*: introduce function for sequence numbers

Don't directly use `time()` for generating sequence numbers for two
reasons:
1. `time()` can go backwards (due to NTP or time adjustments)
2. Coverity Scan warns every time we truncate a `time_t` variable for
   good reason (verify that we are Y2K38 ready).

Found by Coverity Scan (CID 1519812, 1519786, 1519783 and 1519772)

Signed-off-by: Rafael Zalamena <rzalamena@opensourcerouting.org>

1 files changed, 18 insertions, 0 deletions

diff --git a/lib/network.h b/lib/network.h
index 10ed917572..c163eab8f7 100644
--- a/lib/network.h
+++ b/lib/network.h
@@ -82,6 +82,24 @@ extern float ntohf(float);
 #endif
 
 /**
+ * Generate a sequence number using monotonic clock with a same second call
+ * protection to help guarantee a unique incremental sequence number that never
+ * goes back (except when wrapping/overflow).
+ *
+ * **NOTE** this function is not thread safe since it uses `static` variable.
+ *
+ * This function and `frr_sequence32_next` should be used to initialize
+ * sequence numbers without directly calling other `time_t` returning
+ * functions because of `time_t` truncation warnings.
+ *
+ * \returns `uint64_t` number based on the monotonic clock.
+ */
+extern uint64_t frr_sequence_next(void);
+
+/** Same as `frr_sequence_next` but returns truncated number. */
+extern uint32_t frr_sequence32_next(void);
+
+/**
  * Helper function that returns a random long value. The main purpose of
  * this function is to hide a `random()` call that gets flagged by coverity
  * scan and put it into one place.