usr/src/uts/common/netinet/tcp_timer.h

   1 /*
   2  * Copyright (c) 1982, 1986 Regents of the University of California.
   3  * All rights reserved.
   4  * Copyright (c) 2016 by Delphix. All rights reserved.
   5  *
   6  * Redistribution and use in source and binary forms are permitted
   7  * provided that the above copyright notice and this paragraph are
   8  * duplicated in all such forms and that any documentation,
   9  * advertising materials, and other materials related to such
  10  * distribution and use acknowledge that the software was developed
  11  * by the University of California, Berkeley.  The name of the
  12  * University may not be used to endorse or promote products derived
  13  * from this software without specific prior written permission.
  14  */
  15
  16 /*
  17  * Definitions of the TCP timers.  These timers are counted
  18  * down PR_SLOWHZ times a second.
  19  */
  20
  21 #ifndef _NETINET_TCP_TIMER_H
  22 #define _NETINET_TCP_TIMER_H
  23
  24 #pragma ident   "%Z%%M% %I%     %E% SMI"
  25 /* tcp_timer.h 1.13 89/06/16 SMI; from UCB 7.6 6/29/88 */
  26
  27 #ifdef  __cplusplus
  28 extern "C" {
  29 #endif
  30
  31 #define TCPT_NTIMERS    4
  32
  33 #define TCPT_REXMT      0               /* retransmit */
  34 #define TCPT_PERSIST    1               /* retransmit persistance */
  35 #define TCPT_KEEP       2               /* keep alive */
  36 #define TCPT_2MSL       3               /* 2*msl quiet time timer */
  37
  38 /*
  39  * The TCPT_REXMT timer is used to force retransmissions.
  40  * The TCP has the TCPT_REXMT timer set whenever segments
  41  * have been sent for which ACKs are expected but not yet
  42  * received.  If an ACK is received which advances tp->snd_una,
  43  * then the retransmit timer is cleared (if there are no more
  44  * outstanding segments) or reset to the base value (if there
  45  * are more ACKs expected).  Whenever the retransmit timer goes off,
  46  * we retransmit one unacknowledged segment, and do a backoff
  47  * on the retransmit timer.
  48  *
  49  * The TCPT_PERSIST timer is used to keep window size information
  50  * flowing even if the window goes shut.  If all previous transmissions
  51  * have been acknowledged (so that there are no retransmissions in progress),
  52  * and the window is too small to bother sending anything, then we start
  53  * the TCPT_PERSIST timer.  When it expires, if the window is nonzero,
  54  * we go to transmit state.  Otherwise, at intervals send a single byte
  55  * into the peer's window to force it to update our window information.
  56  * We do this at most as often as TCPT_PERSMIN time intervals,
  57  * but no more frequently than the current estimate of round-trip
  58  * packet time.  The TCPT_PERSIST timer is cleared whenever we receive
  59  * a window update from the peer.
  60  *
  61  * The TCPT_KEEP timer is used to keep connections alive.  If a
  62  * connection is idle (no segments received) for TCPTV_KEEP_INIT amount of time,
  63  * but not yet established, then we drop the connection.  Once the connection
  64  * is established, if the connection is idle for TCPTV_KEEP_IDLE time
  65  * (and keepalives have been enabled on the socket), we begin to probe
  66  * the connection.  We force the peer to send us a segment by sending:
  67  *      <SEQ=SND.UNA-1><ACK=RCV.NXT><CTL=ACK>
  68  * This segment is (deliberately) outside the window, and should elicit
  69  * an ack segment in response from the peer.  If, despite the TCPT_KEEP
  70  * initiated segments we cannot elicit a response from a peer in TCPT_MAXIDLE
  71  * amount of time probing, then we drop the connection.
  72  */
  73
  74 #define TCP_TTL         60              /* default time to live for TCP segs */
  75 /*
  76  * Time constants.
  77  */
  78 #define TCPTV_MSL       (30*PR_SLOWHZ)          /* max seg lifetime (hah!) */
  79 #define TCPTV_SRTTBASE  0                       /* base roundtrip time; */
  80                                                 /* if 0, no idea yet */
  81 #define TCPTV_SRTTDFLT  (3*PR_SLOWHZ)           /* assumed RTT if no info */
  82
  83 #define TCPTV_PERSMIN   (5*PR_SLOWHZ)           /* retransmit persistance */
  84 #define TCPTV_PERSMAX   (60*PR_SLOWHZ)          /* maximum persist interval */
  85
  86 #define TCPTV_KEEP_INIT (75*PR_SLOWHZ)          /* initial connect keep alive */
  87 #define TCPTV_KEEP_IDLE (120*60*PR_SLOWHZ)      /* dflt time before probing */
  88 #define TCPTV_KEEPINTVL (75*PR_SLOWHZ)          /* default probe interval */
  89 #define TCPTV_KEEPCNT   8                       /* max probes before drop */
  90
  91 #define TCPTV_MIN       (1*PR_SLOWHZ)           /* minimum allowable value */
  92 #define TCPTV_REXMTMAX  (64*PR_SLOWHZ)          /* max allowable REXMT value */
  93
  94 #define TCP_LINGERTIME  120                     /* linger at most 2 minutes */
  95
  96 #define TCP_MAXRXTSHIFT 12                      /* maximum retransmits */
  97
  98 #ifdef  TCPTIMERS
  99 char *tcptimers[] =
 100         { "REXMT", "PERSIST", "KEEP", "2MSL" };
 101 #endif
 102
 103 /*
 104  * Force a time value to be in a certain range.
 105  */
 106 #define TCPT_RANGESET(tv, value, tvmin, tvmax) { \
 107         (tv) = (value); \
 108         if ((tv) < (tvmin)) \
 109                 (tv) = (tvmin); \
 110         else if ((tv) > (tvmax)) \
 111                 (tv) = (tvmax); \
 112 }
 113
 114 #ifdef  __cplusplus
 115 }
 116 #endif
 117
 118 #endif  /* _NETINET_TCP_TIMER_H */