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 * 6 * This file is part of the SCTP kernel implementation 7 * 8 * These functions handle output processing. 9 * 10 * This SCTP implementation is free software; 11 * you can redistribute it and/or modify it under the terms of 12 * the GNU General Public License as published by 13 * the Free Software Foundation; either version 2, or (at your option) 14 * any later version. 15 * 16 * This SCTP implementation is distributed in the hope that it 17 * will be useful, but WITHOUT ANY WARRANTY; without even the implied 18 * ************************ 19 * warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. 20 * See the GNU General Public License for more details. 21 * 22 * You should have received a copy of the GNU General Public License 23 * along with GNU CC; see the file COPYING. If not, write to 24 * the Free Software Foundation, 59 Temple Place - Suite 330, 25 * Boston, MA 02111-1307, USA. 26 * 27 * Please send any bug reports or fixes you make to the 28 * email address(es): 29 * lksctp developers <lksctp-developers@lists.sourceforge.net> 30 * 31 * Or submit a bug report through the following website: 32 * http://www.sf.net/projects/lksctp 33 * 34 * Written or modified by: 35 * La Monte H.P. Yarroll <piggy@acm.org> 36 * Karl Knutson <karl@athena.chicago.il.us> 37 * Jon Grimm <jgrimm@austin.ibm.com> 38 * Sridhar Samudrala <sri@us.ibm.com> 39 * 40 * Any bugs reported given to us we will try to fix... any fixes shared will 41 * be incorporated into the next SCTP release. 42 */ 43 44 #include <linux/types.h> 45 #include <linux/kernel.h> 46 #include <linux/wait.h> 47 #include <linux/time.h> 48 #include <linux/ip.h> 49 #include <linux/ipv6.h> 50 #include <linux/init.h> 51 #include <net/inet_ecn.h> 52 #include <net/icmp.h> 53 #include <net/net_namespace.h> 54 55 #ifndef TEST_FRAME 56 #include <net/tcp.h> 57 #endif /* TEST_FRAME (not defined) */ 58 59 #include <linux/socket.h> /* for sa_family_t */ 60 #include <net/sock.h> 61 62 #include <net/sctp/sctp.h> 63 #include <net/sctp/sm.h> 64 #include <net/sctp/checksum.h> 65 66 /* Forward declarations for private helpers. */ 67 static sctp_xmit_t sctp_packet_append_data(struct sctp_packet *packet, 68 struct sctp_chunk *chunk); 69 70 /* Config a packet. 71 * This appears to be a followup set of initializations. 72 */ 73 struct sctp_packet *sctp_packet_config(struct sctp_packet *packet, 74 __u32 vtag, int ecn_capable) 75 { 76 struct sctp_chunk *chunk = NULL; 77 78 SCTP_DEBUG_PRINTK("%s: packet:%p vtag:0x%x\n", __func__, 79 packet, vtag); 80 81 packet->vtag = vtag; 82 packet->has_cookie_echo = 0; 83 packet->has_sack = 0; 84 packet->has_auth = 0; 85 packet->has_data = 0; 86 packet->ipfragok = 0; 87 packet->auth = NULL; 88 89 if (ecn_capable && sctp_packet_empty(packet)) { 90 chunk = sctp_get_ecne_prepend(packet->transport->asoc); 91 92 /* If there a is a prepend chunk stick it on the list before 93 * any other chunks get appended. 94 */ 95 if (chunk) 96 sctp_packet_append_chunk(packet, chunk); 97 } 98 99 return packet; 100 } 101 102 /* Initialize the packet structure. */ 103 struct sctp_packet *sctp_packet_init(struct sctp_packet *packet, 104 struct sctp_transport *transport, 105 __u16 sport, __u16 dport) 106 { 107 struct sctp_association *asoc = transport->asoc; 108 size_t overhead; 109 110 SCTP_DEBUG_PRINTK("%s: packet:%p transport:%p\n", __func__, 111 packet, transport); 112 113 packet->transport = transport; 114 packet->source_port = sport; 115 packet->destination_port = dport; 116 INIT_LIST_HEAD(&packet->chunk_list); 117 if (asoc) { 118 struct sctp_sock *sp = sctp_sk(asoc->base.sk); 119 overhead = sp->pf->af->net_header_len; 120 } else { 121 overhead = sizeof(struct ipv6hdr); 122 } 123 overhead += sizeof(struct sctphdr); 124 packet->overhead = overhead; 125 packet->size = overhead; 126 packet->vtag = 0; 127 packet->has_cookie_echo = 0; 128 packet->has_sack = 0; 129 packet->has_auth = 0; 130 packet->has_data = 0; 131 packet->ipfragok = 0; 132 packet->malloced = 0; 133 packet->auth = NULL; 134 return packet; 135 } 136 137 /* Free a packet. */ 138 void sctp_packet_free(struct sctp_packet *packet) 139 { 140 struct sctp_chunk *chunk, *tmp; 141 142 SCTP_DEBUG_PRINTK("%s: packet:%p\n", __func__, packet); 143 144 list_for_each_entry_safe(chunk, tmp, &packet->chunk_list, list) { 145 list_del_init(&chunk->list); 146 sctp_chunk_free(chunk); 147 } 148 149 if (packet->malloced) 150 kfree(packet); 151 } 152 153 /* This routine tries to append the chunk to the offered packet. If adding 154 * the chunk causes the packet to exceed the path MTU and COOKIE_ECHO chunk 155 * is not present in the packet, it transmits the input packet. 156 * Data can be bundled with a packet containing a COOKIE_ECHO chunk as long 157 * as it can fit in the packet, but any more data that does not fit in this 158 * packet can be sent only after receiving the COOKIE_ACK. 159 */ 160 sctp_xmit_t sctp_packet_transmit_chunk(struct sctp_packet *packet, 161 struct sctp_chunk *chunk, 162 int one_packet) 163 { 164 sctp_xmit_t retval; 165 int error = 0; 166 167 SCTP_DEBUG_PRINTK("%s: packet:%p chunk:%p\n", __func__, 168 packet, chunk); 169 170 switch ((retval = (sctp_packet_append_chunk(packet, chunk)))) { 171 case SCTP_XMIT_PMTU_FULL: 172 if (!packet->has_cookie_echo) { 173 error = sctp_packet_transmit(packet); 174 if (error < 0) 175 chunk->skb->sk->sk_err = -error; 176 177 /* If we have an empty packet, then we can NOT ever 178 * return PMTU_FULL. 179 */ 180 if (!one_packet) 181 retval = sctp_packet_append_chunk(packet, 182 chunk); 183 } 184 break; 185 186 case SCTP_XMIT_RWND_FULL: 187 case SCTP_XMIT_OK: 188 case SCTP_XMIT_NAGLE_DELAY: 189 break; 190 } 191 192 return retval; 193 } 194 195 /* Try to bundle an auth chunk into the packet. */ 196 static sctp_xmit_t sctp_packet_bundle_auth(struct sctp_packet *pkt, 197 struct sctp_chunk *chunk) 198 { 199 struct sctp_association *asoc = pkt->transport->asoc; 200 struct sctp_chunk *auth; 201 sctp_xmit_t retval = SCTP_XMIT_OK; 202 203 /* if we don't have an association, we can't do authentication */ 204 if (!asoc) 205 return retval; 206 207 /* See if this is an auth chunk we are bundling or if 208 * auth is already bundled. 209 */ 210 if (chunk->chunk_hdr->type == SCTP_CID_AUTH || pkt->auth) 211 return retval; 212 213 /* if the peer did not request this chunk to be authenticated, 214 * don't do it 215 */ 216 if (!chunk->auth) 217 return retval; 218 219 auth = sctp_make_auth(asoc); 220 if (!auth) 221 return retval; 222 223 retval = sctp_packet_append_chunk(pkt, auth); 224 225 return retval; 226 } 227 228 /* Try to bundle a SACK with the packet. */ 229 static sctp_xmit_t sctp_packet_bundle_sack(struct sctp_packet *pkt, 230 struct sctp_chunk *chunk) 231 { 232 sctp_xmit_t retval = SCTP_XMIT_OK; 233 234 /* If sending DATA and haven't aleady bundled a SACK, try to 235 * bundle one in to the packet. 236 */ 237 if (sctp_chunk_is_data(chunk) && !pkt->has_sack && 238 !pkt->has_cookie_echo) { 239 struct sctp_association *asoc; 240 asoc = pkt->transport->asoc; 241 242 if (asoc->a_rwnd > asoc->rwnd) { 243 struct sctp_chunk *sack; 244 asoc->a_rwnd = asoc->rwnd; 245 sack = sctp_make_sack(asoc); 246 if (sack) { 247 struct timer_list *timer; 248 retval = sctp_packet_append_chunk(pkt, sack); 249 asoc->peer.sack_needed = 0; 250 timer = &asoc->timers[SCTP_EVENT_TIMEOUT_SACK]; 251 if (timer_pending(timer) && del_timer(timer)) 252 sctp_association_put(asoc); 253 } 254 } 255 } 256 return retval; 257 } 258 259 /* Append a chunk to the offered packet reporting back any inability to do 260 * so. 261 */ 262 sctp_xmit_t sctp_packet_append_chunk(struct sctp_packet *packet, 263 struct sctp_chunk *chunk) 264 { 265 sctp_xmit_t retval = SCTP_XMIT_OK; 266 __u16 chunk_len = WORD_ROUND(ntohs(chunk->chunk_hdr->length)); 267 size_t psize; 268 size_t pmtu; 269 int too_big; 270 271 SCTP_DEBUG_PRINTK("%s: packet:%p chunk:%p\n", __func__, packet, 272 chunk); 273 274 /* Try to bundle AUTH chunk */ 275 retval = sctp_packet_bundle_auth(packet, chunk); 276 if (retval != SCTP_XMIT_OK) 277 goto finish; 278 279 /* Try to bundle SACK chunk */ 280 retval = sctp_packet_bundle_sack(packet, chunk); 281 if (retval != SCTP_XMIT_OK) 282 goto finish; 283 284 psize = packet->size; 285 pmtu = ((packet->transport->asoc) ? 286 (packet->transport->asoc->pathmtu) : 287 (packet->transport->pathmtu)); 288 289 too_big = (psize + chunk_len > pmtu); 290 291 /* Decide if we need to fragment or resubmit later. */ 292 if (too_big) { 293 /* It's OK to fragmet at IP level if any one of the following 294 * is true: 295 * 1. The packet is empty (meaning this chunk is greater 296 * the MTU) 297 * 2. The chunk we are adding is a control chunk 298 * 3. The packet doesn't have any data in it yet and data 299 * requires authentication. 300 */ 301 if (sctp_packet_empty(packet) || !sctp_chunk_is_data(chunk) || 302 (!packet->has_data && chunk->auth)) { 303 /* We no longer do re-fragmentation. 304 * Just fragment at the IP layer, if we 305 * actually hit this condition 306 */ 307 packet->ipfragok = 1; 308 goto append; 309 310 } else { 311 retval = SCTP_XMIT_PMTU_FULL; 312 goto finish; 313 } 314 } 315 316 append: 317 /* We believe that this chunk is OK to add to the packet (as 318 * long as we have the cwnd for it). 319 */ 320 321 /* DATA is a special case since we must examine both rwnd and cwnd 322 * before we send DATA. 323 */ 324 switch (chunk->chunk_hdr->type) { 325 case SCTP_CID_DATA: 326 retval = sctp_packet_append_data(packet, chunk); 327 /* Disallow SACK bundling after DATA. */ 328 packet->has_sack = 1; 329 /* Disallow AUTH bundling after DATA */ 330 packet->has_auth = 1; 331 /* Let it be knows that packet has DATA in it */ 332 packet->has_data = 1; 333 if (SCTP_XMIT_OK != retval) 334 goto finish; 335 break; 336 case SCTP_CID_COOKIE_ECHO: 337 packet->has_cookie_echo = 1; 338 break; 339 340 case SCTP_CID_SACK: 341 packet->has_sack = 1; 342 break; 343 344 case SCTP_CID_AUTH: 345 packet->has_auth = 1; 346 packet->auth = chunk; 347 break; 348 } 349 350 /* It is OK to send this chunk. */ 351 list_add_tail(&chunk->list, &packet->chunk_list); 352 packet->size += chunk_len; 353 chunk->transport = packet->transport; 354 finish: 355 return retval; 356 } 357 358 /* All packets are sent to the network through this function from 359 * sctp_outq_tail(). 360 * 361 * The return value is a normal kernel error return value. 362 */ 363 int sctp_packet_transmit(struct sctp_packet *packet) 364 { 365 struct sctp_transport *tp = packet->transport; 366 struct sctp_association *asoc = tp->asoc; 367 struct sctphdr *sh; 368 __be32 crc32 = __constant_cpu_to_be32(0); 369 struct sk_buff *nskb; 370 struct sctp_chunk *chunk, *tmp; 371 struct sock *sk; 372 int err = 0; 373 int padding; /* How much padding do we need? */ 374 __u8 has_data = 0; 375 struct dst_entry *dst = tp->dst; 376 unsigned char *auth = NULL; /* pointer to auth in skb data */ 377 __u32 cksum_buf_len = sizeof(struct sctphdr); 378 379 SCTP_DEBUG_PRINTK("%s: packet:%p\n", __func__, packet); 380 381 /* Do NOT generate a chunkless packet. */ 382 if (list_empty(&packet->chunk_list)) 383 return err; 384 385 /* Set up convenience variables... */ 386 chunk = list_entry(packet->chunk_list.next, struct sctp_chunk, list); 387 sk = chunk->skb->sk; 388 389 /* Allocate the new skb. */ 390 nskb = alloc_skb(packet->size + LL_MAX_HEADER, GFP_ATOMIC); 391 if (!nskb) 392 goto nomem; 393 394 /* Make sure the outbound skb has enough header room reserved. */ 395 skb_reserve(nskb, packet->overhead + LL_MAX_HEADER); 396 397 /* Set the owning socket so that we know where to get the 398 * destination IP address. 399 */ 400 skb_set_owner_w(nskb, sk); 401 402 /* The 'obsolete' field of dst is set to 2 when a dst is freed. */ 403 if (!dst || (dst->obsolete > 1)) { 404 dst_release(dst); 405 sctp_transport_route(tp, NULL, sctp_sk(sk)); 406 if (asoc && (asoc->param_flags & SPP_PMTUD_ENABLE)) { 407 sctp_assoc_sync_pmtu(asoc); 408 } 409 } 410 nskb->dst = dst_clone(tp->dst); 411 if (!nskb->dst) 412 goto no_route; 413 dst = nskb->dst; 414 415 /* Build the SCTP header. */ 416 sh = (struct sctphdr *)skb_push(nskb, sizeof(struct sctphdr)); 417 sh->source = htons(packet->source_port); 418 sh->dest = htons(packet->destination_port); 419 420 /* From 6.8 Adler-32 Checksum Calculation: 421 * After the packet is constructed (containing the SCTP common 422 * header and one or more control or DATA chunks), the 423 * transmitter shall: 424 * 425 * 1) Fill in the proper Verification Tag in the SCTP common 426 * header and initialize the checksum field to 0's. 427 */ 428 sh->vtag = htonl(packet->vtag); 429 sh->checksum = 0; 430 431 /** 432 * 6.10 Bundling 433 * 434 * An endpoint bundles chunks by simply including multiple 435 * chunks in one outbound SCTP packet. ... 436 */ 437 438 /** 439 * 3.2 Chunk Field Descriptions 440 * 441 * The total length of a chunk (including Type, Length and 442 * Value fields) MUST be a multiple of 4 bytes. If the length 443 * of the chunk is not a multiple of 4 bytes, the sender MUST 444 * pad the chunk with all zero bytes and this padding is not 445 * included in the chunk length field. The sender should 446 * never pad with more than 3 bytes. 447 * 448 * [This whole comment explains WORD_ROUND() below.] 449 */ 450 SCTP_DEBUG_PRINTK("***sctp_transmit_packet***\n"); 451 list_for_each_entry_safe(chunk, tmp, &packet->chunk_list, list) { 452 list_del_init(&chunk->list); 453 if (sctp_chunk_is_data(chunk)) { 454 455 if (!chunk->has_tsn) { 456 sctp_chunk_assign_ssn(chunk); 457 sctp_chunk_assign_tsn(chunk); 458 459 /* 6.3.1 C4) When data is in flight and when allowed 460 * by rule C5, a new RTT measurement MUST be made each 461 * round trip. Furthermore, new RTT measurements 462 * SHOULD be made no more than once per round-trip 463 * for a given destination transport address. 464 */ 465 466 if (!tp->rto_pending) { 467 chunk->rtt_in_progress = 1; 468 tp->rto_pending = 1; 469 } 470 } else 471 chunk->resent = 1; 472 473 chunk->sent_at = jiffies; 474 has_data = 1; 475 } 476 477 padding = WORD_ROUND(chunk->skb->len) - chunk->skb->len; 478 if (padding) 479 memset(skb_put(chunk->skb, padding), 0, padding); 480 481 /* if this is the auth chunk that we are adding, 482 * store pointer where it will be added and put 483 * the auth into the packet. 484 */ 485 if (chunk == packet->auth) 486 auth = skb_tail_pointer(nskb); 487 488 cksum_buf_len += chunk->skb->len; 489 memcpy(skb_put(nskb, chunk->skb->len), 490 chunk->skb->data, chunk->skb->len); 491 492 SCTP_DEBUG_PRINTK("%s %p[%s] %s 0x%x, %s %d, %s %d, %s %d\n", 493 "*** Chunk", chunk, 494 sctp_cname(SCTP_ST_CHUNK( 495 chunk->chunk_hdr->type)), 496 chunk->has_tsn ? "TSN" : "No TSN", 497 chunk->has_tsn ? 498 ntohl(chunk->subh.data_hdr->tsn) : 0, 499 "length", ntohs(chunk->chunk_hdr->length), 500 "chunk->skb->len", chunk->skb->len, 501 "rtt_in_progress", chunk->rtt_in_progress); 502 503 /* 504 * If this is a control chunk, this is our last 505 * reference. Free data chunks after they've been 506 * acknowledged or have failed. 507 */ 508 if (!sctp_chunk_is_data(chunk)) 509 sctp_chunk_free(chunk); 510 } 511 512 /* SCTP-AUTH, Section 6.2 513 * The sender MUST calculate the MAC as described in RFC2104 [2] 514 * using the hash function H as described by the MAC Identifier and 515 * the shared association key K based on the endpoint pair shared key 516 * described by the shared key identifier. The 'data' used for the 517 * computation of the AUTH-chunk is given by the AUTH chunk with its 518 * HMAC field set to zero (as shown in Figure 6) followed by all 519 * chunks that are placed after the AUTH chunk in the SCTP packet. 520 */ 521 if (auth) 522 sctp_auth_calculate_hmac(asoc, nskb, 523 (struct sctp_auth_chunk *)auth, 524 GFP_ATOMIC); 525 526 /* 2) Calculate the Adler-32 checksum of the whole packet, 527 * including the SCTP common header and all the 528 * chunks. 529 * 530 * Note: Adler-32 is no longer applicable, as has been replaced 531 * by CRC32-C as described in <draft-ietf-tsvwg-sctpcsum-02.txt>. 532 */ 533 if (!(dst->dev->features & NETIF_F_NO_CSUM)) { 534 crc32 = sctp_start_cksum((__u8 *)sh, cksum_buf_len); 535 crc32 = sctp_end_cksum(crc32); 536 } else 537 nskb->ip_summed = CHECKSUM_UNNECESSARY; 538 539 /* 3) Put the resultant value into the checksum field in the 540 * common header, and leave the rest of the bits unchanged. 541 */ 542 sh->checksum = crc32; 543 544 /* IP layer ECN support 545 * From RFC 2481 546 * "The ECN-Capable Transport (ECT) bit would be set by the 547 * data sender to indicate that the end-points of the 548 * transport protocol are ECN-capable." 549 * 550 * Now setting the ECT bit all the time, as it should not cause 551 * any problems protocol-wise even if our peer ignores it. 552 * 553 * Note: The works for IPv6 layer checks this bit too later 554 * in transmission. See IP6_ECN_flow_xmit(). 555 */ 556 (*tp->af_specific->ecn_capable)(nskb->sk); 557 558 /* Set up the IP options. */ 559 /* BUG: not implemented 560 * For v4 this all lives somewhere in sk->sk_opt... 561 */ 562 563 /* Dump that on IP! */ 564 if (asoc && asoc->peer.last_sent_to != tp) { 565 /* Considering the multiple CPU scenario, this is a 566 * "correcter" place for last_sent_to. --xguo 567 */ 568 asoc->peer.last_sent_to = tp; 569 } 570 571 if (has_data) { 572 struct timer_list *timer; 573 unsigned long timeout; 574 575 tp->last_time_used = jiffies; 576 577 /* Restart the AUTOCLOSE timer when sending data. */ 578 if (sctp_state(asoc, ESTABLISHED) && asoc->autoclose) { 579 timer = &asoc->timers[SCTP_EVENT_TIMEOUT_AUTOCLOSE]; 580 timeout = asoc->timeouts[SCTP_EVENT_TIMEOUT_AUTOCLOSE]; 581 582 if (!mod_timer(timer, jiffies + timeout)) 583 sctp_association_hold(asoc); 584 } 585 } 586 587 SCTP_DEBUG_PRINTK("***sctp_transmit_packet*** skb len %d\n", 588 nskb->len); 589 590 nskb->local_df = packet->ipfragok; 591 (*tp->af_specific->sctp_xmit)(nskb, tp); 592 593 out: 594 packet->size = packet->overhead; 595 return err; 596 no_route: 597 kfree_skb(nskb); 598 IP_INC_STATS_BH(&init_net, IPSTATS_MIB_OUTNOROUTES); 599 600 /* FIXME: Returning the 'err' will effect all the associations 601 * associated with a socket, although only one of the paths of the 602 * association is unreachable. 603 * The real failure of a transport or association can be passed on 604 * to the user via notifications. So setting this error may not be 605 * required. 606 */ 607 /* err = -EHOSTUNREACH; */ 608 err: 609 /* Control chunks are unreliable so just drop them. DATA chunks 610 * will get resent or dropped later. 611 */ 612 613 list_for_each_entry_safe(chunk, tmp, &packet->chunk_list, list) { 614 list_del_init(&chunk->list); 615 if (!sctp_chunk_is_data(chunk)) 616 sctp_chunk_free(chunk); 617 } 618 goto out; 619 nomem: 620 err = -ENOMEM; 621 goto err; 622 } 623 624 /******************************************************************** 625 * 2nd Level Abstractions 626 ********************************************************************/ 627 628 /* This private function handles the specifics of appending DATA chunks. */ 629 static sctp_xmit_t sctp_packet_append_data(struct sctp_packet *packet, 630 struct sctp_chunk *chunk) 631 { 632 sctp_xmit_t retval = SCTP_XMIT_OK; 633 size_t datasize, rwnd, inflight; 634 struct sctp_transport *transport = packet->transport; 635 __u32 max_burst_bytes; 636 struct sctp_association *asoc = transport->asoc; 637 struct sctp_sock *sp = sctp_sk(asoc->base.sk); 638 struct sctp_outq *q = &asoc->outqueue; 639 640 /* RFC 2960 6.1 Transmission of DATA Chunks 641 * 642 * A) At any given time, the data sender MUST NOT transmit new data to 643 * any destination transport address if its peer's rwnd indicates 644 * that the peer has no buffer space (i.e. rwnd is 0, see Section 645 * 6.2.1). However, regardless of the value of rwnd (including if it 646 * is 0), the data sender can always have one DATA chunk in flight to 647 * the receiver if allowed by cwnd (see rule B below). This rule 648 * allows the sender to probe for a change in rwnd that the sender 649 * missed due to the SACK having been lost in transit from the data 650 * receiver to the data sender. 