1 /* SCTP kernel reference 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
8 * This file is part of the SCTP kernel reference Implementation
10 * This module provides the abstraction for an SCTP tranport representing
11 * a remote transport address. For local transport addresses, we just use
14 * The SCTP reference 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)
20 * The SCTP reference 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.
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.
31 * Please send any bug reports or fixes you make to the
33 * lksctp developers <lksctp-developers@lists.sourceforge.net>
35 * Or submit a bug report through the following website:
36 * http://www.sf.net/projects/lksctp
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>
47 * Any bugs reported given to us we will try to fix... any fixes shared will
48 * be incorporated into the next SCTP release.
51 #include <linux/types.h>
52 #include <linux/random.h>
53 #include <net/sctp/sctp.h>
54 #include <net/sctp/sm.h>
56 /* 1st Level Abstractions. */
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,
63 /* Copy in the address. */
65 flip_to_h(&peer->ipaddr_h, &peer->ipaddr);
66 peer->af_specific = sctp_get_af_specific(addr->sa.sa_family);
70 memset(&peer->saddr, 0, sizeof(union sctp_addr));
71 memset(&peer->saddr_h, 0, sizeof(union sctp_addr));
73 /* From 6.3.1 RTO Calculation:
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'.
80 peer->rto = msecs_to_jiffies(sctp_rto_initial);
83 peer->rto_pending = 0;
85 peer->last_time_heard = jiffies;
86 peer->last_time_used = jiffies;
87 peer->last_time_ecne_reduced = jiffies;
89 peer->init_sent_count = 0;
91 peer->param_flags = SPP_HB_DISABLE |
96 /* Initialize the default path max_retrans. */
97 peer->pathmaxrxt = sctp_max_retrans_path;
98 peer->error_count = 0;
100 INIT_LIST_HEAD(&peer->transmitted);
101 INIT_LIST_HEAD(&peer->send_ready);
102 INIT_LIST_HEAD(&peer->transports);
104 /* Set up the retransmission timer. */
105 init_timer(&peer->T3_rtx_timer);
106 peer->T3_rtx_timer.function = sctp_generate_t3_rtx_event;
107 peer->T3_rtx_timer.data = (unsigned long)peer;
109 /* Set up the heartbeat timer. */
110 init_timer(&peer->hb_timer);
111 peer->hb_timer.function = sctp_generate_heartbeat_event;
112 peer->hb_timer.data = (unsigned long)peer;
114 /* Initialize the 64-bit random nonce sent with heartbeat. */
115 get_random_bytes(&peer->hb_nonce, sizeof(peer->hb_nonce));
117 atomic_set(&peer->refcnt, 1);
122 /* Initialize the state information for SFR-CACC */
123 peer->cacc.changeover_active = 0;
124 peer->cacc.cycling_changeover = 0;
125 peer->cacc.next_tsn_at_change = 0;
126 peer->cacc.cacc_saw_newack = 0;
131 /* Allocate and initialize a new transport. */
132 struct sctp_transport *sctp_transport_new(const union sctp_addr *addr,
135 struct sctp_transport *transport;
137 transport = t_new(struct sctp_transport, gfp);
141 if (!sctp_transport_init(transport, addr, gfp))
144 transport->malloced = 1;
145 SCTP_DBG_OBJCNT_INC(transport);
156 /* This transport is no longer needed. Free up if possible, or
157 * delay until it last reference count.
159 void sctp_transport_free(struct sctp_transport *transport)
163 /* Try to delete the heartbeat timer. */
164 if (del_timer(&transport->hb_timer))
165 sctp_transport_put(transport);
167 /* Delete the T3_rtx timer if it's active.
168 * There is no point in not doing this now and letting
169 * structure hang around in memory since we know
170 * the tranport is going away.
172 if (timer_pending(&transport->T3_rtx_timer) &&
173 del_timer(&transport->T3_rtx_timer))
174 sctp_transport_put(transport);
177 sctp_transport_put(transport);
180 /* Destroy the transport data structure.
181 * Assumes there are no more users of this structure.
