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 #include <linux/slab.h>
  17
  18 #include <net/inet_sock.h>
  19 #include <net/sock.h>
  20
  21 #include "ackvec.h"
  22 #include "ccid.h"
  23 #include "dccp.h"
  24
  25 static inline void dccp_event_ack_sent(struct sock *sk)
  26 {
  27         inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK);
  28 }
  29
  30 static void dccp_skb_entail(struct sock *sk, struct sk_buff *skb)
  31 {
  32         skb_set_owner_w(skb, sk);
  33         WARN_ON(sk->sk_send_head);
  34         sk->sk_send_head = skb;
  35 }
  36
  37 /*
  38  * All SKB's seen here are completely headerless. It is our
  39  * job to build the DCCP header, and pass the packet down to
  40  * IP so it can do the same plus pass the packet off to the
  41  * device.
  42  */
  43 static int dccp_transmit_skb(struct sock *sk, struct sk_buff *skb)
  44 {
  45         if (likely(skb != NULL)) {
  46                 const struct inet_sock *inet = inet_sk(sk);
  47                 const struct inet_connection_sock *icsk = inet_csk(sk);
  48                 struct dccp_sock *dp = dccp_sk(sk);
  49                 struct dccp_skb_cb *dcb = DCCP_SKB_CB(skb);
  50                 struct dccp_hdr *dh;
  51                 /* XXX For now we're using only 48 bits sequence numbers */
  52                 const u32 dccp_header_size = sizeof(*dh) +
  53                                              sizeof(struct dccp_hdr_ext) +
  54                                           dccp_packet_hdr_len(dcb->dccpd_type);
  55                 int err, set_ack = 1;
  56                 u64 ackno = dp->dccps_gsr;
  57                 /*
  58                  * Increment GSS here already in case the option code needs it.
  59                  * Update GSS for real only if option processing below succeeds.
  60                  */
  61                 dcb->dccpd_seq = ADD48(dp->dccps_gss, 1);
  62
  63                 switch (dcb->dccpd_type) {
  64                 case DCCP_PKT_DATA:
  65                         set_ack = 0;
  66                         /* fall through */
  67                 case DCCP_PKT_DATAACK:
  68                 case DCCP_PKT_RESET:
  69                         break;
  70
  71                 case DCCP_PKT_REQUEST:
  72                         set_ack = 0;
  73                         /* Use ISS on the first (non-retransmitted) Request. */
  74                         if (icsk->icsk_retransmits == 0)
  75                                 dcb->dccpd_seq = dp->dccps_iss;
  76                         /* fall through */
  77
  78                 case DCCP_PKT_SYNC:
  79                 case DCCP_PKT_SYNCACK:
  80                         ackno = dcb->dccpd_ack_seq;
  81                         /* fall through */
  82                 default:
  83                         /*
  84                          * Set owner/destructor: some skbs are allocated via
  85                          * alloc_skb (e.g. when retransmission may happen).
  86                          * Only Data, DataAck, and Reset packets should come
  87                          * through here with skb->sk set.
  88                          */
  89                         WARN_ON(skb->sk);
  90                         skb_set_owner_w(skb, sk);
  91                         break;
  92                 }
  93
  94                 if (dccp_insert_options(sk, skb)) {
  95                         kfree_skb(skb);
  96                         return -EPROTO;
  97                 }
  98
  99
 100                 /* Build DCCP header and checksum it. */
 101                 dh = dccp_zeroed_hdr(skb, dccp_header_size);
 102                 dh->dccph_type  = dcb->dccpd_type;
 103                 dh->dccph_sport = inet->inet_sport;
 104                 dh->dccph_dport = inet->inet_dport;
 105                 dh->dccph_doff  = (dccp_header_size + dcb->dccpd_opt_len) / 4;
 106                 dh->dccph_ccval = dcb->dccpd_ccval;
 107                 dh->dccph_cscov = dp->dccps_pcslen;
 108                 /* XXX For now we're using only 48 bits sequence numbers */
 109                 dh->dccph_x     = 1;
 110
 111                 dccp_update_gss(sk, dcb->dccpd_seq);
 112                 dccp_hdr_set_seq(dh, dp->dccps_gss);
 113                 if (set_ack)
 114                         dccp_hdr_set_ack(dccp_hdr_ack_bits(skb), ackno);
 115
 116                 switch (dcb->dccpd_type) {
 117                 case DCCP_PKT_REQUEST:
 118                         dccp_hdr_request(skb)->dccph_req_service =
 119                                                         dp->dccps_service;
 120                         /*
 121                          * Limit Ack window to ISS <= P.ackno <= GSS, so that
 122                          * only Responses to Requests we sent are considered.
