Allow secondary DNS xfr: items to be hostnames that are resolved to IP addresses when generating the nsd configuration

CHANGELOG.md

@@ -12,6 +12,7 @@ Control panel:
 
 * Control panel pages can be opened in a new tab/window and bookmarked and browser history navigation now works.
 * Add a Copy button to put the rsync backup public key on clipboard.
+* Allow secondary DNS xfr: items added in the control panel to be hostnames too.
 * Fixed issue where sshkeygen fails when IPv6 is disabled.
 * Fixed issue opening munin reports.
 * Fixed report formatting in status emails sent to the administrator.

management/dns_update.py

@@ -1005,32 +1005,33 @@ def get_secondary_dns(custom_dns, mode=None):
 				values.append(hostname)
 				continue
 
-			# This is a hostname. Before including in zone xfr lines,
-			# resolve to an IP address. Otherwise just return the hostname.
-			# It may not resolve to IPv6, so don't throw an exception if it
-			# doesn't.
-			if not hostname.startswith("xfr:"):
-				if mode == "xfr":
-					try:
-						response = resolver.resolve(hostname+'.', "A", raise_on_no_answer=False)
-						values.extend(map(str, response))
-					except dns.exception.DNSException:
-						pass
-						
-					try:
-						response = resolver.resolve(hostname+'.', "AAAA", raise_on_no_answer=False)
-						values.extend(map(str, response))
-					except dns.exception.DNSException:
-						pass
-					continue
-				values.append(hostname)
+			# If the entry starts with "xfr:" only include it in the zone transfer settings.
+			if hostname.startswith("xfr:"):
+				if mode != "xfr": continue
+				hostname = hostname[4:]
 
-			# This is a zone-xfer-only IP address. Do not return if
-			# we're querying for NS record hostnames. Only return if
-			# we're querying for zone xfer IP addresses - return the
-			# IP address.
-			elif mode == "xfr":
-				values.append(hostname[4:])
+			# If is a hostname, before including in zone xfr lines,
+			# resolve to an IP address.
+			# It may not resolve to IPv6, so don't throw an exception if it
+			# doesn't. Skip the entry if there is a DNS error.
+			if mode == "xfr":
+				try:
+					ipaddress.ip_interface(hostname) # test if it's an IP address or CIDR notation
+					values.append(hostname)
+				except ValueError:
+					try:
+						response = dns.resolver.resolve(hostname+'.', "A", raise_on_no_answer=False)
+						values.extend(map(str, response))
+					except dns.exception.DNSException:
+						pass
+					try:
+						response = dns.resolver.resolve(hostname+'.', "AAAA", raise_on_no_answer=False)
+						values.extend(map(str, response))
+					except dns.exception.DNSException:
+						pass
+
+			else:
+				values.append(hostname)
 
 	return values
 

management/templates/custom-dns.html

@@ -96,7 +96,7 @@
     <div class="col-sm-offset-1 col-sm-11">
       <p class="small">
         Multiple secondary servers can be separated with commas or spaces (i.e., <code>ns2.hostingcompany.com ns3.hostingcompany.com</code>).
-        To enable zone transfers to additional servers without listing them as secondary nameservers, add an IP address or subnet using <code>xfr:10.20.30.40</code> or <code>xfr:10.0.0.0/8</code>.
+        To enable zone transfers to additional servers without listing them as secondary nameservers, prefix a hostname, IP address, or subnet with <code>xfr:</code>, e.g. <code>xfr:10.20.30.40</code> or <code>xfr:10.0.0.0/8</code>.
       </p>
       <p id="secondarydns-clear-instructions" style="display: none" class="small">
         Clear the input field above and click Update to use this machine itself as secondary DNS, which is the default/normal setup.