git.oblomov.eu Git - linux-2.6/blob - net/dccp/output.c

   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                 case DCCP_PKT_RESET:
  65                         break;
  66
  67                 case DCCP_PKT_REQUEST:
  68                         set_ack = 0;
  69                         /* fall through */
  70
  71                 case DCCP_PKT_SYNC:
  72                 case DCCP_PKT_SYNCACK:
  73                         ackno = dcb->dccpd_ack_seq;
  74                         /* fall through */
  75                 default:
  76                         /*
  77                          * Set owner/destructor: some skbs are allocated via
  78                          * alloc_skb (e.g. when retransmission may happen).
  79                          * Only Data, DataAck, and Reset packets should come
  80                          * through here with skb->sk set.
  81                          */
  82                         WARN_ON(skb->sk);
  83                         skb_set_owner_w(skb, sk);
  84                         break;
  85                 }
  86
  87                 dcb->dccpd_seq = dp->dccps_gss;
  88
  89                 if (dccp_insert_options(sk, skb)) {
  90                         kfree_skb(skb);
  91                         return -EPROTO;
  92                 }
  93
  94
  95                 /* Build DCCP header and checksum it. */
  96                 dh = dccp_zeroed_hdr(skb, dccp_header_size);
  97                 dh->dccph_type  = dcb->dccpd_type;
  98                 dh->dccph_sport = inet->sport;
  99                 dh->dccph_dport = inet->dport;
 100                 dh->dccph_doff  = (dccp_header_size + dcb->dccpd_opt_len) / 4;
 101                 dh->dccph_ccval = dcb->dccpd_ccval;
 102                 dh->dccph_cscov = dp->dccps_pcslen;
 103                 /* XXX For now we're using only 48 bits sequence numbers */
 104                 dh->dccph_x     = 1;
 105
 106                 dp->dccps_awh = dp->dccps_gss;
 107                 dccp_hdr_set_seq(dh, dp->dccps_gss);
 108                 if (set_ack)
 109                         dccp_hdr_set_ack(dccp_hdr_ack_bits(skb), ackno);
 110
 111                 switch (dcb->dccpd_type) {
 112                 case DCCP_PKT_REQUEST:
 113                         dccp_hdr_request(skb)->dccph_req_service =
 114                                                         dp->dccps_service;
 115                         break;
 116                 case DCCP_PKT_RESET:
 117                         dccp_hdr_reset(skb)->dccph_reset_code =
 118                                                         dcb->dccpd_reset_code;
 119                         break;
 120                 }
 121
 122                 icsk->icsk_af_ops->send_check(sk, 0, skb);
 123
 124                 if (set_ack)
 125                         dccp_event_ack_sent(sk);
 126
 127                 DCCP_INC_STATS(DCCP_MIB_OUTSEGS);
 128
 129                 memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));
 130                 err = icsk->icsk_af_ops->queue_xmit(skb, 0);
 131                 return net_xmit_eval(err);
 132         }
 133         return -ENOBUFS;
 134 }
 135
 136 unsigned int dccp_sync_mss(struct sock *sk, u32 pmtu)
 137 {
 138         struct inet_connection_sock *icsk = inet_csk(sk);
 139         struct dccp_sock *dp = dccp_sk(sk);
 140         int mss_now = (pmtu - icsk->icsk_af_ops->net_header_len -
 141                        sizeof(struct dccp_hdr) - sizeof(struct dccp_hdr_ext));
