2 * INET An implementation of the TCP/IP protocol suite for the LINUX
3 * operating system. INET is implemented using the BSD Socket
4 * interface as the means of communication with the user level.
6 * Implementation of the Transmission Control Protocol(TCP).
9 * Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
10 * Mark Evans, <evansmp@uhura.aston.ac.uk>
11 * Corey Minyard <wf-rch!minyard@relay.EU.net>
12 * Florian La Roche, <flla@stud.uni-sb.de>
13 * Charles Hedrick, <hedrick@klinzhai.rutgers.edu>
14 * Linus Torvalds, <torvalds@cs.helsinki.fi>
15 * Alan Cox, <gw4pts@gw4pts.ampr.org>
16 * Matthew Dillon, <dillon@apollo.west.oic.com>
17 * Arnt Gulbrandsen, <agulbra@nvg.unit.no>
18 * Jorge Cwik, <jorge@laser.satlink.net>
21 #include <linux/module.h>
22 #include <linux/gfp.h>
25 int sysctl_tcp_thin_linear_timeouts __read_mostly
;
28 * tcp_write_err() - close socket and save error info
29 * @sk: The socket the error has appeared on.
31 * Returns: Nothing (void)
34 static void tcp_write_err(struct sock
*sk
)
36 sk
->sk_err
= sk
->sk_err_soft
? : ETIMEDOUT
;
37 sk
->sk_error_report(sk
);
40 __NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPABORTONTIMEOUT
);
44 * tcp_out_of_resources() - Close socket if out of resources
45 * @sk: pointer to current socket
46 * @do_reset: send a last packet with reset flag
48 * Do not allow orphaned sockets to eat all our resources.
49 * This is direct violation of TCP specs, but it is required
50 * to prevent DoS attacks. It is called when a retransmission timeout
51 * or zero probe timeout occurs on orphaned socket.
53 * Criteria is still not confirmed experimentally and may change.
54 * We kill the socket, if:
55 * 1. If number of orphaned sockets exceeds an administratively configured
57 * 2. If we have strong memory pressure.
59 static int tcp_out_of_resources(struct sock
*sk
, bool do_reset
)
61 struct tcp_sock
*tp
= tcp_sk(sk
);
64 /* If peer does not open window for long time, or did not transmit
65 * anything for long time, penalize it. */
66 if ((s32
)(tcp_jiffies32
- tp
->lsndtime
) > 2*TCP_RTO_MAX
|| !do_reset
)
69 /* If some dubious ICMP arrived, penalize even more. */
73 if (tcp_check_oom(sk
, shift
)) {
74 /* Catch exceptional cases, when connection requires reset.
75 * 1. Last segment was sent recently. */
76 if ((s32
)(tcp_jiffies32
- tp
->lsndtime
) <= TCP_TIMEWAIT_LEN
||
77 /* 2. Window is closed. */
78 (!tp
->snd_wnd
&& !tp
->packets_out
))
81 tcp_send_active_reset(sk
, GFP_ATOMIC
);
83 __NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPABORTONMEMORY
);
90 * tcp_orphan_retries() - Returns maximal number of retries on an orphaned socket
91 * @sk: Pointer to the current socket.
92 * @alive: bool, socket alive state
94 static int tcp_orphan_retries(struct sock
*sk
, bool alive
)
96 int retries
= sock_net(sk
)->ipv4
.sysctl_tcp_orphan_retries
; /* May be zero. */
98 /* We know from an ICMP that something is wrong. */
99 if (sk
->sk_err_soft
&& !alive
)
102 /* However, if socket sent something recently, select some safe
103 * number of retries. 8 corresponds to >100 seconds with minimal
105 if (retries
== 0 && alive
)
110 static void tcp_mtu_probing(struct inet_connection_sock
*icsk
, struct sock
*sk
)
112 struct net
*net
= sock_net(sk
);
114 /* Black hole detection */
115 if (net
->ipv4
.sysctl_tcp_mtu_probing
) {
116 if (!icsk
->icsk_mtup
.enabled
) {
117 icsk
->icsk_mtup
.enabled
= 1;
118 icsk
->icsk_mtup
.probe_timestamp
= tcp_jiffies32
;
119 tcp_sync_mss(sk
, icsk
->icsk_pmtu_cookie
);
121 struct net
*net
= sock_net(sk
);
122 struct tcp_sock
*tp
= tcp_sk(sk
);
125 mss
= tcp_mtu_to_mss(sk
, icsk
->icsk_mtup
.search_low
) >> 1;
126 mss
= min(net
->ipv4
.sysctl_tcp_base_mss
, mss
);
127 mss
= max(mss
, 68 - tp
->tcp_header_len
);
128 icsk
->icsk_mtup
.search_low
= tcp_mss_to_mtu(sk
, mss
);
129 tcp_sync_mss(sk
, icsk
->icsk_pmtu_cookie
);
136 * retransmits_timed_out() - returns true if this connection has timed out
137 * @sk: The current socket
138 * @boundary: max number of retransmissions
139 * @timeout: A custom timeout value.
