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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 "ackvec.h"
  20 #include "ccid.h"
  21 #include "dccp.h"
  22
  23 static inline void dccp_event_ack_sent(struct sock *sk)
  24 {
  25         inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK);
  26 }
  27
  28 /*
  29  * All SKB's seen here are completely headerless. It is our
  30  * job to build the DCCP header, and pass the packet down to
  31  * IP so it can do the same plus pass the packet off to the
  32  * device.
  33  */
  34 int dccp_transmit_skb(struct sock *sk, struct sk_buff *skb)
  35 {
  36         if (likely(skb != NULL)) {
  37                 const struct inet_sock *inet = inet_sk(sk);
  38                 struct dccp_sock *dp = dccp_sk(sk);
  39                 struct dccp_skb_cb *dcb = DCCP_SKB_CB(skb);
  40                 struct dccp_hdr *dh;
  41                 /* XXX For now we're using only 48 bits sequence numbers */
  42                 const int dccp_header_size = sizeof(*dh) +
  43                                              sizeof(struct dccp_hdr_ext) +
  44                                           dccp_packet_hdr_len(dcb->dccpd_type);
  45                 int err, set_ack = 1;
  46                 u64 ackno = dp->dccps_gsr;
  47
  48                 dccp_inc_seqno(&dp->dccps_gss);
  49
  50                 switch (dcb->dccpd_type) {
  51                 case DCCP_PKT_DATA:
  52                         set_ack = 0;
  53                         break;
  54                 case DCCP_PKT_SYNC:
  55                 case DCCP_PKT_SYNCACK:
  56                         ackno = dcb->dccpd_seq;
  57                         break;
  58                 }
  59
  60                 dcb->dccpd_seq = dp->dccps_gss;
  61                 dccp_insert_options(sk, skb);
  62
  63                 skb->h.raw = skb_push(skb, dccp_header_size);
  64                 dh = dccp_hdr(skb);
  65                 /*
  66                  * Data packets are not cloned as they are never retransmitted
  67                  */
  68                 if (skb_cloned(skb))
  69                         skb_set_owner_w(skb, sk);
  70
  71                 /* Build DCCP header and checksum it. */
  72                 memset(dh, 0, dccp_header_size);
  73                 dh->dccph_type  = dcb->dccpd_type;
  74                 dh->dccph_sport = inet->sport;
  75                 dh->dccph_dport = inet->dport;
  76                 dh->dccph_doff  = (dccp_header_size + dcb->dccpd_opt_len) / 4;
  77                 dh->dccph_ccval = dcb->dccpd_ccval;
  78                 /* XXX For now we're using only 48 bits sequence numbers */
  79                 dh->dccph_x     = 1;
  80
  81                 dp->dccps_awh = dp->dccps_gss;
  82                 dccp_hdr_set_seq(dh, dp->dccps_gss);
  83                 if (set_ack)
  84                         dccp_hdr_set_ack(dccp_hdr_ack_bits(skb), ackno);
  85
  86                 switch (dcb->dccpd_type) {
  87                 case DCCP_PKT_REQUEST:
  88                         dccp_hdr_request(skb)->dccph_req_service =
  89                                                         dp->dccps_service;
  90                         break;
  91                 case DCCP_PKT_RESET:
  92                         dccp_hdr_reset(skb)->dccph_reset_code =
  93                                                         dcb->dccpd_reset_code;
  94                         break;
  95                 }
  96
  97                 dh->dccph_checksum = dccp_v4_checksum(skb, inet->saddr,
  98                                                       inet->daddr);
  99
 100                 if (set_ack)
 101                         dccp_event_ack_sent(sk);
 102
 103                 DCCP_INC_STATS(DCCP_MIB_OUTSEGS);
 104
 105                 err = ip_queue_xmit(skb, 0);
 106                 if (err <= 0)
 107                         return err;
 108
 109                 /* NET_XMIT_CN is special. It does not guarantee,
 110                  * that this packet is lost. It tells that device
 111                  * is about to start to drop packets or already
 112                  * drops some packets of the same priority and
 113                  * invokes us to send less aggressively.
