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 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 45 46 #include <linux/types.h> 47 #include <linux/kernel.h> 48 #include <linux/wait.h> 49 #include <linux/time.h> 50 #include <linux/ip.h> 51 #include <linux/ipv6.h> 52 #include <linux/init.h> 53 #include <linux/slab.h> 54 #include <net/inet_ecn.h> 55 #include <net/ip.h> 56 #include <net/icmp.h> 57 #include <net/net_namespace.h> 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_chunk(struct sctp_packet *packet, 68 struct sctp_chunk *chunk); 69 static sctp_xmit_t sctp_packet_can_append_data(struct sctp_packet *packet, 70 struct sctp_chunk *chunk); 71 static void sctp_packet_append_data(struct sctp_packet *packet, 72 struct sctp_chunk *chunk); 73 static sctp_xmit_t sctp_packet_will_fit(struct sctp_packet *packet, 74 struct sctp_chunk *chunk, 75 u16 chunk_len); 76 77 static void sctp_packet_reset(struct sctp_packet *packet) 78 { 79 packet->size = packet->overhead; 80 packet->has_cookie_echo = 0; 81 packet->has_sack = 0; 82 packet->has_data = 0; 83 packet->has_auth = 0; 84 packet->ipfragok = 0; 85 packet->auth = NULL; 86 } 87 88 /* Config a packet. 89 * This appears to be a followup set of initializations. 90 */ 91 struct sctp_packet *sctp_packet_config(struct sctp_packet *packet, 92 __u32 vtag, int ecn_capable) 93 { 94 struct sctp_chunk *chunk = NULL; 95 96 SCTP_DEBUG_PRINTK("%s: packet:%p vtag:0x%x\n", __func__, 97 packet, vtag); 98 99 packet->vtag = vtag; 100 101 if (ecn_capable && sctp_packet_empty(packet)) { 102 chunk = sctp_get_ecne_prepend(packet->transport->asoc); 103 104 /* If there a is a prepend chunk stick it on the list before 105 * any other chunks get appended. 106 */ 107 if (chunk) 108 sctp_packet_append_chunk(packet, chunk); 109 } 110 111 return packet; 112 } 113 114 /* Initialize the packet structure. */ 115 struct sctp_packet *sctp_packet_init(struct sctp_packet *packet, 116 struct sctp_transport *transport, 117 __u16 sport, __u16 dport) 118 { 119 struct sctp_association *asoc = transport->asoc; 120 size_t overhead; 121 122 SCTP_DEBUG_PRINTK("%s: packet:%p transport:%p\n", __func__, 123 packet, transport); 124 125 packet->transport = transport; 126 packet->source_port = sport; 127 packet->destination_port = dport; 128 INIT_LIST_HEAD(&packet->chunk_list); 129 if (asoc) { 130 struct sctp_sock *sp = sctp_sk(asoc->base.sk); 131 overhead = sp->pf->af->net_header_len; 132 } else { 133 overhead = sizeof(struct ipv6hdr); 134 } 135 overhead += sizeof(struct sctphdr); 136 packet->overhead = overhead; 137 sctp_packet_reset(packet); 138 packet->vtag = 0; 139 packet->malloced = 0; 140 return packet; 141 } 142 143 /* Free a packet. */ 144 void sctp_packet_free(struct sctp_packet *packet) 145 { 146 struct sctp_chunk *chunk, *tmp; 147 148 SCTP_DEBUG_PRINTK("%s: packet:%p\n", __func__, packet); 149 150 list_for_each_entry_safe(chunk, tmp, &packet->chunk_list, list) { 151 list_del_init(&chunk->list); 152 sctp_chunk_free(chunk); 153 } 154 155 if (packet->malloced) 156 kfree(packet); 157 } 158 159 /* This routine tries to append the chunk to the offered packet. If adding 160 * the chunk causes the packet to exceed the path MTU and COOKIE_ECHO chunk 161 * is not present in the packet, it transmits the input packet. 