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>From srk@sanger.ac.uk Thu Dec 23 23:19:37 2004
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Date: Thu, 23 Dec 2004 22:22:52 +0000
From: Simon Kelley <srk@sanger.ac.uk>
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To: bob@ngi.it
Subject: Re: dnsmasq help needed
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>tcpdump -n -i eth0 port 53
>shows activity for "dig www.apple.com" every time, while for all other
>names I can try, the activity on port 53 eth0 occurs only on the first
>try (I am talking about repeated tries at short intervals weel under
>the 50 seconds) while the rest is obviously cached.
That looked a little odd, so I tried it myself and got the same result.
Poking around I found a bug which has been there pretty much since the
first versions of dnsmasq. Since its effect is to inhibit caching off a
very few names, I guess nobody has ever noticed it before.
To hit the problem, a name has to be a CNAME, and the actual A record
which it points to has to have the original name as a leading substring
of its name.
www.apple.com hits this:
; <<>> DiG 9.2.4rc5 <<>> @127.0.0.1 -p 10000 www.apple.com
;; global options: printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 24807
;; flags: qr rd ra; QUERY: 1, ANSWER: 2, AUTHORITY: 0, ADDITIONAL: 0
;; QUESTION SECTION:
;www.apple.com. IN A
;; ANSWER SECTION:
www.apple.com. 1735 IN CNAME www.apple.com.akadns.net.
www.apple.com.akadns.net. 55 IN A 17.254.0.91
;; Query time: 22 msec
;; SERVER: 127.0.0.1#10000(127.0.0.1)
;; WHEN: Thu Dec 23 21:58:26 2004
;; MSG SIZE rcvd: 85
www.apple.com is CNAME, pointing to www.apple.com.akadns.net, which has
www.apple.com at its begining.
I think this gets some kind of record for bug subtlety, it will be
nailed in the next release.
Cheers,
Simon.
[ Please could you forward the above to the debian-user list. I found
the thread via Google and have no easy way to post to the list and keep
the threading intact.]
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