linux/net/dccp/output.c
<<
>>
Prefs
   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
  25static inline void dccp_event_ack_sent(struct sock *sk)
  26{
  27        inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK);
  28}
  29
  30/* enqueue @skb on sk_send_head for retransmission, return clone to send now */
  31static struct sk_buff *dccp_skb_entail(struct sock *sk, struct sk_buff *skb)
  32{
  33        skb_set_owner_w(skb, sk);
  34        WARN_ON(sk->sk_send_head);
  35        sk->sk_send_head = skb;
  36        return skb_clone(sk->sk_send_head, gfp_any());
  37}
  38
  39/*
  40 * All SKB's seen here are completely headerless. It is our
  41 * job to build the DCCP header, and pass the packet down to
  42 * IP so it can do the same plus pass the packet off to the
  43 * device.
  44 */
  45static int dccp_transmit_skb(struct sock *sk, struct sk_buff *skb)
  46{
  47        if (likely(skb != NULL)) {
  48                struct inet_sock *inet = inet_sk(sk);
  49                const struct inet_connection_sock *icsk = inet_csk(sk);
  50                struct dccp_sock *dp = dccp_sk(sk);
  51                struct dccp_skb_cb *dcb = DCCP_SKB_CB(skb);
  52                struct dccp_hdr *dh;
  53                /* XXX For now we're using only 48 bits sequence numbers */
  54                const u32 dccp_header_size = sizeof(*dh) +
  55                                             sizeof(struct dccp_hdr_ext) +
  56                                          dccp_packet_hdr_len(dcb->dccpd_type);
  57                int err, set_ack = 1;
  58                u64 ackno = dp->dccps_gsr;
  59                /*
  60                 * Increment GSS here already in case the option code needs it.
  61                 * Update GSS for real only if option processing below succeeds.
  62                 */
  63                dcb->dccpd_seq = ADD48(dp->dccps_gss, 1);
  64
  65                switch (dcb->dccpd_type) {
  66                case DCCP_PKT_DATA:
  67                        set_ack = 0;
  68                        /* fall through */
  69                case DCCP_PKT_DATAACK:
  70                case DCCP_PKT_RESET:
  71                        break;
  72
  73                case DCCP_PKT_REQUEST:
  74                        set_ack = 0;
  75                        /* Use ISS on the first (non-retransmitted) Request. */
  76                        if (icsk->icsk_retransmits == 0)
  77                                dcb->dccpd_seq = dp->dccps_iss;
  78                        /* fall through */
  79
  80                case DCCP_PKT_SYNC:
  81                case DCCP_PKT_SYNCACK:
  82                        ackno = dcb->dccpd_ack_seq;
  83                        /* fall through */
  84                default:
  85                        /*
  86                         * Set owner/destructor: some skbs are allocated via
  87                         * alloc_skb (e.g. when retransmission may happen).
  88                         * Only Data, DataAck, and Reset packets should come
  89                         * through here with skb->sk set.
  90                         */
  91                        WARN_ON(skb->sk);
  92                        skb_set_owner_w(skb, sk);
  93                        break;
  94                }
  95
  96                if (dccp_insert_options(sk, skb)) {
  97                        kfree_skb(skb);
  98                        return -EPROTO;
  99                }
 100
 101
 102                /* Build DCCP header and checksum it. */
 103                dh = dccp_zeroed_hdr(skb, dccp_header_size);
 104                dh->dccph_type  = dcb->dccpd_type;
 105                dh->dccph_sport = inet->inet_sport;
 106                dh->dccph_dport = inet->inet_dport;
 107                dh->dccph_doff  = (dccp_header_size + dcb->dccpd_opt_len) / 4;
 108                dh->dccph_ccval = dcb->dccpd_ccval;
 109                dh->dccph_cscov = dp->dccps_pcslen;
 110                /* XXX For now we're using only 48 bits sequence numbers */
 111                dh->dccph_x     = 1;
 112
 113                dccp_update_gss(sk, dcb->dccpd_seq);
 114                dccp_hdr_set_seq(dh, dp->dccps_gss);
 115                if (set_ack)
 116                        dccp_hdr_set_ack(dccp_hdr_ack_bits(skb), ackno);
 117
 118                switch (dcb->dccpd_type) {
 119                case DCCP_PKT_REQUEST:
 120                        dccp_hdr_request(skb)->dccph_req_service =
 121                                                        dp->dccps_service;
 122                        /*
 123                         * Limit Ack window to ISS <= P.ackno <= GSS, so that
 124                         * only Responses to Requests we sent are considered.