162 * Data can be bundled with a packet containing a COOKIE_ECHO chunk as long 163 * as it can fit in the packet, but any more data that does not fit in this 164 * packet can be sent only after receiving the COOKIE_ACK. 165 */ 166 sctp_xmit_t sctp_packet_transmit_chunk(struct sctp_packet *packet, 167 struct sctp_chunk *chunk, 168 int one_packet) 169 { 170 sctp_xmit_t retval; 171 int error = 0; 172 173 SCTP_DEBUG_PRINTK("%s: packet:%p chunk:%p\n", __func__, 174 packet, chunk); 175 176 switch ((retval = (sctp_packet_append_chunk(packet, chunk)))) { 177 case SCTP_XMIT_PMTU_FULL: 178 if (!packet->has_cookie_echo) { 179 error = sctp_packet_transmit(packet); 180 if (error < 0) 181 chunk->skb->sk->sk_err = -error; 182 183 /* If we have an empty packet, then we can NOT ever 184 * return PMTU_FULL. 185 */ 186 if (!one_packet) 187 retval = sctp_packet_append_chunk(packet, 188 chunk); 189 } 190 break; 191 192 case SCTP_XMIT_RWND_FULL: 193 case SCTP_XMIT_OK: 194 case SCTP_XMIT_NAGLE_DELAY: 195 break; 196 } 197 198 return retval; 199 } 200 201 /* Try to bundle an auth chunk into the packet. */ 202 static sctp_xmit_t sctp_packet_bundle_auth(struct sctp_packet *pkt, 203 struct sctp_chunk *chunk) 204 { 205 struct sctp_association *asoc = pkt->transport->asoc; 206 struct sctp_chunk *auth; 207 sctp_xmit_t retval = SCTP_XMIT_OK; 208 209 /* if we don't have an association, we can't do authentication */ 210 if (!asoc) 211 return retval; 212 213 /* See if this is an auth chunk we are bundling or if 214 * auth is already bundled. 215 */ 216 if (chunk->chunk_hdr->type == SCTP_CID_AUTH || pkt->has_auth) 217 return retval; 218 219 /* if the peer did not request this chunk to be authenticated, 220 * don't do it 221 */ 222 if (!chunk->auth) 223 return retval; 224 225 auth = sctp_make_auth(asoc); 226 if (!auth) 227 return retval; 228 229 retval = __sctp_packet_append_chunk(pkt, auth); 230 231 if (retval != SCTP_XMIT_OK) 232 sctp_chunk_free(auth); 233 234 return retval; 235 } 236 237 /* Try to bundle a SACK with the packet. */ 238 static sctp_xmit_t sctp_packet_bundle_sack(struct sctp_packet *pkt, 239 struct sctp_chunk *chunk) 240 { 241 sctp_xmit_t retval = SCTP_XMIT_OK; 242 243 /* If sending DATA and haven't aleady bundled a SACK, try to 244 * bundle one in to the packet. 245 */ 246 if (sctp_chunk_is_data(chunk) && !pkt->has_sack && 247 !pkt->has_cookie_echo) { 248 struct sctp_association *asoc; 249 struct timer_list *timer; 250 asoc = pkt->transport->asoc; 251 timer = &asoc->timers[SCTP_EVENT_TIMEOUT_SACK]; 252 253 /* If the SACK timer is running, we have a pending SACK */ 254 if (timer_pending(timer)) { 255 struct sctp_chunk *sack; 256 257 if (pkt->transport->sack_generation != 258 pkt->transport->asoc->peer.sack_generation) 259 return retval; 260 261 asoc->a_rwnd = asoc->rwnd; 262 sack = sctp_make_sack(asoc); 263 if (sack) { 264 retval = __sctp_packet_append_chunk(pkt, sack); 265 if (retval != SCTP_XMIT_OK) { 266 sctp_chunk_free(sack); 267 goto out; 268 } 269 asoc->peer.sack_needed = 0; 270 if (del_timer(timer)) 271 sctp_association_put(asoc); 272 } 273 } 274 } 275 out: 276 return retval; 277 } 278 279 280 /* Append a chunk to the offered packet reporting back any inability to do 281 * so. 282 */ 283 static sctp_xmit_t __sctp_packet_append_chunk(struct sctp_packet *packet, 284 struct sctp_chunk *chunk) 285 { 286 sctp_xmit_t