 123                          */
 124                         dp->dccps_awl = dp->dccps_iss;
 125                         break;
 126                 case DCCP_PKT_RESET:
 127                         dccp_hdr_reset(skb)->dccph_reset_code =
 128                                                         dcb->dccpd_reset_code;
 129                         break;
 130                 }
 131
 132                 icsk->icsk_af_ops->send_check(sk, skb);
 133
 134                 if (set_ack)
 135                         dccp_event_ack_sent(sk);
 136
 137                 DCCP_INC_STATS(DCCP_MIB_OUTSEGS);
 138
 139                 err = icsk->icsk_af_ops->queue_xmit(skb);
 140                 return net_xmit_eval(err);
 141         }
 142         return -ENOBUFS;
 143 }
 144
 145 /**
 146  * dccp_determine_ccmps  -  Find out about CCID-specfic packet-size limits
 147  * We only consider the HC-sender CCID for setting the CCMPS (RFC 4340, 14.),
 148  * since the RX CCID is restricted to feedback packets (Acks), which are small
 149  * in comparison with the data traffic. A value of 0 means "no current CCMPS".
 150  */
 151 static u32 dccp_determine_ccmps(const struct dccp_sock *dp)
 152 {
 153         const struct ccid *tx_ccid = dp->dccps_hc_tx_ccid;
 154
 155         if (tx_ccid == NULL || tx_ccid->ccid_ops == NULL)
 156                 return 0;
 157         return tx_ccid->ccid_ops->ccid_ccmps;
 158 }
 159
 160 unsigned int dccp_sync_mss(struct sock *sk, u32 pmtu)
 161 {
 162         struct inet_connection_sock *icsk = inet_csk(sk);
 163         struct dccp_sock *dp = dccp_sk(sk);
 164         u32 ccmps = dccp_determine_ccmps(dp);
 165         u32 cur_mps = ccmps ? min(pmtu, ccmps) : pmtu;
 166
 167         /* Account for header lengths and IPv4/v6 option overhead */
 168         cur_mps -= (icsk->icsk_af_ops->net_header_len + icsk->icsk_ext_hdr_len +
 169                     sizeof(struct dccp_hdr) + sizeof(struct dccp_hdr_ext));
 170
 171         /*
 172          * Leave enough headroom for common DCCP header options.
