It is possible to have an IPv6 number that represents an IPv4 number.

Implement support for this feature where it should be possible to:

• Encode an IPv4 number in IPv6
• Convert an IPv4 mapped IPv6 to a plain IPv4 number
• Convert an IPv4 number to an IPv4-Mapped IPv6 number
  etc

References:
Re: Deprecate the "IPv4-compatible IPv6 address"
Special-Use IPv6 Addresses