Linux-2.6.12-rc2v2.6.12-rc2

Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.

Let it rip!

1 files changed, 656 insertions, 0 deletions

diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c
new file mode 100644
index 000000000000..85b279f1e935
--- /dev/null
+++ b/net/ipv4/tcp_timer.c
@@ -0,0 +1,656 @@
+/*
+ * 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).
+ *
+ * Version:	$Id: tcp_timer.c,v 1.88 2002/02/01 22:01:04 davem Exp $
+ *
+ * Authors:	Ross Biro, <bir7@leland.Stanford.Edu>
+ *		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>
+#include <net/tcp.h>
+
+int sysctl_tcp_syn_retries = TCP_SYN_RETRIES; 
+int sysctl_tcp_synack_retries = TCP_SYNACK_RETRIES; 
+int sysctl_tcp_keepalive_time = TCP_KEEPALIVE_TIME;
+int sysctl_tcp_keepalive_probes = TCP_KEEPALIVE_PROBES;
+int sysctl_tcp_keepalive_intvl = TCP_KEEPALIVE_INTVL;
+int sysctl_tcp_retries1 = TCP_RETR1;
+int sysctl_tcp_retries2 = TCP_RETR2;
+int sysctl_tcp_orphan_retries;
+
+static void tcp_write_timer(unsigned long);
+static void tcp_delack_timer(unsigned long);
+static void tcp_keepalive_timer (unsigned long data);
+
+#ifdef TCP_DEBUG
+const char tcp_timer_bug_msg[] = KERN_DEBUG "tcpbug: unknown timer value\n";
+EXPORT_SYMBOL(tcp_timer_bug_msg);
+#endif
+
+/*
+ * Using different timers for retransmit, delayed acks and probes
+ * We may wish use just one timer maintaining a list of expire jiffies 
+ * to optimize.
+ */
+
+void tcp_init_xmit_timers(struct sock *sk)
+{
+	struct tcp_sock *tp = tcp_sk(sk);
+
+	init_timer(&tp->retransmit_timer);
+	tp->retransmit_timer.function=&tcp_write_timer;
+	tp->retransmit_timer.data = (unsigned long) sk;
+	tp->pending = 0;
+
+	init_timer(&tp->delack_timer);
+	tp->delack_timer.function=&tcp_delack_timer;
+	tp->delack_timer.data = (unsigned long) sk;
+	tp->ack.pending = 0;
+
+	init_timer(&sk->sk_timer);
+	sk->sk_timer.function	= &tcp_keepalive_timer;
+	sk->sk_timer.data	= (unsigned long)sk;
+}
+
+void tcp_clear_xmit_timers(struct sock *sk)
+{
+	struct tcp_sock *tp = tcp_sk(sk);
+
+	tp->pending = 0;
+	sk_stop_timer(sk, &tp->retransmit_timer);
+
+	tp->ack.pending = 0;
+	tp->ack.blocked = 0;
+	sk_stop_timer(sk, &tp->delack_timer);
+
+	sk_stop_timer(sk, &sk->sk_timer);
+}
+
+static void tcp_write_err(struct sock *sk)
+{
+	sk->sk_err = sk->sk_err_soft ? : ETIMEDOUT;
+	sk->sk_error_report(sk);
+
+	tcp_done(sk);
+	NET_INC_STATS_BH(LINUX_MIB_TCPABORTONTIMEOUT);
+}
+
+/* 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.
+ *
+ * Criterium is still not confirmed experimentally and may change.
