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                  * 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_has_sleeper(sk))
 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, 0, len);
 305                         if (err)
 306                                 DCCP_BUG("err=%d after ccid_hc_tx_packet_sent",
 307                                          err);
 308                 } else {
 309                         dccp_pr_debug("packet discarded due to err=%d\n", err);
 310                         kfree_skb(skb);
 311                 }
 312         }
 313 }
 314
 315 /**
 316  * dccp_retransmit_skb  -  Retransmit Request, Close, or CloseReq packets
 317  * There are only four retransmittable packet types in DCCP:
 318  * - Request  in client-REQUEST  state (sec. 8.1.1),
 319  * - CloseReq in server-CLOSEREQ state (sec. 8.3),
 320  * - Close    in   node-CLOSING  state (sec. 8.3),
 321  * - Acks in client-PARTOPEN state (sec. 8.1.5, handled by dccp_delack_timer()).
 322  * This function expects sk->sk_send_head to contain the original skb.
 323  */
 324 int dccp_retransmit_skb(struct sock *sk)
 325 {
 326         WARN_ON(sk->sk_send_head == NULL);
 327
 328         if (inet_csk(sk)->icsk_af_ops->rebuild_header(sk) != 0)
 329                 return -EHOSTUNREACH; /* Routing failure or similar. */
 330
 331         /* this count is used to distinguish original and retransmitted skb */
 332         inet_csk(sk)->icsk_retransmits++;
 333
 334         return dccp_transmit_skb(sk, skb_clone(sk->sk_send_head, GFP_ATOMIC));
 335 }
 336
 337 struct sk_buff *dccp_make_response(struct sock *sk, struct dst_entry *dst,
 338                                    struct request_sock *req)
 339 {
 340         struct dccp_hdr *dh;
 341         struct dccp_request_sock *dreq;
 342         const u32 dccp_header_size = sizeof(struct dccp_hdr) +
 343                                      sizeof(struct dccp_hdr_ext) +
 344                                      sizeof(struct dccp_hdr_response);
 345         struct sk_buff *skb = sock_wmalloc(sk, sk->sk_prot->max_header, 1,
 346                                            GFP_ATOMIC);
 347         if (skb == NULL)
 348                 return NULL;
 349
 350         /* Reserve space for headers. */
 351         skb_reserve(skb, sk->sk_prot->max_header);
 352
 353         skb_dst_set(skb, dst_clone(dst));
 354
 355         dreq = dccp_rsk(req);
 356         if (inet_rsk(req)->acked)       /* increase ISS upon retransmission */
 357                 dccp_inc_seqno(&dreq->dreq_iss);
 358         DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_RESPONSE;
 359         DCCP_SKB_CB(skb)->dccpd_seq  = dreq->dreq_iss;
 360
 361         /* Resolve feature dependencies resulting from choice of CCID */
 362         if (dccp_feat_server_ccid_dependencies(dreq))
 363                 goto response_failed;
 364
 365         if (dccp_insert_options_rsk(dreq, skb))
 366                 goto response_failed;
 367
 368         /* Build and checksum header */
 369         dh = dccp_zeroed_hdr(skb, dccp_header_size);
 370
 371         dh->dccph_sport = inet_rsk(req)->loc_port;
 372         dh->dccph_dport = inet_rsk(req)->rmt_port;
 373         dh->dccph_doff  = (dccp_header_size +
 374                            DCCP_SKB_CB(skb)->dccpd_opt_len) / 4;
 375         dh->dccph_type  = DCCP_PKT_RESPONSE;
 376         dh->dccph_x     = 1;
 377         dccp_hdr_set_seq(dh, dreq->dreq_iss);
 378         dccp_hdr_set_ack(dccp_hdr_ack_bits(skb), dreq->dreq_isr);
 379         dccp_hdr_response(skb)->dccph_resp_service = dreq->dreq_service;