 142
 143         /* Now subtract optional transport overhead */
 144         mss_now -= icsk->icsk_ext_hdr_len;
 145
 146         /*
 147          * FIXME: this should come from the CCID infrastructure, where, say,
 148          * TFRC will say it wants TIMESTAMPS, ELAPSED time, etc, for now lets
 149          * put a rough estimate for NDP + TIMESTAMP + TIMESTAMP_ECHO + ELAPSED
 150          * TIME + TFRC_OPT_LOSS_EVENT_RATE + TFRC_OPT_RECEIVE_RATE + padding to
 151          * make it a multiple of 4
 152          */
 153
 154         mss_now -= ((5 + 6 + 10 + 6 + 6 + 6 + 3) / 4) * 4;
 155
 156         /* And store cached results */
 157         icsk->icsk_pmtu_cookie = pmtu;
 158         dp->dccps_mss_cache = mss_now;
 159
 160         return mss_now;
 161 }
 162
 163 EXPORT_SYMBOL_GPL(dccp_sync_mss);
 164
 165 void dccp_write_space(struct sock *sk)
 166 {
 167         read_lock(&sk->sk_callback_lock);
 168
 169         if (sk->sk_sleep && waitqueue_active(sk->sk_sleep))
 170                 wake_up_interruptible(sk->sk_sleep);
 171         /* Should agree with poll, otherwise some programs break */
 172         if (sock_writeable(sk))
 173                 sk_wake_async(sk, 2, POLL_OUT);
 174
 175         read_unlock(&sk->sk_callback_lock);
 176 }
 177
 178 /**
 179  * dccp_wait_for_ccid - Wait for ccid to tell us we can send a packet
 180  * @sk:    socket to wait for
 181  * @skb:   current skb to pass on for waiting
 182  * @delay: sleep timeout in milliseconds (> 0)
 183  * This function is called by default when the socket is closed, and
 184  * when a non-zero linger time is set on the socket. For consistency
 185  */
 186 static int dccp_wait_for_ccid(struct sock *sk, struct sk_buff *skb, int delay)
 187 {
 188         struct dccp_sock *dp = dccp_sk(sk);
 189         DEFINE_WAIT(wait);
 190         unsigned long jiffdelay;
 191         int rc;
 192
 193         do {
 194                 dccp_pr_debug("delayed send by %d msec\n", delay);
 195                 jiffdelay = msecs_to_jiffies(delay);
 196
 197                 prepare_to_wait(sk->sk_sleep, &wait, TASK_INTERRUPTIBLE);
 198
 199                 sk->sk_write_pending++;
 200                 release_sock(sk);
 201                 schedule_timeout(jiffdelay);
 202                 lock_sock(sk);
 203                 sk->sk_write_pending--;
 204
 205                 if (sk->sk_err)
 206                         goto do_error;
 207                 if (signal_pending(current))
 208                         goto do_interrupted;
 209
 210                 rc = ccid_hc_tx_send_packet(dp->dccps_hc_tx_ccid, sk, skb);
 211         } while ((delay = rc) > 0);
 212 out:
 213         finish_wait(sk->sk_sleep, &wait);
 214         return rc;
 215
 216 do_error:
 217         rc = -EPIPE;
 218         goto out;
 219 do_interrupted:
 220         rc = -EINTR;
 221         goto out;
 222 }
 223
 224 void dccp_write_xmit(struct sock *sk, int block)
 225 {
 226         struct dccp_sock *dp = dccp_sk(sk);
 227         struct sk_buff *skb;
 228
 229         while ((skb = skb_peek(&sk->sk_write_queue))) {
 230                 int err = ccid_hc_tx_send_packet(dp->dccps_hc_tx_ccid, sk, skb);
 231
 232                 if (err > 0) {
 233                         if (!block) {
 234                                 sk_reset_timer(sk, &dp->dccps_xmit_timer,
 235                                                 msecs_to_jiffies(err)+jiffies);
 236                                 break;
