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457c8996 | 1 | // SPDX-License-Identifier: GPL-2.0-only |
1da177e4 LT |
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 | * | |
02c30a84 | 9 | * Authors: Ross Biro |
1da177e4 LT |
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> | |
5a0e3ad6 | 23 | #include <linux/gfp.h> |
1da177e4 LT |
24 | #include <net/tcp.h> |
25 | ||
b701a99e JM |
26 | static u32 tcp_clamp_rto_to_user_timeout(const struct sock *sk) |
27 | { | |
28 | struct inet_connection_sock *icsk = inet_csk(sk); | |
29 | u32 elapsed, start_ts; | |
9efdda4e | 30 | s32 remaining; |
b701a99e | 31 | |
7ae18975 YC |
32 | start_ts = tcp_sk(sk)->retrans_stamp; |
33 | if (!icsk->icsk_user_timeout) | |
b701a99e JM |
34 | return icsk->icsk_rto; |
35 | elapsed = tcp_time_stamp(tcp_sk(sk)) - start_ts; | |
9efdda4e ED |
36 | remaining = icsk->icsk_user_timeout - elapsed; |
37 | if (remaining <= 0) | |
b701a99e | 38 | return 1; /* user timeout has passed; fire ASAP */ |
9efdda4e ED |
39 | |
40 | return min_t(u32, icsk->icsk_rto, msecs_to_jiffies(remaining)); | |
b701a99e JM |
41 | } |
42 | ||
344db93a EC |
43 | u32 tcp_clamp_probe0_to_user_timeout(const struct sock *sk, u32 when) |
44 | { | |
45 | struct inet_connection_sock *icsk = inet_csk(sk); | |
46 | u32 remaining; | |
47 | s32 elapsed; | |
48 | ||
49 | if (!icsk->icsk_user_timeout || !icsk->icsk_probes_tstamp) | |
50 | return when; | |
51 | ||
52 | elapsed = tcp_jiffies32 - icsk->icsk_probes_tstamp; | |
53 | if (unlikely(elapsed < 0)) | |
54 | elapsed = 0; | |
55 | remaining = msecs_to_jiffies(icsk->icsk_user_timeout) - elapsed; | |
56 | remaining = max_t(u32, remaining, TCP_TIMEOUT_MIN); | |
57 | ||
58 | return min_t(u32, remaining, when); | |
59 | } | |
60 | ||
c380d37e RS |
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 | ||
1da177e4 LT |
68 | static void tcp_write_err(struct sock *sk) |
69 | { | |
e13ec3da | 70 | WRITE_ONCE(sk->sk_err, READ_ONCE(sk->sk_err_soft) ? : ETIMEDOUT); |
e3ae2365 | 71 | sk_error_report(sk); |
1da177e4 | 72 | |
e05836ac | 73 | tcp_write_queue_purge(sk); |
1da177e4 | 74 | tcp_done(sk); |
02a1d6e7 | 75 | __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTONTIMEOUT); |
1da177e4 LT |
76 | } |
77 | ||
c380d37e RS |
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 | |
1da177e4 | 82 | * |
c380d37e RS |
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 | * | |
4ee806d5 DS |
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 | * | |
c380d37e RS |
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. | |
4ee806d5 | 100 | * 3. If our net namespace is exiting. |
1da177e4 | 101 | */ |
b248230c | 102 | static int tcp_out_of_resources(struct sock *sk, bool do_reset) |
1da177e4 LT |
103 | { |
104 | struct tcp_sock *tp = tcp_sk(sk); | |
ad1af0fe | 105 | int shift = 0; |
1da177e4 | 106 | |
e905a9ed | 107 | /* If peer does not open window for long time, or did not transmit |
1da177e4 | 108 | * anything for long time, penalize it. */ |
d635fbe2 | 109 | if ((s32)(tcp_jiffies32 - tp->lsndtime) > 2*TCP_RTO_MAX || !do_reset) |
ad1af0fe | 110 | shift++; |
1da177e4 LT |
111 | |
112 | /* If some dubious ICMP arrived, penalize even more. */ | |
cee1af82 | 113 | if (READ_ONCE(sk->sk_err_soft)) |
ad1af0fe | 114 | shift++; |
1da177e4 | 115 | |
efcdbf24 | 116 | if (tcp_check_oom(sk, shift)) { |
1da177e4 LT |
117 | /* Catch exceptional cases, when connection requires reset. |
118 | * 1. Last segment was sent recently. */ | |
d635fbe2 | 119 | if ((s32)(tcp_jiffies32 - tp->lsndtime) <= TCP_TIMEWAIT_LEN || |
1da177e4 LT |
120 | /* 2. Window is closed. */ |
121 | (!tp->snd_wnd && !tp->packets_out)) | |
b248230c | 122 | do_reset = true; |
1da177e4 LT |
123 | if (do_reset) |
124 | tcp_send_active_reset(sk, GFP_ATOMIC); | |
125 | tcp_done(sk); | |
02a1d6e7 | 126 | __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTONMEMORY); |
