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                                 SCTP_INC_STATS(asoc->base.net,
 286                                                SCTP_MIB_OUTCTRLCHUNKS);
 287                                 asoc->stats.octrlchunks++;
 288                                 asoc->peer.sack_needed = 0;
 289                                 if (del_timer(timer))
 290                                         sctp_association_put(asoc);
 291                         }
 292                 }
 293         }
 294 out:
 295         return retval;
 296 }
 297
 298
 299 /* Append a chunk to the offered packet reporting back any inability to do
 300  * so.
 301  */
 302 static enum sctp_xmit __sctp_packet_append_chunk(struct sctp_packet *packet,
 303                                                  struct sctp_chunk *chunk)
 304 {
 305         __u16 chunk_len = SCTP_PAD4(ntohs(chunk->chunk_hdr->length));
 306         enum sctp_xmit retval = SCTP_XMIT_OK;
 307
 308         /* Check to see if this chunk will fit into the packet */
 309         retval = sctp_packet_will_fit(packet, chunk, chunk_len);
 310         if (retval != SCTP_XMIT_OK)
 311                 goto finish;
 312
 313         /* We believe that this chunk is OK to add to the packet */
 314         switch (chunk->chunk_hdr->type) {
 315         case SCTP_CID_DATA:
 316         case SCTP_CID_I_DATA:
 317                 /* Account for the data being in the packet */
 318                 sctp_packet_append_data(packet, chunk);
 319                 /* Disallow SACK bundling after DATA. */
 320                 packet->has_sack = 1;
 321                 /* Disallow AUTH bundling after DATA */
 322                 packet->has_auth = 1;
 323                 /* Let it be knows that packet has DATA in it */
 324                 packet->has_data = 1;
 325                 /* timestamp the chunk for rtx purposes */
 326                 chunk->sent_at = jiffies;
 327                 /* Mainly used for prsctp RTX policy */
 328                 chunk->sent_count++;
 329                 break;
 330         case SCTP_CID_COOKIE_ECHO:
 331                 packet->has_cookie_echo = 1;
 332                 break;
 333
 334         case SCTP_CID_SACK:
 335                 packet->has_sack = 1;
 336                 if (chunk->asoc)
 337                         chunk->asoc->stats.osacks++;
 338                 break;
 339
 340         case SCTP_CID_AUTH:
 341                 packet->has_auth = 1;
 342                 packet->auth = chunk;
 343                 break;
 344         }
 345
 346         /* It is OK to send this chunk.  */
 347         list_add_tail(&chunk->list, &packet->chunk_list);
 348         packet->size += chunk_len;
 349         chunk->transport = packet->transport;
 350 finish:
 351         return retval;
 352 }
 353
 354 /* Append a chunk to the offered packet reporting back any inability to do
 355  * so.
 356  */
 357 enum sctp_xmit sctp_packet_append_chunk(struct sctp_packet *packet,
 358                                         struct sctp_chunk *chunk)
 359 {
 360         enum sctp_xmit retval = SCTP_XMIT_OK;
 361
 362         pr_debug("%s: packet:%p chunk:%p\n", __func__, packet, chunk);
 363
 364         /* Data chunks are special.  Before seeing what else we can
 365          * bundle into this packet, check to see if we are allowed to
 366          * send this DATA.
