CHANGES revision 225736
1# @(#)CHANGES 5.1 (Berkeley) 5/11/93 2# $FreeBSD: stable/9/usr.sbin/timed/timed/CHANGES 72646 2001-02-18 10:44:00Z asmodai $ 3 4This new version is almost identical to the timed and timedc code 5that has been shipped for years by a workstation vendor. 6 7Among the many changes: 8 9improve `timedc msite` to accept a list of hostnames. 10 11change slave-masters to answer the packets generated by `timedc msite` 12 with the name of the real master, not their own. This makes it 13 possible to "chase the chain" of slave servers to the ultimate 14 master. 15 16much improve the log caused by `timedc trace on`: 17 -made `timed -t` work. 18 -suppression of repeated entries, which both slowed down the daemon 19 (sometimes catastrophically) and tended to make disks fill up 20 even more quickly. 21 -better time stamps on log entries 22 -more messages 23 -dump information about slaves, master, and so on each time 24 a message asking the log be turned on is received, and 25 when the log is turned off. 26 -fewer CPU cycles 27 28use a hash table to keep track of slaves, instead of the stupid linear 29 list. This becomes handy with hundreds of slaves, instead of 30 the original design limit of "a room with a few VAX's." 31 32separate the main protocol timer from that used to look for other networks 33 to master. 34 35time stamp packets received by the daemon, so that time corrections 36 are not made (even more) inaccurate by waiting in the internal, 37 timed queue while the daemon is processing other messages. 38 39made -n and -i work with subnets not named in /etc/networks 40 41compute the median of the measured clocks, instead of the average 42 of "good" times. 43 44vastly improve the accuracy of the clock difference measure by 45 `timedc clockdiff`. 46 47use adjtime() when possible, and directly set the clock only when 48 necessary. 49 50when the requested adjustment is small, perform only part of it, to 51 damp oscillations and improve the long term accuracy of the 52 adjustments. 53 54fix uncounted core-dumps on machines that do not allow dereferencing 0 55 in both the daemon and timedc. 56 57fix "master loop detection". 58 59fix several cases in which multi-homed masters could get into shouting 60 matches, consuming all available network bandwidth and CPU cycles 61 (which ever runs out first), and convincing all bystanders to stop 62 advancing their own clocks. 63 64refuse to behave badly when other machines do. Instead of arguing forever, 65 go off and sulk when other machines refuse to play by the rules. 66 67increase the maximum number of clients. 68 69add "-F host,host2,..." to "freerun" or "trust" only some hosts. This 70 is handy both when only some machines should be trusted to let 71 root use the `date` command to change time in the network. 72 73 It is also handy when one machine has some other way of adjusting 74 its clock, whether NTP or a direct radio or atomic connection. 75 "-F localhost" causes `timed` to "trust" only itself. 76 77 It is also handy to build a hierarchy of timed masters crossing 78 networks. The TSP protocol has no provision of "goodness of clock", 79 no natural way to completely heal network paritions. Judicious 80 use of -F or -G can cause each gateway to trust only itself and 81 machines closer to a central machine with a radio or atomic clock. 82 83add #ifdef code that supports NIS "netgroups" of trusted hosts, which 84 can be easier to administer than -F. 85 86add #ifdef code to compute an aged total adjustment. This can be used 87 in systems that can make long term changes in their system clock 88 frequency, e.g. "timetrim" in the Silicon Graphics kernel. 89 90 91Problems observed by others that are unresolved include: 92 93Practically any users can send to the master TSP messages and this 94 way corrupt the reliability of the system. Authentication 95 of messages should be provided. Unfortunately, that would 96 require changing the protocol with all of the implied 97 compatiblity problems. Fortunately, the new -F and -G args 98 can be used to cause the daemon to ignore time changes from 99 untrusted machines. 100 101MAN. The limit of 1013 on the number of slaves hosts should be doc'ed. 102 103 It should be dynamically allocated with no limit. On a 104 large network, one host could possibly master over many 105 more than 30 hosts. Given the timers in the code and 106 effectively in the protocol, and the time required by each 107 master to talk to each slave, it is not practical to have 108 more than 200-300 slaves. The master cannot keep up because 109 the slave-chatting is single-threaded. when the master 110 gets behind, slaves start demanding elections. To 111 significantly increase the number of slaves would require 112 multi-treading things, and given that a network with more 113 than 300 directly addressable machines has worse problems 114 than keep the time of day right, not worth worrying about. 115 116UGLY,CODE. timedc/cmds.c has a lots of repeated code in it. 117 118**** The first thing is that each command is set up as if it 119 were an individual program taking argc and argv. A more 120 conventional calling style should be used. I don't think 121 any of the routines take more than a couple arguments. 122 123UGLY. fxn definition syntax does't follow convention: 124 has type on same line. 125 126**** It needs to be fixed at least enough that tags 127 will work on it. An entire cleanup might be nice later, but 128 is noncritical. 129 130LOBBY(mildly),CODE: Would be very convenient if date(1) took a 131 +-<number> argument to set the time relatively. With 132 the advent of timed it is now reasonable to synchronize 133 with WWV, which is nearly impossible to do "by hand" 134 with just an absolute date, and scripts are too slow. 135 format could be +-nn...nn.ss, where the '.' is required 136 to remove ambiguity. 137 138**** If you want to do it go ahead. It sounds useful. As far as 139 syntax goes, the normal format for the date should work just 140 fine for this. If the date is preceded by a plus or minus, 141 the change is relative, otherwise it is absolute. 142 143 144Vernon Schryver. 145vjs@sgi.com 146