1 /* SCTP kernel implementation
2 * (C) Copyright IBM Corp. 2001, 2004
3 * Copyright (c) 1999-2000 Cisco, Inc.
4 * Copyright (c) 1999-2001 Motorola, Inc.
5 * Copyright (c) 2001-2003 Intel Corp.
6 *
7 * This file is part of the SCTP kernel implementation
8 *
9 * These functions implement the sctp_outq class. The outqueue handles
10 * bundling and queueing of outgoing SCTP chunks.
11 *
12 * This SCTP implementation is free software;
13 * you can redistribute it and/or modify it under the terms of
14 * the GNU General Public License as published by
15 * the Free Software Foundation; either version 2, or (at your option)
16 * any later version.
17 *
18 * This SCTP implementation is distributed in the hope that it
19 * will be useful, but WITHOUT ANY WARRANTY; without even the implied
20 * ************************
21 * warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
22 * See the GNU General Public License for more details.
23 *
24 * You should have received a copy of the GNU General Public License
25 * along with GNU CC; see the file COPYING. If not, see
26 * <http://www.gnu.org/licenses/>.
27 *
28 * Please send any bug reports or fixes you make to the
29 * email address(es):
30 * lksctp developers <linux-sctp@vger.kernel.org>
31 *
32 * Written or modified by:
33 * La Monte H.P. Yarroll <piggy@acm.org>
34 * Karl Knutson <karl@athena.chicago.il.us>
35 * Perry Melange <pmelange@null.cc.uic.edu>
36 * Xingang Guo <xingang.guo@intel.com>
37 * Hui Huang <hui.huang@nokia.com>
38 * Sridhar Samudrala <sri@us.ibm.com>
39 * Jon Grimm <jgrimm@us.ibm.com>
40 */
41
42 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
43
44 #include <linux/types.h>
45 #include <linux/list.h> /* For struct list_head */
46 #include <linux/socket.h>
47 #include <linux/ip.h>
48 #include <linux/slab.h>
49 #include <net/sock.h> /* For skb_set_owner_w */
50
51 #include <net/sctp/sctp.h>
52 #include <net/sctp/sm.h>
53
54 /* Declare internal functions here. */
55 static int sctp_acked(struct sctp_sackhdr *sack, __u32 tsn);
56 static void sctp_check_transmitted(struct sctp_outq *q,
57 struct list_head *transmitted_queue,
58 struct sctp_transport *transport,
59 union sctp_addr *saddr,
60 struct sctp_sackhdr *sack,
61 __u32 *highest_new_tsn);
62
63 static void sctp_mark_missing(struct sctp_outq *q,
64 struct list_head *transmitted_queue,
65 struct sctp_transport *transport,
66 __u32 highest_new_tsn,
67 int count_of_newacks);
68
69 static void sctp_generate_fwdtsn(struct sctp_outq *q, __u32 sack_ctsn);
70
71 static void sctp_outq_flush(struct sctp_outq *q, int rtx_timeout, gfp_t gfp);
72
73 /* Add data to the front of the queue. */
sctp_outq_head_data(struct sctp_outq * q,struct sctp_chunk * ch)74 static inline void sctp_outq_head_data(struct sctp_outq *q,
75 struct sctp_chunk *ch)
76 {
77 list_add(&ch->list, &q->out_chunk_list);
78 q->out_qlen += ch->skb->len;
79 }
80
81 /* Take data from the front of the queue. */
sctp_outq_dequeue_data(struct sctp_outq * q)82 static inline struct sctp_chunk *sctp_outq_dequeue_data(struct sctp_outq *q)
83 {
84 struct sctp_chunk *ch = NULL;
85
86 if (!list_empty(&q->out_chunk_list)) {
87 struct list_head *entry = q->out_chunk_list.next;
88
89 ch = list_entry(entry, struct sctp_chunk, list);
90 list_del_init(entry);
91 q->out_qlen -= ch->skb->len;
92 }
93 return ch;
94 }
95 /* Add data chunk to the end of the queue. */
sctp_outq_tail_data(struct sctp_outq * q,struct sctp_chunk * ch)96 static inline void sctp_outq_tail_data(struct sctp_outq *q,
97 struct sctp_chunk *ch)
98 {
99 list_add_tail(&ch->list, &q->out_chunk_list);
100 q->out_qlen += ch->skb->len;
101 }
102
103 /*
104 * SFR-CACC algorithm:
105 * D) If count_of_newacks is greater than or equal to 2
106 * and t was not sent to the current primary then the
107 * sender MUST NOT increment missing report count for t.
108 */
sctp_cacc_skip_3_1_d(struct sctp_transport * primary,struct sctp_transport * transport,int count_of_newacks)109 static inline int sctp_cacc_skip_3_1_d(struct sctp_transport *primary,
110 struct sctp_transport *transport,
111 int count_of_newacks)
112 {
113 if (count_of_newacks >= 2 && transport != primary)
114 return 1;
115 return 0;
116 }
117
118 /*
119 * SFR-CACC algorithm:
120 * F) If count_of_newacks is less than 2, let d be the
121 * destination to which t was sent. If cacc_saw_newack
122 * is 0 for destination d, then the sender MUST NOT
123 * increment missing report count for t.
124 */
sctp_cacc_skip_3_1_f(struct sctp_transport * transport,int count_of_newacks)125 static inline int sctp_cacc_skip_3_1_f(struct sctp_transport *transport,
126 int count_of_newacks)
127 {
128 if (count_of_newacks < 2 &&
129 (transport && !transport->cacc.cacc_saw_newack))
130 return 1;
131 return 0;
132 }
133
134 /*
135 * SFR-CACC algorithm:
136 * 3.1) If CYCLING_CHANGEOVER is 0, the sender SHOULD
137 * execute steps C, D, F.
138 *
139 * C has been implemented in sctp_outq_sack
140 */
sctp_cacc_skip_3_1(struct sctp_transport * primary,struct sctp_transport * transport,int count_of_newacks)141 static inline int sctp_cacc_skip_3_1(struct sctp_transport *primary,
142 struct sctp_transport *transport,
143 int count_of_newacks)
144 {
145 if (!primary->cacc.cycling_changeover) {
146 if (sctp_cacc_skip_3_1_d(primary, transport, count_of_newacks))
147 return 1;
148 if (sctp_cacc_skip_3_1_f(transport, count_of_newacks))
149 return 1;
150 return 0;
151 }
152 return 0;
153 }
154
155 /*
156 * SFR-CACC algorithm:
157 * 3.2) Else if CYCLING_CHANGEOVER is 1, and t is less
158 * than next_tsn_at_change of the current primary, then
159 * the sender MUST NOT increment missing report count
160 * for t.
161 */
sctp_cacc_skip_3_2(struct sctp_transport * primary,__u32 tsn)162 static inline int sctp_cacc_skip_3_2(struct sctp_transport *primary, __u32 tsn)
163 {
164 if (primary->cacc.cycling_changeover &&
165 TSN_lt(tsn, primary->cacc.next_tsn_at_change))
166 return 1;
167 return 0;
168 }
169
170 /*
171 * SFR-CACC algorithm:
172 * 3) If the missing report count for TSN t is to be
173 * incremented according to [RFC2960] and
174 * [SCTP_STEWART-2002], and CHANGEOVER_ACTIVE is set,
175 * then the sender MUST further execute steps 3.1 and
176 * 3.2 to determine if the missing report count for
177 * TSN t SHOULD NOT be incremented.
178 *
179 * 3.3) If 3.1 and 3.2 do not dictate that the missing
180 * report count for t should not be incremented, then
181 * the sender SHOULD increment missing report count for
182 * t (according to [RFC2960] and [SCTP_STEWART_2002]).
183 */
sctp_cacc_skip(struct sctp_transport * primary,struct sctp_transport * transport,int count_of_newacks,__u32 tsn)184 static inline int sctp_cacc_skip(struct sctp_transport *primary,
185 struct sctp_transport *transport,
186 int count_of_newacks,
187 __u32 tsn)
188 {
189 if (primary->cacc.changeover_active &&
190 (sctp_cacc_skip_3_1(primary, transport, count_of_newacks) ||
191 sctp_cacc_skip_3_2(primary, tsn)))
192 return 1;
193 return 0;
194 }
195
196 /* Initialize an existing sctp_outq. This does the boring stuff.
197 * You still need to define handlers if you really want to DO
198 * something with this structure...
199 */
sctp_outq_init(struct sctp_association * asoc,struct sctp_outq * q)200 void sctp_outq_init(struct sctp_association *asoc, struct sctp_outq *q)
201 {
202 memset(q, 0, sizeof(struct sctp_outq));
203
204 q->asoc = asoc;
205 INIT_LIST_HEAD(&q->out_chunk_list);
206 INIT_LIST_HEAD(&q->control_chunk_list);
207 INIT_LIST_HEAD(&q->retransmit);
208 INIT_LIST_HEAD(&q->sacked);
209 INIT_LIST_HEAD(&q->abandoned);
210 }
211
212 /* Free the outqueue structure and any related pending chunks.