 367          */
 368         if (sctp_chunk_is_data(chunk)) {
 369                 retval = sctp_packet_can_append_data(packet, chunk);
 370                 if (retval != SCTP_XMIT_OK)
 371                         goto finish;
 372         }
 373
 374         /* Try to bundle AUTH chunk */
 375         retval = sctp_packet_bundle_auth(packet, chunk);
 376         if (retval != SCTP_XMIT_OK)
 377                 goto finish;
 378
 379         /* Try to bundle SACK chunk */
 380         retval = sctp_packet_bundle_sack(packet, chunk);
 381         if (retval != SCTP_XMIT_OK)
 382                 goto finish;
 383
 384         retval = __sctp_packet_append_chunk(packet, chunk);
 385
 386 finish:
 387         return retval;
 388 }
 389
 390 static void sctp_packet_gso_append(struct sk_buff *head, struct sk_buff *skb)
 391 {
 392         if (SCTP_OUTPUT_CB(head)->last == head)
 393                 skb_shinfo(head)->frag_list = skb;
 394         else
 395                 SCTP_OUTPUT_CB(head)->last->next = skb;
 396         SCTP_OUTPUT_CB(head)->last = skb;
 397
 398         head->truesize += skb->truesize;
 399         head->data_len += skb->len;
 400         head->len += skb->len;
 401         refcount_add(skb->truesize, &head->sk->sk_wmem_alloc);
 402
 403         __skb_header_release(skb);
 404 }
 405
 406 static int sctp_packet_pack(struct sctp_packet *packet,
 407                             struct sk_buff *head, int gso, gfp_t gfp)
 408 {
 409         struct sctp_transport *tp = packet->transport;
 410         struct sctp_auth_chunk *auth = NULL;
 411         struct sctp_chunk *chunk, *tmp;
 412         int pkt_count = 0, pkt_size;
 413         struct sock *sk = head->sk;
 414         struct sk_buff *nskb;
 415         int auth_len = 0;
 416
 417         if (gso) {
 418                 skb_shinfo(head)->gso_type = sk->sk_gso_type;
 419                 SCTP_OUTPUT_CB(head)->last = head;
 420         } else {
 421                 nskb = head;
 422                 pkt_size = packet->size;
 423                 goto merge;
 424         }
 425
 426         do {
 427                 /* calculate the pkt_size and alloc nskb */
 428                 pkt_size = packet->overhead;
 429                 list_for_each_entry_safe(chunk, tmp, &packet->chunk_list,
 430                                          list) {
 431                         int padded = SCTP_PAD4(chunk->skb->len);
 432
 433                         if (chunk == packet->auth)
 434                                 auth_len = padded;
 435                         else if (auth_len + padded + packet->overhead >
 436                                  tp->pathmtu)
 437                                 return 0;
 438                         else if (pkt_size + padded > tp->pathmtu)
 439                                 break;
 440                         pkt_size += padded;
 441                 }
 442                 nskb = alloc_skb(pkt_size + MAX_HEADER, gfp);
 443                 if (!nskb)
 444                         return 0;
 445                 skb_reserve(nskb, packet->overhead + MAX_HEADER);
 446
 447 merge:
 448                 /* merge chunks into nskb and append nskb into head list */
 449                 pkt_size -= packet->overhead;
 450                 list_for_each_entry_safe(chunk, tmp, &packet->chunk_list, list) {
 451                         int padding;
 452
 453                         list_del_init(&chunk->list);
 454                         if (sctp_chunk_is_data(chunk)) {
 455                                 if (!sctp_chunk_retransmitted(chunk) &&
 456                                     !tp->rto_pending) {
 457                                         chunk->rtt_in_progress = 1;
 458                                         tp->rto_pending = 1;
 459                                 }
 460                         }
 461
 462                         padding = SCTP_PAD4(chunk->skb->len) - chunk->skb->len;
 463                         if (padding)
 464                                 skb_put_zero(chunk->skb, padding);
 465
 466                         if (chunk == packet->auth)
 467                                 auth = (struct sctp_auth_chunk *)
 468                                                         skb_tail_pointer(nskb);
 469
