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/ip.h> 53 #include <net/icmp.h> 54 #include <net/net_namespace.h> 55 56 #include <linux/socket.h> /* for sa_family_t */ 57 #include <net/sock.h> 58 59 #include <net/sctp/sctp.h> 60 #include <net/sctp/sm.h> 61 #include <net/sctp/checksum.h> 62 63 /* Forward declarations for private helpers. */ 64 static sctp_xmit_t sctp_packet_append_data(struct sctp_packet *packet, 65 struct sctp_chunk *chunk); 66 67 /* Config a packet. 68 * This appears to be a followup set of initializations. 69 */ 70 struct sctp_packet *sctp_packet_config(struct sctp_packet *packet, 71 __u32 vtag, int ecn_capable) 72 { 73 struct sctp_chunk *chunk = NULL; 74 75 SCTP_DEBUG_PRINTK("%s: packet:%p vtag:0x%x\n", __func__, 76 packet, vtag); 77 78 packet->vtag = vtag; 79 packet->has_cookie_echo = 0; 80 packet->has_sack = 0; 81 packet->has_auth = 0; 82 packet->has_data = 0; 83 packet->ipfragok = 0; 84 packet->auth = NULL; 85 86 if (ecn_capable && sctp_packet_empty(packet)) { 87 chunk = sctp_get_ecne_prepend(packet->transport->asoc); 88 89 /* If there a is a prepend chunk stick it on the list before 90 * any other chunks get appended. 91 */ 92 if (chunk) 93 sctp_packet_append_chunk(packet, chunk); 94 } 95 96 return packet; 97 } 98 99 /* Initialize the packet structure. */ 100 struct sctp_packet *sctp_packet_init(struct sctp_packet *packet, 101 struct sctp_transport *transport, 102 __u16 sport, __u16 dport) 103 { 104 struct sctp_association *asoc = transport->asoc; 105 size_t overhead; 106 107 SCTP_DEBUG_PRINTK("%s: packet:%p transport:%p\n", __func__, 108 packet, transport); 109 110 packet->transport = transport; 111 packet->source_port = sport; 112 packet->destination_port = dport; 113 INIT_LIST_HEAD(&packet->chunk_list); 114 if (asoc) { 115 struct sctp_sock *sp = sctp_sk(asoc->base.sk); 116 overhead = sp->pf->af->net_header_len; 117 } else { 118 overhead = sizeof(struct ipv6hdr); 119 } 120 overhead += sizeof(struct sctphdr); 121 packet->overhead = overhead; 122 packet->size = overhead; 123 packet->vtag = 0; 124 packet->has_cookie_echo = 0; 125 packet->has_sack = 0; 126 packet->has_auth = 0; 127 packet->has_data = 0; 128 packet->ipfragok = 0; 129 packet->malloced = 0; 130 packet->auth = NULL; 131 return packet; 132 } 133 134 /* Free a packet. */ 135 void sctp_packet_free(struct sctp_packet *packet) 136 { 137 struct sctp_chunk *chunk, *tmp; 138 139 SCTP_DEBUG_PRINTK("%s: packet:%p\n", __func__, packet); 140 141 list_for_each_entry_safe(chunk, tmp, &packet->chunk_list, list) { 142 list_del_init(&chunk->list); 143 sctp_chunk_free(chunk); 144 } 145 146 if (packet->malloced) 147 kfree(packet); 148 } 149 150 /* This routine tries to append the chunk to the offered packet. If adding 151 * the chunk causes the packet to exceed the path MTU and COOKIE_ECHO chunk 152 * is not present in the packet, it transmits the input packet. 