CoreDNS Example

README.md

custom_coredns

Testing

To test you can run the below samples against your coredns, assuming the default configurations I've customised are used.

dig @127.0.0.1 -p 10053 ip-172-55-55-66.us-west-1.compute.internal
dig @127.0.0.1 -p 10053 CH version.bind TXT
dig @127.0.0.1 -p 10053 example.org

Future plans?

• This example currently uses file for the zones but can be flipped to redis and sql in the future if I decide I want to build my own coredns binary.

Corefile

(global_configurations) {
    log {
      class all
    }
    errors
    cache
    prometheus :9153
}

coredns.io:5300 {
    import global_configurations
    file /root/coredns/zones/db.coredns.io
}

example.io:53 {
    import global_configurations
    file /root/coredns/zones/db.example.io {
      reload 10s
    }
    # erratic {
    #     delay
    # }
}

amazonaws.com:53 {
  forward . 9.9.9.9
}

testing.com:53 {
  forward . /etc/resolv.conf
}

example.org {
  whoami
}

.:53 {
    import global_configurations
    reload
    ready
    whoami
    health
    # kubernetes
    forward . 8.8.8.8
    chaos CustomVersion NormalAuthors
    rewrite name foo.example.com amazon.com
    # This replicates the behaviour of Amazons VPC DNS, which returns the ip address of an instance from the hostname in the query. Note: in this case the <az>.compute.internal component of the query is essentially ignored.
    template IN A {
      match ^ip-(?P<a>[0-9]*)-(?P<b>[0-9]*)-(?P<c>[0-9]*)-(?P<d>[0-9]*).*.$
      answer "{{ .Name }} 60 IN A {{ .Group.a }}.{{ .Group.b }}.{{ .Group.c }}.{{ .Group.d }}"
      fallthrough
    }
}

db.coredns.io

; coredns.io zone
coredns.io	IN	SOA	sns.dns.icann.org. noc.dns.icann.org. 2015082541 7200 3600 1209600 3600

new.coredns.io	IN	CNAME	google.com

db.example.io

; example.io zone
example.io  IN  SOA sns.dns.icann.org. noc.dns.icann.org. 2015082543 7200 3600 1209600 3600

again.example.io.	IN	CNAME	amazon.com.
test.example.io.	IN	A	172.31.0.1
example.io.	IN	A	169.254.0.1
test2.example.io.	IN	A	128.9.9.1
test3.example.io.	IN	A	192.168.1.1

docker-compose.yml

version: '3.7'

services:
  coredns:
    image: coredns/coredns
    container_name: coredns
    restart: always
    command: -conf /root/coredns/Corefile
    volumes:
      - ./zonefiles/:/root/coredns/zones/:ro
      - ./Corefile:/root/coredns/Corefile:ro
    ports:
      - 5300:5300/udp
      - 9153:9153/udp
      - 8181:8181
      - 10053:53/udp
      - 8880:8080
    networks:
      - general

networks:
  general:
    driver: bridge