183 static void sctp_transport_destroy(struct sctp_transport *transport)
185 SCTP_ASSERT(transport->dead, "Transport is not dead", return);
188 sctp_association_put(transport->asoc);
190 sctp_packet_free(&transport->packet);
192 dst_release(transport->dst);
194 SCTP_DBG_OBJCNT_DEC(transport);
197 /* Start T3_rtx timer if it is not already running and update the heartbeat
198 * timer. This routine is called every time a DATA chunk is sent.
200 void sctp_transport_reset_timers(struct sctp_transport *transport)
202 /* RFC 2960 6.3.2 Retransmission Timer Rules
204 * R1) Every time a DATA chunk is sent to any address(including a
205 * retransmission), if the T3-rtx timer of that address is not running
206 * start it running so that it will expire after the RTO of that
210 if (!timer_pending(&transport->T3_rtx_timer))
211 if (!mod_timer(&transport->T3_rtx_timer,
212 jiffies + transport->rto))
213 sctp_transport_hold(transport);
215 /* When a data chunk is sent, reset the heartbeat interval. */
216 if (!mod_timer(&transport->hb_timer,
217 sctp_transport_timeout(transport)))
218 sctp_transport_hold(transport);
221 /* This transport has been assigned to an association.
222 * Initialize fields from the association or from the sock itself.
223 * Register the reference count in the association.
225 void sctp_transport_set_owner(struct sctp_transport *transport,
226 struct sctp_association *asoc)
228 transport->asoc = asoc;
229 sctp_association_hold(asoc);
232 /* Initialize the pmtu of a transport. */
233 void sctp_transport_pmtu(struct sctp_transport *transport)
235 struct dst_entry *dst;
237 dst = transport->af_specific->get_dst(NULL, &transport->ipaddr_h, NULL);
240 transport->pathmtu = dst_mtu(dst);
243 transport->pathmtu = SCTP_DEFAULT_MAXSEGMENT;
246 /* Caches the dst entry and source address for a transport's destination
249 void sctp_transport_route(struct sctp_transport *transport,
250 union sctp_addr *saddr, struct sctp_sock *opt)
252 struct sctp_association *asoc = transport->asoc;
253 struct sctp_af *af = transport->af_specific;
254 union sctp_addr *daddr = &transport->ipaddr_h;
255 struct dst_entry *dst;
257 dst = af->get_dst(asoc, daddr, saddr);
260 memcpy(&transport->saddr_h, saddr, sizeof(union sctp_addr));
262 af->get_saddr(asoc, dst, daddr, &transport->saddr_h);
263 flip_to_n(&transport->saddr, &transport->saddr_h);
265 transport->dst = dst;
266 if ((transport->param_flags & SPP_PMTUD_DISABLE) && transport->pathmtu) {
270 transport->pathmtu = dst_mtu(dst);
272 /* Initialize sk->sk_rcv_saddr, if the transport is the
273 * association's active path for getsockname().
275 if (asoc && (transport == asoc->peer.active_path))
276 opt->pf->af->to_sk_saddr(&transport->saddr_h,
279 transport->pathmtu = SCTP_DEFAULT_MAXSEGMENT;
282 /* Hold a reference to a transport. */
283 void sctp_transport_hold(struct sctp_transport *transport)
285 atomic_inc(&transport->refcnt);
288 /* Release a reference to a transport and clean up
289 * if there are no more references.
291 void sctp_transport_put(struct sctp_transport *transport)
293 if (atomic_dec_and_test(&transport->refcnt))
294 sctp_transport_destroy(transport);
297 /* Update transport's RTO based on the newly calculated RTT. */
298 void sctp_transport_update_rto(struct sctp_transport *tp, __u32 rtt)
300 /* Check for valid transport. */
301 SCTP_ASSERT(tp, "NULL transport", return);
303 /* We should not be doing any RTO updates unless rto_pending is set. */
304 SCTP_ASSERT(tp->rto_pending, "rto_pending not set", return);
306 if (tp->rttvar || tp->srtt) {
307 /* 6.3.1 C3) When a new RTT measurement R' is made, set
308 * RTTVAR <- (1 - RTO.Beta) * RTTVAR + RTO.Beta * |SRTT - R'|
309 * SRTT <- (1 - RTO.Alpha) * SRTT + RTO.Alpha * R'
312 /* Note: The above algorithm has been rewritten to
313 * express rto_beta and rto_alpha as inverse powers
315 * For example, assuming the default value of RTO.Alpha of
316 * 1/8, rto_alpha would be expressed as 3.
