net/sctp/output.c

   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         int error = 0;
 184
 185         pr_debug("%s: packet:%p size:%Zu chunk:%p size:%d\n", __func__,
 186                  packet, packet->size, chunk, chunk->skb ? chunk->skb->len : -1);
 187
 188         switch ((retval = (sctp_packet_append_chunk(packet, chunk)))) {
 189         case SCTP_XMIT_PMTU_FULL:
 190                 if (!packet->has_cookie_echo) {
 191                         error = sctp_packet_transmit(packet, gfp);
 192                         if (error < 0)
 193                                 chunk->skb->sk->sk_err = -error;
 194
 195                         /* If we have an empty packet, then we can NOT ever
 196                          * return PMTU_FULL.
 197                          */
 198                         if (!one_packet)
 199                                 retval = sctp_packet_append_chunk(packet,
 200                                                                   chunk);
 201                 }
 202                 break;
 203
 204         case SCTP_XMIT_RWND_FULL:
 205         case SCTP_XMIT_OK:
 206         case SCTP_XMIT_DELAY:
 207                 break;
 208         }
 209
 210         return retval;
 211 }
 212
 213 /* Try to bundle an auth chunk into the packet. */
 214 static sctp_xmit_t sctp_packet_bundle_auth(struct sctp_packet *pkt,
 215                                            struct sctp_chunk *chunk)
 216 {
 217         struct sctp_association *asoc = pkt->transport->asoc;
 218         struct sctp_chunk *auth;
 219         sctp_xmit_t retval = SCTP_XMIT_OK;
 220
 221         /* if we don't have an association, we can't do authentication */
 222         if (!asoc)
 223                 return retval;
 224
 225         /* See if this is an auth chunk we are bundling or if
 226          * auth is already bundled.
 227          */
 228         if (chunk->chunk_hdr->type == SCTP_CID_AUTH || pkt->has_auth)
 229                 return retval;
 230
 231         /* if the peer did not request this chunk to be authenticated,
 232          * don't do it
 233          */
 234         if (!chunk->auth)
 235                 return retval;
 236
 237         auth = sctp_make_auth(asoc);
 238         if (!auth)
 239                 return retval;
 240
 241         retval = __sctp_packet_append_chunk(pkt, auth);
 242
 243         if (retval != SCTP_XMIT_OK)
 244                 sctp_chunk_free(auth);
 245
 246         return retval;
 247 }
 248
 249 /* Try to bundle a SACK with the packet. */
 250 static sctp_xmit_t sctp_packet_bundle_sack(struct sctp_packet *pkt,
 251                                            struct sctp_chunk *chunk)
 252 {
 253         sctp_xmit_t retval = SCTP_XMIT_OK;
 254
 255         /* If sending DATA and haven't aleady bundled a SACK, try to
 256          * bundle one in to the packet.
 257          */
 258         if (sctp_chunk_is_data(chunk) && !pkt->has_sack &&
 259             !pkt->has_cookie_echo) {
 260                 struct sctp_association *asoc;
 261                 struct timer_list *timer;
 262                 asoc = pkt->transport->asoc;
 263                 timer = &asoc->timers[SCTP_EVENT_TIMEOUT_SACK];
 264
 265                 /* If the SACK timer is running, we have a pending SACK */
 266                 if (timer_pending(timer)) {
 267                         struct sctp_chunk *sack;
 268
 269                         if (pkt->transport->sack_generation !=
 270                             pkt->transport->asoc->peer.sack_generation)
 271                                 return retval;
 272
 273                         asoc->a_rwnd = asoc->rwnd;
 274                         sack = sctp_make_sack(asoc);
 275                         if (sack) {
 276                                 retval = __sctp_packet_append_chunk(pkt, sack);
 277                                 if (retval != SCTP_XMIT_OK) {
 278                                         sctp_chunk_free(sack);
 279                                         goto out;
 280                                 }
 281                                 asoc->peer.sack_needed = 0;
 282                                 if (del_timer(timer))
 283                                         sctp_association_put(asoc);
 284                         }
 285                 }
 286         }
 287 out:
 288         return retval;
 289 }
 290
 291
 292 /* Append a chunk to the offered packet reporting back any inability to do
 293  * so.
