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							sizeof(struct sk_buff));
 416			}
 417			continue;
 418		}
 419
 420		/* If we are doing  retransmission due to a timeout or pmtu
 421		 * discovery, only the  chunks that are not yet acked should
 422		 * be added to the retransmit queue.
 423		 */
 424		if ((reason == SCTP_RTXR_FAST_RTX  &&
 425			    (chunk->fast_retransmit == SCTP_NEED_FRTX)) ||
 426		    (reason != SCTP_RTXR_FAST_RTX  && !chunk->tsn_gap_acked)) {
 427			/* RFC 2960 6.2.1 Processing a Received SACK
 428			 *
 429			 * C) Any time a DATA chunk is marked for
 430			 * retransmission (via either T3-rtx timer expiration
 431			 * (Section 6.3.3) or via fast retransmit
 432			 * (Section 7.2.4)), add the data size of those
 433			 * chunks to the rwnd.
 434			 */
 435			q->asoc->peer.rwnd += (sctp_data_size(chunk) +
 436						sizeof(struct sk_buff));
 437			q->outstanding_bytes -= sctp_data_size(chunk);
 438			if (chunk->transport)
 439				transport->flight_size -= sctp_data_size(chunk);
 440
 441			/* sctpimpguide-05 Section 2.8.2
 442			 * M5) If a T3-rtx timer expires, the
 443			 * 'TSN.Missing.Report' of all affected TSNs is set
 444			 * to 0.
 445			 */
 446			chunk->tsn_missing_report = 0;
 447
 448			/* If a chunk that is being used for RTT measurement
 449			 * has to be retransmitted, we cannot use this chunk
 450			 * anymore for RTT measurements. Reset rto_pending so
 451			 * that a new RTT measurement is started when a new
 452			 * data chunk is sent.
 453			 */
 454			if (chunk->rtt_in_progress) {
 455				chunk->rtt_in_progress = 0;
 456				transport->rto_pending = 0;
 457			}
 458
 
 
 459			/* Move the chunk to the retransmit queue. The chunks
 460			 * on the retransmit queue are always kept in order.
 461			 */
 462			list_del_init(lchunk);
 463			sctp_insert_list(&q->retransmit, lchunk);
 464		}
 465	}
 466
 467	SCTP_DEBUG_PRINTK("%s: transport: %p, reason: %d, "
 468			  "cwnd: %d, ssthresh: %d, flight_size: %d, "
 469			  "pba: %d\n", __func__,
 470			  transport, reason,
 471			  transport->cwnd, transport->ssthresh,
 472			  transport->flight_size,
 473			  transport->partial_bytes_acked);
 474
 475}
 476
 477/* Mark all the eligible packets on a transport for retransmission and force
 478 * one packet out.
 479 */
 480void sctp_retransmit(struct sctp_outq *q, struct sctp_transport *transport,
 481		     sctp_retransmit_reason_t reason)
 482{
 
