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 struct sctp_stream_out *streamout;
357
358 if (!SCTP_PR_PRIO_ENABLED(chk->sinfo.sinfo_flags) ||
359 chk->sinfo.sinfo_timetolive <= sinfo->sinfo_timetolive)
360 continue;
361
362 list_del_init(&chk->transmitted_list);
363 sctp_insert_list(&asoc->outqueue.abandoned,
364 &chk->transmitted_list);
365
366 streamout = &asoc->stream.out[chk->sinfo.sinfo_stream];
367 asoc->sent_cnt_removable--;
368 asoc->abandoned_sent[SCTP_PR_INDEX(PRIO)]++;
369 streamout->abandoned_sent[SCTP_PR_INDEX(PRIO)]++;
370
371 if (queue != &asoc->outqueue.retransmit &&
372 !chk->tsn_gap_acked) {
373 if (chk->transport)
374 chk->transport->flight_size -=
375 sctp_data_size(chk);
376 asoc->outqueue.outstanding_bytes -= sctp_data_size(chk);
377 }
378
379 msg_len -= SCTP_DATA_SNDSIZE(chk) +
380 sizeof(struct sk_buff) +
381 sizeof(struct sctp_chunk);
382 if (msg_len <= 0)
383 break;
384 }
385
386 return msg_len;
387 }
388
sctp_prsctp_prune_unsent(struct sctp_association * asoc,struct sctp_sndrcvinfo * sinfo,int msg_len)389 static int sctp_prsctp_prune_unsent(struct sctp_association *asoc,
390 struct sctp_sndrcvinfo *sinfo, int msg_len)
391 {
392 struct sctp_outq *q = &asoc->outqueue;
393 struct sctp_chunk *chk, *temp;
394
395 list_for_each_entry_safe(chk, temp, &q->out_chunk_list, list) {
396 if (!SCTP_PR_PRIO_ENABLED(chk->sinfo.sinfo_flags) ||
397 chk->sinfo.sinfo_timetolive <= sinfo->sinfo_timetolive)
398 continue;
399
400 list_del_init(&chk->list);
401 q->out_qlen -= chk->skb->len;
402 asoc->sent_cnt_removable--;
403 asoc->abandoned_unsent[SCTP_PR_INDEX(PRIO)]++;
404 if (chk->sinfo.sinfo_stream < asoc->stream.outcnt) {
405 struct sctp_stream_out *streamout =
406 &asoc->stream.out[chk->sinfo.sinfo_stream];
407
408 streamout->abandoned_unsent[SCTP_PR_INDEX(PRIO)]++;
409 }
410
411 msg_len -= SCTP_DATA_SNDSIZE(chk) +
412 sizeof(struct sk_buff) +
413 sizeof(struct sctp_chunk);
414 sctp_chunk_free(chk);
415 if (msg_len <= 0)
416 break;
417 }
418
419 return msg_len;
420 }
421
422 /* Abandon the chunks according their priorities */
sctp_prsctp_prune(struct sctp_association * asoc,struct sctp_sndrcvinfo * sinfo,int msg_len)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. */
sctp_retransmit_mark(struct sctp_outq * q,struct sctp_transport * transport,__u8 reason)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 */
sctp_retransmit(struct sctp_outq * q,struct sctp_transport * transport,enum sctp_retransmit_reason reason)537 void sctp_retransmit(struct sctp_outq *q, struct sctp_transport *transport,
538 enum sctp_retransmit_reason reason)
539 {
540 struct net *net = sock_net(q->asoc->base.sk);
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 break;
554 case SCTP_RTXR_FAST_RTX:
555 SCTP_INC_STATS(net, SCTP_MIB_FAST_RETRANSMITS);
556 sctp_transport_lower_cwnd(transport, SCTP_LOWER_CWND_FAST_RTX);
557 q->fast_rtx = 1;
558 break;
559 case SCTP_RTXR_PMTUD:
560 SCTP_INC_STATS(net, SCTP_MIB_PMTUD_RETRANSMITS);
561 break;
562 case SCTP_RTXR_T1_RTX:
563 SCTP_INC_STATS(net, SCTP_MIB_T1_RETRANSMITS);
564 transport->asoc->init_retries++;
565 break;
566 default:
567 BUG();
568 }
569
570 sctp_retransmit_mark(q, transport, reason);
571
572 /* PR-SCTP A5) Any time the T3-rtx timer expires, on any destination,
573 * the sender SHOULD try to advance the "Advanced.Peer.Ack.Point" by
574 * following the procedures outlined in C1 - C5.
575 */
576 if (reason == SCTP_RTXR_T3_RTX)
577 sctp_generate_fwdtsn(q, q->asoc->ctsn_ack_point);
578
579 /* Flush the queues only on timeout, since fast_rtx is only
580 * triggered during sack processing and the queue
581 * will be flushed at the end.
582 */
583 if (reason != SCTP_RTXR_FAST_RTX)
584 sctp_outq_flush(q, /* rtx_timeout */ 1, GFP_ATOMIC);
585 }
586
587 /*
588 * Transmit DATA chunks on the retransmit queue. Upon return from
589 * sctp_outq_flush_rtx() the packet 'pkt' may contain chunks which
590 * need to be transmitted by the caller.
591 * We assume that pkt->transport has already been set.
592 *
593 * The return value is a normal kernel error return value.
594 */
sctp_outq_flush_rtx(struct sctp_outq * q,struct sctp_packet * pkt,int rtx_timeout,int * start_timer)595 static int sctp_outq_flush_rtx(struct sctp_outq *q, struct sctp_packet *pkt,
596 int rtx_timeout, int *start_timer)
597 {
598 struct sctp_transport *transport = pkt->transport;
599 struct sctp_chunk *chunk, *chunk1;
600 struct list_head *lqueue;
601 enum sctp_xmit status;
602 int error = 0;
603 int timer = 0;
604 int done = 0;
605 int fast_rtx;
606
607 lqueue = &q->retransmit;
608 fast_rtx = q->fast_rtx;
609
610 /* This loop handles time-out retransmissions, fast retransmissions,
611 * and retransmissions due to opening of whindow.
612 *
613 * RFC 2960 6.3.3 Handle T3-rtx Expiration
614 *
615 * E3) Determine how many of the earliest (i.e., lowest TSN)
616 * outstanding DATA chunks for the address for which the
617 * T3-rtx has expired will fit into a single packet, subject
618 * to the MTU constraint for the path corresponding to the
619 * destination transport address to which the retransmission
620 * is being sent (this may be different from the address for
621 * which the timer expires [see Section 6.4]). Call this value
622 * K. Bundle and retransmit those K DATA chunks in a single
623 * packet to the destination endpoint.
624 *
625 * [Just to be painfully clear, if we are retransmitting
626 * because a timeout just happened, we should send only ONE
627 * packet of retransmitted data.]
628 *
629 * For fast retransmissions we also send only ONE packet. However,
630 * if we are just flushing the queue due to open window, we'll
631 * try to send as much as possible.
