tcp_timer.c 16.4 KB
Newer Older
L
Linus Torvalds 已提交
1 2 3 4 5 6 7
/*
 * INET		An implementation of the TCP/IP protocol suite for the LINUX
 *		operating system.  INET is implemented using the  BSD Socket
 *		interface as the means of communication with the user level.
 *
 *		Implementation of the Transmission Control Protocol(TCP).
 *
8
 * Authors:	Ross Biro
L
Linus Torvalds 已提交
9 10 11 12 13 14 15 16 17 18 19 20 21
 *		Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
 *		Mark Evans, <evansmp@uhura.aston.ac.uk>
 *		Corey Minyard <wf-rch!minyard@relay.EU.net>
 *		Florian La Roche, <flla@stud.uni-sb.de>
 *		Charles Hedrick, <hedrick@klinzhai.rutgers.edu>
 *		Linus Torvalds, <torvalds@cs.helsinki.fi>
 *		Alan Cox, <gw4pts@gw4pts.ampr.org>
 *		Matthew Dillon, <dillon@apollo.west.oic.com>
 *		Arnt Gulbrandsen, <agulbra@nvg.unit.no>
 *		Jorge Cwik, <jorge@laser.satlink.net>
 */

#include <linux/module.h>
22
#include <linux/gfp.h>
L
Linus Torvalds 已提交
23 24
#include <net/tcp.h>

25 26 27 28 29 30 31 32
int sysctl_tcp_syn_retries __read_mostly = TCP_SYN_RETRIES;
int sysctl_tcp_synack_retries __read_mostly = TCP_SYNACK_RETRIES;
int sysctl_tcp_keepalive_time __read_mostly = TCP_KEEPALIVE_TIME;
int sysctl_tcp_keepalive_probes __read_mostly = TCP_KEEPALIVE_PROBES;
int sysctl_tcp_keepalive_intvl __read_mostly = TCP_KEEPALIVE_INTVL;
int sysctl_tcp_retries1 __read_mostly = TCP_RETR1;
int sysctl_tcp_retries2 __read_mostly = TCP_RETR2;
int sysctl_tcp_orphan_retries __read_mostly;
A
Andreas Petlund 已提交
33
int sysctl_tcp_thin_linear_timeouts __read_mostly;
L
Linus Torvalds 已提交
34 35 36 37 38

static void tcp_write_timer(unsigned long);
static void tcp_delack_timer(unsigned long);
static void tcp_keepalive_timer (unsigned long data);

39 40 41 42 43
void tcp_init_xmit_timers(struct sock *sk)
{
	inet_csk_init_xmit_timers(sk, &tcp_write_timer, &tcp_delack_timer,
				  &tcp_keepalive_timer);
}
44 45
EXPORT_SYMBOL(tcp_init_xmit_timers);

L
Linus Torvalds 已提交
46 47 48 49 50 51
static void tcp_write_err(struct sock *sk)
{
	sk->sk_err = sk->sk_err_soft ? : ETIMEDOUT;
	sk->sk_error_report(sk);

	tcp_done(sk);
52
	NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPABORTONTIMEOUT);
L
Linus Torvalds 已提交
53 54 55 56 57 58 59
}

/* Do not allow orphaned sockets to eat all our resources.
 * This is direct violation of TCP specs, but it is required
 * to prevent DoS attacks. It is called when a retransmission timeout
 * or zero probe timeout occurs on orphaned socket.
 *
S
Stephen Hemminger 已提交
60
 * Criteria is still not confirmed experimentally and may change.
L
Linus Torvalds 已提交
61 62 63 64 65 66 67 68
 * We kill the socket, if:
 * 1. If number of orphaned sockets exceeds an administratively configured
 *    limit.
 * 2. If we have strong memory pressure.
 */
static int tcp_out_of_resources(struct sock *sk, int do_reset)
{
	struct tcp_sock *tp = tcp_sk(sk);
69
	int shift = 0;
L
Linus Torvalds 已提交
70

