4 * An implementation of the DCCP protocol
5 * Arnaldo Carvalho de Melo <acme@conectiva.com.br>
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.
13 #include <linux/dccp.h>
14 #include <linux/skbuff.h>
15 #include <linux/slab.h>
23 /* rate-limit for syncs in reply to sequence-invalid packets; RFC 4340, 7.5.4 */
24 int sysctl_dccp_sync_ratelimit __read_mostly = HZ / 8;
26 static void dccp_enqueue_skb(struct sock *sk, struct sk_buff *skb)
28 __skb_pull(skb, dccp_hdr(skb)->dccph_doff * 4);
29 __skb_queue_tail(&sk->sk_receive_queue, skb);
30 skb_set_owner_r(skb, sk);
31 sk->sk_data_ready(sk, 0);
34 static void dccp_fin(struct sock *sk, struct sk_buff *skb)
37 * On receiving Close/CloseReq, both RD/WR shutdown are performed.
38 * RFC 4340, 8.3 says that we MAY send further Data/DataAcks after
39 * receiving the closing segment, but there is no guarantee that such
40 * data will be processed at all.
42 sk->sk_shutdown = SHUTDOWN_MASK;
43 sock_set_flag(sk, SOCK_DONE);
44 dccp_enqueue_skb(sk, skb);
47 static int dccp_rcv_close(struct sock *sk, struct sk_buff *skb)
51 switch (sk->sk_state) {
53 * We ignore Close when received in one of the following states:
54 * - CLOSED (may be a late or duplicate packet)
55 * - PASSIVE_CLOSEREQ (the peer has sent a CloseReq earlier)
56 * - RESPOND (already handled by dccp_check_req)
60 * Simultaneous-close: receiving a Close after sending one. This
61 * can happen if both client and server perform active-close and
62 * will result in an endless ping-pong of crossing and retrans-
63 * mitted Close packets, which only terminates when one of the
64 * nodes times out (min. 64 seconds). Quicker convergence can be
65 * achieved when one of the nodes acts as tie-breaker.
66 * This is ok as both ends are done with data transfer and each
67 * end is just waiting for the other to acknowledge termination.
69 if (dccp_sk(sk)->dccps_role != DCCP_ROLE_CLIENT)
73 case DCCP_ACTIVE_CLOSEREQ:
74 dccp_send_reset(sk, DCCP_RESET_CODE_CLOSED);
79 /* Give waiting application a chance to read pending data */
82 dccp_set_state(sk, DCCP_PASSIVE_CLOSE);
84 case DCCP_PASSIVE_CLOSE:
86 * Retransmitted Close: we have already enqueued the first one.
88 sk_wake_async(sk, SOCK_WAKE_WAITD, POLL_HUP);
93 static int dccp_rcv_closereq(struct sock *sk, struct sk_buff *skb)
98 * Step 7: Check for unexpected packet types
99 * If (S.is_server and P.type == CloseReq)
100 * Send Sync packet acknowledging P.seqno
101 * Drop packet and return
103 if (dccp_sk(sk)->dccps_role != DCCP_ROLE_CLIENT) {
104 dccp_send_sync(sk, DCCP_SKB_CB(skb)->dccpd_seq, DCCP_PKT_SYNC);
108 /* Step 13: process relevant Client states < CLOSEREQ */
109 switch (sk->sk_state) {
110 case DCCP_REQUESTING:
111 dccp_send_close(sk, 0);
112 dccp_set_state(sk, DCCP_CLOSING);
116 /* Give waiting application a chance to read pending data */
119 dccp_set_state(sk, DCCP_PASSIVE_CLOSEREQ);
121 case DCCP_PASSIVE_CLOSEREQ:
122 sk_wake_async(sk, SOCK_WAKE_WAITD, POLL_HUP);
127 static u16 dccp_reset_code_convert(const u8 code)
129 const u16 error_code[] = {
130 [DCCP_RESET_CODE_CLOSED] = 0, /* normal termination */
