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) ? min(READ_ONCE(tp->dst->dev->gso_max_size),
 138                                                 GSO_LEGACY_MAX_SIZE)
 139                                           : asoc->pathmtu;
 140         rcu_read_unlock();
 141 }
 142
 143 /* Initialize the packet structure. */
 144 void sctp_packet_init(struct sctp_packet *packet,
 145                       struct sctp_transport *transport,
 146                       __u16 sport, __u16 dport)
 147 {
 148         pr_debug("%s: packet:%p transport:%p\n", __func__, packet, transport);
 149
 150         packet->transport = transport;
 151         packet->source_port = sport;
 152         packet->destination_port = dport;
 153         INIT_LIST_HEAD(&packet->chunk_list);
 154         /* The overhead will be calculated by sctp_packet_config() */
 155         packet->overhead = 0;
 156         sctp_packet_reset(packet);
 157         packet->vtag = 0;
 158 }
 159
 160 /* Free a packet.  */
 161 void sctp_packet_free(struct sctp_packet *packet)
 162 {
 163         struct sctp_chunk *chunk, *tmp;
 164
 165         pr_debug("%s: packet:%p\n", __func__, packet);
 166
 167         list_for_each_entry_safe(chunk, tmp, &packet->chunk_list, list) {
 168                 list_del_init(&chunk->list);
 169                 sctp_chunk_free(chunk);
 170         }
 171 }
 172
 173 /* This routine tries to append the chunk to the offered packet. If adding
 174  * the chunk causes the packet to exceed the path MTU and COOKIE_ECHO chunk
 175  * is not present in the packet, it transmits the input packet.
 176  * Data can be bundled with a packet containing a COOKIE_ECHO chunk as long
 177  * as it can fit in the packet, but any more data that does not fit in this
 178  * packet can be sent only after receiving the COOKIE_ACK.
 179  */
 180 enum sctp_xmit sctp_packet_transmit_chunk(struct sctp_packet *packet,
 181                                           struct sctp_chunk *chunk,
 182                                           int one_packet, gfp_t gfp)
 183 {
 184         enum sctp_xmit retval;
 185
 186         pr_debug("%s: packet:%p size:%zu chunk:%p size:%d\n", __func__,
 187                  packet, packet->size, chunk, chunk->skb ? chunk->skb->len : -1);
 188
 189         switch ((retval = (sctp_packet_append_chunk(packet, chunk)))) {
 190         case SCTP_XMIT_PMTU_FULL:
 191                 if (!packet->has_cookie_echo) {
 192                         int error = 0;
 193
 194                         error = sctp_packet_transmit(packet, gfp);
 195                         if (error < 0)
 196                                 chunk->skb->sk->sk_err = -error;
 197
 198                         /* If we have an empty packet, then we can NOT ever
 199                          * return PMTU_FULL.
 200                          */
 201                         if (!one_packet)
 202                                 retval = sctp_packet_append_chunk(packet,
 203                                                                   chunk);
 204                 }
 205                 break;
 206
 207         case SCTP_XMIT_RWND_FULL:
 208         case SCTP_XMIT_OK:
 209         case SCTP_XMIT_DELAY:
 210                 break;
 211         }
 212
 213         return retval;
 214 }
 215
 216 /* Try to bundle a pad chunk into a packet with a heartbeat chunk for PLPMTUTD probe */
 217 static enum sctp_xmit sctp_packet_bundle_pad(struct sctp_packet *pkt, struct sctp_chunk *chunk)
 218 {
 219         struct sctp_transport *t = pkt->transport;
 220         struct sctp_chunk *pad;
 221         int overhead = 0;
 222
 223         if (!chunk->pmtu_probe)
 224                 return SCTP_XMIT_OK;
 225
 226         /* calculate the Padding Data size for the pad chunk */
 227         overhead += sizeof(struct sctphdr) + sizeof(struct sctp_chunkhdr);
 228         overhead += sizeof(struct sctp_sender_hb_info) + sizeof(struct sctp_pad_chunk);
 229         pad = sctp_make_pad(t->asoc, t->pl.probe_size - overhead);
 230         if (!pad)
 231                 return SCTP_XMIT_DELAY;
 232
 233         list_add_tail(&pad->list, &pkt->chunk_list);
 234         pkt->size += SCTP_PAD4(ntohs(pad->chunk_hdr->length));
 235         chunk->transport = t;
 236
 237         return SCTP_XMIT_OK;
 238 }
 239
 240 /* Try to bundle an auth chunk into the packet. */
 241 static enum sctp_xmit sctp_packet_bundle_auth(struct sctp_packet *pkt,
 242                                               struct sctp_chunk *chunk)
 243 {
 244         struct sctp_association *asoc = pkt->transport->asoc;
 245         enum sctp_xmit retval = SCTP_XMIT_OK;
 246         struct sctp_chunk *auth;
 247
 248         /* if we don't have an association, we can't do authentication */
 249         if (!asoc)
 250                 return retval;
 251
 252         /* See if this is an auth chunk we are bundling or if
 253          * auth is already bundled.
