net/dccp/output.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  *  net/dccp/output.c
   4  *
   5  *  An implementation of the DCCP protocol
   6  *  Arnaldo Carvalho de Melo <acme@conectiva.com.br>
   7  */
   8
   9 #include <linux/dccp.h>
  10 #include <linux/kernel.h>
  11 #include <linux/skbuff.h>
  12 #include <linux/slab.h>
  13 #include <linux/sched/signal.h>
  14
  15 #include <net/inet_sock.h>
  16 #include <net/sock.h>
  17
  18 #include "ackvec.h"
  19 #include "ccid.h"
  20 #include "dccp.h"
  21
  22 static inline void dccp_event_ack_sent(struct sock *sk)
  23 {
  24         inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK);
  25 }
  26
  27 /* enqueue @skb on sk_send_head for retransmission, return clone to send now */
  28 static struct sk_buff *dccp_skb_entail(struct sock *sk, struct sk_buff *skb)
  29 {
  30         skb_set_owner_w(skb, sk);
  31         WARN_ON(sk->sk_send_head);
  32         sk->sk_send_head = skb;
  33         return skb_clone(sk->sk_send_head, gfp_any());
  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                 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                         fallthrough;
  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                         fallthrough;
  76
  77                 case DCCP_PKT_SYNC:
  78                 case DCCP_PKT_SYNCACK:
  79                         ackno = dcb->dccpd_ack_seq;
  80                         fallthrough;
  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->inet_sport;
 103                 dh->dccph_dport = inet->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, 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(sk, skb, &inet->cork.fl);
 139                 return net_xmit_eval(err);
 140         }
 141         return -ENOBUFS;
 142 }
 143
 144 /**
 145  * dccp_determine_ccmps  -  Find out about CCID-specific packet-size limits
 146  * @dp: socket to find packet size limits of
 147  *
 148  * We only consider the HC-sender CCID for setting the CCMPS (RFC 4340, 14.),
 149  * since the RX CCID is restricted to feedback packets (Acks), which are small
 150  * in comparison with the data traffic. A value of 0 means "no current CCMPS".
 151  */
 152 static u32 dccp_determine_ccmps(const struct dccp_sock *dp)
 153 {
 154         const struct ccid *tx_ccid = dp->dccps_hc_tx_ccid;
 155
 156         if (tx_ccid == NULL || tx_ccid->ccid_ops == NULL)
 157                 return 0;
 158         return tx_ccid->ccid_ops->ccid_ccmps;
 159 }
 160
 161 unsigned int dccp_sync_mss(struct sock *sk, u32 pmtu)
 162 {
 163         struct inet_connection_sock *icsk = inet_csk(sk);
 164         struct dccp_sock *dp = dccp_sk(sk);
 165         u32 ccmps = dccp_determine_ccmps(dp);
 166         u32 cur_mps = ccmps ? min(pmtu, ccmps) : pmtu;
 167
 168         /* Account for header lengths and IPv4/v6 option overhead */
 169         cur_mps -= (icsk->icsk_af_ops->net_header_len + icsk->icsk_ext_hdr_len +
 170                     sizeof(struct dccp_hdr) + sizeof(struct dccp_hdr_ext));
 171
 172         /*
 173          * Leave enough headroom for common DCCP header options.