632 */
633 list_for_each_entry_safe(chunk, chunk1, lqueue, transmitted_list) {
634 /* If the chunk is abandoned, move it to abandoned list. */
635 if (sctp_chunk_abandoned(chunk)) {
636 list_del_init(&chunk->transmitted_list);
637 sctp_insert_list(&q->abandoned,
638 &chunk->transmitted_list);
639 continue;
640 }
641
642 /* Make sure that Gap Acked TSNs are not retransmitted. A
643 * simple approach is just to move such TSNs out of the
644 * way and into a 'transmitted' queue and skip to the
645 * next chunk.
646 */
647 if (chunk->tsn_gap_acked) {
648 list_move_tail(&chunk->transmitted_list,
649 &transport->transmitted);
650 continue;
651 }
652
653 /* If we are doing fast retransmit, ignore non-fast_rtransmit
654 * chunks
655 */
656 if (fast_rtx && !chunk->fast_retransmit)
657 continue;
658
659 redo:
660 /* Attempt to append this chunk to the packet. */
661 status = sctp_packet_append_chunk(pkt, chunk);
662
663 switch (status) {
664 case SCTP_XMIT_PMTU_FULL:
665 if (!pkt->has_data && !pkt->has_cookie_echo) {
666 /* If this packet did not contain DATA then
667 * retransmission did not happen, so do it
668 * again. We'll ignore the error here since
669 * control chunks are already freed so there
670 * is nothing we can do.
671 */
672 sctp_packet_transmit(pkt, GFP_ATOMIC);
673 goto redo;
674 }
675
676 /* Send this packet. */
677 error = sctp_packet_transmit(pkt, GFP_ATOMIC);
678
679 /* If we are retransmitting, we should only
680 * send a single packet.
681 * Otherwise, try appending this chunk again.
682 */
683 if (rtx_timeout || fast_rtx)
684 done = 1;
685 else
686 goto redo;
687
688 /* Bundle next chunk in the next round. */
689 break;
690
691 case SCTP_XMIT_RWND_FULL:
692 /* Send this packet. */
693 error = sctp_packet_transmit(pkt, GFP_ATOMIC);
694
695 /* Stop sending DATA as there is no more room
696 * at the receiver.
697 */
698 done = 1;
699 break;
700
701 case SCTP_XMIT_DELAY:
702 /* Send this packet. */
703 error = sctp_packet_transmit(pkt, GFP_ATOMIC);
704
705 /* Stop sending DATA because of nagle delay. */
706 done = 1;
707 break;
708
709 default:
710 /* The append was successful, so add this chunk to
711 * the transmitted list.
712 */
713 list_move_tail(&chunk->transmitted_list,
714 &transport->transmitted);
715
716 /* Mark the chunk as ineligible for fast retransmit
717 * after it is retransmitted.
718 */
719 if (chunk->fast_retransmit == SCTP_NEED_FRTX)
720 chunk->fast_retransmit = SCTP_DONT_FRTX;
721
722 q->asoc->stats.rtxchunks++;
723 break;
724 }
725
726 /* Set the timer if there were no errors */
727 if (!error && !timer)
728 timer = 1;
729
730 if (done)
731 break;
732 }
733
734 /* If we are here due to a retransmit timeout or a fast
735 * retransmit and if there are any chunks left in the retransmit
736 * queue that could not fit in the PMTU sized packet, they need
737 * to be marked as ineligible for a subsequent fast retransmit.
738 */
739 if (rtx_timeout || fast_rtx) {
740 list_for_each_entry(chunk1, lqueue, transmitted_list) {
741 if (chunk1->fast_retransmit == SCTP_NEED_FRTX)
742 chunk1->fast_retransmit = SCTP_DONT_FRTX;
743 }
744 }
745
746 *start_timer = timer;
747
748 /* Clear fast retransmit hint */
749 if (fast_rtx)
750 q->fast_rtx = 0;
751
752 return error;
753 }
754
755 /* Cork the outqueue so queued chunks are really queued. */
sctp_outq_uncork(struct sctp_outq * q,gfp_t gfp)756 void sctp_outq_uncork(struct sctp_outq *q, gfp_t gfp)
757 {
758 if (q->cork)
759 q->cork = 0;
760
761 sctp_outq_flush(q, 0, gfp);
762 }
763
764
765 /*
766 * Try to flush an outqueue.
767 *
768 * Description: Send everything in q which we legally can, subject to
769 * congestion limitations.
770 * * Note: This function can be called from multiple contexts so appropriate
771 * locking concerns must be made. Today we use the sock lock to protect
772 * this function.
773 */
sctp_outq_flush(struct sctp_outq * q,int rtx_timeout,gfp_t gfp)774 static void sctp_outq_flush(struct sctp_outq *q, int rtx_timeout, gfp_t gfp)
775 {
776 struct sctp_packet *packet;
777 struct sctp_packet singleton;
778 struct sctp_association *asoc = q->asoc;
779 __u16 sport = asoc->base.bind_addr.port;
780 __u16 dport = asoc->peer.port;
781 __u32 vtag = asoc->peer.i.init_tag;
782 struct sctp_transport *transport = NULL;
783 struct sctp_transport *new_transport;
784 struct sctp_chunk *chunk, *tmp;
785 enum sctp_xmit status;
786 int error = 0;
787 int start_timer = 0;
788 int one_packet = 0;
789
790 /* These transports have chunks to send. */
791 struct list_head transport_list;
792 struct list_head *ltransport;
793
794 INIT_LIST_HEAD(&transport_list);
795 packet = NULL;
796
797 /*
798 * 6.10 Bundling
799 * ...
800 * When bundling control chunks with DATA chunks, an
801 * endpoint MUST place control chunks first in the outbound
802 * SCTP packet. The transmitter MUST transmit DATA chunks
803 * within a SCTP packet in increasing order of TSN.
804 * ...
805 */
806
807 list_for_each_entry_safe(chunk, tmp, &q->control_chunk_list, list) {
808 /* RFC 5061, 5.3
809 * F1) This means that until such time as the ASCONF
810 * containing the add is acknowledged, the sender MUST
811 * NOT use the new IP address as a source for ANY SCTP
812 * packet except on carrying an ASCONF Chunk.
813 */
814 if (asoc->src_out_of_asoc_ok &&
815 chunk->chunk_hdr->type != SCTP_CID_ASCONF)
816 continue;
817
818 list_del_init(&chunk->list);
819
820 /* Pick the right transport to use. */
821 new_transport = chunk->transport;
822
823 if (!new_transport) {
824 /*
825 * If we have a prior transport pointer, see if
826 * the destination address of the chunk
827 * matches the destination address of the
828 * current transport. If not a match, then
829 * try to look up the transport with a given
830 * destination address. We do this because
831 * after processing ASCONFs, we may have new
832 * transports created.
833 */
834 if (transport &&
835 sctp_cmp_addr_exact(&chunk->dest,
836 &transport->ipaddr))
837 new_transport = transport;
838 else
839 new_transport = sctp_assoc_lookup_paddr(asoc,
840 &chunk->dest);
841
842 /* if we still don't have a new transport, then
843 * use the current active path.
