Line data Source code
1 : // SPDX-License-Identifier: GPL-2.0-only
2 : /*
3 : * INET An implementation of the TCP/IP protocol suite for the LINUX
4 : * operating system. INET is implemented using the BSD Socket
5 : * interface as the means of communication with the user level.
6 : *
7 : * Implementation of the Transmission Control Protocol(TCP).
8 : *
9 : * Authors: Ross Biro
10 : * Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
11 : * Mark Evans, <evansmp@uhura.aston.ac.uk>
12 : * Corey Minyard <wf-rch!minyard@relay.EU.net>
13 : * Florian La Roche, <flla@stud.uni-sb.de>
14 : * Charles Hedrick, <hedrick@klinzhai.rutgers.edu>
15 : * Linus Torvalds, <torvalds@cs.helsinki.fi>
16 : * Alan Cox, <gw4pts@gw4pts.ampr.org>
17 : * Matthew Dillon, <dillon@apollo.west.oic.com>
18 : * Arnt Gulbrandsen, <agulbra@nvg.unit.no>
19 : * Jorge Cwik, <jorge@laser.satlink.net>
20 : */
21 :
22 : #include <linux/module.h>
23 : #include <linux/gfp.h>
24 : #include <net/tcp.h>
25 :
26 0 : static u32 tcp_clamp_rto_to_user_timeout(const struct sock *sk)
27 : {
28 0 : struct inet_connection_sock *icsk = inet_csk(sk);
29 0 : u32 elapsed, start_ts;
30 0 : s32 remaining;
31 :
32 0 : start_ts = tcp_sk(sk)->retrans_stamp;
33 0 : if (!icsk->icsk_user_timeout)
34 0 : return icsk->icsk_rto;
35 0 : elapsed = tcp_time_stamp(tcp_sk(sk)) - start_ts;
36 0 : remaining = icsk->icsk_user_timeout - elapsed;
37 0 : if (remaining <= 0)
38 : return 1; /* user timeout has passed; fire ASAP */
39 :
40 0 : return min_t(u32, icsk->icsk_rto, msecs_to_jiffies(remaining));
41 : }
42 :
43 0 : u32 tcp_clamp_probe0_to_user_timeout(const struct sock *sk, u32 when)
44 : {
45 0 : struct inet_connection_sock *icsk = inet_csk(sk);
46 0 : u32 remaining;
47 0 : s32 elapsed;
48 :
49 0 : if (!icsk->icsk_user_timeout || !icsk->icsk_probes_tstamp)
50 : return when;
51 :
52 0 : elapsed = tcp_jiffies32 - icsk->icsk_probes_tstamp;
53 0 : if (unlikely(elapsed < 0))
54 0 : elapsed = 0;
55 0 : remaining = msecs_to_jiffies(icsk->icsk_user_timeout) - elapsed;
56 0 : remaining = max_t(u32, remaining, TCP_TIMEOUT_MIN);
57 :
58 0 : return min_t(u32, remaining, when);
59 : }
60 :
61 : /**
62 : * tcp_write_err() - close socket and save error info
63 : * @sk: The socket the error has appeared on.
64 : *
65 : * Returns: Nothing (void)
66 : */
67 :
68 0 : static void tcp_write_err(struct sock *sk)
69 : {
70 0 : sk->sk_err = sk->sk_err_soft ? : ETIMEDOUT;
71 0 : sk->sk_error_report(sk);
72 :
73 0 : tcp_write_queue_purge(sk);
74 0 : tcp_done(sk);
75 0 : __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTONTIMEOUT);
76 0 : }
77 :
78 : /**
79 : * tcp_out_of_resources() - Close socket if out of resources
80 : * @sk: pointer to current socket
81 : * @do_reset: send a last packet with reset flag
82 : *
83 : * Do not allow orphaned sockets to eat all our resources.
84 : * This is direct violation of TCP specs, but it is required
85 : * to prevent DoS attacks. It is called when a retransmission timeout
86 : * or zero probe timeout occurs on orphaned socket.
87 : *
88 : * Also close if our net namespace is exiting; in that case there is no
89 : * hope of ever communicating again since all netns interfaces are already
90 : * down (or about to be down), and we need to release our dst references,
91 : * which have been moved to the netns loopback interface, so the namespace
92 : * can finish exiting. This condition is only possible if we are a kernel
93 : * socket, as those do not hold references to the namespace.
94 : *
95 : * Criteria is still not confirmed experimentally and may change.
96 : * We kill the socket, if:
97 : * 1. If number of orphaned sockets exceeds an administratively configured
98 : * limit.
