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NetBSD/sys/netinet/tcp_timer.c

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/* $NetBSD: tcp_timer.c,v 1.65 2003/10/27 07:43:01 itojun Exp $ */
/*
* Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of the project nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
/*-
* Copyright (c) 1997, 1998, 2001 The NetBSD Foundation, Inc.
* All rights reserved.
*
* This code is derived from software contributed to The NetBSD Foundation
* by Jason R. Thorpe and Kevin M. Lahey of the Numerical Aerospace Simulation
* Facility, NASA Ames Research Center.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the NetBSD
* Foundation, Inc. and its contributors.
* 4. Neither the name of The NetBSD Foundation nor the names of its
* contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
/*
* Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995
* The Regents of the University of California. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* @(#)tcp_timer.c 8.2 (Berkeley) 5/24/95
*/
#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: tcp_timer.c,v 1.65 2003/10/27 07:43:01 itojun Exp $");
#include "opt_inet.h"
#include "opt_tcp_debug.h"
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/malloc.h>
#include <sys/mbuf.h>
#include <sys/socket.h>
#include <sys/socketvar.h>
#include <sys/protosw.h>
#include <sys/errno.h>
#include <sys/kernel.h>
#include <net/if.h>
#include <net/route.h>
#include <netinet/in.h>
#include <netinet/in_systm.h>
#include <netinet/ip.h>
#include <netinet/in_pcb.h>
#include <netinet/ip_var.h>
#ifdef INET6
#ifndef INET
#include <netinet/in.h>
#endif
#include <netinet/ip6.h>
#include <netinet6/in6_pcb.h>
#endif
#include <netinet/tcp.h>
#include <netinet/tcp_fsm.h>
#include <netinet/tcp_seq.h>
#include <netinet/tcp_timer.h>
#include <netinet/tcp_var.h>
#include <netinet/tcpip.h>
#ifdef TCP_DEBUG
#include <netinet/tcp_debug.h>
#endif
/*
* Various tunable timer parameters. These are initialized in tcp_init(),
* unless they are patched.
*/
int tcp_keepidle = 0;
int tcp_keepintvl = 0;
int tcp_keepcnt = 0; /* max idle probes */
int tcp_maxpersistidle = 0; /* max idle time in persist */
int tcp_maxidle; /* computed in tcp_slowtimo() */
/*
* Time to delay the ACK. This is initialized in tcp_init(), unless
* its patched.
*/
int tcp_delack_ticks = 0;
void tcp_timer_rexmt(void *);
void tcp_timer_persist(void *);
void tcp_timer_keep(void *);
void tcp_timer_2msl(void *);
const tcp_timer_func_t tcp_timer_funcs[TCPT_NTIMERS] = {
tcp_timer_rexmt,
tcp_timer_persist,
tcp_timer_keep,
tcp_timer_2msl,
};
/*
* Timer state initialization, called from tcp_init().
*/
void
tcp_timer_init(void)
{
if (tcp_keepidle == 0)
tcp_keepidle = TCPTV_KEEP_IDLE;
if (tcp_keepintvl == 0)
tcp_keepintvl = TCPTV_KEEPINTVL;
if (tcp_keepcnt == 0)
tcp_keepcnt = TCPTV_KEEPCNT;
if (tcp_maxpersistidle == 0)
tcp_maxpersistidle = TCPTV_KEEP_IDLE;
if (tcp_delack_ticks == 0)
tcp_delack_ticks = TCP_DELACK_TICKS;
}
/*
* Return how many timers are currently being invoked.
*/
int
tcp_timers_invoking(struct tcpcb *tp)
{
int i;
int count = 0;
for (i = 0; i < TCPT_NTIMERS; i++)
if (callout_invoking(&tp->t_timer[i]))
count++;
if (callout_invoking(&tp->t_delack_ch))
count++;
return count;
}
/*
* Callout to process delayed ACKs for a TCPCB.
*/
void
tcp_delack(void *arg)
{
struct tcpcb *tp = arg;
int s;
/*
* If tcp_output() wasn't able to transmit the ACK
* for whatever reason, it will restart the delayed
* ACK callout.
