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         }
 122
 123         /* If there a is a prepend chunk stick it on the list before
 124          * any other chunks get appended.
 125          */
 126         if (ecn_capable) {
 127                 struct sctp_chunk *chunk = sctp_get_ecne_prepend(asoc);
 128
 129                 if (chunk)
 130                         sctp_packet_append_chunk(packet, chunk);
 131         }
 132
 133         if (!tp->dst)
 134                 return;
 135
 136         /* set packet max_size with gso_max_size if gso is enabled*/
 137         rcu_read_lock();
 138         if (__sk_dst_get(sk) != tp->dst) {
 139                 dst_hold(tp->dst);
 140                 sk_setup_caps(sk, tp->dst);
 141         }
 142         packet->max_size = sk_can_gso(sk) ? tp->dst->dev->gso_max_size
 143                                           : asoc->pathmtu;
 144         rcu_read_unlock();
 145 }
 146
 147 /* Initialize the packet structure. */
 148 void sctp_packet_init(struct sctp_packet *packet,
 149                       struct sctp_transport *transport,
 150                       __u16 sport, __u16 dport)
 151 {
 152         pr_debug("%s: packet:%p transport:%p\n", __func__, packet, transport);
 153
 154         packet->transport = transport;
 155         packet->source_port = sport;
 156         packet->destination_port = dport;
 157         INIT_LIST_HEAD(&packet->chunk_list);
 158         /* The overhead will be calculated by sctp_packet_config() */
 159         packet->overhead = 0;
 160         sctp_packet_reset(packet);
 161         packet->vtag = 0;
 162 }
 163
 164 /* Free a packet.  */
 165 void sctp_packet_free(struct sctp_packet *packet)
 166 {
 167         struct sctp_chunk *chunk, *tmp;
 168
 169         pr_debug("%s: packet:%p\n", __func__, packet);
 170
 171         list_for_each_entry_safe(chunk, tmp, &packet->chunk_list, list) {
 172                 list_del_init(&chunk->list);
 173                 sctp_chunk_free(chunk);
 174         }
 175 }
 176
 177 /* This routine tries to append the chunk to the offered packet. If adding
 178  * the chunk causes the packet to exceed the path MTU and COOKIE_ECHO chunk
 179  * is not present in the packet, it transmits the input packet.
 180  * Data can be bundled with a packet containing a COOKIE_ECHO chunk as long
 181  * as it can fit in the packet, but any more data that does not fit in this
 182  * packet can be sent only after receiving the COOKIE_ACK.
 183  */
 184 enum sctp_xmit sctp_packet_transmit_chunk(struct sctp_packet *packet,
 185                                           struct sctp_chunk *chunk,
 186                                           int one_packet, gfp_t gfp)
 187 {
 188         enum sctp_xmit retval;
 189
 190         pr_debug("%s: packet:%p size:%zu chunk:%p size:%d\n", __func__,
 191                  packet, packet->size, chunk, chunk->skb ? chunk->skb->len : -1);
 192
 193         switch ((retval = (sctp_packet_append_chunk(packet, chunk)))) {
 194         case SCTP_XMIT_PMTU_FULL:
 195                 if (!packet->has_cookie_echo) {
 196                         int error = 0;
 197
 198                         error = sctp_packet_transmit(packet, gfp);
 199                         if (error < 0)
 200                                 chunk->skb->sk->sk_err = -error;
 201
 202                         /* If we have an empty packet, then we can NOT ever
 203                          * return PMTU_FULL.
 204                          */
 205                         if (!one_packet)
 206                                 retval = sctp_packet_append_chunk(packet,
 207                                                                   chunk);
 208                 }
 209                 break;
 210
 211         case SCTP_XMIT_RWND_FULL:
 212         case SCTP_XMIT_OK:
 213         case SCTP_XMIT_DELAY:
 214                 break;
 215         }
 216
 217         return retval;
 218 }
 219
 220 /* Try to bundle an auth chunk into the packet. */
 221 static enum sctp_xmit sctp_packet_bundle_auth(struct sctp_packet *pkt,
 222                                               struct sctp_chunk *chunk)
 223 {
 224         struct sctp_association *asoc = pkt->transport->asoc;
 225         enum sctp_xmit retval = SCTP_XMIT_OK;
 226         struct sctp_chunk *auth;
 227
 228         /* if we don't have an association, we can't do authentication */
 229         if (!asoc)
 230                 return retval;
 231
 232         /* See if this is an auth chunk we are bundling or if
 233          * auth is already bundled.
 234          */
 235         if (chunk->chunk_hdr->type == SCTP_CID_AUTH || pkt->has_auth)
 236                 return retval;
 237
 238         /* if the peer did not request this chunk to be authenticated,
 239          * don't do it
 240          */
 241         if (!chunk->auth)
 242                 return retval;
 243
 244         auth = sctp_make_auth(asoc, chunk->shkey->key_id);
 245         if (!auth)
 246                 return retval;
 247
 248         auth->shkey = chunk->shkey;
 249         sctp_auth_shkey_hold(auth->shkey);
 250
 251         retval = __sctp_packet_append_chunk(pkt, auth);
 252
 253         if (retval != SCTP_XMIT_OK)
 254                 sctp_chunk_free(auth);
 255
 256         return retval;
 257 }
 258
 259 /* Try to bundle a SACK with the packet. */
 260 static enum sctp_xmit sctp_packet_bundle_sack(struct sctp_packet *pkt,
 261                                               struct sctp_chunk *chunk)
 262 {
 263         enum sctp_xmit retval = SCTP_XMIT_OK;
 264
 265         /* If sending DATA and haven't aleady bundled a SACK, try to
 266          * bundle one in to the packet.
 267          */
 268         if (sctp_chunk_is_data(chunk) && !pkt->has_sack &&
 269             !pkt->has_cookie_echo) {
 270                 struct sctp_association *asoc;
 271                 struct timer_list *timer;
 272                 asoc = pkt->transport->asoc;
 273                 timer = &asoc->timers[SCTP_EVENT_TIMEOUT_SACK];
 274
 275                 /* If the SACK timer is running, we have a pending SACK */
 276                 if (timer_pending(timer)) {
 277                         struct sctp_chunk *sack;
 278
 279                         if (pkt->transport->sack_generation !=
 280                             pkt->transport->asoc->peer.sack_generation)
 281                                 return retval;
 282
 283                         asoc->a_rwnd = asoc->rwnd;
 284                         sack = sctp_make_sack(asoc);
 285                         if (sack) {
 286                                 retval = __sctp_packet_append_chunk(pkt, sack);
 287                                 if (retval != SCTP_XMIT_OK) {
 288                                         sctp_chunk_free(sack);
 289                                         goto out;
 290                                 }
 291                                 asoc->peer.sack_needed = 0;
 292                                 if (del_timer(timer))
 293                                         sctp_association_put(asoc);
 294                         }
 295                 }
 296         }
 297 out:
 298         return retval;
 299 }
 300
 301
 302 /* Append a chunk to the offered packet reporting back any inability to do
 303  * so.
 304  */
 305 static enum sctp_xmit __sctp_packet_append_chunk(struct sctp_packet *packet,
 306                                                  struct sctp_chunk *chunk)
 307 {
 308         __u16 chunk_len = SCTP_PAD4(ntohs(chunk->chunk_hdr->length));
 309         enum sctp_xmit retval = SCTP_XMIT_OK;
 310
 311         /* Check to see if this chunk will fit into the packet */
 312         retval = sctp_packet_will_fit(packet, chunk, chunk_len);
 313         if (retval != SCTP_XMIT_OK)
 314                 goto finish;
 315
 316         /* We believe that this chunk is OK to add to the packet */
 317         switch (chunk->chunk_hdr->type) {
 318         case SCTP_CID_DATA:
 319         case SCTP_CID_I_DATA:
 320                 /* Account for the data being in the packet */
 321                 sctp_packet_append_data(packet, chunk);
 322                 /* Disallow SACK bundling after DATA. */
 323                 packet->has_sack = 1;
 324                 /* Disallow AUTH bundling after DATA */
 325                 packet->has_auth = 1;
 326                 /* Let it be knows that packet has DATA in it */
 327                 packet->has_data = 1;
 328                 /* timestamp the chunk for rtx purposes */
 329                 chunk->sent_at = jiffies;
 330                 /* Mainly used for prsctp RTX policy */
 331                 chunk->sent_count++;
 332                 break;
 333         case SCTP_CID_COOKIE_ECHO:
 334                 packet->has_cookie_echo = 1;
 335                 break;
 336
 337         case SCTP_CID_SACK:
 338                 packet->has_sack = 1;
 339                 if (chunk->asoc)
 340                         chunk->asoc->stats.osacks++;
 341                 break;
 342
 343         case SCTP_CID_AUTH:
 344                 packet->has_auth = 1;
 345                 packet->auth = chunk;
 346                 break;
 347         }
 348
 349         /* It is OK to send this chunk.  */
 350         list_add_tail(&chunk->list, &packet->chunk_list);
 351         packet->size += chunk_len;
 352         chunk->transport = packet->transport;
 353 finish:
 354         return retval;
 355 }
 356
 357 /* Append a chunk to the offered packet reporting back any inability to do
 358  * so.