99 : * 2. If we have strong memory pressure.
100 : * 3. If our net namespace is exiting.
101 : */
102 0 : static int tcp_out_of_resources(struct sock *sk, bool do_reset)
103 : {
104 0 : struct tcp_sock *tp = tcp_sk(sk);
105 0 : int shift = 0;
106 :
107 : /* If peer does not open window for long time, or did not transmit
108 : * anything for long time, penalize it. */
109 0 : if ((s32)(tcp_jiffies32 - tp->lsndtime) > 2*TCP_RTO_MAX || !do_reset)
110 0 : shift++;
111 :
112 : /* If some dubious ICMP arrived, penalize even more. */
113 0 : if (sk->sk_err_soft)
114 0 : shift++;
115 :
116 0 : if (tcp_check_oom(sk, shift)) {
117 : /* Catch exceptional cases, when connection requires reset.
118 : * 1. Last segment was sent recently. */
119 0 : if ((s32)(tcp_jiffies32 - tp->lsndtime) <= TCP_TIMEWAIT_LEN ||
120 : /* 2. Window is closed. */
121 0 : (!tp->snd_wnd && !tp->packets_out))
122 : do_reset = true;
123 0 : if (do_reset)
124 0 : tcp_send_active_reset(sk, GFP_ATOMIC);
125 0 : tcp_done(sk);
126 0 : __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTONMEMORY);
127 0 : return 1;
128 : }
129 :
130 0 : if (!check_net(sock_net(sk))) {
131 : /* Not possible to send reset; just close */
132 : tcp_done(sk);
133 : return 1;
134 : }
135 :
136 : return 0;
137 : }
138 :
139 : /**
140 : * tcp_orphan_retries() - Returns maximal number of retries on an orphaned socket
141 : * @sk: Pointer to the current socket.
142 : * @alive: bool, socket alive state
143 : */
144 0 : static int tcp_orphan_retries(struct sock *sk, bool alive)
145 : {
146 0 : int retries = sock_net(sk)->ipv4.sysctl_tcp_orphan_retries; /* May be zero. */
147 :
148 : /* We know from an ICMP that something is wrong. */
149 0 : if (sk->sk_err_soft && !alive)
150 0 : retries = 0;
151 :
152 : /* However, if socket sent something recently, select some safe
153 : * number of retries. 8 corresponds to >100 seconds with minimal
154 : * RTO of 200msec. */
155 0 : if (retries == 0 && alive)
156 0 : retries = 8;
157 0 : return retries;
158 : }
159 :
160 0 : static void tcp_mtu_probing(struct inet_connection_sock *icsk, struct sock *sk)
161 : {
162 0 : const struct net *net = sock_net(sk);
163 0 : int mss;
164 :
165 : /* Black hole detection */
166 0 : if (!net->ipv4.sysctl_tcp_mtu_probing)
167 : return;
168 :
169 0 : if (!icsk->icsk_mtup.enabled) {
170 0 : icsk->icsk_mtup.enabled = 1;
171 0 : icsk->icsk_mtup.probe_timestamp = tcp_jiffies32;
172 : } else {
173 0 : mss = tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_low) >> 1;
174 0 : mss = min(net->ipv4.sysctl_tcp_base_mss, mss);
175 0 : mss = max(mss, net->ipv4.sysctl_tcp_mtu_probe_floor);
176 0 : mss = max(mss, net->ipv4.sysctl_tcp_min_snd_mss);
177 0 : icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, mss);
178 : }
179 0 : tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);
180 : }
181 :
182 0 : static unsigned int tcp_model_timeout(struct sock *sk,
183 : unsigned int boundary,
184 : unsigned int rto_base)
185 : {
186 0 : unsigned int linear_backoff_thresh, timeout;
187 :
188 0 : linear_backoff_thresh = ilog2(TCP_RTO_MAX / rto_base);
189 0 : if (boundary <= linear_backoff_thresh)
190 0 : timeout = ((2 << boundary) - 1) * rto_base;
191 : else
192 0 : timeout = ((2 << linear_backoff_thresh) - 1) * rto_base +
193 0 : (boundary - linear_backoff_thresh) * TCP_RTO_MAX;
194 0 : return jiffies_to_msecs(timeout);
195 : }
196 : /**
197 : * retransmits_timed_out() - returns true if this connection has timed out
198 : * @sk: The current socket
199 : * @boundary: max number of retransmissions
200 : * @timeout: A custom timeout value.
201 : * If set to 0 the default timeout is calculated and used.
202 : * Using TCP_RTO_MIN and the number of unsuccessful retransmits.
