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 <linux-sctp@vger.kernel.org>
  29  *
  30  * Written or modified by:
  31  *    La Monte H.P. Yarroll <piggy@acm.org>
  32  *    Karl Knutson          <karl@athena.chicago.il.us>
  33  *    Jon Grimm             <jgrimm@austin.ibm.com>
  34  *    Sridhar Samudrala     <sri@us.ibm.com>
  35  */
  36
  37 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  38
  39 #include <linux/types.h>
  40 #include <linux/kernel.h>
  41 #include <linux/wait.h>
  42 #include <linux/time.h>
  43 #include <linux/ip.h>
  44 #include <linux/ipv6.h>
  45 #include <linux/init.h>
  46 #include <linux/slab.h>
  47 #include <net/inet_ecn.h>
  48 #include <net/ip.h>
  49 #include <net/icmp.h>
  50 #include <net/net_namespace.h>
  51
  52 #include <linux/socket.h> /* for sa_family_t */
  53 #include <net/sock.h>
  54
  55 #include <net/sctp/sctp.h>
  56 #include <net/sctp/sm.h>
  57 #include <net/sctp/checksum.h>
  58
  59 /* Forward declarations for private helpers. */
  60 static enum sctp_xmit __sctp_packet_append_chunk(struct sctp_packet *packet,
  61                                                  struct sctp_chunk *chunk);
  62 static enum sctp_xmit sctp_packet_can_append_data(struct sctp_packet *packet,
  63                                                   struct sctp_chunk *chunk);
  64 static void sctp_packet_append_data(struct sctp_packet *packet,
  65                                     struct sctp_chunk *chunk);
  66 static enum sctp_xmit sctp_packet_will_fit(struct sctp_packet *packet,
  67                                            struct sctp_chunk *chunk,
  68                                            u16 chunk_len);
  69
  70 static void sctp_packet_reset(struct sctp_packet *packet)
  71 {
  72         /* sctp_packet_transmit() relies on this to reset size to the
  73          * current overhead after sending packets.
  74          */
  75         packet->size = packet->overhead;
  76
  77         packet->has_cookie_echo = 0;
  78         packet->has_sack = 0;
  79         packet->has_data = 0;
  80         packet->has_auth = 0;
  81         packet->ipfragok = 0;
  82         packet->auth = NULL;
  83 }
  84
  85 /* Config a packet.
  86  * This appears to be a followup set of initializations.
  87  */
  88 void sctp_packet_config(struct sctp_packet *packet, __u32 vtag,
  89                         int ecn_capable)
  90 {
  91         struct sctp_transport *tp = packet->transport;
  92         struct sctp_association *asoc = tp->asoc;
  93         struct sctp_sock *sp = NULL;
  94         struct sock *sk;
  95
  96         pr_debug("%s: packet:%p vtag:0x%x\n", __func__, packet, vtag);
  97         packet->vtag = vtag;
  98
  99         /* do the following jobs only once for a flush schedule */
 100         if (!sctp_packet_empty(packet))
 101                 return;
 102
 103         /* set packet max_size with pathmtu, then calculate overhead */
 104         packet->max_size = tp->pathmtu;
 105
 106         if (asoc) {
 107                 sk = asoc->base.sk;
 108                 sp = sctp_sk(sk);
 109         }
 110         packet->overhead = sctp_mtu_payload(sp, 0, 0);
 111         packet->size = packet->overhead;
 112
 113         if (!asoc)
 114                 return;
 115
 116         /* update dst or transport pathmtu if in need */
 117         if (!sctp_transport_dst_check(tp)) {
 118                 sctp_transport_route(tp, NULL, sp);
 119                 if (asoc->param_flags & SPP_PMTUD_ENABLE)
 120                         sctp_assoc_sync_pmtu(asoc);
 121         } else if (!sctp_transport_pmtu_check(tp)) {
 122                 if (asoc->param_flags & SPP_PMTUD_ENABLE)
 123                         sctp_assoc_sync_pmtu(asoc);
 124         }
 125
 126         if (asoc->pmtu_pending) {
 127                 if (asoc->param_flags & SPP_PMTUD_ENABLE)
 128                         sctp_assoc_sync_pmtu(asoc);
 129                 asoc->pmtu_pending = 0;
 130         }
 131
 132         /* If there a is a prepend chunk stick it on the list before
 133          * any other chunks get appended.
