1// SPDX-License-Identifier: GPL-2.0-or-later
   2/* SCTP kernel implementation
   3 * (C) Copyright IBM Corp. 2001, 2004
   4 * Copyright (c) 1999-2000 Cisco, Inc.
   5 * Copyright (c) 1999-2001 Motorola, Inc.
   6 * Copyright (c) 2001-2003 Intel Corp.
   7 *
   8 * This file is part of the SCTP kernel implementation
   9 *
  10 * These functions implement the sctp_outq class.   The outqueue handles
  11 * bundling and queueing of outgoing SCTP chunks.
  12 *
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
  13 * Please send any bug reports or fixes you make to the
  14 * email address(es):
  15 *    lksctp developers <linux-sctp@vger.kernel.org>
  16 *
  17 * Written or modified by:
  18 *    La Monte H.P. Yarroll <piggy@acm.org>
  19 *    Karl Knutson          <karl@athena.chicago.il.us>
  20 *    Perry Melange         <pmelange@null.cc.uic.edu>
  21 *    Xingang Guo           <xingang.guo@intel.com>
  22 *    Hui Huang 	    <hui.huang@nokia.com>
  23 *    Sridhar Samudrala     <sri@us.ibm.com>
  24 *    Jon Grimm             <jgrimm@us.ibm.com>
  25 */
  26
  27#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  28
  29#include <linux/types.h>
  30#include <linux/list.h>   /* For struct list_head */
  31#include <linux/socket.h>
  32#include <linux/ip.h>
  33#include <linux/slab.h>
  34#include <net/sock.h>	  /* For skb_set_owner_w */
  35
  36#include <net/sctp/sctp.h>
  37#include <net/sctp/sm.h>
  38#include <net/sctp/stream_sched.h>
  39
  40/* Declare internal functions here.  */
  41static int sctp_acked(struct sctp_sackhdr *sack, __u32 tsn);
  42static void sctp_check_transmitted(struct sctp_outq *q,
  43				   struct list_head *transmitted_queue,
  44				   struct sctp_transport *transport,
  45				   union sctp_addr *saddr,
  46				   struct sctp_sackhdr *sack,
  47				   __u32 *highest_new_tsn);
  48
  49static void sctp_mark_missing(struct sctp_outq *q,
  50			      struct list_head *transmitted_queue,
  51			      struct sctp_transport *transport,
  52			      __u32 highest_new_tsn,
  53			      int count_of_newacks);
  54
  55static void sctp_outq_flush(struct sctp_outq *q, int rtx_timeout, gfp_t gfp);
  56
  57/* Add data to the front of the queue. */
  58static inline void sctp_outq_head_data(struct sctp_outq *q,
  59				       struct sctp_chunk *ch)
  60{
  61	struct sctp_stream_out_ext *oute;
  62	__u16 stream;
  63
  64	list_add(&ch->list, &q->out_chunk_list);
  65	q->out_qlen += ch->skb->len;
  66
  67	stream = sctp_chunk_stream_no(ch);
  68	oute = SCTP_SO(&q->asoc->stream, stream)->ext;
  69	list_add(&ch->stream_list, &oute->outq);
  70}
  71
  72/* Take data from the front of the queue. */
  73static inline struct sctp_chunk *sctp_outq_dequeue_data(struct sctp_outq *q)
  74{
  75	return q->sched->dequeue(q);
  76}
  77
  78/* Add data chunk to the end of the queue. */
  79static inline void sctp_outq_tail_data(struct sctp_outq *q,
  80				       struct sctp_chunk *ch)
  81{
  82	struct sctp_stream_out_ext *oute;
  83	__u16 stream;
  84
  85	list_add_tail(&ch->list, &q->out_chunk_list);
  86	q->out_qlen += ch->skb->len;
  87
  88	stream = sctp_chunk_stream_no(ch);
  89	oute = SCTP_SO(&q->asoc->stream, stream)->ext;
  90	list_add_tail(&ch->stream_list, &oute->outq);
  91}
  92
  93/*
  94 * SFR-CACC algorithm:
  95 * D) If count_of_newacks is greater than or equal to 2
  96 * and t was not sent to the current primary then the
  97 * sender MUST NOT increment missing report count for t.
  98 */
  99static inline int sctp_cacc_skip_3_1_d(struct sctp_transport *primary,
 100				       struct sctp_transport *transport,
 101				       int count_of_newacks)
 102{
 103	if (count_of_newacks >= 2 && transport != primary)
 104		return 1;
 105	return 0;
 106}
 107
 108/*
 109 * SFR-CACC algorithm:
 110 * F) If count_of_newacks is less than 2, let d be the
 111 * destination to which t was sent. If cacc_saw_newack
 112 * is 0 for destination d, then the sender MUST NOT
 113 * increment missing report count for t.
 114 */
 115static inline int sctp_cacc_skip_3_1_f(struct sctp_transport *transport,
 116				       int count_of_newacks)
 117{
 118	if (count_of_newacks < 2 &&
 119			(transport && !transport->cacc.cacc_saw_newack))
 120		return 1;
 121	return 0;
 122}
 123
 124/*
 125 * SFR-CACC algorithm:
 126 * 3.1) If CYCLING_CHANGEOVER is 0, the sender SHOULD
 127 * execute steps C, D, F.
 128 *
 129 * C has been implemented in sctp_outq_sack
 130 */
 131static inline int sctp_cacc_skip_3_1(struct sctp_transport *primary,
 132				     struct sctp_transport *transport,
 133				     int count_of_newacks)
 134{
 135	if (!primary->cacc.cycling_changeover) {
 136		if (sctp_cacc_skip_3_1_d(primary, transport, count_of_newacks))
 137			return 1;
 138		if (sctp_cacc_skip_3_1_f(transport, count_of_newacks))
 139			return 1;
 140		return 0;
 141	}
 142	return 0;
 143}
 144
 145/*
 146 * SFR-CACC algorithm:
 147 * 3.2) Else if CYCLING_CHANGEOVER is 1, and t is less
 148 * than next_tsn_at_change of the current primary, then
 149 * the sender MUST NOT increment missing report count
 150 * for t.
 151 */
 152static inline int sctp_cacc_skip_3_2(struct sctp_transport *primary, __u32 tsn)
 153{
 154	if (primary->cacc.cycling_changeover &&
 155	    TSN_lt(tsn, primary->cacc.next_tsn_at_change))
 156		return 1;
 157	return 0;
 158}
 159
 160/*
 161 * SFR-CACC algorithm:
 162 * 3) If the missing report count for TSN t is to be
 163 * incremented according to [RFC2960] and
 164 * [SCTP_STEWART-2002], and CHANGEOVER_ACTIVE is set,
 165 * then the sender MUST further execute steps 3.1 and
 166 * 3.2 to determine if the missing report count for
 167 * TSN t SHOULD NOT be incremented.
 168 *
 169 * 3.3) If 3.1 and 3.2 do not dictate that the missing
 170 * report count for t should not be incremented, then
 171 * the sender SHOULD increment missing report count for
 172 * t (according to [RFC2960] and [SCTP_STEWART_2002]).
 173 */
 174static inline int sctp_cacc_skip(struct sctp_transport *primary,
 175				 struct sctp_transport *transport,
 176				 int count_of_newacks,
 177				 __u32 tsn)
 178{
 179	if (primary->cacc.changeover_active &&
 180	    (sctp_cacc_skip_3_1(primary, transport, count_of_newacks) ||
 181	     sctp_cacc_skip_3_2(primary, tsn)))
 182		return 1;
 183	return 0;
 184}
 185
 186/* Initialize an existing sctp_outq.  This does the boring stuff.
 187 * You still need to define handlers if you really want to DO
 188 * something with this structure...
 189 */
 190void sctp_outq_init(struct sctp_association *asoc, struct sctp_outq *q)
 191{
 192	memset(q, 0, sizeof(struct sctp_outq));
 193
 194	q->asoc = asoc;
 195	INIT_LIST_HEAD(&q->out_chunk_list);
 196	INIT_LIST_HEAD(&q->control_chunk_list);
 197	INIT_LIST_HEAD(&q->retransmit);
 198	INIT_LIST_HEAD(&q->sacked);
 199	INIT_LIST_HEAD(&q->abandoned);
 200	sctp_sched_set_sched(asoc, sctp_sk(asoc->base.sk)->default_ss);
 201}
 202
 203/* Free the outqueue structure and any related pending chunks.
 204 */
 205static void __sctp_outq_teardown(struct sctp_outq *q)
 206{
 207	struct sctp_transport *transport;
 208	struct list_head *lchunk, *temp;
 209	struct sctp_chunk *chunk, *tmp;
 210
 211	/* Throw away unacknowledged chunks. */
 212	list_for_each_entry(transport, &q->asoc->peer.transport_addr_list,
 213			transports) {
 214		while ((lchunk = sctp_list_dequeue(&transport->transmitted)) != NULL) {
 215			chunk = list_entry(lchunk, struct sctp_chunk,
 216					   transmitted_list);
 217			/* Mark as part of a failed message. */
 218			sctp_chunk_fail(chunk, q->error);
 219			sctp_chunk_free(chunk);
 220		}
 221	}
 222
 223	/* Throw away chunks that have been gap ACKed.  */
 224	list_for_each_safe(lchunk, temp, &q->sacked) {
 225		list_del_init(lchunk);
 226		chunk = list_entry(lchunk, struct sctp_chunk,
 227				   transmitted_list);
 228		sctp_chunk_fail(chunk, q->error);
 229		sctp_chunk_free(chunk);
 230	}
 231
 232	/* Throw away any chunks in the retransmit queue. */
 233	list_for_each_safe(lchunk, temp, &q->retransmit) {
 234		list_del_init(lchunk);
 235		chunk = list_entry(lchunk, struct sctp_chunk,
 236				   transmitted_list);
 237		sctp_chunk_fail(chunk, q->error);
 238		sctp_chunk_free(chunk);
 239	}
 240
 241	/* Throw away any chunks that are in the abandoned queue. */
 242	list_for_each_safe(lchunk, temp, &q->abandoned) {
 243		list_del_init(lchunk);
 244		chunk = list_entry(lchunk, struct sctp_chunk,
 245				   transmitted_list);
 246		sctp_chunk_fail(chunk, q->error);
 247		sctp_chunk_free(chunk);
 248	}
 249
 250	/* Throw away any leftover data chunks. */
 251	while ((chunk = sctp_outq_dequeue_data(q)) != NULL) {
 252		sctp_sched_dequeue_done(q, chunk);
 253
 254		/* Mark as send failure. */
 255		sctp_chunk_fail(chunk, q->error);
 256		sctp_chunk_free(chunk);
 257	}
 258
 259	/* Throw away any leftover control chunks. */
 260	list_for_each_entry_safe(chunk, tmp, &q->control_chunk_list, list) {
 261		list_del_init(&chunk->list);
 262		sctp_chunk_free(chunk);
 263	}
 264}
 265
 266void sctp_outq_teardown(struct sctp_outq *q)
 267{
 268	__sctp_outq_teardown(q);
 269	sctp_outq_init(q->asoc, q);
 270}
 271
 272/* Free the outqueue structure and any related pending chunks.  */
 273void sctp_outq_free(struct sctp_outq *q)
 274{
 275	/* Throw away leftover chunks. */
 276	__sctp_outq_teardown(q);
 277}
 278
 279/* Put a new chunk in an sctp_outq.  */
 280void sctp_outq_tail(struct sctp_outq *q, struct sctp_chunk *chunk, gfp_t gfp)
 281{
 282	struct net *net = sock_net(q->asoc->base.sk);
 283
 284	pr_debug("%s: outq:%p, chunk:%p[%s]\n", __func__, q, chunk,
 285		 chunk && chunk->chunk_hdr ?
 286		 sctp_cname(SCTP_ST_CHUNK(chunk->chunk_hdr->type)) :
 287		 "illegal chunk");
 288
 289	/* If it is data, queue it up, otherwise, send it
 290	 * immediately.
 291	 */
 292	if (sctp_chunk_is_data(chunk)) {
 293		pr_debug("%s: outqueueing: outq:%p, chunk:%p[%s])\n",
 294			 __func__, q, chunk, chunk && chunk->chunk_hdr ?
 295			 sctp_cname(SCTP_ST_CHUNK(chunk->chunk_hdr->type)) :
 296			 "illegal chunk");
 297
 298		sctp_outq_tail_data(q, chunk);
 299		if (chunk->asoc->peer.prsctp_capable &&
 300		    SCTP_PR_PRIO_ENABLED(chunk->sinfo.sinfo_flags))
 301			chunk->asoc->sent_cnt_removable++;
 302		if (chunk->chunk_hdr->flags & SCTP_DATA_UNORDERED)
 303			SCTP_INC_STATS(net, SCTP_MIB_OUTUNORDERCHUNKS);
 304		else
 305			SCTP_INC_STATS(net, SCTP_MIB_OUTORDERCHUNKS);
 306	} else {
 307		list_add_tail(&chunk->list, &q->control_chunk_list);
 308		SCTP_INC_STATS(net, SCTP_MIB_OUTCTRLCHUNKS);
 309	}
 310
 311	if (!q->cork)
 312		sctp_outq_flush(q, 0, gfp);
 313}
 314
 315/* Insert a chunk into the sorted list based on the TSNs.  The retransmit list
 316 * and the abandoned list are in ascending order.
 317 */
 318static void sctp_insert_list(struct list_head *head, struct list_head *new)
 319{
 320	struct list_head *pos;
 321	struct sctp_chunk *nchunk, *lchunk;
 322	__u32 ntsn, ltsn;
 323	int done = 0;
 324
 325	nchunk = list_entry(new, struct sctp_chunk, transmitted_list);
 326	ntsn = ntohl(nchunk->subh.data_hdr->tsn);
 327
 328	list_for_each(pos, head) {
 329		lchunk = list_entry(pos, struct sctp_chunk, transmitted_list);
 330		ltsn = ntohl(lchunk->subh.data_hdr->tsn);
 331		if (TSN_lt(ntsn, ltsn)) {
 332			list_add(new, pos->prev);
 333			done = 1;
 334			break;
 335		}
 336	}
 337	if (!done)
 338		list_add_tail(new, head);
 339}
 340
 341static int sctp_prsctp_prune_sent(struct sctp_association *asoc,
 342				  struct sctp_sndrcvinfo *sinfo,
 343				  struct list_head *queue, int msg_len)
 344{
 345	struct sctp_chunk *chk, *temp;
 346
 347	list_for_each_entry_safe(chk, temp, queue, transmitted_list) {
 348		struct sctp_stream_out *streamout;
 349
 350		if (!chk->msg->abandoned &&
 351		    (!SCTP_PR_PRIO_ENABLED(chk->sinfo.sinfo_flags) ||
 352		     chk->sinfo.sinfo_timetolive <= sinfo->sinfo_timetolive))
 353			continue;
 354
 355		chk->msg->abandoned = 1;
 356		list_del_init(&chk->transmitted_list);
 357		sctp_insert_list(&asoc->outqueue.abandoned,
 358				 &chk->transmitted_list);
 359
 360		streamout = SCTP_SO(&asoc->stream, chk->sinfo.sinfo_stream);
 361		asoc->sent_cnt_removable--;
 362		asoc->abandoned_sent[SCTP_PR_INDEX(PRIO)]++;
 363		streamout->ext->abandoned_sent[SCTP_PR_INDEX(PRIO)]++;
 364
 365		if (queue != &asoc->outqueue.retransmit &&
 366		    !chk->tsn_gap_acked) {
 367			if (chk->transport)
 368				chk->transport->flight_size -=
 369						sctp_data_size(chk);
 370			asoc->outqueue.outstanding_bytes -= sctp_data_size(chk);
 371		}
 372
 373		msg_len -= chk->skb->truesize + sizeof(struct sctp_chunk);
 