203 : *
204 : * The default "timeout" value this function can calculate and use
205 : * is equivalent to the timeout of a TCP Connection
206 : * after "boundary" unsuccessful, exponentially backed-off
207 : * retransmissions with an initial RTO of TCP_RTO_MIN.
208 : */
209 0 : static bool retransmits_timed_out(struct sock *sk,
210 : unsigned int boundary,
211 : unsigned int timeout)
212 : {
213 0 : unsigned int start_ts;
214 :
215 0 : if (!inet_csk(sk)->icsk_retransmits)
216 : return false;
217 :
218 0 : start_ts = tcp_sk(sk)->retrans_stamp;
219 0 : if (likely(timeout == 0)) {
220 0 : unsigned int rto_base = TCP_RTO_MIN;
221 :
222 0 : if ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV))
223 0 : rto_base = tcp_timeout_init(sk);
224 0 : timeout = tcp_model_timeout(sk, boundary, rto_base);
225 : }
226 :
227 0 : return (s32)(tcp_time_stamp(tcp_sk(sk)) - start_ts - timeout) >= 0;
228 : }
229 :
230 : /* A write timeout has occurred. Process the after effects. */
231 0 : static int tcp_write_timeout(struct sock *sk)
232 : {
233 0 : struct inet_connection_sock *icsk = inet_csk(sk);
234 0 : struct tcp_sock *tp = tcp_sk(sk);
235 0 : struct net *net = sock_net(sk);
236 0 : bool expired = false, do_reset;
237 0 : int retry_until;
238 :
239 0 : if ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV)) {
240 0 : if (icsk->icsk_retransmits)
241 0 : __dst_negative_advice(sk);
242 0 : retry_until = icsk->icsk_syn_retries ? : net->ipv4.sysctl_tcp_syn_retries;
243 0 : expired = icsk->icsk_retransmits >= retry_until;
244 : } else {
245 0 : if (retransmits_timed_out(sk, net->ipv4.sysctl_tcp_retries1, 0)) {
246 : /* Black hole detection */
247 0 : tcp_mtu_probing(icsk, sk);
248 :
249 0 : __dst_negative_advice(sk);
250 : }
251 :
252 0 : retry_until = net->ipv4.sysctl_tcp_retries2;
253 0 : if (sock_flag(sk, SOCK_DEAD)) {
254 0 : const bool alive = icsk->icsk_rto < TCP_RTO_MAX;
255 :
256 0 : retry_until = tcp_orphan_retries(sk, alive);
257 0 : do_reset = alive ||
258 0 : !retransmits_timed_out(sk, retry_until, 0);
259 :
260 0 : if (tcp_out_of_resources(sk, do_reset))
261 : return 1;
262 : }
263 : }
264 0 : if (!expired)
265 0 : expired = retransmits_timed_out(sk, retry_until,
266 : icsk->icsk_user_timeout);
267 0 : tcp_fastopen_active_detect_blackhole(sk, expired);
268 :
269 0 : if (BPF_SOCK_OPS_TEST_FLAG(tp, BPF_SOCK_OPS_RTO_CB_FLAG))
270 0 : tcp_call_bpf_3arg(sk, BPF_SOCK_OPS_RTO_CB,
271 0 : icsk->icsk_retransmits,
272 : icsk->icsk_rto, (int)expired);
273 :
274 0 : if (expired) {
275 : /* Has it gone just too far? */
276 0 : tcp_write_err(sk);
277 0 : return 1;
278 : }
279 :
280 0 : if (sk_rethink_txhash(sk)) {
281 0 : tp->timeout_rehash++;
282 0 : __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPTIMEOUTREHASH);
283 : }
284 :
285 : return 0;
286 : }
287 :
288 : /* Called with BH disabled */
289 5 : void tcp_delack_timer_handler(struct sock *sk)
290 : {
291 5 : struct inet_connection_sock *icsk = inet_csk(sk);
292 :
293 5 : sk_mem_reclaim_partial(sk);
294 :
295 5 : if (((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN)) ||
296 5 : !(icsk->icsk_ack.pending & ICSK_ACK_TIMER))
297 3 : goto out;
298 :
299 2 : if (time_after(icsk->icsk_ack.timeout, jiffies)) {
300 0 : sk_reset_timer(sk, &icsk->icsk_delack_timer, icsk->icsk_ack.timeout);
301 0 : goto out;
302 : }
303 2 : icsk->icsk_ack.pending &= ~ICSK_ACK_TIMER;
304 :
305 2 : if (inet_csk_ack_scheduled(sk)) {
306 2 : if (!inet_csk_in_pingpong_mode(sk)) {
307 : /* Delayed ACK missed: inflate ATO. */
308 0 : icsk->icsk_ack.ato = min(icsk->icsk_ack.ato << 1, icsk->icsk_rto);
309 : } else {
310 : /* Delayed ACK missed: leave pingpong mode and
311 : * deflate ATO.