 470                         skb_put_data(nskb, chunk->skb->data, chunk->skb->len);
 471
 472                         pr_debug("*** Chunk:%p[%s] %s 0x%x, length:%d, chunk->skb->len:%d, rtt_in_progress:%d\n",
 473                                  chunk,
 474                                  sctp_cname(SCTP_ST_CHUNK(chunk->chunk_hdr->type)),
 475                                  chunk->has_tsn ? "TSN" : "No TSN",
 476                                  chunk->has_tsn ? ntohl(chunk->subh.data_hdr->tsn) : 0,
 477                                  ntohs(chunk->chunk_hdr->length), chunk->skb->len,
 478                                  chunk->rtt_in_progress);
 479
 480                         pkt_size -= SCTP_PAD4(chunk->skb->len);
 481
 482                         if (!sctp_chunk_is_data(chunk) && chunk != packet->auth)
 483                                 sctp_chunk_free(chunk);
 484
 485                         if (!pkt_size)
 486                                 break;
 487                 }
 488
 489                 if (auth) {
 490                         sctp_auth_calculate_hmac(tp->asoc, nskb, auth,
 491                                                  packet->auth->shkey, gfp);
 492                         /* free auth if no more chunks, or add it back */
 493                         if (list_empty(&packet->chunk_list))
 494                                 sctp_chunk_free(packet->auth);
 495                         else
 496                                 list_add(&packet->auth->list,
 497                                          &packet->chunk_list);
 498                 }
 499
 500                 if (gso)
 501                         sctp_packet_gso_append(head, nskb);
 502
 503                 pkt_count++;
 504         } while (!list_empty(&packet->chunk_list));
 505
 506         if (gso) {
 507                 memset(head->cb, 0, max(sizeof(struct inet_skb_parm),
 508                                         sizeof(struct inet6_skb_parm)));
 509                 skb_shinfo(head)->gso_segs = pkt_count;
 510                 skb_shinfo(head)->gso_size = GSO_BY_FRAGS;
 511                 goto chksum;
 512         }
 513
 514         if (sctp_checksum_disable)
 515                 return 1;
 516
 517         if (!(tp->dst->dev->features & NETIF_F_SCTP_CRC) ||
 518             dst_xfrm(tp->dst) || packet->ipfragok || tp->encap_port) {
 519                 struct sctphdr *sh =
 520                         (struct sctphdr *)skb_transport_header(head);
 521
 522                 sh->checksum = sctp_compute_cksum(head, 0);
 523         } else {
 524 chksum:
 525                 head->ip_summed = CHECKSUM_PARTIAL;
 526                 head->csum_not_inet = 1;
 527                 head->csum_start = skb_transport_header(head) - head->head;
 528                 head->csum_offset = offsetof(struct sctphdr, checksum);
 529         }
 530
 531         return pkt_count;
 532 }
 533
 534 /* All packets are sent to the network through this function from
 535  * sctp_outq_tail().
 536  *
 537  * The return value is always 0 for now.
 538  */
 539 int sctp_packet_transmit(struct sctp_packet *packet, gfp_t gfp)
 540 {
 541         struct sctp_transport *tp = packet->transport;
 542         struct sctp_association *asoc = tp->asoc;
 543         struct sctp_chunk *chunk, *tmp;
 544         int pkt_count, gso = 0;
 545         struct sk_buff *head;
 546         struct sctphdr *sh;
 547         struct sock *sk;
 548
 549         pr_debug("%s: packet:%p\n", __func__, packet);
 550         if (list_empty(&packet->chunk_list))
 551                 return 0;
 552         chunk = list_entry(packet->chunk_list.next, struct sctp_chunk, list);
 553         sk = chunk->skb->sk;
 554
 555         /* check gso */
 556         if (packet->size > tp->pathmtu && !packet->ipfragok) {
 557                 if (!sk_can_gso(sk)) {
 558                         pr_err_once("Trying to GSO but underlying device doesn't support it.");
 559                         goto out;
 560                 }
 561                 gso = 1;
 562         }
 563
 564         /* alloc head skb */
 565         head = alloc_skb((gso ? packet->overhead : packet->size) +
 566                          MAX_HEADER, gfp);
 567         if (!head)
 568                 goto out;
