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
;