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, see 24 * <http://www.gnu.org/licenses/>. 25 * 26 * Please send any bug reports or fixes you make to the 27 * email address(es): 28 * lksctp developers <linux-sctp@vger.kernel.org> 29 * 30 * Written or modified by: 31 * La Monte H.P. Yarroll <piggy@acm.org> 32 * Karl Knutson <karl@athena.chicago.il.us> 33 * Jon Grimm <jgrimm@austin.ibm.com> 34 * Sridhar Samudrala <sri@us.ibm.com> 35 */ 36 37 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 38 39 #include <linux/types.h> 40 #include <linux/kernel.h> 41 #include <linux/wait.h> 42 #include <linux/time.h> 43 #include <linux/ip.h> 44 #include <linux/ipv6.h> 45 #include <linux/init.h> 46 #include <linux/slab.h> 47 #include <net/inet_ecn.h> 48 #include <net/ip.h> 49 #include <net/icmp.h> 50 #include <net/net_namespace.h> 51 52 #include <linux/socket.h> /* for sa_family_t */ 53 #include <net/sock.h> 54 55 #include <net/sctp/sctp.h> 56 #include <net/sctp/sm.h> 57 #include <net/sctp/checksum.h> 58 59 /* Forward declarations for private helpers. */ 60 static sctp_xmit_t __sctp_packet_append_chunk(struct sctp_packet *packet, 61 struct sctp_chunk *chunk); 62 static sctp_xmit_t sctp_packet_can_append_data(struct sctp_packet *packet, 63 struct sctp_chunk *chunk); 64 static void sctp_packet_append_data(struct sctp_packet *packet, 65 struct sctp_chunk *chunk); 66 static sctp_xmit_t sctp_packet_will_fit(struct sctp_packet *packet, 67 struct sctp_chunk *chunk, 68 u16 chunk_len); 69 70 static void sctp_packet_reset(struct sctp_packet *packet) 71 { 72 packet->size = packet->overhead; 73 packet->has_cookie_echo = 0; 74 packet->has_sack = 0; 75 packet->has_data = 0; 76 packet->has_auth = 0; 77 packet->ipfragok = 0; 78 packet->auth = NULL; 79 } 80 81 /* Config a packet. 82 * This appears to be a followup set of initializations. 83 */ 84 struct sctp_packet *sctp_packet_config(struct sctp_packet *packet, 85 __u32 vtag, int ecn_capable) 86 { 87 struct sctp_transport *tp = packet->transport; 88 struct sctp_association *asoc = tp->asoc; 89 90 pr_debug("%s: packet:%p vtag:0x%x\n", __func__, packet, vtag); 91 92 packet->vtag = vtag; 93 94 if (asoc && tp->dst) { 95 struct sock *sk = asoc->base.sk; 96 97 rcu_read_lock(); 98 if (__sk_dst_get(sk) != tp->dst) { 99 dst_hold(tp->dst); 100 sk_setup_caps(sk, tp->dst); 101 } 102 103 if (sk_can_gso(sk)) { 104 struct net_device *dev = tp->dst->dev; 105 106 packet->max_size = dev->gso_max_size; 107 } else { 108 packet->max_size = asoc->pathmtu; 109 } 110 rcu_read_unlock(); 111 112 } else { 113 packet->max_size = tp->pathmtu; 114 } 115 116 if (ecn_capable && sctp_packet_empty(packet)) { 117 struct sctp_chunk *chunk; 118 119 /* If there a is a prepend chunk stick it on the list before 120 * any other chunks get appended. 121 */ 122 chunk = sctp_get_ecne_prepend(asoc); 123 if (chunk) 124 sctp_packet_append_chunk(packet, chunk); 125 } 126 127 return packet; 128 } 129 130 /* Initialize the packet structure. */ 131 struct sctp_packet *sctp_packet_init(struct sctp_packet *packet, 132 struct sctp_transport *transport, 133 __u16 sport, __u16 dport) 134 { 135 struct sctp_association *asoc = transport->asoc; 136 size_t overhead; 137 138 pr_debug("%s: packet:%p transport:%p\n", __func__, packet, transport); 139 140 packet->transport = transport; 141 packet->source_port = sport; 142 packet->destination_port = dport; 143 INIT_LIST_HEAD(&packet->chunk_list); 