interface: Introduce a method to test the time stamping information validity.

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

interface.c

@@ -42,3 +42,8 @@ void interface_set_name(struct interface *iface, const char *name)
 {
 	strncpy(iface->name, name, MAX_IFNAME_SIZE);
 }
+
+bool interface_tsinfo_valid(struct interface *iface)
+{
+	return iface->ts_info.valid ? true : false;
+}

interface.h

@@ -7,6 +7,7 @@
 #ifndef HAVE_INTERFACE_H
 #define HAVE_INTERFACE_H
 
+#include <stdbool.h>
 #include <sys/queue.h>
 #include "sk.h"
 
@@ -74,4 +75,11 @@ void interface_set_label(struct interface *iface, const char *label);
  */
 void interface_set_name(struct interface *iface, const char *name);
 
+/**
+ * Tests whether an interface's time stamping information is valid or not.
+ * @param iface  The interface of interest.
+ * @return       True if the time stamping information is valid, false otherwise.
+ */
+bool interface_tsinfo_valid(struct interface *iface);
+
 #endif