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.  */
  42static int sctp_acked(struct sctp_sackhdr *sack, __u32 tsn);
  43static 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
  50static 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
  56static void sctp_outq_flush(struct sctp_outq *q, int rtx_timeout, gfp_t gfp);
  57
  58/* Add data to the front of the queue. */
  59static 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(&ch->list, &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(&ch->stream_list, &oute->outq);
  71}
  72
  73/* Take data from the front of the queue. */
  74static 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. */
  80static 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(&ch->list, &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(&ch->stream_list, &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 */
 100static 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 */
 116static 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 */
 132static 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 */
 153static 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 */
 175static 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 */
 191void 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(&q->out_chunk_list);
 197	INIT_LIST_HEAD(&q->control_chunk_list);
 198	INIT_LIST_HEAD(&q->retransmit);
 199	INIT_LIST_HEAD(&q->sacked);
 200	INIT_LIST_HEAD(&q->abandoned);
 201	sctp_sched_set_sched(asoc, sctp_sk(asoc->base.sk)->default_ss);
 202}
 203
 204/* Free the outqueue structure and any related pending chunks.
 205 */
 206static 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(&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, 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(lchunk);
 227		chunk = list_entry(lchunk, struct sctp_chunk,
 228				   transmitted_list);
 229		sctp_chunk_fail(chunk, 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(lchunk);
 236		chunk = list_entry(lchunk, struct sctp_chunk,
 237				   transmitted_list);
 238		sctp_chunk_fail(chunk, 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(lchunk);
 245		chunk = list_entry(lchunk, struct sctp_chunk,
 246				   transmitted_list);
 247		sctp_chunk_fail(chunk, 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, chunk);
 254
 255		/* Mark as send failure. */
 256		sctp_chunk_fail(chunk, 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(&chunk->list);
 263		sctp_chunk_free(chunk);
 264	}
 265}
 266
 267void sctp_outq_teardown(struct sctp_outq *q)
 268{
 269	__sctp_outq_teardown(q);
 270	sctp_outq_init(q->asoc, q);
 271}
 272
 273/* Free the outqueue structure and any related pending chunks.  */
 274void 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.  */
 281void 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, 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(&chunk->list, &q->control_chunk_list);
 309		SCTP_INC_STATS(net, SCTP_MIB_OUTCTRLCHUNKS);
 310	}
 311
 312	if (!q->cork)
 313		sctp_outq_flush(q, 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 */
 319static 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, pos->prev);
 334			done = 1;
 335			break;
 336		}
 337	}
 338	if (!done)
 339		list_add_tail(new, head);
 340}
 341
 342static 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(&chk->transmitted_list);
 358		sctp_insert_list(&asoc->outqueue.abandoned,
 359				 &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(chk);
 371			asoc->outqueue.outstanding_bytes -= sctp_data_size(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
 382static 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
 388	q->sched->unsched_all(&asoc->stream);
 389
 390	list_for_each_entry_safe(chk, temp, &q->out_chunk_list, list) {
 391		if (!chk->msg->abandoned &&
 392		    (!(chk->chunk_hdr->flags & SCTP_DATA_FIRST_FRAG) ||
 393		     !SCTP_PR_PRIO_ENABLED(chk->sinfo.sinfo_flags) ||
 394		     chk->sinfo.sinfo_timetolive <= sinfo->sinfo_timetolive))
 395			continue;
 396
 397		chk->msg->abandoned = 1;
 398		sctp_sched_dequeue_common(q, chk);
 399		asoc->sent_cnt_removable--;
 400		asoc->abandoned_unsent[SCTP_PR_INDEX(PRIO)]++;
 401		if (chk->sinfo.sinfo_stream < asoc->stream.outcnt) {
 402			struct sctp_stream_out *streamout =
 403				SCTP_SO(&asoc->stream, chk->sinfo.sinfo_stream);
 404
 405			streamout->ext->abandoned_unsent[SCTP_PR_INDEX(PRIO)]++;
 406		}
 407
 408		msg_len -= chk->skb->truesize + sizeof(struct sctp_chunk);
 409		sctp_chunk_free(chk);
 410		if (msg_len <= 0)
 411			break;
 412	}
 413
 414	q->sched->sched_all(&asoc->stream);
 415
 416	return msg_len;
 417}
 418
 419/* Abandon the chunks according their priorities */
 420void sctp_prsctp_prune(struct sctp_association *asoc,
 421		       struct sctp_sndrcvinfo *sinfo, int msg_len)
 422{
 423	struct sctp_transport *transport;
 424
 425	if (!asoc->peer.prsctp_capable || !asoc->sent_cnt_removable)
 426		return;
 427
 428	msg_len = sctp_prsctp_prune_sent(asoc, sinfo,
 429					 &asoc->outqueue.retransmit,
 430					 msg_len);
 431	if (msg_len <= 0)
 432		return;
 433
 434	list_for_each_entry(transport, &asoc->peer.transport_addr_list,
 435			    transports) {
 436		msg_len = sctp_prsctp_prune_sent(asoc, sinfo,
 437						 &transport->transmitted,
 438						 msg_len);
 439		if (msg_len <= 0)
 440			return;
 441	}
 442
 443	sctp_prsctp_prune_unsent(asoc, sinfo, msg_len);
 444}
 445
 446/* Mark all the eligible packets on a transport for retransmission.  */
 447void sctp_retransmit_mark(struct sctp_outq *q,
 448			  struct sctp_transport *transport,
 449			  __u8 reason)
 450{
 451	struct list_head *lchunk, *ltemp;
 452	struct sctp_chunk *chunk;
 453
 454	/* Walk through the specified transmitted queue.  */
 455	list_for_each_safe(lchunk, ltemp, &transport->transmitted) {
 456		chunk = list_entry(lchunk, struct sctp_chunk,
 457				   transmitted_list);
 458
 459		/* If the chunk is abandoned, move it to abandoned list. */
 460		if (sctp_chunk_abandoned(chunk)) {
 461			list_del_init(lchunk);
 462			sctp_insert_list(&q->abandoned, lchunk);
 463
 464			/* If this chunk has not been previousely acked,
 465			 * stop considering it 'outstanding'.  Our peer
 466			 * will most likely never see it since it will
 467			 * not be retransmitted
 468			 */
 469			if (!chunk->tsn_gap_acked) {
 470				if (chunk->transport)
 471					chunk->transport->flight_size -=
 472							sctp_data_size(chunk);
 473				q->outstanding_bytes -= sctp_data_size(chunk);
 474				q->asoc->peer.rwnd += sctp_data_size(chunk);
 475			}
 476			continue;
 477		}
 478
 479		/* If we are doing  retransmission due to a timeout or pmtu
 480		 * discovery, only the  chunks that are not yet acked should
 481		 * be added to the retransmit queue.
 482		 */
 483		if ((reason == SCTP_RTXR_FAST_RTX  &&
 484			    (chunk->fast_retransmit == SCTP_NEED_FRTX)) ||
 485		    (reason != SCTP_RTXR_FAST_RTX  && !chunk->tsn_gap_acked)) {
 486			/* RFC 2960 6.2.1 Processing a Received SACK
 487			 *
 488			 * C) Any time a DATA chunk is marked for
 489			 * retransmission (via either T3-rtx timer expiration
 490			 * (Section 6.3.3) or via fast retransmit
 491			 * (Section 7.2.4)), add the data size of those
 492			 * chunks to the rwnd.
 493			 */
 494			q->asoc->peer.rwnd += sctp_data_size(chunk);
 495			q->outstanding_bytes -= sctp_data_size(chunk);
 496			if (chunk->transport)
 497				transport->flight_size -= sctp_data_size(chunk);
 498
 499			/* sctpimpguide-05 Section 2.8.2
 500			 * M5) If a T3-rtx timer expires, the
 501			 * 'TSN.Missing.Report' of all affected TSNs is set
 502			 * to 0.
 503			 */
 504			chunk->tsn_missing_report = 0;
 505
 506			/* If a chunk that is being used for RTT measurement
 507			 * has to be retransmitted, we cannot use this chunk
 508			 * anymore for RTT measurements. Reset rto_pending so
 509			 * that a new RTT measurement is started when a new
 510			 * data chunk is sent.
