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From: piet@cwi.nl (Piet Beertema)
Newsgroups: comp.mail.sendmail
Subject: Re: Local Configuration Error
Message-ID: <2223@charon.cwi.nl>
Date: 24 Sep 90 19:07:56 GMT
References: <1990Sep19.002139.32095@mp.cs.niu.edu> <2199@charon.cwi.nl> <1990Sep20.182739.29113@mp.cs.niu.edu>
Sender: news@cwi.nl
Organization: CWI, Amsterdam
Lines: 60


		In both cases only the local MX record is discarded (but
		marked) and all other MX records are stored and sorted.
	You must be looking at different source code to mine. In the
	5.64 release from Berkeley, as soon as an MX record pointing
	to the local host is found its preference is recorded, and any
	further MX records are only stored into an array for sorting
	if they have a lower preference.
I'm using sendmail-5.64+IDA. But here's the relevant part of
the original Berkeley version:

	......
	while (--ancount >= 0 && cp < eom && nmx < MAXMXHOSTS) {
		if ((n = dn_expand((char *)&answer, eom, cp, bp, buflen)) < 0)
			break;
		......
		if (!strcasecmp(bp, localhost)) {
			if (seenlocal == 0 || pref < localpref)
				localpref = pref;
			seenlocal = 1;
			continue;
		}
		prefer[nmx] = pref;
		mxhosts[nmx++] = bp;
		n = strlen(bp) + 1;
		bp += n;
		buflen -= n;
	}
	if (nmx == 0) {
punt:		mxhosts[0] = strcpy(hostbuf, host);
		return(1);
	}

	/* sort the records */
	for (i = 0; i < nmx; i++) {

The !strcasecmp() matches only for the MX record pointing to the
local host; that record is discarded, but marked in seenlocal.
All other (previous or later) MX records are stored in mxhosts[]
and sorted later on. Care is taken of multiple MX records pointing
to the local host: only the one with the lowest value (highest
priority) is taken into account.

If the above is wrong, please tell me where it is wrong.


As Brian Kantor pointed out, the match on localhost fails if for
one reason or another $w has not been set to the fully qualified
domain name of the local host (which can be useful if e.g. the
unqualified name is the uucp name). This can easily be corrected by
using `gethostbyname(localhost)->h_name' in the comparison instead
of localhost itself. This is in line with how localhost is obtained
elsewhere (via myhostname() which uses gethostbyname()). It is also
correct in the sense that, since $w defines the local host, it by
definition resides in the local domain and thus can be made fully
qualified with the local domain.


--
	Piet Beertema, CWI, Amsterdam	(piet@cwi.nl)