Lookup ASN and AS Name

[jamesharr]

One thing that is pretty common in the network engineering field is to look up an IP's AS Number and/or looking up an ASN's name based on its number. I think it'd be a very useful addition to dns toys.

There's a lot of ways to implement this:

• acting as a proxy for the CYMRU DNS service (with or without using an external dependency)
• using HTTP API services
• Implementing the lookup internally and pre-caching/refreshing the data periodically. I'm figuring that's probably a point best left for discussion.

Draft usage example:

# Lookup an ASN 
% dy 8.8.8.8.origin
% dy 2001:4860:4860::8844.origin
"15169"  # simplified form
"AS15169"  # alternative
"15169 | 8.8.8.0/24 | US | arin | 2023-12-28"  # Same output that CYMRU uses; has the most information in it
"AS15169 GOOGLE, US"  # Another acceptable output, cidr-report.org format


% dy 15619.asn
% dy as15619.asn
"GOOGLE, US"  # Simplest form
"AS15169 GOOGLE, US"  # cidr-report.org format
"15169 | US | arin | 2000-03-30 | GOOGLE, US"  # Same output that CYMRU uses; has the most information in it

References:

• Go library utilizing CYMRU's DNS based lookup service - https://pkg.go.dev/github.com/jamesog/iptoasn
  • Underlying service https://www.team-cymru.com/ip-asn-mapping#comp-l529r139
  • https://github.com/jamesog/iptoasn/blob/master/iptoasn.go#L92-L93 - IP-to-ASN lookup
  • https://github.com/jamesog/iptoasn/blob/master/iptoasn.go#L158 - AS-name lookup
• based on prior research, this is what most people use for ASN -> AS-Name mapping
  • http://www.cidr-report.org/as2.0/autnums.html
  • https://bgp.potaroo.net/cidr/autnums.html - alias for the above
  • https://github.com/hadiasghari/pyasn/blob/master/pyasn-utils/pyasn_util_asnames.py#L42C16-L42C62 - usage in pyasn