 254          */
 255         if (chunk->chunk_hdr->type == SCTP_CID_AUTH || pkt->has_auth)
 256                 return retval;
 257
 258         /* if the peer did not request this chunk to be authenticated,
 259          * don't do it
 260          */
 261         if (!chunk->auth)
 262                 return retval;
 263
 264         auth = sctp_make_auth(asoc, chunk->shkey->key_id);
 265         if (!auth)
 266                 return retval;
 267
 268         auth->shkey = chunk->shkey;
 269         sctp_auth_shkey_hold(auth->shkey);
 270
 271         retval = __sctp_packet_append_chunk(pkt, auth);
 272
 273         if (retval != SCTP_XMIT_OK)
 274                 sctp_chunk_free(auth);
 275
 276         return retval;
 277 }
 278
 279 /* Try to bundle a SACK with the packet. */
 280 static enum sctp_xmit sctp_packet_bundle_sack(struct sctp_packet *pkt,
 281                                               struct sctp_chunk *chunk)
 282 {
 283         enum sctp_xmit retval = SCTP_XMIT_OK;
 284
 285         /* If sending DATA and haven't aleady bundled a SACK, try to
 286          * bundle one in to the packet.
 287          */
 288         if (sctp_chunk_is_data(chunk) && !pkt->has_sack &&
 289             !pkt->has_cookie_echo) {
 290                 struct sctp_association *asoc;
 291                 struct timer_list *timer;
 292                 asoc = pkt->transport->asoc;
 293                 timer = &asoc->timers[SCTP_EVENT_TIMEOUT_SACK];
 294
 295                 /* If the SACK timer is running, we have a pending SACK */
 296                 if (timer_pending(timer)) {
 297                         struct sctp_chunk *sack;
 298
 299                         if (pkt->transport->sack_generation !=
 300                             pkt->transport->asoc->peer.sack_generation)
 301                                 return retval;
 302
 303                         asoc->a_rwnd = asoc->rwnd;
 304                         sack = sctp_make_sack(asoc);
 305                         if (sack) {
 306                                 retval = __sctp_packet_append_chunk(pkt, sack);
 307                                 if (retval != SCTP_XMIT_OK) {
 308                                         sctp_chunk_free(sack);
 309                                         goto out;
 310                                 }
 311                                 SCTP_INC_STATS(asoc->base.net,
 312                                                SCTP_MIB_OUTCTRLCHUNKS);
 313                                 asoc->stats.octrlchunks++;
 314                                 asoc->peer.sack_needed = 0;
 315                                 if (del_timer(timer))
 316                                         sctp_association_put(asoc);
 317                         }
 318                 }
 319         }
 320 out:
 321         return retval;
 322 }
 323
 324
 325 /* Append a chunk to the offered packet reporting back any inability to do
 326  * so.
