Nick Andrew <n...@nick-andrew.net> writes:
> On Sun, Mar 28, 2010 at 11:23:35AM +1100, Daniel Pittman wrote:
>
>> FWIW, I got very sick of this years and years ago, so I took to installing
>> the distribution packaged version of bind on my machine and configuring the
>> system to use localhost for name resolution.
>
> dnscache works well for that too. See http://cr.yp.to/ or http://tinydns.org/
> or http://github.com/nickandrew/djbdns
Oh, cool. Someone talked DJB into relicensing dnscache so that it can be
distributed patched, rather than requiring the original. That must make life
better for folks like you who want to use it.
Anyway, I have a bit of an aversion to the software: aside from the (formerly)
awful license conditions, I had a couple of clients who ended up with really
nasty problems from dnscache.
(Executive summary: probably not a problem any more. ;)
Way back when a 256/64 kbit ADSL connection was fast and expensive, a couple
of places I supported used software that incorporated dnscache, and had the
ability to use DNS RBLs for inbound email.
So, it turns out that dnscache had a fixed ten second timeout for a response
from the upstream DNS server. If it receives a reply outside that window it
will reject the reply; it also resends queries if they time out.
Apparently, though, if you manage to list enough RBLs you can get in a
situation where dnscache is sending requests, which all time out because the
link RTT is more than ten seconds — just from the load of sending
retransmitted queries.
Which meant that two or three emails inbound at once could result in a
situation where their network link got saturated, and stayed that way until
dnscache gave up on all the queries.
Gosh, was that fun.
Anyway, these days that is unlikely to be a problem: either the code will be
patched to play nice, or the increase in bandwidth makes the odds of breaking
pretty slim.
Daniel
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