#!/usr/bin/env lua

local ubus = require "ubus"
local fs = require "nixio.fs"

local conn = ubus.connect()
if not conn then
	error("Failed to connect to ubus")
	return
end

local args = "-n"
local duration = ""

if arg[1] ~= nil then
	args = arg[1]
	if arg[2] ~= "" then
		duration = arg[2]
	end
end

local filter = fs.stat("/tmp/tcpdump_filter")
if filter then
	args = args .. " -F /tmp/tcpdump_filter"
end

local ubus_objects = {
	tcpdump = {
	}
}

conn:add( ubus_objects )

os.execute("sleep 1")

local command = "tcpdump -l " .. args .. " 2>&1"

if duration ~= "" then
	command = "timeout " .. duration .. " " .. command
end

local pipe = io.popen(command)

for line in pipe:lines() do
		local params = {
				data = line
		}
		conn:notify(ubus_objects.tcpdump.__ubusobj, "tcpdump.data", params)
end

local pcap = fs.stat("/tmp/capture.pcap0")
if pcap then
	fs.move("/tmp/capture.pcap0","/tmp/capture.pcap")
	fs.remove("/tmp/capture.pcap1")
end

if filter then
	fs.remove("/tmp/tcpdump_filter")
end

conn:close()
pipe:close()

fs.remove("/var/run/packet_capture.pid")