 134          */
 135         if (ecn_capable) {
 136                 struct sctp_chunk *chunk = sctp_get_ecne_prepend(asoc);
 137
 138                 if (chunk)
 139                         sctp_packet_append_chunk(packet, chunk);
 140         }
 141
 142         if (!tp->dst)
 143                 return;
 144
 145         /* set packet max_size with gso_max_size if gso is enabled*/
 146         rcu_read_lock();
 147         if (__sk_dst_get(sk) != tp->dst) {
 148                 dst_hold(tp->dst);
 149                 sk_setup_caps(sk, tp->dst);
 150         }
 151         packet->max_size = sk_can_gso(sk) ? tp->dst->dev->gso_max_size
 152                                           : asoc->pathmtu;
 153         rcu_read_unlock();
 154 }
 155
 156 /* Initialize the packet structure. */
 157 void sctp_packet_init(struct sctp_packet *packet,
 158                       struct sctp_transport *transport,
 159                       __u16 sport, __u16 dport)
 160 {
 161         pr_debug("%s: packet:%p transport:%p\n", __func__, packet, transport);
 162
 163         packet->transport = transport;
 164         packet->source_port = sport;
 165         packet->destination_port = dport;
 166         INIT_LIST_HEAD(&packet->chunk_list);
 167         /* The overhead will be calculated by sctp_packet_config() */
 168         packet->overhead = 0;
 169         sctp_packet_reset(packet);
 170         packet->vtag = 0;
 171 }
 172
 173 /* Free a packet.  */
 174 void sctp_packet_free(struct sctp_packet *packet)
 175 {
 176         struct sctp_chunk *chunk, *tmp;
 177
 178         pr_debug("%s: packet:%p\n", __func__, packet);
 179
 180         list_for_each_entry_safe(chunk, tmp, &packet->chunk_list, list) {
 181                 list_del_init(&chunk->list);
 182                 sctp_chunk_free(chunk);
 183         }
 184 }
 185
 186 /* This routine tries to append the chunk to the offered packet. If adding
 187  * the chunk causes the packet to exceed the path MTU and COOKIE_ECHO chunk
 188  * is not present in the packet, it transmits the input packet.
 189  * Data can be bundled with a packet containing a COOKIE_ECHO chunk as long
 190  * as it can fit in the packet, but any more data that does not fit in this
 191  * packet can be sent only after receiving the COOKIE_ACK.
 192  */
 193 enum sctp_xmit sctp_packet_transmit_chunk(struct sctp_packet *packet,
 194                                           struct sctp_chunk *chunk,
 195                                           int one_packet, gfp_t gfp)
 196 {
 197         enum sctp_xmit retval;
 198
 199         pr_debug("%s: packet:%p size:%zu chunk:%p size:%d\n", __func__,
 200                  packet, packet->size, chunk, chunk->skb ? chunk->skb->len : -1);
 201
 202         switch ((retval = (sctp_packet_append_chunk(packet, chunk)))) {
 203         case SCTP_XMIT_PMTU_FULL:
 204                 if (!packet->has_cookie_echo) {
 205                         int error = 0;
 206
 207                         error = sctp_packet_transmit(packet, gfp);
 208                         if (error < 0)
 209                                 chunk->skb->sk->sk_err = -error;
 210
 211                         /* If we have an empty packet, then we can NOT ever
 212                          * return PMTU_FULL.
 213                          */
 214                         if (!one_packet)
 215                                 retval = sctp_packet_append_chunk(packet,
 216                                                                   chunk);
 217                 }
 218                 break;
 219
 220         case SCTP_XMIT_RWND_FULL:
 221         case SCTP_XMIT_OK:
 222         case SCTP_XMIT_DELAY:
 223                 break;
 224         }
 225
 226         return retval;
 227 }
 228
 229 /* Try to bundle an auth chunk into the packet. */
 230 static enum sctp_xmit sctp_packet_bundle_auth(struct sctp_packet *pkt,
 231                                               struct sctp_chunk *chunk)
 232 {
 233         struct sctp_association *asoc = pkt->transport->asoc;
 234         enum sctp_xmit retval = SCTP_XMIT_OK;
 235         struct sctp_chunk *auth;
 236
 237         /* if we don't have an association, we can't do authentication */
 238         if (!asoc)
 239                 return retval;
 240
 241         /* See if this is an auth chunk we are bundling or if
 242          * auth is already bundled.