318 tp->rttvar = tp->rttvar - (tp->rttvar >> sctp_rto_beta)
319 + ((abs(tp->srtt - rtt)) >> sctp_rto_beta);
320 tp->srtt = tp->srtt - (tp->srtt >> sctp_rto_alpha)
321 + (rtt >> sctp_rto_alpha);
323 /* 6.3.1 C2) When the first RTT measurement R is made, set
324 * SRTT <- R, RTTVAR <- R/2.
327 tp->rttvar = rtt >> 1;
330 /* 6.3.1 G1) Whenever RTTVAR is computed, if RTTVAR = 0, then
331 * adjust RTTVAR <- G, where G is the CLOCK GRANULARITY.
334 tp->rttvar = SCTP_CLOCK_GRANULARITY;
336 /* 6.3.1 C3) After the computation, update RTO <- SRTT + 4 * RTTVAR. */
337 tp->rto = tp->srtt + (tp->rttvar << 2);
339 /* 6.3.1 C6) Whenever RTO is computed, if it is less than RTO.Min
340 * seconds then it is rounded up to RTO.Min seconds.
342 if (tp->rto < tp->asoc->rto_min)
343 tp->rto = tp->asoc->rto_min;
345 /* 6.3.1 C7) A maximum value may be placed on RTO provided it is
346 * at least RTO.max seconds.
348 if (tp->rto > tp->asoc->rto_max)
349 tp->rto = tp->asoc->rto_max;
353 /* Reset rto_pending so that a new RTT measurement is started when a
354 * new data chunk is sent.
358 SCTP_DEBUG_PRINTK("%s: transport: %p, rtt: %d, srtt: %d "
359 "rttvar: %d, rto: %ld\n", __FUNCTION__,
360 tp, rtt, tp->srtt, tp->rttvar, tp->rto);
363 /* This routine updates the transport's cwnd and partial_bytes_acked
364 * parameters based on the bytes acked in the received SACK.
366 void sctp_transport_raise_cwnd(struct sctp_transport *transport,
367 __u32 sack_ctsn, __u32 bytes_acked)
369 __u32 cwnd, ssthresh, flight_size, pba, pmtu;
371 cwnd = transport->cwnd;
372 flight_size = transport->flight_size;
374 /* The appropriate cwnd increase algorithm is performed if, and only
375 * if the cumulative TSN has advanced and the congestion window is
376 * being fully utilized.
378 if ((transport->asoc->ctsn_ack_point >= sack_ctsn) ||
379 (flight_size < cwnd))
382 ssthresh = transport->ssthresh;
383 pba = transport->partial_bytes_acked;
384 pmtu = transport->asoc->pathmtu;
386 if (cwnd <= ssthresh) {
387 /* RFC 2960 7.2.1, sctpimpguide-05 2.14.2 When cwnd is less
388 * than or equal to ssthresh an SCTP endpoint MUST use the
389 * slow start algorithm to increase cwnd only if the current
390 * congestion window is being fully utilized and an incoming
391 * SACK advances the Cumulative TSN Ack Point. Only when these
392 * two conditions are met can the cwnd be increased otherwise
393 * the cwnd MUST not be increased. If these conditions are met
394 * then cwnd MUST be increased by at most the lesser of
395 * 1) the total size of the previously outstanding DATA
396 * chunk(s) acknowledged, and 2) the destination's path MTU.
398 if (bytes_acked > pmtu)
402 SCTP_DEBUG_PRINTK("%s: SLOW START: transport: %p, "
403 "bytes_acked: %d, cwnd: %d, ssthresh: %d, "
404 "flight_size: %d, pba: %d\n",
406 transport, bytes_acked, cwnd,
407 ssthresh, flight_size, pba);
409 /* RFC 2960 7.2.2 Whenever cwnd is greater than ssthresh,
410 * upon each SACK arrival that advances the Cumulative TSN Ack
411 * Point, increase partial_bytes_acked by the total number of
412 * bytes of all new chunks acknowledged in that SACK including
413 * chunks acknowledged by the new Cumulative TSN Ack and by
416 * When partial_bytes_acked is equal to or greater than cwnd
417 * and before the arrival of the SACK the sender had cwnd or
418 * more bytes of data outstanding (i.e., before arrival of the
419 * SACK, flightsize was greater than or equal to cwnd),
420 * increase cwnd by MTU, and reset partial_bytes_acked to
421 * (partial_bytes_acked - cwnd).
