Merge tag 'arc-5.2-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/vgupta/arc
[sfrench/cifs-2.6.git] / net / sctp / outqueue.c
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
40 /* Declare internal functions here.  */
41 static int sctp_acked(struct sctp_sackhdr *sack, __u32 tsn);
42 static void sctp_check_transmitted(struct sctp_outq *q,
43                                    struct list_head *transmitted_queue,
44                                    struct sctp_transport *transport,
45                                    union sctp_addr *saddr,
46                                    struct sctp_sackhdr *sack,
47                                    __u32 *highest_new_tsn);
48
49 static void sctp_mark_missing(struct sctp_outq *q,
50                               struct list_head *transmitted_queue,
51                               struct sctp_transport *transport,
52                               __u32 highest_new_tsn,
53                               int count_of_newacks);
54
55 static void sctp_outq_flush(struct sctp_outq *q, int rtx_timeout, gfp_t gfp);
56
57 /* Add data to the front of the queue. */
58 static inline void sctp_outq_head_data(struct sctp_outq *q,
59                                        struct sctp_chunk *ch)
60 {
61         struct sctp_stream_out_ext *oute;
62         __u16 stream;
63
64         list_add(&ch->list, &q->out_chunk_list);
65         q->out_qlen += ch->skb->len;
66
67         stream = sctp_chunk_stream_no(ch);
68         oute = SCTP_SO(&q->asoc->stream, stream)->ext;
69         list_add(&ch->stream_list, &oute->outq);
70 }
71
72 /* Take data from the front of the queue. */
73 static inline struct sctp_chunk *sctp_outq_dequeue_data(struct sctp_outq *q)
74 {
75         return q->sched->dequeue(q);
76 }
77
78 /* Add data chunk to the end of the queue. */
79 static inline void sctp_outq_tail_data(struct sctp_outq *q,
80                                        struct sctp_chunk *ch)
81 {
82         struct sctp_stream_out_ext *oute;
83         __u16 stream;
84
85         list_add_tail(&ch->list, &q->out_chunk_list);
86         q->out_qlen += ch->skb->len;
87
88         stream = sctp_chunk_stream_no(ch);
89         oute = SCTP_SO(&q->asoc->stream, stream)->ext;
90         list_add_tail(&ch->stream_list, &oute->outq);
91 }
92
93 /*
94  * SFR-CACC algorithm:
95  * D) If count_of_newacks is greater than or equal to 2
96  * and t was not sent to the current primary then the
97  * sender MUST NOT increment missing report count for t.
98  */
99 static inline int sctp_cacc_skip_3_1_d(struct sctp_transport *primary,
100                                        struct sctp_transport *transport,
101                                        int count_of_newacks)
102 {
103         if (count_of_newacks >= 2 && transport != primary)
104                 return 1;
105         return 0;
106 }
107
108 /*
109  * SFR-CACC algorithm:
110  * F) If count_of_newacks is less than 2, let d be the
111  * destination to which t was sent. If cacc_saw_newack
112  * is 0 for destination d, then the sender MUST NOT
113  * increment missing report count for t.
114  */
115 static inline int sctp_cacc_skip_3_1_f(struct sctp_transport *transport,
116                                        int count_of_newacks)
117 {
118         if (count_of_newacks < 2 &&
119                         (transport && !transport->cacc.cacc_saw_newack))
120                 return 1;
121         return 0;
122 }
123
124 /*
125  * SFR-CACC algorithm:
126  * 3.1) If CYCLING_CHANGEOVER is 0, the sender SHOULD
127  * execute steps C, D, F.
128  *
129  * C has been implemented in sctp_outq_sack
130  */
131 static inline int sctp_cacc_skip_3_1(struct sctp_transport *primary,
132                                      struct sctp_transport *transport,
133                                      int count_of_newacks)
134 {
135         if (!primary->cacc.cycling_changeover) {
136                 if (sctp_cacc_skip_3_1_d(primary, transport, count_of_newacks))
137                         return 1;
138                 if (sctp_cacc_skip_3_1_f(transport, count_of_newacks))
139                         return 1;
140                 return 0;
141         }
142         return 0;
143 }
144
145 /*
146  * SFR-CACC algorithm:
147  * 3.2) Else if CYCLING_CHANGEOVER is 1, and t is less
148  * than next_tsn_at_change of the current primary, then
149  * the sender MUST NOT increment missing report count
150  * for t.
151  */
152 static inline int sctp_cacc_skip_3_2(struct sctp_transport *primary, __u32 tsn)
153 {
154         if (primary->cacc.cycling_changeover &&
155             TSN_lt(tsn, primary->cacc.next_tsn_at_change))
156                 return 1;
157         return 0;
158 }
159
160 /*
161  * SFR-CACC algorithm:
162  * 3) If the missing report count for TSN t is to be
163  * incremented according to [RFC2960] and
164  * [SCTP_STEWART-2002], and CHANGEOVER_ACTIVE is set,
165  * then the sender MUST further execute steps 3.1 and
166  * 3.2 to determine if the missing report count for
167  * TSN t SHOULD NOT be incremented.
168  *
169  * 3.3) If 3.1 and 3.2 do not dictate that the missing
170  * report count for t should not be incremented, then
171  * the sender SHOULD increment missing report count for
172  * t (according to [RFC2960] and [SCTP_STEWART_2002]).
173  */
174 static inline int sctp_cacc_skip(struct sctp_transport *primary,
175                                  struct sctp_transport *transport,
176                                  int count_of_newacks,
177                                  __u32 tsn)
178 {
179         if (primary->cacc.changeover_active &&
180             (sctp_cacc_skip_3_1(primary, transport, count_of_newacks) ||
181              sctp_cacc_skip_3_2(primary, tsn)))
182                 return 1;
183         return 0;
184 }
185
186 /* Initialize an existing sctp_outq.  This does the boring stuff.
187  * You still need to define handlers if you really want to DO
188  * something with this structure...
189  */
190 void sctp_outq_init(struct sctp_association *asoc, struct sctp_outq *q)
191 {
192         memset(q, 0, sizeof(struct sctp_outq));
193
194         q->asoc = asoc;
195         INIT_LIST_HEAD(&q->out_chunk_list);
196         INIT_LIST_HEAD(&q->control_chunk_list);
197         INIT_LIST_HEAD(&q->retransmit);
198         INIT_LIST_HEAD(&q->sacked);
199         INIT_LIST_HEAD(&q->abandoned);
200         sctp_sched_set_sched(asoc, sctp_sk(asoc->base.sk)->default_ss);
201 }
202
203 /* Free the outqueue structure and any related pending chunks.
204  */
205 static void __sctp_outq_teardown(struct sctp_outq *q)
206 {
207         struct sctp_transport *transport;
208         struct list_head *lchunk, *temp;
209         struct sctp_chunk *chunk, *tmp;
210
211         /* Throw away unacknowledged chunks. */
212         list_for_each_entry(transport, &q->asoc->peer.transport_addr_list,
213                         transports) {
214                 while ((lchunk = sctp_list_dequeue(&transport->transmitted)) != NULL) {
215                         chunk = list_entry(lchunk, struct sctp_chunk,
216                                            transmitted_list);
217                         /* Mark as part of a failed message. */
218                         sctp_chunk_fail(chunk, q->error);
219                         sctp_chunk_free(chunk);
220                 }
221         }
222
223         /* Throw away chunks that have been gap ACKed.  */
224         list_for_each_safe(lchunk, temp, &q->sacked) {
225                 list_del_init(lchunk);
226                 chunk = list_entry(lchunk, struct sctp_chunk,
227                                    transmitted_list);
228                 sctp_chunk_fail(chunk, q->error);
229                 sctp_chunk_free(chunk);
230         }
231
232         /* Throw away any chunks in the retransmit queue. */
233         list_for_each_safe(lchunk, temp, &q->retransmit) {
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 that are in the abandoned queue. */
242         list_for_each_safe(lchunk, temp, &q->abandoned) {
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 leftover data chunks. */
251         while ((chunk = sctp_outq_dequeue_data(q)) != NULL) {
252                 sctp_sched_dequeue_done(q, chunk);
253
254                 /* Mark as send failure. */
255                 sctp_chunk_fail(chunk, q->error);
256                 sctp_chunk_free(chunk);
257         }
258
259         /* Throw away any leftover control chunks. */
260         list_for_each_entry_safe(chunk, tmp, &q->control_chunk_list, list) {
261                 list_del_init(&chunk->list);
262                 sctp_chunk_free(chunk);
263         }
264 }
265
266 void sctp_outq_teardown(struct sctp_outq *q)
267 {
268         __sctp_outq_teardown(q);
269         sctp_outq_init(q->asoc, q);
270 }
271
272 /* Free the outqueue structure and any related pending chunks.  */
273 void sctp_outq_free(struct sctp_outq *q)
274 {
275         /* Throw away leftover chunks. */
276         __sctp_outq_teardown(q);
277 }
278
279 /* Put a new chunk in an sctp_outq.  */
280 void sctp_outq_tail(struct sctp_outq *q, struct sctp_chunk *chunk, gfp_t gfp)
281 {
282         struct net *net = sock_net(q->asoc->base.sk);
283
284         pr_debug("%s: outq:%p, chunk:%p[%s]\n", __func__, q, chunk,
285                  chunk && chunk->chunk_hdr ?