 359  */
 360 enum sctp_xmit sctp_packet_append_chunk(struct sctp_packet *packet,
 361                                         struct sctp_chunk *chunk)
 362 {
 363         enum sctp_xmit retval = SCTP_XMIT_OK;
 364
 365         pr_debug("%s: packet:%p chunk:%p\n", __func__, packet, chunk);
 366
 367         /* Data chunks are special.  Before seeing what else we can
 368          * bundle into this packet, check to see if we are allowed to
 369          * send this DATA.
 370          */
 371         if (sctp_chunk_is_data(chunk)) {
 372                 retval = sctp_packet_can_append_data(packet, chunk);
 373                 if (retval != SCTP_XMIT_OK)
 374                         goto finish;
 375         }
 376
 377         /* Try to bundle AUTH chunk */
 378         retval = sctp_packet_bundle_auth(packet, chunk);
 379         if (retval != SCTP_XMIT_OK)
 380                 goto finish;
 381
 382         /* Try to bundle SACK chunk */
 383         retval = sctp_packet_bundle_sack(packet, chunk);
 384         if (retval != SCTP_XMIT_OK)
 385                 goto finish;
 386
 387         retval = __sctp_packet_append_chunk(packet, chunk);
 388
 389 finish:
 390         return retval;
 391 }
 392
 393 static void sctp_packet_release_owner(struct sk_buff *skb)
 394 {
 395         sk_free(skb->sk);
 396 }
 397
 398 static void sctp_packet_set_owner_w(struct sk_buff *skb, struct sock *sk)
 399 {
 400         skb_orphan(skb);
 401         skb->sk = sk;
 402         skb->destructor = sctp_packet_release_owner;
 403
 404         /*
 405          * The data chunks have already been accounted for in sctp_sendmsg(),
 406          * therefore only reserve a single byte to keep socket around until
 407          * the packet has been transmitted.
 408          */
 409         refcount_inc(&sk->sk_wmem_alloc);
 410 }
 411
 412 static void sctp_packet_gso_append(struct sk_buff *head, struct sk_buff *skb)
 413 {
 414         if (SCTP_OUTPUT_CB(head)->last == head)
 415                 skb_shinfo(head)->frag_list = skb;
 416         else
 417                 SCTP_OUTPUT_CB(head)->last->next = skb;
 418         SCTP_OUTPUT_CB(head)->last = skb;
 419
 420         head->truesize += skb->truesize;
 421         head->data_len += skb->len;
 422         head->len += skb->len;
 423
 424         __skb_header_release(skb);
 425 }
 426
 427 static int sctp_packet_pack(struct sctp_packet *packet,
 428                             struct sk_buff *head, int gso, gfp_t gfp)
 429 {
 430         struct sctp_transport *tp = packet->transport;
 431         struct sctp_auth_chunk *auth = NULL;
 432         struct sctp_chunk *chunk, *tmp;
 433         int pkt_count = 0, pkt_size;
 434         struct sock *sk = head->sk;
 435         struct sk_buff *nskb;
 436         int auth_len = 0;
 437
 438         if (gso) {
 439                 skb_shinfo(head)->gso_type = sk->sk_gso_type;
 440                 SCTP_OUTPUT_CB(head)->last = head;
 441         } else {
 442                 nskb = head;
 443                 pkt_size = packet->size;
 444                 goto merge;
 445         }
 446
 447         do {
 448                 /* calculate the pkt_size and alloc nskb */
 449                 pkt_size = packet->overhead;
 450                 list_for_each_entry_safe(chunk, tmp, &packet->chunk_list,
 451                                          list) {
 452                         int padded = SCTP_PAD4(chunk->skb->len);
 453
 454                         if (chunk == packet->auth)
 455                                 auth_len = padded;
 456                         else if (auth_len + padded + packet->overhead >
 457                                  tp->pathmtu)
 458                                 return 0;
 459                         else if (pkt_size + padded > tp->pathmtu)
 460                                 break;
 461                         pkt_size += padded;
 462                 }
 463                 nskb = alloc_skb(pkt_size + MAX_HEADER, gfp);
 464                 if (!nskb)
 465                         return 0;
 466                 skb_reserve(nskb, packet->overhead + MAX_HEADER);
 467
 468 merge:
 469                 /* merge chunks into nskb and append nskb into head list */
 470                 pkt_size -= packet->overhead;
 471                 list_for_each_entry_safe(chunk, tmp, &packet->chunk_list, list) {
 472                         int padding;
 473
 474                         list_del_init(&chunk->list);
 475                         if (sctp_chunk_is_data(chunk)) {
 476                                 if (!sctp_chunk_retransmitted(chunk) &&
 477                                     !tp->rto_pending) {
 478                                         chunk->rtt_in_progress = 1;
 479                                         tp->rto_pending = 1;
 480                                 }
 481                         }
 482
 483                         padding = SCTP_PAD4(chunk->skb->len) - chunk->skb->len;
 484                         if (padding)
 485                                 skb_put_zero(chunk->skb, padding);
 486
 487                         if (chunk == packet->auth)
 488                                 auth = (struct sctp_auth_chunk *)
 489                                                         skb_tail_pointer(nskb);
 490
 491                         skb_put_data(nskb, chunk->skb->data, chunk->skb->len);
 492
 493                         pr_debug("*** Chunk:%p[%s] %s 0x%x, length:%d, chunk->skb->len:%d, rtt_in_progress:%d\n",
 494                                  chunk,
 495                                  sctp_cname(SCTP_ST_CHUNK(chunk->chunk_hdr->type)),
 496                                  chunk->has_tsn ? "TSN" : "No TSN",
 497                                  chunk->has_tsn ? ntohl(chunk->subh.data_hdr->tsn) : 0,
 498                                  ntohs(chunk->chunk_hdr->length), chunk->skb->len,
 499                                  chunk->rtt_in_progress);
 500
 501                         pkt_size -= SCTP_PAD4(chunk->skb->len);
 502
 503                         if (!sctp_chunk_is_data(chunk) && chunk != packet->auth)
 504                                 sctp_chunk_free(chunk);
 505
 506                         if (!pkt_size)
 507                                 break;
 508                 }
 509
 510                 if (auth) {
 511                         sctp_auth_calculate_hmac(tp->asoc, nskb, auth,
 512                                                  packet->auth->shkey, gfp);
 513                         /* free auth if no more chunks, or add it back */
 514                         if (list_empty(&packet->chunk_list))
 515                                 sctp_chunk_free(packet->auth);
 516                         else
 517                                 list_add(&packet->auth->list,
 518                                          &packet->chunk_list);
 519                 }
 520
 521                 if (gso)
 522                         sctp_packet_gso_append(head, nskb);
 523
 524                 pkt_count++;
 525         } while (!list_empty(&packet->chunk_list));
 526
 527         if (gso) {
 528                 memset(head->cb, 0, max(sizeof(struct inet_skb_parm),
 529                                         sizeof(struct inet6_skb_parm)));
 530                 skb_shinfo(head)->gso_segs = pkt_count;
 531                 skb_shinfo(head)->gso_size = GSO_BY_FRAGS;
 532                 rcu_read_lock();
 533                 if (skb_dst(head) != tp->dst) {
 534                         dst_hold(tp->dst);
 535                         sk_setup_caps(sk, tp->dst);
 536                 }
 537                 rcu_read_unlock();
 538                 goto chksum;
 539         }
 540
 541         if (sctp_checksum_disable)
 542                 return 1;
 543
 544         if (!(skb_dst(head)->dev->features & NETIF_F_SCTP_CRC) ||
 545             dst_xfrm(skb_dst(head)) || packet->ipfragok) {
 546                 struct sctphdr *sh =
 547                         (struct sctphdr *)skb_transport_header(head);
 548
 549                 sh->checksum = sctp_compute_cksum(head, 0);
 550         } else {
 551 chksum:
 552                 head->ip_summed = CHECKSUM_PARTIAL;
 553                 head->csum_not_inet = 1;
 554                 head->csum_start = skb_transport_header(head) - head->head;
 555                 head->csum_offset = offsetof(struct sctphdr, checksum);
 556         }
 557
 558         return pkt_count;
 559 }
 560
 561 /* All packets are sent to the network through this function from
 562  * sctp_outq_tail().
