rancher-dns

README

rancher-dns

A simple DNS server that returns different answers depending on the IP address of the client making the request.

Usage

  rancher-dns [--debug] [--listen host:port] [--ttl num] --answers /path/to/answers.json

Compile

  godep go build

CLI Options

Option	Default	Description
--debug	off	If present, more debug info is logged
--listen	0.0.0.0:53	IP address and port to listen on (TCP & UDP)
--answers	./answers.json	Path to a JSON file with client-specific answers
--ttl	600	TTL for local (non-recursive) responses that are returned

JSON Answers File

The answers file should be a JSON map with a key for each client IP address.

• Each key is a map of FQDN to an array of answers.
• Top-level keys should be IP addresses
  • A special key "default" will be checked if no IP address match is found
• 2nd-level keys should be fully qualified, ending in a dot.
  • A special key "recurse" can contain a list of servers to make a recursive query to if no answer is found locally.

{
  "default": {
    "recurse": ["8.8.8.8"],
    "rancher.com.": ["1.2.3.4"]
  },
  "10.1.2.2": {
    "mysql.": ["10.1.2.3"],
    "web.": ["10.1.2.4","10.1.2.5","10.1.2.6"]
  },
  "192.168.0.2": {
    "recurse": ["8.8.4.4:53","8.8.8.8"],
    "mysql.": ["192.168.0.3"],
    "web.": ["192.168.0.4","192.168.0.5","192.168.0.6"]
  }
}

Answering queries

A query is answered by returning the first match of:

• An entry in the answers map for the client's IP.
• An entry in the answers map in the "default" key.
• If there is a "recurse" key for the client's IP, perform recursive lookup on each of those servers (in order).
• If there is a "recurse" key for the "default", perform recursive lookup on each of those servers (in order).
• Do not pass go, do not collect $200. Return SERVFAIL.

Limitations

• Only A records are currently supported.

License

Copyright (c) 2015 Rancher Labs, Inc.

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.