File

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−local adns = require "net.adns";
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−local inet_pton = require "util.net".pton;
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−local inet_ntop = require "util.net".ntop;
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−local idna_to_ascii = require "util.encodings".idna.to_ascii;
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−local unpack = table.unpack or unpack; -- luacheck: ignore 113
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−
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−local methods = {};
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−local resolver_mt = { __index = methods };
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−
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−-- TODO Respect use_ipv4, use_ipv6
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−-- FIXME RFC 6724
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−-- FIXME #1428 Reuse DNS resolver object (from service resolver)
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−-- FIXME #1429 Close DNS resolver object when done
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−
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−-- Find the next target to connect to, and
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−-- pass it to cb()
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−function methods:next(cb)
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−	if self.targets then
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−		if #self.targets == 0 then
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−			cb(nil);
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−			return;
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−		end
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−		local next_target = table.remove(self.targets, 1);
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−		cb(unpack(next_target, 1, 4));
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−		return;
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−	end
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−
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−	if not self.hostname then
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−		-- FIXME report IDNA error
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−		cb(nil);
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−		return;
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−	end
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−
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−	local targets = {};
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−	local n = 2;
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−	local function ready()
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−		n = n - 1;
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−		if n > 0 then return; end
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−		self.targets = targets;
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−		self:next(cb);
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−	end
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−
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−	-- Resolve DNS to target list
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−	local dns_resolver = adns.resolver();
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−
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−	if not self.extra or self.extra.use_ipv4 ~= false then
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−		dns_resolver:lookup(function (answer)
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−			if answer then
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−				for _, record in ipairs(answer) do
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−					table.insert(targets, { self.conn_type.."4", record.a, self.port, self.extra });
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−				end
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−			end
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−			ready();
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−		end, self.hostname, "A", "IN");
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−	else
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−		ready();
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−	end
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−
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−	if not self.extra or self.extra.use_ipv6 ~= false then
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−		dns_resolver:lookup(function (answer)
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−			if answer then
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−				for _, record in ipairs(answer) do
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−					table.insert(targets, { self.conn_type.."6", record.aaaa, self.port, self.extra });
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−				end
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−			end
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−			ready();
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−		end, self.hostname, "AAAA", "IN");
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−	else
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−		ready();
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−	end
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−end
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−
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−local function new(hostname, port, conn_type, extra)
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−	local ascii_host = idna_to_ascii(hostname);
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−	local targets = nil;
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−
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−	local is_ip = inet_pton(hostname);
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−	if not is_ip and hostname:sub(1,1) == '[' then
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−		is_ip = inet_pton(hostname:sub(2,-2));
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−	end
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−	if is_ip then
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−		hostname = inet_ntop(is_ip);
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−		if #is_ip == 16 then
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−			targets = { { conn_type.."6", hostname, port, extra } };
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−		elseif #is_ip == 4 then
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−			targets = { { conn_type.."4", hostname, port, extra } };
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−		end
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−	end
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−
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−	return setmetatable({
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−		hostname = ascii_host;
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−		port = port;
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−		conn_type = conn_type or "tcp";
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−		extra = extra;
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−		targets = targets;
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−	}, resolver_mt);
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−end
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−
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−return {
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−	new = new;
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−};