286                  sctp_cname(SCTP_ST_CHUNK(chunk->chunk_hdr->type)) :
287                  "illegal chunk");
288
289         /* If it is data, queue it up, otherwise, send it
290          * immediately.
291          */
292         if (sctp_chunk_is_data(chunk)) {
293                 pr_debug("%s: outqueueing: outq:%p, chunk:%p[%s])\n",
294                          __func__, q, chunk, chunk && chunk->chunk_hdr ?
295                          sctp_cname(SCTP_ST_CHUNK(chunk->chunk_hdr->type)) :
296                          "illegal chunk");
297
298                 sctp_outq_tail_data(q, chunk);
299                 if (chunk->asoc->peer.prsctp_capable &&
300                     SCTP_PR_PRIO_ENABLED(chunk->sinfo.sinfo_flags))
301                         chunk->asoc->sent_cnt_removable++;
302                 if (chunk->chunk_hdr->flags & SCTP_DATA_UNORDERED)
303                         SCTP_INC_STATS(net, SCTP_MIB_OUTUNORDERCHUNKS);
304                 else
305                         SCTP_INC_STATS(net, SCTP_MIB_OUTORDERCHUNKS);
306         } else {
307                 list_add_tail(&chunk->list, &q->control_chunk_list);
308                 SCTP_INC_STATS(net, SCTP_MIB_OUTCTRLCHUNKS);
309         }
310
311         if (!q->cork)
312                 sctp_outq_flush(q, 0, gfp);
313 }
314
315 /* Insert a chunk into the sorted list based on the TSNs.  The retransmit list
316  * and the abandoned list are in ascending order.
317  */
318 static void sctp_insert_list(struct list_head *head, struct list_head *new)
319 {
320         struct list_head *pos;
321         struct sctp_chunk *nchunk, *lchunk;
322         __u32 ntsn, ltsn;
323         int done = 0;
324
325         nchunk = list_entry(new, struct sctp_chunk, transmitted_list);
326         ntsn = ntohl(nchunk->subh.data_hdr->tsn);
327
328         list_for_each(pos, head) {
329                 lchunk = list_entry(pos, struct sctp_chunk, transmitted_list);
330                 ltsn = ntohl(lchunk->subh.data_hdr->tsn);
331                 if (TSN_lt(ntsn, ltsn)) {
332                         list_add(new, pos->prev);
333                         done = 1;
334                         break;
335                 }
336         }
337         if (!done)
338                 list_add_tail(new, head);
339 }
340
341 static int sctp_prsctp_prune_sent(struct sctp_association *asoc,
342                                   struct sctp_sndrcvinfo *sinfo,
343                                   struct list_head *queue, int msg_len)
344 {
345         struct sctp_chunk *chk, *temp;
346
347         list_for_each_entry_safe(chk, temp, queue, transmitted_list) {
348                 struct sctp_stream_out *streamout;
349
350                 if (!chk->msg->abandoned &&
351                     (!SCTP_PR_PRIO_ENABLED(chk->sinfo.sinfo_flags) ||
352                      chk->sinfo.sinfo_timetolive <= sinfo->sinfo_timetolive))
353                         continue;
354
355                 chk->msg->abandoned = 1;
356                 list_del_init(&chk->transmitted_list);
357                 sctp_insert_list(&asoc->outqueue.abandoned,
358                                  &chk->transmitted_list);
359
360                 streamout = SCTP_SO(&asoc->stream, chk->sinfo.sinfo_stream);
361                 asoc->sent_cnt_removable--;
362                 asoc->abandoned_sent[SCTP_PR_INDEX(PRIO)]++;
363                 streamout->ext->abandoned_sent[SCTP_PR_INDEX(PRIO)]++;
364
365                 if (queue != &asoc->outqueue.retransmit &&
366                     !chk->tsn_gap_acked) {
367                         if (chk->transport)
368                                 chk->transport->flight_size -=
369                                                 sctp_data_size(chk);
370                         asoc->outqueue.outstanding_bytes -= sctp_data_size(chk);
371                 }
372
373                 msg_len -= chk->skb->truesize + sizeof(struct sctp_chunk);
374                 if (msg_len <= 0)
375                         break;
376         }
377
378         return msg_len;
379 }
380
381 static int sctp_prsctp_prune_unsent(struct sctp_association *asoc,
382                                     struct sctp_sndrcvinfo *sinfo, int msg_len)
383 {
384         struct sctp_outq *q = &asoc->outqueue;
385         struct sctp_chunk *chk, *temp;
386
387         q->sched->unsched_all(&asoc->stream);
388
389         list_for_each_entry_safe(chk, temp, &q->out_chunk_list, list) {
390                 if (!chk->msg->abandoned &&
391                     (!(chk->chunk_hdr->flags & SCTP_DATA_FIRST_FRAG) ||
392                      !SCTP_PR_PRIO_ENABLED(chk->sinfo.sinfo_flags) ||
393                      chk->sinfo.sinfo_timetolive <= sinfo->sinfo_timetolive))
394                         continue;
395
396                 chk->msg->abandoned = 1;
397                 sctp_sched_dequeue_common(q, chk);
398                 asoc->sent_cnt_removable--;
399                 asoc->abandoned_unsent[SCTP_PR_INDEX(PRIO)]++;
400                 if (chk->sinfo.sinfo_stream < asoc->stream.outcnt) {
401                         struct sctp_stream_out *streamout =
402                                 SCTP_SO(&asoc->stream, chk->sinfo.sinfo_stream);
403
404                         streamout->ext->abandoned_unsent[SCTP_PR_INDEX(PRIO)]++;
405                 }
406
407                 msg_len -= chk->skb->truesize + sizeof(struct sctp_chunk);
408                 sctp_chunk_free(chk);
409                 if (msg_len <= 0)
410                         break;
411         }
412
413         q->sched->sched_all(&asoc->stream);
414
415         return msg_len;
416 }
417
418 /* Abandon the chunks according their priorities */
419 void sctp_prsctp_prune(struct sctp_association *asoc,
420                        struct sctp_sndrcvinfo *sinfo, int msg_len)
421 {
422         struct sctp_transport *transport;
423
424         if (!asoc->peer.prsctp_capable || !asoc->sent_cnt_removable)
425                 return;
426
427         msg_len = sctp_prsctp_prune_sent(asoc, sinfo,
428                                          &asoc->outqueue.retransmit,
429                                          msg_len);
430         if (msg_len <= 0)
431                 return;
432
433         list_for_each_entry(transport, &asoc->peer.transport_addr_list,
434                             transports) {
435                 msg_len = sctp_prsctp_prune_sent(asoc, sinfo,
436                                                  &transport->transmitted,
437                                                  msg_len);
438                 if (msg_len <= 0)
439                         return;
440         }
441
442         sctp_prsctp_prune_unsent(asoc, sinfo, msg_len);
443 }
444
445 /* Mark all the eligible packets on a transport for retransmission.  */
446 void sctp_retransmit_mark(struct sctp_outq *q,
447                           struct sctp_transport *transport,
448                           __u8 reason)
449 {
450         struct list_head *lchunk, *ltemp;
451         struct sctp_chunk *chunk;
452
453         /* Walk through the specified transmitted queue.  */
454         list_for_each_safe(lchunk, ltemp, &transport->transmitted) {
455                 chunk = list_entry(lchunk, struct sctp_chunk,
456                                    transmitted_list);
457
458                 /* If the chunk is abandoned, move it to abandoned list. */
459                 if (sctp_chunk_abandoned(chunk)) {
460                         list_del_init(lchunk);
461                         sctp_insert_list(&q->abandoned, lchunk);
462
463                         /* If this chunk has not been previousely acked,
464                          * stop considering it 'outstanding'.  Our peer
465                          * will most likely never see it since it will
466                          * not be retransmitted
467                          */
468                         if (!chunk->tsn_gap_acked) {
469                                 if (chunk->transport)
470                                         chunk->transport->flight_size -=
471                                                         sctp_data_size(chunk);
472                                 q->outstanding_bytes -= sctp_data_size(chunk);
473                                 q->asoc->peer.rwnd += sctp_data_size(chunk);
474                         }
475                         continue;
476                 }
477
478                 /* If we are doing  retransmission due to a timeout or pmtu
479                  * discovery, only the  chunks that are not yet acked should
480                  * be added to the retransmit queue.
