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   1 /*
   2  *  net/dccp/output.c
   3  *
   4  *  An implementation of the DCCP protocol
   5  *  Arnaldo Carvalho de Melo <acme@conectiva.com.br>
   6  *
   7  *      This program is free software; you can redistribute it and/or
   8  *      modify it under the terms of the GNU General Public License
   9  *      as published by the Free Software Foundation; either version
  10  *      2 of the License, or (at your option) any later version.
  11  */
  12
  13 #include <linux/dccp.h>
  14 #include <linux/kernel.h>
  15 #include <linux/skbuff.h>
  16
  17 #include <net/inet_sock.h>
  18 #include <net/sock.h>
  19
  20 #include "ackvec.h"
  21 #include "ccid.h"
  22 #include "dccp.h"
  23
  24 static inline void dccp_event_ack_sent(struct sock *sk)
  25 {
  26         inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK);
  27 }
  28
  29 static void dccp_skb_entail(struct sock *sk, struct sk_buff *skb)
  30 {
  31         skb_set_owner_w(skb, sk);
  32         WARN_ON(sk->sk_send_head);
  33         sk->sk_send_head = skb;
  34 }
  35
  36 /*
  37  * All SKB's seen here are completely headerless. It is our
  38  * job to build the DCCP header, and pass the packet down to
  39  * IP so it can do the same plus pass the packet off to the
  40  * device.
  41  */
  42 static int dccp_transmit_skb(struct sock *sk, struct sk_buff *skb)
  43 {
  44         if (likely(skb != NULL)) {
  45                 const struct inet_sock *inet = inet_sk(sk);
  46                 const struct inet_connection_sock *icsk = inet_csk(sk);
  47                 struct dccp_sock *dp = dccp_sk(sk);
  48                 struct dccp_skb_cb *dcb = DCCP_SKB_CB(skb);
  49                 struct dccp_hdr *dh;
  50                 /* XXX For now we're using only 48 bits sequence numbers */
  51                 const u32 dccp_header_size = sizeof(*dh) +
  52                                              sizeof(struct dccp_hdr_ext) +
  53                                           dccp_packet_hdr_len(dcb->dccpd_type);
  54                 int err, set_ack = 1;
  55                 u64 ackno = dp->dccps_gsr;
  56
  57                 dccp_inc_seqno(&dp->dccps_gss);
  58
  59                 switch (dcb->dccpd_type) {
  60                 case DCCP_PKT_DATA:
  61                         set_ack = 0;
  62                         /* fall through */
  63                 case DCCP_PKT_DATAACK:
  64                         break;
  65
  66                 case DCCP_PKT_REQUEST:
  67                         set_ack = 0;
  68                         /* fall through */
  69
  70                 case DCCP_PKT_SYNC:
  71                 case DCCP_PKT_SYNCACK:
  72                         ackno = dcb->dccpd_seq;
  73                         /* fall through */
  74                 default:
  75                         /*
  76                          * Only data packets should come through with skb->sk
  77                          * set.