144 if (asoc) { 145 struct sctp_sock *sp = sctp_sk(asoc->base.sk); 146 overhead = sp->pf->af->net_header_len; 147 } else { 148 overhead = sizeof(struct ipv6hdr); 149 } 150 overhead += sizeof(struct sctphdr); 151 packet->overhead = overhead; 152 sctp_packet_reset(packet); 153 packet->vtag = 0; 154 155 return packet; 156 } 157 158 /* Free a packet. */ 159 void sctp_packet_free(struct sctp_packet *packet) 160 { 161 struct sctp_chunk *chunk, *tmp; 162 163 pr_debug("%s: packet:%p\n", __func__, packet); 164 165 list_for_each_entry_safe(chunk, tmp, &packet->chunk_list, list) { 166 list_del_init(&chunk->list); 167 sctp_chunk_free(chunk); 168 } 169 } 170 171 /* This routine tries to append the chunk to the offered packet. If adding 172 * the chunk causes the packet to exceed the path MTU and COOKIE_ECHO chunk 173 * is not present in the packet, it transmits the input packet. 174 * Data can be bundled with a packet containing a COOKIE_ECHO chunk as long 175 * as it can fit in the packet, but any more data that does not fit in this 176 * packet can be sent only after receiving the COOKIE_ACK. 177 */ 178 sctp_xmit_t sctp_packet_transmit_chunk(struct sctp_packet *packet, 179 struct sctp_chunk *chunk, 180 int one_packet, gfp_t gfp) 181 { 182 sctp_xmit_t retval; 183 184 pr_debug("%s: packet:%p size:%Zu chunk:%p size:%d\n", __func__, 185 packet, packet->size, chunk, chunk->skb ? chunk->skb->len : -1); 186 187 switch ((retval = (sctp_packet_append_chunk(packet, chunk)))) { 188 case SCTP_XMIT_PMTU_FULL: 189 if (!packet->has_cookie_echo) { 190 int error = 0; 191 192 error = sctp_packet_transmit(packet, gfp); 193 if (error < 0) 194 chunk->skb->sk->sk_err = -error; 195 196 /* If we have an empty packet, then we can NOT ever 197 * return PMTU_FULL. 198 */ 199 if (!one_packet) 200 retval = sctp_packet_append_chunk(packet, 201 chunk); 202 } 203 break; 204 205 case SCTP_XMIT_RWND_FULL: 206 case SCTP_XMIT_OK: 207 case SCTP_XMIT_DELAY: 208 break; 209 } 210 211 return retval; 212 } 213 214 /* Try to bundle an auth chunk into the packet. */ 215 static sctp_xmit_t sctp_packet_bundle_auth(struct sctp_packet *pkt, 216 struct sctp_chunk *chunk) 217 { 218 struct sctp_association *asoc = pkt->transport->asoc; 219 struct sctp_chunk *auth; 220 sctp_xmit_t retval = SCTP_XMIT_OK; 221 222 /* if we don't have an association, we can't do authentication */ 223 if (!asoc) 224 return retval; 225 226 /* See if this is an auth chunk we are bundling or if 227 * auth is already bundled. 228 */ 229 if (chunk->chunk_hdr->type == SCTP_CID_AUTH || pkt->has_auth) 230 return retval; 231 232 /* if the peer did not request this chunk to be authenticated, 233 * don't do it 234 */ 235 if (!chunk->auth) 236 return retval; 237 238 auth = sctp_make_auth(asoc); 239 if (!auth) 240 return retval; 241 242 retval = __sctp_packet_append_chunk(pkt, auth); 243 244 if (retval != SCTP_XMIT_OK) 245 sctp_chunk_free(auth); 246 247 return retval; 248 } 249 250 /* Try to bundle a SACK with the packet. */ 251 static sctp_xmit_t sctp_packet_bundle_sack(struct sctp_packet *pkt, 252 struct sctp_chunk *chunk) 253 { 254 sctp_xmit_t retval = SCTP_XMIT_OK; 255 256 /* If sending DATA and haven't aleady bundled a SACK, try to 257 * bundle one in to the packet. 