xref: /openbmc/linux/net/sctp/outqueue.c (revision ee89bd6b)
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 				   union sctp_addr *saddr,
67 				   struct sctp_sackhdr *sack,
68 				   __u32 *highest_new_tsn);
69 
70 static void sctp_mark_missing(struct sctp_outq *q,
71 			      struct list_head *transmitted_queue,
72 			      struct sctp_transport *transport,
73 			      __u32 highest_new_tsn,
74 			      int count_of_newacks);
75 
76 static void sctp_generate_fwdtsn(struct sctp_outq *q, __u32 sack_ctsn);
77 
78 static int sctp_outq_flush(struct sctp_outq *q, int rtx_timeout);
79 
80 /* Add data to the front of the queue. */
81 static inline void sctp_outq_head_data(struct sctp_outq *q,
82 					struct sctp_chunk *ch)
83 {
84 	list_add(&ch->list, &q->out_chunk_list);
85 	q->out_qlen += ch->skb->len;
86 }
87 
88 /* Take data from the front of the queue. */
89 static inline struct sctp_chunk *sctp_outq_dequeue_data(struct sctp_outq *q)
90 {
91 	struct sctp_chunk *ch = NULL;
92 
93 	if (!list_empty(&q->out_chunk_list)) {
94 		struct list_head *entry = q->out_chunk_list.next;
95 
96 		ch = list_entry(entry, struct sctp_chunk, list);
97 		list_del_init(entry);
98 		q->out_qlen -= ch->skb->len;
99 	}
100 	return ch;
101 }
102 /* Add data chunk to the end of the queue. */
103 static inline void sctp_outq_tail_data(struct sctp_outq *q,
104 				       struct sctp_chunk *ch)
105 {
106 	list_add_tail(&ch->list, &q->out_chunk_list);
107 	q->out_qlen += ch->skb->len;
108 }
109 
110 /*
111  * SFR-CACC algorithm:
112  * D) If count_of_newacks is greater than or equal to 2
113  * and t was not sent to the current primary then the
114  * sender MUST NOT increment missing report count for t.
115  */
116 static inline int sctp_cacc_skip_3_1_d(struct sctp_transport *primary,
117 				       struct sctp_transport *transport,
118 				       int count_of_newacks)
119 {
120 	if (count_of_newacks >=2 && transport != primary)
121 		return 1;
122 	return 0;
123 }
124 
125 /*
126  * SFR-CACC algorithm:
127  * F) If count_of_newacks is less than 2, let d be the
128  * destination to which t was sent. If cacc_saw_newack
129  * is 0 for destination d, then the sender MUST NOT
130  * increment missing report count for t.
131  */
132 static inline int sctp_cacc_skip_3_1_f(struct sctp_transport *transport,
133 				       int count_of_newacks)
134 {
135 	if (count_of_newacks < 2 &&
136 			(transport && !transport->cacc.cacc_saw_newack))
137 		return 1;
138 	return 0;
139 }
140 
141 /*
142  * SFR-CACC algorithm:
143  * 3.1) If CYCLING_CHANGEOVER is 0, the sender SHOULD
144  * execute steps C, D, F.
145  *
146  * C has been implemented in sctp_outq_sack
147  */
148 static inline int sctp_cacc_skip_3_1(struct sctp_transport *primary,
149 				     struct sctp_transport *transport,
150 				     int count_of_newacks)
151 {
152 	if (!primary->cacc.cycling_changeover) {
153 		if (sctp_cacc_skip_3_1_d(primary, transport, count_of_newacks))
154 			return 1;
155 		if (sctp_cacc_skip_3_1_f(transport, count_of_newacks))
156 			return 1;
157 		return 0;
158 	}
159 	return 0;
160 }
161 
162 /*
163  * SFR-CACC algorithm:
164  * 3.2) Else if CYCLING_CHANGEOVER is 1, and t is less
165  * than next_tsn_at_change of the current primary, then
166  * the sender MUST NOT increment missing report count
167  * for t.
168  */
169 static inline int sctp_cacc_skip_3_2(struct sctp_transport *primary, __u32 tsn)
170 {
171 	if (primary->cacc.cycling_changeover &&
172 	    TSN_lt(tsn, primary->cacc.next_tsn_at_change))
173 		return 1;
174 	return 0;
175 }
176 
177 /*
178  * SFR-CACC algorithm:
179  * 3) If the missing report count for TSN t is to be
180  * incremented according to [RFC2960] and
181  * [SCTP_STEWART-2002], and CHANGEOVER_ACTIVE is set,
182  * then the sender MUST further execute steps 3.1 and
183  * 3.2 to determine if the missing report count for
184  * TSN t SHOULD NOT be incremented.
185  *
186  * 3.3) If 3.1 and 3.2 do not dictate that the missing
187  * report count for t should not be incremented, then
188  * the sender SHOULD increment missing report count for
189  * t (according to [RFC2960] and [SCTP_STEWART_2002]).
190  */
191 static inline int sctp_cacc_skip(struct sctp_transport *primary,
192 				 struct sctp_transport *transport,
193 				 int count_of_newacks,
194 				 __u32 tsn)
195 {
196 	if (primary->cacc.changeover_active &&
197 	    (sctp_cacc_skip_3_1(primary, transport, count_of_newacks) ||
198 	     sctp_cacc_skip_3_2(primary, tsn)))
199 		return 1;
200 	return 0;
201 }
202 
203 /* Initialize an existing sctp_outq.  This does the boring stuff.
204  * You still need to define handlers if you really want to DO
205  * something with this structure...
206  */
207 void sctp_outq_init(struct sctp_association *asoc, struct sctp_outq *q)
208 {
209 	q->asoc = asoc;
210 	INIT_LIST_HEAD(&q->out_chunk_list);
211 	INIT_LIST_HEAD(&q->control_chunk_list);
212 	INIT_LIST_HEAD(&q->retransmit);
213 	INIT_LIST_HEAD(&q->sacked);
214 	INIT_LIST_HEAD(&q->abandoned);
215 
216 	q->fast_rtx = 0;
217 	q->outstanding_bytes = 0;
218 	q->empty = 1;
219 	q->cork  = 0;
220 	q->out_qlen = 0;
221 }
222 
223 /* Free the outqueue structure and any related pending chunks.
