xref: /openbmc/linux/net/sctp/transport.c (revision b6dcefde)
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 #include <linux/types.h>
52 #include <linux/random.h>
53 #include <net/sctp/sctp.h>
54 #include <net/sctp/sm.h>
55 
56 /* 1st Level Abstractions.  */
57 
58 /* Initialize a new transport from provided memory.  */
59 static struct sctp_transport *sctp_transport_init(struct sctp_transport *peer,
60 						  const union sctp_addr *addr,
61 						  gfp_t gfp)
62 {
63 	/* Copy in the address.  */
64 	peer->ipaddr = *addr;
65 	peer->af_specific = sctp_get_af_specific(addr->sa.sa_family);
66 	peer->asoc = NULL;
67 
68 	peer->dst = NULL;
69 	memset(&peer->saddr, 0, sizeof(union sctp_addr));
70 
71 	/* From 6.3.1 RTO Calculation:
72 	 *
73 	 * C1) Until an RTT measurement has been made for a packet sent to the
74 	 * given destination transport address, set RTO to the protocol
75 	 * parameter 'RTO.Initial'.
76 	 */
77 	peer->rto = msecs_to_jiffies(sctp_rto_initial);
78 	peer->rtt = 0;
79 	peer->rttvar = 0;
80 	peer->srtt = 0;
81 	peer->rto_pending = 0;
82 	peer->hb_sent = 0;
83 	peer->fast_recovery = 0;
84 
85 	peer->last_time_heard = jiffies;
86 	peer->last_time_ecne_reduced = jiffies;
87 
88 	peer->init_sent_count = 0;
89 
90 	peer->param_flags = SPP_HB_DISABLE |
91 			    SPP_PMTUD_ENABLE |
92 			    SPP_SACKDELAY_ENABLE;
93 	peer->hbinterval  = 0;
94 
95 	/* Initialize the default path max_retrans.  */
96 	peer->pathmaxrxt  = sctp_max_retrans_path;
97 	peer->error_count = 0;
98 
99 	INIT_LIST_HEAD(&peer->transmitted);
100 	INIT_LIST_HEAD(&peer->send_ready);
101 	INIT_LIST_HEAD(&peer->transports);
102 
103 	peer->T3_rtx_timer.expires = 0;
104 	peer->hb_timer.expires = 0;
105 
106 	setup_timer(&peer->T3_rtx_timer, sctp_generate_t3_rtx_event,
107 			(unsigned long)peer);
108 	setup_timer(&peer->hb_timer, sctp_generate_heartbeat_event,
109 			(unsigned long)peer);
110 
111 	/* Initialize the 64-bit random nonce sent with heartbeat. */
112 	get_random_bytes(&peer->hb_nonce, sizeof(peer->hb_nonce));
113 
114 	atomic_set(&peer->refcnt, 1);
115 	peer->dead = 0;
116 
117 	peer->malloced = 0;
118 
119 	/* Initialize the state information for SFR-CACC */
120 	peer->cacc.changeover_active = 0;
121 	peer->cacc.cycling_changeover = 0;
122 	peer->cacc.next_tsn_at_change = 0;
123 	peer->cacc.cacc_saw_newack = 0;
124 
125 	return peer;
126 }
127 
128 /* Allocate and initialize a new transport.  */
129 struct sctp_transport *sctp_transport_new(const union sctp_addr *addr,
130 					  gfp_t gfp)
131 {
132 	struct sctp_transport *transport;
133 
134 	transport = t_new(struct sctp_transport, gfp);
135 	if (!transport)
136 		goto fail;
137 
138 	if (!sctp_transport_init(transport, addr, gfp))
139 		goto fail_init;
140 
141 	transport->malloced = 1;
142 	SCTP_DBG_OBJCNT_INC(transport);
143 
144 	return transport;
145 
146 fail_init:
147 	kfree(transport);
148 
149 fail:
150 	return NULL;
151 }
152 
153 /* This transport is no longer needed.  Free up if possible, or
154  * delay until it last reference count.
155  */
156 void sctp_transport_free(struct sctp_transport *transport)
157 {
158 	transport->dead = 1;
159 
160 	/* Try to delete the heartbeat timer.  */
161 	if (del_timer(&transport->hb_timer))
162 		sctp_transport_put(transport);
163 
164 	/* Delete the T3_rtx timer if it's active.
