1/* SCTP kernel implementation
   2 * (C) Copyright IBM Corp. 2001, 2004
   3 * Copyright (c) 1999-2000 Cisco, Inc.
   4 * Copyright (c) 1999-2001 Motorola, Inc.
   5 * Copyright (c) 2001-2003 Intel Corp.
   6 *
   7 * This file is part of the SCTP kernel implementation
   8 *
   9 * These functions implement the sctp_outq class.   The outqueue handles
  10 * bundling and queueing of outgoing SCTP chunks.
  11 *
  12 * This SCTP implementation is free software;
  13 * you can redistribute it and/or modify it under the terms of
  14 * the GNU General Public License as published by
  15 * the Free Software Foundation; either version 2, or (at your option)
  16 * any later version.
  17 *
  18 * This SCTP implementation is distributed in the hope that it
  19 * will be useful, but WITHOUT ANY WARRANTY; without even the implied
  20 *                 ************************
  21 * warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
  22 * See the GNU General Public License for more details.
  23 *
  24 * You should have received a copy of the GNU General Public License
  25 * along with GNU CC; see the file COPYING.  If not, see
  26 * <http://www.gnu.org/licenses/>.
  27 *
  28 * Please send any bug reports or fixes you make to the
  29 * email address(es):
  30 *    lksctp developers <linux-sctp@vger.kernel.org>
  31 *
  32 * Written or modified by:
  33 *    La Monte H.P. Yarroll <piggy@acm.org>
  34 *    Karl Knutson          <karl@athena.chicago.il.us>
  35 *    Perry Melange         <pmelange@null.cc.uic.edu>
  36 *    Xingang Guo           <xingang.guo@intel.com>
  37 *    Hui Huang 	    <hui.huang@nokia.com>
  38 *    Sridhar Samudrala     <sri@us.ibm.com>
  39 *    Jon Grimm             <jgrimm@us.ibm.com>
  40 */
  41
  42#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  43
  44#include <linux/types.h>
  45#include <linux/list.h>   /* For struct list_head */
  46#include <linux/socket.h>
  47#include <linux/ip.h>
  48#include <linux/slab.h>
  49#include <net/sock.h>	  /* For skb_set_owner_w */
  50
  51#include <net/sctp/sctp.h>
  52#include <net/sctp/sm.h>
  53#include <net/sctp/stream_sched.h>
 
  54
  55/* Declare internal functions here.  */
  56static int sctp_acked(struct sctp_sackhdr *sack, __u32 tsn);
  57static void sctp_check_transmitted(struct sctp_outq *q,
  58				   struct list_head *transmitted_queue,
  59				   struct sctp_transport *transport,
  60				   union sctp_addr *saddr,
  61				   struct sctp_sackhdr *sack,
  62				   __u32 *highest_new_tsn);
  63
  64static void sctp_mark_missing(struct sctp_outq *q,
  65			      struct list_head *transmitted_queue,
  66			      struct sctp_transport *transport,
  67			      __u32 highest_new_tsn,
  68			      int count_of_newacks);
  69
  70static void sctp_outq_flush(struct sctp_outq *q, int rtx_timeout, gfp_t gfp);
  71
  72/* Add data to the front of the queue. */
  73static inline void sctp_outq_head_data(struct sctp_outq *q,
  74				       struct sctp_chunk *ch)
  75{
  76	struct sctp_stream_out_ext *oute;
  77	__u16 stream;
  78
  79	list_add(&ch->list, &q->out_chunk_list);
  80	q->out_qlen += ch->skb->len;
  81
  82	stream = sctp_chunk_stream_no(ch);
  83	oute = q->asoc->stream.out[stream].ext;
  84	list_add(&ch->stream_list, &oute->outq);
  85}
  86
  87/* Take data from the front of the queue. */
  88static inline struct sctp_chunk *sctp_outq_dequeue_data(struct sctp_outq *q)
  89{
  90	return q->sched->dequeue(q);
  91}
  92
  93/* Add data chunk to the end of the queue. */
  94static inline void sctp_outq_tail_data(struct sctp_outq *q,
  95				       struct sctp_chunk *ch)
  96{
  97	struct sctp_stream_out_ext *oute;
  98	__u16 stream;
  99
 100	list_add_tail(&ch->list, &q->out_chunk_list);
 101	q->out_qlen += ch->skb->len;
 102
 103	stream = sctp_chunk_stream_no(ch);
 104	oute = q->asoc->stream.out[stream].ext;
 105	list_add_tail(&ch->stream_list, &oute->outq);
 106}
 107
 108/*
 109 * SFR-CACC algorithm:
 110 * D) If count_of_newacks is greater than or equal to 2
 111 * and t was not sent to the current primary then the
 112 * sender MUST NOT increment missing report count for t.
 113 */
 114static inline int sctp_cacc_skip_3_1_d(struct sctp_transport *primary,
 115				       struct sctp_transport *transport,
 116				       int count_of_newacks)
 117{
 118	if (count_of_newacks >= 2 && transport != primary)
 119		return 1;
 120	return 0;
 121}
 122
 123/*
 124 * SFR-CACC algorithm:
 125 * F) If count_of_newacks is less than 2, let d be the
 126 * destination to which t was sent. If cacc_saw_newack
 127 * is 0 for destination d, then the sender MUST NOT
 128 * increment missing report count for t.
 129 */
 130static inline int sctp_cacc_skip_3_1_f(struct sctp_transport *transport,
 131				       int count_of_newacks)
 132{
 133	if (count_of_newacks < 2 &&
 134			(transport && !transport->cacc.cacc_saw_newack))
 135		return 1;
 136	return 0;
 137}
 138
 139/*
 140 * SFR-CACC algorithm:
 141 * 3.1) If CYCLING_CHANGEOVER is 0, the sender SHOULD
 142 * execute steps C, D, F.
 143 *
 144 * C has been implemented in sctp_outq_sack
 145 */
 146static inline int sctp_cacc_skip_3_1(struct sctp_transport *primary,
 147				     struct sctp_transport *transport,
 148				     int count_of_newacks)
 149{
 150	if (!primary->cacc.cycling_changeover) {
 151		if (sctp_cacc_skip_3_1_d(primary, transport, count_of_newacks))
 152			return 1;
 153		if (sctp_cacc_skip_3_1_f(transport, count_of_newacks))
 154			return 1;
 155		return 0;
 156	}
 157	return 0;
 158}
 159
 160/*
 161 * SFR-CACC algorithm:
 162 * 3.2) Else if CYCLING_CHANGEOVER is 1, and t is less
 163 * than next_tsn_at_change of the current primary, then
 164 * the sender MUST NOT increment missing report count
 165 * for t.
 166 */
 167static inline int sctp_cacc_skip_3_2(struct sctp_transport *primary, __u32 tsn)
 168{
 169	if (primary->cacc.cycling_changeover &&
 170	    TSN_lt(tsn, primary->cacc.next_tsn_at_change))
 171		return 1;
 172	return 0;
 173}
 174
 175/*
 176 * SFR-CACC algorithm:
 177 * 3) If the missing report count for TSN t is to be
 178 * incremented according to [RFC2960] and
 179 * [SCTP_STEWART-2002], and CHANGEOVER_ACTIVE is set,
 180 * then the sender MUST further execute steps 3.1 and
 181 * 3.2 to determine if the missing report count for
 182 * TSN t SHOULD NOT be incremented.
 183 *
 184 * 3.3) If 3.1 and 3.2 do not dictate that the missing
 185 * report count for t should not be incremented, then
 186 * the sender SHOULD increment missing report count for
 187 * t (according to [RFC2960] and [SCTP_STEWART_2002]).
 188 */
 189static inline int sctp_cacc_skip(struct sctp_transport *primary,
 190				 struct sctp_transport *transport,
 191				 int count_of_newacks,
 192				 __u32 tsn)
 193{
 194	if (primary->cacc.changeover_active &&
 195	    (sctp_cacc_skip_3_1(primary, transport, count_of_newacks) ||
 196	     sctp_cacc_skip_3_2(primary, tsn)))
 197		return 1;
 198	return 0;
 199}
 200
 201/* Initialize an existing sctp_outq.  This does the boring stuff.
 202 * You still need to define handlers if you really want to DO
 203 * something with this structure...
 204 */
 205void sctp_outq_init(struct sctp_association *asoc, struct sctp_outq *q)
 206{
 207	memset(q, 0, sizeof(struct sctp_outq));
 208
 209	q->asoc = asoc;
 210	INIT_LIST_HEAD(&q->out_chunk_list);
 211	INIT_LIST_HEAD(&q->control_chunk_list);
 212	INIT_LIST_HEAD(&q->retransmit);
 213	INIT_LIST_HEAD(&q->sacked);
 214	INIT_LIST_HEAD(&q->abandoned);
 215	sctp_sched_set_sched(asoc, SCTP_SS_FCFS);
 216}
 217
 218/* Free the outqueue structure and any related pending chunks.
 219 */
 220static void __sctp_outq_teardown(struct sctp_outq *q)
 221{
 222	struct sctp_transport *transport;
 223	struct list_head *lchunk, *temp;
 224	struct sctp_chunk *chunk, *tmp;
 225
 226	/* Throw away unacknowledged chunks. */
 227	list_for_each_entry(transport, &q->asoc->peer.transport_addr_list,
 228			transports) {
 229		while ((lchunk = sctp_list_dequeue(&transport->transmitted)) != NULL) {
 230			chunk = list_entry(lchunk, struct sctp_chunk,
 231					   transmitted_list);
 232			/* Mark as part of a failed message. */
 233			sctp_chunk_fail(chunk, q->error);
 234			sctp_chunk_free(chunk);
 235		}
 236	}
 237
 238	/* Throw away chunks that have been gap ACKed.  */
 239	list_for_each_safe(lchunk, temp, &q->sacked) {
 240		list_del_init(lchunk);
 241		chunk = list_entry(lchunk, struct sctp_chunk,
 242				   transmitted_list);
 243		sctp_chunk_fail(chunk, q->error);
 244		sctp_chunk_free(chunk);
 245	}
 246
 247	/* Throw away any chunks in the retransmit queue. */
 248	list_for_each_safe(lchunk, temp, &q->retransmit) {
 249		list_del_init(lchunk);
 250		chunk = list_entry(lchunk, struct sctp_chunk,
 251				   transmitted_list);
 252		sctp_chunk_fail(chunk, q->error);
 253		sctp_chunk_free(chunk);
 254	}
 255
 256	/* Throw away any chunks that are in the abandoned queue. */
 257	list_for_each_safe(lchunk, temp, &q->abandoned) {
 258		list_del_init(lchunk);
 259		chunk = list_entry(lchunk, struct sctp_chunk,
 260				   transmitted_list);
 261		sctp_chunk_fail(chunk, q->error);
 262		sctp_chunk_free(chunk);
 263	}
 264
 265	/* Throw away any leftover data chunks. */
 266	while ((chunk = sctp_outq_dequeue_data(q)) != NULL) {
 267		sctp_sched_dequeue_done(q, chunk);
 268
 269		/* Mark as send failure. */
 270		sctp_chunk_fail(chunk, q->error);
 271		sctp_chunk_free(chunk);
 272	}
 273
 274	/* Throw away any leftover control chunks. */
 275	list_for_each_entry_safe(chunk, tmp, &q->control_chunk_list, list) {
 276		list_del_init(&chunk->list);
 277		sctp_chunk_free(chunk);
 278	}
 279}
 280
 281void sctp_outq_teardown(struct sctp_outq *q)
 282{
 283	__sctp_outq_teardown(q);
 284	sctp_outq_init(q->asoc, q);
 285}
 286
 287/* Free the outqueue structure and any related pending chunks.  */
 288void sctp_outq_free(struct sctp_outq *q)
 289{
 290	/* Throw away leftover chunks. */
 291	__sctp_outq_teardown(q);
 292}
 293
 294/* Put a new chunk in an sctp_outq.  */
 295void sctp_outq_tail(struct sctp_outq *q, struct sctp_chunk *chunk, gfp_t gfp)
 296{
 297	struct net *net = sock_net(q->asoc->base.sk);
 298
 299	pr_debug("%s: outq:%p, chunk:%p[%s]\n", __func__, q, chunk,
 300		 chunk && chunk->chunk_hdr ?
 301		 sctp_cname(SCTP_ST_CHUNK(chunk->chunk_hdr->type)) :
 302		 "illegal chunk");
 303
 304	/* If it is data, queue it up, otherwise, send it
 305	 * immediately.
 306	 */
 307	if (sctp_chunk_is_data(chunk)) {
 308		pr_debug("%s: outqueueing: outq:%p, chunk:%p[%s])\n",
 309			 __func__, q, chunk, chunk && chunk->chunk_hdr ?
 310			 sctp_cname(SCTP_ST_CHUNK(chunk->chunk_hdr->type)) :
 311			 "illegal chunk");
 312
 313		sctp_outq_tail_data(q, chunk);
 314		if (chunk->asoc->peer.prsctp_capable &&
 315		    SCTP_PR_PRIO_ENABLED(chunk->sinfo.sinfo_flags))
 316			chunk->asoc->sent_cnt_removable++;
 317		if (chunk->chunk_hdr->flags & SCTP_DATA_UNORDERED)
 318			SCTP_INC_STATS(net, SCTP_MIB_OUTUNORDERCHUNKS);
 319		else
 320			SCTP_INC_STATS(net, SCTP_MIB_OUTORDERCHUNKS);
 321	} else {
 322		list_add_tail(&chunk->list, &q->control_chunk_list);
 323		SCTP_INC_STATS(net, SCTP_MIB_OUTCTRLCHUNKS);
 324	}
 325
 326	if (!q->cork)
 327		sctp_outq_flush(q, 0, gfp);
 328}
 329
 330/* Insert a chunk into the sorted list based on the TSNs.  The retransmit list
 331 * and the abandoned list are in ascending order.
 332 */
 333static void sctp_insert_list(struct list_head *head, struct list_head *new)
 334{
 335	struct list_head *pos;
 336	struct sctp_chunk *nchunk, *lchunk;
 337	__u32 ntsn, ltsn;
 338	int done = 0;
 339
 340	nchunk = list_entry(new, struct sctp_chunk, transmitted_list);
 341	ntsn = ntohl(nchunk->subh.data_hdr->tsn);
 342
 343	list_for_each(pos, head) {
 344		lchunk = list_entry(pos, struct sctp_chunk, transmitted_list);
 345		ltsn = ntohl(lchunk->subh.data_hdr->tsn);
 346		if (TSN_lt(ntsn, ltsn)) {
 347			list_add(new, pos->prev);
 348			done = 1;
 349			break;
 350		}
 351	}
 352	if (!done)
 353		list_add_tail(new, head);
 354}
 355
 356static int sctp_prsctp_prune_sent(struct sctp_association *asoc,
 357				  struct sctp_sndrcvinfo *sinfo,
 358				  struct list_head *queue, int msg_len)
 359{
 360	struct sctp_chunk *chk, *temp;
 361
 362	list_for_each_entry_safe(chk, temp, queue, transmitted_list) {
 363		struct sctp_stream_out *streamout;
 364
 365		if (!chk->msg->abandoned &&
 366		    (!SCTP_PR_PRIO_ENABLED(chk->sinfo.sinfo_flags) ||
 367		     chk->sinfo.sinfo_timetolive <= sinfo->sinfo_timetolive))
 368			continue;
 369
 370		chk->msg->abandoned = 1;
 371		list_del_init(&chk->transmitted_list);
 372		sctp_insert_list(&asoc->outqueue.abandoned,
 373				 &chk->transmitted_list);
 374
 375		streamout = &asoc->stream.out[chk->sinfo.sinfo_stream];
 376		asoc->sent_cnt_removable--;
 377		asoc->abandoned_sent[SCTP_PR_INDEX(PRIO)]++;
 378		streamout->ext->abandoned_sent[SCTP_PR_INDEX(PRIO)]++;
 379
 380		if (queue != &asoc->outqueue.retransmit &&
 381		    !chk->tsn_gap_acked) {
 382			if (chk->transport)
 383				chk->transport->flight_size -=
 384						sctp_data_size(chk);
 385			asoc->outqueue.outstanding_bytes -= sctp_data_size(chk);
 386		}
 387
 388		msg_len -= SCTP_DATA_SNDSIZE(chk) +
 389			   sizeof(struct sk_buff) +
 390			   sizeof(struct sctp_chunk);
 391		if (msg_len <= 0)
 392			break;
 393	}
 394
 395	return msg_len;
 396}
 397
 398static int sctp_prsctp_prune_unsent(struct sctp_association *asoc,
 399				    struct sctp_sndrcvinfo *sinfo, int msg_len)
 400{
 401	struct sctp_outq *q = &asoc->outqueue;
 402	struct sctp_chunk *chk, *temp;
 
