hwmon: tegra: tsensor: improve counter accuracy
[linux-2.6.git] / net / sctp / outqueue.c
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, write to
26  * the Free Software Foundation, 59 Temple Place - Suite 330,
27  * Boston, MA 02111-1307, USA.
28  *
29  * Please send any bug reports or fixes you make to the
30  * email address(es):
31  *    lksctp developers <lksctp-developers@lists.sourceforge.net>
32  *
33  * Or submit a bug report through the following website:
34  *    http://www.sf.net/projects/lksctp
35  *
36  * Written or modified by:
37  *    La Monte H.P. Yarroll <piggy@acm.org>
38  *    Karl Knutson          <karl@athena.chicago.il.us>
39  *    Perry Melange         <pmelange@null.cc.uic.edu>
40  *    Xingang Guo           <xingang.guo@intel.com>
41  *    Hui Huang             <hui.huang@nokia.com>
42  *    Sridhar Samudrala     <sri@us.ibm.com>
43  *    Jon Grimm             <jgrimm@us.ibm.com>
44  *
45  * Any bugs reported given to us we will try to fix... any fixes shared will
46  * be incorporated into the next SCTP release.
47  */
48
49 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
50
51 #include <linux/types.h>
52 #include <linux/list.h>   /* For struct list_head */
53 #include <linux/socket.h>
54 #include <linux/ip.h>
55 #include <linux/slab.h>
56 #include <net/sock.h>     /* For skb_set_owner_w */
57
58 #include <net/sctp/sctp.h>
59 #include <net/sctp/sm.h>
60
61 /* Declare internal functions here.  */
62 static int sctp_acked(struct sctp_sackhdr *sack, __u32 tsn);
63 static void sctp_check_transmitted(struct sctp_outq *q,
64                                    struct list_head *transmitted_queue,
65                                    struct sctp_transport *transport,
66                                    struct sctp_sackhdr *sack,
67                                    __u32 *highest_new_tsn);
68
69 static void sctp_mark_missing(struct sctp_outq *q,
70                               struct list_head *transmitted_queue,
71                               struct sctp_transport *transport,
72                               __u32 highest_new_tsn,
73                               int count_of_newacks);
74
75 static void sctp_generate_fwdtsn(struct sctp_outq *q, __u32 sack_ctsn);
76
77 static int sctp_outq_flush(struct sctp_outq *q, int rtx_timeout);
78
79 /* Add data to the front of the queue. */
80 static inline void sctp_outq_head_data(struct sctp_outq *q,
81                                         struct sctp_chunk *ch)
82 {
83         list_add(&ch->list, &q->out_chunk_list);
84         q->out_qlen += ch->skb->len;
85 }
86
87 /* Take data from the front of the queue. */
88 static inline struct sctp_chunk *sctp_outq_dequeue_data(struct sctp_outq *q)
89 {
90         struct sctp_chunk *ch = NULL;
91
92         if (!list_empty(&q->out_chunk_list)) {
93                 struct list_head *entry = q->out_chunk_list.next;
94
95                 ch = list_entry(entry, struct sctp_chunk, list);
96                 list_del_init(entry);
97                 q->out_qlen -= ch->skb->len;
98         }
99         return ch;
100 }
101 /* Add data chunk to the end of the queue. */
102 static inline void sctp_outq_tail_data(struct sctp_outq *q,
103                                        struct sctp_chunk *ch)
104 {
105         list_add_tail(&ch->list, &q->out_chunk_list);
106         q->out_qlen += ch->skb->len;
107 }
108
109 /*
110  * SFR-CACC algorithm:
111  * D) If count_of_newacks is greater than or equal to 2
112  * and t was not sent to the current primary then the
113  * sender MUST NOT increment missing report count for t.
114  */
115 static inline int sctp_cacc_skip_3_1_d(struct sctp_transport *primary,
116                                        struct sctp_transport *transport,
117                                        int count_of_newacks)
118 {
119         if (count_of_newacks >=2 && transport != primary)
120                 return 1;
121         return 0;
122 }
123
124 /*
125  * SFR-CACC algorithm:
126  * F) If count_of_newacks is less than 2, let d be the
127  * destination to which t was sent. If cacc_saw_newack
128  * is 0 for destination d, then the sender MUST NOT
129  * increment missing report count for t.
130  */
131 static inline int sctp_cacc_skip_3_1_f(struct sctp_transport *transport,
132                                        int count_of_newacks)
133 {
134         if (count_of_newacks < 2 &&
135                         (transport && !transport->cacc.cacc_saw_newack))
136                 return 1;
137         return 0;
138 }
139
140 /*
141  * SFR-CACC algorithm:
142  * 3.1) If CYCLING_CHANGEOVER is 0, the sender SHOULD
143  * execute steps C, D, F.
144  *
145  * C has been implemented in sctp_outq_sack
146  */
147 static inline int sctp_cacc_skip_3_1(struct sctp_transport *primary,
148                                      struct sctp_transport *transport,
149                                      int count_of_newacks)
150 {
151         if (!primary->cacc.cycling_changeover) {
152                 if (sctp_cacc_skip_3_1_d(primary, transport, count_of_newacks))
153                         return 1;
154                 if (sctp_cacc_skip_3_1_f(transport, count_of_newacks))
155                         return 1;
156                 return 0;
157         }
158         return 0;
159 }
160
161 /*
162  * SFR-CACC algorithm:
163  * 3.2) Else if CYCLING_CHANGEOVER is 1, and t is less
164  * than next_tsn_at_change of the current primary, then
165  * the sender MUST NOT increment missing report count
166  * for t.
167  */
168 static inline int sctp_cacc_skip_3_2(struct sctp_transport *primary, __u32 tsn)
169 {
170         if (primary->cacc.cycling_changeover &&
171             TSN_lt(tsn, primary->cacc.next_tsn_at_change))
172                 return 1;
173         return 0;
174 }
175
176 /*
177  * SFR-CACC algorithm:
178  * 3) If the missing report count for TSN t is to be
179  * incremented according to [RFC2960] and
180  * [SCTP_STEWART-2002], and CHANGEOVER_ACTIVE is set,
181  * then the sender MUST further execute steps 3.1 and
182  * 3.2 to determine if the missing report count for
183  * TSN t SHOULD NOT be incremented.
184  *
185  * 3.3) If 3.1 and 3.2 do not dictate that the missing
186  * report count for t should not be incremented, then
187  * the sender SHOULD increment missing report count for
188  * t (according to [RFC2960] and [SCTP_STEWART_2002]).
189  */
190 static inline int sctp_cacc_skip(struct sctp_transport *primary,
191                                  struct sctp_transport *transport,
192                                  int count_of_newacks,
193                                  __u32 tsn)
194 {
195         if (primary->cacc.changeover_active &&
196             (sctp_cacc_skip_3_1(primary, transport, count_of_newacks) ||
197              sctp_cacc_skip_3_2(primary, tsn)))
198                 return 1;
199         return 0;
200 }
201
202 /* Initialize an existing sctp_outq.  This does the boring stuff.
203  * You still need to define handlers if you really want to DO
204  * something with this structure...
205  */
206 void sctp_outq_init(struct sctp_association *asoc, struct sctp_outq *q)
207 {
208         q->asoc = asoc;
209         INIT_LIST_HEAD(&q->out_chunk_list);
210         INIT_LIST_HEAD(&q->control_chunk_list);
211         INIT_LIST_HEAD(&q->retransmit);
212         INIT_LIST_HEAD(&q->sacked);
213         INIT_LIST_HEAD(&q->abandoned);
214
215         q->fast_rtx = 0;
216         q->outstanding_bytes = 0;
217         q->empty = 1;
218         q->cork  = 0;
219
220         q->malloced = 0;
221         q->out_qlen = 0;
222 }
223
224 /* Free the outqueue structure and any related pending chunks.
225  */
226 void sctp_outq_teardown(struct sctp_outq *q)
227 {
228         struct sctp_transport *transport;
229         struct list_head *lchunk, *temp;
230         struct sctp_chunk *chunk, *tmp;
231
232         /* Throw away unacknowledged chunks. */
233         list_for_each_entry(transport, &q->asoc->peer.transport_addr_list,
234                         transports) {
235                 while ((lchunk = sctp_list_dequeue(&transport->transmitted)) != NULL) {
236                         chunk = list_entry(lchunk, struct sctp_chunk,
237                                            transmitted_list);
238                         /* Mark as part of a failed message. */
239                         sctp_chunk_fail(chunk, q->error);
240                         sctp_chunk_free(chunk);
241                 }
242         }
243
244         /* Throw away chunks that have been gap ACKed.  */
245         list_for_each_safe(lchunk, temp, &q->sacked) {
246                 list_del_init(lchunk);
247                 chunk = list_entry(lchunk, struct sctp_chunk,
248                                    transmitted_list);
249                 sctp_chunk_fail(chunk, q->error);
250                 sctp_chunk_free(chunk);
251         }
252
253         /* Throw away any chunks in the retransmit queue. */
254         list_for_each_safe(lchunk, temp, &q->retransmit) {
255                 list_del_init(lchunk);
256                 chunk = list_entry(lchunk, struct sctp_chunk,
257                                    transmitted_list);
258                 sctp_chunk_fail(chunk, q->error);
259                 sctp_chunk_free(chunk);
260         }
261
262         /* Throw away any chunks that are in the abandoned queue. */
263         list_for_each_safe(lchunk, temp, &q->abandoned) {
264                 list_del_init(lchunk);
265                 chunk = list_entry(lchunk, struct sctp_chunk,
266                                    transmitted_list);
267                 sctp_chunk_fail(chunk, q->error);
268                 sctp_chunk_free(chunk);
269         }
270
271         /* Throw away any leftover data chunks. */
272         while ((chunk = sctp_outq_dequeue_data(q)) != NULL) {
273
274                 /* Mark as send failure. */
275                 sctp_chunk_fail(chunk, q->error);
276                 sctp_chunk_free(chunk);
277         }
278
279         q->error = 0;
280
281         /* Throw away any leftover control chunks. */
282         list_for_each_entry_safe(chunk, tmp, &q->control_chunk_list, list) {
283                 list_del_init(&chunk->list);
284                 sctp_chunk_free(chunk);
285         }
286 }
287
288 /* Free the outqueue structure and any related pending chunks.  */
289 void sctp_outq_free(struct sctp_outq *q)
290 {
291         /* Throw away leftover chunks. */
292         sctp_outq_teardown(q);
293
294         /* If we were kmalloc()'d, free the memory.  */
295         if (q->malloced)
296                 kfree(q);
297 }
298
299 /* Put a new chunk in an sctp_outq.  */
300 int sctp_outq_tail(struct sctp_outq *q, struct sctp_chunk *chunk)
301 {
302         int error = 0;
303
304         SCTP_DEBUG_PRINTK("sctp_outq_tail(%p, %p[%s])\n",
305                           q, chunk, chunk && chunk->chunk_hdr ?