153 * Data can be bundled with a packet containing a COOKIE_ECHO chunk as long 154 * as it can fit in the packet, but any more data that does not fit in this 155 * packet can be sent only after receiving the COOKIE_ACK. 156 */ 157 sctp_xmit_t sctp_packet_transmit_chunk(struct sctp_packet *packet, 158 struct sctp_chunk *chunk, 159 int one_packet) 160 { 161 sctp_xmit_t retval; 162 int error = 0; 163 164 SCTP_DEBUG_PRINTK("%s: packet:%p chunk:%p\n", __func__, 165 packet, chunk); 166 167 switch ((retval = (sctp_packet_append_chunk(packet, chunk)))) { 168 case SCTP_XMIT_PMTU_FULL: 169 if (!packet->has_cookie_echo) { 170 error = sctp_packet_transmit(packet); 171 if (error < 0) 172 chunk->skb->sk->sk_err = -error; 173 174 /* If we have an empty packet, then we can NOT ever 175 * return PMTU_FULL. 176 */ 177 if (!one_packet) 178 retval = sctp_packet_append_chunk(packet, 179 chunk); 180 } 181 break; 182 183 case SCTP_XMIT_RWND_FULL: 184 case SCTP_XMIT_OK: 185 case SCTP_XMIT_NAGLE_DELAY: 186 break; 187 } 188 189 return retval; 190 } 191 192 /* Try to bundle an auth chunk into the packet. */ 193 static sctp_xmit_t sctp_packet_bundle_auth(struct sctp_packet *pkt, 194 struct sctp_chunk *chunk) 195 { 196 struct sctp_association *asoc = pkt->transport->asoc; 197 struct sctp_chunk *auth; 198 sctp_xmit_t retval = SCTP_XMIT_OK; 199 200 /* if we don't have an association, we can't do authentication */ 201 if (!asoc) 202 return retval; 203 204 /* See if this is an auth chunk we are bundling or if 205 * auth is already bundled. 206 */ 207 if (chunk->chunk_hdr->type == SCTP_CID_AUTH || pkt->auth) 208 return retval; 209 210 /* if the peer did not request this chunk to be authenticated, 211 * don't do it 212 */ 213 if (!chunk->auth) 214 return retval; 215 216 auth = sctp_make_auth(asoc); 217 if (!auth) 218 return retval; 219 220 retval = sctp_packet_append_chunk(pkt, auth); 221 222 return retval; 223 } 224 225 /* Try to bundle a SACK with the packet. */ 226 static sctp_xmit_t sctp_packet_bundle_sack(struct sctp_packet *pkt, 227 struct sctp_chunk *chunk) 228 { 229 sctp_xmit_t retval = SCTP_XMIT_OK; 230 231 /* If sending DATA and haven't aleady bundled a SACK, try to 232 * bundle one in to the packet. 233 */ 234 if (sctp_chunk_is_data(chunk) && !pkt->has_sack && 235 !pkt->has_cookie_echo) { 236 struct sctp_association *asoc; 237 asoc = pkt->transport->asoc; 238 239 if (asoc->a_rwnd > asoc->rwnd) { 240 struct sctp_chunk *sack; 241 asoc->a_rwnd = asoc->rwnd; 242 sack = sctp_make_sack(asoc); 243 if (sack) { 244 struct timer_list *timer; 245 retval = sctp_packet_append_chunk(pkt, sack); 246 asoc->peer.sack_needed = 0; 247 timer = &asoc->timers[SCTP_EVENT_TIMEOUT_SACK]; 248 if (timer_pending(timer) && del_timer(timer)) 249 sctp_association_put(asoc); 250 } 251 } 252 } 253 return retval; 254 } 255 256 /* Append a chunk to the offered packet reporting back any inability to do 257 * so. 258 */ 259 sctp_xmit_t sctp_packet_append_chunk(struct sctp_packet *packet, 260 struct sctp_chunk *chunk) 261 { 262 sctp_xmit_t retval = SCTP_XMIT_OK; 263 __u16 chunk_len = WORD_ROUND(ntohs(chunk->chunk_hdr->length)); 264 size_t psize; 265 size_t pmtu; 266 int too_big; 267 268 SCTP_DEBUG_PRINTK("%s: packet:%p chunk:%p\n", __func__, packet, 269 chunk); 270 271 /* Try to bundle AUTH chunk */ 272 retval = sctp_packet_bundle_auth(packet, chunk); 273 if (retval != SCTP_XMIT_OK) 274 goto finish; 275 276 /* Try to bundle SACK chunk */ 277 retval = sctp_packet_bundle_sack(packet, chunk); 278 if (retval != SCTP_XMIT_OK) 279 goto finish; 280 281 psize = packet->size; 282 pmtu = ((packet->transport->asoc) ? 