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                         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
  92                 /* Build DCCP header and checksum it. */
  93                 dh = dccp_zeroed_hdr(skb, dccp_header_size);
  94                 dh->dccph_type  = dcb->dccpd_type;
  95                 dh->dccph_sport = inet->sport;
  96                 dh->dccph_dport = inet->dport;
  97                 dh->dccph_doff  = (dccp_header_size + dcb->dccpd_opt_len) / 4;
  98                 dh->dccph_ccval = dcb->dccpd_ccval;
  99                 dh->dccph_cscov = dp->dccps_pcslen;
 100                 /* XXX For now we're using only 48 bits sequence numbers */
 101                 dh->dccph_x     = 1;
 102
 103                 dp->dccps_awh = dp->dccps_gss;
 104                 dccp_hdr_set_seq(dh, dp->dccps_gss);
 105                 if (set_ack)
 106                         dccp_hdr_set_ack(dccp_hdr_ack_bits(skb), ackno);
 107
 108                 switch (dcb->dccpd_type) {
 109                 case DCCP_PKT_REQUEST:
 110                         dccp_hdr_request(skb)->dccph_req_service =
 111                                                         dp->dccps_service;
 112                         break;
 113                 case DCCP_PKT_RESET:
 114                         dccp_hdr_reset(skb)->dccph_reset_code =
 115                                                         dcb->dccpd_reset_code;
 116                         break;
 117                 }
 118
 119                 icsk->icsk_af_ops->send_check(sk, 0, skb);
 120
 121                 if (set_ack)
 122                         dccp_event_ack_sent(sk);
 123
 124                 DCCP_INC_STATS(DCCP_MIB_OUTSEGS);
 125
 126                 memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));
 127                 err = icsk->icsk_af_ops->queue_xmit(skb, sk, 0);
 128                 if (err <= 0)
 129                         return err;
 130
 131                 /* NET_XMIT_CN is special. It does not guarantee,
 132                  * that this packet is lost. It tells that device
 133                  * is about to start to drop packets or already
 134                  * drops some packets of the same priority and
 135                  * invokes us to send less aggressively.
 136                  */
 137                 return err == NET_XMIT_CN ? 0 : err;
 138         }
 139         return -ENOBUFS;
 140 }
 141
 142 unsigned int dccp_sync_mss(struct sock *sk, u32 pmtu)
 143 {
 144         struct inet_connection_sock *icsk = inet_csk(sk);
 145         struct dccp_sock *dp = dccp_sk(sk);
 146         int mss_now = (pmtu - icsk->icsk_af_ops->net_header_len -
 147                        sizeof(struct dccp_hdr) - sizeof(struct dccp_hdr_ext));
 148
 149         /* Now subtract optional transport overhead */
 150         mss_now -= icsk->icsk_ext_hdr_len;
 151
 152         /*
 153          * FIXME: this should come from the CCID infrastructure, where, say,
 154          * TFRC will say it wants TIMESTAMPS, ELAPSED time, etc, for now lets
 155          * put a rough estimate for NDP + TIMESTAMP + TIMESTAMP_ECHO + ELAPSED
 156          * TIME + TFRC_OPT_LOSS_EVENT_RATE + TFRC_OPT_RECEIVE_RATE + padding to
 157          * make it a multiple of 4
 158          */
 159
 160         mss_now -= ((5 + 6 + 10 + 6 + 6 + 6 + 3) / 4) * 4;
 161
 162         /* And store cached results */
 163         icsk->icsk_pmtu_cookie = pmtu;
 164         dp->dccps_mss_cache = mss_now;
 165
 166         return mss_now;
 167 }
 168
 169 EXPORT_SYMBOL_GPL(dccp_sync_mss);
 170
 171 void dccp_write_space(struct sock *sk)
 172 {
 173         read_lock(&sk->sk_callback_lock);
 174
 175         if (sk->sk_sleep && waitqueue_active(sk->sk_sleep))
 176                 wake_up_interruptible(sk->sk_sleep);
 177         /* Should agree with poll, otherwise some programs break */
 178         if (sock_writeable(sk))
 179                 sk_wake_async(sk, 2, POLL_OUT);
 180
 181         read_unlock(&sk->sk_callback_lock);
 182 }
 183
 184 /**
 185  * dccp_wait_for_ccid - Wait for ccid to tell us we can send a packet
 186  * @sk: socket to wait for
 187  * @timeo: for how long
 188  */
 189 static int dccp_wait_for_ccid(struct sock *sk, struct sk_buff *skb,
 190                               long *timeo)
 191 {
 192         struct dccp_sock *dp = dccp_sk(sk);
 193         DEFINE_WAIT(wait);
 194         long delay;
 195         int rc;
 196
 197         while (1) {
 198                 prepare_to_wait(sk->sk_sleep, &wait, TASK_INTERRUPTIBLE);
 199
 200                 if (sk->sk_err)
 201                         goto do_error;
 202                 if (!*timeo)