  78                          */
  79                         WARN_ON(skb->sk);
  80                         skb_set_owner_w(skb, sk);
  81                         break;
  82                 }
  83
  84                 dcb->dccpd_seq = dp->dccps_gss;
  85
  86                 if (dccp_insert_options(sk, skb)) {
  87                         kfree_skb(skb);
  88                         return -EPROTO;
  89                 }
  90
  91
  92                 /* Build DCCP header and checksum it. */
  93                 dh = dccp_zeroed_hdr(skb, dccp_header_size);
  94                 dh->dccph_type  = dcb->dccpd_type;
  95                 dh->dccph_sport = inet->sport;
  96                 dh->dccph_dport = inet->dport;
  97                 dh->dccph_doff  = (dccp_header_size + dcb->dccpd_opt_len) / 4;
  98                 dh->dccph_ccval = dcb->dccpd_ccval;
  99                 dh->dccph_cscov = dp->dccps_pcslen;
 100                 /* XXX For now we're using only 48 bits sequence numbers */
 101                 dh->dccph_x     = 1;
 102
 103                 dp->dccps_awh = dp->dccps_gss;
 104                 dccp_hdr_set_seq(dh, dp->dccps_gss);
 105                 if (set_ack)
 106                         dccp_hdr_set_ack(dccp_hdr_ack_bits(skb), ackno);
 107
 108                 switch (dcb->dccpd_type) {
 109                 case DCCP_PKT_REQUEST:
 110                         dccp_hdr_request(skb)->dccph_req_service =
 111                                                         dp->dccps_service;
 112                         break;
 113                 case DCCP_PKT_RESET:
 114                         dccp_hdr_reset(skb)->dccph_reset_code =
 115                                                         dcb->dccpd_reset_code;
 116                         break;
 117                 }
 118
 119                 icsk->icsk_af_ops->send_check(sk, 0, skb);
 120
 121                 if (set_ack)
 122                         dccp_event_ack_sent(sk);
 123
 124                 DCCP_INC_STATS(DCCP_MIB_OUTSEGS);
 125
 126                 memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));
 127                 err = icsk->icsk_af_ops->queue_xmit(skb, 0);
 128                 return net_xmit_eval(err);
 129         }
 130         return -ENOBUFS;
 131 }
 132
 133 unsigned int dccp_sync_mss(struct sock *sk, u32 pmtu)
 134 {
 135         struct inet_connection_sock *icsk = inet_csk(sk);
 136         struct dccp_sock *dp = dccp_sk(sk);
 137         int mss_now = (pmtu - icsk->icsk_af_ops->net_header_len -
 138                        sizeof(struct dccp_hdr) - sizeof(struct dccp_hdr_ext));
 139
 140         /* Now subtract optional transport overhead */
 141         mss_now -= icsk->icsk_ext_hdr_len;
 142
 143         /*
 144          * FIXME: this should come from the CCID infrastructure, where, say,
 145          * TFRC will say it wants TIMESTAMPS, ELAPSED time, etc, for now lets
 146          * put a rough estimate for NDP + TIMESTAMP + TIMESTAMP_ECHO + ELAPSED
 147          * TIME + TFRC_OPT_LOSS_EVENT_RATE + TFRC_OPT_RECEIVE_RATE + padding to
 148          * make it a multiple of 4
 149          */
 150
 151         mss_now -= ((5 + 6 + 10 + 6 + 6 + 6 + 3) / 4) * 4;
 152
 153         /* And store cached results */
 154         icsk->icsk_pmtu_cookie = pmtu;
 155         dp->dccps_mss_cache = mss_now;
 156
 157         return mss_now;
 158 }
 159
 160 EXPORT_SYMBOL_GPL(dccp_sync_mss);
 161
 162 void dccp_write_space(struct sock *sk)
 163 {
 164         read_lock(&sk->sk_callback_lock);
 165
 166         if (sk->sk_sleep && waitqueue_active(sk->sk_sleep))
 167                 wake_up_interruptible(sk->sk_sleep);
 168         /* Should agree with poll, otherwise some programs break */
 169         if (sock_writeable(sk))
 170                 sk_wake_async(sk, 2, POLL_OUT);
 171
 172         read_unlock(&sk->sk_callback_lock);
 173 }
 174
 175 /**