131 [DCCP_RESET_CODE_UNSPECIFIED] = 0, /* nothing known */
132 [DCCP_RESET_CODE_ABORTED] = ECONNRESET,
134 [DCCP_RESET_CODE_NO_CONNECTION] = ECONNREFUSED,
135 [DCCP_RESET_CODE_CONNECTION_REFUSED] = ECONNREFUSED,
136 [DCCP_RESET_CODE_TOO_BUSY] = EUSERS,
137 [DCCP_RESET_CODE_AGGRESSION_PENALTY] = EDQUOT,
139 [DCCP_RESET_CODE_PACKET_ERROR] = ENOMSG,
140 [DCCP_RESET_CODE_BAD_INIT_COOKIE] = EBADR,
141 [DCCP_RESET_CODE_BAD_SERVICE_CODE] = EBADRQC,
142 [DCCP_RESET_CODE_OPTION_ERROR] = EILSEQ,
143 [DCCP_RESET_CODE_MANDATORY_ERROR] = EOPNOTSUPP,
146 return code >= DCCP_MAX_RESET_CODES ? 0 : error_code[code];
149 static void dccp_rcv_reset(struct sock *sk, struct sk_buff *skb)
151 u16 err = dccp_reset_code_convert(dccp_hdr_reset(skb)->dccph_reset_code);
155 /* Queue the equivalent of TCP fin so that dccp_recvmsg exits the loop */
158 if (err && !sock_flag(sk, SOCK_DEAD))
159 sk_wake_async(sk, SOCK_WAKE_IO, POLL_ERR);
160 dccp_time_wait(sk, DCCP_TIME_WAIT, 0);
163 static void dccp_handle_ackvec_processing(struct sock *sk, struct sk_buff *skb)
165 struct dccp_ackvec *av = dccp_sk(sk)->dccps_hc_rx_ackvec;
169 if (DCCP_SKB_CB(skb)->dccpd_ack_seq != DCCP_PKT_WITHOUT_ACK_SEQ)
170 dccp_ackvec_clear_state(av, DCCP_SKB_CB(skb)->dccpd_ack_seq);
171 dccp_ackvec_input(av, skb);
174 static void dccp_deliver_input_to_ccids(struct sock *sk, struct sk_buff *skb)
176 const struct dccp_sock *dp = dccp_sk(sk);
178 /* Don't deliver to RX CCID when node has shut down read end. */
179 if (!(sk->sk_shutdown & RCV_SHUTDOWN))
180 ccid_hc_rx_packet_recv(dp->dccps_hc_rx_ccid, sk, skb);
182 * Until the TX queue has been drained, we can not honour SHUT_WR, since
183 * we need received feedback as input to adjust congestion control.
185 if (sk->sk_write_queue.qlen > 0 || !(sk->sk_shutdown & SEND_SHUTDOWN))
186 ccid_hc_tx_packet_recv(dp->dccps_hc_tx_ccid, sk, skb);
189 static int dccp_check_seqno(struct sock *sk, struct sk_buff *skb)
191 const struct dccp_hdr *dh = dccp_hdr(skb);
192 struct dccp_sock *dp = dccp_sk(sk);
193 u64 lswl, lawl, seqno = DCCP_SKB_CB(skb)->dccpd_seq,
194 ackno = DCCP_SKB_CB(skb)->dccpd_ack_seq;
197 * Step 5: Prepare sequence numbers for Sync
198 * If P.type == Sync or P.type == SyncAck,
199 * If S.AWL <= P.ackno <= S.AWH and P.seqno >= S.SWL,
200 * / * P is valid, so update sequence number variables
201 * accordingly. After this update, P will pass the tests
202 * in Step 6. A SyncAck is generated if necessary in
204 * Update S.GSR, S.SWL, S.SWH
206 * Drop packet and return
208 if (dh->dccph_type == DCCP_PKT_SYNC ||
209 dh->dccph_type == DCCP_PKT_SYNCACK) {
210 if (between48(ackno, dp->dccps_awl, dp->dccps_awh) &&
211 dccp_delta_seqno(dp->dccps_swl, seqno) >= 0)
212 dccp_update_gsr(sk, seqno);
218 * Step 6: Check sequence numbers
219 * Let LSWL = S.SWL and LAWL = S.AWL
220 * If P.type == CloseReq or P.type == Close or P.type == Reset,
221 * LSWL := S.GSR + 1, LAWL := S.GAR
222 * If LSWL <= P.seqno <= S.SWH
223 * and (P.ackno does not exist or LAWL <= P.ackno <= S.AWH),
224 * Update S.GSR, S.SWL, S.SWH
228 lswl = dp->dccps_swl;
229 lawl = dp->dccps_awl;