 403
 404	q->sched->unsched_all(&asoc->stream);
 405
 406	list_for_each_entry_safe(chk, temp, &q->out_chunk_list, list) {
 407		if (!chk->msg->abandoned &&
 408		    (!(chk->chunk_hdr->flags & SCTP_DATA_FIRST_FRAG) ||
 409		     !SCTP_PR_PRIO_ENABLED(chk->sinfo.sinfo_flags) ||
 410		     chk->sinfo.sinfo_timetolive <= sinfo->sinfo_timetolive))
 411			continue;
 412
 413		chk->msg->abandoned = 1;
 414		sctp_sched_dequeue_common(q, chk);
 415		asoc->sent_cnt_removable--;
 416		asoc->abandoned_unsent[SCTP_PR_INDEX(PRIO)]++;
 417		if (chk->sinfo.sinfo_stream < asoc->stream.outcnt) {
 418			struct sctp_stream_out *streamout =
 419				&asoc->stream.out[chk->sinfo.sinfo_stream];
 420
 421			streamout->ext->abandoned_unsent[SCTP_PR_INDEX(PRIO)]++;
 422		}
 423
 424		msg_len -= SCTP_DATA_SNDSIZE(chk) +
 425			   sizeof(struct sk_buff) +
 426			   sizeof(struct sctp_chunk);
 
 
 