+ * 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);
+	int orphans = atomic_read(&tcp_orphan_count);
+
+	/* If peer does not open window for long time, or did not transmit 
+	 * anything for long time, penalize it. */
+	if ((s32)(tcp_time_stamp - tp->lsndtime) > 2*TCP_RTO_MAX || !do_reset)
+		orphans <<= 1;
+
+	/* If some dubious ICMP arrived, penalize even more. */
+	if (sk->sk_err_soft)
+		orphans <<= 1;
+
+	if (orphans >= sysctl_tcp_max_orphans ||
+	    (sk->sk_wmem_queued > SOCK_MIN_SNDBUF &&
+	     atomic_read(&tcp_memory_allocated) > sysctl_tcp_mem[2])) {
+		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);
+		NET_INC_STATS_BH(LINUX_MIB_TCPABORTONMEMORY);
+		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;
+}
+
+/* A write timeout has occurred. Process the after effects. */
+static int tcp_write_timeout(struct sock *sk)
+{
+	struct tcp_sock *tp = tcp_sk(sk);
+	int retry_until;
+
+	if ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV)) {
+		if (tp->retransmits)
+			dst_negative_advice(&sk->sk_dst_cache);
+		retry_until = tp->syn_retries ? : sysctl_tcp_syn_retries;
+	} else {
+		if (tp->retransmits >= sysctl_tcp_retries1) {
+			/* NOTE. draft-ietf-tcpimpl-pmtud-01.txt requires pmtu black
+			   hole detection. :-(
+
+			   It is place to make it. It is not made. I do not want
+			   to make it. It is disguisting. It does not work in any
+			   case. Let me to cite the same draft, which requires for
+			   us to implement this:
+
+   "The one security concern raised by this memo is that ICMP black holes
+   are often caused by over-zealous security administrators who block
+   all ICMP messages.  It is vitally important that those who design and
+   deploy security systems understand the impact of strict filtering on
+   upper-layer protocols.  The safest web site in the world is worthless
+   if most TCP implementations cannot transfer data from it.  It would
+   be far nicer to have all of the black holes fixed rather than fixing
+   all of the TCP implementations."
+
+                           Golden words :-).
+		   */
+
+			dst_negative_advice(&sk->sk_dst_cache);
+		}
+
+		retry_until = sysctl_tcp_retries2;
+		if (sock_flag(sk, SOCK_DEAD)) {
+			int alive = (tp->rto < TCP_RTO_MAX);
+ 
+			retry_until = tcp_orphan_retries(sk, alive);
+
+			if (tcp_out_of_resources(sk, alive || tp->retransmits < retry_until))
+				return 1;
+		}
+	}
+
+	if (tp->retransmits >= retry_until) {
+		/* Has it gone just too far? */
+		tcp_write_err(sk);
+		return 1;
+	}
+	return 0;
+}
+
+static void tcp_delack_timer(unsigned long data)
+{
+	struct sock *sk = (struct sock*)data;
+	struct tcp_sock *tp = tcp_sk(sk);
+
+	bh_lock_sock(sk);
+	if (sock_owned_by_user(sk)) {
+		/* Try again later. */
+		tp->ack.blocked = 1;
+		NET_INC_STATS_BH(LINUX_MIB_DELAYEDACKLOCKED);
+		sk_reset_timer(sk, &tp->delack_timer, jiffies + TCP_DELACK_MIN);
+		goto out_unlock;
+	}
+
+	sk_stream_mem_reclaim(sk);
+
+	if (sk->sk_state == TCP_CLOSE || !(tp->ack.pending & TCP_ACK_TIMER))
+		goto out;
+
+	if (time_after(tp->ack.timeout, jiffies)) {
+		sk_reset_timer(sk, &tp->delack_timer, tp->ack.timeout);
+		goto out;
+	}
+	tp->ack.pending &= ~TCP_ACK_TIMER;
+
+	if (skb_queue_len(&tp->ucopy.prequeue)) {
+		struct sk_buff *skb;
+
+		NET_ADD_STATS_BH(LINUX_MIB_TCPSCHEDULERFAILED, 
+				 skb_queue_len(&tp->ucopy.prequeue));
+
+		while ((skb = __skb_dequeue(&tp->ucopy.prequeue)) != NULL)
+			sk->sk_backlog_rcv(sk, skb);
+
+		tp->ucopy.memory = 0;
+	}
+
+	if (tcp_ack_scheduled(tp)) {
+		if (!tp->ack.pingpong) {
+			/* Delayed ACK missed: inflate ATO. */
+			tp->ack.ato = min(tp->ack.ato << 1, tp->rto);
+		} else {
+			/* Delayed ACK missed: leave pingpong mode and
+			 * deflate ATO.