retval = SCTP_XMIT_OK; 287 __u16 chunk_len = WORD_ROUND(ntohs(chunk->chunk_hdr->length)); 288 289 /* Check to see if this chunk will fit into the packet */ 290 retval = sctp_packet_will_fit(packet, chunk, chunk_len); 291 if (retval != SCTP_XMIT_OK) 292 goto finish; 293 294 /* We believe that this chunk is OK to add to the packet */ 295 switch (chunk->chunk_hdr->type) { 296 case SCTP_CID_DATA: 297 /* Account for the data being in the packet */ 298 sctp_packet_append_data(packet, chunk); 299 /* Disallow SACK bundling after DATA. */ 300 packet->has_sack = 1; 301 /* Disallow AUTH bundling after DATA */ 302 packet->has_auth = 1; 303 /* Let it be knows that packet has DATA in it */ 304 packet->has_data = 1; 305 /* timestamp the chunk for rtx purposes */ 306 chunk->sent_at = jiffies; 307 break; 308 case SCTP_CID_COOKIE_ECHO: 309 packet->has_cookie_echo = 1; 310 break; 311 312 case SCTP_CID_SACK: 313 packet->has_sack = 1; 314 if (chunk->asoc) 315 chunk->asoc->stats.osacks++; 316 break; 317 318 case SCTP_CID_AUTH: 319 packet->has_auth = 1; 320 packet->auth = chunk; 321 break; 322 } 323 324 /* It is OK to send this chunk. */ 325 list_add_tail(&chunk->list, &packet->chunk_list); 326 packet->size += chunk_len; 327 chunk->transport = packet->transport; 328 finish: 329 return retval; 330 } 331 332 /* Append a chunk to the offered packet reporting back any inability to do 333 * so. 334 */ 335 sctp_xmit_t sctp_packet_append_chunk(struct sctp_packet *packet, 336 struct sctp_chunk *chunk) 337 { 338 sctp_xmit_t retval = SCTP_XMIT_OK; 339 340 SCTP_DEBUG_PRINTK("%s: packet:%p chunk:%p\n", __func__, packet, 341 chunk); 342 343 /* Data chunks are special. Before seeing what else we can 344 * bundle into this packet, check to see if we are allowed to 345 * send this DATA. 346 */ 347 if (sctp_chunk_is_data(chunk)) { 348 retval = sctp_packet_can_append_data(packet, chunk); 349 if (retval != SCTP_XMIT_OK) 350 goto finish; 351 } 352 353 /* Try to bundle AUTH chunk */ 354 retval = sctp_packet_bundle_auth(packet, chunk); 355 if (retval != SCTP_XMIT_OK) 356 goto finish; 357 358 /* Try to bundle SACK chunk */ 359 retval = sctp_packet_bundle_sack(packet, chunk); 360 if (retval != SCTP_XMIT_OK) 361 goto finish; 362 363 retval = __sctp_packet_append_chunk(packet, chunk); 364 365 finish: 366 return retval; 367 } 368 369 static void sctp_packet_release_owner(struct sk_buff *skb) 370 { 371 sk_free(skb->sk); 372 } 373 374 static void sctp_packet_set_owner_w(struct sk_buff *skb, struct sock *sk) 375 { 376 skb_orphan(skb); 377 skb->sk = sk; 378 skb->destructor = sctp_packet_release_owner; 379 380 /* 381 * The data chunks have already been accounted for in sctp_sendmsg(), 382 * therefore only reserve a single byte to keep socket around until 383 * the packet has been transmitted. 384 */ 385 atomic_inc(&sk->sk_wmem_alloc); 386 } 387 388 /* All packets are sent to the network through this function from 389 * sctp_outq_tail(). 390 * 391 * The return value is a normal kernel error return value. 