283 (packet->transport->asoc->pathmtu) : 284 (packet->transport->pathmtu)); 285 286 too_big = (psize + chunk_len > pmtu); 287 288 /* Decide if we need to fragment or resubmit later. */ 289 if (too_big) { 290 /* It's OK to fragmet at IP level if any one of the following 291 * is true: 292 * 1. The packet is empty (meaning this chunk is greater 293 * the MTU) 294 * 2. The chunk we are adding is a control chunk 295 * 3. The packet doesn't have any data in it yet and data 296 * requires authentication. 297 */ 298 if (sctp_packet_empty(packet) || !sctp_chunk_is_data(chunk) || 299 (!packet->has_data && chunk->auth)) { 300 /* We no longer do re-fragmentation. 301 * Just fragment at the IP layer, if we 302 * actually hit this condition 303 */ 304 packet->ipfragok = 1; 305 goto append; 306 307 } else { 308 retval = SCTP_XMIT_PMTU_FULL; 309 goto finish; 310 } 311 } 312 313 append: 314 /* We believe that this chunk is OK to add to the packet (as 315 * long as we have the cwnd for it). 316 */ 317 318 /* DATA is a special case since we must examine both rwnd and cwnd 319 * before we send DATA. 320 */ 321 switch (chunk->chunk_hdr->type) { 322 case SCTP_CID_DATA: 323 retval = sctp_packet_append_data(packet, chunk); 324 if (SCTP_XMIT_OK != retval) 325 goto finish; 326 /* Disallow SACK bundling after DATA. */ 327 packet->has_sack = 1; 328 /* Disallow AUTH bundling after DATA */ 329 packet->has_auth = 1; 330 /* Let it be knows that packet has DATA in it */ 331 packet->has_data = 1; 332 /* timestamp the chunk for rtx purposes */ 333 chunk->sent_at = jiffies; 334 break; 335 case SCTP_CID_COOKIE_ECHO: 336 packet->has_cookie_echo = 1; 337 break; 338 339 case SCTP_CID_SACK: 340 packet->has_sack = 1; 341 break; 342 343 case SCTP_CID_AUTH: 344 packet->has_auth = 1; 345 packet->auth = chunk; 346 break; 347 } 348 349 /* It is OK to send this chunk. */ 350 list_add_tail(&chunk->list, &packet->chunk_list); 351 packet->size += chunk_len; 352 chunk->transport = packet->transport; 353 finish: 354 return retval; 355 } 356 357 /* All packets are sent to the network through this function from 358 * sctp_outq_tail(). 359 * 360 * The return value is a normal kernel error return value. 361 */ 362 int sctp_packet_transmit(struct sctp_packet *packet) 363 { 364 struct sctp_transport *tp = packet->transport; 365 struct sctp_association *asoc = tp->asoc; 366 struct sctphdr *sh; 367 struct sk_buff *nskb; 368 struct sctp_chunk *chunk, *tmp; 369 struct sock *sk; 370 int err = 0; 371 int padding; /* How much padding do we need? */ 372 __u8 has_data = 0; 373 struct dst_entry *dst = tp->dst; 374 unsigned char *auth = NULL; /* pointer to auth in skb data */ 375 __u32 cksum_buf_len = sizeof(struct sctphdr); 376 377 SCTP_DEBUG_PRINTK("%s: packet:%p\n", __func__, packet); 378 379 /* Do NOT generate a chunkless packet. */ 380 if (list_empty(&packet->chunk_list)) 381 return err; 382 383 /* Set up convenience variables... */ 384 chunk = list_entry(packet->chunk_list.next, struct sctp_chunk, list); 385 sk = chunk->skb->sk; 386 387 /* Allocate the new skb. */ 388 nskb = alloc_skb(packet->size + LL_MAX_HEADER, GFP_ATOMIC); 389 if (!nskb) 390 goto nomem; 391 392 /* Make sure the outbound skb has enough header room reserved. */ 393 skb_reserve(nskb, packet->overhead + LL_MAX_HEADER); 394 395 /* Set the owning socket so that we know where to get the 396 * destination IP address. 