From http://archives.seul.org/tor/relays/Mar-2010/msg00006.html :

   As I understand it, the bug should show up on relays that don't set
   Address to an IP address (so they need to resolve their Address
   line or their hostname to guess their IP address), and their
   hostname or Address line fails to resolve -- at that point they'll
   pick a random 4 bytes out of memory and call that their address. At
   the same time, relays that *do* successfully resolve their address
   will ignore the result, and only come up with a useful address if
   their interface address happens to be a public IP address.