 511			 */
 512			if (chunk->rtt_in_progress) {
 513				chunk->rtt_in_progress = 0;
 514				transport->rto_pending = 0;
 515			}
 516
 517			/* Move the chunk to the retransmit queue. The chunks
 518			 * on the retransmit queue are always kept in order.
 519			 */
 520			list_del_init(lchunk);
 521			sctp_insert_list(&q->retransmit, lchunk);
 522		}
 523	}
 524
 525	pr_debug("%s: transport:%p, reason:%d, cwnd:%d, ssthresh:%d, "
 526		 "flight_size:%d, pba:%d\n", __func__, transport, reason,
 527		 transport->cwnd, transport->ssthresh, transport->flight_size,
 528		 transport->partial_bytes_acked);
 529}
 530
 531/* Mark all the eligible packets on a transport for retransmission and force
 532 * one packet out.
 533 */
 534void sctp_retransmit(struct sctp_outq *q, struct sctp_transport *transport,
 535		     enum sctp_retransmit_reason reason)
 536{
 537	struct net *net = q->asoc->base.net;
 538
 539	switch (reason) {
 540	case SCTP_RTXR_T3_RTX:
 541		SCTP_INC_STATS(net, SCTP_MIB_T3_RETRANSMITS);
 542		sctp_transport_lower_cwnd(transport, SCTP_LOWER_CWND_T3_RTX);
 543		/* Update the retran path if the T3-rtx timer has expired for
 544		 * the current retran path.
 545		 */
 546		if (transport == transport->asoc->peer.retran_path)
 547			sctp_assoc_update_retran_path(transport->asoc);
 548		transport->asoc->rtx_data_chunks +=
 549			transport->asoc->unack_data;
 550		break;
 551	case SCTP_RTXR_FAST_RTX:
 552		SCTP_INC_STATS(net, SCTP_MIB_FAST_RETRANSMITS);
 553		sctp_transport_lower_cwnd(transport, SCTP_LOWER_CWND_FAST_RTX);
 554		q->fast_rtx = 1;
 555		break;
 556	case SCTP_RTXR_PMTUD:
 557		SCTP_INC_STATS(net, SCTP_MIB_PMTUD_RETRANSMITS);
 558		break;
 559	case SCTP_RTXR_T1_RTX:
 560		SCTP_INC_STATS(net, SCTP_MIB_T1_RETRANSMITS);
 561		transport->asoc->init_retries++;
 562		break;
 563	default:
 564		BUG();
 565	}
 566
 567	sctp_retransmit_mark(q, transport, reason);
 568
 569	/* PR-SCTP A5) Any time the T3-rtx timer expires, on any destination,
 570	 * the sender SHOULD try to advance the "Advanced.Peer.Ack.Point" by
 571	 * following the procedures outlined in C1 - C5.
 572	 */
 573	if (reason == SCTP_RTXR_T3_RTX)
 574		q->asoc->stream.si->generate_ftsn(q, q->asoc->ctsn_ack_point);
 575
 576	/* Flush the queues only on timeout, since fast_rtx is only
 577	 * triggered during sack processing and the queue
 578	 * will be flushed at the end.
 579	 */
 580	if (reason != SCTP_RTXR_FAST_RTX)
 581		sctp_outq_flush(q, /* rtx_timeout */ 1, GFP_ATOMIC);
 582}
 583
 584/*
 585 * Transmit DATA chunks on the retransmit queue.  Upon return from
 586 * __sctp_outq_flush_rtx() the packet 'pkt' may contain chunks which
 587 * need to be transmitted by the caller.
 588 * We assume that pkt->transport has already been set.
 589 *
 590 * The return value is a normal kernel error return value.
 591 */
 592static int __sctp_outq_flush_rtx(struct sctp_outq *q, struct sctp_packet *pkt,
 593				 int rtx_timeout, int *start_timer, gfp_t gfp)
 594{
 595	struct sctp_transport *transport = pkt->transport;
 596	struct sctp_chunk *chunk, *chunk1;
 597	struct list_head *lqueue;
 598	enum sctp_xmit status;
 599	int error = 0;
 600	int timer = 0;
 601	int done = 0;
 602	int fast_rtx;
 603
 604	lqueue = &q->retransmit;
 605	fast_rtx = q->fast_rtx;
 606
 607	/* This loop handles time-out retransmissions, fast retransmissions,
 608	 * and retransmissions due to opening of whindow.
 609	 *
 610	 * RFC 2960 6.3.3 Handle T3-rtx Expiration
 611	 *
 612	 * E3) Determine how many of the earliest (i.e., lowest TSN)
 613	 * outstanding DATA chunks for the address for which the
 614	 * T3-rtx has expired will fit into a single packet, subject
 615	 * to the MTU constraint for the path corresponding to the
 616	 * destination transport address to which the retransmission
 617	 * is being sent (this may be different from the address for
 618	 * which the timer expires [see Section 6.4]). Call this value
 619	 * K. Bundle and retransmit those K DATA chunks in a single
 620	 * packet to the destination endpoint.
 621	 *
 622	 * [Just to be painfully clear, if we are retransmitting
 623	 * because a timeout just happened, we should send only ONE
 624	 * packet of retransmitted data.]
 625	 *
 626	 * For fast retransmissions we also send only ONE packet.  However,
 627	 * if we are just flushing the queue due to open window, we'll
 628	 * try to send as much as possible.
 629	 */
 630	list_for_each_entry_safe(chunk, chunk1, lqueue, transmitted_list) {
 631		/* If the chunk is abandoned, move it to abandoned list. */
 632		if (sctp_chunk_abandoned(chunk)) {
 633			list_del_init(&chunk->transmitted_list);
 634			sctp_insert_list(&q->abandoned,
 635					 &chunk->transmitted_list);
 636			continue;
 637		}
 638
 639		/* Make sure that Gap Acked TSNs are not retransmitted.  A
 640		 * simple approach is just to move such TSNs out of the
 641		 * way and into a 'transmitted' queue and skip to the
 642		 * next chunk.
 643		 */
 644		if (chunk->tsn_gap_acked) {
 645			list_move_tail(&chunk->transmitted_list,
 646				       &transport->transmitted);
 647			continue;
 648		}
 649
 650		/* If we are doing fast retransmit, ignore non-fast_rtransmit
 651		 * chunks
 652		 */
 653		if (fast_rtx && !chunk->fast_retransmit)
 654			continue;
 655
 656redo:
 657		/* Attempt to append this chunk to the packet. */
 658		status = sctp_packet_append_chunk(pkt, chunk);
 659
 660		switch (status) {
 661		case SCTP_XMIT_PMTU_FULL:
 662			if (!pkt->has_data && !pkt->has_cookie_echo) {
 663				/* If this packet did not contain DATA then
 664				 * retransmission did not happen, so do it
 665				 * again.  We'll ignore the error here since
 666				 * control chunks are already freed so there
 667				 * is nothing we can do.
 668				 */
 669				sctp_packet_transmit(pkt, gfp);
 670				goto redo;
 671			}
 672
 673			/* Send this packet.  */
 674			error = sctp_packet_transmit(pkt, gfp);
 675
 676			/* If we are retransmitting, we should only
 677			 * send a single packet.
 678			 * Otherwise, try appending this chunk again.
 679			 */
 680			if (rtx_timeout || fast_rtx)
 681				done = 1;
 682			else
 683				goto redo;
 684
 685			/* Bundle next chunk in the next round.  */
 686			break;
 687
 688		case SCTP_XMIT_RWND_FULL:
 689			/* Send this packet. */
 690			error = sctp_packet_transmit(pkt, gfp);
 691
 692			/* Stop sending DATA as there is no more room
 693			 * at the receiver.
 694			 */
 695			done = 1;
 696			break;
 697
 698		case SCTP_XMIT_DELAY:
 699			/* Send this packet. */
 700			error = sctp_packet_transmit(pkt, gfp);
 701
 702			/* Stop sending DATA because of nagle delay. */
 703			done = 1;
 704			break;
 705
 706		default:
 707			/* The append was successful, so add this chunk to
 708			 * the transmitted list.
 709			 */
 710			list_move_tail(&chunk->transmitted_list,
 711				       &transport->transmitted);
 712
 713			/* Mark the chunk as ineligible for fast retransmit
 714			 * after it is retransmitted.
