1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* SCTP kernel implementation 3 * (C) Copyright IBM Corp. 2001, 2004 4 * Copyright (c) 1999-2000 Cisco, Inc. 5 * Copyright (c) 1999-2001 Motorola, Inc. 6 * Copyright (c) 2001-2003 Intel Corp. 7 * 8 * This file is part of the SCTP kernel implementation 9 * 10 * These functions implement the sctp_outq class. The outqueue handles 11 * bundling and queueing of outgoing SCTP chunks. 12 * 13 * Please send any bug reports or fixes you make to the 14 * email address(es): 15 * lksctp developers <linux-sctp@vger.kernel.org> 16 * 17 * Written or modified by: 18 * La Monte H.P. Yarroll <piggy@acm.org> 19 * Karl Knutson <karl@athena.chicago.il.us> 20 * Perry Melange <pmelange@null.cc.uic.edu> 21 * Xingang Guo <xingang.guo@intel.com> 22 * Hui Huang <hui.huang@nokia.com> 23 * Sridhar Samudrala <sri@us.ibm.com> 24 * Jon Grimm <jgrimm@us.ibm.com> 25 */ 26 27 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 28 29 #include <linux/types.h> 30 #include <linux/list.h> /* For struct list_head */ 31 #include <linux/socket.h> 32 #include <linux/ip.h> 33 #include <linux/slab.h> 34 #include <net/sock.h> /* For skb_set_owner_w */ 35 36 #include <net/sctp/sctp.h> 37 #include <net/sctp/sm.h> 38 #include <net/sctp/stream_sched.h> 39 #include <trace/events/sctp.h> 40 41 /* Declare internal functions here. */ 42 static int sctp_acked(struct sctp_sackhdr *sack, __u32 tsn); 43 static void sctp_check_transmitted(struct sctp_outq *q, 44 struct list_head *transmitted_queue, 45 struct sctp_transport *transport, 46 union sctp_addr *saddr, 47 struct sctp_sackhdr *sack, 48 __u32 *highest_new_tsn); 49 50 static void sctp_mark_missing(struct sctp_outq *q, 51 struct list_head *transmitted_queue, 52 struct sctp_transport *transport, 53 __u32 highest_new_tsn, 54 int count_of_newacks); 55 56 static void sctp_outq_flush(struct sctp_outq *q, int rtx_timeout, gfp_t gfp); 57 58 /* Add data to the front of the queue. */ 59 static inline void sctp_outq_head_data(struct sctp_outq *q, 60 struct sctp_chunk *ch) 61 { 62 struct sctp_stream_out_ext *oute; 63 __u16 stream; 64 65 list_add(&ch->list, &q->out_chunk_list); 66 q->out_qlen += ch->skb->len; 67 68 stream = sctp_chunk_stream_no(ch); 69 oute = SCTP_SO(&q->asoc->stream, stream)->ext; 70 list_add(&ch->stream_list, &oute->outq); 71 } 72 73 /* Take data from the front of the queue. */ 74 static inline struct sctp_chunk *sctp_outq_dequeue_data(struct sctp_outq *q) 75 { 76 return q->sched->dequeue(q); 77 } 78 79 /* Add data chunk to the end of the queue. */ 80 static inline void sctp_outq_tail_data(struct sctp_outq *q, 81 struct sctp_chunk *ch) 82 { 83 struct sctp_stream_out_ext *oute; 84 __u16 stream; 85 86 list_add_tail(&ch->list, &q->out_chunk_list); 87 q->out_qlen += ch->skb->len; 88 89 stream = sctp_chunk_stream_no(ch); 90 oute = SCTP_SO(&q->asoc->stream, stream)->ext; 91 list_add_tail(&ch->stream_list, &oute->outq); 92 } 93 94 /* 95 * SFR-CACC algorithm: 96 * D) If count_of_newacks is greater than or equal to 2 97 * and t was not sent to the current primary then the 98 * sender MUST NOT increment missing report count for t. 99 */ 100 static inline int sctp_cacc_skip_3_1_d(struct sctp_transport *primary, 101 struct sctp_transport *transport, 102 int count_of_newacks) 103 { 104 if (count_of_newacks >= 2 && transport != primary) 105 return 1; 106 return 0; 107 } 108 109 /* 110 * SFR-CACC algorithm: 111 * F) If count_of_newacks is less than 2, let d be the 112 * destination to which t was sent. If cacc_saw_newack 113 * is 0 for destination d, then the sender MUST NOT 114 * increment missing report count for t. 115 */ 116 static inline int sctp_cacc_skip_3_1_f(struct sctp_transport *transport, 117 int count_of_newacks) 118 { 119 if (count_of_newacks < 2 && 120 (transport && !transport->cacc.cacc_saw_newack)) 121 return 1; 122 return 0; 123 } 124 125 /* 126 * SFR-CACC algorithm: 127 * 3.1) If CYCLING_CHANGEOVER is 0, the sender SHOULD 128 * execute steps C, D, F. 129 * 130 * C has been implemented in sctp_outq_sack 131 */ 132 static inline int sctp_cacc_skip_3_1(struct sctp_transport *primary, 133 struct sctp_transport *transport, 134 int count_of_newacks) 135 { 136 if (!primary->cacc.cycling_changeover) { 137 if (sctp_cacc_skip_3_1_d(primary, transport, count_of_newacks)) 138 return 1; 139 if (sctp_cacc_skip_3_1_f(transport, count_of_newacks)) 140 return 1; 141 return 0; 142 } 143 return 0; 144 } 145 146 /* 147 * SFR-CACC algorithm: 148 * 3.2) Else if CYCLING_CHANGEOVER is 1, and t is less 149 * than next_tsn_at_change of the current primary, then 150 * the sender MUST NOT increment missing report count 151 * for t. 152 */ 153 static inline int sctp_cacc_skip_3_2(struct sctp_transport *primary, __u32 tsn) 154 { 155 if (primary->cacc.cycling_changeover && 156 TSN_lt(tsn, primary->cacc.next_tsn_at_change)) 157 return 1; 158 return 0; 159 } 160 161 /* 162 * SFR-CACC algorithm: 163 * 3) If the missing report count for TSN t is to be 164 * incremented according to [RFC2960] and 165 * [SCTP_STEWART-2002], and CHANGEOVER_ACTIVE is set, 166 * then the sender MUST further execute steps 3.1 and 167 * 3.2 to determine if the missing report count for 168 * TSN t SHOULD NOT be incremented. 169 * 170 * 3.3) If 3.1 and 3.2 do not dictate that the missing 171 * report count for t should not be incremented, then 172 * the sender SHOULD increment missing report count for 173 * t (according to [RFC2960] and [SCTP_STEWART_2002]). 174 */ 175 static inline int sctp_cacc_skip(struct sctp_transport *primary, 176 struct sctp_transport *transport, 177 int count_of_newacks, 178 __u32 tsn) 179 { 180 if (primary->cacc.changeover_active && 181 (sctp_cacc_skip_3_1(primary, transport, count_of_newacks) || 182 sctp_cacc_skip_3_2(primary, tsn))) 183 return 1; 184 return 0; 185 } 186 187 /* Initialize an existing sctp_outq. This does the boring stuff. 188 * You still need to define handlers if you really want to DO 189 * something with this structure... 190 */ 191 void sctp_outq_init(struct sctp_association *asoc, struct sctp_outq *q) 192 { 193 memset(q, 0, sizeof(struct sctp_outq)); 194 195 q->asoc = asoc; 196 INIT_LIST_HEAD(&q->out_chunk_list); 197 INIT_LIST_HEAD(&q->control_chunk_list); 198 INIT_LIST_HEAD(&q->retransmit); 199 INIT_LIST_HEAD(&q->sacked); 200 INIT_LIST_HEAD(&q->abandoned); 201 sctp_sched_set_sched(asoc, sctp_sk(asoc->base.sk)->default_ss); 202 } 203 204 /* Free the outqueue structure and any related pending chunks. 