1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /* SCTP kernel implementation
3 * (C) Copyright IBM Corp. 2001, 2004
4 * Copyright (c) 1999-2000 Cisco, Inc.
5 * Copyright (c) 1999-2001 Motorola, Inc.
6 * Copyright (c) 2001-2003 Intel Corp.
7 *
8 * This file is part of the SCTP kernel implementation
9 *
10 * These functions implement the sctp_outq class. The outqueue handles
11 * bundling and queueing of outgoing SCTP chunks.
12 *
13 * Please send any bug reports or fixes you make to the
14 * email address(es):
15 * lksctp developers <linux-sctp@vger.kernel.org>
16 *
17 * Written or modified by:
18 * La Monte H.P. Yarroll <piggy@acm.org>
19 * Karl Knutson <karl@athena.chicago.il.us>
20 * Perry Melange <pmelange@null.cc.uic.edu>
21 * Xingang Guo <xingang.guo@intel.com>
22 * Hui Huang <hui.huang@nokia.com>
23 * Sridhar Samudrala <sri@us.ibm.com>
24 * Jon Grimm <jgrimm@us.ibm.com>
25 */
26
27 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
28
29 #include <linux/types.h>
30 #include <linux/list.h> /* For struct list_head */
31 #include <linux/socket.h>
32 #include <linux/ip.h>
33 #include <linux/slab.h>
34 #include <net/sock.h> /* For skb_set_owner_w */
35
36 #include <net/sctp/sctp.h>
37 #include <net/sctp/sm.h>
38 #include <net/sctp/stream_sched.h>
39 #include <trace/events/sctp.h>
40
41 /* Declare internal functions here. */
42 static int sctp_acked(struct sctp_sackhdr *sack, __u32 tsn);
43 static void sctp_check_transmitted(struct sctp_outq *q,
44 struct list_head *transmitted_queue,
45 struct sctp_transport *transport,
46 union sctp_addr *saddr,
47 struct sctp_sackhdr *sack,
48 __u32 *highest_new_tsn);
49
50 static void sctp_mark_missing(struct sctp_outq *q,
51 struct list_head *transmitted_queue,
52 struct sctp_transport *transport,
53 __u32 highest_new_tsn,
54 int count_of_newacks);
55
56 static void sctp_outq_flush(struct sctp_outq *q, int rtx_timeout, gfp_t gfp);
57
58 /* Add data to the front of the queue. */
59 static inline void sctp_outq_head_data(struct sctp_outq *q,
60 struct sctp_chunk *ch)
61 {
62 struct sctp_stream_out_ext *oute;
63 __u16 stream;
64
65 list_add(&ch->list, &q->out_chunk_list);
66 q->out_qlen += ch->skb->len;
67
68 stream = sctp_chunk_stream_no(ch);
69 oute = SCTP_SO(&q->asoc->stream, stream)->ext;
70 list_add(&ch->stream_list, &oute->outq);
71 }
72
73 /* Take data from the front of the queue. */
74 static inline struct sctp_chunk *sctp_outq_dequeue_data(struct sctp_outq *q)
75 {
76 return q->sched->dequeue(q);
77 }
78
79 /* Add data chunk to the end of the queue. */
80 static inline void sctp_outq_tail_data(struct sctp_outq *q,
81 struct sctp_chunk *ch)
82 {
83 struct sctp_stream_out_ext *oute;
84 __u16 stream;
85
86 list_add_tail(&ch->list, &q->out_chunk_list);
87 q->out_qlen += ch->skb->len;
88
89 stream = sctp_chunk_stream_no(ch);
90 oute = SCTP_SO(&q->asoc->stream, stream)->ext;
91 list_add_tail(&ch->stream_list, &oute->outq);
92 }
93
94 /*
95 * SFR-CACC algorithm:
96 * D) If count_of_newacks is greater than or equal to 2
97 * and t was not sent to the current primary then the
98 * sender MUST NOT increment missing report count for t.
99 */
100 static inline int sctp_cacc_skip_3_1_d(struct sctp_transport *primary,
101 struct sctp_transport *transport,
102 int count_of_newacks)
103 {
104 if (count_of_newacks >= 2 && transport != primary)
105 return 1;
106 return 0;
107 }
108
109 /*
110 * SFR-CACC algorithm:
111 * F) If count_of_newacks is less than 2, let d be the
112 * destination to which t was sent. If cacc_saw_newack
113 * is 0 for destination d, then the sender MUST NOT
114 * increment missing report count for t.
115 */
116 static inline int sctp_cacc_skip_3_1_f(struct sctp_transport *transport,
117 int count_of_newacks)
118 {
119 if (count_of_newacks < 2 &&
120 (transport && !transport->cacc.cacc_saw_newack))
121 return 1;
122 return 0;
123 }
124
125 /*
126 * SFR-CACC algorithm:
127 * 3.1) If CYCLING_CHANGEOVER is 0, the sender SHOULD
128 * execute steps C, D, F.
129 *
130 * C has been implemented in sctp_outq_sack
131 */
132 static inline int sctp_cacc_skip_3_1(struct sctp_transport *primary,
133 struct sctp_transport *transport,
134 int count_of_newacks)
135 {
136 if (!primary->cacc.cycling_changeover) {
137 if (sctp_cacc_skip_3_1_d(primary, transport, count_of_newacks))
138 return 1;
139 if (sctp_cacc_skip_3_1_f(transport, count_of_newacks))
140 return 1;
141 return 0;
142 }
143 return 0;
144 }
145
146 /*
147 * SFR-CACC algorithm:
148 * 3.2) Else if CYCLING_CHANGEOVER is 1, and t is less
149 * than next_tsn_at_change of the current primary, then
150 * the sender MUST NOT increment missing report count
151 * for t.
152 */
153 static inline int sctp_cacc_skip_3_2(struct sctp_transport *primary, __u32 tsn)
154 {
155 if (primary->cacc.cycling_changeover &&
156 TSN_lt(tsn, primary->cacc.next_tsn_at_change))
157 return 1;
158 return 0;
159 }
160
161 /*
162 * SFR-CACC algorithm:
163 * 3) If the missing report count for TSN t is to be
164 * incremented according to [RFC2960] and
165 * [SCTP_STEWART-2002], and CHANGEOVER_ACTIVE is set,
166 * then the sender MUST further execute steps 3.1 and
167 * 3.2 to determine if the missing report count for
168 * TSN t SHOULD NOT be incremented.
169 *
170 * 3.3) If 3.1 and 3.2 do not dictate that the missing
171 * report count for t should not be incremented, then
172 * the sender SHOULD increment missing report count for
173 * t (according to [RFC2960] and [SCTP_STEWART_2002]).
174 */
175 static inline int sctp_cacc_skip(struct sctp_transport *primary,
176 struct sctp_transport *transport,
177 int count_of_newacks,
178 __u32 tsn)
179 {
180 if (primary->cacc.changeover_active &&
181 (sctp_cacc_skip_3_1(primary, transport, count_of_newacks) ||
182 sctp_cacc_skip_3_2(primary, tsn)))
183 return 1;
184 return 0;
185 }
186
187 /* Initialize an existing sctp_outq. This does the boring stuff.
188 * You still need to define handlers if you really want to DO
189 * something with this structure...
190 */
191 void sctp_outq_init(struct sctp_association *asoc, struct sctp_outq *q)
192 {
193 memset(q, 0, sizeof(struct sctp_outq));
194
195 q->asoc = asoc;
196 INIT_LIST_HEAD(&q->out_chunk_list);
197 INIT_LIST_HEAD(&q->control_chunk_list);
198 INIT_LIST_HEAD(&q->retransmit);
199 INIT_LIST_HEAD(&q->sacked);
200 INIT_LIST_HEAD(&q->abandoned);
201 sctp_sched_set_sched(asoc, sctp_sk(asoc->base.sk)->default_ss);
202 }
203
204 /* Free the outqueue structure and any related pending chunks.
205 */
206 static void __sctp_outq_teardown(struct sctp_outq *q)
207 {
208 struct sctp_transport *transport;
209 struct list_head *lchunk, *temp;
210 struct sctp_chunk *chunk, *tmp;
211
212 /* Throw away unacknowledged chunks. */
213 list_for_each_entry(transport, &q->asoc->peer.transport_addr_list,
214 transports) {
215 while ((lchunk = sctp_list_dequeue(&transport->transmitted)) != NULL) {
216 chunk = list_entry(lchunk, struct sctp_chunk,
217 transmitted_list);
218 /* Mark as part of a failed message. */
219 sctp_chunk_fail(chunk, q->error);
220 sctp_chunk_free(chunk);
221 }
222 }
223
224 /* Throw away chunks that have been gap ACKed. */
225 list_for_each_safe(lchunk, temp, &q->sacked) {
226 list_del_init(lchunk);
227 chunk = list_entry(lchunk, struct sctp_chunk,
228 transmitted_list);
229 sctp_chunk_fail(chunk, q->error);
230 sctp_chunk_free(chunk);
231 }
232
233 /* Throw away any chunks in the retransmit queue. */
234 list_for_each_safe(lchunk, temp, &q->retransmit) {
235 list_del_init(lchunk);
236 chunk = list_entry(lchunk, struct sctp_chunk,
237 transmitted_list);
238 sctp_chunk_fail(chunk, q->error);
239 sctp_chunk_free(chunk);
240 }
241
242 /* Throw away any chunks that are in the abandoned queue. */
243 list_for_each_safe(lchunk, temp, &q->abandoned) {
244 list_del_init(lchunk);
245 chunk = list_entry(lchunk, struct sctp_chunk,
246 transmitted_list);
247 sctp_chunk_fail(chunk, q->error);
248 sctp_chunk_free(chunk);
249 }
250
251 /* Throw away any leftover data chunks. */
252 while ((chunk = sctp_outq_dequeue_data(q)) != NULL) {
253 sctp_sched_dequeue_done(q, chunk);
254
255 /* Mark as send failure. */
256 sctp_chunk_fail(chunk, q->error);
257 sctp_chunk_free(chunk);
258 }
259
260 /* Throw away any leftover control chunks. */
261 list_for_each_entry_safe(chunk, tmp, &q->control_chunk_list, list) {
262 list_del_init(&chunk->list);
263 sctp_chunk_free(chunk);
264 }
265 }
266
267 void sctp_outq_teardown(struct sctp_outq *q)
268 {
269 __sctp_outq_teardown(q);
270 sctp_outq_init(q->asoc, q);
271 }
272
273 /* Free the outqueue structure and any related pending chunks. */
274 void sctp_outq_free(struct sctp_outq *q)
275 {
276 /* Throw away leftover chunks. */
277 __sctp_outq_teardown(q);
278 }
279
280 /* Put a new chunk in an sctp_outq. */
281 void sctp_outq_tail(struct sctp_outq *q, struct sctp_chunk *chunk, gfp_t gfp)
282 {
283 struct net *net = q->asoc->base.net;
284
285 pr_debug("%s: outq:%p, chunk:%p[%s]\n", __func__, q, chunk,
286 chunk && chunk->chunk_hdr ?