 483	int error = 0;
 484
 485	switch(reason) {
 486	case SCTP_RTXR_T3_RTX:
 487		SCTP_INC_STATS(SCTP_MIB_T3_RETRANSMITS);
 488		sctp_transport_lower_cwnd(transport, SCTP_LOWER_CWND_T3_RTX);
 489		/* Update the retran path if the T3-rtx timer has expired for
 490		 * the current retran path.
 491		 */
 492		if (transport == transport->asoc->peer.retran_path)
 493			sctp_assoc_update_retran_path(transport->asoc);
 494		transport->asoc->rtx_data_chunks +=
 495			transport->asoc->unack_data;
 496		break;
 497	case SCTP_RTXR_FAST_RTX:
 498		SCTP_INC_STATS(SCTP_MIB_FAST_RETRANSMITS);
 499		sctp_transport_lower_cwnd(transport, SCTP_LOWER_CWND_FAST_RTX);
 500		q->fast_rtx = 1;
 501		break;
 502	case SCTP_RTXR_PMTUD:
 503		SCTP_INC_STATS(SCTP_MIB_PMTUD_RETRANSMITS);
 504		break;
 505	case SCTP_RTXR_T1_RTX:
 506		SCTP_INC_STATS(SCTP_MIB_T1_RETRANSMITS);
 507		transport->asoc->init_retries++;
 508		break;
 509	default:
 510		BUG();
 511	}
 512
 513	sctp_retransmit_mark(q, transport, reason);
 514
 515	/* PR-SCTP A5) Any time the T3-rtx timer expires, on any destination,
 516	 * the sender SHOULD try to advance the "Advanced.Peer.Ack.Point" by
 517	 * following the procedures outlined in C1 - C5.
 518	 */
 519	if (reason == SCTP_RTXR_T3_RTX)
 520		sctp_generate_fwdtsn(q, q->asoc->ctsn_ack_point);
 521
 522	/* Flush the queues only on timeout, since fast_rtx is only
 523	 * triggered during sack processing and the queue
 524	 * will be flushed at the end.
 525	 */
 526	if (reason != SCTP_RTXR_FAST_RTX)
 527		error = sctp_outq_flush(q, /* rtx_timeout */ 1);
 528
 529	if (error)
 530		q->asoc->base.sk->sk_err = -error;
 531}
 532
 533/*
 534 * Transmit DATA chunks on the retransmit queue.  Upon return from
 535 * sctp_outq_flush_rtx() the packet 'pkt' may contain chunks which
 536 * need to be transmitted by the caller.
 537 * We assume that pkt->transport has already been set.
 538 *
 539 * The return value is a normal kernel error return value.
 540 */
 541static int sctp_outq_flush_rtx(struct sctp_outq *q, struct sctp_packet *pkt,
 542			       int rtx_timeout, int *start_timer)
 543{
 544	struct list_head *lqueue;
 545	struct sctp_transport *transport = pkt->transport;
 546	sctp_xmit_t status;
 547	struct sctp_chunk *chunk, *chunk1;
 548	int fast_rtx;
 549	int error = 0;
 550	int timer = 0;
 551	int done = 0;
 552
 553	lqueue = &q->retransmit;
 554	fast_rtx = q->fast_rtx;
 555
 556	/* This loop handles time-out retransmissions, fast retransmissions,
 557	 * and retransmissions due to opening of whindow.
 558	 *
 559	 * RFC 2960 6.3.3 Handle T3-rtx Expiration
 560	 *
 561	 * E3) Determine how many of the earliest (i.e., lowest TSN)
 562	 * outstanding DATA chunks for the address for which the
 563	 * T3-rtx has expired will fit into a single packet, subject
 564	 * to the MTU constraint for the path corresponding to the
 565	 * destination transport address to which the retransmission
 566	 * is being sent (this may be different from the address for
 567	 * which the timer expires [see Section 6.4]). Call this value
 568	 * K. Bundle and retransmit those K DATA chunks in a single
 569	 * packet to the destination endpoint.
 570	 *
 571	 * [Just to be painfully clear, if we are retransmitting
 572	 * because a timeout just happened, we should send only ONE
 573	 * packet of retransmitted data.]
 574	 *
 575	 * For fast retransmissions we also send only ONE packet.  However,
 576	 * if we are just flushing the queue due to open window, we'll
 577	 * try to send as much as possible.
 578	 */
 579	list_for_each_entry_safe(chunk, chunk1, lqueue, transmitted_list) {
 580		/* If the chunk is abandoned, move it to abandoned list. */
 581		if (sctp_chunk_abandoned(chunk)) {
 582			list_del_init(&chunk->transmitted_list);
 583			sctp_insert_list(&q->abandoned,
 584					 &chunk->transmitted_list);
 585			continue;
 586		}
 587
 588		/* Make sure that Gap Acked TSNs are not retransmitted.  A
 589		 * simple approach is just to move such TSNs out of the
 590		 * way and into a 'transmitted' queue and skip to the
 591		 * next chunk.
 592		 */
 593		if (chunk->tsn_gap_acked) {
 594			list_del(&chunk->transmitted_list);
 595			list_add_tail(&chunk->transmitted_list,
 596					&transport->transmitted);
 597			continue;
 598		}
 599
 600		/* If we are doing fast retransmit, ignore non-fast_rtransmit
 601		 * chunks
 602		 */
 603		if (fast_rtx && !chunk->fast_retransmit)
 604			continue;
 605
 606redo:
 607		/* Attempt to append this chunk to the packet. */
 608		status = sctp_packet_append_chunk(pkt, chunk);
 609
 610		switch (status) {
 611		case SCTP_XMIT_PMTU_FULL:
 612			if (!pkt->has_data && !pkt->has_cookie_echo) {
 613				/* If this packet did not contain DATA then
 614				 * retransmission did not happen, so do it
 615				 * again.  We'll ignore the error here since
 616				 * control chunks are already freed so there
 617				 * is nothing we can do.
 618				 */
 619				sctp_packet_transmit(pkt);
 620				goto redo;
 621			}
 622
 623			/* Send this packet.  */
 624			error = sctp_packet_transmit(pkt);
 625
 626			/* If we are retransmitting, we should only
 627			 * send a single packet.
 628			 * Otherwise, try appending this chunk again.
 629			 */
 630			if (rtx_timeout || fast_rtx)
 631				done = 1;
 632			else
 633				goto redo;
 634
 635			/* Bundle next chunk in the next round.  */
 636			break;
 637
 638		case SCTP_XMIT_RWND_FULL:
 639			/* Send this packet. */
 640			error = sctp_packet_transmit(pkt);
 641
 642			/* Stop sending DATA as there is no more room
 643			 * at the receiver.
 644			 */
 645			done = 1;
 646			break;
 647
 648		case SCTP_XMIT_NAGLE_DELAY:
 649			/* Send this packet. */
 650			error = sctp_packet_transmit(pkt);
 651
 652			/* Stop sending DATA because of nagle delay. */
 653			done = 1;
 654			break;
 655
 656		default:
 657			/* The append was successful, so add this chunk to
 658			 * the transmitted list.
 659			 */
 660			list_del(&chunk->transmitted_list);
 661			list_add_tail(&chunk->transmitted_list,
 662					&transport->transmitted);
 663
 664			/* Mark the chunk as ineligible for fast retransmit
 665			 * after it is retransmitted.
 666			 */
 667			if (chunk->fast_retransmit == SCTP_NEED_FRTX)
 668				chunk->fast_retransmit = SCTP_DONT_FRTX;
 669
 670			q->empty = 0;
 671			break;
 672		}
 673
 674		/* Set the timer if there were no errors */
 675		if (!error && !timer)
 676			timer = 1;
 677
 678		if (done)
 679			break;
 680	}
 681
 682	/* If we are here due to a retransmit timeout or a fast
 683	 * retransmit and if there are any chunks left in the retransmit
 684	 * queue that could not fit in the PMTU sized packet, they need
 685	 * to be marked as ineligible for a subsequent fast retransmit.
 686	 */
 687	if (rtx_timeout || fast_rtx) {
 688		list_for_each_entry(chunk1, lqueue, transmitted_list) {
 689			if (chunk1->fast_retransmit == SCTP_NEED_FRTX)
 690				chunk1->fast_retransmit = SCTP_DONT_FRTX;
 691		}
 692	}
 693
 694	*start_timer = timer;
 695
 696	/* Clear fast retransmit hint */
 697	if (fast_rtx)
 698		q->fast_rtx = 0;
 699
 700	return error;
 701}
 702
 703/* Cork the outqueue so queued chunks are really queued. */
 704int sctp_outq_uncork(struct sctp_outq *q)
 705{
 706	int error = 0;
 707	if (q->cork)
 708		q->cork = 0;
 709	error = sctp_outq_flush(q, 0);
 710	return error;
 711}
 712
 713
 714/*
 715 * Try to flush an outqueue.
 716 *
 717 * Description: Send everything in q which we legally can, subject to
 718 * congestion limitations.
 719 * * Note: This function can be called from multiple contexts so appropriate
 720 * locking concerns must be made.  Today we use the sock lock to protect
 721 * this function.
 722 */
 723static int sctp_outq_flush(struct sctp_outq *q, int rtx_timeout)
 724{
 725	struct sctp_packet *packet;
 726	struct sctp_packet singleton;
 727	struct sctp_association *asoc = q->asoc;
 728	__u16 sport = asoc->base.bind_addr.port;
 729	__u16 dport = asoc->peer.port;
 730	__u32 vtag = asoc->peer.i.init_tag;
 731	struct sctp_transport *transport = NULL;
 732	struct sctp_transport *new_transport;
 733	struct sctp_chunk *chunk, *tmp;
 734	sctp_xmit_t status;
 735	int error = 0;
 736	int start_timer = 0;
 737	int one_packet = 0;
 738
 739	/* These transports have chunks to send. */
 740	struct list_head transport_list;
 741	struct list_head *ltransport;
 742
 743	INIT_LIST_HEAD(&transport_list);
 744	packet = NULL;
 745
 746	/*
 747	 * 6.10 Bundling
 748	 *   ...
 749	 *   When bundling control chunks with DATA chunks, an
 750	 *   endpoint MUST place control chunks first in the outbound
 751	 *   SCTP packet.  The transmitter MUST transmit DATA chunks
 752	 *   within a SCTP packet in increasing order of TSN.
 753	 *   ...
 754	 */
 755
 756	list_for_each_entry_safe(chunk, tmp, &q->control_chunk_list, list) {
 757		/* RFC 5061, 5.3
 758		 * F1) This means that until such time as the ASCONF
 759		 * containing the add is acknowledged, the sender MUST
 760		 * NOT use the new IP address as a source for ANY SCTP
 761		 * packet except on carrying an ASCONF Chunk.
 762		 */
 763		if (asoc->src_out_of_asoc_ok &&
 764		    chunk->chunk_hdr->type != SCTP_CID_ASCONF)
 765			continue;
 766
 767		list_del_init(&chunk->list);
 768
 769		/* Pick the right transport to use. */
 770		new_transport = chunk->transport;
 771
 772		if (!new_transport) {
 773			/*
 774			 * If we have a prior transport pointer, see if
 775			 * the destination address of the chunk
 776			 * matches the destination address of the
 777			 * current transport.  If not a match, then
 778			 * try to look up the transport with a given
 779			 * destination address.  We do this because
 780			 * after processing ASCONFs, we may have new
 781			 * transports created.
 782			 */
 783			if (transport &&
 784			    sctp_cmp_addr_exact(&chunk->dest,
 785						&transport->ipaddr))
 786					new_transport = transport;
 787			else
 788				new_transport = sctp_assoc_lookup_paddr(asoc,
 789								&chunk->dest);
 790
 791			/* if we still don't have a new transport, then
 792			 * use the current active path.
 793			 */
 794			if (!new_transport)
 795				new_transport = asoc->peer.active_path;
 796		} else if ((new_transport->state == SCTP_INACTIVE) ||
 797			   (new_transport->state == SCTP_UNCONFIRMED)) {
 