 715			 */
 716			if (chunk->fast_retransmit == SCTP_NEED_FRTX)
 717				chunk->fast_retransmit = SCTP_DONT_FRTX;
 718
 719			q->asoc->stats.rtxchunks++;
 720			break;
 721		}
 722
 723		/* Set the timer if there were no errors */
 724		if (!error && !timer)
 725			timer = 1;
 726
 727		if (done)
 728			break;
 729	}
 730
 731	/* If we are here due to a retransmit timeout or a fast
 732	 * retransmit and if there are any chunks left in the retransmit
 733	 * queue that could not fit in the PMTU sized packet, they need
 734	 * to be marked as ineligible for a subsequent fast retransmit.
 735	 */
 736	if (rtx_timeout || fast_rtx) {
 737		list_for_each_entry(chunk1, lqueue, transmitted_list) {
 738			if (chunk1->fast_retransmit == SCTP_NEED_FRTX)
 739				chunk1->fast_retransmit = SCTP_DONT_FRTX;
 740		}
 741	}
 742
 743	*start_timer = timer;
 744
 745	/* Clear fast retransmit hint */
 746	if (fast_rtx)
 747		q->fast_rtx = 0;
 748
 749	return error;
 750}
 751
 752/* Cork the outqueue so queued chunks are really queued. */
 753void sctp_outq_uncork(struct sctp_outq *q, gfp_t gfp)
 754{
 755	if (q->cork)
 756		q->cork = 0;
 757
 758	sctp_outq_flush(q, 0, gfp);
 759}
 760
 761static int sctp_packet_singleton(struct sctp_transport *transport,
 762				 struct sctp_chunk *chunk, gfp_t gfp)
 763{
 764	const struct sctp_association *asoc = transport->asoc;
 765	const __u16 sport = asoc->base.bind_addr.port;
 766	const __u16 dport = asoc->peer.port;
 767	const __u32 vtag = asoc->peer.i.init_tag;
 768	struct sctp_packet singleton;
 769
 770	sctp_packet_init(&singleton, transport, sport, dport);
 771	sctp_packet_config(&singleton, vtag, 0);
 772	if (sctp_packet_append_chunk(&singleton, chunk) != SCTP_XMIT_OK) {
 773		list_del_init(&chunk->list);
 774		sctp_chunk_free(chunk);
 775		return -ENOMEM;
 776	}
 777	return sctp_packet_transmit(&singleton, gfp);
 778}
 779
 780/* Struct to hold the context during sctp outq flush */
 781struct sctp_flush_ctx {
 782	struct sctp_outq *q;
 783	/* Current transport being used. It's NOT the same as curr active one */
 784	struct sctp_transport *transport;
 785	/* These transports have chunks to send. */
 786	struct list_head transport_list;
 787	struct sctp_association *asoc;
 788	/* Packet on the current transport above */
 789	struct sctp_packet *packet;
 790	gfp_t gfp;
 791};
 792
 793/* transport: current transport */
 794static void sctp_outq_select_transport(struct sctp_flush_ctx *ctx,
 795				       struct sctp_chunk *chunk)
 796{
 797	struct sctp_transport *new_transport = chunk->transport;
 798
 799	if (!new_transport) {
 800		if (!sctp_chunk_is_data(chunk)) {
 801			/* If we have a prior transport pointer, see if
 802			 * the destination address of the chunk
 803			 * matches the destination address of the
 804			 * current transport.  If not a match, then
 805			 * try to look up the transport with a given
 806			 * destination address.  We do this because
 807			 * after processing ASCONFs, we may have new
 808			 * transports created.
 809			 */
 810			if (ctx->transport && sctp_cmp_addr_exact(&chunk->dest,
 811							&ctx->transport->ipaddr))
 812				new_transport = ctx->transport;
 813			else
 814				new_transport = sctp_assoc_lookup_paddr(ctx->asoc,
 815								  &chunk->dest);
 816		}
 817
 818		/* if we still don't have a new transport, then
 819		 * use the current active path.
 820		 */
 821		if (!new_transport)
 822			new_transport = ctx->asoc->peer.active_path;
 823	} else {
 824		__u8 type;
 825
 826		switch (new_transport->state) {
 827		case SCTP_INACTIVE:
 828		case SCTP_UNCONFIRMED:
 829		case SCTP_PF:
 830			/* If the chunk is Heartbeat or Heartbeat Ack,
 831			 * send it to chunk->transport, even if it's
 832			 * inactive.
 833			 *
 834			 * 3.3.6 Heartbeat Acknowledgement:
 835			 * ...
 836			 * A HEARTBEAT ACK is always sent to the source IP
 837			 * address of the IP datagram containing the
 838			 * HEARTBEAT chunk to which this ack is responding.
 839			 * ...
 840			 *
 841			 * ASCONF_ACKs also must be sent to the source.
 842			 */
 843			type = chunk->chunk_hdr->type;
 844			if (type != SCTP_CID_HEARTBEAT &&
 845			    type != SCTP_CID_HEARTBEAT_ACK &&
 846			    type != SCTP_CID_ASCONF_ACK)
 847				new_transport = ctx->asoc->peer.active_path;
 848			break;
 849		default:
 850			break;
 851		}
 852	}
 853
 854	/* Are we switching transports? Take care of transport locks. */
 855	if (new_transport != ctx->transport) {
 856		ctx->transport = new_transport;
 857		ctx->packet = &ctx->transport->packet;
 858
 859		if (list_empty(&ctx->transport->send_ready))
 860			list_add_tail(&ctx->transport->send_ready,
 861				      &ctx->transport_list);
 862
 863		sctp_packet_config(ctx->packet,
 864				   ctx->asoc->peer.i.init_tag,
 865				   ctx->asoc->peer.ecn_capable);
 866		/* We've switched transports, so apply the
 867		 * Burst limit to the new transport.
 868		 */
 869		sctp_transport_burst_limited(ctx->transport);
 870	}
 871}
 872
 873static void sctp_outq_flush_ctrl(struct sctp_flush_ctx *ctx)
 874{
 875	struct sctp_chunk *chunk, *tmp;
 876	enum sctp_xmit status;
 877	int one_packet, error;
 878
 879	list_for_each_entry_safe(chunk, tmp, &ctx->q->control_chunk_list, list) {
 880		one_packet = 0;
 881
 882		/* RFC 5061, 5.3
 883		 * F1) This means that until such time as the ASCONF
 884		 * containing the add is acknowledged, the sender MUST
 885		 * NOT use the new IP address as a source for ANY SCTP
 886		 * packet except on carrying an ASCONF Chunk.
 887		 */
 888		if (ctx->asoc->src_out_of_asoc_ok &&
 889		    chunk->chunk_hdr->type != SCTP_CID_ASCONF)
 890			continue;
 891
 892		list_del_init(&chunk->list);
 893
 894		/* Pick the right transport to use. Should always be true for
 895		 * the first chunk as we don't have a transport by then.
 896		 */
 897		sctp_outq_select_transport(ctx, chunk);
 898
 899		switch (chunk->chunk_hdr->type) {
 900		/* 6.10 Bundling
 901		 *   ...
 902		 *   An endpoint MUST NOT bundle INIT, INIT ACK or SHUTDOWN
 903		 *   COMPLETE with any other chunks.  [Send them immediately.]
 904		 */
 905		case SCTP_CID_INIT:
 906		case SCTP_CID_INIT_ACK:
 907		case SCTP_CID_SHUTDOWN_COMPLETE:
 908			error = sctp_packet_singleton(ctx->transport, chunk,
 909						      ctx->gfp);
 910			if (error < 0) {
 911				ctx->asoc->base.sk->sk_err = -error;
 912				return;
 913			}
 914			break;
 915
 916		case SCTP_CID_ABORT:
 917			if (sctp_test_T_bit(chunk))
 918				ctx->packet->vtag = ctx->asoc->c.my_vtag;
 919			fallthrough;
 920
 921		/* The following chunks are "response" chunks, i.e.
 922		 * they are generated in response to something we
 923		 * received.  If we are sending these, then we can
 924		 * send only 1 packet containing these chunks.
