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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/config.h>
  14 #include <linux/dccp.h>
  15 #include <linux/skbuff.h>
  16
  17 #include <net/sock.h>
  18
  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 /*
  28  * All SKB's seen here are completely headerless. It is our
  29  * job to build the DCCP header, and pass the packet down to
  30  * IP so it can do the same plus pass the packet off to the
  31  * device.
  32  */
  33 int dccp_transmit_skb(struct sock *sk, struct sk_buff *skb)
  34 {
  35         if (likely(skb != NULL)) {
  36                 const struct inet_sock *inet = inet_sk(sk);
  37                 struct dccp_sock *dp = dccp_sk(sk);
  38                 struct dccp_skb_cb *dcb = DCCP_SKB_CB(skb);
  39                 struct dccp_hdr *dh;
  40                 /* XXX For now we're using only 48 bits sequence numbers */
  41                 const int dccp_header_size = sizeof(*dh) +
  42                                              sizeof(struct dccp_hdr_ext) +
  43                                           dccp_packet_hdr_len(dcb->dccpd_type);
  44                 int err, set_ack = 1;
  45                 u64 ackno = dp->dccps_gsr;
  46
  47                 dccp_inc_seqno(&dp->dccps_gss);
  48
  49                 switch (dcb->dccpd_type) {
  50                 case DCCP_PKT_DATA:
  51                         set_ack = 0;
  52                         break;
  53                 case DCCP_PKT_SYNC:
  54                 case DCCP_PKT_SYNCACK:
  55                         ackno = dcb->dccpd_seq;
  56                         break;
  57                 }
  58
  59                 dcb->dccpd_seq = dp->dccps_gss;
  60                 dccp_insert_options(sk, skb);
  61
  62                 skb->h.raw = skb_push(skb, dccp_header_size);
  63                 dh = dccp_hdr(skb);
  64                 /*
  65                  * Data packets are not cloned as they are never retransmitted
  66                  */
  67                 if (skb_cloned(skb))
  68                         skb_set_owner_w(skb, sk);
  69
  70                 /* Build DCCP header and checksum it. */
  71                 memset(dh, 0, dccp_header_size);
  72                 dh->dccph_type  = dcb->dccpd_type;
  73                 dh->dccph_sport = inet->sport;
  74                 dh->dccph_dport = inet->dport;
  75                 dh->dccph_doff  = (dccp_header_size + dcb->dccpd_opt_len) / 4;
  76                 dh->dccph_ccval = dcb->dccpd_ccval;
  77                 /* XXX For now we're using only 48 bits sequence numbers */
  78                 dh->dccph_x     = 1;
  79
  80                 dp->dccps_awh = dp->dccps_gss;
  81                 dccp_hdr_set_seq(dh, dp->dccps_gss);
  82                 if (set_ack)
  83                         dccp_hdr_set_ack(dccp_hdr_ack_bits(skb), ackno);
  84
  85                 switch (dcb->dccpd_type) {
  86                 case DCCP_PKT_REQUEST:
  87                         dccp_hdr_request(skb)->dccph_req_service =
  88                                                         dp->dccps_service;
  89                         break;
  90                 case DCCP_PKT_RESET:
  91                         dccp_hdr_reset(skb)->dccph_reset_code =
  92                                                         dcb->dccpd_reset_code;
  93                         break;
  94                 }
  95
  96                 dh->dccph_checksum = dccp_v4_checksum(skb, inet->saddr,
  97                                                       inet->daddr);
  98
  99                 if (set_ack)
 100                         dccp_event_ack_sent(sk);
 101
 102                 DCCP_INC_STATS(DCCP_MIB_OUTSEGS);
 103
 104                 err = ip_queue_xmit(skb, 0);
 105                 if (err <= 0)
 106                         return err;
 107
 108                 /* NET_XMIT_CN is special. It does not guarantee,
 109                  * that this packet is lost. It tells that device
 110                  * is about to start to drop packets or already
 111                  * drops some packets of the same priority and
 112                  * invokes us to send less aggressively.
 113                  */
 114                 return err == NET_XMIT_CN ? 0 : err;
 115         }
 116         return -ENOBUFS;
 117 }
 118
 119 unsigned int dccp_sync_mss(struct sock *sk, u32 pmtu)
 120 {
 121         struct dccp_sock *dp = dccp_sk(sk);
 122         int mss_now;
 123
 124         /*
 125          * FIXME: we really should be using the af_specific thing to support
 126          *        IPv6.