 176  * dccp_wait_for_ccid - Wait for ccid to tell us we can send a packet
 177  * @sk: socket to wait for
 178  */
 179 static int dccp_wait_for_ccid(struct sock *sk, struct sk_buff *skb)
 180 {
 181         struct dccp_sock *dp = dccp_sk(sk);
 182         DEFINE_WAIT(wait);
 183         unsigned long delay;
 184         int rc;
 185
 186         while (1) {
 187                 prepare_to_wait(sk->sk_sleep, &wait, TASK_INTERRUPTIBLE);
 188
 189                 if (sk->sk_err)
 190                         goto do_error;
 191                 if (signal_pending(current))
 192                         goto do_interrupted;
 193
 194                 rc = ccid_hc_tx_send_packet(dp->dccps_hc_tx_ccid, sk, skb);
 195                 if (rc <= 0)
 196                         break;
 197                 delay = msecs_to_jiffies(rc);
 198                 sk->sk_write_pending++;
 199                 release_sock(sk);
 200                 schedule_timeout(delay);
 201                 lock_sock(sk);
 202                 sk->sk_write_pending--;
 203         }
 204 out:
 205         finish_wait(sk->sk_sleep, &wait);
 206         return rc;
 207
 208 do_error:
 209         rc = -EPIPE;
 210         goto out;
 211 do_interrupted:
 212         rc = -EINTR;
 213         goto out;
 214 }
 215
 216 void dccp_write_xmit(struct sock *sk, int block)
 217 {
 218         struct dccp_sock *dp = dccp_sk(sk);
 219         struct sk_buff *skb;
 220
 221         while ((skb = skb_peek(&sk->sk_write_queue))) {
 222                 int err = ccid_hc_tx_send_packet(dp->dccps_hc_tx_ccid, sk, skb);
 223
 224                 if (err > 0) {
 225                         if (!block) {
 226                                 sk_reset_timer(sk, &dp->dccps_xmit_timer,
 227                                                 msecs_to_jiffies(err)+jiffies);
 228                                 break;
 229                         } else
 230                                 err = dccp_wait_for_ccid(sk, skb);
 231                         if (err && err != -EINTR)
 232                                 DCCP_BUG("err=%d after dccp_wait_for_ccid", err);
 233                 }
 234
 235                 skb_dequeue(&sk->sk_write_queue);
 236                 if (err == 0) {
 237                         struct dccp_skb_cb *dcb = DCCP_SKB_CB(skb);
 238                         const int len = skb->len;
 239
 240                         if (sk->sk_state == DCCP_PARTOPEN) {
 241                                 /* See 8.1.5.  Handshake Completion */
 242                                 inet_csk_schedule_ack(sk);
 243                                 inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
 244                                                   inet_csk(sk)->icsk_rto,
 245                                                   DCCP_RTO_MAX);
 246                                 dcb->dccpd_type = DCCP_PKT_DATAACK;
 247                         } else if (dccp_ack_pending(sk))
 248                                 dcb->dccpd_type = DCCP_PKT_DATAACK;
 249                         else
 250                                 dcb->dccpd_type = DCCP_PKT_DATA;
 251
 252                         err = dccp_transmit_skb(sk, skb);
 253                         ccid_hc_tx_packet_sent(dp->dccps_hc_tx_ccid, sk, 0, len);
 254                         if (err)
 255                                 DCCP_BUG("err=%d after ccid_hc_tx_packet_sent",
 256                                          err);
 257                 } else {
 258                         dccp_pr_debug("packet discarded\n");
 259                         kfree_skb(skb);
 260                 }
 261         }
 262 }
 263
 264 int dccp_retransmit_skb(struct sock *sk, struct sk_buff *skb)
 265 {
 266         if (inet_csk(sk)->icsk_af_ops->rebuild_header(sk) != 0)
 267                 return -EHOSTUNREACH; /* Routing failure or similar. */
 268
 269         return dccp_transmit_skb(sk, (skb_cloned(skb) ?
