Disallow same nameserver with multiple glues

domains/forms.py

@@ -121,6 +121,16 @@ class NameserverForm(MntFormMixin, WhoisObjectFormMixin, forms.ModelForm):
 				if not found:
 					raise forms.ValidationError("You have glue IPs set, but this domain is not under a domain you control.")
 
+			if ipv4 or ipv6:
+				try:
+					ns = Nameserver.objects.get(Q(name=name) & (Q(glueIPv4__isnull=False) | Q(glueIPv6__isnull=False)))
+					if self._create or ns.pk != self.instance.pk:
+						nsMnts = ", ".join(n.handle for n in ns.mnt_by.all())
+
+						raise forms.ValidationError("Only one nameserver for this domain can have glue records and one already exists (maintained by %s)" % nsMnts)
+				except Nameserver.DoesNotExist:
+					pass
+
 			failedMnts = set()
 			for ns in Nameserver.objects.filter(name=name, mnt_by__in=mntBy):
 				if self._create or self.instance.pk != ns.pk: