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 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         struct sock *sk;
  90
  91         pr_debug("%s: packet:%p vtag:0x%x\n", __func__, packet, vtag);
  92         packet->vtag = vtag;
  93
  94         /* do the following jobs only once for a flush schedule */
  95         if (!sctp_packet_empty(packet))
  96                 return;
  97
  98         /* set packet max_size with pathmtu */
  99         packet->max_size = tp->pathmtu;
 100         if (!asoc)
 101                 return;
 102
 103         /* update dst or transport pathmtu if in need */
 104         sk = asoc->base.sk;
 105         if (!sctp_transport_dst_check(tp)) {
 106                 sctp_transport_route(tp, NULL, sctp_sk(sk));
 107                 if (asoc->param_flags & SPP_PMTUD_ENABLE)
 108                         sctp_assoc_sync_pmtu(asoc);
 109         } else if (!sctp_transport_pmtu_check(tp)) {
 110                 if (asoc->param_flags & SPP_PMTUD_ENABLE)
 111                         sctp_assoc_sync_pmtu(asoc);
 112         }
 113
 114         /* If there a is a prepend chunk stick it on the list before
 115          * any other chunks get appended.
 116          */
 117         if (ecn_capable) {
 118                 struct sctp_chunk *chunk = sctp_get_ecne_prepend(asoc);
 119
 120                 if (chunk)
 121                         sctp_packet_append_chunk(packet, chunk);
 122         }
 123
 124         if (!tp->dst)
 125                 return;
 126
 127         /* set packet max_size with gso_max_size if gso is enabled*/
 128         rcu_read_lock();
 129         if (__sk_dst_get(sk) != tp->dst) {
 130                 dst_hold(tp->dst);
 131                 sk_setup_caps(sk, tp->dst);
 132         }
 133         packet->max_size = sk_can_gso(sk) ? tp->dst->dev->gso_max_size
 134                                           : asoc->pathmtu;
 135         rcu_read_unlock();
 136 }
 137
 138 /* Initialize the packet structure. */
 139 void sctp_packet_init(struct sctp_packet *packet,
 140                       struct sctp_transport *transport,
 141                       __u16 sport, __u16 dport)
 142 {
 143         struct sctp_association *asoc = transport->asoc;
 144         size_t overhead;
 145
 146         pr_debug("%s: packet:%p transport:%p\n", __func__, packet, transport);
 147
 148         packet->transport = transport;
 149         packet->source_port = sport;
 150         packet->destination_port = dport;
 151         INIT_LIST_HEAD(&packet->chunk_list);
 152         if (asoc) {
 153                 struct sctp_sock *sp = sctp_sk(asoc->base.sk);
 154                 overhead = sp->pf->af->net_header_len;
 155         } else {
 156                 overhead = sizeof(struct ipv6hdr);
 157         }
 158         overhead += sizeof(struct sctphdr);
 159         packet->overhead = overhead;
 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 sctp_xmit_t sctp_packet_transmit_chunk(struct sctp_packet *packet,
 185                                        struct sctp_chunk *chunk,
 186                                        int one_packet, gfp_t gfp)
 187 {
 188         sctp_xmit_t 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 sctp_xmit_t sctp_packet_bundle_auth(struct sctp_packet *pkt,
 222                                            struct sctp_chunk *chunk)
 223 {
 224         struct sctp_association *asoc = pkt->transport->asoc;
 225         struct sctp_chunk *auth;
 226         sctp_xmit_t retval = SCTP_XMIT_OK;
 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);
 245         if (!auth)
 246                 return retval;
 247
 248         retval = __sctp_packet_append_chunk(pkt, auth);
 249
 250         if (retval != SCTP_XMIT_OK)
 251                 sctp_chunk_free(auth);
 252
 253         return retval;
 254 }
 255
 256 /* Try to bundle a SACK with the packet. */
 257 static sctp_xmit_t sctp_packet_bundle_sack(struct sctp_packet *pkt,
 258                                            struct sctp_chunk *chunk)
 259 {
 260         sctp_xmit_t retval = SCTP_XMIT_OK;
 261
 262         /* If sending DATA and haven't aleady bundled a SACK, try to
 263          * bundle one in to the packet.