 270                                       pskb_copy(skb, GFP_ATOMIC):
 271                                       skb_clone(skb, GFP_ATOMIC)));
 272 }
 273
 274 struct sk_buff *dccp_make_response(struct sock *sk, struct dst_entry *dst,
 275                                    struct request_sock *req)
 276 {
 277         struct dccp_hdr *dh;
 278         struct dccp_request_sock *dreq;
 279         const u32 dccp_header_size = sizeof(struct dccp_hdr) +
 280                                      sizeof(struct dccp_hdr_ext) +
 281                                      sizeof(struct dccp_hdr_response);
 282         struct sk_buff *skb = sock_wmalloc(sk, sk->sk_prot->max_header, 1,
 283                                            GFP_ATOMIC);
 284         if (skb == NULL)
 285                 return NULL;
 286
 287         /* Reserve space for headers. */
 288         skb_reserve(skb, sk->sk_prot->max_header);
 289
 290         skb->dst = dst_clone(dst);
 291
 292         dreq = dccp_rsk(req);
 293         if (inet_rsk(req)->acked)       /* increase ISS upon retransmission */
 294                 dccp_inc_seqno(&dreq->dreq_iss);
 295         DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_RESPONSE;
 296         DCCP_SKB_CB(skb)->dccpd_seq  = dreq->dreq_iss;
 297
 298         if (dccp_insert_options(sk, skb)) {
 299                 kfree_skb(skb);
 300                 return NULL;
 301         }
 302
 303         /* Build and checksum header */
 304         dh = dccp_zeroed_hdr(skb, dccp_header_size);
 305
 306         dh->dccph_sport = inet_sk(sk)->sport;
 307         dh->dccph_dport = inet_rsk(req)->rmt_port;
 308         dh->dccph_doff  = (dccp_header_size +
 309                            DCCP_SKB_CB(skb)->dccpd_opt_len) / 4;
 310         dh->dccph_type  = DCCP_PKT_RESPONSE;
 311         dh->dccph_x     = 1;
 312         dccp_hdr_set_seq(dh, dreq->dreq_iss);
 313         dccp_hdr_set_ack(dccp_hdr_ack_bits(skb), dreq->dreq_isr);
 314         dccp_hdr_response(skb)->dccph_resp_service = dreq->dreq_service;
 315
 316         dccp_csum_outgoing(skb);
 317
 318         /* We use `acked' to remember that a Response was already sent. */
 319         inet_rsk(req)->acked = 1;
 320         DCCP_INC_STATS(DCCP_MIB_OUTSEGS);
 321         return skb;
 322 }
 323
 324 EXPORT_SYMBOL_GPL(dccp_make_response);
 325
 326 static struct sk_buff *dccp_make_reset(struct sock *sk, struct dst_entry *dst,
 327                                        const enum dccp_reset_codes code)
 328 {
 329         struct dccp_hdr *dh;
 330         struct dccp_sock *dp = dccp_sk(sk);
 331         const u32 dccp_header_size = sizeof(struct dccp_hdr) +
 332                                      sizeof(struct dccp_hdr_ext) +
 333                                      sizeof(struct dccp_hdr_reset);
 334         struct sk_buff *skb = sock_wmalloc(sk, sk->sk_prot->max_header, 1,
 335                                            GFP_ATOMIC);
 336         if (skb == NULL)
 337                 return NULL;
 338
 339         /* Reserve space for headers. */
 340         skb_reserve(skb, sk->sk_prot->max_header);
 341
 342         skb->dst = dst_clone(dst);
 343
 344         dccp_inc_seqno(&dp->dccps_gss);
 345
 346         DCCP_SKB_CB(skb)->dccpd_reset_code = code;
 347         DCCP_SKB_CB(skb)->dccpd_type       = DCCP_PKT_RESET;
 348         DCCP_SKB_CB(skb)->dccpd_seq        = dp->dccps_gss;
 349
 350         if (dccp_insert_options(sk, skb)) {
 351                 kfree_skb(skb);
 352                 return NULL;
 353         }
 354
 355         dh = dccp_zeroed_hdr(skb, dccp_header_size);
 356
 357         dh->dccph_sport = inet_sk(sk)->sport;
 358         dh->dccph_dport = inet_sk(sk)->dport;
 359         dh->dccph_doff  = (dccp_header_size +
 360                            DCCP_SKB_CB(skb)->dccpd_opt_len) / 4;
 361         dh->dccph_type  = DCCP_PKT_RESET;
 362         dh->dccph_x     = 1;
 363         dccp_hdr_set_seq(dh, dp->dccps_gss);
 364         dccp_hdr_set_ack(dccp_hdr_ack_bits(skb), dp->dccps_gsr);
 365
 366         dccp_hdr_reset(skb)->dccph_reset_code = code;
 367         inet_csk(sk)->icsk_af_ops->send_check(sk, 0, skb);
 368
 369         DCCP_INC_STATS(DCCP_MIB_OUTSEGS);
 370         return skb;
 371 }
 372
 373 int dccp_send_reset(struct sock *sk, enum dccp_reset_codes code)
 374 {
 375         /*
 376          * FIXME: what if rebuild_header fails?
