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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                  * Increment GSS here already in case the option code needs it.
  58                  * Update GSS for real only if option processing below succeeds.
  59                  */
  60                 dcb->dccpd_seq = ADD48(dp->dccps_gss, 1);
  61
  62                 switch (dcb->dccpd_type) {
  63                 case DCCP_PKT_DATA:
  64                         set_ack = 0;
  65                         /* fall through */
  66                 case DCCP_PKT_DATAACK:
  67                 case DCCP_PKT_RESET:
  68                         break;
  69
  70                 case DCCP_PKT_REQUEST:
  71                         set_ack = 0;
  72                         /* Use ISS on the first (non-retransmitted) Request. */
  73                         if (icsk->icsk_retransmits == 0)
  74                                 dcb->dccpd_seq = dp->dccps_iss;
  75                         /* fall through */
  76
  77                 case DCCP_PKT_SYNC:
  78                 case DCCP_PKT_SYNCACK:
  79                         ackno = dcb->dccpd_ack_seq;
  80                         /* fall through */
  81                 default:
  82                         /*
  83                          * Set owner/destructor: some skbs are allocated via
  84                          * alloc_skb (e.g. when retransmission may happen).
  85                          * Only Data, DataAck, and Reset packets should come
  86                          * through here with skb->sk set.
  87                          */
  88                         WARN_ON(skb->sk);
  89                         skb_set_owner_w(skb, sk);
  90                         break;
  91                 }
  92
  93                 if (dccp_insert_options(sk, skb)) {
  94                         kfree_skb(skb);
  95                         return -EPROTO;
  96                 }
  97
  98
  99                 /* Build DCCP header and checksum it. */
 100                 dh = dccp_zeroed_hdr(skb, dccp_header_size);
 101                 dh->dccph_type  = dcb->dccpd_type;
 102                 dh->dccph_sport = inet->sport;
 103                 dh->dccph_dport = inet->dport;
 104                 dh->dccph_doff  = (dccp_header_size + dcb->dccpd_opt_len) / 4;
 105                 dh->dccph_ccval = dcb->dccpd_ccval;
 106                 dh->dccph_cscov = dp->dccps_pcslen;
 107                 /* XXX For now we're using only 48 bits sequence numbers */
 108                 dh->dccph_x     = 1;
 109
 110                 dccp_update_gss(sk, dcb->dccpd_seq);
 111                 dccp_hdr_set_seq(dh, dp->dccps_gss);
 112                 if (set_ack)
 113                         dccp_hdr_set_ack(dccp_hdr_ack_bits(skb), ackno);
 114
 115                 switch (dcb->dccpd_type) {
 116                 case DCCP_PKT_REQUEST:
 117                         dccp_hdr_request(skb)->dccph_req_service =
 118                                                         dp->dccps_service;
 119                         /*
 120                          * Limit Ack window to ISS <= P.ackno <= GSS, so that
 121                          * only Responses to Requests we sent are considered.
 122                          */
 123                         dp->dccps_awl = dp->dccps_iss;
 124                         break;
 125                 case DCCP_PKT_RESET:
 126                         dccp_hdr_reset(skb)->dccph_reset_code =
 127                                                         dcb->dccpd_reset_code;
 128                         break;
 129                 }
 130
 131                 icsk->icsk_af_ops->send_check(sk, 0, skb);
 132
 133                 if (set_ack)
 134                         dccp_event_ack_sent(sk);
 135
 136                 DCCP_INC_STATS(DCCP_MIB_OUTSEGS);
 137
 138                 err = icsk->icsk_af_ops->queue_xmit(skb, 0);
 139                 return net_xmit_eval(err);
 140         }
 141         return -ENOBUFS;
 142 }
 143
 144 /**
 145  * dccp_determine_ccmps  -  Find out about CCID-specfic packet-size limits
 146  * We only consider the HC-sender CCID for setting the CCMPS (RFC 4340, 14.),
 147  * since the RX CCID is restricted to feedback packets (Acks), which are small
 148  * in comparison with the data traffic. A value of 0 means "no current CCMPS".