 294  */
 295 static sctp_xmit_t __sctp_packet_append_chunk(struct sctp_packet *packet,
 296                                               struct sctp_chunk *chunk)
 297 {
 298         sctp_xmit_t retval = SCTP_XMIT_OK;
 299         __u16 chunk_len = WORD_ROUND(ntohs(chunk->chunk_hdr->length));
 300
 301         /* Check to see if this chunk will fit into the packet */
 302         retval = sctp_packet_will_fit(packet, chunk, chunk_len);
 303         if (retval != SCTP_XMIT_OK)
 304                 goto finish;
 305
 306         /* We believe that this chunk is OK to add to the packet */
 307         switch (chunk->chunk_hdr->type) {
 308         case SCTP_CID_DATA:
 309                 /* Account for the data being in the packet */
 310                 sctp_packet_append_data(packet, chunk);
 311                 /* Disallow SACK bundling after DATA. */
 312                 packet->has_sack = 1;
 313                 /* Disallow AUTH bundling after DATA */
 314                 packet->has_auth = 1;
 315                 /* Let it be knows that packet has DATA in it */
 316                 packet->has_data = 1;
 317                 /* timestamp the chunk for rtx purposes */
 318                 chunk->sent_at = jiffies;
 319                 /* Mainly used for prsctp RTX policy */
 320                 chunk->sent_count++;
 321                 break;
 322         case SCTP_CID_COOKIE_ECHO:
 323                 packet->has_cookie_echo = 1;
 324                 break;
 325
 326         case SCTP_CID_SACK:
 327                 packet->has_sack = 1;
 328                 if (chunk->asoc)
 329                         chunk->asoc->stats.osacks++;
 330                 break;
 331
 332         case SCTP_CID_AUTH:
 333                 packet->has_auth = 1;
 334                 packet->auth = chunk;
 335                 break;
 336         }
 337
 338         /* It is OK to send this chunk.  */
 339         list_add_tail(&chunk->list, &packet->chunk_list);
 340         packet->size += chunk_len;
 341         chunk->transport = packet->transport;
 342 finish:
 343         return retval;
 344 }
 345
 346 /* Append a chunk to the offered packet reporting back any inability to do
 347  * so.
 348  */
 349 sctp_xmit_t sctp_packet_append_chunk(struct sctp_packet *packet,
 350                                      struct sctp_chunk *chunk)
 351 {
 352         sctp_xmit_t retval = SCTP_XMIT_OK;
 353
 354         pr_debug("%s: packet:%p chunk:%p\n", __func__, packet, chunk);
 355
 356         /* Data chunks are special.  Before seeing what else we can
 357          * bundle into this packet, check to see if we are allowed to
 358          * send this DATA.
 359          */
 360         if (sctp_chunk_is_data(chunk)) {
 361                 retval = sctp_packet_can_append_data(packet, chunk);
 362                 if (retval != SCTP_XMIT_OK)
 363                         goto finish;
 364         }
 365
 366         /* Try to bundle AUTH chunk */
 367         retval = sctp_packet_bundle_auth(packet, chunk);
 368         if (retval != SCTP_XMIT_OK)
 369                 goto finish;
 370
 371         /* Try to bundle SACK chunk */
 372         retval = sctp_packet_bundle_sack(packet, chunk);
 373         if (retval != SCTP_XMIT_OK)
 374                 goto finish;
 375
 376         retval = __sctp_packet_append_chunk(packet, chunk);
 377
 378 finish:
 379         return retval;
 380 }
 381
 382 static void sctp_packet_release_owner(struct sk_buff *skb)
 383 {
 384         sk_free(skb->sk);
 385 }
 386
 387 static void sctp_packet_set_owner_w(struct sk_buff *skb, struct sock *sk)
 388 {
 389         skb_orphan(skb);
 390         skb->sk = sk;
 391         skb->destructor = sctp_packet_release_owner;
 392
 393         /*
 394          * The data chunks have already been accounted for in sctp_sendmsg(),
 395          * therefore only reserve a single byte to keep socket around until
 396          * the packet has been transmitted.
