linux/net/sctp/output.c
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   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                break;
 315
 316            case SCTP_CID_AUTH:
 317                packet->has_auth = 1;
 318                packet->auth = chunk;
 319                break;
 320        }
 321
 322        /* It is OK to send this chunk.  */
 323        list_add_tail(&chunk->list, &packet->chunk_list);
 324        packet->size += chunk_len;
 325        chunk->transport = packet->transport;
 326finish:
 327        return retval;
 328}
 329
 330/* Append a chunk to the offered packet reporting back any inability to do
 331 * so.
 332 */
 333sctp_xmit_t sctp_packet_append_chunk(struct sctp_packet *packet,
 334                                     struct sctp_chunk *chunk)
 335{
 336        sctp_xmit_t retval = SCTP_XMIT_OK;
 337
 338        SCTP_DEBUG_PRINTK("%s: packet:%p chunk:%p\n", __func__, packet,
 339                          chunk);
 340
 341        /* Data chunks are special.  Before seeing what else we can
 342         * bundle into this packet, check to see if we are allowed to
 343         * send this DATA.
 344         */
 345        if (sctp_chunk_is_data(chunk)) {
 346                retval = sctp_packet_can_append_data(packet, chunk);
 347                if (retval != SCTP_XMIT_OK)
 348                        goto finish;
 349        }
 350
 351        /* Try to bundle AUTH chunk */
 352        retval = sctp_packet_bundle_auth(packet, chunk);
 353        if (retval != SCTP_XMIT_OK)
 354                goto finish;
 355
 356        /* Try to bundle SACK chunk */
 357        retval = sctp_packet_bundle_sack(packet, chunk);
 358        if (retval != SCTP_XMIT_OK)
 359                goto finish;
 360
 361        retval = __sctp_packet_append_chunk(packet, chunk);
 362
 363finish:
 364        return retval;
 365}
 366
 367static void sctp_packet_release_owner(struct sk_buff *skb)
 368{
 369        sk_free(skb->sk);
 370}
 371
 372static void sctp_packet_set_owner_w(struct sk_buff *skb, struct sock *sk)
 373{
 374        skb_orphan(skb);
 375        skb->sk = sk;
 376        skb->destructor = sctp_packet_release_owner;
 377
 378        /*
 379         * The data chunks have already been accounted for in sctp_sendmsg(),
 380         * therefore only reserve a single byte to keep socket around until
 381         * the packet has been transmitted.
 382         */
 383        atomic_inc(&sk->sk_wmem_alloc);
 384}
 385
 386/* All packets are sent to the network through this function from
 387 * sctp_outq_tail().
 388 *
 389 * The return value is a normal kernel error return value.
 390 */
 391int sctp_packet_transmit(struct sctp_packet *packet)
 392{
 393        struct sctp_transport *tp = packet->transport;
 394        struct sctp_association *asoc = tp->asoc;
 395        struct sctphdr *sh;
 396        struct sk_buff *nskb;
 397        struct sctp_chunk *chunk, *tmp;
 398        struct sock *sk;
 399        int err = 0;
 400        int padding;            /* How much padding do we need?  */
 401        __u8 has_data = 0;
 402        struct dst_entry *dst = tp->dst;
 403        unsigned char *auth = NULL;     /* pointer to auth in skb data */
 404        __u32 cksum_buf_len = sizeof(struct sctphdr);
 405
 406        SCTP_DEBUG_PRINTK("%s: packet:%p\n", __func__, packet);
 407
 408        /* Do NOT generate a chunkless packet. */
 409        if (list_empty(&packet->chunk_list))
 410                return err;
 411
 412        /* Set up convenience variables... */
 413        chunk = list_entry(packet->chunk_list.next, struct sctp_chunk, list);
 414        sk = chunk->skb->sk;
 415
 416        /* Allocate the new skb.  */
 417        nskb = alloc_skb(packet->size + LL_MAX_HEADER, GFP_ATOMIC);
 418        if (!nskb)
 419                goto nomem;
 420
 421        /* Make sure the outbound skb has enough header room reserved. */
 422        skb_reserve(nskb, packet->overhead + LL_MAX_HEADER);
 423
 424        /* Set the owning socket so that we know where to get the
 425         * destination IP address.
