summaryrefslogtreecommitdiffstats
path: root/net/sctp/transport.c
blob: 5d3c71bbd197b1804273f26658273c86fa9f9b4a (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
/* SCTP kernel implementation
 * Copyright (c) 1999-2000 Cisco, Inc.
 * Copyright (c) 1999-2001 Motorola, Inc.
 * Copyright (c) 2001-2003 International Business Machines Corp.
 * Copyright (c) 2001 Intel Corp.
 * Copyright (c) 2001 La Monte H.P. Yarroll
 *
 * This file is part of the SCTP kernel implementation
 *
 * This module provides the abstraction for an SCTP tranport representing
 * a remote transport address.  For local transport addresses, we just use
 * union sctp_addr.
 *
 * This SCTP implementation is free software;
 * you can redistribute it and/or modify it under the terms of
 * the GNU General Public License as published by
 * the Free Software Foundation; either version 2, or (at your option)
 * any later version.
 *
 * This SCTP implementation is distributed in the hope that it
 * will be useful, but WITHOUT ANY WARRANTY; without even the implied
 *                 ************************
 * warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 * See the GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with GNU CC; see the file COPYING.  If not, write to
 * the Free Software Foundation, 59 Temple Place - Suite 330,
 * Boston, MA 02111-1307, USA.
 *
 * Please send any bug reports or fixes you make to the
 * email address(es):
 *    lksctp developers <lksctp-developers@lists.sourceforge.net>
 *
 * Or submit a bug report through the following website:
 *    http://www.sf.net/projects/lksctp
 *
 * Written or modified by:
 *    La Monte H.P. Yarroll <piggy@acm.org>
 *    Karl Knutson          <karl@athena.chicago.il.us>
 *    Jon Grimm             <jgrimm@us.ibm.com>
 *    Xingang Guo           <xingang.guo@intel.com>
 *    Hui Huang             <hui.huang@nokia.com>
 *    Sridhar Samudrala	    <sri@us.ibm.com>
 *    Ardelle Fan	    <ardelle.fan@intel.com>
 *
 * Any bugs reported given to us we will try to fix... any fixes shared will
 * be incorporated into the next SCTP release.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/slab.h>
#include <linux/types.h>
#include <linux/random.h>
#include <net/sctp/sctp.h>
#include <net/sctp/sm.h>

/* 1st Level Abstractions.  */

/* Initialize a new transport from provided memory.  */
static struct sctp_transport *sctp_transport_init(struct net *net,
						  struct sctp_transport *peer,
						  const union sctp_addr *addr,
						  gfp_t gfp)
{
	/* Copy in the address.  */
	peer->ipaddr = *addr;
	peer->af_specific = sctp_get_af_specific(addr->sa.sa_family);
	memset(&peer->saddr, 0, sizeof(union sctp_addr));

	peer->sack_generation = 0;

	/* From 6.3.1 RTO Calculation:
	 *
	 * C1) Until an RTT measurement has been made for a packet sent to the
	 * given destination transport address, set RTO to the protocol
	 * parameter 'RTO.Initial'.
	 */
	peer->rto = msecs_to_jiffies(net->sctp.rto_initial);

	peer->last_time_heard = jiffies;
	peer->last_time_ecne_reduced = jiffies;

	peer->param_flags = SPP_HB_DISABLE |
			    SPP_PMTUD_ENABLE |
			    SPP_SACKDELAY_ENABLE;

	/* Initialize the default path max_retrans.  */
	peer->pathmaxrxt  = net->sctp.max_retrans_path;
	peer->pf_retrans  = net->sctp.pf_retrans;

	INIT_LIST_HEAD(&peer->transmitted);
	INIT_LIST_HEAD(&peer->send_ready);
	INIT_LIST_HEAD(&peer->transports);

	setup_timer(&peer->T3_rtx_timer, sctp_generate_t3_rtx_event,
			(unsigned long)peer);
	setup_timer(&peer->hb_timer, sctp_generate_heartbeat_event,
			(unsigned long)peer);
	setup_timer(&peer->proto_unreach_timer,
		    sctp_generate_proto_unreach_event, (unsigned long)peer);