 114                  */
 115                 return err == NET_XMIT_CN ? 0 : err;
 116         }
 117         return -ENOBUFS;
 118 }
 119
 120 unsigned int dccp_sync_mss(struct sock *sk, u32 pmtu)
 121 {
 122         struct dccp_sock *dp = dccp_sk(sk);
 123         int mss_now;
 124
 125         /*
 126          * FIXME: we really should be using the af_specific thing to support
 127          *        IPv6.
 128          * mss_now = pmtu - tp->af_specific->net_header_len -
 129          *           sizeof(struct dccp_hdr) - sizeof(struct dccp_hdr_ext);
 130          */
 131         mss_now = pmtu - sizeof(struct iphdr) - sizeof(struct dccp_hdr) -
 132                   sizeof(struct dccp_hdr_ext);
 133
 134         /* Now subtract optional transport overhead */
 135         mss_now -= dp->dccps_ext_header_len;
 136
 137         /*
 138          * FIXME: this should come from the CCID infrastructure, where, say,
 139          * TFRC will say it wants TIMESTAMPS, ELAPSED time, etc, for now lets
 140          * put a rough estimate for NDP + TIMESTAMP + TIMESTAMP_ECHO + ELAPSED
 141          * TIME + TFRC_OPT_LOSS_EVENT_RATE + TFRC_OPT_RECEIVE_RATE + padding to
 142          * make it a multiple of 4
 143          */
 144
 145         mss_now -= ((5 + 6 + 10 + 6 + 6 + 6 + 3) / 4) * 4;
 146
 147         /* And store cached results */
 148         dp->dccps_pmtu_cookie = pmtu;
 149         dp->dccps_mss_cache = mss_now;
 150
 151         return mss_now;
 152 }
 153
 154 void dccp_write_space(struct sock *sk)
 155 {
 156         read_lock(&sk->sk_callback_lock);
 157
 158         if (sk->sk_sleep && waitqueue_active(sk->sk_sleep))
 159                 wake_up_interruptible(sk->sk_sleep);
 160         /* Should agree with poll, otherwise some programs break */
 161         if (sock_writeable(sk))
 162                 sk_wake_async(sk, 2, POLL_OUT);
 163
 164         read_unlock(&sk->sk_callback_lock);
 165 }
 166
 167 /**
 168  * dccp_wait_for_ccid - Wait for ccid to tell us we can send a packet
 169  * @sk: socket to wait for
 170  * @timeo: for how long
 171  */
 172 static int dccp_wait_for_ccid(struct sock *sk, struct sk_buff *skb,
 173                               long *timeo)
 174 {
 175         struct dccp_sock *dp = dccp_sk(sk);
 176         DEFINE_WAIT(wait);
 177         long delay;
 178         int rc;
 179
 180         while (1) {
 181                 prepare_to_wait(sk->sk_sleep, &wait, TASK_INTERRUPTIBLE);
 182
 183                 if (sk->sk_err || (sk->sk_shutdown & SEND_SHUTDOWN))
 184                         goto do_error;
 185                 if (!*timeo)
 186                         goto do_nonblock;
 187                 if (signal_pending(current))
 188                         goto do_interrupted;
 189
 190                 rc = ccid_hc_tx_send_packet(dp->dccps_hc_tx_ccid, sk, skb,
 191                                             skb->len);
 192                 if (rc <= 0)
 193                         break;
 194                 delay = msecs_to_jiffies(rc);
 195                 if (delay > *timeo || delay < 0)
 196                         goto do_nonblock;
 197
 198                 sk->sk_write_pending++;
 199                 release_sock(sk);
 200                 *timeo -= 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_nonblock:
 212         rc = -EAGAIN;
 213         goto out;
 214 do_interrupted:
 215         rc = sock_intr_errno(*timeo);
 216         goto out;
 217 }
 218
 219 int dccp_write_xmit(struct sock *sk, struct sk_buff *skb, long *timeo)
 220 {
 221         const struct dccp_sock *dp = dccp_sk(sk);
 222         int err = ccid_hc_tx_send_packet(dp->dccps_hc_tx_ccid, sk, skb,
 223                                          skb->len);
 224
 225         if (err > 0)
 226                 err = dccp_wait_for_ccid(sk, skb, timeo);
 227
 228         if (err == 0) {
 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                 } else if (dccp_ack_pending(sk))
 240                         dcb->dccpd_type = DCCP_PKT_DATAACK;
 241                 else
 242                         dcb->dccpd_type = DCCP_PKT_DATA;
 243
 244                 err = dccp_transmit_skb(sk, skb);
 245                 ccid_hc_tx_packet_sent(dp->dccps_hc_tx_ccid, sk, 0, len);
 246         }
 247
 248         return err;
 249 }
 250
 251 int dccp_retransmit_skb(struct sock *sk, struct sk_buff *skb)
 252 {
 253         if (inet_sk_rebuild_header(sk) != 0)
 254                 return -EHOSTUNREACH; /* Routing failure or similar. */
 255
 256         return dccp_transmit_skb(sk, (skb_cloned(skb) ?
