doc: add documentation for TlsGetCertSerial Lua function

diff --git a/doc/userguide/output/lua-output.rst b/doc/userguide/output/lua-output.rst
index 158c0505b06f8cd41dfaf053ef22229f7c768375..21e278a5e2d1548c5a0460d770b27eb626c3fc8a 100644 (file)
--- a/doc/userguide/output/lua-output.rst
+++ b/doc/userguide/output/lua-output.rst
@@ -457,6 +457,22 @@ Example:
   end
 
 
+TlsGetCertSerial
+~~~~~~~~~~~~~~~~
+
+Get TLS certificate serial number through TlsGetCertSerial.
+
+Example:
+
+::
+
+  function log (args)
+      serial = TlsGetCertSerial()
+      if serial then
+          -- do something
+      end
+  end
+
 SSH
 ---