 327  */
 328 static enum sctp_xmit __sctp_packet_append_chunk(struct sctp_packet *packet,
 329                                                  struct sctp_chunk *chunk)
 330 {
 331         __u16 chunk_len = SCTP_PAD4(ntohs(chunk->chunk_hdr->length));
 332         enum sctp_xmit retval = SCTP_XMIT_OK;
 333
 334         /* Check to see if this chunk will fit into the packet */
 335         retval = sctp_packet_will_fit(packet, chunk, chunk_len);
 336         if (retval != SCTP_XMIT_OK)
 337                 goto finish;
 338
 339         /* We believe that this chunk is OK to add to the packet */
 340         switch (chunk->chunk_hdr->type) {
 341         case SCTP_CID_DATA:
 342         case SCTP_CID_I_DATA:
 343                 /* Account for the data being in the packet */
 344                 sctp_packet_append_data(packet, chunk);
 345                 /* Disallow SACK bundling after DATA. */
 346                 packet->has_sack = 1;
 347                 /* Disallow AUTH bundling after DATA */
 348                 packet->has_auth = 1;
 349                 /* Let it be knows that packet has DATA in it */
 350                 packet->has_data = 1;
 351                 /* timestamp the chunk for rtx purposes */
 352                 chunk->sent_at = jiffies;
 353                 /* Mainly used for prsctp RTX policy */
 354                 chunk->sent_count++;
 355                 break;
 356         case SCTP_CID_COOKIE_ECHO:
 357                 packet->has_cookie_echo = 1;
 358                 break;
 359
 360         case SCTP_CID_SACK:
 361                 packet->has_sack = 1;
 362                 if (chunk->asoc)
 363                         chunk->asoc->stats.osacks++;
 364                 break;
 365
 366         case SCTP_CID_AUTH:
 367                 packet->has_auth = 1;
 368                 packet->auth = chunk;
 369                 break;
 370         }
 371
 372         /* It is OK to send this chunk.  */
 373         list_add_tail(&chunk->list, &packet->chunk_list);
 374         packet->size += chunk_len;
 375         chunk->transport = packet->transport;
 376 finish:
 377         return retval;
 378 }
 379
 380 /* Append a chunk to the offered packet reporting back any inability to do
 381  * so.
 382  */
 383 enum sctp_xmit sctp_packet_append_chunk(struct sctp_packet *packet,
 384                                         struct sctp_chunk *chunk)
 385 {
 386         enum sctp_xmit retval = SCTP_XMIT_OK;
 387
 388         pr_debug("%s: packet:%p chunk:%p\n", __func__, packet, chunk);
 389
 390         /* Data chunks are special.  Before seeing what else we can
 391          * bundle into this packet, check to see if we are allowed to
 392          * send this DATA.
 393          */
 394         if (sctp_chunk_is_data(chunk)) {
 395                 retval = sctp_packet_can_append_data(packet, chunk);
 396                 if (retval != SCTP_XMIT_OK)
 397                         goto finish;
 398         }
 399
 400         /* Try to bundle AUTH chunk */
 401         retval = sctp_packet_bundle_auth(packet, chunk);
 402         if (retval != SCTP_XMIT_OK)
 403                 goto finish;
 404
 405         /* Try to bundle SACK chunk */
 406         retval = sctp_packet_bundle_sack(packet, chunk);
 407         if (retval != SCTP_XMIT_OK)
 408                 goto finish;
 409
 410         retval = __sctp_packet_append_chunk(packet, chunk);
 411         if (retval != SCTP_XMIT_OK)
 412                 goto finish;
 413
 414         retval = sctp_packet_bundle_pad(packet, chunk);
 415
 416 finish:
 417         return retval;
 418 }
 419
 420 static void sctp_packet_gso_append(struct sk_buff *head, struct sk_buff *skb)
 421 {
 422         if (SCTP_OUTPUT_CB(head)->last == head)
 423                 skb_shinfo(head)->frag_list = skb;
 424         else
 425                 SCTP_OUTPUT_CB(head)->last->next = skb;
 426         SCTP_OUTPUT_CB(head)->last = skb;
 427
 428         head->truesize += skb->truesize;
 429         head->data_len += skb->len;
 430         head->len += skb->len;
 431         refcount_add(skb->truesize, &head->sk->sk_wmem_alloc);
 432
 433         __skb_header_release(skb);
 434 }
 435
 436 static int sctp_packet_pack(struct sctp_packet *packet,
 437                             struct sk_buff *head, int gso, gfp_t gfp)
 438 {
 439         struct sctp_transport *tp = packet->transport;
 440         struct sctp_auth_chunk *auth = NULL;
 441         struct sctp_chunk *chunk, *tmp;
 442         int pkt_count = 0, pkt_size;
 443         struct sock *sk = head->sk;
 444         struct sk_buff *nskb;
 445         int auth_len = 0;
 446
 447         if (gso) {
 448                 skb_shinfo(head)->gso_type = sk->sk_gso_type;
 449                 SCTP_OUTPUT_CB(head)->last = head;
 450         } else {
 451                 nskb = head;
 452                 pkt_size = packet->size;
 453                 goto merge;
 454         }
 455
 456         do {
 457                 /* calculate the pkt_size and alloc nskb */
 458                 pkt_size = packet->overhead;
