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 #include <trace/hooks/net.h>
26
tcp_clamp_rto_to_user_timeout(const struct sock * sk)27 static u32 tcp_clamp_rto_to_user_timeout(const struct sock *sk)
28 {
29 struct inet_connection_sock *icsk = inet_csk(sk);
30 u32 elapsed, start_ts, user_timeout;
31 s32 remaining;
32
33 start_ts = tcp_sk(sk)->retrans_stamp;
34 user_timeout = READ_ONCE(icsk->icsk_user_timeout);
35 if (!user_timeout)
36 return icsk->icsk_rto;
37 elapsed = tcp_time_stamp(tcp_sk(sk)) - start_ts;
38 remaining = user_timeout - elapsed;
39 if (remaining <= 0)
40 return 1; /* user timeout has passed; fire ASAP */
41
42 return min_t(u32, icsk->icsk_rto, msecs_to_jiffies(remaining));
43 }
44
tcp_clamp_probe0_to_user_timeout(const struct sock * sk,u32 when)45 u32 tcp_clamp_probe0_to_user_timeout(const struct sock *sk, u32 when)
46 {
47 struct inet_connection_sock *icsk = inet_csk(sk);
48 u32 remaining, user_timeout;
49 s32 elapsed;
50
51 user_timeout = READ_ONCE(icsk->icsk_user_timeout);
52 if (!user_timeout || !icsk->icsk_probes_tstamp)
53 return when;
54
55 elapsed = tcp_jiffies32 - icsk->icsk_probes_tstamp;
56 if (unlikely(elapsed < 0))
57 elapsed = 0;
58 remaining = msecs_to_jiffies(user_timeout) - elapsed;
59 remaining = max_t(u32, remaining, TCP_TIMEOUT_MIN);
60
61 return min_t(u32, remaining, when);
62 }
63
64 /**
65 * tcp_write_err() - close socket and save error info
66 * @sk: The socket the error has appeared on.
67 *
68 * Returns: Nothing (void)
69 */
70
tcp_write_err(struct sock * sk)71 static void tcp_write_err(struct sock *sk)
72 {
73 tcp_done_with_error(sk, READ_ONCE(sk->sk_err_soft) ? : ETIMEDOUT);
74 __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTONTIMEOUT);
75 }
76
77 /**
78 * tcp_out_of_resources() - Close socket if out of resources
79 * @sk: pointer to current socket
80 * @do_reset: send a last packet with reset flag
81 *
82 * Do not allow orphaned sockets to eat all our resources.
83 * This is direct violation of TCP specs, but it is required
84 * to prevent DoS attacks. It is called when a retransmission timeout
85 * or zero probe timeout occurs on orphaned socket.
86 *
87 * Also close if our net namespace is exiting; in that case there is no
88 * hope of ever communicating again since all netns interfaces are already
89 * down (or about to be down), and we need to release our dst references,
90 * which have been moved to the netns loopback interface, so the namespace
91 * can finish exiting. This condition is only possible if we are a kernel
92 * socket, as those do not hold references to the namespace.
93 *
94 * Criteria is still not confirmed experimentally and may change.
95 * We kill the socket, if:
96 * 1. If number of orphaned sockets exceeds an administratively configured
97 * limit.
98 * 2. If we have strong memory pressure.
99 * 3. If our net namespace is exiting.
100 */
tcp_out_of_resources(struct sock * sk,bool do_reset)101 static int tcp_out_of_resources(struct sock *sk, bool do_reset)
102 {
103 struct tcp_sock *tp = tcp_sk(sk);
104 int shift = 0;
105
106 /* If peer does not open window for long time, or did not transmit
107 * anything for long time, penalize it. */
108 if ((s32)(tcp_jiffies32 - tp->lsndtime) > 2*TCP_RTO_MAX || !do_reset)
109 shift++;
110
111 /* If some dubious ICMP arrived, penalize even more. */
112 if (READ_ONCE(sk->sk_err_soft))
113 shift++;
114
115 if (tcp_check_oom(sk, shift)) {
116 /* Catch exceptional cases, when connection requires reset.
117 * 1. Last segment was sent recently. */
118 if ((s32)(tcp_jiffies32 - tp->lsndtime) <= TCP_TIMEWAIT_LEN ||
119 /* 2. Window is closed. */
120 (!tp->snd_wnd && !tp->packets_out))
121 do_reset = true;
122 if (do_reset)
123 tcp_send_active_reset(sk, GFP_ATOMIC);
124 tcp_done(sk);
125 __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTONMEMORY);
126 return 1;
127 }
128
129 if (!check_net(sock_net(sk))) {
130 /* Not possible to send reset; just close */
131 tcp_done(sk);
132 return 1;
133 }
134
135 return 0;
136 }
137
138 /**
139 * tcp_orphan_retries() - Returns maximal number of retries on an orphaned socket
140 * @sk: Pointer to the current socket.