 397          */
 398         atomic_inc(&sk->sk_wmem_alloc);
 399 }
 400
 401 /* All packets are sent to the network through this function from
 402  * sctp_outq_tail().
 403  *
 404  * The return value is a normal kernel error return value.
 405  */
 406 int sctp_packet_transmit(struct sctp_packet *packet, gfp_t gfp)
 407 {
 408         struct sctp_transport *tp = packet->transport;
 409         struct sctp_association *asoc = tp->asoc;
 410         struct sctphdr *sh;
 411         struct sk_buff *nskb = NULL, *head = NULL;
 412         struct sctp_chunk *chunk, *tmp;
 413         struct sock *sk;
 414         int err = 0;
 415         int padding;            /* How much padding do we need?  */
 416         int pkt_size;
 417         __u8 has_data = 0;
 418         int gso = 0;
 419         int pktcount = 0;
 420         struct dst_entry *dst;
 421         unsigned char *auth = NULL;     /* pointer to auth in skb data */
 422
 423         pr_debug("%s: packet:%p\n", __func__, packet);
 424
 425         /* Do NOT generate a chunkless packet. */
 426         if (list_empty(&packet->chunk_list))
 427                 return err;
 428
 429         /* Set up convenience variables... */
 430         chunk = list_entry(packet->chunk_list.next, struct sctp_chunk, list);
 431         sk = chunk->skb->sk;
 432
 433         /* Allocate the head skb, or main one if not in GSO */
 434         if (packet->size > tp->pathmtu && !packet->ipfragok) {
 435                 if (sk_can_gso(sk)) {
 436                         gso = 1;
 437                         pkt_size = packet->overhead;
 438                 } else {
 439                         /* If this happens, we trash this packet and try
 440                          * to build a new one, hopefully correct this
 441                          * time. Application may notice this error.
 442                          */
 443                         pr_err_once("Trying to GSO but underlying device doesn't support it.");
 444                         goto nomem;
 445                 }
 446         } else {
 447                 pkt_size = packet->size;
 448         }
 449         head = alloc_skb(pkt_size + MAX_HEADER, gfp);
 450         if (!head)
 451                 goto nomem;
 452         if (gso) {
 453                 NAPI_GRO_CB(head)->last = head;
 454                 skb_shinfo(head)->gso_type = sk->sk_gso_type;
 455         }
 456
 457         /* Make sure the outbound skb has enough header room reserved. */
 458         skb_reserve(head, packet->overhead + MAX_HEADER);
 459
 460         /* Set the owning socket so that we know where to get the
 461          * destination IP address.
 462          */
 463         sctp_packet_set_owner_w(head, sk);
 464
 465         if (!sctp_transport_dst_check(tp)) {
 466                 sctp_transport_route(tp, NULL, sctp_sk(sk));
 467                 if (asoc && (asoc->param_flags & SPP_PMTUD_ENABLE)) {
 468                         sctp_assoc_sync_pmtu(sk, asoc);
 469                 }
 470         }
 471         dst = dst_clone(tp->dst);
 472         if (!dst)
 473                 goto no_route;
 474         skb_dst_set(head, dst);
 475
 476         /* Build the SCTP header.  */
 477         sh = (struct sctphdr *)skb_push(head, sizeof(struct sctphdr));
 478         skb_reset_transport_header(head);
 479         sh->source = htons(packet->source_port);
 480         sh->dest   = htons(packet->destination_port);
 481
 482         /* From 6.8 Adler-32 Checksum Calculation:
 483          * After the packet is constructed (containing the SCTP common
 484          * header and one or more control or DATA chunks), the
 485          * transmitter shall:
 486          *
 487          * 1) Fill in the proper Verification Tag in the SCTP common
 488          *    header and initialize the checksum field to 0's.