 459                 list_for_each_entry_safe(chunk, tmp, &packet->chunk_list,
 460                                          list) {
 461                         int padded = SCTP_PAD4(chunk->skb->len);
 462
 463                         if (chunk == packet->auth)
 464                                 auth_len = padded;
 465                         else if (auth_len + padded + packet->overhead >
 466                                  tp->pathmtu)
 467                                 return 0;
 468                         else if (pkt_size + padded > tp->pathmtu)
 469                                 break;
 470                         pkt_size += padded;
 471                 }
 472                 nskb = alloc_skb(pkt_size + MAX_HEADER, gfp);
 473                 if (!nskb)
 474                         return 0;
 475                 skb_reserve(nskb, packet->overhead + MAX_HEADER);
 476
 477 merge:
 478                 /* merge chunks into nskb and append nskb into head list */
 479                 pkt_size -= packet->overhead;
 480                 list_for_each_entry_safe(chunk, tmp, &packet->chunk_list, list) {
 481                         int padding;
 482
 483                         list_del_init(&chunk->list);
 484                         if (sctp_chunk_is_data(chunk)) {
 485                                 if (!sctp_chunk_retransmitted(chunk) &&
 486                                     !tp->rto_pending) {
 487                                         chunk->rtt_in_progress = 1;
 488                                         tp->rto_pending = 1;
 489                                 }
 490                         }
 491
 492                         padding = SCTP_PAD4(chunk->skb->len) - chunk->skb->len;
 493                         if (padding)
 494                                 skb_put_zero(chunk->skb, padding);
 495
 496                         if (chunk == packet->auth)
 497                                 auth = (struct sctp_auth_chunk *)
 498                                                         skb_tail_pointer(nskb);
 499
 500                         skb_put_data(nskb, chunk->skb->data, chunk->skb->len);
 501
 502                         pr_debug("*** Chunk:%p[%s] %s 0x%x, length:%d, chunk->skb->len:%d, rtt_in_progress:%d\n",
 503                                  chunk,
 504                                  sctp_cname(SCTP_ST_CHUNK(chunk->chunk_hdr->type)),
 505                                  chunk->has_tsn ? "TSN" : "No TSN",
 506                                  chunk->has_tsn ? ntohl(chunk->subh.data_hdr->tsn) : 0,
 507                                  ntohs(chunk->chunk_hdr->length), chunk->skb->len,
 508                                  chunk->rtt_in_progress);
 509
 510                         pkt_size -= SCTP_PAD4(chunk->skb->len);
 511
 512                         if (!sctp_chunk_is_data(chunk) && chunk != packet->auth)
 513                                 sctp_chunk_free(chunk);
 514
 515                         if (!pkt_size)
 516                                 break;
 517                 }
 518
 519                 if (auth) {
 520                         sctp_auth_calculate_hmac(tp->asoc, nskb, auth,
 521                                                  packet->auth->shkey, gfp);
 522                         /* free auth if no more chunks, or add it back */
 523                         if (list_empty(&packet->chunk_list))
 524                                 sctp_chunk_free(packet->auth);
 525                         else
 526                                 list_add(&packet->auth->list,
 527                                          &packet->chunk_list);
 528                 }
 529
 530                 if (gso)
 531                         sctp_packet_gso_append(head, nskb);
 532
 533                 pkt_count++;
 534         } while (!list_empty(&packet->chunk_list));
 535
 536         if (gso) {
 537                 memset(head->cb, 0, max(sizeof(struct inet_skb_parm),
 538                                         sizeof(struct inet6_skb_parm)));
 539                 skb_shinfo(head)->gso_segs = pkt_count;
 540                 skb_shinfo(head)->gso_size = GSO_BY_FRAGS;
 541                 goto chksum;
 542         }
 543
 544         if (sctp_checksum_disable)
 545                 return 1;
 546
 547         if (!(tp->dst->dev->features & NETIF_F_SCTP_CRC) ||
 548             dst_xfrm(tp->dst) || packet->ipfragok || tp->encap_port) {
 549                 struct sctphdr *sh =
 550                         (struct sctphdr *)skb_transport_header(head);
 551
 552                 sh->checksum = sctp_compute_cksum(head, 0);
 553         } else {
 554 chksum:
 555                 head->ip_summed = CHECKSUM_PARTIAL;
 556                 head->csum_not_inet = 1;
 557                 head->csum_start = skb_transport_header(head) - head->head;
 558                 head->csum_offset = offsetof(struct sctphdr, checksum);
 559         }
 560
 561         return pkt_count;
 562 }
 563
 564 /* All packets are sent to the network through this function from
 565  * sctp_outq_tail().