306                           sctp_cname(SCTP_ST_CHUNK(chunk->chunk_hdr->type))
307                           : "Illegal Chunk");
308
309         /* If it is data, queue it up, otherwise, send it
310          * immediately.
311          */
312         if (sctp_chunk_is_data(chunk)) {
313                 /* Is it OK to queue data chunks?  */
314                 /* From 9. Termination of Association
315                  *
316                  * When either endpoint performs a shutdown, the
317                  * association on each peer will stop accepting new
318                  * data from its user and only deliver data in queue
319                  * at the time of sending or receiving the SHUTDOWN
320                  * chunk.
321                  */
322                 switch (q->asoc->state) {
323                 case SCTP_STATE_CLOSED:
324                 case SCTP_STATE_SHUTDOWN_PENDING:
325                 case SCTP_STATE_SHUTDOWN_SENT:
326                 case SCTP_STATE_SHUTDOWN_RECEIVED:
327                 case SCTP_STATE_SHUTDOWN_ACK_SENT:
328                         /* Cannot send after transport endpoint shutdown */
329                         error = -ESHUTDOWN;
330                         break;
331
332                 default:
333                         SCTP_DEBUG_PRINTK("outqueueing (%p, %p[%s])\n",
334                           q, chunk, chunk && chunk->chunk_hdr ?
335                           sctp_cname(SCTP_ST_CHUNK(chunk->chunk_hdr->type))
336                           : "Illegal Chunk");
337
338                         sctp_outq_tail_data(q, chunk);
339                         if (chunk->chunk_hdr->flags & SCTP_DATA_UNORDERED)
340                                 SCTP_INC_STATS(SCTP_MIB_OUTUNORDERCHUNKS);
341                         else
342                                 SCTP_INC_STATS(SCTP_MIB_OUTORDERCHUNKS);
343                         q->empty = 0;
344                         break;
345                 }
346         } else {
347                 list_add_tail(&chunk->list, &q->control_chunk_list);
348                 SCTP_INC_STATS(SCTP_MIB_OUTCTRLCHUNKS);
349         }
350
351         if (error < 0)
352                 return error;
353
354         if (!q->cork)
355                 error = sctp_outq_flush(q, 0);
356
357         return error;
358 }
359
360 /* Insert a chunk into the sorted list based on the TSNs.  The retransmit list
361  * and the abandoned list are in ascending order.
362  */
363 static void sctp_insert_list(struct list_head *head, struct list_head *new)
364 {
365         struct list_head *pos;
366         struct sctp_chunk *nchunk, *lchunk;
367         __u32 ntsn, ltsn;
368         int done = 0;
369
370         nchunk = list_entry(new, struct sctp_chunk, transmitted_list);
371         ntsn = ntohl(nchunk->subh.data_hdr->tsn);
372
373         list_for_each(pos, head) {
374                 lchunk = list_entry(pos, struct sctp_chunk, transmitted_list);
375                 ltsn = ntohl(lchunk->subh.data_hdr->tsn);
376                 if (TSN_lt(ntsn, ltsn)) {
377                         list_add(new, pos->prev);
378                         done = 1;
379                         break;
380                 }
381         }
382         if (!done)
383                 list_add_tail(new, head);
384 }
385
386 /* Mark all the eligible packets on a transport for retransmission.  */
387 void sctp_retransmit_mark(struct sctp_outq *q,
388                           struct sctp_transport *transport,
389                           __u8 reason)
390 {
391         struct list_head *lchunk, *ltemp;
392         struct sctp_chunk *chunk;
393
394         /* Walk through the specified transmitted queue.  */
395         list_for_each_safe(lchunk, ltemp, &transport->transmitted) {
396                 chunk = list_entry(lchunk, struct sctp_chunk,
397                                    transmitted_list);
398
399                 /* If the chunk is abandoned, move it to abandoned list. */
400                 if (sctp_chunk_abandoned(chunk)) {
401                         list_del_init(lchunk);
402                         sctp_insert_list(&q->abandoned, lchunk);
403
404                         /* If this chunk has not been previousely acked,
405                          * stop considering it 'outstanding'.  Our peer
406                          * will most likely never see it since it will
407                          * not be retransmitted
408                          */
409                         if (!chunk->tsn_gap_acked) {
410                                 if (chunk->transport)
411                                         chunk->transport->flight_size -=
412                                                         sctp_data_size(chunk);
413                                 q->outstanding_bytes -= sctp_data_size(chunk);
414                                 q->asoc->peer.rwnd += sctp_data_size(chunk);
415                         }
416                         continue;
417                 }
418
419                 /* If we are doing  retransmission due to a timeout or pmtu
420                  * discovery, only the  chunks that are not yet acked should
421                  * be added to the retransmit queue.
422                  */
423                 if ((reason == SCTP_RTXR_FAST_RTX  &&
424                             (chunk->fast_retransmit == SCTP_NEED_FRTX)) ||
425                     (reason != SCTP_RTXR_FAST_RTX  && !chunk->tsn_gap_acked)) {
426                         /* RFC 2960 6.2.1 Processing a Received SACK
427                          *
428                          * C) Any time a DATA chunk is marked for
429                          * retransmission (via either T3-rtx timer expiration
430                          * (Section 6.3.3) or via fast retransmit
431                          * (Section 7.2.4)), add the data size of those
432                          * chunks to the rwnd.
433                          */
434                         q->asoc->peer.rwnd += sctp_data_size(chunk);
435                         q->outstanding_bytes -= sctp_data_size(chunk);
436                         if (chunk->transport)
437                                 transport->flight_size -= sctp_data_size(chunk);
438
439                         /* sctpimpguide-05 Section 2.8.2
440                          * M5) If a T3-rtx timer expires, the
441                          * 'TSN.Missing.Report' of all affected TSNs is set
442                          * to 0.
443                          */
444                         chunk->tsn_missing_report = 0;
445
446                         /* If a chunk that is being used for RTT measurement
447                          * has to be retransmitted, we cannot use this chunk
448                          * anymore for RTT measurements. Reset rto_pending so
449                          * that a new RTT measurement is started when a new
450                          * data chunk is sent.
451                          */
452                         if (chunk->rtt_in_progress) {
453                                 chunk->rtt_in_progress = 0;
454                                 transport->rto_pending = 0;
455                         }
456
457                         /* Move the chunk to the retransmit queue. The chunks
458                          * on the retransmit queue are always kept in order.
459                          */
460                         list_del_init(lchunk);
461                         sctp_insert_list(&q->retransmit, lchunk);
462                 }
463         }
464
465         SCTP_DEBUG_PRINTK("%s: transport: %p, reason: %d, "
466                           "cwnd: %d, ssthresh: %d, flight_size: %d, "
467                           "pba: %d\n", __func__,
468                           transport, reason,
469                           transport->cwnd, transport->ssthresh,
470                           transport->flight_size,
471                           transport->partial_bytes_acked);
472
473 }
474
475 /* Mark all the eligible packets on a transport for retransmission and force
476  * one packet out.
477  */
478 void sctp_retransmit(struct sctp_outq *q, struct sctp_transport *transport,
479                      sctp_retransmit_reason_t reason)
480 {
481         int error = 0;
482
483         switch(reason) {
484         case SCTP_RTXR_T3_RTX:
485                 SCTP_INC_STATS(SCTP_MIB_T3_RETRANSMITS);
486                 sctp_transport_lower_cwnd(transport, SCTP_LOWER_CWND_T3_RTX);
487                 /* Update the retran path if the T3-rtx timer has expired for
488                  * the current retran path.
489                  */
490                 if (transport == transport->asoc->peer.retran_path)
491                         sctp_assoc_update_retran_path(transport->asoc);
492                 transport->asoc->rtx_data_chunks +=
493                         transport->asoc->unack_data;
494                 break;
495         case SCTP_RTXR_FAST_RTX:
496                 SCTP_INC_STATS(SCTP_MIB_FAST_RETRANSMITS);
497                 sctp_transport_lower_cwnd(transport, SCTP_LOWER_CWND_FAST_RTX);
498                 q->fast_rtx = 1;
499                 break;
500         case SCTP_RTXR_PMTUD:
501                 SCTP_INC_STATS(SCTP_MIB_PMTUD_RETRANSMITS);
502                 break;
503         case SCTP_RTXR_T1_RTX:
504                 SCTP_INC_STATS(SCTP_MIB_T1_RETRANSMITS);
505                 transport->asoc->init_retries++;
506                 break;
507         default:
508                 BUG();
509         }
510
511         sctp_retransmit_mark(q, transport, reason);
512
513         /* PR-SCTP A5) Any time the T3-rtx timer expires, on any destination,
514          * the sender SHOULD try to advance the "Advanced.Peer.Ack.Point" by
515          * following the procedures outlined in C1 - C5.