 377          * Should we be doing a rebuild_header here?
 378          */
 379         int err = inet_sk_rebuild_header(sk);
 380
 381         if (err == 0) {
 382                 struct sk_buff *skb = dccp_make_reset(sk, sk->sk_dst_cache,
 383                                                       code);
 384                 if (skb != NULL) {
 385                         memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));
 386                         err = inet_csk(sk)->icsk_af_ops->queue_xmit(skb, 0);
 387                         return net_xmit_eval(err);
 388                 }
 389         }
 390
 391         return err;
 392 }
 393
 394 /*
 395  * Do all connect socket setups that can be done AF independent.
 396  */
 397 static inline void dccp_connect_init(struct sock *sk)
 398 {
 399         struct dccp_sock *dp = dccp_sk(sk);
 400         struct dst_entry *dst = __sk_dst_get(sk);
 401         struct inet_connection_sock *icsk = inet_csk(sk);
 402
 403         sk->sk_err = 0;
 404         sock_reset_flag(sk, SOCK_DONE);
 405
 406         dccp_sync_mss(sk, dst_mtu(dst));
 407
 408         /*
 409          * SWL and AWL are initially adjusted so that they are not less than
 410          * the initial Sequence Numbers received and sent, respectively:
 411          *      SWL := max(GSR + 1 - floor(W/4), ISR),
 412          *      AWL := max(GSS - W' + 1, ISS).
 413          * These adjustments MUST be applied only at the beginning of the
 414          * connection.
 415          */
 416         dccp_update_gss(sk, dp->dccps_iss);
 417         dccp_set_seqno(&dp->dccps_awl, max48(dp->dccps_awl, dp->dccps_iss));
 418
 419         /* S.GAR - greatest valid acknowledgement number received on a non-Sync;
 420          *         initialized to S.ISS (sec. 8.5)                            */
 421         dp->dccps_gar = dp->dccps_iss;
 422
 423         icsk->icsk_retransmits = 0;
 424 }
 425
 426 int dccp_connect(struct sock *sk)
 427 {
 428         struct sk_buff *skb;
 429         struct inet_connection_sock *icsk = inet_csk(sk);
 430
 431         dccp_connect_init(sk);
 432
 433         skb = alloc_skb(sk->sk_prot->max_header, sk->sk_allocation);
 434         if (unlikely(skb == NULL))
 435                 return -ENOBUFS;
 436
 437         /* Reserve space for headers. */
 438         skb_reserve(skb, sk->sk_prot->max_header);
 439
 440         DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_REQUEST;
 441
 442         dccp_skb_entail(sk, skb);
 443         dccp_transmit_skb(sk, skb_clone(skb, GFP_KERNEL));
 444         DCCP_INC_STATS(DCCP_MIB_ACTIVEOPENS);
 445
 446         /* Timer for repeating the REQUEST until an answer. */
 447         inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
 448                                   icsk->icsk_rto, DCCP_RTO_MAX);
 449         return 0;
 450 }
 451
 452 EXPORT_SYMBOL_GPL(dccp_connect);
 453
 454 void dccp_send_ack(struct sock *sk)
 455 {
 456         /* If we have been reset, we may not send again. */
 457         if (sk->sk_state != DCCP_CLOSED) {
 458                 struct sk_buff *skb = alloc_skb(sk->sk_prot->max_header,
 459                                                 GFP_ATOMIC);
 460
 461                 if (skb == NULL) {
 462                         inet_csk_schedule_ack(sk);
 463                         inet_csk(sk)->icsk_ack.ato = TCP_ATO_MIN;
 464                         inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
 465                                                   TCP_DELACK_MAX,
 466                                                   DCCP_RTO_MAX);
 467                         return;
 468                 }
 469
 470                 /* Reserve space for headers */
 471                 skb_reserve(skb, sk->sk_prot->max_header);
 472                 DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_ACK;
 473                 dccp_transmit_skb(sk, skb);
 474         }
 475 }
 476
 477 EXPORT_SYMBOL_GPL(dccp_send_ack);
 478
 479 void dccp_send_delayed_ack(struct sock *sk)
 480 {
 481         struct inet_connection_sock *icsk = inet_csk(sk);
 482         /*
 483          * FIXME: tune this timer. elapsed time fixes the skew, so no problem
 484          * with using 2s, and active senders also piggyback the ACK into a
 485          * DATAACK packet, so this is really for quiescent senders.
