+#if VLIB_BUFFER_TRACE_TRAJECTORY > 0
+ /** trace trajectory data - we use a specific cacheline for that in the
+ * buffer when it is compiled-in */
+#define VLIB_BUFFER_TRACE_TRAJECTORY_MAX 31
+#define VLIB_BUFFER_TRACE_TRAJECTORY_SZ 64
+#define VLIB_BUFFER_TRACE_TRAJECTORY_INIT(b) (b)->trajectory_nb = 0
+ CLIB_ALIGN_MARK (trajectory, 64);
+ u16 trajectory_nb;
+ u16 trajectory_trace[VLIB_BUFFER_TRACE_TRAJECTORY_MAX];
+#else /* VLIB_BUFFER_TRACE_TRAJECTORY */
+#define VLIB_BUFFER_TRACE_TRAJECTORY_SZ 0
+#define VLIB_BUFFER_TRACE_TRAJECTORY_INIT(b)
+#endif /* VLIB_BUFFER_TRACE_TRAJECTORY */
+
+ /** start of buffer headroom */
+ CLIB_ALIGN_MARK (headroom, 64);