URL https://opencores.org/ocsvn/openrisc_me/openrisc_me/trunk

Subversion Repositories openrisc_me

[/] [openrisc/] [trunk/] [rtos/] [rtems/] [c/] [src/] [libnetworking/] [netinet/] [tcp_timer.c] - Blame information for rev 389

Go to most recent revision | Details | Compare with Previous | View Log


/*
 * 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
 *      $Id: tcp_timer.c,v 1.2 2001-09-27 12:01:56 chris Exp $
 */
 
#include "opt_tcpdebug.h"
 
#ifndef TUBA_INCLUDE
#include <sys/param.h>
#include <sys/queue.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/sysctl.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 <machine/cpu.h>        /* before tcp_seq.h, for tcp_random18() */
 
#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>
#ifdef TCPDEBUG
#include <netinet/tcp_debug.h>
#endif
 
int     tcp_keepinit = TCPTV_KEEP_INIT;
SYSCTL_INT(_net_inet_tcp, TCPCTL_KEEPINIT, keepinit,
        CTLFLAG_RW, &tcp_keepinit , 0, "");
 
int     tcp_keepidle = TCPTV_KEEP_IDLE;
SYSCTL_INT(_net_inet_tcp, TCPCTL_KEEPIDLE, keepidle,
        CTLFLAG_RW, &tcp_keepidle , 0, "");
 
static int      tcp_keepintvl = TCPTV_KEEPINTVL;
SYSCTL_INT(_net_inet_tcp, TCPCTL_KEEPINTVL, keepintvl,
        CTLFLAG_RW, &tcp_keepintvl , 0, "");
 
static int      always_keepalive = 0;
SYSCTL_INT(_net_inet_tcp, OID_AUTO, always_keepalive,
        CTLFLAG_RW, &always_keepalive , 0, "");
 
static int      tcp_keepcnt = TCPTV_KEEPCNT;
        /* max idle probes */
static int      tcp_maxpersistidle = TCPTV_KEEP_IDLE;
        /* max idle time in persist */
int     tcp_maxidle;
#else /* TUBA_INCLUDE */
 
static  int tcp_maxpersistidle;
#endif /* TUBA_INCLUDE */
 
/*
 * Fast timeout routine for processing delayed acks
 */
void
tcp_fasttimo()
{
        register struct inpcb *inp;
        register struct tcpcb *tp;
        int s;
 
        s = splnet();
 
        for (inp = tcb.lh_first; inp != NULL; inp = inp->inp_list.le_next) {
                if ((tp = (struct tcpcb *)inp->inp_ppcb) &&
                    (tp->t_flags & TF_DELACK)) {
                        tp->t_flags &= ~TF_DELACK;
                        tp->t_flags |= TF_ACKNOW;
                        tcpstat.tcps_delack++;
                        (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 *ip, *ipnxt;
        register struct tcpcb *tp;
        register int i;
        int s;
#ifdef TCPDEBUG
        int ostate;
#endif
 
        s = splnet();
 
        tcp_maxidle = tcp_keepcnt * tcp_keepintvl;
 
        ip = tcb.lh_first;
        if (ip == NULL) {
                splx(s);
                return;
        }
        /*
         * Search through tcb's and update active timers.
         */
        for (; ip != NULL; ip = ipnxt) {
                ipnxt = ip->inp_list.le_next;
                tp = intotcpcb(ip);
                if (tp == 0 || tp->t_state == TCPS_LISTEN)
                        continue;
                for (i = 0; i < TCPT_NTIMERS; i++) {
                        if (tp->t_timer[i] && --tp->t_timer[i] == 0) {
#ifdef TCPDEBUG
                                ostate = tp->t_state;
#endif
                                tp = tcp_timers(tp, i);
                                if (tp == NULL)
                                        goto tpgone;
#ifdef TCPDEBUG
                                if (tp->t_inpcb->inp_socket->so_options
                                    & SO_DEBUG)
                                        tcp_trace(TA_USER, ostate, tp,
                                                  (struct tcpiphdr *)0,
                                                  PRU_SLOWTIMO);
#endif
                        }
                }
                tp->t_idle++;
                tp->t_duration++;
                if (tp->t_rtt)
                        tp->t_rtt++;
tpgone:
                ;
        }
        tcp_iss += TCP_ISSINCR/PR_SLOWHZ;               /* increment iss */
#ifdef TCP_COMPAT_42
        if ((int)tcp_iss < 0)
                tcp_iss = TCP_ISSINCR;                  /* XXX */
#endif
        tcp_now++;                                      /* for timestamps */
        splx(s);
}
#ifndef TUBA_INCLUDE
 