213 */
__sctp_outq_teardown(struct sctp_outq * q)214 static void __sctp_outq_teardown(struct sctp_outq *q)
215 {
216 struct sctp_transport *transport;
217 struct list_head *lchunk, *temp;
218 struct sctp_chunk *chunk, *tmp;
219
220 /* Throw away unacknowledged chunks. */
221 list_for_each_entry(transport, &q->asoc->peer.transport_addr_list,
222 transports) {
223 while ((lchunk = sctp_list_dequeue(&transport->transmitted)) != NULL) {
224 chunk = list_entry(lchunk, struct sctp_chunk,
225 transmitted_list);
226 /* Mark as part of a failed message. */
227 sctp_chunk_fail(chunk, q->error);
228 sctp_chunk_free(chunk);
229 }
230 }
231
232 /* Throw away chunks that have been gap ACKed. */
233 list_for_each_safe(lchunk, temp, &q->sacked) {
234 list_del_init(lchunk);
235 chunk = list_entry(lchunk, struct sctp_chunk,
236 transmitted_list);
237 sctp_chunk_fail(chunk, q->error);
238 sctp_chunk_free(chunk);
239 }
240
241 /* Throw away any chunks in the retransmit queue. */
242 list_for_each_safe(lchunk, temp, &q->retransmit) {
243 list_del_init(lchunk);
244 chunk = list_entry(lchunk, struct sctp_chunk,
245 transmitted_list);
246 sctp_chunk_fail(chunk, q->error);
247 sctp_chunk_free(chunk);
248 }
249
250 /* Throw away any chunks that are in the abandoned queue. */
251 list_for_each_safe(lchunk, temp, &q->abandoned) {
252 list_del_init(lchunk);
253 chunk = list_entry(lchunk, struct sctp_chunk,
254 transmitted_list);
255 sctp_chunk_fail(chunk, q->error);
256 sctp_chunk_free(chunk);
257 }
258
259 /* Throw away any leftover data chunks. */
260 while ((chunk = sctp_outq_dequeue_data(q)) != NULL) {
261
262 /* Mark as send failure. */
263 sctp_chunk_fail(chunk, q->error);
264 sctp_chunk_free(chunk);
265 }
266
267 /* Throw away any leftover control chunks. */
268 list_for_each_entry_safe(chunk, tmp, &q->control_chunk_list, list) {
269 list_del_init(&chunk->list);
270 sctp_chunk_free(chunk);
271 }
272 }
273
sctp_outq_teardown(struct sctp_outq * q)274 void sctp_outq_teardown(struct sctp_outq *q)
275 {
276 __sctp_outq_teardown(q);
277 sctp_outq_init(q->asoc, q);
278 }
279
280 /* Free the outqueue structure and any related pending chunks. */
sctp_outq_free(struct sctp_outq * q)281 void sctp_outq_free(struct sctp_outq *q)
282 {
283 /* Throw away leftover chunks. */
284 __sctp_outq_teardown(q);
285 }
286
287 /* Put a new chunk in an sctp_outq. */
sctp_outq_tail(struct sctp_outq * q,struct sctp_chunk * chunk,gfp_t gfp)288 void sctp_outq_tail(struct sctp_outq *q, struct sctp_chunk *chunk, gfp_t gfp)
289 {
290 struct net *net = sock_net(q->asoc->base.sk);
291
292 pr_debug("%s: outq:%p, chunk:%p[%s]\n", __func__, q, chunk,
293 chunk && chunk->chunk_hdr ?
294 sctp_cname(SCTP_ST_CHUNK(chunk->chunk_hdr->type)) :
295 "illegal chunk");
296
297 /* If it is data, queue it up, otherwise, send it
298 * immediately.
299 */
300 if (sctp_chunk_is_data(chunk)) {
301 pr_debug("%s: outqueueing: outq:%p, chunk:%p[%s])\n",
302 __func__, q, chunk, chunk && chunk->chunk_hdr ?
303 sctp_cname(SCTP_ST_CHUNK(chunk->chunk_hdr->type)) :
304 "illegal chunk");
305
306 sctp_outq_tail_data(q, chunk);
307 if (chunk->asoc->peer.prsctp_capable &&
308 SCTP_PR_PRIO_ENABLED(chunk->sinfo.sinfo_flags))
309 chunk->asoc->sent_cnt_removable++;
310 if (chunk->chunk_hdr->flags & SCTP_DATA_UNORDERED)
311 SCTP_INC_STATS(net, SCTP_MIB_OUTUNORDERCHUNKS);
312 else
313 SCTP_INC_STATS(net, SCTP_MIB_OUTORDERCHUNKS);
314 } else {
315 list_add_tail(&chunk->list, &q->control_chunk_list);
316 SCTP_INC_STATS(net, SCTP_MIB_OUTCTRLCHUNKS);
317 }
318
319 if (!q->cork)
320 sctp_outq_flush(q, 0, gfp);
321 }
322
323 /* Insert a chunk into the sorted list based on the TSNs. The retransmit list
324 * and the abandoned list are in ascending order.
325 */
sctp_insert_list(struct list_head * head,struct list_head * new)326 static void sctp_insert_list(struct list_head *head, struct list_head *new)
327 {
328 struct list_head *pos;
329 struct sctp_chunk *nchunk, *lchunk;
330 __u32 ntsn, ltsn;
331 int done = 0;
332
333 nchunk = list_entry(new, struct sctp_chunk, transmitted_list);
334 ntsn = ntohl(nchunk->subh.data_hdr->tsn);
335
336 list_for_each(pos, head) {
337 lchunk = list_entry(pos, struct sctp_chunk, transmitted_list);
338 ltsn = ntohl(lchunk->subh.data_hdr->tsn);
339 if (TSN_lt(ntsn, ltsn)) {
340 list_add(new, pos->prev);
341 done = 1;
342 break;
343 }
344 }
345 if (!done)
346 list_add_tail(new, head);
347 }
348
sctp_prsctp_prune_sent(struct sctp_association * asoc,struct sctp_sndrcvinfo * sinfo,struct list_head * queue,int msg_len)349 static int sctp_prsctp_prune_sent(struct sctp_association *asoc,
350 struct sctp_sndrcvinfo *sinfo,
351 struct list_head *queue, int msg_len)
352 {
353 struct sctp_chunk *chk, *temp;
354
355 list_for_each_entry_safe(chk, temp, queue, transmitted_list) {
356 if (!SCTP_PR_PRIO_ENABLED(chk->sinfo.sinfo_flags) ||
357 chk->sinfo.sinfo_timetolive <= sinfo->sinfo_timetolive)
358 continue;
359
360 list_del_init(&chk->transmitted_list);
361 sctp_insert_list(&asoc->outqueue.abandoned,
362 &chk->transmitted_list);
363
364 asoc->sent_cnt_removable--;
365 asoc->abandoned_sent[SCTP_PR_INDEX(PRIO)]++;
366
367 if (queue != &asoc->outqueue.retransmit &&
368 !chk->tsn_gap_acked) {
369 if (chk->transport)
370 chk->transport->flight_size -=
371 sctp_data_size(chk);
372 asoc->outqueue.outstanding_bytes -= sctp_data_size(chk);
373 }
374
375 msg_len -= SCTP_DATA_SNDSIZE(chk) +
376 sizeof(struct sk_buff) +
377 sizeof(struct sctp_chunk);
378 if (msg_len <= 0)
379 break;
380 }
381
382 return msg_len;
383 }
384
sctp_prsctp_prune_unsent(struct sctp_association * asoc,struct sctp_sndrcvinfo * sinfo,int msg_len)385 static int sctp_prsctp_prune_unsent(struct sctp_association *asoc,
386 struct sctp_sndrcvinfo *sinfo, int msg_len)
387 {
388 struct sctp_outq *q = &asoc->outqueue;
389 struct sctp_chunk *chk, *temp;
390
391 list_for_each_entry_safe(chk, temp, &q->out_chunk_list, list) {
392 if (!SCTP_PR_PRIO_ENABLED(chk->sinfo.sinfo_flags) ||
393 chk->sinfo.sinfo_timetolive <= sinfo->sinfo_timetolive)
394 continue;
395
396 list_del_init(&chk->list);
397 q->out_qlen -= chk->skb->len;
398 asoc->sent_cnt_removable--;
399 asoc->abandoned_unsent[SCTP_PR_INDEX(PRIO)]++;
400
401 msg_len -= SCTP_DATA_SNDSIZE(chk) +
402 sizeof(struct sk_buff) +
403 sizeof(struct sctp_chunk);
404 sctp_chunk_free(chk);
405 if (msg_len <= 0)
406 break;
407 }
408
409 return msg_len;
410 }
411
412 /* Abandon the chunks according their priorities */
sctp_prsctp_prune(struct sctp_association * asoc,struct sctp_sndrcvinfo * sinfo,int msg_len)413 void sctp_prsctp_prune(struct sctp_association *asoc,
414 struct sctp_sndrcvinfo *sinfo, int msg_len)
415 {
416 struct sctp_transport *transport;
417
418 if (!asoc->peer.prsctp_capable || !asoc->sent_cnt_removable)
419 return;
420
421 msg_len = sctp_prsctp_prune_sent(asoc, sinfo,
422 &asoc->outqueue.retransmit,
423 msg_len);
424 if (msg_len <= 0)
425 return;
426
427 list_for_each_entry(transport, &asoc->peer.transport_addr_list,
428 transports) {
429 msg_len = sctp_prsctp_prune_sent(asoc, sinfo,
430 &transport->transmitted,
431 msg_len);
432 if (msg_len <= 0)
433 return;
434 }
435
436 sctp_prsctp_prune_unsent(asoc, sinfo, msg_len);
437 }
438
439 /* Mark all the eligible packets on a transport for retransmission. */
sctp_retransmit_mark(struct sctp_outq * q,struct sctp_transport * transport,__u8 reason)440 void sctp_retransmit_mark(struct sctp_outq *q,
441 struct sctp_transport *transport,
442 __u8 reason)
443 {
444 struct list_head *lchunk, *ltemp;
445 struct sctp_chunk *chunk;
446
447 /* Walk through the specified transmitted queue. */
448 list_for_each_safe(lchunk, ltemp, &transport->transmitted) {
449 chunk = list_entry(lchunk, struct sctp_chunk,
450 transmitted_list);
451
452 /* If the chunk is abandoned, move it to abandoned list. */
453 if (sctp_chunk_abandoned(chunk)) {
454 list_del_init(lchunk);
455 sctp_insert_list(&q->abandoned, lchunk);
456
457 /* If this chunk has not been previousely acked,
458 * stop considering it 'outstanding'. Our peer
459 * will most likely never see it since it will
460 * not be retransmitted
461 */
462 if (!chunk->tsn_gap_acked) {
463 if (chunk->transport)
464 chunk->transport->flight_size -=
465 sctp_data_size(chunk);
466 q->outstanding_bytes -= sctp_data_size(chunk);
467 q->asoc->peer.rwnd += sctp_data_size(chunk);
468 }
469 continue;
470 }
471
472 /* If we are doing retransmission due to a timeout or pmtu
473 * discovery, only the chunks that are not yet acked should
474 * be added to the retransmit queue.