205 */ 206 static void __sctp_outq_teardown(struct sctp_outq *q) 207 { 208 struct sctp_transport *transport; 209 struct list_head *lchunk, *temp; 210 struct sctp_chunk *chunk, *tmp; 211 212 /* Throw away unacknowledged chunks. */ 213 list_for_each_entry(transport, &q->asoc->peer.transport_addr_list, 214 transports) { 215 while ((lchunk = sctp_list_dequeue(&transport->transmitted)) != NULL) { 216 chunk = list_entry(lchunk, struct sctp_chunk, 217 transmitted_list); 218 /* Mark as part of a failed message. */ 219 sctp_chunk_fail(chunk, q->error); 220 sctp_chunk_free(chunk); 221 } 222 } 223 224 /* Throw away chunks that have been gap ACKed. */ 225 list_for_each_safe(lchunk, temp, &q->sacked) { 226 list_del_init(lchunk); 227 chunk = list_entry(lchunk, struct sctp_chunk, 228 transmitted_list); 229 sctp_chunk_fail(chunk, q->error); 230 sctp_chunk_free(chunk); 231 } 232 233 /* Throw away any chunks in the retransmit queue. */ 234 list_for_each_safe(lchunk, temp, &q->retransmit) { 235 list_del_init(lchunk); 236 chunk = list_entry(lchunk, struct sctp_chunk, 237 transmitted_list); 238 sctp_chunk_fail(chunk, q->error); 239 sctp_chunk_free(chunk); 240 } 241 242 /* Throw away any chunks that are in the abandoned queue. */ 243 list_for_each_safe(lchunk, temp, &q->abandoned) { 244 list_del_init(lchunk); 245 chunk = list_entry(lchunk, struct sctp_chunk, 246 transmitted_list); 247 sctp_chunk_fail(chunk, q->error); 248 sctp_chunk_free(chunk); 249 } 250 251 /* Throw away any leftover data chunks. */ 252 while ((chunk = sctp_outq_dequeue_data(q)) != NULL) { 253 sctp_sched_dequeue_done(q, chunk); 254 255 /* Mark as send failure. */ 256 sctp_chunk_fail(chunk, q->error); 257 sctp_chunk_free(chunk); 258 } 259 260 /* Throw away any leftover control chunks. */ 261 list_for_each_entry_safe(chunk, tmp, &q->control_chunk_list, list) { 262 list_del_init(&chunk->list); 263 sctp_chunk_free(chunk); 264 } 265 } 266 267 void sctp_outq_teardown(struct sctp_outq *q) 268 { 269 __sctp_outq_teardown(q); 270 sctp_outq_init(q->asoc, q); 271 } 272 273 /* Free the outqueue structure and any related pending chunks. */ 274 void sctp_outq_free(struct sctp_outq *q) 275 { 276 /* Throw away leftover chunks. */ 277 __sctp_outq_teardown(q); 278 } 279 280 /* Put a new chunk in an sctp_outq. */ 281 void sctp_outq_tail(struct sctp_outq *q, struct sctp_chunk *chunk, gfp_t gfp) 282 { 283 struct net *net = q->asoc->base.net; 284 285 pr_debug("%s: outq:%p, chunk:%p[%s]\n", __func__, q, chunk, 286 chunk && chunk->chunk_hdr ? 287 sctp_cname(SCTP_ST_CHUNK(chunk->chunk_hdr->type)) : 288 "illegal chunk"); 289 290 /* If it is data, queue it up, otherwise, send it 291 * immediately. 292 */ 293 if (sctp_chunk_is_data(chunk)) { 294 pr_debug("%s: outqueueing: outq:%p, chunk:%p[%s])\n", 295 __func__, q, chunk, chunk && chunk->chunk_hdr ? 296 sctp_cname(SCTP_ST_CHUNK(chunk->chunk_hdr->type)) : 297 "illegal chunk"); 298 299 sctp_outq_tail_data(q, chunk); 300 if (chunk->asoc->peer.prsctp_capable && 301 SCTP_PR_PRIO_ENABLED(chunk->sinfo.sinfo_flags)) 302 chunk->asoc->sent_cnt_removable++; 303 if (chunk->chunk_hdr->flags & SCTP_DATA_UNORDERED) 304 SCTP_INC_STATS(net, SCTP_MIB_OUTUNORDERCHUNKS); 305 else 306 SCTP_INC_STATS(net, SCTP_MIB_OUTORDERCHUNKS); 307 } else { 308 list_add_tail(&chunk->list, &q->control_chunk_list); 309 SCTP_INC_STATS(net, SCTP_MIB_OUTCTRLCHUNKS); 310 } 311 312 if (!q->cork) 313 sctp_outq_flush(q, 0, gfp); 314 } 315 316 /* Insert a chunk into the sorted list based on the TSNs. The retransmit list 317 * and the abandoned list are in ascending order. 318 */ 319 static void sctp_insert_list(struct list_head *head, struct list_head *new) 320 { 321 struct list_head *pos; 322 struct sctp_chunk *nchunk, *lchunk; 323 __u32 ntsn, ltsn; 324 int done = 0; 325 326 nchunk = list_entry(new, struct sctp_chunk, transmitted_list); 327 ntsn = ntohl(nchunk->subh.data_hdr->tsn); 328 329 list_for_each(pos, head) { 330 lchunk = list_entry(pos, struct sctp_chunk, transmitted_list); 331 ltsn = ntohl(lchunk->subh.data_hdr->tsn); 332 if (TSN_lt(ntsn, ltsn)) { 333 list_add(new, pos->prev); 334 done = 1; 335 break; 336 } 337 } 338 if (!done) 339 list_add_tail(new, head); 340 } 341 342 static int sctp_prsctp_prune_sent(struct sctp_association *asoc, 343 struct sctp_sndrcvinfo *sinfo, 344 struct list_head *queue, int msg_len) 345 { 346 struct sctp_chunk *chk, *temp; 347 348 list_for_each_entry_safe(chk, temp, queue, transmitted_list) { 349 struct sctp_stream_out *streamout; 350 351 if (!chk->msg->abandoned && 352 (!SCTP_PR_PRIO_ENABLED(chk->sinfo.sinfo_flags) || 353 chk->sinfo.sinfo_timetolive <= sinfo->sinfo_timetolive)) 354 continue; 355 356 chk->msg->abandoned = 1; 357 list_del_init(&chk->transmitted_list); 358 sctp_insert_list(&asoc->outqueue.abandoned, 359 &chk->transmitted_list); 360 361 streamout = SCTP_SO(&asoc->stream, chk->sinfo.sinfo_stream); 362 asoc->sent_cnt_removable--; 363 asoc->abandoned_sent[SCTP_PR_INDEX(PRIO)]++; 364 streamout->ext->abandoned_sent[SCTP_PR_INDEX(PRIO)]++; 365 366 if (queue != &asoc->outqueue.retransmit && 367 !chk->tsn_gap_acked) { 368 if (chk->transport) 369 chk->transport->flight_size -= 370 sctp_data_size(chk); 371 asoc->outqueue.outstanding_bytes -= sctp_data_size(chk); 372 } 373 374 msg_len -= chk->skb->truesize + sizeof(struct sctp_chunk); 375 if (msg_len <= 0) 376 break; 377 } 378 379 return msg_len; 380 } 381 382 static int sctp_prsctp_prune_unsent(struct sctp_association *asoc, 383 struct sctp_sndrcvinfo *sinfo, int msg_len) 384 { 385 struct sctp_outq *q = &asoc->outqueue; 386 struct sctp_chunk *chk, *temp; 387 388 q->sched->unsched_all(&asoc->stream); 389 390 list_for_each_entry_safe(chk, temp, &q->out_chunk_list, list) { 391 if (!chk->msg->abandoned && 392 (!(chk->chunk_hdr->flags & SCTP_DATA_FIRST_FRAG) || 393 !SCTP_PR_PRIO_ENABLED(chk->sinfo.sinfo_flags) || 394 chk->sinfo.sinfo_timetolive <= sinfo->sinfo_timetolive)) 395 continue; 396 397 chk->msg->abandoned = 1; 398 sctp_sched_dequeue_common(q, chk); 399 asoc->sent_cnt_removable--; 400 asoc->abandoned_unsent[SCTP_PR_INDEX(PRIO)]++; 401 if (chk->sinfo.sinfo_stream < asoc->stream.outcnt) { 402 struct sctp_stream_out *streamout = 403 SCTP_SO(&asoc->stream, chk->sinfo.sinfo_stream); 404 405 streamout->ext->abandoned_unsent[SCTP_PR_INDEX(PRIO)]++; 406 } 407 408 msg_len -= chk->skb->truesize + sizeof(struct sctp_chunk); 409 sctp_chunk_free(chk); 410 if (msg_len <= 0) 411 break; 412 } 413 414 q->sched->sched_all(&asoc->stream); 415 416 return msg_len; 417 } 418 419 /* Abandon the chunks according their priorities */ 420 void sctp_prsctp_prune(struct sctp_association *asoc, 421 struct sctp_sndrcvinfo *sinfo, int msg_len) 422 { 423 struct sctp_transport *transport; 424 425 if (!asoc->peer.prsctp_capable || !asoc->sent_cnt_removable) 426 return; 427 428 msg_len = sctp_prsctp_prune_sent(asoc, sinfo, 429 &asoc->outqueue.retransmit, 430 msg_len); 431 if (msg_len <= 0) 432 return; 433 434 list_for_each_entry(transport, &asoc->peer.transport_addr_list, 435 transports) { 436 msg_len = sctp_prsctp_prune_sent(asoc, sinfo, 437 &transport->transmitted, 438 msg_len); 439 if (msg_len <= 0) 440 return; 441 } 442 443 sctp_prsctp_prune_unsent(asoc, sinfo, msg_len); 444 } 445 446 /* Mark all the eligible packets on a transport for