routerrpc+record: move custom set validation

record/custom_records.go

@@ -1,5 +1,7 @@
 package record
 
+import "fmt"
+
 const (
 	// CustomTypeStart is the start of the custom tlv type range as defined
 	// in BOLT 01.
@@ -8,3 +10,15 @@ const (
 
 // CustomSet stores a set of custom key/value pairs.
 type CustomSet map[uint64][]byte
+
+// Validate checks that all custom records are in the custom type range.
+func (c CustomSet) Validate() error {
+	for key := range c {
+		if key < CustomTypeStart {
+			return fmt.Errorf("no custom records with types "+
+				"below %v allowed", CustomTypeStart)
+		}
+	}
+
+	return nil
+}