net/sctp/output.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /* SCTP kernel implementation
   3  * (C) Copyright IBM Corp. 2001, 2004
   4  * Copyright (c) 1999-2000 Cisco, Inc.
   5  * Copyright (c) 1999-2001 Motorola, Inc.
   6  *
   7  * This file is part of the SCTP kernel implementation
   8  *
   9  * These functions handle output processing.
  10  *
  11  * Please send any bug reports or fixes you make to the
  12  * email address(es):
  13  *    lksctp developers <linux-sctp@vger.kernel.org>
  14  *
  15  * Written or modified by:
  16  *    La Monte H.P. Yarroll <piggy@acm.org>
  17  *    Karl Knutson          <karl@athena.chicago.il.us>
  18  *    Jon Grimm             <jgrimm@austin.ibm.com>
  19  *    Sridhar Samudrala     <sri@us.ibm.com>
  20  */
  21
  22 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  23
  24 #include <linux/types.h>
  25 #include <linux/kernel.h>
  26 #include <linux/wait.h>
  27 #include <linux/time.h>
  28 #include <linux/ip.h>
  29 #include <linux/ipv6.h>
  30 #include <linux/init.h>
  31 #include <linux/slab.h>
  32 #include <net/inet_ecn.h>
  33 #include <net/ip.h>
  34 #include <net/icmp.h>
  35 #include <net/net_namespace.h>
  36
  37 #include <linux/socket.h> /* for sa_family_t */
  38 #include <net/sock.h>
  39
  40 #include <net/sctp/sctp.h>
  41 #include <net/sctp/sm.h>
  42 #include <net/sctp/checksum.h>
  43
  44 /* Forward declarations for private helpers. */
  45 static enum sctp_xmit __sctp_packet_append_chunk(struct sctp_packet *packet,
  46                                                  struct sctp_chunk *chunk);
  47 static enum sctp_xmit sctp_packet_can_append_data(struct sctp_packet *packet,
  48                                                   struct sctp_chunk *chunk);
  49 static void sctp_packet_append_data(struct sctp_packet *packet,
  50                                     struct sctp_chunk *chunk);
  51 static enum sctp_xmit sctp_packet_will_fit(struct sctp_packet *packet,
  52                                            struct sctp_chunk *chunk,
  53                                            u16 chunk_len);
  54
  55 static void sctp_packet_reset(struct sctp_packet *packet)
  56 {
  57         /* sctp_packet_transmit() relies on this to reset size to the
  58          * current overhead after sending packets.
  59          */
  60         packet->size = packet->overhead;
  61
  62         packet->has_cookie_echo = 0;
  63         packet->has_sack = 0;
  64         packet->has_data = 0;
  65         packet->has_auth = 0;
  66         packet->ipfragok = 0;
  67         packet->auth = NULL;
  68 }
  69
  70 /* Config a packet.
  71  * This appears to be a followup set of initializations.
  72  */
  73 void sctp_packet_config(struct sctp_packet *packet, __u32 vtag,
  74                         int ecn_capable)
  75 {
  76         struct sctp_transport *tp = packet->transport;
  77         struct sctp_association *asoc = tp->asoc;
  78         struct sctp_sock *sp = NULL;
  79         struct sock *sk;
  80
  81         pr_debug("%s: packet:%p vtag:0x%x\n", __func__, packet, vtag);
  82         packet->vtag = vtag;
  83
  84         /* do the following jobs only once for a flush schedule */
  85         if (!sctp_packet_empty(packet))
  86                 return;
  87
  88         /* set packet max_size with pathmtu, then calculate overhead */
  89         packet->max_size = tp->pathmtu;
  90
  91         if (asoc) {
  92                 sk = asoc->base.sk;
  93                 sp = sctp_sk(sk);
  94         }
  95         packet->overhead = sctp_mtu_payload(sp, 0, 0);
  96         packet->size = packet->overhead;
  97
  98         if (!asoc)
  99                 return;
 100
 101         /* update dst or transport pathmtu if in need */
 102         if (!sctp_transport_dst_check(tp)) {
 103                 sctp_transport_route(tp, NULL, sp);
 104                 if (asoc->param_flags & SPP_PMTUD_ENABLE)
 105                         sctp_assoc_sync_pmtu(asoc);
 106         } else if (!sctp_transport_pmtu_check(tp)) {
 107                 if (asoc->param_flags & SPP_PMTUD_ENABLE)
 108                         sctp_assoc_sync_pmtu(asoc);
 109         }
 110
 111         if (asoc->pmtu_pending) {
 112                 if (asoc->param_flags & SPP_PMTUD_ENABLE)
 113                         sctp_assoc_sync_pmtu(asoc);
 114                 asoc->pmtu_pending = 0;
 115         }
 116
 117         /* If there a is a prepend chunk stick it on the list before
 118          * any other chunks get appended.
