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 void sctp_packet_config(struct sctp_packet *packet, __u32 vtag,
  85                         int ecn_capable)
  86 {
  87         struct sctp_transport *tp = packet->transport;
  88         struct sctp_association *asoc = tp->asoc;
  89
  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
 128 /* Initialize the packet structure. */
 129 void sctp_packet_init(struct sctp_packet *packet,
 130                       struct sctp_transport *transport,
 131                       __u16 sport, __u16 dport)
 132 {
 133         struct sctp_association *asoc = transport->asoc;
 134         size_t overhead;
 135
 136         pr_debug("%s: packet:%p transport:%p\n", __func__, packet, transport);
 137
 138         packet->transport = transport;
 139         packet->source_port = sport;
 140         packet->destination_port = dport;
 141         INIT_LIST_HEAD(&packet->chunk_list);
 142         if (asoc) {
 143                 struct sctp_sock *sp = sctp_sk(asoc->base.sk);
 144                 overhead = sp->pf->af->net_header_len;
 145         } else {
 146                 overhead = sizeof(struct ipv6hdr);
 147         }
 148         overhead += sizeof(struct sctphdr);
 149         packet->overhead = overhead;
 150         sctp_packet_reset(packet);
 151         packet->vtag = 0;
 152 }
 153
 154 /* Free a packet.  */
 155 void sctp_packet_free(struct sctp_packet *packet)
 156 {
 157         struct sctp_chunk *chunk, *tmp;
 158
 159         pr_debug("%s: packet:%p\n", __func__, packet);
 160
 161         list_for_each_entry_safe(chunk, tmp, &packet->chunk_list, list) {
 162                 list_del_init(&chunk->list);
 163                 sctp_chunk_free(chunk);
 164         }
 165 }
 166
 167 /* This routine tries to append the chunk to the offered packet. If adding
 168  * the chunk causes the packet to exceed the path MTU and COOKIE_ECHO chunk
 169  * is not present in the packet, it transmits the input packet.
 170  * Data can be bundled with a packet containing a COOKIE_ECHO chunk as long
 171  * as it can fit in the packet, but any more data that does not fit in this
 172  * packet can be sent only after receiving the COOKIE_ACK.
 173  */
 174 sctp_xmit_t sctp_packet_transmit_chunk(struct sctp_packet *packet,
 175                                        struct sctp_chunk *chunk,
 176                                        int one_packet, gfp_t gfp)
 177 {
 178         sctp_xmit_t retval;
 179
 180         pr_debug("%s: packet:%p size:%zu chunk:%p size:%d\n", __func__,
 181                  packet, packet->size, chunk, chunk->skb ? chunk->skb->len : -1);
 182
 183         switch ((retval = (sctp_packet_append_chunk(packet, chunk)))) {
 184         case SCTP_XMIT_PMTU_FULL:
 185                 if (!packet->has_cookie_echo) {
 186                         int error = 0;
 187
 188                         error = sctp_packet_transmit(packet, gfp);
 189                         if (error < 0)
 190                                 chunk->skb->sk->sk_err = -error;
 191
 192                         /* If we have an empty packet, then we can NOT ever
 193                          * return PMTU_FULL.
 194                          */
 195                         if (!one_packet)
 196                                 retval = sctp_packet_append_chunk(packet,
 197                                                                   chunk);
 198                 }
 199                 break;
 200
 201         case SCTP_XMIT_RWND_FULL:
 202         case SCTP_XMIT_OK:
 203         case SCTP_XMIT_DELAY:
 204                 break;
 205         }
 206
 207         return retval;
 208 }
 209
 210 /* Try to bundle an auth chunk into the packet. */
 211 static sctp_xmit_t sctp_packet_bundle_auth(struct sctp_packet *pkt,
 212                                            struct sctp_chunk *chunk)
 213 {
 214         struct sctp_association *asoc = pkt->transport->asoc;
 215         struct sctp_chunk *auth;
 216         sctp_xmit_t retval = SCTP_XMIT_OK;
 217
 218         /* if we don't have an association, we can't do authentication */
 219         if (!asoc)
 220                 return retval;
 221
 222         /* See if this is an auth chunk we are bundling or if
 223          * auth is already bundled.
