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56 lines
1.7 KiB
56 lines
1.7 KiB
#!/usr/bin/env bcc-lua
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--[[
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Copyright 2016 Marek Vavrusa <mvavrusa@cloudflare.com>
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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]]
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-- Simple parsing example of UDP/DNS that counts frequency of QTYPEs.
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-- It shows how to parse packet variable-length packet structures.
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local ffi = require("ffi")
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local bpf = require("bpf")
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local S = require("syscall")
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-- Shared part of the program
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local map = assert(bpf.map('array', 256))
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-- Kernel-space part of the program
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local prog = bpf.socket('lo', function (skb)
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local ip = pkt.ip -- Accept only UDP messages
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if ip.proto ~= c.ip.proto_udp then return false end
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local udp = ip.udp -- Only messages >12 octets (DNS header)
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if udp.length < 12 then return false end
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-- Unroll QNAME (up to 2 labels)
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udp = udp.data + 12
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local label = udp[0]
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if label > 0 then
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udp = udp + label + 1
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label = udp[0]
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if label > 0 then
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udp = udp + label + 1
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end
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end
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-- Track QTYPE (low types)
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if udp[0] == 0 then
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local qtype = udp[2] -- Low octet from QTYPE
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xadd(map[qtype], 1)
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end
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end)
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-- User-space part of the program
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for _ = 1, 10 do
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for k,v in map.pairs,map,0 do
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v = tonumber(v)
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if v > 0 then
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print(string.format('TYPE%d: %d', k, v))
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end
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end
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S.sleep(1)
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end |