 243          */
 244         if (chunk->chunk_hdr->type == SCTP_CID_AUTH || pkt->has_auth)
 245                 return retval;
 246
 247         /* if the peer did not request this chunk to be authenticated,
 248          * don't do it
 249          */
 250         if (!chunk->auth)
 251                 return retval;
 252
 253         auth = sctp_make_auth(asoc, chunk->shkey->key_id);
 254         if (!auth)
 255                 return retval;
 256
 257         auth->shkey = chunk->shkey;
 258         sctp_auth_shkey_hold(auth->shkey);
 259
 260         retval = __sctp_packet_append_chunk(pkt, auth);
 261
 262         if (retval != SCTP_XMIT_OK)
 263                 sctp_chunk_free(auth);
 264
 265         return retval;
 266 }
 267
 268 /* Try to bundle a SACK with the packet. */
 269 static enum sctp_xmit sctp_packet_bundle_sack(struct sctp_packet *pkt,
 270                                               struct sctp_chunk *chunk)
 271 {
 272         enum sctp_xmit retval = SCTP_XMIT_OK;
 273
 274         /* If sending DATA and haven't aleady bundled a SACK, try to
 275          * bundle one in to the packet.
 276          */
 277         if (sctp_chunk_is_data(chunk) && !pkt->has_sack &&
 278             !pkt->has_cookie_echo) {
 279                 struct sctp_association *asoc;
 280                 struct timer_list *timer;
 281                 asoc = pkt->transport->asoc;
 282                 timer = &asoc->timers[SCTP_EVENT_TIMEOUT_SACK];
 283
 284                 /* If the SACK timer is running, we have a pending SACK */
 285                 if (timer_pending(timer)) {
 286                         struct sctp_chunk *sack;
 287
 288                         if (pkt->transport->sack_generation !=
 289                             pkt->transport->asoc->peer.sack_generation)
 290                                 return retval;
 291
 292                         asoc->a_rwnd = asoc->rwnd;
 293                         sack = sctp_make_sack(asoc);
 294                         if (sack) {
 295                                 retval = __sctp_packet_append_chunk(pkt, sack);
 296                                 if (retval != SCTP_XMIT_OK) {
 297                                         sctp_chunk_free(sack);
 298                                         goto out;
 299                                 }
 300                                 asoc->peer.sack_needed = 0;
 301                                 if (del_timer(timer))
 302                                         sctp_association_put(asoc);
 303                         }
 304                 }
 305         }
 306 out:
 307         return retval;
 308 }
 309
 310
 311 /* Append a chunk to the offered packet reporting back any inability to do
 312  * so.
 313  */
 314 static enum sctp_xmit __sctp_packet_append_chunk(struct sctp_packet *packet,
 315                                                  struct sctp_chunk *chunk)
 316 {
 317         __u16 chunk_len = SCTP_PAD4(ntohs(chunk->chunk_hdr->length));
 318         enum sctp_xmit retval = SCTP_XMIT_OK;
 319
 320         /* Check to see if this chunk will fit into the packet */
 321         retval = sctp_packet_will_fit(packet, chunk, chunk_len);
 322         if (retval != SCTP_XMIT_OK)
 323                 goto finish;
 324
 325         /* We believe that this chunk is OK to add to the packet */
 326         switch (chunk->chunk_hdr->type) {
 327         case SCTP_CID_DATA:
 328         case SCTP_CID_I_DATA:
 329                 /* Account for the data being in the packet */
 330                 sctp_packet_append_data(packet, chunk);
 331                 /* Disallow SACK bundling after DATA. */
 332                 packet->has_sack = 1;
 333                 /* Disallow AUTH bundling after DATA */
 334                 packet->has_auth = 1;
 335                 /* Let it be knows that packet has DATA in it */
 336                 packet->has_data = 1;
 337                 /* timestamp the chunk for rtx purposes */
 338                 chunk->sent_at = jiffies;
 339                 /* Mainly used for prsctp RTX policy */
 340                 chunk->sent_count++;
 341                 break;
 342         case SCTP_CID_COOKIE_ECHO:
 343                 packet->has_cookie_echo = 1;
 344                 break;
 345
 346         case SCTP_CID_SACK:
 347                 packet->has_sack = 1;
 348                 if (chunk->asoc)
 349                         chunk->asoc->stats.osacks++;
 350                 break;
 351
 352         case SCTP_CID_AUTH:
 353                 packet->has_auth = 1;
 354                 packet->auth = chunk;
 355                 break;
 356         }
 357
 358         /* It is OK to send this chunk.  */
 359         list_add_tail(&chunk->list, &packet->chunk_list);
 360         packet->size += chunk_len;
 361         chunk->transport = packet->transport;
 362 finish:
 363         return retval;
 364 }
 365
 366 /* Append a chunk to the offered packet reporting back any inability to do
 367  * so.