 
 374		if (msg_len <= 0)
 375			break;
 376	}
 377
 378	return msg_len;
 379}
 380
 381static int sctp_prsctp_prune_unsent(struct sctp_association *asoc,
 382				    struct sctp_sndrcvinfo *sinfo, int msg_len)
 383{
 384	struct sctp_outq *q = &asoc->outqueue;
 385	struct sctp_chunk *chk, *temp;
 386
 387	q->sched->unsched_all(&asoc->stream);
 388
 389	list_for_each_entry_safe(chk, temp, &q->out_chunk_list, list) {
 390		if (!chk->msg->abandoned &&
 391		    (!(chk->chunk_hdr->flags & SCTP_DATA_FIRST_FRAG) ||
 392		     !SCTP_PR_PRIO_ENABLED(chk->sinfo.sinfo_flags) ||
 393		     chk->sinfo.sinfo_timetolive <= sinfo->sinfo_timetolive))
 394			continue;
 395
 396		chk->msg->abandoned = 1;
 397		sctp_sched_dequeue_common(q, chk);
 398		asoc->sent_cnt_removable--;
 399		asoc->abandoned_unsent[SCTP_PR_INDEX(PRIO)]++;
 400		if (chk->sinfo.sinfo_stream < asoc->stream.outcnt) {
 401			struct sctp_stream_out *streamout =
 402				SCTP_SO(&asoc->stream, chk->sinfo.sinfo_stream);
 403
 404			streamout->ext->abandoned_unsent[SCTP_PR_INDEX(PRIO)]++;
 405		}
 406
 407		msg_len -= chk->skb->truesize + sizeof(struct sctp_chunk);
 