 237                         } else
 238                                 err = dccp_wait_for_ccid(sk, skb, err);
 239                         if (err && err != -EINTR)
 240                                 DCCP_BUG("err=%d after dccp_wait_for_ccid", err);
 241                 }
 242
 243                 skb_dequeue(&sk->sk_write_queue);
 244                 if (err == 0) {
 245                         struct dccp_skb_cb *dcb = DCCP_SKB_CB(skb);
 246                         const int len = skb->len;
 247
 248                         if (sk->sk_state == DCCP_PARTOPEN) {
 249                                 /* See 8.1.5.  Handshake Completion */
 250                                 inet_csk_schedule_ack(sk);
 251                                 inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
 252                                                   inet_csk(sk)->icsk_rto,
 253                                                   DCCP_RTO_MAX);
 254                                 dcb->dccpd_type = DCCP_PKT_DATAACK;
 255                         } else if (dccp_ack_pending(sk))
 256                                 dcb->dccpd_type = DCCP_PKT_DATAACK;
 257                         else
 258                                 dcb->dccpd_type = DCCP_PKT_DATA;
 259
 260                         err = dccp_transmit_skb(sk, skb);
 261                         ccid_hc_tx_packet_sent(dp->dccps_hc_tx_ccid, sk, 0, len);
 262                         if (err)
 263                                 DCCP_BUG("err=%d after ccid_hc_tx_packet_sent",
 264                                          err);
 265                 } else {
 266                         dccp_pr_debug("packet discarded due to err=%d\n", err);
 267                         kfree_skb(skb);
 268                 }
 269         }
 270 }
 271
 272 int dccp_retransmit_skb(struct sock *sk, struct sk_buff *skb)
 273 {
 274         if (inet_csk(sk)->icsk_af_ops->rebuild_header(sk) != 0)
 275                 return -EHOSTUNREACH; /* Routing failure or similar. */
 276
 277         return dccp_transmit_skb(sk, (skb_cloned(skb) ?
 278                                       pskb_copy(skb, GFP_ATOMIC):
 279                                       skb_clone(skb, GFP_ATOMIC)));
 280 }
 281
 282 struct sk_buff *dccp_make_response(struct sock *sk, struct dst_entry *dst,
 283                                    struct request_sock *req)
 284 {
 285         struct dccp_hdr *dh;
 286         struct dccp_request_sock *dreq;
 287         const u32 dccp_header_size = sizeof(struct dccp_hdr) +
 288                                      sizeof(struct dccp_hdr_ext) +
 289                                      sizeof(struct dccp_hdr_response);
 290         struct sk_buff *skb = sock_wmalloc(sk, sk->sk_prot->max_header, 1,
 291                                            GFP_ATOMIC);
 292         if (skb == NULL)
 293                 return NULL;
 294
 295         /* Reserve space for headers. */
 296         skb_reserve(skb, sk->sk_prot->max_header);
 297
 298         skb->dst = dst_clone(dst);
 299
 300         dreq = dccp_rsk(req);
 301         if (inet_rsk(req)->acked)       /* increase ISS upon retransmission */
 302                 dccp_inc_seqno(&dreq->dreq_iss);
 303         DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_RESPONSE;
 304         DCCP_SKB_CB(skb)->dccpd_seq  = dreq->dreq_iss;
 305
 306         if (dccp_insert_options(sk, skb)) {
 307                 kfree_skb(skb);
