interface: Introduce a method to get the time stamping information.

In order to prevent users from open coding this logic, this patch
provides a method that populates the time stamping information from
the interface label.

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

interface.c

@@ -6,6 +6,11 @@
  */
 #include "interface.h"
 
+int interface_get_tsinfo(struct interface *iface)
+{
+	return sk_get_ts_info(iface->ts_label, &iface->ts_info);
+}
+
 const char *interface_label(struct interface *iface)
 {
 	return iface->ts_label;

interface.h

@@ -24,6 +24,13 @@ struct interface {
 	struct sk_ts_info ts_info;
 };
 
+/**
+ * Populate the time stamping information of a given interface.
+ * @param iface  The interface of interest.
+ * @return       zero on success, negative on failure.
+ */
+int interface_get_tsinfo(struct interface *iface);
+
 /**
  * Obtain the time stamping label of a network interface.  This can be
  * different from the name of the interface when bonding is in effect.