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 <[email protected]>
  29  *
  30  * Written or modified by:
  31  *    La Monte H.P. Yarroll <[email protected]>
  32  *    Karl Knutson          <[email protected]>
  33  *    Jon Grimm             <[email protected]>
  34  *    Sridhar Samudrala     <[email protected]>
  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 enum sctp_xmit __sctp_packet_append_chunk(struct sctp_packet *packet,
  61                                                  struct sctp_chunk *chunk);
  62 static enum sctp_xmit 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 enum sctp_xmit 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 void sctp_packet_config(struct sctp_packet *packet, __u32 vtag,
  85                         int ecn_capable)
  86 {
  87         struct sctp_transport *tp = packet->transport;
  88         struct sctp_association *asoc = tp->asoc;
  89         struct sock *sk;
  90
  91         pr_debug("%s: packet:%p vtag:0x%x\n", __func__, packet, vtag);
  92         packet->vtag = vtag;
  93
  94         /* do the following jobs only once for a flush schedule */
  95         if (!sctp_packet_empty(packet))
  96                 return;
  97
  98         /* set packet max_size with pathmtu */
  99         packet->max_size = tp->pathmtu;
 100         if (!asoc)
 101                 return;
 102
 103         /* update dst or transport pathmtu if in need */
 104         sk = asoc->base.sk;
 105         if (!sctp_transport_dst_check(tp)) {
 106                 sctp_transport_route(tp, NULL, sctp_sk(sk));
 107                 if (asoc->param_flags & SPP_PMTUD_ENABLE)
 108                         sctp_assoc_sync_pmtu(asoc);
 109         } else if (!sctp_transport_pmtu_check(tp)) {
 110                 if (asoc->param_flags & SPP_PMTUD_ENABLE)
 111                         sctp_assoc_sync_pmtu(asoc);
 112         }
 113
 114         /* If there a is a prepend chunk stick it on the list before
 115          * any other chunks get appended.
 116          */
 117         if (ecn_capable) {
 118                 struct sctp_chunk *chunk = sctp_get_ecne_prepend(asoc);
 119
 120                 if (chunk)
 121                         sctp_packet_append_chunk(packet, chunk);
 122         }
 123
 124         if (!tp->dst)
 125                 return;
 126
 127         /* set packet max_size with gso_max_size if gso is enabled*/
 128         rcu_read_lock();
 129         if (__sk_dst_get(sk) != tp->dst) {
 130                 dst_hold(tp->dst);
 131                 sk_setup_caps(sk, tp->dst);
 132         }
 133         packet->max_size = sk_can_gso(sk) ? tp->dst->dev->gso_max_size
 134                                           : asoc->pathmtu;
 135         rcu_read_unlock();
 136 }
 137
 138 /* Initialize the packet structure. */
 139 void sctp_packet_init(struct sctp_packet *packet,
 140                       struct sctp_transport *transport,
 141                       __u16 sport, __u16 dport)
 142 {
 143         struct sctp_association *asoc = transport->asoc;
 144         size_t overhead;
 145
 146         pr_debug("%s: packet:%p transport:%p\n", __func__, packet, transport);
 147
 148         packet->transport = transport;
 149         packet->source_port = sport;
 150         packet->destination_port = dport;
 151         INIT_LIST_HEAD(&packet->chunk_list);
 152         if (asoc) {
 153                 struct sctp_sock *sp = sctp_sk(asoc->base.sk);
 154                 overhead = sp->pf->af->net_header_len;
 155         } else {
 156                 overhead = sizeof(struct ipv6hdr);
 157         }
 158         overhead += sizeof(struct sctphdr);
 159         packet->overhead = overhead;
 160         sctp_packet_reset(packet);
 161         packet->vtag = 0;
 162 }
 163
 164 /* Free a packet.  */
 165 void sctp_packet_free(struct sctp_packet *packet)
 166 {
 167         struct sctp_chunk *chunk, *tmp;
 168
 169         pr_debug("%s: packet:%p\n", __func__, packet);
 170
 171         list_for_each_entry_safe(chunk, tmp, &packet->chunk_list, list) {
 172                 list_del_init(&chunk->list);
 173                 sctp_chunk_free(chunk);
 174         }
 175 }
 176
 177 /* This routine tries to append the chunk to the offered packet. If adding
 178  * the chunk causes the packet to exceed the path MTU and COOKIE_ECHO chunk
 179  * is not present in the packet, it transmits the input packet.