1da177e4 LT |
127 | return 1; |
128 | } | |
4ee806d5 DS |
129 | |
130 | if (!check_net(sock_net(sk))) { | |
131 | /* Not possible to send reset; just close */ | |
132 | tcp_done(sk); | |
133 | return 1; | |
134 | } | |
135 | ||
1da177e4 LT |
136 | return 0; |
137 | } | |
138 | ||
c380d37e RS |
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 | */ | |
7533ce30 | 144 | static int tcp_orphan_retries(struct sock *sk, bool alive) |
1da177e4 | 145 | { |
39e24435 | 146 | int retries = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_orphan_retries); /* May be zero. */ |
1da177e4 LT |
147 | |
148 | /* We know from an ICMP that something is wrong. */ | |
cee1af82 | 149 | if (READ_ONCE(sk->sk_err_soft) && !alive) |
1da177e4 LT |
150 | 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 | if (retries == 0 && alive) | |
156 | retries = 8; | |
157 | return retries; | |
158 | } | |
159 | ||
ce55dd36 ED |
160 | static void tcp_mtu_probing(struct inet_connection_sock *icsk, struct sock *sk) |
161 | { | |
d0f36847 ED |
162 | const struct net *net = sock_net(sk); |
163 | int mss; | |
b0f9ca53 | 164 | |
ce55dd36 | 165 | /* Black hole detection */ |
f47d00e0 | 166 | if (!READ_ONCE(net->ipv4.sysctl_tcp_mtu_probing)) |
d0f36847 ED |
167 | return; |
168 | ||
169 | if (!icsk->icsk_mtup.enabled) { | |
170 | icsk->icsk_mtup.enabled = 1; | |
171 | icsk->icsk_mtup.probe_timestamp = tcp_jiffies32; | |
172 | } else { | |
173 | mss = tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_low) >> 1; | |
88d78bc0 | 174 | mss = min(READ_ONCE(net->ipv4.sysctl_tcp_base_mss), mss); |
8e92d442 | 175 | mss = max(mss, READ_ONCE(net->ipv4.sysctl_tcp_mtu_probe_floor)); |
78eb166c | 176 | mss = max(mss, READ_ONCE(net->ipv4.sysctl_tcp_min_snd_mss)); |
d0f36847 | 177 | icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, mss); |
ce55dd36 | 178 | } |
d0f36847 | 179 | tcp_sync_mss(sk, icsk->icsk_pmtu_cookie); |
ce55dd36 ED |
180 | } |
181 | ||
01a523b0 YC |
182 | static unsigned int tcp_model_timeout(struct sock *sk, |
183 | unsigned int boundary, | |
184 | unsigned int rto_base) | |
185 | { | |
186 | unsigned int linear_backoff_thresh, timeout; | |
187 | ||
188 | linear_backoff_thresh = ilog2(TCP_RTO_MAX / rto_base); | |
189 | if (boundary <= linear_backoff_thresh) | |
190 | timeout = ((2 << boundary) - 1) * rto_base; | |
191 | else | |
192 | timeout = ((2 << linear_backoff_thresh) - 1) * rto_base + | |
193 | (boundary - linear_backoff_thresh) * TCP_RTO_MAX; | |
194 | return jiffies_to_msecs(timeout); | |
195 | } | |
c380d37e RS |
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. | |
c380d37e RS |
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 | |
ce682ef6 | 207 | * retransmissions with an initial RTO of TCP_RTO_MIN. |
2f7de571 DL |
208 | */ |
209 | static bool retransmits_timed_out(struct sock *sk, | |
dca43c75 | 210 | unsigned int boundary, |
ce682ef6 | 211 | unsigned int timeout) |
2f7de571 | 212 | { |
01a523b0 | 213 | unsigned int start_ts; |
2f7de571 DL |
214 | |
215 | if (!inet_csk(sk)->icsk_retransmits) | |
216 | return false; | |
217 | ||
7ae18975 | 218 | start_ts = tcp_sk(sk)->retrans_stamp; |
3256a2d6 ED |
219 | if (likely(timeout == 0)) { |
220 | unsigned int rto_base = TCP_RTO_MIN; | |
221 | ||
222 | if ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV)) | |
223 | rto_base = tcp_timeout_init(sk); | |
224 | timeout = tcp_model_timeout(sk, boundary, rto_base); | |
225 | } | |
01a523b0 | 226 | |
9efdda4e | 227 | return (s32)(tcp_time_stamp(tcp_sk(sk)) - start_ts - timeout) >= 0; |
2f7de571 DL |
228 | } |
229 | ||
1da177e4 LT |
230 | /* A write timeout has occurred. Process the after effects. */ |
231 | static int tcp_write_timeout(struct sock *sk) | |
232 | { | |
5d424d5a | 233 | struct inet_connection_sock *icsk = inet_csk(sk); |
c968601d | 234 | struct tcp_sock *tp = tcp_sk(sk); |
6fa25166 | 235 | struct net *net = sock_net(sk); |
a41e8a88 | 236 | bool expired = false, do_reset; |
1da177e4 LT |
237 | int retry_until; |
238 | ||
239 | if ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV)) { | |
9c30ae83 YC |
240 | if (icsk->icsk_retransmits) |
241 | __dst_negative_advice(sk); | |
20a3b1c0 KI |
242 | retry_until = icsk->icsk_syn_retries ? : |
243 | READ_ONCE(net->ipv4.sysctl_tcp_syn_retries); | |
ce682ef6 | 244 | expired = icsk->icsk_retransmits >= retry_until; |
1da177e4 | 245 | } else { |
39e24435 | 246 | if (retransmits_timed_out(sk, READ_ONCE(net->ipv4.sysctl_tcp_retries1), 0)) { |
5d424d5a | 247 | /* Black hole detection */ |
ce55dd36 | 248 | tcp_mtu_probing(icsk, sk); |
1da177e4 | 249 | |
9c30ae83 | 250 | __dst_negative_advice(sk); |
1da177e4 LT |
251 | } |
252 | ||
39e24435 | 253 | retry_until = READ_ONCE(net->ipv4.sysctl_tcp_retries2); |
1da177e4 | 254 | if (sock_flag(sk, SOCK_DEAD)) { |
7533ce30 | 255 | const bool alive = icsk->icsk_rto < TCP_RTO_MAX; |
e905a9ed | 256 | |
1da177e4 | 257 | retry_until = tcp_orphan_retries(sk, alive); |
6fa12c85 | 258 | do_reset = alive || |
ce682ef6 | 259 | !retransmits_timed_out(sk, retry_until, 0); |
1da177e4 | 260 | |
6fa12c85 | 261 | if (tcp_out_of_resources(sk, do_reset)) |
1da177e4 LT |
262 | return 1; |
263 | } | |
a41e8a88 ED |
264 | } |
265 | if (!expired) | |
ce682ef6 ED |
266 | expired = retransmits_timed_out(sk, retry_until, |
267 | icsk->icsk_user_timeout); | |
7268586b | 268 | tcp_fastopen_active_detect_blackhole(sk, expired); |
f89013f6 LB |
269 | |
270 | if (BPF_SOCK_OPS_TEST_FLAG(tp, BPF_SOCK_OPS_RTO_CB_FLAG)) | |
271 | tcp_call_bpf_3arg(sk, BPF_SOCK_OPS_RTO_CB, | |
272 | icsk->icsk_retransmits, | |
273 | icsk->icsk_rto, (int)expired); | |
274 | ||
ce682ef6 | 275 | if (expired) { |
1da177e4 LT |
276 | /* Has it gone just too far? */ |
277 | tcp_write_err(sk); | |
278 | return 1; | |
279 | } | |
f89013f6 | 280 | |
9c30ae83 YC |
281 | if (sk_rethink_txhash(sk)) { |
282 | tp->timeout_rehash++; | |
283 | __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPTIMEOUTREHASH); | |
284 | } | |
285 | ||
1da177e4 LT |
286 | return 0; |
287 | } | |
288 | ||
c10d9310 | 289 | /* Called with BH disabled */ |
6f458dfb | 290 | void tcp_delack_timer_handler(struct sock *sk) |
1da177e4 | 291 | { |
463c84b9 | 292 | struct inet_connection_sock *icsk = inet_csk(sk); |
1da177e4 | 293 | |
02b2faaf ED |
294 | if (((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN)) || |
295 | !(icsk->icsk_ack.pending & ICSK_ACK_TIMER)) | |
4890b686 | 296 | return; |
1da177e4 | 297 | |
463c84b9 ACM |
298 | if (time_after(icsk->icsk_ack.timeout, jiffies)) { |
299 | sk_reset_timer(sk, &icsk->icsk_delack_timer, icsk->icsk_ack.timeout); | |
4890b686 | 300 | return; |
1da177e4 | 301 | } |
463c84b9 | 302 | icsk->icsk_ack.pending &= ~ICSK_ACK_TIMER; |
1da177e4 | 303 | |
463c84b9 | 304 | if (inet_csk_ack_scheduled(sk)) { |
31954cd8 | 305 | if (!inet_csk_in_pingpong_mode(sk)) { |
1da177e4 | 306 | /* Delayed ACK missed: inflate ATO. */ |
463c84b9 | 307 | icsk->icsk_ack.ato = min(icsk->icsk_ack.ato << 1, icsk->icsk_rto); |
1da177e4 LT |
308 | } else { |
309 | /* Delayed ACK missed: leave pingpong mode and | |
310 | * deflate ATO. | |
311 | */ | |
31954cd8 | 312 | inet_csk_exit_pingpong_mode(sk); |
463c84b9 | 313 | icsk->icsk_ack.ato = TCP_ATO_MIN; |
1da177e4 | 314 | } |
4688eb7c | 315 | tcp_mstamp_refresh(tcp_sk(sk)); |
1da177e4 | 316 | tcp_send_ack(sk); |
02a1d6e7 | 317 | __NET_INC_STATS(sock_net(sk), LINUX_MIB_DELAYEDACKS); |
1da177e4 | 318 | } |
6f458dfb ED |
319 | } |
320 | ||
c380d37e RS |
321 | |
322 | /** | |
323 | * tcp_delack_timer() - The TCP delayed ACK timeout handler | |
3628e3cb | 324 | * @t: Pointer to the timer. (gets casted to struct sock *) |
c380d37e RS |
325 | * |
326 | * This function gets (indirectly) called when the kernel timer for a TCP packet | |
