uDNS

uDNS is a small DNS server that takes in a pre-defined set of domain names and the IPs that each domain name maps to. The mappings should be inputted with a JSON file in a format described below.

uDNS runs on localhost and serves whatever port is specified in the command line arguments. uDNS serves both UDP and TCP connections.

If uDNS does not find the requested domain in the explicitly mapped section of the JSON, uDNS will respond with the IPs given in the otherwise section of the JSON. The otherwise section is mandatory.

JSON format

{
  "mappings": [
    {"domain1": ["ip1", "ip2", "etc"]},
    {"domain2": ["ip3", "ip4", "etc"]},
    {"domain3": ["ip5"]},
  ],

  "otherwise": ["defaultip1", "defaultip2", "etc"]
}

An example can be found in sample_zonefile.json

Caveat

You should not include any two records like this: host1.example.com and example.com

A DNS request for host1.example.com could return the A-record associated with host1.example.com or example.com, depending on your luck.

Running

python3 uDNS.py ip_addr port zone_file [--rr]

For a detailed description of flags, see python3 uDNS.py -h

Use with Apache Traffic Server

In records.config, add configuration lines: CONFIG proxy.config.dns.nameservers STRING ip_address:PORT and CONFIG proxy.config.dns.round_robin_nameservers INT 0, where PORT is whatever port you want uDNS to serve on.
Run uDNS on Ip_addr:PORT
Now all domains mapped in the uDNS JSON config file should be mapped by ATS as well