 
 408		sctp_chunk_free(chk);
 409		if (msg_len <= 0)
 410			break;
 411	}
 412
 413	q->sched->sched_all(&asoc->stream);
 414
 415	return msg_len;
 416}
 417
 418/* Abandon the chunks according their priorities */
 419void sctp_prsctp_prune(struct sctp_association *asoc,
 420		       struct sctp_sndrcvinfo *sinfo, int msg_len)
 421{
 422	struct sctp_transport *transport;
 423
 424	if (!asoc->peer.prsctp_capable || !asoc->sent_cnt_removable)
 425		return;
 426
 427	msg_len = sctp_prsctp_prune_sent(asoc, sinfo,
 428					 &asoc->outqueue.retransmit,
 429					 msg_len);
 430	if (msg_len <= 0)
 431		return;
 432
 433	list_for_each_entry(transport, &asoc->peer.transport_addr_list,
 434			    transports) {
 435		msg_len = sctp_prsctp_prune_sent(asoc, sinfo,
 436						 &transport->transmitted,
 437						 msg_len);
 438		if (msg_len <= 0)
 439			return;
 440	}
 441
 442	sctp_prsctp_prune_unsent(asoc, sinfo, msg_len);
 443}
 444
 445/* Mark all the eligible packets on a transport for retransmission.  */
 446void sctp_retransmit_mark(struct sctp_outq *q,
 447			  struct sctp_transport *transport,
 448			  __u8 reason)
 449{
 450	struct list_head *lchunk, *ltemp;
 451	struct sctp_chunk *chunk;
 452
 453	/* Walk through the specified transmitted queue.  */
 454	list_for_each_safe(lchunk, ltemp, &transport->transmitted) {
 455		chunk = list_entry(lchunk, struct sctp_chunk,
 456				   transmitted_list);
 457
 458		/* If the chunk is abandoned, move it to abandoned list. */
 459		if (sctp_chunk_abandoned(chunk)) {
 460			list_del_init(lchunk);
 461			sctp_insert_list(&q->abandoned, lchunk);
 462
 463			/* If this chunk has not been previousely acked,
 464			 * stop considering it 'outstanding'.  Our peer
 465			 * will most likely never see it since it will
 466			 * not be retransmitted
 467			 */
 468			if (!chunk->tsn_gap_acked) {
 469				if (chunk->transport)
 470					chunk->transport->flight_size -=
 471							sctp_data_size(chunk);
 472				q->outstanding_bytes -= sctp_data_size(chunk);
 473				q->asoc->peer.rwnd += sctp_data_size(chunk);
 474			}
 475			continue;
 476		}
 477
 478		/* If we are doing  retransmission due to a timeout or pmtu
 479		 * discovery, only the  chunks that are not yet acked should
 480		 * be added to the retransmit queue.
 481		 */
 482		if ((reason == SCTP_RTXR_FAST_RTX  &&
 483			    (chunk->fast_retransmit == SCTP_NEED_FRTX)) ||
 484		    (reason != SCTP_RTXR_FAST_RTX  && !chunk->tsn_gap_acked)) {
 485			/* RFC 2960 6.2.1 Processing a Received SACK
 486			 *
 487			 * C) Any time a DATA chunk is marked for
 488			 * retransmission (via either T3-rtx timer expiration
 489			 * (Section 6.3.3) or via fast retransmit
 490			 * (Section 7.2.4)), add the data size of those
 491			 * chunks to the rwnd.
 492			 */
 493			q->asoc->peer.rwnd += sctp_data_size(chunk);
 494			q->outstanding_bytes -= sctp_data_size(chunk);
 495			if (chunk->transport)
 496				transport->flight_size -= sctp_data_size(chunk);
 497
 498			/* sctpimpguide-05 Section 2.8.2
 499			 * M5) If a T3-rtx timer expires, the
 500			 * 'TSN.Missing.Report' of all affected TSNs is set
 501			 * to 0.
 502			 */
 503			chunk->tsn_missing_report = 0;
 504
 505			/* If a chunk that is being used for RTT measurement
 506			 * has to be retransmitted, we cannot use this chunk
 507			 * anymore for RTT measurements. Reset rto_pending so
 508			 * that a new RTT measurement is started when a new
 509			 * data chunk is sent.
 510			 */
 511			if (chunk->rtt_in_progress) {
 512				chunk->rtt_in_progress = 0;
 513				transport->rto_pending = 0;
 514			}
 515
 516			/* Move the chunk to the retransmit queue. The chunks
 517			 * on the retransmit queue are always kept in order.
 518			 */
 519			list_del_init(lchunk);
 520			sctp_insert_list(&q->retransmit, lchunk);
 521		}
 522	}
 523
 524	pr_debug("%s: transport:%p, reason:%d, cwnd:%d, ssthresh:%d, "
 525		 "flight_size:%d, pba:%d\n", __func__, transport, reason,
 526		 transport->cwnd, transport->ssthresh, transport->flight_size,
 527		 transport->partial_bytes_acked);
 528}
 529
 530/* Mark all the eligible packets on a transport for retransmission and force
 531 * one packet out.
 532 */
 533void sctp_retransmit(struct sctp_outq *q, struct sctp_transport *transport,
 534		     enum sctp_retransmit_reason reason)
 535{
 536	struct net *net = sock_net(q->asoc->base.sk);
 537
 538	switch (reason) {
 539	case SCTP_RTXR_T3_RTX:
 540		SCTP_INC_STATS(net, SCTP_MIB_T3_RETRANSMITS);
 541		sctp_transport_lower_cwnd(transport, SCTP_LOWER_CWND_T3_RTX);
 542		/* Update the retran path if the T3-rtx timer has expired for
 543		 * the current retran path.
 544		 */
 545		if (transport == transport->asoc->peer.retran_path)
 546			sctp_assoc_update_retran_path(transport->asoc);
 547		transport->asoc->rtx_data_chunks +=
 548			transport->asoc->unack_data;
 549		break;
 550	case SCTP_RTXR_FAST_RTX:
 551		SCTP_INC_STATS(net, SCTP_MIB_FAST_RETRANSMITS);
 552		sctp_transport_lower_cwnd(transport, SCTP_LOWER_CWND_FAST_RTX);
 553		q->fast_rtx = 1;
 554		break;
 555	case SCTP_RTXR_PMTUD:
 556		SCTP_INC_STATS(net, SCTP_MIB_PMTUD_RETRANSMITS);
 557		break;
 558	case SCTP_RTXR_T1_RTX:
 559		SCTP_INC_STATS(net, SCTP_MIB_T1_RETRANSMITS);
 560		transport->asoc->init_retries++;
 561		break;
 562	default:
 563		BUG();
 564	}
 565
 566	sctp_retransmit_mark(q, transport, reason);
 567
 568	/* PR-SCTP A5) Any time the T3-rtx timer expires, on any destination,
 569	 * the sender SHOULD try to advance the "Advanced.Peer.Ack.Point" by
 570	 * following the procedures outlined in C1 - C5.
 571	 */
 572	if (reason == SCTP_RTXR_T3_RTX)
 573		q->asoc->stream.si->generate_ftsn(q, q->asoc->ctsn_ack_point);
 574
 575	/* Flush the queues only on timeout, since fast_rtx is only
 576	 * triggered during sack processing and the queue
 577	 * will be flushed at the end.
 578	 */
 579	if (reason != SCTP_RTXR_FAST_RTX)
 580		sctp_outq_flush(q, /* rtx_timeout */ 1, GFP_ATOMIC);
 581}
 582
 583/*
 584 * Transmit DATA chunks on the retransmit queue.  Upon return from
 585 * __sctp_outq_flush_rtx() the packet 'pkt' may contain chunks which
 586 * need to be transmitted by the caller.
 587 * We assume that pkt->transport has already been set.
 588 *
 589 * The return value is a normal kernel error return value.
 590 */
 591static int __sctp_outq_flush_rtx(struct sctp_outq *q, struct sctp_packet *pkt,
 592				 int rtx_timeout, int *start_timer, gfp_t gfp)
 593{
 594	struct sctp_transport *transport = pkt->transport;
 595	struct sctp_chunk *chunk, *chunk1;
 596	struct list_head *lqueue;
 597	enum sctp_xmit status;
 598	int error = 0;
 599	int timer = 0;
 600	int done = 0;
 601	int fast_rtx;
 602
 603	lqueue = &q->retransmit;
 604	fast_rtx = q->fast_rtx;
 605
 606	/* This loop handles time-out retransmissions, fast retransmissions,
 607	 * and retransmissions due to opening of whindow.
 608	 *
 609	 * RFC 2960 6.3.3 Handle T3-rtx Expiration
 610	 *
 611	 * E3) Determine how many of the earliest (i.e., lowest TSN)
 612	 * outstanding DATA chunks for the address for which the
 613	 * T3-rtx has expired will fit into a single packet, subject
 614	 * to the MTU constraint for the path corresponding to the
 615	 * destination transport address to which the retransmission
 616	 * is being sent (this may be different from the address for
 617	 * which the timer expires [see Section 6.4]). Call this value
 618	 * K. Bundle and retransmit those K DATA chunks in a single
 619	 * packet to the destination endpoint.
 620	 *
 621	 * [Just to be painfully clear, if we are retransmitting
 622	 * because a timeout just happened, we should send only ONE
 623	 * packet of retransmitted data.]
 624	 *
 625	 * For fast retransmissions we also send only ONE packet.  However,
 626	 * if we are just flushing the queue due to open window, we'll
 627	 * try to send as much as possible.
 628	 */
 629	list_for_each_entry_safe(chunk, chunk1, lqueue, transmitted_list) {
 630		/* If the chunk is abandoned, move it to abandoned list. */
 631		if (sctp_chunk_abandoned(chunk)) {
 632			list_del_init(&chunk->transmitted_list);
 633			sctp_insert_list(&q->abandoned,
 634					 &chunk->transmitted_list);
 635			continue;
 636		}
 637
 638		/* Make sure that Gap Acked TSNs are not retransmitted.  A
 639		 * simple approach is just to move such TSNs out of the
 640		 * way and into a 'transmitted' queue and skip to the
 641		 * next chunk.
 642		 */
 643		if (chunk->tsn_gap_acked) {
 644			list_move_tail(&chunk->transmitted_list,
 645				       &transport->transmitted);
 646			continue;
 647		}
 648
 649		/* If we are doing fast retransmit, ignore non-fast_rtransmit
 650		 * chunks
 651		 */
 652		if (fast_rtx && !chunk->fast_retransmit)
 653			continue;
 654
 655redo:
 656		/* Attempt to append this chunk to the packet. */
 657		status = sctp_packet_append_chunk(pkt, chunk);
 658
 659		switch (status) {
 660		case SCTP_XMIT_PMTU_FULL:
 661			if (!pkt->has_data && !pkt->has_cookie_echo) {
 662				/* If this packet did not contain DATA then
 663				 * retransmission did not happen, so do it
 664				 * again.  We'll ignore the error here since
 665				 * control chunks are already freed so there
 666				 * is nothing we can do.
 667				 */
 668				sctp_packet_transmit(pkt, gfp);
 669				goto redo;
 670			}
 671
 672			/* Send this packet.  */
 673			error = sctp_packet_transmit(pkt, gfp);
 674
 675			/* If we are retransmitting, we should only
 676			 * send a single packet.
 677			 * Otherwise, try appending this chunk again.
 678			 */
 679			if (rtx_timeout || fast_rtx)
 680				done = 1;
 681			else
 682				goto redo;
 683
 684			/* Bundle next chunk in the next round.  */
 685			break;
 686
 687		case SCTP_XMIT_RWND_FULL:
 688			/* Send this packet. */
 689			error = sctp_packet_transmit(pkt, gfp);
 690
 691			/* Stop sending DATA as there is no more room
 692			 * at the receiver.
 693			 */
 694			done = 1;
 695			break;
 696
 697		case SCTP_XMIT_DELAY:
 698			/* Send this packet. */
 699			error = sctp_packet_transmit(pkt, gfp);
 700
 701			/* Stop sending DATA because of nagle delay. */
 702			done = 1;
 703			break;
 704
 705		default:
 706			/* The append was successful, so add this chunk to
 707			 * the transmitted list.
 708			 */
 709			list_move_tail(&chunk->transmitted_list,
 710				       &transport->transmitted);
 711
 712			/* Mark the chunk as ineligible for fast retransmit
 713			 * after it is retransmitted.
 714			 */
 715			if (chunk->fast_retransmit == SCTP_NEED_FRTX)
 716				chunk->fast_retransmit = SCTP_DONT_FRTX;
 717
 718			q->asoc->stats.rtxchunks++;
 719			break;
 720		}
 721
 722		/* Set the timer if there were no errors */
 723		if (!error && !timer)
 724			timer = 1;
 725
 726		if (done)
 727			break;
 728	}
 729
 730	/* If we are here due to a retransmit timeout or a fast
 731	 * retransmit and if there are any chunks left in the retransmit
 732	 * queue that could not fit in the PMTU sized packet, they need
 733	 * to be marked as ineligible for a subsequent fast retransmit.
 734	 */
 735	if (rtx_timeout || fast_rtx) {
 736		list_for_each_entry(chunk1, lqueue, transmitted_list) {
 737			if (chunk1->fast_retransmit == SCTP_NEED_FRTX)
 738				chunk1->fast_retransmit = SCTP_DONT_FRTX;
 739		}
 740	}
 741
 742	*start_timer = timer;
 743
 744	/* Clear fast retransmit hint */
 745	if (fast_rtx)
 746		q->fast_rtx = 0;
 747
 748	return error;
 749}
 750
 751/* Cork the outqueue so queued chunks are really queued. */
 752void sctp_outq_uncork(struct sctp_outq *q, gfp_t gfp)
 753{
 754	if (q->cork)
 755		q->cork = 0;
 756
 757	sctp_outq_flush(q, 0, gfp);
 758}
 759
 760static int sctp_packet_singleton(struct sctp_transport *transport,
 761				 struct sctp_chunk *chunk, gfp_t gfp)
 