retransmission. */ 447 void sctp_retransmit_mark(struct sctp_outq *q, 448 struct sctp_transport *transport, 449 __u8 reason) 450 { 451 struct list_head *lchunk, *ltemp; 452 struct sctp_chunk *chunk; 453 454 /* Walk through the specified transmitted queue. */ 455 list_for_each_safe(lchunk, ltemp, &transport->transmitted) { 456 chunk = list_entry(lchunk, struct sctp_chunk, 457 transmitted_list); 458 459 /* If the chunk is abandoned, move it to abandoned list. */ 460 if (sctp_chunk_abandoned(chunk)) { 461 list_del_init(lchunk); 462 sctp_insert_list(&q->abandoned, lchunk); 463 464 /* If this chunk has not been previousely acked, 465 * stop considering it 'outstanding'. Our peer 466 * will most likely never see it since it will 467 * not be retransmitted 468 */ 469 if (!chunk->tsn_gap_acked) { 470 if (chunk->transport) 471 chunk->transport->flight_size -= 472 sctp_data_size(chunk); 473 q->outstanding_bytes -= sctp_data_size(chunk); 474 q->asoc->peer.rwnd += sctp_data_size(chunk); 475 } 476 continue; 477 } 478 479 /* If we are doing retransmission due to a timeout or pmtu 480 * discovery, only the chunks that are not yet acked should 481 * be added to the retransmit queue. 482 */ 483 if ((reason == SCTP_RTXR_FAST_RTX && 484 (chunk->fast_retransmit == SCTP_NEED_FRTX)) || 485 (reason != SCTP_RTXR_FAST_RTX && !chunk->tsn_gap_acked)) { 486 /* RFC 2960 6.2.1 Processing a Received SACK 487 * 488 * C) Any time a DATA chunk is marked for 489 * retransmission (via either T3-rtx timer expiration 490 * (Section 6.3.3) or via fast retransmit 491 * (Section 7.2.4)), add the data size of those 492 * chunks to the rwnd. 493 */ 494 q->asoc->peer.rwnd += sctp_data_size(chunk); 495 q->outstanding_bytes -= sctp_data_size(chunk); 496 if (chunk->transport) 497 transport->flight_size -= sctp_data_size(chunk); 498 499 /* sctpimpguide-05 Section 2.8.2 500 * M5) If a T3-rtx timer expires, the 501 * 'TSN.Missing.Report' of all affected TSNs is set 502 * to 0. 503 */ 504 chunk->tsn_missing_report = 0; 505 506 /* If a chunk that is being used for RTT measurement 507 * has to be retransmitted, we cannot use this chunk 508 * anymore for RTT measurements. Reset rto_pending so 509 * that a new RTT measurement is started when a new 510 * data chunk is sent. 511 */ 512 if (chunk->rtt_in_progress) { 513 chunk->rtt_in_progress = 0; 514 transport->rto_pending = 0; 515 } 516 517 /* Move the chunk to the retransmit queue. The chunks 518 * on the retransmit queue are always kept in order. 519 */ 520 list_del_init(lchunk); 521 sctp_insert_list(&q->retransmit, lchunk); 522 } 523 } 524 525 pr_debug("%s: transport:%p, reason:%d, cwnd:%d, ssthresh:%d, " 526 "flight_size:%d, pba:%d\n", __func__, transport, reason, 527 transport->cwnd, transport->ssthresh, transport->flight_size, 528 transport->partial_bytes_acked); 529 } 530 531 /* Mark all the eligible packets on a transport for retransmission and force 532 * one packet out. 533 */ 534 void sctp_retransmit(struct sctp_outq *q, struct sctp_transport *transport, 535 enum sctp_retransmit_reason reason) 536 { 537 struct net *net = q->asoc->base.net; 538 539 switch (reason) { 540 case SCTP_RTXR_T3_RTX: 541 SCTP_INC_STATS(net, SCTP_MIB_T3_RETRANSMITS); 542 sctp_transport_lower_cwnd(transport, SCTP_LOWER_CWND_T3_RTX); 543 /* Update the retran path if the T3-rtx timer has expired for 544 * the current retran path. 545 */ 546 if (transport == transport->asoc->peer.retran_path) 547 sctp_assoc_update_retran_path(transport->asoc); 548 transport->asoc->rtx_data_chunks += 549 transport->asoc->unack_data; 550 if (transport->pl.state == SCTP_PL_COMPLETE && 551 transport->asoc->unack_data) 552 sctp_transport_reset_probe_timer(transport); 553 break; 554 case SCTP_RTXR_FAST_RTX: 555 SCTP_INC_STATS(net, SCTP_MIB_FAST_RETRANSMITS); 556 sctp_transport_lower_cwnd(transport, SCTP_LOWER_CWND_FAST_RTX); 557 q->fast_rtx = 1; 558 break; 559 case SCTP_RTXR_PMTUD: 560 SCTP_INC_STATS(net, SCTP_MIB_PMTUD_RETRANSMITS); 561 break; 562 case SCTP_RTXR_T1_RTX: 563 SCTP_INC_STATS(net, SCTP_MIB_T1_RETRANSMITS); 564 transport->asoc->init_retries++; 565 break; 566 default: 567 BUG(); 568 } 569 570 sctp_retransmit_mark(q, transport, reason); 571 572 /* PR-SCTP A5) Any time the T3-rtx timer expires, on any destination, 573 * the sender SHOULD try to advance the "Advanced.Peer.Ack.Point" by 574 * following the procedures outlined in C1 - C5. 575 */ 576 if (reason == SCTP_RTXR_T3_RTX) 577 q->asoc->stream.si->generate_ftsn(q, q->asoc->ctsn_ack_point); 578 579 /* Flush the queues only on timeout, since fast_rtx is only 580 * triggered during sack processing and the queue 581 * will be flushed at the end. 582 */ 583 if (reason != SCTP_RTXR_FAST_RTX) 584 sctp_outq_flush(q, /* rtx_timeout */ 1, GFP_ATOMIC); 585 } 586 587 /* 588 * Transmit DATA chunks on the retransmit queue. Upon return from 589 * __sctp_outq_flush_rtx() the packet 'pkt' may contain chunks which 590 * need to be transmitted by the caller. 591 * We assume that pkt->transport has already been set. 592 * 593 * The return value is a normal kernel error return value. 594 */ 595 static int __sctp_outq_flush_rtx(struct sctp_outq *q, struct sctp_packet *pkt, 596 int rtx_timeout, int *start_timer, gfp_t gfp) 597 { 598 struct sctp_transport *transport = pkt->transport; 599 struct sctp_chunk *chunk, *chunk1; 600 struct list_head *lqueue; 601 enum sctp_xmit status; 602 int error = 0; 603 int timer = 0; 604 int done = 0; 605 int fast_rtx; 606 607 lqueue = &q->retransmit; 608 fast_rtx = q->fast_rtx; 609 610 /* This loop handles time-out retransmissions, fast retransmissions, 611 * and retransmissions due to opening of whindow. 612 * 613 * RFC 2960 6.3.3 Handle T3-rtx Expiration 614 * 615 * E3) Determine how many of the earliest (i.e., lowest TSN) 616 * outstanding DATA chunks for the address for which the 617 * T3-rtx has expired will fit into a single packet, subject 618 * to the MTU constraint for the path corresponding to the 619 * destination transport address to which the retransmission 620 * is being sent (this may be different from the address for 621 * which the timer expires [see Section 6.4]). Call this value 622 * K. Bundle and retransmit those K DATA chunks in a single 623 * packet to the destination endpoint. 624 * 625 * [Just to be painfully clear, if we are retransmitting 626 * because a timeout just happened, we should send only ONE 627 * packet of retransmitted data.] 628 * 629 * For fast retransmissions we also send only ONE packet. However, 630 * if we are just flushing the queue due to open window, we'll 631 * try to send as much as possible. 632 */ 633 list_for_each_entry_safe(chunk, chunk1, lqueue, transmitted_list) { 634 /* If the chunk is abandoned, move it to abandoned list. */ 635 if (sctp_chunk_abandoned(chunk)) { 636 list_del_init(&chunk->transmitted_list); 637 sctp_insert_list(&q->abandoned, 638 &chunk->transmitted_list); 639 continue; 640 } 641 642 /* Make sure that Gap Acked TSNs are not retransmitted. A 643 * simple approach is just to move such TSNs out of the 644 * way and into a 'transmitted' queue and skip to the 645 * next chunk. 