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 <linux-sctp@vger.kernel.org> 30 * 31 * Written or modified by: 32 * La Monte H.P. Yarroll <piggy@acm.org> 33 * Karl Knutson <karl@athena.chicago.il.us> 34 * Jon Grimm <jgrimm@austin.ibm.com> 35 * Sridhar Samudrala <sri@us.ibm.com> 36 */ 37 38 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 39 40 #include <linux/types.h> 41 #include <linux/kernel.h> 42 #include <linux/wait.h> 43 #include <linux/time.h> 44 #include <linux/ip.h> 45 #include <linux/ipv6.h> 46 #include <linux/init.h> 47 #include <linux/slab.h> 48 #include <net/inet_ecn.h> 49 #include <net/ip.h> 50 #include <net/icmp.h> 51 #include <net/net_namespace.h> 52 53 #include <linux/socket.h> /* for sa_family_t */ 54 #include <net/sock.h> 55 56 #include <net/sctp/sctp.h> 57 #include <net/sctp/sm.h> 58 #include <net/sctp/checksum.h> 59 60 /* Forward declarations for private helpers. */ 61 static sctp_xmit_t __sctp_packet_append_chunk(struct sctp_packet *packet, 62 struct sctp_chunk *chunk); 63 static sctp_xmit_t sctp_packet_can_append_data(struct sctp_packet *packet, 64 struct sctp_chunk *chunk); 65 static void sctp_packet_append_data(struct sctp_packet *packet, 66 struct sctp_chunk *chunk); 67 static sctp_xmit_t sctp_packet_will_fit(struct sctp_packet *packet, 68 struct sctp_chunk *chunk, 69 u16 chunk_len); 70 71 static void sctp_packet_reset(struct sctp_packet *packet) 72 { 73 packet->size = packet->overhead; 74 packet->has_cookie_echo = 0; 75 packet->has_sack = 0; 76 packet->has_data = 0; 77 packet->has_auth = 0; 78 packet->ipfragok = 0; 79 packet->auth = NULL; 80 } 81 82 /* Config a packet. 83 * This appears to be a followup set of initializations. 84 */ 85 struct sctp_packet *sctp_packet_config(struct sctp_packet *packet, 86 __u32 vtag, int ecn_capable) 87 { 88 struct sctp_chunk *chunk = NULL; 89 90 pr_debug("%s: packet:%p vtag:0x%x\n", __func__, packet, vtag); 91 92 packet->vtag = vtag; 93 94 if (ecn_capable && sctp_packet_empty(packet)) { 95 chunk = sctp_get_ecne_prepend(packet->transport->asoc); 96 97 /* If there a is a prepend chunk stick it on the list before 98 * any other chunks get appended. 99 */ 100 if (chunk) 101 sctp_packet_append_chunk(packet, chunk); 102 } 103 104 return packet; 105 } 106 107 /* Initialize the packet structure. */ 108 struct sctp_packet *sctp_packet_init(struct sctp_packet *packet, 109 struct sctp_transport *transport, 110 __u16 sport, __u16 dport) 111 { 112 struct sctp_association *asoc = transport->asoc; 113 size_t overhead; 114 115 pr_debug("%s: packet:%p transport:%p\n", __func__, packet, transport); 116 117 packet->transport = transport; 118 packet->source_port = sport; 119 packet->destination_port = dport; 120 INIT_LIST_HEAD(&packet->chunk_list); 121 if (asoc) { 122 struct sctp_sock *sp = sctp_sk(asoc->base.sk); 123 overhead = sp->pf->af->net_header_len; 124 } else { 125 overhead = sizeof(struct ipv6hdr); 126 } 127 overhead += sizeof(struct sctphdr); 128 packet->overhead = overhead; 129 sctp_packet_reset(packet); 130 packet->vtag = 0; 131 132 return packet; 133 } 134 135 /* Free a packet. */ 136 void sctp_packet_free(struct sctp_packet *packet) 137 { 138 struct sctp_chunk *chunk, *tmp; 139 140 pr_debug("%s: packet:%p\n", __func__, packet); 141 142 list_for_each_entry_safe(chunk, tmp, &packet->chunk_list, list) { 143 list_del_init(&chunk->list); 144 sctp_chunk_free(chunk); 145 } 146 } 147 148 /* This routine tries to append the chunk to the offered packet. If adding 149 * the chunk causes the packet to exceed the path MTU and COOKIE_ECHO chunk 150 * is not present in the packet, it transmits the input packet. 