141 * @alive: bool, socket alive state
142 */
tcp_orphan_retries(struct sock * sk,bool alive)143 static int tcp_orphan_retries(struct sock *sk, bool alive)
144 {
145 int retries = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_orphan_retries); /* May be zero. */
146
147 /* We know from an ICMP that something is wrong. */
148 if (READ_ONCE(sk->sk_err_soft) && !alive)
149 retries = 0;
150
151 /* However, if socket sent something recently, select some safe
152 * number of retries. 8 corresponds to >100 seconds with minimal
153 * RTO of 200msec. */
154 if (retries == 0 && alive)
155 retries = 8;
156 return retries;
157 }
158
tcp_mtu_probing(struct inet_connection_sock * icsk,struct sock * sk)159 static void tcp_mtu_probing(struct inet_connection_sock *icsk, struct sock *sk)
160 {
161 const struct net *net = sock_net(sk);
162 int mss;
163
164 /* Black hole detection */
165 if (!READ_ONCE(net->ipv4.sysctl_tcp_mtu_probing))
166 return;
167
168 if (!icsk->icsk_mtup.enabled) {
169 icsk->icsk_mtup.enabled = 1;
170 icsk->icsk_mtup.probe_timestamp = tcp_jiffies32;
171 } else {
172 mss = tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_low) >> 1;
173 mss = min(READ_ONCE(net->ipv4.sysctl_tcp_base_mss), mss);
174 mss = max(mss, READ_ONCE(net->ipv4.sysctl_tcp_mtu_probe_floor));
175 mss = max(mss, READ_ONCE(net->ipv4.sysctl_tcp_min_snd_mss));
176 icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, mss);
177 }
178 tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);
179 }
180
tcp_model_timeout(struct sock * sk,unsigned int boundary,unsigned int rto_base)181 static unsigned int tcp_model_timeout(struct sock *sk,
182 unsigned int boundary,
183 unsigned int rto_base)
184 {
185 unsigned int linear_backoff_thresh, timeout;
186
187 linear_backoff_thresh = ilog2(TCP_RTO_MAX / rto_base);
188 if (boundary <= linear_backoff_thresh)
189 timeout = ((2 << boundary) - 1) * rto_base;
190 else
191 timeout = ((2 << linear_backoff_thresh) - 1) * rto_base +
192 (boundary - linear_backoff_thresh) * TCP_RTO_MAX;
193 return jiffies_to_msecs(timeout);
194 }
195 /**
196 * retransmits_timed_out() - returns true if this connection has timed out
197 * @sk: The current socket
198 * @boundary: max number of retransmissions
199 * @timeout: A custom timeout value.
200 * If set to 0 the default timeout is calculated and used.
201 * Using TCP_RTO_MIN and the number of unsuccessful retransmits.
202 *
203 * The default "timeout" value this function can calculate and use
204 * is equivalent to the timeout of a TCP Connection
205 * after "boundary" unsuccessful, exponentially backed-off
206 * retransmissions with an initial RTO of TCP_RTO_MIN.