844 */
845 if (!new_transport)
846 new_transport = asoc->peer.active_path;
847 } else if ((new_transport->state == SCTP_INACTIVE) ||
848 (new_transport->state == SCTP_UNCONFIRMED) ||
849 (new_transport->state == SCTP_PF)) {
850 /* If the chunk is Heartbeat or Heartbeat Ack,
851 * send it to chunk->transport, even if it's
852 * inactive.
853 *
854 * 3.3.6 Heartbeat Acknowledgement:
855 * ...
856 * A HEARTBEAT ACK is always sent to the source IP
857 * address of the IP datagram containing the
858 * HEARTBEAT chunk to which this ack is responding.
859 * ...
860 *
861 * ASCONF_ACKs also must be sent to the source.
862 */
863 if (chunk->chunk_hdr->type != SCTP_CID_HEARTBEAT &&
864 chunk->chunk_hdr->type != SCTP_CID_HEARTBEAT_ACK &&
865 chunk->chunk_hdr->type != SCTP_CID_ASCONF_ACK)
866 new_transport = asoc->peer.active_path;
867 }
868
869 /* Are we switching transports?
870 * Take care of transport locks.
871 */
872 if (new_transport != transport) {
873 transport = new_transport;
874 if (list_empty(&transport->send_ready)) {
875 list_add_tail(&transport->send_ready,
876 &transport_list);
877 }
878 packet = &transport->packet;
879 sctp_packet_config(packet, vtag,
880 asoc->peer.ecn_capable);
881 }
882
883 switch (chunk->chunk_hdr->type) {
884 /*
885 * 6.10 Bundling
886 * ...
887 * An endpoint MUST NOT bundle INIT, INIT ACK or SHUTDOWN
888 * COMPLETE with any other chunks. [Send them immediately.]
889 */
890 case SCTP_CID_INIT:
891 case SCTP_CID_INIT_ACK:
892 case SCTP_CID_SHUTDOWN_COMPLETE:
893 sctp_packet_init(&singleton, transport, sport, dport);
894 sctp_packet_config(&singleton, vtag, 0);
895 sctp_packet_append_chunk(&singleton, chunk);
896 error = sctp_packet_transmit(&singleton, gfp);
897 if (error < 0) {
898 asoc->base.sk->sk_err = -error;
899 return;
900 }
901 break;
902
903 case SCTP_CID_ABORT:
904 if (sctp_test_T_bit(chunk)) {
905 packet->vtag = asoc->c.my_vtag;
906 }
907 /* The following chunks are "response" chunks, i.e.
908 * they are generated in response to something we
909 * received. If we are sending these, then we can
910 * send only 1 packet containing these chunks.
911 */
912 case SCTP_CID_HEARTBEAT_ACK:
913 case SCTP_CID_SHUTDOWN_ACK:
914 case SCTP_CID_COOKIE_ACK:
915 case SCTP_CID_COOKIE_ECHO:
916 case SCTP_CID_ERROR:
917 case SCTP_CID_ECN_CWR:
918 case SCTP_CID_ASCONF_ACK:
919 one_packet = 1;
920 /* Fall through */
921
922 case SCTP_CID_SACK:
923 case SCTP_CID_HEARTBEAT:
924 case SCTP_CID_SHUTDOWN:
925 case SCTP_CID_ECN_ECNE:
926 case SCTP_CID_ASCONF:
927 case SCTP_CID_FWD_TSN:
928 case SCTP_CID_RECONF:
929 status = sctp_packet_transmit_chunk(packet, chunk,
930 one_packet, gfp);
931 if (status != SCTP_XMIT_OK) {
932 /* put the chunk back */
933 list_add(&chunk->list, &q->control_chunk_list);
934 break;
935 }
936
937 asoc->stats.octrlchunks++;
938 /* PR-SCTP C5) If a FORWARD TSN is sent, the
939 * sender MUST assure that at least one T3-rtx
940 * timer is running.
941 */
942 if (chunk->chunk_hdr->type == SCTP_CID_FWD_TSN) {
943 sctp_transport_reset_t3_rtx(transport);
944 transport->last_time_sent = jiffies;
945 }
946
947 if (chunk == asoc->strreset_chunk)
948 sctp_transport_reset_reconf_timer(transport);
949
950 break;
951
952 default:
953 /* We built a chunk with an illegal type! */
954 BUG();
955 }
956 }
957
958 if (q->asoc->src_out_of_asoc_ok)
959 goto sctp_flush_out;
960
961 /* Is it OK to send data chunks? */
962 switch (asoc->state) {
963 case SCTP_STATE_COOKIE_ECHOED:
964 /* Only allow bundling when this packet has a COOKIE-ECHO
965 * chunk.
966 */
967 if (!packet || !packet->has_cookie_echo)
968 break;
969
970 /* fallthru */
971 case SCTP_STATE_ESTABLISHED:
972 case SCTP_STATE_SHUTDOWN_PENDING:
973 case SCTP_STATE_SHUTDOWN_RECEIVED:
974 /*
975 * RFC 2960 6.1 Transmission of DATA Chunks
976 *
977 * C) When the time comes for the sender to transmit,
978 * before sending new DATA chunks, the sender MUST
979 * first transmit any outstanding DATA chunks which
980 * are marked for retransmission (limited by the
981 * current cwnd).
982 */
983 if (!list_empty(&q->retransmit)) {
984 if (asoc->peer.retran_path->state == SCTP_UNCONFIRMED)
985 goto sctp_flush_out;
986 if (transport == asoc->peer.retran_path)
987 goto retran;
988
989 /* Switch transports & prepare the packet. */
990
991 transport = asoc->peer.retran_path;
992
993 if (list_empty(&transport->send_ready)) {
994 list_add_tail(&transport->send_ready,
995 &transport_list);
996 }
997
998 packet = &transport->packet;
999 sctp_packet_config(packet, vtag,
1000 asoc->peer.ecn_capable);
1001 retran:
1002 error = sctp_outq_flush_rtx(q, packet,
1003 rtx_timeout, &start_timer);
1004 if (error < 0)
1005 asoc->base.sk->sk_err = -error;
1006
1007 if (start_timer) {
1008 sctp_transport_reset_t3_rtx(transport);
1009 transport->last_time_sent = jiffies;
1010 }
1011
1012 /* This can happen on COOKIE-ECHO resend. Only
1013 * one chunk can get bundled with a COOKIE-ECHO.
1014 */
1015 if (packet->has_cookie_echo)
1016 goto sctp_flush_out;
1017
1018 /* Don't send new data if there is still data
1019 * waiting to retransmit.
1020 */
1021 if (!list_empty(&q->retransmit))
1022 goto sctp_flush_out;
1023 }
1024
1025 /* Apply Max.Burst limitation to the current transport in
1026 * case it will be used for new data. We are going to
1027 * rest it before we return, but we want to apply the limit
1028 * to the currently queued data.
1029 */
1030 if (transport)
1031 sctp_transport_burst_limited(transport);
1032
1033 /* Finally, transmit new packets. */
1034 while ((chunk = sctp_outq_dequeue_data(q)) != NULL) {
1035 __u32 sid = ntohs(chunk->subh.data_hdr->stream);
1036
1037 /* RFC 2960 6.5 Every DATA chunk MUST carry a valid
1038 * stream identifier.
