1/* SCTP kernel implementation
   2 * (C) Copyright IBM Corp. 2001, 2004
   3 * Copyright (c) 1999-2000 Cisco, Inc.
   4 * Copyright (c) 1999-2001 Motorola, Inc.
   5 * Copyright (c) 2001-2003 Intel Corp.
   6 *
   7 * This file is part of the SCTP kernel implementation
   8 *
   9 * These functions implement the sctp_outq class.   The outqueue handles
  10 * bundling and queueing of outgoing SCTP chunks.
  11 *
  12 * This SCTP implementation is free software;
  13 * you can redistribute it and/or modify it under the terms of
  14 * the GNU General Public License as published by
  15 * the Free Software Foundation; either version 2, or (at your option)
  16 * any later version.
  17 *
  18 * This SCTP implementation is distributed in the hope that it
  19 * will be useful, but WITHOUT ANY WARRANTY; without even the implied
  20 *                 ************************
  21 * warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
  22 * See the GNU General Public License for more details.
  23 *
  24 * You should have received a copy of the GNU General Public License
  25 * along with GNU CC; see the file COPYING.  If not, write to
  26 * the Free Software Foundation, 59 Temple Place - Suite 330,
  27 * Boston, MA 02111-1307, USA.
  28 *
  29 * Please send any bug reports or fixes you make to the
  30 * email address(es):
  31 *    lksctp developers <lksctp-developers@lists.sourceforge.net>
  32 *
  33 * Or submit a bug report through the following website:
  34 *    http://www.sf.net/projects/lksctp
  35 *
  36 * Written or modified by:
  37 *    La Monte H.P. Yarroll <piggy@acm.org>
  38 *    Karl Knutson          <karl@athena.chicago.il.us>
  39 *    Perry Melange         <pmelange@null.cc.uic.edu>
  40 *    Xingang Guo           <xingang.guo@intel.com>
  41 *    Hui Huang 	    <hui.huang@nokia.com>
  42 *    Sridhar Samudrala     <sri@us.ibm.com>
  43 *    Jon Grimm             <jgrimm@us.ibm.com>
  44 *
  45 * Any bugs reported given to us we will try to fix... any fixes shared will
  46 * be incorporated into the next SCTP release.
  47 */
  48
  49#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  50
  51#include <linux/types.h>
  52#include <linux/list.h>   /* For struct list_head */
  53#include <linux/socket.h>
  54#include <linux/ip.h>
  55#include <linux/slab.h>
  56#include <net/sock.h>	  /* For skb_set_owner_w */
  57
  58#include <net/sctp/sctp.h>
  59#include <net/sctp/sm.h>
  60
  61/* Declare internal functions here.  */
  62static int sctp_acked(struct sctp_sackhdr *sack, __u32 tsn);
  63static void sctp_check_transmitted(struct sctp_outq *q,
  64				   struct list_head *transmitted_queue,
  65				   struct sctp_transport *transport,
 
  66				   struct sctp_sackhdr *sack,
  67				   __u32 *highest_new_tsn);
  68
  69static void sctp_mark_missing(struct sctp_outq *q,
  70			      struct list_head *transmitted_queue,
  71			      struct sctp_transport *transport,
  72			      __u32 highest_new_tsn,
  73			      int count_of_newacks);
  74
  75static void sctp_generate_fwdtsn(struct sctp_outq *q, __u32 sack_ctsn);
  76
  77static int sctp_outq_flush(struct sctp_outq *q, int rtx_timeout);
  78
  79/* Add data to the front of the queue. */
  80static inline void sctp_outq_head_data(struct sctp_outq *q,
  81					struct sctp_chunk *ch)
  82{
  83	list_add(&ch->list, &q->out_chunk_list);
  84	q->out_qlen += ch->skb->len;
  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	struct sctp_chunk *ch = NULL;
  91
  92	if (!list_empty(&q->out_chunk_list)) {
  93		struct list_head *entry = q->out_chunk_list.next;
  94
  95		ch = list_entry(entry, struct sctp_chunk, list);
  96		list_del_init(entry);
  97		q->out_qlen -= ch->skb->len;
  98	}
  99	return ch;
 100}
 101/* Add data chunk to the end of the queue. */
 102static inline void sctp_outq_tail_data(struct sctp_outq *q,
 103				       struct sctp_chunk *ch)
 104{
 105	list_add_tail(&ch->list, &q->out_chunk_list);
 106	q->out_qlen += ch->skb->len;
 107}
 108
 109/*
 110 * SFR-CACC algorithm:
 111 * D) If count_of_newacks is greater than or equal to 2
 112 * and t was not sent to the current primary then the
 113 * sender MUST NOT increment missing report count for t.
 114 */
 115static inline int sctp_cacc_skip_3_1_d(struct sctp_transport *primary,
 116				       struct sctp_transport *transport,
 117				       int count_of_newacks)
 118{
 119	if (count_of_newacks >=2 && transport != primary)
 120		return 1;
 121	return 0;
 122}
 123
 124/*
 125 * SFR-CACC algorithm:
 126 * F) If count_of_newacks is less than 2, let d be the
 127 * destination to which t was sent. If cacc_saw_newack
 128 * is 0 for destination d, then the sender MUST NOT
 129 * increment missing report count for t.
 130 */
 131static inline int sctp_cacc_skip_3_1_f(struct sctp_transport *transport,
 132				       int count_of_newacks)
 133{
 134	if (count_of_newacks < 2 &&
 135			(transport && !transport->cacc.cacc_saw_newack))
 136		return 1;
 137	return 0;
 138}
 139
 140/*
 141 * SFR-CACC algorithm:
 142 * 3.1) If CYCLING_CHANGEOVER is 0, the sender SHOULD
 143 * execute steps C, D, F.
 144 *
 145 * C has been implemented in sctp_outq_sack
 146 */
 147static inline int sctp_cacc_skip_3_1(struct sctp_transport *primary,
 148				     struct sctp_transport *transport,
 149				     int count_of_newacks)
 150{
 151	if (!primary->cacc.cycling_changeover) {
 152		if (sctp_cacc_skip_3_1_d(primary, transport, count_of_newacks))
 153			return 1;
 154		if (sctp_cacc_skip_3_1_f(transport, count_of_newacks))
 155			return 1;
 156		return 0;
 157	}
 158	return 0;
 159}
 160
 161/*
 162 * SFR-CACC algorithm:
 163 * 3.2) Else if CYCLING_CHANGEOVER is 1, and t is less
 164 * than next_tsn_at_change of the current primary, then
 165 * the sender MUST NOT increment missing report count
 166 * for t.
 167 */
 168static inline int sctp_cacc_skip_3_2(struct sctp_transport *primary, __u32 tsn)
 169{
 170	if (primary->cacc.cycling_changeover &&
 171	    TSN_lt(tsn, primary->cacc.next_tsn_at_change))
 172		return 1;
 173	return 0;
 174}
 175
 176/*
 177 * SFR-CACC algorithm:
 178 * 3) If the missing report count for TSN t is to be
 179 * incremented according to [RFC2960] and
 180 * [SCTP_STEWART-2002], and CHANGEOVER_ACTIVE is set,
 181 * then the sender MUST further execute steps 3.1 and
 182 * 3.2 to determine if the missing report count for
 183 * TSN t SHOULD NOT be incremented.
 184 *
 185 * 3.3) If 3.1 and 3.2 do not dictate that the missing
 186 * report count for t should not be incremented, then
 187 * the sender SHOULD increment missing report count for
 188 * t (according to [RFC2960] and [SCTP_STEWART_2002]).
 189 */
 190static inline int sctp_cacc_skip(struct sctp_transport *primary,
 191				 struct sctp_transport *transport,
 192				 int count_of_newacks,
 193				 __u32 tsn)
 194{
 195	if (primary->cacc.changeover_active &&
 196	    (sctp_cacc_skip_3_1(primary, transport, count_of_newacks) ||
 197	     sctp_cacc_skip_3_2(primary, tsn)))
 198		return 1;
 199	return 0;
 200}
 201
 202/* Initialize an existing sctp_outq.  This does the boring stuff.
 203 * You still need to define handlers if you really want to DO
 204 * something with this structure...
 205 */
 206void sctp_outq_init(struct sctp_association *asoc, struct sctp_outq *q)
 207{
 
