1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* 3 * net/dccp/output.c 4 * 5 * An implementation of the DCCP protocol 6 * Arnaldo Carvalho de Melo <acme@conectiva.com.br> 7 */ 8 9 #include <linux/dccp.h> 10 #include <linux/kernel.h> 11 #include <linux/skbuff.h> 12 #include <linux/slab.h> 13 #include <linux/sched/signal.h> 14 15 #include <net/inet_sock.h> 16 #include <net/sock.h> 17 18 #include "ackvec.h" 19 #include "ccid.h" 20 #include "dccp.h" 21 22 static inline void dccp_event_ack_sent(struct sock *sk) 23 { 24 inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK); 25 } 26 27 /* enqueue @skb on sk_send_head for retransmission, return clone to send now */ 28 static struct sk_buff *dccp_skb_entail(struct sock *sk, struct sk_buff *skb) 29 { 30 skb_set_owner_w(skb, sk); 31 WARN_ON(sk->sk_send_head); 32 sk->sk_send_head = skb; 33 return skb_clone(sk->sk_send_head, gfp_any()); 34 } 35 36 /* 37 * All SKB's seen here are completely headerless. It is our 38 * job to build the DCCP header, and pass the packet down to 39 * IP so it can do the same plus pass the packet off to the 40 * device. 41 */ 42 static int dccp_transmit_skb(struct sock *sk, struct sk_buff *skb) 43 { 44 if (likely(skb != NULL)) { 45 struct inet_sock *inet = inet_sk(sk); 46 const struct inet_connection_sock *icsk = inet_csk(sk); 47 struct dccp_sock *dp = dccp_sk(sk); 48 struct dccp_skb_cb *dcb = DCCP_SKB_CB(skb); 49 struct dccp_hdr *dh; 50 /* XXX For now we're using only 48 bits sequence numbers */ 51 const u32 dccp_header_size = sizeof(*dh) + 52 sizeof(struct dccp_hdr_ext) + 53 dccp_packet_hdr_len(dcb->dccpd_type); 54 int err, set_ack = 1; 55 u64 ackno = dp->dccps_gsr; 56 /* 57 * Increment GSS here already in case the option code needs it. 58 * Update GSS for real only if option processing below succeeds. 59 */ 60 dcb->dccpd_seq = ADD48(dp->dccps_gss, 1); 61 62 switch (dcb->dccpd_type) { 63 case DCCP_PKT_DATA: 64 set_ack = 0; 65 fallthrough; 66 case DCCP_PKT_DATAACK: 67 case DCCP_PKT_RESET: 68 break; 69 70 case DCCP_PKT_REQUEST: 71 set_ack = 0; 72 /* Use ISS on the first (non-retransmitted) Request. */ 73 if (icsk->icsk_retransmits == 0) 74 dcb->dccpd_seq = dp->dccps_iss; 75 fallthrough; 76 77 case DCCP_PKT_SYNC: 78 case DCCP_PKT_SYNCACK: 79 ackno = dcb->dccpd_ack_seq; 80 fallthrough; 81 default: 82 /* 83 * Set owner/destructor: some skbs are allocated via 84 * alloc_skb (e.g. when retransmission may happen). 85 * Only Data, DataAck, and Reset packets should come 86 * through here with skb->sk set. 87 */ 88 WARN_ON(skb->sk); 89 skb_set_owner_w(skb, sk); 90 break; 91 } 92 93 if (dccp_insert_options(sk, skb)) { 94 kfree_skb(skb); 95 return -EPROTO; 96 } 97 98 99 /* Build DCCP header and checksum it. */ 100 dh = dccp_zeroed_hdr(skb, dccp_header_size); 101 dh->dccph_type = dcb->dccpd_type; 102 dh->dccph_sport = inet->inet_sport; 103 dh->dccph_dport = inet->inet_dport; 104 dh->dccph_doff = (dccp_header_size + dcb->dccpd_opt_len) / 4; 105 dh->dccph_ccval = dcb->dccpd_ccval; 106 dh->dccph_cscov = dp->dccps_pcslen; 107 /* XXX For now we're using only 48 bits sequence numbers */ 108 dh->dccph_x = 1; 109 110 dccp_update_gss(sk, dcb->dccpd_seq); 111 dccp_hdr_set_seq(dh, dp->dccps_gss); 112 if (set_ack) 113 dccp_hdr_set_ack(dccp_hdr_ack_bits(skb), ackno); 114 115 switch (dcb->dccpd_type) { 116 case DCCP_PKT_REQUEST: 117 dccp_hdr_request(skb)->dccph_req_service = 118 dp->dccps_service; 119 /* 120 * Limit Ack window to ISS <= P.ackno <= GSS, so that 121 * only Responses to Requests we sent are considered. 