System Calls that do DNS

[Doug Hardie]

I have an unusual situation.  A program is doing a DNS lookup and often the IP address has no reverse DNS entries.  As a result the program hangs for several timeouts.  The call is not being made directly in its code, but is occurring in a system call.  There are no specific calls to DNS, its something else doing it.  I have been trying to track down which system call is doing it, but without success so far.  I have tried syslog calls around each of the system calls I thought might be the culprit, but my guessing is not very good.  How can I identify the system call that is calling DNS?  If I can find it, I hopefully can find another way to do whatever it does that does not involve a reverse DNS lookup.