 173          * This only considers options which may appear on DCCP-Data packets, as
 174          * per table 3 in RFC 4340, 5.8. When running out of space for other
 175          * options (eg. Ack Vector which can take up to 255 bytes), it is better
 176          * to schedule a separate Ack. Thus we leave headroom for the following:
 177          *  - 1 byte for Slow Receiver (11.6)
 178          *  - 6 bytes for Timestamp (13.1)
 179          *  - 10 bytes for Timestamp Echo (13.3)
 180          *  - 8 bytes for NDP count (7.7, when activated)
 181          *  - 6 bytes for Data Checksum (9.3)
 182          *  - %DCCPAV_MIN_OPTLEN bytes for Ack Vector size (11.4, when enabled)
 183          */
 184         cur_mps -= roundup(1 + 6 + 10 + dp->dccps_send_ndp_count * 8 + 6 +
 185                            (dp->dccps_hc_rx_ackvec ? DCCPAV_MIN_OPTLEN : 0), 4);
 186
 187         /* And store cached results */
 188         icsk->icsk_pmtu_cookie = pmtu;
 189         dp->dccps_mss_cache = cur_mps;
 190
 191         return cur_mps;
 192 }
 193
 194 EXPORT_SYMBOL_GPL(dccp_sync_mss);
 195
 196 void dccp_write_space(struct sock *sk)
 197 {
 198         struct socket_wq *wq;
 199
 200         rcu_read_lock();
 201         wq = rcu_dereference(sk->sk_wq);
 202         if (wq_has_sleeper(wq))
 203                 wake_up_interruptible(&wq->wait);
 204         /* Should agree with poll, otherwise some programs break */
 205         if (sock_writeable(sk))
 206                 sk_wake_async(sk, SOCK_WAKE_SPACE, POLL_OUT);
 207
 208         rcu_read_unlock();
 209 }
 210
 211 /**
 212  * dccp_wait_for_ccid - Wait for ccid to tell us we can send a packet
 213  * @sk:    socket to wait for
 214  * @skb:   current skb to pass on for waiting
 215  * @delay: sleep timeout in milliseconds (> 0)
 216  * This function is called by default when the socket is closed, and
 217  * when a non-zero linger time is set on the socket. For consistency
 218  */
 219 static int dccp_wait_for_ccid(struct sock *sk, struct sk_buff *skb, int delay)
 220 {
 221         struct dccp_sock *dp = dccp_sk(sk);
 222         DEFINE_WAIT(wait);
 223         unsigned long jiffdelay;
 224         int rc;
 225
 226         do {
 227                 dccp_pr_debug("delayed send by %d msec\n", delay);
 228                 jiffdelay = msecs_to_jiffies(delay);
 229
 230                 prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);
 231
 232                 sk->sk_write_pending++;
 233                 release_sock(sk);
 234                 schedule_timeout(jiffdelay);
 235                 lock_sock(sk);
 236                 sk->sk_write_pending--;
 237
 238                 if (sk->sk_err)
 239                         goto do_error;
 240                 if (signal_pending(current))
 241                         goto do_interrupted;
 242
 243                 rc = ccid_hc_tx_send_packet(dp->dccps_hc_tx_ccid, sk, skb);
 244         } while ((delay = rc) > 0);
 245 out:
 246         finish_wait(sk_sleep(sk), &wait);
 247         return rc;
 248
 249 do_error:
 250         rc = -EPIPE;
 251         goto out;
 252 do_interrupted:
 253         rc = -EINTR;
 254         goto out;
 255 }
 256
 257 void dccp_write_xmit(struct sock *sk, int block)
 258 {
 259         struct dccp_sock *dp = dccp_sk(sk);
 260         struct sk_buff *skb;
 261
 262         while ((skb = skb_peek(&sk->sk_write_queue))) {
 263                 int err = ccid_hc_tx_send_packet(dp->dccps_hc_tx_ccid, sk, skb);
 264
 265                 if (err > 0) {
 266                         if (!block) {
 267                                 sk_reset_timer(sk, &dp->dccps_xmit_timer,
 268                                                 msecs_to_jiffies(err)+jiffies);
 269                                 break;
 270                         } else
 271                                 err = dccp_wait_for_ccid(sk, skb, err);
 272                         if (err && err != -EINTR)
 273                                 DCCP_BUG("err=%d after dccp_wait_for_ccid", err);
 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                                 const u32 cur_mps = dp->dccps_mss_cache - DCCP_FEATNEG_OVERHEAD;
 283                                 /*
 284                                  * See 8.1.5 - Handshake Completion.
 285                                  *
 286                                  * For robustness we resend Confirm options until the client has
 287                                  * entered OPEN. During the initial feature negotiation, the MPS
 288                                  * is smaller than usual, reduced by the Change/Confirm options.