287 sctp_cname(SCTP_ST_CHUNK(chunk->chunk_hdr->type)) :
288 "illegal chunk");
289
290 /* If it is data, queue it up, otherwise, send it
291 * immediately.
292 */
293 if (sctp_chunk_is_data(chunk)) {
294 pr_debug("%s: outqueueing: outq:%p, chunk:%p[%s])\n",
295 __func__, q, chunk, chunk && chunk->chunk_hdr ?
296 sctp_cname(SCTP_ST_CHUNK(chunk->chunk_hdr->type)) :
297 "illegal chunk");
298
299 sctp_outq_tail_data(q, chunk);
300 if (chunk->asoc->peer.prsctp_capable &&
301 SCTP_PR_PRIO_ENABLED(chunk->sinfo.sinfo_flags))
302 chunk->asoc->sent_cnt_removable++;
303 if (chunk->chunk_hdr->flags & SCTP_DATA_UNORDERED)
304 SCTP_INC_STATS(net, SCTP_MIB_OUTUNORDERCHUNKS);
305 else
306 SCTP_INC_STATS(net, SCTP_MIB_OUTORDERCHUNKS);
307 } else {
308 list_add_tail(&chunk->list, &q->control_chunk_list);
309 SCTP_INC_STATS(net, SCTP_MIB_OUTCTRLCHUNKS);
310 }
311
312 if (!q->cork)
313 sctp_outq_flush(q, 0, gfp);
314 }
315
316 /* Insert a chunk into the sorted list based on the TSNs. The retransmit list
317 * and the abandoned list are in ascending order.
318 */
319 static void sctp_insert_list(struct list_head *head, struct list_head *new)
320 {
321 struct list_head *pos;
322 struct sctp_chunk *nchunk, *lchunk;
323 __u32 ntsn, ltsn;
324 int done = 0;
325
326 nchunk = list_entry(new, struct sctp_chunk, transmitted_list);
327 ntsn = ntohl(nchunk->subh.data_hdr->tsn);
328
329 list_for_each(pos, head) {
330 lchunk = list_entry(pos, struct sctp_chunk, transmitted_list);
331 ltsn = ntohl(lchunk->subh.data_hdr->tsn);
332 if (TSN_lt(ntsn, ltsn)) {
333 list_add(new, pos->prev);
334 done = 1;
335 break;
336 }
337 }
338 if (!done)
339 list_add_tail(new, head);
340 }
341
342 static int sctp_prsctp_prune_sent(struct sctp_association *asoc,
343 struct sctp_sndrcvinfo *sinfo,
344 struct list_head *queue, int msg_len)
345 {
346 struct sctp_chunk *chk, *temp;
347
348 list_for_each_entry_safe(chk, temp, queue, transmitted_list) {
349 struct sctp_stream_out *streamout;
350
351 if (!chk->msg->abandoned &&
352 (!SCTP_PR_PRIO_ENABLED(chk->sinfo.sinfo_flags) ||
353 chk->sinfo.sinfo_timetolive <= sinfo->sinfo_timetolive))
354 continue;
355
356 chk->msg->abandoned = 1;
357 list_del_init(&chk->transmitted_list);
358 sctp_insert_list(&asoc->outqueue.abandoned,
359 &chk->transmitted_list);
360
361 streamout = SCTP_SO(&asoc->stream, chk->sinfo.sinfo_stream);
362 asoc->sent_cnt_removable--;
363 asoc->abandoned_sent[SCTP_PR_INDEX(PRIO)]++;
364 streamout->ext->abandoned_sent[SCTP_PR_INDEX(PRIO)]++;
365
366 if (queue != &asoc->outqueue.retransmit &&
367 !chk->tsn_gap_acked) {
368 if (chk->transport)
369 chk->transport->flight_size -=
370 sctp_data_size(chk);
371 asoc->outqueue.outstanding_bytes -= sctp_data_size(chk);
372 }
373
374 msg_len -= chk->skb->truesize + sizeof(struct sctp_chunk);
375 if (msg_len <= 0)
376 break;
377 }
378
379 return msg_len;
380 }
381
382 static int sctp_prsctp_prune_unsent(struct sctp_association *asoc,
383 struct sctp_sndrcvinfo *sinfo, int msg_len)
384 {
385 struct sctp_outq *q = &asoc->outqueue;
386 struct sctp_chunk *chk, *temp;
387 struct sctp_stream_out *sout;
388
389 q->sched->unsched_all(&asoc->stream);
390
391 list_for_each_entry_safe(chk, temp, &q->out_chunk_list, list) {
392 if (!chk->msg->abandoned &&
393 (!(chk->chunk_hdr->flags & SCTP_DATA_FIRST_FRAG) ||
394 !SCTP_PR_PRIO_ENABLED(chk->sinfo.sinfo_flags) ||
395 chk->sinfo.sinfo_timetolive <= sinfo->sinfo_timetolive))
396 continue;
397
398 chk->msg->abandoned = 1;
399 sctp_sched_dequeue_common(q, chk);
400 asoc->sent_cnt_removable--;
401 asoc->abandoned_unsent[SCTP_PR_INDEX(PRIO)]++;
402
403 sout = SCTP_SO(&asoc->stream, chk->sinfo.sinfo_stream);
404 sout->ext->abandoned_unsent[SCTP_PR_INDEX(PRIO)]++;
405
406 /* clear out_curr if all frag chunks are pruned */
407 if (asoc->stream.out_curr == sout &&
408 list_is_last(&chk->frag_list, &chk->msg->chunks))
409 asoc->stream.out_curr = NULL;
410
411 msg_len -= chk->skb->truesize + sizeof(struct sctp_chunk);
412 sctp_chunk_free(chk);
413 if (msg_len <= 0)
414 break;
415 }
416
417 q->sched->sched_all(&asoc->stream);
418
419 return msg_len;
420 }
421
422 /* Abandon the chunks according their priorities */
423 void sctp_prsctp_prune(struct sctp_association *asoc,
424 struct sctp_sndrcvinfo *sinfo, int msg_len)
425 {
426 struct sctp_transport *transport;
427
428 if (!asoc->peer.prsctp_capable || !asoc->sent_cnt_removable)
429 return;
430
431 msg_len = sctp_prsctp_prune_sent(asoc, sinfo,
432 &asoc->outqueue.retransmit,
433 msg_len);
434 if (msg_len <= 0)
435 return;
436
437 list_for_each_entry(transport, &asoc->peer.transport_addr_list,
438 transports) {
439 msg_len = sctp_prsctp_prune_sent(asoc, sinfo,
440 &transport->transmitted,
441 msg_len);
442 if (msg_len <= 0)
443 return;
444 }
445
446 sctp_prsctp_prune_unsent(asoc, sinfo, msg_len);
447 }
448
449 /* Mark all the eligible packets on a transport for retransmission. */
450 void sctp_retransmit_mark(struct sctp_outq *q,
451 struct sctp_transport *transport,
452 __u8 reason)
453 {
454 struct list_head *lchunk, *ltemp;
455 struct sctp_chunk *chunk;
456
457 /* Walk through the specified transmitted queue. */
458 list_for_each_safe(lchunk, ltemp, &transport->transmitted) {
459 chunk = list_entry(lchunk, struct sctp_chunk,
460 transmitted_list);
461
462 /* If the chunk is abandoned, move it to abandoned list. */
463 if (sctp_chunk_abandoned(chunk)) {
464 list_del_init(lchunk);
465 sctp_insert_list(&q->abandoned, lchunk);
466
467 /* If this chunk has not been previousely acked,
468 * stop considering it 'outstanding'. Our peer
469 * will most likely never see it since it will
470 * not be retransmitted
471 */
472 if (!chunk->tsn_gap_acked) {
473 if (chunk->transport)
474 chunk->transport->flight_size -=
475 sctp_data_size(chunk);
476 q->outstanding_bytes -= sctp_data_size(chunk);
477 q->asoc->peer.rwnd += sctp_data_size(chunk);
478 }
479 continue;
480 }
481
482 /* If we are doing retransmission due to a timeout or pmtu
483 * discovery, only the chunks that are not yet acked should
484 * be added to the retransmit queue.