224  */
225 static void __sctp_outq_teardown(struct sctp_outq *q)
226 {
227 	struct sctp_transport *transport;
228 	struct list_head *lchunk, *temp;
229 	struct sctp_chunk *chunk, *tmp;
230 
231 	/* Throw away unacknowledged chunks. */
232 	list_for_each_entry(transport, &q->asoc->peer.transport_addr_list,
233 			transports) {
234 		while ((lchunk = sctp_list_dequeue(&transport->transmitted)) != NULL) {
235 			chunk = list_entry(lchunk, struct sctp_chunk,
236 					   transmitted_list);
237 			/* Mark as part of a failed message. */
238 			sctp_chunk_fail(chunk, q->error);
239 			sctp_chunk_free(chunk);
240 		}
241 	}
242 
243 	/* Throw away chunks that have been gap ACKed.  */
244 	list_for_each_safe(lchunk, temp, &q->sacked) {
245 		list_del_init(lchunk);
246 		chunk = list_entry(lchunk, struct sctp_chunk,
247 				   transmitted_list);
248 		sctp_chunk_fail(chunk, q->error);
249 		sctp_chunk_free(chunk);
250 	}
251 
252 	/* Throw away any chunks in the retransmit queue. */
253 	list_for_each_safe(lchunk, temp, &q->retransmit) {
254 		list_del_init(lchunk);
255 		chunk = list_entry(lchunk, struct sctp_chunk,
256 				   transmitted_list);
257 		sctp_chunk_fail(chunk, q->error);
258 		sctp_chunk_free(chunk);
259 	}
260 
261 	/* Throw away any chunks that are in the abandoned queue. */
262 	list_for_each_safe(lchunk, temp, &q->abandoned) {
263 		list_del_init(lchunk);
264 		chunk = list_entry(lchunk, struct sctp_chunk,
265 				   transmitted_list);
266 		sctp_chunk_fail(chunk, q->error);
267 		sctp_chunk_free(chunk);
268 	}
269 
270 	/* Throw away any leftover data chunks. */
271 	while ((chunk = sctp_outq_dequeue_data(q)) != NULL) {
272 
273 		/* Mark as send failure. */
274 		sctp_chunk_fail(chunk, q->error);
275 		sctp_chunk_free(chunk);
276 	}
277 
278 	/* Throw away any leftover control chunks. */
279 	list_for_each_entry_safe(chunk, tmp, &q->control_chunk_list, list) {
280 		list_del_init(&chunk->list);
281 		sctp_chunk_free(chunk);
282 	}
283 }
284 
285 void sctp_outq_teardown(struct sctp_outq *q)
286 {
287 	__sctp_outq_teardown(q);
288 	sctp_outq_init(q->asoc, q);
289 }
290 
291 /* Free the outqueue structure and any related pending chunks.  */
292 void sctp_outq_free(struct sctp_outq *q)
293 {
294 	/* Throw away leftover chunks. */
295 	__sctp_outq_teardown(q);
296 }
297 
298 /* Put a new chunk in an sctp_outq.  */
299 int sctp_outq_tail(struct sctp_outq *q, struct sctp_chunk *chunk)
300 {
301 	struct net *net = sock_net(q->asoc->base.sk);
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(net, SCTP_MIB_OUTUNORDERCHUNKS);
341 			else
342 				SCTP_INC_STATS(net, 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(net, 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 	struct net *net = sock_net(q->asoc->base.sk);
482 	int error = 0;
483 
484 	switch(reason) {
485 	case SCTP_RTXR_T3_RTX:
486 		SCTP_INC_STATS(net, SCTP_MIB_T3_RETRANSMITS);
487 		sctp_transport_lower_cwnd(transport, SCTP_LOWER_CWND_T3_RTX);
488 		/* Update the retran path if the T3-rtx timer has expired for
489 		 * the current retran path.
490 		 */
491 		if (transport == transport->asoc->peer.retran_path)
492 			sctp_assoc_update_retran_path(transport->asoc);
493 		transport->asoc->rtx_data_chunks +=
494 			transport->asoc->unack_data;
495 		break;
496 	case SCTP_RTXR_FAST_RTX:
497 		SCTP_INC_STATS(net, SCTP_MIB_FAST_RETRANSMITS);
498 		sctp_transport_lower_cwnd(transport, SCTP_LOWER_CWND_FAST_RTX);
499 		q->fast_rtx = 1;
500 		break;
501 	case SCTP_RTXR_PMTUD:
502 		SCTP_INC_STATS(net, SCTP_MIB_PMTUD_RETRANSMITS);
503 		break;
504 	case SCTP_RTXR_T1_RTX:
505 		SCTP_INC_STATS(net, SCTP_MIB_T1_RETRANSMITS);
506 		transport->asoc->init_retries++;
507 		break;
508 	default:
509 		BUG();
510 	}
511 
512 	sctp_retransmit_mark(q, transport, reason);
513 
514 	/* PR-SCTP A5) Any time the T3-rtx timer expires, on any destination,
515 	 * the sender SHOULD try to advance the "Advanced.Peer.Ack.Point" by
516 	 * following the procedures outlined in C1 - C5.
517 	 */
518 	if (reason == SCTP_RTXR_T3_RTX)
519 		sctp_generate_fwdtsn(q, q->asoc->ctsn_ack_point);
520 
521 	/* Flush the queues only on timeout, since fast_rtx is only
522 	 * triggered during sack processing and the queue
523 	 * will be flushed at the end.
524 	 */
525 	if (reason != SCTP_RTXR_FAST_RTX)
526 		error = sctp_outq_flush(q, /* rtx_timeout */ 1);
527 
528 	if (error)
529 		q->asoc->base.sk->sk_err = -error;
530 }
531 
532 /*
533  * Transmit DATA chunks on the retransmit queue.  Upon return from
534  * sctp_outq_flush_rtx() the packet 'pkt' may contain chunks which
535  * need to be transmitted by the caller.
536  * We assume that pkt->transport has already been set.
537  *
538  * The return value is a normal kernel error return value.
539  */
540 static int sctp_outq_flush_rtx(struct sctp_outq *q, struct sctp_packet *pkt,
541 			       int rtx_timeout, int *start_timer)
542 {
543 	struct list_head *lqueue;
544 	struct sctp_transport *transport = pkt->transport;
545 	sctp_xmit_t status;
546 	struct sctp_chunk *chunk, *chunk1;
547 	int fast_rtx;
548 	int error = 0;
549 	int timer = 0;
550 	int done = 0;
551 
552 	lqueue = &q->retransmit;
553 	fast_rtx = q->fast_rtx;
554 
555 	/* This loop handles time-out retransmissions, fast retransmissions,
556 	 * and retransmissions due to opening of whindow.
557 	 *
558 	 * RFC 2960 6.3.3 Handle T3-rtx Expiration
559 	 *
560 	 * E3) Determine how many of the earliest (i.e., lowest TSN)
561 	 * outstanding DATA chunks for the address for which the
562 	 * T3-rtx has expired will fit into a single packet, subject
563 	 * to the MTU constraint for the path corresponding to the
564 	 * destination transport address to which the retransmission
565 	 * is being sent (this may be different from the address for
566 	 * which the timer expires [see Section 6.4]). Call this value
567 	 * K. Bundle and retransmit those K DATA chunks in a single
568 	 * packet to the destination endpoint.
569 	 *
570 	 * [Just to be painfully clear, if we are retransmitting
571 	 * because a timeout just happened, we should send only ONE
572 	 * packet of retransmitted data.]
573 	 *
574 	 * For fast retransmissions we also send only ONE packet.  However,
575 	 * if we are just flushing the queue due to open window, we'll
576 	 * try to send as much as possible.
577 	 */
578 	list_for_each_entry_safe(chunk, chunk1, lqueue, transmitted_list) {
579 		/* If the chunk is abandoned, move it to abandoned list. */
580 		if (sctp_chunk_abandoned(chunk)) {
581 			list_del_init(&chunk->transmitted_list);
582 			sctp_insert_list(&q->abandoned,
583 					 &chunk->transmitted_list);
584 			continue;
585 		}
586 
587 		/* Make sure that Gap Acked TSNs are not retransmitted.  A
588 		 * simple approach is just to move such TSNs out of the
589 		 * way and into a 'transmitted' queue and skip to the
590 		 * next chunk.
591 		 */
592 		if (chunk->tsn_gap_acked) {
593 			list_move_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_move_tail(&chunk->transmitted_list,
659 				       &transport->transmitted);
660 
661 			/* Mark the chunk as ineligible for fast retransmit
662 			 * after it is retransmitted.
663 			 */
664 			if (chunk->fast_retransmit == SCTP_NEED_FRTX)
665 				chunk->fast_retransmit = SCTP_DONT_FRTX;
666 
667 			q->empty = 0;
668 			q->asoc->stats.rtxchunks++;
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 	if (q->cork)
705 		q->cork = 0;
706 
707 	return sctp_outq_flush(q, 0);
708 }
709 
710 
711 /*
712  * Try to flush an outqueue.
713  *
714  * Description: Send everything in q which we legally can, subject to
715  * congestion limitations.
716  * * Note: This function can be called from multiple contexts so appropriate
717  * locking concerns must be made.  Today we use the sock lock to protect
718  * this function.