71
	/* If peer does not open window for long time, or did not transmit
L
Linus Torvalds 已提交
72 73
	 * anything for long time, penalize it. */
	if ((s32)(tcp_time_stamp - tp->lsndtime) > 2*TCP_RTO_MAX || !do_reset)
74
		shift++;
L
Linus Torvalds 已提交
75 76 77

	/* If some dubious ICMP arrived, penalize even more. */
	if (sk->sk_err_soft)
78
		shift++;
L
Linus Torvalds 已提交
79

80
	if (tcp_too_many_orphans(sk, shift)) {
L
Linus Torvalds 已提交
81 82 83 84 85 86 87 88 89 90 91 92
		if (net_ratelimit())
			printk(KERN_INFO "Out of socket memory\n");

		/* Catch exceptional cases, when connection requires reset.
		 *      1. Last segment was sent recently. */
		if ((s32)(tcp_time_stamp - tp->lsndtime) <= TCP_TIMEWAIT_LEN ||
		    /*  2. Window is closed. */
		    (!tp->snd_wnd && !tp->packets_out))
			do_reset = 1;
		if (do_reset)
			tcp_send_active_reset(sk, GFP_ATOMIC);
		tcp_done(sk);
93
		NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPABORTONMEMORY);
L
Linus Torvalds 已提交
94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115
		return 1;
	}
	return 0;
}

/* Calculate maximal number or retries on an orphaned socket. */
static int tcp_orphan_retries(struct sock *sk, int alive)
{
	int retries = sysctl_tcp_orphan_retries; /* May be zero. */

	/* We know from an ICMP that something is wrong. */
	if (sk->sk_err_soft && !alive)
		retries = 0;

	/* However, if socket sent something recently, select some safe
	 * number of retries. 8 corresponds to >100 seconds with minimal
	 * RTO of 200msec. */
	if (retries == 0 && alive)
		retries = 8;
	return retries;
}

116 117 118 119 120 121 122 123 124
static void tcp_mtu_probing(struct inet_connection_sock *icsk, struct sock *sk)
{
	/* Black hole detection */
	if (sysctl_tcp_mtu_probing) {
		if (!icsk->icsk_mtup.enabled) {
			icsk->icsk_mtup.enabled = 1;
			tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);
		} else {
			struct tcp_sock *tp = tcp_sk(sk);
125 126
			int mss;

127
			mss = tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_low) >> 1;
128 129 130 131 132 133 134 135
			mss = min(sysctl_tcp_base_mss, mss);
			mss = max(mss, 68 - tp->tcp_header_len);
			icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, mss);
			tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);
		}
	}
}

136
/* This function calculates a "timeout" which is equivalent to the timeout of a
D
Daniel Mack 已提交
137
 * TCP connection after "boundary" unsuccessful, exponentially backed-off
138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164
 * retransmissions with an initial RTO of TCP_RTO_MIN.
 */
static bool retransmits_timed_out(struct sock *sk,
				  unsigned int boundary)
{
	unsigned int timeout, linear_backoff_thresh;
	unsigned int start_ts;

	if (!inet_csk(sk)->icsk_retransmits)
		return false;

	if (unlikely(!tcp_sk(sk)->retrans_stamp))
		start_ts = TCP_SKB_CB(tcp_write_queue_head(sk))->when;
	else
		start_ts = tcp_sk(sk)->retrans_stamp;

	linear_backoff_thresh = ilog2(TCP_RTO_MAX/TCP_RTO_MIN);

	if (boundary <= linear_backoff_thresh)
		timeout = ((2 << boundary) - 1) * TCP_RTO_MIN;
	else
		timeout = ((2 << linear_backoff_thresh) - 1) * TCP_RTO_MIN +
			  (boundary - linear_backoff_thresh) * TCP_RTO_MAX;

	return (tcp_time_stamp - start_ts) >= timeout;
}

L
Linus Torvalds 已提交
165 166 167
/* A write timeout has occurred. Process the after effects. */
static int tcp_write_timeout(struct sock *sk)
{
J
John Heffner 已提交
168
	struct inet_connection_sock *icsk = inet_csk(sk);
L
Linus Torvalds 已提交
169
	int retry_until;
170
	bool do_reset;
L
Linus Torvalds 已提交
171 172