516          */
517         if (reason == SCTP_RTXR_T3_RTX)
518                 sctp_generate_fwdtsn(q, q->asoc->ctsn_ack_point);
519
520         /* Flush the queues only on timeout, since fast_rtx is only
521          * triggered during sack processing and the queue
522          * will be flushed at the end.
523          */
524         if (reason != SCTP_RTXR_FAST_RTX)
525                 error = sctp_outq_flush(q, /* rtx_timeout */ 1);
526
527         if (error)
528                 q->asoc->base.sk->sk_err = -error;
529 }
530
531 /*
532  * Transmit DATA chunks on the retransmit queue.  Upon return from
533  * sctp_outq_flush_rtx() the packet 'pkt' may contain chunks which
534  * need to be transmitted by the caller.
535  * We assume that pkt->transport has already been set.
536  *
537  * The return value is a normal kernel error return value.
538  */
539 static int sctp_outq_flush_rtx(struct sctp_outq *q, struct sctp_packet *pkt,
540                                int rtx_timeout, int *start_timer)
541 {
542         struct list_head *lqueue;
543         struct sctp_transport *transport = pkt->transport;
544         sctp_xmit_t status;
545         struct sctp_chunk *chunk, *chunk1;
546         int fast_rtx;
547         int error = 0;
548         int timer = 0;
549         int done = 0;
550
551         lqueue = &q->retransmit;
552         fast_rtx = q->fast_rtx;
553
554         /* This loop handles time-out retransmissions, fast retransmissions,
555          * and retransmissions due to opening of whindow.
556          *
557          * RFC 2960 6.3.3 Handle T3-rtx Expiration
558          *
559          * E3) Determine how many of the earliest (i.e., lowest TSN)
560          * outstanding DATA chunks for the address for which the
561          * T3-rtx has expired will fit into a single packet, subject
562          * to the MTU constraint for the path corresponding to the
563          * destination transport address to which the retransmission
564          * is being sent (this may be different from the address for
565          * which the timer expires [see Section 6.4]). Call this value
566          * K. Bundle and retransmit those K DATA chunks in a single
567          * packet to the destination endpoint.
568          *
569          * [Just to be painfully clear, if we are retransmitting
570          * because a timeout just happened, we should send only ONE
571          * packet of retransmitted data.]
572          *
573          * For fast retransmissions we also send only ONE packet.  However,
574          * if we are just flushing the queue due to open window, we'll
575          * try to send as much as possible.
576          */
577         list_for_each_entry_safe(chunk, chunk1, lqueue, transmitted_list) {
578                 /* If the chunk is abandoned, move it to abandoned list. */
579                 if (sctp_chunk_abandoned(chunk)) {
580                         list_del_init(&chunk->transmitted_list);
581                         sctp_insert_list(&q->abandoned,
582                                          &chunk->transmitted_list);
583                         continue;
584                 }
585
586                 /* Make sure that Gap Acked TSNs are not retransmitted.  A
587                  * simple approach is just to move such TSNs out of the
588                  * way and into a 'transmitted' queue and skip to the
589                  * next chunk.
590                  */
591                 if (chunk->tsn_gap_acked) {
592                         list_del(&chunk->transmitted_list);
593                         list_add_tail(&chunk->transmitted_list,
594                                         &transport->transmitted);
595                         continue;
596                 }
597
598                 /* If we are doing fast retransmit, ignore non-fast_rtransmit
599                  * chunks
600                  */
601                 if (fast_rtx && !chunk->fast_retransmit)
602                         continue;
603
604 redo:
605                 /* Attempt to append this chunk to the packet. */
606                 status = sctp_packet_append_chunk(pkt, chunk);
607
608                 switch (status) {
609                 case SCTP_XMIT_PMTU_FULL:
610                         if (!pkt->has_data && !pkt->has_cookie_echo) {
611                                 /* If this packet did not contain DATA then
612                                  * retransmission did not happen, so do it
613                                  * again.  We'll ignore the error here since
614                                  * control chunks are already freed so there
615                                  * is nothing we can do.
616                                  */
617                                 sctp_packet_transmit(pkt);
618                                 goto redo;
619                         }
620
621                         /* Send this packet.  */
622                         error = sctp_packet_transmit(pkt);
623
624                         /* If we are retransmitting, we should only
625                          * send a single packet.
626                          * Otherwise, try appending this chunk again.
627                          */
628                         if (rtx_timeout || fast_rtx)
629                                 done = 1;
630                         else
631                                 goto redo;
632
633                         /* Bundle next chunk in the next round.  */
634                         break;
635
636                 case SCTP_XMIT_RWND_FULL:
637                         /* Send this packet. */
638                         error = sctp_packet_transmit(pkt);
639
640                         /* Stop sending DATA as there is no more room
641                          * at the receiver.
642                          */
643                         done = 1;
644                         break;
645
646                 case SCTP_XMIT_NAGLE_DELAY:
647                         /* Send this packet. */
648                         error = sctp_packet_transmit(pkt);
649
650                         /* Stop sending DATA because of nagle delay. */
651                         done = 1;
652                         break;
653
654                 default:
655                         /* The append was successful, so add this chunk to
656                          * the transmitted list.
657                          */
658                         list_del(&chunk->transmitted_list);
659                         list_add_tail(&chunk->transmitted_list,
660                                         &transport->transmitted);
661
662                         /* Mark the chunk as ineligible for fast retransmit
663                          * after it is retransmitted.
664                          */
665                         if (chunk->fast_retransmit == SCTP_NEED_FRTX)
666                                 chunk->fast_retransmit = SCTP_DONT_FRTX;
667
668                         q->empty = 0;
669                         break;
670                 }
671
672                 /* Set the timer if there were no errors */
673                 if (!error && !timer)
674                         timer = 1;
675
676                 if (done)
677                         break;
678         }
679
680         /* If we are here due to a retransmit timeout or a fast
681          * retransmit and if there are any chunks left in the retransmit
682          * queue that could not fit in the PMTU sized packet, they need
683          * to be marked as ineligible for a subsequent fast retransmit.
684          */
685         if (rtx_timeout || fast_rtx) {
686                 list_for_each_entry(chunk1, lqueue, transmitted_list) {
687                         if (chunk1->fast_retransmit == SCTP_NEED_FRTX)
688                                 chunk1->fast_retransmit = SCTP_DONT_FRTX;
689                 }
690         }
691
692         *start_timer = timer;
693
694         /* Clear fast retransmit hint */
695         if (fast_rtx)
696                 q->fast_rtx = 0;
697
698         return error;
699 }
700
701 /* Cork the outqueue so queued chunks are really queued. */
702 int sctp_outq_uncork(struct sctp_outq *q)
703 {
704         int error = 0;
705         if (q->cork)
706                 q->cork = 0;
707         error = sctp_outq_flush(q, 0);
708         return error;
709 }
710
711
712 /*
713  * Try to flush an outqueue.
714  *
715  * Description: Send everything in q which we legally can, subject to
716  * congestion limitations.
717  * * Note: This function can be called from multiple contexts so appropriate
718  * locking concerns must be made.  Today we use the sock lock to protect
719  * this function.
720  */
721 static int sctp_outq_flush(struct sctp_outq *q, int rtx_timeout)
722 {
723         struct sctp_packet *packet;
724         struct sctp_packet singleton;
725         struct sctp_association *asoc = q->asoc;
726         __u16 sport = asoc->base.bind_addr.port;
727         __u16 dport = asoc->peer.port;
728         __u32 vtag = asoc->peer.i.init_tag;
729         struct sctp_transport *transport = NULL;
730         struct sctp_transport *new_transport;
731         struct sctp_chunk *chunk, *tmp;
732         sctp_xmit_t status;
733         int error = 0;
734         int start_timer = 0;
735         int one_packet = 0;
736
737         /* These transports have chunks to send. */
738         struct list_head transport_list;
739         struct list_head *ltransport;
740
741         INIT_LIST_HEAD(&transport_list);
742         packet = NULL;
743
744         /*
745          * 6.10 Bundling
746          *   ...
747          *   When bundling control chunks with DATA chunks, an
748          *   endpoint MUST place control chunks first in the outbound
749          *   SCTP packet.  The transmitter MUST transmit DATA chunks
750          *   within a SCTP packet in increasing order of TSN.
751          *   ...
752          */
753
754         list_for_each_entry_safe(chunk, tmp, &q->control_chunk_list, list) {
755                 /* RFC 5061, 5.3
756                  * F1) This means that until such time as the ASCONF
757                  * containing the add is acknowledged, the sender MUST
758                  * NOT use the new IP address as a source for ANY SCTP
759                  * packet except on carrying an ASCONF Chunk.
760                  */
761                 if (asoc->src_out_of_asoc_ok &&
762                     chunk->chunk_hdr->type != SCTP_CID_ASCONF)
763                         continue;
764
765                 list_del_init(&chunk->list);
766
767                 /* Pick the right transport to use. */
768                 new_transport = chunk->transport;
769
770                 if (!new_transport) {
771                         /*
772                          * If we have a prior transport pointer, see if
773                          * the destination address of the chunk
774                          * matches the destination address of the
775                          * current transport.  If not a match, then
776                          * try to look up the transport with a given
777                          * destination address.  We do this because
778                          * after processing ASCONFs, we may have new
779                          * transports created.