719  */
720 static int sctp_outq_flush(struct sctp_outq *q, int rtx_timeout)
721 {
722 	struct sctp_packet *packet;
723 	struct sctp_packet singleton;
724 	struct sctp_association *asoc = q->asoc;
725 	__u16 sport = asoc->base.bind_addr.port;
726 	__u16 dport = asoc->peer.port;
727 	__u32 vtag = asoc->peer.i.init_tag;
728 	struct sctp_transport *transport = NULL;
729 	struct sctp_transport *new_transport;
730 	struct sctp_chunk *chunk, *tmp;
731 	sctp_xmit_t status;
732 	int error = 0;
733 	int start_timer = 0;
734 	int one_packet = 0;
735 
736 	/* These transports have chunks to send. */
737 	struct list_head transport_list;
738 	struct list_head *ltransport;
739 
740 	INIT_LIST_HEAD(&transport_list);
741 	packet = NULL;
742 
743 	/*
744 	 * 6.10 Bundling
745 	 *   ...
746 	 *   When bundling control chunks with DATA chunks, an
747 	 *   endpoint MUST place control chunks first in the outbound
748 	 *   SCTP packet.  The transmitter MUST transmit DATA chunks
749 	 *   within a SCTP packet in increasing order of TSN.
750 	 *   ...
751 	 */
752 
753 	list_for_each_entry_safe(chunk, tmp, &q->control_chunk_list, list) {
754 		/* RFC 5061, 5.3
755 		 * F1) This means that until such time as the ASCONF
756 		 * containing the add is acknowledged, the sender MUST
757 		 * NOT use the new IP address as a source for ANY SCTP
758 		 * packet except on carrying an ASCONF Chunk.
759 		 */
760 		if (asoc->src_out_of_asoc_ok &&
761 		    chunk->chunk_hdr->type != SCTP_CID_ASCONF)
762 			continue;
763 
764 		list_del_init(&chunk->list);
765 
766 		/* Pick the right transport to use. */
767 		new_transport = chunk->transport;
768 
769 		if (!new_transport) {
770 			/*
771 			 * If we have a prior transport pointer, see if
772 			 * the destination address of the chunk
773 			 * matches the destination address of the
774 			 * current transport.  If not a match, then
775 			 * try to look up the transport with a given
776 			 * destination address.  We do this because
777 			 * after processing ASCONFs, we may have new
778 			 * transports created.
779 			 */
780 			if (transport &&
781 			    sctp_cmp_addr_exact(&chunk->dest,
782 						&transport->ipaddr))
783 					new_transport = transport;
784 			else
785 				new_transport = sctp_assoc_lookup_paddr(asoc,
786 								&chunk->dest);
787 
788 			/* if we still don't have a new transport, then
789 			 * use the current active path.
790 			 */
791 			if (!new_transport)
792 				new_transport = asoc->peer.active_path;
793 		} else if ((new_transport->state == SCTP_INACTIVE) ||
794 			   (new_transport->state == SCTP_UNCONFIRMED) ||
795 			   (new_transport->state == SCTP_PF)) {
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 {
878 				asoc->stats.octrlchunks++;
879 				/* PR-SCTP C5) If a FORWARD TSN is sent, the
880 				 * sender MUST assure that at least one T3-rtx
881 				 * timer is running.
882 				 */
883 				if (chunk->chunk_hdr->type == SCTP_CID_FWD_TSN)
884 					sctp_transport_reset_timers(transport);
885 			}
886 			break;
887 
888 		default:
889 			/* We built a chunk with an illegal type! */
890 			BUG();
891 		}
892 	}
893 
894 	if (q->asoc->src_out_of_asoc_ok)
895 		goto sctp_flush_out;
896 
897 	/* Is it OK to send data chunks?  */
898 	switch (asoc->state) {
899 	case SCTP_STATE_COOKIE_ECHOED:
900 		/* Only allow bundling when this packet has a COOKIE-ECHO
901 		 * chunk.
902 		 */
903 		if (!packet || !packet->has_cookie_echo)
904 			break;
905 
906 		/* fallthru */
907 	case SCTP_STATE_ESTABLISHED:
908 	case SCTP_STATE_SHUTDOWN_PENDING:
909 	case SCTP_STATE_SHUTDOWN_RECEIVED:
910 		/*
911 		 * RFC 2960 6.1  Transmission of DATA Chunks
912 		 *
913 		 * C) When the time comes for the sender to transmit,
914 		 * before sending new DATA chunks, the sender MUST
915 		 * first transmit any outstanding DATA chunks which
916 		 * are marked for retransmission (limited by the
917 		 * current cwnd).
918 		 */
919 		if (!list_empty(&q->retransmit)) {
920 			if (asoc->peer.retran_path->state == SCTP_UNCONFIRMED)
921 				goto sctp_flush_out;
922 			if (transport == asoc->peer.retran_path)
923 				goto retran;
924 
925 			/* Switch transports & prepare the packet.  */
926 
927 			transport = asoc->peer.retran_path;
928 
929 			if (list_empty(&transport->send_ready)) {
930 				list_add_tail(&transport->send_ready,
931 					      &transport_list);
932 			}
933 
934 			packet = &transport->packet;
935 			sctp_packet_config(packet, vtag,
936 					   asoc->peer.ecn_capable);
937 		retran:
938 			error = sctp_outq_flush_rtx(q, packet,
939 						    rtx_timeout, &start_timer);
940 
941 			if (start_timer)
942 				sctp_transport_reset_timers(transport);
943 
944 			/* This can happen on COOKIE-ECHO resend.  Only
945 			 * one chunk can get bundled with a COOKIE-ECHO.
946 			 */
947 			if (packet->has_cookie_echo)
948 				goto sctp_flush_out;
949 
950 			/* Don't send new data if there is still data
951 			 * waiting to retransmit.
952 			 */
953 			if (!list_empty(&q->retransmit))
954 				goto sctp_flush_out;
955 		}
956 
957 		/* Apply Max.Burst limitation to the current transport in
958 		 * case it will be used for new data.  We are going to
959 		 * rest it before we return, but we want to apply the limit
960 		 * to the currently queued data.
961 		 */
962 		if (transport)
963 			sctp_transport_burst_limited(transport);
964 
965 		/* Finally, transmit new packets.  */
966 		while ((chunk = sctp_outq_dequeue_data(q)) != NULL) {
967 			/* RFC 2960 6.5 Every DATA chunk MUST carry a valid
968 			 * stream identifier.
969 			 */
970 			if (chunk->sinfo.sinfo_stream >=
971 			    asoc->c.sinit_num_ostreams) {
972 
973 				/* Mark as failed send. */
974 				sctp_chunk_fail(chunk, SCTP_ERROR_INV_STRM);
975 				sctp_chunk_free(chunk);
976 				continue;
977 			}
978 
979 			/* Has this chunk expired? */
980 			if (sctp_chunk_abandoned(chunk)) {
981 				sctp_chunk_fail(chunk, 0);
982 				sctp_chunk_free(chunk);
983 				continue;
984 			}
985 
986 			/* If there is a specified transport, use it.
987 			 * Otherwise, we want to use the active path.
988 			 */
989 			new_transport = chunk->transport;
990 			if (!new_transport ||
991 			    ((new_transport->state == SCTP_INACTIVE) ||
992 			     (new_transport->state == SCTP_UNCONFIRMED) ||
993 			     (new_transport->state == SCTP_PF)))
994 				new_transport = asoc->peer.active_path;
995 			if (new_transport->state == SCTP_UNCONFIRMED)
996 				continue;
997 
998 			/* Change packets if necessary.  */
999 			if (new_transport != transport) {
1000 				transport = new_transport;
1001 
1002 				/* Schedule to have this transport's
1003 				 * packet flushed.
1004 				 */
1005 				if (list_empty(&transport->send_ready)) {
1006 					list_add_tail(&transport->send_ready,
1007 						      &transport_list);
1008 				}
1009 
1010 				packet = &transport->packet;
1011 				sctp_packet_config(packet, vtag,
1012 						   asoc->peer.ecn_capable);
1013 				/* We've switched transports, so apply the
1014 				 * Burst limit to the new transport.
1015 				 */
1016 				sctp_transport_burst_limited(transport);
1017 			}
1018 
1019 			SCTP_DEBUG_PRINTK("sctp_outq_flush(%p, %p[%s]), ",
1020 					  q, chunk,
1021 					  chunk && chunk->chunk_hdr ?