 289                                  */
 290                                 if (!list_empty(&dp->dccps_featneg) && len > cur_mps) {
 291                                         DCCP_WARN("Payload too large (%d) for featneg.\n", len);
 292                                         dccp_send_ack(sk);
 293                                         dccp_feat_list_purge(&dp->dccps_featneg);
 294                                 }
 295
 296                                 inet_csk_schedule_ack(sk);
 297                                 inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
 298                                                   inet_csk(sk)->icsk_rto,
 299                                                   DCCP_RTO_MAX);
 300                                 dcb->dccpd_type = DCCP_PKT_DATAACK;
 301                         } else if (dccp_ack_pending(sk))
 302                                 dcb->dccpd_type = DCCP_PKT_DATAACK;
 303                         else
 304                                 dcb->dccpd_type = DCCP_PKT_DATA;
 305
 306                         err = dccp_transmit_skb(sk, skb);
 307                         ccid_hc_tx_packet_sent(dp->dccps_hc_tx_ccid, sk, 0, len);
 308                         if (err)
 309                                 DCCP_BUG("err=%d after ccid_hc_tx_packet_sent",
 310                                          err);
 311                 } else {
 312                         dccp_pr_debug("packet discarded due to err=%d\n", err);
 313                         kfree_skb(skb);
 314                 }
 315         }
 316 }
 317
 318 /**
 319  * dccp_retransmit_skb  -  Retransmit Request, Close, or CloseReq packets
 320  * There are only four retransmittable packet types in DCCP:
 321  * - Request  in client-REQUEST  state (sec. 8.1.1),
 322  * - CloseReq in server-CLOSEREQ state (sec. 8.3),
 323  * - Close    in   node-CLOSING  state (sec. 8.3),
 324  * - Acks in client-PARTOPEN state (sec. 8.1.5, handled by dccp_delack_timer()).
 325  * This function expects sk->sk_send_head to contain the original skb.
 326  */
 327 int dccp_retransmit_skb(struct sock *sk)
 328 {
 329         WARN_ON(sk->sk_send_head == NULL);
 330
 331         if (inet_csk(sk)->icsk_af_ops->rebuild_header(sk) != 0)
 332                 return -EHOSTUNREACH; /* Routing failure or similar. */
 333
 334         /* this count is used to distinguish original and retransmitted skb */
 335         inet_csk(sk)->icsk_retransmits++;
 336
 337         return dccp_transmit_skb(sk, skb_clone(sk->sk_send_head, GFP_ATOMIC));
 338 }
 339
 340 struct sk_buff *dccp_make_response(struct sock *sk, struct dst_entry *dst,
 341                                    struct request_sock *req)
 342 {
 343         struct dccp_hdr *dh;
 344         struct dccp_request_sock *dreq;
 345         const u32 dccp_header_size = sizeof(struct dccp_hdr) +
 346                                      sizeof(struct dccp_hdr_ext) +
 347                                      sizeof(struct dccp_hdr_response);
 348         struct sk_buff *skb = sock_wmalloc(sk, sk->sk_prot->max_header, 1,
 349                                            GFP_ATOMIC);
 350         if (skb == NULL)
 351                 return NULL;
 352
 353         /* Reserve space for headers. */
 354         skb_reserve(skb, sk->sk_prot->max_header);
 355
 356         skb_dst_set(skb, dst_clone(dst));
 357
 358         dreq = dccp_rsk(req);
 359         if (inet_rsk(req)->acked)       /* increase ISS upon retransmission */
 360                 dccp_inc_seqno(&dreq->dreq_iss);
 361         DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_RESPONSE;
 362         DCCP_SKB_CB(skb)->dccpd_seq  = dreq->dreq_iss;
 363
 364         /* Resolve feature dependencies resulting from choice of CCID */
