root/net/dccp/output.c

DEFINITIONS

1. dccp_event_ack_sent
2. dccp_skb_entail
3. dccp_transmit_skb
4. dccp_determine_ccmps
5. dccp_sync_mss
6. dccp_write_space
7. dccp_wait_for_ccid
8. dccp_xmit_packet
9. dccp_flush_write_queue
10. dccp_write_xmit
11. dccp_retransmit_skb
12. dccp_make_response
13. dccp_ctl_make_reset
14. dccp_send_reset
15. dccp_connect
16. dccp_send_ack
17. dccp_send_delayed_ack
18. dccp_send_sync
19. dccp_send_close

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