 
 208	q->asoc = asoc;
 209	INIT_LIST_HEAD(&q->out_chunk_list);
 210	INIT_LIST_HEAD(&q->control_chunk_list);
 211	INIT_LIST_HEAD(&q->retransmit);
 212	INIT_LIST_HEAD(&q->sacked);
 213	INIT_LIST_HEAD(&q->abandoned);
 214
 215	q->fast_rtx = 0;
 216	q->outstanding_bytes = 0;
 217	q->empty = 1;
 218	q->cork  = 0;
 219
 220	q->malloced = 0;
 221	q->out_qlen = 0;
 222}
 223
 224/* Free the outqueue structure and any related pending chunks.
 225 */
 226void sctp_outq_teardown(struct sctp_outq *q)
 227{
 228	struct sctp_transport *transport;
 229	struct list_head *lchunk, *temp;
 230	struct sctp_chunk *chunk, *tmp;
 231
 232	/* Throw away unacknowledged chunks. */
 233	list_for_each_entry(transport, &q->asoc->peer.transport_addr_list,
 234			transports) {
 235		while ((lchunk = sctp_list_dequeue(&transport->transmitted)) != NULL) {
 236			chunk = list_entry(lchunk, struct sctp_chunk,
 237					   transmitted_list);
 238			/* Mark as part of a failed message. */
 239			sctp_chunk_fail(chunk, q->error);
 240			sctp_chunk_free(chunk);
 241		}
 242	}
 243
 244	/* Throw away chunks that have been gap ACKed.  */
 245	list_for_each_safe(lchunk, temp, &q->sacked) {
 246		list_del_init(lchunk);
 247		chunk = list_entry(lchunk, struct sctp_chunk,
 248				   transmitted_list);
 249		sctp_chunk_fail(chunk, q->error);
 250		sctp_chunk_free(chunk);
 251	}
 252
 253	/* Throw away any chunks in the retransmit queue. */
 254	list_for_each_safe(lchunk, temp, &q->retransmit) {
 255		list_del_init(lchunk);
 256		chunk = list_entry(lchunk, struct sctp_chunk,
 257				   transmitted_list);
 258		sctp_chunk_fail(chunk, q->error);
 259		sctp_chunk_free(chunk);
 260	}
 261
 262	/* Throw away any chunks that are in the abandoned queue. */
 263	list_for_each_safe(lchunk, temp, &q->abandoned) {
 264		list_del_init(lchunk);
 265		chunk = list_entry(lchunk, struct sctp_chunk,
 266				   transmitted_list);
 267		sctp_chunk_fail(chunk, q->error);
 268		sctp_chunk_free(chunk);
 269	}
 270
 271	/* Throw away any leftover data chunks. */
 272	while ((chunk = sctp_outq_dequeue_data(q)) != NULL) {
 273
 274		/* Mark as send failure. */
 275		sctp_chunk_fail(chunk, q->error);
 276		sctp_chunk_free(chunk);
 277	}
 278
 279	q->error = 0;
 280
 281	/* Throw away any leftover control chunks. */
 282	list_for_each_entry_safe(chunk, tmp, &q->control_chunk_list, list) {
 283		list_del_init(&chunk->list);
 284		sctp_chunk_free(chunk);
 285	}
 286}
 287
 
 
 
 
 
 
 288/* Free the outqueue structure and any related pending chunks.  */
 289void sctp_outq_free(struct sctp_outq *q)
 290{
 291	/* Throw away leftover chunks. */
 292	sctp_outq_teardown(q);
 293
 294	/* If we were kmalloc()'d, free the memory.  */
 295	if (q->malloced)
 296		kfree(q);
 297}
 298
 299/* Put a new chunk in an sctp_outq.  */
 300int sctp_outq_tail(struct sctp_outq *q, struct sctp_chunk *chunk)
 301{
 
 302	int error = 0;
 303
 304	SCTP_DEBUG_PRINTK("sctp_outq_tail(%p, %p[%s])\n",
 305			  q, chunk, chunk && chunk->chunk_hdr ?
 306			  sctp_cname(SCTP_ST_CHUNK(chunk->chunk_hdr->type))
 307			  : "Illegal Chunk");
 308
 309	/* If it is data, queue it up, otherwise, send it
 310	 * immediately.
 311	 */
 312	if (sctp_chunk_is_data(chunk)) {
 313		/* Is it OK to queue data chunks?  */
 314		/* From 9. Termination of Association
 315		 *
 316		 * When either endpoint performs a shutdown, the
 317		 * association on each peer will stop accepting new
 318		 * data from its user and only deliver data in queue
 319		 * at the time of sending or receiving the SHUTDOWN
 320		 * chunk.
 321		 */
 322		switch (q->asoc->state) {
 323		case SCTP_STATE_CLOSED:
 324		case SCTP_STATE_SHUTDOWN_PENDING:
 325		case SCTP_STATE_SHUTDOWN_SENT:
 326		case SCTP_STATE_SHUTDOWN_RECEIVED:
 327		case SCTP_STATE_SHUTDOWN_ACK_SENT:
 328			/* Cannot send after transport endpoint shutdown */
 329			error = -ESHUTDOWN;
 330			break;
 331
 332		default:
 333			SCTP_DEBUG_PRINTK("outqueueing (%p, %p[%s])\n",
 334			  q, chunk, chunk && chunk->chunk_hdr ?
 335			  sctp_cname(SCTP_ST_CHUNK(chunk->chunk_hdr->type))
 336			  : "Illegal Chunk");
 337
 
 338			sctp_outq_tail_data(q, chunk);
 339			if (chunk->chunk_hdr->flags & SCTP_DATA_UNORDERED)
 340				SCTP_INC_STATS(SCTP_MIB_OUTUNORDERCHUNKS);
 341			else
 342				SCTP_INC_STATS(SCTP_MIB_OUTORDERCHUNKS);
 343			q->empty = 0;
 344			break;
 345		}
 346	} else {
 347		list_add_tail(&chunk->list, &q->control_chunk_list);
 348		SCTP_INC_STATS(SCTP_MIB_OUTCTRLCHUNKS);
 349	}
 350
 351	if (error < 0)
 352		return error;
 353
 354	if (!q->cork)
 355		error = sctp_outq_flush(q, 0);
 356
 357	return error;
 358}
 359
 360/* Insert a chunk into the sorted list based on the TSNs.  The retransmit list
 361 * and the abandoned list are in ascending order.
 362 */
 363static void sctp_insert_list(struct list_head *head, struct list_head *new)
 364{
 365	struct list_head *pos;
 366	struct sctp_chunk *nchunk, *lchunk;
 367	__u32 ntsn, ltsn;
 368	int done = 0;
 369
 370	nchunk = list_entry(new, struct sctp_chunk, transmitted_list);
 371	ntsn = ntohl(nchunk->subh.data_hdr->tsn);
 372
 373	list_for_each(pos, head) {
 374		lchunk = list_entry(pos, struct sctp_chunk, transmitted_list);
 375		ltsn = ntohl(lchunk->subh.data_hdr->tsn);
 376		if (TSN_lt(ntsn, ltsn)) {
 377			list_add(new, pos->prev);
 378			done = 1;
 379			break;
 380		}
 381	}
 382	if (!done)
 383		list_add_tail(new, head);
 384}
 385
 386/* Mark all the eligible packets on a transport for retransmission.  */
 387void sctp_retransmit_mark(struct sctp_outq *q,
 388			  struct sctp_transport *transport,
 389			  __u8 reason)
 390{
 391	struct list_head *lchunk, *ltemp;
 392	struct sctp_chunk *chunk;
 393
 394	/* Walk through the specified transmitted queue.  */
 395	list_for_each_safe(lchunk, ltemp, &transport->transmitted) {
 396		chunk = list_entry(lchunk, struct sctp_chunk,
 397				   transmitted_list);
 398
 399		/* If the chunk is abandoned, move it to abandoned list. */
 400		if (sctp_chunk_abandoned(chunk)) {
 401			list_del_init(lchunk);
 402			sctp_insert_list(&q->abandoned, lchunk);
 403
 404			/* If this chunk has not been previousely acked,
 405			 * stop considering it 'outstanding'.  Our peer
 406			 * will most likely never see it since it will
 407			 * not be retransmitted
 408			 */
 409			if (!chunk->tsn_gap_acked) {
 410				if (chunk->transport)
 411					chunk->transport->flight_size -=
 412							sctp_data_size(chunk);
 413				q->outstanding_bytes -= sctp_data_size(chunk);
 414				q->asoc->peer.rwnd += sctp_data_size(chunk);
 415			}
 416			continue;
 417		}
 418
 419		/* If we are doing  retransmission due to a timeout or pmtu
 420		 * discovery, only the  chunks that are not yet acked should
 421		 * be added to the retransmit queue.
 422		 */
 423		if ((reason == SCTP_RTXR_FAST_RTX  &&
 424			    (chunk->fast_retransmit == SCTP_NEED_FRTX)) ||
 425		    (reason != SCTP_RTXR_FAST_RTX  && !chunk->tsn_gap_acked)) {
 426			/* RFC 2960 6.2.1 Processing a Received SACK
 427			 *
 428			 * C) Any time a DATA chunk is marked for
 429			 * retransmission (via either T3-rtx timer expiration
 430			 * (Section 6.3.3) or via fast retransmit
 431			 * (Section 7.2.4)), add the data size of those
 432			 * chunks to the rwnd.
 433			 */
 434			q->asoc->peer.rwnd += sctp_data_size(chunk);
 435			q->outstanding_bytes -= sctp_data_size(chunk);
 436			if (chunk->transport)
 437				transport->flight_size -= sctp_data_size(chunk);
 438
 439			/* sctpimpguide-05 Section 2.8.2
 440			 * M5) If a T3-rtx timer expires, the
 441			 * 'TSN.Missing.Report' of all affected TSNs is set
 442			 * to 0.
 443			 */
 444			chunk->tsn_missing_report = 0;
 445
 446			/* If a chunk that is being used for RTT measurement
 447			 * has to be retransmitted, we cannot use this chunk
 448			 * anymore for RTT measurements. Reset rto_pending so
 449			 * that a new RTT measurement is started when a new
 450			 * data chunk is sent.
 451			 */
 452			if (chunk->rtt_in_progress) {
 453				chunk->rtt_in_progress = 0;
 454				transport->rto_pending = 0;
 455			}
 456
 
 
 457			/* Move the chunk to the retransmit queue. The chunks
 458			 * on the retransmit queue are always kept in order.
 459			 */
 460			list_del_init(lchunk);
 461			sctp_insert_list(&q->retransmit, lchunk);
 462		}
 463	}
 464
 465	SCTP_DEBUG_PRINTK("%s: transport: %p, reason: %d, "
 466			  "cwnd: %d, ssthresh: %d, flight_size: %d, "
 467			  "pba: %d\n", __func__,
 468			  transport, reason,
 469			  transport->cwnd, transport->ssthresh,
 470			  transport->flight_size,
 471			  transport->partial_bytes_acked);
 472
 473}
 474
 475/* Mark all the eligible packets on a transport for retransmission and force
 476 * one packet out.
 477 */
 478void sctp_retransmit(struct sctp_outq *q, struct sctp_transport *transport,
 479		     sctp_retransmit_reason_t reason)
 480{
 
