hath: Hath manipulates network blocks in CIDR notation.

Hath is a Haskell program for working with network blocks in CIDR notation. When dealing with blocks of network addresses, there are a few things that one usually wants to do with them:

• Create a regular expression matching the CIDR block(s). This is because grep will throw up if you feed it CIDR.

• Combine small blocks into larger ones. For example, if you have two consecutive /24s, they might combine into a larger /23.

• View the result of block combination in a useful way.

• List them.

• Find their associated PTR records.

Hath has several modes to perform these functions:

Regexed

This computes a (Perl-compatible) regular expression matching the input CIDR blocks. It's the default mode of operation.

Reduced

This combines small blocks into larger ones where possible, and eliminates redundant blocks. The output should be equivalent to the input, though.

Duped

Shows only the blocks that would be removed by reduce; that is, it shows the ones that would get combined into larger blocks or are simply redundant.

Diffed

Shows what would change if you used reduce. Uses diff-like notation.

Listed

List the IP addresses contained within the given CIDRs.

Reversed

Perform reverse DNS (PTR) lookups on the IP addresses contained within the given CIDRs.

Examples:

Compute a (Perl-compatible) regular expression matching the input CIDR blocks. It's the default mode of operation.

$ hath <<< "10.0.0.0/29 10.0.0.8/29"
((10).(0).(0).(0|1|2|3|4|5|6|7|8|9|10|11|12|13|14|15))

Combine two /24s into a /23:

$ hath reduced <<< "10.0.0.0/24 10.0.1.0/24"
10.0.0.0/23

List the addresses in 192.168.0.240/29:

$ hath listed <<< "192.168.0.240/29"
192.168.0.240
192.168.0.241
192.168.0.242
192.168.0.243
192.168.0.244
192.168.0.245
192.168.0.246
192.168.0.247

Perform PTR lookups on all of 198.41.0.4/30:

$ hath reversed <<< "198.41.0.4/30"
198.41.0.4: a.root-servers.net.
198.41.0.5:
198.41.0.6: rs.internic.net.
198.41.0.7:

The DNS lookups are usually the bottleneck for this mode, but we can perform them in parallel. Simply pass the number of threads to the GHC runtime on the command line; for example, the following will perform 25 lookups in parallel:

$ hath reversed +RTS -N25 <<< "198.41.0.4/24"
198.41.0.4: a.root-servers.net.
198.41.0.5:
198.41.0.6: rs.internic.net.
...

The command-line syntax and complete set of options are documented in the man page.