FreeBSD-5.3/sys/netinet/tcp_timer.c
/*
* 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.
* 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
* $FreeBSD: src/sys/netinet/tcp_timer.c,v 1.66 2004/08/16 18:32:07 rwatson Exp $
*/
#include "opt_inet6.h"
#include "opt_tcpdebug.h"
#include "opt_tcp_sack.h"
#include <sys/param.h>
#include <sys/kernel.h>
#include <sys/lock.h>
#include <sys/mbuf.h>
#include <sys/mutex.h>
#include <sys/protosw.h>
#include <sys/socket.h>
#include <sys/socketvar.h>
#include <sys/sysctl.h>
#include <sys/systm.h>
#include <net/route.h>
#include <netinet/in.h>
#include <netinet/in_pcb.h>
#include <netinet/in_systm.h>
#ifdef INET6
#include <netinet6/in6_pcb.h>
#endif
#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/tcpip.h>
#ifdef TCPDEBUG
#include <netinet/tcp_debug.h>
#endif
static int
sysctl_msec_to_ticks(SYSCTL_HANDLER_ARGS)
{
int error, s, tt;
tt = *(int *)oidp->oid_arg1;
s = (int)((int64_t)tt * 1000 / hz);
error = sysctl_handle_int(oidp, &s, 0, req);
if (error || !req->newptr)
return (error);
tt = (int)((int64_t)s * hz / 1000);
if (tt < 1)
return (EINVAL);
*(int *)oidp->oid_arg1 = tt;
return (0);
}
int tcp_keepinit;
SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPINIT, keepinit, CTLTYPE_INT|CTLFLAG_RW,
&tcp_keepinit, 0, sysctl_msec_to_ticks, "I", "");
int tcp_keepidle;
SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPIDLE, keepidle, CTLTYPE_INT|CTLFLAG_RW,
&tcp_keepidle, 0, sysctl_msec_to_ticks, "I", "");
int tcp_keepintvl;
SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPINTVL, keepintvl, CTLTYPE_INT|CTLFLAG_RW,
&tcp_keepintvl, 0, sysctl_msec_to_ticks, "I", "");
int tcp_delacktime;
SYSCTL_PROC(_net_inet_tcp, TCPCTL_DELACKTIME, delacktime,
CTLTYPE_INT|CTLFLAG_RW, &tcp_delacktime, 0, sysctl_msec_to_ticks, "I",
"Time before a delayed ACK is sent");
int tcp_msl;
SYSCTL_PROC(_net_inet_tcp, OID_AUTO, msl, CTLTYPE_INT|CTLFLAG_RW,
&tcp_msl, 0, sysctl_msec_to_ticks, "I", "Maximum segment lifetime");
int tcp_rexmit_min;
SYSCTL_PROC(_net_inet_tcp, OID_AUTO, rexmit_min, CTLTYPE_INT|CTLFLAG_RW,
&tcp_rexmit_min, 0, sysctl_msec_to_ticks, "I", "Minimum Retransmission Timeout");
int tcp_rexmit_slop;
SYSCTL_PROC(_net_inet_tcp, OID_AUTO, rexmit_slop, CTLTYPE_INT|CTLFLAG_RW,
&tcp_rexmit_slop, 0, sysctl_msec_to_ticks, "I", "Retransmission Timer Slop");
static int always_keepalive = 1;
SYSCTL_INT(_net_inet_tcp, OID_AUTO, always_keepalive, CTLFLAG_RW,
&always_keepalive , 0, "Assume SO_KEEPALIVE on all TCP connections");
static int tcp_keepcnt = TCPTV_KEEPCNT;
/* max idle probes */
int tcp_maxpersistidle;
/* max idle time in persist */
int tcp_maxidle;
/*
* Tcp protocol timeout routine called every 500 ms.
* Updates timestamps used for TCP
* causes finite state machine actions if timers expire.
*/
void
tcp_slowtimo()
{
int s;
s = splnet();
tcp_maxidle = tcp_keepcnt * tcp_keepintvl;
splx(s);
INP_INFO_WLOCK(&tcbinfo);
(void) tcp_timer_2msl_tw(0);
INP_INFO_WUNLOCK(&tcbinfo);
}
/*
* Cancel all timers for TCP tp.
