1	// SPDX-License-Identifier: GPL-2.0-or-later
2	/* SCTP kernel implementation
3	* (C) Copyright IBM Corp. 2001, 2004
4	* Copyright (c) 1999-2000 Cisco, Inc.
5	* Copyright (c) 1999-2001 Motorola, Inc.
6	* Copyright (c) 2001-2003 Intel Corp.
7	*
8	* This file is part of the SCTP kernel implementation
9	*
10	* These functions implement the sctp_outq class. The outqueue handles
11	* bundling and queueing of outgoing SCTP chunks.
12	*
13	* Please send any bug reports or fixes you make to the
14	* email address(es):
15	* lksctp developers <linux-sctp@vger.kernel.org>
16	*
17	* Written or modified by:
18	* La Monte H.P. Yarroll <piggy@acm.org>
19	* Karl Knutson <karl@athena.chicago.il.us>
20	* Perry Melange <pmelange@null.cc.uic.edu>
21	* Xingang Guo <xingang.guo@intel.com>
22	* Hui Huang <hui.huang@nokia.com>
23	* Sridhar Samudrala <sri@us.ibm.com>
24	* Jon Grimm <jgrimm@us.ibm.com>
25	*/
26
27	#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
28
29	#include <linux/types.h>
30	#include <linux/list.h> /* For struct list_head */
31	#include <linux/socket.h>
32	#include <linux/ip.h>
33	#include <linux/slab.h>
34	#include <net/sock.h> /* For skb_set_owner_w */
35
36	#include <net/sctp/sctp.h>
37	#include <net/sctp/sm.h>
38	#include <net/sctp/stream_sched.h>
39	#include <trace/events/sctp.h>
40
41	/* Declare internal functions here. */
42	static int sctp_acked(struct sctp_sackhdr *sack, __u32 tsn);
43	static void sctp_check_transmitted(struct sctp_outq *q,
44	struct list_head *transmitted_queue,
45	struct sctp_transport *transport,
46	union sctp_addr *saddr,
47	struct sctp_sackhdr *sack,
48	__u32 *highest_new_tsn);
49
50	static void sctp_mark_missing(struct sctp_outq *q,
51	struct list_head *transmitted_queue,
52	struct sctp_transport *transport,
53	__u32 highest_new_tsn,
54	int count_of_newacks);
55
56	static void sctp_outq_flush(struct sctp_outq *q, int rtx_timeout, gfp_t gfp);
57
58	/* Add data to the front of the queue. */
59	static inline void sctp_outq_head_data(struct sctp_outq *q,
60	struct sctp_chunk *ch)
61	{
62	struct sctp_stream_out_ext *oute;
63	__u16 stream;
64
65	list_add(new: &ch->list, head: &q->out_chunk_list);
66	q->out_qlen += ch->skb->len;
67
68	stream = sctp_chunk_stream_no(ch);
69	oute = SCTP_SO(&q->asoc->stream, stream)->ext;
70	list_add(new: &ch->stream_list, head: &oute->outq);
71	}
72
73	/* Take data from the front of the queue. */
74	static inline struct sctp_chunk *sctp_outq_dequeue_data(struct sctp_outq *q)
75	{
76	return q->sched->dequeue(q);
77	}
78
79	/* Add data chunk to the end of the queue. */
80	static inline void sctp_outq_tail_data(struct sctp_outq *q,
81	struct sctp_chunk *ch)
82	{
83	struct sctp_stream_out_ext *oute;
84	__u16 stream;
85
86	list_add_tail(new: &ch->list, head: &q->out_chunk_list);
87	q->out_qlen += ch->skb->len;
88
89	stream = sctp_chunk_stream_no(ch);
90	oute = SCTP_SO(&q->asoc->stream, stream)->ext;
91	list_add_tail(new: &ch->stream_list, head: &oute->outq);
92	}
93
94	/*
95	* SFR-CACC algorithm:
96	* D) If count_of_newacks is greater than or equal to 2
97	* and t was not sent to the current primary then the
98	* sender MUST NOT increment missing report count for t.
99	*/
100	static inline int sctp_cacc_skip_3_1_d(struct sctp_transport *primary,
101	struct sctp_transport *transport,
102	int count_of_newacks)
103	{
104	if (count_of_newacks >= 2 && transport != primary)
105	return 1;
106	return 0;
107	}
108
109	/*
110	* SFR-CACC algorithm:
111	* F) If count_of_newacks is less than 2, let d be the
112	* destination to which t was sent. If cacc_saw_newack
113	* is 0 for destination d, then the sender MUST NOT
114	* increment missing report count for t.
115	*/
116	static inline int sctp_cacc_skip_3_1_f(struct sctp_transport *transport,
117	int count_of_newacks)
118	{
119	if (count_of_newacks < 2 &&
120	(transport && !transport->cacc.cacc_saw_newack))
121	return 1;
122	return 0;
123	}
124
125	/*
126	* SFR-CACC algorithm:
127	* 3.1) If CYCLING_CHANGEOVER is 0, the sender SHOULD
128	* execute steps C, D, F.
129	*
130	* C has been implemented in sctp_outq_sack
131	*/
132	static inline int sctp_cacc_skip_3_1(struct sctp_transport *primary,
133	struct sctp_transport *transport,
134	int count_of_newacks)
135	{
136	if (!primary->cacc.cycling_changeover) {
137	if (sctp_cacc_skip_3_1_d(primary, transport, count_of_newacks))
138	return 1;
139	if (sctp_cacc_skip_3_1_f(transport, count_of_newacks))
140	return 1;
141	return 0;
142	}
143	return 0;
144	}
145
146	/*
147	* SFR-CACC algorithm:
148	* 3.2) Else if CYCLING_CHANGEOVER is 1, and t is less
149	* than next_tsn_at_change of the current primary, then
150	* the sender MUST NOT increment missing report count
151	* for t.
152	*/
153	static inline int sctp_cacc_skip_3_2(struct sctp_transport *primary, __u32 tsn)
154	{
155	if (primary->cacc.cycling_changeover &&
156	TSN_lt(tsn, primary->cacc.next_tsn_at_change))
157	return 1;
158	return 0;
159	}
160
161	/*
162	* SFR-CACC algorithm:
163	* 3) If the missing report count for TSN t is to be
164	* incremented according to [RFC2960] and
165	* [SCTP_STEWART-2002], and CHANGEOVER_ACTIVE is set,
166	* then the sender MUST further execute steps 3.1 and
167	* 3.2 to determine if the missing report count for
168	* TSN t SHOULD NOT be incremented.
169	*
170	* 3.3) If 3.1 and 3.2 do not dictate that the missing
171	* report count for t should not be incremented, then
172	* the sender SHOULD increment missing report count for
173	* t (according to [RFC2960] and [SCTP_STEWART_2002]).
174	*/
175	static inline int sctp_cacc_skip(struct sctp_transport *primary,
176	struct sctp_transport *transport,
177	int count_of_newacks,
178	__u32 tsn)
179	{
180	if (primary->cacc.changeover_active &&
181	(sctp_cacc_skip_3_1(primary, transport, count_of_newacks) ||
182	sctp_cacc_skip_3_2(primary, tsn)))
183	return 1;
184	return 0;
185	}
186
187	/* Initialize an existing sctp_outq. This does the boring stuff.
188	* You still need to define handlers if you really want to DO
189	* something with this structure...
190	*/
191	void sctp_outq_init(struct sctp_association *asoc, struct sctp_outq *q)
192	{
193	memset(q, 0, sizeof(struct sctp_outq));
194
195	q->asoc = asoc;
196	INIT_LIST_HEAD(list: &q->out_chunk_list);
197	INIT_LIST_HEAD(list: &q->control_chunk_list);
198	INIT_LIST_HEAD(list: &q->retransmit);
199	INIT_LIST_HEAD(list: &q->sacked);
200	INIT_LIST_HEAD(list: &q->abandoned);
201	sctp_sched_set_sched(asoc, sched: sctp_sk(sk: asoc->base.sk)->default_ss);
202	}
203
204	/* Free the outqueue structure and any related pending chunks.