 257                                       pskb_copy(skb, GFP_ATOMIC):
 258                                       skb_clone(skb, GFP_ATOMIC)));
 259 }
 260
 261 struct sk_buff *dccp_make_response(struct sock *sk, struct dst_entry *dst,
 262                                    struct request_sock *req)
 263 {
 264         struct dccp_hdr *dh;
 265         struct dccp_request_sock *dreq;
 266         const int dccp_header_size = sizeof(struct dccp_hdr) +
 267                                      sizeof(struct dccp_hdr_ext) +
 268                                      sizeof(struct dccp_hdr_response);
 269         struct sk_buff *skb = sock_wmalloc(sk, MAX_HEADER + DCCP_MAX_OPT_LEN +
 270                                                dccp_header_size, 1,
 271                                            GFP_ATOMIC);
 272         if (skb == NULL)
 273                 return NULL;
 274
 275         /* Reserve space for headers. */
 276         skb_reserve(skb, MAX_HEADER + DCCP_MAX_OPT_LEN + dccp_header_size);
 277
 278         skb->dst = dst_clone(dst);
 279         skb->csum = 0;
 280
 281         dreq = dccp_rsk(req);
 282         DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_RESPONSE;
 283         DCCP_SKB_CB(skb)->dccpd_seq  = dreq->dreq_iss;
 284         dccp_insert_options(sk, skb);
 285
 286         skb->h.raw = skb_push(skb, dccp_header_size);
 287
 288         dh = dccp_hdr(skb);
 289         memset(dh, 0, dccp_header_size);
 290
 291         dh->dccph_sport = inet_sk(sk)->sport;
 292         dh->dccph_dport = inet_rsk(req)->rmt_port;
 293         dh->dccph_doff  = (dccp_header_size +
 294                            DCCP_SKB_CB(skb)->dccpd_opt_len) / 4;
 295         dh->dccph_type  = DCCP_PKT_RESPONSE;
 296         dh->dccph_x     = 1;
 297         dccp_hdr_set_seq(dh, dreq->dreq_iss);
 298         dccp_hdr_set_ack(dccp_hdr_ack_bits(skb), dreq->dreq_isr);
 299         dccp_hdr_response(skb)->dccph_resp_service = dreq->dreq_service;
 300
 301         dh->dccph_checksum = dccp_v4_checksum(skb, inet_rsk(req)->loc_addr,
 302                                               inet_rsk(req)->rmt_addr);
 303
 304         DCCP_INC_STATS(DCCP_MIB_OUTSEGS);
 305         return skb;
 306 }
 307
 308 struct sk_buff *dccp_make_reset(struct sock *sk, struct dst_entry *dst,
 309                                 const enum dccp_reset_codes code)
 310
 311 {
 312         struct dccp_hdr *dh;
 313         struct dccp_sock *dp = dccp_sk(sk);
 314         const int dccp_header_size = sizeof(struct dccp_hdr) +
 315                                      sizeof(struct dccp_hdr_ext) +
 316                                      sizeof(struct dccp_hdr_reset);
 317         struct sk_buff *skb = sock_wmalloc(sk, MAX_HEADER + DCCP_MAX_OPT_LEN +
 318                                                dccp_header_size, 1,
 319                                            GFP_ATOMIC);
 320         if (skb == NULL)
 321                 return NULL;
 322
 323         /* Reserve space for headers. */
 324         skb_reserve(skb, MAX_HEADER + DCCP_MAX_OPT_LEN + dccp_header_size);
 325
 326         skb->dst = dst_clone(dst);
 327         skb->csum = 0;
 328
 329         dccp_inc_seqno(&dp->dccps_gss);
 330
 331         DCCP_SKB_CB(skb)->dccpd_reset_code = code;
 332         DCCP_SKB_CB(skb)->dccpd_type       = DCCP_PKT_RESET;
 333         DCCP_SKB_CB(skb)->dccpd_seq        = dp->dccps_gss;
 334         dccp_insert_options(sk, skb);
 335
 336         skb->h.raw = skb_push(skb, dccp_header_size);
 337
 338         dh = dccp_hdr(skb);
 339         memset(dh, 0, dccp_header_size);
 340
 341         dh->dccph_sport = inet_sk(sk)->sport;
 342         dh->dccph_dport = inet_sk(sk)->dport;