 125                         */
 126                        dp->dccps_awl = dp->dccps_iss;
 127                        break;
 128                case DCCP_PKT_RESET:
 129                        dccp_hdr_reset(skb)->dccph_reset_code =
 130                                                        dcb->dccpd_reset_code;
 131                        break;
 132                }
 133
 134                icsk->icsk_af_ops->send_check(sk, skb);
 135
 136                if (set_ack)
 137                        dccp_event_ack_sent(sk);
 138
 139                DCCP_INC_STATS(DCCP_MIB_OUTSEGS);
 140
 141                err = icsk->icsk_af_ops->queue_xmit(skb, &inet->cork.fl);
 142                return net_xmit_eval(err);
 143        }
 144        return -ENOBUFS;
 145}
 146
 147/**
 148 * dccp_determine_ccmps  -  Find out about CCID-specific packet-size limits
 149 * We only consider the HC-sender CCID for setting the CCMPS (RFC 4340, 14.),
 150 * since the RX CCID is restricted to feedback packets (Acks), which are small
 151 * in comparison with the data traffic. A value of 0 means "no current CCMPS".
 152 */
 153static u32 dccp_determine_ccmps(const struct dccp_sock *dp)
 154{
 155        const struct ccid *tx_ccid = dp->dccps_hc_tx_ccid;
 156
 157        if (tx_ccid == NULL || tx_ccid->ccid_ops == NULL)
 158                return 0;
 159        return tx_ccid->ccid_ops->ccid_ccmps;
 160}
 161
 162unsigned int dccp_sync_mss(struct sock *sk, u32 pmtu)
 163{
 164        struct inet_connection_sock *icsk = inet_csk(sk);
 165        struct dccp_sock *dp = dccp_sk(sk);
 166        u32 ccmps = dccp_determine_ccmps(dp);
 167        u32 cur_mps = ccmps ? min(pmtu, ccmps) : pmtu;
 168
 169        /* Account for header lengths and IPv4/v6 option overhead */
 170        cur_mps -= (icsk->icsk_af_ops->net_header_len + icsk->icsk_ext_hdr_len +
 171                    sizeof(struct dccp_hdr) + sizeof(struct dccp_hdr_ext));
 172
 173        /*
 174         * Leave enough headroom for common DCCP header options.
 175         * This only considers options which may appear on DCCP-Data packets, as
 176         * per table 3 in RFC 4340, 5.8. When running out of space for other
 177         * options (eg. Ack Vector which can take up to 255 bytes), it is better
 178         * to schedule a separate Ack. Thus we leave headroom for the following:
 179         *  - 1 byte for Slow Receiver (11.6)
 180         *  - 6 bytes for Timestamp (13.1)
 181         *  - 10 bytes for Timestamp Echo (13.3)
 182         *  - 8 bytes for NDP count (7.7, when activated)
 183         *  - 6 bytes for Data Checksum (9.3)
 184         *  - %DCCPAV_MIN_OPTLEN bytes for Ack Vector size (11.4, when enabled)
 185         */
 186        cur_mps -= roundup(1 + 6 + 10 + dp->dccps_send_ndp_count * 8 + 6 +
 187                           (dp->dccps_hc_rx_ackvec ? DCCPAV_MIN_OPTLEN : 0), 4);
 188
 189        /* And store cached results */
 190        icsk->icsk_pmtu_cookie = pmtu;
 191        dp->dccps_mss_cache = cur_mps;
 192
 193        return cur_mps;
 194}
 195
 196EXPORT_SYMBOL_GPL(dccp_sync_mss);
 197
 198void dccp_write_space(struct sock *sk)
 199{
 200        struct socket_wq *wq;
 201
 202        rcu_read_lock();
 203        wq = rcu_dereference(sk->sk_wq);
 204        if (wq_has_sleeper(wq))
 205                wake_up_interruptible(&wq->wait);
 206        /* Should agree with poll, otherwise some programs break */
 207        if (sock_writeable(sk))
 208                sk_wake_async(sk, SOCK_WAKE_SPACE, POLL_OUT);
 209
 210        rcu_read_unlock();
 211}
 212
 213/**
 214 * dccp_wait_for_ccid  -  Await CCID send permission
 215 * @sk:    socket to wait for
 216 * @delay: timeout in jiffies
 217 *
 218 * This is used by CCIDs which need to delay the send time in process context.
