net/sctp/output.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /* SCTP kernel implementation
   3  * (C) Copyright IBM Corp. 2001, 2004
   4  * Copyright (c) 1999-2000 Cisco, Inc.
   5  * Copyright (c) 1999-2001 Motorola, Inc.
   6  *
   7  * This file is part of the SCTP kernel implementation
   8  *
   9  * These functions handle output processing.
  10  *
  11  * Please send any bug reports or fixes you make to the
  12  * email address(es):
  13  *    lksctp developers <linux-sctp@vger.kernel.org>
  14  *
  15  * Written or modified by:
  16  *    La Monte H.P. Yarroll <piggy@acm.org>
  17  *    Karl Knutson          <karl@athena.chicago.il.us>
  18  *    Jon Grimm             <jgrimm@austin.ibm.com>
  19  *    Sridhar Samudrala     <sri@us.ibm.com>
  20  */
  21
  22 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  23
  24 #include <linux/types.h>
  25 #include <linux/kernel.h>
  26 #include <linux/wait.h>
  27 #include <linux/time.h>
  28 #include <linux/ip.h>
  29 #include <linux/ipv6.h>
  30 #include <linux/init.h>
  31 #include <linux/slab.h>
  32 #include <net/inet_ecn.h>
  33 #include <net/ip.h>
  34 #include <net/icmp.h>
  35 #include <net/net_namespace.h>
  36
  37 #include <linux/socket.h> /* for sa_family_t */
  38 #include <net/sock.h>
  39
  40 #include <net/sctp/sctp.h>
  41 #include <net/sctp/sm.h>
  42 #include <net/sctp/checksum.h>
  43
  44 /* Forward declarations for private helpers. */
  45 static enum sctp_xmit __sctp_packet_append_chunk(struct sctp_packet *packet,
  46                                                  struct sctp_chunk *chunk);
  47 static enum sctp_xmit sctp_packet_can_append_data(struct sctp_packet *packet,
  48                                                   struct sctp_chunk *chunk);
  49 static void sctp_packet_append_data(struct sctp_packet *packet,
  50                                     struct sctp_chunk *chunk);
  51 static enum sctp_xmit sctp_packet_will_fit(struct sctp_packet *packet,
  52                                            struct sctp_chunk *chunk,
  53                                            u16 chunk_len);
  54
  55 static void sctp_packet_reset(struct sctp_packet *packet)
  56 {
  57         /* sctp_packet_transmit() relies on this to reset size to the
  58          * current overhead after sending packets.
  59          */
  60         packet->size = packet->overhead;
  61
  62         packet->has_cookie_echo = 0;
  63         packet->has_sack = 0;
  64         packet->has_data = 0;
  65         packet->has_auth = 0;
  66         packet->ipfragok = 0;
  67         packet->auth = NULL;
  68 }
  69
  70 /* Config a packet.
  71  * This appears to be a followup set of initializations.
  72  */
  73 void sctp_packet_config(struct sctp_packet *packet, __u32 vtag,
  74                         int ecn_capable)
  75 {
  76         struct sctp_transport *tp = packet->transport;
  77         struct sctp_association *asoc = tp->asoc;
  78         struct sctp_sock *sp = NULL;
  79         struct sock *sk;
  80
  81         pr_debug("%s: packet:%p vtag:0x%x\n", __func__, packet, vtag);
  82         packet->vtag = vtag;
  83
  84         /* do the following jobs only once for a flush schedule */
  85         if (!sctp_packet_empty(packet))
  86                 return;
  87
  88         /* set packet max_size with pathmtu, then calculate overhead */
  89         packet->max_size = tp->pathmtu;
  90
  91         if (asoc) {
  92                 sk = asoc->base.sk;
  93                 sp = sctp_sk(sk);
  94         }
  95         packet->overhead = sctp_mtu_payload(sp, 0, 0);
  96         packet->size = packet->overhead;
  97
  98         if (!asoc)
  99                 return;
 100
 101         /* update dst or transport pathmtu if in need */
 102         if (!sctp_transport_dst_check(tp)) {
 103                 sctp_transport_route(tp, NULL, sp);
 104                 if (asoc->param_flags & SPP_PMTUD_ENABLE)
 105                         sctp_assoc_sync_pmtu(asoc);
 106         } else if (!sctp_transport_pl_enabled(tp) &&
 107                    asoc->param_flags & SPP_PMTUD_ENABLE) {
 108                 if (!sctp_transport_pmtu_check(tp))
 109                         sctp_assoc_sync_pmtu(asoc);
 110         }
 111
 112         if (asoc->pmtu_pending) {
 113                 if (asoc->param_flags & SPP_PMTUD_ENABLE)
 114                         sctp_assoc_sync_pmtu(asoc);
 115                 asoc->pmtu_pending = 0;
 116         }
 117
 118         /* If there a is a prepend chunk stick it on the list before
 119          * any other chunks get appended.