481                  */
482                 if ((reason == SCTP_RTXR_FAST_RTX  &&
483                             (chunk->fast_retransmit == SCTP_NEED_FRTX)) ||
484                     (reason != SCTP_RTXR_FAST_RTX  && !chunk->tsn_gap_acked)) {
485                         /* RFC 2960 6.2.1 Processing a Received SACK
486                          *
487                          * C) Any time a DATA chunk is marked for
488                          * retransmission (via either T3-rtx timer expiration
489                          * (Section 6.3.3) or via fast retransmit
490                          * (Section 7.2.4)), add the data size of those
491                          * chunks to the rwnd.
492                          */
493                         q->asoc->peer.rwnd += sctp_data_size(chunk);
494                         q->outstanding_bytes -= sctp_data_size(chunk);
495                         if (chunk->transport)
496                                 transport->flight_size -= sctp_data_size(chunk);
497
498                         /* sctpimpguide-05 Section 2.8.2
499                          * M5) If a T3-rtx timer expires, the
500                          * 'TSN.Missing.Report' of all affected TSNs is set
501                          * to 0.
502                          */
503                         chunk->tsn_missing_report = 0;
504
505                         /* If a chunk that is being used for RTT measurement
506                          * has to be retransmitted, we cannot use this chunk
507                          * anymore for RTT measurements. Reset rto_pending so
508                          * that a new RTT measurement is started when a new
509                          * data chunk is sent.
510                          */
511                         if (chunk->rtt_in_progress) {
512                                 chunk->rtt_in_progress = 0;
513                                 transport->rto_pending = 0;
514                         }
515
516                         /* Move the chunk to the retransmit queue. The chunks
517                          * on the retransmit queue are always kept in order.
518                          */
519                         list_del_init(lchunk);
520                         sctp_insert_list(&q->retransmit, lchunk);
521                 }
522         }
523
524         pr_debug("%s: transport:%p, reason:%d, cwnd:%d, ssthresh:%d, "
525                  "flight_size:%d, pba:%d\n", __func__, transport, reason,
526                  transport->cwnd, transport->ssthresh, transport->flight_size,
527                  transport->partial_bytes_acked);
528 }
529
530 /* Mark all the eligible packets on a transport for retransmission and force
531  * one packet out.
532  */
533 void sctp_retransmit(struct sctp_outq *q, struct sctp_transport *transport,
534                      enum sctp_retransmit_reason reason)
535 {
536         struct net *net = sock_net(q->asoc->base.sk);
537
538         switch (reason) {
539         case SCTP_RTXR_T3_RTX:
540                 SCTP_INC_STATS(net, SCTP_MIB_T3_RETRANSMITS);
541                 sctp_transport_lower_cwnd(transport, SCTP_LOWER_CWND_T3_RTX);
542                 /* Update the retran path if the T3-rtx timer has expired for
543                  * the current retran path.
544                  */
545                 if (transport == transport->asoc->peer.retran_path)
546                         sctp_assoc_update_retran_path(transport->asoc);
547                 transport->asoc->rtx_data_chunks +=
548                         transport->asoc->unack_data;
549                 break;
550         case SCTP_RTXR_FAST_RTX:
551                 SCTP_INC_STATS(net, SCTP_MIB_FAST_RETRANSMITS);
552                 sctp_transport_lower_cwnd(transport, SCTP_LOWER_CWND_FAST_RTX);
553                 q->fast_rtx = 1;
554                 break;
555         case SCTP_RTXR_PMTUD:
556                 SCTP_INC_STATS(net, SCTP_MIB_PMTUD_RETRANSMITS);
557                 break;
558         case SCTP_RTXR_T1_RTX:
559                 SCTP_INC_STATS(net, SCTP_MIB_T1_RETRANSMITS);
560                 transport->asoc->init_retries++;
561                 break;
562         default:
563                 BUG();
564         }
565
566         sctp_retransmit_mark(q, transport, reason);
567
568         /* PR-SCTP A5) Any time the T3-rtx timer expires, on any destination,
569          * the sender SHOULD try to advance the "Advanced.Peer.Ack.Point" by
570          * following the procedures outlined in C1 - C5.
571          */
572         if (reason == SCTP_RTXR_T3_RTX)
573                 q->asoc->stream.si->generate_ftsn(q, q->asoc->ctsn_ack_point);
574
575         /* Flush the queues only on timeout, since fast_rtx is only
576          * triggered during sack processing and the queue
577          * will be flushed at the end.
578          */
579         if (reason != SCTP_RTXR_FAST_RTX)
580                 sctp_outq_flush(q, /* rtx_timeout */ 1, GFP_ATOMIC);
581 }
582
583 /*
584  * Transmit DATA chunks on the retransmit queue.  Upon return from
585  * __sctp_outq_flush_rtx() the packet 'pkt' may contain chunks which
586  * need to be transmitted by the caller.
587  * We assume that pkt->transport has already been set.
588  *
589  * The return value is a normal kernel error return value.
590  */
591 static int __sctp_outq_flush_rtx(struct sctp_outq *q, struct sctp_packet *pkt,
592                                  int rtx_timeout, int *start_timer, gfp_t gfp)
593 {
594         struct sctp_transport *transport = pkt->transport;
595         struct sctp_chunk *chunk, *chunk1;
596         struct list_head *lqueue;
597         enum sctp_xmit status;
598         int error = 0;
599         int timer = 0;
600         int done = 0;
601         int fast_rtx;
602
603         lqueue = &q->retransmit;
604         fast_rtx = q->fast_rtx;
605
606         /* This loop handles time-out retransmissions, fast retransmissions,
607          * and retransmissions due to opening of whindow.
608          *
609          * RFC 2960 6.3.3 Handle T3-rtx Expiration
610          *
611          * E3) Determine how many of the earliest (i.e., lowest TSN)
612          * outstanding DATA chunks for the address for which the
613          * T3-rtx has expired will fit into a single packet, subject
614          * to the MTU constraint for the path corresponding to the
615          * destination transport address to which the retransmission
616          * is being sent (this may be different from the address for
617          * which the timer expires [see Section 6.4]). Call this value
618          * K. Bundle and retransmit those K DATA chunks in a single
619          * packet to the destination endpoint.
620          *
621          * [Just to be painfully clear, if we are retransmitting
622          * because a timeout just happened, we should send only ONE
623          * packet of retransmitted data.]
624          *
625          * For fast retransmissions we also send only ONE packet.  However,
626          * if we are just flushing the queue due to open window, we'll
627          * try to send as much as possible.
