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   1 /*
   2  *  net/dccp/output.c
   3  *
   4  *  An implementation of the DCCP protocol
   5  *  Arnaldo Carvalho de Melo <acme@conectiva.com.br>
   6  *
   7  *      This program is free software; you can redistribute it and/or
   8  *      modify it under the terms of the GNU General Public License
   9  *      as published by the Free Software Foundation; either version
  10  *      2 of the License, or (at your option) any later version.
  11  */
  12
  13 #include <linux/dccp.h>
  14 #include <linux/kernel.h>
  15 #include <linux/skbuff.h>
  16
  17 #include <net/inet_sock.h>
  18 #include <net/sock.h>
  19
  20 #include "ackvec.h"
  21 #include "ccid.h"
  22 #include "dccp.h"
  23
  24 static inline void dccp_event_ack_sent(struct sock *sk)
  25 {
  26         inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK);
  27 }
  28
  29 static void dccp_skb_entail(struct sock *sk, struct sk_buff *skb)
  30 {
  31         skb_set_owner_w(skb, sk);
  32         WARN_ON(sk->sk_send_head);
  33         sk->sk_send_head = skb;
  34 }
  35
  36 /*
  37  * All SKB's seen here are completely headerless. It is our
  38  * job to build the DCCP header, and pass the packet down to
  39  * IP so it can do the same plus pass the packet off to the
  40  * device.
  41  */
  42 static int dccp_transmit_skb(struct sock *sk, struct sk_buff *skb)
  43 {
  44         if (likely(skb != NULL)) {
  45                 const struct inet_sock *inet = inet_sk(sk);
  46                 const struct inet_connection_sock *icsk = inet_csk(sk);
  47                 struct dccp_sock *dp = dccp_sk(sk);
  48                 struct dccp_skb_cb *dcb = DCCP_SKB_CB(skb);
  49                 struct dccp_hdr *dh;
  50                 /* XXX For now we're using only 48 bits sequence numbers */
  51                 const u32 dccp_header_size = sizeof(*dh) +
  52                                              sizeof(struct dccp_hdr_ext) +
  53                                           dccp_packet_hdr_len(dcb->dccpd_type);
  54                 int err, set_ack = 1;
  55                 u64 ackno = dp->dccps_gsr;
  56
  57                 dccp_inc_seqno(&dp->dccps_gss);
  58
  59                 switch (dcb->dccpd_type) {
  60                 case DCCP_PKT_DATA:
  61                         set_ack = 0;
  62                         /* fall through */
  63                 case DCCP_PKT_DATAACK:
  64                         break;
  65
  66                 case DCCP_PKT_REQUEST:
  67                         set_ack = 0;
  68                         /* fall through */
  69
  70                 case DCCP_PKT_SYNC:
  71                 case DCCP_PKT_SYNCACK:
  72                         ackno = dcb->dccpd_seq;
  73                         /* fall through */
  74                 default:
  75                         /*
  76                          * Only data packets should come through with skb->sk
  77                          * set.
  78                          */
  79                         WARN_ON(skb->sk);
  80                         skb_set_owner_w(skb, sk);
  81                         break;
  82                 }
  83
  84                 dcb->dccpd_seq = dp->dccps_gss;
  85
  86                 if (dccp_insert_options(sk, skb)) {
  87                         kfree_skb(skb);
  88                         return -EPROTO;
  89                 }
  90
  91                 skb->h.raw = skb_push(skb, dccp_header_size);
  92                 dh = dccp_hdr(skb);
  93
  94                 /* Build DCCP header and checksum it. */
  95                 memset(dh, 0, dccp_header_size);
  96                 dh->dccph_type  = dcb->dccpd_type;
  97                 dh->dccph_sport = inet->sport;
  98                 dh->dccph_dport = inet->dport;
  99                 dh->dccph_doff  = (dccp_header_size + dcb->dccpd_opt_len) / 4;
 100                 dh->dccph_ccval = dcb->dccpd_ccval;
 101                 /* XXX For now we're using only 48 bits sequence numbers */
 102                 dh->dccph_x     = 1;
 103
 104                 dp->dccps_awh = dp->dccps_gss;
 105                 dccp_hdr_set_seq(dh, dp->dccps_gss);
 106                 if (set_ack)
 107                         dccp_hdr_set_ack(dccp_hdr_ack_bits(skb), ackno);
 108
 109                 switch (dcb->dccpd_type) {
 110                 case DCCP_PKT_REQUEST:
 111                         dccp_hdr_request(skb)->dccph_req_service =
 112                                                         dp->dccps_service;
 113                         break;
 114                 case DCCP_PKT_RESET:
 115                         dccp_hdr_reset(skb)->dccph_reset_code =
 116                                                         dcb->dccpd_reset_code;
 117                         break;
 118                 }
 119
 120                 icsk->icsk_af_ops->send_check(sk, skb->len, skb);
 121
 122                 if (set_ack)
 123                         dccp_event_ack_sent(sk);
 124
 125                 DCCP_INC_STATS(DCCP_MIB_OUTSEGS);
 126
 127                 memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));
 128                 err = icsk->icsk_af_ops->queue_xmit(skb, 0);
 129                 if (err <= 0)
 130                         return err;
 131
 132                 /* NET_XMIT_CN is special. It does not guarantee,
 133                  * that this packet is lost. It tells that device
 134                  * is about to start to drop packets or already
 135                  * drops some packets of the same priority and
 136                  * invokes us to send less aggressively.