 365         if (dccp_feat_server_ccid_dependencies(dreq))
 366                 goto response_failed;
 367
 368         if (dccp_insert_options_rsk(dreq, skb))
 369                 goto response_failed;
 370
 371         /* Build and checksum header */
 372         dh = dccp_zeroed_hdr(skb, dccp_header_size);
 373
 374         dh->dccph_sport = inet_rsk(req)->loc_port;
 375         dh->dccph_dport = inet_rsk(req)->rmt_port;
 376         dh->dccph_doff  = (dccp_header_size +
 377                            DCCP_SKB_CB(skb)->dccpd_opt_len) / 4;
 378         dh->dccph_type  = DCCP_PKT_RESPONSE;
 379         dh->dccph_x     = 1;
 380         dccp_hdr_set_seq(dh, dreq->dreq_iss);
 381         dccp_hdr_set_ack(dccp_hdr_ack_bits(skb), dreq->dreq_isr);
 382         dccp_hdr_response(skb)->dccph_resp_service = dreq->dreq_service;
 383
 384         dccp_csum_outgoing(skb);
 385
 386         /* We use `acked' to remember that a Response was already sent. */
 387         inet_rsk(req)->acked = 1;
 388         DCCP_INC_STATS(DCCP_MIB_OUTSEGS);
 389         return skb;
 390 response_failed:
 391         kfree_skb(skb);
 392         return NULL;
 393 }
 394
 395 EXPORT_SYMBOL_GPL(dccp_make_response);
 396
 397 /* answer offending packet in @rcv_skb with Reset from control socket @ctl */
 398 struct sk_buff *dccp_ctl_make_reset(struct sock *sk, struct sk_buff *rcv_skb)
 399 {
 400         struct dccp_hdr *rxdh = dccp_hdr(rcv_skb), *dh;
 401         struct dccp_skb_cb *dcb = DCCP_SKB_CB(rcv_skb);
 402         const u32 dccp_hdr_reset_len = sizeof(struct dccp_hdr) +
 403                                        sizeof(struct dccp_hdr_ext) +
 404                                        sizeof(struct dccp_hdr_reset);
 405         struct dccp_hdr_reset *dhr;
 406         struct sk_buff *skb;
 407
 408         skb = alloc_skb(sk->sk_prot->max_header, GFP_ATOMIC);
 409         if (skb == NULL)
 410                 return NULL;
 411
 412         skb_reserve(skb, sk->sk_prot->max_header);
 413
 414         /* Swap the send and the receive. */
 415         dh = dccp_zeroed_hdr(skb, dccp_hdr_reset_len);
 416         dh->dccph_type  = DCCP_PKT_RESET;
 417         dh->dccph_sport = rxdh->dccph_dport;
 418         dh->dccph_dport = rxdh->dccph_sport;
 419         dh->dccph_doff  = dccp_hdr_reset_len / 4;
 420         dh->dccph_x     = 1;
 421
 422         dhr = dccp_hdr_reset(skb);
 423         dhr->dccph_reset_code = dcb->dccpd_reset_code;
 424
 425         switch (dcb->dccpd_reset_code) {
 426         case DCCP_RESET_CODE_PACKET_ERROR:
 427                 dhr->dccph_reset_data[0] = rxdh->dccph_type;
 428                 break;
 429         case DCCP_RESET_CODE_OPTION_ERROR:      /* fall through */
 430         case DCCP_RESET_CODE_MANDATORY_ERROR:
 431                 memcpy(dhr->dccph_reset_data, dcb->dccpd_reset_data, 3);
 432                 break;
 433         }
 434         /*
 435          * From RFC 4340, 8.3.1:
 436          *   If P.ackno exists, set R.seqno := P.ackno + 1.
 437          *   Else set R.seqno := 0.
 438          */
 439         if (dcb->dccpd_ack_seq != DCCP_PKT_WITHOUT_ACK_SEQ)
 440                 dccp_hdr_set_seq(dh, ADD48(dcb->dccpd_ack_seq, 1));
 441         dccp_hdr_set_ack(dccp_hdr_ack_bits(skb), dcb->dccpd_seq);
 442
 443         dccp_csum_outgoing(skb);
 444         return skb;
 445 }
 446
 447 EXPORT_SYMBOL_GPL(dccp_ctl_make_reset);
 448
 449 /* send Reset on established socket, to close or abort the connection */
 450 int dccp_send_reset(struct sock *sk, enum dccp_reset_codes code)
 451 {
 452         struct sk_buff *skb;
 453         /*
 454          * FIXME: what if rebuild_header fails?
 455          * Should we be doing a rebuild_header here?
