Er. But isn't this (a) whether you interpret NODATA (aka No Error) as
NXDOMAIN or otherwise a DNS client library and/or DNSBL query function
decision, and (b) does DNS really return "No Error" for b.a if there's
no RR for b.a, but there is one for c.b.a?
Per my previous message, the answer to (b) is yes, according to
RFC 4592, but there's a lot of buggy software that gets it wrong.
dnscache has a fixed size outstanding query buffer (compile-time 100
queries IIRC), and throws queries away if you overflow it.
For the handful of computers that use my cache, it hasn't been a problem.
Note "handful".
Indeed. If I find that I have to run the mail system for a major
multinational corporation, I expect I'll use something else. djbdns
hasn't been updated since 2001, when its query limits were reasonable.
But that's Dan for you.
... I'm talking about a single mail server doing 4-8 DNS queries per
email, and 20-100 emails/second blowing a dnscache instance's brains out.
That reminds me, any chance of getting running some IP/timestamp logs
through my DNSBL analyzer and see how much a cache helps a busy setup
like yours?
R's,
John
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