main.go

package main

import (
	"fmt"
	"github.com/miekg/dns"
)

func main() {
	// Create a DNS server instance
	server := &dns.Server{Addr: ":53", Net: "udp"}

	// Handle DNS queries
	dns.HandleFunc(".", func(w dns.ResponseWriter, r *dns.Msg) {
		m := new(dns.Msg)
		m.SetReply(r)

		for _, q := range r.Question {
			if q.Qtype == dns.TypeCNAME {
				cname := "example.com." // Replace with your CNAME target

				// Create a CNAME RR with a TTL of 3600 seconds (1 hour)
				cnameRR := &dns.CNAME{
					Hdr: dns.RR_Header{
						Name:   q.Name,
						Rrtype: dns.TypeCNAME,
						Class:  dns.ClassINET,
						Ttl:    3600,
					},
					Target: cname,
				}

				// Add the CNAME RR to the answer section
				m.Answer = append(m.Answer, cnameRR)

				// Check if Chrome can resolve the CNAME target
				// (You can add this part back if needed)
			} else {
				// Handle unspecified queries here
				defaultIP := "192.168.1.1" // Replace with your desired default IP address

				// Create an A or AAAA RR depending on the query type
				if q.Qtype == dns.TypeA {
					rr, err := dns.NewRR(fmt.Sprintf("%s IN A %s", q.Name, defaultIP))
					if err == nil {
						m.Answer = append(m.Answer, rr)
					}
				} else if q.Qtype == dns.TypeAAAA {
					rr, err := dns.NewRR(fmt.Sprintf("%s IN AAAA %s", q.Name, defaultIP))
					if err == nil {
						m.Answer = append(m.Answer, rr)
					}
				}
			}
		}

		if len(m.Answer) > 0 {
			w.WriteMsg(m)
		} else {
			dns.HandleFailed(w, r)
		}
	})

	// Start the DNS server
	go func() {
		if err := server.ListenAndServe(); err != nil {
			fmt.Printf("DNS server error: %v\n", err)
		}
	}()

	fmt.Println("DNS server listening on :53 (UDP)...")
	select {}
}