780                          */
781                         if (transport &&
782                             sctp_cmp_addr_exact(&chunk->dest,
783                                                 &transport->ipaddr))
784                                         new_transport = transport;
785                         else
786                                 new_transport = sctp_assoc_lookup_paddr(asoc,
787                                                                 &chunk->dest);
788
789                         /* if we still don't have a new transport, then
790                          * use the current active path.
791                          */
792                         if (!new_transport)
793                                 new_transport = asoc->peer.active_path;
794                 } else if ((new_transport->state == SCTP_INACTIVE) ||
795                            (new_transport->state == SCTP_UNCONFIRMED)) {
796                         /* If the chunk is Heartbeat or Heartbeat Ack,
797                          * send it to chunk->transport, even if it's
798                          * inactive.
799                          *
800                          * 3.3.6 Heartbeat Acknowledgement:
801                          * ...
802                          * A HEARTBEAT ACK is always sent to the source IP
803                          * address of the IP datagram containing the
804                          * HEARTBEAT chunk to which this ack is responding.
805                          * ...
806                          *
807                          * ASCONF_ACKs also must be sent to the source.
808                          */
809                         if (chunk->chunk_hdr->type != SCTP_CID_HEARTBEAT &&
810                             chunk->chunk_hdr->type != SCTP_CID_HEARTBEAT_ACK &&
811                             chunk->chunk_hdr->type != SCTP_CID_ASCONF_ACK)
812                                 new_transport = asoc->peer.active_path;
813                 }
814
815                 /* Are we switching transports?
816                  * Take care of transport locks.
817                  */
818                 if (new_transport != transport) {
819                         transport = new_transport;
820                         if (list_empty(&transport->send_ready)) {
821                                 list_add_tail(&transport->send_ready,
822                                               &transport_list);
823                         }
824                         packet = &transport->packet;
825                         sctp_packet_config(packet, vtag,
826                                            asoc->peer.ecn_capable);
827                 }
828
829                 switch (chunk->chunk_hdr->type) {
830                 /*
831                  * 6.10 Bundling
832                  *   ...
833                  *   An endpoint MUST NOT bundle INIT, INIT ACK or SHUTDOWN
834                  *   COMPLETE with any other chunks.  [Send them immediately.]
835                  */
836                 case SCTP_CID_INIT:
837                 case SCTP_CID_INIT_ACK:
838                 case SCTP_CID_SHUTDOWN_COMPLETE:
839                         sctp_packet_init(&singleton, transport, sport, dport);
840                         sctp_packet_config(&singleton, vtag, 0);
841                         sctp_packet_append_chunk(&singleton, chunk);
842                         error = sctp_packet_transmit(&singleton);
843                         if (error < 0)
844                                 return error;
845                         break;
846
847                 case SCTP_CID_ABORT:
848                         if (sctp_test_T_bit(chunk)) {
849                                 packet->vtag = asoc->c.my_vtag;
850                         }
851                 /* The following chunks are "response" chunks, i.e.
852                  * they are generated in response to something we
853                  * received.  If we are sending these, then we can
854                  * send only 1 packet containing these chunks.
855                  */
856                 case SCTP_CID_HEARTBEAT_ACK:
857                 case SCTP_CID_SHUTDOWN_ACK:
858                 case SCTP_CID_COOKIE_ACK:
859                 case SCTP_CID_COOKIE_ECHO:
860                 case SCTP_CID_ERROR:
861                 case SCTP_CID_ECN_CWR:
862                 case SCTP_CID_ASCONF_ACK:
863                         one_packet = 1;
864                         /* Fall through */
865
866                 case SCTP_CID_SACK:
867                 case SCTP_CID_HEARTBEAT:
868                 case SCTP_CID_SHUTDOWN:
869                 case SCTP_CID_ECN_ECNE:
870                 case SCTP_CID_ASCONF:
871                 case SCTP_CID_FWD_TSN:
872                         status = sctp_packet_transmit_chunk(packet, chunk,
873                                                             one_packet);
874                         if (status  != SCTP_XMIT_OK) {
875                                 /* put the chunk back */
876                                 list_add(&chunk->list, &q->control_chunk_list);
877                         } else if (chunk->chunk_hdr->type == SCTP_CID_FWD_TSN) {
878                                 /* PR-SCTP C5) If a FORWARD TSN is sent, the
879                                  * sender MUST assure that at least one T3-rtx
880                                  * timer is running.
881                                  */
882                                 sctp_transport_reset_timers(transport);
883                         }
884                         break;
885
886                 default:
887                         /* We built a chunk with an illegal type! */
888                         BUG();
889                 }
890         }
891
892         if (q->asoc->src_out_of_asoc_ok)
893                 goto sctp_flush_out;
894
895         /* Is it OK to send data chunks?  */
896         switch (asoc->state) {
897         case SCTP_STATE_COOKIE_ECHOED:
898                 /* Only allow bundling when this packet has a COOKIE-ECHO
899                  * chunk.
900                  */
901                 if (!packet || !packet->has_cookie_echo)
902                         break;
903
904                 /* fallthru */
905         case SCTP_STATE_ESTABLISHED:
906         case SCTP_STATE_SHUTDOWN_PENDING:
907         case SCTP_STATE_SHUTDOWN_RECEIVED:
908                 /*
909                  * RFC 2960 6.1  Transmission of DATA Chunks
910                  *
911                  * C) When the time comes for the sender to transmit,
912                  * before sending new DATA chunks, the sender MUST
913                  * first transmit any outstanding DATA chunks which
914                  * are marked for retransmission (limited by the
915                  * current cwnd).
916                  */
917                 if (!list_empty(&q->retransmit)) {
918                         if (asoc->peer.retran_path->state == SCTP_UNCONFIRMED)
919                                 goto sctp_flush_out;
920                         if (transport == asoc->peer.retran_path)
921                                 goto retran;
922
923                         /* Switch transports & prepare the packet.  */
924
925                         transport = asoc->peer.retran_path;
926
927                         if (list_empty(&transport->send_ready)) {
928                                 list_add_tail(&transport->send_ready,
929                                               &transport_list);
930                         }
931
932                         packet = &transport->packet;
933                         sctp_packet_config(packet, vtag,
934                                            asoc->peer.ecn_capable);
935                 retran:
936                         error = sctp_outq_flush_rtx(q, packet,
937                                                     rtx_timeout, &start_timer);
938
939                         if (start_timer)
940                                 sctp_transport_reset_timers(transport);
941
942                         /* This can happen on COOKIE-ECHO resend.  Only
943                          * one chunk can get bundled with a COOKIE-ECHO.
944                          */
945                         if (packet->has_cookie_echo)
946                                 goto sctp_flush_out;
947
948                         /* Don't send new data if there is still data
949                          * waiting to retransmit.
950                          */
951                         if (!list_empty(&q->retransmit))
952                                 goto sctp_flush_out;
953                 }
954
955                 /* Apply Max.Burst limitation to the current transport in
956                  * case it will be used for new data.  We are going to
957                  * rest it before we return, but we want to apply the limit
958                  * to the currently queued data.
959                  */
960                 if (transport)
961                         sctp_transport_burst_limited(transport);
962
963                 /* Finally, transmit new packets.  */
964                 while ((chunk = sctp_outq_dequeue_data(q)) != NULL) {
965                         /* RFC 2960 6.5 Every DATA chunk MUST carry a valid
966                          * stream identifier.
967                          */
968                         if (chunk->sinfo.sinfo_stream >=
969                             asoc->c.sinit_num_ostreams) {
970
971                                 /* Mark as failed send. */
972                                 sctp_chunk_fail(chunk, SCTP_ERROR_INV_STRM);
973                                 sctp_chunk_free(chunk);
974                                 continue;
975                         }
976
977                         /* Has this chunk expired? */
978                         if (sctp_chunk_abandoned(chunk)) {
979                                 sctp_chunk_fail(chunk, 0);
980                                 sctp_chunk_free(chunk);
981                                 continue;
982                         }
983
984                         /* If there is a specified transport, use it.
985                          * Otherwise, we want to use the active path.
986                          */
987                         new_transport = chunk->transport;
988                         if (!new_transport ||
989                             ((new_transport->state == SCTP_INACTIVE) ||
990                              (new_transport->state == SCTP_UNCONFIRMED)))
991                                 new_transport = asoc->peer.active_path;
992                         if (new_transport->state == SCTP_UNCONFIRMED)
993                                 continue;
994
995                         /* Change packets if necessary.  */
996                         if (new_transport != transport) {
997                                 transport = new_transport;
998
999                                 /* Schedule to have this transport's
1000                                  * packet flushed.
1001                                  */
1002                                 if (list_empty(&transport->send_ready)) {
1003                                         list_add_tail(&transport->send_ready,
1004                                                       &transport_list);
1005                                 }
1006
1007                                 packet = &transport->packet;
1008                                 sctp_packet_config(packet, vtag,
1009                                                    asoc->peer.ecn_capable);
1010                                 /* We've switched transports, so apply the
1011                                  * Burst limit to the new transport.
1012                                  */
1013                                 sctp_transport_burst_limited(transport);
1014                         }
1015
1016                         SCTP_DEBUG_PRINTK("sctp_outq_flush(%p, %p[%s]), ",
1017                                           q, chunk,
1018                                           chunk && chunk->chunk_hdr ?