 137                  */
 138                 return err == NET_XMIT_CN ? 0 : err;
 139         }
 140         return -ENOBUFS;
 141 }
 142
 143 unsigned int dccp_sync_mss(struct sock *sk, u32 pmtu)
 144 {
 145         struct inet_connection_sock *icsk = inet_csk(sk);
 146         struct dccp_sock *dp = dccp_sk(sk);
 147         int mss_now = (pmtu - icsk->icsk_af_ops->net_header_len -
 148                        sizeof(struct dccp_hdr) - sizeof(struct dccp_hdr_ext));
 149
 150         /* Now subtract optional transport overhead */
 151         mss_now -= icsk->icsk_ext_hdr_len;
 152
 153         /*
 154          * FIXME: this should come from the CCID infrastructure, where, say,
 155          * TFRC will say it wants TIMESTAMPS, ELAPSED time, etc, for now lets
 156          * put a rough estimate for NDP + TIMESTAMP + TIMESTAMP_ECHO + ELAPSED
 157          * TIME + TFRC_OPT_LOSS_EVENT_RATE + TFRC_OPT_RECEIVE_RATE + padding to
 158          * make it a multiple of 4
 159          */
 160
 161         mss_now -= ((5 + 6 + 10 + 6 + 6 + 6 + 3) / 4) * 4;
 162
 163         /* And store cached results */
 164         icsk->icsk_pmtu_cookie = pmtu;
 165         dp->dccps_mss_cache = mss_now;
 166
 167         return mss_now;
 168 }
 169
 170 EXPORT_SYMBOL_GPL(dccp_sync_mss);
 171
 172 void dccp_write_space(struct sock *sk)
 173 {
 174         read_lock(&sk->sk_callback_lock);
 175
 176         if (sk->sk_sleep && waitqueue_active(sk->sk_sleep))
 177                 wake_up_interruptible(sk->sk_sleep);
 178         /* Should agree with poll, otherwise some programs break */
 179         if (sock_writeable(sk))
 180                 sk_wake_async(sk, 2, POLL_OUT);
 181
 182         read_unlock(&sk->sk_callback_lock);
 183 }
 184
 185 /**
 186  * dccp_wait_for_ccid - Wait for ccid to tell us we can send a packet
 187  * @sk: socket to wait for
 188  * @timeo: for how long
 189  */
 190 static int dccp_wait_for_ccid(struct sock *sk, struct sk_buff *skb,
 191                               long *timeo)
 192 {
 193         struct dccp_sock *dp = dccp_sk(sk);
 194         DEFINE_WAIT(wait);
 195         long delay;
 196         int rc;
 197
 198         while (1) {
 199                 prepare_to_wait(sk->sk_sleep, &wait, TASK_INTERRUPTIBLE);
 200
 201                 if (sk->sk_err)
 202                         goto do_error;
 203                 if (!*timeo)
 204                         goto do_nonblock;
 205                 if (signal_pending(current))
 206                         goto do_interrupted;
 207
 208                 rc = ccid_hc_tx_send_packet(dp->dccps_hc_tx_ccid, sk, skb,
 209                                             skb->len);
 210                 if (rc <= 0)
 211                         break;
 212                 delay = msecs_to_jiffies(rc);
 213                 if (delay > *timeo || delay < 0)
 214                         goto do_nonblock;
 215
 216                 sk->sk_write_pending++;
 217                 release_sock(sk);
 218                 *timeo -= schedule_timeout(delay);
 219                 lock_sock(sk);
 220                 sk->sk_write_pending--;
 221         }
 222 out:
 223         finish_wait(sk->sk_sleep, &wait);
 224         return rc;
 225
 226 do_error:
 227         rc = -EPIPE;
 228         goto out;
 229 do_nonblock:
 230         rc = -EAGAIN;
 231         goto out;
 232 do_interrupted:
 233         rc = sock_intr_errno(*timeo);
 234         goto out;
 235 }
 236
 237 static void dccp_write_xmit_timer(unsigned long data) {