628          */
629         list_for_each_entry_safe(chunk, chunk1, lqueue, transmitted_list) {
630                 /* If the chunk is abandoned, move it to abandoned list. */
631                 if (sctp_chunk_abandoned(chunk)) {
632                         list_del_init(&chunk->transmitted_list);
633                         sctp_insert_list(&q->abandoned,
634                                          &chunk->transmitted_list);
635                         continue;
636                 }
637
638                 /* Make sure that Gap Acked TSNs are not retransmitted.  A
639                  * simple approach is just to move such TSNs out of the
640                  * way and into a 'transmitted' queue and skip to the
641                  * next chunk.
642                  */
643                 if (chunk->tsn_gap_acked) {
644                         list_move_tail(&chunk->transmitted_list,
645                                        &transport->transmitted);
646                         continue;
647                 }
648
649                 /* If we are doing fast retransmit, ignore non-fast_rtransmit
650                  * chunks
651                  */
652                 if (fast_rtx && !chunk->fast_retransmit)
653                         continue;
654
655 redo:
656                 /* Attempt to append this chunk to the packet. */
657                 status = sctp_packet_append_chunk(pkt, chunk);
658
659                 switch (status) {
660                 case SCTP_XMIT_PMTU_FULL:
661                         if (!pkt->has_data && !pkt->has_cookie_echo) {
662                                 /* If this packet did not contain DATA then
663                                  * retransmission did not happen, so do it
664                                  * again.  We'll ignore the error here since
665                                  * control chunks are already freed so there
666                                  * is nothing we can do.
667                                  */
668                                 sctp_packet_transmit(pkt, gfp);
669                                 goto redo;
670                         }
671
672                         /* Send this packet.  */
673                         error = sctp_packet_transmit(pkt, gfp);
674
675                         /* If we are retransmitting, we should only
676                          * send a single packet.
677                          * Otherwise, try appending this chunk again.
678                          */
679                         if (rtx_timeout || fast_rtx)
680                                 done = 1;
681                         else
682                                 goto redo;
683
684                         /* Bundle next chunk in the next round.  */
685                         break;
686
687                 case SCTP_XMIT_RWND_FULL:
688                         /* Send this packet. */
689                         error = sctp_packet_transmit(pkt, gfp);
690
691                         /* Stop sending DATA as there is no more room
692                          * at the receiver.
693                          */
694                         done = 1;
695                         break;
696
697                 case SCTP_XMIT_DELAY:
698                         /* Send this packet. */
699                         error = sctp_packet_transmit(pkt, gfp);
700
701                         /* Stop sending DATA because of nagle delay. */
702                         done = 1;
703                         break;
704
705                 default:
706                         /* The append was successful, so add this chunk to
707                          * the transmitted list.
708                          */
709                         list_move_tail(&chunk->transmitted_list,
710                                        &transport->transmitted);
711
712                         /* Mark the chunk as ineligible for fast retransmit
713                          * after it is retransmitted.
714                          */
715                         if (chunk->fast_retransmit == SCTP_NEED_FRTX)
716                                 chunk->fast_retransmit = SCTP_DONT_FRTX;
717
718                         q->asoc->stats.rtxchunks++;
719                         break;
720                 }
721
722                 /* Set the timer if there were no errors */
723                 if (!error && !timer)
724                         timer = 1;
725
726                 if (done)
727                         break;
728         }
729
730         /* If we are here due to a retransmit timeout or a fast
731          * retransmit and if there are any chunks left in the retransmit
732          * queue that could not fit in the PMTU sized packet, they need
733          * to be marked as ineligible for a subsequent fast retransmit.
734          */
735         if (rtx_timeout || fast_rtx) {
736                 list_for_each_entry(chunk1, lqueue, transmitted_list) {
737                         if (chunk1->fast_retransmit == SCTP_NEED_FRTX)
738                                 chunk1->fast_retransmit = SCTP_DONT_FRTX;
739                 }
740         }
741
742         *start_timer = timer;
743
744         /* Clear fast retransmit hint */
745         if (fast_rtx)
746                 q->fast_rtx = 0;
747
748         return error;
749 }
750
751 /* Cork the outqueue so queued chunks are really queued. */
752 void sctp_outq_uncork(struct sctp_outq *q, gfp_t gfp)
753 {
754         if (q->cork)
755                 q->cork = 0;
756
757         sctp_outq_flush(q, 0, gfp);
758 }
759
760 static int sctp_packet_singleton(struct sctp_transport *transport,
761                                  struct sctp_chunk *chunk, gfp_t gfp)
762 {
763         const struct sctp_association *asoc = transport->asoc;
764         const __u16 sport = asoc->base.bind_addr.port;
765         const __u16 dport = asoc->peer.port;
766         const __u32 vtag = asoc->peer.i.init_tag;
767         struct sctp_packet singleton;
768
769         sctp_packet_init(&singleton, transport, sport, dport);
770         sctp_packet_config(&singleton, vtag, 0);
771         sctp_packet_append_chunk(&singleton, chunk);
772         return sctp_packet_transmit(&singleton, gfp);
773 }
774
775 /* Struct to hold the context during sctp outq flush */
776 struct sctp_flush_ctx {
777         struct sctp_outq *q;
778         /* Current transport being used. It's NOT the same as curr active one */
779         struct sctp_transport *transport;
780         /* These transports have chunks to send. */
781         struct list_head transport_list;
782         struct sctp_association *asoc;
783         /* Packet on the current transport above */
784         struct sctp_packet *packet;
785         gfp_t gfp;
786 };
787
788 /* transport: current transport */
789 static void sctp_outq_select_transport(struct sctp_flush_ctx *ctx,
790                                        struct sctp_chunk *chunk)
791 {
792         struct sctp_transport *new_transport = chunk->transport;
793
794         if (!new_transport) {
795                 if (!sctp_chunk_is_data(chunk)) {
796                         /* If we have a prior transport pointer, see if
797                          * the destination address of the chunk
798                          * matches the destination address of the
799                          * current transport.  If not a match, then
800                          * try to look up the transport with a given
801                          * destination address.  We do this because
802                          * after processing ASCONFs, we may have new
803                          * transports created.
804                          */
805                         if (ctx->transport && sctp_cmp_addr_exact(&chunk->dest,
806                                                         &ctx->transport->ipaddr))
807                                 new_transport = ctx->transport;
808                         else
809                                 new_transport = sctp_assoc_lookup_paddr(ctx->asoc,
810                                                                   &chunk->dest);
811                 }
812
813                 /* if we still don't have a new transport, then
814                  * use the current active path.
815                  */
816                 if (!new_transport)
817                         new_transport = ctx->asoc->peer.active_path;
818         } else {
819                 __u8 type;
820
821                 switch (new_transport->state) {
822                 case SCTP_INACTIVE:
823                 case SCTP_UNCONFIRMED:
824                 case SCTP_PF:
825                         /* If the chunk is Heartbeat or Heartbeat Ack,
826                          * send it to chunk->transport, even if it's
827                          * inactive.
828                          *
829                          * 3.3.6 Heartbeat Acknowledgement:
830                          * ...
831                          * A HEARTBEAT ACK is always sent to the source IP
832                          * address of the IP datagram containing the
833                          * HEARTBEAT chunk to which this ack is responding.
834                          * ...
835                          *
836                          * ASCONF_ACKs also must be sent to the source.
837                          */
838                         type = chunk->chunk_hdr->type;
839                         if (type != SCTP_CID_HEARTBEAT &&
840                             type != SCTP_CID_HEARTBEAT_ACK &&
841                             type != SCTP_CID_ASCONF_ACK)
842                                 new_transport = ctx->asoc->peer.active_path;
843                         break;
844                 default:
845                         break;
846                 }
847         }
848
849         /* Are we switching transports? Take care of transport locks. */
850         if (new_transport != ctx->transport) {
851                 ctx->transport = new_transport;
852                 ctx->packet = &ctx->transport->packet;
853
854                 if (list_empty(&ctx->transport->send_ready))
855                         list_add_tail(&ctx->transport->send_ready,
856                                       &ctx->transport_list);
857
858                 sctp_packet_config(ctx->packet,
859                                    ctx->asoc->peer.i.init_tag,
860                                    ctx->asoc->peer.ecn_capable);
861                 /* We've switched transports, so apply the
862                  * Burst limit to the new transport.