 264          */
 265         if (sctp_chunk_is_data(chunk) && !pkt->has_sack &&
 266             !pkt->has_cookie_echo) {
 267                 struct sctp_association *asoc;
 268                 struct timer_list *timer;
 269                 asoc = pkt->transport->asoc;
 270                 timer = &asoc->timers[SCTP_EVENT_TIMEOUT_SACK];
 271
 272                 /* If the SACK timer is running, we have a pending SACK */
 273                 if (timer_pending(timer)) {
 274                         struct sctp_chunk *sack;
 275
 276                         if (pkt->transport->sack_generation !=
 277                             pkt->transport->asoc->peer.sack_generation)
 278                                 return retval;
 279
 280                         asoc->a_rwnd = asoc->rwnd;
 281                         sack = sctp_make_sack(asoc);
 282                         if (sack) {
 283                                 retval = __sctp_packet_append_chunk(pkt, sack);
 284                                 if (retval != SCTP_XMIT_OK) {
 285                                         sctp_chunk_free(sack);
 286                                         goto out;
 287                                 }
 288                                 asoc->peer.sack_needed = 0;
 289                                 if (del_timer(timer))
 290                                         sctp_association_put(asoc);
 291                         }
 292                 }
 293         }
 294 out:
 295         return retval;
 296 }
 297
 298
 299 /* Append a chunk to the offered packet reporting back any inability to do
 300  * so.
 301  */
 302 static sctp_xmit_t __sctp_packet_append_chunk(struct sctp_packet *packet,
 303                                               struct sctp_chunk *chunk)
 304 {
 305         sctp_xmit_t retval = SCTP_XMIT_OK;
 306         __u16 chunk_len = SCTP_PAD4(ntohs(chunk->chunk_hdr->length));
 307
 308         /* Check to see if this chunk will fit into the packet */
 309         retval = sctp_packet_will_fit(packet, chunk, chunk_len);
 310         if (retval != SCTP_XMIT_OK)
 311                 goto finish;
 312
 313         /* We believe that this chunk is OK to add to the packet */
 314         switch (chunk->chunk_hdr->type) {
 315         case SCTP_CID_DATA:
 316                 /* Account for the data being in the packet */
 317                 sctp_packet_append_data(packet, chunk);
 318                 /* Disallow SACK bundling after DATA. */
 319                 packet->has_sack = 1;
 320                 /* Disallow AUTH bundling after DATA */
 321                 packet->has_auth = 1;
 322                 /* Let it be knows that packet has DATA in it */
 323                 packet->has_data = 1;
 324                 /* timestamp the chunk for rtx purposes */
 325                 chunk->sent_at = jiffies;
 326                 /* Mainly used for prsctp RTX policy */
 327                 chunk->sent_count++;
 328                 break;
 329         case SCTP_CID_COOKIE_ECHO:
 330                 packet->has_cookie_echo = 1;
 331                 break;
 332
 333         case SCTP_CID_SACK:
 334                 packet->has_sack = 1;
 335                 if (chunk->asoc)
 336                         chunk->asoc->stats.osacks++;
 337                 break;
 338
 339         case SCTP_CID_AUTH:
 340                 packet->has_auth = 1;
 341                 packet->auth = chunk;
 342                 break;
 343         }
 344
 345         /* It is OK to send this chunk.  */
 346         list_add_tail(&chunk->list, &packet->chunk_list);
 347         packet->size += chunk_len;
 348         chunk->transport = packet->transport;
 349 finish:
 350         return retval;
 351 }
 352
 353 /* Append a chunk to the offered packet reporting back any inability to do
 354  * so.
