1 /* 2 * Copyright (c) 1982, 1986, 1988, 1993 3 * The Regents of the University of California. All rights reserved. 4 * 5 * %sccs.include.redist.c% 6 * 7 * @(#)spp_timer.h 8.1 (Berkeley) 06/10/93 8 */ 9 10 /* 11 * Definitions of the SPP timers. These timers are counted 12 * down PR_SLOWHZ times a second. 13 */ 14 #define SPPT_NTIMERS 4 15 16 #define SPPT_REXMT 0 /* retransmit */ 17 #define SPPT_PERSIST 1 /* retransmit persistance */ 18 #define SPPT_KEEP 2 /* keep alive */ 19 #define SPPT_2MSL 3 /* 2*msl quiet time timer */ 20 21 /* 22 * The SPPT_REXMT timer is used to force retransmissions. 23 * The SPP has the SPPT_REXMT timer set whenever segments 24 * have been sent for which ACKs are expected but not yet 25 * received. If an ACK is received which advances tp->snd_una, 26 * then the retransmit timer is cleared (if there are no more 27 * outstanding segments) or reset to the base value (if there 28 * are more ACKs expected). Whenever the retransmit timer goes off, 29 * we retransmit one unacknowledged segment, and do a backoff 30 * on the retransmit timer. 31 * 32 * The SPPT_PERSIST timer is used to keep window size information 33 * flowing even if the window goes shut. If all previous transmissions 34 * have been acknowledged (so that there are no retransmissions in progress), 35 * and the window is too small to bother sending anything, then we start 36 * the SPPT_PERSIST timer. When it expires, if the window is nonzero, 37 * we go to transmit state. Otherwise, at intervals send a single byte 38 * into the peer's window to force him to update our window information. 39 * We do this at most as often as SPPT_PERSMIN time intervals, 40 * but no more frequently than the current estimate of round-trip 41 * packet time. The SPPT_PERSIST timer is cleared whenever we receive 42 * a window update from the peer. 43 * 44 * The SPPT_KEEP timer is used to keep connections alive. If an 45 * connection is idle (no segments received) for SPPTV_KEEP amount of time, 46 * but not yet established, then we drop the connection. If the connection 47 * is established, then we force the peer to send us a segment by sending: 48 * <SEQ=SND.UNA-1><ACK=RCV.NXT><CTL=ACK> 49 * This segment is (deliberately) outside the window, and should elicit 50 * an ack segment in response from the peer. If, despite the SPPT_KEEP 51 * initiated segments we cannot elicit a response from a peer in SPPT_MAXIDLE 52 * amount of time, then we drop the connection. 53 */ 54 55 #define SPP_TTL 30 /* default time to live for SPP segs */ 56 /* 57 * Time constants. 58 */ 59 #define SPPTV_MSL ( 15*PR_SLOWHZ) /* max seg lifetime */ 60 #define SPPTV_SRTTBASE 0 /* base roundtrip time; 61 if 0, no idea yet */ 62 #define SPPTV_SRTTDFLT ( 3*PR_SLOWHZ) /* assumed RTT if no info */ 63 64 #define SPPTV_PERSMIN ( 5*PR_SLOWHZ) /* retransmit persistance */ 65 #define SPPTV_PERSMAX ( 60*PR_SLOWHZ) /* maximum persist interval */ 66 67 #define SPPTV_KEEP ( 75*PR_SLOWHZ) /* keep alive - 75 secs */ 68 #define SPPTV_MAXIDLE ( 8*SPPTV_KEEP) /* maximum allowable idle 69 time before drop conn */ 70 71 #define SPPTV_MIN ( 1*PR_SLOWHZ) /* minimum allowable value */ 72 #define SPPTV_REXMTMAX ( 64*PR_SLOWHZ) /* max allowable REXMT value */ 73 74 #define SPP_LINGERTIME 120 /* linger at most 2 minutes */ 75 76 #define SPP_MAXRXTSHIFT 12 /* maximum retransmits */ 77 78 #ifdef SPPTIMERS 79 char *spptimers[] = 80 { "REXMT", "PERSIST", "KEEP", "2MSL" }; 81 #endif 82 83 /* 84 * Force a time value to be in a certain range. 85 */ 86 #define SPPT_RANGESET(tv, value, tvmin, tvmax) { \ 87 (tv) = (value); \ 88 if ((tv) < (tvmin)) \ 89 (tv) = (tvmin); \ 90 else if ((tv) > (tvmax)) \ 91 (tv) = (tvmax); \ 92 } 93 94 #ifdef KERNEL 95 extern int spp_backoff[]; 96 #endif 97