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From: chris@umcp-cs.UUCP (Chris Torek)
Newsgroups: net.bugs.4bsd
Subject: Re: ruptime reports 0 users (it's *worse*)
Message-ID: <2490@umcp-cs.UUCP>
Date: Sun, 8-Dec-85 00:26:33 EST
Article-I.D.: umcp-cs.2490
Posted: Sun Dec  8 00:26:33 1985
Date-Received: Mon, 9-Dec-85 03:25:30 EST
References: <5444@allegra.UUCP> <629@pucc-j>
Organization: U of Maryland, Computer Science Dept., College Park, MD
Lines: 31

In article <629@pucc-j> rsk@pucc-j (Wombat) writes:

>In article <5444@allegra.UUCP> mp@allegra.UUCP (Mark Plotnick)

[gives a fix for a ruptime bug]

>Mark's fix is correct, and does fix the problem with the reading of
>the whod file (Thanks Mark!) but it doesn't attack the next problem,
>which is that (apparently) the UDP packetsize winds up restricting
>the maximum number of users that will be reported to 41...

Actually, at least in our kernel, the maximum datagram size is 2048
bytes.  Of course, most kernels will not allow this to be sent as
a broadcast packet, because of this statement in netinet/ip_output.c:

		if (ip->ip_len > ifp->if_mtu) {
			error = EMSGSIZE;
			goto bad;
		}

We turned this off long ago when (for reasons that are no longer
important) we had to use a tiny ETHERMTU.  Just `#ifdef notdef'
out the code and it all works again.  I guess that the reason for
the restriction was that reassembling broadcast fragments is a
great burden on every machine on the network; but broadcasts may
only be sent by the super-user, who is presumed to know what he is
doing.
-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 4251)
UUCP:	seismo!umcp-cs!chris
CSNet:	chris@umcp-cs		ARPA:	chris@mimsy.umd.edu