jijiechen / coredns-httpfetch-plugin

coredns-httpfetch-plugin

This plugin gets an A record from an HTTP upstream server.

Usage

To activate the plugin you need to compile CoreDNS with the plugin added to plugin.cfg

https://github.com/jijiechen/coredns-httpfetch-plugin

Then add it to Corefile:

{
   httpfetch {
      # the base URL of the upstream HTTP endpoint 
      url https://httpfetch.example.org/

      # the HTTP method to use when sending query requests
      method POST

      # template for building URL query string when sending query requests
      query "dns_name={{ .DnsName }}"

      # template for building request body when sending query requests
      body "{{ (dict \"dns_name\" .DnsName) | toJson }}"

      # Headers to add when sending query requests
      header "Authorization: Bearer XXX"
      header "Content-Type: application/json"
      
      # Template to extract resolved IP address from the response
      # If omiited, the whole response body will be used as the IP address
      analyze_ip "{{ (.Body | fromJson).ip_address  }}"

      # Template to extract ttl (time to last in seconds) from the response
      # ttl defaults to 60 seconds 
      analyze_ttl "{{ (.Body | fromJson).ttl  }}"
   }
}

Only the url config parameter is mandatory.

The following fields support the Go Template syntax and functions provided by the Sprig library are available. See more from its website at http://masterminds.github.io/sprig/

• query
• body
• analyze_ip
• analyze_ttl

Available fields for query and body:

• DnsName the currently querying dns name

Available fields for analyze_ip and analyze_ttl:

• Body response body returned from upstream HTTP server
• Header response headers returned from upstream HTTP server

Trouble escaping your configuration? You may also refer to the Caddyfile documentation at https://caddyserver.com/docs/caddyfile This is because CoreDNS uses Caddy as its underlying engine.

Developing locally

You can test the plugin functionality with CoreDNS by adding the following to go.mod in the source code directory of coredns.

replace github.com/jijiechen/coredns-httpfetch-plugin => <path-to-you-local-copy>/coredns-httpfetch-plugin