 368  */
 369 enum sctp_xmit sctp_packet_append_chunk(struct sctp_packet *packet,
 370                                         struct sctp_chunk *chunk)
 371 {
 372         enum sctp_xmit retval = SCTP_XMIT_OK;
 373
 374         pr_debug("%s: packet:%p chunk:%p\n", __func__, packet, chunk);
 375
 376         /* Data chunks are special.  Before seeing what else we can
 377          * bundle into this packet, check to see if we are allowed to
 378          * send this DATA.
 379          */
 380         if (sctp_chunk_is_data(chunk)) {
 381                 retval = sctp_packet_can_append_data(packet, chunk);
 382                 if (retval != SCTP_XMIT_OK)
 383                         goto finish;
 384         }
 385
 386         /* Try to bundle AUTH chunk */
 387         retval = sctp_packet_bundle_auth(packet, chunk);
 388         if (retval != SCTP_XMIT_OK)
 389                 goto finish;
 390
 391         /* Try to bundle SACK chunk */
 392         retval = sctp_packet_bundle_sack(packet, chunk);
 393         if (retval != SCTP_XMIT_OK)
 394                 goto finish;
 395
 396         retval = __sctp_packet_append_chunk(packet, chunk);
 397
 398 finish:
 399         return retval;
 400 }
 401
 402 static void sctp_packet_gso_append(struct sk_buff *head, struct sk_buff *skb)
 403 {
 404         if (SCTP_OUTPUT_CB(head)->last == head)
 405                 skb_shinfo(head)->frag_list = skb;
 406         else
 407                 SCTP_OUTPUT_CB(head)->last->next = skb;
 408         SCTP_OUTPUT_CB(head)->last = skb;
 409
 410         head->truesize += skb->truesize;
 411         head->data_len += skb->len;
 412         head->len += skb->len;
 413
 414         __skb_header_release(skb);
 415 }
 416
 417 static int sctp_packet_pack(struct sctp_packet *packet,
 418                             struct sk_buff *head, int gso, gfp_t gfp)
 419 {
 420         struct sctp_transport *tp = packet->transport;
 421         struct sctp_auth_chunk *auth = NULL;
 422         struct sctp_chunk *chunk, *tmp;
 423         int pkt_count = 0, pkt_size;
 424         struct sock *sk = head->sk;
 425         struct sk_buff *nskb;
 426         int auth_len = 0;
 427
 428         if (gso) {
 429                 skb_shinfo(head)->gso_type = sk->sk_gso_type;
 430                 SCTP_OUTPUT_CB(head)->last = head;
 431         } else {
 432                 nskb = head;
 433                 pkt_size = packet->size;
 434                 goto merge;
 435         }
 436
 437         do {
 438                 /* calculate the pkt_size and alloc nskb */
 439                 pkt_size = packet->overhead;
 440                 list_for_each_entry_safe(chunk, tmp, &packet->chunk_list,
 441                                          list) {
 442                         int padded = SCTP_PAD4(chunk->skb->len);
 443
 444                         if (chunk == packet->auth)
 445                                 auth_len = padded;
 446                         else if (auth_len + padded + packet->overhead >
 447                                  tp->pathmtu)
 448                                 return 0;
 449                         else if (pkt_size + padded > tp->pathmtu)
 450                                 break;
 451                         pkt_size += padded;
 452                 }
 453                 nskb = alloc_skb(pkt_size + MAX_HEADER, gfp);
 454                 if (!nskb)
 455                         return 0;
 456                 skb_reserve(nskb, packet->overhead + MAX_HEADER);
 457
 458 merge:
 459                 /* merge chunks into nskb and append nskb into head list */
 460                 pkt_size -= packet->overhead;
 461                 list_for_each_entry_safe(chunk, tmp, &packet->chunk_list, list) {
 462                         int padding;
 463
 464                         list_del_init(&chunk->list);
 465                         if (sctp_chunk_is_data(chunk)) {
 466                                 if (!sctp_chunk_retransmitted(chunk) &&