 481	int error = 0;
 482
 483	switch(reason) {
 484	case SCTP_RTXR_T3_RTX:
 485		SCTP_INC_STATS(SCTP_MIB_T3_RETRANSMITS);
 486		sctp_transport_lower_cwnd(transport, SCTP_LOWER_CWND_T3_RTX);
 487		/* Update the retran path if the T3-rtx timer has expired for
 488		 * the current retran path.
 489		 */
 490		if (transport == transport->asoc->peer.retran_path)
 491			sctp_assoc_update_retran_path(transport->asoc);
 492		transport->asoc->rtx_data_chunks +=
 493			transport->asoc->unack_data;
 494		break;
 495	case SCTP_RTXR_FAST_RTX:
 496		SCTP_INC_STATS(SCTP_MIB_FAST_RETRANSMITS);
 497		sctp_transport_lower_cwnd(transport, SCTP_LOWER_CWND_FAST_RTX);
 498		q->fast_rtx = 1;
 499		break;
 500	case SCTP_RTXR_PMTUD:
 501		SCTP_INC_STATS(SCTP_MIB_PMTUD_RETRANSMITS);
 502		break;
 503	case SCTP_RTXR_T1_RTX:
 504		SCTP_INC_STATS(SCTP_MIB_T1_RETRANSMITS);
 505		transport->asoc->init_retries++;
 506		break;
 507	default:
 508		BUG();
 509	}
 510
 511	sctp_retransmit_mark(q, transport, reason);
 512
 513	/* PR-SCTP A5) Any time the T3-rtx timer expires, on any destination,
 514	 * the sender SHOULD try to advance the "Advanced.Peer.Ack.Point" by
 515	 * following the procedures outlined in C1 - C5.
 516	 */
 517	if (reason == SCTP_RTXR_T3_RTX)
 518		sctp_generate_fwdtsn(q, q->asoc->ctsn_ack_point);
 519
 520	/* Flush the queues only on timeout, since fast_rtx is only
 521	 * triggered during sack processing and the queue
 522	 * will be flushed at the end.
 523	 */
 524	if (reason != SCTP_RTXR_FAST_RTX)
 525		error = sctp_outq_flush(q, /* rtx_timeout */ 1);
 526
 527	if (error)
 528		q->asoc->base.sk->sk_err = -error;
 529}
 530
 531/*
 532 * Transmit DATA chunks on the retransmit queue.  Upon return from
 533 * sctp_outq_flush_rtx() the packet 'pkt' may contain chunks which
 534 * need to be transmitted by the caller.
 535 * We assume that pkt->transport has already been set.
 536 *
 537 * The return value is a normal kernel error return value.
 538 */
 539static int sctp_outq_flush_rtx(struct sctp_outq *q, struct sctp_packet *pkt,
 540			       int rtx_timeout, int *start_timer)
 541{
 542	struct list_head *lqueue;
 543	struct sctp_transport *transport = pkt->transport;
 544	sctp_xmit_t status;
 545	struct sctp_chunk *chunk, *chunk1;
 546	int fast_rtx;
 547	int error = 0;
 548	int timer = 0;
 549	int done = 0;
 550
 551	lqueue = &q->retransmit;
 552	fast_rtx = q->fast_rtx;
 553
 554	/* This loop handles time-out retransmissions, fast retransmissions,
 555	 * and retransmissions due to opening of whindow.
 556	 *
 557	 * RFC 2960 6.3.3 Handle T3-rtx Expiration
 558	 *
 559	 * E3) Determine how many of the earliest (i.e., lowest TSN)
 560	 * outstanding DATA chunks for the address for which the
 561	 * T3-rtx has expired will fit into a single packet, subject
 562	 * to the MTU constraint for the path corresponding to the
 563	 * destination transport address to which the retransmission
 564	 * is being sent (this may be different from the address for
 565	 * which the timer expires [see Section 6.4]). Call this value
 566	 * K. Bundle and retransmit those K DATA chunks in a single
 567	 * packet to the destination endpoint.
 568	 *
 569	 * [Just to be painfully clear, if we are retransmitting
 570	 * because a timeout just happened, we should send only ONE
 571	 * packet of retransmitted data.]
 572	 *
 573	 * For fast retransmissions we also send only ONE packet.  However,
 574	 * if we are just flushing the queue due to open window, we'll
 575	 * try to send as much as possible.
 576	 */
 577	list_for_each_entry_safe(chunk, chunk1, lqueue, transmitted_list) {
 578		/* If the chunk is abandoned, move it to abandoned list. */
 579		if (sctp_chunk_abandoned(chunk)) {
 580			list_del_init(&chunk->transmitted_list);
 581			sctp_insert_list(&q->abandoned,
 582					 &chunk->transmitted_list);
 583			continue;
 584		}
 585
 586		/* Make sure that Gap Acked TSNs are not retransmitted.  A
 587		 * simple approach is just to move such TSNs out of the
 588		 * way and into a 'transmitted' queue and skip to the
 589		 * next chunk.
 590		 */
 591		if (chunk->tsn_gap_acked) {
 592			list_del(&chunk->transmitted_list);
 593			list_add_tail(&chunk->transmitted_list,
 594					&transport->transmitted);
 595			continue;
 596		}
 597
 598		/* If we are doing fast retransmit, ignore non-fast_rtransmit
 599		 * chunks
 600		 */
 601		if (fast_rtx && !chunk->fast_retransmit)
 602			continue;
 603
 604redo:
 605		/* Attempt to append this chunk to the packet. */
 606		status = sctp_packet_append_chunk(pkt, chunk);
 607
 608		switch (status) {
 609		case SCTP_XMIT_PMTU_FULL:
 610			if (!pkt->has_data && !pkt->has_cookie_echo) {
 611				/* If this packet did not contain DATA then
 612				 * retransmission did not happen, so do it
 613				 * again.  We'll ignore the error here since
 614				 * control chunks are already freed so there
 615				 * is nothing we can do.
 616				 */
 617				sctp_packet_transmit(pkt);
 618				goto redo;
 619			}
 620
 621			/* Send this packet.  */
 622			error = sctp_packet_transmit(pkt);
 623
 624			/* If we are retransmitting, we should only
 625			 * send a single packet.
 626			 * Otherwise, try appending this chunk again.
 627			 */
 628			if (rtx_timeout || fast_rtx)
 629				done = 1;
 630			else
 631				goto redo;
 632
 633			/* Bundle next chunk in the next round.  */
 634			break;
 635
 636		case SCTP_XMIT_RWND_FULL:
 637			/* Send this packet. */
 638			error = sctp_packet_transmit(pkt);
 639
 640			/* Stop sending DATA as there is no more room
 641			 * at the receiver.
 642			 */
 643			done = 1;
 644			break;
 645
 646		case SCTP_XMIT_NAGLE_DELAY:
 647			/* Send this packet. */
 648			error = sctp_packet_transmit(pkt);
 649
 650			/* Stop sending DATA because of nagle delay. */
 651			done = 1;
 652			break;
 653
 654		default:
 655			/* The append was successful, so add this chunk to
 656			 * the transmitted list.
 657			 */
 658			list_del(&chunk->transmitted_list);
 659			list_add_tail(&chunk->transmitted_list,
 660					&transport->transmitted);
 661
 662			/* Mark the chunk as ineligible for fast retransmit
 663			 * after it is retransmitted.
 664			 */
 665			if (chunk->fast_retransmit == SCTP_NEED_FRTX)
 666				chunk->fast_retransmit = SCTP_DONT_FRTX;
 667
 668			q->empty = 0;
 669			break;
 670		}
 671
 672		/* Set the timer if there were no errors */
 673		if (!error && !timer)
 674			timer = 1;
 675
 676		if (done)
 677			break;
 678	}
 679
 680	/* If we are here due to a retransmit timeout or a fast
 681	 * retransmit and if there are any chunks left in the retransmit
 682	 * queue that could not fit in the PMTU sized packet, they need
 683	 * to be marked as ineligible for a subsequent fast retransmit.
 684	 */
 685	if (rtx_timeout || fast_rtx) {
 686		list_for_each_entry(chunk1, lqueue, transmitted_list) {
 687			if (chunk1->fast_retransmit == SCTP_NEED_FRTX)
 688				chunk1->fast_retransmit = SCTP_DONT_FRTX;
 689		}
 690	}
 691
 692	*start_timer = timer;
 693
 694	/* Clear fast retransmit hint */
 695	if (fast_rtx)
 696		q->fast_rtx = 0;
 697
 698	return error;
 699}
 700
 701/* Cork the outqueue so queued chunks are really queued. */
 702int sctp_outq_uncork(struct sctp_outq *q)
 703{
 704	int error = 0;
 705	if (q->cork)
 706		q->cork = 0;
 707	error = sctp_outq_flush(q, 0);
 708	return error;
 709}
 710
 711
 712/*
 713 * Try to flush an outqueue.
 714 *
 715 * Description: Send everything in q which we legally can, subject to
 716 * congestion limitations.
 717 * * Note: This function can be called from multiple contexts so appropriate
 718 * locking concerns must be made.  Today we use the sock lock to protect
 719 * this function.
 720 */
 721static int sctp_outq_flush(struct sctp_outq *q, int rtx_timeout)
 722{
 723	struct sctp_packet *packet;
 724	struct sctp_packet singleton;
 725	struct sctp_association *asoc = q->asoc;
 726	__u16 sport = asoc->base.bind_addr.port;
 727	__u16 dport = asoc->peer.port;
 728	__u32 vtag = asoc->peer.i.init_tag;
 729	struct sctp_transport *transport = NULL;
 730	struct sctp_transport *new_transport;
 731	struct sctp_chunk *chunk, *tmp;
 732	sctp_xmit_t status;
 733	int error = 0;
 734	int start_timer = 0;
 735	int one_packet = 0;
 736
 737	/* These transports have chunks to send. */
 738	struct list_head transport_list;
 739	struct list_head *ltransport;
 740
 741	INIT_LIST_HEAD(&transport_list);
 742	packet = NULL;
 743
 744	/*
 745	 * 6.10 Bundling
 746	 *   ...
 747	 *   When bundling control chunks with DATA chunks, an
 748	 *   endpoint MUST place control chunks first in the outbound
 749	 *   SCTP packet.  The transmitter MUST transmit DATA chunks
 750	 *   within a SCTP packet in increasing order of TSN.
 751	 *   ...
 752	 */
 753
 754	list_for_each_entry_safe(chunk, tmp, &q->control_chunk_list, list) {
 755		/* RFC 5061, 5.3
 756		 * F1) This means that until such time as the ASCONF
 757		 * containing the add is acknowledged, the sender MUST
 758		 * NOT use the new IP address as a source for ANY SCTP
 759		 * packet except on carrying an ASCONF Chunk.
 760		 */
 761		if (asoc->src_out_of_asoc_ok &&
 762		    chunk->chunk_hdr->type != SCTP_CID_ASCONF)
 763			continue;
 764
 765		list_del_init(&chunk->list);
 766
 767		/* Pick the right transport to use. */
 768		new_transport = chunk->transport;
 769
 770		if (!new_transport) {
 771			/*
 772			 * If we have a prior transport pointer, see if
 773			 * the destination address of the chunk
 774			 * matches the destination address of the
 775			 * current transport.  If not a match, then
 776			 * try to look up the transport with a given
 777			 * destination address.  We do this because
 778			 * after processing ASCONFs, we may have new
 779			 * transports created.
 780			 */
 781			if (transport &&
 782			    sctp_cmp_addr_exact(&chunk->dest,
 783						&transport->ipaddr))
 784					new_transport = transport;
 785			else
 786				new_transport = sctp_assoc_lookup_paddr(asoc,
 787								&chunk->dest);
 788
 789			/* if we still don't have a new transport, then
 790			 * use the current active path.
 791			 */
 792			if (!new_transport)
 793				new_transport = asoc->peer.active_path;
 794		} else if ((new_transport->state == SCTP_INACTIVE) ||
 795			   (new_transport->state == SCTP_UNCONFIRMED)) {
 