475 */
476 if ((reason == SCTP_RTXR_FAST_RTX &&
477 (chunk->fast_retransmit == SCTP_NEED_FRTX)) ||
478 (reason != SCTP_RTXR_FAST_RTX && !chunk->tsn_gap_acked)) {
479 /* RFC 2960 6.2.1 Processing a Received SACK
480 *
481 * C) Any time a DATA chunk is marked for
482 * retransmission (via either T3-rtx timer expiration
483 * (Section 6.3.3) or via fast retransmit
484 * (Section 7.2.4)), add the data size of those
485 * chunks to the rwnd.
486 */
487 q->asoc->peer.rwnd += sctp_data_size(chunk);
488 q->outstanding_bytes -= sctp_data_size(chunk);
489 if (chunk->transport)
490 transport->flight_size -= sctp_data_size(chunk);
491
492 /* sctpimpguide-05 Section 2.8.2
493 * M5) If a T3-rtx timer expires, the
494 * 'TSN.Missing.Report' of all affected TSNs is set
495 * to 0.
496 */
497 chunk->tsn_missing_report = 0;
498
499 /* If a chunk that is being used for RTT measurement
500 * has to be retransmitted, we cannot use this chunk
501 * anymore for RTT measurements. Reset rto_pending so
502 * that a new RTT measurement is started when a new
503 * data chunk is sent.
504 */
505 if (chunk->rtt_in_progress) {
506 chunk->rtt_in_progress = 0;
507 transport->rto_pending = 0;
508 }
509
510 chunk->resent = 1;
511
512 /* Move the chunk to the retransmit queue. The chunks
513 * on the retransmit queue are always kept in order.
514 */
515 list_del_init(lchunk);
516 sctp_insert_list(&q->retransmit, lchunk);
517 }
518 }
519
520 pr_debug("%s: transport:%p, reason:%d, cwnd:%d, ssthresh:%d, "
521 "flight_size:%d, pba:%d\n", __func__, transport, reason,
522 transport->cwnd, transport->ssthresh, transport->flight_size,
523 transport->partial_bytes_acked);
524 }
525
526 /* Mark all the eligible packets on a transport for retransmission and force
527 * one packet out.
528 */
sctp_retransmit(struct sctp_outq * q,struct sctp_transport * transport,sctp_retransmit_reason_t reason)529 void sctp_retransmit(struct sctp_outq *q, struct sctp_transport *transport,
530 sctp_retransmit_reason_t reason)
531 {
532 struct net *net = sock_net(q->asoc->base.sk);
533
534 switch (reason) {
535 case SCTP_RTXR_T3_RTX:
536 SCTP_INC_STATS(net, SCTP_MIB_T3_RETRANSMITS);
537 sctp_transport_lower_cwnd(transport, SCTP_LOWER_CWND_T3_RTX);
538 /* Update the retran path if the T3-rtx timer has expired for
539 * the current retran path.
540 */
541 if (transport == transport->asoc->peer.retran_path)
542 sctp_assoc_update_retran_path(transport->asoc);
543 transport->asoc->rtx_data_chunks +=
544 transport->asoc->unack_data;
545 break;
546 case SCTP_RTXR_FAST_RTX:
547 SCTP_INC_STATS(net, SCTP_MIB_FAST_RETRANSMITS);
548 sctp_transport_lower_cwnd(transport, SCTP_LOWER_CWND_FAST_RTX);
549 q->fast_rtx = 1;
550 break;
551 case SCTP_RTXR_PMTUD:
552 SCTP_INC_STATS(net, SCTP_MIB_PMTUD_RETRANSMITS);
553 break;
554 case SCTP_RTXR_T1_RTX:
555 SCTP_INC_STATS(net, SCTP_MIB_T1_RETRANSMITS);
556 transport->asoc->init_retries++;
557 break;
558 default:
559 BUG();
560 }
561
562 sctp_retransmit_mark(q, transport, reason);
563
564 /* PR-SCTP A5) Any time the T3-rtx timer expires, on any destination,
565 * the sender SHOULD try to advance the "Advanced.Peer.Ack.Point" by
566 * following the procedures outlined in C1 - C5.
567 */
568 if (reason == SCTP_RTXR_T3_RTX)
569 sctp_generate_fwdtsn(q, q->asoc->ctsn_ack_point);
570
571 /* Flush the queues only on timeout, since fast_rtx is only
572 * triggered during sack processing and the queue
573 * will be flushed at the end.
574 */
575 if (reason != SCTP_RTXR_FAST_RTX)
576 sctp_outq_flush(q, /* rtx_timeout */ 1, GFP_ATOMIC);
577 }
578
579 /*
580 * Transmit DATA chunks on the retransmit queue. Upon return from
581 * sctp_outq_flush_rtx() the packet 'pkt' may contain chunks which
582 * need to be transmitted by the caller.
583 * We assume that pkt->transport has already been set.
584 *
585 * The return value is a normal kernel error return value.
586 */
sctp_outq_flush_rtx(struct sctp_outq * q,struct sctp_packet * pkt,int rtx_timeout,int * start_timer)587 static int sctp_outq_flush_rtx(struct sctp_outq *q, struct sctp_packet *pkt,
588 int rtx_timeout, int *start_timer)
589 {
590 struct list_head *lqueue;
591 struct sctp_transport *transport = pkt->transport;
592 sctp_xmit_t status;
593 struct sctp_chunk *chunk, *chunk1;
594 int fast_rtx;
595 int error = 0;
596 int timer = 0;
597 int done = 0;
598
599 lqueue = &q->retransmit;
600 fast_rtx = q->fast_rtx;
601
602 /* This loop handles time-out retransmissions, fast retransmissions,
603 * and retransmissions due to opening of whindow.
604 *
605 * RFC 2960 6.3.3 Handle T3-rtx Expiration
606 *
607 * E3) Determine how many of the earliest (i.e., lowest TSN)
608 * outstanding DATA chunks for the address for which the
609 * T3-rtx has expired will fit into a single packet, subject
610 * to the MTU constraint for the path corresponding to the
611 * destination transport address to which the retransmission
612 * is being sent (this may be different from the address for
613 * which the timer expires [see Section 6.4]). Call this value
614 * K. Bundle and retransmit those K DATA chunks in a single
615 * packet to the destination endpoint.
616 *
617 * [Just to be painfully clear, if we are retransmitting
618 * because a timeout just happened, we should send only ONE
619 * packet of retransmitted data.]
620 *
621 * For fast retransmissions we also send only ONE packet. However,
622 * if we are just flushing the queue due to open window, we'll
623 * try to send as much as possible.
624 */
625 list_for_each_entry_safe(chunk, chunk1, lqueue, transmitted_list) {
626 /* If the chunk is abandoned, move it to abandoned list. */
627 if (sctp_chunk_abandoned(chunk)) {
628 list_del_init(&chunk->transmitted_list);
629 sctp_insert_list(&q->abandoned,
630 &chunk->transmitted_list);
631 continue;
632 }
633
634 /* Make sure that Gap Acked TSNs are not retransmitted. A
635 * simple approach is just to move such TSNs out of the
636 * way and into a 'transmitted' queue and skip to the
637 * next chunk.
638 */
639 if (chunk->tsn_gap_acked) {
640 list_move_tail(&chunk->transmitted_list,
641 &transport->transmitted);
642 continue;
643 }
644
645 /* If we are doing fast retransmit, ignore non-fast_rtransmit
646 * chunks
647 */
648 if (fast_rtx && !chunk->fast_retransmit)
649 continue;
650
651 redo:
652 /* Attempt to append this chunk to the packet. */
653 status = sctp_packet_append_chunk(pkt, chunk);
654
655 switch (status) {
656 case SCTP_XMIT_PMTU_FULL:
657 if (!pkt->has_data && !pkt->has_cookie_echo) {
658 /* If this packet did not contain DATA then
659 * retransmission did not happen, so do it
660 * again. We'll ignore the error here since
661 * control chunks are already freed so there
662 * is nothing we can do.
663 */
664 sctp_packet_transmit(pkt, GFP_ATOMIC);
665 goto redo;
666 }
667
668 /* Send this packet. */
669 error = sctp_packet_transmit(pkt, GFP_ATOMIC);
670
671 /* If we are retransmitting, we should only
672 * send a single packet.
673 * Otherwise, try appending this chunk again.