 120          */
 121         if (ecn_capable) {
 122                 struct sctp_chunk *chunk = sctp_get_ecne_prepend(asoc);
 123
 124                 if (chunk)
 125                         sctp_packet_append_chunk(packet, chunk);
 126         }
 127
 128         if (!tp->dst)
 129                 return;
 130
 131         /* set packet max_size with gso_max_size if gso is enabled*/
 132         rcu_read_lock();
 133         if (__sk_dst_get(sk) != tp->dst) {
 134                 dst_hold(tp->dst);
 135                 sk_setup_caps(sk, tp->dst);
 136         }
 137         packet->max_size = sk_can_gso(sk) ? tp->dst->dev->gso_max_size
 138                                           : asoc->pathmtu;
 139         rcu_read_unlock();
 140 }
 141
 142 /* Initialize the packet structure. */
 143 void sctp_packet_init(struct sctp_packet *packet,
 144                       struct sctp_transport *transport,
 145                       __u16 sport, __u16 dport)
 146 {
 147         pr_debug("%s: packet:%p transport:%p\n", __func__, packet, transport);
 148
 149         packet->transport = transport;
 150         packet->source_port = sport;
 151         packet->destination_port = dport;
 152         INIT_LIST_HEAD(&packet->chunk_list);
 153         /* The overhead will be calculated by sctp_packet_config() */
 154         packet->overhead = 0;
 155         sctp_packet_reset(packet);
 156         packet->vtag = 0;
 157 }
 158
 159 /* Free a packet.  */
 160 void sctp_packet_free(struct sctp_packet *packet)
 161 {
 162         struct sctp_chunk *chunk, *tmp;
 163
 164         pr_debug("%s: packet:%p\n", __func__, packet);
 165
 166         list_for_each_entry_safe(chunk, tmp, &packet->chunk_list, list) {
 167                 list_del_init(&chunk->list);
 168                 sctp_chunk_free(chunk);
 169         }
 170 }
 171
 172 /* This routine tries to append the chunk to the offered packet. If adding
 173  * the chunk causes the packet to exceed the path MTU and COOKIE_ECHO chunk
 174  * is not present in the packet, it transmits the input packet.
 175  * Data can be bundled with a packet containing a COOKIE_ECHO chunk as long
 176  * as it can fit in the packet, but any more data that does not fit in this
 177  * packet can be sent only after receiving the COOKIE_ACK.
 178  */
 179 enum sctp_xmit sctp_packet_transmit_chunk(struct sctp_packet *packet,
 180                                           struct sctp_chunk *chunk,
 181                                           int one_packet, gfp_t gfp)
 182 {
 183         enum sctp_xmit retval;
 184
 185         pr_debug("%s: packet:%p size:%zu chunk:%p size:%d\n", __func__,
 186                  packet, packet->size, chunk, chunk->skb ? chunk->skb->len : -1);
 187
 188         switch ((retval = (sctp_packet_append_chunk(packet, chunk)))) {
 189         case SCTP_XMIT_PMTU_FULL:
 190                 if (!packet->has_cookie_echo) {
 191                         int error = 0;
 192
 193                         error = sctp_packet_transmit(packet, gfp);
 194                         if (error < 0)
 195                                 chunk->skb->sk->sk_err = -error;
 196
 197                         /* If we have an empty packet, then we can NOT ever
 198                          * return PMTU_FULL.