151 * Data can be bundled with a packet containing a COOKIE_ECHO chunk as long 152 * as it can fit in the packet, but any more data that does not fit in this 153 * packet can be sent only after receiving the COOKIE_ACK. 154 */ 155 sctp_xmit_t sctp_packet_transmit_chunk(struct sctp_packet *packet, 156 struct sctp_chunk *chunk, 157 int one_packet) 158 { 159 sctp_xmit_t retval; 160 int error = 0; 161 162 pr_debug("%s: packet:%p chunk:%p\n", __func__, packet, chunk); 163 164 switch ((retval = (sctp_packet_append_chunk(packet, chunk)))) { 165 case SCTP_XMIT_PMTU_FULL: 166 if (!packet->has_cookie_echo) { 167 error = sctp_packet_transmit(packet); 168 if (error < 0) 169 chunk->skb->sk->sk_err = -error; 170 171 /* If we have an empty packet, then we can NOT ever 172 * return PMTU_FULL. 173 */ 174 if (!one_packet) 175 retval = sctp_packet_append_chunk(packet, 176 chunk); 177 } 178 break; 179 180 case SCTP_XMIT_RWND_FULL: 181 case SCTP_XMIT_OK: 182 case SCTP_XMIT_NAGLE_DELAY: 183 break; 184 } 185 186 return retval; 187 } 188 189 /* Try to bundle an auth chunk into the packet. */ 190 static sctp_xmit_t sctp_packet_bundle_auth(struct sctp_packet *pkt, 191 struct sctp_chunk *chunk) 192 { 193 struct sctp_association *asoc = pkt->transport->asoc; 194 struct sctp_chunk *auth; 195 sctp_xmit_t retval = SCTP_XMIT_OK; 196 197 /* if we don't have an association, we can't do authentication */ 198 if (!asoc) 199 return retval; 200 201 /* See if this is an auth chunk we are bundling or if 202 * auth is already bundled. 203 */ 204 if (chunk->chunk_hdr->type == SCTP_CID_AUTH || pkt->has_auth) 205 return retval; 206 207 /* if the peer did not request this chunk to be authenticated, 208 * don't do it 209 */ 210 if (!chunk->auth) 211 return retval; 212 213 auth = sctp_make_auth(asoc); 214 if (!auth) 215 return retval; 216 217 retval = __sctp_packet_append_chunk(pkt, auth); 218 219 if (retval != SCTP_XMIT_OK) 220 sctp_chunk_free(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 struct timer_list *timer; 238 asoc = pkt->transport->asoc; 239 timer = &asoc->timers[SCTP_EVENT_TIMEOUT_SACK]; 240 241 /* If the SACK timer is running, we have a pending SACK */ 242 if (timer_pending(timer)) { 243 struct sctp_chunk *sack; 244 245 if (pkt->transport->sack_generation != 246 pkt->transport->asoc->peer.sack_generation) 247 return retval; 248 249 asoc->a_rwnd = asoc->rwnd; 250 sack = sctp_make_sack(asoc); 251 if (sack) { 252 retval = __sctp_packet_append_chunk(pkt, sack); 253 if (retval != SCTP_XMIT_OK) { 254 sctp_chunk_free(sack); 255 goto out; 256 } 257 asoc->peer.sack_needed = 0; 258 if (del_timer(timer)) 259 sctp_association_put(asoc); 260 } 261 } 262 } 263 out: 264 return retval; 265 } 266 267 268 /* Append a chunk to the offered packet reporting back any inability to do 269 * so. 270 */ 271 static sctp_xmit_t __sctp_packet_append_chunk(struct sctp_packet *packet, 272 struct sctp_chunk *chunk) 273 { 274 sctp_xmit_t retval = SCTP_XMIT_OK; 275 __u16 chunk_len = WORD_ROUND(ntohs(chunk->chunk_hdr->length)); 276 277 /* Check to see if this chunk will fit into the packet */ 278 retval = sctp_packet_will_fit(packet, chunk, chunk_len); 279 if (retval != SCTP_XMIT_OK) 280 goto finish; 281 282 /* We believe that this chunk is OK to add to the packet */ 283 switch (chunk->chunk_hdr->type) { 284 case SCTP_CID_DATA: 285 /* Account for the data being in the packet */ 286 sctp_packet_append_data(packet, chunk); 287 /* Disallow SACK bundling after DATA. */ 288 packet->has_sack = 1; 289 /* Disallow AUTH bundling after DATA */ 290 packet->has_auth = 1; 291 /* Let it be knows that packet has DATA in it */ 292 packet->has_data = 1; 293 /* timestamp the chunk for rtx purposes */ 294 chunk->sent_at = jiffies; 295 break; 296 case SCTP_CID_COOKIE_ECHO: 297 packet->has_cookie_echo = 1; 298 break; 299 300 case SCTP_CID_SACK: 301 packet->has_sack = 1; 302 if (chunk->asoc) 303 chunk->asoc->stats.osacks++; 304 break; 305 306 case SCTP_CID_AUTH: 307 packet->has_auth = 1; 308 packet->auth = chunk; 309 break; 310 } 311 312 /* It is OK to send this chunk. */ 313 list_add_tail(&chunk->list, &packet->chunk_list); 314 packet->size += chunk_len; 315 chunk->transport = packet->transport; 316 finish: 317 return retval; 318 } 319 320 /* Append a chunk to the offered packet reporting back any inability to do 321 * so. 322 */ 323 sctp_xmit_t sctp_packet_append_chunk(struct sctp_packet *packet, 324 struct sctp_chunk *chunk) 325 { 326 sctp_xmit_t retval = SCTP_XMIT_OK; 327 328 pr_debug("%s: packet:%p chunk:%p\n", __func__, packet, chunk); 329 330 /* Data chunks are special. Before seeing what else we can 331 * bundle into this packet, check to see if we are allowed to 332 * send this DATA. 333 */ 334 if (sctp_chunk_is_data(chunk)) { 335 retval = sctp_packet_can_append_data(packet, chunk); 336 if (retval != SCTP_XMIT_OK) 337 goto finish; 338 } 339 340 /* Try to bundle AUTH chunk */ 341 retval = sctp_packet_bundle_auth(packet, chunk); 342 if (retval != SCTP_XMIT_OK) 343 goto finish; 344 345 /* Try to bundle SACK chunk */ 346 retval = sctp_packet_bundle_sack(packet, chunk); 347 if (retval != SCTP_XMIT_OK) 348 goto finish; 349 350 retval = __sctp_packet_append_chunk(packet, chunk); 351 352 finish: 353 return retval; 354 } 355 356 static void sctp_packet_release_owner(struct sk_buff *skb) 357 { 358 sk_free(skb->sk); 359 } 360 361 static void sctp_packet_set_owner_w(struct sk_buff *skb, struct sock *sk) 362 { 363 skb_orphan(skb); 364 skb->sk = sk; 365 skb->destructor = sctp_packet_release_owner; 366 367 /* 368 * The data chunks have already been accounted for in sctp_sendmsg(), 369 * therefore only reserve a single byte to keep socket around until 370 * the packet has been transmitted. 371 */ 372 atomic_inc(&sk->sk_wmem_alloc); 373 } 374 375 /* All packets are sent to the network through this function from 376 * sctp_outq_tail(). 377 * 378 * The return value is a normal kernel error return value. 