863                  */
864                 sctp_transport_burst_limited(ctx->transport);
865         }
866 }
867
868 static void sctp_outq_flush_ctrl(struct sctp_flush_ctx *ctx)
869 {
870         struct sctp_chunk *chunk, *tmp;
871         enum sctp_xmit status;
872         int one_packet, error;
873
874         list_for_each_entry_safe(chunk, tmp, &ctx->q->control_chunk_list, list) {
875                 one_packet = 0;
876
877                 /* RFC 5061, 5.3
878                  * F1) This means that until such time as the ASCONF
879                  * containing the add is acknowledged, the sender MUST
880                  * NOT use the new IP address as a source for ANY SCTP
881                  * packet except on carrying an ASCONF Chunk.
882                  */
883                 if (ctx->asoc->src_out_of_asoc_ok &&
884                     chunk->chunk_hdr->type != SCTP_CID_ASCONF)
885                         continue;
886
887                 list_del_init(&chunk->list);
888
889                 /* Pick the right transport to use. Should always be true for
890                  * the first chunk as we don't have a transport by then.
891                  */
892                 sctp_outq_select_transport(ctx, chunk);
893
894                 switch (chunk->chunk_hdr->type) {
895                 /* 6.10 Bundling
896                  *   ...
897                  *   An endpoint MUST NOT bundle INIT, INIT ACK or SHUTDOWN
898                  *   COMPLETE with any other chunks.  [Send them immediately.]
899                  */
900                 case SCTP_CID_INIT:
901                 case SCTP_CID_INIT_ACK:
902                 case SCTP_CID_SHUTDOWN_COMPLETE:
903                         error = sctp_packet_singleton(ctx->transport, chunk,
904                                                       ctx->gfp);
905                         if (error < 0) {
906                                 ctx->asoc->base.sk->sk_err = -error;
907                                 return;
908                         }
909                         break;
910
911                 case SCTP_CID_ABORT:
912                         if (sctp_test_T_bit(chunk))
913                                 ctx->packet->vtag = ctx->asoc->c.my_vtag;
914                         /* fallthru */
915
916                 /* The following chunks are "response" chunks, i.e.
917                  * they are generated in response to something we
918                  * received.  If we are sending these, then we can
919                  * send only 1 packet containing these chunks.
920                  */
921                 case SCTP_CID_HEARTBEAT_ACK:
922                 case SCTP_CID_SHUTDOWN_ACK:
923                 case SCTP_CID_COOKIE_ACK:
924                 case SCTP_CID_COOKIE_ECHO:
925                 case SCTP_CID_ERROR:
926                 case SCTP_CID_ECN_CWR:
927                 case SCTP_CID_ASCONF_ACK:
928                         one_packet = 1;
929                         /* Fall through */
930
931                 case SCTP_CID_SACK:
932                 case SCTP_CID_HEARTBEAT:
933                 case SCTP_CID_SHUTDOWN:
934                 case SCTP_CID_ECN_ECNE:
935                 case SCTP_CID_ASCONF:
936                 case SCTP_CID_FWD_TSN:
937                 case SCTP_CID_I_FWD_TSN:
938                 case SCTP_CID_RECONF:
939                         status = sctp_packet_transmit_chunk(ctx->packet, chunk,
940                                                             one_packet, ctx->gfp);
941                         if (status != SCTP_XMIT_OK) {
942                                 /* put the chunk back */
943                                 list_add(&chunk->list, &ctx->q->control_chunk_list);
944                                 break;
945                         }
946
947                         ctx->asoc->stats.octrlchunks++;
948                         /* PR-SCTP C5) If a FORWARD TSN is sent, the
949                          * sender MUST assure that at least one T3-rtx
950                          * timer is running.
951                          */
952                         if (chunk->chunk_hdr->type == SCTP_CID_FWD_TSN ||
953                             chunk->chunk_hdr->type == SCTP_CID_I_FWD_TSN) {
954                                 sctp_transport_reset_t3_rtx(ctx->transport);
955                                 ctx->transport->last_time_sent = jiffies;
956                         }
957
958                         if (chunk == ctx->asoc->strreset_chunk)
959                                 sctp_transport_reset_reconf_timer(ctx->transport);
960
961                         break;
962
963                 default:
964                         /* We built a chunk with an illegal type! */
965                         BUG();
966                 }
967         }
968 }
969
970 /* Returns false if new data shouldn't be sent */
971 static bool sctp_outq_flush_rtx(struct sctp_flush_ctx *ctx,
972                                 int rtx_timeout)
973 {
974         int error, start_timer = 0;
975
976         if (ctx->asoc->peer.retran_path->state == SCTP_UNCONFIRMED)
977                 return false;
978
979         if (ctx->transport != ctx->asoc->peer.retran_path) {
980                 /* Switch transports & prepare the packet.  */
981                 ctx->transport = ctx->asoc->peer.retran_path;
982                 ctx->packet = &ctx->transport->packet;
983
984                 if (list_empty(&ctx->transport->send_ready))
985                         list_add_tail(&ctx->transport->send_ready,
986                                       &ctx->transport_list);
987
988                 sctp_packet_config(ctx->packet, ctx->asoc->peer.i.init_tag,
989                                    ctx->asoc->peer.ecn_capable);
990         }
991
992         error = __sctp_outq_flush_rtx(ctx->q, ctx->packet, rtx_timeout,
993                                       &start_timer, ctx->gfp);
994         if (error < 0)
995                 ctx->asoc->base.sk->sk_err = -error;
996
997         if (start_timer) {
998                 sctp_transport_reset_t3_rtx(ctx->transport);
999                 ctx->transport->last_time_sent = jiffies;
1000         }
1001
1002         /* This can happen on COOKIE-ECHO resend.  Only
1003          * one chunk can get bundled with a COOKIE-ECHO.
1004          */
1005         if (ctx->packet->has_cookie_echo)
1006                 return false;
1007
1008         /* Don't send new data if there is still data
1009          * waiting to retransmit.
1010          */
1011         if (!list_empty(&ctx->q->retransmit))
1012                 return false;
1013
1014         return true;
1015 }
1016
1017 static void sctp_outq_flush_data(struct sctp_flush_ctx *ctx,
1018                                  int rtx_timeout)
1019 {
1020         struct sctp_chunk *chunk;
1021         enum sctp_xmit status;
1022
1023         /* Is it OK to send data chunks?  */
1024         switch (ctx->asoc->state) {
1025         case SCTP_STATE_COOKIE_ECHOED:
1026                 /* Only allow bundling when this packet has a COOKIE-ECHO
1027                  * chunk.
1028                  */
1029                 if (!ctx->packet || !ctx->packet->has_cookie_echo)
1030                         return;
1031
1032                 /* fall through */
1033         case SCTP_STATE_ESTABLISHED:
1034         case SCTP_STATE_SHUTDOWN_PENDING:
1035         case SCTP_STATE_SHUTDOWN_RECEIVED:
1036                 break;
1037
1038         default:
1039                 /* Do nothing. */
1040                 return;
1041         }
1042
1043         /* RFC 2960 6.1  Transmission of DATA Chunks
1044          *
1045          * C) When the time comes for the sender to transmit,
1046          * before sending new DATA chunks, the sender MUST
1047          * first transmit any outstanding DATA chunks which
1048          * are marked for retransmission (limited by the
1049          * current cwnd).
1050          */
1051         if (!list_empty(&ctx->q->retransmit) &&
1052             !sctp_outq_flush_rtx(ctx, rtx_timeout))
1053                 return;
1054
1055         /* Apply Max.Burst limitation to the current transport in
1056          * case it will be used for new data.  We are going to
1057          * rest it before we return, but we want to apply the limit
1058          * to the currently queued data.