 199                          */
 200                         if (!one_packet)
 201                                 retval = sctp_packet_append_chunk(packet,
 202                                                                   chunk);
 203                 }
 204                 break;
 205
 206         case SCTP_XMIT_RWND_FULL:
 207         case SCTP_XMIT_OK:
 208         case SCTP_XMIT_DELAY:
 209                 break;
 210         }
 211
 212         return retval;
 213 }
 214
 215 /* Try to bundle a pad chunk into a packet with a heartbeat chunk for PLPMTUTD probe */
 216 static enum sctp_xmit sctp_packet_bundle_pad(struct sctp_packet *pkt, struct sctp_chunk *chunk)
 217 {
 218         struct sctp_transport *t = pkt->transport;
 219         struct sctp_chunk *pad;
 220         int overhead = 0;
 221
 222         if (!chunk->pmtu_probe)
 223                 return SCTP_XMIT_OK;
 224
 225         /* calculate the Padding Data size for the pad chunk */
 226         overhead += sizeof(struct sctphdr) + sizeof(struct sctp_chunkhdr);
 227         overhead += sizeof(struct sctp_sender_hb_info) + sizeof(struct sctp_pad_chunk);
 228         pad = sctp_make_pad(t->asoc, t->pl.probe_size - overhead);
 229         if (!pad)
 230                 return SCTP_XMIT_DELAY;
 231
 232         list_add_tail(&pad->list, &pkt->chunk_list);
 233         pkt->size += SCTP_PAD4(ntohs(pad->chunk_hdr->length));
 234         chunk->transport = t;
 235
 236         return SCTP_XMIT_OK;
 237 }
 238
 239 /* Try to bundle an auth chunk into the packet. */
 240 static enum sctp_xmit sctp_packet_bundle_auth(struct sctp_packet *pkt,
 241                                               struct sctp_chunk *chunk)
 242 {
 243         struct sctp_association *asoc = pkt->transport->asoc;
 244         enum sctp_xmit retval = SCTP_XMIT_OK;
 245         struct sctp_chunk *auth;
 246
 247         /* if we don't have an association, we can't do authentication */
 248         if (!asoc)
 249                 return retval;
 250
 251         /* See if this is an auth chunk we are bundling or if
 252          * auth is already bundled.
 253          */
 254         if (chunk->chunk_hdr->type == SCTP_CID_AUTH || pkt->has_auth)
 255                 return retval;
 256
 257         /* if the peer did not request this chunk to be authenticated,
 258          * don't do it
 259          */
 260         if (!chunk->auth)
 261                 return retval;
 262
 263         auth = sctp_make_auth(asoc, chunk->shkey->key_id);
 264         if (!auth)
 265                 return retval;
 266
 267         auth->shkey = chunk->shkey;
 268         sctp_auth_shkey_hold(auth->shkey);
 269
 270         retval = __sctp_packet_append_chunk(pkt, auth);
 271
 272         if (retval != SCTP_XMIT_OK)
 273                 sctp_chunk_free(auth);
 274
 275         return retval;
 276 }
 277
 278 /* Try to bundle a SACK with the packet. */
 279 static enum sctp_xmit sctp_packet_bundle_sack(struct sctp_packet *pkt,
 280                                               struct sctp_chunk *chunk)
 281 {
 282         enum sctp_xmit retval = SCTP_XMIT_OK;
 283
 284         /* If sending DATA and haven't aleady bundled a SACK, try to
 285          * bundle one in to the packet.
 286          */
 287         if (sctp_chunk_is_data(chunk) && !pkt->has_sack &&
 288             !pkt->has_cookie_echo) {
 289                 struct sctp_association *asoc;
 290                 struct timer_list *timer;
 291                 asoc = pkt->transport->asoc;
 292                 timer = &asoc->timers[SCTP_EVENT_TIMEOUT_SACK];
 293
 294                 /* If the SACK timer is running, we have a pending SACK */
 295                 if (timer_pending(timer)) {
 296                         struct sctp_chunk *sack;
 297
 298                         if (pkt->transport->sack_generation !=
 299                             pkt->transport->asoc->peer.sack_generation)
 300                                 return retval;
 301
 302                         asoc->a_rwnd = asoc->rwnd;
 303                         sack = sctp_make_sack(asoc);
 304                         if (sack) {
 305                                 retval = __sctp_packet_append_chunk(pkt, sack);
 306                                 if (retval != SCTP_XMIT_OK) {
 307                                         sctp_chunk_free(sack);
 308                                         goto out;
 309                                 }
 310                                 SCTP_INC_STATS(asoc->base.net,
 311                                                SCTP_MIB_OUTCTRLCHUNKS);
 312                                 asoc->stats.octrlchunks++;
 313                                 asoc->peer.sack_needed = 0;
 314                                 if (del_timer(timer))
 315                                         sctp_association_put(asoc);
 316                         }
 317                 }
 318         }
 319 out:
 320         return retval;
 321 }
 322
 323
 324 /* Append a chunk to the offered packet reporting back any inability to do
 325  * so.