 925		 */
 926		case SCTP_CID_HEARTBEAT_ACK:
 927		case SCTP_CID_SHUTDOWN_ACK:
 928		case SCTP_CID_COOKIE_ACK:
 929		case SCTP_CID_COOKIE_ECHO:
 930		case SCTP_CID_ERROR:
 931		case SCTP_CID_ECN_CWR:
 932		case SCTP_CID_ASCONF_ACK:
 933			one_packet = 1;
 934			fallthrough;
 935
 936		case SCTP_CID_HEARTBEAT:
 937			if (chunk->pmtu_probe) {
 938				sctp_packet_singleton(ctx->transport, chunk, ctx->gfp);
 939				break;
 940			}
 941			fallthrough;
 942		case SCTP_CID_SACK:
 
 943		case SCTP_CID_SHUTDOWN:
 944		case SCTP_CID_ECN_ECNE:
 945		case SCTP_CID_ASCONF:
 946		case SCTP_CID_FWD_TSN:
 947		case SCTP_CID_I_FWD_TSN:
 948		case SCTP_CID_RECONF:
 949			status = sctp_packet_transmit_chunk(ctx->packet, chunk,
 950							    one_packet, ctx->gfp);
 951			if (status != SCTP_XMIT_OK) {
 952				/* put the chunk back */
 953				list_add(&chunk->list, &ctx->q->control_chunk_list);
 954				break;
 955			}
 956
 957			ctx->asoc->stats.octrlchunks++;
 958			/* PR-SCTP C5) If a FORWARD TSN is sent, the
 959			 * sender MUST assure that at least one T3-rtx
 960			 * timer is running.
 961			 */
 962			if (chunk->chunk_hdr->type == SCTP_CID_FWD_TSN ||
 963			    chunk->chunk_hdr->type == SCTP_CID_I_FWD_TSN) {
 964				sctp_transport_reset_t3_rtx(ctx->transport);
 965				ctx->transport->last_time_sent = jiffies;
 966			}
 967
 968			if (chunk == ctx->asoc->strreset_chunk)
 969				sctp_transport_reset_reconf_timer(ctx->transport);
 970
 971			break;
 972
 973		default:
 974			/* We built a chunk with an illegal type! */
 975			BUG();
 976		}
 977	}
 978}
 979
 980/* Returns false if new data shouldn't be sent */
 981static bool sctp_outq_flush_rtx(struct sctp_flush_ctx *ctx,
 982				int rtx_timeout)
 983{
 984	int error, start_timer = 0;
 985
 986	if (ctx->asoc->peer.retran_path->state == SCTP_UNCONFIRMED)
 987		return false;
 988
 989	if (ctx->transport != ctx->asoc->peer.retran_path) {
 990		/* Switch transports & prepare the packet.  */
 991		ctx->transport = ctx->asoc->peer.retran_path;
 992		ctx->packet = &ctx->transport->packet;
 993
 994		if (list_empty(&ctx->transport->send_ready))
 995			list_add_tail(&ctx->transport->send_ready,
 996				      &ctx->transport_list);
 997
 998		sctp_packet_config(ctx->packet, ctx->asoc->peer.i.init_tag,
 999				   ctx->asoc->peer.ecn_capable);
1000	}
1001
1002	error = __sctp_outq_flush_rtx(ctx->q, ctx->packet, rtx_timeout,
1003				      &start_timer, ctx->gfp);
1004	if (error < 0)
1005		ctx->asoc->base.sk->sk_err = -error;
1006
1007	if (start_timer) {
1008		sctp_transport_reset_t3_rtx(ctx->transport);
1009		ctx->transport->last_time_sent = jiffies;
1010	}
1011
1012	/* This can happen on COOKIE-ECHO resend.  Only
1013	 * one chunk can get bundled with a COOKIE-ECHO.
1014	 */
1015	if (ctx->packet->has_cookie_echo)
1016		return false;
1017
1018	/* Don't send new data if there is still data
1019	 * waiting to retransmit.
1020	 */
1021	if (!list_empty(&ctx->q->retransmit))
1022		return false;
1023
1024	return true;
1025}
1026
1027static void sctp_outq_flush_data(struct sctp_flush_ctx *ctx,
1028				 int rtx_timeout)
1029{
1030	struct sctp_chunk *chunk;
1031	enum sctp_xmit status;
1032
1033	/* Is it OK to send data chunks?  */
1034	switch (ctx->asoc->state) {
1035	case SCTP_STATE_COOKIE_ECHOED:
1036		/* Only allow bundling when this packet has a COOKIE-ECHO
1037		 * chunk.
1038		 */
1039		if (!ctx->packet || !ctx->packet->has_cookie_echo)
1040			return;
1041
1042		fallthrough;
1043	case SCTP_STATE_ESTABLISHED:
1044	case SCTP_STATE_SHUTDOWN_PENDING:
1045	case SCTP_STATE_SHUTDOWN_RECEIVED:
1046		break;
1047
1048	default:
1049		/* Do nothing. */
1050		return;
1051	}
1052
1053	/* RFC 2960 6.1  Transmission of DATA Chunks
1054	 *
1055	 * C) When the time comes for the sender to transmit,
1056	 * before sending new DATA chunks, the sender MUST
1057	 * first transmit any outstanding DATA chunks which
1058	 * are marked for retransmission (limited by the
1059	 * current cwnd).
1060	 */
1061	if (!list_empty(&ctx->q->retransmit) &&
1062	    !sctp_outq_flush_rtx(ctx, rtx_timeout))
1063		return;
1064
1065	/* Apply Max.Burst limitation to the current transport in
1066	 * case it will be used for new data.  We are going to
1067	 * rest it before we return, but we want to apply the limit
1068	 * to the currently queued data.
1069	 */
1070	if (ctx->transport)
1071		sctp_transport_burst_limited(ctx->transport);
1072
1073	/* Finally, transmit new packets.  */
1074	while ((chunk = sctp_outq_dequeue_data(ctx->q)) != NULL) {
1075		__u32 sid = ntohs(chunk->subh.data_hdr->stream);
1076		__u8 stream_state = SCTP_SO(&ctx->asoc->stream, sid)->state;
1077
1078		/* Has this chunk expired? */
1079		if (sctp_chunk_abandoned(chunk)) {
1080			sctp_sched_dequeue_done(ctx->q, chunk);
1081			sctp_chunk_fail(chunk, 0);
1082			sctp_chunk_free(chunk);
1083			continue;
1084		}
1085
1086		if (stream_state == SCTP_STREAM_CLOSED) {
1087			sctp_outq_head_data(ctx->q, chunk);
1088			break;
1089		}
1090
1091		sctp_outq_select_transport(ctx, chunk);
1092
1093		pr_debug("%s: outq:%p, chunk:%p[%s], tx-tsn:0x%x skb->head:%p skb->users:%d\n",
1094			 __func__, ctx->q, chunk, chunk && chunk->chunk_hdr ?
1095			 sctp_cname(SCTP_ST_CHUNK(chunk->chunk_hdr->type)) :
1096			 "illegal chunk", ntohl(chunk->subh.data_hdr->tsn),
1097			 chunk->skb ? chunk->skb->head : NULL, chunk->skb ?
1098			 refcount_read(&chunk->skb->users) : -1);
1099
1100		/* Add the chunk to the packet.  */
1101		status = sctp_packet_transmit_chunk(ctx->packet, chunk, 0,
1102						    ctx->gfp);
1103		if (status != SCTP_XMIT_OK) {
1104			/* We could not append this chunk, so put
1105			 * the chunk back on the output queue.
1106			 */
1107			pr_debug("%s: could not transmit tsn:0x%x, status:%d\n",
1108				 __func__, ntohl(chunk->subh.data_hdr->tsn),
1109				 status);
1110
1111			sctp_outq_head_data(ctx->q, chunk);
1112			break;
1113		}
1114
1115		/* The sender is in the SHUTDOWN-PENDING state,
1116		 * The sender MAY set the I-bit in the DATA
1117		 * chunk header.
1118		 */
1119		if (ctx->asoc->state == SCTP_STATE_SHUTDOWN_PENDING)
1120			chunk->chunk_hdr->flags |= SCTP_DATA_SACK_IMM;
1121		if (chunk->chunk_hdr->flags & SCTP_DATA_UNORDERED)
1122			ctx->asoc->stats.ouodchunks++;
1123		else
1124			ctx->asoc->stats.oodchunks++;
1125
1126		/* Only now it's safe to consider this
1127		 * chunk as sent, sched-wise.