379 */ 380 int sctp_packet_transmit(struct sctp_packet *packet) 381 { 382 struct sctp_transport *tp = packet->transport; 383 struct sctp_association *asoc = tp->asoc; 384 struct sctphdr *sh; 385 struct sk_buff *nskb; 386 struct sctp_chunk *chunk, *tmp; 387 struct sock *sk; 388 int err = 0; 389 int padding; /* How much padding do we need? */ 390 __u8 has_data = 0; 391 struct dst_entry *dst = tp->dst; 392 unsigned char *auth = NULL; /* pointer to auth in skb data */ 393 394 pr_debug("%s: packet:%p\n", __func__, packet); 395 396 /* Do NOT generate a chunkless packet. */ 397 if (list_empty(&packet->chunk_list)) 398 return err; 399 400 /* Set up convenience variables... */ 401 chunk = list_entry(packet->chunk_list.next, struct sctp_chunk, list); 402 sk = chunk->skb->sk; 403 404 /* Allocate the new skb. */ 405 nskb = alloc_skb(packet->size + LL_MAX_HEADER, GFP_ATOMIC); 406 if (!nskb) 407 goto nomem; 408 409 /* Make sure the outbound skb has enough header room reserved. */ 410 skb_reserve(nskb, packet->overhead + LL_MAX_HEADER); 411 412 /* Set the owning socket so that we know where to get the 413 * destination IP address. 414 */ 415 sctp_packet_set_owner_w(nskb, sk); 416 417 if (!sctp_transport_dst_check(tp)) { 418 sctp_transport_route(tp, NULL, sctp_sk(sk)); 419 if (asoc && (asoc->param_flags & SPP_PMTUD_ENABLE)) { 420 sctp_assoc_sync_pmtu(sk, asoc); 421 } 422 } 423 dst = dst_clone(tp->dst); 424 skb_dst_set(nskb, dst); 425 if (!dst) 426 goto no_route; 427 428 /* Build the SCTP header. */ 429 sh = (struct sctphdr *)skb_push(nskb, sizeof(struct sctphdr)); 430 skb_reset_transport_header(nskb); 431 sh->source = htons(packet->source_port); 432 sh->dest = htons(packet->destination_port); 433 434 /* From 6.8 Adler-32 Checksum Calculation: 435 * After the packet is constructed (containing the SCTP common 436 * header and one or more control or DATA chunks), the 437 * transmitter shall: 438 * 439 * 1) Fill in the proper Verification Tag in the SCTP common 440 * header and initialize the checksum field to 0's. 441 */ 442 sh->vtag = htonl(packet->vtag); 443 sh->checksum = 0; 444 445 /** 446 * 6.10 Bundling 447 * 448 * An endpoint bundles chunks by simply including multiple 449 * chunks in one outbound SCTP packet. ... 450 */ 451 452 /** 453 * 3.2 Chunk Field Descriptions 454 * 455 * The total length of a chunk (including Type, Length and 456 * Value fields) MUST be a multiple of 4 bytes. If the length 457 * of the chunk is not a multiple of 4 bytes, the sender MUST 458 * pad the chunk with all zero bytes and this padding is not 459 * included in the chunk length field. The sender should 460 * never pad with more than 3 bytes. 461 * 462 * [This whole comment explains WORD_ROUND() below.] 463 */ 464 465 pr_debug("***sctp_transmit_packet***\n"); 466 467 list_for_each_entry_safe(chunk, tmp, &packet->chunk_list, list) { 468 list_del_init(&chunk->list); 469 if (sctp_chunk_is_data(chunk)) { 470 /* 6.3.1 C4) When data is in flight and when allowed 471 * by rule C5, a new RTT measurement MUST be made each 472 * round trip. Furthermore, new RTT measurements 473 * SHOULD be made no more than once per round-trip 474 * for a given destination transport address. 475 */ 476 477 if (!chunk->resent && !tp->rto_pending) { 478 chunk->rtt_in_progress = 1; 479 tp->rto_pending = 1; 480 } 481 482 has_data = 1; 483 } 484 485 padding = WORD_ROUND(chunk->skb->len) - chunk->skb->len; 486 if (padding) 487 memset(skb_put(chunk->skb, padding), 0, padding); 488 489 /* if this is the auth chunk that we are adding, 490 * store pointer where it will be added and put 491 * the auth into the packet. 