231 if (dh->dccph_type == DCCP_PKT_CLOSEREQ ||
232 dh->dccph_type == DCCP_PKT_CLOSE ||
233 dh->dccph_type == DCCP_PKT_RESET) {
234 lswl = ADD48(dp->dccps_gsr, 1);
235 lawl = dp->dccps_gar;
238 if (between48(seqno, lswl, dp->dccps_swh) &&
239 (ackno == DCCP_PKT_WITHOUT_ACK_SEQ ||
240 between48(ackno, lawl, dp->dccps_awh))) {
241 dccp_update_gsr(sk, seqno);
243 if (dh->dccph_type != DCCP_PKT_SYNC &&
244 (ackno != DCCP_PKT_WITHOUT_ACK_SEQ))
245 dp->dccps_gar = ackno;
247 unsigned long now = jiffies;
249 * Step 6: Check sequence numbers
251 * If P.type == Reset,
252 * Send Sync packet acknowledging S.GSR
254 * Send Sync packet acknowledging P.seqno
255 * Drop packet and return
257 * These Syncs are rate-limited as per RFC 4340, 7.5.4:
258 * at most 1 / (dccp_sync_rate_limit * HZ) Syncs per second.
260 if (time_before(now, (dp->dccps_rate_last +
261 sysctl_dccp_sync_ratelimit)))
264 DCCP_WARN("Step 6 failed for %s packet, "
265 "(LSWL(%llu) <= P.seqno(%llu) <= S.SWH(%llu)) and "
266 "(P.ackno %s or LAWL(%llu) <= P.ackno(%llu) <= S.AWH(%llu), "
267 "sending SYNC...\n", dccp_packet_name(dh->dccph_type),
268 (unsigned long long) lswl, (unsigned long long) seqno,
269 (unsigned long long) dp->dccps_swh,
270 (ackno == DCCP_PKT_WITHOUT_ACK_SEQ) ? "doesn't exist"
272 (unsigned long long) lawl, (unsigned long long) ackno,
273 (unsigned long long) dp->dccps_awh);
275 dp->dccps_rate_last = now;
277 if (dh->dccph_type == DCCP_PKT_RESET)
278 seqno = dp->dccps_gsr;
279 dccp_send_sync(sk, seqno, DCCP_PKT_SYNC);
286 static int __dccp_rcv_established(struct sock *sk, struct sk_buff *skb,
287 const struct dccp_hdr *dh, const unsigned len)
289 struct dccp_sock *dp = dccp_sk(sk);
291 switch (dccp_hdr(skb)->dccph_type) {
292 case DCCP_PKT_DATAACK:
295 * FIXME: schedule DATA_DROPPED (RFC 4340, 11.7.2) if and when
296 * - sk_shutdown == RCV_SHUTDOWN, use Code 1, "Not Listening"
297 * - sk_receive_queue is full, use Code 2, "Receive Buffer"
299 dccp_enqueue_skb(sk, skb);
305 * Step 9: Process Reset
306 * If P.type == Reset,
307 * Tear down connection
308 * S.state := TIMEWAIT
310 * Drop packet and return
312 dccp_rcv_reset(sk, skb);
314 case DCCP_PKT_CLOSEREQ:
315 if (dccp_rcv_closereq(sk, skb))
319 if (dccp_rcv_close(sk, skb))
322 case DCCP_PKT_REQUEST:
324 * or (S.is_server and P.type == Response)
325 * or (S.is_client and P.type == Request)
326 * or (S.state >= OPEN and P.type == Request
327 * and P.seqno >= S.OSR)
328 * or (S.state >= OPEN and P.type == Response
329 * and P.seqno >= S.OSR)
330 * or (S.state == RESPOND and P.type == Data),
331 * Send Sync packet acknowledging P.seqno
332 * Drop packet and return
334 if (dp->dccps_role != DCCP_ROLE_LISTEN)
337 case DCCP_PKT_RESPONSE:
338 if (dp->dccps_role != DCCP_ROLE_CLIENT)
341 if (dccp_delta_seqno(dp->dccps_osr,
342 DCCP_SKB_CB(skb)->dccpd_seq) >= 0) {
344 dccp_send_sync(sk, DCCP_SKB_CB(skb)->dccpd_seq,
349 dccp_send_sync(sk, DCCP_SKB_CB(skb)->dccpd_seq,
352 * From RFC 4340, sec. 5.7
354 * As with DCCP-Ack packets, DCCP-Sync and DCCP-SyncAck packets
355 * MAY have non-zero-length application data areas, whose
356 * contents receivers MUST ignore.