 355  */
 356 sctp_xmit_t sctp_packet_append_chunk(struct sctp_packet *packet,
 357                                      struct sctp_chunk *chunk)
 358 {
 359         sctp_xmit_t retval = SCTP_XMIT_OK;
 360
 361         pr_debug("%s: packet:%p chunk:%p\n", __func__, packet, chunk);
 362
 363         /* Data chunks are special.  Before seeing what else we can
 364          * bundle into this packet, check to see if we are allowed to
 365          * send this DATA.
 366          */
 367         if (sctp_chunk_is_data(chunk)) {
 368                 retval = sctp_packet_can_append_data(packet, chunk);
 369                 if (retval != SCTP_XMIT_OK)
 370                         goto finish;
 371         }
 372
 373         /* Try to bundle AUTH chunk */
 374         retval = sctp_packet_bundle_auth(packet, chunk);
 375         if (retval != SCTP_XMIT_OK)
 376                 goto finish;
 377
 378         /* Try to bundle SACK chunk */
 379         retval = sctp_packet_bundle_sack(packet, chunk);
 380         if (retval != SCTP_XMIT_OK)
 381                 goto finish;
 382
 383         retval = __sctp_packet_append_chunk(packet, chunk);
 384
 385 finish:
 386         return retval;
 387 }
 388
 389 static void sctp_packet_release_owner(struct sk_buff *skb)
 390 {
 391         sk_free(skb->sk);
 392 }
 393
 394 static void sctp_packet_set_owner_w(struct sk_buff *skb, struct sock *sk)
 395 {
 396         skb_orphan(skb);
 397         skb->sk = sk;
 398         skb->destructor = sctp_packet_release_owner;
 399
 400         /*
 401          * The data chunks have already been accounted for in sctp_sendmsg(),
 402          * therefore only reserve a single byte to keep socket around until
 403          * the packet has been transmitted.
 404          */
 405         refcount_inc(&sk->sk_wmem_alloc);
 406 }
 407
 408 static int sctp_packet_pack(struct sctp_packet *packet,
 409                             struct sk_buff *head, int gso, gfp_t gfp)
 410 {
 411         struct sctp_transport *tp = packet->transport;
 412         struct sctp_auth_chunk *auth = NULL;
 413         struct sctp_chunk *chunk, *tmp;
 414         int pkt_count = 0, pkt_size;
 415         struct sock *sk = head->sk;
 416         struct sk_buff *nskb;
 417         int auth_len = 0;
 418
 419         if (gso) {
 420                 skb_shinfo(head)->gso_type = sk->sk_gso_type;
 421                 NAPI_GRO_CB(head)->last = head;
 422         } else {
 423                 nskb = head;
 424                 pkt_size = packet->size;
 425                 goto merge;
 426         }
 427
 428         do {
 429                 /* calculate the pkt_size and alloc nskb */
 430                 pkt_size = packet->overhead;
 431                 list_for_each_entry_safe(chunk, tmp, &packet->chunk_list,
 432                                          list) {
 433                         int padded = SCTP_PAD4(chunk->skb->len);
 434
 435                         if (chunk == packet->auth)
 436                                 auth_len = padded;
 437                         else if (auth_len + padded + packet->overhead >
 438                                  tp->pathmtu)
 439                                 return 0;
 440                         else if (pkt_size + padded > tp->pathmtu)
 441                                 break;
 442                         pkt_size += padded;
 443                 }
 444                 nskb = alloc_skb(pkt_size + MAX_HEADER, gfp);
 445                 if (!nskb)
 446                         return 0;
 447                 skb_reserve(nskb, packet->overhead + MAX_HEADER);
 448
 449 merge:
 450                 /* merge chunks into nskb and append nskb into head list */
 451                 pkt_size -= packet->overhead;
 452                 list_for_each_entry_safe(chunk, tmp, &packet->chunk_list, list) {
 453                         int padding;
 454
 455                         list_del_init(&chunk->list);
 456                         if (sctp_chunk_is_data(chunk)) {
 457                                 if (!sctp_chunk_retransmitted(chunk) &&
 458                                     !tp->rto_pending) {
 459                                         chunk->rtt_in_progress = 1;