122 */ 123 dp->dccps_awl = dp->dccps_iss; 124 break; 125 case DCCP_PKT_RESET: 126 dccp_hdr_reset(skb)->dccph_reset_code = 127 dcb->dccpd_reset_code; 128 break; 129 } 130 131 icsk->icsk_af_ops->send_check(sk, skb); 132 133 if (set_ack) 134 dccp_event_ack_sent(sk); 135 136 DCCP_INC_STATS(DCCP_MIB_OUTSEGS); 137 138 err = icsk->icsk_af_ops->queue_xmit(sk, skb, &inet->cork.fl); 139 return net_xmit_eval(err); 140 } 141 return -ENOBUFS; 142 } 143 144 /** 145 * dccp_determine_ccmps - Find out about CCID-specific packet-size limits 146 * @dp: socket to find packet size limits of 147 * 148 * We only consider the HC-sender CCID for setting the CCMPS (RFC 4340, 14.), 149 * since the RX CCID is restricted to feedback packets (Acks), which are small 150 * in comparison with the data traffic. A value of 0 means "no current CCMPS". 151 */ 152 static u32 dccp_determine_ccmps(const struct dccp_sock *dp) 153 { 154 const struct ccid *tx_ccid = dp->dccps_hc_tx_ccid; 155 156 if (tx_ccid == NULL || tx_ccid->ccid_ops == NULL) 157 return 0; 158 return tx_ccid->ccid_ops->ccid_ccmps; 159 } 160 161 unsigned int dccp_sync_mss(struct sock *sk, u32 pmtu) 162 { 163 struct inet_connection_sock *icsk = inet_csk(sk); 164 struct dccp_sock *dp = dccp_sk(sk); 165 u32 ccmps = dccp_determine_ccmps(dp); 166 u32 cur_mps = ccmps ? min(pmtu, ccmps) : pmtu; 167 168 /* Account for header lengths and IPv4/v6 option overhead */ 169 cur_mps -= (icsk->icsk_af_ops->net_header_len + icsk->icsk_ext_hdr_len + 170 sizeof(struct dccp_hdr) + sizeof(struct dccp_hdr_ext)); 171 172 /* 173 * Leave enough headroom for common DCCP header options. 174 * This only considers options which may appear on DCCP-Data packets, as 175 * per table 3 in RFC 4340, 5.8. When running out of space for other 176 * options (eg. Ack Vector which can take up to 255 bytes), it is better 177 * to schedule a separate Ack. Thus we leave headroom for the following: 178 * - 1 byte for Slow Receiver (11.6) 179 * - 6 bytes for Timestamp (13.1) 180 * - 10 bytes for Timestamp Echo (13.3) 181 * - 8 bytes for NDP count (7.7, when activated) 182 * - 6 bytes for Data Checksum (9.3) 183 * - %DCCPAV_MIN_OPTLEN bytes for Ack Vector size (11.4, when enabled) 184 */ 185 cur_mps -= roundup(1 + 6 + 10 + dp->dccps_send_ndp_count * 8 + 6 + 186 (dp->dccps_hc_rx_ackvec ? DCCPAV_MIN_OPTLEN : 0), 4); 187 188 /* And store cached results */ 189 icsk->icsk_pmtu_cookie = pmtu; 190 WRITE_ONCE(dp->dccps_mss_cache, cur_mps); 191 192 return cur_mps; 193 } 194 195 EXPORT_SYMBOL_GPL(dccp_sync_mss); 196 197 void dccp_write_space(struct sock *sk) 198 { 199 struct socket_wq *wq; 200 201 rcu_read_lock(); 202 wq = rcu_dereference(sk->sk_wq); 203 if (skwq_has_sleeper(wq)) 204 wake_up_interruptible(&wq->wait); 205 /* Should agree with poll, otherwise some programs break */ 206 if (sock_writeable(sk)) 207 sk_wake_async(sk, SOCK_WAKE_SPACE, POLL_OUT); 208 209 rcu_read_unlock(); 210 } 211 212 /** 213 * dccp_wait_for_ccid - Await CCID send permission 214 * @sk: socket to wait for 215 * @delay: timeout in jiffies 216 * 217 * This is used by CCIDs which need to delay the send time in process context. 