Lua /etc/resolv.conf parser and some refactoring

rootfs/etc/nginx/lua/util/dns.lua

@@ -1,7 +1,6 @@
 local resolver = require("resty.dns.resolver")
 local lrucache = require("resty.lrucache")
-local configuration = require("configuration")
-local util = require("util")
+local resolv_conf = require("util.resolv_conf")
 
 local _M = {}
 local CACHE_SIZE = 10000
@@ -59,7 +58,7 @@ function _M.resolve(host)
 
   local r
   r, err = resolver:new{
-    nameservers = util.deepcopy(configuration.nameservers),
+    nameservers = resolv_conf.nameservers,
     retrans = 5,
     timeout = 2000,  -- 2 sec
   }

rootfs/etc/nginx/lua/util/resolv_conf.lua

@@ -0,0 +1,79 @@
+local ngx_re_split = require("ngx.re").split
+
+local ngx_log = ngx.log
+local ngx_ERR = ngx.ERR
+
+local CONF_PATH = "/etc/resolv.conf"
+
+local nameservers, search, ndots = {}, {}, 1
+
+local function set_search(parts)
+  local length = #parts
+
+  for i = 2, length, 1 do
+    search[i-1] = parts[i]
+  end
+end
+
+local function set_ndots(parts)
+  local option = parts[2]
+  if not option then
+    return
+  end
+
+  local option_parts, err = ngx_re_split(option, ":")
+  if err then
+    ngx_log(ngx_ERR, err)
+    return
+  end
+
+  if option_parts[1] ~= "ndots" then
+    return
+  end
+
+  ndots = tonumber(option_parts[2])
+end
+
+local function is_comment(line)
+  return line:sub(1, 1) == "#"
+end
+
+local function parse_line(line)
+  if is_comment(line) then
+    return
+  end
+
+  local parts, err = ngx_re_split(line, "\\s+")
+  if err then
+    ngx_log(ngx_ERR, err)
+  end
+
+  local keyword, value = parts[1], parts[2]
+
+  if keyword == "nameserver" then
+    nameservers[#nameservers + 1] = value
+  elseif keyword == "search" then
+    set_search(parts)
+  elseif keyword == "options" then
+    set_ndots(parts)
+  end
+end
+
+do
+  local f, err = io.open(CONF_PATH, "r")
+  if not f then
+    error("could not open " .. CONF_PATH .. ": " .. tostring(err))
+  end
+
+  for line in f:lines() do
+    parse_line(line)
+  end
+
+  f:close()
+end
+
+return {
+  nameservers = nameservers,
+  search = search,
+  ndots = ndots,
+}