	/* Initialize the 64-bit random nonce sent with heartbeat. */
	get_random_bytes(&peer->hb_nonce, sizeof(peer->hb_nonce));

	atomic_set(&peer->refcnt, 1);

	return peer;
}

/* Allocate and initialize a new transport.  */
struct sctp_transport *sctp_transport_new(struct net *net,
					  const union sctp_addr *addr,
					  gfp_t gfp)
{
	struct sctp_transport *transport;

	transport = kzalloc(sizeof(*transport), gfp);
	if (!transport)
		goto fail;

	if (!sctp_transport_init(net, transport, addr, gfp))
		goto fail_init;

	SCTP_DBG_OBJCNT_INC(transport);

	return transport;

fail_init:
	kfree(transport);

fail:
	return NULL;
}

/* This transport is no longer needed.  Free up if possible, or
 * delay until it last reference count.
 */
void sctp_transport_free(struct sctp_transport *transport)
{
	transport->dead = 1;

	/* Try to delete the heartbeat timer.  */
	if (del_timer(&transport->hb_timer))
		sctp_transport_put(transport);

	/* Delete the T3_rtx timer if it's active.
	 * There is no point in not doing this now and letting
	 * structure hang around in memory since we know
	 * the tranport is going away.
	 */
	if (del_timer(&transport->T3_rtx_timer))
		sctp_transport_put(transport);

	/* Delete the ICMP proto unreachable timer if it's active. */
	if (del_timer(&transport->proto_unreach_timer))
		sctp_association_put(transport->asoc);

	sctp_transport_put(transport);
}

static void sctp_transport_destroy_rcu(struct rcu_head *head)
{
	struct sctp_transport *transport;

	transport = container_of(head, struct sctp_transport, rcu);

	dst_release(transport->dst);
	kfree(transport);
	SCTP_DBG_OBJCNT_DEC(transport);
}

/* Destroy the transport data structure.
 * Assumes there are no more users of this structure.
 */
static void sctp_transport_destroy(struct sctp_transport *transport)
{
	SCTP_ASSERT(transport->dead, "Transport is not dead", return);

	call_rcu(&transport->rcu, sctp_transport_destroy_rcu);

	sctp_packet_free(&transport->packet);

	if (transport->asoc)
		sctp_association_put(transport->asoc);
}

/* Start T3_rtx timer if it is not already running and update the heartbeat
 * timer.  This routine is called every time a DATA chunk is sent.
 */
void sctp_transport_reset_timers(struct sctp_transport *transport)
{
	/* RFC 2960 6.3.2 Retransmission Timer Rules
	 *
	 * R1) Every time a DATA chunk is sent to any address(including a
	 * retransmission), if the T3-rtx timer of that address is not running
	 * start it running so that it will expire after the RTO of that
	 * address.
	 */

	if (!timer_pending(&transport->T3_rtx_timer))
		if (!mod_timer(&transport->T3_rtx_timer,
			       jiffies + transport->rto))
			sctp_transport_hold(transport);

	/* When a data chunk is sent, reset the heartbeat interval.  */
	if (!mod_timer(&transport->hb_timer,
		       sctp_transport_timeout(transport)))
	    sctp_transport_hold(transport);
}

/* This transport has been assigned to an association.
 * Initialize fields from the association or from the sock itself.
 * Register the reference count in the association.
 */
void sctp_transport_set_owner(struct sctp_transport *transport,
			      struct sctp_association *asoc)
{
	transport->asoc = asoc;
	sctp_association_hold(asoc);
}

/* Initialize the pmtu of a transport. */
void sctp_transport_pmtu(struct sctp_transport *transport, struct sock *sk)
{
	/* If we don't have a fresh route, look one up */
	if (!transport->dst || transport->dst->obsolete) {
		dst_release(transport->dst);
		transport->af_specific->get_dst(transport, &transport->saddr,
						&transport->fl, sk);
	}

	if (transport->dst) {
		transport->pathmtu = dst_mtu(transport->dst);
	} else
		transport->pathmtu = SCTP_DEFAULT_MAXSEGMENT;
}

void sctp_transport_update_pmtu(struct sock *sk, struct sctp_transport *t, u32 pmtu)
{
	struct dst_entry *dst;