165 	 * There is no point in not doing this now and letting
166 	 * structure hang around in memory since we know
167 	 * the tranport is going away.
168 	 */
169 	if (timer_pending(&transport->T3_rtx_timer) &&
170 	    del_timer(&transport->T3_rtx_timer))
171 		sctp_transport_put(transport);
172 
173 
174 	sctp_transport_put(transport);
175 }
176 
177 /* Destroy the transport data structure.
178  * Assumes there are no more users of this structure.
179  */
180 static void sctp_transport_destroy(struct sctp_transport *transport)
181 {
182 	SCTP_ASSERT(transport->dead, "Transport is not dead", return);
183 
184 	if (transport->asoc)
185 		sctp_association_put(transport->asoc);
186 
187 	sctp_packet_free(&transport->packet);
188 
189 	dst_release(transport->dst);
190 	kfree(transport);
191 	SCTP_DBG_OBJCNT_DEC(transport);
192 }
193 
194 /* Start T3_rtx timer if it is not already running and update the heartbeat
195  * timer.  This routine is called every time a DATA chunk is sent.
196  */
197 void sctp_transport_reset_timers(struct sctp_transport *transport, int force)
198 {
199 	/* RFC 2960 6.3.2 Retransmission Timer Rules
200 	 *
201 	 * R1) Every time a DATA chunk is sent to any address(including a
202 	 * retransmission), if the T3-rtx timer of that address is not running
203 	 * start it running so that it will expire after the RTO of that
204 	 * address.
205 	 */
206 
207 	if (force || !timer_pending(&transport->T3_rtx_timer))
208 		if (!mod_timer(&transport->T3_rtx_timer,
209 			       jiffies + transport->rto))
210 			sctp_transport_hold(transport);
211 
212 	/* When a data chunk is sent, reset the heartbeat interval.  */
213 	if (!mod_timer(&transport->hb_timer,
214 		       sctp_transport_timeout(transport)))
215 	    sctp_transport_hold(transport);
216 }
217 
218 /* This transport has been assigned to an association.
219  * Initialize fields from the association or from the sock itself.
220  * Register the reference count in the association.
221  */
222 void sctp_transport_set_owner(struct sctp_transport *transport,
223 			      struct sctp_association *asoc)
224 {
225 	transport->asoc = asoc;
226 	sctp_association_hold(asoc);
227 }
228 
229 /* Initialize the pmtu of a transport. */
230 void sctp_transport_pmtu(struct sctp_transport *transport)
231 {
232 	struct dst_entry *dst;
233 
234 	dst = transport->af_specific->get_dst(NULL, &transport->ipaddr, NULL);
235 
236 	if (dst) {
237 		transport->pathmtu = dst_mtu(dst);
238 		dst_release(dst);
239 	} else
240 		transport->pathmtu = SCTP_DEFAULT_MAXSEGMENT;
241 }
242 
243 /* this is a complete rip-off from __sk_dst_check
244  * the cookie is always 0 since this is how it's used in the
245  * pmtu code
246  */
247 static struct dst_entry *sctp_transport_dst_check(struct sctp_transport *t)
248 {
249 	struct dst_entry *dst = t->dst;
250 
251 	if (dst && dst->obsolete && dst->ops->check(dst, 0) == NULL) {
252 		dst_release(t->dst);
253 		t->dst = NULL;
254 		return NULL;
255 	}
256 
257 	return dst;
258 }
259 
260 void sctp_transport_update_pmtu(struct sctp_transport *t, u32 pmtu)
261 {
262 	struct dst_entry *dst;
263 
264 	if (unlikely(pmtu < SCTP_DEFAULT_MINSEGMENT)) {
265 		printk(KERN_WARNING "%s: Reported pmtu %d too low, "
266 		       "using default minimum of %d\n",
267 		       __func__, pmtu,
268 		       SCTP_DEFAULT_MINSEGMENT);
269 		/* Use default minimum segment size and disable
270 		 * pmtu discovery on this transport.
271 		 */
272 		t->pathmtu = SCTP_DEFAULT_MINSEGMENT;
273 	} else {
274 		t->pathmtu = pmtu;
275 	}
276 
277 	dst = sctp_transport_dst_check(t);
278 	if (dst)
279 		dst->ops->update_pmtu(dst, pmtu);
280 }
281 
282 /* Caches the dst entry and source address for a transport's destination
283  * address.