1022 					  sctp_cname(SCTP_ST_CHUNK(
1023 						  chunk->chunk_hdr->type))
1024 					  : "Illegal Chunk");
1025 
1026 			SCTP_DEBUG_PRINTK("TX TSN 0x%x skb->head "
1027 					"%p skb->users %d.\n",
1028 					ntohl(chunk->subh.data_hdr->tsn),
1029 					chunk->skb ?chunk->skb->head : NULL,
1030 					chunk->skb ?
1031 					atomic_read(&chunk->skb->users) : -1);
1032 
1033 			/* Add the chunk to the packet.  */
1034 			status = sctp_packet_transmit_chunk(packet, chunk, 0);
1035 
1036 			switch (status) {
1037 			case SCTP_XMIT_PMTU_FULL:
1038 			case SCTP_XMIT_RWND_FULL:
1039 			case SCTP_XMIT_NAGLE_DELAY:
1040 				/* We could not append this chunk, so put
1041 				 * the chunk back on the output queue.
1042 				 */
1043 				SCTP_DEBUG_PRINTK("sctp_outq_flush: could "
1044 					"not transmit TSN: 0x%x, status: %d\n",
1045 					ntohl(chunk->subh.data_hdr->tsn),
1046 					status);
1047 				sctp_outq_head_data(q, chunk);
1048 				goto sctp_flush_out;
1049 				break;
1050 
1051 			case SCTP_XMIT_OK:
1052 				/* The sender is in the SHUTDOWN-PENDING state,
1053 				 * The sender MAY set the I-bit in the DATA
1054 				 * chunk header.
1055 				 */
1056 				if (asoc->state == SCTP_STATE_SHUTDOWN_PENDING)
1057 					chunk->chunk_hdr->flags |= SCTP_DATA_SACK_IMM;
1058 				if (chunk->chunk_hdr->flags & SCTP_DATA_UNORDERED)
1059 					asoc->stats.ouodchunks++;
1060 				else
1061 					asoc->stats.oodchunks++;
1062 
1063 				break;
1064 
1065 			default:
1066 				BUG();
1067 			}
1068 
1069 			/* BUG: We assume that the sctp_packet_transmit()
1070 			 * call below will succeed all the time and add the
1071 			 * chunk to the transmitted list and restart the
1072 			 * timers.
1073 			 * It is possible that the call can fail under OOM
1074 			 * conditions.
1075 			 *
1076 			 * Is this really a problem?  Won't this behave
1077 			 * like a lost TSN?
1078 			 */
1079 			list_add_tail(&chunk->transmitted_list,
1080 				      &transport->transmitted);
1081 
1082 			sctp_transport_reset_timers(transport);
1083 
1084 			q->empty = 0;
1085 
1086 			/* Only let one DATA chunk get bundled with a
1087 			 * COOKIE-ECHO chunk.
1088 			 */
1089 			if (packet->has_cookie_echo)
1090 				goto sctp_flush_out;
1091 		}
1092 		break;
1093 
1094 	default:
1095 		/* Do nothing.  */
1096 		break;
1097 	}
1098 
1099 sctp_flush_out:
1100 
1101 	/* Before returning, examine all the transports touched in
1102 	 * this call.  Right now, we bluntly force clear all the
1103 	 * transports.  Things might change after we implement Nagle.
1104 	 * But such an examination is still required.
1105 	 *
1106 	 * --xguo
1107 	 */
1108 	while ((ltransport = sctp_list_dequeue(&transport_list)) != NULL ) {
1109 		struct sctp_transport *t = list_entry(ltransport,
1110 						      struct sctp_transport,
1111 						      send_ready);
1112 		packet = &t->packet;
1113 		if (!sctp_packet_empty(packet))
1114 			error = sctp_packet_transmit(packet);
1115 
1116 		/* Clear the burst limited state, if any */
1117 		sctp_transport_burst_reset(t);
1118 	}
1119 
1120 	return error;
1121 }
1122 
1123 /* Update unack_data based on the incoming SACK chunk */
1124 static void sctp_sack_update_unack_data(struct sctp_association *assoc,
1125 					struct sctp_sackhdr *sack)
1126 {
1127 	sctp_sack_variable_t *frags;
1128 	__u16 unack_data;
1129 	int i;
1130 
1131 	unack_data = assoc->next_tsn - assoc->ctsn_ack_point - 1;
1132 
1133 	frags = sack->variable;
1134 	for (i = 0; i < ntohs(sack->num_gap_ack_blocks); i++) {
1135 		unack_data -= ((ntohs(frags[i].gab.end) -
1136 				ntohs(frags[i].gab.start) + 1));
1137 	}
1138 
1139 	assoc->unack_data = unack_data;
1140 }
1141 
1142 /* This is where we REALLY process a SACK.
1143  *
1144  * Process the SACK against the outqueue.  Mostly, this just frees
1145  * things off the transmitted queue.
1146  */
1147 int sctp_outq_sack(struct sctp_outq *q, struct sctp_chunk *chunk)
1148 {
1149 	struct sctp_association *asoc = q->asoc;
1150 	struct sctp_sackhdr *sack = chunk->subh.sack_hdr;
1151 	struct sctp_transport *transport;
1152 	struct sctp_chunk *tchunk = NULL;
1153 	struct list_head *lchunk, *transport_list, *temp;
1154 	sctp_sack_variable_t *frags = sack->variable;
1155 	__u32 sack_ctsn, ctsn, tsn;
1156 	__u32 highest_tsn, highest_new_tsn;
1157 	__u32 sack_a_rwnd;
1158 	unsigned int outstanding;
1159 	struct sctp_transport *primary = asoc->peer.primary_path;
1160 	int count_of_newacks = 0;
1161 	int gap_ack_blocks;
1162 	u8 accum_moved = 0;
1163 
1164 	/* Grab the association's destination address list. */
1165 	transport_list = &asoc->peer.transport_addr_list;
1166 
1167 	sack_ctsn = ntohl(sack->cum_tsn_ack);
1168 	gap_ack_blocks = ntohs(sack->num_gap_ack_blocks);
1169 	asoc->stats.gapcnt += gap_ack_blocks;
1170 	/*
1171 	 * SFR-CACC algorithm:
1172 	 * On receipt of a SACK the sender SHOULD execute the
1173 	 * following statements.
1174 	 *
1175 	 * 1) If the cumulative ack in the SACK passes next tsn_at_change
1176 	 * on the current primary, the CHANGEOVER_ACTIVE flag SHOULD be
1177 	 * cleared. The CYCLING_CHANGEOVER flag SHOULD also be cleared for
1178 	 * all destinations.
1179 	 * 2) If the SACK contains gap acks and the flag CHANGEOVER_ACTIVE
1180 	 * is set the receiver of the SACK MUST take the following actions:
1181 	 *
1182 	 * A) Initialize the cacc_saw_newack to 0 for all destination
1183 	 * addresses.
1184 	 *
1185 	 * Only bother if changeover_active is set. Otherwise, this is
1186 	 * totally suboptimal to do on every SACK.
1187 	 */
1188 	if (primary->cacc.changeover_active) {
1189 		u8 clear_cycling = 0;
1190 
1191 		if (TSN_lte(primary->cacc.next_tsn_at_change, sack_ctsn)) {
1192 			primary->cacc.changeover_active = 0;
1193 			clear_cycling = 1;
1194 		}
1195 
1196 		if (clear_cycling || gap_ack_blocks) {
1197 			list_for_each_entry(transport, transport_list,
1198 					transports) {
1199 				if (clear_cycling)
1200 					transport->cacc.cycling_changeover = 0;
1201 				if (gap_ack_blocks)
1202 					transport->cacc.cacc_saw_newack = 0;
1203 			}
1204 		}
1205 	}
1206 
1207 	/* Get the highest TSN in the sack. */
1208 	highest_tsn = sack_ctsn;
1209 	if (gap_ack_blocks)
1210 		highest_tsn += ntohs(frags[gap_ack_blocks - 1].gab.end);
1211 
1212 	if (TSN_lt(asoc->highest_sacked, highest_tsn))
1213 		asoc->highest_sacked = highest_tsn;
1214 
1215 	highest_new_tsn = sack_ctsn;
1216 
1217 	/* Run through the retransmit queue.  Credit bytes received
1218 	 * and free those chunks that we can.