327 | * of this socket expires. Calls tcp_delack_timer_handler() to do the actual work. | |
328 | * | |
329 | * Returns: Nothing (void) | |
330 | */ | |
59f379f9 | 331 | static void tcp_delack_timer(struct timer_list *t) |
6f458dfb | 332 | { |
59f379f9 KC |
333 | struct inet_connection_sock *icsk = |
334 | from_timer(icsk, t, icsk_delack_timer); | |
335 | struct sock *sk = &icsk->icsk_inet.sk; | |
6f458dfb ED |
336 | |
337 | bh_lock_sock(sk); | |
338 | if (!sock_owned_by_user(sk)) { | |
339 | tcp_delack_timer_handler(sk); | |
340 | } else { | |
02a1d6e7 | 341 | __NET_INC_STATS(sock_net(sk), LINUX_MIB_DELAYEDACKLOCKED); |
6f458dfb | 342 | /* deleguate our work to tcp_release_cb() */ |
7aa5470c | 343 | if (!test_and_set_bit(TCP_DELACK_TIMER_DEFERRED, &sk->sk_tsq_flags)) |
144d56e9 | 344 | sock_hold(sk); |
6f458dfb | 345 | } |
1da177e4 LT |
346 | bh_unlock_sock(sk); |
347 | sock_put(sk); | |
348 | } | |
349 | ||
350 | static void tcp_probe_timer(struct sock *sk) | |
351 | { | |
6687e988 | 352 | struct inet_connection_sock *icsk = inet_csk(sk); |
75c119af | 353 | struct sk_buff *skb = tcp_send_head(sk); |
1da177e4 LT |
354 | struct tcp_sock *tp = tcp_sk(sk); |
355 | int max_probes; | |
356 | ||
75c119af | 357 | if (tp->packets_out || !skb) { |
6687e988 | 358 | icsk->icsk_probes_out = 0; |
9d9b1ee0 | 359 | icsk->icsk_probes_tstamp = 0; |
1da177e4 LT |
360 | return; |
361 | } | |
362 | ||
b248230c YC |
363 | /* RFC 1122 4.2.2.17 requires the sender to stay open indefinitely as |
364 | * long as the receiver continues to respond probes. We support this by | |
365 | * default and reset icsk_probes_out with incoming ACKs. But if the | |
366 | * socket is orphaned or the user specifies TCP_USER_TIMEOUT, we | |
367 | * kill the socket when the retry count and the time exceeds the | |
368 | * corresponding system limit. We also implement similar policy when | |
369 | * we use RTO to probe window in tcp_retransmit_timer(). | |
1da177e4 | 370 | */ |
9d9b1ee0 EC |
371 | if (!icsk->icsk_probes_tstamp) |
372 | icsk->icsk_probes_tstamp = tcp_jiffies32; | |
373 | else if (icsk->icsk_user_timeout && | |
374 | (s32)(tcp_jiffies32 - icsk->icsk_probes_tstamp) >= | |
375 | msecs_to_jiffies(icsk->icsk_user_timeout)) | |
376 | goto abort; | |
1da177e4 | 377 | |
39e24435 | 378 | max_probes = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_retries2); |
1da177e4 | 379 | if (sock_flag(sk, SOCK_DEAD)) { |
7533ce30 | 380 | const bool alive = inet_csk_rto_backoff(icsk, TCP_RTO_MAX) < TCP_RTO_MAX; |
e905a9ed | 381 | |
1da177e4 | 382 | max_probes = tcp_orphan_retries(sk, alive); |
b248230c YC |
383 | if (!alive && icsk->icsk_backoff >= max_probes) |
384 | goto abort; | |
385 | if (tcp_out_of_resources(sk, true)) | |
1da177e4 LT |
386 | return; |
387 | } | |
388 | ||
3976535a | 389 | if (icsk->icsk_probes_out >= max_probes) { |
b248230c | 390 | abort: tcp_write_err(sk); |
1da177e4 LT |
391 | } else { |
392 | /* Only send another probe if we didn't close things up. */ | |
393 | tcp_send_probe0(sk); | |
394 | } | |
395 | } | |
396 | ||
8336886f JC |
397 | /* |
398 | * Timer for Fast Open socket to retransmit SYNACK. Note that the | |
399 | * sk here is the child socket, not the parent (listener) socket. | |
400 | */ | |
d983ea6f | 401 | static void tcp_fastopen_synack_timer(struct sock *sk, struct request_sock *req) |
8336886f JC |
402 | { |
403 | struct inet_connection_sock *icsk = inet_csk(sk); | |
c7d13c8f | 404 | struct tcp_sock *tp = tcp_sk(sk); |
20a3b1c0 | 405 | int max_retries; |
8336886f | 406 | |
42cb80a2 | 407 | req->rsk_ops->syn_ack_timeout(req); |
8336886f | 408 | |
20a3b1c0 KI |
409 | /* add one more retry for fastopen */ |
410 | max_retries = icsk->icsk_syn_retries ? : | |
411 | READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_synack_retries) + 1; | |
412 | ||
e6c022a4 | 413 | if (req->num_timeout >= max_retries) { |
8336886f JC |
414 | tcp_write_err(sk); |
415 | return; | |
416 | } | |
8c3cfe19 YC |
417 | /* Lower cwnd after certain SYNACK timeout like tcp_init_transfer() */ |
418 | if (icsk->icsk_retransmits == 1) | |
419 | tcp_enter_loss(sk); | |
8336886f JC |
420 | /* XXX (TFO) - Unlike regular SYN-ACK retransmit, we ignore error |
421 | * returned from rtx_syn_ack() to make it more persistent like | |
422 | * regular retransmit because if the child socket has been accepted | |
423 | * it's not good to give up too easily. | |
424 | */ | |
e6c022a4 ED |
425 | inet_rtx_syn_ack(sk, req); |
426 | req->num_timeout++; | |
7e32b443 | 427 | icsk->icsk_retransmits++; |
c7d13c8f YC |
428 | if (!tp->retrans_stamp) |
429 | tp->retrans_stamp = tcp_time_stamp(tp); | |
8336886f | 430 | inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, |
8ea731d4 | 431 | req->timeout << req->num_timeout, TCP_RTO_MAX); |
8336886f JC |
432 | } |
433 | ||
1da177e4 | 434 | |
c380d37e RS |
435 | /** |
436 | * tcp_retransmit_timer() - The TCP retransmit timeout handler | |
437 | * @sk: Pointer to the current socket. | |
438 | * | |
439 | * This function gets called when the kernel timer for a TCP packet | |
440 | * of this socket expires. | |
441 | * | |
974d8f86 | 442 | * It handles retransmission, timer adjustment and other necessary measures. |
c380d37e RS |
443 | * |
444 | * Returns: Nothing (void) | |
445 | */ | |
f1ecd5d9 | 446 | void tcp_retransmit_timer(struct sock *sk) |
1da177e4 LT |
447 | { |
448 | struct tcp_sock *tp = tcp_sk(sk); | |
ae5c3f40 | 449 | struct net *net = sock_net(sk); |
463c84b9 | 450 | struct inet_connection_sock *icsk = inet_csk(sk); |
d983ea6f | 451 | struct request_sock *req; |
0d580fbd | 452 | struct sk_buff *skb; |
1da177e4 | 453 | |
d983ea6f ED |
454 | req = rcu_dereference_protected(tp->fastopen_rsk, |
455 | lockdep_sock_is_held(sk)); | |
456 | if (req) { | |
37561f68 JC |
457 | WARN_ON_ONCE(sk->sk_state != TCP_SYN_RECV && |
458 | sk->sk_state != TCP_FIN_WAIT1); | |
d983ea6f | 459 | tcp_fastopen_synack_timer(sk, req); |
8336886f JC |
460 | /* Before we receive ACK to our SYN-ACK don't retransmit |
461 | * anything else (e.g., data or FIN segments). | |
462 | */ | |
463 | return; | |
464 | } | |
0d580fbd ED |
465 | |
466 | if (!tp->packets_out) | |
467 | return; | |
468 | ||
469 | skb = tcp_rtx_queue_head(sk); | |
470 | if (WARN_ON_ONCE(!skb)) | |
88f8598d | 471 | return; |
1da177e4 | 472 | |
9b717a8d ND |
473 | tp->tlp_high_seq = 0; |
474 | ||
1da177e4 LT |
475 | if (!tp->snd_wnd && !sock_flag(sk, SOCK_DEAD) && |
476 | !((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV))) { | |
477 | /* Receiver dastardly shrinks window. Our retransmits | |
478 | * become zero probes, but we should not timeout this | |
479 | * connection. If the socket is an orphan, time it out, | |
480 | * we cannot allow such beasts to hang infinitely. | |
481 | */ | |
569508c9 YH |
482 | struct inet_sock *inet = inet_sk(sk); |
483 | if (sk->sk_family == AF_INET) { | |
ba7a46f1 JP |
484 | net_dbg_ratelimited("Peer %pI4:%u/%u unexpectedly shrunk window %u:%u (repaired)\n", |
485 | &inet->inet_daddr, | |
486 | ntohs(inet->inet_dport), | |
487 | inet->inet_num, | |
488 | tp->snd_una, tp->snd_nxt); | |
1da177e4 | 489 | } |
dfd56b8b | 490 | #if IS_ENABLED(CONFIG_IPV6) |
569508c9 | 491 | else if (sk->sk_family == AF_INET6) { |
ba7a46f1 JP |
492 | net_dbg_ratelimited("Peer %pI6:%u/%u unexpectedly shrunk window %u:%u (repaired)\n", |
493 | &sk->sk_v6_daddr, | |
494 | ntohs(inet->inet_dport), | |
495 | inet->inet_num, | |
496 | tp->snd_una, tp->snd_nxt); | |
569508c9 | 497 | } |
1da177e4 | 498 | #endif |
70eabf0e | 499 | if (tcp_jiffies32 - tp->rcv_tstamp > TCP_RTO_MAX) { |
1da177e4 LT |
500 | tcp_write_err(sk); |
501 | goto out; | |
502 | } | |
5ae344c9 | 503 | tcp_enter_loss(sk); |
0d580fbd | 504 | tcp_retransmit_skb(sk, skb, 1); |
1da177e4 LT |
505 | __sk_dst_reset(sk); |
506 | goto out_reset_timer; | |
507 | } | |
508 | ||
e1561fe2 | 509 | __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPTIMEOUTS); |
1da177e4 LT |
510 | if (tcp_write_timeout(sk)) |
511 | goto out; | |
512 | ||
463c84b9 | 513 | if (icsk->icsk_retransmits == 0) { |
e1561fe2 | 514 | int mib_idx = 0; |
40b215e5 | 515 | |
c60ce4e2 | 516 | if (icsk->icsk_ca_state == TCP_CA_Recovery) { |
bc079e9e IJ |
517 | if (tcp_is_sack(tp)) |
518 | mib_idx = LINUX_MIB_TCPSACKRECOVERYFAIL; | |
519 | else | |
520 | mib_idx = LINUX_MIB_TCPRENORECOVERYFAIL; | |
6687e988 | 521 | } else if (icsk->icsk_ca_state == TCP_CA_Loss) { |
40b215e5 | 522 | mib_idx = LINUX_MIB_TCPLOSSFAILURES; |
c60ce4e2 IJ |
523 | } else if ((icsk->icsk_ca_state == TCP_CA_Disorder) || |
524 | tp->sacked_out) { | |
525 | if (tcp_is_sack(tp)) | |
526 | mib_idx = LINUX_MIB_TCPSACKFAILURES; | |
527 | else | |
528 | mib_idx = LINUX_MIB_TCPRENOFAILURES; | |
1da177e4 | 529 | } |
e1561fe2 YC |
530 | if (mib_idx) |
531 | __NET_INC_STATS(sock_net(sk), mib_idx); | |
1da177e4 LT |
532 | } |
533 | ||
5ae344c9 | 534 | tcp_enter_loss(sk); |
1da177e4 | 535 | |
590d2026 | 536 | icsk->icsk_retransmits++; |
75c119af | 537 | if (tcp_retransmit_skb(sk, tcp_rtx_queue_head(sk), 1) > 0) { |
1da177e4 | 538 | /* Retransmission failed because of local congestion, |
590d2026 | 539 | * Let senders fight for local resources conservatively. |
1da177e4 | 540 | */ |
463c84b9 | 541 | inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, |
590d2026 | 542 | TCP_RESOURCE_PROBE_INTERVAL, |
3f421baa | 543 | TCP_RTO_MAX); |
1da177e4 LT |
544 | goto out; |
545 | } | |
546 | ||
547 | /* Increase the timeout each time we retransmit. Note that | |
548 | * we do not increase the rtt estimate. rto is initialized | |
549 | * from rtt, but increases here. Jacobson (SIGCOMM 88) suggests | |
550 | * that doubling rto each time is the least we can get away with. | |
551 | * In KA9Q, Karn uses this for the first few times, and then | |
552 | * goes to quadratic. netBSD doubles, but only goes up to *64, | |
553 | * and clamps at 1 to 64 sec afterwards. Note that 120 sec is | |
554 | * defined in the protocol as the maximum possible RTT. I guess | |
555 | * we'll have to use something other than TCP to talk to the | |
556 | * University of Mars. | |
557 | * | |
558 | * PAWS allows us longer timeouts and large windows, so once | |
559 | * implemented ftp to mars will work nicely. We will have to fix | |
560 | * the 120 second clamps though! | |
561 | */ | |
463c84b9 | 562 | icsk->icsk_backoff++; |
1da177e4 LT |
563 | |
564 | out_reset_timer: | |
36e31b0a AP |
565 | /* If stream is thin, use linear timeouts. Since 'icsk_backoff' is |
566 | * used to reset timer, set to 0. Recalculate 'icsk_rto' as this | |
567 | * might be increased if the stream oscillates between thin and thick, | |
568 | * thus the old value might already be too high compared to the value | |
569 | * set by 'tcp_set_rto' in tcp_input.c which resets the rto without | |
570 | * backoff. Limit to TCP_THIN_LINEAR_RETRIES before initiating | |
571 | * exponential backoff behaviour to avoid continue hammering | |
572 | * linear-timeout retransmissions into a black hole | |
573 | */ | |
574 | if (sk->sk_state == TCP_ESTABLISHED && | |
7c6f2a86 | 575 | (tp->thin_lto || READ_ONCE(net->ipv4.sysctl_tcp_thin_linear_timeouts)) && |
36e31b0a AP |
576 | tcp_stream_is_thin(tp) && |
577 | icsk->icsk_retransmits <= TCP_THIN_LINEAR_RETRIES) { | |
578 | icsk->icsk_backoff = 0; | |
579 | icsk->icsk_rto = min(__tcp_set_rto(tp), TCP_RTO_MAX); | |
580 | } else { | |
581 | /* Use normal (exponential) backoff */ | |
582 | icsk->icsk_rto = min(icsk->icsk_rto << 1, TCP_RTO_MAX); | |
583 | } | |
b701a99e JM |
584 | inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, |
585 | tcp_clamp_rto_to_user_timeout(sk), TCP_RTO_MAX); | |