 174          * This only considers options which may appear on DCCP-Data packets, as
 175          * per table 3 in RFC 4340, 5.8. When running out of space for other
 176          * options (eg. Ack Vector which can take up to 255 bytes), it is better
 177          * to schedule a separate Ack. Thus we leave headroom for the following:
 178          *  - 1 byte for Slow Receiver (11.6)
 179          *  - 6 bytes for Timestamp (13.1)
 180          *  - 10 bytes for Timestamp Echo (13.3)
 181          *  - 8 bytes for NDP count (7.7, when activated)
 182          *  - 6 bytes for Data Checksum (9.3)
 183          *  - %DCCPAV_MIN_OPTLEN bytes for Ack Vector size (11.4, when enabled)
 184          */
 185         cur_mps -= roundup(1 + 6 + 10 + dp->dccps_send_ndp_count * 8 + 6 +
 186                            (dp->dccps_hc_rx_ackvec ? DCCPAV_MIN_OPTLEN : 0), 4);
 187
 188         /* And store cached results */
 189         icsk->icsk_pmtu_cookie = pmtu;
 190         dp->dccps_mss_cache = cur_mps;
 191
 192         return cur_mps;
 193 }
 194
 195 EXPORT_SYMBOL_GPL(dccp_sync_mss);
 196
 197 void dccp_write_space(struct sock *sk)
 198 {
 199         struct socket_wq *wq;
 200
 201         rcu_read_lock();
 202         wq = rcu_dereference(sk->sk_wq);
 203         if (skwq_has_sleeper(wq))
 204                 wake_up_interruptible(&wq->wait);
 205         /* Should agree with poll, otherwise some programs break */
 206         if (sock_writeable(sk))
 207                 sk_wake_async(sk, SOCK_WAKE_SPACE, POLL_OUT);
 208
 209         rcu_read_unlock();
 210 }
 211
 212 /**
 213  * dccp_wait_for_ccid  -  Await CCID send permission
 214  * @sk:    socket to wait for
 215  * @delay: timeout in jiffies
 216  *
 217  * This is used by CCIDs which need to delay the send time in process context.
 218  */
 219 static int dccp_wait_for_ccid(struct sock *sk, unsigned long delay)
 220 {
 221         DEFINE_WAIT(wait);
 222         long remaining;
 223
 224         prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);
 225         sk->sk_write_pending++;
 226         release_sock(sk);
 227
 228         remaining = schedule_timeout(delay);
 229
 230         lock_sock(sk);
 231         sk->sk_write_pending--;
 232         finish_wait(sk_sleep(sk), &wait);
 233
 234         if (signal_pending(current) || sk->sk_err)
 235                 return -1;
 236         return remaining;
 237 }
 238
 239 /**
 240  * dccp_xmit_packet  -  Send data packet under control of CCID
 241  * @sk: socket to send data packet on
 242  *
 243  * Transmits next-queued payload and informs CCID to account for the packet.
 244  */
 245 static void dccp_xmit_packet(struct sock *sk)
 246 {
 247         int err, len;
 248         struct dccp_sock *dp = dccp_sk(sk);
 249         struct sk_buff *skb = dccp_qpolicy_pop(sk);
 250
 251         if (unlikely(skb == NULL))
 252                 return;
 253         len = skb->len;
 254
 255         if (sk->sk_state == DCCP_PARTOPEN) {
 256                 const u32 cur_mps = dp->dccps_mss_cache - DCCP_FEATNEG_OVERHEAD;
 257                 /*
 258                  * See 8.1.5 - Handshake Completion.
 259                  *
 260                  * For robustness we resend Confirm options until the client has
 261                  * entered OPEN. During the initial feature negotiation, the MPS
 262                  * is smaller than usual, reduced by the Change/Confirm options.
 263                  */
 264                 if (!list_empty(&dp->dccps_featneg) && len > cur_mps) {
 265                         DCCP_WARN("Payload too large (%d) for featneg.\n", len);
 266                         dccp_send_ack(sk);
 267                         dccp_feat_list_purge(&dp->dccps_featneg);
 268                 }
 269
 270                 inet_csk_schedule_ack(sk);
 271                 inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
 272                                               inet_csk(sk)->icsk_rto,
 273                                               DCCP_RTO_MAX);
 274                 DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_DATAACK;
 275         } else if (dccp_ack_pending(sk)) {
 276                 DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_DATAACK;
 277         } else {
 278                 DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_DATA;
 279         }
 280
 281         err = dccp_transmit_skb(sk, skb);
 282         if (err)
 283                 dccp_pr_debug("transmit_skb() returned err=%d\n", err);
 284         /*
 285          * Register this one as sent even if an error occurred. To the remote
 286          * end a local packet drop is indistinguishable from network loss, i.e.