312 : */
313 2 : inet_csk_exit_pingpong_mode(sk);
314 2 : icsk->icsk_ack.ato = TCP_ATO_MIN;
315 : }
316 2 : tcp_mstamp_refresh(tcp_sk(sk));
317 2 : tcp_send_ack(sk);
318 2 : __NET_INC_STATS(sock_net(sk), LINUX_MIB_DELAYEDACKS);
319 : }
320 :
321 0 : out:
322 5 : if (tcp_under_memory_pressure(sk))
323 0 : sk_mem_reclaim(sk);
324 5 : }
325 :
326 :
327 : /**
328 : * tcp_delack_timer() - The TCP delayed ACK timeout handler
329 : * @t: Pointer to the timer. (gets casted to struct sock *)
330 : *
331 : * This function gets (indirectly) called when the kernel timer for a TCP packet
332 : * of this socket expires. Calls tcp_delack_timer_handler() to do the actual work.
333 : *
334 : * Returns: Nothing (void)
335 : */
336 5 : static void tcp_delack_timer(struct timer_list *t)
337 : {
338 5 : struct inet_connection_sock *icsk =
339 5 : from_timer(icsk, t, icsk_delack_timer);
340 5 : struct sock *sk = &icsk->icsk_inet.sk;
341 :
342 5 : bh_lock_sock(sk);
343 5 : if (!sock_owned_by_user(sk)) {
344 5 : tcp_delack_timer_handler(sk);
345 : } else {
346 0 : __NET_INC_STATS(sock_net(sk), LINUX_MIB_DELAYEDACKLOCKED);
347 : /* deleguate our work to tcp_release_cb() */
348 0 : if (!test_and_set_bit(TCP_DELACK_TIMER_DEFERRED, &sk->sk_tsq_flags))
349 0 : sock_hold(sk);
350 : }
351 5 : bh_unlock_sock(sk);
352 5 : sock_put(sk);
353 5 : }
354 :
355 0 : static void tcp_probe_timer(struct sock *sk)
356 : {
357 0 : struct inet_connection_sock *icsk = inet_csk(sk);
358 0 : struct sk_buff *skb = tcp_send_head(sk);
359 0 : struct tcp_sock *tp = tcp_sk(sk);
360 0 : int max_probes;
361 :
362 0 : if (tp->packets_out || !skb) {
363 0 : icsk->icsk_probes_out = 0;
364 0 : icsk->icsk_probes_tstamp = 0;
365 0 : return;
366 : }
367 :
368 : /* RFC 1122 4.2.2.17 requires the sender to stay open indefinitely as
369 : * long as the receiver continues to respond probes. We support this by
370 : * default and reset icsk_probes_out with incoming ACKs. But if the
371 : * socket is orphaned or the user specifies TCP_USER_TIMEOUT, we
372 : * kill the socket when the retry count and the time exceeds the
373 : * corresponding system limit. We also implement similar policy when
374 : * we use RTO to probe window in tcp_retransmit_timer().
375 : */
376 0 : if (!icsk->icsk_probes_tstamp)
377 0 : icsk->icsk_probes_tstamp = tcp_jiffies32;
378 0 : else if (icsk->icsk_user_timeout &&
379 0 : (s32)(tcp_jiffies32 - icsk->icsk_probes_tstamp) >=
380 0 : msecs_to_jiffies(icsk->icsk_user_timeout))
381 0 : goto abort;
382 :
383 0 : max_probes = sock_net(sk)->ipv4.sysctl_tcp_retries2;
384 0 : if (sock_flag(sk, SOCK_DEAD)) {
385 0 : const bool alive = inet_csk_rto_backoff(icsk, TCP_RTO_MAX) < TCP_RTO_MAX;
386 :
387 0 : max_probes = tcp_orphan_retries(sk, alive);
388 0 : if (!alive && icsk->icsk_backoff >= max_probes)
389 0 : goto abort;
390 0 : if (tcp_out_of_resources(sk, true))
391 : return;
392 : }
393 :
394 0 : if (icsk->icsk_probes_out >= max_probes) {
395 0 : abort: tcp_write_err(sk);
396 : } else {
397 : /* Only send another probe if we didn't close things up. */
398 0 : tcp_send_probe0(sk);
399 : }
400 : }
401 :
402 : /*
403 : * Timer for Fast Open socket to retransmit SYNACK. Note that the
404 : * sk here is the child socket, not the parent (listener) socket.