 460                                         tp->rto_pending = 1;
 461                                 }
 462                         }
 463
 464                         padding = SCTP_PAD4(chunk->skb->len) - chunk->skb->len;
 465                         if (padding)
 466                                 skb_put_zero(chunk->skb, padding);
 467
 468                         if (chunk == packet->auth)
 469                                 auth = (struct sctp_auth_chunk *)
 470                                                         skb_tail_pointer(nskb);
 471
 472                         skb_put_data(nskb, chunk->skb->data, chunk->skb->len);
 473
 474                         pr_debug("*** Chunk:%p[%s] %s 0x%x, length:%d, chunk->skb->len:%d, rtt_in_progress:%d\n",
 475                                  chunk,
 476                                  sctp_cname(SCTP_ST_CHUNK(chunk->chunk_hdr->type)),
 477                                  chunk->has_tsn ? "TSN" : "No TSN",
 478                                  chunk->has_tsn ? ntohl(chunk->subh.data_hdr->tsn) : 0,
 479                                  ntohs(chunk->chunk_hdr->length), chunk->skb->len,
 480                                  chunk->rtt_in_progress);
 481
 482                         pkt_size -= SCTP_PAD4(chunk->skb->len);
 483
 484                         if (!sctp_chunk_is_data(chunk) && chunk != packet->auth)
 485                                 sctp_chunk_free(chunk);
 486
 487                         if (!pkt_size)
 488                                 break;
 489                 }
 490
 491                 if (auth) {
 492                         sctp_auth_calculate_hmac(tp->asoc, nskb, auth, gfp);
 493                         /* free auth if no more chunks, or add it back */
 494                         if (list_empty(&packet->chunk_list))
 495                                 sctp_chunk_free(packet->auth);
 496                         else
 497                                 list_add(&packet->auth->list,
 498                                          &packet->chunk_list);
 499                 }
 500
 501                 if (gso) {
 502                         if (skb_gro_receive(&head, nskb)) {
 503                                 kfree_skb(nskb);
 504                                 return 0;
 505                         }
 506                         if (WARN_ON_ONCE(skb_shinfo(head)->gso_segs >=
 507                                          sk->sk_gso_max_segs))
 508                                 return 0;
 509                 }
 510
 511                 pkt_count++;
 512         } while (!list_empty(&packet->chunk_list));
 513
 514         if (gso) {
 515                 memset(head->cb, 0, max(sizeof(struct inet_skb_parm),
 516                                         sizeof(struct inet6_skb_parm)));
 517                 skb_shinfo(head)->gso_segs = pkt_count;
 518                 skb_shinfo(head)->gso_size = GSO_BY_FRAGS;
 519                 rcu_read_lock();
 520                 if (skb_dst(head) != tp->dst) {
 521                         dst_hold(tp->dst);
 522                         sk_setup_caps(sk, tp->dst);
 523                 }
 524                 rcu_read_unlock();
 525                 goto chksum;
 526         }
 527
 528         if (sctp_checksum_disable)
 529                 return 1;
 530
 531         if (!(skb_dst(head)->dev->features & NETIF_F_SCTP_CRC) ||
 532             dst_xfrm(skb_dst(head)) || packet->ipfragok) {
 533                 struct sctphdr *sh =
 534                         (struct sctphdr *)skb_transport_header(head);
 535
 536                 sh->checksum = sctp_compute_cksum(head, 0);
 537         } else {
 538 chksum:
 539                 head->ip_summed = CHECKSUM_PARTIAL;
 540                 head->csum_not_inet = 1;
 541                 head->csum_start = skb_transport_header(head) - head->head;
 542                 head->csum_offset = offsetof(struct sctphdr, checksum);
 543         }
 544
 545         return pkt_count;
 546 }
 547
 548 /* All packets are sent to the network through this function from
 549  * sctp_outq_tail().
 550  *
 551  * The return value is always 0 for now.