207 */
retransmits_timed_out(struct sock * sk,unsigned int boundary,unsigned int timeout)208 static bool retransmits_timed_out(struct sock *sk,
209 unsigned int boundary,
210 unsigned int timeout)
211 {
212 unsigned int start_ts;
213
214 if (!inet_csk(sk)->icsk_retransmits)
215 return false;
216
217 start_ts = tcp_sk(sk)->retrans_stamp;
218 if (likely(timeout == 0)) {
219 unsigned int rto_base = TCP_RTO_MIN;
220
221 if ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV))
222 rto_base = tcp_timeout_init(sk);
223 timeout = tcp_model_timeout(sk, boundary, rto_base);
224 }
225
226 return (s32)(tcp_time_stamp(tcp_sk(sk)) - start_ts - timeout) >= 0;
227 }
228
229 /* A write timeout has occurred. Process the after effects. */
tcp_write_timeout(struct sock * sk)230 static int tcp_write_timeout(struct sock *sk)
231 {
232 struct inet_connection_sock *icsk = inet_csk(sk);
233 struct tcp_sock *tp = tcp_sk(sk);
234 struct net *net = sock_net(sk);
235 bool expired = false, do_reset;
236 int retry_until, max_retransmits;
237
238 if ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV)) {
239 if (icsk->icsk_retransmits)
240 __dst_negative_advice(sk);
241 /* Paired with WRITE_ONCE() in tcp_sock_set_syncnt() */
242 retry_until = READ_ONCE(icsk->icsk_syn_retries) ? :
243 READ_ONCE(net->ipv4.sysctl_tcp_syn_retries);
244
245 max_retransmits = retry_until;
246 if (sk->sk_state == TCP_SYN_SENT)
247 max_retransmits += READ_ONCE(net->ipv4.sysctl_tcp_syn_linear_timeouts);
248
249 expired = icsk->icsk_retransmits >= max_retransmits;
250 } else {
251 if (retransmits_timed_out(sk, READ_ONCE(net->ipv4.sysctl_tcp_retries1), 0)) {
252 /* Black hole detection */
253 tcp_mtu_probing(icsk, sk);
254 trace_android_vh_tcp_write_timeout_estab_retrans(sk);
255
256 __dst_negative_advice(sk);
257 }
258
259 retry_until = READ_ONCE(net->ipv4.sysctl_tcp_retries2);
260 if (sock_flag(sk, SOCK_DEAD)) {
261 const bool alive = icsk->icsk_rto < TCP_RTO_MAX;
262
263 retry_until = tcp_orphan_retries(sk, alive);
264 do_reset = alive ||
265 !retransmits_timed_out(sk, retry_until, 0);
266
267 if (tcp_out_of_resources(sk, do_reset))
268 return 1;
269 }
270 }
271 if (!expired)
272 expired = retransmits_timed_out(sk, retry_until,
273 READ_ONCE(icsk->icsk_user_timeout));
274 tcp_fastopen_active_detect_blackhole(sk, expired);
275
276 if (BPF_SOCK_OPS_TEST_FLAG(tp, BPF_SOCK_OPS_RTO_CB_FLAG))
277 tcp_call_bpf_3arg(sk, BPF_SOCK_OPS_RTO_CB,
278 icsk->icsk_retransmits,
279 icsk->icsk_rto, (int)expired);
280
281 if (expired) {
282 /* Has it gone just too far? */
283
284 trace_android_vh_tcp_state_change(sk, TCP_STATE_CHANGE_REASON_SYN_TIMEOUT, 0);
285
286 tcp_write_err(sk);
287 return 1;
288 }
289
290 trace_android_vh_tcp_state_change(sk, TCP_STATE_CHANGE_REASON_RETRANSMIT, 0);
291
292 if (sk_rethink_txhash(sk)) {
293 tp->timeout_rehash++;
294 __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPTIMEOUTREHASH);
295 }
296
297 return 0;
298 }
299
300 /* Called with BH disabled */
tcp_delack_timer_handler(struct sock * sk)301 void tcp_delack_timer_handler(struct sock *sk)
302 {
303 struct inet_connection_sock *icsk = inet_csk(sk);
304 struct tcp_sock *tp = tcp_sk(sk);
305
306 if ((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN))
307 return;
308
309 /* Handling the sack compression case */
310 if (tp->compressed_ack) {
311 tcp_mstamp_refresh(tp);
312 tcp_sack_compress_send_ack(sk);
313 return;
314 }
315
316 if (!(icsk->icsk_ack.pending & ICSK_ACK_TIMER))
317 return;
318
319 if (time_after(icsk->icsk_ack.timeout, jiffies)) {
320 sk_reset_timer(sk, &icsk->icsk_delack_timer, icsk->icsk_ack.timeout);
321 return;
322 }
323 icsk->icsk_ack.pending &= ~ICSK_ACK_TIMER;
324
325 if (inet_csk_ack_scheduled(sk)) {
326 if (!inet_csk_in_pingpong_mode(sk)) {
327 /* Delayed ACK missed: inflate ATO. */
328 icsk->icsk_ack.ato = min(icsk->icsk_ack.ato << 1, icsk->icsk_rto);
329 } else {
330 /* Delayed ACK missed: leave pingpong mode and
331 * deflate ATO.