 219 */
 220static int dccp_wait_for_ccid(struct sock *sk, unsigned long delay)
 221{
 222        DEFINE_WAIT(wait);
 223        long remaining;
 224
 225        prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);
 226        sk->sk_write_pending++;
 227        release_sock(sk);
 228
 229        remaining = schedule_timeout(delay);
 230
 231        lock_sock(sk);
 232        sk->sk_write_pending--;
 233        finish_wait(sk_sleep(sk), &wait);
 234
 235        if (signal_pending(current) || sk->sk_err)
 236                return -1;
 237        return remaining;
 238}
 239
 240/**
 241 * dccp_xmit_packet  -  Send data packet under control of CCID
 242 * Transmits next-queued payload and informs CCID to account for the packet.
 243 */
 244static void dccp_xmit_packet(struct sock *sk)
 245{
 246        int err, len;
 247        struct dccp_sock *dp = dccp_sk(sk);
 248        struct sk_buff *skb = dccp_qpolicy_pop(sk);
 249
 250        if (unlikely(skb == NULL))
 251                return;
 252        len = skb->len;
 253
 254        if (sk->sk_state == DCCP_PARTOPEN) {
 255                const u32 cur_mps = dp->dccps_mss_cache - DCCP_FEATNEG_OVERHEAD;
 256                /*
 257                 * See 8.1.5 - Handshake Completion.
 258                 *
 259                 * For robustness we resend Confirm options until the client has
 260                 * entered OPEN. During the initial feature negotiation, the MPS
 261                 * is smaller than usual, reduced by the Change/Confirm options.
 262                 */
 263                if (!list_empty(&dp->dccps_featneg) && len > cur_mps) {
 264                        DCCP_WARN("Payload too large (%d) for featneg.\n", len);
 265                        dccp_send_ack(sk);
 266                        dccp_feat_list_purge(&dp->dccps_featneg);
 267                }
 268
 269                inet_csk_schedule_ack(sk);
 270                inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
 271                                              inet_csk(sk)->icsk_rto,
 272                                              DCCP_RTO_MAX);
 273                DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_DATAACK;
 274        } else if (dccp_ack_pending(sk)) {
 275                DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_DATAACK;
 276        } else {
 277                DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_DATA;
 278        }
 279
 280        err = dccp_transmit_skb(sk, skb);
 281        if (err)
 282                dccp_pr_debug("transmit_skb() returned err=%d\n", err);
 283        /*
 284         * Register this one as sent even if an error occurred. To the remote
 285         * end a local packet drop is indistinguishable from network loss, i.e.
 286         * any local drop will eventually be reported via receiver feedback.
 287         */
 288        ccid_hc_tx_packet_sent(dp->dccps_hc_tx_ccid, sk, len);
 289
 290        /*
 291         * If the CCID needs to transfer additional header options out-of-band
 292         * (e.g. Ack Vectors or feature-negotiation options), it activates this
 293         * flag to schedule a Sync. The Sync will automatically incorporate all
 294         * currently pending header options, thus clearing the backlog.
 295         */
 296        if (dp->dccps_sync_scheduled)
 297                dccp_send_sync(sk, dp->dccps_gsr, DCCP_PKT_SYNC);
 298}
 299
 300/**
 301 * dccp_flush_write_queue  -  Drain queue at end of connection
 302 * Since dccp_sendmsg queues packets without waiting for them to be sent, it may
 303 * happen that the TX queue is not empty at the end of a connection. We give the
 304 * HC-sender CCID a grace period of up to @time_budget jiffies. If this function
 305 * returns with a non-empty write queue, it will be purged later.
 306 */
 307void dccp_flush_write_queue(struct sock *sk, long *time_budget)
 308{
 309        struct dccp_sock *dp = dccp_sk(sk);
 310        struct sk_buff *skb;
 311        long delay, rc;
 312
 313        while (*time_budget > 0 && (skb = skb_peek(&sk->sk_write_queue))) {
 314                rc = ccid_hc_tx_send_packet(dp->dccps_hc_tx_ccid, sk, skb);
 315
 316                switch (ccid_packet_dequeue_eval(rc)) {
 317                case CCID_PACKET_WILL_DEQUEUE_LATER:
 318                        /*
 319                         * If the CCID determines when to send, the next sending
 320                         * time is unknown or the CCID may not even send again
 321                         * (e.g. remote host crashes or lost Ack packets).