 127          * mss_now = pmtu - tp->af_specific->net_header_len -
 128          *           sizeof(struct dccp_hdr) - sizeof(struct dccp_hdr_ext);
 129          */
 130         mss_now = pmtu - sizeof(struct iphdr) - sizeof(struct dccp_hdr) -
 131                   sizeof(struct dccp_hdr_ext);
 132
 133         /* Now subtract optional transport overhead */
 134         mss_now -= dp->dccps_ext_header_len;
 135
 136         /*
 137          * FIXME: this should come from the CCID infrastructure, where, say,
 138          * TFRC will say it wants TIMESTAMPS, ELAPSED time, etc, for now lets
 139          * put a rough estimate for NDP + TIMESTAMP + TIMESTAMP_ECHO + ELAPSED
 140          * TIME + TFRC_OPT_LOSS_EVENT_RATE + TFRC_OPT_RECEIVE_RATE + padding to
 141          * make it a multiple of 4
 142          */
 143
 144         mss_now -= ((5 + 6 + 10 + 6 + 6 + 6 + 3) / 4) * 4;
 145
 146         /* And store cached results */
 147         dp->dccps_pmtu_cookie = pmtu;
 148         dp->dccps_mss_cache = mss_now;
 149
 150         return mss_now;
 151 }
 152
 153 void dccp_write_space(struct sock *sk)
 154 {
 155         read_lock(&sk->sk_callback_lock);
 156
 157         if (sk->sk_sleep && waitqueue_active(sk->sk_sleep))
 158                 wake_up_interruptible(sk->sk_sleep);
 159         /* Should agree with poll, otherwise some programs break */
 160         if (sock_writeable(sk))
 161                 sk_wake_async(sk, 2, POLL_OUT);
 162
 163         read_unlock(&sk->sk_callback_lock);
 164 }
 165
 166 /**
 167  * dccp_wait_for_ccid - Wait for ccid to tell us we can send a packet
 168  * @sk: socket to wait for
 169  * @timeo: for how long
 170  */
 171 static int dccp_wait_for_ccid(struct sock *sk, struct sk_buff *skb,
 172                               long *timeo)
 173 {
 174         struct dccp_sock *dp = dccp_sk(sk);
 175         DEFINE_WAIT(wait);
 176         long delay;
 177         int rc;
 178
 179         while (1) {
 180                 prepare_to_wait(sk->sk_sleep, &wait, TASK_INTERRUPTIBLE);
 181
 182                 if (sk->sk_err || (sk->sk_shutdown & SEND_SHUTDOWN))
 183                         goto do_error;
 184                 if (!*timeo)
 185                         goto do_nonblock;
 186                 if (signal_pending(current))
 187                         goto do_interrupted;
 188
 189                 rc = ccid_hc_tx_send_packet(dp->dccps_hc_tx_ccid, sk, skb,
 190                                             skb->len);
 191                 if (rc <= 0)
 192                         break;
 193                 delay = msecs_to_jiffies(rc);
 194                 if (delay > *timeo || delay < 0)
 195                         goto do_nonblock;
 196
 197                 sk->sk_write_pending++;
 198                 release_sock(sk);
 199                 *timeo -= schedule_timeout(delay);
 200                 lock_sock(sk);
 201                 sk->sk_write_pending--;
 202         }
 203 out:
 204         finish_wait(sk->sk_sleep, &wait);
 205         return rc;
 206
 207 do_error:
 208         rc = -EPIPE;
 209         goto out;
 210 do_nonblock:
 211         rc = -EAGAIN;
 212         goto out;
 213 do_interrupted:
 214         rc = sock_intr_errno(*timeo);
 215         goto out;
 216 }
 217
 218 int dccp_write_xmit(struct sock *sk, struct sk_buff *skb, long *timeo)
 219 {
 220         const struct dccp_sock *dp = dccp_sk(sk);
 221         int err = ccid_hc_tx_send_packet(dp->dccps_hc_tx_ccid, sk, skb,
 222                                          skb->len);
 223
 224         if (err > 0)
 225                 err = dccp_wait_for_ccid(sk, skb, timeo);
 226
 227         if (err == 0) {
 228                 const struct dccp_ackpkts *ap = dp->dccps_hc_rx_ackpkts;
 229                 struct dccp_skb_cb *dcb = DCCP_SKB_CB(skb);
 230                 const int len = skb->len;
 231
 232                 if (sk->sk_state == DCCP_PARTOPEN) {
 233                         /* See 8.1.5.  Handshake Completion */
 234                         inet_csk_schedule_ack(sk);
 235                         inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
 236                                                   inet_csk(sk)->icsk_rto,
 237                                                   DCCP_RTO_MAX);
 238                         dcb->dccpd_type = DCCP_PKT_DATAACK;
 239                         /*
 240                          * FIXME: we really should have a
 241                          * dccps_ack_pending or use icsk.
