Subject: [netmod] domain-name

From: Ladislav Lhotka <[email-masked]>
Date: Mon, 17 Aug 2015 15:12:31 +0200

Hi,

it seems the typedef "domain-name" in the "ietf-inet-types" (RFC 6991)
is too restrictive: characters in domain names are not limited to
[a-zA-Z0-9_]. RFC 2181 says:

   The DNS itself places only one restriction on the particular labels
   that can be used to identify resource records.  That one restriction
   relates to the length of the label and the full name.  The length of
   any one label is limited to between 1 and 63 octets.  A full domain
   name is limited to 255 octets (including the separators).  The zero
   length full name is defined as representing the root of the DNS tree,
   and is typically written and displayed as ".".  Those restrictions
   aside, any binary string whatever can be used as the label of any
   resource record.  Similarly, any binary string can serve as the value
   of any record that includes a domain name as some or all of its value
   (SOA, NS, MX, PTR, CNAME, and any others that may be added).
   Implementations of the DNS protocols must not place any restrictions
   on the labels that can be used.  In particular, DNS servers must not
   refuse to serve a zone because it contains labels that might not be
   acceptable to some DNS client programs.  A DNS server may be
   configurable to issue warnings when loading, or even to refuse to
   load, a primary zone containing labels that might be considered
   questionable, however this should not happen by default.

In particular, wildcard domain names (RFC 4592) are rejected by the
"domain-name" pattern.

Lada

-- 
Ladislav Lhotka, CZ.NIC Labs
PGP Key ID: E74E8C0C