 569         skb_reserve(head, packet->overhead + MAX_HEADER);
 570         skb_set_owner_w(head, sk);
 571
 572         /* set sctp header */
 573         sh = skb_push(head, sizeof(struct sctphdr));
 574         skb_reset_transport_header(head);
 575         sh->source = htons(packet->source_port);
 576         sh->dest = htons(packet->destination_port);
 577         sh->vtag = htonl(packet->vtag);
 578         sh->checksum = 0;
 579
 580         /* drop packet if no dst */
 581         if (!tp->dst) {
 582                 IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTNOROUTES);
 583                 kfree_skb(head);
 584                 goto out;
 585         }
 586
 587         rcu_read_lock();
 588         if (__sk_dst_get(sk) != tp->dst) {
 589                 dst_hold(tp->dst);
 590                 sk_setup_caps(sk, tp->dst);
 591         }
 592         rcu_read_unlock();
 593
 594         /* pack up chunks */
 595         pkt_count = sctp_packet_pack(packet, head, gso, gfp);
 596         if (!pkt_count) {
 597                 kfree_skb(head);
 598                 goto out;
 599         }
 600         pr_debug("***sctp_transmit_packet*** skb->len:%d\n", head->len);
 601
 602         /* start autoclose timer */
 603         if (packet->has_data && sctp_state(asoc, ESTABLISHED) &&
 604             asoc->timeouts[SCTP_EVENT_TIMEOUT_AUTOCLOSE]) {
 605                 struct timer_list *timer =
 606                         &asoc->timers[SCTP_EVENT_TIMEOUT_AUTOCLOSE];
 607                 unsigned long timeout =
 608                         asoc->timeouts[SCTP_EVENT_TIMEOUT_AUTOCLOSE];
 609
 610                 if (!mod_timer(timer, jiffies + timeout))
 611                         sctp_association_hold(asoc);
 612         }
 613
 614         /* sctp xmit */
 615         tp->af_specific->ecn_capable(sk);
 616         if (asoc) {
 617                 asoc->stats.opackets += pkt_count;
 618                 if (asoc->peer.last_sent_to != tp)
 619                         asoc->peer.last_sent_to = tp;
 620         }
 621         head->ignore_df = packet->ipfragok;
 622         if (tp->dst_pending_confirm)
 623                 skb_set_dst_pending_confirm(head, 1);
 624         /* neighbour should be confirmed on successful transmission or
 625          * positive error
 626          */
 627         if (tp->af_specific->sctp_xmit(head, tp) >= 0 &&
 628             tp->dst_pending_confirm)
 629                 tp->dst_pending_confirm = 0;
 630
 631 out:
 632         list_for_each_entry_safe(chunk, tmp, &packet->chunk_list, list) {
 633                 list_del_init(&chunk->list);
 634                 if (!sctp_chunk_is_data(chunk))
 635                         sctp_chunk_free(chunk);
 636         }
 637         sctp_packet_reset(packet);
 638         return 0;
 639 }
 640
 641 /********************************************************************
 642  * 2nd Level Abstractions
 643  ********************************************************************/
 644
 645 /* This private function check to see if a chunk can be added */
 646 static enum sctp_xmit sctp_packet_can_append_data(struct sctp_packet *packet,
 647                                                   struct sctp_chunk *chunk)
 648 {
 649         size_t datasize, rwnd, inflight, flight_size;
 650         struct sctp_transport *transport = packet->transport;
 651         struct sctp_association *asoc = transport->asoc;
 652         struct sctp_outq *q = &asoc->outqueue;
 653
 654         /* RFC 2960 6.1  Transmission of DATA Chunks
 655          *
 656          * A) At any given time, the data sender MUST NOT transmit new data to
 657          * any destination transport address if its peer's rwnd indicates
 658          * that the peer has no buffer space (i.e. rwnd is 0, see Section
 659          * 6.2.1).  However, regardless of the value of rwnd (including if it
 660          * is 0), the data sender can always have one DATA chunk in flight to
 661          * the receiver if allowed by cwnd (see rule B below).  This rule
 662          * allows the sender to probe for a change in rwnd that the sender
 663          * missed due to the SACK having been lost in transit from the data
 664          * receiver to the data sender.