 
 
 
 
 
 
 
 
 762{
 763	const struct sctp_association *asoc = transport->asoc;
 764	const __u16 sport = asoc->base.bind_addr.port;
 765	const __u16 dport = asoc->peer.port;
 766	const __u32 vtag = asoc->peer.i.init_tag;
 767	struct sctp_packet singleton;
 
 
 
 
 
 
 
 
 
 
 
 768
 769	sctp_packet_init(&singleton, transport, sport, dport);
 770	sctp_packet_config(&singleton, vtag, 0);
 771	sctp_packet_append_chunk(&singleton, chunk);
 772	return sctp_packet_transmit(&singleton, gfp);
 773}
 774
 775/* Struct to hold the context during sctp outq flush */
 776struct sctp_flush_ctx {
 777	struct sctp_outq *q;
 778	/* Current transport being used. It's NOT the same as curr active one */
 779	struct sctp_transport *transport;
 780	/* These transports have chunks to send. */
 781	struct list_head transport_list;
 782	struct sctp_association *asoc;
 783	/* Packet on the current transport above */
 784	struct sctp_packet *packet;
 785	gfp_t gfp;
 786};
 787
 788/* transport: current transport */
 789static void sctp_outq_select_transport(struct sctp_flush_ctx *ctx,
 790				       struct sctp_chunk *chunk)
 791{
 792	struct sctp_transport *new_transport = chunk->transport;
 793
 794	if (!new_transport) {
 795		if (!sctp_chunk_is_data(chunk)) {
 796			/* If we have a prior transport pointer, see if
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 797			 * the destination address of the chunk
 798			 * matches the destination address of the
 799			 * current transport.  If not a match, then
 800			 * try to look up the transport with a given
 801			 * destination address.  We do this because
 802			 * after processing ASCONFs, we may have new
 803			 * transports created.
 804			 */
 805			if (ctx->transport && sctp_cmp_addr_exact(&chunk->dest,
 806							&ctx->transport->ipaddr))
 807				new_transport = ctx->transport;
 
 808			else
 809				new_transport = sctp_assoc_lookup_paddr(ctx->asoc,
 810								  &chunk->dest);
 811		}
 812
 813		/* if we still don't have a new transport, then
 814		 * use the current active path.
 815		 */
 816		if (!new_transport)
 817			new_transport = ctx->asoc->peer.active_path;
 818	} else {
 819		__u8 type;
 820
 821		switch (new_transport->state) {
 822		case SCTP_INACTIVE:
 823		case SCTP_UNCONFIRMED:
 824		case SCTP_PF:
 825			/* If the chunk is Heartbeat or Heartbeat Ack,
 826			 * send it to chunk->transport, even if it's
 827			 * inactive.
 828			 *
 829			 * 3.3.6 Heartbeat Acknowledgement:
 830			 * ...
 831			 * A HEARTBEAT ACK is always sent to the source IP
 832			 * address of the IP datagram containing the
 833			 * HEARTBEAT chunk to which this ack is responding.
 834			 * ...
 835			 *
 836			 * ASCONF_ACKs also must be sent to the source.
 837			 */
 838			type = chunk->chunk_hdr->type;
 839			if (type != SCTP_CID_HEARTBEAT &&
 840			    type != SCTP_CID_HEARTBEAT_ACK &&
 841			    type != SCTP_CID_ASCONF_ACK)
 842				new_transport = ctx->asoc->peer.active_path;
 843			break;
 844		default:
 845			break;
 846		}
 847	}
 848
 849	/* Are we switching transports? Take care of transport locks. */
 850	if (new_transport != ctx->transport) {
 851		ctx->transport = new_transport;
 852		ctx->packet = &ctx->transport->packet;
 853
 854		if (list_empty(&ctx->transport->send_ready))
 855			list_add_tail(&ctx->transport->send_ready,
 856				      &ctx->transport_list);
 857
 858		sctp_packet_config(ctx->packet,
 859				   ctx->asoc->peer.i.init_tag,
 860				   ctx->asoc->peer.ecn_capable);
 861		/* We've switched transports, so apply the
 862		 * Burst limit to the new transport.
 863		 */
 864		sctp_transport_burst_limited(ctx->transport);
 865	}
 866}
 867
 868static void sctp_outq_flush_ctrl(struct sctp_flush_ctx *ctx)
 869{
 870	struct sctp_chunk *chunk, *tmp;
 871	enum sctp_xmit status;
 872	int one_packet, error;
 873
 874	list_for_each_entry_safe(chunk, tmp, &ctx->q->control_chunk_list, list) {
 875		one_packet = 0;
 876
 877		/* RFC 5061, 5.3
 878		 * F1) This means that until such time as the ASCONF
 879		 * containing the add is acknowledged, the sender MUST
 880		 * NOT use the new IP address as a source for ANY SCTP
 881		 * packet except on carrying an ASCONF Chunk.
 882		 */
 883		if (ctx->asoc->src_out_of_asoc_ok &&
 884		    chunk->chunk_hdr->type != SCTP_CID_ASCONF)
 885			continue;
 886
 887		list_del_init(&chunk->list);
 888
 889		/* Pick the right transport to use. Should always be true for
 890		 * the first chunk as we don't have a transport by then.
 891		 */
 892		sctp_outq_select_transport(ctx, chunk);
 
 
 
 
 
 
 
 
 
 893
 894		switch (chunk->chunk_hdr->type) {
 895		/* 6.10 Bundling
 
 896		 *   ...
 897		 *   An endpoint MUST NOT bundle INIT, INIT ACK or SHUTDOWN
 898		 *   COMPLETE with any other chunks.  [Send them immediately.]
 899		 */
 900		case SCTP_CID_INIT:
 901		case SCTP_CID_INIT_ACK:
 902		case SCTP_CID_SHUTDOWN_COMPLETE:
 903			error = sctp_packet_singleton(ctx->transport, chunk,
 904						      ctx->gfp);
 