 566  *
 567  * The return value is always 0 for now.
 568  */
 569 int sctp_packet_transmit(struct sctp_packet *packet, gfp_t gfp)
 570 {
 571         struct sctp_transport *tp = packet->transport;
 572         struct sctp_association *asoc = tp->asoc;
 573         struct sctp_chunk *chunk, *tmp;
 574         int pkt_count, gso = 0;
 575         struct sk_buff *head;
 576         struct sctphdr *sh;
 577         struct sock *sk;
 578
 579         pr_debug("%s: packet:%p\n", __func__, packet);
 580         if (list_empty(&packet->chunk_list))
 581                 return 0;
 582         chunk = list_entry(packet->chunk_list.next, struct sctp_chunk, list);
 583         sk = chunk->skb->sk;
 584
 585         if (packet->size > tp->pathmtu && !packet->ipfragok && !chunk->pmtu_probe) {
 586                 if (tp->pl.state == SCTP_PL_ERROR) { /* do IP fragmentation if in Error state */
 587                         packet->ipfragok = 1;
 588                 } else {
 589                         if (!sk_can_gso(sk)) { /* check gso */
 590                                 pr_err_once("Trying to GSO but underlying device doesn't support it.");
 591                                 goto out;
 592                         }
 593                         gso = 1;
 594                 }
 595         }
 596
 597         /* alloc head skb */
 598         head = alloc_skb((gso ? packet->overhead : packet->size) +
 599                          MAX_HEADER, gfp);
 600         if (!head)
 601                 goto out;
 602         skb_reserve(head, packet->overhead + MAX_HEADER);
 603         skb_set_owner_w(head, sk);
 604
 605         /* set sctp header */
 606         sh = skb_push(head, sizeof(struct sctphdr));
 607         skb_reset_transport_header(head);
 608         sh->source = htons(packet->source_port);
 609         sh->dest = htons(packet->destination_port);
 610         sh->vtag = htonl(packet->vtag);
 611         sh->checksum = 0;
 612
 613         /* drop packet if no dst */
 614         if (!tp->dst) {
 615                 IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTNOROUTES);
 616                 kfree_skb(head);
 617                 goto out;
 618         }
 619
 620         /* pack up chunks */
 621         pkt_count = sctp_packet_pack(packet, head, gso, gfp);
 622         if (!pkt_count) {
 623                 kfree_skb(head);
 624                 goto out;
 625         }
 626         pr_debug("***sctp_transmit_packet*** skb->len:%d\n", head->len);
 627
 628         /* start autoclose timer */
 629         if (packet->has_data && sctp_state(asoc, ESTABLISHED) &&
 630             asoc->timeouts[SCTP_EVENT_TIMEOUT_AUTOCLOSE]) {
 631                 struct timer_list *timer =
 632                         &asoc->timers[SCTP_EVENT_TIMEOUT_AUTOCLOSE];
 633                 unsigned long timeout =
 634                         asoc->timeouts[SCTP_EVENT_TIMEOUT_AUTOCLOSE];
 635
 636                 if (!mod_timer(timer, jiffies + timeout))
 637                         sctp_association_hold(asoc);
 638         }
 639
 640         /* sctp xmit */
 641         tp->af_specific->ecn_capable(sk);
 642         if (asoc) {
 643                 asoc->stats.opackets += pkt_count;
 644                 if (asoc->peer.last_sent_to != tp)
 645                         asoc->peer.last_sent_to = tp;
 646         }
 647         head->ignore_df = packet->ipfragok;
 648         if (tp->dst_pending_confirm)
 649                 skb_set_dst_pending_confirm(head, 1);
 650         /* neighbour should be confirmed on successful transmission or
 651          * positive error
 652          */
 653         if (tp->af_specific->sctp_xmit(head, tp) >= 0 &&
 654             tp->dst_pending_confirm)
 655                 tp->dst_pending_confirm = 0;
 656
 657 out:
 658         list_for_each_entry_safe(chunk, tmp, &packet->chunk_list, list) {
 659                 list_del_init(&chunk->list);
 660                 if (!sctp_chunk_is_data(chunk))
 661                         sctp_chunk_free(chunk);
 662         }
 663         sctp_packet_reset(packet);
 664         return 0;
 665 }
 666
 667 /********************************************************************
 668  * 2nd Level Abstractions
 669  ********************************************************************/
 670
 671 /* This private function check to see if a chunk can be added */
 672 static enum sctp_xmit sctp_packet_can_append_data(struct sctp_packet *packet,
 673                                                   struct sctp_chunk *chunk)
 674 {
 675         size_t datasize, rwnd, inflight, flight_size;
 676         struct sctp_transport *transport = packet->transport;
 677         struct sctp_association *asoc = transport->asoc;
 678         struct sctp_outq *q = &asoc->outqueue;
 679
 680         /* RFC 2960 6.1  Transmission of DATA Chunks
 681          *
 682          * A) At any given time, the data sender MUST NOT transmit new data to
 683          * any destination transport address if its peer's rwnd indicates
 684          * that the peer has no buffer space (i.e. rwnd is 0, see Section
 685          * 6.2.1).  However, regardless of the value of rwnd (including if it
 686          * is 0), the data sender can always have one DATA chunk in flight to
 687          * the receiver if allowed by cwnd (see rule B below).  This rule
 688          * allows the sender to probe for a change in rwnd that the sender
 689          * missed due to the SACK having been lost in transit from the data
 690          * receiver to the data sender.
 691          */
 692
 693         rwnd = asoc->peer.rwnd;
 694         inflight = q->outstanding_bytes;
 695         flight_size = transport->flight_size;
 696
 697         datasize = sctp_data_size(chunk);
 698
 699         if (datasize > rwnd && inflight > 0)
 700                 /* We have (at least) one data chunk in flight,
 701                  * so we can't fall back to rule 6.1 B).
 702                  */
 703                 return SCTP_XMIT_RWND_FULL;
 704
 705         /* RFC 2960 6.1  Transmission of DATA Chunks
 706          *
 707          * B) At any given time, the sender MUST NOT transmit new data
 708          * to a given transport address if it has cwnd or more bytes
 709          * of data outstanding to that transport address.
 710          */
 711         /* RFC 7.2.4 & the Implementers Guide 2.8.
 712          *
 713          * 3) ...
 714          *    When a Fast Retransmit is being performed the sender SHOULD
 715          *    ignore the value of cwnd and SHOULD NOT delay retransmission.
 716          */
 717         if (chunk->fast_retransmit != SCTP_NEED_FRTX &&
 718             flight_size >= transport->cwnd)
 719                 return SCTP_XMIT_RWND_FULL;
 720
 721         /* Nagle's algorithm to solve small-packet problem:
 722          * Inhibit the sending of new chunks when new outgoing data arrives
 723          * if any previously transmitted data on the connection remains
 724          * unacknowledged.
 725          */
 726
 727         if ((sctp_sk(asoc->base.sk)->nodelay || inflight == 0) &&
 728             !asoc->force_delay)
 729                 /* Nothing unacked */
 730                 return SCTP_XMIT_OK;
 731
 732         if (!sctp_packet_empty(packet))
 733                 /* Append to packet */
 734                 return SCTP_XMIT_OK;
 735
 736         if (!sctp_state(asoc, ESTABLISHED))
 737                 return SCTP_XMIT_OK;
 738
 739         /* Check whether this chunk and all the rest of pending data will fit
 740          * or delay in hopes of bundling a full sized packet.