 149  */
 150 static u32 dccp_determine_ccmps(const struct dccp_sock *dp)
 151 {
 152         const struct ccid *tx_ccid = dp->dccps_hc_tx_ccid;
 153
 154         if (tx_ccid == NULL || tx_ccid->ccid_ops == NULL)
 155                 return 0;
 156         return tx_ccid->ccid_ops->ccid_ccmps;
 157 }
 158
 159 unsigned int dccp_sync_mss(struct sock *sk, u32 pmtu)
 160 {
 161         struct inet_connection_sock *icsk = inet_csk(sk);
 162         struct dccp_sock *dp = dccp_sk(sk);
 163         u32 ccmps = dccp_determine_ccmps(dp);
 164         u32 cur_mps = ccmps ? min(pmtu, ccmps) : pmtu;
 165
 166         /* Account for header lengths and IPv4/v6 option overhead */
 167         cur_mps -= (icsk->icsk_af_ops->net_header_len + icsk->icsk_ext_hdr_len +
 168                     sizeof(struct dccp_hdr) + sizeof(struct dccp_hdr_ext));
 169
 170         /*
 171          * Leave enough headroom for common DCCP header options.
 172          * This only considers options which may appear on DCCP-Data packets, as
 173          * per table 3 in RFC 4340, 5.8. When running out of space for other
 174          * options (eg. Ack Vector which can take up to 255 bytes), it is better
 175          * to schedule a separate Ack. Thus we leave headroom for the following:
 176          *  - 1 byte for Slow Receiver (11.6)
 177          *  - 6 bytes for Timestamp (13.1)
 178          *  - 10 bytes for Timestamp Echo (13.3)
 179          *  - 8 bytes for NDP count (7.7, when activated)
 180          *  - 6 bytes for Data Checksum (9.3)
 181          *  - %DCCPAV_MIN_OPTLEN bytes for Ack Vector size (11.4, when enabled)
 182          */
 183         cur_mps -= roundup(1 + 6 + 10 + dp->dccps_send_ndp_count * 8 + 6 +
 184                            (dp->dccps_hc_rx_ackvec ? DCCPAV_MIN_OPTLEN : 0), 4);
 185
 186         /* And store cached results */
 187         icsk->icsk_pmtu_cookie = pmtu;
 188         dp->dccps_mss_cache = cur_mps;
 189
 190         return cur_mps;
 191 }
 192
 193 EXPORT_SYMBOL_GPL(dccp_sync_mss);
 194
 195 void dccp_write_space(struct sock *sk)
 196 {
 197         read_lock(&sk->sk_callback_lock);
 198
 199         if (sk->sk_sleep && waitqueue_active(sk->sk_sleep))
 200                 wake_up_interruptible(sk->sk_sleep);
 201         /* Should agree with poll, otherwise some programs break */
 202         if (sock_writeable(sk))
 203                 sk_wake_async(sk, SOCK_WAKE_SPACE, POLL_OUT);
 204
 205         read_unlock(&sk->sk_callback_lock);
 206 }
 207
 208 /**
 209  * dccp_wait_for_ccid - Wait for ccid to tell us we can send a packet
 210  * @sk:    socket to wait for
 211  * @skb:   current skb to pass on for waiting
 212  * @delay: sleep timeout in milliseconds (> 0)
 213  * This function is called by default when the socket is closed, and
 214  * when a non-zero linger time is set on the socket. For consistency
 215  */
 216 static int dccp_wait_for_ccid(struct sock *sk, struct sk_buff *skb, int delay)
 217 {
 218         struct dccp_sock *dp = dccp_sk(sk);
 219         DEFINE_WAIT(wait);
 220         unsigned long jiffdelay;
 221         int rc;
 222
 223         do {
 224                 dccp_pr_debug("delayed send by %d msec\n", delay);
 225                 jiffdelay = msecs_to_jiffies(delay);
 226
 227                 prepare_to_wait(sk->sk_sleep, &wait, TASK_INTERRUPTIBLE);
 228
 229                 sk->sk_write_pending++;
 230                 release_sock(sk);
 231                 schedule_timeout(jiffdelay);
 232                 lock_sock(sk);
 233                 sk->sk_write_pending--;
 234
 235                 if (sk->sk_err)
 236                         goto do_error;
 237                 if (signal_pending(current))
 238                         goto do_interrupted;
 239
 240                 rc = ccid_hc_tx_send_packet(dp->dccps_hc_tx_ccid, sk, skb);
 241         } while ((delay = rc) > 0);
 242 out:
 243         finish_wait(sk->sk_sleep, &wait);
 244         return rc;
 245
 246 do_error:
 247         rc = -EPIPE;
 248         goto out;
 249 do_interrupted:
 250         rc = -EINTR;
 251         goto out;
 252 }
 253
 254 void dccp_write_xmit(struct sock *sk, int block)
 255 {
 256         struct dccp_sock *dp = dccp_sk(sk);
 257         struct sk_buff *skb;
 258
 259         while ((skb = skb_peek(&sk->sk_write_queue))) {
 260                 int err = ccid_hc_tx_send_packet(dp->dccps_hc_tx_ccid, sk, skb);
 261
 262                 if (err > 0) {
 263                         if (!block) {
 264                                 sk_reset_timer(sk, &dp->dccps_xmit_timer,
 265                                                 msecs_to_jiffies(err)+jiffies);
 266                                 break;
 267                         } else
 268                                 err = dccp_wait_for_ccid(sk, skb, err);
 269                         if (err && err != -EINTR)
 270                                 DCCP_BUG("err=%d after dccp_wait_for_ccid", err);
 271                 }
 272
 273                 skb_dequeue(&sk->sk_write_queue);
 274                 if (err == 0) {
 275                         struct dccp_skb_cb *dcb = DCCP_SKB_CB(skb);
 276                         const int len = skb->len;
 277
 278                         if (sk->sk_state == DCCP_PARTOPEN) {
 279                                 const u32 cur_mps = dp->dccps_mss_cache - DCCP_FEATNEG_OVERHEAD;
 280                                 /*
 281                                  * See 8.1.5 - Handshake Completion.
 282                                  *
 283                                  * For robustness we resend Confirm options until the client has
 284                                  * entered OPEN. During the initial feature negotiation, the MPS
 285                                  * is smaller than usual, reduced by the Change/Confirm options.
 286                                  */
 287                                 if (!list_empty(&dp->dccps_featneg) && len > cur_mps) {
 288                                         DCCP_WARN("Payload too large (%d) for featneg.\n", len);
 289                                         dccp_send_ack(sk);
 290                                         dccp_feat_list_purge(&dp->dccps_featneg);
 291                                 }
 292
 293                                 inet_csk_schedule_ack(sk);
 294                                 inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
 295                                                   inet_csk(sk)->icsk_rto,
 296                                                   DCCP_RTO_MAX);
 297                                 dcb->dccpd_type = DCCP_PKT_DATAACK;
 298                         } else if (dccp_ack_pending(sk))
 299                                 dcb->dccpd_type = DCCP_PKT_DATAACK;
 300                         else
 301                                 dcb->dccpd_type = DCCP_PKT_DATA;
 302
 303                         err = dccp_transmit_skb(sk, skb);
 304                         ccid_hc_tx_packet_sent(dp->dccps_hc_tx_ccid, sk, len);
 305                         if (err)
 306                                 DCCP_BUG("err=%d after ccid_hc_tx_packet_sent",
 307                                          err);
 308                         if (dp->dccps_sync_scheduled)
 309                                 dccp_send_sync(sk, dp->dccps_gsr, DCCP_PKT_SYNC);
 310                 } else {
 311                         dccp_pr_debug("packet discarded due to err=%d\n", err);
 312                         kfree_skb(skb);
 313                 }
 314         }
 315 }
 316
 317 /**
 318  * dccp_retransmit_skb  -  Retransmit Request, Close, or CloseReq packets
 319  * There are only four retransmittable packet types in DCCP:
 320  * - Request  in client-REQUEST  state (sec. 8.1.1),
 321  * - CloseReq in server-CLOSEREQ state (sec. 8.3),
 322  * - Close    in   node-CLOSING  state (sec. 8.3),
 323  * - Acks in client-PARTOPEN state (sec. 8.1.5, handled by dccp_delack_timer()).