205	*/
206	static void __sctp_outq_teardown(struct sctp_outq *q)
207	{
208	struct sctp_transport *transport;
209	struct list_head *lchunk, *temp;
210	struct sctp_chunk *chunk, *tmp;
211
212	/* Throw away unacknowledged chunks. */
213	list_for_each_entry(transport, &q->asoc->peer.transport_addr_list,
214	transports) {
215	while ((lchunk = sctp_list_dequeue(list: &transport->transmitted)) != NULL) {
216	chunk = list_entry(lchunk, struct sctp_chunk,
217	transmitted_list);
218	/* Mark as part of a failed message. */
219	sctp_chunk_fail(chunk, error: q->error);
220	sctp_chunk_free(chunk);
221	}
222	}
223
224	/* Throw away chunks that have been gap ACKed. */
225	list_for_each_safe(lchunk, temp, &q->sacked) {
226	list_del_init(entry: lchunk);
227	chunk = list_entry(lchunk, struct sctp_chunk,
228	transmitted_list);
229	sctp_chunk_fail(chunk, error: q->error);
230	sctp_chunk_free(chunk);
231	}
232
233	/* Throw away any chunks in the retransmit queue. */
234	list_for_each_safe(lchunk, temp, &q->retransmit) {
235	list_del_init(entry: lchunk);
236	chunk = list_entry(lchunk, struct sctp_chunk,
237	transmitted_list);
238	sctp_chunk_fail(chunk, error: q->error);
239	sctp_chunk_free(chunk);
240	}
241
242	/* Throw away any chunks that are in the abandoned queue. */
243	list_for_each_safe(lchunk, temp, &q->abandoned) {
244	list_del_init(entry: lchunk);
245	chunk = list_entry(lchunk, struct sctp_chunk,
246	transmitted_list);
247	sctp_chunk_fail(chunk, error: q->error);
248	sctp_chunk_free(chunk);
249	}
250
251	/* Throw away any leftover data chunks. */
252	while ((chunk = sctp_outq_dequeue_data(q)) != NULL) {
253	sctp_sched_dequeue_done(q, ch: chunk);
254
255	/* Mark as send failure. */
256	sctp_chunk_fail(chunk, error: q->error);
257	sctp_chunk_free(chunk);
258	}
259
260	/* Throw away any leftover control chunks. */
261	list_for_each_entry_safe(chunk, tmp, &q->control_chunk_list, list) {
262	list_del_init(entry: &chunk->list);
263	sctp_chunk_free(chunk);
264	}
265	}
266
267	void sctp_outq_teardown(struct sctp_outq *q)
268	{
269	__sctp_outq_teardown(q);
270	sctp_outq_init(asoc: q->asoc, q);
271	}
272
273	/* Free the outqueue structure and any related pending chunks. */
274	void sctp_outq_free(struct sctp_outq *q)
275	{
276	/* Throw away leftover chunks. */
277	__sctp_outq_teardown(q);
278	}
279
280	/* Put a new chunk in an sctp_outq. */
281	void sctp_outq_tail(struct sctp_outq *q, struct sctp_chunk *chunk, gfp_t gfp)
282	{
283	struct net *net = q->asoc->base.net;
284
285	pr_debug("%s: outq:%p, chunk:%p[%s]\n", __func__, q, chunk,
286	chunk && chunk->chunk_hdr ?
287	sctp_cname(SCTP_ST_CHUNK(chunk->chunk_hdr->type)) :
288	"illegal chunk");
289
290	/* If it is data, queue it up, otherwise, send it
291	* immediately.
292	*/
293	if (sctp_chunk_is_data(chunk)) {
294	pr_debug("%s: outqueueing: outq:%p, chunk:%p[%s])\n",
295	__func__, q, chunk, chunk && chunk->chunk_hdr ?
296	sctp_cname(SCTP_ST_CHUNK(chunk->chunk_hdr->type)) :
297	"illegal chunk");
298
299	sctp_outq_tail_data(q, ch: chunk);
300	if (chunk->asoc->peer.prsctp_capable &&
301	SCTP_PR_PRIO_ENABLED(chunk->sinfo.sinfo_flags))
302	chunk->asoc->sent_cnt_removable++;
303	if (chunk->chunk_hdr->flags & SCTP_DATA_UNORDERED)
304	SCTP_INC_STATS(net, SCTP_MIB_OUTUNORDERCHUNKS);
305	else
306	SCTP_INC_STATS(net, SCTP_MIB_OUTORDERCHUNKS);
307	} else {
308	list_add_tail(new: &chunk->list, head: &q->control_chunk_list);
309	SCTP_INC_STATS(net, SCTP_MIB_OUTCTRLCHUNKS);
310	}
311
312	if (!q->cork)
313	sctp_outq_flush(q, rtx_timeout: 0, gfp);
314	}
315
316	/* Insert a chunk into the sorted list based on the TSNs. The retransmit list
317	* and the abandoned list are in ascending order.
318	*/
319	static void sctp_insert_list(struct list_head *head, struct list_head *new)
320	{
321	struct list_head *pos;
322	struct sctp_chunk *nchunk, *lchunk;
323	__u32 ntsn, ltsn;
324	int done = 0;
325
326	nchunk = list_entry(new, struct sctp_chunk, transmitted_list);
327	ntsn = ntohl(nchunk->subh.data_hdr->tsn);
328
329	list_for_each(pos, head) {
330	lchunk = list_entry(pos, struct sctp_chunk, transmitted_list);
331	ltsn = ntohl(lchunk->subh.data_hdr->tsn);
332	if (TSN_lt(ntsn, ltsn)) {
333	list_add(new, head: pos->prev);
334	done = 1;
335	break;
336	}
337	}
338	if (!done)
339	list_add_tail(new, head);
340	}
341
342	static int sctp_prsctp_prune_sent(struct sctp_association *asoc,
343	struct sctp_sndrcvinfo *sinfo,
344	struct list_head *queue, int msg_len)
345	{
346	struct sctp_chunk *chk, *temp;
347
348	list_for_each_entry_safe(chk, temp, queue, transmitted_list) {
349	struct sctp_stream_out *streamout;
350
351	if (!chk->msg->abandoned &&
352	(!SCTP_PR_PRIO_ENABLED(chk->sinfo.sinfo_flags) ||
353	chk->sinfo.sinfo_timetolive <= sinfo->sinfo_timetolive))
354	continue;
355
356	chk->msg->abandoned = 1;
357	list_del_init(entry: &chk->transmitted_list);
358	sctp_insert_list(head: &asoc->outqueue.abandoned,
359	new: &chk->transmitted_list);
360
361	streamout = SCTP_SO(&asoc->stream, chk->sinfo.sinfo_stream);
362	asoc->sent_cnt_removable--;
363	asoc->abandoned_sent[SCTP_PR_INDEX(PRIO)]++;
364	streamout->ext->abandoned_sent[SCTP_PR_INDEX(PRIO)]++;
365
366	if (queue != &asoc->outqueue.retransmit &&
367	!chk->tsn_gap_acked) {
368	if (chk->transport)
369	chk->transport->flight_size -=
370	sctp_data_size(chunk: chk);
371	asoc->outqueue.outstanding_bytes -= sctp_data_size(chunk: chk);
372	}
373
374	msg_len -= chk->skb->truesize + sizeof(struct sctp_chunk);
375	if (msg_len <= 0)
376	break;
377	}
378
379	return msg_len;
380	}
381
382	static int sctp_prsctp_prune_unsent(struct sctp_association *asoc,
383	struct sctp_sndrcvinfo *sinfo, int msg_len)
384	{
385	struct sctp_outq *q = &asoc->outqueue;
386	struct sctp_chunk *chk, *temp;
387	struct sctp_stream_out *sout;
388
389	q->sched->unsched_all(&asoc->stream);
390
391	list_for_each_entry_safe(chk, temp, &q->out_chunk_list, list) {
392	if (!chk->msg->abandoned &&
393	(!(chk->chunk_hdr->flags & SCTP_DATA_FIRST_FRAG) ||
394	!SCTP_PR_PRIO_ENABLED(chk->sinfo.sinfo_flags) ||
395	chk->sinfo.sinfo_timetolive <= sinfo->sinfo_timetolive))
396	continue;
397
398	chk->msg->abandoned = 1;
399	sctp_sched_dequeue_common(q, ch: chk);
400	asoc->sent_cnt_removable--;
401	asoc->abandoned_unsent[SCTP_PR_INDEX(PRIO)]++;
402
403	sout = SCTP_SO(&asoc->stream, chk->sinfo.sinfo_stream);
404	sout->ext->abandoned_unsent[SCTP_PR_INDEX(PRIO)]++;
405
406	/* clear out_curr if all frag chunks are pruned */
407	if (asoc->stream.out_curr == sout &&
408	list_is_last(list: &chk->frag_list, head: &chk->msg->chunks))
409	asoc->stream.out_curr = NULL;
410
411	msg_len -= chk->skb->truesize + sizeof(struct sctp_chunk);
412	sctp_chunk_free(chk);
413	if (msg_len <= 0)
414	break;
415	}
416
417	q->sched->sched_all(&asoc->stream);
418
419	return msg_len;
420	}
421
422	/* Abandon the chunks according their priorities */
423	void sctp_prsctp_prune(struct sctp_association *asoc,
424	struct sctp_sndrcvinfo *sinfo, int msg_len)
425	{
426	struct sctp_transport *transport;
427
428	if (!asoc->peer.prsctp_capable || !asoc->sent_cnt_removable)
429	return;
430
431	msg_len = sctp_prsctp_prune_sent(asoc, sinfo,
432	queue: &asoc->outqueue.retransmit,
433	msg_len);
434	if (msg_len <= 0)
435	return;
436
437	list_for_each_entry(transport, &asoc->peer.transport_addr_list,
438	transports) {
439	msg_len = sctp_prsctp_prune_sent(asoc, sinfo,
440	queue: &transport->transmitted,
441	msg_len);
442	if (msg_len <= 0)
443	return;
444	}
445
446	sctp_prsctp_prune_unsent(asoc, sinfo, msg_len);
447	}
448
449	/* Mark all the eligible packets on a transport for retransmission. */
450	void sctp_retransmit_mark(struct sctp_outq *q,
451	struct sctp_transport *transport,
452	__u8 reason)
453	{
454	struct list_head *lchunk, *ltemp;
455	struct sctp_chunk *chunk;
456
457	/* Walk through the specified transmitted queue. */
458	list_for_each_safe(lchunk, ltemp, &transport->transmitted) {
459	chunk = list_entry(lchunk, struct sctp_chunk,
460	transmitted_list);
461
462	/* If the chunk is abandoned, move it to abandoned list. */
463	if (sctp_chunk_abandoned(chunk)) {
464	list_del_init(entry: lchunk);
465	sctp_insert_list(head: &q->abandoned, new: lchunk);
466
467	/* If this chunk has not been previousely acked,
468	* stop considering it 'outstanding'. Our peer
469	* will most likely never see it since it will
470	* not be retransmitted
471	*/
472	if (!chunk->tsn_gap_acked) {
473	if (chunk->transport)
474	chunk->transport->flight_size -=
475	sctp_data_size(chunk);
476	q->outstanding_bytes -= sctp_data_size(chunk);
477	q->asoc->peer.rwnd += sctp_data_size(chunk);
478	}
479	continue;
480	}
481
482	/* If we are doing retransmission due to a timeout or pmtu
483	* discovery, only the chunks that are not yet acked should
484	* be added to the retransmit queue.
