+ *
+ * Returns 1 if the requested service port is unambiguous and pingable;
+ * @pmap is filled in with the version, port, and transport protocol used
+ * during the successful ping. Note that if a port is already specified
+ * in @pmap and it matches the rpcbind query result, nfs_probe_port() does
+ * not perform an RPC ping.
+ *
+ * If an error occurs or the requested service isn't available, zero is
+ * returned; rpccreateerr.cf_stat is set to reflect the nature of the error.