 119          */
 120         if (ecn_capable) {
 121                 struct sctp_chunk *chunk = sctp_get_ecne_prepend(asoc);
 122
 123                 if (chunk)
 124                         sctp_packet_append_chunk(packet, chunk);
 125         }
 126
 127         if (!tp->dst)
 128                 return;
 129
 130         /* set packet max_size with gso_max_size if gso is enabled*/
 131         rcu_read_lock();
 132         if (__sk_dst_get(sk) != tp->dst) {
 133                 dst_hold(tp->dst);
 134                 sk_setup_caps(sk, tp->dst);
 135         }
 136         packet->max_size = sk_can_gso(sk) ? tp->dst->dev->gso_max_size
 137                                           : asoc->pathmtu;
 138         rcu_read_unlock();
 139 }
 140
 141 /* Initialize the packet structure. */
 142 void sctp_packet_init(struct sctp_packet *packet,
 143                       struct sctp_transport *transport,
 144                       __u16 sport, __u16 dport)
 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         /* The overhead will be calculated by sctp_packet_config() */
 153         packet->overhead = 0;
 154         sctp_packet_reset(packet);
 155         packet->vtag = 0;
 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 enum sctp_xmit sctp_packet_transmit_chunk(struct sctp_packet *packet,
 179                                           struct sctp_chunk *chunk,
 180                                           int one_packet, gfp_t gfp)
 181 {
 182         enum sctp_xmit 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 enum sctp_xmit sctp_packet_bundle_auth(struct sctp_packet *pkt,
 216                                               struct sctp_chunk *chunk)
 217 {
 218         struct sctp_association *asoc = pkt->transport->asoc;
 219         enum sctp_xmit retval = SCTP_XMIT_OK;
 220         struct sctp_chunk *auth;
 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, chunk->shkey->key_id);
 239         if (!auth)
 240                 return retval;
 241
 242         auth->shkey = chunk->shkey;
 243         sctp_auth_shkey_hold(auth->shkey);
 244
 245         retval = __sctp_packet_append_chunk(pkt, auth);
 246
 247         if (retval != SCTP_XMIT_OK)
 248                 sctp_chunk_free(auth);
 249
 250         return retval;
 251 }
 252
 253 /* Try to bundle a SACK with the packet. */
 254 static enum sctp_xmit sctp_packet_bundle_sack(struct sctp_packet *pkt,
 255                                               struct sctp_chunk *chunk)
 256 {
 257         enum sctp_xmit retval = SCTP_XMIT_OK;
 258
 259         /* If sending DATA and haven't aleady bundled a SACK, try to
 260          * bundle one in to the packet.
 261          */
 262         if (sctp_chunk_is_data(chunk) && !pkt->has_sack &&
 263             !pkt->has_cookie_echo) {
 264                 struct sctp_association *asoc;
 265                 struct timer_list *timer;
 266                 asoc = pkt->transport->asoc;
 267                 timer = &asoc->timers[SCTP_EVENT_TIMEOUT_SACK];
 268
 269                 /* If the SACK timer is running, we have a pending SACK */
 270                 if (timer_pending(timer)) {
 271                         struct sctp_chunk *sack;
 272
 273                         if (pkt->transport->sack_generation !=
 274                             pkt->transport->asoc->peer.sack_generation)
 275                                 return retval;
 276
 277                         asoc->a_rwnd = asoc->rwnd;
 278                         sack = sctp_make_sack(asoc);
 279                         if (sack) {
 280                                 retval = __sctp_packet_append_chunk(pkt, sack);
 281                                 if (retval != SCTP_XMIT_OK) {
 282                                         sctp_chunk_free(sack);
 283                                         goto out;
 284                                 }
 285                                 asoc->peer.sack_needed = 0;
 286                                 if (del_timer(timer))
 287                                         sctp_association_put(asoc);
 288                         }
 289                 }
 290         }
 291 out:
 292         return retval;
 293 }
 294
 295
 296 /* Append a chunk to the offered packet reporting back any inability to do
 297  * so.
