Moved unexpected gateway check from flows to hosts

scripts/lua/modules/check_definitions/host/unexpected_gateway.lua

@@ -0,0 +1,47 @@
+--
+-- (C) 2019-24 - ntop.org
+--
+
+local checks = require("checks")
+local alerts_api = require "alerts_api"
+local alert_consts = require("alert_consts")
+local host_alert_keys = require "host_alert_keys"
+
+local UNEXPECTED_SCRIPTS_ENABLED_CACHE_KEY = "ntopng.cache.checks.unexpected_scripts_enabled"
+
+-- #################################################################
+
+local script = {
+   -- Script category
+   category = checks.check_categories.security,
+
+   -- This module is disabled by default
+   default_enabled = false,
+
+   -- This script is only for alerts generation
+   alert_id = host_alert_keys.host_alert_unexpected_gateway,
+
+   -- Specify the default value whe clicking on the "Reset Default" button
+   default_value = {
+      items = {},
+   },
+
+   gui = {
+      i18n_title        = "flow_checks.unexpected_gateway_title",
+      i18n_description  = "flow_checks.unexpected_gateway_description",
+   }
+}
+
+-- #################################################################
+
+function script.onEnable(hook, hook_config)
+   -- Set a flag to indicate to the notifications system that an unexpected script
+   -- has been enabled
+   if isEmptyString(ntop.getCache(UNEXPECTED_SCRIPTS_ENABLED_CACHE_KEY)) then
+      ntop.setCache(UNEXPECTED_SCRIPTS_ENABLED_CACHE_KEY, "1")
+   end
+end
+
+-- #################################################################
+
+return script