 563  *
 564  * The return value is always 0 for now.
 565  */
 566 int sctp_packet_transmit(struct sctp_packet *packet, gfp_t gfp)
 567 {
 568         struct sctp_transport *tp = packet->transport;
 569         struct sctp_association *asoc = tp->asoc;
 570         struct sctp_chunk *chunk, *tmp;
 571         int pkt_count, gso = 0;
 572         struct dst_entry *dst;
 573         struct sk_buff *head;
 574         struct sctphdr *sh;
 575         struct sock *sk;
 576
 577         pr_debug("%s: packet:%p\n", __func__, packet);
 578         if (list_empty(&packet->chunk_list))
 579                 return 0;
 580         chunk = list_entry(packet->chunk_list.next, struct sctp_chunk, list);
 581         sk = chunk->skb->sk;
 582
 583         /* check gso */
 584         if (packet->size > tp->pathmtu && !packet->ipfragok) {
 585                 if (!sk_can_gso(sk)) {
 586                         pr_err_once("Trying to GSO but underlying device doesn't support it.");
 587                         goto out;
 588                 }
 589                 gso = 1;
 590         }
 591
 592         /* alloc head skb */
 593         head = alloc_skb((gso ? packet->overhead : packet->size) +
 594                          MAX_HEADER, gfp);
 595         if (!head)
 596                 goto out;
 597         skb_reserve(head, packet->overhead + MAX_HEADER);
 598         sctp_packet_set_owner_w(head, sk);
 599
 600         /* set sctp header */
 601         sh = skb_push(head, sizeof(struct sctphdr));
 602         skb_reset_transport_header(head);
 603         sh->source = htons(packet->source_port);
 604         sh->dest = htons(packet->destination_port);
 605         sh->vtag = htonl(packet->vtag);
 606         sh->checksum = 0;
 607
 608         /* drop packet if no dst */
 609         dst = dst_clone(tp->dst);
 610         if (!dst) {
 611                 IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTNOROUTES);
 612                 kfree_skb(head);
 613                 goto out;
 614         }
 615         skb_dst_set(head, dst);
 616
 617         /* pack up chunks */
 618         pkt_count = sctp_packet_pack(packet, head, gso, gfp);
 619         if (!pkt_count) {
 620                 kfree_skb(head);
 621                 goto out;
 622         }
 623         pr_debug("***sctp_transmit_packet*** skb->len:%d\n", head->len);
 624
 625         /* start autoclose timer */
 626         if (packet->has_data && sctp_state(asoc, ESTABLISHED) &&
 627             asoc->timeouts[SCTP_EVENT_TIMEOUT_AUTOCLOSE]) {
 628                 struct timer_list *timer =
 629                         &asoc->timers[SCTP_EVENT_TIMEOUT_AUTOCLOSE];
 630                 unsigned long timeout =
 631                         asoc->timeouts[SCTP_EVENT_TIMEOUT_AUTOCLOSE];
 632
 633                 if (!mod_timer(timer, jiffies + timeout))
 634                         sctp_association_hold(asoc);
 635         }
 636
 637         /* sctp xmit */
 638         tp->af_specific->ecn_capable(sk);
 639         if (asoc) {
 640                 asoc->stats.opackets += pkt_count;
 641                 if (asoc->peer.last_sent_to != tp)
 642                         asoc->peer.last_sent_to = tp;
 643         }
 644         head->ignore_df = packet->ipfragok;
 645         if (tp->dst_pending_confirm)
 646                 skb_set_dst_pending_confirm(head, 1);
 647         /* neighbour should be confirmed on successful transmission or
 648          * positive error
 649          */
 650         if (tp->af_specific->sctp_xmit(head, tp) >= 0 &&
 651             tp->dst_pending_confirm)
 652                 tp->dst_pending_confirm = 0;
 653
 654 out:
 655         list_for_each_entry_safe(chunk, tmp, &packet->chunk_list, list) {
