1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
|
local adns = require "net.adns";
local basic = require "net.resolvers.basic";
local methods = {};
local resolver_mt = { __index = methods };
-- Find the next target to connect to, and
-- pass it to cb()
function methods:next(cb)
if self.targets then
if #self.targets == 0 then
cb(nil);
return;
end
local next_target = table.remove(self.targets, 1);
self.resolver = basic.new(unpack(next_target, 1, 4));
self.resolver:next(function (...)
if ... == nil then
self:next(cb);
else
cb(...);
end
end);
return;
end
local targets = {};
local function ready()
self.targets = targets;
self:next(cb);
end
-- Resolve DNS to target list
local dns_resolver = adns.resolver();
dns_resolver:lookup(function (answer)
if answer then
if #answer == 0 then
if self.extra and self.extra.default_port then
table.insert(targets, { self.hostname, self.extra.default_port, self.conn_type, self.extra });
end
ready();
return;
end
if #answer == 1 and answer[1].srv.target == "." then -- No service here
ready();
return;
end
table.sort(answer, function (a, b) return a.priority > b.priority end);
for _, record in ipairs(answer) do
table.insert(targets, { record.srv.target, record.srv.port, self.conn_type, self.extra });
end
end
ready();
end, "_" .. self.service .. "._" .. self.conn_type .. "." .. self.hostname, "SRV", "IN");
end
local function new(hostname, service, conn_type, extra)
return setmetatable({
hostname = hostname;
service = service;
conn_type = conn_type or "tcp";
extra = extra;
}, resolver_mt);
end
return {
new = new;
};
|