 180  * Data can be bundled with a packet containing a COOKIE_ECHO chunk as long
 181  * as it can fit in the packet, but any more data that does not fit in this
 182  * packet can be sent only after receiving the COOKIE_ACK.
 183  */
 184 enum sctp_xmit sctp_packet_transmit_chunk(struct sctp_packet *packet,
 185                                           struct sctp_chunk *chunk,
 186                                           int one_packet, gfp_t gfp)
 187 {
 188         enum sctp_xmit retval;
 189
 190         pr_debug("%s: packet:%p size:%zu chunk:%p size:%d\n", __func__,
 191                  packet, packet->size, chunk, chunk->skb ? chunk->skb->len : -1);
 192
 193         switch ((retval = (sctp_packet_append_chunk(packet, chunk)))) {
 194         case SCTP_XMIT_PMTU_FULL:
 195                 if (!packet->has_cookie_echo) {
 196                         int error = 0;
 197
 198                         error = sctp_packet_transmit(packet, gfp);
 199                         if (error < 0)
 200                                 chunk->skb->sk->sk_err = -error;
 201
 202                         /* If we have an empty packet, then we can NOT ever
 203                          * return PMTU_FULL.
 204                          */
 205                         if (!one_packet)
 206                                 retval = sctp_packet_append_chunk(packet,
 207                                                                   chunk);
 208                 }
 209                 break;
 210
 211         case SCTP_XMIT_RWND_FULL:
 212         case SCTP_XMIT_OK:
 213         case SCTP_XMIT_DELAY:
 214                 break;
 215         }
 216
 217         return retval;
 218 }
 219
 220 /* Try to bundle an auth chunk into the packet. */
 221 static enum sctp_xmit sctp_packet_bundle_auth(struct sctp_packet *pkt,
 222                                               struct sctp_chunk *chunk)
 223 {
 224         struct sctp_association *asoc = pkt->transport->asoc;
 225         enum sctp_xmit retval = SCTP_XMIT_OK;
 226         struct sctp_chunk *auth;
 227
 228         /* if we don't have an association, we can't do authentication */
 229         if (!asoc)
 230                 return retval;
 231
 232         /* See if this is an auth chunk we are bundling or if
 233          * auth is already bundled.
 234          */
 235         if (chunk->chunk_hdr->type == SCTP_CID_AUTH || pkt->has_auth)
 236                 return retval;
 237
 238         /* if the peer did not request this chunk to be authenticated,
 239          * don't do it
 240          */
 241         if (!chunk->auth)
 242                 return retval;
 243
 244         auth = sctp_make_auth(asoc, chunk->shkey->key_id);
 245         if (!auth)
 246                 return retval;
 247
 248         auth->shkey = chunk->shkey;
 249         sctp_auth_shkey_hold(auth->shkey);
 250
 251         retval = __sctp_packet_append_chunk(pkt, auth);
 252
 253         if (retval != SCTP_XMIT_OK)
 254                 sctp_chunk_free(auth);
 255
 256         return retval;
 257 }
 258
 259 /* Try to bundle a SACK with the packet. */
 260 static enum sctp_xmit sctp_packet_bundle_sack(struct sctp_packet *pkt,
 261                                               struct sctp_chunk *chunk)
 262 {
 263         enum sctp_xmit retval = SCTP_XMIT_OK;
 264
 265         /* If sending DATA and haven't aleady bundled a SACK, try to
 266          * bundle one in to the packet.