646 */ 647 if (chunk->tsn_gap_acked) { 648 list_move_tail(&chunk->transmitted_list, 649 &transport->transmitted); 650 continue; 651 } 652 653 /* If we are doing fast retransmit, ignore non-fast_rtransmit 654 * chunks 655 */ 656 if (fast_rtx && !chunk->fast_retransmit) 657 continue; 658 659 redo: 660 /* Attempt to append this chunk to the packet. */ 661 status = sctp_packet_append_chunk(pkt, chunk); 662 663 switch (status) { 664 case SCTP_XMIT_PMTU_FULL: 665 if (!pkt->has_data && !pkt->has_cookie_echo) { 666 /* If this packet did not contain DATA then 667 * retransmission did not happen, so do it 668 * again. We'll ignore the error here since 669 * control chunks are already freed so there 670 * is nothing we can do. 671 */ 672 sctp_packet_transmit(pkt, gfp); 673 goto redo; 674 } 675 676 /* Send this packet. */ 677 error = sctp_packet_transmit(pkt, gfp); 678 679 /* If we are retransmitting, we should only 680 * send a single packet. 681 * Otherwise, try appending this chunk again. 682 */ 683 if (rtx_timeout || fast_rtx) 684 done = 1; 685 else 686 goto redo; 687 688 /* Bundle next chunk in the next round. */ 689 break; 690 691 case SCTP_XMIT_RWND_FULL: 692 /* Send this packet. */ 693 error = sctp_packet_transmit(pkt, gfp); 694 695 /* Stop sending DATA as there is no more room 696 * at the receiver. 697 */ 698 done = 1; 699 break; 700 701 case SCTP_XMIT_DELAY: 702 /* Send this packet. */ 703 error = sctp_packet_transmit(pkt, gfp); 704 705 /* Stop sending DATA because of nagle delay. */ 706 done = 1; 707 break; 708 709 default: 710 /* The append was successful, so add this chunk to 711 * the transmitted list. 712 */ 713 list_move_tail(&chunk->transmitted_list, 714 &transport->transmitted); 715 716 /* Mark the chunk as ineligible for fast retransmit 717 * after it is retransmitted. 718 */ 719 if (chunk->fast_retransmit == SCTP_NEED_FRTX) 720 chunk->fast_retransmit = SCTP_DONT_FRTX; 721 722 q->asoc->stats.rtxchunks++; 723 break; 724 } 725 726 /* Set the timer if there were no errors */ 727 if (!error && !timer) 728 timer = 1; 729 730 if (done) 731 break; 732 } 733 734 /* If we are here due to a retransmit timeout or a fast 735 * retransmit and if there are any chunks left in the retransmit 736 * queue that could not fit in the PMTU sized packet, they need 737 * to be marked as ineligible for a subsequent fast retransmit. 738 */ 739 if (rtx_timeout || fast_rtx) { 740 list_for_each_entry(chunk1, lqueue, transmitted_list) { 741 if (chunk1->fast_retransmit == SCTP_NEED_FRTX) 742 chunk1->fast_retransmit = SCTP_DONT_FRTX; 743 } 744 } 745 746 *start_timer = timer; 747 748 /* Clear fast retransmit hint */ 749 if (fast_rtx) 750 q->fast_rtx = 0; 751 752 return error; 753 } 754 755 /* Cork the outqueue so queued chunks are really queued. */ 756 void sctp_outq_uncork(struct sctp_outq *q, gfp_t gfp) 757 { 758 if (q->cork) 759 q->cork = 0; 760 761 sctp_outq_flush(q, 0, gfp); 762 } 763 764 static int sctp_packet_singleton(struct sctp_transport *transport, 765 struct sctp_chunk *chunk, gfp_t gfp) 766 { 767 const struct sctp_association *asoc = transport->asoc; 768 const __u16 sport = asoc->base.bind_addr.port; 769 const __u16 dport = asoc->peer.port; 770 const __u32 vtag = asoc->peer.i.init_tag; 771 struct sctp_packet singleton; 772 773 sctp_packet_init(&singleton, transport, sport, dport); 774 sctp_packet_config(&singleton, vtag, 0); 775 if (sctp_packet_append_chunk(&singleton, chunk) != SCTP_XMIT_OK) { 776 list_del_init(&chunk->list); 777 sctp_chunk_free(chunk); 778 return -ENOMEM; 779 } 780 return sctp_packet_transmit(&singleton, gfp); 781 } 782 783 /* Struct to hold the context during sctp outq flush */ 784 struct sctp_flush_ctx { 785 struct sctp_outq *q; 786 /* Current transport being used. It's NOT the same as curr active one */ 787 struct sctp_transport *transport; 788 /* These transports have chunks to send. */ 789 struct list_head transport_list; 790 struct sctp_association *asoc; 791 /* Packet on the current transport above */ 792 struct sctp_packet *packet; 793 gfp_t gfp; 794 }; 795 796 /* transport: current transport */ 797 static void sctp_outq_select_transport(struct sctp_flush_ctx *ctx, 798 struct sctp_chunk *chunk) 799 { 800 struct sctp_transport *new_transport = chunk->transport; 801 802 if (!new_transport) { 803 if (!sctp_chunk_is_data(chunk)) { 804 /* If we have a prior transport pointer, see if 805 * the destination address of the chunk 806 * matches the destination address of the 807 * current transport. If not a match, then 808 * try to look up the transport with a given 809 * destination address. We do this because 810 * after processing ASCONFs, we may have new 811 * transports created. 812 */ 813 if (ctx->transport && sctp_cmp_addr_exact(&chunk->dest, 814 &ctx->transport->ipaddr)) 815 new_transport = ctx->transport; 816 else 817 new_transport = sctp_assoc_lookup_paddr(ctx->asoc, 818 &chunk->dest); 819 } 820 821 /* if we still don't have a new transport, then 822 * use the current active path. 823 */ 824 if (!new_transport) 825 new_transport = ctx->asoc->peer.active_path; 826 } else { 827 __u8 type; 828 829 switch (new_transport->state) { 830 case SCTP_INACTIVE: 831 case SCTP_UNCONFIRMED: 832 case SCTP_PF: 833 /* If the chunk is Heartbeat or Heartbeat Ack, 834 * send it to chunk->transport, even if it's 835 * inactive. 836 * 837 * 3.3.6 Heartbeat Acknowledgement: 838 * ... 839 * A HEARTBEAT ACK is always sent to the source IP 840 * address of the IP datagram containing the 841 * HEARTBEAT chunk to which this ack is responding. 842 * ... 843 * 844 * ASCONF_ACKs also must be sent to the source. 845 */ 846 type = chunk->chunk_hdr->type; 847 if (type != SCTP_CID_HEARTBEAT && 848 type != SCTP_CID_HEARTBEAT_ACK && 849 type != SCTP_CID_ASCONF_ACK) 850 new_transport = ctx->asoc->peer.active_path; 851 break; 852 default: 853 break; 854 } 855 } 856 857 /* Are we switching transports? Take care of transport locks. */ 858 if (new_transport != ctx->transport) { 859 ctx->transport = new_transport; 860 ctx->packet = &ctx->transport->packet; 861 862 if (list_empty(&ctx->transport->send_ready)) 863 list_add_tail(&ctx->transport->send_ready, 864 &ctx->transport_list); 865 866 sctp_packet_config(ctx->packet, 867 ctx->asoc->peer.i.init_tag, 868 ctx->asoc->peer.ecn_capable); 869 /* We've switched transports, so apply the 870 * Burst limit to the new transport. 