 298  */
 299 static enum sctp_xmit __sctp_packet_append_chunk(struct sctp_packet *packet,
 300                                                  struct sctp_chunk *chunk)
 301 {
 302         __u16 chunk_len = SCTP_PAD4(ntohs(chunk->chunk_hdr->length));
 303         enum sctp_xmit retval = SCTP_XMIT_OK;
 304
 305         /* Check to see if this chunk will fit into the packet */
 306         retval = sctp_packet_will_fit(packet, chunk, chunk_len);
 307         if (retval != SCTP_XMIT_OK)
 308                 goto finish;
 309
 310         /* We believe that this chunk is OK to add to the packet */
 311         switch (chunk->chunk_hdr->type) {
 312         case SCTP_CID_DATA:
 313         case SCTP_CID_I_DATA:
 314                 /* Account for the data being in the packet */
 315                 sctp_packet_append_data(packet, chunk);
 316                 /* Disallow SACK bundling after DATA. */
 317                 packet->has_sack = 1;
 318                 /* Disallow AUTH bundling after DATA */
 319                 packet->has_auth = 1;
 320                 /* Let it be knows that packet has DATA in it */
 321                 packet->has_data = 1;
 322                 /* timestamp the chunk for rtx purposes */
 323                 chunk->sent_at = jiffies;
 324                 /* Mainly used for prsctp RTX policy */
 325                 chunk->sent_count++;
 326                 break;
 327         case SCTP_CID_COOKIE_ECHO:
 328                 packet->has_cookie_echo = 1;
 329                 break;
 330
 331         case SCTP_CID_SACK:
 332                 packet->has_sack = 1;
 333                 if (chunk->asoc)
 334                         chunk->asoc->stats.osacks++;
 335                 break;
 336
 337         case SCTP_CID_AUTH:
 338                 packet->has_auth = 1;
 339                 packet->auth = chunk;
 340                 break;
 341         }
 342
 343         /* It is OK to send this chunk.  */
 344         list_add_tail(&chunk->list, &packet->chunk_list);
 345         packet->size += chunk_len;
 346         chunk->transport = packet->transport;
 347 finish:
 348         return retval;
 349 }
 350
 351 /* Append a chunk to the offered packet reporting back any inability to do
 352  * so.
 353  */
 354 enum sctp_xmit sctp_packet_append_chunk(struct sctp_packet *packet,
 355                                         struct sctp_chunk *chunk)
 356 {
 357         enum sctp_xmit retval = SCTP_XMIT_OK;
 358
 359         pr_debug("%s: packet:%p chunk:%p\n", __func__, packet, chunk);
 360
 361         /* Data chunks are special.  Before seeing what else we can
 362          * bundle into this packet, check to see if we are allowed to
 363          * send this DATA.
 364          */
 365         if (sctp_chunk_is_data(chunk)) {
 366                 retval = sctp_packet_can_append_data(packet, chunk);
 367                 if (retval != SCTP_XMIT_OK)
 368                         goto finish;
 369         }
 370
 371         /* Try to bundle AUTH chunk */
 372         retval = sctp_packet_bundle_auth(packet, chunk);
 373         if (retval != SCTP_XMIT_OK)
 374                 goto finish;
 375
 376         /* Try to bundle SACK chunk */
 377         retval = sctp_packet_bundle_sack(packet, chunk);
 378         if (retval != SCTP_XMIT_OK)
 379                 goto finish;
 380
 381         retval = __sctp_packet_append_chunk(packet, chunk);
 382
 383 finish:
 384         return retval;
 385 }
 386
 387 static void sctp_packet_gso_append(struct sk_buff *head, struct sk_buff *skb)
 388 {
 389         if (SCTP_OUTPUT_CB(head)->last == head)
 390                 skb_shinfo(head)->frag_list = skb;
 391         else
 392                 SCTP_OUTPUT_CB(head)->last->next = skb;
 393         SCTP_OUTPUT_CB(head)->last = skb;
 394
 395         head->truesize += skb->truesize;
 396         head->data_len += skb->len;
 397         head->len += skb->len;
 398         refcount_add(skb->truesize, &head->sk->sk_wmem_alloc);
 399
 400         __skb_header_release(skb);
 401 }
 402
 403 static int sctp_packet_pack(struct sctp_packet *packet,
 404                             struct sk_buff *head, int gso, gfp_t gfp)
 405 {
 406         struct sctp_transport *tp = packet->transport;
 407         struct sctp_auth_chunk *auth = NULL;
 408         struct sctp_chunk *chunk, *tmp;
 409         int pkt_count = 0, pkt_size;
 410         struct sock *sk = head->sk;
 411         struct sk_buff *nskb;
 412         int auth_len = 0;
 413
 414         if (gso) {
 415                 skb_shinfo(head)->gso_type = sk->sk_gso_type;
 416                 SCTP_OUTPUT_CB(head)->last = head;
