xref: /openbmc/linux/net/sctp/transport.c (revision d2999e1b)
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.  */
55 static 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_get();
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.  */
106 struct 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 
123 fail_init:
124 	kfree(transport);
125 
126 fail:
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  */
133 void sctp_transport_free(struct sctp_transport *transport)
134 {
135 	transport->dead = 1;
136 
137 	/* Try to delete the heartbeat timer.  */
138 	if (del_timer(&transport->hb_timer))
139 		sctp_transport_put(transport);
140 
141 	/* Delete the T3_rtx timer if it's active.
142 	 * There is no point in not doing this now and letting
143 	 * structure hang around in memory since we know
144 	 * the tranport is going away.
145 	 */
146 	if (del_timer(&transport->T3_rtx_timer))
147 		sctp_transport_put(transport);
148 
149 	/* Delete the ICMP proto unreachable timer if it's active. */
150 	if (del_timer(&transport->proto_unreach_timer))
151 		sctp_association_put(transport->asoc);
152 
153 	sctp_transport_put(transport);
154 }
155 
156 static void sctp_transport_destroy_rcu(struct rcu_head *head)
157 {
158 	struct sctp_transport *transport;
159 
160 	transport = container_of(head, struct sctp_transport, rcu);
161 
162 	dst_release(transport->dst);
163 	kfree(transport);
164 	SCTP_DBG_OBJCNT_DEC(transport);
165 }
166 
167 /* Destroy the transport data structure.
168  * Assumes there are no more users of this structure.
169  */
170 static void sctp_transport_destroy(struct sctp_transport *transport)
171 {
172 	if (unlikely(!transport->dead)) {
173 		WARN(1, "Attempt to destroy undead transport %p!\n", transport);
174 		return;
175 	}
176 
177 	sctp_packet_free(&transport->packet);
178 
179 	if (transport->asoc)
180 		sctp_association_put(transport->asoc);
181 
182 	call_rcu(&transport->rcu, sctp_transport_destroy_rcu);
183 }
184 
185 /* Start T3_rtx timer if it is not already running and update the heartbeat
186  * timer.  This routine is called every time a DATA chunk is sent.
187  */
188 void sctp_transport_reset_timers(struct sctp_transport *transport)
189 {
190 	/* RFC 2960 6.3.2 Retransmission Timer Rules
191 	 *
192 	 * R1) Every time a DATA chunk is sent to any address(including a
193 	 * retransmission), if the T3-rtx timer of that address is not running
194 	 * start it running so that it will expire after the RTO of that
195 	 * address.
196 	 */
197 
198 	if (!timer_pending(&transport->T3_rtx_timer))
199 		if (!mod_timer(&transport->T3_rtx_timer,
200 			       jiffies + transport->rto))
201 			sctp_transport_hold(transport);
202 
203 	/* When a data chunk is sent, reset the heartbeat interval.  */
204 	if (!mod_timer(&transport->hb_timer,
205 		       sctp_transport_timeout(transport)))
206 	    sctp_transport_hold(transport);
207 }
208 
209 /* This transport has been assigned to an association.
210  * Initialize fields from the association or from the sock itself.
211  * Register the reference count in the association.
212  */
213 void sctp_transport_set_owner(struct sctp_transport *transport,
214 			      struct sctp_association *asoc)
215 {
216 	transport->asoc = asoc;
217 	sctp_association_hold(asoc);
218 }
219 
220 /* Initialize the pmtu of a transport. */
221 void sctp_transport_pmtu(struct sctp_transport *transport, struct sock *sk)
222 {
223 	/* If we don't have a fresh route, look one up */
224 	if (!transport->dst || transport->dst->obsolete) {
225 		dst_release(transport->dst);
226 		transport->af_specific->get_dst(transport, &transport->saddr,
227 						&transport->fl, sk);
228 	}
229 
230 	if (transport->dst) {
231 		transport->pathmtu = dst_mtu(transport->dst);
232 	} else
233 		transport->pathmtu = SCTP_DEFAULT_MAXSEGMENT;
234 }
235 
236 void sctp_transport_update_pmtu(struct sock *sk, struct sctp_transport *t, u32 pmtu)
237 {
238 	struct dst_entry *dst;
239 
240 	if (unlikely(pmtu < SCTP_DEFAULT_MINSEGMENT)) {
241 		pr_warn("%s: Reported pmtu %d too low, using default minimum of %d\n",
242 			__func__, pmtu,
243 			SCTP_DEFAULT_MINSEGMENT);
244 		/* Use default minimum segment size and disable
245 		 * pmtu discovery on this transport.