218 */ 219 static int dccp_wait_for_ccid(struct sock *sk, unsigned long delay) 220 { 221 DEFINE_WAIT(wait); 222 long remaining; 223 224 prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE); 225 sk->sk_write_pending++; 226 release_sock(sk); 227 228 remaining = schedule_timeout(delay); 229 230 lock_sock(sk); 231 sk->sk_write_pending--; 232 finish_wait(sk_sleep(sk), &wait); 233 234 if (signal_pending(current) || sk->sk_err) 235 return -1; 236 return remaining; 237 } 238 239 /** 240 * dccp_xmit_packet - Send data packet under control of CCID 241 * @sk: socket to send data packet on 242 * 243 * Transmits next-queued payload and informs CCID to account for the packet. 244 */ 245 static void dccp_xmit_packet(struct sock *sk) 246 { 247 int err, len; 248 struct dccp_sock *dp = dccp_sk(sk); 249 struct sk_buff *skb = dccp_qpolicy_pop(sk); 250 251 if (unlikely(skb == NULL)) 252 return; 253 len = skb->len; 254 255 if (sk->sk_state == DCCP_PARTOPEN) { 256 const u32 cur_mps = dp->dccps_mss_cache - DCCP_FEATNEG_OVERHEAD; 257 /* 258 * See 8.1.5 - Handshake Completion. 259 * 260 * For robustness we resend Confirm options until the client has 261 * entered OPEN. During the initial feature negotiation, the MPS 262 * is smaller than usual, reduced by the Change/Confirm options. 263 */ 264 if (!list_empty(&dp->dccps_featneg) && len > cur_mps) { 265 DCCP_WARN("Payload too large (%d) for featneg.\n", len); 266 dccp_send_ack(sk); 267 dccp_feat_list_purge(&dp->dccps_featneg); 268 } 269 270 inet_csk_schedule_ack(sk); 271 inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK, 272 inet_csk(sk)->icsk_rto, 273 DCCP_RTO_MAX); 274 DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_DATAACK; 275 } else if (dccp_ack_pending(sk)) { 276 DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_DATAACK; 277 } else { 278 DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_DATA; 279 } 280 281 err = dccp_transmit_skb(sk, skb); 282 if (err) 283 dccp_pr_debug("transmit_skb() returned err=%d\n", err); 284 /* 285 * Register this one as sent even if an error occurred. To the remote 286 * end a local packet drop is indistinguishable from network loss, i.e. 287 * any local drop will eventually be reported via receiver feedback. 288 */ 289 ccid_hc_tx_packet_sent(dp->dccps_hc_tx_ccid, sk, len); 290 291 /* 292 * If the CCID needs to transfer additional header options out-of-band 293 * (e.g. Ack Vectors or feature-negotiation options), it activates this 294 * flag to schedule a Sync. The Sync will automatically incorporate all 295 * currently pending header options, thus clearing the backlog. 296 */ 297 if (dp->dccps_sync_scheduled) 298 dccp_send_sync(sk, dp->dccps_gsr, DCCP_PKT_SYNC); 299 } 300 301 /** 302 * dccp_flush_write_queue - Drain queue at end of connection 303 * @sk: socket to be drained 304 * @time_budget: time allowed to drain the queue 305 * 306 * Since dccp_sendmsg queues packets without waiting for them to be sent, it may 307 * happen that the TX queue is not empty at the end of a connection. We give the 308 * HC-sender CCID a grace period of up to @time_budget jiffies. If this function 309 * returns with a non-empty write queue, it will be purged later. 310 */ 311 void dccp_flush_write_queue(struct sock *sk, long *time_budget) 312 { 313 struct dccp_sock *dp = dccp_sk(sk); 314 struct sk_buff *skb; 315 long delay, rc; 316 317 while (*time_budget > 0 && (skb = skb_peek(&sk->sk_write_queue))) { 318 rc = ccid_hc_tx_send_packet(dp->dccps_hc_tx_ccid, sk, skb); 319 320 switch (ccid_packet_dequeue_eval(rc)) { 321 case CCID_PACKET_WILL_DEQUEUE_LATER: 322 /* 323 * If the CCID determines when to send, the next sending 324 * time is unknown or the CCID may not even send again 325 * (e.g. remote host crashes or lost Ack packets). 326 */ 327 DCCP_WARN("CCID did not manage to send all packets\n"); 328 return; 329 case CCID_PACKET_DELAY: 330 delay = msecs_to_jiffies(rc); 331 if (delay > *time_budget) 332 return; 333 rc = dccp_wait_for_ccid(sk, delay); 334 if (rc < 0) 335 return; 336 *time_budget -= (delay - rc); 337 /* check again if we can send now */ 338 break; 339 case CCID_PACKET_SEND_AT_ONCE: 340 dccp_xmit_packet(sk); 341 break; 342 case CCID_PACKET_ERR: 343 skb_dequeue(&sk->sk_write_queue); 344 kfree_skb(skb); 345 dccp_pr_debug("packet discarded due to err=%ld\n", rc); 346 } 347 } 348 } 349 350 void dccp_write_xmit(struct sock *sk) 351 { 352 struct dccp_sock *dp = dccp_sk(sk); 353 struct sk_buff *skb; 354 355 while ((skb = dccp_qpolicy_top(sk))) { 356 int rc = ccid_hc_tx_send_packet(dp->dccps_hc_tx_ccid, sk, skb); 357 358 switch (ccid_packet_dequeue_eval(rc)) { 359 case CCID_PACKET_WILL_DEQUEUE_LATER: 360 return; 361 case CCID_PACKET_DELAY: 362 sk_reset_timer(sk, &dp->dccps_xmit_timer, 363 jiffies + msecs_to_jiffies(rc)); 364 return; 365 case CCID_PACKET_SEND_AT_ONCE: 366 dccp_xmit_packet(sk); 367 break; 368 case CCID_PACKET_ERR: 369 dccp_qpolicy_drop(sk, skb); 370 dccp_pr_debug("packet discarded due to err=%d\n", rc); 371 } 372 } 373 } 374 375 /** 376 * dccp_retransmit_skb - Retransmit Request, Close, or CloseReq packets 377 * @sk: socket to perform retransmit on 378 * 379 * There are only four retransmittable packet types in DCCP: 380 * - Request in client-REQUEST state (sec. 8.1.1), 381 * - CloseReq in server-CLOSEREQ state (sec. 8.3), 382 * - Close in node-CLOSING state (sec. 8.3), 383 * - Acks in client-PARTOPEN state (sec. 8.1.5, handled by dccp_delack_timer()). 384 * This function expects sk->sk_send_head to contain the original skb. 385 */ 386 int dccp_retransmit_skb(struct sock *sk) 387 { 388 WARN_ON(sk->sk_send_head == NULL); 389 390 if (inet_csk(sk)->icsk_af_ops->rebuild_header(sk) != 0) 391 return -EHOSTUNREACH; /* Routing failure or similar. */ 392 393 /* this count is used to distinguish original and retransmitted skb */ 394 inet_csk(sk)->icsk_retransmits++; 395 396 return dccp_transmit_skb(sk, skb_clone(sk->sk_send_head, GFP_ATOMIC)); 397 } 398 399 struct sk_buff *dccp_make_response(const struct sock *sk, struct dst_entry *dst, 400 struct request_sock *req) 401 { 402 struct dccp_hdr *dh; 403 struct dccp_request_sock *dreq; 404 const u32 dccp_header_size = sizeof(struct dccp_hdr) + 405 sizeof(struct dccp_hdr_ext) + 406 sizeof(struct dccp_hdr_response); 407 struct sk_buff *skb; 408 409 /* sk is marked const to clearly express we dont hold socket lock. 410 * sock_wmalloc() will atomically change sk->sk_wmem_alloc, 411 * it is safe to promote sk to non const. 