 426         */
 427        sctp_packet_set_owner_w(nskb, sk);
 428
 429        if (!sctp_transport_dst_check(tp)) {
 430                sctp_transport_route(tp, NULL, sctp_sk(sk));
 431                if (asoc && (asoc->param_flags & SPP_PMTUD_ENABLE)) {
 432                        sctp_assoc_sync_pmtu(sk, asoc);
 433                }
 434        }
 435        dst = dst_clone(tp->dst);
 436        skb_dst_set(nskb, dst);
 437        if (!dst)
 438                goto no_route;
 439
 440        /* Build the SCTP header.  */
 441        sh = (struct sctphdr *)skb_push(nskb, sizeof(struct sctphdr));
 442        skb_reset_transport_header(nskb);
 443        sh->source = htons(packet->source_port);
 444        sh->dest   = htons(packet->destination_port);
 445
 446        /* From 6.8 Adler-32 Checksum Calculation:
 447         * After the packet is constructed (containing the SCTP common
 448         * header and one or more control or DATA chunks), the
 449         * transmitter shall:
 450         *
 451         * 1) Fill in the proper Verification Tag in the SCTP common
 452         *    header and initialize the checksum field to 0's.
 453         */
 454        sh->vtag     = htonl(packet->vtag);
 455        sh->checksum = 0;
 456
 457        /**
 458         * 6.10 Bundling
 459         *
 460         *    An endpoint bundles chunks by simply including multiple
 461         *    chunks in one outbound SCTP packet.  ...
 462         */
 463
 464        /**
 465         * 3.2  Chunk Field Descriptions
 466         *
 467         * The total length of a chunk (including Type, Length and
 468         * Value fields) MUST be a multiple of 4 bytes.  If the length
 469         * of the chunk is not a multiple of 4 bytes, the sender MUST
 470         * pad the chunk with all zero bytes and this padding is not
 471         * included in the chunk length field.  The sender should
 472         * never pad with more than 3 bytes.
 473         *
 474         * [This whole comment explains WORD_ROUND() below.]
 475         */
 476        SCTP_DEBUG_PRINTK("***sctp_transmit_packet***\n");
 477        list_for_each_entry_safe(chunk, tmp, &packet->chunk_list, list) {
 478                list_del_init(&chunk->list);
 479                if (sctp_chunk_is_data(chunk)) {
 480                        /* 6.3.1 C4) When data is in flight and when allowed
 481                         * by rule C5, a new RTT measurement MUST be made each
 482                         * round trip.  Furthermore, new RTT measurements
 483                         * SHOULD be made no more than once per round-trip
 484                         * for a given destination transport address.
 485                         */
 486
 487                        if (!tp->rto_pending) {
 488                                chunk->rtt_in_progress = 1;
 489                                tp->rto_pending = 1;
 490                        }
 491                        has_data = 1;
 492                }
 493
 494                padding = WORD_ROUND(chunk->skb->len) - chunk->skb->len;
 495                if (padding)
 496                        memset(skb_put(chunk->skb, padding), 0, padding);
 497
 498                /* if this is the auth chunk that we are adding,
 499                 * store pointer where it will be added and put
 500                 * the auth into the packet.
 501                 */
 502                if (chunk == packet->auth)
 503                        auth = skb_tail_pointer(nskb);
 504
 505                cksum_buf_len += chunk->skb->len;
 506                memcpy(skb_put(nskb, chunk->skb->len),
 507                               chunk->skb->data, chunk->skb->len);
 508
 509                SCTP_DEBUG_PRINTK("%s %p[%s] %s 0x%x, %s %d, %s %d, %s %d\n",
 510                                  "*** Chunk", chunk,
 511                                  sctp_cname(SCTP_ST_CHUNK(
 512                                          chunk->chunk_hdr->type)),
 513                                  chunk->has_tsn ? "TSN" : "No TSN",
 514                                  chunk->has_tsn ?