 741          */
 742         if (chunk->skb->len + q->out_qlen > transport->pathmtu -
 743             packet->overhead - sctp_datachk_len(&chunk->asoc->stream) - 4)
 744                 /* Enough data queued to fill a packet */
 745                 return SCTP_XMIT_OK;
 746
 747         /* Don't delay large message writes that may have been fragmented */
 748         if (!chunk->msg->can_delay)
 749                 return SCTP_XMIT_OK;
 750
 751         /* Defer until all data acked or packet full */
 752         return SCTP_XMIT_DELAY;
 753 }
 754
 755 /* This private function does management things when adding DATA chunk */
 756 static void sctp_packet_append_data(struct sctp_packet *packet,
 757                                 struct sctp_chunk *chunk)
 758 {
 759         struct sctp_transport *transport = packet->transport;
 760         size_t datasize = sctp_data_size(chunk);
 761         struct sctp_association *asoc = transport->asoc;
 762         u32 rwnd = asoc->peer.rwnd;
 763
 764         /* Keep track of how many bytes are in flight over this transport. */
 765         transport->flight_size += datasize;
 766
 767         /* Keep track of how many bytes are in flight to the receiver. */
 768         asoc->outqueue.outstanding_bytes += datasize;
 769
 770         /* Update our view of the receiver's rwnd. */
 771         if (datasize < rwnd)
 772                 rwnd -= datasize;
 773         else
 774                 rwnd = 0;
 775
 776         asoc->peer.rwnd = rwnd;
 777         sctp_chunk_assign_tsn(chunk);
 778         asoc->stream.si->assign_number(chunk);
 779 }
 780
 781 static enum sctp_xmit sctp_packet_will_fit(struct sctp_packet *packet,
 782                                            struct sctp_chunk *chunk,
 783                                            u16 chunk_len)
 784 {
 785         enum sctp_xmit retval = SCTP_XMIT_OK;
 786         size_t psize, pmtu, maxsize;
 787
 788         /* Don't bundle in this packet if this chunk's auth key doesn't
 789          * match other chunks already enqueued on this packet. Also,
 790          * don't bundle the chunk with auth key if other chunks in this
 791          * packet don't have auth key.
 792          */
 793         if ((packet->auth && chunk->shkey != packet->auth->shkey) ||
 794             (!packet->auth && chunk->shkey &&
 795              chunk->chunk_hdr->type != SCTP_CID_AUTH))
 796                 return SCTP_XMIT_PMTU_FULL;
 797
 798         psize = packet->size;
 799         if (packet->transport->asoc)
 800                 pmtu = packet->transport->asoc->pathmtu;
 801         else
 802                 pmtu = packet->transport->pathmtu;
 803
 804         /* Decide if we need to fragment or resubmit later. */
 805         if (psize + chunk_len > pmtu) {
 806                 /* It's OK to fragment at IP level if any one of the following
 807                  * is true:
 808                  *      1. The packet is empty (meaning this chunk is greater
 809                  *         the MTU)
 810                  *      2. The packet doesn't have any data in it yet and data
 811                  *         requires authentication.
 812                  */
 813                 if (sctp_packet_empty(packet) ||
 814                     (!packet->has_data && chunk->auth)) {
 815                         /* We no longer do re-fragmentation.
 816                          * Just fragment at the IP layer, if we
 817                          * actually hit this condition
 818                          */
 819                         packet->ipfragok = 1;
 820                         goto out;
 821                 }
 822
 823                 /* Similarly, if this chunk was built before a PMTU
 824                  * reduction, we have to fragment it at IP level now. So
 825                  * if the packet already contains something, we need to
 826                  * flush.
 827                  */
 828                 maxsize = pmtu - packet->overhead;
 829                 if (packet->auth)
 830                         maxsize -= SCTP_PAD4(packet->auth->skb->len);
 831                 if (chunk_len > maxsize)
 832                         retval = SCTP_XMIT_PMTU_FULL;
 833
 834                 /* It is also okay to fragment if the chunk we are
 835                  * adding is a control chunk, but only if current packet
 836                  * is not a GSO one otherwise it causes fragmentation of
 837                  * a large frame. So in this case we allow the
 838                  * fragmentation by forcing it to be in a new packet.
 839                  */
 840                 if (!sctp_chunk_is_data(chunk) && packet->has_data)
 841                         retval = SCTP_XMIT_PMTU_FULL;
 842
 843                 if (psize + chunk_len > packet->max_size)
 844                         /* Hit GSO/PMTU limit, gotta flush */
 845                         retval = SCTP_XMIT_PMTU_FULL;
 846
 847                 if (!packet->transport->burst_limited &&
 848                     psize + chunk_len > (packet->transport->cwnd >> 1))
 849                         /* Do not allow a single GSO packet to use more
 850                          * than half of cwnd.
 851                          */
 852                         retval = SCTP_XMIT_PMTU_FULL;
 853
 854                 if (packet->transport->burst_limited &&
 855                     psize + chunk_len > (packet->transport->burst_limited >> 1))
 856                         /* Do not allow a single GSO packet to use more
 857                          * than half of original cwnd.
 858                          */
 859                         retval = SCTP_XMIT_PMTU_FULL;
 860                 /* Otherwise it will fit in the GSO packet */
 861         }
 862
 863 out:
 864         return retval;
 865 }