1 files changed, 15 insertions, 0 deletions
diff --git a/middleware/pkg/dnsutil/cname.go b/middleware/pkg/dnsutil/cname.go
new file mode 100644
index 000000000..281e03218
--- /dev/null
+++ b/middleware/pkg/dnsutil/cname.go
@@ -0,0 +1,15 @@
+package dnsutil
+
+import "github.com/miekg/dns"
+
+// DuplicateCNAME returns true if r already exists in records.
+func DuplicateCNAME(r *dns.CNAME, records []dns.RR) bool {
+	for _, rec := range records {
+		if v, ok := rec.(*dns.CNAME); ok {
+			if v.Target == r.Target {
+				return true
+			}
+		}
+	}
+	return false
+}