485 */
486 if ((reason == SCTP_RTXR_FAST_RTX &&
487 (chunk->fast_retransmit == SCTP_NEED_FRTX)) ||
488 (reason != SCTP_RTXR_FAST_RTX && !chunk->tsn_gap_acked)) {
489 /* RFC 2960 6.2.1 Processing a Received SACK
490 *
491 * C) Any time a DATA chunk is marked for
492 * retransmission (via either T3-rtx timer expiration
493 * (Section 6.3.3) or via fast retransmit
494 * (Section 7.2.4)), add the data size of those
495 * chunks to the rwnd.
496 */
497 q->asoc->peer.rwnd += sctp_data_size(chunk);
498 q->outstanding_bytes -= sctp_data_size(chunk);
499 if (chunk->transport)
500 transport->flight_size -= sctp_data_size(chunk);
501
502 /* sctpimpguide-05 Section 2.8.2
503 * M5) If a T3-rtx timer expires, the
504 * 'TSN.Missing.Report' of all affected TSNs is set
505 * to 0.
506 */
507 chunk->tsn_missing_report = 0;
508
509 /* If a chunk that is being used for RTT measurement
510 * has to be retransmitted, we cannot use this chunk
511 * anymore for RTT measurements. Reset rto_pending so
512 * that a new RTT measurement is started when a new
513 * data chunk is sent.
514 */
515 if (chunk->rtt_in_progress) {
516 chunk->rtt_in_progress = 0;
517 transport->rto_pending = 0;
518 }
519
520 /* Move the chunk to the retransmit queue. The chunks
521 * on the retransmit queue are always kept in order.
522 */
523 list_del_init(lchunk);
524 sctp_insert_list(&q->retransmit, lchunk);
525 }
526 }
527
528 pr_debug("%s: transport:%p, reason:%d, cwnd:%d, ssthresh:%d, "
529 "flight_size:%d, pba:%d\n", __func__, transport, reason,
530 transport->cwnd, transport->ssthresh, transport->flight_size,
531 transport->partial_bytes_acked);
532 }
533
534 /* Mark all the eligible packets on a transport for retransmission and force
535 * one packet out.
536 */
537 void sctp_retransmit(struct sctp_outq *q, struct sctp_transport *transport,
538 enum sctp_retransmit_reason reason)
539 {
540 struct net *net = q->asoc->base.net;
541
542 switch (reason) {
543 case SCTP_RTXR_T3_RTX:
544 SCTP_INC_STATS(net, SCTP_MIB_T3_RETRANSMITS);
545 sctp_transport_lower_cwnd(transport, SCTP_LOWER_CWND_T3_RTX);
546 /* Update the retran path if the T3-rtx timer has expired for
547 * the current retran path.
548 */
549 if (transport == transport->asoc->peer.retran_path)
550 sctp_assoc_update_retran_path(transport->asoc);
551 transport->asoc->rtx_data_chunks +=
552 transport->asoc->unack_data;
553 if (transport->pl.state == SCTP_PL_COMPLETE &&
554 transport->asoc->unack_data)
555 sctp_transport_reset_probe_timer(transport);
556 break;
557 case SCTP_RTXR_FAST_RTX:
558 SCTP_INC_STATS(net, SCTP_MIB_FAST_RETRANSMITS);
559 sctp_transport_lower_cwnd(transport, SCTP_LOWER_CWND_FAST_RTX);
560 q->fast_rtx = 1;
561 break;
562 case SCTP_RTXR_PMTUD:
563 SCTP_INC_STATS(net, SCTP_MIB_PMTUD_RETRANSMITS);
564 break;
565 case SCTP_RTXR_T1_RTX:
566 SCTP_INC_STATS(net, SCTP_MIB_T1_RETRANSMITS);
567 transport->asoc->init_retries++;
568 break;
569 default:
570 BUG();
571 }
572
573 sctp_retransmit_mark(q, transport, reason);
574
575 /* PR-SCTP A5) Any time the T3-rtx timer expires, on any destination,
576 * the sender SHOULD try to advance the "Advanced.Peer.Ack.Point" by
577 * following the procedures outlined in C1 - C5.
578 */
579 if (reason == SCTP_RTXR_T3_RTX)
580 q->asoc->stream.si->generate_ftsn(q, q->asoc->ctsn_ack_point);
581
582 /* Flush the queues only on timeout, since fast_rtx is only
583 * triggered during sack processing and the queue
584 * will be flushed at the end.
585 */
586 if (reason != SCTP_RTXR_FAST_RTX)
587 sctp_outq_flush(q, /* rtx_timeout */ 1, GFP_ATOMIC);
588 }
589
590 /*
591 * Transmit DATA chunks on the retransmit queue. Upon return from
592 * __sctp_outq_flush_rtx() the packet 'pkt' may contain chunks which
593 * need to be transmitted by the caller.
594 * We assume that pkt->transport has already been set.
595 *
596 * The return value is a normal kernel error return value.
597 */
598 static int __sctp_outq_flush_rtx(struct sctp_outq *q, struct sctp_packet *pkt,
599 int rtx_timeout, int *start_timer, gfp_t gfp)
600 {
601 struct sctp_transport *transport = pkt->transport;
602 struct sctp_chunk *chunk, *chunk1;
603 struct list_head *lqueue;
604 enum sctp_xmit status;
605 int error = 0;
606 int timer = 0;
607 int done = 0;
608 int fast_rtx;
609
610 lqueue = &q->retransmit;
611 fast_rtx = q->fast_rtx;
612
613 /* This loop handles time-out retransmissions, fast retransmissions,
614 * and retransmissions due to opening of whindow.
615 *
616 * RFC 2960 6.3.3 Handle T3-rtx Expiration
617 *
618 * E3) Determine how many of the earliest (i.e., lowest TSN)
619 * outstanding DATA chunks for the address for which the
620 * T3-rtx has expired will fit into a single packet, subject
621 * to the MTU constraint for the path corresponding to the
622 * destination transport address to which the retransmission
623 * is being sent (this may be different from the address for
624 * which the timer expires [see Section 6.4]). Call this value
625 * K. Bundle and retransmit those K DATA chunks in a single
626 * packet to the destination endpoint.
627 *
628 * [Just to be painfully clear, if we are retransmitting
629 * because a timeout just happened, we should send only ONE
630 * packet of retransmitted data.]
631 *
632 * For fast retransmissions we also send only ONE packet. However,
633 * if we are just flushing the queue due to open window, we'll
634 * try to send as much as possible.
635 */
636 list_for_each_entry_safe(chunk, chunk1, lqueue, transmitted_list) {
637 /* If the chunk is abandoned, move it to abandoned list. */
638 if (sctp_chunk_abandoned(chunk)) {
639 list_del_init(&chunk->transmitted_list);
640 sctp_insert_list(&q->abandoned,
641 &chunk->transmitted_list);
642 continue;
643 }
644
645 /* Make sure that Gap Acked TSNs are not retransmitted. A
646 * simple approach is just to move such TSNs out of the
647 * way and into a 'transmitted' queue and skip to the
648 * next chunk.
649 */
650 if (chunk->tsn_gap_acked) {
651 list_move_tail(&chunk->transmitted_list,
652 &transport->transmitted);
653 continue;
654 }
655
656 /* If we are doing fast retransmit, ignore non-fast_rtransmit
657 * chunks
658 */
659 if (fast_rtx && !chunk->fast_retransmit)
660 continue;
661
662 redo:
663 /* Attempt to append this chunk to the packet. */
664 status = sctp_packet_append_chunk(pkt, chunk);
665
666 switch (status) {
667 case SCTP_XMIT_PMTU_FULL:
668 if (!pkt->has_data && !pkt->has_cookie_echo) {
669 /* If this packet did not contain DATA then
670 * retransmission did not happen, so do it
671 * again. We'll ignore the error here since
672 * control chunks are already freed so there
673 * is nothing we can do.
674 */
675 sctp_packet_transmit(pkt, gfp);
676 goto redo;
677 }
678
679 /* Send this packet. */
680 error = sctp_packet_transmit(pkt, gfp);
681
682 /* If we are retransmitting, we should only
683 * send a single packet.
684 * Otherwise, try appending this chunk again.
685 */
686 if (rtx_timeout || fast_rtx)
687 done = 1;
688 else
689 goto redo;
690
691 /* Bundle next chunk in the next round. */
692 break;
693
694 case SCTP_XMIT_RWND_FULL:
695 /* Send this packet. */
696 error = sctp_packet_transmit(pkt, gfp);
697
698 /* Stop sending DATA as there is no more room
699 * at the receiver.
700 */
701 done = 1;
702 break;
703
704 case SCTP_XMIT_DELAY:
705 /* Send this packet. */
706 error = sctp_packet_transmit(pkt, gfp);
707
708 /* Stop sending DATA because of nagle delay. */
709 done = 1;
710 break;
711
712 default:
713 /* The append was successful, so add this chunk to
714 * the transmitted list.
715 */
716 list_move_tail(&chunk->transmitted_list,
717 &transport->transmitted);
718
719 /* Mark the chunk as ineligible for fast retransmit
720 * after it is retransmitted.
721 */
722 if (chunk->fast_retransmit == SCTP_NEED_FRTX)
723 chunk->fast_retransmit = SCTP_DONT_FRTX;
724
725 q->asoc->stats.rtxchunks++;
726 break;
727 }
728
729 /* Set the timer if there were no errors */
730 if (!error && !timer)
731 timer = 1;
732
733 if (done)
734 break;
735 }
736
737 /* If we are here due to a retransmit timeout or a fast
738 * retransmit and if there are any chunks left in the retransmit
739 * queue that could not fit in the PMTU sized packet, they need
740 * to be marked as ineligible for a subsequent fast retransmit.