 796			/* If the chunk is Heartbeat or Heartbeat Ack,
 797			 * send it to chunk->transport, even if it's
 798			 * inactive.
 799			 *
 800			 * 3.3.6 Heartbeat Acknowledgement:
 801			 * ...
 802			 * A HEARTBEAT ACK is always sent to the source IP
 803			 * address of the IP datagram containing the
 804			 * HEARTBEAT chunk to which this ack is responding.
 805			 * ...
 806			 *
 807			 * ASCONF_ACKs also must be sent to the source.
 808			 */
 809			if (chunk->chunk_hdr->type != SCTP_CID_HEARTBEAT &&
 810			    chunk->chunk_hdr->type != SCTP_CID_HEARTBEAT_ACK &&
 811			    chunk->chunk_hdr->type != SCTP_CID_ASCONF_ACK)
 812				new_transport = asoc->peer.active_path;
 813		}
 814
 815		/* Are we switching transports?
 816		 * Take care of transport locks.
 817		 */
 818		if (new_transport != transport) {
 819			transport = new_transport;
 820			if (list_empty(&transport->send_ready)) {
 821				list_add_tail(&transport->send_ready,
 822					      &transport_list);
 823			}
 824			packet = &transport->packet;
 825			sctp_packet_config(packet, vtag,
 826					   asoc->peer.ecn_capable);
 827		}
 828
 829		switch (chunk->chunk_hdr->type) {
 830		/*
 831		 * 6.10 Bundling
 832		 *   ...
 833		 *   An endpoint MUST NOT bundle INIT, INIT ACK or SHUTDOWN
 834		 *   COMPLETE with any other chunks.  [Send them immediately.]
 835		 */
 836		case SCTP_CID_INIT:
 837		case SCTP_CID_INIT_ACK:
 838		case SCTP_CID_SHUTDOWN_COMPLETE:
 839			sctp_packet_init(&singleton, transport, sport, dport);
 840			sctp_packet_config(&singleton, vtag, 0);
 841			sctp_packet_append_chunk(&singleton, chunk);
 842			error = sctp_packet_transmit(&singleton);
 843			if (error < 0)
 844				return error;
 845			break;
 846
 847		case SCTP_CID_ABORT:
 848			if (sctp_test_T_bit(chunk)) {
 849				packet->vtag = asoc->c.my_vtag;
 850			}
 851		/* The following chunks are "response" chunks, i.e.
 852		 * they are generated in response to something we
 853		 * received.  If we are sending these, then we can
 854		 * send only 1 packet containing these chunks.
 855		 */
 856		case SCTP_CID_HEARTBEAT_ACK:
 857		case SCTP_CID_SHUTDOWN_ACK:
 858		case SCTP_CID_COOKIE_ACK:
 859		case SCTP_CID_COOKIE_ECHO:
 860		case SCTP_CID_ERROR:
 861		case SCTP_CID_ECN_CWR:
 862		case SCTP_CID_ASCONF_ACK:
 863			one_packet = 1;
 864			/* Fall through */
 865
 866		case SCTP_CID_SACK:
 867		case SCTP_CID_HEARTBEAT:
 868		case SCTP_CID_SHUTDOWN:
 869		case SCTP_CID_ECN_ECNE:
 870		case SCTP_CID_ASCONF:
 871		case SCTP_CID_FWD_TSN:
 872			status = sctp_packet_transmit_chunk(packet, chunk,
 873							    one_packet);
 874			if (status  != SCTP_XMIT_OK) {
 875				/* put the chunk back */
 876				list_add(&chunk->list, &q->control_chunk_list);
 877			} else if (chunk->chunk_hdr->type == SCTP_CID_FWD_TSN) {
 
 878				/* PR-SCTP C5) If a FORWARD TSN is sent, the
 879				 * sender MUST assure that at least one T3-rtx
 880				 * timer is running.
 881				 */
 882				sctp_transport_reset_timers(transport);
 
 
 
 883			}
 884			break;
 885
 886		default:
 887			/* We built a chunk with an illegal type! */
 888			BUG();
 889		}
 890	}
 891
 892	if (q->asoc->src_out_of_asoc_ok)
 893		goto sctp_flush_out;
 894
 895	/* Is it OK to send data chunks?  */
 896	switch (asoc->state) {
 897	case SCTP_STATE_COOKIE_ECHOED:
 898		/* Only allow bundling when this packet has a COOKIE-ECHO
 899		 * chunk.
 900		 */
 901		if (!packet || !packet->has_cookie_echo)
 902			break;
 903
 904		/* fallthru */
 905	case SCTP_STATE_ESTABLISHED:
 906	case SCTP_STATE_SHUTDOWN_PENDING:
 907	case SCTP_STATE_SHUTDOWN_RECEIVED:
 908		/*
 909		 * RFC 2960 6.1  Transmission of DATA Chunks
 910		 *
 911		 * C) When the time comes for the sender to transmit,
 912		 * before sending new DATA chunks, the sender MUST
 913		 * first transmit any outstanding DATA chunks which
 914		 * are marked for retransmission (limited by the
 915		 * current cwnd).
 916		 */
 917		if (!list_empty(&q->retransmit)) {
 918			if (asoc->peer.retran_path->state == SCTP_UNCONFIRMED)
 919				goto sctp_flush_out;
 920			if (transport == asoc->peer.retran_path)
 921				goto retran;
 922
 923			/* Switch transports & prepare the packet.  */
 924
 925			transport = asoc->peer.retran_path;
 926
 927			if (list_empty(&transport->send_ready)) {
 928				list_add_tail(&transport->send_ready,
 929					      &transport_list);
 930			}
 931
 932			packet = &transport->packet;
 933			sctp_packet_config(packet, vtag,
 934					   asoc->peer.ecn_capable);
 935		retran:
 936			error = sctp_outq_flush_rtx(q, packet,
 937						    rtx_timeout, &start_timer);
 938
 939			if (start_timer)
 940				sctp_transport_reset_timers(transport);
 
 
 941
 942			/* This can happen on COOKIE-ECHO resend.  Only
 943			 * one chunk can get bundled with a COOKIE-ECHO.
 944			 */
 945			if (packet->has_cookie_echo)
 946				goto sctp_flush_out;
 947
 948			/* Don't send new data if there is still data
 949			 * waiting to retransmit.
 950			 */
 951			if (!list_empty(&q->retransmit))
 952				goto sctp_flush_out;
 953		}
 954
 955		/* Apply Max.Burst limitation to the current transport in
 956		 * case it will be used for new data.  We are going to
 957		 * rest it before we return, but we want to apply the limit
 958		 * to the currently queued data.
 959		 */
 960		if (transport)
 961			sctp_transport_burst_limited(transport);
 962
 963		/* Finally, transmit new packets.  */
 964		while ((chunk = sctp_outq_dequeue_data(q)) != NULL) {
 965			/* RFC 2960 6.5 Every DATA chunk MUST carry a valid
 966			 * stream identifier.
 967			 */
 968			if (chunk->sinfo.sinfo_stream >=
 969			    asoc->c.sinit_num_ostreams) {
 970
 971				/* Mark as failed send. */
 972				sctp_chunk_fail(chunk, SCTP_ERROR_INV_STRM);
 973				sctp_chunk_free(chunk);
 974				continue;
 975			}
 976
 977			/* Has this chunk expired? */
 978			if (sctp_chunk_abandoned(chunk)) {
 979				sctp_chunk_fail(chunk, 0);
 980				sctp_chunk_free(chunk);
 981				continue;
 982			}
 983
 984			/* If there is a specified transport, use it.
 985			 * Otherwise, we want to use the active path.
 986			 */
 987			new_transport = chunk->transport;
 988			if (!new_transport ||
 989			    ((new_transport->state == SCTP_INACTIVE) ||
 990			     (new_transport->state == SCTP_UNCONFIRMED)))
 