140 * If set to 0 the default timeout is calculated and used.
141 * Using TCP_RTO_MIN and the number of unsuccessful retransmits.
143 * The default "timeout" value this function can calculate and use
144 * is equivalent to the timeout of a TCP Connection
145 * after "boundary" unsuccessful, exponentially backed-off
146 * retransmissions with an initial RTO of TCP_RTO_MIN.
148 static bool retransmits_timed_out(struct sock
*sk
,
149 unsigned int boundary
,
150 unsigned int timeout
)
152 const unsigned int rto_base
= TCP_RTO_MIN
;
153 unsigned int linear_backoff_thresh
, start_ts
;
155 if (!inet_csk(sk
)->icsk_retransmits
)
158 start_ts
= tcp_sk(sk
)->retrans_stamp
;
159 if (unlikely(!start_ts
))
160 start_ts
= tcp_skb_timestamp(tcp_write_queue_head(sk
));
162 if (likely(timeout
== 0)) {
163 linear_backoff_thresh
= ilog2(TCP_RTO_MAX
/rto_base
);
165 if (boundary
<= linear_backoff_thresh
)
166 timeout
= ((2 << boundary
) - 1) * rto_base
;
168 timeout
= ((2 << linear_backoff_thresh
) - 1) * rto_base
+
169 (boundary
- linear_backoff_thresh
) * TCP_RTO_MAX
;
171 return (tcp_time_stamp(tcp_sk(sk
)) - start_ts
) >= jiffies_to_msecs(timeout
);
174 /* A write timeout has occurred. Process the after effects. */
175 static int tcp_write_timeout(struct sock
*sk
)
177 struct inet_connection_sock
*icsk
= inet_csk(sk
);
178 struct tcp_sock
*tp
= tcp_sk(sk
);
179 struct net
*net
= sock_net(sk
);
180 bool expired
, do_reset
;
183 if ((1 << sk
->sk_state
) & (TCPF_SYN_SENT
| TCPF_SYN_RECV
)) {
184 if (icsk
->icsk_retransmits
) {
185 dst_negative_advice(sk
);
186 if (tp
->syn_fastopen
|| tp
->syn_data
)
187 tcp_fastopen_cache_set(sk
, 0, NULL
, true, 0);
188 if (tp
->syn_data
&& icsk
->icsk_retransmits
== 1)
189 NET_INC_STATS(sock_net(sk
),
190 LINUX_MIB_TCPFASTOPENACTIVEFAIL
);
191 } else if (!tp
->syn_data
&& !tp
->syn_fastopen
) {
192 sk_rethink_txhash(sk
);
194 retry_until
= icsk
->icsk_syn_retries
? : net
->ipv4
.sysctl_tcp_syn_retries
;
195 expired
= icsk
->icsk_retransmits
>= retry_until
;
197 if (retransmits_timed_out(sk
, net
->ipv4
.sysctl_tcp_retries1
, 0)) {
198 /* Some middle-boxes may black-hole Fast Open _after_
199 * the handshake. Therefore we conservatively disable
200 * Fast Open on this path on recurring timeouts after
201 * successful Fast Open.