	if (unlikely(pmtu < SCTP_DEFAULT_MINSEGMENT)) {
		pr_warn("%s: Reported pmtu %d too low, using default minimum of %d\n",
			__func__, pmtu,
			SCTP_DEFAULT_MINSEGMENT);
		/* Use default minimum segment size and disable
		 * pmtu discovery on this transport.
		 */
		t->pathmtu = SCTP_DEFAULT_MINSEGMENT;
	} else {
		t->pathmtu = pmtu;
	}

	dst = sctp_transport_dst_check(t);
	if (!dst)
		t->af_specific->get_dst(t, &t->saddr, &t->fl, sk);

	if (dst) {
		dst->ops->update_pmtu(dst, sk, NULL, pmtu);

		dst = sctp_transport_dst_check(t);
		if (!dst)
			t->af_specific->get_dst(t, &t->saddr, &t->fl, sk);
	}
}

/* Caches the dst entry and source address for a transport's destination
 * address.
 */
void sctp_transport_route(struct sctp_transport *transport,
			  union sctp_addr *saddr, struct sctp_sock *opt)
{
	struct sctp_association *asoc = transport->asoc;
	struct sctp_af *af = transport->af_specific;

	af->get_dst(transport, saddr, &transport->fl, sctp_opt2sk(opt));

	if (saddr)
		memcpy(&transport->saddr, saddr, sizeof(union sctp_addr));
	else
		af->get_saddr(opt, transport, &transport->fl);

	if ((transport->param_flags & SPP_PMTUD_DISABLE) && transport->pathmtu) {
		return;
	}
	if (transport->dst) {
		transport->pathmtu = dst_mtu(transport->dst);

		/* Initialize sk->sk_rcv_saddr, if the transport is the
		 * association's active path for getsockname().
		 */
		if (asoc && (!asoc->peer.primary_path ||
				(transport == asoc->peer.active_path)))
			opt->pf->af->to_sk_saddr(&transport->saddr,
						 asoc->base.sk);
	} else
		transport->pathmtu = SCTP_DEFAULT_MAXSEGMENT;
}

/* Hold a reference to a transport.  */
void sctp_transport_hold(struct sctp_transport *transport)
{
	atomic_inc(&transport->refcnt);
}

/* Release a reference to a transport and clean up
 * if there are no more references.
 */
void sctp_transport_put(struct sctp_transport *transport)
{
	if (atomic_dec_and_test(&transport->refcnt))
		sctp_transport_destroy(transport);
}

/* Update transport's RTO based on the newly calculated RTT. */
void sctp_transport_update_rto(struct sctp_transport *tp, __u32 rtt)
{
	/* Check for valid transport.  */
	SCTP_ASSERT(tp, "NULL transport", return);

	/* We should not be doing any RTO updates unless rto_pending is set.  */
	SCTP_ASSERT(tp->rto_pending, "rto_pending not set", return);

	if (tp->rttvar || tp->srtt) {
		struct net *net = sock_net(tp->asoc->base.sk);
		/* 6.3.1 C3) When a new RTT measurement R' is made, set
		 * RTTVAR <- (1 - RTO.Beta) * RTTVAR + RTO.Beta * |SRTT - R'|
		 * SRTT <- (1 - RTO.Alpha) * SRTT + RTO.Alpha * R'
		 */

		/* Note:  The above algorithm has been rewritten to
		 * express rto_beta and rto_alpha as inverse powers
		 * of two.
		 * For example, assuming the default value of RTO.Alpha of
		 * 1/8, rto_alpha would be expressed as 3.
		 */
		tp->rttvar = tp->rttvar - (tp->rttvar >> net->sctp.rto_beta)
			+ (((__u32)abs64((__s64)tp->srtt - (__s64)rtt)) >> net->sctp.rto_beta);
		tp->srtt = tp->srtt - (tp->srtt >> net->sctp.rto_alpha)
			+ (rtt >> net->sctp.rto_alpha);
	} else {
		/* 6.3.1 C2) When the first RTT measurement R is made, set
		 * SRTT <- R, RTTVAR <- R/2.
		 */
		tp->srtt = rtt;
		tp->rttvar = rtt >> 1;
	}