 380
 381         dccp_csum_outgoing(skb);
 382
 383         /* We use `acked' to remember that a Response was already sent. */
 384         inet_rsk(req)->acked = 1;
 385         DCCP_INC_STATS(DCCP_MIB_OUTSEGS);
 386         return skb;
 387 response_failed:
 388         kfree_skb(skb);
 389         return NULL;
 390 }
 391
 392 EXPORT_SYMBOL_GPL(dccp_make_response);
 393
 394 /* answer offending packet in @rcv_skb with Reset from control socket @ctl */
 395 struct sk_buff *dccp_ctl_make_reset(struct sock *sk, struct sk_buff *rcv_skb)
 396 {
 397         struct dccp_hdr *rxdh = dccp_hdr(rcv_skb), *dh;
 398         struct dccp_skb_cb *dcb = DCCP_SKB_CB(rcv_skb);
 399         const u32 dccp_hdr_reset_len = sizeof(struct dccp_hdr) +
 400                                        sizeof(struct dccp_hdr_ext) +
 401                                        sizeof(struct dccp_hdr_reset);
 402         struct dccp_hdr_reset *dhr;
 403         struct sk_buff *skb;
 404
 405         skb = alloc_skb(sk->sk_prot->max_header, GFP_ATOMIC);
 406         if (skb == NULL)
 407                 return NULL;
 408
 409         skb_reserve(skb, sk->sk_prot->max_header);
 410
 411         /* Swap the send and the receive. */
 412         dh = dccp_zeroed_hdr(skb, dccp_hdr_reset_len);
 413         dh->dccph_type  = DCCP_PKT_RESET;
 414         dh->dccph_sport = rxdh->dccph_dport;
 415         dh->dccph_dport = rxdh->dccph_sport;
 416         dh->dccph_doff  = dccp_hdr_reset_len / 4;
 417         dh->dccph_x     = 1;
 418
 419         dhr = dccp_hdr_reset(skb);
 420         dhr->dccph_reset_code = dcb->dccpd_reset_code;
 421
 422         switch (dcb->dccpd_reset_code) {
 423         case DCCP_RESET_CODE_PACKET_ERROR:
 424                 dhr->dccph_reset_data[0] = rxdh->dccph_type;
 425                 break;
 426         case DCCP_RESET_CODE_OPTION_ERROR:      /* fall through */
 427         case DCCP_RESET_CODE_MANDATORY_ERROR:
 428                 memcpy(dhr->dccph_reset_data, dcb->dccpd_reset_data, 3);
 429                 break;
 430         }
 431         /*
 432          * From RFC 4340, 8.3.1:
 433          *   If P.ackno exists, set R.seqno := P.ackno + 1.
 434          *   Else set R.seqno := 0.
 435          */
 436         if (dcb->dccpd_ack_seq != DCCP_PKT_WITHOUT_ACK_SEQ)
 437                 dccp_hdr_set_seq(dh, ADD48(dcb->dccpd_ack_seq, 1));
 438         dccp_hdr_set_ack(dccp_hdr_ack_bits(skb), dcb->dccpd_seq);
 439
 440         dccp_csum_outgoing(skb);
 441         return skb;
 442 }
 443
 444 EXPORT_SYMBOL_GPL(dccp_ctl_make_reset);
 445
 446 /* send Reset on established socket, to close or abort the connection */
 447 int dccp_send_reset(struct sock *sk, enum dccp_reset_codes code)
 448 {
 449         struct sk_buff *skb;
 450         /*
 451          * FIXME: what if rebuild_header fails?
 452          * Should we be doing a rebuild_header here?
 453          */
 454         int err = inet_csk(sk)->icsk_af_ops->rebuild_header(sk);
 455
 456         if (err != 0)
 457                 return err;
 458
 459         skb = sock_wmalloc(sk, sk->sk_prot->max_header, 1, GFP_ATOMIC);
 460         if (skb == NULL)
 461                 return -ENOBUFS;
 462
 463         /* Reserve space for headers and prepare control bits. */
 464         skb_reserve(skb, sk->sk_prot->max_header);
 465         DCCP_SKB_CB(skb)->dccpd_type       = DCCP_PKT_RESET;
 466         DCCP_SKB_CB(skb)->dccpd_reset_code = code;
 467
 468         return dccp_transmit_skb(sk, skb);
 469 }
 470
 471 /*
 472  * Do all connect socket setups that can be done AF independent.