 324  * This function expects sk->sk_send_head to contain the original skb.
 325  */
 326 int dccp_retransmit_skb(struct sock *sk)
 327 {
 328         WARN_ON(sk->sk_send_head == NULL);
 329
 330         if (inet_csk(sk)->icsk_af_ops->rebuild_header(sk) != 0)
 331                 return -EHOSTUNREACH; /* Routing failure or similar. */
 332
 333         /* this count is used to distinguish original and retransmitted skb */
 334         inet_csk(sk)->icsk_retransmits++;
 335
 336         return dccp_transmit_skb(sk, skb_clone(sk->sk_send_head, GFP_ATOMIC));
 337 }
 338
 339 struct sk_buff *dccp_make_response(struct sock *sk, struct dst_entry *dst,
 340                                    struct request_sock *req)
 341 {
 342         struct dccp_hdr *dh;
 343         struct dccp_request_sock *dreq;
 344         const u32 dccp_header_size = sizeof(struct dccp_hdr) +
 345                                      sizeof(struct dccp_hdr_ext) +
 346                                      sizeof(struct dccp_hdr_response);
 347         struct sk_buff *skb = sock_wmalloc(sk, sk->sk_prot->max_header, 1,
 348                                            GFP_ATOMIC);
 349         if (skb == NULL)
 350                 return NULL;
 351
 352         /* Reserve space for headers. */
 353         skb_reserve(skb, sk->sk_prot->max_header);
 354
 355         skb->dst = dst_clone(dst);
 356
 357         dreq = dccp_rsk(req);
 358         if (inet_rsk(req)->acked)       /* increase ISS upon retransmission */
 359                 dccp_inc_seqno(&dreq->dreq_iss);
 360         DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_RESPONSE;
 361         DCCP_SKB_CB(skb)->dccpd_seq  = dreq->dreq_iss;
 362
 363         /* Resolve feature dependencies resulting from choice of CCID */
 364         if (dccp_feat_server_ccid_dependencies(dreq))
 365                 goto response_failed;
 366
 367         if (dccp_insert_options_rsk(dreq, skb))
 368                 goto response_failed;
 369
 370         /* Build and checksum header */
 371         dh = dccp_zeroed_hdr(skb, dccp_header_size);
 372
 373         dh->dccph_sport = inet_sk(sk)->sport;
 374         dh->dccph_dport = inet_rsk(req)->rmt_port;
 375         dh->dccph_doff  = (dccp_header_size +
 376                            DCCP_SKB_CB(skb)->dccpd_opt_len) / 4;
 377         dh->dccph_type  = DCCP_PKT_RESPONSE;
 378         dh->dccph_x     = 1;
 379         dccp_hdr_set_seq(dh, dreq->dreq_iss);
 380         dccp_hdr_set_ack(dccp_hdr_ack_bits(skb), dreq->dreq_isr);
 381         dccp_hdr_response(skb)->dccph_resp_service = dreq->dreq_service;
 382
 383         dccp_csum_outgoing(skb);
 384
 385         /* We use `acked' to remember that a Response was already sent. */
 386         inet_rsk(req)->acked = 1;
 387         DCCP_INC_STATS(DCCP_MIB_OUTSEGS);
 388         return skb;
 389 response_failed:
 390         kfree_skb(skb);
 391         return NULL;
 392 }
 393
 394 EXPORT_SYMBOL_GPL(dccp_make_response);
 395
 396 /* answer offending packet in @rcv_skb with Reset from control socket @ctl */
