DNS LATENCY TEST for Pi-hole (lua)

dns_tester.lua

local cURL = require "cURL"

-- caching functions to get faster loop experience
local str_gmatch = string.gmatch
local str_find = string.find

function string:split(sep)
  local i = 1
  local t = {}
  for token in str_gmatch(self, "[^" .. sep .. "]+") do
    t[i] = token
    i = i + 1
  end
  return t
end

local output_file_name = "dns-bench-output.txt"
local file, err = io.open(output_file_name,'a')
if not file then
  print(err)
  return
end

local function write_to_file(...)
  for i = 1, select("#", ...) do
    local text = select(i, ...)
    file:write(text, "\n")
  end
end

local print = function(...)
  print(...)
  write_to_file(...)
end

print("\nPerfoming a ping test through all Pi-hole upstream dns providers\nDownloading page...")

local body_html = ""
local function save_page(data)
  body_html = body_html .. data
end

local c, err = cURL.easy{
  url = "https://docs.pi-hole.net/guides/dns/upstream-dns-providers/",
  ssl_verifypeer = false,
  ssl_verifyhost = false,
  writefunction=save_page
}:perform()

local status  = c:getinfo_response_code()
print("curl status: " .. status..string.format(" [%s]", status == 200 and "Done" or "Fail"))

if status ~= 200 then return end

local function get_tag(body_text, tag, explict_tag)
  local i = 1
  local t = {}
  local pattern = explict_tag and "<"..tag..".->(.-)</"..tag..">" or "<"..tag..">(.-)</"..tag..">"
  for v in str_gmatch(body_text, pattern) do
      t[i] = v
      i = i + 1
  end
  return t
end

local dns_names = get_tag(body_html, "h3", true)
local uls = get_tag(body_html, "ul", false)
table.remove(uls, 3) -- we are not going to use opendns FamilyShield nah fam

local os_isWin = os.getenv('OS') and true or false
local ipv6_support = true

local pings = {}
for i = 1, #dns_names do
  local dns_query = uls[i]:split("\n")
  local dns_name = dns_names[i]:split("<")[1]

  if dns_name == "Custom" then break end

  print("\n"..dns_name)

  local ping = {}

  for v = 1, #dns_query do
    local dns_ip = dns_query[v]:split("<li>")[1]
    local is_v6 = false
    if string.match(dns_ip, "(IPv6)") then
      if not ipv6_support then
        break
      end
      dns_ip = dns_ip:split(" ")[1]
      is_v6 = true
    end

    print(dns_ip)

    local ping_cmd = os_isWin and "ping "..dns_ip or "ping -c 4 "..dns_ip
    if is_v6 then
      ping_cmd = os_isWin and ping_cmd or "ping6 "..dns_ip
    end

    local pipe = io.popen(ping_cmd)
    local output = pipe:read("*all")
    local output_splitted = os_isWin and output:split("=") or output:split("/")
    local measured_ping = output_splitted[os_isWin and #output_splitted or #output_splitted-2]

    if ipv6_support then
      if not measured_ping or str_find(measured_ping:gsub("%s+", ""), "4%(100%%") then -- 4(100% lost)
        ipv6_support = false
        print("IPv6 not supported. Skipping")
        break
      end
    end
    ping[v] = tonumber(measured_ping:match("%S+"))
    pipe:close()
  end
  pings[dns_name] = ping
  print("Measured ping: "..table.concat(ping, ", "))
end

local function get_lowest(table)
  local min = math.huge
  for i = 1, #table do
    local num = table[i]
    if min > num then
      min = num
    end
  end
  return min
end

print("\nPING   DNS SERVICE")

local best_dns
local min = math.huge
for dns, dns_pings in pairs(pings) do
  local dns_lowest_ping = get_lowest(dns_pings)
  if min > dns_lowest_ping then
    min = dns_lowest_ping
    best_dns = dns
  end
  print(string.format("%.1f", dns_lowest_ping) .. "ms" .. " "..dns)
end

print("\nYour best choice would be: " .. best_dns .. "\nLatency(ms): " .. min)
print("\nOutput saved to "..output_file_name)

file:close()

ATTENTION!
Lua-cURL required