485	*/
486	if ((reason == SCTP_RTXR_FAST_RTX &&
487	(chunk->fast_retransmit == SCTP_NEED_FRTX)) ||
488	(reason != SCTP_RTXR_FAST_RTX && !chunk->tsn_gap_acked)) {
489	/* RFC 2960 6.2.1 Processing a Received SACK
490	*
491	* C) Any time a DATA chunk is marked for
492	* retransmission (via either T3-rtx timer expiration
493	* (Section 6.3.3) or via fast retransmit
494	* (Section 7.2.4)), add the data size of those
495	* chunks to the rwnd.
496	*/
497	q->asoc->peer.rwnd += sctp_data_size(chunk);
498	q->outstanding_bytes -= sctp_data_size(chunk);
499	if (chunk->transport)
500	transport->flight_size -= sctp_data_size(chunk);
501
502	/* sctpimpguide-05 Section 2.8.2
503	* M5) If a T3-rtx timer expires, the
504	* 'TSN.Missing.Report' of all affected TSNs is set
505	* to 0.
506	*/
507	chunk->tsn_missing_report = 0;
508
509	/* If a chunk that is being used for RTT measurement
510	* has to be retransmitted, we cannot use this chunk
511	* anymore for RTT measurements. Reset rto_pending so
512	* that a new RTT measurement is started when a new
513	* data chunk is sent.
514	*/
515	if (chunk->rtt_in_progress) {
516	chunk->rtt_in_progress = 0;
517	transport->rto_pending = 0;
518	}
519
520	/* Move the chunk to the retransmit queue. The chunks
521	* on the retransmit queue are always kept in order.
522	*/
523	list_del_init(entry: lchunk);
524	sctp_insert_list(head: &q->retransmit, new: lchunk);
525	}
526	}
527
528	pr_debug("%s: transport:%p, reason:%d, cwnd:%d, ssthresh:%d, "
529	"flight_size:%d, pba:%d\n", __func__, transport, reason,
530	transport->cwnd, transport->ssthresh, transport->flight_size,
531	transport->partial_bytes_acked);
532	}
533
534	/* Mark all the eligible packets on a transport for retransmission and force
535	* one packet out.
536	*/
537	void sctp_retransmit(struct sctp_outq *q, struct sctp_transport *transport,
538	enum sctp_retransmit_reason reason)
539	{
540	struct net *net = q->asoc->base.net;
541
542	switch (reason) {
543	case SCTP_RTXR_T3_RTX:
544	SCTP_INC_STATS(net, SCTP_MIB_T3_RETRANSMITS);
545	sctp_transport_lower_cwnd(t: transport, reason: SCTP_LOWER_CWND_T3_RTX);
546	/* Update the retran path if the T3-rtx timer has expired for
547	* the current retran path.
548	*/
549	if (transport == transport->asoc->peer.retran_path)
550	sctp_assoc_update_retran_path(transport->asoc);
551	transport->asoc->rtx_data_chunks +=
552	transport->asoc->unack_data;
553	if (transport->pl.state == SCTP_PL_COMPLETE &&
554	transport->asoc->unack_data)
555	sctp_transport_reset_probe_timer(transport);
556	break;
557	case SCTP_RTXR_FAST_RTX:
558	SCTP_INC_STATS(net, SCTP_MIB_FAST_RETRANSMITS);
559	sctp_transport_lower_cwnd(t: transport, reason: SCTP_LOWER_CWND_FAST_RTX);
560	q->fast_rtx = 1;
561	break;
562	case SCTP_RTXR_PMTUD:
563	SCTP_INC_STATS(net, SCTP_MIB_PMTUD_RETRANSMITS);
564	break;
565	case SCTP_RTXR_T1_RTX:
566	SCTP_INC_STATS(net, SCTP_MIB_T1_RETRANSMITS);
567	transport->asoc->init_retries++;
568	break;
569	default:
570	BUG();
571	}
572
573	sctp_retransmit_mark(q, transport, reason);
574
575	/* PR-SCTP A5) Any time the T3-rtx timer expires, on any destination,
576	* the sender SHOULD try to advance the "Advanced.Peer.Ack.Point" by
577	* following the procedures outlined in C1 - C5.
578	*/
579	if (reason == SCTP_RTXR_T3_RTX)
580	q->asoc->stream.si->generate_ftsn(q, q->asoc->ctsn_ack_point);
581
582	/* Flush the queues only on timeout, since fast_rtx is only
583	* triggered during sack processing and the queue
584	* will be flushed at the end.
585	*/
586	if (reason != SCTP_RTXR_FAST_RTX)
587	sctp_outq_flush(q, /* rtx_timeout */ 1, GFP_ATOMIC);
588	}
589
590	/*
591	* Transmit DATA chunks on the retransmit queue. Upon return from
592	* __sctp_outq_flush_rtx() the packet 'pkt' may contain chunks which
593	* need to be transmitted by the caller.
594	* We assume that pkt->transport has already been set.
595	*
596	* The return value is a normal kernel error return value.
597	*/
598	static int __sctp_outq_flush_rtx(struct sctp_outq *q, struct sctp_packet *pkt,
599	int rtx_timeout, int *start_timer, gfp_t gfp)
600	{
601	struct sctp_transport *transport = pkt->transport;
602	struct sctp_chunk *chunk, *chunk1;
603	struct list_head *lqueue;
604	enum sctp_xmit status;
605	int error = 0;
606	int timer = 0;
607	int done = 0;
608	int fast_rtx;
609
610	lqueue = &q->retransmit;
611	fast_rtx = q->fast_rtx;
612
613	/* This loop handles time-out retransmissions, fast retransmissions,
614	* and retransmissions due to opening of whindow.
615	*
616	* RFC 2960 6.3.3 Handle T3-rtx Expiration
617	*
618	* E3) Determine how many of the earliest (i.e., lowest TSN)
619	* outstanding DATA chunks for the address for which the
620	* T3-rtx has expired will fit into a single packet, subject
621	* to the MTU constraint for the path corresponding to the
622	* destination transport address to which the retransmission
623	* is being sent (this may be different from the address for
624	* which the timer expires [see Section 6.4]). Call this value
625	* K. Bundle and retransmit those K DATA chunks in a single
626	* packet to the destination endpoint.
627	*
628	* [Just to be painfully clear, if we are retransmitting
629	* because a timeout just happened, we should send only ONE
630	* packet of retransmitted data.]
631	*
632	* For fast retransmissions we also send only ONE packet. However,
633	* if we are just flushing the queue due to open window, we'll
634	* try to send as much as possible.
635	*/
636	list_for_each_entry_safe(chunk, chunk1, lqueue, transmitted_list) {
637	/* If the chunk is abandoned, move it to abandoned list. */
638	if (sctp_chunk_abandoned(chunk)) {
639	list_del_init(entry: &chunk->transmitted_list);
640	sctp_insert_list(head: &q->abandoned,
641	new: &chunk->transmitted_list);
642	continue;
643	}
644
645	/* Make sure that Gap Acked TSNs are not retransmitted. A
646	* simple approach is just to move such TSNs out of the
647	* way and into a 'transmitted' queue and skip to the
648	* next chunk.
649	*/
650	if (chunk->tsn_gap_acked) {
651	list_move_tail(list: &chunk->transmitted_list,
652	head: &transport->transmitted);
653	continue;
654	}
655
656	/* If we are doing fast retransmit, ignore non-fast_rtransmit
657	* chunks
658	*/
659	if (fast_rtx && !chunk->fast_retransmit)
660	continue;
661
662	redo:
663	/* Attempt to append this chunk to the packet. */
664	status = sctp_packet_append_chunk(packet: pkt, chunk);
665
666	switch (status) {
667	case SCTP_XMIT_PMTU_FULL:
668	if (!pkt->has_data && !pkt->has_cookie_echo) {
669	/* If this packet did not contain DATA then
670	* retransmission did not happen, so do it
671	* again. We'll ignore the error here since
672	* control chunks are already freed so there
673	* is nothing we can do.
674	*/
675	sctp_packet_transmit(pkt, gfp);
676	goto redo;
677	}
678
679	/* Send this packet. */
680	error = sctp_packet_transmit(pkt, gfp);
681
682	/* If we are retransmitting, we should only
683	* send a single packet.
684	* Otherwise, try appending this chunk again.
685	*/
686	if (rtx_timeout || fast_rtx)
687	done = 1;
688	else
689	goto redo;
690
691	/* Bundle next chunk in the next round. */
692	break;
693
694	case SCTP_XMIT_RWND_FULL:
695	/* Send this packet. */
696	error = sctp_packet_transmit(pkt, gfp);
697
698	/* Stop sending DATA as there is no more room
699	* at the receiver.
700	*/
701	done = 1;
702	break;
703
704	case SCTP_XMIT_DELAY:
705	/* Send this packet. */
706	error = sctp_packet_transmit(pkt, gfp);
707
708	/* Stop sending DATA because of nagle delay. */
709	done = 1;
710	break;
711
712	default:
713	/* The append was successful, so add this chunk to
714	* the transmitted list.
