This program performs reverse DNS lookups for network blocks or an input file. The requests can be performed mulit-threaded.
./res <subnet or filename to resolve> <forks>
Example 1 - mass resolve 192.168.1.0/24 with 64 forks
./res 192.168.1 64
Example 2 - mass resolve 10.0.0.0/8 with 128 forks
./res 10 128
Example 3 - mass resolve from a file called iplist with 10 forks
./res iplist 10
res-2 is a slightly updated version to fix compilation warnings and a crash bug on certain systems.