 308                 return NULL;
 309         }
 310
 311         /* Build and checksum header */
 312         dh = dccp_zeroed_hdr(skb, dccp_header_size);
 313
 314         dh->dccph_sport = inet_sk(sk)->sport;
 315         dh->dccph_dport = inet_rsk(req)->rmt_port;
 316         dh->dccph_doff  = (dccp_header_size +
 317                            DCCP_SKB_CB(skb)->dccpd_opt_len) / 4;
 318         dh->dccph_type  = DCCP_PKT_RESPONSE;
 319         dh->dccph_x     = 1;
 320         dccp_hdr_set_seq(dh, dreq->dreq_iss);
 321         dccp_hdr_set_ack(dccp_hdr_ack_bits(skb), dreq->dreq_isr);
 322         dccp_hdr_response(skb)->dccph_resp_service = dreq->dreq_service;
 323
 324         dccp_csum_outgoing(skb);
 325
 326         /* We use `acked' to remember that a Response was already sent. */
 327         inet_rsk(req)->acked = 1;
 328         DCCP_INC_STATS(DCCP_MIB_OUTSEGS);
 329         return skb;
 330 }
 331
 332 EXPORT_SYMBOL_GPL(dccp_make_response);
 333
 334 /* answer offending packet in @rcv_skb with Reset from control socket @ctl */
 335 struct sk_buff *dccp_ctl_make_reset(struct socket *ctl, struct sk_buff *rcv_skb)
 336 {
 337         struct dccp_hdr *rxdh = dccp_hdr(rcv_skb), *dh;
 338         struct dccp_skb_cb *dcb = DCCP_SKB_CB(rcv_skb);
 339         const u32 dccp_hdr_reset_len = sizeof(struct dccp_hdr) +
 340                                        sizeof(struct dccp_hdr_ext) +
 341                                        sizeof(struct dccp_hdr_reset);
 342         struct dccp_hdr_reset *dhr;
 343         struct sk_buff *skb;
 344
 345         skb = alloc_skb(ctl->sk->sk_prot->max_header, GFP_ATOMIC);
 346         if (skb == NULL)
 347                 return NULL;
 348
 349         skb_reserve(skb, ctl->sk->sk_prot->max_header);
 350
 351         /* Swap the send and the receive. */
 352         dh = dccp_zeroed_hdr(skb, dccp_hdr_reset_len);
 353         dh->dccph_type  = DCCP_PKT_RESET;
 354         dh->dccph_sport = rxdh->dccph_dport;
 355         dh->dccph_dport = rxdh->dccph_sport;
 356         dh->dccph_doff  = dccp_hdr_reset_len / 4;
 357         dh->dccph_x     = 1;
 358
 359         dhr = dccp_hdr_reset(skb);
 360         dhr->dccph_reset_code = dcb->dccpd_reset_code;
 361
 362         switch (dcb->dccpd_reset_code) {
 363         case DCCP_RESET_CODE_PACKET_ERROR:
 364                 dhr->dccph_reset_data[0] = rxdh->dccph_type;
 365                 break;
 366         case DCCP_RESET_CODE_OPTION_ERROR:      /* fall through */
 367         case DCCP_RESET_CODE_MANDATORY_ERROR:
 368                 memcpy(dhr->dccph_reset_data, dcb->dccpd_reset_data, 3);
 369                 break;
 370         }
 371         /*
 372          * From RFC 4340, 8.3.1:
 373          *   If P.ackno exists, set R.seqno := P.ackno + 1.
 374          *   Else set R.seqno := 0.
 375          */
 376         if (dcb->dccpd_ack_seq != DCCP_PKT_WITHOUT_ACK_SEQ)
 377                 dccp_hdr_set_seq(dh, ADD48(dcb->dccpd_ack_seq, 1));
 378         dccp_hdr_set_ack(dccp_hdr_ack_bits(skb), dcb->dccpd_seq);
 379
 380         dccp_csum_outgoing(skb);
 381         return skb;
 382 }
 383
 384 EXPORT_SYMBOL_GPL(dccp_ctl_make_reset);
 385
 386 /* send Reset on established socket, to close or abort the connection */
 387 int dccp_send_reset(struct sock *sk, enum dccp_reset_codes code)
 388 {
 389         struct sk_buff *skb;
 390         /*
 391          * FIXME: what if rebuild_header fails?
 392          * Should we be doing a rebuild_header here?