715	*/
716	list_move_tail(list: &chunk->transmitted_list,
717	head: &transport->transmitted);
718
719	/* Mark the chunk as ineligible for fast retransmit
720	* after it is retransmitted.
721	*/
722	if (chunk->fast_retransmit == SCTP_NEED_FRTX)
723	chunk->fast_retransmit = SCTP_DONT_FRTX;
724
725	q->asoc->stats.rtxchunks++;
726	break;
727	}
728
729	/* Set the timer if there were no errors */
730	if (!error && !timer)
731	timer = 1;
732
733	if (done)
734	break;
735	}
736
737	/* If we are here due to a retransmit timeout or a fast
738	* retransmit and if there are any chunks left in the retransmit
739	* queue that could not fit in the PMTU sized packet, they need
740	* to be marked as ineligible for a subsequent fast retransmit.
741	*/
742	if (rtx_timeout || fast_rtx) {
743	list_for_each_entry(chunk1, lqueue, transmitted_list) {
744	if (chunk1->fast_retransmit == SCTP_NEED_FRTX)
745	chunk1->fast_retransmit = SCTP_DONT_FRTX;
746	}
747	}
748
749	*start_timer = timer;
750
751	/* Clear fast retransmit hint */
752	if (fast_rtx)
753	q->fast_rtx = 0;
754
755	return error;
756	}
757
758	/* Cork the outqueue so queued chunks are really queued. */
759	void sctp_outq_uncork(struct sctp_outq *q, gfp_t gfp)
760	{
761	if (q->cork)
762	q->cork = 0;
763
764	sctp_outq_flush(q, rtx_timeout: 0, gfp);
765	}
766
767	static int sctp_packet_singleton(struct sctp_transport *transport,
768	struct sctp_chunk *chunk, gfp_t gfp)
769	{
770	const struct sctp_association *asoc = transport->asoc;
771	const __u16 sport = asoc->base.bind_addr.port;
772	const __u16 dport = asoc->peer.port;
773	const __u32 vtag = asoc->peer.i.init_tag;
774	struct sctp_packet singleton;
775
776	sctp_packet_init(&singleton, transport, sport, dport);
777	sctp_packet_config(&singleton, vtag, 0);
778	if (sctp_packet_append_chunk(packet: &singleton, chunk) != SCTP_XMIT_OK) {
779	list_del_init(entry: &chunk->list);
780	sctp_chunk_free(chunk);
781	return -ENOMEM;
782	}
783	return sctp_packet_transmit(&singleton, gfp);
784	}
785
786	/* Struct to hold the context during sctp outq flush */
787	struct sctp_flush_ctx {
788	struct sctp_outq *q;
789	/* Current transport being used. It's NOT the same as curr active one */
790	struct sctp_transport *transport;
791	/* These transports have chunks to send. */
792	struct list_head transport_list;
793	struct sctp_association *asoc;
794	/* Packet on the current transport above */
795	struct sctp_packet *packet;
796	gfp_t gfp;
797	};
798
799	/* transport: current transport */
800	static void sctp_outq_select_transport(struct sctp_flush_ctx *ctx,
801	struct sctp_chunk *chunk)
802	{
803	struct sctp_transport *new_transport = chunk->transport;
804
805	if (!new_transport) {
806	if (!sctp_chunk_is_data(chunk)) {
807	/* If we have a prior transport pointer, see if
808	* the destination address of the chunk
809	* matches the destination address of the
810	* current transport. If not a match, then
811	* try to look up the transport with a given
812	* destination address. We do this because
813	* after processing ASCONFs, we may have new
814	* transports created.
815	*/
816	if (ctx->transport && sctp_cmp_addr_exact(ss1: &chunk->dest,
817	ss2: &ctx->transport->ipaddr))
818	new_transport = ctx->transport;
819	else
820	new_transport = sctp_assoc_lookup_paddr(ctx->asoc,
821	&chunk->dest);
822	}
823
824	/* if we still don't have a new transport, then
825	* use the current active path.
826	*/
827	if (!new_transport)
828	new_transport = ctx->asoc->peer.active_path;
829	} else {
830	__u8 type;
831
832	switch (new_transport->state) {
833	case SCTP_INACTIVE:
834	case SCTP_UNCONFIRMED:
835	case SCTP_PF:
836	/* If the chunk is Heartbeat or Heartbeat Ack,
837	* send it to chunk->transport, even if it's
838	* inactive.
839	*
840	* 3.3.6 Heartbeat Acknowledgement:
841	* ...
842	* A HEARTBEAT ACK is always sent to the source IP
843	* address of the IP datagram containing the
844	* HEARTBEAT chunk to which this ack is responding.
845	* ...
846	*
847	* ASCONF_ACKs also must be sent to the source.
848	*/
849	type = chunk->chunk_hdr->type;
850	if (type != SCTP_CID_HEARTBEAT &&
851	type != SCTP_CID_HEARTBEAT_ACK &&
852	type != SCTP_CID_ASCONF_ACK)
853	new_transport = ctx->asoc->peer.active_path;
854	break;
855	default:
856	break;
857	}
858	}
859
860	/* Are we switching transports? Take care of transport locks. */
861	if (new_transport != ctx->transport) {
862	ctx->transport = new_transport;
863	ctx->packet = &ctx->transport->packet;
864
865	if (list_empty(head: &ctx->transport->send_ready))
866	list_add_tail(new: &ctx->transport->send_ready,
867	head: &ctx->transport_list);
868
869	sctp_packet_config(ctx->packet,
870	vtag: ctx->asoc->peer.i.init_tag,
871	ctx->asoc->peer.ecn_capable);
872	/* We've switched transports, so apply the
873	* Burst limit to the new transport.
874	*/
875	sctp_transport_burst_limited(ctx->transport);
876	}
877	}
878
879	static void sctp_outq_flush_ctrl(struct sctp_flush_ctx *ctx)
880	{
881	struct sctp_chunk *chunk, *tmp;
882	enum sctp_xmit status;
883	int one_packet, error;
884
885	list_for_each_entry_safe(chunk, tmp, &ctx->q->control_chunk_list, list) {
886	one_packet = 0;
887
888	/* RFC 5061, 5.3
889	* F1) This means that until such time as the ASCONF
890	* containing the add is acknowledged, the sender MUST
891	* NOT use the new IP address as a source for ANY SCTP
892	* packet except on carrying an ASCONF Chunk.
893	*/
894	if (ctx->asoc->src_out_of_asoc_ok &&
895	chunk->chunk_hdr->type != SCTP_CID_ASCONF)
896	continue;
897
898	list_del_init(entry: &chunk->list);
899
900	/* Pick the right transport to use. Should always be true for
901	* the first chunk as we don't have a transport by then.
902	*/
903	sctp_outq_select_transport(ctx, chunk);
904
905	switch (chunk->chunk_hdr->type) {
906	/* 6.10 Bundling
907	* ...
908	* An endpoint MUST NOT bundle INIT, INIT ACK or SHUTDOWN
909	* COMPLETE with any other chunks. [Send them immediately.]
910	*/
911	case SCTP_CID_INIT:
912	case SCTP_CID_INIT_ACK:
913	case SCTP_CID_SHUTDOWN_COMPLETE:
914	error = sctp_packet_singleton(transport: ctx->transport, chunk,
915	gfp: ctx->gfp);
916	if (error < 0) {
917	ctx->asoc->base.sk->sk_err = -error;
918	return;
919	}
920	ctx->asoc->stats.octrlchunks++;
921	break;
922
923	case SCTP_CID_ABORT:
924	if (sctp_test_T_bit(chunk))
925	ctx->packet->vtag = ctx->asoc->c.my_vtag;
926	fallthrough;
927
928	/* The following chunks are "response" chunks, i.e.
929	* they are generated in response to something we
930	* received. If we are sending these, then we can
931	* send only 1 packet containing these chunks.
932	*/
933	case SCTP_CID_HEARTBEAT_ACK:
934	case SCTP_CID_SHUTDOWN_ACK:
935	case SCTP_CID_COOKIE_ACK:
936	case SCTP_CID_COOKIE_ECHO:
937	case SCTP_CID_ERROR:
938	case SCTP_CID_ECN_CWR:
939	case SCTP_CID_ASCONF_ACK:
940	one_packet = 1;
941	fallthrough;
942
943	case SCTP_CID_HEARTBEAT:
944	if (chunk->pmtu_probe) {
945	error = sctp_packet_singleton(transport: ctx->transport,
946	chunk, gfp: ctx->gfp);
947	if (!error)
948	ctx->asoc->stats.octrlchunks++;
949	break;
950	}
951	fallthrough;
952	case SCTP_CID_SACK:
953	case SCTP_CID_SHUTDOWN:
954	case SCTP_CID_ECN_ECNE:
955	case SCTP_CID_ASCONF:
956	case SCTP_CID_FWD_TSN:
957	case SCTP_CID_I_FWD_TSN:
958	case SCTP_CID_RECONF:
959	status = sctp_packet_transmit_chunk(packet: ctx->packet, chunk,
960	one_packet, gfp: ctx->gfp);
961	if (status != SCTP_XMIT_OK) {
962	/* put the chunk back */
963	list_add(new: &chunk->list, head: &ctx->q->control_chunk_list);
964	break;
965	}
966
967	ctx->asoc->stats.octrlchunks++;
968	/* PR-SCTP C5) If a FORWARD TSN is sent, the
969	* sender MUST assure that at least one T3-rtx
970	* timer is running.
