update nameserver

Author: wafuwafu13

check-dns/lib/nameserver.go

@@ -3,6 +3,8 @@
 package checkdns
 
 import (
+	"net"
+	"fmt"
 	"github.com/miekg/dns"
 )
 
@@ -11,5 +13,20 @@ func adapterAddress() (string, error) {
 	if err != nil {
 		return "", err
 	}
-	return conf.Servers[0], nil
+	nameserver := conf.Servers[0]
+	// ref: https://github.com/miekg/exdns/blob/d851fa434ad51cb84500b3e18b8aa7d3bead2c51/q/q.go#L148-L153
+	// if the nameserver is from /etc/resolv.conf the [ and ] are already
+	// added, thereby breaking net.ParseIP. Check for this and don't
+	// fully qualify such a name
+	if nameserver[0] == '[' && nameserver[len(nameserver)-1] == ']' {
+		nameserver = nameserver[1 : len(nameserver)-1]
+	}
+	// ref: https://github.com/miekg/exdns/blob/d851fa434ad51cb84500b3e18b8aa7d3bead2c51/q/q.go#L154-L158
+	if net.ParseIP(nameserver) == nil {
+		nameserver = dns.Fqdn(nameserver)
+	}
+	if net.ParseIP(nameserver) == nil {
+		return "", fmt.Errorf("invalid nameserver: %s", nameserver)
+	}
+	return nameserver, nil
 }

check-dns/lib/nameserver_windows.go

@@ -9,7 +9,7 @@ import (
 	"unsafe"
 )
 
-// https://go.dev/src/net/interface_windows.go
+// ref: https://go.dev/src/net/interface_windows.go
 func adapterAddress() (string, error) {
 	var b []byte
 	l := uint32(15000) // recommended initial size
@@ -33,5 +33,13 @@ func adapterAddress() (string, error) {
 	for aa := (*windows.IpAdapterAddresses)(unsafe.Pointer(&b[0])); aa != nil; aa = aa.Next {
 		aas = append(aas, aa)
 	}
-	return aas[0].FirstDnsServerAddress.Address.IP().String(), nil
+  nameserver := aas[0].FirstDnsServerAddress.Address.IP().String()
+	// ref: https://github.com/miekg/exdns/blob/d851fa434ad51cb84500b3e18b8aa7d3bead2c51/q/q.go#L154-L158
+	if net.ParseIP(nameserver) == nil {
+		nameserver = dns.Fqdn(nameserver)
+	}
+	if net.ParseIP(nameserver) == nil {
+		return "", fmt.Errorf("invalid nameserver: %s", nameserver)
+	}
+	return nameserver, nil
 }