nginx-dns-routing.conf

user  nginx;
worker_processes  auto;

load_module modules/ngx_stream_js_module.so;

error_log  /var/log/nginx/error.log notice;
pid        /var/run/nginx.pid;

events {
    worker_connections  1024;
}

stream {

  # logging
  log_format  dns   '$remote_addr [$time_local] $protocol "$dns_qname" "$upstream_pool"';
  access_log /var/log/nginx/dns-access.log dns;

  # import NJS module
  js_import /etc/nginx/njs.d/dns/dns.js;

  # NJS function to get the dns_qname, requires a js_preread in the server to populate the variable from the DNS packet
  js_set $dns_qname dns.get_qname;

  # This maps the qname domain to the DNS server for routing
  map $dns_qname $upstream_pool {
    hostnames;
    *.nginx dnsmasq;
    *.k8s dnsmasq;
    default google;
  }

  # Google upstream
  upstream google {
    zone dns 64k;
    server 8.8.8.8:53;
  }

  # dnsmasq local upstream
  upstream dnsmasq {
    zone dns 64k;
    server 192.168.64.1:53;
  }

  # DNS(TCP) Serverr
  server {
    listen 53;
    js_preread dns.preread_dns_request;
    proxy_pass $upstream_pool;
  }

  # DNS(UDP) Server
  server {
    listen 53 udp;
    js_preread dns.preread_dns_request;
    proxy_responses 1;
    proxy_pass $upstream_pool;
  }

}