 467                                     !tp->rto_pending) {
 468                                         chunk->rtt_in_progress = 1;
 469                                         tp->rto_pending = 1;
 470                                 }
 471                         }
 472
 473                         padding = SCTP_PAD4(chunk->skb->len) - chunk->skb->len;
 474                         if (padding)
 475                                 skb_put_zero(chunk->skb, padding);
 476
 477                         if (chunk == packet->auth)
 478                                 auth = (struct sctp_auth_chunk *)
 479                                                         skb_tail_pointer(nskb);
 480
 481                         skb_put_data(nskb, chunk->skb->data, chunk->skb->len);
 482
 483                         pr_debug("*** Chunk:%p[%s] %s 0x%x, length:%d, chunk->skb->len:%d, rtt_in_progress:%d\n",
 484                                  chunk,
 485                                  sctp_cname(SCTP_ST_CHUNK(chunk->chunk_hdr->type)),
 486                                  chunk->has_tsn ? "TSN" : "No TSN",
 487                                  chunk->has_tsn ? ntohl(chunk->subh.data_hdr->tsn) : 0,
 488                                  ntohs(chunk->chunk_hdr->length), chunk->skb->len,
 489                                  chunk->rtt_in_progress);
 490
 491                         pkt_size -= SCTP_PAD4(chunk->skb->len);
 492
 493                         if (!sctp_chunk_is_data(chunk) && chunk != packet->auth)
 494                                 sctp_chunk_free(chunk);
 495
 496                         if (!pkt_size)
 497                                 break;
 498                 }
 499
 500                 if (auth) {
 501                         sctp_auth_calculate_hmac(tp->asoc, nskb, auth,
 502                                                  packet->auth->shkey, gfp);
 503                         /* free auth if no more chunks, or add it back */
 504                         if (list_empty(&packet->chunk_list))
 505                                 sctp_chunk_free(packet->auth);
 506                         else
 507                                 list_add(&packet->auth->list,
 508                                          &packet->chunk_list);
 509                 }
 510
 511                 if (gso)
 512                         sctp_packet_gso_append(head, nskb);
 513
 514                 pkt_count++;
 515         } while (!list_empty(&packet->chunk_list));
 516
 517         if (gso) {
 518                 memset(head->cb, 0, max(sizeof(struct inet_skb_parm),
 519                                         sizeof(struct inet6_skb_parm)));
 520                 skb_shinfo(head)->gso_segs = pkt_count;
 521                 skb_shinfo(head)->gso_size = GSO_BY_FRAGS;
 522                 rcu_read_lock();
 523                 if (skb_dst(head) != tp->dst) {
 524                         dst_hold(tp->dst);
 525                         sk_setup_caps(sk, tp->dst);
 526                 }
 527                 rcu_read_unlock();
 528                 goto chksum;
 529         }
 530
 531         if (sctp_checksum_disable)
 532                 return 1;
 533
 534         if (!(skb_dst(head)->dev->features & NETIF_F_SCTP_CRC) ||
 535             dst_xfrm(skb_dst(head)) || packet->ipfragok) {
 536                 struct sctphdr *sh =
 537                         (struct sctphdr *)skb_transport_header(head);
 538
 539                 sh->checksum = sctp_compute_cksum(head, 0);
 540         } else {
 541 chksum:
 542                 head->ip_summed = CHECKSUM_PARTIAL;
 543                 head->csum_not_inet = 1;
 544                 head->csum_start = skb_transport_header(head) - head->head;
 545                 head->csum_offset = offsetof(struct sctphdr, checksum);
 546         }
 547
 548         return pkt_count;
 549 }
 550
 551 /* All packets are sent to the network through this function from
 552  * sctp_outq_tail().