1019                                           sctp_cname(SCTP_ST_CHUNK(
1020                                                   chunk->chunk_hdr->type))
1021                                           : "Illegal Chunk");
1022
1023                         SCTP_DEBUG_PRINTK("TX TSN 0x%x skb->head "
1024                                         "%p skb->users %d.\n",
1025                                         ntohl(chunk->subh.data_hdr->tsn),
1026                                         chunk->skb ?chunk->skb->head : NULL,
1027                                         chunk->skb ?
1028                                         atomic_read(&chunk->skb->users) : -1);
1029
1030                         /* Add the chunk to the packet.  */
1031                         status = sctp_packet_transmit_chunk(packet, chunk, 0);
1032
1033                         switch (status) {
1034                         case SCTP_XMIT_PMTU_FULL:
1035                         case SCTP_XMIT_RWND_FULL:
1036                         case SCTP_XMIT_NAGLE_DELAY:
1037                                 /* We could not append this chunk, so put
1038                                  * the chunk back on the output queue.
1039                                  */
1040                                 SCTP_DEBUG_PRINTK("sctp_outq_flush: could "
1041                                         "not transmit TSN: 0x%x, status: %d\n",
1042                                         ntohl(chunk->subh.data_hdr->tsn),
1043                                         status);
1044                                 sctp_outq_head_data(q, chunk);
1045                                 goto sctp_flush_out;
1046                                 break;
1047
1048                         case SCTP_XMIT_OK:
1049                                 /* The sender is in the SHUTDOWN-PENDING state,
1050                                  * The sender MAY set the I-bit in the DATA
1051                                  * chunk header.
1052                                  */
1053                                 if (asoc->state == SCTP_STATE_SHUTDOWN_PENDING)
1054                                         chunk->chunk_hdr->flags |= SCTP_DATA_SACK_IMM;
1055
1056                                 break;
1057
1058                         default:
1059                                 BUG();
1060                         }
1061
1062                         /* BUG: We assume that the sctp_packet_transmit()
1063                          * call below will succeed all the time and add the
1064                          * chunk to the transmitted list and restart the
1065                          * timers.
1066                          * It is possible that the call can fail under OOM
1067                          * conditions.
1068                          *
1069                          * Is this really a problem?  Won't this behave
1070                          * like a lost TSN?
1071                          */
1072                         list_add_tail(&chunk->transmitted_list,
1073                                       &transport->transmitted);
1074
1075                         sctp_transport_reset_timers(transport);
1076
1077                         q->empty = 0;
1078
1079                         /* Only let one DATA chunk get bundled with a
1080                          * COOKIE-ECHO chunk.
1081                          */
1082                         if (packet->has_cookie_echo)
1083                                 goto sctp_flush_out;
1084                 }
1085                 break;
1086
1087         default:
1088                 /* Do nothing.  */
1089                 break;
1090         }
1091
1092 sctp_flush_out:
1093
1094         /* Before returning, examine all the transports touched in
1095          * this call.  Right now, we bluntly force clear all the
1096          * transports.  Things might change after we implement Nagle.
1097          * But such an examination is still required.
1098          *
1099          * --xguo
1100          */
1101         while ((ltransport = sctp_list_dequeue(&transport_list)) != NULL ) {
1102                 struct sctp_transport *t = list_entry(ltransport,
1103                                                       struct sctp_transport,
1104                                                       send_ready);
1105                 packet = &t->packet;
1106                 if (!sctp_packet_empty(packet))
1107                         error = sctp_packet_transmit(packet);
1108
1109                 /* Clear the burst limited state, if any */
1110                 sctp_transport_burst_reset(t);
1111         }
1112
1113         return error;
1114 }
1115
1116 /* Update unack_data based on the incoming SACK chunk */
1117 static void sctp_sack_update_unack_data(struct sctp_association *assoc,
1118                                         struct sctp_sackhdr *sack)
1119 {
1120         sctp_sack_variable_t *frags;
1121         __u16 unack_data;
1122         int i;
1123
1124         unack_data = assoc->next_tsn - assoc->ctsn_ack_point - 1;
1125
1126         frags = sack->variable;
1127         for (i = 0; i < ntohs(sack->num_gap_ack_blocks); i++) {
1128                 unack_data -= ((ntohs(frags[i].gab.end) -
1129                                 ntohs(frags[i].gab.start) + 1));
1130         }
1131
1132         assoc->unack_data = unack_data;
1133 }
1134
1135 /* This is where we REALLY process a SACK.
1136  *
1137  * Process the SACK against the outqueue.  Mostly, this just frees
1138  * things off the transmitted queue.
1139  */
1140 int sctp_outq_sack(struct sctp_outq *q, struct sctp_sackhdr *sack)
1141 {
1142         struct sctp_association *asoc = q->asoc;
1143         struct sctp_transport *transport;
1144         struct sctp_chunk *tchunk = NULL;
1145         struct list_head *lchunk, *transport_list, *temp;
1146         sctp_sack_variable_t *frags = sack->variable;
1147         __u32 sack_ctsn, ctsn, tsn;
1148         __u32 highest_tsn, highest_new_tsn;
1149         __u32 sack_a_rwnd;
1150         unsigned outstanding;
1151         struct sctp_transport *primary = asoc->peer.primary_path;
1152         int count_of_newacks = 0;
1153         int gap_ack_blocks;
1154         u8 accum_moved = 0;
1155
1156         /* Grab the association's destination address list. */
1157         transport_list = &asoc->peer.transport_addr_list;
1158
1159         sack_ctsn = ntohl(sack->cum_tsn_ack);
1160         gap_ack_blocks = ntohs(sack->num_gap_ack_blocks);
1161         /*
1162          * SFR-CACC algorithm:
1163          * On receipt of a SACK the sender SHOULD execute the
1164          * following statements.
1165          *
1166          * 1) If the cumulative ack in the SACK passes next tsn_at_change
1167          * on the current primary, the CHANGEOVER_ACTIVE flag SHOULD be
1168          * cleared. The CYCLING_CHANGEOVER flag SHOULD also be cleared for
1169          * all destinations.
1170          * 2) If the SACK contains gap acks and the flag CHANGEOVER_ACTIVE
1171          * is set the receiver of the SACK MUST take the following actions:
1172          *
1173          * A) Initialize the cacc_saw_newack to 0 for all destination
1174          * addresses.
1175          *
1176          * Only bother if changeover_active is set. Otherwise, this is
1177          * totally suboptimal to do on every SACK.
1178          */
1179         if (primary->cacc.changeover_active) {
1180                 u8 clear_cycling = 0;
1181
1182                 if (TSN_lte(primary->cacc.next_tsn_at_change, sack_ctsn)) {
1183                         primary->cacc.changeover_active = 0;
1184                         clear_cycling = 1;
1185                 }
1186
1187                 if (clear_cycling || gap_ack_blocks) {
1188                         list_for_each_entry(transport, transport_list,
1189                                         transports) {
1190                                 if (clear_cycling)
1191                                         transport->cacc.cycling_changeover = 0;
1192                                 if (gap_ack_blocks)
1193                                         transport->cacc.cacc_saw_newack = 0;
1194                         }
1195                 }
1196         }
1197
1198         /* Get the highest TSN in the sack. */
1199         highest_tsn = sack_ctsn;
1200         if (gap_ack_blocks)
1201                 highest_tsn += ntohs(frags[gap_ack_blocks - 1].gab.end);
1202
1203         if (TSN_lt(asoc->highest_sacked, highest_tsn))
1204                 asoc->highest_sacked = highest_tsn;
1205
1206         highest_new_tsn = sack_ctsn;
1207
1208         /* Run through the retransmit queue.  Credit bytes received
1209          * and free those chunks that we can.
1210          */
1211         sctp_check_transmitted(q, &q->retransmit, NULL, sack, &highest_new_tsn);
1212
1213         /* Run through the transmitted queue.
1214          * Credit bytes received and free those chunks which we can.
1215          *
1216          * This is a MASSIVE candidate for optimization.
1217          */
1218         list_for_each_entry(transport, transport_list, transports) {
1219                 sctp_check_transmitted(q, &transport->transmitted,
1220                                        transport, sack, &highest_new_tsn);
1221                 /*
1222                  * SFR-CACC algorithm:
1223                  * C) Let count_of_newacks be the number of
1224                  * destinations for which cacc_saw_newack is set.
1225                  */
1226                 if (transport->cacc.cacc_saw_newack)
1227                         count_of_newacks ++;
1228         }
1229
1230         /* Move the Cumulative TSN Ack Point if appropriate.  */
1231         if (TSN_lt(asoc->ctsn_ack_point, sack_ctsn)) {
1232                 asoc->ctsn_ack_point = sack_ctsn;
1233                 accum_moved = 1;
1234         }
1235
1236         if (gap_ack_blocks) {
1237
1238                 if (asoc->fast_recovery && accum_moved)
1239                         highest_new_tsn = highest_tsn;
1240
1241                 list_for_each_entry(transport, transport_list, transports)
1242                         sctp_mark_missing(q, &transport->transmitted, transport,
1243                                           highest_new_tsn, count_of_newacks);
1244         }
1245
1246         /* Update unack_data field in the assoc. */
1247         sctp_sack_update_unack_data(asoc, sack);
1248
1249         ctsn = asoc->ctsn_ack_point;
1250
1251         /* Throw away stuff rotting on the sack queue.  */
1252         list_for_each_safe(lchunk, temp, &q->sacked) {
1253                 tchunk = list_entry(lchunk, struct sctp_chunk,
1254                                     transmitted_list);
1255                 tsn = ntohl(tchunk->subh.data_hdr->tsn);
1256                 if (TSN_lte(tsn, ctsn)) {
1257                         list_del_init(&tchunk->transmitted_list);
1258                         sctp_chunk_free(tchunk);
1259                 }
1260         }
1261
1262         /* ii) Set rwnd equal to the newly received a_rwnd minus the
1263          *     number of bytes still outstanding after processing the
1264          *     Cumulative TSN Ack and the Gap Ack Blocks.