 267          */
 268         if (sctp_chunk_is_data(chunk) && !pkt->has_sack &&
 269             !pkt->has_cookie_echo) {
 270                 struct sctp_association *asoc;
 271                 struct timer_list *timer;
 272                 asoc = pkt->transport->asoc;
 273                 timer = &asoc->timers[SCTP_EVENT_TIMEOUT_SACK];
 274
 275                 /* If the SACK timer is running, we have a pending SACK */
 276                 if (timer_pending(timer)) {
 277                         struct sctp_chunk *sack;
 278
 279                         if (pkt->transport->sack_generation !=
 280                             pkt->transport->asoc->peer.sack_generation)
 281                                 return retval;
 282
 283                         asoc->a_rwnd = asoc->rwnd;
 284                         sack = sctp_make_sack(asoc);
 285                         if (sack) {
 286                                 retval = __sctp_packet_append_chunk(pkt, sack);
 287                                 if (retval != SCTP_XMIT_OK) {
 288                                         sctp_chunk_free(sack);
 289                                         goto out;
 290                                 }
 291                                 asoc->peer.sack_needed = 0;
 292                                 if (del_timer(timer))
 293                                         sctp_association_put(asoc);
 294                         }
 295                 }
 296         }
 297 out:
 298         return retval;
 299 }
 300
 301
 302 /* Append a chunk to the offered packet reporting back any inability to do
 303  * so.
 304  */
 305 static enum sctp_xmit __sctp_packet_append_chunk(struct sctp_packet *packet,
 306                                                  struct sctp_chunk *chunk)
 307 {
 308         __u16 chunk_len = SCTP_PAD4(ntohs(chunk->chunk_hdr->length));
 309         enum sctp_xmit retval = SCTP_XMIT_OK;
 310
 311         /* Check to see if this chunk will fit into the packet */
 312         retval = sctp_packet_will_fit(packet, chunk, chunk_len);
 313         if (retval != SCTP_XMIT_OK)
 314                 goto finish;
 315
 316         /* We believe that this chunk is OK to add to the packet */
 317         switch (chunk->chunk_hdr->type) {
 318         case SCTP_CID_DATA:
 319         case SCTP_CID_I_DATA:
 320                 /* Account for the data being in the packet */
 321                 sctp_packet_append_data(packet, chunk);
 322                 /* Disallow SACK bundling after DATA. */
 323                 packet->has_sack = 1;
 324                 /* Disallow AUTH bundling after DATA */
 325                 packet->has_auth = 1;
 326                 /* Let it be knows that packet has DATA in it */
 327                 packet->has_data = 1;
 328                 /* timestamp the chunk for rtx purposes */
 329                 chunk->sent_at = jiffies;
 330                 /* Mainly used for prsctp RTX policy */
 331                 chunk->sent_count++;
 332                 break;
 333         case SCTP_CID_COOKIE_ECHO:
 334                 packet->has_cookie_echo = 1;
 335                 break;
 336
 337         case SCTP_CID_SACK:
 338                 packet->has_sack = 1;
 339                 if (chunk->asoc)
 340                         chunk->asoc->stats.osacks++;
 341                 break;
 342
 343         case SCTP_CID_AUTH:
 344                 packet->has_auth = 1;
 345                 packet->auth = chunk;
 346                 break;
 347         }
 348
 349         /* It is OK to send this chunk.  */
 350         list_add_tail(&chunk->list, &packet->chunk_list);
 351         packet->size += chunk_len;
 352         chunk->transport = packet->transport;
 353 finish:
 354         return retval;
 355 }
 356
 357 /* Append a chunk to the offered packet reporting back any inability to do
 358  * so.
 359  */
 360 enum sctp_xmit sctp_packet_append_chunk(struct sctp_packet *packet,
 361                                         struct sctp_chunk *chunk)
 362 {
 363         enum sctp_xmit retval = SCTP_XMIT_OK;
 364
 365         pr_debug("%s: packet:%p chunk:%p\n", __func__, packet, chunk);
 366
 367         /* Data chunks are special.  Before seeing what else we can
 368          * bundle into this packet, check to see if we are allowed to
 369          * send this DATA.