 991				new_transport = asoc->peer.active_path;
 992			if (new_transport->state == SCTP_UNCONFIRMED)
 
 
 
 993				continue;
 
 994
 995			/* Change packets if necessary.  */
 996			if (new_transport != transport) {
 997				transport = new_transport;
 998
 999				/* Schedule to have this transport's
1000				 * packet flushed.
1001				 */
1002				if (list_empty(&transport->send_ready)) {
1003					list_add_tail(&transport->send_ready,
1004						      &transport_list);
1005				}
1006
1007				packet = &transport->packet;
1008				sctp_packet_config(packet, vtag,
1009						   asoc->peer.ecn_capable);
1010				/* We've switched transports, so apply the
1011				 * Burst limit to the new transport.
1012				 */
1013				sctp_transport_burst_limited(transport);
1014			}
1015
1016			SCTP_DEBUG_PRINTK("sctp_outq_flush(%p, %p[%s]), ",
1017					  q, chunk,
1018					  chunk && chunk->chunk_hdr ?
1019					  sctp_cname(SCTP_ST_CHUNK(
1020						  chunk->chunk_hdr->type))
1021					  : "Illegal Chunk");
1022
1023			SCTP_DEBUG_PRINTK("TX TSN 0x%x skb->head "
1024					"%p skb->users %d.\n",
1025					ntohl(chunk->subh.data_hdr->tsn),
1026					chunk->skb ?chunk->skb->head : NULL,
1027					chunk->skb ?
1028					atomic_read(&chunk->skb->users) : -1);
1029
1030			/* Add the chunk to the packet.  */
1031			status = sctp_packet_transmit_chunk(packet, chunk, 0);
1032
1033			switch (status) {
1034			case SCTP_XMIT_PMTU_FULL:
1035			case SCTP_XMIT_RWND_FULL:
1036			case SCTP_XMIT_NAGLE_DELAY:
1037				/* We could not append this chunk, so put
1038				 * the chunk back on the output queue.
1039				 */
1040				SCTP_DEBUG_PRINTK("sctp_outq_flush: could "
1041					"not transmit TSN: 0x%x, status: %d\n",
1042					ntohl(chunk->subh.data_hdr->tsn),
1043					status);
1044				sctp_outq_head_data(q, chunk);
1045				goto sctp_flush_out;
1046				break;
1047
1048			case SCTP_XMIT_OK:
1049				/* The sender is in the SHUTDOWN-PENDING state,
1050				 * The sender MAY set the I-bit in the DATA
1051				 * chunk header.
1052				 */
1053				if (asoc->state == SCTP_STATE_SHUTDOWN_PENDING)
1054					chunk->chunk_hdr->flags |= SCTP_DATA_SACK_IMM;
 
 
 
 
1055
1056				break;
1057
1058			default:
1059				BUG();
1060			}
1061
1062			/* BUG: We assume that the sctp_packet_transmit()
1063			 * call below will succeed all the time and add the
1064			 * chunk to the transmitted list and restart the
1065			 * timers.
1066			 * It is possible that the call can fail under OOM
1067			 * conditions.
1068			 *
1069			 * Is this really a problem?  Won't this behave
1070			 * like a lost TSN?
1071			 */
1072			list_add_tail(&chunk->transmitted_list,
1073				      &transport->transmitted);
1074
1075			sctp_transport_reset_timers(transport);
1076
1077			q->empty = 0;
1078
1079			/* Only let one DATA chunk get bundled with a
1080			 * COOKIE-ECHO chunk.
1081			 */
1082			if (packet->has_cookie_echo)
1083				goto sctp_flush_out;
1084		}
1085		break;
1086
1087	default:
1088		/* Do nothing.  */
1089		break;
1090	}
1091
1092sctp_flush_out:
1093
1094	/* Before returning, examine all the transports touched in
1095	 * this call.  Right now, we bluntly force clear all the
1096	 * transports.  Things might change after we implement Nagle.
1097	 * But such an examination is still required.
1098	 *
1099	 * --xguo
1100	 */
1101	while ((ltransport = sctp_list_dequeue(&transport_list)) != NULL ) {
1102		struct sctp_transport *t = list_entry(ltransport,
1103						      struct sctp_transport,
1104						      send_ready);
1105		packet = &t->packet;
1106		if (!sctp_packet_empty(packet))
1107			error = sctp_packet_transmit(packet);
1108
1109		/* Clear the burst limited state, if any */
1110		sctp_transport_burst_reset(t);
1111	}
1112
1113	return error;
1114}
1115
1116/* Update unack_data based on the incoming SACK chunk */
1117static void sctp_sack_update_unack_data(struct sctp_association *assoc,
1118					struct sctp_sackhdr *sack)
1119{
1120	sctp_sack_variable_t *frags;
1121	__u16 unack_data;
1122	int i;
1123
1124	unack_data = assoc->next_tsn - assoc->ctsn_ack_point - 1;
1125
1126	frags = sack->variable;
1127	for (i = 0; i < ntohs(sack->num_gap_ack_blocks); i++) {
1128		unack_data -= ((ntohs(frags[i].gab.end) -
1129				ntohs(frags[i].gab.start) + 1));
1130	}
1131
1132	assoc->unack_data = unack_data;
1133}
1134
1135/* This is where we REALLY process a SACK.
1136 *
1137 * Process the SACK against the outqueue.  Mostly, this just frees
1138 * things off the transmitted queue.
1139 */
1140int sctp_outq_sack(struct sctp_outq *q, struct sctp_sackhdr *sack)
1141{
1142	struct sctp_association *asoc = q->asoc;
 
1143	struct sctp_transport *transport;
1144	struct sctp_chunk *tchunk = NULL;
1145	struct list_head *lchunk, *transport_list, *temp;
1146	sctp_sack_variable_t *frags = sack->variable;
1147	__u32 sack_ctsn, ctsn, tsn;
1148	__u32 highest_tsn, highest_new_tsn;
1149	__u32 sack_a_rwnd;
1150	unsigned int outstanding;
1151	struct sctp_transport *primary = asoc->peer.primary_path;
1152	int count_of_newacks = 0;
1153	int gap_ack_blocks;
1154	u8 accum_moved = 0;
1155
1156	/* Grab the association's destination address list. */
1157	transport_list = &asoc->peer.transport_addr_list;
1158
1159	sack_ctsn = ntohl(sack->cum_tsn_ack);
1160	gap_ack_blocks = ntohs(sack->num_gap_ack_blocks);
 
1161	/*
1162	 * SFR-CACC algorithm:
1163	 * On receipt of a SACK the sender SHOULD execute the
1164	 * following statements.
1165	 *
1166	 * 1) If the cumulative ack in the SACK passes next tsn_at_change
1167	 * on the current primary, the CHANGEOVER_ACTIVE flag SHOULD be
1168	 * cleared. The CYCLING_CHANGEOVER flag SHOULD also be cleared for
1169	 * all destinations.
1170	 * 2) If the SACK contains gap acks and the flag CHANGEOVER_ACTIVE
1171	 * is set the receiver of the SACK MUST take the following actions:
1172	 *
1173	 * A) Initialize the cacc_saw_newack to 0 for all destination
1174	 * addresses.
1175	 *
1176	 * Only bother if changeover_active is set. Otherwise, this is
1177	 * totally suboptimal to do on every SACK.
1178	 */
1179	if (primary->cacc.changeover_active) {
1180		u8 clear_cycling = 0;
1181
1182		if (TSN_lte(primary->cacc.next_tsn_at_change, sack_ctsn)) {
1183			primary->cacc.changeover_active = 0;
1184			clear_cycling = 1;
1185		}
1186
1187		if (clear_cycling || gap_ack_blocks) {
1188			list_for_each_entry(transport, transport_list,
1189					transports) {
1190				if (clear_cycling)
1191					transport->cacc.cycling_changeover = 0;
1192				if (gap_ack_blocks)
1193					transport->cacc.cacc_saw_newack = 0;
1194			}
1195		}
1196	}
1197
1198	/* Get the highest TSN in the sack. */
1199	highest_tsn = sack_ctsn;
1200	if (gap_ack_blocks)
1201		highest_tsn += ntohs(frags[gap_ack_blocks - 1].gab.end);
1202
1203	if (TSN_lt(asoc->highest_sacked, highest_tsn))
1204		asoc->highest_sacked = highest_tsn;
1205
1206	highest_new_tsn = sack_ctsn;
1207
1208	/* Run through the retransmit queue.  Credit bytes received
1209	 * and free those chunks that we can.
1210	 */
1211	sctp_check_transmitted(q, &q->retransmit, NULL, sack, &highest_new_tsn);
1212
1213	/* Run through the transmitted queue.
1214	 * Credit bytes received and free those chunks which we can.
1215	 *
1216	 * This is a MASSIVE candidate for optimization.
1217	 */
1218	list_for_each_entry(transport, transport_list, transports) {
1219		sctp_check_transmitted(q, &transport->transmitted,
1220				       transport, sack, &highest_new_tsn);
 