 322                         */
 323                        DCCP_WARN("CCID did not manage to send all packets\n");
 324                        return;
 325                case CCID_PACKET_DELAY:
 326                        delay = msecs_to_jiffies(rc);
 327                        if (delay > *time_budget)
 328                                return;
 329                        rc = dccp_wait_for_ccid(sk, delay);
 330                        if (rc < 0)
 331                                return;
 332                        *time_budget -= (delay - rc);
 333                        /* check again if we can send now */
 334                        break;
 335                case CCID_PACKET_SEND_AT_ONCE:
 336                        dccp_xmit_packet(sk);
 337                        break;
 338                case CCID_PACKET_ERR:
 339                        skb_dequeue(&sk->sk_write_queue);
 340                        kfree_skb(skb);
 341                        dccp_pr_debug("packet discarded due to err=%ld\n", rc);
 342                }
 343        }
 344}
 345
 346void dccp_write_xmit(struct sock *sk)
 347{
 348        struct dccp_sock *dp = dccp_sk(sk);
 349        struct sk_buff *skb;
 350
 351        while ((skb = dccp_qpolicy_top(sk))) {
 352                int rc = ccid_hc_tx_send_packet(dp->dccps_hc_tx_ccid, sk, skb);
 353
 354                switch (ccid_packet_dequeue_eval(rc)) {
 355                case CCID_PACKET_WILL_DEQUEUE_LATER:
 356                        return;
 357                case CCID_PACKET_DELAY:
 358                        sk_reset_timer(sk, &dp->dccps_xmit_timer,
 359                                       jiffies + msecs_to_jiffies(rc));
 360                        return;
 361                case CCID_PACKET_SEND_AT_ONCE:
 362                        dccp_xmit_packet(sk);
 363                        break;
 364                case CCID_PACKET_ERR:
 365                        dccp_qpolicy_drop(sk, skb);
 366                        dccp_pr_debug("packet discarded due to err=%d\n", rc);
 367                }
 368        }
 369}
 370
 371/**
 372 * dccp_retransmit_skb  -  Retransmit Request, Close, or CloseReq packets
 373 * There are only four retransmittable packet types in DCCP:
 374 * - Request  in client-REQUEST  state (sec. 8.1.1),
 375 * - CloseReq in server-CLOSEREQ state (sec. 8.3),
 376 * - Close    in   node-CLOSING  state (sec. 8.3),
 377 * - Acks in client-PARTOPEN state (sec. 8.1.5, handled by dccp_delack_timer()).
 378 * This function expects sk->sk_send_head to contain the original skb.
 379 */
 380int dccp_retransmit_skb(struct sock *sk)
 381{
 382        WARN_ON(sk->sk_send_head == NULL);
 383
 384        if (inet_csk(sk)->icsk_af_ops->rebuild_header(sk) != 0)
 385                return -EHOSTUNREACH; /* Routing failure or similar. */
 386
 387        /* this count is used to distinguish original and retransmitted skb */
 388        inet_csk(sk)->icsk_retransmits++;
 389
 390        return dccp_transmit_skb(sk, skb_clone(sk->sk_send_head, GFP_ATOMIC));
 391}
 392
 393struct sk_buff *dccp_make_response(struct sock *sk, struct dst_entry *dst,
 394                                   struct request_sock *req)
 395{
 396        struct dccp_hdr *dh;
 397        struct dccp_request_sock *dreq;
 398        const u32 dccp_header_size = sizeof(struct dccp_hdr) +
 399                                     sizeof(struct dccp_hdr_ext) +
 400                                     sizeof(struct dccp_hdr_response);
 401        struct sk_buff *skb = sock_wmalloc(sk, sk->sk_prot->max_header, 1,
 402                                           GFP_ATOMIC);