 287          * any local drop will eventually be reported via receiver feedback.
 288          */
 289         ccid_hc_tx_packet_sent(dp->dccps_hc_tx_ccid, sk, len);
 290
 291         /*
 292          * If the CCID needs to transfer additional header options out-of-band
 293          * (e.g. Ack Vectors or feature-negotiation options), it activates this
 294          * flag to schedule a Sync. The Sync will automatically incorporate all
 295          * currently pending header options, thus clearing the backlog.
 296          */
 297         if (dp->dccps_sync_scheduled)
 298                 dccp_send_sync(sk, dp->dccps_gsr, DCCP_PKT_SYNC);
 299 }
 300
 301 /**
 302  * dccp_flush_write_queue  -  Drain queue at end of connection
 303  * @sk: socket to be drained
 304  * @time_budget: time allowed to drain the queue
 305  *
 306  * Since dccp_sendmsg queues packets without waiting for them to be sent, it may
 307  * happen that the TX queue is not empty at the end of a connection. We give the
 308  * HC-sender CCID a grace period of up to @time_budget jiffies. If this function
 309  * returns with a non-empty write queue, it will be purged later.
 310  */
 311 void dccp_flush_write_queue(struct sock *sk, long *time_budget)
 312 {
 313         struct dccp_sock *dp = dccp_sk(sk);
 314         struct sk_buff *skb;
 315         long delay, rc;
 316
 317         while (*time_budget > 0 && (skb = skb_peek(&sk->sk_write_queue))) {
 318                 rc = ccid_hc_tx_send_packet(dp->dccps_hc_tx_ccid, sk, skb);
 319
 320                 switch (ccid_packet_dequeue_eval(rc)) {
 321                 case CCID_PACKET_WILL_DEQUEUE_LATER:
 322                         /*
 323                          * If the CCID determines when to send, the next sending
 324                          * time is unknown or the CCID may not even send again
 325                          * (e.g. remote host crashes or lost Ack packets).
 326                          */
 327                         DCCP_WARN("CCID did not manage to send all packets\n");
 328                         return;
 329                 case CCID_PACKET_DELAY:
 330                         delay = msecs_to_jiffies(rc);
 331                         if (delay > *time_budget)
 332                                 return;
 333                         rc = dccp_wait_for_ccid(sk, delay);
 334                         if (rc < 0)
 335                                 return;
 336                         *time_budget -= (delay - rc);
 337                         /* check again if we can send now */
 338                         break;
 339                 case CCID_PACKET_SEND_AT_ONCE:
 340                         dccp_xmit_packet(sk);
 341                         break;
 342                 case CCID_PACKET_ERR:
 343                         skb_dequeue(&sk->sk_write_queue);
 344                         kfree_skb(skb);
 345                         dccp_pr_debug("packet discarded due to err=%ld\n", rc);
 346                 }
 347         }
 348 }
 349
 350 void dccp_write_xmit(struct sock *sk)
 351 {
 352         struct dccp_sock *dp = dccp_sk(sk);
 353         struct sk_buff *skb;
 354
 355         while ((skb = dccp_qpolicy_top(sk))) {
 356                 int rc = ccid_hc_tx_send_packet(dp->dccps_hc_tx_ccid, sk, skb);
 357
 358                 switch (ccid_packet_dequeue_eval(rc)) {
 359                 case CCID_PACKET_WILL_DEQUEUE_LATER:
 360                         return;
 361                 case CCID_PACKET_DELAY:
 362                         sk_reset_timer(sk, &dp->dccps_xmit_timer,
 363                                        jiffies + msecs_to_jiffies(rc));
 364                         return;
 365                 case CCID_PACKET_SEND_AT_ONCE:
 366                         dccp_xmit_packet(sk);
 367                         break;
 368                 case CCID_PACKET_ERR:
 369                         dccp_qpolicy_drop(sk, skb);
 370                         dccp_pr_debug("packet discarded due to err=%d\n", rc);
 371                 }
 372         }
 373 }
 374
 375 /**
 376  * dccp_retransmit_skb  -  Retransmit Request, Close, or CloseReq packets
 377  * @sk: socket to perform retransmit on
 378  *
 379  * There are only four retransmittable packet types in DCCP:
 380  * - Request  in client-REQUEST  state (sec. 8.1.1),
 381  * - CloseReq in server-CLOSEREQ state (sec. 8.3),
 382  * - Close    in   node-CLOSING  state (sec. 8.3),
 383  * - Acks in client-PARTOPEN state (sec. 8.1.5, handled by dccp_delack_timer()).
 384  * This function expects sk->sk_send_head to contain the original skb.
 385  */
 386 int dccp_retransmit_skb(struct sock *sk)
 387 {
 388         WARN_ON(sk->sk_send_head == NULL);
 389
 390         if (inet_csk(sk)->icsk_af_ops->rebuild_header(sk) != 0)
 391                 return -EHOSTUNREACH; /* Routing failure or similar. */
 392
 393         /* this count is used to distinguish original and retransmitted skb */
 394         inet_csk(sk)->icsk_retransmits++;
 395
 396         return dccp_transmit_skb(sk, skb_clone(sk->sk_send_head, GFP_ATOMIC));
 397 }
 398
 399 struct sk_buff *dccp_make_response(const struct sock *sk, struct dst_entry *dst,
 400                                    struct request_sock *req)
 401 {
 402         struct dccp_hdr *dh;
 403         struct dccp_request_sock *dreq;
 404         const u32 dccp_header_size = sizeof(struct dccp_hdr) +
 405                                      sizeof(struct dccp_hdr_ext) +
 406                                      sizeof(struct dccp_hdr_response);
 407         struct sk_buff *skb;
 408
 409         /* sk is marked const to clearly express we dont hold socket lock.
 410          * sock_wmalloc() will atomically change sk->sk_wmem_alloc,
 411          * it is safe to promote sk to non const.
 412          */
 413         skb = sock_wmalloc((struct sock *)sk, MAX_DCCP_HEADER, 1,
 414                            GFP_ATOMIC);
 415         if (!skb)
 416                 return NULL;
 417
 418         skb_reserve(skb, MAX_DCCP_HEADER);
 419
 420         skb_dst_set(skb, dst_clone(dst));
 421
 422         dreq = dccp_rsk(req);
 423         if (inet_rsk(req)->acked)       /* increase GSS upon retransmission */
 424                 dccp_inc_seqno(&dreq->dreq_gss);
 425         DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_RESPONSE;
 426         DCCP_SKB_CB(skb)->dccpd_seq  = dreq->dreq_gss;
 427
 428         /* Resolve feature dependencies resulting from choice of CCID */
 429         if (dccp_feat_server_ccid_dependencies(dreq))
 430                 goto response_failed;
 431
 432         if (dccp_insert_options_rsk(dreq, skb))
 433                 goto response_failed;
 434
 435         /* Build and checksum header */
 436         dh = dccp_zeroed_hdr(skb, dccp_header_size);
 437
 438         dh->dccph_sport = htons(inet_rsk(req)->ir_num);
 439         dh->dccph_dport = inet_rsk(req)->ir_rmt_port;
 440         dh->dccph_doff  = (dccp_header_size +
 441                            DCCP_SKB_CB(skb)->dccpd_opt_len) / 4;
 442         dh->dccph_type  = DCCP_PKT_RESPONSE;
 443         dh->dccph_x     = 1;
 444         dccp_hdr_set_seq(dh, dreq->dreq_gss);
 445         dccp_hdr_set_ack(dccp_hdr_ack_bits(skb), dreq->dreq_gsr);
 446         dccp_hdr_response(skb)->dccph_resp_service = dreq->dreq_service;
 447
 448         dccp_csum_outgoing(skb);
