register_codec(type_code, codec)

Register an RDATA codec for a given type code

get_codec(type_code) -> codec

Look up the RDATA codec for a given type code

format_ipv6(groups) -> address

Format 8 u16 groups into RFC5952 canonical IPv6 string

Formats an array of 8 16-bit groups into RFC5952 canonical form:

• Lowercase hex, no leading zeros
• Longest run of consecutive zero groups replaced with ::
• :: only used for runs of 2 or more zero groups
• Leftmost longest run wins on tie

parse_ipv6(address) -> groups, err

Parse an IPv6 address string into 8 u16 groups

Parses an IPv6 address with :: expansion. Returns an array of 8 u16 values, or nil and an error message.