1219 	 */
1220 	sctp_check_transmitted(q, &q->retransmit, NULL, NULL, sack, &highest_new_tsn);
1221 
1222 	/* Run through the transmitted queue.
1223 	 * Credit bytes received and free those chunks which we can.
1224 	 *
1225 	 * This is a MASSIVE candidate for optimization.
1226 	 */
1227 	list_for_each_entry(transport, transport_list, transports) {
1228 		sctp_check_transmitted(q, &transport->transmitted,
1229 				       transport, &chunk->source, sack,
1230 				       &highest_new_tsn);
1231 		/*
1232 		 * SFR-CACC algorithm:
1233 		 * C) Let count_of_newacks be the number of
1234 		 * destinations for which cacc_saw_newack is set.
1235 		 */
1236 		if (transport->cacc.cacc_saw_newack)
1237 			count_of_newacks ++;
1238 	}
1239 
1240 	/* Move the Cumulative TSN Ack Point if appropriate.  */
1241 	if (TSN_lt(asoc->ctsn_ack_point, sack_ctsn)) {
1242 		asoc->ctsn_ack_point = sack_ctsn;
1243 		accum_moved = 1;
1244 	}
1245 
1246 	if (gap_ack_blocks) {
1247 
1248 		if (asoc->fast_recovery && accum_moved)
1249 			highest_new_tsn = highest_tsn;
1250 
1251 		list_for_each_entry(transport, transport_list, transports)
1252 			sctp_mark_missing(q, &transport->transmitted, transport,
1253 					  highest_new_tsn, count_of_newacks);
1254 	}
1255 
1256 	/* Update unack_data field in the assoc. */
1257 	sctp_sack_update_unack_data(asoc, sack);
1258 
1259 	ctsn = asoc->ctsn_ack_point;
1260 
1261 	/* Throw away stuff rotting on the sack queue.  */
1262 	list_for_each_safe(lchunk, temp, &q->sacked) {
1263 		tchunk = list_entry(lchunk, struct sctp_chunk,
1264 				    transmitted_list);
1265 		tsn = ntohl(tchunk->subh.data_hdr->tsn);
1266 		if (TSN_lte(tsn, ctsn)) {
1267 			list_del_init(&tchunk->transmitted_list);
1268 			sctp_chunk_free(tchunk);
1269 		}
1270 	}
1271 
1272 	/* ii) Set rwnd equal to the newly received a_rwnd minus the
1273 	 *     number of bytes still outstanding after processing the
1274 	 *     Cumulative TSN Ack and the Gap Ack Blocks.
1275 	 */
1276 
1277 	sack_a_rwnd = ntohl(sack->a_rwnd);
1278 	outstanding = q->outstanding_bytes;
1279 
1280 	if (outstanding < sack_a_rwnd)
1281 		sack_a_rwnd -= outstanding;
1282 	else
1283 		sack_a_rwnd = 0;
1284 
1285 	asoc->peer.rwnd = sack_a_rwnd;
1286 
1287 	sctp_generate_fwdtsn(q, sack_ctsn);
1288 
1289 	SCTP_DEBUG_PRINTK("%s: sack Cumulative TSN Ack is 0x%x.\n",
1290 			  __func__, sack_ctsn);
1291 	SCTP_DEBUG_PRINTK("%s: Cumulative TSN Ack of association, "
1292 			  "%p is 0x%x. Adv peer ack point: 0x%x\n",
1293 			  __func__, asoc, ctsn, asoc->adv_peer_ack_point);
1294 
1295 	/* See if all chunks are acked.
1296 	 * Make sure the empty queue handler will get run later.
1297 	 */
1298 	q->empty = (list_empty(&q->out_chunk_list) &&
1299 		    list_empty(&q->retransmit));
1300 	if (!q->empty)
1301 		goto finish;
1302 
1303 	list_for_each_entry(transport, transport_list, transports) {
1304 		q->empty = q->empty && list_empty(&transport->transmitted);
1305 		if (!q->empty)
1306 			goto finish;
1307 	}
1308 
1309 	SCTP_DEBUG_PRINTK("sack queue is empty.\n");
1310 finish:
1311 	return q->empty;
1312 }
1313 
1314 /* Is the outqueue empty?  */
1315 int sctp_outq_is_empty(const struct sctp_outq *q)
1316 {
1317 	return q->empty;
1318 }
1319 
1320 /********************************************************************
1321  * 2nd Level Abstractions
1322  ********************************************************************/
1323 
1324 /* Go through a transport's transmitted list or the association's retransmit
1325  * list and move chunks that are acked by the Cumulative TSN Ack to q->sacked.
1326  * The retransmit list will not have an associated transport.
1327  *
1328  * I added coherent debug information output.	--xguo
1329  *
1330  * Instead of printing 'sacked' or 'kept' for each TSN on the
1331  * transmitted_queue, we print a range: SACKED: TSN1-TSN2, TSN3, TSN4-TSN5.
1332  * KEPT TSN6-TSN7, etc.
1333  */
1334 static void sctp_check_transmitted(struct sctp_outq *q,
1335 				   struct list_head *transmitted_queue,
1336 				   struct sctp_transport *transport,
1337 				   union sctp_addr *saddr,
1338 				   struct sctp_sackhdr *sack,
1339 				   __u32 *highest_new_tsn_in_sack)
1340 {
1341 	struct list_head *lchunk;
1342 	struct sctp_chunk *tchunk;
1343 	struct list_head tlist;
1344 	__u32 tsn;
1345 	__u32 sack_ctsn;
1346 	__u32 rtt;
1347 	__u8 restart_timer = 0;
1348 	int bytes_acked = 0;
1349 	int migrate_bytes = 0;
1350 
1351 	/* These state variables are for coherent debug output. --xguo */
1352 
1353 #if SCTP_DEBUG
1354 	__u32 dbg_ack_tsn = 0;	/* An ACKed TSN range starts here... */
1355 	__u32 dbg_last_ack_tsn = 0;  /* ...and finishes here.	     */
1356 	__u32 dbg_kept_tsn = 0;	/* An un-ACKed range starts here...  */
1357 	__u32 dbg_last_kept_tsn = 0; /* ...and finishes here.	     */
1358 
1359 	/* 0 : The last TSN was ACKed.
1360 	 * 1 : The last TSN was NOT ACKed (i.e. KEPT).
1361 	 * -1: We need to initialize.
1362 	 */
1363 	int dbg_prt_state = -1;
1364 #endif /* SCTP_DEBUG */
1365 
1366 	sack_ctsn = ntohl(sack->cum_tsn_ack);
1367 
1368 	INIT_LIST_HEAD(&tlist);
1369 
1370 	/* The while loop will skip empty transmitted queues. */
1371 	while (NULL != (lchunk = sctp_list_dequeue(transmitted_queue))) {
1372 		tchunk = list_entry(lchunk, struct sctp_chunk,
1373 				    transmitted_list);
1374 
1375 		if (sctp_chunk_abandoned(tchunk)) {
1376 			/* Move the chunk to abandoned list. */
1377 			sctp_insert_list(&q->abandoned, lchunk);
1378 
1379 			/* If this chunk has not been acked, stop
1380 			 * considering it as 'outstanding'.
1381 			 */
1382 			if (!tchunk->tsn_gap_acked) {
1383 				if (tchunk->transport)
1384 					tchunk->transport->flight_size -=
1385 							sctp_data_size(tchunk);
1386 				q->outstanding_bytes -= sctp_data_size(tchunk);
1387 			}
1388 			continue;
1389 		}
1390 
1391 		tsn = ntohl(tchunk->subh.data_hdr->tsn);
1392 		if (sctp_acked(sack, tsn)) {
1393 			/* If this queue is the retransmit queue, the
1394 			 * retransmit timer has already reclaimed
1395 			 * the outstanding bytes for this chunk, so only
1396 			 * count bytes associated with a transport.