397 */ 398 skb_set_owner_w(nskb, sk); 399 400 /* The 'obsolete' field of dst is set to 2 when a dst is freed. */ 401 if (!dst || (dst->obsolete > 1)) { 402 dst_release(dst); 403 sctp_transport_route(tp, NULL, sctp_sk(sk)); 404 if (asoc && (asoc->param_flags & SPP_PMTUD_ENABLE)) { 405 sctp_assoc_sync_pmtu(asoc); 406 } 407 } 408 dst = dst_clone(tp->dst); 409 skb_dst_set(nskb, dst); 410 if (!dst) 411 goto no_route; 412 413 /* Build the SCTP header. */ 414 sh = (struct sctphdr *)skb_push(nskb, sizeof(struct sctphdr)); 415 skb_reset_transport_header(nskb); 416 sh->source = htons(packet->source_port); 417 sh->dest = htons(packet->destination_port); 418 419 /* From 6.8 Adler-32 Checksum Calculation: 420 * After the packet is constructed (containing the SCTP common 421 * header and one or more control or DATA chunks), the 422 * transmitter shall: 423 * 424 * 1) Fill in the proper Verification Tag in the SCTP common 425 * header and initialize the checksum field to 0's. 426 */ 427 sh->vtag = htonl(packet->vtag); 428 sh->checksum = 0; 429 430 /** 431 * 6.10 Bundling 432 * 433 * An endpoint bundles chunks by simply including multiple 434 * chunks in one outbound SCTP packet. ... 435 */ 436 437 /** 438 * 3.2 Chunk Field Descriptions 439 * 440 * The total length of a chunk (including Type, Length and 441 * Value fields) MUST be a multiple of 4 bytes. If the length 442 * of the chunk is not a multiple of 4 bytes, the sender MUST 443 * pad the chunk with all zero bytes and this padding is not 444 * included in the chunk length field. The sender should 445 * never pad with more than 3 bytes. 446 * 447 * [This whole comment explains WORD_ROUND() below.] 448 */ 449 SCTP_DEBUG_PRINTK("***sctp_transmit_packet***\n"); 450 list_for_each_entry_safe(chunk, tmp, &packet->chunk_list, list) { 451 list_del_init(&chunk->list); 452 if (sctp_chunk_is_data(chunk)) { 453 454 if (!chunk->has_tsn) { 455 sctp_chunk_assign_ssn(chunk); 456 sctp_chunk_assign_tsn(chunk); 457 458 /* 6.3.1 C4) When data is in flight and when allowed 459 * by rule C5, a new RTT measurement MUST be made each 460 * round trip. Furthermore, new RTT measurements 461 * SHOULD be made no more than once per round-trip 462 * for a given destination transport address. 463 */ 464 465 if (!tp->rto_pending) { 466 chunk->rtt_in_progress = 1; 467 tp->rto_pending = 1; 468 } 469 } else 470 chunk->resent = 1; 471 472 has_data = 1; 473 } 474 475 padding = WORD_ROUND(chunk->skb->len) - chunk->skb->len; 476 if (padding) 477 memset(skb_put(chunk->skb, padding), 0, padding); 478 479 /* if this is the auth chunk that we are adding, 480 * store pointer where it will be added and put 481 * the auth into the packet. 