 370          */
 371         if (sctp_chunk_is_data(chunk)) {
 372                 retval = sctp_packet_can_append_data(packet, chunk);
 373                 if (retval != SCTP_XMIT_OK)
 374                         goto finish;
 375         }
 376
 377         /* Try to bundle AUTH chunk */
 378         retval = sctp_packet_bundle_auth(packet, chunk);
 379         if (retval != SCTP_XMIT_OK)
 380                 goto finish;
 381
 382         /* Try to bundle SACK chunk */
 383         retval = sctp_packet_bundle_sack(packet, chunk);
 384         if (retval != SCTP_XMIT_OK)
 385                 goto finish;
 386
 387         retval = __sctp_packet_append_chunk(packet, chunk);
 388
 389 finish:
 390         return retval;
 391 }
 392
 393 static void sctp_packet_release_owner(struct sk_buff *skb)
 394 {
 395         sk_free(skb->sk);
 396 }
 397
 398 static void sctp_packet_set_owner_w(struct sk_buff *skb, struct sock *sk)
 399 {
 400         skb_orphan(skb);
 401         skb->sk = sk;
 402         skb->destructor = sctp_packet_release_owner;
 403
 404         /*
 405          * The data chunks have already been accounted for in sctp_sendmsg(),
 406          * therefore only reserve a single byte to keep socket around until
 407          * the packet has been transmitted.
 408          */
 409         refcount_inc(&sk->sk_wmem_alloc);
 410 }
 411
 412 static int sctp_packet_pack(struct sctp_packet *packet,
 413                             struct sk_buff *head, int gso, gfp_t gfp)
 414 {
 415         struct sctp_transport *tp = packet->transport;
 416         struct sctp_auth_chunk *auth = NULL;
 417         struct sctp_chunk *chunk, *tmp;
 418         int pkt_count = 0, pkt_size;
 419         struct sock *sk = head->sk;
 420         struct sk_buff *nskb;
 421         int auth_len = 0;
 422
 423         if (gso) {
 424                 skb_shinfo(head)->gso_type = sk->sk_gso_type;
 425                 NAPI_GRO_CB(head)->last = head;
 426         } else {
 427                 nskb = head;
 428                 pkt_size = packet->size;
 429                 goto merge;
 430         }
 431
 432         do {
 433                 /* calculate the pkt_size and alloc nskb */
 434                 pkt_size = packet->overhead;
 435                 list_for_each_entry_safe(chunk, tmp, &packet->chunk_list,
 436                                          list) {
 437                         int padded = SCTP_PAD4(chunk->skb->len);
 438
 439                         if (chunk == packet->auth)
 440                                 auth_len = padded;
 441                         else if (auth_len + padded + packet->overhead >
 442                                  tp->pathmtu)
 443                                 return 0;
 444                         else if (pkt_size + padded > tp->pathmtu)
 445                                 break;
 446                         pkt_size += padded;
 447                 }
 448                 nskb = alloc_skb(pkt_size + MAX_HEADER, gfp);
 449                 if (!nskb)
 450                         return 0;
 451                 skb_reserve(nskb, packet->overhead + MAX_HEADER);
 452
 453 merge:
 454                 /* merge chunks into nskb and append nskb into head list */
 455                 pkt_size -= packet->overhead;
 456                 list_for_each_entry_safe(chunk, tmp, &packet->chunk_list, list) {
 457                         int padding;
 458
 459                         list_del_init(&chunk->list);
 460                         if (sctp_chunk_is_data(chunk)) {
 461                                 if (!sctp_chunk_retransmitted(chunk) &&
 462                                     !tp->rto_pending) {
 463                                         chunk->rtt_in_progress = 1;
 464                                         tp->rto_pending = 1;
 465                                 }
 466                         }
 467
 468                         padding = SCTP_PAD4(chunk->skb->len) - chunk->skb->len;