361 DCCP_INC_STATS_BH(DCCP_MIB_INERRS);
367 int dccp_rcv_established(struct sock *sk, struct sk_buff *skb,
368 const struct dccp_hdr *dh, const unsigned len)
370 if (dccp_check_seqno(sk, skb))
373 if (dccp_parse_options(sk, NULL, skb))
376 dccp_handle_ackvec_processing(sk, skb);
377 dccp_deliver_input_to_ccids(sk, skb);
379 return __dccp_rcv_established(sk, skb, dh, len);
385 EXPORT_SYMBOL_GPL(dccp_rcv_established);
387 static int dccp_rcv_request_sent_state_process(struct sock *sk,
389 const struct dccp_hdr *dh,
393 * Step 4: Prepare sequence numbers in REQUEST
394 * If S.state == REQUEST,
395 * If (P.type == Response or P.type == Reset)
396 * and S.AWL <= P.ackno <= S.AWH,
397 * / * Set sequence number variables corresponding to the
398 * other endpoint, so P will pass the tests in Step 6 * /
399 * Set S.GSR, S.ISR, S.SWL, S.SWH
400 * / * Response processing continues in Step 10; Reset
401 * processing continues in Step 9 * /
403 if (dh->dccph_type == DCCP_PKT_RESPONSE) {
404 const struct inet_connection_sock *icsk = inet_csk(sk);
405 struct dccp_sock *dp = dccp_sk(sk);
406 long tstamp = dccp_timestamp();
408 if (!between48(DCCP_SKB_CB(skb)->dccpd_ack_seq,
409 dp->dccps_awl, dp->dccps_awh)) {
410 dccp_pr_debug("invalid ackno: S.AWL=%llu, "
411 "P.ackno=%llu, S.AWH=%llu\n",
412 (unsigned long long)dp->dccps_awl,
413 (unsigned long long)DCCP_SKB_CB(skb)->dccpd_ack_seq,
414 (unsigned long long)dp->dccps_awh);
415 goto out_invalid_packet;
419 * If option processing (Step 8) failed, return 1 here so that
420 * dccp_v4_do_rcv() sends a Reset. The Reset code depends on
421 * the option type and is set in dccp_parse_options().
423 if (dccp_parse_options(sk, NULL, skb))
426 /* Obtain usec RTT sample from SYN exchange (used by TFRC). */
427 if (likely(dp->dccps_options_received.dccpor_timestamp_echo))
428 dp->dccps_syn_rtt = dccp_sample_rtt(sk, 10 * (tstamp -
429 dp->dccps_options_received.dccpor_timestamp_echo));
431 /* Stop the REQUEST timer */
432 inet_csk_clear_xmit_timer(sk, ICSK_TIME_RETRANS);
433 WARN_ON(sk->sk_send_head == NULL);
434 kfree_skb(sk->sk_send_head);
435 sk->sk_send_head = NULL;
438 * Set ISR, GSR from packet. ISS was set in dccp_v{4,6}_connect
439 * and GSS in dccp_transmit_skb(). Setting AWL/AWH and SWL/SWH
440 * is done as part of activating the feature values below, since
441 * these settings depend on the local/remote Sequence Window
442 * features, which were undefined or not confirmed until now.
444 dp->dccps_gsr = dp->dccps_isr = DCCP_SKB_CB(skb)->dccpd_seq;
446 dccp_sync_mss(sk, icsk->icsk_pmtu_cookie);
449 * Step 10: Process REQUEST state (second part)
450 * If S.state == REQUEST,
451 * / * If we get here, P is a valid Response from the
452 * server (see Step 4), and we should move to
453 * PARTOPEN state. PARTOPEN means send an Ack,
454 * don't send Data packets, retransmit Acks
455 * periodically, and always include any Init Cookie
456 * from the Response * /
457 * S.state := PARTOPEN
459 * Continue with S.state == PARTOPEN
460 * / * Step 12 will send the Ack completing the
461 * three-way handshake * /
463 dccp_set_state(sk, DCCP_PARTOPEN);
466 * If feature negotiation was successful, activate features now;
467 * an activation failure means that this host could not activate
468 * one ore more features (e.g. insufficient memory), which would
469 * leave at least one feature in an undefined state.