392 */ 393 int sctp_packet_transmit(struct sctp_packet *packet) 394 { 395 struct sctp_transport *tp = packet->transport; 396 struct sctp_association *asoc = tp->asoc; 397 struct sctphdr *sh; 398 struct sk_buff *nskb; 399 struct sctp_chunk *chunk, *tmp; 400 struct sock *sk; 401 int err = 0; 402 int padding; /* How much padding do we need? */ 403 __u8 has_data = 0; 404 struct dst_entry *dst = tp->dst; 405 unsigned char *auth = NULL; /* pointer to auth in skb data */ 406 __u32 cksum_buf_len = sizeof(struct sctphdr); 407 408 SCTP_DEBUG_PRINTK("%s: packet:%p\n", __func__, packet); 409 410 /* Do NOT generate a chunkless packet. */ 411 if (list_empty(&packet->chunk_list)) 412 return err; 413 414 /* Set up convenience variables... */ 415 chunk = list_entry(packet->chunk_list.next, struct sctp_chunk, list); 416 sk = chunk->skb->sk; 417 418 /* Allocate the new skb. */ 419 nskb = alloc_skb(packet->size + LL_MAX_HEADER, GFP_ATOMIC); 420 if (!nskb) 421 goto nomem; 422 423 /* Make sure the outbound skb has enough header room reserved. */ 424 skb_reserve(nskb, packet->overhead + LL_MAX_HEADER); 425 426 /* Set the owning socket so that we know where to get the 427 * destination IP address. 428 */ 429 sctp_packet_set_owner_w(nskb, sk); 430 431 if (!sctp_transport_dst_check(tp)) { 432 sctp_transport_route(tp, NULL, sctp_sk(sk)); 433 if (asoc && (asoc->param_flags & SPP_PMTUD_ENABLE)) { 434 sctp_assoc_sync_pmtu(sk, asoc); 435 } 436 } 437 dst = dst_clone(tp->dst); 438 skb_dst_set(nskb, dst); 439 if (!dst) 440 goto no_route; 441 442 /* Build the SCTP header. */ 443 sh = (struct sctphdr *)skb_push(nskb, sizeof(struct sctphdr)); 444 skb_reset_transport_header(nskb); 445 sh->source = htons(packet->source_port); 446 sh->dest = htons(packet->destination_port); 447 448 /* From 6.8 Adler-32 Checksum Calculation: 449 * After the packet is constructed (containing the SCTP common 450 * header and one or more control or DATA chunks), the 451 * transmitter shall: 452 * 453 * 1) Fill in the proper Verification Tag in the SCTP common 454 * header and initialize the checksum field to 0's. 455 */ 456 sh->vtag = htonl(packet->vtag); 457 sh->checksum = 0; 458 459 /** 460 * 6.10 Bundling 461 * 462 * An endpoint bundles chunks by simply including multiple 463 * chunks in one outbound SCTP packet. ... 464 */ 465 466 /** 467 * 3.2 Chunk Field Descriptions 468 * 469 * The total length of a chunk (including Type, Length and 470 * Value fields) MUST be a multiple of 4 bytes. If the length 471 * of the chunk is not a multiple of 4 bytes, the sender MUST 472 * pad the chunk with all zero bytes and this padding is not 473 * included in the chunk length field. The sender should 474 * never pad with more than 3 bytes. 475 * 476 * [This whole comment explains WORD_ROUND() below.] 477 */ 478 SCTP_DEBUG_PRINTK("***sctp_transmit_packet***\n"); 479 list_for_each_entry_safe(chunk, tmp, &packet->chunk_list, list) { 480 list_del_init(&chunk->list); 481 if (sctp_chunk_is_data(chunk)) { 482 /* 6.3.1 C4) When data is in flight and when allowed 483 * by rule C5, a new RTT measurement MUST be made each 484 * round trip. Furthermore, new RTT measurements 485 * SHOULD be made no more than once per round-trip 486 * for a given destination transport address. 487 */ 488 489 if (!tp->rto_pending) { 490 chunk->rtt_in_progress = 1; 491 tp->rto_pending = 1; 492 } 493 has_data = 1; 494 } 495 496 padding = WORD_ROUND(chunk->skb->len) - chunk->skb->len; 497 if (padding) 498 memset(skb_put(chunk->skb, padding), 0, padding); 499 500 /* if this is the auth chunk that we are adding, 501 * store pointer where it will be added and put 502 * the auth into the packet. 