Tor sends a RESOLVEFAILED event when a reverse lookup succeeds.

Having SETEVENTS ADDRMAP and STREAM, I get

650 STREAM 23575 NEWRESOLVE 0 8.8.8.8:0 PURPOSE=DNS_REQUEST
650 STREAM 23575 NEW 7180 8.8.8.8:0 SOURCE_ADDR=(Tor_internal):58649 PURPOSE=DNS_REQUEST
650 STREAM 23575 SENTRESOLVE 7180 8.8.8.8:0
650 ADDRMAP REVERSE[8.8.8.8] google-public-dns-a.google.com "2011-07-07 01:55:07" EXPIRES="2011-07-07 05:55:07"
650 STREAM 23575 FAILED 7180 8.8.8.8:0 REASON=RESOLVEFAILED
650 STREAM 23575 CLOSED 7180 8.8.8.8:0 REASON=DONE

or something similar with any successful reverse DNS request. I'm using 0.2.3.1-alpha-dev (git-e273890b).

Trac:
Username: katmagic

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