1039 */
1040 if (chunk->sinfo.sinfo_stream >= asoc->stream.outcnt) {
1041
1042 /* Mark as failed send. */
1043 sctp_chunk_fail(chunk, SCTP_ERROR_INV_STRM);
1044 if (asoc->peer.prsctp_capable &&
1045 SCTP_PR_PRIO_ENABLED(chunk->sinfo.sinfo_flags))
1046 asoc->sent_cnt_removable--;
1047 sctp_chunk_free(chunk);
1048 continue;
1049 }
1050
1051 /* Has this chunk expired? */
1052 if (sctp_chunk_abandoned(chunk)) {
1053 sctp_chunk_fail(chunk, 0);
1054 sctp_chunk_free(chunk);
1055 continue;
1056 }
1057
1058 if (asoc->stream.out[sid].state == SCTP_STREAM_CLOSED) {
1059 sctp_outq_head_data(q, chunk);
1060 goto sctp_flush_out;
1061 }
1062
1063 /* If there is a specified transport, use it.
1064 * Otherwise, we want to use the active path.
1065 */
1066 new_transport = chunk->transport;
1067 if (!new_transport ||
1068 ((new_transport->state == SCTP_INACTIVE) ||
1069 (new_transport->state == SCTP_UNCONFIRMED) ||
1070 (new_transport->state == SCTP_PF)))
1071 new_transport = asoc->peer.active_path;
1072 if (new_transport->state == SCTP_UNCONFIRMED) {
1073 WARN_ONCE(1, "Attempt to send packet on unconfirmed path.");
1074 sctp_chunk_fail(chunk, 0);
1075 sctp_chunk_free(chunk);
1076 continue;
1077 }
1078
1079 /* Change packets if necessary. */
1080 if (new_transport != transport) {
1081 transport = new_transport;
1082
1083 /* Schedule to have this transport's
1084 * packet flushed.
1085 */
1086 if (list_empty(&transport->send_ready)) {
1087 list_add_tail(&transport->send_ready,
1088 &transport_list);
1089 }
1090
1091 packet = &transport->packet;
1092 sctp_packet_config(packet, vtag,
1093 asoc->peer.ecn_capable);
1094 /* We've switched transports, so apply the
1095 * Burst limit to the new transport.
1096 */
1097 sctp_transport_burst_limited(transport);
1098 }
1099
1100 pr_debug("%s: outq:%p, chunk:%p[%s], tx-tsn:0x%x skb->head:%p "
1101 "skb->users:%d\n",
1102 __func__, q, chunk, chunk && chunk->chunk_hdr ?
1103 sctp_cname(SCTP_ST_CHUNK(chunk->chunk_hdr->type)) :
1104 "illegal chunk", ntohl(chunk->subh.data_hdr->tsn),
1105 chunk->skb ? chunk->skb->head : NULL, chunk->skb ?
1106 refcount_read(&chunk->skb->users) : -1);
1107
1108 /* Add the chunk to the packet. */
1109 status = sctp_packet_transmit_chunk(packet, chunk, 0, gfp);
1110
1111 switch (status) {
1112 case SCTP_XMIT_PMTU_FULL:
1113 case SCTP_XMIT_RWND_FULL:
1114 case SCTP_XMIT_DELAY:
1115 /* We could not append this chunk, so put
1116 * the chunk back on the output queue.
1117 */
1118 pr_debug("%s: could not transmit tsn:0x%x, status:%d\n",
1119 __func__, ntohl(chunk->subh.data_hdr->tsn),
1120 status);
1121
1122 sctp_outq_head_data(q, chunk);
1123 goto sctp_flush_out;
1124
1125 case SCTP_XMIT_OK:
1126 /* The sender is in the SHUTDOWN-PENDING state,
1127 * The sender MAY set the I-bit in the DATA
1128 * chunk header.
1129 */
1130 if (asoc->state == SCTP_STATE_SHUTDOWN_PENDING)
1131 chunk->chunk_hdr->flags |= SCTP_DATA_SACK_IMM;
1132 if (chunk->chunk_hdr->flags & SCTP_DATA_UNORDERED)
1133 asoc->stats.ouodchunks++;
1134 else
1135 asoc->stats.oodchunks++;
1136
1137 break;
1138
1139 default:
1140 BUG();
1141 }
1142
1143 /* BUG: We assume that the sctp_packet_transmit()
1144 * call below will succeed all the time and add the
1145 * chunk to the transmitted list and restart the
1146 * timers.
1147 * It is possible that the call can fail under OOM
1148 * conditions.
1149 *
1150 * Is this really a problem? Won't this behave
1151 * like a lost TSN?
1152 */
1153 list_add_tail(&chunk->transmitted_list,
1154 &transport->transmitted);
1155
1156 sctp_transport_reset_t3_rtx(transport);
1157 transport->last_time_sent = jiffies;
1158
1159 /* Only let one DATA chunk get bundled with a
1160 * COOKIE-ECHO chunk.
1161 */
1162 if (packet->has_cookie_echo)
1163 goto sctp_flush_out;
1164 }
1165 break;
1166
1167 default:
1168 /* Do nothing. */
1169 break;
1170 }
1171
1172 sctp_flush_out:
1173
1174 /* Before returning, examine all the transports touched in
1175 * this call. Right now, we bluntly force clear all the
1176 * transports. Things might change after we implement Nagle.
1177 * But such an examination is still required.
1178 *
1179 * --xguo
1180 */
1181 while ((ltransport = sctp_list_dequeue(&transport_list)) != NULL) {
1182 struct sctp_transport *t = list_entry(ltransport,
1183 struct sctp_transport,
1184 send_ready);
1185 packet = &t->packet;
1186 if (!sctp_packet_empty(packet)) {
1187 error = sctp_packet_transmit(packet, gfp);
1188 if (error < 0)
1189 asoc->base.sk->sk_err = -error;
1190 }
1191
1192 /* Clear the burst limited state, if any */
1193 sctp_transport_burst_reset(t);
1194 }
1195 }
1196
1197 /* Update unack_data based on the incoming SACK chunk */
sctp_sack_update_unack_data(struct sctp_association * assoc,struct sctp_sackhdr * sack)1198 static void sctp_sack_update_unack_data(struct sctp_association *assoc,
1199 struct sctp_sackhdr *sack)
1200 {
1201 union sctp_sack_variable *frags;
1202 __u16 unack_data;
1203 int i;
1204
1205 unack_data = assoc->next_tsn - assoc->ctsn_ack_point - 1;
1206
1207 frags = sack->variable;
1208 for (i = 0; i < ntohs(sack->num_gap_ack_blocks); i++) {
1209 unack_data -= ((ntohs(frags[i].gab.end) -
1210 ntohs(frags[i].gab.start) + 1));
1211 }
1212
1213 assoc->unack_data = unack_data;
1214 }
1215
1216 /* This is where we REALLY process a SACK.
1217 *
1218 * Process the SACK against the outqueue. Mostly, this just frees
1219 * things off the transmitted queue.