503 */ 504 if (chunk == packet->auth) 505 auth = skb_tail_pointer(nskb); 506 507 cksum_buf_len += chunk->skb->len; 508 memcpy(skb_put(nskb, chunk->skb->len), 509 chunk->skb->data, chunk->skb->len); 510 511 SCTP_DEBUG_PRINTK("%s %p[%s] %s 0x%x, %s %d, %s %d, %s %d\n", 512 "*** Chunk", chunk, 513 sctp_cname(SCTP_ST_CHUNK( 514 chunk->chunk_hdr->type)), 515 chunk->has_tsn ? "TSN" : "No TSN", 516 chunk->has_tsn ? 517 ntohl(chunk->subh.data_hdr->tsn) : 0, 518 "length", ntohs(chunk->chunk_hdr->length), 519 "chunk->skb->len", chunk->skb->len, 520 "rtt_in_progress", chunk->rtt_in_progress); 521 522 /* 523 * If this is a control chunk, this is our last 524 * reference. Free data chunks after they've been 525 * acknowledged or have failed. 526 */ 527 if (!sctp_chunk_is_data(chunk)) 528 sctp_chunk_free(chunk); 529 } 530 531 /* SCTP-AUTH, Section 6.2 532 * The sender MUST calculate the MAC as described in RFC2104 [2] 533 * using the hash function H as described by the MAC Identifier and 534 * the shared association key K based on the endpoint pair shared key 535 * described by the shared key identifier. The 'data' used for the 536 * computation of the AUTH-chunk is given by the AUTH chunk with its 537 * HMAC field set to zero (as shown in Figure 6) followed by all 538 * chunks that are placed after the AUTH chunk in the SCTP packet. 539 */ 540 if (auth) 541 sctp_auth_calculate_hmac(asoc, nskb, 542 (struct sctp_auth_chunk *)auth, 543 GFP_ATOMIC); 544 545 /* 2) Calculate the Adler-32 checksum of the whole packet, 546 * including the SCTP common header and all the 547 * chunks. 548 * 549 * Note: Adler-32 is no longer applicable, as has been replaced 550 * by CRC32-C as described in <draft-ietf-tsvwg-sctpcsum-02.txt>. 551 */ 552 if (!sctp_checksum_disable) { 553 if (!(dst->dev->features & NETIF_F_SCTP_CSUM)) { 554 __u32 crc32 = sctp_start_cksum((__u8 *)sh, cksum_buf_len); 555 556 /* 3) Put the resultant value into the checksum field in the 557 * common header, and leave the rest of the bits unchanged. 558 */ 559 sh->checksum = sctp_end_cksum(crc32); 560 } else { 561 /* no need to seed pseudo checksum for SCTP */ 562 nskb->ip_summed = CHECKSUM_PARTIAL; 563 nskb->csum_start = (skb_transport_header(nskb) - 564 nskb->head); 565 nskb->csum_offset = offsetof(struct sctphdr, checksum); 566 } 567 } 568 569 /* IP layer ECN support 570 * From RFC 2481 571 * "The ECN-Capable Transport (ECT) bit would be set by the 572 * data sender to indicate that the end-points of the 573 * transport protocol are ECN-capable." 574 * 575 * Now setting the ECT bit all the time, as it should not cause 576 * any problems protocol-wise even if our peer ignores it. 577 * 578 * Note: The works for IPv6 layer checks this bit too later 579 * in transmission. See IP6_ECN_flow_xmit(). 580 */ 581 (*tp->af_specific->ecn_capable)(nskb->sk); 582 583 /* Set up the IP options. */ 584 /* BUG: not implemented 585 * For v4 this all lives somewhere in sk->sk_opt... 586 */ 587 588 /* Dump that on IP! */ 589 if (asoc) { 590 asoc->stats.opackets++; 591 if (asoc->peer.last_sent_to != tp) 592 /* Considering the multiple CPU scenario, this is a 593 * "correcter" place for last_sent_to. --xguo 594 */ 595 asoc->peer.last_sent_to = tp; 596 } 597 598 if (has_data) { 599 struct timer_list *timer; 600 unsigned long timeout; 