/*
 * Cancel all timers for TCP tp.
 */
void
tcp_canceltimers(tp)
        struct tcpcb *tp;
{
        register int i;
 
        for (i = 0; i < TCPT_NTIMERS; i++)
                tp->t_timer[i] = 0;
}
 
int     tcp_backoff[TCP_MAXRXTSHIFT + 1] =
    { 1, 2, 4, 8, 16, 32, 64, 64, 64, 64, 64, 64, 64 };
 
static int tcp_totbackoff = 511;        /* sum of tcp_backoff[] */
 
/*
 * TCP timer processing.
 */
struct tcpcb *
tcp_timers(tp, timer)
        register struct tcpcb *tp;
        int timer;
{
        register int rexmt;
 
        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 &&
                    tp->t_idle <= tcp_maxidle)
                        tp->t_timer[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++;
                rexmt = TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift];
                TCPT_RANGESET(tp->t_rxtcur, rexmt,
                    tp->t_rttmin, TCPTV_REXMTMAX);
                tp->t_timer[TCPT_REXMT] = tp->t_rxtcur;
                /*
                 * 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;
                /*
                 * Force a segment to be sent.
                 */
                tp->t_flags |= TF_ACKNOW;
                /*
                 * If timing a segment in this window, stop the timer.
                 */
                tp->t_rtt = 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;
                }
                (void) tcp_output(tp);
                break;
 
        /*
         * Persistance timer into zero window.
         * Force a byte to be output, if possible.
         */
        case TCPT_PERSIST:
                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) {
                        u_long maxidle = TCP_REXMTVAL(tp);
                        if (maxidle < tp->t_rttmin)
                                maxidle = tp->t_rttmin;
                        maxidle *= tcp_totbackoff;
                        if (tp->t_idle >= tcp_maxpersistidle ||
                            tp->t_idle >= maxidle) {
                                tcpstat.tcps_persistdrop++;
                                tp = tcp_drop(tp, ETIMEDOUT);
                                break;
                        }
                }
                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 (tp->t_state < TCPS_ESTABLISHED)
                        goto dropit;
                if ((always_keepalive ||
                    tp->t_inpcb->inp_socket->so_options & SO_KEEPALIVE) &&
                    tp->t_state <= TCPS_CLOSING) {
                        if (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++;
#ifdef TCP_COMPAT_42
                        /*
                         * The keepalive packet must have nonzero length
                         * to get a 4.2 host to respond.
                         */
                        tcp_respond(tp, tp->t_template, (struct mbuf *)NULL,
                            tp->rcv_nxt - 1, tp->snd_una - 1, 0);
#else
                        tcp_respond(tp, tp->t_template, (struct mbuf *)NULL,
                            tp->rcv_nxt, tp->snd_una - 1, 0);
#endif
                        tp->t_timer[TCPT_KEEP] = tcp_keepintvl;
                } else
                        tp->t_timer[TCPT_KEEP] = tcp_keepidle;
                break;
        dropit:
                tcpstat.tcps_keepdrops++;
                tp = tcp_drop(tp, ETIMEDOUT);
                break;
        }
        return (tp);
}
#endif /* TUBA_INCLUDE */

Browse

Tools

Subversion Repositories openrisc_me

[/] [openrisc/] [trunk/] [rtos/] [rtems/] [c/] [src/] [libnetworking/] [netinet/] [tcp_timer.c] - Blame information for rev 389