405 : */
406 0 : static void tcp_fastopen_synack_timer(struct sock *sk, struct request_sock *req)
407 : {
408 0 : struct inet_connection_sock *icsk = inet_csk(sk);
409 0 : int max_retries = icsk->icsk_syn_retries ? :
410 0 : sock_net(sk)->ipv4.sysctl_tcp_synack_retries + 1; /* add one more retry for fastopen */
411 0 : struct tcp_sock *tp = tcp_sk(sk);
412 :
413 0 : req->rsk_ops->syn_ack_timeout(req);
414 :
415 0 : if (req->num_timeout >= max_retries) {
416 0 : tcp_write_err(sk);
417 0 : return;
418 : }
419 : /* Lower cwnd after certain SYNACK timeout like tcp_init_transfer() */
420 0 : if (icsk->icsk_retransmits == 1)
421 0 : tcp_enter_loss(sk);
422 : /* XXX (TFO) - Unlike regular SYN-ACK retransmit, we ignore error
423 : * returned from rtx_syn_ack() to make it more persistent like
424 : * regular retransmit because if the child socket has been accepted
425 : * it's not good to give up too easily.
426 : */
427 0 : inet_rtx_syn_ack(sk, req);
428 0 : req->num_timeout++;
429 0 : icsk->icsk_retransmits++;
430 0 : if (!tp->retrans_stamp)
431 0 : tp->retrans_stamp = tcp_time_stamp(tp);
432 0 : inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
433 0 : TCP_TIMEOUT_INIT << req->num_timeout, TCP_RTO_MAX);
434 : }
435 :
436 :
437 : /**
438 : * tcp_retransmit_timer() - The TCP retransmit timeout handler
439 : * @sk: Pointer to the current socket.
440 : *
441 : * This function gets called when the kernel timer for a TCP packet
442 : * of this socket expires.
443 : *
444 : * It handles retransmission, timer adjustment and other necesarry measures.
445 : *
446 : * Returns: Nothing (void)
447 : */
448 0 : void tcp_retransmit_timer(struct sock *sk)
449 : {
450 0 : struct tcp_sock *tp = tcp_sk(sk);
451 0 : struct net *net = sock_net(sk);
452 0 : struct inet_connection_sock *icsk = inet_csk(sk);
453 0 : struct request_sock *req;
454 0 : struct sk_buff *skb;
455 :
456 0 : req = rcu_dereference_protected(tp->fastopen_rsk,
457 : lockdep_sock_is_held(sk));
458 0 : if (req) {
459 0 : WARN_ON_ONCE(sk->sk_state != TCP_SYN_RECV &&
460 : sk->sk_state != TCP_FIN_WAIT1);
461 0 : tcp_fastopen_synack_timer(sk, req);
462 : /* Before we receive ACK to our SYN-ACK don't retransmit
463 : * anything else (e.g., data or FIN segments).
464 : */
465 0 : return;
466 : }
467 :
468 0 : if (!tp->packets_out)
469 : return;
470 :
471 0 : skb = tcp_rtx_queue_head(sk);
472 0 : if (WARN_ON_ONCE(!skb))
473 : return;
474 :
475 0 : tp->tlp_high_seq = 0;
476 :
477 0 : if (!tp->snd_wnd && !sock_flag(sk, SOCK_DEAD) &&
478 0 : !((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV))) {
479 : /* Receiver dastardly shrinks window. Our retransmits
480 : * become zero probes, but we should not timeout this
481 : * connection. If the socket is an orphan, time it out,
482 : * we cannot allow such beasts to hang infinitely.
