Fix closest encloser

middleware/file/closest.go

@@ -4,13 +4,19 @@ import "github.com/miekg/dns"
 
 // ClosestEncloser returns the closest encloser for rr.
 func (z *Zone) ClosestEncloser(rr dns.RR) string {
-	elem := z.Tree.Prev(rr)
-	if elem == nil {
-		// SOA?
-		return ""
+	// tree/tree.go does not store a parent *Node pointer, so we can't
+	// just follow up the tree. TODO(miek): fix.
+
+	offset, end := dns.NextLabel(rr.Header().Name, 0)
+	for !end {
+		elem := z.Tree.Get(rr)
+		if elem != nil {
+			return elem.Name()
+		}
+		rr.Header().Name = rr.Header().Name[offset:]
+
+		offset, end = dns.NextLabel(rr.Header().Name, offset)
 	}
-	for _, r := range elem.All() {
-		return r.Header().Name
-	}
-	return ""
+
+	return z.SOA.Header().Name
 }