	if ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV)) {
173
		if (icsk->icsk_retransmits)
E
Eric Dumazet 已提交
174
			dst_negative_advice(sk);
175
		retry_until = icsk->icsk_syn_retries ? : sysctl_tcp_syn_retries;
L
Linus Torvalds 已提交
176
	} else {
177
		if (retransmits_timed_out(sk, sysctl_tcp_retries1)) {
J
John Heffner 已提交
178
			/* Black hole detection */
179
			tcp_mtu_probing(icsk, sk);
L
Linus Torvalds 已提交
180

E
Eric Dumazet 已提交
181
			dst_negative_advice(sk);
L
Linus Torvalds 已提交
182 183 184 185
		}

		retry_until = sysctl_tcp_retries2;
		if (sock_flag(sk, SOCK_DEAD)) {
186
			const int alive = (icsk->icsk_rto < TCP_RTO_MAX);
187

L
Linus Torvalds 已提交
188
			retry_until = tcp_orphan_retries(sk, alive);
189 190
			do_reset = alive ||
				   !retransmits_timed_out(sk, retry_until);
L
Linus Torvalds 已提交
191

192
			if (tcp_out_of_resources(sk, do_reset))
L
Linus Torvalds 已提交
193 194 195 196
				return 1;
		}
	}

197
	if (retransmits_timed_out(sk, retry_until)) {
L
Linus Torvalds 已提交
198 199 200 201 202 203 204 205 206
		/* Has it gone just too far? */
		tcp_write_err(sk);
		return 1;
	}
	return 0;
}

static void tcp_delack_timer(unsigned long data)
{
207
	struct sock *sk = (struct sock *)data;
L
Linus Torvalds 已提交
208
	struct tcp_sock *tp = tcp_sk(sk);
209
	struct inet_connection_sock *icsk = inet_csk(sk);
L
Linus Torvalds 已提交
210 211 212 213

	bh_lock_sock(sk);
	if (sock_owned_by_user(sk)) {
		/* Try again later. */
214
		icsk->icsk_ack.blocked = 1;
215
		NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_DELAYEDACKLOCKED);
216
		sk_reset_timer(sk, &icsk->icsk_delack_timer, jiffies + TCP_DELACK_MIN);
L
Linus Torvalds 已提交
217 218 219
		goto out_unlock;
	}

220
	sk_mem_reclaim_partial(sk);
L
Linus Torvalds 已提交
221

222
	if (sk->sk_state == TCP_CLOSE || !(icsk->icsk_ack.pending & ICSK_ACK_TIMER))
L
Linus Torvalds 已提交
223 224
		goto out;

225 226
	if (time_after(icsk->icsk_ack.timeout, jiffies)) {
		sk_reset_timer(sk, &icsk->icsk_delack_timer, icsk->icsk_ack.timeout);
L
Linus Torvalds 已提交
227 228
		goto out;
	}
229
	icsk->icsk_ack.pending &= ~ICSK_ACK_TIMER;
L
Linus Torvalds 已提交
230

231
	if (!skb_queue_empty(&tp->ucopy.prequeue)) {
L
Linus Torvalds 已提交
232 233
		struct sk_buff *skb;

234
		NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPSCHEDULERFAILED);
L
Linus Torvalds 已提交
235 236

		while ((skb = __skb_dequeue(&tp->ucopy.prequeue)) != NULL)
P
Peter Zijlstra 已提交
237
			sk_backlog_rcv(sk, skb);
L
Linus Torvalds 已提交
238 239 240 241