*/
s = splsoftnet();
callout_ack(&tp->t_delack_ch);
if (tcp_isdead(tp)) {
splx(s);
return;
}
tp->t_flags |= TF_ACKNOW;
(void) tcp_output(tp);
splx(s);
}
/*
* Tcp protocol timeout routine called every 500 ms.
* Updates the timers in all active tcb's and
* causes finite state machine actions if timers expire.
*/
void
tcp_slowtimo()
{
int s;
s = splsoftnet();
tcp_maxidle = tcp_keepcnt * tcp_keepintvl;
tcp_iss_seq += TCP_ISSINCR; /* increment iss */
tcp_now++; /* for timestamps */
splx(s);
}
/*
* Cancel all timers for TCP tp.
*/
void
tcp_canceltimers(tp)
struct tcpcb *tp;
{
int i;
for (i = 0; i < TCPT_NTIMERS; i++)
TCP_TIMER_DISARM(tp, i);
}
const int tcp_backoff[TCP_MAXRXTSHIFT + 1] =
{ 1, 2, 4, 8, 16, 32, 64, 64, 64, 64, 64, 64, 64 };
const int tcp_totbackoff = 511; /* sum of tcp_backoff[] */
/*
* TCP timer processing.
*/
void
tcp_timer_rexmt(void *arg)
{
struct tcpcb *tp = arg;
uint32_t rto;
int s;
#ifdef TCP_DEBUG
struct socket *so = NULL;
short ostate;
#endif
s = splsoftnet();
callout_ack(&tp->t_timer[TCPT_KEEP]);
if (tcp_isdead(tp)) {
splx(s);
return;
}
#ifdef TCP_DEBUG
#ifdef INET
if (tp->t_inpcb)
so = tp->t_inpcb->inp_socket;
#endif
#ifdef INET6
if (tp->t_in6pcb)
so = tp->t_in6pcb->in6p_socket;
#endif
ostate = tp->t_state;
#endif /* TCP_DEBUG */
/*
* Retransmission timer went off. Message has not
* been acked within retransmit interval. Back off
* to a longer retransmit interval and retransmit one segment.
*/
if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) {
tp->t_rxtshift = TCP_MAXRXTSHIFT;
tcpstat.tcps_timeoutdrop++;
tp = tcp_drop(tp, tp->t_softerror ?
tp->t_softerror : ETIMEDOUT);
goto out;
}
tcpstat.tcps_rexmttimeo++;
rto = TCP_REXMTVAL(tp);
if (rto < tp->t_rttmin)
rto = tp->t_rttmin;
TCPT_RANGESET(tp->t_rxtcur, rto * tcp_backoff[tp->t_rxtshift],
tp->t_rttmin, TCPTV_REXMTMAX);
TCP_TIMER_ARM(tp, TCPT_REXMT, tp->t_rxtcur);
/*
* If we are losing and we are trying path MTU discovery,
* try turning it off. This will avoid black holes in
* the network which suppress or fail to send "packet
* too big" ICMP messages. We should ideally do
* lots more sophisticated searching to find the right
* value here...
*/
if (tp->t_mtudisc && tp->t_rxtshift > TCP_MAXRXTSHIFT / 6) {
tcpstat.tcps_pmtublackhole++;
#ifdef INET
/* try turning PMTUD off */
if (tp->t_inpcb)
tp->t_mtudisc = 0;
#endif
#ifdef INET6
/* try using IPv6 minimum MTU */
if (tp->t_in6pcb)
tp->t_mtudisc = 0;
#endif
/* XXX: more sophisticated Black hole recovery code? */
}
/*
* If losing, let the lower level know and try for
* a better route. Also, if we backed off this far,
* our srtt estimate is probably bogus. Clobber it
* so we'll take the next rtt measurement as our srtt;
* move the current srtt into rttvar to keep the current
* retransmit times until then.
