, transport, bytes_acked, cwnd, ssthresh,
438 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
460 pr_debug("%s: congestion avoidance: transport:%p, "
461 "bytes_acked:%d, cwnd:%d, ssthresh:%d, "
462 "flight_size:%d, pba:%d\n", __func__,
463 transport, bytes_acked, cwnd, ssthresh,
464 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 */
474void 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
559 pr_debug("%s: transport:%p, reason:%d, cwnd:%d, ssthresh:%d\n",
560 __func__, transport, reason, transport->cwnd,
561 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
574void 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 || asoc->max_burst == 0)
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 */
593void 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? */
602unsigned long sctp_transport_timeout(struct sctp_transport *trans)
603{
604 /* RTO + timer slack +/- 50% of RTO */
605 unsigned long timeout = trans->rto >> 1;
606
607 if (trans->state != SCTP_UNCONFIRMED &&
608 trans->state != SCTP_PF)
609 timeout += trans->hbinterval;
610
611 return timeout;
612}
613
614/* Reset transport variables to their initial values */
615void sctp_transport_reset(struct sctp_transport *t)
616{
617 struct sctp_association *asoc = t->asoc;
618
619 /* RFC 2960 (bis), Section 5.2.4
620 * All the congestion control parameters (e.g., cwnd, ssthresh)
621 * related to this peer MUST be reset to their initial values
622 * (see Section 6.2.1)
623 */
624 t->cwnd = min(4*asoc->pathmtu, max_t(__u32, 2*asoc->pathmtu, 4380));
625 t->burst_limited = 0;
626 t->ssthresh = asoc->peer.i.a_rwnd;
627 t->rto = asoc->rto_initial;
628 sctp_max_rto(asoc, t);
629 t->rtt = 0;
630 t->srtt = 0;
631 t->rttvar = 0;
632
633 /* Reset these additional varibles so that we have a clean
634 * slate.
635 */
636 t->partial_bytes_acked = 0;
637 t->flight_size = 0;
638 t->error_count = 0;
639 t->rto_pending = 0;
640 t->hb_sent = 0;
641
642 /* Initialize the state information for SFR-CACC */
643 t->cacc.changeover_active = 0;
644 t->cacc.cycling_changeover = 0;
645 t->cacc.next_tsn_at_change = 0;
646 t->cacc.cacc_saw_newack = 0;
647}
648
649/* Schedule retransmission on the given transport */
650void sctp_transport_immediate_rtx(struct sctp_transport *t)
651{
652 /* Stop pending T3_rtx_timer */
653 if (del_timer(&t->T3_rtx_timer))
654 sctp_transport_put(t);
655
656 sctp_retransmit(&t->asoc->outqueue, t, SCTP_RTXR_T3_RTX);
657 if (!timer_pending(&t->T3_rtx_timer)) {
658 if (!mod_timer(&t->T3_rtx_timer, jiffies + t->rto))
659 sctp_transport_hold(t);
660 }
661}