 489          */
 490         sh->vtag     = htonl(packet->vtag);
 491         sh->checksum = 0;
 492
 493         pr_debug("***sctp_transmit_packet***\n");
 494
 495         do {
 496                 /* Set up convenience variables... */
 497                 chunk = list_entry(packet->chunk_list.next, struct sctp_chunk, list);
 498                 pktcount++;
 499
 500                 /* Calculate packet size, so it fits in PMTU. Leave
 501                  * other chunks for the next packets.
 502                  */
 503                 if (gso) {
 504                         pkt_size = packet->overhead;
 505                         list_for_each_entry(chunk, &packet->chunk_list, list) {
 506                                 int padded = WORD_ROUND(chunk->skb->len);
 507
 508                                 if (pkt_size + padded > tp->pathmtu)
 509                                         break;
 510                                 pkt_size += padded;
 511                         }
 512
 513                         /* Allocate a new skb. */
 514                         nskb = alloc_skb(pkt_size + MAX_HEADER, gfp);
 515                         if (!nskb)
 516                                 goto nomem;
 517
 518                         /* Make sure the outbound skb has enough header
 519                          * room reserved.
 520                          */
 521                         skb_reserve(nskb, packet->overhead + MAX_HEADER);
 522                 } else {
 523                         nskb = head;
 524                 }
 525
 526                 /**
 527                  * 3.2  Chunk Field Descriptions
 528                  *
 529                  * The total length of a chunk (including Type, Length and
 530                  * Value fields) MUST be a multiple of 4 bytes.  If the length
 531                  * of the chunk is not a multiple of 4 bytes, the sender MUST
 532                  * pad the chunk with all zero bytes and this padding is not
 533                  * included in the chunk length field.  The sender should
 534                  * never pad with more than 3 bytes.
 535                  *
 536                  * [This whole comment explains WORD_ROUND() below.]
 537                  */
 538
 539                 pkt_size -= packet->overhead;
 540                 list_for_each_entry_safe(chunk, tmp, &packet->chunk_list, list) {
 541                         list_del_init(&chunk->list);
 542                         if (sctp_chunk_is_data(chunk)) {
 543                                 /* 6.3.1 C4) When data is in flight and when allowed
 544                                  * by rule C5, a new RTT measurement MUST be made each
 545                                  * round trip.  Furthermore, new RTT measurements
 546                                  * SHOULD be made no more than once per round-trip
 547                                  * for a given destination transport address.
 548                                  */
 549
 550                                 if (!chunk->resent && !tp->rto_pending) {
 551                                         chunk->rtt_in_progress = 1;
 552                                         tp->rto_pending = 1;
 553                                 }
 554
 555                                 has_data = 1;
 556                         }
 557
 558                         padding = WORD_ROUND(chunk->skb->len) - chunk->skb->len;
 559                         if (padding)
 560                                 memset(skb_put(chunk->skb, padding), 0, padding);
 561
 562                         /* if this is the auth chunk that we are adding,
 563                          * store pointer where it will be added and put
 564                          * the auth into the packet.
 565                          */
 566                         if (chunk == packet->auth)
 567                                 auth = skb_tail_pointer(nskb);
 568
 569                         memcpy(skb_put(nskb, chunk->skb->len),
 570                                chunk->skb->data, chunk->skb->len);
 571
 572                         pr_debug("*** Chunk:%p[%s] %s 0x%x, length:%d, chunk->skb->len:%d, rtt_in_progress:%d\n",
 573                                  chunk,
 574                                  sctp_cname(SCTP_ST_CHUNK(chunk->chunk_hdr->type)),
 575                                  chunk->has_tsn ? "TSN" : "No TSN",
 576                                  chunk->has_tsn ? ntohl(chunk->subh.data_hdr->tsn) : 0,
 577                                  ntohs(chunk->chunk_hdr->length), chunk->skb->len,
 578                                  chunk->rtt_in_progress);
 579
 580                         /* If this is a control chunk, this is our last
 581                          * reference. Free data chunks after they've been
 582                          * acknowledged or have failed.