 665          */
 666
 667         rwnd = asoc->peer.rwnd;
 668         inflight = q->outstanding_bytes;
 669         flight_size = transport->flight_size;
 670
 671         datasize = sctp_data_size(chunk);
 672
 673         if (datasize > rwnd && inflight > 0)
 674                 /* We have (at least) one data chunk in flight,
 675                  * so we can't fall back to rule 6.1 B).
 676                  */
 677                 return SCTP_XMIT_RWND_FULL;
 678
 679         /* RFC 2960 6.1  Transmission of DATA Chunks
 680          *
 681          * B) At any given time, the sender MUST NOT transmit new data
 682          * to a given transport address if it has cwnd or more bytes
 683          * of data outstanding to that transport address.
 684          */
 685         /* RFC 7.2.4 & the Implementers Guide 2.8.
 686          *
 687          * 3) ...
 688          *    When a Fast Retransmit is being performed the sender SHOULD
 689          *    ignore the value of cwnd and SHOULD NOT delay retransmission.
 690          */
 691         if (chunk->fast_retransmit != SCTP_NEED_FRTX &&
 692             flight_size >= transport->cwnd)
 693                 return SCTP_XMIT_RWND_FULL;
 694
 695         /* Nagle's algorithm to solve small-packet problem:
 696          * Inhibit the sending of new chunks when new outgoing data arrives
 697          * if any previously transmitted data on the connection remains
 698          * unacknowledged.
 699          */
 700
 701         if ((sctp_sk(asoc->base.sk)->nodelay || inflight == 0) &&
 702             !asoc->force_delay)
 703                 /* Nothing unacked */
 704                 return SCTP_XMIT_OK;
 705
 706         if (!sctp_packet_empty(packet))
 707                 /* Append to packet */
 708                 return SCTP_XMIT_OK;
 709
 710         if (!sctp_state(asoc, ESTABLISHED))
 711                 return SCTP_XMIT_OK;
 712
 713         /* Check whether this chunk and all the rest of pending data will fit
 714          * or delay in hopes of bundling a full sized packet.
 715          */
 716         if (chunk->skb->len + q->out_qlen > transport->pathmtu -
 717             packet->overhead - sctp_datachk_len(&chunk->asoc->stream) - 4)
 718                 /* Enough data queued to fill a packet */
 719                 return SCTP_XMIT_OK;
 720
 721         /* Don't delay large message writes that may have been fragmented */
 722         if (!chunk->msg->can_delay)
 723                 return SCTP_XMIT_OK;
 724
 725         /* Defer until all data acked or packet full */
 726         return SCTP_XMIT_DELAY;
 727 }
 728
 729 /* This private function does management things when adding DATA chunk */
 730 static void sctp_packet_append_data(struct sctp_packet *packet,
 731                                 struct sctp_chunk *chunk)
 732 {
 733         struct sctp_transport *transport = packet->transport;
 734         size_t datasize = sctp_data_size(chunk);
 735         struct sctp_association *asoc = transport->asoc;
 736         u32 rwnd = asoc->peer.rwnd;
 737
 738         /* Keep track of how many bytes are in flight over this transport. */
 739         transport->flight_size += datasize;
 740
 741         /* Keep track of how many bytes are in flight to the receiver. */
 742         asoc->outqueue.outstanding_bytes += datasize;
 743
 744         /* Update our view of the receiver's rwnd. */
 745         if (datasize < rwnd)
 746                 rwnd -= datasize;
 747         else
 748                 rwnd = 0;
 749
 750         asoc->peer.rwnd = rwnd;
 751         sctp_chunk_assign_tsn(chunk);
 752         asoc->stream.si->assign_number(chunk);
 753 }
 754
 755 static enum sctp_xmit sctp_packet_will_fit(struct sctp_packet *packet,
 756                                            struct sctp_chunk *chunk,
 757                                            u16 chunk_len)
 758 {
 759         enum sctp_xmit retval = SCTP_XMIT_OK;
 760         size_t psize, pmtu, maxsize;
 761
 762         /* Don't bundle in this packet if this chunk's auth key doesn't
 763          * match other chunks already enqueued on this packet. Also,
 764          * don't bundle the chunk with auth key if other chunks in this
 765          * packet don't have auth key.