*/
void
tcp_canceltimers(tp)
struct tcpcb *tp;
{
callout_stop(tp->tt_2msl);
callout_stop(tp->tt_persist);
callout_stop(tp->tt_keep);
callout_stop(tp->tt_rexmt);
}
int tcp_syn_backoff[TCP_MAXRXTSHIFT + 1] =
{ 1, 1, 1, 1, 1, 2, 4, 8, 16, 32, 64, 64, 64 };
int tcp_backoff[TCP_MAXRXTSHIFT + 1] =
{ 1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 512, 512, 512 };
static int tcp_totbackoff = 2559; /* sum of tcp_backoff[] */
/*
* TCP timer processing.
*/
void
tcp_timer_delack(xtp)
void *xtp;
{
struct tcpcb *tp = xtp;
int s;
struct inpcb *inp;
s = splnet();
INP_INFO_RLOCK(&tcbinfo);
inp = tp->t_inpcb;
if (!inp) {
INP_INFO_RUNLOCK(&tcbinfo);
splx(s);
return;
}
INP_LOCK(inp);
INP_INFO_RUNLOCK(&tcbinfo);
if (callout_pending(tp->tt_delack) || !callout_active(tp->tt_delack)) {
INP_UNLOCK(inp);
splx(s);
return;
}
callout_deactivate(tp->tt_delack);
tp->t_flags |= TF_ACKNOW;
tcpstat.tcps_delack++;
(void) tcp_output(tp);
INP_UNLOCK(inp);
splx(s);
}
void
tcp_timer_2msl(xtp)
void *xtp;
{
struct tcpcb *tp = xtp;
int s;
struct inpcb *inp;
#ifdef TCPDEBUG
int ostate;
ostate = tp->t_state;
#endif
s = splnet();
INP_INFO_WLOCK(&tcbinfo);
inp = tp->t_inpcb;
if (!inp) {
INP_INFO_WUNLOCK(&tcbinfo);
splx(s);
return;
}
INP_LOCK(inp);
tcp_free_sackholes(tp);
if (callout_pending(tp->tt_2msl) || !callout_active(tp->tt_2msl)) {
INP_UNLOCK(tp->t_inpcb);
INP_INFO_WUNLOCK(&tcbinfo);
splx(s);
return;
}
callout_deactivate(tp->tt_2msl);
/*
* 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 &&
(ticks - tp->t_rcvtime) <= tcp_maxidle)
callout_reset(tp->tt_2msl, tcp_keepintvl,
tcp_timer_2msl, tp);
else
tp = tcp_close(tp);
#ifdef TCPDEBUG
if (tp && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0,
PRU_SLOWTIMO);
#endif
if (tp)
INP_UNLOCK(inp);
INP_INFO_WUNLOCK(&tcbinfo);
splx(s);
}
struct twlist {
LIST_HEAD(, tcptw) tw_list;
struct tcptw tw_tail;
};
#define TWLIST_NLISTS 2
static struct twlist twl_2msl[TWLIST_NLISTS];
static struct twlist *tw_2msl_list[] = { &twl_2msl[0], &twl_2msl[1], NULL };
void
tcp_timer_init(void)
{
int i;
struct twlist *twl;
for (i = 0; i < TWLIST_NLISTS; i++) {
twl = &twl_2msl[i];
LIST_INIT(&twl->tw_list);
LIST_INSERT_HEAD(&twl->tw_list, &twl->tw_tail, tw_2msl);
}
}
void
tcp_timer_2msl_reset(struct tcptw *tw, int timeo)
{
int i;
struct tcptw *tw_tail;
if (tw->tw_time != 0)
LIST_REMOVE(tw, tw_2msl);
tw->tw_time = timeo + ticks;
i = timeo > tcp_msl ? 1 : 0;
tw_tail = &twl_2msl[i].tw_tail;
LIST_INSERT_BEFORE(tw_tail, tw, tw_2msl);
}
void
tcp_timer_2msl_stop(struct tcptw *tw)
{
if (tw->tw_time != 0)
LIST_REMOVE(tw, tw_2msl);
