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