1265          */
1266
1267         sack_a_rwnd = ntohl(sack->a_rwnd);
1268         outstanding = q->outstanding_bytes;
1269
1270         if (outstanding < sack_a_rwnd)
1271                 sack_a_rwnd -= outstanding;
1272         else
1273                 sack_a_rwnd = 0;
1274
1275         asoc->peer.rwnd = sack_a_rwnd;
1276
1277         sctp_generate_fwdtsn(q, sack_ctsn);
1278
1279         SCTP_DEBUG_PRINTK("%s: sack Cumulative TSN Ack is 0x%x.\n",
1280                           __func__, sack_ctsn);
1281         SCTP_DEBUG_PRINTK("%s: Cumulative TSN Ack of association, "
1282                           "%p is 0x%x. Adv peer ack point: 0x%x\n",
1283                           __func__, asoc, ctsn, asoc->adv_peer_ack_point);
1284
1285         /* See if all chunks are acked.
1286          * Make sure the empty queue handler will get run later.
1287          */
1288         q->empty = (list_empty(&q->out_chunk_list) &&
1289                     list_empty(&q->retransmit));
1290         if (!q->empty)
1291                 goto finish;
1292
1293         list_for_each_entry(transport, transport_list, transports) {
1294                 q->empty = q->empty && list_empty(&transport->transmitted);
1295                 if (!q->empty)
1296                         goto finish;
1297         }
1298
1299         SCTP_DEBUG_PRINTK("sack queue is empty.\n");
1300 finish:
1301         return q->empty;
1302 }
1303
1304 /* Is the outqueue empty?  */
1305 int sctp_outq_is_empty(const struct sctp_outq *q)
1306 {
1307         return q->empty;
1308 }
1309
1310 /********************************************************************
1311  * 2nd Level Abstractions
1312  ********************************************************************/
1313
1314 /* Go through a transport's transmitted list or the association's retransmit
1315  * list and move chunks that are acked by the Cumulative TSN Ack to q->sacked.
1316  * The retransmit list will not have an associated transport.
1317  *
1318  * I added coherent debug information output.   --xguo
1319  *
1320  * Instead of printing 'sacked' or 'kept' for each TSN on the
1321  * transmitted_queue, we print a range: SACKED: TSN1-TSN2, TSN3, TSN4-TSN5.
1322  * KEPT TSN6-TSN7, etc.
1323  */
1324 static void sctp_check_transmitted(struct sctp_outq *q,
1325                                    struct list_head *transmitted_queue,
1326                                    struct sctp_transport *transport,
1327                                    struct sctp_sackhdr *sack,
1328                                    __u32 *highest_new_tsn_in_sack)
1329 {
1330         struct list_head *lchunk;
1331         struct sctp_chunk *tchunk;
1332         struct list_head tlist;
1333         __u32 tsn;
1334         __u32 sack_ctsn;
1335         __u32 rtt;
1336         __u8 restart_timer = 0;
1337         int bytes_acked = 0;
1338         int migrate_bytes = 0;
1339
1340         /* These state variables are for coherent debug output. --xguo */
1341
1342 #if SCTP_DEBUG
1343         __u32 dbg_ack_tsn = 0;  /* An ACKed TSN range starts here... */
1344         __u32 dbg_last_ack_tsn = 0;  /* ...and finishes here.        */
1345         __u32 dbg_kept_tsn = 0; /* An un-ACKed range starts here...  */
1346         __u32 dbg_last_kept_tsn = 0; /* ...and finishes here.        */
1347
1348         /* 0 : The last TSN was ACKed.
1349          * 1 : The last TSN was NOT ACKed (i.e. KEPT).
1350          * -1: We need to initialize.
1351          */
1352         int dbg_prt_state = -1;
1353 #endif /* SCTP_DEBUG */
1354
1355         sack_ctsn = ntohl(sack->cum_tsn_ack);
1356
1357         INIT_LIST_HEAD(&tlist);
1358
1359         /* The while loop will skip empty transmitted queues. */
1360         while (NULL != (lchunk = sctp_list_dequeue(transmitted_queue))) {
1361                 tchunk = list_entry(lchunk, struct sctp_chunk,
1362                                     transmitted_list);
1363
1364                 if (sctp_chunk_abandoned(tchunk)) {
1365                         /* Move the chunk to abandoned list. */
1366                         sctp_insert_list(&q->abandoned, lchunk);
1367
1368                         /* If this chunk has not been acked, stop
1369                          * considering it as 'outstanding'.
1370                          */
1371                         if (!tchunk->tsn_gap_acked) {
1372                                 if (tchunk->transport)
1373                                         tchunk->transport->flight_size -=
1374                                                         sctp_data_size(tchunk);
1375                                 q->outstanding_bytes -= sctp_data_size(tchunk);
1376                         }
1377                         continue;
1378                 }
1379
1380                 tsn = ntohl(tchunk->subh.data_hdr->tsn);
1381                 if (sctp_acked(sack, tsn)) {
1382                         /* If this queue is the retransmit queue, the
1383                          * retransmit timer has already reclaimed
1384                          * the outstanding bytes for this chunk, so only
1385                          * count bytes associated with a transport.
1386                          */
1387                         if (transport) {
1388                                 /* If this chunk is being used for RTT
1389                                  * measurement, calculate the RTT and update
1390                                  * the RTO using this value.
1391                                  *
1392                                  * 6.3.1 C5) Karn's algorithm: RTT measurements
1393                                  * MUST NOT be made using packets that were
1394                                  * retransmitted (and thus for which it is
1395                                  * ambiguous whether the reply was for the
1396                                  * first instance of the packet or a later
1397                                  * instance).
1398                                  */
1399                                 if (!tchunk->tsn_gap_acked &&
1400                                     tchunk->rtt_in_progress) {
1401                                         tchunk->rtt_in_progress = 0;
1402                                         rtt = jiffies - tchunk->sent_at;
1403                                         sctp_transport_update_rto(transport,
1404                                                                   rtt);
1405                                 }
1406                         }
1407
1408                         /* If the chunk hasn't been marked as ACKED,
1409                          * mark it and account bytes_acked if the
1410                          * chunk had a valid transport (it will not
1411                          * have a transport if ASCONF had deleted it
1412                          * while DATA was outstanding).
1413                          */
1414                         if (!tchunk->tsn_gap_acked) {
1415                                 tchunk->tsn_gap_acked = 1;
1416                                 *highest_new_tsn_in_sack = tsn;
1417                                 bytes_acked += sctp_data_size(tchunk);
1418                                 if (!tchunk->transport)
1419                                         migrate_bytes += sctp_data_size(tchunk);
1420                         }
1421
1422                         if (TSN_lte(tsn, sack_ctsn)) {
1423                                 /* RFC 2960  6.3.2 Retransmission Timer Rules
1424                                  *
1425                                  * R3) Whenever a SACK is received
1426                                  * that acknowledges the DATA chunk
1427                                  * with the earliest outstanding TSN
1428                                  * for that address, restart T3-rtx
1429                                  * timer for that address with its
1430                                  * current RTO.
1431                                  */
1432                                 restart_timer = 1;
1433
1434                                 if (!tchunk->tsn_gap_acked) {
1435                                         /*
1436                                          * SFR-CACC algorithm:
1437                                          * 2) If the SACK contains gap acks
1438                                          * and the flag CHANGEOVER_ACTIVE is
1439                                          * set the receiver of the SACK MUST
1440                                          * take the following action:
1441                                          *
1442                                          * B) For each TSN t being acked that
1443                                          * has not been acked in any SACK so
1444                                          * far, set cacc_saw_newack to 1 for
1445                                          * the destination that the TSN was
1446                                          * sent to.
1447                                          */
1448                                         if (transport &&
1449                                             sack->num_gap_ack_blocks &&
1450                                             q->asoc->peer.primary_path->cacc.
1451                                             changeover_active)
1452                                                 transport->cacc.cacc_saw_newack
1453                                                         = 1;
1454                                 }
1455
1456                                 list_add_tail(&tchunk->transmitted_list,
1457                                               &q->sacked);
1458                         } else {
1459                                 /* RFC2960 7.2.4, sctpimpguide-05 2.8.2
1460                                  * M2) Each time a SACK arrives reporting
1461                                  * 'Stray DATA chunk(s)' record the highest TSN
1462                                  * reported as newly acknowledged, call this
1463                                  * value 'HighestTSNinSack'. A newly
1464                                  * acknowledged DATA chunk is one not
1465                                  * previously acknowledged in a SACK.
1466                                  *
1467                                  * When the SCTP sender of data receives a SACK
1468                                  * chunk that acknowledges, for the first time,
1469                                  * the receipt of a DATA chunk, all the still
1470                                  * unacknowledged DATA chunks whose TSN is
1471                                  * older than that newly acknowledged DATA
1472                                  * chunk, are qualified as 'Stray DATA chunks'.
1473                                  */
1474                                 list_add_tail(lchunk, &tlist);
1475                         }
1476
1477 #if SCTP_DEBUG
1478                         switch (dbg_prt_state) {
1479                         case 0: /* last TSN was ACKed */
1480                                 if (dbg_last_ack_tsn + 1 == tsn) {
1481                                         /* This TSN belongs to the
1482                                          * current ACK range.