483 : */
484 0 : struct inet_sock *inet = inet_sk(sk);
485 0 : if (sk->sk_family == AF_INET) {
486 0 : net_dbg_ratelimited("Peer %pI4:%u/%u unexpectedly shrunk window %u:%u (repaired)\n",
487 : &inet->inet_daddr,
488 : ntohs(inet->inet_dport),
489 : inet->inet_num,
490 : tp->snd_una, tp->snd_nxt);
491 : }
492 : #if IS_ENABLED(CONFIG_IPV6)
493 : else if (sk->sk_family == AF_INET6) {
494 : net_dbg_ratelimited("Peer %pI6:%u/%u unexpectedly shrunk window %u:%u (repaired)\n",
495 : &sk->sk_v6_daddr,
496 : ntohs(inet->inet_dport),
497 : inet->inet_num,
498 : tp->snd_una, tp->snd_nxt);
499 : }
500 : #endif
501 0 : if (tcp_jiffies32 - tp->rcv_tstamp > TCP_RTO_MAX) {
502 0 : tcp_write_err(sk);
503 0 : goto out;
504 : }
505 0 : tcp_enter_loss(sk);
506 0 : tcp_retransmit_skb(sk, skb, 1);
507 0 : __sk_dst_reset(sk);
508 0 : goto out_reset_timer;
509 : }
510 :
511 0 : __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPTIMEOUTS);
512 0 : if (tcp_write_timeout(sk))
513 0 : goto out;
514 :
515 0 : if (icsk->icsk_retransmits == 0) {
516 0 : int mib_idx = 0;
517 :
518 0 : if (icsk->icsk_ca_state == TCP_CA_Recovery) {
519 0 : if (tcp_is_sack(tp))
520 : mib_idx = LINUX_MIB_TCPSACKRECOVERYFAIL;
521 : else
522 : mib_idx = LINUX_MIB_TCPRENORECOVERYFAIL;
523 0 : } else if (icsk->icsk_ca_state == TCP_CA_Loss) {
524 : mib_idx = LINUX_MIB_TCPLOSSFAILURES;
525 0 : } else if ((icsk->icsk_ca_state == TCP_CA_Disorder) ||
526 0 : tp->sacked_out) {
527 0 : if (tcp_is_sack(tp))
528 : mib_idx = LINUX_MIB_TCPSACKFAILURES;
529 : else
530 : mib_idx = LINUX_MIB_TCPRENOFAILURES;
531 : }
532 : if (mib_idx)
533 0 : __NET_INC_STATS(sock_net(sk), mib_idx);
534 : }
535 :
536 0 : tcp_enter_loss(sk);
537 :
538 0 : icsk->icsk_retransmits++;
539 0 : if (tcp_retransmit_skb(sk, tcp_rtx_queue_head(sk), 1) > 0) {
540 : /* Retransmission failed because of local congestion,
541 : * Let senders fight for local resources conservatively.
542 : */
543 0 : inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
544 : TCP_RESOURCE_PROBE_INTERVAL,
545 : TCP_RTO_MAX);
546 0 : goto out;
547 : }
548 :
549 : /* Increase the timeout each time we retransmit. Note that
550 : * we do not increase the rtt estimate. rto is initialized
551 : * from rtt, but increases here. Jacobson (SIGCOMM 88) suggests
552 : * that doubling rto each time is the least we can get away with.
553 : * In KA9Q, Karn uses this for the first few times, and then
554 : * goes to quadratic. netBSD doubles, but only goes up to *64,
555 : * and clamps at 1 to 64 sec afterwards. Note that 120 sec is
556 : * defined in the protocol as the maximum possible RTT. I guess
557 : * we'll have to use something other than TCP to talk to the
558 : * University of Mars.
559 : *
560 : * PAWS allows us longer timeouts and large windows, so once
561 : * implemented ftp to mars will work nicely. We will have to fix
562 : * the 120 second clamps though!
563 : */
564 0 : icsk->icsk_backoff++;
565 :
566 0 : out_reset_timer:
567 : /* If stream is thin, use linear timeouts. Since 'icsk_backoff' is
568 : * used to reset timer, set to 0. Recalculate 'icsk_rto' as this
569 : * might be increased if the stream oscillates between thin and thick,
570 : * thus the old value might already be too high compared to the value
571 : * set by 'tcp_set_rto' in tcp_input.c which resets the rto without
572 : * backoff. Limit to TCP_THIN_LINEAR_RETRIES before initiating
573 : * exponential backoff behaviour to avoid continue hammering
574 : * linear-timeout retransmissions into a black hole
575 : */
576 0 : if (sk->sk_state == TCP_ESTABLISHED &&
577 0 : (tp->thin_lto || net->ipv4.sysctl_tcp_thin_linear_timeouts) &&
578 0 : tcp_stream_is_thin(tp) &&
579 0 : icsk->icsk_retransmits <= TCP_THIN_LINEAR_RETRIES) {
580 0 : icsk->icsk_backoff = 0;
581 0 : icsk->icsk_rto = min(__tcp_set_rto(tp), TCP_RTO_MAX);
582 : } else {
583 : /* Use normal (exponential) backoff */
584 0 : icsk->icsk_rto = min(icsk->icsk_rto << 1, TCP_RTO_MAX);
585 : }
586 0 : inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
587 0 : tcp_clamp_rto_to_user_timeout(sk), TCP_RTO_MAX);
588 0 : if (retransmits_timed_out(sk, net->ipv4.sysctl_tcp_retries1 + 1, 0))
589 0 : __sk_dst_reset(sk);
590 :
591 0 : out:;
592 : }
593 :
594 : /* Called with bottom-half processing disabled.