492 */ 493 if (chunk == packet->auth) 494 auth = skb_tail_pointer(nskb); 495 496 memcpy(skb_put(nskb, chunk->skb->len), 497 chunk->skb->data, chunk->skb->len); 498 499 pr_debug("*** Chunk:%p[%s] %s 0x%x, length:%d, chunk->skb->len:%d, " 500 "rtt_in_progress:%d\n", chunk, 501 sctp_cname(SCTP_ST_CHUNK(chunk->chunk_hdr->type)), 502 chunk->has_tsn ? "TSN" : "No TSN", 503 chunk->has_tsn ? ntohl(chunk->subh.data_hdr->tsn) : 0, 504 ntohs(chunk->chunk_hdr->length), chunk->skb->len, 505 chunk->rtt_in_progress); 506 507 /* 508 * If this is a control chunk, this is our last 509 * reference. Free data chunks after they've been 510 * acknowledged or have failed. 511 */ 512 if (!sctp_chunk_is_data(chunk)) 513 sctp_chunk_free(chunk); 514 } 515 516 /* SCTP-AUTH, Section 6.2 517 * The sender MUST calculate the MAC as described in RFC2104 [2] 518 * using the hash function H as described by the MAC Identifier and 519 * the shared association key K based on the endpoint pair shared key 520 * described by the shared key identifier. The 'data' used for the 521 * computation of the AUTH-chunk is given by the AUTH chunk with its 522 * HMAC field set to zero (as shown in Figure 6) followed by all 523 * chunks that are placed after the AUTH chunk in the SCTP packet. 524 */ 525 if (auth) 526 sctp_auth_calculate_hmac(asoc, nskb, 527 (struct sctp_auth_chunk *)auth, 528 GFP_ATOMIC); 529 530 /* 2) Calculate the Adler-32 checksum of the whole packet, 531 * including the SCTP common header and all the 532 * chunks. 533 * 534 * Note: Adler-32 is no longer applicable, as has been replaced 535 * by CRC32-C as described in <draft-ietf-tsvwg-sctpcsum-02.txt>. 536 */ 537 if (!sctp_checksum_disable) { 538 if (!(dst->dev->features & NETIF_F_SCTP_CSUM) || 539 (dst_xfrm(dst) != NULL) || packet->ipfragok) { 540 sh->checksum = sctp_compute_cksum(nskb, 0); 541 } else { 542 /* no need to seed pseudo checksum for SCTP */ 543 nskb->ip_summed = CHECKSUM_PARTIAL; 544 nskb->csum_start = (skb_transport_header(nskb) - 545 nskb->head); 546 nskb->csum_offset = offsetof(struct sctphdr, checksum); 547 } 548 } 549 550 /* IP layer ECN support 551 * From RFC 2481 552 * "The ECN-Capable Transport (ECT) bit would be set by the 553 * data sender to indicate that the end-points of the 554 * transport protocol are ECN-capable." 555 * 556 * Now setting the ECT bit all the time, as it should not cause 557 * any problems protocol-wise even if our peer ignores it. 558 * 559 * Note: The works for IPv6 layer checks this bit too later 560 * in transmission. See IP6_ECN_flow_xmit(). 561 */ 562 (*tp->af_specific->ecn_capable)(nskb->sk); 563 564 /* Set up the IP options. */ 565 /* BUG: not implemented 566 * For v4 this all lives somewhere in sk->sk_opt... 567 */ 568 569 /* Dump that on IP! */ 570 if (asoc) { 571 asoc->stats.opackets++; 572 if (asoc->peer.last_sent_to != tp) 573 /* Considering the multiple CPU scenario, this is a 574 * "correcter" place for last_sent_to. --xguo 575 */ 576 asoc->peer.last_sent_to = tp; 577 } 578 579 if (has_data) { 580 struct timer_list *timer; 581 unsigned