 242                          */
 243                 } else if (inet_csk_ack_scheduled(sk) ||
 244                            dp->dccps_timestamp_echo != 0 ||
 245                            (dp->dccps_options.dccpo_send_ack_vector &&
 246                             ap->dccpap_buf_ackno != DCCP_MAX_SEQNO + 1 &&
 247                             ap->dccpap_ack_seqno == DCCP_MAX_SEQNO + 1))
 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         }
 255
 256         return err;
 257 }
 258
 259 int dccp_retransmit_skb(struct sock *sk, struct sk_buff *skb)
 260 {
 261         if (inet_sk_rebuild_header(sk) != 0)
 262                 return -EHOSTUNREACH; /* Routing failure or similar. */
 263
 264         return dccp_transmit_skb(sk, (skb_cloned(skb) ?
 265                                       pskb_copy(skb, GFP_ATOMIC):
 266                                       skb_clone(skb, GFP_ATOMIC)));
 267 }
 268
 269 struct sk_buff *dccp_make_response(struct sock *sk, struct dst_entry *dst,
 270                                    struct request_sock *req)
 271 {
 272         struct dccp_hdr *dh;
 273         struct dccp_request_sock *dreq;
 274         const int dccp_header_size = sizeof(struct dccp_hdr) +
 275                                      sizeof(struct dccp_hdr_ext) +
 276                                      sizeof(struct dccp_hdr_response);
 277         struct sk_buff *skb = sock_wmalloc(sk, MAX_HEADER + DCCP_MAX_OPT_LEN +
 278                                                dccp_header_size, 1,
 279                                            GFP_ATOMIC);
 280         if (skb == NULL)
 281                 return NULL;
 282
 283         /* Reserve space for headers. */
 284         skb_reserve(skb, MAX_HEADER + DCCP_MAX_OPT_LEN + dccp_header_size);
 285
 286         skb->dst = dst_clone(dst);
 287         skb->csum = 0;
 288
 289         dreq = dccp_rsk(req);
 290         DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_RESPONSE;
 291         DCCP_SKB_CB(skb)->dccpd_seq  = dreq->dreq_iss;
 292         dccp_insert_options(sk, skb);
 293
 294         skb->h.raw = skb_push(skb, dccp_header_size);
 295
 296         dh = dccp_hdr(skb);
 297         memset(dh, 0, dccp_header_size);
 298
 299         dh->dccph_sport = inet_sk(sk)->sport;
 300         dh->dccph_dport = inet_rsk(req)->rmt_port;
 301         dh->dccph_doff  = (dccp_header_size +
 302                            DCCP_SKB_CB(skb)->dccpd_opt_len) / 4;
 303         dh->dccph_type  = DCCP_PKT_RESPONSE;
 304         dh->dccph_x     = 1;
 305         dccp_hdr_set_seq(dh, dreq->dreq_iss);
 306         dccp_hdr_set_ack(dccp_hdr_ack_bits(skb), dreq->dreq_isr);
 307         dccp_hdr_response(skb)->dccph_resp_service = dreq->dreq_service;
 308
 309         dh->dccph_checksum = dccp_v4_checksum(skb, inet_rsk(req)->loc_addr,
 310                                               inet_rsk(req)->rmt_addr);
 311
 312         DCCP_INC_STATS(DCCP_MIB_OUTSEGS);
 313         return skb;
 314 }
 315
 316 struct sk_buff *dccp_make_reset(struct sock *sk, struct dst_entry *dst,
 317                                 const enum dccp_reset_codes code)
 318
 319 {
 320         struct dccp_hdr *dh;
 321         struct dccp_sock *dp = dccp_sk(sk);
 322         const int dccp_header_size = sizeof(struct dccp_hdr) +
 323                                      sizeof(struct dccp_hdr_ext) +
 324                                      sizeof(struct dccp_hdr_reset);
 325         struct sk_buff *skb = sock_wmalloc(sk, MAX_HEADER + DCCP_MAX_OPT_LEN +
 326                                                dccp_header_size, 1,
 327                                            GFP_ATOMIC);
 328         if (skb == NULL)
 329                 return NULL;
 330
 331         /* Reserve space for headers. */
 332         skb_reserve(skb, MAX_HEADER + DCCP_MAX_OPT_LEN + dccp_header_size);
 333
 334         skb->dst = dst_clone(dst);
 335         skb->csum = 0;
 336
 337         dccp_inc_seqno(&dp->dccps_gss);
 338
 339         DCCP_SKB_CB(skb)->dccpd_reset_code = code;
 340         DCCP_SKB_CB(skb)->dccpd_type       = DCCP_PKT_RESET;