203 if (tp
->syn_data_acked
) {
204 tcp_fastopen_cache_set(sk
, 0, NULL
, true, 0);
205 if (icsk
->icsk_retransmits
== net
->ipv4
.sysctl_tcp_retries1
)
206 NET_INC_STATS(sock_net(sk
),
207 LINUX_MIB_TCPFASTOPENACTIVEFAIL
);
209 /* Black hole detection */
210 tcp_mtu_probing(icsk
, sk
);
212 dst_negative_advice(sk
);
214 sk_rethink_txhash(sk
);
217 retry_until
= net
->ipv4
.sysctl_tcp_retries2
;
218 if (sock_flag(sk
, SOCK_DEAD
)) {
219 const bool alive
= icsk
->icsk_rto
< TCP_RTO_MAX
;
221 retry_until
= tcp_orphan_retries(sk
, alive
);
223 !retransmits_timed_out(sk
, retry_until
, 0);
225 if (tcp_out_of_resources(sk
, do_reset
))
228 expired
= retransmits_timed_out(sk
, retry_until
,
229 icsk
->icsk_user_timeout
);
232 /* Has it gone just too far? */
239 /* Called with BH disabled */
240 void tcp_delack_timer_handler(struct sock
*sk
)
242 struct inet_connection_sock
*icsk
= inet_csk(sk
);
244 sk_mem_reclaim_partial(sk
);
246 if (((1 << sk
->sk_state
) & (TCPF_CLOSE
| TCPF_LISTEN
)) ||
247 !(icsk
->icsk_ack
.pending
& ICSK_ACK_TIMER
))
250 if (time_after(icsk
->icsk_ack
.timeout
, jiffies
)) {
251 sk_reset_timer(sk
, &icsk
->icsk_delack_timer
, icsk
->icsk_ack
.timeout
);
254 icsk
->icsk_ack
.pending
&= ~ICSK_ACK_TIMER
;
256 if (inet_csk_ack_scheduled(sk
)) {
257 if (!icsk
->icsk_ack
.pingpong
) {
258 /* Delayed ACK missed: inflate ATO. */
259 icsk
->icsk_ack
.ato
= min(icsk
->icsk_ack
.ato
<< 1, icsk
->icsk_rto
);
261 /* Delayed ACK missed: leave pingpong mode and
264 icsk
->icsk_ack
.pingpong
= 0;
265 icsk
->icsk_ack
.ato
= TCP_ATO_MIN
;
268 __NET_INC_STATS(sock_net(sk
), LINUX_MIB_DELAYEDACKS
);
272 if (tcp_under_memory_pressure(sk
))
278 * tcp_delack_timer() - The TCP delayed ACK timeout handler
279 * @data: Pointer to the current socket. (gets casted to struct sock *)
281 * This function gets (indirectly) called when the kernel timer for a TCP packet
282 * of this socket expires. Calls tcp_delack_timer_handler() to do the actual work.
284 * Returns: Nothing (void)
286 static void tcp_delack_timer(unsigned long data
)
288 struct sock
*sk
= (struct sock
*)data
;
291 if (!sock_owned_by_user(sk
)) {
292 tcp_delack_timer_handler(sk
);
294 inet_csk(sk
)->icsk_ack
.blocked
= 1;
295 __NET_INC_STATS(sock_net(sk
), LINUX_MIB_DELAYEDACKLOCKED
);
296 /* deleguate our work to tcp_release_cb() */
297 if (!test_and_set_bit(TCP_DELACK_TIMER_DEFERRED
, &sk
->sk_tsq_flags
))
304 static void tcp_probe_timer(struct sock
*sk
)
306 struct inet_connection_sock
*icsk
= inet_csk(sk
);
307 struct tcp_sock
*tp
= tcp_sk(sk
);
311 if (tp
->packets_out
|| !tcp_send_head(sk
)) {
312 icsk
->icsk_probes_out
= 0;
316 /* RFC 1122 4.2.2.17 requires the sender to stay open indefinitely as
317 * long as the receiver continues to respond probes. We support this by
318 * default and reset icsk_probes_out with incoming ACKs. But if the
319 * socket is orphaned or the user specifies TCP_USER_TIMEOUT, we
320 * kill the socket when the retry count and the time exceeds the
321 * corresponding system limit. We also implement similar policy when
322 * we use RTO to probe window in tcp_retransmit_timer().
324 start_ts
= tcp_skb_timestamp(tcp_send_head(sk
));
326 tcp_send_head(sk
)->skb_mstamp
= tp
->tcp_mstamp
;
327 else if (icsk
->icsk_user_timeout
&&
328 (s32
)(tcp_time_stamp(tp
) - start_ts
) >
329 jiffies_to_msecs(icsk
->icsk_user_timeout
))
332 max_probes
= sock_net(sk
)->ipv4
.sysctl_tcp_retries2
;
333 if (sock_flag(sk
, SOCK_DEAD
)) {
334 const bool alive
= inet_csk_rto_backoff(icsk
, TCP_RTO_MAX
) < TCP_RTO_MAX
;
336 max_probes
= tcp_orphan_retries(sk
, alive
);
337 if (!alive
&& icsk
->icsk_backoff
>= max_probes
)
339 if (tcp_out_of_resources(sk
, true))
343 if (icsk
->icsk_probes_out
> max_probes
) {
344 abort
: tcp_write_err(sk
);
346 /* Only send another probe if we didn't close things up. */
352 * Timer for Fast Open socket to retransmit SYNACK. Note that the
353 * sk here is the child socket, not the parent (listener) socket.