long timeout; 582 583 /* Restart the AUTOCLOSE timer when sending data. */ 584 if (sctp_state(asoc, ESTABLISHED) && 585 asoc->timeouts[SCTP_EVENT_TIMEOUT_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 pr_debug("***sctp_transmit_packet*** skb->len:%d\n", nskb->len); 595 596 nskb->local_df = packet->ipfragok; 597 (*tp->af_specific->sctp_xmit)(nskb, tp); 598 599 out: 600 sctp_packet_reset(packet); 601 return err; 602 no_route: 603 kfree_skb(nskb); 604 IP_INC_STATS_BH(sock_net(asoc->base.sk), IPSTATS_MIB_OUTNOROUTES); 605 606 /* FIXME: Returning the 'err' will effect all the associations 607 * associated with a socket, although only one of the paths of the 608 * association is unreachable. 609 * The real failure of a transport or association can be passed on 610 * to the user via notifications. So setting this error may not be 611 * required. 612 */ 613 /* err = -EHOSTUNREACH; */ 614 err: 615 /* Control chunks are unreliable so just drop them. DATA chunks 616 * will get resent or dropped later. 617 */ 618 619 list_for_each_entry_safe(chunk, tmp, &packet->chunk_list, list) { 620 list_del_init(&chunk->list); 621 if (!sctp_chunk_is_data(chunk)) 622 sctp_chunk_free(chunk); 623 } 624 goto out; 625 nomem: 626 err = -ENOMEM; 627 goto err; 628 } 629 630 /******************************************************************** 631 * 2nd Level Abstractions 632 ********************************************************************/ 633 634 /* This private function check to see if a chunk can be added */ 635 static sctp_xmit_t sctp_packet_can_append_data(struct sctp_packet *packet, 636 struct sctp_chunk *chunk) 637 { 638 sctp_xmit_t retval = SCTP_XMIT_OK; 639 size_t datasize, rwnd, inflight, flight_size; 640 struct sctp_transport *transport = packet->transport; 641 struct sctp_association *asoc = transport->asoc; 642 struct sctp_outq *q = &asoc->outqueue; 643 644 /* RFC 2960 6.1 Transmission of DATA Chunks 645 * 646 * A) At any given time, the data sender MUST NOT transmit new data to 647 * any destination transport address if its peer's rwnd indicates 648 * that the peer has no buffer space (i.e. rwnd is 0, see Section 649 * 6.2.1). However, regardless of the value of rwnd (including if it 650 * is 0), the data sender can always have one DATA chunk in flight to 651 * the receiver if allowed by cwnd (see rule B below). This rule 652 * allows the sender to probe for a change in rwnd that the sender 653 * missed due to the SACK having been lost in transit from the data 654 * receiver to the data sender. 655 */ 656 657 rwnd = asoc->peer.rwnd; 658 inflight = q->outstanding_bytes; 659 flight_size = transport->flight_size; 660 661 datasize = sctp_data_size(chunk); 662 663 if (datasize > rwnd) { 664 if (inflight > 0) { 665 /* We have (at least) one data chunk in flight, 666 * so we can't fall back to rule 6.1 B). 667 */ 668 retval = SCTP_XMIT_RWND_FULL; 669 goto finish; 670 } 671 } 672 673 /* RFC 2960 6.1 Transmission of DATA Chunks 674 * 675 * B) At any given time, the sender MUST NOT transmit new data 676 * to a given transport address if it has cwnd or more bytes 677 * of data outstanding to that transport address. 678 */ 679 /* RFC 7.2.4 & the Implementers Guide 2.8. 680 * 681 * 3) ... 