 456          */
 457         int err = inet_csk(sk)->icsk_af_ops->rebuild_header(sk);
 458
 459         if (err != 0)
 460                 return err;
 461
 462         skb = sock_wmalloc(sk, sk->sk_prot->max_header, 1, GFP_ATOMIC);
 463         if (skb == NULL)
 464                 return -ENOBUFS;
 465
 466         /* Reserve space for headers and prepare control bits. */
 467         skb_reserve(skb, sk->sk_prot->max_header);
 468         DCCP_SKB_CB(skb)->dccpd_type       = DCCP_PKT_RESET;
 469         DCCP_SKB_CB(skb)->dccpd_reset_code = code;
 470
 471         return dccp_transmit_skb(sk, skb);
 472 }
 473
 474 /*
 475  * Do all connect socket setups that can be done AF independent.
 476  */
 477 static inline void dccp_connect_init(struct sock *sk)
 478 {
 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         /* Initialise GAR as per 8.5; AWL/AWH are set in dccp_transmit_skb() */
 489         dp->dccps_gar = dp->dccps_iss;
 490
 491         icsk->icsk_retransmits = 0;
 492 }
 493
 494 int dccp_connect(struct sock *sk)
 495 {
 496         struct sk_buff *skb;
 497         struct inet_connection_sock *icsk = inet_csk(sk);
 498
 499         /* do not connect if feature negotiation setup fails */
 500         if (dccp_feat_finalise_settings(dccp_sk(sk)))
 501                 return -EPROTO;
 502
 503         dccp_connect_init(sk);
 504
 505         skb = alloc_skb(sk->sk_prot->max_header, sk->sk_allocation);
 506         if (unlikely(skb == NULL))
 507                 return -ENOBUFS;
 508
 509         /* Reserve space for headers. */
 510         skb_reserve(skb, sk->sk_prot->max_header);
 511
 512         DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_REQUEST;
 513
 514         dccp_skb_entail(sk, skb);
 515         dccp_transmit_skb(sk, skb_clone(skb, GFP_KERNEL));
 516         DCCP_INC_STATS(DCCP_MIB_ACTIVEOPENS);
 517
 518         /* Timer for repeating the REQUEST until an answer. */
 519         inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
 520                                   icsk->icsk_rto, DCCP_RTO_MAX);
 521         return 0;
 522 }
 523
 524 EXPORT_SYMBOL_GPL(dccp_connect);
 525
 526 void dccp_send_ack(struct sock *sk)
 527 {
 528         /* If we have been reset, we may not send again. */
 529         if (sk->sk_state != DCCP_CLOSED) {
 530                 struct sk_buff *skb = alloc_skb(sk->sk_prot->max_header,
 531                                                 GFP_ATOMIC);
 532
 533                 if (skb == NULL) {
 534                         inet_csk_schedule_ack(sk);
 535                         inet_csk(sk)->icsk_ack.ato = TCP_ATO_MIN;
 536                         inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
 537                                                   TCP_DELACK_MAX,
 538                                                   DCCP_RTO_MAX);
 539                         return;
 540                 }
 541
 542                 /* Reserve space for headers */
 543                 skb_reserve(skb, sk->sk_prot->max_header);
 544                 DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_ACK;
 545                 dccp_transmit_skb(sk, skb);
 546         }
 547 }
 548
 549 EXPORT_SYMBOL_GPL(dccp_send_ack);
 550
 551 #if 0
 552 /* FIXME: Is this still necessary (11.3) - currently nowhere used by DCCP. */
 553 void dccp_send_delayed_ack(struct sock *sk)
 554 {
 555         struct inet_connection_sock *icsk = inet_csk(sk);
 556         /*
 557          * FIXME: tune this timer. elapsed time fixes the skew, so no problem
 558          * with using 2s, and active senders also piggyback the ACK into a
 559          * DATAACK packet, so this is really for quiescent senders.