39e24435 | 586 | if (retransmits_timed_out(sk, READ_ONCE(net->ipv4.sysctl_tcp_retries1) + 1, 0)) |
1da177e4 LT |
587 | __sk_dst_reset(sk); |
588 | ||
589 | out:; | |
590 | } | |
591 | ||
c380d37e RS |
592 | /* Called with bottom-half processing disabled. |
593 | Called by tcp_write_timer() */ | |
6f458dfb | 594 | void tcp_write_timer_handler(struct sock *sk) |
1da177e4 | 595 | { |
463c84b9 | 596 | struct inet_connection_sock *icsk = inet_csk(sk); |
1da177e4 LT |
597 | int event; |
598 | ||
02b2faaf ED |
599 | if (((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN)) || |
600 | !icsk->icsk_pending) | |
4890b686 | 601 | return; |
1da177e4 | 602 | |
463c84b9 ACM |
603 | if (time_after(icsk->icsk_timeout, jiffies)) { |
604 | sk_reset_timer(sk, &icsk->icsk_retransmit_timer, icsk->icsk_timeout); | |
4890b686 | 605 | return; |
1da177e4 LT |
606 | } |
607 | ||
9a568de4 | 608 | tcp_mstamp_refresh(tcp_sk(sk)); |
463c84b9 | 609 | event = icsk->icsk_pending; |
1da177e4 LT |
610 | |
611 | switch (event) { | |
57dde7f7 YC |
612 | case ICSK_TIME_REO_TIMEOUT: |
613 | tcp_rack_reo_timeout(sk); | |
614 | break; | |
6ba8a3b1 ND |
615 | case ICSK_TIME_LOSS_PROBE: |
616 | tcp_send_loss_probe(sk); | |
617 | break; | |
463c84b9 | 618 | case ICSK_TIME_RETRANS: |
6ba8a3b1 | 619 | icsk->icsk_pending = 0; |
1da177e4 LT |
620 | tcp_retransmit_timer(sk); |
621 | break; | |
463c84b9 | 622 | case ICSK_TIME_PROBE0: |
6ba8a3b1 | 623 | icsk->icsk_pending = 0; |
1da177e4 LT |
624 | tcp_probe_timer(sk); |
625 | break; | |
626 | } | |
6f458dfb ED |
627 | } |
628 | ||
59f379f9 | 629 | static void tcp_write_timer(struct timer_list *t) |
6f458dfb | 630 | { |
59f379f9 KC |
631 | struct inet_connection_sock *icsk = |
632 | from_timer(icsk, t, icsk_retransmit_timer); | |
633 | struct sock *sk = &icsk->icsk_inet.sk; | |
6f458dfb ED |
634 | |
635 | bh_lock_sock(sk); | |
636 | if (!sock_owned_by_user(sk)) { | |
637 | tcp_write_timer_handler(sk); | |
638 | } else { | |
c380d37e | 639 | /* delegate our work to tcp_release_cb() */ |
7aa5470c | 640 | if (!test_and_set_bit(TCP_WRITE_TIMER_DEFERRED, &sk->sk_tsq_flags)) |
144d56e9 | 641 | sock_hold(sk); |
6f458dfb | 642 | } |
1da177e4 LT |
643 | bh_unlock_sock(sk); |
644 | sock_put(sk); | |
645 | } | |
646 | ||
42cb80a2 | 647 | void tcp_syn_ack_timeout(const struct request_sock *req) |
72659ecc | 648 | { |
42cb80a2 ED |
649 | struct net *net = read_pnet(&inet_rsk(req)->ireq_net); |
650 | ||
02a1d6e7 | 651 | __NET_INC_STATS(net, LINUX_MIB_TCPTIMEOUTS); |
72659ecc OP |
652 | } |
653 | EXPORT_SYMBOL(tcp_syn_ack_timeout); | |
654 | ||
1da177e4 LT |
655 | void tcp_set_keepalive(struct sock *sk, int val) |
656 | { | |
657 | if ((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN)) | |
658 | return; | |
659 | ||
660 | if (val && !sock_flag(sk, SOCK_KEEPOPEN)) | |
463c84b9 | 661 | inet_csk_reset_keepalive_timer(sk, keepalive_time_when(tcp_sk(sk))); |
1da177e4 | 662 | else if (!val) |
463c84b9 | 663 | inet_csk_delete_keepalive_timer(sk); |
1da177e4 | 664 | } |
4b9d07a4 | 665 | EXPORT_SYMBOL_GPL(tcp_set_keepalive); |
1da177e4 LT |
666 | |
667 | ||
59f379f9 | 668 | static void tcp_keepalive_timer (struct timer_list *t) |
1da177e4 | 669 | { |
59f379f9 | 670 | struct sock *sk = from_timer(sk, t, sk_timer); |
6687e988 | 671 | struct inet_connection_sock *icsk = inet_csk(sk); |
1da177e4 | 672 | struct tcp_sock *tp = tcp_sk(sk); |
6c37e5de | 673 | u32 elapsed; |
1da177e4 LT |
674 | |
675 | /* Only process if socket is not in use. */ | |
676 | bh_lock_sock(sk); | |
677 | if (sock_owned_by_user(sk)) { | |
e905a9ed | 678 | /* Try again later. */ |
463c84b9 | 679 | inet_csk_reset_keepalive_timer (sk, HZ/20); |
1da177e4 LT |
680 | goto out; |
681 | } | |
682 | ||
683 | if (sk->sk_state == TCP_LISTEN) { | |
fa76ce73 | 684 | pr_err("Hmm... keepalive on a LISTEN ???\n"); |
1da177e4 LT |
685 | goto out; |
686 | } | |
687 | ||
4688eb7c | 688 | tcp_mstamp_refresh(tp); |