674 */
675 if (rtx_timeout || fast_rtx)
676 done = 1;
677 else
678 goto redo;
679
680 /* Bundle next chunk in the next round. */
681 break;
682
683 case SCTP_XMIT_RWND_FULL:
684 /* Send this packet. */
685 error = sctp_packet_transmit(pkt, GFP_ATOMIC);
686
687 /* Stop sending DATA as there is no more room
688 * at the receiver.
689 */
690 done = 1;
691 break;
692
693 case SCTP_XMIT_DELAY:
694 /* Send this packet. */
695 error = sctp_packet_transmit(pkt, GFP_ATOMIC);
696
697 /* Stop sending DATA because of nagle delay. */
698 done = 1;
699 break;
700
701 default:
702 /* The append was successful, so add this chunk to
703 * the transmitted list.
704 */
705 list_move_tail(&chunk->transmitted_list,
706 &transport->transmitted);
707
708 /* Mark the chunk as ineligible for fast retransmit
709 * after it is retransmitted.
710 */
711 if (chunk->fast_retransmit == SCTP_NEED_FRTX)
712 chunk->fast_retransmit = SCTP_DONT_FRTX;
713
714 q->asoc->stats.rtxchunks++;
715 break;
716 }
717
718 /* Set the timer if there were no errors */
719 if (!error && !timer)
720 timer = 1;
721
722 if (done)
723 break;
724 }
725
726 /* If we are here due to a retransmit timeout or a fast
727 * retransmit and if there are any chunks left in the retransmit
728 * queue that could not fit in the PMTU sized packet, they need
729 * to be marked as ineligible for a subsequent fast retransmit.
730 */
731 if (rtx_timeout || fast_rtx) {
732 list_for_each_entry(chunk1, lqueue, transmitted_list) {
733 if (chunk1->fast_retransmit == SCTP_NEED_FRTX)
734 chunk1->fast_retransmit = SCTP_DONT_FRTX;
735 }
736 }
737
738 *start_timer = timer;
739
740 /* Clear fast retransmit hint */
741 if (fast_rtx)
742 q->fast_rtx = 0;
743
744 return error;
745 }
746
747 /* Cork the outqueue so queued chunks are really queued. */
sctp_outq_uncork(struct sctp_outq * q,gfp_t gfp)748 void sctp_outq_uncork(struct sctp_outq *q, gfp_t gfp)
749 {
750 if (q->cork)
751 q->cork = 0;
752
753 sctp_outq_flush(q, 0, gfp);
754 }
755
756
757 /*
758 * Try to flush an outqueue.
759 *
760 * Description: Send everything in q which we legally can, subject to
761 * congestion limitations.
762 * * Note: This function can be called from multiple contexts so appropriate
763 * locking concerns must be made. Today we use the sock lock to protect
764 * this function.
765 */
sctp_outq_flush(struct sctp_outq * q,int rtx_timeout,gfp_t gfp)766 static void sctp_outq_flush(struct sctp_outq *q, int rtx_timeout, gfp_t gfp)
767 {
768 struct sctp_packet *packet;
769 struct sctp_packet singleton;
770 struct sctp_association *asoc = q->asoc;
771 __u16 sport = asoc->base.bind_addr.port;
772 __u16 dport = asoc->peer.port;
773 __u32 vtag = asoc->peer.i.init_tag;
774 struct sctp_transport *transport = NULL;
775 struct sctp_transport *new_transport;
776 struct sctp_chunk *chunk, *tmp;
777 sctp_xmit_t status;
778 int error = 0;
779 int start_timer = 0;
780 int one_packet = 0;
781
782 /* These transports have chunks to send. */
783 struct list_head transport_list;
784 struct list_head *ltransport;
785
786 INIT_LIST_HEAD(&transport_list);
787 packet = NULL;
788
789 /*
790 * 6.10 Bundling
791 * ...
792 * When bundling control chunks with DATA chunks, an
793 * endpoint MUST place control chunks first in the outbound
794 * SCTP packet. The transmitter MUST transmit DATA chunks
795 * within a SCTP packet in increasing order of TSN.
796 * ...
797 */
798
799 list_for_each_entry_safe(chunk, tmp, &q->control_chunk_list, list) {
800 /* RFC 5061, 5.3
801 * F1) This means that until such time as the ASCONF
802 * containing the add is acknowledged, the sender MUST
803 * NOT use the new IP address as a source for ANY SCTP
804 * packet except on carrying an ASCONF Chunk.
805 */
806 if (asoc->src_out_of_asoc_ok &&
807 chunk->chunk_hdr->type != SCTP_CID_ASCONF)
808 continue;
809
810 list_del_init(&chunk->list);
811
812 /* Pick the right transport to use. */
813 new_transport = chunk->transport;
814
815 if (!new_transport) {
816 /*
817 * If we have a prior transport pointer, see if
818 * the destination address of the chunk
819 * matches the destination address of the
820 * current transport. If not a match, then
821 * try to look up the transport with a given
822 * destination address. We do this because
823 * after processing ASCONFs, we may have new
824 * transports created.
825 */
826 if (transport &&
827 sctp_cmp_addr_exact(&chunk->dest,
828 &transport->ipaddr))
829 new_transport = transport;
830 else
831 new_transport = sctp_assoc_lookup_paddr(asoc,
832 &chunk->dest);
833
834 /* if we still don't have a new transport, then
835 * use the current active path.
836 */
837 if (!new_transport)
838 new_transport = asoc->peer.active_path;
839 } else if ((new_transport->state == SCTP_INACTIVE) ||
840 (new_transport->state == SCTP_UNCONFIRMED) ||
841 (new_transport->state == SCTP_PF)) {
842 /* If the chunk is Heartbeat or Heartbeat Ack,
843 * send it to chunk->transport, even if it's
844 * inactive.
845 *
846 * 3.3.6 Heartbeat Acknowledgement:
847 * ...
848 * A HEARTBEAT ACK is always sent to the source IP
849 * address of the IP datagram containing the
850 * HEARTBEAT chunk to which this ack is responding.
851 * ...
852 *
853 * ASCONF_ACKs also must be sent to the source.
854 */
855 if (chunk->chunk_hdr->type != SCTP_CID_HEARTBEAT &&
856 chunk->chunk_hdr->type != SCTP_CID_HEARTBEAT_ACK &&
857 chunk->chunk_hdr->type != SCTP_CID_ASCONF_ACK)
858 new_transport = asoc->peer.active_path;
859 }
860
861 /* Are we switching transports?
862 * Take care of transport locks.
863 */
864 if (new_transport != transport) {
865 transport = new_transport;
866 if (list_empty(&transport->send_ready)) {
867 list_add_tail(&transport->send_ready,
868 &transport_list);
869 }
870 packet = &transport->packet;
871 sctp_packet_config(packet, vtag,
872 asoc->peer.ecn_capable);
873 }
874
875 switch (chunk->chunk_hdr->type) {
876 /*
877 * 6.10 Bundling
878 * ...
879 * An endpoint MUST NOT bundle INIT, INIT ACK or SHUTDOWN
880 * COMPLETE with any other chunks. [Send them immediately.]
881 */
882 case SCTP_CID_INIT:
883 case SCTP_CID_INIT_ACK:
884 case SCTP_CID_SHUTDOWN_COMPLETE:
885 sctp_packet_init(&singleton, transport, sport, dport);
886 sctp_packet_config(&singleton, vtag, 0);
887 sctp_packet_append_chunk(&singleton, chunk);
888 error = sctp_packet_transmit(&singleton, gfp);
889 if (error < 0) {
890 asoc->base.sk->sk_err = -error;
891 return;
892 }
893 break;
894
895 case SCTP_CID_ABORT:
896 if (sctp_test_T_bit(chunk)) {
897 packet->vtag = asoc->c.my_vtag;
898 }
899 /* The following chunks are "response" chunks, i.e.
900 * they are generated in response to something we
901 * received. If we are sending these, then we can
902 * send only 1 packet containing these chunks.
903 */
904 case SCTP_CID_HEARTBEAT_ACK:
905 case SCTP_CID_SHUTDOWN_ACK:
906 case SCTP_CID_COOKIE_ACK:
907 case SCTP_CID_COOKIE_ECHO:
908 case SCTP_CID_ERROR:
909 case SCTP_CID_ECN_CWR:
910 case SCTP_CID_ASCONF_ACK:
911 one_packet = 1;
912 /* Fall through */
913
914 case SCTP_CID_SACK:
915 case SCTP_CID_HEARTBEAT:
916 case SCTP_CID_SHUTDOWN:
917 case SCTP_CID_ECN_ECNE:
918 case SCTP_CID_ASCONF:
919 case SCTP_CID_FWD_TSN:
920 status = sctp_packet_transmit_chunk(packet, chunk,
921 one_packet, gfp);
922 if (status != SCTP_XMIT_OK) {
923 /* put the chunk back */
924 list_add(&chunk->list, &q->control_chunk_list);
925 } else {
926 asoc->stats.octrlchunks++;
927 /* PR-SCTP C5) If a FORWARD TSN is sent, the
928 * sender MUST assure that at least one T3-rtx
929 * timer is running.
930 */
931 if (chunk->chunk_hdr->type == SCTP_CID_FWD_TSN) {
932 sctp_transport_reset_t3_rtx(transport);
933 transport->last_time_sent = jiffies;
934 }
935 }
936 break;
937
938 default:
939 /* We built a chunk with an illegal type! */
940 BUG();
941 }
942 }
943
944 if (q->asoc->src_out_of_asoc_ok)
945 goto sctp_flush_out;
946
947 /* Is it OK to send data chunks? */
948 switch (asoc->state) {
949 case SCTP_STATE_COOKIE_ECHOED:
950 /* Only allow bundling when this packet has a COOKIE-ECHO
951 * chunk.