595 : Called by tcp_write_timer() */
596 5 : void tcp_write_timer_handler(struct sock *sk)
597 : {
598 5 : struct inet_connection_sock *icsk = inet_csk(sk);
599 5 : int event;
600 :
601 5 : if (((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN)) ||
602 5 : !icsk->icsk_pending)
603 5 : goto out;
604 :
605 0 : if (time_after(icsk->icsk_timeout, jiffies)) {
606 0 : sk_reset_timer(sk, &icsk->icsk_retransmit_timer, icsk->icsk_timeout);
607 0 : goto out;
608 : }
609 :
610 0 : tcp_mstamp_refresh(tcp_sk(sk));
611 0 : event = icsk->icsk_pending;
612 :
613 0 : switch (event) {
614 0 : case ICSK_TIME_REO_TIMEOUT:
615 0 : tcp_rack_reo_timeout(sk);
616 0 : break;
617 0 : case ICSK_TIME_LOSS_PROBE:
618 0 : tcp_send_loss_probe(sk);
619 0 : break;
620 0 : case ICSK_TIME_RETRANS:
621 0 : icsk->icsk_pending = 0;
622 0 : tcp_retransmit_timer(sk);
623 0 : break;
624 0 : case ICSK_TIME_PROBE0:
625 0 : icsk->icsk_pending = 0;
626 0 : tcp_probe_timer(sk);
627 0 : break;
628 : }
629 :
630 5 : out:
631 5 : sk_mem_reclaim(sk);
632 5 : }
633 :
634 5 : static void tcp_write_timer(struct timer_list *t)
635 : {
636 5 : struct inet_connection_sock *icsk =
637 5 : from_timer(icsk, t, icsk_retransmit_timer);
638 5 : struct sock *sk = &icsk->icsk_inet.sk;
639 :
640 5 : bh_lock_sock(sk);
641 5 : if (!sock_owned_by_user(sk)) {
642 5 : tcp_write_timer_handler(sk);
643 : } else {
644 : /* delegate our work to tcp_release_cb() */
645 0 : if (!test_and_set_bit(TCP_WRITE_TIMER_DEFERRED, &sk->sk_tsq_flags))
646 0 : sock_hold(sk);
647 : }
648 5 : bh_unlock_sock(sk);
649 5 : sock_put(sk);
650 5 : }
651 :
652 0 : void tcp_syn_ack_timeout(const struct request_sock *req)
653 : {
654 0 : struct net *net = read_pnet(&inet_rsk(req)->ireq_net);
655 :
656 0 : __NET_INC_STATS(net, LINUX_MIB_TCPTIMEOUTS);
657 0 : }
658 : EXPORT_SYMBOL(tcp_syn_ack_timeout);
659 :
660 4 : void tcp_set_keepalive(struct sock *sk, int val)
661 : {
662 4 : if ((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN))
663 : return;
664 :
665 8 : if (val && !sock_flag(sk, SOCK_KEEPOPEN))
666 8 : inet_csk_reset_keepalive_timer(sk, keepalive_time_when(tcp_sk(sk)));
667 0 : else if (!val)
668 0 : inet_csk_delete_keepalive_timer(sk);
669 : }
670 : EXPORT_SYMBOL_GPL(tcp_set_keepalive);
671 :
672 :
673 0 : static void tcp_keepalive_timer (struct timer_list *t)
674 : {
675 0 : struct sock *sk = from_timer(sk, t, sk_timer);
676 0 : struct inet_connection_sock *icsk = inet_csk(sk);
677 0 : struct tcp_sock *tp = tcp_sk(sk);
678 0 : u32 elapsed;
679 :
680 : /* Only process if socket is not in use. */
681 0 : bh_lock_sock(sk);
682 0 : if (sock_owned_by_user(sk)) {
683 : /* Try again later. */
684 0 : inet_csk_reset_keepalive_timer (sk, HZ/20);
685 0 : goto out;
686 : }
687 :
688 0 : if (sk->sk_state == TCP_LISTEN) {
689 0 : pr_err("Hmm... keepalive on a LISTEN ???\n");
690 0 : goto out;
691 : }
692 :
693 0 : tcp_mstamp_refresh(tp);
694 0 : if (sk->sk_state == TCP_FIN_WAIT2 && sock_flag(sk, SOCK_DEAD)) {
695 0 : if (tp->linger2 >= 0) {
696 0 : const int tmo = tcp_fin_time(sk) - TCP_TIMEWAIT_LEN;
697 :
698 0 : if (tmo > 0) {
699 0 : tcp_time_wait(sk, TCP_FIN_WAIT2, tmo);
700 0 : goto out;
701 : }
702 : }
703 0 : tcp_send_active_reset(sk, GFP_ATOMIC);
704 0 : goto death;
705 : }
706 :
707 0 : if (!sock_flag(sk, SOCK_KEEPOPEN) ||
708 0 : ((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_SYN_SENT)))
709 0 : goto out;
710 :
711 0 : elapsed = keepalive_time_when(tp);
712 :
713 : /* It is alive without keepalive 8) */
714 0 : if (tp->packets_out || !tcp_write_queue_empty(sk))
715 0 : goto resched;
716 :
717 0 : elapsed = keepalive_time_elapsed(tp);
718 :
719 0 : if (elapsed >= keepalive_time_when(tp)) {
720 : /* If the TCP_USER_TIMEOUT option is enabled, use that
721 : * to determine when to timeout instead.