 583                          * Re-queue auth chunks if needed.
 584                          */
 585                         pkt_size -= WORD_ROUND(chunk->skb->len);
 586
 587                         if (!sctp_chunk_is_data(chunk) && chunk != packet->auth)
 588                                 sctp_chunk_free(chunk);
 589
 590                         if (!pkt_size)
 591                                 break;
 592                 }
 593
 594                 /* SCTP-AUTH, Section 6.2
 595                  *    The sender MUST calculate the MAC as described in RFC2104 [2]
 596                  *    using the hash function H as described by the MAC Identifier and
 597                  *    the shared association key K based on the endpoint pair shared key
 598                  *    described by the shared key identifier.  The 'data' used for the
 599                  *    computation of the AUTH-chunk is given by the AUTH chunk with its
 600                  *    HMAC field set to zero (as shown in Figure 6) followed by all
 601                  *    chunks that are placed after the AUTH chunk in the SCTP packet.
 602                  */
 603                 if (auth)
 604                         sctp_auth_calculate_hmac(asoc, nskb,
 605                                                  (struct sctp_auth_chunk *)auth,
 606                                                  gfp);
 607
 608                 if (packet->auth) {
 609                         if (!list_empty(&packet->chunk_list)) {
 610                                 /* We will generate more packets, so re-queue
 611                                  * auth chunk.
 612                                  */
 613                                 list_add(&packet->auth->list,
 614                                          &packet->chunk_list);
 615                         } else {
 616                                 sctp_chunk_free(packet->auth);
 617                                 packet->auth = NULL;
 618                         }
 619                 }
 620
 621                 if (!gso)
 622                         break;
 623
 624                 if (skb_gro_receive(&head, nskb))
 625                         goto nomem;
 626                 nskb = NULL;
 627                 if (WARN_ON_ONCE(skb_shinfo(head)->gso_segs >=
 628                                  sk->sk_gso_max_segs))
 629                         goto nomem;
 630         } while (!list_empty(&packet->chunk_list));
 631
 632         /* 2) Calculate the Adler-32 checksum of the whole packet,
 633          *    including the SCTP common header and all the
 634          *    chunks.
 635          *
 636          * Note: Adler-32 is no longer applicable, as has been replaced
 637          * by CRC32-C as described in <draft-ietf-tsvwg-sctpcsum-02.txt>.
 638          *
 639          * If it's a GSO packet, it's postponed to sctp_skb_segment.
 640          */
 641         if (!sctp_checksum_disable || gso) {
 642                 if (!gso && (!(dst->dev->features & NETIF_F_SCTP_CRC) ||
 643                              dst_xfrm(dst) || packet->ipfragok)) {
 644                         sh->checksum = sctp_compute_cksum(head, 0);
 645                 } else {
 646                         /* no need to seed pseudo checksum for SCTP */
 647                         head->ip_summed = CHECKSUM_PARTIAL;
 648                         head->csum_start = skb_transport_header(head) - head->head;
 649                         head->csum_offset = offsetof(struct sctphdr, checksum);
 650                 }
 651         }
 652
 653         /* IP layer ECN support
 654          * From RFC 2481
 655          *  "The ECN-Capable Transport (ECT) bit would be set by the
 656          *   data sender to indicate that the end-points of the
 657          *   transport protocol are ECN-capable."
 658          *
 659          * Now setting the ECT bit all the time, as it should not cause
 660          * any problems protocol-wise even if our peer ignores it.
 661          *
 662          * Note: The works for IPv6 layer checks this bit too later
 663          * in transmission.  See IP6_ECN_flow_xmit().
 664          */
 665         tp->af_specific->ecn_capable(sk);
 666
 667         /* Set up the IP options.  */
 668         /* BUG: not implemented
 669          * For v4 this all lives somewhere in sk->sk_opt...