482 */ 483 if (chunk == packet->auth) 484 auth = skb_tail_pointer(nskb); 485 486 cksum_buf_len += chunk->skb->len; 487 memcpy(skb_put(nskb, chunk->skb->len), 488 chunk->skb->data, chunk->skb->len); 489 490 SCTP_DEBUG_PRINTK("%s %p[%s] %s 0x%x, %s %d, %s %d, %s %d\n", 491 "*** Chunk", chunk, 492 sctp_cname(SCTP_ST_CHUNK( 493 chunk->chunk_hdr->type)), 494 chunk->has_tsn ? "TSN" : "No TSN", 495 chunk->has_tsn ? 496 ntohl(chunk->subh.data_hdr->tsn) : 0, 497 "length", ntohs(chunk->chunk_hdr->length), 498 "chunk->skb->len", chunk->skb->len, 499 "rtt_in_progress", chunk->rtt_in_progress); 500 501 /* 502 * If this is a control chunk, this is our last 503 * reference. Free data chunks after they've been 504 * acknowledged or have failed. 505 */ 506 if (!sctp_chunk_is_data(chunk)) 507 sctp_chunk_free(chunk); 508 } 509 510 /* SCTP-AUTH, Section 6.2 511 * The sender MUST calculate the MAC as described in RFC2104 [2] 512 * using the hash function H as described by the MAC Identifier and 513 * the shared association key K based on the endpoint pair shared key 514 * described by the shared key identifier. The 'data' used for the 515 * computation of the AUTH-chunk is given by the AUTH chunk with its 516 * HMAC field set to zero (as shown in Figure 6) followed by all 517 * chunks that are placed after the AUTH chunk in the SCTP packet. 518 */ 519 if (auth) 520 sctp_auth_calculate_hmac(asoc, nskb, 521 (struct sctp_auth_chunk *)auth, 522 GFP_ATOMIC); 523 524 /* 2) Calculate the Adler-32 checksum of the whole packet, 525 * including the SCTP common header and all the 526 * chunks. 527 * 528 * Note: Adler-32 is no longer applicable, as has been replaced 529 * by CRC32-C as described in <draft-ietf-tsvwg-sctpcsum-02.txt>. 530 */ 531 if (!sctp_checksum_disable && 532 !(dst->dev->features & (NETIF_F_NO_CSUM | NETIF_F_SCTP_CSUM))) { 533 __u32 crc32 = sctp_start_cksum((__u8 *)sh, cksum_buf_len); 534 535 /* 3) Put the resultant value into the checksum field in the 536 * common header, and leave the rest of the bits unchanged. 537 */ 538 sh->checksum = sctp_end_cksum(crc32); 539 } else { 540 if (dst->dev->features & NETIF_F_SCTP_CSUM) { 541 /* no need to seed psuedo checksum for SCTP */ 542 nskb->ip_summed = CHECKSUM_PARTIAL; 543 nskb->csum_start = (skb_transport_header(nskb) - 544 nskb->head); 545 nskb->csum_offset = offsetof(struct sctphdr, checksum); 546 } else { 547 nskb->ip_summed = CHECKSUM_UNNECESSARY; 548 } 549 } 550 551 /* IP layer ECN support 552 * From RFC 2481 553 * "The ECN-Capable Transport (ECT) bit would be set by the 554 * data sender to indicate that the end-points of the 555 * transport protocol are ECN-capable." 556 * 557 * Now setting the ECT bit all the time, as it should not cause 558 * any problems protocol-wise even if our peer ignores it. 559 * 560 * Note: The works for IPv6 layer checks this bit too later 561 * in transmission. See IP6_ECN_flow_xmit(). 