sys/netinet/tcp_timer.h

   1 /*
   2  * Copyright (c) 1982, 1986, 1993
   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. Neither the name of the University nor the names of its contributors
  14  *    may be used to endorse or promote products derived from this software
  15  *    without specific prior written permission.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  27  * SUCH DAMAGE.
  28  *
  29  *      @(#)tcp_timer.h 8.1 (Berkeley) 6/10/93
  30  * $FreeBSD: src/sys/netinet/tcp_timer.h,v 1.18.2.1 2002/08/16 22:16:39 dillon Exp $
  31  * $DragonFly: src/sys/netinet/tcp_timer.h,v 1.3 2003/08/23 11:18:00 rob Exp $
  32  */
  33
  34 #ifndef _NETINET_TCP_TIMER_H_
  35 #define _NETINET_TCP_TIMER_H_
  36
  37 /*
  38  * The TCPT_REXMT timer is used to force retransmissions.
  39  * The TCP has the TCPT_REXMT timer set whenever segments
  40  * have been sent for which ACKs are expected but not yet
  41  * received.  If an ACK is received which advances tp->snd_una,
  42  * then the retransmit timer is cleared (if there are no more
  43  * outstanding segments) or reset to the base value (if there
  44  * are more ACKs expected).  Whenever the retransmit timer goes off,
  45  * we retransmit one unacknowledged segment, and do a backoff
  46  * on the retransmit timer.
  47  *
  48  * The TCPT_PERSIST timer is used to keep window size information
  49  * flowing even if the window goes shut.  If all previous transmissions
  50  * have been acknowledged (so that there are no retransmissions in progress),
  51  * and the window is too small to bother sending anything, then we start
  52  * the TCPT_PERSIST timer.  When it expires, if the window is nonzero,
  53  * we go to transmit state.  Otherwise, at intervals send a single byte
  54  * into the peer's window to force him to update our window information.
  55  * We do this at most as often as TCPT_PERSMIN time intervals,
  56  * but no more frequently than the current estimate of round-trip
  57  * packet time.  The TCPT_PERSIST timer is cleared whenever we receive
  58  * a window update from the peer.
  59  *
  60  * The TCPT_KEEP timer is used to keep connections alive.  If an
  61  * connection is idle (no segments received) for TCPTV_KEEP_INIT amount of time,
  62  * but not yet established, then we drop the connection.  Once the connection
  63  * is established, if the connection is idle for TCPTV_KEEP_IDLE time
  64  * (and keepalives have been enabled on the socket), we begin to probe
  65  * the connection.  We force the peer to send us a segment by sending:
  66  *      <SEQ=SND.UNA-1><ACK=RCV.NXT><CTL=ACK>
  67  * This segment is (deliberately) outside the window, and should elicit
  68  * an ack segment in response from the peer.  If, despite the TCPT_KEEP
  69  * initiated segments we cannot elicit a response from a peer in TCPT_MAXIDLE
  70  * amount of time probing, then we drop the connection.
  71  */
  72
  73 /*
  74  * Time constants.
  75  */
  76 #define TCPTV_MSL       ( 30*hz)                /* max seg lifetime (hah!) */
  77 #define TCPTV_SRTTBASE  0                       /* base roundtrip time;
  78                                                    if 0, no idea yet */
  79 #define TCPTV_RTOBASE3  (  3*hz)                /* assumed RTO if no info */
  80 #define TCPTV_RTOBASE1  (  1*hz)                /* assumed RTO (RFC 6298) */
  81 #define TCPTV_SRTTDFLT  (  3*hz)                /* assumed RTT if no info */
  82
  83 #define TCPTV_PERSMIN   (  5*hz)                /* retransmit persistence */
  84 #define TCPTV_PERSMAX   ( 60*hz)                /* maximum persist interval */
  85
  86 #define TCPTV_KEEP_INIT ( 75*hz)                /* initial connect keepalive */
  87 #define TCPTV_KEEP_IDLE (120*60*hz)             /* dflt time before probing */
  88 #define TCPTV_KEEPINTVL ( 75*hz)                /* default probe interval */
  89 #define TCPTV_KEEPCNT   8                       /* max probes before drop */
  90
  91 /*
  92  * TCPTV_MIN represents the minimum allowed retransmit interval.  It
  93  * is currently one second but will ultimately be reduced to 3 ticks
  94  * for algorithmic stability, leaving the 200ms variance to deal with
  95  * delayed-acks, protocol overheads.  A 1 second minimum badly breaks
  96  * throughput on any network faster then a modem that has minor but
  97  * continuous packet loss unrelated to congestion, such as on a wireless
  98  * network.