258 */ 259 if (sctp_chunk_is_data(chunk) && !pkt->has_sack && 260 !pkt->has_cookie_echo) { 261 struct sctp_association *asoc; 262 struct timer_list *timer; 263 asoc = pkt->transport->asoc; 264 timer = &asoc->timers[SCTP_EVENT_TIMEOUT_SACK]; 265 266 /* If the SACK timer is running, we have a pending SACK */ 267 if (timer_pending(timer)) { 268 struct sctp_chunk *sack; 269 270 if (pkt->transport->sack_generation != 271 pkt->transport->asoc->peer.sack_generation) 272 return retval; 273 274 asoc->a_rwnd = asoc->rwnd; 275 sack = sctp_make_sack(asoc); 276 if (sack) { 277 retval = __sctp_packet_append_chunk(pkt, sack); 278 if (retval != SCTP_XMIT_OK) { 279 sctp_chunk_free(sack); 280 goto out; 281 } 282 asoc->peer.sack_needed = 0; 283 if (del_timer(timer)) 284 sctp_association_put(asoc); 285 } 286 } 287 } 288 out: 289 return retval; 290 } 291 292 293 /* Append a chunk to the offered packet reporting back any inability to do 294 * so. 295 */ 296 static sctp_xmit_t __sctp_packet_append_chunk(struct sctp_packet *packet, 297 struct sctp_chunk *chunk) 298 { 299 sctp_xmit_t retval = SCTP_XMIT_OK; 300 __u16 chunk_len = SCTP_PAD4(ntohs(chunk->chunk_hdr->length)); 301 302 /* Check to see if this chunk will fit into the packet */ 303 retval = sctp_packet_will_fit(packet, chunk, chunk_len); 304 if (retval != SCTP_XMIT_OK) 305 goto finish; 306 307 /* We believe that this chunk is OK to add to the packet */ 308 switch (chunk->chunk_hdr->type) { 309 case SCTP_CID_DATA: 310 /* Account for the data being in the packet */ 311 sctp_packet_append_data(packet, chunk); 312 /* Disallow SACK bundling after DATA. */ 313 packet->has_sack = 1; 314 /* Disallow AUTH bundling after DATA */ 315 packet->has_auth = 1; 316 /* Let it be knows that packet has DATA in it */ 317 packet->has_data = 1; 318 /* timestamp the chunk for rtx purposes */ 319 chunk->sent_at = jiffies; 320 /* Mainly used for prsctp RTX policy */ 321 chunk->sent_count++; 322 break; 323 case SCTP_CID_COOKIE_ECHO: 324 packet->has_cookie_echo = 1; 325 break; 326 327 case SCTP_CID_SACK: 328 packet->has_sack = 1; 329 if (chunk->asoc) 330 chunk->asoc->stats.osacks++; 331 break; 332 333 case SCTP_CID_AUTH: 334 packet->has_auth = 1; 335 packet->auth = chunk; 336 break; 337 } 338 339 /* It is OK to send this chunk. */ 340 list_add_tail(&chunk->list, &packet->chunk_list); 341 packet->size += chunk_len; 342 chunk->transport = packet->transport; 343 finish: 344 return retval; 345 } 346 347 /* Append a chunk to the offered packet reporting back any inability to do 348 * so. 349 */ 350 sctp_xmit_t sctp_packet_append_chunk(struct sctp_packet *packet, 351 struct sctp_chunk *chunk) 352 { 353 sctp_xmit_t retval = SCTP_XMIT_OK; 354 355 pr_debug("%s: packet:%p chunk:%p\n", __func__, packet, chunk); 356 357 /* Data chunks are special. Before seeing what else we can 358 * bundle into this packet, check to see if we are allowed to 359 * send this DATA. 360 */ 361 if (sctp_chunk_is_data(chunk)) { 362 retval = sctp_packet_can_append_data(packet, chunk); 363 if (retval != SCTP_XMIT_OK) 364 goto finish; 365 } 366 367 /* Try to bundle AUTH chunk */ 368 retval = sctp_packet_bundle_auth(packet, chunk); 369 if (retval != SCTP_XMIT_OK) 370 goto finish; 371 372 /* Try to bundle SACK chunk */ 373 retval = sctp_packet_bundle_sack(packet, chunk); 374 if (retval != SCTP_XMIT_OK) 375 goto finish; 376 377 retval = __sctp_packet_append_chunk(packet, chunk); 378 379 finish: 380 return retval; 381 } 382 383 static void sctp_packet_release_owner(struct sk_buff *skb) 384 { 385 sk_free(skb->sk); 386 } 387 388 static void sctp_packet_set_owner_w(struct sk_buff *skb, struct sock *sk) 389 { 390 skb_orphan(skb); 391 skb->sk = sk; 392 skb->destructor = sctp_packet_release_owner; 393 394 /* 395 * The data chunks have already been accounted for in sctp_sendmsg(), 396 * therefore only reserve a single byte to keep socket around until 397 * the packet has been transmitted. 