1397 			 */
1398 			if (transport) {
1399 				/* If this chunk is being used for RTT
1400 				 * measurement, calculate the RTT and update
1401 				 * the RTO using this value.
1402 				 *
1403 				 * 6.3.1 C5) Karn's algorithm: RTT measurements
1404 				 * MUST NOT be made using packets that were
1405 				 * retransmitted (and thus for which it is
1406 				 * ambiguous whether the reply was for the
1407 				 * first instance of the packet or a later
1408 				 * instance).
1409 				 */
1410 				if (!tchunk->tsn_gap_acked &&
1411 				    tchunk->rtt_in_progress) {
1412 					tchunk->rtt_in_progress = 0;
1413 					rtt = jiffies - tchunk->sent_at;
1414 					sctp_transport_update_rto(transport,
1415 								  rtt);
1416 				}
1417 			}
1418 
1419 			/* If the chunk hasn't been marked as ACKED,
1420 			 * mark it and account bytes_acked if the
1421 			 * chunk had a valid transport (it will not
1422 			 * have a transport if ASCONF had deleted it
1423 			 * while DATA was outstanding).
1424 			 */
1425 			if (!tchunk->tsn_gap_acked) {
1426 				tchunk->tsn_gap_acked = 1;
1427 				*highest_new_tsn_in_sack = tsn;
1428 				bytes_acked += sctp_data_size(tchunk);
1429 				if (!tchunk->transport)
1430 					migrate_bytes += sctp_data_size(tchunk);
1431 			}
1432 
1433 			if (TSN_lte(tsn, sack_ctsn)) {
1434 				/* RFC 2960  6.3.2 Retransmission Timer Rules
1435 				 *
1436 				 * R3) Whenever a SACK is received
1437 				 * that acknowledges the DATA chunk
1438 				 * with the earliest outstanding TSN
1439 				 * for that address, restart T3-rtx
1440 				 * timer for that address with its
1441 				 * current RTO.
1442 				 */
1443 				restart_timer = 1;
1444 
1445 				if (!tchunk->tsn_gap_acked) {
1446 					/*
1447 					 * SFR-CACC algorithm:
1448 					 * 2) If the SACK contains gap acks
1449 					 * and the flag CHANGEOVER_ACTIVE is
1450 					 * set the receiver of the SACK MUST
1451 					 * take the following action:
1452 					 *
1453 					 * B) For each TSN t being acked that
1454 					 * has not been acked in any SACK so
1455 					 * far, set cacc_saw_newack to 1 for
1456 					 * the destination that the TSN was
1457 					 * sent to.
1458 					 */
1459 					if (transport &&
1460 					    sack->num_gap_ack_blocks &&
1461 					    q->asoc->peer.primary_path->cacc.
1462 					    changeover_active)
1463 						transport->cacc.cacc_saw_newack
1464 							= 1;
1465 				}
1466 
1467 				list_add_tail(&tchunk->transmitted_list,
1468 					      &q->sacked);
1469 			} else {
1470 				/* RFC2960 7.2.4, sctpimpguide-05 2.8.2
1471 				 * M2) Each time a SACK arrives reporting
1472 				 * 'Stray DATA chunk(s)' record the highest TSN
1473 				 * reported as newly acknowledged, call this
1474 				 * value 'HighestTSNinSack'. A newly
1475 				 * acknowledged DATA chunk is one not
1476 				 * previously acknowledged in a SACK.
1477 				 *
1478 				 * When the SCTP sender of data receives a SACK
1479 				 * chunk that acknowledges, for the first time,
1480 				 * the receipt of a DATA chunk, all the still
1481 				 * unacknowledged DATA chunks whose TSN is
1482 				 * older than that newly acknowledged DATA
1483 				 * chunk, are qualified as 'Stray DATA chunks'.
1484 				 */
1485 				list_add_tail(lchunk, &tlist);
1486 			}
1487 
1488 #if SCTP_DEBUG
1489 			switch (dbg_prt_state) {
1490 			case 0:	/* last TSN was ACKed */
1491 				if (dbg_last_ack_tsn + 1 == tsn) {
1492 					/* This TSN belongs to the
1493 					 * current ACK range.
1494 					 */
1495 					break;
1496 				}
1497 
1498 				if (dbg_last_ack_tsn != dbg_ack_tsn) {
1499 					/* Display the end of the
1500 					 * current range.
1501 					 */
1502 					SCTP_DEBUG_PRINTK_CONT("-%08x",
1503 							       dbg_last_ack_tsn);
1504 				}
1505 
1506 				/* Start a new range.  */
1507 				SCTP_DEBUG_PRINTK_CONT(",%08x", tsn);
1508 				dbg_ack_tsn = tsn;
1509 				break;
1510 
1511 			case 1:	/* The last TSN was NOT ACKed. */
1512 				if (dbg_last_kept_tsn != dbg_kept_tsn) {
1513 					/* Display the end of current range. */
1514 					SCTP_DEBUG_PRINTK_CONT("-%08x",
1515 							       dbg_last_kept_tsn);
1516 				}
1517 
1518 				SCTP_DEBUG_PRINTK_CONT("\n");
1519 
1520 				/* FALL THROUGH... */
1521 			default:
1522 				/* This is the first-ever TSN we examined.  */
1523 				/* Start a new range of ACK-ed TSNs.  */
1524 				SCTP_DEBUG_PRINTK("ACKed: %08x", tsn);
1525 				dbg_prt_state = 0;
1526 				dbg_ack_tsn = tsn;
1527 			}
1528 
1529 			dbg_last_ack_tsn = tsn;
1530 #endif /* SCTP_DEBUG */
1531 
1532 		} else {
1533 			if (tchunk->tsn_gap_acked) {
1534 				SCTP_DEBUG_PRINTK("%s: Receiver reneged on "
1535 						  "data TSN: 0x%x\n",
1536 						  __func__,
1537 						  tsn);
1538 				tchunk->tsn_gap_acked = 0;
1539 
1540 				if (tchunk->transport)
1541 					bytes_acked -= sctp_data_size(tchunk);
1542 
1543 				/* RFC 2960 6.3.2 Retransmission Timer Rules
1544 				 *
1545 				 * R4) Whenever a SACK is received missing a
1546 				 * TSN that was previously acknowledged via a
1547 				 * Gap Ack Block, start T3-rtx for the
1548 				 * destination address to which the DATA
1549 				 * chunk was originally
1550 				 * transmitted if it is not already running.