332 */
333 inet_csk_exit_pingpong_mode(sk);
334 icsk->icsk_ack.ato = TCP_ATO_MIN;
335 }
336 tcp_mstamp_refresh(tp);
337 tcp_send_ack(sk);
338 __NET_INC_STATS(sock_net(sk), LINUX_MIB_DELAYEDACKS);
339 }
340 }
341
342
343 /**
344 * tcp_delack_timer() - The TCP delayed ACK timeout handler
345 * @t: Pointer to the timer. (gets casted to struct sock *)
346 *
347 * This function gets (indirectly) called when the kernel timer for a TCP packet
348 * of this socket expires. Calls tcp_delack_timer_handler() to do the actual work.
349 *
350 * Returns: Nothing (void)
351 */
tcp_delack_timer(struct timer_list * t)352 static void tcp_delack_timer(struct timer_list *t)
353 {
354 struct inet_connection_sock *icsk =
355 from_timer(icsk, t, icsk_delack_timer);
356 struct sock *sk = &icsk->icsk_inet.sk;
357
358 bh_lock_sock(sk);
359 if (!sock_owned_by_user(sk)) {
360 tcp_delack_timer_handler(sk);
361 } else {
362 __NET_INC_STATS(sock_net(sk), LINUX_MIB_DELAYEDACKLOCKED);
363 /* deleguate our work to tcp_release_cb() */
364 if (!test_and_set_bit(TCP_DELACK_TIMER_DEFERRED, &sk->sk_tsq_flags))
365 sock_hold(sk);
366 }
367 bh_unlock_sock(sk);
368 sock_put(sk);
369 }
370
tcp_probe_timer(struct sock * sk)371 static void tcp_probe_timer(struct sock *sk)
372 {
373 struct inet_connection_sock *icsk = inet_csk(sk);
374 struct sk_buff *skb = tcp_send_head(sk);
375 struct tcp_sock *tp = tcp_sk(sk);
376 int max_probes;
377
378 if (tp->packets_out || !skb) {
379 icsk->icsk_probes_out = 0;
380 icsk->icsk_probes_tstamp = 0;
381 return;
382 }
383
384 /* RFC 1122 4.2.2.17 requires the sender to stay open indefinitely as
385 * long as the receiver continues to respond probes. We support this by
386 * default and reset icsk_probes_out with incoming ACKs. But if the
387 * socket is orphaned or the user specifies TCP_USER_TIMEOUT, we
388 * kill the socket when the retry count and the time exceeds the
389 * corresponding system limit. We also implement similar policy when
390 * we use RTO to probe window in tcp_retransmit_timer().
391 */
392 if (!icsk->icsk_probes_tstamp) {
393 icsk->icsk_probes_tstamp = tcp_jiffies32;
394 } else {
395 u32 user_timeout = READ_ONCE(icsk->icsk_user_timeout);
396
397 if (user_timeout &&
398 (s32)(tcp_jiffies32 - icsk->icsk_probes_tstamp) >=
399 msecs_to_jiffies(user_timeout))
400 goto abort;
401 }
402 max_probes = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_retries2);
403 if (sock_flag(sk, SOCK_DEAD)) {
404 const bool alive = inet_csk_rto_backoff(icsk, TCP_RTO_MAX) < TCP_RTO_MAX;
405
406 max_probes = tcp_orphan_retries(sk, alive);
407 if (!alive && icsk->icsk_backoff >= max_probes)
408 goto abort;
409 if (tcp_out_of_resources(sk, true))
410 return;
411 }
412
413 if (icsk->icsk_probes_out >= max_probes) {
414 abort: tcp_write_err(sk);
415 } else {
416 /* Only send another probe if we didn't close things up. */
417 tcp_send_probe0(sk);
418 }
419 }
420
421 /*
422 * Timer for Fast Open socket to retransmit SYNACK. Note that the
423 * sk here is the child socket, not the parent (listener) socket.
424 */
tcp_fastopen_synack_timer(struct sock * sk,struct request_sock * req)425 static void tcp_fastopen_synack_timer(struct sock *sk, struct request_sock *req)
426 {
427 struct inet_connection_sock *icsk = inet_csk(sk);
428 struct tcp_sock *tp = tcp_sk(sk);
429 int max_retries;
430
431 req->rsk_ops->syn_ack_timeout(req);
432
433 /* Add one more retry for fastopen.
434 * Paired with WRITE_ONCE() in tcp_sock_set_syncnt()
435 */
436 max_retries = READ_ONCE(icsk->icsk_syn_retries) ? :
437 READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_synack_retries) + 1;
438
439 if (req->num_timeout >= max_retries) {
440 tcp_write_err(sk);
441 return;
442 }
443 /* Lower cwnd after certain SYNACK timeout like tcp_init_transfer() */
444 if (icsk->icsk_retransmits == 1)
445 tcp_enter_loss(sk);
446 /* XXX (TFO) - Unlike regular SYN-ACK retransmit, we ignore error
447 * returned from rtx_syn_ack() to make it more persistent like
448 * regular retransmit because if the child socket has been accepted
449 * it's not good to give up too easily.