601 602 /* Restart the AUTOCLOSE timer when sending data. */ 603 if (sctp_state(asoc, ESTABLISHED) && asoc->autoclose) { 604 timer = &asoc->timers[SCTP_EVENT_TIMEOUT_AUTOCLOSE]; 605 timeout = asoc->timeouts[SCTP_EVENT_TIMEOUT_AUTOCLOSE]; 606 607 if (!mod_timer(timer, jiffies + timeout)) 608 sctp_association_hold(asoc); 609 } 610 } 611 612 SCTP_DEBUG_PRINTK("***sctp_transmit_packet*** skb len %d\n", 613 nskb->len); 614 615 nskb->local_df = packet->ipfragok; 616 (*tp->af_specific->sctp_xmit)(nskb, tp); 617 618 out: 619 sctp_packet_reset(packet); 620 return err; 621 no_route: 622 kfree_skb(nskb); 623 IP_INC_STATS_BH(sock_net(asoc->base.sk), IPSTATS_MIB_OUTNOROUTES); 624 625 /* FIXME: Returning the 'err' will effect all the associations 626 * associated with a socket, although only one of the paths of the 627 * association is unreachable. 628 * The real failure of a transport or association can be passed on 629 * to the user via notifications. So setting this error may not be 630 * required. 631 */ 632 /* err = -EHOSTUNREACH; */ 633 err: 634 /* Control chunks are unreliable so just drop them. DATA chunks 635 * will get resent or dropped later. 636 */ 637 638 list_for_each_entry_safe(chunk, tmp, &packet->chunk_list, list) { 639 list_del_init(&chunk->list); 640 if (!sctp_chunk_is_data(chunk)) 641 sctp_chunk_free(chunk); 642 } 643 goto out; 644 nomem: 645 err = -ENOMEM; 646 goto err; 647 } 648 649 /******************************************************************** 650 * 2nd Level Abstractions 651 ********************************************************************/ 652 653 /* This private function check to see if a chunk can be added */ 654 static sctp_xmit_t sctp_packet_can_append_data(struct sctp_packet *packet, 655 struct sctp_chunk *chunk) 656 { 657 sctp_xmit_t retval = SCTP_XMIT_OK; 658 size_t datasize, rwnd, inflight, flight_size; 659 struct sctp_transport *transport = packet->transport; 660 struct sctp_association *asoc = transport->asoc; 661 struct sctp_outq *q = &asoc->outqueue; 662 663 /* RFC 2960 6.1 Transmission of DATA Chunks 664 * 665 * A) At any given time, the data sender MUST NOT transmit new data to 666 * any destination transport address if its peer's rwnd indicates 667 * that the peer has no buffer space (i.e. rwnd is 0, see Section 668 * 6.2.1). However, regardless of the value of rwnd (including if it 669 * is 0), the data sender can always have one DATA chunk in flight to 670 * the receiver if allowed by cwnd (see rule B below). This rule 671 * allows the sender to probe for a change in rwnd that the sender 672 * missed due to the SACK having been lost in transit from the data 673 * receiver to the data sender. 674 */ 675 676 rwnd = asoc->peer.rwnd; 677 inflight = q->outstanding_bytes; 678 flight_size = transport->flight_size; 679 680 datasize = sctp_data_size(chunk); 681 682 if (datasize > rwnd) { 683 if (inflight > 0) { 684 /* We have (at least) one data chunk in flight, 685 * so we can't fall back to rule 6.1 B). 686 */ 687 retval = SCTP_XMIT_RWND_FULL; 688 goto finish; 689 } 690 } 691 692 /* RFC 2960 6.1 Transmission of DATA Chunks 693 * 694 * B) At any given time, the sender MUST NOT transmit new data 695 * to a given transport address if it has cwnd or more bytes 696 * of data outstanding to that transport address. 