}
struct tcptw *
tcp_timer_2msl_tw(int reuse)
{
struct tcptw *tw, *tw_tail;
struct twlist *twl;
int i;
for (i = 0; i < 2; i++) {
twl = tw_2msl_list[i];
tw_tail = &twl->tw_tail;
for (;;) {
tw = LIST_FIRST(&twl->tw_list);
if (tw == tw_tail || (!reuse && tw->tw_time > ticks))
break;
INP_LOCK(tw->tw_inpcb);
if (tcp_twclose(tw, reuse) != NULL)
return (tw);
}
}
return (NULL);
}
void
tcp_timer_keep(xtp)
void *xtp;
{
struct tcpcb *tp = xtp;
struct tcptemp *t_template;
int s;
struct inpcb *inp;
#ifdef TCPDEBUG
int ostate;
ostate = tp->t_state;
#endif
s = splnet();
INP_INFO_WLOCK(&tcbinfo);
inp = tp->t_inpcb;
if (!inp) {
INP_INFO_WUNLOCK(&tcbinfo);
splx(s);
return;
}
INP_LOCK(inp);
if (callout_pending(tp->tt_keep) || !callout_active(tp->tt_keep)) {
INP_UNLOCK(inp);
INP_INFO_WUNLOCK(&tcbinfo);
splx(s);
return;
}
callout_deactivate(tp->tt_keep);
/*
* Keep-alive timer went off; send something
* or drop connection if idle for too long.
*/
tcpstat.tcps_keeptimeo++;
if (tp->t_state < TCPS_ESTABLISHED)
goto dropit;
if ((always_keepalive || inp->inp_socket->so_options & SO_KEEPALIVE) &&
tp->t_state <= TCPS_CLOSING) {
if ((ticks - 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++;
t_template = tcpip_maketemplate(inp);
if (t_template) {
tcp_respond(tp, t_template->tt_ipgen,
&t_template->tt_t, (struct mbuf *)NULL,
tp->rcv_nxt, tp->snd_una - 1, 0);
(void) m_free(dtom(t_template));
}
callout_reset(tp->tt_keep, tcp_keepintvl, tcp_timer_keep, tp);
} else
callout_reset(tp->tt_keep, tcp_keepidle, tcp_timer_keep, tp);
#ifdef TCPDEBUG
if (inp->inp_socket->so_options & SO_DEBUG)
tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0,
PRU_SLOWTIMO);
#endif
INP_UNLOCK(inp);
INP_INFO_WUNLOCK(&tcbinfo);
splx(s);
return;
dropit:
tcpstat.tcps_keepdrops++;
tp = tcp_drop(tp, ETIMEDOUT);
#ifdef TCPDEBUG
if (tp && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0,
PRU_SLOWTIMO);
#endif
if (tp)
INP_UNLOCK(tp->t_inpcb);
INP_INFO_WUNLOCK(&tcbinfo);
splx(s);
}
void
tcp_timer_persist(xtp)
void *xtp;
{
struct tcpcb *tp = xtp;
int s;
struct inpcb *inp;
#ifdef TCPDEBUG
int ostate;
ostate = tp->t_state;
#endif
s = splnet();
INP_INFO_WLOCK(&tcbinfo);
inp = tp->t_inpcb;
if (!inp) {
INP_INFO_WUNLOCK(&tcbinfo);
splx(s);
return;
}
INP_LOCK(inp);
if (callout_pending(tp->tt_persist) || !callout_active(tp->tt_persist)){
INP_UNLOCK(inp);
INP_INFO_WUNLOCK(&tcbinfo);
splx(s);
return;
}
callout_deactivate(tp->tt_persist);
/*
* Persistance timer into zero window.
* Force a byte to be output, if possible.
*/
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.