 224          */
 225         if (chunk->chunk_hdr->type == SCTP_CID_AUTH || pkt->has_auth)
 226                 return retval;
 227
 228         /* if the peer did not request this chunk to be authenticated,
 229          * don't do it
 230          */
 231         if (!chunk->auth)
 232                 return retval;
 233
 234         auth = sctp_make_auth(asoc);
 235         if (!auth)
 236                 return retval;
 237
 238         retval = __sctp_packet_append_chunk(pkt, auth);
 239
 240         if (retval != SCTP_XMIT_OK)
 241                 sctp_chunk_free(auth);
 242
 243         return retval;
 244 }
 245
 246 /* Try to bundle a SACK with the packet. */
 247 static sctp_xmit_t sctp_packet_bundle_sack(struct sctp_packet *pkt,
 248                                            struct sctp_chunk *chunk)
 249 {
 250         sctp_xmit_t retval = SCTP_XMIT_OK;
 251
 252         /* If sending DATA and haven't aleady bundled a SACK, try to
 253          * bundle one in to the packet.
 254          */
 255         if (sctp_chunk_is_data(chunk) && !pkt->has_sack &&
 256             !pkt->has_cookie_echo) {
 257                 struct sctp_association *asoc;
 258                 struct timer_list *timer;
 259                 asoc = pkt->transport->asoc;
 260                 timer = &asoc->timers[SCTP_EVENT_TIMEOUT_SACK];
 261
 262                 /* If the SACK timer is running, we have a pending SACK */
 263                 if (timer_pending(timer)) {
 264                         struct sctp_chunk *sack;
 265
 266                         if (pkt->transport->sack_generation !=
 267                             pkt->transport->asoc->peer.sack_generation)
 268                                 return retval;
 269
 270                         asoc->a_rwnd = asoc->rwnd;
 271                         sack = sctp_make_sack(asoc);
 272                         if (sack) {
 273                                 retval = __sctp_packet_append_chunk(pkt, sack);
 274                                 if (retval != SCTP_XMIT_OK) {
 275                                         sctp_chunk_free(sack);
 276                                         goto out;
 277                                 }
 278                                 asoc->peer.sack_needed = 0;
 279                                 if (del_timer(timer))
 280                                         sctp_association_put(asoc);
 281                         }
 282                 }
 283         }
 284 out:
 285         return retval;
 286 }
 287
 288
 289 /* Append a chunk to the offered packet reporting back any inability to do
 290  * so.
 291  */
 292 static sctp_xmit_t __sctp_packet_append_chunk(struct sctp_packet *packet,
 293                                               struct sctp_chunk *chunk)
 294 {
 295         sctp_xmit_t retval = SCTP_XMIT_OK;
 296         __u16 chunk_len = SCTP_PAD4(ntohs(chunk->chunk_hdr->length));
 297
 298         /* Check to see if this chunk will fit into the packet */
 299         retval = sctp_packet_will_fit(packet, chunk, chunk_len);
 300         if (retval != SCTP_XMIT_OK)
 301                 goto finish;
 302
 303         /* We believe that this chunk is OK to add to the packet */
 304         switch (chunk->chunk_hdr->type) {
 305         case SCTP_CID_DATA:
 306                 /* Account for the data being in the packet */
 307                 sctp_packet_append_data(packet, chunk);
 308                 /* Disallow SACK bundling after DATA. */
 309                 packet->has_sack = 1;
 310                 /* Disallow AUTH bundling after DATA */
 311                 packet->has_auth = 1;
 312                 /* Let it be knows that packet has DATA in it */
 313                 packet->has_data = 1;
 314                 /* timestamp the chunk for rtx purposes */
 315                 chunk->sent_at = jiffies;
 316                 /* Mainly used for prsctp RTX policy */
 317                 chunk->sent_count++;
 318                 break;
 319         case SCTP_CID_COOKIE_ECHO:
 320                 packet->has_cookie_echo = 1;
 321                 break;
 322
 323         case SCTP_CID_SACK:
 324                 packet->has_sack = 1;
 325                 if (chunk->asoc)
 326                         chunk->asoc->stats.osacks++;
 327                 break;
 328
 329         case SCTP_CID_AUTH:
 330                 packet->has_auth = 1;
 331                 packet->auth = chunk;
 332                 break;
 333         }
 334
 335         /* It is OK to send this chunk.  */
 336         list_add_tail(&chunk->list, &packet->chunk_list);
 337         packet->size += chunk_len;
 338         chunk->transport = packet->transport;
 339 finish:
 340         return retval;
 341 }
 342
 343 /* Append a chunk to the offered packet reporting back any inability to do
 344  * so.
