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local adns = require "net.adns";
local basic = require "net.resolvers.basic";
local idna_to_ascii = require "util.encodings".idna.to_ascii;
local unpack = table.unpack or unpack; -- luacheck: ignore 113
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
if not self.hostname then
-- FIXME report IDNA error
cb(nil);
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, err)
if not answer and not err then
-- net.adns returns nil if there are zero records or nxdomain
answer = {};
end
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.srv.priority < b.srv.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 = idna_to_ascii(hostname);
service = service;
conn_type = conn_type or "tcp";
extra = extra;
}, resolver_mt);
end
return {
new = new;
};
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