GeoDNS Config Tool

The dnsconfig tool helps create configuration/zone files for the GeoDNS server.

It'll take a less verbose JSON configuration and expand it to GeoDNS format. The format also helps reusing certain bits of configuration so changes can be done in fewer places (active IPs, for example).

Command line options

-config: name of the zones config file. Defaults to ./config/zones.json.
-output: name of output directory. Defaults to ./dns/.

Configuration files

zones: Master list of zones to generate.
nodes: List of servers.
geomap: Mapping servers to 'geo targets'.
labels: Labels (hostnames) to insert into the zone.

Zones

The zones.json file manages the list of zones to be generated. It references the other three configuration files which then can be re-used for each zone or be unique as appropriate.

By default config/zones.json. You can specify another with the -config parameter.

{
    "some.example.com": {
            "contact": "noc@example.com",
            "ttl":     120,
            "max_hosts": 2,
            "ns":      ["ns1.example.com", "ns2.example.com"],
            "labels":  "labels.json",
            "nodes":   "nodes.json",
            "geomap":  "geomap.json"
    }
}

The options are:

contact: Used for the SOA contact field.
ttl: Time-to-live configuration for the DNS replies (in seconds).
max_hosts: Maximum number of IPs to return in each reply.
ns: List of nameservers for the zone.
targeting: Targeting options for GeoDNS (for example "region regiongroup country continent @", the default is "country continent @").
labels, nodes and geomap: Filename for data configuration (see below). The filenames are relative to the location of the zone configuration.

Multiple zones can be specified in the file.

Nodes

List of named "nodes" (servers). The name is only used as an identifier to match data in the other configuration files, not in replies. Setting active to zero will remove this node from the output data.

The IP address is a default to be used when the server is used in a DNS reply, it can be overridden in the labels file.

{
 "edge01.any": { "ip": "10.0.0.1", "active": 1 },
 "edge04.any": { "ip": "10.0.0.4", "active": 1 },

 "edge01.lax": { "ip": "10.0.1.1", "active": 1 },
 "edge01.sea": { "ip": "10.0.2.1", "active": 0 }
}

Geomap

A geomap maps the nodes to "targets" (countries and continents). Each node has a list of targets it will "match".

The special "@" target is the default target if there are no more specific matches.

An equal sign followed by a number specifies a "weight", higher weights will be returned in answers more often. The default weight is 100.

The "key" in the data structure can have wildcards ("") matching any non-dot character. To match "foo.bar" you can use ".bar", "foo." or ".*".

If a key starts with "^" and/or ends with "$" the string will just be used straight as a regular expression.

{
    "*.any": [ "@" ],
    "*.sin": [ "sg", "th", "id", "my" ],
    "*.ams": [ "europe", "nl", "fr" ],
    "*.lhr": [ "europe=1000", "uk" ],
    "*.sea": [ "us" ],
    "^hat-server.*": [ "au"],
    "flex04.ams04": [ "europe=1" ]
}

Labels

Labels are 'host names' in the zone. The value for each key is a hash with node names (must match an entry in the nodes config) and an optional IP override.

The override can also be another hash with the elements 'active' (defaults to true) and 'ip' (optional). 'active' can be specified as true, 1, false or 0.

Only A records are currently supported.

{
    "some.example":  {
        "edge01.any": "",
        "flex01.sin": ""
    },
    "alias.example": {
        "group": "some.example"
    },
    "another.test": {
        "edge01.any": "10.1.1.10",
        "flex01.sin": "10.20.1.10",
        "edge01.lhr": ""
    },
    "zone4": {
        "edge01.sea": { "active": true, ip: "10.1.2.3" },
        "edge01.any": { "active": 0 }
    }
}

gpstrive/geodns-config