952 */
953 if (!packet || !packet->has_cookie_echo)
954 break;
955
956 /* fallthru */
957 case SCTP_STATE_ESTABLISHED:
958 case SCTP_STATE_SHUTDOWN_PENDING:
959 case SCTP_STATE_SHUTDOWN_RECEIVED:
960 /*
961 * RFC 2960 6.1 Transmission of DATA Chunks
962 *
963 * C) When the time comes for the sender to transmit,
964 * before sending new DATA chunks, the sender MUST
965 * first transmit any outstanding DATA chunks which
966 * are marked for retransmission (limited by the
967 * current cwnd).
968 */
969 if (!list_empty(&q->retransmit)) {
970 if (asoc->peer.retran_path->state == SCTP_UNCONFIRMED)
971 goto sctp_flush_out;
972 if (transport == asoc->peer.retran_path)
973 goto retran;
974
975 /* Switch transports & prepare the packet. */
976
977 transport = asoc->peer.retran_path;
978
979 if (list_empty(&transport->send_ready)) {
980 list_add_tail(&transport->send_ready,
981 &transport_list);
982 }
983
984 packet = &transport->packet;
985 sctp_packet_config(packet, vtag,
986 asoc->peer.ecn_capable);
987 retran:
988 error = sctp_outq_flush_rtx(q, packet,
989 rtx_timeout, &start_timer);
990 if (error < 0)
991 asoc->base.sk->sk_err = -error;
992
993 if (start_timer) {
994 sctp_transport_reset_t3_rtx(transport);
995 transport->last_time_sent = jiffies;
996 }
997
998 /* This can happen on COOKIE-ECHO resend. Only
999 * one chunk can get bundled with a COOKIE-ECHO.
1000 */
1001 if (packet->has_cookie_echo)
1002 goto sctp_flush_out;
1003
1004 /* Don't send new data if there is still data
1005 * waiting to retransmit.
1006 */
1007 if (!list_empty(&q->retransmit))
1008 goto sctp_flush_out;
1009 }
1010
1011 /* Apply Max.Burst limitation to the current transport in
1012 * case it will be used for new data. We are going to
1013 * rest it before we return, but we want to apply the limit
1014 * to the currently queued data.
1015 */
1016 if (transport)
1017 sctp_transport_burst_limited(transport);
1018
1019 /* Finally, transmit new packets. */
1020 while ((chunk = sctp_outq_dequeue_data(q)) != NULL) {
1021 /* RFC 2960 6.5 Every DATA chunk MUST carry a valid
1022 * stream identifier.
1023 */
1024 if (chunk->sinfo.sinfo_stream >=
1025 asoc->c.sinit_num_ostreams) {
1026
1027 /* Mark as failed send. */
1028 sctp_chunk_fail(chunk, SCTP_ERROR_INV_STRM);
1029 if (asoc->peer.prsctp_capable &&
1030 SCTP_PR_PRIO_ENABLED(chunk->sinfo.sinfo_flags))
1031 asoc->sent_cnt_removable--;
1032 sctp_chunk_free(chunk);
1033 continue;
1034 }
1035
1036 /* Has this chunk expired? */
1037 if (sctp_chunk_abandoned(chunk)) {
1038 sctp_chunk_fail(chunk, 0);
1039 sctp_chunk_free(chunk);
1040 continue;
1041 }
1042
1043 /* If there is a specified transport, use it.
1044 * Otherwise, we want to use the active path.
1045 */
1046 new_transport = chunk->transport;
1047 if (!new_transport ||
1048 ((new_transport->state == SCTP_INACTIVE) ||
1049 (new_transport->state == SCTP_UNCONFIRMED) ||
1050 (new_transport->state == SCTP_PF)))
1051 new_transport = asoc->peer.active_path;
1052 if (new_transport->state == SCTP_UNCONFIRMED) {
1053 WARN_ONCE(1, "Atempt to send packet on unconfirmed path.");
1054 sctp_chunk_fail(chunk, 0);
1055 sctp_chunk_free(chunk);
1056 continue;
1057 }
1058
1059 /* Change packets if necessary. */
1060 if (new_transport != transport) {
1061 transport = new_transport;
1062
1063 /* Schedule to have this transport's
1064 * packet flushed.
1065 */
1066 if (list_empty(&transport->send_ready)) {
1067 list_add_tail(&transport->send_ready,
1068 &transport_list);
1069 }
1070
1071 packet = &transport->packet;
1072 sctp_packet_config(packet, vtag,
1073 asoc->peer.ecn_capable);
1074 /* We've switched transports, so apply the
1075 * Burst limit to the new transport.
1076 */
1077 sctp_transport_burst_limited(transport);
1078 }
1079
1080 pr_debug("%s: outq:%p, chunk:%p[%s], tx-tsn:0x%x skb->head:%p "
1081 "skb->users:%d\n",
1082 __func__, q, chunk, chunk && chunk->chunk_hdr ?
1083 sctp_cname(SCTP_ST_CHUNK(chunk->chunk_hdr->type)) :
1084 "illegal chunk", ntohl(chunk->subh.data_hdr->tsn),
1085 chunk->skb ? chunk->skb->head : NULL, chunk->skb ?
1086 atomic_read(&chunk->skb->users) : -1);
1087
1088 /* Add the chunk to the packet. */
1089 status = sctp_packet_transmit_chunk(packet, chunk, 0, gfp);
1090
1091 switch (status) {
1092 case SCTP_XMIT_PMTU_FULL:
1093 case SCTP_XMIT_RWND_FULL:
1094 case SCTP_XMIT_DELAY:
1095 /* We could not append this chunk, so put
1096 * the chunk back on the output queue.
1097 */
1098 pr_debug("%s: could not transmit tsn:0x%x, status:%d\n",
1099 __func__, ntohl(chunk->subh.data_hdr->tsn),
1100 status);
1101
1102 sctp_outq_head_data(q, chunk);
1103 goto sctp_flush_out;
1104
1105 case SCTP_XMIT_OK:
1106 /* The sender is in the SHUTDOWN-PENDING state,
1107 * The sender MAY set the I-bit in the DATA
1108 * chunk header.
1109 */
1110 if (asoc->state == SCTP_STATE_SHUTDOWN_PENDING)
1111 chunk->chunk_hdr->flags |= SCTP_DATA_SACK_IMM;
1112 if (chunk->chunk_hdr->flags & SCTP_DATA_UNORDERED)
1113 asoc->stats.ouodchunks++;
1114 else
1115 asoc->stats.oodchunks++;
1116
1117 break;
1118
1119 default:
1120 BUG();
1121 }
1122
1123 /* BUG: We assume that the sctp_packet_transmit()
1124 * call below will succeed all the time and add the
1125 * chunk to the transmitted list and restart the
1126 * timers.
1127 * It is possible that the call can fail under OOM
1128 * conditions.
1129 *
1130 * Is this really a problem? Won't this behave
1131 * like a lost TSN?
1132 */
1133 list_add_tail(&chunk->transmitted_list,
1134 &transport->transmitted);
1135
1136 sctp_transport_reset_t3_rtx(transport);
1137 transport->last_time_sent = jiffies;
1138
1139 /* Only let one DATA chunk get bundled with a
1140 * COOKIE-ECHO chunk.
1141 */
1142 if (packet->has_cookie_echo)
1143 goto sctp_flush_out;
1144 }
1145 break;
1146
1147 default:
1148 /* Do nothing. */
1149 break;
1150 }
1151
1152 sctp_flush_out:
1153
1154 /* Before returning, examine all the transports touched in
1155 * this call. Right now, we bluntly force clear all the
1156 * transports. Things might change after we implement Nagle.
1157 * But such an examination is still required.
1158 *
1159 * --xguo
1160 */
1161 while ((ltransport = sctp_list_dequeue(&transport_list)) != NULL) {
1162 struct sctp_transport *t = list_entry(ltransport,
1163 struct sctp_transport,
1164 send_ready);
1165 packet = &t->packet;
1166 if (!sctp_packet_empty(packet)) {
1167 error = sctp_packet_transmit(packet, gfp);
1168 if (error < 0)
1169 asoc->base.sk->sk_err = -error;
1170 }
1171
1172 /* Clear the burst limited state, if any */
1173 sctp_transport_burst_reset(t);
1174 }
1175 }
1176
1177 /* Update unack_data based on the incoming SACK chunk */
sctp_sack_update_unack_data(struct sctp_association * assoc,struct sctp_sackhdr * sack)1178 static void sctp_sack_update_unack_data(struct sctp_association *assoc,
1179 struct sctp_sackhdr *sack)
1180 {
1181 sctp_sack_variable_t *frags;
1182 __u16 unack_data;
1183 int i;
1184
1185 unack_data = assoc->next_tsn - assoc->ctsn_ack_point - 1;
1186
1187 frags = sack->variable;
1188 for (i = 0; i < ntohs(sack->num_gap_ack_blocks); i++) {
1189 unack_data -= ((ntohs(frags[i].gab.end) -
1190 ntohs(frags[i].gab.start) + 1));
1191 }
1192
1193 assoc->unack_data = unack_data;
1194 }
1195
1196 /* This is where we REALLY process a SACK.
1197 *
1198 * Process the SACK against the outqueue. Mostly, this just frees
1199 * things off the transmitted queue.