 553  *
 554  * The return value is always 0 for now.
 555  */
 556 int sctp_packet_transmit(struct sctp_packet *packet, gfp_t gfp)
 557 {
 558         struct sctp_transport *tp = packet->transport;
 559         struct sctp_association *asoc = tp->asoc;
 560         struct sctp_chunk *chunk, *tmp;
 561         int pkt_count, gso = 0;
 562         struct dst_entry *dst;
 563         struct sk_buff *head;
 564         struct sctphdr *sh;
 565         struct sock *sk;
 566
 567         pr_debug("%s: packet:%p\n", __func__, packet);
 568         if (list_empty(&packet->chunk_list))
 569                 return 0;
 570         chunk = list_entry(packet->chunk_list.next, struct sctp_chunk, list);
 571         sk = chunk->skb->sk;
 572
 573         /* check gso */
 574         if (packet->size > tp->pathmtu && !packet->ipfragok) {
 575                 if (!sk_can_gso(sk)) {
 576                         pr_err_once("Trying to GSO but underlying device doesn't support it.");
 577                         goto out;
 578                 }
 579                 gso = 1;
 580         }
 581
 582         /* alloc head skb */
 583         head = alloc_skb((gso ? packet->overhead : packet->size) +
 584                          MAX_HEADER, gfp);
 585         if (!head)
 586                 goto out;
 587         skb_reserve(head, packet->overhead + MAX_HEADER);
 588         skb_set_owner_w(head, sk);
 589
 590         /* set sctp header */
 591         sh = skb_push(head, sizeof(struct sctphdr));
 592         skb_reset_transport_header(head);
 593         sh->source = htons(packet->source_port);
 594         sh->dest = htons(packet->destination_port);
 595         sh->vtag = htonl(packet->vtag);
 596         sh->checksum = 0;
 597
 598         /* drop packet if no dst */
 599         dst = dst_clone(tp->dst);
 600         if (!dst) {
 601                 IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTNOROUTES);
 602                 kfree_skb(head);
 603                 goto out;
 604         }
 605         skb_dst_set(head, dst);
 606
 607         /* pack up chunks */
 608         pkt_count = sctp_packet_pack(packet, head, gso, gfp);
 609         if (!pkt_count) {
 610                 kfree_skb(head);
 611                 goto out;
 612         }
 613         pr_debug("***sctp_transmit_packet*** skb->len:%d\n", head->len);
 614
 615         /* start autoclose timer */
 616         if (packet->has_data && sctp_state(asoc, ESTABLISHED) &&
 617             asoc->timeouts[SCTP_EVENT_TIMEOUT_AUTOCLOSE]) {
 618                 struct timer_list *timer =
 619                         &asoc->timers[SCTP_EVENT_TIMEOUT_AUTOCLOSE];
 620                 unsigned long timeout =
 621                         asoc->timeouts[SCTP_EVENT_TIMEOUT_AUTOCLOSE];
 622
 623                 if (!mod_timer(timer, jiffies + timeout))
 624                         sctp_association_hold(asoc);
 625         }
 626
 627         /* sctp xmit */
 628         tp->af_specific->ecn_capable(sk);
 629         if (asoc) {
 630                 asoc->stats.opackets += pkt_count;
 631                 if (asoc->peer.last_sent_to != tp)
 632                         asoc->peer.last_sent_to = tp;
 633         }
 634         head->ignore_df = packet->ipfragok;
 635         if (tp->dst_pending_confirm)
 636                 skb_set_dst_pending_confirm(head, 1);
 637         /* neighbour should be confirmed on successful transmission or
 638          * positive error
 639          */
 640         if (tp->af_specific->sctp_xmit(head, tp) >= 0 &&
 641             tp->dst_pending_confirm)
 642                 tp->dst_pending_confirm = 0;
 643
 644 out:
 645         list_for_each_entry_safe(chunk, tmp, &packet->chunk_list, list) {
 646                 list_del_init(&chunk->list);
 647                 if (!sctp_chunk_is_data(chunk))
 648                         sctp_chunk_free(chunk);
 649         }
 650         sctp_packet_reset(packet);
 651         return 0;
 652 }
 653
 654 /********************************************************************
 655  * 2nd Level Abstractions
 656  ********************************************************************/
 657
 658 /* This private function check to see if a chunk can be added */
 659 static enum sctp_xmit sctp_packet_can_append_data(struct sctp_packet *packet,
 660                                                   struct sctp_chunk *chunk)
 661 {
 662         size_t datasize, rwnd, inflight, flight_size;
 663         struct sctp_transport *transport = packet->transport;
 664         struct sctp_association *asoc = transport->asoc;
 665         struct sctp_outq *q = &asoc->outqueue;
 666
 667         /* RFC 2960 6.1  Transmission of DATA Chunks
 668          *
 669          * A) At any given time, the data sender MUST NOT transmit new data to
 670          * any destination transport address if its peer's rwnd indicates
 671          * that the peer has no buffer space (i.e. rwnd is 0, see Section
 672          * 6.2.1).  However, regardless of the value of rwnd (including if it
 673          * is 0), the data sender can always have one DATA chunk in flight to
 674          * the receiver if allowed by cwnd (see rule B below).  This rule
 675          * allows the sender to probe for a change in rwnd that the sender
 676          * missed due to the SACK having been lost in transit from the data
 677          * receiver to the data sender.