741 */
742 if (rtx_timeout || fast_rtx) {
743 list_for_each_entry(chunk1, lqueue, transmitted_list) {
744 if (chunk1->fast_retransmit == SCTP_NEED_FRTX)
745 chunk1->fast_retransmit = SCTP_DONT_FRTX;
746 }
747 }
748
749 *start_timer = timer;
750
751 /* Clear fast retransmit hint */
752 if (fast_rtx)
753 q->fast_rtx = 0;
754
755 return error;
756 }
757
758 /* Cork the outqueue so queued chunks are really queued. */
759 void sctp_outq_uncork(struct sctp_outq *q, gfp_t gfp)
760 {
761 if (q->cork)
762 q->cork = 0;
763
764 sctp_outq_flush(q, 0, gfp);
765 }
766
767 static int sctp_packet_singleton(struct sctp_transport *transport,
768 struct sctp_chunk *chunk, gfp_t gfp)
769 {
770 const struct sctp_association *asoc = transport->asoc;
771 const __u16 sport = asoc->base.bind_addr.port;
772 const __u16 dport = asoc->peer.port;
773 const __u32 vtag = asoc->peer.i.init_tag;
774 struct sctp_packet singleton;
775
776 sctp_packet_init(&singleton, transport, sport, dport);
777 sctp_packet_config(&singleton, vtag, 0);
778 if (sctp_packet_append_chunk(&singleton, chunk) != SCTP_XMIT_OK) {
779 list_del_init(&chunk->list);
780 sctp_chunk_free(chunk);
781 return -ENOMEM;
782 }
783 return sctp_packet_transmit(&singleton, gfp);
784 }
785
786 /* Struct to hold the context during sctp outq flush */
787 struct sctp_flush_ctx {
788 struct sctp_outq *q;
789 /* Current transport being used. It's NOT the same as curr active one */
790 struct sctp_transport *transport;
791 /* These transports have chunks to send. */
792 struct list_head transport_list;
793 struct sctp_association *asoc;
794 /* Packet on the current transport above */
795 struct sctp_packet *packet;
796 gfp_t gfp;
797 };
798
799 /* transport: current transport */
800 static void sctp_outq_select_transport(struct sctp_flush_ctx *ctx,
801 struct sctp_chunk *chunk)
802 {
803 struct sctp_transport *new_transport = chunk->transport;
804
805 if (!new_transport) {
806 if (!sctp_chunk_is_data(chunk)) {
807 /* If we have a prior transport pointer, see if
808 * the destination address of the chunk
809 * matches the destination address of the
810 * current transport. If not a match, then
811 * try to look up the transport with a given
812 * destination address. We do this because
813 * after processing ASCONFs, we may have new
814 * transports created.
815 */
816 if (ctx->transport && sctp_cmp_addr_exact(&chunk->dest,
817 &ctx->transport->ipaddr))
818 new_transport = ctx->transport;
819 else
820 new_transport = sctp_assoc_lookup_paddr(ctx->asoc,
821 &chunk->dest);
822 }
823
824 /* if we still don't have a new transport, then
825 * use the current active path.
826 */
827 if (!new_transport)
828 new_transport = ctx->asoc->peer.active_path;
829 } else {
830 __u8 type;
831
832 switch (new_transport->state) {
833 case SCTP_INACTIVE:
834 case SCTP_UNCONFIRMED:
835 case SCTP_PF:
836 /* If the chunk is Heartbeat or Heartbeat Ack,
837 * send it to chunk->transport, even if it's
838 * inactive.
839 *
840 * 3.3.6 Heartbeat Acknowledgement:
841 * ...
842 * A HEARTBEAT ACK is always sent to the source IP
843 * address of the IP datagram containing the
844 * HEARTBEAT chunk to which this ack is responding.
845 * ...
846 *
847 * ASCONF_ACKs also must be sent to the source.
848 */
849 type = chunk->chunk_hdr->type;
850 if (type != SCTP_CID_HEARTBEAT &&
851 type != SCTP_CID_HEARTBEAT_ACK &&
852 type != SCTP_CID_ASCONF_ACK)
853 new_transport = ctx->asoc->peer.active_path;
854 break;
855 default:
856 break;
857 }
858 }
859
860 /* Are we switching transports? Take care of transport locks. */
861 if (new_transport != ctx->transport) {
862 ctx->transport = new_transport;
863 ctx->packet = &ctx->transport->packet;
864
865 if (list_empty(&ctx->transport->send_ready))
866 list_add_tail(&ctx->transport->send_ready,
867 &ctx->transport_list);
868
869 sctp_packet_config(ctx->packet,
870 ctx->asoc->peer.i.init_tag,
871 ctx->asoc->peer.ecn_capable);
872 /* We've switched transports, so apply the
873 * Burst limit to the new transport.
874 */
875 sctp_transport_burst_limited(ctx->transport);
876 }
877 }
878
879 static void sctp_outq_flush_ctrl(struct sctp_flush_ctx *ctx)
880 {
881 struct sctp_chunk *chunk, *tmp;
882 enum sctp_xmit status;
883 int one_packet, error;
884
885 list_for_each_entry_safe(chunk, tmp, &ctx->q->control_chunk_list, list) {
886 one_packet = 0;
887
888 /* RFC 5061, 5.3
889 * F1) This means that until such time as the ASCONF
890 * containing the add is acknowledged, the sender MUST
891 * NOT use the new IP address as a source for ANY SCTP
892 * packet except on carrying an ASCONF Chunk.
893 */
894 if (ctx->asoc->src_out_of_asoc_ok &&
895 chunk->chunk_hdr->type != SCTP_CID_ASCONF)
896 continue;
897
898 list_del_init(&chunk->list);
899
900 /* Pick the right transport to use. Should always be true for
901 * the first chunk as we don't have a transport by then.
902 */
903 sctp_outq_select_transport(ctx, chunk);
904
905 switch (chunk->chunk_hdr->type) {
906 /* 6.10 Bundling
907 * ...
908 * An endpoint MUST NOT bundle INIT, INIT ACK or SHUTDOWN
909 * COMPLETE with any other chunks. [Send them immediately.]
910 */
911 case SCTP_CID_INIT:
912 case SCTP_CID_INIT_ACK:
913 case SCTP_CID_SHUTDOWN_COMPLETE:
914 error = sctp_packet_singleton(ctx->transport, chunk,
915 ctx->gfp);
916 if (error < 0) {
917 ctx->asoc->base.sk->sk_err = -error;
918 return;
919 }
920 ctx->asoc->stats.octrlchunks++;
921 break;
922
923 case SCTP_CID_ABORT:
924 if (sctp_test_T_bit(chunk))
925 ctx->packet->vtag = ctx->asoc->c.my_vtag;
926 fallthrough;
927
928 /* The following chunks are "response" chunks, i.e.
929 * they are generated in response to something we
930 * received. If we are sending these, then we can
931 * send only 1 packet containing these chunks.
932 */
933 case SCTP_CID_HEARTBEAT_ACK:
934 case SCTP_CID_SHUTDOWN_ACK:
935 case SCTP_CID_COOKIE_ACK:
936 case SCTP_CID_COOKIE_ECHO:
937 case SCTP_CID_ERROR:
938 case SCTP_CID_ECN_CWR:
939 case SCTP_CID_ASCONF_ACK:
940 one_packet = 1;
941 fallthrough;
942
943 case SCTP_CID_HEARTBEAT:
944 if (chunk->pmtu_probe) {
945 error = sctp_packet_singleton(ctx->transport,
946 chunk, ctx->gfp);
947 if (!error)
948 ctx->asoc->stats.octrlchunks++;
949 break;
950 }
951 fallthrough;
952 case SCTP_CID_SACK:
953 case SCTP_CID_SHUTDOWN:
954 case SCTP_CID_ECN_ECNE:
955 case SCTP_CID_ASCONF:
956 case SCTP_CID_FWD_TSN:
957 case SCTP_CID_I_FWD_TSN:
958 case SCTP_CID_RECONF:
959 status = sctp_packet_transmit_chunk(ctx->packet, chunk,
960 one_packet, ctx->gfp);
961 if (status != SCTP_XMIT_OK) {
962 /* put the chunk back */
963 list_add(&chunk->list, &ctx->q->control_chunk_list);
964 break;
965 }
966
967 ctx->asoc->stats.octrlchunks++;
968 /* PR-SCTP C5) If a FORWARD TSN is sent, the
969 * sender MUST assure that at least one T3-rtx
970 * timer is running.