284  */
285 void sctp_transport_route(struct sctp_transport *transport,
286 			  union sctp_addr *saddr, struct sctp_sock *opt)
287 {
288 	struct sctp_association *asoc = transport->asoc;
289 	struct sctp_af *af = transport->af_specific;
290 	union sctp_addr *daddr = &transport->ipaddr;
291 	struct dst_entry *dst;
292 
293 	dst = af->get_dst(asoc, daddr, saddr);
294 
295 	if (saddr)
296 		memcpy(&transport->saddr, saddr, sizeof(union sctp_addr));
297 	else
298 		af->get_saddr(opt, asoc, dst, daddr, &transport->saddr);
299 
300 	transport->dst = dst;
301 	if ((transport->param_flags & SPP_PMTUD_DISABLE) && transport->pathmtu) {
302 		return;
303 	}
304 	if (dst) {
305 		transport->pathmtu = dst_mtu(dst);
306 
307 		/* Initialize sk->sk_rcv_saddr, if the transport is the
308 		 * association's active path for getsockname().
309 		 */
310 		if (asoc && (!asoc->peer.primary_path ||
311 				(transport == asoc->peer.active_path)))
312 			opt->pf->af->to_sk_saddr(&transport->saddr,
313 						 asoc->base.sk);
314 	} else
315 		transport->pathmtu = SCTP_DEFAULT_MAXSEGMENT;
316 }
317 
318 /* Hold a reference to a transport.  */
319 void sctp_transport_hold(struct sctp_transport *transport)
320 {
321 	atomic_inc(&transport->refcnt);
322 }
323 
324 /* Release a reference to a transport and clean up
325  * if there are no more references.
326  */
327 void sctp_transport_put(struct sctp_transport *transport)
328 {
329 	if (atomic_dec_and_test(&transport->refcnt))
330 		sctp_transport_destroy(transport);
331 }
332 
333 /* Update transport's RTO based on the newly calculated RTT. */
334 void sctp_transport_update_rto(struct sctp_transport *tp, __u32 rtt)
335 {
336 	/* Check for valid transport.  */
337 	SCTP_ASSERT(tp, "NULL transport", return);
338 
339 	/* We should not be doing any RTO updates unless rto_pending is set.  */
340 	SCTP_ASSERT(tp->rto_pending, "rto_pending not set", return);
341 
342 	if (tp->rttvar || tp->srtt) {
343 		/* 6.3.1 C3) When a new RTT measurement R' is made, set
344 		 * RTTVAR <- (1 - RTO.Beta) * RTTVAR + RTO.Beta * |SRTT - R'|
345 		 * SRTT <- (1 - RTO.Alpha) * SRTT + RTO.Alpha * R'
346 		 */
347 
348 		/* Note:  The above algorithm has been rewritten to
349 		 * express rto_beta and rto_alpha as inverse powers
350 		 * of two.
351 		 * For example, assuming the default value of RTO.Alpha of
352 		 * 1/8, rto_alpha would be expressed as 3.
353 		 */
354 		tp->rttvar = tp->rttvar - (tp->rttvar >> sctp_rto_beta)
355 			+ ((abs(tp->srtt - rtt)) >> sctp_rto_beta);
356 		tp->srtt = tp->srtt - (tp->srtt >> sctp_rto_alpha)
357 			+ (rtt >> sctp_rto_alpha);
358 	} else {
359 		/* 6.3.1 C2) When the first RTT measurement R is made, set
360 		 * SRTT <- R, RTTVAR <- R/2.
361 		 */
362 		tp->srtt = rtt;
363 		tp->rttvar = rtt >> 1;
364 	}
365 
366 	/* 6.3.1 G1) Whenever RTTVAR is computed, if RTTVAR = 0, then
367 	 * adjust RTTVAR <- G, where G is the CLOCK GRANULARITY.
368 	 */
369 	if (tp->rttvar == 0)
370 		tp->rttvar = SCTP_CLOCK_GRANULARITY;
371 
372 	/* 6.3.1 C3) After the computation, update RTO <- SRTT + 4 * RTTVAR. */
373 	tp->rto = tp->srtt + (tp->rttvar << 2);
374 
375 	/* 6.3.1 C6) Whenever RTO is computed, if it is less than RTO.Min
376 	 * seconds then it is rounded up to RTO.Min seconds.