 798			/* If the chunk is Heartbeat or Heartbeat Ack,
 799			 * send it to chunk->transport, even if it's
 800			 * inactive.
 801			 *
 802			 * 3.3.6 Heartbeat Acknowledgement:
 803			 * ...
 804			 * A HEARTBEAT ACK is always sent to the source IP
 805			 * address of the IP datagram containing the
 806			 * HEARTBEAT chunk to which this ack is responding.
 807			 * ...
 808			 *
 809			 * ASCONF_ACKs also must be sent to the source.
 810			 */
 811			if (chunk->chunk_hdr->type != SCTP_CID_HEARTBEAT &&
 812			    chunk->chunk_hdr->type != SCTP_CID_HEARTBEAT_ACK &&
 813			    chunk->chunk_hdr->type != SCTP_CID_ASCONF_ACK)
 814				new_transport = asoc->peer.active_path;
 815		}
 816
 817		/* Are we switching transports?
 818		 * Take care of transport locks.
 819		 */
 820		if (new_transport != transport) {
 821			transport = new_transport;
 822			if (list_empty(&transport->send_ready)) {
 823				list_add_tail(&transport->send_ready,
 824					      &transport_list);
 825			}
 826			packet = &transport->packet;
 827			sctp_packet_config(packet, vtag,
 828					   asoc->peer.ecn_capable);
 829		}
 830
 831		switch (chunk->chunk_hdr->type) {
 832		/*
 833		 * 6.10 Bundling
 834		 *   ...
 835		 *   An endpoint MUST NOT bundle INIT, INIT ACK or SHUTDOWN
 836		 *   COMPLETE with any other chunks.  [Send them immediately.]
 837		 */
 838		case SCTP_CID_INIT:
 839		case SCTP_CID_INIT_ACK:
 840		case SCTP_CID_SHUTDOWN_COMPLETE:
 841			sctp_packet_init(&singleton, transport, sport, dport);
 842			sctp_packet_config(&singleton, vtag, 0);
 843			sctp_packet_append_chunk(&singleton, chunk);
 844			error = sctp_packet_transmit(&singleton);
 845			if (error < 0)
 846				return error;
 847			break;
 848
 849		case SCTP_CID_ABORT:
 850			if (sctp_test_T_bit(chunk)) {
 851				packet->vtag = asoc->c.my_vtag;
 852			}
 853		/* The following chunks are "response" chunks, i.e.
 854		 * they are generated in response to something we
 855		 * received.  If we are sending these, then we can
 856		 * send only 1 packet containing these chunks.
 857		 */
 858		case SCTP_CID_HEARTBEAT_ACK:
 859		case SCTP_CID_SHUTDOWN_ACK:
 860		case SCTP_CID_COOKIE_ACK:
 861		case SCTP_CID_COOKIE_ECHO:
 862		case SCTP_CID_ERROR:
 863		case SCTP_CID_ECN_CWR:
 864		case SCTP_CID_ASCONF_ACK:
 865			one_packet = 1;
 866			/* Fall through */
 867
 868		case SCTP_CID_SACK:
 869		case SCTP_CID_HEARTBEAT:
 870		case SCTP_CID_SHUTDOWN:
 871		case SCTP_CID_ECN_ECNE:
 872		case SCTP_CID_ASCONF:
 873		case SCTP_CID_FWD_TSN:
 874			status = sctp_packet_transmit_chunk(packet, chunk,
 875							    one_packet);
 876			if (status  != SCTP_XMIT_OK) {
 877				/* put the chunk back */
 878				list_add(&chunk->list, &q->control_chunk_list);
 879			} else if (chunk->chunk_hdr->type == SCTP_CID_FWD_TSN) {
 
 880				/* PR-SCTP C5) If a FORWARD TSN is sent, the
 881				 * sender MUST assure that at least one T3-rtx
 882				 * timer is running.
 883				 */
 884				sctp_transport_reset_timers(transport);
 
 
 
 885			}
 886			break;
 887
 888		default:
 889			/* We built a chunk with an illegal type! */
 890			BUG();
 891		}
 892	}
 893
 894	if (q->asoc->src_out_of_asoc_ok)
 895		goto sctp_flush_out;
 896
 897	/* Is it OK to send data chunks?  */
 898	switch (asoc->state) {
 899	case SCTP_STATE_COOKIE_ECHOED:
 900		/* Only allow bundling when this packet has a COOKIE-ECHO
 901		 * chunk.
 902		 */
 903		if (!packet || !packet->has_cookie_echo)
 904			break;
 905
 906		/* fallthru */
 907	case SCTP_STATE_ESTABLISHED:
 908	case SCTP_STATE_SHUTDOWN_PENDING:
 909	case SCTP_STATE_SHUTDOWN_RECEIVED:
 910		/*
 911		 * RFC 2960 6.1  Transmission of DATA Chunks
 912		 *
 913		 * C) When the time comes for the sender to transmit,
 914		 * before sending new DATA chunks, the sender MUST
 915		 * first transmit any outstanding DATA chunks which
 916		 * are marked for retransmission (limited by the
 917		 * current cwnd).
 918		 */
 919		if (!list_empty(&q->retransmit)) {
 
 
 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
 993			/* Change packets if necessary.  */
 994			if (new_transport != transport) {
 995				transport = new_transport;
 996
 997				/* Schedule to have this transport's
 998				 * packet flushed.
 999				 */
1000				if (list_empty(&transport->send_ready)) {
1001					list_add_tail(&transport->send_ready,
1002						      &transport_list);
1003				}
1004
1005				packet = &transport->packet;
1006				sctp_packet_config(packet, vtag,
1007						   asoc->peer.ecn_capable);
1008				/* We've switched transports, so apply the
1009				 * Burst limit to the new transport.
1010				 */
1011				sctp_transport_burst_limited(transport);
1012			}
1013
1014			SCTP_DEBUG_PRINTK("sctp_outq_flush(%p, %p[%s]), ",
1015					  q, chunk,
1016					  chunk && chunk->chunk_hdr ?
1017					  sctp_cname(SCTP_ST_CHUNK(
1018						  chunk->chunk_hdr->type))
1019					  : "Illegal Chunk");
1020
1021			SCTP_DEBUG_PRINTK("TX TSN 0x%x skb->head "
1022					"%p skb->users %d.\n",
1023					ntohl(chunk->subh.data_hdr->tsn),
1024					chunk->skb ?chunk->skb->head : NULL,
1025					chunk->skb ?
1026					atomic_read(&chunk->skb->users) : -1);
1027
1028			/* Add the chunk to the packet.  */
1029			status = sctp_packet_transmit_chunk(packet, chunk, 0);
1030
1031			switch (status) {
1032			case SCTP_XMIT_PMTU_FULL:
1033			case SCTP_XMIT_RWND_FULL:
1034			case SCTP_XMIT_NAGLE_DELAY:
1035				/* We could not append this chunk, so put
1036				 * the chunk back on the output queue.
1037				 */
1038				SCTP_DEBUG_PRINTK("sctp_outq_flush: could "
1039					"not transmit TSN: 0x%x, status: %d\n",
1040					ntohl(chunk->subh.data_hdr->tsn),
1041					status);
1042				sctp_outq_head_data(q, chunk);
1043				goto sctp_flush_out;
1044				break;
1045
1046			case SCTP_XMIT_OK:
1047				/* The sender is in the SHUTDOWN-PENDING state,
1048				 * The sender MAY set the I-bit in the DATA
1049				 * chunk header.
1050				 */
1051				if (asoc->state == SCTP_STATE_SHUTDOWN_PENDING)
1052					chunk->chunk_hdr->flags |= SCTP_DATA_SACK_IMM;
 
