recursor

README

recursor - CoreDNS Plugin

The recursor resolves domains using defined IP addresses or resolving other mapped domains using defined resolvers.

Use Case

Config Syntax / Examples

Corefile

recursor {   
    [external-yaml config-file-path]
    [external-json config-file-path]

    [verbose 0..2]
    zone: demo.svc
    resolver dns-c {
        urls udp://1.1.1.1:53 udp://1.0.0.1:53
        timeout_ms 500
    }
    resolver dns-g {
        urls udp://8.8.8.8:53 udp://8.8.4.4:53
    }  
    alias alias1 {
        hosts www.example.org www.example.com
        resolver_name dns-c
        ttl 11
    }
    alias alias2 {
        ips 10.0.0.1 10.0.0.2
        ttl 12
    }
    alias alias3 {
        ips 10.0.0.1 10.0.0.2
        hosts www.example.net
        resolver_name dns-g
        ttl 13
    }
    alias alias4 {
        hosts www.example.net
        ttl 14
    }  
}

External YAML

zone: demo.svc
resolvers:
  dns-c:
    urls: [ udp://1.1.1.1:53, udp://1.0.0.1:53 ]
    timeout_ms: 500
  dns-g:
    urls: [ udp://8.8.8.8:53, udp://8.8.4.4:53 ]
aliases:
  alias1:
    hosts: [ www.example.org, www.example.com ]
    resolver_name: dns-c
    ttl: 11
  alias2:
    ips: [ 10.0.0.1, 10.0.0.2 ]
    ttl: 12
  alias3:
    ips: [ 10.0.0.1, 10.0.0.2 ]
    hosts: [ www.example.net ]
    resolver_name: dns-g
    ttl: 13
  alias4:
    hosts: [ www.example.net ]
    ttl: 14

External JSON

{
  "zone": "demo.svc",
  "resolvers": {
    "dns-c": {
      "urls": [ "udp://1.1.1.1:53", "udp://1.0.0.1:53" ],
      "timeout_ms": 500
    },
    "dns-g": {
      "urls": [ "udp://8.8.8.8:53", "udp://8.8.4.4:53" ]
    }
  },
  "aliases": {
    "alias1": {
      "hosts": [ "www.example.org", "www.example.com" ],
      "resolver_name": "dns-c",
      "ttl": 11
    },
    "alias2": {
      "ips": [ "10.0.0.1", "10.0.0.2" ],
      "ttl": 12
    },
    "alias3": {
      "ips": [ "10.0.0.1", "10.0.0.2" ],
      "hosts": [ "www.example.net" ],
      "resolver_name": "dns-g",
      "ttl": 13
    },
    "alias4": {
      "hosts": [ "www.example.net" ],
      "ttl": 14
    }
  }
}

More examples

Metrics

• Definition
• Grafana Dashboard

Run It

Build It

#!/usr/bin/env bash

set -eux
# Extract coredns source code
tar xzvf coredns.src.tar.gz
pushd coredns
  # Add external plugins
  go get github.com/kinjelom/coredns-recursor@latest
  echo -e "recursor:github.com/kinjelom/coredns-recursor" >> plugin.cfg
  # Build
  go generate
  go build
  ./coredns -plugins
popd

Deployments Ready to Use

• BOSH Release
• Kubernetes

Try it

Helpful commands:

dig alias1.demo.svc @127.0.0.1 -p 1053
nslookup -port=1053 -debug -type=A alias2.demo.svc 127.0.0.1