 326  */
 327 static enum sctp_xmit __sctp_packet_append_chunk(struct sctp_packet *packet,
 328                                                  struct sctp_chunk *chunk)
 329 {
 330         __u16 chunk_len = SCTP_PAD4(ntohs(chunk->chunk_hdr->length));
 331         enum sctp_xmit retval = SCTP_XMIT_OK;
 332
 333         /* Check to see if this chunk will fit into the packet */
 334         retval = sctp_packet_will_fit(packet, chunk, chunk_len);
 335         if (retval != SCTP_XMIT_OK)
 336                 goto finish;
 337
 338         /* We believe that this chunk is OK to add to the packet */
 339         switch (chunk->chunk_hdr->type) {
 340         case SCTP_CID_DATA:
 341         case SCTP_CID_I_DATA:
 342                 /* Account for the data being in the packet */
 343                 sctp_packet_append_data(packet, chunk);
 344                 /* Disallow SACK bundling after DATA. */
 345                 packet->has_sack = 1;
 346                 /* Disallow AUTH bundling after DATA */
 347                 packet->has_auth = 1;
 348                 /* Let it be knows that packet has DATA in it */
 349                 packet->has_data = 1;
 350                 /* timestamp the chunk for rtx purposes */
 351                 chunk->sent_at = jiffies;
 352                 /* Mainly used for prsctp RTX policy */
 353                 chunk->sent_count++;
 354                 break;
 355         case SCTP_CID_COOKIE_ECHO:
 356                 packet->has_cookie_echo = 1;
 357                 break;
 358
 359         case SCTP_CID_SACK:
 360                 packet->has_sack = 1;
 361                 if (chunk->asoc)
 362                         chunk->asoc->stats.osacks++;
 363                 break;
 364
 365         case SCTP_CID_AUTH:
 366                 packet->has_auth = 1;
 367                 packet->auth = chunk;
 368                 break;
 369         }
 370
 371         /* It is OK to send this chunk.  */
 372         list_add_tail(&chunk->list, &packet->chunk_list);
 373         packet->size += chunk_len;
 374         chunk->transport = packet->transport;
 375 finish:
 376         return retval;
 377 }
 378
 379 /* Append a chunk to the offered packet reporting back any inability to do
 380  * so.
 381  */
 382 enum sctp_xmit sctp_packet_append_chunk(struct sctp_packet *packet,
 383                                         struct sctp_chunk *chunk)
 384 {
 385         enum sctp_xmit retval = SCTP_XMIT_OK;
 386
 387         pr_debug("%s: packet:%p chunk:%p\n", __func__, packet, chunk);
 388
 389         /* Data chunks are special.  Before seeing what else we can
 390          * bundle into this packet, check to see if we are allowed to
 391          * send this DATA.
 392          */
 393         if (sctp_chunk_is_data(chunk)) {
 394                 retval = sctp_packet_can_append_data(packet, chunk);
 395                 if (retval != SCTP_XMIT_OK)
 396                         goto finish;
 397         }
 398
 399         /* Try to bundle AUTH chunk */
 400         retval = sctp_packet_bundle_auth(packet, chunk);
 401         if (retval != SCTP_XMIT_OK)
 402                 goto finish;
 403
 404         /* Try to bundle SACK chunk */
 405         retval = sctp_packet_bundle_sack(packet, chunk);
 406         if (retval != SCTP_XMIT_OK)
 407                 goto finish;
 408
 409         retval = __sctp_packet_append_chunk(packet, chunk);
 410         if (retval != SCTP_XMIT_OK)
 411                 goto finish;
 412
 413         retval = sctp_packet_bundle_pad(packet, chunk);
 414
 415 finish:
 416         return retval;
 417 }
 418
 419 static void sctp_packet_gso_append(struct sk_buff *head, struct sk_buff *skb)
 420 {
 421         if (SCTP_OUTPUT_CB(head)->last == head)
 422                 skb_shinfo(head)->frag_list = skb;
 423         else
 424                 SCTP_OUTPUT_CB(head)->last->next = skb;
 425         SCTP_OUTPUT_CB(head)->last = skb;
 426
 427         head->truesize += skb->truesize;
 428         head->data_len += skb->len;
 429         head->len += skb->len;
 430         refcount_add(skb->truesize, &head->sk->sk_wmem_alloc);
 431
 432         __skb_header_release(skb);
 433 }
 434
 435 static int sctp_packet_pack(struct sctp_packet *packet,
 436                             struct sk_buff *head, int gso, gfp_t gfp)
 437 {
 438         struct sctp_transport *tp = packet->transport;
 439         struct sctp_auth_chunk *auth = NULL;
 440         struct sctp_chunk *chunk, *tmp;
 441         int pkt_count = 0, pkt_size;
 442         struct sock *sk = head->sk;
 443         struct sk_buff *nskb;
 444         int auth_len = 0;
 445
 446         if (gso) {
 447                 skb_shinfo(head)->gso_type = sk->sk_gso_type;
 448                 SCTP_OUTPUT_CB(head)->last = head;
 449         } else {
 450                 nskb = head;
 451                 pkt_size = packet->size;
 452                 goto merge;
 453         }
 454
 455         do {
 456                 /* calculate the pkt_size and alloc nskb */
 457                 pkt_size = packet->overhead;