 397 struct sk_buff *dccp_ctl_make_reset(struct sock *sk, struct sk_buff *rcv_skb)
 398 {
 399         struct dccp_hdr *rxdh = dccp_hdr(rcv_skb), *dh;
 400         struct dccp_skb_cb *dcb = DCCP_SKB_CB(rcv_skb);
 401         const u32 dccp_hdr_reset_len = sizeof(struct dccp_hdr) +
 402                                        sizeof(struct dccp_hdr_ext) +
 403                                        sizeof(struct dccp_hdr_reset);
 404         struct dccp_hdr_reset *dhr;
 405         struct sk_buff *skb;
 406
 407         skb = alloc_skb(sk->sk_prot->max_header, GFP_ATOMIC);
 408         if (skb == NULL)
 409                 return NULL;
 410
 411         skb_reserve(skb, sk->sk_prot->max_header);
 412
 413         /* Swap the send and the receive. */
 414         dh = dccp_zeroed_hdr(skb, dccp_hdr_reset_len);
 415         dh->dccph_type  = DCCP_PKT_RESET;
 416         dh->dccph_sport = rxdh->dccph_dport;
 417         dh->dccph_dport = rxdh->dccph_sport;
 418         dh->dccph_doff  = dccp_hdr_reset_len / 4;
 419         dh->dccph_x     = 1;
 420
 421         dhr = dccp_hdr_reset(skb);
 422         dhr->dccph_reset_code = dcb->dccpd_reset_code;
 423
 424         switch (dcb->dccpd_reset_code) {
 425         case DCCP_RESET_CODE_PACKET_ERROR:
 426                 dhr->dccph_reset_data[0] = rxdh->dccph_type;
 427                 break;
 428         case DCCP_RESET_CODE_OPTION_ERROR:      /* fall through */
 429         case DCCP_RESET_CODE_MANDATORY_ERROR:
 430                 memcpy(dhr->dccph_reset_data, dcb->dccpd_reset_data, 3);
 431                 break;
 432         }
 433         /*
 434          * From RFC 4340, 8.3.1:
 435          *   If P.ackno exists, set R.seqno := P.ackno + 1.
 436          *   Else set R.seqno := 0.
 437          */
 438         if (dcb->dccpd_ack_seq != DCCP_PKT_WITHOUT_ACK_SEQ)
 439                 dccp_hdr_set_seq(dh, ADD48(dcb->dccpd_ack_seq, 1));
 440         dccp_hdr_set_ack(dccp_hdr_ack_bits(skb), dcb->dccpd_seq);
 441
 442         dccp_csum_outgoing(skb);
 443         return skb;
 444 }
 445
 446 EXPORT_SYMBOL_GPL(dccp_ctl_make_reset);
 447
 448 /* send Reset on established socket, to close or abort the connection */
 449 int dccp_send_reset(struct sock *sk, enum dccp_reset_codes code)
 450 {
 451         struct sk_buff *skb;
 452         /*
 453          * FIXME: what if rebuild_header fails?
 454          * Should we be doing a rebuild_header here?
 455          */
 456         int err = inet_csk(sk)->icsk_af_ops->rebuild_header(sk);
 457
 458         if (err != 0)
 459                 return err;
 460
 461         skb = sock_wmalloc(sk, sk->sk_prot->max_header, 1, GFP_ATOMIC);
 462         if (skb == NULL)
 463                 return -ENOBUFS;
 464
 465         /* Reserve space for headers and prepare control bits. */
 466         skb_reserve(skb, sk->sk_prot->max_header);
 467         DCCP_SKB_CB(skb)->dccpd_type       = DCCP_PKT_RESET;
 468         DCCP_SKB_CB(skb)->dccpd_reset_code = code;
 469
 470         return dccp_transmit_skb(sk, skb);
 471 }
 472
 473 /*
 474  * Do all connect socket setups that can be done AF independent.