450 */
451 inet_rtx_syn_ack(sk, req);
452 req->num_timeout++;
453 icsk->icsk_retransmits++;
454 if (!tp->retrans_stamp)
455 tp->retrans_stamp = tcp_time_stamp(tp);
456 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
457 req->timeout << req->num_timeout, TCP_RTO_MAX);
458 }
459
tcp_rtx_probe0_timed_out(const struct sock * sk,const struct sk_buff * skb)460 static bool tcp_rtx_probe0_timed_out(const struct sock *sk,
461 const struct sk_buff *skb)
462 {
463 const struct inet_connection_sock *icsk = inet_csk(sk);
464 u32 user_timeout = READ_ONCE(icsk->icsk_user_timeout);
465 const struct tcp_sock *tp = tcp_sk(sk);
466 int timeout = TCP_RTO_MAX * 2;
467 u32 rtx_delta;
468 s32 rcv_delta;
469
470 rtx_delta = (u32)msecs_to_jiffies(tcp_time_stamp(tp) -
471 (tp->retrans_stamp ?: tcp_skb_timestamp(skb)));
472
473 if (user_timeout) {
474 /* If user application specified a TCP_USER_TIMEOUT,
475 * it does not want win 0 packets to 'reset the timer'
476 * while retransmits are not making progress.
477 */
478 if (rtx_delta > user_timeout)
479 return true;
480 timeout = min_t(u32, timeout, msecs_to_jiffies(user_timeout));
481 }
482
483 /* Note: timer interrupt might have been delayed by at least one jiffy,
484 * and tp->rcv_tstamp might very well have been written recently.
485 * rcv_delta can thus be negative.
486 */
487 rcv_delta = icsk->icsk_timeout - tp->rcv_tstamp;
488 if (rcv_delta <= timeout)
489 return false;
490
491 return rtx_delta > timeout;
492 }
493
494 /**
495 * tcp_retransmit_timer() - The TCP retransmit timeout handler
496 * @sk: Pointer to the current socket.
497 *
498 * This function gets called when the kernel timer for a TCP packet
499 * of this socket expires.
500 *
501 * It handles retransmission, timer adjustment and other necessary measures.
502 *
503 * Returns: Nothing (void)
504 */
tcp_retransmit_timer(struct sock * sk)505 void tcp_retransmit_timer(struct sock *sk)
506 {
507 struct tcp_sock *tp = tcp_sk(sk);
508 struct net *net = sock_net(sk);
509 struct inet_connection_sock *icsk = inet_csk(sk);
510 struct request_sock *req;
511 struct sk_buff *skb;
512
513 req = rcu_dereference_protected(tp->fastopen_rsk,
514 lockdep_sock_is_held(sk));
515 if (req) {
516 WARN_ON_ONCE(sk->sk_state != TCP_SYN_RECV &&
517 sk->sk_state != TCP_FIN_WAIT1);
518 tcp_fastopen_synack_timer(sk, req);
519 /* Before we receive ACK to our SYN-ACK don't retransmit
520 * anything else (e.g., data or FIN segments).
521 */
522 return;
523 }
524
525 if (!tp->packets_out)
526 return;
527
528 skb = tcp_rtx_queue_head(sk);
529 if (WARN_ON_ONCE(!skb))
530 return;
531
532 if (!tp->snd_wnd && !sock_flag(sk, SOCK_DEAD) &&
533 !((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV))) {
534 /* Receiver dastardly shrinks window. Our retransmits
535 * become zero probes, but we should not timeout this
536 * connection. If the socket is an orphan, time it out,
537 * we cannot allow such beasts to hang infinitely.