 
 
 
1053
1054				break;
1055
1056			default:
1057				BUG();
1058			}
1059
1060			/* BUG: We assume that the sctp_packet_transmit()
1061			 * call below will succeed all the time and add the
1062			 * chunk to the transmitted list and restart the
1063			 * timers.
1064			 * It is possible that the call can fail under OOM
1065			 * conditions.
1066			 *
1067			 * Is this really a problem?  Won't this behave
1068			 * like a lost TSN?
1069			 */
1070			list_add_tail(&chunk->transmitted_list,
1071				      &transport->transmitted);
1072
1073			sctp_transport_reset_timers(transport);
1074
1075			q->empty = 0;
1076
1077			/* Only let one DATA chunk get bundled with a
1078			 * COOKIE-ECHO chunk.
1079			 */
1080			if (packet->has_cookie_echo)
1081				goto sctp_flush_out;
1082		}
1083		break;
1084
1085	default:
1086		/* Do nothing.  */
1087		break;
1088	}
1089
1090sctp_flush_out:
1091
1092	/* Before returning, examine all the transports touched in
1093	 * this call.  Right now, we bluntly force clear all the
1094	 * transports.  Things might change after we implement Nagle.
1095	 * But such an examination is still required.
1096	 *
1097	 * --xguo
1098	 */
1099	while ((ltransport = sctp_list_dequeue(&transport_list)) != NULL ) {
1100		struct sctp_transport *t = list_entry(ltransport,
1101						      struct sctp_transport,
1102						      send_ready);
1103		packet = &t->packet;
1104		if (!sctp_packet_empty(packet))
1105			error = sctp_packet_transmit(packet);
1106
1107		/* Clear the burst limited state, if any */
1108		sctp_transport_burst_reset(t);
1109	}
1110
1111	return error;
1112}
1113
1114/* Update unack_data based on the incoming SACK chunk */
1115static void sctp_sack_update_unack_data(struct sctp_association *assoc,
1116					struct sctp_sackhdr *sack)
1117{
1118	sctp_sack_variable_t *frags;
1119	__u16 unack_data;
1120	int i;
1121
1122	unack_data = assoc->next_tsn - assoc->ctsn_ack_point - 1;
1123
1124	frags = sack->variable;
1125	for (i = 0; i < ntohs(sack->num_gap_ack_blocks); i++) {
1126		unack_data -= ((ntohs(frags[i].gab.end) -
1127				ntohs(frags[i].gab.start) + 1));
1128	}
1129
1130	assoc->unack_data = unack_data;
1131}
1132
1133/* This is where we REALLY process a SACK.
1134 *
1135 * Process the SACK against the outqueue.  Mostly, this just frees
1136 * things off the transmitted queue.
1137 */
1138int sctp_outq_sack(struct sctp_outq *q, struct sctp_sackhdr *sack)
1139{
1140	struct sctp_association *asoc = q->asoc;
 
1141	struct sctp_transport *transport;
1142	struct sctp_chunk *tchunk = NULL;
1143	struct list_head *lchunk, *transport_list, *temp;
1144	sctp_sack_variable_t *frags = sack->variable;
1145	__u32 sack_ctsn, ctsn, tsn;
1146	__u32 highest_tsn, highest_new_tsn;
1147	__u32 sack_a_rwnd;
1148	unsigned outstanding;
1149	struct sctp_transport *primary = asoc->peer.primary_path;
1150	int count_of_newacks = 0;
1151	int gap_ack_blocks;
1152	u8 accum_moved = 0;
1153
1154	/* Grab the association's destination address list. */
1155	transport_list = &asoc->peer.transport_addr_list;
1156
1157	sack_ctsn = ntohl(sack->cum_tsn_ack);
1158	gap_ack_blocks = ntohs(sack->num_gap_ack_blocks);
 
1159	/*
1160	 * SFR-CACC algorithm:
1161	 * On receipt of a SACK the sender SHOULD execute the
1162	 * following statements.
1163	 *
1164	 * 1) If the cumulative ack in the SACK passes next tsn_at_change
1165	 * on the current primary, the CHANGEOVER_ACTIVE flag SHOULD be
1166	 * cleared. The CYCLING_CHANGEOVER flag SHOULD also be cleared for
1167	 * all destinations.
1168	 * 2) If the SACK contains gap acks and the flag CHANGEOVER_ACTIVE
1169	 * is set the receiver of the SACK MUST take the following actions:
1170	 *
1171	 * A) Initialize the cacc_saw_newack to 0 for all destination
1172	 * addresses.
1173	 *
1174	 * Only bother if changeover_active is set. Otherwise, this is
1175	 * totally suboptimal to do on every SACK.
1176	 */
1177	if (primary->cacc.changeover_active) {
1178		u8 clear_cycling = 0;
1179
1180		if (TSN_lte(primary->cacc.next_tsn_at_change, sack_ctsn)) {
1181			primary->cacc.changeover_active = 0;
1182			clear_cycling = 1;
1183		}
1184
1185		if (clear_cycling || gap_ack_blocks) {
1186			list_for_each_entry(transport, transport_list,
1187					transports) {
1188				if (clear_cycling)
1189					transport->cacc.cycling_changeover = 0;
1190				if (gap_ack_blocks)
1191					transport->cacc.cacc_saw_newack = 0;
1192			}
1193		}
1194	}
1195
1196	/* Get the highest TSN in the sack. */
1197	highest_tsn = sack_ctsn;
1198	if (gap_ack_blocks)
1199		highest_tsn += ntohs(frags[gap_ack_blocks - 1].gab.end);
1200
1201	if (TSN_lt(asoc->highest_sacked, highest_tsn))
1202		asoc->highest_sacked = highest_tsn;
1203
1204	highest_new_tsn = sack_ctsn;
1205
1206	/* Run through the retransmit queue.  Credit bytes received
1207	 * and free those chunks that we can.
1208	 */
1209	sctp_check_transmitted(q, &q->retransmit, NULL, sack, &highest_new_tsn);
1210
1211	/* Run through the transmitted queue.
1212	 * Credit bytes received and free those chunks which we can.
1213	 *
1214	 * This is a MASSIVE candidate for optimization.
1215	 */
1216	list_for_each_entry(transport, transport_list, transports) {
1217		sctp_check_transmitted(q, &transport->transmitted,
1218				       transport, sack, &highest_new_tsn);
 