 449
 450         /* We use `acked' to remember that a Response was already sent. */
 451         inet_rsk(req)->acked = 1;
 452         DCCP_INC_STATS(DCCP_MIB_OUTSEGS);
 453         return skb;
 454 response_failed:
 455         kfree_skb(skb);
 456         return NULL;
 457 }
 458
 459 EXPORT_SYMBOL_GPL(dccp_make_response);
 460
 461 /* answer offending packet in @rcv_skb with Reset from control socket @ctl */
 462 struct sk_buff *dccp_ctl_make_reset(struct sock *sk, struct sk_buff *rcv_skb)
 463 {
 464         struct dccp_hdr *rxdh = dccp_hdr(rcv_skb), *dh;
 465         struct dccp_skb_cb *dcb = DCCP_SKB_CB(rcv_skb);
 466         const u32 dccp_hdr_reset_len = sizeof(struct dccp_hdr) +
 467                                        sizeof(struct dccp_hdr_ext) +
 468                                        sizeof(struct dccp_hdr_reset);
 469         struct dccp_hdr_reset *dhr;
 470         struct sk_buff *skb;
 471
 472         skb = alloc_skb(sk->sk_prot->max_header, GFP_ATOMIC);
 473         if (skb == NULL)
 474                 return NULL;
 475
 476         skb_reserve(skb, sk->sk_prot->max_header);
 477
 478         /* Swap the send and the receive. */
 479         dh = dccp_zeroed_hdr(skb, dccp_hdr_reset_len);
 480         dh->dccph_type  = DCCP_PKT_RESET;
 481         dh->dccph_sport = rxdh->dccph_dport;
 482         dh->dccph_dport = rxdh->dccph_sport;
 483         dh->dccph_doff  = dccp_hdr_reset_len / 4;
 484         dh->dccph_x     = 1;
 485
 486         dhr = dccp_hdr_reset(skb);
 487         dhr->dccph_reset_code = dcb->dccpd_reset_code;
 488
 489         switch (dcb->dccpd_reset_code) {
 490         case DCCP_RESET_CODE_PACKET_ERROR:
 491                 dhr->dccph_reset_data[0] = rxdh->dccph_type;
 492                 break;
 493         case DCCP_RESET_CODE_OPTION_ERROR:
 494         case DCCP_RESET_CODE_MANDATORY_ERROR:
 495                 memcpy(dhr->dccph_reset_data, dcb->dccpd_reset_data, 3);
 496                 break;
 497         }
 498         /*
 499          * From RFC 4340, 8.3.1:
 500          *   If P.ackno exists, set R.seqno := P.ackno + 1.
 501          *   Else set R.seqno := 0.
 502          */
 503         if (dcb->dccpd_ack_seq != DCCP_PKT_WITHOUT_ACK_SEQ)
 504                 dccp_hdr_set_seq(dh, ADD48(dcb->dccpd_ack_seq, 1));
 505         dccp_hdr_set_ack(dccp_hdr_ack_bits(skb), dcb->dccpd_seq);
 506
 507         dccp_csum_outgoing(skb);
 508         return skb;
 509 }
 510
 511 EXPORT_SYMBOL_GPL(dccp_ctl_make_reset);
 512
 513 /* send Reset on established socket, to close or abort the connection */
 514 int dccp_send_reset(struct sock *sk, enum dccp_reset_codes code)
 515 {
 516         struct sk_buff *skb;
 517         /*
 518          * FIXME: what if rebuild_header fails?
 519          * Should we be doing a rebuild_header here?