 345  */
 346 sctp_xmit_t sctp_packet_append_chunk(struct sctp_packet *packet,
 347                                      struct sctp_chunk *chunk)
 348 {
 349         sctp_xmit_t retval = SCTP_XMIT_OK;
 350
 351         pr_debug("%s: packet:%p chunk:%p\n", __func__, packet, chunk);
 352
 353         /* Data chunks are special.  Before seeing what else we can
 354          * bundle into this packet, check to see if we are allowed to
 355          * send this DATA.
 356          */
 357         if (sctp_chunk_is_data(chunk)) {
 358                 retval = sctp_packet_can_append_data(packet, chunk);
 359                 if (retval != SCTP_XMIT_OK)
 360                         goto finish;
 361         }
 362
 363         /* Try to bundle AUTH chunk */
 364         retval = sctp_packet_bundle_auth(packet, chunk);
 365         if (retval != SCTP_XMIT_OK)
 366                 goto finish;
 367
 368         /* Try to bundle SACK chunk */
 369         retval = sctp_packet_bundle_sack(packet, chunk);
 370         if (retval != SCTP_XMIT_OK)
 371                 goto finish;
 372
 373         retval = __sctp_packet_append_chunk(packet, chunk);
 374
 375 finish:
 376         return retval;
 377 }
 378
 379 static void sctp_packet_release_owner(struct sk_buff *skb)
 380 {
 381         sk_free(skb->sk);
 382 }
 383
 384 static void sctp_packet_set_owner_w(struct sk_buff *skb, struct sock *sk)
 385 {
 386         skb_orphan(skb);
 387         skb->sk = sk;
 388         skb->destructor = sctp_packet_release_owner;
 389
 390         /*
 391          * The data chunks have already been accounted for in sctp_sendmsg(),
 392          * therefore only reserve a single byte to keep socket around until
 393          * the packet has been transmitted.
 394          */
 395         atomic_inc(&sk->sk_wmem_alloc);
 396 }
 397
 398 static int sctp_packet_pack(struct sctp_packet *packet,
 399                             struct sk_buff *head, int gso, gfp_t gfp)
 400 {
 401         struct sctp_transport *tp = packet->transport;
 402         struct sctp_auth_chunk *auth = NULL;
 403         struct sctp_chunk *chunk, *tmp;
 404         int pkt_count = 0, pkt_size;
 405         struct sock *sk = head->sk;
 406         struct sk_buff *nskb;
 407         int auth_len = 0;
 408
 409         if (gso) {
 410                 skb_shinfo(head)->gso_type = sk->sk_gso_type;
 411                 NAPI_GRO_CB(head)->last = head;
 412         } else {
 413                 nskb = head;
 414                 pkt_size = packet->size;
 415                 goto merge;
 416         }
 417
 418         do {
 419                 /* calculate the pkt_size and alloc nskb */
 420                 pkt_size = packet->overhead;
 421                 list_for_each_entry_safe(chunk, tmp, &packet->chunk_list,
 422                                          list) {
 423                         int padded = SCTP_PAD4(chunk->skb->len);
 424
 425                         if (chunk == packet->auth)
 426                                 auth_len = padded;
 427                         else if (auth_len + padded + packet->overhead >
 428                                  tp->pathmtu)
 429                                 return 0;
 430                         else if (pkt_size + padded > tp->pathmtu)
 431                                 break;
 432                         pkt_size += padded;
 433                 }
 434                 nskb = alloc_skb(pkt_size + MAX_HEADER, gfp);
 435                 if (!nskb)
 436                         return 0;
 437                 skb_reserve(nskb, packet->overhead + MAX_HEADER);
 438
 439 merge:
 440                 /* merge chunks into nskb and append nskb into head list */
 441                 pkt_size -= packet->overhead;
 442                 list_for_each_entry_safe(chunk, tmp, &packet->chunk_list, list) {
 443                         int padding;
 444
 445                         list_del_init(&chunk->list);
 446                         if (sctp_chunk_is_data(chunk)) {
 447                                 if (!sctp_chunk_retransmitted(chunk) &&
 448                                     !tp->rto_pending) {