1219		/*
1220		 * SFR-CACC algorithm:
1221		 * C) Let count_of_newacks be the number of
1222		 * destinations for which cacc_saw_newack is set.
1223		 */
1224		if (transport->cacc.cacc_saw_newack)
1225			count_of_newacks ++;
1226	}
1227
1228	/* Move the Cumulative TSN Ack Point if appropriate.  */
1229	if (TSN_lt(asoc->ctsn_ack_point, sack_ctsn)) {
1230		asoc->ctsn_ack_point = sack_ctsn;
1231		accum_moved = 1;
1232	}
1233
1234	if (gap_ack_blocks) {
1235
1236		if (asoc->fast_recovery && accum_moved)
1237			highest_new_tsn = highest_tsn;
1238
1239		list_for_each_entry(transport, transport_list, transports)
1240			sctp_mark_missing(q, &transport->transmitted, transport,
1241					  highest_new_tsn, count_of_newacks);
1242	}
1243
1244	/* Update unack_data field in the assoc. */
1245	sctp_sack_update_unack_data(asoc, sack);
1246
1247	ctsn = asoc->ctsn_ack_point;
1248
1249	/* Throw away stuff rotting on the sack queue.  */
1250	list_for_each_safe(lchunk, temp, &q->sacked) {
1251		tchunk = list_entry(lchunk, struct sctp_chunk,
1252				    transmitted_list);
1253		tsn = ntohl(tchunk->subh.data_hdr->tsn);
1254		if (TSN_lte(tsn, ctsn)) {
1255			list_del_init(&tchunk->transmitted_list);
1256			sctp_chunk_free(tchunk);
1257		}
1258	}
1259
1260	/* ii) Set rwnd equal to the newly received a_rwnd minus the
1261	 *     number of bytes still outstanding after processing the
1262	 *     Cumulative TSN Ack and the Gap Ack Blocks.
1263	 */
1264
1265	sack_a_rwnd = ntohl(sack->a_rwnd);
 
1266	outstanding = q->outstanding_bytes;
1267
1268	if (outstanding < sack_a_rwnd)
1269		sack_a_rwnd -= outstanding;
1270	else
1271		sack_a_rwnd = 0;
1272
1273	asoc->peer.rwnd = sack_a_rwnd;
1274
1275	sctp_generate_fwdtsn(q, sack_ctsn);
1276
1277	SCTP_DEBUG_PRINTK("%s: sack Cumulative TSN Ack is 0x%x.\n",
1278			  __func__, sack_ctsn);
1279	SCTP_DEBUG_PRINTK("%s: Cumulative TSN Ack of association, "
1280			  "%p is 0x%x. Adv peer ack point: 0x%x\n",
1281			  __func__, asoc, ctsn, asoc->adv_peer_ack_point);
1282
1283	/* See if all chunks are acked.
1284	 * Make sure the empty queue handler will get run later.
1285	 */
1286	q->empty = (list_empty(&q->out_chunk_list) &&
1287		    list_empty(&q->retransmit));
1288	if (!q->empty)
1289		goto finish;
1290
1291	list_for_each_entry(transport, transport_list, transports) {
1292		q->empty = q->empty && list_empty(&transport->transmitted);
1293		if (!q->empty)
1294			goto finish;
1295	}
1296
1297	SCTP_DEBUG_PRINTK("sack queue is empty.\n");
1298finish:
1299	return q->empty;
1300}
1301
1302/* Is the outqueue empty?  */
 
 
 
1303int sctp_outq_is_empty(const struct sctp_outq *q)
1304{
1305	return q->empty;
 
1306}
1307
1308/********************************************************************
1309 * 2nd Level Abstractions
1310 ********************************************************************/
1311
1312/* Go through a transport's transmitted list or the association's retransmit
1313 * list and move chunks that are acked by the Cumulative TSN Ack to q->sacked.
1314 * The retransmit list will not have an associated transport.
1315 *
1316 * I added coherent debug information output.	--xguo
1317 *
1318 * Instead of printing 'sacked' or 'kept' for each TSN on the
1319 * transmitted_queue, we print a range: SACKED: TSN1-TSN2, TSN3, TSN4-TSN5.
1320 * KEPT TSN6-TSN7, etc.
1321 */
1322static void sctp_check_transmitted(struct sctp_outq *q,
1323				   struct list_head *transmitted_queue,
1324				   struct sctp_transport *transport,
 
1325				   struct sctp_sackhdr *sack,
1326				   __u32 *highest_new_tsn_in_sack)
1327{
1328	struct list_head *lchunk;
1329	struct sctp_chunk *tchunk;
1330	struct list_head tlist;
1331	__u32 tsn;
1332	__u32 sack_ctsn;
1333	__u32 rtt;
1334	__u8 restart_timer = 0;
1335	int bytes_acked = 0;
1336	int migrate_bytes = 0;
1337
1338	/* These state variables are for coherent debug output. --xguo */
1339
1340#if SCTP_DEBUG
1341	__u32 dbg_ack_tsn = 0;	/* An ACKed TSN range starts here... */
1342	__u32 dbg_last_ack_tsn = 0;  /* ...and finishes here.	     */
1343	__u32 dbg_kept_tsn = 0;	/* An un-ACKed range starts here...  */
1344	__u32 dbg_last_kept_tsn = 0; /* ...and finishes here.	     */
1345
1346	/* 0 : The last TSN was ACKed.
1347	 * 1 : The last TSN was NOT ACKed (i.e. KEPT).
1348	 * -1: We need to initialize.
1349	 */
1350	int dbg_prt_state = -1;
1351#endif /* SCTP_DEBUG */
1352
1353	sack_ctsn = ntohl(sack->cum_tsn_ack);
1354
1355	INIT_LIST_HEAD(&tlist);
1356
1357	/* The while loop will skip empty transmitted queues. */
1358	while (NULL != (lchunk = sctp_list_dequeue(transmitted_queue))) {
1359		tchunk = list_entry(lchunk, struct sctp_chunk,
1360				    transmitted_list);
1361
1362		if (sctp_chunk_abandoned(tchunk)) {
1363			/* Move the chunk to abandoned list. */
1364			sctp_insert_list(&q->abandoned, lchunk);
1365
1366			/* If this chunk has not been acked, stop
1367			 * considering it as 'outstanding'.
1368			 */
1369			if (!tchunk->tsn_gap_acked) {
1370				if (tchunk->transport)
1371					tchunk->transport->flight_size -=
1372							sctp_data_size(tchunk);
1373				q->outstanding_bytes -= sctp_data_size(tchunk);
1374			}
1375			continue;
1376		}
1377
1378		tsn = ntohl(tchunk->subh.data_hdr->tsn);
1379		if (sctp_acked(sack, tsn)) {
1380			/* If this queue is the retransmit queue, the
1381			 * retransmit timer has already reclaimed
1382			 * the outstanding bytes for this chunk, so only
1383			 * count bytes associated with a transport.
1384			 */
1385			if (transport) {
1386				/* If this chunk is being used for RTT
1387				 * measurement, calculate the RTT and update
1388				 * the RTO using this value.
1389				 *
1390				 * 6.3.1 C5) Karn's algorithm: RTT measurements
1391				 * MUST NOT be made using packets that were
1392				 * retransmitted (and thus for which it is
1393				 * ambiguous whether the reply was for the
1394				 * first instance of the packet or a later
1395				 * instance).
1396				 */
1397				if (!tchunk->tsn_gap_acked &&
 