 427		sctp_chunk_free(chk);
 428		if (msg_len <= 0)
 429			break;
 430	}
 431
 432	q->sched->sched_all(&asoc->stream);
 433
 434	return msg_len;
 435}
 436
 437/* Abandon the chunks according their priorities */
 438void sctp_prsctp_prune(struct sctp_association *asoc,
 439		       struct sctp_sndrcvinfo *sinfo, int msg_len)
 440{
 441	struct sctp_transport *transport;
 442
 443	if (!asoc->peer.prsctp_capable || !asoc->sent_cnt_removable)
 444		return;
 445
 446	msg_len = sctp_prsctp_prune_sent(asoc, sinfo,
 447					 &asoc->outqueue.retransmit,
 448					 msg_len);
 449	if (msg_len <= 0)
 450		return;
 451
 452	list_for_each_entry(transport, &asoc->peer.transport_addr_list,
 453			    transports) {
 454		msg_len = sctp_prsctp_prune_sent(asoc, sinfo,
 455						 &transport->transmitted,
 456						 msg_len);
 457		if (msg_len <= 0)
 458			return;
 459	}
 460
 461	sctp_prsctp_prune_unsent(asoc, sinfo, msg_len);
 462}
 463
 464/* Mark all the eligible packets on a transport for retransmission.  */
 465void sctp_retransmit_mark(struct sctp_outq *q,
 466			  struct sctp_transport *transport,
 467			  __u8 reason)
 468{
 469	struct list_head *lchunk, *ltemp;
 470	struct sctp_chunk *chunk;
 471
 472	/* Walk through the specified transmitted queue.  */
 473	list_for_each_safe(lchunk, ltemp, &transport->transmitted) {
 474		chunk = list_entry(lchunk, struct sctp_chunk,
 475				   transmitted_list);
 476
 477		/* If the chunk is abandoned, move it to abandoned list. */
 478		if (sctp_chunk_abandoned(chunk)) {
 479			list_del_init(lchunk);
 480			sctp_insert_list(&q->abandoned, lchunk);
 481
 482			/* If this chunk has not been previousely acked,
 483			 * stop considering it 'outstanding'.  Our peer
 484			 * will most likely never see it since it will
 485			 * not be retransmitted
 486			 */
 487			if (!chunk->tsn_gap_acked) {
 488				if (chunk->transport)
 489					chunk->transport->flight_size -=
 490							sctp_data_size(chunk);
 491				q->outstanding_bytes -= sctp_data_size(chunk);
 492				q->asoc->peer.rwnd += sctp_data_size(chunk);
 493			}
 494			continue;
 495		}
 496
 497		/* If we are doing  retransmission due to a timeout or pmtu
 498		 * discovery, only the  chunks that are not yet acked should
 499		 * be added to the retransmit queue.
 500		 */
 501		if ((reason == SCTP_RTXR_FAST_RTX  &&
 502			    (chunk->fast_retransmit == SCTP_NEED_FRTX)) ||
 503		    (reason != SCTP_RTXR_FAST_RTX  && !chunk->tsn_gap_acked)) {
 504			/* RFC 2960 6.2.1 Processing a Received SACK
 505			 *
 506			 * C) Any time a DATA chunk is marked for
 507			 * retransmission (via either T3-rtx timer expiration
 508			 * (Section 6.3.3) or via fast retransmit
 509			 * (Section 7.2.4)), add the data size of those
 510			 * chunks to the rwnd.
 511			 */
 512			q->asoc->peer.rwnd += sctp_data_size(chunk);
 513			q->outstanding_bytes -= sctp_data_size(chunk);
 514			if (chunk->transport)
 515				transport->flight_size -= sctp_data_size(chunk);
 516
 517			/* sctpimpguide-05 Section 2.8.2
 518			 * M5) If a T3-rtx timer expires, the
 519			 * 'TSN.Missing.Report' of all affected TSNs is set
 520			 * to 0.
 521			 */
 522			chunk->tsn_missing_report = 0;
 523
 524			/* If a chunk that is being used for RTT measurement
 525			 * has to be retransmitted, we cannot use this chunk
 526			 * anymore for RTT measurements. Reset rto_pending so
 527			 * that a new RTT measurement is started when a new
 528			 * data chunk is sent.
 529			 */
 530			if (chunk->rtt_in_progress) {
 531				chunk->rtt_in_progress = 0;
 532				transport->rto_pending = 0;
 533			}
 534
 535			/* Move the chunk to the retransmit queue. The chunks
 536			 * on the retransmit queue are always kept in order.
 537			 */
 538			list_del_init(lchunk);
 539			sctp_insert_list(&q->retransmit, lchunk);
 540		}
 541	}
 542
 543	pr_debug("%s: transport:%p, reason:%d, cwnd:%d, ssthresh:%d, "
 544		 "flight_size:%d, pba:%d\n", __func__, transport, reason,
 545		 transport->cwnd, transport->ssthresh, transport->flight_size,
 546		 transport->partial_bytes_acked);
 547}
 548
 549/* Mark all the eligible packets on a transport for retransmission and force
 550 * one packet out.
 551 */
 552void sctp_retransmit(struct sctp_outq *q, struct sctp_transport *transport,
 553		     enum sctp_retransmit_reason reason)
 554{
 555	struct net *net = sock_net(q->asoc->base.sk);
 556
 557	switch (reason) {
 558	case SCTP_RTXR_T3_RTX:
 559		SCTP_INC_STATS(net, SCTP_MIB_T3_RETRANSMITS);
 560		sctp_transport_lower_cwnd(transport, SCTP_LOWER_CWND_T3_RTX);
 561		/* Update the retran path if the T3-rtx timer has expired for
 562		 * the current retran path.
 563		 */
 564		if (transport == transport->asoc->peer.retran_path)
 565			sctp_assoc_update_retran_path(transport->asoc);
 566		transport->asoc->rtx_data_chunks +=
 567			transport->asoc->unack_data;
 
 
 
 568		break;
 569	case SCTP_RTXR_FAST_RTX:
 570		SCTP_INC_STATS(net, SCTP_MIB_FAST_RETRANSMITS);
 571		sctp_transport_lower_cwnd(transport, SCTP_LOWER_CWND_FAST_RTX);
 572		q->fast_rtx = 1;
 573		break;
 574	case SCTP_RTXR_PMTUD:
 575		SCTP_INC_STATS(net, SCTP_MIB_PMTUD_RETRANSMITS);
 576		break;
 577	case SCTP_RTXR_T1_RTX:
 578		SCTP_INC_STATS(net, SCTP_MIB_T1_RETRANSMITS);
 579		transport->asoc->init_retries++;
 580		break;
 581	default:
 582		BUG();
 583	}
 584
 585	sctp_retransmit_mark(q, transport, reason);
 586
 587	/* PR-SCTP A5) Any time the T3-rtx timer expires, on any destination,
 588	 * the sender SHOULD try to advance the "Advanced.Peer.Ack.Point" by
 589	 * following the procedures outlined in C1 - C5.
 590	 */
 591	if (reason == SCTP_RTXR_T3_RTX)
 592		q->asoc->stream.si->generate_ftsn(q, q->asoc->ctsn_ack_point);
 593
 594	/* Flush the queues only on timeout, since fast_rtx is only
 595	 * triggered during sack processing and the queue
 596	 * will be flushed at the end.
 597	 */
 598	if (reason != SCTP_RTXR_FAST_RTX)
 599		sctp_outq_flush(q, /* rtx_timeout */ 1, GFP_ATOMIC);
 600}
 601
 602/*
 603 * Transmit DATA chunks on the retransmit queue.  Upon return from
 604 * sctp_outq_flush_rtx() the packet 'pkt' may contain chunks which
 605 * need to be transmitted by the caller.
 606 * We assume that pkt->transport has already been set.
 607 *
 608 * The return value is a normal kernel error return value.
 609 */
 610static int sctp_outq_flush_rtx(struct sctp_outq *q, struct sctp_packet *pkt,
 611			       int rtx_timeout, int *start_timer)
 612{
 613	struct sctp_transport *transport = pkt->transport;
 614	struct sctp_chunk *chunk, *chunk1;
 615	struct list_head *lqueue;
 616	enum sctp_xmit status;
 617	int error = 0;
 618	int timer = 0;
 619	int done = 0;
 620	int fast_rtx;
 621
 622	lqueue = &q->retransmit;
 623	fast_rtx = q->fast_rtx;
 624
 625	/* This loop handles time-out retransmissions, fast retransmissions,
 626	 * and retransmissions due to opening of whindow.
 627	 *
 628	 * RFC 2960 6.3.3 Handle T3-rtx Expiration
 629	 *
 630	 * E3) Determine how many of the earliest (i.e., lowest TSN)
 631	 * outstanding DATA chunks for the address for which the
 632	 * T3-rtx has expired will fit into a single packet, subject
 633	 * to the MTU constraint for the path corresponding to the
 634	 * destination transport address to which the retransmission
 635	 * is being sent (this may be different from the address for
 636	 * which the timer expires [see Section 6.4]). Call this value
 637	 * K. Bundle and retransmit those K DATA chunks in a single
 638	 * packet to the destination endpoint.
 639	 *
 640	 * [Just to be painfully clear, if we are retransmitting
 641	 * because a timeout just happened, we should send only ONE
 642	 * packet of retransmitted data.]
 643	 *
 644	 * For fast retransmissions we also send only ONE packet.  However,
 645	 * if we are just flushing the queue due to open window, we'll
 646	 * try to send as much as possible.
 647	 */
 648	list_for_each_entry_safe(chunk, chunk1, lqueue, transmitted_list) {
 649		/* If the chunk is abandoned, move it to abandoned list. */
 650		if (sctp_chunk_abandoned(chunk)) {
 651			list_del_init(&chunk->transmitted_list);
 652			sctp_insert_list(&q->abandoned,
 653					 &chunk->transmitted_list);
 654			continue;
 655		}
 656
 657		/* Make sure that Gap Acked TSNs are not retransmitted.  A
 658		 * simple approach is just to move such TSNs out of the
 659		 * way and into a 'transmitted' queue and skip to the
 660		 * next chunk.
 661		 */
 662		if (chunk->tsn_gap_acked) {
 663			list_move_tail(&chunk->transmitted_list,
 664				       &transport->transmitted);
 665			continue;
 666		}
 667
 668		/* If we are doing fast retransmit, ignore non-fast_rtransmit
 669		 * chunks
 670		 */
 671		if (fast_rtx && !chunk->fast_retransmit)
 672			continue;
 673
 674redo:
 675		/* Attempt to append this chunk to the packet. */
 676		status = sctp_packet_append_chunk(pkt, chunk);
 677
 678		switch (status) {
 679		case SCTP_XMIT_PMTU_FULL:
 680			if (!pkt->has_data && !pkt->has_cookie_echo) {
 681				/* If this packet did not contain DATA then
 682				 * retransmission did not happen, so do it
 683				 * again.  We'll ignore the error here since
 684				 * control chunks are already freed so there
 685				 * is nothing we can do.
 686				 */
 687				sctp_packet_transmit(pkt, GFP_ATOMIC);
 688				goto redo;
 689			}
 690
 691			/* Send this packet.  */
 692			error = sctp_packet_transmit(pkt, GFP_ATOMIC);
 693
 694			/* If we are retransmitting, we should only
 695			 * send a single packet.
 696			 * Otherwise, try appending this chunk again.
 697			 */
 698			if (rtx_timeout || fast_rtx)
 699				done = 1;
 700			else
 701				goto redo;
 702
 703			/* Bundle next chunk in the next round.  */
 704			break;
 705
 706		case SCTP_XMIT_RWND_FULL:
 707			/* Send this packet. */
 708			error = sctp_packet_transmit(pkt, GFP_ATOMIC);
 709
 710			/* Stop sending DATA as there is no more room
 711			 * at the receiver.
 712			 */
 713			done = 1;
 714			break;
 715
 716		case SCTP_XMIT_DELAY:
 717			/* Send this packet. */
 718			error = sctp_packet_transmit(pkt, GFP_ATOMIC);
 719
 720			/* Stop sending DATA because of nagle delay. */
 721			done = 1;
 722			break;
 723
 724		default:
 725			/* The append was successful, so add this chunk to
 726			 * the transmitted list.
 727			 */
 728			list_move_tail(&chunk->transmitted_list,
 729				       &transport->transmitted);
 730
 731			/* Mark the chunk as ineligible for fast retransmit
 732			 * after it is retransmitted.
 733			 */
 734			if (chunk->fast_retransmit == SCTP_NEED_FRTX)
 735				chunk->fast_retransmit = SCTP_DONT_FRTX;
 736
 737			q->asoc->stats.rtxchunks++;
 738			break;
 739		}
 740
 741		/* Set the timer if there were no errors */
 742		if (!error && !timer)
 743			timer = 1;
 744
 745		if (done)
 746			break;
 747	}
 748
 749	/* If we are here due to a retransmit timeout or a fast
 750	 * retransmit and if there are any chunks left in the retransmit
 751	 * queue that could not fit in the PMTU sized packet, they need
 752	 * to be marked as ineligible for a subsequent fast retransmit.
 753	 */
 754	if (rtx_timeout || fast_rtx) {
 755		list_for_each_entry(chunk1, lqueue, transmitted_list) {
 756			if (chunk1->fast_retransmit == SCTP_NEED_FRTX)
 757				chunk1->fast_retransmit = SCTP_DONT_FRTX;
 758		}
 759	}
 760
 761	*start_timer = timer;
 762
 763	/* Clear fast retransmit hint */
 764	if (fast_rtx)
 765		q->fast_rtx = 0;
 766
 767	return error;
 768}
 769
 770/* Cork the outqueue so queued chunks are really queued. */
 771void sctp_outq_uncork(struct sctp_outq *q, gfp_t gfp)
 772{
 773	if (q->cork)
 774		q->cork = 0;
 775
 776	sctp_outq_flush(q, 0, gfp);
 777}
 778
 779
 780/*
 781 * Try to flush an outqueue.
 782 *
 783 * Description: Send everything in q which we legally can, subject to
 784 * congestion limitations.
 785 * * Note: This function can be called from multiple contexts so appropriate
 786 * locking concerns must be made.  Today we use the sock lock to protect
 787 * this function.
 788 */
 789static void sctp_outq_flush(struct sctp_outq *q, int rtx_timeout, gfp_t gfp)
 790{
 791	struct sctp_packet *packet;
 