398 */ 399 atomic_inc(&sk->sk_wmem_alloc); 400 } 401 402 static int sctp_packet_pack(struct sctp_packet *packet, 403 struct sk_buff *head, int gso, gfp_t gfp) 404 { 405 struct sctp_transport *tp = packet->transport; 406 struct sctp_auth_chunk *auth = NULL; 407 struct sctp_chunk *chunk, *tmp; 408 int pkt_count = 0, pkt_size; 409 struct sock *sk = head->sk; 410 struct sk_buff *nskb; 411 int auth_len = 0; 412 413 if (gso) { 414 skb_shinfo(head)->gso_type = sk->sk_gso_type; 415 NAPI_GRO_CB(head)->last = head; 416 } else { 417 nskb = head; 418 pkt_size = packet->size; 419 goto merge; 420 } 421 422 do { 423 /* calculate the pkt_size and alloc nskb */ 424 pkt_size = packet->overhead; 425 list_for_each_entry_safe(chunk, tmp, &packet->chunk_list, 426 list) { 427 int padded = SCTP_PAD4(chunk->skb->len); 428 429 if (chunk == packet->auth) 430 auth_len = padded; 431 else if (auth_len + padded + packet->overhead > 432 tp->pathmtu) 433 return 0; 434 else if (pkt_size + padded > tp->pathmtu) 435 break; 436 pkt_size += padded; 437 } 438 nskb = alloc_skb(pkt_size + MAX_HEADER, gfp); 439 if (!nskb) 440 return 0; 441 skb_reserve(nskb, packet->overhead + MAX_HEADER); 442 443 merge: 444 /* merge chunks into nskb and append nskb into head list */ 445 pkt_size -= packet->overhead; 446 list_for_each_entry_safe(chunk, tmp, &packet->chunk_list, list) { 447 int padding; 448 449 list_del_init(&chunk->list); 450 if (sctp_chunk_is_data(chunk)) { 451 if (!sctp_chunk_retransmitted(chunk) && 452 !tp->rto_pending) { 453 chunk->rtt_in_progress = 1; 454 tp->rto_pending = 1; 455 } 456 } 457 458 padding = SCTP_PAD4(chunk->skb->len) - chunk->skb->len; 459 if (padding) 460 memset(skb_put(chunk->skb, padding), 0, padding); 461 462 if (chunk == packet->auth) 463 auth = (struct sctp_auth_chunk *) 464 skb_tail_pointer(nskb); 465 466 memcpy(skb_put(nskb, chunk->skb->len), chunk->skb->data, 467 chunk->skb->len); 468 469 pr_debug("*** Chunk:%p[%s] %s 0x%x, length:%d, chunk->skb->len:%d, rtt_in_progress:%d\n", 470 chunk, 471 sctp_cname(SCTP_ST_CHUNK(chunk->chunk_hdr->type)), 472 chunk->has_tsn ? "TSN" : "No TSN", 473 chunk->has_tsn ? ntohl(chunk->subh.data_hdr->tsn) : 0, 474 ntohs(chunk->chunk_hdr->length), chunk->skb->len, 475 chunk->rtt_in_progress); 476 477 pkt_size -= SCTP_PAD4(chunk->skb->len); 478 479 if (!sctp_chunk_is_data(chunk) && chunk != packet->auth) 480 sctp_chunk_free(chunk); 481 482 if (!pkt_size) 483 break; 484 } 485 486 if (auth) { 487 sctp_auth_calculate_hmac(tp->asoc, nskb, auth, gfp); 488 /* free auth if no more chunks, or add it back */ 489 if (list_empty(&packet->chunk_list)) 490 sctp_chunk_free(packet->auth); 491 else 492 list_add(&packet->auth->list, 493 &packet->chunk_list); 494 } 495 496 if (gso) { 497 if (skb_gro_receive(&head, nskb)) { 498 kfree_skb(nskb); 499 return 0; 500 } 501 if (WARN_ON_ONCE(skb_shinfo(head)->gso_segs >= 502 sk->sk_gso_max_segs)) 503 return 0; 504 } 505 506 pkt_count++; 507 } while (!list_empty(&packet->chunk_list)); 508 509 if (gso) { 510 memset(head->cb, 0, max(sizeof(struct inet_skb_parm), 511 sizeof(struct inet6_skb_parm))); 512 skb_shinfo(head)->gso_segs = pkt_count; 513 skb_shinfo(head)->gso_size = GSO_BY_FRAGS; 514 rcu_read_lock(); 515 if (skb_dst(head) != tp->dst) { 516 dst_hold(tp->dst); 517 sk_setup_caps(sk, tp->dst); 518 } 519 rcu_read_unlock(); 520 goto chksum; 521 } 522 523 if (sctp_checksum_disable) 524 return 1; 525 526 if (!