355 static void tcp_fastopen_synack_timer(struct sock
*sk
)
357 struct inet_connection_sock
*icsk
= inet_csk(sk
);
358 int max_retries
= icsk
->icsk_syn_retries
? :
359 sock_net(sk
)->ipv4
.sysctl_tcp_synack_retries
+ 1; /* add one more retry for fastopen */
360 struct request_sock
*req
;
362 req
= tcp_sk(sk
)->fastopen_rsk
;
363 req
->rsk_ops
->syn_ack_timeout(req
);
365 if (req
->num_timeout
>= max_retries
) {
369 /* XXX (TFO) - Unlike regular SYN-ACK retransmit, we ignore error
370 * returned from rtx_syn_ack() to make it more persistent like
371 * regular retransmit because if the child socket has been accepted
372 * it's not good to give up too easily.
374 inet_rtx_syn_ack(sk
, req
);
376 icsk
->icsk_retransmits
++;
377 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
,
378 TCP_TIMEOUT_INIT
<< req
->num_timeout
, TCP_RTO_MAX
);
383 * tcp_retransmit_timer() - The TCP retransmit timeout handler
384 * @sk: Pointer to the current socket.
386 * This function gets called when the kernel timer for a TCP packet
387 * of this socket expires.
389 * It handles retransmission, timer adjustment and other necesarry measures.
391 * Returns: Nothing (void)
393 void tcp_retransmit_timer(struct sock
*sk
)
395 struct tcp_sock
*tp
= tcp_sk(sk
);
396 struct net
*net
= sock_net(sk
);
397 struct inet_connection_sock
*icsk
= inet_csk(sk
);
399 if (tp
->fastopen_rsk
) {
400 WARN_ON_ONCE(sk
->sk_state
!= TCP_SYN_RECV
&&
401 sk
->sk_state
!= TCP_FIN_WAIT1
);
402 tcp_fastopen_synack_timer(sk
);
403 /* Before we receive ACK to our SYN-ACK don't retransmit
404 * anything else (e.g., data or FIN segments).
408 if (!tp
->packets_out
)
411 WARN_ON(tcp_write_queue_empty(sk
));
413 tp
->tlp_high_seq
= 0;
415 if (!tp
->snd_wnd
&& !sock_flag(sk
, SOCK_DEAD
) &&
416 !((1 << sk
->sk_state
) & (TCPF_SYN_SENT
| TCPF_SYN_RECV
))) {
417 /* Receiver dastardly shrinks window. Our retransmits
418 * become zero probes, but we should not timeout this
419 * connection. If the socket is an orphan, time it out,
420 * we cannot allow such beasts to hang infinitely.
422 struct inet_sock
*inet
= inet_sk(sk
);
423 if (sk
->sk_family
== AF_INET
) {
424 net_dbg_ratelimited("Peer %pI4:%u/%u unexpectedly shrunk window %u:%u (repaired)\n",
426 ntohs(inet
->inet_dport
),
428 tp
->snd_una
, tp
->snd_nxt
);
430 #if IS_ENABLED(CONFIG_IPV6)
431 else if (sk
->sk_family
== AF_INET6
) {
432 net_dbg_ratelimited("Peer %pI6:%u/%u unexpectedly shrunk window %u:%u (repaired)\n",
434 ntohs(inet
->inet_dport
),
436 tp
->snd_una
, tp
->snd_nxt
);
439 if (tcp_jiffies32
- tp
->rcv_tstamp
> TCP_RTO_MAX
) {
444 tcp_retransmit_skb(sk
, tcp_write_queue_head(sk
), 1);
446 goto out_reset_timer
;
449 if (tcp_write_timeout(sk
))
452 if (icsk
->icsk_retransmits
== 0) {
455 if (icsk
->icsk_ca_state
== TCP_CA_Recovery
) {
457 mib_idx
= LINUX_MIB_TCPSACKRECOVERYFAIL
;
459 mib_idx
= LINUX_MIB_TCPRENORECOVERYFAIL
;
460 } else if (icsk
->icsk_ca_state
== TCP_CA_Loss
) {
461 mib_idx
= LINUX_MIB_TCPLOSSFAILURES
;
462 } else if ((icsk
->icsk_ca_state
== TCP_CA_Disorder
) ||
465 mib_idx
= LINUX_MIB_TCPSACKFAILURES
;
467 mib_idx
= LINUX_MIB_TCPRENOFAILURES
;
469 mib_idx
= LINUX_MIB_TCPTIMEOUTS
;
471 __NET_INC_STATS(sock_net(sk
), mib_idx
);
476 if (tcp_retransmit_skb(sk
, tcp_write_queue_head(sk
), 1) > 0) {
477 /* Retransmission failed because of local congestion,
480 if (!icsk
->icsk_retransmits
)
481 icsk
->icsk_retransmits
= 1;
482 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
,
483 min(icsk
->icsk_rto
, TCP_RESOURCE_PROBE_INTERVAL
),
488 /* Increase the timeout each time we retransmit. Note that
489 * we do not increase the rtt estimate. rto is initialized
490 * from rtt, but increases here. Jacobson (SIGCOMM 88) suggests
491 * that doubling rto each time is the least we can get away with.