 
 905			if (error < 0) {
 906				ctx->asoc->base.sk->sk_err = -error;
 907				return;
 908			}
 909			break;
 910
 911		case SCTP_CID_ABORT:
 912			if (sctp_test_T_bit(chunk))
 913				ctx->packet->vtag = ctx->asoc->c.my_vtag;
 914			/* fallthru */
 915
 916		/* The following chunks are "response" chunks, i.e.
 917		 * they are generated in response to something we
 918		 * received.  If we are sending these, then we can
 919		 * send only 1 packet containing these chunks.
 920		 */
 921		case SCTP_CID_HEARTBEAT_ACK:
 922		case SCTP_CID_SHUTDOWN_ACK:
 923		case SCTP_CID_COOKIE_ACK:
 924		case SCTP_CID_COOKIE_ECHO:
 925		case SCTP_CID_ERROR:
 926		case SCTP_CID_ECN_CWR:
 927		case SCTP_CID_ASCONF_ACK:
 928			one_packet = 1;
 929			/* Fall through */
 930
 931		case SCTP_CID_SACK:
 932		case SCTP_CID_HEARTBEAT:
 933		case SCTP_CID_SHUTDOWN:
 934		case SCTP_CID_ECN_ECNE:
 935		case SCTP_CID_ASCONF:
 936		case SCTP_CID_FWD_TSN:
 937		case SCTP_CID_I_FWD_TSN:
 938		case SCTP_CID_RECONF:
 939			status = sctp_packet_transmit_chunk(ctx->packet, chunk,
 940							    one_packet, ctx->gfp);
 941			if (status != SCTP_XMIT_OK) {
 942				/* put the chunk back */
 943				list_add(&chunk->list, &ctx->q->control_chunk_list);
 944				break;
 945			}
 946
 947			ctx->asoc->stats.octrlchunks++;
 948			/* PR-SCTP C5) If a FORWARD TSN is sent, the
 949			 * sender MUST assure that at least one T3-rtx
 950			 * timer is running.
 951			 */
 952			if (chunk->chunk_hdr->type == SCTP_CID_FWD_TSN ||
 953			    chunk->chunk_hdr->type == SCTP_CID_I_FWD_TSN) {
 954				sctp_transport_reset_t3_rtx(ctx->transport);
 955				ctx->transport->last_time_sent = jiffies;
 956			}
 957
 958			if (chunk == ctx->asoc->strreset_chunk)
 959				sctp_transport_reset_reconf_timer(ctx->transport);
 960
 961			break;
 962
 963		default:
 964			/* We built a chunk with an illegal type! */
 965			BUG();
 966		}
 967	}
 968}
 969
 970/* Returns false if new data shouldn't be sent */
 971static bool sctp_outq_flush_rtx(struct sctp_flush_ctx *ctx,
 972				int rtx_timeout)
 973{
 974	int error, start_timer = 0;
 975
 976	if (ctx->asoc->peer.retran_path->state == SCTP_UNCONFIRMED)
 977		return false;
 978
 979	if (ctx->transport != ctx->asoc->peer.retran_path) {
 980		/* Switch transports & prepare the packet.  */
 981		ctx->transport = ctx->asoc->peer.retran_path;
 982		ctx->packet = &ctx->transport->packet;
 983
 984		if (list_empty(&ctx->transport->send_ready))
 985			list_add_tail(&ctx->transport->send_ready,
 986				      &ctx->transport_list);
 987
 988		sctp_packet_config(ctx->packet, ctx->asoc->peer.i.init_tag,
 989				   ctx->asoc->peer.ecn_capable);
 990	}
 991
 992	error = __sctp_outq_flush_rtx(ctx->q, ctx->packet, rtx_timeout,
 993				      &start_timer, ctx->gfp);
 994	if (error < 0)
 995		ctx->asoc->base.sk->sk_err = -error;
 996
 997	if (start_timer) {
 998		sctp_transport_reset_t3_rtx(ctx->transport);
 999		ctx->transport->last_time_sent = jiffies;
1000	}
1001
1002	/* This can happen on COOKIE-ECHO resend.  Only
1003	 * one chunk can get bundled with a COOKIE-ECHO.
1004	 */
1005	if (ctx->packet->has_cookie_echo)
1006		return false;
1007
1008	/* Don't send new data if there is still data
1009	 * waiting to retransmit.
1010	 */
1011	if (!list_empty(&ctx->q->retransmit))
1012		return false;
1013
1014	return true;
1015}
1016
1017static void sctp_outq_flush_data(struct sctp_flush_ctx *ctx,
1018				 int rtx_timeout)
1019{
1020	struct sctp_chunk *chunk;
1021	enum sctp_xmit status;
1022
1023	/* Is it OK to send data chunks?  */
1024	switch (ctx->asoc->state) {
1025	case SCTP_STATE_COOKIE_ECHOED:
1026		/* Only allow bundling when this packet has a COOKIE-ECHO
1027		 * chunk.
1028		 */
1029		if (!ctx->packet || !ctx->packet->has_cookie_echo)
1030			return;
1031
1032		/* fall through */
1033	case SCTP_STATE_ESTABLISHED:
1034	case SCTP_STATE_SHUTDOWN_PENDING:
1035	case SCTP_STATE_SHUTDOWN_RECEIVED:
1036		break;
1037
1038	default:
1039		/* Do nothing. */
1040		return;
1041	}
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1042
1043	/* RFC 2960 6.1  Transmission of DATA Chunks
1044	 *
1045	 * C) When the time comes for the sender to transmit,
1046	 * before sending new DATA chunks, the sender MUST
1047	 * first transmit any outstanding DATA chunks which
1048	 * are marked for retransmission (limited by the
1049	 * current cwnd).
1050	 */
1051	if (!list_empty(&ctx->q->retransmit) &&
1052	    !sctp_outq_flush_rtx(ctx, rtx_timeout))
1053		return;
1054
1055	/* Apply Max.Burst limitation to the current transport in
1056	 * case it will be used for new data.  We are going to
1057	 * rest it before we return, but we want to apply the limit
1058	 * to the currently queued data.
1059	 */
1060	if (ctx->transport)
1061		sctp_transport_burst_limited(ctx->transport);
1062
1063	/* Finally, transmit new packets.  */
1064	while ((chunk = sctp_outq_dequeue_data(ctx->q)) != NULL) {
1065		__u32 sid = ntohs(chunk->subh.data_hdr->stream);
1066		__u8 stream_state = SCTP_SO(&ctx->asoc->stream, sid)->state;
 
1067
1068		/* Has this chunk expired? */
1069		if (sctp_chunk_abandoned(chunk)) {
1070			sctp_sched_dequeue_done(ctx->q, chunk);
1071			sctp_chunk_fail(chunk, 0);
1072			sctp_chunk_free(chunk);
1073			continue;
1074		}
1075
1076		if (stream_state == SCTP_STREAM_CLOSED) {
1077			sctp_outq_head_data(ctx->q, chunk);
1078			break;
1079		}
 
 
 
1080
1081		sctp_outq_select_transport(ctx, chunk);
 
 
 
 
 
 
 
 
 
 
1082
1083		pr_debug("%s: outq:%p, chunk:%p[%s], tx-tsn:0x%x skb->head:%p skb->users:%d\n",
1084			 __func__, ctx->q, chunk, chunk && chunk->chunk_hdr ?
1085			 sctp_cname(SCTP_ST_CHUNK(chunk->chunk_hdr->type)) :
1086			 "illegal chunk", ntohl(chunk->subh.data_hdr->tsn),
1087			 chunk->skb ? chunk->skb->head : NULL, chunk->skb ?
1088			 refcount_read(&chunk->skb->users) : -1);
1089
1090		/* Add the chunk to the packet.  */
1091		status = sctp_packet_transmit_chunk(ctx->packet, chunk, 0,
1092						    ctx->gfp);
1093		if (status != SCTP_XMIT_OK) {
1094			/* We could not append this chunk, so put
1095			 * the chunk back on the output queue.
1096			 */
1097			pr_debug("%s: could not transmit tsn:0x%x, status:%d\n",
1098				 __func__, ntohl(chunk->subh.data_hdr->tsn),
1099				 status);
1100
1101			sctp_outq_head_data(ctx->q, chunk);
1102			break;
1103		}
 
 
 
 
 
 
 
 
 
 
 
 
 
1104
1105		/* The sender is in the SHUTDOWN-PENDING state,
1106		 * The sender MAY set the I-bit in the DATA
1107		 * chunk header.
1108		 */
1109		if (ctx->asoc->state == SCTP_STATE_SHUTDOWN_PENDING)
1110			chunk->chunk_hdr->flags |= SCTP_DATA_SACK_IMM;
1111		if (chunk->chunk_hdr->flags & SCTP_DATA_UNORDERED)
1112			ctx->asoc->stats.ouodchunks++;
1113		else
1114			ctx->asoc->stats.oodchunks++;
1115
1116		/* Only now it's safe to consider this
1117		 * chunk as sent, sched-wise.
1118		 */
1119		sctp_sched_dequeue_done(ctx->q, chunk);
 
 
 
1120
1121		list_add_tail(&chunk->transmitted_list,
1122			      &ctx->transport->transmitted);
 
 
 
 
 
 
1123
1124		sctp_transport_reset_t3_rtx(ctx->transport);
1125		ctx->transport->last_time_sent = jiffies;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1126
1127		/* Only let one DATA chunk get bundled with a
1128		 * COOKIE-ECHO chunk.
1129		 */
1130		if (ctx->packet->has_cookie_echo)
1131			break;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1132	}
1133}
1134
1135static void sctp_outq_flush_transports(struct sctp_flush_ctx *ctx)
1136{
1137	struct list_head *ltransport;
1138	struct sctp_packet *packet;
1139	struct sctp_transport *t;
1140	int error = 0;
1141
1142	while ((ltransport = sctp_list_dequeue(&ctx->transport_list)) != NULL) {
1143		t = list_entry(ltransport, struct sctp_transport, send_ready);
 
 
 
 
 
 
 
 
 