1059          */
1060         if (ctx->transport)
1061                 sctp_transport_burst_limited(ctx->transport);
1062
1063         /* Finally, transmit new packets.  */
1064         while ((chunk = sctp_outq_dequeue_data(ctx->q)) != NULL) {
1065                 __u32 sid = ntohs(chunk->subh.data_hdr->stream);
1066                 __u8 stream_state = SCTP_SO(&ctx->asoc->stream, sid)->state;
1067
1068                 /* Has this chunk expired? */
1069                 if (sctp_chunk_abandoned(chunk)) {
1070                         sctp_sched_dequeue_done(ctx->q, chunk);
1071                         sctp_chunk_fail(chunk, 0);
1072                         sctp_chunk_free(chunk);
1073                         continue;
1074                 }
1075
1076                 if (stream_state == SCTP_STREAM_CLOSED) {
1077                         sctp_outq_head_data(ctx->q, chunk);
1078                         break;
1079                 }
1080
1081                 sctp_outq_select_transport(ctx, chunk);
1082
1083                 pr_debug("%s: outq:%p, chunk:%p[%s], tx-tsn:0x%x skb->head:%p skb->users:%d\n",
1084                          __func__, ctx->q, chunk, chunk && chunk->chunk_hdr ?
1085                          sctp_cname(SCTP_ST_CHUNK(chunk->chunk_hdr->type)) :
1086                          "illegal chunk", ntohl(chunk->subh.data_hdr->tsn),
1087                          chunk->skb ? chunk->skb->head : NULL, chunk->skb ?
1088                          refcount_read(&chunk->skb->users) : -1);
1089
1090                 /* Add the chunk to the packet.  */
1091                 status = sctp_packet_transmit_chunk(ctx->packet, chunk, 0,
1092                                                     ctx->gfp);
1093                 if (status != SCTP_XMIT_OK) {
1094                         /* We could not append this chunk, so put
1095                          * the chunk back on the output queue.
1096                          */
1097                         pr_debug("%s: could not transmit tsn:0x%x, status:%d\n",
1098                                  __func__, ntohl(chunk->subh.data_hdr->tsn),
1099                                  status);
1100
1101                         sctp_outq_head_data(ctx->q, chunk);
1102                         break;
1103                 }
1104
1105                 /* The sender is in the SHUTDOWN-PENDING state,
1106                  * The sender MAY set the I-bit in the DATA
1107                  * chunk header.
1108                  */
1109                 if (ctx->asoc->state == SCTP_STATE_SHUTDOWN_PENDING)
1110                         chunk->chunk_hdr->flags |= SCTP_DATA_SACK_IMM;
1111                 if (chunk->chunk_hdr->flags & SCTP_DATA_UNORDERED)
1112                         ctx->asoc->stats.ouodchunks++;
1113                 else
1114                         ctx->asoc->stats.oodchunks++;
1115
1116                 /* Only now it's safe to consider this
1117                  * chunk as sent, sched-wise.
1118                  */
1119                 sctp_sched_dequeue_done(ctx->q, chunk);
1120
1121                 list_add_tail(&chunk->transmitted_list,
1122                               &ctx->transport->transmitted);
1123
1124                 sctp_transport_reset_t3_rtx(ctx->transport);
1125                 ctx->transport->last_time_sent = jiffies;
1126
1127                 /* Only let one DATA chunk get bundled with a
1128                  * COOKIE-ECHO chunk.
1129                  */
1130                 if (ctx->packet->has_cookie_echo)
1131                         break;
1132         }
1133 }
1134
1135 static void sctp_outq_flush_transports(struct sctp_flush_ctx *ctx)
1136 {
1137         struct list_head *ltransport;
1138         struct sctp_packet *packet;
1139         struct sctp_transport *t;
1140         int error = 0;
1141
1142         while ((ltransport = sctp_list_dequeue(&ctx->transport_list)) != NULL) {
1143                 t = list_entry(ltransport, struct sctp_transport, send_ready);
1144                 packet = &t->packet;
1145                 if (!sctp_packet_empty(packet)) {
1146                         error = sctp_packet_transmit(packet, ctx->gfp);
1147                         if (error < 0)
1148                                 ctx->q->asoc->base.sk->sk_err = -error;
1149                 }
1150
1151                 /* Clear the burst limited state, if any */
1152                 sctp_transport_burst_reset(t);
1153         }
1154 }
1155
1156 /* Try to flush an outqueue.
1157  *
1158  * Description: Send everything in q which we legally can, subject to
1159  * congestion limitations.
1160  * * Note: This function can be called from multiple contexts so appropriate
1161  * locking concerns must be made.  Today we use the sock lock to protect
1162  * this function.
1163  */
1164
1165 static void sctp_outq_flush(struct sctp_outq *q, int rtx_timeout, gfp_t gfp)
1166 {
1167         struct sctp_flush_ctx ctx = {
1168                 .q = q,
1169                 .transport = NULL,
1170                 .transport_list = LIST_HEAD_INIT(ctx.transport_list),
1171                 .asoc = q->asoc,
1172                 .packet = NULL,
1173                 .gfp = gfp,
1174         };
1175
1176         /* 6.10 Bundling
1177          *   ...
1178          *   When bundling control chunks with DATA chunks, an
1179          *   endpoint MUST place control chunks first in the outbound
1180          *   SCTP packet.  The transmitter MUST transmit DATA chunks
1181          *   within a SCTP packet in increasing order of TSN.
1182          *   ...
1183          */
1184
1185         sctp_outq_flush_ctrl(&ctx);
1186
1187         if (q->asoc->src_out_of_asoc_ok)
1188                 goto sctp_flush_out;
1189
1190         sctp_outq_flush_data(&ctx, rtx_timeout);
1191
1192 sctp_flush_out:
1193
1194         sctp_outq_flush_transports(&ctx);
1195 }
1196
1197 /* Update unack_data based on the incoming SACK chunk */
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  */
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         asoc->stream.si->generate_ftsn(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  */
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  */
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 && !tchunk->tsn_gap_acked) {
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 (!sctp_chunk_retransmitted(tchunk) &&
1463                                     tchunk->rtt_in_progress) {
1464                                         tchunk->rtt_in_progress = 0;
1465                                         rtt = jiffies - tchunk->sent_at;
1466                                         sctp_transport_update_rto(transport,
1467                                                                   rtt);
1468                                 }
1469
1470                                 if (TSN_lte(tsn, sack_ctsn)) {
1471                                         /*
1472                                          * SFR-CACC algorithm:
1473                                          * 2) If the SACK contains gap acks
1474                                          * and the flag CHANGEOVER_ACTIVE is
1475                                          * set the receiver of the SACK MUST
1476                                          * take the following action:
1477                                          *
1478                                          * B) For each TSN t being acked that
1479                                          * has not been acked in any SACK so
1480                                          * far, set cacc_saw_newack to 1 for
1481                                          * the destination that the TSN was
1482                                          * sent to.
1483                                          */
1484                                         if (sack->num_gap_ack_blocks &&
1485                                             q->asoc->peer.primary_path->cacc.
1486                                             changeover_active)
1487                                                 transport->cacc.cacc_saw_newack
1488                                                         = 1;
1489                                 }
1490                         }
1491
1492                         /* If the chunk hasn't been marked as ACKED,
1493                          * mark it and account bytes_acked if the
1494                          * chunk had a valid transport (it will not
1495                          * have a transport if ASCONF had deleted it
1496                          * while DATA was outstanding).
1497                          */
1498                         if (!tchunk->tsn_gap_acked) {
1499                                 tchunk->tsn_gap_acked = 1;
1500                                 if (TSN_lt(*highest_new_tsn_in_sack, tsn))
1501                                         *highest_new_tsn_in_sack = tsn;
1502                                 bytes_acked += sctp_data_size(tchunk);
1503                                 if (!tchunk->transport)
1504                                         migrate_bytes += sctp_data_size(tchunk);
1505                                 forward_progress = true;
1506                         }
1507
1508                         if (TSN_lte(tsn, sack_ctsn)) {
1509                                 /* RFC 2960  6.3.2 Retransmission Timer Rules
1510                                  *
1511                                  * R3) Whenever a SACK is received
1512                                  * that acknowledges the DATA chunk
1513                                  * with the earliest outstanding TSN
1514                                  * for that address, restart T3-rtx
1515                                  * timer for that address with its
1516                                  * current RTO.
