linux/net/sctp/output.c
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   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. */
  45static enum sctp_xmit __sctp_packet_append_chunk(struct sctp_packet *packet,
  46                                                 struct sctp_chunk *chunk);
  47static enum sctp_xmit sctp_packet_can_append_data(struct sctp_packet *packet,
  48                                                  struct sctp_chunk *chunk);
  49static void sctp_packet_append_data(struct sctp_packet *packet,
  50                                    struct sctp_chunk *chunk);
  51static enum sctp_xmit sctp_packet_will_fit(struct sctp_packet *packet,
  52                                           struct sctp_chunk *chunk,
  53                                           u16 chunk_len);
  54
  55static 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 */
  73void 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. */
 143void 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.  */
 160void 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 */
 179enum 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 */
 216static 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. */
 240static 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. */
 279static 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        }
 319out:
 320        return retval;
 321}
 322
 323
 324/* Append a chunk to the offered packet reporting back any inability to do
 325 * so.
 326 */
 327static 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;
 375finish:
 376        return retval;
 377}
 378
 379/* Append a chunk to the offered packet reporting back any inability to do
 380 * so.
 381 */
 382enum 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
 415finish:
 416        return retval;
 417}
 418
 419static 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
 435static 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
 476merge:
 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 {
 553chksum:
 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 */
 568int 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
 653out:
 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 */
 668static 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 */
 752static 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
 777static 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
 859out:
 860        return retval;
 861}
 862