1220 */
sctp_outq_sack(struct sctp_outq * q,struct sctp_chunk * chunk)1221 int sctp_outq_sack(struct sctp_outq *q, struct sctp_chunk *chunk)
1222 {
1223 struct sctp_association *asoc = q->asoc;
1224 struct sctp_sackhdr *sack = chunk->subh.sack_hdr;
1225 struct sctp_transport *transport;
1226 struct sctp_chunk *tchunk = NULL;
1227 struct list_head *lchunk, *transport_list, *temp;
1228 union sctp_sack_variable *frags = sack->variable;
1229 __u32 sack_ctsn, ctsn, tsn;
1230 __u32 highest_tsn, highest_new_tsn;
1231 __u32 sack_a_rwnd;
1232 unsigned int outstanding;
1233 struct sctp_transport *primary = asoc->peer.primary_path;
1234 int count_of_newacks = 0;
1235 int gap_ack_blocks;
1236 u8 accum_moved = 0;
1237
1238 /* Grab the association's destination address list. */
1239 transport_list = &asoc->peer.transport_addr_list;
1240
1241 sack_ctsn = ntohl(sack->cum_tsn_ack);
1242 gap_ack_blocks = ntohs(sack->num_gap_ack_blocks);
1243 asoc->stats.gapcnt += gap_ack_blocks;
1244 /*
1245 * SFR-CACC algorithm:
1246 * On receipt of a SACK the sender SHOULD execute the
1247 * following statements.
1248 *
1249 * 1) If the cumulative ack in the SACK passes next tsn_at_change
1250 * on the current primary, the CHANGEOVER_ACTIVE flag SHOULD be
1251 * cleared. The CYCLING_CHANGEOVER flag SHOULD also be cleared for
1252 * all destinations.
1253 * 2) If the SACK contains gap acks and the flag CHANGEOVER_ACTIVE
1254 * is set the receiver of the SACK MUST take the following actions:
1255 *
1256 * A) Initialize the cacc_saw_newack to 0 for all destination
1257 * addresses.
1258 *
1259 * Only bother if changeover_active is set. Otherwise, this is
1260 * totally suboptimal to do on every SACK.
1261 */
1262 if (primary->cacc.changeover_active) {
1263 u8 clear_cycling = 0;
1264
1265 if (TSN_lte(primary->cacc.next_tsn_at_change, sack_ctsn)) {
1266 primary->cacc.changeover_active = 0;
1267 clear_cycling = 1;
1268 }
1269
1270 if (clear_cycling || gap_ack_blocks) {
1271 list_for_each_entry(transport, transport_list,
1272 transports) {
1273 if (clear_cycling)
1274 transport->cacc.cycling_changeover = 0;
1275 if (gap_ack_blocks)
1276 transport->cacc.cacc_saw_newack = 0;
1277 }
1278 }
1279 }
1280
1281 /* Get the highest TSN in the sack. */
1282 highest_tsn = sack_ctsn;
1283 if (gap_ack_blocks)
1284 highest_tsn += ntohs(frags[gap_ack_blocks - 1].gab.end);
1285
1286 if (TSN_lt(asoc->highest_sacked, highest_tsn))
1287 asoc->highest_sacked = highest_tsn;
1288
1289 highest_new_tsn = sack_ctsn;
1290
1291 /* Run through the retransmit queue. Credit bytes received
1292 * and free those chunks that we can.
1293 */
1294 sctp_check_transmitted(q, &q->retransmit, NULL, NULL, sack, &highest_new_tsn);
1295
1296 /* Run through the transmitted queue.
1297 * Credit bytes received and free those chunks which we can.
1298 *
1299 * This is a MASSIVE candidate for optimization.
1300 */
1301 list_for_each_entry(transport, transport_list, transports) {
1302 sctp_check_transmitted(q, &transport->transmitted,
1303 transport, &chunk->source, sack,
1304 &highest_new_tsn);
1305 /*
1306 * SFR-CACC algorithm:
1307 * C) Let count_of_newacks be the number of
1308 * destinations for which cacc_saw_newack is set.
1309 */
1310 if (transport->cacc.cacc_saw_newack)
1311 count_of_newacks++;
1312 }
1313
1314 /* Move the Cumulative TSN Ack Point if appropriate. */
1315 if (TSN_lt(asoc->ctsn_ack_point, sack_ctsn)) {
1316 asoc->ctsn_ack_point = sack_ctsn;
1317 accum_moved = 1;
1318 }
1319
1320 if (gap_ack_blocks) {
1321
1322 if (asoc->fast_recovery && accum_moved)
1323 highest_new_tsn = highest_tsn;
1324
1325 list_for_each_entry(transport, transport_list, transports)
1326 sctp_mark_missing(q, &transport->transmitted, transport,
1327 highest_new_tsn, count_of_newacks);
1328 }
1329
1330 /* Update unack_data field in the assoc. */
1331 sctp_sack_update_unack_data(asoc, sack);
1332
1333 ctsn = asoc->ctsn_ack_point;
1334
1335 /* Throw away stuff rotting on the sack queue. */
1336 list_for_each_safe(lchunk, temp, &q->sacked) {
1337 tchunk = list_entry(lchunk, struct sctp_chunk,
1338 transmitted_list);
1339 tsn = ntohl(tchunk->subh.data_hdr->tsn);
1340 if (TSN_lte(tsn, ctsn)) {
1341 list_del_init(&tchunk->transmitted_list);
1342 if (asoc->peer.prsctp_capable &&
1343 SCTP_PR_PRIO_ENABLED(chunk->sinfo.sinfo_flags))
1344 asoc->sent_cnt_removable--;
1345 sctp_chunk_free(tchunk);
1346 }
1347 }
1348
1349 /* ii) Set rwnd equal to the newly received a_rwnd minus the
1350 * number of bytes still outstanding after processing the
1351 * Cumulative TSN Ack and the Gap Ack Blocks.
1352 */
1353
1354 sack_a_rwnd = ntohl(sack->a_rwnd);
1355 asoc->peer.zero_window_announced = !sack_a_rwnd;
1356 outstanding = q->outstanding_bytes;
1357
1358 if (outstanding < sack_a_rwnd)
1359 sack_a_rwnd -= outstanding;
1360 else
1361 sack_a_rwnd = 0;
1362
1363 asoc->peer.rwnd = sack_a_rwnd;
1364
1365 sctp_generate_fwdtsn(q, sack_ctsn);
1366
1367 pr_debug("%s: sack cumulative tsn ack:0x%x\n", __func__, sack_ctsn);
1368 pr_debug("%s: cumulative tsn ack of assoc:%p is 0x%x, "
1369 "advertised peer ack point:0x%x\n", __func__, asoc, ctsn,
1370 asoc->adv_peer_ack_point);
1371
1372 return sctp_outq_is_empty(q);
1373 }
1374
1375 /* Is the outqueue empty?
1376 * The queue is empty when we have not pending data, no in-flight data
1377 * and nothing pending retransmissions.