1551 				 */
1552 				restart_timer = 1;
1553 			}
1554 
1555 			list_add_tail(lchunk, &tlist);
1556 
1557 #if SCTP_DEBUG
1558 			/* See the above comments on ACK-ed TSNs. */
1559 			switch (dbg_prt_state) {
1560 			case 1:
1561 				if (dbg_last_kept_tsn + 1 == tsn)
1562 					break;
1563 
1564 				if (dbg_last_kept_tsn != dbg_kept_tsn)
1565 					SCTP_DEBUG_PRINTK_CONT("-%08x",
1566 							       dbg_last_kept_tsn);
1567 
1568 				SCTP_DEBUG_PRINTK_CONT(",%08x", tsn);
1569 				dbg_kept_tsn = tsn;
1570 				break;
1571 
1572 			case 0:
1573 				if (dbg_last_ack_tsn != dbg_ack_tsn)
1574 					SCTP_DEBUG_PRINTK_CONT("-%08x",
1575 							       dbg_last_ack_tsn);
1576 				SCTP_DEBUG_PRINTK_CONT("\n");
1577 
1578 				/* FALL THROUGH... */
1579 			default:
1580 				SCTP_DEBUG_PRINTK("KEPT: %08x",tsn);
1581 				dbg_prt_state = 1;
1582 				dbg_kept_tsn = tsn;
1583 			}
1584 
1585 			dbg_last_kept_tsn = tsn;
1586 #endif /* SCTP_DEBUG */
1587 		}
1588 	}
1589 
1590 #if SCTP_DEBUG
1591 	/* Finish off the last range, displaying its ending TSN.  */
1592 	switch (dbg_prt_state) {
1593 	case 0:
1594 		if (dbg_last_ack_tsn != dbg_ack_tsn) {
1595 			SCTP_DEBUG_PRINTK_CONT("-%08x\n", dbg_last_ack_tsn);
1596 		} else {
1597 			SCTP_DEBUG_PRINTK_CONT("\n");
1598 		}
1599 	break;
1600 
1601 	case 1:
1602 		if (dbg_last_kept_tsn != dbg_kept_tsn) {
1603 			SCTP_DEBUG_PRINTK_CONT("-%08x\n", dbg_last_kept_tsn);
1604 		} else {
1605 			SCTP_DEBUG_PRINTK_CONT("\n");
1606 		}
1607 	}
1608 #endif /* SCTP_DEBUG */
1609 	if (transport) {
1610 		if (bytes_acked) {
1611 			struct sctp_association *asoc = transport->asoc;
1612 
1613 			/* We may have counted DATA that was migrated
1614 			 * to this transport due to DEL-IP operation.
1615 			 * Subtract those bytes, since the were never
1616 			 * send on this transport and shouldn't be
1617 			 * credited to this transport.
1618 			 */
1619 			bytes_acked -= migrate_bytes;
1620 
1621 			/* 8.2. When an outstanding TSN is acknowledged,
1622 			 * the endpoint shall clear the error counter of
1623 			 * the destination transport address to which the
1624 			 * DATA chunk was last sent.
1625 			 * The association's overall error counter is
1626 			 * also cleared.
1627 			 */
1628 			transport->error_count = 0;
1629 			transport->asoc->overall_error_count = 0;
1630 
1631 			/*
1632 			 * While in SHUTDOWN PENDING, we may have started
1633 			 * the T5 shutdown guard timer after reaching the
1634 			 * retransmission limit. Stop that timer as soon
1635 			 * as the receiver acknowledged any data.
1636 			 */
1637 			if (asoc->state == SCTP_STATE_SHUTDOWN_PENDING &&
1638 			    del_timer(&asoc->timers
1639 				[SCTP_EVENT_TIMEOUT_T5_SHUTDOWN_GUARD]))
1640 					sctp_association_put(asoc);
1641 
1642 			/* Mark the destination transport address as
1643 			 * active if it is not so marked.
1644 			 */
1645 			if ((transport->state == SCTP_INACTIVE ||
1646 			     transport->state == SCTP_UNCONFIRMED) &&
1647 			    sctp_cmp_addr_exact(&transport->ipaddr, saddr)) {
1648 				sctp_assoc_control_transport(
1649 					transport->asoc,
1650 					transport,
1651 					SCTP_TRANSPORT_UP,
1652 					SCTP_RECEIVED_SACK);
1653 			}
1654 
1655 			sctp_transport_raise_cwnd(transport, sack_ctsn,
1656 						  bytes_acked);
1657 
1658 			transport->flight_size -= bytes_acked;
1659 			if (transport->flight_size == 0)
1660 				transport->partial_bytes_acked = 0;
1661 			q->outstanding_bytes -= bytes_acked + migrate_bytes;
1662 		} else {
1663 			/* RFC 2960 6.1, sctpimpguide-06 2.15.2
1664 			 * When a sender is doing zero window probing, it
1665 			 * should not timeout the association if it continues
1666 			 * to receive new packets from the receiver. The
1667 			 * reason is that the receiver MAY keep its window
1668 			 * closed for an indefinite time.
1669 			 * A sender is doing zero window probing when the
1670 			 * receiver's advertised window is zero, and there is
1671 			 * only one data chunk in flight to the receiver.
1672 			 *
1673 			 * Allow the association to timeout while in SHUTDOWN
1674 			 * PENDING or SHUTDOWN RECEIVED in case the receiver
1675 			 * stays in zero window mode forever.
1676 			 */
1677 			if (!q->asoc->peer.rwnd &&
1678 			    !list_empty(&tlist) &&
1679 			    (sack_ctsn+2 == q->asoc->next_tsn) &&
1680 			    q->asoc->state < SCTP_STATE_SHUTDOWN_PENDING) {
1681 				SCTP_DEBUG_PRINTK("%s: SACK received for zero "
1682 						  "window probe: %u\n",
1683 						  __func__, sack_ctsn);
1684 				q->asoc->overall_error_count = 0;
1685 				transport->error_count = 0;
1686 			}
1687 		}
1688 
1689 		/* RFC 2960 6.3.2 Retransmission Timer Rules
1690 		 *
1691 		 * R2) Whenever all outstanding data sent to an address have
1692 		 * been acknowledged, turn off the T3-rtx timer of that
1693 		 * address.
1694 		 */
1695 		if (!transport->flight_size) {
1696 			if (del_timer(&transport->T3_rtx_timer))
1697 				sctp_transport_put(transport);
1698 		} else if (restart_timer) {
1699 			if (!mod_timer(&transport->T3_rtx_timer,
1700 				       jiffies + transport->rto))
1701 				sctp_transport_hold(transport);
1702 		}
1703 	}
1704 
1705 	list_splice(&tlist, transmitted_queue);
1706 }
1707 
1708 /* Mark chunks as missing and consequently may get retransmitted. */
1709 static void sctp_mark_missing(struct sctp_outq *q,
1710 			      struct list_head *transmitted_queue,
1711 			      struct sctp_transport *transport,
1712 			      __u32 highest_new_tsn_in_sack,
1713 			      int count_of_newacks)
1714 {
1715 	struct sctp_chunk *chunk;
1716 	__u32 tsn;
1717 	char do_fast_retransmit = 0;
1718 	struct sctp_association *asoc = q->asoc;
1719 	struct sctp_transport *primary = asoc->peer.primary_path;
1720 
1721 	list_for_each_entry(chunk, transmitted_queue, transmitted_list) {
1722 
1723 		tsn = ntohl(chunk->subh.data_hdr->tsn);
1724 
1725 		/* RFC 2960 7.2.4, sctpimpguide-05 2.8.2 M3) Examine all
1726 		 * 'Unacknowledged TSN's', if the TSN number of an
1727 		 * 'Unacknowledged TSN' is smaller than the 'HighestTSNinSack'
1728 		 * value, increment the 'TSN.Missing.Report' count on that
1729 		 * chunk if it has NOT been fast retransmitted or marked for
1730 		 * fast retransmit already.
1731 		 */
1732 		if (chunk->fast_retransmit == SCTP_CAN_FRTX &&
1733 		    !chunk->tsn_gap_acked &&
1734 		    TSN_lt(tsn, highest_new_tsn_in_sack)) {
1735 
1736 			/* SFR-CACC may require us to skip marking
1737 			 * this chunk as missing.
1738 			 */
1739 			if (!transport || !sctp_cacc_skip(primary,
1740 						chunk->transport,
1741 						count_of_newacks, tsn)) {
1742 				chunk->tsn_missing_report++;
1743 
1744 				SCTP_DEBUG_PRINTK(
1745 					"%s: TSN 0x%x missing counter: %d\n",
1746 					__func__, tsn,
1747 					chunk->tsn_missing_report);
1748 			}
1749 		}
1750 		/*
1751 		 * M4) If any DATA chunk is found to have a
1752 		 * 'TSN.Missing.Report'
1753 		 * value larger than or equal to 3, mark that chunk for
1754 		 * retransmission and start the fast retransmit procedure.