 552  */
 553 int sctp_packet_transmit(struct sctp_packet *packet, gfp_t gfp)
 554 {
 555         struct sctp_transport *tp = packet->transport;
 556         struct sctp_association *asoc = tp->asoc;
 557         struct sctp_chunk *chunk, *tmp;
 558         int pkt_count, gso = 0;
 559         struct dst_entry *dst;
 560         struct sk_buff *head;
 561         struct sctphdr *sh;
 562         struct sock *sk;
 563
 564         pr_debug("%s: packet:%p\n", __func__, packet);
 565         if (list_empty(&packet->chunk_list))
 566                 return 0;
 567         chunk = list_entry(packet->chunk_list.next, struct sctp_chunk, list);
 568         sk = chunk->skb->sk;
 569
 570         /* check gso */
 571         if (packet->size > tp->pathmtu && !packet->ipfragok) {
 572                 if (!sk_can_gso(sk)) {
 573                         pr_err_once("Trying to GSO but underlying device doesn't support it.");
 574                         goto out;
 575                 }
 576                 gso = 1;
 577         }
 578
 579         /* alloc head skb */
 580         head = alloc_skb((gso ? packet->overhead : packet->size) +
 581                          MAX_HEADER, gfp);
 582         if (!head)
 583                 goto out;
 584         skb_reserve(head, packet->overhead + MAX_HEADER);
 585         sctp_packet_set_owner_w(head, sk);
 586
 587         /* set sctp header */
 588         sh = skb_push(head, sizeof(struct sctphdr));
 589         skb_reset_transport_header(head);
 590         sh->source = htons(packet->source_port);
 591         sh->dest = htons(packet->destination_port);
 592         sh->vtag = htonl(packet->vtag);
 593         sh->checksum = 0;
 594
 595         /* drop packet if no dst */
 596         dst = dst_clone(tp->dst);
 597         if (!dst) {
 598                 IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTNOROUTES);
 599                 kfree_skb(head);
 600                 goto out;
 601         }
 602         skb_dst_set(head, dst);
 603
 604         /* pack up chunks */
 605         pkt_count = sctp_packet_pack(packet, head, gso, gfp);
 606         if (!pkt_count) {
 607                 kfree_skb(head);
 608                 goto out;
 609         }
 610         pr_debug("***sctp_transmit_packet*** skb->len:%d\n", head->len);
 611
 612         /* start autoclose timer */
 613         if (packet->has_data && sctp_state(asoc, ESTABLISHED) &&
 614             asoc->timeouts[SCTP_EVENT_TIMEOUT_AUTOCLOSE]) {
 615                 struct timer_list *timer =
 616                         &asoc->timers[SCTP_EVENT_TIMEOUT_AUTOCLOSE];
 617                 unsigned long timeout =
 618                         asoc->timeouts[SCTP_EVENT_TIMEOUT_AUTOCLOSE];
 619
 620                 if (!mod_timer(timer, jiffies + timeout))
 621                         sctp_association_hold(asoc);
 622         }
 623
 624         /* sctp xmit */
 625         tp->af_specific->ecn_capable(sk);
 626         if (asoc) {
 627                 asoc->stats.opackets += pkt_count;
 628                 if (asoc->peer.last_sent_to != tp)
 629                         asoc->peer.last_sent_to = tp;
 630         }
 631         head->ignore_df = packet->ipfragok;
 632         if (tp->dst_pending_confirm)
 633                 skb_set_dst_pending_confirm(head, 1);
 634         /* neighbour should be confirmed on successful transmission or
 635          * positive error
 636          */
 637         if (tp->af_specific->sctp_xmit(head, tp) >= 0 &&
 638             tp->dst_pending_confirm)
 639                 tp->dst_pending_confirm = 0;
 640
 641 out:
 642         list_for_each_entry_safe(chunk, tmp, &packet->chunk_list, list) {
 643                 list_del_init(&chunk->list);
 644                 if (!sctp_chunk_is_data(chunk))
 645                         sctp_chunk_free(chunk);
 646         }
 647         sctp_packet_reset(packet);
 648         return 0;
 649 }
 650
 651 /********************************************************************
 652  * 2nd Level Abstractions
 653  ********************************************************************/
 654
 655 /* This private function check to see if a chunk can be added */
 656 static sctp_xmit_t sctp_packet_can_append_data(struct sctp_packet *packet,
 657                                            struct sctp_chunk *chunk)
 658 {
 659         size_t datasize, rwnd, inflight, flight_size;
 660         struct sctp_transport *transport = packet->transport;
 661         struct sctp_association *asoc = transport->asoc;
 662         struct sctp_outq *q = &asoc->outqueue;
 663
 664         /* RFC 2960 6.1  Transmission of DATA Chunks
 665          *
 666          * A) At any given time, the data sender MUST NOT transmit new data to
 667          * any destination transport address if its peer's rwnd indicates
 668          * that the peer has no buffer space (i.e. rwnd is 0, see Section
 669          * 6.2.1).  However, regardless of the value of rwnd (including if it
 670          * is 0), the data sender can always have one DATA chunk in flight to
 671          * the receiver if allowed by cwnd (see rule B below).  This rule
 672          * allows the sender to probe for a change in rwnd that the sender
 673          * missed due to the SACK having been lost in transit from the data
 674          * receiver to the data sender.