 343         dh->dccph_doff  = (dccp_header_size +
 344                            DCCP_SKB_CB(skb)->dccpd_opt_len) / 4;
 345         dh->dccph_type  = DCCP_PKT_RESET;
 346         dh->dccph_x     = 1;
 347         dccp_hdr_set_seq(dh, dp->dccps_gss);
 348         dccp_hdr_set_ack(dccp_hdr_ack_bits(skb), dp->dccps_gsr);
 349
 350         dccp_hdr_reset(skb)->dccph_reset_code = code;
 351
 352         dh->dccph_checksum = dccp_v4_checksum(skb, inet_sk(sk)->saddr,
 353                                               inet_sk(sk)->daddr);
 354
 355         DCCP_INC_STATS(DCCP_MIB_OUTSEGS);
 356         return skb;
 357 }
 358
 359 /*
 360  * Do all connect socket setups that can be done AF independent.
 361  */
 362 static inline void dccp_connect_init(struct sock *sk)
 363 {
 364         struct dst_entry *dst = __sk_dst_get(sk);
 365         struct inet_connection_sock *icsk = inet_csk(sk);
 366
 367         sk->sk_err = 0;
 368         sock_reset_flag(sk, SOCK_DONE);
 369
 370         dccp_sync_mss(sk, dst_mtu(dst));
 371
 372         /*
 373          * FIXME: set dp->{dccps_swh,dccps_swl}, with
 374          * something like dccp_inc_seq
 375          */
 376
 377         icsk->icsk_retransmits = 0;
 378 }
 379
 380 int dccp_connect(struct sock *sk)
 381 {
 382         struct sk_buff *skb;
 383         struct inet_connection_sock *icsk = inet_csk(sk);
 384
 385         dccp_connect_init(sk);
 386
 387         skb = alloc_skb(MAX_DCCP_HEADER + 15, sk->sk_allocation);
 388         if (unlikely(skb == NULL))
 389                 return -ENOBUFS;
 390
 391         /* Reserve space for headers. */
 392         skb_reserve(skb, MAX_DCCP_HEADER);
 393
 394         DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_REQUEST;
 395         skb->csum = 0;
 396         skb_set_owner_w(skb, sk);
 397
 398         BUG_TRAP(sk->sk_send_head == NULL);
 399         sk->sk_send_head = skb;
 400         dccp_transmit_skb(sk, skb_clone(skb, GFP_KERNEL));
 401         DCCP_INC_STATS(DCCP_MIB_ACTIVEOPENS);
 402
 403         /* Timer for repeating the REQUEST until an answer. */
 404         inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
 405                                   icsk->icsk_rto, DCCP_RTO_MAX);
 406         return 0;
 407 }
 408
 409 void dccp_send_ack(struct sock *sk)
 410 {
 411         /* If we have been reset, we may not send again. */
 412         if (sk->sk_state != DCCP_CLOSED) {
 413                 struct sk_buff *skb = alloc_skb(MAX_DCCP_HEADER, GFP_ATOMIC);
 414
 415                 if (skb == NULL) {
 416                         inet_csk_schedule_ack(sk);
 417                         inet_csk(sk)->icsk_ack.ato = TCP_ATO_MIN;
 418                         inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
 419                                                   TCP_DELACK_MAX,
 420                                                   DCCP_RTO_MAX);
 421                         return;
 422                 }
 423
 424                 /* Reserve space for headers */
 425                 skb_reserve(skb, MAX_DCCP_HEADER);
 426                 skb->csum = 0;
 427                 DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_ACK;
 428                 skb_set_owner_w(skb, sk);
 429                 dccp_transmit_skb(sk, skb);
 430         }
 431 }
 432
 433 EXPORT_SYMBOL_GPL(dccp_send_ack);
 434
 435 void dccp_send_delayed_ack(struct sock *sk)
 436 {
 437         struct inet_connection_sock *icsk = inet_csk(sk);
 438         /*
 439          * FIXME: tune this timer. elapsed time fixes the skew, so no problem
 440          * with using 2s, and active senders also piggyback the ACK into a
 441          * DATAACK packet, so this is really for quiescent senders.