1200 */
sctp_outq_sack(struct sctp_outq * q,struct sctp_chunk * chunk)1201 int sctp_outq_sack(struct sctp_outq *q, struct sctp_chunk *chunk)
1202 {
1203 struct sctp_association *asoc = q->asoc;
1204 struct sctp_sackhdr *sack = chunk->subh.sack_hdr;
1205 struct sctp_transport *transport;
1206 struct sctp_chunk *tchunk = NULL;
1207 struct list_head *lchunk, *transport_list, *temp;
1208 sctp_sack_variable_t *frags = sack->variable;
1209 __u32 sack_ctsn, ctsn, tsn;
1210 __u32 highest_tsn, highest_new_tsn;
1211 __u32 sack_a_rwnd;
1212 unsigned int outstanding;
1213 struct sctp_transport *primary = asoc->peer.primary_path;
1214 int count_of_newacks = 0;
1215 int gap_ack_blocks;
1216 u8 accum_moved = 0;
1217
1218 /* Grab the association's destination address list. */
1219 transport_list = &asoc->peer.transport_addr_list;
1220
1221 sack_ctsn = ntohl(sack->cum_tsn_ack);
1222 gap_ack_blocks = ntohs(sack->num_gap_ack_blocks);
1223 asoc->stats.gapcnt += gap_ack_blocks;
1224 /*
1225 * SFR-CACC algorithm:
1226 * On receipt of a SACK the sender SHOULD execute the
1227 * following statements.
1228 *
1229 * 1) If the cumulative ack in the SACK passes next tsn_at_change
1230 * on the current primary, the CHANGEOVER_ACTIVE flag SHOULD be
1231 * cleared. The CYCLING_CHANGEOVER flag SHOULD also be cleared for
1232 * all destinations.
1233 * 2) If the SACK contains gap acks and the flag CHANGEOVER_ACTIVE
1234 * is set the receiver of the SACK MUST take the following actions:
1235 *
1236 * A) Initialize the cacc_saw_newack to 0 for all destination
1237 * addresses.
1238 *
1239 * Only bother if changeover_active is set. Otherwise, this is
1240 * totally suboptimal to do on every SACK.
1241 */
1242 if (primary->cacc.changeover_active) {
1243 u8 clear_cycling = 0;
1244
1245 if (TSN_lte(primary->cacc.next_tsn_at_change, sack_ctsn)) {
1246 primary->cacc.changeover_active = 0;
1247 clear_cycling = 1;
1248 }
1249
1250 if (clear_cycling || gap_ack_blocks) {
1251 list_for_each_entry(transport, transport_list,
1252 transports) {
1253 if (clear_cycling)
1254 transport->cacc.cycling_changeover = 0;
1255 if (gap_ack_blocks)
1256 transport->cacc.cacc_saw_newack = 0;
1257 }
1258 }
1259 }
1260
1261 /* Get the highest TSN in the sack. */
1262 highest_tsn = sack_ctsn;
1263 if (gap_ack_blocks)
1264 highest_tsn += ntohs(frags[gap_ack_blocks - 1].gab.end);
1265
1266 if (TSN_lt(asoc->highest_sacked, highest_tsn))
1267 asoc->highest_sacked = highest_tsn;
1268
1269 highest_new_tsn = sack_ctsn;
1270
1271 /* Run through the retransmit queue. Credit bytes received
1272 * and free those chunks that we can.
1273 */
1274 sctp_check_transmitted(q, &q->retransmit, NULL, NULL, sack, &highest_new_tsn);
1275
1276 /* Run through the transmitted queue.
1277 * Credit bytes received and free those chunks which we can.
1278 *
1279 * This is a MASSIVE candidate for optimization.
1280 */
1281 list_for_each_entry(transport, transport_list, transports) {
1282 sctp_check_transmitted(q, &transport->transmitted,
1283 transport, &chunk->source, sack,
1284 &highest_new_tsn);
1285 /*
1286 * SFR-CACC algorithm:
1287 * C) Let count_of_newacks be the number of
1288 * destinations for which cacc_saw_newack is set.
1289 */
1290 if (transport->cacc.cacc_saw_newack)
1291 count_of_newacks++;
1292 }
1293
1294 /* Move the Cumulative TSN Ack Point if appropriate. */
1295 if (TSN_lt(asoc->ctsn_ack_point, sack_ctsn)) {
1296 asoc->ctsn_ack_point = sack_ctsn;
1297 accum_moved = 1;
1298 }
1299
1300 if (gap_ack_blocks) {
1301
1302 if (asoc->fast_recovery && accum_moved)
1303 highest_new_tsn = highest_tsn;
1304
1305 list_for_each_entry(transport, transport_list, transports)
1306 sctp_mark_missing(q, &transport->transmitted, transport,
1307 highest_new_tsn, count_of_newacks);
1308 }
1309
1310 /* Update unack_data field in the assoc. */
1311 sctp_sack_update_unack_data(asoc, sack);
1312
1313 ctsn = asoc->ctsn_ack_point;
1314
1315 /* Throw away stuff rotting on the sack queue. */
1316 list_for_each_safe(lchunk, temp, &q->sacked) {
1317 tchunk = list_entry(lchunk, struct sctp_chunk,
1318 transmitted_list);
1319 tsn = ntohl(tchunk->subh.data_hdr->tsn);
1320 if (TSN_lte(tsn, ctsn)) {
1321 list_del_init(&tchunk->transmitted_list);
1322 if (asoc->peer.prsctp_capable &&
1323 SCTP_PR_PRIO_ENABLED(chunk->sinfo.sinfo_flags))
1324 asoc->sent_cnt_removable--;
1325 sctp_chunk_free(tchunk);
1326 }
1327 }
1328
1329 /* ii) Set rwnd equal to the newly received a_rwnd minus the
1330 * number of bytes still outstanding after processing the
1331 * Cumulative TSN Ack and the Gap Ack Blocks.
1332 */
1333
1334 sack_a_rwnd = ntohl(sack->a_rwnd);
1335 asoc->peer.zero_window_announced = !sack_a_rwnd;
1336 outstanding = q->outstanding_bytes;
1337
1338 if (outstanding < sack_a_rwnd)
1339 sack_a_rwnd -= outstanding;
1340 else
1341 sack_a_rwnd = 0;
1342
1343 asoc->peer.rwnd = sack_a_rwnd;
1344
1345 sctp_generate_fwdtsn(q, sack_ctsn);
1346
1347 pr_debug("%s: sack cumulative tsn ack:0x%x\n", __func__, sack_ctsn);
1348 pr_debug("%s: cumulative tsn ack of assoc:%p is 0x%x, "
1349 "advertised peer ack point:0x%x\n", __func__, asoc, ctsn,
1350 asoc->adv_peer_ack_point);
1351
1352 return sctp_outq_is_empty(q);
1353 }
1354
1355 /* Is the outqueue empty?
1356 * The queue is empty when we have not pending data, no in-flight data
1357 * and nothing pending retransmissions.
1358 */
sctp_outq_is_empty(const struct sctp_outq * q)1359 int sctp_outq_is_empty(const struct sctp_outq *q)
1360 {
1361 return q->out_qlen == 0 && q->outstanding_bytes == 0 &&
1362 list_empty(&q->retransmit);
1363 }
1364
1365 /********************************************************************
1366 * 2nd Level Abstractions
1367 ********************************************************************/
1368
1369 /* Go through a transport's transmitted list or the association's retransmit
1370 * list and move chunks that are acked by the Cumulative TSN Ack to q->sacked.
1371 * The retransmit list will not have an associated transport.
1372 *
1373 * I added coherent debug information output. --xguo
1374 *
1375 * Instead of printing 'sacked' or 'kept' for each TSN on the
1376 * transmitted_queue, we print a range: SACKED: TSN1-TSN2, TSN3, TSN4-TSN5.
1377 * KEPT TSN6-TSN7, etc.
1378 */
sctp_check_transmitted(struct sctp_outq * q,struct list_head * transmitted_queue,struct sctp_transport * transport,union sctp_addr * saddr,struct sctp_sackhdr * sack,__u32 * highest_new_tsn_in_sack)1379 static void sctp_check_transmitted(struct sctp_outq *q,
1380 struct list_head *transmitted_queue,
1381 struct sctp_transport *transport,
1382 union sctp_addr *saddr,
1383 struct sctp_sackhdr *sack,
1384 __u32 *highest_new_tsn_in_sack)
1385 {
1386 struct list_head *lchunk;
1387 struct sctp_chunk *tchunk;
1388 struct list_head tlist;
1389 __u32 tsn;
1390 __u32 sack_ctsn;
1391 __u32 rtt;
1392 __u8 restart_timer = 0;
1393 int bytes_acked = 0;
1394 int migrate_bytes = 0;
1395 bool forward_progress = false;
1396
1397 sack_ctsn = ntohl(sack->cum_tsn_ack);
1398
1399 INIT_LIST_HEAD(&tlist);
1400
1401 /* The while loop will skip empty transmitted queues. */
1402 while (NULL != (lchunk = sctp_list_dequeue(transmitted_queue))) {
1403 tchunk = list_entry(lchunk, struct sctp_chunk,
1404 transmitted_list);
1405
1406 if (sctp_chunk_abandoned(tchunk)) {
1407 /* Move the chunk to abandoned list. */
1408 sctp_insert_list(&q->abandoned, lchunk);
1409
1410 /* If this chunk has not been acked, stop
1411 * considering it as 'outstanding'.