 
 
 792	struct sctp_packet singleton;
 793	struct sctp_association *asoc = q->asoc;
 794	__u16 sport = asoc->base.bind_addr.port;
 795	__u16 dport = asoc->peer.port;
 796	__u32 vtag = asoc->peer.i.init_tag;
 797	struct sctp_transport *transport = NULL;
 798	struct sctp_transport *new_transport;
 799	struct sctp_chunk *chunk, *tmp;
 800	enum sctp_xmit status;
 801	int error = 0;
 802	int start_timer = 0;
 803	int one_packet = 0;
 804
 805	/* These transports have chunks to send. */
 806	struct list_head transport_list;
 807	struct list_head *ltransport;
 808
 809	INIT_LIST_HEAD(&transport_list);
 810	packet = NULL;
 811
 812	/*
 813	 * 6.10 Bundling
 814	 *   ...
 815	 *   When bundling control chunks with DATA chunks, an
 816	 *   endpoint MUST place control chunks first in the outbound
 817	 *   SCTP packet.  The transmitter MUST transmit DATA chunks
 818	 *   within a SCTP packet in increasing order of TSN.
 819	 *   ...
 820	 */
 821
 822	list_for_each_entry_safe(chunk, tmp, &q->control_chunk_list, list) {
 823		/* RFC 5061, 5.3
 824		 * F1) This means that until such time as the ASCONF
 825		 * containing the add is acknowledged, the sender MUST
 826		 * NOT use the new IP address as a source for ANY SCTP
 827		 * packet except on carrying an ASCONF Chunk.
 828		 */
 829		if (asoc->src_out_of_asoc_ok &&
 830		    chunk->chunk_hdr->type != SCTP_CID_ASCONF)
 831			continue;
 832
 
 
 
 833		list_del_init(&chunk->list);
 
 
 
 
 
 834
 835		/* Pick the right transport to use. */
 836		new_transport = chunk->transport;
 
 
 
 
 
 
 
 
 
 
 837
 838		if (!new_transport) {
 839			/*
 840			 * If we have a prior transport pointer, see if
 
 
 
 
 
 
 841			 * the destination address of the chunk
 842			 * matches the destination address of the
 843			 * current transport.  If not a match, then
 844			 * try to look up the transport with a given
 845			 * destination address.  We do this because
 846			 * after processing ASCONFs, we may have new
 847			 * transports created.
 848			 */
 849			if (transport &&
 850			    sctp_cmp_addr_exact(&chunk->dest,
 851						&transport->ipaddr))
 852					new_transport = transport;
 853			else
 854				new_transport = sctp_assoc_lookup_paddr(asoc,
 855								&chunk->dest);
 
 856
 857			/* if we still don't have a new transport, then
 858			 * use the current active path.
 859			 */
 860			if (!new_transport)
 861				new_transport = asoc->peer.active_path;
 862		} else if ((new_transport->state == SCTP_INACTIVE) ||
 863			   (new_transport->state == SCTP_UNCONFIRMED) ||
 864			   (new_transport->state == SCTP_PF)) {
 
 
 
 
 865			/* If the chunk is Heartbeat or Heartbeat Ack,
 866			 * send it to chunk->transport, even if it's
 867			 * inactive.
 868			 *
 869			 * 3.3.6 Heartbeat Acknowledgement:
 870			 * ...
 871			 * A HEARTBEAT ACK is always sent to the source IP
 872			 * address of the IP datagram containing the
 873			 * HEARTBEAT chunk to which this ack is responding.
 874			 * ...
 875			 *
 876			 * ASCONF_ACKs also must be sent to the source.
 877			 */
 878			if (chunk->chunk_hdr->type != SCTP_CID_HEARTBEAT &&
 879			    chunk->chunk_hdr->type != SCTP_CID_HEARTBEAT_ACK &&
 880			    chunk->chunk_hdr->type != SCTP_CID_ASCONF_ACK)
 881				new_transport = asoc->peer.active_path;
 
 
 
 
 882		}
 
 883
 884		/* Are we switching transports?
 885		 * Take care of transport locks.
 
 
 
 
 
 
 
 
 
 
 
 
 886		 */
 887		if (new_transport != transport) {
 888			transport = new_transport;
 889			if (list_empty(&transport->send_ready)) {
 890				list_add_tail(&transport->send_ready,
 891					      &transport_list);
 892			}
 893			packet = &transport->packet;
 894			sctp_packet_config(packet, vtag,
 895					   asoc->peer.ecn_capable);
 896		}
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 897
 898		switch (chunk->chunk_hdr->type) {
 899		/*
 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			sctp_packet_init(&singleton, transport, sport, dport);
 909			sctp_packet_config(&singleton, vtag, 0);
 910			sctp_packet_append_chunk(&singleton, chunk);
 911			error = sctp_packet_transmit(&singleton, gfp);
 912			if (error < 0) {
 913				asoc->base.sk->sk_err = -error;
 914				return;
 915			}
 
 916			break;
 917
 918		case SCTP_CID_ABORT:
 919			if (sctp_test_T_bit(chunk))
 920				packet->vtag = asoc->c.my_vtag;
 921			/* fallthru */
 
 922		/* The following chunks are "response" chunks, i.e.
 923		 * they are generated in response to something we
 924		 * received.  If we are sending these, then we can
 925		 * send only 1 packet containing these chunks.
 926		 */
 927		case SCTP_CID_HEARTBEAT_ACK:
 928		case SCTP_CID_SHUTDOWN_ACK:
 929		case SCTP_CID_COOKIE_ACK:
 930		case SCTP_CID_COOKIE_ECHO:
 931		case SCTP_CID_ERROR:
 932		case SCTP_CID_ECN_CWR:
 933		case SCTP_CID_ASCONF_ACK:
 934			one_packet = 1;
 935			/* Fall through */
 936
 937		case SCTP_CID_SACK:
 938		case SCTP_CID_HEARTBEAT:
 
 
 
 
 
 
 
 
 