 203                         goto do_nonblock;
 204                 if (signal_pending(current))
 205                         goto do_interrupted;
 206
 207                 rc = ccid_hc_tx_send_packet(dp->dccps_hc_tx_ccid, sk, skb,
 208                                             skb->len);
 209                 if (rc <= 0)
 210                         break;
 211                 delay = msecs_to_jiffies(rc);
 212                 if (delay > *timeo || delay < 0)
 213                         goto do_nonblock;
 214
 215                 sk->sk_write_pending++;
 216                 release_sock(sk);
 217                 *timeo -= schedule_timeout(delay);
 218                 lock_sock(sk);
 219                 sk->sk_write_pending--;
 220         }
 221 out:
 222         finish_wait(sk->sk_sleep, &wait);
 223         return rc;
 224
 225 do_error:
 226         rc = -EPIPE;
 227         goto out;
 228 do_nonblock:
 229         rc = -EAGAIN;
 230         goto out;
 231 do_interrupted:
 232         rc = sock_intr_errno(*timeo);
 233         goto out;
 234 }
 235
 236 static void dccp_write_xmit_timer(unsigned long data) {
 237         struct sock *sk = (struct sock *)data;
 238         struct dccp_sock *dp = dccp_sk(sk);
 239
 240         bh_lock_sock(sk);
 241         if (sock_owned_by_user(sk))
 242                 sk_reset_timer(sk, &dp->dccps_xmit_timer, jiffies+1);
 243         else
 244                 dccp_write_xmit(sk, 0);
 245         bh_unlock_sock(sk);
 246         sock_put(sk);
 247 }
 248
 249 void dccp_write_xmit(struct sock *sk, int block)
 250 {
 251         struct dccp_sock *dp = dccp_sk(sk);
 252         struct sk_buff *skb;
 253         long timeo = DCCP_XMIT_TIMEO;   /* If a packet is taking longer than
 254                                            this we have other issues */
 255
 256         while ((skb = skb_peek(&sk->sk_write_queue))) {
 257                 int err = ccid_hc_tx_send_packet(dp->dccps_hc_tx_ccid, sk, skb,
 258                                          skb->len);
 259
 260                 if (err > 0) {
 261                         if (!block) {
 262                                 sk_reset_timer(sk, &dp->dccps_xmit_timer,
 263                                                 msecs_to_jiffies(err)+jiffies);
 264                                 break;
 265                         } else {
 266                                 err = dccp_wait_for_ccid(sk, skb, &timeo);
 267                                 timeo = DCCP_XMIT_TIMEO;
 268                         }
 269                         if (err) {
 270                                 printk(KERN_CRIT "%s:err at dccp_wait_for_ccid"
 271                                                  " %d\n", __FUNCTION__, err);
 272                                 dump_stack();
 273                         }
 274                 }
 275
 276                 skb_dequeue(&sk->sk_write_queue);
 277                 if (err == 0) {
 278                         struct dccp_skb_cb *dcb = DCCP_SKB_CB(skb);
 279                         const int len = skb->len;
 280
 281                         if (sk->sk_state == DCCP_PARTOPEN) {
 282                                 /* See 8.1.5.  Handshake Completion */
 283                                 inet_csk_schedule_ack(sk);
 284                                 inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
 285                                                   inet_csk(sk)->icsk_rto,
 286                                                   DCCP_RTO_MAX);
 287                                 dcb->dccpd_type = DCCP_PKT_DATAACK;
 288                         } else if (dccp_ack_pending(sk))
 289                                 dcb->dccpd_type = DCCP_PKT_DATAACK;
 290                         else
 291                                 dcb->dccpd_type = DCCP_PKT_DATA;
 292
 293                         err = dccp_transmit_skb(sk, skb);
 294                         ccid_hc_tx_packet_sent(dp->dccps_hc_tx_ccid, sk, 0, len);
 295                         if (err) {
 296                                 printk(KERN_CRIT "%s:err from "
 297                                                  "ccid_hc_tx_packet_sent %d\n",
 298                                                  __FUNCTION__, err);
 299                                 dump_stack();
 300                         }
 301                 } else
 302                         kfree(skb);
 303         }
 304 }
 305
 306 int dccp_retransmit_skb(struct sock *sk, struct sk_buff *skb)
 307 {
 308         if (inet_csk(sk)->icsk_af_ops->rebuild_header(sk) != 0)
 309                 return -EHOSTUNREACH; /* Routing failure or similar. */
 310
 311         return dccp_transmit_skb(sk, (skb_cloned(skb) ?