Line No.	Rev	Author	Line
1	30	unneback	`/*`
2			`* Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995`
3			`* The Regents of the University of California. All rights reserved.`
4			`*`
5			`* Redistribution and use in source and binary forms, with or without`
6			`* modification, are permitted provided that the following conditions`
7			`* are met:`
8			`* 1. Redistributions of source code must retain the above copyright`
9			`* notice, this list of conditions and the following disclaimer.`
10			`* 2. Redistributions in binary form must reproduce the above copyright`
11			`* notice, this list of conditions and the following disclaimer in the`
12			`* documentation and/or other materials provided with the distribution.`
13			`* 3. All advertising materials mentioning features or use of this software`
14			`* must display the following acknowledgement:`
15			`* This product includes software developed by the University of`
16			`* California, Berkeley and its contributors.`
17			`* 4. Neither the name of the University nor the names of its contributors`
18			`* may be used to endorse or promote products derived from this software`
19			`* without specific prior written permission.`
20			`*`
21			* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
22			`* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE`
23			`* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE`
24			`* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE`
25			`* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL`
26			`* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS`
27			`* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)`
28			`* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT`
29			`* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY`
30			`* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF`
31			`* SUCH DAMAGE.`
32			`*`
33			`* @(#)tcp_timer.c 8.2 (Berkeley) 5/24/95`
34			`* $Id: tcp_timer.c,v 1.2 2001-09-27 12:01:56 chris Exp $`
35			`*/`
36
37			`#include "opt_tcpdebug.h"`
38
39			`#ifndef TUBA_INCLUDE`
40			`#include <sys/param.h>`
41			`#include <sys/queue.h>`
42			`#include <sys/systm.h>`
43			`#include <sys/kernel.h>`
44			`#include <sys/sysctl.h>`
45			`#include <sys/malloc.h>`
46			`#include <sys/mbuf.h>`
47			`#include <sys/socket.h>`
48			`#include <sys/socketvar.h>`
49			`#include <sys/protosw.h>`
50			`#include <sys/errno.h>`
51
52			`#include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */`
53
54			`#include <net/if.h>`
55			`#include <net/route.h>`
56
57			`#include <netinet/in.h>`
58			`#include <netinet/in_systm.h>`
59			`#include <netinet/ip.h>`
60			`#include <netinet/in_pcb.h>`
61			`#include <netinet/ip_var.h>`
62			`#include <netinet/tcp.h>`
63			`#include <netinet/tcp_fsm.h>`
64			`#include <netinet/tcp_seq.h>`
65			`#include <netinet/tcp_timer.h>`
66			`#include <netinet/tcp_var.h>`
67			`#include <netinet/tcpip.h>`
68			`#ifdef TCPDEBUG`
69			`#include <netinet/tcp_debug.h>`
70			`#endif`
71
72			`int tcp_keepinit = TCPTV_KEEP_INIT;`
73			`SYSCTL_INT(_net_inet_tcp, TCPCTL_KEEPINIT, keepinit,`
74			`CTLFLAG_RW, &tcp_keepinit , 0, "");`
75
76			`int tcp_keepidle = TCPTV_KEEP_IDLE;`
77			`SYSCTL_INT(_net_inet_tcp, TCPCTL_KEEPIDLE, keepidle,`