1517                                  */
1518                                 restart_timer = 1;
1519                                 forward_progress = true;
1520
1521                                 list_add_tail(&tchunk->transmitted_list,
1522                                               &q->sacked);
1523                         } else {
1524                                 /* RFC2960 7.2.4, sctpimpguide-05 2.8.2
1525                                  * M2) Each time a SACK arrives reporting
1526                                  * 'Stray DATA chunk(s)' record the highest TSN
1527                                  * reported as newly acknowledged, call this
1528                                  * value 'HighestTSNinSack'. A newly
1529                                  * acknowledged DATA chunk is one not
1530                                  * previously acknowledged in a SACK.
1531                                  *
1532                                  * When the SCTP sender of data receives a SACK
1533                                  * chunk that acknowledges, for the first time,
1534                                  * the receipt of a DATA chunk, all the still
1535                                  * unacknowledged DATA chunks whose TSN is
1536                                  * older than that newly acknowledged DATA
1537                                  * chunk, are qualified as 'Stray DATA chunks'.
1538                                  */
1539                                 list_add_tail(lchunk, &tlist);
1540                         }
1541                 } else {
1542                         if (tchunk->tsn_gap_acked) {
1543                                 pr_debug("%s: receiver reneged on data TSN:0x%x\n",
1544                                          __func__, tsn);
1545
1546                                 tchunk->tsn_gap_acked = 0;
1547
1548                                 if (tchunk->transport)
1549                                         bytes_acked -= sctp_data_size(tchunk);
1550
1551                                 /* RFC 2960 6.3.2 Retransmission Timer Rules
1552                                  *
1553                                  * R4) Whenever a SACK is received missing a
1554                                  * TSN that was previously acknowledged via a
1555                                  * Gap Ack Block, start T3-rtx for the
1556                                  * destination address to which the DATA
1557                                  * chunk was originally
1558                                  * transmitted if it is not already running.
1559                                  */
1560                                 restart_timer = 1;
1561                         }
1562
1563                         list_add_tail(lchunk, &tlist);
1564                 }
1565         }
1566
1567         if (transport) {
1568                 if (bytes_acked) {
1569                         struct sctp_association *asoc = transport->asoc;
1570
1571                         /* We may have counted DATA that was migrated
1572                          * to this transport due to DEL-IP operation.
1573                          * Subtract those bytes, since the were never
1574                          * send on this transport and shouldn't be
1575                          * credited to this transport.
1576                          */
1577                         bytes_acked -= migrate_bytes;
1578
1579                         /* 8.2. When an outstanding TSN is acknowledged,
1580                          * the endpoint shall clear the error counter of
1581                          * the destination transport address to which the
1582                          * DATA chunk was last sent.
1583                          * The association's overall error counter is
1584                          * also cleared.
1585                          */
1586                         transport->error_count = 0;
1587                         transport->asoc->overall_error_count = 0;
1588                         forward_progress = true;
1589
1590                         /*
1591                          * While in SHUTDOWN PENDING, we may have started
1592                          * the T5 shutdown guard timer after reaching the
1593                          * retransmission limit. Stop that timer as soon
1594                          * as the receiver acknowledged any data.
1595                          */
1596                         if (asoc->state == SCTP_STATE_SHUTDOWN_PENDING &&
1597                             del_timer(&asoc->timers
1598                                 [SCTP_EVENT_TIMEOUT_T5_SHUTDOWN_GUARD]))
1599                                         sctp_association_put(asoc);
1600
1601                         /* Mark the destination transport address as
1602                          * active if it is not so marked.
1603                          */
1604                         if ((transport->state == SCTP_INACTIVE ||
1605                              transport->state == SCTP_UNCONFIRMED) &&
1606                             sctp_cmp_addr_exact(&transport->ipaddr, saddr)) {
1607                                 sctp_assoc_control_transport(
1608                                         transport->asoc,
1609                                         transport,
1610                                         SCTP_TRANSPORT_UP,
1611                                         SCTP_RECEIVED_SACK);
1612                         }
1613
1614                         sctp_transport_raise_cwnd(transport, sack_ctsn,
1615                                                   bytes_acked);
1616
1617                         transport->flight_size -= bytes_acked;
1618                         if (transport->flight_size == 0)
1619                                 transport->partial_bytes_acked = 0;
1620                         q->outstanding_bytes -= bytes_acked + migrate_bytes;
1621                 } else {
1622                         /* RFC 2960 6.1, sctpimpguide-06 2.15.2
1623                          * When a sender is doing zero window probing, it
1624                          * should not timeout the association if it continues
1625                          * to receive new packets from the receiver. The
1626                          * reason is that the receiver MAY keep its window
1627                          * closed for an indefinite time.
1628                          * A sender is doing zero window probing when the
1629                          * receiver's advertised window is zero, and there is
1630                          * only one data chunk in flight to the receiver.
1631                          *
1632                          * Allow the association to timeout while in SHUTDOWN
1633                          * PENDING or SHUTDOWN RECEIVED in case the receiver
1634                          * stays in zero window mode forever.
1635                          */
1636                         if (!q->asoc->peer.rwnd &&
1637                             !list_empty(&tlist) &&
1638                             (sack_ctsn+2 == q->asoc->next_tsn) &&
1639                             q->asoc->state < SCTP_STATE_SHUTDOWN_PENDING) {
1640                                 pr_debug("%s: sack received for zero window "
1641                                          "probe:%u\n", __func__, sack_ctsn);
1642
1643                                 q->asoc->overall_error_count = 0;
1644                                 transport->error_count = 0;
1645                         }
1646                 }
1647
1648                 /* RFC 2960 6.3.2 Retransmission Timer Rules
1649                  *
1650                  * R2) Whenever all outstanding data sent to an address have
1651                  * been acknowledged, turn off the T3-rtx timer of that
1652                  * address.
1653                  */
1654                 if (!transport->flight_size) {
1655                         if (del_timer(&transport->T3_rtx_timer))
1656                                 sctp_transport_put(transport);
1657                 } else if (restart_timer) {
1658                         if (!mod_timer(&transport->T3_rtx_timer,
1659                                        jiffies + transport->rto))
1660                                 sctp_transport_hold(transport);
1661                 }
1662
1663                 if (forward_progress) {
1664                         if (transport->dst)
1665                                 sctp_transport_dst_confirm(transport);
1666                 }
1667         }
1668
1669         list_splice(&tlist, transmitted_queue);
1670 }
1671
1672 /* Mark chunks as missing and consequently may get retransmitted. */
1673 static void sctp_mark_missing(struct sctp_outq *q,
1674                               struct list_head *transmitted_queue,
1675                               struct sctp_transport *transport,
1676                               __u32 highest_new_tsn_in_sack,
1677                               int count_of_newacks)
1678 {
1679         struct sctp_chunk *chunk;
1680         __u32 tsn;
1681         char do_fast_retransmit = 0;
1682         struct sctp_association *asoc = q->asoc;
1683         struct sctp_transport *primary = asoc->peer.primary_path;
1684
1685         list_for_each_entry(chunk, transmitted_queue, transmitted_list) {
1686
1687                 tsn = ntohl(chunk->subh.data_hdr->tsn);
1688
1689                 /* RFC 2960 7.2.4, sctpimpguide-05 2.8.2 M3) Examine all
1690                  * 'Unacknowledged TSN's', if the TSN number of an
1691                  * 'Unacknowledged TSN' is smaller than the 'HighestTSNinSack'
1692                  * value, increment the 'TSN.Missing.Report' count on that
1693                  * chunk if it has NOT been fast retransmitted or marked for
1694                  * fast retransmit already.
1695                  */
1696                 if (chunk->fast_retransmit == SCTP_CAN_FRTX &&
1697                     !chunk->tsn_gap_acked &&
1698                     TSN_lt(tsn, highest_new_tsn_in_sack)) {
1699
1700                         /* SFR-CACC may require us to skip marking
1701                          * this chunk as missing.
1702                          */
1703                         if (!transport || !sctp_cacc_skip(primary,
1704                                                 chunk->transport,
1705                                                 count_of_newacks, tsn)) {
1706                                 chunk->tsn_missing_report++;
1707
1708                                 pr_debug("%s: tsn:0x%x missing counter:%d\n",
1709                                          __func__, tsn, chunk->tsn_missing_report);
1710                         }
1711                 }
1712                 /*
1713                  * M4) If any DATA chunk is found to have a
1714                  * 'TSN.Missing.Report'
1715                  * value larger than or equal to 3, mark that chunk for
1716                  * retransmission and start the fast retransmit procedure.