*/
if (tp->t_rxtshift == TCP_MAXRXTSHIFT &&
((ticks - tp->t_rcvtime) >= tcp_maxpersistidle ||
(ticks - tp->t_rcvtime) >= TCP_REXMTVAL(tp) * 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:
#ifdef TCPDEBUG
if (tp && tp->t_inpcb->inp_socket->so_options & SO_DEBUG)
tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0,
PRU_SLOWTIMO);
#endif
if (tp)
INP_UNLOCK(inp);
INP_INFO_WUNLOCK(&tcbinfo);
splx(s);
}
void
tcp_timer_rexmt(xtp)
void *xtp;
{
struct tcpcb *tp = xtp;
int s;
int rexmt;
int headlocked;
struct inpcb *inp;
#ifdef TCPDEBUG
int ostate;
ostate = tp->t_state;
#endif
s = splnet();
INP_INFO_WLOCK(&tcbinfo);
headlocked = 1;
inp = tp->t_inpcb;
if (!inp) {
INP_INFO_WUNLOCK(&tcbinfo);
splx(s);
return;
}
INP_LOCK(inp);
if (callout_pending(tp->tt_rexmt) || !callout_active(tp->tt_rexmt)) {
INP_UNLOCK(inp);
INP_INFO_WUNLOCK(&tcbinfo);
splx(s);
return;
}
callout_deactivate(tp->tt_rexmt);
tcp_free_sackholes(tp);
/*
* 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;
}
INP_INFO_WUNLOCK(&tcbinfo);
headlocked = 0;
if (tp->t_rxtshift == 1) {
/*
* first retransmit; record ssthresh and cwnd so they can
* be recovered if this turns out to be a "bad" retransmit.
* A retransmit is considered "bad" if an ACK for this
* segment is received within RTT/2 interval; the assumption
* here is that the ACK was already in flight. See
* "On Estimating End-to-End Network Path Properties" by
* Allman and Paxson for more details.
*/
tp->snd_cwnd_prev = tp->snd_cwnd;
tp->snd_ssthresh_prev = tp->snd_ssthresh;
tp->snd_recover_prev = tp->snd_recover;
if (IN_FASTRECOVERY(tp))
tp->t_flags |= TF_WASFRECOVERY;
else
tp->t_flags &= ~TF_WASFRECOVERY;
tp->t_badrxtwin = ticks + (tp->t_srtt >> (TCP_RTT_SHIFT + 1));
}
tcpstat.tcps_rexmttimeo++;
if (tp->t_state == TCPS_SYN_SENT)
rexmt = TCP_REXMTVAL(tp) * tcp_syn_backoff[tp->t_rxtshift];
else
rexmt = TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift];
TCPT_RANGESET(tp->t_rxtcur, rexmt,
tp->t_rttmin, TCPTV_REXMTMAX);
/*
* Disable rfc1323 and rfc1644 if we havn't got any response to
* our third SYN to work-around some broken terminal servers
* (most of which have hopefully been retired) that have bad VJ
* header compression code which trashes TCP segments containing
* unknown-to-them TCP options.
*/
if ((tp->t_state == TCPS_SYN_SENT) && (tp->t_rxtshift == 3))
tp->t_flags &= ~(TF_REQ_SCALE|TF_REQ_TSTMP|TF_REQ_CC);
/*
* 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 INET6
if ((tp->t_inpcb->inp_vflag & INP_IPV6) != 0)
in6_losing(tp->t_inpcb);
else
#endif
tp->t_rttvar += (tp->t_srtt >> TCP_RTT_SHIFT);
tp->t_srtt = 0;
}
tp->snd_nxt = tp->snd_una;
tp->snd_recover = tp->snd_max;
/*
* Force a segment to be sent.
*/
tp->t_flags |= TF_ACKNOW;
/*
* If timing a segment in this window, stop the timer.
*/
tp->t_rtttime = 0;
/*
* 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_maxseg;
if (win < 2)
win = 2;
tp->snd_cwnd = tp->t_maxseg;
tp->snd_ssthresh = win * tp->t_maxseg;
tp->t_dupacks = 0;
}
EXIT_FASTRECOVERY(tp);
(void) tcp_output(tp);
out:
#ifdef TCPDEBUG
if (tp && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0,
PRU_SLOWTIMO);
#endif
if (tp)
INP_UNLOCK(inp);
if (headlocked)
INP_INFO_WUNLOCK(&tcbinfo);
splx(s);
}