Classless Inter-Domain Routing (CIDR) utilities for Elixir

To use this library, just add :cidr as a dependency to your mix.exs file:

defp deps do
  [
    {:cidr, ">= 1.1.0"}
  ]
end

Passing an IP address string into CIDR.parse returns a %CIDR{} struct. It contains the first and the last address of the range as Erlang IP tuples, the amount of hosts the range covers and the network mask.

iex(1)> cidr = "1.2.3.4/24" |> CIDR.parse
%CIDR{first: {1, 2, 3, 0}, last: {1, 2, 3, 255}, hosts: 256, mask: 24}

You can query the struct for all of its fields:

iex(2)> cidr.first
{1, 2, 3, 0}
iex(3)> cidr.hosts
256

And use it to see if other IP addresses fall in the same range:

iex(4)> cidr |> CIDR.match!({1,2,3,100})
true
iex(5)> cidr |> CIDR.match!({1,2,4,1})
false

The match!/2 function also supports IP strings:

iex(6)> cidr |> CIDR.match!("1.2.3.100")
true
iex(7)> cidr |> CIDR.match!("1.2.4.1")
false

Please note that match!/2 throws an ArgumentError when you pass in a value that does not represent a valid IP address or when you try to match an IPv4 address with an IPv6 range and vice-versa. We also provide match/2, a non-throwing version that returns tagged tuples:

iex(8)> cidr |> CIDR.match("1.2.3.100")
{:ok, true}
iex(9)> cidr |> CIDR.match("1.2.4.1")
{:ok, false}
iex(10)> cidr |> CIDR.match("1.2.3.1000")
{:error, "Tuple is not a valid IP address."}

IPv4 deaggregation works as well. It returns a list of the largest possible networks for an IPv4 range in the format of $first_ip-$last_ip:

iex(1)> CIDR.parse_range("192.168.1.0-192.168.2.0")
[
  %CIDR{first: {192, 168, 1, 0}, hosts: 256, last: {192, 168, 1, 255}, mask: 24},
  %CIDR{first: {192, 168, 2, 0}, hosts: 1, last: {192, 168, 2, 0}, mask: 32}
]

See Collective Code Construction Contract (C4)

Mozilla Public License 2.0