 515                                  ntohl(chunk->subh.data_hdr->tsn) : 0,
 516                                  "length", ntohs(chunk->chunk_hdr->length),
 517                                  "chunk->skb->len", chunk->skb->len,
 518                                  "rtt_in_progress", chunk->rtt_in_progress);
 519
 520                /*
 521                 * If this is a control chunk, this is our last
 522                 * reference. Free data chunks after they've been
 523                 * acknowledged or have failed.
 524                 */
 525                if (!sctp_chunk_is_data(chunk))
 526                        sctp_chunk_free(chunk);
 527        }
 528
 529        /* SCTP-AUTH, Section 6.2
 530         *    The sender MUST calculate the MAC as described in RFC2104 [2]
 531         *    using the hash function H as described by the MAC Identifier and
 532         *    the shared association key K based on the endpoint pair shared key
 533         *    described by the shared key identifier.  The 'data' used for the
 534         *    computation of the AUTH-chunk is given by the AUTH chunk with its
 535         *    HMAC field set to zero (as shown in Figure 6) followed by all
 536         *    chunks that are placed after the AUTH chunk in the SCTP packet.
 537         */
 538        if (auth)
 539                sctp_auth_calculate_hmac(asoc, nskb,
 540                                        (struct sctp_auth_chunk *)auth,
 541                                        GFP_ATOMIC);
 542
 543        /* 2) Calculate the Adler-32 checksum of the whole packet,
 544         *    including the SCTP common header and all the
 545         *    chunks.
 546         *
 547         * Note: Adler-32 is no longer applicable, as has been replaced
 548         * by CRC32-C as described in <draft-ietf-tsvwg-sctpcsum-02.txt>.
 549         */
 550        if (!sctp_checksum_disable) {
 551                if (!(dst->dev->features & NETIF_F_SCTP_CSUM)) {
 552                        __u32 crc32 = sctp_start_cksum((__u8 *)sh, cksum_buf_len);
 553
 554                        /* 3) Put the resultant value into the checksum field in the
 555                         *    common header, and leave the rest of the bits unchanged.
 556                         */
 557                        sh->checksum = sctp_end_cksum(crc32);
 558                } else {
 559                        /* no need to seed pseudo checksum for SCTP */
 560                        nskb->ip_summed = CHECKSUM_PARTIAL;
 561                        nskb->csum_start = (skb_transport_header(nskb) -
 562                                            nskb->head);
 563                        nskb->csum_offset = offsetof(struct sctphdr, checksum);
 564                }
 565        }
 566
 567        /* IP layer ECN support
 568         * From RFC 2481
 569         *  "The ECN-Capable Transport (ECT) bit would be set by the
 570         *   data sender to indicate that the end-points of the
 571         *   transport protocol are ECN-capable."
 572         *
 573         * Now setting the ECT bit all the time, as it should not cause
 574         * any problems protocol-wise even if our peer ignores it.
 575         *
 576         * Note: The works for IPv6 layer checks this bit too later
 577         * in transmission.  See IP6_ECN_flow_xmit().
 578         */
 579        (*tp->af_specific->ecn_capable)(nskb->sk);
 580
 581        /* Set up the IP options.  */
 582        /* BUG: not implemented
 583         * For v4 this all lives somewhere in sk->sk_opt...