 678          */
 679
 680         rwnd = asoc->peer.rwnd;
 681         inflight = q->outstanding_bytes;
 682         flight_size = transport->flight_size;
 683
 684         datasize = sctp_data_size(chunk);
 685
 686         if (datasize > rwnd && inflight > 0)
 687                 /* We have (at least) one data chunk in flight,
 688                  * so we can't fall back to rule 6.1 B).
 689                  */
 690                 return SCTP_XMIT_RWND_FULL;
 691
 692         /* RFC 2960 6.1  Transmission of DATA Chunks
 693          *
 694          * B) At any given time, the sender MUST NOT transmit new data
 695          * to a given transport address if it has cwnd or more bytes
 696          * of data outstanding to that transport address.
 697          */
 698         /* RFC 7.2.4 & the Implementers Guide 2.8.
 699          *
 700          * 3) ...
 701          *    When a Fast Retransmit is being performed the sender SHOULD
 702          *    ignore the value of cwnd and SHOULD NOT delay retransmission.
 703          */
 704         if (chunk->fast_retransmit != SCTP_NEED_FRTX &&
 705             flight_size >= transport->cwnd)
 706                 return SCTP_XMIT_RWND_FULL;
 707
 708         /* Nagle's algorithm to solve small-packet problem:
 709          * Inhibit the sending of new chunks when new outgoing data arrives
 710          * if any previously transmitted data on the connection remains
 711          * unacknowledged.
 712          */
 713
 714         if ((sctp_sk(asoc->base.sk)->nodelay || inflight == 0) &&
 715             !asoc->force_delay)
 716                 /* Nothing unacked */
 717                 return SCTP_XMIT_OK;
 718
 719         if (!sctp_packet_empty(packet))
 720                 /* Append to packet */
 721                 return SCTP_XMIT_OK;
 722
 723         if (!sctp_state(asoc, ESTABLISHED))
 724                 return SCTP_XMIT_OK;
 725
 726         /* Check whether this chunk and all the rest of pending data will fit
 727          * or delay in hopes of bundling a full sized packet.