 475  */
 476 int dccp_connect(struct sock *sk)
 477 {
 478         struct sk_buff *skb;
 479         struct dccp_sock *dp = dccp_sk(sk);
 480         struct dst_entry *dst = __sk_dst_get(sk);
 481         struct inet_connection_sock *icsk = inet_csk(sk);
 482
 483         sk->sk_err = 0;
 484         sock_reset_flag(sk, SOCK_DONE);
 485
 486         dccp_sync_mss(sk, dst_mtu(dst));
 487
 488         /* do not connect if feature negotiation setup fails */
 489         if (dccp_feat_finalise_settings(dccp_sk(sk)))
 490                 return -EPROTO;
 491
 492         /* Initialise GAR as per 8.5; AWL/AWH are set in dccp_transmit_skb() */
 493         dp->dccps_gar = dp->dccps_iss;
 494
 495         skb = alloc_skb(sk->sk_prot->max_header, sk->sk_allocation);
 496         if (unlikely(skb == NULL))
 497                 return -ENOBUFS;
 498
 499         /* Reserve space for headers. */
 500         skb_reserve(skb, sk->sk_prot->max_header);
 501
 502         DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_REQUEST;
 503
 504         dccp_skb_entail(sk, skb);
 505         dccp_transmit_skb(sk, skb_clone(skb, GFP_KERNEL));
 506         DCCP_INC_STATS(DCCP_MIB_ACTIVEOPENS);
 507
 508         /* Timer for repeating the REQUEST until an answer. */
 509         icsk->icsk_retransmits = 0;
 510         inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
 511                                   icsk->icsk_rto, DCCP_RTO_MAX);
 512         return 0;
 513 }
 514
 515 EXPORT_SYMBOL_GPL(dccp_connect);
 516
 517 void dccp_send_ack(struct sock *sk)
 518 {
 519         /* If we have been reset, we may not send again. */
 520         if (sk->sk_state != DCCP_CLOSED) {
 521                 struct sk_buff *skb = alloc_skb(sk->sk_prot->max_header,
 522                                                 GFP_ATOMIC);
 523
 524                 if (skb == NULL) {
 525                         inet_csk_schedule_ack(sk);
 526                         inet_csk(sk)->icsk_ack.ato = TCP_ATO_MIN;
 527                         inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
 528                                                   TCP_DELACK_MAX,
 529                                                   DCCP_RTO_MAX);
 530                         return;
 531                 }
 532
 533                 /* Reserve space for headers */
 534                 skb_reserve(skb, sk->sk_prot->max_header);
 535                 DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_ACK;
 536                 dccp_transmit_skb(sk, skb);
 537         }
 538 }
 539
 540 EXPORT_SYMBOL_GPL(dccp_send_ack);
 541
 542 #if 0
 543 /* FIXME: Is this still necessary (11.3) - currently nowhere used by DCCP. */
 544 void dccp_send_delayed_ack(struct sock *sk)
 545 {
 546         struct inet_connection_sock *icsk = inet_csk(sk);
 547         /*
 548          * FIXME: tune this timer. elapsed time fixes the skew, so no problem
 549          * with using 2s, and active senders also piggyback the ACK into a
 550          * DATAACK packet, so this is really for quiescent senders.
 551          */
 552         unsigned long timeout = jiffies + 2 * HZ;
 553
 554         /* Use new timeout only if there wasn't a older one earlier. */
 555         if (icsk->icsk_ack.pending & ICSK_ACK_TIMER) {
 556                 /* If delack timer was blocked or is about to expire,
 557                  * send ACK now.