246 		 */
247 		t->pathmtu = SCTP_DEFAULT_MINSEGMENT;
248 	} else {
249 		t->pathmtu = pmtu;
250 	}
251 
252 	dst = sctp_transport_dst_check(t);
253 	if (!dst)
254 		t->af_specific->get_dst(t, &t->saddr, &t->fl, sk);
255 
256 	if (dst) {
257 		dst->ops->update_pmtu(dst, sk, NULL, pmtu);
258 
259 		dst = sctp_transport_dst_check(t);
260 		if (!dst)
261 			t->af_specific->get_dst(t, &t->saddr, &t->fl, sk);
262 	}
263 }
264 
265 /* Caches the dst entry and source address for a transport's destination
266  * address.
267  */
268 void sctp_transport_route(struct sctp_transport *transport,
269 			  union sctp_addr *saddr, struct sctp_sock *opt)
270 {
271 	struct sctp_association *asoc = transport->asoc;
272 	struct sctp_af *af = transport->af_specific;
273 
274 	af->get_dst(transport, saddr, &transport->fl, sctp_opt2sk(opt));
275 
276 	if (saddr)
277 		memcpy(&transport->saddr, saddr, sizeof(union sctp_addr));
278 	else
279 		af->get_saddr(opt, transport, &transport->fl);
280 
281 	if ((transport->param_flags & SPP_PMTUD_DISABLE) && transport->pathmtu) {
282 		return;
283 	}
284 	if (transport->dst) {
285 		transport->pathmtu = dst_mtu(transport->dst);
286 
287 		/* Initialize sk->sk_rcv_saddr, if the transport is the
288 		 * association's active path for getsockname().
289 		 */
290 		if (asoc && (!asoc->peer.primary_path ||
291 				(transport == asoc->peer.active_path)))
292 			opt->pf->af->to_sk_saddr(&transport->saddr,
293 						 asoc->base.sk);
294 	} else
295 		transport->pathmtu = SCTP_DEFAULT_MAXSEGMENT;
296 }
297 
298 /* Hold a reference to a transport.  */
299 void sctp_transport_hold(struct sctp_transport *transport)
300 {
301 	atomic_inc(&transport->refcnt);
302 }
303 
304 /* Release a reference to a transport and clean up
305  * if there are no more references.
306  */
307 void sctp_transport_put(struct sctp_transport *transport)
308 {
309 	if (atomic_dec_and_test(&transport->refcnt))
310 		sctp_transport_destroy(transport);
311 }
312 
313 /* Update transport's RTO based on the newly calculated RTT. */
314 void sctp_transport_update_rto(struct sctp_transport *tp, __u32 rtt)
315 {
316 	if (unlikely(!tp->rto_pending))
317 		/* We should not be doing any RTO updates unless rto_pending is set.  */
318 		pr_debug("%s: rto_pending not set on transport %p!\n", __func__, tp);
319 
320 	if (tp->rttvar || tp->srtt) {
321 		struct net *net = sock_net(tp->asoc->base.sk);
322 		/* 6.3.1 C3) When a new RTT measurement R' is made, set
323 		 * RTTVAR <- (1 - RTO.Beta) * RTTVAR + RTO.Beta * |SRTT - R'|
324 		 * SRTT <- (1 - RTO.Alpha) * SRTT + RTO.Alpha * R'
325 		 */
326 
327 		/* Note:  The above algorithm has been rewritten to
328 		 * express rto_beta and rto_alpha as inverse powers
329 		 * of two.
330 		 * For example, assuming the default value of RTO.Alpha of
331 		 * 1/8, rto_alpha would be expressed as 3.
332 		 */
333 		tp->rttvar = tp->rttvar - (tp->rttvar >> net->sctp.rto_beta)
334 			+ (((__u32)abs64((__s64)tp->srtt - (__s64)rtt)) >> net->sctp.rto_beta);
335 		tp->srtt = tp->srtt - (tp->srtt >> net->sctp.rto_alpha)
336 			+ (rtt >> net->sctp.rto_alpha);
337 	} else {
338 		/* 6.3.1 C2) When the first RTT measurement R is made, set
339 		 * SRTT <- R, RTTVAR <- R/2.
340 		 */
341 		tp->srtt = rtt;
342 		tp->rttvar = rtt >> 1;
343 	}
344 
345 	/* 6.3.1 G1) Whenever RTTVAR is computed, if RTTVAR = 0, then
346 	 * adjust RTTVAR <- G, where G is the CLOCK GRANULARITY.