871 */ 872 sctp_transport_burst_limited(ctx->transport); 873 } 874 } 875 876 static void sctp_outq_flush_ctrl(struct sctp_flush_ctx *ctx) 877 { 878 struct sctp_chunk *chunk, *tmp; 879 enum sctp_xmit status; 880 int one_packet, error; 881 882 list_for_each_entry_safe(chunk, tmp, &ctx->q->control_chunk_list, list) { 883 one_packet = 0; 884 885 /* RFC 5061, 5.3 886 * F1) This means that until such time as the ASCONF 887 * containing the add is acknowledged, the sender MUST 888 * NOT use the new IP address as a source for ANY SCTP 889 * packet except on carrying an ASCONF Chunk. 890 */ 891 if (ctx->asoc->src_out_of_asoc_ok && 892 chunk->chunk_hdr->type != SCTP_CID_ASCONF) 893 continue; 894 895 list_del_init(&chunk->list); 896 897 /* Pick the right transport to use. Should always be true for 898 * the first chunk as we don't have a transport by then. 899 */ 900 sctp_outq_select_transport(ctx, chunk); 901 902 switch (chunk->chunk_hdr->type) { 903 /* 6.10 Bundling 904 * ... 905 * An endpoint MUST NOT bundle INIT, INIT ACK or SHUTDOWN 906 * COMPLETE with any other chunks. [Send them immediately.] 907 */ 908 case SCTP_CID_INIT: 909 case SCTP_CID_INIT_ACK: 910 case SCTP_CID_SHUTDOWN_COMPLETE: 911 error = sctp_packet_singleton(ctx->transport, chunk, 912 ctx->gfp); 913 if (error < 0) { 914 ctx->asoc->base.sk->sk_err = -error; 915 return; 916 } 917 break; 918 919 case SCTP_CID_ABORT: 920 if (sctp_test_T_bit(chunk)) 921 ctx->packet->vtag = ctx->asoc->c.my_vtag; 922 fallthrough; 923 924 /* The following chunks are "response" chunks, i.e. 925 * they are generated in response to something we 926 * received. If we are sending these, then we can 927 * send only 1 packet containing these chunks. 928 */ 929 case SCTP_CID_HEARTBEAT_ACK: 930 case SCTP_CID_SHUTDOWN_ACK: 931 case SCTP_CID_COOKIE_ACK: 932 case SCTP_CID_COOKIE_ECHO: 933 case SCTP_CID_ERROR: 934 case SCTP_CID_ECN_CWR: 935 case SCTP_CID_ASCONF_ACK: 936 one_packet = 1; 937 fallthrough; 938 939 case SCTP_CID_HEARTBEAT: 940 if (chunk->pmtu_probe) { 941 sctp_packet_singleton(ctx->transport, chunk, ctx->gfp); 942 break; 943 } 944 fallthrough; 945 case SCTP_CID_SACK: 946 case SCTP_CID_SHUTDOWN: 947 case SCTP_CID_ECN_ECNE: 948 case SCTP_CID_ASCONF: 949 case SCTP_CID_FWD_TSN: 950 case SCTP_CID_I_FWD_TSN: 951 case SCTP_CID_RECONF: 952 status = sctp_packet_transmit_chunk(ctx->packet, chunk, 953 one_packet, ctx->gfp); 954 if (status != SCTP_XMIT_OK) { 955 /* put the chunk back */ 956 list_add(&chunk->list, &ctx->q->control_chunk_list); 957 break; 958 } 959 960 ctx->asoc->stats.octrlchunks++; 961 /* PR-SCTP C5) If a FORWARD TSN is sent, the 962 * sender MUST assure that at least one T3-rtx 963 * timer is running. 964 */ 965 if (chunk->chunk_hdr->type == SCTP_CID_FWD_TSN || 966 chunk->chunk_hdr->type == SCTP_CID_I_FWD_TSN) { 967 sctp_transport_reset_t3_rtx(ctx->transport); 968 ctx->transport->last_time_sent = jiffies; 969 } 970 971 if (chunk == ctx->asoc->strreset_chunk) 972 sctp_transport_reset_reconf_timer(ctx->transport); 973 974 break; 975 976 default: 977 /* We built a chunk with an illegal type! */ 978 BUG(); 979 } 980 } 981 } 982 983 /* Returns false if new data shouldn't be sent */ 984 static bool sctp_outq_flush_rtx(struct sctp_flush_ctx *ctx, 985 int rtx_timeout) 986 { 987 int error, start_timer = 0; 988 989 if (ctx->asoc->peer.retran_path->state == SCTP_UNCONFIRMED) 990 return false; 991 992 if (ctx->transport != ctx->asoc->peer.retran_path) { 993 /* Switch transports & prepare the packet. */ 994 ctx->transport = ctx->asoc->peer.retran_path; 995 ctx->packet = &ctx->transport->packet; 996 997 if (list_empty(&ctx->transport->send_ready)) 998 list_add_tail(&ctx->transport->send_ready, 999 &ctx->transport_list); 1000 1001 sctp_packet_config(ctx->packet, ctx->asoc->peer.i.init_tag, 1002 ctx->asoc->peer.ecn_capable); 1003 } 1004 1005 error = __sctp_outq_flush_rtx(ctx->q, ctx->packet, rtx_timeout, 1006 &start_timer, ctx->gfp); 1007 if (error < 0) 1008 ctx->asoc->base.sk->sk_err = -error; 1009 1010 if (start_timer) { 1011 sctp_transport_reset_t3_rtx(ctx->transport); 1012 ctx->transport->last_time_sent = jiffies; 1013 } 1014 1015 /* This can happen on COOKIE-ECHO resend. Only 1016 * one chunk can get bundled with a COOKIE-ECHO. 1017 */ 1018 if (ctx->packet->has_cookie_echo) 1019 return false; 1020 1021 /* Don't send new data if there is still data 1022 * waiting to retransmit. 1023 */ 1024 if (!list_empty(&ctx->q->retransmit)) 1025 return false; 1026 1027 return true; 1028 } 1029 1030 static void sctp_outq_flush_data(struct sctp_flush_ctx *ctx, 1031 int rtx_timeout) 1032 { 1033 struct sctp_chunk *chunk; 1034 enum sctp_xmit status; 1035 1036 /* Is it OK to send data chunks? */ 1037 switch (ctx->asoc->state) { 1038 case SCTP_STATE_COOKIE_ECHOED: 1039 /* Only allow bundling when this packet has a COOKIE-ECHO 1040 * chunk. 1041 */ 1042 if (!ctx->packet || !ctx->packet->has_cookie_echo) 1043 return; 1044 1045 fallthrough; 1046 case SCTP_STATE_ESTABLISHED: 1047 case SCTP_STATE_SHUTDOWN_PENDING: 1048 case SCTP_STATE_SHUTDOWN_RECEIVED: 1049 break; 1050 1051 default: 1052 /* Do nothing. */ 1053 return; 1054 } 1055 1056 /* RFC 2960 6.1 Transmission of DATA Chunks 1057 * 1058 * C) When the time comes for the sender to transmit, 1059 * before sending new DATA chunks, the sender MUST 1060 * first transmit any outstanding DATA chunks which 1061 * are marked for retransmission (limited by the 1062 * current cwnd). 1063 */ 1064 if (!list_empty(&ctx->q->retransmit) && 1065 !sctp_outq_flush_rtx(ctx, rtx_timeout)) 1066 return; 1067 1068 /* Apply Max.Burst limitation to the current transport in 1069 * case it will be used for new data. We are going to 1070 * rest it before we return, but we want to apply the limit 1071 * to the currently queued data. 1072 */ 1073 if (ctx->transport) 1074 sctp_transport_burst_limited(ctx->transport); 1075 1076 /* Finally, transmit new packets. */ 1077 while ((chunk = sctp_outq_dequeue_data(ctx->q)) != NULL) { 1078 __u32 sid = ntohs(chunk->subh.data_hdr->stream); 1079 __u8 stream_state = SCTP_SO(&ctx->asoc->stream, sid)->state; 1080 1081 /* Has this chunk expired? */ 1082 if (sctp_chunk_abandoned(chunk)) { 1083 sctp_sched_dequeue_done(ctx->q, chunk); 1084 sctp_chunk_fail(chunk, 0); 1085 sctp_chunk_free(chunk); 1086 continue; 1087 } 1088 1089 if (stream_state == SCTP_STREAM_CLOSED) { 1090 sctp_outq_head_data(ctx->q, chunk); 1091 break; 1092 } 1093 1094 sctp_outq_select_transport(ctx, chunk); 1095 1096 pr_debug("%s: outq:%p, chunk:%p[%s], tx-tsn:0x%x skb->head:%p skb->users:%d\n", 1097 __func__, ctx->q, chunk, chunk && chunk->chunk_hdr ? 1098 sctp_cname(SCTP_ST_CHUNK(chunk->chunk_hdr->type)) : 1099 "illegal chunk", ntohl(chunk->subh.data_hdr->tsn), 1100 chunk->skb ? chunk->skb->head : NULL, chunk->skb ? 1101 refcount_read(&chunk->skb->users) : -1); 1102 1103 /* Add the chunk to the packet. */ 1104 status = sctp_packet_transmit_chunk(ctx->packet, chunk, 0, 1105 ctx->gfp); 1106 if (status != SCTP_XMIT_OK) { 1107 /* We could not append this chunk, so put 1108 * the chunk back on the output queue. 