*/
if (tp->t_rxtshift > TCP_MAXRXTSHIFT / 4) {
#ifdef INET
if (tp->t_inpcb)
in_losing(tp->t_inpcb);
#endif
#ifdef INET6
if (tp->t_in6pcb)
in6_losing(tp->t_in6pcb);
#endif
tp->t_rttvar += (tp->t_srtt >> TCP_RTT_SHIFT);
tp->t_srtt = 0;
}
tp->snd_nxt = tp->snd_una;
/*
* If timing a segment in this window, stop the timer.
*/
tp->t_rtttime = 0;
/*
* Remember if we are retransmitting a SYN, because if
* we do, set the initial congestion window must be set
* to 1 segment.
*/
if (tp->t_state == TCPS_SYN_SENT)
tp->t_flags |= TF_SYN_REXMT;
/*
* Close the congestion window down to one segment
* (we'll open it by one segment for each ack we get).
* Since we probably have a window's worth of unacked
* data accumulated, this "slow start" keeps us from
* dumping all that data as back-to-back packets (which
* might overwhelm an intermediate gateway).
*
* There are two phases to the opening: Initially we
* open by one mss on each ack. This makes the window
* size increase exponentially with time. If the
* window is larger than the path can handle, this
* exponential growth results in dropped packet(s)
* almost immediately. To get more time between
* drops but still "push" the network to take advantage
* of improving conditions, we switch from exponential
* to linear window opening at some threshhold size.
* For a threshhold, we use half the current window
* size, truncated to a multiple of the mss.
*
* (the minimum cwnd that will give us exponential
* growth is 2 mss. We don't allow the threshhold
* to go below this.)
*/
{
u_int win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_segsz;
if (win < 2)
win = 2;
/* Loss Window MUST be one segment. */
tp->snd_cwnd = tp->t_segsz;
tp->snd_ssthresh = win * tp->t_segsz;
tp->t_dupacks = 0;
}
(void) tcp_output(tp);
out:
#ifdef TCP_DEBUG
if (tp && so->so_options & SO_DEBUG)
tcp_trace(TA_USER, ostate, tp, NULL,
PRU_SLOWTIMO | (TCPT_REXMT << 8));
#endif
splx(s);
}
void
tcp_timer_persist(void *arg)
{
struct tcpcb *tp = arg;
uint32_t rto;
int s;
#ifdef TCP_DEBUG
struct socket *so = NULL;
short ostate;
#endif
s = splsoftnet();
callout_ack(&tp->t_timer[TCPT_PERSIST]);
if (tcp_isdead(tp)) {
splx(s);
return;
}
#ifdef TCP_DEBUG
#ifdef INET
if (tp->t_inpcb)
so = tp->t_inpcb->inp_socket;
#endif
#ifdef INET6
if (tp->t_in6pcb)
so = tp->t_in6pcb->in6p_socket;
#endif
ostate = tp->t_state;
#endif /* TCP_DEBUG */
/*
* Persistance timer into zero window.
* Force a byte to be output, if possible.
*/
/*
* Hack: if the peer is dead/unreachable, we do not
* time out if the window is closed. After a full
* backoff, drop the connection if the idle time
* (no responses to probes) reaches the maximum
* backoff that we would use if retransmitting.
*/
rto = TCP_REXMTVAL(tp);
if (rto < tp->t_rttmin)
rto = tp->t_rttmin;
if (tp->t_rxtshift == TCP_MAXRXTSHIFT &&
((tcp_now - tp->t_rcvtime) >= tcp_maxpersistidle ||
(tcp_now - tp->t_rcvtime) >= rto * tcp_totbackoff)) {
tcpstat.tcps_persistdrops++;
tp = tcp_drop(tp, ETIMEDOUT);
goto out;
}
tcpstat.tcps_persisttimeo++;
tcp_setpersist(tp);
tp->t_force = 1;
(void) tcp_output(tp);
tp->t_force = 0;
out:
#ifdef TCP_DEBUG
if (tp && so->so_options & SO_DEBUG)
tcp_trace(TA_USER, ostate, tp, NULL,
PRU_SLOWTIMO | (TCPT_PERSIST << 8));
#endif
splx(s);
}
void
tcp_timer_keep(void *arg)
{
struct tcpcb *tp = arg;
struct socket *so = NULL; /* Quell compiler warning */
int s;
#ifdef TCP_DEBUG
short ostate;
#endif
s = splsoftnet();
callout_ack(&tp->t_timer[TCPT_KEEP]);
if (tcp_isdead(tp)) {
splx(s);
return;
}
#ifdef TCP_DEBUG
ostate = tp->t_state;
#endif /* TCP_DEBUG */
/*
* Keep-alive timer went off; send something
* or drop connection if idle for too long.