1221		/*
1222		 * SFR-CACC algorithm:
1223		 * C) Let count_of_newacks be the number of
1224		 * destinations for which cacc_saw_newack is set.
1225		 */
1226		if (transport->cacc.cacc_saw_newack)
1227			count_of_newacks ++;
1228	}
1229
1230	/* Move the Cumulative TSN Ack Point if appropriate.  */
1231	if (TSN_lt(asoc->ctsn_ack_point, sack_ctsn)) {
1232		asoc->ctsn_ack_point = sack_ctsn;
1233		accum_moved = 1;
1234	}
1235
1236	if (gap_ack_blocks) {
1237
1238		if (asoc->fast_recovery && accum_moved)
1239			highest_new_tsn = highest_tsn;
1240
1241		list_for_each_entry(transport, transport_list, transports)
1242			sctp_mark_missing(q, &transport->transmitted, transport,
1243					  highest_new_tsn, count_of_newacks);
1244	}
1245
1246	/* Update unack_data field in the assoc. */
1247	sctp_sack_update_unack_data(asoc, sack);
1248
1249	ctsn = asoc->ctsn_ack_point;
1250
1251	/* Throw away stuff rotting on the sack queue.  */
1252	list_for_each_safe(lchunk, temp, &q->sacked) {
1253		tchunk = list_entry(lchunk, struct sctp_chunk,
1254				    transmitted_list);
1255		tsn = ntohl(tchunk->subh.data_hdr->tsn);
1256		if (TSN_lte(tsn, ctsn)) {
1257			list_del_init(&tchunk->transmitted_list);
1258			sctp_chunk_free(tchunk);
1259		}
1260	}
1261
1262	/* ii) Set rwnd equal to the newly received a_rwnd minus the
1263	 *     number of bytes still outstanding after processing the
1264	 *     Cumulative TSN Ack and the Gap Ack Blocks.
1265	 */
1266
1267	sack_a_rwnd = ntohl(sack->a_rwnd);
 
1268	outstanding = q->outstanding_bytes;
1269
1270	if (outstanding < sack_a_rwnd)
1271		sack_a_rwnd -= outstanding;
1272	else
1273		sack_a_rwnd = 0;
1274
1275	asoc->peer.rwnd = sack_a_rwnd;
1276
1277	sctp_generate_fwdtsn(q, sack_ctsn);
1278
1279	SCTP_DEBUG_PRINTK("%s: sack Cumulative TSN Ack is 0x%x.\n",
1280			  __func__, sack_ctsn);
1281	SCTP_DEBUG_PRINTK("%s: Cumulative TSN Ack of association, "
1282			  "%p is 0x%x. Adv peer ack point: 0x%x\n",
1283			  __func__, asoc, ctsn, asoc->adv_peer_ack_point);
1284
1285	/* See if all chunks are acked.
1286	 * Make sure the empty queue handler will get run later.
1287	 */
1288	q->empty = (list_empty(&q->out_chunk_list) &&
1289		    list_empty(&q->retransmit));
1290	if (!q->empty)
1291		goto finish;
1292
1293	list_for_each_entry(transport, transport_list, transports) {
1294		q->empty = q->empty && list_empty(&transport->transmitted);
1295		if (!q->empty)
1296			goto finish;
1297	}
1298
1299	SCTP_DEBUG_PRINTK("sack queue is empty.\n");
1300finish:
1301	return q->empty;
1302}
1303
1304/* Is the outqueue empty?  */
 
 
 
1305int sctp_outq_is_empty(const struct sctp_outq *q)
1306{
1307	return q->empty;
 
1308}
1309
1310/********************************************************************
1311 * 2nd Level Abstractions
1312 ********************************************************************/
1313
1314/* Go through a transport's transmitted list or the association's retransmit
1315 * list and move chunks that are acked by the Cumulative TSN Ack to q->sacked.
1316 * The retransmit list will not have an associated transport.
1317 *
1318 * I added coherent debug information output.	--xguo
1319 *
1320 * Instead of printing 'sacked' or 'kept' for each TSN on the
1321 * transmitted_queue, we print a range: SACKED: TSN1-TSN2, TSN3, TSN4-TSN5.
1322 * KEPT TSN6-TSN7, etc.
1323 */
1324static void sctp_check_transmitted(struct sctp_outq *q,
1325				   struct list_head *transmitted_queue,
1326				   struct sctp_transport *transport,
 
1327				   struct sctp_sackhdr *sack,
1328				   __u32 *highest_new_tsn_in_sack)
1329{
1330	struct list_head *lchunk;
1331	struct sctp_chunk *tchunk;
1332	struct list_head tlist;
1333	__u32 tsn;
1334	__u32 sack_ctsn;
1335	__u32 rtt;
1336	__u8 restart_timer = 0;
1337	int bytes_acked = 0;
1338	int migrate_bytes = 0;
1339
1340	/* These state variables are for coherent debug output. --xguo */
1341
1342#if SCTP_DEBUG
1343	__u32 dbg_ack_tsn = 0;	/* An ACKed TSN range starts here... */
1344	__u32 dbg_last_ack_tsn = 0;  /* ...and finishes here.	     */
1345	__u32 dbg_kept_tsn = 0;	/* An un-ACKed range starts here...  */
1346	__u32 dbg_last_kept_tsn = 0; /* ...and finishes here.	     */
1347
1348	/* 0 : The last TSN was ACKed.
1349	 * 1 : The last TSN was NOT ACKed (i.e. KEPT).
1350	 * -1: We need to initialize.
1351	 */
1352	int dbg_prt_state = -1;
1353#endif /* SCTP_DEBUG */
1354
1355	sack_ctsn = ntohl(sack->cum_tsn_ack);
1356
1357	INIT_LIST_HEAD(&tlist);
1358
1359	/* The while loop will skip empty transmitted queues. */
1360	while (NULL != (lchunk = sctp_list_dequeue(transmitted_queue))) {
1361		tchunk = list_entry(lchunk, struct sctp_chunk,
1362				    transmitted_list);
1363
1364		if (sctp_chunk_abandoned(tchunk)) {
1365			/* Move the chunk to abandoned list. */
1366			sctp_insert_list(&q->abandoned, lchunk);
1367
1368			/* If this chunk has not been acked, stop
1369			 * considering it as 'outstanding'.
1370			 */
1371			if (!tchunk->tsn_gap_acked) {
1372				if (tchunk->transport)
1373					tchunk->transport->flight_size -=
1374							sctp_data_size(tchunk);
1375				q->outstanding_bytes -= sctp_data_size(tchunk);
1376			}
1377			continue;
1378		}
1379
1380		tsn = ntohl(tchunk->subh.data_hdr->tsn);
1381		if (sctp_acked(sack, tsn)) {
1382			/* If this queue is the retransmit queue, the
1383			 * retransmit timer has already reclaimed
1384			 * the outstanding bytes for this chunk, so only
1385			 * count bytes associated with a transport.
1386			 */
1387			if (transport) {
1388				/* If this chunk is being used for RTT
1389				 * measurement, calculate the RTT and update
1390				 * the RTO using this value.
1391				 *
1392				 * 6.3.1 C5) Karn's algorithm: RTT measurements
1393				 * MUST NOT be made using packets that were
1394				 * retransmitted (and thus for which it is
1395				 * ambiguous whether the reply was for the
1396				 * first instance of the packet or a later
1397				 * instance).
1398				 */
1399				if (!tchunk->tsn_gap_acked &&
 
1400				    tchunk->rtt_in_progress) {
1401					tchunk->rtt_in_progress = 0;
1402					rtt = jiffies - tchunk->sent_at;
1403					sctp_transport_update_rto(transport,
1404								  rtt);
1405				}
1406			}
1407
1408			/* If the chunk hasn't been marked as ACKED,
1409			 * mark it and account bytes_acked if the
1410			 * chunk had a valid transport (it will not
1411			 * have a transport if ASCONF had deleted it
1412			 * while DATA was outstanding).
1413			 */
1414			if (!tchunk->tsn_gap_acked) {
1415				tchunk->tsn_gap_acked = 1;
1416				*highest_new_tsn_in_sack = tsn;
 
1417				bytes_acked += sctp_data_size(tchunk);
1418				if (!tchunk->transport)
1419					migrate_bytes += sctp_data_size(tchunk);
 
1420			}
1421
1422			if (TSN_lte(tsn, sack_ctsn)) {
1423				/* RFC 2960  6.3.2 Retransmission Timer Rules
1424				 *
1425				 * R3) Whenever a SACK is received
1426				 * that acknowledges the DATA chunk
1427				 * with the earliest outstanding TSN
1428				 * for that address, restart T3-rtx
1429				 * timer for that address with its
1430				 * current RTO.
1431				 */
1432				restart_timer = 1;
 