 469                         if (padding)
 470                                 skb_put_zero(chunk->skb, padding);
 471
 472                         if (chunk == packet->auth)
 473                                 auth = (struct sctp_auth_chunk *)
 474                                                         skb_tail_pointer(nskb);
 475
 476                         skb_put_data(nskb, chunk->skb->data, chunk->skb->len);
 477
 478                         pr_debug("*** Chunk:%p[%s] %s 0x%x, length:%d, chunk->skb->len:%d, rtt_in_progress:%d\n",
 479                                  chunk,
 480                                  sctp_cname(SCTP_ST_CHUNK(chunk->chunk_hdr->type)),
 481                                  chunk->has_tsn ? "TSN" : "No TSN",
 482                                  chunk->has_tsn ? ntohl(chunk->subh.data_hdr->tsn) : 0,
 483                                  ntohs(chunk->chunk_hdr->length), chunk->skb->len,
 484                                  chunk->rtt_in_progress);
 485
 486                         pkt_size -= SCTP_PAD4(chunk->skb->len);
 487
 488                         if (!sctp_chunk_is_data(chunk) && chunk != packet->auth)
 489                                 sctp_chunk_free(chunk);
 490
 491                         if (!pkt_size)
 492                                 break;
 493                 }
 494
 495                 if (auth) {
 496                         sctp_auth_calculate_hmac(tp->asoc, nskb, auth,
 497                                                  packet->auth->shkey, gfp);
 498                         /* free auth if no more chunks, or add it back */
 499                         if (list_empty(&packet->chunk_list))
 500                                 sctp_chunk_free(packet->auth);
 501                         else
 502                                 list_add(&packet->auth->list,
 503                                          &packet->chunk_list);
 504                 }
 505
 506                 if (gso) {
 507                         if (skb_gro_receive(&head, nskb)) {
 508                                 kfree_skb(nskb);
 509                                 return 0;
 510                         }
 511                         if (WARN_ON_ONCE(skb_shinfo(head)->gso_segs >=
 512                                          sk->sk_gso_max_segs))
 513                                 return 0;
 514                 }
 515
 516                 pkt_count++;
 517         } while (!list_empty(&packet->chunk_list));
 518
 519         if (gso) {
 520                 memset(head->cb, 0, max(sizeof(struct inet_skb_parm),
 521                                         sizeof(struct inet6_skb_parm)));
 522                 skb_shinfo(head)->gso_segs = pkt_count;
 523                 skb_shinfo(head)->gso_size = GSO_BY_FRAGS;
 524                 rcu_read_lock();
 525                 if (skb_dst(head) != tp->dst) {
 526                         dst_hold(tp->dst);
 527                         sk_setup_caps(sk, tp->dst);
 528                 }
 529                 rcu_read_unlock();
 530                 goto chksum;
 531         }
 532
 533         if (sctp_checksum_disable)
 534                 return 1;
 535
 536         if (!(skb_dst(head)->dev->features & NETIF_F_SCTP_CRC) ||
 537             dst_xfrm(skb_dst(head)) || packet->ipfragok) {
 538                 struct sctphdr *sh =
 539                         (struct sctphdr *)skb_transport_header(head);
 540
 541                 sh->checksum = sctp_compute_cksum(head, 0);
 542         } else {
 543 chksum:
 544                 head->ip_summed = CHECKSUM_PARTIAL;
 545                 head->csum_not_inet = 1;
 546                 head->csum_start = skb_transport_header(head) - head->head;
 547                 head->csum_offset = offsetof(struct sctphdr, checksum);
 548         }
 549
 550         return pkt_count;
 551 }
 552
 553 /* All packets are sent to the network through this function from
 554  * sctp_outq_tail().
 555  *
 556  * The return value is always 0 for now.
