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

The ts_label field of the interface is set in different ways by different
callers.  In order to prevent users from open coding the logic that sets
the label, this patch adds an appropriate method.

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

interface.c

@@ -28,6 +28,11 @@ const char *interface_name(struct interface *iface)
 	return iface->name;
 }
 
+void interface_set_label(struct interface *iface, const char *label)
+{
+	strncpy(iface->ts_label, label, MAX_IFNAME_SIZE);
+}
+
 void interface_set_name(struct interface *iface, const char *name)
 {
 	strncpy(iface->name, name, MAX_IFNAME_SIZE);

interface.h

@@ -53,6 +53,13 @@ const char *interface_label(struct interface *iface);
  */
 const char *interface_name(struct interface *iface);
 
+/**
+ * Set the time stamping label of a given interface.
+ * @param iface  The interface of interest.
+ * @param name   The desired label for the interface.
+ */
+void interface_set_label(struct interface *iface, const char *label);
+
 /**
  * Set the name of a given interface.
  * @param iface  The interface of interest.