377 	 */
378 	if (tp->rto < tp->asoc->rto_min)
379 		tp->rto = tp->asoc->rto_min;
380 
381 	/* 6.3.1 C7) A maximum value may be placed on RTO provided it is
382 	 * at least RTO.max seconds.
383 	 */
384 	if (tp->rto > tp->asoc->rto_max)
385 		tp->rto = tp->asoc->rto_max;
386 
387 	tp->rtt = rtt;
388 
389 	/* Reset rto_pending so that a new RTT measurement is started when a
390 	 * new data chunk is sent.
391 	 */
392 	tp->rto_pending = 0;
393 
394 	SCTP_DEBUG_PRINTK("%s: transport: %p, rtt: %d, srtt: %d "
395 			  "rttvar: %d, rto: %ld\n", __func__,
396 			  tp, rtt, tp->srtt, tp->rttvar, tp->rto);
397 }
398 
399 /* This routine updates the transport's cwnd and partial_bytes_acked
400  * parameters based on the bytes acked in the received SACK.
401  */
402 void sctp_transport_raise_cwnd(struct sctp_transport *transport,
403 			       __u32 sack_ctsn, __u32 bytes_acked)
404 {
405 	__u32 cwnd, ssthresh, flight_size, pba, pmtu;
406 
407 	cwnd = transport->cwnd;
408 	flight_size = transport->flight_size;
409 
410 	/* See if we need to exit Fast Recovery first */
411 	if (transport->fast_recovery &&
412 	    TSN_lte(transport->fast_recovery_exit, sack_ctsn))
413 		transport->fast_recovery = 0;
414 
415 	/* The appropriate cwnd increase algorithm is performed if, and only
416 	 * if the cumulative TSN whould advanced and the congestion window is
417 	 * being fully utilized.
418 	 */
419 	if (TSN_lte(sack_ctsn, transport->asoc->ctsn_ack_point) ||
420 	    (flight_size < cwnd))
421 		return;
422 
423 	ssthresh = transport->ssthresh;
424 	pba = transport->partial_bytes_acked;
425 	pmtu = transport->asoc->pathmtu;
426 
427 	if (cwnd <= ssthresh) {
428 		/* RFC 4960 7.2.1
429 		 * o  When cwnd is less than or equal to ssthresh, an SCTP
430 		 *    endpoint MUST use the slow-start algorithm to increase
431 		 *    cwnd only if the current congestion window is being fully
432 		 *    utilized, an incoming SACK advances the Cumulative TSN
433 		 *    Ack Point, and the data sender is not in Fast Recovery.
434 		 *    Only when these three conditions are met can the cwnd be
435 		 *    increased; otherwise, the cwnd MUST not be increased.
436 		 *    If these conditions are met, then cwnd MUST be increased
437 		 *    by, at most, the lesser of 1) the total size of the
438 		 *    previously outstanding DATA chunk(s) acknowledged, and
439 		 *    2) the destination's path MTU.  This upper bound protects
440 		 *    against the ACK-Splitting attack outlined in [SAVAGE99].
441 		 */
442 		if (transport->fast_recovery)
443 			return;
444 
445 		if (bytes_acked > pmtu)
446 			cwnd += pmtu;
447 		else
448 			cwnd += bytes_acked;
449 		SCTP_DEBUG_PRINTK("%s: SLOW START: transport: %p, "
450 				  "bytes_acked: %d, cwnd: %d, ssthresh: %d, "
451 				  "flight_size: %d, pba: %d\n",
452 				  __func__,
453 				  transport, bytes_acked, cwnd,
454 				  ssthresh, flight_size, pba);
455 	} else {
456 		/* RFC 2960 7.2.2 Whenever cwnd is greater than ssthresh,
457 		 * upon each SACK arrival that advances the Cumulative TSN Ack
458 		 * Point, increase partial_bytes_acked by the total number of
459 		 * bytes of all new chunks acknowledged in that SACK including
460 		 * chunks acknowledged by the new Cumulative TSN Ack and by
461 		 * Gap Ack Blocks.
