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Tor DNS lookups failing

A few months ago I modified Snakes on a Tor to do DNS lookups through various nodes and compare the results. At the time there was a node that was intermittently giving users an ad page instead of a real page. I found then that the only node that was returning an IP address that was incorrect was "whistlersmother," but I didn't report that here because I was a little unsure about my methodology.

Last week I started scanning again with a better idea of what I was doing. Notably, the latest Tor alpha resets the DNS cache on NEWNYM, so I didn't have to much with the Tor source to stop it from caching the lookups. After a couple of days of scanning, I haven't found any nodes returning incorrect information, but I have seen more lookup failures than I remember seeing last time. This jibes with my personal experience, where I feel like I've seen more DNS lookup failures than previously.

I was wondering, first, if other people are seeing fairly frequent erroneous DNS failures. Secondly, is there anything Tor can do to improve the situation, like requesting a second lookup via another circuit if one reports a failure, or maybe not caching failures? I'm not sure either of those is a good solution, but right now when I get a failure I have to either wait for the circuit to time out or send Tor NEWNYM. Otherwise the result seems to be cached, so a reload in my web browser just gives me the Privoxy error page again.


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