 417         } else {
 418                 nskb = head;
 419                 pkt_size = packet->size;
 420                 goto merge;
 421         }
 422
 423         do {
 424                 /* calculate the pkt_size and alloc nskb */
 425                 pkt_size = packet->overhead;
 426                 list_for_each_entry_safe(chunk, tmp, &packet->chunk_list,
 427                                          list) {
 428                         int padded = SCTP_PAD4(chunk->skb->len);
 429
 430                         if (chunk == packet->auth)
 431                                 auth_len = padded;
 432                         else if (auth_len + padded + packet->overhead >
 433                                  tp->pathmtu)
 434                                 return 0;
 435                         else if (pkt_size + padded > tp->pathmtu)
 436                                 break;
 437                         pkt_size += padded;
 438                 }
 439                 nskb = alloc_skb(pkt_size + MAX_HEADER, gfp);
 440                 if (!nskb)
 441                         return 0;
 442                 skb_reserve(nskb, packet->overhead + MAX_HEADER);
 443
 444 merge:
 445                 /* merge chunks into nskb and append nskb into head list */
 446                 pkt_size -= packet->overhead;
 447                 list_for_each_entry_safe(chunk, tmp, &packet->chunk_list, list) {
 448                         int padding;
 449
 450                         list_del_init(&chunk->list);
 451                         if (sctp_chunk_is_data(chunk)) {
 452                                 if (!sctp_chunk_retransmitted(chunk) &&
 453                                     !tp->rto_pending) {
 454                                         chunk->rtt_in_progress = 1;
 455                                         tp->rto_pending = 1;
 456                                 }
 457                         }
 458
 459                         padding = SCTP_PAD4(chunk->skb->len) - chunk->skb->len;
 460                         if (padding)
 461                                 skb_put_zero(chunk->skb, padding);
 462
 463                         if (chunk == packet->auth)
 464                                 auth = (struct sctp_auth_chunk *)
 465                                                         skb_tail_pointer(nskb);
 466
 467                         skb_put_data(nskb, chunk->skb->data, 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,
 488                                                  packet->auth->shkey, gfp);
 489                         /* free auth if no more chunks, or add it back */
 490                         if (list_empty(&packet->chunk_list))
 491                                 sctp_chunk_free(packet->auth);
 492                         else
 493                                 list_add(&packet->auth->list,
 494                                          &packet->chunk_list);
 495                 }
 496
 497                 if (gso)
 498                         sctp_packet_gso_append(head, nskb);
 499
 500                 pkt_count++;
 501         } while (!list_empty(&packet->chunk_list));
 502
 503         if (gso) {
 504                 memset(head->cb, 0, max(sizeof(struct inet_skb_parm),
 505                                         sizeof(struct inet6_skb_parm)));
 506                 skb_shinfo(head)->gso_segs = pkt_count;
 507                 skb_shinfo(head)->gso_size = GSO_BY_FRAGS;
 508                 rcu_read_lock();
 509                 if (skb_dst(head) != tp->dst) {
 510                         dst_hold(tp->dst);
 511                         sk_setup_caps(sk, tp->dst);
 512                 }
 513                 rcu_read_unlock();
 514                 goto chksum;
 515         }
 516
 517         if (sctp_checksum_disable)
 518                 return 1;
 519
 520         if (!(skb_dst(head)->dev->features & NETIF_F_SCTP_CRC) ||
 521             dst_xfrm(skb_dst(head)) || packet->ipfragok) {
 522                 struct sctphdr *sh =
 523                         (struct sctphdr *)skb_transport_header(head);
 524
 525                 sh->checksum = sctp_compute_cksum(head, 0);
 526         } else {
 527 chksum:
 528                 head->ip_summed = CHECKSUM_PARTIAL;
 529                 head->csum_not_inet = 1;
 530                 head->csum_start = skb_transport_header(head) - head->head;
 531                 head->csum_offset = offsetof(struct sctphdr, checksum);
 532         }
 533
 534         return pkt_count;
 535 }
 536
 537 /* All packets are sent to the network through this function from
 538  * sctp_outq_tail().