1128		 */
1129		sctp_sched_dequeue_done(ctx->q, chunk);
1130
1131		list_add_tail(&chunk->transmitted_list,
1132			      &ctx->transport->transmitted);
1133
1134		sctp_transport_reset_t3_rtx(ctx->transport);
1135		ctx->transport->last_time_sent = jiffies;
1136
1137		/* Only let one DATA chunk get bundled with a
1138		 * COOKIE-ECHO chunk.
1139		 */
1140		if (ctx->packet->has_cookie_echo)
1141			break;
1142	}
1143}
1144
1145static void sctp_outq_flush_transports(struct sctp_flush_ctx *ctx)
1146{
1147	struct sock *sk = ctx->asoc->base.sk;
1148	struct list_head *ltransport;
1149	struct sctp_packet *packet;
1150	struct sctp_transport *t;
1151	int error = 0;
1152
1153	while ((ltransport = sctp_list_dequeue(&ctx->transport_list)) != NULL) {
1154		t = list_entry(ltransport, struct sctp_transport, send_ready);
1155		packet = &t->packet;
1156		if (!sctp_packet_empty(packet)) {
1157			rcu_read_lock();
1158			if (t->dst && __sk_dst_get(sk) != t->dst) {
1159				dst_hold(t->dst);
1160				sk_setup_caps(sk, t->dst);
1161			}
1162			rcu_read_unlock();
1163			error = sctp_packet_transmit(packet, ctx->gfp);
1164			if (error < 0)
1165				ctx->q->asoc->base.sk->sk_err = -error;
1166		}
1167
1168		/* Clear the burst limited state, if any */
1169		sctp_transport_burst_reset(t);
1170	}
1171}
1172
1173/* Try to flush an outqueue.
1174 *
1175 * Description: Send everything in q which we legally can, subject to
1176 * congestion limitations.
1177 * * Note: This function can be called from multiple contexts so appropriate
1178 * locking concerns must be made.  Today we use the sock lock to protect
1179 * this function.
1180 */
1181
1182static void sctp_outq_flush(struct sctp_outq *q, int rtx_timeout, gfp_t gfp)
1183{
1184	struct sctp_flush_ctx ctx = {
1185		.q = q,
1186		.transport = NULL,
1187		.transport_list = LIST_HEAD_INIT(ctx.transport_list),
1188		.asoc = q->asoc,
1189		.packet = NULL,
1190		.gfp = gfp,
1191	};
1192
1193	/* 6.10 Bundling
1194	 *   ...
1195	 *   When bundling control chunks with DATA chunks, an
1196	 *   endpoint MUST place control chunks first in the outbound
1197	 *   SCTP packet.  The transmitter MUST transmit DATA chunks
1198	 *   within a SCTP packet in increasing order of TSN.
1199	 *   ...
1200	 */
1201
1202	sctp_outq_flush_ctrl(&ctx);
1203
1204	if (q->asoc->src_out_of_asoc_ok)
1205		goto sctp_flush_out;
1206
1207	sctp_outq_flush_data(&ctx, rtx_timeout);
1208
1209sctp_flush_out:
1210
1211	sctp_outq_flush_transports(&ctx);
1212}
1213
1214/* Update unack_data based on the incoming SACK chunk */
1215static void sctp_sack_update_unack_data(struct sctp_association *assoc,
1216					struct sctp_sackhdr *sack)
1217{
1218	union sctp_sack_variable *frags;
1219	__u16 unack_data;
1220	int i;
1221
1222	unack_data = assoc->next_tsn - assoc->ctsn_ack_point - 1;
1223
1224	frags = sack->variable;
1225	for (i = 0; i < ntohs(sack->num_gap_ack_blocks); i++) {
1226		unack_data -= ((ntohs(frags[i].gab.end) -
1227				ntohs(frags[i].gab.start) + 1));
1228	}
1229
1230	assoc->unack_data = unack_data;
1231}
1232
1233/* This is where we REALLY process a SACK.
1234 *
1235 * Process the SACK against the outqueue.  Mostly, this just frees
1236 * things off the transmitted queue.
1237 */
1238int sctp_outq_sack(struct sctp_outq *q, struct sctp_chunk *chunk)
1239{
1240	struct sctp_association *asoc = q->asoc;
1241	struct sctp_sackhdr *sack = chunk->subh.sack_hdr;
1242	struct sctp_transport *transport;
1243	struct sctp_chunk *tchunk = NULL;
1244	struct list_head *lchunk, *transport_list, *temp;
1245	union sctp_sack_variable *frags = sack->variable;
1246	__u32 sack_ctsn, ctsn, tsn;
1247	__u32 highest_tsn, highest_new_tsn;
1248	__u32 sack_a_rwnd;
1249	unsigned int outstanding;
1250	struct sctp_transport *primary = asoc->peer.primary_path;
1251	int count_of_newacks = 0;
1252	int gap_ack_blocks;
1253	u8 accum_moved = 0;
1254
1255	/* Grab the association's destination address list. */
1256	transport_list = &asoc->peer.transport_addr_list;
1257
1258	/* SCTP path tracepoint for congestion control debugging. */
1259	if (trace_sctp_probe_path_enabled()) {
1260		list_for_each_entry(transport, transport_list, transports)
1261			trace_sctp_probe_path(transport, asoc);
1262	}
1263
1264	sack_ctsn = ntohl(sack->cum_tsn_ack);
1265	gap_ack_blocks = ntohs(sack->num_gap_ack_blocks);
1266	asoc->stats.gapcnt += gap_ack_blocks;
1267	/*
1268	 * SFR-CACC algorithm:
1269	 * On receipt of a SACK the sender SHOULD execute the
1270	 * following statements.
1271	 *
1272	 * 1) If the cumulative ack in the SACK passes next tsn_at_change
1273	 * on the current primary, the CHANGEOVER_ACTIVE flag SHOULD be
1274	 * cleared. The CYCLING_CHANGEOVER flag SHOULD also be cleared for
1275	 * all destinations.
1276	 * 2) If the SACK contains gap acks and the flag CHANGEOVER_ACTIVE
1277	 * is set the receiver of the SACK MUST take the following actions:
1278	 *
1279	 * A) Initialize the cacc_saw_newack to 0 for all destination
1280	 * addresses.
1281	 *
1282	 * Only bother if changeover_active is set. Otherwise, this is
1283	 * totally suboptimal to do on every SACK.
1284	 */
1285	if (primary->cacc.changeover_active) {
1286		u8 clear_cycling = 0;
1287
1288		if (TSN_lte(primary->cacc.next_tsn_at_change, sack_ctsn)) {
1289			primary->cacc.changeover_active = 0;
1290			clear_cycling = 1;
1291		}
1292
1293		if (clear_cycling || gap_ack_blocks) {
1294			list_for_each_entry(transport, transport_list,
1295					transports) {
1296				if (clear_cycling)
1297					transport->cacc.cycling_changeover = 0;
1298				if (gap_ack_blocks)
1299					transport->cacc.cacc_saw_newack = 0;
1300			}
1301		}
1302	}
1303
1304	/* Get the highest TSN in the sack. */
1305	highest_tsn = sack_ctsn;
1306	if (gap_ack_blocks)
1307		highest_tsn += ntohs(frags[gap_ack_blocks - 1].gab.end);
1308
1309	if (TSN_lt(asoc->highest_sacked, highest_tsn))
1310		asoc->highest_sacked = highest_tsn;
1311
1312	highest_new_tsn = sack_ctsn;
1313
1314	/* Run through the retransmit queue.  Credit bytes received
1315	 * and free those chunks that we can.
1316	 */
1317	sctp_check_transmitted(q, &q->retransmit, NULL, NULL, sack, &highest_new_tsn);
1318
1319	/* Run through the transmitted queue.
1320	 * Credit bytes received and free those chunks which we can.
1321	 *
1322	 * This is a MASSIVE candidate for optimization.
1323	 */
1324	list_for_each_entry(transport, transport_list, transports) {
1325		sctp_check_transmitted(q, &transport->transmitted,
1326				       transport, &chunk->source, sack,
1327				       &highest_new_tsn);
1328		/*
1329		 * SFR-CACC algorithm:
1330		 * C) Let count_of_newacks be the number of
1331		 * destinations for which cacc_saw_newack is set.