682 * When a Fast Retransmit is being performed the sender SHOULD 683 * ignore the value of cwnd and SHOULD NOT delay retransmission. 684 */ 685 if (chunk->fast_retransmit != SCTP_NEED_FRTX) 686 if (flight_size >= transport->cwnd) { 687 retval = SCTP_XMIT_RWND_FULL; 688 goto finish; 689 } 690 691 /* Nagle's algorithm to solve small-packet problem: 692 * Inhibit the sending of new chunks when new outgoing data arrives 693 * if any previously transmitted data on the connection remains 694 * unacknowledged. 695 */ 696 if (!sctp_sk(asoc->base.sk)->nodelay && sctp_packet_empty(packet) && 697 inflight && sctp_state(asoc, ESTABLISHED)) { 698 unsigned int max = transport->pathmtu - packet->overhead; 699 unsigned int len = chunk->skb->len + q->out_qlen; 700 701 /* Check whether this chunk and all the rest of pending 702 * data will fit or delay in hopes of bundling a full 703 * sized packet. 704 * Don't delay large message writes that may have been 705 * fragmeneted into small peices. 706 */ 707 if ((len < max) && chunk->msg->can_delay) { 708 retval = SCTP_XMIT_NAGLE_DELAY; 709 goto finish; 710 } 711 } 712 713 finish: 714 return retval; 715 } 716 717 /* This private function does management things when adding DATA chunk */ 718 static void sctp_packet_append_data(struct sctp_packet *packet, 719 struct sctp_chunk *chunk) 720 { 721 struct sctp_transport *transport = packet->transport; 722 size_t datasize = sctp_data_size(chunk); 723 struct sctp_association *asoc = transport->asoc; 724 u32 rwnd = asoc->peer.rwnd; 725 726 /* Keep track of how many bytes are in flight over this transport. */ 727 transport->flight_size += datasize; 728 729 /* Keep track of how many bytes are in flight to the receiver. */ 730 asoc->outqueue.outstanding_bytes += datasize; 731 732 /* Update our view of the receiver's rwnd. */ 733 if (datasize < rwnd) 734 rwnd -= datasize; 735 else 736 rwnd = 0; 737 738 asoc->peer.rwnd = rwnd; 739 /* Has been accepted for transmission. */ 740 if (!asoc->peer.prsctp_capable) 741 chunk->msg->can_abandon = 0; 742 sctp_chunk_assign_tsn(chunk); 743 sctp_chunk_assign_ssn(chunk); 744 } 745 746 static sctp_xmit_t sctp_packet_will_fit(struct sctp_packet *packet, 747 struct sctp_chunk *chunk, 748 u16 chunk_len) 749 { 750 size_t psize; 751 size_t pmtu; 752 int too_big; 753 sctp_xmit_t retval = SCTP_XMIT_OK; 754 755 psize = packet->size; 756 pmtu = ((packet->transport->asoc) ? 757 (packet->transport->asoc->pathmtu) : 758 (packet->transport->pathmtu)); 759 760 too_big = (psize + chunk_len > pmtu); 761 762 /* Decide if we need to fragment or resubmit later. */ 763 if (too_big) { 764 /* It's OK to fragmet at IP level if any one of the following 765 * is true: 766 * 1. The packet is empty (meaning this chunk is greater 767 * the MTU) 768 * 2. The chunk we are adding is a control chunk 769 * 3. The packet doesn't have any data in it yet and data 770 * requires authentication. 771 */ 772 if (sctp_packet_empty(packet) || !sctp_chunk_is_data(chunk) || 773 (!packet->has_data && chunk->auth)) { 774 /* We no longer do re-fragmentation. 775 * Just fragment at the IP layer, if we 776 * actually hit this condition 777 */ 778 packet->ipfragok = 1; 779 } else { 780 retval = SCTP_XMIT_PMTU_FULL; 781 } 782 } 783 784 return retval; 785 } 786