[dns-wg] Syntax of the "nserver:" Attribute in Domain Objects

On 21/08/2012 10:28, Wilfried Woeber, UniVie/ACOnet wrote:

Hi Peter, Wilfried,

> Well, I guess it takes Anand to describe the motivations for the changes,
> but from a SW point of view, it might be a tad more "beautiful" to move
> away from lists in the tag:value pairs. this *might* make parsing cleaner.

Simple attribute:value pairs are indeed easier to parse in code. At the
moment, the syntax allows for lists in nserver: attributes, so a user
could, in theory, submit something like this:

nserver: ns1.example.com   # first name server
  192.0.2.1   # IPv4 address of name server
  2001:db8::1 # IPv6 address of name server
  ns2.example.com 192.0.2.2 2001:db8::2  # name server and glue together

This is quite complex to parse, because the code has to deal with the
comments and continuation lines, and then try to make sense of what is a
name server and what is glue in that single line.

There are currently 599900 domain objects in the RIPE Database, of which
only 18 use the list syntax in nserver attributes. We have to maintain
extra code just to deal with these, so we would really like it if the
syntax were restricted to simple attribute:value pairs.

> OTOH, unless implicitely required by business rules or otherwise, I presume
> it would be allowed to submit
> 
> nserver: ns1.2.0.192.in-addr.arpa 192.0.2.1
> nserver: ns2.2.0.192.in-addr.arpa 2001:db8::2
> nserver: ns1.2.0.192.in-addr.arpa 2001:db8::1
> nserver: ns2.2.0.192.in-addr.arpa 2001:db8::2
> 
> or any other permutations? Leading to complex value gathering code again...

Yes, this would of course be allowed. The code to handle these would
simply transform each line into the following DNS records:

ns1.2.0.192.in-addr.arpa 172800 IN A 192.0.2.1
ns2.2.0.192.in-addr.arpa 172800 IN AAAA 2001:db8::2
ns1.2.0.192.in-addr.arpa 172800 IN AAAA 2001:db8::1
ns2.2.0.192.in-addr.arpa 172800 IN AAAA 2001:db8::2

In a DNS zone, the order of the records does not matter, and the DNS
server into which this zone is loaded will handle it (duplicates would
be discarded too). The code to turn such nserver attributes into DNS
records is not at all complex.

>> It would appear more natural to me to list all IP addresses on a single line
>> after the name server's name.

This does look more natural. However, we'd have to write code to expect
the following:

nserver: ns1.example.com <addr1> <addr2> ... <addrN>

This is easier to parse than the current list syntax, but code would
still have to transform this into appropriate records for delegation
testing and eventual delegation.

We still prefer the simple syntax of:

nserver: name <optional address>

However, we're quite eager to hear from our users to see what they think.

Regards,

Anand Buddhdev
RIPE NCC