 341         DCCP_SKB_CB(skb)->dccpd_seq        = dp->dccps_gss;
 342         dccp_insert_options(sk, skb);
 343
 344         skb->h.raw = skb_push(skb, dccp_header_size);
 345
 346         dh = dccp_hdr(skb);
 347         memset(dh, 0, dccp_header_size);
 348
 349         dh->dccph_sport = inet_sk(sk)->sport;
 350         dh->dccph_dport = inet_sk(sk)->dport;
 351         dh->dccph_doff  = (dccp_header_size +
 352                            DCCP_SKB_CB(skb)->dccpd_opt_len) / 4;
 353         dh->dccph_type  = DCCP_PKT_RESET;
 354         dh->dccph_x     = 1;
 355         dccp_hdr_set_seq(dh, dp->dccps_gss);
 356         dccp_hdr_set_ack(dccp_hdr_ack_bits(skb), dp->dccps_gsr);
 357
 358         dccp_hdr_reset(skb)->dccph_reset_code = code;
 359
 360         dh->dccph_checksum = dccp_v4_checksum(skb, inet_sk(sk)->saddr,
 361                                               inet_sk(sk)->daddr);
 362
 363         DCCP_INC_STATS(DCCP_MIB_OUTSEGS);
 364         return skb;
 365 }
 366
 367 /*
 368  * Do all connect socket setups that can be done AF independent.
 369  */
 370 static inline void dccp_connect_init(struct sock *sk)
 371 {
 372         struct dst_entry *dst = __sk_dst_get(sk);
 373         struct inet_connection_sock *icsk = inet_csk(sk);
 374
 375         sk->sk_err = 0;
 376         sock_reset_flag(sk, SOCK_DONE);
 377
 378         dccp_sync_mss(sk, dst_mtu(dst));
 379
 380         /*
 381          * FIXME: set dp->{dccps_swh,dccps_swl}, with
 382          * something like dccp_inc_seq
 383          */
 384
 385         icsk->icsk_retransmits = 0;
 386 }
 387
 388 int dccp_connect(struct sock *sk)
 389 {
 390         struct sk_buff *skb;
 391         struct inet_connection_sock *icsk = inet_csk(sk);
 392
 393         dccp_connect_init(sk);
 394
 395         skb = alloc_skb(MAX_DCCP_HEADER + 15, sk->sk_allocation);
 396         if (unlikely(skb == NULL))
 397                 return -ENOBUFS;
 398
 399         /* Reserve space for headers. */
 400         skb_reserve(skb, MAX_DCCP_HEADER);
 401
 402         DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_REQUEST;
 403         skb->csum = 0;
 404         skb_set_owner_w(skb, sk);
 405
 406         BUG_TRAP(sk->sk_send_head == NULL);
 407         sk->sk_send_head = skb;
 408         dccp_transmit_skb(sk, skb_clone(skb, GFP_KERNEL));
 409         DCCP_INC_STATS(DCCP_MIB_ACTIVEOPENS);
 410
 411         /* Timer for repeating the REQUEST until an answer. */
 412         inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
 413                                   icsk->icsk_rto, DCCP_RTO_MAX);
 414         return 0;
 415 }
 416
 417 void dccp_send_ack(struct sock *sk)
 418 {
 419         /* If we have been reset, we may not send again. */
 420         if (sk->sk_state != DCCP_CLOSED) {
 421                 struct sk_buff *skb = alloc_skb(MAX_DCCP_HEADER, GFP_ATOMIC);
 422
 423                 if (skb == NULL) {
 424                         inet_csk_schedule_ack(sk);
 425                         inet_csk(sk)->icsk_ack.ato = TCP_ATO_MIN;
 426                         inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
 427                                                   TCP_DELACK_MAX,
 428                                                   DCCP_RTO_MAX);
 429                         return;
 430                 }
 431
 432                 /* Reserve space for headers */
 433                 skb_reserve(skb, MAX_DCCP_HEADER);
 434                 skb->csum = 0;
 435                 DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_ACK;
 436                 skb_set_owner_w(skb, sk);
 437                 dccp_transmit_skb(sk, skb);
 438         }
 439 }
 440
 441 EXPORT_SYMBOL_GPL(dccp_send_ack);
 442
 443 void dccp_send_delayed_ack(struct sock *sk)
 444 {
 445         struct inet_connection_sock *icsk = inet_csk(sk);
 446         /*
 447          * FIXME: tune this timer. elapsed time fixes the skew, so no problem
 448          * with using 2s, and active senders also piggyback the ACK into a
 449          * DATAACK packet, so this is really for quiescent senders.
