Implement getter for application constants

Implements #3944

scripts/lua/rest/v1/get/l7/application/consts.lua

@@ -0,0 +1,31 @@
+--
+-- (C) 2013-20 - ntop.org
+--
+
+local dirs = ntop.getDirs()
+package.path = dirs.installdir .. "/scripts/lua/modules/?.lua;" .. package.path
+
+require "lua_utils"
+local json = require "dkjson"
+local rest_utils = require "rest_utils"
+
+--
+-- Read all the defined L7 application protocols
+-- Example: curl -u admin:admin http://localhost:3000/lua/rest/v1/get/l7/application/consts.lua
+--
+-- NOTE: in case of invalid login, no error is returned but redirected to login
+--
+
+sendHTTPHeader('application/json')
+
+local rc = rest_utils.consts_ok
+local res = {}
+
+local applications = interface.getnDPIProtocols()
+
+for application, application_id in pairs(applications) do
+   res[application] = {application_id = tonumber(application_id)}
+end
+
+print(rest_utils.rc(rc, res))
+