 486          */
 487         unsigned long timeout = jiffies + 2 * HZ;
 488
 489         /* Use new timeout only if there wasn't a older one earlier. */
 490         if (icsk->icsk_ack.pending & ICSK_ACK_TIMER) {
 491                 /* If delack timer was blocked or is about to expire,
 492                  * send ACK now.
 493                  *
 494                  * FIXME: check the "about to expire" part
 495                  */
 496                 if (icsk->icsk_ack.blocked) {
 497                         dccp_send_ack(sk);
 498                         return;
 499                 }
 500
 501                 if (!time_before(timeout, icsk->icsk_ack.timeout))
 502                         timeout = icsk->icsk_ack.timeout;
 503         }
 504         icsk->icsk_ack.pending |= ICSK_ACK_SCHED | ICSK_ACK_TIMER;
 505         icsk->icsk_ack.timeout = timeout;
 506         sk_reset_timer(sk, &icsk->icsk_delack_timer, timeout);
 507 }
 508
 509 void dccp_send_sync(struct sock *sk, const u64 seq,
 510                     const enum dccp_pkt_type pkt_type)
 511 {
 512         /*
 513          * We are not putting this on the write queue, so
 514          * dccp_transmit_skb() will set the ownership to this
 515          * sock.
 516          */
 517         struct sk_buff *skb = alloc_skb(sk->sk_prot->max_header, GFP_ATOMIC);
 518
 519         if (skb == NULL)
 520                 /* FIXME: how to make sure the sync is sent? */
 521                 return;
 522
 523         /* Reserve space for headers and prepare control bits. */
 524         skb_reserve(skb, sk->sk_prot->max_header);
 525         DCCP_SKB_CB(skb)->dccpd_type = pkt_type;
 526         DCCP_SKB_CB(skb)->dccpd_seq = seq;
 527
 528         dccp_transmit_skb(sk, skb);
 529 }
 530
 531 EXPORT_SYMBOL_GPL(dccp_send_sync);
 532
 533 /*
 534  * Send a DCCP_PKT_CLOSE/CLOSEREQ. The caller locks the socket for us. This
 535  * cannot be allowed to fail queueing a DCCP_PKT_CLOSE/CLOSEREQ frame under
 536  * any circumstances.
 537  */
 538 void dccp_send_close(struct sock *sk, const int active)
 539 {
 540         struct dccp_sock *dp = dccp_sk(sk);
 541         struct sk_buff *skb;
 542         const gfp_t prio = active ? GFP_KERNEL : GFP_ATOMIC;
 543
 544         skb = alloc_skb(sk->sk_prot->max_header, prio);
 545         if (skb == NULL)
 546                 return;
 547
 548         /* Reserve space for headers and prepare control bits. */
 549         skb_reserve(skb, sk->sk_prot->max_header);
 550         DCCP_SKB_CB(skb)->dccpd_type = dp->dccps_role == DCCP_ROLE_CLIENT ?
 551                                         DCCP_PKT_CLOSE : DCCP_PKT_CLOSEREQ;
 552
 553         if (active) {
 554                 dccp_write_xmit(sk, 1);
 555                 dccp_skb_entail(sk, skb);
 556                 dccp_transmit_skb(sk, skb_clone(skb, prio));
 557                 /* FIXME do we need a retransmit timer here? */
 558         } else
 559                 dccp_transmit_skb(sk, skb);
 560 }