	/* 6.3.1 G1) Whenever RTTVAR is computed, if RTTVAR = 0, then
	 * adjust RTTVAR <- G, where G is the CLOCK GRANULARITY.
	 */
	if (tp->rttvar == 0)
		tp->rttvar = SCTP_CLOCK_GRANULARITY;

	/* 6.3.1 C3) After the computation, update RTO <- SRTT + 4 * RTTVAR. */
	tp->rto = tp->srtt + (tp->rttvar << 2);

	/* 6.3.1 C6) Whenever RTO is computed, if it is less than RTO.Min
	 * seconds then it is rounded up to RTO.Min seconds.
	 */
	if (tp->rto < tp->asoc->rto_min)
		tp->rto = tp->asoc->rto_min;

	/* 6.3.1 C7) A maximum value may be placed on RTO provided it is
	 * at least RTO.max seconds.
	 */
	if (tp->rto > tp->asoc->rto_max)
		tp->rto = tp->asoc->rto_max;

	sctp_max_rto(tp->asoc, tp);
	tp->rtt = rtt;

	/* Reset rto_pending so that a new RTT measurement is started when a
	 * new data chunk is sent.
	 */
	tp->rto_pending = 0;

	SCTP_DEBUG_PRINTK("%s: transport: %p, rtt: %d, srtt: %d "
			  "rttvar: %d, rto: %ld\n", __func__,
			  tp, rtt, tp->srtt, tp->rttvar, tp->rto);
}

/* This routine updates the transport's cwnd and partial_bytes_acked
 * parameters based on the bytes acked in the received SACK.
 */
void sctp_transport_raise_cwnd(struct sctp_transport *transport,
			       __u32 sack_ctsn, __u32 bytes_acked)
{
	struct sctp_association *asoc = transport->asoc;
	__u32 cwnd, ssthresh, flight_size, pba, pmtu;

	cwnd = transport->cwnd;
	flight_size = transport->flight_size;

	/* See if we need to exit Fast Recovery first */
	if (asoc->fast_recovery &&
	    TSN_lte(asoc->fast_recovery_exit, sack_ctsn))
		asoc->fast_recovery = 0;

	/* The appropriate cwnd increase algorithm is performed if, and only
	 * if the cumulative TSN whould advanced and the congestion window is
	 * being fully utilized.
	 */
	if (TSN_lte(sack_ctsn, transport->asoc->ctsn_ack_point) ||
	    (flight_size < cwnd))
		return;

	ssthresh = transport->ssthresh;
	pba = transport->partial_bytes_acked;
	pmtu = transport->asoc->pathmtu;

	if (cwnd <= ssthresh) {
		/* RFC 4960 7.2.1
		 * o  When cwnd is less than or equal to ssthresh, an SCTP
		 *    endpoint MUST use the slow-start algorithm to increase
		 *    cwnd only if the current congestion window is being fully
		 *    utilized, an incoming SACK advances the Cumulative TSN
		 *    Ack Point, and the data sender is not in Fast Recovery.
		 *    Only when these three conditions are met can the cwnd be
		 *    increased; otherwise, the cwnd MUST not be increased.
		 *    If these conditions are met, then cwnd MUST be increased
		 *    by, at most, the lesser of 1) the total size of the
		 *    previously outstanding DATA chunk(s) acknowledged, and
		 *    2) the destination's path MTU.  This upper bound protects
		 *    against the ACK-Splitting attack outlined in [SAVAGE99].
		 */
		if (asoc->fast_recovery)
			return;