722 : */
723 0 : if ((icsk->icsk_user_timeout != 0 &&
724 0 : elapsed >= msecs_to_jiffies(icsk->icsk_user_timeout) &&
725 0 : icsk->icsk_probes_out > 0) ||
726 0 : (icsk->icsk_user_timeout == 0 &&
727 0 : icsk->icsk_probes_out >= keepalive_probes(tp))) {
728 0 : tcp_send_active_reset(sk, GFP_ATOMIC);
729 0 : tcp_write_err(sk);
730 0 : goto out;
731 : }
732 0 : if (tcp_write_wakeup(sk, LINUX_MIB_TCPKEEPALIVE) <= 0) {
733 0 : icsk->icsk_probes_out++;
734 0 : elapsed = keepalive_intvl_when(tp);
735 : } else {
736 : /* If keepalive was lost due to local congestion,
737 : * try harder.
738 : */
739 : elapsed = TCP_RESOURCE_PROBE_INTERVAL;
740 : }
741 : } else {
742 : /* It is tp->rcv_tstamp + keepalive_time_when(tp) */
743 0 : elapsed = keepalive_time_when(tp) - elapsed;
744 : }
745 :
746 0 : sk_mem_reclaim(sk);
747 :
748 0 : resched:
749 0 : inet_csk_reset_keepalive_timer (sk, elapsed);
750 0 : goto out;
751 :
752 0 : death:
753 0 : tcp_done(sk);
754 :
755 0 : out:
756 0 : bh_unlock_sock(sk);
757 0 : sock_put(sk);
758 0 : }
759 :
760 0 : static enum hrtimer_restart tcp_compressed_ack_kick(struct hrtimer *timer)
761 : {
762 0 : struct tcp_sock *tp = container_of(timer, struct tcp_sock, compressed_ack_timer);
763 0 : struct sock *sk = (struct sock *)tp;
764 :
765 0 : bh_lock_sock(sk);
766 0 : if (!sock_owned_by_user(sk)) {
767 0 : if (tp->compressed_ack) {
768 : /* Since we have to send one ack finally,
769 : * substract one from tp->compressed_ack to keep
770 : * LINUX_MIB_TCPACKCOMPRESSED accurate.
771 : */
772 0 : tp->compressed_ack--;
773 0 : tcp_send_ack(sk);
774 : }
775 : } else {
776 0 : if (!test_and_set_bit(TCP_DELACK_TIMER_DEFERRED,
777 0 : &sk->sk_tsq_flags))
778 0 : sock_hold(sk);
779 : }
780 0 : bh_unlock_sock(sk);
781 :
782 0 : sock_put(sk);
783 :
784 0 : return HRTIMER_NORESTART;
785 : }
786 :
787 7 : void tcp_init_xmit_timers(struct sock *sk)
788 : {
789 7 : inet_csk_init_xmit_timers(sk, &tcp_write_timer, &tcp_delack_timer,
790 : &tcp_keepalive_timer);
791 7 : hrtimer_init(&tcp_sk(sk)->pacing_timer, CLOCK_MONOTONIC,
792 : HRTIMER_MODE_ABS_PINNED_SOFT);
793 7 : tcp_sk(sk)->pacing_timer.function = tcp_pace_kick;
794 :
795 7 : hrtimer_init(&tcp_sk(sk)->compressed_ack_timer, CLOCK_MONOTONIC,
796 : HRTIMER_MODE_REL_PINNED_SOFT);
797 7 : tcp_sk(sk)->compressed_ack_timer.function = tcp_compressed_ack_kick;
798 7 : }
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