Create a DNS Responder using CoreDNS

README.md

Create a DNS Responder using CoreDNS

Notes

• do not use bind 127.0.0.1 when running from a container, as it prevents the requests from being handled.

coredns.target

[Unit]
Description=CoreDNS DNS server
Documentation=https://coredns.io
After=network.target

[Service]
PermissionsStartOnly=true
PIDFile=/home/coredns/coredns.pid
LimitNOFILE=8192
User=coredns
WorkingDirectory=/home/coredns
ExecStartPre=/sbin/setcap cap_net_bind_service=+ep /opt/bin/coredns
ExecStart=/opt/bin/coredns -pidfile /home/coredns/coredns.pid -conf=/etc/coredns/Corefile
ExecReload=/bin/kill -SIGUSR1 $MAINPID
Restart=on-failure

[Install]
WantedBy=multi-user.target

Corefile

.:53 {
    log
    errors
    
    #bind 127.0.0.1

    proxy . /etc/resolv.conf

    template IN A {
      match "^(?P<a>[0-9]*)[.](?P<b>[0-9]*)[.](?P<c>[0-9]*)[.](?P<d>[0-9]*)[.](xip.io|nip.io|local|dev)[.]$"
      answer "{{ .Name }} 60 IN A {{ .Group.a}}.{{ .Group.b }}.{{ .Group.c }}.{{ .Group.d }}"
      fallthrough
    }
}

run.sh

docker pull coredns/coredns:latest
docker run --name coredns \
    -v $PWD/Corefile:/etc/coredns/Corefile \
    -v /etc/resolv.conf:/etc/resolv.conf \
    -p 127.0.0.1:53:53/tcp \
    -p 127.0.0.1:53:53/udp \
    -d coredns/coredns -conf /etc/coredns/Corefile