471 if (dccp_feat_activate_values(sk, &dp->dccps_featneg))
472 goto unable_to_proceed;
474 /* Make sure socket is routed, for correct metrics. */
475 icsk->icsk_af_ops->rebuild_header(sk);
477 if (!sock_flag(sk, SOCK_DEAD)) {
478 sk->sk_state_change(sk);
479 sk_wake_async(sk, SOCK_WAKE_IO, POLL_OUT);
482 if (sk->sk_write_pending || icsk->icsk_ack.pingpong ||
483 icsk->icsk_accept_queue.rskq_defer_accept) {
484 /* Save one ACK. Data will be ready after
485 * several ticks, if write_pending is set.
487 * It may be deleted, but with this feature tcpdumps
488 * look so _wonderfully_ clever, that I was not able
489 * to stand against the temptation 8) --ANK
492 * OK, in DCCP we can as well do a similar trick, its
493 * even in the draft, but there is no need for us to
494 * schedule an ack here, as dccp_sendmsg does this for
495 * us, also stated in the draft. -acme
505 /* dccp_v4_do_rcv will send a reset */
506 DCCP_SKB_CB(skb)->dccpd_reset_code = DCCP_RESET_CODE_PACKET_ERROR;
510 DCCP_SKB_CB(skb)->dccpd_reset_code = DCCP_RESET_CODE_ABORTED;
512 * We mark this socket as no longer usable, so that the loop in
513 * dccp_sendmsg() terminates and the application gets notified.
515 dccp_set_state(sk, DCCP_CLOSED);
520 static int dccp_rcv_respond_partopen_state_process(struct sock *sk,
522 const struct dccp_hdr *dh,
525 struct dccp_sock *dp = dccp_sk(sk);
526 u32 sample = dp->dccps_options_received.dccpor_timestamp_echo;
529 switch (dh->dccph_type) {
531 inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK);
534 if (sk->sk_state == DCCP_RESPOND)
536 case DCCP_PKT_DATAACK:
539 * FIXME: we should be reseting the PARTOPEN (DELACK) timer
540 * here but only if we haven't used the DELACK timer for
541 * something else, like sending a delayed ack for a TIMESTAMP
542 * echo, etc, for now were not clearing it, sending an extra
543 * ACK when there is nothing else to do in DELACK is not a big
547 /* Stop the PARTOPEN timer */
548 if (sk->sk_state == DCCP_PARTOPEN)
549 inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK);
551 /* Obtain usec RTT sample from SYN exchange (used by TFRC). */
552 if (likely(sample)) {
553 long delta = dccp_timestamp() - sample;
555 dp->dccps_syn_rtt = dccp_sample_rtt(sk, 10 * delta);
558 dp->dccps_osr = DCCP_SKB_CB(skb)->dccpd_seq;
559 dccp_set_state(sk, DCCP_OPEN);
561 if (dh->dccph_type == DCCP_PKT_DATAACK ||
562 dh->dccph_type == DCCP_PKT_DATA) {
563 __dccp_rcv_established(sk, skb, dh, len);
564 queued = 1; /* packet was queued
565 (by __dccp_rcv_established) */
573 int dccp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
574 struct dccp_hdr *dh, unsigned len)
576 struct dccp_sock *dp = dccp_sk(sk);
577 struct dccp_skb_cb *dcb = DCCP_SKB_CB(skb);
578 const int old_state = sk->sk_state;
582 * Step 3: Process LISTEN state
584 * If S.state == LISTEN,
585 * If P.type == Request or P contains a valid Init Cookie option,
586 * (* Must scan the packet's options to check for Init
587 * Cookies. Only Init Cookies are processed here,
588 * however; other options are processed in Step 8. This
589 * scan need only be performed if the endpoint uses Init
591 * (* Generate a new socket and switch to that socket *)
592 * Set S := new socket for this port pair