 403        if (skb == NULL)
 404                return NULL;
 405
 406        /* Reserve space for headers. */
 407        skb_reserve(skb, sk->sk_prot->max_header);
 408
 409        skb_dst_set(skb, dst_clone(dst));
 410
 411        dreq = dccp_rsk(req);
 412        if (inet_rsk(req)->acked)       /* increase GSS upon retransmission */
 413                dccp_inc_seqno(&dreq->dreq_gss);
 414        DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_RESPONSE;
 415        DCCP_SKB_CB(skb)->dccpd_seq  = dreq->dreq_gss;
 416
 417        /* Resolve feature dependencies resulting from choice of CCID */
 418        if (dccp_feat_server_ccid_dependencies(dreq))
 419                goto response_failed;
 420
 421        if (dccp_insert_options_rsk(dreq, skb))
 422                goto response_failed;
 423
 424        /* Build and checksum header */
 425        dh = dccp_zeroed_hdr(skb, dccp_header_size);
 426
 427        dh->dccph_sport = inet_rsk(req)->loc_port;
 428        dh->dccph_dport = inet_rsk(req)->rmt_port;
 429        dh->dccph_doff  = (dccp_header_size +
 430                           DCCP_SKB_CB(skb)->dccpd_opt_len) / 4;
 431        dh->dccph_type  = DCCP_PKT_RESPONSE;
 432        dh->dccph_x     = 1;
 433        dccp_hdr_set_seq(dh, dreq->dreq_gss);
 434        dccp_hdr_set_ack(dccp_hdr_ack_bits(skb), dreq->dreq_gsr);
 435        dccp_hdr_response(skb)->dccph_resp_service = dreq->dreq_service;
 436
 437        dccp_csum_outgoing(skb);
 438
 439        /* We use `acked' to remember that a Response was already sent. */
 440        inet_rsk(req)->acked = 1;
 441        DCCP_INC_STATS(DCCP_MIB_OUTSEGS);
 442        return skb;
 443response_failed:
 444        kfree_skb(skb);
 445        return NULL;
 446}
 447
 448EXPORT_SYMBOL_GPL(dccp_make_response);
 449
 450/* answer offending packet in @rcv_skb with Reset from control socket @ctl */
 451struct sk_buff *dccp_ctl_make_reset(struct sock *sk, struct sk_buff *rcv_skb)
 452{
 453        struct dccp_hdr *rxdh = dccp_hdr(rcv_skb), *dh;
 454        struct dccp_skb_cb *dcb = DCCP_SKB_CB(rcv_skb);
 455        const u32 dccp_hdr_reset_len = sizeof(struct dccp_hdr) +
 456                                       sizeof(struct dccp_hdr_ext) +
 457                                       sizeof(struct dccp_hdr_reset);
 458        struct dccp_hdr_reset *dhr;
 459        struct sk_buff *skb;
 460
 461        skb = alloc_skb(sk->sk_prot->max_header, GFP_ATOMIC);
 462        if (skb == NULL)
 463                return NULL;
 464
 465        skb_reserve(skb, sk->sk_prot->max_header);
 466
 467        /* Swap the send and the receive. */
 468        dh = dccp_zeroed_hdr(skb, dccp_hdr_reset_len);
 469        dh->dccph_type  = DCCP_PKT_RESET;
 470        dh->dccph_sport = rxdh->dccph_dport;
 471        dh->dccph_dport = rxdh->dccph_sport;
 472        dh->dccph_doff  = dccp_hdr_reset_len / 4;
 473        dh->dccph_x     = 1;
 474
 475        dhr = dccp_hdr_reset(skb);
 476        dhr->dccph_reset_code = dcb->dccpd_reset_code;
 477
 478        switch (dcb->dccpd_reset_code) {
 479        case DCCP_RESET_CODE_PACKET_ERROR:
 480                dhr->dccph_reset_data[0] = rxdh->dccph_type;
 481                break;
 482        case DCCP_RESET_CODE_OPTION_ERROR:      /* fall through */
 483        case DCCP_RESET_CODE_MANDATORY_ERROR:
 484                memcpy(dhr->dccph_reset_data, dcb->dccpd_reset_data, 3);
 485                break;
 486        }
 487        /*
 488         * From RFC 4340, 8.3.1:
 489         *   If P.ackno exists, set R.seqno := P.ackno + 1.
 490         *   Else set R.seqno := 0.