492 * In KA9Q, Karn uses this for the first few times, and then
493 * goes to quadratic. netBSD doubles, but only goes up to *64,
494 * and clamps at 1 to 64 sec afterwards. Note that 120 sec is
495 * defined in the protocol as the maximum possible RTT. I guess
496 * we'll have to use something other than TCP to talk to the
497 * University of Mars.
499 * PAWS allows us longer timeouts and large windows, so once
500 * implemented ftp to mars will work nicely. We will have to fix
501 * the 120 second clamps though!
503 icsk
->icsk_backoff
++;
504 icsk
->icsk_retransmits
++;
507 /* If stream is thin, use linear timeouts. Since 'icsk_backoff' is
508 * used to reset timer, set to 0. Recalculate 'icsk_rto' as this
509 * might be increased if the stream oscillates between thin and thick,
510 * thus the old value might already be too high compared to the value
511 * set by 'tcp_set_rto' in tcp_input.c which resets the rto without
512 * backoff. Limit to TCP_THIN_LINEAR_RETRIES before initiating
513 * exponential backoff behaviour to avoid continue hammering
514 * linear-timeout retransmissions into a black hole
516 if (sk
->sk_state
== TCP_ESTABLISHED
&&
517 (tp
->thin_lto
|| sysctl_tcp_thin_linear_timeouts
) &&
518 tcp_stream_is_thin(tp
) &&
519 icsk
->icsk_retransmits
<= TCP_THIN_LINEAR_RETRIES
) {
520 icsk
->icsk_backoff
= 0;
521 icsk
->icsk_rto
= min(__tcp_set_rto(tp
), TCP_RTO_MAX
);
523 /* Use normal (exponential) backoff */
524 icsk
->icsk_rto
= min(icsk
->icsk_rto
<< 1, TCP_RTO_MAX
);
526 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
, icsk
->icsk_rto
, TCP_RTO_MAX
);
527 if (retransmits_timed_out(sk
, net
->ipv4
.sysctl_tcp_retries1
+ 1, 0))
533 /* Called with bottom-half processing disabled.