1412 */
1413 if (transmitted_queue != &q->retransmit &&
1414 !tchunk->tsn_gap_acked) {
1415 if (tchunk->transport)
1416 tchunk->transport->flight_size -=
1417 sctp_data_size(tchunk);
1418 q->outstanding_bytes -= sctp_data_size(tchunk);
1419 }
1420 continue;
1421 }
1422
1423 tsn = ntohl(tchunk->subh.data_hdr->tsn);
1424 if (sctp_acked(sack, tsn)) {
1425 /* If this queue is the retransmit queue, the
1426 * retransmit timer has already reclaimed
1427 * the outstanding bytes for this chunk, so only
1428 * count bytes associated with a transport.
1429 */
1430 if (transport) {
1431 /* If this chunk is being used for RTT
1432 * measurement, calculate the RTT and update
1433 * the RTO using this value.
1434 *
1435 * 6.3.1 C5) Karn's algorithm: RTT measurements
1436 * MUST NOT be made using packets that were
1437 * retransmitted (and thus for which it is
1438 * ambiguous whether the reply was for the
1439 * first instance of the packet or a later
1440 * instance).
1441 */
1442 if (!tchunk->tsn_gap_acked &&
1443 !tchunk->resent &&
1444 tchunk->rtt_in_progress) {
1445 tchunk->rtt_in_progress = 0;
1446 rtt = jiffies - tchunk->sent_at;
1447 sctp_transport_update_rto(transport,
1448 rtt);
1449 }
1450 }
1451
1452 /* If the chunk hasn't been marked as ACKED,
1453 * mark it and account bytes_acked if the
1454 * chunk had a valid transport (it will not
1455 * have a transport if ASCONF had deleted it
1456 * while DATA was outstanding).
1457 */
1458 if (!tchunk->tsn_gap_acked) {
1459 tchunk->tsn_gap_acked = 1;
1460 if (TSN_lt(*highest_new_tsn_in_sack, tsn))
1461 *highest_new_tsn_in_sack = tsn;
1462 bytes_acked += sctp_data_size(tchunk);
1463 if (!tchunk->transport)
1464 migrate_bytes += sctp_data_size(tchunk);
1465 forward_progress = true;
1466 }
1467
1468 if (TSN_lte(tsn, sack_ctsn)) {
1469 /* RFC 2960 6.3.2 Retransmission Timer Rules
1470 *
1471 * R3) Whenever a SACK is received
1472 * that acknowledges the DATA chunk
1473 * with the earliest outstanding TSN
1474 * for that address, restart T3-rtx
1475 * timer for that address with its
1476 * current RTO.
1477 */
1478 restart_timer = 1;
1479 forward_progress = true;
1480
1481 if (!tchunk->tsn_gap_acked) {
1482 /*
1483 * SFR-CACC algorithm:
1484 * 2) If the SACK contains gap acks
1485 * and the flag CHANGEOVER_ACTIVE is
1486 * set the receiver of the SACK MUST
1487 * take the following action:
1488 *
1489 * B) For each TSN t being acked that
1490 * has not been acked in any SACK so
1491 * far, set cacc_saw_newack to 1 for
1492 * the destination that the TSN was
1493 * sent to.
1494 */
1495 if (transport &&
1496 sack->num_gap_ack_blocks &&
1497 q->asoc->peer.primary_path->cacc.
1498 changeover_active)
1499 transport->cacc.cacc_saw_newack
1500 = 1;
1501 }
1502
1503 list_add_tail(&tchunk->transmitted_list,
1504 &q->sacked);
1505 } else {
1506 /* RFC2960 7.2.4, sctpimpguide-05 2.8.2
1507 * M2) Each time a SACK arrives reporting
1508 * 'Stray DATA chunk(s)' record the highest TSN
1509 * reported as newly acknowledged, call this
1510 * value 'HighestTSNinSack'. A newly
1511 * acknowledged DATA chunk is one not
1512 * previously acknowledged in a SACK.
1513 *
1514 * When the SCTP sender of data receives a SACK
1515 * chunk that acknowledges, for the first time,
1516 * the receipt of a DATA chunk, all the still
1517 * unacknowledged DATA chunks whose TSN is
1518 * older than that newly acknowledged DATA
1519 * chunk, are qualified as 'Stray DATA chunks'.
1520 */
1521 list_add_tail(lchunk, &tlist);
1522 }
1523 } else {
1524 if (tchunk->tsn_gap_acked) {
1525 pr_debug("%s: receiver reneged on data TSN:0x%x\n",
1526 __func__, tsn);
1527
1528 tchunk->tsn_gap_acked = 0;
1529
1530 if (tchunk->transport)
1531 bytes_acked -= sctp_data_size(tchunk);
1532
1533 /* RFC 2960 6.3.2 Retransmission Timer Rules
1534 *
1535 * R4) Whenever a SACK is received missing a
1536 * TSN that was previously acknowledged via a
1537 * Gap Ack Block, start T3-rtx for the
1538 * destination address to which the DATA
1539 * chunk was originally
1540 * transmitted if it is not already running.
1541 */
1542 restart_timer = 1;
1543 }
1544
1545 list_add_tail(lchunk, &tlist);
1546 }
1547 }
1548
1549 if (transport) {
1550 if (bytes_acked) {
1551 struct sctp_association *asoc = transport->asoc;
1552
1553 /* We may have counted DATA that was migrated
1554 * to this transport due to DEL-IP operation.
1555 * Subtract those bytes, since the were never
1556 * send on this transport and shouldn't be
1557 * credited to this transport.
1558 */
1559 bytes_acked -= migrate_bytes;
1560
1561 /* 8.2. When an outstanding TSN is acknowledged,
1562 * the endpoint shall clear the error counter of
1563 * the destination transport address to which the
1564 * DATA chunk was last sent.
1565 * The association's overall error counter is
1566 * also cleared.
1567 */
1568 transport->error_count = 0;
1569 transport->asoc->overall_error_count = 0;
1570 forward_progress = true;
1571
1572 /*
1573 * While in SHUTDOWN PENDING, we may have started
1574 * the T5 shutdown guard timer after reaching the
1575 * retransmission limit. Stop that timer as soon
1576 * as the receiver acknowledged any data.
1577 */
1578 if (asoc->state == SCTP_STATE_SHUTDOWN_PENDING &&
1579 del_timer(&asoc->timers
1580 [SCTP_EVENT_TIMEOUT_T5_SHUTDOWN_GUARD]))
1581 sctp_association_put(asoc);
1582
1583 /* Mark the destination transport address as
1584 * active if it is not so marked.
1585 */
1586 if ((transport->state == SCTP_INACTIVE ||
1587 transport->state == SCTP_UNCONFIRMED) &&
1588 sctp_cmp_addr_exact(&transport->ipaddr, saddr)) {
1589 sctp_assoc_control_transport(
1590 transport->asoc,
1591 transport,
1592 SCTP_TRANSPORT_UP,
1593 SCTP_RECEIVED_SACK);
1594 }
1595
1596 sctp_transport_raise_cwnd(transport, sack_ctsn,
1597 bytes_acked);
1598
1599 transport->flight_size -= bytes_acked;
1600 if (transport->flight_size == 0)
1601 transport->partial_bytes_acked = 0;
1602 q->outstanding_bytes -= bytes_acked + migrate_bytes;
1603 } else {
1604 /* RFC 2960 6.1, sctpimpguide-06 2.15.2
1605 * When a sender is doing zero window probing, it
1606 * should not timeout the association if it continues
1607 * to receive new packets from the receiver. The
1608 * reason is that the receiver MAY keep its window
1609 * closed for an indefinite time.
1610 * A sender is doing zero window probing when the
1611 * receiver's advertised window is zero, and there is
1612 * only one data chunk in flight to the receiver.
1613 *
1614 * Allow the association to timeout while in SHUTDOWN
1615 * PENDING or SHUTDOWN RECEIVED in case the receiver
1616 * stays in zero window mode forever.
1617 */
1618 if (!q->asoc->peer.rwnd &&
1619 !list_empty(&tlist) &&
1620 (sack_ctsn+2 == q->asoc->next_tsn) &&
1621 q->asoc->state < SCTP_STATE_SHUTDOWN_PENDING) {
1622 pr_debug("%s: sack received for zero window "
1623 "probe:%u\n", __func__, sack_ctsn);
1624
1625 q->asoc->overall_error_count = 0;
1626 transport->error_count = 0;
1627 }
1628 }
1629
1630 /* RFC 2960 6.3.2 Retransmission Timer Rules
1631 *
1632 * R2) Whenever all outstanding data sent to an address have
1633 * been acknowledged, turn off the T3-rtx timer of that
1634 * address.
1635 */
1636 if (!transport->flight_size) {
1637 if (del_timer(&transport->T3_rtx_timer))
1638 sctp_transport_put(transport);
1639 } else if (restart_timer) {
1640 if (!mod_timer(&transport->T3_rtx_timer,
1641 jiffies + transport->rto))
1642 sctp_transport_hold(transport);
1643 }
1644
1645 if (forward_progress) {
1646 if (transport->dst)
1647 dst_confirm(transport->dst);
1648 }
1649 }
1650
1651 list_splice(&tlist, transmitted_queue);
1652 }
1653
1654 /* Mark chunks as missing and consequently may get retransmitted. */
sctp_mark_missing(struct sctp_outq * q,struct list_head * transmitted_queue,struct sctp_transport * transport,__u32 highest_new_tsn_in_sack,int count_of_newacks)1655 static void sctp_mark_missing(struct sctp_outq *q,
1656 struct list_head *transmitted_queue,
1657 struct sctp_transport *transport,
1658 __u32 highest_new_tsn_in_sack,
1659 int count_of_newacks)
1660 {
1661 struct sctp_chunk *chunk;
1662 __u32 tsn;
1663 char do_fast_retransmit = 0;
1664 struct sctp_association *asoc = q->asoc;
1665 struct sctp_transport *primary = asoc->peer.primary_path;
1666
1667 list_for_each_entry(chunk, transmitted_queue, transmitted_list) {
1668
1669 tsn = ntohl(chunk->subh.data_hdr->tsn);
1670
1671 /* RFC 2960 7.2.4, sctpimpguide-05 2.8.2 M3) Examine all
1672 * 'Unacknowledged TSN's', if the TSN number of an
1673 * 'Unacknowledged TSN' is smaller than the 'HighestTSNinSack'
1674 * value, increment the 'TSN.Missing.Report' count on that
1675 * chunk if it has NOT been fast retransmitted or marked for
1676 * fast retransmit already.