 557  */
 558 int sctp_packet_transmit(struct sctp_packet *packet, gfp_t gfp)
 559 {
 560         struct sctp_transport *tp = packet->transport;
 561         struct sctp_association *asoc = tp->asoc;
 562         struct sctp_chunk *chunk, *tmp;
 563         int pkt_count, gso = 0;
 564         struct dst_entry *dst;
 565         struct sk_buff *head;
 566         struct sctphdr *sh;
 567         struct sock *sk;
 568
 569         pr_debug("%s: packet:%p\n", __func__, packet);
 570         if (list_empty(&packet->chunk_list))
 571                 return 0;
 572         chunk = list_entry(packet->chunk_list.next, struct sctp_chunk, list);
 573         sk = chunk->skb->sk;
 574
 575         /* check gso */
 576         if (packet->size > tp->pathmtu && !packet->ipfragok) {
 577                 if (!sk_can_gso(sk)) {
 578                         pr_err_once("Trying to GSO but underlying device doesn't support it.");
 579                         goto out;
 580                 }
 581                 gso = 1;
 582         }
 583
 584         /* alloc head skb */
 585         head = alloc_skb((gso ? packet->overhead : packet->size) +
 586                          MAX_HEADER, gfp);
 587         if (!head)
 588                 goto out;
 589         skb_reserve(head, packet->overhead + MAX_HEADER);
 590         sctp_packet_set_owner_w(head, sk);
 591
 592         /* set sctp header */
 593         sh = skb_push(head, sizeof(struct sctphdr));
 594         skb_reset_transport_header(head);
 595         sh->source = htons(packet->source_port);
 596         sh->dest = htons(packet->destination_port);
 597         sh->vtag = htonl(packet->vtag);
 598         sh->checksum = 0;
 599
 600         /* drop packet if no dst */
 601         dst = dst_clone(tp->dst);
 602         if (!dst) {
 603                 IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTNOROUTES);
 604                 kfree_skb(head);
 605                 goto out;
 606         }
 607         skb_dst_set(head, dst);
 608
 609         /* pack up chunks */
 610         pkt_count = sctp_packet_pack(packet, head, gso, gfp);
 611         if (!pkt_count) {
 612                 kfree_skb(head);
 613                 goto out;
 614         }
 615         pr_debug("***sctp_transmit_packet*** skb->len:%d\n", head->len);
 616
 617         /* start autoclose timer */
 618         if (packet->has_data && sctp_state(asoc, ESTABLISHED) &&
 619             asoc->timeouts[SCTP_EVENT_TIMEOUT_AUTOCLOSE]) {
 620                 struct timer_list *timer =
 621                         &asoc->timers[SCTP_EVENT_TIMEOUT_AUTOCLOSE];
 622                 unsigned long timeout =
 623                         asoc->timeouts[SCTP_EVENT_TIMEOUT_AUTOCLOSE];
 624
 625                 if (!mod_timer(timer, jiffies + timeout))
 626                         sctp_association_hold(asoc);
 627         }
 628
 629         /* sctp xmit */
 630         tp->af_specific->ecn_capable(sk);
 631         if (asoc) {
 632                 asoc->stats.opackets += pkt_count;
 633                 if (asoc->peer.last_sent_to != tp)
 634                         asoc->peer.last_sent_to = tp;
 635         }
 636         head->ignore_df = packet->ipfragok;
 637         if (tp->dst_pending_confirm)
 638                 skb_set_dst_pending_confirm(head, 1);
 639         /* neighbour should be confirmed on successful transmission or
 640          * positive error
 641          */
 642         if (tp->af_specific->sctp_xmit(head, tp) >= 0 &&
 643             tp->dst_pending_confirm)
 644                 tp->dst_pending_confirm = 0;
 645
 646 out:
 647         list_for_each_entry_safe(chunk, tmp, &packet->chunk_list, list) {
 648                 list_del_init(&chunk->list);
 649                 if (!sctp_chunk_is_data(chunk))
 650                         sctp_chunk_free(chunk);
 651         }
 652         sctp_packet_reset(packet);
 653         return 0;
 654 }
 655
 656 /********************************************************************
 657  * 2nd Level Abstractions
 658  ********************************************************************/
 659
 660 /* This private function check to see if a chunk can be added */
 661 static enum sctp_xmit sctp_packet_can_append_data(struct sctp_packet *packet,
 662                                                   struct sctp_chunk *chunk)
 663 {
 664         size_t datasize, rwnd, inflight, flight_size;
 665         struct sctp_transport *transport = packet->transport;
 666         struct sctp_association *asoc = transport->asoc;
 667         struct sctp_outq *q = &asoc->outqueue;
 668
 669         /* RFC 2960 6.1  Transmission of DATA Chunks
 670          *
 671          * A) At any given time, the data sender MUST NOT transmit new data to
 672          * any destination transport address if its peer's rwnd indicates
 673          * that the peer has no buffer space (i.e. rwnd is 0, see Section
 674          * 6.2.1).  However, regardless of the value of rwnd (including if it
 675          * is 0), the data sender can always have one DATA chunk in flight to
 676          * the receiver if allowed by cwnd (see rule B below).  This rule
 677          * allows the sender to probe for a change in rwnd that the sender
 678          * missed due to the SACK having been lost in transit from the data
 679          * receiver to the data sender.