 442          */
 443         unsigned long timeout = jiffies + 2 * HZ;
 444
 445         /* Use new timeout only if there wasn't a older one earlier. */
 446         if (icsk->icsk_ack.pending & ICSK_ACK_TIMER) {
 447                 /* If delack timer was blocked or is about to expire,
 448                  * send ACK now.
 449                  *
 450                  * FIXME: check the "about to expire" part
 451                  */
 452                 if (icsk->icsk_ack.blocked) {
 453                         dccp_send_ack(sk);
 454                         return;
 455                 }
 456
 457                 if (!time_before(timeout, icsk->icsk_ack.timeout))
 458                         timeout = icsk->icsk_ack.timeout;
 459         }
 460         icsk->icsk_ack.pending |= ICSK_ACK_SCHED | ICSK_ACK_TIMER;
 461         icsk->icsk_ack.timeout = timeout;
 462         sk_reset_timer(sk, &icsk->icsk_delack_timer, timeout);
 463 }
 464
 465 void dccp_send_sync(struct sock *sk, const u64 seq,
 466                     const enum dccp_pkt_type pkt_type)
 467 {
 468         /*
 469          * We are not putting this on the write queue, so
 470          * dccp_transmit_skb() will set the ownership to this
 471          * sock.
 472          */
 473         struct sk_buff *skb = alloc_skb(MAX_DCCP_HEADER, GFP_ATOMIC);
 474
 475         if (skb == NULL)
 476                 /* FIXME: how to make sure the sync is sent? */
 477                 return;
 478
 479         /* Reserve space for headers and prepare control bits. */
 480         skb_reserve(skb, MAX_DCCP_HEADER);
 481         skb->csum = 0;
 482         DCCP_SKB_CB(skb)->dccpd_type = pkt_type;
 483         DCCP_SKB_CB(skb)->dccpd_seq = seq;
 484
 485         skb_set_owner_w(skb, sk);
 486         dccp_transmit_skb(sk, skb);
 487 }
 488
 489 /*
 490  * Send a DCCP_PKT_CLOSE/CLOSEREQ. The caller locks the socket for us. This
 491  * cannot be allowed to fail queueing a DCCP_PKT_CLOSE/CLOSEREQ frame under
 492  * any circumstances.
 493  */
 494 void dccp_send_close(struct sock *sk, const int active)
 495 {
 496         struct dccp_sock *dp = dccp_sk(sk);
 497         struct sk_buff *skb;
 498         const unsigned int prio = active ? GFP_KERNEL : GFP_ATOMIC;
 499
 500         skb = alloc_skb(sk->sk_prot->max_header, prio);
 501         if (skb == NULL)
 502                 return;
 503
 504         /* Reserve space for headers and prepare control bits. */
 505         skb_reserve(skb, sk->sk_prot->max_header);
 506         skb->csum = 0;
 507         DCCP_SKB_CB(skb)->dccpd_type = dp->dccps_role == DCCP_ROLE_CLIENT ?
 508                                         DCCP_PKT_CLOSE : DCCP_PKT_CLOSEREQ;
 509
 510         skb_set_owner_w(skb, sk);
 511         if (active) {
 512                 BUG_TRAP(sk->sk_send_head == NULL);
 513                 sk->sk_send_head = skb;
 514                 dccp_transmit_skb(sk, skb_clone(skb, prio));
 515         } else
 516                 dccp_transmit_skb(sk, skb);
 517 }