412 */ 413 skb = sock_wmalloc((struct sock *)sk, MAX_DCCP_HEADER, 1, 414 GFP_ATOMIC); 415 if (!skb) 416 return NULL; 417 418 skb_reserve(skb, MAX_DCCP_HEADER); 419 420 skb_dst_set(skb, dst_clone(dst)); 421 422 dreq = dccp_rsk(req); 423 if (inet_rsk(req)->acked) /* increase GSS upon retransmission */ 424 dccp_inc_seqno(&dreq->dreq_gss); 425 DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_RESPONSE; 426 DCCP_SKB_CB(skb)->dccpd_seq = dreq->dreq_gss; 427 428 /* Resolve feature dependencies resulting from choice of CCID */ 429 if (dccp_feat_server_ccid_dependencies(dreq)) 430 goto response_failed; 431 432 if (dccp_insert_options_rsk(dreq, skb)) 433 goto response_failed; 434 435 /* Build and checksum header */ 436 dh = dccp_zeroed_hdr(skb, dccp_header_size); 437 438 dh->dccph_sport = htons(inet_rsk(req)->ir_num); 439 dh->dccph_dport = inet_rsk(req)->ir_rmt_port; 440 dh->dccph_doff = (dccp_header_size + 441 DCCP_SKB_CB(skb)->dccpd_opt_len) / 4; 442 dh->dccph_type = DCCP_PKT_RESPONSE; 443 dh->dccph_x = 1; 444 dccp_hdr_set_seq(dh, dreq->dreq_gss); 445 dccp_hdr_set_ack(dccp_hdr_ack_bits(skb), dreq->dreq_gsr); 446 dccp_hdr_response(skb)->dccph_resp_service = dreq->dreq_service; 447 448 dccp_csum_outgoing(skb); 449 450 /* We use `acked' to remember that a Response was already sent. */ 451 inet_rsk(req)->acked = 1; 452 DCCP_INC_STATS(DCCP_MIB_OUTSEGS); 453 return skb; 454 response_failed: 455 kfree_skb(skb); 456 return NULL; 457 } 458 459 EXPORT_SYMBOL_GPL(dccp_make_response); 460 461 /* answer offending packet in @rcv_skb with Reset from control socket @ctl */ 462 struct sk_buff *dccp_ctl_make_reset(struct sock *sk, struct sk_buff *rcv_skb) 463 { 464 struct dccp_hdr *rxdh = dccp_hdr(rcv_skb), *dh; 465 struct dccp_skb_cb *dcb = DCCP_SKB_CB(rcv_skb); 466 const u32 dccp_hdr_reset_len = sizeof(struct dccp_hdr) + 467 sizeof(struct dccp_hdr_ext) + 468 sizeof(struct dccp_hdr_reset); 469 struct dccp_hdr_reset *dhr; 470 struct sk_buff *skb; 471 472 skb = alloc_skb(sk->sk_prot->max_header, GFP_ATOMIC); 473 if (skb == NULL) 474 return NULL; 475 476 skb_reserve(skb, sk->sk_prot->max_header); 477 478 /* Swap the send and the receive. */ 479 dh = dccp_zeroed_hdr(skb, dccp_hdr_reset_len); 480 dh->dccph_type = DCCP_PKT_RESET; 481 dh->dccph_sport = rxdh->dccph_dport; 482 dh->dccph_dport = rxdh->dccph_sport; 483 dh->dccph_doff = dccp_hdr_reset_len / 4; 484 dh->dccph_x = 1; 485 486 dhr = dccp_hdr_reset(skb); 487 dhr->dccph_reset_code = dcb->dccpd_reset_code; 488 489 switch (dcb->dccpd_reset_code) { 490 case DCCP_RESET_CODE_PACKET_ERROR: 491 dhr->dccph_reset_data[0] = rxdh->dccph_type; 492 break; 493 case DCCP_RESET_CODE_OPTION_ERROR: 494 case DCCP_RESET_CODE_MANDATORY_ERROR: 495 memcpy(dhr->dccph_reset_data, dcb->dccpd_reset_data, 3); 496 break; 497 } 498 /* 499 * From RFC 4340, 8.3.1: 500 * If P.ackno exists, set R.seqno := P.ackno + 1. 501 * Else set R.seqno := 0. 