/* $OpenBSD: tcp_timer.c,v 1.39 2007/06/15 18:23:07 markus Exp $ */
/* $NetBSD: tcp_timer.c,v 1.14 1996/02/13 23:44:09 christos Exp $ */
/*
* Copyright (c) 1982, 1986, 1988, 1990, 1993
* 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 8.1 (Berkeley) 6/10/93
*/
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/mbuf.h>
#include <sys/socket.h>
#include <sys/socketvar.h>
#include <sys/protosw.h>
#include <sys/kernel.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_timer.h>
#include <netinet/tcp_var.h>
#include <netinet/ip_icmp.h>
#include <netinet/tcp_seq.h>
int tcp_keepidle;
int tcp_keepintvl;
int tcp_maxpersistidle; /* max idle time in persist */
int tcp_maxidle;
/*
* Time to delay the ACK. This is initialized in tcp_init(), unless
* its patched.
*/
int tcp_delack_ticks;
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_maxpersistidle == 0)
tcp_maxpersistidle = TCPTV_KEEP_IDLE;
if (tcp_delack_ticks == 0)
tcp_delack_ticks = TCP_DELACK_TICKS;
}
/*
* 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();
if (tp->t_flags & TF_DEAD) {
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 = TCPTV_KEEPCNT * tcp_keepintvl;
#ifdef TCP_COMPAT_42
tcp_iss += TCP_ISSINCR/PR_SLOWHZ; /* increment iss */
if ((int)tcp_iss < 0)
tcp_iss = 0; /* XXX */
#else
tcp_iss += TCP_ISSINCR2/PR_SLOWHZ; /* increment iss */
#endif /* TCP_COMPAT_42 */
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);
}
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.
*/
#ifdef TCP_SACK
void tcp_timer_freesack(struct tcpcb *);
void
tcp_timer_freesack(struct tcpcb *tp)
{
struct sackhole *p, *q;
/*
* Free SACK holes for 2MSL and REXMT timers.
*/
q = tp->snd_holes;
while (q != NULL) {
p = q;
q = q->next;
pool_put(&sackhl_pool, p);
}
tp->snd_holes = 0;
#ifdef TCP_FACK
tp->snd_fack = tp->snd_una;
tp->retran_data = 0;
tp->snd_awnd = 0;
#endif /* TCP_FACK */
}
#endif /* TCP_SACK */
void
tcp_timer_rexmt(void *arg)
{
struct tcpcb *tp = arg;
uint32_t rto;
int s;
s = splsoftnet();
if (tp->t_flags & TF_DEAD) {
splx(s);
return;
}
if ((tp->t_flags & TF_PMTUD_PEND) && tp->t_inpcb &&
SEQ_GEQ(tp->t_pmtud_th_seq, tp->snd_una) &&
SEQ_LT(tp->t_pmtud_th_seq, (int)(tp->snd_una + tp->t_maxseg))) {
extern struct sockaddr_in icmpsrc;
struct icmp icmp;
tp->t_flags &= ~TF_PMTUD_PEND;
/* XXX create fake icmp message with relevant entries */
icmp.icmp_nextmtu = tp->t_pmtud_nextmtu;
icmp.icmp_ip.ip_len = tp->t_pmtud_ip_len;
icmp.icmp_ip.ip_hl = tp->t_pmtud_ip_hl;
icmpsrc.sin_addr = tp->t_inpcb->inp_faddr;
icmp_mtudisc(&icmp);
/*
* Notify all connections to the same peer about
* new mss and trigger retransmit.
*/
in_pcbnotifyall(&tcbtable, sintosa(&icmpsrc), EMSGSIZE,
tcp_mtudisc);
splx(s);
return;
}
#ifdef TCP_SACK
tcp_timer_freesack(tp);
#endif
if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) {
tp->t_rxtshift = TCP_MAXRXTSHIFT;
tcpstat.tcps_timeoutdrop++;
(void)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 (ip_mtudisc && tp->t_inpcb &&
TCPS_HAVEESTABLISHED(tp->t_state) &&
tp->t_rxtshift > TCP_MAXRXTSHIFT / 6) {
struct inpcb *inp = tp->t_inpcb;
struct rtentry *rt = NULL;
struct sockaddr_in sin;
/* No data to send means path mtu is not a problem */
if (!inp->inp_socket->so_snd.sb_cc)
goto leave;
rt = in_pcbrtentry(inp);
/* Check if path MTU discovery is disabled already */
if (rt && (rt->rt_flags & RTF_HOST) &&
(rt->rt_rmx.rmx_locks & RTV_MTU))
goto leave;
rt = NULL;
switch(tp->pf) {
#ifdef INET6
case PF_INET6:
/*
* We can not turn off path MTU for IPv6.