 450          */
 451         unsigned long timeout = jiffies + 2 * HZ;
 452
 453         /* Use new timeout only if there wasn't a older one earlier. */
 454         if (icsk->icsk_ack.pending & ICSK_ACK_TIMER) {
 455                 /* If delack timer was blocked or is about to expire,
 456                  * send ACK now.
 457                  *
 458                  * FIXME: check the "about to expire" part
 459                  */
 460                 if (icsk->icsk_ack.blocked) {
 461                         dccp_send_ack(sk);
 462                         return;
 463                 }
 464
 465                 if (!time_before(timeout, icsk->icsk_ack.timeout))
 466                         timeout = icsk->icsk_ack.timeout;
 467         }
 468         icsk->icsk_ack.pending |= ICSK_ACK_SCHED | ICSK_ACK_TIMER;
 469         icsk->icsk_ack.timeout = timeout;
 470         sk_reset_timer(sk, &icsk->icsk_delack_timer, timeout);
 471 }
 472
 473 void dccp_send_sync(struct sock *sk, const u64 seq,
 474                     const enum dccp_pkt_type pkt_type)
 475 {
 476         /*
 477          * We are not putting this on the write queue, so
 478          * dccp_transmit_skb() will set the ownership to this
 479          * sock.
 480          */
 481         struct sk_buff *skb = alloc_skb(MAX_DCCP_HEADER, GFP_ATOMIC);
 482
 483         if (skb == NULL)
 484                 /* FIXME: how to make sure the sync is sent? */
 485                 return;
 486
 487         /* Reserve space for headers and prepare control bits. */
 488         skb_reserve(skb, MAX_DCCP_HEADER);
 489         skb->csum = 0;
 490         DCCP_SKB_CB(skb)->dccpd_type = pkt_type;
 491         DCCP_SKB_CB(skb)->dccpd_seq = seq;
 492
 493         skb_set_owner_w(skb, sk);
 494         dccp_transmit_skb(sk, skb);
 495 }
 496
 497 /*
 498  * Send a DCCP_PKT_CLOSE/CLOSEREQ. The caller locks the socket for us. This
 499  * cannot be allowed to fail queueing a DCCP_PKT_CLOSE/CLOSEREQ frame under
 500  * any circumstances.
 501  */
 502 void dccp_send_close(struct sock *sk, const int active)
 503 {
 504         struct dccp_sock *dp = dccp_sk(sk);
 505         struct sk_buff *skb;
 506         const unsigned int prio = active ? GFP_KERNEL : GFP_ATOMIC;
 507
 508         skb = alloc_skb(sk->sk_prot->max_header, prio);
 509         if (skb == NULL)
 510                 return;
 511
 512         /* Reserve space for headers and prepare control bits. */
 513         skb_reserve(skb, sk->sk_prot->max_header);
 514         skb->csum = 0;
 515         DCCP_SKB_CB(skb)->dccpd_type = dp->dccps_role == DCCP_ROLE_CLIENT ?
 516                                         DCCP_PKT_CLOSE : DCCP_PKT_CLOSEREQ;
 517
 518         skb_set_owner_w(skb, sk);
 519         if (active) {
 520                 BUG_TRAP(sk->sk_send_head == NULL);
 521                 sk->sk_send_head = skb;
 522                 dccp_transmit_skb(sk, skb_clone(skb, prio));
 523         } else
 524                 dccp_transmit_skb(sk, skb);
 525 }