 312                                       pskb_copy(skb, GFP_ATOMIC):
 313                                       skb_clone(skb, GFP_ATOMIC)));
 314 }
 315
 316 struct sk_buff *dccp_make_response(struct sock *sk, struct dst_entry *dst,
 317                                    struct request_sock *req)
 318 {
 319         struct dccp_hdr *dh;
 320         struct dccp_request_sock *dreq;
 321         const u32 dccp_header_size = sizeof(struct dccp_hdr) +
 322                                      sizeof(struct dccp_hdr_ext) +
 323                                      sizeof(struct dccp_hdr_response);
 324         struct sk_buff *skb = sock_wmalloc(sk, sk->sk_prot->max_header, 1,
 325                                            GFP_ATOMIC);
 326         if (skb == NULL)
 327                 return NULL;
 328
 329         /* Reserve space for headers. */
 330         skb_reserve(skb, sk->sk_prot->max_header);
 331
 332         skb->dst = dst_clone(dst);
 333
 334         dreq = dccp_rsk(req);
 335         if (inet_rsk(req)->acked)       /* increase ISS upon retransmission */
 336                 dccp_inc_seqno(&dreq->dreq_iss);
 337         DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_RESPONSE;
 338         DCCP_SKB_CB(skb)->dccpd_seq  = dreq->dreq_iss;
 339
 340         if (dccp_insert_options(sk, skb)) {
 341                 kfree_skb(skb);
 342                 return NULL;
 343         }
 344
 345         dh = dccp_zeroed_hdr(skb, dccp_header_size);
 346
 347         dh->dccph_sport = inet_sk(sk)->sport;
 348         dh->dccph_dport = inet_rsk(req)->rmt_port;
 349         dh->dccph_doff  = (dccp_header_size +
 350                            DCCP_SKB_CB(skb)->dccpd_opt_len) / 4;
 351         dh->dccph_type  = DCCP_PKT_RESPONSE;
 352         dh->dccph_x     = 1;
 353         dccp_hdr_set_seq(dh, dreq->dreq_iss);
 354         dccp_hdr_set_ack(dccp_hdr_ack_bits(skb), dreq->dreq_isr);
 355         dccp_hdr_response(skb)->dccph_resp_service = dreq->dreq_service;
 356
 357         dccp_csum_outgoing(skb);
 358
 359         /* We use `acked' to remember that a Response was already sent. */
 360         inet_rsk(req)->acked = 1;
 361         DCCP_INC_STATS(DCCP_MIB_OUTSEGS);
 362         return skb;
 363 }
 364
 365 EXPORT_SYMBOL_GPL(dccp_make_response);
 366
 367 static struct sk_buff *dccp_make_reset(struct sock *sk, struct dst_entry *dst,
 368                                        const enum dccp_reset_codes code)
 369
 370 {
 371         struct dccp_hdr *dh;
 372         struct dccp_sock *dp = dccp_sk(sk);
 373         const u32 dccp_header_size = sizeof(struct dccp_hdr) +
 374                                      sizeof(struct dccp_hdr_ext) +
 375                                      sizeof(struct dccp_hdr_reset);
 376         struct sk_buff *skb = sock_wmalloc(sk, sk->sk_prot->max_header, 1,
 377                                            GFP_ATOMIC);
 378         if (skb == NULL)
 379                 return NULL;