 656                 list_del_init(&chunk->list);
 657                 if (!sctp_chunk_is_data(chunk))
 658                         sctp_chunk_free(chunk);
 659         }
 660         sctp_packet_reset(packet);
 661         return 0;
 662 }
 663
 664 /********************************************************************
 665  * 2nd Level Abstractions
 666  ********************************************************************/
 667
 668 /* This private function check to see if a chunk can be added */
 669 static enum sctp_xmit sctp_packet_can_append_data(struct sctp_packet *packet,
 670                                                   struct sctp_chunk *chunk)
 671 {
 672         size_t datasize, rwnd, inflight, flight_size;
 673         struct sctp_transport *transport = packet->transport;
 674         struct sctp_association *asoc = transport->asoc;
 675         struct sctp_outq *q = &asoc->outqueue;
 676
 677         /* RFC 2960 6.1  Transmission of DATA Chunks
 678          *
 679          * A) At any given time, the data sender MUST NOT transmit new data to
 680          * any destination transport address if its peer's rwnd indicates
 681          * that the peer has no buffer space (i.e. rwnd is 0, see Section
 682          * 6.2.1).  However, regardless of the value of rwnd (including if it
 683          * is 0), the data sender can always have one DATA chunk in flight to
 684          * the receiver if allowed by cwnd (see rule B below).  This rule
 685          * allows the sender to probe for a change in rwnd that the sender
 686          * missed due to the SACK having been lost in transit from the data
 687          * receiver to the data sender.
 688          */
 689
 690         rwnd = asoc->peer.rwnd;
 691         inflight = q->outstanding_bytes;
 692         flight_size = transport->flight_size;
 693
 694         datasize = sctp_data_size(chunk);
 695
 696         if (datasize > rwnd && inflight > 0)
 697                 /* We have (at least) one data chunk in flight,
 698                  * so we can't fall back to rule 6.1 B).
 699                  */
 700                 return SCTP_XMIT_RWND_FULL;
 701
 702         /* RFC 2960 6.1  Transmission of DATA Chunks
 703          *
 704          * B) At any given time, the sender MUST NOT transmit new data
 705          * to a given transport address if it has cwnd or more bytes
 706          * of data outstanding to that transport address.
 707          */
 708         /* RFC 7.2.4 & the Implementers Guide 2.8.
 709          *
 710          * 3) ...
 711          *    When a Fast Retransmit is being performed the sender SHOULD
 712          *    ignore the value of cwnd and SHOULD NOT delay retransmission.
 713          */
 714         if (chunk->fast_retransmit != SCTP_NEED_FRTX &&
 715             flight_size >= transport->cwnd)
 716                 return SCTP_XMIT_RWND_FULL;
 717
 718         /* Nagle's algorithm to solve small-packet problem:
 719          * Inhibit the sending of new chunks when new outgoing data arrives
 720          * if any previously transmitted data on the connection remains
 721          * unacknowledged.
 722          */
 723
 724         if ((sctp_sk(asoc->base.sk)->nodelay || inflight == 0) &&
 725             !asoc->force_delay)
 726                 /* Nothing unacked */
 727                 return SCTP_XMIT_OK;
 728
 729         if (!sctp_packet_empty(packet))
 730                 /* Append to packet */
 731                 return SCTP_XMIT_OK;
 732
 733         if (!sctp_state(asoc, ESTABLISHED))
 734                 return SCTP_XMIT_OK;
 735
 736         /* Check whether this chunk and all the rest of pending data will fit
 737          * or delay in hopes of bundling a full sized packet.