971	*/
972	if (chunk->chunk_hdr->type == SCTP_CID_FWD_TSN ||
973	chunk->chunk_hdr->type == SCTP_CID_I_FWD_TSN) {
974	sctp_transport_reset_t3_rtx(ctx->transport);
975	ctx->transport->last_time_sent = jiffies;
976	}
977
978	if (chunk == ctx->asoc->strreset_chunk)
979	sctp_transport_reset_reconf_timer(transport: ctx->transport);
980
981	break;
982
983	default:
984	/* We built a chunk with an illegal type! */
985	BUG();
986	}
987	}
988	}
989
990	/* Returns false if new data shouldn't be sent */
991	static bool sctp_outq_flush_rtx(struct sctp_flush_ctx *ctx,
992	int rtx_timeout)
993	{
994	int error, start_timer = 0;
995
996	if (ctx->asoc->peer.retran_path->state == SCTP_UNCONFIRMED)
997	return false;
998
999	if (ctx->transport != ctx->asoc->peer.retran_path) {
1000	/* Switch transports & prepare the packet. */
1001	ctx->transport = ctx->asoc->peer.retran_path;
1002	ctx->packet = &ctx->transport->packet;
1003
1004	if (list_empty(head: &ctx->transport->send_ready))
1005	list_add_tail(new: &ctx->transport->send_ready,
1006	head: &ctx->transport_list);
1007
1008	sctp_packet_config(ctx->packet, vtag: ctx->asoc->peer.i.init_tag,
1009	ctx->asoc->peer.ecn_capable);
1010	}
1011
1012	error = __sctp_outq_flush_rtx(q: ctx->q, pkt: ctx->packet, rtx_timeout,
1013	start_timer: &start_timer, gfp: ctx->gfp);
1014	if (error < 0)
1015	ctx->asoc->base.sk->sk_err = -error;
1016
1017	if (start_timer) {
1018	sctp_transport_reset_t3_rtx(ctx->transport);
1019	ctx->transport->last_time_sent = jiffies;
1020	}
1021
1022	/* This can happen on COOKIE-ECHO resend. Only
1023	* one chunk can get bundled with a COOKIE-ECHO.
1024	*/
1025	if (ctx->packet->has_cookie_echo)
1026	return false;
1027
1028	/* Don't send new data if there is still data
1029	* waiting to retransmit.
1030	*/
1031	if (!list_empty(head: &ctx->q->retransmit))
1032	return false;
1033
1034	return true;
1035	}
1036
1037	static void sctp_outq_flush_data(struct sctp_flush_ctx *ctx,
1038	int rtx_timeout)
1039	{
1040	struct sctp_chunk *chunk;
1041	enum sctp_xmit status;
1042
1043	/* Is it OK to send data chunks? */
1044	switch (ctx->asoc->state) {
1045	case SCTP_STATE_COOKIE_ECHOED:
1046	/* Only allow bundling when this packet has a COOKIE-ECHO
1047	* chunk.
1048	*/
1049	if (!ctx->packet || !ctx->packet->has_cookie_echo)
1050	return;
1051
1052	fallthrough;
1053	case SCTP_STATE_ESTABLISHED:
1054	case SCTP_STATE_SHUTDOWN_PENDING:
1055	case SCTP_STATE_SHUTDOWN_RECEIVED:
1056	break;
1057
1058	default:
1059	/* Do nothing. */
1060	return;
1061	}
1062
1063	/* RFC 2960 6.1 Transmission of DATA Chunks
1064	*
1065	* C) When the time comes for the sender to transmit,
1066	* before sending new DATA chunks, the sender MUST
1067	* first transmit any outstanding DATA chunks which
1068	* are marked for retransmission (limited by the
1069	* current cwnd).
1070	*/
1071	if (!list_empty(head: &ctx->q->retransmit) &&
1072	!sctp_outq_flush_rtx(ctx, rtx_timeout))
1073	return;
1074
1075	/* Apply Max.Burst limitation to the current transport in
1076	* case it will be used for new data. We are going to
1077	* rest it before we return, but we want to apply the limit
1078	* to the currently queued data.
1079	*/
1080	if (ctx->transport)
1081	sctp_transport_burst_limited(ctx->transport);
1082
1083	/* Finally, transmit new packets. */
1084	while ((chunk = sctp_outq_dequeue_data(q: ctx->q)) != NULL) {
1085	__u32 sid = ntohs(chunk->subh.data_hdr->stream);
1086	__u8 stream_state = SCTP_SO(&ctx->asoc->stream, sid)->state;
1087
1088	/* Has this chunk expired? */
1089	if (sctp_chunk_abandoned(chunk)) {
1090	sctp_sched_dequeue_done(q: ctx->q, ch: chunk);
1091	sctp_chunk_fail(chunk, error: 0);
1092	sctp_chunk_free(chunk);
1093	continue;
1094	}
1095
1096	if (stream_state == SCTP_STREAM_CLOSED) {
1097	sctp_outq_head_data(q: ctx->q, ch: chunk);
1098	break;
1099	}
1100
1101	sctp_outq_select_transport(ctx, chunk);
1102
1103	pr_debug("%s: outq:%p, chunk:%p[%s], tx-tsn:0x%x skb->head:%p skb->users:%d\n",
1104	__func__, ctx->q, chunk, chunk && chunk->chunk_hdr ?
1105	sctp_cname(SCTP_ST_CHUNK(chunk->chunk_hdr->type)) :
1106	"illegal chunk", ntohl(chunk->subh.data_hdr->tsn),
1107	chunk->skb ? chunk->skb->head : NULL, chunk->skb ?
1108	refcount_read(&chunk->skb->users) : -1);
1109
1110	/* Add the chunk to the packet. */
1111	status = sctp_packet_transmit_chunk(packet: ctx->packet, chunk, one_packet: 0,
1112	gfp: ctx->gfp);
1113	if (status != SCTP_XMIT_OK) {
1114	/* We could not append this chunk, so put
1115	* the chunk back on the output queue.
1116	*/
1117	pr_debug("%s: could not transmit tsn:0x%x, status:%d\n",
1118	__func__, ntohl(chunk->subh.data_hdr->tsn),
1119	status);
1120
1121	sctp_outq_head_data(q: ctx->q, ch: chunk);
1122	break;
1123	}
1124
1125	/* The sender is in the SHUTDOWN-PENDING state,
1126	* The sender MAY set the I-bit in the DATA
1127	* chunk header.
1128	*/
1129	if (ctx->asoc->state == SCTP_STATE_SHUTDOWN_PENDING)
1130	chunk->chunk_hdr->flags |= SCTP_DATA_SACK_IMM;
1131	if (chunk->chunk_hdr->flags & SCTP_DATA_UNORDERED)
1132	ctx->asoc->stats.ouodchunks++;
1133	else
1134	ctx->asoc->stats.oodchunks++;
1135
1136	/* Only now it's safe to consider this
1137	* chunk as sent, sched-wise.
1138	*/
1139	sctp_sched_dequeue_done(q: ctx->q, ch: chunk);
1140
1141	list_add_tail(new: &chunk->transmitted_list,
1142	head: &ctx->transport->transmitted);
1143
1144	sctp_transport_reset_t3_rtx(ctx->transport);
1145	ctx->transport->last_time_sent = jiffies;
1146
1147	/* Only let one DATA chunk get bundled with a
1148	* COOKIE-ECHO chunk.
1149	*/
1150	if (ctx->packet->has_cookie_echo)
1151	break;
1152	}
1153	}
1154
1155	static void sctp_outq_flush_transports(struct sctp_flush_ctx *ctx)
1156	{
1157	struct sock *sk = ctx->asoc->base.sk;
1158	struct list_head *ltransport;
1159	struct sctp_packet *packet;
1160	struct sctp_transport *t;
1161	int error = 0;
1162
1163	while ((ltransport = sctp_list_dequeue(list: &ctx->transport_list)) != NULL) {
1164	t = list_entry(ltransport, struct sctp_transport, send_ready);
1165	packet = &t->packet;
1166	if (!sctp_packet_empty(packet)) {
1167	rcu_read_lock();
1168	if (t->dst && __sk_dst_get(sk) != t->dst) {
1169	dst_hold(dst: t->dst);
1170	sk_setup_caps(sk, dst: t->dst);
1171	}
1172	rcu_read_unlock();
1173	error = sctp_packet_transmit(packet, ctx->gfp);
1174	if (error < 0)
1175	ctx->q->asoc->base.sk->sk_err = -error;
1176	}
1177
1178	/* Clear the burst limited state, if any */
1179	sctp_transport_burst_reset(t);
1180	}
1181	}
1182
1183	/* Try to flush an outqueue.
1184	*
1185	* Description: Send everything in q which we legally can, subject to
1186	* congestion limitations.
1187	* * Note: This function can be called from multiple contexts so appropriate
1188	* locking concerns must be made. Today we use the sock lock to protect
1189	* this function.
1190	*/
1191
1192	static void sctp_outq_flush(struct sctp_outq *q, int rtx_timeout, gfp_t gfp)
1193	{
1194	struct sctp_flush_ctx ctx = {
1195	.q = q,
1196	.transport = NULL,
1197	.transport_list = LIST_HEAD_INIT(ctx.transport_list),
1198	.asoc = q->asoc,
1199	.packet = NULL,
1200	.gfp = gfp,
1201	};
1202
1203	/* 6.10 Bundling
1204	* ...
1205	* When bundling control chunks with DATA chunks, an
1206	* endpoint MUST place control chunks first in the outbound
1207	* SCTP packet. The transmitter MUST transmit DATA chunks
1208	* within a SCTP packet in increasing order of TSN.