78			`CTLFLAG_RW, &tcp_keepidle , 0, "");`
79
80			`static int tcp_keepintvl = TCPTV_KEEPINTVL;`
81			`SYSCTL_INT(_net_inet_tcp, TCPCTL_KEEPINTVL, keepintvl,`
82			`CTLFLAG_RW, &tcp_keepintvl , 0, "");`
83
84			`static int always_keepalive = 0;`
85			`SYSCTL_INT(_net_inet_tcp, OID_AUTO, always_keepalive,`
86			`CTLFLAG_RW, &always_keepalive , 0, "");`
87
88			`static int tcp_keepcnt = TCPTV_KEEPCNT;`
89			`/* max idle probes */`
90			`static int tcp_maxpersistidle = TCPTV_KEEP_IDLE;`
91			`/* max idle time in persist */`
92			`int tcp_maxidle;`
93			`#else /* TUBA_INCLUDE */`
94
95			`static int tcp_maxpersistidle;`
96			`#endif /* TUBA_INCLUDE */`
97
98			`/*`
99			`* Fast timeout routine for processing delayed acks`
100			`*/`
101			`void`
102			`tcp_fasttimo()`
103			`{`
104			`register struct inpcb *inp;`
105			`register struct tcpcb *tp;`
106			`int s;`
107
108			`s = splnet();`
109
110			`for (inp = tcb.lh_first; inp != NULL; inp = inp->inp_list.le_next) {`
111			`if ((tp = (struct tcpcb *)inp->inp_ppcb) &&`
112			`(tp->t_flags & TF_DELACK)) {`
113			`tp->t_flags &= ~TF_DELACK;`
114			`tp->t_flags \|= TF_ACKNOW;`
115			`tcpstat.tcps_delack++;`
116			`(void) tcp_output(tp);`
117			`}`
118			`}`
119			`splx(s);`
120			`}`
121
122			`/*`
123			`* Tcp protocol timeout routine called every 500 ms.`
124			`* Updates the timers in all active tcb's and`
125			`* causes finite state machine actions if timers expire.`
126			`*/`
127			`void`
128			`tcp_slowtimo()`
129			`{`
130			`register struct inpcb ip, ipnxt;`
131			`register struct tcpcb *tp;`
132			`register int i;`
133			`int s;`
134			`#ifdef TCPDEBUG`
135			`int ostate;`
136			`#endif`
137
138			`s = splnet();`
139
140			`tcp_maxidle = tcp_keepcnt * tcp_keepintvl;`
141
142			`ip = tcb.lh_first;`
143			`if (ip == NULL) {`
144			`splx(s);`
145			`return;`
146			`}`
147			`/*`
148			`* Search through tcb's and update active timers.`
149			`*/`
150			`for (; ip != NULL; ip = ipnxt) {`
151			`ipnxt = ip->inp_list.le_next;`
152			`tp = intotcpcb(ip);`
153			`if (tp == 0 \|\| tp->t_state == TCPS_LISTEN)`
154			`continue;`
155			`for (i = 0; i < TCPT_NTIMERS; i++) {`
156			`if (tp->t_timer[i] && --tp->t_timer[i] == 0) {`
157			`#ifdef TCPDEBUG`
158			`ostate = tp->t_state;`
159			`#endif`
160			`tp = tcp_timers(tp, i);`
161			`if (tp == NULL)`
162			`goto tpgone;`
163			`#ifdef TCPDEBUG`
164			`if (tp->t_inpcb->inp_socket->so_options`
165			`& SO_DEBUG)`
166			`tcp_trace(TA_USER, ostate, tp,`
167			`(struct tcpiphdr *)0,`
168			`PRU_SLOWTIMO);`
169			`#endif`
170			`}`
171			`}`
172			`tp->t_idle++;`
173			`tp->t_duration++;`
174			`if (tp->t_rtt)`
175			`tp->t_rtt++;`
176			`tpgone:`
177			`;`
178			`}`
179			`tcp_iss += TCP_ISSINCR/PR_SLOWHZ; /* increment iss */`
180			`#ifdef TCP_COMPAT_42`
181			`if ((int)tcp_iss < 0)`
182			`tcp_iss = TCP_ISSINCR; /* XXX */`
183			`#endif`
184			`tcp_now++; /* for timestamps */`
185			`splx(s);`
186			`}`
187			`#ifndef TUBA_INCLUDE`
188
189			`/*`
190			`* Cancel all timers for TCP tp.`
191			`*/`
192			`void`
193			`tcp_canceltimers(tp)`
194			`struct tcpcb *tp;`
195			`{`
196			`register int i;`
197
198			`for (i = 0; i < TCPT_NTIMERS; i++)`
199			`tp->t_timer[i] = 0;`
200			`}`
201
202			`int tcp_backoff[TCP_MAXRXTSHIFT + 1] =`