502 */ 503 if (dcb->dccpd_ack_seq != DCCP_PKT_WITHOUT_ACK_SEQ) 504 dccp_hdr_set_seq(dh, ADD48(dcb->dccpd_ack_seq, 1)); 505 dccp_hdr_set_ack(dccp_hdr_ack_bits(skb), dcb->dccpd_seq); 506 507 dccp_csum_outgoing(skb); 508 return skb; 509 } 510 511 EXPORT_SYMBOL_GPL(dccp_ctl_make_reset); 512 513 /* send Reset on established socket, to close or abort the connection */ 514 int dccp_send_reset(struct sock *sk, enum dccp_reset_codes code) 515 { 516 struct sk_buff *skb; 517 /* 518 * FIXME: what if rebuild_header fails? 519 * Should we be doing a rebuild_header here? 520 */ 521 int err = inet_csk(sk)->icsk_af_ops->rebuild_header(sk); 522 523 if (err != 0) 524 return err; 525 526 skb = sock_wmalloc(sk, sk->sk_prot->max_header, 1, GFP_ATOMIC); 527 if (skb == NULL) 528 return -ENOBUFS; 529 530 /* Reserve space for headers and prepare control bits. */ 531 skb_reserve(skb, sk->sk_prot->max_header); 532 DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_RESET; 533 DCCP_SKB_CB(skb)->dccpd_reset_code = code; 534 535 return dccp_transmit_skb(sk, skb); 536 } 537 538 /* 539 * Do all connect socket setups that can be done AF independent. 540 */ 541 int dccp_connect(struct sock *sk) 542 { 543 struct sk_buff *skb; 544 struct dccp_sock *dp = dccp_sk(sk); 545 struct dst_entry *dst = __sk_dst_get(sk); 546 struct inet_connection_sock *icsk = inet_csk(sk); 547 548 sk->sk_err = 0; 549 sock_reset_flag(sk, SOCK_DONE); 550 551 dccp_sync_mss(sk, dst_mtu(dst)); 552 553 /* do not connect if feature negotiation setup fails */ 554 if (dccp_feat_finalise_settings(dccp_sk(sk))) 555 return -EPROTO; 556 557 /* Initialise GAR as per 8.5; AWL/AWH are set in dccp_transmit_skb() */ 558 dp->dccps_gar = dp->dccps_iss; 559 560 skb = alloc_skb(sk->sk_prot->max_header, sk->sk_allocation); 561 if (unlikely(skb == NULL)) 562 return -ENOBUFS; 563 564 /* Reserve space for headers. */ 565 skb_reserve(skb, sk->sk_prot->max_header); 566 567 DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_REQUEST; 568 569 dccp_transmit_skb(sk, dccp_skb_entail(sk, skb)); 570 DCCP_INC_STATS(DCCP_MIB_ACTIVEOPENS); 571 572 /* Timer for repeating the REQUEST until an answer. */ 573 icsk->icsk_retransmits = 0; 574 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, 575 icsk->icsk_rto, DCCP_RTO_MAX); 576 return 0; 577 } 578 579 EXPORT_SYMBOL_GPL(dccp_connect); 580 581 void dccp_send_ack(struct sock *sk) 582 { 583 /* If we have been reset, we may not send again. */ 584 if (sk->sk_state != DCCP_CLOSED) { 585 struct sk_buff *skb = alloc_skb(sk->sk_prot->max_header, 586 GFP_ATOMIC); 587 588 if (skb == NULL) { 589 inet_csk_schedule_ack(sk); 590 inet_csk(sk)->icsk_ack.ato = TCP_ATO_MIN; 591 inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK, 592 TCP_DELACK_MAX, 593 DCCP_RTO_MAX); 594 return; 595 } 596 597 /* Reserve space for headers */ 598 skb_reserve(skb, sk->sk_prot->max_header); 599 DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_ACK; 600 dccp_transmit_skb(sk, skb); 601 } 602 } 603 604 EXPORT_SYMBOL_GPL(dccp_send_ack); 605 606 #if 0 607 /* FIXME: Is this still necessary (11.3) - currently nowhere used by DCCP. */ 608 void dccp_send_delayed_ack(struct sock *sk) 609 { 610 struct inet_connection_sock *icsk = inet_csk(sk); 611 /* 612 * FIXME: tune this timer. elapsed time fixes the skew, so no problem 613 * with using 2s, and active senders also piggyback the ACK into a 614 * DATAACK packet, so this is really for quiescent senders. 