1209	* ...
1210	*/
1211
1212	sctp_outq_flush_ctrl(ctx: &ctx);
1213
1214	if (q->asoc->src_out_of_asoc_ok)
1215	goto sctp_flush_out;
1216
1217	sctp_outq_flush_data(ctx: &ctx, rtx_timeout);
1218
1219	sctp_flush_out:
1220
1221	sctp_outq_flush_transports(ctx: &ctx);
1222	}
1223
1224	/* Update unack_data based on the incoming SACK chunk */
1225	static void sctp_sack_update_unack_data(struct sctp_association *assoc,
1226	struct sctp_sackhdr *sack)
1227	{
1228	union sctp_sack_variable *frags;
1229	__u16 unack_data;
1230	int i;
1231
1232	unack_data = assoc->next_tsn - assoc->ctsn_ack_point - 1;
1233
1234	frags = (union sctp_sack_variable *)(sack + 1);
1235	for (i = 0; i < ntohs(sack->num_gap_ack_blocks); i++) {
1236	unack_data -= ((ntohs(frags[i].gab.end) -
1237	ntohs(frags[i].gab.start) + 1));
1238	}
1239
1240	assoc->unack_data = unack_data;
1241	}
1242
1243	/* This is where we REALLY process a SACK.
1244	*
1245	* Process the SACK against the outqueue. Mostly, this just frees
1246	* things off the transmitted queue.
1247	*/
1248	int sctp_outq_sack(struct sctp_outq *q, struct sctp_chunk *chunk)
1249	{
1250	struct sctp_association *asoc = q->asoc;
1251	struct sctp_sackhdr *sack = chunk->subh.sack_hdr;
1252	struct sctp_transport *transport;
1253	struct sctp_chunk *tchunk = NULL;
1254	struct list_head *lchunk, *transport_list, *temp;
1255	__u32 sack_ctsn, ctsn, tsn;
1256	__u32 highest_tsn, highest_new_tsn;
1257	__u32 sack_a_rwnd;
1258	unsigned int outstanding;
1259	struct sctp_transport *primary = asoc->peer.primary_path;
1260	int count_of_newacks = 0;
1261	int gap_ack_blocks;
1262	u8 accum_moved = 0;
1263
1264	/* Grab the association's destination address list. */
1265	transport_list = &asoc->peer.transport_addr_list;
1266
1267	/* SCTP path tracepoint for congestion control debugging. */
1268	if (trace_sctp_probe_path_enabled()) {
1269	list_for_each_entry(transport, transport_list, transports)
1270	trace_sctp_probe_path(sp: transport, asoc);
1271	}
1272
1273	sack_ctsn = ntohl(sack->cum_tsn_ack);
1274	gap_ack_blocks = ntohs(sack->num_gap_ack_blocks);
1275	asoc->stats.gapcnt += gap_ack_blocks;
1276	/*
1277	* SFR-CACC algorithm:
1278	* On receipt of a SACK the sender SHOULD execute the
1279	* following statements.
1280	*
1281	* 1) If the cumulative ack in the SACK passes next tsn_at_change
1282	* on the current primary, the CHANGEOVER_ACTIVE flag SHOULD be
1283	* cleared. The CYCLING_CHANGEOVER flag SHOULD also be cleared for
1284	* all destinations.
1285	* 2) If the SACK contains gap acks and the flag CHANGEOVER_ACTIVE
1286	* is set the receiver of the SACK MUST take the following actions:
1287	*
1288	* A) Initialize the cacc_saw_newack to 0 for all destination
1289	* addresses.
1290	*
1291	* Only bother if changeover_active is set. Otherwise, this is
1292	* totally suboptimal to do on every SACK.
1293	*/
1294	if (primary->cacc.changeover_active) {
1295	u8 clear_cycling = 0;
1296
1297	if (TSN_lte(primary->cacc.next_tsn_at_change, sack_ctsn)) {
1298	primary->cacc.changeover_active = 0;
1299	clear_cycling = 1;
1300	}
1301
1302	if (clear_cycling || gap_ack_blocks) {
1303	list_for_each_entry(transport, transport_list,
1304	transports) {
1305	if (clear_cycling)
1306	transport->cacc.cycling_changeover = 0;
1307	if (gap_ack_blocks)
1308	transport->cacc.cacc_saw_newack = 0;
1309	}
1310	}
1311	}
1312
1313	/* Get the highest TSN in the sack. */
1314	highest_tsn = sack_ctsn;
1315	if (gap_ack_blocks) {
1316	union sctp_sack_variable *frags =
1317	(union sctp_sack_variable *)(sack + 1);
1318
1319	highest_tsn += ntohs(frags[gap_ack_blocks - 1].gab.end);
1320	}
1321
1322	if (TSN_lt(asoc->highest_sacked, highest_tsn))
1323	asoc->highest_sacked = highest_tsn;
1324
1325	highest_new_tsn = sack_ctsn;
1326
1327	/* Run through the retransmit queue. Credit bytes received
1328	* and free those chunks that we can.
1329	*/
1330	sctp_check_transmitted(q, transmitted_queue: &q->retransmit, NULL, NULL, sack, highest_new_tsn: &highest_new_tsn);
1331
1332	/* Run through the transmitted queue.
1333	* Credit bytes received and free those chunks which we can.
1334	*
1335	* This is a MASSIVE candidate for optimization.
1336	*/
1337	list_for_each_entry(transport, transport_list, transports) {
1338	sctp_check_transmitted(q, transmitted_queue: &transport->transmitted,
1339	transport, saddr: &chunk->source, sack,
1340	highest_new_tsn: &highest_new_tsn);
1341	/*
1342	* SFR-CACC algorithm:
1343	* C) Let count_of_newacks be the number of
1344	* destinations for which cacc_saw_newack is set.
1345	*/
1346	if (transport->cacc.cacc_saw_newack)
1347	count_of_newacks++;
1348	}
1349
1350	/* Move the Cumulative TSN Ack Point if appropriate. */
1351	if (TSN_lt(asoc->ctsn_ack_point, sack_ctsn)) {
1352	asoc->ctsn_ack_point = sack_ctsn;
1353	accum_moved = 1;
1354	}
1355
1356	if (gap_ack_blocks) {
1357
1358	if (asoc->fast_recovery && accum_moved)
1359	highest_new_tsn = highest_tsn;
1360
1361	list_for_each_entry(transport, transport_list, transports)
1362	sctp_mark_missing(q, transmitted_queue: &transport->transmitted, transport,
1363	highest_new_tsn, count_of_newacks);
1364	}
1365
1366	/* Update unack_data field in the assoc. */
1367	sctp_sack_update_unack_data(assoc: asoc, sack);
1368
1369	ctsn = asoc->ctsn_ack_point;
1370
1371	/* Throw away stuff rotting on the sack queue. */
1372	list_for_each_safe(lchunk, temp, &q->sacked) {
1373	tchunk = list_entry(lchunk, struct sctp_chunk,
1374	transmitted_list);
1375	tsn = ntohl(tchunk->subh.data_hdr->tsn);
1376	if (TSN_lte(tsn, ctsn)) {
1377	list_del_init(entry: &tchunk->transmitted_list);
1378	if (asoc->peer.prsctp_capable &&
1379	SCTP_PR_PRIO_ENABLED(chunk->sinfo.sinfo_flags))
1380	asoc->sent_cnt_removable--;
1381	sctp_chunk_free(tchunk);
1382	}
1383	}
1384
1385	/* ii) Set rwnd equal to the newly received a_rwnd minus the
1386	* number of bytes still outstanding after processing the
1387	* Cumulative TSN Ack and the Gap Ack Blocks.
1388	*/
1389
1390	sack_a_rwnd = ntohl(sack->a_rwnd);
1391	asoc->peer.zero_window_announced = !sack_a_rwnd;
1392	outstanding = q->outstanding_bytes;
1393
1394	if (outstanding < sack_a_rwnd)
1395	sack_a_rwnd -= outstanding;
1396	else
1397	sack_a_rwnd = 0;
1398
1399	asoc->peer.rwnd = sack_a_rwnd;
1400
1401	asoc->stream.si->generate_ftsn(q, sack_ctsn);
1402
1403	pr_debug("%s: sack cumulative tsn ack:0x%x\n", __func__, sack_ctsn);
1404	pr_debug("%s: cumulative tsn ack of assoc:%p is 0x%x, "
1405	"advertised peer ack point:0x%x\n", __func__, asoc, ctsn,
1406	asoc->adv_peer_ack_point);
1407
1408	return sctp_outq_is_empty(q);
1409	}
1410
1411	/* Is the outqueue empty?
1412	* The queue is empty when we have not pending data, no in-flight data
1413	* and nothing pending retransmissions.
1414	*/
1415	int sctp_outq_is_empty(const struct sctp_outq *q)
1416	{
1417	return q->out_qlen == 0 && q->outstanding_bytes == 0 &&
1418	list_empty(head: &q->retransmit);
1419	}
1420
1421	/********************************************************************
1422	* 2nd Level Abstractions
1423	********************************************************************/
1424
1425	/* Go through a transport's transmitted list or the association's retransmit
1426	* list and move chunks that are acked by the Cumulative TSN Ack to q->sacked.
1427	* The retransmit list will not have an associated transport.
1428	*
1429	* I added coherent debug information output. --xguo
1430	*
1431	* Instead of printing 'sacked' or 'kept' for each TSN on the
1432	* transmitted_queue, we print a range: SACKED: TSN1-TSN2, TSN3, TSN4-TSN5.