(skb_dst(head)->dev->features & NETIF_F_SCTP_CRC) || 527 dst_xfrm(skb_dst(head)) || packet->ipfragok) { 528 struct sctphdr *sh = 529 (struct sctphdr *)skb_transport_header(head); 530 531 sh->checksum = sctp_compute_cksum(head, 0); 532 } else { 533 chksum: 534 head->ip_summed = CHECKSUM_PARTIAL; 535 head->csum_start = skb_transport_header(head) - head->head; 536 head->csum_offset = offsetof(struct sctphdr, checksum); 537 } 538 539 return pkt_count; 540 } 541 542 /* All packets are sent to the network through this function from 543 * sctp_outq_tail(). 544 * 545 * The return value is always 0 for now. 546 */ 547 int sctp_packet_transmit(struct sctp_packet *packet, gfp_t gfp) 548 { 549 struct sctp_transport *tp = packet->transport; 550 struct sctp_association *asoc = tp->asoc; 551 struct sctp_chunk *chunk, *tmp; 552 int pkt_count, gso = 0; 553 struct dst_entry *dst; 554 struct sk_buff *head; 555 struct sctphdr *sh; 556 struct sock *sk; 557 558 pr_debug("%s: packet:%p\n", __func__, packet); 559 if (list_empty(&packet->chunk_list)) 560 return 0; 561 chunk = list_entry(packet->chunk_list.next, struct sctp_chunk, list); 562 sk = chunk->skb->sk; 563 564 /* check gso */ 565 if (packet->size > tp->pathmtu && !packet->ipfragok) { 566 if (!sk_can_gso(sk)) { 567 pr_err_once("Trying to GSO but underlying device doesn't support it."); 568 goto out; 569 } 570 gso = 1; 571 } 572 573 /* alloc head skb */ 574 head = alloc_skb((gso ? packet->overhead : packet->size) + 575 MAX_HEADER, gfp); 576 if (!head) 577 goto out; 578 skb_reserve(head, packet->overhead + MAX_HEADER); 579 sctp_packet_set_owner_w(head, sk); 580 581 /* set sctp header */ 582 sh = (struct sctphdr *)skb_push(head, sizeof(struct sctphdr)); 583 skb_reset_transport_header(head); 584 sh->source = htons(packet->source_port); 585 sh->dest = htons(packet->destination_port); 586 sh->vtag = htonl(packet->vtag); 587 sh->checksum = 0; 588 589 /* update dst if in need */ 590 if (!sctp_transport_dst_check(tp)) { 591 sctp_transport_route(tp, NULL, sctp_sk(sk)); 592 if (asoc && asoc->param_flags & SPP_PMTUD_ENABLE) 593 sctp_assoc_sync_pmtu(sk, asoc); 594 } 595 dst = dst_clone(tp->dst); 596 if (!dst) { 597 IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTNOROUTES); 598 kfree_skb(head); 599 goto out; 600 } 601 skb_dst_set(head, dst); 602 603 /* pack up chunks */ 604 pkt_count = sctp_packet_pack(packet, head, gso, gfp); 605 if (!pkt_count) { 606 kfree_skb(head); 607 goto out; 608 } 609 pr_debug("***sctp_transmit_packet*** skb->len:%d\n", head->len); 610 611 /* start autoclose timer */ 612 if (packet->has_data && sctp_state(asoc, ESTABLISHED) && 613 asoc->timeouts[SCTP_EVENT_TIMEOUT_AUTOCLOSE]) { 614 struct timer_list *timer = 615 &asoc->timers[SCTP_EVENT_TIMEOUT_AUTOCLOSE]; 616 unsigned long timeout = 617 asoc->timeouts[SCTP_EVENT_TIMEOUT_AUTOCLOSE]; 618 619 if (!mod_timer(timer, jiffies + timeout)) 620 sctp_association_hold(asoc); 621 } 622 623 /* sctp xmit */ 624 tp->af_specific->ecn_capable(sk); 625 if (asoc) { 626 asoc->stats.opackets += pkt_count; 627 if (asoc->peer.last_sent_to != tp) 628 asoc->peer.last_sent_to = tp; 