		if (bytes_acked > pmtu)
			cwnd += pmtu;
		else
			cwnd += bytes_acked;
		SCTP_DEBUG_PRINTK("%s: SLOW START: transport: %p, "
				  "bytes_acked: %d, cwnd: %d, ssthresh: %d, "
				  "flight_size: %d, pba: %d\n",
				  __func__,
				  transport, bytes_acked, cwnd,
				  ssthresh, flight_size, pba);
	} else {
		/* RFC 2960 7.2.2 Whenever cwnd is greater than ssthresh,
		 * upon each SACK arrival that advances the Cumulative TSN Ack
		 * Point, increase partial_bytes_acked by the total number of
		 * bytes of all new chunks acknowledged in that SACK including
		 * chunks acknowledged by the new Cumulative TSN Ack and by
		 * Gap Ack Blocks.
		 *
		 * When partial_bytes_acked is equal to or greater than cwnd
		 * and before the arrival of the SACK the sender had cwnd or
		 * more bytes of data outstanding (i.e., before arrival of the
		 * SACK, flightsize was greater than or equal to cwnd),
		 * increase cwnd by MTU, and reset partial_bytes_acked to
		 * (partial_bytes_acked - cwnd).
		 */
		pba += bytes_acked;
		if (pba >= cwnd) {
			cwnd += pmtu;
			pba = ((cwnd < pba) ? (pba - cwnd) : 0);
		}
		SCTP_DEBUG_PRINTK("%s: CONGESTION AVOIDANCE: "
				  "transport: %p, bytes_acked: %d, cwnd: %d, "
				  "ssthresh: %d, flight_size: %d, pba: %d\n",
				  __func__,
				  transport, bytes_acked, cwnd,
				  ssthresh, flight_size, pba);
	}

	transport->cwnd = cwnd;
	transport->partial_bytes_acked = pba;
}

/* This routine is used to lower the transport's cwnd when congestion is
 * detected.
 */
void sctp_transport_lower_cwnd(struct sctp_transport *transport,
			       sctp_lower_cwnd_t reason)
{
	struct sctp_association *asoc = transport->asoc;

	switch (reason) {
	case SCTP_LOWER_CWND_T3_RTX:
		/* RFC 2960 Section 7.2.3, sctpimpguide
		 * When the T3-rtx timer expires on an address, SCTP should
		 * perform slow start by:
		 *      ssthresh = max(cwnd/2, 4*MTU)
		 *      cwnd = 1*MTU
		 *      partial_bytes_acked = 0
		 */
		transport->ssthresh = max(transport->cwnd/2,
					  4*asoc->pathmtu);
		transport->cwnd = asoc->pathmtu;

		/* T3-rtx also clears fast recovery */
		asoc->fast_recovery = 0;
		break;

	case SCTP_LOWER_CWND_FAST_RTX:
		/* RFC 2960 7.2.4 Adjust the ssthresh and cwnd of the
		 * destination address(es) to which the missing DATA chunks
		 * were last sent, according to the formula described in
		 * Section 7.2.3.
		 *
		 * RFC 2960 7.2.3, sctpimpguide Upon detection of packet
		 * losses from SACK (see Section 7.2.4), An endpoint
		 * should do the following:
		 *      ssthresh = max(cwnd/2, 4*MTU)
		 *      cwnd = ssthresh
		 *      partial_bytes_acked = 0
		 */
		if (asoc->fast_recovery)
			return;

		/* Mark Fast recovery */
		asoc->fast_recovery = 1;
		asoc->fast_recovery_exit = asoc->next_tsn - 1;

		transport->ssthresh = max(transport->cwnd/2,
					  4*asoc->pathmtu);
		transport->cwnd = transport->ssthresh;
		break;

	case SCTP_LOWER_CWND_ECNE:
		/* RFC 2481 Section 6.1.2.
		 * If the sender receives an ECN-Echo ACK packet
		 * then the sender knows that congestion was encountered in the
		 * network on the path from the sender to the receiver. The
		 * indication of congestion should be treated just as a
		 * congestion loss in non-ECN Capable TCP. That is, the TCP
		 * source halves the congestion window "cwnd" and reduces the
		 * slow start threshold "ssthresh".
		 * A critical condition is that TCP does not react to
		 * congestion indications more than once every window of
		 * data (or more loosely more than once every round-trip time).
		 */
		if (time_after(jiffies, transport->last_time_ecne_reduced +
					transport->rtt)) {
			transport->ssthresh = max(transport->cwnd/2,
						  4*asoc->pathmtu);
			transport->cwnd = transport->ssthresh;
			transport->last_time_ecne_reduced = jiffies;
		}
		break;