*/
tcpstat.tcps_keeptimeo++;
if (TCPS_HAVEESTABLISHED(tp->t_state) == 0)
goto dropit;
#ifdef INET
if (tp->t_inpcb)
so = tp->t_inpcb->inp_socket;
#endif
#ifdef INET6
if (tp->t_in6pcb)
so = tp->t_in6pcb->in6p_socket;
#endif
if (so->so_options & SO_KEEPALIVE &&
tp->t_state <= TCPS_CLOSE_WAIT) {
if ((tcp_maxidle > 0) &&
((tcp_now - tp->t_rcvtime) >=
tcp_keepidle + tcp_maxidle))
goto dropit;
/*
* Send a packet designed to force a response
* if the peer is up and reachable:
* either an ACK if the connection is still alive,
* or an RST if the peer has closed the connection
* due to timeout or reboot.
* Using sequence number tp->snd_una-1
* causes the transmitted zero-length segment
* to lie outside the receive window;
* by the protocol spec, this requires the
* correspondent TCP to respond.
*/
tcpstat.tcps_keepprobe++;
if (tcp_compat_42) {
/*
* The keepalive packet must have nonzero
* length to get a 4.2 host to respond.
*/
(void)tcp_respond(tp, tp->t_template,
(struct mbuf *)NULL, NULL, tp->rcv_nxt - 1,
tp->snd_una - 1, 0);
} else {
(void)tcp_respond(tp, tp->t_template,
(struct mbuf *)NULL, NULL, tp->rcv_nxt,
tp->snd_una - 1, 0);
}
TCP_TIMER_ARM(tp, TCPT_KEEP, tcp_keepintvl);
} else
TCP_TIMER_ARM(tp, TCPT_KEEP, tcp_keepidle);
#ifdef TCP_DEBUG
if (tp && so->so_options & SO_DEBUG)
tcp_trace(TA_USER, ostate, tp, NULL,
PRU_SLOWTIMO | (TCPT_KEEP << 8));
#endif
splx(s);
return;
dropit:
tcpstat.tcps_keepdrops++;
(void) tcp_drop(tp, ETIMEDOUT);
splx(s);
}
void
tcp_timer_2msl(void *arg)
{
struct tcpcb *tp = arg;
int s;
#ifdef TCP_DEBUG
struct socket *so = NULL;
short ostate;
#endif
s = splsoftnet();
callout_ack(&tp->t_timer[TCPT_2MSL]);
if (tcp_isdead(tp)) {
splx(s);
return;
}
#ifdef TCP_DEBUG
#ifdef INET
if (tp->t_inpcb)
so = tp->t_inpcb->inp_socket;
#endif
#ifdef INET6
if (tp->t_in6pcb)
so = tp->t_in6pcb->in6p_socket;
#endif
ostate = tp->t_state;
#endif /* TCP_DEBUG */
/*
* 2 MSL timeout in shutdown went off. If we're closed but
* still waiting for peer to close and connection has been idle
* too long, or if 2MSL time is up from TIME_WAIT, delete connection
* control block. Otherwise, check again in a bit.
*/
if (tp->t_state != TCPS_TIME_WAIT &&
((tcp_maxidle == 0) || ((tcp_now - tp->t_rcvtime) <= tcp_maxidle)))
TCP_TIMER_ARM(tp, TCPT_2MSL, tcp_keepintvl);
else
tp = tcp_close(tp);
#ifdef TCP_DEBUG
if (tp && so->so_options & SO_DEBUG)
tcp_trace(TA_USER, ostate, tp, NULL,
PRU_SLOWTIMO | (TCPT_2MSL << 8));
#endif
splx(s);
}
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