 766          */
 767         if ((packet->auth && chunk->shkey != packet->auth->shkey) ||
 768             (!packet->auth && chunk->shkey &&
 769              chunk->chunk_hdr->type != SCTP_CID_AUTH))
 770                 return SCTP_XMIT_PMTU_FULL;
 771
 772         psize = packet->size;
 773         if (packet->transport->asoc)
 774                 pmtu = packet->transport->asoc->pathmtu;
 775         else
 776                 pmtu = packet->transport->pathmtu;
 777
 778         /* Decide if we need to fragment or resubmit later. */
 779         if (psize + chunk_len > pmtu) {
 780                 /* It's OK to fragment at IP level if any one of the following
 781                  * is true:
 782                  *      1. The packet is empty (meaning this chunk is greater
 783                  *         the MTU)
 784                  *      2. The packet doesn't have any data in it yet and data
 785                  *         requires authentication.
 786                  */
 787                 if (sctp_packet_empty(packet) ||
 788                     (!packet->has_data && chunk->auth)) {
 789                         /* We no longer do re-fragmentation.
 790                          * Just fragment at the IP layer, if we
 791                          * actually hit this condition
 792                          */
 793                         packet->ipfragok = 1;
 794                         goto out;
 795                 }
 796
 797                 /* Similarly, if this chunk was built before a PMTU
 798                  * reduction, we have to fragment it at IP level now. So
 799                  * if the packet already contains something, we need to
 800                  * flush.
 801                  */
 802                 maxsize = pmtu - packet->overhead;
 803                 if (packet->auth)
 804                         maxsize -= SCTP_PAD4(packet->auth->skb->len);
 805                 if (chunk_len > maxsize)
 806                         retval = SCTP_XMIT_PMTU_FULL;
 807
 808                 /* It is also okay to fragment if the chunk we are
 809                  * adding is a control chunk, but only if current packet
 810                  * is not a GSO one otherwise it causes fragmentation of
 811                  * a large frame. So in this case we allow the
 812                  * fragmentation by forcing it to be in a new packet.
 813                  */
 814                 if (!sctp_chunk_is_data(chunk) && packet->has_data)
 815                         retval = SCTP_XMIT_PMTU_FULL;
 816
 817                 if (psize + chunk_len > packet->max_size)
 818                         /* Hit GSO/PMTU limit, gotta flush */
 819                         retval = SCTP_XMIT_PMTU_FULL;
 820
 821                 if (!packet->transport->burst_limited &&
 822                     psize + chunk_len > (packet->transport->cwnd >> 1))
 823                         /* Do not allow a single GSO packet to use more
 824                          * than half of cwnd.
 825                          */
 826                         retval = SCTP_XMIT_PMTU_FULL;
 827
 828                 if (packet->transport->burst_limited &&
 829                     psize + chunk_len > (packet->transport->burst_limited >> 1))
 830                         /* Do not allow a single GSO packet to use more
 831                          * than half of original cwnd.
 832                          */
 833                         retval = SCTP_XMIT_PMTU_FULL;
 834                 /* Otherwise it will fit in the GSO packet */
 835         }
 836
 837 out:
 838         return retval;
 839 }