net/resolvers/basic.lua

   1 local adns = require "net.adns";
   2 local inet_pton = require "util.net".pton;
   3 local unpack = table.unpack or unpack; -- luacheck: ignore 113
   4
   5 local methods = {};
   6 local resolver_mt = { __index = methods };
   7
   8 -- Find the next target to connect to, and
   9 -- pass it to cb()
  10 function methods:next(cb)
  11         if self.targets then
  12                 if #self.targets == 0 then
  13                         cb(nil);
  14                         return;
  15                 end
  16                 local next_target = table.remove(self.targets, 1);
  17                 cb(unpack(next_target, 1, 4));
  18                 return;
  19         end
  20
  21         local targets = {};
  22         local n = 2;
  23         local function ready()
  24                 n = n - 1;
  25                 if n > 0 then return; end
  26                 self.targets = targets;
  27                 self:next(cb);
  28         end
  29
  30         local is_ip = inet_pton(self.hostname);
  31         if is_ip then
  32                 if #is_ip == 16 then
  33                         cb(self.conn_type.."6", self.hostname, self.port, self.extra);
  34                 elseif #is_ip == 4 then
  35                         cb(self.conn_type.."4", self.hostname, self.port, self.extra);
  36                 end
  37                 return;
  38         end
  39
  40         -- Resolve DNS to target list
  41         local dns_resolver = adns.resolver();
  42         dns_resolver:lookup(function (answer)
  43                 if answer then
  44                         for _, record in ipairs(answer) do
  45                                 table.insert(targets, { self.conn_type.."4", record.a, self.port, self.extra });
  46                         end
  47                 end
  48                 ready();
  49         end, self.hostname, "A", "IN");
  50
  51         dns_resolver:lookup(function (answer)
  52                 if answer then
  53                         for _, record in ipairs(answer) do
  54                                 table.insert(targets, { self.conn_type.."6", record.aaaa, self.port, self.extra });
  55                         end
  56                 end
  57                 ready();
  58         end, self.hostname, "AAAA", "IN");
  59 end
  60
  61 local function new(hostname, port, conn_type, extra)
  62         return setmetatable({
  63                 hostname = hostname;
  64                 port = port;
  65                 conn_type = conn_type or "tcp";
  66                 extra = extra;
  67         }, resolver_mt);
  68 end
  69
  70 return {
  71         new = new;
  72 };