534 Called by tcp_write_timer() */
535 void tcp_write_timer_handler(struct sock
*sk
)
537 struct inet_connection_sock
*icsk
= inet_csk(sk
);
540 if (((1 << sk
->sk_state
) & (TCPF_CLOSE
| TCPF_LISTEN
)) ||
544 if (time_after(icsk
->icsk_timeout
, jiffies
)) {
545 sk_reset_timer(sk
, &icsk
->icsk_retransmit_timer
, icsk
->icsk_timeout
);
549 tcp_mstamp_refresh(tcp_sk(sk
));
550 event
= icsk
->icsk_pending
;
553 case ICSK_TIME_REO_TIMEOUT
:
554 tcp_rack_reo_timeout(sk
);
556 case ICSK_TIME_LOSS_PROBE
:
557 tcp_send_loss_probe(sk
);
559 case ICSK_TIME_RETRANS
:
560 icsk
->icsk_pending
= 0;
561 tcp_retransmit_timer(sk
);
563 case ICSK_TIME_PROBE0
:
564 icsk
->icsk_pending
= 0;
573 static void tcp_write_timer(unsigned long data
)
575 struct sock
*sk
= (struct sock
*)data
;
578 if (!sock_owned_by_user(sk
)) {
579 tcp_write_timer_handler(sk
);
581 /* delegate our work to tcp_release_cb() */
582 if (!test_and_set_bit(TCP_WRITE_TIMER_DEFERRED
, &sk
->sk_tsq_flags
))
589 void tcp_syn_ack_timeout(const struct request_sock
*req
)
591 struct net
*net
= read_pnet(&inet_rsk(req
)->ireq_net
);
593 __NET_INC_STATS(net
, LINUX_MIB_TCPTIMEOUTS
);
595 EXPORT_SYMBOL(tcp_syn_ack_timeout
);
597 void tcp_set_keepalive(struct sock
*sk
, int val
)
599 if ((1 << sk
->sk_state
) & (TCPF_CLOSE
| TCPF_LISTEN
))
602 if (val
&& !sock_flag(sk
, SOCK_KEEPOPEN
))
603 inet_csk_reset_keepalive_timer(sk
, keepalive_time_when(tcp_sk(sk
)));
605 inet_csk_delete_keepalive_timer(sk
);
607 EXPORT_SYMBOL_GPL(tcp_set_keepalive
);
610 static void tcp_keepalive_timer (unsigned long data
)
612 struct sock
*sk
= (struct sock
*) data
;
613 struct inet_connection_sock
*icsk
= inet_csk(sk
);
614 struct tcp_sock
*tp
= tcp_sk(sk
);
617 /* Only process if socket is not in use. */
619 if (sock_owned_by_user(sk
)) {
620 /* Try again later. */
621 inet_csk_reset_keepalive_timer (sk
, HZ
/20);
625 if (sk
->sk_state
== TCP_LISTEN
) {
626 pr_err("Hmm... keepalive on a LISTEN ???\n");
630 if (sk
->sk_state
== TCP_FIN_WAIT2
&& sock_flag(sk
, SOCK_DEAD
)) {
631 if (tp
->linger2
>= 0) {
632 const int tmo
= tcp_fin_time(sk
) - TCP_TIMEWAIT_LEN
;
635 tcp_time_wait(sk
, TCP_FIN_WAIT2
, tmo
);
639 tcp_send_active_reset(sk
, GFP_ATOMIC
);
643 if (!sock_flag(sk
, SOCK_KEEPOPEN
) ||
644 ((1 << sk
->sk_state
) & (TCPF_CLOSE
| TCPF_SYN_SENT
)))
647 elapsed
= keepalive_time_when(tp
);
649 /* It is alive without keepalive 8) */
650 if (tp
->packets_out
|| tcp_send_head(sk
))
653 elapsed
= keepalive_time_elapsed(tp
);
655 if (elapsed
>= keepalive_time_when(tp
)) {
656 /* If the TCP_USER_TIMEOUT option is enabled, use that
657 * to determine when to timeout instead.
659 if ((icsk
->icsk_user_timeout
!= 0 &&
660 elapsed
>= icsk
->icsk_user_timeout
&&
661 icsk
->icsk_probes_out
> 0) ||
662 (icsk
->icsk_user_timeout
== 0 &&
663 icsk
->icsk_probes_out
>= keepalive_probes(tp
))) {
664 tcp_send_active_reset(sk
, GFP_ATOMIC
);
668 if (tcp_write_wakeup(sk
, LINUX_MIB_TCPKEEPALIVE
) <= 0) {
669 icsk
->icsk_probes_out
++;
670 elapsed
= keepalive_intvl_when(tp
);
672 /* If keepalive was lost due to local congestion,
675 elapsed
= TCP_RESOURCE_PROBE_INTERVAL
;
678 /* It is tp->rcv_tstamp + keepalive_time_when(tp) */
679 elapsed
= keepalive_time_when(tp
) - elapsed
;
685 inet_csk_reset_keepalive_timer (sk
, elapsed
);
696 void tcp_init_xmit_timers(struct sock
*sk
)
698 inet_csk_init_xmit_timers(sk
, &tcp_write_timer
, &tcp_delack_timer
,
699 &tcp_keepalive_timer
);
700 hrtimer_init(&tcp_sk(sk
)->pacing_timer
, CLOCK_MONOTONIC
,
701 HRTIMER_MODE_ABS_PINNED
);
702 tcp_sk(sk
)->pacing_timer
.function
= tcp_pace_kick
;