 393          */
 394         int err = inet_sk_rebuild_header(sk);
 395
 396         if (err != 0)
 397                 return err;
 398
 399         skb = sock_wmalloc(sk, sk->sk_prot->max_header, 1, GFP_ATOMIC);
 400         if (skb == NULL)
 401                 return -ENOBUFS;
 402
 403         /* Reserve space for headers and prepare control bits. */
 404         skb_reserve(skb, sk->sk_prot->max_header);
 405         DCCP_SKB_CB(skb)->dccpd_type       = DCCP_PKT_RESET;
 406         DCCP_SKB_CB(skb)->dccpd_reset_code = code;
 407
 408         return dccp_transmit_skb(sk, skb);
 409 }
 410
 411 /*
 412  * Do all connect socket setups that can be done AF independent.
 413  */
 414 static inline void dccp_connect_init(struct sock *sk)
 415 {
 416         struct dccp_sock *dp = dccp_sk(sk);
 417         struct dst_entry *dst = __sk_dst_get(sk);
 418         struct inet_connection_sock *icsk = inet_csk(sk);
 419
 420         sk->sk_err = 0;
 421         sock_reset_flag(sk, SOCK_DONE);
 422
 423         dccp_sync_mss(sk, dst_mtu(dst));
 424
 425         /*
 426          * SWL and AWL are initially adjusted so that they are not less than
 427          * the initial Sequence Numbers received and sent, respectively:
 428          *      SWL := max(GSR + 1 - floor(W/4), ISR),
 429          *      AWL := max(GSS - W' + 1, ISS).
 430          * These adjustments MUST be applied only at the beginning of the
 431          * connection.
 432          */
 433         dccp_update_gss(sk, dp->dccps_iss);
 434         dccp_set_seqno(&dp->dccps_awl, max48(dp->dccps_awl, dp->dccps_iss));
 435
 436         /* S.GAR - greatest valid acknowledgement number received on a non-Sync;
 437          *         initialized to S.ISS (sec. 8.5)                            */
 438         dp->dccps_gar = dp->dccps_iss;
 439
 440         icsk->icsk_retransmits = 0;
 441 }
 442
 443 int dccp_connect(struct sock *sk)
 444 {
 445         struct sk_buff *skb;
 446         struct inet_connection_sock *icsk = inet_csk(sk);
 447
 448         dccp_connect_init(sk);
 449
 450         skb = alloc_skb(sk->sk_prot->max_header, sk->sk_allocation);
 451         if (unlikely(skb == NULL))
 452                 return -ENOBUFS;
 453
 454         /* Reserve space for headers. */
 455         skb_reserve(skb, sk->sk_prot->max_header);
 456
 457         DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_REQUEST;
 458
 459         dccp_skb_entail(sk, skb);
 460         dccp_transmit_skb(sk, skb_clone(skb, GFP_KERNEL));
 461         DCCP_INC_STATS(DCCP_MIB_ACTIVEOPENS);
 462
 463         /* Timer for repeating the REQUEST until an answer. */
 464         inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
 465                                   icsk->icsk_rto, DCCP_RTO_MAX);
 466         return 0;
 467 }
 468
 469 EXPORT_SYMBOL_GPL(dccp_connect);
 470
 471 void dccp_send_ack(struct sock *sk)
 472 {
 473         /* If we have been reset, we may not send again. */
 474         if (sk->sk_state != DCCP_CLOSED) {
 475                 struct sk_buff *skb = alloc_skb(sk->sk_prot->max_header,
 476                                                 GFP_ATOMIC);
 477
 478                 if (skb == NULL) {
 479                         inet_csk_schedule_ack(sk);
 480                         inet_csk(sk)->icsk_ack.ato = TCP_ATO_MIN;
 481                         inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
 482                                                   TCP_DELACK_MAX,
 483                                                   DCCP_RTO_MAX);
 484                         return;
 485                 }
 486
 487                 /* Reserve space for headers */
 488                 skb_reserve(skb, sk->sk_prot->max_header);
 489                 DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_ACK;
 490                 dccp_transmit_skb(sk, skb);
 491         }
 492 }
 493
 494 EXPORT_SYMBOL_GPL(dccp_send_ack);
 495
 496 /* FIXME: Is this still necessary (11.3) - currently nowhere used by DCCP. */
 497 void dccp_send_delayed_ack(struct sock *sk)
 498 {
 499         struct inet_connection_sock *icsk = inet_csk(sk);
 500         /*
 501          * FIXME: tune this timer. elapsed time fixes the skew, so no problem
 502          * with using 2s, and active senders also piggyback the ACK into a
 503          * DATAACK packet, so this is really for quiescent senders.