 939		case SCTP_CID_SHUTDOWN:
 940		case SCTP_CID_ECN_ECNE:
 941		case SCTP_CID_ASCONF:
 942		case SCTP_CID_FWD_TSN:
 943		case SCTP_CID_I_FWD_TSN:
 944		case SCTP_CID_RECONF:
 945			status = sctp_packet_transmit_chunk(packet, chunk,
 946							    one_packet, gfp);
 947			if (status  != SCTP_XMIT_OK) {
 948				/* put the chunk back */
 949				list_add(&chunk->list, &q->control_chunk_list);
 950				break;
 951			}
 952
 953			asoc->stats.octrlchunks++;
 954			/* PR-SCTP C5) If a FORWARD TSN is sent, the
 955			 * sender MUST assure that at least one T3-rtx
 956			 * timer is running.
 957			 */
 958			if (chunk->chunk_hdr->type == SCTP_CID_FWD_TSN ||
 959			    chunk->chunk_hdr->type == SCTP_CID_I_FWD_TSN) {
 960				sctp_transport_reset_t3_rtx(transport);
 961				transport->last_time_sent = jiffies;
 962			}
 963
 964			if (chunk == asoc->strreset_chunk)
 965				sctp_transport_reset_reconf_timer(transport);
 966
 967			break;
 968
 969		default:
 970			/* We built a chunk with an illegal type! */
 971			BUG();
 972		}
 973	}
 
 974
 975	if (q->asoc->src_out_of_asoc_ok)
 976		goto sctp_flush_out;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 977
 978	/* Is it OK to send data chunks?  */
 979	switch (asoc->state) {
 980	case SCTP_STATE_COOKIE_ECHOED:
 981		/* Only allow bundling when this packet has a COOKIE-ECHO
 982		 * chunk.
 983		 */
 984		if (!packet || !packet->has_cookie_echo)
 985			break;
 986
 987		/* fallthru */
 988	case SCTP_STATE_ESTABLISHED:
 989	case SCTP_STATE_SHUTDOWN_PENDING:
 990	case SCTP_STATE_SHUTDOWN_RECEIVED:
 991		/*
 992		 * RFC 2960 6.1  Transmission of DATA Chunks
 993		 *
 994		 * C) When the time comes for the sender to transmit,
 995		 * before sending new DATA chunks, the sender MUST
 996		 * first transmit any outstanding DATA chunks which
 997		 * are marked for retransmission (limited by the
 998		 * current cwnd).
 999		 */
1000		if (!list_empty(&q->retransmit)) {
1001			if (asoc->peer.retran_path->state == SCTP_UNCONFIRMED)
1002				goto sctp_flush_out;
1003			if (transport == asoc->peer.retran_path)
1004				goto retran;
1005
1006			/* Switch transports & prepare the packet.  */
1007
1008			transport = asoc->peer.retran_path;
1009
1010			if (list_empty(&transport->send_ready)) {
1011				list_add_tail(&transport->send_ready,
1012					      &transport_list);
1013			}
1014
1015			packet = &transport->packet;
1016			sctp_packet_config(packet, vtag,
1017					   asoc->peer.ecn_capable);
1018		retran:
1019			error = sctp_outq_flush_rtx(q, packet,
1020						    rtx_timeout, &start_timer);
1021			if (error < 0)
1022				asoc->base.sk->sk_err = -error;
1023
1024			if (start_timer) {
1025				sctp_transport_reset_t3_rtx(transport);
1026				transport->last_time_sent = jiffies;
1027			}
1028
1029			/* This can happen on COOKIE-ECHO resend.  Only
1030			 * one chunk can get bundled with a COOKIE-ECHO.
1031			 */
1032			if (packet->has_cookie_echo)
1033				goto sctp_flush_out;
1034
1035			/* Don't send new data if there is still data
1036			 * waiting to retransmit.
1037			 */
1038			if (!list_empty(&q->retransmit))
1039				goto sctp_flush_out;
1040		}
1041
1042		/* Apply Max.Burst limitation to the current transport in
1043		 * case it will be used for new data.  We are going to
1044		 * rest it before we return, but we want to apply the limit
1045		 * to the currently queued data.
1046		 */
1047		if (transport)
1048			sctp_transport_burst_limited(transport);
1049
1050		/* Finally, transmit new packets.  */
1051		while ((chunk = sctp_outq_dequeue_data(q)) != NULL) {
1052			__u32 sid = ntohs(chunk->subh.data_hdr->stream);
1053
1054			/* Has this chunk expired? */
1055			if (sctp_chunk_abandoned(chunk)) {
1056				sctp_sched_dequeue_done(q, chunk);
1057				sctp_chunk_fail(chunk, 0);
1058				sctp_chunk_free(chunk);
1059				continue;
1060			}
1061
1062			if (asoc->stream.out[sid].state == SCTP_STREAM_CLOSED) {
1063				sctp_outq_head_data(q, chunk);
1064				goto sctp_flush_out;
1065			}
 
 
 
 
 
 
 
1066
1067			/* If there is a specified transport, use it.
1068			 * Otherwise, we want to use the active path.
1069			 */
1070			new_transport = chunk->transport;
1071			if (!new_transport ||
1072			    ((new_transport->state == SCTP_INACTIVE) ||
1073			     (new_transport->state == SCTP_UNCONFIRMED) ||
1074			     (new_transport->state == SCTP_PF)))
1075				new_transport = asoc->peer.active_path;
1076			if (new_transport->state == SCTP_UNCONFIRMED) {
1077				WARN_ONCE(1, "Attempt to send packet on unconfirmed path.");
1078				sctp_sched_dequeue_done(q, chunk);
1079				sctp_chunk_fail(chunk, 0);
1080				sctp_chunk_free(chunk);
1081				continue;
1082			}
1083
1084			/* Change packets if necessary.  */
1085			if (new_transport != transport) {
1086				transport = new_transport;
 
1087
1088				/* Schedule to have this transport's
1089				 * packet flushed.
1090				 */
1091				if (list_empty(&transport->send_ready)) {
1092					list_add_tail(&transport->send_ready,
1093						      &transport_list);
1094				}
1095
1096				packet = &transport->packet;
1097				sctp_packet_config(packet, vtag,
1098						   asoc->peer.ecn_capable);
1099				/* We've switched transports, so apply the
1100				 * Burst limit to the new transport.
1101				 */
1102				sctp_transport_burst_limited(transport);
1103			}
1104
1105			pr_debug("%s: outq:%p, chunk:%p[%s], tx-tsn:0x%x skb->head:%p "
1106				 "skb->users:%d\n",
1107				 __func__, q, chunk, chunk && chunk->chunk_hdr ?
1108				 sctp_cname(SCTP_ST_CHUNK(chunk->chunk_hdr->type)) :
1109				 "illegal chunk", ntohl(chunk->subh.data_hdr->tsn),
1110				 chunk->skb ? chunk->skb->head : NULL, chunk->skb ?
1111				 refcount_read(&chunk->skb->users) : -1);
1112
1113			/* Add the chunk to the packet.  */
1114			status = sctp_packet_transmit_chunk(packet, chunk, 0, gfp);
1115
1116			switch (status) {
1117			case SCTP_XMIT_PMTU_FULL:
1118			case SCTP_XMIT_RWND_FULL:
1119			case SCTP_XMIT_DELAY:
1120				/* We could not append this chunk, so put
1121				 * the chunk back on the output queue.
1122				 */
1123				pr_debug("%s: could not transmit tsn:0x%x, status:%d\n",
1124					 __func__, ntohl(chunk->subh.data_hdr->tsn),
1125					 status);
1126
1127				sctp_outq_head_data(q, chunk);
1128				goto sctp_flush_out;
1129
1130			case SCTP_XMIT_OK:
1131				/* The sender is in the SHUTDOWN-PENDING state,
1132				 * The sender MAY set the I-bit in the DATA
1133				 * chunk header.
1134				 */
1135				if (asoc->state == SCTP_STATE_SHUTDOWN_PENDING)
1136					chunk->chunk_hdr->flags |= SCTP_DATA_SACK_IMM;
1137				if (chunk->chunk_hdr->flags & SCTP_DATA_UNORDERED)
1138					asoc->stats.ouodchunks++;
1139				else
1140					asoc->stats.oodchunks++;
1141
1142				/* Only now it's safe to consider this
1143				 * chunk as sent, sched-wise.
1144				 */
1145				sctp_sched_dequeue_done(q, chunk);
 
 
 
 
 
 
 
 
 
 
 
 
 
1146
1147				break;
 
 
1148
1149			default:
1150				BUG();
1151			}
 
 
 
 
 
 
 
1152
1153			/* BUG: We assume that the sctp_packet_transmit()
1154			 * call below will succeed all the time and add the
1155			 * chunk to the transmitted list and restart the
1156			 * timers.
1157			 * It is possible that the call can fail under OOM
1158			 * conditions.
1159			 *
1160			 * Is this really a problem?  Won't this behave
1161			 * like a lost TSN?
1162			 */
1163			list_add_tail(&chunk->transmitted_list,
1164				      &transport->transmitted);
1165
1166			sctp_transport_reset_t3_rtx(transport);
1167			transport->last_time_sent = jiffies;
1168
1169			/* Only let one DATA chunk get bundled with a
1170			 * COOKIE-ECHO chunk.
1171			 */
1172			if (packet->has_cookie_echo)
1173				goto sctp_flush_out;
1174		}
1175		break;
1176
1177	default:
1178		/* Do nothing.  */
1179		break;
 
 
1180	}
 
1181
1182sctp_flush_out:
 
 
 
 
 
 
1183
1184	/* Before returning, examine all the transports touched in
1185	 * this call.  Right now, we bluntly force clear all the
1186	 * transports.  Things might change after we implement Nagle.
1187	 * But such an examination is still required.
1188	 *
1189	 * --xguo
1190	 */
1191	while ((ltransport = sctp_list_dequeue(&transport_list)) != NULL) {
1192		struct sctp_transport *t = list_entry(ltransport,
1193						      struct sctp_transport,
1194						      send_ready);
1195		packet = &t->packet;
1196		if (!sctp_packet_empty(packet)) {
1197			error = sctp_packet_transmit(packet, gfp);
 
 
 
 
 