		tp->ucopy.memory = 0;
	}

242 243
	if (inet_csk_ack_scheduled(sk)) {
		if (!icsk->icsk_ack.pingpong) {
L
Linus Torvalds 已提交
244
			/* Delayed ACK missed: inflate ATO. */
245
			icsk->icsk_ack.ato = min(icsk->icsk_ack.ato << 1, icsk->icsk_rto);
L
Linus Torvalds 已提交
246 247 248 249
		} else {
			/* Delayed ACK missed: leave pingpong mode and
			 * deflate ATO.
			 */
250 251
			icsk->icsk_ack.pingpong = 0;
			icsk->icsk_ack.ato      = TCP_ATO_MIN;
L
Linus Torvalds 已提交
252 253
		}
		tcp_send_ack(sk);
254
		NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_DELAYEDACKS);
L
Linus Torvalds 已提交
255 256 257 258 259
	}
	TCP_CHECK_TIMER(sk);

out:
	if (tcp_memory_pressure)
260
		sk_mem_reclaim(sk);
L
Linus Torvalds 已提交
261 262 263 264 265 266 267
out_unlock:
	bh_unlock_sock(sk);
	sock_put(sk);
}

static void tcp_probe_timer(struct sock *sk)
{
268
	struct inet_connection_sock *icsk = inet_csk(sk);
L
Linus Torvalds 已提交
269 270 271
	struct tcp_sock *tp = tcp_sk(sk);
	int max_probes;

272
	if (tp->packets_out || !tcp_send_head(sk)) {
273
		icsk->icsk_probes_out = 0;
L
Linus Torvalds 已提交
274 275 276 277 278 279 280 281 282 283
		return;
	}

	/* *WARNING* RFC 1122 forbids this
	 *
	 * It doesn't AFAIK, because we kill the retransmit timer -AK
	 *
	 * FIXME: We ought not to do it, Solaris 2.5 actually has fixing
	 * this behaviour in Solaris down as a bug fix. [AC]
	 *
284
	 * Let me to explain. icsk_probes_out is zeroed by incoming ACKs
L
Linus Torvalds 已提交
285 286 287 288 289 290 291 292 293 294
	 * even if they advertise zero window. Hence, connection is killed only
	 * if we received no ACKs for normal connection timeout. It is not killed
	 * only because window stays zero for some time, window may be zero
	 * until armageddon and even later. We are in full accordance
	 * with RFCs, only probe timer combines both retransmission timeout
	 * and probe timeout in one bottle.				--ANK
	 */
	max_probes = sysctl_tcp_retries2;

	if (sock_flag(sk, SOCK_DEAD)) {
295
		const int alive = ((icsk->icsk_rto << icsk->icsk_backoff) < TCP_RTO_MAX);
296

L
Linus Torvalds 已提交
297 298
		max_probes = tcp_orphan_retries(sk, alive);

299
		if (tcp_out_of_resources(sk, alive || icsk->icsk_probes_out <= max_probes))
L
Linus Torvalds 已提交
300 301 302
			return;
	}

303
	if (icsk->icsk_probes_out > max_probes) {
L
Linus Torvalds 已提交
304 305 306 307 308 309 310 311 312 313 314
		tcp_write_err(sk);
	} else {
		/* Only send another probe if we didn't close things up. */
		tcp_send_probe0(sk);
	}
}

/*
 *	The TCP retransmit timer.
 */

315
void tcp_retransmit_timer(struct sock *sk)
L
Linus Torvalds 已提交
316 317
{
	struct tcp_sock *tp = tcp_sk(sk);
318
	struct inet_connection_sock *icsk = inet_csk(sk);
L
Linus Torvalds 已提交
319 320 321 322

	if (!tp->packets_out)
		goto out;