1109 */ 1110 pr_debug("%s: could not transmit tsn:0x%x, status:%d\n", 1111 __func__, ntohl(chunk->subh.data_hdr->tsn), 1112 status); 1113 1114 sctp_outq_head_data(ctx->q, chunk); 1115 break; 1116 } 1117 1118 /* The sender is in the SHUTDOWN-PENDING state, 1119 * The sender MAY set the I-bit in the DATA 1120 * chunk header. 1121 */ 1122 if (ctx->asoc->state == SCTP_STATE_SHUTDOWN_PENDING) 1123 chunk->chunk_hdr->flags |= SCTP_DATA_SACK_IMM; 1124 if (chunk->chunk_hdr->flags & SCTP_DATA_UNORDERED) 1125 ctx->asoc->stats.ouodchunks++; 1126 else 1127 ctx->asoc->stats.oodchunks++; 1128 1129 /* Only now it's safe to consider this 1130 * chunk as sent, sched-wise. 1131 */ 1132 sctp_sched_dequeue_done(ctx->q, chunk); 1133 1134 list_add_tail(&chunk->transmitted_list, 1135 &ctx->transport->transmitted); 1136 1137 sctp_transport_reset_t3_rtx(ctx->transport); 1138 ctx->transport->last_time_sent = jiffies; 1139 1140 /* Only let one DATA chunk get bundled with a 1141 * COOKIE-ECHO chunk. 1142 */ 1143 if (ctx->packet->has_cookie_echo) 1144 break; 1145 } 1146 } 1147 1148 static void sctp_outq_flush_transports(struct sctp_flush_ctx *ctx) 1149 { 1150 struct sock *sk = ctx->asoc->base.sk; 1151 struct list_head *ltransport; 1152 struct sctp_packet *packet; 1153 struct sctp_transport *t; 1154 int error = 0; 1155 1156 while ((ltransport = sctp_list_dequeue(&ctx->transport_list)) != NULL) { 1157 t = list_entry(ltransport, struct sctp_transport, send_ready); 1158 packet = &t->packet; 1159 if (!sctp_packet_empty(packet)) { 1160 rcu_read_lock(); 1161 if (t->dst && __sk_dst_get(sk) != t->dst) { 1162 dst_hold(t->dst); 1163 sk_setup_caps(sk, t->dst); 1164 } 1165 rcu_read_unlock(); 1166 error = sctp_packet_transmit(packet, ctx->gfp); 1167 if (error < 0) 1168 ctx->q->asoc->base.sk->sk_err = -error; 1169 } 1170 1171 /* Clear the burst limited state, if any */ 1172 sctp_transport_burst_reset(t); 1173 } 1174 } 1175 1176 /* Try to flush an outqueue. 1177 * 1178 * Description: Send everything in q which we legally can, subject to 1179 * congestion limitations. 1180 * * Note: This function can be called from multiple contexts so appropriate 1181 * locking concerns must be made. Today we use the sock lock to protect 1182 * this function. 1183 */ 1184 1185 static void sctp_outq_flush(struct sctp_outq *q, int rtx_timeout, gfp_t gfp) 1186 { 1187 struct sctp_flush_ctx ctx = { 1188 .q = q, 1189 .transport = NULL, 1190 .transport_list = LIST_HEAD_INIT(ctx.transport_list), 1191 .asoc = q->asoc, 1192 .packet = NULL, 1193 .gfp = gfp, 1194 }; 1195 1196 /* 6.10 Bundling 1197 * ... 1198 * When bundling control chunks with DATA chunks, an 1199 * endpoint MUST place control chunks first in the outbound 1200 * SCTP packet. The transmitter MUST transmit DATA chunks 1201 * within a SCTP packet in increasing order of TSN. 1202 * ... 1203 */ 1204 1205 sctp_outq_flush_ctrl(&ctx); 1206 1207 if (q->asoc->src_out_of_asoc_ok) 1208 goto sctp_flush_out; 1209 1210 sctp_outq_flush_data(&ctx, rtx_timeout); 1211 1212 sctp_flush_out: 1213 1214 sctp_outq_flush_transports(&ctx); 1215 } 1216 1217 /* Update unack_data based on the incoming SACK chunk */ 1218 static void sctp_sack_update_unack_data(struct sctp_association *assoc, 1219 struct sctp_sackhdr *sack) 1220 { 1221 union sctp_sack_variable *frags; 1222 __u16 unack_data; 1223 int i; 1224 1225 unack_data = assoc->next_tsn - assoc->ctsn_ack_point - 1; 1226 1227 frags = sack->variable; 1228 for (i = 0; i < ntohs(sack->num_gap_ack_blocks); i++) { 1229 unack_data -= ((ntohs(frags[i].gab.end) - 1230 ntohs(frags[i].gab.start) + 1)); 1231 } 1232 1233 assoc->unack_data = unack_data; 1234 } 1235 1236 /* This is where we REALLY process a SACK. 1237 * 1238 * Process the SACK against the outqueue. Mostly, this just frees 1239 * things off the transmitted queue. 1240 */ 1241 int sctp_outq_sack(struct sctp_outq *q, struct sctp_chunk *chunk) 1242 { 1243 struct sctp_association *asoc = q->asoc; 1244 struct sctp_sackhdr *sack = chunk->subh.sack_hdr; 1245 struct sctp_transport *transport; 1246 struct sctp_chunk *tchunk = NULL; 1247 struct list_head *lchunk, *transport_list, *temp; 1248 union sctp_sack_variable *frags = sack->variable; 1249 __u32 sack_ctsn, ctsn, tsn; 1250 __u32 highest_tsn, highest_new_tsn; 1251 __u32 sack_a_rwnd; 1252 unsigned int outstanding; 1253 struct sctp_transport *primary = asoc->peer.primary_path; 1254 int count_of_newacks = 0; 1255 int gap_ack_blocks; 1256 u8 accum_moved = 0; 1257 1258 /* Grab the association's destination address list. */ 1259 transport_list = &asoc->peer.transport_addr_list; 1260 1261 /* SCTP path tracepoint for congestion control debugging. */ 1262 if (trace_sctp_probe_path_enabled()) { 1263 list_for_each_entry(transport, transport_list, transports) 1264 trace_sctp_probe_path(transport, asoc); 1265 } 1266 1267 sack_ctsn = ntohl(sack->cum_tsn_ack); 1268 gap_ack_blocks = ntohs(sack->num_gap_ack_blocks); 1269 asoc->stats.gapcnt += gap_ack_blocks; 1270 /* 1271 * SFR-CACC algorithm: 1272 * On receipt of a SACK the sender SHOULD execute the 1273 * following statements. 1274 * 1275 * 1) If the cumulative ack in the SACK passes next tsn_at_change 1276 * on the current primary, the CHANGEOVER_ACTIVE flag SHOULD be 1277 * cleared. The CYCLING_CHANGEOVER flag SHOULD also be cleared for 1278 * all destinations. 1279 * 2) If the SACK contains gap acks and the flag CHANGEOVER_ACTIVE 1280 * is set the receiver of the SACK MUST take the following actions: 1281 * 1282 * A) Initialize the cacc_saw_newack to 0 for all destination 1283 * addresses. 1284 * 1285 * Only bother if changeover_active is set. Otherwise, this is 1286 * totally suboptimal to do on every SACK. 1287 */ 1288 if (primary->cacc.changeover_active) { 1289 u8 clear_cycling = 0; 1290 1291 if (TSN_lte(primary->cacc.next_tsn_at_change, sack_ctsn)) { 1292 primary->cacc.changeover_active = 0; 1293 clear_cycling = 1; 1294 } 1295 1296 if (clear_cycling || gap_ack_blocks) { 1297 list_for_each_entry(transport, transport_list, 1298 transports) { 1299 if (clear_cycling) 1300 transport->cacc.cycling_changeover = 0; 1301 if (gap_ack_blocks) 1302 transport->cacc.cacc_saw_newack = 0; 1303 } 1304 } 1305 } 1306 1307 /* Get the highest TSN in the sack. */ 1308 highest_tsn = sack_ctsn; 1309 if (gap_ack_blocks) 1310 highest_tsn += ntohs(frags[gap_ack_blocks - 1].gab.end); 1311 1312 if (TSN_lt(asoc->highest_sacked, highest_tsn)) 1313 asoc->highest_sacked = highest_tsn; 1314 1315 highest_new_tsn = sack_ctsn; 1316 1317 /* Run through the retransmit queue. Credit bytes received 1318 * and free those chunks that we can. 1319 */ 1320 sctp_check_transmitted(q, &q->retransmit, NULL, NULL, sack, &highest_new_tsn); 1321 1322 /* Run through the transmitted queue. 1323 * Credit bytes received and free those chunks which we can. 1324 * 1325 * This is a MASSIVE candidate for optimization. 