 
1198			if (error < 0)
1199				asoc->base.sk->sk_err = -error;
1200		}
1201
1202		/* Clear the burst limited state, if any */
1203		sctp_transport_burst_reset(t);
1204	}
1205}
1206
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1207/* Update unack_data based on the incoming SACK chunk */
1208static void sctp_sack_update_unack_data(struct sctp_association *assoc,
1209					struct sctp_sackhdr *sack)
1210{
1211	union sctp_sack_variable *frags;
1212	__u16 unack_data;
1213	int i;
1214
1215	unack_data = assoc->next_tsn - assoc->ctsn_ack_point - 1;
1216
1217	frags = sack->variable;
1218	for (i = 0; i < ntohs(sack->num_gap_ack_blocks); i++) {
1219		unack_data -= ((ntohs(frags[i].gab.end) -
1220				ntohs(frags[i].gab.start) + 1));
1221	}
1222
1223	assoc->unack_data = unack_data;
1224}
1225
1226/* This is where we REALLY process a SACK.
1227 *
1228 * Process the SACK against the outqueue.  Mostly, this just frees
1229 * things off the transmitted queue.
1230 */
1231int sctp_outq_sack(struct sctp_outq *q, struct sctp_chunk *chunk)
1232{
1233	struct sctp_association *asoc = q->asoc;
1234	struct sctp_sackhdr *sack = chunk->subh.sack_hdr;
1235	struct sctp_transport *transport;
1236	struct sctp_chunk *tchunk = NULL;
1237	struct list_head *lchunk, *transport_list, *temp;
1238	union sctp_sack_variable *frags = sack->variable;
1239	__u32 sack_ctsn, ctsn, tsn;
1240	__u32 highest_tsn, highest_new_tsn;
1241	__u32 sack_a_rwnd;
1242	unsigned int outstanding;
1243	struct sctp_transport *primary = asoc->peer.primary_path;
1244	int count_of_newacks = 0;
1245	int gap_ack_blocks;
1246	u8 accum_moved = 0;
1247
1248	/* Grab the association's destination address list. */
1249	transport_list = &asoc->peer.transport_addr_list;
1250
 
 
 
 
 
 
1251	sack_ctsn = ntohl(sack->cum_tsn_ack);
1252	gap_ack_blocks = ntohs(sack->num_gap_ack_blocks);
1253	asoc->stats.gapcnt += gap_ack_blocks;
1254	/*
1255	 * SFR-CACC algorithm:
1256	 * On receipt of a SACK the sender SHOULD execute the
1257	 * following statements.
1258	 *
1259	 * 1) If the cumulative ack in the SACK passes next tsn_at_change
1260	 * on the current primary, the CHANGEOVER_ACTIVE flag SHOULD be
1261	 * cleared. The CYCLING_CHANGEOVER flag SHOULD also be cleared for
1262	 * all destinations.
1263	 * 2) If the SACK contains gap acks and the flag CHANGEOVER_ACTIVE
1264	 * is set the receiver of the SACK MUST take the following actions:
1265	 *
1266	 * A) Initialize the cacc_saw_newack to 0 for all destination
1267	 * addresses.
1268	 *
1269	 * Only bother if changeover_active is set. Otherwise, this is
1270	 * totally suboptimal to do on every SACK.
1271	 */
1272	if (primary->cacc.changeover_active) {
1273		u8 clear_cycling = 0;
1274
1275		if (TSN_lte(primary->cacc.next_tsn_at_change, sack_ctsn)) {
1276			primary->cacc.changeover_active = 0;
1277			clear_cycling = 1;
1278		}
1279
1280		if (clear_cycling || gap_ack_blocks) {
1281			list_for_each_entry(transport, transport_list,
1282					transports) {
1283				if (clear_cycling)
1284					transport->cacc.cycling_changeover = 0;
1285				if (gap_ack_blocks)
1286					transport->cacc.cacc_saw_newack = 0;
1287			}
1288		}
1289	}
1290
1291	/* Get the highest TSN in the sack. */
1292	highest_tsn = sack_ctsn;
1293	if (gap_ack_blocks)
 
 
 
1294		highest_tsn += ntohs(frags[gap_ack_blocks - 1].gab.end);
 