1433	* KEPT TSN6-TSN7, etc.
1434	*/
1435	static void sctp_check_transmitted(struct sctp_outq *q,
1436	struct list_head *transmitted_queue,
1437	struct sctp_transport *transport,
1438	union sctp_addr *saddr,
1439	struct sctp_sackhdr *sack,
1440	__u32 *highest_new_tsn_in_sack)
1441	{
1442	struct list_head *lchunk;
1443	struct sctp_chunk *tchunk;
1444	struct list_head tlist;
1445	__u32 tsn;
1446	__u32 sack_ctsn;
1447	__u32 rtt;
1448	__u8 restart_timer = 0;
1449	int bytes_acked = 0;
1450	int migrate_bytes = 0;
1451	bool forward_progress = false;
1452
1453	sack_ctsn = ntohl(sack->cum_tsn_ack);
1454
1455	INIT_LIST_HEAD(list: &tlist);
1456
1457	/* The while loop will skip empty transmitted queues. */
1458	while (NULL != (lchunk = sctp_list_dequeue(list: transmitted_queue))) {
1459	tchunk = list_entry(lchunk, struct sctp_chunk,
1460	transmitted_list);
1461
1462	if (sctp_chunk_abandoned(tchunk)) {
1463	/* Move the chunk to abandoned list. */
1464	sctp_insert_list(head: &q->abandoned, new: lchunk);
1465
1466	/* If this chunk has not been acked, stop
1467	* considering it as 'outstanding'.
1468	*/
1469	if (transmitted_queue != &q->retransmit &&
1470	!tchunk->tsn_gap_acked) {
1471	if (tchunk->transport)
1472	tchunk->transport->flight_size -=
1473	sctp_data_size(chunk: tchunk);
1474	q->outstanding_bytes -= sctp_data_size(chunk: tchunk);
1475	}
1476	continue;
1477	}
1478
1479	tsn = ntohl(tchunk->subh.data_hdr->tsn);
1480	if (sctp_acked(sack, tsn)) {
1481	/* If this queue is the retransmit queue, the
1482	* retransmit timer has already reclaimed
1483	* the outstanding bytes for this chunk, so only
1484	* count bytes associated with a transport.
1485	*/
1486	if (transport && !tchunk->tsn_gap_acked) {
1487	/* If this chunk is being used for RTT
1488	* measurement, calculate the RTT and update
1489	* the RTO using this value.
1490	*
1491	* 6.3.1 C5) Karn's algorithm: RTT measurements
1492	* MUST NOT be made using packets that were
1493	* retransmitted (and thus for which it is
1494	* ambiguous whether the reply was for the
1495	* first instance of the packet or a later
1496	* instance).
1497	*/
1498	if (!sctp_chunk_retransmitted(tchunk) &&
1499	tchunk->rtt_in_progress) {
1500	tchunk->rtt_in_progress = 0;
1501	rtt = jiffies - tchunk->sent_at;
1502	sctp_transport_update_rto(transport,
1503	rtt);
1504	}
1505
1506	if (TSN_lte(tsn, sack_ctsn)) {
1507	/*
1508	* SFR-CACC algorithm:
1509	* 2) If the SACK contains gap acks
1510	* and the flag CHANGEOVER_ACTIVE is
1511	* set the receiver of the SACK MUST
1512	* take the following action:
1513	*
1514	* B) For each TSN t being acked that
1515	* has not been acked in any SACK so
1516	* far, set cacc_saw_newack to 1 for
1517	* the destination that the TSN was
1518	* sent to.
1519	*/
1520	if (sack->num_gap_ack_blocks &&
1521	q->asoc->peer.primary_path->cacc.
1522	changeover_active)
1523	transport->cacc.cacc_saw_newack
1524	= 1;
1525	}
1526	}
1527
1528	/* If the chunk hasn't been marked as ACKED,
1529	* mark it and account bytes_acked if the
1530	* chunk had a valid transport (it will not
1531	* have a transport if ASCONF had deleted it
1532	* while DATA was outstanding).
1533	*/
1534	if (!tchunk->tsn_gap_acked) {
1535	tchunk->tsn_gap_acked = 1;
1536	if (TSN_lt(*highest_new_tsn_in_sack, tsn))
1537	*highest_new_tsn_in_sack = tsn;
1538	bytes_acked += sctp_data_size(chunk: tchunk);
1539	if (!tchunk->transport)
1540	migrate_bytes += sctp_data_size(chunk: tchunk);
1541	forward_progress = true;
1542	}
1543
1544	if (TSN_lte(tsn, sack_ctsn)) {
1545	/* RFC 2960 6.3.2 Retransmission Timer Rules
1546	*
1547	* R3) Whenever a SACK is received
1548	* that acknowledges the DATA chunk
1549	* with the earliest outstanding TSN
1550	* for that address, restart T3-rtx
1551	* timer for that address with its
1552	* current RTO.
1553	*/
1554	restart_timer = 1;
1555	forward_progress = true;
1556
1557	list_add_tail(new: &tchunk->transmitted_list,
1558	head: &q->sacked);
1559	} else {
1560	/* RFC2960 7.2.4, sctpimpguide-05 2.8.2
1561	* M2) Each time a SACK arrives reporting
1562	* 'Stray DATA chunk(s)' record the highest TSN
1563	* reported as newly acknowledged, call this
1564	* value 'HighestTSNinSack'. A newly
1565	* acknowledged DATA chunk is one not
1566	* previously acknowledged in a SACK.
1567	*
1568	* When the SCTP sender of data receives a SACK
1569	* chunk that acknowledges, for the first time,
1570	* the receipt of a DATA chunk, all the still
1571	* unacknowledged DATA chunks whose TSN is
1572	* older than that newly acknowledged DATA
1573	* chunk, are qualified as 'Stray DATA chunks'.
1574	*/
1575	list_add_tail(new: lchunk, head: &tlist);
1576	}
1577	} else {
1578	if (tchunk->tsn_gap_acked) {
1579	pr_debug("%s: receiver reneged on data TSN:0x%x\n",
1580	__func__, tsn);
1581
1582	tchunk->tsn_gap_acked = 0;
1583
1584	if (tchunk->transport)
1585	bytes_acked -= sctp_data_size(chunk: tchunk);
1586
1587	/* RFC 2960 6.3.2 Retransmission Timer Rules
1588	*
1589	* R4) Whenever a SACK is received missing a
1590	* TSN that was previously acknowledged via a
1591	* Gap Ack Block, start T3-rtx for the
1592	* destination address to which the DATA
1593	* chunk was originally
1594	* transmitted if it is not already running.
1595	*/
1596	restart_timer = 1;
1597	}
1598
1599	list_add_tail(new: lchunk, head: &tlist);
1600	}
1601	}
1602
1603	if (transport) {
1604	if (bytes_acked) {
1605	struct sctp_association *asoc = transport->asoc;
1606
1607	/* We may have counted DATA that was migrated
1608	* to this transport due to DEL-IP operation.
1609	* Subtract those bytes, since the were never
1610	* send on this transport and shouldn't be
1611	* credited to this transport.
1612	*/
1613	bytes_acked -= migrate_bytes;
1614
1615	/* 8.2. When an outstanding TSN is acknowledged,
1616	* the endpoint shall clear the error counter of
1617	* the destination transport address to which the
1618	* DATA chunk was last sent.
1619	* The association's overall error counter is
1620	* also cleared.
1621	*/
1622	transport->error_count = 0;
1623	transport->asoc->overall_error_count = 0;
1624	forward_progress = true;
1625
1626	/*
1627	* While in SHUTDOWN PENDING, we may have started
1628	* the T5 shutdown guard timer after reaching the
1629	* retransmission limit. Stop that timer as soon
1630	* as the receiver acknowledged any data.
1631	*/
1632	if (asoc->state == SCTP_STATE_SHUTDOWN_PENDING &&
1633	del_timer(timer: &asoc->timers
1634	[SCTP_EVENT_TIMEOUT_T5_SHUTDOWN_GUARD]))
1635	sctp_association_put(asoc);
1636
1637	/* Mark the destination transport address as
1638	* active if it is not so marked.
1639	*/
1640	if ((transport->state == SCTP_INACTIVE ||
1641	transport->state == SCTP_UNCONFIRMED) &&
1642	sctp_cmp_addr_exact(ss1: &transport->ipaddr, ss2: saddr)) {
1643	sctp_assoc_control_transport(
1644	asoc: transport->asoc,
1645	transport,
1646	command: SCTP_TRANSPORT_UP,
1647	error: SCTP_RECEIVED_SACK);
1648	}
1649
1650	sctp_transport_raise_cwnd(transport, sack_ctsn,
1651	bytes_acked);
1652
1653	transport->flight_size -= bytes_acked;
1654	if (transport->flight_size == 0)
1655	transport->partial_bytes_acked = 0;
1656	q->outstanding_bytes -= bytes_acked + migrate_bytes;
1657	} else {
1658	/* RFC 2960 6.1, sctpimpguide-06 2.15.2
1659	* When a sender is doing zero window probing, it
1660	* should not timeout the association if it continues
1661	* to receive new packets from the receiver. The
1662	* reason is that the receiver MAY keep its window
1663	* closed for an indefinite time.
1664	* A sender is doing zero window probing when the
1665	* receiver's advertised window is zero, and there is
1666	* only one data chunk in flight to the receiver.
1667	*
1668	* Allow the association to timeout while in SHUTDOWN
1669	* PENDING or SHUTDOWN RECEIVED in case the receiver
1670	* stays in zero window mode forever.