1398				    tchunk->rtt_in_progress) {
1399					tchunk->rtt_in_progress = 0;
1400					rtt = jiffies - tchunk->sent_at;
1401					sctp_transport_update_rto(transport,
1402								  rtt);
1403				}
1404			}
1405
1406			/* If the chunk hasn't been marked as ACKED,
1407			 * mark it and account bytes_acked if the
1408			 * chunk had a valid transport (it will not
1409			 * have a transport if ASCONF had deleted it
1410			 * while DATA was outstanding).
1411			 */
1412			if (!tchunk->tsn_gap_acked) {
1413				tchunk->tsn_gap_acked = 1;
1414				*highest_new_tsn_in_sack = tsn;
 
1415				bytes_acked += sctp_data_size(tchunk);
1416				if (!tchunk->transport)
1417					migrate_bytes += sctp_data_size(tchunk);
 
1418			}
1419
1420			if (TSN_lte(tsn, sack_ctsn)) {
1421				/* RFC 2960  6.3.2 Retransmission Timer Rules
1422				 *
1423				 * R3) Whenever a SACK is received
1424				 * that acknowledges the DATA chunk
1425				 * with the earliest outstanding TSN
1426				 * for that address, restart T3-rtx
1427				 * timer for that address with its
1428				 * current RTO.
1429				 */
1430				restart_timer = 1;
 
1431
1432				if (!tchunk->tsn_gap_acked) {
1433					/*
1434					 * SFR-CACC algorithm:
1435					 * 2) If the SACK contains gap acks
1436					 * and the flag CHANGEOVER_ACTIVE is
1437					 * set the receiver of the SACK MUST
1438					 * take the following action:
1439					 *
1440					 * B) For each TSN t being acked that
1441					 * has not been acked in any SACK so
1442					 * far, set cacc_saw_newack to 1 for
1443					 * the destination that the TSN was
1444					 * sent to.
1445					 */
1446					if (transport &&
1447					    sack->num_gap_ack_blocks &&
1448					    q->asoc->peer.primary_path->cacc.
1449					    changeover_active)
1450						transport->cacc.cacc_saw_newack
1451							= 1;
1452				}
1453
1454				list_add_tail(&tchunk->transmitted_list,
1455					      &q->sacked);
1456			} else {
1457				/* RFC2960 7.2.4, sctpimpguide-05 2.8.2
1458				 * M2) Each time a SACK arrives reporting
1459				 * 'Stray DATA chunk(s)' record the highest TSN
1460				 * reported as newly acknowledged, call this
1461				 * value 'HighestTSNinSack'. A newly
1462				 * acknowledged DATA chunk is one not
1463				 * previously acknowledged in a SACK.
1464				 *
1465				 * When the SCTP sender of data receives a SACK
1466				 * chunk that acknowledges, for the first time,
1467				 * the receipt of a DATA chunk, all the still
1468				 * unacknowledged DATA chunks whose TSN is
1469				 * older than that newly acknowledged DATA
1470				 * chunk, are qualified as 'Stray DATA chunks'.
1471				 */
1472				list_add_tail(lchunk, &tlist);
1473			}
1474
1475#if SCTP_DEBUG
1476			switch (dbg_prt_state) {
1477			case 0:	/* last TSN was ACKed */
1478				if (dbg_last_ack_tsn + 1 == tsn) {
1479					/* This TSN belongs to the
1480					 * current ACK range.
1481					 */
1482					break;
1483				}
1484
1485				if (dbg_last_ack_tsn != dbg_ack_tsn) {
1486					/* Display the end of the
1487					 * current range.
1488					 */
1489					SCTP_DEBUG_PRINTK_CONT("-%08x",
1490							       dbg_last_ack_tsn);
1491				}
1492
1493				/* Start a new range.  */
1494				SCTP_DEBUG_PRINTK_CONT(",%08x", tsn);
1495				dbg_ack_tsn = tsn;
1496				break;
1497
1498			case 1:	/* The last TSN was NOT ACKed. */
1499				if (dbg_last_kept_tsn != dbg_kept_tsn) {
1500					/* Display the end of current range. */
1501					SCTP_DEBUG_PRINTK_CONT("-%08x",
1502							       dbg_last_kept_tsn);
1503				}
1504
1505				SCTP_DEBUG_PRINTK_CONT("\n");
1506
1507				/* FALL THROUGH... */
1508			default:
1509				/* This is the first-ever TSN we examined.  */
1510				/* Start a new range of ACK-ed TSNs.  */
1511				SCTP_DEBUG_PRINTK("ACKed: %08x", tsn);
1512				dbg_prt_state = 0;
1513				dbg_ack_tsn = tsn;
1514			}
1515
1516			dbg_last_ack_tsn = tsn;
1517#endif /* SCTP_DEBUG */
1518
1519		} else {
1520			if (tchunk->tsn_gap_acked) {
1521				SCTP_DEBUG_PRINTK("%s: Receiver reneged on "
1522						  "data TSN: 0x%x\n",
1523						  __func__,
1524						  tsn);
1525				tchunk->tsn_gap_acked = 0;
1526
1527				if (tchunk->transport)
1528					bytes_acked -= sctp_data_size(tchunk);
1529
1530				/* RFC 2960 6.3.2 Retransmission Timer Rules
1531				 *
1532				 * R4) Whenever a SACK is received missing a
1533				 * TSN that was previously acknowledged via a
1534				 * Gap Ack Block, start T3-rtx for the
1535				 * destination address to which the DATA
1536				 * chunk was originally
1537				 * transmitted if it is not already running.
1538				 */
1539				restart_timer = 1;
1540			}
1541
1542			list_add_tail(lchunk, &tlist);
1543
1544#if SCTP_DEBUG
1545			/* See the above comments on ACK-ed TSNs. */
1546			switch (dbg_prt_state) {
1547			case 1:
1548				if (dbg_last_kept_tsn + 1 == tsn)
1549					break;
1550
1551				if (dbg_last_kept_tsn != dbg_kept_tsn)
1552					SCTP_DEBUG_PRINTK_CONT("-%08x",
1553							       dbg_last_kept_tsn);
1554
1555				SCTP_DEBUG_PRINTK_CONT(",%08x", tsn);
1556				dbg_kept_tsn = tsn;
1557				break;
1558
1559			case 0:
1560				if (dbg_last_ack_tsn != dbg_ack_tsn)
1561					SCTP_DEBUG_PRINTK_CONT("-%08x",
1562							       dbg_last_ack_tsn);
1563				SCTP_DEBUG_PRINTK_CONT("\n");
1564
1565				/* FALL THROUGH... */
1566			default:
1567				SCTP_DEBUG_PRINTK("KEPT: %08x",tsn);
1568				dbg_prt_state = 1;
1569				dbg_kept_tsn = tsn;
1570			}
1571
1572			dbg_last_kept_tsn = tsn;
1573#endif /* SCTP_DEBUG */
1574		}
1575	}
1576
1577#if SCTP_DEBUG
1578	/* Finish off the last range, displaying its ending TSN.  */
1579	switch (dbg_prt_state) {
1580	case 0:
1581		if (dbg_last_ack_tsn != dbg_ack_tsn) {
1582			SCTP_DEBUG_PRINTK_CONT("-%08x\n", dbg_last_ack_tsn);
1583		} else {
1584			SCTP_DEBUG_PRINTK_CONT("\n");
1585		}
1586	break;
1587
1588	case 1:
1589		if (dbg_last_kept_tsn != dbg_kept_tsn) {
1590			SCTP_DEBUG_PRINTK_CONT("-%08x\n", dbg_last_kept_tsn);
1591		} else {
1592			SCTP_DEBUG_PRINTK_CONT("\n");
1593		}
1594	}
1595#endif /* SCTP_DEBUG */
1596	if (transport) {
1597		if (bytes_acked) {
1598			struct sctp_association *asoc = transport->asoc;
1599
1600			/* We may have counted DATA that was migrated
1601			 * to this transport due to DEL-IP operation.
1602			 * Subtract those bytes, since the were never
1603			 * send on this transport and shouldn't be
1604			 * credited to this transport.
1605			 */
1606			bytes_acked -= migrate_bytes;
1607
1608			/* 8.2. When an outstanding TSN is acknowledged,
1609			 * the endpoint shall clear the error counter of
1610			 * the destination transport address to which the
1611			 * DATA chunk was last sent.
1612			 * The association's overall error counter is
1613			 * also cleared.
1614			 */
1615			transport->error_count = 0;
1616			transport->asoc->overall_error_count = 0;
 
