NetBSD/sys/netinet/tcp_timer.c

408 lines
13 KiB
C

/* $NetBSD: tcp_timer.c,v 1.43 1998/09/10 10:47:00 mouse Exp $ */
/*-
* Copyright (c) 1997, 1998 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. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the University of
* California, Berkeley and its contributors.
* 4. 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/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 <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>
#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>
int tcp_keepidle = TCPTV_KEEP_IDLE;
int tcp_keepintvl = TCPTV_KEEPINTVL;
int tcp_keepcnt = TCPTV_KEEPCNT; /* max idle probes */
int tcp_maxpersistidle = TCPTV_KEEP_IDLE; /* max idle time in persist */
int tcp_maxidle;
struct tcp_delack_head tcp_delacks;
/*
* Fast timeout routine for processing delayed acks
*/
void
tcp_fasttimo()
{
register struct tcpcb *tp, *ntp;
int s;
s = splsoftnet();
for (tp = tcp_delacks.lh_first; tp != NULL; tp = ntp) {
/*
* If tcp_output() can't transmit the ACK for whatever
* reason, it will remain on the queue for the next
* time the heartbeat ticks.
*/
ntp = tp->t_delack.le_next;
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()
{
register struct inpcb *inp, *ninp;
register struct tcpcb *tp;
int s;
register long i;
static int syn_cache_last = 0;
s = splsoftnet();
tcp_maxidle = tcp_keepcnt * tcp_keepintvl;
/*
* Search through tcb's and update active timers.
*/
inp = tcbtable.inpt_queue.cqh_first;
if (inp == (struct inpcb *)0) { /* XXX */
splx(s);
return;
}
for (; inp != (struct inpcb *)&tcbtable.inpt_queue; inp = ninp) {
ninp = inp->inp_queue.cqe_next;
tp = intotcpcb(inp);
if (tp == 0 || tp->t_state == TCPS_LISTEN)
continue;
for (i = 0; i < TCPT_NTIMERS; i++) {
if (TCP_TIMER_ISEXPIRED(tp, i)) {
TCP_TIMER_DISARM(tp, i);
(void) tcp_usrreq(tp->t_inpcb->inp_socket,
PRU_SLOWTIMO, (struct mbuf *)0,
(struct mbuf *)i, (struct mbuf *)0,
(struct proc *)0);
/* XXX NOT MP SAFE */
if ((ninp == (void *)&tcbtable.inpt_queue &&
tcbtable.inpt_queue.cqh_last != inp) ||
ninp->inp_queue.cqe_prev != inp)
goto tpgone;
}
}
tp->t_idle++;
if (tp->t_rtt)
tp->t_rtt++;
tpgone:
;
}
tcp_iss_seq += TCP_ISSINCR; /* increment iss */
tcp_now++; /* for timestamps */
if (++syn_cache_last >= tcp_syn_cache_interval) {
syn_cache_timer();
syn_cache_last = 0;
}
splx(s);
}
/*
* Cancel all timers for TCP tp.
*/
void
tcp_canceltimers(tp)
struct tcpcb *tp;
{
register int i;
for (i = 0; i < TCPT_NTIMERS; i++)
TCP_TIMER_DISARM(tp, i);
}
int tcp_backoff[TCP_MAXRXTSHIFT + 1] =
{ 1, 2, 4, 8, 16, 32, 64, 64, 64, 64, 64, 64, 64 };
int tcp_totbackoff = 511; /* sum of tcp_backoff[] */
/*
* TCP timer processing.
*/
struct tcpcb *
tcp_timers(tp, timer)
register struct tcpcb *tp;
int timer;
{
short rto;
switch (timer) {
/*
* 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.
*/
case TCPT_2MSL:
if (tp->t_state != TCPS_TIME_WAIT &&
((tcp_maxidle == 0) || (tp->t_idle <= tcp_maxidle)))
TCP_TIMER_ARM(tp, TCPT_2MSL, tcp_keepintvl);
else
tp = tcp_close(tp);
break;
/*
* Retransmission timer went off. Message has not
* been acked within retransmit interval. Back off
* to a longer retransmit interval and retransmit one segment.
*/
case TCPT_REXMT:
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);
break;
}
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 0
/*
* 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 (ip_mtudisc && tp->t_rxtshift > TCP_MAXRXTSHIFT / 6) {
struct inpcb *inp = tp->t_inpcb;
struct rtentry *rt = in_pcbrtentry(inp);
/* XXX: Black hole recovery code goes here */
}
#endif
/*
* 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) {
in_losing(tp->t_inpcb);
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_rtt = 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);
break;
/*
* Persistance timer into zero window.
* Force a byte to be output, if possible.
*/
case TCPT_PERSIST:
/*
* 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 &&
(tp->t_idle >= tcp_maxpersistidle ||
tp->t_idle >= rto * tcp_totbackoff)) {
tcpstat.tcps_persistdrops++;
tp = tcp_drop(tp, ETIMEDOUT);
break;
}
tcpstat.tcps_persisttimeo++;
tcp_setpersist(tp);
tp->t_force = 1;
(void) tcp_output(tp);
tp->t_force = 0;
break;
/*
* Keep-alive timer went off; send something
* or drop connection if idle for too long.
*/
case TCPT_KEEP:
tcpstat.tcps_keeptimeo++;
if (TCPS_HAVEESTABLISHED(tp->t_state) == 0)
goto dropit;
if (tp->t_inpcb->inp_socket->so_options & SO_KEEPALIVE &&
tp->t_state <= TCPS_CLOSE_WAIT) {
if ((tcp_maxidle > 0) &&
(tp->t_idle >= 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, tp->rcv_nxt - 1,
tp->snd_una - 1, 0);
} else {
(void)tcp_respond(tp, tp->t_template,
(struct mbuf *)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);
break;
dropit:
tcpstat.tcps_keepdrops++;
tp = tcp_drop(tp, ETIMEDOUT);
break;
}
return (tp);
}