+			 */
+			tp->ack.pingpong = 0;
+			tp->ack.ato = TCP_ATO_MIN;
+		}
+		tcp_send_ack(sk);
+		NET_INC_STATS_BH(LINUX_MIB_DELAYEDACKS);
+	}
+	TCP_CHECK_TIMER(sk);
+
+out:
+	if (tcp_memory_pressure)
+		sk_stream_mem_reclaim(sk);
+out_unlock:
+	bh_unlock_sock(sk);
+	sock_put(sk);
+}
+
+static void tcp_probe_timer(struct sock *sk)
+{
+	struct tcp_sock *tp = tcp_sk(sk);
+	int max_probes;
+
+	if (tp->packets_out || !sk->sk_send_head) {
+		tp->probes_out = 0;
+		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]
+	 *
+	 * Let me to explain. probes_out is zeroed by incoming ACKs
+	 * 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)) {
+		int alive = ((tp->rto<<tp->backoff) < TCP_RTO_MAX);
+ 
+		max_probes = tcp_orphan_retries(sk, alive);
+
+		if (tcp_out_of_resources(sk, alive || tp->probes_out <= max_probes))
+			return;
+	}
+
+	if (tp->probes_out > max_probes) {
+		tcp_write_err(sk);
+	} else {
+		/* Only send another probe if we didn't close things up. */
+		tcp_send_probe0(sk);
+	}
+}
+
+/*
+ *	The TCP retransmit timer.
+ */
+
+static void tcp_retransmit_timer(struct sock *sk)
+{
+	struct tcp_sock *tp = tcp_sk(sk);
+
+	if (!tp->packets_out)
+		goto out;
+
+	BUG_TRAP(!skb_queue_empty(&sk->sk_write_queue));
+
+	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
+		if (net_ratelimit()) {
+			struct inet_sock *inet = inet_sk(sk);
+			printk(KERN_DEBUG "TCP: Treason uncloaked! Peer %u.%u.%u.%u:%u/%u shrinks window %u:%u. Repaired.\n",
+			       NIPQUAD(inet->daddr), htons(inet->dport),
+			       inet->num, tp->snd_una, tp->snd_nxt);
+		}
+#endif
+		if (tcp_time_stamp - tp->rcv_tstamp > TCP_RTO_MAX) {
+			tcp_write_err(sk);
+			goto out;
+		}
+		tcp_enter_loss(sk, 0);
+		tcp_retransmit_skb(sk, skb_peek(&sk->sk_write_queue));
+		__sk_dst_reset(sk);
+		goto out_reset_timer;
+	}
+
+	if (tcp_write_timeout(sk))
+		goto out;
+
+	if (tp->retransmits == 0) {
+		if (tp->ca_state == TCP_CA_Disorder || tp->ca_state == TCP_CA_Recovery) {
+			if (tp->rx_opt.sack_ok) {
+				if (tp->ca_state == TCP_CA_Recovery)
+					NET_INC_STATS_BH(LINUX_MIB_TCPSACKRECOVERYFAIL);
+				else
+					NET_INC_STATS_BH(LINUX_MIB_TCPSACKFAILURES);
+			} else {
+				if (tp->ca_state == TCP_CA_Recovery)
+					NET_INC_STATS_BH(LINUX_MIB_TCPRENORECOVERYFAIL);
+				else
+					NET_INC_STATS_BH(LINUX_MIB_TCPRENOFAILURES);
+			}
+		} else if (tp->ca_state == TCP_CA_Loss) {
+			NET_INC_STATS_BH(LINUX_MIB_TCPLOSSFAILURES);
+		} else {
+			NET_INC_STATS_BH(LINUX_MIB_TCPTIMEOUTS);
+		}
+	}
+
+	if (tcp_use_frto(sk)) {
+		tcp_enter_frto(sk);
+	} else {
+		tcp_enter_loss(sk, 0);
+	}
+
+	if (tcp_retransmit_skb(sk, skb_peek(&sk->sk_write_queue)) > 0) {
+		/* Retransmission failed because of local congestion,
+		 * do not backoff.