 473  */
 474 static inline void dccp_connect_init(struct sock *sk)
 475 {
 476         struct dccp_sock *dp = dccp_sk(sk);
 477         struct dst_entry *dst = __sk_dst_get(sk);
 478         struct inet_connection_sock *icsk = inet_csk(sk);
 479
 480         sk->sk_err = 0;
 481         sock_reset_flag(sk, SOCK_DONE);
 482
 483         dccp_sync_mss(sk, dst_mtu(dst));
 484
 485         /* Initialise GAR as per 8.5; AWL/AWH are set in dccp_transmit_skb() */
 486         dp->dccps_gar = dp->dccps_iss;
 487
 488         icsk->icsk_retransmits = 0;
 489 }
 490
 491 int dccp_connect(struct sock *sk)
 492 {
 493         struct sk_buff *skb;
 494         struct inet_connection_sock *icsk = inet_csk(sk);
 495
 496         /* do not connect if feature negotiation setup fails */
 497         if (dccp_feat_finalise_settings(dccp_sk(sk)))
 498                 return -EPROTO;
 499
 500         dccp_connect_init(sk);
 501
 502         skb = alloc_skb(sk->sk_prot->max_header, sk->sk_allocation);
 503         if (unlikely(skb == NULL))
 504                 return -ENOBUFS;
 505
 506         /* Reserve space for headers. */
 507         skb_reserve(skb, sk->sk_prot->max_header);
 508
 509         DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_REQUEST;
 510
 511         dccp_skb_entail(sk, skb);
 512         dccp_transmit_skb(sk, skb_clone(skb, GFP_KERNEL));
 513         DCCP_INC_STATS(DCCP_MIB_ACTIVEOPENS);
 514
 515         /* Timer for repeating the REQUEST until an answer. */
 516         inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
 517                                   icsk->icsk_rto, DCCP_RTO_MAX);
 518         return 0;
 519 }
 520
 521 EXPORT_SYMBOL_GPL(dccp_connect);
 522
 523 void dccp_send_ack(struct sock *sk)
 524 {
 525         /* If we have been reset, we may not send again. */
 526         if (sk->sk_state != DCCP_CLOSED) {
 527                 struct sk_buff *skb = alloc_skb(sk->sk_prot->max_header,
 528                                                 GFP_ATOMIC);
 529
 530                 if (skb == NULL) {
 531                         inet_csk_schedule_ack(sk);
 532                         inet_csk(sk)->icsk_ack.ato = TCP_ATO_MIN;
 533                         inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
 534                                                   TCP_DELACK_MAX,
 535                                                   DCCP_RTO_MAX);
 536                         return;
 537                 }
 538
 539                 /* Reserve space for headers */
 540                 skb_reserve(skb, sk->sk_prot->max_header);
 541                 DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_ACK;
 542                 dccp_transmit_skb(sk, skb);
 543         }
 544 }
 545
 546 EXPORT_SYMBOL_GPL(dccp_send_ack);
 547
 548 #if 0
 549 /* FIXME: Is this still necessary (11.3) - currently nowhere used by DCCP. */
 550 void dccp_send_delayed_ack(struct sock *sk)
 551 {
 552         struct inet_connection_sock *icsk = inet_csk(sk);
 553         /*
 554          * FIXME: tune this timer. elapsed time fixes the skew, so no problem
 555          * with using 2s, and active senders also piggyback the ACK into a
 556          * DATAACK packet, so this is really for quiescent senders.
 557          */
 558         unsigned long timeout = jiffies + 2 * HZ;
 559
 560         /* Use new timeout only if there wasn't a older one earlier. */
 561         if (icsk->icsk_ack.pending & ICSK_ACK_TIMER) {
 562                 /* If delack timer was blocked or is about to expire,
 563                  * send ACK now.
 564                  *
 565                  * FIXME: check the "about to expire" part
 566                  */
 567                 if (icsk->icsk_ack.blocked) {
 568                         dccp_send_ack(sk);
 569                         return;
 570                 }
 571
 572                 if (!time_before(timeout, icsk->icsk_ack.timeout))
 573                         timeout = icsk->icsk_ack.timeout;
 574         }
 575         icsk->icsk_ack.pending |= ICSK_ACK_SCHED | ICSK_ACK_TIMER;
 576         icsk->icsk_ack.timeout = timeout;
 577         sk_reset_timer(sk, &icsk->icsk_delack_timer, timeout);
 578 }
 579 #endif
 580
 581 void dccp_send_sync(struct sock *sk, const u64 ackno,
 582                     const enum dccp_pkt_type pkt_type)
 583 {
 584         /*
 585          * We are not putting this on the write queue, so
 586          * dccp_transmit_skb() will set the ownership to this
 587          * sock.
 588          */
 589         struct sk_buff *skb = alloc_skb(sk->sk_prot->max_header, GFP_ATOMIC);
 590
 591         if (skb == NULL) {
 592                 /* FIXME: how to make sure the sync is sent? */
 593                 DCCP_CRIT("could not send %s", dccp_packet_name(pkt_type));
 594                 return;
 595         }
 596
 597         /* Reserve space for headers and prepare control bits. */
 598         skb_reserve(skb, sk->sk_prot->max_header);
 599         DCCP_SKB_CB(skb)->dccpd_type = pkt_type;
 600         DCCP_SKB_CB(skb)->dccpd_ack_seq = ackno;
 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 }