xref: /original-bsd/sys/netns/spp_timer.h (revision bbb96de4)
1 /*
2  * Copyright (c) 1982, 1986, 1988 Regents of the University of California.
3  * All rights reserved.
4  *
5  * %sccs.include.redist.c%
6  *
7  *	@(#)spp_timer.h	7.3 (Berkeley) 06/28/90
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