 504          */
 505         unsigned long timeout = jiffies + 2 * HZ;
 506
 507         /* Use new timeout only if there wasn't a older one earlier. */
 508         if (icsk->icsk_ack.pending & ICSK_ACK_TIMER) {
 509                 /* If delack timer was blocked or is about to expire,
 510                  * send ACK now.
 511                  *
 512                  * FIXME: check the "about to expire" part
 513                  */
 514                 if (icsk->icsk_ack.blocked) {
 515                         dccp_send_ack(sk);
 516                         return;
 517                 }
 518
 519                 if (!time_before(timeout, icsk->icsk_ack.timeout))
 520                         timeout = icsk->icsk_ack.timeout;
 521         }
 522         icsk->icsk_ack.pending |= ICSK_ACK_SCHED | ICSK_ACK_TIMER;
 523         icsk->icsk_ack.timeout = timeout;
 524         sk_reset_timer(sk, &icsk->icsk_delack_timer, timeout);
 525 }
 526
 527 void dccp_send_sync(struct sock *sk, const u64 ackno,
 528                     const enum dccp_pkt_type pkt_type)
 529 {
 530         /*
 531          * We are not putting this on the write queue, so
 532          * dccp_transmit_skb() will set the ownership to this
 533          * sock.
 534          */
 535         struct sk_buff *skb = alloc_skb(sk->sk_prot->max_header, GFP_ATOMIC);
 536
 537         if (skb == NULL) {
 538                 /* FIXME: how to make sure the sync is sent? */
 539                 DCCP_CRIT("could not send %s", dccp_packet_name(pkt_type));
 540                 return;
 541         }
 542
 543         /* Reserve space for headers and prepare control bits. */
 544         skb_reserve(skb, sk->sk_prot->max_header);
 545         DCCP_SKB_CB(skb)->dccpd_type = pkt_type;
 546         DCCP_SKB_CB(skb)->dccpd_ack_seq = ackno;
 547
 548         dccp_transmit_skb(sk, skb);
 549 }
 550
 551 EXPORT_SYMBOL_GPL(dccp_send_sync);
 552
 553 /*
 554  * Send a DCCP_PKT_CLOSE/CLOSEREQ. The caller locks the socket for us. This
 555  * cannot be allowed to fail queueing a DCCP_PKT_CLOSE/CLOSEREQ frame under
 556  * any circumstances.
 557  */
 558 void dccp_send_close(struct sock *sk, const int active)
 559 {
 560         struct dccp_sock *dp = dccp_sk(sk);
 561         struct sk_buff *skb;
 562         const gfp_t prio = active ? GFP_KERNEL : GFP_ATOMIC;
 563
 564         skb = alloc_skb(sk->sk_prot->max_header, prio);
 565         if (skb == NULL)
 566                 return;
 567
 568         /* Reserve space for headers and prepare control bits. */
 569         skb_reserve(skb, sk->sk_prot->max_header);
 570         DCCP_SKB_CB(skb)->dccpd_type = dp->dccps_role == DCCP_ROLE_CLIENT ?
 571                                         DCCP_PKT_CLOSE : DCCP_PKT_CLOSEREQ;
 572
 573         if (active) {
 574                 dccp_write_xmit(sk, 1);
 575                 dccp_skb_entail(sk, skb);
 576                 dccp_transmit_skb(sk, skb_clone(skb, prio));
 577                 /* FIXME do we need a retransmit timer here? */
 578         } else
 579                 dccp_transmit_skb(sk, skb);
 580 }