added possibility to replay received opts

Author: andreaf74

lib/resty/dns/server.lua

@@ -285,7 +285,7 @@ function _M.decode_request(self, req)
             local rdata = nil
             if rdlen > 0 then
                 -- get whole rdata
-                rdata = byte(self.buf, self.pos - 1, self.pos + rdlen)
+                rdata = strsub(self.buf, self.pos +1   , self.pos + rdlen)
 
                 -- parse OPTION-CODE
                 self.pos = self.pos + 2
@@ -387,6 +387,12 @@ local function _encode_4byt(x)
 end
 
 
+local function _encode_1byt(x)
+    local lo = band(x, 0xFF)
+
+    return char(lo)
+end
+
 local function _encode_2byt(x)
     local hi = band(rshift(x, 8), 0x00FF)
     local lo = band(x, 0x00FF)
@@ -472,12 +478,14 @@ function _M.encode_response(self)
     end
 
     for i = 1, self.response.header.arcount do
-        buf = buf .. _encode_name(self.response.arsections[i].name)
+       	buf = buf .. _encode_name(self.response.arsections[i].name)
         buf = buf .. _encode_2byt(self.response.arsections[i].type)
         buf = buf .. _encode_2byt(self.response.arsections[i].class)
         buf = buf .. _encode_4byt(self.response.arsections[i].ttl or 0x258)
         buf = buf .. _encode_2byt(self.response.arsections[i].rdlength)
-        buf = buf .. self.response.arsections[i].rdata
+        if self.response.arsections[i].rdlength > 0 then 
+		    buf = buf .. self.response.arsections[i].rdata
+	i   end
     end
 
     return buf
@@ -531,7 +539,7 @@ function _M.create_a_answer(self, name, ttl, ipv4)
     return nil
 end
 
-function _M.replay_additional_opt(self)
+function _M.replay_additional_opts(self)
 
     for i = 1, #self.request.additionals do
         local additional = self.request.additionals[i]