Reworks plugin loading and structure

Implements #4358

scripts/plugins/alerts/network/udp_unidirectional/manifest.lua

@@ -0,0 +1,10 @@
+--
+-- (C) 2019-20 - ntop.org
+--
+
+return {
+  title = "UDP Unidirectional",
+  description = "Detects UDP unidirectional flows",
+  author = "ntop",
+  dependencies = {},
+}

scripts/plugins/alerts/network/udp_unidirectional/user_scripts/flow/udp_unidirectional.lua

@@ -0,0 +1,62 @@
+--
+-- (C) 2019-20 - ntop.org
+--
+
+-- Companion scripts (in addition to i18n)
+-- scripts/callbacks/status_defs/status_udp_unidirectional.lua
+-- scripts/callbacks/interface/flow/udp.lua
+
+local flow_consts = require("flow_consts")
+local user_scripts = require("user_scripts")
+
+-- #################################################################
+
+local script = {
+   -- Script category
+   category = user_scripts.script_categories.network,
+
+   l4_proto = "udp",
+
+   -- NOTE: hooks defined below
+   hooks = {},
+
+   gui = {
+      i18n_title = "flow_callbacks_config.udp_unidirectional",
+      i18n_description = "flow_callbacks_config.udp_unidirectional_description",
+   }
+}
+
+-- #################################################################
+
+local function unidirectionalProtoWhitelist(proto_id)
+   if(
+      (proto_id == 8)         -- MDNS
+	 or (proto_id == 17)  -- Syslog
+	 or (proto_id == 18)  -- DHCP
+      	 or (proto_id == 87)  -- RTP
+	 or (proto_id == 103) -- DHCPV6
+	 or (proto_id == 128) -- NetFlow
+      	 or (proto_id == 129) -- sFlow
+   ) then
+      return(true)
+   end
+   
+   return(false) -- Not whitelisted
+end
+
+-- #################################################################
+
+function script.hooks.all(now)
+   if((flow.getPacketsRcvd() == 0) and (flow.getPacketsSent() > 0)) then
+      -- Now check if the recipient isn't a broadcast/multicast address
+      if(flow.isServerUnicast() and not(unidirectionalProtoWhitelist(flow.getnDPIAppProtoId()))) then
+         flow.setStatus(flow_consts.status_types.status_udp_unidirectional, 5--[[ flow score]], 5--[[ cli score ]], 1--[[ srv score ]])
+      end
+   else
+      flow.clearStatus(flow_consts.status_types.status_udp_unidirectional)
+   end
+end
+
+-- #################################################################
+
+return script