538 */
539 struct inet_sock *inet = inet_sk(sk);
540 u32 rtx_delta;
541
542 rtx_delta = tcp_time_stamp(tp) - (tp->retrans_stamp ?: tcp_skb_timestamp(skb));
543 if (sk->sk_family == AF_INET) {
544 net_dbg_ratelimited("Probing zero-window on %pI4:%u/%u, seq=%u:%u, recv %ums ago, lasting %ums\n",
545 &inet->inet_daddr, ntohs(inet->inet_dport),
546 inet->inet_num, tp->snd_una, tp->snd_nxt,
547 jiffies_to_msecs(jiffies - tp->rcv_tstamp),
548 rtx_delta);
549 }
550 #if IS_ENABLED(CONFIG_IPV6)
551 else if (sk->sk_family == AF_INET6) {
552 net_dbg_ratelimited("Probing zero-window on %pI6:%u/%u, seq=%u:%u, recv %ums ago, lasting %ums\n",
553 &sk->sk_v6_daddr, ntohs(inet->inet_dport),
554 inet->inet_num, tp->snd_una, tp->snd_nxt,
555 jiffies_to_msecs(jiffies - tp->rcv_tstamp),
556 rtx_delta);
557 }
558 #endif
559 if (tcp_rtx_probe0_timed_out(sk, skb)) {
560 tcp_write_err(sk);
561 goto out;
562 }
563 tcp_enter_loss(sk);
564 tcp_retransmit_skb(sk, skb, 1);
565 __sk_dst_reset(sk);
566 goto out_reset_timer;
567 }
568
569 __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPTIMEOUTS);
570 if (tcp_write_timeout(sk))
571 goto out;
572
573 if (icsk->icsk_retransmits == 0) {
574 int mib_idx = 0;
575
576 if (icsk->icsk_ca_state == TCP_CA_Recovery) {
577 if (tcp_is_sack(tp))
578 mib_idx = LINUX_MIB_TCPSACKRECOVERYFAIL;
579 else
580 mib_idx = LINUX_MIB_TCPRENORECOVERYFAIL;
581 } else if (icsk->icsk_ca_state == TCP_CA_Loss) {
582 mib_idx = LINUX_MIB_TCPLOSSFAILURES;
583 } else if ((icsk->icsk_ca_state == TCP_CA_Disorder) ||
584 tp->sacked_out) {
585 if (tcp_is_sack(tp))
586 mib_idx = LINUX_MIB_TCPSACKFAILURES;
587 else
588 mib_idx = LINUX_MIB_TCPRENOFAILURES;
589 }
590 if (mib_idx)
591 __NET_INC_STATS(sock_net(sk), mib_idx);
592 }
593
594 tcp_enter_loss(sk);
595
596 icsk->icsk_retransmits++;
597 if (tcp_retransmit_skb(sk, tcp_rtx_queue_head(sk), 1) > 0) {
598 /* Retransmission failed because of local congestion,
599 * Let senders fight for local resources conservatively.
600 */
601 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
602 TCP_RESOURCE_PROBE_INTERVAL,
603 TCP_RTO_MAX);
604 goto out;
605 }
606
607 /* Increase the timeout each time we retransmit. Note that
608 * we do not increase the rtt estimate. rto is initialized
609 * from rtt, but increases here. Jacobson (SIGCOMM 88) suggests
610 * that doubling rto each time is the least we can get away with.
611 * In KA9Q, Karn uses this for the first few times, and then
612 * goes to quadratic. netBSD doubles, but only goes up to *64,
613 * and clamps at 1 to 64 sec afterwards. Note that 120 sec is
614 * defined in the protocol as the maximum possible RTT. I guess
615 * we'll have to use something other than TCP to talk to the
616 * University of Mars.
617 *
618 * PAWS allows us longer timeouts and large windows, so once
619 * implemented ftp to mars will work nicely. We will have to fix
620 * the 120 second clamps though!
621 */
622 icsk->icsk_backoff++;
623
624 out_reset_timer:
625 /* If stream is thin, use linear timeouts. Since 'icsk_backoff' is
626 * used to reset timer, set to 0. Recalculate 'icsk_rto' as this
627 * might be increased if the stream oscillates between thin and thick,
628 * thus the old value might already be too high compared to the value
629 * set by 'tcp_set_rto' in tcp_input.c which resets the rto without
630 * backoff. Limit to TCP_THIN_LINEAR_RETRIES before initiating
631 * exponential backoff behaviour to avoid continue hammering
632 * linear-timeout retransmissions into a black hole
633 */
634 if (sk->sk_state == TCP_ESTABLISHED &&
635 (tp->thin_lto || READ_ONCE(net->ipv4.sysctl_tcp_thin_linear_timeouts)) &&
636 tcp_stream_is_thin(tp) &&
637 icsk->icsk_retransmits <= TCP_THIN_LINEAR_RETRIES) {
638 icsk->icsk_backoff = 0;
639 icsk->icsk_rto = clamp(__tcp_set_rto(tp),
640 tcp_rto_min(sk),
641 TCP_RTO_MAX);
642 } else if (sk->sk_state != TCP_SYN_SENT ||
643 icsk->icsk_backoff >
644 READ_ONCE(net->ipv4.sysctl_tcp_syn_linear_timeouts)) {
645 /* Use normal (exponential) backoff unless linear timeouts are
646 * activated.