1144		packet = &t->packet;
1145		if (!sctp_packet_empty(packet)) {
1146			error = sctp_packet_transmit(packet, ctx->gfp);
1147			if (error < 0)
1148				ctx->q->asoc->base.sk->sk_err = -error;
1149		}
1150
1151		/* Clear the burst limited state, if any */
1152		sctp_transport_burst_reset(t);
1153	}
1154}
1155
1156/* Try to flush an outqueue.
1157 *
1158 * Description: Send everything in q which we legally can, subject to
1159 * congestion limitations.
1160 * * Note: This function can be called from multiple contexts so appropriate
1161 * locking concerns must be made.  Today we use the sock lock to protect
1162 * this function.
1163 */
1164
1165static void sctp_outq_flush(struct sctp_outq *q, int rtx_timeout, gfp_t gfp)
1166{
1167	struct sctp_flush_ctx ctx = {
1168		.q = q,
1169		.transport = NULL,
1170		.transport_list = LIST_HEAD_INIT(ctx.transport_list),
1171		.asoc = q->asoc,
1172		.packet = NULL,
1173		.gfp = gfp,
1174	};
1175
1176	/* 6.10 Bundling
1177	 *   ...
1178	 *   When bundling control chunks with DATA chunks, an
1179	 *   endpoint MUST place control chunks first in the outbound
1180	 *   SCTP packet.  The transmitter MUST transmit DATA chunks
1181	 *   within a SCTP packet in increasing order of TSN.
1182	 *   ...
1183	 */
1184
1185	sctp_outq_flush_ctrl(&ctx);
1186
1187	if (q->asoc->src_out_of_asoc_ok)
1188		goto sctp_flush_out;
1189
1190	sctp_outq_flush_data(&ctx, rtx_timeout);
1191
1192sctp_flush_out:
1193
1194	sctp_outq_flush_transports(&ctx);
1195}
1196
1197/* Update unack_data based on the incoming SACK chunk */
1198static void sctp_sack_update_unack_data(struct sctp_association *assoc,
1199					struct sctp_sackhdr *sack)
1200{
1201	union sctp_sack_variable *frags;
1202	__u16 unack_data;
1203	int i;
1204
1205	unack_data = assoc->next_tsn - assoc->ctsn_ack_point - 1;
1206
1207	frags = sack->variable;
1208	for (i = 0; i < ntohs(sack->num_gap_ack_blocks); i++) {
1209		unack_data -= ((ntohs(frags[i].gab.end) -
1210				ntohs(frags[i].gab.start) + 1));
1211	}
1212
1213	assoc->unack_data = unack_data;
1214}
1215
1216/* This is where we REALLY process a SACK.
1217 *
1218 * Process the SACK against the outqueue.  Mostly, this just frees
1219 * things off the transmitted queue.
1220 */
1221int sctp_outq_sack(struct sctp_outq *q, struct sctp_chunk *chunk)
1222{
1223	struct sctp_association *asoc = q->asoc;
1224	struct sctp_sackhdr *sack = chunk->subh.sack_hdr;
1225	struct sctp_transport *transport;
1226	struct sctp_chunk *tchunk = NULL;
1227	struct list_head *lchunk, *transport_list, *temp;
1228	union sctp_sack_variable *frags = sack->variable;
1229	__u32 sack_ctsn, ctsn, tsn;
1230	__u32 highest_tsn, highest_new_tsn;
1231	__u32 sack_a_rwnd;
1232	unsigned int outstanding;
1233	struct sctp_transport *primary = asoc->peer.primary_path;
1234	int count_of_newacks = 0;
1235	int gap_ack_blocks;
1236	u8 accum_moved = 0;
1237
1238	/* Grab the association's destination address list. */
1239	transport_list = &asoc->peer.transport_addr_list;
1240
1241	sack_ctsn = ntohl(sack->cum_tsn_ack);
1242	gap_ack_blocks = ntohs(sack->num_gap_ack_blocks);
1243	asoc->stats.gapcnt += gap_ack_blocks;
1244	/*
1245	 * SFR-CACC algorithm:
1246	 * On receipt of a SACK the sender SHOULD execute the
1247	 * following statements.
1248	 *
1249	 * 1) If the cumulative ack in the SACK passes next tsn_at_change
1250	 * on the current primary, the CHANGEOVER_ACTIVE flag SHOULD be
1251	 * cleared. The CYCLING_CHANGEOVER flag SHOULD also be cleared for
1252	 * all destinations.
1253	 * 2) If the SACK contains gap acks and the flag CHANGEOVER_ACTIVE
1254	 * is set the receiver of the SACK MUST take the following actions:
1255	 *
1256	 * A) Initialize the cacc_saw_newack to 0 for all destination
1257	 * addresses.
1258	 *
1259	 * Only bother if changeover_active is set. Otherwise, this is
1260	 * totally suboptimal to do on every SACK.
1261	 */
1262	if (primary->cacc.changeover_active) {
1263		u8 clear_cycling = 0;
1264
1265		if (TSN_lte(primary->cacc.next_tsn_at_change, sack_ctsn)) {
1266			primary->cacc.changeover_active = 0;
1267			clear_cycling = 1;
1268		}
1269
1270		if (clear_cycling || gap_ack_blocks) {
1271			list_for_each_entry(transport, transport_list,
1272					transports) {
1273				if (clear_cycling)
1274					transport->cacc.cycling_changeover = 0;
1275				if (gap_ack_blocks)
1276					transport->cacc.cacc_saw_newack = 0;
1277			}
1278		}
1279	}
1280
1281	/* Get the highest TSN in the sack. */
1282	highest_tsn = sack_ctsn;
1283	if (gap_ack_blocks)
1284		highest_tsn += ntohs(frags[gap_ack_blocks - 1].gab.end);
1285
1286	if (TSN_lt(asoc->highest_sacked, highest_tsn))
1287		asoc->highest_sacked = highest_tsn;
1288
1289	highest_new_tsn = sack_ctsn;
1290
1291	/* Run through the retransmit queue.  Credit bytes received
1292	 * and free those chunks that we can.
1293	 */
1294	sctp_check_transmitted(q, &q->retransmit, NULL, NULL, sack, &highest_new_tsn);
1295
1296	/* Run through the transmitted queue.
1297	 * Credit bytes received and free those chunks which we can.
1298	 *
1299	 * This is a MASSIVE candidate for optimization.
1300	 */
1301	list_for_each_entry(transport, transport_list, transports) {
1302		sctp_check_transmitted(q, &transport->transmitted,
1303				       transport, &chunk->source, sack,
1304				       &highest_new_tsn);
1305		/*
1306		 * SFR-CACC algorithm:
1307		 * C) Let count_of_newacks be the number of
1308		 * destinations for which cacc_saw_newack is set.
1309		 */
1310		if (transport->cacc.cacc_saw_newack)
1311			count_of_newacks++;
1312	}
1313
1314	/* Move the Cumulative TSN Ack Point if appropriate.  */
1315	if (TSN_lt(asoc->ctsn_ack_point, sack_ctsn)) {
1316		asoc->ctsn_ack_point = sack_ctsn;
1317		accum_moved = 1;
1318	}
1319
1320	if (gap_ack_blocks) {
1321
1322		if (asoc->fast_recovery && accum_moved)
1323			highest_new_tsn = highest_tsn;
1324
1325		list_for_each_entry(transport, transport_list, transports)
1326			sctp_mark_missing(q, &transport->transmitted, transport,
1327					  highest_new_tsn, count_of_newacks);
1328	}
1329
1330	/* Update unack_data field in the assoc. */
1331	sctp_sack_update_unack_data(asoc, sack);
1332
1333	ctsn = asoc->ctsn_ack_point;
1334
1335	/* Throw away stuff rotting on the sack queue.  */
1336	list_for_each_safe(lchunk, temp, &q->sacked) {
1337		tchunk = list_entry(lchunk, struct sctp_chunk,
1338				    transmitted_list);
1339		tsn = ntohl(tchunk->subh.data_hdr->tsn);
1340		if (TSN_lte(tsn, ctsn)) {
1341			list_del_init(&tchunk->transmitted_list);
1342			if (asoc->peer.prsctp_capable &&
1343			    SCTP_PR_PRIO_ENABLED(chunk->sinfo.sinfo_flags))
1344				asoc->sent_cnt_removable--;
1345			sctp_chunk_free(tchunk);
1346		}
1347	}
1348
1349	/* ii) Set rwnd equal to the newly received a_rwnd minus the
1350	 *     number of bytes still outstanding after processing the
1351	 *     Cumulative TSN Ack and the Gap Ack Blocks.
1352	 */
1353
1354	sack_a_rwnd = ntohl(sack->a_rwnd);
1355	asoc->peer.zero_window_announced = !sack_a_rwnd;
1356	outstanding = q->outstanding_bytes;
1357
1358	if (outstanding < sack_a_rwnd)
1359		sack_a_rwnd -= outstanding;
1360	else
1361		sack_a_rwnd = 0;
1362
1363	asoc->peer.rwnd = sack_a_rwnd;
1364
1365	asoc->stream.si->generate_ftsn(q, sack_ctsn);
1366
1367	pr_debug("%s: sack cumulative tsn ack:0x%x\n", __func__, sack_ctsn);
1368	pr_debug("%s: cumulative tsn ack of assoc:%p is 0x%x, "
1369		 "advertised peer ack point:0x%x\n", __func__, asoc, ctsn,
1370		 asoc->adv_peer_ack_point);
1371
1372	return sctp_outq_is_empty(q);
1373}
1374
1375/* Is the outqueue empty?
1376 * The queue is empty when we have not pending data, no in-flight data
1377 * and nothing pending retransmissions.
1378 */
1379int sctp_outq_is_empty(const struct sctp_outq *q)
1380{
1381	return q->out_qlen == 0 && q->outstanding_bytes == 0 &&
1382	       list_empty(&q->retransmit);
1383}
1384
1385/********************************************************************
1386 * 2nd Level Abstractions
1387 ********************************************************************/
1388
1389/* Go through a transport's transmitted list or the association's retransmit
1390 * list and move chunks that are acked by the Cumulative TSN Ack to q->sacked.
1391 * The retransmit list will not have an associated transport.
1392 *
1393 * I added coherent debug information output.	--xguo
1394 *
1395 * Instead of printing 'sacked' or 'kept' for each TSN on the
1396 * transmitted_queue, we print a range: SACKED: TSN1-TSN2, TSN3, TSN4-TSN5.
1397 * KEPT TSN6-TSN7, etc.
1398 */
1399static void sctp_check_transmitted(struct sctp_outq *q,
1400				   struct list_head *transmitted_queue,
1401				   struct sctp_transport *transport,
1402				   union sctp_addr *saddr,
1403				   struct sctp_sackhdr *sack,
1404				   __u32 *highest_new_tsn_in_sack)
1405{
1406	struct list_head *lchunk;
1407	struct sctp_chunk *tchunk;
1408	struct list_head tlist;
1409	__u32 tsn;
1410	__u32 sack_ctsn;
1411	__u32 rtt;
1412	__u8 restart_timer = 0;
1413	int bytes_acked = 0;
1414	int migrate_bytes = 0;
1415	bool forward_progress = false;
1416
1417	sack_ctsn = ntohl(sack->cum_tsn_ack);
1418
1419	INIT_LIST_HEAD(&tlist);
1420
1421	/* The while loop will skip empty transmitted queues. */
1422	while (NULL != (lchunk = sctp_list_dequeue(transmitted_queue))) {
1423		tchunk = list_entry(lchunk, struct sctp_chunk,
1424				    transmitted_list);
1425
1426		if (sctp_chunk_abandoned(tchunk)) {
1427			/* Move the chunk to abandoned list. */
1428			sctp_insert_list(&q->abandoned, lchunk);
1429
1430			/* If this chunk has not been acked, stop
1431			 * considering it as 'outstanding'.
1432			 */
1433			if (transmitted_queue != &q->retransmit &&
1434			    !tchunk->tsn_gap_acked) {
1435				if (tchunk->transport)
1436					tchunk->transport->flight_size -=
1437							sctp_data_size(tchunk);
1438				q->outstanding_bytes -= sctp_data_size(tchunk);
1439			}
1440			continue;
1441		}
1442
1443		tsn = ntohl(tchunk->subh.data_hdr->tsn);
1444		if (sctp_acked(sack, tsn)) {
1445			/* If this queue is the retransmit queue, the
1446			 * retransmit timer has already reclaimed
1447			 * the outstanding bytes for this chunk, so only
1448			 * count bytes associated with a transport.
1449			 */
1450			if (transport && !tchunk->tsn_gap_acked) {
1451				/* If this chunk is being used for RTT
1452				 * measurement, calculate the RTT and update
1453				 * the RTO using this value.
1454				 *
1455				 * 6.3.1 C5) Karn's algorithm: RTT measurements
1456				 * MUST NOT be made using packets that were
1457				 * retransmitted (and thus for which it is
1458				 * ambiguous whether the reply was for the
1459				 * first instance of the packet or a later
1460				 * instance).
1461				 */
1462				if (!sctp_chunk_retransmitted(tchunk) &&
 