 539  *
 540  * The return value is always 0 for now.
 541  */
 542 int sctp_packet_transmit(struct sctp_packet *packet, gfp_t gfp)
 543 {
 544         struct sctp_transport *tp = packet->transport;
 545         struct sctp_association *asoc = tp->asoc;
 546         struct sctp_chunk *chunk, *tmp;
 547         int pkt_count, gso = 0;
 548         struct dst_entry *dst;
 549         struct sk_buff *head;
 550         struct sctphdr *sh;
 551         struct sock *sk;
 552
 553         pr_debug("%s: packet:%p\n", __func__, packet);
 554         if (list_empty(&packet->chunk_list))
 555                 return 0;
 556         chunk = list_entry(packet->chunk_list.next, struct sctp_chunk, list);
 557         sk = chunk->skb->sk;
 558
 559         /* check gso */
 560         if (packet->size > tp->pathmtu && !packet->ipfragok) {
 561                 if (!sk_can_gso(sk)) {
 562                         pr_err_once("Trying to GSO but underlying device doesn't support it.");
 563                         goto out;
 564                 }
 565                 gso = 1;
 566         }
 567
 568         /* alloc head skb */
 569         head = alloc_skb((gso ? packet->overhead : packet->size) +
 570                          MAX_HEADER, gfp);
 571         if (!head)
 572                 goto out;
 573         skb_reserve(head, packet->overhead + MAX_HEADER);
 574         skb_set_owner_w(head, sk);
 575
 576         /* set sctp header */
 577         sh = skb_push(head, sizeof(struct sctphdr));
 578         skb_reset_transport_header(head);
 579         sh->source = htons(packet->source_port);
 580         sh->dest = htons(packet->destination_port);
 581         sh->vtag = htonl(packet->vtag);
 582         sh->checksum = 0;
 583
 584         /* drop packet if no dst */
 585         dst = dst_clone(tp->dst);
 586         if (!dst) {
 587                 IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTNOROUTES);
 588                 kfree_skb(head);
 589                 goto out;
 590         }
 591         skb_dst_set(head, dst);
 592
 593         /* pack up chunks */
 594         pkt_count = sctp_packet_pack(packet, head, gso, gfp);
 595         if (!pkt_count) {
 596                 kfree_skb(head);
 597                 goto out;
 598         }
 599         pr_debug("***sctp_transmit_packet*** skb->len:%d\n", head->len);
 600
 601         /* start autoclose timer */
 602         if (packet->has_data && sctp_state(asoc, ESTABLISHED) &&
 603             asoc->timeouts[SCTP_EVENT_TIMEOUT_AUTOCLOSE]) {
 604                 struct timer_list *timer =
 605                         &asoc->timers[SCTP_EVENT_TIMEOUT_AUTOCLOSE];
 606                 unsigned long timeout =
 607                         asoc->timeouts[SCTP_EVENT_TIMEOUT_AUTOCLOSE];
 608
 609                 if (!mod_timer(timer, jiffies + timeout))
 610                         sctp_association_hold(asoc);
 611         }
 612
 613         /* sctp xmit */
 614         tp->af_specific->ecn_capable(sk);
 615         if (asoc) {
 616                 asoc->stats.opackets += pkt_count;
 617                 if (asoc->peer.last_sent_to != tp)
 618                         asoc->peer.last_sent_to = tp;
 619         }
 620         head->ignore_df = packet->ipfragok;
 621         if (tp->dst_pending_confirm)
 622                 skb_set_dst_pending_confirm(head, 1);
 623         /* neighbour should be confirmed on successful transmission or
 624          * positive error
 625          */
 626         if (tp->af_specific->sctp_xmit(head, tp) >= 0 &&
 627             tp->dst_pending_confirm)
 628                 tp->dst_pending_confirm = 0;
 629
 630 out:
 631         list_for_each_entry_safe(chunk, tmp, &packet->chunk_list, list) {