 675          */
 676
 677         rwnd = asoc->peer.rwnd;
 678         inflight = q->outstanding_bytes;
 679         flight_size = transport->flight_size;
 680
 681         datasize = sctp_data_size(chunk);
 682
 683         if (datasize > rwnd && inflight > 0)
 684                 /* We have (at least) one data chunk in flight,
 685                  * so we can't fall back to rule 6.1 B).
 686                  */
 687                 return SCTP_XMIT_RWND_FULL;
 688
 689         /* RFC 2960 6.1  Transmission of DATA Chunks
 690          *
 691          * B) At any given time, the sender MUST NOT transmit new data
 692          * to a given transport address if it has cwnd or more bytes
 693          * of data outstanding to that transport address.
 694          */
 695         /* RFC 7.2.4 & the Implementers Guide 2.8.
 696          *
 697          * 3) ...
 698          *    When a Fast Retransmit is being performed the sender SHOULD
 699          *    ignore the value of cwnd and SHOULD NOT delay retransmission.
 700          */
 701         if (chunk->fast_retransmit != SCTP_NEED_FRTX &&
 702             flight_size >= transport->cwnd)
 703                 return SCTP_XMIT_RWND_FULL;
 704
 705         /* Nagle's algorithm to solve small-packet problem:
 706          * Inhibit the sending of new chunks when new outgoing data arrives
 707          * if any previously transmitted data on the connection remains
 708          * unacknowledged.
 709          */
 710
 711         if ((sctp_sk(asoc->base.sk)->nodelay || inflight == 0) &&
 712             !asoc->force_delay)
 713                 /* Nothing unacked */
 714                 return SCTP_XMIT_OK;
 715
 716         if (!sctp_packet_empty(packet))
 717                 /* Append to packet */
 718                 return SCTP_XMIT_OK;
 719
 720         if (!sctp_state(asoc, ESTABLISHED))
 721                 return SCTP_XMIT_OK;
 722
 723         /* Check whether this chunk and all the rest of pending data will fit
 724          * or delay in hopes of bundling a full sized packet.