462 		 *
463 		 * When partial_bytes_acked is equal to or greater than cwnd
464 		 * and before the arrival of the SACK the sender had cwnd or
465 		 * more bytes of data outstanding (i.e., before arrival of the
466 		 * SACK, flightsize was greater than or equal to cwnd),
467 		 * increase cwnd by MTU, and reset partial_bytes_acked to
468 		 * (partial_bytes_acked - cwnd).
469 		 */
470 		pba += bytes_acked;
471 		if (pba >= cwnd) {
472 			cwnd += pmtu;
473 			pba = ((cwnd < pba) ? (pba - cwnd) : 0);
474 		}
475 		SCTP_DEBUG_PRINTK("%s: CONGESTION AVOIDANCE: "
476 				  "transport: %p, bytes_acked: %d, cwnd: %d, "
477 				  "ssthresh: %d, flight_size: %d, pba: %d\n",
478 				  __func__,
479 				  transport, bytes_acked, cwnd,
480 				  ssthresh, flight_size, pba);
481 	}
482 
483 	transport->cwnd = cwnd;
484 	transport->partial_bytes_acked = pba;
485 }
486 
487 /* This routine is used to lower the transport's cwnd when congestion is
488  * detected.
489  */
490 void sctp_transport_lower_cwnd(struct sctp_transport *transport,
491 			       sctp_lower_cwnd_t reason)
492 {
493 	switch (reason) {
494 	case SCTP_LOWER_CWND_T3_RTX:
495 		/* RFC 2960 Section 7.2.3, sctpimpguide
496 		 * When the T3-rtx timer expires on an address, SCTP should
497 		 * perform slow start by:
498 		 *      ssthresh = max(cwnd/2, 4*MTU)
499 		 *      cwnd = 1*MTU
500 		 *      partial_bytes_acked = 0
501 		 */
502 		transport->ssthresh = max(transport->cwnd/2,
503 					  4*transport->asoc->pathmtu);
504 		transport->cwnd = transport->asoc->pathmtu;
505 
506 		/* T3-rtx also clears fast recovery on the transport */
507 		transport->fast_recovery = 0;
508 		break;
509 
510 	case SCTP_LOWER_CWND_FAST_RTX:
511 		/* RFC 2960 7.2.4 Adjust the ssthresh and cwnd of the
512 		 * destination address(es) to which the missing DATA chunks
513 		 * were last sent, according to the formula described in
514 		 * Section 7.2.3.
515 		 *
516 		 * RFC 2960 7.2.3, sctpimpguide Upon detection of packet
517 		 * losses from SACK (see Section 7.2.4), An endpoint
518 		 * should do the following:
519 		 *      ssthresh = max(cwnd/2, 4*MTU)
520 		 *      cwnd = ssthresh
521 		 *      partial_bytes_acked = 0
522 		 */
523 		if (transport->fast_recovery)
524 			return;
525 
526 		/* Mark Fast recovery */
527 		transport->fast_recovery = 1;
528 		transport->fast_recovery_exit = transport->asoc->next_tsn - 1;
529 
530 		transport->ssthresh = max(transport->cwnd/2,
531 					  4*transport->asoc->pathmtu);
532 		transport->cwnd = transport->ssthresh;
533 		break;
534 
535 	case SCTP_LOWER_CWND_ECNE:
536 		/* RFC 2481 Section 6.1.2.
537 		 * If the sender receives an ECN-Echo ACK packet
538 		 * then the sender knows that congestion was encountered in the
539 		 * network on the path from the sender to the receiver. The
540 		 * indication of congestion should be treated just as a
541 		 * congestion loss in non-ECN Capable TCP. That is, the TCP
542 		 * source halves the congestion window "cwnd" and reduces the
543 		 * slow start threshold "ssthresh".
544 		 * A critical condition is that TCP does not react to
545 		 * congestion indications more than once every window of
546 		 * data (or more loosely more than once every round-trip time).