* Do nothing for now, maybe lower to
* minimum MTU.
*/
break;
#endif
case PF_INET:
bzero(&sin, sizeof(struct sockaddr_in));
sin.sin_family = AF_INET;
sin.sin_len = sizeof(struct sockaddr_in);
sin.sin_addr = inp->inp_faddr;
rt = icmp_mtudisc_clone(sintosa(&sin));
break;
}
if (rt != NULL) {
/* Disable path MTU discovery */
if ((rt->rt_rmx.rmx_locks & RTV_MTU) == 0) {
rt->rt_rmx.rmx_locks |= RTV_MTU;
in_rtchange(inp, 0);
}
rtfree(rt);
}
leave:
;
}
/*
* 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 defined(TCP_SACK)
/*
* Note: We overload snd_last to function also as the
* snd_last variable described in RFC 2582
*/
tp->snd_last = tp->snd_max;
#endif /* TCP_SACK */
/*
* If timing a segment in this window, stop the timer.
*/
tp->t_rtttime = 0;
#ifdef TCP_ECN
/*
* if ECN is enabled, there might be a broken firewall which
* blocks ecn packets. fall back to non-ecn.
*/
if ((tp->t_state == TCPS_SYN_SENT || tp->t_state == TCPS_SYN_RECEIVED)
&& tcp_do_ecn && !(tp->t_flags & TF_DISABLE_ECN))
tp->t_flags |= TF_DISABLE_ECN;
#endif
/*
* 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 threshold size.
* For a threshold, 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 threshold
* to go below this.)
*/
{
u_long win = ulmin(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_maxseg;
if (win < 2)
win = 2;
tp->snd_cwnd = tp->t_maxseg;
tp->snd_ssthresh = win * tp->t_maxseg;
tp->t_dupacks = 0;
#ifdef TCP_ECN
tp->snd_last = tp->snd_max;
tp->t_flags |= TF_SEND_CWR;
#endif
#if 1 /* TCP_ECN */
tcpstat.tcps_cwr_timeout++;
#endif
}
(void) tcp_output(tp);
out:
splx(s);
}
void
tcp_timer_persist(void *arg)
{
struct tcpcb *tp = arg;
uint32_t rto;
int s;
s = splsoftnet();
if ((tp->t_flags & TF_DEAD) ||
TCP_TIMER_ISARMED(tp, TCPT_REXMT)) {
splx(s);
return;
}
tcpstat.tcps_persisttimeo++;
/*
* 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_persistdrop++;
tp = tcp_drop(tp, ETIMEDOUT);
goto out;
}
tcp_setpersist(tp);
tp->t_force = 1;
(void) tcp_output(tp);
tp->t_force = 0;
out:
splx(s);
}
void
tcp_timer_keep(void *arg)
{
struct tcpcb *tp = arg;
int s;
s = splsoftnet();
if (tp->t_flags & TF_DEAD) {
splx(s);
return;
}
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_CLOSING) {
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++;
#ifdef TCP_COMPAT_42
/*
* The keepalive packet must have nonzero length
* to get a 4.2 host to respond.
*/
tcp_respond(tp, mtod(tp->t_template, caddr_t),
(struct mbuf *)NULL, tp->rcv_nxt - 1, tp->snd_una - 1, 0);
#else
tcp_respond(tp, mtod(tp->t_template, caddr_t),
(struct mbuf *)NULL, tp->rcv_nxt, tp->snd_una - 1, 0);
#endif
TCP_TIMER_ARM(tp, TCPT_KEEP, tcp_keepintvl);
} else
TCP_TIMER_ARM(tp, TCPT_KEEP, tcp_keepidle);
splx(s);
return;
dropit:
tcpstat.tcps_keepdrops++;
tp = tcp_drop(tp, ETIMEDOUT);
splx(s);
}
void
tcp_timer_2msl(void *arg)
{
struct tcpcb *tp = arg;
int s;
s = splsoftnet();
if (tp->t_flags & TF_DEAD) {
splx(s);
return;
}
#ifdef TCP_SACK
tcp_timer_freesack(tp);
#endif
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);
splx(s);
}