From mboxrd@z Thu Jan  1 00:00:00 1970
Message-Id: <9B525D75-6CBB-4E95-BE4F-83FCC7F1393B@ar.aichi-u.ac.jp>
From: Kenji Arisawa <arisawa@ar.aichi-u.ac.jp>
To: Fans of the OS Plan 9 from Bell Labs <9fans@9fans.net>
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Date: Sun, 24 Aug 2008 20:23:14 +0900
Subject: [9fans] dns failure in smtp
Topicbox-Message-UUID: 066a234e-ead4-11e9-9d60-3106f5b1d025

Sorry for noise.

Someone in this list send me a mail but I cannot reply to the mail
because of dns failure in smtp.
This is a private message to him.

ar% pwd
/sys/log
ar% tail smtp.fail
ar Aug 24 08:30:13 dns: dns failure (net!sounine.nanosouffle.net)
ar Aug 24 09:40:13 dns: dns failure (net!sounine.nanosouffle.net)
ar Aug 24 10:50:13 dns: dns failure (net!sounine.nanosouffle.net)
ar Aug 24 12:00:13 dns: dns failure (net!sounine.nanosouffle.net)
ar Aug 24 13:10:14 dns: dns failure (net!sounine.nanosouffle.net)
ar Aug 24 14:20:13 dns: dns failure (net!sounine.nanosouffle.net)
ar Aug 24 15:30:13 dns: dns failure (net!sounine.nanosouffle.net)
ar Aug 24 16:40:13 dns: dns failure (net!sounine.nanosouffle.net)
ar Aug 24 17:50:13 dns: dns failure (net!sounine.nanosouffle.net)
ar Aug 24 19:16:08 dns: dns failure (net!sounine.nanosouffle.net)
ar% ndb/dnsquery
 > sounine.nanosouffle.net mx
!dns: resource does not exist
 > sounine.nanosouffle.net
sounine.nanosouffle.net ip	75.58.233.41
 >


I think mx record is required in official dns server, although I feel
the condition is too strict.

/sys/src/cmd/upas/smtp/mxdial.c

	nmx = 0;
	snprint(buf, sizeof buf, "%s mx", ds->host);
	if(debug)
		fprint(2, "sending %s '%s'\n", dnsname, buf);
	/*
	 * don't hang indefinitely in the write to /net/dns.
	 */
	n = timedwrite(fd, buf, strlen(buf), 60*1000);
	if(n < 0){
		rerrstr(buf, sizeof buf);
		if(debug)
			fprint(2, "dns: %s\n", buf);
		if(strstr(buf, "dns failure")){
			/* if dns fails for the mx lookup, we have to stop */
			close(fd);
			return -1;
		}
	} else {


Kenji Arisawa
Email: arisawa@aichi-u.ac.jp