1 /* 2 * Copyright (c) 1982, 1986, 1988 Regents of the University of California. 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms are permitted 6 * provided that this notice is preserved and that due credit is given 7 * to the University of California at Berkeley. The name of the University 8 * may not be used to endorse or promote products derived from this 9 * software without specific prior written permission. This software 10 * is provided ``as is'' without express or implied warranty. 11 * 12 * @(#)spp_timer.h 7.1 (Berkeley) 03/12/88 13 */ 14 15 /* 16 * Definitions of the SPP timers. These timers are counted 17 * down PR_SLOWHZ times a second. 18 */ 19 #define SPPT_NTIMERS 4 20 21 #define SPPT_REXMT 0 /* retransmit */ 22 #define SPPT_PERSIST 1 /* retransmit persistance */ 23 #define SPPT_KEEP 2 /* keep alive */ 24 #define SPPT_2MSL 3 /* 2*msl quiet time timer */ 25 26 /* 27 * The SPPT_REXMT timer is used to force retransmissions. 28 * The SPP has the SPPT_REXMT timer set whenever segments 29 * have been sent for which ACKs are expected but not yet 30 * received. If an ACK is received which advances tp->snd_una, 31 * then the retransmit timer is cleared (if there are no more 32 * outstanding segments) or reset to the base value (if there 33 * are more ACKs expected). Whenever the retransmit timer goes off, 34 * we retransmit one unacknowledged segment, and do a backoff 35 * on the retransmit timer. 36 * 37 * The SPPT_PERSIST timer is used to keep window size information 38 * flowing even if the window goes shut. If all previous transmissions 39 * have been acknowledged (so that there are no retransmissions in progress), 40 * and the window is too small to bother sending anything, then we start 41 * the SPPT_PERSIST timer. When it expires, if the window is nonzero, 42 * we go to transmit state. Otherwise, at intervals send a single byte 43 * into the peer's window to force him to update our window information. 44 * We do this at most as often as SPPT_PERSMIN time intervals, 45 * but no more frequently than the current estimate of round-trip 46 * packet time. The SPPT_PERSIST timer is cleared whenever we receive 47 * a window update from the peer. 48 * 49 * The SPPT_KEEP timer is used to keep connections alive. If an 50 * connection is idle (no segments received) for SPPTV_KEEP amount of time, 51 * but not yet established, then we drop the connection. If the connection 52 * is established, then we force the peer to send us a segment by sending: 53 * <SEQ=SND.UNA-1><ACK=RCV.NXT><CTL=ACK> 54 * This segment is (deliberately) outside the window, and should elicit 55 * an ack segment in response from the peer. If, despite the SPPT_KEEP 56 * initiated segments we cannot elicit a response from a peer in SPPT_MAXIDLE 57 * amount of time, then we drop the connection. 58 */ 59 60 #define SPP_TTL 30 /* default time to live for SPP segs */ 61 /* 62 * Time constants. 63 */ 64 #define SPPTV_MSL ( 15*PR_SLOWHZ) /* max seg lifetime */ 65 #define SPPTV_SRTTBASE 0 /* base roundtrip time; 66 if 0, no idea yet */ 67 #define SPPTV_SRTTDFLT ( 3*PR_SLOWHZ) /* assumed RTT if no info */ 68 69 #define SPPTV_PERSMIN ( 5*PR_SLOWHZ) /* retransmit persistance */ 70 #define SPPTV_PERSMAX ( 60*PR_SLOWHZ) /* maximum persist interval */ 71 72 #define SPPTV_KEEP ( 75*PR_SLOWHZ) /* keep alive - 75 secs */ 73 #define SPPTV_MAXIDLE ( 8*SPPTV_KEEP) /* maximum allowable idle 74 time before drop conn */ 75 76 #define SPPTV_MIN ( 1*PR_SLOWHZ) /* minimum allowable value */ 77 #define SPPTV_REXMTMAX ( 64*PR_SLOWHZ) /* max allowable REXMT value */ 78 79 #define SPP_LINGERTIME 120 /* linger at most 2 minutes */ 80 81 #define SPP_MAXRXTSHIFT 12 /* maximum retransmits */ 82 83 #ifdef SPPTIMERS 84 char *spptimers[] = 85 { "REXMT", "PERSIST", "KEEP", "2MSL" }; 86 #endif 87 88 /* 89 * Force a time value to be in a certain range. 90 */ 91 #define SPPT_RANGESET(tv, value, tvmin, tvmax) { \ 92 (tv) = (value); \ 93 if ((tv) < (tvmin)) \ 94 (tv) = (tvmin); \ 95 else if ((tv) > (tvmax)) \ 96 (tv) = (tvmax); \ 97 } 98 99 #ifdef KERNEL 100 extern int spp_backoff[]; 101 #endif 102