1433
1434				if (!tchunk->tsn_gap_acked) {
1435					/*
1436					 * SFR-CACC algorithm:
1437					 * 2) If the SACK contains gap acks
1438					 * and the flag CHANGEOVER_ACTIVE is
1439					 * set the receiver of the SACK MUST
1440					 * take the following action:
1441					 *
1442					 * B) For each TSN t being acked that
1443					 * has not been acked in any SACK so
1444					 * far, set cacc_saw_newack to 1 for
1445					 * the destination that the TSN was
1446					 * sent to.
1447					 */
1448					if (transport &&
1449					    sack->num_gap_ack_blocks &&
1450					    q->asoc->peer.primary_path->cacc.
1451					    changeover_active)
1452						transport->cacc.cacc_saw_newack
1453							= 1;
1454				}
1455
1456				list_add_tail(&tchunk->transmitted_list,
1457					      &q->sacked);
1458			} else {
1459				/* RFC2960 7.2.4, sctpimpguide-05 2.8.2
1460				 * M2) Each time a SACK arrives reporting
1461				 * 'Stray DATA chunk(s)' record the highest TSN
1462				 * reported as newly acknowledged, call this
1463				 * value 'HighestTSNinSack'. A newly
1464				 * acknowledged DATA chunk is one not
1465				 * previously acknowledged in a SACK.
1466				 *
1467				 * When the SCTP sender of data receives a SACK
1468				 * chunk that acknowledges, for the first time,
1469				 * the receipt of a DATA chunk, all the still
1470				 * unacknowledged DATA chunks whose TSN is
1471				 * older than that newly acknowledged DATA
1472				 * chunk, are qualified as 'Stray DATA chunks'.
1473				 */
1474				list_add_tail(lchunk, &tlist);
1475			}
1476
1477#if SCTP_DEBUG
1478			switch (dbg_prt_state) {
1479			case 0:	/* last TSN was ACKed */
1480				if (dbg_last_ack_tsn + 1 == tsn) {
1481					/* This TSN belongs to the
1482					 * current ACK range.
1483					 */
1484					break;
1485				}
1486
1487				if (dbg_last_ack_tsn != dbg_ack_tsn) {
1488					/* Display the end of the
1489					 * current range.
1490					 */
1491					SCTP_DEBUG_PRINTK_CONT("-%08x",
1492							       dbg_last_ack_tsn);
1493				}
1494
1495				/* Start a new range.  */
1496				SCTP_DEBUG_PRINTK_CONT(",%08x", tsn);
1497				dbg_ack_tsn = tsn;
1498				break;
1499
1500			case 1:	/* The last TSN was NOT ACKed. */
1501				if (dbg_last_kept_tsn != dbg_kept_tsn) {
1502					/* Display the end of current range. */
1503					SCTP_DEBUG_PRINTK_CONT("-%08x",
1504							       dbg_last_kept_tsn);
1505				}
1506
1507				SCTP_DEBUG_PRINTK_CONT("\n");
1508
1509				/* FALL THROUGH... */
1510			default:
1511				/* This is the first-ever TSN we examined.  */
1512				/* Start a new range of ACK-ed TSNs.  */
1513				SCTP_DEBUG_PRINTK("ACKed: %08x", tsn);
1514				dbg_prt_state = 0;
1515				dbg_ack_tsn = tsn;
1516			}
1517
1518			dbg_last_ack_tsn = tsn;
1519#endif /* SCTP_DEBUG */
1520
1521		} else {
1522			if (tchunk->tsn_gap_acked) {
1523				SCTP_DEBUG_PRINTK("%s: Receiver reneged on "
1524						  "data TSN: 0x%x\n",
1525						  __func__,
1526						  tsn);
1527				tchunk->tsn_gap_acked = 0;
1528
1529				if (tchunk->transport)
1530					bytes_acked -= sctp_data_size(tchunk);
1531
1532				/* RFC 2960 6.3.2 Retransmission Timer Rules
1533				 *
1534				 * R4) Whenever a SACK is received missing a
1535				 * TSN that was previously acknowledged via a
1536				 * Gap Ack Block, start T3-rtx for the
1537				 * destination address to which the DATA
1538				 * chunk was originally
1539				 * transmitted if it is not already running.
1540				 */
1541				restart_timer = 1;
1542			}
1543
1544			list_add_tail(lchunk, &tlist);
1545
1546#if SCTP_DEBUG
1547			/* See the above comments on ACK-ed TSNs. */
1548			switch (dbg_prt_state) {
1549			case 1:
1550				if (dbg_last_kept_tsn + 1 == tsn)
1551					break;
1552
1553				if (dbg_last_kept_tsn != dbg_kept_tsn)
1554					SCTP_DEBUG_PRINTK_CONT("-%08x",
1555							       dbg_last_kept_tsn);
1556
1557				SCTP_DEBUG_PRINTK_CONT(",%08x", tsn);
1558				dbg_kept_tsn = tsn;
1559				break;
1560
1561			case 0:
1562				if (dbg_last_ack_tsn != dbg_ack_tsn)
1563					SCTP_DEBUG_PRINTK_CONT("-%08x",
1564							       dbg_last_ack_tsn);
1565				SCTP_DEBUG_PRINTK_CONT("\n");
1566
1567				/* FALL THROUGH... */
1568			default:
1569				SCTP_DEBUG_PRINTK("KEPT: %08x",tsn);
1570				dbg_prt_state = 1;
1571				dbg_kept_tsn = tsn;
1572			}
1573
1574			dbg_last_kept_tsn = tsn;
1575#endif /* SCTP_DEBUG */
1576		}
1577	}
1578
1579#if SCTP_DEBUG
1580	/* Finish off the last range, displaying its ending TSN.  */
1581	switch (dbg_prt_state) {
1582	case 0:
1583		if (dbg_last_ack_tsn != dbg_ack_tsn) {
1584			SCTP_DEBUG_PRINTK_CONT("-%08x\n", dbg_last_ack_tsn);
1585		} else {
1586			SCTP_DEBUG_PRINTK_CONT("\n");
1587		}
1588	break;
1589
1590	case 1:
1591		if (dbg_last_kept_tsn != dbg_kept_tsn) {
1592			SCTP_DEBUG_PRINTK_CONT("-%08x\n", dbg_last_kept_tsn);
1593		} else {
1594			SCTP_DEBUG_PRINTK_CONT("\n");
1595		}
1596	}
1597#endif /* SCTP_DEBUG */
1598	if (transport) {
1599		if (bytes_acked) {
1600			struct sctp_association *asoc = transport->asoc;
1601
1602			/* We may have counted DATA that was migrated
1603			 * to this transport due to DEL-IP operation.
1604			 * Subtract those bytes, since the were never
1605			 * send on this transport and shouldn't be
1606			 * credited to this transport.
1607			 */
1608			bytes_acked -= migrate_bytes;
1609
1610			/* 8.2. When an outstanding TSN is acknowledged,
1611			 * the endpoint shall clear the error counter of
1612			 * the destination transport address to which the
1613			 * DATA chunk was last sent.
1614			 * The association's overall error counter is
1615			 * also cleared.
1616			 */
1617			transport->error_count = 0;
1618			transport->asoc->overall_error_count = 0;
 
1619
1620			/*
1621			 * While in SHUTDOWN PENDING, we may have started
1622			 * the T5 shutdown guard timer after reaching the
1623			 * retransmission limit. Stop that timer as soon
1624			 * as the receiver acknowledged any data.
1625			 */
1626			if (asoc->state == SCTP_STATE_SHUTDOWN_PENDING &&
1627			    del_timer(&asoc->timers
1628				[SCTP_EVENT_TIMEOUT_T5_SHUTDOWN_GUARD]))
1629					sctp_association_put(asoc);
1630
1631			/* Mark the destination transport address as
1632			 * active if it is not so marked.
1633			 */
1634			if ((transport->state == SCTP_INACTIVE) ||
1635			    (transport->state == SCTP_UNCONFIRMED)) {
 
1636				sctp_assoc_control_transport(
1637					transport->asoc,
1638					transport,
1639					SCTP_TRANSPORT_UP,
1640					SCTP_RECEIVED_SACK);
1641			}
1642
1643			sctp_transport_raise_cwnd(transport, sack_ctsn,
1644						  bytes_acked);
1645
1646			transport->flight_size -= bytes_acked;
1647			if (transport->flight_size == 0)
1648				transport->partial_bytes_acked = 0;
1649			q->outstanding_bytes -= bytes_acked + migrate_bytes;
1650		} else {
1651			/* RFC 2960 6.1, sctpimpguide-06 2.15.2
1652			 * When a sender is doing zero window probing, it
1653			 * should not timeout the association if it continues
1654			 * to receive new packets from the receiver. The
1655			 * reason is that the receiver MAY keep its window
1656			 * closed for an indefinite time.
1657			 * A sender is doing zero window probing when the
1658			 * receiver's advertised window is zero, and there is
1659			 * only one data chunk in flight to the receiver.
1660			 *
1661			 * Allow the association to timeout while in SHUTDOWN
1662			 * PENDING or SHUTDOWN RECEIVED in case the receiver
1663			 * stays in zero window mode forever.
1664			 */
1665			if (!q->asoc->peer.rwnd &&
1666			    !list_empty(&tlist) &&
1667			    (sack_ctsn+2 == q->asoc->next_tsn) &&
1668			    q->asoc->state < SCTP_STATE_SHUTDOWN_PENDING) {
1669				SCTP_DEBUG_PRINTK("%s: SACK received for zero "
1670						  "window probe: %u\n",
1671						  __func__, sack_ctsn);
1672				q->asoc->overall_error_count = 0;
1673				transport->error_count = 0;
1674			}
1675		}
1676
1677		/* RFC 2960 6.3.2 Retransmission Timer Rules
1678		 *
1679		 * R2) Whenever all outstanding data sent to an address have
1680		 * been acknowledged, turn off the T3-rtx timer of that
1681		 * address.
1682		 */
1683		if (!transport->flight_size) {
1684			if (timer_pending(&transport->T3_rtx_timer) &&
1685			    del_timer(&transport->T3_rtx_timer)) {
1686				sctp_transport_put(transport);
1687			}
1688		} else if (restart_timer) {
1689			if (!mod_timer(&transport->T3_rtx_timer,
1690				       jiffies + transport->rto))
1691				sctp_transport_hold(transport);
1692		}
 
 
 
 
 
