Specs

dns_ptr(prefix()) :: String.t()

Returns a reverse DNS name (pointer) for given pfx.

The prefix will be padded right with 0-bits to a multiple of 8 for IPv4 prefixes and to a multiple of 4 for IPv6 prefixes. Note that this might give unexpected results. So dns_ptr/1 works best if the prefix given is actually a multiple of 4 or 8.

Examples

iex> dns_ptr("10.10.0.0/16")
"10.10.in-addr.arpa"

# "1.2.3.0/23" actually encodes as %Pfx{bits: <<1, 2, 1::size(7)>>, maxlen: 32}
# and padding right with 0-bits to a /24 yields the 1.2.2.0/24 ...
iex> dns_ptr("1.2.3.0/23")
"2.2.1.in-addr.arpa"

iex> dns_ptr("acdc:1976::/32")
"6.7.9.1.c.d.c.a.ip6.arpa"

iex> dns_ptr("acdc:1975::b1ba:2021")
"1.2.0.2.a.b.1.b.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.5.7.9.1.c.d.c.a.ip6.arpa"