647 */
648 icsk->icsk_rto = min(icsk->icsk_rto << 1, TCP_RTO_MAX);
649
650 trace_android_vh_tcp_fastsyn(sk);
651 }
652 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
653 tcp_clamp_rto_to_user_timeout(sk), TCP_RTO_MAX);
654 if (retransmits_timed_out(sk, READ_ONCE(net->ipv4.sysctl_tcp_retries1) + 1, 0))
655 __sk_dst_reset(sk);
656
657 out:;
658 }
659
660 /* Called with bottom-half processing disabled.
661 Called by tcp_write_timer() */
tcp_write_timer_handler(struct sock * sk)662 void tcp_write_timer_handler(struct sock *sk)
663 {
664 struct inet_connection_sock *icsk = inet_csk(sk);
665 int event;
666
667 if (((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN)) ||
668 !icsk->icsk_pending)
669 return;
670
671 if (time_after(icsk->icsk_timeout, jiffies)) {
672 sk_reset_timer(sk, &icsk->icsk_retransmit_timer, icsk->icsk_timeout);
673 return;
674 }
675
676 tcp_mstamp_refresh(tcp_sk(sk));
677 event = icsk->icsk_pending;
678
679 switch (event) {
680 case ICSK_TIME_REO_TIMEOUT:
681 tcp_rack_reo_timeout(sk);
682 break;
683 case ICSK_TIME_LOSS_PROBE:
684 tcp_send_loss_probe(sk);
685 break;
686 case ICSK_TIME_RETRANS:
687 icsk->icsk_pending = 0;
688 tcp_retransmit_timer(sk);
689 break;
690 case ICSK_TIME_PROBE0:
691 icsk->icsk_pending = 0;
692 tcp_probe_timer(sk);
693 break;
694 }
695 }
696
tcp_write_timer(struct timer_list * t)697 static void tcp_write_timer(struct timer_list *t)
698 {
699 struct inet_connection_sock *icsk =
700 from_timer(icsk, t, icsk_retransmit_timer);
701 struct sock *sk = &icsk->icsk_inet.sk;
702
703 bh_lock_sock(sk);
704 if (!sock_owned_by_user(sk)) {
705 tcp_write_timer_handler(sk);
706 } else {
707 /* delegate our work to tcp_release_cb() */
708 if (!test_and_set_bit(TCP_WRITE_TIMER_DEFERRED, &sk->sk_tsq_flags))
709 sock_hold(sk);
710 }
711 bh_unlock_sock(sk);
712 sock_put(sk);
713 }
714
tcp_syn_ack_timeout(const struct request_sock * req)715 void tcp_syn_ack_timeout(const struct request_sock *req)
716 {
717 struct net *net = read_pnet(&inet_rsk(req)->ireq_net);
718
719 __NET_INC_STATS(net, LINUX_MIB_TCPTIMEOUTS);
720 }
721 EXPORT_SYMBOL(tcp_syn_ack_timeout);
722
tcp_set_keepalive(struct sock * sk,int val)723 void tcp_set_keepalive(struct sock *sk, int val)
724 {
725 if ((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN))
726 return;
727
728 if (val && !sock_flag(sk, SOCK_KEEPOPEN))
729 inet_csk_reset_keepalive_timer(sk, keepalive_time_when(tcp_sk(sk)));
730 else if (!val)
731 inet_csk_delete_keepalive_timer(sk);
732 }
733 EXPORT_SYMBOL_GPL(tcp_set_keepalive);
734
735
tcp_keepalive_timer(struct timer_list * t)736 static void tcp_keepalive_timer (struct timer_list *t)
737 {
738 struct sock *sk = from_timer(sk, t, sk_timer);
739 struct inet_connection_sock *icsk = inet_csk(sk);
740 struct tcp_sock *tp = tcp_sk(sk);
741 u32 elapsed;
742
743 /* Only process if socket is not in use. */
744 bh_lock_sock(sk);
745 if (sock_owned_by_user(sk)) {
746 /* Try again later. */
747 inet_csk_reset_keepalive_timer (sk, HZ/20);
748 goto out;
749 }
750
751 if (sk->sk_state == TCP_LISTEN) {
752 pr_err("Hmm... keepalive on a LISTEN ???\n");