+		 */
+		if (!tp->retransmits)
+			tp->retransmits=1;
+		tcp_reset_xmit_timer(sk, TCP_TIME_RETRANS,
+				     min(tp->rto, TCP_RESOURCE_PROBE_INTERVAL));
+		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!
+	 */
+	tp->backoff++;
+	tp->retransmits++;
+
+out_reset_timer:
+	tp->rto = min(tp->rto << 1, TCP_RTO_MAX);
+	tcp_reset_xmit_timer(sk, TCP_TIME_RETRANS, tp->rto);
+	if (tp->retransmits > sysctl_tcp_retries1)
+		__sk_dst_reset(sk);
+
+out:;
+}
+
+static void tcp_write_timer(unsigned long data)
+{
+	struct sock *sk = (struct sock*)data;
+	struct tcp_sock *tp = tcp_sk(sk);
+	int event;
+
+	bh_lock_sock(sk);
+	if (sock_owned_by_user(sk)) {
+		/* Try again later */
+		sk_reset_timer(sk, &tp->retransmit_timer, jiffies + (HZ / 20));
+		goto out_unlock;
+	}
+
+	if (sk->sk_state == TCP_CLOSE || !tp->pending)
+		goto out;
+
+	if (time_after(tp->timeout, jiffies)) {
+		sk_reset_timer(sk, &tp->retransmit_timer, tp->timeout);
+		goto out;
+	}
+
+	event = tp->pending;
+	tp->pending = 0;
+
+	switch (event) {
+	case TCP_TIME_RETRANS:
+		tcp_retransmit_timer(sk);
+		break;
+	case TCP_TIME_PROBE0:
+		tcp_probe_timer(sk);
+		break;
+	}
+	TCP_CHECK_TIMER(sk);
+
+out:
+	sk_stream_mem_reclaim(sk);
+out_unlock:
+	bh_unlock_sock(sk);
+	sock_put(sk);
+}
+
+/*
+ *	Timer for listening sockets
+ */
+
+static void tcp_synack_timer(struct sock *sk)
+{
+	struct tcp_sock *tp = tcp_sk(sk);
+	struct tcp_listen_opt *lopt = tp->listen_opt;
+	int max_retries = tp->syn_retries ? : sysctl_tcp_synack_retries;
+	int thresh = max_retries;
+	unsigned long now = jiffies;
+	struct open_request **reqp, *req;
+	int i, budget;
+
+	if (lopt == NULL || lopt->qlen == 0)
+		return;
+
+	/* Normally all the openreqs are young and become mature
+	 * (i.e. converted to established socket) for first timeout.
+	 * If synack was not acknowledged for 3 seconds, it means
+	 * one of the following things: synack was lost, ack was lost,
+	 * rtt is high or nobody planned to ack (i.e. synflood).
+	 * When server is a bit loaded, queue is populated with old
+	 * open requests, reducing effective size of queue.
+	 * When server is well loaded, queue size reduces to zero
+	 * after several minutes of work. It is not synflood,
+	 * it is normal operation. The solution is pruning
+	 * too old entries overriding normal timeout, when
+	 * situation becomes dangerous.
+	 *
+	 * Essentially, we reserve half of room for young
+	 * embrions; and abort old ones without pity, if old
+	 * ones are about to clog our table.