594 * Choose S.ISS (initial seqno) or set from Init Cookies
595 * Initialize S.GAR := S.ISS
596 * Set S.ISR, S.GSR, S.SWL, S.SWH from packet or Init
597 * Cookies Continue with S.state == RESPOND
598 * (* A Response packet will be generated in Step 11 *)
600 * Generate Reset(No Connection) unless P.type == Reset
601 * Drop packet and return
603 if (sk->sk_state == DCCP_LISTEN) {
604 if (dh->dccph_type == DCCP_PKT_REQUEST) {
605 if (inet_csk(sk)->icsk_af_ops->conn_request(sk,
610 if (dh->dccph_type == DCCP_PKT_RESET)
613 /* Caller (dccp_v4_do_rcv) will send Reset */
614 dcb->dccpd_reset_code = DCCP_RESET_CODE_NO_CONNECTION;
618 if (sk->sk_state != DCCP_REQUESTING && sk->sk_state != DCCP_RESPOND) {
619 if (dccp_check_seqno(sk, skb))
623 * Step 8: Process options and mark acknowledgeable
625 if (dccp_parse_options(sk, NULL, skb))
628 dccp_handle_ackvec_processing(sk, skb);
629 dccp_deliver_input_to_ccids(sk, skb);
633 * Step 9: Process Reset
634 * If P.type == Reset,
635 * Tear down connection
636 * S.state := TIMEWAIT
638 * Drop packet and return
640 if (dh->dccph_type == DCCP_PKT_RESET) {
641 dccp_rcv_reset(sk, skb);
644 * Step 7: Check for unexpected packet types
645 * If (S.is_server and P.type == Response)
646 * or (S.is_client and P.type == Request)
647 * or (S.state == RESPOND and P.type == Data),
648 * Send Sync packet acknowledging P.seqno
649 * Drop packet and return
651 } else if ((dp->dccps_role != DCCP_ROLE_CLIENT &&
652 dh->dccph_type == DCCP_PKT_RESPONSE) ||
653 (dp->dccps_role == DCCP_ROLE_CLIENT &&
654 dh->dccph_type == DCCP_PKT_REQUEST) ||
655 (sk->sk_state == DCCP_RESPOND &&
656 dh->dccph_type == DCCP_PKT_DATA)) {
657 dccp_send_sync(sk, dcb->dccpd_seq, DCCP_PKT_SYNC);
659 } else if (dh->dccph_type == DCCP_PKT_CLOSEREQ) {
660 if (dccp_rcv_closereq(sk, skb))
663 } else if (dh->dccph_type == DCCP_PKT_CLOSE) {
664 if (dccp_rcv_close(sk, skb))
669 switch (sk->sk_state) {
671 dcb->dccpd_reset_code = DCCP_RESET_CODE_NO_CONNECTION;
674 case DCCP_REQUESTING:
675 queued = dccp_rcv_request_sent_state_process(sk, skb, dh, len);
684 queued = dccp_rcv_respond_partopen_state_process(sk, skb,
689 if (dh->dccph_type == DCCP_PKT_ACK ||
690 dh->dccph_type == DCCP_PKT_DATAACK) {
693 sk->sk_state_change(sk);
694 sk_wake_async(sk, SOCK_WAKE_IO, POLL_OUT);
697 } else if (unlikely(dh->dccph_type == DCCP_PKT_SYNC)) {
698 dccp_send_sync(sk, dcb->dccpd_seq, DCCP_PKT_SYNCACK);
709 EXPORT_SYMBOL_GPL(dccp_rcv_state_process);
712 * dccp_sample_rtt - Validate and finalise computation of RTT sample
713 * @delta: number of microseconds between packet and acknowledgment
714 * The routine is kept generic to work in different contexts. It should be
715 * called immediately when the ACK used for the RTT sample arrives.
717 u32 dccp_sample_rtt(struct sock *sk, long delta)
719 /* dccpor_elapsed_time is either zeroed out or set and > 0 */
720 delta -= dccp_sk(sk)->dccps_options_received.dccpor_elapsed_time * 10;
722 if (unlikely(delta <= 0)) {
723 DCCP_WARN("unusable RTT sample %ld, using min\n", delta);
724 return DCCP_SANE_RTT_MIN;
726 if (unlikely(delta > DCCP_SANE_RTT_MAX)) {
727 DCCP_WARN("RTT sample %ld too large, using max\n", delta);
728 return DCCP_SANE_RTT_MAX;