discordBots/cmd/domaincheckbot/dns/domain.go

package dns

import (
	"fmt"
	"github.com/miekg/dns"
	"net"
	"slices"
	"strings"
)

type Domain struct {
	Name string
	NS   []string
}

func CheckDomain(domain, tld string) Domain {
	nameservers := []string{}
	// Create a new DNS message
	m := new(dns.Msg)
	// Set the question section of the message with the domain and query type
	m.SetQuestion(dns.Fqdn(fmt.Sprintf("%v.%v", domain, tld)), dns.TypeNS)

	// Create a DNS client
	c := new(dns.Client)
	// Define the .com TLD server
	ns, err := net.LookupNS(tld)
	if err != nil {
		return Domain{
			Name: domain + "." + tld,
			NS:   nameservers,
		}
	}
	var tldServer string
	if len(ns) > 0 {
		tldServer = strings.Trim(ns[0].Host, ".") + ":53"
	} else {
		//log.Fatalf("Could not resolve %v", tld)
		return Domain{
			Name: domain + "." + tld,
			NS:   nameservers,
		}
	}

	// Send the DNS query to the TLD server
	r, _, err := c.Exchange(m, tldServer)
	if err != nil {
		//log.Fatalf("Failed to query the TLD server: %v", err)
		return Domain{
			Name: domain + "." + tld,
			NS:   nameservers,
		}
	}

	// Check for response errors
	if r.Rcode != dns.RcodeSuccess {
		//log.Fatalf("Failed to get a valid response: %v", r.Rcode)
		return Domain{
			Name: domain + "." + tld,
			NS:   nameservers,
		}
	}

	// Print the nameservers from the response
	for _, ans := range r.Ns {
		if ns, ok := ans.(*dns.NS); ok {
			nameservers = append(nameservers, strings.ToLower(ns.Ns))
		}
	}

	slices.Sort(nameservers)
	return Domain{
		Name: domain + "." + tld,
		NS:   nameservers,
	}
}