	case SCTP_LOWER_CWND_INACTIVE:
		/* RFC 2960 Section 7.2.1, sctpimpguide
		 * When the endpoint does not transmit data on a given
		 * transport address, the cwnd of the transport address
		 * should be adjusted to max(cwnd/2, 4*MTU) per RTO.
		 * NOTE: Although the draft recommends that this check needs
		 * to be done every RTO interval, we do it every hearbeat
		 * interval.
		 */
		transport->cwnd = max(transport->cwnd/2,
					 4*asoc->pathmtu);
		break;
	}

	transport->partial_bytes_acked = 0;
	SCTP_DEBUG_PRINTK("%s: transport: %p reason: %d cwnd: "
			  "%d ssthresh: %d\n", __func__,
			  transport, reason,
			  transport->cwnd, transport->ssthresh);
}

/* Apply Max.Burst limit to the congestion window:
 * sctpimpguide-05 2.14.2
 * D) When the time comes for the sender to
 * transmit new DATA chunks, the protocol parameter Max.Burst MUST
 * first be applied to limit how many new DATA chunks may be sent.
 * The limit is applied by adjusting cwnd as follows:
 * 	if ((flightsize+ Max.Burst * MTU) < cwnd)
 * 		cwnd = flightsize + Max.Burst * MTU
 */

void sctp_transport_burst_limited(struct sctp_transport *t)
{
	struct sctp_association *asoc = t->asoc;
	u32 old_cwnd = t->cwnd;
	u32 max_burst_bytes;

	if (t->burst_limited)
		return;

	max_burst_bytes = t->flight_size + (asoc->max_burst * asoc->pathmtu);
	if (max_burst_bytes < old_cwnd) {
		t->cwnd = max_burst_bytes;
		t->burst_limited = old_cwnd;
	}
}

/* Restore the old cwnd congestion window, after the burst had it's
 * desired effect.
 */
void sctp_transport_burst_reset(struct sctp_transport *t)
{
	if (t->burst_limited) {
		t->cwnd = t->burst_limited;
		t->burst_limited = 0;
	}
}

/* What is the next timeout value for this transport? */
unsigned long sctp_transport_timeout(struct sctp_transport *t)
{
	unsigned long timeout;
	timeout = t->rto + sctp_jitter(t->rto);
	if ((t->state != SCTP_UNCONFIRMED) &&
	    (t->state != SCTP_PF))
		timeout += t->hbinterval;
	timeout += jiffies;
	return timeout;
}

/* Reset transport variables to their initial values */
void sctp_transport_reset(struct sctp_transport *t)
{
	struct sctp_association *asoc = t->asoc;

	/* RFC 2960 (bis), Section 5.2.4
	 * All the congestion control parameters (e.g., cwnd, ssthresh)
	 * related to this peer MUST be reset to their initial values
	 * (see Section 6.2.1)
	 */
	t->cwnd = min(4*asoc->pathmtu, max_t(__u32, 2*asoc->pathmtu, 4380));
	t->burst_limited = 0;
	t->ssthresh = asoc->peer.i.a_rwnd;
	t->rto = asoc->rto_initial;
	sctp_max_rto(asoc, t);
	t->rtt = 0;
	t->srtt = 0;
	t->rttvar = 0;

	/* Reset these additional varibles so that we have a clean
	 * slate.
	 */
	t->partial_bytes_acked = 0;
	t->flight_size = 0;
	t->error_count = 0;
	t->rto_pending = 0;
	t->hb_sent = 0;

	/* Initialize the state information for SFR-CACC */
	t->cacc.changeover_active = 0;
	t->cacc.cycling_changeover = 0;
	t->cacc.next_tsn_at_change = 0;
	t->cacc.cacc_saw_newack = 0;
}

/* Schedule retransmission on the given transport */
void sctp_transport_immediate_rtx(struct sctp_transport *t)
{
	/* Stop pending T3_rtx_timer */
	if (del_timer(&t->T3_rtx_timer))
		sctp_transport_put(t);

	sctp_retransmit(&t->asoc->outqueue, t, SCTP_RTXR_T3_RTX);
	if (!timer_pending(&t->T3_rtx_timer)) {
		if (!mod_timer(&t->T3_rtx_timer, jiffies + t->rto))
			sctp_transport_hold(t);
	}
	return;
}
OpenPOWER on IntegriCloud