1295
1296	if (TSN_lt(asoc->highest_sacked, highest_tsn))
1297		asoc->highest_sacked = highest_tsn;
1298
1299	highest_new_tsn = sack_ctsn;
1300
1301	/* Run through the retransmit queue.  Credit bytes received
1302	 * and free those chunks that we can.
1303	 */
1304	sctp_check_transmitted(q, &q->retransmit, NULL, NULL, sack, &highest_new_tsn);
1305
1306	/* Run through the transmitted queue.
1307	 * Credit bytes received and free those chunks which we can.
1308	 *
1309	 * This is a MASSIVE candidate for optimization.
1310	 */
1311	list_for_each_entry(transport, transport_list, transports) {
1312		sctp_check_transmitted(q, &transport->transmitted,
1313				       transport, &chunk->source, sack,
1314				       &highest_new_tsn);
1315		/*
1316		 * SFR-CACC algorithm:
1317		 * C) Let count_of_newacks be the number of
1318		 * destinations for which cacc_saw_newack is set.
1319		 */
1320		if (transport->cacc.cacc_saw_newack)
1321			count_of_newacks++;
1322	}
1323
1324	/* Move the Cumulative TSN Ack Point if appropriate.  */
1325	if (TSN_lt(asoc->ctsn_ack_point, sack_ctsn)) {
1326		asoc->ctsn_ack_point = sack_ctsn;
1327		accum_moved = 1;
1328	}
1329
1330	if (gap_ack_blocks) {
1331
1332		if (asoc->fast_recovery && accum_moved)
1333			highest_new_tsn = highest_tsn;
1334
1335		list_for_each_entry(transport, transport_list, transports)
1336			sctp_mark_missing(q, &transport->transmitted, transport,
1337					  highest_new_tsn, count_of_newacks);
1338	}
1339
1340	/* Update unack_data field in the assoc. */
1341	sctp_sack_update_unack_data(asoc, sack);
1342
1343	ctsn = asoc->ctsn_ack_point;
1344
1345	/* Throw away stuff rotting on the sack queue.  */
1346	list_for_each_safe(lchunk, temp, &q->sacked) {
1347		tchunk = list_entry(lchunk, struct sctp_chunk,
1348				    transmitted_list);
1349		tsn = ntohl(tchunk->subh.data_hdr->tsn);
1350		if (TSN_lte(tsn, ctsn)) {
1351			list_del_init(&tchunk->transmitted_list);
1352			if (asoc->peer.prsctp_capable &&
1353			    SCTP_PR_PRIO_ENABLED(chunk->sinfo.sinfo_flags))
1354				asoc->sent_cnt_removable--;
1355			sctp_chunk_free(tchunk);
1356		}
1357	}
1358
1359	/* ii) Set rwnd equal to the newly received a_rwnd minus the
1360	 *     number of bytes still outstanding after processing the
1361	 *     Cumulative TSN Ack and the Gap Ack Blocks.
1362	 */
1363
1364	sack_a_rwnd = ntohl(sack->a_rwnd);
1365	asoc->peer.zero_window_announced = !sack_a_rwnd;
1366	outstanding = q->outstanding_bytes;
1367
1368	if (outstanding < sack_a_rwnd)
1369		sack_a_rwnd -= outstanding;
1370	else
1371		sack_a_rwnd = 0;
1372
1373	asoc->peer.rwnd = sack_a_rwnd;
1374
1375	asoc->stream.si->generate_ftsn(q, sack_ctsn);
1376
1377	pr_debug("%s: sack cumulative tsn ack:0x%x\n", __func__, sack_ctsn);
1378	pr_debug("%s: cumulative tsn ack of assoc:%p is 0x%x, "
1379		 "advertised peer ack point:0x%x\n", __func__, asoc, ctsn,
1380		 asoc->adv_peer_ack_point);
1381
1382	return sctp_outq_is_empty(q);
1383}
1384
1385/* Is the outqueue empty?
1386 * The queue is empty when we have not pending data, no in-flight data
1387 * and nothing pending retransmissions.
1388 */
1389int sctp_outq_is_empty(const struct sctp_outq *q)
1390{
1391	return q->out_qlen == 0 && q->outstanding_bytes == 0 &&
1392	       list_empty(&q->retransmit);
1393}
1394
1395/********************************************************************
1396 * 2nd Level Abstractions
1397 ********************************************************************/
1398
1399/* Go through a transport's transmitted list or the association's retransmit
1400 * list and move chunks that are acked by the Cumulative TSN Ack to q->sacked.
1401 * The retransmit list will not have an associated transport.
1402 *
1403 * I added coherent debug information output.	--xguo
1404 *
1405 * Instead of printing 'sacked' or 'kept' for each TSN on the
1406 * transmitted_queue, we print a range: SACKED: TSN1-TSN2, TSN3, TSN4-TSN5.
1407 * KEPT TSN6-TSN7, etc.
1408 */
1409static void sctp_check_transmitted(struct sctp_outq *q,
1410				   struct list_head *transmitted_queue,
1411				   struct sctp_transport *transport,
1412				   union sctp_addr *saddr,
1413				   struct sctp_sackhdr *sack,
1414				   __u32 *highest_new_tsn_in_sack)
1415{
1416	struct list_head *lchunk;
1417	struct sctp_chunk *tchunk;
1418	struct list_head tlist;
1419	__u32 tsn;
1420	__u32 sack_ctsn;
1421	__u32 rtt;
1422	__u8 restart_timer = 0;
1423	int bytes_acked = 0;
1424	int migrate_bytes = 0;
1425	bool forward_progress = false;
1426
1427	sack_ctsn = ntohl(sack->cum_tsn_ack);
1428
1429	INIT_LIST_HEAD(&tlist);
1430
1431	/* The while loop will skip empty transmitted queues. */
1432	while (NULL != (lchunk = sctp_list_dequeue(transmitted_queue))) {
1433		tchunk = list_entry(lchunk, struct sctp_chunk,
1434				    transmitted_list);
1435
1436		if (sctp_chunk_abandoned(tchunk)) {
1437			/* Move the chunk to abandoned list. */
1438			sctp_insert_list(&q->abandoned, lchunk);
1439
1440			/* If this chunk has not been acked, stop
1441			 * considering it as 'outstanding'.
1442			 */
1443			if (transmitted_queue != &q->retransmit &&
1444			    !tchunk->tsn_gap_acked) {
1445				if (tchunk->transport)
1446					tchunk->transport->flight_size -=
1447							sctp_data_size(tchunk);
1448				q->outstanding_bytes -= sctp_data_size(tchunk);
1449			}
1450			continue;
1451		}
1452
1453		tsn = ntohl(tchunk->subh.data_hdr->tsn);
1454		if (sctp_acked(sack, tsn)) {
1455			/* If this queue is the retransmit queue, the
1456			 * retransmit timer has already reclaimed
1457			 * the outstanding bytes for this chunk, so only
1458			 * count bytes associated with a transport.
1459			 */
1460			if (transport) {
1461				/* If this chunk is being used for RTT
1462				 * measurement, calculate the RTT and update
1463				 * the RTO using this value.
1464				 *
1465				 * 6.3.1 C5) Karn's algorithm: RTT measurements
1466				 * MUST NOT be made using packets that were
1467				 * retransmitted (and thus for which it is
1468				 * ambiguous whether the reply was for the
1469				 * first instance of the packet or a later
1470				 * instance).
1471				 */
1472				if (!tchunk->tsn_gap_acked &&
1473				    !sctp_chunk_retransmitted(tchunk) &&
1474				    tchunk->rtt_in_progress) {
1475					tchunk->rtt_in_progress = 0;
1476					rtt = jiffies - tchunk->sent_at;
1477					sctp_transport_update_rto(transport,
1478								  rtt);
1479				}
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1480			}
1481
1482			/* If the chunk hasn't been marked as ACKED,
1483			 * mark it and account bytes_acked if the
1484			 * chunk had a valid transport (it will not
1485			 * have a transport if ASCONF had deleted it
1486			 * while DATA was outstanding).
1487			 */
1488			if (!tchunk->tsn_gap_acked) {
1489				tchunk->tsn_gap_acked = 1;
1490				if (TSN_lt(*highest_new_tsn_in_sack, tsn))
1491					*highest_new_tsn_in_sack = tsn;
1492				bytes_acked += sctp_data_size(tchunk);
1493				if (!tchunk->transport)
1494					migrate_bytes += sctp_data_size(tchunk);
1495				forward_progress = true;
1496			}
1497
1498			if (TSN_lte(tsn, sack_ctsn)) {
1499				/* RFC 2960  6.3.2 Retransmission Timer Rules
1500				 *
1501				 * R3) Whenever a SACK is received
1502				 * that acknowledges the DATA chunk
1503				 * with the earliest outstanding TSN
1504				 * for that address, restart T3-rtx
1505				 * timer for that address with its
1506				 * current RTO.
1507				 */
1508				restart_timer = 1;
1509				forward_progress = true;
1510
1511				if (!tchunk->tsn_gap_acked) {
1512					/*
1513					 * SFR-CACC algorithm:
1514					 * 2) If the SACK contains gap acks
1515					 * and the flag CHANGEOVER_ACTIVE is
1516					 * set the receiver of the SACK MUST
1517					 * take the following action:
1518					 *
1519					 * B) For each TSN t being acked that
1520					 * has not been acked in any SACK so
1521					 * far, set cacc_saw_newack to 1 for
1522					 * the destination that the TSN was
1523					 * sent to.
1524					 */
1525					if (transport &&
1526					    sack->num_gap_ack_blocks &&
1527					    q->asoc->peer.primary_path->cacc.
1528					    changeover_active)
1529						transport->cacc.cacc_saw_newack
1530							= 1;
1531				}
1532
1533				list_add_tail(&tchunk->transmitted_list,
1534					      &q->sacked);
1535			} else {
1536				/* RFC2960 7.2.4, sctpimpguide-05 2.8.2
1537				 * M2) Each time a SACK arrives reporting
1538				 * 'Stray DATA chunk(s)' record the highest TSN
1539				 * reported as newly acknowledged, call this
1540				 * value 'HighestTSNinSack'. A newly
1541				 * acknowledged DATA chunk is one not
1542				 * previously acknowledged in a SACK.
1543				 *
1544				 * When the SCTP sender of data receives a SACK
1545				 * chunk that acknowledges, for the first time,
1546				 * the receipt of a DATA chunk, all the still
1547				 * unacknowledged DATA chunks whose TSN is
1548				 * older than that newly acknowledged DATA
1549				 * chunk, are qualified as 'Stray DATA chunks'.
1550				 */
1551				list_add_tail(lchunk, &tlist);
1552			}
1553		} else {
1554			if (tchunk->tsn_gap_acked) {
1555				pr_debug("%s: receiver reneged on data TSN:0x%x\n",
1556					 __func__, tsn);
1557
1558				tchunk->tsn_gap_acked = 0;
1559
1560				if (tchunk->transport)
1561					bytes_acked -= sctp_data_size(tchunk);
1562
1563				/* RFC 2960 6.3.2 Retransmission Timer Rules
1564				 *
1565				 * R4) Whenever a SACK is received missing a
1566				 * TSN that was previously acknowledged via a
1567				 * Gap Ack Block, start T3-rtx for the
1568				 * destination address to which the DATA
1569				 * chunk was originally
1570				 * transmitted if it is not already running.
1571				 */
1572				restart_timer = 1;
1573			}
1574
1575			list_add_tail(lchunk, &tlist);
1576		}
1577	}
1578
1579	if (transport) {
1580		if (bytes_acked) {
1581			struct sctp_association *asoc = transport->asoc;
1582
1583			/* We may have counted DATA that was migrated
1584			 * to this transport due to DEL-IP operation.
1585			 * Subtract those bytes, since the were never
1586			 * send on this transport and shouldn't be
1587			 * credited to this transport.
1588			 */
1589			bytes_acked -= migrate_bytes;
1590
1591			/* 8.2. When an outstanding TSN is acknowledged,
1592			 * the endpoint shall clear the error counter of
1593			 * the destination transport address to which the
1594			 * DATA chunk was last sent.
1595			 * The association's overall error counter is
1596			 * also cleared.
1597			 */
1598			transport->error_count = 0;
1599			transport->asoc->overall_error_count = 0;
1600			forward_progress = true;
1601
1602			/*
1603			 * While in SHUTDOWN PENDING, we may have started
1604			 * the T5 shutdown guard timer after reaching the