 728          */
 729         if (chunk->skb->len + q->out_qlen > transport->pathmtu -
 730             packet->overhead - sctp_datachk_len(&chunk->asoc->stream) - 4)
 731                 /* Enough data queued to fill a packet */
 732                 return SCTP_XMIT_OK;
 733
 734         /* Don't delay large message writes that may have been fragmented */
 735         if (!chunk->msg->can_delay)
 736                 return SCTP_XMIT_OK;
 737
 738         /* Defer until all data acked or packet full */
 739         return SCTP_XMIT_DELAY;
 740 }
 741
 742 /* This private function does management things when adding DATA chunk */
 743 static void sctp_packet_append_data(struct sctp_packet *packet,
 744                                 struct sctp_chunk *chunk)
 745 {
 746         struct sctp_transport *transport = packet->transport;
 747         size_t datasize = sctp_data_size(chunk);
 748         struct sctp_association *asoc = transport->asoc;
 749         u32 rwnd = asoc->peer.rwnd;
 750
 751         /* Keep track of how many bytes are in flight over this transport. */
 752         transport->flight_size += datasize;
 753
 754         /* Keep track of how many bytes are in flight to the receiver. */
 755         asoc->outqueue.outstanding_bytes += datasize;
 756
 757         /* Update our view of the receiver's rwnd. */
 758         if (datasize < rwnd)
 759                 rwnd -= datasize;
 760         else
 761                 rwnd = 0;
 762
 763         asoc->peer.rwnd = rwnd;
 764         sctp_chunk_assign_tsn(chunk);
 765         asoc->stream.si->assign_number(chunk);
 766 }
 767
 768 static enum sctp_xmit sctp_packet_will_fit(struct sctp_packet *packet,
 769                                            struct sctp_chunk *chunk,
 770                                            u16 chunk_len)
 771 {
 772         enum sctp_xmit retval = SCTP_XMIT_OK;
 773         size_t psize, pmtu, maxsize;
 774
 775         /* Don't bundle in this packet if this chunk's auth key doesn't
 776          * match other chunks already enqueued on this packet. Also,
 777          * don't bundle the chunk with auth key if other chunks in this
 778          * packet don't have auth key.
 779          */
 780         if ((packet->auth && chunk->shkey != packet->auth->shkey) ||
 781             (!packet->auth && chunk->shkey &&
 782              chunk->chunk_hdr->type != SCTP_CID_AUTH))
 783                 return SCTP_XMIT_PMTU_FULL;
 784
 785         psize = packet->size;
 786         if (packet->transport->asoc)
 787                 pmtu = packet->transport->asoc->pathmtu;
 788         else
 789                 pmtu = packet->transport->pathmtu;
 790
 791         /* Decide if we need to fragment or resubmit later. */
 792         if (psize + chunk_len > pmtu) {
 793                 /* It's OK to fragment at IP level if any one of the following
 794                  * is true:
 795                  *      1. The packet is empty (meaning this chunk is greater
 796                  *         the MTU)
 797                  *      2. The packet doesn't have any data in it yet and data
 798                  *         requires authentication.
 799                  */
 800                 if (sctp_packet_empty(packet) ||
 801                     (!packet->has_data && chunk->auth)) {
 802                         /* We no longer do re-fragmentation.
 803                          * Just fragment at the IP layer, if we
 804                          * actually hit this condition
 805                          */
 806                         packet->ipfragok = 1;
 807                         goto out;
 808                 }
 809
 810                 /* Similarly, if this chunk was built before a PMTU
 811                  * reduction, we have to fragment it at IP level now. So
 812                  * if the packet already contains something, we need to
 813                  * flush.
 814                  */
 815                 maxsize = pmtu - packet->overhead;
 816                 if (packet->auth)
 817                         maxsize -= SCTP_PAD4(packet->auth->skb->len);
 818                 if (chunk_len > maxsize)
 819                         retval = SCTP_XMIT_PMTU_FULL;
 820
 821                 /* It is also okay to fragment if the chunk we are
 822                  * adding is a control chunk, but only if current packet
 823                  * is not a GSO one otherwise it causes fragmentation of
 824                  * a large frame. So in this case we allow the
 825                  * fragmentation by forcing it to be in a new packet.
 826                  */
 827                 if (!sctp_chunk_is_data(chunk) && packet->has_data)
 828                         retval = SCTP_XMIT_PMTU_FULL;
 829
 830                 if (psize + chunk_len > packet->max_size)
 831                         /* Hit GSO/PMTU limit, gotta flush */
 832                         retval = SCTP_XMIT_PMTU_FULL;
 833
 834                 if (!packet->transport->burst_limited &&
 835                     psize + chunk_len > (packet->transport->cwnd >> 1))
 836                         /* Do not allow a single GSO packet to use more
 837                          * than half of cwnd.
 838                          */
 839                         retval = SCTP_XMIT_PMTU_FULL;
 840
 841                 if (packet->transport->burst_limited &&
 842                     psize + chunk_len > (packet->transport->burst_limited >> 1))
 843                         /* Do not allow a single GSO packet to use more
 844                          * than half of original cwnd.
 845                          */
 846                         retval = SCTP_XMIT_PMTU_FULL;
 847                 /* Otherwise it will fit in the GSO packet */
 848         }
 849
 850 out:
 851         return retval;
 852 }