 670          */
 671
 672         /* Dump that on IP!  */
 673         if (asoc) {
 674                 asoc->stats.opackets += pktcount;
 675                 if (asoc->peer.last_sent_to != tp)
 676                         /* Considering the multiple CPU scenario, this is a
 677                          * "correcter" place for last_sent_to.  --xguo
 678                          */
 679                         asoc->peer.last_sent_to = tp;
 680         }
 681
 682         if (has_data) {
 683                 struct timer_list *timer;
 684                 unsigned long timeout;
 685
 686                 /* Restart the AUTOCLOSE timer when sending data. */
 687                 if (sctp_state(asoc, ESTABLISHED) &&
 688                     asoc->timeouts[SCTP_EVENT_TIMEOUT_AUTOCLOSE]) {
 689                         timer = &asoc->timers[SCTP_EVENT_TIMEOUT_AUTOCLOSE];
 690                         timeout = asoc->timeouts[SCTP_EVENT_TIMEOUT_AUTOCLOSE];
 691
 692                         if (!mod_timer(timer, jiffies + timeout))
 693                                 sctp_association_hold(asoc);
 694                 }
 695         }
 696
 697         pr_debug("***sctp_transmit_packet*** skb->len:%d\n", head->len);
 698
 699         if (gso) {
 700                 /* Cleanup our debris for IP stacks */
 701                 memset(head->cb, 0, max(sizeof(struct inet_skb_parm),
 702                                         sizeof(struct inet6_skb_parm)));
 703
 704                 skb_shinfo(head)->gso_segs = pktcount;
 705                 skb_shinfo(head)->gso_size = GSO_BY_FRAGS;
 706
 707                 /* We have to refresh this in case we are xmiting to
 708                  * more than one transport at a time
 709                  */
 710                 rcu_read_lock();
 711                 if (__sk_dst_get(sk) != tp->dst) {
 712                         dst_hold(tp->dst);
 713                         sk_setup_caps(sk, tp->dst);
 714                 }
 715                 rcu_read_unlock();
 716         }
 717         head->ignore_df = packet->ipfragok;
 718         tp->af_specific->sctp_xmit(head, tp);
 719
 720 out:
 721         sctp_packet_reset(packet);
 722         return err;
 723 no_route:
 724         kfree_skb(head);
 725         if (nskb != head)
 726                 kfree_skb(nskb);
 727
 728         if (asoc)
 729                 IP_INC_STATS(sock_net(asoc->base.sk), IPSTATS_MIB_OUTNOROUTES);
 730
 731         /* FIXME: Returning the 'err' will effect all the associations
 732          * associated with a socket, although only one of the paths of the
 733          * association is unreachable.
 734          * The real failure of a transport or association can be passed on
 735          * to the user via notifications. So setting this error may not be
 736          * required.
 737          */
 738          /* err = -EHOSTUNREACH; */
 739 err:
 740         /* Control chunks are unreliable so just drop them.  DATA chunks
 741          * will get resent or dropped later.
 742          */
 743
 744         list_for_each_entry_safe(chunk, tmp, &packet->chunk_list, list) {
 745                 list_del_init(&chunk->list);
 746                 if (!sctp_chunk_is_data(chunk))
 747                         sctp_chunk_free(chunk);
 748         }
 749         goto out;
 750 nomem:
 751         if (packet->auth && list_empty(&packet->auth->list))
 752                 sctp_chunk_free(packet->auth);
 753         err = -ENOMEM;
 754         goto err;
 755 }
 756
 757 /********************************************************************
 758  * 2nd Level Abstractions
 759  ********************************************************************/
 760
 761 /* This private function check to see if a chunk can be added */
 762 static sctp_xmit_t sctp_packet_can_append_data(struct sctp_packet *packet,
 763                                            struct sctp_chunk *chunk)
 764 {
 765         size_t datasize, rwnd, inflight, flight_size;
 766         struct sctp_transport *transport = packet->transport;
 767         struct sctp_association *asoc = transport->asoc;
 768         struct sctp_outq *q = &asoc->outqueue;
 769
 770         /* RFC 2960 6.1  Transmission of DATA Chunks
 771          *
 772          * A) At any given time, the data sender MUST NOT transmit new data to
 773          * any destination transport address if its peer's rwnd indicates
 774          * that the peer has no buffer space (i.e. rwnd is 0, see Section
 775          * 6.2.1).  However, regardless of the value of rwnd (including if it
 776          * is 0), the data sender can always have one DATA chunk in flight to
 777          * the receiver if allowed by cwnd (see rule B below).  This rule
 778          * allows the sender to probe for a change in rwnd that the sender
 779          * missed due to the SACK having been lost in transit from the data
 780          * receiver to the data sender.