629 } 630 head->ignore_df = packet->ipfragok; 631 tp->af_specific->sctp_xmit(head, tp); 632 633 out: 634 list_for_each_entry_safe(chunk, tmp, &packet->chunk_list, list) { 635 list_del_init(&chunk->list); 636 if (!sctp_chunk_is_data(chunk)) 637 sctp_chunk_free(chunk); 638 } 639 sctp_packet_reset(packet); 640 return 0; 641 } 642 643 /******************************************************************** 644 * 2nd Level Abstractions 645 ********************************************************************/ 646 647 /* This private function check to see if a chunk can be added */ 648 static sctp_xmit_t sctp_packet_can_append_data(struct sctp_packet *packet, 649 struct sctp_chunk *chunk) 650 { 651 size_t datasize, rwnd, inflight, flight_size; 652 struct sctp_transport *transport = packet->transport; 653 struct sctp_association *asoc = transport->asoc; 654 struct sctp_outq *q = &asoc->outqueue; 655 656 /* RFC 2960 6.1 Transmission of DATA Chunks 657 * 658 * A) At any given time, the data sender MUST NOT transmit new data to 659 * any destination transport address if its peer's rwnd indicates 660 * that the peer has no buffer space (i.e. rwnd is 0, see Section 661 * 6.2.1). However, regardless of the value of rwnd (including if it 662 * is 0), the data sender can always have one DATA chunk in flight to 663 * the receiver if allowed by cwnd (see rule B below). This rule 664 * allows the sender to probe for a change in rwnd that the sender 665 * missed due to the SACK having been lost in transit from the data 666 * receiver to the data sender. 667 */ 668 669 rwnd = asoc->peer.rwnd; 670 inflight = q->outstanding_bytes; 671 flight_size = transport->flight_size; 672 673 datasize = sctp_data_size(chunk); 674 675 if (datasize > rwnd && inflight > 0) 676 /* We have (at least) one data chunk in flight, 677 * so we can't fall back to rule 6.1 B). 678 */ 679 return SCTP_XMIT_RWND_FULL; 680 681 /* RFC 2960 6.1 Transmission of DATA Chunks 682 * 683 * B) At any given time, the sender MUST NOT transmit new data 684 * to a given transport address if it has cwnd or more bytes 685 * of data outstanding to that transport address. 686 */ 687 /* RFC 7.2.4 & the Implementers Guide 2.8. 688 * 689 * 3) ... 690 * When a Fast Retransmit is being performed the sender SHOULD 691 * ignore the value of cwnd and SHOULD NOT delay retransmission. 692 */ 693 if (chunk->fast_retransmit != SCTP_NEED_FRTX && 694 flight_size >= transport->cwnd) 695 return SCTP_XMIT_RWND_FULL; 696 697 /* Nagle's algorithm to solve small-packet problem: 698 * Inhibit the sending of new chunks when new outgoing data arrives 699 * if any previously transmitted data on the connection remains 700 * unacknowledged. 701 */ 702 703 if (sctp_sk(asoc->base.sk)->nodelay) 704 /* Nagle disabled */ 705 return SCTP_XMIT_OK; 706 707 if (!sctp_packet_empty(packet)) 708 /* Append to packet */ 709 return SCTP_XMIT_OK; 710 711 if (inflight == 0) 712 /* Nothing unacked */ 713 return SCTP_XMIT_OK; 714 715 if (!sctp_state(asoc, ESTABLISHED)) 716 return SCTP_XMIT_OK; 717 718 /* Check whether this chunk and all the rest of pending data will fit 719 * or delay in hopes of bundling a full sized packet. 