1463				    tchunk->rtt_in_progress) {
1464					tchunk->rtt_in_progress = 0;
1465					rtt = jiffies - tchunk->sent_at;
1466					sctp_transport_update_rto(transport,
1467								  rtt);
1468				}
1469
1470				if (TSN_lte(tsn, sack_ctsn)) {
1471					/*
1472					 * SFR-CACC algorithm:
1473					 * 2) If the SACK contains gap acks
1474					 * and the flag CHANGEOVER_ACTIVE is
1475					 * set the receiver of the SACK MUST
1476					 * take the following action:
1477					 *
1478					 * B) For each TSN t being acked that
1479					 * has not been acked in any SACK so
1480					 * far, set cacc_saw_newack to 1 for
1481					 * the destination that the TSN was
1482					 * sent to.
1483					 */
1484					if (sack->num_gap_ack_blocks &&
1485					    q->asoc->peer.primary_path->cacc.
1486					    changeover_active)
1487						transport->cacc.cacc_saw_newack
1488							= 1;
1489				}
1490			}
1491
1492			/* If the chunk hasn't been marked as ACKED,
1493			 * mark it and account bytes_acked if the
1494			 * chunk had a valid transport (it will not
1495			 * have a transport if ASCONF had deleted it
1496			 * while DATA was outstanding).
1497			 */
1498			if (!tchunk->tsn_gap_acked) {
1499				tchunk->tsn_gap_acked = 1;
1500				if (TSN_lt(*highest_new_tsn_in_sack, tsn))
1501					*highest_new_tsn_in_sack = tsn;
1502				bytes_acked += sctp_data_size(tchunk);
1503				if (!tchunk->transport)
1504					migrate_bytes += sctp_data_size(tchunk);
1505				forward_progress = true;
1506			}
1507
1508			if (TSN_lte(tsn, sack_ctsn)) {
1509				/* RFC 2960  6.3.2 Retransmission Timer Rules
1510				 *
1511				 * R3) Whenever a SACK is received
1512				 * that acknowledges the DATA chunk
1513				 * with the earliest outstanding TSN
1514				 * for that address, restart T3-rtx
1515				 * timer for that address with its
1516				 * current RTO.
1517				 */
1518				restart_timer = 1;
1519				forward_progress = true;
1520
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1521				list_add_tail(&tchunk->transmitted_list,
1522					      &q->sacked);
1523			} else {
1524				/* RFC2960 7.2.4, sctpimpguide-05 2.8.2
1525				 * M2) Each time a SACK arrives reporting
1526				 * 'Stray DATA chunk(s)' record the highest TSN
1527				 * reported as newly acknowledged, call this
1528				 * value 'HighestTSNinSack'. A newly
1529				 * acknowledged DATA chunk is one not
1530				 * previously acknowledged in a SACK.
1531				 *
1532				 * When the SCTP sender of data receives a SACK
1533				 * chunk that acknowledges, for the first time,
1534				 * the receipt of a DATA chunk, all the still
1535				 * unacknowledged DATA chunks whose TSN is
1536				 * older than that newly acknowledged DATA
1537				 * chunk, are qualified as 'Stray DATA chunks'.
1538				 */
1539				list_add_tail(lchunk, &tlist);
1540			}
1541		} else {
1542			if (tchunk->tsn_gap_acked) {
1543				pr_debug("%s: receiver reneged on data TSN:0x%x\n",
1544					 __func__, tsn);
1545
1546				tchunk->tsn_gap_acked = 0;
1547
1548				if (tchunk->transport)
1549					bytes_acked -= sctp_data_size(tchunk);
1550
1551				/* RFC 2960 6.3.2 Retransmission Timer Rules
1552				 *
1553				 * R4) Whenever a SACK is received missing a
1554				 * TSN that was previously acknowledged via a
1555				 * Gap Ack Block, start T3-rtx for the
1556				 * destination address to which the DATA
1557				 * chunk was originally
1558				 * transmitted if it is not already running.
1559				 */
1560				restart_timer = 1;
1561			}
1562
1563			list_add_tail(lchunk, &tlist);
1564		}
1565	}
1566
1567	if (transport) {
1568		if (bytes_acked) {
1569			struct sctp_association *asoc = transport->asoc;
1570
1571			/* We may have counted DATA that was migrated
1572			 * to this transport due to DEL-IP operation.
1573			 * Subtract those bytes, since the were never
1574			 * send on this transport and shouldn't be
1575			 * credited to this transport.
1576			 */
1577			bytes_acked -= migrate_bytes;
1578
1579			/* 8.2. When an outstanding TSN is acknowledged,
1580			 * the endpoint shall clear the error counter of
1581			 * the destination transport address to which the
1582			 * DATA chunk was last sent.
1583			 * The association's overall error counter is
1584			 * also cleared.
1585			 */
1586			transport->error_count = 0;
1587			transport->asoc->overall_error_count = 0;
1588			forward_progress = true;
1589
1590			/*
1591			 * While in SHUTDOWN PENDING, we may have started
1592			 * the T5 shutdown guard timer after reaching the
1593			 * retransmission limit. Stop that timer as soon
1594			 * as the receiver acknowledged any data.
1595			 */
1596			if (asoc->state == SCTP_STATE_SHUTDOWN_PENDING &&
1597			    del_timer(&asoc->timers
1598				[SCTP_EVENT_TIMEOUT_T5_SHUTDOWN_GUARD]))
1599					sctp_association_put(asoc);
1600
1601			/* Mark the destination transport address as
1602			 * active if it is not so marked.
1603			 */
1604			if ((transport->state == SCTP_INACTIVE ||
1605			     transport->state == SCTP_UNCONFIRMED) &&
1606			    sctp_cmp_addr_exact(&transport->ipaddr, saddr)) {
1607				sctp_assoc_control_transport(
1608					transport->asoc,
1609					transport,
1610					SCTP_TRANSPORT_UP,
1611					SCTP_RECEIVED_SACK);
1612			}
1613
1614			sctp_transport_raise_cwnd(transport, sack_ctsn,
1615						  bytes_acked);
1616
1617			transport->flight_size -= bytes_acked;
1618			if (transport->flight_size == 0)
1619				transport->partial_bytes_acked = 0;
1620			q->outstanding_bytes -= bytes_acked + migrate_bytes;
1621		} else {
1622			/* RFC 2960 6.1, sctpimpguide-06 2.15.2
1623			 * When a sender is doing zero window probing, it
1624			 * should not timeout the association if it continues
1625			 * to receive new packets from the receiver. The
1626			 * reason is that the receiver MAY keep its window
1627			 * closed for an indefinite time.
1628			 * A sender is doing zero window probing when the
1629			 * receiver's advertised window is zero, and there is
1630			 * only one data chunk in flight to the receiver.
1631			 *
1632			 * Allow the association to timeout while in SHUTDOWN
1633			 * PENDING or SHUTDOWN RECEIVED in case the receiver
1634			 * stays in zero window mode forever.
1635			 */
1636			if (!q->asoc->peer.rwnd &&
1637			    !list_empty(&tlist) &&
1638			    (sack_ctsn+2 == q->asoc->next_tsn) &&
1639			    q->asoc->state < SCTP_STATE_SHUTDOWN_PENDING) {
1640				pr_debug("%s: sack received for zero window "
1641					 "probe:%u\n", __func__, sack_ctsn);
1642
1643				q->asoc->overall_error_count = 0;
1644				transport->error_count = 0;
1645			}
1646		}
1647
1648		/* RFC 2960 6.3.2 Retransmission Timer Rules
1649		 *
1650		 * R2) Whenever all outstanding data sent to an address have
1651		 * been acknowledged, turn off the T3-rtx timer of that
1652		 * address.
1653		 */
1654		if (!transport->flight_size) {
1655			if (del_timer(&transport->T3_rtx_timer))
1656				sctp_transport_put(transport);
1657		} else if (restart_timer) {
1658			if (!mod_timer(&transport->T3_rtx_timer,
1659				       jiffies + transport->rto))
1660				sctp_transport_hold(transport);
1661		}
1662
1663		if (forward_progress) {
1664			if (transport->dst)
1665				sctp_transport_dst_confirm(transport);
1666		}
1667	}
1668
1669	list_splice(&tlist, transmitted_queue);
1670}
1671
1672/* Mark chunks as missing and consequently may get retransmitted. */
1673static void sctp_mark_missing(struct sctp_outq *q,
1674			      struct list_head *transmitted_queue,
1675			      struct sctp_transport *transport,
1676			      __u32 highest_new_tsn_in_sack,
1677			      int count_of_newacks)
1678{
1679	struct sctp_chunk *chunk;
1680	__u32 tsn;