 380
 381         /* Reserve space for headers. */
 382         skb_reserve(skb, sk->sk_prot->max_header);
 383
 384         skb->dst = dst_clone(dst);
 385
 386         dccp_inc_seqno(&dp->dccps_gss);
 387
 388         DCCP_SKB_CB(skb)->dccpd_reset_code = code;
 389         DCCP_SKB_CB(skb)->dccpd_type       = DCCP_PKT_RESET;
 390         DCCP_SKB_CB(skb)->dccpd_seq        = dp->dccps_gss;
 391
 392         if (dccp_insert_options(sk, skb)) {
 393                 kfree_skb(skb);
 394                 return NULL;
 395         }
 396
 397         dh = dccp_zeroed_hdr(skb, dccp_header_size);
 398
 399         dh->dccph_sport = inet_sk(sk)->sport;
 400         dh->dccph_dport = inet_sk(sk)->dport;
 401         dh->dccph_doff  = (dccp_header_size +
 402                            DCCP_SKB_CB(skb)->dccpd_opt_len) / 4;
 403         dh->dccph_type  = DCCP_PKT_RESET;
 404         dh->dccph_x     = 1;
 405         dccp_hdr_set_seq(dh, dp->dccps_gss);
 406         dccp_hdr_set_ack(dccp_hdr_ack_bits(skb), dp->dccps_gsr);
 407
 408         dccp_hdr_reset(skb)->dccph_reset_code = code;
 409         inet_csk(sk)->icsk_af_ops->send_check(sk, 0, skb);
 410
 411         DCCP_INC_STATS(DCCP_MIB_OUTSEGS);
 412         return skb;
 413 }
 414
 415 int dccp_send_reset(struct sock *sk, enum dccp_reset_codes code)
 416 {
 417         /*
 418          * FIXME: what if rebuild_header fails?
 419          * Should we be doing a rebuild_header here?
 420          */
 421         int err = inet_sk_rebuild_header(sk);
 422
 423         if (err == 0) {
 424                 struct sk_buff *skb = dccp_make_reset(sk, sk->sk_dst_cache,
 425                                                       code);
 426                 if (skb != NULL) {
 427                         memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));
 428                         err = inet_csk(sk)->icsk_af_ops->queue_xmit(skb, sk, 0);
 429                         if (err == NET_XMIT_CN)
 430                                 err = 0;
 431                 }
 432         }
 433
 434         return err;
 435 }
 436
 437 /*
 438  * Do all connect socket setups that can be done AF independent.
 439  */
 440 static inline void dccp_connect_init(struct sock *sk)
 441 {
 442         struct dccp_sock *dp = dccp_sk(sk);
 443         struct dst_entry *dst = __sk_dst_get(sk);
 444         struct inet_connection_sock *icsk = inet_csk(sk);
 445
 446         sk->sk_err = 0;
 447         sock_reset_flag(sk, SOCK_DONE);
 448
 449         dccp_sync_mss(sk, dst_mtu(dst));
 450
 451         /*
 452          * SWL and AWL are initially adjusted so that they are not less than
 453          * the initial Sequence Numbers received and sent, respectively:
 454          *      SWL := max(GSR + 1 - floor(W/4), ISR),
 455          *      AWL := max(GSS - W' + 1, ISS).
 456          * These adjustments MUST be applied only at the beginning of the
 457          * connection.