1677 */
1678 if (chunk->fast_retransmit == SCTP_CAN_FRTX &&
1679 !chunk->tsn_gap_acked &&
1680 TSN_lt(tsn, highest_new_tsn_in_sack)) {
1681
1682 /* SFR-CACC may require us to skip marking
1683 * this chunk as missing.
1684 */
1685 if (!transport || !sctp_cacc_skip(primary,
1686 chunk->transport,
1687 count_of_newacks, tsn)) {
1688 chunk->tsn_missing_report++;
1689
1690 pr_debug("%s: tsn:0x%x missing counter:%d\n",
1691 __func__, tsn, chunk->tsn_missing_report);
1692 }
1693 }
1694 /*
1695 * M4) If any DATA chunk is found to have a
1696 * 'TSN.Missing.Report'
1697 * value larger than or equal to 3, mark that chunk for
1698 * retransmission and start the fast retransmit procedure.
1699 */
1700
1701 if (chunk->tsn_missing_report >= 3) {
1702 chunk->fast_retransmit = SCTP_NEED_FRTX;
1703 do_fast_retransmit = 1;
1704 }
1705 }
1706
1707 if (transport) {
1708 if (do_fast_retransmit)
1709 sctp_retransmit(q, transport, SCTP_RTXR_FAST_RTX);
1710
1711 pr_debug("%s: transport:%p, cwnd:%d, ssthresh:%d, "
1712 "flight_size:%d, pba:%d\n", __func__, transport,
1713 transport->cwnd, transport->ssthresh,
1714 transport->flight_size, transport->partial_bytes_acked);
1715 }
1716 }
1717
1718 /* Is the given TSN acked by this packet? */
sctp_acked(struct sctp_sackhdr * sack,__u32 tsn)1719 static int sctp_acked(struct sctp_sackhdr *sack, __u32 tsn)
1720 {
1721 int i;
1722 sctp_sack_variable_t *frags;
1723 __u16 tsn_offset, blocks;
1724 __u32 ctsn = ntohl(sack->cum_tsn_ack);
1725
1726 if (TSN_lte(tsn, ctsn))
1727 goto pass;
1728
1729 /* 3.3.4 Selective Acknowledgement (SACK) (3):
1730 *
1731 * Gap Ack Blocks:
1732 * These fields contain the Gap Ack Blocks. They are repeated
1733 * for each Gap Ack Block up to the number of Gap Ack Blocks
1734 * defined in the Number of Gap Ack Blocks field. All DATA
1735 * chunks with TSNs greater than or equal to (Cumulative TSN
1736 * Ack + Gap Ack Block Start) and less than or equal to
1737 * (Cumulative TSN Ack + Gap Ack Block End) of each Gap Ack
1738 * Block are assumed to have been received correctly.
1739 */
1740
1741 frags = sack->variable;
1742 blocks = ntohs(sack->num_gap_ack_blocks);
1743 tsn_offset = tsn - ctsn;
1744 for (i = 0; i < blocks; ++i) {
1745 if (tsn_offset >= ntohs(frags[i].gab.start) &&
1746 tsn_offset <= ntohs(frags[i].gab.end))
1747 goto pass;
1748 }
1749
1750 return 0;
1751 pass:
1752 return 1;
1753 }
1754
sctp_get_skip_pos(struct sctp_fwdtsn_skip * skiplist,int nskips,__be16 stream)1755 static inline int sctp_get_skip_pos(struct sctp_fwdtsn_skip *skiplist,
1756 int nskips, __be16 stream)
1757 {
1758 int i;
1759
1760 for (i = 0; i < nskips; i++) {
1761 if (skiplist[i].stream == stream)
1762 return i;
1763 }
1764 return i;
1765 }
1766
1767 /* Create and add a fwdtsn chunk to the outq's control queue if needed. */
sctp_generate_fwdtsn(struct sctp_outq * q,__u32 ctsn)1768 static void sctp_generate_fwdtsn(struct sctp_outq *q, __u32 ctsn)
1769 {
1770 struct sctp_association *asoc = q->asoc;
1771 struct sctp_chunk *ftsn_chunk = NULL;
1772 struct sctp_fwdtsn_skip ftsn_skip_arr[10];
1773 int nskips = 0;
1774 int skip_pos = 0;
1775 __u32 tsn;
1776 struct sctp_chunk *chunk;
1777 struct list_head *lchunk, *temp;
1778
1779 if (!asoc->peer.prsctp_capable)
1780 return;
1781
1782 /* PR-SCTP C1) Let SackCumAck be the Cumulative TSN ACK carried in the
1783 * received SACK.
1784 *
1785 * If (Advanced.Peer.Ack.Point < SackCumAck), then update
1786 * Advanced.Peer.Ack.Point to be equal to SackCumAck.
1787 */
1788 if (TSN_lt(asoc->adv_peer_ack_point, ctsn))
1789 asoc->adv_peer_ack_point = ctsn;
1790
1791 /* PR-SCTP C2) Try to further advance the "Advanced.Peer.Ack.Point"
1792 * locally, that is, to move "Advanced.Peer.Ack.Point" up as long as
1793 * the chunk next in the out-queue space is marked as "abandoned" as
1794 * shown in the following example:
1795 *
1796 * Assuming that a SACK arrived with the Cumulative TSN ACK 102
1797 * and the Advanced.Peer.Ack.Point is updated to this value:
1798 *
1799 * out-queue at the end of ==> out-queue after Adv.Ack.Point
1800 * normal SACK processing local advancement
1801 * ... ...
1802 * Adv.Ack.Pt-> 102 acked 102 acked
1803 * 103 abandoned 103 abandoned
1804 * 104 abandoned Adv.Ack.P-> 104 abandoned
1805 * 105 105
1806 * 106 acked 106 acked
1807 * ... ...
1808 *
1809 * In this example, the data sender successfully advanced the
1810 * "Advanced.Peer.Ack.Point" from 102 to 104 locally.
1811 */
1812 list_for_each_safe(lchunk, temp, &q->abandoned) {
1813 chunk = list_entry(lchunk, struct sctp_chunk,
1814 transmitted_list);
1815 tsn = ntohl(chunk->subh.data_hdr->tsn);
1816
1817 /* Remove any chunks in the abandoned queue that are acked by
1818 * the ctsn.
1819 */
1820 if (TSN_lte(tsn, ctsn)) {
1821 list_del_init(lchunk);
1822 sctp_chunk_free(chunk);
1823 } else {
1824 if (TSN_lte(tsn, asoc->adv_peer_ack_point+1)) {
1825 asoc->adv_peer_ack_point = tsn;
1826 if (chunk->chunk_hdr->flags &
1827 SCTP_DATA_UNORDERED)
1828 continue;
1829 skip_pos = sctp_get_skip_pos(&ftsn_skip_arr[0],
1830 nskips,
1831 chunk->subh.data_hdr->stream);
1832 ftsn_skip_arr[skip_pos].stream =
1833 chunk->subh.data_hdr->stream;
1834 ftsn_skip_arr[skip_pos].ssn =
1835 chunk->subh.data_hdr->ssn;
1836 if (skip_pos == nskips)
1837 nskips++;
1838 if (nskips == 10)
1839 break;
1840 } else
1841 break;
1842 }
1843 }
1844
1845 /* PR-SCTP C3) If, after step C1 and C2, the "Advanced.Peer.Ack.Point"
1846 * is greater than the Cumulative TSN ACK carried in the received
1847 * SACK, the data sender MUST send the data receiver a FORWARD TSN
1848 * chunk containing the latest value of the
1849 * "Advanced.Peer.Ack.Point".
1850 *
1851 * C4) For each "abandoned" TSN the sender of the FORWARD TSN SHOULD
1852 * list each stream and sequence number in the forwarded TSN. This
1853 * information will enable the receiver to easily find any
1854 * stranded TSN's waiting on stream reorder queues. Each stream
1855 * SHOULD only be reported once; this means that if multiple
1856 * abandoned messages occur in the same stream then only the
1857 * highest abandoned stream sequence number is reported. If the
1858 * total size of the FORWARD TSN does NOT fit in a single MTU then
1859 * the sender of the FORWARD TSN SHOULD lower the
1860 * Advanced.Peer.Ack.Point to the last TSN that will fit in a
1861 * single MTU.
1862 */
1863 if (asoc->adv_peer_ack_point > ctsn)
1864 ftsn_chunk = sctp_make_fwdtsn(asoc, asoc->adv_peer_ack_point,
1865 nskips, &ftsn_skip_arr[0]);
1866
1867 if (ftsn_chunk) {
1868 list_add_tail(&ftsn_chunk->list, &q->control_chunk_list);
1869 SCTP_INC_STATS(sock_net(asoc->base.sk), SCTP_MIB_OUTCTRLCHUNKS);
1870 }
1871 }
1872