 560          */
 561         unsigned long timeout = jiffies + 2 * HZ;
 562
 563         /* Use new timeout only if there wasn't a older one earlier. */
 564         if (icsk->icsk_ack.pending & ICSK_ACK_TIMER) {
 565                 /* If delack timer was blocked or is about to expire,
 566                  * send ACK now.
 567                  *
 568                  * FIXME: check the "about to expire" part
 569                  */
 570                 if (icsk->icsk_ack.blocked) {
 571                         dccp_send_ack(sk);
 572                         return;
 573                 }
 574
 575                 if (!time_before(timeout, icsk->icsk_ack.timeout))
 576                         timeout = icsk->icsk_ack.timeout;
 577         }
 578         icsk->icsk_ack.pending |= ICSK_ACK_SCHED | ICSK_ACK_TIMER;
 579         icsk->icsk_ack.timeout = timeout;
 580         sk_reset_timer(sk, &icsk->icsk_delack_timer, timeout);
 581 }
 582 #endif
 583
 584 void dccp_send_sync(struct sock *sk, const u64 ackno,
 585                     const enum dccp_pkt_type pkt_type)
 586 {
 587         /*
 588          * We are not putting this on the write queue, so
 589          * dccp_transmit_skb() will set the ownership to this
 590          * sock.
 591          */
 592         struct sk_buff *skb = alloc_skb(sk->sk_prot->max_header, GFP_ATOMIC);
 593
 594         if (skb == NULL) {
 595                 /* FIXME: how to make sure the sync is sent? */
 596                 DCCP_CRIT("could not send %s", dccp_packet_name(pkt_type));
 597                 return;
 598         }
 599
 600         /* Reserve space for headers and prepare control bits. */
 601         skb_reserve(skb, sk->sk_prot->max_header);
 602         DCCP_SKB_CB(skb)->dccpd_type = pkt_type;
 603         DCCP_SKB_CB(skb)->dccpd_ack_seq = ackno;
 604
 605         dccp_transmit_skb(sk, skb);
 606 }
 607
 608 EXPORT_SYMBOL_GPL(dccp_send_sync);
 609
 610 /*
 611  * Send a DCCP_PKT_CLOSE/CLOSEREQ. The caller locks the socket for us. This
 612  * cannot be allowed to fail queueing a DCCP_PKT_CLOSE/CLOSEREQ frame under
 613  * any circumstances.
 614  */
 615 void dccp_send_close(struct sock *sk, const int active)
 616 {
 617         struct dccp_sock *dp = dccp_sk(sk);
 618         struct sk_buff *skb;
 619         const gfp_t prio = active ? GFP_KERNEL : GFP_ATOMIC;
 620
 621         skb = alloc_skb(sk->sk_prot->max_header, prio);
 622         if (skb == NULL)
 623                 return;
 624
 625         /* Reserve space for headers and prepare control bits. */
 626         skb_reserve(skb, sk->sk_prot->max_header);
 627         if (dp->dccps_role == DCCP_ROLE_SERVER && !dp->dccps_server_timewait)
 628                 DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_CLOSEREQ;
 629         else
 630                 DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_CLOSE;
 631
 632         if (active) {
 633                 dccp_write_xmit(sk, 1);
 634                 dccp_skb_entail(sk, skb);
 635                 dccp_transmit_skb(sk, skb_clone(skb, prio));
 636                 /*
 637                  * Retransmission timer for active-close: RFC 4340, 8.3 requires
 638                  * to retransmit the Close/CloseReq until the CLOSING/CLOSEREQ
 639                  * state can be left. The initial timeout is 2 RTTs.
 640                  * Since RTT measurement is done by the CCIDs, there is no easy
 641                  * way to get an RTT sample. The fallback RTT from RFC 4340, 3.4
 642                  * is too low (200ms); we use a high value to avoid unnecessary
 643                  * retransmissions when the link RTT is > 0.2 seconds.
 644                  * FIXME: Let main module sample RTTs and use that instead.
 645                  */
 646                 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
 647                                           DCCP_TIMEOUT_INIT, DCCP_RTO_MAX);
 648         } else
 649                 dccp_transmit_skb(sk, skb);
 650 }