562 */ 563 (*tp->af_specific->ecn_capable)(nskb->sk); 564 565 /* Set up the IP options. */ 566 /* BUG: not implemented 567 * For v4 this all lives somewhere in sk->sk_opt... 568 */ 569 570 /* Dump that on IP! */ 571 if (asoc && asoc->peer.last_sent_to != tp) { 572 /* Considering the multiple CPU scenario, this is a 573 * "correcter" place for last_sent_to. --xguo 574 */ 575 asoc->peer.last_sent_to = tp; 576 } 577 578 if (has_data) { 579 struct timer_list *timer; 580 unsigned long timeout; 581 582 tp->last_time_used = jiffies; 583 584 /* Restart the AUTOCLOSE timer when sending data. */ 585 if (sctp_state(asoc, ESTABLISHED) && asoc->autoclose) { 586 timer = &asoc->timers[SCTP_EVENT_TIMEOUT_AUTOCLOSE]; 587 timeout = asoc->timeouts[SCTP_EVENT_TIMEOUT_AUTOCLOSE]; 588 589 if (!mod_timer(timer, jiffies + timeout)) 590 sctp_association_hold(asoc); 591 } 592 } 593 594 SCTP_DEBUG_PRINTK("***sctp_transmit_packet*** skb len %d\n", 595 nskb->len); 596 597 nskb->local_df = packet->ipfragok; 598 (*tp->af_specific->sctp_xmit)(nskb, tp); 599 600 out: 601 packet->size = packet->overhead; 602 return err; 603 no_route: 604 kfree_skb(nskb); 605 IP_INC_STATS_BH(&init_net, IPSTATS_MIB_OUTNOROUTES); 606 607 /* FIXME: Returning the 'err' will effect all the associations 608 * associated with a socket, although only one of the paths of the 609 * association is unreachable. 610 * The real failure of a transport or association can be passed on 611 * to the user via notifications. So setting this error may not be 612 * required. 613 */ 614 /* err = -EHOSTUNREACH; */ 615 err: 616 /* Control chunks are unreliable so just drop them. DATA chunks 617 * will get resent or dropped later. 618 */ 619 620 list_for_each_entry_safe(chunk, tmp, &packet->chunk_list, list) { 621 list_del_init(&chunk->list); 622 if (!sctp_chunk_is_data(chunk)) 623 sctp_chunk_free(chunk); 624 } 625 goto out; 626 nomem: 627 err = -ENOMEM; 628 goto err; 629 } 630 631 /******************************************************************** 632 * 2nd Level Abstractions 633 ********************************************************************/ 634 635 /* This private function handles the specifics of appending DATA chunks. */ 636 static sctp_xmit_t sctp_packet_append_data(struct sctp_packet *packet, 637 struct sctp_chunk *chunk) 638 { 639 sctp_xmit_t retval = SCTP_XMIT_OK; 640 size_t datasize, rwnd, inflight; 641 struct sctp_transport *transport = packet->transport; 642 __u32 max_burst_bytes; 643 struct sctp_association *asoc = transport->asoc; 644 struct sctp_sock *sp = sctp_sk(asoc->base.sk); 645 struct sctp_outq *q = &asoc->outqueue; 646 647 /* RFC 2960 6.1 Transmission of DATA Chunks 648 * 649 * A) At any given time, the data sender MUST NOT transmit new data to 650 * any destination transport address if its peer's rwnd indicates 651 * that the peer has no buffer space (i.e. rwnd is 0, see Section 652 * 6.2.1). However, regardless of the value of rwnd (including if it 653 * is 0), the data sender can always have one DATA chunk in flight to 654 * the receiver if allowed by cwnd (see rule B below). This rule 655 * allows the sender to probe for a change in rwnd that the sender 656 * missed due to the SACK having been lost in transit from the data 657 * receiver to the data sender. 658 */ 659 660 rwnd = asoc->peer.rwnd; 661 inflight = asoc->outqueue.outstanding_bytes; 662 663 datasize = sctp_data_size(chunk); 664 665 if (datasize > rwnd) { 666 if (inflight > 0) { 667 /* We have (at least) one data chunk in flight, 668 * so we can't fall back to rule 6.1 B). 