 584         */
 585
 586        /* Dump that on IP!  */
 587        if (asoc && asoc->peer.last_sent_to != tp) {
 588                /* Considering the multiple CPU scenario, this is a
 589                 * "correcter" place for last_sent_to.  --xguo
 590                 */
 591                asoc->peer.last_sent_to = tp;
 592        }
 593
 594        if (has_data) {
 595                struct timer_list *timer;
 596                unsigned long timeout;
 597
 598                /* Restart the AUTOCLOSE timer when sending data. */
 599                if (sctp_state(asoc, ESTABLISHED) && asoc->autoclose) {
 600                        timer = &asoc->timers[SCTP_EVENT_TIMEOUT_AUTOCLOSE];
 601                        timeout = asoc->timeouts[SCTP_EVENT_TIMEOUT_AUTOCLOSE];
 602
 603                        if (!mod_timer(timer, jiffies + timeout))
 604                                sctp_association_hold(asoc);
 605                }
 606        }
 607
 608        SCTP_DEBUG_PRINTK("***sctp_transmit_packet*** skb len %d\n",
 609                          nskb->len);
 610
 611        nskb->local_df = packet->ipfragok;
 612        (*tp->af_specific->sctp_xmit)(nskb, tp);
 613
 614out:
 615        sctp_packet_reset(packet);
 616        return err;
 617no_route:
 618        kfree_skb(nskb);
 619        IP_INC_STATS_BH(&init_net, IPSTATS_MIB_OUTNOROUTES);
 620
 621        /* FIXME: Returning the 'err' will effect all the associations
 622         * associated with a socket, although only one of the paths of the
 623         * association is unreachable.
 624         * The real failure of a transport or association can be passed on
 625         * to the user via notifications. So setting this error may not be
 626         * required.
 627         */
 628         /* err = -EHOSTUNREACH; */
 629err:
 630        /* Control chunks are unreliable so just drop them.  DATA chunks
 631         * will get resent or dropped later.
 632         */
 633
 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        goto out;
 640nomem:
 641        err = -ENOMEM;
 642        goto err;
 643}
 644
 645/********************************************************************
 646 * 2nd Level Abstractions
 647 ********************************************************************/
 648
 649/* This private function check to see if a chunk can be added */
 650static sctp_xmit_t sctp_packet_can_append_data(struct sctp_packet *packet,
 651                                           struct sctp_chunk *chunk)
 652{
 653        sctp_xmit_t retval = SCTP_XMIT_OK;
 654        size_t datasize, rwnd, inflight, flight_size;
 655        struct sctp_transport *transport = packet->transport;
 656        struct sctp_association *asoc = transport->asoc;
 657        struct sctp_outq *q = &asoc->outqueue;
 658
 659        /* RFC 2960 6.1  Transmission of DATA Chunks
 660         *
 661         * A) At any given time, the data sender MUST NOT transmit new data to
 662         * any destination transport address if its peer's rwnd indicates
 663         * that the peer has no buffer space (i.e. rwnd is 0, see Section
 664         * 6.2.1).  However, regardless of the value of rwnd (including if it
 665         * is 0), the data sender can always have one DATA chunk in flight to
 666         * the receiver if allowed by cwnd (see rule B below).  This rule
 667         * allows the sender to probe for a change in rwnd that the sender
 668         * missed due to the SACK having been lost in transit from the data
 669         * receiver to the data sender.
 670         */
 671
 672        rwnd = asoc->peer.rwnd;
 673        inflight = q->outstanding_bytes;
 674        flight_size = transport->flight_size;
 675
 676        datasize = sctp_data_size(chunk);
 677
 678        if (datasize > rwnd) {
 679                if (inflight > 0) {
 680                        /* We have (at least) one data chunk in flight,
 681                         * so we can't fall back to rule 6.1 B).
 682                         */
 683                        retval = SCTP_XMIT_RWND_FULL;
 684                        goto finish;
 685                }
 686        }
 687
 688        /* RFC 2960 6.1  Transmission of DATA Chunks
 689         *
 690         * B) At any given time, the sender MUST NOT transmit new data
 691         * to a given transport address if it has cwnd or more bytes
 692         * of data outstanding to that transport address.
 693         */
 694        /* RFC 7.2.4 & the Implementers Guide 2.8.
 695         *
 696         * 3) ...
 697         *    When a Fast Retransmit is being performed the sender SHOULD
 698         *    ignore the value of cwnd and SHOULD NOT delay retransmission.