 781          */
 782
 783         rwnd = asoc->peer.rwnd;
 784         inflight = q->outstanding_bytes;
 785         flight_size = transport->flight_size;
 786
 787         datasize = sctp_data_size(chunk);
 788
 789         if (datasize > rwnd && inflight > 0)
 790                 /* We have (at least) one data chunk in flight,
 791                  * so we can't fall back to rule 6.1 B).
 792                  */
 793                 return SCTP_XMIT_RWND_FULL;
 794
 795         /* RFC 2960 6.1  Transmission of DATA Chunks
 796          *
 797          * B) At any given time, the sender MUST NOT transmit new data
 798          * to a given transport address if it has cwnd or more bytes
 799          * of data outstanding to that transport address.
 800          */
 801         /* RFC 7.2.4 & the Implementers Guide 2.8.
 802          *
 803          * 3) ...
 804          *    When a Fast Retransmit is being performed the sender SHOULD
 805          *    ignore the value of cwnd and SHOULD NOT delay retransmission.
 806          */
 807         if (chunk->fast_retransmit != SCTP_NEED_FRTX &&
 808             flight_size >= transport->cwnd)
 809                 return SCTP_XMIT_RWND_FULL;
 810
 811         /* Nagle's algorithm to solve small-packet problem:
 812          * Inhibit the sending of new chunks when new outgoing data arrives
 813          * if any previously transmitted data on the connection remains
 814          * unacknowledged.
 815          */
 816
 817         if (sctp_sk(asoc->base.sk)->nodelay)
 818                 /* Nagle disabled */
 819                 return SCTP_XMIT_OK;
 820
 821         if (!sctp_packet_empty(packet))
 822                 /* Append to packet */
 823                 return SCTP_XMIT_OK;
 824
 825         if (inflight == 0)
 826                 /* Nothing unacked */
 827                 return SCTP_XMIT_OK;
 828
 829         if (!sctp_state(asoc, ESTABLISHED))
 830                 return SCTP_XMIT_OK;
 831
 832         /* Check whether this chunk and all the rest of pending data will fit
 833          * or delay in hopes of bundling a full sized packet.
