interface: Introduce a method to initialize the time stamping label.

In many cases, the time stamping label will be the same as the name of
the interface.  In order to prevent users from open coding the logic that
initializes the label from the interface name, this patch add an
appropriate method.

Signed-off-by: Richard Cochran <richardcochran@gmail.com>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>

interface.c

@@ -6,6 +6,13 @@
  */
 #include "interface.h"
 
+void interface_ensure_tslabel(struct interface *iface)
+{
+	if (!iface->ts_label[0]) {
+		strncpy(iface->ts_label, iface->name, MAX_IFNAME_SIZE);
+	}
+}
+
 int interface_get_tsinfo(struct interface *iface)
 {
 	return sk_get_ts_info(iface->ts_label, &iface->ts_info);

interface.h

@@ -24,6 +24,12 @@ struct interface {
 	struct sk_ts_info ts_info;
 };
 
+/**
+ * Ensures that an interface has a proper time stamping label.
+ * @param iface  The interface of interest.
+ */
+void interface_ensure_tslabel(struct interface *iface);
+
 /**
  * Populate the time stamping information of a given interface.
  * @param iface  The interface of interest.