Tor DNS lookups failing

[Jay Goodman Tamboli]

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.

Thanks,

/jgt
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