1681	char do_fast_retransmit = 0;
1682	struct sctp_association *asoc = q->asoc;
1683	struct sctp_transport *primary = asoc->peer.primary_path;
1684
1685	list_for_each_entry(chunk, transmitted_queue, transmitted_list) {
1686
1687		tsn = ntohl(chunk->subh.data_hdr->tsn);
1688
1689		/* RFC 2960 7.2.4, sctpimpguide-05 2.8.2 M3) Examine all
1690		 * 'Unacknowledged TSN's', if the TSN number of an
1691		 * 'Unacknowledged TSN' is smaller than the 'HighestTSNinSack'
1692		 * value, increment the 'TSN.Missing.Report' count on that
1693		 * chunk if it has NOT been fast retransmitted or marked for
1694		 * fast retransmit already.
1695		 */
1696		if (chunk->fast_retransmit == SCTP_CAN_FRTX &&
1697		    !chunk->tsn_gap_acked &&
1698		    TSN_lt(tsn, highest_new_tsn_in_sack)) {
1699
1700			/* SFR-CACC may require us to skip marking
1701			 * this chunk as missing.
1702			 */
1703			if (!transport || !sctp_cacc_skip(primary,
1704						chunk->transport,
1705						count_of_newacks, tsn)) {
1706				chunk->tsn_missing_report++;
1707
1708				pr_debug("%s: tsn:0x%x missing counter:%d\n",
1709					 __func__, tsn, chunk->tsn_missing_report);
1710			}
1711		}
1712		/*
1713		 * M4) If any DATA chunk is found to have a
1714		 * 'TSN.Missing.Report'
1715		 * value larger than or equal to 3, mark that chunk for
1716		 * retransmission and start the fast retransmit procedure.
1717		 */
1718
1719		if (chunk->tsn_missing_report >= 3) {
1720			chunk->fast_retransmit = SCTP_NEED_FRTX;
1721			do_fast_retransmit = 1;
1722		}
1723	}
1724
1725	if (transport) {
1726		if (do_fast_retransmit)
1727			sctp_retransmit(q, transport, SCTP_RTXR_FAST_RTX);
1728
1729		pr_debug("%s: transport:%p, cwnd:%d, ssthresh:%d, "
1730			 "flight_size:%d, pba:%d\n",  __func__, transport,
1731			 transport->cwnd, transport->ssthresh,
1732			 transport->flight_size, transport->partial_bytes_acked);
1733	}
1734}
1735
1736/* Is the given TSN acked by this packet?  */
1737static int sctp_acked(struct sctp_sackhdr *sack, __u32 tsn)
1738{
1739	__u32 ctsn = ntohl(sack->cum_tsn_ack);
1740	union sctp_sack_variable *frags;
1741	__u16 tsn_offset, blocks;
1742	int i;
1743
1744	if (TSN_lte(tsn, ctsn))
1745		goto pass;
1746
1747	/* 3.3.4 Selective Acknowledgment (SACK) (3):
1748	 *
1749	 * Gap Ack Blocks:
1750	 *  These fields contain the Gap Ack Blocks. They are repeated
1751	 *  for each Gap Ack Block up to the number of Gap Ack Blocks
1752	 *  defined in the Number of Gap Ack Blocks field. All DATA
1753	 *  chunks with TSNs greater than or equal to (Cumulative TSN
1754	 *  Ack + Gap Ack Block Start) and less than or equal to
1755	 *  (Cumulative TSN Ack + Gap Ack Block End) of each Gap Ack
1756	 *  Block are assumed to have been received correctly.
1757	 */
1758
1759	frags = sack->variable;
1760	blocks = ntohs(sack->num_gap_ack_blocks);
1761	tsn_offset = tsn - ctsn;
1762	for (i = 0; i < blocks; ++i) {
1763		if (tsn_offset >= ntohs(frags[i].gab.start) &&
1764		    tsn_offset <= ntohs(frags[i].gab.end))
1765			goto pass;
1766	}
1767
1768	return 0;
1769pass:
1770	return 1;
1771}
1772
1773static inline int sctp_get_skip_pos(struct sctp_fwdtsn_skip *skiplist,
1774				    int nskips, __be16 stream)
1775{
1776	int i;
1777
1778	for (i = 0; i < nskips; i++) {
1779		if (skiplist[i].stream == stream)
1780			return i;
1781	}
1782	return i;
1783}
1784
1785/* Create and add a fwdtsn chunk to the outq's control queue if needed. */
1786void sctp_generate_fwdtsn(struct sctp_outq *q, __u32 ctsn)
1787{
1788	struct sctp_association *asoc = q->asoc;
1789	struct sctp_chunk *ftsn_chunk = NULL;
1790	struct sctp_fwdtsn_skip ftsn_skip_arr[10];
1791	int nskips = 0;
1792	int skip_pos = 0;
1793	__u32 tsn;
1794	struct sctp_chunk *chunk;
1795	struct list_head *lchunk, *temp;
1796
1797	if (!asoc->peer.prsctp_capable)
1798		return;
1799
1800	/* PR-SCTP C1) Let SackCumAck be the Cumulative TSN ACK carried in the
1801	 * received SACK.
1802	 *
1803	 * If (Advanced.Peer.Ack.Point < SackCumAck), then update
1804	 * Advanced.Peer.Ack.Point to be equal to SackCumAck.
1805	 */
1806	if (TSN_lt(asoc->adv_peer_ack_point, ctsn))
1807		asoc->adv_peer_ack_point = ctsn;
1808
1809	/* PR-SCTP C2) Try to further advance the "Advanced.Peer.Ack.Point"
1810	 * locally, that is, to move "Advanced.Peer.Ack.Point" up as long as
1811	 * the chunk next in the out-queue space is marked as "abandoned" as
1812	 * shown in the following example:
1813	 *
1814	 * Assuming that a SACK arrived with the Cumulative TSN ACK 102
1815	 * and the Advanced.Peer.Ack.Point is updated to this value:
1816	 *
1817	 *   out-queue at the end of  ==>   out-queue after Adv.Ack.Point
1818	 *   normal SACK processing           local advancement
1819	 *                ...                           ...
1820	 *   Adv.Ack.Pt-> 102 acked                     102 acked
1821	 *                103 abandoned                 103 abandoned
1822	 *                104 abandoned     Adv.Ack.P-> 104 abandoned
1823	 *                105                           105
1824	 *                106 acked                     106 acked
1825	 *                ...                           ...
1826	 *
1827	 * In this example, the data sender successfully advanced the
1828	 * "Advanced.Peer.Ack.Point" from 102 to 104 locally.
1829	 */
1830	list_for_each_safe(lchunk, temp, &q->abandoned) {
1831		chunk = list_entry(lchunk, struct sctp_chunk,
1832					transmitted_list);
1833		tsn = ntohl(chunk->subh.data_hdr->tsn);
1834
1835		/* Remove any chunks in the abandoned queue that are acked by
1836		 * the ctsn.
1837		 */
1838		if (TSN_lte(tsn, ctsn)) {
1839			list_del_init(lchunk);
1840			sctp_chunk_free(chunk);
1841		} else {
1842			if (TSN_lte(tsn, asoc->adv_peer_ack_point+1)) {
1843				asoc->adv_peer_ack_point = tsn;
1844				if (chunk->chunk_hdr->flags &
1845					 SCTP_DATA_UNORDERED)
1846					continue;
1847				skip_pos = sctp_get_skip_pos(&ftsn_skip_arr[0],
1848						nskips,
1849						chunk->subh.data_hdr->stream);
1850				ftsn_skip_arr[skip_pos].stream =
1851					chunk->subh.data_hdr->stream;
1852				ftsn_skip_arr[skip_pos].ssn =
1853					 chunk->subh.data_hdr->ssn;
1854				if (skip_pos == nskips)
1855					nskips++;
1856				if (nskips == 10)
1857					break;
1858			} else
1859				break;
1860		}
1861	}
1862
1863	/* PR-SCTP C3) If, after step C1 and C2, the "Advanced.Peer.Ack.Point"
1864	 * is greater than the Cumulative TSN ACK carried in the received
1865	 * SACK, the data sender MUST send the data receiver a FORWARD TSN
1866	 * chunk containing the latest value of the
1867	 * "Advanced.Peer.Ack.Point".
1868	 *
1869	 * C4) For each "abandoned" TSN the sender of the FORWARD TSN SHOULD
1870	 * list each stream and sequence number in the forwarded TSN. This
1871	 * information will enable the receiver to easily find any
1872	 * stranded TSN's waiting on stream reorder queues. Each stream
1873	 * SHOULD only be reported once; this means that if multiple
1874	 * abandoned messages occur in the same stream then only the
1875	 * highest abandoned stream sequence number is reported. If the
1876	 * total size of the FORWARD TSN does NOT fit in a single MTU then
1877	 * the sender of the FORWARD TSN SHOULD lower the
1878	 * Advanced.Peer.Ack.Point to the last TSN that will fit in a
1879	 * single MTU.
1880	 */
1881	if (asoc->adv_peer_ack_point > ctsn)
1882		ftsn_chunk = sctp_make_fwdtsn(asoc, asoc->adv_peer_ack_point,
1883					      nskips, &ftsn_skip_arr[0]);
1884
1885	if (ftsn_chunk) {
1886		list_add_tail(&ftsn_chunk->list, &q->control_chunk_list);
1887		SCTP_INC_STATS(sock_net(asoc->base.sk), SCTP_MIB_OUTCTRLCHUNKS);
1888	}
1889}