1483                                          */
1484                                         break;
1485                                 }
1486
1487                                 if (dbg_last_ack_tsn != dbg_ack_tsn) {
1488                                         /* Display the end of the
1489                                          * current range.
1490                                          */
1491                                         SCTP_DEBUG_PRINTK_CONT("-%08x",
1492                                                                dbg_last_ack_tsn);
1493                                 }
1494
1495                                 /* Start a new range.  */
1496                                 SCTP_DEBUG_PRINTK_CONT(",%08x", tsn);
1497                                 dbg_ack_tsn = tsn;
1498                                 break;
1499
1500                         case 1: /* The last TSN was NOT ACKed. */
1501                                 if (dbg_last_kept_tsn != dbg_kept_tsn) {
1502                                         /* Display the end of current range. */
1503                                         SCTP_DEBUG_PRINTK_CONT("-%08x",
1504                                                                dbg_last_kept_tsn);
1505                                 }
1506
1507                                 SCTP_DEBUG_PRINTK_CONT("\n");
1508
1509                                 /* FALL THROUGH... */
1510                         default:
1511                                 /* This is the first-ever TSN we examined.  */
1512                                 /* Start a new range of ACK-ed TSNs.  */
1513                                 SCTP_DEBUG_PRINTK("ACKed: %08x", tsn);
1514                                 dbg_prt_state = 0;
1515                                 dbg_ack_tsn = tsn;
1516                         }
1517
1518                         dbg_last_ack_tsn = tsn;
1519 #endif /* SCTP_DEBUG */
1520
1521                 } else {
1522                         if (tchunk->tsn_gap_acked) {
1523                                 SCTP_DEBUG_PRINTK("%s: Receiver reneged on "
1524                                                   "data TSN: 0x%x\n",
1525                                                   __func__,
1526                                                   tsn);
1527                                 tchunk->tsn_gap_acked = 0;
1528
1529                                 if (tchunk->transport)
1530                                         bytes_acked -= sctp_data_size(tchunk);
1531
1532                                 /* RFC 2960 6.3.2 Retransmission Timer Rules
1533                                  *
1534                                  * R4) Whenever a SACK is received missing a
1535                                  * TSN that was previously acknowledged via a
1536                                  * Gap Ack Block, start T3-rtx for the
1537                                  * destination address to which the DATA
1538                                  * chunk was originally
1539                                  * transmitted if it is not already running.
1540                                  */
1541                                 restart_timer = 1;
1542                         }
1543
1544                         list_add_tail(lchunk, &tlist);
1545
1546 #if SCTP_DEBUG
1547                         /* See the above comments on ACK-ed TSNs. */
1548                         switch (dbg_prt_state) {
1549                         case 1:
1550                                 if (dbg_last_kept_tsn + 1 == tsn)
1551                                         break;
1552
1553                                 if (dbg_last_kept_tsn != dbg_kept_tsn)
1554                                         SCTP_DEBUG_PRINTK_CONT("-%08x",
1555                                                                dbg_last_kept_tsn);
1556
1557                                 SCTP_DEBUG_PRINTK_CONT(",%08x", tsn);
1558                                 dbg_kept_tsn = tsn;
1559                                 break;
1560
1561                         case 0:
1562                                 if (dbg_last_ack_tsn != dbg_ack_tsn)
1563                                         SCTP_DEBUG_PRINTK_CONT("-%08x",
1564                                                                dbg_last_ack_tsn);
1565                                 SCTP_DEBUG_PRINTK_CONT("\n");
1566
1567                                 /* FALL THROUGH... */
1568                         default:
1569                                 SCTP_DEBUG_PRINTK("KEPT: %08x",tsn);
1570                                 dbg_prt_state = 1;
1571                                 dbg_kept_tsn = tsn;
1572                         }
1573
1574                         dbg_last_kept_tsn = tsn;
1575 #endif /* SCTP_DEBUG */
1576                 }
1577         }
1578
1579 #if SCTP_DEBUG
1580         /* Finish off the last range, displaying its ending TSN.  */
1581         switch (dbg_prt_state) {
1582         case 0:
1583                 if (dbg_last_ack_tsn != dbg_ack_tsn) {
1584                         SCTP_DEBUG_PRINTK_CONT("-%08x\n", dbg_last_ack_tsn);
1585                 } else {
1586                         SCTP_DEBUG_PRINTK_CONT("\n");
1587                 }
1588         break;
1589
1590         case 1:
1591                 if (dbg_last_kept_tsn != dbg_kept_tsn) {
1592                         SCTP_DEBUG_PRINTK_CONT("-%08x\n", dbg_last_kept_tsn);
1593                 } else {
1594                         SCTP_DEBUG_PRINTK_CONT("\n");
1595                 }
1596         }
1597 #endif /* SCTP_DEBUG */
1598         if (transport) {
1599                 if (bytes_acked) {
1600                         struct sctp_association *asoc = transport->asoc;
1601
1602                         /* We may have counted DATA that was migrated
1603                          * to this transport due to DEL-IP operation.
1604                          * Subtract those bytes, since the were never
1605                          * send on this transport and shouldn't be
1606                          * credited to this transport.
1607                          */
1608                         bytes_acked -= migrate_bytes;
1609
1610                         /* 8.2. When an outstanding TSN is acknowledged,
1611                          * the endpoint shall clear the error counter of
1612                          * the destination transport address to which the
1613                          * DATA chunk was last sent.
1614                          * The association's overall error counter is
1615                          * also cleared.
1616                          */
1617                         transport->error_count = 0;
1618                         transport->asoc->overall_error_count = 0;
1619
1620                         /*
1621                          * While in SHUTDOWN PENDING, we may have started
1622                          * the T5 shutdown guard timer after reaching the
1623                          * retransmission limit. Stop that timer as soon
1624                          * as the receiver acknowledged any data.
1625                          */
1626                         if (asoc->state == SCTP_STATE_SHUTDOWN_PENDING &&
1627                             del_timer(&asoc->timers
1628                                 [SCTP_EVENT_TIMEOUT_T5_SHUTDOWN_GUARD]))
1629                                         sctp_association_put(asoc);
1630
1631                         /* Mark the destination transport address as
1632                          * active if it is not so marked.
1633                          */
1634                         if ((transport->state == SCTP_INACTIVE) ||
1635                             (transport->state == SCTP_UNCONFIRMED)) {
1636                                 sctp_assoc_control_transport(
1637                                         transport->asoc,
1638                                         transport,
1639                                         SCTP_TRANSPORT_UP,
1640                                         SCTP_RECEIVED_SACK);
1641                         }
1642
1643                         sctp_transport_raise_cwnd(transport, sack_ctsn,
1644                                                   bytes_acked);
1645
1646                         transport->flight_size -= bytes_acked;
1647                         if (transport->flight_size == 0)
1648                                 transport->partial_bytes_acked = 0;
1649                         q->outstanding_bytes -= bytes_acked + migrate_bytes;
1650                 } else {
1651                         /* RFC 2960 6.1, sctpimpguide-06 2.15.2
1652                          * When a sender is doing zero window probing, it
1653                          * should not timeout the association if it continues
1654                          * to receive new packets from the receiver. The
1655                          * reason is that the receiver MAY keep its window
1656                          * closed for an indefinite time.
1657                          * A sender is doing zero window probing when the
1658                          * receiver's advertised window is zero, and there is
1659                          * only one data chunk in flight to the receiver.
1660                          *
1661                          * Allow the association to timeout while in SHUTDOWN
1662                          * PENDING or SHUTDOWN RECEIVED in case the receiver
1663                          * stays in zero window mode forever.
1664                          */
1665                         if (!q->asoc->peer.rwnd &&
1666                             !list_empty(&tlist) &&
1667                             (sack_ctsn+2 == q->asoc->next_tsn) &&
1668                             q->asoc->state < SCTP_STATE_SHUTDOWN_PENDING) {
1669                                 SCTP_DEBUG_PRINTK("%s: SACK received for zero "
1670                                                   "window probe: %u\n",
1671                                                   __func__, sack_ctsn);
1672                                 q->asoc->overall_error_count = 0;
1673                                 transport->error_count = 0;
1674                         }
1675                 }
1676
1677                 /* RFC 2960 6.3.2 Retransmission Timer Rules
1678                  *
1679                  * R2) Whenever all outstanding data sent to an address have
1680                  * been acknowledged, turn off the T3-rtx timer of that
1681                  * address.
1682                  */
1683                 if (!transport->flight_size) {
1684                         if (timer_pending(&transport->T3_rtx_timer) &&
1685                             del_timer(&transport->T3_rtx_timer)) {
1686                                 sctp_transport_put(transport);
1687                         }
1688                 } else if (restart_timer) {
1689                         if (!mod_timer(&transport->T3_rtx_timer,
1690                                        jiffies + transport->rto))
1691                                 sctp_transport_hold(transport);
1692                 }
1693         }
1694
1695         list_splice(&tlist, transmitted_queue);
1696 }
1697
1698 /* Mark chunks as missing and consequently may get retransmitted. */
1699 static void sctp_mark_missing(struct sctp_outq *q,
1700                               struct list_head *transmitted_queue,
1701                               struct sctp_transport *transport,
1702                               __u32 highest_new_tsn_in_sack,
1703                               int count_of_newacks)
1704 {
1705         struct sctp_chunk *chunk;
1706         __u32 tsn;
1707         char do_fast_retransmit = 0;
1708         struct sctp_association *asoc = q->asoc;
1709         struct sctp_transport *primary = asoc->peer.primary_path;
1710
1711         list_for_each_entry(chunk, transmitted_queue, transmitted_list) {
1712
1713                 tsn = ntohl(chunk->subh.data_hdr->tsn);
1714
1715                 /* RFC 2960 7.2.4, sctpimpguide-05 2.8.2 M3) Examine all
1716                  * 'Unacknowledged TSN's', if the TSN number of an
1717                  * 'Unacknowledged TSN' is smaller than the 'HighestTSNinSack'
1718                  * value, increment the 'TSN.Missing.Report' count on that
1719                  * chunk if it has NOT been fast retransmitted or marked for
1720                  * fast retransmit already.