971 */
972 if (chunk->chunk_hdr->type == SCTP_CID_FWD_TSN ||
973 chunk->chunk_hdr->type == SCTP_CID_I_FWD_TSN) {
974 sctp_transport_reset_t3_rtx(ctx->transport);
975 ctx->transport->last_time_sent = jiffies;
976 }
977
978 if (chunk == ctx->asoc->strreset_chunk)
979 sctp_transport_reset_reconf_timer(ctx->transport);
980
981 break;
982
983 default:
984 /* We built a chunk with an illegal type! */
985 BUG();
986 }
987 }
988 }
989
990 /* Returns false if new data shouldn't be sent */
991 static bool sctp_outq_flush_rtx(struct sctp_flush_ctx *ctx,
992 int rtx_timeout)
993 {
994 int error, start_timer = 0;
995
996 if (ctx->asoc->peer.retran_path->state == SCTP_UNCONFIRMED)
997 return false;
998
999 if (ctx->transport != ctx->asoc->peer.retran_path) {
1000 /* Switch transports & prepare the packet. */
1001 ctx->transport = ctx->asoc->peer.retran_path;
1002 ctx->packet = &ctx->transport->packet;
1003
1004 if (list_empty(&ctx->transport->send_ready))
1005 list_add_tail(&ctx->transport->send_ready,
1006 &ctx->transport_list);
1007
1008 sctp_packet_config(ctx->packet, ctx->asoc->peer.i.init_tag,
1009 ctx->asoc->peer.ecn_capable);
1010 }
1011
1012 error = __sctp_outq_flush_rtx(ctx->q, ctx->packet, rtx_timeout,
1013 &start_timer, ctx->gfp);
1014 if (error < 0)
1015 ctx->asoc->base.sk->sk_err = -error;
1016
1017 if (start_timer) {
1018 sctp_transport_reset_t3_rtx(ctx->transport);
1019 ctx->transport->last_time_sent = jiffies;
1020 }
1021
1022 /* This can happen on COOKIE-ECHO resend. Only
1023 * one chunk can get bundled with a COOKIE-ECHO.
1024 */
1025 if (ctx->packet->has_cookie_echo)
1026 return false;
1027
1028 /* Don't send new data if there is still data
1029 * waiting to retransmit.
1030 */
1031 if (!list_empty(&ctx->q->retransmit))
1032 return false;
1033
1034 return true;
1035 }
1036
1037 static void sctp_outq_flush_data(struct sctp_flush_ctx *ctx,
1038 int rtx_timeout)
1039 {
1040 struct sctp_chunk *chunk;
1041 enum sctp_xmit status;
1042
1043 /* Is it OK to send data chunks? */
1044 switch (ctx->asoc->state) {
1045 case SCTP_STATE_COOKIE_ECHOED:
1046 /* Only allow bundling when this packet has a COOKIE-ECHO
1047 * chunk.
1048 */
1049 if (!ctx->packet || !ctx->packet->has_cookie_echo)
1050 return;
1051
1052 fallthrough;
1053 case SCTP_STATE_ESTABLISHED:
1054 case SCTP_STATE_SHUTDOWN_PENDING:
1055 case SCTP_STATE_SHUTDOWN_RECEIVED:
1056 break;
1057
1058 default:
1059 /* Do nothing. */
1060 return;
1061 }
1062
1063 /* RFC 2960 6.1 Transmission of DATA Chunks
1064 *
1065 * C) When the time comes for the sender to transmit,
1066 * before sending new DATA chunks, the sender MUST
1067 * first transmit any outstanding DATA chunks which
1068 * are marked for retransmission (limited by the
1069 * current cwnd).
1070 */
1071 if (!list_empty(&ctx->q->retransmit) &&
1072 !sctp_outq_flush_rtx(ctx, rtx_timeout))
1073 return;
1074
1075 /* Apply Max.Burst limitation to the current transport in
1076 * case it will be used for new data. We are going to
1077 * rest it before we return, but we want to apply the limit
1078 * to the currently queued data.
1079 */
1080 if (ctx->transport)
1081 sctp_transport_burst_limited(ctx->transport);
1082
1083 /* Finally, transmit new packets. */
1084 while ((chunk = sctp_outq_dequeue_data(ctx->q)) != NULL) {
1085 __u32 sid = ntohs(chunk->subh.data_hdr->stream);
1086 __u8 stream_state = SCTP_SO(&ctx->asoc->stream, sid)->state;
1087
1088 /* Has this chunk expired? */
1089 if (sctp_chunk_abandoned(chunk)) {
1090 sctp_sched_dequeue_done(ctx->q, chunk);
1091 sctp_chunk_fail(chunk, 0);
1092 sctp_chunk_free(chunk);
1093 continue;
1094 }
1095
1096 if (stream_state == SCTP_STREAM_CLOSED) {
1097 sctp_outq_head_data(ctx->q, chunk);
1098 break;
1099 }
1100
1101 sctp_outq_select_transport(ctx, chunk);
1102
1103 pr_debug("%s: outq:%p, chunk:%p[%s], tx-tsn:0x%x skb->head:%p skb->users:%d\n",
1104 __func__, ctx->q, chunk, chunk && chunk->chunk_hdr ?
1105 sctp_cname(SCTP_ST_CHUNK(chunk->chunk_hdr->type)) :
1106 "illegal chunk", ntohl(chunk->subh.data_hdr->tsn),
1107 chunk->skb ? chunk->skb->head : NULL, chunk->skb ?
1108 refcount_read(&chunk->skb->users) : -1);
1109
1110 /* Add the chunk to the packet. */
1111 status = sctp_packet_transmit_chunk(ctx->packet, chunk, 0,
1112 ctx->gfp);
1113 if (status != SCTP_XMIT_OK) {
1114 /* We could not append this chunk, so put
1115 * the chunk back on the output queue.
1116 */
1117 pr_debug("%s: could not transmit tsn:0x%x, status:%d\n",
1118 __func__, ntohl(chunk->subh.data_hdr->tsn),
1119 status);
1120
1121 sctp_outq_head_data(ctx->q, chunk);
1122 break;
1123 }
1124
1125 /* The sender is in the SHUTDOWN-PENDING state,
1126 * The sender MAY set the I-bit in the DATA
1127 * chunk header.
1128 */
1129 if (ctx->asoc->state == SCTP_STATE_SHUTDOWN_PENDING)
1130 chunk->chunk_hdr->flags |= SCTP_DATA_SACK_IMM;
1131 if (chunk->chunk_hdr->flags & SCTP_DATA_UNORDERED)
1132 ctx->asoc->stats.ouodchunks++;
1133 else
1134 ctx->asoc->stats.oodchunks++;
1135
1136 /* Only now it's safe to consider this
1137 * chunk as sent, sched-wise.
1138 */
1139 sctp_sched_dequeue_done(ctx->q, chunk);
1140
1141 list_add_tail(&chunk->transmitted_list,
1142 &ctx->transport->transmitted);
1143
1144 sctp_transport_reset_t3_rtx(ctx->transport);
1145 ctx->transport->last_time_sent = jiffies;
1146
1147 /* Only let one DATA chunk get bundled with a
1148 * COOKIE-ECHO chunk.
1149 */
1150 if (ctx->packet->has_cookie_echo)
1151 break;
1152 }
1153 }
1154
1155 static void sctp_outq_flush_transports(struct sctp_flush_ctx *ctx)
1156 {
1157 struct sock *sk = ctx->asoc->base.sk;
1158 struct list_head *ltransport;
1159 struct sctp_packet *packet;
1160 struct sctp_transport *t;
1161 int error = 0;
1162
1163 while ((ltransport = sctp_list_dequeue(&ctx->transport_list)) != NULL) {
1164 t = list_entry(ltransport, struct sctp_transport, send_ready);
1165 packet = &t->packet;
1166 if (!sctp_packet_empty(packet)) {
1167 rcu_read_lock();
1168 if (t->dst && __sk_dst_get(sk) != t->dst) {
1169 dst_hold(t->dst);
1170 sk_setup_caps(sk, t->dst);
1171 }
1172 rcu_read_unlock();
1173 error = sctp_packet_transmit(packet, ctx->gfp);
1174 if (error < 0)
1175 ctx->q->asoc->base.sk->sk_err = -error;
1176 }
1177
1178 /* Clear the burst limited state, if any */
1179 sctp_transport_burst_reset(t);
1180 }
1181 }
1182
1183 /* Try to flush an outqueue.
1184 *
1185 * Description: Send everything in q which we legally can, subject to
1186 * congestion limitations.
1187 * * Note: This function can be called from multiple contexts so appropriate
1188 * locking concerns must be made. Today we use the sock lock to protect
1189 * this function.
1190 */
1191
1192 static void sctp_outq_flush(struct sctp_outq *q, int rtx_timeout, gfp_t gfp)
1193 {
1194 struct sctp_flush_ctx ctx = {
1195 .q = q,
1196 .transport = NULL,
1197 .transport_list = LIST_HEAD_INIT(ctx.transport_list),
1198 .asoc = q->asoc,
1199 .packet = NULL,
1200 .gfp = gfp,
1201 };
1202
1203 /* 6.10 Bundling
1204 * ...
1205 * When bundling control chunks with DATA chunks, an
1206 * endpoint MUST place control chunks first in the outbound
1207 * SCTP packet. The transmitter MUST transmit DATA chunks
1208 * within a SCTP packet in increasing order of TSN.
1209 * ...
1210 */
1211
1212 sctp_outq_flush_ctrl(&ctx);
1213
1214 if (q->asoc->src_out_of_asoc_ok)
1215 goto sctp_flush_out;
1216
1217 sctp_outq_flush_data(&ctx, rtx_timeout);
1218
1219 sctp_flush_out:
1220
1221 sctp_outq_flush_transports(&ctx);
1222 }
1223
1224 /* Update unack_data based on the incoming SACK chunk */
1225 static void sctp_sack_update_unack_data(struct sctp_association *assoc,
1226 struct sctp_sackhdr *sack)
1227 {
1228 union sctp_sack_variable *frags;
1229 __u16 unack_data;
1230 int i;
1231
1232 unack_data = assoc->next_tsn - assoc->ctsn_ack_point - 1;
1233
1234 frags = (union sctp_sack_variable *)(sack + 1);
1235 for (i = 0; i < ntohs(sack->num_gap_ack_blocks); i++) {
1236 unack_data -= ((ntohs(frags[i].gab.end) -
1237 ntohs(frags[i].gab.start) + 1));
1238 }
1239
1240 assoc->unack_data = unack_data;
1241 }
1242
1243 /* This is where we REALLY process a SACK.