347 	 */
348 	if (tp->rttvar == 0)
349 		tp->rttvar = SCTP_CLOCK_GRANULARITY;
350 
351 	/* 6.3.1 C3) After the computation, update RTO <- SRTT + 4 * RTTVAR. */
352 	tp->rto = tp->srtt + (tp->rttvar << 2);
353 
354 	/* 6.3.1 C6) Whenever RTO is computed, if it is less than RTO.Min
355 	 * seconds then it is rounded up to RTO.Min seconds.
356 	 */
357 	if (tp->rto < tp->asoc->rto_min)
358 		tp->rto = tp->asoc->rto_min;
359 
360 	/* 6.3.1 C7) A maximum value may be placed on RTO provided it is
361 	 * at least RTO.max seconds.
362 	 */
363 	if (tp->rto > tp->asoc->rto_max)
364 		tp->rto = tp->asoc->rto_max;
365 
366 	sctp_max_rto(tp->asoc, tp);
367 	tp->rtt = rtt;
368 
369 	/* Reset rto_pending so that a new RTT measurement is started when a
370 	 * new data chunk is sent.
371 	 */
372 	tp->rto_pending = 0;
373 
374 	pr_debug("%s: transport:%p, rtt:%d, srtt:%d rttvar:%d, rto:%ld\n",
375 		 __func__, tp, rtt, tp->srtt, tp->rttvar, tp->rto);
376 }
377 
378 /* This routine updates the transport's cwnd and partial_bytes_acked
379  * parameters based on the bytes acked in the received SACK.
380  */
381 void sctp_transport_raise_cwnd(struct sctp_transport *transport,
382 			       __u32 sack_ctsn, __u32 bytes_acked)
383 {
384 	struct sctp_association *asoc = transport->asoc;
385 	__u32 cwnd, ssthresh, flight_size, pba, pmtu;
386 
387 	cwnd = transport->cwnd;
388 	flight_size = transport->flight_size;
389 
390 	/* See if we need to exit Fast Recovery first */
391 	if (asoc->fast_recovery &&
392 	    TSN_lte(asoc->fast_recovery_exit, sack_ctsn))
393 		asoc->fast_recovery = 0;
394 
395 	/* The appropriate cwnd increase algorithm is performed if, and only
396 	 * if the cumulative TSN whould advanced and the congestion window is
397 	 * being fully utilized.
398 	 */
399 	if (TSN_lte(sack_ctsn, transport->asoc->ctsn_ack_point) ||
400 	    (flight_size < cwnd))
401 		return;
402 
403 	ssthresh = transport->ssthresh;
404 	pba = transport->partial_bytes_acked;
405 	pmtu = transport->asoc->pathmtu;
406 
407 	if (cwnd <= ssthresh) {
408 		/* RFC 4960 7.2.1
409 		 * o  When cwnd is less than or equal to ssthresh, an SCTP
410 		 *    endpoint MUST use the slow-start algorithm to increase
411 		 *    cwnd only if the current congestion window is being fully
412 		 *    utilized, an incoming SACK advances the Cumulative TSN
413 		 *    Ack Point, and the data sender is not in Fast Recovery.
414 		 *    Only when these three conditions are met can the cwnd be
415 		 *    increased; otherwise, the cwnd MUST not be increased.
416 		 *    If these conditions are met, then cwnd MUST be increased
417 		 *    by, at most, the lesser of 1) the total size of the
418 		 *    previously outstanding DATA chunk(s) acknowledged, and
419 		 *    2) the destination's path MTU.  This upper bound protects
420 		 *    against the ACK-Splitting attack outlined in [SAVAGE99].
421 		 */
422 		if (asoc->fast_recovery)
423 			return;
424 
425 		if (bytes_acked > pmtu)
426 			cwnd += pmtu;
427 		else
428 			cwnd += bytes_acked;
429 
430 		pr_debug("%s: slow start: transport:%p, bytes_acked:%d, "
431 			 "cwnd:%d, ssthresh:%d, flight_size:%d, pba:%d\n",
432 			 __func__, transport, bytes_acked, cwnd, ssthresh,
433 			 flight_size, pba);
434 	} else {
435 		/* RFC 2960 7.2.2 Whenever cwnd is greater than ssthresh,
436 		 * upon each SACK arrival that advances the Cumulative TSN Ack
437 		 * Point, increase partial_bytes_acked by the total number of
438 		 * bytes of all new chunks acknowledged in that SACK including
439 		 * chunks acknowledged by the new Cumulative TSN Ack and by
440 		 * Gap Ack Blocks.