720 */ 721 if (chunk->skb->len + q->out_qlen > 722 transport->pathmtu - packet->overhead - sizeof(sctp_data_chunk_t) - 4) 723 /* Enough data queued to fill a packet */ 724 return SCTP_XMIT_OK; 725 726 /* Don't delay large message writes that may have been fragmented */ 727 if (!chunk->msg->can_delay) 728 return SCTP_XMIT_OK; 729 730 /* Defer until all data acked or packet full */ 731 return SCTP_XMIT_DELAY; 732 } 733 734 /* This private function does management things when adding DATA chunk */ 735 static void sctp_packet_append_data(struct sctp_packet *packet, 736 struct sctp_chunk *chunk) 737 { 738 struct sctp_transport *transport = packet->transport; 739 size_t datasize = sctp_data_size(chunk); 740 struct sctp_association *asoc = transport->asoc; 741 u32 rwnd = asoc->peer.rwnd; 742 743 /* Keep track of how many bytes are in flight over this transport. */ 744 transport->flight_size += datasize; 745 746 /* Keep track of how many bytes are in flight to the receiver. */ 747 asoc->outqueue.outstanding_bytes += datasize; 748 749 /* Update our view of the receiver's rwnd. */ 750 if (datasize < rwnd) 751 rwnd -= datasize; 752 else 753 rwnd = 0; 754 755 asoc->peer.rwnd = rwnd; 756 sctp_chunk_assign_tsn(chunk); 757 sctp_chunk_assign_ssn(chunk); 758 } 759 760 static sctp_xmit_t sctp_packet_will_fit(struct sctp_packet *packet, 761 struct sctp_chunk *chunk, 762 u16 chunk_len) 763 { 764 size_t psize, pmtu, maxsize; 765 sctp_xmit_t retval = SCTP_XMIT_OK; 766 767 psize = packet->size; 768 if (packet->transport->asoc) 769 pmtu = packet->transport->asoc->pathmtu; 770 else 771 pmtu = packet->transport->pathmtu; 772 773 /* Decide if we need to fragment or resubmit later. */ 774 if (psize + chunk_len > pmtu) { 775 /* It's OK to fragment at IP level if any one of the following 776 * is true: 777 * 1. The packet is empty (meaning this chunk is greater 778 * the MTU) 779 * 2. The packet doesn't have any data in it yet and data 780 * requires authentication. 781 */ 782 if (sctp_packet_empty(packet) || 783 (!packet->has_data && chunk->auth)) { 784 /* We no longer do re-fragmentation. 785 * Just fragment at the IP layer, if we 786 * actually hit this condition 787 */ 788 packet->ipfragok = 1; 789 goto out; 790 } 791 792 /* Similarly, if this chunk was built before a PMTU 793 * reduction, we have to fragment it at IP level now. So 794 * if the packet already contains something, we need to 795 * flush. 796 */ 797 maxsize = pmtu - packet->overhead; 798 if (packet->auth) 799 maxsize -= SCTP_PAD4(packet->auth->skb->len); 800 if (chunk_len > maxsize) 801 retval = SCTP_XMIT_PMTU_FULL; 802 803 /* It is also okay to fragment if the chunk we are 804 * adding is a control chunk, but only if current packet 805 * is not a GSO one otherwise it causes fragmentation of 806 * a large frame. So in this case we allow the 807 * fragmentation by forcing it to be in a new packet. 808 */ 809 if (!sctp_chunk_is_data(chunk) && packet->has_data) 810 retval = SCTP_XMIT_PMTU_FULL; 811 812 if (psize + chunk_len > packet->max_size) 813 /* Hit GSO/PMTU limit, gotta flush */ 814 retval = SCTP_XMIT_PMTU_FULL; 815 816 if (!packet->transport->burst_limited && 817 psize + chunk_len > (packet->transport->cwnd >> 1)) 818 /* Do not allow a single GSO packet to use more 819 * than half of cwnd. 820 */ 821 retval = SCTP_XMIT_PMTU_FULL; 822 823 if (packet->transport->burst_limited && 824 psize + chunk_len > (packet->transport->burst_limited >> 1)) 825 /* Do not allow a single GSO packet to use more 826 * than half of original cwnd. 827 */ 828 retval = SCTP_XMIT_PMTU_FULL; 829 /* Otherwise it will fit in the GSO packet */ 830 } 831 832 out: 833 return retval; 834 } 835