1332		 */
1333		if (transport->cacc.cacc_saw_newack)
1334			count_of_newacks++;
1335	}
1336
1337	/* Move the Cumulative TSN Ack Point if appropriate.  */
1338	if (TSN_lt(asoc->ctsn_ack_point, sack_ctsn)) {
1339		asoc->ctsn_ack_point = sack_ctsn;
1340		accum_moved = 1;
1341	}
1342
1343	if (gap_ack_blocks) {
1344
1345		if (asoc->fast_recovery && accum_moved)
1346			highest_new_tsn = highest_tsn;
1347
1348		list_for_each_entry(transport, transport_list, transports)
1349			sctp_mark_missing(q, &transport->transmitted, transport,
1350					  highest_new_tsn, count_of_newacks);
1351	}
1352
1353	/* Update unack_data field in the assoc. */
1354	sctp_sack_update_unack_data(asoc, sack);
1355
1356	ctsn = asoc->ctsn_ack_point;
1357
1358	/* Throw away stuff rotting on the sack queue.  */
1359	list_for_each_safe(lchunk, temp, &q->sacked) {
1360		tchunk = list_entry(lchunk, struct sctp_chunk,
1361				    transmitted_list);
1362		tsn = ntohl(tchunk->subh.data_hdr->tsn);
1363		if (TSN_lte(tsn, ctsn)) {
1364			list_del_init(&tchunk->transmitted_list);
1365			if (asoc->peer.prsctp_capable &&
1366			    SCTP_PR_PRIO_ENABLED(chunk->sinfo.sinfo_flags))
1367				asoc->sent_cnt_removable--;
1368			sctp_chunk_free(tchunk);
1369		}
1370	}
1371
1372	/* ii) Set rwnd equal to the newly received a_rwnd minus the
1373	 *     number of bytes still outstanding after processing the
1374	 *     Cumulative TSN Ack and the Gap Ack Blocks.
1375	 */
1376
1377	sack_a_rwnd = ntohl(sack->a_rwnd);
1378	asoc->peer.zero_window_announced = !sack_a_rwnd;
1379	outstanding = q->outstanding_bytes;
1380
1381	if (outstanding < sack_a_rwnd)
1382		sack_a_rwnd -= outstanding;
1383	else
1384		sack_a_rwnd = 0;
1385
1386	asoc->peer.rwnd = sack_a_rwnd;
1387
1388	asoc->stream.si->generate_ftsn(q, sack_ctsn);
1389
1390	pr_debug("%s: sack cumulative tsn ack:0x%x\n", __func__, sack_ctsn);
1391	pr_debug("%s: cumulative tsn ack of assoc:%p is 0x%x, "
1392		 "advertised peer ack point:0x%x\n", __func__, asoc, ctsn,
1393		 asoc->adv_peer_ack_point);
1394
1395	return sctp_outq_is_empty(q);
1396}
1397
1398/* Is the outqueue empty?
1399 * The queue is empty when we have not pending data, no in-flight data
1400 * and nothing pending retransmissions.
1401 */
1402int sctp_outq_is_empty(const struct sctp_outq *q)
1403{
1404	return q->out_qlen == 0 && q->outstanding_bytes == 0 &&
1405	       list_empty(&q->retransmit);
1406}
1407
1408/********************************************************************
1409 * 2nd Level Abstractions
1410 ********************************************************************/
1411
1412/* Go through a transport's transmitted list or the association's retransmit
1413 * list and move chunks that are acked by the Cumulative TSN Ack to q->sacked.
1414 * The retransmit list will not have an associated transport.
1415 *
1416 * I added coherent debug information output.	--xguo
1417 *
1418 * Instead of printing 'sacked' or 'kept' for each TSN on the
1419 * transmitted_queue, we print a range: SACKED: TSN1-TSN2, TSN3, TSN4-TSN5.
1420 * KEPT TSN6-TSN7, etc.
1421 */
1422static void sctp_check_transmitted(struct sctp_outq *q,
1423				   struct list_head *transmitted_queue,
1424				   struct sctp_transport *transport,
1425				   union sctp_addr *saddr,
1426				   struct sctp_sackhdr *sack,
1427				   __u32 *highest_new_tsn_in_sack)
1428{
1429	struct list_head *lchunk;
1430	struct sctp_chunk *tchunk;
1431	struct list_head tlist;
1432	__u32 tsn;
1433	__u32 sack_ctsn;
1434	__u32 rtt;
1435	__u8 restart_timer = 0;
1436	int bytes_acked = 0;
1437	int migrate_bytes = 0;
1438	bool forward_progress = false;
1439
1440	sack_ctsn = ntohl(sack->cum_tsn_ack);
1441
1442	INIT_LIST_HEAD(&tlist);
1443
1444	/* The while loop will skip empty transmitted queues. */
1445	while (NULL != (lchunk = sctp_list_dequeue(transmitted_queue))) {
1446		tchunk = list_entry(lchunk, struct sctp_chunk,
1447				    transmitted_list);
1448
1449		if (sctp_chunk_abandoned(tchunk)) {
1450			/* Move the chunk to abandoned list. */
1451			sctp_insert_list(&q->abandoned, lchunk);
1452
1453			/* If this chunk has not been acked, stop
1454			 * considering it as 'outstanding'.
1455			 */
1456			if (transmitted_queue != &q->retransmit &&
1457			    !tchunk->tsn_gap_acked) {
1458				if (tchunk->transport)
1459					tchunk->transport->flight_size -=
1460							sctp_data_size(tchunk);
1461				q->outstanding_bytes -= sctp_data_size(tchunk);
1462			}
1463			continue;
1464		}
1465
1466		tsn = ntohl(tchunk->subh.data_hdr->tsn);
1467		if (sctp_acked(sack, tsn)) {
1468			/* If this queue is the retransmit queue, the
1469			 * retransmit timer has already reclaimed
1470			 * the outstanding bytes for this chunk, so only
1471			 * count bytes associated with a transport.
1472			 */
1473			if (transport && !tchunk->tsn_gap_acked) {
1474				/* If this chunk is being used for RTT
1475				 * measurement, calculate the RTT and update
1476				 * the RTO using this value.
1477				 *
1478				 * 6.3.1 C5) Karn's algorithm: RTT measurements
1479				 * MUST NOT be made using packets that were
1480				 * retransmitted (and thus for which it is
1481				 * ambiguous whether the reply was for the
1482				 * first instance of the packet or a later
1483				 * instance).
1484				 */
1485				if (!sctp_chunk_retransmitted(tchunk) &&
1486				    tchunk->rtt_in_progress) {
1487					tchunk->rtt_in_progress = 0;
1488					rtt = jiffies - tchunk->sent_at;
1489					sctp_transport_update_rto(transport,
1490								  rtt);
1491				}
1492
1493				if (TSN_lte(tsn, sack_ctsn)) {
1494					/*
1495					 * SFR-CACC algorithm:
1496					 * 2) If the SACK contains gap acks
1497					 * and the flag CHANGEOVER_ACTIVE is
1498					 * set the receiver of the SACK MUST
1499					 * take the following action:
1500					 *
1501					 * B) For each TSN t being acked that
1502					 * has not been acked in any SACK so
1503					 * far, set cacc_saw_newack to 1 for
1504					 * the destination that the TSN was
1505					 * sent to.
1506					 */
1507					if (sack->num_gap_ack_blocks &&
1508					    q->asoc->peer.primary_path->cacc.
1509					    changeover_active)
1510						transport->cacc.cacc_saw_newack
1511							= 1;
1512				}
1513			}
1514
1515			/* If the chunk hasn't been marked as ACKED,
1516			 * mark it and account bytes_acked if the
1517			 * chunk had a valid transport (it will not
1518			 * have a transport if ASCONF had deleted it
1519			 * while DATA was outstanding).