 458                 list_for_each_entry_safe(chunk, tmp, &packet->chunk_list,
 459                                          list) {
 460                         int padded = SCTP_PAD4(chunk->skb->len);
 461
 462                         if (chunk == packet->auth)
 463                                 auth_len = padded;
 464                         else if (auth_len + padded + packet->overhead >
 465                                  tp->pathmtu)
 466                                 return 0;
 467                         else if (pkt_size + padded > tp->pathmtu)
 468                                 break;
 469                         pkt_size += padded;
 470                 }
 471                 nskb = alloc_skb(pkt_size + MAX_HEADER, gfp);
 472                 if (!nskb)
 473                         return 0;
 474                 skb_reserve(nskb, packet->overhead + MAX_HEADER);
 475
 476 merge:
 477                 /* merge chunks into nskb and append nskb into head list */
 478                 pkt_size -= packet->overhead;
 479                 list_for_each_entry_safe(chunk, tmp, &packet->chunk_list, list) {
 480                         int padding;
 481
 482                         list_del_init(&chunk->list);
 483                         if (sctp_chunk_is_data(chunk)) {
 484                                 if (!sctp_chunk_retransmitted(chunk) &&
 485                                     !tp->rto_pending) {
 486                                         chunk->rtt_in_progress = 1;
 487                                         tp->rto_pending = 1;
 488                                 }
 489                         }
 490
 491                         padding = SCTP_PAD4(chunk->skb->len) - chunk->skb->len;
 492                         if (padding)
 493                                 skb_put_zero(chunk->skb, padding);
 494
 495                         if (chunk == packet->auth)
 496                                 auth = (struct sctp_auth_chunk *)
 497                                                         skb_tail_pointer(nskb);
 498
 499                         skb_put_data(nskb, chunk->skb->data, chunk->skb->len);
 500
 501                         pr_debug("*** Chunk:%p[%s] %s 0x%x, length:%d, chunk->skb->len:%d, rtt_in_progress:%d\n",
 502                                  chunk,
 503                                  sctp_cname(SCTP_ST_CHUNK(chunk->chunk_hdr->type)),
 504                                  chunk->has_tsn ? "TSN" : "No TSN",
 505                                  chunk->has_tsn ? ntohl(chunk->subh.data_hdr->tsn) : 0,
 506                                  ntohs(chunk->chunk_hdr->length), chunk->skb->len,
 507                                  chunk->rtt_in_progress);
 508
 509                         pkt_size -= SCTP_PAD4(chunk->skb->len);
 510
 511                         if (!sctp_chunk_is_data(chunk) && chunk != packet->auth)
 512                                 sctp_chunk_free(chunk);
 513
 514                         if (!pkt_size)
 515                                 break;
 516                 }
 517
 518                 if (auth) {
 519                         sctp_auth_calculate_hmac(tp->asoc, nskb, auth,
 520                                                  packet->auth->shkey, gfp);
 521                         /* free auth if no more chunks, or add it back */
 522                         if (list_empty(&packet->chunk_list))
 523                                 sctp_chunk_free(packet->auth);
 524                         else
 525                                 list_add(&packet->auth->list,
 526                                          &packet->chunk_list);
 527                 }
 528
 529                 if (gso)
 530                         sctp_packet_gso_append(head, nskb);
 531
 532                 pkt_count++;
 533         } while (!list_empty(&packet->chunk_list));
 534
 535         if (gso) {
 536                 memset(head->cb, 0, max(sizeof(struct inet_skb_parm),
 537                                         sizeof(struct inet6_skb_parm)));
 538                 skb_shinfo(head)->gso_segs = pkt_count;
 539                 skb_shinfo(head)->gso_size = GSO_BY_FRAGS;
 540                 goto chksum;
 541         }
 542
 543         if (sctp_checksum_disable)
 544                 return 1;
 545
 546         if (!(tp->dst->dev->features & NETIF_F_SCTP_CRC) ||
 547             dst_xfrm(tp->dst) || packet->ipfragok || tp->encap_port) {
 548                 struct sctphdr *sh =
 549                         (struct sctphdr *)skb_transport_header(head);
 550
 551                 sh->checksum = sctp_compute_cksum(head, 0);
 552         } else {
 553 chksum:
 554                 head->ip_summed = CHECKSUM_PARTIAL;
 555                 head->csum_not_inet = 1;
 556                 head->csum_start = skb_transport_header(head) - head->head;
 557                 head->csum_offset = offsetof(struct sctphdr, checksum);
 558         }
 559
 560         return pkt_count;
 561 }
 562
 563 /* All packets are sent to the network through this function from
 564  * sctp_outq_tail().
