linux/net/sctp/output.c
<<
>>
Prefs
   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. */
  67static sctp_xmit_t __sctp_packet_append_chunk(struct sctp_packet *packet,
  68                                              struct sctp_chunk *chunk);
  69static sctp_xmit_t sctp_packet_can_append_data(struct sctp_packet *packet,
  70                                           struct sctp_chunk *chunk);
  71static void sctp_packet_append_data(struct sctp_packet *packet,
  72                                           struct sctp_chunk *chunk);
  73static sctp_xmit_t sctp_packet_will_fit(struct sctp_packet *packet,
  74                                        struct sctp_chunk *chunk,
  75                                        u16 chunk_len);
  76
  77static 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 */
  91struct 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. */
 115struct 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.  */
 144void 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 */
 166sctp_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. */
 202static 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. */
 238static 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        }
 275out:
 276        return retval;
 277}
 278
 279
 280/* Append a chunk to the offered packet reporting back any inability to do
 281 * so.
 282 */
 283static 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;
 328finish:
 329        return retval;
 330}
 331
 332/* Append a chunk to the offered packet reporting back any inability to do
 333 * so.
 334 */
 335sctp_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
 365finish:
 366        return retval;
 367}
 368
 369static void sctp_packet_release_owner(struct sk_buff *skb)
 370{
 371        sk_free(skb->sk);
 372}
 373
 374static 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 */
 393int 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
 618out:
 619        sctp_packet_reset(packet);
 620        return err;
 621no_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; */
 633err:
 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;
 644nomem:
 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 */
 654static 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
 732finish:
 733        return retval;
 734}
 735
 736/* This private function does management things when adding DATA chunk */
 737static 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
 765static 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
lxr.linux.no kindly hosted by Redpill Linpro AS, provider of Linux consulting and operations services since 1995.