 834          */
 835         if (chunk->skb->len + q->out_qlen >
 836                 transport->pathmtu - packet->overhead - sizeof(sctp_data_chunk_t) - 4)
 837                 /* Enough data queued to fill a packet */
 838                 return SCTP_XMIT_OK;
 839
 840         /* Don't delay large message writes that may have been fragmented */
 841         if (!chunk->msg->can_delay)
 842                 return SCTP_XMIT_OK;
 843
 844         /* Defer until all data acked or packet full */
 845         return SCTP_XMIT_DELAY;
 846 }
 847
 848 /* This private function does management things when adding DATA chunk */
 849 static void sctp_packet_append_data(struct sctp_packet *packet,
 850                                 struct sctp_chunk *chunk)
 851 {
 852         struct sctp_transport *transport = packet->transport;
 853         size_t datasize = sctp_data_size(chunk);
 854         struct sctp_association *asoc = transport->asoc;
 855         u32 rwnd = asoc->peer.rwnd;
 856
 857         /* Keep track of how many bytes are in flight over this transport. */
 858         transport->flight_size += datasize;
 859
 860         /* Keep track of how many bytes are in flight to the receiver. */
 861         asoc->outqueue.outstanding_bytes += datasize;
 862
 863         /* Update our view of the receiver's rwnd. */
 864         if (datasize < rwnd)
 865                 rwnd -= datasize;
 866         else
 867                 rwnd = 0;
 868
 869         asoc->peer.rwnd = rwnd;
 870         /* Has been accepted for transmission. */
 871         if (!asoc->peer.prsctp_capable)
 872                 chunk->msg->can_abandon = 0;
 873         sctp_chunk_assign_tsn(chunk);
 874         sctp_chunk_assign_ssn(chunk);
 875 }
 876
 877 static sctp_xmit_t sctp_packet_will_fit(struct sctp_packet *packet,
 878                                         struct sctp_chunk *chunk,
 879                                         u16 chunk_len)
 880 {
 881         size_t psize, pmtu, maxsize;
 882         sctp_xmit_t retval = SCTP_XMIT_OK;
 883
 884         psize = packet->size;
 885         if (packet->transport->asoc)
 886                 pmtu = packet->transport->asoc->pathmtu;
 887         else
 888                 pmtu = packet->transport->pathmtu;
 889
 890         /* Decide if we need to fragment or resubmit later. */
 891         if (psize + chunk_len > pmtu) {
 892                 /* It's OK to fragment at IP level if any one of the following
 893                  * is true:
 894                  *      1. The packet is empty (meaning this chunk is greater
 895                  *         the MTU)
 896                  *      2. The packet doesn't have any data in it yet and data
 897                  *         requires authentication.
 898                  */
 899                 if (sctp_packet_empty(packet) ||
 900                     (!packet->has_data && chunk->auth)) {
 901                         /* We no longer do re-fragmentation.
 902                          * Just fragment at the IP layer, if we
 903                          * actually hit this condition
 904                          */
 905                         packet->ipfragok = 1;
 906                         goto out;
 907                 }
 908
 909                 /* Similarly, if this chunk was built before a PMTU
 910                  * reduction, we have to fragment it at IP level now. So
 911                  * if the packet already contains something, we need to
 912                  * flush.
 913                  */
 914                 maxsize = pmtu - packet->overhead;
 915                 if (packet->auth)
 916                         maxsize -= WORD_ROUND(packet->auth->skb->len);
 917                 if (chunk_len > maxsize)
 918                         retval = SCTP_XMIT_PMTU_FULL;
 919
 920                 /* It is also okay to fragment if the chunk we are
 921                  * adding is a control chunk, but only if current packet
 922                  * is not a GSO one otherwise it causes fragmentation of
 923                  * a large frame. So in this case we allow the
 924                  * fragmentation by forcing it to be in a new packet.
 925                  */
 926                 if (!sctp_chunk_is_data(chunk) && packet->has_data)
 927                         retval = SCTP_XMIT_PMTU_FULL;
 928
 929                 if (psize + chunk_len > packet->max_size)
 930                         /* Hit GSO/PMTU limit, gotta flush */
 931                         retval = SCTP_XMIT_PMTU_FULL;
 932
 933                 if (!packet->transport->burst_limited &&
 934                     psize + chunk_len > (packet->transport->cwnd >> 1))
 935                         /* Do not allow a single GSO packet to use more
 936                          * than half of cwnd.
 937                          */
 938                         retval = SCTP_XMIT_PMTU_FULL;
 939
 940                 if (packet->transport->burst_limited &&
 941                     psize + chunk_len > (packet->transport->burst_limited >> 1))
 942                         /* Do not allow a single GSO packet to use more
 943                          * than half of original cwnd.
 944                          */
 945                         retval = SCTP_XMIT_PMTU_FULL;
 946                 /* Otherwise it will fit in the GSO packet */
 947         }
 948
 949 out:
 950         return retval;
 951 }