1244 *
1245 * Process the SACK against the outqueue. Mostly, this just frees
1246 * things off the transmitted queue.
1247 */
1248 int sctp_outq_sack(struct sctp_outq *q, struct sctp_chunk *chunk)
1249 {
1250 struct sctp_association *asoc = q->asoc;
1251 struct sctp_sackhdr *sack = chunk->subh.sack_hdr;
1252 struct sctp_transport *transport;
1253 struct sctp_chunk *tchunk = NULL;
1254 struct list_head *lchunk, *transport_list, *temp;
1255 __u32 sack_ctsn, ctsn, tsn;
1256 __u32 highest_tsn, highest_new_tsn;
1257 __u32 sack_a_rwnd;
1258 unsigned int outstanding;
1259 struct sctp_transport *primary = asoc->peer.primary_path;
1260 int count_of_newacks = 0;
1261 int gap_ack_blocks;
1262 u8 accum_moved = 0;
1263
1264 /* Grab the association's destination address list. */
1265 transport_list = &asoc->peer.transport_addr_list;
1266
1267 /* SCTP path tracepoint for congestion control debugging. */
1268 if (trace_sctp_probe_path_enabled()) {
1269 list_for_each_entry(transport, transport_list, transports)
1270 trace_sctp_probe_path(transport, asoc);
1271 }
1272
1273 sack_ctsn = ntohl(sack->cum_tsn_ack);
1274 gap_ack_blocks = ntohs(sack->num_gap_ack_blocks);
1275 asoc->stats.gapcnt += gap_ack_blocks;
1276 /*
1277 * SFR-CACC algorithm:
1278 * On receipt of a SACK the sender SHOULD execute the
1279 * following statements.
1280 *
1281 * 1) If the cumulative ack in the SACK passes next tsn_at_change
1282 * on the current primary, the CHANGEOVER_ACTIVE flag SHOULD be
1283 * cleared. The CYCLING_CHANGEOVER flag SHOULD also be cleared for
1284 * all destinations.
1285 * 2) If the SACK contains gap acks and the flag CHANGEOVER_ACTIVE
1286 * is set the receiver of the SACK MUST take the following actions:
1287 *
1288 * A) Initialize the cacc_saw_newack to 0 for all destination
1289 * addresses.
1290 *
1291 * Only bother if changeover_active is set. Otherwise, this is
1292 * totally suboptimal to do on every SACK.
1293 */
1294 if (primary->cacc.changeover_active) {
1295 u8 clear_cycling = 0;
1296
1297 if (TSN_lte(primary->cacc.next_tsn_at_change, sack_ctsn)) {
1298 primary->cacc.changeover_active = 0;
1299 clear_cycling = 1;
1300 }
1301
1302 if (clear_cycling || gap_ack_blocks) {
1303 list_for_each_entry(transport, transport_list,
1304 transports) {
1305 if (clear_cycling)
1306 transport->cacc.cycling_changeover = 0;
1307 if (gap_ack_blocks)
1308 transport->cacc.cacc_saw_newack = 0;
1309 }
1310 }
1311 }
1312
1313 /* Get the highest TSN in the sack. */
1314 highest_tsn = sack_ctsn;
1315 if (gap_ack_blocks) {
1316 union sctp_sack_variable *frags =
1317 (union sctp_sack_variable *)(sack + 1);
1318
1319 highest_tsn += ntohs(frags[gap_ack_blocks - 1].gab.end);
1320 }
1321
1322 if (TSN_lt(asoc->highest_sacked, highest_tsn))
1323 asoc->highest_sacked = highest_tsn;
1324
1325 highest_new_tsn = sack_ctsn;
1326
1327 /* Run through the retransmit queue. Credit bytes received
1328 * and free those chunks that we can.
1329 */
1330 sctp_check_transmitted(q, &q->retransmit, NULL, NULL, sack, &highest_new_tsn);
1331
1332 /* Run through the transmitted queue.
1333 * Credit bytes received and free those chunks which we can.
1334 *
1335 * This is a MASSIVE candidate for optimization.
1336 */
1337 list_for_each_entry(transport, transport_list, transports) {
1338 sctp_check_transmitted(q, &transport->transmitted,
1339 transport, &chunk->source, sack,
1340 &highest_new_tsn);
1341 /*
1342 * SFR-CACC algorithm:
1343 * C) Let count_of_newacks be the number of
1344 * destinations for which cacc_saw_newack is set.
1345 */
1346 if (transport->cacc.cacc_saw_newack)
1347 count_of_newacks++;
1348 }
1349
1350 /* Move the Cumulative TSN Ack Point if appropriate. */
1351 if (TSN_lt(asoc->ctsn_ack_point, sack_ctsn)) {
1352 asoc->ctsn_ack_point = sack_ctsn;
1353 accum_moved = 1;
1354 }
1355
1356 if (gap_ack_blocks) {
1357
1358 if (asoc->fast_recovery && accum_moved)
1359 highest_new_tsn = highest_tsn;
1360
1361 list_for_each_entry(transport, transport_list, transports)
1362 sctp_mark_missing(q, &transport->transmitted, transport,
1363 highest_new_tsn, count_of_newacks);
1364 }
1365
1366 /* Update unack_data field in the assoc. */
1367 sctp_sack_update_unack_data(asoc, sack);
1368
1369 ctsn = asoc->ctsn_ack_point;
1370
1371 /* Throw away stuff rotting on the sack queue. */
1372 list_for_each_safe(lchunk, temp, &q->sacked) {
1373 tchunk = list_entry(lchunk, struct sctp_chunk,
1374 transmitted_list);
1375 tsn = ntohl(tchunk->subh.data_hdr->tsn);
1376 if (TSN_lte(tsn, ctsn)) {
1377 list_del_init(&tchunk->transmitted_list);
1378 if (asoc->peer.prsctp_capable &&
1379 SCTP_PR_PRIO_ENABLED(chunk->sinfo.sinfo_flags))
1380 asoc->sent_cnt_removable--;
1381 sctp_chunk_free(tchunk);
1382 }
1383 }
1384
1385 /* ii) Set rwnd equal to the newly received a_rwnd minus the
1386 * number of bytes still outstanding after processing the
1387 * Cumulative TSN Ack and the Gap Ack Blocks.
1388 */
1389
1390 sack_a_rwnd = ntohl(sack->a_rwnd);
1391 asoc->peer.zero_window_announced = !sack_a_rwnd;
1392 outstanding = q->outstanding_bytes;
1393
1394 if (outstanding < sack_a_rwnd)
1395 sack_a_rwnd -= outstanding;
1396 else
1397 sack_a_rwnd = 0;
1398
1399 asoc->peer.rwnd = sack_a_rwnd;
1400
1401 asoc->stream.si->generate_ftsn(q, sack_ctsn);
1402
1403 pr_debug("%s: sack cumulative tsn ack:0x%x\n", __func__, sack_ctsn);
1404 pr_debug("%s: cumulative tsn ack of assoc:%p is 0x%x, "
1405 "advertised peer ack point:0x%x\n", __func__, asoc, ctsn,
1406 asoc->adv_peer_ack_point);
1407
1408 return sctp_outq_is_empty(q);
1409 }
1410
1411 /* Is the outqueue empty?
1412 * The queue is empty when we have not pending data, no in-flight data
1413 * and nothing pending retransmissions.
1414 */
1415 int sctp_outq_is_empty(const struct sctp_outq *q)
1416 {
1417 return q->out_qlen == 0 && q->outstanding_bytes == 0 &&
1418 list_empty(&q->retransmit);
1419 }
1420
1421 /********************************************************************
1422 * 2nd Level Abstractions
1423 ********************************************************************/
1424
1425 /* Go through a transport's transmitted list or the association's retransmit
1426 * list and move chunks that are acked by the Cumulative TSN Ack to q->sacked.
1427 * The retransmit list will not have an associated transport.
1428 *
1429 * I added coherent debug information output. --xguo
1430 *
1431 * Instead of printing 'sacked' or 'kept' for each TSN on the
1432 * transmitted_queue, we print a range: SACKED: TSN1-TSN2, TSN3, TSN4-TSN5.
1433 * KEPT TSN6-TSN7, etc.
1434 */
1435 static void sctp_check_transmitted(struct sctp_outq *q,
1436 struct list_head *transmitted_queue,
1437 struct sctp_transport *transport,
1438 union sctp_addr *saddr,
1439 struct sctp_sackhdr *sack,
1440 __u32 *highest_new_tsn_in_sack)
1441 {
1442 struct list_head *lchunk;
1443 struct sctp_chunk *tchunk;
1444 struct list_head tlist;
1445 __u32 tsn;
1446 __u32 sack_ctsn;
1447 __u32 rtt;
1448 __u8 restart_timer = 0;
1449 int bytes_acked = 0;
1450 int migrate_bytes = 0;
1451 bool forward_progress = false;
1452
1453 sack_ctsn = ntohl(sack->cum_tsn_ack);
1454
1455 INIT_LIST_HEAD(&tlist);
1456
1457 /* The while loop will skip empty transmitted queues. */
1458 while (NULL != (lchunk = sctp_list_dequeue(transmitted_queue))) {
1459 tchunk = list_entry(lchunk, struct sctp_chunk,
1460 transmitted_list);
1461
1462 if (sctp_chunk_abandoned(tchunk)) {
1463 /* Move the chunk to abandoned list. */
1464 sctp_insert_list(&q->abandoned, lchunk);
1465
1466 /* If this chunk has not been acked, stop
1467 * considering it as 'outstanding'.