 632                 list_del_init(&chunk->list);
 633                 if (!sctp_chunk_is_data(chunk))
 634                         sctp_chunk_free(chunk);
 635         }
 636         sctp_packet_reset(packet);
 637         return 0;
 638 }
 639
 640 /********************************************************************
 641  * 2nd Level Abstractions
 642  ********************************************************************/
 643
 644 /* This private function check to see if a chunk can be added */
 645 static enum sctp_xmit sctp_packet_can_append_data(struct sctp_packet *packet,
 646                                                   struct sctp_chunk *chunk)
 647 {
 648         size_t datasize, rwnd, inflight, flight_size;
 649         struct sctp_transport *transport = packet->transport;
 650         struct sctp_association *asoc = transport->asoc;
 651         struct sctp_outq *q = &asoc->outqueue;
 652
 653         /* RFC 2960 6.1  Transmission of DATA Chunks
 654          *
 655          * A) At any given time, the data sender MUST NOT transmit new data to
 656          * any destination transport address if its peer's rwnd indicates
 657          * that the peer has no buffer space (i.e. rwnd is 0, see Section
 658          * 6.2.1).  However, regardless of the value of rwnd (including if it
 659          * is 0), the data sender can always have one DATA chunk in flight to
 660          * the receiver if allowed by cwnd (see rule B below).  This rule
 661          * allows the sender to probe for a change in rwnd that the sender
 662          * missed due to the SACK having been lost in transit from the data
 663          * receiver to the data sender.
 664          */
 665
 666         rwnd = asoc->peer.rwnd;
 667         inflight = q->outstanding_bytes;
 668         flight_size = transport->flight_size;
 669
 670         datasize = sctp_data_size(chunk);
 671
 672         if (datasize > rwnd && inflight > 0)
 673                 /* We have (at least) one data chunk in flight,
 674                  * so we can't fall back to rule 6.1 B).
 675                  */
 676                 return SCTP_XMIT_RWND_FULL;
 677
 678         /* RFC 2960 6.1  Transmission of DATA Chunks
 679          *
 680          * B) At any given time, the sender MUST NOT transmit new data
 681          * to a given transport address if it has cwnd or more bytes
 682          * of data outstanding to that transport address.
 683          */
 684         /* RFC 7.2.4 & the Implementers Guide 2.8.
 685          *
 686          * 3) ...
 687          *    When a Fast Retransmit is being performed the sender SHOULD
 688          *    ignore the value of cwnd and SHOULD NOT delay retransmission.
 689          */
 690         if (chunk->fast_retransmit != SCTP_NEED_FRTX &&
 691             flight_size >= transport->cwnd)
 692                 return SCTP_XMIT_RWND_FULL;
 693
 694         /* Nagle's algorithm to solve small-packet problem:
 695          * Inhibit the sending of new chunks when new outgoing data arrives
 696          * if any previously transmitted data on the connection remains
 697          * unacknowledged.
 698          */
 699
 700         if ((sctp_sk(asoc->base.sk)->nodelay || inflight == 0) &&
 701             !asoc->force_delay)
 702                 /* Nothing unacked */
 703                 return SCTP_XMIT_OK;
 704
 705         if (!sctp_packet_empty(packet))
 706                 /* Append to packet */
 707                 return SCTP_XMIT_OK;
 708
 709         if (!sctp_state(asoc, ESTABLISHED))
 710                 return SCTP_XMIT_OK;
 711
 712         /* Check whether this chunk and all the rest of pending data will fit
 713          * or delay in hopes of bundling a full sized packet.