203			`{ 1, 2, 4, 8, 16, 32, 64, 64, 64, 64, 64, 64, 64 };`
204
205			`static int tcp_totbackoff = 511; /* sum of tcp_backoff[] */`
206
207			`/*`
208			`* TCP timer processing.`
209			`*/`
210			`struct tcpcb *`
211			`tcp_timers(tp, timer)`
212			`register struct tcpcb *tp;`
213			`int timer;`
214			`{`
215			`register int rexmt;`
216
217			`switch (timer) {`
218
219			`/*`
220			`* 2 MSL timeout in shutdown went off. If we're closed but`
221			`* still waiting for peer to close and connection has been idle`
222			`* too long, or if 2MSL time is up from TIME_WAIT, delete connection`
223			`* control block. Otherwise, check again in a bit.`
224			`*/`
225			`case TCPT_2MSL:`
226			`if (tp->t_state != TCPS_TIME_WAIT &&`
227			`tp->t_idle <= tcp_maxidle)`
228			`tp->t_timer[TCPT_2MSL] = tcp_keepintvl;`
229			`else`
230			`tp = tcp_close(tp);`
231			`break;`
232
233			`/*`
234			`* Retransmission timer went off. Message has not`
235			`* been acked within retransmit interval. Back off`
236			`* to a longer retransmit interval and retransmit one segment.`
237			`*/`
238			`case TCPT_REXMT:`
239			`if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) {`
240			`tp->t_rxtshift = TCP_MAXRXTSHIFT;`
241			`tcpstat.tcps_timeoutdrop++;`
242			`tp = tcp_drop(tp, tp->t_softerror ?`
243			`tp->t_softerror : ETIMEDOUT);`
244			`break;`
245			`}`
246			`tcpstat.tcps_rexmttimeo++;`
247			`rexmt = TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift];`
248			`TCPT_RANGESET(tp->t_rxtcur, rexmt,`
249			`tp->t_rttmin, TCPTV_REXMTMAX);`
250			`tp->t_timer[TCPT_REXMT] = tp->t_rxtcur;`
251			`/*`
252			`* If losing, let the lower level know and try for`
253			`* a better route. Also, if we backed off this far,`
254			`* our srtt estimate is probably bogus. Clobber it`
255			`* so we'll take the next rtt measurement as our srtt;`
256			`* move the current srtt into rttvar to keep the current`
257			`* retransmit times until then.`
258			`*/`
259			`if (tp->t_rxtshift > TCP_MAXRXTSHIFT / 4) {`
260			`in_losing(tp->t_inpcb);`
261			`tp->t_rttvar += (tp->t_srtt >> TCP_RTT_SHIFT);`
262			`tp->t_srtt = 0;`
263			`}`
264			`tp->snd_nxt = tp->snd_una;`
265			`/*`
266			`* Force a segment to be sent.`
267			`*/`
268			`tp->t_flags \|= TF_ACKNOW;`
269			`/*`
270			`* If timing a segment in this window, stop the timer.`
271			`*/`
272			`tp->t_rtt = 0;`
273			`/*`
274			`* Close the congestion window down to one segment`
275			`* (we'll open it by one segment for each ack we get).`
276			`* Since we probably have a window's worth of unacked`
277			`* data accumulated, this "slow start" keeps us from`
278			`* dumping all that data as back-to-back packets (which`
279			`* might overwhelm an intermediate gateway).`
280			`*`
281			`* There are two phases to the opening: Initially we`
282			`* open by one mss on each ack. This makes the window`
283			`* size increase exponentially with time. If the`
284			`* window is larger than the path can handle, this`
285			`* exponential growth results in dropped packet(s)`
286			`* almost immediately. To get more time between`
287			`* drops but still "push" the network to take advantage`
288			`* of improving conditions, we switch from exponential`
289			`* to linear window opening at some threshhold size.`