1378 */
sctp_outq_is_empty(const struct sctp_outq * q)1379 int sctp_outq_is_empty(const struct sctp_outq *q)
1380 {
1381 return q->out_qlen == 0 && q->outstanding_bytes == 0 &&
1382 list_empty(&q->retransmit);
1383 }
1384
1385 /********************************************************************
1386 * 2nd Level Abstractions
1387 ********************************************************************/
1388
1389 /* Go through a transport's transmitted list or the association's retransmit
1390 * list and move chunks that are acked by the Cumulative TSN Ack to q->sacked.
1391 * The retransmit list will not have an associated transport.
1392 *
1393 * I added coherent debug information output. --xguo
1394 *
1395 * Instead of printing 'sacked' or 'kept' for each TSN on the
1396 * transmitted_queue, we print a range: SACKED: TSN1-TSN2, TSN3, TSN4-TSN5.
1397 * KEPT TSN6-TSN7, etc.
1398 */
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)1399 static void sctp_check_transmitted(struct sctp_outq *q,
1400 struct list_head *transmitted_queue,
1401 struct sctp_transport *transport,
1402 union sctp_addr *saddr,
1403 struct sctp_sackhdr *sack,
1404 __u32 *highest_new_tsn_in_sack)
1405 {
1406 struct list_head *lchunk;
1407 struct sctp_chunk *tchunk;
1408 struct list_head tlist;
1409 __u32 tsn;
1410 __u32 sack_ctsn;
1411 __u32 rtt;
1412 __u8 restart_timer = 0;
1413 int bytes_acked = 0;
1414 int migrate_bytes = 0;
1415 bool forward_progress = false;
1416
1417 sack_ctsn = ntohl(sack->cum_tsn_ack);
1418
1419 INIT_LIST_HEAD(&tlist);
1420
1421 /* The while loop will skip empty transmitted queues. */
1422 while (NULL != (lchunk = sctp_list_dequeue(transmitted_queue))) {
1423 tchunk = list_entry(lchunk, struct sctp_chunk,
1424 transmitted_list);
1425
1426 if (sctp_chunk_abandoned(tchunk)) {
1427 /* Move the chunk to abandoned list. */
1428 sctp_insert_list(&q->abandoned, lchunk);
1429
1430 /* If this chunk has not been acked, stop
1431 * considering it as 'outstanding'.
1432 */
1433 if (transmitted_queue != &q->retransmit &&
1434 !tchunk->tsn_gap_acked) {
1435 if (tchunk->transport)
1436 tchunk->transport->flight_size -=
1437 sctp_data_size(tchunk);
1438 q->outstanding_bytes -= sctp_data_size(tchunk);
1439 }
1440 continue;
1441 }
1442
1443 tsn = ntohl(tchunk->subh.data_hdr->tsn);
1444 if (sctp_acked(sack, tsn)) {
1445 /* If this queue is the retransmit queue, the
1446 * retransmit timer has already reclaimed
1447 * the outstanding bytes for this chunk, so only
1448 * count bytes associated with a transport.
1449 */
1450 if (transport) {
1451 /* If this chunk is being used for RTT
1452 * measurement, calculate the RTT and update
1453 * the RTO using this value.
1454 *
1455 * 6.3.1 C5) Karn's algorithm: RTT measurements
1456 * MUST NOT be made using packets that were
1457 * retransmitted (and thus for which it is
1458 * ambiguous whether the reply was for the
1459 * first instance of the packet or a later
1460 * instance).
1461 */
1462 if (!tchunk->tsn_gap_acked &&
1463 !sctp_chunk_retransmitted(tchunk) &&
1464 tchunk->rtt_in_progress) {
1465 tchunk->rtt_in_progress = 0;
1466 rtt = jiffies - tchunk->sent_at;
1467 sctp_transport_update_rto(transport,
1468 rtt);
1469 }
1470 }
1471
1472 /* If the chunk hasn't been marked as ACKED,
1473 * mark it and account bytes_acked if the
1474 * chunk had a valid transport (it will not
1475 * have a transport if ASCONF had deleted it
1476 * while DATA was outstanding).
1477 */
1478 if (!tchunk->tsn_gap_acked) {
1479 tchunk->tsn_gap_acked = 1;
1480 if (TSN_lt(*highest_new_tsn_in_sack, tsn))
1481 *highest_new_tsn_in_sack = tsn;
1482 bytes_acked += sctp_data_size(tchunk);
1483 if (!tchunk->transport)
1484 migrate_bytes += sctp_data_size(tchunk);
1485 forward_progress = true;
1486 }
1487
1488 if (TSN_lte(tsn, sack_ctsn)) {
1489 /* RFC 2960 6.3.2 Retransmission Timer Rules
1490 *
1491 * R3) Whenever a SACK is received
1492 * that acknowledges the DATA chunk
1493 * with the earliest outstanding TSN
1494 * for that address, restart T3-rtx
1495 * timer for that address with its
1496 * current RTO.
1497 */
1498 restart_timer = 1;
1499 forward_progress = true;
1500
1501 if (!tchunk->tsn_gap_acked) {
1502 /*
1503 * SFR-CACC algorithm:
1504 * 2) If the SACK contains gap acks
1505 * and the flag CHANGEOVER_ACTIVE is
1506 * set the receiver of the SACK MUST
1507 * take the following action:
1508 *
1509 * B) For each TSN t being acked that
1510 * has not been acked in any SACK so
1511 * far, set cacc_saw_newack to 1 for
1512 * the destination that the TSN was
1513 * sent to.
1514 */
1515 if (transport &&
1516 sack->num_gap_ack_blocks &&
1517 q->asoc->peer.primary_path->cacc.
1518 changeover_active)
1519 transport->cacc.cacc_saw_newack
1520 = 1;
1521 }
1522
1523 list_add_tail(&tchunk->transmitted_list,
1524 &q->sacked);
1525 } else {
1526 /* RFC2960 7.2.4, sctpimpguide-05 2.8.2
1527 * M2) Each time a SACK arrives reporting
1528 * 'Stray DATA chunk(s)' record the highest TSN
1529 * reported as newly acknowledged, call this
1530 * value 'HighestTSNinSack'. A newly
1531 * acknowledged DATA chunk is one not
1532 * previously acknowledged in a SACK.
1533 *
1534 * When the SCTP sender of data receives a SACK
1535 * chunk that acknowledges, for the first time,
1536 * the receipt of a DATA chunk, all the still
1537 * unacknowledged DATA chunks whose TSN is
1538 * older than that newly acknowledged DATA
1539 * chunk, are qualified as 'Stray DATA chunks'.
1540 */
1541 list_add_tail(lchunk, &tlist);
1542 }
1543 } else {
1544 if (tchunk->tsn_gap_acked) {
1545 pr_debug("%s: receiver reneged on data TSN:0x%x\n",
1546 __func__, tsn);
1547
1548 tchunk->tsn_gap_acked = 0;
1549
1550 if (tchunk->transport)
1551 bytes_acked -= sctp_data_size(tchunk);
1552
1553 /* RFC 2960 6.3.2 Retransmission Timer Rules
1554 *
1555 * R4) Whenever a SACK is received missing a
1556 * TSN that was previously acknowledged via a
1557 * Gap Ack Block, start T3-rtx for the
1558 * destination address to which the DATA
1559 * chunk was originally
1560 * transmitted if it is not already running.