 558                  *
 559                  * FIXME: check the "about to expire" part
 560                  */
 561                 if (icsk->icsk_ack.blocked) {
 562                         dccp_send_ack(sk);
 563                         return;
 564                 }
 565
 566                 if (!time_before(timeout, icsk->icsk_ack.timeout))
 567                         timeout = icsk->icsk_ack.timeout;
 568         }
 569         icsk->icsk_ack.pending |= ICSK_ACK_SCHED | ICSK_ACK_TIMER;
 570         icsk->icsk_ack.timeout = timeout;
 571         sk_reset_timer(sk, &icsk->icsk_delack_timer, timeout);
 572 }
 573 #endif
 574
 575 void dccp_send_sync(struct sock *sk, const u64 ackno,
 576                     const enum dccp_pkt_type pkt_type)
 577 {
 578         /*
 579          * We are not putting this on the write queue, so
 580          * dccp_transmit_skb() will set the ownership to this
 581          * sock.
 582          */
 583         struct sk_buff *skb = alloc_skb(sk->sk_prot->max_header, GFP_ATOMIC);
 584
 585         if (skb == NULL) {
 586                 /* FIXME: how to make sure the sync is sent? */
 587                 DCCP_CRIT("could not send %s", dccp_packet_name(pkt_type));
 588                 return;
 589         }
 590
 591         /* Reserve space for headers and prepare control bits. */
 592         skb_reserve(skb, sk->sk_prot->max_header);
 593         DCCP_SKB_CB(skb)->dccpd_type = pkt_type;
 594         DCCP_SKB_CB(skb)->dccpd_ack_seq = ackno;
 595
 596         /*
 597          * Clear the flag in case the Sync was scheduled for out-of-band data,
 598          * such as carrying a long Ack Vector.
 599          */
 600         dccp_sk(sk)->dccps_sync_scheduled = 0;
 601
 602         dccp_transmit_skb(sk, skb);
 603 }
 604
 605 EXPORT_SYMBOL_GPL(dccp_send_sync);
 606
 607 /*
 608  * Send a DCCP_PKT_CLOSE/CLOSEREQ. The caller locks the socket for us. This
 609  * cannot be allowed to fail queueing a DCCP_PKT_CLOSE/CLOSEREQ frame under
 610  * any circumstances.
 611  */
 612 void dccp_send_close(struct sock *sk, const int active)
 613 {
 614         struct dccp_sock *dp = dccp_sk(sk);
 615         struct sk_buff *skb;
 616         const gfp_t prio = active ? GFP_KERNEL : GFP_ATOMIC;
 617
 618         skb = alloc_skb(sk->sk_prot->max_header, prio);
 619         if (skb == NULL)
 620                 return;
 621
 622         /* Reserve space for headers and prepare control bits. */
 623         skb_reserve(skb, sk->sk_prot->max_header);
 624         if (dp->dccps_role == DCCP_ROLE_SERVER && !dp->dccps_server_timewait)
 625                 DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_CLOSEREQ;
 626         else
 627                 DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_CLOSE;
 628
 629         if (active) {
 630                 dccp_write_xmit(sk, 1);
 631                 dccp_skb_entail(sk, skb);
 632                 dccp_transmit_skb(sk, skb_clone(skb, prio));
 633                 /*
 634                  * Retransmission timer for active-close: RFC 4340, 8.3 requires
 635                  * to retransmit the Close/CloseReq until the CLOSING/CLOSEREQ
 636                  * state can be left. The initial timeout is 2 RTTs.
 637                  * Since RTT measurement is done by the CCIDs, there is no easy
 638                  * way to get an RTT sample. The fallback RTT from RFC 4340, 3.4
 639                  * is too low (200ms); we use a high value to avoid unnecessary
 640                  * retransmissions when the link RTT is > 0.2 seconds.
 641                  * FIXME: Let main module sample RTTs and use that instead.
 642                  */
 643                 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
 644                                           DCCP_TIMEOUT_INIT, DCCP_RTO_MAX);
 645         } else
 646                 dccp_transmit_skb(sk, skb);
 647 }