753 goto out;
754 }
755
756 tcp_mstamp_refresh(tp);
757 if (sk->sk_state == TCP_FIN_WAIT2 && sock_flag(sk, SOCK_DEAD)) {
758 if (READ_ONCE(tp->linger2) >= 0) {
759 const int tmo = tcp_fin_time(sk) - TCP_TIMEWAIT_LEN;
760
761 if (tmo > 0) {
762 tcp_time_wait(sk, TCP_FIN_WAIT2, tmo);
763 goto out;
764 }
765 }
766 tcp_send_active_reset(sk, GFP_ATOMIC);
767 goto death;
768 }
769
770 if (!sock_flag(sk, SOCK_KEEPOPEN) ||
771 ((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_SYN_SENT)))
772 goto out;
773
774 elapsed = keepalive_time_when(tp);
775
776 /* It is alive without keepalive 8) */
777 if (tp->packets_out || !tcp_write_queue_empty(sk))
778 goto resched;
779
780 elapsed = keepalive_time_elapsed(tp);
781
782 if (elapsed >= keepalive_time_when(tp)) {
783 u32 user_timeout = READ_ONCE(icsk->icsk_user_timeout);
784
785 /* If the TCP_USER_TIMEOUT option is enabled, use that
786 * to determine when to timeout instead.
787 */
788 if ((user_timeout != 0 &&
789 elapsed >= msecs_to_jiffies(user_timeout) &&
790 icsk->icsk_probes_out > 0) ||
791 (user_timeout == 0 &&
792 icsk->icsk_probes_out >= keepalive_probes(tp))) {
793 tcp_send_active_reset(sk, GFP_ATOMIC);
794 tcp_write_err(sk);
795 goto out;
796 }
797 if (tcp_write_wakeup(sk, LINUX_MIB_TCPKEEPALIVE) <= 0) {
798 icsk->icsk_probes_out++;
799 elapsed = keepalive_intvl_when(tp);
800 } else {
801 /* If keepalive was lost due to local congestion,
802 * try harder.
803 */
804 elapsed = TCP_RESOURCE_PROBE_INTERVAL;
805 }
806 } else {
807 /* It is tp->rcv_tstamp + keepalive_time_when(tp) */
808 elapsed = keepalive_time_when(tp) - elapsed;
809 }
810
811 resched:
812 inet_csk_reset_keepalive_timer (sk, elapsed);
813 goto out;
814
815 death:
816 tcp_done(sk);
817
818 out:
819 bh_unlock_sock(sk);
820 sock_put(sk);
821 }
822
tcp_compressed_ack_kick(struct hrtimer * timer)823 static enum hrtimer_restart tcp_compressed_ack_kick(struct hrtimer *timer)
824 {
825 struct tcp_sock *tp = container_of(timer, struct tcp_sock, compressed_ack_timer);
826 struct sock *sk = (struct sock *)tp;
827
828 bh_lock_sock(sk);
829 if (!sock_owned_by_user(sk)) {
830 if (tp->compressed_ack) {
831 /* Since we have to send one ack finally,
832 * subtract one from tp->compressed_ack to keep
833 * LINUX_MIB_TCPACKCOMPRESSED accurate.
834 */
835 tp->compressed_ack--;
836 tcp_send_ack(sk);
837 }
838 } else {
839 if (!test_and_set_bit(TCP_DELACK_TIMER_DEFERRED,
840 &sk->sk_tsq_flags))
841 sock_hold(sk);
842 }
843 bh_unlock_sock(sk);
844
845 sock_put(sk);
846
847 return HRTIMER_NORESTART;
848 }
849
tcp_init_xmit_timers(struct sock * sk)850 void tcp_init_xmit_timers(struct sock *sk)
851 {
852 inet_csk_init_xmit_timers(sk, &tcp_write_timer, &tcp_delack_timer,
853 &tcp_keepalive_timer);
854 hrtimer_init(&tcp_sk(sk)->pacing_timer, CLOCK_MONOTONIC,
855 HRTIMER_MODE_ABS_PINNED_SOFT);
856 tcp_sk(sk)->pacing_timer.function = tcp_pace_kick;
857
858 hrtimer_init(&tcp_sk(sk)->compressed_ack_timer, CLOCK_MONOTONIC,
859 HRTIMER_MODE_REL_PINNED_SOFT);
860 tcp_sk(sk)->compressed_ack_timer.function = tcp_compressed_ack_kick;
861 }
862