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 */ 119