1605			 * retransmission limit. Stop that timer as soon
1606			 * as the receiver acknowledged any data.
1607			 */
1608			if (asoc->state == SCTP_STATE_SHUTDOWN_PENDING &&
1609			    del_timer(&asoc->timers
1610				[SCTP_EVENT_TIMEOUT_T5_SHUTDOWN_GUARD]))
1611					sctp_association_put(asoc);
1612
1613			/* Mark the destination transport address as
1614			 * active if it is not so marked.
1615			 */
1616			if ((transport->state == SCTP_INACTIVE ||
1617			     transport->state == SCTP_UNCONFIRMED) &&
1618			    sctp_cmp_addr_exact(&transport->ipaddr, saddr)) {
1619				sctp_assoc_control_transport(
1620					transport->asoc,
1621					transport,
1622					SCTP_TRANSPORT_UP,
1623					SCTP_RECEIVED_SACK);
1624			}
1625
1626			sctp_transport_raise_cwnd(transport, sack_ctsn,
1627						  bytes_acked);
1628
1629			transport->flight_size -= bytes_acked;
1630			if (transport->flight_size == 0)
1631				transport->partial_bytes_acked = 0;
1632			q->outstanding_bytes -= bytes_acked + migrate_bytes;
1633		} else {
1634			/* RFC 2960 6.1, sctpimpguide-06 2.15.2
1635			 * When a sender is doing zero window probing, it
1636			 * should not timeout the association if it continues
1637			 * to receive new packets from the receiver. The
1638			 * reason is that the receiver MAY keep its window
1639			 * closed for an indefinite time.
1640			 * A sender is doing zero window probing when the
1641			 * receiver's advertised window is zero, and there is
1642			 * only one data chunk in flight to the receiver.
1643			 *
1644			 * Allow the association to timeout while in SHUTDOWN
1645			 * PENDING or SHUTDOWN RECEIVED in case the receiver
1646			 * stays in zero window mode forever.
1647			 */
1648			if (!q->asoc->peer.rwnd &&
1649			    !list_empty(&tlist) &&
1650			    (sack_ctsn+2 == q->asoc->next_tsn) &&
1651			    q->asoc->state < SCTP_STATE_SHUTDOWN_PENDING) {
1652				pr_debug("%s: sack received for zero window "
1653					 "probe:%u\n", __func__, sack_ctsn);
1654
1655				q->asoc->overall_error_count = 0;
1656				transport->error_count = 0;
1657			}
1658		}
1659
1660		/* RFC 2960 6.3.2 Retransmission Timer Rules
1661		 *
1662		 * R2) Whenever all outstanding data sent to an address have
1663		 * been acknowledged, turn off the T3-rtx timer of that
1664		 * address.
1665		 */
1666		if (!transport->flight_size) {
1667			if (del_timer(&transport->T3_rtx_timer))
1668				sctp_transport_put(transport);
1669		} else if (restart_timer) {
1670			if (!mod_timer(&transport->T3_rtx_timer,
1671				       jiffies + transport->rto))
1672				sctp_transport_hold(transport);
1673		}
1674
1675		if (forward_progress) {
1676			if (transport->dst)
1677				sctp_transport_dst_confirm(transport);
1678		}
1679	}
1680
1681	list_splice(&tlist, transmitted_queue);
1682}
1683
1684/* Mark chunks as missing and consequently may get retransmitted. */
1685static void sctp_mark_missing(struct sctp_outq *q,
1686			      struct list_head *transmitted_queue,
1687			      struct sctp_transport *transport,
1688			      __u32 highest_new_tsn_in_sack,
1689			      int count_of_newacks)
1690{
1691	struct sctp_chunk *chunk;
1692	__u32 tsn;
1693	char do_fast_retransmit = 0;
1694	struct sctp_association *asoc = q->asoc;
1695	struct sctp_transport *primary = asoc->peer.primary_path;
1696
1697	list_for_each_entry(chunk, transmitted_queue, transmitted_list) {
1698
1699		tsn = ntohl(chunk->subh.data_hdr->tsn);
1700
1701		/* RFC 2960 7.2.4, sctpimpguide-05 2.8.2 M3) Examine all
1702		 * 'Unacknowledged TSN's', if the TSN number of an
1703		 * 'Unacknowledged TSN' is smaller than the 'HighestTSNinSack'
1704		 * value, increment the 'TSN.Missing.Report' count on that
1705		 * chunk if it has NOT been fast retransmitted or marked for
1706		 * fast retransmit already.
1707		 */
1708		if (chunk->fast_retransmit == SCTP_CAN_FRTX &&
1709		    !chunk->tsn_gap_acked &&
1710		    TSN_lt(tsn, highest_new_tsn_in_sack)) {
1711
1712			/* SFR-CACC may require us to skip marking
1713			 * this chunk as missing.
1714			 */
1715			if (!transport || !sctp_cacc_skip(primary,
1716						chunk->transport,
1717						count_of_newacks, tsn)) {
1718				chunk->tsn_missing_report++;
1719
1720				pr_debug("%s: tsn:0x%x missing counter:%d\n",
1721					 __func__, tsn, chunk->tsn_missing_report);
1722			}
1723		}
1724		/*
1725		 * M4) If any DATA chunk is found to have a
1726		 * 'TSN.Missing.Report'
1727		 * value larger than or equal to 3, mark that chunk for
1728		 * retransmission and start the fast retransmit procedure.
1729		 */
1730
1731		if (chunk->tsn_missing_report >= 3) {
1732			chunk->fast_retransmit = SCTP_NEED_FRTX;
1733			do_fast_retransmit = 1;
1734		}
1735	}
1736
1737	if (transport) {
1738		if (do_fast_retransmit)
1739			sctp_retransmit(q, transport, SCTP_RTXR_FAST_RTX);
1740
1741		pr_debug("%s: transport:%p, cwnd:%d, ssthresh:%d, "
1742			 "flight_size:%d, pba:%d\n",  __func__, transport,
1743			 transport->cwnd, transport->ssthresh,
1744			 transport->flight_size, transport->partial_bytes_acked);
1745	}
1746}
1747
1748/* Is the given TSN acked by this packet?  */
1749static int sctp_acked(struct sctp_sackhdr *sack, __u32 tsn)
1750{
1751	__u32 ctsn = ntohl(sack->cum_tsn_ack);
1752	union sctp_sack_variable *frags;
1753	__u16 tsn_offset, blocks;
1754	int i;
1755
1756	if (TSN_lte(tsn, ctsn))
1757		goto pass;
1758
1759	/* 3.3.4 Selective Acknowledgement (SACK) (3):
1760	 *
1761	 * Gap Ack Blocks:
1762	 *  These fields contain the Gap Ack Blocks. They are repeated
1763	 *  for each Gap Ack Block up to the number of Gap Ack Blocks
1764	 *  defined in the Number of Gap Ack Blocks field. All DATA
1765	 *  chunks with TSNs greater than or equal to (Cumulative TSN
1766	 *  Ack + Gap Ack Block Start) and less than or equal to
1767	 *  (Cumulative TSN Ack + Gap Ack Block End) of each Gap Ack
1768	 *  Block are assumed to have been received correctly.
1769	 */
1770
1771	frags = sack->variable;
1772	blocks = ntohs(sack->num_gap_ack_blocks);
1773	tsn_offset = tsn - ctsn;
1774	for (i = 0; i < blocks; ++i) {
1775		if (tsn_offset >= ntohs(frags[i].gab.start) &&
1776		    tsn_offset <= ntohs(frags[i].gab.end))
1777			goto pass;
1778	}
1779
1780	return 0;
1781pass:
1782	return 1;
1783}
1784
1785static inline int sctp_get_skip_pos(struct sctp_fwdtsn_skip *skiplist,
1786				    int nskips, __be16 stream)
1787{
1788	int i;
1789
1790	for (i = 0; i < nskips; i++) {
1791		if (skiplist[i].stream == stream)
1792			return i;
1793	}
1794	return i;
1795}
1796
1797/* Create and add a fwdtsn chunk to the outq's control queue if needed. */
1798void sctp_generate_fwdtsn(struct sctp_outq *q, __u32 ctsn)
1799{
1800	struct sctp_association *asoc = q->asoc;
1801	struct sctp_chunk *ftsn_chunk = NULL;
1802	struct sctp_fwdtsn_skip ftsn_skip_arr[10];
1803	int nskips = 0;
1804	int skip_pos = 0;
1805	__u32 tsn;
1806	struct sctp_chunk *chunk;
1807	struct list_head *lchunk, *temp;
1808
1809	if (!asoc->peer.prsctp_capable)
1810		return;
1811
1812	/* PR-SCTP C1) Let SackCumAck be the Cumulative TSN ACK carried in the
1813	 * received SACK.
1814	 *
1815	 * If (Advanced.Peer.Ack.Point < SackCumAck), then update
1816	 * Advanced.Peer.Ack.Point to be equal to SackCumAck.
1817	 */
1818	if (TSN_lt(asoc->adv_peer_ack_point, ctsn))
1819		asoc->adv_peer_ack_point = ctsn;
1820
1821	/* PR-SCTP C2) Try to further advance the "Advanced.Peer.Ack.Point"
1822	 * locally, that is, to move "Advanced.Peer.Ack.Point" up as long as
1823	 * the chunk next in the out-queue space is marked as "abandoned" as
1824	 * shown in the following example:
1825	 *
1826	 * Assuming that a SACK arrived with the Cumulative TSN ACK 102
1827	 * and the Advanced.Peer.Ack.Point is updated to this value:
1828	 *
1829	 *   out-queue at the end of  ==>   out-queue after Adv.Ack.Point
1830	 *   normal SACK processing           local advancement
1831	 *                ...                           ...
1832	 *   Adv.Ack.Pt-> 102 acked                     102 acked
1833	 *                103 abandoned                 103 abandoned
1834	 *                104 abandoned     Adv.Ack.P-> 104 abandoned
1835	 *                105                           105
1836	 *                106 acked                     106 acked
1837	 *                ...                           ...
1838	 *
1839	 * In this example, the data sender successfully advanced the
1840	 * "Advanced.Peer.Ack.Point" from 102 to 104 locally.
1841	 */
1842	list_for_each_safe(lchunk, temp, &q->abandoned) {
1843		chunk = list_entry(lchunk, struct sctp_chunk,
1844					transmitted_list);
1845		tsn = ntohl(chunk->subh.data_hdr->tsn);
1846
1847		/* Remove any chunks in the abandoned queue that are acked by
1848		 * the ctsn.
1849		 */
1850		if (TSN_lte(tsn, ctsn)) {
1851			list_del_init(lchunk);
1852			sctp_chunk_free(chunk);
1853		} else {
1854			if (TSN_lte(tsn, asoc->adv_peer_ack_point+1)) {
1855				asoc->adv_peer_ack_point = tsn;
1856				if (chunk->chunk_hdr->flags &
1857					 SCTP_DATA_UNORDERED)
1858					continue;
1859				skip_pos = sctp_get_skip_pos(&ftsn_skip_arr[0],
1860						nskips,
1861						chunk->subh.data_hdr->stream);
1862				ftsn_skip_arr[skip_pos].stream =
1863					chunk->subh.data_hdr->stream;
1864				ftsn_skip_arr[skip_pos].ssn =
1865					 chunk->subh.data_hdr->ssn;
1866				if (skip_pos == nskips)
1867					nskips++;
1868				if (nskips == 10)
1869					break;
1870			} else
1871				break;
1872		}
1873	}
1874
1875	/* PR-SCTP C3) If, after step C1 and C2, the "Advanced.Peer.Ack.Point"
1876	 * is greater than the Cumulative TSN ACK carried in the received
1877	 * SACK, the data sender MUST send the data receiver a FORWARD TSN
1878	 * chunk containing the latest value of the
1879	 * "Advanced.Peer.Ack.Point".
1880	 *
1881	 * C4) For each "abandoned" TSN the sender of the FORWARD TSN SHOULD
1882	 * list each stream and sequence number in the forwarded TSN. This
1883	 * information will enable the receiver to easily find any
1884	 * stranded TSN's waiting on stream reorder queues. Each stream
1885	 * SHOULD only be reported once; this means that if multiple
1886	 * abandoned messages occur in the same stream then only the
1887	 * highest abandoned stream sequence number is reported. If the
1888	 * total size of the FORWARD TSN does NOT fit in a single MTU then
1889	 * the sender of the FORWARD TSN SHOULD lower the
1890	 * Advanced.Peer.Ack.Point to the last TSN that will fit in a
1891	 * single MTU.
1892	 */
1893	if (asoc->adv_peer_ack_point > ctsn)
1894		ftsn_chunk = sctp_make_fwdtsn(asoc, asoc->adv_peer_ack_point,
1895					      nskips, &ftsn_skip_arr[0]);
1896
1897	if (ftsn_chunk) {
1898		list_add_tail(&ftsn_chunk->list, &q->control_chunk_list);
1899		SCTP_INC_STATS(sock_net(asoc->base.sk), SCTP_MIB_OUTCTRLCHUNKS);
1900	}
1901}