isisd: add a debug mode that traces LSP construction

Signed-off-by: Christian Franke <chris@opensourcerouting.org>
diff --git a/isisd/isisd.h b/isisd/isisd.h
index 6e95e8e..51a72ab 100644
--- a/isisd/isisd.h
+++ b/isisd/isisd.h
@@ -166,5 +166,14 @@
 #define DEBUG_EVENTS                     (1<<10)
 #define DEBUG_ZEBRA                      (1<<11)
 #define DEBUG_PACKET_DUMP                (1<<12)
+#define DEBUG_LSP_GEN                    (1<<13)
+
+#define lsp_debug(...) \
+  do \
+    { \
+      if (isis->debugs & DEBUG_LSP_GEN) \
+        zlog_debug(__VA_ARGS__); \
+    } \
+  while (0)
 
 #endif /* ISISD_H */