1617
1618			/*
1619			 * While in SHUTDOWN PENDING, we may have started
1620			 * the T5 shutdown guard timer after reaching the
1621			 * retransmission limit. Stop that timer as soon
1622			 * as the receiver acknowledged any data.
1623			 */
1624			if (asoc->state == SCTP_STATE_SHUTDOWN_PENDING &&
1625			    del_timer(&asoc->timers
1626				[SCTP_EVENT_TIMEOUT_T5_SHUTDOWN_GUARD]))
1627					sctp_association_put(asoc);
1628
1629			/* Mark the destination transport address as
1630			 * active if it is not so marked.
1631			 */
1632			if ((transport->state == SCTP_INACTIVE) ||
1633			    (transport->state == SCTP_UNCONFIRMED)) {
 
1634				sctp_assoc_control_transport(
1635					transport->asoc,
1636					transport,
1637					SCTP_TRANSPORT_UP,
1638					SCTP_RECEIVED_SACK);
1639			}
1640
1641			sctp_transport_raise_cwnd(transport, sack_ctsn,
1642						  bytes_acked);
1643
1644			transport->flight_size -= bytes_acked;
1645			if (transport->flight_size == 0)
1646				transport->partial_bytes_acked = 0;
1647			q->outstanding_bytes -= bytes_acked + migrate_bytes;
1648		} else {
1649			/* RFC 2960 6.1, sctpimpguide-06 2.15.2
1650			 * When a sender is doing zero window probing, it
1651			 * should not timeout the association if it continues
1652			 * to receive new packets from the receiver. The
1653			 * reason is that the receiver MAY keep its window
1654			 * closed for an indefinite time.
1655			 * A sender is doing zero window probing when the
1656			 * receiver's advertised window is zero, and there is
1657			 * only one data chunk in flight to the receiver.
1658			 *
1659			 * Allow the association to timeout while in SHUTDOWN
1660			 * PENDING or SHUTDOWN RECEIVED in case the receiver
1661			 * stays in zero window mode forever.
1662			 */
1663			if (!q->asoc->peer.rwnd &&
1664			    !list_empty(&tlist) &&
1665			    (sack_ctsn+2 == q->asoc->next_tsn) &&
1666			    q->asoc->state < SCTP_STATE_SHUTDOWN_PENDING) {
1667				SCTP_DEBUG_PRINTK("%s: SACK received for zero "
1668						  "window probe: %u\n",
1669						  __func__, sack_ctsn);
1670				q->asoc->overall_error_count = 0;
1671				transport->error_count = 0;
1672			}
1673		}
1674
1675		/* RFC 2960 6.3.2 Retransmission Timer Rules
1676		 *
1677		 * R2) Whenever all outstanding data sent to an address have
1678		 * been acknowledged, turn off the T3-rtx timer of that
1679		 * address.
1680		 */
1681		if (!transport->flight_size) {
1682			if (timer_pending(&transport->T3_rtx_timer) &&
1683			    del_timer(&transport->T3_rtx_timer)) {
1684				sctp_transport_put(transport);
1685			}
1686		} else if (restart_timer) {
1687			if (!mod_timer(&transport->T3_rtx_timer,
1688				       jiffies + transport->rto))
1689				sctp_transport_hold(transport);
1690		}
 
 
 
 
 