290			`* For a threshhold, we use half the current window`
291			`* size, truncated to a multiple of the mss.`
292			`*`
293			`* (the minimum cwnd that will give us exponential`
294			`* growth is 2 mss. We don't allow the threshhold`
295			`* to go below this.)`
296			`*/`
297			`{`
298			`u_int win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_maxseg;`
299			`if (win < 2)`
300			`win = 2;`
301			`tp->snd_cwnd = tp->t_maxseg;`
302			`tp->snd_ssthresh = win * tp->t_maxseg;`
303			`tp->t_dupacks = 0;`
304			`}`
305			`(void) tcp_output(tp);`
306			`break;`
307
308			`/*`
309			`* Persistance timer into zero window.`
310			`* Force a byte to be output, if possible.`
311			`*/`
312			`case TCPT_PERSIST:`
313			`tcpstat.tcps_persisttimeo++;`
314			`/*`
315			`* Hack: if the peer is dead/unreachable, we do not`
316			`* time out if the window is closed. After a full`
317			`* backoff, drop the connection if the idle time`
318			`* (no responses to probes) reaches the maximum`
319			`* backoff that we would use if retransmitting.`
320			`*/`
321			`if (tp->t_rxtshift == TCP_MAXRXTSHIFT) {`
322			`u_long maxidle = TCP_REXMTVAL(tp);`
323			`if (maxidle < tp->t_rttmin)`
324			`maxidle = tp->t_rttmin;`
325			`maxidle *= tcp_totbackoff;`
326			`if (tp->t_idle >= tcp_maxpersistidle \|\|`
327			`tp->t_idle >= maxidle) {`
328			`tcpstat.tcps_persistdrop++;`
329			`tp = tcp_drop(tp, ETIMEDOUT);`
330			`break;`
331			`}`
332			`}`
333			`tcp_setpersist(tp);`
334			`tp->t_force = 1;`
335			`(void) tcp_output(tp);`
336			`tp->t_force = 0;`
337			`break;`
338
339			`/*`
340			`* Keep-alive timer went off; send something`
341			`* or drop connection if idle for too long.`
342			`*/`
343			`case TCPT_KEEP:`
344			`tcpstat.tcps_keeptimeo++;`
345			`if (tp->t_state < TCPS_ESTABLISHED)`
346			`goto dropit;`
347			`if ((always_keepalive \|\|`
348			`tp->t_inpcb->inp_socket->so_options & SO_KEEPALIVE) &&`
349			`tp->t_state <= TCPS_CLOSING) {`
350			`if (tp->t_idle >= tcp_keepidle + tcp_maxidle)`
351			`goto dropit;`
352			`/*`
353			`* Send a packet designed to force a response`
354			`* if the peer is up and reachable:`
355			`* either an ACK if the connection is still alive,`
356			`* or an RST if the peer has closed the connection`
357			`* due to timeout or reboot.`
358			`* Using sequence number tp->snd_una-1`
359			`* causes the transmitted zero-length segment`
360			`* to lie outside the receive window;`
361			`* by the protocol spec, this requires the`
362			`* correspondent TCP to respond.`
363			`*/`
364			`tcpstat.tcps_keepprobe++;`
365			`#ifdef TCP_COMPAT_42`
366			`/*`
367			`* The keepalive packet must have nonzero length`
368			`* to get a 4.2 host to respond.`
369			`*/`
370			`tcp_respond(tp, tp->t_template, (struct mbuf *)NULL,`
371			`tp->rcv_nxt - 1, tp->snd_una - 1, 0);`
372			`#else`
373			`tcp_respond(tp, tp->t_template, (struct mbuf *)NULL,`
374			`tp->rcv_nxt, tp->snd_una - 1, 0);`
375			`#endif`
376			`tp->t_timer[TCPT_KEEP] = tcp_keepintvl;`
377			`} else`
378			`tp->t_timer[TCPT_KEEP] = tcp_keepidle;`
379			`break;`
380			`dropit:`
381			`tcpstat.tcps_keepdrops++;`
382			`tp = tcp_drop(tp, ETIMEDOUT);`
383			`break;`
384			`}`
385			`return (tp);`
386			`}`
387			`#endif /* TUBA_INCLUDE */`