 565  *
 566  * The return value is always 0 for now.
 567  */
 568 int sctp_packet_transmit(struct sctp_packet *packet, gfp_t gfp)
 569 {
 570         struct sctp_transport *tp = packet->transport;
 571         struct sctp_association *asoc = tp->asoc;
 572         struct sctp_chunk *chunk, *tmp;
 573         int pkt_count, gso = 0;
 574         struct sk_buff *head;
 575         struct sctphdr *sh;
 576         struct sock *sk;
 577
 578         pr_debug("%s: packet:%p\n", __func__, packet);
 579         if (list_empty(&packet->chunk_list))
 580                 return 0;
 581         chunk = list_entry(packet->chunk_list.next, struct sctp_chunk, list);
 582         sk = chunk->skb->sk;
 583
 584         /* check gso */
 585         if (packet->size > tp->pathmtu && !packet->ipfragok && !chunk->pmtu_probe) {
 586                 if (!sk_can_gso(sk)) {
 587                         pr_err_once("Trying to GSO but underlying device doesn't support it.");
 588                         goto out;
 589                 }
 590                 gso = 1;
 591         }
 592
 593         /* alloc head skb */
 594         head = alloc_skb((gso ? packet->overhead : packet->size) +
 595                          MAX_HEADER, gfp);
 596         if (!head)
 597                 goto out;
 598         skb_reserve(head, packet->overhead + MAX_HEADER);
 599         skb_set_owner_w(head, sk);
 600
 601         /* set sctp header */
 602         sh = skb_push(head, sizeof(struct sctphdr));
 603         skb_reset_transport_header(head);
 604         sh->source = htons(packet->source_port);
 605         sh->dest = htons(packet->destination_port);
 606         sh->vtag = htonl(packet->vtag);
 607         sh->checksum = 0;
 608
 609         /* drop packet if no dst */
 610         if (!tp->dst) {
 611                 IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTNOROUTES);
 612                 kfree_skb(head);
 613                 goto out;
 614         }
 615
 616         /* pack up chunks */
 617         pkt_count = sctp_packet_pack(packet, head, gso, gfp);
 618         if (!pkt_count) {
 619                 kfree_skb(head);
 620                 goto out;
 621         }
 622         pr_debug("***sctp_transmit_packet*** skb->len:%d\n", head->len);
 623
 624         /* start autoclose timer */
 625         if (packet->has_data && sctp_state(asoc, ESTABLISHED) &&
 626             asoc->timeouts[SCTP_EVENT_TIMEOUT_AUTOCLOSE]) {
 627                 struct timer_list *timer =
 628                         &asoc->timers[SCTP_EVENT_TIMEOUT_AUTOCLOSE];
 629                 unsigned long timeout =
 630                         asoc->timeouts[SCTP_EVENT_TIMEOUT_AUTOCLOSE];
 631
 632                 if (!mod_timer(timer, jiffies + timeout))
 633                         sctp_association_hold(asoc);
 634         }
 635
 636         /* sctp xmit */
 637         tp->af_specific->ecn_capable(sk);
 638         if (asoc) {
 639                 asoc->stats.opackets += pkt_count;
 640                 if (asoc->peer.last_sent_to != tp)
 641                         asoc->peer.last_sent_to = tp;
 642         }
 643         head->ignore_df = packet->ipfragok;
 644         if (tp->dst_pending_confirm)
 645                 skb_set_dst_pending_confirm(head, 1);
 646         /* neighbour should be confirmed on successful transmission or
 647          * positive error
 648          */
 649         if (tp->af_specific->sctp_xmit(head, tp) >= 0 &&
 650             tp->dst_pending_confirm)
 651                 tp->dst_pending_confirm = 0;
 652
 653 out:
 654         list_for_each_entry_safe(chunk, tmp, &packet->chunk_list, list) {
 655                 list_del_init(&chunk->list);
