gprs: Add a lua script to collect buffers on the downlink.

This can be used to throw the data into GNUplot. It collects
the time (from the start of the trace), the buffer data in kbyte
and the number of buffered PDUs. It is assuming that no PDU
is delivered toward the target.

openbsc/contrib/gprs/gprs-buffer-count.lua

@@ -0,0 +1,80 @@
+-- I count the buffer space needed for LLC PDUs in the worse case and print it
+
+do
+	local function init_listener()
+		-- handle the port as NS over IP
+		local udp_port_table = DissectorTable.get("udp.port")
+		local gprs_ns_dis = Dissector.get("gprs_ns")
+		udp_port_table:add(23000,gprs_ns_dis)
+
+		-- bssgp filters
+		local bssgp_pdu_get = Field.new("bssgp.pdu_type")
+		local bssgp_delay_get = Field.new("bssgp.delay_val")
+		local llcgprs_get = Field.new("llcgprs")
+		local pdus = nil
+
+		print("START...")
+
+		local tap = Listener.new("ip", "udp.port == 23000 && bssgp.pdu_type == 0")
+		function tap.packet(pinfo,tvb,ip)
+			local pdu = bssgp_pdu_get()
+			local len = llcgprs_get().len
+			local delay = bssgp_delay_get()
+
+			-- only handle bssgp, but we also want the IP frame
+			if not pdu then
+				return
+			end
+
+			if tonumber(tostring(delay)) == 65535 then
+				pdus = { next = pdus,
+					 len = len,
+					 expires = -1 }
+			else
+				local off = tonumber(tostring(delay)) / 100.0
+				pdus = { next = pdus,
+					 len = len,
+					 expires = pinfo.rel_ts + off }
+			end
+			local now_time = tonumber(tostring(pinfo.rel_ts))
+			local now_size = 0
+			local l = pdus
+			local prev = nil
+			local count = 0
+			while l do
+				if now_time < l.expires or l.expires == -1 then
+					now_size = now_size + l.len
+					prev = l
+					l = l.next
+					count = count + 1
+				else
+					-- delete things
+					if prev == nil then
+						pdus = nil
+						l = nil
+					else
+						prev.next = l.next
+						l = l.next
+					end
+				end
+			end
+--			print("TOTAL: " .. now_time .. " PDU_SIZE: " .. now_size)
+			print(now_time .. " " .. now_size / 1024.0 .. " " .. count)
+--			print("NOW: " .. tostring(pinfo.rel_ts) .. " Delay: " .. tostring(delay) .. " Length: " .. tostring(len))
+		end
+
+		function tap.draw()
+			-- well... this will not be called...
+--			for ip,bssgp_histo in pairs(dumpers) do
+--				print("IP " .. ip)
+--			end
+			print("END")
+		end
+
+		function tap.reset()
+			-- well... this will not be called...
+		end
+	end
+
+	init_listener()
+end