1691	}
1692
1693	list_splice(&tlist, transmitted_queue);
1694}
1695
1696/* Mark chunks as missing and consequently may get retransmitted. */
1697static void sctp_mark_missing(struct sctp_outq *q,
1698			      struct list_head *transmitted_queue,
1699			      struct sctp_transport *transport,
1700			      __u32 highest_new_tsn_in_sack,
1701			      int count_of_newacks)
1702{
1703	struct sctp_chunk *chunk;
1704	__u32 tsn;
1705	char do_fast_retransmit = 0;
1706	struct sctp_association *asoc = q->asoc;
1707	struct sctp_transport *primary = asoc->peer.primary_path;
1708
1709	list_for_each_entry(chunk, transmitted_queue, transmitted_list) {
1710
1711		tsn = ntohl(chunk->subh.data_hdr->tsn);
1712
1713		/* RFC 2960 7.2.4, sctpimpguide-05 2.8.2 M3) Examine all
1714		 * 'Unacknowledged TSN's', if the TSN number of an
1715		 * 'Unacknowledged TSN' is smaller than the 'HighestTSNinSack'
1716		 * value, increment the 'TSN.Missing.Report' count on that
1717		 * chunk if it has NOT been fast retransmitted or marked for
1718		 * fast retransmit already.
1719		 */
1720		if (chunk->fast_retransmit == SCTP_CAN_FRTX &&
1721		    !chunk->tsn_gap_acked &&
1722		    TSN_lt(tsn, highest_new_tsn_in_sack)) {
1723
1724			/* SFR-CACC may require us to skip marking
1725			 * this chunk as missing.
1726			 */
1727			if (!transport || !sctp_cacc_skip(primary,
1728						chunk->transport,
1729						count_of_newacks, tsn)) {
1730				chunk->tsn_missing_report++;
1731
1732				SCTP_DEBUG_PRINTK(
1733					"%s: TSN 0x%x missing counter: %d\n",
1734					__func__, tsn,
1735					chunk->tsn_missing_report);
1736			}
1737		}
1738		/*
1739		 * M4) If any DATA chunk is found to have a
1740		 * 'TSN.Missing.Report'
1741		 * value larger than or equal to 3, mark that chunk for
1742		 * retransmission and start the fast retransmit procedure.
1743		 */
1744
1745		if (chunk->tsn_missing_report >= 3) {
1746			chunk->fast_retransmit = SCTP_NEED_FRTX;
1747			do_fast_retransmit = 1;
1748		}
1749	}
1750
1751	if (transport) {
1752		if (do_fast_retransmit)
1753			sctp_retransmit(q, transport, SCTP_RTXR_FAST_RTX);
1754
1755		SCTP_DEBUG_PRINTK("%s: transport: %p, cwnd: %d, "
1756				  "ssthresh: %d, flight_size: %d, pba: %d\n",
1757				  __func__, transport, transport->cwnd,
1758				  transport->ssthresh, transport->flight_size,
1759				  transport->partial_bytes_acked);
1760	}
1761}
1762
1763/* Is the given TSN acked by this packet?  */
1764static int sctp_acked(struct sctp_sackhdr *sack, __u32 tsn)
1765{
1766	int i;
1767	sctp_sack_variable_t *frags;
1768	__u16 gap;
1769	__u32 ctsn = ntohl(sack->cum_tsn_ack);
1770
1771	if (TSN_lte(tsn, ctsn))
1772		goto pass;
1773
1774	/* 3.3.4 Selective Acknowledgement (SACK) (3):
1775	 *
1776	 * Gap Ack Blocks:
1777	 *  These fields contain the Gap Ack Blocks. They are repeated
1778	 *  for each Gap Ack Block up to the number of Gap Ack Blocks
1779	 *  defined in the Number of Gap Ack Blocks field. All DATA
1780	 *  chunks with TSNs greater than or equal to (Cumulative TSN
1781	 *  Ack + Gap Ack Block Start) and less than or equal to
1782	 *  (Cumulative TSN Ack + Gap Ack Block End) of each Gap Ack
1783	 *  Block are assumed to have been received correctly.
1784	 */
1785
1786	frags = sack->variable;
1787	gap = tsn - ctsn;
1788	for (i = 0; i < ntohs(sack->num_gap_ack_blocks); ++i) {
1789		if (TSN_lte(ntohs(frags[i].gab.start), gap) &&
1790		    TSN_lte(gap, ntohs(frags[i].gab.end)))
1791			goto pass;
1792	}
1793
1794	return 0;
1795pass:
1796	return 1;
1797}
1798
1799static inline int sctp_get_skip_pos(struct sctp_fwdtsn_skip *skiplist,
1800				    int nskips, __be16 stream)
1801{
1802	int i;
1803
1804	for (i = 0; i < nskips; i++) {
1805		if (skiplist[i].stream == stream)
1806			return i;
1807	}
1808	return i;
1809}
1810
1811/* Create and add a fwdtsn chunk to the outq's control queue if needed. */
1812static void sctp_generate_fwdtsn(struct sctp_outq *q, __u32 ctsn)
1813{
1814	struct sctp_association *asoc = q->asoc;
1815	struct sctp_chunk *ftsn_chunk = NULL;
1816	struct sctp_fwdtsn_skip ftsn_skip_arr[10];
1817	int nskips = 0;
1818	int skip_pos = 0;
1819	__u32 tsn;
1820	struct sctp_chunk *chunk;
1821	struct list_head *lchunk, *temp;
1822
1823	if (!asoc->peer.prsctp_capable)
1824		return;
1825
1826	/* PR-SCTP C1) Let SackCumAck be the Cumulative TSN ACK carried in the
1827	 * received SACK.
1828	 *
1829	 * If (Advanced.Peer.Ack.Point < SackCumAck), then update
1830	 * Advanced.Peer.Ack.Point to be equal to SackCumAck.
1831	 */
1832	if (TSN_lt(asoc->adv_peer_ack_point, ctsn))
1833		asoc->adv_peer_ack_point = ctsn;
1834
1835	/* PR-SCTP C2) Try to further advance the "Advanced.Peer.Ack.Point"
1836	 * locally, that is, to move "Advanced.Peer.Ack.Point" up as long as
1837	 * the chunk next in the out-queue space is marked as "abandoned" as
1838	 * shown in the following example:
1839	 *
1840	 * Assuming that a SACK arrived with the Cumulative TSN ACK 102
1841	 * and the Advanced.Peer.Ack.Point is updated to this value:
1842	 *
1843	 *   out-queue at the end of  ==>   out-queue after Adv.Ack.Point
1844	 *   normal SACK processing           local advancement
1845	 *                ...                           ...
1846	 *   Adv.Ack.Pt-> 102 acked                     102 acked
1847	 *                103 abandoned                 103 abandoned
1848	 *                104 abandoned     Adv.Ack.P-> 104 abandoned
1849	 *                105                           105
1850	 *                106 acked                     106 acked
1851	 *                ...                           ...
1852	 *
1853	 * In this example, the data sender successfully advanced the
1854	 * "Advanced.Peer.Ack.Point" from 102 to 104 locally.
1855	 */
1856	list_for_each_safe(lchunk, temp, &q->abandoned) {
1857		chunk = list_entry(lchunk, struct sctp_chunk,
1858					transmitted_list);
1859		tsn = ntohl(chunk->subh.data_hdr->tsn);
1860
1861		/* Remove any chunks in the abandoned queue that are acked by
1862		 * the ctsn.
1863		 */
1864		if (TSN_lte(tsn, ctsn)) {
1865			list_del_init(lchunk);
1866			sctp_chunk_free(chunk);
1867		} else {
1868			if (TSN_lte(tsn, asoc->adv_peer_ack_point+1)) {
1869				asoc->adv_peer_ack_point = tsn;
1870				if (chunk->chunk_hdr->flags &
1871					 SCTP_DATA_UNORDERED)
1872					continue;
1873				skip_pos = sctp_get_skip_pos(&ftsn_skip_arr[0],
1874						nskips,
1875						chunk->subh.data_hdr->stream);
1876				ftsn_skip_arr[skip_pos].stream =
1877					chunk->subh.data_hdr->stream;
1878				ftsn_skip_arr[skip_pos].ssn =
1879					 chunk->subh.data_hdr->ssn;
1880				if (skip_pos == nskips)
1881					nskips++;
1882				if (nskips == 10)
1883					break;
1884			} else
1885				break;
1886		}
1887	}
1888
1889	/* PR-SCTP C3) If, after step C1 and C2, the "Advanced.Peer.Ack.Point"
1890	 * is greater than the Cumulative TSN ACK carried in the received
1891	 * SACK, the data sender MUST send the data receiver a FORWARD TSN
1892	 * chunk containing the latest value of the
1893	 * "Advanced.Peer.Ack.Point".
1894	 *
1895	 * C4) For each "abandoned" TSN the sender of the FORWARD TSN SHOULD
1896	 * list each stream and sequence number in the forwarded TSN. This
1897	 * information will enable the receiver to easily find any
1898	 * stranded TSN's waiting on stream reorder queues. Each stream
1899	 * SHOULD only be reported once; this means that if multiple
1900	 * abandoned messages occur in the same stream then only the
1901	 * highest abandoned stream sequence number is reported. If the
1902	 * total size of the FORWARD TSN does NOT fit in a single MTU then
1903	 * the sender of the FORWARD TSN SHOULD lower the
1904	 * Advanced.Peer.Ack.Point to the last TSN that will fit in a
1905	 * single MTU.
1906	 */
1907	if (asoc->adv_peer_ack_point > ctsn)
1908		ftsn_chunk = sctp_make_fwdtsn(asoc, asoc->adv_peer_ack_point,
1909					      nskips, &ftsn_skip_arr[0]);
1910
1911	if (ftsn_chunk) {
1912		list_add_tail(&ftsn_chunk->list, &q->control_chunk_list);
1913		SCTP_INC_STATS(SCTP_MIB_OUTCTRLCHUNKS);
1914	}
1915}