651 */ 652 653 rwnd = asoc->peer.rwnd; 654 inflight = asoc->outqueue.outstanding_bytes; 655 656 datasize = sctp_data_size(chunk); 657 658 if (datasize > rwnd) { 659 if (inflight > 0) { 660 /* We have (at least) one data chunk in flight, 661 * so we can't fall back to rule 6.1 B). 662 */ 663 retval = SCTP_XMIT_RWND_FULL; 664 goto finish; 665 } 666 } 667 668 /* sctpimpguide-05 2.14.2 669 * D) When the time comes for the sender to 670 * transmit new DATA chunks, the protocol parameter Max.Burst MUST 671 * first be applied to limit how many new DATA chunks may be sent. 672 * The limit is applied by adjusting cwnd as follows: 673 * if ((flightsize + Max.Burst * MTU) < cwnd) 674 * cwnd = flightsize + Max.Burst * MTU 675 */ 676 max_burst_bytes = asoc->max_burst * asoc->pathmtu; 677 if ((transport->flight_size + max_burst_bytes) < transport->cwnd) { 678 transport->cwnd = transport->flight_size + max_burst_bytes; 679 SCTP_DEBUG_PRINTK("%s: cwnd limited by max_burst: " 680 "transport: %p, cwnd: %d, " 681 "ssthresh: %d, flight_size: %d, " 682 "pba: %d\n", 683 __func__, transport, 684 transport->cwnd, 685 transport->ssthresh, 686 transport->flight_size, 687 transport->partial_bytes_acked); 688 } 689 690 /* RFC 2960 6.1 Transmission of DATA Chunks 691 * 692 * B) At any given time, the sender MUST NOT transmit new data 693 * to a given transport address if it has cwnd or more bytes 694 * of data outstanding to that transport address. 695 */ 696 /* RFC 7.2.4 & the Implementers Guide 2.8. 697 * 698 * 3) ... 699 * When a Fast Retransmit is being performed the sender SHOULD 700 * ignore the value of cwnd and SHOULD NOT delay retransmission. 701 */ 702 if (chunk->fast_retransmit != SCTP_NEED_FRTX) 703 if (transport->flight_size >= transport->cwnd) { 704 retval = SCTP_XMIT_RWND_FULL; 705 goto finish; 706 } 707 708 /* Nagle's algorithm to solve small-packet problem: 709 * Inhibit the sending of new chunks when new outgoing data arrives 710 * if any previously transmitted data on the connection remains 711 * unacknowledged. 712 */ 713 if (!sp->nodelay && sctp_packet_empty(packet) && 714 q->outstanding_bytes && sctp_state(asoc, ESTABLISHED)) { 715 unsigned len = datasize + q->out_qlen; 716 717 /* Check whether this chunk and all the rest of pending 718 * data will fit or delay in hopes of bundling a full 719 * sized packet. 720 */ 721 if (len < asoc->frag_point) { 722 retval = SCTP_XMIT_NAGLE_DELAY; 723 goto finish; 724 } 725 } 726 727 /* Keep track of how many bytes are in flight over this transport. */ 728 transport->flight_size += datasize; 729 730 /* Keep track of how many bytes are in flight to the receiver. */ 731 asoc->outqueue.outstanding_bytes += datasize; 732 733 /* Update our view of the receiver's rwnd. Include sk_buff overhead 734 * while updating peer.rwnd so that it reduces the chances of a 735 * receiver running out of receive buffer space even when receive 736 * window is still open. This can happen when a sender is sending 737 * sending small messages. 738 */ 739 datasize += sizeof(struct sk_buff); 740 if (datasize < rwnd) 741 rwnd -= datasize; 742 else 743 rwnd = 0; 744 745 asoc->peer.rwnd = rwnd; 746 /* Has been accepted for transmission. */ 747 if (!asoc->peer.prsctp_capable) 748 chunk->msg->can_abandon = 0; 749 750 finish: 751 return retval; 752 } 753