441 		 *
442 		 * When partial_bytes_acked is equal to or greater than cwnd
443 		 * and before the arrival of the SACK the sender had cwnd or
444 		 * more bytes of data outstanding (i.e., before arrival of the
445 		 * SACK, flightsize was greater than or equal to cwnd),
446 		 * increase cwnd by MTU, and reset partial_bytes_acked to
447 		 * (partial_bytes_acked - cwnd).
448 		 */
449 		pba += bytes_acked;
450 		if (pba >= cwnd) {
451 			cwnd += pmtu;
452 			pba = ((cwnd < pba) ? (pba - cwnd) : 0);
453 		}
454 
455 		pr_debug("%s: congestion avoidance: transport:%p, "
456 			 "bytes_acked:%d, cwnd:%d, ssthresh:%d, "
457 			 "flight_size:%d, pba:%d\n", __func__,
458 			 transport, bytes_acked, cwnd, ssthresh,
459 			 flight_size, pba);
460 	}
461 
462 	transport->cwnd = cwnd;
463 	transport->partial_bytes_acked = pba;
464 }
465 
466 /* This routine is used to lower the transport's cwnd when congestion is
467  * detected.
468  */
469 void sctp_transport_lower_cwnd(struct sctp_transport *transport,
470 			       sctp_lower_cwnd_t reason)
471 {
472 	struct sctp_association *asoc = transport->asoc;
473 
474 	switch (reason) {
475 	case SCTP_LOWER_CWND_T3_RTX:
476 		/* RFC 2960 Section 7.2.3, sctpimpguide
477 		 * When the T3-rtx timer expires on an address, SCTP should
478 		 * perform slow start by:
479 		 *      ssthresh = max(cwnd/2, 4*MTU)
480 		 *      cwnd = 1*MTU
481 		 *      partial_bytes_acked = 0
482 		 */
483 		transport->ssthresh = max(transport->cwnd/2,
484 					  4*asoc->pathmtu);
485 		transport->cwnd = asoc->pathmtu;
486 
487 		/* T3-rtx also clears fast recovery */
488 		asoc->fast_recovery = 0;
489 		break;
490 
491 	case SCTP_LOWER_CWND_FAST_RTX:
492 		/* RFC 2960 7.2.4 Adjust the ssthresh and cwnd of the
493 		 * destination address(es) to which the missing DATA chunks
494 		 * were last sent, according to the formula described in
495 		 * Section 7.2.3.
496 		 *
497 		 * RFC 2960 7.2.3, sctpimpguide Upon detection of packet
498 		 * losses from SACK (see Section 7.2.4), An endpoint
499 		 * should do the following:
500 		 *      ssthresh = max(cwnd/2, 4*MTU)
501 		 *      cwnd = ssthresh
502 		 *      partial_bytes_acked = 0
503 		 */
504 		if (asoc->fast_recovery)
505 			return;
506 
507 		/* Mark Fast recovery */
508 		asoc->fast_recovery = 1;
509 		asoc->fast_recovery_exit = asoc->next_tsn - 1;
510 
511 		transport->ssthresh = max(transport->cwnd/2,
512 					  4*asoc->pathmtu);
513 		transport->cwnd = transport->ssthresh;
514 		break;
515 
516 	case SCTP_LOWER_CWND_ECNE:
517 		/* RFC 2481 Section 6.1.2.
518 		 * If the sender receives an ECN-Echo ACK packet
519 		 * then the sender knows that congestion was encountered in the
520 		 * network on the path from the sender to the receiver. The
521 		 * indication of congestion should be treated just as a
522 		 * congestion loss in non-ECN Capable TCP. That is, the TCP
523 		 * source halves the congestion window "cwnd" and reduces the
524 		 * slow start threshold "ssthresh".
525 		 * A critical condition is that TCP does not react to
526 		 * congestion indications more than once every window of
527 		 * data (or more loosely more than once every round-trip time).
528 		 */
529 		if (time_after(jiffies, transport->last_time_ecne_reduced +
530 					transport->rtt)) {
531 			transport->ssthresh = max(transport->cwnd/2,
532 						  4*asoc->pathmtu);
533 			transport->cwnd = transport->ssthresh;
534 			transport->last_time_ecne_reduced = jiffies;
535 		}
536 		break;
537 
538 	case SCTP_LOWER_CWND_INACTIVE:
539 		/* RFC 2960 Section 7.2.1, sctpimpguide
540 		 * When the endpoint does not transmit data on a given
541 		 * transport address, the cwnd of the transport address
542 		 * should be adjusted to max(cwnd/2, 4*MTU) per RTO.