 680          */
 681
 682         rwnd = asoc->peer.rwnd;
 683         inflight = q->outstanding_bytes;
 684         flight_size = transport->flight_size;
 685
 686         datasize = sctp_data_size(chunk);
 687
 688         if (datasize > rwnd && inflight > 0)
 689                 /* We have (at least) one data chunk in flight,
 690                  * so we can't fall back to rule 6.1 B).
 691                  */
 692                 return SCTP_XMIT_RWND_FULL;
 693
 694         /* RFC 2960 6.1  Transmission of DATA Chunks
 695          *
 696          * B) At any given time, the sender MUST NOT transmit new data
 697          * to a given transport address if it has cwnd or more bytes
 698          * of data outstanding to that transport address.
 699          */
 700         /* RFC 7.2.4 & the Implementers Guide 2.8.
 701          *
 702          * 3) ...
 703          *    When a Fast Retransmit is being performed the sender SHOULD
 704          *    ignore the value of cwnd and SHOULD NOT delay retransmission.
 705          */
 706         if (chunk->fast_retransmit != SCTP_NEED_FRTX &&
 707             flight_size >= transport->cwnd)
 708                 return SCTP_XMIT_RWND_FULL;
 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
 716         if ((sctp_sk(asoc->base.sk)->nodelay || inflight == 0) &&
 717             !asoc->force_delay)
 718                 /* Nothing unacked */
 719                 return SCTP_XMIT_OK;
 720
 721         if (!sctp_packet_empty(packet))
 722                 /* Append to packet */
 723                 return SCTP_XMIT_OK;
 724
 725         if (!sctp_state(asoc, ESTABLISHED))
 726                 return SCTP_XMIT_OK;
 727
 728         /* Check whether this chunk and all the rest of pending data will fit
 729          * or delay in hopes of bundling a full sized packet.
 730          */
 731         if (chunk->skb->len + q->out_qlen > transport->pathmtu -
 732             packet->overhead - sctp_datachk_len(&chunk->asoc->stream) - 4)
 733                 /* Enough data queued to fill a packet */
 734                 return SCTP_XMIT_OK;
 735
 736         /* Don't delay large message writes that may have been fragmented */
 737         if (!chunk->msg->can_delay)
 738                 return SCTP_XMIT_OK;
 739
 740         /* Defer until all data acked or packet full */
 741         return SCTP_XMIT_DELAY;
 742 }
 743
 744 /* This private function does management things when adding DATA chunk */
 745 static void sctp_packet_append_data(struct sctp_packet *packet,
 746                                 struct sctp_chunk *chunk)
 747 {
 748         struct sctp_transport *transport = packet->transport;
 749         size_t datasize = sctp_data_size(chunk);
 750         struct sctp_association *asoc = transport->asoc;
 751         u32 rwnd = asoc->peer.rwnd;
 752
 753         /* Keep track of how many bytes are in flight over this transport. */
 754         transport->flight_size += datasize;
 755
 756         /* Keep track of how many bytes are in flight to the receiver. */
 757         asoc->outqueue.outstanding_bytes += datasize;
 758
 759         /* Update our view of the receiver's rwnd. */
 760         if (datasize < rwnd)
 761                 rwnd -= datasize;
 762         else
 763                 rwnd = 0;
 764
 765         asoc->peer.rwnd = rwnd;
 766         sctp_chunk_assign_tsn(chunk);
 767         asoc->stream.si->assign_number(chunk);
 768 }
 769
 770 static enum sctp_xmit sctp_packet_will_fit(struct sctp_packet *packet,
 771                                            struct sctp_chunk *chunk,
 772                                            u16 chunk_len)
 773 {
 774         enum sctp_xmit retval = SCTP_XMIT_OK;
 775         size_t psize, pmtu, maxsize;
 776
 777         /* Don't bundle in this packet if this chunk's auth key doesn't
 778          * match other chunks already enqueued on this packet. Also,
 779          * don't bundle the chunk with auth key if other chunks in this
 780          * packet don't have auth key.
