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_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.  */
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	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
156static 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 */
170static 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 */
188void 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 */
213void 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. */
221void 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
236void 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 */
268void 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->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.  */
299void 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 */
307void 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. */
314void 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 */
381void 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 */
469void 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
569void 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 */
588void 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? */
597unsigned long sctp_transport_timeout(struct sctp_transport *trans)
598{
599	/* RTO + timer slack +/- 50% of RTO */
600	unsigned long timeout = (trans->rto >> 1) + prandom_u32_max(trans->rto);
601
602	if (trans->state != SCTP_UNCONFIRMED &&
603	    trans->state != SCTP_PF)
604		timeout += trans->hbinterval;
605
606	return timeout + jiffies;
607}
608
609/* Reset transport variables to their initial values */
610void sctp_transport_reset(struct sctp_transport *t)
611{
612	struct sctp_association *asoc = t->asoc;
613
614	/* RFC 2960 (bis), Section 5.2.4
615	 * All the congestion control parameters (e.g., cwnd, ssthresh)
616	 * related to this peer MUST be reset to their initial values
617	 * (see Section 6.2.1)
618	 */
619	t->cwnd = min(4*asoc->pathmtu, max_t(__u32, 2*asoc->pathmtu, 4380));
620	t->burst_limited = 0;
621	t->ssthresh = asoc->peer.i.a_rwnd;
622	t->rto = asoc->rto_initial;
623	sctp_max_rto(asoc, t);
624	t->rtt = 0;
625	t->srtt = 0;
626	t->rttvar = 0;
627
628	/* Reset these additional varibles so that we have a clean
629	 * slate.
630	 */
631	t->partial_bytes_acked = 0;
632	t->flight_size = 0;
633	t->error_count = 0;
634	t->rto_pending = 0;
635	t->hb_sent = 0;
636
637	/* Initialize the state information for SFR-CACC */
638	t->cacc.changeover_active = 0;
639	t->cacc.cycling_changeover = 0;
640	t->cacc.next_tsn_at_change = 0;
641	t->cacc.cacc_saw_newack = 0;
642}
643
644/* Schedule retransmission on the given transport */
645void sctp_transport_immediate_rtx(struct sctp_transport *t)
646{
647	/* Stop pending T3_rtx_timer */
648	if (del_timer(&t->T3_rtx_timer))
649		sctp_transport_put(t);
650
651	sctp_retransmit(&t->asoc->outqueue, t, SCTP_RTXR_T3_RTX);
652	if (!timer_pending(&t->T3_rtx_timer)) {
653		if (!mod_timer(&t->T3_rtx_timer, jiffies + t->rto))
654			sctp_transport_hold(t);
655	}
656}
657