 656                 if (!sctp_chunk_is_data(chunk))
 657                         sctp_chunk_free(chunk);
 658         }
 659         sctp_packet_reset(packet);
 660         return 0;
 661 }
 662
 663 /********************************************************************
 664  * 2nd Level Abstractions
 665  ********************************************************************/
 666
 667 /* This private function check to see if a chunk can be added */
 668 static enum sctp_xmit sctp_packet_can_append_data(struct sctp_packet *packet,
 669                                                   struct sctp_chunk *chunk)
 670 {
 671         size_t datasize, rwnd, inflight, flight_size;
 672         struct sctp_transport *transport = packet->transport;
 673         struct sctp_association *asoc = transport->asoc;
 674         struct sctp_outq *q = &asoc->outqueue;
 675
 676         /* RFC 2960 6.1  Transmission of DATA Chunks
 677          *
 678          * A) At any given time, the data sender MUST NOT transmit new data to
 679          * any destination transport address if its peer's rwnd indicates
 680          * that the peer has no buffer space (i.e. rwnd is 0, see Section
 681          * 6.2.1).  However, regardless of the value of rwnd (including if it
 682          * is 0), the data sender can always have one DATA chunk in flight to
 683          * the receiver if allowed by cwnd (see rule B below).  This rule
 684          * allows the sender to probe for a change in rwnd that the sender
 685          * missed due to the SACK having been lost in transit from the data
 686          * receiver to the data sender.
 687          */
 688
 689         rwnd = asoc->peer.rwnd;
 690         inflight = q->outstanding_bytes;
 691         flight_size = transport->flight_size;
 692
 693         datasize = sctp_data_size(chunk);
 694
 695         if (datasize > rwnd && inflight > 0)
 696                 /* We have (at least) one data chunk in flight,
 697                  * so we can't fall back to rule 6.1 B).
 698                  */
 699                 return SCTP_XMIT_RWND_FULL;
 700
 701         /* RFC 2960 6.1  Transmission of DATA Chunks
 702          *
 703          * B) At any given time, the sender MUST NOT transmit new data
 704          * to a given transport address if it has cwnd or more bytes
 705          * of data outstanding to that transport address.
 706          */
 707         /* RFC 7.2.4 & the Implementers Guide 2.8.
 708          *
 709          * 3) ...
 710          *    When a Fast Retransmit is being performed the sender SHOULD
 711          *    ignore the value of cwnd and SHOULD NOT delay retransmission.
 712          */
 713         if (chunk->fast_retransmit != SCTP_NEED_FRTX &&
 714             flight_size >= transport->cwnd)
 715                 return SCTP_XMIT_RWND_FULL;
 716
 717         /* Nagle's algorithm to solve small-packet problem:
 718          * Inhibit the sending of new chunks when new outgoing data arrives
 719          * if any previously transmitted data on the connection remains
 720          * unacknowledged.
 721          */
 722
 723         if ((sctp_sk(asoc->base.sk)->nodelay || inflight == 0) &&
 724             !asoc->force_delay)
 725                 /* Nothing unacked */
 726                 return SCTP_XMIT_OK;
 727
 728         if (!sctp_packet_empty(packet))
 729                 /* Append to packet */
 730                 return SCTP_XMIT_OK;
 731
 732         if (!sctp_state(asoc, ESTABLISHED))
 733                 return SCTP_XMIT_OK;
 734
 735         /* Check whether this chunk and all the rest of pending data will fit
 736          * or delay in hopes of bundling a full sized packet.
