pub fn canonical(ip: IpAddr) -> IpAddrExpand description
Normalizes an address into the form the kernel will actually route.
IPv4-mapped IPv6 (::ffff:a.b.c.d) becomes the IPv4 address it stands for.
The deprecated IPv4-compatible range (::a.b.c.d, RFC 4291 ยง2.5.5.1) is left
as IPv6 on purpose and handled by is_private, because mapping it to IPv4
would turn ::1 into 0.0.0.1 and quietly lose the loopback meaning.