426 pba = ((cwnd < pba) ? (pba - cwnd) : 0);
428 SCTP_DEBUG_PRINTK("%s: CONGESTION AVOIDANCE: "
429 "transport: %p, bytes_acked: %d, cwnd: %d, "
430 "ssthresh: %d, flight_size: %d, pba: %d\n",
432 transport, bytes_acked, cwnd,
433 ssthresh, flight_size, pba);
436 transport->cwnd = cwnd;
437 transport->partial_bytes_acked = pba;
440 /* This routine is used to lower the transport's cwnd when congestion is
443 void sctp_transport_lower_cwnd(struct sctp_transport *transport,
444 sctp_lower_cwnd_t reason)
447 case SCTP_LOWER_CWND_T3_RTX:
448 /* RFC 2960 Section 7.2.3, sctpimpguide
449 * When the T3-rtx timer expires on an address, SCTP should
450 * perform slow start by:
451 * ssthresh = max(cwnd/2, 4*MTU)
453 * partial_bytes_acked = 0
455 transport->ssthresh = max(transport->cwnd/2,
456 4*transport->asoc->pathmtu);
457 transport->cwnd = transport->asoc->pathmtu;
460 case SCTP_LOWER_CWND_FAST_RTX:
461 /* RFC 2960 7.2.4 Adjust the ssthresh and cwnd of the
462 * destination address(es) to which the missing DATA chunks
463 * were last sent, according to the formula described in
466 * RFC 2960 7.2.3, sctpimpguide Upon detection of packet
467 * losses from SACK (see Section 7.2.4), An endpoint
468 * should do the following:
469 * ssthresh = max(cwnd/2, 4*MTU)
471 * partial_bytes_acked = 0
473 transport->ssthresh = max(transport->cwnd/2,
474 4*transport->asoc->pathmtu);
475 transport->cwnd = transport->ssthresh;
478 case SCTP_LOWER_CWND_ECNE:
479 /* RFC 2481 Section 6.1.2.
480 * If the sender receives an ECN-Echo ACK packet
481 * then the sender knows that congestion was encountered in the
482 * network on the path from the sender to the receiver. The
483 * indication of congestion should be treated just as a
484 * congestion loss in non-ECN Capable TCP. That is, the TCP
485 * source halves the congestion window "cwnd" and reduces the
486 * slow start threshold "ssthresh".
487 * A critical condition is that TCP does not react to
488 * congestion indications more than once every window of
489 * data (or more loosely more than once every round-trip time).
491 if ((jiffies - transport->last_time_ecne_reduced) >
493 transport->ssthresh = max(transport->cwnd/2,
494 4*transport->asoc->pathmtu);
495 transport->cwnd = transport->ssthresh;
496 transport->last_time_ecne_reduced = jiffies;
500 case SCTP_LOWER_CWND_INACTIVE:
501 /* RFC 2960 Section 7.2.1, sctpimpguide
502 * When the endpoint does not transmit data on a given
503 * transport address, the cwnd of the transport address
504 * should be adjusted to max(cwnd/2, 4*MTU) per RTO.
505 * NOTE: Although the draft recommends that this check needs
506 * to be done every RTO interval, we do it every hearbeat
509 if ((jiffies - transport->last_time_used) > transport->rto)
510 transport->cwnd = max(transport->cwnd/2,
511 4*transport->asoc->pathmtu);
515 transport->partial_bytes_acked = 0;
516 SCTP_DEBUG_PRINTK("%s: transport: %p reason: %d cwnd: "
517 "%d ssthresh: %d\n", __FUNCTION__,
519 transport->cwnd, transport->ssthresh);
522 /* What is the next timeout value for this transport? */
523 unsigned long sctp_transport_timeout(struct sctp_transport *t)
525 unsigned long timeout;
526 timeout = t->rto + sctp_jitter(t->rto);
527 if (t->state != SCTP_UNCONFIRMED)
528 timeout += t->hbinterval;