669 */ 670 retval = SCTP_XMIT_RWND_FULL; 671 goto finish; 672 } 673 } 674 675 /* sctpimpguide-05 2.14.2 676 * D) When the time comes for the sender to 677 * transmit new DATA chunks, the protocol parameter Max.Burst MUST 678 * first be applied to limit how many new DATA chunks may be sent. 679 * The limit is applied by adjusting cwnd as follows: 680 * if ((flightsize + Max.Burst * MTU) < cwnd) 681 * cwnd = flightsize + Max.Burst * MTU 682 */ 683 max_burst_bytes = asoc->max_burst * asoc->pathmtu; 684 if ((transport->flight_size + max_burst_bytes) < transport->cwnd) { 685 transport->cwnd = transport->flight_size + max_burst_bytes; 686 SCTP_DEBUG_PRINTK("%s: cwnd limited by max_burst: " 687 "transport: %p, cwnd: %d, " 688 "ssthresh: %d, flight_size: %d, " 689 "pba: %d\n", 690 __func__, transport, 691 transport->cwnd, 692 transport->ssthresh, 693 transport->flight_size, 694 transport->partial_bytes_acked); 695 } 696 697 /* RFC 2960 6.1 Transmission of DATA Chunks 698 * 699 * B) At any given time, the sender MUST NOT transmit new data 700 * to a given transport address if it has cwnd or more bytes 701 * of data outstanding to that transport address. 702 */ 703 /* RFC 7.2.4 & the Implementers Guide 2.8. 704 * 705 * 3) ... 706 * When a Fast Retransmit is being performed the sender SHOULD 707 * ignore the value of cwnd and SHOULD NOT delay retransmission. 708 */ 709 if (chunk->fast_retransmit != SCTP_NEED_FRTX) 710 if (transport->flight_size >= transport->cwnd) { 711 retval = SCTP_XMIT_RWND_FULL; 712 goto finish; 713 } 714 715 /* Nagle's algorithm to solve small-packet problem: 716 * Inhibit the sending of new chunks when new outgoing data arrives 717 * if any previously transmitted data on the connection remains 718 * unacknowledged. 719 */ 720 if (!sp->nodelay && sctp_packet_empty(packet) && 721 q->outstanding_bytes && sctp_state(asoc, ESTABLISHED)) { 722 unsigned len = datasize + q->out_qlen; 723 724 /* Check whether this chunk and all the rest of pending 725 * data will fit or delay in hopes of bundling a full 726 * sized packet. 727 */ 728 if (len < asoc->frag_point) { 729 retval = SCTP_XMIT_NAGLE_DELAY; 730 goto finish; 731 } 732 } 733 734 /* Keep track of how many bytes are in flight over this transport. */ 735 transport->flight_size += datasize; 736 737 /* Keep track of how many bytes are in flight to the receiver. */ 738 asoc->outqueue.outstanding_bytes += datasize; 739 740 /* Update our view of the receiver's rwnd. Include sk_buff overhead 741 * while updating peer.rwnd so that it reduces the chances of a 742 * receiver running out of receive buffer space even when receive 743 * window is still open. This can happen when a sender is sending 744 * sending small messages. 745 */ 746 datasize += sizeof(struct sk_buff); 747 if (datasize < rwnd) 748 rwnd -= datasize; 749 else 750 rwnd = 0; 751 752 asoc->peer.rwnd = rwnd; 753 /* Has been accepted for transmission. */ 754 if (!asoc->peer.prsctp_capable) 755 chunk->msg->can_abandon = 0; 756 757 finish: 758 return retval; 759 } 760