 238         struct sock *sk = (struct sock *)data;
 239         struct dccp_sock *dp = dccp_sk(sk);
 240
 241         bh_lock_sock(sk);
 242         if (sock_owned_by_user(sk))
 243                 sk_reset_timer(sk, &dp->dccps_xmit_timer, jiffies+1);
 244         else
 245                 dccp_write_xmit(sk, 0);
 246         bh_unlock_sock(sk);
 247         sock_put(sk);
 248 }
 249
 250 void dccp_write_xmit(struct sock *sk, int block)
 251 {
 252         struct dccp_sock *dp = dccp_sk(sk);
 253         struct sk_buff *skb;
 254         long timeo = 30000;     /* If a packet is taking longer than 2 secs
 255                                    we have other issues */
 256
 257         while ((skb = skb_peek(&sk->sk_write_queue))) {
 258                 int err = ccid_hc_tx_send_packet(dp->dccps_hc_tx_ccid, sk, skb,
 259                                          skb->len);
 260
 261                 if (err > 0) {
 262                         if (!block) {
 263                                 sk_reset_timer(sk, &dp->dccps_xmit_timer,
 264                                                 msecs_to_jiffies(err)+jiffies);
 265                                 break;
 266                         } else
 267                                 err = dccp_wait_for_ccid(sk, skb, &timeo);
 268                         if (err) {
 269                                 printk(KERN_CRIT "%s:err at dccp_wait_for_ccid"
 270                                                  " %d\n", __FUNCTION__, err);
 271                                 dump_stack();
 272                         }
 273                 }
 274
 275                 skb_dequeue(&sk->sk_write_queue);
 276                 if (err == 0) {
 277                         struct dccp_skb_cb *dcb = DCCP_SKB_CB(skb);
 278                         const int len = skb->len;
 279
 280                         if (sk->sk_state == DCCP_PARTOPEN) {
 281                                 /* See 8.1.5.  Handshake Completion */
 282                                 inet_csk_schedule_ack(sk);
 283                                 inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
 284                                                   inet_csk(sk)->icsk_rto,
 285                                                   DCCP_RTO_MAX);
 286                                 dcb->dccpd_type = DCCP_PKT_DATAACK;
 287                         } else if (dccp_ack_pending(sk))
 288                                 dcb->dccpd_type = DCCP_PKT_DATAACK;
 289                         else
 290                                 dcb->dccpd_type = DCCP_PKT_DATA;
 291
 292                         err = dccp_transmit_skb(sk, skb);
 293                         ccid_hc_tx_packet_sent(dp->dccps_hc_tx_ccid, sk, 0, len);
 294                         if (err) {
 295                                 printk(KERN_CRIT "%s:err from "
 296                                                  "ccid_hc_tx_packet_sent %d\n",
 297                                                  __FUNCTION__, err);
 298                                 dump_stack();
 299                         }
 300                 } else
 301                         kfree(skb);
 302         }
 303 }
 304
 305 int dccp_retransmit_skb(struct sock *sk, struct sk_buff *skb)
 306 {
 307         if (inet_csk(sk)->icsk_af_ops->rebuild_header(sk) != 0)
 308                 return -EHOSTUNREACH; /* Routing failure or similar. */
 309
 310         return dccp_transmit_skb(sk, (skb_cloned(skb) ?