1717                  */
1718
1719                 if (chunk->tsn_missing_report >= 3) {
1720                         chunk->fast_retransmit = SCTP_NEED_FRTX;
1721                         do_fast_retransmit = 1;
1722                 }
1723         }
1724
1725         if (transport) {
1726                 if (do_fast_retransmit)
1727                         sctp_retransmit(q, transport, SCTP_RTXR_FAST_RTX);
1728
1729                 pr_debug("%s: transport:%p, cwnd:%d, ssthresh:%d, "
1730                          "flight_size:%d, pba:%d\n",  __func__, transport,
1731                          transport->cwnd, transport->ssthresh,
1732                          transport->flight_size, transport->partial_bytes_acked);
1733         }
1734 }
1735
1736 /* Is the given TSN acked by this packet?  */
1737 static int sctp_acked(struct sctp_sackhdr *sack, __u32 tsn)
1738 {
1739         __u32 ctsn = ntohl(sack->cum_tsn_ack);
1740         union sctp_sack_variable *frags;
1741         __u16 tsn_offset, blocks;
1742         int i;
1743
1744         if (TSN_lte(tsn, ctsn))
1745                 goto pass;
1746
1747         /* 3.3.4 Selective Acknowledgment (SACK) (3):
1748          *
1749          * Gap Ack Blocks:
1750          *  These fields contain the Gap Ack Blocks. They are repeated
1751          *  for each Gap Ack Block up to the number of Gap Ack Blocks
1752          *  defined in the Number of Gap Ack Blocks field. All DATA
1753          *  chunks with TSNs greater than or equal to (Cumulative TSN
1754          *  Ack + Gap Ack Block Start) and less than or equal to
1755          *  (Cumulative TSN Ack + Gap Ack Block End) of each Gap Ack
1756          *  Block are assumed to have been received correctly.
1757          */
1758
1759         frags = sack->variable;
1760         blocks = ntohs(sack->num_gap_ack_blocks);
1761         tsn_offset = tsn - ctsn;
1762         for (i = 0; i < blocks; ++i) {
1763                 if (tsn_offset >= ntohs(frags[i].gab.start) &&
1764                     tsn_offset <= ntohs(frags[i].gab.end))
1765                         goto pass;
1766         }
1767
1768         return 0;
1769 pass:
1770         return 1;
1771 }
1772
1773 static inline int sctp_get_skip_pos(struct sctp_fwdtsn_skip *skiplist,
1774                                     int nskips, __be16 stream)
1775 {
1776         int i;
1777
1778         for (i = 0; i < nskips; i++) {
1779                 if (skiplist[i].stream == stream)
1780                         return i;
1781         }
1782         return i;
1783 }
1784
1785 /* Create and add a fwdtsn chunk to the outq's control queue if needed. */
1786 void sctp_generate_fwdtsn(struct sctp_outq *q, __u32 ctsn)
1787 {
1788         struct sctp_association *asoc = q->asoc;
1789         struct sctp_chunk *ftsn_chunk = NULL;
1790         struct sctp_fwdtsn_skip ftsn_skip_arr[10];
1791         int nskips = 0;
1792         int skip_pos = 0;
1793         __u32 tsn;
1794         struct sctp_chunk *chunk;
1795         struct list_head *lchunk, *temp;
1796
1797         if (!asoc->peer.prsctp_capable)
1798                 return;
1799
1800         /* PR-SCTP C1) Let SackCumAck be the Cumulative TSN ACK carried in the
1801          * received SACK.
1802          *
1803          * If (Advanced.Peer.Ack.Point < SackCumAck), then update
1804          * Advanced.Peer.Ack.Point to be equal to SackCumAck.
1805          */
1806         if (TSN_lt(asoc->adv_peer_ack_point, ctsn))
1807                 asoc->adv_peer_ack_point = ctsn;
1808
1809         /* PR-SCTP C2) Try to further advance the "Advanced.Peer.Ack.Point"
1810          * locally, that is, to move "Advanced.Peer.Ack.Point" up as long as
1811          * the chunk next in the out-queue space is marked as "abandoned" as
1812          * shown in the following example:
1813          *
1814          * Assuming that a SACK arrived with the Cumulative TSN ACK 102
1815          * and the Advanced.Peer.Ack.Point is updated to this value:
1816          *
1817          *   out-queue at the end of  ==>   out-queue after Adv.Ack.Point
1818          *   normal SACK processing           local advancement
1819          *                ...                           ...
1820          *   Adv.Ack.Pt-> 102 acked                     102 acked
1821          *                103 abandoned                 103 abandoned
1822          *                104 abandoned     Adv.Ack.P-> 104 abandoned
1823          *                105                           105
1824          *                106 acked                     106 acked
1825          *                ...                           ...
1826          *
1827          * In this example, the data sender successfully advanced the
1828          * "Advanced.Peer.Ack.Point" from 102 to 104 locally.
1829          */
1830         list_for_each_safe(lchunk, temp, &q->abandoned) {
1831                 chunk = list_entry(lchunk, struct sctp_chunk,
1832                                         transmitted_list);
1833                 tsn = ntohl(chunk->subh.data_hdr->tsn);
1834
1835                 /* Remove any chunks in the abandoned queue that are acked by
1836                  * the ctsn.
1837                  */
1838                 if (TSN_lte(tsn, ctsn)) {
1839                         list_del_init(lchunk);
1840                         sctp_chunk_free(chunk);
1841                 } else {
1842                         if (TSN_lte(tsn, asoc->adv_peer_ack_point+1)) {
1843                                 asoc->adv_peer_ack_point = tsn;
1844                                 if (chunk->chunk_hdr->flags &
1845                                          SCTP_DATA_UNORDERED)
1846                                         continue;
1847                                 skip_pos = sctp_get_skip_pos(&ftsn_skip_arr[0],
1848                                                 nskips,
1849                                                 chunk->subh.data_hdr->stream);
1850                                 ftsn_skip_arr[skip_pos].stream =
1851                                         chunk->subh.data_hdr->stream;
1852                                 ftsn_skip_arr[skip_pos].ssn =
1853                                          chunk->subh.data_hdr->ssn;
1854                                 if (skip_pos == nskips)
1855                                         nskips++;
1856                                 if (nskips == 10)
1857                                         break;
1858                         } else
1859                                 break;
1860                 }
1861         }
1862
1863         /* PR-SCTP C3) If, after step C1 and C2, the "Advanced.Peer.Ack.Point"
1864          * is greater than the Cumulative TSN ACK carried in the received
1865          * SACK, the data sender MUST send the data receiver a FORWARD TSN
1866          * chunk containing the latest value of the
1867          * "Advanced.Peer.Ack.Point".
1868          *
1869          * C4) For each "abandoned" TSN the sender of the FORWARD TSN SHOULD
1870          * list each stream and sequence number in the forwarded TSN. This
1871          * information will enable the receiver to easily find any
1872          * stranded TSN's waiting on stream reorder queues. Each stream
1873          * SHOULD only be reported once; this means that if multiple
1874          * abandoned messages occur in the same stream then only the
1875          * highest abandoned stream sequence number is reported. If the
1876          * total size of the FORWARD TSN does NOT fit in a single MTU then
1877          * the sender of the FORWARD TSN SHOULD lower the
1878          * Advanced.Peer.Ack.Point to the last TSN that will fit in a
1879          * single MTU.
1880          */
1881         if (asoc->adv_peer_ack_point > ctsn)
1882                 ftsn_chunk = sctp_make_fwdtsn(asoc, asoc->adv_peer_ack_point,
1883                                               nskips, &ftsn_skip_arr[0]);
1884
1885         if (ftsn_chunk) {
1886                 list_add_tail(&ftsn_chunk->list, &q->control_chunk_list);
1887                 SCTP_INC_STATS(sock_net(asoc->base.sk), SCTP_MIB_OUTCTRLCHUNKS);
1888         }
1889 }