1468 */
1469 if (transmitted_queue != &q->retransmit &&
1470 !tchunk->tsn_gap_acked) {
1471 if (tchunk->transport)
1472 tchunk->transport->flight_size -=
1473 sctp_data_size(tchunk);
1474 q->outstanding_bytes -= sctp_data_size(tchunk);
1475 }
1476 continue;
1477 }
1478
1479 tsn = ntohl(tchunk->subh.data_hdr->tsn);
1480 if (sctp_acked(sack, tsn)) {
1481 /* If this queue is the retransmit queue, the
1482 * retransmit timer has already reclaimed
1483 * the outstanding bytes for this chunk, so only
1484 * count bytes associated with a transport.
1485 */
1486 if (transport && !tchunk->tsn_gap_acked) {
1487 /* If this chunk is being used for RTT
1488 * measurement, calculate the RTT and update
1489 * the RTO using this value.
1490 *
1491 * 6.3.1 C5) Karn's algorithm: RTT measurements
1492 * MUST NOT be made using packets that were
1493 * retransmitted (and thus for which it is
1494 * ambiguous whether the reply was for the
1495 * first instance of the packet or a later
1496 * instance).
1497 */
1498 if (!sctp_chunk_retransmitted(tchunk) &&
1499 tchunk->rtt_in_progress) {
1500 tchunk->rtt_in_progress = 0;
1501 rtt = jiffies - tchunk->sent_at;
1502 sctp_transport_update_rto(transport,
1503 rtt);
1504 }
1505
1506 if (TSN_lte(tsn, sack_ctsn)) {
1507 /*
1508 * SFR-CACC algorithm:
1509 * 2) If the SACK contains gap acks
1510 * and the flag CHANGEOVER_ACTIVE is
1511 * set the receiver of the SACK MUST
1512 * take the following action:
1513 *
1514 * B) For each TSN t being acked that
1515 * has not been acked in any SACK so
1516 * far, set cacc_saw_newack to 1 for
1517 * the destination that the TSN was
1518 * sent to.
1519 */
1520 if (sack->num_gap_ack_blocks &&
1521 q->asoc->peer.primary_path->cacc.
1522 changeover_active)
1523 transport->cacc.cacc_saw_newack
1524 = 1;
1525 }
1526 }
1527
1528 /* If the chunk hasn't been marked as ACKED,
1529 * mark it and account bytes_acked if the
1530 * chunk had a valid transport (it will not
1531 * have a transport if ASCONF had deleted it
1532 * while DATA was outstanding).
1533 */
1534 if (!tchunk->tsn_gap_acked) {
1535 tchunk->tsn_gap_acked = 1;
1536 if (TSN_lt(*highest_new_tsn_in_sack, tsn))
1537 *highest_new_tsn_in_sack = tsn;
1538 bytes_acked += sctp_data_size(tchunk);
1539 if (!tchunk->transport)
1540 migrate_bytes += sctp_data_size(tchunk);
1541 forward_progress = true;
1542 }
1543
1544 if (TSN_lte(tsn, sack_ctsn)) {
1545 /* RFC 2960 6.3.2 Retransmission Timer Rules
1546 *
1547 * R3) Whenever a SACK is received
1548 * that acknowledges the DATA chunk
1549 * with the earliest outstanding TSN
1550 * for that address, restart T3-rtx
1551 * timer for that address with its
1552 * current RTO.
1553 */
1554 restart_timer = 1;
1555 forward_progress = true;
1556
1557 list_add_tail(&tchunk->transmitted_list,
1558 &q->sacked);
1559 } else {
1560 /* RFC2960 7.2.4, sctpimpguide-05 2.8.2
1561 * M2) Each time a SACK arrives reporting
1562 * 'Stray DATA chunk(s)' record the highest TSN
1563 * reported as newly acknowledged, call this
1564 * value 'HighestTSNinSack'. A newly
1565 * acknowledged DATA chunk is one not
1566 * previously acknowledged in a SACK.
1567 *
1568 * When the SCTP sender of data receives a SACK
1569 * chunk that acknowledges, for the first time,
1570 * the receipt of a DATA chunk, all the still
1571 * unacknowledged DATA chunks whose TSN is
1572 * older than that newly acknowledged DATA
1573 * chunk, are qualified as 'Stray DATA chunks'.
1574 */
1575 list_add_tail(lchunk, &tlist);
1576 }
1577 } else {
1578 if (tchunk->tsn_gap_acked) {
1579 pr_debug("%s: receiver reneged on data TSN:0x%x\n",
1580 __func__, tsn);
1581
1582 tchunk->tsn_gap_acked = 0;
1583
1584 if (tchunk->transport)
1585 bytes_acked -= sctp_data_size(tchunk);
1586
1587 /* RFC 2960 6.3.2 Retransmission Timer Rules
1588 *
1589 * R4) Whenever a SACK is received missing a
1590 * TSN that was previously acknowledged via a
1591 * Gap Ack Block, start T3-rtx for the
1592 * destination address to which the DATA
1593 * chunk was originally
1594 * transmitted if it is not already running.
1595 */
1596 restart_timer = 1;
1597 }
1598
1599 list_add_tail(lchunk, &tlist);
1600 }
1601 }
1602
1603 if (transport) {
1604 if (bytes_acked) {
1605 struct sctp_association *asoc = transport->asoc;
1606
1607 /* We may have counted DATA that was migrated
1608 * to this transport due to DEL-IP operation.
1609 * Subtract those bytes, since the were never
1610 * send on this transport and shouldn't be
1611 * credited to this transport.
1612 */
1613 bytes_acked -= migrate_bytes;
1614
1615 /* 8.2. When an outstanding TSN is acknowledged,
1616 * the endpoint shall clear the error counter of
1617 * the destination transport address to which the
1618 * DATA chunk was last sent.
1619 * The association's overall error counter is
1620 * also cleared.
1621 */
1622 transport->error_count = 0;
1623 transport->asoc->overall_error_count = 0;
1624 forward_progress = true;
1625
1626 /*
1627 * While in SHUTDOWN PENDING, we may have started
1628 * the T5 shutdown guard timer after reaching the
1629 * retransmission limit. Stop that timer as soon
1630 * as the receiver acknowledged any data.
1631 */
1632 if (asoc->state == SCTP_STATE_SHUTDOWN_PENDING &&
1633 del_timer(&asoc->timers
1634 [SCTP_EVENT_TIMEOUT_T5_SHUTDOWN_GUARD]))
1635 sctp_association_put(asoc);
1636
1637 /* Mark the destination transport address as
1638 * active if it is not so marked.
1639 */
1640 if ((transport->state == SCTP_INACTIVE ||
1641 transport->state == SCTP_UNCONFIRMED) &&
1642 sctp_cmp_addr_exact(&transport->ipaddr, saddr)) {
1643 sctp_assoc_control_transport(
1644 transport->asoc,
1645 transport,
1646 SCTP_TRANSPORT_UP,
1647 SCTP_RECEIVED_SACK);
1648 }
1649
1650 sctp_transport_raise_cwnd(transport, sack_ctsn,
1651 bytes_acked);
1652
1653 transport->flight_size -= bytes_acked;
1654 if (transport->flight_size == 0)
1655 transport->partial_bytes_acked = 0;
1656 q->outstanding_bytes -= bytes_acked + migrate_bytes;
1657 } else {
1658 /* RFC 2960 6.1, sctpimpguide-06 2.15.2
1659 * When a sender is doing zero window probing, it
1660 * should not timeout the association if it continues
1661 * to receive new packets from the receiver. The
1662 * reason is that the receiver MAY keep its window
1663 * closed for an indefinite time.
1664 * A sender is doing zero window probing when the
1665 * receiver's advertised window is zero, and there is
1666 * only one data chunk in flight to the receiver.
1667 *
1668 * Allow the association to timeout while in SHUTDOWN
1669 * PENDING or SHUTDOWN RECEIVED in case the receiver
1670 * stays in zero window mode forever.
1671 */
1672 if (!q->asoc->peer.rwnd &&
1673 !list_empty(&tlist) &&
1674 (sack_ctsn+2 == q->asoc->next_tsn) &&
1675 q->asoc->state < SCTP_STATE_SHUTDOWN_PENDING) {
1676 pr_debug("%s: sack received for zero window "
1677 "probe:%u\n", __func__, sack_ctsn);
1678
1679 q->asoc->overall_error_count = 0;
1680 transport->error_count = 0;
1681 }
1682 }
1683
1684 /* RFC 2960 6.3.2 Retransmission Timer Rules
1685 *
1686 * R2) Whenever all outstanding data sent to an address have
1687 * been acknowledged, turn off the T3-rtx timer of that
1688 * address.