 449                                         chunk->rtt_in_progress = 1;
 450                                         tp->rto_pending = 1;
 451                                 }
 452                         }
 453
 454                         padding = SCTP_PAD4(chunk->skb->len) - chunk->skb->len;
 455                         if (padding)
 456                                 memset(skb_put(chunk->skb, padding), 0, padding);
 457
 458                         if (chunk == packet->auth)
 459                                 auth = (struct sctp_auth_chunk *)
 460                                                         skb_tail_pointer(nskb);
 461
 462                         memcpy(skb_put(nskb, chunk->skb->len), chunk->skb->data,
 463                                chunk->skb->len);
 464
 465                         pr_debug("*** Chunk:%p[%s] %s 0x%x, length:%d, chunk->skb->len:%d, rtt_in_progress:%d\n",
 466                                  chunk,
 467                                  sctp_cname(SCTP_ST_CHUNK(chunk->chunk_hdr->type)),
 468                                  chunk->has_tsn ? "TSN" : "No TSN",
 469                                  chunk->has_tsn ? ntohl(chunk->subh.data_hdr->tsn) : 0,
 470                                  ntohs(chunk->chunk_hdr->length), chunk->skb->len,
 471                                  chunk->rtt_in_progress);
 472
 473                         pkt_size -= SCTP_PAD4(chunk->skb->len);
 474
 475                         if (!sctp_chunk_is_data(chunk) && chunk != packet->auth)
 476                                 sctp_chunk_free(chunk);
 477
 478                         if (!pkt_size)
 479                                 break;
 480                 }
 481
 482                 if (auth) {
 483                         sctp_auth_calculate_hmac(tp->asoc, nskb, auth, gfp);
 484                         /* free auth if no more chunks, or add it back */
 485                         if (list_empty(&packet->chunk_list))
 486                                 sctp_chunk_free(packet->auth);
 487                         else
 488                                 list_add(&packet->auth->list,
 489                                          &packet->chunk_list);
 490                 }
 491
 492                 if (gso) {
 493                         if (skb_gro_receive(&head, nskb)) {
 494                                 kfree_skb(nskb);
 495                                 return 0;
 496                         }
 497                         if (WARN_ON_ONCE(skb_shinfo(head)->gso_segs >=
 498                                          sk->sk_gso_max_segs))
 499                                 return 0;
 500                 }
 501
 502                 pkt_count++;
 503         } while (!list_empty(&packet->chunk_list));
 504
 505         if (gso) {
 506                 memset(head->cb, 0, max(sizeof(struct inet_skb_parm),
 507                                         sizeof(struct inet6_skb_parm)));
 508                 skb_shinfo(head)->gso_segs = pkt_count;
 509                 skb_shinfo(head)->gso_size = GSO_BY_FRAGS;
 510                 rcu_read_lock();
 511                 if (skb_dst(head) != tp->dst) {
 512                         dst_hold(tp->dst);
 513                         sk_setup_caps(sk, tp->dst);
 514                 }
 515                 rcu_read_unlock();
 516                 goto chksum;
 517         }
 518
 519         if (sctp_checksum_disable)
 520                 return 1;
 521
 522         if (!(skb_dst(head)->dev->features & NETIF_F_SCTP_CRC) ||
 523             dst_xfrm(skb_dst(head)) || packet->ipfragok) {
 524                 struct sctphdr *sh =
 525                         (struct sctphdr *)skb_transport_header(head);
 526
 527                 sh->checksum = sctp_compute_cksum(head, 0);
 528         } else {
 529 chksum:
 530                 head->ip_summed = CHECKSUM_PARTIAL;
 531                 head->csum_start = skb_transport_header(head) - head->head;
 532                 head->csum_offset = offsetof(struct sctphdr, checksum);
 533         }
 534
 535         return pkt_count;
 536 }
 537
 538 /* All packets are sent to the network through this function from
 539  * sctp_outq_tail().