 725          */
 726         if (chunk->skb->len + q->out_qlen > transport->pathmtu -
 727                 packet->overhead - sizeof(struct sctp_data_chunk) - 4)
 728                 /* Enough data queued to fill a packet */
 729                 return SCTP_XMIT_OK;
 730
 731         /* Don't delay large message writes that may have been fragmented */
 732         if (!chunk->msg->can_delay)
 733                 return SCTP_XMIT_OK;
 734
 735         /* Defer until all data acked or packet full */
 736         return SCTP_XMIT_DELAY;
 737 }
 738
 739 /* This private function does management things when adding DATA chunk */
 740 static void sctp_packet_append_data(struct sctp_packet *packet,
 741                                 struct sctp_chunk *chunk)
 742 {
 743         struct sctp_transport *transport = packet->transport;
 744         size_t datasize = sctp_data_size(chunk);
 745         struct sctp_association *asoc = transport->asoc;
 746         u32 rwnd = asoc->peer.rwnd;
 747
 748         /* Keep track of how many bytes are in flight over this transport. */
 749         transport->flight_size += datasize;
 750
 751         /* Keep track of how many bytes are in flight to the receiver. */
 752         asoc->outqueue.outstanding_bytes += datasize;
 753
 754         /* Update our view of the receiver's rwnd. */
 755         if (datasize < rwnd)
 756                 rwnd -= datasize;
 757         else
 758                 rwnd = 0;
 759
 760         asoc->peer.rwnd = rwnd;
 761         sctp_chunk_assign_tsn(chunk);
 762         sctp_chunk_assign_ssn(chunk);
 763 }
 764
 765 static sctp_xmit_t sctp_packet_will_fit(struct sctp_packet *packet,
 766                                         struct sctp_chunk *chunk,
 767                                         u16 chunk_len)
 768 {
 769         size_t psize, pmtu, maxsize;
 770         sctp_xmit_t retval = SCTP_XMIT_OK;
 771
 772         psize = packet->size;
 773         if (packet->transport->asoc)
 774                 pmtu = packet->transport->asoc->pathmtu;
 775         else
 776                 pmtu = packet->transport->pathmtu;
 777
 778         /* Decide if we need to fragment or resubmit later. */
 779         if (psize + chunk_len > pmtu) {
 780                 /* It's OK to fragment at IP level if any one of the following
 781                  * is true:
 782                  *      1. The packet is empty (meaning this chunk is greater
 783                  *         the MTU)
 784                  *      2. The packet doesn't have any data in it yet and data
 785                  *         requires authentication.
 786                  */
 787                 if (sctp_packet_empty(packet) ||
 788                     (!packet->has_data && chunk->auth)) {
 789                         /* We no longer do re-fragmentation.
 790                          * Just fragment at the IP layer, if we
 791                          * actually hit this condition
 792                          */
 793                         packet->ipfragok = 1;
 794                         goto out;
 795                 }
 796
 797                 /* Similarly, if this chunk was built before a PMTU
 798                  * reduction, we have to fragment it at IP level now. So
 799                  * if the packet already contains something, we need to
 800                  * flush.
 801                  */
 802                 maxsize = pmtu - packet->overhead;
 803                 if (packet->auth)
 804                         maxsize -= SCTP_PAD4(packet->auth->skb->len);
 805                 if (chunk_len > maxsize)
 806                         retval = SCTP_XMIT_PMTU_FULL;
 807
 808                 /* It is also okay to fragment if the chunk we are
 809                  * adding is a control chunk, but only if current packet
 810                  * is not a GSO one otherwise it causes fragmentation of
 811                  * a large frame. So in this case we allow the
 812                  * fragmentation by forcing it to be in a new packet.
 813                  */
 814                 if (!sctp_chunk_is_data(chunk) && packet->has_data)
 815                         retval = SCTP_XMIT_PMTU_FULL;
 816
 817                 if (psize + chunk_len > packet->max_size)
 818                         /* Hit GSO/PMTU limit, gotta flush */
 819                         retval = SCTP_XMIT_PMTU_FULL;
 820
 821                 if (!packet->transport->burst_limited &&
 822                     psize + chunk_len > (packet->transport->cwnd >> 1))
 823                         /* Do not allow a single GSO packet to use more
 824                          * than half of cwnd.
 825                          */
 826                         retval = SCTP_XMIT_PMTU_FULL;
 827
 828                 if (packet->transport->burst_limited &&
 829                     psize + chunk_len > (packet->transport->burst_limited >> 1))
 830                         /* Do not allow a single GSO packet to use more
 831                          * than half of original cwnd.
 832                          */
 833                         retval = SCTP_XMIT_PMTU_FULL;
 834                 /* Otherwise it will fit in the GSO packet */
 835         }
 836
 837 out:
 838         return retval;
 839 }