1721                  */
1722                 if (chunk->fast_retransmit == SCTP_CAN_FRTX &&
1723                     !chunk->tsn_gap_acked &&
1724                     TSN_lt(tsn, highest_new_tsn_in_sack)) {
1725
1726                         /* SFR-CACC may require us to skip marking
1727                          * this chunk as missing.
1728                          */
1729                         if (!transport || !sctp_cacc_skip(primary,
1730                                                 chunk->transport,
1731                                                 count_of_newacks, tsn)) {
1732                                 chunk->tsn_missing_report++;
1733
1734                                 SCTP_DEBUG_PRINTK(
1735                                         "%s: TSN 0x%x missing counter: %d\n",
1736                                         __func__, tsn,
1737                                         chunk->tsn_missing_report);
1738                         }
1739                 }
1740                 /*
1741                  * M4) If any DATA chunk is found to have a
1742                  * 'TSN.Missing.Report'
1743                  * value larger than or equal to 3, mark that chunk for
1744                  * retransmission and start the fast retransmit procedure.
1745                  */
1746
1747                 if (chunk->tsn_missing_report >= 3) {
1748                         chunk->fast_retransmit = SCTP_NEED_FRTX;
1749                         do_fast_retransmit = 1;
1750                 }
1751         }
1752
1753         if (transport) {
1754                 if (do_fast_retransmit)
1755                         sctp_retransmit(q, transport, SCTP_RTXR_FAST_RTX);
1756
1757                 SCTP_DEBUG_PRINTK("%s: transport: %p, cwnd: %d, "
1758                                   "ssthresh: %d, flight_size: %d, pba: %d\n",
1759                                   __func__, transport, transport->cwnd,
1760                                   transport->ssthresh, transport->flight_size,
1761                                   transport->partial_bytes_acked);
1762         }
1763 }
1764
1765 /* Is the given TSN acked by this packet?  */
1766 static int sctp_acked(struct sctp_sackhdr *sack, __u32 tsn)
1767 {
1768         int i;
1769         sctp_sack_variable_t *frags;
1770         __u16 gap;
1771         __u32 ctsn = ntohl(sack->cum_tsn_ack);
1772
1773         if (TSN_lte(tsn, ctsn))
1774                 goto pass;
1775
1776         /* 3.3.4 Selective Acknowledgement (SACK) (3):
1777          *
1778          * Gap Ack Blocks:
1779          *  These fields contain the Gap Ack Blocks. They are repeated
1780          *  for each Gap Ack Block up to the number of Gap Ack Blocks
1781          *  defined in the Number of Gap Ack Blocks field. All DATA
1782          *  chunks with TSNs greater than or equal to (Cumulative TSN
1783          *  Ack + Gap Ack Block Start) and less than or equal to
1784          *  (Cumulative TSN Ack + Gap Ack Block End) of each Gap Ack
1785          *  Block are assumed to have been received correctly.
1786          */
1787
1788         frags = sack->variable;
1789         gap = tsn - ctsn;
1790         for (i = 0; i < ntohs(sack->num_gap_ack_blocks); ++i) {
1791                 if (TSN_lte(ntohs(frags[i].gab.start), gap) &&
1792                     TSN_lte(gap, ntohs(frags[i].gab.end)))
1793                         goto pass;
1794         }
1795
1796         return 0;
1797 pass:
1798         return 1;
1799 }
1800
1801 static inline int sctp_get_skip_pos(struct sctp_fwdtsn_skip *skiplist,
1802                                     int nskips, __be16 stream)
1803 {
1804         int i;
1805
1806         for (i = 0; i < nskips; i++) {
1807                 if (skiplist[i].stream == stream)
1808                         return i;
1809         }
1810         return i;
1811 }
1812
1813 /* Create and add a fwdtsn chunk to the outq's control queue if needed. */
1814 static void sctp_generate_fwdtsn(struct sctp_outq *q, __u32 ctsn)
1815 {
1816         struct sctp_association *asoc = q->asoc;
1817         struct sctp_chunk *ftsn_chunk = NULL;
1818         struct sctp_fwdtsn_skip ftsn_skip_arr[10];
1819         int nskips = 0;
1820         int skip_pos = 0;
1821         __u32 tsn;
1822         struct sctp_chunk *chunk;
1823         struct list_head *lchunk, *temp;
1824
1825         if (!asoc->peer.prsctp_capable)
1826                 return;
1827
1828         /* PR-SCTP C1) Let SackCumAck be the Cumulative TSN ACK carried in the
1829          * received SACK.
1830          *
1831          * If (Advanced.Peer.Ack.Point < SackCumAck), then update
1832          * Advanced.Peer.Ack.Point to be equal to SackCumAck.
1833          */
1834         if (TSN_lt(asoc->adv_peer_ack_point, ctsn))
1835                 asoc->adv_peer_ack_point = ctsn;
1836
1837         /* PR-SCTP C2) Try to further advance the "Advanced.Peer.Ack.Point"
1838          * locally, that is, to move "Advanced.Peer.Ack.Point" up as long as
1839          * the chunk next in the out-queue space is marked as "abandoned" as
1840          * shown in the following example:
1841          *
1842          * Assuming that a SACK arrived with the Cumulative TSN ACK 102
1843          * and the Advanced.Peer.Ack.Point is updated to this value:
1844          *
1845          *   out-queue at the end of  ==>   out-queue after Adv.Ack.Point
1846          *   normal SACK processing           local advancement
1847          *                ...                           ...
1848          *   Adv.Ack.Pt-> 102 acked                     102 acked
1849          *                103 abandoned                 103 abandoned
1850          *                104 abandoned     Adv.Ack.P-> 104 abandoned
1851          *                105                           105
1852          *                106 acked                     106 acked
1853          *                ...                           ...
1854          *
1855          * In this example, the data sender successfully advanced the
1856          * "Advanced.Peer.Ack.Point" from 102 to 104 locally.
1857          */
1858         list_for_each_safe(lchunk, temp, &q->abandoned) {
1859                 chunk = list_entry(lchunk, struct sctp_chunk,
1860                                         transmitted_list);
1861                 tsn = ntohl(chunk->subh.data_hdr->tsn);
1862
1863                 /* Remove any chunks in the abandoned queue that are acked by
1864                  * the ctsn.
1865                  */
1866                 if (TSN_lte(tsn, ctsn)) {
1867                         list_del_init(lchunk);
1868                         sctp_chunk_free(chunk);
1869                 } else {
1870                         if (TSN_lte(tsn, asoc->adv_peer_ack_point+1)) {
1871                                 asoc->adv_peer_ack_point = tsn;
1872                                 if (chunk->chunk_hdr->flags &
1873                                          SCTP_DATA_UNORDERED)
1874                                         continue;
1875                                 skip_pos = sctp_get_skip_pos(&ftsn_skip_arr[0],
1876                                                 nskips,
1877                                                 chunk->subh.data_hdr->stream);
1878                                 ftsn_skip_arr[skip_pos].stream =
1879                                         chunk->subh.data_hdr->stream;
1880                                 ftsn_skip_arr[skip_pos].ssn =
1881                                          chunk->subh.data_hdr->ssn;
1882                                 if (skip_pos == nskips)
1883                                         nskips++;
1884                                 if (nskips == 10)
1885                                         break;
1886                         } else
1887                                 break;
1888                 }
1889         }
1890
1891         /* PR-SCTP C3) If, after step C1 and C2, the "Advanced.Peer.Ack.Point"
1892          * is greater than the Cumulative TSN ACK carried in the received
1893          * SACK, the data sender MUST send the data receiver a FORWARD TSN
1894          * chunk containing the latest value of the
1895          * "Advanced.Peer.Ack.Point".
1896          *
1897          * C4) For each "abandoned" TSN the sender of the FORWARD TSN SHOULD
1898          * list each stream and sequence number in the forwarded TSN. This
1899          * information will enable the receiver to easily find any
1900          * stranded TSN's waiting on stream reorder queues. Each stream
1901          * SHOULD only be reported once; this means that if multiple
1902          * abandoned messages occur in the same stream then only the
1903          * highest abandoned stream sequence number is reported. If the
1904          * total size of the FORWARD TSN does NOT fit in a single MTU then
1905          * the sender of the FORWARD TSN SHOULD lower the
1906          * Advanced.Peer.Ack.Point to the last TSN that will fit in a
1907          * single MTU.
1908          */
1909         if (asoc->adv_peer_ack_point > ctsn)
1910                 ftsn_chunk = sctp_make_fwdtsn(asoc, asoc->adv_peer_ack_point,
1911                                               nskips, &ftsn_skip_arr[0]);
1912
1913         if (ftsn_chunk) {
1914                 list_add_tail(&ftsn_chunk->list, &q->control_chunk_list);
1915                 SCTP_INC_STATS(SCTP_MIB_OUTCTRLCHUNKS);
1916         }
1917 }