1693	}
1694
1695	list_splice(&tlist, transmitted_queue);
1696}
1697
1698/* Mark chunks as missing and consequently may get retransmitted. */
1699static void sctp_mark_missing(struct sctp_outq *q,
1700			      struct list_head *transmitted_queue,
1701			      struct sctp_transport *transport,
1702			      __u32 highest_new_tsn_in_sack,
1703			      int count_of_newacks)
1704{
1705	struct sctp_chunk *chunk;
1706	__u32 tsn;
1707	char do_fast_retransmit = 0;
1708	struct sctp_association *asoc = q->asoc;
1709	struct sctp_transport *primary = asoc->peer.primary_path;
1710
1711	list_for_each_entry(chunk, transmitted_queue, transmitted_list) {
1712
1713		tsn = ntohl(chunk->subh.data_hdr->tsn);
1714
1715		/* RFC 2960 7.2.4, sctpimpguide-05 2.8.2 M3) Examine all
1716		 * 'Unacknowledged TSN's', if the TSN number of an
1717		 * 'Unacknowledged TSN' is smaller than the 'HighestTSNinSack'
1718		 * value, increment the 'TSN.Missing.Report' count on that
1719		 * chunk if it has NOT been fast retransmitted or marked for
1720		 * fast retransmit already.
1721		 */
1722		if (chunk->fast_retransmit == SCTP_CAN_FRTX &&
1723		    !chunk->tsn_gap_acked &&
1724		    TSN_lt(tsn, highest_new_tsn_in_sack)) {
1725
1726			/* SFR-CACC may require us to skip marking
1727			 * this chunk as missing.
1728			 */
1729			if (!transport || !sctp_cacc_skip(primary,
1730						chunk->transport,
1731						count_of_newacks, tsn)) {
1732				chunk->tsn_missing_report++;
1733
1734				SCTP_DEBUG_PRINTK(
1735					"%s: TSN 0x%x missing counter: %d\n",
1736					__func__, tsn,
1737					chunk->tsn_missing_report);
1738			}
1739		}
1740		/*
1741		 * M4) If any DATA chunk is found to have a
1742		 * 'TSN.Missing.Report'
1743		 * value larger than or equal to 3, mark that chunk for
1744		 * retransmission and start the fast retransmit procedure.
1745		 */
1746
1747		if (chunk->tsn_missing_report >= 3) {
1748			chunk->fast_retransmit = SCTP_NEED_FRTX;
1749			do_fast_retransmit = 1;
1750		}
1751	}
1752
1753	if (transport) {
1754		if (do_fast_retransmit)
1755			sctp_retransmit(q, transport, SCTP_RTXR_FAST_RTX);
1756
1757		SCTP_DEBUG_PRINTK("%s: transport: %p, cwnd: %d, "
1758				  "ssthresh: %d, flight_size: %d, pba: %d\n",
1759				  __func__, transport, transport->cwnd,
1760				  transport->ssthresh, transport->flight_size,
1761				  transport->partial_bytes_acked);
1762	}
1763}
1764
1765/* Is the given TSN acked by this packet?  */
1766static int sctp_acked(struct sctp_sackhdr *sack, __u32 tsn)
1767{
1768	int i;
1769	sctp_sack_variable_t *frags;
1770	__u16 gap;
1771	__u32 ctsn = ntohl(sack->cum_tsn_ack);
1772
1773	if (TSN_lte(tsn, ctsn))
1774		goto pass;
1775
1776	/* 3.3.4 Selective Acknowledgement (SACK) (3):
1777	 *
1778	 * Gap Ack Blocks:
1779	 *  These fields contain the Gap Ack Blocks. They are repeated
1780	 *  for each Gap Ack Block up to the number of Gap Ack Blocks
1781	 *  defined in the Number of Gap Ack Blocks field. All DATA
1782	 *  chunks with TSNs greater than or equal to (Cumulative TSN
1783	 *  Ack + Gap Ack Block Start) and less than or equal to
1784	 *  (Cumulative TSN Ack + Gap Ack Block End) of each Gap Ack
1785	 *  Block are assumed to have been received correctly.
1786	 */
1787
1788	frags = sack->variable;
1789	gap = tsn - ctsn;
1790	for (i = 0; i < ntohs(sack->num_gap_ack_blocks); ++i) {
1791		if (TSN_lte(ntohs(frags[i].gab.start), gap) &&
1792		    TSN_lte(gap, ntohs(frags[i].gab.end)))
1793			goto pass;
1794	}
1795
1796	return 0;
1797pass:
1798	return 1;
1799}
1800
1801static inline int sctp_get_skip_pos(struct sctp_fwdtsn_skip *skiplist,
1802				    int nskips, __be16 stream)
1803{
1804	int i;
1805
1806	for (i = 0; i < nskips; i++) {
1807		if (skiplist[i].stream == stream)
1808			return i;
1809	}
1810	return i;
1811}
1812
1813/* Create and add a fwdtsn chunk to the outq's control queue if needed. */
1814static void sctp_generate_fwdtsn(struct sctp_outq *q, __u32 ctsn)
1815{
1816	struct sctp_association *asoc = q->asoc;
1817	struct sctp_chunk *ftsn_chunk = NULL;
1818	struct sctp_fwdtsn_skip ftsn_skip_arr[10];
1819	int nskips = 0;
1820	int skip_pos = 0;
1821	__u32 tsn;
1822	struct sctp_chunk *chunk;
1823	struct list_head *lchunk, *temp;
1824
1825	if (!asoc->peer.prsctp_capable)
1826		return;
1827
1828	/* PR-SCTP C1) Let SackCumAck be the Cumulative TSN ACK carried in the
1829	 * received SACK.
1830	 *
1831	 * If (Advanced.Peer.Ack.Point < SackCumAck), then update
1832	 * Advanced.Peer.Ack.Point to be equal to SackCumAck.
1833	 */
1834	if (TSN_lt(asoc->adv_peer_ack_point, ctsn))
1835		asoc->adv_peer_ack_point = ctsn;
1836
1837	/* PR-SCTP C2) Try to further advance the "Advanced.Peer.Ack.Point"
1838	 * locally, that is, to move "Advanced.Peer.Ack.Point" up as long as
1839	 * the chunk next in the out-queue space is marked as "abandoned" as
1840	 * shown in the following example:
1841	 *
1842	 * Assuming that a SACK arrived with the Cumulative TSN ACK 102
1843	 * and the Advanced.Peer.Ack.Point is updated to this value:
1844	 *
1845	 *   out-queue at the end of  ==>   out-queue after Adv.Ack.Point
1846	 *   normal SACK processing           local advancement
1847	 *                ...                           ...
1848	 *   Adv.Ack.Pt-> 102 acked                     102 acked
1849	 *                103 abandoned                 103 abandoned
1850	 *                104 abandoned     Adv.Ack.P-> 104 abandoned
1851	 *                105                           105
1852	 *                106 acked                     106 acked
1853	 *                ...                           ...
1854	 *
1855	 * In this example, the data sender successfully advanced the
1856	 * "Advanced.Peer.Ack.Point" from 102 to 104 locally.
1857	 */
1858	list_for_each_safe(lchunk, temp, &q->abandoned) {
1859		chunk = list_entry(lchunk, struct sctp_chunk,
1860					transmitted_list);
1861		tsn = ntohl(chunk->subh.data_hdr->tsn);
1862
1863		/* Remove any chunks in the abandoned queue that are acked by
1864		 * the ctsn.
1865		 */
1866		if (TSN_lte(tsn, ctsn)) {
1867			list_del_init(lchunk);
1868			sctp_chunk_free(chunk);
1869		} else {
1870			if (TSN_lte(tsn, asoc->adv_peer_ack_point+1)) {
1871				asoc->adv_peer_ack_point = tsn;
1872				if (chunk->chunk_hdr->flags &
1873					 SCTP_DATA_UNORDERED)
1874					continue;
1875				skip_pos = sctp_get_skip_pos(&ftsn_skip_arr[0],
1876						nskips,
1877						chunk->subh.data_hdr->stream);
1878				ftsn_skip_arr[skip_pos].stream =
1879					chunk->subh.data_hdr->stream;
1880				ftsn_skip_arr[skip_pos].ssn =
1881					 chunk->subh.data_hdr->ssn;
1882				if (skip_pos == nskips)
1883					nskips++;
1884				if (nskips == 10)
1885					break;
1886			} else
1887				break;
1888		}
1889	}
1890
1891	/* PR-SCTP C3) If, after step C1 and C2, the "Advanced.Peer.Ack.Point"
1892	 * is greater than the Cumulative TSN ACK carried in the received
1893	 * SACK, the data sender MUST send the data receiver a FORWARD TSN
1894	 * chunk containing the latest value of the
1895	 * "Advanced.Peer.Ack.Point".
1896	 *
1897	 * C4) For each "abandoned" TSN the sender of the FORWARD TSN SHOULD
1898	 * list each stream and sequence number in the forwarded TSN. This
1899	 * information will enable the receiver to easily find any
1900	 * stranded TSN's waiting on stream reorder queues. Each stream
1901	 * SHOULD only be reported once; this means that if multiple
1902	 * abandoned messages occur in the same stream then only the
1903	 * highest abandoned stream sequence number is reported. If the
1904	 * total size of the FORWARD TSN does NOT fit in a single MTU then
1905	 * the sender of the FORWARD TSN SHOULD lower the
1906	 * Advanced.Peer.Ack.Point to the last TSN that will fit in a
1907	 * single MTU.
1908	 */
1909	if (asoc->adv_peer_ack_point > ctsn)
1910		ftsn_chunk = sctp_make_fwdtsn(asoc, asoc->adv_peer_ack_point,
1911					      nskips, &ftsn_skip_arr[0]);
1912
1913	if (ftsn_chunk) {
1914		list_add_tail(&ftsn_chunk->list, &q->control_chunk_list);
1915		SCTP_INC_STATS(SCTP_MIB_OUTCTRLCHUNKS);
1916	}
1917}