323
	WARN_ON(tcp_write_queue_empty(sk));
L
Linus Torvalds 已提交
324 325 326 327 328 329 330 331 332

	if (!tp->snd_wnd && !sock_flag(sk, SOCK_DEAD) &&
	    !((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV))) {
		/* Receiver dastardly shrinks window. Our retransmits
		 * become zero probes, but we should not timeout this
		 * connection. If the socket is an orphan, time it out,
		 * we cannot allow such beasts to hang infinitely.
		 */
#ifdef TCP_DEBUG
333 334
		struct inet_sock *inet = inet_sk(sk);
		if (sk->sk_family == AF_INET) {
335
			LIMIT_NETDEBUG(KERN_DEBUG "TCP: Peer %pI4:%u/%u unexpectedly shrunk window %u:%u (repaired)\n",
E
Eric Dumazet 已提交
336 337
			       &inet->inet_daddr, ntohs(inet->inet_dport),
			       inet->inet_num, tp->snd_una, tp->snd_nxt);
L
Linus Torvalds 已提交
338
		}
339 340 341
#if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
		else if (sk->sk_family == AF_INET6) {
			struct ipv6_pinfo *np = inet6_sk(sk);
342
			LIMIT_NETDEBUG(KERN_DEBUG "TCP: Peer %pI6:%u/%u unexpectedly shrunk window %u:%u (repaired)\n",
E
Eric Dumazet 已提交
343 344
			       &np->daddr, ntohs(inet->inet_dport),
			       inet->inet_num, tp->snd_una, tp->snd_nxt);
345 346
		}
#endif
L
Linus Torvalds 已提交
347 348 349 350 351 352
#endif
		if (tcp_time_stamp - tp->rcv_tstamp > TCP_RTO_MAX) {
			tcp_write_err(sk);
			goto out;
		}
		tcp_enter_loss(sk, 0);
353
		tcp_retransmit_skb(sk, tcp_write_queue_head(sk));
L
Linus Torvalds 已提交
354 355 356 357 358 359 360
		__sk_dst_reset(sk);
		goto out_reset_timer;
	}

	if (tcp_write_timeout(sk))
		goto out;

361
	if (icsk->icsk_retransmits == 0) {
362 363
		int mib_idx;

364 365 366 367 368 369 370 371 372 373
		if (icsk->icsk_ca_state == TCP_CA_Disorder) {
			if (tcp_is_sack(tp))
				mib_idx = LINUX_MIB_TCPSACKFAILURES;
			else
				mib_idx = LINUX_MIB_TCPRENOFAILURES;
		} else if (icsk->icsk_ca_state == TCP_CA_Recovery) {
			if (tcp_is_sack(tp))
				mib_idx = LINUX_MIB_TCPSACKRECOVERYFAIL;
			else
				mib_idx = LINUX_MIB_TCPRENORECOVERYFAIL;
374
		} else if (icsk->icsk_ca_state == TCP_CA_Loss) {
375
			mib_idx = LINUX_MIB_TCPLOSSFAILURES;
L
Linus Torvalds 已提交
376
		} else {
377
			mib_idx = LINUX_MIB_TCPTIMEOUTS;
L
Linus Torvalds 已提交
378
		}
379
		NET_INC_STATS_BH(sock_net(sk), mib_idx);
L
Linus Torvalds 已提交
380 381 382 383 384 385 386 387
	}

	if (tcp_use_frto(sk)) {
		tcp_enter_frto(sk);
	} else {
		tcp_enter_loss(sk, 0);
	}

388
	if (tcp_retransmit_skb(sk, tcp_write_queue_head(sk)) > 0) {
L
Linus Torvalds 已提交
389 390 391
		/* Retransmission failed because of local congestion,
		 * do not backoff.
		 */
392 393 394
		if (!icsk->icsk_retransmits)
			icsk->icsk_retransmits = 1;
		inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
395 396
					  min(icsk->icsk_rto, TCP_RESOURCE_PROBE_INTERVAL),
					  TCP_RTO_MAX);
L
Linus Torvalds 已提交
397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414
		goto out;
	}

