I just spent a dickens of a time trying to figure out why my gethostbyaddr's were simply failing halfway through.
I'm returning a log of page visits, and with each new IP, I wanted to pull the hostname of the IP. On each report page, I'm pulling 500 lines from my Db, but only maybe 25 IPs on average. Sometimes this report would generate in under 15 seconds, other times it would fail with a connection reset.
It turns out that several of the IPs in my Db looked like this: x.255.x.x. gethostbyaddr really hates that and simply dies when it reaches one of these IPs.
For my case, I purged the Db and prevented the logging of IPs that contain 255.