1326 */ 1327 list_for_each_entry(transport, transport_list, transports) { 1328 sctp_check_transmitted(q, &transport->transmitted, 1329 transport, &chunk->source, sack, 1330 &highest_new_tsn); 1331 /* 1332 * SFR-CACC algorithm: 1333 * C) Let count_of_newacks be the number of 1334 * destinations for which cacc_saw_newack is set. 1335 */ 1336 if (transport->cacc.cacc_saw_newack) 1337 count_of_newacks++; 1338 } 1339 1340 /* Move the Cumulative TSN Ack Point if appropriate. */ 1341 if (TSN_lt(asoc->ctsn_ack_point, sack_ctsn)) { 1342 asoc->ctsn_ack_point = sack_ctsn; 1343 accum_moved = 1; 1344 } 1345 1346 if (gap_ack_blocks) { 1347 1348 if (asoc->fast_recovery && accum_moved) 1349 highest_new_tsn = highest_tsn; 1350 1351 list_for_each_entry(transport, transport_list, transports) 1352 sctp_mark_missing(q, &transport->transmitted, transport, 1353 highest_new_tsn, count_of_newacks); 1354 } 1355 1356 /* Update unack_data field in the assoc. */ 1357 sctp_sack_update_unack_data(asoc, sack); 1358 1359 ctsn = asoc->ctsn_ack_point; 1360 1361 /* Throw away stuff rotting on the sack queue. */ 1362 list_for_each_safe(lchunk, temp, &q->sacked) { 1363 tchunk = list_entry(lchunk, struct sctp_chunk, 1364 transmitted_list); 1365 tsn = ntohl(tchunk->subh.data_hdr->tsn); 1366 if (TSN_lte(tsn, ctsn)) { 1367 list_del_init(&tchunk->transmitted_list); 1368 if (asoc->peer.prsctp_capable && 1369 SCTP_PR_PRIO_ENABLED(chunk->sinfo.sinfo_flags)) 1370 asoc->sent_cnt_removable--; 1371 sctp_chunk_free(tchunk); 1372 } 1373 } 1374 1375 /* ii) Set rwnd equal to the newly received a_rwnd minus the 1376 * number of bytes still outstanding after processing the 1377 * Cumulative TSN Ack and the Gap Ack Blocks. 1378 */ 1379 1380 sack_a_rwnd = ntohl(sack->a_rwnd); 1381 asoc->peer.zero_window_announced = !sack_a_rwnd; 1382 outstanding = q->outstanding_bytes; 1383 1384 if (outstanding < sack_a_rwnd) 1385 sack_a_rwnd -= outstanding; 1386 else 1387 sack_a_rwnd = 0; 1388 1389 asoc->peer.rwnd = sack_a_rwnd; 1390 1391 asoc->stream.si->generate_ftsn(q, sack_ctsn); 1392 1393 pr_debug("%s: sack cumulative tsn ack:0x%x\n", __func__, sack_ctsn); 1394 pr_debug("%s: cumulative tsn ack of assoc:%p is 0x%x, " 1395 "advertised peer ack point:0x%x\n", __func__, asoc, ctsn, 1396 asoc->adv_peer_ack_point); 1397 1398 return sctp_outq_is_empty(q); 1399 } 1400 1401 /* Is the outqueue empty? 1402 * The queue is empty when we have not pending data, no in-flight data 1403 * and nothing pending retransmissions. 1404 */ 1405 int sctp_outq_is_empty(const struct sctp_outq *q) 1406 { 1407 return q->out_qlen == 0 && q->outstanding_bytes == 0 && 1408 list_empty(&q->retransmit); 1409 } 1410 1411 /******************************************************************** 1412 * 2nd Level Abstractions 1413 ********************************************************************/ 1414 1415 /* Go through a transport's transmitted list or the association's retransmit 1416 * list and move chunks that are acked by the Cumulative TSN Ack to q->sacked. 1417 * The retransmit list will not have an associated transport. 1418 * 1419 * I added coherent debug information output. --xguo 1420 * 1421 * Instead of printing 'sacked' or 'kept' for each TSN on the 1422 * transmitted_queue, we print a range: SACKED: TSN1-TSN2, TSN3, TSN4-TSN5. 1423 * KEPT TSN6-TSN7, etc. 1424 */ 1425 static void sctp_check_transmitted(struct sctp_outq *q, 1426 struct list_head *transmitted_queue, 1427 struct sctp_transport *transport, 1428 union sctp_addr *saddr, 1429 struct sctp_sackhdr *sack, 1430 __u32 *highest_new_tsn_in_sack) 1431 { 1432 struct list_head *lchunk; 1433 struct sctp_chunk *tchunk; 1434 struct list_head tlist; 1435 __u32 tsn; 1436 __u32 sack_ctsn; 1437 __u32 rtt; 1438 __u8 restart_timer = 0; 1439 int bytes_acked = 0; 1440 int migrate_bytes = 0; 1441 bool forward_progress = false; 1442 1443 sack_ctsn = ntohl(sack->cum_tsn_ack); 1444 1445 INIT_LIST_HEAD(&tlist); 1446 1447 /* The while loop will skip empty transmitted queues. */ 1448 while (NULL != (lchunk = sctp_list_dequeue(transmitted_queue))) { 1449 tchunk = list_entry(lchunk, struct sctp_chunk, 1450 transmitted_list); 1451 1452 if (sctp_chunk_abandoned(tchunk)) { 1453 /* Move the chunk to abandoned list. */ 1454 sctp_insert_list(&q->abandoned, lchunk); 1455 1456 /* If this chunk has not been acked, stop 1457 * considering it as 'outstanding'. 1458 */ 1459 if (transmitted_queue != &q->retransmit && 1460 !tchunk->tsn_gap_acked) { 1461 if (tchunk->transport) 1462 tchunk->transport->flight_size -= 1463 sctp_data_size(tchunk); 1464 q->outstanding_bytes -= sctp_data_size(tchunk); 1465 } 1466 continue; 1467 } 1468 1469 tsn = ntohl(tchunk->subh.data_hdr->tsn); 1470 if (sctp_acked(sack, tsn)) { 1471 /* If this queue is the retransmit queue, the 1472 * retransmit timer has already reclaimed 1473 * the outstanding bytes for this chunk, so only 1474 * count bytes associated with a transport. 1475 */ 1476 if (transport && !tchunk->tsn_gap_acked) { 1477 /* If this chunk is being used for RTT 1478 * measurement, calculate the RTT and update 1479 * the RTO using this value. 1480 * 1481 * 6.3.1 C5) Karn's algorithm: RTT measurements 1482 * MUST NOT be made using packets that were 1483 * retransmitted (and thus for which it is 1484 * ambiguous whether the reply was for the 1485 * first instance of the packet or a later 1486 * instance). 1487 */ 1488 if (!sctp_chunk_retransmitted(tchunk) && 1489 tchunk->rtt_in_progress) { 1490 tchunk->rtt_in_progress = 0; 1491 rtt = jiffies - tchunk->sent_at; 1492 sctp_transport_update_rto(transport, 1493 rtt); 1494 } 1495 1496 if (TSN_lte(tsn, sack_ctsn)) { 1497 /* 1498 * SFR-CACC algorithm: 1499 * 2) If the SACK contains gap acks 1500 * and the flag CHANGEOVER_ACTIVE is 1501 * set the receiver of the SACK MUST 1502 * take the following action: 1503 * 1504 * B) For each TSN t being acked that 1505 * has not been acked in any SACK so 1506 * far, set cacc_saw_newack to 1 for 1507 * the destination that the TSN was 1508 * sent to. 1509 */ 1510 if (sack->num_gap_ack_blocks && 1511 q->asoc->peer.primary_path->cacc. 1512 changeover_active) 1513 transport->cacc.cacc_saw_newack 1514 = 1; 1515 } 1516 } 1517 1518 /* If the chunk hasn't been marked as ACKED, 1519 * mark it and account bytes_acked if the 1520 * chunk had a valid transport (it will not 1521 * have a transport if ASCONF had deleted it 1522 * while DATA was outstanding). 