547 		 */
548 		if (time_after(jiffies, transport->last_time_ecne_reduced +
549 					transport->rtt)) {
550 			transport->ssthresh = max(transport->cwnd/2,
551 						  4*transport->asoc->pathmtu);
552 			transport->cwnd = transport->ssthresh;
553 			transport->last_time_ecne_reduced = jiffies;
554 		}
555 		break;
556 
557 	case SCTP_LOWER_CWND_INACTIVE:
558 		/* RFC 2960 Section 7.2.1, sctpimpguide
559 		 * When the endpoint does not transmit data on a given
560 		 * transport address, the cwnd of the transport address
561 		 * should be adjusted to max(cwnd/2, 4*MTU) per RTO.
562 		 * NOTE: Although the draft recommends that this check needs
563 		 * to be done every RTO interval, we do it every hearbeat
564 		 * interval.
565 		 */
566 		transport->cwnd = max(transport->cwnd/2,
567 					 4*transport->asoc->pathmtu);
568 		break;
569 	}
570 
571 	transport->partial_bytes_acked = 0;
572 	SCTP_DEBUG_PRINTK("%s: transport: %p reason: %d cwnd: "
573 			  "%d ssthresh: %d\n", __func__,
574 			  transport, reason,
575 			  transport->cwnd, transport->ssthresh);
576 }
577 
578 /* Apply Max.Burst limit to the congestion window:
579  * sctpimpguide-05 2.14.2
580  * D) When the time comes for the sender to
581  * transmit new DATA chunks, the protocol parameter Max.Burst MUST
582  * first be applied to limit how many new DATA chunks may be sent.
583  * The limit is applied by adjusting cwnd as follows:
584  * 	if ((flightsize+ Max.Burst * MTU) < cwnd)
585  * 		cwnd = flightsize + Max.Burst * MTU
586  */
587 
588 void sctp_transport_burst_limited(struct sctp_transport *t)
589 {
590 	struct sctp_association *asoc = t->asoc;
591 	u32 old_cwnd = t->cwnd;
592 	u32 max_burst_bytes;
593 
594 	if (t->burst_limited)
595 		return;
596 
597 	max_burst_bytes = t->flight_size + (asoc->max_burst * asoc->pathmtu);
598 	if (max_burst_bytes < old_cwnd) {
599 		t->cwnd = max_burst_bytes;
600 		t->burst_limited = old_cwnd;
601 	}
602 }
603 
604 /* Restore the old cwnd congestion window, after the burst had it's
605  * desired effect.
606  */
607 void sctp_transport_burst_reset(struct sctp_transport *t)
608 {
609 	if (t->burst_limited) {
610 		t->cwnd = t->burst_limited;
611 		t->burst_limited = 0;
612 	}
613 }
614 
615 /* What is the next timeout value for this transport? */
616 unsigned long sctp_transport_timeout(struct sctp_transport *t)
617 {
618 	unsigned long timeout;
619 	timeout = t->rto + sctp_jitter(t->rto);
620 	if (t->state != SCTP_UNCONFIRMED)
621 		timeout += t->hbinterval;
622 	timeout += jiffies;
623 	return timeout;
624 }
625 
626 /* Reset transport variables to their initial values */
627 void sctp_transport_reset(struct sctp_transport *t)
628 {
629 	struct sctp_association *asoc = t->asoc;
630 
631 	/* RFC 2960 (bis), Section 5.2.4
632 	 * All the congestion control parameters (e.g., cwnd, ssthresh)
633 	 * related to this peer MUST be reset to their initial values
634 	 * (see Section 6.2.1)
635 	 */
636 	t->cwnd = min(4*asoc->pathmtu, max_t(__u32, 2*asoc->pathmtu, 4380));
637 	t->burst_limited = 0;
638 	t->ssthresh = asoc->peer.i.a_rwnd;
639 	t->rto = asoc->rto_initial;
640 	t->rtt = 0;
641 	t->srtt = 0;
642 	t->rttvar = 0;
643 
644 	/* Reset these additional varibles so that we have a clean
645 	 * slate.
646 	 */
647 	t->partial_bytes_acked = 0;
648 	t->flight_size = 0;
649 	t->error_count = 0;
650 	t->rto_pending = 0;
651 	t->hb_sent = 0;
652 	t->fast_recovery = 0;
653 
654 	/* Initialize the state information for SFR-CACC */
655 	t->cacc.changeover_active = 0;
656 	t->cacc.cycling_changeover = 0;
657 	t->cacc.next_tsn_at_change = 0;
658 	t->cacc.cacc_saw_newack = 0;
659 }
660