 520          */
 521         int err = inet_csk(sk)->icsk_af_ops->rebuild_header(sk);
 522
 523         if (err != 0)
 524                 return err;
 525
 526         skb = sock_wmalloc(sk, sk->sk_prot->max_header, 1, GFP_ATOMIC);
 527         if (skb == NULL)
 528                 return -ENOBUFS;
 529
 530         /* Reserve space for headers and prepare control bits. */
 531         skb_reserve(skb, sk->sk_prot->max_header);
 532         DCCP_SKB_CB(skb)->dccpd_type       = DCCP_PKT_RESET;
 533         DCCP_SKB_CB(skb)->dccpd_reset_code = code;
 534
 535         return dccp_transmit_skb(sk, skb);
 536 }
 537
 538 /*
 539  * Do all connect socket setups that can be done AF independent.
 540  */
 541 int dccp_connect(struct sock *sk)
 542 {
 543         struct sk_buff *skb;
 544         struct dccp_sock *dp = dccp_sk(sk);
 545         struct dst_entry *dst = __sk_dst_get(sk);
 546         struct inet_connection_sock *icsk = inet_csk(sk);
 547
 548         sk->sk_err = 0;
 549         sock_reset_flag(sk, SOCK_DONE);
 550
 551         dccp_sync_mss(sk, dst_mtu(dst));
 552
 553         /* do not connect if feature negotiation setup fails */
 554         if (dccp_feat_finalise_settings(dccp_sk(sk)))
 555                 return -EPROTO;
 556
 557         /* Initialise GAR as per 8.5; AWL/AWH are set in dccp_transmit_skb() */
 558         dp->dccps_gar = dp->dccps_iss;
 559
 560         skb = alloc_skb(sk->sk_prot->max_header, sk->sk_allocation);
 561         if (unlikely(skb == NULL))
 562                 return -ENOBUFS;
 563
 564         /* Reserve space for headers. */
 565         skb_reserve(skb, sk->sk_prot->max_header);
 566
 567         DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_REQUEST;
 568
 569         dccp_transmit_skb(sk, dccp_skb_entail(sk, skb));
 570         DCCP_INC_STATS(DCCP_MIB_ACTIVEOPENS);
 571
 572         /* Timer for repeating the REQUEST until an answer. */
 573         icsk->icsk_retransmits = 0;
 574         inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
 575                                   icsk->icsk_rto, DCCP_RTO_MAX);
 576         return 0;
 577 }
 578
 579 EXPORT_SYMBOL_GPL(dccp_connect);
 580
 581 void dccp_send_ack(struct sock *sk)
 582 {
 583         /* If we have been reset, we may not send again. */
 584         if (sk->sk_state != DCCP_CLOSED) {
 585                 struct sk_buff *skb = alloc_skb(sk->sk_prot->max_header,
 586                                                 GFP_ATOMIC);
 587
 588                 if (skb == NULL) {
 589                         inet_csk_schedule_ack(sk);
 590                         inet_csk(sk)->icsk_ack.ato = TCP_ATO_MIN;
 591                         inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
 592                                                   TCP_DELACK_MAX,
 593                                                   DCCP_RTO_MAX);
 594                         return;
 595                 }
 596
 597                 /* Reserve space for headers */
 598                 skb_reserve(skb, sk->sk_prot->max_header);
 599                 DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_ACK;
 600                 dccp_transmit_skb(sk, skb);
 601         }
 602 }
 603
 604 EXPORT_SYMBOL_GPL(dccp_send_ack);
 605
 606 #if 0
 607 /* FIXME: Is this still necessary (11.3) - currently nowhere used by DCCP. */
 608 void dccp_send_delayed_ack(struct sock *sk)
 609 {
 610         struct inet_connection_sock *icsk = inet_csk(sk);
 611         /*
 612          * FIXME: tune this timer. elapsed time fixes the skew, so no problem
 613          * with using 2s, and active senders also piggyback the ACK into a
 614          * DATAACK packet, so this is really for quiescent senders.
 615          */
 616         unsigned long timeout = jiffies + 2 * HZ;
 617
 618         /* Use new timeout only if there wasn't a older one earlier. */
 619         if (icsk->icsk_ack.pending & ICSK_ACK_TIMER) {
 620                 /* If delack timer was blocked or is about to expire,
 621                  * send ACK now.