543 		 * NOTE: Although the draft recommends that this check needs
544 		 * to be done every RTO interval, we do it every hearbeat
545 		 * interval.
546 		 */
547 		transport->cwnd = max(transport->cwnd/2,
548 					 4*asoc->pathmtu);
549 		break;
550 	}
551 
552 	transport->partial_bytes_acked = 0;
553 
554 	pr_debug("%s: transport:%p, reason:%d, cwnd:%d, ssthresh:%d\n",
555 		 __func__, transport, reason, transport->cwnd,
556 		 transport->ssthresh);
557 }
558 
559 /* Apply Max.Burst limit to the congestion window:
560  * sctpimpguide-05 2.14.2
561  * D) When the time comes for the sender to
562  * transmit new DATA chunks, the protocol parameter Max.Burst MUST
563  * first be applied to limit how many new DATA chunks may be sent.
564  * The limit is applied by adjusting cwnd as follows:
565  * 	if ((flightsize+ Max.Burst * MTU) < cwnd)
566  * 		cwnd = flightsize + Max.Burst * MTU
567  */
568 
569 void sctp_transport_burst_limited(struct sctp_transport *t)
570 {
571 	struct sctp_association *asoc = t->asoc;
572 	u32 old_cwnd = t->cwnd;
573 	u32 max_burst_bytes;
574 
575 	if (t->burst_limited || asoc->max_burst == 0)
576 		return;
577 
578 	max_burst_bytes = t->flight_size + (asoc->max_burst * asoc->pathmtu);
579 	if (max_burst_bytes < old_cwnd) {
580 		t->cwnd = max_burst_bytes;
581 		t->burst_limited = old_cwnd;
582 	}
583 }
584 
585 /* Restore the old cwnd congestion window, after the burst had it's
586  * desired effect.
587  */
588 void sctp_transport_burst_reset(struct sctp_transport *t)
589 {
590 	if (t->burst_limited) {
591 		t->cwnd = t->burst_limited;
592 		t->burst_limited = 0;
593 	}
594 }
595 
596 /* What is the next timeout value for this transport? */
597 unsigned long sctp_transport_timeout(struct sctp_transport *t)
598 {
599 	unsigned long timeout;
600 	timeout = t->rto + sctp_jitter(t->rto);
601 	if ((t->state != SCTP_UNCONFIRMED) &&
602 	    (t->state != SCTP_PF))
603 		timeout += t->hbinterval;
604 	timeout += jiffies;
605 	return timeout;
606 }
607 
608 /* Reset transport variables to their initial values */
609 void sctp_transport_reset(struct sctp_transport *t)
610 {
611 	struct sctp_association *asoc = t->asoc;
612 
613 	/* RFC 2960 (bis), Section 5.2.4
614 	 * All the congestion control parameters (e.g., cwnd, ssthresh)
615 	 * related to this peer MUST be reset to their initial values
616 	 * (see Section 6.2.1)
617 	 */
618 	t->cwnd = min(4*asoc->pathmtu, max_t(__u32, 2*asoc->pathmtu, 4380));
619 	t->burst_limited = 0;
620 	t->ssthresh = asoc->peer.i.a_rwnd;
621 	t->rto = asoc->rto_initial;
622 	sctp_max_rto(asoc, t);
623 	t->rtt = 0;
624 	t->srtt = 0;
625 	t->rttvar = 0;
626 
627 	/* Reset these additional varibles so that we have a clean
628 	 * slate.
629 	 */
630 	t->partial_bytes_acked = 0;
631 	t->flight_size = 0;
632 	t->error_count = 0;
633 	t->rto_pending = 0;
634 	t->hb_sent = 0;
635 
636 	/* Initialize the state information for SFR-CACC */
637 	t->cacc.changeover_active = 0;
638 	t->cacc.cycling_changeover = 0;
639 	t->cacc.next_tsn_at_change = 0;
640 	t->cacc.cacc_saw_newack = 0;
641 }
642 
643 /* Schedule retransmission on the given transport */
644 void sctp_transport_immediate_rtx(struct sctp_transport *t)
645 {
646 	/* Stop pending T3_rtx_timer */
647 	if (del_timer(&t->T3_rtx_timer))
648 		sctp_transport_put(t);
649 
650 	sctp_retransmit(&t->asoc->outqueue, t, SCTP_RTXR_T3_RTX);
651 	if (!timer_pending(&t->T3_rtx_timer)) {
652 		if (!mod_timer(&t->T3_rtx_timer, jiffies + t->rto))
653 			sctp_transport_hold(t);
654 	}
655 }
656