 491         */
 492        if (dcb->dccpd_ack_seq != DCCP_PKT_WITHOUT_ACK_SEQ)
 493                dccp_hdr_set_seq(dh, ADD48(dcb->dccpd_ack_seq, 1));
 494        dccp_hdr_set_ack(dccp_hdr_ack_bits(skb), dcb->dccpd_seq);
 495
 496        dccp_csum_outgoing(skb);
 497        return skb;
 498}
 499
 500EXPORT_SYMBOL_GPL(dccp_ctl_make_reset);
 501
 502/* send Reset on established socket, to close or abort the connection */
 503int dccp_send_reset(struct sock *sk, enum dccp_reset_codes code)
 504{
 505        struct sk_buff *skb;
 506        /*
 507         * FIXME: what if rebuild_header fails?
 508         * Should we be doing a rebuild_header here?
 509         */
 510        int err = inet_csk(sk)->icsk_af_ops->rebuild_header(sk);
 511
 512        if (err != 0)
 513                return err;
 514
 515        skb = sock_wmalloc(sk, sk->sk_prot->max_header, 1, GFP_ATOMIC);
 516        if (skb == NULL)
 517                return -ENOBUFS;
 518
 519        /* Reserve space for headers and prepare control bits. */
 520        skb_reserve(skb, sk->sk_prot->max_header);
 521        DCCP_SKB_CB(skb)->dccpd_type       = DCCP_PKT_RESET;
 522        DCCP_SKB_CB(skb)->dccpd_reset_code = code;
 523
 524        return dccp_transmit_skb(sk, skb);
 525}
 526
 527/*
 528 * Do all connect socket setups that can be done AF independent.
 529 */
 530int dccp_connect(struct sock *sk)
 531{
 532        struct sk_buff *skb;
 533        struct dccp_sock *dp = dccp_sk(sk);
 534        struct dst_entry *dst = __sk_dst_get(sk);
 535        struct inet_connection_sock *icsk = inet_csk(sk);
 536
 537        sk->sk_err = 0;
 538        sock_reset_flag(sk, SOCK_DONE);
 539
 540        dccp_sync_mss(sk, dst_mtu(dst));
 541
 542        /* do not connect if feature negotiation setup fails */
 543        if (dccp_feat_finalise_settings(dccp_sk(sk)))
 544                return -EPROTO;
 545
 546        /* Initialise GAR as per 8.5; AWL/AWH are set in dccp_transmit_skb() */
 547        dp->dccps_gar = dp->dccps_iss;
 548
 549        skb = alloc_skb(sk->sk_prot->max_header, sk->sk_allocation);
 550        if (unlikely(skb == NULL))
 551                return -ENOBUFS;
 552
 553        /* Reserve space for headers. */
 554        skb_reserve(skb, sk->sk_prot->max_header);
 555
 556        DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_REQUEST;
 557
 558        dccp_transmit_skb(sk, dccp_skb_entail(sk, skb));
 559        DCCP_INC_STATS(DCCP_MIB_ACTIVEOPENS);
 560
 561        /* Timer for repeating the REQUEST until an answer. */
 562        icsk->icsk_retransmits = 0;
 563        inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
 564                                  icsk->icsk_rto, DCCP_RTO_MAX);
 565        return 0;
 566}
 567
 568EXPORT_SYMBOL_GPL(dccp_connect);
 569
 570void dccp_send_ack(struct sock *sk)
 571{
 572        /* If we have been reset, we may not send again. */
 573        if (sk->sk_state != DCCP_CLOSED) {
 574                struct sk_buff *skb = alloc_skb(sk->sk_prot->max_header,
 575                                                GFP_ATOMIC);
 576
 577                if (skb == NULL) {
 578                        inet_csk_schedule_ack(sk);
 579                        inet_csk(sk)->icsk_ack.ato = TCP_ATO_MIN;
 580                        inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
 581                                                  TCP_DELACK_MAX,
 582                                                  DCCP_RTO_MAX);
 583                        return;
 584                }
 585
 586                /* Reserve space for headers */
 587                skb_reserve(skb, sk->sk_prot->max_header);
 588                DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_ACK;
 589                dccp_transmit_skb(sk, skb);
 590        }
 591}
 592
 593EXPORT_SYMBOL_GPL(dccp_send_ack);
 594
 595#if 0
 596/* FIXME: Is this still necessary (11.3) - currently nowhere used by DCCP. */
 597void dccp_send_delayed_ack(struct sock *sk)
 598{
 599        struct inet_connection_sock *icsk = inet_csk(sk);
 600        /*
 601         * FIXME: tune this timer. elapsed time fixes the skew, so no problem
 602         * with using 2s, and active senders also piggyback the ACK into a
 603         * DATAACK packet, so this is really for quiescent senders.