 622                  *
 623                  * FIXME: check the "about to expire" part
 624                  */
 625                 if (icsk->icsk_ack.blocked) {
 626                         dccp_send_ack(sk);
 627                         return;
 628                 }
 629
 630                 if (!time_before(timeout, icsk->icsk_ack.timeout))
 631                         timeout = icsk->icsk_ack.timeout;
 632         }
 633         icsk->icsk_ack.pending |= ICSK_ACK_SCHED | ICSK_ACK_TIMER;
 634         icsk->icsk_ack.timeout = timeout;
 635         sk_reset_timer(sk, &icsk->icsk_delack_timer, timeout);
 636 }
 637 #endif
 638
 639 void dccp_send_sync(struct sock *sk, const u64 ackno,
 640                     const enum dccp_pkt_type pkt_type)
 641 {
 642         /*
 643          * We are not putting this on the write queue, so
 644          * dccp_transmit_skb() will set the ownership to this
 645          * sock.
 646          */
 647         struct sk_buff *skb = alloc_skb(sk->sk_prot->max_header, GFP_ATOMIC);
 648
 649         if (skb == NULL) {
 650                 /* FIXME: how to make sure the sync is sent? */
 651                 DCCP_CRIT("could not send %s", dccp_packet_name(pkt_type));
 652                 return;
 653         }
 654
 655         /* Reserve space for headers and prepare control bits. */
 656         skb_reserve(skb, sk->sk_prot->max_header);
 657         DCCP_SKB_CB(skb)->dccpd_type = pkt_type;
 658         DCCP_SKB_CB(skb)->dccpd_ack_seq = ackno;
 659
 660         /*
 661          * Clear the flag in case the Sync was scheduled for out-of-band data,
 662          * such as carrying a long Ack Vector.
 663          */
 664         dccp_sk(sk)->dccps_sync_scheduled = 0;
 665
 666         dccp_transmit_skb(sk, skb);
 667 }
 668
 669 EXPORT_SYMBOL_GPL(dccp_send_sync);
 670
 671 /*
 672  * Send a DCCP_PKT_CLOSE/CLOSEREQ. The caller locks the socket for us. This
 673  * cannot be allowed to fail queueing a DCCP_PKT_CLOSE/CLOSEREQ frame under
 674  * any circumstances.
 675  */
 676 void dccp_send_close(struct sock *sk, const int active)
 677 {
 678         struct dccp_sock *dp = dccp_sk(sk);
 679         struct sk_buff *skb;
 680         const gfp_t prio = active ? GFP_KERNEL : GFP_ATOMIC;
 681
 682         skb = alloc_skb(sk->sk_prot->max_header, prio);
 683         if (skb == NULL)
 684                 return;
 685
 686         /* Reserve space for headers and prepare control bits. */
 687         skb_reserve(skb, sk->sk_prot->max_header);
 688         if (dp->dccps_role == DCCP_ROLE_SERVER && !dp->dccps_server_timewait)
 689                 DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_CLOSEREQ;
 690         else
 691                 DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_CLOSE;
 692
 693         if (active) {
 694                 skb = dccp_skb_entail(sk, skb);
 695                 /*
 696                  * Retransmission timer for active-close: RFC 4340, 8.3 requires
 697                  * to retransmit the Close/CloseReq until the CLOSING/CLOSEREQ
 698                  * state can be left. The initial timeout is 2 RTTs.
 699                  * Since RTT measurement is done by the CCIDs, there is no easy
 700                  * way to get an RTT sample. The fallback RTT from RFC 4340, 3.4
 701                  * is too low (200ms); we use a high value to avoid unnecessary
 702                  * retransmissions when the link RTT is > 0.2 seconds.
 703                  * FIXME: Let main module sample RTTs and use that instead.
 704                  */
 705                 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
 706                                           DCCP_TIMEOUT_INIT, DCCP_RTO_MAX);
 707         }
 708         dccp_transmit_skb(sk, skb);
 709 }