Initial commit

pkg/resolver/resolver.go

@@ -0,0 +1,74 @@
+package resolver
+
+import (
+	"errors"
+	"fmt"
+	"log"
+	"strings"
+
+	"git.linuxrocker.com/mattburchett/go_tab-magic/pkg/config"
+	"github.com/miekg/dns"
+)
+
+// LookupName returns IPv4 address from A record or error.
+func lookupName(fqdn, serverAddr string) (string, error) {
+	m := &dns.Msg{}
+	m.SetQuestion(dns.Fqdn(fqdn), dns.TypeA)
+	in, err := dns.Exchange(m, serverAddr)
+	if err != nil {
+		return "", err
+	}
+	if len(in.Answer) < 1 {
+		return "", errors.New("no Answer")
+	}
+	if a, ok := in.Answer[0].(*dns.A); ok {
+		ip := a.A.String()
+		return ip, nil
+	}
+	return "", errors.New("no A record returned")
+}
+
+func PerformZoneTransfer(config config.Config) {
+	data := make([]string, 0)
+
+	// Do the transfer
+	for _, i := range config.Domains {
+		server := fmt.Sprintf("%s:%d", config.Resolver, config.ResolverPort)
+		tr := dns.Transfer{}
+		m := &dns.Msg{}
+		m.SetAxfr(dns.Fqdn(i))
+		in, err := tr.In(m, server)
+		if err != nil {
+			log.Fatal(err)
+		}
+		for ex := range in {
+			for _, a := range ex.RR {
+				var ip, hostname, txt string
+				switch v := a.(type) {
+				case *dns.TXT:
+					txt = string(v.Txt[0])
+					hostname = v.Hdr.Name
+					cip, err := lookupName(strings.TrimRight(v.Hdr.Name, "."), server)
+					if err != nil || cip == "" {
+						continue
+					}
+					ip = cip
+				case *dns.A:
+					ip = v.A.String()
+					hostname = v.Hdr.Name
+				case *dns.CNAME:
+					cip, err := lookupName(v.Target, server)
+					if err != nil || cip == "" {
+						continue
+					}
+					ip = cip
+					hostname = v.Hdr.Name
+				default:
+					continue
+				}
+				data = append(data, fmt.Sprintf("%v %v %v", hostname, ip, txt))
+			}
+		}
+	}
+	fmt.Println(data)
+}