fix dns bug , see issue #605

examples/main.lua

@@ -9,6 +9,7 @@ skynet.start(function()
 	if not skynet.getenv "daemon" then
 		local console = skynet.newservice("console")
 	end
+--[[
 	skynet.newservice("debug_console",8000)
 	skynet.newservice("simpledb")
 	local watchdog = skynet.newservice("watchdog")
@@ -18,5 +19,6 @@ skynet.start(function()
 		nodelay = true,
 	})
 	skynet.error("Watchdog listen on", 8888)
+]]
 	skynet.exit()
 end)

lualib/dns.lua

@@ -87,6 +87,7 @@ local weak = {__mode = "kv"}
 local CACHE = {}
 
 local dns = {}
+local request_pool = {}
 
 function dns.flush()
 	CACHE[QTYPE.A] = setmetatable({},weak)
@@ -113,7 +114,21 @@ end
 local next_tid = 1
 local function gen_tid()
 	local tid = next_tid
-	next_tid = next_tid + 1
+	if request_pool[tid] then
+		tid = nil
+		for i = 1, 65535 do
+			-- find available tid
+			if not request_pool[i] then
+				tid = i
+				break
+			end
+		end
+		assert(tid)
+	end
+	next_tid = tid + 1
+	if next_tid > 65535 then
+		next_tid = 1
+	end
 	return tid
 end
 
@@ -205,7 +220,6 @@ local function unpack_rdata(qtype, chunk)
 end
 
 local dns_server
-local request_pool = {}
 
 local function resolve(content)
 	if #content < DNS_HEADER_LEN then