	/* Increase the timeout each time we retransmit.  Note that
	 * we do not increase the rtt estimate.  rto is initialized
	 * from rtt, but increases here.  Jacobson (SIGCOMM 88) suggests
	 * that doubling rto each time is the least we can get away with.
	 * In KA9Q, Karn uses this for the first few times, and then
	 * goes to quadratic.  netBSD doubles, but only goes up to *64,
	 * and clamps at 1 to 64 sec afterwards.  Note that 120 sec is
	 * defined in the protocol as the maximum possible RTT.  I guess
	 * we'll have to use something other than TCP to talk to the
	 * University of Mars.
	 *
	 * PAWS allows us longer timeouts and large windows, so once
	 * implemented ftp to mars will work nicely. We will have to fix
	 * the 120 second clamps though!
	 */
415 416
	icsk->icsk_backoff++;
	icsk->icsk_retransmits++;
L
Linus Torvalds 已提交
417 418

out_reset_timer:
A
Andreas Petlund 已提交
419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437
	/* If stream is thin, use linear timeouts. Since 'icsk_backoff' is
	 * used to reset timer, set to 0. Recalculate 'icsk_rto' as this
	 * might be increased if the stream oscillates between thin and thick,
	 * thus the old value might already be too high compared to the value
	 * set by 'tcp_set_rto' in tcp_input.c which resets the rto without
	 * backoff. Limit to TCP_THIN_LINEAR_RETRIES before initiating
	 * exponential backoff behaviour to avoid continue hammering
	 * linear-timeout retransmissions into a black hole
	 */
	if (sk->sk_state == TCP_ESTABLISHED &&
	    (tp->thin_lto || sysctl_tcp_thin_linear_timeouts) &&
	    tcp_stream_is_thin(tp) &&
	    icsk->icsk_retransmits <= TCP_THIN_LINEAR_RETRIES) {
		icsk->icsk_backoff = 0;
		icsk->icsk_rto = min(__tcp_set_rto(tp), TCP_RTO_MAX);
	} else {
		/* Use normal (exponential) backoff */
		icsk->icsk_rto = min(icsk->icsk_rto << 1, TCP_RTO_MAX);
	}
438
	inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, icsk->icsk_rto, TCP_RTO_MAX);
439
	if (retransmits_timed_out(sk, sysctl_tcp_retries1 + 1))
L
Linus Torvalds 已提交
440 441 442 443 444 445 446
		__sk_dst_reset(sk);

out:;
}

static void tcp_write_timer(unsigned long data)
{
447
	struct sock *sk = (struct sock *)data;
448
	struct inet_connection_sock *icsk = inet_csk(sk);
L
Linus Torvalds 已提交
449 450 451 452 453
	int event;

	bh_lock_sock(sk);
	if (sock_owned_by_user(sk)) {
		/* Try again later */
454
		sk_reset_timer(sk, &icsk->icsk_retransmit_timer, jiffies + (HZ / 20));
L
Linus Torvalds 已提交
455 456 457
		goto out_unlock;
	}

458
	if (sk->sk_state == TCP_CLOSE || !icsk->icsk_pending)
L
Linus Torvalds 已提交
459 460
		goto out;

461 462
	if (time_after(icsk->icsk_timeout, jiffies)) {
		sk_reset_timer(sk, &icsk->icsk_retransmit_timer, icsk->icsk_timeout);
L
Linus Torvalds 已提交
463 464 465
		goto out;
	}

466 467
	event = icsk->icsk_pending;
	icsk->icsk_pending = 0;
L
Linus Torvalds 已提交
468 469

	switch (event) {
470
	case ICSK_TIME_RETRANS:
L
Linus Torvalds 已提交
471 472
		tcp_retransmit_timer(sk);
		break;
473
	case ICSK_TIME_PROBE0:
L
Linus Torvalds 已提交
474 475 476 477 478 479
		tcp_probe_timer(sk);
		break;
	}
	TCP_CHECK_TIMER(sk);

out:
480
	sk_mem_reclaim(sk);
L
Linus Torvalds 已提交
481 482 483 484 485
out_unlock:
	bh_unlock_sock(sk);
	sock_put(sk);
}

486 487 488 489 490 491
/*
 *	Timer for listening sockets
 */

static void tcp_synack_timer(struct sock *sk)
{
492 493
	inet_csk_reqsk_queue_prune(sk, TCP_SYNQ_INTERVAL,
				   TCP_TIMEOUT_INIT, TCP_RTO_MAX);
L
Linus Torvalds 已提交
494 495
}