1755 		 */
1756 
1757 		if (chunk->tsn_missing_report >= 3) {
1758 			chunk->fast_retransmit = SCTP_NEED_FRTX;
1759 			do_fast_retransmit = 1;
1760 		}
1761 	}
1762 
1763 	if (transport) {
1764 		if (do_fast_retransmit)
1765 			sctp_retransmit(q, transport, SCTP_RTXR_FAST_RTX);
1766 
1767 		SCTP_DEBUG_PRINTK("%s: transport: %p, cwnd: %d, "
1768 				  "ssthresh: %d, flight_size: %d, pba: %d\n",
1769 				  __func__, transport, transport->cwnd,
1770 				  transport->ssthresh, transport->flight_size,
1771 				  transport->partial_bytes_acked);
1772 	}
1773 }
1774 
1775 /* Is the given TSN acked by this packet?  */
1776 static int sctp_acked(struct sctp_sackhdr *sack, __u32 tsn)
1777 {
1778 	int i;
1779 	sctp_sack_variable_t *frags;
1780 	__u16 gap;
1781 	__u32 ctsn = ntohl(sack->cum_tsn_ack);
1782 
1783 	if (TSN_lte(tsn, ctsn))
1784 		goto pass;
1785 
1786 	/* 3.3.4 Selective Acknowledgement (SACK) (3):
1787 	 *
1788 	 * Gap Ack Blocks:
1789 	 *  These fields contain the Gap Ack Blocks. They are repeated
1790 	 *  for each Gap Ack Block up to the number of Gap Ack Blocks
1791 	 *  defined in the Number of Gap Ack Blocks field. All DATA
1792 	 *  chunks with TSNs greater than or equal to (Cumulative TSN
1793 	 *  Ack + Gap Ack Block Start) and less than or equal to
1794 	 *  (Cumulative TSN Ack + Gap Ack Block End) of each Gap Ack
1795 	 *  Block are assumed to have been received correctly.
1796 	 */
1797 
1798 	frags = sack->variable;
1799 	gap = tsn - ctsn;
1800 	for (i = 0; i < ntohs(sack->num_gap_ack_blocks); ++i) {
1801 		if (TSN_lte(ntohs(frags[i].gab.start), gap) &&
1802 		    TSN_lte(gap, ntohs(frags[i].gab.end)))
1803 			goto pass;
1804 	}
1805 
1806 	return 0;
1807 pass:
1808 	return 1;
1809 }
1810 
1811 static inline int sctp_get_skip_pos(struct sctp_fwdtsn_skip *skiplist,
1812 				    int nskips, __be16 stream)
1813 {
1814 	int i;
1815 
1816 	for (i = 0; i < nskips; i++) {
1817 		if (skiplist[i].stream == stream)
1818 			return i;
1819 	}
1820 	return i;
1821 }
1822 
1823 /* Create and add a fwdtsn chunk to the outq's control queue if needed. */
1824 static void sctp_generate_fwdtsn(struct sctp_outq *q, __u32 ctsn)
1825 {
1826 	struct sctp_association *asoc = q->asoc;
1827 	struct sctp_chunk *ftsn_chunk = NULL;
1828 	struct sctp_fwdtsn_skip ftsn_skip_arr[10];
1829 	int nskips = 0;
1830 	int skip_pos = 0;
1831 	__u32 tsn;
1832 	struct sctp_chunk *chunk;
1833 	struct list_head *lchunk, *temp;
1834 
1835 	if (!asoc->peer.prsctp_capable)
1836 		return;
1837 
1838 	/* PR-SCTP C1) Let SackCumAck be the Cumulative TSN ACK carried in the
1839 	 * received SACK.
1840 	 *
1841 	 * If (Advanced.Peer.Ack.Point < SackCumAck), then update
1842 	 * Advanced.Peer.Ack.Point to be equal to SackCumAck.
1843 	 */
1844 	if (TSN_lt(asoc->adv_peer_ack_point, ctsn))
1845 		asoc->adv_peer_ack_point = ctsn;
1846 
1847 	/* PR-SCTP C2) Try to further advance the "Advanced.Peer.Ack.Point"
1848 	 * locally, that is, to move "Advanced.Peer.Ack.Point" up as long as
1849 	 * the chunk next in the out-queue space is marked as "abandoned" as
1850 	 * shown in the following example:
1851 	 *
1852 	 * Assuming that a SACK arrived with the Cumulative TSN ACK 102
1853 	 * and the Advanced.Peer.Ack.Point is updated to this value:
1854 	 *
1855 	 *   out-queue at the end of  ==>   out-queue after Adv.Ack.Point
1856 	 *   normal SACK processing           local advancement
1857 	 *                ...                           ...
1858 	 *   Adv.Ack.Pt-> 102 acked                     102 acked
1859 	 *                103 abandoned                 103 abandoned
1860 	 *                104 abandoned     Adv.Ack.P-> 104 abandoned
1861 	 *                105                           105
1862 	 *                106 acked                     106 acked
1863 	 *                ...                           ...
1864 	 *
1865 	 * In this example, the data sender successfully advanced the
1866 	 * "Advanced.Peer.Ack.Point" from 102 to 104 locally.
1867 	 */
1868 	list_for_each_safe(lchunk, temp, &q->abandoned) {
1869 		chunk = list_entry(lchunk, struct sctp_chunk,
1870 					transmitted_list);
1871 		tsn = ntohl(chunk->subh.data_hdr->tsn);
1872 
1873 		/* Remove any chunks in the abandoned queue that are acked by
1874 		 * the ctsn.
1875 		 */
1876 		if (TSN_lte(tsn, ctsn)) {
1877 			list_del_init(lchunk);
1878 			sctp_chunk_free(chunk);
1879 		} else {
1880 			if (TSN_lte(tsn, asoc->adv_peer_ack_point+1)) {
1881 				asoc->adv_peer_ack_point = tsn;
1882 				if (chunk->chunk_hdr->flags &
1883 					 SCTP_DATA_UNORDERED)
1884 					continue;
1885 				skip_pos = sctp_get_skip_pos(&ftsn_skip_arr[0],
1886 						nskips,
1887 						chunk->subh.data_hdr->stream);
1888 				ftsn_skip_arr[skip_pos].stream =
1889 					chunk->subh.data_hdr->stream;
1890 				ftsn_skip_arr[skip_pos].ssn =
1891 					 chunk->subh.data_hdr->ssn;
1892 				if (skip_pos == nskips)
1893 					nskips++;
1894 				if (nskips == 10)
1895 					break;
1896 			} else
1897 				break;
1898 		}
1899 	}
1900 
1901 	/* PR-SCTP C3) If, after step C1 and C2, the "Advanced.Peer.Ack.Point"
1902 	 * is greater than the Cumulative TSN ACK carried in the received
1903 	 * SACK, the data sender MUST send the data receiver a FORWARD TSN
1904 	 * chunk containing the latest value of the
1905 	 * "Advanced.Peer.Ack.Point".
1906 	 *
1907 	 * C4) For each "abandoned" TSN the sender of the FORWARD TSN SHOULD
1908 	 * list each stream and sequence number in the forwarded TSN. This
1909 	 * information will enable the receiver to easily find any
1910 	 * stranded TSN's waiting on stream reorder queues. Each stream
1911 	 * SHOULD only be reported once; this means that if multiple
1912 	 * abandoned messages occur in the same stream then only the
1913 	 * highest abandoned stream sequence number is reported. If the
1914 	 * total size of the FORWARD TSN does NOT fit in a single MTU then
1915 	 * the sender of the FORWARD TSN SHOULD lower the
1916 	 * Advanced.Peer.Ack.Point to the last TSN that will fit in a
1917 	 * single MTU.
1918 	 */
1919 	if (asoc->adv_peer_ack_point > ctsn)
1920 		ftsn_chunk = sctp_make_fwdtsn(asoc, asoc->adv_peer_ack_point,
1921 					      nskips, &ftsn_skip_arr[0]);
1922 
1923 	if (ftsn_chunk) {
1924 		list_add_tail(&ftsn_chunk->list, &q->control_chunk_list);
1925 		SCTP_INC_STATS(sock_net(asoc->base.sk), SCTP_MIB_OUTCTRLCHUNKS);
1926 	}
1927 }
1928