1561 */
1562 restart_timer = 1;
1563 }
1564
1565 list_add_tail(lchunk, &tlist);
1566 }
1567 }
1568
1569 if (transport) {
1570 if (bytes_acked) {
1571 struct sctp_association *asoc = transport->asoc;
1572
1573 /* We may have counted DATA that was migrated
1574 * to this transport due to DEL-IP operation.
1575 * Subtract those bytes, since the were never
1576 * send on this transport and shouldn't be
1577 * credited to this transport.
1578 */
1579 bytes_acked -= migrate_bytes;
1580
1581 /* 8.2. When an outstanding TSN is acknowledged,
1582 * the endpoint shall clear the error counter of
1583 * the destination transport address to which the
1584 * DATA chunk was last sent.
1585 * The association's overall error counter is
1586 * also cleared.
1587 */
1588 transport->error_count = 0;
1589 transport->asoc->overall_error_count = 0;
1590 forward_progress = true;
1591
1592 /*
1593 * While in SHUTDOWN PENDING, we may have started
1594 * the T5 shutdown guard timer after reaching the
1595 * retransmission limit. Stop that timer as soon
1596 * as the receiver acknowledged any data.
1597 */
1598 if (asoc->state == SCTP_STATE_SHUTDOWN_PENDING &&
1599 del_timer(&asoc->timers
1600 [SCTP_EVENT_TIMEOUT_T5_SHUTDOWN_GUARD]))
1601 sctp_association_put(asoc);
1602
1603 /* Mark the destination transport address as
1604 * active if it is not so marked.
1605 */
1606 if ((transport->state == SCTP_INACTIVE ||
1607 transport->state == SCTP_UNCONFIRMED) &&
1608 sctp_cmp_addr_exact(&transport->ipaddr, saddr)) {
1609 sctp_assoc_control_transport(
1610 transport->asoc,
1611 transport,
1612 SCTP_TRANSPORT_UP,
1613 SCTP_RECEIVED_SACK);
1614 }
1615
1616 sctp_transport_raise_cwnd(transport, sack_ctsn,
1617 bytes_acked);
1618
1619 transport->flight_size -= bytes_acked;
1620 if (transport->flight_size == 0)
1621 transport->partial_bytes_acked = 0;
1622 q->outstanding_bytes -= bytes_acked + migrate_bytes;
1623 } else {
1624 /* RFC 2960 6.1, sctpimpguide-06 2.15.2
1625 * When a sender is doing zero window probing, it
1626 * should not timeout the association if it continues
1627 * to receive new packets from the receiver. The
1628 * reason is that the receiver MAY keep its window
1629 * closed for an indefinite time.
1630 * A sender is doing zero window probing when the
1631 * receiver's advertised window is zero, and there is
1632 * only one data chunk in flight to the receiver.
1633 *
1634 * Allow the association to timeout while in SHUTDOWN
1635 * PENDING or SHUTDOWN RECEIVED in case the receiver
1636 * stays in zero window mode forever.
1637 */
1638 if (!q->asoc->peer.rwnd &&
1639 !list_empty(&tlist) &&
1640 (sack_ctsn+2 == q->asoc->next_tsn) &&
1641 q->asoc->state < SCTP_STATE_SHUTDOWN_PENDING) {
1642 pr_debug("%s: sack received for zero window "
1643 "probe:%u\n", __func__, sack_ctsn);
1644
1645 q->asoc->overall_error_count = 0;
1646 transport->error_count = 0;
1647 }
1648 }
1649
1650 /* RFC 2960 6.3.2 Retransmission Timer Rules
1651 *
1652 * R2) Whenever all outstanding data sent to an address have
1653 * been acknowledged, turn off the T3-rtx timer of that
1654 * address.
1655 */
1656 if (!transport->flight_size) {
1657 if (del_timer(&transport->T3_rtx_timer))
1658 sctp_transport_put(transport);
1659 } else if (restart_timer) {
1660 if (!mod_timer(&transport->T3_rtx_timer,
1661 jiffies + transport->rto))
1662 sctp_transport_hold(transport);
1663 }
1664
1665 if (forward_progress) {
1666 if (transport->dst)
1667 sctp_transport_dst_confirm(transport);
1668 }
1669 }
1670
1671 list_splice(&tlist, transmitted_queue);
1672 }
1673
1674 /* 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)1675 static void sctp_mark_missing(struct sctp_outq *q,
1676 struct list_head *transmitted_queue,
1677 struct sctp_transport *transport,
1678 __u32 highest_new_tsn_in_sack,
1679 int count_of_newacks)
1680 {
1681 struct sctp_chunk *chunk;
1682 __u32 tsn;
1683 char do_fast_retransmit = 0;
1684 struct sctp_association *asoc = q->asoc;
1685 struct sctp_transport *primary = asoc->peer.primary_path;
1686
1687 list_for_each_entry(chunk, transmitted_queue, transmitted_list) {
1688
1689 tsn = ntohl(chunk->subh.data_hdr->tsn);
1690
1691 /* RFC 2960 7.2.4, sctpimpguide-05 2.8.2 M3) Examine all
1692 * 'Unacknowledged TSN's', if the TSN number of an
1693 * 'Unacknowledged TSN' is smaller than the 'HighestTSNinSack'
1694 * value, increment the 'TSN.Missing.Report' count on that
1695 * chunk if it has NOT been fast retransmitted or marked for
1696 * fast retransmit already.
1697 */
1698 if (chunk->fast_retransmit == SCTP_CAN_FRTX &&
1699 !chunk->tsn_gap_acked &&
1700 TSN_lt(tsn, highest_new_tsn_in_sack)) {
1701
1702 /* SFR-CACC may require us to skip marking
1703 * this chunk as missing.
1704 */
1705 if (!transport || !sctp_cacc_skip(primary,
1706 chunk->transport,
1707 count_of_newacks, tsn)) {
1708 chunk->tsn_missing_report++;
1709
1710 pr_debug("%s: tsn:0x%x missing counter:%d\n",
1711 __func__, tsn, chunk->tsn_missing_report);
1712 }
1713 }
1714 /*
1715 * M4) If any DATA chunk is found to have a
1716 * 'TSN.Missing.Report'
1717 * value larger than or equal to 3, mark that chunk for
1718 * retransmission and start the fast retransmit procedure.