 738          */
 739         if (chunk->skb->len + q->out_qlen > transport->pathmtu -
 740             packet->overhead - sctp_datachk_len(&chunk->asoc->stream) - 4)
 741                 /* Enough data queued to fill a packet */
 742                 return SCTP_XMIT_OK;
 743
 744         /* Don't delay large message writes that may have been fragmented */
 745         if (!chunk->msg->can_delay)
 746                 return SCTP_XMIT_OK;
 747
 748         /* Defer until all data acked or packet full */
 749         return SCTP_XMIT_DELAY;
 750 }
 751
 752 /* This private function does management things when adding DATA chunk */
 753 static void sctp_packet_append_data(struct sctp_packet *packet,
 754                                 struct sctp_chunk *chunk)
 755 {
 756         struct sctp_transport *transport = packet->transport;
 757         size_t datasize = sctp_data_size(chunk);
 758         struct sctp_association *asoc = transport->asoc;
 759         u32 rwnd = asoc->peer.rwnd;
 760
 761         /* Keep track of how many bytes are in flight over this transport. */
 762         transport->flight_size += datasize;
 763
 764         /* Keep track of how many bytes are in flight to the receiver. */
 765         asoc->outqueue.outstanding_bytes += datasize;
 766
 767         /* Update our view of the receiver's rwnd. */
 768         if (datasize < rwnd)
 769                 rwnd -= datasize;
 770         else
 771                 rwnd = 0;
 772
 773         asoc->peer.rwnd = rwnd;
 774         sctp_chunk_assign_tsn(chunk);
 775         asoc->stream.si->assign_number(chunk);
 776 }
 777
 778 static enum sctp_xmit sctp_packet_will_fit(struct sctp_packet *packet,
 779                                            struct sctp_chunk *chunk,
 780                                            u16 chunk_len)
 781 {
 782         enum sctp_xmit retval = SCTP_XMIT_OK;
 783         size_t psize, pmtu, maxsize;
 784
 785         /* Don't bundle in this packet if this chunk's auth key doesn't
 786          * match other chunks already enqueued on this packet. Also,
 787          * don't bundle the chunk with auth key if other chunks in this
 788          * packet don't have auth key.
 789          */
 790         if ((packet->auth && chunk->shkey != packet->auth->shkey) ||
 791             (!packet->auth && chunk->shkey &&
 792              chunk->chunk_hdr->type != SCTP_CID_AUTH))
 793                 return SCTP_XMIT_PMTU_FULL;
 794
 795         psize = packet->size;
 796         if (packet->transport->asoc)
 797                 pmtu = packet->transport->asoc->pathmtu;
 798         else
 799                 pmtu = packet->transport->pathmtu;
 800
 801         /* Decide if we need to fragment or resubmit later. */
 802         if (psize + chunk_len > pmtu) {
 803                 /* It's OK to fragment at IP level if any one of the following
 804                  * is true:
 805                  *      1. The packet is empty (meaning this chunk is greater
 806                  *         the MTU)
 807                  *      2. The packet doesn't have any data in it yet and data
 808                  *         requires authentication.
 809                  */
 810                 if (sctp_packet_empty(packet) ||
 811                     (!packet->has_data && chunk->auth)) {
 812                         /* We no longer do re-fragmentation.
 813                          * Just fragment at the IP layer, if we
 814                          * actually hit this condition
 815                          */
 816                         packet->ipfragok = 1;
 817                         goto out;
 818                 }
 819
 820                 /* Similarly, if this chunk was built before a PMTU
 821                  * reduction, we have to fragment it at IP level now. So
 822                  * if the packet already contains something, we need to
 823                  * flush.
 824                  */
 825                 maxsize = pmtu - packet->overhead;
 826                 if (packet->auth)
 827                         maxsize -= SCTP_PAD4(packet->auth->skb->len);
 828                 if (chunk_len > maxsize)
 829                         retval = SCTP_XMIT_PMTU_FULL;
 830
 831                 /* It is also okay to fragment if the chunk we are
 832                  * adding is a control chunk, but only if current packet
 833                  * is not a GSO one otherwise it causes fragmentation of
 834                  * a large frame. So in this case we allow the
 835                  * fragmentation by forcing it to be in a new packet.
 836                  */
 837                 if (!sctp_chunk_is_data(chunk) && packet->has_data)
 838                         retval = SCTP_XMIT_PMTU_FULL;
 839
 840                 if (psize + chunk_len > packet->max_size)
 841                         /* Hit GSO/PMTU limit, gotta flush */
 842                         retval = SCTP_XMIT_PMTU_FULL;
 843
 844                 if (!packet->transport->burst_limited &&
 845                     psize + chunk_len > (packet->transport->cwnd >> 1))
 846                         /* Do not allow a single GSO packet to use more
 847                          * than half of cwnd.
 848                          */
 849                         retval = SCTP_XMIT_PMTU_FULL;
 850
 851                 if (packet->transport->burst_limited &&
 852                     psize + chunk_len > (packet->transport->burst_limited >> 1))
 853                         /* Do not allow a single GSO packet to use more
 854                          * than half of original cwnd.
 855                          */
 856                         retval = SCTP_XMIT_PMTU_FULL;
 857                 /* Otherwise it will fit in the GSO packet */
 858         }
 859
 860 out:
 861         return retval;
 862 }