Create basic Snabb Switch app

snabb-create-app.lua

#!/usr/bin/env luajit

local main_template = [=[
local config = require("core.config")
local app = require("core.app")
local link = require("core.link")

local pcap = require("apps.pcap.pcap")
local <?= app_name ?> = require("<?= basename ?>.<?= app_name ?>")

function run (parameters)
   if not (#parameters == 2) then
      error("Usage: <?= basename ?>.<?= app_name ?> <input.pcap> <output.pcap>")
   end
   local input = parameters[1]
   local output = parameters[2]

   local c = config.new()
   config.app(c, "incoming", pcap.PcapReader, input)
   config.app(c, "<?= app_name ?>", <?= app_name ?>.<?= app_name ?>)
   config.app(c, "outgoing", pcap.PcapWriter, output)

   config.link(c, "incoming.output -> <?= app_name ?>.input")
   config.link(c, "<?= app_name ?>.output -> outgoing.input")

   app.configure(c)
   app.main({duration = 1, report = { showlinks = true}})
end

run(main.parameters)
]=]

local app_template = [=[
module(...,package.seeall)

<?= app_name ?> = {}

function <?= app_name ?>:new()
   local result = { packet_counter = 0 }
   return setmetatable(result, { __index = <?= app_name ?> })
end

function <?= app_name ?>:push(p)
   local i = assert(self.input.input, "input port not found")
   local o = assert(self.output.output, "output port not found")

   while not link.empty(i) and not link.full(o) do
      self:process_packet(i, o)
      self.packet_counter = self.packet_counter + 1
   end
end

function <?= app_name ?>:process_packet(i, o)
   local p = link.receive(i)

   if self.packet_counter % 2 == 0 then
      link.transmit(o, p)
   else
      packet.free(p)
   end
end
]=]

local function execute(command)
   local handle = io.popen(command)
   local result = handle:read("*a")
   handle:close()
end

local function write(content, filename)
   local f = io.open(filename, "w+")
   f:write(content)
   f:close()   
end

if #arg == 0 then
   error("snabb-create-app basename app_name")
end

local env = {
   basename = arg[1],
   app_name = arg[2]
}

local function replace(content, env)
   for k,v in pairs(env) do
      content = content:gsub("<%?=%s"..k.."%s%?>", v)
   end
   return content
end

local app_path = env.basename:gsub("%.", "%/")
execute(("mkdir -p %s"):format(app_path))
write(replace(main_template, env), app_path.."/main.lua")
write(replace(app_template, env), ("%s/%s.lua"):format(app_path, env.app_name))
print("Created app '"..app_path.."'")

-- Print how to use
local input = "apps/packet_filter/samples/v6.pcap"
local output = "/tmp/output.pcap"
print("Run 'sudo make && sudo ./snabb snsh "..app_path.."/main.lua "..input.." "..output.."'")