1671	*/
1672	if (!q->asoc->peer.rwnd &&
1673	!list_empty(head: &tlist) &&
1674	(sack_ctsn+2 == q->asoc->next_tsn) &&
1675	q->asoc->state < SCTP_STATE_SHUTDOWN_PENDING) {
1676	pr_debug("%s: sack received for zero window "
1677	"probe:%u\n", __func__, sack_ctsn);
1678
1679	q->asoc->overall_error_count = 0;
1680	transport->error_count = 0;
1681	}
1682	}
1683
1684	/* RFC 2960 6.3.2 Retransmission Timer Rules
1685	*
1686	* R2) Whenever all outstanding data sent to an address have
1687	* been acknowledged, turn off the T3-rtx timer of that
1688	* address.
1689	*/
1690	if (!transport->flight_size) {
1691	if (del_timer(timer: &transport->T3_rtx_timer))
1692	sctp_transport_put(transport);
1693	} else if (restart_timer) {
1694	if (!mod_timer(timer: &transport->T3_rtx_timer,
1695	expires: jiffies + transport->rto))
1696	sctp_transport_hold(transport);
1697	}
1698
1699	if (forward_progress) {
1700	if (transport->dst)
1701	sctp_transport_dst_confirm(t: transport);
1702	}
1703	}
1704
1705	list_splice(list: &tlist, head: 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	transport: chunk->transport,
1741	count_of_newacks, tsn)) {
1742	chunk->tsn_missing_report++;
1743
1744	pr_debug("%s: tsn:0x%x missing counter:%d\n",
1745	__func__, tsn, chunk->tsn_missing_report);
1746	}
1747	}
1748	/*
1749	* M4) If any DATA chunk is found to have a
1750	* 'TSN.Missing.Report'
1751	* value larger than or equal to 3, mark that chunk for
1752	* retransmission and start the fast retransmit procedure.
1753	*/
1754
1755	if (chunk->tsn_missing_report >= 3) {
1756	chunk->fast_retransmit = SCTP_NEED_FRTX;
1757	do_fast_retransmit = 1;
1758	}
1759	}
1760
1761	if (transport) {
1762	if (do_fast_retransmit)
1763	sctp_retransmit(q, transport, reason: SCTP_RTXR_FAST_RTX);
1764
1765	pr_debug("%s: transport:%p, cwnd:%d, ssthresh:%d, "
1766	"flight_size:%d, pba:%d\n", __func__, transport,
1767	transport->cwnd, transport->ssthresh,
1768	transport->flight_size, transport->partial_bytes_acked);
1769	}
1770	}
1771
1772	/* Is the given TSN acked by this packet? */
1773	static int sctp_acked(struct sctp_sackhdr *sack, __u32 tsn)
1774	{
1775	__u32 ctsn = ntohl(sack->cum_tsn_ack);
1776	union sctp_sack_variable *frags;
1777	__u16 tsn_offset, blocks;
1778	int i;
1779
1780	if (TSN_lte(tsn, ctsn))
1781	goto pass;
1782
1783	/* 3.3.4 Selective Acknowledgment (SACK) (3):
1784	*
1785	* Gap Ack Blocks:
1786	* These fields contain the Gap Ack Blocks. They are repeated
1787	* for each Gap Ack Block up to the number of Gap Ack Blocks
1788	* defined in the Number of Gap Ack Blocks field. All DATA
1789	* chunks with TSNs greater than or equal to (Cumulative TSN
1790	* Ack + Gap Ack Block Start) and less than or equal to
1791	* (Cumulative TSN Ack + Gap Ack Block End) of each Gap Ack
1792	* Block are assumed to have been received correctly.
1793	*/
1794
1795	frags = (union sctp_sack_variable *)(sack + 1);
1796	blocks = ntohs(sack->num_gap_ack_blocks);
1797	tsn_offset = tsn - ctsn;
1798	for (i = 0; i < blocks; ++i) {
1799	if (tsn_offset >= ntohs(frags[i].gab.start) &&
1800	tsn_offset <= ntohs(frags[i].gab.end))
1801	goto pass;
1802	}
1803
1804	return 0;
1805	pass:
1806	return 1;
1807	}
1808
1809	static inline int sctp_get_skip_pos(struct sctp_fwdtsn_skip *skiplist,
1810	int nskips, __be16 stream)
1811	{
1812	int i;
1813
1814	for (i = 0; i < nskips; i++) {
1815	if (skiplist[i].stream == stream)
1816	return i;
1817	}
1818	return i;
1819	}
1820
1821	/* Create and add a fwdtsn chunk to the outq's control queue if needed. */
1822	void sctp_generate_fwdtsn(struct sctp_outq *q, __u32 ctsn)
1823	{
1824	struct sctp_association *asoc = q->asoc;
1825	struct sctp_chunk *ftsn_chunk = NULL;
1826	struct sctp_fwdtsn_skip ftsn_skip_arr[10];
1827	int nskips = 0;
1828	int skip_pos = 0;
1829	__u32 tsn;
1830	struct sctp_chunk *chunk;
1831	struct list_head *lchunk, *temp;
1832
1833	if (!asoc->peer.prsctp_capable)
1834	return;
1835
1836	/* PR-SCTP C1) Let SackCumAck be the Cumulative TSN ACK carried in the
1837	* received SACK.
1838	*
1839	* If (Advanced.Peer.Ack.Point < SackCumAck), then update
1840	* Advanced.Peer.Ack.Point to be equal to SackCumAck.
1841	*/
1842	if (TSN_lt(asoc->adv_peer_ack_point, ctsn))
1843	asoc->adv_peer_ack_point = ctsn;
1844
1845	/* PR-SCTP C2) Try to further advance the "Advanced.Peer.Ack.Point"
1846	* locally, that is, to move "Advanced.Peer.Ack.Point" up as long as
1847	* the chunk next in the out-queue space is marked as "abandoned" as
1848	* shown in the following example:
1849	*
1850	* Assuming that a SACK arrived with the Cumulative TSN ACK 102
1851	* and the Advanced.Peer.Ack.Point is updated to this value:
1852	*
1853	* out-queue at the end of ==> out-queue after Adv.Ack.Point
1854	* normal SACK processing local advancement
1855	* ... ...
1856	* Adv.Ack.Pt-> 102 acked 102 acked
1857	* 103 abandoned 103 abandoned
1858	* 104 abandoned Adv.Ack.P-> 104 abandoned
1859	* 105 105
1860	* 106 acked 106 acked
1861	* ... ...
1862	*
1863	* In this example, the data sender successfully advanced the
1864	* "Advanced.Peer.Ack.Point" from 102 to 104 locally.
1865	*/
1866	list_for_each_safe(lchunk, temp, &q->abandoned) {
1867	chunk = list_entry(lchunk, struct sctp_chunk,
1868	transmitted_list);
1869	tsn = ntohl(chunk->subh.data_hdr->tsn);
1870
1871	/* Remove any chunks in the abandoned queue that are acked by
1872	* the ctsn.
1873	*/
1874	if (TSN_lte(tsn, ctsn)) {
1875	list_del_init(entry: lchunk);
1876	sctp_chunk_free(chunk);
1877	} else {
1878	if (TSN_lte(tsn, asoc->adv_peer_ack_point+1)) {
1879	asoc->adv_peer_ack_point = tsn;
1880	if (chunk->chunk_hdr->flags &
1881	SCTP_DATA_UNORDERED)
1882	continue;
1883	skip_pos = sctp_get_skip_pos(skiplist: &ftsn_skip_arr[0],
1884	nskips,
1885	stream: chunk->subh.data_hdr->stream);
1886	ftsn_skip_arr[skip_pos].stream =
1887	chunk->subh.data_hdr->stream;
1888	ftsn_skip_arr[skip_pos].ssn =
1889	chunk->subh.data_hdr->ssn;
1890	if (skip_pos == nskips)
1891	nskips++;
1892	if (nskips == 10)
1893	break;
1894	} else
1895	break;
1896	}
1897	}
1898
1899	/* PR-SCTP C3) If, after step C1 and C2, the "Advanced.Peer.Ack.Point"
1900	* is greater than the Cumulative TSN ACK carried in the received
1901	* SACK, the data sender MUST send the data receiver a FORWARD TSN
1902	* chunk containing the latest value of the
1903	* "Advanced.Peer.Ack.Point".
1904	*
1905	* C4) For each "abandoned" TSN the sender of the FORWARD TSN SHOULD
1906	* list each stream and sequence number in the forwarded TSN. This
1907	* information will enable the receiver to easily find any
1908	* stranded TSN's waiting on stream reorder queues. Each stream
1909	* SHOULD only be reported once; this means that if multiple
1910	* abandoned messages occur in the same stream then only the
1911	* highest abandoned stream sequence number is reported. If the
1912	* total size of the FORWARD TSN does NOT fit in a single MTU then
1913	* the sender of the FORWARD TSN SHOULD lower the
1914	* Advanced.Peer.Ack.Point to the last TSN that will fit in a
1915	* single MTU.
1916	*/
1917	if (asoc->adv_peer_ack_point > ctsn)
1918	ftsn_chunk = sctp_make_fwdtsn(asoc, new_cum_tsn: asoc->adv_peer_ack_point,
1919	nstreams: nskips, skiplist: &ftsn_skip_arr[0]);
1920
1921	if (ftsn_chunk) {
1922	list_add_tail(new: &ftsn_chunk->list, head: &q->control_chunk_list);
1923	SCTP_INC_STATS(asoc->base.net, SCTP_MIB_OUTCTRLCHUNKS);
1924	}
1925	}
1926