  99  */
 100 #define TCPTV_MIN       ( hz/2 )                /* minimum allowable value */
 101 #define TCPTV_CPU_VAR   ( hz/10)                /* cpu variance (100ms) */
 102 #define TCPTV_REXMTMAX  ( 64*hz)                /* max allowable REXMT value */
 103
 104 #define TCPTV_TWTRUNC   8                       /* RTO factor to truncate TW */
 105
 106 #define TCP_LINGERTIME  120                     /* linger at most 2 minutes */
 107
 108 #define TCP_MAXRXTSHIFT 12                      /* maximum retransmits */
 109
 110 #define TCPTV_DELACK    (hz / PR_FASTHZ / 2)    /* 100ms timeout */
 111
 112 #ifdef  TCPTIMERS
 113 static const char *tcptimers[] =
 114     { "REXMT", "PERSIST", "KEEP", "2MSL" };
 115 #endif
 116
 117 /*
 118  * Force a time value to be in a certain range.
 119  */
 120 #define TCPT_RANGESET(tv, value, tvmin, tvmax) do { \
 121         (tv) = (value) + tcp_rexmit_slop; \
 122         if ((u_long)(tv) < (u_long)(tvmin)) \
 123                 (tv) = (tvmin); \
 124         else if ((u_long)(tv) > (u_long)(tvmax)) \
 125                 (tv) = (tvmax); \
 126 } while(0)
 127
 128 #ifdef _KERNEL
 129
 130 #define TCPTV_RTOBASE \
 131         (tcp_low_rtobase ? TCPTV_RTOBASE1 : TCPTV_RTOBASE3)
 132
 133 struct tcpcb;
 134 struct netmsg_tcp_timer {
 135         struct netmsg_base tt_msg;
 136         struct tcpcb    *tt_tcb;
 137         int             tt_cpuid;               /* owner cpuid */
 138         lwkt_port_t     tt_msgport;             /* owner msgport */
 139         uint32_t        tt_tasks;               /* pending tasks */
 140         uint32_t        tt_running_tasks;       /* running tasks */
 141         uint32_t        tt_prev_tasks;          /* prev pending tasks (debug) */
 142 };
 143
 144 struct tcp_callout {
 145         struct callout  tc_callout;
 146         uint32_t        tc_task;                /* callout's task id */
 147 };
 148
 149 extern int tcp_keepinit;                /* time to establish connection */
 150 extern int tcp_keepidle;                /* time before keepalive probes begin */
 151 extern int tcp_keepintvl;               /* time between keepalive probes */
 152 extern int tcp_keepcnt;                 /* maximum number of keepalive probes */
 153 extern int tcp_delacktime;              /* time before sending a delayed ACK */
 154 extern int tcp_maxpersistidle;
 155 extern int tcp_rexmit_min;
 156 extern int tcp_rexmit_slop;
 157 extern int tcp_msl;
 158 extern int tcp_ttl;                     /* time to live for TCP segs */
 159 extern int tcp_backoff[];               /* rxt backoff for data */
 160 extern int tcp_syn_backoff[];           /* rxt backoff for SYN */
 161 extern int tcp_syn_backoff_low[];       /* rxt backoff for SYN w/ RFC6298 */
 162
 163 void    tcp_timer_2msl(void *xtp);
 164 void    tcp_timer_keep(void *xtp);
 165 void    tcp_timer_persist(void *xtp);
 166 void    tcp_timer_rexmt(void *xtp);
 167 void    tcp_timer_delack(void *xtp);
 168 void    tcp_inittimers(struct tcpcb *);
 169
 170 struct lwkt_port;
 171 void    tcp_create_timermsg(struct tcpcb *, struct lwkt_port *);
 172 void    tcp_destroy_timermsg(struct tcpcb *);
 173
 174 #endif /* _KERNEL */
 175
 176 #endif /* !_NETINET_TCP_TIMER_H_ */