 737          */
 738         if (chunk->skb->len + q->out_qlen > transport->pathmtu -
 739             packet->overhead - sctp_datachk_len(&chunk->asoc->stream) - 4)
 740                 /* Enough data queued to fill a packet */
 741                 return SCTP_XMIT_OK;
 742
 743         /* Don't delay large message writes that may have been fragmented */
 744         if (!chunk->msg->can_delay)
 745                 return SCTP_XMIT_OK;
 746
 747         /* Defer until all data acked or packet full */
 748         return SCTP_XMIT_DELAY;
 749 }
 750
 751 /* This private function does management things when adding DATA chunk */
 752 static void sctp_packet_append_data(struct sctp_packet *packet,
 753                                 struct sctp_chunk *chunk)
 754 {
 755         struct sctp_transport *transport = packet->transport;
 756         size_t datasize = sctp_data_size(chunk);
 757         struct sctp_association *asoc = transport->asoc;
 758         u32 rwnd = asoc->peer.rwnd;
 759
 760         /* Keep track of how many bytes are in flight over this transport. */
 761         transport->flight_size += datasize;
 762
 763         /* Keep track of how many bytes are in flight to the receiver. */
 764         asoc->outqueue.outstanding_bytes += datasize;
 765
 766         /* Update our view of the receiver's rwnd. */
 767         if (datasize < rwnd)
 768                 rwnd -= datasize;
 769         else
 770                 rwnd = 0;
 771
 772         asoc->peer.rwnd = rwnd;
 773         sctp_chunk_assign_tsn(chunk);
 774         asoc->stream.si->assign_number(chunk);
 775 }
 776
 777 static enum sctp_xmit sctp_packet_will_fit(struct sctp_packet *packet,
 778                                            struct sctp_chunk *chunk,
 779                                            u16 chunk_len)
 780 {
 781         enum sctp_xmit retval = SCTP_XMIT_OK;
 782         size_t psize, pmtu, maxsize;
 783
 784         /* Don't bundle in this packet if this chunk's auth key doesn't
 785          * match other chunks already enqueued on this packet. Also,
 786          * don't bundle the chunk with auth key if other chunks in this
 787          * packet don't have auth key.
 788          */
 789         if ((packet->auth && chunk->shkey != packet->auth->shkey) ||
 790             (!packet->auth && chunk->shkey &&
 791              chunk->chunk_hdr->type != SCTP_CID_AUTH))
 792                 return SCTP_XMIT_PMTU_FULL;
 793
 794         psize = packet->size;
 795         if (packet->transport->asoc)
 796                 pmtu = packet->transport->asoc->pathmtu;
 797         else
 798                 pmtu = packet->transport->pathmtu;
 799
 800         /* Decide if we need to fragment or resubmit later. */
 801         if (psize + chunk_len > pmtu) {
 802                 /* It's OK to fragment at IP level if any one of the following
 803                  * is true:
 804                  *      1. The packet is empty (meaning this chunk is greater
 805                  *         the MTU)
 806                  *      2. The packet doesn't have any data in it yet and data
 807                  *         requires authentication.
 808                  */
 809                 if (sctp_packet_empty(packet) ||
 810                     (!packet->has_data && chunk->auth)) {
 811                         /* We no longer do re-fragmentation.
 812                          * Just fragment at the IP layer, if we
 813                          * actually hit this condition
 814                          */
 815                         packet->ipfragok = 1;
 816                         goto out;
 817                 }
 818
 819                 /* Similarly, if this chunk was built before a PMTU
 820                  * reduction, we have to fragment it at IP level now. So
 821                  * if the packet already contains something, we need to
 822                  * flush.
 823                  */
 824                 maxsize = pmtu - packet->overhead;
 825                 if (packet->auth)
 826                         maxsize -= SCTP_PAD4(packet->auth->skb->len);
 827                 if (chunk_len > maxsize)
 828                         retval = SCTP_XMIT_PMTU_FULL;
 829
 830                 /* It is also okay to fragment if the chunk we are
 831                  * adding is a control chunk, but only if current packet
 832                  * is not a GSO one otherwise it causes fragmentation of
 833                  * a large frame. So in this case we allow the
 834                  * fragmentation by forcing it to be in a new packet.
 835                  */
 836                 if (!sctp_chunk_is_data(chunk) && packet->has_data)
 837                         retval = SCTP_XMIT_PMTU_FULL;
 838
 839                 if (psize + chunk_len > packet->max_size)
 840                         /* Hit GSO/PMTU limit, gotta flush */
 841                         retval = SCTP_XMIT_PMTU_FULL;
 842
 843                 if (!packet->transport->burst_limited &&
 844                     psize + chunk_len > (packet->transport->cwnd >> 1))
 845                         /* Do not allow a single GSO packet to use more
 846                          * than half of cwnd.
 847                          */
 848                         retval = SCTP_XMIT_PMTU_FULL;
 849
 850                 if (packet->transport->burst_limited &&
 851                     psize + chunk_len > (packet->transport->burst_limited >> 1))
 852                         /* Do not allow a single GSO packet to use more
 853                          * than half of original cwnd.
 854                          */
 855                         retval = SCTP_XMIT_PMTU_FULL;
 856                 /* Otherwise it will fit in the GSO packet */
 857         }
 858
 859 out:
 860         return retval;
 861 }