496 497 498 499 500 501
void tcp_syn_ack_timeout(struct sock *sk, struct request_sock *req)
{
	NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPTIMEOUTS);
}
EXPORT_SYMBOL(tcp_syn_ack_timeout);

L
Linus Torvalds 已提交
502 503 504 505 506 507
void tcp_set_keepalive(struct sock *sk, int val)
{
	if ((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN))
		return;

	if (val && !sock_flag(sk, SOCK_KEEPOPEN))
508
		inet_csk_reset_keepalive_timer(sk, keepalive_time_when(tcp_sk(sk)));
L
Linus Torvalds 已提交
509
	else if (!val)
510
		inet_csk_delete_keepalive_timer(sk);
L
Linus Torvalds 已提交
511 512 513 514 515 516
}


static void tcp_keepalive_timer (unsigned long data)
{
	struct sock *sk = (struct sock *) data;
517
	struct inet_connection_sock *icsk = inet_csk(sk);
L
Linus Torvalds 已提交
518
	struct tcp_sock *tp = tcp_sk(sk);
519
	u32 elapsed;
L
Linus Torvalds 已提交
520 521 522 523

	/* Only process if socket is not in use. */
	bh_lock_sock(sk);
	if (sock_owned_by_user(sk)) {
524
		/* Try again later. */
525
		inet_csk_reset_keepalive_timer (sk, HZ/20);
L
Linus Torvalds 已提交
526 527 528 529 530 531 532 533 534 535
		goto out;
	}

	if (sk->sk_state == TCP_LISTEN) {
		tcp_synack_timer(sk);
		goto out;
	}

	if (sk->sk_state == TCP_FIN_WAIT2 && sock_flag(sk, SOCK_DEAD)) {
		if (tp->linger2 >= 0) {
536
			const int tmo = tcp_fin_time(sk) - TCP_TIMEWAIT_LEN;
L
Linus Torvalds 已提交
537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552

			if (tmo > 0) {
				tcp_time_wait(sk, TCP_FIN_WAIT2, tmo);
				goto out;
			}
		}
		tcp_send_active_reset(sk, GFP_ATOMIC);
		goto death;
	}

	if (!sock_flag(sk, SOCK_KEEPOPEN) || sk->sk_state == TCP_CLOSE)
		goto out;

	elapsed = keepalive_time_when(tp);

	/* It is alive without keepalive 8) */
553
	if (tp->packets_out || tcp_send_head(sk))
L
Linus Torvalds 已提交
554 555
		goto resched;

556
	elapsed = keepalive_time_elapsed(tp);
L
Linus Torvalds 已提交
557 558

	if (elapsed >= keepalive_time_when(tp)) {
E
Eric Dumazet 已提交
559
		if (icsk->icsk_probes_out >= keepalive_probes(tp)) {
L
Linus Torvalds 已提交
560 561 562 563 564
			tcp_send_active_reset(sk, GFP_ATOMIC);
			tcp_write_err(sk);
			goto out;
		}
		if (tcp_write_wakeup(sk) <= 0) {
565
			icsk->icsk_probes_out++;
L
Linus Torvalds 已提交
566 567 568 569 570 571 572 573 574 575 576 577 578
			elapsed = keepalive_intvl_when(tp);
		} else {
			/* If keepalive was lost due to local congestion,
			 * try harder.
			 */
			elapsed = TCP_RESOURCE_PROBE_INTERVAL;
		}
	} else {
		/* It is tp->rcv_tstamp + keepalive_time_when(tp) */
		elapsed = keepalive_time_when(tp) - elapsed;
	}

	TCP_CHECK_TIMER(sk);
579
	sk_mem_reclaim(sk);
L
Linus Torvalds 已提交
580 581

resched:
582
	inet_csk_reset_keepalive_timer (sk, elapsed);
L
Linus Torvalds 已提交
583 584
	goto out;

585
death:
L
Linus Torvalds 已提交
586 587 588 589 590 591
	tcp_done(sk);

out:
	bh_unlock_sock(sk);
	sock_put(sk);
}