1520			 */
1521			if (!tchunk->tsn_gap_acked) {
1522				tchunk->tsn_gap_acked = 1;
1523				if (TSN_lt(*highest_new_tsn_in_sack, tsn))
1524					*highest_new_tsn_in_sack = tsn;
1525				bytes_acked += sctp_data_size(tchunk);
1526				if (!tchunk->transport)
1527					migrate_bytes += sctp_data_size(tchunk);
1528				forward_progress = true;
1529			}
1530
1531			if (TSN_lte(tsn, sack_ctsn)) {
1532				/* RFC 2960  6.3.2 Retransmission Timer Rules
1533				 *
1534				 * R3) Whenever a SACK is received
1535				 * that acknowledges the DATA chunk
1536				 * with the earliest outstanding TSN
1537				 * for that address, restart T3-rtx
1538				 * timer for that address with its
1539				 * current RTO.
1540				 */
1541				restart_timer = 1;
1542				forward_progress = true;
1543
1544				list_add_tail(&tchunk->transmitted_list,
1545					      &q->sacked);
1546			} else {
1547				/* RFC2960 7.2.4, sctpimpguide-05 2.8.2
1548				 * M2) Each time a SACK arrives reporting
1549				 * 'Stray DATA chunk(s)' record the highest TSN
1550				 * reported as newly acknowledged, call this
1551				 * value 'HighestTSNinSack'. A newly
1552				 * acknowledged DATA chunk is one not
1553				 * previously acknowledged in a SACK.
1554				 *
1555				 * When the SCTP sender of data receives a SACK
1556				 * chunk that acknowledges, for the first time,
1557				 * the receipt of a DATA chunk, all the still
1558				 * unacknowledged DATA chunks whose TSN is
1559				 * older than that newly acknowledged DATA
1560				 * chunk, are qualified as 'Stray DATA chunks'.
1561				 */
1562				list_add_tail(lchunk, &tlist);
1563			}
1564		} else {
1565			if (tchunk->tsn_gap_acked) {
1566				pr_debug("%s: receiver reneged on data TSN:0x%x\n",
1567					 __func__, tsn);
1568
1569				tchunk->tsn_gap_acked = 0;
1570
1571				if (tchunk->transport)
1572					bytes_acked -= sctp_data_size(tchunk);
1573
1574				/* RFC 2960 6.3.2 Retransmission Timer Rules
1575				 *
1576				 * R4) Whenever a SACK is received missing a
1577				 * TSN that was previously acknowledged via a
1578				 * Gap Ack Block, start T3-rtx for the
1579				 * destination address to which the DATA
1580				 * chunk was originally
1581				 * transmitted if it is not already running.
1582				 */
1583				restart_timer = 1;
1584			}
1585
1586			list_add_tail(lchunk, &tlist);
1587		}
1588	}
1589
1590	if (transport) {
1591		if (bytes_acked) {
1592			struct sctp_association *asoc = transport->asoc;
1593
1594			/* We may have counted DATA that was migrated
1595			 * to this transport due to DEL-IP operation.
1596			 * Subtract those bytes, since the were never
1597			 * send on this transport and shouldn't be
1598			 * credited to this transport.
1599			 */
1600			bytes_acked -= migrate_bytes;
1601
1602			/* 8.2. When an outstanding TSN is acknowledged,
1603			 * the endpoint shall clear the error counter of
1604			 * the destination transport address to which the
1605			 * DATA chunk was last sent.
1606			 * The association's overall error counter is
1607			 * also cleared.
1608			 */
1609			transport->error_count = 0;
1610			transport->asoc->overall_error_count = 0;
1611			forward_progress = true;
1612
1613			/*
1614			 * While in SHUTDOWN PENDING, we may have started
1615			 * the T5 shutdown guard timer after reaching the
1616			 * retransmission limit. Stop that timer as soon
1617			 * as the receiver acknowledged any data.
1618			 */
1619			if (asoc->state == SCTP_STATE_SHUTDOWN_PENDING &&
1620			    del_timer(&asoc->timers
1621				[SCTP_EVENT_TIMEOUT_T5_SHUTDOWN_GUARD]))
1622					sctp_association_put(asoc);
1623
1624			/* Mark the destination transport address as
1625			 * active if it is not so marked.
1626			 */
1627			if ((transport->state == SCTP_INACTIVE ||
1628			     transport->state == SCTP_UNCONFIRMED) &&
1629			    sctp_cmp_addr_exact(&transport->ipaddr, saddr)) {
1630				sctp_assoc_control_transport(
1631					transport->asoc,
1632					transport,
1633					SCTP_TRANSPORT_UP,
1634					SCTP_RECEIVED_SACK);
1635			}
1636
1637			sctp_transport_raise_cwnd(transport, sack_ctsn,
1638						  bytes_acked);
1639
1640			transport->flight_size -= bytes_acked;
1641			if (transport->flight_size == 0)
1642				transport->partial_bytes_acked = 0;
1643			q->outstanding_bytes -= bytes_acked + migrate_bytes;
1644		} else {
1645			/* RFC 2960 6.1, sctpimpguide-06 2.15.2
1646			 * When a sender is doing zero window probing, it
1647			 * should not timeout the association if it continues
1648			 * to receive new packets from the receiver. The
1649			 * reason is that the receiver MAY keep its window
1650			 * closed for an indefinite time.
1651			 * A sender is doing zero window probing when the
1652			 * receiver's advertised window is zero, and there is
1653			 * only one data chunk in flight to the receiver.
1654			 *
1655			 * Allow the association to timeout while in SHUTDOWN
1656			 * PENDING or SHUTDOWN RECEIVED in case the receiver
1657			 * stays in zero window mode forever.
1658			 */
1659			if (!q->asoc->peer.rwnd &&
1660			    !list_empty(&tlist) &&
1661			    (sack_ctsn+2 == q->asoc->next_tsn) &&
1662			    q->asoc->state < SCTP_STATE_SHUTDOWN_PENDING) {
1663				pr_debug("%s: sack received for zero window "
1664					 "probe:%u\n", __func__, sack_ctsn);
1665
1666				q->asoc->overall_error_count = 0;
1667				transport->error_count = 0;
1668			}
1669		}
1670
1671		/* RFC 2960 6.3.2 Retransmission Timer Rules
1672		 *
1673		 * R2) Whenever all outstanding data sent to an address have
1674		 * been acknowledged, turn off the T3-rtx timer of that
1675		 * address.
1676		 */
1677		if (!transport->flight_size) {
1678			if (del_timer(&transport->T3_rtx_timer))
1679				sctp_transport_put(transport);
1680		} else if (restart_timer) {
1681			if (!mod_timer(&transport->T3_rtx_timer,
1682				       jiffies + transport->rto))
1683				sctp_transport_hold(transport);
1684		}
1685
1686		if (forward_progress) {
1687			if (transport->dst)
1688				sctp_transport_dst_confirm(transport);
1689		}
1690	}
1691
1692	list_splice(&tlist, transmitted_queue);
1693}
1694
1695/* Mark chunks as missing and consequently may get retransmitted. */
1696static void sctp_mark_missing(struct sctp_outq *q,
1697			      struct list_head *transmitted_queue,
1698			      struct sctp_transport *transport,
1699			      __u32 highest_new_tsn_in_sack,
1700			      int count_of_newacks)
1701{
1702	struct sctp_chunk *chunk;
1703	__u32 tsn;
1704	char do_fast_retransmit = 0;
1705	struct sctp_association *asoc = q->asoc;
1706	struct sctp_transport *primary = asoc->peer.primary_path;
1707
1708	list_for_each_entry(chunk, transmitted_queue, transmitted_list) {
1709
1710		tsn = ntohl(chunk->subh.data_hdr->tsn);
1711
1712		/* RFC 2960 7.2.4, sctpimpguide-05 2.8.2 M3) Examine all
1713		 * 'Unacknowledged TSN's', if the TSN number of an
1714		 * 'Unacknowledged TSN' is smaller than the 'HighestTSNinSack'
1715		 * value, increment the 'TSN.Missing.Report' count on that
1716		 * chunk if it has NOT been fast retransmitted or marked for
1717		 * fast retransmit already.
1718		 */
1719		if (chunk->fast_retransmit == SCTP_CAN_FRTX &&
1720		    !chunk->tsn_gap_acked &&
1721		    TSN_lt(tsn, highest_new_tsn_in_sack)) {
1722
1723			/* SFR-CACC may require us to skip marking
1724			 * this chunk as missing.