 311                                       pskb_copy(skb, GFP_ATOMIC):
 312                                       skb_clone(skb, GFP_ATOMIC)));
 313 }
 314
 315 struct sk_buff *dccp_make_response(struct sock *sk, struct dst_entry *dst,
 316                                    struct request_sock *req)
 317 {
 318         struct dccp_hdr *dh;
 319         struct dccp_request_sock *dreq;
 320         const u32 dccp_header_size = sizeof(struct dccp_hdr) +
 321                                      sizeof(struct dccp_hdr_ext) +
 322                                      sizeof(struct dccp_hdr_response);
 323         struct sk_buff *skb = sock_wmalloc(sk, sk->sk_prot->max_header, 1,
 324                                            GFP_ATOMIC);
 325         if (skb == NULL)
 326                 return NULL;
 327
 328         /* Reserve space for headers. */
 329         skb_reserve(skb, sk->sk_prot->max_header);
 330
 331         skb->dst = dst_clone(dst);
 332         skb->csum = 0;
 333
 334         dreq = dccp_rsk(req);
 335         DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_RESPONSE;
 336         DCCP_SKB_CB(skb)->dccpd_seq  = dreq->dreq_iss;
 337
 338         if (dccp_insert_options(sk, skb)) {
 339                 kfree_skb(skb);
 340                 return NULL;
 341         }
 342
 343         skb->h.raw = skb_push(skb, dccp_header_size);
 344
 345         dh = dccp_hdr(skb);
 346         memset(dh, 0, dccp_header_size);
 347
 348         dh->dccph_sport = inet_sk(sk)->sport;
 349         dh->dccph_dport = inet_rsk(req)->rmt_port;
 350         dh->dccph_doff  = (dccp_header_size +
 351                            DCCP_SKB_CB(skb)->dccpd_opt_len) / 4;
 352         dh->dccph_type  = DCCP_PKT_RESPONSE;
 353         dh->dccph_x     = 1;
 354         dccp_hdr_set_seq(dh, dreq->dreq_iss);
 355         dccp_hdr_set_ack(dccp_hdr_ack_bits(skb), dreq->dreq_isr);
 356         dccp_hdr_response(skb)->dccph_resp_service = dreq->dreq_service;
 357
 358         DCCP_INC_STATS(DCCP_MIB_OUTSEGS);
 359         return skb;
 360 }
 361
 362 EXPORT_SYMBOL_GPL(dccp_make_response);
 363
 364 static struct sk_buff *dccp_make_reset(struct sock *sk, struct dst_entry *dst,
 365                                        const enum dccp_reset_codes code)
 366
 367 {
 368         struct dccp_hdr *dh;
 369         struct dccp_sock *dp = dccp_sk(sk);
 370         const u32 dccp_header_size = sizeof(struct dccp_hdr) +
 371                                      sizeof(struct dccp_hdr_ext) +
 372                                      sizeof(struct dccp_hdr_reset);
 373         struct sk_buff *skb = sock_wmalloc(sk, sk->sk_prot->max_header, 1,
 374                                            GFP_ATOMIC);
 375         if (skb == NULL)
 376                 return NULL;
 377
 378         /* Reserve space for headers. */
 379         skb_reserve(skb, sk->sk_prot->max_header);
 380
 381         skb->dst = dst_clone(dst);
 382         skb->csum = 0;
 383
 384         dccp_inc_seqno(&dp->dccps_gss);
 385
 386         DCCP_SKB_CB(skb)->dccpd_reset_code = code;
 387         DCCP_SKB_CB(skb)->dccpd_type       = DCCP_PKT_RESET;
 388         DCCP_SKB_CB(skb)->dccpd_seq        = dp->dccps_gss;
 389
 390         if (dccp_insert_options(sk, skb)) {
 391                 kfree_skb(skb);
 392                 return NULL;
 393         }
 394
 395         skb->h.raw = skb_push(skb, dccp_header_size);
 396
 397         dh = dccp_hdr(skb);
 398         memset(dh, 0, dccp_header_size);
 399
 400         dh->dccph_sport = inet_sk(sk)->sport;
 401         dh->dccph_dport = inet_sk(sk)->dport;
 402         dh->dccph_doff  = (dccp_header_size +
 403                            DCCP_SKB_CB(skb)->dccpd_opt_len) / 4;
 404         dh->dccph_type  = DCCP_PKT_RESET;
 405         dh->dccph_x     = 1;
 406         dccp_hdr_set_seq(dh, dp->dccps_gss);
 407         dccp_hdr_set_ack(dccp_hdr_ack_bits(skb), dp->dccps_gsr);
 408
 409         dccp_hdr_reset(skb)->dccph_reset_code = code;
 410         inet_csk(sk)->icsk_af_ops->send_check(sk, skb->len, skb);
 411
 412         DCCP_INC_STATS(DCCP_MIB_OUTSEGS);
 413         return skb;
 414 }
 415
 416 int dccp_send_reset(struct sock *sk, enum dccp_reset_codes code)
 417 {
 418         /*
 419          * FIXME: what if rebuild_header fails?