615 */ 616 unsigned long timeout = jiffies + 2 * HZ; 617 618 /* Use new timeout only if there wasn't a older one earlier. */ 619 if (icsk->icsk_ack.pending & ICSK_ACK_TIMER) { 620 /* If delack timer was blocked or is about to expire, 621 * send ACK now. 622 * 623 * FIXME: check the "about to expire" part 624 */ 625 if (icsk->icsk_ack.blocked) { 626 dccp_send_ack(sk); 627 return; 628 } 629 630 if (!time_before(timeout, icsk->icsk_ack.timeout)) 631 timeout = icsk->icsk_ack.timeout; 632 } 633 icsk->icsk_ack.pending |= ICSK_ACK_SCHED | ICSK_ACK_TIMER; 634 icsk->icsk_ack.timeout = timeout; 635 sk_reset_timer(sk, &icsk->icsk_delack_timer, timeout); 636 } 637 #endif 638 639 void dccp_send_sync(struct sock *sk, const u64 ackno, 640 const enum dccp_pkt_type pkt_type) 641 { 642 /* 643 * We are not putting this on the write queue, so 644 * dccp_transmit_skb() will set the ownership to this 645 * sock. 646 */ 647 struct sk_buff *skb = alloc_skb(sk->sk_prot->max_header, GFP_ATOMIC); 648 649 if (skb == NULL) { 650 /* FIXME: how to make sure the sync is sent? */ 651 DCCP_CRIT("could not send %s", dccp_packet_name(pkt_type)); 652 return; 653 } 654 655 /* Reserve space for headers and prepare control bits. */ 656 skb_reserve(skb, sk->sk_prot->max_header); 657 DCCP_SKB_CB(skb)->dccpd_type = pkt_type; 658 DCCP_SKB_CB(skb)->dccpd_ack_seq = ackno; 659 660 /* 661 * Clear the flag in case the Sync was scheduled for out-of-band data, 662 * such as carrying a long Ack Vector. 663 */ 664 dccp_sk(sk)->dccps_sync_scheduled = 0; 665 666 dccp_transmit_skb(sk, skb); 667 } 668 669 EXPORT_SYMBOL_GPL(dccp_send_sync); 670 671 /* 672 * Send a DCCP_PKT_CLOSE/CLOSEREQ. The caller locks the socket for us. This 673 * cannot be allowed to fail queueing a DCCP_PKT_CLOSE/CLOSEREQ frame under 674 * any circumstances. 675 */ 676 void dccp_send_close(struct sock *sk, const int active) 677 { 678 struct dccp_sock *dp = dccp_sk(sk); 679 struct sk_buff *skb; 680 const gfp_t prio = active ? GFP_KERNEL : GFP_ATOMIC; 681 682 skb = alloc_skb(sk->sk_prot->max_header, prio); 683 if (skb == NULL) 684 return; 685 686 /* Reserve space for headers and prepare control bits. */ 687 skb_reserve(skb, sk->sk_prot->max_header); 688 if (dp->dccps_role == DCCP_ROLE_SERVER && !dp->dccps_server_timewait) 689 DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_CLOSEREQ; 690 else 691 DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_CLOSE; 692 693 if (active) { 694 skb = dccp_skb_entail(sk, skb); 695 /* 696 * Retransmission timer for active-close: RFC 4340, 8.3 requires 697 * to retransmit the Close/CloseReq until the CLOSING/CLOSEREQ 698 * state can be left. The initial timeout is 2 RTTs. 699 * Since RTT measurement is done by the CCIDs, there is no easy 700 * way to get an RTT sample. The fallback RTT from RFC 4340, 3.4 701 * is too low (200ms); we use a high value to avoid unnecessary 702 * retransmissions when the link RTT is > 0.2 seconds. 703 * FIXME: Let main module sample RTTs and use that instead. 704 */ 705 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, 706 DCCP_TIMEOUT_INIT, DCCP_RTO_MAX); 707 } 708 dccp_transmit_skb(sk, skb); 709 } 710