 540  *
 541  * The return value is always 0 for now.
 542  */
 543 int sctp_packet_transmit(struct sctp_packet *packet, gfp_t gfp)
 544 {
 545         struct sctp_transport *tp = packet->transport;
 546         struct sctp_association *asoc = tp->asoc;
 547         struct sctp_chunk *chunk, *tmp;
 548         int pkt_count, gso = 0;
 549         struct dst_entry *dst;
 550         struct sk_buff *head;
 551         struct sctphdr *sh;
 552         struct sock *sk;
 553
 554         pr_debug("%s: packet:%p\n", __func__, packet);
 555         if (list_empty(&packet->chunk_list))
 556                 return 0;
 557         chunk = list_entry(packet->chunk_list.next, struct sctp_chunk, list);
 558         sk = chunk->skb->sk;
 559
 560         /* check gso */
 561         if (packet->size > tp->pathmtu && !packet->ipfragok) {
 562                 if (!sk_can_gso(sk)) {
 563                         pr_err_once("Trying to GSO but underlying device doesn't support it.");
 564                         goto out;
 565                 }
 566                 gso = 1;
 567         }
 568
 569         /* alloc head skb */
 570         head = alloc_skb((gso ? packet->overhead : packet->size) +
 571                          MAX_HEADER, gfp);
 572         if (!head)
 573                 goto out;
 574         skb_reserve(head, packet->overhead + MAX_HEADER);
 575         sctp_packet_set_owner_w(head, sk);
 576
 577         /* set sctp header */
 578         sh = (struct sctphdr *)skb_push(head, sizeof(struct sctphdr));
 579         skb_reset_transport_header(head);
 580         sh->source = htons(packet->source_port);
 581         sh->dest = htons(packet->destination_port);
 582         sh->vtag = htonl(packet->vtag);
 583         sh->checksum = 0;
 584
 585         /* update dst if in need */
 586         if (!sctp_transport_dst_check(tp)) {
 587                 sctp_transport_route(tp, NULL, sctp_sk(sk));
 588                 if (asoc && asoc->param_flags & SPP_PMTUD_ENABLE)
 589                         sctp_assoc_sync_pmtu(sk, asoc);
 590         }
 591         dst = dst_clone(tp->dst);
 592         if (!dst) {
 593                 IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTNOROUTES);
 594                 kfree_skb(head);
 595                 goto out;
 596         }
 597         skb_dst_set(head, dst);
 598
 599         /* pack up chunks */
 600         pkt_count = sctp_packet_pack(packet, head, gso, gfp);
 601         if (!pkt_count) {
 602                 kfree_skb(head);
 603                 goto out;
 604         }
 605         pr_debug("***sctp_transmit_packet*** skb->len:%d\n", head->len);
 606
 607         /* start autoclose timer */
 608         if (packet->has_data && sctp_state(asoc, ESTABLISHED) &&
 609             asoc->timeouts[SCTP_EVENT_TIMEOUT_AUTOCLOSE]) {
 610                 struct timer_list *timer =
 611                         &asoc->timers[SCTP_EVENT_TIMEOUT_AUTOCLOSE];
 612                 unsigned long timeout =
 613                         asoc->timeouts[SCTP_EVENT_TIMEOUT_AUTOCLOSE];
 614
 615                 if (!mod_timer(timer, jiffies + timeout))
 616                         sctp_association_hold(asoc);
 617         }
 618
 619         /* sctp xmit */
 620         tp->af_specific->ecn_capable(sk);
 621         if (asoc) {
 622                 asoc->stats.opackets += pkt_count;
 623                 if (asoc->peer.last_sent_to != tp)
 624                         asoc->peer.last_sent_to = tp;
 625         }
 626         head->ignore_df = packet->ipfragok;
 627         if (tp->dst_pending_confirm)
 628                 skb_set_dst_pending_confirm(head, 1);
 629         /* neighbour should be confirmed on successful transmission or
 630          * positive error
 631          */