 420          * Should we be doing a rebuild_header here?
 421          */
 422         int err = inet_sk_rebuild_header(sk);
 423
 424         if (err == 0) {
 425                 struct sk_buff *skb = dccp_make_reset(sk, sk->sk_dst_cache,
 426                                                       code);
 427                 if (skb != NULL) {
 428                         memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));
 429                         err = inet_csk(sk)->icsk_af_ops->queue_xmit(skb, 0);
 430                         if (err == NET_XMIT_CN)
 431                                 err = 0;
 432                 }
 433         }
 434
 435         return err;
 436 }
 437
 438 /*
 439  * Do all connect socket setups that can be done AF independent.
 440  */
 441 static inline void dccp_connect_init(struct sock *sk)
 442 {
 443         struct dccp_sock *dp = dccp_sk(sk);
 444         struct dst_entry *dst = __sk_dst_get(sk);
 445         struct inet_connection_sock *icsk = inet_csk(sk);
 446
 447         sk->sk_err = 0;
 448         sock_reset_flag(sk, SOCK_DONE);
 449
 450         dccp_sync_mss(sk, dst_mtu(dst));
 451
 452         dccp_update_gss(sk, dp->dccps_iss);
 453         /*
 454          * SWL and AWL are initially adjusted so that they are not less than
 455          * the initial Sequence Numbers received and sent, respectively:
 456          *      SWL := max(GSR + 1 - floor(W/4), ISR),
 457          *      AWL := max(GSS - W' + 1, ISS).
 458          * These adjustments MUST be applied only at the beginning of the
 459          * connection.
 460          */
 461         dccp_set_seqno(&dp->dccps_awl, max48(dp->dccps_awl, dp->dccps_iss));
 462
 463         icsk->icsk_retransmits = 0;
 464         init_timer(&dp->dccps_xmit_timer);
 465         dp->dccps_xmit_timer.data = (unsigned long)sk;
 466         dp->dccps_xmit_timer.function = dccp_write_xmit_timer;
 467 }
 468
 469 int dccp_connect(struct sock *sk)
 470 {
 471         struct sk_buff *skb;
 472         struct inet_connection_sock *icsk = inet_csk(sk);
 473
 474         dccp_connect_init(sk);
 475
 476         skb = alloc_skb(sk->sk_prot->max_header, sk->sk_allocation);
 477         if (unlikely(skb == NULL))
 478                 return -ENOBUFS;
 479
 480         /* Reserve space for headers. */
 481         skb_reserve(skb, sk->sk_prot->max_header);
 482
 483         DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_REQUEST;
 484         skb->csum = 0;
 485
 486         dccp_skb_entail(sk, skb);
 487         dccp_transmit_skb(sk, skb_clone(skb, GFP_KERNEL));
 488         DCCP_INC_STATS(DCCP_MIB_ACTIVEOPENS);
 489
 490         /* Timer for repeating the REQUEST until an answer. */
 491         inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
 492                                   icsk->icsk_rto, DCCP_RTO_MAX);
 493         return 0;
 494 }
 495
 496 EXPORT_SYMBOL_GPL(dccp_connect);
 497
 498 void dccp_send_ack(struct sock *sk)
 499 {
 500         /* If we have been reset, we may not send again. */
 501         if (sk->sk_state != DCCP_CLOSED) {
 502                 struct sk_buff *skb = alloc_skb(sk->sk_prot->max_header,
 503                                                 GFP_ATOMIC);
 504
 505                 if (skb == NULL) {
 506                         inet_csk_schedule_ack(sk);
 507                         inet_csk(sk)->icsk_ack.ato = TCP_ATO_MIN;
 508                         inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
 509                                                   TCP_DELACK_MAX,
 510                                                   DCCP_RTO_MAX);
 511                         return;
 512                 }
 513
 514                 /* Reserve space for headers */
 515                 skb_reserve(skb, sk->sk_prot->max_header);
 516                 skb->csum = 0;
 517                 DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_ACK;
 518                 dccp_transmit_skb(sk, skb);
 519         }
 520 }
 521
 522 EXPORT_SYMBOL_GPL(dccp_send_ack);
 523
 524 void dccp_send_delayed_ack(struct sock *sk)
 525 {
 526         struct inet_connection_sock *icsk = inet_csk(sk);
 527         /*
 528          * FIXME: tune this timer. elapsed time fixes the skew, so no problem
 529          * with using 2s, and active senders also piggyback the ACK into a
 530          * DATAACK packet, so this is really for quiescent senders.