697 */ 698 /* RFC 7.2.4 & the Implementers Guide 2.8. 699 * 700 * 3) ... 701 * When a Fast Retransmit is being performed the sender SHOULD 702 * ignore the value of cwnd and SHOULD NOT delay retransmission. 703 */ 704 if (chunk->fast_retransmit != SCTP_NEED_FRTX) 705 if (flight_size >= transport->cwnd) { 706 retval = SCTP_XMIT_RWND_FULL; 707 goto finish; 708 } 709 710 /* Nagle's algorithm to solve small-packet problem: 711 * Inhibit the sending of new chunks when new outgoing data arrives 712 * if any previously transmitted data on the connection remains 713 * unacknowledged. 714 */ 715 if (!sctp_sk(asoc->base.sk)->nodelay && sctp_packet_empty(packet) && 716 inflight && sctp_state(asoc, ESTABLISHED)) { 717 unsigned int max = transport->pathmtu - packet->overhead; 718 unsigned int len = chunk->skb->len + q->out_qlen; 719 720 /* Check whether this chunk and all the rest of pending 721 * data will fit or delay in hopes of bundling a full 722 * sized packet. 723 * Don't delay large message writes that may have been 724 * fragmeneted into small peices. 725 */ 726 if ((len < max) && chunk->msg->can_delay) { 727 retval = SCTP_XMIT_NAGLE_DELAY; 728 goto finish; 729 } 730 } 731 732 finish: 733 return retval; 734 } 735 736 /* This private function does management things when adding DATA chunk */ 737 static void sctp_packet_append_data(struct sctp_packet *packet, 738 struct sctp_chunk *chunk) 739 { 740 struct sctp_transport *transport = packet->transport; 741 size_t datasize = sctp_data_size(chunk); 742 struct sctp_association *asoc = transport->asoc; 743 u32 rwnd = asoc->peer.rwnd; 744 745 /* Keep track of how many bytes are in flight over this transport. */ 746 transport->flight_size += datasize; 747 748 /* Keep track of how many bytes are in flight to the receiver. */ 749 asoc->outqueue.outstanding_bytes += datasize; 750 751 /* Update our view of the receiver's rwnd. */ 752 if (datasize < rwnd) 753 rwnd -= datasize; 754 else 755 rwnd = 0; 756 757 asoc->peer.rwnd = rwnd; 758 /* Has been accepted for transmission. */ 759 if (!asoc->peer.prsctp_capable) 760 chunk->msg->can_abandon = 0; 761 sctp_chunk_assign_tsn(chunk); 762 sctp_chunk_assign_ssn(chunk); 763 } 764 765 static sctp_xmit_t sctp_packet_will_fit(struct sctp_packet *packet, 766 struct sctp_chunk *chunk, 767 u16 chunk_len) 768 { 769 size_t psize; 770 size_t pmtu; 771 int too_big; 772 sctp_xmit_t retval = SCTP_XMIT_OK; 773 774 psize = packet->size; 775 pmtu = ((packet->transport->asoc) ? 776 (packet->transport->asoc->pathmtu) : 777 (packet->transport->pathmtu)); 778 779 too_big = (psize + chunk_len > pmtu); 780 781 /* Decide if we need to fragment or resubmit later. */ 782 if (too_big) { 783 /* It's OK to fragmet at IP level if any one of the following 784 * is true: 785 * 1. The packet is empty (meaning this chunk is greater 786 * the MTU) 787 * 2. The chunk we are adding is a control chunk 788 * 3. The packet doesn't have any data in it yet and data 789 * requires authentication. 790 */ 791 if (sctp_packet_empty(packet) || !sctp_chunk_is_data(chunk) || 792 (!packet->has_data && chunk->auth)) { 793 /* We no longer do re-fragmentation. 794 * Just fragment at the IP layer, if we 795 * actually hit this condition 796 */ 797 packet->ipfragok = 1; 798 } else { 799 retval = SCTP_XMIT_PMTU_FULL; 800 } 801 } 802 803 return retval; 804 } 805