1719 */
1720
1721 if (chunk->tsn_missing_report >= 3) {
1722 chunk->fast_retransmit = SCTP_NEED_FRTX;
1723 do_fast_retransmit = 1;
1724 }
1725 }
1726
1727 if (transport) {
1728 if (do_fast_retransmit)
1729 sctp_retransmit(q, transport, SCTP_RTXR_FAST_RTX);
1730
1731 pr_debug("%s: transport:%p, cwnd:%d, ssthresh:%d, "
1732 "flight_size:%d, pba:%d\n", __func__, transport,
1733 transport->cwnd, transport->ssthresh,
1734 transport->flight_size, transport->partial_bytes_acked);
1735 }
1736 }
1737
1738 /* Is the given TSN acked by this packet? */
sctp_acked(struct sctp_sackhdr * sack,__u32 tsn)1739 static int sctp_acked(struct sctp_sackhdr *sack, __u32 tsn)
1740 {
1741 __u32 ctsn = ntohl(sack->cum_tsn_ack);
1742 union sctp_sack_variable *frags;
1743 __u16 tsn_offset, blocks;
1744 int i;
1745
1746 if (TSN_lte(tsn, ctsn))
1747 goto pass;
1748
1749 /* 3.3.4 Selective Acknowledgement (SACK) (3):
1750 *
1751 * Gap Ack Blocks:
1752 * These fields contain the Gap Ack Blocks. They are repeated
1753 * for each Gap Ack Block up to the number of Gap Ack Blocks
1754 * defined in the Number of Gap Ack Blocks field. All DATA
1755 * chunks with TSNs greater than or equal to (Cumulative TSN
1756 * Ack + Gap Ack Block Start) and less than or equal to
1757 * (Cumulative TSN Ack + Gap Ack Block End) of each Gap Ack
1758 * Block are assumed to have been received correctly.
1759 */
1760
1761 frags = sack->variable;
1762 blocks = ntohs(sack->num_gap_ack_blocks);
1763 tsn_offset = tsn - ctsn;
1764 for (i = 0; i < blocks; ++i) {
1765 if (tsn_offset >= ntohs(frags[i].gab.start) &&
1766 tsn_offset <= ntohs(frags[i].gab.end))
1767 goto pass;
1768 }
1769
1770 return 0;
1771 pass:
1772 return 1;
1773 }
1774
sctp_get_skip_pos(struct sctp_fwdtsn_skip * skiplist,int nskips,__be16 stream)1775 static inline int sctp_get_skip_pos(struct sctp_fwdtsn_skip *skiplist,
1776 int nskips, __be16 stream)
1777 {
1778 int i;
1779
1780 for (i = 0; i < nskips; i++) {
1781 if (skiplist[i].stream == stream)
1782 return i;
1783 }
1784 return i;
1785 }
1786
1787 /* Create and add a fwdtsn chunk to the outq's control queue if needed. */
sctp_generate_fwdtsn(struct sctp_outq * q,__u32 ctsn)1788 static void sctp_generate_fwdtsn(struct sctp_outq *q, __u32 ctsn)
1789 {
1790 struct sctp_association *asoc = q->asoc;
1791 struct sctp_chunk *ftsn_chunk = NULL;
1792 struct sctp_fwdtsn_skip ftsn_skip_arr[10];
1793 int nskips = 0;
1794 int skip_pos = 0;
1795 __u32 tsn;
1796 struct sctp_chunk *chunk;
1797 struct list_head *lchunk, *temp;
1798
1799 if (!asoc->peer.prsctp_capable)
1800 return;
1801
1802 /* PR-SCTP C1) Let SackCumAck be the Cumulative TSN ACK carried in the
1803 * received SACK.
1804 *
1805 * If (Advanced.Peer.Ack.Point < SackCumAck), then update
1806 * Advanced.Peer.Ack.Point to be equal to SackCumAck.
1807 */
1808 if (TSN_lt(asoc->adv_peer_ack_point, ctsn))
1809 asoc->adv_peer_ack_point = ctsn;
1810
1811 /* PR-SCTP C2) Try to further advance the "Advanced.Peer.Ack.Point"
1812 * locally, that is, to move "Advanced.Peer.Ack.Point" up as long as
1813 * the chunk next in the out-queue space is marked as "abandoned" as
1814 * shown in the following example:
1815 *
1816 * Assuming that a SACK arrived with the Cumulative TSN ACK 102
1817 * and the Advanced.Peer.Ack.Point is updated to this value:
1818 *
1819 * out-queue at the end of ==> out-queue after Adv.Ack.Point
1820 * normal SACK processing local advancement
1821 * ... ...
1822 * Adv.Ack.Pt-> 102 acked 102 acked
1823 * 103 abandoned 103 abandoned
1824 * 104 abandoned Adv.Ack.P-> 104 abandoned
1825 * 105 105
1826 * 106 acked 106 acked
1827 * ... ...
1828 *
1829 * In this example, the data sender successfully advanced the
1830 * "Advanced.Peer.Ack.Point" from 102 to 104 locally.
1831 */
1832 list_for_each_safe(lchunk, temp, &q->abandoned) {
1833 chunk = list_entry(lchunk, struct sctp_chunk,
1834 transmitted_list);
1835 tsn = ntohl(chunk->subh.data_hdr->tsn);
1836
1837 /* Remove any chunks in the abandoned queue that are acked by
1838 * the ctsn.
1839 */
1840 if (TSN_lte(tsn, ctsn)) {
1841 list_del_init(lchunk);
1842 sctp_chunk_free(chunk);
1843 } else {
1844 if (TSN_lte(tsn, asoc->adv_peer_ack_point+1)) {
1845 asoc->adv_peer_ack_point = tsn;
1846 if (chunk->chunk_hdr->flags &
1847 SCTP_DATA_UNORDERED)
1848 continue;
1849 skip_pos = sctp_get_skip_pos(&ftsn_skip_arr[0],
1850 nskips,
1851 chunk->subh.data_hdr->stream);
1852 ftsn_skip_arr[skip_pos].stream =
1853 chunk->subh.data_hdr->stream;
1854 ftsn_skip_arr[skip_pos].ssn =
1855 chunk->subh.data_hdr->ssn;
1856 if (skip_pos == nskips)
1857 nskips++;
1858 if (nskips == 10)
1859 break;
1860 } else
1861 break;
1862 }
1863 }
1864
1865 /* PR-SCTP C3) If, after step C1 and C2, the "Advanced.Peer.Ack.Point"
1866 * is greater than the Cumulative TSN ACK carried in the received
1867 * SACK, the data sender MUST send the data receiver a FORWARD TSN
1868 * chunk containing the latest value of the
1869 * "Advanced.Peer.Ack.Point".
1870 *
1871 * C4) For each "abandoned" TSN the sender of the FORWARD TSN SHOULD
1872 * list each stream and sequence number in the forwarded TSN. This
1873 * information will enable the receiver to easily find any
1874 * stranded TSN's waiting on stream reorder queues. Each stream
1875 * SHOULD only be reported once; this means that if multiple
1876 * abandoned messages occur in the same stream then only the
1877 * highest abandoned stream sequence number is reported. If the
1878 * total size of the FORWARD TSN does NOT fit in a single MTU then
1879 * the sender of the FORWARD TSN SHOULD lower the
1880 * Advanced.Peer.Ack.Point to the last TSN that will fit in a
1881 * single MTU.
1882 */
1883 if (asoc->adv_peer_ack_point > ctsn)
1884 ftsn_chunk = sctp_make_fwdtsn(asoc, asoc->adv_peer_ack_point,
1885 nskips, &ftsn_skip_arr[0]);
1886
1887 if (ftsn_chunk) {
1888 list_add_tail(&ftsn_chunk->list, &q->control_chunk_list);
1889 SCTP_INC_STATS(sock_net(asoc->base.sk), SCTP_MIB_OUTCTRLCHUNKS);
1890 }
1891 }
1892