 781          */
 782         if ((packet->auth && chunk->shkey != packet->auth->shkey) ||
 783             (!packet->auth && chunk->shkey &&
 784              chunk->chunk_hdr->type != SCTP_CID_AUTH))
 785                 return SCTP_XMIT_PMTU_FULL;
 786
 787         psize = packet->size;
 788         if (packet->transport->asoc)
 789                 pmtu = packet->transport->asoc->pathmtu;
 790         else
 791                 pmtu = packet->transport->pathmtu;
 792
 793         /* Decide if we need to fragment or resubmit later. */
 794         if (psize + chunk_len > pmtu) {
 795                 /* It's OK to fragment at IP level if any one of the following
 796                  * is true:
 797                  *      1. The packet is empty (meaning this chunk is greater
 798                  *         the MTU)
 799                  *      2. The packet doesn't have any data in it yet and data
 800                  *         requires authentication.
 801                  */
 802                 if (sctp_packet_empty(packet) ||
 803                     (!packet->has_data && chunk->auth)) {
 804                         /* We no longer do re-fragmentation.
 805                          * Just fragment at the IP layer, if we
 806                          * actually hit this condition
 807                          */
 808                         packet->ipfragok = 1;
 809                         goto out;
 810                 }
 811
 812                 /* Similarly, if this chunk was built before a PMTU
 813                  * reduction, we have to fragment it at IP level now. So
 814                  * if the packet already contains something, we need to
 815                  * flush.
 816                  */
 817                 maxsize = pmtu - packet->overhead;
 818                 if (packet->auth)
 819                         maxsize -= SCTP_PAD4(packet->auth->skb->len);
 820                 if (chunk_len > maxsize)
 821                         retval = SCTP_XMIT_PMTU_FULL;
 822
 823                 /* It is also okay to fragment if the chunk we are
 824                  * adding is a control chunk, but only if current packet
 825                  * is not a GSO one otherwise it causes fragmentation of
 826                  * a large frame. So in this case we allow the
 827                  * fragmentation by forcing it to be in a new packet.
 828                  */
 829                 if (!sctp_chunk_is_data(chunk) && packet->has_data)
 830                         retval = SCTP_XMIT_PMTU_FULL;
 831
 832                 if (psize + chunk_len > packet->max_size)
 833                         /* Hit GSO/PMTU limit, gotta flush */
 834                         retval = SCTP_XMIT_PMTU_FULL;
 835
 836                 if (!packet->transport->burst_limited &&
 837                     psize + chunk_len > (packet->transport->cwnd >> 1))
 838                         /* Do not allow a single GSO packet to use more
 839                          * than half of cwnd.
 840                          */
 841                         retval = SCTP_XMIT_PMTU_FULL;
 842
 843                 if (packet->transport->burst_limited &&
 844                     psize + chunk_len > (packet->transport->burst_limited >> 1))
 845                         /* Do not allow a single GSO packet to use more
 846                          * than half of original cwnd.
 847                          */
 848                         retval = SCTP_XMIT_PMTU_FULL;
 849                 /* Otherwise it will fit in the GSO packet */
 850         }
 851
 852 out:
 853         return retval;
 854 }