1da177e4 LT |
689 | if (sk->sk_state == TCP_FIN_WAIT2 && sock_flag(sk, SOCK_DEAD)) { |
690 | if (tp->linger2 >= 0) { | |
463c84b9 | 691 | const int tmo = tcp_fin_time(sk) - TCP_TIMEWAIT_LEN; |
1da177e4 LT |
692 | |
693 | if (tmo > 0) { | |
694 | tcp_time_wait(sk, TCP_FIN_WAIT2, tmo); | |
695 | goto out; | |
696 | } | |
697 | } | |
698 | tcp_send_active_reset(sk, GFP_ATOMIC); | |
699 | goto death; | |
700 | } | |
701 | ||
2dda6400 ED |
702 | if (!sock_flag(sk, SOCK_KEEPOPEN) || |
703 | ((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_SYN_SENT))) | |
1da177e4 LT |
704 | goto out; |
705 | ||
706 | elapsed = keepalive_time_when(tp); | |
707 | ||
708 | /* It is alive without keepalive 8) */ | |
75c119af | 709 | if (tp->packets_out || !tcp_write_queue_empty(sk)) |
1da177e4 LT |
710 | goto resched; |
711 | ||
6c37e5de | 712 | elapsed = keepalive_time_elapsed(tp); |
1da177e4 LT |
713 | |
714 | if (elapsed >= keepalive_time_when(tp)) { | |
dca43c75 JC |
715 | /* If the TCP_USER_TIMEOUT option is enabled, use that |
716 | * to determine when to timeout instead. | |
717 | */ | |
718 | if ((icsk->icsk_user_timeout != 0 && | |
9bcc66e1 | 719 | elapsed >= msecs_to_jiffies(icsk->icsk_user_timeout) && |
dca43c75 JC |
720 | icsk->icsk_probes_out > 0) || |
721 | (icsk->icsk_user_timeout == 0 && | |
722 | icsk->icsk_probes_out >= keepalive_probes(tp))) { | |
1da177e4 LT |
723 | tcp_send_active_reset(sk, GFP_ATOMIC); |
724 | tcp_write_err(sk); | |
725 | goto out; | |
726 | } | |
e520af48 | 727 | if (tcp_write_wakeup(sk, LINUX_MIB_TCPKEEPALIVE) <= 0) { |
6687e988 | 728 | icsk->icsk_probes_out++; |
1da177e4 LT |
729 | elapsed = keepalive_intvl_when(tp); |
730 | } else { | |
731 | /* If keepalive was lost due to local congestion, | |
732 | * try harder. | |
733 | */ | |
734 | elapsed = TCP_RESOURCE_PROBE_INTERVAL; | |
735 | } | |
736 | } else { | |
737 | /* It is tp->rcv_tstamp + keepalive_time_when(tp) */ | |
738 | elapsed = keepalive_time_when(tp) - elapsed; | |
739 | } | |
740 | ||
1da177e4 | 741 | resched: |
463c84b9 | 742 | inet_csk_reset_keepalive_timer (sk, elapsed); |
1da177e4 LT |
743 | goto out; |
744 | ||
e905a9ed | 745 | death: |
1da177e4 LT |
746 | tcp_done(sk); |
747 | ||
748 | out: | |
749 | bh_unlock_sock(sk); | |
750 | sock_put(sk); | |
751 | } | |
6f458dfb | 752 | |
5d9f4262 ED |
753 | static enum hrtimer_restart tcp_compressed_ack_kick(struct hrtimer *timer) |
754 | { | |
755 | struct tcp_sock *tp = container_of(timer, struct tcp_sock, compressed_ack_timer); | |
756 | struct sock *sk = (struct sock *)tp; | |
757 | ||
758 | bh_lock_sock(sk); | |
759 | if (!sock_owned_by_user(sk)) { | |
2b195850 ED |
760 | if (tp->compressed_ack) { |
761 | /* Since we have to send one ack finally, | |
974d8f86 | 762 | * subtract one from tp->compressed_ack to keep |
2b195850 ED |
763 | * LINUX_MIB_TCPACKCOMPRESSED accurate. |
764 | */ | |
765 | tp->compressed_ack--; | |
5d9f4262 | 766 | tcp_send_ack(sk); |
2b195850 | 767 | } |
5d9f4262 ED |
768 | } else { |
769 | if (!test_and_set_bit(TCP_DELACK_TIMER_DEFERRED, | |
770 | &sk->sk_tsq_flags)) | |
771 | sock_hold(sk); | |
772 | } | |
773 | bh_unlock_sock(sk); | |
774 | ||
775 | sock_put(sk); | |
776 | ||
777 | return HRTIMER_NORESTART; | |
778 | } | |
779 | ||
6f458dfb ED |
780 | void tcp_init_xmit_timers(struct sock *sk) |
781 | { | |
782 | inet_csk_init_xmit_timers(sk, &tcp_write_timer, &tcp_delack_timer, | |
783 | &tcp_keepalive_timer); | |
fb420d5d | 784 | hrtimer_init(&tcp_sk(sk)->pacing_timer, CLOCK_MONOTONIC, |
73a6bab5 | 785 | HRTIMER_MODE_ABS_PINNED_SOFT); |
218af599 | 786 | tcp_sk(sk)->pacing_timer.function = tcp_pace_kick; |
5d9f4262 ED |
787 | |
788 | hrtimer_init(&tcp_sk(sk)->compressed_ack_timer, CLOCK_MONOTONIC, | |
789 | HRTIMER_MODE_REL_PINNED_SOFT); | |
790 | tcp_sk(sk)->compressed_ack_timer.function = tcp_compressed_ack_kick; | |
6f458dfb | 791 | } |