 699         */
 700        if (chunk->fast_retransmit != SCTP_NEED_FRTX)
 701                if (flight_size >= transport->cwnd) {
 702                        retval = SCTP_XMIT_RWND_FULL;
 703                        goto finish;
 704                }
 705
 706        /* Nagle's algorithm to solve small-packet problem:
 707         * Inhibit the sending of new chunks when new outgoing data arrives
 708         * if any previously transmitted data on the connection remains
 709         * unacknowledged.
 710         */
 711        if (!sctp_sk(asoc->base.sk)->nodelay && sctp_packet_empty(packet) &&
 712            inflight && sctp_state(asoc, ESTABLISHED)) {
 713                unsigned int max = transport->pathmtu - packet->overhead;
 714                unsigned int len = chunk->skb->len + q->out_qlen;
 715
 716                /* Check whether this chunk and all the rest of pending
 717                 * data will fit or delay in hopes of bundling a full
 718                 * sized packet.
 719                 * Don't delay large message writes that may have been
 720                 * fragmeneted into small peices.
 721                 */
 722                if ((len < max) && chunk->msg->can_delay) {
 723                        retval = SCTP_XMIT_NAGLE_DELAY;
 724                        goto finish;
 725                }
 726        }
 727
 728finish:
 729        return retval;
 730}
 731
 732/* This private function does management things when adding DATA chunk */
 733static void sctp_packet_append_data(struct sctp_packet *packet,
 734                                struct sctp_chunk *chunk)
 735{
 736        struct sctp_transport *transport = packet->transport;
 737        size_t datasize = sctp_data_size(chunk);
 738        struct sctp_association *asoc = transport->asoc;
 739        u32 rwnd = asoc->peer.rwnd;
 740
 741        /* Keep track of how many bytes are in flight over this transport. */
 742        transport->flight_size += datasize;
 743
 744        /* Keep track of how many bytes are in flight to the receiver. */
 745        asoc->outqueue.outstanding_bytes += datasize;
 746
 747        /* Update our view of the receiver's rwnd. */
 748        if (datasize < rwnd)
 749                rwnd -= datasize;
 750        else
 751                rwnd = 0;
 752
 753        asoc->peer.rwnd = rwnd;
 754        /* Has been accepted for transmission. */
 755        if (!asoc->peer.prsctp_capable)
 756                chunk->msg->can_abandon = 0;
 757        sctp_chunk_assign_tsn(chunk);
 758        sctp_chunk_assign_ssn(chunk);
 759}
 760
 761static sctp_xmit_t sctp_packet_will_fit(struct sctp_packet *packet,
 762                                        struct sctp_chunk *chunk,
 763                                        u16 chunk_len)
 764{
 765        size_t psize;
 766        size_t pmtu;
 767        int too_big;
 768        sctp_xmit_t retval = SCTP_XMIT_OK;
 769
 770        psize = packet->size;
 771        pmtu  = ((packet->transport->asoc) ?
 772                (packet->transport->asoc->pathmtu) :
 773                (packet->transport->pathmtu));
 774
 775        too_big = (psize + chunk_len > pmtu);
 776
 777        /* Decide if we need to fragment or resubmit later. */
 778        if (too_big) {
 779                /* It's OK to fragmet at IP level if any one of the following
 780                 * is true:
 781                 *      1. The packet is empty (meaning this chunk is greater
 782                 *         the MTU)
 783                 *      2. The chunk we are adding is a control chunk
 784                 *      3. The packet doesn't have any data in it yet and data
 785                 *      requires authentication.
 786                 */
 787                if (sctp_packet_empty(packet) || !sctp_chunk_is_data(chunk) ||
 788                    (!packet->has_data && chunk->auth)) {
 789                        /* We no longer do re-fragmentation.
 790                         * Just fragment at the IP layer, if we
 791                         * actually hit this condition
 792                         */
 793                        packet->ipfragok = 1;
 794                } else {
 795                        retval = SCTP_XMIT_PMTU_FULL;
 796                }
 797        }
 798
 799        return retval;
 800}
 801
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