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Filename : sock-protolen.lua
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#!/usr/bin/env bcc-lua
--[[
Copyright 2016 Marek Vavrusa <mvavrusa@cloudflare.com>

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
]]
-- This program counts total bytes received per-protocol in 64-bit counters.
-- The map backend is array in this case to avoid key allocations.
-- increments counter for each packet of given type seen
-- Rewrite of https://github.com/torvalds/linux/blob/master/samples/bpf/sock_example.c
local ffi = require("ffi")
local bpf = require("bpf")
local S = require("syscall")

-- Shared part of the program
local map = bpf.map('array', 256, ffi.typeof('uint32_t'), ffi.typeof('uint64_t'))
-- Kernel-space part of the program
bpf.socket('lo', function (skb)
	local proto = pkt.ip.proto  -- Get byte (ip.proto) from frame at [23]
	xadd(map[proto], skb.len)   -- Atomic `map[proto] += <payload length>`
end)
-- User-space part of the program
for _ = 1, 10 do
	local icmp, udp, tcp = map[1], map[17], map[6]
	print(string.format('TCP %d UDP %d ICMP %d bytes',
		tonumber(tcp or 0), tonumber(udp or 0), tonumber(icmp or 0)))
	S.sleep(1)
end