1523 */ 1524 if (!tchunk->tsn_gap_acked) { 1525 tchunk->tsn_gap_acked = 1; 1526 if (TSN_lt(*highest_new_tsn_in_sack, tsn)) 1527 *highest_new_tsn_in_sack = tsn; 1528 bytes_acked += sctp_data_size(tchunk); 1529 if (!tchunk->transport) 1530 migrate_bytes += sctp_data_size(tchunk); 1531 forward_progress = true; 1532 } 1533 1534 if (TSN_lte(tsn, sack_ctsn)) { 1535 /* RFC 2960 6.3.2 Retransmission Timer Rules 1536 * 1537 * R3) Whenever a SACK is received 1538 * that acknowledges the DATA chunk 1539 * with the earliest outstanding TSN 1540 * for that address, restart T3-rtx 1541 * timer for that address with its 1542 * current RTO. 1543 */ 1544 restart_timer = 1; 1545 forward_progress = true; 1546 1547 list_add_tail(&tchunk->transmitted_list, 1548 &q->sacked); 1549 } else { 1550 /* RFC2960 7.2.4, sctpimpguide-05 2.8.2 1551 * M2) Each time a SACK arrives reporting 1552 * 'Stray DATA chunk(s)' record the highest TSN 1553 * reported as newly acknowledged, call this 1554 * value 'HighestTSNinSack'. A newly 1555 * acknowledged DATA chunk is one not 1556 * previously acknowledged in a SACK. 1557 * 1558 * When the SCTP sender of data receives a SACK 1559 * chunk that acknowledges, for the first time, 1560 * the receipt of a DATA chunk, all the still 1561 * unacknowledged DATA chunks whose TSN is 1562 * older than that newly acknowledged DATA 1563 * chunk, are qualified as 'Stray DATA chunks'. 1564 */ 1565 list_add_tail(lchunk, &tlist); 1566 } 1567 } else { 1568 if (tchunk->tsn_gap_acked) { 1569 pr_debug("%s: receiver reneged on data TSN:0x%x\n", 1570 __func__, tsn); 1571 1572 tchunk->tsn_gap_acked = 0; 1573 1574 if (tchunk->transport) 1575 bytes_acked -= sctp_data_size(tchunk); 1576 1577 /* RFC 2960 6.3.2 Retransmission Timer Rules 1578 * 1579 * R4) Whenever a SACK is received missing a 1580 * TSN that was previously acknowledged via a 1581 * Gap Ack Block, start T3-rtx for the 1582 * destination address to which the DATA 1583 * chunk was originally 1584 * transmitted if it is not already running. 1585 */ 1586 restart_timer = 1; 1587 } 1588 1589 list_add_tail(lchunk, &tlist); 1590 } 1591 } 1592 1593 if (transport) { 1594 if (bytes_acked) { 1595 struct sctp_association *asoc = transport->asoc; 1596 1597 /* We may have counted DATA that was migrated 1598 * to this transport due to DEL-IP operation. 1599 * Subtract those bytes, since the were never 1600 * send on this transport and shouldn't be 1601 * credited to this transport. 1602 */ 1603 bytes_acked -= migrate_bytes; 1604 1605 /* 8.2. When an outstanding TSN is acknowledged, 1606 * the endpoint shall clear the error counter of 1607 * the destination transport address to which the 1608 * DATA chunk was last sent. 1609 * The association's overall error counter is 1610 * also cleared. 1611 */ 1612 transport->error_count = 0; 1613 transport->asoc->overall_error_count = 0; 1614 forward_progress = true; 1615 1616 /* 1617 * While in SHUTDOWN PENDING, we may have started 1618 * the T5 shutdown guard timer after reaching the 1619 * retransmission limit. Stop that timer as soon 1620 * as the receiver acknowledged any data. 1621 */ 1622 if (asoc->state == SCTP_STATE_SHUTDOWN_PENDING && 1623 del_timer(&asoc->timers 1624 [SCTP_EVENT_TIMEOUT_T5_SHUTDOWN_GUARD])) 1625 sctp_association_put(asoc); 1626 1627 /* Mark the destination transport address as 1628 * active if it is not so marked. 1629 */ 1630 if ((transport->state == SCTP_INACTIVE || 1631 transport->state == SCTP_UNCONFIRMED) && 1632 sctp_cmp_addr_exact(&transport->ipaddr, saddr)) { 1633 sctp_assoc_control_transport( 1634 transport->asoc, 1635 transport, 1636 SCTP_TRANSPORT_UP, 1637 SCTP_RECEIVED_SACK); 1638 } 1639 1640 sctp_transport_raise_cwnd(transport, sack_ctsn, 1641 bytes_acked); 1642 1643 transport->flight_size -= bytes_acked; 1644 if (transport->flight_size == 0) 1645 transport->partial_bytes_acked = 0; 1646 q->outstanding_bytes -= bytes_acked + migrate_bytes; 1647 } else { 1648 /* RFC 2960 6.1, sctpimpguide-06 2.15.2 1649 * When a sender is doing zero window probing, it 1650 * should not timeout the association if it continues 1651 * to receive new packets from the receiver. The 1652 * reason is that the receiver MAY keep its window 1653 * closed for an indefinite time. 1654 * A sender is doing zero window probing when the 1655 * receiver's advertised window is zero, and there is 1656 * only one data chunk in flight to the receiver. 1657 * 1658 * Allow the association to timeout while in SHUTDOWN 1659 * PENDING or SHUTDOWN RECEIVED in case the receiver 1660 * stays in zero window mode forever. 1661 */ 1662 if (!q->asoc->peer.rwnd && 1663 !list_empty(&tlist) && 1664 (sack_ctsn+2 == q->asoc->next_tsn) && 1665 q->asoc->state < SCTP_STATE_SHUTDOWN_PENDING) { 1666 pr_debug("%s: sack received for zero window " 1667 "probe:%u\n", __func__, sack_ctsn); 1668 1669 q->asoc->overall_error_count = 0; 1670 transport->error_count = 0; 1671 } 1672 } 1673 1674 /* RFC 2960 6.3.2 Retransmission Timer Rules 1675 * 1676 * R2) Whenever all outstanding data sent to an address have 1677 * been acknowledged, turn off the T3-rtx timer of that 1678 * address. 1679 */ 1680 if (!transport->flight_size) { 1681 if (del_timer(&transport->T3_rtx_timer)) 1682 sctp_transport_put(transport); 1683 } else if (restart_timer) { 1684 if (!mod_timer(&transport->T3_rtx_timer, 1685 jiffies + transport->rto)) 1686 sctp_transport_hold(transport); 1687 } 1688 1689 if (forward_progress) { 1690 if (transport->dst) 1691 sctp_transport_dst_confirm(transport); 1692 } 1693 } 1694 1695 list_splice(&tlist, transmitted_queue); 1696 } 1697 1698 /* Mark chunks as missing and consequently may get retransmitted. */ 1699 static 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 pr_debug("%s: tsn:0x%x missing counter:%d\n", 1735 __func__, tsn, 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 pr_debug("%s: transport:%p, cwnd:%d, ssthresh:%d, " 1756 "flight_size:%d, pba:%d\n", __func__, transport, 1757 transport->cwnd, transport->ssthresh, 1758 transport->flight_size, transport->partial_bytes_acked); 1759 } 1760 } 1761 1762 /* Is the given TSN acked by this packet? */ 1763 static int sctp_acked(struct sctp_sackhdr *sack, __u32 tsn) 1764 { 1765 __u32 ctsn = ntohl(sack->cum_tsn_ack); 1766 union sctp_sack_variable *frags; 1767 __u16 tsn_offset, blocks; 1768 int i; 1769 1770 if (TSN_lte(tsn, ctsn)) 1771 goto pass; 1772 1773 /* 3.3.4 Selective Acknowledgment (SACK) (3): 1774 * 1775 * Gap Ack Blocks: 1776 * These fields contain the Gap Ack Blocks. They are repeated 1777 * for each Gap Ack Block up to the number of Gap Ack Blocks 1778 * defined in the Number of Gap Ack Blocks field. All DATA 1779 * chunks with TSNs greater than or equal to (Cumulative TSN 1780 * Ack + Gap Ack Block Start) and less than or equal to 1781 * (Cumulative TSN Ack + Gap Ack Block End) of each Gap Ack 1782 * Block are assumed to have been received correctly. 1783 */ 1784 1785 frags = sack->variable; 1786 blocks = ntohs(sack->num_gap_ack_blocks); 1787 tsn_offset = tsn - ctsn; 1788 for (i = 0; i < blocks; ++i) { 1789 if (tsn_offset >= ntohs(frags[i].gab.start) && 1790 tsn_offset <= ntohs(frags[i].gab.end)) 1791 goto pass; 1792 } 1793 1794 return 0; 1795 pass: 1796 return 1; 1797 } 1798 1799 static 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. */ 1812 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(asoc->base.net, SCTP_MIB_OUTCTRLCHUNKS); 1914 } 1915 } 1916