1725			 */
1726			if (!transport || !sctp_cacc_skip(primary,
1727						chunk->transport,
1728						count_of_newacks, tsn)) {
1729				chunk->tsn_missing_report++;
1730
1731				pr_debug("%s: tsn:0x%x missing counter:%d\n",
1732					 __func__, tsn, chunk->tsn_missing_report);
1733			}
1734		}
1735		/*
1736		 * M4) If any DATA chunk is found to have a
1737		 * 'TSN.Missing.Report'
1738		 * value larger than or equal to 3, mark that chunk for
1739		 * retransmission and start the fast retransmit procedure.
1740		 */
1741
1742		if (chunk->tsn_missing_report >= 3) {
1743			chunk->fast_retransmit = SCTP_NEED_FRTX;
1744			do_fast_retransmit = 1;
1745		}
1746	}
1747
1748	if (transport) {
1749		if (do_fast_retransmit)
1750			sctp_retransmit(q, transport, SCTP_RTXR_FAST_RTX);
1751
1752		pr_debug("%s: transport:%p, cwnd:%d, ssthresh:%d, "
1753			 "flight_size:%d, pba:%d\n",  __func__, transport,
1754			 transport->cwnd, transport->ssthresh,
1755			 transport->flight_size, transport->partial_bytes_acked);
1756	}
1757}
1758
1759/* Is the given TSN acked by this packet?  */
1760static int sctp_acked(struct sctp_sackhdr *sack, __u32 tsn)
1761{
1762	__u32 ctsn = ntohl(sack->cum_tsn_ack);
1763	union sctp_sack_variable *frags;
1764	__u16 tsn_offset, blocks;
1765	int i;
1766
1767	if (TSN_lte(tsn, ctsn))
1768		goto pass;
1769
1770	/* 3.3.4 Selective Acknowledgment (SACK) (3):
1771	 *
1772	 * Gap Ack Blocks:
1773	 *  These fields contain the Gap Ack Blocks. They are repeated
1774	 *  for each Gap Ack Block up to the number of Gap Ack Blocks
1775	 *  defined in the Number of Gap Ack Blocks field. All DATA
1776	 *  chunks with TSNs greater than or equal to (Cumulative TSN
1777	 *  Ack + Gap Ack Block Start) and less than or equal to
1778	 *  (Cumulative TSN Ack + Gap Ack Block End) of each Gap Ack
1779	 *  Block are assumed to have been received correctly.
1780	 */
1781
1782	frags = sack->variable;
1783	blocks = ntohs(sack->num_gap_ack_blocks);
1784	tsn_offset = tsn - ctsn;
1785	for (i = 0; i < blocks; ++i) {
1786		if (tsn_offset >= ntohs(frags[i].gab.start) &&
1787		    tsn_offset <= ntohs(frags[i].gab.end))
1788			goto pass;
1789	}
1790
1791	return 0;
1792pass:
1793	return 1;
1794}
1795
1796static inline int sctp_get_skip_pos(struct sctp_fwdtsn_skip *skiplist,
1797				    int nskips, __be16 stream)
1798{
1799	int i;
1800
1801	for (i = 0; i < nskips; i++) {
1802		if (skiplist[i].stream == stream)
1803			return i;
1804	}
1805	return i;
1806}
1807
1808/* Create and add a fwdtsn chunk to the outq's control queue if needed. */
1809void sctp_generate_fwdtsn(struct sctp_outq *q, __u32 ctsn)
1810{
1811	struct sctp_association *asoc = q->asoc;
1812	struct sctp_chunk *ftsn_chunk = NULL;
1813	struct sctp_fwdtsn_skip ftsn_skip_arr[10];
1814	int nskips = 0;
1815	int skip_pos = 0;
1816	__u32 tsn;
1817	struct sctp_chunk *chunk;
1818	struct list_head *lchunk, *temp;
1819
1820	if (!asoc->peer.prsctp_capable)
1821		return;
1822
1823	/* PR-SCTP C1) Let SackCumAck be the Cumulative TSN ACK carried in the
1824	 * received SACK.
1825	 *
1826	 * If (Advanced.Peer.Ack.Point < SackCumAck), then update
1827	 * Advanced.Peer.Ack.Point to be equal to SackCumAck.
1828	 */
1829	if (TSN_lt(asoc->adv_peer_ack_point, ctsn))
1830		asoc->adv_peer_ack_point = ctsn;
1831
1832	/* PR-SCTP C2) Try to further advance the "Advanced.Peer.Ack.Point"
1833	 * locally, that is, to move "Advanced.Peer.Ack.Point" up as long as
1834	 * the chunk next in the out-queue space is marked as "abandoned" as
1835	 * shown in the following example:
1836	 *
1837	 * Assuming that a SACK arrived with the Cumulative TSN ACK 102
1838	 * and the Advanced.Peer.Ack.Point is updated to this value:
1839	 *
1840	 *   out-queue at the end of  ==>   out-queue after Adv.Ack.Point
1841	 *   normal SACK processing           local advancement
1842	 *                ...                           ...
1843	 *   Adv.Ack.Pt-> 102 acked                     102 acked
1844	 *                103 abandoned                 103 abandoned
1845	 *                104 abandoned     Adv.Ack.P-> 104 abandoned
1846	 *                105                           105
1847	 *                106 acked                     106 acked
1848	 *                ...                           ...
1849	 *
1850	 * In this example, the data sender successfully advanced the
1851	 * "Advanced.Peer.Ack.Point" from 102 to 104 locally.
1852	 */
1853	list_for_each_safe(lchunk, temp, &q->abandoned) {
1854		chunk = list_entry(lchunk, struct sctp_chunk,
1855					transmitted_list);
1856		tsn = ntohl(chunk->subh.data_hdr->tsn);
1857
1858		/* Remove any chunks in the abandoned queue that are acked by
1859		 * the ctsn.
1860		 */
1861		if (TSN_lte(tsn, ctsn)) {
1862			list_del_init(lchunk);
1863			sctp_chunk_free(chunk);
1864		} else {
1865			if (TSN_lte(tsn, asoc->adv_peer_ack_point+1)) {
1866				asoc->adv_peer_ack_point = tsn;
1867				if (chunk->chunk_hdr->flags &
1868					 SCTP_DATA_UNORDERED)
1869					continue;
1870				skip_pos = sctp_get_skip_pos(&ftsn_skip_arr[0],
1871						nskips,
1872						chunk->subh.data_hdr->stream);
1873				ftsn_skip_arr[skip_pos].stream =
1874					chunk->subh.data_hdr->stream;
1875				ftsn_skip_arr[skip_pos].ssn =
1876					 chunk->subh.data_hdr->ssn;
1877				if (skip_pos == nskips)
1878					nskips++;
1879				if (nskips == 10)
1880					break;
1881			} else
1882				break;
1883		}
1884	}
1885
1886	/* PR-SCTP C3) If, after step C1 and C2, the "Advanced.Peer.Ack.Point"
1887	 * is greater than the Cumulative TSN ACK carried in the received
1888	 * SACK, the data sender MUST send the data receiver a FORWARD TSN
1889	 * chunk containing the latest value of the
1890	 * "Advanced.Peer.Ack.Point".
1891	 *
1892	 * C4) For each "abandoned" TSN the sender of the FORWARD TSN SHOULD
1893	 * list each stream and sequence number in the forwarded TSN. This
1894	 * information will enable the receiver to easily find any
1895	 * stranded TSN's waiting on stream reorder queues. Each stream
1896	 * SHOULD only be reported once; this means that if multiple
1897	 * abandoned messages occur in the same stream then only the
1898	 * highest abandoned stream sequence number is reported. If the
1899	 * total size of the FORWARD TSN does NOT fit in a single MTU then
1900	 * the sender of the FORWARD TSN SHOULD lower the
1901	 * Advanced.Peer.Ack.Point to the last TSN that will fit in a
1902	 * single MTU.
1903	 */
1904	if (asoc->adv_peer_ack_point > ctsn)
1905		ftsn_chunk = sctp_make_fwdtsn(asoc, asoc->adv_peer_ack_point,
1906					      nskips, &ftsn_skip_arr[0]);
1907
1908	if (ftsn_chunk) {
1909		list_add_tail(&ftsn_chunk->list, &q->control_chunk_list);
1910		SCTP_INC_STATS(asoc->base.net, SCTP_MIB_OUTCTRLCHUNKS);
1911	}
1912}