+	 */
+	if (lopt->qlen>>(lopt->max_qlen_log-1)) {
+		int young = (lopt->qlen_young<<1);
+
+		while (thresh > 2) {
+			if (lopt->qlen < young)
+				break;
+			thresh--;
+			young <<= 1;
+		}
+	}
+
+	if (tp->defer_accept)
+		max_retries = tp->defer_accept;
+
+	budget = 2*(TCP_SYNQ_HSIZE/(TCP_TIMEOUT_INIT/TCP_SYNQ_INTERVAL));
+	i = lopt->clock_hand;
+
+	do {
+		reqp=&lopt->syn_table[i];
+		while ((req = *reqp) != NULL) {
+			if (time_after_eq(now, req->expires)) {
+				if ((req->retrans < thresh ||
+				     (req->acked && req->retrans < max_retries))
+				    && !req->class->rtx_syn_ack(sk, req, NULL)) {
+					unsigned long timeo;
+
+					if (req->retrans++ == 0)
+						lopt->qlen_young--;
+					timeo = min((TCP_TIMEOUT_INIT << req->retrans),
+						    TCP_RTO_MAX);
+					req->expires = now + timeo;
+					reqp = &req->dl_next;
+					continue;
+				}
+
+				/* Drop this request */
+				write_lock(&tp->syn_wait_lock);
+				*reqp = req->dl_next;
+				write_unlock(&tp->syn_wait_lock);
+				lopt->qlen--;
+				if (req->retrans == 0)
+					lopt->qlen_young--;
+				tcp_openreq_free(req);
+				continue;
+			}
+			reqp = &req->dl_next;
+		}
+
+		i = (i+1)&(TCP_SYNQ_HSIZE-1);
+
+	} while (--budget > 0);
+
+	lopt->clock_hand = i;
+
+	if (lopt->qlen)
+		tcp_reset_keepalive_timer(sk, TCP_SYNQ_INTERVAL);
+}
+
+void tcp_delete_keepalive_timer (struct sock *sk)
+{
+	sk_stop_timer(sk, &sk->sk_timer);
+}
+
+void tcp_reset_keepalive_timer (struct sock *sk, unsigned long len)
+{
+	sk_reset_timer(sk, &sk->sk_timer, jiffies + len);
+}
+
+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))
+		tcp_reset_keepalive_timer(sk, keepalive_time_when(tcp_sk(sk)));
+	else if (!val)
+		tcp_delete_keepalive_timer(sk);
+}
+
+
+static void tcp_keepalive_timer (unsigned long data)
+{
+	struct sock *sk = (struct sock *) data;
+	struct tcp_sock *tp = tcp_sk(sk);
+	__u32 elapsed;
+
+	/* Only process if socket is not in use. */
+	bh_lock_sock(sk);
+	if (sock_owned_by_user(sk)) {
+		/* Try again later. */ 
+		tcp_reset_keepalive_timer (sk, HZ/20);
+		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) {
+			int tmo = tcp_fin_time(tp) - TCP_TIMEWAIT_LEN;
+
+			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) */
+	if (tp->packets_out || sk->sk_send_head)
+		goto resched;
+
+	elapsed = tcp_time_stamp - tp->rcv_tstamp;
+
+	if (elapsed >= keepalive_time_when(tp)) {
+		if ((!tp->keepalive_probes && tp->probes_out >= sysctl_tcp_keepalive_probes) ||
+		     (tp->keepalive_probes && tp->probes_out >= tp->keepalive_probes)) {
+			tcp_send_active_reset(sk, GFP_ATOMIC);
+			tcp_write_err(sk);
+			goto out;
+		}
+		if (tcp_write_wakeup(sk) <= 0) {
+			tp->probes_out++;
+			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);
+	sk_stream_mem_reclaim(sk);
+
+resched:
+	tcp_reset_keepalive_timer (sk, elapsed);
+	goto out;
+
+death:	
+	tcp_done(sk);
+
+out:
+	bh_unlock_sock(sk);
+	sock_put(sk);
+}
+
+EXPORT_SYMBOL(tcp_clear_xmit_timers);
+EXPORT_SYMBOL(tcp_delete_keepalive_timer);
+EXPORT_SYMBOL(tcp_init_xmit_timers);
+EXPORT_SYMBOL(tcp_reset_keepalive_timer);