 714          */
 715         if (chunk->skb->len + q->out_qlen > transport->pathmtu -
 716             packet->overhead - sctp_datachk_len(&chunk->asoc->stream) - 4)
 717                 /* Enough data queued to fill a packet */
 718                 return SCTP_XMIT_OK;
 719
 720         /* Don't delay large message writes that may have been fragmented */
 721         if (!chunk->msg->can_delay)
 722                 return SCTP_XMIT_OK;
 723
 724         /* Defer until all data acked or packet full */
 725         return SCTP_XMIT_DELAY;
 726 }
 727
 728 /* This private function does management things when adding DATA chunk */
 729 static void sctp_packet_append_data(struct sctp_packet *packet,
 730                                 struct sctp_chunk *chunk)
 731 {
 732         struct sctp_transport *transport = packet->transport;
 733         size_t datasize = sctp_data_size(chunk);
 734         struct sctp_association *asoc = transport->asoc;
 735         u32 rwnd = asoc->peer.rwnd;
 736
 737         /* Keep track of how many bytes are in flight over this transport. */
 738         transport->flight_size += datasize;
 739
 740         /* Keep track of how many bytes are in flight to the receiver. */
 741         asoc->outqueue.outstanding_bytes += datasize;
 742
 743         /* Update our view of the receiver's rwnd. */
 744         if (datasize < rwnd)
 745                 rwnd -= datasize;
 746         else
 747                 rwnd = 0;
 748
 749         asoc->peer.rwnd = rwnd;
 750         sctp_chunk_assign_tsn(chunk);
 751         asoc->stream.si->assign_number(chunk);
 752 }
 753
 754 static enum sctp_xmit sctp_packet_will_fit(struct sctp_packet *packet,
 755                                            struct sctp_chunk *chunk,
 756                                            u16 chunk_len)
 757 {
 758         enum sctp_xmit retval = SCTP_XMIT_OK;
 759         size_t psize, pmtu, maxsize;
 760
 761         /* Don't bundle in this packet if this chunk's auth key doesn't
 762          * match other chunks already enqueued on this packet. Also,
 763          * don't bundle the chunk with auth key if other chunks in this
 764          * packet don't have auth key.
 765          */
 766         if ((packet->auth && chunk->shkey != packet->auth->shkey) ||
 767             (!packet->auth && chunk->shkey &&
 768              chunk->chunk_hdr->type != SCTP_CID_AUTH))
 769                 return SCTP_XMIT_PMTU_FULL;
 770
 771         psize = packet->size;
 772         if (packet->transport->asoc)
 773                 pmtu = packet->transport->asoc->pathmtu;
 774         else
 775                 pmtu = packet->transport->pathmtu;
 776
 777         /* Decide if we need to fragment or resubmit later. */
 778         if (psize + chunk_len > pmtu) {
 779                 /* It's OK to fragment at IP level if any one of the following
 780                  * is true:
 781                  *      1. The packet is empty (meaning this chunk is greater
 782                  *         the MTU)
 783                  *      2. The packet doesn't have any data in it yet and data
 784                  *         requires authentication.
 785                  */
 786                 if (sctp_packet_empty(packet) ||
 787                     (!packet->has_data && chunk->auth)) {
 788                         /* We no longer do re-fragmentation.
 789                          * Just fragment at the IP layer, if we
 790                          * actually hit this condition
 791                          */
 792                         packet->ipfragok = 1;
 793                         goto out;
 794                 }
 795
 796                 /* Similarly, if this chunk was built before a PMTU
 797                  * reduction, we have to fragment it at IP level now. So
 798                  * if the packet already contains something, we need to
 799                  * flush.
 800                  */
 801                 maxsize = pmtu - packet->overhead;
 802                 if (packet->auth)
 803                         maxsize -= SCTP_PAD4(packet->auth->skb->len);
 804                 if (chunk_len > maxsize)
 805                         retval = SCTP_XMIT_PMTU_FULL;
 806
 807                 /* It is also okay to fragment if the chunk we are
 808                  * adding is a control chunk, but only if current packet
 809                  * is not a GSO one otherwise it causes fragmentation of
 810                  * a large frame. So in this case we allow the
 811                  * fragmentation by forcing it to be in a new packet.
 812                  */
 813                 if (!sctp_chunk_is_data(chunk) && packet->has_data)
 814                         retval = SCTP_XMIT_PMTU_FULL;
 815
 816                 if (psize + chunk_len > packet->max_size)
 817                         /* Hit GSO/PMTU limit, gotta flush */
 818                         retval = SCTP_XMIT_PMTU_FULL;
 819
 820                 if (!packet->transport->burst_limited &&
 821                     psize + chunk_len > (packet->transport->cwnd >> 1))
 822                         /* Do not allow a single GSO packet to use more
 823                          * than half of cwnd.
 824                          */
 825                         retval = SCTP_XMIT_PMTU_FULL;
 826
 827                 if (packet->transport->burst_limited &&
 828                     psize + chunk_len > (packet->transport->burst_limited >> 1))
 829                         /* Do not allow a single GSO packet to use more
 830                          * than half of original cwnd.
 831                          */
 832                         retval = SCTP_XMIT_PMTU_FULL;
 833                 /* Otherwise it will fit in the GSO packet */
 834         }
 835
 836 out:
 837         return retval;
 838 }