1689 */
1690 if (!transport->flight_size) {
1691 if (del_timer(&transport->T3_rtx_timer))
1692 sctp_transport_put(transport);
1693 } else if (restart_timer) {
1694 if (!mod_timer(&transport->T3_rtx_timer,
1695 jiffies + transport->rto))
1696 sctp_transport_hold(transport);
1697 }
1698
1699 if (forward_progress) {
1700 if (transport->dst)
1701 sctp_transport_dst_confirm(transport);
1702 }
1703 }
1704
1705 list_splice(&tlist, transmitted_queue);
1706 }
1707
1708 /* Mark chunks as missing and consequently may get retransmitted. */
1709 static void sctp_mark_missing(struct sctp_outq *q,
1710 struct list_head *transmitted_queue,
1711 struct sctp_transport *transport,
1712 __u32 highest_new_tsn_in_sack,
1713 int count_of_newacks)
1714 {
1715 struct sctp_chunk *chunk;
1716 __u32 tsn;
1717 char do_fast_retransmit = 0;
1718 struct sctp_association *asoc = q->asoc;
1719 struct sctp_transport *primary = asoc->peer.primary_path;
1720
1721 list_for_each_entry(chunk, transmitted_queue, transmitted_list) {
1722
1723 tsn = ntohl(chunk->subh.data_hdr->tsn);
1724
1725 /* RFC 2960 7.2.4, sctpimpguide-05 2.8.2 M3) Examine all
1726 * 'Unacknowledged TSN's', if the TSN number of an
1727 * 'Unacknowledged TSN' is smaller than the 'HighestTSNinSack'
1728 * value, increment the 'TSN.Missing.Report' count on that
1729 * chunk if it has NOT been fast retransmitted or marked for
1730 * fast retransmit already.
1731 */
1732 if (chunk->fast_retransmit == SCTP_CAN_FRTX &&
1733 !chunk->tsn_gap_acked &&
1734 TSN_lt(tsn, highest_new_tsn_in_sack)) {
1735
1736 /* SFR-CACC may require us to skip marking
1737 * this chunk as missing.
1738 */
1739 if (!transport || !sctp_cacc_skip(primary,
1740 chunk->transport,
1741 count_of_newacks, tsn)) {
1742 chunk->tsn_missing_report++;
1743
1744 pr_debug("%s: tsn:0x%x missing counter:%d\n",
1745 __func__, tsn, chunk->tsn_missing_report);
1746 }
1747 }
1748 /*
1749 * M4) If any DATA chunk is found to have a
1750 * 'TSN.Missing.Report'
1751 * value larger than or equal to 3, mark that chunk for
1752 * retransmission and start the fast retransmit procedure.
1753 */
1754
1755 if (chunk->tsn_missing_report >= 3) {
1756 chunk->fast_retransmit = SCTP_NEED_FRTX;
1757 do_fast_retransmit = 1;
1758 }
1759 }
1760
1761 if (transport) {
1762 if (do_fast_retransmit)
1763 sctp_retransmit(q, transport, SCTP_RTXR_FAST_RTX);
1764
1765 pr_debug("%s: transport:%p, cwnd:%d, ssthresh:%d, "
1766 "flight_size:%d, pba:%d\n", __func__, transport,
1767 transport->cwnd, transport->ssthresh,
1768 transport->flight_size, transport->partial_bytes_acked);
1769 }
1770 }
1771
1772 /* Is the given TSN acked by this packet? */
1773 static int sctp_acked(struct sctp_sackhdr *sack, __u32 tsn)
1774 {
1775 __u32 ctsn = ntohl(sack->cum_tsn_ack);
1776 union sctp_sack_variable *frags;
1777 __u16 tsn_offset, blocks;
1778 int i;
1779
1780 if (TSN_lte(tsn, ctsn))
1781 goto pass;
1782
1783 /* 3.3.4 Selective Acknowledgment (SACK) (3):
1784 *
1785 * Gap Ack Blocks:
1786 * These fields contain the Gap Ack Blocks. They are repeated
1787 * for each Gap Ack Block up to the number of Gap Ack Blocks
1788 * defined in the Number of Gap Ack Blocks field. All DATA
1789 * chunks with TSNs greater than or equal to (Cumulative TSN
1790 * Ack + Gap Ack Block Start) and less than or equal to
1791 * (Cumulative TSN Ack + Gap Ack Block End) of each Gap Ack
1792 * Block are assumed to have been received correctly.
1793 */
1794
1795 frags = (union sctp_sack_variable *)(sack + 1);
1796 blocks = ntohs(sack->num_gap_ack_blocks);
1797 tsn_offset = tsn - ctsn;
1798 for (i = 0; i < blocks; ++i) {
1799 if (tsn_offset >= ntohs(frags[i].gab.start) &&
1800 tsn_offset <= ntohs(frags[i].gab.end))
1801 goto pass;
1802 }
1803
1804 return 0;
1805 pass:
1806 return 1;
1807 }
1808
1809 static inline int sctp_get_skip_pos(struct sctp_fwdtsn_skip *skiplist,
1810 int nskips, __be16 stream)
1811 {
1812 int i;
1813
1814 for (i = 0; i < nskips; i++) {
1815 if (skiplist[i].stream == stream)
1816 return i;
1817 }
1818 return i;
1819 }
1820
1821 /* Create and add a fwdtsn chunk to the outq's control queue if needed. */
1822 void sctp_generate_fwdtsn(struct sctp_outq *q, __u32 ctsn)
1823 {
1824 struct sctp_association *asoc = q->asoc;
1825 struct sctp_chunk *ftsn_chunk = NULL;
1826 struct sctp_fwdtsn_skip ftsn_skip_arr[10];
1827 int nskips = 0;
1828 int skip_pos = 0;
1829 __u32 tsn;
1830 struct sctp_chunk *chunk;
1831 struct list_head *lchunk, *temp;
1832
1833 if (!asoc->peer.prsctp_capable)
1834 return;
1835
1836 /* PR-SCTP C1) Let SackCumAck be the Cumulative TSN ACK carried in the
1837 * received SACK.
1838 *
1839 * If (Advanced.Peer.Ack.Point < SackCumAck), then update
1840 * Advanced.Peer.Ack.Point to be equal to SackCumAck.
1841 */
1842 if (TSN_lt(asoc->adv_peer_ack_point, ctsn))
1843 asoc->adv_peer_ack_point = ctsn;
1844
1845 /* PR-SCTP C2) Try to further advance the "Advanced.Peer.Ack.Point"
1846 * locally, that is, to move "Advanced.Peer.Ack.Point" up as long as
1847 * the chunk next in the out-queue space is marked as "abandoned" as
1848 * shown in the following example:
1849 *
1850 * Assuming that a SACK arrived with the Cumulative TSN ACK 102
1851 * and the Advanced.Peer.Ack.Point is updated to this value:
1852 *
1853 * out-queue at the end of ==> out-queue after Adv.Ack.Point
1854 * normal SACK processing local advancement
1855 * ... ...
1856 * Adv.Ack.Pt-> 102 acked 102 acked
1857 * 103 abandoned 103 abandoned
1858 * 104 abandoned Adv.Ack.P-> 104 abandoned
1859 * 105 105
1860 * 106 acked 106 acked
1861 * ... ...
1862 *
1863 * In this example, the data sender successfully advanced the
1864 * "Advanced.Peer.Ack.Point" from 102 to 104 locally.
1865 */
1866 list_for_each_safe(lchunk, temp, &q->abandoned) {
1867 chunk = list_entry(lchunk, struct sctp_chunk,
1868 transmitted_list);
1869 tsn = ntohl(chunk->subh.data_hdr->tsn);
1870
1871 /* Remove any chunks in the abandoned queue that are acked by
1872 * the ctsn.
1873 */
1874 if (TSN_lte(tsn, ctsn)) {
1875 list_del_init(lchunk);
1876 sctp_chunk_free(chunk);
1877 } else {
1878 if (TSN_lte(tsn, asoc->adv_peer_ack_point+1)) {
1879 asoc->adv_peer_ack_point = tsn;
1880 if (chunk->chunk_hdr->flags &
1881 SCTP_DATA_UNORDERED)
1882 continue;
1883 skip_pos = sctp_get_skip_pos(&ftsn_skip_arr[0],
1884 nskips,
1885 chunk->subh.data_hdr->stream);
1886 ftsn_skip_arr[skip_pos].stream =
1887 chunk->subh.data_hdr->stream;
1888 ftsn_skip_arr[skip_pos].ssn =
1889 chunk->subh.data_hdr->ssn;
1890 if (skip_pos == nskips)
1891 nskips++;
1892 if (nskips == 10)
1893 break;
1894 } else
1895 break;
1896 }
1897 }
1898
1899 /* PR-SCTP C3) If, after step C1 and C2, the "Advanced.Peer.Ack.Point"
1900 * is greater than the Cumulative TSN ACK carried in the received
1901 * SACK, the data sender MUST send the data receiver a FORWARD TSN
1902 * chunk containing the latest value of the
1903 * "Advanced.Peer.Ack.Point".
1904 *
1905 * C4) For each "abandoned" TSN the sender of the FORWARD TSN SHOULD
1906 * list each stream and sequence number in the forwarded TSN. This
1907 * information will enable the receiver to easily find any
1908 * stranded TSN's waiting on stream reorder queues. Each stream
1909 * SHOULD only be reported once; this means that if multiple
1910 * abandoned messages occur in the same stream then only the
1911 * highest abandoned stream sequence number is reported. If the
1912 * total size of the FORWARD TSN does NOT fit in a single MTU then
1913 * the sender of the FORWARD TSN SHOULD lower the
1914 * Advanced.Peer.Ack.Point to the last TSN that will fit in a
1915 * single MTU.
1916 */
1917 if (asoc->adv_peer_ack_point > ctsn)
1918 ftsn_chunk = sctp_make_fwdtsn(asoc, asoc->adv_peer_ack_point,
1919 nskips, &ftsn_skip_arr[0]);
1920
1921 if (ftsn_chunk) {
1922 list_add_tail(&ftsn_chunk->list, &q->control_chunk_list);
1923 SCTP_INC_STATS(asoc->base.net, SCTP_MIB_OUTCTRLCHUNKS);
1924 }
1925 }
1926
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