Date: Tue, 11 Apr 2000 17:20:04 -0700 (PDT) From: Bill Fenner <fenner@research.att.com> To: freebsd-bugs@FreeBSD.org Subject: Re: misc/17889: certain type of DNS queries seem to get dropped by DNS server Message-ID: <200004120020.RAA56354@freefall.freebsd.org>
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The following reply was made to PR misc/17889; it has been noted by GNATS.
From: Bill Fenner <fenner@research.att.com>
To: adrian.roy@bigfoot.com
Cc: freebsd-gnats-submit@freebsd.org
Subject: Re: misc/17889: certain type of DNS queries seem to get dropped by DNS server
Date: Tue, 11 Apr 2000 17:12:41 -0700
>I check the DNS server and it is saying that there was a DNS query from the
>4.0 machine looking for info on the 3.3 machine. It says the DNS query was
>of type 28, and that it was invalid, and that it will be dropped.
This is a query for an IPv6 address. Does it really drop it, or does it
reply with an empty reply? Here's what happens when I telnet to my 4.0
box ("emachine.attlabs.att.com") from my 3.4 box ("mango.attlabs.att.com"):
% tcpdump -s 1500 udp port domain
tcpdump: listening on dc0
17:02:28.499255 emachine.attlabs.att.com.1206 > mp-dns.attlabs.att.com.domain: 33870+ PTR? 114.2.197.135.in-addr.arpa. (44)
17:02:28.501048 mp-dns.attlabs.att.com.domain > emachine.attlabs.att.com.1206: 33870* 1/7/7 PTR mango.attlabs.att.com. (371) (DF)
17:02:28.501915 emachine.attlabs.att.com.1207 > mp-dns.attlabs.att.com.domain: 33871+ AAAA? mango.attlabs.att.com. (39)
17:02:28.502909 mp-dns.attlabs.att.com.domain > emachine.attlabs.att.com.1207: 33871* 0/1/0 (106) (DF)
17:02:28.503140 emachine.attlabs.att.com.1208 > mp-dns.attlabs.att.com.domain: 33872+ AAAA? mango.attlabs.att.com.attlabs.att.com. (55)
17:02:28.504185 mp-dns.attlabs.att.com.domain > emachine.attlabs.att.com.1208: 33872 NXDomain* 0/1/0 (122) (DF)
17:02:28.504554 emachine.attlabs.att.com.1209 > mp-dns.attlabs.att.com.domain: 33873+ AAAA? mango.attlabs.att.com. (39)
17:02:28.505574 mp-dns.attlabs.att.com.domain > emachine.attlabs.att.com.1209: 33873* 0/1/0 (106) (DF)
17:02:28.505736 emachine.attlabs.att.com.1210 > mp-dns.attlabs.att.com.domain: 33874+ AAAA? mango.attlabs.att.com.attlabs.att.com. (55)
17:02:28.506769 mp-dns.attlabs.att.com.domain > emachine.attlabs.att.com.1210: 33874 NXDomain* 0/1/0 (122) (DF)
17:02:28.507112 emachine.attlabs.att.com.1211 > mp-dns.attlabs.att.com.domain: 33875+ A? mango.attlabs.att.com. (39)
17:02:28.509445 mp-dns.attlabs.att.com.domain > emachine.attlabs.att.com.1211: 33875* 1/11/10 A 135.197.2.114 (494) (DF)
If all of those AAAA? queries had to time out because the server was
dropping them instead of replying that it had no information, that
would explain why it takes so long.
I recommend:
1) Running that same tcpdump on your 4.0 machine to see what is going on
2) Trying a dig to see how your name server handles queries for aaaa
records; "dig @nameserver aaaa some.host.name.". It should reply
with an empty answer section.
3) If the name server is really dropping the queries instead of replying
to them, report this bug to the authors.
Meanwhile, you could work around the problem by using one of your
FreeBSD boxes as a name server instead of your NT box; FreeBSD comes
with a working name server.
Bill
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