 531          */
 532         unsigned long timeout = jiffies + 2 * HZ;
 533
 534         /* Use new timeout only if there wasn't a older one earlier. */
 535         if (icsk->icsk_ack.pending & ICSK_ACK_TIMER) {
 536                 /* If delack timer was blocked or is about to expire,
 537                  * send ACK now.
 538                  *
 539                  * FIXME: check the "about to expire" part
 540                  */
 541                 if (icsk->icsk_ack.blocked) {
 542                         dccp_send_ack(sk);
 543                         return;
 544                 }
 545
 546                 if (!time_before(timeout, icsk->icsk_ack.timeout))
 547                         timeout = icsk->icsk_ack.timeout;
 548         }
 549         icsk->icsk_ack.pending |= ICSK_ACK_SCHED | ICSK_ACK_TIMER;
 550         icsk->icsk_ack.timeout = timeout;
 551         sk_reset_timer(sk, &icsk->icsk_delack_timer, timeout);
 552 }
 553
 554 void dccp_send_sync(struct sock *sk, const u64 seq,
 555                     const enum dccp_pkt_type pkt_type)
 556 {
 557         /*
 558          * We are not putting this on the write queue, so
 559          * dccp_transmit_skb() will set the ownership to this
 560          * sock.
 561          */
 562         struct sk_buff *skb = alloc_skb(sk->sk_prot->max_header, GFP_ATOMIC);
 563
 564         if (skb == NULL)
 565                 /* FIXME: how to make sure the sync is sent? */
 566                 return;
 567
 568         /* Reserve space for headers and prepare control bits. */
 569         skb_reserve(skb, sk->sk_prot->max_header);
 570         skb->csum = 0;
 571         DCCP_SKB_CB(skb)->dccpd_type = pkt_type;
 572         DCCP_SKB_CB(skb)->dccpd_seq = seq;
 573
 574         dccp_transmit_skb(sk, skb);
 575 }
 576
 577 EXPORT_SYMBOL_GPL(dccp_send_sync);
 578
 579 /*
 580  * Send a DCCP_PKT_CLOSE/CLOSEREQ. The caller locks the socket for us. This
 581  * cannot be allowed to fail queueing a DCCP_PKT_CLOSE/CLOSEREQ frame under
 582  * any circumstances.
 583  */
 584 void dccp_send_close(struct sock *sk, const int active)
 585 {
 586         struct dccp_sock *dp = dccp_sk(sk);
 587         struct sk_buff *skb;
 588         const gfp_t prio = active ? GFP_KERNEL : GFP_ATOMIC;
 589
 590         skb = alloc_skb(sk->sk_prot->max_header, prio);
 591         if (skb == NULL)
 592                 return;
 593
 594         /* Reserve space for headers and prepare control bits. */
 595         skb_reserve(skb, sk->sk_prot->max_header);
 596         skb->csum = 0;
 597         DCCP_SKB_CB(skb)->dccpd_type = dp->dccps_role == DCCP_ROLE_CLIENT ?
 598                                         DCCP_PKT_CLOSE : DCCP_PKT_CLOSEREQ;
 599
 600         if (active) {
 601                 dccp_write_xmit(sk, 1);
 602                 dccp_skb_entail(sk, skb);
 603                 dccp_transmit_skb(sk, skb_clone(skb, prio));
 604                 /* FIXME do we need a retransmit timer here? */
 605         } else
 606                 dccp_transmit_skb(sk, skb);
 607 }