 632         if (tp->af_specific->sctp_xmit(head, tp) >= 0 &&
 633             tp->dst_pending_confirm)
 634                 tp->dst_pending_confirm = 0;
 635
 636 out:
 637         list_for_each_entry_safe(chunk, tmp, &packet->chunk_list, list) {
 638                 list_del_init(&chunk->list);
 639                 if (!sctp_chunk_is_data(chunk))
 640                         sctp_chunk_free(chunk);
 641         }
 642         sctp_packet_reset(packet);
 643         return 0;
 644 }
 645
 646 /********************************************************************
 647  * 2nd Level Abstractions
 648  ********************************************************************/
 649
 650 /* This private function check to see if a chunk can be added */
 651 static sctp_xmit_t sctp_packet_can_append_data(struct sctp_packet *packet,
 652                                            struct sctp_chunk *chunk)
 653 {
 654         size_t datasize, rwnd, inflight, flight_size;
 655         struct sctp_transport *transport = packet->transport;
 656         struct sctp_association *asoc = transport->asoc;
 657         struct sctp_outq *q = &asoc->outqueue;
 658
 659         /* RFC 2960 6.1  Transmission of DATA Chunks
 660          *
 661          * A) At any given time, the data sender MUST NOT transmit new data to
 662          * any destination transport address if its peer's rwnd indicates
 663          * that the peer has no buffer space (i.e. rwnd is 0, see Section
 664          * 6.2.1).  However, regardless of the value of rwnd (including if it
 665          * is 0), the data sender can always have one DATA chunk in flight to
 666          * the receiver if allowed by cwnd (see rule B below).  This rule
 667          * allows the sender to probe for a change in rwnd that the sender
 668          * missed due to the SACK having been lost in transit from the data
 669          * receiver to the data sender.
 670          */
 671
 672         rwnd = asoc->peer.rwnd;
 673         inflight = q->outstanding_bytes;
 674         flight_size = transport->flight_size;
 675
 676         datasize = sctp_data_size(chunk);
 677
 678         if (datasize > rwnd && inflight > 0)
 679                 /* We have (at least) one data chunk in flight,
 680                  * so we can't fall back to rule 6.1 B).
 681                  */
 682                 return SCTP_XMIT_RWND_FULL;
 683
 684         /* RFC 2960 6.1  Transmission of DATA Chunks
 685          *
 686          * B) At any given time, the sender MUST NOT transmit new data
 687          * to a given transport address if it has cwnd or more bytes
 688          * of data outstanding to that transport address.
 689          */
 690         /* RFC 7.2.4 & the Implementers Guide 2.8.
 691          *
 692          * 3) ...
 693          *    When a Fast Retransmit is being performed the sender SHOULD
 694          *    ignore the value of cwnd and SHOULD NOT delay retransmission.
 695          */
 696         if (chunk->fast_retransmit != SCTP_NEED_FRTX &&
 697             flight_size >= transport->cwnd)
 698                 return SCTP_XMIT_RWND_FULL;
 699
 700         /* Nagle's algorithm to solve small-packet problem:
 701          * Inhibit the sending of new chunks when new outgoing data arrives
 702          * if any previously transmitted data on the connection remains
 703          * unacknowledged.
 704          */
 705
 706         if ((sctp_sk(asoc->base.sk)->nodelay || inflight == 0) &&
 707             !chunk->msg->force_delay)
 708                 /* Nothing unacked */
 709                 return SCTP_XMIT_OK;
 710
 711         if (!sctp_packet_empty(packet))
 712                 /* Append to packet */
 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 }