 604         */
 605        unsigned long timeout = jiffies + 2 * HZ;
 606
 607        /* Use new timeout only if there wasn't a older one earlier. */
 608        if (icsk->icsk_ack.pending & ICSK_ACK_TIMER) {
 609                /* If delack timer was blocked or is about to expire,
 610                 * send ACK now.
 611                 *
 612                 * FIXME: check the "about to expire" part
 613                 */
 614                if (icsk->icsk_ack.blocked) {
 615                        dccp_send_ack(sk);
 616                        return;
 617                }
 618
 619                if (!time_before(timeout, icsk->icsk_ack.timeout))
 620                        timeout = icsk->icsk_ack.timeout;
 621        }
 622        icsk->icsk_ack.pending |= ICSK_ACK_SCHED | ICSK_ACK_TIMER;
 623        icsk->icsk_ack.timeout = timeout;
 624        sk_reset_timer(sk, &icsk->icsk_delack_timer, timeout);
 625}
 626#endif
 627
 628void dccp_send_sync(struct sock *sk, const u64 ackno,
 629                    const enum dccp_pkt_type pkt_type)
 630{
 631        /*
 632         * We are not putting this on the write queue, so
 633         * dccp_transmit_skb() will set the ownership to this
 634         * sock.
 635         */
 636        struct sk_buff *skb = alloc_skb(sk->sk_prot->max_header, GFP_ATOMIC);
 637
 638        if (skb == NULL) {
 639                /* FIXME: how to make sure the sync is sent? */
 640                DCCP_CRIT("could not send %s", dccp_packet_name(pkt_type));
 641                return;
 642        }
 643
 644        /* Reserve space for headers and prepare control bits. */
 645        skb_reserve(skb, sk->sk_prot->max_header);
 646        DCCP_SKB_CB(skb)->dccpd_type = pkt_type;
 647        DCCP_SKB_CB(skb)->dccpd_ack_seq = ackno;
 648
 649        /*
 650         * Clear the flag in case the Sync was scheduled for out-of-band data,
 651         * such as carrying a long Ack Vector.
 652         */
 653        dccp_sk(sk)->dccps_sync_scheduled = 0;
 654
 655        dccp_transmit_skb(sk, skb);
 656}
 657
 658EXPORT_SYMBOL_GPL(dccp_send_sync);
 659
 660/*
 661 * Send a DCCP_PKT_CLOSE/CLOSEREQ. The caller locks the socket for us. This
 662 * cannot be allowed to fail queueing a DCCP_PKT_CLOSE/CLOSEREQ frame under
 663 * any circumstances.
 664 */
 665void dccp_send_close(struct sock *sk, const int active)
 666{
 667        struct dccp_sock *dp = dccp_sk(sk);
 668        struct sk_buff *skb;
 669        const gfp_t prio = active ? GFP_KERNEL : GFP_ATOMIC;
 670
 671        skb = alloc_skb(sk->sk_prot->max_header, prio);
 672        if (skb == NULL)
 673                return;
 674
 675        /* Reserve space for headers and prepare control bits. */
 676        skb_reserve(skb, sk->sk_prot->max_header);
 677        if (dp->dccps_role == DCCP_ROLE_SERVER && !dp->dccps_server_timewait)
 678                DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_CLOSEREQ;
 679        else
 680                DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_CLOSE;
 681
 682        if (active) {
 683                skb = dccp_skb_entail(sk, skb);
 684                /*
 685                 * Retransmission timer for active-close: RFC 4340, 8.3 requires
 686                 * to retransmit the Close/CloseReq until the CLOSING/CLOSEREQ
 687                 * state can be left. The initial timeout is 2 RTTs.
 688                 * Since RTT measurement is done by the CCIDs, there is no easy
 689                 * way to get an RTT sample. The fallback RTT from RFC 4340, 3.4
 690                 * is too low (200ms); we use a high value to avoid unnecessary
 691                 * retransmissions when the link RTT is > 0.2 seconds.
 692                 * FIXME: Let main module sample RTTs and use that instead.
 693                 */
 694                inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
 695                                          DCCP_TIMEOUT_INIT, DCCP_RTO_MAX);
 696        }
 697        dccp_transmit_skb(sk, skb);
 698}
 699
lxr.linux.no kindly hosted by Redpill Linpro AS, provider of Linux consulting and operations services since 1995.