 458          */
 459         dccp_update_gss(sk, dp->dccps_iss);
 460         dccp_set_seqno(&dp->dccps_awl, max48(dp->dccps_awl, dp->dccps_iss));
 461
 462         /* S.GAR - greatest valid acknowledgement number received on a non-Sync;
 463          *         initialized to S.ISS (sec. 8.5)                            */
 464         dp->dccps_gar = dp->dccps_iss;
 465
 466         icsk->icsk_retransmits = 0;
 467         init_timer(&dp->dccps_xmit_timer);
 468         dp->dccps_xmit_timer.data = (unsigned long)sk;
 469         dp->dccps_xmit_timer.function = dccp_write_xmit_timer;
 470 }
 471
 472 int dccp_connect(struct sock *sk)
 473 {
 474         struct sk_buff *skb;
 475         struct inet_connection_sock *icsk = inet_csk(sk);
 476
 477         dccp_connect_init(sk);
 478
 479         skb = alloc_skb(sk->sk_prot->max_header, sk->sk_allocation);
 480         if (unlikely(skb == NULL))
 481                 return -ENOBUFS;
 482
 483         /* Reserve space for headers. */
 484         skb_reserve(skb, sk->sk_prot->max_header);
 485
 486         DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_REQUEST;
 487
 488         dccp_skb_entail(sk, skb);
 489         dccp_transmit_skb(sk, skb_clone(skb, GFP_KERNEL));
 490         DCCP_INC_STATS(DCCP_MIB_ACTIVEOPENS);
 491
 492         /* Timer for repeating the REQUEST until an answer. */
 493         inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
 494                                   icsk->icsk_rto, DCCP_RTO_MAX);
 495         return 0;
 496 }
 497
 498 EXPORT_SYMBOL_GPL(dccp_connect);
 499
 500 void dccp_send_ack(struct sock *sk)
 501 {
 502         /* If we have been reset, we may not send again. */
 503         if (sk->sk_state != DCCP_CLOSED) {
 504                 struct sk_buff *skb = alloc_skb(sk->sk_prot->max_header,
 505                                                 GFP_ATOMIC);
 506
 507                 if (skb == NULL) {
 508                         inet_csk_schedule_ack(sk);
 509                         inet_csk(sk)->icsk_ack.ato = TCP_ATO_MIN;
 510                         inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
 511                                                   TCP_DELACK_MAX,
 512                                                   DCCP_RTO_MAX);
 513                         return;
 514                 }
 515
 516                 /* Reserve space for headers */
 517                 skb_reserve(skb, sk->sk_prot->max_header);
 518                 DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_ACK;
 519                 dccp_transmit_skb(sk, skb);
 520         }
 521 }
 522
 523 EXPORT_SYMBOL_GPL(dccp_send_ack);
 524
 525 void dccp_send_delayed_ack(struct sock *sk)
 526 {
 527         struct inet_connection_sock *icsk = inet_csk(sk);
 528         /*
 529          * FIXME: tune this timer. elapsed time fixes the skew, so no problem
 530          * with using 2s, and active senders also piggyback the ACK into a
 531          * DATAACK packet, so this is really for quiescent senders.
 532          */
 533         unsigned long timeout = jiffies + 2 * HZ;
 534
 535         /* Use new timeout only if there wasn't a older one earlier. */
 536         if (icsk->icsk_ack.pending & ICSK_ACK_TIMER) {
 537                 /* If delack timer was blocked or is about to expire,
 538                  * send ACK now.
 539                  *
 540                  * FIXME: check the "about to expire" part
 541                  */
 542                 if (icsk->icsk_ack.blocked) {
 543                         dccp_send_ack(sk);
 544                         return;
 545                 }
 546
 547                 if (!time_before(timeout, icsk->icsk_ack.timeout))
 548                         timeout = icsk->icsk_ack.timeout;
 549         }
 550         icsk->icsk_ack.pending |= ICSK_ACK_SCHED | ICSK_ACK_TIMER;
 551         icsk->icsk_ack.timeout = timeout;
 552         sk_reset_timer(sk, &icsk->icsk_delack_timer, timeout);
 553 }
 554
 555 void dccp_send_sync(struct sock *sk, const u64 seq,
 556                     const enum dccp_pkt_type pkt_type)
 557 {
 558         /*
 559          * We are not putting this on the write queue, so
 560          * dccp_transmit_skb() will set the ownership to this
 561          * sock.
 562          */
 563         struct sk_buff *skb = alloc_skb(sk->sk_prot->max_header, GFP_ATOMIC);
 564
 565         if (skb == NULL)
 566                 /* FIXME: how to make sure the sync is sent? */
 567                 return;
 568
 569         /* Reserve space for headers and prepare control bits. */
 570         skb_reserve(skb, sk->sk_prot->max_header);
 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         DCCP_SKB_CB(skb)->dccpd_type = dp->dccps_role == DCCP_ROLE_CLIENT ?
 597                                         DCCP_PKT_CLOSE : DCCP_PKT_CLOSEREQ;
 598
 599         if (active) {
 600                 dccp_write_xmit(sk, 1);
 601                 dccp_skb_entail(sk, skb);
 602                 dccp_transmit_skb(sk, skb_clone(skb, prio));
 603                 /* FIXME do we need a retransmit timer here? */
 604         } else
 605                 dccp_transmit_skb(sk, skb);
 606 }