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